Note: Descriptions are shown in the official language in which they were submitted.
CA 02572001 2006-12-22
A LUBRICATING OIL COMPOSITION FOR AUTOMATIC TRANSMISSIONS
The present invention relates to a lubricating oil composition. In particular,
the
invention relates to a lubricating oil composition for automatic transmissions
of
internal combustion engines, in which the lubricating oil composition shows a
high torque transmission capacity and a prolonged shudder inhibition.
BACKGROUND OF THE INVENTION
Automatic transmissions in automobiles comprise a torque converter, a wet
multi-plate clutch, a gear mechanism, and a mechanism controlling these
elements. The torque transmission capacity is automatically set according to
the speed of automobile and the degree of load. Modern automatic
transmissions further comprise a lockup clutch mounted to the torque
converter,
so as to improve fuel economy. The use of the lockup clutch enables engine
torque to be transmitted to the automatic transmission according to driving
conditions in addition to the driving force transmitted through a lubricating
oil.
However, since the torque variation produced by the operation of the lockup
clutch sometimes disturbs passengers due to shudder, the lockup clutch is
generally set to operate only under high speed driving conditions giving less
torque variation.
Under low speed driving conditions as when an automobile starts, loss of
driving force transmission is caused between the engine output revolution and
the transmission input revolution. Therefore, enough improvement of fuel
economy is not attained. Accordingly, automatic transmissions adopt a slip
control system by which the lockup mechanism can operate under the low
speed driving conditions and the transmission loss can be reduced. However,
when the clutch is subjected to control by the slip control system, abnormal
vibration of the body of automobile (i.e., shudder) takes place on the
friction
surface of the lockup clutch. At low road speeds vehicle operation is rough
and
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engine vibration is transmitted through the drive train. Rough operation and
engine vibration are not acceptable to drivers. The lock-up system requires
specific automatic transmission fluid characteristics in terms of anti-shudder
durability to perform smoothly.
Shudder is known as a stick-slip phenomenon and is related to the frictional
coefficient and velocity called p-V characteristic. Shudder occurs when the
sliding rate (V) in the lockup clutch increases and the coefficient of
friction ( )
decreases. Thus, it is desirable to employ a lubricating oil (automatic.
transmission fluid) which shows a favorable -V character, i.e., the friction
coefficient increases when the sliding rate increases, and keeps the favorable
-V character for a prolonged period of time, i.e., prolonged shudder
inhibition
performance. Positive dp/dV in the -V characteristics are required to prevent
shudder.
JASO (Japanese Automobile Standard Organization) M349:2001 describes a
standard oil T-III which shows standard shudder inhibition performance and
torque transmission capacity. However, there is given no information with
respect to the formulation of the T-III standard oil.
Prolonged shudder inhibition can be attained by incorporating a friction
modifier
(generally, friction decreasing agent). However, if too much friction modifier
is
incorporated into a lubricating oil, the friction coefficient of the wet
clutch
extremely decreases and hence enough torque transmission capacity cannot
be obtained.
U.S. Patent No. 4,948,523 discloses a lubricating composition, preferably
essentially free of zinc dihydrocarbyldithiophosphate compounds, and
optionally free of chlorine containing silver lubricity agents, comprising a
major
proportion of an oil of lubricating, viscosity and a minor amount of a silver
protective agent comprising the reaction product of a C5 to C6o carboxylic
acid
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and at least one amine selected from the group consisting of (1) guanidine,
urea, and thiourea compounds; (2) C, to C20 hydrocarbyl or hydroxy-substituted
hydrocarbyl mono-amines, alkylene diamines, and (3) polyalkylene polyamines;
and N-alkyl glycine.
U.S. Patent No. 5,395,539 discloses certain hydrocarbon soluble or dispersible
amide reaction products (Component-1), and mixtures, and/or acid amine salts
of Component-1 and certain acid/esters (Component-2), which are useful as
friction modifying additives for oleaginous compositions such as lubricating
oils,
including power transmitting fluids, particularly automatic transmission
fluids
(ATF), and to the oleaginous compositions in which they are contained.
U.S. Patent No. 5,916,852 discloses lubricating fluids which include an
additive
combination comprising a compound having the general formula R-NH2 with
oil-soluble phosphorus compounds, an ashless dispersant, and, optionally,
other amine containing friction modifiers provide lubricating fluids which
exhibit
excellent break-in characteristics that are capable of preventing "green
shudder" in automatic transmissions.
U.S. Patent No. 6,303,547 discloses lubricant formulations containing the
reaction product of at least one C5 to Cw carboxylic acid and at least one
amine selected from the group consisting of guanidine, aminoguanidine, urea,
thiourea and salts thereof is useful as a gear oil additive. The lubricant
formulations exhibit excellent low and high temperature rheology and are
particularly suited for use in automotive and industrial gear applications.
Lubricants of the present invention exhibit improved performance properties,
such as increased axle efficiencies and lower axle temperatures, improved
limited slip performance, reduced chatter, improved frictional durability
and/or
improved power divider performance compared to lubricant formulations that
do not contain said reaction products.
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Japanese Patent Publication No. 2001-247532 discloses fatty acid amide
compounds used for surface lubricant, vehicle component and thermal
recording materials, has three or more amide groups in a molecule having the
formula RICONH(CH2)m((NCOR2XCH2)õ ),NHCOR3, where R1-R3 is a C12 to C5
alkyl or alkenyl group, m and n 1-3, and I = 1-4.
U.S. Patent Application Publication No. 2002/0072478A1 discloses a
lubricating oil and one or more succinimide-modified compounds having long-
lasting anti-shudder property, enhanced transmission torque capacity for wet
clutches and/or wet brakes, and excellent shifting property for automatic
transmissions and continuously variable transmissions.
Japanese Patent No. 3330245 discloses lubricating oil compositions for slide
guide surfaces containing nitrogen-containing compounds of polyamines and
amides in mineral and/or synthetic oil.
U.S. Patent Application Publication No. 2005/0124506 Al discloses an additive
compound comprising a non-borated and/or borated reaction product, in which
the reaction product is obtained by reacting a linear or branched, saturated
or
unsaturated monovalent aliphatic acid having 8 to 22 carbon atoms, urea, and
polyalkylenepolyamine, when employed in a lubricating oil composition is
favorably employable as an automatic transmission fluid of internal combustion
engines.
The anti-shudder durability and shifting property and the transmission torque
capacity are in a trade-off relation. Therefore, it is desired to develop a
lubricant composition having all of these properties.
In view of this dilemma, the object of the present invention is to provide a
novel
lubricant composition which can retain anti-shudder durability for extended
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periods and has high transmission torque capacity and improved shifting
property.
SUMMARY OF THE INVENTION
The present invention provides a lubricating oil composition employable in
automatic transmissions of internal combustion engines. The lubricating oil
composition of the present invention has a high torque transmission capacity
and prolonged shudder inhibition when used as an automatic transmission fluid
(ATF) in automatic transmissions of internal combustion engines.
It is desirable that an automatic transmission fluid not only should show a
high
shudder inhibiting ability when the transmission fluid is first used, but also
should keep the high shudder inhibiting ability for a prolonged period of time
without substantial decrease of the inhibiting ability and further should show
a
high torque transmission capacity.
Accordingly, the present invention relates to a lubricating oil composition
employable as an ATF in internal combustion engines having the beneficial
performances mentioned above.
The present invention relates to a lubricating oil composition comprising a
major amount of base oil of lubricating viscosity and the following additives
in
the following amounts based on a total amount of the lubricating oil
composition:
(A) 0.1 to 10 wt.% of a succinic acid ester,
(B) 0.01 to 2 wt.% of a phosphorous acid ester,
(C) 0.1 to 5 wt.% of an amide compound which is a reaction product
obtained by reaction of a linear or branched, saturated or
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unsaturated monovalent aliphatic acid having 8 to 22 carbon atoms,
urea, and polyalkylenepolyamine,
(D) 0.01 to 2 wt.% of an overbased metal-containing detergent, and
(E) 0.01 to 1 wt.% of a corrosion inhibitor.
According to another aspect of the present invention, there is provided a
lubricating oil composition comprising a base oil of lubricating viscosity and
the
following additives in the following amounts based on the total amount of the
composition:
(A) 0.1 to 10 wt.% of a succinic acid ester,
(B) 0.01 to 2 wt.% of a phosphorous acid ester,
(C) 0.1 to 5 wt.% of an amide compound which is a reaction product
obtained by reaction of a linear or branched, saturated or
unsaturated monovalent aliphatic acid having 8 to 22 carbon atoms,
urea, and a polyalkylenepolyamine,
(D) 0.01 to 2 wt.% of an overbased metal-containing detergent, and
(E) 0.01 to 1 wt.% of a corrosion inhibitor.
The present invention further relates to a method of reducing shudder in an
automatic transmission of an internal combustion engine by adding the
lubricating oil composition of the present invention to an automatic
transmission and operating the engine.
Among other factors, the present invention is based on the surprising
discovery
that the lubricating oil composition of the present invention provides high
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transmission torque capacity and prolonged shudder inhibition when employed
in an automatic transmission of an internal combustion engine. The lubricating
oil composition is useful as a method for reducing shudder when used as an
automatic transmission fluid. Accordingly the present invention is also
directed
to the use of the present additive compound in an automatic transmission fluid
to reduce shudder in an automatic transmission of an internal combustion
engine. The lubricating oil composition of the present invention has high
stability with respect to the shudder inhibition, the torque transmission
capacity
and the shift performance, which are important properties of an automatic
transmission fluid.
DETAILED DESCRIPTION OF THE INVENTION
As described in U.S. Patent Application Publication No. 2005/0124506 Al, the
amide compound employed in the automatic transmission oil shows shudder
inhibition performance retention, i.e., prolonged shudder inhibition time.
However, the present invention will show that U.S. Patent Application
Publication No. 2005/0124506 Al does not have fully satisfactory
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CA 02572001 2006-12-22
characteristics in torque transmission capacity and shift performance despite
having better characteristics compared to the standard T-III reference oil
used
in the JASO M349:2001 test. The torque transmission capacity and the shift
performance relate to response depending upon the slide of the clutch and to
shock in gear shifting, respectively. Accordingly, if the torque transmission
capacity and the shift performance fluctuate, the response of the clutch and
the
shock in gear shifting are liable to fluctuate, respectively.
Thus, it is an object of the present invention to provide a lubricating oil
composition containing additives for further effectively utilizing the amide
compound disclosed in U.S. Patent Application Publication No. 2005/0124506
Al. In particular, the present invention provides a lubricating oil
composition
which is excellent not only in shudder inhibition performance, i.e., prolonged
shudder inhibition time, but also in the stability of the torque transmission
capacity and the shift performance.
The preferred embodiments of the lubricating oil composition according to the
present invention will be described in further detail below.
Succinic Acid Ester
The lubricating oil composition of the present invention contains a succinic
acid
ester (Component A) in an amount of 0.1 to 10, wt.%, preferably 0.1 to 5 wt.%,
based on the total amount of the lubricating oil composition.
The succinic acid ester is preferably an ester derived from a polyol and an
alkenyl-substituted succinic anhydride prepared by reaction between malefic
anhydride and polyolefin having a number average molecular weight of 450 to
5,000. The polyolefin preferably is polybutene. The polyol preferably is a
polyhydric alcohol having 12 or less carbon atoms such as glycerol,
erythritol,
pentaerythritol, dipentaerythritol, heptanediol, hexanetriol, or butanetriol.
Particularly preferred is pentaerythritol.
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The process for preparing the polybutenylsuccinic anhydride by the reaction
between polybutene and maleic anhydride is generally performed by a
chlorination method utilizing chlorine. While this reaction is advantageous in
giving a high reaction yield, it has disadvantageous feature in that a large
amount (for instance, approx. 2,000 ppm) of chlorine remains in the finally
obtained succinimide product. In contrast, a thermal reaction process
utilizing
no chlorine gives a final reaction product having an extremely low chlorine
content (such as 40 ppm or less). It is known that an improved thermal
reaction
process employing a highly reactive polybutene (containing at least approx.
50% of methylvinylidene structure) in place of the conventional polybutene
(containing mainly l3-olefin structure) gives a high reaction yield. The
improved
thermal reaction process is further advantageous because the reaction ratio of
the polybutene increases, and the resulting dispersant contains the effective
product (succinimide) in a high concentration. Accordingly, it is preferred
that
the polybutenylsuccinic anhydride is produced from the highly reactive
polybutene by a thermal process and the resulting polybutenylsuccinic
anhydride is reacted with a polyhydric alcohol such as pentaerythritol to
prepare the succinic acid ester.
In the lubricating oil composition of the present invention, the succinic acid
ester can be used in combination with a polybutenyl-substituted succinic imide
having a number average molecular weight of 300 to 5,000 or a modified
succinic imide obtained by reacting the polybutenyl-substituted succinic imide
with boric acid, alcohol, aldehyde, ketone, alkyiphenol, cyclic carbonate,
organic acid or inorganic acid such as phosphoric acid.
Phosphorous Acid Ester
The lubricating oil composition of the present invention contains a
phosphorous
acid ester (Component B) in an amount of 0.01 to 2 wt.%, preferably 0.05 to
0.5 wt.%, based on the total amount of the lubricating oil composition.
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The phosphorous acid ester serves as a friction modifier and an anti-wear
agent in the lubricating oil composition of the present invention.
The phosphorous acid ester preferably is an aliphatic secondary phosphite or
an aromatic secondary phosphite. Examples of the aliphatic secondary
phosphites include a secondary phosphite having a hydrocarbon group of 3 to
18 carbon atoms (e.g., dipropyl hydrogen phosphite, dibutyl hydrogen
phosphite, dioctyl hydrogen phosphite, didecyl hydrogen phosphite, dilauryl
hydrogen phosphite, dioleyl hydrogen phosphite) and a mixed dialkyl hydrogen
phosphite having a hydrocarbon group of 12 carbon atoms and a hydrocarbon
group of 14 carbon atoms. Examples of the aromatic secondary phosphites
include diphenyl hydrogen phosphite. The phosphorous acid ester may be in
the form of an amine salt. Examples of the amine salts include a linear or
branched chain aliphatic amine having 8 to 18 carbon atoms such as octyl
amine, decyl amine, lauryl amine, capryl amine, coconut amine, tallow amine
or oleyl amine.
Amide Compound
The lubricating oil composition of the present invention contains a non-
borated
(I) and/or borated (II) amide compound (Component C) which is a reaction
product in which the reaction product is obtained by reacting a linear or
branched, saturated or unsaturated monovalent aliphatic acid having 8 to 22
carbon atoms, urea, and polyalkylenepolyamine. The additive compounds I
and II of Compound C can be employed singly or in combination. The amount
of Component C employed in the lubricating oil composition of the present
invention will be in an amount of 0.1 to 5 wt.%, preferably 0.2 to 4 wt.%,
based
on the total amount of the lubricating oil composition.
Additive compound I comprises the reaction product of a linear or branched,
saturated or unsaturated monovalent aliphatic acid having 8 to 22 carbon
atoms, urea, and polyalkylenepolyamine.
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Additive compound II comprises the borated reaction product in which the
reaction product is obtained by reacting a linear or branched, saturated or
unsaturated monovalent aliphatic acid having 8 to 22 carbon atoms, urea, and
polyalkylenepolyamine with boric acid compound.
Monovalent Aliphatic Acid
The monovalent aliphatic acid is a compound which is represented by the
formula:
R4 (COOH)y
or anhydride thereof, wherein R4 represents a hydrocarbyI group having about
2 to 50 carbon atoms, and y represents an integer of 1 to 4.
The monovalent aliphatic acid employed for the preparation of the amide
compound of the present invention is a linear or branched, saturated or
unsaturated monovalent aliphatic acid containing 8 to 22 carbon atoms.
Examples of the aliphatic acids include octanoic acid, lauric acid, myristic
acid,
palmitic acid, stearic acid, isostearic acid, oleic acid, and behenic acid.
Particularly preferred is isostearic acid.
Urea
Any ordinarily employable urea such as urea of industrial purity grade can be
employed.
PolyaIkylenepolyamine
Preferred is a polyalkylenepolyamine containing 2 to 30 carbon atoms and 2 to
15 nitrogen atoms, each of at least two nitrogen atoms constituting primary
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amine. Preferably, the alkylene groups of such polyalkylenepolyamines will
contain form 2 to 6 carbon atoms, more preferably form 2 to 4 carbon atoms.
The nitrogen atom other than the nitrogen atoms constituting primary amine
generally constitutes secondary amine.
Examples of suitable polyalkylenepolyamines include ethylenediamine,
propylenediamine, isopropylenediamine, butylenediamine, pentylenediamine,
hexyeenediamine, diethylenetriamine, dipropylenetriamine,
dimethylaminopropylamine, dilsopropylenetriamine, dibuhylenetriamine, di-sec-
butylenetriamine, triethylenetetraamine, tripropylenetetraamine,
triisobutylenetetraamine, tetraethylenepentamine, pentaethylenehexamine,
hexaethyleneheptamine, dimethylaminopropylamine, and mixtures thereof.
Particularly suitable polyalkylenepolyamines are those having the formula:
H2N-(R5NH)z--H
wherein R5 is a straight- or branched-chain alkylene group having 2 to 6
carbon
atoms, preferably 2 to 4 carbon atoms, most preferably about 2 carbon atoms,
i.e., ethylene (-CH2CH2-); and z is an integer from 1 to 4, preferably I to 2.
Particularly preferred polyalkylenepolyamines are ethylenediamine,
diethylenetriamine, triethylenetetraamine, tetraethylenepenta mine,
pentaethylenehexamine, and hexaethyleneheptamine. Particularly preferred is
hexaethyleneheptamine.
Many of the polyamines suitable for use in the present invention are
commercially available and others may be prepared by methods that are well
known in the art. For example, methods for preparing amines and their
reactions are detailed in Sidgewick's "The Organic Chemistry of Nitrogen",
Clarendon Press, Oxford, 1966; Noller's "Chemistry of Organic Compounds",
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Saunders, Philadelphia, 2nd Ed., 1957; and Kirk-Othmer's "Encyclopedia of
Chemical Technology", 2nd Ed., especially Volume 2, pp. 99-116.
The amide compound of the present invention can be obtained by reacting the
acid compound (i.e., monovalent aliphatic acid), urea, the amine compound
(i.e., polyalkylenepolyamine) in such conditions (i.e., ratio and nature) that
the
resulting reaction compound shows an oil-soluble property. The amide
compound of the present invention is preferably obtained by reacting one mole
of the monovalent aliphatic acid, 0.01 to 2 moles (preferably 0.03 to 0.5
moles)
of urea, and 0.1 to I mole (preferably 0.125 to 0.5 moles) of
polyalkylenepolyamine. The reaction can be performed generally at 100-250 C,
preferably at 150-200 C, generally for 1-30 hours, preferably for 2-6 hours.
Since the reaction is a condensation reaction, it is preferred that the
produced
water is-removed continuously. The progress of the reaction can be checked
by measuring the production of water.
The above-mentioned reaction product can be preferably borated by the
reaction using a boric acid compound to yield the borated amide compound (B).
The reaction can be carried out by adding to the above-mentioned reaction
product a solid boric acid compound in such amount that the amount of boron
in the boric acid compound is 0.001 to 0.25 weight part based one weight part
of nitrogen in the above-mentioned reaction product, and heating the mixture
to
100-160 C at an atmospheric pressure or a reduced pressure (reduced to 6.7
kPa) for 5-12 hours. The reaction is preferably continued until the solid
boric
acid compound diminishes in the reaction mixture.
Overbased Metal-Containing Detergent
The lubricating oil composition of the present invention contains an overbased
metal-containing detergent (Component D) in an amount of 0.01 to 2 wt.%,
preferably 0.01 to I wt.%, based on the total amount of the lubricating oil
composition.
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The overbased metal-containing detergent generally has a total base number
of 10 to 500 mg=KOH/g. Examples of the overbased metal-containing
detergents include alkali or alkaline earth metal salts or overbased products
of
petroleum sulfonic acids, alkylbenzenesulfonic acids, and
alkyloxybenzenesutfonic acids. They are preferably used singly or in
combination. As the alkaline earth metal salts, Mg or Ca salts are preferred.
The sulfonates thereof having a total base number of 10 to 500 mg=KOH/g are
generally used. Further, a sulfurized phenate or unsulfurized salicylate can
be
employed singly or In combination.
Corrosion Inhibitor
The lubricating oil composition of the present invention contains a corrosion
inhibitor (Component E) in an amount of 0.01 to I wt.%, preferably 0.01 to 0.5
wt.%, based on the total amount of the lubricating oil composition.
The corrosion inhibitor preferably is a copper corrosion inhibitor. The copper
corrosion inhibitor can be a thiazole compound, a triazole compound or a
thiadiazole compound. Examples of these compounds include benzotriazole,
tolyltriazole, octyltriazole, decyltriazole, dodecyltriazole, 2-
mercaptobenzothiazole, 2,5-dimercapto-1,3,4-thiadiazole, 2-mercapto-5-
hydrocarbyldithio-1,3,4-thiadiazote, and 2,5-bis(hydrocarbyldithio)-1,3,4-
thiadiazole.
In order to protect copper from corrosion, two or more corrosion inhibitors
having different chemical structures are preferably used in combination rather
than one corrosion inhibitor is singly used. For example, a triazole compound
and a thiadiazole are preferably used in combination. Particularly preferred
is a
combination of tolyltriazole and 2,5-bis(hydrocarbyldithio)-1,3,4-thiadiazote
in a
weight ratio of 1:10 to 10:1.
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Other employable corrosion inhibitors include alkenylsuccinic acid and its
anhydride. Examples of these compounds include tetrapropenyssuccinic acid,
tetrapropenylsuccinic anhydride, tetradocenylsuccinic acid,
tetradocenylsuccinic anhydride, octadecenylsuccinic acid, and
octadecenylsuccinic anhydride. Otherwise, an alkenylsuccinic acid having an
alkenyl group of 8 to 24 carbon atoms, and a half ester of this
alkenylsuccinic
acid with an alcohol such as polyglycol can be employed as the corrosion
inhibitor. In addition, an amine compound, an acidic phosphoric acid ester, an
ethoxylated amine compound, an imidazoline compound, an aminosuccinic
acid, or their derivatives can be employed as the corrosion inhibitor.
The lubricating oil composition of the present invention is prepared by adding
the above-described amounts of components A to E into a base oil of
lubricating viscosity.
Lubricating Oil Composition
The lubricating oil composition of the present invention will comprise a major
amount of base oil of lubricating viscosity and the components (A-E) as
described above.
Base oil as used herein is defined as a base stock or blend of base stocks
which is a lubricant component that is produced by a single manufacturer to
the
same specifications (independent of feed source or manufacturer's location);
that meets the same manufacturer's specification; and that is identified by a
unique formula, product identification number, or both. Base stocks may be
manufactured using a variety of different processes including but not limited
to
distillation, solvent refining, hydrogen processing, oligomerization,
esterification,
and rerefining. Rerefined stock shall be substantially free from materials
introduced through manufacturing, contamination, or previous use. The base
oil of this invention maybe any natural or synthetic lubricating base oil
fraction
particularly those having a kinematic viscosity at 1000 Centigrade (C) and
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about 4 centistokes (cSt) to about 20 cSt. Hydrocarbon synthetic oils may
include, for example, oils prepared from the polymerization, of ethylene,
polyalphaolefin or PAO, or from hydrocarbon synthesis procedures using
carbon monoxide and hydrogen gases such as in a Fisher-Tropsch process. A
preferred base oil is one that comprises little, if any, heavy fraction; e.g.,
little, if
any, lube oil fraction of viscosity about 20 cSt or higher at about 100 C.
Oils
used as the base oil will be selected or blended depending on the desired end
use and the additives in the finished oil to give the desired grade of engine
oil,
e.g. a lubricating oil composition having an SAE Viscosity Grade of OW, OW-20,
OW-30, OW-40, OW-50, OW-60, 5W, 5W-20, 5W-30, 5W-40, 5W-50, 5W-60,
IOW, IOW-20, IOW-30, 1 OW-40, 1OW-50, 15W, 15W-20, 15W-30, or 15W-40.
There are no specific conditions with respect to the base oil, provided that
the
base oil is selected from the base stocks generally employed for preparing
lubricating oil compositions. The base oil may be derived from natural
lubricating oils, synthetic lubricating oils or mixtures thereof. Suitable
base oil
includes base stocks obtained by isomerization of synthetic wax and slack wax,
as well as hydrocrackate base stocks produced by hydrocracking (rather than
solvent extracting) the aromatic and polar components of the crude. Suitable
base oils include those in all API categories I, Il, III, IV and V as defined
in API
Publication 1509, 14th Edition, Addendum 1, December 1998. Saturates levels
and viscosity indices for Group I, II and III base oils are listed in Table 1.
Group
IV base oils are polyalphaolefins (PAO). Group V base oils include all other
base oils not included in Group I, 11, III, or IV. Group III base oils are
preferred.
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TABLE 1
Saturates, Sulfur and Viscosity Index of Group I, II, Ill, IV and V Base
Stocks
Saturates (As determined by ASTM Viscosity Index
D2007)
Group (As determined by ASTM D4294,
Sulfur (As determined by ASTM
D2270) ASTM D4297 or ASTM D3120)
I Less than 90 % saturates and/or Greater than or equal to 80 and
Greater than to 0.03 % sulfur less than 120
Greater than or equal to 90 % Greater than or equal to 80 and
II saturates and less than or equal to less than 120
0.03 % sulfur
Greater than or equal to 90 %
Ill saturates and less than or equal to Greater than or equal to 120
0.03% sulfur
IV All Polyalphaolefins (PAOs)
V All others not included in Groups I, 11, Ill, or IV
Natural lubricating oils may include animal oils, vegetable oils (e.g.,
rapeseed
oils, castor oils and lard oil), petroleum oils, mineral oils, and oils
derived from
coal or shale.
Synthetic oils may include hydrocarbon oils and halo-substituted hydrocarbon
oils such as polymerized and inter-polymerized olefins, alkylbenzenes,
polyphenyls, alkylated diphenyl ethers, alkylated diphenyl sulfides, as well
as
their derivatives, analogues and homologues thereof, and the like. Synthetic
lubricating.oils also include alkylene oxide polymers, interpolymers,
copolymers
and derivatives thereof wherein the terminal hydroxyl groups have been
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modified by esterification, etherification, etc. Another suitable class of
synthetic
lubricating oils comprises the esters of dicarboxylic acids with a variety of
alcohols. Esters useful as synthetic oils also include those made from C5 to
C12
monocarboxylic acids and polyols and polyol ethers. Tri-alkyl phosphate ester
oils such as those exemplified by tri-n-butyl phosphate and tri-iso-butyl
phosphate are also suitable for use as base oils.
Silicon-based oils (such as the polyalkyl-, polyaryl-, polyalkoxy-, or
polyaryloxy-
siloxane oils and silicate oils) comprise another useful class of synthetic
lubricating oils. Other synthetic lubricating oils include liquid esters of
phosphorus-containing acids, polymeric tetrahydrofurans, polyalphaolefins, and
the like.
The base oil may be derived from unrefined, refined, rerefined oils, or
mixtures
thereof. Unrefined oils are obtained directly from a natural source or
synthetic
source (e.g., coal, shale, or tar sand bitumen) without further purification
or
treatment. Examples of unrefined oils include a shale oil obtained directly
from
a retorting operation, a petroleum oil obtained directly from distillation, or
an
ester oil obtained directly from an esterification process, each of which may
then be used without further treatment. Refined oils are similar to the
unrefined
oils except that refined oils have been treated in one or more purification
steps
to improve. one or more properties. Suitable purification techniques include
distillation, hydrocracking, hydrotreating, dewaxing, solvent extraction, acid
or
base extraction, filtration, and percolation, all of which are known to those
skilled in the art. Rerefined oils are obtained by treating used oils in
processes
similar to those used to obtain the refined oils. These rerefined oils are
also
known as reclaimed or reprocessed oils and often are additionally processed
by techniques for removal of spent additives and oil breakdown products.
Base oil derived from the hydroisomerization of wax may also be used, either
alone or in combination with the aforesaid natural and/or synthetic base oil.
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Such wax isomerate oil is produced by the hydroisomerization of natural or
synthetic waxes or mixtures thereof over a hydroisomerization catalyst.
It is preferred to use a major amount of base oil of lubricating viscosity in
the
lubricating oil of the present invention. A major amount of base oil as
defined
herein comprises 40 wt % or more. Preferred amounts of base oil of lubricating
viscosity comprise 40 to 99.9 wt %, preferably greater than 50 to 97 wt %,
more preferably 60 to 97 wt % of the lubricating oil composition. (When weight
percent is used herein, it is based on the total weight percent of the
lubricating
oil composition unless otherwise specified.)
The lubricating oil composition of the present invention has high stability
with
respect to shudder inhibition, torque transmission capacity and shift
performance, which are important properties of automatic transmission fluids.
It
is known that lubricating oils are nowadays required not to need replacement
from the time when they are once installed in new cars to the cars are
abandoned, i.e., "fill-for-life" is required of the lubricating oils. From
this
viewpoint, the lubricating oil composition of the present invention is also
advantageous.
The lubricating oil composition of the present invention can further contain
various lubricating oil additives available in the art. Examples of the
optionally
incorporable additives include viscosity index improvers, anti-wear agents,
friction modifiers, oxidation inhibitors, seal swelling agents, dyes, and pour
point depressants. Particularly preferred additive is diphenyl hydrogen
phosphite which is known as an anti-wear agent.
A number of the above-mentioned optionally incorporable additives are well
known. Details of such additives are described below.
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Viscosity Index Improver
Examples of the viscosity index improvers include non-dispersant type
viscosity
index improvers such as copolymers of various methacrylic acid esters and one
or more other monomers and their hydrogenated products and dispersant type
viscosity index improvers such as copolymers of various methacrylic acid
esters and, nitrogen-containing monomers. Other non-dispersant type or
dispersant type viscosity index improvers such as copolymers of ethylene and
a-olefins (e.g., propylene, 1-butene, and 1-pentene) and their hydrogenated
products, and polyacrylic acid esters are also useful in the present
invention.
The lubricating oil composition of the present invention generally contains a
viscosity index improver in an amount of 1 to 20 wt. %, preferably I to 8 wt.
%,
based on the total amount of the lubricating oil composition.
Anti-Wear Agent and Friction Modifier
if desired, zinc dialkyldithiophosphate, which is a known additive serving as
an
anti-wear agent, an oxidation inhibitor, and an extreme-pressure agent, can be
incorporated into the lubricating oil composition of the present invention.
Oxidation Inhibitor
It is preferred that the lubricating oil composition of the present invention
further contains an oxidation inhibitor such as a hindered phenol compound, a
diarylamine compound, or a molybdenum compound in an amount of 0.01 to 5
wt. % based on the total amount of the lubricating oil composition.
Examples of the hindered phenol compounds include 2,6-di-t-butyl-p-cresol,
4,4'-methylenebis(2,6-di-t-butylphenol), 4,4'-methylenebis(6-t-butyl-o-
cresol),
4,4'-isopropylidenebis(2,6-di-t-butylphenol), 4,4'-bis(2,6-di-t-butylphenol),
2,2'-
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CA 02572001 2006-12-22
methylenebis(4-methyl-6-t-butylphenol), 4,4'-thiobis(2-methyl-6-t-
butylphenol),
2,2-thiodiethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], octyl 3-
(3,5-
di-t-butyl-4-hydroxyphenyl)propionate, octadecyl 3-(3,5-di-t-butyl-4-
hydroxyphenyl)propionate and octyl 3-(5-t-butyl-4-hydroxy-3-
methylphenyl)propionate.
Examples of the diarylamine compounds include an alkyldiphenylamine
containing a.mixture of alkyl groups having 4 to 9 carbon atoms, p,p'-
dioctyldiphenylamine, phenyl-a-naphthylamine, phenyl-[i-naphthylamine,
alkylated a-naphthylamine, and alkylated phenyl-a-naphthylamine. Each of the
hindered phenol compounds and diarylamine compounds can be used singly
or in combination. Other oil soluble oxidation inhibitors can be employed in
combination.
The oxidation inhibitor can be a molybdenum-containing compound which is a
multi-functional additive. The molybdenum-containing compound is preferably
contained in the lubricating oil composition in an amount of 30 to 1,000 ppm
in
terms of the molybdenum content.
Examples of the molybdenum-containing compounds are molybdenum-
containing imide, amide or amine compounds. Sulfur-containing
oxymolybdenum-succinimide complex compound can improve high
temperature detergency and oxidation inhibition, and hence is favorably
employed. Sulfated oxymolybdenum dithiocarbamate and sulfated
oxymolybdenum dithiophosphate can improve oxidation inhibition, wear
inhibition, and reduction of friction coefficient, and hence are favorably
employed.
Dv
When the lubricating oil composition of the present invention is employed as
an
ATF, the oil composition is preferably colored by a dye such as red dye.
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CA 02572001 2006-12-22
Pour Point Depressant
Examples of the pour point depressants include polymethacrylic acid esters,
polyacrylic acid esters, polyacrylamides, condensation products of paraffin
wax
and aromatic compounds.
Seal Swelling Agent
When the lubricating oil composition of the present invention is used as an
ATF,
a seal swelling agent which swells elastomer sealing material placed in the
automatic transmission system may be used. Examples of the seal swelling
agents include oil-soluble dialkylesters of dibasic acids such as adipic acid,
azelaic acid, sebacic acid, or phthalic acid. Examples of preferred seal
swelling
agents include an adipic acid ester, an azelaic acid ester or a sebacic acid
ester of an alkanol having 8 to 13 carbon atoms, and a phthalic acid ester of
an
alkanol having 4 to 13 carbon atoms.
EXAMPLES
The invention will be further illustrated by the following examples, which set
forth particularly advantageous method embodiments. While the Examples are
provided to illustrate the present invention, they are not intended to limit
it.
Example I
Preparation of the Amide Compound
In one aspect, the amide compound employed in the lubricating oil composition
of the present invention is a reaction product prepared from monovalent
aliphatic acid, urea and polyalkylenepolyamine.
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In a four-necked flask equipped with a stirrer, a thermometer, and a
dehydrating device were placed 1,034 g (3.5 mol) of isostearic acid and 15 g
(0.25 mol) of urea. The resulting mixture was heated to 100 C, and 137.5 g
(0.5 mol) of hexaethyleneheptamine was dropwise added to the heated mixture
under replacement of the reaction atmosphere with nitrogen gas. After the
addition was complete, the reaction mixture in the flask was gradually heated
to reach 160 C within 3 hours. Water produced by the reaction in the course of
heating was removed from the flask. Finally, the pressure of inside of the
flask
was reduced to 6.7 kPa, so as to completely remove the produced water. The
finally obtained reaction product (reaction product A) was a brown liquid
having
a nitrogen content of 4.3 wt.%.
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Example 2
The lubricating oil composition of the present invention was prepared by
blending the following components in the designated amounts.
Weight part(s)
Succinic acid ester 3.0
Succinimide 0.5
Borated succinimide 0.5
Overbased calcium sulfonate (TBN = 320) 0.15
Amide compound 1.0
Oleic acid 0.25
Tertiary alkyl (C12.14) primary amine 0.1
Diphenyl hydrogen phosphite 0.15
Tolyltriazole 0.1
2,5-B is(hydrocarbyldithio)-1,3,4-thiadiazole 0.03
Dioctyldiphenylamine 0.4
2,6-Di-t-butylphenol 0.25
Silicone oil (anti-foaming agent) 0.002
Nitrogen-containing polymethacrylate
(viscosity index improver) 5.7
Base oil (refined mineral oil) 87.768
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Comparative Example A
The lubricating oil composition of Comparative Example A was prepared as
described in Example 2 except no succinic acid ester was used and the
amounts of succinimide and borated succinimide were 3.0 weight parts and 1.5
weight parts, respectively. This is essentially the lubricating oil
composition
described in U.S. Patent Application Publication No. 2005/0124506 Al.
Comparative Example B
As a reference, the standard oil T-111 was prepared as Comparative Example B.
According to JASO M348:2002 (SAE No. 2 test) and JASO M349:2001 (LVFA
test), the T-111 standard oil shows standards for the torque transmission
capacity, the shift performance and the shudder inhibition performance.
Each of the lubricating oil compositions of Example 2 and Comparative
Examples A and B were examined for its shudder inhibition performance
retention and torque transmission capacity according to the following
measuring procedures. The results are set forth in Table 2.
(1) Shudder inhibition performance retention
The shudder inhibition was measured according to Shudder Inhibition
Performance Test Method for Automobiles and Automobile Automatic
Transmission Fluid (defined in JASO M349.2001). In the measurements, an
LVFA (Low Velocity Friction Apparatus) tester was employed, and d /dV (0.3)
and d /dV (0.9) were determined under the following test conditions:
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CA 02572001 2006-12-22
- Test conditions
Friction material: ZDR 522. OK, Steel plate (FZ132-8Y2)
Oil volume: 150 mL
- Break-in operation
Oil temperature: 80 C, Surface pressure: 1 MPa,
Sliding rate: 0.6 m/s, Period: 30 min.
After the break-in operation was complete, the friction character was measured
according to the below-stated -V character-measuring conditions.
ON Character-measuring conditions
Oil temperature: 40 C, 80 C, 120 C,
Surface pressure: 1 MPa, Sliding rate: 0 to 1.5 m/s
After the first measurement of p-V character was complete, the retention
ability
was evaluated by measuring -V character at the lapse of the predetermined
period of time by repeating the same measuring procedure.
- Retention ability conditions
Oil temperature: 120 C, Surface pressure: 1 MPa,
Sliding rate: 0.9 m/s, Sliding period: 30 min.
Rest: one min., Measurement: Every 24 hours
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- Measurements
d /dV (0.3): dp/dV (m/s) at sliding rate of 0.3 m/s
dpJdV (0.9): d 1dV (m/s) at sliding rate of 0.9 m/s
Shudder life: period of time until one of d /dV (0.3) and d /dV (0.9) became a
minus value. A shorter period was adopted as the shudder life.
(2) Transmissive torque capacity
Dynamic friction test and static friction test were carried out by means of
SAE
No.2 Tester according to Friction Test Method for Automobiles and Automobile
Automatic Transmission Fluid (defined in JASO M348.2002).
Friction material
Friction material: FZ127-24-Y12, Steel plate (FZ132-8Y2)
- Dynamic friction measurement
Inertial moment of inertia disc: 0.343 kg=m2
Oil temperature: 100 C
Rotation: 3,600 rpm
Surface pressure of friction plate: 785 MPa
Test cycle: 30 sec./cycle, Test number: 5,000 cycles
- Static friction measurement
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Rotation: 0.7 rpm
Oil temperature: 100 C
Surface pressure of friction plate: 785 MPa
Test period: 3 min. after initiation of rotation
Test cycle: after 1, 5, 10, 20, 50, 100, 200, 500, 1000, 2000, 3000, 4000,
and 5000 cycles
- Measurement
Static friction coefficient ( s) at the maximum torque caused when the
rotation
at 0.7 rpm starts and static coefficient ( t) at the lapse of 2 seconds.
Transmission torque capacity was evaluated by the value of t. The t value
larger than 0.100 means that the transmission torque capacity is high, and a
further larger t value means a higher transmission torque capacity.
Table 2. Test Results
Shudder
Inhibition Torque Transmission Capacity
Performance
Shudder t t At t t t
Inhibition Life after after after after after after
(hr.) 50 500 1000 2000 3000 5000
cycles cycles cycles cycles cycles cycles
Ex.1 264 0.118 0.120 0.120 0.121 0.121 0.121
Comp. 192 0.131 0.131 0.129 0.125 0.123 0.121
Ex. A
Comp. 48 0.141 0.142 0.139 0.135 0.132 0.133
Ex. 8
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The JASO M318 specification requires a minimum of 85% of t against the T-
III reference oil (Comp. Ex. B). This means t should be 0.112 (0.132 x 0.85).
Example 1 meets this JASO M318 specification requirement as the t is 0.118.
Another important performance feature is stability (durability) over a
prolonged
time period as indicated by the variation of t (max-min at 50-5,000cycles)
over
time. For Example 1, the t variation is <0.004 while Comparative Example A
and Comparative Example B were each >0.010. As can be seen by the torque
transmission capacity results the variation over time is very low indicating
excellent retention of torque transmission capacity throughout the life of the
lubricating oil composition of the present invention. This is an important
property reflecting the ability of the lubricating oil composition to maintain
its
function for a prolong period of operation.
Another aspect of the lubricating oil composition of the present invention is
shudder inhibition performance which reflects the smoothness of the
engagement of the slip control lock-up clutch. This impacts the comfort of the
passenger during operation without vibration or shuddder. The results indicate
a longer retention of shudder inhibition performance by the lubricating oil
composition of the present invention. The shudder inhibition life of the
lubricating oil composition of the present invention (Example 1) was about 1.4
times longer than Comparative Example A and about 5.5 times longer than the
Comparative Example B (T-III reference oil).
The above results demonstrate that, as compared with the lubricating oil
composition of U.S. Patent Application Publication No. 2005/0124506 Al
(Comparative Example A) which comprises the amide compound in
combination with succinic imide, overbased calcium sulfonate (overbased
metal-containing calcium alkylsulfonate), diphenyl hydrogen phosphite
(phosphorous acid ester) and tolyltriazole (corrosion inhibitor), a
lubricating oil
composition using succinic acid ester, as in the case of the present
invention,
in place of the succinic imide not only has improved long-term stability of
both
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CA 02572001 2006-12-22
the torque transmission capacity and the shift performance but also has
prolonged retention of shudder inhibition performance.
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