U.S. patent application number 10/512575 was filed with the patent office on 2006-03-09 for grease composition.
Invention is credited to Takashi Arai, Hirotsugu Kinoshita, Souichi Nomura, Kiyomi Sakamoto.
Application Number | 20060052257 10/512575 |
Document ID | / |
Family ID | 29267638 |
Filed Date | 2006-03-09 |
United States Patent
Application |
20060052257 |
Kind Code |
A1 |
Kinoshita; Hirotsugu ; et
al. |
March 9, 2006 |
Grease composition
Abstract
A grease composition containing a lubricant base oil, diurea
compounds represented by the following general formulas (1) to (3),
and an organic molybdenum compound; wherein respective contents of
the diurea compounds represented by the following general formulas
(1) to (3) satisfy conditions defined by the following expressions
(4) and (5); and wherein the organic molybdenum compound is
contained by 0.1 to 20 mass % based on the total amount of the
grease composition: ##STR1## where R.sup.1 is a hydrocarbon group
containing an aromatic ring, R.sup.2 is a divalent hydrocarbon
group, and R.sup.3 is a hydrocarbon group containing an aliphatic
ring; 5.ltoreq.W.sub.1+W.sub.2+W.sub.3.ltoreq.30 (4)
0.1.ltoreq.(W.sub.1+0.5.times.W.sub.2)/(W.sub.1+W.sub.2+W.sub.3).ltoreq.1-
.0 (5) where W.sub.1, W.sub.2, and W.sub.3 are respective contents
(mass %) of the diurea compounds represented by general formulas
(1) to (3) based on the total amount of the grease composition.
Inventors: |
Kinoshita; Hirotsugu;
(Yokohama-shi, JP) ; Nomura; Souichi; (Edogawa-ku,
JP) ; Arai; Takashi; (Yokohama-shi, JP) ;
Sakamoto; Kiyomi; (Yokohama-shi, JP) |
Correspondence
Address: |
FINNEGAN, HENDERSON, FARABOW, GARRETT & DUNNER;LLP
901 NEW YORK AVENUE, NW
WASHINGTON
DC
20001-4413
US
|
Family ID: |
29267638 |
Appl. No.: |
10/512575 |
Filed: |
April 22, 2003 |
PCT Filed: |
April 22, 2003 |
PCT NO: |
PCT/JP03/05114 |
371 Date: |
June 22, 2005 |
Current U.S.
Class: |
508/364 ;
508/379; 508/552 |
Current CPC
Class: |
C10N 2040/04 20130101;
C10M 2205/12 20130101; C10M 2205/0206 20130101; C10M 2215/1026
20130101; C10M 2219/068 20130101; C10N 2040/046 20200501; C10N
2040/045 20200501; C10M 2223/049 20130101; C10M 169/06 20130101;
C10N 2010/12 20130101; C10M 2223/045 20130101; C10N 2030/06
20130101; C10M 2223/00 20130101; C10M 169/00 20130101; C10N 2040/02
20130101; C10M 2223/042 20130101; C10N 2020/01 20200501 |
Class at
Publication: |
508/364 ;
508/379; 508/552 |
International
Class: |
C10M 169/06 20060101
C10M169/06 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 26, 2002 |
JP |
2002-127125 |
Claims
1. A grease composition containing a lubricant base oil, diurea
compounds represented by the following general formulas (1) to (3),
and an organic molybdenum compound; wherein respective contents of
the diurea compounds represented by the following general formulas
(1) to (3) satisfy conditions defined by the following expressions
(4) and (5); and wherein the organic molybdenum compound is
contained by 0.1 to 20 mass % based on the total amount of the
grease composition: ##STR7## where R.sup.1 is a hydrocarbon group
containing an aromatic ring, R.sup.2 is a divalent hydrocarbon
group, and R.sup.3 is a hydrocarbon group containing an aliphatic
ring; 5.ltoreq.W.sub.1+W.sub.2+W.sub.3.ltoreq.30 (4)
0.1.ltoreq.(W.sub.1+0.5.times.W.sub.2)/(W.sub.1+W.sub.2+W.sub.3).ltoreq.1-
.0 (5) where W.sub.1, W.sub.2, and W.sub.3 are respective contents
(mass %) of the diurea compounds represented by general formulas
(1) to (3) based on the total amount of the grease composition.
Description
TECHNICAL FIELD
[0001] The present invention relates to a grease composition; and,
more specifically, to a grease composition favorably used in a
constant velocity joint, a bearing for a continuously variable
transmission, a bearing for both a car and a railway vehicle,
etc.
BACKGROUND ART
[0002] Various mechanical elements where metals contact with each
other, such as constant velocity joints for a shaft transmitting a
driving force from a transmission of a car to its tires, bearings
for continuously variable transmissions of cars and the like, and
axle bearings for cars and railway vehicles are filled with grease
acting as a lubricant.
[0003] The grease used in these various mechanical elements is
required to suppress the temperature rise in its early stage of use
from the viewpoint of extending life in particular, and reduce the
friction from the viewpoints of extending life and saving
energy.
[0004] As a method of suppressing the temperature rise, the kinetic
viscosity of a base oil of grease has been lowered in general. As a
method of reducing the friction, the use of various additives such
as organic molybdenum compounds and organic zinc compounds has been
known.
DISCLOSURE OF THE INVENTION
[0005] However, it has been quite difficult for the above-mentioned
conventional methods to suppress the temperature rise in the early
stage of use and reduce the friction at the same time. For example,
when the kinetic viscosity of the base oil is lowered in order to
suppress the temperature rise in the early stage of use, the oil
film thickness decreases so that metals are more likely to contact
with each other, whereby the friction/wear tends to increase.
Further, there is a fear of the life shortening at a high
temperature.
[0006] Also, under recent circumstances where load has been
increasing as various mechanical elements such as constant velocity
joints, bearings for continuously variable transmissions, and axle
bearings for cars and railway vehicles have been attaining higher
performances and lighter weights, properties demanded for the
grease to suppress the temperature rise in the early stage of use
and lower the friction have been increasing.
[0007] In view of the above-mentioned problem of the prior art, it
is an object of the present invention to provide a grease
composition which can realize, at a high level, the suppression of
the temperature rise in the early stage of use and the reduction of
the friction.
[0008] The inventors conducted diligent studies in order to achieve
the above-mentioned object and, as a result, have found that a
grease composition in which specific diurea and organic molybdenum
compounds are compounded at respective predetermined compounding
ratios in a lubricant base oil can suppress the temperature rise in
constant velocity joints, bearings for continuously variable
transmissions, axle bearings for cars and railway vehicles, and the
like in their early stage of use and lower the friction therein,
thereby completing the present invention.
[0009] Namely, the grease composition in accordance with the
present invention is one containing a lubricant base oil, diurea
compounds represented by the following general formulas (1) to (3),
and an organic molybdenum compound; wherein respective contents of
the diurea compounds represented by the following general formulas
(1) to (3) satisfy conditions defined by the following expressions
(4) and (5); and wherein the organic molybdenum compound is
contained by 0.1 to 20 mass % based on the total amount of the
grease composition: ##STR2## where R.sup.1 is a hydrocarbon group
containing an aromatic ring, R.sup.2 is a divalent hydrocarbon
group, and R.sup.3 is a hydrocarbon group containing an aliphatic
ring; 5.ltoreq.W.sub.1+W.sub.2+W.sub.3.ltoreq.30 (4)
0.1.ltoreq.(W.sub.1+0.5.times.W.sub.2)/(W.sub.1+W.sub.2+W.sub.3).ltoreq.1-
.0 (5) where W.sub.1, W.sub.2, and W.sub.3 are respective contents
(each expressed by the unit of mass %) of the diurea compounds
represented by general formulas (1) to (3) based on the total
amount of the grease composition.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIGS. 1A and 1B are perspective and top plan views showing a
test piece used in a friction test, respectively.
BEST MODES FOR CARRYING OUT THE INVENTION
[0011] In the following, preferred embodiments of the present
invention will be explained in detail.
[0012] Examples of the lubricant base oil used in the grease
composition of the present invention are mineral oils and/or
synthetic oils.
[0013] Examples of the mineral oils are those obtained by a method
usually carried out in a lubricant manufacturing process in a
petroleum refining industry, more specifically, those obtained when
a lubricant fraction yielded by distilling a crude oil under normal
pressure and under reduced pressure is refined by carrying out at
least one of processes of solvent deasphalting, solvent extraction,
hydrocracking, solvent dewaxing, contact dewaxing, hydro-refining,
washing with sulfuric acid, clay treatment, etc.
[0014] Specific examples of the synthetic oils include poly
.alpha.-olefins such as polybutene, 1-octene oligomer, and 1-decene
oligomer or their hydrogenated products; diesters such as
ditridecyl glutarate, di(2-ethylhexyl) adipate, diisodecyl adipate,
ditridecyl adipate, and di(3-ethylhexyl) sebacate; polyol esters
such as trimethylolpropane caprylate, trimethylolpropane
pelargonate, pentaerythritol 2-ethylhexanoate, and pentaerythritol
pelargonate; aromatic ester oils such as trioctyl trimellitate,
tridecyl trimellitate, and tetraoctyl pyromellitate; complex esters
which are esters formed by a mixed fatty acid of a dibasic acid and
a monobasic acid, and a polyhydric alcohol; alkyl naphthalene;
alkyl benzene; polyoxyalkylene glycol; polyphenyl ether;
dialkyldiphenyl ether; silicone oil; and their mixtures.
[0015] The kinetic viscosity of the lubricant base oil at
100.degree. C. is preferably 2 to 40 mm.sup.2/s, more preferably 3
to 20 mm.sup.2/s. The viscosity index of the base oil is preferably
at least 90, more preferably at least 100.
[0016] In the present invention, diurea compounds represented by
the following general formulas (1) to (3) are added as a thickener
to the lubricant base oil: ##STR3##
[0017] In the above-mentioned formulas (1) to (3), R.sup.1 is a
hydrocarbon group containing an aromatic ring. Examples of such a
group include phenyl group, naphthyl group, alkylaryl groups in
which at least one alkyl group is added to these groups as a
substituent, and arylalkyl groups in which aryl groups such as
phenyl and naphthyl groups are added to alkyl groups as
substituents.
[0018] Though the number of carbons in the hydrocarbon group
containing an aromatic ring represented by R.sup.1 is not limited
in particular, one with a carbon number of 7 to 12 is preferably
used. Specific examples of the hydrocarbon group containing an
aromatic ring with such a carbon number include toluyl group, xylyl
group, .beta.-phenacyl group, t-butylphenyl group, dodecylphenyl
group, benzyl group, and methylbenzyl group.
[0019] R.sup.2 in general formulas (1) to (3) is a divalent
hydrocarbon group (preferably with a carbon number of 6 to 20, a
carbon number of 6 to 15 in particular) Examples of such a
hydrocarbon group include linear or branched alkylene groups,
linear or branched alkenylene groups, cycloalkylene groups, and
aromatic groups. Among them, ethylene group,
2,2-dimethyl-4-methylhexylene group, and groups represented by the
following formulas (6) to (14) are preferred, the groups
represented by the formulas (7) and (9) in particular: ##STR4##
[0020] In general formulas (2) and (3), R.sup.3 is a hydrocarbon
group containing an aliphatic ring. Though the number of carbons
contained in the hydrocarbon group containing an aliphatic ring
represented by R.sup.3 is not restricted in particular, one with a
carbon number of 7 to 12 is preferably used.
[0021] As the hydrocarbon group containing an aliphatic ring
represented by R.sup.3, cyclohexyl group or alkylcyclohexyl group
is preferably used. Specific examples include methylcyclohexyl
group, dimethylcyclohexyl group, ethylcyclohexyl group,
diethylcyclohexyl group, propylcyclohexyl group,
isopropylcyclohexyl group, 1-methyl-3-propylcyclohexyl group,
butylcyclohexyl group, pentylcyclohexyl group,
pentylmethylcyclohexyl group, and hexylcyclohexyl group, among
which cyclohexyl group, methylcyclohexyl group, dimethylcyclohexyl
group, and ethylcyclohexyl group are more preferable.
[0022] The respective contents of the diurea compounds represented
by general formulas (1) to (3) are required to satisfy the
conditions represented by the following expressions (4) and (5):
5.ltoreq.W.sub.1+W.sub.2+W.sub.3.ltoreq.30 (4)
0.1.ltoreq.(W.sub.1+0.5.times.W.sub.2)/(W.sub.1+W.sub.2+W.sub.3).ltoreq.1-
.0 (5) where W.sub.1, W.sub.2, and W.sub.3 are respective contents
(each expressed by the unit of mass %) of the diurea compounds
represented by general formulas (1) to (3) based on the total
amount of the grease composition.
[0023] As expression (4) shows, the sum W.sub.1+W.sub.2+W.sub.3 of
contents of the diurea compounds represented by general formulas
(1) to (3) is 5 to 30 mass % based on the total amount of the
grease composition. When the sum W.sub.1+W.sub.2+W.sub.3 is less
than 5 mass %, the effect of the thickener is so weak that the
composition fails to become sufficiently greasy. For the same
reason, W.sub.1+W.sub.2+W.sub.3 is preferably at least 10 mass %.
When W.sub.1+W.sub.2+W.sub.3 exceeds 30 mass %, the composition
becomes too hard as a grease, thereby failing to exhibit a
sufficient lubricating property. For the same reason,
W.sub.1+W.sub.2+W.sub.3 is preferably 20 mass % or less.
[0024] When (W.sub.1+0.5.times.W.sub.2)/(W.sub.1+W.sub.2+W.sub.3)
in expression (5) is less than 0.1, the effect of suppressing the
temperature rise in the early stage of use becomes weaker. For the
same reason, (W.sub.1+0.5.times.W.sub.2)/(W.sub.1+W.sub.2+W.sub.3)
is preferably at least 0.2, more preferably at least 0.3, further
preferably at least 0.4. Similarly, from the viewpoint of the
effect of suppressing the temperature rise in the early stage of
use, (W.sub.1+0.5.times.W.sub.2)/(W.sub.1+W.sub.2+W.sub.3) is
preferably not greater than 0.7, more preferably less than 0.55,
further preferably less than 0.5.
[0025] Though urea type thickeners apt to become harder as time
passes in general, the grease composition of the present invention
is relatively less likely to harden. For making it further less
likely to harden,
(W.sub.1+0.5.times.W.sub.2)/(W.sub.1+W.sub.2+W.sub.3) is preferably
at least 0.3, more preferably at least 0.35, further preferably at
least 0.4, at least 0.45 in particular.
[0026] For example, these diurea compounds are obtained when a
diisocyanate represented by the general formula of
OCN--R.sup.2--NCO and an amine represented by the general formula
of R.sup.1--NH.sub.2 and/or R.sup.3--NH.sub.2 are caused to react
against each other at a temperature of 10.degree. to 200.degree. C.
in the base oil. Here, R.sup.1, R.sup.2, and R.sup.3 correspond to
those of (1) to (3), respectively.
[0027] When the value of
(W.sub.1+0.5.times.W.sub.2)/(W.sub.1+W.sub.2+W.sub.3) in expression
(5) is not 1, the diurea compounds may be a mixture of a reaction
product of diisocyanate and the amine represented by
R.sup.1--NH.sub.2, and a reaction product of diisocyanate and the
amine represented by R.sup.3--NH.sub.2; or a reaction product of
diisocyanate and a mixture of the amine represented by
R.sup.1--NH.sub.2 and the amine represented by
R.sup.3--NH.sub.2.
[0028] The grease composition of the present invention further
contains an organic molybdenum compound in addition to the
above-mentioned lubricant base oil and diurea compounds. Examples
of the organic molybdenum compound include a phosphate or
thiophosphate ester derivative represented by the following general
formula (15) and a dithiocarbamate ester derivative represented by
the following general formula (16): ##STR5##
[0029] In general formulas (15) and (16), R may be identical or
different, each representing a hydrocarbon group with a carbon
number of at least 1; c pieces of X may be identical or different,
each representing an oxygen atom or sulfur atom; and each of a, b,
and c represents an integer of 1 to 6.
[0030] Examples of the hydrocarbon group represented by R in the
above-mentioned formulas (15) and (16) include alkyl groups with a
carbon number of 1 to 24, cycloalkyl groups with a carbon number of
5 to 7, alkylcycloalkyl groups with a carbon number of 6 to 11,
aryl groups with a carbon number of 6 to 18, alkylaryl groups with
a carbon number of 7 to 24, and arylalkyl groups with a carbon
number of 7 to 12.
[0031] Specific examples of the above-mentioned alkyl groups
include methyl group, ethyl group, propyl group (including all the
branched isomers thereof), pentyl group (including all the branched
isomers thereof), hexyl group (including all the branched isomers
thereof), heptyl group (including all the branched isomers
thereof), octyl group (including all the branched isomers thereof),
nonyl group (including all the branched isomers thereof), decyl
group (including all the branched isomers thereof), undecyl group
(including all the branched isomers thereof), dodecyl group
(including all the branched isomers thereof), tridecyl group
(including all the branched isomers thereof), tetradecyl group
(including all the branched isomers thereof), pentadecyl group
(including all the branched isomers thereof), hexadecyl group
(including all the branched isomers thereof), heptadecyl group
(including all the branched isomers thereof), octadecyl group
(including all the branched isomers thereof), nonadecyl group
(including all the branched isomers thereof), icosyl group
(including all the branched isomers thereof), henicosyl group
(including all the branched isomers thereof), docosyl group
(including all the branched isomers thereof), tricosyl group
(including all the branched isomers thereof), and tetracosyl group
(including all the branched isomers thereof).
[0032] Specific examples of the above-mentioned cycloalkyl groups
include cyclopentyl group, cyclohexyl group, and cycloheptyl
group.
[0033] Specific examples of the above-mentioned alkylcycloalkyl
groups include methylcyclopentyl group (including all the
substituted isomers thereof), ethylcyclopentyl group (including all
the substituted isomers thereof), dimethylcyclopentyl group
(including all the substituted isomers thereof), propylcyclopentyl
group (including all the branched isomers and substituted isomers
thereof), methylethylcyclopentyl group (including all the
substituted isomers thereof), trimethylcyclopentyl group (including
all the substituted isomers thereof), butylcyclopentyl group
(including all the branched isomers and substituted isomers
thereof), methylpropylcyclopentyl group (including all the branched
isomers and substituted isomers thereof), diethylcyclopentyl group
(including all the substituted isomers thereof),
dimethylcyclopentyl group (including all the substituted isomers
thereof), methylcyclohexyl group (including all the substituted
isomers thereof), ethylcyclohexyl group (including all the
substituted isomers thereof), dimethylcyclohexyl group (including
all the substituted isomers thereof), propylcyclohexyl group
(including all the branched isomers and substituted isomers
thereof), methylethylcyclohexyl group (including all the
substituted isomers thereof), trimethylcyclohexyl group (including
all the substituted isomers thereof), butylcyclohexyl group
(including all the branched isomers and substituted isomers
thereof), methylpropylcyclohexyl group (including all the branched
isomers and substituted isomers thereof), diethylcyclohexyl group
(including all the substituted isomers thereof),
dimethylethylcyclohexyl group (including all the substituted
isomers thereof), methylcycloheptyl group (including all the
substituted isomers thereof), ethylcycloheptyl group (including all
the substituted isomers thereof), dimethylcycloheptyl group
(including all the substituted isomers thereof), propylcycloheptyl
group (including all the substituted isomers thereof),
methylethylcycloheptyl group (including all the substituted isomers
thereof), trimethylcycloheptyl group (including all the substituted
isomers thereof), butylcycloheptyl group (including all the
branched isomers and substituted isomers thereof),
methylpropylcycloheptyl group (including all the branched isomers
and substituted isomers thereof), diethylcycloheptyl group
(including all the substituted isomers thereof), and
dimethylethylcycloheptyl group (including all the substituted
isomers thereof).
[0034] Specific examples of the above-mentioned aryl groups include
phenyl group and naphthyl group.
[0035] Specific examples of the above-mentioned alkylaryl groups
include tolyl group (including all the substituted isomers
thereof), xylyl group (including all the substituted isomers
thereof), ethylphenyl group (including all the substituted isomers
thereof), propylphenyl group (including all the branched isomers
and substituted isomers thereof), methylethylphenyl group
(including all the substituted isomers thereof), trimethylphenyl
group (including all the substituted isomers thereof), butylphenyl
group (including all the branched isomers and substituted isomers
thereof), methylpropylphenyl group (including all the branched
isomers and substituted isomers thereof), diethylphenyl group
(including all the substituted isomers thereof),
dimethylethylphenyl group (including all the substituted isomers
thereof), pentylphenyl group (including all the branched isomers
and substituted isomers thereof), hexylphenyl group (including all
the branched isomers and substituted isomers thereof), heptylphenyl
group (including all the branched isomers and substituted isomers
thereof), octylphenyl group (including all the branched isomers and
substituted isomers thereof), nonylphenyl group (including all the
branched isomers and substituted isomers thereof), decylphenyl
group (including all the branched isomers and substituted isomers
thereof), undecylphenyl group (including all the branched isomers
and substituted isomers thereof), dodecylphenyl group (including
all the branched isomers and substituted isomers thereof),
tridecylphenyl group (including all the branched isomers and
substituted isomers thereof), tetradecylphenyl group (including all
the branched isomers and substituted isomers thereof),
pentadecylphenyl group (including all the branched isomers and
substituted isomers thereof), hexadecylphenyl group (including all
the branched isomers and substituted isomers thereof),
heptadecylphenyl group (including all the branched isomers and
substituted isomers thereof), and octadecylphenyl group (including
all the branched isomers and substituted isomers thereof).
[0036] Examples of the arylalkyl groups include benzyl group,
phenethyl group, phenylpropyl group (including all the branched
isomers thereof), and phenylbutyl group (including all the branched
isomers and substituted isomers thereof).
[0037] Specific examples of the compounds represented by the
above-mentioned general formulas (15) and (16) include molybdenum
phosphate, molybdenum thiophosphate, molybdenum dithiophosphate,
and molybdenum dithiocarbamate.
[0038] The phosphate or thiophosphate ester derivative represented
by the above-mentioned formula (15) and the dithiocarbamate ester
derivative represented by the above-mentioned formula (16) are
compounds usually obtained by causing a phosphate ester, a
thiophosphate ester, or a dithiocarbamate ester to react with an
inorganic molybdenum compound (molybdenum trioxide, molybdenum
oxide, salts thereof, etc.) together with a sulfur source if
necessary.
[0039] Since molybdenum can take various valences, the compounds
obtained by the above-mentioned reaction are usually mixtures.
Among them, the most typical compounds are those represented by the
following compounds (17) and (18): ##STR6##
[0040] As the organic molybdenum compound in the present invention,
the respective compounds represented by the above-mentioned general
formulas (15) and (16) may be used separately or in a mixture. For
use in bearing grease, the compound represented by the
above-mentioned general formula (16) is more preferable because of
its better thermal stability.
[0041] The content of the organic molybdenum compound in the
present invention is at least 0.1 mass %, preferably at least 0.5
mass %, based on the total amount of the grease composition. On the
other hand, the content is not greater than 20 mass %, preferably
not greater than 10 mass %. The friction reducing effect of the
grease is insufficient when the content of the organic molybdenum
compound is less than 0.1 mass %, whereas the friction reducing
effect cannot be obtained in proportion to the amount of addition
when the content exceeds 20 mass %.
[0042] For improving the resistance to fretting, it will be
preferred if at least one species of compound selected from the
group consisting of paraffin oxides and phosphorus compounds is
added to the grease composition of the present invention. When
these compounds are added, a higher level of resistance to fretting
can be achieved over a long period in a constant velocity joint in
which micromotion wear (fretting) is likely to become problematic
upon minute reciprocation in particular.
[0043] Examples of the paraffin oxides used in the present
invention include paraffin oxide, salts of paraffin oxide, and
esters of paraffin oxide. Examples of paraffin oxide mentioned here
include those obtained by oxidizing petroleum waxes such as
paraffin wax, microcrystalline wax, and slack wax, or a synthetic
wax such as polyolefin wax. Examples of the salts of paraffin oxide
include alkali metal salts, alkaline earth metal salts, and amine
salts of paraffin oxide. Examples of the esters of paraffin oxide
include esters formed between an alcohol (most preferably methanol)
having a carbon number of 1 to 24 (preferably 1 to 12, more
preferably 1 to 6) and paraffin oxide. The paraffin oxides used in
the present invention may have any properties. However, from the
viewpoint of the resistance to fretting, their melting point is
preferably at least 25.degree. C., more preferably 30.degree. C.,
but preferably not higher than 110.degree. C., more preferably not
higher than 70.degree. C. The total acid number is preferably at
least 0.2 mgKOH/g, more preferably at least 1 mgKOH/g, but
preferably not greater than 65 mgKOH/g, more preferably not greater
than 40 mgKOH/g.
[0044] Specific examples of the phosphorus compounds include
phosphate esters, acid phosphate esters, amine salts of acid
phosphate esters, chlorinated phosphate esters, phosphite esters,
and thiophosphate esters. These phosphorus compounds are esters
formed between phosphoric acid, phosphorous acid, or thiophosphoric
acid and an alkanol or polyether alcohol, or their derivatives.
[0045] More specific examples of phosphate esters include tributyl
phosphate, tripentyl phosphate, trihexyl phosphate, triheptyl
phosphate, trioctyl phosphate, trinonyl phosphate, tridecyl
phosphate, triundecyl phosphate, tridodecyl phosphate, tritridecyl
phosphate, tritetradecyl phosphate, tripentadecyl phosphate,
trihexadecyl phosphate, triheptadecyl phosphate, trioctadecyl
phosphate, trioleyl phosphate, triphenyl phosphate, tricresyl
phosphate, trixylenyl phosphate, cresyldiphenyl phosphate, and
xylenyldiphenyl phosphate.
[0046] Examples of the acid phosphate esters include monobutyl acid
phosphate, monopentyl acid phosphate, monohexyl acid phosphate,
monoheptyl acid phosphate, monooctyl acid phosphate, monononyl acid
phosphate, monodecyl acid phosphate, monoundecyl acid phosphate,
monododecyl acid phosphate, monotridecyl acid phosphate,
monotetradecyl acid phosphate, monopentadecyl acid phosphate,
monohexadecyl acid phosphate, monoheptadecyl acid phosphate,
monooctadecyl acid phosphate, monooleyl acid phosphate, dibutyl
acid phosphate, dipentyl acid phosphate, dihexyl acid phosphate,
diheptyl acid phosphate, dioctyl acid phosphate, dinonyl acid
phosphate, didecyl acid phosphate, diundecyl acid phosphate,
didodecyl acid phosphate, ditridecyl acid phosphate, ditetradecyl
acid phosphate, dipentadecyl acid phosphate, dihexadecyl acid
phosphate, diheptadecyl acid phosphate, dioctadecyl acid phosphate,
and dioleyl acid phosphate.
[0047] Examples of the amine salts of acid phosphate esters include
salts formed between the acid phosphate esters and amines such as
methylamine, ethylamine, propylamine, butylamine, pentylamine,
hexylamine, heptylamine, octylamine, dimethylamine, diethylamine,
dipropylamine, dibutylamine, dipentylamine, dihexylamine,
diheptylamine, dioctylamine, trimethylamine, triethylamine,
tripropylamine, tributylamine, tripentylamine, trihexylamine,
triheptylamine, and trioctylamine.
[0048] Examples of the chlorinated phosphate esters include
tris(dichloropropyl)phosphate, tris(chloroethyl)phosphate,
tris(chlorophenyl)phosphate, and polyoxyalkylene
bis[di(chloroalkyl)]phosphate.
[0049] Examples of the phosphite esters include phosphite diesters
such as dibutyl hydrogen phosphite, dipentyl hydrogen phosphite,
dihexyl hydrogen phosphite, diheptyl hydrogen phosphite, dioctyl
hydrogen phosphite, dinonyl hydrogen phosphite, didecyl hydrogen
phosphite, diundecyl hydrogen phosphite, didodecyl hydrogen
phosphite, dioleyl hydrogen phosphite, diphenyl hydrogen phosphite,
and dicresyl hydrogen phosphite; and phosphite triesters such as
tributyl phosphite, tripentyl phosphite, trihexyl phosphite,
triheptyl phosphite, trioctyl phosphite, trinonyl phosphite,
tridecyl phosphite, triundecyl phosphite, tridodecyl phosphite,
trioleyl phosphite, triphenyl phosphite, and tricresyl
phosphite.
[0050] Examples of phosphorothionate include tributyl
phosphorothionate, tripentyl phosphorothionate, trihexyl
phosphorothionate, triheptyl phosphorothionate, trioctyl
phosphorothionate, trinonyl phosphorothionate, tridecyl
phosphorothionate, triundecyl phosphorothionate, tridodecyl
phosphorothionate, tritridecyl phosphorothionate, tritetradecyl
phosphorothionate, tripentadecyl phosphorothionate, trihexadecyl
phosphorothionate, triheptadecyl phosphorothionate, trioctadecyl
phosphorothionate, trioleyl phosphorothionate, triphenyl
phosphorothionate, tricresyl phosphorothionate, trixylenyl
phosphorothionate, cresyldiphenyl phosphorothionate,
xylenyldiphenyl phosphorothionate,
tris(n-propylphenyl)phosphorothionate,
tris(isopropylphenyl)phosphorothionate,
tris(n-butylphenyl)phosphorothionate,
tris(isobutylphenyl)phosphorothionate,
tris(s-butylphenyl)phosphorothionate, and
tris(t-butylphenyl)phosphorothionate.
[0051] The above-mentioned phosphorus compounds may be used one by
one or in a mixture of two or more.
[0052] Among them, because of better resistance to fretting,
phosphite esters are preferable, phosphite diesters are more
preferable, and diphenyl hydrogen phosphite is further
preferable.
[0053] The content of at least one compound selected from the group
consisting of the paraffin oxides and phosphorus compounds is
preferably at least 0.5 mass %, more preferably at least 1.0 mass
%, based on the total amount of the grease composition. When the
content is less than 0.5 mass %, the resistance to fretting tends
to become insufficient in the grease. On the other hand, the
content is preferably not greater than 15 mass %, more preferably
10 mass %. When the content exceeds 15 mass %, the resistance to
fretting cannot be obtained in proportion to the amount of
addition.
[0054] For further improving the resistance to fretting,
(W.sub.1+0.5.times.W.sub.2)/(W.sub.1+W.sub.2+W.sub.3) in expression
(5) is preferably at least 0.3, more preferably at least 0.35,
further preferably at least 0.4, furthermore preferably at least
0.45, but is preferably not greater than 0.7, more preferably not
greater than 0.6, further preferably less than 0.5.
[0055] For improving performances, the grease composition of the
present invention can further contain solid lubricants, extreme
pressure agents, antioxidants, oily agents, antirusts, viscosity
index improvers, etc. when necessary as long as its properties do
not deteriorate.
[0056] Specific examples of the solid lubricants include graphite,
graphite fluoride, polytetrafluoroethylene, molybdenum disulfide,
antimony sulfide, and alkali (earth) metal borates.
[0057] Specific examples of the extreme pressure agents include
organic zinc compounds such as zinc dialkyldithiophosphate and zinc
diaryldithiophosphate; and sulfur-containing compounds such as
dihydrocarbyl polysulfide, sulfide esters, thiazole compounds, and
thiadiazole compounds.
[0058] Specific examples of the antioxidants include phenol type
compounds such as 2,6-di-t-butylphenol and 2,6-di-t-butyl-p-cresol;
amine type compounds such as dialkyldiphenylamine,
phenyl-.alpha.-naphthylamine, and
p-alkylphenyl-.alpha.-naphthylamine; sulfur type compounds; and
phenothiazine type compounds.
[0059] Specific examples of the oily agents include amines such as
laurylamine, myristylamine, palmitylamine, stearylamine, and
oleylamine; higher alcohols such as lauryl alcohol, myristyl
alcohol, palmityl alcohol, stearyl alcohol, and oleyl alcohol;
higher fatty acids such as lauric acid, myristic acid, palmitic
acid, stearic acid, and oleic acid; fatty acid esters such as
methyl laurate, methyl myristate, methyl palmitate, methyl
stearate, and methyl oleate; amides such as laurylamide,
myristylamide, palmitylamide, stearylamide, and oleylamide; and
fats and oils.
[0060] Specific examples of the antirusts include metal soaps;
polyhydric alcohol partial esters such as sorbitan fatty acid
esters; amines; phosphoric acid; and phosphates.
[0061] Specific examples of the viscosity index improvers include
polymethacrylate, polyisobutylene, and polystyrene.
[0062] The grease composition of the present invention can be
prepared, for example, by mixing and stirring the diurea compounds
represented by general formulas (1) to (3) and an organic
molybdenum compound, together with other additives if necessary,
with a lubricant base oil; and passing thus obtained mixture
through a roll mill or the like. The grease composition can also be
made by adding the material components of the diurea compounds
represented by general formulas (1) to (3) to the lubricant base
oil beforehand; melting them together; stirring and mixing them so
as to prepare the diurea compounds; then mixing and stirring them
with the organic molybdenum compound, together with other additives
if necessary; and passing thus obtained mixture through a roll mill
or the like.
[0063] The grease composition of the present invention is excellent
in suppressing temperature rises and reducing friction, and thus is
useful as a grease for various gears of constant velocity joints,
constant velocity gears, and transmission gears, and various
bearings such as ball bearings and roller bearings, and is
favorably used in constant velocity joints, bearings for
continuously variable transmissions, gears and bearings for
ironmaking equipment, axle bearings for cars/railway vehicles, etc.
in particular.
EXAMPLES
[0064] In the following, details of the present invention will be
explained more specifically with reference to examples and
comparative examples. However, the following examples do not
restrict the present invention at all.
Examples 1 to 7 and Comparative Examples 1 to 5
[0065] Using poly-.alpha.-olefin (having a kinetic viscosity of 48
mm.sup.2/s at 40.degree. C.) as a lubricant base oil,
diphenylmethane-4,4'-diisocyanate (MDI) was dissolved into the base
oil by heating, and monoamines listed in Tables 1 and 2, each
dissolved in the base oil, were added thereto. Various additives
listed in the following were added to thus generated gel-like
materials, so as to yield the compositions shown in Tables 1 and 2,
and after stirring, the resulting mixtures were passed through a
roll mill, so as to yield the grease compositions of Examples 1 to
7 and Comparative Examples 1 to 5. The values of
W.sub.1+W.sub.2+W.sub.3 and
(W.sub.1+0.5.times.W.sub.2)/(W.sub.1+W.sub.2+W.sub.3) in thus
obtained grease compositions are shown in Tables 1 and 2. In Table
2, the cells for W.sub.1+W.sub.2+W.sub.3 in Comparative Examples 4
and 5 show their respective total thickener amounts instead of
W.sub.1+W.sub.2+W.sub.3.
[0066] Additives:
[0067] MoDTC (molybdenum dioctyldithiocarbamate)
[0068] MoDTP (molybdenum dioctyldithiophosphate)
[0069] MoP (molybdenum dibutylphosphate)
[0070] Boron type friction modifier (potassium borate type friction
modifier)
[0071] paraffin oxide (paraffin oxide ester (ester formed between
paraffin oxide obtained by oxidizing slack wax and methanol, with a
total acid number of 33 mgKOH/g and a saponification number of 130
mgKOH/g))
[0072] dihydrogen phosphite (diphenyl hydrogen phosphite)
[0073] The following temperature rise and friction tests were
carried out for the grease compositions of Examples 1 to 7 and
Comparative Examples 1 to 5.
[0074] Temperature Rise Test
[0075] Into a deep groove ball bearing having an inner ring
diameter of 55 mm, an outer ring diameter of 90 mm, and a width of
11 mm, 4.0 g of grease were sealed, and the bearing was rotated
under a condition with an inner ring rotating speed of 9000 rpm and
an axial load of 5000 N. The bearing outer ring temperature at that
time was measured, whereby a temperature rise .DELTA.T was
determined. Thus obtained results are shown in Tables 1 and 2.
[0076] Friction Test
[0077] FIGS. 1A and 1B are perspective and top plan views showing a
test piece used in a friction test, respectively. As depicted, a
needle holder 2 (14 mm.times.10 mm.times.2.5 mm) formed at the
center part of a lower disc 1 (24 mm in diameter.times.7.9 mm) was
filled with 1 g of each grease composition. Then, three needles
(each having a size of 3 mm in diameter.times.13.8 mm) were
accommodated in the needle holder 2, and an upper disc 4 (20 mm in
diameter.times.13 mm) was disposed thereon. These test pieces were
set in, an SRV friction tester such that the angle .theta. [deg]
(needle set angle) formed between a line l.sub.1, perpendicular to
sliding directions of the upper disc 4, passing the center O of the
upper face of the lower disc 1 and a line l.sub.2, parallel to the
longitudinal direction of the needle 3, passing the center O became
30 deg, and a friction test was carried out under a condition with
a frequency of 40 Hz, an amplitude of 3 mm, a load of 1000 N, and a
temperature of 80.degree. C. Table 1 and 2 show the respective
friction coefficients obtained 10 minutes thereafter when using the
individual grease compositions.
[0078] Fretting Resistance Test
[0079] Using a Fafnir friction oxidation tester, a fretting
resistance test was carried out in conformity to ASTM D4170, so as
to measure the amount of wear. Using a thrust bearing 51204
(manufactured by NSK Ltd.) as a bearing, the test was conducted for
2 hours at room temperature. In this test, the grease compositions
made 1 day before were used as samples. Tables 1 and 2 show the
results.
[0080] Measurement of Consistency
[0081] For each of the grease compositions of Examples 1 to 7 and
Comparative Examples 1 to 5, consistency was measured after the
lapse of 1 day from the making and after the lapse of 3 months from
the making. Tables 1 and 2 show the results. TABLE-US-00001 TABLE 1
Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example
7 Thickener MDI[mol] 5 10 5 1 10 10 10 monoamine p-toluidine 1 9 7
2 9 9 9 [mol] cyclohexylamine 9 11 3 -- 11 11 11 octadecylamine --
-- -- -- -- -- -- W.sub.1 + W.sub.2 + W.sub.3 [mass %] 18 18 18 20
18 18 18 (W.sub.1 + 0.5 .times. W.sub.2) 0.1 0.45 0.7 1.0 0.45 0.45
0.45 {overscore ((W.sub.1 + W.sub.2 + W.sub.3))} Base oil PAO [mass
%] 80 80 80 78 77 79 77.5 Additive MoDTC [mass %] 2 2 2 2 -- -- 2
MoDTP [mass %] -- -- -- -- 5 -- -- MoP [mass %] -- -- -- -- -- 3 --
boron type friction modifier [mass %] -- -- -- -- -- -- -- paraffin
oxide [mass %] -- -- -- -- -- -- 2 dihydrogen phosphite [mass %] --
-- -- -- -- -- 0.5 Temperature rise .DELTA.T (.degree. C.) 104 94
100 98 97 102 105 Friction coefficient 0.090 0.070 0.080 0.085
0.080 0.090 0.080 Fretting resistance (amount of wear [mg]) 2.9 1.6
2.7 2.8 1.8 1.8 0.2 Consistency (60 W) 1 day after making 272 286
295 293 300 291 296 3 months after making 257 282 298 291 305 288
290
[0082] TABLE-US-00002 TABLE 2 Comparative Comparative Comparative
Comparative Comparative Example 1 Example 2 Example 3 Example 4
Example 5 Thickener MDI[mol] 1 10 10 1 1 monoamine p-toluidine -- 9
9 -- -- [mol] cyclohexylamine 2 11 11 1 1 octadecylamine -- -- -- 1
1 W.sub.1 + W.sub.2 + W.sub.3 [mass %] 18 18 18 (18) (18) (W.sub.1
+ 0.5 .times. W.sub.2) 0 0.45 0.45 0 0 {overscore ((W.sub.1 +
W.sub.2 + W.sub.3))} Base oil PAO [mass %] 80 82 80 80 77.5
Additive MoDTC [mass %] 2 -- -- 2 2 MoDTP [mass %] -- -- -- -- --
MoP [mass %] -- -- -- -- -- boron type friction modifier [mass %]
-- -- 2 -- -- paraffin oxide [mass %] -- -- -- -- 2 dihydrogen
phosphite [mass %] -- -- -- -- 0.5 Temperature rise .DELTA.T
(.degree. C.) 138 130 135 >150 >150 Friction coefficient
0.120 0.130 0.095 0.130 0.130 Fretting resistance (amount of wear
[mg]) 7.0 2.0 2.1 8.5 1.5 Consistency (60 W) 1 day after making 275
281 288 270 276 3 months after making 252 283 289 227 214
[0083] As shown in Table 1, it was verified that the grease
compositions of Examples 1 to 7 were excellent in friction
characteristics and temperature rise suppression. Also, the grease
compositions of Examples 6 and 7 to which a paraffin oxide and a
phosphorus compound were added exhibited a very high level of
resistance to fretting.
[0084] By contrast, the grease composition of Comparative Example 1
shown in Table 2 was insufficient in terms of friction
characteristics, whereas temperature rose greatly when the grease
compositions of Comparative Examples 2 and 3 were used.
INDUSTRIAL APPLICABILITY
[0085] As explained in the foregoing, by adding the diurea
compounds represented by general formulas (1) to (3) and an organic
molybdenum compound into a lubricant base oil at their respective
specific compounding ratios, the grease composition of the present
invention can realize, at a high level, the suppression of the
temperature rise in the early stage of use and the reduction of the
friction.
* * * * *