DESCRIPTION
TitIe of Invention: GREASE COMPOSITION
Technical Field
[0001] The present invention relates to a grease composition.
5 Background Art
[0002] A grease is a semi-solid lubricant prepared by dispersing a
fibrous thickener in a base oil, and readily adheres to portions to be
lubricated and barely leaks therefrom compared to lubricant oils. For
this reason, the grease can simplify the structure of a lubricant system;
10 the grease is used mainly in lubrication of mechanical components such
as antifriction bearings, sliding bearings, ball screws, linear guides, and
gears, and is widely used in industrial machines and mechanical systems
for transportation.
[0003] While a reduction in energy consumption has been demanded
15 recently, a reduction in energy loss of a variety of mechanical systems
has been also an urgent problem to be solved. In cases of engine oils
for vehicles, it is believed that it is effective to reduce the viscosity of
the lubricating base oil as much as possible to ensure low he1
consumption, and to optimize the formulation with a variety of additives
20 such as a friction reducing agent to reduce energy loss due to the
viscous resistance of the lubricant oil and reduce the frictional resistance
of a sliding portion (Patent Literature 1).
[0004] On the other hand, in the viscous resistance of a grease which is
a non-Newtonian fluid, not only the viscosity of the base oil but also an
25 apparent viscosity including the structwal viscosity attributed to the
fibrous thickener dispersed in the base oil should be considered. The
apparent viscosity can be simply expressed in terms of so-called
consistency; it is known that as the consistency is high (soft), the
viscous resistance is low won Patent Literature 1).
Citation List
5 Patent Literature
[0005] Patent Literature 1 : Japanese Unexamined Patent Publication
NO. 2012-102281
Non Patent Literature
[0006] Non Patent Literature 1: Junkatuguriisu no Kiso to Oyou (Basics
10 and Applications of Lubricating Greases), pp. 49 to 89, edited by Grease
Working Group, Japanese Society of Tribologists, Yokendo Co., Ltd.,
2007
Summary of Invention
Technical Problem
15 [0007J However, it is not always easy for the grease to ensure an
appropriate consistency suitable for application to mechanical systems
while the viscous resistance is reduced. Namely, if the grease is
excessively soft, the grease scatters due to a centrifugal force
accompanied by a rotary motion, or leaks from mechanical components.
20 In contrast, if the grease is excessively hard, sliding resistance is
generated to obstruct a desired motion. Namely, in cases of
conventional greases, an optimal formulation has been carried out only
by adjusting a balance between the base oil composition and the amount
of the thickener, and any other way has not been found.
25 [0008] The problem to be solved by the present invention is to provide
a grease composition which has a low sliding resistance and can
significantly reduce the power consumption of mechanical components,
particularly the power consumption during rotation of bearings.
Solution to Problem
[0009] The present inventors, who have conducted extensive research
5 to solve the problem above, have found that a mixture of predetermined
amounts of specific base oils having different properties as base oils for
a grease can significantly reduce power consumption during rotation of
bearings compared to greases in which the base oils are used singly.
[0010] To reduce the energy needed to rotate a bearing to reduce energy
10 consumption, it is important to reduce the rolling resistance and the
sliding resistance between a rotational element of a bearing (ball, roller)
and bearing rings (inner ring and outer ring) as much as possible;
usually, it is believed that a reduction in the viscosity of a base oil for a
lubricant oil agent (lubricant oil or grease) and compounding, as an
15 additive, of an oiliness improver having an effect of reducing friction
are effective. However, in the case of the grease, a base oil needs to be
exposed to a high temperature condition during production of a
thickener; therefore, a reduction in viscosity has been limited because of
evaporation of the base oil and safety reasons. Furthermore, the
20 additives for reducing friction have a problem in that the effects are
reduced with the time of service. In contsast, the present inventors
have paid attention to the oil film forming ability of the sliding portion
of the bearing and a change in viscosity caused by the temperature of
the lubricating base oil, and have found that to form a sufficient oil film
25 between the rotational element of the bearing and the bearing ring to
reduce the energy loss caused by direct contact of these components,
containing a component having a molecule having a large steric
structure, specifically a component (%Ca determined by n-d-M ring
analysis) containing an aromatic compound in the base oil components,
and containing a paraffin component having a high viscosity index
5 (%CP determined by n-d-M ring analysis) in a good balance to prevent a
reduction in viscosity accompanied by an increase in temperature are
effective.
[0011] The present invention has been made based on the above
knowledge, and provides a grease composition according to [I] to [9].
10 [0012] [1] A grease composition comprising: a lubricating base oil;
and a thickener, wherein the lubricating base oil comprises
a first lubricating base oil having a %CA of 2 to 8 and a %Cp of 50 to 75,
the %CA and the %Cp being values determined by n-d-M ring analysis
according to ASTM D3238, and a second lubricating base oil having
15 a %CA of 1 or less, a %Cp of 70 or more, and a urea adduct value of 4%
by mass or less, the %CA and the %Cp being values determined by
n-d-M ring analysis according to ASTM D3238, and wherein a content
of the first lubricating base oil is 5 to 90% by mass and a content of the
second lubricating base oil is 10 to 95% by mass, based on a total
20 amount of the lubricating base oil.
[2] The grease composition according to [I], wherein the
grease composition has a consistency of 220 to 300.
[3] The grease composition according to [I] or [2], further
comprising an osganomolybdenum compound.
[4] The grease composition according to [3], wherein the
organomolybdenum compound comprises at least one selected from
molybdenum dithiocarbamates and molybdenum dithiophosphates.
[5] The grease composition according to any one of [I] to
[4], wherein the first lubricating base oil has a kinematic viscosity at
40°C of 10 to 700 rnm2/s and a viscosity index of 90 to 120.
5 [6] The grease composition according to any one of [I] to
[5], wherein the second lubricating base oil has a kinematic viscosity at
40°C of 10 to 5000 mm2/s and a viscosity index of 110 to 150.
[7] The grease composition according to any one of [I] to
[6], wherein the second lubricating base oil compsises at least one
10 selected from mineral oils and synthetic hydrocarbons.
[8] The grease composition according to any one of [I] to
[7], wherein the thickener comprises at least one selected from metal
soap compounds and urea compounds.
[9] A grease composition comprising: a lubricating bke oil;
15 a thickener; and an organomolybdenurn compound, wherein the
lubricating base oil comprises a first lubricating base oil having a %CA
of 2 to 8 and a %Cp of 50 to 75, the %CA and the %Cp being values
determined by n-d-M ring analysis according to ASTM D3238, and a
second lubricating base oil having a %CA of 1 or less and a %Cp of 70
20 or more, the %CA and the %Cp being values determined by n-d-M ring
analysis according to ASTM D3238, wherein a content of the first
lubricatiug base oil is 5 to 90% by mass and a content of the second
lubricating base oil is 10 to 95% by mass, based on a total amount of the
lubricating base oil, and wherein the grease composition has a
25 consistency of 220 to 300.
Advantageous Effects of Invention
[0013] The grease composition according to the present invention
attains a significant effect that the amount of electric power consumed
during rotation of bearings is small.
Description of Embodime~~fs
5 [0014] Hereinafter, suitable embodiments according to the present
invention will be described in detail.
[0015] The grease composition according to an embodiment of the
present invention comprises a lubricating base oil and a thickener. The
lubricating base oil comprises a first lubricating base oil having a %CA
10 of 2 to 8 and a %Cp of 50 to 75, which are values determined by n-d-M
ring analysis according to ASTM D3238, and a second lubricating base
oil having a %CA of 1 or less and a %Cp of 70 or more, which are values
detesmined by n-d-M ring analysis according to ASTM D3238, and a
urea adduct value of 4% by mass or less. In the mixing ratio of the
15 first lubricating base oil to the second lubricating base oil, the content of
the first lubricating base oil is 5 to 90% by mass and the content of the
second lubricating base oil is 10 to 95% by mass based on the total
amount of the lubricating base oil.
[0016] In the present embodiment, the present inventors have paid
20 attention to the oil film forming ability of the sliding portion of the
bearing and a change in viscosity caused by the temperature of the
lubricating base oil, and has found a knowledge that to fomi a sufficient
oil film between the rotational element of the bearing and the bearing
ring to reduce the energy loss caused by direct contact of these
25 components, a "wedge effect" accompanied by rotation of the bearing
ring and the rotational element of the bearing is utilized, and containing
a base oil forming molecule having a large stei-ic stlucture, specifically a
component PACA determined by n-d-M ring analysis) containing an
aromatic in the base oil components is effective; based on this
knowledge, the first lubricating base oil is used.
5 [0017] In the values determined by n-d-M ring analysis according to
ASTM D3238, the first lubricating base oil has a %Ca of 2 to 8,
preferably 2 to 6, more preferably 4 to 6. If the %CA is less than 2, the
effect of reducing energy loss is insufficient, and if the %CA is more
than 8, the content of the paraftin component is readily relatively
10 reduced, resulting in a lasge reduction in viscosity at high temperatures
and thus an insufficient oil film forming ability.
[0018] The first lubricating base oil has a %Cp of 50 to 75, preferably
60 to 70. If the %Cp is less than 50, a reduction in viscosity at high
tempemtures is large and the oil film forming ability is inferior, and if
15 the %Cp is more than 75, the content of the component containing an
aromatic is readily relatively reduced, and the effect of reducing enesgy
loss is insufficient.
[0019] The viscosity index of the first lubricating base oil is preferably
90 to 120, more preferably 95 to 115, still more preferably 100 to 110.
20 If the viscosity index is 90 or more, a reduction in viscosity caused by
an increase in temperature can be prevented, fhther improving the oil
film forming ability.
[0020] The kinematic viscosity at 40°C of the first lubricating base oil
is not limited in particular; to safely prepare a gsease having excellent
25 lubrication propel-ties, the kinematic viscosity at 40°C of the first
lubricating base oil is preferably 10 to 700 mm2/s, more preferably 20 to
500 mm2/s, still more preferably 25 to 70 mm2/s.
[0021] The viscosity index and the kinematic viscosity at 40°C in the
present invention, respectively, indicate the viscosity index and the
kinematic viscosity at 40°C measured according to JIS I(2283.
5 [0022] Examples of the first lubricating base oil include lubricant oil
fractions prepared by refining through various r e f ~ n gp rocesses
distilled oils obtained by distilling crude oil under normal pressuse or
further distilling crude oil under reduced pressure, and having a %CA of
2 to 8 and a %Cp of 50 to 75, which are values determined by n-d-M
10 ring analysis according to ASTM D3238. The refining process
includes hydrorefining, solvent extraction, and solvent dewaxing, which
can be c o m b i i in an appropriate order to process the distilled oil to
obtain the first lubricating base oil according to the present
embodiment. Mixtures of two or more refined oils having different
15 properties obtained by processing different crude oils or distilled oils
through a comb'mation of different processes in different orders are also
useful. As long as the properties of the resulting k t lubricating base
oil are adjusted such that the above-mentioned physical properties are
satisfied, any first lubricating base oil obtained by any method can be
20 preferably used.
[0023] In the present embodiment, the second lubricating base oil is
used based on the present inventors' knowledge that containing linear
hydrocarbon components and paraffin components having low
coefficients of traction in a base oil is effective in the closest site
25 between the rotational element of the bearing and the bearing ring
providing elastohydrodynamic lubrication.
[0024] In contrast, if an amount of the paraffin components is large in
the lubricating base oil but the paraffin components do not have an
appropriate degree of branching, an increase in viscosity is enhanced in
the low temperature range, so that the torque is increased at the start of
5 the bearing at low temperatures to cause practical problems; the present
inventors have considered these problems, have conducted firther
research, and have found that a urea adduct value is effective as an
index of the paraffrn content causing an increase in torque at the start of
the bearing at low temperatures. Moreover, the present inventors have
10 found that if a second lubricating base oil satisfying the specific
conditions of the urea adduct value, the %Cp, and the %CA is mixed
with the fust lubricating base oil, the torque of the bearing at
temperatures ranging fiom normal temperature to high temperature can
be reduced while a rapid increase in starting torque at low temperatures
15 is prevented.
[0025] In the value determined by n-d-M ring analysis according to
ASTM D3238, the %CA of the second lubricating base oil is 1 or less,
preferably 0.8 or less. If the %CA is more than 1, suitable para&
components having low coefficients of traction cannot be sufficiently
20 fed to the closest site between the rotational element of the bearing and
the bearing ring providing elastohydrodynamic lubrication.
LO0261 The %Cp of the second lubricating base oil is 70 or more,
preferably 75 or more, more preferably 80 or more. If the %Cp is less
than 70, the effect of reducing the coefficient of traction in the closest
25 site between the rotational element of the bearing and the bearing ring
providing elastohydrodynamic lubrication is insufficient.
[0027] The urea adduct value of the second lubricating base oil is 4%
by mass or less, preferably 3.5% by mass or less, more preferably 3%
by mass or less to prevent an increase in viscosity in the low
temperature range and prevent an increase in torque at the start of the
5 bearing at low temperatures. Although the urea adduct value of the
second lubricating base oil may be 0% by mass, the urea adduct value of
the second lubricating base oil is preferably 0.1% by mass or more,
more preferably 0.5% by mass or more because a lubricating base oil
having a higher viscosity index can be obtained while an increase in
10 torque at the start of the bearing at low temperatures is sufficiently
prevented, the dewaxing conditions are relaxed, and economic
efficiency is high.
COO281 The urea adduct value in the present invention is measured by
the following method. 100 g of a sample oil (lubricating base oil)
15 weighed is placed in a round-bottomed flask; 200 g of urea, 360 ml of
toluene, and 40 ml of methanol are added, and are stirred at room
temperature for 6 hours. Thereby, white granular crystals are
generated in the reaction solution as a urea adduct product. The
reaction solution is filtered with a 1-micron filter to extract the
20 generated white granular crystals; the obtained crystals are washed with
50 ml of toluene 6 times. The recovered white csystals are placed in a
flask; 300 ml of pure water and 300 ml of toluene are added, and are
stirred at 80°C for 1 hour. The aqueous phase is separated and
removed though a separation fbnnel, and the toluene phase is washed
25 with 300 ml of pure water 3 times. A desiccant (sodium sulfate) is
added to the toluene phase to dry the toluene phase; then, toluene is
evaporated. The proportion (mass percentage) of the urea adduct
product thus obtained to the sample oil is defined as a urea adduct value.
[0029] In the measurement of the urea adduct value, components
among isoparaffins, causing an increase in torque at the start of the
5 bearing at low temperatures, and normal paraffins, if remaining in the
lubricating base oil, can be surely and accurately collected as urea
adduct products; for this reason, the urea adduct product is
advantageous as an index of the proportion of normal paraffins and the
specific isoparafhs contained. The present inventors have verified by
10 analysis using GC and NMR that the main components of the urea
adduct product are urea adduct products of normal paraffins and
isoparaffins having 6 or more carbon atoms from the terminal of the
main chain to the branched site.
[0030] The viscosity index of the second lubricating base oil is 110 to
15 150, preferably 115 to 140, more preferably 125 to 140. If the
viscosity index is 110 or more, a reduction in viscosity at high
temperatures can be prevented, ht-ther improving the oil film forming
ability. If the viscosity index is 150 or less, production cost to obtain
the lubricating base oil is superior.
20 [0031] The kinematic viscosity at 40°C of the second lubricating base
oil is preferably 10 to 5000 mm2/s, more preferably 20 to 3000 m d s ,
still more preferably 25 to 70 m d s . If the kinematic viscosity at
40°C is 10 &/s or more, a reduction in flash point can be prevented,
and a grease can be safely produced. If the kinematic viscosity at 40°C
25 is 5000 d s or less, an increase in viscous resistance can be
prevented, and moreover, energy saving properties are superior.
[0032] It is preferred that the second lubricating base oil be one or more
selected from mineral oils and synthetic hydrocarbon oils having the
above-mentioned properties. A mixed base oil of a mineral oil and a
synthetic hydrocarbon oil can be used as the second lubricating base oil.
5 [0033] Examples of the mineral oils for the second lubricating base oil
include lubricant oil fractions prepared by refining through various
processes distilled oils obtained by distilling ci-ude oil under nonnal
pressure or krther distilling the resulting oil under reduced pressure,
and having a %CA of 1 or less and a %Cp of 75 or more, which are
10 values determined by n-d-M ring analysis according to ASTM D3238,
and a urea adduct value of 4% by mass or less. The refining process
includes hydrocracking, hydrorefining, solvent extraction, solvent
dewaxing, and hydrogenation dewaxing, which can be combined in an
appropriate order to process the distilled oil to obtain the second
15 lubricating base oil component according to the present invention.
Mixtures of two or more refined oils having diierent properties
obtained by processing different clude oils or distilled oils through a
combination of different processes in different orders are also useful.
As long as the properties of the resulting second lubricating base oil ase
20 adjusted such that the above-mentioned physical properties are satisfied,
any second lubricating base oil obtained by any method can be
preferably used.
[0034] Examples of the synthetic hydrocarbon oils for the second
lubricating base oil include polyolefins, such as poly-a-olefins,
25 polybutene, and copolymers of two or more olefins, allcylbenzene, and
alkylnaphthalene having a %CA of 1 or less and a %Cp of 75 or more,
which are values determined by n-d-M ring analysis according to
ASTM D3238, and a urea adduct value of 4% by mass or less. Among
these, poly-a-olefins are preferred in view of availability, cost, viscosity
prope~ties, oxidation stability, and suitability for system members.
5 Among poly-a-olefins, polymerized products such as 1-dodecene and
1-decene are more preferred in view of cost.
[0035] In the present embodiment, the second lubricating base oil may
consist of only one of the mineral oil and the synthetic hydrocarbon oil,
or may be a mixture of these oils. Namely, examples of a prefelred
10 combination of the fvst lubricating base oil and the second lubricating
base oil include a first lubricating base oil (mineral oil) and a second
lubricating base oil (mineral oil), a first lubricating base oil (mineral oil)
and a second lubricating base oil (synthetic hydrocarbon oil), or a fimt
lubricating base oil (mineral oil) and a second lubricating base oil
15 (mixed base oil of a mineral oil and a synthetic hydrocarbon). These
first lubricating base oils (mineral oils), second lubricating base oils
(mineral oils), and second lubricating base oils (synthetic hydrocarbon
oils) may be used singly or in combinations of two or more.
[0036] The content of the first lubricating base oil is 5 to 90% by mass,
20 preferably 10 to 80% by mass, more preferably 30 to 60% by mass
based on the total amount of the lubricating base oil. The content of
the second lubricating base oil is 10 to 95% by tnass, preferably 20 to
90% by mass, more preferably 40 to 70% by mass based on the total
amount of the lubricating base oil. If the contents of the first and
25 second lubricating base oils are out of these ranges, a desired effect of
reducing power consumption may not be attained.
[0037] The content of the lubricating base oil is preferably 70 to 98%
by mass, pasticulasly preferably 80 to 97% by mass based on the total
amount of the grease composition.
COO381 It is prefeued that the thickener have one or more selected from
5 metal soap compounds (also referred to as "metal soap thickeners") and
usea compounds (also referred to as "urea thickeners").
LO0391 Examples of the metal soap thickeners include simple soaps and
complex soaps. The simple soap is a metal soap prepare by
saponifying a fatty acid or an oil or fat wifh an alkali metal hydroxide or
10 an alkaline earth metal hydroxide. The complex soap is prepared by
forming a combination of a fatty acid used for a simple soap and an
organic acid having a different molecular structure into a composite
form. The fatty acid may be a fatty acid derivative having a hydroxy
group. The f&y acid may be an aliphatic carboxylic acid such as
15 stearic acid or may be an aromatic casboqdic acid such as terephthalic
acid. As the fatty acid, aliphatic mono- or dicasboxylic acids, such as
aliphatic carboxylic acids having 6 to 20 carbon atoms are used;
particularly aliphatic monocarboxylic acids having 12 to 20 carbon
atoms and aliphatic dicarboxylic acids having 6 to 14 carbon atoms are
20 preferably used. As the fatty acid, aliphatic monocarboxylic acids
containing one hydroxyl group are preferred. As the organic acid used
in combination with the fatty acid in the complex soap, acetic acid,
dibasic acid such as azelaic acid or sebacic acid, and benzoic acid are
suitable.
25 [0040] As the metal for the metal soap thickener, alkali metals such as
lithium and sodium, alkaline earth metals such as calcium, and
amphoteric metals such as aluminum are used. Among these, alkali
metals, particularly lithium is preferably used.
[0041] These metal soap thickeners may be used singly or in
combinations of two or more. The content of the metal soap thickener
5 is preferably 2 to 30% by mass, more preferably 3 to 20% by mass, still
more preferably 10 to 20% by mass based on the total amount of the
grease composition, for example.
[0042] As the urea thickener, for example, diurea compounds obtained
by a reaction of diisocyanate and monoamine, and polyurea compounds
10 obtained by a reaction of diisocyanate and monoamine or diamine can
be used.
[0043] Examples of the diisocyanate include aliphatic diisocyanates and
aromatic diisocyanates. Examples of the aliphatic diisocyanates
include diisocyanates having a saturated andlor unsaturated linear,
15 branched, or alicyclic hydrocarbon group. For example, phenylene
diisocyanate, tolylene diisocyanate, diphenyl diisocyanate,
diphenylmethane diisocyanate, octadecane diisocyanate, decane
diisocyanate, and hexane diisocyanate are prefesred. Examples of the
lnonoamine include aliphatic monoamines and aromatic monoamines.
20 Examples of the aliphatic monoamines include monoamines having a
saturated and/or unsaturated linear, branched, or alicyclic hydrocarbon
group. For example, octylamine, dodecylamine, hexadecylamine,
stearylarnine, oleylatnine, aniline, p-toluidine, and cyclohexylamine are
preferred. Examples of the diarnine include aliphatic diamines and
25 aromatic diamines. Examples of the aliphatic diamines include
diamines having a saturated and/or unsaturated lineat; branched, or
alicyclic hydrocarbon group. For example, ethylenediamine,
propanediamine, butanediamine, hexanediamine, octanediamine,
phenylenediamine, tolylenediamine, xylenediamine, and
diaminodiphenylmethane are preferred.
5 [0044] These urea thickeners may be used singly or in combinations of
two or more. The content of the urea thickener is preferably 2 to 30%
by mass, more preferably 3 to 20% by mass, still more preferably 10 to
20% by mass based on the total amount of the grease composition.
[0045] It is preferred that the grease composition contain an
10 organomolybdenum compound. Thereby, the life of the bearing can be
increased. Examples of the organomolybdenum compound can
include molybdenum dithiocarbamate, molybdenum dithiophosphate,
amine complexes of molybdenum, succinimide complexes of
molybdenum, molybdenum salts of organic acid, and molybdenum salts
15 of alcohol. Among these, molybdenum dithiocarbamate and
molybdenum dithiophosphate are prefexed to increase the life of the
bearing.
[0046] As molybdenum dithiocarbamate, for example, a compound
represented by the following formula (1) can be used.
20 [Chemical Formula 11
[0047] In the formula (I), R', R', R3, and R4 may be the same or
different, and each represent a hydrocarbon group such as an alkyl
group having 2 to 24 carbon atoms, preferably 4 to 13 carbon atoms or
an aryl group (including an alkylaryl group) having 6 to 24 carbon
atoms, preferably S to 15 carbon atoms; and XI, x2,x 3,an d x4m ay be
the same or different, and each represent a sulfur atom or an oxygen
atom. The alkyl group here includes a primary alkyl group, a
5 secondary alkyl group, and a tertiary akyl group. These groups may
be lineaf'or branched.
[0048] Preferred examples of the alkyl group include an ethyl group, a
propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl
group, an octyl group, a nonyl group, a decyl group, an undecyl group, a
10 dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group,
a hexadecyl group, a heptadecyl group, and an octadecyl group. These
may be a primary alkyl group, a secondary allcyl group, or a tertiary
allcyl group, and may be linear or branched. Preferred examples of the
(a1kyl)aryl group include a phenyl group, a tolyl group, an ethylphenyl
15 group, a propylphenyl group, a butylphenyl group, a pentylphenyl
group, a hexylphenyl group, an octylphenyl group, a nonylphenyl
group, a decylphenyl group, an undecylphenyl group, and a
dodecylphenyl group. The alkyl group in the (alky1)alyl group may be
a primaiy alkyl group, a secondary alkyl group, or tertiary alkyl group,
20 and may be linear or branched. The (alky1)aryl group includes all of
the substitution isomers different &om each other in substitution
position of the alkyl group on the aryl group.
[0049] Examples of more preferred tnolybdenum dithiocarbamate can
specifically include molybdenum diethyldithiocarbamate sulfide,
25 molybdenum dipropyldithiocarbamate sulfide, molybdenum
dibutyldithiocarbatnate sulfide, molybdenum dipentyldithiocarbamate
sulfide, molybdenum dihexyldithiocarbamate sulfide, molybdenuin
dioctyldithiocarbamate sulfide, molybdenum didecyldithiocarbamate
sulfide, molybde~ium didodecyldithiocarbamate sulfide, molybdenum
di(butylpheny1)dithiocarbamate sulfide, molybdenum
5 di(nonylpheny1)dithiocarbamate sulfide, oxymolybdenum
diethyldithiocarbamate sulfide, oxymolybdenum
dipropyldithiocarbamate sulfide, oxymolybdenum
dibutyldithiocarbainate sulfide, oxymolybdenum
dipentyldithiocarbamate sulfide, oxymolybdenum
10 dihexyldithiocarbamate sulfide, oxymolybdenum
dioctyldithiocarbamate sulfide, oxymolybdenum
didecyldithiocarbamate sulfide, oxymolybdenum
didodecyldithtocarbamate sulfide, oxymolybdenum
di(butylpheny1)dithiocarbamate sulfide, oxymolybdenum
15 di(nonylpheny1)dithiocarbamate sulfide, and mixtures thereof. The
akyl group in these molybdenum dithiocarbamates may be linear or
branched, and in the alkylphenyl group, the attached position of the
alkyl group is arbitray. As these molybdenum dithiocarbamates,
compounds having hydrocarbon groups having different carbon atoms
20 andlor structures in one molecule can also be preferably used.
[OOSO] As molybdenum dithiophosphate, those commercially available
as lubricant oil additives can be used; for example, a compound
represented by the following formula (2) can be used.
[0051]
25 [Chemical Formula 21
[0052] In the fomiula (2), R' and R~ may be the same or different Eom
each other, and each represent a hydrocarbon group having one or more
carbon atoms; x', x6, x7, x8, and x9 may be the same or different from
5 each other, and each represent an oxygen atom or a sulfur atom; and a,
b, and c each represent an integer of 1 to 6; provided that at least one of
x*, x6, x7, x8, and x9 represents a sulfur atom. Examples of the
hydrocarbon groups represented as R~ and R~ include an alkyl group
having 1 to 24 carbon atoms, a cycloallcjl group having 5 to 7 carbon
10 atoms, an allcylcycloalkyl group having 6 to 11 carbon atoms, an aryl
group having 6 to 18 carbon atoms, an alkylaryl group having 7 to 24
carbon atoms, and an arylalkyl group having 7 to 12 carbon atoms.
[0053] The content of the organomolybdenum compound is preferably
300 mass pprn or more, more preferably 500 mass pprn or more, still
15 more preferably 600 mass ppm or more, particularly preferably 700
mass pprn or more in terms of the amount of the molybdenum element
based on the total amount of the grease composition to increase the life
of the bearing. The content of the organomolybdenum compound is
preferably 50000 mass pprn or less, more preferably 40000 mass pprn or
20 less, still more preferably 30000 mass ppm or less in tenns of the
amount of the molybdenum element based on the total amount of the
grease composition in view of the effect of the added
organomolybdenum compound on the perfolmance of the bearing and
production cost. The content of the organomolybdenum compound is
preferably 0.1% by mass or more, more preferably 0.5% by mass or
more, still more preferably 1% by mass or more in teims of the weight
5 of the molybdenum compound based on the total amount of the grease
composition. The content of the organomolybdenum compound is
preferably 15% by mass or less, more preferably 10% by mass or less,
still more preferably 5% by mass or less in teims of the weight of the
molybdenum compound based on the total amount of the grease
10 composition in view of the effect of the added organomolybdenum
coinpound on the perfoimance of the bearing and production cost. '
[0054] The grease composition can contain additives usually used in
lubricant oils and greases in addition to the components above when
necessaly. Examples of the additives include detergents, dispersants,
15 wear preventing agents, viscosity index improvers, antioxidants,
extreme-pressure agents, lust inhibitors, corrosion inhibitors, metal
deactivators, and solid lubricants. The content of these additives is
preferably 10% by mass or less, more preferably 5% by mass or less
based on the total amount of the grease composition.
20 [0055] The consistency of the grease composition is preferably 220 to
300, more preferably 225 to 295, still more preferably 230 to 290,
particularly preferably 230 to 285. If the consistency is the grease
composition within this range, the amount of electric power consumed
during rotation of bearings can be significantly reduced. Examples of
25 the method of adjusting the consistency of the grease composition
include a method of adjusting the types and the mixing proportion of the
above-described first lubricating base oil, second lubricating base oil,
and thickener, and a method of mixing the respective components
during production of the grease composition described later (such as the
number of mixing operations, the heating temperature, the cooling rate,
5 and the roll condition).
[0056] The consistency in the present invention indicates the worked
penetration measured according to JIS K2220. The specific
measurement conditions are as follows. A sample is placed in a pot for
measuring a consistency, and the pot is kept at 25OC; then, the sample is
10 mixed with 60 reciprocating motions of a specified mixer for 1 minute.
Next, an excess sample is removed with a spatula to smooth the surface
of the sample, and a specified cone is dropped into the sample for 5
seconds; the value obtained by multiply the depth (rnrn) of the cone
entering the sample by 10 is defined as the worked penetration.
15 [0057] Another embodiment according to the present invention is a
grease composition comprising a lubricating base oil, a thickener, and
an organomolybdenum compound, wherein the lubricating base oil
comprises a first lubricating base oil having a %CA of 2 to 8 and a %Cp
of 50 to 75, which are values deteimined by n-d-M ring analysis
20 according to ASTM D3238, and a second lubricating base oil having
a %CA of 1 or less and a %Cp of 70 or more, which are values
determined by n-d-M ring analysis according to ASTM D3238, the
content of the first lubricating base oil is 5 to 90% by mass and the
content of the second lubricating base oil is 10 to 95% by mass based on
25 the total amount of the lubricating base oil, and the consistency is 220 to
300. This embodiment attains significant effects, i.e., compatibility
between a reduction in power consumption during rotation of bearings
and an increase in life of bearings.
[0058] The method of producing the grease composition according to
the present embodiment comprises a step of mixing a first lubricating
5 base oil, a second lubricating base oil, and a thickener to obtain a grease
compositi~n. The first lubricating base oil is mixed with the second
lubricating base oil such that the content of the first lubricating base oil
is 5 to 90% by mass and the content of the second lubricating base oil is
10 to 95% by mass based on the total amount of the lubricating base oil.
10 [0059] In the present embodiment, a thickener preliminarily prepared
may be mixed with the %st and second lubricating base oils, or raw
materials for the thickener may be compounded with the first lubricating
base oil, the second lubricating base oil, or a mixed base oil thereof, and
the raw materials may be reacted in the base oil to obtain a thickener.
15 For example, if a metal soap thickener is used, the metal soap thickener
may be compounded with the lubricating base oil in the form of a metal
soap; or a carboxylic acid and a metal source (such as a metal salt or a
metal salt hydroxide) may be separately compounded with the
lubricating base oil, and the carboxylic acid may be reacted with the
20 metal source during production of the grease to prepare a metal soap
thickener. If a urea thickener is used, the urea thickener in the form of
a urea compound may be compounded with the lubricating base oil; or a
diisocyanate and an amine (such as a monoamine or a diamine) may be
compounded with the lubricating base oil, and the diisocyanate may be
25 reacted with the alnine during production of the grease to prepare a urea
thickener.
[0060] The grease composition obtained by mixing the first lubricating
base oil, the second lubricating base oil, and the thickener can be
dispersed with a roll or a mill when necessaly.
Examples
5 [0061] Hereinafier, the present invention will be described more
specifically based on Examples, but the present invention will not be
limited to the Examples below.
[0062] pase oil A]
A lubricating base oil having the following properties and
10 obtained by solvent refining a distilled oil obtained by distillation under
reduced pressure of a residue of distillation under normal pressure was
used as base oil A.
Kinematic viscosity at 40°C: 37.6 m d s
Viscosity index: 107
15 Flash point: 220°C
%Cp: 66
%CA: 5.2
[0063] pase oil B]
A bottom fraction obtained from a he1 oil hydsocracker was
20 used as a raw material for a lubricating base oil, and hydroprocessing
was performed with a hydroprocessing catalyst. At this time, the
reaction temperature and the liquid hourly space velocity wese adjusted
such that the cracking rate of normal paraffin in the raw material oils
was 10% by mass or less. Furthelmore, the processed product
25 obtained by hydsoprocessing was subjected to hydrogenation dewaxing
in the temperature range of 315 to 325OC with a zeolite hydrogenation
dewaxing catalyst having a noble metal whose content was adjusted to
0.1 to 5% by mass; thereby, a dewaxed oil was obtained. Furthemore,
the dewaxed oil was hydrorefined with a hydrorefining catalyst.
Subsequently, a lubricating base oil having the following properties and
5 obtained by distillation was used as base oil B.
Kinematic viscosity at 40°C: 36.8 m d s
Viscosity index: 130
Flash point: 240°C
%C,: 79
10 %C*: 0
Urea adduct value: 2% by mass
[0064] [Base oil C]
A synthetic hydrocarbon having the following properties, i.e.,
poly-a-olefin (Durasyn 166 manufactured by INEOS Group AG) was
15 used as base oil C.
Kinematic viscosity at 40°C: 30.8 mm2/s
Viscosity index: 135
Flash point: 250°C
%Cp: 91
20 %C*: 0
Urea adduct value: 0% by mass
[0065] [Base oil Dl
A kaction separated through distillation under reduced pressure
of a solvent refined base oil was solvent extracted with flwfbral, was
25 then hydroprocessed, and was solvent dewaxed with a mixed solvent of
methyl ethyl ketone and toluene. The wax content removed during
solvent dewaxing and obtained as a slack wax was used as a raw
material for a lubricating base oil, and hydroprocessing was performed.
At this time, the reaction temperature and the liquid hourly space
velocity were adjusted, the temperature condition on hydrogenation
dewaxing of the processed product obtained by hydroprocessing was
adjusted to a low temperature of about 300°C, and the dewaxed oil
obtained was hydrorefmed. Subsequently, a lubricating base oil
having the following properties and a urea adduct value of 5% by mass,
and obtained by distillation was used as base oil D.
Kinematic viscosity at 40°C: 32.0 mm2/s
Viscosity index: 130
Flash point: 240°C
%Cp: 75
%C*: 0
Urea adduct value: 5% by mass
[0066] [Test oils 1-1 to 1-10]
Base oils A, B, C, and D were placed in a stainless steel
container in amounts to be compounded shown in Tables 1 and 2
(expressed by % by mass). When a urea compound was used as the
thickener, raw materials for the urea compound, i.e., an anine and an
isocyanate were added to the lubricating base oil in the container, were
heated to 150°C, and were stirsed with a magnetic stirrer to react the
amine and the diisocyanate. After dying, the reaction product was
cooled to room temperature to obtain a semi-solid composition. When
a metal soap compound was used as the thickener, lithium stearate was
added to the lubricating base oil, was heated to 200°C, and then was
cooled to obtain a semi-solid composition. Furthennore, a phenol
antioxidant di-t-butyl-p-cresol was added to each of the resulting
semi-solid compositions, and was dispersed with a triple roll mill to
obtain grease compositions having the compositions shown in Tables 1.
5 and 2.
100671 [Evaluation test I]
The amount of electric power consumed during rotation of a
bearing in use of each grease composition was measured by the
following method. As the bearing, a double-row tapered roller bearing
10 4T-CRI-0868 manufactured by NTN Corporation was used. The
inside of the bearing was sufficiently washed with an organic solvent
before the test, and an experiment oil agent (grease composition) was
then injected into gaps between a roller, a bearing ring, and a retainer of
the bearing with a syringe. In the experiment, 4 bearings in total (2
15 bearings x 2 pairs) filled with the same oil agent were used. The inner
ring of the bearing was fixed, and the bearing was rotated through a
pulley with an electric motor (manufactured by YASKAWA Electric
Corporation, TYPE: FEQ, 2.2 kW) in a certain diiection to measure the
amount of the power consumption of the electric motor with an electric
20 power meter (manufactured by HIOKI E.E. CORPORATION, CE3169,
CLAMP ON POWER HiTESTER). The number of rotations of the
bearing was 1300 ipm, the temperature was room temperature, and the
integrated power consumption (kW) during continuous rotation for 2
hours was compared. The number of repetitions of the experiment was
25 3 times. The obtained results are shown in Tables 1 and 2. The
power consumption and the electric power reduction rate (%: relative to
Test oil 1-6) of the beasing in Tables 1 and 2 are the average values of
the three experiments. In the electric power reduction rate in the
present Examples, cases where the power consuml>tion is lower than the
reference are shown by negative numeric valxtes.
[0068] [Table 11
[0069] [Table 21
[0070] [Test oils 2-1 to 2-12]
Base oils A, B, C, and D, and the thickener were placed in a
stainless steel container in amounts to be compounded (expressed by %
5 by mass) shown in Tables 3 to 5. When a metal soap compound
(simple soap) was used as the thickener, lithium stearate was added to
the lubricating base oil, and was heated to 200°C; the resultant was then
cooled to obtain a semi-solid composition. When a metal soap
compound (complex soap) was used as the thickener, 12-hydsoxystearic
10 acid, azelaic acid, and lithium hydroxide were added to the lubricating
base oil, were heated to 200°C, and were reacted to form a complex
soap, which was cooled to obtain a semi-solid composition. 'When a
urea compound was used as the thickener, raw materials for the urea
compound, i.e., an arnine and an isocyanate were added to the
lubricating base oil in the container, were heated to 150°C, and were
stirred with a magnetic stirrer to react the arnine and the diisocyanate.
After diying, the reaction product was cooled to room temperature to
5 obtain a semi-solid composition. Furthermore, a phenol antioxidant
di-t-butyl-p-cresol was added to each of the resulting semi-solid
co~npositionsa, nd was dispersed with a triple roll mill to obtain grease
compositions having the compositions shown in Tables 3 to 5. In the
resulting grease compositions, the consistency (worked penetration) was
10 measured according to JIS K2220.
[0071] [Evaluation test 2-11
The amount of electric power consumed during rotation of a
bearing in use of each grease composition was measured by the
following method. As the bearing, a double-row ball bearing
15 7008A-DF manufactured by NSK Ltd. was used. The inside of the
bearing was sufficiently washed with an organic solvent before the test,
an experiment oil agent (grease composition) was injected into gaps
between bails, a bearing ring, and a retainer of the bearing with a
syringe. In the experiment, 4 bearings in total (2 bearings x 2 pairs)
20 filled with the same oil agent were used. The inner ring of the bearing
was fixed, and the bearing was rotated through a pulley with an electric
motor (manufactured by YASKAWA Electric Corporation, TYPE: FEQ,
2.2 kW) in a certain direction to measure the amount of the power
consumption of the electric motor with an electric power meter
25 (manufactured by HIOKI E.E. CORPORATION, CE3169, CLAMP ON
POWER HiTESTER). The number of rotations of the bearing was
1300 rpm, the temperature was room temperature, and the integrated
power consumption (kW) during continuous rotation for 2 hours was
compared. The number of repetitions of the experiment was 3 times.
The obtained results are shown in Tables 3 to 5. The power
5 consumption and the electric power reduction rate (%: relative to test oil
2-11) of the bearing in Tables 3 to 5 are the average values of the three
experiments.
[0072] [Evaluation test 2-21
Each of the grease compositions was subjected to the same test
10 as that in Evaluation test 1. The obtained results are shown in Tables 3
to 5. The power consumption and the electric power reduction rate
(Oh relative to test oil 2-11) of the bearing in Tables 3 to 5 are the
average values of the three experiments.

[0074] [Table 41
Base oils A and B, the thickener, and organomolybdenum
compounds molybdenum dithiocarbmate (molybdenum element
5 content of 29% by mass, sulfur element content of 28% by mass) and
molybdenum dithiophosphate (molybdenum element content of 8% by
mass, phosphor element content of 6% by mass, sulfur element content
of 12% by mass) were placed in a stainless steel container in amounts to
be compounded shown in Tables 6 and 7 (expressed by % by mass.
10 Also the values in terms of the molybdenum element are shown).
When a metal soap compound (simple soap) was used as the thickener,
lithium stearate was added to the lubricating base oil, and heated to
200°C; the resultant mixture was then cooled to obtain a semi-solid
composition. When a metal soap compound (complex soap) was used
as the thickener, 12-hydroxystearic acid, azelaic acid, and lithium
5 hydroxide were added to the lubricating base oil, heated to 200°C, and
reacted to form a complex soap, and the resulting mixture was cooled to
obtain a semi-solid composition. When a urea compound was used as
the thickener, raw materials for the urea compound, i.e., an a~ninea nd
an isocyanate were added to the lubricating base oil in the container,
10 heated to 150°C, and stirred with a magnetic stirrer to react the amine
and the diisocyanate. After dying, the resulting mixture was cooled to
room temperature to obtain a semi-solid composition. Furthemore,
other additives (such as a phenol antioxidant and a corrosion inhibitor)
were added to each of the resulting semi-solid compositions, and were
15 dispersed with a triple roll mill to obtain grease compositions having the
compositions shown in Tables 6 and 7. For the resulting grease
compositions, the consistency (worked penetration) was measured
according to JIS K2220,
[0077] [Evaluation test 3-1 (life of bearing)]
20 The grease compositions were each subjected to a high
temperature grease bearing life test. Specifically, according to
ASTM-D3336, 2 g of a sample grease was filled into a bearing
(6204ZZ), the bearing was continuously operated at a temperature of
150°C, the number of rotations of 10000 rpm, and a thrust load of 66 N,
25 and the time until abnormal operation was caused accompanied by
lubrication failure was recorded as the Life (h) of the bearing.
[0078] [Evaluation test 3-2 (power consumption of bearing)]
The grease compositions were each subjected to the same test as
in Evaluation test 2-1. The obtained results are shown in Tables 6 and
7. The power consumption and the electric power reduction rate (%:
5 relative to test oil 3-7) of the beasing in Tables 6 and 7 are the average
values of the three experiments.
[0079] [Table 61
(in terms of amount of
Evaluation test 3-2
[0080] [Table 71
Evaluation test 3-2
Industrial Applicability
[0081] The grease composition according to the present invention
attains a significant effect that the amount of electric power consumed
during rotation of bearings is small. Accordingly, the grease according
to the present invention can be suitably used in lubrication of
mechanical components such as antifiiction bearings, sliding bearings,
ball screws, linear guides, and gears, and are useful in industrial
machines and mechanical systems for transportation.

CLAJMS
1. A grease composition comprising:
a lubricating base oil; and
a thickener,
wherein the lubricating base oil comprises
a fist lubricating base oil having a %CA of 2 to 8 and
a %Cp of 50 to 75, the %CA and the %Cp being values determined by
n-d-M ring analysis according to ASTM D3238, and
a second lubricating base oil having a %CA of 1 or less,
10 a %Cp of 70 or more, and a urea adduct value of 4% by mass or less,
the %CA and the %Cp being values determined by n-d-M ring analysis
according to ASTM D3238,
and wherein a content of the first lubricating base oil is 5 to 90%
by mass and a content of the second lubricating base oil is 10 to 95% by
15 mass, based on a total amount of the lubricating base oil.
2. The grease composition according to claim 1, wherein the
grease composition has a consistency of 220 to 300.
3. The grease composition according to claim 1 or 2, further
comprising an organomolybdenum compound.
20 4. The grease composition according to claim 3, wherein the
organomolybdenum compound comprises at least one selected &om
molybdenum dithiocarbamates and molybdenum dithiophosphates.
5. The grease composition according to any one of claims 1 to 4,
wherein the fist lubricating base oil has a kinematic viscosity at 40°C
25 of 10 to 700 mm2/s and a viscosity index of 90 to 120.
6. The grease composition according to any one of claims 1 to 5,
wllerein the second lubricating base oil has a kinematic viscosity at
40°C of 10 to SO00 d s and aviscosity i~idexo f 110 to 150.
7. The grease co~nposition according to any one of claims 1 to 6,
wherein the second l~lbricatkigb ase oil cotnprises at least one. selected
5 from mineral oils and synthetic hydrocarbons.
8. The grease co~nposition according to atiy one of claims 1 to 7,
wherein the thickener comprises at least one selected from metal soap
compounds and urea compounds.
9. A grease composition comprising:
10 a lubricating base oil;
a thickener; and
an organomolybdenwn compound,
wherein the lubricating base oil comprises
a &st lubricating base oil having a %CA of 2 to 8 and
15 a %Cp of SO to 75, the %CA and the %Cp being values detetlllined by
I n-d-M ring analysis according to ASTM D323 8, and
a second lubricating base oil having a %CA of 1 or less
and a %Cp of 70 or more, the %CA and the %CF being values
determined by n-d-M ring analysis according to ASTM D3238,
wherein a content of tlie first lubricating base oil is 5 t'o 90% by
mass and a content of the second Iubricatiug base oil is 10 to 95% by
mass, based on a total amount of the lubricating base oil,
and wherein the grease coraposition has a consistency of 220 to
300.