U.S. patent application number 17/230482 was filed with the patent office on 2021-10-21 for grease composition for electrical contacts.
This patent application is currently assigned to KYODO YUSHI CO., LTD.. The applicant listed for this patent is DENSO CORPORATION, KYODO YUSHI CO., LTD.. Invention is credited to Ryuji AOKI, Shozo IKEJIMA, Chiemi NAKAYAMA, Takahiro NIHIRA, Takahiro NOZU, Daisuke TSUTSUI.
Application Number | 20210324294 17/230482 |
Document ID | / |
Family ID | 1000005533873 |
Filed Date | 2021-10-21 |
United States Patent
Application |
20210324294 |
Kind Code |
A1 |
NIHIRA; Takahiro ; et
al. |
October 21, 2021 |
GREASE COMPOSITION FOR ELECTRICAL CONTACTS
Abstract
The present invention provides a grease composition for
electrical contacts, including: a thickener; a base oil; and an
organic sulfur compound, wherein the organic sulfur compound is a
compound having no heterocycle containing nitrogen in a molecule
thereof.
Inventors: |
NIHIRA; Takahiro; (Tokyo,
JP) ; NAKAYAMA; Chiemi; (Suzuka-shi, JP) ;
TSUTSUI; Daisuke; (Yokohama-shi, JP) ; IKEJIMA;
Shozo; (Okazaki-shi, JP) ; AOKI; Ryuji;
(Kariya-city, JP) ; NOZU; Takahiro; (Kariya-city,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KYODO YUSHI CO., LTD.
DENSO CORPORATION |
Fujisawa-shi
Kariya-shi |
|
JP
JP |
|
|
Assignee: |
KYODO YUSHI CO., LTD.
Fujisawa-shi
JP
DENSO CORPORATION
Kariya-shi
JP
|
Family ID: |
1000005533873 |
Appl. No.: |
17/230482 |
Filed: |
April 14, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10M 2223/047 20130101;
C10M 169/06 20130101; C10N 2050/10 20130101; C10N 2020/02 20130101;
C10N 2040/17 20200501; C10M 2213/0626 20130101; C10M 2219/082
20130101; C10M 2207/1256 20130101; C10M 135/20 20130101; C10M
2205/0285 20130101; C10M 2215/1026 20130101 |
International
Class: |
C10M 169/06 20060101
C10M169/06; C10M 107/10 20060101 C10M107/10; C10M 119/06 20060101
C10M119/06; C10M 135/20 20060101 C10M135/20 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 17, 2020 |
JP |
2020-074249 |
Claims
1. A grease composition for electrical contacts, comprising a
thickener, a base oil, and an organic sulfur compound, wherein the
organic sulfur compound is a compound having no heterocycle
containing nitrogen in a molecule thereof.
2. The grease composition according to claim 1, wherein the organic
sulfur compound is at least one selected from the group consisting
of thiols, disulfides, alkylthiophenes, sulfides of oils or fats,
sulfides of olefins, and thiophosphoric acid or esters thereof.
3. The grease composition according to claim 1, wherein the organic
sulfur compound is at least one selected from the group consisting
of thiols.
4. The grease composition according to claim 1, wherein the organic
sulfur compound is a thiol having a linear or branched alkyl group
having 6 to 24 carbon atoms.
5. The grease composition according to claim 1, wherein the organic
sulfur compound is stearyl mercaptan.
6. The grease composition according to claim 1, wherein the organic
sulfur compound is contained in an amount of about 0.001 to 5% by
mass based on the total mass of the composition.
7. The grease composition according to claim 1, wherein the base
oil is a synthetic hydrocarbon oil.
8. The grease composition according to claim 1, wherein the base
oil is poly-alpha-olefin.
9. The grease composition according to claim 1, wherein a kinematic
viscosity of the base oil at 40.degree. C. is about 200 mm.sup.2/s
or less.
10. The grease composition according to claim 1, wherein the base
oil is contained in an amount of about 40 to 97% by mass based on
the total mass of the composition.
11. The grease composition according to claim 1, wherein the
thickener is at least one selected from the group consisting of Li
soaps, urea compounds, polytetrafluoroethylene, inorganic fine
particles, and calcium sulfonate complex.
12. The grease composition according to claim 1, wherein the
thickener is polytetrafluoroethylene.
13. The grease composition according to claim 1, wherein the
thickener has a primary particle diameter of about 80 to 400
nm.
14. The grease composition according to claim 1, wherein the
thickener is contained in an amount of about 2 to 59% by mass based
on the total mass of the composition.
15. The grease composition according to claim 1, further comprising
at least one additives selected from the group consisting of
antioxidants, rust inhibitors, metal corrosion inhibitors, oiliness
improvers, and viscosity index improvers.
16. The grease composition according to claim 15, wherein the
additive is contained in an amount of about 0.01 to 20% by mass
based on the total mass of the composition.
17. The grease composition according to claim 1, wherein the
composition has a 60-stroke worked penetration measured according
to JIS K2220 7 of about 220 to 400.
18. The grease composition according to claim 1, wherein a material
of the electrical contacts is gold or a gold alloy.
Description
TECHNICAL FIELD
[0001] The present invention relates to a grease composition for
electrical contacts having excellent wear resistance of gold
plating.
BACKGROUND ART
[0002] As electrical contacts and connectors used in electrical
products, OA equipment, in-vehicle electrical components, various
types of facility equipment, and the like, contact materials are
used in which plating of gold or a gold alloy, which has excellent
conductivity, oxidation resistance, and corrosion resistance among
metals, is applied to the base metal of copper or a copper alloy to
ensure good conductivity.
[0003] In recent years, many mechanical parts are required to be
reduced in cost, and the electrical contacts, which are a part of
them, are also naturally required to be reduced in cost. One of the
methods of reducing the cost of electrical contacts is to reduce
the thickness of gold plating to reduce the amount of gold used,
which is a factor in increasing the cost. However, gold is subject
to adhesion and wear due to sliding. When the thickness of the gold
plating is reduced, there is more concern than before about the
exposure of the base metal due to the progress of wear, the
subsequent oxidation of the base metal, and the poor
conductivity.
[0004] As a countermeasure, the life of the electrical contact can
be improved by using a lubricant having excellent wear resistance
of gold plating. As a lubricant for reducing the wear of gold
plating, a lubricant added with mercaptobenzothiazole or
dibenzothiazyl disulfide has been reported (Patent Literature
1).
CITATION LIST
Patent Literature
[0005] [Patent Literature 1] Japanese Patent Application
Publication No. 2005-068391
SUMMARY OF INVENTION
Technical Problems
[0006] However, in order to meet the demand for further thinning of
gold plating, it is further required to improve the wear resistance
of gold plating. Patent Literature 1 states that thickening can
prevent oil from dripping from the plating surface, but when the
viscosity of the oil decreases under high temperature, there is
still a concern that the oil will drip and stain the peripheral
members.
[0007] From the above, an object to be achieved by the present
invention is to provide a grease composition for electrical
contacts in which the wear resistance of gold plating is improved
more than before while preventing the peripheral members from being
stained due to the dripping of the lubricant.
Solution to Problems
[0008] In response to the above-mentioned object of improving wear
resistance, the present inventors have improved the wear resistance
of gold plating more than before by using an organic sulfur
compound containing no heterocyclic nitrogen.
[0009] The present invention makes it possible to provide a grease
composition having improved wear resistance of gold plating.
According to the grease composition of the present invention, it is
possible to improve the life of an electrical contact having a
small thickness of gold plating.
1. A grease composition for electrical contacts, comprising a
thickener, a base oil, and an organic sulfur compound, wherein the
organic sulfur compound is a compound having no heterocycle
containing nitrogen in a molecule thereof. 2. The grease
composition according to item 1, wherein the organic sulfur
compound is at least one selected from the group consisting of
thiols, disulfides, alkylthiophenes, sulfides of oils or fats,
sulfides of olefins, and thiophosphoric acid or esters thereof. 3.
The grease composition according to item 1, wherein the organic
sulfur compound is at least one selected from the group consisting
of thiols. 4. The grease composition according to item 1, wherein
the organic sulfur compound is a thiol having a linear or branched
alkyl group having 6 to 24 carbon atoms. 5. The grease composition
according to item 1, wherein the organic sulfur compound is stearyl
mercaptan. 6. The grease composition according to any one of items
1 to 5, wherein the organic sulfur compound is contained in an
amount of about 0.001 to 5% by mass based on the total mass of the
composition. 7. The grease composition according to any one of
items 1 to 6, wherein the base oil is a synthetic hydrocarbon oil.
8. The grease composition according to any one of items 1 to 7,
wherein the base oil is poly-alpha-olefin. 9. The grease
composition according to any one of items 1 to 8, wherein a
kinematic viscosity of the base oil at 40.degree. C. is about 200
mm.sup.2/s or less. 10. The grease composition according to any one
of items 1 to 9, wherein the base oil is contained in an amount of
about 40 to 97% by mass based on the total mass of the composition.
11. The grease composition according to any one of items 1 to 10,
wherein the thickener is at least one selected from the group
consisting of Li soaps, urea compounds, polytetrafluoroethylene,
inorganic fine particles, and calcium sulfonate complex. 12. The
grease composition according to any one of items 1 to 11, wherein
the thickener is polytetrafluoroethylene. 13. The grease
composition according to any one of items 1 to 12, wherein the
thickener has a primary particle diameter of about 80 to 400 nm.
14. The grease composition according to any one of items 1 to 13,
wherein the thickener is contained in an amount of about 2 to 59%
by mass based on the total mass of the composition. 15. The grease
composition according to any one of items 1 to 14, further
comprising at least one additives selected from the group
consisting of antioxidants, rust inhibitors, metal corrosion
inhibitors, oiliness improvers, and viscosity index improvers. 16.
The grease composition according to item 15, wherein the additive
is contained in an amount of about 0.01 to 20% by mass based on the
total mass of the composition. 17. The grease composition according
to any one of items 1 to 16, wherein the composition has a
60-stroke worked penetration measured according to JIS K2220 7 of
about 220 to 400. 18. The grease composition according to any one
of items 1 to 17, wherein a material of the electrical contacts is
gold or a gold alloy.
DESCRIPTION OF EMBODIMENTS
<Thickener>
[0010] The thickener used in the grease composition of the present
invention is not particularly limited. Specific examples include
soap-based thickeners typified by Li soaps such as lithium stearate
and lithium 12-hydroxystearate, and Li complex soaps; urea-based
compounds typified by diurea compounds; organic thickeners typified
by polytetrafluoroethylene (PTFE) and sodium terephthalate;
inorganic fine particles typified by organic bentonite and silica;
and calcium sulfonate complex.
[0011] Among these, one or more selected from the group consisting
of Li soaps, urea compounds, PTFE, inorganic fine particles, and
calcium sulfonate complex are preferable.
[0012] More preferable are PTFE, silica, diurea compounds, and
calcium sulfonate complex. These can withstand use at high
temperatures because the thickener can remain solid even at high
temperatures due to its high melting point. In particular, PTFE 15
preferable.
[0013] PTFE has a primary particle diameter of preferably about 80
to 400 nm, and more preferably about 100 to 200 nm, from the
viewpoint of having an appropriate thickening ability. In addition,
those produced by the direct polymerization method are preferable.
As a result, the grease can be kept in a semi-solid state. Note
that in the present specification, the primary particle size means
the average particle size of the primary particles (that is, it
refers to the basic constituent particles of the substance, and
those that are formed by aggregation of primary particles and
behave as one particle are called secondary particles), and refers
to the arithmetic mean value of the values measured with an
electron microscope.
[0014] Silica has a specific surface area of preferably about 15 to
410 m.sup.2/g from the viewpoint of having an appropriate
thickening ability. Note that in the present specification, the
specific surface area refers to a value measured by the BET
method.
[0015] The diurea compound is represented by the following formula
(I)
R1-NHCONH--R2-NHCONH--R3 (I),
where R1 and R3 may be the same or different from each other, and
represent a C6-30 alkyl group, a C5-8 cycloalkyl group, or a C6-10
aryl group, and R2 represents a divalent aromatic hydrocarbon group
having 6 to 15 carbon atoms.
[0016] Among the diurea compounds, so-called aliphatic diurea
compounds, in which R1 and R3 are the same or different C6-30 alkyl
groups, are preferable from the viewpoint of improving the grease
fluidity by undergoing shearing in the vicinity of the contact
surface. Among these, diurea compounds in which both R1 and R3 are
C8 alkyl groups, diurea compounds in which both R1 and R3 are C18
alkyl groups, and diurea compounds in which one of R1 and R3 is a
C8 alkyl group and the other is a C18 alkyl are preferable.
[0017] The calcium sulfonate complex is a complex (complex soap)
containing calcium sulfonate and a calcium salt of an acid other
than sulfonic acid.
[0018] Examples of the sulfonic acid constituting the calcium
sulfonate include dodecylbenzene sulfonic acid, dinonylnaphthalene
sulfonic acid, and petroleum sulfonic acid. As the sulfonic acid,
dodecylbenzene sulfonic acid is preferable.
[0019] Examples of the acid other than the sulfonic acid include
12-hydroxystearic acid and acetic acid.
[0020] As the calcium sulfonate complex used in the present
invention, a complex formed from dodecylbenzene sulfonic acid,
12-hydroxystearic acid, and acetic acid with a calcium source is
particularly preferable. That is, a salt of any two acids selected
from the group consisting of dodecylbenzene sulfonic acid,
12-hydroxystearic acid, and acetic acid with calcium is preferable.
This complex contains calcium dodecylbenzenesulfonate, calcium
12-hydroxystearate, and calcium acetate. The complex may also
contain calcium borate and calcium carbonate.
[0021] The amount of the thickener in the grease composition of the
present invention is preferably about 2 to 59% by mass, more
preferably about 4 to 49% by mass, and particularly preferably
about 30 to 49% by mass, based on the total mass of the
composition. An amount of about 2% by mass or more is preferable
from the viewpoint of keeping the grease in a semi-solid state and
preventing the grease from flowing out of the contact portion. An
amount of about 59% by mass or less is preferable because the
grease is not too hard, an appropriate fluidity is maintained, and
application is facilitated.
<Base Oil>
[0022] The base oil used in the grease composition of the present
invention is preferably a synthetic hydrocarbon oil. Although a
base oil other than synthetic hydrocarbon oils can be used, it is
preferable to use only a synthetic hydrocarbon oil from the
viewpoint of heat resistance, low temperature, and resin
compatibility. Examples of the synthetic hydrocarbon oil include
poly(.alpha.-olefin) (PAO), polybutene, polyethylene, and olefin
polymers such as a copolymer of .alpha.-olefin and ethylene. A
poly(.alpha.-olefin) is preferable from the viewpoint that a low
viscosity base oil can be selected.
[0023] The kinematic viscosity of the base oil at 40.degree. C. is
preferably about 200 mm.sup.2/s or less. Thereby, appropriate low
temperature fluidity can be ensured. The kinematic viscosity of the
base oil at 40.degree. C. is preferably about 15 mm.sup.2/s or
more, and more preferably about 60 to 200 mm.sup.2/s.
[0024] The content of the base oil in the grease composition of the
present invention is an amount usually used for producing grease,
and is, for example, about 40 to 97% by mass, and is preferably
about 50 to 95% by mass, and more preferably about 55 to 90% by
mass, from the viewpoint of allowing the grease to retain a
sufficient amount of base oil.
<Organic Sulfur Compound>
[0025] The organic sulfur compound in the present invention acts as
an anti-wear additive. In general, in an anti-wear additive having
sulfur, the anti-wear additive is adsorbed on the friction surface,
and the sulfur element reacts with the friction surface to form a
wear resistant film. Without wishing to be bound by any theory, it
is considered that the organic sulfur compound used in the present
invention has no heterocyclic nitrogen in the molecule, and thus is
less likely to inhibit the adsorption of sulfur on gold or the gold
alloy as the friction surface, and can form a film having effective
wear resistance.
[0026] Specific examples of the organic sulfur compound used in the
present invention include thiols, disulfides, alkylthiophenes,
sulfide oils and/or fats, olefin sulfides, alkylthiophosphates, and
alkylthiophosphate esters. Thiols, alkylthiophosphates, and
alkylthiophosphate esters are preferable, and thiols are
particularly preferable.
[0027] Examples of the thiol include a thiol having a linear or
branched alkyl group having 6 to 24 carbon atoms. A thiol having a
linear or branched alkyl group having 14 to 20 carbon atoms is
preferable, a thiol having a linear alkyl group having 16 to 20
carbon atoms is more preferable, and a thiol having a linear alkyl
group having 18 carbon atoms is most preferable.
[0028] Examples of the disulfides include dialkyl disulfides,
dibenzyl disulfide, diallyl disulfide, dicyclohexyl disulfide, and
diphenyl disulfide. Dibenzyl disulfide is preferable.
[0029] Examples of the alkylthiophenes include thiophene in which
one or two linear or branched alkyl groups having 1 to 24 carbon
atoms are bonded to the thiophene ring. The sulfide oils and/or
fats are also called sulfide esters, and refer to sulfides of fatty
acid glycerin esters and fatty acid esters. The sulfide oils and/or
fats may be active or inactive. Active oils and/or fats are
preferable. Note that when the color changes to green or black in
the copper strip corrosion test (a test to evaluate whether a
copper strip turns green or black after immersing the copper strip
in a 5% solution of the additive and allowing it to stand at
100.degree. C. for 3 hours), it is active. A typical compound is
represented by the following formulas (1) and (2), where R is a
hydrocarbon group in the formula, and x is a number of 1 or
more.
##STR00001##
[0030] The olefin sulfide refers to a sulfide of an olefin, and
refers to a compound represented by the general formula R--(S)n-R',
where R and R' are each independently a linear or branched olefin,
and may contain a sulfur atom in the chain, and n is an integer of
1 or more. The olefin sulfide may be active or inactive. Active
olefins are preferable. Note that the meaning of the term "active"
is the same as that described for the sulfide oils and/or fats.
Typical sulfide olefins are represented by the following formulas
(3) and (4).
##STR00002##
[0031] The organic thiophosphoric acid is represented by the
formula (RO).sub.3-xR.sub.xPS, where R is a hydrocarbon group, and
also includes ones in which the RO portion is replaced with RS.
[0032] Examples of the alkylthiophosphate esters include compounds
represented by the following formula (5).
##STR00003##
[0033] where R is H, C1-C10 alkyl. R is preferably H or
tert-butyl.
[0034] The amount of the organic sulfur compound in the grease
composition of the present invention is preferably about 0.001 to
5% by mass (sulfur equivalent: about 9.5.times.10.sup.-5 to 1.3%),
more preferably about 0.01 to 5% by mass (about 9.5.times.10.sup.-4
to 1.3%), and particularly preferably about 0.01 to 2% by mass
(about 9.5.times.10' to 0.52%), based on the total mass of the
composition. When the amount is about 0.001% by mass or more
(sulfur equivalent: about 9.5.times.10.sup.-5% or more), the wear
reduction effect of Au plating can be expected. An amount of about
5% by mass or less (sulfur equivalent: about 1.3% or less) is
preferable from the viewpoint of obtaining the wear reduction
effect at an economically reasonable concentration and preventing
the odor caused by a large amount of sulfur compounds.
<Other Additives>
[0035] For the grease composition of the present invention, any
additive generally used for grease compositions can be used, if
necessary. For example, antioxidants, rust inhibitors, metal
corrosion inhibitors, oiliness improvers, viscosity index improvers
and the like can be mentioned.
[0036] Examples of the antioxidants include amine-based,
phenol-based, quinoline-based, sulfur-based ones, and zinc
dithiophosphate, and amine-based ones are preferable. Examples of
the amine-based ones include phenyl-.alpha.-naphthylamine,
alkylphenyl-.alpha.-naphthylamine, and alkyl diphenyl amine, and
alkyl diphenyl amine is particularly preferable.
[0037] Examples of the rust inhibitors include zinc-based,
carboxylic acid-based, carboxylate-based, amine-based, and
sulfonate-based ones, and sulfonate-based ones, particularly Ca
sulfonate is preferable. Examples of the Ca sulfonate include a
calcium salt of petroleum sulfonic acid obtained by sulfonation of
aromatic hydrocarbon components in lubricating oil fraction, a
calcium salt of synthetic sulfonic acids such as dinonylnaphthalene
sulfonic acid and alkylbenzene sulfonic acid, an overbasic calcium
salt of petroleum sulfonic acid, and an overbasic calcium salt of
alkyl aromatic sulfonic acid, and overbasic Ca sulfonate is
particularly preferable.
[0038] Examples of the metal corrosion inhibitors include
benzimidazole-based and benzotriazole-based ones, and
benzotriazole-based ones are preferable. Examples of the
benzotriazole-based ones include 1,2,3-benzotriazole,
1,H-benzotriazole, 4-methyl-1,H-benzotriazole,
4-carboxy-1,H-benzotriazole, sodium tolyltriazole,
5-methyl-1,H-benzotriazole, benzotriazole butyl ether, silver
benzotriazole, 5-chloro-1,H-benzotriazole, 1-chloro-benzotriazole,
1-di(C8H17)aminomethyl-benzotriazole,
2,3-dihydroxypropyl-benzotriazole,
1,2-dicarboxyethyl-benzotriazole, (C8H17)aminomethyl-benzotriazole,
bis(benzotriazole-1-yl-methyl) (C8H17)amine,
N,N-bis(2-ethylhexyl)-4-methyl-1H-benzotriazole-1-methyl amine, and
N,N-bis(2-ethylhexyl)-5-methyl-1H-benzotriazole-1-methylamine, and
1-[N,N-bis(2-ethylhexyl)aminomethyl]-4-methylbenzotriazole is
particularly preferable.
[0039] Examples of the oiliness improvers include fatty acids,
fatty acid esters, and phosphoric acid esters.
[0040] Examples of the viscosity index improvers include
polymethacrylate-based, polyisobutylene-based, ethylene-propylene
copolymer-based, and styrene-butadiene hydrogenated copolymer-based
ones.
[0041] The content of these additives is usually about 0.01 to 20%
by mass, and preferably about 0.1 to 5% by mass, based on the total
amount of the grease composition.
<Penetration>
[0042] The penetration of the grease composition of the present
invention means a 60-stroke worked penetration. The penetration is
preferably about 220 to 400, and more preferably about 265 to 385,
from the viewpoint of maintaining an appropriate hardness and
achieving both coatability and appropriate fluidity.
<Production Method>
[0043] The grease composition of the present invention can be
easily produced by mixing the above-mentioned components and
additional additives in a desired blending ratio by a conventional
method.
<Use>
[0044] The use of the grease of the present invention, that is, the
type of contact coated with the grease does not matter. For
example, sliding contacts, connector contacts, and brush contacts
can be mentioned.
Example 1
<Test Grease>
[0045] The components used to prepare the grease compositions of
Examples and Comparative Examples are as follows.
(Thickener)
[0046] PTFE: Primary particle diameter 120 nm [0047] Silica:
Specific surface area 170.+-.20 m.sup.2/g [0048] Aliphatic diurea:
Reaction product of diphenylmethane diisocyanate, octylamine, and
octadecylamine [0049] Calcium sulfonate complex: A mixture of a Ca
salt of each acid, produced from dodecylbenzene sulfonic acid,
12-hydroxystearic acid, acetic acid, calcium carbonate, and
Ca(OH).sub.2, with Ca salts of any two of these acids. This mixture
contains calcium borate and calcium carbonate. [0050] Li soap:
Lithium 12-hydroxystearate
(Base Oil)
[0051] Poly-alpha-olefin: The kinematic viscosities at 40.degree.
C. and 100.degree. C. are as presented in Tables 2 and 3. The
kinematic viscosity was measured according to JIS K 2220 23.
(Organic Sulfur Compound)
[0052] A thiol (stearyl mercaptan), a sulfide (dibenzyl disulfide),
a thiophene (octadecylthiophene), an olefin sulfide (active type),
a mixture of sulfide oil and/or fat and olefin sulfide (inactive
type), thiophosphoric acid, and a thiophosphate ester were used.
Table 1 presents the structural formula of each compound.
TABLE-US-00001 TABLE 1 Name Molecular Structure Thiol ##STR00004##
Disulfide ##STR00005## Thiophene ##STR00006## Olefin Sulfide
(Active) ##STR00007## Mixture of Sulfide Oil and/or Fat and Olefin
Sulfide (Inactive) ##STR00008## ##STR00009## Olefin Sulfide
##STR00010## Sulfide Oil and/or Fat Thiophosphoric Acid
##STR00011## Thiophosphate Ester ##STR00012## Mercaptobenzothiazole
(For Comparison) ##STR00013## Dibenzothiazyl Disulfide (For
Comparison) ##STR00014## ##STR00015##
(Additional Additives)
[0053] Antioxidant: Alkyl Diphenyl Amine
[0054] The components presented above were used in the amounts in %
by mass presented in Table 2 or Table 3 to prepare grease
compositions of Examples and Comparative Examples. An alkyl
diphenyl amine was added in the compositions in an amount of 2% by
mass for Examples and not for Comparative Examples. The balance is
the base oil. The worked penetration of the grease composition was
unified to 315. The worked penetration was measured by JIS K2220
7.
(Production of Base Grease Whose Thickener is Aliphatic Diurea)
[0055] In the base oil, 1 mol of diphenylmethane diisocyanate was
reacted at a ratio of 2 mol of a predetermined amine and cooled to
obtain a base grease.
(Production of Base Grease Whose Thickener is Li Soap)
[0056] Lithium 12-hydroxystearate was stirred in the base oil and
then heated to 230.degree. C. Then, the mixture was cooled to
100.degree. C. or lower with stirring to obtain a base grease.
(Production of Grease Composition in which the Thickener is Ca
Sulfonate Complex)
[0057] Dodecylbenzene sulfonic acid, 12-hydroxystearic acid, acetic
acid, calcium carbonate, and calcium hydroxide were stirred in the
base oil and heated to 170.degree. C. Then, boric acid and calcium
hydroxide were added and further stirred, and then cooled to
100.degree. C. or lower with stirring to obtain a base grease.
[0058] An additive was added to each of the base greases obtained
above in the ratio presented in Tables 2 and 3, and the test grease
composition was prepared by dispersing them with a three-roll
mill.
(Production of Grease Composition in which the Thickener is PTFE or
Silica)
[0059] The test grease compositions were prepared by blending the
additives with the base oil in the ratios presented in Tables 2 and
3, then adding PTFE or silica and dispersing them with a three-roll
mill.
<Test Method>
[0060] Wear resistance was evaluated by a fine sliding test.
Specifically, grease was applied to the following flat-plate test
piece to a thickness of 120 .mu.m. The flat-plate test piece was
driven by reciprocating motion with the embossed test piece pressed
from above the grease coating film with a specified load. After
sliding at a specified speed a specified number of times, the
amount of wear of the embossed test piece was measured with a laser
microscope.
[Test Conditions]
[0061] Flat-plate test piece: Plate thickness 0.25 mm, Au plating
(outermost layer)/Ni plating/Cu base material
[0062] Embossed test piece: Plate thickness 0.25 mm, Au plating
(outermost layer)/Ni plating/Cu base material
[0063] Temperature: 25.degree. C.
[0064] Load: 4.9 N
[0065] Speed: 0.1 mm/s
[0066] Sliding width: 0.3 mm
[0067] Number of slides: 1000 cycles
[0068] Grease coating thickness: 120 .mu.m
Evaluation: Wear amount 22000 .mu.m.sup.3 or less . . . O
(acceptable) [0069] Wear amount over 22000 .mu.m.sup.3 . . .
.times.(unacceptable)
TABLE-US-00002 [0069] TABLE 2 Example 1 Example 2 Example 3 Example
4 Example 5 Example 6 Thickener PTFE PTFE PTFE PTFE PTFE PTFE % by
Mass 35 35 35 35 35 35 Base Oil PAO PAO PAO PAO PAO PAO Kinematic
Viscosity 107 107 107 107 107 107 of Base Oil at 40.degree. C.
Organic Sulfur Thiol Sulfide Thiophene Olefin Mixture of Sulfide
Thiophosphoric Compound Sulfide Oil and/or Fat and Acid (Active)
Olefin Sulfide (Inactive) % by Mass 2 2 2 2 2 2 Wear Amount
[.mu.m.sup.3] 9870 15700 19900 18300 15600 13300 Determination
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. Comparative Comparative Example 7
Example 8 Example 1 Example 2 Thickener PTFE PTFE PTFE PTFE % by
Mass 35 35 35 35 Base Oil PAO PAO PAO PAO Kinematic Viscosity 107
107 107 107 of Base Oil at 40.degree. C. Organic Sulfur
Thiophosphate Thiol Mercapto- Dibenzothiazyl Compound Ester
benzothiazole Disulfide % by Mass 2 0.02 2 2 Wear Amount
[.mu.m.sup.3] 12300 17100 28300 33500 Determination .largecircle.
.largecircle. X X
TABLE-US-00003 TABLE 3 Comparative Comparative Comparative
Comparative Comparative Example 9 Example 10 Example 11 Example 12
Example 3 Example 4 Example 5 Example 6 Example 7 Thickener Silica
Aliphatic Ca Sulfonate Li Soap PTFE Silica Aliphatic Ca Sulfonate
Li Soap Diurea Complex Diurea Complex % by Mass 11.5 8.5 27 14.5 35
11.5 8.5 27 14.5 Base Oil PAO PAO PAO PAO PAO PAO PAO PAO PAO
Kinematic Viscosity 107 107 107 107 107 107 107 107 107 of Base Oil
at 40.degree. C. Organic Sulfur Thiol Thiol Thiol Thiol None None
None None None Compound % by Mass 2 2 2 2 0 0 0 0 0 Wear Amount
[.mu.m.sup.3] 9770 16300 16500 8890 41500 43900 53500 36600 22300
Determination .largecircle. .largecircle. .largecircle.
.largecircle. X X X X X
[0070] Examples 1 to 7, which used at least one selected from
thiols, sulfides, thiophenes, sulfide oils and/or fats olefin
(active type), mixture of sulfide oils and/or fats and sulfide
olefin (inactive type), thiophosphoric acid, and thiophosphate
esters as an additive, are superior in wear resistance as compared
with Comparative Examples 1 and 2.
[0071] This improvement is observed in all of PTFE, silica,
aliphatic diurea, calcium sulfonate complex, Li soap, urea-based
thickener, and PTFE (Examples 1, 8 to 11). Therefore, by using the
organic sulfur compound specified in the present invention, it is
possible to improve the wear resistance of the electrical contact
made of gold or a gold alloy regardless of the thickener and the
base oil.
* * * * *