JP2021172667A - Grease composition for electric contact - Google Patents

Abstract

To provide an improved grease composition for an electric contact.SOLUTION: The grease composition for the electric contact comprises a thickener, a base oil, and an organic sulfur compound, wherein the organic sulfur compound is a compound having no heterocycle containing nitrogen in its molecule.SELECTED DRAWING: None

Description

The present invention relates to a grease composition for electrical contacts having excellent wear resistance of gold plating.

As electrical contacts and connectors used in electrical products, OA equipment, in-vehicle electrical components, equipment for various equipment, etc., in order to ensure good conductivity, it has excellent conductivity among metals, and has oxidation resistance and corrosion resistance. A contact material is used in which gold or a gold alloy with excellent properties is plated on copper or the base metal of the copper alloy.
In recent years, many mechanical parts are required to be reduced in cost, and the electrical contacts, which are a part of them, are naturally required to be reduced in cost. One of the methods for 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 tends to stick 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 continuity.
As a countermeasure for this, improvement of the life of the electric contact can be mentioned by using a lubricant having excellent wear resistance against gold plating. As a lubricant for reducing wear of gold plating, a lubricant to which mercaptobenzothiazole or dibenzothiazyldisulfide is added (Patent Document 1) has been reported.

Japanese Unexamined Patent Publication No. 2005-068391

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 Document 1 states that thickening can prevent oil from dripping from the plating surface, but if the viscosity of the oil decreases at high temperatures, there is a concern that the oil will dripping and stain the peripheral members. It still remains.
Based on the above, the problem to be solved 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 soiled due to the dripping of the lubricant. It is to be.

In response to the above-mentioned problem of improving wear resistance, the present inventors have improved the wear resistance of gold plating by using an organic sulfur compound containing no heterocyclic nitrogen.
1. 1. The grease composition for electrical contacts containing a thickener, a base oil, and an organic sulfur compound, wherein the organic sulfur compound is a compound having no heterocycle containing nitrogen in its molecule. ..
2. The grease composition according to 1 above, wherein the organic sulfur compound is at least one selected from the group consisting of thiols, disulfides, alkylthiophenes, sulfides of fats and oils or olefins, and thiophosphates or esters thereof.
3. 3. The grease composition according to 1 or 2 above, wherein the base oil is a synthetic hydrocarbon oil.
4. The grease composition according to any one of 1 to 3 above, wherein the base oil dynamic viscosity is 200 mm ^{2 / s or less at 40 ° C.}
5. The grease composition according to any one of 1 to 4 above, wherein the thickener is one or more selected from the group consisting of Li soap, urea compound, polytetrafluoroethylene, inorganic fine particles, and calcium sulfonate complex.
6. The grease composition according to any one of 1 to 5 above, wherein the material of the electrical contact is gold or a gold alloy.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a grease composition having improved wear resistance of gold plating. According to the grease composition of the present invention, the life of an electric contact having a thin gold plating can be improved.

<Thickener>
The thickener used in the grease composition of the present invention is not particularly limited. Specifically, Li soaps such as lithium stearate and lithium 12-hydroxystearate, soap-based thickeners typified by Li-complex soaps; urea-based compounds typified by diurea compounds; polytetrafluoroethylene (PTFE). ) And organic thickeners typified by sodium terephthalate; inorganic fine particles typified by organic bentonite and silica; calcium sulfonate complex and the like.
Of these, one or more selected from the group consisting of Li soap, urea compound, PTFE, inorganic fine particles, and calcium sulfonate complex is preferable.
More preferably, it is PTFE, silica, diurea compound, 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 is preferable.
The PTFE has a primary particle size of 80 to 400 nm, more preferably 100 to 200 nm, from the viewpoint of having an appropriate thickening ability. Further, those produced by the direct polymerization method are preferable. As a result, the grease can be kept in a semi-solid state. In the present specification, the primary particle size is the average of primary particles (that is, the basic constituent particles of the substance; those in which the primary particles aggregate and appear to behave as one particle are referred to as secondary particles). It means the particle size and refers to the arithmetic average value of the values measured with an electron microscope.
The silica preferably has a specific surface area of 15 to 410 m ² / g from the viewpoint of having an appropriate thickening ability. In this specification, the specific surface area refers to a value measured by the BET method.

The diurea compound is represented by the following formula (I).
R1-NHCONH-R2-NHCONH-R3 (I)
(In the formula, 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 is 2 having 6 to 15 carbon atoms. Indicates a valent aromatic hydrocarbon group.)
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 them, a diurea compound in which R1 and R3 are both C8 alkyl groups, a diurea compound in which both R1 and R3 are C18 alkyl groups, and one of R1 and R3 is a C8 alkyl group and the other is a C18 alkyl group. Diurea compounds are preferred.

The calcium sulfonate complex is a complex (complex soap) containing calcium sulfonate and a calcium salt of an acid other than sulfonic acid.
Examples of the sulfonic acid constituting calcium sulfonate include dodecylbenzene sulfonic acid, dinonylnaphthalene sulfonic acid, petroleum sulfonic acid and the like. As the sulfonic acid, dodecylbenzene sulfonic acid is preferable.
Examples of acids other than sulfonic acid include 12-hydroxystearic acid and acetic acid.
As the calcium sulfonate complex used in the present invention, a complex formed from dodecylbenzenesulfonic acid, 12-hydroxystearic acid, acetic acid and 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 and calcium is preferable. This complex contains calcium dodecylbenzene sulfonate, calcium 12-hydroxystearate, and calcium acetate. The complex may also contain calcium borate and calcium carbonate.

The amount of the thickener in the grease composition of the present invention is preferably 2 to 59% by mass, more preferably 4 to 49% by mass, and particularly preferably 30 to 49% by mass, based on the total mass of the composition. be. By making it 2% by mass or more, it is preferable from the viewpoint of keeping the grease in a semi-solid state and preventing the grease from flowing out from the contact portion. When it is 59% by mass or less, the grease is not too hard, an appropriate fluidity is maintained, and it is preferable from the viewpoint of facilitating coating.

<Base oil>
The base oil used in the grease composition of the present invention is preferably a synthetic hydrocarbon oil. Although a base oil other than the synthetic hydrocarbon oil can be used, it is preferable to use only the synthetic hydrocarbon oil from the viewpoint of heat resistance, low temperature, and resin compatibility. Examples of the synthetic hydrocarbon oil include polyα-olefin (PAO), polybutene, polyethylene, and olefin polymers such as a copolymer of α-olefin and ethylene. A poly-α-olefin is preferable from the viewpoint that a low-viscosity base oil can be selected.
The kinematic viscosity of the base oil at 40 ° C. ^{is preferably 200 mm 2} / s or less. Thereby, appropriate low temperature fluidity can be ensured. The kinematic viscosity of the base oil at 40 ° C. ^{is preferably 15 mm 2} / s or more. More preferably, it is 60 to 200 mm ^{2 / s.}
The content of the base oil in the grease composition of the present invention is an amount usually used for producing the grease, for example, 40 to 97% by mass, and from the viewpoint of allowing the grease to retain a sufficient amount of the base oil. , 50-95% by mass, more preferably 55-90% by mass.

<Organosulfur compounds>
The organic sulfur compound in the present invention acts as an abrasion resistant agent. Generally, in a wear resistant agent having sulfur, the wear resistant agent is adsorbed on the friction surface, and the sulfur element reacts with the friction surface to form a wear resistant film. Although not bound by any theory, the organic sulfur compound used in the present invention does not have heterocyclic nitrogen in the molecule, so that adsorption of sulfur to gold or a gold alloy, which is a friction surface, is inhibited. It is considered that a film that is difficult and has effective abrasion resistance can be formed.
Specific examples of the organic sulfur compound used in the present invention include thiols, disulfides, alkylthiophenes, oils and fats sulfides, olefins sulfides, alkylthiophosphates, and alkylthiophosphates. Thiols, alkylthiophosphates and alkylthiophosphates are preferred, with thiols being particularly preferred.

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.
Examples of the disulfide include dialkyl disulfide, dibenzyl disulfide, diallyl disulfide, dicyclohexyl disulfide, and diphenyl disulfide. Dibenzyl disulfide is preferred.
Examples of the alkylthiophene include thiophene in which one or two linear or branched alkyl groups having 1 to 24 carbon atoms are bonded to the thiophene ring.
Sulfated fats and oils are also called sulfide esters and refer to fatty acid glycerin esters and sulfides of fatty acid esters. The sulfide fats and oils may be active or inactive. Active fats and oils are preferable. In addition, when the color changes to green or black by the copper plate corrosion test (a test in which the copper plate is immersed in a 5% solution of the additive, allowed to stand at 100 ° C. for 3 hours, and then evaluated whether the copper plate turns green or black). It is active. Representative compounds are represented by the following formulas (1) and (2). (R is a hydrocarbon group in the formula, and x is a number of 1 or more.)

The sulphide olefin refers to a sulfide of an olefin and refers to a compound represented by the general formula R- (S) n-R'(in the formula, R and R'are linear or branched olefins independently of each other. Yes, the chain may contain a sulfur atom, where n is an integer greater than or equal to 1). The olefin sulfide may be active or inert. Active olefins are preferred. The meaning of the term "activity" is the same as that described for sulfide fats and oils. Typical sulfide olefins are represented by the following formulas (3) and (4).

The organic thiophosphate is represented by the formula (RO) _3-x R _x PS (in the formula, R is a hydrocarbon group), and the one in which the RO portion is replaced with RS is also included.
Examples of the alkylthiophosphate include a compound represented by the following formula (5).

式中、ＲはＨ，Ｃ１〜Ｃ１０アルキルである。Ｒは、Ｈ又はｔｅｒｔ−ブチルであるのが好ましい。

In the formula, R is H, C1-C10 alkyl. R is preferably H or tert-butyl.

The amount of the organic sulfur compound in the grease composition of the present invention is preferably 0.001 to 5% by mass (sulfur equivalent: 9.5 × 10 ^{-5 to} 1.3%) based on the total mass of the composition. ), More preferably 0.01 to 5% by mass (9.5 × 10 ^{-4 to} 1.3%), and particularly preferably 0.01 to 2% by mass (9.5 × 10 ^{-4 to} 0.52%). ). By setting it to 0.001% by mass or more (sulfur conversion amount: 9.5 × 10 ^-5 % or more), the wear reduction effect of Au plating can be expected. By setting the content to 5% by mass or less (sulfur conversion amount: 1.3% or less), it is preferable to obtain an effect of reducing wear at an economically rational concentration and to prevent an odor due to a large amount of sulfur compounds.

<Other additives>
For the grease composition of the present invention, any additive generally used for the grease composition can be used, if necessary. For example, antioxidants, rust inhibitors, metal corrosion inhibitors, oily agents, viscosity index improvers and the like can be mentioned.
Examples of the antioxidant include amine-based, phenol-based, quinoline-based, sulfur-based, zinc dithiophosphate and the like, but amine-based agents are preferable. Examples of the amine system include phenyl α-naphthylamine, alkylphenyl α-naphthylamine, alkyldiphenylamine and the like, and alkyldiphenylamine is particularly preferable.
Examples of the rust preventive agent include zinc-based, carboxylic acid-based, carboxylate-based, amine-based, and sulfonate-based, but sulfonate-based, particularly Ca sulfonate is preferable. Ca sulfonates include calcium salts of petroleum sulfonic acids obtained by sulfonated aromatic hydrocarbon components in lubricating oil distillates, calcium salts of synthetic sulfonic acids such as dinonylnaphthalene sulfonic acid and alkylbenzene sulfonic acid, and petroleum sulfonates. Examples thereof include a hyperbasic calcium salt of an acid and a hyperbasic calcium salt of an alkyl aromatic sulfonic acid, and a hyperbasic Ca sulfonate is particularly preferable.

Examples of the metal corrosion inhibitor include benzimidazole type and benzotriazole type, but benzotriazole type is preferable. Benzotriazoles include 1,2,3-benzotriazole, 1,H-benzotriazole, 4-methyl-1, H-benzotriazole, 4-carboxy-1, H-benzotriazole, sodium triltriazole, 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-methylamine, N, N-bis (2-ethylhexyl) -5-methyl-1H-benzotriazole-1-methylamine, etc., in particular 1- [N, N-bis (2-ethylhexyl) aminomethyl] -4-methylbenzotriazole is preferable.

Examples of the oily agent include fatty acids, fatty acid esters, and phosphoric acid esters.
Examples of the viscosity index improver include polymethacrylate-based, polyisobutylene-based, ethylene-propylene copolymer-based, and styrene-butadiene hydrogenated copolymer-based.
The content of these additives is usually 0.01 to 20% by mass, preferably 0.1 to 5% by mass, based on the total amount of the grease composition.

<Consistency>
The consistency of the grease composition of the present invention means a miscibility of 60 times. The consistency is preferably 220 to 400, and more preferably 265 to 385, from the viewpoint of maintaining an appropriate hardness and achieving both coatability and appropriate fluidity.
<Manufacturing method>
The grease composition of the present invention can be easily produced by mixing the above-mentioned components and other additives in a desired blending ratio by a conventional method.
<Use>
The application of the grease of the present invention, that is, the type of contact to which the grease is applied does not matter. For example, sliding contacts, connector contacts, and brush contacts can be mentioned.

<Test grease>
The components used to prepare the grease compositions of Examples and Comparative Examples are as follows.
(Thickener)
-PTFE: Primary particle size 120 nm
-Silica: Specific surface area 170 ± 20 m ² / g
-Adioxy diurea: a reaction product of diphenylmethane diisosianate with octylamine and octadecylamine-Calcium sulfonate complex: Produced from dodecylbenzenesulfonic acid, 12-hydroxystearic acid, acetic acid, calcium carbonate, and Ca (OH) _2. , A mixture of the Ca salt of each acid and the Ca salt of any two of these acids. This mixture contains calcium borate and calcium carbonate.
・ Li soap: 12 lithium hydrostearate

(Base oil)
-Polyalphaolefin: The kinematic viscosities at 40 ° C and 100 ° C are as shown in Tables 2 and 3. The kinematic viscosity is JIS K 2220 23. Measured according to.

(Organosulfur compounds)
Thiol (stearyl mercaptan), sulfide (dibenzyldisulfide), thiophene (octadecylthiophene), olefin sulfide (active type), mixture of sulfide oil and fat and olefin sulfide (inactive type), thiophosphate, and thiophosphate ester were used. The structural formula of each compound is shown in Table 1.

(Other additives)
-Antioxidant: Alkyldiphenylamine The components shown above were used in the mass% shown in Table 2 or Table 3 to prepare grease compositions of Examples and Comparative Examples. Alkyldiphenylamine was added in the composition in an amount of 2% by mass for Examples and not for Comparative Examples. The rest is the base oil. The miscibility of the grease composition was unified to 315. The miscibility is JIS K2220 7. Measured by.

(Manufacturing of base grease whose thickener is aliphatic diurea)
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.

(Manufacture of base grease whose thickener is Li soap)
Lithium 12-hydroxystearate was stirred in the base oil and then heated to 230 ° C. Then, the mixture was cooled to 100 ° C. or lower with stirring to obtain a base grease.

(Manufacture of grease composition in which the thickener is a Ca sulfonate complex)
In the base oil, dodecylbenzenesulfonic acid, 12-hydroxystearic acid, acetic acid, calcium carbonate and calcium hydroxide were stirred and heated to 170 ° C. Then, boric acid and calcium hydroxide were added and further stirred, and then cooled to 100 ° C. or lower with stirring to obtain a base grease.

Additives were added to each of the base greases obtained above at the ratios shown in Tables 2 and 3, and the test grease compositions were prepared by dispersing them with a three-roll mill.

(Manufacture of grease composition in which the thickener is PTFE or silica)
Additives were added to the base oil in the proportions shown in Tables 2 and 3, then PTFE or silica was added, and the mixture was dispersed with a three-roll mill to prepare a test grease composition.

<Test method>
Abrasion resistance was evaluated by a fine sliding test. Specifically, grease is applied to the following flat plate test piece to a thickness of 120 μm, and the flat plate test piece is driven by reciprocating motion with the embossed test piece pressed against 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]
Flat plate test piece: Plate thickness 0.25 mm, Au plating (outermost layer) / Ni plating / Cu base material Embossed test piece: Plate thickness 0.25 mm, Au plating (outermost layer) / Ni plating / Cu base material Temperature: 25 ° C
Load: 4.9N
Speed: 0.1 mm / s
Sliding width: 0.3 mm
Number of slides: 1000 cycles Grease application thickness: 120 μm
Evaluation: Wear amount 22000 μm ³ or less ・ ・ ・ 〇 (pass)
Amount of wear 22000 μm Over ³・ ・ ・ × (Failure)

Examples 1 to 1 using at least one selected from thiol, sulfide, thiophene, sulfide oil and fat olefin (active type), mixture of sulfide oil and fat and sulfide olefin (inactive type), thiophosphate, and thiophosphate ester as additives. 7 is superior in abrasion resistance as compared with Comparative Examples 1 and 2.
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 electric contact made of gold or a gold alloy regardless of the thickener and the base oil.

Claims (6)

The grease composition for electrical contacts containing a thickener, a base oil, and an organic sulfur compound, wherein the organic sulfur compound is a compound having no heterocycle containing nitrogen in its molecule. .. 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 fats and oils or olefins, and thiophosphates or esters thereof. The grease composition according to claim 1 or 2, wherein the base oil is a synthetic hydrocarbon oil. The grease composition according to any one of claims 1 to 3, wherein the base oil dynamic viscosity is 200 mm ^{2 / s or less at 40 ° C.} The grease composition according to any one of claims 1 to 4, wherein the thickener is at least one selected from the group consisting of Li soap, urea compound, polytetrafluoroethylene, inorganic fine particles, and calcium sulfonate complex. thing. The grease composition according to any one of claims 1 to 5, wherein the material of the electrical contact is gold or a gold alloy.