JPS6239637B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for protecting silver contacts of switches such as electronic equipment. Traditionally, mineral oil-based greases have been used to protect contacts. However, when mineral oil-based grease is used, the contact resistance is unstable even if the plating condition of the silver surface of the contact is improved. Older light-acting type switches had the drawback of malfunctioning over time and poor reliability. In addition, poor sulfidation resistance has been a problem with silver contacts made of phosphor bronze or nickel silver. Silicone grease, which has become popular in recent years, solves these problems to a considerable extent, but it is still not sufficient, so in Japanese Patent Publication No. 51-33254, polyorganosiloxane By adding fatty acid esters and mercaptans, we are proposing a silicone grease that improves sulfidation resistance and stability of contact resistance, and has the ability to restore the performance of contacts that have suffered from poor performance.
However, even then, improvements in operating life and malfunction over time were not satisfactory. This is presumed to be because polydimethylsiloxane, polymethylphenylsiloxane, and the like used as base oils for silicone grease have a limited lubricating performance. The present inventors used a polyorganosiloxane having a long-chain alkoxy group with a carbon number of 4 or more as the base oil for silicone grease, and added a sulfur-containing extreme pressure lubricity improver to improve the lubricity on the surface of silver contacts. The present inventors have discovered that the silver contact has a marked improvement in performance, and as a result, the operational life of the silver contact can be extended and malfunctions can be prevented. That is, the present invention has the following formula: 1(A) General formula [R ¹ _a R ² _b SiO〓〓〓] _o (wherein, R ¹ is an alkyl group having 4 to 14 carbon atoms, and R ² is an alkyl group having 3 or less carbon atoms. represents a monovalent hydrocarbon group selected from the group consisting of atom, alkenyl, and aryl groups, where a+b is 1.9 to 2.7, the ratio of a to a+b is at least 0.05, and n is a number that satisfies the following viscosity. ), 100 parts by weight of a polyorganosiloxane having a viscosity of 10 to 100,000 cSt at 25°C, (B) 0.001 to 3 parts by weight of a sulfur-containing extreme pressure lubricity improver, and (C) a thickener. The present invention relates to a method for protecting silver contacts, characterized in that silicone grease consisting essentially of silicone grease is used as a contact protectant. Component (A) of the present invention has the general formula [R ¹ _a R ² _b SiO
It is a polyorganosiloxane represented by _o (R ¹ , R ² , a, b, and n are as described above). Because it contains a long-chain alkyl group represented by R ¹ in the side chain, it has superior lubricity compared to conventionally used polydimethylsiloxane, and also has excellent lubricity with components (B) and (C). It has good solubility and is easy to form into grease. If R ¹ is too small, that is, if the ratio of a to a+b is less than 0.05, such features cannot be obtained. If the number of carbon atoms in R ¹ is too large, it will be inconvenient to handle and the thermal stability will decrease. 14 or less is preferred. Examples of R ² include a methyl group, an ethyl group, a propyl group, a vinyl group, a phenyl group, and a methyl group is preferred from the viewpoint of ease of synthesis and heat resistance. The molecular structure may be linear, cyclic, or slightly branched, but
If the value of a+b is less than 1.9, the grease will become hard and cannot be used. Linear oils are preferred from the viewpoint of fluidity as a base oil and ease of synthesis. Siloxy units in linear molecules include R ¹ R ² SiO, R
¹ ₂ SiO, R ² ₂ SiO, R ² ₃ SiO _1/2 , etc.
Due to ease of synthesis, the general formula R ² ₃ SiO(R ¹ R ² SiO) _p
A polyorganosiloxane represented by (R ² SiO) _q SiR ² ₃ (p, q are integers satisfying the above-mentioned conditions regarding a, b, n) is most preferred. The viscosity of component (A) is 10 to 100000 cSt at 25℃
and preferably ranges from 20 to 1000 cSt. If it is lower than 10 cSt, problems such as easy separation of this component from the grease, large volatilization, and easy flow of the grease will occur, and if it is higher than 100,000 cSt, the lubricity of the contact will deteriorate. Since such long-chain alkyl group-containing polysiloxanes have good solubility in polybutene, paraffin, etc., they can also be added to the composition of the present invention in order to improve adhesiveness and slippage. There is an advantage. Therefore, by mixing the composition of the present invention with a mineral oil-based grease, the touch when operating a switch or tuner can be made soft and smooth. Conventional greases using polydimethylsiloxane separate over time even when mixed with mineral oil-based greases. Component (B) of the present invention is a sulfur-containing extreme pressure lubricity improver that has low volatility, such as hexyl mercaptan, octyl mercaptan, nonyl mercaptan, decyl mercaptan, dodecyl mercaptan, cetyl mercaptan, lauryl mercaptan, Examples include mercaptans such as stearyl mercaptan, zinc dialkyldithiophosphate, dibenzyl disulfide, and sulfurized spam oil, but from the viewpoint of effectiveness, mercaptans, especially
Alkyl mercaptans having 10 or more carbon atoms are preferred. The blending amount of component (B) is 0.001 to 3 parts by weight, preferably 0.1 to 1 part by weight, per 100 parts by weight of component (A). If the amount is less than this, sufficient lubricating oil will not be obtained, and if it is more than this, the odor will be strong and contact resistance will be abnormal, which is not appropriate. In particular, since mercaptans also have a sulfuration prevention effect, it is preferable to add 0.1 part by weight or more. Component (C) of the present invention imparts appropriate consistency to the polyorganosiloxane of component (A), and includes fine silica powder, higher fatty acid salts of metals, and the like. As the silica fine powder, atomized silica, silica aerogel, precipitated silica, etc., with a comparative area of 50 m ² /g or more, are generally used. Higher fatty acid salts of metals include laurates, myristates, palmitates, etc. of aluminum, zinc, lead, manganese, lithium, calcium, barium, strontium, copper, bismuth, chromium, nickel, etc.
Examples include stearate and oleate. These may be used alone or in combination,
The blending amount is 100% of component (A) in order to obtain an appropriate consistency.
It is preferably 0.01 to 25 parts by weight. The grease consisting of (A) to (C) is applied to the surface of the silver contact of the switch to a thickness of 0.01 to 500μ, preferably 0.5 to 50μ. If it is thinner than 0.01μ, the contact will wear out quickly, and if it is thicker than 500μ, the grease will collect in one place, causing it to stick out or hinder operation. When applying, the grease may be used as it is, but it is preferable to dilute it with a low boiling point solvent because it allows for more uniform application. The present invention makes it possible to improve the sulfidation resistance, stability of contact resistance, and operating life of silver contacts. The present invention will be explained below with reference to Examples. In the examples, all parts are by weight, and the viscosity is the value at 25°C. Example 1 A polydiorganosiloxane blocked at both ends with trimethylsilyl groups shown in Table 1 was used as the base oil.

[Table] Silicone grease was prepared using the ingredients shown in Table 2. Fine silica powder has a specific surface area that has been surface-treated with octamethylcyclotetrasiloxane.
200 m ² /g of fumed silica. Numbers indicate the number of copies of each component. Using these greases, changes in contact resistance and changes in operating force were measured for a switch contact made of phosphor bronze plated with silver to a thickness of approximately 3 μm and having a contact load of 10 g. The results are shown in Table 3. Actuation forces were measured with the spring removed from the switch components.

【table】

[Table] Example 2 A polydiorganosiloxane blocked at both ends with trimethylsilyl groups shown in Table 4 was used as the base oil.

[Table] 5.5 parts of the fine silica powder used in Example 1 and 1.2 parts of lauryl mercaptan were mixed with base oil and 100 parts, and greases 10 and 11 of the present invention were mixed.
adjusted. Table 5 shows the results of the same measurements as in Example 1 using these greases.

【table】

Claims (1)

[Claims] 1 (A) General formula [R ¹ _a R ² _b SiO〓〓〓] _o (wherein, R ¹ is carbon number 4
~14 alkyl group, ^R2 represents a monovalent hydrocarbon group selected from the group consisting of an alkyl group, an alkenyl group, and an aryl group having 3 or less carbon atoms,
a+b is 1.9 to 2.7, the ratio of a to a+b is at least 0.05, n is a number that satisfies the following viscosity), and the viscosity at 25°C is 10 to 2.7.
The use of a silicone grease consisting essentially of 100 parts by weight of polyorganosiloxane having a molecular weight of 100,000 cSt, (B) 0.001 to 3 parts by weight of a sulfur-containing extreme pressure lubricity improver, and (C) a thickener is used as a contact protectant. Features a method of protecting silver contacts. 2 (A) is a linear polyorganosiloxane,
A method according to claim 1. 3 (A) is the general formula R ² ₃ SiO (R ¹ R ² SiO) _p (R ² ₂ SiO) _q SiR ² ₃ (wherein, R ¹ and R ² are the values of p+q and The ratio of p to p+q is the first term a,
2. The method according to claim 2, wherein the polyorganosiloxane is a polyorganosiloxane represented by: 4. The method according to claim 1, wherein R ² in (A) is a methyl group. 5. The method according to claim 1, wherein (A) has a viscosity of 20 to 1000 cSt at 25°C. 6. The method of claim 1, wherein (B) is a mercaptan. 7. The method according to claim 6, wherein (B) is an alkyl mercaptan having 10 or more carbon atoms.