JP2000103966A - Silicone rubber composition for rubber contact and rubber contact - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a silicone rubber composition for a rubber contact, capable of forming a rubber contact having an excellent click feeling, and a rubber contact having an excellent click feeling made from the composition. SOLUTION: This silicone rubber composition for a rubber contact and a rubber contact obtained by curing the silicone rubber composition comprise a silicone rubber composition containing petaloid inorganic powder (e.g. calcium silicate powder or hydrochloric acid-treated calcium silicate powder) or inorganic powder having at least 200 ml/100g oil absorption measured by a method defined by JIS K 6,220-1995 and at least 0.014 ml/m2 oil absorption based on BET specific surface area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicone rubber composition for a rubber contact and a rubber contact, and more particularly to a silicone rubber composition for a rubber contact capable of forming a rubber contact having a good click feeling, and this composition. And a rubber contact having a good click feeling.

[0002]

2. Description of the Related Art Silicone rubber compositions for forming rubber contacts include, for example, organopolysiloxanes, reinforcing silica having a BET specific surface area of 50 m ² / g or more, organosilicon compounds containing silicon-bonded alkoxy groups, Rubber composition comprising a silicone and a curing agent
(See JP-A-4-108857), an organopolysiloxane containing at least two alkenyl groups in one molecule, an organopolysiloxane resin containing at least two alkenyl groups in one molecule, and an organic resin. Silicone rubber composition comprising an oxide (JP-A-5-2952
No. 67), an organopolysiloxane containing at least two alkenyl groups in one molecule, an organopolysiloxane resin containing at least two alkenyl groups in one molecule, an organohydrogenpolysiloxane, and a platinum-based resin. Silicone rubber composition comprising a catalyst
(See JP-A-5-295268), an organopolysiloxane containing an alkenyl group and having an average degree of polymerization of 100 or more, a reinforcing silica having a BET specific surface area of 50 m ² / g or more, and 1,1,3. And 3-tetraorganodisiloxane-1,3-diol (see JP-A-7-133433). However, the click sensation of the rubber contact formed by these silicone rubber compositions was not sufficient.

[0003]

DISCLOSURE OF THE INVENTION The present inventors have intensively studied the above-mentioned problems, and as a result, have reached the present invention. That is, an object of the present invention is to provide a silicone rubber composition for a rubber contact capable of forming a rubber contact having a good click feeling, and to be formed by this composition.
An object of the present invention is to provide a rubber contact having a good click feeling.

[0004]

The silicone rubber composition for rubber contact of the present invention has a petal-like inorganic powder or an oil absorption of at least 200 ml / 100 g as measured by the method specified in JIS K 6220-1995. And the oil absorption with respect to the BET specific surface area is at least 0.5.
It is characterized by comprising a silicone rubber composition containing an inorganic powder of 014 ml / m ² . Further, the rubber contact of the present invention is characterized by comprising a cured product of the above silicone rubber composition.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the silicone rubber composition for rubber contact of the present invention will be described in detail. The silicone rubber composition for rubber contact of the present invention is characterized by comprising a silicone rubber composition containing petal-like inorganic powder. This petal-like inorganic powder is a filler for imparting good mechanical properties and a click feeling to a rubber contact formed by curing the present composition. As the petal-like inorganic powder, petal-like crystalline calcium silicate powder,
A silica powder in which the content of the SiO ₂ component is increased by treating the calcium silicate powder with an acid such as hydrochloric acid is exemplified. In particular, the content of the SiO ₂ component is reduced to 90% by weight by subjecting the calcium silicate powder to acid treatment.
The silica powder described above is preferable because the transparency of the obtained silicone rubber can be improved. Further, an inorganic powder obtained by hydrophobizing the surface of the petal-like inorganic powder with an organosilicon compound such as an organosilane, an organosilazane, an organopolysiloxane, or a diorganocyclopolysiloxane can also be used. The particle diameter of the petal-like inorganic powder is preferably 50 μm or less, and the BET specific surface area is preferably at least 50 m ² / g, particularly, the BET specific surface area is at least 100 m ² / g. Is preferred.

[0006] The silicone rubber composition for rubber contact of the present invention has a phthalic acid content of phthalic acid measured by the method described in 6.21 “Oil absorption” specified in JIS K 6220-1995 (Testing method for rubber compounding agents). It is characterized by comprising a silicone rubber composition containing an inorganic powder having an oil absorption of dibutyl of at least 200 ml / 100 g and an oil absorption of at least 0.014 ml / m ² with respect to the BET specific surface area. This inorganic powder is a filler for imparting good mechanical properties and a click feeling to a rubber contact formed by curing the present composition. Examples of the inorganic powder include a calcium silicate powder and a silica powder.
Particularly, silica powder is preferable because the transparency of the obtained silicone rubber can be improved. further,
An inorganic powder obtained by subjecting the surface of the inorganic powder to hydrophobic treatment with an organosilicon compound such as organosilane, organosilazane, organopolysiloxane, or diorganocyclopolysiloxane can also be used. The particle size of this inorganic powder is 50
μm or less, and the BET specific surface area is preferably at least 50 m ² / g.
In particular, the BET specific surface area is at least 100 m ² / g
It is preferred that

In the silicone rubber composition for rubber contact of the present invention, petal-like inorganic powder or JI
The oil absorption measured by the method specified in SK 6220-1995 is at least 200 ml / 100 g, and the BET
The oil absorption based on the specific surface area is at least 0.014 ml /
Although the inorganic powder as essential as m ^2, and particularly preferably an inorganic powder serving also as these conditions, Examples of such an inorganic powder, (FLORITE R of Tokuyama Corporation) Petal-like calcium silicate powder, Alternatively, a powder obtained by pulverizing it is exemplified.

In the present composition, the content of these inorganic powders is preferably in the range of 1 to 100 parts by weight based on 100 parts by weight of the main component organopolysiloxane. This is because, according to the composition in which the content of these inorganic powders is less than the lower limit of this range, it tends to be difficult to give a good click feeling to the obtained rubber contact, This is because it tends to be difficult to mix an amount of the inorganic powder exceeding the upper limit of this range into the organopolysiloxane as the main component.

[0009] The curing mechanism of the silicone rubber composition for rubber contact of the present invention is not limited, and includes, for example, a room temperature curing type silicone rubber composition and a heat curing type silicone rubber composition. It is preferably an object. Examples of the heat-curable silicone rubber composition include a hydrosilylation reaction-curable silicone rubber composition and an organic peroxide-curable silicone rubber composition, and particularly, an organic peroxide-curable silicone rubber composition. Preferably, there is.

This organic peroxide-curable silicone rubber composition is, for example, a composition comprising at least (A) an alkenyl group-containing organopolysiloxane and (B) an organic peroxide. The alkenyl group-containing organopolysiloxane (A) is a main component of the present composition, and preferably has a linear or partially branched linear molecular structure. Examples of the alkenyl group in the component (A) include a vinyl group, an allyl group, a butynyl group, and a hexenyl group. In the component (A), the silicon-bonded organic group other than the alkenyl group includes an alkyl group such as a methyl group, an ethyl group and a propyl group; an aryl group such as a phenyl group, a tolyl group and a xylyl group; Examples thereof include an aralkyl group such as a phenethyl group; and a substituted or unsubstituted monovalent hydrocarbon group such as a halogenated alkyl group such as a 3,3,3-trifluoropropyl group. Examples of the organopolysiloxane of the component (A) include dimethyl siloxane / methyl vinyl siloxane copolymer having both ends of molecular chain trimethylsiloxy group, dimethyl polysiloxane having both ends of molecular chain dimethyl vinyl siloxy group, and dimethyl both ends of molecular chain. Examples thereof include a vinylsiloxy group-blocked dimethylsiloxane / methylvinylsiloxane copolymer, and a dimethylsiloxane / methylvinylsiloxane copolymer blocked at both molecular chain terminal silanol groups.

The organic peroxide of the component (B) is a curing agent for the present composition. Specifically, dicumyl peroxide, di-t-butyl peroxide, t-butyl cumyl peroxide, , 5-Dimethyl-2,5-di (t-
Butylperoxy) hexane, 2,5-dimethyl-2,
5-di (benzoylperoxy) hexane, 2,5-dimethyl-2,5-di (t-butylperoxy) -3,3,5
-Trimethylcyclohexane, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, parachlorobenzoyl peroxide, t-butylperoxyisopropyl monocarbonate.

In the present composition, the content of the component (B) is not limited as long as the composition can be cured, but practically, 0.1 to 100 parts by weight of the component (A). Preferably it is in the range of 15 parts by weight.

Further, by using a curing agent comprising a silicon-bonded hydrogen atom-containing organopolysiloxane and a platinum-based catalyst in place of the organic peroxide as the component (B), a hydrosilylation reaction-curable silicone rubber composition can be obtained. You can also. Examples of the organopolysiloxane containing a silicon atom-bonded hydrogen atom include methyl hydrogen polysiloxane having a trimethylsiloxy group at both ends of a molecular chain, dimethylpolysiloxane having a dimethylhydrogensiloxy group at both ends of a molecular chain, and dimethyl having a trimethylsiloxy group having both ends of a molecular chain. A siloxane / methylhydrogensiloxane copolymer is exemplified. Examples of the platinum catalyst include chloroplatinic acid, an alcohol solution of chloroplatinic acid, a ketone complex of platinum, an olefin complex of platinum, and an alkenylsiloxane complex of platinum.

The content of the organopolysiloxane containing silicon-bonded hydrogen atoms is not limited as long as it can cure the present composition. However, practically, it is based on 1 mol of the alkenyl group in the component (A). The amount of silicon-bonded hydrogen atoms in the silicon-bonded hydrogen atom-containing organopolysiloxane is preferably in the range of 0.5 to 20 mol. Further, the content of the platinum-based catalyst is not limited as long as it can promote the curing reaction of the present composition, but practically, the platinum-based catalyst is used in an amount of 1,000,000 parts by weight of the component (A). Of the platinum metal is preferably in the range of 0.1 to 500 parts by weight.

In the present composition, fumed silica powder, wet silica powder, and the surfaces of these powders are coated with an organosilane, an organosilazane, an organopolysiloxane, or the like, as long as the object of the present invention is not impaired. Reinforcing fillers such as powders that have been hydrophobized with an organosilicon compound such as diorganocyclopolysiloxane; non-crystalline fillers such as crystalline silica powder, calcium carbonate powder, mica powder, magnesium oxide powder, aluminum oxide powder, magnesium hydroxide powder, etc. Reinforcing filler; pigment such as red iron oxide, titanium dioxide, various organic pigments; heat-resistant agent such as rare earth oxide, rare earth hydroxide, cerium silanolate, cerium fatty acid salt; benzotriazole, fumed titanium dioxide, manganese carbonate, Flame retardants such as zinc carbonate; internal release agents such as calcium stearate; molecules Both ends silanol group-blocked dimethylsiloxane oligomer, molecular chain silanol group-blocked dimethylsiloxane / methylvinylsiloxane copolymer oligomer, both ends silanol group-methylphenylsiloxane oligomer, both ends silanol group-blocked dimethylsiloxane / methylphenyl Siloxane copolymer oligomer, Methyl-blocked silanol group at both ends of molecular chain
Processing aids such as (3,3,3-trifluoropropyl) siloxane oligomer; and may further contain a plasticizer and the like. Further, when the present composition is a hydrosilylation reaction-curable type, for the purpose of adjusting the curing time of the present composition, an acetylene-based compound, a hydrazine-based compound, a triazole-based compound, a phosphine-based compound, a mercaptan-based compound, or the like. A curing retarder may be contained.

The present composition can be prepared by mixing the above components. Examples of an apparatus for preparing the present composition include a kneader mixer, a pressure kneader mixer, a two-roller, and a three-roller.

Next, the rubber contact of the present invention will be described in detail. The rubber contact of the present invention is formed by the above silicone rubber composition for rubber contact. The rubber contact of the present invention can be used as an audio device; a video device; an OA device; a keyboard such as an electronic typewriter, a word processor and a computer; a telephone device such as a push phone, a cordless phone and a mobile phone; It is a member used.

As the rubber contact of the present invention, a thin-walled deformable portion extending outward from the outer peripheral edge of the main body constituting the push button is integrally formed. It shows the feeling. A contact member may be formed on the bottom surface of the main body.

Examples of the method of forming the rubber contact of the present invention include a method of molding the above-mentioned silicone rubber composition for rubber contact by various molding methods such as a compression molding method, a transfer molding method and an injection molding method. You. When the viscosity of the present composition is low, a molding method usually used for molding a liquid silicone rubber composition can be used, and for example, a liquid injection molding method can be used.

[0020]

EXAMPLES The silicone rubber composition for rubber contact and the rubber contact of the present invention will be described in more detail with reference to examples. The hardness, tensile strength, and elongation of the silicone rubber were determined by press-vulcanizing the silicone rubber composition at 170 ° C. for 10 minutes, and then vulcanizing at 200 ° C. for 4 hours. Using a silicone rubber sheet, this was measured according to the method specified in JIS K 6250: 1998 (general rules for physical test methods for vulcanized rubber and thermoplastic rubber). The rebound resilience of the silicone rubber was 29 mm in diameter and 12.7 mm in thickness, prepared in the same manner as above.
Was measured according to the method specified in JIS K 6250: 1998. Further, after vulcanizing the silicone rubber composition at 170 ° C. for 10 minutes, it was further vulcanized at 200 ° C. for 4 hours to produce a rubber contact as shown in FIG. In addition, in the rubber contact of this time, the content of the inorganic powder in the silicone rubber composition was adjusted so that the peak load value was constant, and the click rates of these rubber contacts were adjusted by the key shown in FIG. From the change in stress when a load was applied to, was determined by the following equation. Click rate (%) = 100 × (F1-F2) / F1 F1: Peak load (gf) F2: Contact load (gf)

Example 1 Raw rubber-like dimethylvinylsiloxy group-blocked dimethylsiloxane-methylvinylsiloxane copolymer having both ends of molecular chain (vinyl group content = 0.07)
100% by weight, calcium silicate powder having a petal-like crystal structure (Flolite R of Tokuyama Corporation;
Average particle size = 25 μm, content of SiO ₂ component = 67% by weight, BET specific surface area = 121 m ² / g, oil absorption = 430 m
l / 100 g, oil absorption / BET specific surface area = 0.036 ml /
m ² ) 35 parts by weight and 10 parts by weight of a dimethylsiloxane oligomer having silanol groups at both ends of a molecular chain were charged into a kneader mixer and kneaded under heating to prepare a silicone rubber-based compound. Next, 2,5-dimethyl-2,5 was added to 100 parts by weight of the compound.
A silicone rubber composition was prepared by adding 0.3 parts by weight of -di (t-butylperoxy) hexane and kneading with two rolls. The hardness, tensile strength, elongation, and rebound resilience of the silicone rubber obtained by curing the silicone rubber composition, the peak load value of the rubber contact made using the silicone rubber composition, and click The percentages were measured and the results are shown in Table 1.

[Example 2] In Example 1, instead of calcium silicate powder, calcium silicate powder having a petal-like crystal structure (average particle size =
5 μm, content of SiO ₂ component = 67% by weight, BET specific surface area = 124 m ² / g, oil absorption = 280 ml / 100
g, an oil absorption / BET specific surface area = 0.023 ml / m ² ), except that the same amounts were blended to prepare a silicone rubber composition in the same manner as in Example 1. The hardness, tensile strength, elongation, and rebound resilience of the silicone rubber obtained by curing this silicone rubber composition, and the load value (peak load value) of a rubber contact made using this silicone rubber composition ) And click rate were measured, and the results are shown in Table 1.

Example 3 In Example 1, instead of calcium silicate powder, calcium silicate powder having petal-like crystal structure (average particle size = 19 μm, SiO ₂ component Content = 95% by weight, BE
T specific surface area = 304 m ² / g, oil absorption = 350 ml / 10
A silicone rubber composition was prepared in the same manner as in Example 1, except that the same amount of 0 g, oil absorption / BET specific surface area = 0.012 ml / m ² ) was blended. The hardness, tensile strength, elongation, and rebound resilience of the silicone rubber obtained by curing the silicone rubber composition, the peak load value of the rubber contact made using the silicone rubber composition, and click The percentages were measured and the results are shown in Table 1. The silicone rubber sheet (2m thick)
m) (light at 580 nm) was determined using air as a blank and found to be 5%. The light transmittance of the silicone rubber sheet (2 mm thick) prepared in Example 1 was used.
(Light at 580 nm) was 0%. From this, it was found that this silicone rubber sheet was more transparent than the silicone rubber sheet prepared in Example 1.

[Comparative Example 1]
Spherical wet-process silica powder (Japanese
NIPSEAL LP; BET ratio table of this silica industry
Area = 200m^Two/ G, oil absorption = 157 ml / 100 g,
Oil absorption / BET specific surface area = 0.008 ml / m^Two ) 50 times
Parts silanol groups at both ends of the molecular chain.
Except that the amount of the oxane oligomer was 5 parts by weight,
A silicone rubber composition was prepared in the same manner as in Example 1.
Silicone obtained by curing this silicone rubber composition
Rubber hardness, tensile strength, elongation, and rebound resilience
In addition, rubber made using this silicone rubber composition
-Contact load value (peak load value) and click
The results are shown in Table 1.
Was.

[Comparative Example 2] In Example 1, instead of the calcium silicate powder, dry silica powder (Aerosil 200 of Nippon Silica Industry Co., Ltd .; BET specific surface area =
50 parts by weight of 200 m ² / g, oil absorption = 252 ml / 100 g, oil absorption / BET specific surface area = 0.013 ml / m ² ), and 14 parts by weight of a dimethylsiloxane oligomer having a silanol group blocked at both ends of a molecular chain. A silicone rubber composition was prepared in the same manner as in Example 1, except that The hardness, tensile strength, elongation, and rebound resilience of the silicone rubber obtained by curing this silicone rubber composition, and the load value (peak load value) of a rubber contact made using this silicone rubber composition ) And click rate were measured, and the results are shown in Table 1.

[Comparative Example 3] In Example 1, instead of the calcium silicate powder, dry silica powder (Aerosil 50, Nippon Silica Kogyo Co., Ltd .; BET specific surface area = 5)
0 m ² / g, oil absorption = 110 ml / 100 g, oil absorption / B
ET specific surface area = 0.022 ml / m ² ), and the silicone rubber was prepared in the same manner as in Example 1 except that the compounding amount of the dimethylsiloxane oligomer having silanol groups at both ends of the molecular chain was 2.5 parts by weight. A composition was prepared. The hardness, tensile strength, elongation, and rebound resilience of the silicone rubber obtained by curing this silicone rubber composition, and the load value (peak load value) of a rubber contact made using this silicone rubber composition ) And click rate were measured, and the results are shown in Table 1.

[0027]

[Table 1]

Example 4 Raw rubber-like dimethylvinylsiloxy group-blocked dimethylsiloxane-methylvinylsiloxane copolymer at both ends of molecular chain (vinyl group content = 0.07)
100% by weight, calcium silicate powder having a petal-like crystal structure (Flolite R of Tokuyama Corporation;
Average particle size = 25 μm, content of SiO ₂ component = 67% by weight, BET specific surface area = 121 m ² / g, oil absorption = 430 m
l / 100 g, oil absorption / BET specific surface area = 0.036 ml /
m ² ) 35 parts by weight, dry silica powder (Aerosil 200 of Nippon Aerosil Co., Ltd .; BET specific surface area = 200)
m ² / g, oil absorption = 252 ml / 100 g, oil absorption / BE
20 parts by weight of T specific surface area = 0.013 ml / m ² ) and 16 parts by weight of a dimethylsiloxane oligomer having silanol groups at both ends of a molecular chain were charged into a kneader mixer, and kneaded under heating to prepare a silicone rubber base compound. Next, 2,5-
0.3 parts by weight of dimethyl-2,5-di (t-butylperoxy) hexane was added and kneaded with a two-roll mill to prepare a silicone rubber composition. The hardness, tensile strength, elongation, and rebound resilience of the silicone rubber obtained by curing the silicone rubber composition, and the load value of a rubber contact made using the silicone rubber composition
(Value of peak load) and click rate were measured, and the results are shown in Table 2.

[Example 5] In Example 4, instead of calcium silicate powder, calcium silicate powder having a petal-like crystal structure (average particle size =
5 μm, content of SiO ₂ component = 67% by weight, BET specific surface area = 124 m ² / g, oil absorption = 280 ml / 100
g, an oil absorption / BET specific surface area = 0.023 ml / m ² ), except that the same amounts were blended to prepare a silicone rubber composition in the same manner as in Example 4. The hardness, tensile strength, elongation, and rebound resilience of the silicone rubber obtained by curing this silicone rubber composition, and the load value (peak load value) of a rubber contact made using this silicone rubber composition ) And click rate were measured, and the results are shown in Table 2.

Example 6 In Example 4, calcium silicate powder having a petal-like crystal structure (average particle size = 19 μm, SiO ₂ component Content = 95% by weight, BE
T specific surface area = 304 m ² / g, oil absorption = 350 ml / 10
A silicone rubber composition was prepared in the same manner as in Example 4, except that the same amount of 0 g, oil absorption / BET specific surface area = 0.012 ml / m ² ) was blended. Hardness, tensile strength, elongation of the silicone rubber obtained by curing this silicone rubber composition,
And the rebound resilience, and the load value (peak load value) and click rate of the rubber contact prepared using this silicone rubber composition were measured. The results are shown in Table 2.

Comparative Example 4 In Example 4, instead of the calcium silicate powder, a wet-processed silica powder (Nip Seal LP, manufactured by Nippon Silica Co., Ltd .; BET specific surface area =
50 parts by weight of 200 m ² / g, oil absorption = 157 ml / 100 g, oil absorption / BET specific surface area = 0.008 ml / m ² ), the mixing amount of the dry process silica powder was 30 parts by weight, and both ends of the molecular chain were used. A silicone rubber composition was prepared in the same manner as in Example 4, except that the amount of the silanol group-blocked dimethylsiloxane oligomer was changed to 19 parts by weight. The hardness, tensile strength, elongation, and rebound resilience of the silicone rubber obtained by curing this silicone rubber composition, and the load value (peak load value) of a rubber contact made using this silicone rubber composition ) And click rate were measured, and the results are shown in Table 2.

[Comparative Example 5] In Example 4, the calcium silicate powder was not blended, the blending amount of the dry silica powder was 100 parts by weight, and the blending amount of the dimethylsiloxane oligomer having a silanol group at both ends of the molecular chain was 10 parts. A silicone rubber composition was prepared in the same manner as in Example 4 except that the amount was changed to parts by weight. The hardness, tensile strength, elongation, and rebound resilience of the silicone rubber obtained by curing this silicone rubber composition, and the load value (peak load value) of a rubber contact made using this silicone rubber composition ) And CTR, and the results are shown in Table 2.
It was shown to.

[0033]

[Table 2]

[Example 7] A dimethylsiloxane / methylvinylsiloxane copolymer having a dimethylvinylsiloxy group at both ends of a raw rubber-like molecular chain (vinyl group content = 0.07)
100% by weight of silica powder (fine seal P8 of Tokuyama Corporation; BET specific surface area = 142 m ² /
g, oil absorption = 250 ml / 100 g, oil absorption / BET specific surface area = 0.018 ml / m ² ), 50 parts by weight, and 8.5 parts by weight of a dimethylsiloxane oligomer having silanol groups at both ends of a molecular chain, and 8.5 parts by weight, A silicone rubber-based compound was prepared by kneading under heating. Next, 2,5-dimethyl-2,5-di (t-butylperoxy) was added to 100 parts by weight of the compound.
A silicone rubber composition was prepared by mixing 0.3 parts by weight of hexane and kneading with two rolls. The hardness, tensile strength, elongation, and rebound resilience of the silicone rubber obtained by curing this silicone rubber composition, and the load value (peak load value) of a rubber contact made using this silicone rubber composition ) And click rate were measured, and the results are shown in Table 3. Also,
The light transmittance (5 mm) of this silicone rubber sheet (2 mm thick)
(Light at 80 nm) was determined using air as a blank and found to be 32%.

Example 8 In Example 7, silica powder (fine seal E70 of Tokuyama Corporation; BET specific surface area = 146 m ² / g, oil absorption 280 ml / 100 g, oil absorption / BET ratio) was used in place of the silica powder. Surface area =
0.019 ml / m ² ), and the amount of the dimethylsiloxane oligomer having a silanol group blocked at both ends of the molecular chain was 6
A silicone rubber composition was prepared in the same manner as in Example 7 except that the amount was changed to parts by weight. The hardness, tensile strength, elongation, and hardness of the silicone rubber obtained by curing the silicone rubber composition
And the rebound resilience, and the load value (peak load value) and click rate of a rubber contact prepared using this silicone rubber composition were measured. The results are shown in Table 3. The light transmittance (580 nm light) of this silicone rubber sheet (thickness: 2 mm) was determined to be 29% using air as a blank.

Example 9 In Example 7, silica powder (fine seal E50 manufactured by Tokuyama Corporation; BET specific surface area = 202 m ² / g, oil absorption = 290 ml / 100 g, oil absorption / BET) was used instead of silica powder. Specific surface area =
0.014 ml / m ² ), and the amount of the dimethylsiloxane oligomer having a silanol group capped at both ends of the molecular chain was 6%.
A silicone rubber composition was prepared in the same manner as in Example 7 except for blending by weight. The hardness, tensile strength, elongation, and rebound resilience of the silicone rubber obtained by curing this silicone rubber composition, and the load value (peak load value) of a rubber contact made using this silicone rubber composition ), And CTR,
Table 3 shows the results. The light transmittance (580 nm light) of this silicone rubber sheet (thickness: 2 mm)
When air was determined as a blank, it was 55%.

Comparative Example 6 In Example 7, silica powder (Fine Seal X37 manufactured by Tokuyama Corporation; BET specific surface area = 262 m ² / g, oil absorption = 260 ml / 100 g, oil absorption / BET) was used instead of silica powder. Specific surface area =
0.010 ml / m ² ) was prepared in the same manner as in Example 7 except that 35 parts by weight of the silicone rubber composition was prepared. The hardness, tensile strength, elongation, and rebound resilience of the silicone rubber obtained by curing this silicone rubber composition, and the load value (peak load value) of a rubber contact made using this silicone rubber composition ) And click rate were measured, and the results are shown in Table 3.

Comparative Example 7 In Example 7, silica powder (fine seal K41 manufactured by Tokuyama Corporation; BET specific surface area = 332 m ² / g, oil absorption = 270 ml / 100 g, oil absorption / BET) was used instead of silica powder. Specific surface area =
A silicone rubber composition was prepared in the same manner as in Example 7 except that 35 parts by weight of 0.008 ml / m ² ) was added. The hardness, tensile strength, elongation, and rebound resilience of the silicone rubber obtained by curing this silicone rubber composition, and the value of the peak load (peak load) of the rubber contact made using this silicone rubber composition And the click rate were measured, and the results are shown in Table 3.

[0039]

[Table 3]

Comparative Example 8 A dimethylsiloxane / methylvinylsiloxane copolymer having a dimethylvinylsiloxy group at both ends of a raw rubber in the form of a raw rubber (vinyl group content = 0.07)
100% by weight, amorphous calcium silicate powder (Solex CM of Tokuyama Corporation; average particle size =
13.3 μm, content of SiO ₂ component = 58% by weight, BE
T specific surface area = 70 m ² / g, oil absorption = 110 ml / 100
g, oil absorption / BET specific surface area = 0.016 ml / m ² ) 35
Parts by weight and 4 parts by weight of a dimethylsiloxane oligomer having silanol groups at both ends of the molecular chain were charged into a kneader mixer and kneaded under heating to prepare a silicone rubber-based compound. Next, 2,5-dimethyl-2,5-di (t-t) was added to 100 parts by weight of the compound.
A silicone rubber composition was prepared by adding 0.3 parts by weight of butylperoxy) hexane and kneading with two rolls. The silicone rubber composition obtained by curing the silicone rubber composition had a white appearance, a hardness of 36, a tensile strength of 2.2 MPa, an elongation of 350%, and a rebound resilience of 83%. Met. The load value (peak load value) of the rubber contact formed by this silicone rubber composition was 66 gf, and the click rate was 33%.
%Met.

[0041]

EFFECT OF THE INVENTION The silicone rubber composition for rubber contact of the present invention is made of petal-like inorganic powder or JIS K
Since it contains an inorganic powder having an oil absorption of at least 200 ml / 100 g measured by the method specified in 6220-1995 and an oil absorption of at least 0.014 ml / m ² with respect to the BET specific surface area, It has the feature that it can form a rubber contact with a click feeling,
A rubber contact using this silicone rubber composition is characterized by having a good click feeling.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a rubber contact created in an example.

FIG. 2 is a graph showing a relationship between a stress and a stroke for obtaining a load value and a click rate of a rubber contact.

[Explanation of symbols]

 F1: Peak load F2: Contact load

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01H 1/06 H01H 1/06 H 13/14 13/14 A

Claims (10)

[Claims] 1. A silicone rubber composition for rubber contacts, comprising a silicone rubber composition containing petal-like inorganic powder. 2. The silicone rubber composition for rubber contact according to claim 1, wherein the petal-like inorganic powder is a calcium silicate powder or a silica powder. 3. The silicone rubber composition for a rubber contact according to claim 1, wherein the silicone rubber composition is a heat-curable silicone rubber composition. 4. The silicone rubber composition for rubber contacts according to claim 3, wherein the heat-curable silicone rubber composition is an organic peroxide-curable silicone rubber composition. 5. A rubber contact obtained by curing the silicone rubber composition according to claim 1. 6. An inorganic powder having an oil absorption of at least 200 ml / 100 g as measured by the method specified in JIS K 6220-1995 and having an oil absorption of at least 0.014 ml / m ² with respect to the BET specific surface area. A silicone rubber composition for a rubber contact, comprising a silicone rubber composition to be formed. 7. The silicone rubber composition for rubber contacts according to claim 6, wherein the inorganic powder is a calcium silicate powder or a silica powder. 8. The silicone rubber composition for a rubber contact according to claim 6, wherein the silicone rubber composition is a heat-curable silicone rubber composition. 9. The silicone rubber composition for rubber contacts according to claim 8, wherein the heat-curable silicone rubber composition is an organic peroxide-curable silicone rubber composition. 10. A rubber contact obtained by curing the silicone rubber composition according to claim 6.