JP5924303B2 - Conductive silicone rubber composition - Google Patents

Description

  The present invention relates to a conductive silicone rubber composition that provides a cured conductive silicone rubber. In particular, it contains a predetermined amount of metal powder surface-treated with higher fatty acids, has excellent storage stability, and when cured with organic peroxide, vulcanization time is shortened by adding organohydrogenpolysiloxane. It is related with the conductive silicone rubber composition which can be made and can accelerate a production cycle.

  The conductive silicone rubber composition containing silver powder becomes a low-resistance silicone rubber, so it is used as an adhesive for electromagnetic wave shielding materials, quartz crystal substrates, and die bonding agents for semiconductor devices. Yes. As the conductive silicone rubber composition using silver powder, a condensation curable conductive silicone rubber composition (Japanese Patent Laid-Open No. 60-199057: Patent Document 1), a room temperature curable conductive silicone rubber composition (Japanese Patent Laid-Open No. 2005-2005). No. -298661: Patent Document 2) and addition reaction curable conductive silicone rubber compositions (Japanese Patent Laid-Open Nos. 03-170581 and 2006-328302: Patent Documents 3 and 4).

  In order to connect between electronic circuit boards and the like, an electrical connector (Japanese Patent Laid-Open No. 2004-31203: Patent Document 5) in which a plurality of conductive silicone rubber elements are penetrated and supported by an insulating substrate, a conductive silicone rubber layer, A zebra connector (Japanese Patent Laid-Open No. 2005-100844: Patent Document 6) in which an insulating elastomer layer is laminated in a zebra shape is used. These connectors are connected by compressing rubber.

  The silver powder used for these may be agglomerated during storage. Aggregation can be suppressed by surface treatment with a higher fatty acid or the like, but if it is contained in silicone rubber and cured with an organic peroxide, the vulcanization rate will be slowed and productivity will deteriorate. End up. Further, if the primary vulcanization is insufficient, there is a problem that the resistance value increases even if the secondary vulcanization is performed.

Japanese Patent Laid-Open No. 60-199057 JP 2005-298661 A Japanese Patent Laid-Open No. 03-170581 JP 2006-328302 A JP 2004-31203 A JP 2005-1000088 A1

  The present invention has been made in view of the above circumstances, and can contain a specific amount of a conductive filler such as silver powder surface-treated with a higher fatty acid, and even when cured with an organic peroxide, the vulcanization time can be shortened. An object of the present invention is to provide a conductive silicone rubber composition that gives a silicone rubber having a good resistance value after secondary vulcanization.

  As a result of intensive studies to achieve the above object, the present inventor used a specific amount of metal powder such as silver powder surface-treated with a higher fatty acid by using organohydrogenpolysiloxane in combination with an organic peroxide. However, the present inventors have found that the vulcanization time can be shortened and completed the present invention.

Accordingly, the present invention provides the following conductive silicone rubber composition.
[Claim 1]
(A) The following average composition formula (I)
R ¹ _n SiO _{(4-n) / 2} (I)
(In the formula, R ¹ is the same or different unsubstituted or substituted monovalent hydrocarbon group, and n is a positive number of 1.95 to 2.04.)
100 parts by mass of an organopolysiloxane represented by
(B) 50 to 800 parts by mass of silver powder having a tap density surface-treated with a higher fatty acid of 0.3 to 1.5 g / cm ³ and a specific surface area (BET method) of 0.2 to 1.6 m ² / g ,
(C) Organohydrogenpolysiloxane 0.001 to 20 parts by mass,
(D) Organic peroxide An organic peroxide-curable conductive silicone rubber composition containing an effective amount.
[Claim 2]
The conductive silicone rubber composition according to claim 1, wherein the silver powder is a spherical primary particle aggregated three-dimensionally.

  According to the present invention, it is possible to provide a conductive silicone rubber composition that can shorten the vulcanization time and is excellent in storage stability.

It is explanatory drawing of the measuring method of resistance value.

Hereinafter, the present invention will be described in detail.
[(A) component]
The organopolysiloxane of component (A) is the main component (base polymer) of the composition of the present invention, and the following average composition formula (I)
R ¹ _n SiO _{(4-n) / 2} (I)
(In the formula, R ¹ is the same or different unsubstituted or substituted monovalent hydrocarbon group, and n is a positive number of 1.95 to 2.04.)
It is shown by.

In the above formula (I), R ¹ includes the same or different unsubstituted or substituted monovalent hydrocarbon group having 1 to 20, preferably 1 to 12, more preferably 1 to 8. Specific examples of R ¹ include alkyl groups such as methyl group, ethyl group, propyl group, and butyl group; cycloalkyl groups such as cyclohexyl group; alkenyl groups such as vinyl group, allyl group, butenyl group, and hexenyl group; phenyl group An aryl group such as a tolyl group; an aralkyl group such as a β-phenylpropyl group; or a chloro group in which some or all of the hydrogen atoms bonded to the carbon atoms of these hydrocarbon groups are substituted with a halogen atom, a cyano group, or the like. A methyl group, a trifluoropropyl group, a cyanoethyl group and the like can be mentioned.

  In the above formula (I), n is a positive number of 1.95 to 2.04, preferably 1.98 to 2.02. If n is not in the range of 1.95 to 2.04, the cured product of the resulting composition may not exhibit sufficient rubber elasticity.

  The organopolysiloxane of component (A) is preferably one whose molecular chain ends are blocked with a trimethylsilyl group, dimethylvinylsilyl group, dimethylhydroxysilyl group, methyldivinylsilyl group, trivinylsilyl group, etc. It is particularly preferred that it is blocked with a silyl group having two vinyl groups (for example, dimethylvinylsilyl group, methyldivinylsilyl group, trivinylsilyl group, etc.).

The organopolysiloxane of component (A) has at least two (for example, about 2 to 50, preferably about 2 to 20) alkenyl groups bonded to silicon atoms in one molecule. Specifically, R ¹ Of these, 0.001 to 10 mol%, particularly 0.01 to 5 mol% is preferably an alkenyl group. Examples of the alkenyl group preferably include a vinyl group and an allyl group, and particularly preferably a vinyl group.

The organopolysiloxane of component (A) is usually a raw rubber-like organopolysiloxane that is not self-fluxing at room temperature (25 ° C.), and its average degree of polymerization is usually 100 or more (particularly 1, 000 or more), more preferably in the range of 3,000 to 100,000, and particularly preferably in the range of 4,000 to 20,000. The average degree of polymerization is measured by GPC (gel permeation chromatography) using polystyrene as a molecular weight marker, for example, toluene as a developing solvent,
Formula: Number average degree of polymerization = number average molecular weight / (A) The number average degree of polymerization can be obtained by calculating the molecular weight of the repeating unit of the component (A). When a plurality of types of repeating units are contained in the component (A), the “molecular weight of the repeating unit of the component (A)” in the above formula is the number average molecular weight of the plurality of types of repeating units. The organopolysiloxane of component (A) may be used alone or in combination of two or more having different average degrees of polymerization and molecular structures.

[Component (B)]
The metal powder of component (B) has a surface treated with a higher fatty acid. The metal powder includes noble metal powders such as silver, gold, platinum and palladium, and non-noble metals such as copper, copper alloys and nickel. Examples thereof include plating metal powder such as powder, silver plating copper powder, nickel plating copper powder and the like. Silver powder is particularly preferable. As the silver of the silver powder, pure silver or a silver alloy is used. Typical examples of the silver alloy include silver-copper alloys and silver-palladium alloys containing 50% by mass or more (for example, 50 to 99% by mass) of silver, particularly 70% by mass or more (for example, 70 to 95% by mass). Examples thereof include silver alloys having metals such as zinc, tin, magnesium, and nickel.

  As the shape of the metal powder such as silver powder surface-treated with the higher fatty acid (B), known flaky (flaky), spherical, dendritic (dendritic), spherical primary particles are three-dimensional. Among these, there are aggregated shapes and the like, and among these, flaky silver powder and silver powder having a shape in which spherical primary particles are aggregated three-dimensionally are particularly preferable.

The metal powder surface-treated with the higher fatty acid (B) preferably has a tap density of 1.5 g / cm ³ or less. More preferably, it is 0.1-1.3 g / cm < ³ >, and especially 0.3-1.2 g / cm < ³ > is desirable. When the tap density exceeds 1.5 g / cm ³ , deagglomeration hardly occurs and dispersibility may deteriorate. The true density (true specific gravity) −tap density (bulk specific gravity), which is the difference between the true density (or true specific gravity) and the tap density (or bulk specific gravity), is preferably 7.3 g / cm ³ or more, more preferably 7.5 g / cm ³ or more. If it is less than 7.3 g / cm ³ , dispersibility may deteriorate.

The tap density is a kind of bulk density and is often used synonymously with bulk specific gravity. The bulk density is measured by a value (g / cm ³ ) obtained by dividing the mass by the volume when the powder is filled in a certain container. When powder is filled, it is called bulk density (Loose) when it is packed as coarsely as possible, and it is called bulk density (Tapped) when it is packed so as to be as dense as possible. This is called tap density.

  (B) As for metal powders, such as silver powder surface-treated with the higher fatty acid of a component, 0.01-10 micrometers of average particle diameters of primary particles are preferable, and the range of average particle diameters of 0.1-5 micrometers is especially preferable. If the average particle size is too small, oxides are likely to be formed on the surface, and if the average particle size is too large, the resistance stability of the conductive silicone rubber may be lowered.

(B) As for metal powders, such as silver powder surface-treated with the higher fatty acid of a component, the average particle diameter of aggregated particles exceeds 10 micrometers, and 1,000 micrometers or less are preferable, and the average particle diameter of 15-800 micrometers is especially preferable. When the thickness is 10 μm or less, aggregation progresses with time, and non-uniform aggregation may occur. When the thickness exceeds 1,000 μm, the surface shape may not be smooth when a conductive paste is used. The average particle diameter can be determined by a general particle size distribution measurement method such as a laser method or a sedimentation method. Usually, the cumulative weight average diameter in particle size distribution measurement by laser light diffraction; D ₅₀ (or median) (Diameter) or the like.
Moreover, the specific surface area (BET method) of the metal powder of (B) component should just be about 0.2-1.6 m < ² > / g normally, Preferably it is 0.3-1.2 m < ² > / g, More preferably Is 0.4 to 0.8 m ² / g. If the specific surface area (BET method) is too small, the flowability of the composition will deteriorate during molding of the material, and if it is too large, the composition will flow too much and the resistance will increase.

  Metal powder such as silver powder surface-treated with the higher fatty acid (B) can be obtained by reducing an aqueous metal salt solution with a reducing agent, depositing it on the cathode by electrolysis, or melting the metal in water or in an inert gas. Obtained by spraying or the like. For example, in the case of silver powder, they are reduced silver powder, electrolytic silver powder, and atomized silver powder, respectively. Reduced silver powder is prepared by reducing an aqueous silver nitrate solution with a reducing agent such as hydrazine, formaldehyde, and ascorbic acid, and is prepared in granular form. . Atomized silver powder is prepared by spraying molten silver heated and melted at 1,000 ° C. or higher into water or an inert gas. Alternatively, silver-coated copper powder is produced by coating silver particles on a copper surface as shown in JP-A-3-247702, JP-A-4-268811, and the like by a method called an atomizing method.

  The metal powder (particularly silver powder, etc.) of component (B), when not surface-treated, aggregates during long-term storage in the silicone rubber composition and is separated from the silicone rubber matrix and lacks storability. From the point of storage stability of the composition, silver powder surface-treated with a saturated or unsaturated higher fatty acid such as lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, arachidic acid, behenic acid, etc. It is necessary to use metal powder, and by using the surface-treated metal powder, aggregation during long-term storage can be effectively suppressed in the silicone rubber composition.

  (B) The compounding quantity of a component is 50-800 mass parts with respect to 100 mass parts of (A) component, Preferably it is 100-700 mass parts. This is because when the component (B) is less than 50 parts by mass relative to 100 parts by mass of the component (A), sufficient conductivity cannot be imparted to the resulting silicone rubber, and 800 parts by mass. If it exceeds 1, the workability of the resulting composition is significantly impaired.

[Component (C)]
The organohydrogenpolysiloxane of component (C) is an organic component of component (D), which will be described later, due to higher fatty acids used to prevent the metal powder of component (B) from aggregating and separating during long-term storage. Effectively prevents the curing reaction due to peroxide from being inhibited or delayed, and effectively promotes the curing reaction of the composition even if the component (B) is a metal powder surface-treated with a higher fatty acid or the like. For blending. As the organohydrogenpolysiloxane of component (C), 2 or more (usually 2 to 200), preferably 3 or more (for example, about 3 to 150) SiH groups (for silicon atoms) per molecule. As long as it contains (bonded hydrogen atoms), it may be linear, cyclic or branched, and is known as a crosslinking agent for addition reaction curable silicone rubber compositions (usually silicon atoms in one molecule) An organohydrogenpolysiloxane having a number (or degree of polymerization) of 2 to 200, particularly about 3 to 150, can be used. For example, an organohydrogenpolysiloxane represented by the following average composition formula (II) Etc. can be used.
R ² _p H _q SiO _{(4-pq) / 2} (II)

In the above average composition formula (II), R ² represents an unsubstituted or substituted monovalent hydrocarbon group, which may be the same or different and excludes an aliphatic unsaturated bond. preferable. Usually, those having 1 to 12 carbon atoms, particularly 1 to 8 carbon atoms are preferred. Specifically, alkyl groups such as methyl group, ethyl group and propyl group, cycloalkyl groups such as cyclohexyl group, vinyl group, allyl group and butenyl. Groups, alkenyl groups such as hexenyl groups, aryl groups such as phenyl groups and tolyl groups, aralkyl groups such as benzyl groups, 2-phenylethyl groups and 2-phenylpropyl groups, and some or all of the hydrogen atoms of these groups Is a group substituted with a halogen atom or the like, for example, a 3,3,3-trifluoropropyl group. Note that p and q are 0 ≦ p <3, preferably 1 ≦ p ≦ 2.2, 0 <q ≦ 3, preferably 0.002 ≦ q ≦ 1, 0 <p + q ≦ 3, preferably 1.002 ≦. It is a positive number satisfying p + q ≦ 3.

  Organohydrogenpolysiloxane has 2 or more, preferably 3 or more SiH groups in one molecule, which may be at the molecular chain end or in the middle of the molecular chain (molecular chain non-terminal). , Or both.

（式中、ｋは２〜１０の整数、ｓ及びｔは０〜１０の整数である。） Specific examples of such organohydrogenpolysiloxanes include compounds having the following structural formula.

(In the formula, k is an integer of 2 to 10, and s and t are integers of 0 to 10.)

  The compounding amount of the organohydrogenpolysiloxane is 0.001 to 20 parts by mass, more preferably 0.01 to 10 parts by mass, still more preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the component (A). Is preferred. If the blending amount is too small, there is no effect of increasing the vulcanization rate, and if the blending amount is too large, the resistance value may increase.

  In addition, in order to improve the dispersibility in the silicone rubber composition, the component (C) is uniformly uniform with an organopolysiloxane (for example, the alkenyl group-containing organopolysiloxane of the component (A)) or a reinforcing silica filler. It may be added in the form of a paste by mixing.

[(D) Organic peroxide]
Examples of the organic peroxide used as the component (D) include benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, p-methylbenzoyl peroxide, o-methylbenzoyl peroxide, and 2,4-dicumyl peroxide. Oxide, 2,5-dimethyl-bis (2,5-t-butylperoxy) hexane, di-t-butylperoxide, t-butylperbenzoate, 1,6-hexanediol-bis-t-butylperoxy And carbonate.

  The addition amount of the organic peroxide is preferably 0.1 to 10 parts by mass, particularly preferably 0.2 to 5 parts by mass with respect to 100 parts by mass in total of the components (A) and (B). If the amount added is too small, it may be difficult to cure, and if it is too much, there will be no further effect and it will not be economical, and the decomposition residue may increase.

[Reinforcing silica]
In the present invention, reinforcing silica may be added to the organopolysiloxane of component (A) in order to impart mechanical strength and the like. Examples of the reinforcing silica include fumed silica and precipitated (wet) silica. These silicas preferably has a specific surface area by the BET method is 50 m ² / g or more, particularly preferably 100 to 400 m ² / g. Such silica may be silica whose surface is treated with a surface treating agent such as organopolysiloxane, silazane, chlorosilane, or alkoxysilane, if necessary. In addition, the above surface treatment agent may be added to the organopolysiloxane as the component (A) when the fine powder silica is added.

  The compounding of the reinforcing silica is arbitrary, but 0 to 100 parts by mass, preferably 1 to 80 parts by mass, and particularly preferably 5 to 50 parts by mass with respect to 100 parts by mass of the organopolysiloxane of the component (A). If the amount is too small, sufficient rubber strength may not be obtained. Furthermore, in the case of millable rubber made from raw rubber, processability may be reduced. Moreover, when there are too many compounding quantities, it may become difficult to mix | blend and a rubber physical property may fall.

  The conductive silicone rubber composition of the present invention becomes a silicone rubber having excellent conductivity by heat curing. As the molding method, a known molding method may be selected according to the shape and size of the target molded product. For example, methods such as injection molding, compression molding, injection molding, calendar molding, extrusion molding, coating, and screen printing are exemplified. The curing condition may be a known condition in the molding method, and is generally about several seconds to one day at a temperature of 60 to 200 ° C. Further, for the purpose of reducing the compression set of the cured product, reducing the low-molecular siloxane component remaining in the silicone rubber, or removing the decomposition product of the organic peroxide, preferably 100 ° C. or higher, preferably May be post-cured (secondary curing) in an oven at 150 to 250 ° C. for 30 minutes or longer, preferably about 1 to 70 hours, preferably 1 to 10 hours.

  The cured product of the conductive silicone rubber composition thus obtained has a 10% compression resistance value of 0.03Ω or less and can be used as an electrical connector material.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to a following example. In addition, an average degree of polymerization shows the number average degree of polymerization of polystyrene conversion by GPC (toluene developing solvent).

Vulcanization characteristics According to JIS K6300, the vulcanization characteristics were measured under the condition of 165 ° C./3 minutes using an MDR rheometer (manufactured by Alpha Technologies). The results are shown in Table 1.
t10: When heated to 165 ° C. and the torque value after 3 minutes is 100% vulcanization,
Time required for vulcanization to proceed 10% t90: When heated to 165 ° C. and torque value at 3 minutes passed is 100% vulcanization,
Time required for vulcanization to proceed 90%

A methyl hydrogen polysiloxane paste was prepared as follows.
[Preparation of methyl hydrogen polysiloxane paste]
Hydrophobized fumed silica (R-972, manufactured by Nippon Aerosil Co., Ltd.) having 50 parts by mass of dimethylpolysiloxane raw rubber having both ends of the molecular chain blocked with dimethylvinylsiloxy groups and a specific surface area of 110 m ² / g 7 parts by mass, methylhydrogenpolysiloxane having SiH groups in the side chain (polymerization degree 38, SiH group content; 0.0074 mol / g molecular chain both ends trimethylsiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane copolymer 43 parts by mass were kneaded to prepare a methyl hydrogen polysiloxane paste (methyl hydrogen polysiloxane concentration: 43% by mass).

[Example 1]
100 parts by mass of an organopolysiloxane having 99.825 mol% dimethylsiloxane units, 0.15 mol% methylvinylsiloxane units and 0.025 mol% dimethylvinylsiloxane units and having an average degree of polymerization of about 6,000, A composition A was prepared by uniformly kneading 450 parts by mass of a tap density of 1.39 g / cm ³ , a specific surface area of 0.61 m ² / g, and a surface stearic acid-treated product.
Methyl hydrogen polysiloxane having a SiH group in the side chain with respect to 100 parts by mass of Composition A (polymerization degree 38, SiH group content; 0.0074 mol / g molecular chain both ends trimethylsiloxy group-capped dimethylsiloxane / methylhydro Gensiloxane copolymer) 0.13 parts by mass and 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane 0.5 parts by mass were added under the conditions of 170 ° C. and 100 kgf / cm ² . A press cure was performed for 5 minutes to produce a 1 mm sheet. Next, post-curing was performed in an oven at 150 ° C. for 1 hour.

From this sheet, a sample of thickness × width × length = 1.0 × 1.0 × 2.0 mm was cut out, and as shown in FIG. 1, electrode 1 (height × width × length = 0.1 × 20 × 30 mm) and the electrode 2 (height × width × length = 0.1 × 1.0 × 30 mm) with the sample 3 sandwiched in the direction shown in FIG. 1 (direction perpendicular to the electrode 2), The sample was compressed to 10% using a linear motor actuator (GLM20-040 type, manufactured by THK), and the resistance value (Ω) at this time was measured. The results are shown in Table 1.
Further, a sample of thickness × width × length = 1.0 × 20 × 150 mm was cut out from the sheet, and the volume resistivity of this sample was measured according to SRIS-2301. The results are shown in Table 1.
In addition, as a result of observing the composition A after storing it at room temperature (25 ° C.) for 1 month, aggregation and separation of silver powder in the composition A were not observed.

[Example 2]
Methyl hydrogen polysiloxane having an SiH group in the side chain (polymerization degree 38, SiH group content; 0.0074 mol / g molecular chain both ends trimethylsiloxy group-blocked dimethyl siloxane / methyl hydrogen siloxane copolymer) A silicone rubber composition was prepared in the same manner as in Example 1 except that the amount was changed from 13 parts by mass to 0.44 parts by mass and measured in the same manner.

[Example 3]
Instead of methylhydrogenpolysiloxane having a SiH group in the side chain (polymerization degree 38, SiH group content; 0.0074 mol / g molecular chain both ends trimethylsiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane copolymer) A silicone rubber composition was prepared in the same manner as in Example 1 except that 0.31 parts by mass of the methyl hydrogen polysiloxane paste (methyl hydrogen polysiloxane concentration; 43% by mass) was used, and the measurement was performed in the same manner. did.

[Example 4]
100 parts by mass of an organopolysiloxane having 99.825 mol% dimethylsiloxane units, 0.15 mol% methylvinylsiloxane units and 0.025 mol% dimethylvinylsiloxane units and having an average degree of polymerization of about 6,000, Tap density 1.39 g / cm ³ , specific surface area 0.61 m ² / g, surface stearic acid-treated product) 450 parts by mass, methyl hydrogen polysiloxane having a SiH group at both molecular chain terminals and side chains (polymerization degree 16, SiH group content: 0.72 parts by mass of a dimethylhydrogensiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane copolymer having a molecular chain at both ends of 0.0031 mol / g) was uniformly kneaded to prepare composition B.
0.5 parts by mass of 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane is added to 100 parts by mass of Composition B, and pressed for 5 minutes at 170 ° C. and 100 kgf / cm ^2. Curing was performed to produce a 1 mm sheet. Next, post-curing was performed in an oven at 150 ° C. for 1 hour.

From this sheet, a sample of thickness × width × length = 1.0 × 1.0 × 2.0 mm was cut out, and as shown in FIG. 1, electrode 1 (height × width × length = 0.1 × 20 × 30 mm) and the electrode 2 (height × width × length = 0.1 × 1.0 × 30 mm) with the sample 3 sandwiched in the direction shown in FIG. 1 (direction perpendicular to the electrode 2), The sample was compressed to 10% using a linear motor actuator (GLM20-040 type, manufactured by THK), and the resistance value at this time was measured. The results are shown in Table 1.
Further, a sample of thickness × width × length = 1.0 × 20 × 150 mm was cut out from the sheet, and the volume resistivity of this sample was measured according to SRIS-2301. The results are shown in Table 1.
In addition, as a result of observing the composition B after storage at room temperature (25 ° C.) for 1 month, no aggregation or separation of silver powder in the composition B was observed.

[Example 5]
Methyl hydrogen polysiloxane having SiH groups at both ends and side chains of the molecular chain (polymerization degree 16, SiH group content; 0.0031 mol / g molecular chain both ends dimethyl hydrogen siloxy group-blocked dimethyl siloxane / methyl hydrogen siloxane A silicone rubber composition was prepared in the same manner as in Example 4 except that the copolymer was changed from 0.72 parts by mass to 1.21 parts by mass, and measured in the same manner.

[Example 6]
Instead of methylhydrogenpolysiloxane having a SiH group in the side chain (polymerization degree 38, SiH group content; 0.0074 mol / g molecular chain both ends trimethylsiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane copolymer) , Methyl hydrogen polysiloxane having SiH groups at both ends of the molecular chain (polymerization degree 18, SiH group content; 0.0013 mol / g molecular chain both ends dimethylhydrogensiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane copolymer A silicone rubber composition was prepared in the same manner as in Example 1 except that 0.13 parts by mass of coalescence was used, and measurement was performed in the same manner.

[Comparative Example 1]
Do not add methylhydrogenpolysiloxane having SiH group in the side chain (polymerization degree 38, SiH group content; 0.0074 mol / g molecular chain both ends trimethylsiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane copolymer) Except for the above, a silicone rubber composition was prepared in the same manner as in Example 1 and measured in the same manner.

[Comparative Example 2]
170 ° C., rather than the 5 minutes press cured under conditions of 100 kgf / cm ^2, is 170 ° C., except for press cured 10 minutes at a 100 kgf / cm ^2, was measured in the same manner as in Comparative Example 1.

1 Electrode 2 Electrode 3 Sample

Claims (2)

(A) The following average composition formula (I)
R ¹ _n SiO _{(4-n) / 2} (I)
(In the formula, R ¹ is the same or different unsubstituted or substituted monovalent hydrocarbon group, and n is a positive number of 1.95 to 2.04.)
100 parts by mass of an organopolysiloxane represented by
(B) 50 to 800 parts by mass of silver powder having a tap density surface-treated with a higher fatty acid of 0.3 to 1.5 g / cm ³ and a specific surface area (BET method) of 0.2 to 1.6 m ² / g ,
(C) Organohydrogenpolysiloxane 0.001 to 20 parts by mass,
(D) Organic peroxide An organic peroxide-curable conductive silicone rubber composition containing an effective amount. The conductive silicone rubber composition according to claim 1, wherein the silver powder is a spherical primary particle aggregated three-dimensionally.

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