JPS61195161A - Conductive rubber - Google Patents

Abstract

PURPOSE:To obtain the titled rubber of outstanding processing workability, breaking strength and water resistance, suitable for electromagnetic shielding materials, etc., by incorporating conductive carbon black in a rubber component comprising organic rubber and specific polyorganosiloxane followed by crosslinking. CONSTITUTION:The objective rubber with a volume resistivity 10<-3>-10<7>OMEGA.cm can be obtained by incorporating (I) 100pts.wt. of a rubber composition comprising (A) an organic rubber with a Mooney viscosity ML1+4 20-160 (e.g. natural rubber) and (B) a polyorganosiloxane of formula (R and R' are each hydrocarbon substituent; n >=3) with >=6 (pref. 20-50)mol% of the substituents R and R' being such hydrocarbon group as to be >=350 (pref >=700) in the Small's molecular attraction force constant in a weight ratio (A)/(B)=95/5-0/100 (pref. 80/20-20/80) with (C) 5-200 (pref. 10-150)pts.wt. of conductive carbon black with an average particle size <=1,000Angstrom followed by crosslinking.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to conductive rubber, and more particularly to a novel conductive rubber that is excellent in workability, breaking strength, water resistance, and hot water resistance.

[Prior Art] Generally speaking, conductive rubber, especially conductive rubber for electronics, is the most reliable one obtained by molding a conductive silicone rubber composition made by blending carbon black with polyorganosiloxane. It is widely used because it is expensive.

However, when conductive rubber is used as mechanical parts, such as interconnectors used in display devices such as calculators and digital watches, or movable contacts in keyboard devices, it is generally made of glass plates containing boron oxide. Because the movable contacts made of conductive rubber are held under pressure for a long period of time in liquid crystal display devices, the conductive rubber may adhere or stick to the glass plate in a relatively humid atmosphere and may need to be replaced for some reason. Even if they become necessary, it becomes difficult or completely impossible to replace them. Furthermore, if a voltage is applied at a high frequency of approximately 6 KHz to 20 MHz and this is used in a high humidity atmosphere, leakage may occur due to carbon black particles exuding and moving from the conductive rubber. The original functions of the display device will be impaired. Furthermore, due to the friction of the movable contact with the edge portion of the printed circuit board, the conductive rubber material constituting the movable contact gradually accumulates between the electrodes in the form of polishing powder, eventually leading to a short circuit.

In addition, in the compression discharge test, the conductive silicone rubber contact behaves like a suction cup against the fixed contact, and is difficult to separate even after the applied pressure is removed. For the purpose of preventing such a phenomenon, attempts have been made to process the surface of the contact to have concavities and convexities; however, contacts processed in this manner have the disadvantage that they cause disturbances in signal waveforms and the like.

In addition, when conventional conductive rubber made of polyorganosiloxane is filled with a large amount of conductive agent such as carbon black for the purpose of obtaining high conductivity, the breaking strength is extremely reduced and the workability of secondary processing is reduced. It had the disadvantage of being significantly inferior.

Therefore, in order to improve the drawbacks of such conductive rubber made of polyorganosiloxane, various studies have been made, and one representative method is:

A method using a rubber mixture formed by mixing polyorganosiloxane and organic rubber (Japanese Patent Laid-Open No. 56-88442) has been proposed.

[Problems to be Solved by the Invention] However, since organic rubber and polyorganosiloxane inherently have no affinity, organic rubber and polyorganosiloxane are extremely easy to separate. For this reason, mixtures of organic rubber and polyorganosiloxane have extremely poor storage stability when unvulcanized, tend to adversely affect the quality and characteristics of the final product, and are extremely difficult to manage.

Therefore, there is currently a strong desire for a conductive rubber that does not have such problems, has high conductivity, high strength, has excellent moisture resistance, water resistance, and hot water resistance, and does not cause filler oozing. .

cMeans for solving problems] The present invention solves the above conventional problems and improves heat resistance.

The present invention provides a conductive rubber that has excellent water resistance, hot water resistance, and breakage characteristics, and has no oozing of carbon black, which is a conductive agent, or separation of organic rubber and silicone rubber, and has excellent processing workability. .

Contains rubber and conductive carbon black, is crosslinked, and has a volume resistivity of 10-3 to 1O-3 to 1
A conductive rubber in the range of 0.07 Ω cm, characterized in that the rubber components are as shown below (a) and the composition ratio is as shown below (b).

(B) Rubber component: (A) organic rubber and (B) polyorganosiloxane, or (B) contains polyorganosiloxane;
The polyorganosiloxane is a polyorganosiloxane represented by the general formula (in the formula, R is a hydrocarbon substituent, and n is an integer of 3 or more), and the substituent R
, at least 6 mol% or more is a hydrocarbon substituent having a Small molecular attraction constant of 350 or more.

(B) Composition ratio: The ratio of (A) organic rubber to (B) polyorganosiloxane is (A)/(B) = 9515 to O/100.

The main points are as follows.

That is, 1. The present inventors have developed polyorganosiloxane, Asui l+-Right Rubber J#-0÷1, and Zeno? Improves the heat resistance, water resistance, hot water resistance, and breaking strength of conductive rubber made of non-conductive rubber, solves problems such as leakage of conductive agent and separation of organic rubber and silicone rubber, and provides excellent processing workability. In order to obtain conductive rubber, we investigated the primary structure of polyorganosiloxane and the conductive filler from the viewpoints of exudation of the filler, affinity with organic rubber, and the combination of conductivity and reinforcing properties of the filler. ■ Only the specific polyorganosiloxane of the present invention exhibits strong interaction with carbon black, which is used as an excellent reinforcing agent for ordinary organic rubbers, resulting in significantly improved particle dispersibility and no exudation of carbon black. ■ This carbon black has a high affinity for both organic rubber and polyorganosiloxane, which improves storage stability in an unvulcanized state and improves processing workability. , Also, ■ Because it is reinforced with carbon black, water is adsorbed around the silica, unlike conventional silicone rubber compositions containing silica, which eliminates the reinforcing effect of silica on polyorganosiloxane, and The present invention was completed based on the discovery that the hydrolysis of siloxane is not promoted.

The present invention will be explained in detail below.

The conductive rubber of the present invention contains rubber and conductive carbon black, and among these, the rubber components are (A) organic rubber and (B) polyorganosiloxane, or (B)
) Consisting of polyorganosiloxane.

(A) Organic rubbers include natural rubber, isoprene rubber,
Ethylene-α olefin rubber such as styrene-butadiene rubber, butadiene rubber, acrylonitrile-butadiene rubber, etc., butyl rubber, halogenated butyl rubber, fluororubber, acrylic rubber, epichlorohydrin rubber, ethylene-vinyl acetate copolymer, ethylene-7 acrylate rubber , polyurethane rubber, etc.

(A) The Mooney viscosity ML of organic rubber is
is in the range of 20-160, preferably 1◆4 or 30-100, particularly preferably 40-90. By using an organic rubber having such a viscosity, a rubber composition having stable quality and properties can be obtained. If the Mooney viscosity of the organic rubber is outside the above range, kneading workability and dispersibility will deteriorate, resulting in poor quality.
It becomes difficult to maintain the characteristics.

In addition, (B) polyorganosiloxane has the general formula (where R and R' are hydrocarbon substituents, n represents an integer of 3 or more, and R may be the same or different. , ), in which the substituent R
, at least 6 mol% or more of Sm ^ 11
order 2al ten-striped island (1ζ 0 to I μ convex)
It is a polyorganosiloxane having a fluorine substituent (hereinafter sometimes referred to as a "reinforcing substituent").

Here, the molecular attraction constants of Small are P, A, Sm
“Journal of Applied
Chemistry” Volume 3, pp. 71-80 (195
The polyorganosiloxane used in the present invention contains at least 6 mol %, preferably 10 to 70 mol %, more preferably 15 mol % of the substituents R and f in the above general formula. -60 mol%, particularly preferably 20-50 mol%, of Sma of 35°0 or more
It has a constant molecular attraction of II. This Sma l
The molecular attraction constant of l is preferably 500 or more, particularly 700 or more.

Substituents with a small molecular attraction constant of 350 or more include phenyl group, m-methylphenyl group, p-methylphenyl group, p-ethylphyonyl group, p-isopropylphenyl group, m-5ec butylphenyl group. , m-te
rt-butylphenyl group, p-3ee-butyl7z-nyl group, p-terL-butylphenyl group 1m-phenylphenyl group, p-phenylphenyl group, p-benzylphenyl group, β-naphthyl group, α-naphthyl, 2,4 -dimethylphenyl group, 2.5-dimethylphenyl group, 3.4-
Dimethylphenyl group, 3.5-dimethylphenyl group, O
-methoxyphenyl group, m-methoxyphenyl group,
p-methoxyphenyl group, m-phenoxyphenyl group,
p-phenoxyphenyl group, 4-methoxy-3-methylphenyl group, 6-medoxy-3-methylphenyl group, 3
．． 4-dimethoxyphenyl group, 2-methyl-4-methoxy-5-isopropylphenyl group, phenoxymethyl group, O-fluorophenyl group, m-fluorophenyl group,
p-fluorophenyl group, O-chlorophenyl group, p-
Chlorophenyl group, 2,3-dichlorophenyl group, 2,
4-dichlorophenyl group, 2.5-dichlorophenyl group, 2.6-dichlorophenyl group, 3,4-dichlorophenyl group, 3,5-dichlorophenyl group, 2,3.4-trichlorophenyl group, 2,3.5-trichlorophenyl group Chlorophenyl group, 2.3.6-trichlorophenyl group, 2,4.5-
) dichlorophenyl group, 2,3.

4,5-tetrachlorophenyl group, 2,3,4,6-tetrachlorophenyl group, 2,3,5.6-titrachlorophenyl group, pentachlorophenyl group, 0-bromophenyl group, m-bromophenyl group, p -Bromophenyl group, p-cyanophenyl group, p-aminophenyl group, p-
Aromatics and derivatives thereof, exemplified by hydroxyphenyl group, m-cyanophenyl group, m-aminophenyl group, 2-phenylethyl group, 2-phenylpropyl group, acenaphthyl group, indolyl group, anthracyl group, phenanthryl group, etc. Aromatic groups, organic groups containing aromatic derivatives in their structures, furyl groups, furfuryl groups, l-pyridyl groups, 2-pyridyl groups. 3-Pyridyl group, biridazyl group, biradyl group, quinolyl group, isoquinolyl group, triazinyl group, triazoyl group, thiophenyl group, oxazyl group, etc. A heterocycle or a derivative thereof, or a heterocycle or heterocycle derivative in its structure Organic groups containing, 2-hydroxycarbonylethyl group, 2-hydroxycarbonylpropyl group, 1-methyl-2-hydroxycarbonylethyl group, dimethylhydroxycarbonylethyl group, 2-methoxycarbonylethyl group, 2-ethoxycarbonylethyl group, 2 -methoxycarbonylpropyl group, 1-methyl-
2-methoxycarbonylethyl group, 1-methyl-2-ethoxycarbonylethyl group, dimethylmethoxycarbonylmethyl group, dimethylethoxycarbonylmethyl group, 2
-dihydraminocarbonylethyl group, 2-dimethylaminocarbonylethyl group, 2-diethylaminocarbonylethyl group, 2-dimethylaminocarbonylprobyl group, 2-diethylaminocarbonylprobyl group, 1-methyl-2=dimethylaminocarbonylethyl group , 1-methyl-2-diethylaminocarbonylethyl group, dimethyl(dimethylaminocarbonyl)methyl group, dimethyl(diethylaminocarbonyl)methyl group, etc., organic acid esters, organic acid derivatives (especially carboxyl groups and/or or a derivative containing an amide group) and an organic group containing them in its structure, a poly-l-butynisine group,
C= in the structure exemplified by polyvinylethylene group, poly-1-methyl-1-butynylene group, higher unsaturated acid residue, etc.
Examples include, but are not limited to, organic groups having multiple C double bonds, higher fatty acid residues, long-chain alkyl groups, and polyoxyalkylene groups.

Among these, organic groups having an aromatic nucleus in their structure, particularly organic groups having a benzene ring, are particularly preferred.

(B) The degree of polymerization of the polyorganosiloxane, that is, n in the general formula is 100 or more, preferably 2000 or more,
More preferably, it is 5000 or more.
If the degree of polymerization is less than 100, it will be difficult to be reinforced with carbon black, and workability at the time of crosstalk will be poor.

The polyorganosiloxane (B) used in the present invention is preferably substantially linear, but may have a partially branched or network structure.

In the present invention, in order to impart sufficient physical properties to the resulting rubber, the polyorganosiloxane is crosslinked or co-crosslinked with an organic rubber to form a network structure.

Therefore, the substituents R, [ of polyorganosiloxane are
A structure having at least one C=,=C2 double bond in the range of 0.02 to 20 mol%, preferably 0.03 to 10 mol%, particularly preferably 0.05 to 5 mol%. (hereinafter sometimes referred to as a "crosslinking substituent"), but especially when using a crosslinking agent other than organic peroxide, the above-mentioned crosslinking substituent is It is preferable that the substituent has a C═C double bond via at least one carbon atom, and that the crosslinkable substituent has 5 or more carbon atoms.

Examples of crosslinkable substituents include vinyl groups, fluorenyl groups such as allyl groups, alkylidene norbornyl groups such as ethylidene norbornyl groups and methylene norbornyl groups, dicyclopentenyl groups, 4-pentenyl groups, and 4-hexenyl groups. group, cyclooctenyl group, etc., but the substituent may be any substituent having a structure having at least one or more C═C═C aliphatic bond, and is not limited to these.

In the present invention, among the substituents of the polyorganosiloxane, there are no particular restrictions on the substituents other than the above-mentioned reinforcing substituents and crosslinking substituents.Other substituents include methyl groups, ethyl groups, and propyl groups. , butyl group, pentyl group, hexyl group, octyl group, decyl group, and other alkyl groups, and halogenated alkyl groups such as chloromethyl group. However, ease of synthesis and heat resistance as a silicone rubber composition, A methyl group is most preferred in order to provide properties such as weather resistance.

Vulcanizing agents used in crosslinking or co-crosslinking reactions include:
Methyl ethyl ketone peroxide, cyclohexanone peroxide, 3,3.4-trimethylcyclohexanone peroxide, methylcyclohexanone peroxide, methyl acetoacetate peroxide, acetylacetone peroxide, 1.1-bis(t-butylperoxy)-3, 3,5-trimethylcyclohexane, 1.1
-bis(t-butylperoxy)cyclohexane, ? ,
2-2-tert-butylperoxy)octane, n-butyl-4,4-bis(t-butylperoxy)valerate, 2,2-bis(t-butylperoxy)butane, 7-
Butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, p-methane hydroperoxide, dicumyl peroxide, 2゜5-dimethylhexane-2,5-dihydroperoxide, 1,1,3.3 -tetramethylbutylhydroperoxide, di-t-butylperoxide, t-butylcumyl peroxide, α,α'-bis(t-butylperoxy-m-isopropyl)benzene, 2,5-dimethyl-2
, 5-di(t-butylperoxy)hexane, 2.5-
Dimethyl-2,5-di(t-butylperoxy)hexine-3, acetyl peroxide, isobutyryl peroxide, octanoyl peroxide, decanoyl peroxide, lauroyl peroxide 1', 3,5.5- Trimethylhexanoyl peroxide, sulfonic peroxide, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, m-)lioyl peroxide, diisopropyl peroxydicarbonate, di-2-
Ethylhexyl peroxycarbonate, di-n-propyl peroxycarbonate, dimyristyl peroxydicarbonate, diallyl peroxydicarbonate,
Di-2-ethoxyethyl peroxydicarbonate, dimethoxyisopropyl peroxycarbonate, di(
3-Methyl-3-methoxybutyl) peroxycarbonate.

t-butylperoxyacetate, t-butylperoxyisobutyrate, t-butylperoxybiparate,
t-Butyl peroxy neodecanoate, cumyl peroxy neodecanoate, 1-butyl peroxy-2-ethyl octanoate.

t-Butylperoxy-3,5,5-)listylhexanoate, t-butylperoxylaurate, t-butylperoxybenzoate, di-7-butylperoxyisophthalate, 2,5-dimethyl-2 , 5-di(benzoylperoxy)hexane, t-butylperoxymaleic acid, t-butylperoxyisopropyl carbonate, cumylperoxyoctanoate, t-hexylperoxyvivalate, E-butylperoxyneohexa organic peroxides, sulfur, sulfur-like compounds, dipentamethylenethiuram tetrasulfide, tetramethylthiuram, etc. Thiuram compounds such as disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, 2-
Thiazole compounds such as (4-morpholino-dithio)benzothiazole, 4,4°-dithiol compounds, N, N'
-4-thiobis(hexahydro-2H-7zebinone-2
), alkylphenol disulfide, sulfur donor exemplified by polymer polysulfide, P-quinone oxime, p'
, p'-dibenzoylquinone oxime, polynitrosobenzene, N-(2-methyl-2-nitropropyl)-4
- Oxime and nitroso compounds such as nitronaniline, alkylphenol/formaldehyde resins, heat-reactive phenol resins, melamine/formaldehyde condensates, triazine formaldehyde condensates, halogenated alkylphenol/formaldehyde resins, etc. Sulfurizing agent, dithiol compound, poly7m
Examples include a wide range of crosslinking agents such as polyols, metal oxides, alkylphenol resins, and quinoids.

Note that a part of the polyorganosiloxane used in the present application can be substituted with another polyorganosiloxane, such as polydimethylsiloxane, within a range that does not impair the effects of the present invention. In that case, the amount of other polyorganosiloxanes is 1 part of the polyorganosiloxane used in the present application.
100 parts by weight or less, preferably 50 parts by weight
Parts by weight or less.

The conductive carbon black blended into the conductive rubber of the present invention not only imparts conductivity to the rubber but also imparts strength to it. In view of this reinforcing effect, the conductive carbon black used has an average particle diameter of 100% as measured by an electron microscope.
If the average particle diameter of the conductive carbon black exceeds IQQOA, it is difficult to obtain a reinforcing effect sufficient to obtain sufficient physical properties.

Specifically, as the conductive carbon black, CF (
Conductive Furnace), 5CF (Superconductive Furnace)
, XCF (special conductive furnace), acetylene black, Ketjen black, etc.

In addition, in the present invention, reinforcing carbon black having an average particle diameter of 100 OA or less, for example, SRF%GPF%HMF, is used to impart strength.

ACEF, FF, FEF, HAF, l
5FF, SAF, EPC, MPC, HPC, CC,
GERMAN etc. may be used together.

In the present invention, the composition ratio of (A) organic rubber and (B) polyorganosiloxane is (A)/(B) -9515 to 0
/l 00, preferably (A)/(B)=80
/20 to 20/80. When hot water resistance is required for conductive rubber, (A)/(B)=70/30-5
If the ratio of the polyorganosiloxane (B), which is preferably 0150, is less than 5%, it will be difficult to obtain sufficient heat resistance.

The amount of carbon black to be blended is 5 to 2 parts by weight based on 100 parts by weight of the organic rubber and polyorganosiloxane.
00 parts by weight, preferably 10 to 150 parts by weight, more preferably 25 to 100 parts by weight. If the amount of carbon black is less than 5 parts by weight based on 100 parts by weight of the total amount of organic rubber and polyorganosiloxane, it is difficult to obtain sufficient conductivity and reinforcing effect.

If it exceeds 200 parts by weight, the crosstalk workability tends to deteriorate significantly.

The conductive rubber of the present invention is mainly reinforced with carbon black and is given conductivity, but if necessary, conductive fillers other than carbon black may be blended.
Conductive fillers that can be used include aluminum, silver,
Examples include metal powders and fibers represented by gold, iron, nickel, copper, etc., metal fusion materials represented by tin oxide, zinc oxide, etc., carbon fibers, graphite, etc., but they are usually used as conductive fillers. It is not limited to these, as long as it is.

The rubber of the present invention may contain reinforcing or non-reinforcing fillers, if necessary. These fillers include fumed silica, precipitated silica, silica aerogel, ground quartz, diatomaceous earth, titanium oxide, zinc oxide, magnesium carbonate, aluminum sulfate, calcium sulfate, barium sulfate, mica, asbestos, glass powder, carbon black, etc. is exemplified. The surface of these fillers may be treated with an organic silicon compound, polydiorganosiloxane, etc. to make them hydrophobic.

In addition, other known heat resistance imparting agents, flame retardants, softeners, thermal conductivity imparting agents, vulcanization accelerators, vulcanization accelerating aids, processing aids, etc. may be blended.

The conductive rubber of the present invention has various excellent properties such as excellent water resistance, hot water resistance, heat resistance, and weather resistance, as well as high mechanical strength. By adjusting the blending amount or by combining with other conductive fillers, the volume resistivity value can be provided in an extremely wide range of 1 G-3 to 10' Ω·cm. (For example, for applications that require high conductivity such as switches, lO""3 to 10"Ω・cm
For applications that do not require high conductivity, such as static electricity removal, those in the range of 104 to 1O7 Ω·cm are preferably used. ) Therefore, the conductive rubber of the present invention can be used in electromagnetic shielding materials, shielding gaskets, static eliminators, non-static conveyor belts, conductive tires, carpets, conductive rolls, elastic electrodes, electric plating molds, planar heating elements, and construction. Electric heating materials for objects, heating elements used in outdoor equipment, conductive paint, black conductive ink, interconnectors, conductive sheets, pressure-sensitive resistive elements, flexible electrical circuit boards, elastomer switches, electric wires, OA equipment. It is extremely useful as a material for parts, movable contacts, various other antistatic materials, and conductive rubber products.

[Function] The conductive rubber containing (A) organic rubber and (B) polyorganosiloxane and conductive carbon black, or (B) polyorganosiloxane and conductive carbon black of the present invention has excellent conductivity. Moreover, it has excellent storage stability when unvulcanized, processing workability, mechanical strength, heat resistance,
Hot water resistant.

It also has excellent physical properties such as durability. This is because the polyorganosiloxane having a specific substituent according to the present invention has a strong affinity with carbon black, can be mixed with carbon black with extremely good dispersibility, and can be mixed with general organic rubber. By intervening carbon black, it is possible to obtain stability not found in conventional organic rubber-polyorganosiloxane rubber, and,
This is because conductive carbon black provides excellent conductivity and is effectively reinforced.

[Examples] The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded.

Examples 1 and 2, Comparative Examples 1 to 4 The raw materials with the compositions shown in Table 1 were heated to a temperature of 40°C or 8°C in the container.
After kneading with a rubber mixer at 0°C, it was formed into a sheet using rolls with a surface temperature of 25°C or 50°C. This is 1OX10X
O, filled into a 1cm mold, 50Kg/crn”, 17
10-15 minutes at 0”o.

After heating and pressurizing, the mold was demolded.

Table 1 shows the properties of the vulcanized rubber obtained.

Note that in Table 1, *1 to *11 are as follows.

*1: Degree of polymerization 8000. Phenyl group (Small molecular attraction constant 735) 30 mol%, vinyl group 0.5 mol%, other substituents are methyl groups (Sall molecular attraction constant 210 polyorganosiloxane *2: polymerization Polyorganosiloxane with a degree of 8000, vinyl group 0.2 mol%, and other substituents are methyl groups *3: RSS No. 1 *4 = Ketjen Black ECTy pe (average particle size 300A) *5: Nikki 7 Aerosil 200 manufactured by Aerosil Co., Ltd. *6: 2,5-dimethyl-2,5-di-t-butyl peroxyhexane diluted with polydimethylsiloxane, organic peroxide content 50% *7: 24 hours after crosstalk Observation results after being left to stand *8: Observation results after stimulating the vulcanizate with ultrasound for 2 hours *9: Tensile speed 300+m/m1n (DIN No. 3) *1O: Autoclaved at 180℃ Rate of change determined by hot water treatment for 15 hours and measurement under the same conditions as *9
%) *11: After heating in the oven at 160℃ for 96 hours, *9
From Table 1, which was obtained by measuring under the same conditions as , the following is recognized.

That is, in Example 1, Small's molecular attraction constant 735
Since it contains a polyorganosiloxane having 30 mo1% of phenyl groups, it is effectively reinforced with carbon black, and a conductive rubber with high conductivity and high strength can be obtained. Moreover, since silica is not used as a reinforcing agent, it has good hot water resistance, maintains the heat resistance of silicone, and does not exude carbon black. It contains rubber, and exhibits even better hot water resistance than Example 1.

Comparative Example 1 did not introduce a substituent with Small's molecular attraction constant of 350 or more in comparison with the above example, so it was not reinforced by carbon black and the fracture properties deteriorated.
Moreover, exudation of carbon black can be seen.

Comparative Example 2 is an attempt to improve the physical properties by adding white carbon to Comparative Example 1 and reinforcing it with silica. Exudation can be seen.

Compared to Example 2, Comparative Example 3 has no affinity between the polyorganosiloxane and carbon black, so there is no anchoring effect of the organic rubber/polyorganosiloxane by the carbon black, so it is difficult to separate the organic rubber and polyorganosiloxane. The storage stability in the unvulcanized state becomes extremely poor, and at the same time, the strength also becomes weak.

Comparative Example 4 is a product in which carbon black is blended with natural rubber, but since there is no polyorganosiloxane, the heat resistance is extremely poor.

Example 3. Comparative Example 5 The contact point 3 of the push button switch 1 shown in FIG. 1 was made using the rubbers of Example 1 and Comparative Example 1, and the contact point 3 of the push button switch 1 shown in FIG. did.

In FIG. 1, 2 is a dome, 4 is a fixed electrode, and 5 is a substrate.

The results are shown in Table 2.

[Effects] As detailed above, the conductive rubber of the present invention has a molecular attraction constant of 350 for (A) organic rubber and (B) Small.
It is a crosslinked rubber comprising a polyorganosiloxane having the above substituents or this specific polyorganosiloxane and reinforced with conductive carbon black.

This particular polyorganosiloxane thus exhibits good affinity with carbon black and is extremely stably mixed with organic rubber. Therefore, the conductive rubber of the present invention not only has excellent conductivity, but also has no exudation of carbon black or separation from organic rubber, and has extremely excellent storage stability.

Moreover, because it is reinforced with carbon black, the resulting rubber has extremely high strength, durability, heat resistance, water resistance,
Excellent hot water resistance and weather resistance.

Therefore, the conductive rubber of the present invention is extremely useful as a material for various conductive rubber products.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a push button switch produced in Example 3 and Comparative Example 5. l...Switch, 2...Dome, 3...Contact, 4...Fixed electrode, 5...φ board.

Claims (1)

[Claims] (1) Contains rubber and conductive carbon black, is crosslinked, and has a volume resistivity of 10^-^3 to 1
A conductive rubber in the range of 0^7 Ω·cm, characterized in that the rubber components are as shown below (a) and the composition ratio is as shown below (b). (B) Rubber components: (A) organic rubber and (B) polyorganosiloxane, or (B) contains polyorganosiloxane;
Polyorganosiloxane is a substituted polyorganosiloxane represented by the general formula ▲ There are mathematical formulas, chemical formulas, tables, etc. group R,
Of these, at least 6 mol% or more is a hydrocarbon substituent having a Small molecular attraction constant of 350 or more. (B) Composition ratio: The ratio of (A) organic rubber to (B) polyorganosiloxane is (A)/(B) = 95/-0/100.