JPH08120176A - Semiconductive silicone rubber composition - Google Patents

Abstract

PURPOSE: To obtain a semiconductive silicone rubber composition useful for forming a semiconductive silicone rubber having volume resistivity of 10<2> -10<10> Ω.cm and of extremely little variation. CONSTITUTION: This semiconductive silicone rubber composition is composed of (A) 100 pts.wt. of a diorgano polyslioxane having an alkenyl group containing at least two silicon atoms in a molecule, (B) 2-30 pts.wt. of carbon black, (C) 2-20 pts.wt. of an electrically conductive whisker of a metal compound such as a potassium titanate whisker having a tin oxide layer and/or an antimony oxide layer on the surface and (D) a curing agent in an amount sufficient for curing the composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductive silicone rubber composition, more specifically, a volume resistivity of 10 ² to 10 ^10.
Provided is a semiconductive silicone rubber composition for forming a semiconductive silicone rubber having a value of Ω · cm and a very small variation in the value.

[0002]

2. Description of the Related Art Silicone rubber compositions containing carbon black (JP-A-55-12065)
No. 6) or a silicone rubber composition containing silver-coated potassium titanate whiskers (JP-A-5-194).
No. 856), a highly conductive silicone rubber having a volume resistivity of less than 10 ² Ω · cm and little variation in its value is formed by blending a large amount of the above-mentioned conductive filler. You can

However, in these compositions, the volume resistivity was 10 ² by reducing the compounding amount of the above-mentioned conductive filler.
Attempting to form a semiconductive silicone rubber having a resistivity of about 10 ¹⁰ Ω · cm causes a large variation in volume resistivity, which is often a big problem.

[0004]

The present inventors have arrived at the present invention as a result of extensive studies to solve the above problems. That is, the object of the present invention is to obtain a volume resistivity of 10 ²
The purpose of the present invention is to provide a semiconductive silicone rubber composition for forming a semiconductive silicone rubber, which has a value of about 10 ¹⁰ Ω · cm and has a very small variation in the value.

[0005]

MEANS FOR SOLVING THE PROBLEMS AND ACTIONS OF THE INVENTION The present invention provides (A) 100 parts by weight of diorganopolysiloxane having at least two silicon-bonded alkenyl groups in one molecule, (B) carbon black 2-30 The present invention relates to a semiconductive silicone rubber composition comprising 1 part by weight, (C) 2 to 20 parts by weight of a metal compound type conductive whisker, and (D) a curing agent (a sufficient amount to cure the composition).

The semiconductive silicone rubber composition of the present invention will be described in detail below. The component (A), the diorganopolysiloxane, is the main ingredient of the composition, and it is necessary that it has at least two silicon-bonded alkenyl groups in one molecule. Examples of the silicon atom-bonded alkenyl group in the component (A) include a vinyl group, an allyl group, a butenyl group, a pentenyl group and a hexenyl group, and a vinyl group and a hexenyl group are preferable. The bonding position of the alkenyl group in the component (A) is not particularly limited, and examples thereof include a molecular chain terminal, a molecular chain side chain, a molecular chain terminal and a molecular chain side chain. Examples of the silicon atom-bonded organic group other than the alkenyl group in the component (A) include, for example, alkyl groups such as methyl group, ethyl group, propyl group, butyl group and pentyl group, phenyl group, tolyl group, xylyl group, etc. An aryl group, a benzyl group, an aralkyl group such as a phenethyl group, a chloropropyl group, a 3,3,3-trifluoropropyl group,
Examples thereof include a substituted or unsubstituted monovalent hydrocarbon group such as a 3-chloropropyl group and a 2-cyanoethyl group, and a methyl group and a phenyl group are preferable. Further, the molecular structure of the component (A) is substantially linear, but a part of the molecular structure may have a branched structure. In addition, the viscosity of the component (A) is not particularly limited, and practically preferably, the viscosity at 25 ° C. is from 50 centipoises to raw rubber-like viscosity, and more preferably, the viscosity at 25 ° C. is 100 centipoises to raw rubber-like. Up to viscosity.

Examples of the diorganopolysiloxane of the component (A) include a dimethylsiloxy / methylvinylsiloxane copolymer capped with trimethylsiloxy groups at both molecular chain terminals, and a methylvinylsiloxane with trimethylsiloxy groups capped at both molecular chain terminals. Methylphenylsiloxane copolymer, dimethylsiloxy group-capped dimethylsiloxysiloxane-methylvinylsiloxane-Methylphenylsiloxane copolymer, dimethylsiloxy group-capped dimethylsiloxane-methylvinylsiloxane-
Methyl (3,3,3-trifluoropropyl) siloxane copolymer, dimethylvinylsiloxy group-blocked dimethylpolysiloxane at both molecular chain ends, dimethylvinylsiloxy group-blocked methylphenylpolysiloxane at both molecular chain ends, dimethylvinylsiloxane at both molecular chain ends Siloxy group-blocked methyl (3
3,3-trifluoropropyl) siloxane copolymer,
Molecular chain both ends dimethylvinylsiloxy group blocked dimethylsiloxane / methylvinylsiloxane copolymer, molecular chain both ends dimethylvinylsiloxy group blocked dimethylsiloxane / methylphenylsiloxane copolymer, molecular chain both ends dimethylvinylsiloxy group blocked dimethylsiloxane Methyl (3,3,3-trifluoropropyl) siloxane copolymer, dimethylvinylsiloxy group-capped dimethylsiloxane at both molecular chain ends, methylvinylsiloxane, methylphenylsiloxane copolymer, silanol group-capped dimethylsiloxane at both molecular chain ends Methyl vinyl siloxane copolymer, silanol group-blocked methyl vinyl siloxane / methyl (3,3,3-trifluoropropyl)
Examples thereof include siloxane copolymers and silanol group-capped dimethylsiloxane / methylvinylsiloxane / methylphenylsiloxane copolymers having molecular chain terminals at both ends. As the component (A), these diorganopolysiloxanes may be blended alone or as a mixture of two or more.

The carbon black as the component (B) is a component for imparting semiconductivity to the silicone rubber obtained by curing the composition. The component (B) is not particularly limited, and examples thereof include furnace black, lamp black, channel black, and thermal black, and examples of the raw materials thereof include oil black and acetylene black. The characteristics of the component (B) are not particularly limited, but for example, its surface area is 10 m ²
/ G or more, especially 50m ²
/ G or more, and its oil absorption is 5
0 ml / 100 g to 350 ml / 10
It is preferably 0 g. Such a component (B) includes Continex CF, Continex SCF (above, product name of Continental Carbon Co., Ltd.), Vulcan C, Vulcan SC, Vulcan XC-72 (above product name of Kyabobot; product name), Asahi HS- 500 (manufactured by Asahi Carbon Co., Ltd .; trade name), Ketsu Chen Black EC (manufactured by Lion Akzo Co., Ltd .; trade name), Koratsuku L (manufactured by Degussa Co., trade name), Denka Black (manufactured by Denki Kagaku Kogyo Co., Ltd .; trade name) First name) is available.

The blending amount of the component (B) is in the range of 2 to 30 parts by weight with respect to 100 parts by weight of the component (A). this is,
The blending amount of the component (B) is 2 with respect to 100 parts by weight of the component (A).
This is because if it is less than 30 parts by weight, or if it exceeds 30 parts by weight, the obtained silicone rubber is not semi-conductive or its volume resistivity varies greatly. Further, when the amount of the component (B) compounded exceeds 30 parts by weight relative to 100 parts by weight of the component (A), the fluidity of the obtained silicone rubber composition is remarkably reduced, and the handling workability thereof is reduced. This is because it will decrease.

The metal compound type conductive whiskers as the component (C) are components for imparting semiconductivity to the silicone rubber obtained by curing the composition, and are used in combination with the carbon black as the component (B). This makes it possible to suppress variations in the volume resistivity of the semiconductive silicone rubber obtained. Examples of the metal compound whiskers, which are the main component (C), include potassium titanate whiskers, silicon carbide whiskers, zinc oxide whiskers, aluminum borate whiskers, and titanium dioxide whiskers.
Examples of the component (C) include the above metal compound whiskers, the above metal compound whiskers having a silver layer on the surface,
The above-mentioned metal compound whiskers having a conductive carbon layer on the surface and the above-mentioned metal compound whiskers having a tin oxide layer and / or an antimony oxide layer on the surface can be mentioned.
The method for producing the component (C) is not particularly limited, and examples thereof include a method of coating the surface of the above metal compound whiskers with silver by a silver mirror reaction, and a method of coating the surface of the above metal compound whiskers with C.
Examples thereof include a method of depositing conductive carbon by the VD vapor deposition method and a method of adsorbing conductive tin oxide doped with antimony oxide on the surface of the above metal compound whiskers by a wet adsorption method. The component (C) has a whisker shape, and its size is not particularly limited, but for example, the average fiber length of the component (C) is preferably in the range of 1 to 100 μm, and particularly, in the range of 10 to 20 μm. Is preferred. Further, the fiber diameter of the component (C) is preferably in the range of 0.01 to 10 μm, particularly 0.2 to 0.5 μm.
It is preferably within the range. Further, the oil absorption of the component (C) is preferably in the range of 10 to 300 ml / 100 g, and particularly preferably in the range of 150 to 250 ml / 100 g. As the component (C), potassium titanate whiskers having a conductive carbon layer on the surface are available as dentol BK, and potassium titanate whiskers having a tin oxide layer and an antimony oxide layer on the surface are available as dentol WK. Further, potassium titanate whiskers having a silver layer on the surface are available as Super Dentol (the above, manufactured by Otsuka Chemical Co., Ltd .; trade name).

The compounding amount of the component (C) is in the range of 2 to 20 parts by weight with respect to 100 parts by weight of the component (A). this is,
The compounding amount of the component (C) is 2 with respect to 100 parts by weight of the component (A).
When the amount is less than 20 parts by weight or exceeds 20 parts by weight, the obtained silicone rubber is not semiconductive and the volume resistivity varies greatly. Further, the blending amount of the component (C) is the same as that of the component (A) 1
This is because if it exceeds 20 parts by weight with respect to 00 parts by weight, the fluidity of the obtained silicone rubber composition is remarkably lowered and the handling workability thereof is deteriorated.

The component (D) curing agent is a component for curing the composition. Examples of the component (D) include organic peroxides and a mixture of an organohydrogenpolysiloxane having at least two silicon-bonded hydrogen atoms in one molecule and a platinum catalyst. Examples of the organic peroxide as the component (D) include benzoyl peroxide, t-butyl perbenzoate, 2,4-dichlorobenzoyl peroxide, monochlorobenzoyl peroxide,
Dicumyl peroxide, 2,5-dimethyl-2,5-
Di (t-butylperoxy) hexane may be mentioned. Examples of the organohydrogenpolysiloxane in the component (D) include, for example, methylhydrogenpolysiloxane blocked with trimethylsiloxy groups at both ends of the molecular chain, and dimethylsiloxane / methylhydrogensiloxane copolymer blocked with trimethylsiloxy groups at both ends of the molecular chain. Dimethylpolysiloxane with dimethylhydrogensiloxy group blocked at both ends of the molecular chain, dimethylsiloxane / methylhydrogensiloxane copolymer with dimethylhydrogensiloxy group blocked at both ends of the molecular chain, methylphenylsiloxane / methylhydro with trimethylsiloxy group blocked at both ends of the molecular chain Examples of the platinum-based catalyst in the component (D) include platinum black, chloroplatinic acid, a platinum-olefin complex, a platinum-alkenylsiloxane complex, and a chloroplatinic acid adduct. Lucol solution, platinum-supported fine powder silica, platinum-supported activated carbon, and thermoplastic organic resin fine particles containing these platinum-based catalysts such as polycarbonate resin, polymethylmethacrylate resin, polystyrene resin, nylon resin, silicone resin, etc. To be

The blending amount of the component (D) is an amount sufficient to cure the composition. For example, when the component (D) is an organic peroxide, it is added to 100 parts by weight of the component (A). 0.1 to
It is preferably in the range of 10 parts by weight, and (D)
When the component is a mixture of the organohydrogenpolysiloxane and the platinum-based catalyst, the amount of the organohydrogenpolysiloxane in the component (D) is 10
The amount of the platinum-based catalyst in the component (D) is preferably 0.5 to 20 parts by weight with respect to 0 part by weight, and the platinum metal content in the catalyst is (A). It is preferably within the range of 0.1 to 1000 parts by weight with respect to 1 million parts by weight of the component.

The composition comprises the above-mentioned components (A) to (D), but other optional components such as fumed silica, wet silica and fumed oxidation can be used as long as the object of the present invention is not impaired. Reinforcing filler such as titanium, and
The surface of these reinforcing fillers is treated with an organosilicon compound such as an organoalkoxysilane, an organohalosilane, an organosilazane, a diorganosiloxane oligomer whose molecular chain ends are blocked with silanol groups, or a cyclic organosiloxane. Reinforcing fillers may be mentioned. The method of treating the surface of these reinforcing fillers with an organic silicon compound is not particularly limited, and may be one obtained by treating these reinforcing fillers with the above organic silicon compound in advance. Reinforcing filler (A)
When blended into the components, the above organosilicon compound may be blended together and treated. The particle size and surface area of such a reinforcing filler are not particularly limited, but the particle size is preferably 50 mμ or less, and the surface area is preferably 50 m ² / g or more, and particularly,
It is preferably 250 m ² / g or more. In addition, as other optional components, for example, quartz fine powder, fused silica, titanium oxide, magnesium oxide, aluminum oxide, aluminum silicate, calcium silicate, magnesium silicate, calcium carbonate, magnesium carbonate, diatomaceous earth, Non-reinforcing fillers such as talc, mica, clay, aluminum hydroxide, aluminum nitride, silicon nitride, and boron nitride, heat-resistant agents such as iron oxide, cerium oxide, and cerium fatty acid salts, antistatic agents such as surfactants, difficult Examples thereof include a flame retardant, an internal mold release agent, a plasticizer, and a branched or resinous organopolysiloxane containing a vinyl group. Furthermore, when a mixture of an organohydrogenpolysiloxane and a platinum-based catalyst is used as the component (D), 3-methyl-1-butyn-3-ol, for the purpose of adjusting the pot life of the composition, Alkyne alcohols such as 3,5-dimethyl-1-hexyn-3-ol and phenylbutynol, 3-methyl-3-penten-1-yne,
Enyne compounds such as 3,5-dimethyl-3-hexen-1-yne, 1,3,5,7-tetramethyl-1,3
5,7-Tetravinylcyclotetrasiloxane, 1,
Suppression of addition reaction of 3,5,7-tetramethyl-1,3,5,7-tetrahexenylcyclotetrasiloxane, methyltris (methylisobutynoxy) silane, benzotriazole, acetylene compound, hydrogen peroxide compound, etc. Agents can be added.

The composition comprises the above-mentioned components (A) to (D),
And, it is prepared by uniformly mixing with other optional components. The method for preparing the present composition is not particularly limited, and, for example, after preparing a composition comprising the above-mentioned components (A) to (C), the component (D) is kneaded with a roll (commonly known as catalysis). Rising) is generally performed. The apparatus for preparing the composition comprising the above components (A) to (C) is not particularly limited, and examples thereof include a Henschel mixer, a Ross mixer, a kneader mixer, and a twin-screw continuous kneading extruder. Further, in order to prepare the composition of the present invention, for example, in the above-mentioned kneading device, the component (A) is uniformly kneaded with the component (B) and the component (C), and then the component (D) is kneaded. The method is to uniformly knead the components (B) and (C) to a part of the components (A), and then mix the rest of the components (A) and the components (D) and knead them uniformly. You can

In the semiconductive silicone rubber composition of the present invention, the volume resistivity of the silicone rubber obtained by curing the composition is in the range of 10 ² to 10 ¹⁰ Ω · cm, and the variation in the value is caused. Since it is extremely small, it can be used in antistatic materials, semiconductive rolls, and the like. The conditions for molding a roll using the present composition are not particularly limited. For example, the present composition is coated on a roll core metal by a known rubber molding machine such as a compression molding machine, an injection molding machine, or a transfer molding machine. The semiconductive roll can be formed by heating at 50 ° C to 250 ° C for several seconds to several minutes. Alternatively, a semi-conductive roll can be formed by coating the present composition on the surface of a conventional roll and then curing the composition.

[0017]

EXAMPLES The semiconductive silicone rubber composition of the present invention will be described in detail with reference to Examples. In the examples, the viscosity is a value measured at 25 ° C. Also,
The volume resistivity of silicone rubber is specified in JIS C 2123 (electrical silicone rubber compound test method) for the silicone rubber sheets of Samples (1) to (10) prepared by curing a semiconductive silicone rubber composition. It was measured by the method. The average value of the volume resistivities of these silicone rubbers was obtained, and the dispersion of these volume resistivities was evaluated by the standard deviation of the common logarithm of the volume resistivities.

[Example 1] A dimethylsiloxane in which both ends of a raw rubber-like molecular chain were blocked with trimethylsiloxy groups.
Methyl vinyl siloxane copolymer (the molar ratio of dimethyl siloxane and methyl vinyl siloxane is 99.84:
It is 0.16. This average degree of polymerization is 3000. )
100 parts by weight, 30 parts by weight of fumed silica having a surface area of 200 m ² / g, and 5 parts by weight of dimethylpolysiloxane capped with silanol groups at both molecular chain ends of 30 centipoise were premixed with a kneader mixer, and then heated at 170 ° C. Mixed. After this, Ketjen Black EC
(Product name of carbon black manufactured by Lion Akzo Co., Ltd .: surface area = 1000 m ² / g, oil absorption = 340 ml / 100 g) 4 parts by weight, DENTOL WK-20
0 (trade name of potassium titanate whiskers having a tin oxide layer and an antimony oxide layer on the surface manufactured by Otsuka Chemical Co., Ltd .: average fiber length = 10 to 20 μm, fiber diameter = 0.2 to
0.5 μm, oil absorption = 170-220 ml / 1
00g) 10 parts by weight were uniformly mixed to prepare a silicone rubber base (I). Next, 100 parts by weight of this silicone rubber base (I) and 1 part by weight of 2,5-dimethyl-bis (2,5-t-butylperoxy) hexane were uniformly mixed with a two-roll to form a semi-finished product of the present invention. A conductive silicone rubber composition was prepared. This silicone rubber composition is heated and pressed at 170 ° C. for 10 minutes,
Ten 1 mm-thick silicone rubber sheets were prepared, and these were further heated in a hot air circulation type oven at 200 ° C. for 4 hours. The volume resistivity of the silicone rubber sheet thus obtained was measured. The results are shown in Table 1.

Comparative Example 1 A semiconductive silicone rubber composition was prepared in the same manner as in Example 1 except that Denthol WK-200 was not added. This silicone rubber composition was cured in the same manner as in Example 1 to prepare 10 silicone rubber sheets. The volume resistivity of the silicone rubber sheet thus obtained was measured. The results are shown in Table 1.

[Example 2] 100 parts by weight of dimethylpolysiloxane (vinyl group content = 0.23% by weight) in which both ends of a 2,000 centipoise molecular chain were blocked with dimethylvinylsiloxy groups, and an average particle diameter was 5 μm. 30 parts by weight of quartz fine powder, Denka Black (trade name of carbon black manufactured by Denki Kagaku Kogyo Co., Ltd .: surface area = 61 m ² /
g, oil absorption = 125 ml / 100 g) 7 parts by weight and Dentol WK-200 (manufactured by Otsuka Chemical Co., Ltd .:
5 parts by weight (trade name) were uniformly mixed with a Ross mixer. Then to this, the formula:

Embedded image 2 parts by weight of a methylhydrogensiloxane / dimethylsiloxane copolymer in which both ends of the molecular chain represented by are blocked with trimethylsiloxy groups and an isopropyl alcohol solution of chloroplatinic acid (content as platinum metal in solution =
0.5 parts by weight (1% by weight) were uniformly mixed to prepare the semiconductive silicone rubber composition of the present invention. This silicone rubber composition was cured in the same manner as in Example 1 to prepare 10 silicone rubber sheets. The volume resistivity of the silicone rubber sheet thus obtained was measured. The results are shown in Table 1.

Comparative Example 2 A semiconductive silicone rubber composition was prepared in the same manner as in Example 2 except that Dentol WK-200 was not added. This silicone rubber composition was cured in the same manner as in Example 2 to prepare 10 silicone rubber sheets. The volume resistivity of the silicone rubber sheet thus obtained was measured. The results are shown in Table 1.

[0022]

[Table 1]

[0023]

The semiconductive silicone rubber composition of the present invention contains (B) carbon black and (C) metal compound type conductive whiskers in the respective predetermined amounts, and therefore has a volume resistivity of 10 ² to 10 10. It has a characteristic of being ¹⁰ Ω · cm, and it is possible to form a semi-conductive silicone rubber with a very small variation in the value.

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Claims (2)

[Claims] 1. (A) 100 parts by weight of diorganopolysiloxane having at least two silicon-bonded alkenyl groups in one molecule, (B) 2 to 30 parts by weight of carbon black, (C) metal compound-based conductivity A semiconductive silicone rubber composition comprising 2 to 20 parts by weight of whiskers and (D) a curing agent (a sufficient amount to cure the composition). 2. The semiconductive silicone rubber composition according to claim 1, wherein the component (C) is a potassium titanate whisker having a tin oxide layer and / or an antimony oxide layer on its surface.