JP2011122042A - Addition-curable silicone rubber composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an addition-curable silicone rubber composition that permits reducing the influence of a vulcanization inhibiting component derived from carbon black when subjected to addition cure vulcanization in a millable type silicone rubber composition to which carbon black exclusive of acetylene black for reasons of material design is added and blended. <P>SOLUTION: In the addition-curable silicone rubber composition to which carbon black is added, a compound having a skeleton composed of hydrocarbon is mixed in an amount of 0.1-20 mass% based on the total of the compound and a silicone rubber composition including the components (A) and (C)-(E) as follows: (A) an organopolysiloxane with a polymerization degree of 100 or more which is represented by the formula: R<SP>1</SP><SB>a</SB>SiO<SB>(4-a)/2</SB>(wherein R<SP>1</SP>represents a monovalent hydrocarbon group and two or more of R<SP>1</SP>in a molecule are aliphatic unsaturated groups; and a is 1.95 to 2.05), (C) carbon black, (D) an organohydrogenpolysiloxane containing two or more silicon atom-bonded hydrogen atoms in a molecule and (E) a hydrosilylation reaction catalyst. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an addition-curable silicone rubber composition containing organopolysiloxane as a main component and cured by hydrosilylation addition reaction, and in particular, a system in which carbon black is added for the purpose of imparting conductivity or coloring. The present invention relates to a millable type addition-curable silicone rubber composition capable of reducing the influence of a vulcanization inhibiting component contained as an impurity in carbon black.

  Silicone rubber compositions to which carbon black is added mainly for the purpose of imparting conductivity or coloring are mainly used for electrical and electronic equipment. The vulcanization at this time is a method by peroxide vulcanization represented by 2,5-dimethyl-2,5-bis (tertiarybutylperoxy) hexane as a vulcanizing agent, or addition using a hydrosilylation reaction. One of the methods by vulcanization is mainstream. When vulcanizing and molding a silicone rubber composition, there are cases of extrusion molding and calendar molding by atmospheric pressure hot-air vulcanization. In this case, inhibition of vulcanization by oxygen and decomposition of peroxide in the method by peroxide vulcanization In consideration of the influence of the residue on the conductivity, a method by addition vulcanization is generally selected. However, carbon black added for the purpose of imparting conductivity or coloring contains impurities such as sulfur and nitrogen-containing compounds derived from petroleum, natural gas, liquefied petroleum gas, etc., which are raw materials for carbon black. In many cases, these sulfur and nitrogen-containing compounds are known to cause vulcanization inhibition during addition vulcanization. When addition vulcanization of a silicone rubber composition, it is very susceptible to the above sulfur and nitrogen-containing compounds, and particularly when only carbon black is added as a filler, the sulfur mass contained in the carbon black If it exceeds 50 ppm, the vulcanization will be delayed.

On the other hand, there are so many grades of carbon black, among which acetylene black made from acetylene gas contains almost no sulfur or nitrogen-containing compounds, and a silicone rubber composition containing this acetylene black is used. It is well known that addition vulcanization does not inhibit vulcanization. However, there are many cases in which acetylene black is not selected for material design because the desired conductive properties cannot be obtained even when acetylene black is used, or because it is disadvantageous in cost compared to general furnace black. .
In addition, the following literature is mentioned as a prior art relevant to this invention.

JP-A-54-139659 JP-A-55-108455 Japanese Patent Laid-Open No. Sho 56-120761 Japanese Patent Laid-Open No. 61-062528 JP 2007-186544 A

  The present invention has been made in view of the above circumstances, and for reasons of material design, in a millable silicone rubber composition containing and blending carbon black other than acetylene black, vulcanization inhibition derived from carbon black during addition vulcanization An object of the present invention is to provide an addition-curable silicone rubber composition in which the influence of components is reduced. In particular, it is difficult to control the amount of the vulcanization inhibiting component in the carbon black at the time of carbon production, and it is difficult to obtain vulcanization inhibiting components, particularly carbon having a sulfur amount within a certain range. Variations are likely to occur and may affect the properties of the molded product. An object of the present invention is to provide a silicone rubber composition in which the influence is reduced and stable characteristics are easily obtained.

As a result of intensive studies to achieve the above object, the present inventor has obtained a compound having a hydrocarbon as a skeleton in an addition curable silicone rubber composition to which carbon black, particularly carbon black other than acetylene black, is added. By mixing 0.1 to 20% by mass of the compound and the following (A), (C) to (E) components, preferably 0.1 to 20% by mass in the total of the silicone rubber composition comprising the component (B), carbon black is derived. It has been found that a material capable of reducing the influence of vulcanization inhibition due to sulfur, particularly sulfur, can be obtained, and the present invention has been made.
The hydrocarbon-based compound, which is a characteristic component of the present invention, may be oily (liquid) or rubbery at room temperature (25 ° C.). The effect of reducing the influence of inhibition tends to be large.

That is, the present invention provides the following addition-curable silicone rubber composition.
[Claim 1]
An addition-curable silicone rubber composition comprising the following (1) and (2), wherein (2) is in the range of 0.1 to 20% by mass with respect to the total of (1) and (2): Addition-curable silicone rubber composition in an amount.
(1) An organopolysiloxane composition comprising the following (A) to (E).
(A) The following average composition formula (I)
R ¹ _a SiO _{(4-a) / 2} (I)
Wherein R ¹ is the same or different unsubstituted or substituted monovalent hydrocarbon group, and at least two in one molecule are aliphatic unsaturated groups. A is 1.95 to 2.05 (It is a positive number.)
100 parts by mass of an organopolysiloxane having a degree of polymerization represented by
(B) 0-100 mass parts of silica,
(C) 1 to 10 parts by mass of carbon black,
(D) 0.1-30 parts by mass of an organohydrogenpolysiloxane containing hydrogen atoms bonded to at least two silicon atoms in one molecule;
(E) Hydrosilylation reaction catalyst Catalytic amount (2) Compound having hydrocarbon as skeleton.
[Claim 2]
(1) The component (C) is at least one carbon black other than acetylene black selected from furnace black, channel black, and thermal black, and the amount of sulfur present in the system is 50 ppm or more. The addition-curable silicone rubber composition described.
[Claim 3]
(1) Component (C) is at least one carbon black other than acetylene black selected from furnace black, channel black, and thermal black, and (B) component silica is based on 100 parts by mass of component (A). The addition-curable silicone rubber composition according to claim 1, wherein the amount of sulfur present in the system is 200 ppm or more.
[Claim 4]
The addition-curable silicone rubber according to any one of claims 1 to 3, wherein (2) is a paraffinic oil and has an amount of 0.1 to 5% by mass relative to the total of (1) and (2). Composition.
[Claim 5]
The addition-curable silicone rubber composition according to any one of claims 1 to 3, wherein (2) is EPDM and is in an amount of 0.5 to 20 mass% with respect to the total of (1) and (2). .

  The silicone rubber composition of the present invention is a millable type material that can be extruded, calendered, and the like (that is, a non-flowable high-viscosity paste that can be kneaded in a kneader such as a roll mill). There is an addition-curing silicone rubber composition by hydrosilylation reaction to which carbon black is added mainly for the purpose of imparting conductivity or coloring. It is a silicone rubber composition to which a specific amount of a vulcanization inhibiting component derived from carbon black, especially a hydrocarbon-based compound is added in order to reduce the influence of sulfur. Stable vulcanization characteristics and conductive characteristics can be obtained without affecting the characteristics of the resin.

The addition-curable silicone rubber composition of the present invention comprises the following (1) and (2).
(1) An organopolysiloxane composition comprising the following (A) to (E).
(A) The following average composition formula (I)
R ¹ _a SiO _{(4-a) / 2} (I)
Wherein R ¹ is the same or different unsubstituted or substituted monovalent hydrocarbon group, and at least two in one molecule are aliphatic unsaturated groups. A is 1.95 to 2.05 (It is a positive number.)
100 parts by mass of an organopolysiloxane having a degree of polymerization represented by
(B) 0-100 mass parts of silica,
(C) 1 to 10 parts by mass of carbon black,
(D) 0.1-30 parts by mass of an organohydrogenpolysiloxane containing hydrogen atoms bonded to at least two silicon atoms in one molecule;
(E) Hydrosilylation reaction catalyst Catalytic amount (2) Compound having hydrocarbon as skeleton.

In the composition (1) constituting the silicone rubber composition of the present invention, the component (A) as the main agent (base polymer) preferably has a degree of polymerization represented by the following average composition formula (I) of 100 or more. Is a linear organopolysiloxane.
R ¹ _a SiO _{(4-a) / 2} (I)
Wherein R ¹ is the same or different unsubstituted or substituted monovalent hydrocarbon group, and at least two in one molecule are aliphatic unsaturated groups. A is 1.95 to 2.05 (It is a positive number.)

In the above average composition formula (I), R ¹ represents the same or different unsubstituted or substituted monovalent hydrocarbon group, usually having 1 to 12 carbon atoms, particularly preferably having 1 to 8 carbon atoms. Are an alkyl group such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, a hexyl group or an octyl group, a cycloalkyl group such as a cyclopentyl group or a cyclohexyl group, a vinyl group, An alkenyl group such as an allyl group, a propenyl group, a cycloalkenyl group such as a cyclohexenyl group, an aryl group such as a phenyl group and a tolyl group, an aralkyl group such as a benzyl group and a 2-phenylethyl group, or a hydrogen atom of these groups Examples include a group in which a part or all of them are substituted with a halogen atom or a cyano group, and a methyl group, a vinyl group, a phenyl group, or a trifluoropropyl group. Preferred, in particular methyl, vinyl is preferable.

This organopolysiloxane is preferably a straight chain in which the main chain is composed of repeating diorganosiloxane units and both ends of the molecular chain are blocked with triorganosiloxy groups or hydroxydiorganosiloxy groups. In particular, the repeating structure of diorganosiloxane units (R ¹ ₂ SiO _2/2 , R ¹ is the same as above, the same shall apply hereinafter) constituting the main chain of the organopolysiloxane consists of repeating dimethylsiloxane units only Or a diphenylsiloxane unit having a phenyl group, a vinyl group, a 3,3,3-trifluoropropyl group or the like as a substituent as a part of a dimethylpolysiloxane structure composed of repeating dimethylsiloxane units constituting the main chain, Methylphenylsiloxane units, methylvinylsiloxane units, methyl-3,3,3 And those obtained by introducing a diorganosiloxane unit such trifluoropropyl siloxane units are preferred.

Note that both ends of the molecular chain are, for example, triorganosiloxy groups (R ¹ ₃ SiO _1/2 ) such as trimethylsiloxy group, dimethylphenylsiloxy group, vinyldimethylsiloxy group, divinylmethylsiloxy group, trivinylsiloxy group, hydroxy It is preferably blocked with a hydroxydiorganosiloxy group such as a dimethylsiloxy group (R ¹ ₂ (HO) SiO _1/2 ).

The organopolysiloxane as the component (A) has 2 or more, usually 2 to 50, preferably about 2 to 20 alkenyl groups, cycloalkenyl groups and other aliphatic unsaturated groups in one molecule. The aliphatic unsaturated group is preferably an alkenyl group, particularly a vinyl group. In this case, all the R ¹ in 0.01 to 20 mol%, in particular 0.02 to 10 mol%, and more preferably 0.02 to 5 mol% is an aliphatic unsaturated group. The aliphatic unsaturated group may be bonded to the silicon atom at the end of the molecular chain, or may be bonded to the silicon atom in the middle of the molecular chain (non-terminal of the molecular chain), or both. In addition, it is preferably bonded to at least a silicon atom at the end of the molecular chain.

Moreover, a is a positive number of 1.95 to 2.05, preferably 1.98 to 2.02, more preferably 1.99 to 2.01. Further, in all R ^{1 s} , 80% by mole or more, preferably 90% by mole or more, more preferably 95% by mole or more, and more preferably all R ¹ except aliphatic unsaturated groups are alkyl groups, particularly methyl groups. This is desirable from the viewpoint of ensuring transparency.

The organopolysiloxane of component (A) has a triorganosiloxy group (R ¹ ₃ SiO _{1 /} R ¹⁾ such as trimethylsiloxy group, dimethylphenylsiloxy group, dimethylvinylsiloxy group, methyldivinylsiloxy group, trivinylsiloxy group at the molecular chain end. ₂ ) or a straight chain which is blocked with a dimethylhydroxysiloxy group and the main chain is composed of repeating diorganosiloxane units (R ¹ ₂ SiO _2/2 ) described above can be preferably exemplified.
Particularly preferred are the types of substituents in the molecule (that is, unsubstituted or substituted monovalent hydrocarbon groups bonded to silicon atoms) as methyl vinyl polysiloxane, methyl phenyl vinyl polysiloxane, methyl trifluoropropyl vinyl poly Examples thereof include siloxane.

  Such an organopolysiloxane can be obtained by, for example, hydrolyzing and condensing one or more organohalogenosilanes, or by converting a cyclic polysiloxane (siloxane trimer, tetramer, etc.) to alkaline or acidic. It can obtain by ring-opening polymerization using the catalyst of. These are basically linear diorganopolysiloxanes, but the component (A) may be a mixture of two or more different molecular weights (degree of polymerization) and molecular structures.

  The degree of polymerization of the organopolysiloxane is 100 or more (usually 100 to 100,000), preferably 500 to 100,000, more preferably 1,000 to 100,000, and particularly preferably 2,000 to 50,000. 000, more preferably 3,000 to 20,000, particularly preferably a raw rubber that does not have self-fluidity at room temperature (25 ° C.). This degree of polymerization can be measured as a weight average degree of polymerization in terms of polystyrene by gel permeation chromatography (GPC) analysis.

Component (B), silica, is a fine powder reinforcing filler (that is, reinforcing filler) added to obtain a silicone rubber composition having excellent mechanical strength. Usually, as the reinforcing silica used in the silicone rubber composition, the specific surface area (BET method) such as fumed silica (that is, fumed silica), precipitated silica and the like is usually 50 m ² / g or more, preferably 50 to 400m ² / g, more preferably include reinforcing silica filler of about 100 to 300 m ² / g.

  Component (B) is added in an amount of 0 to 100 parts by weight, preferably 1 to 60 parts by weight, more preferably 5 to 60 parts by weight, based on 100 parts by weight of organopolysiloxane (A). In the present invention, the carbon black of component (C) can serve as a reinforcing filler, so that mechanical strength can be obtained even when silica is not blended (that is, even at 0 parts by mass), but more satisfactory mechanical strength can be obtained. In order to obtain it, or since the effect which adsorb | sucks the sulfur content in carbon black can be anticipated, it is preferable to mix | blend 1 mass part or more with respect to 100 mass parts of (A) component, More preferably, it is 5 mass parts or more. If it exceeds 100 parts by mass, it will be difficult to disperse the silica in the silicone polymer. In the present invention, since the reinforcing effect by carbon black can also be expected, the upper limit of the number of added silica is 100 parts by weight, preferably 60 parts by weight, more preferably about 45 parts by weight with respect to 100 parts by weight of component (A). That's fine.

  Component (C), carbon black, is blended for the purpose of imparting conductivity, coloring, and the like, and is not particularly limited as carbon black, and known ones can be used, such as furnace black, channel black, It is preferable to use at least one selected from thermal black, particularly one or more of the above carbon blacks other than acetylene black.

  When carbon black is classified according to general production methods, it can be divided into furnace method, channel method, thermal method (including acetylene black method) and the like. The furnace method is a method in which creosote oil or the like is partially burned in a space surrounded by appropriate turbulent diffusion in a fireproof room, and then the water droplets are cooled with water. Furnace black is called the channel method. The channel method is a method in which the diffusion flame is partially burned in a space that is not enclosed and collides with a cold surface (channel plate). The carbon produced by this method is called channel black, and the thermal method. Is a method in which the checker structure of refractory bricks is sufficiently heated and the raw material is thermally decomposed here or a method similar thereto, and the carbon produced by this method is called thermal black. Among them, the carbon produced by the production method by exothermic decomposition in the space surrounded by acetylene is called acetylene black.

  In producing carbon black in this way, carbon black except acetylene black produced by burning acetylene gas is produced by burning petroleum-derived raw materials, and as a result, sulfur is unavoidable as a normal impurity. Will be included. For example, in the case of FEF (Fast Extracting Furnace) grade carbon, the content is about 0.5% by mass. Although this FEF grade carbon is known as a grade suitable for extrusion molding, when this grade is added at a blending ratio of about 10% by mass with respect to the conventional silicone rubber composition, the sulfur content mass in the system is about It was about 500 ppm, and addition vulcanization was not possible at all due to inhibition of vulcanization by sulfur. From this, when only carbon black is used as a filler, a grade with a relatively low sulfur content is selected for the silicone rubber composition, or the blending amount is limited, so that the sulfur-containing mass of the entire composition is 50 ppm. By adjusting to below the level, it became possible to use without affecting the vulcanization characteristics and other rubber properties.

  Further, when silica and carbon black are used in combination as a filler, particularly in a silicone rubber composition in which the silica of the component (B) is added in an amount of 1 part by mass or more, particularly 5 parts by mass or more, the sulfur of the entire composition When the contained mass is adjusted to 200 ppm or less, it can be used without affecting the vulcanization characteristics and other rubber properties. The above values are examples when the component (E) is used in a catalytic amount (1 to 200 ppm), but 50 ppm when there is no silica, and 200 ppm when silica is present affects the vulcanization rate and rubber properties. It is considered a boundary level of sulfur content that does not reach, and in the case of a composition containing sulfur in an amount exceeding these boundary levels, vulcanization inhibition is unavoidable.

  Strict control of the sulfur content is considered difficult due to the production method of carbon black. Therefore, in a system in which a predetermined amount of carbon black is added, the vulcanization speed and physical properties of the rubber are affected according to the amount of sulfur in the added carbon black. In order to avoid this influence, there is a method of increasing the amount of catalyst, but the increase in the amount of catalyst adds to the cost of the product, resulting in a disadvantage in cost. Compared to the catalyst, the method using silica together is inexpensive, and the boundary level of the sulfur amount is higher than that of the system without silica, and it is relatively effective against vulcanization inhibition.

  The amount of carbon black added is 1 to 10 parts by mass, preferably 2 to 5 parts by mass, with respect to 100 parts by mass of the organopolysiloxane of component (A). When the amount is less than 1 part by mass, the effect of imparting conductivity or coloring is small, and when the amount is more than 10 parts by mass, the conductivity can be sufficiently imparted, but the workability is reduced such as difficulty in molding. Furthermore, when the effect of coloring is expected, since the effect is sufficiently seen at about 2 parts by mass, there is no advantage of increasing the addition amount beyond that.

The organohydrogenpolysiloxane of component (D) acts as a crosslinking agent and contains hydrogen atoms (SiH groups) bonded to at least two silicon atoms in one molecule. Conventionally known organohydrogenpolysiloxane represented by (II) is applicable.
^{_{R 2 b H c SiO (4}} -bc) / 2 (II)

Here, R ² is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 6 carbon atoms, and preferably has no aliphatic unsaturated bond. Specific examples include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, an alkyl group such as a pentyl group and a hexyl group, a cycloalkyl group such as a cyclohexyl group, and a phenyl group. At least a part of hydrogen atoms of the monovalent hydrocarbon group such as an aryl group, an aralkyl group such as a benzyl group, an unsubstituted monovalent hydrocarbon group such as an 3,3,3-trifluoropropyl group, or a cyanomethyl group is halogenated A substituted monovalent hydrocarbon group such as a substituted alkyl group substituted with an atom or a cyano group.
b is 0.7 to 2.1, c is 0.01 to 1.0, and b + c is 0.8 to 3.0, preferably b is 0.8 to 2.0, and c is 0.10 to 1 0.0, more preferably 0.18 to 1.0, still more preferably 0.2 to 1.0, and b + c is a positive number satisfying 1.0 to 2.5.

  Further, the molecular structure of the organohydrogenpolysiloxane may be any of linear, cyclic, branched, and three-dimensional network structures. In this case, the number of silicon atoms in one molecule (or the degree of polymerization) is preferably 2 to 300, particularly about 4 to 200 at room temperature. The hydrogen atom (SiH group) bonded to the silicon atom may be at the end of the molecular chain, at the side chain (in the middle of the molecular chain), or both, and at least two (usually normal) 2 to 300), preferably 3 or more (for example, 3 to 200), more preferably about 4 to 150.

Specific examples of the organohydrogenpolysiloxane of component (D) include 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, and methylhydrogencyclopolysiloxane. Siloxane, methylhydrogensiloxane-dimethylsiloxane cyclic copolymer, tris (dimethylhydrogensiloxy) methylsilane, tris (dimethylhydrogensiloxy) phenylsilane, trimethylsiloxy group-blocked methylhydrogenpolysiloxane, trimethylsiloxy group at both ends Blocked dimethylsiloxane / methylhydrogensiloxane copolymer, dimethylhydrogensiloxy group-blocked dimethylpolysiloxane at both ends, dimethylhydrogensiloxy group-blocked dimethylsiloxane at both ends Tyrhydrogensiloxane copolymer, trimethylsiloxy group-capped methylhydrogensiloxane / diphenylsiloxane copolymer, trimethylsiloxy group-capped methylhydrogensiloxane / diphenylsiloxane / dimethylsiloxane copolymer, cyclic methylhydrogenpolypropylene Siloxane, cyclic methylhydrogensiloxane / dimethylsiloxane copolymer, cyclic methylhydrogensiloxane / diphenylsiloxane / dimethylsiloxane copolymer, copolymer consisting of (CH ₃ ) ₂ HSiO _1/2 units and SiO _4/2 units In the compound, a copolymer composed of (CH ₃ ) ₂ HSiO _1/2 unit, SiO _4/2 unit and (C ₆ H ₅ ) SiO _3/2 unit, etc. Or all other ethyl groups, propyl groups, etc. And those substituted with an aryl group such as an alkyl group or a phenyl group.

The compounding amount of the organohydrogenpolysiloxane is 0.1 to 30 parts by mass, more preferably 0.1 to 10 parts by mass, and still more preferably 0.3 to 100 parts by mass of the organopolysiloxane of the component (A). It is preferable to set it as 10 mass parts. When the blending amount is within this range, desirable rubber properties (rubber hardness, tensile strength, tear strength, elongation, compression set, etc.) and a composition that gives a cured silicone rubber with good heat resistance can be easily designed. .
Further, for the same reason, this organohydrogenpolysiloxane has a hydrogen atom bonded to a silicon atom in component (D) with respect to an aliphatic unsaturated group such as an alkenyl group bonded to a silicon atom in component (A) ( That is, it is preferably blended in such an amount that the molar ratio of SiH groups is 0.5 to 10 mol / mol, preferably 0.8 to 6 mol / mol, more preferably 1 to 5 mol / mol.

  (E) The hydrosilylation reaction catalyst of a component can apply a well-known thing, for example, platinum black, chloroplatinum chloride, chloroplatinic acid, the reaction product of chloroplatinic acid and monohydric alcohol, chloroplatinic acid and olefin And platinum group catalysts such as platinum catalysts such as platinum bisacetoacetate, palladium catalysts and rhodium catalysts. In addition, the compounding quantity of this hydrosilylation reaction catalyst can be made into a catalyst quantity, and is 0.5-1,000 ppm normally with respect to the mass of (A) component as a platinum group metal, Preferably it is about 1-200 ppm. .

  (2) Compound having hydrocarbon as a skeleton (hydrocarbon compound) as paraffinic oil (that is, methane series hydrocarbon liquid at room temperature (25 ° C.)) or EPDM (ethylene / propylene / diene copolymer) ) Is exemplified. Examples of paraffinic oils include rubber compounded oils that are generally compounded in synthetic rubber, such as Diana process oil manufactured by Idemitsu Kosan Co., Ltd. and a sampler manufactured by Nippon Sun Oil. Examples of the EPDM include commercially available Mitsui Chemicals and Sumitomo Chemical. Structurally, it is represented by ethylene / α-olefin / non-conjugated polyene random copolymer rubber, and 1,4-hexadiene, dicyclopentadiene, ethylidene norbornene, vinyl norbornene, etc. are also known for the non-conjugated polyene portion. However, it is not particularly limited by its structure.

  (2) The compounding quantity of the hydrocarbon compound of a component is 0.1-20 mass% in the sum total of (1) component and (2) component, Preferably it is 0.5-10 mass%. When the blending amount of the hydrocarbon compound is within this range, vulcanization inhibition due to impurities in the carbon black can be effectively suppressed without adversely affecting the physical properties and workability of the cured silicone rubber.

In addition, 0.1-5 mass% is preferable in the sum total of (1) component and (2) component when adding paraffinic oil, and 0.5-2 mass% is more preferable. If it is less than 0.1% by mass, the effect of reducing the vulcanization inhibition may be insufficient. If it exceeds 5% by mass, the Williams plasticity of the silicone rubber composition is lowered, and the processability is deteriorated. May have an effect on the physical properties of rubber, such as a decrease in hardness.
The addition amount in the case of blending EPDM is preferably 0.5 to 20% by mass, more preferably 1 to 10% by mass in the total of component (1) and component (2). If it is less than 0.5% by mass, the effect of reducing the vulcanization inhibition may be insufficient, and if it exceeds 20% by mass, the properties of EPDM come out and become harder than conventional silicone rubber compositions. There is a risk that workability will be deteriorated. EPDM is less effective than paraffinic oil when added in a small amount, but has the advantage that it does not easily cause a decrease in plasticity or hardness.

  To the silicone rubber composition of the present invention, in addition to the above components, a flame retardant imparting agent, a colorant other than carbon, and the like can be added as long as the object of the present invention is not impaired.

  The silicone rubber composition of the present invention can be obtained by kneading predetermined amounts of the above-described components with a two-roll, kneader, Banbury mixer or the like.

  When the silicone rubber composition of the present invention is molded, the molding method is not particularly limited, but press molding, extrusion molding, calendar molding, and the like are possible. Moreover, the curing conditions are not particularly limited. Generally, heat curing at 80 to 500 ° C., particularly 100 to 400 ° C., for 5 seconds to 1 hour, particularly about 30 seconds to 30 minutes can be employed. Moreover, you may post-cure at 100-200 degreeC for about 10 minutes-10 hours.

The silicone rubber composition of the present invention is capable of atmospheric pressure hot-air vulcanization and calender molding, and when cured by addition vulcanization, reduces the influence of vulcanization-inhibiting components contained in carbon black, mainly sulfur. obtain. The silicone rubber composition in which the hydrocarbon compound is added in an amount of 0.1 to 20% by mass in the total of the compound and the component (1) described above causes variations in the vulcanization rate and affects the properties of the molded product. Stable vulcanization characteristics and conductive characteristics can be obtained without causing any problems. That is, even if the silicone rubber composition has a sulfur content in the composition of 50 ppm or more, usually 50 to 500 ppm, particularly 50 to 300 ppm, it may affect the vulcanization characteristics and other rubber properties. Can be used without
Furthermore, when silica is blended with the silicone rubber composition, the combined use of carbon black and silica increases the boundary level with respect to sulfur as compared with the case of carbon black alone, and is relatively strong in inhibiting vulcanization. That is, when the silica compound is added to the above-described hydrocarbon compound-containing silicone rubber composition in an amount of 1 to 100 parts by mass, particularly 5 to 100 parts by mass, with respect to 100 parts by mass of the component (A), the sulfur-containing mass in the composition Can be used without affecting the vulcanization characteristics and other rubber properties, even if the silicone rubber composition is 200 ppm or more, usually 200 to 600 ppm, particularly 200 to 400 ppm.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited to a following example. In addition, the unit of a compounding quantity is a mass part. Moreover, a weight average molecular weight and a weight average polymerization degree are the polystyrene conversion values in a gel permeation chromatography (GPC) analysis.

[Preparation of compound]
Main chain is dimethylsiloxane unit ((CH ₃ ) ₂ SiO _2/2 ) 99.86 mol% and methyl vinyl siloxane unit ((CH ₂ ═CH) (CH ₃ ) SiO _2/2 ) 0.10 mol%, molecule Raw rubber-like organopolysiloxane comprising 0.04 mol% of vinyldimethylsiloxy units ((CH ₂ ═CH) (CH ₃ ) ₂ SiO _1/2 ) as a chain-end blocking group and having an average degree of polymerization of about 5,000 100 parts, 45 parts of dry silica having a BET specific surface area of 200 m ² / g, 12 parts of silanol group-blocked dimethylpolysiloxane having a viscosity of 30 mPa · s as a dispersant were added, kneaded with a kneader, and 2 parts at 170 ° C. A compound was prepared by heat treatment for a period of time.

[Example 1-4]
Asahi # 60 (manufactured by Asahi Carbon Co., Ltd., sulfur impurity content: 0.54 mass%) as carbon black was added to and mixed with the above compound with two rolls each in the addition amount shown in Table 1. In addition, Diana Process Oil PW-380 (manufactured by Idemitsu Kosan Co., Ltd.) as a paraffinic oil, or PX-046 (manufactured by Mitsui Chemicals, Inc.) as EPDM at an addition amount shown in Table 1 with two rolls each. Added and mixed.
Addition cross-linking curing agent C-25A (platinum catalyst) / C-25B (organohydrogenpolysiloxane) (both manufactured by Shin-Etsu Chemical Co., Ltd.) 0.5 parts / 2.0 parts after kneading with two rolls Added and mixed uniformly. Thereafter, press curing was performed at 120 ° C. and 7 MPa for 10 minutes, followed by post curing at 200 ° C. for 4 hours to prepare a test sheet. Using this, the physical properties of rubber were measured by the methods described below. Further, the vulcanization characteristics were measured by the following method using an MDR rheometer.

[Comparative Example 1-3]
Sheets were molded in the same manner as in Example 1 with the addition amounts shown in Table 1, and rubber physical properties and vulcanization characteristics were measured.

[Comparative Example 4-6, Example 5-8]
Instead of using the above-prepared compound, raw rubber without a silica as a base polymer (main chain is dimethylsiloxane unit ((CH ₃ ) ₂ SiO _2/2 ) 99.81 mol% and methylvinylsiloxane unit ((CH ₂ = CH) (CH ₃ ) SiO _2/2 ) 0.15 mol%, vinyldimethylsiloxy unit ((CH ₂ ═CH) (CH ₃ ) ₂ SiO _1/2 ) 0.04 mol% as a blocking group at the end of the molecular chain The vulcanization characteristics were measured in the same manner as in Example 1 with the addition amount shown in Table 2 using an organopolysiloxane having an average degree of polymerization of about 5,000.

〔系内硫黄量〕
組成物に配合するカーボンブラック中に含まれる硫黄不純物含有量から算出した値
〔判定〕
○：加硫遅れなし
△：加硫遅れ（ｔ９０が２分以上である）
×：加硫しない

[Sulfur content in the system]
A value calculated from the content of sulfur impurities contained in the carbon black blended in the composition [determination]
○: No vulcanization delay Δ: Vulcanization delay (t90 is 2 minutes or more)
×: Not vulcanized

〔系内硫黄量〕
組成物に配合するカーボンブラック中に含まれる硫黄不純物含有量から算出した値
〔判定〕
○：加硫遅れなし
△：加硫遅れ（ｔ９０が２分以上である）
×：加硫しない

[Sulfur content in the system]
A value calculated from the content of sulfur impurities contained in the carbon black blended in the composition [determination]
○: No vulcanization delay Δ: Vulcanization delay (t90 is 2 minutes or more)
×: Not vulcanized

Physical property measurement method The rubber composition was cured by press curing at 120 ° C./10 minutes and then post curing at 200 ° C. for 4 hours, and the hardness (durometer A) was measured according to JIS K6249.

Vulcanization characteristics According to JIS K6300, the vulcanization characteristics were measured under the conditions of 150 ° C./10 minutes using an MDR rheometer (manufactured by Alpha Technologies).
t10: Time required for vulcanization to proceed 10% (= vulcanization start point)
t90: Time required for 90% vulcanization to proceed (= optimum vulcanization point)
MH: Maximum torque (maximum value in a specific time in a region where the vulcanization curve is stable, the specific time in this example is 10 minutes)

Claims (5)

An addition-curable silicone rubber composition comprising the following (1) and (2), wherein (2) is in the range of 0.1 to 20% by mass with respect to the total of (1) and (2): Addition-curable silicone rubber composition in an amount.
(1) An organopolysiloxane composition comprising the following (A) to (E).
(A) The following average composition formula (I)
R ¹ _a SiO _{(4-a) / 2} (I)
Wherein R ¹ is the same or different unsubstituted or substituted monovalent hydrocarbon group, and at least two in one molecule are aliphatic unsaturated groups. A is 1.95 to 2.05 (It is a positive number.)
100 parts by mass of an organopolysiloxane having a degree of polymerization represented by
(B) 0-100 mass parts of silica,
(C) 1 to 10 parts by mass of carbon black,
(D) 0.1-30 parts by mass of an organohydrogenpolysiloxane containing hydrogen atoms bonded to at least two silicon atoms in one molecule;
(E) Hydrosilylation reaction catalyst Catalytic amount (2) Compound having hydrocarbon as skeleton.   (1) The component (C) is at least one carbon black other than acetylene black selected from furnace black, channel black, and thermal black, and the amount of sulfur present in the system is 50 ppm or more. The addition-curable silicone rubber composition described.   (1) Component (C) is at least one carbon black other than acetylene black selected from furnace black, channel black, and thermal black, and (B) component silica is based on 100 parts by mass of component (A). The addition-curable silicone rubber composition according to claim 1, wherein the amount of sulfur present in the system is 200 ppm or more.   The addition-curable silicone rubber according to any one of claims 1 to 3, wherein (2) is a paraffinic oil and has an amount of 0.1 to 5% by mass relative to the total of (1) and (2). Composition.   The addition-curable silicone rubber composition according to any one of claims 1 to 3, wherein (2) is EPDM and is in an amount of 0.5 to 20 mass% with respect to the total of (1) and (2). .