JP2005350582A - Silicone rubber composition and its cured product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silicone rubber composition which has proper fluidity on molding works and is cured to give the silicone rubber cured product that has excellent mechanical characteristics, low elastic modulus, good self adhesiveness to substrates, and excellent dielectric breakdown characteristics, little oozes out a liquid silicone polymer, and is useful as a sealing material such as a potting material for electric / electronic parts or a sealant. <P>SOLUTION: This silicone rubber composition is characterized by comprising a specific alkenyl group-containing organopolysiloxane, a specified diorgano hydrogen siloxy-terminated organopolysiloxane as a chain extender, a specific organo hydrogen polysiloxne as a cross-linking agent, and a hydroxysilylation catalyst, wherein the ratio of the number of hydrogen atoms bound to silicon atoms in the chain extender to the sum of the number of hydrogen atoms bound to silicon atoms in the chain extender and the number of hydrogen atoms bound to silicon atoms in the cross-linking agent is a specific value, and the ratio of the number of the hydrogen atoms bound to the silicon atoms in the chain extender to the number of alkenyl groups bound to silicon atoms in the alkenyl group-containing organopolysiloxane is also a specific value. And a cured product of the silicone rubber composition. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention has excellent mechanical properties, low elastic modulus, good self-adhesion with a substrate, and excellent dielectric breakdown properties, which are useful as sealing materials such as potting materials and sealing materials for electric and electronic parts. In addition, the present invention relates to an addition reaction curable type silicone rubber composition that gives a cured silicone rubber with less liquid silicone polymer seepage, and a cured product thereof.

  Silicone rubber is widely used as a sealing material for electrical and electronic parts because it has excellent electrical insulation, stability of electrical properties and flexibility. In particular, a silicone gel cured product, which is a gel-like cured product, is an agar-like material cured by lowering the crosslinking density, and has low elastic modulus, excellent stress relaxation characteristics, and vibration / impact absorption. Used as a sealing material for products, various power modules, coating materials for sensors, potting materials, etc. The silicone gel cured product in the present invention means a cured product having a low cross-linking density that has a low hardness that does not show an effective rubber hardness value in a type E durometer and that has fluidity under stress. The term “type E durometer” means a cured product that has a hardness of 0 or more and does not exhibit fluidity under stress.

  However, although it is a cured silicone gel having the above-mentioned excellent characteristics, it has low mechanical strength and adheres to the base material but does not have strong adhesiveness, so there are restrictions on the usable electrical and electronic parts. there were. Thus, there is an increasing demand for a silicone rubber potting material and a sealing material having excellent mechanical strength and good self-adhesiveness with a base material while maintaining a low elastic modulus.

Accordingly, various studies have been conducted for the purpose of achieving the above requirements. As a conventional method for obtaining a tough silicone gel or rubber cured product used for a potting material or a sealing material, it is bonded to a first organopolysiloxane having a vinyl group at its terminal and a silicon atom as a chain extender. There is one in which a second disiloxane having two hydrogen atoms or a liquid diorganohydrogensiloxy-terminated organopolysiloxane is used in combination, and an organohydrogenpolysiloxane as a crosslinking agent is subjected to addition reaction curing with a platinum-based catalyst. In this case, the number of silicon-bonded hydrogen atoms present in the chain extender is at least 80% of the total number of silicon-bonded hydrogen atoms present in the combination of the chain extender and the organohydrogenpolysiloxane. And the molar ratio of silicon-bonded hydrogen atoms present in the chain extender to vinyl groups present in the first organopolysiloxane is 0.8 to 1.2 (see, for example, Patent Document 1). .) Further, as a conventional method for improving the mechanical strength of a cured silicone rubber, an example in which a specific branched polyorganosiloxane is blended with an addition reaction curable composition (for example, see Patent Document 2) is known. It has been.
Japanese Patent Laid-Open No. 7-188559 JP-A-7-62244

As a conventional method for obtaining a monolith by bonding a silicone gel or a rubber composition used for a potting material or a sealing material to a base material through a crosslinking reaction, an addition reaction curable composition may be made of SiO _{4. / 2} unit as a basic constituent unit and a compound containing an alkoxysilyl group-containing silicone resin (for example, see Patent Document 3), addition-curable functional groups (SiH groups and alkenyl groups) and adhesive functionalities Examples include those in which an organosilicon compound having both groups (alkoxysilyl group, epoxy group, etc.) is added to an addition reaction curable composition (for example, see Patent Document 4).
JP-A-4-31766 Japanese Patent Laid-Open No. 6-340813

  Furthermore, as a method for improving the dielectric breakdown characteristics of the silicone gel or rubber cured product used for the potting material and the sealing material and reducing the bleeding of the liquid silicone polymer, a method of increasing the crosslinking density is known. is there. The electrical insulation strength measured by using a spherical electrode according to JIS C2210 and embedding the electrode with a silicone gel or rubber cured product is 20-30 kV / mm for the silicone gel cured product, whereas the hardness is type E. A silicone rubber cured product of about 5 to 50 by durometer has a value of 50 kV / mm or more. However, a rubbery cured product with a high modulus of elasticity with a high crosslinking density for the purpose of improving dielectric breakdown characteristics has a much larger thermal stress generated during expansion of heat than a gel. When used as a potting material or sealing material for electrical / electronic parts, bonding wires and solder cannot withstand excessive thermal stress in the heat cycle test, resulting in cracks or breakage, and the reliability of electrical / electronic parts decreases. It is known.

  As described above, although various studies have been made to solve each problem, it has excellent mechanical properties, low elastic modulus, good self-adhesion with the substrate, and excellent dielectric breakdown properties. In addition, a silicone gel or rubber cured product that satisfies all of the properties that the liquid silicone polymer does not ooze out has not been completed yet.

  The present invention has been made in view of the above circumstances, and has excellent fluidity after curing, low elastic modulus, good self-adhesion with a base material, and excellent insulation after having a suitable fluidity during molding. Addition reaction curable silicone rubber composition that has a destructive property and has little oozing out of liquid silicone polymer, and provides a cured silicone rubber useful as a sealing material for potting materials and sealing materials for electrical and electronic parts. The purpose is to provide.

The present invention comprises a specific alkenyl group-containing organopolysiloxane, a specific diorganohydrogensiloxy-terminated organopolysiloxane as a chain extender, a specific organohydrogen polysiloxane as a crosslinker, and a hydrosilylation catalyst, and the chain extension The number of hydrogen atoms bonded to silicon atoms present in the agent (NH _B ) and the total number of hydrogen atoms bonded to silicon atoms present in the crosslinking agent and the chain extender (NH _T ) the ratio _(NH B / NH T), and NH _B and the ratio of the alkenyl group-containing the number of alkenyl groups bonded to silicon atoms present in the organopolysiloxane _{(NA) (NH B / NA} ) is curable is a specific The present invention relates to a silicone rubber composition and a cured product thereof.

That is, according to the present invention, (A) an average of about two alkenyl groups bonded to a silicon atom exist in one molecule, and other organic groups bonded to the silicon atom are double bonds (ethylene bonds) ) Or a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms that does not contain a triple bond (acetylene bond), and has a viscosity at 25 ° C. and a shear rate of 0.9 s ⁻¹ of 10 mPa · s to 30 100 parts by weight of an alkenyl group-containing organopolysiloxane that is 1,000 mPa · s or less,

末端ではないオルガノポリシロキサン単位が式（２）

であり（ただし、Ｒ^１は炭素原子間の結合に二重結合あるいは三重結合を含まない置換もしくは非置換の炭素数１以上２０以下の１価炭化水素基である）、２５℃、せん断速度０．９ｓ^−１における粘度が１０ｍＰａ・ｓ以上３０，０００ｍＰａ・ｓ以下であるジオルガノ水素シロキシ末端オルガノポリシロキサン４０重量部以上１２０重量部以下、 (B) the terminal unit is formula (1),

Non-terminal organopolysiloxane units are of formula (2)

(Wherein R ¹ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms that does not contain a double bond or triple bond in the bond between carbon atoms), 25 ° C., shear rate 0 Diorganohydrogensiloxy-terminated organopolysiloxane having a viscosity at .9 s ⁻¹ of 10 mPa · s to 30,000 mPa · s, 40 parts by weight to 120 parts by weight,

で表され（ただし、Ｒ^２、Ｒ^３は同一又は異なる炭素原子間の結合に二重結合あるいは三重結合を含まない置換もしくは非置換の炭素数１以上２０以下の１価炭化水素基）、ｍは３以上の自然数、ｎは０以上の整数、ｍ＋ｎが１０以上５００以下、かつｎ／（ｍ＋ｎ）が０以上０．７以下であるオルガノ水素ポリシロキサン、及び (C) General formula (3)

(Wherein R ² and R ³ are substituted or unsubstituted monovalent hydrocarbon groups having 1 to 20 carbon atoms that do not contain a double bond or a triple bond in the bond between the same or different carbon atoms), m Is a natural number of 3 or more, n is an integer of 0 or more, m + n is 10 or more and 500 or less, and n / (m + n) is 0 or more and 0.7 or less, and

(D) including a catalytic amount of a hydrosilylation catalyst that promotes curing of the composition, the number of hydrogen atoms bonded to silicon atoms (NH _B ) present in the component ( _B ), and the component (C) the total number of the number of NH _B of the hydrogen atoms bonded to existing silicon atoms (NH _T) ratio of _(NH B / NH _T) is 0.7 to 0.8, and the NH _B (a) The ratio (NH _B / NA) to the number (NA) of alkenyl groups bonded to silicon atoms in the component is 0.6 or more and 0.8 or less, and

The hardness after curing of the composition comprising the components (A) to (D) was measured at a test piece thickness of about 10 mm using a type E durometer according to the durometer hardness test method specified in JIS K6253. The present invention relates to a curable silicone rubber composition that is sometimes from 5 to 50 and a cured product thereof. In addition, the curing conditions of the silicone rubber composition are not particularly limited, but the silicone rubber composition is usually left at room temperature for 10 minutes to 3 days or by heat treatment at a temperature of 10 to 160 ° C. A preferable curing condition is a heat treatment at a temperature of 60 to 160 ° C. for about 10 to 180 minutes.

  The silicone rubber composition of the present invention has an appropriate fluidity during molding, but has excellent mechanical properties after curing, low elastic modulus, good self-adhesion with a substrate, and excellent dielectric breakdown properties. It is possible to provide a cured silicone rubber that is useful as a sealing material such as a potting material and a sealing material for electric and electronic parts, and has a small amount of liquid silicone polymer seepage.

The present invention will be specifically described.
The component (A) of the present invention has an average of about 2, preferably 1.6 to 2.2 alkenyl groups bonded to silicon atoms, and other organic groups bonded to silicon atoms. Is a substituted or unsubstituted monovalent hydrocarbon group having 1 or more and 20 or less carbon atoms that does not contain a double bond or a triple bond in the bond between carbon atoms, and has a viscosity at 25 ° C. and a shear rate of 0.9 s ⁻¹ . An alkenyl group-containing organopolysiloxane of 10 mPa · s or more and 30,000 mPa · s or less.

  (A) As an alkenyl group of a component, C2-C8 alkenyl groups, such as a vinyl group, an allyl group, 1-butenyl group, 1-hexenyl group, can be illustrated, Preferably a vinyl group, An allyl group, particularly preferably a vinyl group. These alkenyl groups react with the component (C) described below to form a network structure, and it is necessary that they are present in the molecule in an average of about 2, preferably 1.6 to 2.2. . Such an alkenyl group may be bonded to a silicon atom at the end of the molecular chain, or may be bonded to a silicon atom in the middle of the molecular chain. From the viewpoint of the curing reaction rate, an alkenyl group organopolysiloxane in which an alkenyl group is bonded only to the silicon atom at the end of the molecular chain is preferred.

  The other organic group bonded to the silicon atom of component (A) is preferably a substituted or unsubstituted monovalent hydrocarbon group containing no double bond or triple bond in the bond between carbon atoms having 1 to 12 carbon atoms. Specifically, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, t-butyl group, pentyl group, neopentyl group, hexyl group, 2-ethylhexyl group, heptyl group, octyl group, Alkyl groups such as nonyl group, decyl group and dodecyl group; cycloalkyl groups such as cyclopentyl group, cyclohexyl group and cycloheptyl group; aryl groups such as phenyl group, tolyl group, xylyl group, biphenyl group and naphthyl group; benzyl group, Aralkyl groups such as phenylethyl group, phenylpropyl group, methylbenzyl group; hydrogen atoms in these hydrocarbon groups Chloromethyl group, 2-bromoethyl group, 3,3,3-trifluoropropyl group, 3-chloropropyl group, chlorophenyl group, dibromophenyl group, tetrachlorophenyl partially or wholly substituted by halogen atom, cyano group, etc. And substituted hydrocarbon groups such as a group, a difluorophenyl group, a β-cyanoethyl group, a γ-cyanopropyl group, and a β-cyanopropyl group. Particularly preferred organic groups are a methyl group, a phenyl group, and a 3,3,3-trifluoropropyl group.

The alkenyl group-containing organopolysiloxane (A) may be linear or branched, or a mixture thereof. This alkenyl group-containing organopolysiloxane is produced by methods known to those skilled in the art. In order to use the silicone rubber composition of the present invention for a sealing material such as a potting material or a sealing material for electric / electronic parts, the composition needs to have appropriate fluidity and is cured. The cured silicone rubber also needs to have appropriate mechanical properties. From such a viewpoint, the viscosity of the component (A) is desirably in the range of 10 mPa · s to 30,000 mPa · s at 25 ° C. and a shear rate of 0.9 s ⁻¹ , more preferably 100 mPa · s or more. It is 10,000 mPa · s or less, particularly preferably in the range of 200 mPa · s to 5,000 mPa · s.

末端ではないオルガノポリシロキサン単位が式（２）

であり（ただし、Ｒ^１は炭素原子間の結合に二重結合あるいは三重結合を含まない置換もしくは非置換の炭素数１以上２０以下の１価炭化水素基である）、２５℃、せん断速度０．９ｓ^−１における粘度が１０ｍＰａ・ｓ以上３０，０００ｍＰａ・ｓ以下であるジオルガノ水素シロキシ末端オルガノポリシロキサンである。 The component (B) of the present invention which is a chain extender has a terminal unit represented by the formula (1),

Non-terminal organopolysiloxane units are of formula (2)

(Wherein R ¹ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms that does not contain a double bond or triple bond in the bond between carbon atoms), 25 ° C., shear rate 0 A diorganohydrogensiloxy-terminated organopolysiloxane having a viscosity at .9 s ⁻¹ of 10 mPa · s to 30,000 mPa · s.

R ¹ of component (B) is, for example, a substituted or unsubstituted monovalent hydrocarbon group containing no double bond or triple bond in the bond between carbon atoms having 1 to 20 carbon atoms, preferably having 1 to 1 carbon atoms. A substituted or unsubstituted monovalent hydrocarbon group containing no double bond or triple bond in the bond between 12 carbon atoms, specifically, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, Alkyl groups such as isobutyl group, t-butyl group, pentyl group, neopentyl group, hexyl group, 2-ethylhexyl group, heptyl group, octyl group, nonyl group, decyl group, dodecyl group; cyclopentyl group, cyclohexyl group, cycloheptyl group A cycloalkyl group such as phenyl group, tolyl group, xylyl group, biphenyl group and naphthyl group; benzyl group and phenylethyl group An aralkyl group such as phenylpropyl group or methylbenzyl group; a chloromethyl group, 2-bromoethyl group, 3, 3 in which part or all of the hydrogen atoms in these hydrocarbon groups are substituted by a halogen atom, a cyano group, etc. , Substituted hydrocarbons such as 3-trifluoropropyl group, 3-chloropropyl group, chlorophenyl group, dibromophenyl group, tetrachlorophenyl group, difluorophenyl group, β-cyanoethyl group, γ-cyanopropyl group, β-cyanopropyl group Groups and the like. More preferred R ¹ is a methyl group, a phenyl group, or a 3,3,3-trifluoropropyl group, and particularly preferred R ¹ is a methyl group.

  In order to solve the problems of the present invention, the specific component (B) of the present invention is present in the silicone rubber composition of the present invention. During curing, a hydrogen atom bonded to silicon at the end of the molecular chain of component (B) reacts with an alkenyl group bonded to silicon of component (A) to produce two or more components (A) and (B). Formation of bonded relatively long organopolysiloxane molecular chains provides a cured silicone rubber having excellent mechanical properties and low elastic modulus after curing while having adequate fluidity during molding operations.

The chain extender of the component (B) may be linear or branched, or may be a mixture thereof, more preferably linear. This diorganohydrogensiloxy-terminated organopolysiloxane is prepared by methods known to those skilled in the art. Further, in order to use the silicone rubber composition of the present invention for a sealing material such as a potting material or a sealing material for electric / electronic parts, the composition needs to have appropriate fluidity, and An appropriate viscosity is selected in order to exhibit the effect of chain extension with the component (A). From such a standpoint, the viscosity of the component (B) is desirably in the range of 10 mPa · s to 30,000 mPa · s at 25 ° C. and a shear rate of 0.9 s ⁻¹ , more preferably 100 mPa · s or more. It is 10,000 mPa · s or less, particularly preferably in the range of 200 mPa · s to 5,000 mPa · s. Furthermore, in order to further exert the effect of chain extension with the component (A), it is desirable that the component (A) and the component (B) have the same level of viscosity, and (B) with respect to the viscosity of the component (A). The viscosity ratio of the components is more preferably 0.5 or more and 1.5 or less, and particularly preferably 0.8 or more and 1.2 or less.

  The blending amount of the component (B) of the present invention is determined by the balance between the chain extension due to the reaction with the component (A) and the crosslinking reaction between the later-described component (C) and the component (A), which is a crosslinking agent. A) 40 parts by weight or more and 120 parts by weight or less with respect to 100 parts by weight of the component. The blending amount of the component (B) is more preferably 50 parts by weight or more and 100 parts by weight or less.

で表され（ただし、Ｒ^２、Ｒ^３は同一又は異なる炭素原子間の結合に二重結合あるいは三重結合を含まない置換もしくは非置換の炭素数１以上２０以下の１価炭化水素基）、ｍは３以上の自然数、ｎは０以上の整数、ｍ＋ｎが１０以上５００以下、かつｎ／（ｍ＋ｎ）が０以上０．７以下であるオルガノ水素ポリシロキサンである。 (C) component which is a crosslinking agent of this invention is general formula (3).

(Wherein R ² and R ³ are substituted or unsubstituted monovalent hydrocarbon groups having 1 to 20 carbon atoms that do not contain a double bond or a triple bond in the bond between the same or different carbon atoms), m Is a natural number of 3 or more, n is an integer of 0 or more, m + n is 10 or more and 500 or less, and n / (m + n) is 0 or more and 0.7 or less.

R ² and R ³ of the component (C) are, for example, a substituted or unsubstituted monovalent hydrocarbon group containing no double bond or triple bond in the bond between carbon atoms having 1 to 20 carbon atoms, preferably carbon. A substituted or unsubstituted monovalent hydrocarbon group containing no double bond or triple bond in the bond between carbon atoms of 1 to 12, specifically a methyl group, an ethyl group, a propyl group, an isopropyl group, Alkyl group such as butyl group, isobutyl group, t-butyl group, pentyl group, neopentyl group, hexyl group, 2-ethylhexyl group, heptyl group, octyl group, nonyl group, decyl group, dodecyl group; cyclopentyl group, cyclohexyl group, Cycloalkyl groups such as cycloheptyl group; aryl groups such as phenyl group, tolyl group, xylyl group, biphenyl group, naphthyl group; benzyl group, phenyl Aralkyl groups such as til, phenylpropyl, and methylbenzyl; chloromethyl, 2-bromoethyl, 3 or all of hydrogen atoms in these hydrocarbon groups are substituted by halogen atoms, cyano groups, etc. , 3,3-trifluoropropyl group, 3-chloropropyl group, chlorophenyl group, dibromophenyl group, tetrachlorophenyl group, difluorophenyl group, β-cyanoethyl group, γ-cyanopropyl group, β-cyanopropyl group, etc. A hydrocarbon group etc. are mentioned. More preferable R ² and R ³ are a methyl group, a phenyl group, and a 3,3,3-trifluoropropyl group, particularly preferable R ² is a methyl group, and particularly preferable R ³ is a methyl group and a phenyl group.

  (C) As for the preferable range of m + n and n / (m + n) of a component, m + n is 10 or more and 500 or less, and n / (m + n) is 0 or more and 0.7 or less. When n / (m + n) exceeds 0.7, the adhesion to the substrate is lowered. More preferable ranges of m + n and n / (m + n) are m + n of 20 or more and 200 or less, and n / (m + n) of 0 or more and 0.5 or less.

  The hydrogen atom bonded to the silicon atom of component (C) may be located either at the end of the molecular chain or in the middle of the molecular chain, or may be located at both. Furthermore, the structure of the organohydrogenpolysiloxane may be linear, branched, cyclic or network, or a mixture thereof. This organohydrogenpolysiloxane is prepared by methods known to those skilled in the art.

The blending amounts of the component (B) and the component (C) with respect to the component (A) of the present invention are 0.7 ≦ (NH _B / NH _T ) ≦ 0.8 and 0.6 ≦ (NH _B / NA) ≦ It is determined to satisfy 0.8. NH _B / NH _T is in the range of 0.7 ≦ (NH _B / NH _T ) ≦ 0.8. If it is less than 0.7, the chain extension by the component (A) and the component (B) is insufficient. This is because the mechanical properties cannot be obtained, and when it exceeds 0.8, sufficient hardness cannot be obtained. NH _B / NA is in the range of 0.6 ≦ (NH _B /NA)≦0.8. If it is less than 0.6, chain extension by the component (A) and the component (B) is insufficient, and the elasticity is low. This is because the object of the present invention, which is excellent in mechanical properties even though the ratio, cannot be achieved, and when it exceeds 0.8, uniform crosslinking cannot be obtained.

The hydrosilylation catalyst for curing the silicone rubber composition of the present invention, which is the component (D) of the present invention, is usually used. Examples of the metal and its compound include platinum, rhodium, palladium, ruthenium. , And iridium, preferably platinum. The metal is optionally fixed to a particulate carrier material (eg, activated carbon, aluminum oxide, silicon oxide). As the hydrosilylation catalyst, it is preferable to use platinum and a platinum compound. Platinum compounds include platinum halides (eg, PtCl ₄ , H ₂ PtCl ₄ .6H ₂ O, Na ₂ PtCl ₄ .4H ₂ O), platinum-olefin complexes, platinum-alcohol complexes, platinum-alcolate complexes, platinum- Ether complexes, platinum-aldehyde complexes, platinum-ketone complexes, platinum-vinylsiloxane complexes (eg, platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complexes, bis- (γ-picoline)) -Platinum dichloride, trimethylenedipyridine-platinum dichloride, dicyclopentadiene-platinum dichloride, cyclooctadiene-platinum dichloride, cyclopentadiene-platinum dichloride), bis (alkynyl) bis (triphenylphosphine) platinum complex, bis (alkynyl) (Cyclooctadiene) platinum complex And the like. The hydrosilylation catalyst can also be used in a microencapsulated form. In this case, the particulate solid containing a catalyst and insoluble in the organopolysiloxane is, for example, a thermoplastic resin (for example, a polyester resin or a silicone resin). The hydrosilylation catalyst can also be used in the form of an inclusion compound, for example, in a cyclodextrin. The addition amount of the hydrosilylation catalyst is a catalytic amount, and when a platinum catalyst is used, the platinum metal in the silicone rubber composition is preferably 0.1 to 500 ppm, particularly preferably 1 to 200 ppm.

  Further, the hardness after curing of the composition comprising the components (A) to (D) of the present invention is 5 or more when measured according to JIS K6253 using a type E durometer when the thickness of the test piece is about 10 mm. In order to solve the problem of the present invention, it is necessary to be 50 or less. The reason why the hardness is in this range is that if the hardness is less than 5, excellent mechanical properties cannot be obtained, and if the hardness exceeds 50, a low elastic modulus cannot be achieved. A more preferable range of hardness is 5 or more and 30 or less, and a particularly preferable range is 5 or more and 20 or less.

  In the silicone rubber composition of the present invention, various compounding agents known per se can be added in addition to the components (A) to (D). For example, fumed silica, silica aerosil, precipitated silica, ground silica, diatomaceous earth, iron oxide, zinc oxide, titanium oxide, calcium carbonate, magnesium carbonate, zinc carbonate, aluminum hydroxide, aluminum oxide, hydrotalcite, carbon black By adding an inorganic filler, the hardness, mechanical strength, etc. of the cured silicone rubber obtained from the composition of the present invention can be adjusted. Also, pigments, dyes, flame retardants, heat resistance improvers, UV stabilizers, hollow inorganic fillers, hollow organic fillers, silicone resin or rubbery spherical fillers, and the like can be added. A silane coupling agent having an alkoxysilyl group, an epoxy group, an acid anhydride group, a peroxysilyl group, or the like can also be added. Furthermore, it is also possible to control the curing reaction by adding a reaction control agent such as a polymethylvinylsiloxane cyclic compound, an acetylene compound, or an organic phosphorus compound. The amount of these compounding agents used is arbitrary as long as the properties of the resulting cured silicone rubber are not impaired.

  The silicone rubber composition of the present invention can be prepared by mixing all components at room temperature. For this purpose, any mixing technique and apparatus disclosed in the prior art can be used. The equipment used can depend on the ingredients and the viscosity of the final curable composition. Suitable mixers include paddle mixers, kneader mixers and planetary mixers. It may be desirable to mix the components while cooling to avoid premature curing of the composition.

  The silicone rubber is molded by injecting the silicone rubber composition of the present invention into an appropriate mold and curing the composition, or applying the composition onto an appropriate substrate and then curing the composition. This is performed by a conventionally known method. Curing is usually carried out at a temperature of 10 to 160 ° C. by standing at room temperature for about 10 minutes to 3 days or by heat treatment.

  The present invention will be specifically described based on examples, but the present invention is not limited to the following examples.

[Example 1]
(A) Vinyl group-containing dimethylpolysiloxane having a viscosity of 1,500 mPa · s (25 ° C., shear rate: 0.9 s ⁻¹ ) having an average of about two vinyl groups bonded to silicon atoms at the molecular chain terminals in one molecule. = 100 parts by weight, (B) Dimethyl hydrogen siloxy-terminated dimethyl having a viscosity of 1,500 mPa · s (25 ° C., shear rate 0.9 s ⁻¹ ), where both ends of the molecular chain as a chain extender are blocked with dimethyl hydrogen siloxy groups Polysiloxane = 75 parts by weight, (C) Organohydrogenpolysiloxane-1 wherein R ² and R ^{3 in} the following general formula (3) are methyl groups, m + n = 32, and n / (m + n) = 0.06 = 0.21 parts by weight, (D) platinum-vinylsiloxane complex in an amount of 100 ppm of platinum metal in the composition of this example, ethynylcyclohexanol = 0.05 parts by weight To obtain a composition. The composition had NH _B / NH _T of 0.75 and NH _B / NA of 0.75. Next, this composition was heat-treated at 150 ° C. for 30 minutes to obtain a cured silicone rubber. Further, the cured silicone rubber was subjected to hardness measurement, tensile test, dynamic property test, and adhesion test by the following methods, and the results are shown in Table 1.

Hardness: Measured with a type E durometer hardness meter according to JIS K6253. The thickness of the test piece is about 10 mm.
Tensile test: Measured using a dumbbell-shaped No. 3 test piece in accordance with JIS K6251.
Complex shear elastic modulus G ^* : The complex shear elastic modulus at 23 ° C. and a shear frequency of 1 Hz was measured with a viscoelasticity measuring device RS-150 rheo-stress manufactured by HAAKE. The thickness of the test piece is about 5 mm, the cone used is a parallel plate with a diameter of 35 mm, and the strain amplitude is ± 1%.
Adhesion test: The silicone rubber composition was heated and cured at 150 ° C. for 30 minutes to bond two aluminum plate test pieces, and a tensile shear bond strength test was performed according to JIS K6850. The adhesive layer has a width of about 25 mm, a length of about 12 mm, and a thickness of about 0.5 mm. A similar test was performed using a PET film test piece instead of the aluminum plate test piece.

[Example 2]
(C) except that ^R 2, ^{R 3} is a methyl group, m + n = 32, n / (m + n) = organohydrogenpolysiloxane -2 = 0.23 parts by weight of 0.25 ingredients above general formula (3) Prepared a composition in the same manner as in Example 1 to obtain a cured silicone rubber. The composition had an NH _B / NH _T of 0.78 and an NH _B / NA of 0.75. Further, the cured silicone rubber was tested in the same manner as in Example 1, and the results are shown in Table 1.

[Example 3]
In component (C), R ^{2 in the} general formula (3) is a methyl group, R ³ is a methyl group and a phenyl group, and the ratio of the number of methyl groups to phenyl groups is methyl group: phenyl group = 1.8. The composition was prepared in the same manner as in Example 1 except that organohydrogenpolysiloxane-3 = 0.42 parts by weight, m + n = 32, n / (m + n) = 0.50, and silicone rubber. A cured product was obtained. The composition had an NH _B / NH _T of 0.74 and an NH _B / NA of 0.75. Further, the cured silicone rubber was tested in the same manner as in Example 1, and the results are shown in Table 1.

[Example 4]
The component (C) is an organohydrogenpolysiloxane where R ² and R ^{3 in} the general formula (3) are methyl groups, m + n = 40, and n / (m + n) = 0.65 = 0.67 parts by weight Except for the above, a composition was prepared in the same manner as in Example 1 to obtain a cured silicone rubber. The composition had an NH _B / NH _T of 0.72 and an NH _B / NA of 0.75. Further, the cured silicone rubber was tested in the same manner as in Example 1, and the results are shown in Table 1.

[Comparative Example 1]
A composition was obtained in the same manner as in Example 1 except that the component (B) was changed from 75 to 55 parts by weight, and the component (C) was changed from 0.21 to 0.17 parts by weight. Next, heat treatment was performed in the same manner as in Example 1, and hardness measurement and tensile test were performed in the same manner as in Example 1. However, the cured product could not be measured because it was gel. The results of the dynamic property test and the adhesion test are shown in Table 2. The composition had an NH _B / NH _T of 0.73 and an NH _B / NA of 0.55.

[Comparative Example 2]
A composition was obtained in the same manner as in Example 1 except that the component (C) was changed from 0.21 parts by weight to 0.09 parts by weight. Next, heat treatment was performed in the same manner as in Example 1, and hardness measurement and tensile test were performed in the same manner as in Example 1. However, the cured product could not be measured because it was gel. The results of the dynamic property test and the adhesion test are shown in Table 2. The composition had an NH _B / NH _T of 0.88 and an NH _B / NA of 0.75.

[Comparative Example 3]
The component (C) is an organohydrogenpolysiloxane where R ² and R ^{3 in} the general formula (3) are methyl groups, m + n = 40, and n / (m + n) = 0.90-5 = 2.10 parts by weight Except for the above, a composition was prepared in the same manner as in Example 1 to obtain a cured silicone rubber. The composition had an NH _B / NH _T of 0.74 and an NH _B / NA of 0.75. Further, the cured silicone rubber was tested in the same manner as in Example 1, and the results are shown in Table 2.

  As is apparent from Tables 1 and 2, the cured silicone rubber obtained by curing the addition reaction curable silicone rubber composition of the present invention has superior adhesion to the base material compared to the comparative example, and Excellent balance between tensile strength and low elastic modulus.

  The cured silicone rubber of the present invention has excellent mechanical properties, low elastic modulus, good self-adhesiveness with a substrate, excellent dielectric breakdown properties, and less liquid silicone polymer seepage. Sealing materials such as potting materials and sealing materials for electrical and electronic parts, for example, car electronics products such as igniters, regulators, ABS, airflow sensors, various power modules, coating materials for sensors, sealing materials for potting materials, etc. It can be used suitably.

Claims (6)

(A) Substituents or non-substituents in which an average of about two alkenyl groups bonded to a silicon atom are present in one molecule and other organic groups bonded to the silicon atom do not contain double or triple bonds Alkenyl group-containing organopolysiloxane 100 which is a monovalent hydrocarbon group having 1 to 20 carbon atoms and having a viscosity at 25 ° C. and a shear rate of 0.9 s ⁻¹ of 10 mPa · s to 30,000 mPa · s. Parts by weight,
(B) the terminal unit is formula (1),

Non-terminal organopolysiloxane units are of formula (2)

(Wherein R ¹ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms that does not contain a double bond or triple bond in the bond between carbon atoms), 25 ° C., shear rate 0 Diorganohydrogensiloxy-terminated organopolysiloxane having a viscosity at .9 s ⁻¹ of 10 mPa · s to 30,000 mPa · s, 40 parts by weight to 120 parts by weight,
(C) General formula (3)

(Wherein R ² and R ³ are substituted or unsubstituted monovalent hydrocarbon groups having 1 to 20 carbon atoms that do not contain a double bond or a triple bond in the bond between the same or different carbon atoms), m Is a natural number of 3 or more, n is an integer of 0 or more, m + n is 10 or more and 500 or less, and n / (m + n) is 0 or more and 0.7 or less, and (D) curing of the composition. Curing characterized in that it contains a promoting amount of hydrosilylation catalyst and the hardness after curing of the composition comprising the components (A) to (D) is 5 or more and 50 or less on a type E durometer Silicone rubber composition.
However, the number of hydrogen atoms bonded to silicon atoms existing in the component (B) (NH _B ), the number of hydrogen atoms bonded to silicon atoms existing in the component (C), and the total number of NH _B ( NH _T) ratio of _(NH B / NH _T) is 0.7 to 0.8, and the ratio of NH _B and (a) and the number of alkenyl groups bonded to silicon atoms in component (NA) (NH _B / NA) is 0.6 or more and 0.8 or less. The viscosity of component (A) at 25 ° C. and a shear rate of 0.9 s ⁻¹ is 100 mPa · s to 10,000 mPa · s, and the viscosity of component (B) at 25 ° C. and a shear rate of 0.9 s ⁻¹ is 100 mPa · s. The curable silicone rubber composition according to claim 1, wherein the curable silicone rubber composition is s to 10,000 mPa · s.   The curable silicone rubber composition according to claim 1, wherein n / (m + n) of the component (C) is 0 or more and 0.5 or less.   The ratio of the viscosity of (B) component to the viscosity of (A) component is 0.5 or more and 1.5 or less, The curable silicone rubber composition in any one of Claims 1-3 characterized by the above-mentioned.   Hardened | cured material formed by hardening the curable silicone rubber composition in any one of Claims 1-4.   6. The cured product according to claim 5, wherein the cured product is a sealing material for electric / electronic parts.