JP2015052026A - Addition-curable liquid silicone rubber composition and silicone rubber cured product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an addition-curable silicone rubber composition that gives a cured product having high hardness, high extensibility, high tensile strength and high tear strength.SOLUTION: The addition-curable silicone rubber composition comprises the following components in each predetermined amount: (A) an alkenyl group-containing straight-chain organopolysiloxane which contains an alkenyl group bonded to a silicon atom at both ends of the molecular chain and no alkenyl group along the molecular chain, which has an average polymerization degree of 2,000 or less, and which is liquid at room temperature; (B) an organohydrogenpolysiloxane having two SiH groups in one molecule; (C) an organohydrogenpolysiloxane having three or more SiH groups in one molecule; (D) fumed silica; and (F) an addition reaction catalyst. A molar ratio of SiH groups in the (B) component to alkenyl groups in the (A) component is 0.01 to 2.0. The addition-curable silicone rubber composition gives a silicone rubber cured product having a hardness scale of 75 or more measured with a durometer type A and an elongation at break of 300% or more.

Description

  The present invention relates to an addition-curable silicone rubber composition that gives a cured product (silicone rubber) having a high hardness (hardness measured by durometer A of 75 or more) and a cured silicone rubber obtained by heat-curing the composition. More specifically, even if the hardness after curing is high, it is possible to form a silicone rubber having a high elongation (elongation at break of 300% or more), which is particularly useful when used as a food application. The present invention relates to a composition and a cured silicone rubber obtained by heat-curing the composition.

  Silicone rubber is heat resistant, cold resistant, safe, good in appearance (transparency), soft to the touch, and durable, so it can be used in medical, food, craft, electrical / electronic, automobile, office machine, etc. Widely used in the field. In particular, addition reaction curing type silicone rubber compositions are used favorably for medical and food applications from the viewpoint of safety, such as the organic peroxide curing type does not produce by-products due to decomposition of organic peroxides. ing. Silicone rubbers used for food applications often require hardness (durometer; type A) of 75 or more, elongation of 300% or more, and tear strength of 8 kN / m or more. Generally, high hardness of silicone rubber is achieved by high filling with an inorganic filler. However, in this case, since there is no elongation, the use is limited.

  Japanese Patent Application Laid-Open No. 7-331079 (Patent Document 1) proposes a high elongation, high strength, high hardness rubber in which silicone raw rubber is highly filled with silicone resin and reinforcing silica. However, recently, the use of liquid silicone rubber for injection molding has been demanded from the viewpoints of shortening molding time and complication of the structure of molded products. If the above method is applied to liquid silicone rubber, the viscosity becomes too high. Therefore, there is a problem that molding becomes difficult.

  Japanese Patent Application Laid-Open No. 2006-1953 (Patent Document 2) proposes a liquid silicone rubber having a high hardness and a relatively high elongation obtained by heat-treating an organopolysiloxane having a vinyl group in a side chain with silica. Japanese Patent Laid-Open No. 2006-1954 (Patent Document 3) proposes a silicone rubber having a high hardness and a relatively high elongation to which a nonfunctional organopolysiloxane is added. However, in any case, the elongation does not exceed 300%, and the tear strength is low in these methods, so that there is a problem that the molded product is torn at the time of demolding.

JP 7-331079 A JP 2006-1953 A JP 2006-1954 A

  The present invention has been made in order to improve the above circumstances, and a liquid addition-curable silicone rubber composition and a silicone rubber which give a cured product (silicone rubber) having high hardness, high extensibility, high tensile strength and tear strength It aims at providing hardened | cured material.

  As a result of intensive studies to achieve the above object, the present inventor has an alkenyl group-containing organopolysiloxane having a specific molecular structure having an alkenyl group only at the molecular chain end, and two SiH groups in one molecule. At least one silica surface treatment agent selected from silanes and silazane compounds containing an alkenyl group, in combination with an organohydrogenpolysiloxane and an organohydrogenpolysiloxane having 3 or more SiH groups in one molecule It was found that by combining fumed silica surface-treated with a silicone rubber composition that gives a silicone rubber having high hardness and high extensibility, and high tensile strength and tear strength, the present invention has been made. Is.

That is, the present invention provides the following addition-curable silicone rubber composition and cured silicone rubber.
[1]
(A) An alkenyl group-containing linear organosilane that contains an alkenyl group bonded to a silicon atom at both ends of the molecular chain and does not have an alkenyl group in the middle of the molecular chain and has an average degree of polymerization of 2,000 or less at room temperature Polysiloxane: 100 parts by mass (B) Organohydrogenpolysiloxane containing two hydrogen atoms (SiH groups) bonded to silicon atoms in one molecule: 0.01-20 parts by mass (C) Bonded to silicon atoms Organohydrogenpolysiloxane containing 3 or more hydrogen atoms (SiH groups) in one molecule: 0.2 to 20 parts by mass (D) Fumed silica having a specific surface area of 130 m ² / g or more by BET method: 30 ~ 60 parts by mass (E) At least one silica surface treatment agent selected from silanes containing alkenyl groups and silazane compounds: Fumed silica 10 0.01-5 parts by mass with respect to parts by mass (F) addition reaction catalyst: containing a catalytic amount, molar ratio of SiH groups in component (B) to alkenyl groups in component (A) (SiH groups / Alkenyl group) is an addition curable silicone rubber composition that provides a cured silicone rubber having a durometer A hardness meter of 75 or more and an elongation at break of 300% or more. object.
[2]
(E) The addition-curable silicone rubber composition according to [1], wherein the component is 1,3-divinyl-1,1,3,3-tetramethyldisilazane.
[3]
Furthermore, the addition-curable silicone rubber composition according to [1] or [2], further comprising (G) 1 to 40 parts by mass of a silica surface treatment agent not containing an alkenyl group with respect to 100 parts by mass of component (D).
[4]
Furthermore, (H) the siloxane unit containing an alkenyl group is 1 to 100 mol% in the total siloxane units, the alkenyl group is contained in the middle of the molecular chain, and the viscosity at 25 ° C. is 200,000 mPa · s or less. The addition-curable silicone rubber composition according to any one of [1] to [3], which contains 0.01 to 20 parts by mass of an alkenyl group-containing organopolysiloxane with respect to 100 parts by mass of component (A).
[5]
(H) The addition-curable silicone rubber composition according to [4], wherein the component is 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane.
[6]
The addition-curable silicone rubber composition according to any one of [1] to [5], which has a viscosity at 25 ° C. in the range of 50 to 5,000 Pa · s and is for liquid injection molding.
[7]
The addition-curable silicone rubber composition according to any one of [1] to [6], which provides a cured silicone rubber having a tear strength of 8 kN / m or more.
[8]
Silicone having a hardness by durometer A hardness meter of 75 or more and an elongation at break of 300% or more obtained by heat curing the addition-curable silicone rubber composition according to any one of [1] to [7] Rubber cured product.

  According to the present invention, a combination of specific amounts of the above components (A) to (F), and optionally a combination of specific amounts of the components (G) and (H) in addition to the components (A) to (F), A silicone rubber composition that provides a silicone rubber with high hardness, high elongation, and high tensile strength and tear strength can be provided.

（式中、Ｒ¹は互いに同一又は異種の炭素数２〜１０、好ましくは２〜８の非置換又は置換アルケニル基であり、Ｒ²はアルケニル基等の脂肪族不飽和結合を含有しない、互いに同一又は異種の炭素数１〜１０、好ましくは１〜８の非置換又は置換１価炭化水素基である。ｎは２，０００以下、通常１００〜１，５００、好ましくは１５０〜１，０００、より好ましくは４００〜８００である。） Hereinafter, the present invention will be described in more detail.
[(A) component]
First, the component (A) contains an alkenyl group bonded to one silicon atom (that is, two in one molecule) at both ends of the molecular chain, particularly at both ends of the molecular chain, A linear alkenyl group-containing organopolysiloxane which is liquid at room temperature (25 ° C.) and has an average degree of polymerization of 2,000 or less having no alkenyl group is the main component (base polymer) of the present composition. As the component A), one or more of those represented by the following general formula (I) can be used.

(In the formula, R ¹ is an unsubstituted or substituted alkenyl group having the same or different carbon number of 2 to 10, preferably 2 to 8, and R ² does not contain an aliphatic unsaturated bond such as an alkenyl group. An unsubstituted or substituted monovalent hydrocarbon group having the same or different carbon number of 1 to 10, preferably 1 to 8. n is 2,000 or less, usually 100 to 1,500, preferably 150 to 1,000, More preferably, it is 400-800.)

Here, as the unsubstituted or substituted alkenyl group having 2 to 10 carbon atoms, preferably 2 to 8 carbon atoms represented by R ¹ , vinyl group, allyl group, propenyl group, butenyl group, hexenyl group, octenyl group, etc. Examples include alkenyl groups and those in which some or all of the hydrogen atoms in these groups are substituted with halogen atoms such as fluorine, bromine and chlorine, cyano groups, and the like. A vinyl group, an allyl group, and a propenyl group are preferable, and a vinyl group is more preferable.

Further, the unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, preferably 1 to 8 carbon atoms bonded to the silicon atom represented by R ² does not contain an aliphatic unsaturated bond such as an alkenyl group. For example, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, cyclohexyl group, octyl group, nonyl group, decyl group, etc. An alkyl group, a phenyl group, a tolyl group, an xylyl group, an aryl group such as a naphthyl group, an aralkyl group such as a benzyl group, a phenylethyl group, or a phenylpropyl group, or a part or all of hydrogen atoms of these groups Substituted with halogen atoms such as bromine and chlorine, cyano groups, etc., such as chloromethyl, chloropropyl, bromoethyl, Roropuropiru group, but cyanoethyl group and the like, all R ² in 90 mol% or more, and particularly it is preferable that all R ² groups are methyl groups.

  The structure of this organopolysiloxane is such that both ends of the molecular chain are blocked with alkenyl diorganosiloxy groups (for example, vinyldimethylsiloxy group, vinylmethylphenylsiloxy group, allyldimethylsiloxy group, etc.), and the main chain is a diorganosiloxane unit ( For example, a diorganopolysiloxane with a linear structure consisting of random repeats of dimethylsiloxane units, methylphenylsiloxane units, diphenylsiloxane units, methyltrifluoropropylsiloxane units, etc., with a branched structure in the middle of the molecular chain When the addition reaction with the component (B) is carried out, not only chain length extension but also crosslinking reaction occurs together, and the extensibility of the cured silicone rubber is lowered.

  From the viewpoint that the alkenyl group-containing organopolysiloxane of component (A) has a high hardness (hardness by durometer A of 75 or more) and a highly extensible (elongation at break of 300% or more) cured silicone rubber, Regarding the molecular weight, the average degree of polymerization (weight average degree of polymerization, hereinafter the same) is 2,000 or less, preferably 100 to 1,500, more preferably 150 to 1,000, and still more preferably 400 to 800. If it is less than 100, sufficient rubber feeling may not be obtained, and if it is more than 2,000, the viscosity becomes high and molding becomes difficult. In the present invention, the degree of polymerization (or molecular weight) is usually determined as the weight average degree of polymerization (or weight average molecular weight) in terms of polystyrene in gel permeation chromatography (GPC) analysis using toluene or the like as a developing solvent. it can.

  The organopolysiloxane is a self-fluid liquid at room temperature (25 ° C.) if the average degree of polymerization is 2,000 or less, particularly 1,500 or less. The viscosity of the organopolysiloxane at 25 ° C. is preferably 100 to 200,000 mPa · s, particularly 500 to 150,000 mPa · s. In the present invention, the viscosity can be measured with a rotational viscometer (for example, BL type, BH type, BS type, cone plate type, etc.) (hereinafter the same).

  In addition, as the component (A), as long as it is a linear organopolysiloxane containing an alkenyl group bonded to silicon atoms at both ends of the molecular chain, the molecular structure (for example, an alkenyldiorganosiloxy group at the molecular chain end, One type or two or more types having different substituents in the diorganosiloxane unit in the main chain and the degree of polymerization can be used in combination.

Thus, the organopolysiloxane of component (A) is specifically a diorganoalkenylsiloxy group-capped diorganopolysiloxane having molecular chain terminals at both ends. The “organo group” in the siloxane means the same as the unsubstituted or substituted monovalent hydrocarbon group excluding the alkenyl group represented by R ² in the formula (I).

[Component (B)]
The organohydrogenpolysiloxane of component (B) is an organohydrogenpolysiloxane having a hydrogen atom (SiH group) bonded to two silicon atoms in one molecule (that is, a bifunctional organohydrogenpolysiloxane). The SiH group in the molecule has a hydrosilyl addition reaction with the alkenyl group bonded to the silicon atoms at both ends of the molecular chain in the component (A), and has the effect of extending the chain length of the component (A). .

  The organohydrogenpolysiloxane as the component (B) is preferably a linear or cyclic structure. Only two SiH groups (silicon-bonded hydrogen atoms) contained in the molecule are bonded to the silicon atom in the middle of the molecular chain (non-terminal molecular chain) even if bonded to the silicon atom at the molecular chain end. It may be a thing, and the thing couple | bonded one each to both of these may be sufficient.

Examples of the component (B) organohydrogenpolysiloxane include:
Diorganohydrogensiloxy group-blocked diorganopolysiloxane at both molecular chain ends,
An organohydrogensiloxane / diorganosiloxane copolymer having both ends of the molecular chain blocked with triorganosiloxy groups and containing two organohydrogensiloxane units in the main chain;
An organohydrogensiloxane / diorganosiloxane copolymer containing one organohydrogensiloxane unit in the main chain, one end of which is blocked with a diorganohydrogensiloxy group and the other end is blocked with a triorganosiloxy group. Polymer,
Examples thereof include organohydrogensiloxane / diorganosiloxane cyclic copolymers containing two organohydrogensiloxane units.

（式中、Ｒ³は炭素数１〜１０の非置換又は置換の１価炭化水素基、ｍは１〜３００の整数、好ましくは１〜１００の整数、より好ましくは２〜２５の整数であり、ｋは０〜３００の整数、好ましくは１〜１００の整数、より好ましくは２〜２５の整数であり、ｐは２〜１０の整数、好ましくは２〜６の整数、より好ましくは２〜５の整数を示す。）
で示される構造を有するものが例示できる。 Specifically, the hydrogen polysiloxane includes the following general formulas (IIa) to (IIc):

(In the formula, R ³ is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, m is an integer of 1 to 300, preferably an integer of 1 to 100, more preferably an integer of 2 to 25. , K is an integer of 0-300, preferably an integer of 1-100, more preferably an integer of 2-25, p is an integer of 2-10, preferably an integer of 2-6, more preferably 2-5. Indicates an integer.)
What has the structure shown by can be illustrated.

Here, the unsubstituted or substituted monovalent hydrocarbon group having 1 to 10, preferably 1 to 8 carbon atoms represented by R ³ does not contain an aliphatic unsaturated bond such as an alkenyl group. And the same groups as those exemplified as R ² in the general formula (I) of the component (A) described above can be mentioned, for example, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, cyclohexyl group, octyl group, nonyl group, alkyl group such as decyl group, aryl group such as phenyl group, tolyl group, xylyl group, naphthyl group, benzyl group, phenyl group Aralkyl groups such as ethyl group and phenylpropyl group, and some or all of hydrogen atoms of these groups are halogen atoms such as fluorine, bromine and chlorine, cyano groups, etc. Such as a chloromethyl group, a chloropropyl group, a bromoethyl group, a trifluoropropyl group, a cyanoethyl group and the like, and an epoxy ring (for example, a glycidyl group, a glycidoxy group, a 3,4-epoxycyclohexyl group, 2,3-epoxycyclohexyl group, etc.), alkoxysilyl groups (for example, trimethoxysilyl group, triethoxysilyl group, methyldimethoxysilyl group, etc.), hydrocarbon groups having functional groups such as silanol group (hydroxysilyl group), etc. However, it is preferable that 90% by mole or more of all R ³ , in particular, all R ³ are methyl groups.

  The number (or degree of polymerization) of silicon atoms in one molecule of the component (B) organohydrogenpolysiloxane is usually 2 to 303, preferably 2 to 100, and is liquid at room temperature (25 ° C.). Are preferably used.

  The content of hydrogen atoms (SiH groups) bonded to silicon atoms of the organohydrogenpolysiloxane of component (B) is preferably 0.00009 to 0.015 mol / g, more preferably 0. .00027 to 0.010 mol / g.

  The amount of the organohydrogenpolysiloxane (B) is 0.01 to 20 parts by weight, preferably 0.1 to 15 parts by weight, more preferably 0.2 to 100 parts by weight of the component (A). -10 parts by mass, more preferably 0.2-8 parts by mass. If the blending amount of the component (B) is too small, a sufficient chain extension effect cannot be obtained, resulting in a low-extension rubber, and if it exceeds 20 parts by mass, the rubber physical properties are deteriorated and are not good. It is an economy.

  Moreover, in this invention, the total molar ratio (SiH group / alkenyl group) of the SiH group contained in (B) component with respect to the silicon atom bond alkenyl group in (A) component is 0.01-2.0. In particular, the component (B) is blended so as to be about 0.05 to 1.8. If the total molar ratio of the SiH groups contained in the component (B) to the silicon atom-bonded alkenyl group in the component (A) is lower than 0.01, a sufficient chain length extension effect of the component (A) cannot be obtained. The rubber has a low elongation, and even when it is higher than 2.0, the chain length extension effect is reduced and the rubber physical properties are remarkably lowered.

[Component (C)]
The organohydrogenpolysiloxane of component (C) is an organohydrogenpolysiloxane containing a hydrogen atom (SiH group) bonded to three or more silicon atoms in one molecule (that is, a polyfunctional compound having three or more functionalities). (Organohydrogenpolysiloxane) which acts as a curing agent (crosslinking agent) in the composition of the present invention. The organohydrogenpolysiloxane of component (C) is a polyfunctional organohydrogenpolysiloxane containing hydrogen atoms (SiH groups) bonded to three or more silicon atoms in one molecule. The component B) is clearly differentiated.

  More specifically, the organohydrogenpolysiloxane of component (C) may not contain reactive groups other than SiH groups (for example, aliphatic unsaturated groups such as alkenyl groups) in the molecule. Preferred is an organohydrogenpolysiloxane having 3 or more hydrogen atoms (that is, SiH groups) bonded to a silicon atom in one molecule, and more preferably not having an aromatic group such as a phenyl group in the molecule.

  The organohydrogenpolysiloxane of component (C) is represented by the following average composition formula (III), and is at least 3 (usually 3 to 200), preferably 4 or more (usually 4 to 200), more preferably 5 to 100, still more preferably about 8 to 50 hydrogen atoms bonded to silicon atoms (SiH groups) are preferably used.

^{_{R 4 q H r SiO (4}} -qr) / 2 (III)
(Wherein R ⁴ is a monovalent hydrocarbon group excluding an unsubstituted or halogen-substituted aliphatic unsaturated bond having 1 to 10 carbon atoms, preferably 1 to 8 carbon atoms, and q is 0.7 to 2. 1 and r are 0.001 to 1.0 and q + r is a positive number satisfying 0.8 to 3.0.)

In the above formula, as the unsubstituted or halogen-substituted monovalent hydrocarbon group having 1 to 10 carbon atoms of R ^4, the same as those exemplified as R ² in the general formula (I) in the component (A) can be mentioned. However, it preferably does not contain an aryl group such as a phenyl group or an aromatic hydrocarbon group such as an aralkyl group. Specifically, it is preferably an alkyl group, particularly a methyl group.
Further, q is 0.7 to 2.1, preferably 0.8 to 2.0, r is 0.001 to 1.0, preferably 0.01 to 1.0, and q + r is 0.8. It is a positive number satisfying 8-3.0, preferably 1.0-2.5.

The molecular structure of the organohydrogenpolysiloxane (C) may be any of linear, cyclic, branched, and three-dimensional network structures. In this case, the number (or degree of polymerization) of silicon atoms in one molecule is usually 3 to 300, preferably 4 to 200, more preferably 10 to 200, still more preferably 15 to 100, and room temperature. A liquid at 25 ° C. is preferably used.
In addition, the hydrogen atom couple | bonded with a silicon atom may be located in either the molecular chain terminal, the middle of a molecular chain (molecular chain non-terminal), and may be located in both.

Examples of the organohydrogenpolysiloxane containing a hydrogen atom (SiH group) bonded to three or more silicon atoms in one molecule of the component (C) include 1,3,5,7-tetramethylcyclotetrasiloxane, Methylhydrogencyclopolysiloxane, methylhydrogensiloxane / dimethylsiloxane cyclic copolymer, tris (dimethylhydrogensiloxy) methylsilane, trimethylsiloxy group-capped methylhydrogenpolysiloxane, trimethylsiloxy group-capped dimethylsiloxane / methyl siloxane copolymers, both ends endcapped with dimethyl hydrogen siloxy group dimethylsiloxane-methylhydrogensiloxane copolymers, copolymers consisting of (CH _{3) 2} HSiO _1/2 units and SiO _4/2 units, ( H _{3) 3} SiO _1/2 units and (CH ₃₎ consists of ₂ HSiO _1/2 units and SiO _4/2 units, copolymers composed of the (CH _{3) 2} HSiO _1/2 units and SiO _4/2 units Copolymers comprising (CH ₃ ) SiO _3/2 units, copolymers comprising (CH ₃ ) ₂ HSiO _1/2 units, SiO _4/2 units and (CH ₃ ) ₂ SiO _2/2 units, etc. Is mentioned.

  As content of the hydrogen atom (SiH group) couple | bonded with the silicon atom of (C) component organohydrogen polysiloxane, it is preferable that it is 0.003-0.017 mol / g, More preferably, it is 0.005. -0.017 mol / g. If it is less than 0.003 mol / g, crosslinking may be insufficient, and if it exceeds 0.017 mol / g, it may become an unstable substance.

  The blending amount of the organohydrogenpolysiloxane of component (C) is 0.2 to 20 parts by weight, preferably 0.3 to 18 parts by weight, particularly 0.5 to 15 parts by weight per 100 parts by weight of component (A). Part. When the amount is less than 0.2 parts by mass, the crosslinking becomes insufficient, resulting in a sticky rubber. When the amount is more than 20 parts by mass, the physical properties of the rubber are deteriorated, which is uneconomical.

  The ratio of the component (B) to the component (C) is the ratio of the number of moles of SiH groups in the component (B) to the number of moles of SiH groups in the component (C): [SiH in the component (B) Group] / [SiH group in component (C)] (molar ratio) is preferably 1/99 to 70/30, more preferably 3/97 to 60/40, still more preferably 5/50 to 50/50. It is desirable to use at such a ratio that it is in the range. If this ratio is less than 1/99, the rubber may have low extensibility, and if it is more than 70/30, the rubber physical properties may deteriorate.

  In the present invention, the total SiH functional group amount of the component (B) and the component (C) and the alkenyl group amount of the entire composition (particularly the component (A) and the components (E) and (H) described later) The molar ratio (SiH group / alkenyl group) is preferably 0.8 to 5.0, more preferably 1.0 to 4.0, and still more preferably 1.2 to 3.0. It is used so that it is in the range. If it is less than 0.8, crosslinking may be insufficient, resulting in a sticky rubber, and if it exceeds 5.0, rubber physical properties may be deteriorated.

[(D) component]
Component (D), fumed silica (fumed silica), is essential as a reinforcing silica-based filler for imparting sufficient strength to the cured silicone rubber. The specific surface area of fumed silica by the BET method is 130 m ² / g or more, usually 130 to 400 m ² / g, preferably 150 to 350 m ² / g. If it is smaller than 130 m ² / g, sufficient strength cannot be obtained, and the transparency of the molded product also decreases. If it is larger than 400 m ² / g, blending may become difficult or discoloration may occur. is there.

  The compounding quantity of a fumed silica is 30-60 mass parts with respect to 100 mass parts of (A) component, and it is preferable that it is 35-50 mass parts. When the blending amount is less than 30 parts by mass, sufficient rubber strength cannot be obtained. When the blending amount is more than 60 parts by mass, the viscosity becomes so high that molding is impossible.

  The fumed silica of component (D) is at least one silica surface treating agent selected from (E) alkenyl group-containing silane and silazane compound, which will be described later, or this component (E) and will be described later ( G) It is used by performing a surface treatment in combination with a silica surface treatment agent not containing an alkenyl group. In this case, the fumed silica of component (D) is prepared by kneading silicone oil (that is, part or all of organopolysiloxane of component (A)) and component (D) when preparing the composition. When the base compound is prepared, the surface treatment agent of these components (E) is added at the same time, and if necessary in the presence of a small amount of water, it is heated and mixed (for example, 120 to 180 ° C., particularly 130 to 170 ° C. For 30 minutes to 6 hours, particularly 1 hour to 4 hours), and it is preferable to use it after surface treatment (in-situ treatment) during preparation of the composition.

[(E) component]
As the at least one silica surface treating agent selected from the silane containing an alkenyl group as the component (E) and a silazane compound, 1,3-divinyl-1,1,3,3-tetramethyldisilazane, 1,1 , 3,3-tetravinyl-1,3-dimethyldisilazane, 1-vinyl-1,1,3,3,3-pentamethyldisilazane, 1,1,1,3,5,5,5-heptamethyl -Vinyl group-containing disilazane such as 3-vinyltrisilazane, organosilazane such as trisilazane, vinyl group-containing aminosilane such as N, N-dimethylaminodimethylvinylsilane, trimethoxyvinylsilane, triethoxyvinylsilane, methyldimethoxyvinylsilane, Examples include vinyl group-containing alkoxysilanes such as methoxydimethylvinylsilane, particularly 1,3- Vinyl-1,1,3,3-tetramethyl disilazane and trimethoxy vinyl silane is preferred.

  (E) The compounding quantity of the at least 1 sort (s) of silica surface treating agent chosen from the silane and silazane compound which contain the alkenyl group of a component is 0.01-5 mass parts with respect to 100 mass parts of said fumed silica, Especially 0. It is preferable that it is 1-3 mass parts. If the blending amount is less than 0.01 parts by mass, sufficient strength cannot be obtained, and if it is more than 5 parts by mass, rubber elasticity is lost.

[(F) component]
As the addition reaction catalyst for component (F), platinum black, platinous chloride, chloroplatinic acid, a reaction product of chloroplatinic acid and monovalent alcohol, a complex of chloroplatinic acid and olefins, platinum bisacetate Known platinum group metal catalysts may be used as hydrosilylation addition reaction catalysts such as platinum-based catalysts such as acetate, palladium-based catalysts, and rhodium-based catalysts. In addition, the compounding quantity of this addition reaction catalyst can be made into a catalyst quantity, and 0.5-1,000 ppm with respect to the total amount of (A) and (B) component normally as mass conversion of a platinum group metal, Particularly, it is about 1 to 500 ppm.

[(G) component]
In the composition of the present invention, a silica surface treatment agent ((G) component) not containing an alkenyl group can be used in combination with the (E) component as an optional component added as necessary. As the silica surface treatment agent not containing an alkenyl group as component (G), alkylsilazanes having no alkenyl group, alkylsilazanes such as alkylchlorosilane, hexamethyldisilazane, silane coupling agents, titanate treatment agents, fatty acids Any known material such as an ester may be used alone, or two or more may be used simultaneously or at different timings.

  The amount of the silica surface treatment agent ((G) component) not containing these alkenyl groups is preferably 0 to 50 parts by weight, more preferably 1 to 40 parts by weight, based on 100 parts by weight of the fumed silica. Part, particularly 2 to 30 parts by weight. If the blending amount is more than 50 parts by mass, the addition reaction may be hindered or the reinforcing effect of the rubber may be reduced.

[(H) component]
In the composition of the present invention, an alkenyl group-containing organopolysiloxane having an alkenyl group in the middle of the molecular chain and having a viscosity at 25 ° C. of 200,000 mPa · s or less as an optional component added as necessary (( Component H) can be further added as a rubber reinforcing material. This component (H) is a siloxane unit in which 1 to 100 mol% of all siloxane units contain an alkenyl group (for example, a monofunctional siloxy such as a trialkenylsiloxy unit, a dialkenylorganosiloxy unit, and an alkenyldiorganosiloxy unit). Unit, bifunctional siloxane unit such as alkenylorganosiloxane unit, trifunctional siloxane unit such as alkenylsilsesquioxane unit, etc.), and alkenyl group-containing organopoly having a viscosity at 25 ° C. of 20,000 mPa · s or less Although it is a siloxane, the component (H) is an alkenyl group bonded to a silicon atom in the middle of a molecular chain (non-terminal molecular chain) (that is, an alkenyl group bonded to a silicon atom in a difunctional diorganosiloxane unit). Is clearly differentiated from the component (A) in that it is essential A.

As this (H) component, the 1 type (s) or 2 or more types of what is shown by the following average compositional formula (IV) can be used, for example.
R ⁵ _s SiO _{(4-s) / 2} (IV)
Wherein R ⁵ is an unsubstituted or substituted monovalent hydrocarbon group having the same or different carbon number of 1 to 10, preferably 1 to 8, and s is 1.5 to 2.8, preferably 1. (It is a positive number in the range of 8 to 2.5, more preferably 1.95 to 2.05.)

Here, the unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms represented by R ⁵ is a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, or a tert-butyl group. , Pentyl group, neopentyl group, hexyl group, cyclohexyl group, octyl group, nonyl group, alkyl group such as decyl group, aryl group such as phenyl group, tolyl group, xylyl group, naphthyl group, benzyl group, phenylethyl group, phenylpropylene An aralkyl group such as a ruthel group, a vinyl group, an allyl group, a propenyl group, an isopropenyl group, a butenyl group, a hexenyl group, a cyclohexenyl group, an alkenyl group such as an octenyl group, and some or all of the hydrogen atoms of these groups Substituted by halogen atoms such as fluorine, bromine and chlorine, cyano groups, etc., such as chloromethyl group, chloroprop Group, bromoethyl group, trifluoropropyl group, but cyanoethyl group and the like, 50 mol% or more of the total R ^5, and particularly it is preferable that all of R ^5, except the alkenyl group is a methyl group.

In addition, at least three of R ⁵ are preferably alkenyl groups (preferably having 2 to 8 carbon atoms, more preferably 2 to 6 carbon atoms, and particularly preferably a vinyl group).
In addition, content of an alkenyl group is 1.0 * 10 < ^-4 > -1.5 * 10 in this organopolysiloxane as an average of the whole alkenyl group containing organopolysiloxane of (H) component contained in a composition. ⁻² mol / g, particularly 2.0 × 10 ^{−4 to} 1.3 × 10 ⁻² mol / g is preferable. If the amount of the alkenyl group is less than 1.0 × 10 ⁻⁴ mol / g, there may be no rubber reinforcing effect, and if it exceeds 1.5 × 10 ⁻² mol / g, the hydrosilylation reaction is inhibited. There is a fear.
In the component (H), the siloxane unit containing an alkenyl group is 1 to 100 mol%, preferably 3 to 100 mol% in the total siloxane units, from the viewpoint of increasing rubber hardness or improving strength. is there.

  The alkenyl group-containing organopolysiloxane of component (H) is an alkenyl group bonded to a silicon atom in the middle of a molecular chain (non-terminal molecular chain) (that is, an alkenyl bonded to a silicon atom in a difunctional diorganosiloxane unit). Group) is required to be contained in the molecule, but the alkenyl group bonded to the silicon atom at the end of the molecular chain may or may not be contained.

The structure of the organopolysiloxane may have a cyclic structure, a branched structure, or a linear structure.
Regarding the molecular weight, in the case of a cyclic body, the degree of polymerization (or the number of silicon atoms in the molecule) is usually 3 to 10, and such an organopolysiloxane is particularly preferable because of its ease of production. , 7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane, and other vinylmethylcyclopolysiloxanes and (vinylmethylsiloxane / dimethylsiloxane) cyclic copolymers are preferred. In the case of a branched structure or a linear structure, the average degree of polymerization (weight average degree of polymerization) is 2,000 or less, usually 10 to 1,500, and preferably 30 to 1,000. If it is less than 10, sufficient rubber feeling may not be obtained, and if it is more than 2,000, the viscosity becomes high and molding may be difficult. Specific examples of the organopolysiloxane having a linear structure include a triorganosiloxy group-capped diorganosiloxane / alkenylorganosiloxane copolymer with both molecular chains and a diorganoalkenylsiloxy group-capped diorganosiloxane with both molecular chains. Alkenylorganosiloxane copolymer, molecular chain both ends organodialkenylsiloxy group-blocked diorganosiloxane / alkenylorganosiloxane copolymer, molecular chain both ends trialkenylsiloxy group-blocked diorganosiloxane / alkenylorganosiloxane copolymer (however, Examples of the organo group include linear diorganopolysiloxanes containing an alkenyl group as a side chain substituent in the main chain, such as an aliphatic unsaturated group such as an alkenyl group.

  The viscosity at 25 ° C. of the alkenyl group-containing organopolysiloxane may be 200,000 mPa · s or less, and the lower limit of the viscosity is not particularly limited, but is usually 0.1 mPa · s or more.

  (H) As for the compounding quantity at the time of mix | blending a component, 0.01-20 mass parts is preferable with respect to 100 mass parts of (A) component, More preferably, it is 0.1-10 mass parts. If the amount is too small, the effect of blending the component (H) may not appear in the rubber physical properties. If the amount is too large, the curing speed and the physical properties of the rubber may decrease.

[Other ingredients]
Other components include fillers such as precipitated silica, quartz powder, diatomaceous earth, and calcium carbonate, conductive agents such as carbon black, conductive zinc white, and metal powder, nitrogen-containing compounds, acetylene compounds, and phosphorus as necessary. Compounds, nitrile compounds, carboxylates, tin compounds, mercury compounds, acetylene compounds such as ethynylcyclohexanol, hydrosilylation reaction control agents such as sulfur compounds, heat-resistant agents such as iron oxide and cerium oxide, dimethyl silicone oil, etc. It is optional to add a release agent, an adhesiveness imparting agent, a thixotropic property imparting agent and the like.

  The silicone rubber composition of the present invention can be produced by mixing the above-mentioned components, but is liquid at room temperature (25 ° C.), particularly a viscosity of 50 to 5,000 Pa · s, particularly 100 to 3,000 Pa. -What is s is preferable.

  As a method for molding and curing the silicone rubber composition, a conventional method can be adopted, but a liquid injection molding method is suitably employed as the molding method. Further, as the curing conditions, heat treatment conditions of 120 to 230 ° C. for 3 seconds to 10 minutes, preferably 150 to 210 ° C. for about 5 seconds to 3 minutes may be employed.

  In the present invention, the cured product (silicone rubber) obtained by curing the silicone rubber composition has a hardness of 75 or more according to a durometer A hardness meter. When the hardness is less than 75, when used for a tableware container or the like, the silicone rubber is deformed due to the load of the contents. The said hardness can be achieved by adjusting suitably the compounding ratio of (C)-(F) component and the (H) component depending on the case.

  The elongation at break of this silicone rubber is preferably 300% or more, particularly preferably 350% or more, and the tear strength [crescent type] is preferably 8 kN / m or more, particularly preferably 10 kN / m or more. The tensile strength is preferably 3 MPa or more, particularly 5 MPa or more. If the elongation at the time of cutting is less than 300%, the rubber will tear at the time of demolding. Further, when the tear strength is less than 8 kN / m and the tensile strength is less than 3 MPa, the rubber may be torn during demolding. The said characteristic can be achieved by mix | blending (A)-(F) component with a suitable compounding ratio. In the present invention, hardness, elongation at break, tear strength, and tensile strength are values measured according to JIS-K6249.

  The silicone rubber of the present invention is suitably used for food applications, particularly food trays and confectionery molds.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples and comparative examples, but the present invention is not limited to the following examples. In addition, a part shows a mass part by the following example. The average degree of polymerization indicates a weight average degree of polymerization in terms of polystyrene in gel permeation chromatography (GPC) analysis using toluene as a developing solvent. The viscosity is a value measured at 25 ° C. by a rotational viscometer.

[Example 1]
Fumed silica with 55 parts of dimethylpolysiloxane (A1) having an average degree of polymerization of 750 blocked at both ends of the molecular chain with dimethylvinylsiloxy groups and a viscosity of 30,000 mPa · s, and a specific surface area of 300 m ² / g ( Nippon Aerosil Co., Ltd., Aerosil 300) 40 parts, hexamethyldisilazane 6.5 parts, 1,3-divinyl-1,1,3,3-tetramethyldisilazane 1.5 parts, water 2.0 parts After mixing for 30 minutes, the temperature was raised to 150 ° C., and stirring was continued for 3 hours, followed by cooling to obtain a silicone rubber base. To 100 parts of this silicone rubber base, 25 parts of the dimethylpolysiloxane (A1), 1.0 part of 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane, both molecular chains Bifunctional organohydrogen poly whose ends are blocked with dimethylhydrogensiloxy groups and all monovalent hydrocarbon groups bonded to silicon atoms other than oxygen and hydrogen atoms bonded directly to silicon atoms are methyl groups Siloxane (B1) (polymerization degree 20, molecular chain both ends dimethylhydrogensiloxy group-blocked dimethylpolysiloxane, SiH group amount 0.0014 mol / g) 1.0 part [SiH group in (B1) / (A1) Alkenyl group = 0.5 (mol / mol)], both ends of the molecular chain blocked with trimethylsiloxy groups, and oxygen atoms directly bonded to silicon atoms Polyfunctional organohydrogenpolysiloxane (C1) in which all monovalent hydrocarbon groups bonded to silicon atoms other than hydrogen atoms are methyl groups (polymerization degree 68, molecular chain both ends trimethylsiloxy group-capped dimethylsiloxane -Methyl hydrogen siloxane copolymer, SiH group amount 0.011 mol / g) 4.15 parts, [(B1) component and (C1) component in total SiH groups in composition / all alkenyl groups in composition = 1. 5 (mol / mol)], 0.04 part of ethynylcyclohexanol was added as a reaction control agent, and stirring was continued for 15 minutes to obtain a silicone rubber composition [BS type viscometer at 25 ° C., rotor No. 7, at 2 rpm. Of 1800 Pa · s] was obtained.

  This silicone rubber composition was mixed with 0.1 part of a platinum catalyst (Pt concentration 1% by mass), cured at 150 ° C. for 5 minutes, and then cured at 150 ° C. for 1 hour in an oven. Table 1 shows the results of measuring hardness, tensile strength, elongation at break, and tear strength (crescent type) based on JIS-K6249.

で示される一分子中に２個のＳｉＨ基を有する環状の２官能性オルガノハイドロジェンポリシロキサン（Ｂ２）（ＳｉＨ基量０．００６２モル／ｇ）０．８部［（Ｂ２）中のＳｉＨ基／（Ａ１）中のアルケニル基＝１．７（モル／モル）］、実施例１の分子鎖両末端がトリメチルシロキシ基で封鎖され、側鎖にケイ素原子結合水素基を有する多官能性のオルガノハイドロジェンポリシロキサン（Ｃ１）を４．５部［（Ｂ２）成分と（Ｃ１）成分中の合計ＳｉＨ基／組成物中の全アルケニル基＝１．７（モル／モル）］、反応制御剤としてエチニルシクロヘキサノール０．０５部を添加し、１５分撹拌を続けて、シリコーンゴム組成物［２５℃でのＢＳ型粘度計、ローター７番、２ｒｐｍでの測定結果が１，６００Ｐａ・ｓ］を得た。 [Example 2]
55 parts of dimethylpolysiloxane (A1) of Example 1, 40 parts of fumed silica (Aerosil 300 manufactured by Nippon Aerosil Co., Ltd.) having a specific surface area of 300 m ² / g, 6.5 parts of hexamethyldisilazane, 1,3- After mixing 1.5 parts of divinyl-1,1,3,3-tetramethyldisilazane and 2.0 parts of water at room temperature for 30 minutes, the temperature is raised to 150 ° C., stirring is continued for 3 hours, and the silicone rubber is cooled. Got the base. To 100 parts of this silicone rubber base, 25 parts of dimethylpolysiloxane (A1) of Example 1, 1.0 part of 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane, The following formula (V)

A cyclic bifunctional organohydrogenpolysiloxane (B2) having two SiH groups in one molecule represented by (0.82 mol / g of SiH groups) [SiH groups in (B2) / Alkenyl group in (A1) = 1.7 (mol / mol)], polyfunctional organo having both ends of the molecular chain of Example 1 blocked with a trimethylsiloxy group and having a silicon-bonded hydrogen group in the side chain 4.5 parts of hydrogen polysiloxane (C1) [total SiH groups in components (B2) and (C1) / total alkenyl groups in the composition = 1.7 (mol / mol)], as a reaction control agent 0.05 part of ethynylcyclohexanol was added and stirring was continued for 15 minutes to obtain a silicone rubber composition [BS type viscometer at 25 ° C., rotor No. 7, measurement result at 2, rpm was 1,600 Pa · s]. It was.

  This silicone rubber composition was mixed with 0.1 part of a platinum catalyst (Pt concentration 1% by mass), cured at 150 ° C. for 5 minutes, and then cured at 150 ° C. for 1 hour in an oven. Table 1 shows the results of measuring hardness, tensile strength, elongation at break, and tear strength (crescent type) based on JIS-K6249.

[Comparative Example 1]
55 parts of dimethylpolysiloxane (A1) of Example 1, 40 parts of fumed silica (Aerosil 300 manufactured by Nippon Aerosil Co., Ltd.) having a specific surface area of 300 m ² / g, 6.5 parts of hexamethyldisilazane, 1,3- After mixing 1.5 parts of divinyl-1,1,3,3-tetramethyldisilazane and 2.0 parts of water at room temperature for 30 minutes, the temperature is raised to 150 ° C., stirring is continued for 3 hours, and the silicone rubber is cooled. Got the base. To 100 parts of this silicone rubber base, 25 parts of dimethylpolysiloxane (A1) of Example 1, 1.0 part of 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane, 4.3 parts of polyfunctional organohydrogenpolysiloxane (C1) having both ends of the molecular chain of Example 1 blocked with trimethylsiloxy groups and having silicon-bonded hydrogen atoms in the side chain [total in (C1) component SiH groups / total alkenyl groups in the composition = 1.5 (mol / mol)], 0.04 part of ethynylcyclohexanol was added as a reaction control agent, and stirring was continued for 15 minutes to obtain a silicone rubber composition [25 ° C. The BS viscometer, rotor No. 7, and the measurement result at 2 rpm were 1,900 Pa · s].

  This silicone rubber composition was mixed with 0.1 part of a platinum catalyst (Pt concentration 1% by mass), cured at 150 ° C. for 5 minutes, and then cured at 150 ° C. for 1 hour in an oven. Table 1 shows the results of measuring hardness, tensile strength, elongation at break, and tear strength (crescent type) based on JIS-K6249.

[Comparative Example 2]
55 parts of dimethylpolysiloxane (A1) of Example 1, 40 parts of fumed silica (Aerosil 300 manufactured by Nippon Aerosil Co., Ltd.) having a specific surface area of 300 m ² / g, 8.0 parts of hexamethyldisilazane, 2.0 of water After mixing the parts at room temperature for 30 minutes, the temperature was raised to 150 ° C., stirring was continued for 3 hours, and the mixture was cooled to obtain a silicone rubber base. 100 parts of this silicone rubber base is 25 parts of dimethylpolysiloxane (A1) of Example 1, both ends of the molecular chain of Example 1 are blocked with dimethylhydrogensiloxy groups, and all side chain substituents are methyl groups. 1.0 part of bifunctional organohydrogenpolysiloxane (B1) [SiH group in (B1) / alkenyl group in (A1) = 0.5 (mol / mol)], both ends of the molecular chain of Example 1 Is blocked with a trimethylsiloxy group and 2.25 parts of a polyfunctional organohydrogenpolysiloxane (C1) having a silicon atom-bonded hydrogen group in the side chain [total SiH groups / (B1) component and (C1) component / Total alkenyl groups in the composition = 1.8 (mol / mol)], 0.05 part of ethynylcyclohexanol was added as a reaction control agent, and stirring was continued for 15 minutes. Things [BS type viscometer at 25 ° C., No. 7 rotor, the measurement result of at 2rpm is 2,000 Pa · s] was obtained.

  This silicone rubber composition was mixed with 0.1 part of a platinum catalyst (Pt concentration 1% by mass), cured at 150 ° C. for 5 minutes, and then cured at 150 ° C. for 1 hour in an oven. Table 1 shows the results of measuring hardness, tensile strength, elongation at break, and tear strength (crescent type) based on JIS-K6249.

[Comparative Example 3]
55 parts of dimethylpolysiloxane (A1) of Example 1, 40 parts of fumed silica (Aerosil 300 manufactured by Nippon Aerosil Co., Ltd.) having a specific surface area of 300 m ² / g, 6.5 parts of hexamethyldisilazane, 1,3- After mixing 1.5 parts of divinyl-1,1,3,3-tetramethyldisilazane and 2.0 parts of water at room temperature for 30 minutes, the temperature is raised to 150 ° C., stirring is continued for 3 hours, and the silicone rubber is cooled. Got the base. To 100 parts of this silicone rubber base, 25 parts of dimethylpolysiloxane (A1) of Example 1, 1.0 part of 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane, A polyfunctional organohydro group in which both ends of the molecular chain are blocked with dimethylhydrogensiloxy groups, and all of the monovalent hydrocarbon groups bonded to silicon atoms other than oxygen and hydrogen atoms bonded directly to silicon atoms are methyl groups. Genpolysiloxane (C2) (molecular chain dimethylhydrogensiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane copolymer having a degree of polymerization of 20, SiH group amount 0.0053 mol / g) 1.0 part [(C2 ) In SiH group / alkenyl group in (A1) = 1.8 (mol / mol)], both ends of the molecular chain of Example 1 are trimethylshiro 4.4 parts of polyfunctional organohydrogenpolysiloxane (C1) blocked with a silyl group and having a silicon atom-bonded hydrogen group in the side chain [total SiH groups / composition in components (C2) and (C1) All alkenyl groups in the mixture = 1.7 (mol / mol)], 0.05 part of ethynylcyclohexanol was added as a reaction control agent, and stirring was continued for 15 minutes to obtain a silicone rubber composition [BS type viscosity at 25 ° C. A total of 1,900 Pa · s was obtained as a result of measurement at rotor No. 7, 2 rpm.

  This silicone rubber composition was mixed with 0.1 part of a platinum catalyst (Pt concentration 1% by mass), cured at 150 ° C. for 5 minutes, and then cured at 150 ° C. for 1 hour in an oven. Table 1 shows the results of measuring hardness, tensile strength, elongation at break, and tear strength (crescent type) based on JIS-K6249.

Claims (8)

(A) An alkenyl group-containing linear organosilane that contains an alkenyl group bonded to a silicon atom at both ends of the molecular chain and does not have an alkenyl group in the middle of the molecular chain and has an average degree of polymerization of 2,000 or less at room temperature Polysiloxane: 100 parts by mass (B) Organohydrogenpolysiloxane containing two hydrogen atoms (SiH groups) bonded to silicon atoms in one molecule: 0.01-20 parts by mass (C) Bonded to silicon atoms Organohydrogenpolysiloxane containing 3 or more hydrogen atoms (SiH groups) in one molecule: 0.2 to 20 parts by mass (D) Fumed silica having a specific surface area of 130 m ² / g or more by BET method: 30 ~ 60 parts by mass (E) At least one silica surface treatment agent selected from silanes containing alkenyl groups and silazane compounds: Fumed silica 10 0.01-5 parts by mass with respect to parts by mass (F) addition reaction catalyst: containing a catalytic amount, molar ratio of SiH groups in component (B) to alkenyl groups in component (A) (SiH groups / Alkenyl group) is an addition curable silicone rubber composition that provides a cured silicone rubber having a durometer A hardness meter of 75 or more and an elongation at break of 300% or more. object.   The addition-curable silicone rubber composition according to claim 1, wherein the component (E) is 1,3-divinyl-1,1,3,3-tetramethyldisilazane.   The addition curable silicone rubber composition according to claim 1 or 2, further comprising (G) 1 to 40 parts by mass of a silica surface treating agent not containing an alkenyl group with respect to 100 parts by mass of the component (D).   Furthermore, (H) the siloxane unit containing an alkenyl group is 1 to 100 mol% in the total siloxane units, the alkenyl group is contained in the middle of the molecular chain, and the viscosity at 25 ° C. is 200,000 mPa · s or less. The addition-curable silicone rubber composition according to any one of claims 1 to 3, wherein the alkenyl group-containing organopolysiloxane is contained in an amount of 0.01 to 20 parts by mass with respect to 100 parts by mass of the component (A).   The addition curable silicone rubber composition according to claim 4, wherein the component (H) is 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane.   The addition-curable silicone rubber composition according to any one of claims 1 to 5, which has a viscosity at 25 ° C in the range of 50 to 5,000 Pa · s and is for liquid injection molding.   The addition-curable silicone rubber composition according to any one of claims 1 to 6, which provides a cured silicone rubber having a tear strength of 8 kN / m or more.   A silicone rubber having a durometer A hardness meter hardness of 75 or more and an elongation at break of 300% or more obtained by heat-curing the addition-curable silicone rubber composition according to any one of claims 1 to 7. Cured product.