JP4947309B2 - Oil-bleeding addition curable silicone rubber composition and cured product thereof - Google Patents

Description

  The present invention relates to a reactive volatile siloxane compound, in particular, an oil-bleeding addition-curable silicone having a low content of a volatile siloxane compound containing a hydrogen atom bonded to a silicon atom (hereinafter abbreviated as SiH functional group). The present invention relates to a rubber composition and a cured product thereof.

  Silicone rubber is widely used in various fields, taking advantage of heat resistance, cold resistance, electrical properties, and the like. Auto parts are used in oil seals, connector seals, rubber plugs, O-rings, diaphragms, distributor grommets, etc., especially in the areas of connectors and distributor grommets. As a result of pursuing workability, sealing performance after installation, waterproofness, and insulation, it is recognized that oil-bleedable silicone rubber that oils bleed on the surface of the molded product is effective. Is widely used.

  However, since the siloxane polymer forming the silicone rubber is produced by an equilibrium reaction of the siloxane oligomer with acid or alkali, the degree of polymerization is always called a considerable amount of low-molecular siloxane regardless of the degree of polymerization (ie, It is known that there are so-called non-functional cyclic siloxanes having no reactive groups such as SiH functional groups and alkenyl functional groups in the molecule, the number of silicon atoms in one molecule being 20 or less. ing. Such low molecular weight siloxane is removed by volatilization at high temperature under reduced pressure, but it is difficult to completely remove it, and it is 0.5% by mass (about 5,000 ppm) of about 1% by mass or less. Level will remain. These low-molecular siloxanes are slightly evaporated from the cured rubber and adhere to the surroundings not only in a high-temperature atmosphere but also at room temperature, resulting in cloudiness and turbidity, contact failure, adhesion inhibition, and surface hydrophobicity. It is known to cause various problems. In particular, automobile parts used in the engine room are exposed to high temperatures, but there are a large number of electrical wirings and electrical contacts, so contact failure due to these volatile components has become a particularly serious problem. These can be reduced considerably by post-curing the cured rubber at high temperature, but when the rubber is used in a sealed state or when it is used in combination with a resin with low heat resistance, it is exposed to high temperatures. There are problems such as being unable to.

  For example, JP-A-3-157474 (Patent Document 1) discloses an addition reaction curable silicone rubber adhesive having a low molecular siloxane content of 500 ppm or less having a vapor pressure of 10 mmHg or more at 200 ° C. JP-A-6-54405 (Patent Document 2) discloses a fixing roller having a polymerization degree of 20 or less and a low molecular siloxane content of 0.75 wt% or less. JP-A-4-311764 (Patent Document 3) discloses a method for obtaining a siloxane polymer having a low content of low molecular weight siloxane by extending the chain length with a polymer having SiH functional groups at both ends of the molecular chain. Japanese Patent Laid-Open No. 5-47437 (Patent Document 4) discloses a waterproof connector made of an addition reaction type liquid silicone rubber having a low-boiling siloxane content of 10 or less in polymerization and 75 ppm or less.

  However, even if the content of low-molecular siloxane is reduced in this way, the above-mentioned problems and low-molecular siloxane that volatilizes from the cured product and adheres to surrounding substances can be easily removed by means such as wiping with a solvent. There was a problem that it was difficult.

JP-A-3-157474 Japanese Examined Patent Publication No. 6-54405 Japanese Unexamined Patent Publication No. 4-3111764 JP-A-5-47437

  The present invention was made in view of the above circumstances, the amount of low-molecular siloxane components from the cured product is small, the occurrence of cloudiness and turbidity due to the volatilized low-molecular siloxane adhering to the surroundings, the cause of contact failure, adhesion An object of the present invention is to provide an oil-bleedable addition-curable silicone rubber composition suitable for automobile parts such as waterproof connectors that can obtain a cured product free from problems such as inhibition and hydrophobicity of the surface, and a cured product thereof.

As a result of intensive studies to achieve the above-mentioned object, the present inventors, as a low-molecular siloxane component, separately from such non-functional low-molecular siloxane component, reaction of SiH functional group or the like in the molecule. It has been found that a low-molecular cyclic siloxane component having a functional group is also contained in a considerable amount in the siloxane polymer forming the silicone rubber.
The non-functional low-molecular siloxane as described above is volatilized from a rubber cured product and can be easily removed by wiping with a solvent when adhering to a surrounding substance. The low molecular cyclic siloxane component possessed adheres to the substrate due to its reactivity and cannot be easily removed. Thus, since SiH functional group containing siloxane has reactivity, it discovered that there was a much bigger problem compared with non-functional low molecular siloxanes, such as a dimethylsiloxane type.

  However, the low molecular siloxanes exemplified in the above-mentioned JP-A-3-157474 (Patent Document 1) and JP-A-4-47437 (Patent Document 4) are non-functional type cyclic or linear siloxanes ( No mention is made of low molecular siloxanes containing SiH functional groups, only dimethylpolysiloxane). In addition, the low molecular siloxane disclosed in Japanese Patent Publication No. 6-54405 (Patent Document 2) is only described as a 3-20 mer cyclic polysiloxane, and there is no specific structure example. Is not described at all. Further, JP-A-4-311764 (Patent Document 3) does not describe a specific structure of low molecular siloxane. In addition to these, various patents relating to low molecular weight siloxanes have been filed, but none of the low molecular weight siloxanes containing SiH functional groups have been described.

As a result of further studies, the present inventors have found that in an addition reaction curable silicone rubber composition, the polymer component itself having a SiH functional group is indispensable for curing the composition as a crosslinking agent. The content of the volatile low-molecular cyclic siloxane component having a SiH functional group derived from a crosslinking agent contained in the polymer component having a SiH functional group (that is, an organohydrogenpolysiloxane component) is below a specific level. It was found that control is important in solving the above problems.
That is, in the addition-curable silicone rubber composition, the content of the low-molecular siloxane having a reactive group such as a SiH functional group having a polymerization degree of 10 or less, particularly a low-molecular cyclic siloxane, is 0.5% by mass of the total composition. By making the following, various problems such as poor contact around the cured product due to volatilization of low molecular weight siloxane, poor adhesion, turbid appearance, and SiH functional low molecular weight siloxane reacts with the surrounding substances and adheres. Thus, the present inventors have found that the problem that it cannot be easily removed can be solved, and the present invention has been made.

（式中、ｎは１〜９の整数、ｍは１〜９の整数、かつ、ｎ＋ｍは３〜１０の整数である。Ｒは炭素数１〜１０の非置換又は置換の１価炭化水素基で、同一であっても異なっても良い。）
〔５〕式（５）において、ｎが１〜９の整数、ｍが１〜３の整数であり、かつ、ｎ＋ｍが３〜１０の整数である〔４〕記載のオイルブリード性付加硬化型シリコーンゴム組成物。
〔６〕重合度が１０以下でＳｉＨ官能基を有しないオルガノポリシロキサンの含有量が（Ａ）及び（Ｂ）成分中０．５質量％以下である〔１〕〜〔５〕のいずれかに記載のオイルブリード性付加硬化型シリコーンゴム組成物。
〔７〕重合度が１０以下でＳｉＨ官能基を有しないオルガノポリシロキサンが、下記式（２）で示される環状オルガノポリシロキサンである〔６〕記載のオイルブリード性付加硬化型シリコーンゴム組成物。

（式中、ｘは３〜１０の整数であり、Ｒは炭素数１〜１０の非置換又は置換の１価炭化水素基で、同一であっても異なっても良い。）
〔８〕（Ｃ）成分が、重合度（分子中の珪素原子の数）が１１以上の、直鎖状、環状、分岐状又は三次元網状構造のオルガノハイドロジェンポリシロキサンであることを特徴とする〔１〕〜〔７〕のいずれかに記載のオイルブリード性付加硬化型シリコーンゴム組成物。
〔９〕（Ｃ）成分が、下記式（４）で示される直鎖状オルガノハイドロジェンポリシロキサンである〔８〕記載のオイルブリード性付加硬化型シリコーンゴム組成物。

（式中、ｙは１〜９８の整数、ｚは２〜５０の整数、かつ、ｙ＋ｚは９〜１００の整数である。Ｒ²は〔１〕記載の通りであり、同一であっても異なっても良い。Ｒ³はＲ²又は水素原子である。）
〔１０〕（Ｃ）成分の分子中の全炭素原子数に対する珪素原子に結合する全水素原子数が、モル比で、０．０５＜［水素原子］／［炭素原子］＜０．７である〔１〕〜〔９〕のいずれかに記載のオイルブリード性付加硬化型シリコーンゴム組成物。
〔１１〕重合度が１０以下でＳｉＨ官能基を一分子中に１個以上含有するオルガノポリシロキサンの含有量が（Ｃ）成分中１０．０質量％以下である〔１〕〜〔１０〕のいずれかに記載のオイルブリード性付加硬化型シリコーンゴム組成物。
〔１２〕〔１〕〜〔１１〕のいずれかに記載のオイルブリード性付加硬化型シリコーンゴム組成物を硬化させてなるオイルブリード性シリコーンゴム硬化物。
〔１３〕硬化物中における、重合度が１０以下でＳｉＨ官能基を一分子中に１個以上含有するオルガノポリシロキサンの含有量が０．２質量％以下である〔１２〕記載のオイルブリード性シリコーンゴム硬化物。
Accordingly, the present invention provides the following oil-bleedable addition curable silicone rubber composition and cured product thereof.
[1] (A) Organopolysiloxane R ¹ _a SiO _{(4-a) / 2} (1 ₎ containing an alkenyl group bonded to at least two silicon atoms in one molecule represented by the following average composition formula (1) )
(Wherein R ¹ is an unsubstituted or fluorine-substituted monovalent hydrocarbon group selected from an alkyl group, an alkenyl group, an aryl group, an aralkyl group, and a trifluoropropyl group having 1 to 8 carbon atoms; A positive number of .5 to 2.8.): 100 parts by mass,
(B) an organic group bonded to a silicon atom contains a phenyl group, the content of the phenyl group is 10 to 35 mol% of the total organic group, and does not contain a silicon atom-bonded hydrogen atom and an alkenyl group; Phenyl group-containing organopolysiloxane having a viscosity at 25 ° C. of 10 to 5,000 mPa · s: 0.5 to 20 parts by mass
(C) Organohydrogenpolysiloxane containing at least two hydrogen atoms (SiH functional group) bonded to a silicon atom represented by the following average composition formula (3) in one molecule: R ² _b H _c SiO _{(4-bc ) / 2} (3)
(Wherein R ² is an unsubstituted or fluorine-substituted monovalent hydrocarbon group selected from an alkyl group, an aryl group, an aralkyl group and a trifluoropropyl group having 1 to 8 carbon atoms, and b is 0.7 to 2.1 and c are 0.001 to 1.0, and b + c is a positive number satisfying 0.8 to 3.0.): 0.3 to 20 parts by mass,
(D) Addition reaction catalyst: The organohydrogenpolysiloxane which contains a catalyst amount and (C) component is heated at 180 ° C. for 6 hours under stirring under a reduced pressure of 100 Pa, and then blown with nitrogen gas. It is obtained by removing low molecular siloxane components including SiH group-containing low molecular siloxane by bubbling for 4 hours and then flowing in a thin film of 100 μm or less on a hot plate heated to 200 ° C. under a reduced pressure of 20 Pa or less. Oil-bleeding addition reaction curing type in which the degree of polymerization is 10 or less and the content of organopolysiloxane containing one or more SiH functional groups in one molecule is 0.20% by mass or less based on the entire composition Silicone rubber composition.
[2] The molar ratio of the SiH functional group in the component (C) to the silicon atom-bonded alkenyl group in the component (A) is in the range of SiH / alkenyl group (molar ratio) = 0.6 to 3.0. [1] The oil-bleeding addition-curable silicone rubber composition according to [1].
[3] The organopolysiloxane having a degree of polymerization of 10 or less and containing at least one SiH functional group in one molecule is an organohydrogensiloxane-diorganosiloxane cyclic copolymer. Oil-bleeding addition-curable silicone rubber composition.
[4] The oil according to [3], wherein the organopolysiloxane having a degree of polymerization of 10 or less and containing at least one SiH functional group in a molecule is a cyclic organohydrogenpolysiloxane represented by the following formula (5): Bleed addition-curable silicone rubber composition.

(In the formula, n is an integer of 1 to 9, m is an integer of 1 to 9, and n + m is an integer of 3 to 10. R is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms. And may be the same or different.)
[5] Oil-bleeding addition-curable silicone according to [4], wherein in formula (5), n is an integer of 1 to 9, m is an integer of 1 to 3, and n + m is an integer of 3 to 10. Rubber composition.
[6] The content of the organopolysiloxane having a degree of polymerization of 10 or less and having no SiH functional group is 0.5% by mass or less in the components (A) and (B) [1] to [5] The oil bleedable addition curable silicone rubber composition described.
[7] The oil-bleeding addition-curable silicone rubber composition according to [6], wherein the organopolysiloxane having a degree of polymerization of 10 or less and having no SiH functional group is a cyclic organopolysiloxane represented by the following formula (2).

(In the formula, x is an integer of 3 to 10, and R is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, which may be the same or different.)
[8] The component (C) is an organohydrogenpolysiloxane having a degree of polymerization (number of silicon atoms in the molecule) of 11 or more and having a linear, cyclic, branched or three-dimensional network structure. The oil-bleeding addition-curable silicone rubber composition according to any one of [1] to [7].
[9] The oil-bleeding addition curable silicone rubber composition according to [8], wherein the component (C) is a linear organohydrogenpolysiloxane represented by the following formula (4).

(In the formula, y is an integer of 1 to 98, z is an integer of 2 to 50, and y + z is an integer of 9 to 100. R ² is as described in [1]. R ³ is R ² or a hydrogen atom.)
[10] The total number of hydrogen atoms bonded to silicon atoms relative to the total number of carbon atoms in the molecule of component (C) is 0.05 <[hydrogen atom] / [carbon atom] <0.7 in terms of molar ratio. [1] The oil-bleeding addition curable silicone rubber composition according to any one of [9].
[11] The content of organopolysiloxane having a degree of polymerization of 10 or less and containing at least one SiH functional group in one molecule is 10.0% by mass or less in component (C). The oil bleedable addition curable silicone rubber composition according to any one of the above.
[12] A cured oil bleedable silicone rubber composition obtained by curing the oil bleedable addition curable silicone rubber composition according to any one of [1] to [11].
[13] Oil bleedability according to [12], wherein the cured product has a degree of polymerization of 10 or less and an organopolysiloxane content of one or more SiH functional groups in one molecule is 0.2% by mass or less. Silicone rubber cured product.

  The oil bleed addition curable silicone rubber composition of the present invention has a low molecular weight that reacts with and adheres to a peripheral material containing at least one SiH functional group in one molecule from the cured product with a polymerization degree of 10 or less. The volatilization of the siloxane component is small, and the cured product can be free from problems such as cloudiness and turbidity due to adhesion of the low molecular weight siloxane component to the surroundings, contact failure, adhesion inhibition or re-adhesion, and surface hydrophobicity.

  The organopolysiloxane having an average of at least two alkenyl groups in one molecule as the component (A) of the present invention is the main component (base polymer) of the composition and does not contain a phenyl group in the molecule. In a certain point, it is differentiated from the component (B) described later, and as the alkenyl group-containing organopolysiloxane, those represented by the following average composition formula (1) can be suitably used. Here, the average value of alkenyl groups in one molecule is the number average value of alkenyl groups per molecule determined from the polystyrene-equivalent number average molecular weight (number average degree of polymerization) in GPC (gel permeation chromatography) analysis. means.

R ¹ _a SiO _{(4-a) / 2} (1)
Wherein R ¹ is an unsubstituted or substituted monovalent hydrocarbon group having the same or different carbon number of 1 to 10, preferably 1 to 8, and a is 1.5 to 2.8, preferably 1. (It is a positive number of 8 to 2.5, more preferably 1.95 to 2.05.)

Here, as the unsubstituted or substituted monovalent hydrocarbon group bonded to the silicon atom represented by R ¹ , a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, Aryl group, benzyl group, phenylethyl group, phenylpropylene group, except for alkyl groups such as pentyl group, neopentyl group, hexyl group, cyclohexyl group, octyl group, nonyl group, decyl group, etc., tolyl group, xylyl group, naphthyl group, etc. 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., for example, chloromethyl group, chloro Propyl group, bromoethyl group, trifluoropropyl group, but cyanoethyl group and the like, it is preferable that as the R ¹ other than the alkenyl group is unsubstituted or substituted alkyl group, with methyl being especially more than 90 mol% of the total R ¹ It is preferable that all R ¹ except the alkenyl group is a methyl group.

Further, at least two of R ¹ must be alkenyl groups (preferably having 2 to 8 carbon atoms, more preferably 2 to 6 carbon atoms, and particularly preferably a vinyl group). The alkenyl group content in the organopolysiloxane is 5.0 × 10 ^{−6 to} 5.0 × 10 ⁻³ mol / g, particularly 1.0 × 10 ^{−5 to} 1.0 × 10 ⁻³ mol / g. g is preferable. If the amount of the alkenyl group is less than 5.0 × 10 ⁻⁶ mol / g, the rubber hardness is low and sufficient sealing properties may not be obtained, and more than 5.0 × 10 ⁻³ mol / g. In some cases, the crosslink density becomes too high and the rubber becomes brittle. This alkenyl group may be bonded to a silicon atom at the end of the molecular chain, may be bonded to a silicon atom in the middle of the molecular chain, or may be bonded to both.

  The structure of the organopolysiloxane usually has a linear structure in which the main chain is basically composed of repeating diorganosiloxane units, and both ends of the molecular chain are blocked with triorganosiloxy groups. A branched structure, a ring structure, etc. may be sufficient. The molecular weight is not particularly limited, and is a liquid having a low viscosity (usually a viscosity at 25 ° C. by a rotational viscometer or the like is 100 to 1,000,000 mPa · s, preferably 300 to 500,000 mPa · s, more preferably From about 1,000 to 100,000 mPa · s) to a raw rubbery form having a high viscosity (or almost no fluidity at room temperature (25 ° C.)) (for example, the viscosity at 25 ° C. exceeds 1,000,000 mPa · s) In particular, those having a high viscosity (high polymerization degree) of about 2,000,000 to 10,000,000 mPa · s (average polymerization degree of about 3,000 to 10,000) or more can be used.

  Furthermore, as the alkenyl group-containing organopolysiloxane (base polymer) of the component (A), the non-functional (that is, functionalities involved in the hydrosilylation addition reaction between the component (A) and the component (C) described in the prior art). It is preferable that the content of the low molecular weight siloxane component (which does not have a functional group) is reduced to a predetermined amount or less, specifically, the content of the low molecular weight siloxane not having a functional group having a polymerization degree of 10 or less. In the component (A), the amount is 0.5% by mass or less (0 to 0.5% by mass), preferably 0.2% by mass or less (0 to 0.2% by mass), more preferably 0.1% by mass. % Or less (0 to 0.1% by mass). If the content of the non-functional low-molecular siloxane component exceeds 0.5% by mass, not only will it adversely affect peripheral parts by volatilization itself, but also volatilization of reactive low-molecular siloxanes having SiH functional groups. There are problems such as making it easier.

（式中、ｘは３〜１０の整数であり、Ｒは炭素数１〜１０の非置換又は置換の１価炭化水素基で、同一であっても異なっても良く、前記Ｒ¹と同様のものが例示できるが、アルケニル基に代表される脂肪族不飽和基などの架橋反応に関与する官能基を含有しないことが好ましい。） More specific examples of such non-functional low-molecular siloxane components include diorganocyclopolysiloxanes having a cyclic structure represented by the following formula (2).

(In the formula, x is an integer of 3 to 10, R is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, which may be the same or different, and is the same as R ¹ described above. (It is preferable that a functional group involved in a crosslinking reaction such as an aliphatic unsaturated group represented by an alkenyl group is not contained.)

  As a method of reducing the non-functional low-molecular siloxane component, a method of vaporizing and removing the low-molecular siloxane component under high-temperature heating of about 200 to 300 ° C. under reduced pressure, or during or after the vaporization removal, Further, there is a method for promoting vaporization by blowing an inert gas.

  In the alkenyl group-containing organopolysiloxane of component (A), a reactive low molecular siloxane having a polymerization degree of 10 or less and containing at least one SiH functional group in one molecule is usually substantially It is not contained at a level that causes problems.

  The (B) component phenyl group-containing organopolysiloxane imparts performance such as workability at the time of assembly, airtightness, waterproofness, etc. by bleeding from the molded product after the rubber composition is cured. Incompatible with the alkenyl group-containing organopolysiloxane of component (A) and not involved in the crosslinking reaction during rubber curing (that is, silicon-bonded alkenyl groups and silicon-bonded hydrogen atoms involved in hydrosilylation addition reaction in the molecule) (It does not contain a functional group such as (SiH group)). As such, the organic group bonded to the silicon atom contains a phenyl group, preferably the phenyl group content is 10 to 35 mol%, more preferably 15 to 32 mol% of the total organic groups. Is. If it is less than 10 mol%, it may not bleed from the cured product, and if it exceeds 35 mol%, it may be separated during storage before curing.

The phenyl group-containing organopolysiloxane preferably does not contain a functional group involved in a crosslinking reaction such as an alkenyl group or a silicon atom-bonded hydrogen atom (SiH functional group). Furthermore, it is more preferable not to have a functional group such as a silanol group, an alkoxysilyl group, an epoxy group, or an amino group.
Specifically, as the component (B), both ends of the molecular chain are blocked with either a trimethylsiloxy group, a hydroxydimethylsiloxy group, a methyldiphenylsiloxy group, or a dimethylphenylsiloxy group, a dimethylsiloxane / diphenylsiloxane copolymer, Examples include linear methylphenyl silicone oil such as dimethylsiloxane / methylphenylsiloxane copolymer.

The viscosity of such a phenyl group-containing organopolysiloxane is preferably 10 to 5,000 mPa · s (25 ° C.), more preferably 50 to 1,000 mPa · s, and still more preferably 100 to 500 mPa · s from the viewpoint of bleeding. If the s is less than 10 mPa · s, the compatibility with the molded product may be high and the bleed property may be insufficient. If it is higher than 5,000 mPa · s, the initial bleed property may be deteriorated, and the bleed may occur. There may be a problem that the surface is sticky due to oil. The viscosity can be measured with a rotational viscometer or the like.
Moreover, these phenyl group containing organopolysiloxanes may mix | blend only 1 type, and may mix 2 or more types from which phenyl group content and molecular weight differ.

  The compounding amount of these phenyl group-containing organopolysiloxanes is 0.5 to 20 parts by mass, preferably 1 to 10 parts by mass with respect to 100 parts by mass of component (A), and the compounding amount is less than 0.5 parts by mass. Sufficient bleed property cannot be obtained, and if it exceeds 20 parts by mass, mold stains will occur or the rubber properties will be adversely affected.

  Furthermore, the phenyl group-containing organopolysiloxane of component (B) has a functional group described in the prior art (that is, has a functional group involved in the hydrosilylation addition reaction between component (A) and component (C)). It is preferable that the content of the low molecular siloxane component is reduced to a predetermined amount or less. Specifically, the content of the low molecular siloxane having no functional group having a polymerization degree of 10 or less is ( In the components A) and (B), 0.5% by mass or less (0-0.5% by mass), preferably 0.2% by mass or less (0-0.2% by mass), more preferably 0.1% by mass. % Or less (0 to 0.1% by mass) is desirable. If the content of the non-functional low-molecular siloxane component exceeds 0.5% by mass, not only will it adversely affect peripheral parts by volatilization itself, but also volatilization of reactive low-molecular siloxanes having SiH functional groups. Problems such as making it easy may occur.

（式中、ｘは３〜１０の整数であり、Ｒは炭素数１〜１０の非置換又は置換の１価炭化水素基で、同一であっても異なっても良く、前記Ｒ¹と同様のものが例示できるが、アルケニル基に代表される脂肪族不飽和基などの架橋反応に関与する官能基を含有しないことが好ましい。） More specific examples of such non-functional low-molecular siloxane components include diorganocyclopolysiloxanes having a cyclic structure represented by the following formula (2).

(In the formula, x is an integer of 3 to 10, R is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, which may be the same or different, and is the same as R ¹ described above. (It is preferable that a functional group involved in a crosslinking reaction such as an aliphatic unsaturated group represented by an alkenyl group is not contained.)

  As a method of reducing the non-functional low-molecular siloxane component, a method of vaporizing and removing the low-molecular siloxane component under high-temperature heating of about 200 to 300 ° C. under reduced pressure, or during or after the vaporization removal, Further, there is a method for promoting vaporization by blowing an inert gas.

  In addition, in the phenyl group-containing organopolysiloxane of the component (B), a reactive low molecular siloxane having a degree of polymerization of 10 or less and containing one or more SiH functional groups in one molecule is usually substantially It is not contained at a level that causes problems.

The organohydrogenpolysiloxane of component (C) is, for example, the following average composition formula (3)
R ² _b H _c SiO _{(4-bc) / 2} (3)
(In the formula, R ² is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, b is 0.7 to 2.1, c is 0.001 to 1.0, and b + c. Is a positive number satisfying 0.8 to 3.0.)
And has at least 2 (usually 2 to 300), preferably 3 or more (for example, 3 to 200), more preferably about 4 to 150 silicon-bonded hydrogen atoms in one molecule. One or two or more of them are preferably used.

Here, as the monovalent hydrocarbon group for R ² , 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 Group, nonyl group, alkyl group such as decyl group, aryl group such as phenyl group, tolyl group, xylyl group, naphthyl group, aralkyl group such as benzyl group, phenylethyl group, phenylpropyl group, and hydrogen atom of these groups Are substituted with a halogen atom such as fluorine, bromine or chlorine, a cyano group, such as chloromethyl group, chloropropyl group, bromoethyl group, trifluoropropyl group, cyanoethyl group, etc. Those having no group unsaturated group are preferred. Moreover, b is preferably 0.8 to 2.0, c is preferably 0.01 to 1.0, and b + c is preferably 1.0 to 2.5.

In this case, the number (or degree of polymerization) of silicon atoms in one molecule is 2 to 300, preferably 3 to 250, more preferably 4 to 200, still more preferably 5 to 150, and particularly preferably 11 to 11. About 100 pieces of liquid at room temperature (25 ° C.) (usually about 0.1 to 1,000 mPa · s, preferably about 0.5 to 500 mPa · s with a rotational viscometer or the like) are preferably used.
The hydrogen atom bonded to the silicon atom may be bonded to any silicon atom at the molecular chain end or in the middle of the molecular chain (molecular chain non-terminal), or may be located at both. .

  The molecular structure of the organohydrogenpolysiloxane may be any of linear, cyclic, branched, and three-dimensional network structures, but the linear, branched, or three-dimensional network organohydrogenpolysiloxane. Or one or more selected from organohydrogencyclopolysiloxanes (that is, cyclic polymers composed only of organohydrogensiloxane units), and the degree of polymerization (in the molecule The number of silicon atoms is preferably 11 or more, and is preferably one or more selected from organohydrogenpolysiloxanes containing at least 4 SiH functional groups in one molecule, In particular, the degree of polymerization (number of silicon atoms in the molecule) is 11 or more, and at least 4 Si atoms in one molecule. Containing functional groups, linear, cyclic, is preferably branched or is one or more selected from the organohydrogenpolysiloxane of the three-dimensional network structure.

Here, examples of the linear organohydrogenpolysiloxane include those exemplified by the following formula (4).

In formula (4), y is an integer of 1 to 98, z is an integer of 2 to 50, and y + z is an integer of 9 to 100. R ² is the same as above. R ³ is R ² or a hydrogen atom. Furthermore, 90% or more of all R ² are preferably methyl groups.

In the case of an organohydrogenpolysiloxane having a cyclic structure, all the repeating units are composed of only organohydrogensiloxane units (for example, bifunctional siloxane units represented by R ² HSiO _2/2 ). Or a diorganosiloxane containing a diorganosiloxane unit (for example, R ² ₂ SiO _2/2 ) as part of the repeating unit in addition to the organohydrogensiloxane unit in the molecule. In the case of an organohydrogensiloxane cyclic copolymer, the degree of polymerization (the number of silicon atoms in the molecule) is a highly polymerized cyclic product having a molecular weight of 11 or more, or the number of SiH functional groups in the molecule (ie, The number of organohydrogensiloxane units in the molecule is 4) or more, high concentration SiH functionality It shall be desirable.

The ratio of the total number of hydrogen atoms bonded to silicon atoms to the total number of carbon atoms in the molecule (for example, the total number of carbon atoms in R ² ) is a molar ratio, preferably 0.05 <[hydrogen atom] / [Carbon atom] <0.7, more preferably 0.1 <[hydrogen atom] / [carbon atom] ≦ 0.6, still more preferably 0.15 ≦ [hydrogen atom] / [carbon atom] ≦ 0.5 Particularly preferably, 0.2 ≦ [hydrogen atom] / [carbon atom] ≦ 0.45. If it is 0.7 or more, the density of the SiH functional group may be too high, and foaming may occur, and if it is 0.05 or less, the reaction may be too slow to cause molding defects.

Specific examples of the organohydrogenpolysiloxane of component (C) include 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, tris (hydrogen Dimethylsiloxy) methylsilane, tris (hydrogendimethylsiloxy) phenylsilane, methylhydrogencyclopolysiloxane, trimethylsiloxy group-blocked methylhydrogenpolysiloxane, trimethylsiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane copolymer Dimethylpolysiloxane blocked with dimethylhydrogensiloxy group at both ends, dimethylsiloxane / methylhydrogensiloxane copolymer blocked with dimethylhydrogensiloxy group at both ends, trimethylsilane at both ends Xoxy group-blocked methylhydrogensiloxane / diphenylsiloxane copolymer, both ends trimethylsiloxy group-blocked methylhydrogensiloxane / diphenylsiloxane / dimethylsiloxane copolymer, both ends trimethylsiloxy group-blocked methylhydrogensiloxane / methylphenylsiloxane / dimethyl Siloxane copolymer, dimethylhydrogensiloxy group-capped methylhydrogensiloxane / dimethylsiloxane / diphenylsiloxane copolymer, dimethylhydrogensiloxy group-capped methylhydrogensiloxane / dimethylsiloxane / methylphenylsiloxane copolymer, (CH _{3) 2} HSiO _1/2 units and (CH _{3) 3} made of SiO _1/2 units and SiO _4/2 units, copolymers, (CH _{3) 2} HSiO _1/2 single And copolymers comprising SiO _4/2 units, (CH _{3) 2} HSiO _1/2 units and the SiO _4/2 units (C ₆ H ₅₎ consisting of SiO _3/2 units, copolymers composed like and, In each of these exemplary compounds, those in which part or all of the methyl group is substituted with another alkyl group such as an ethyl group or a propyl group, a phenyl group, or the like can be mentioned.

  The compounding amount of the organohydrogenpolysiloxane of component (C) is 0.3 to 20 parts by mass, preferably 0.5 to 15 parts by mass, more preferably 0.8 to 100 parts by mass of component (A). 10 parts by mass. When the blending amount of the component (C) is too small, the number of crosslinking points decreases (crosslinking density decreases), so that a rubber-like elastic body (rubber cured product) cannot be obtained. After all, sufficient rubber properties cannot be obtained.

  Further, the molar ratio of the hydrogen atom (SiH functional group) bonded to the silicon atom of the organopolysiloxane in the component (C) to the total amount of alkenyl groups bonded to the silicon atom in the component (A) is SiH functional group. / Alkenyl group = 0.6 to 3.0, particularly preferably 0.8 to 2.5, and more preferably 1.2 to 2.2. If this ratio is less than 0.6, a sufficiently crosslinked rubber may not be obtained. If it is more than 3.0, a large amount of unreacted SiH functional group-containing low-molecular siloxane remains after curing. There is a case.

  As the addition reaction catalyst for component (D), platinum black, platinous chloride, chloroplatinic acid, a reaction product of chloroplatinic acid and a monohydric alcohol, a complex of chloroplatinic acid and olefins, chloroplatinic acid and vinyl Known white metal metal catalysts such as complexes with siloxane, platinum-based catalysts such as platinum bisacetoacetate, palladium-based catalysts, rhodium-based catalysts and the like can be mentioned. In addition, the addition amount of this addition reaction catalyst can be made into a catalytic amount. Usually, the total mass of the (A), (B), and (C) components as the platinum group metal, in particular, the (A) component and ( C) 0.5 to 1,000 ppm, particularly 1 to 500 ppm relative to the total mass with the component.

  In addition to these components, if necessary, fillers such as fumed silica, precipitated silica, quartz powder, diatomaceous earth, calcium carbonate, conductive agents such as carbon black, conductive zinc white, metal powder, nitrogen-containing compounds And hydrosilylation reaction control agents such as acetylene compounds, phosphorus compounds, nitrile compounds, carboxylates, tin compounds, mercury compounds, sulfur compounds, heat-resistant agents such as iron oxide and cerium oxide, internal mold release agents such as dimethyl silicone oil, It is optional to add an adhesiveness imparting agent, a thixotropic property imparting agent and the like within a range not impairing the object of the present invention.

  The addition-curable silicone rubber composition of the present invention can be prepared by uniformly mixing the above components using a normal mixing stirrer such as a kneader or a planetary mixer, a kneader or the like.

（式中、ｎは１〜９の整数、ｍは１〜９の整数（特には１〜３の整数）、かつ、ｎ＋ｍは３〜１０の整数である。Ｒは炭素数１〜１０の非置換又は置換の１価炭化水素基で、同一であっても異なっても良く、前記Ｒ¹と同様のものが例示できるが、アルケニル基に代表される脂肪族不飽和基などの架橋反応に関与する官能基を含有しないことが好ましい。）
で示される環状オルガノハイドロジェンポリシロキサン、とりわけ分子中のＳｉＨ官能性基の数（即ち、分子中のオルガノハイドロジェンシロキサン単位の繰返し数ｍ）が１〜３個とＳｉＨ官能性基濃度が低く、かつ重合度（分子中の珪素原子数）が１０以下の低分子環状シロキサンを含むものであるが、この含有量が、組成物全体の質量に対して、特には（Ａ），（Ｂ），（Ｃ），（Ｄ）成分の合計量に対し０．５質量％以下（０〜０．５質量％）、好ましくは０．３０質量％以下（０〜０．３０質量％）、より好ましくは０．２０質量％以下（０〜０．２０質量％）に低減されたものである。これは、ＳｉＨ官能基を有する低分子シロキサンが、従来の無官能性の低分子シロキサンと同様に硬化物中に残存した場合、雰囲気中に揮発して周囲に付着することにより様々な問題を引き起こすだけでなく、更には、ＳｉＨ官能基を有するため、雰囲気中に揮発し、一旦周辺の物質に付着したＳｉＨ官能基低分子シロキサンは、溶剤で拭き取る等の手段では容易に取り除くことも困難であるという問題を回避するために必須とされるものである。 The addition curable silicone rubber composition of the present invention comprising the above components (A) to (D) and other components as necessary is mainly derived from organohydrogenpolysiloxane as a crosslinking agent for component (C). An organopolysiloxane having at least one hydrogen atom (SiH functional group) bonded to a silicon atom with a degree of polymerization of 10 or less, for example, a diorganosiloxane / organohydro with a degree of polymerization of 10 or less Genosiloxane cyclic copolymer, especially the following formula (5)

(In the formula, n is an integer of 1 to 9, m is an integer of 1 to 9 (particularly an integer of 1 to 3), and n + m is an integer of 3 to 10. R is a non-carbon number of 1 to 10) A substituted or substituted monovalent hydrocarbon group which may be the same or different and can be exemplified by the same as R ¹ , but is involved in a crosslinking reaction such as an aliphatic unsaturated group represented by an alkenyl group. It is preferable that the functional group is not contained.)
The number of SiH functional groups in the molecule (that is, the number of repeating organohydrogensiloxane units m in the molecule) is 1 to 3 and the SiH functional group concentration is low, In addition, a low molecular cyclic siloxane having a degree of polymerization (number of silicon atoms in the molecule) of 10 or less is included, and this content is particularly (A), (B), (C ), (D) 0.5% by mass or less (0 to 0.5% by mass), preferably 0.30% by mass or less (0 to 0.30% by mass), more preferably 0. It is reduced to 20% by mass or less (0 to 0.20% by mass). This is because when a low molecular siloxane having a SiH functional group remains in a cured product as in the case of a conventional non-functional low molecular siloxane, it volatilizes in the atmosphere and adheres to the surroundings, causing various problems. In addition, since it has a SiH functional group, it is difficult to easily remove the SiH functional low molecular weight siloxane that has volatilized in the atmosphere and once adhered to the surrounding material by means such as wiping with a solvent. This is essential to avoid the problem.

  In this case, the organohydrogenpolysiloxane of component (C) has at least one hydrogen atom (SiH functional group) bonded to a silicon atom with a polymerization degree of 10 or less (particularly 1 to 3) in one molecule. It is preferable that the content of the low molecular organopolysiloxane to be contained, particularly the cyclic low molecular organopolysiloxane, especially the organohydrogensiloxane-diorganosiloxane cyclic copolymer of the above formula (5) is as small as possible, The content of the low molecular weight organopolysiloxane in the component (C) is 0.5 mass with respect to the entire composition, particularly with respect to the total amount of the components (A), (B), (C), (D). % Is acceptable as long as the content can achieve a% or less. However, the content of the SiH group-containing low molecular weight organopolysiloxane is 10.0% by mass or less (0 to 10.0% by mass), preferably 5.0% by mass or less (0 to 0%) in the component (C). 5.0% by mass), more preferably 3.0% by mass or less (0-3.0% by mass), and still more preferably 2.0% by mass or less (0-2.0% by mass).

Of these SiH group-containing low-molecular cyclic siloxanes, some or most of the addition-reactive crosslinking agent is incorporated into the siloxane matrix in the cured product by the crosslinking reaction of rubber, and in particular, the SiH functional group in the molecule. (Especially, SiH groups in bifunctional siloxane units represented by R ² HSiO _2/2 units, etc., etc., and relatively additional reactivity as hydrogen atoms bonded to silicon atoms in the middle of the molecular chain (non-terminal)) The number of SiH groups is low) and the concentration of SiH functional groups is low, and the molecule has one or more diorganosiloxane units such as R ² ₂ SiO _2/2 units, and the degree of polymerization Since low molecular cyclic siloxanes (number of silicon atoms in the molecule) of 10 or less have low addition reactivity, they remain as free low molecular siloxanes having unreacted SiH functional groups in the cured product. End up. If this volatilizes in the atmosphere at the time of storage or use and adheres to peripheral parts, it causes a great number of problems such as contact failure, adhesion failure, surface hydrophobicity, and appearance change. In particular, if the SiH group-containing low-molecular cyclic siloxane remains in the component (C) in an amount of more than 10.0% by mass, it may remain in a large amount even after curing.

Any method may be used to remove the SiH group-containing low molecular siloxane, but it is removed by heat treatment at a high temperature for a long time as applied to the removal of conventional non-functional low molecular siloxane. This method is not preferable because of the high reactivity of the SiH functional group. The temperature for removing the SiH group-containing low molecular siloxane is preferably 210 ° C. or lower, more preferably 200 ° C. or lower. When the temperature is higher than 210 ° C., it is necessary to use a device such as a thin-film distiller where the oil is not exposed to a high temperature for a long time. In the case of a temperature of 210 ° C. or lower, a method of promoting volatilization of low molecular siloxane, such as not only sufficient stirring in the apparatus but also forced blowing of inert gas (bubbling) is preferable.
As a method for volatilizing the low molecular weight siloxane, a method of volatilizing out of the system by high-temperature stirring under reduced pressure is generally used. In this case, it is preferable to volatilize at a temperature of 150 to 210 ° C. for 10 minutes to 10 hours under a reduced pressure of 1,000 to 1 Pa.

The total content of the non-functional low-molecular siloxane and the SiH-containing low-molecular siloxane in the entire silicone rubber composition is 1% by mass or less (0 to 1% by mass), particularly 0.8% by mass or less (0 to 0%). .8 mass%).
In the present invention, these low molecular siloxane contents are measured by adding 10 cc of acetone to 1 g of a sample collected in a sample bottle and allowing it to stand at room temperature (25 ° C.) for 24 hours, and then extracting the low molecular siloxane content in the acetone. Molecular siloxane is measured by gas chromatographic analysis (FID detector). In this case, the non-functional low molecular siloxane component and the SiH-containing low molecular siloxane component can be identified and discriminated by GC-MS and Si ²⁹ -NMR.

  The curing conditions of the addition curable silicone rubber composition of the present invention may be the same as those of known addition reaction curable silicone rubber compositions. For example, the curing may be sufficiently carried out at room temperature, but may be heated as necessary. In this case, it can be cured by heating at 80 to 250 ° C., particularly 120 to 220 ° C. for 3 seconds to 10 minutes, particularly 5 seconds to 3 minutes.

  Regarding the cured silicone rubber obtained by curing the silicone rubber composition of the present invention, the SiH group-containing low-molecular siloxane is 0.2% by mass or less based on the entire cured product, as in the composition before curing ( 0 to 0.2% by mass), preferably 0.1% by mass or less (0 to 0.1% by mass), more preferably 0.08% by mass or less (0 to 0.08% by mass). The total of the low molecular siloxane and the SiH group-containing low molecular siloxane is 1% by mass or less (0 to 1% by mass), preferably 0.5% by mass or less (0 to 0.5% by mass), particularly 0.2% by mass or less. (0 to 0.2% by mass) is obtained.

The oil bleed cured product of the addition curable silicone rubber composition thus obtained is a cured rubber product because the amount of low molecular siloxane, particularly the low molecular siloxane component having a reactive group, is less than a specific amount. The low-molecular-weight siloxane from volatilization is less volatilized, and problems such as cloudiness and turbidity due to adhesion of the low-molecular-weight siloxane to the surroundings, contact failure, adhesion inhibition, and surface hydrophobicity can be solved.
The cured products can be suitably used as oil seals, connector parts packing, rubber plugs, O-rings, diaphragms, distributor grommets and other automotive parts, in particular, connector cases, wire seals or mat seals. .

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited to these. In the following examples, the content of the non-functional low-molecular siloxane in the alkenyl group-containing organopolysiloxane (base polymer) and the content of the SiH-functional low-molecular siloxane in the crosslinking agent are determined by GC-MS analysis and Si. ^29- NMR was identified and analyzed, and the non-functional and SiH-functional low molecular siloxane content in the entire composition and in the cured silicone rubber was determined according to the method for measuring the low molecular siloxane content described above. This was identified and analyzed by GC-MS analysis and Si ²⁹ -NMR after acetone extraction.

[Reference example]
Low molecular siloxane in the following vinyl group-containing organopolysiloxane (component (A)), low molecular siloxane in phenyl group-containing organopolysiloxane (component (B)) and organohydrogenpolysiloxane (component (C)) The low molecular weight siloxane was reduced as follows.
The low molecular weight siloxane (non-functional low molecular weight siloxane) in the vinyl group-containing organopolysiloxane (A) and the phenyl group-containing organopolysiloxane (B) is 200 with stirring the sample under a reduced pressure of about 100 Pa. After removing the low-molecular-weight siloxane component by heating at 6 ° C. for 6 hours, nitrogen gas was further blown into the sample (bubbling) and the removal operation was performed for 4 hours, and finally at 250 ° C. under reduced pressure of 50 Pa or less. The low molecular siloxane component was reduced by performing a heat removal operation for 2 hours.
The low molecular siloxane in the organohydrogenpolysiloxane of component (C) (including mainly SiH group-containing low molecular siloxane and non-functional low molecular siloxane) is 180 ° C. while stirring the sample under a reduced pressure of about 100 Pa. After removing the low-molecular siloxane component by heating for 6 hours, nitrogen gas was blown into the sample (bubbling) and the removal operation was performed for 4 hours. Further, a sample (oil-like organohydrogenpolysiloxane) was passed through a hot plate heated to 200 ° C. under a reduced pressure of 20 Pa or less in a thin film form of 100 μm or less to reduce the low molecular siloxane component.

[Example 1]
Containing dimethylpolysiloxane having an average degree of polymerization of 500 blocked at both ends with dimethylvinylsiloxy groups and having a polymerization degree of 10 or less and no SiH functional group (ie, non-functional low-molecular siloxane; the same applies hereinafter) Amount = 0.07 mass%] 65 mass parts, 30 mass parts of fumed silica (Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) having a specific surface area of 200 m < ² > / g, 5 mass parts of hexamethyldisilazane, vinyldimethyltrimethoxysilane After mixing 1 part by mass and 2.0 parts by mass of water at room temperature 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.

で示される両末端及び側鎖にＳｉＨ官能基を有するメチルハイドロジェンポリシロキサン［重合度１０以下でＳｉＨ官能基を１〜３個有する前記式（５）で示される低分子環状シロキサンの含有量＝７．５質量％］を１．４質量部［ＳｉＨ／アルケニル基（モル比）＝１．５］、反応制御剤としてエチニルシクロヘキサノール０．０５質量部を添加し、１５分撹拌を続けてシリコーンゴム組成物を得た。
このシリコーンゴム組成物全体中の重合度が１０以下の無官能性及びＳｉＨ官能性の低分子シロキサン含有量を測定した結果、０．１２質量％であり、そのうちＳｉＨ官能基を１個以上含有するものは０．０９質量％（そのうち前記式（５）で示される環状構造のものが０．０８質量％、直鎖状構造のものが０．０１質量％）、官能基を有しないものは０．０４質量％であった。 100 parts by mass of this silicone rubber base, dimethylpolysiloxane having an average polymerization degree of 250 blocked at both ends with dimethylvinylsiloxy groups [content of low-molecular siloxane having a polymerization degree of 10 or less and no SiH functional group = 0. 03% by mass] 30 parts by mass, dimethylsiloxane / diphenylsiloxane copolymer blocked at both ends with trimethylsiloxy groups (polymerization degree 80, diphenyl content 30 mol%) [polymerization degree 10 or less and no SiH functional group Content of low molecular siloxane = 0.02% by mass] 5 parts by mass was added and stirring was continued for 30 minutes.

Methyl hydrogen polysiloxane having SiH functional groups at both ends and side chains represented by [Content of low molecular cyclic siloxane represented by the above formula (5) having 1 to 3 SiH functional groups with a polymerization degree of 10 or less = 7.5 parts by mass] is added 1.4 parts by mass [SiH / alkenyl group (molar ratio) = 1.5], and 0.05 parts by mass of ethynylcyclohexanol is added as a reaction control agent. A rubber composition was obtained.
As a result of measuring the content of non-functional and SiH-functional low molecular siloxane having a degree of polymerization of 10 or less in the entire silicone rubber composition, it was 0.12% by mass, of which at least one SiH functional group was contained. 0.09% by mass (of which 0.08% by mass is the cyclic structure represented by the above formula (5) and 0.01% by mass is the linear structure), and 0% is not functional group. 0.04% by mass.

  This silicone rubber composition was mixed with 0.1 part by mass of a platinum catalyst (Pt concentration: 1% by mass), and after press curing at 120 ° C./10 minutes, a rubber sheet having a thickness of 2 mm was obtained. As a result of measuring the non-functional and SiH functional low molecular siloxane having a degree of polymerization of 10 or less from this rubber sheet by acetone extraction (25 ° C. × 24 hours immersion), it was 0.04% by mass, of which SiH Those containing functional groups are 0.01% by mass (of which the cyclic structure represented by the formula (5) is about 0.01% by mass, and the linear structure is less than 0.001% by mass), What has no functional group was 0.03% by mass.

Table 1 shows the results of measuring the hardness, tensile strength, and elongation at break from this rubber sheet based on JIS-K6249.
Similarly, a test piece of 50 mm × 50 mm was cut out from this rubber sheet, put into a 500 cc metal can together with an iron and aluminum plate of about 25 mm × 50 mm, and left in an oven at 200 ° C. for 2 hours. A 20 mm x 20 mm x 2 mm silicone rubber piece (addition-curing silicone rubber KE1950-40A / B manufactured by Shin-Etsu Chemical Co., Ltd.) is placed in contact with the iron and aluminum plate taken out so that air does not enter between them, and 500 g is further placed thereon. Were placed in an oven at 200 ° C. for 10 hours. After cooling, when the silicone rubber piece was peeled off from the iron and aluminum plate, both iron and aluminum could be peeled without rubber breakage.

[Example 2]
Dimethylpolysiloxane having both ends blocked with trimethylsiloxy groups and having a vinyl group in the side chain and a polymerization degree of 420 (vinyl group content: 0.00022 mol / g) [polymerization degree of 10 or less and no SiH functional group Content of low molecular siloxane = 0.19% by mass] Fumed silica obtained by hydrophobizing the surface of fumed silica having a specific surface area of 130 m ² / g with dimethyldichlorosilane (Aerosil manufactured by Nippon Aerosil Co., Ltd.) R972) After mixing 20 parts by mass, 5 parts by mass of hexamethyldisilazane, and 2.0 parts by mass of water at room temperature 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. .

で示される側鎖にＳｉＨ官能基を有するメチルハイドロジェンポリシロキサン［重合度１０以下でＳｉＨ官能基を１〜３個有する前記式（５）で示される低分子環状シロキサンの含有量＝２．３質量％］を４．０質量部［ＳｉＨ／アルケニル基（モル比）＝２．０］、反応制御剤としてエチニルシクロヘキサノール０．０５質量部を添加し、１５分撹拌を続けてシリコーンゴム組成物を得た。
このシリコーンゴム組成物全体中の重合度が１０以下の無官能性及びＳｉＨ官能性の低分子シロキサン含有量を測定した結果、０．１７質量％であり、そのうちＳｉＨ官能基を１個以上含有するものは０．０５質量％（そのうち前記式（５）で示される環状構造のものが０．０４質量％、直鎖状構造のものが０．０１質量％）、官能基を有しないものは０．１２質量％であった。 90 parts by mass of this silicone rubber base, dimethylpolysiloxane having an average polymerization degree of 180 blocked at both ends with dimethylvinylsiloxy groups [content of low molecular siloxane having a polymerization degree of 10 or less and no SiH functional group = 0. 06 mass%] A dimethylsiloxane / diphenylsiloxane copolymer (polymerization degree 120) with 32 parts by mass and 50 parts by mass of quartz powder having an average particle diameter of 4 μm, stirred for 30 minutes, and further, both ends blocked with trimethylsiloxy groups. , Diphenyl content 20 mol%) [content of low-molecular siloxane having a polymerization degree of 10 or less and no SiH functional group = 0.04 mass%] 3 parts by mass was added and stirring was continued for 30 minutes. As the following formula

Methyl hydrogen polysiloxane having a SiH functional group in the side chain represented by [Content of low-molecular cyclic siloxane represented by the above formula (5) having a polymerization degree of 10 or less and 1 to 3 SiH functional groups = 2.3 % By mass] is 4.0 parts by mass [SiH / alkenyl group (molar ratio) = 2.0], 0.05 parts by mass of ethynylcyclohexanol is added as a reaction control agent, and stirring is continued for 15 minutes to obtain a silicone rubber composition. Got.
As a result of measuring the content of non-functional and SiH-functional low molecular siloxane having a degree of polymerization of 10 or less in the entire silicone rubber composition, it was 0.17% by mass, of which at least one SiH functional group was contained. 0.05% by mass (of which the cyclic structure represented by the formula (5) is 0.04% by mass and the linear structure is 0.01% by mass), and the one having no functional group is 0%. It was 12 mass%.

  This silicone rubber composition was mixed with 0.1 part by mass of a platinum catalyst (Pt concentration: 1% by mass), and after press curing at 120 ° C./10 minutes, a rubber sheet having a thickness of 2 mm was obtained. As a result of measuring the non-functional and SiH functional low molecular siloxane having a degree of polymerization of 10 or less from this rubber sheet by acetone extraction (25 ° C. × 16 hours immersion), it was 0.12% by mass, of which SiH Those containing functional groups are 0.01% by mass (of which the cyclic structure represented by the formula (5) is about 0.01% by mass, and the linear structure is less than 0.001% by mass) What did not have group was 0.11 mass%.

Table 1 shows the results of measuring the hardness, tensile strength, and elongation at break from this rubber sheet based on JIS-K6249.
Furthermore, when the re-adhesion test with an iron and aluminum plate was implemented like Example 1, both were able to peel with respect to KE1950-40A / B rubber sheet, without rubber | gum destruction.

[Example 3]
A raw rubber-like organopolysiloxane comprising 99.30 mol% of dimethylsiloxane units and 0.70 mol% of methylvinylsiloxane units and having both ends blocked with trimethylsiloxy groups and having an average degree of polymerization of about 8000 [with a degree of polymerization of 10 or less. Content of low-molecular siloxane having no SiH functional group = 0.44% by mass] 65 parts by mass, 5 parts by mass of terminal silanol group dimethylpolysiloxane (average polymerization degree 10) as a dispersant, and a specific surface area of 200 m ² / g 30 parts by mass of fumed silica (Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) was added and blended in a pressure kneader to prepare a rubber compound.

で示される側鎖にＳｉＨ官能基を有するメチルハイドロジェンポリシロキサン［重合度１０以下でＳｉＨ官能基を１〜３個有する前記式（５）で示される低分子環状シロキサンの含有量＝１．８質量％］を８．０質量部［ＳｉＨ／アルケニル基（モル比）＝２．５］、反応制御剤としてエチニルシクロヘキサノール０．０５質量部を添加し、２本ロールで１５分ロール練を続けてシリコーンゴム組成物を得た。
このシリコーンゴム組成物全体中の重合度が１０以下の無官能性及びＳｉＨ官能性の低分子シロキサン含有量を測定した結果、０．５２質量％であり、そのうちＳｉＨ官能基を１個以上含有するものは０．１２質量％（そのうち前記式（５）で示される環状構造のものが０．１１質量％、直鎖状構造のものが０．０１質量％）、官能基を有しないものは０．４０質量％であった。 This rubber compound is composed of 98.80 mol% of dimethylsiloxane units and 1.20 mol% of methylvinylsiloxane units in 100 parts by mass of this rubber compound, and a raw rubber-like organosiloxane having an average degree of polymerization of about 8000, which is blocked at both ends with trimethylsiloxy groups. Polysiloxane [content of low molecular weight siloxane having a degree of polymerization of 10 or less and no SiH functional group = 0.39% by mass] 17 parts by mass, a dimethylsiloxane / diphenylsiloxane copolymer blocked at both ends with trimethylsiloxy groups ( Polymerization degree 60, diphenyl content 15 mol%) [polymerization degree 10 or less and low molecular siloxane content not having SiH functional group = 0.03 mass%] 1 part by mass, both ends blocked with trimethylsiloxy groups Dimethylsiloxane / diphenylsiloxane copolymer (degree of polymerization 80, diphenyl content 30 mol) ) [Content of the low molecular weight siloxane having no SiH functional group in polymerization degree 10 or less 0.02 wt%] 2 parts by weight, the following formula as a cross-linking agent

Methyl hydrogen polysiloxane having a SiH functional group in the side chain represented by [Content of low molecular cyclic siloxane represented by the formula (5) having a polymerization degree of 10 or less and 1 to 3 SiH functional groups = 1.8 % By mass] is 8.0 parts by mass [SiH / alkenyl group (molar ratio) = 2.5], 0.05 part by mass of ethynylcyclohexanol is added as a reaction control agent, and roll milling is continued for 15 minutes with two rolls. Thus, a silicone rubber composition was obtained.
As a result of measuring the content of non-functional and SiH-functional low molecular siloxane having a degree of polymerization of 10 or less in the entire silicone rubber composition, it was 0.52% by mass, of which at least one SiH functional group was contained. 0.12% by mass (of which the cyclic structure represented by the formula (5) is 0.11% by mass, and the linear structure is 0.01% by mass), and the one having no functional group is 0% It was 40 mass%.

  This silicone rubber composition was mixed with 0.1 part by mass of a platinum catalyst (Pt concentration: 1% by mass), and after press curing at 120 ° C./10 minutes, a rubber sheet having a thickness of 2 mm was obtained. As a result of measuring the non-functional and SiH-functional low molecular siloxane having a degree of polymerization of 10 or less from this rubber sheet by extraction with acetone (25 ° C. × 16 hours immersion), it was 0.40% by mass, of which SiH Those containing a functional group are 0.03% by mass (of which the cyclic structure represented by the formula (5) is about 0.03% by mass, and the linear structure is less than 0.001% by mass) What did not have group was 0.37 mass%.

Table 1 shows the results of measuring the hardness, tensile strength, and elongation at break from this rubber sheet based on JIS-K6249.
Furthermore, when the re-adhesion test with an iron and aluminum plate was implemented like Example 1, both were able to peel with respect to KE1950-40A / B rubber sheet, without rubber | gum destruction.

[Comparative Example 1]
Dimethylpolysiloxane having an average degree of polymerization of 500 blocked at both ends with dimethylvinylsiloxy groups [content of low-molecular siloxane having a degree of polymerization of 10 or less and no SiH functional group = 0.55% by mass], 65 parts by mass, ratio 30 parts by weight of fumed silica (Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) having a surface area of 200 m ² / g, 5 parts by weight of hexamethyldisilazane, 1 part by weight of vinyldimethyltrimethoxysilane, and 2.0 parts by weight of water at room temperature 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.

で示される両末端及び側鎖にＳｉＨ官能基を有するメチルハイドロジェンポリシロキサンと下記式

で示されるジメチルシロキサン・メチルハイドロジェンシロキサン環状共重合体との混合物［重合度１０以下でＳｉＨ官能基を１〜３個有する前記式（５）で示される低分子環状シロキサンの含有量＝６０．５質量％］を１．５質量部［ＳｉＨ／アルケニル基（モル比）＝１．５］、反応制御剤としてエチニルシクロヘキサノール０．０５質量部を添加し、１５分撹拌を続けてシリコーンゴム組成物を得た。
このシリコーンゴム組成物全体中の重合度が１０以下の無官能性及びＳｉＨ官能性の低分子シロキサン含有量を測定した結果、１．０９質量％であり、そのうちＳｉＨ官能基を１個以上含有するものは０．６４質量％（そのうち前記式（５）で示される環状構造のものが０．５２質量％、直鎖状構造のものが０．１２質量％）、官能基を有しないものは０．４５質量％であった。 100 parts by mass of this silicone rubber base, dimethylpolysiloxane having an average polymerization degree of 250 blocked at both ends with dimethylvinylsiloxy groups [content of low-molecular siloxane having a polymerization degree of 10 or less and no SiH functional group = 0. 32% by mass] 30 parts by mass, dimethylsiloxane / diphenylsiloxane copolymer blocked at both ends with trimethylsiloxy groups (polymerization degree 80, diphenyl content 30 mol%) [polymerization degree 10 or less and no SiH functional group Content of low molecular siloxane = 0.15% by mass] 5 parts by mass was added and stirring was continued for 30 minutes.

A methylhydrogenpolysiloxane having SiH functional groups at both ends and side chains represented by

A mixture with a dimethylsiloxane / methylhydrogensiloxane cyclic copolymer represented by the formula [Content of low-molecular cyclic siloxane represented by the above formula (5) having a polymerization degree of 10 or less and 1 to 3 SiH functional groups = 60. 5 parts by mass] 1.5 parts by mass [SiH / alkenyl group (molar ratio) = 1.5], and 0.05 parts by mass of ethynylcyclohexanol as a reaction control agent were added and stirring was continued for 15 minutes to form a silicone rubber composition. I got a thing.
As a result of measuring the content of non-functional and SiH functional low molecular siloxane having a degree of polymerization of 10 or less in the whole silicone rubber composition, it was 1.09% by mass, of which at least one SiH functional group was contained. 0.64% by mass (of which the cyclic structure represented by the formula (5) is 0.52% by mass and the linear structure is 0.12% by mass), and the one having no functional group is 0 .45% by mass.

  This silicone rubber composition was mixed with 0.1 part by mass of a platinum catalyst (Pt concentration: 1% by mass), and after press curing at 120 ° C./10 minutes, a rubber sheet having a thickness of 2 mm was obtained. As a result of measuring the non-functional and SiH-functional low molecular siloxane having a degree of polymerization of 10 or less from this rubber sheet by acetone extraction (25 ° C. × 16 hours immersion), it was 0.58% by mass, of which SiH 0.13% by mass containing a functional group (of which 0.11% by mass has a cyclic structure represented by the formula (5) and 0.02% by mass has a linear structure), a functional group What did not have was 0.45 mass%.

Table 1 shows the results of measuring the hardness, tensile strength, and elongation at break from this rubber sheet based on JIS-K6249.
Furthermore, when the re-adhesion test with an iron and aluminum plate was carried out in the same manner as in Example 1, the KE1950-40A / B rubber sheet adhered to both, and when it was forcibly removed, the interface was not visible. % Rubber was destroyed.

[Comparative Example 2]
Dimethylpolysiloxane having both ends blocked with trimethylsiloxy groups and having a vinyl group in the side chain and a polymerization degree of 420 (vinyl group content: 0.00022 mol / g) [polymerization degree of 10 or less and no SiH functional group Content of low molecular siloxane = 1.02 mass%] 65 parts by mass, fumed silica having a specific surface area of 130 m ² / g hydrophobized with dimethyldichlorosilane (manufactured by Nippon Aerosil Co., Ltd., Aerosil) R972) After mixing 20 parts by mass, 5 parts by mass of hexamethyldisilazane, and 2.0 parts by mass of water at room temperature 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. .

で示される側鎖にＳｉＨ官能基を有するメチルハイドロジェンポリシロキサン［重合度１０以下でＳｉＨ官能基を１〜３個有する前記式（５）で示される低分子環状シロキサンの含有量＝９．１質量％］を９．６質量部［ＳｉＨ／アルケニル基（モル比）＝２．５］、反応制御剤としてエチニルシクロヘキサノール０．０５質量部を添加し、１５分撹拌を続けてシリコーンゴム組成物を得た。
このシリコーンゴム組成物全体中の重合度が１０以下の無官能性及びＳｉＨ官能性の低分子シロキサン含有量を測定した結果、１．５６質量％であり、そのうちＳｉＨ官能基を１個以上含有するものは０．６９質量％（そのうち前記式（５）で示される環状構造のものが０．５３質量％、直鎖状構造のものが０．１６質量％）、官能基を有しないものは０．８７質量％であった。 90 parts by mass of this silicone rubber base, dimethylpolysiloxane having an average polymerization degree of 180 blocked at both ends with dimethylvinylsiloxy groups [content of low molecular siloxane having a polymerization degree of 10 or less and no SiH functional group = 0. 93% by mass] 32 parts by mass, 50 parts by mass of quartz powder having an average particle size of 4 μm were added and stirred for 30 minutes. Further, a dimethylsiloxane / diphenylsiloxane copolymer having both ends blocked with trimethylsiloxy groups (polymerization degree 120 , Diphenyl content 20 mol%) [content of low molecular siloxane having a polymerization degree of 10 or less and no SiH functional group = 0.18% by mass] 3 parts by mass were added and stirring was continued for 30 minutes. As the following formula

Methyl hydrogen polysiloxane having a SiH functional group in the side chain represented by [Content of low-molecular cyclic siloxane represented by the above formula (5) having a polymerization degree of 10 or less and 1 to 3 SiH functional groups = 9.1 9.6 parts by mass [SiH / alkenyl group (molar ratio) = 2.5], 0.05 part by mass of ethynylcyclohexanol as a reaction control agent was added, and stirring was continued for 15 minutes to obtain a silicone rubber composition. Got.
As a result of measuring the content of non-functional and SiH-functional low molecular siloxane having a degree of polymerization of 10 or less in the entire silicone rubber composition, it was 1.56% by mass, of which at least one SiH functional group was contained. 0.69% by mass (of which 0.53% is the cyclic structure of the formula (5) and 0.16% by mass of the linear structure), and 0% is not functional group. It was .87 mass%.

  This silicone rubber composition was mixed with 0.1 part by mass of a platinum catalyst (Pt concentration: 1% by mass), and after press curing at 120 ° C./10 minutes, a rubber sheet having a thickness of 2 mm was obtained. As a result of measuring the non-functional and SiH-functional low molecular siloxane having a degree of polymerization of 10 or less from this rubber sheet by acetone extraction (25 ° C. × 16 hours immersion), it was 1.04% by mass, of which SiH Those containing a functional group are 0.19% by mass (of which 0.16% by mass is a cyclic structure represented by the formula (5) and 0.03% by mass is a linear structure), What it did not have was 0.85 mass%.

Table 1 shows the results of measuring the hardness, tensile strength, and elongation at break from this rubber sheet based on JIS-K6249.
Furthermore, when the re-adhesion test with an iron and aluminum plate was carried out in the same manner as in Example 1, the KE1950-40A / B rubber sheet adhered to both, and when it was forcibly removed, the interface was not visible. % Rubber was destroyed.

[Comparative Example 3]
A raw rubber-like organopolysiloxane comprising 99.30 mol% of dimethylsiloxane units and 0.70 mol% of methylvinylsiloxane units and having both ends blocked with trimethylsiloxy groups and having an average degree of polymerization of about 8000 [with a degree of polymerization of 10 or less. Content of low-molecular siloxane having no SiH functional group = 1.38% by mass] 65 parts by mass, 5 parts by mass of terminal silanol group dimethylpolysiloxane (average polymerization degree 10) as a dispersant, and a specific surface area of 200 m ² / g 30 parts by mass of fumed silica (Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) was added and blended in a pressure kneader to prepare a rubber compound.

で示される側鎖にＳｉＨ官能基を有するメチルハイドロジェンポリシロキサン［重合度１０以下でＳｉＨ官能基を１〜３個有する前記式（５）で示される低分子環状シロキサンの含有量＝５．１質量％］を１５．１質量部［ＳｉＨ／アルケニル基（モル比）＝３．５］、反応制御剤としてエチニルシクロヘキサノール０．０５質量部を添加し、２本ロールで１５分ロール練を続けてシリコーンゴム組成物を得た。
このシリコーンゴム組成物全体中の重合度が１０以下の無官能性及びＳｉＨ官能性の低分子シロキサン含有量を測定した結果、１．８８質量％であり、そのうちＳｉＨ官能基を１個以上含有するものは０．５６質量％（そのうち前記式（５）で示される環状構造のものが０．５１質量％、直鎖状構造のものが０．０５質量％）、官能基を有しないものは１．３２質量％であった。 This rubber compound is composed of 98.80 mol% of dimethylsiloxane units and 1.20 mol% of methylvinylsiloxane units in 100 parts by mass of this rubber compound, and a raw rubber-like organosiloxane having an average degree of polymerization of about 8000, which is blocked at both ends with trimethylsiloxy groups. Polysiloxane [content of low-molecular-weight siloxane having a degree of polymerization of 10 or less and no SiH functional group = 1.25% by mass] 17 parts by mass, dimethylsiloxane / diphenylsiloxane copolymer blocked at both ends with trimethylsiloxy groups ( Polymerization degree 60, diphenyl content 15 mol%) [polymerization degree 10 or less and low molecular siloxane content not having SiH functional group = 0.03 mass%] 1 part by mass, both ends blocked with trimethylsiloxy groups Dimethylsiloxane / diphenylsiloxane copolymer (degree of polymerization 80, diphenyl content 30 mol) ) [Content of the low molecular weight siloxane having no SiH functional group in polymerization degree 10 or less 0.02 wt%] 2 parts by weight, the following formula as a cross-linking agent

Methyl hydrogen polysiloxane having a SiH functional group in the side chain represented by [Content of low molecular cyclic siloxane represented by the above formula (5) having a polymerization degree of 10 or less and 1 to 3 SiH functional groups = 5.1 % By mass] is 15.1 parts by mass [SiH / alkenyl group (molar ratio) = 3.5], 0.05 part by mass of ethynylcyclohexanol is added as a reaction control agent, and the roll kneading is continued for 15 minutes with two rolls. Thus, a silicone rubber composition was obtained.
As a result of measuring the content of non-functional and SiH-functional low molecular siloxane having a degree of polymerization of 10 or less in the entire silicone rubber composition, it was 1.88% by mass, of which at least one SiH functional group was contained. 0.56% by mass (of which 0.51% by mass is the cyclic structure represented by the above formula (5) and 0.05% by mass is the linear structure), It was 32 mass%.

  This silicone rubber composition was mixed with 0.1 part by mass of a platinum catalyst (Pt concentration: 1% by mass), and after press curing at 120 ° C./10 minutes, a rubber sheet having a thickness of 2 mm was obtained. As a result of measuring the non-functional and SiH-functional low molecular siloxane having a degree of polymerization of 10 or less from this rubber sheet by acetone extraction (25 ° C. × 16 hours immersion), it was 1.49% by mass, of which SiH The functional group containing 0.20% by mass (of which the cyclic structure represented by the formula (5) is 0.18% by mass and the linear structure is 0.02% by mass) What it did not have was 1.29 mass%.

Table 1 shows the results of measuring the hardness, tensile strength, and elongation at break from this rubber sheet based on JIS-K6249.
Furthermore, when the re-adhesion test with iron and an aluminum plate was conducted in the same manner as in Example 1, it adhered to either of the KE1950-40A / B rubber sheet, and when it was forcibly removed, the iron was adhered to the entire adhesion surface. On the other hand, 80% cohesive failure in which an interface of about 20% can be confirmed, and in the case of aluminum, 100% rubber failure occurred.

  As described above, when the silicone rubber sheet obtained by curing the silicone rubber composition is stored in a sealed state together with iron and aluminum, the degree of polymerization is 10 or less and one or more SiH functional groups per molecule (particularly 1 to 1). 3) In the example using the composition containing the low molecular siloxane component contained in a specific amount or less, the low molecular siloxane adhering to the peripheral member (iron and aluminum) could be easily wiped off with a solvent. On the other hand, a comparative example using a composition containing a specific amount of a low-molecular siloxane component having a polymerization degree of 10 or less and containing one or more SiH functional groups in one molecule is SiH on the peripheral members (iron and aluminum). It has been found that functional group-containing low molecular weight siloxane adheres and cannot be easily wiped with a solvent, and rubber breakage may occur due to adhesion.

Claims (13)

(A) Organopolysiloxane containing an alkenyl group bonded to at least two silicon atoms in one molecule represented by the following average composition formula (1) R ¹ _a SiO _{(4-a) / 2} (1)
(Wherein R ¹ is an unsubstituted or fluorine-substituted monovalent hydrocarbon group selected from an alkyl group, an alkenyl group, an aryl group, an aralkyl group, and a trifluoropropyl group having 1 to 8 carbon atoms; A positive number of .5 to 2.8.): 100 parts by mass,
(B) an organic group bonded to a silicon atom contains a phenyl group, the content of the phenyl group is 10 to 35 mol% of the total organic group, and does not contain a silicon atom-bonded hydrogen atom and an alkenyl group; Phenyl group-containing organopolysiloxane having a viscosity at 25 ° C. of 10 to 5,000 mPa · s: 0.5 to 20 parts by mass
(C) Organohydrogenpolysiloxane containing at least two hydrogen atoms (SiH functional group) bonded to a silicon atom represented by the following average composition formula (3) in one molecule: R ² _b H _c SiO _{(4-bc ) / 2} (3)
(Wherein R ² is an unsubstituted or fluorine-substituted monovalent hydrocarbon group selected from an alkyl group, an aryl group, an aralkyl group and a trifluoropropyl group having 1 to 8 carbon atoms, and b is 0.7 to 2.1 and c are 0.001 to 1.0, and b + c is a positive number satisfying 0.8 to 3.0.): 0.3 to 20 parts by mass,
(D) Addition reaction catalyst: The organohydrogenpolysiloxane which contains a catalyst amount and (C) component is heated at 180 ° C. for 6 hours under stirring under a reduced pressure of 100 Pa, and then blown with nitrogen gas. It is obtained by removing low molecular siloxane components including SiH group-containing low molecular siloxane by bubbling for 4 hours and then flowing in a thin film of 100 μm or less on a hot plate heated to 200 ° C. under a reduced pressure of 20 Pa or less. Oil-bleeding addition reaction curing type in which the degree of polymerization is 10 or less and the content of organopolysiloxane containing one or more SiH functional groups in one molecule is 0.20% by mass or less based on the entire composition Silicone rubber composition.   The molar ratio of the SiH functional group in the component (C) to the silicon atom-bonded alkenyl group in the component (A) is in the range of SiH / alkenyl group = 0.6 to 3.0. Oil bleedable addition curable silicone rubber composition.   The oil-bleeding addition curing according to claim 1 or 2, wherein the organopolysiloxane having a degree of polymerization of 10 or less and containing at least one SiH functional group per molecule is an organohydrogensiloxane-diorganosiloxane cyclic copolymer. Type silicone rubber composition. The oil-bleeding addition curing according to claim 3, wherein the organopolysiloxane having a degree of polymerization of 10 or less and containing at least one SiH functional group in a molecule is a cyclic organohydrogenpolysiloxane represented by the following formula (5): Type silicone rubber composition.

(In the formula, n is an integer of 1 to 9, m is an integer of 1 to 9, and n + m is an integer of 3 to 10. R is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms. And may be the same or different.)   The oil-bleeding addition-curable silicone rubber composition according to claim 4, wherein in formula (5), n is an integer of 1 to 9, m is an integer of 1 to 3, and n + m is an integer of 3 to 10. .   The oil bleed according to any one of claims 1 to 5, wherein the content of the organopolysiloxane having a degree of polymerization of 10 or less and having no SiH functional group is 0.5% by mass or less in the components (A) and (B). Addition-curable silicone rubber composition. The oil-bleeding addition-curable silicone rubber composition according to claim 6, wherein the organopolysiloxane having a polymerization degree of 10 or less and having no SiH functional group is a cyclic organopolysiloxane represented by the following formula (2).

(In the formula, x is an integer of 3 to 10, and R is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, which may be the same or different.)   The component (C) is a linear, cyclic, branched or three-dimensional network-organohydrogenpolysiloxane having a degree of polymerization of 11 or more. Oil bleedable addition curable silicone rubber composition. The oil-bleeding addition-curable silicone rubber composition according to claim 8, wherein the component (C) is a linear organohydrogenpolysiloxane represented by the following formula (4).

(Wherein y is an integer from 1 to 98, z is an integer from 2 to 50, and y + z is an integer from 9 to 100. R ² is as defined in claim 1 and is the same or different. R ³ is R ² or a hydrogen atom.)   2. The total number of hydrogen atoms bonded to silicon atoms relative to the total number of carbon atoms in the molecule of component (C) is 0.05 <[hydrogen atom] / [carbon atom] <0.7 in terms of molar ratio. The oil bleedable addition curable silicone rubber composition according to any one of? 9.   The content of organopolysiloxane having a polymerization degree of 10 or less and containing one or more SiH functional groups in one molecule is 10.0% by mass or less in component (C). Oil bleedable addition curable silicone rubber composition.   A cured oil bleedable silicone rubber composition obtained by curing the oil bleedable addition curable silicone rubber composition according to any one of claims 1 to 11.   13. The oil-bleeded silicone rubber cured product according to claim 12, wherein the cured product has a degree of polymerization of 10 or less and an organopolysiloxane content of at least one SiH functional group in one molecule is 0.2% by mass or less. object.