JP2021084966A - Expandable silicone rubber composition and silicone rubber foam - Google Patents

Abstract

To provide an expandable silicone rubber composition having high expansion ratio and to provide a silicone rubber foam.SOLUTION: The expandable silicone rubber composition contains (A) a linear organopolysiloxane containing two or more alkenyl groups bonded to silicon atoms in one molecule and having the number of alkenyl groups of 0.001 mol/100 g to less than 0.06 mol/100 g, (B) a three-dimensional network organopolysiloxane, (C) an organohydrogenpolysiloxane having at least two hydrogen atoms bonded to silicon atoms in one molecule, (D) at least one kind selected from the group consisting of water, alcohol, a silanol group-containing organosilane and a silanol group-containing organosiloxane, (E) a platinum group metal compound, (F) an organosilicon compound having at least one alkynyl group in one molecule, (G) a compound including at least two alkenyl groups in one molecule and having the number of alkenyl groups of 0.06 to 1.5 mol/100 g.SELECTED DRAWING: None

Description

The present invention relates to a foamable silicone rubber composition and a silicone rubber foam.

Since the silicone rubber foam has the heat resistance, cold resistance, electrical insulation and elasticity of the sponge of the silicone rubber, it has low heat conductivity, sound absorption and low heat conductivity in roll applications, building materials, automobile materials, etc. in OA equipment. It is used to promote weight reduction. In addition, when organic resin-based polyurethane foam, which is widely used in the world, burns, black smoke and toxic gas are generated and burn violently, whereas silicone foam is highly flame-retardant and heat generation is suppressed. Therefore, in recent years, studies have been conducted as seats and floor materials for automobiles and railway vehicles.

Silicone rubber foam is produced by various methods depending on its use. A typical one is one in which a foaming agent is added to a gum-like diorganopolysiloxane and cured by heating, and examples of the curing mechanism include an addition reaction using a platinum catalyst and a radical cross-linking reaction using an organic peroxide. Further, as the foaming agent, azo compounds such as azobisisobutyronitrile and 1,1-azobis (cyclohexane-1-methylcarboxylate) are used.

In addition, as a method for producing a foam using a liquid diorganopolysiloxane, Patent Document 1 describes a curing mechanism that involves a dehydrogenation reaction during curing, that is, an organopolysiloxane having a vinyl group, hydrogen poly. A production method using a composition consisting of a siloxane, a silanol group-containing diorganopolysiloxane, a platinum group catalyst, and a hydrosilyl source such as water or alcohol is disclosed. Further, Patent Document 2 discloses a production method in which an acetylene alcohol-based compound is added and foamed and cured by heating. Further, Patent Document 3 discloses a production method in which an inorganic thickener and a nonionic surfactant are added in order to form a fine open cell structure.

Japanese Unexamined Patent Publication No. 9-310025 JP-A-11-124503 JP-A-2019-65079

As the demand for low thermal conductivity, sound absorption and weight reduction has increased in silicone foams, further improvement in foaming ratio has been required.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a foamable silicone rubber composition and a silicone rubber foam having a high foaming ratio.

（式中、Ｒ^１は独立して炭素原子数１〜１０のアルキル基、炭素原子数６〜１２のアリール基、炭素原子数２〜１０のアルケニル基から選択される１価炭化水素基であり、１分子中の少なくとも２個のＲ^１がアルケニル基であり、ａ≧０、ｂ≧０、ｃ≧０、ｄ≧０、ｃ＋ｄ＞０かつａ＋ｂ＋ｃ＋ｄ＝１となる数である。）、
（Ｃ）１分子中に少なくとも２個のケイ素原子に結合した水素原子を含有するオルガノハイドロジェンポリシロキサン：１．０〜８０質量部、
（Ｄ）水、アルコール、シラノール基含有オルガノシラン及びシラノール基含有オルガノシロキサンからなる群から選ばれる少なくとも１種：０．５〜５０質量部、
（Ｅ）白金族金属化合物、
（Ｆ）１分子中にアルキニル基を少なくとも１つ含有する有機ケイ素化合物：０．００１〜０．２質量部、
（Ｇ）１分子中に少なくとも２個のアルケニル基を含み、かつアルケニル基数が０．０６〜１．５モル／１００ｇである化合物：０．０１〜５．０質量部、
を含有するものである発泡性シリコーンゴム組成物を提供する。 In order to achieve the above problems, the present invention
(A) A straight chain containing two or more alkenyl groups having 2 to 8 carbon atoms bonded to silicon atoms in one molecule and having an alkenyl group number of 0.001 mol / 100 g or more and less than 0.06 mol / 100 g. Organopolysiloxane: 100 parts by mass,
(B) Three-dimensional network-like organopolysiloxane represented by the general formula (1): 1 to 100 parts by mass,

(In the formula, R ¹ is a monovalent hydrocarbon group independently selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, and an alkenyl group having 2 to 10 carbon atoms. , 1 ^{R 1} of at least two in the molecule is an alkenyl group, an a ≧ 0, b ≧ 0, c ≧ 0, d ≧ 0, c + d> 0 and the number to be a + b + c + d = 1.),
(C) Organohydrogenpolysiloxane containing hydrogen atoms bonded to at least two silicon atoms in one molecule: 1.0 to 80 parts by mass,
(D) At least one selected from the group consisting of water, alcohol, silanol group-containing organosilane and silanol group-containing organosiloxane: 0.5 to 50 parts by mass,
(E) Platinum group metal compound,
(F) Organosilicon compound containing at least one alkynyl group in one molecule: 0.001 to 0.2 parts by mass,
(G) A compound containing at least two alkenyl groups in one molecule and having an alkenyl group number of 0.06 to 1.5 mol / 100 g: 0.01 to 5.0 parts by mass,
Provided is an effervescent silicone rubber composition containing the above.

With such a composition, a foamable silicone rubber composition having a high foaming ratio can be obtained.

At this time, the component (G) can be a foamable silicone rubber composition which is an organosiloxane containing an alkenyl group bonded to a silicon atom.

With such a composition, a foamable silicone rubber composition having a higher foaming ratio can be obtained by slowly advancing the addition reaction.

Further, the present invention provides a silicone rubber foam made of a cured product of the above-mentioned foamable silicone rubber composition.

Such a silicone rubber foam can be a silicone rubber foam having a high expansion ratio and a low density.

With the foamable silicone rubber composition of the present invention, a silicone rubber foam having a high foaming ratio and a low density can be obtained, which is useful for OA equipment, building materials, automobile materials and the like.

As described above, as the demand for low thermal conductivity, sound absorption and weight reduction has increased in silicone foams, foamable silicone rubber compositions and silicone rubber foams having a high foaming ratio have been required.

As a result of diligent studies on the above problems, the present inventor has a foamable silicone rubber composition containing the components (A) to (G) described later having a high foaming ratio, and the foamable silicone rubber composition described above. The present invention has been completed by finding that the density of a silicone rubber foam made of a cured product of a product can be reduced.

（式中、Ｒ^１は独立して炭素原子数１〜１０のアルキル基、炭素原子数６〜１２のアリール基、炭素原子数２〜１０のアルケニル基から選択される１価炭化水素基であり、１分子中の少なくとも２個のＲ^１がアルケニル基であり、ａ≧０、ｂ≧０、ｃ≧０、ｄ≧０、ｃ＋ｄ＞０かつａ＋ｂ＋ｃ＋ｄ＝１となる数である。）、
（Ｃ）１分子中に少なくとも２個のケイ素原子に結合した水素原子を含有するオルガノハイドロジェンポリシロキサン：１．０〜８０質量部、
（Ｄ）水、アルコール、シラノール基含有オルガノシラン及びシラノール基含有オルガノシロキサンからなる群から選ばれる少なくとも１種：０．５〜５０質量部、
（Ｅ）白金族金属化合物、
（Ｆ）１分子中にアルキニル基を少なくとも１つ含有する有機ケイ素化合物：０．００１〜０．２質量部、
（Ｇ）１分子中に少なくとも２個のアルケニル基を含み、かつアルケニル基数が０．０６〜１．５モル／１００ｇである化合物：０．０１〜５．０質量部、
を含有する発泡性シリコーンゴム組成物である。 That is, the present invention
(A) A straight chain containing two or more alkenyl groups having 2 to 8 carbon atoms bonded to silicon atoms in one molecule and having an alkenyl group number of 0.001 mol / 100 g or more and less than 0.06 mol / 100 g. Organopolysiloxane: 100 parts by mass,
(B) Three-dimensional network-like organopolysiloxane represented by the general formula (1): 1 to 100 parts by mass,

(In the formula, R ¹ is a monovalent hydrocarbon group independently selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, and an alkenyl group having 2 to 10 carbon atoms. , 1 ^{R 1} of at least two in the molecule is an alkenyl group, an a ≧ 0, b ≧ 0, c ≧ 0, d ≧ 0, c + d> 0 and the number to be a + b + c + d = 1.),
(C) Organohydrogenpolysiloxane containing hydrogen atoms bonded to at least two silicon atoms in one molecule: 1.0 to 80 parts by mass,
(D) At least one selected from the group consisting of water, alcohol, silanol group-containing organosilane and silanol group-containing organosiloxane: 0.5 to 50 parts by mass,
(E) Platinum group metal compound,
(F) Organosilicon compound containing at least one alkynyl group in one molecule: 0.001 to 0.2 parts by mass,
(G) A compound containing at least two alkenyl groups in one molecule and having an alkenyl group number of 0.06 to 1.5 mol / 100 g: 0.01 to 5.0 parts by mass,
It is a foamable silicone rubber composition containing.

Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.

[Effervescent silicone rubber composition]
The foamable silicone rubber composition of the present invention contains the following components (A) to (G). The properties of the composition are not particularly limited, but are preferably liquid.

[(A) component]
The component (A) contains two or more alkenyl groups having 2 to 8 carbon atoms bonded to silicon atoms in one molecule, and the number of alkenyl groups is 0.001 mol / 100 g or more and less than 0.06 mol / 100 g. A linear organopolysiloxane.

The position of the silicon atom to which the alkenyl group is bonded in the molecule of the component (A) may be either at the end of the molecular chain or in the middle of the molecular chain, or either one or both may be used. The average number of alkenyl groups directly linked to the silicon atom is 2 or more, preferably 2 to 20, and more preferably 2 to 10 in one molecule of the component (A). The component (A) is particularly preferably a linear diorganopolysiloxane containing at least an alkenyl group bonded to silicon atoms at both ends of the molecular chain.

The number of alkenyl groups of the component (A) is 0.001 mol / 100 g or more and less than 0.06 mol / 100 g, preferably 0.002 to 0.01 mol / 100 g. If it is lower than 0.001 mol / 100 g, the mechanical strength of the foam may be insufficient, and if it exceeds 0.06 mol / 100 g, the reaction rate of the addition reaction may deteriorate.

Examples of the alkenyl group bonded to the silicon atom in the component (A) include those having 2 to 8 carbon atoms, preferably 2 to 4 carbon atoms. Specific examples thereof include a vinyl group, an allyl group, a butenyl group, a pentenyl group, a hexenyl group, a cyclohexenyl group, a heptenyl group and the like, and a vinyl group is particularly preferable.

In the organopolysiloxane of the component (A), examples of the organic group bonded to a silicon atom other than the alkenyl group include an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group and a heptyl group. Aryl groups such as phenyl group, trill group, xsilyl group and naphthyl group; Aralkyl groups such as benzyl group and phenethyl group; Halogen such as chloromethyl group, 3-chloropropyl group and 3,3,3-trifluoropropyl group Examples thereof include an alkylated group, and a methyl group is particularly preferable.

The viscosity of the component (A) at 25 ° C. is preferably in the range of 100 to 500,000 mPa · s, and more preferably in the range of 600 to 200,000 mPa · s. When the viscosity is within this range, the handling workability of the obtained composition is good, and the mechanical properties of the obtained silicone rubber foam are good.

Specific examples of the organopolysiloxane of the component (A) include a trimethylsiloxy group-blocked dimethylsiloxane / methylvinylsiloxane copolymer at both ends of the molecular chain, a trimethylsiloxy group-blocked methylvinylpolysiloxane at both ends of the molecular chain, and trimethyl at both ends of the molecular chain. Syroxy group-blocked dimethylsiloxane / methylvinylsiloxane / methylphenylsiloxane copolymer, molecular chain double-ended dimethylvinyl siloxy group-blocked dimethylpolysiloxane, molecular chain double-ended dimethylvinyl siloxy group-blocked methylvinylpolysiloxane, molecular chain double-ended dimethylvinyl Syroxy group-blocked dimethylsiloxane / methylvinylsiloxane copolymer, molecular chain double-ended dimethylvinylsiloxy group-blocked dimethylsiloxane / methylvinylsiloxane / methylphenylsiloxane copolymer, molecular chain double-ended divinylmethylsiloxy group-blocked dimethylpolysiloxane, molecule Divinylmethylsiloxy group-blocked dimethylsiloxane / methylvinylsiloxane copolymer at both ends of the chain, trivinylsiloxy group-blocked dimethylpolysiloxane at both ends of the molecular chain, trivinylsiloxy group-blocked dimethylsiloxane / methylvinylsiloxane copolymer at both ends of the molecular chain, And a mixture of two or more of these organopolysiloxanes. The component (A) may be used alone or in combination of two or more.

（式中、Ｒ^１は独立して炭素原子数１〜１０のアルキル基、炭素原子数６〜１２のアリール基、炭素原子数２〜１０のアルケニル基から選択される１価炭化水素基であり、１分子中の少なくとも２個のＲ^１がアルケニル基であり、ａ≧０、ｂ≧０、ｃ≧０、ｄ≧０、ｃ＋ｄ＞０かつａ＋ｂ＋ｃ＋ｄ＝１となる数である。） [(B) component]
The component (B) is a three-dimensional network-like organopolysiloxane (silicone resin) represented by the following general formula (1), and is a component that improves the hardness of the silicone rubber foam.

(In the formula, R ¹ is a monovalent hydrocarbon group independently selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, and an alkenyl group having 2 to 10 carbon atoms. , at least two of ^{R 1} are alkenyl groups in one molecule, which is a ≧ 0, b ≧ 0, c ≧ 0, d ≧ 0, c + d> 0 and the number to be a + b + c + d = 1.)

The component (B) is preferably solid at 25 ° C. or gum-like (raw rubber-like) having almost no self-fluidity of 10,000,000 mPa · s or more, particularly 100,000,000 mPa · s or more. With such a three-dimensional network-like organopolysiloxane (silicone resin), the hardness of the silicone rubber foam can be further improved.

In the general formula (1), R ¹ is a monovalent hydrocarbon independently selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, and an alkenyl group having 2 to 10 carbon atoms. a group of at least two per molecule, preferably 2 to 10 ^{R 1} is an alkenyl group.

Examples of the alkenyl group include a vinyl group, an allyl group, a butenyl group, a pentenyl group, a hexenyl group, a cyclohexenyl group, a heptenyl group and the like, and a vinyl group is preferable from the viewpoint of compatibility with other components.

^{Examples of R 1} other than the alkenyl group include an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group and a heptyl group; Aralkyl groups such as a benzyl group and a phenethyl group; alkyl halide groups such as a chloromethyl group, a 3-chloropropyl group and a 3,3,3-trifluoropropyl group can be mentioned, and in particular, a methyl group can be used. preferable.

In the formula (1), the numbers of a, b, c, and d are a ≧ 0, preferably 0.1 <a <0.7, and b ≧ 0, preferably 0 ≦ b ≦ 0.1. Yes, c ≧ 0, preferably 0 ≦ c ≦ 0.8, d ≧ 0, preferably 0 ≦ d ≦ 0.8, c + d> 0, preferably 0.3 <c + d <0.8, More preferably, 0.4 <c + d <0.7, and a + b + c + d = 1.

The content of the alkenyl group bonded to the silicon atom in the component (B) is preferably in the range of 0.01 to 1 mol per 100 g of the component (B) from the viewpoint of the strength and curability of the foam. More preferably, it is in the range of 04 to 0.4 mol / 100 g.

Specific examples of the component (B) include a three-dimensional network-like organopolysiloxane having a structural unit ratio represented by the following formulas (2) to (4). In addition, Vi represents a vinyl group, and Me represents a methyl group (hereinafter, the same applies).

The component (B) may be used alone or in combination of two or more.

The blending amount of the component (B) is 1 to 100 parts by mass, preferably 10 to 60 parts by mass with respect to 100 parts by mass of the organopolysiloxane of the component (A). If it is less than 1 part by mass, a sufficient reinforcing effect cannot be obtained, and if it exceeds 100 parts by mass, the foam may become brittle.

[Component (C)]
The component (C) is a hydrogen atom (that is, a SiH group) bonded to at least 2 (usually 2 to 300), preferably 3 to 150, and more preferably 3 to 100 silicon atoms in one molecule. It is an organohydrogenpolysiloxane containing the above, and reacts with the components (A) and (B) to form a crosslink, and also reacts with the component (D) described later to cause dehydrogenation and foam. Used as an agent.

The component (C) may be linear, branched, cyclic, or a three-dimensional network, and is not particularly limited.

Examples of such an organohydrogenpolysiloxane include an organohydrogenpolysiloxane represented by the following average composition formula (5).

（式中、Ｒ^２は独立に脂肪族不飽和結合を含有しない非置換又は置換の１価炭化水素基、又はアルコキシ基であり、ｅ及びｆは、０＜ｅ＜２、０．８≦ｆ≦２かつ０．８＜ｅ＋ｆ≦３となる数であり、好ましくは０．０５≦ｅ≦１、１．５≦ｆ≦２かつ１．８≦ｅ＋ｆ≦２．７となる数である。また、一分子中のケイ素原子の数（又は重合度）は、好ましくは２〜３００個であり、より好ましくは３〜２００個であり、更に好ましくは４〜１００個である。）

(In the formula, R ² is an unsubstituted or substituted monovalent hydrocarbon group or an alkoxy group independently containing no aliphatic unsaturated bond, and e and f are 0 <e <2, 0.8 ≦ f. The number is ≦ 2 and 0.8 <e + f ≦ 3, preferably 0.05 ≦ e ≦ 1, 1.5 ≦ f ≦ 2 and 1.8 ≦ e + f ≦ 2.7. , The number (or degree of polymerization) of silicon atoms in one molecule is preferably 2 to 300, more preferably 3 to 200, and even more preferably 4 to 100.)

In the above formula (5), the monovalent hydrocarbon radical unsubstituted or substituted free of aliphatic unsaturation of R ^2, the same one as the alkyl group and the aryl group exemplified as R ¹ described above In addition, examples of the alkoxy group include a methoxy group and an ethoxy group, preferably an alkyl group having 1 to 3 carbon atoms such as a methyl group, an ethyl group and an n-propyl group, and 3,3,3-trifluoropropyl. The group is an alkoxy group having 1 to 4 carbon atoms, and particularly preferably a methyl group, a methoxy group, or an ethoxy group.

Examples of such an organohydrogenpolysiloxane include 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethyltetracyclosiloxane, and 1,3,5,7,8-. Siloxane oligomers such as pentamethylpentacyclosiloxane, methylhydrogencyclopolysiloxane, methylhydrogensiloxane / dimethylsiloxane cyclic copolymer, tris (dimethylhydrogensiloxy) methylsilane; trimethylsiloxy group-blocked methylhydrogenpoly at both ends of the molecular chain Siloxane, trimethylsiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane copolymer at both ends of the molecular chain, silanol group-blocked methylhydrogenpolysiloxane at both ends of the molecular chain, silanol group-blocked dimethylsiloxane / methylhydrogensiloxane at both ends of the molecular chain Combined, dimethylhydrogensiloxy group-blocked dimethylpolysiloxane at both ends of the molecular chain, dimethylhydrogensiloxy group-blocked methylhydrogenpolysiloxane at both ends of the molecular chain, dimethylhydrogensiloxy group-blocked dimethylsiloxane at both ends of the molecular chain Polymers, etc .; _{consisting of 1/2} unit of ^{R 2} ₂ (H) SiO and 4/2 units of SiO, optionally R ² ₃ SiO _1/2 unit, R ² ₂ SiO _2/2 unit, R ² (H) SiO Methyl in these compounds, as well as silicone resins that can contain _2/2 units, (H) SiO _3/2 units or R ² SiO _3/2 ^{units (where R 2} is the ^{same as R 2 above).} Examples thereof include those obtained by substituting a part or all of the groups with other alkyl groups such as an ethyl group and a propyl group, and those represented by the following formula.

（式中、Ｒ^２は前記と同じであり、ｐ、ｑはそれぞれ０以上の整数である。括弧内のシロキサン単位の配列順は任意であってよい。）

(In the formula, R ² is the same as above, and p and q are integers of 0 or more, respectively. The arrangement order of the siloxane units in parentheses may be arbitrary.)

The component (C) may be used alone or in combination of two or more.

The organohydrogenpolysiloxane used in the foamable silicone rubber composition of the present invention can be obtained by a known method. For example, general formulas: R ² SiHCl ₂ and R ² ₂ SiHCl (in the formula, R ² is described above. At ^{least one chlorosilane selected from (same as R 2} ) is (co) hydrolyzed, or with the chlorosilane general formulas: R ² ₃ SiCl and R ² ₂ SiCl ₂ (in the formula, R ² is the aforementioned R). It can be obtained by combining at least one type of chlorosilane selected from (same as ^{2), co-hydrolyzing, and condensing.} Further, the organohydrogen polysiloxane may be an equilibrium of the polysiloxane obtained by (co) hydrolysis condensation in this way.

The blending amount of the component (C) is 1.0 to 80 parts by mass, preferably 10 to 20 parts by mass with respect to 100 parts by mass of the component (A). If the amount of the component (C) is too small, the composition of the present invention cannot be sufficiently foamed, while if it is too large, hydrogen atoms bonded to silicon atoms remain in the obtained silicone rubber foam and are cured. It may lead to deterioration of physical properties later.

The number of Si—H groups contained in the component (C) is 0.4 to the total of the vinyl groups of the components (A) and (B) and the hydroxyl groups of the component (D) described later. It is preferably 10 equivalents.

[(D) component]
The component (D) is at least one selected from the group consisting of water, alcohol, a silanol group-containing organosilane, and a silanol group-containing organosiloxane, and is a component having a function of reacting with the component (C) to foam.

Examples of the alcohol include monohydric or polyhydric alcohols having 1 to 12 carbon atoms, and preferably monohydric alkyl alcohols such as methanol, ethanol, propanol, isopropyl alcohol, butanol, lauryl alcohol and octyl alcohol. ..

Examples of the silanol group-containing organosilane include those represented by the following formulas.

（式中、Ｒ^２は前述のＲ^２と同じである。）

(In the equation, R ² is the ^{same as R 2} described above.)

Specific examples of such an organosilane include those represented by the following structural formulas.

Examples of the silanol group-containing organosiloxane include those represented by the following formulas.

（式中、Ｒ^２は前述のＲ^２と同じであり、ｒはｒ≧０、好ましくは１≦ｒ≦５０の整数である。）

(In the equation, R ² is the ^{same as R 2} described above, and r is an integer of r ≧ 0, preferably 1 ≦ r ≦ 50.)

Specific examples of such an organosiloxane include those represented by the following structural formulas.

（式中、ｓは０〜５０、好ましくは２〜１５の整数を示す。）

(In the formula, s represents an integer of 0 to 50, preferably 2 to 15.)

The component (D) may be used alone or in combination of two or more.

The blending amount of the component (D) is 0.5 to 50 parts by mass, preferably 1 to 10 parts by mass with respect to 100 parts by mass of the component (A). If the amount of the component (D) is too small, sufficient foamability cannot be obtained, and if it is too large, the mechanical strength of the obtained silicone rubber foam is lowered.

[(E) component]
The component (E) is a platinum group metal compound, that is, a platinum catalyst, and examples thereof include chloroplatinic acid or various complexes derived from the chloroplatinic acid. Examples of the platinum catalyst include platinum black; chloroplatinic acid; alcohol-modified products of chloroplatinic acid; complexes of chloroplatinic acid with olefins, aldehydes, vinyl siloxanes, acetylene alcohols, etc. It may be used or two or more kinds may be used in combination.

The blending amount of the component (E) may be an effective amount as a catalyst, and usually, the mass of platinum with respect to the entire composition can be 1 ppm or more, for example, 1 to 1,000 ppm, preferably 2 to 500 ppm.

[(F) component]
The component (F) is an organosilicon compound having at least one alkynyl group in one molecule, and is added to control the addition reaction of the foamable silicone rubber composition of the present invention.

Specific examples of the component (F) include a silane compound represented by the following structural formula.

The component (F) may be used alone or in combination of two or more.

The blending amount of the component (F) is 0.001 to 0.2 parts by mass, preferably 0.005 to 0.1 parts by mass with respect to 100 parts by mass of the component (A). If the blending amount is too small, the addition reaction may proceed during the mixing of the foamable silicone rubber composition and gelation may occur. If the blending amount is too large, not only the time until foaming after mixing becomes long but also foaming is poor. May be sufficient.

[(G) component]
The component (G) is a compound containing at least two alkenyl groups in one molecule and having an alkenyl group number of 0.06 to 1.5 mol / 100 g, and is a component that slowly proceeds the addition reaction at room temperature. is there. Since the reaction of the component (C) and the component (D) can be sufficiently proceeded by the gradual progress of the addition reaction, the foamable silicone rubber composition according to the present invention can be sufficiently foamed. ..

The component (G) is preferably an organopolysiloxane containing an alkenyl group. By doing so, the foamable silicone rubber composition having a higher foaming ratio can be obtained by allowing the addition reaction to proceed more slowly. Examples of the organopolysiloxane containing an alkenyl group include compounds represented by the following formulas.

（式中、Ｒ^２は前述のＲ^２と同じ意味であり、Ｒ^３はＲ^２またはビニル基を示す。また、ｔは４または５であり、ｘは１〜１００の整数であり、ｙは０〜５００の整数である。括弧内のシロキサン単位の配列順は任意であってよい。）

(In the formula, R ² has the same meaning ^{as R 2 described above, R 3} represents R ² or a vinyl group, t is 4 or 5, x is an integer of 1 to 100, and y is. It is an integer from 0 to 500. The arrangement order of the siloxane units in parentheses may be arbitrary.)

Specific examples of the component (G) include organopolysiloxane represented by the following formula.

（式中、括弧内のシロキサン単位の配列順は任意であってよい。）

(In the formula, the sequence order of the siloxane units in parentheses may be arbitrary.)

The component (G) may be used alone or in combination of two or more.

The blending amount of the component (G) is 0.01 to 5.0 parts by mass, preferably 0.05 to 1.0 parts by mass with respect to 100 parts by mass of the component (A). If the blending amount is too small, the reaction may proceed rapidly and foaming may be insufficient, and if the blending amount is too large, curing may take too long.

[Other ingredients]
Further, the foamable silicone rubber composition of the present invention includes inorganic fillers such as sprayed silica, fused silica glass, alumina and zinc oxide; fine powders of organic resins such as polymethacrylate resin; heat resistant agents, dyes, pigments and difficulties. It may contain a flammability-imparting agent or the like.

[Preparation method of foamable silicone rubber composition]
In the method for preparing the foamable silicone rubber composition of the present invention, all the components may be mixed at once to prepare, but since the reaction starts at room temperature, two or more kinds of compositions are mixed and used immediately before use. Is preferable.

Examples of the two-component mixed composition include (A) component, (B) component, (D) component, (E) component, (G) component, (H) component and, if necessary, other components. Examples thereof include a composition comprising i-liquid containing (A) component, (B) component, (C) component, (F) component, (H) component and, if necessary, other components.

[Silicone rubber foam]
A silicone rubber foam can be obtained by foaming and curing the foamable silicone rubber composition of the present invention. The foamable silicone rubber composition of the present invention undergoes an addition reaction and a dehydrogenation reaction in 30 minutes to 3 hours even under room temperature (low temperature) conditions such as 0 to 40 ° C. that do not require heating to obtain a silicone rubber foam. be able to. The obtained silicone rubber foam may be used as it is, but it is preferable to post-cure at 100 to 200 ° C. to complete the reaction in order to stabilize the physical properties of the foam.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

In the example below, the viscosity shows the value measured by a BH type rotational viscometer at 23 ° C.

[Examples 1 to 3, Comparative Examples 1 and 2]
The following components (A) to (I) were mixed in the blending amounts shown in Table 1 to prepare foamable silicone rubber compositions of Examples 1 to 3 and Comparative Examples 1 and 2. The components (H) and (I) correspond to other components. The numerical values of each component in Table 1 represent parts by mass.

(A) Polydimethylsiloxane represented by the following average formula (viscosity 30,000 mPa · s, vinyl group amount: 0.0027 mol / 100 g).

(B) _{Consists of SiO 4/2} units, Me ₃ SiO _1/2 units and ViMe ₂ SiO _1/2 units, and the molar ratio of Me ₃ SiO _1/2 and ViMe ₂ SiO _{1/2 to SiO 4/2 is} A silicone resin that is solid at 25 ° C. and has a vinyl group content of 0.085 mol / 100 g.

(C) Methylhydrogenpolysiloxane represented by the following average formula (viscosity 20 mPa · s, hydrogen gas generation amount 375 ml / g).

(D) Water.

(E) A platinum catalyst (platinum atomic weight: 1% by mass) having tetramethyldivinyldisiloxane as a ligand derived from chloroplatinic acid.

(F) Bis [(1,1-dimethyl-2-propynyl) oxy] dimethylsilane.

(G) 2,4,6,8-Tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (vinyl group amount: 1.15 mol / 100 g).

(H) Haze-like silica (specific surface area 300 m ² / g, surface dimethyldichlorosilane treatment).

(I) Aluminum hydroxide (manufactured by Showa Denko KK, H320I, average particle size 10 μm).

In Table 1, the values of [Si−H] / [Si−Vi + OH] are the components (A), (B), vinyl group (Vi) in the component (G), and the component (D). It is the equivalent ratio of the Si—H group in the component (C) to the total of the hydroxyl groups (OH) in.

The foamable silicone rubber compositions of Examples 1 to 3 and Comparative Examples 1 and 2 were each cured at 23 ° C. for 24 hours to obtain a silicone rubber foam.

[Evaluation]
Time when the swelling of the foam stopped, the hardness and density of the silicone rubber foam, the foaming ratio (density of the cured product when cured without adding the component (D) in Example 1; 1.20 / foam Density) and the cell shape of the silicone rubber foam were evaluated. The results are also shown in Table 1.

As shown in Table 1, the silicone rubber foam obtained by curing the foamable silicone rubber composition (Examples 1 to 3) of the present invention is obtained by curing the compositions of Comparative Examples 1 and 2. It can be seen that it is a silicone rubber foam having a high expansion ratio and a low density as compared with the silicone rubber foam. On the other hand, Comparative Example 1 was a silicone rubber foam having a low foaming ratio and a high density because it did not contain the component (G) according to the present invention. Further, in Comparative Example 2, although the amount of the component (F) added as the reaction control agent was increased, the component (G) according to the present invention was not contained, so that the foaming ratio was low and the silicone rubber was foamed at a high density. It was a body. From the above, the silicone rubber foam composed of the foamable silicone rubber composition and the cured product thereof according to the present invention can have a high foaming ratio and a low density.

The present invention is not limited to the above embodiment. The above-described embodiment is an example, and any object having substantially the same configuration as the technical idea described in the claims of the present invention and exhibiting the same effect and effect is the present invention. Is included in the technical scope of.

Claims (3)

(A) A straight chain containing two or more alkenyl groups having 2 to 8 carbon atoms bonded to silicon atoms in one molecule and having an alkenyl group number of 0.001 mol / 100 g or more and less than 0.06 mol / 100 g. Organopolysiloxane: 100 parts by mass,
(B) Three-dimensional network-like organopolysiloxane represented by the general formula (1): 1 to 100 parts by mass,

(In the formula, R ¹ is a monovalent hydrocarbon group independently selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, and an alkenyl group having 2 to 10 carbon atoms. , at least two of ^{R 1} are alkenyl groups in one molecule, which is a ≧ 0, b ≧ 0, c ≧ 0, d ≧ 0, c + d> 0 and the number to be a + b + c + d = 1),
(C) Organohydrogenpolysiloxane containing hydrogen atoms bonded to at least two silicon atoms in one molecule: 1.0 to 80 parts by mass,
(D) At least one selected from the group consisting of water, alcohol, silanol group-containing organosilane and silanol group-containing organosiloxane: 0.5 to 50 parts by mass,
(E) Platinum group metal compound,
(F) Organosilicon compound containing at least one alkynyl group in one molecule: 0.001 to 0.2 parts by mass,
(G) A compound containing at least two alkenyl groups in one molecule and having an alkenyl group number of 0.06 to 1.5 mol / 100 g: 0.01 to 5.0 parts by mass,
A foamable silicone rubber composition characterized by containing. The foamable silicone rubber composition according to claim 1, wherein the component (G) is an organosiloxane containing an alkenyl group bonded to a silicon atom. A silicone rubber foam which comprises a cured product of the foamable silicone rubber composition according to claim 1 or 2.