JP7352454B2 - Expandable silicone rubber composition and silicone rubber foam - Google Patents

Description

The present invention relates to foamable silicone rubber compositions and silicone rubber foams.

Silicone rubber foams combine the heat resistance, cold resistance, and electrical insulation properties of silicone rubber with the elasticity of sponges, so they are used as rolls in office automation equipment, building materials, automobile materials, etc. for low thermal conductivity, sound absorption, and It is used to promote weight reduction. Additionally, when organic resin-based polyurethane foam, which is widely used around the world, burns, it produces black smoke and toxic gas and burns violently, whereas silicone foam is highly flame retardant and generates less heat. For this reason, in recent years, it has been studied for use in seats and flooring materials for automobiles and railway vehicles.

Silicone rubber foams are manufactured in a variety of ways depending on their use. A typical example is one in which a foaming agent is added to a gum-like diorganopolysiloxane and cured by heating, and the curing mechanism includes an addition reaction using a platinum catalyst and a radical crosslinking reaction using an organic peroxide. Further, as a blowing agent, an azo compound such as azobisisobutyronitrile or 1,1-azobis(cyclohexane-1-methylcarboxylate) is used.

In addition, as a method for producing foam using liquid diorganopolysiloxane, Patent Document 1 describes a curing mechanism that involves a dehydrogenation reaction during curing. A manufacturing method using a composition comprising 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 manufacturing method in which an acetylene alcohol compound is added and foamed and hardened by heating. Patent Document 3 discloses a manufacturing method in which an inorganic thickener and a nonionic surfactant are added to form a fine open cell structure.

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

As the demands for lower thermal conductivity, sound absorption, and weight reduction in silicone foams have increased, further improvements in expansion ratio have been required.

The present invention was 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 expansion 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-mentioned problems, in the present invention,
(A) A straight chain containing two or more alkenyl groups having 2 to 8 carbon atoms bonded to a silicon atom 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. organopolysiloxane: 100 parts by mass,
(B) Three-dimensional network organopolysiloxane represented by 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 R ¹ in one molecule are alkenyl groups, and the number satisfies a≧0, b≧0, c≧0, d≧0, c+d>0 and a+b+c+d=1),
(C) organohydrogenpolysiloxane containing at least two hydrogen atoms bonded to silicon atoms in one molecule: 1.0 to 80 parts by mass,
(D) at least one member 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 a foamable silicone rubber composition containing:

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

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

With such a composition, by allowing the addition reaction to proceed slowly, a foamable silicone rubber composition having a higher expansion ratio can be obtained.

The present invention also provides a silicone rubber foam made of a cured product of the above-described foamable silicone rubber composition.

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

The foamable silicone rubber composition of the present invention can provide a silicone rubber foam with a high expansion ratio and low density, and is useful for office automation equipment, building materials, automobile materials, and the like.

As mentioned above, as the demands for lower thermal conductivity, sound absorption, and weight reduction in silicone foams have increased, expandable silicone rubber compositions and silicone rubber foams with high expansion ratios have been sought.

As a result of intensive studies regarding the above-mentioned problems, the present inventors have found that a foamable silicone rubber composition containing components (A) to (G) described below has a high expansion ratio, and that a foamable silicone rubber composition as described above has a high expansion ratio. The present invention was completed based on the discovery that the density of a silicone rubber foam made of a cured product of a silicone rubber foam 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 a silicon atom 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. organopolysiloxane: 100 parts by mass,
(B) Three-dimensional network organopolysiloxane represented by 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 R ¹ in one molecule are alkenyl groups, and the number satisfies a≧0, b≧0, c≧0, d≧0, c+d>0 and a+b+c+d=1),
(C) organohydrogenpolysiloxane containing at least two hydrogen atoms bonded to silicon atoms in one molecule: 1.0 to 80 parts by mass,
(D) at least one member 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 containing:

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

[Foamable silicone rubber composition]
The foamable silicone rubber composition of the present invention contains the following components (A) to (G). In addition, although the property of this composition is not particularly limited, it is preferably liquid.

[(A) Component]
Component (A) contains two or more alkenyl groups having 2 to 8 carbon atoms bonded to a silicon atom 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. It is a certain linear organopolysiloxane.

The position of the silicon atom to which the alkenyl group is bonded in the molecule of component (A) may be either at the end of the molecular chain or in the middle of the molecular chain, or either or both. One molecule of component (A) contains an average of 2 or more alkenyl groups, preferably 2 to 20 alkenyl groups, and more preferably 2 to 10 alkenyl groups directly bonded to a silicon atom. Particularly preferred as component (A) are linear diorganopolysiloxanes containing at least alkenyl groups bonded to silicon atoms at both ends of the molecular chain.

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

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

In the organopolysiloxane of component (A), examples of organic groups bonded to silicon atoms other than alkenyl groups include alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, and heptyl groups. Aryl groups such as phenyl, tolyl, xylyl and naphthyl groups; Aralkyl groups such as benzyl and phenethyl groups; Halogens such as chloromethyl, 3-chloropropyl and 3,3,3-trifluoropropyl groups Examples include alkyl groups, and methyl groups are particularly preferred.

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

Specific examples of organopolysiloxane as component (A) include dimethylsiloxane/methylvinylsiloxane copolymer with trimethylsiloxy groups endblocked at both molecular chain ends, methylvinylpolysiloxane endblocked with trimethylsiloxy groups at both molecular chain ends, and trimethyl endblocked at both molecular chain ends. Siloxy-blocked dimethylsiloxane/methylvinylsiloxane/methylphenylsiloxane copolymer, dimethylpolysiloxane blocked with dimethylvinylsiloxy groups at both molecular chain ends, methylvinylpolysiloxane blocked with dimethylvinylsiloxy groups at both molecular chain ends, dimethylvinyl at both molecular chain ends Siloxy group-blocked dimethylsiloxane/methylvinylsiloxane copolymer, dimethylvinylsiloxy group-blocked dimethylsiloxane/methylvinylsiloxane/methylphenylsiloxane copolymer on both molecular chain ends, dimethylpolysiloxane blocked with divinylmethylsiloxy groups on both molecular chain ends, molecule Dimethylsiloxane/methylvinylsiloxane copolymer with divinylmethylsiloxy groups blocked at both chain ends, dimethylpolysiloxane with trivinylsiloxy groups blocked at both molecular chain ends, dimethylsiloxane/methylvinylsiloxane copolymer with trivinylsiloxy groups blocked at both molecular chain ends, and a mixture of two or more of these organopolysiloxanes. In addition, (A) component may be used individually by 1 type, or may use 2 or more types together.

（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]
Component (B) is a three-dimensional network 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 R ^1s in one molecule are alkenyl groups, and the number satisfies a≧0, b≧0, c≧0, d≧0, c+d>0 and a+b+c+d=1.)

Component (B) is preferably solid or gum-like (raw rubber-like) showing almost no self-flowing properties of 10,000,000 mPa·s or more, especially 100,000,000 mPa·s or more at 25°C. Such a three-dimensional network organopolysiloxane (silicone resin) can further improve the hardness of the silicone rubber foam.

In 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. At least 2, preferably 2 to 10 R ¹ 's in one molecule are alkenyl groups.

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 a vinyl group is preferable from the viewpoint of compatibility with other components.

Examples of R ¹ other than alkenyl groups include alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, and heptyl; aryl groups such as phenyl, tolyl, xylyl, and naphthyl; Examples include aralkyl groups such as benzyl group and phenethyl group; halogenated alkyl groups such as chloromethyl group, 3-chloropropyl group, and 3,3,3-trifluoropropyl group, but methyl group is particularly preferred. preferable.

In formula (1), the numbers a, b, c, and d are respectively 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.

In component (B), the content of alkenyl groups bonded to silicon atoms is preferably in the range of 0.01 to 1 mol per 100 g of component (B) from the viewpoint of the strength and curability of the foam. More preferably, the amount is in the range of 0.04 to 0.4 mol/100 g.

Specific examples of component (B) include three-dimensional network organopolysiloxanes having structural unit ratios represented by the following formulas (2) to (4). Note that Vi represents a vinyl group and Me represents a methyl group (the same applies hereinafter).

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

The amount of component (B) to be blended is 1 to 100 parts by weight, preferably 10 to 60 parts by weight, per 100 parts by weight of the organopolysiloxane (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.

[(C) Component]
Component (C) contains at least 2 (usually 2 to 300), preferably 3 to 150, more preferably 3 to 100 silicon-bonded hydrogen atoms (i.e., SiH groups) in one molecule. It is an organohydrogenpolysiloxane that reacts with components (A) and (B) to form crosslinks, and also acts as a crosslinking agent and foaming agent that reacts with component (D) to cause dehydrogenation and foaming. used as an agent.

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

Examples of such organohydrogenpolysiloxanes include organohydrogenpolysiloxanes 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 independently an unsubstituted or substituted monovalent hydrocarbon group containing no aliphatic unsaturated bond, or an alkoxy group, and e and f are 0<e<2, 0.8≦f ≦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 of silicon atoms (or degree of polymerization) 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), examples of the unsubstituted or substituted monovalent hydrocarbon group containing no aliphatic unsaturated bond for R ² include the same alkyl groups and aryl groups exemplified as R ¹ above. In addition, examples of alkoxy groups include methoxy groups and ethoxy groups, preferably alkyl groups having 1 to 3 carbon atoms such as methyl group, ethyl group, n-propyl group, and 3,3,3-trifluoropropyl group. group, 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 organohydrogenpolysiloxane include 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethyltetracyclosiloxane, 1,3,5,7,8- Siloxane oligomers such as pentamethylpentacyclosiloxane, methylhydrogencyclopolysiloxane, methylhydrogensiloxane/dimethylsiloxane cyclic copolymer, tris(dimethylhydrogensiloxy)methylsilane; Methylhydrogenpolymer with trimethylsiloxy group-blocked at both molecular chain ends Siloxane, dimethylsiloxane/methylhydrogensiloxane copolymer with both molecular chain ends blocked by trimethylsiloxy groups, methylhydrogenpolysiloxane with both molecular chain ends blocked with silanol groups, dimethylsiloxane/methylhydrogensiloxane copolymer with silanol groups blocked at both molecular chain ends Combined, dimethylpolysiloxane with dimethylhydrogensiloxy groups blocked at both molecular chain ends, methylhydrogenpolysiloxane with dimethylhydrogensiloxy groups blocked at both molecular chain ends, dimethylsiloxane/methylhydrogensiloxane with dimethylhydrogensiloxy groups blocked at both molecular chain ends Polymer, etc.: Consisting of R ² ₂ (H) SiO _1/2 units and SiO _4/2 units, optionally R ² ₃ SiO _1/2 units, R ² ₂ SiO _2/2 units, R ² (H) SiO In addition to silicone resins that may 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), methyl Examples include those in which part or all of the group is substituted with other alkyl groups such as ethyl group and propyl group, and those represented by the following formulas.

（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 each an integer of 0 or more. The arrangement order of the siloxane units in parentheses may be arbitrary.)

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, the general formula: R ² SiHCl ₂ and R ² ₂ SiHCl (wherein R ² is the aforementioned R ² is the same as R 2 ), or the chlorosilane and the general formula: R ² ₃ SiCl and R ² ₂ SiCl ₂ (wherein R ² is the above-mentioned R It can be obtained by co-hydrolyzing and condensing a combination of at least one type of chlorosilane selected from (same as ² ). Further, the organohydrogenpolysiloxane may be one obtained by equilibrating the polysiloxane obtained by (co)hydrolytic condensation in this manner.

The blending amount of component (C) is 1.0 to 80 parts by weight, preferably 10 to 20 parts by weight, per 100 parts by weight of component (A). If the amount of 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 will remain in the resulting silicone rubber foam, resulting in hardening. This may lead to deterioration of physical properties later.

Furthermore, the number of Si--H groups contained in component (C) is 0.4 to 0.4 to the sum of vinyl groups in components (A) and (B) and hydroxyl groups in component (D), which will be described later Preferably it is 10 equivalents.

[(D) Component]
Component (D) is at least one member selected from the group consisting of water, alcohol, silanol group-containing organosilane, and silanol group-containing organosiloxane, and is a component that reacts with component (C) to cause foaming.

Examples of the alcohol include monohydric or polyhydric alcohols having 1 to 12 carbon atoms, 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 formula.

（式中、Ｒ^２は前述のＲ^２と同じである。）

(In the formula, R ² is the same as R ² described above.)

Specific examples of such organosilanes include those represented by the following structural formula.

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

（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 formula, 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 organosiloxanes include those represented by the following structural formula.

（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.)

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

The blending amount of component (D) is 0.5 to 50 parts by weight, preferably 1 to 10 parts by weight, per 100 parts by weight of component (A). If the amount of component (D) is too small, sufficient foamability will not be obtained, and if it is too large, the mechanical strength of the resulting silicone rubber foam will be reduced.

[(E) component]
Component (E) is a platinum group metal compound, ie, a platinum catalyst, and includes chloroplatinic acid or various complexes derived therefrom. Examples of platinum catalysts include platinum black; chloroplatinic acid; alcohol-modified products of chloroplatinic acid; complexes of chloroplatinic acid and olefins, aldehydes, vinyl siloxanes, or acetylene alcohols; They may be used or two or more types may be used in combination.

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

[(F) component]
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 component (F) include silane compounds represented by the following structural formula.

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

The blending amount of component (F) is 0.001 to 0.2 parts by mass, preferably 0.005 to 0.1 parts by mass, per 100 parts by mass of component (A). If the amount is too small, an addition reaction may proceed during mixing of the foamable silicone rubber composition and gelation may occur, and if it is too large, not only will it take a long time to foam after mixing, but foaming may fail. Sometimes that's enough.

[(G) component]
Component (G) is a compound that contains at least two alkenyl groups in one molecule and has a number of alkenyl groups of 0.06 to 1.5 mol/100g, and is a component that allows the addition reaction to proceed slowly at room temperature. be. Since the addition reaction proceeds slowly, the reaction between component (C) and component (D) can proceed sufficiently, so that the foamable silicone rubber composition according to the present invention can be sufficiently foamed. .

Component (G) is preferably an organopolysiloxane containing an alkenyl group. In this way, by allowing the addition reaction to proceed more slowly, a foamable silicone rubber composition having a higher expansion ratio can be obtained. Furthermore, examples of organopolysiloxanes containing alkenyl groups 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 from 1 to 100, and y is It is an integer from 0 to 500. The siloxane units in parentheses may be arranged in any order.)

Specific examples of component (G) include organopolysiloxanes 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 siloxane units in parentheses may be arranged in any order.)

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

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

[Other ingredients]
Furthermore, the foamable silicone rubber composition of the present invention contains inorganic fillers such as atomized silica, fused silica glass, alumina, and zinc oxide; fine powder of organic resin such as polymethacrylate resin; heat resistant agents, dyes, pigments, and It may also contain a flammability imparting agent.

[Preparation method of foamable silicone rubber composition]
The foamable silicone rubber composition of the present invention may be prepared by mixing all the components at once, but since the reaction starts at room temperature, two or more compositions are mixed immediately before use. It is preferable.

A two-component mixture type composition includes, for example, component (A), component (B), component (D), component (E), component (G), component (H), and other components as necessary. Examples include a composition consisting of a liquid I containing a component (A), a component (B), a component (C), a component (F), a component (H) and a liquid II containing other components as necessary.

[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, yielding 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 explained using Examples and Comparative Examples, but the present invention is not limited thereto.

In the following examples, the viscosity indicates a value measured using 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 amounts shown in Table 1 to prepare foamable silicone rubber compositions of Examples 1 to 3 and Comparative Examples 1 and 2. Note that the (H) and (I) components correspond to other components. Moreover, the numerical value of each component in Table 1 represents parts by mass.

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

(B) It is composed 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 0.8 and a vinyl group weight of 0.085 mol/100g, which is solid at 25°C.

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

(D) Water.

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

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

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

(H) Fumed silica (specific surface area 300 m ² /g, surface treated with dimethyldichlorosilane).

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

In Table 1, the value of [Si-H]/[Si-Vi + OH] is the vinyl group (Vi) in component (A), component (B), and component (G), and component (D). This is the equivalent ratio of Si--H groups in component (C) to the total hydroxyl groups (OH) in component (C).

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 silicone rubber foams.

[evaluation]
Time when the foam stopped swelling, hardness, density, and expansion ratio of the silicone rubber foam (density of the cured product when cured without adding component (D) in Example 1; 1.20/foam) density) and 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 foams obtained by curing the foamable silicone rubber compositions of the present invention (Examples 1 to 3) are the same as those obtained by curing the compositions of Comparative Examples 1 and 2. It can be seen that the silicone rubber foam has a higher expansion ratio and lower density compared to the silicone rubber foam. On the other hand, Comparative Example 1 did not contain the component (G) according to the present invention, so it was a silicone rubber foam with a low expansion ratio and high density. In addition, in Comparative Example 2, although the added amount of component (F) which is a reaction control agent was increased, it did not contain component (G) according to the present invention, resulting in low expansion ratio and high density silicone rubber foaming. It was the body. From the above, the foamable silicone rubber composition according to the present invention and the silicone rubber foam made of the cured product thereof can have a high expansion ratio and a low density.

Note that the present invention is not limited to the above embodiments. The above-mentioned embodiments are illustrative, and any embodiment that has substantially the same configuration as the technical idea stated in the claims of the present invention and has similar effects is the present invention. covered within the technical scope of.

Claims (1)

(A) A straight chain containing two or more alkenyl groups having 2 to 8 carbon atoms bonded to a silicon atom 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. organopolysiloxane: 100 parts by mass,
(B) Three-dimensional network organopolysiloxane represented by 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 R ¹ in one molecule are alkenyl groups, and the number satisfies 0.1<a<0.7, b≧0, c≧0, d≧0, c+d>0 and a+b+c+d=1. be),
(C) organohydrogenpolysiloxane containing at least two hydrogen atoms bonded to silicon atoms in one molecule: 1.0 to 80 parts by mass,
(D ) Silanol group-containing organosilane : 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) Organopolysiloxane containing at least two alkenyl groups in one molecule represented by the following formula and having an alkenyl group number of 0.06 to 1.5 mol/100 g: 0.01 to 5.0 mass Department,

(In the formula, R ² is independently an unsubstituted or substituted monovalent hydrocarbon group containing no aliphatic unsaturated bond or an alkoxy group, R ³ is R ² or a vinyl group, and x is 1 ~100, and y is an integer from 0 to 500. The siloxane units in parentheses may be arranged in any order.)
1. A foamable silicone rubber composition comprising: