JP4217869B2 - Silicone rubber composition - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a silicone rubber composition that provides a silicone rubber molded article having low thermal conductivity, a low thermal expansion coefficient, and excellent dimensional stability during heating.
[0002]
[Prior art and problems to be solved by the invention]
The heat-curable liquid silicone rubber composition is excellent in moldability and is used in various fields because a cured product having excellent heat resistance, weather resistance, electrical insulation and the like can be obtained after molding. On the other hand, the silicone rubber sponge can be reduced in weight while having excellent performances such as heat resistance, weather resistance, and electrical insulation of the silicone rubber. It can be used in various fields such as the performance as a shock absorbing material (cushion material) utilizing shrinkage, and the use as a heat insulation or heat storage material utilizing low thermal conductivity by enclosing gas.
[0003]
Silicone rubber foam is a material for obtaining such a silicone rubber sponge, and there are a method of adding a pyrolytic foaming agent and a method of using hydrogen gas by-produced during curing. In the method of adding, the toxicity and smell of the decomposition gas are regarded as problems, and in the case of using a platinum catalyst as the curing catalyst, the inhibition of curing by the foaming agent has been a problem. On the other hand, in the method using hydrogen gas produced as a by-product during curing, there are problems such as the explosive nature of hydrogen gas and caution when handling uncured materials during storage. Further, the method of generating gas has a problem that it is difficult to obtain uniformly controlled bubbles, particularly when the silicone rubber composition is a liquid composition.
[0004]
As a method for improving such a point, a rubber containing inorganic hollow powder of glass, ceramics or the like is known. However, since the specific gravity is large, it does not sufficiently contribute to weight reduction. Although it is an inorganic material, its thermal conductivity and cushioning properties are insufficient. Also known are methods of adding hollow fillers made of organic resins and organic resin fillers that expand by heat by encapsulating highly volatile substances (JP-A-5-209080, JP-A-9-137063). However, the organic resin filler has a large coefficient of thermal expansion because the filler itself has elasticity, and the dimensions change greatly at high temperatures, making it impossible to fully utilize the heat resistance of silicone rubber. .
[0005]
Therefore, these compositions are lightweight, have low thermal conductivity and require dimensional stability, sealing materials for automobiles and electrical / electronic devices, gaskets, cushion materials, various connector members for office machines, printers and copying machines. It was unsuitable for various roll materials and various sheet materials in the electric / electronic field.
[0006]
The present invention has been made in view of the above circumstances, and contains an organic resin filler and an inorganic filler that give a cured silicone rubber that is lightweight and has low thermal conductivity, excellent heat resistance, and good dimensional stability during heating. An object is to provide a silicone rubber composition.
[0007]
Means for Solving the Problem and Embodiment of the Invention
As a result of intensive studies in order to achieve the above object, the present inventor has found that a thermosetting organopolysiloxane composition has a non-expanded organic resin micro-hollow filler that can be expanded by heat or an organic resin micro-hollow that has already expanded. It has been found that by adding an inorganic hollow filler to a silicone rubber composition containing a filler, a material that is lightweight, has low thermal conductivity, has a low coefficient of thermal expansion, and has excellent dimensional stability can be obtained. The present invention has been made.
[0008]
  That is, the present invention provides the following thermosetting silicone rubber composition.
[1] (A) As a thermosetting organopolysiloxane composition,
(1) Organopolysiloxane containing an alkenyl group bonded to at least two silicon atoms in one molecule: 100 parts by weight
(2) Organohydrogenpolysiloxane containing hydrogen atoms bonded to at least two silicon atoms in one molecule: 0.1 to 50 parts by weight
(3) Addition reaction catalyst: catalyst amount
100 parts by weight of an addition-curable organopolysiloxane composition consisting of
(B) 0.1-30 parts by weight of an unexpanded organic resin micro hollow filler or an expanded organic resin micro hollow filler that can be expanded by heat,
(C) Inorganic hollow filler selected from silica balloon, carbon balloon, alumina balloon, aluminosilicate balloon and zirconia balloon, having a specific gravity of 0.1 to 0.8 and an average particle diameter of 10 to 200 μm29.7~ 70 parts by weight
A thermosetting silicone rubber composition comprising:
[2] (A) As a thermosetting organopolysiloxane composition,
(A) The following average composition formula (iii)
          R^Three _dSiO_{(4-d) / 2}        (Iii)
(Wherein R^ThreeRepresents a substituted or unsubstituted monovalent hydrocarbon group, R^Three0.0001 to 10 mol% of the alkenyl group is an alkenyl group, and 80 mol% or more is a methyl group. d is a positive number of 1.9 to 2.4. )
100 parts by weight of an organopolysiloxane having an average of at least two alkenyl groups in one molecule represented by
(B) Organic peroxide: Amount of catalyst
Organic peroxide curable organopolysiloxane composition comprising only
                                                          100 parts by weight,
(B) 0.1-30 parts by weight of an unexpanded organic resin micro hollow filler or an expanded organic resin micro hollow filler that can be expanded by heat,
(C) Inorganic hollow filler selected from silica balloon, carbon balloon, alumina balloon, aluminosilicate balloon and zirconia balloon, having a specific gravity of 0.1 to 0.8 and an average particle diameter of 10 to 200 μm 2 to 70 parts by weight
A thermosetting silicone rubber composition comprising:
[0009]
Hereinafter, the present invention will be described in more detail.
The thermosetting organopolysiloxane composition as component (A) of the present invention is preferably an addition reaction curable organopolysiloxane composition or an organic peroxide curable organopolysiloxane composition. The reaction-curable organopolysiloxane composition is
(1) 100 parts by weight of an organopolysiloxane containing an alkenyl group bonded to at least two silicon atoms in one molecule;
(2) 0.1 to 50 parts by weight of an organohydrogenpolysiloxane containing a hydrogen atom bonded to at least two silicon atoms in one molecule;
(3) Addition reaction catalyst Amount of catalyst
What consists only of, and as an organic peroxide curable organopolysiloxane composition,
(A) The following average composition formula (iii)
R^Three _dSiO_{(4-d) / 2}        (Iii)
(Wherein R^ThreeRepresents a substituted or unsubstituted monovalent hydrocarbon group, R^Three0.0001 to 10 mol% of the alkenyl group is an alkenyl group, and 80 mol% or more is a methyl group. d is a positive number of 1.9 to 2.4. )
100 parts by weight of an organopolysiloxane having an average of at least two alkenyl groups in one molecule represented by
(B) Organic peroxide catalyst amount
What consists only of is preferable.
[0010]
Here, as the (1) component of the addition reaction curable organopolysiloxane composition, as the organopolysiloxane having at least two alkenyl groups in one molecule, those represented by the following average composition formula (i) are mainly used. It can be used as (base polymer).
R¹ _aSiO_{(4-a) / 2}        (I)
[0011]
Where R¹Is 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 1.8 to 2.5, More preferably, it is a positive number in the range of 1.95 to 2.05. Where R¹As the unsubstituted or substituted monovalent hydrocarbon group bonded to the silicon atom represented by the following, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, Hexyl group, cyclohexyl group, octyl group, nonyl group, decyl group and other alkyl groups, phenyl group, tolyl group, xylyl group, naphthyl group and other aryl groups, benzyl group, phenylethyl group, phenylpropyl group and other aralkyl groups, Alkenyl groups such as vinyl group, allyl group, propenyl group, isopropenyl group, butenyl group, hexenyl group, cyclohexenyl group, octenyl group, etc., and part or all of the hydrogen atoms of these groups are fluorine, bromine, chlorine, etc. Substituted with a halogen atom, cyano group, etc., such as chloromethyl, chloropropyl, bromoe Group, such as halogen-substituted alkyl group or cyanoethyl group such trifluoropropyl group.
[0012]
In this case, R¹At least two of them must be alkenyl groups (preferably having 2 to 8 carbon atoms, more preferably 2 to 6). The content of the alkenyl group is the total organic group (that is, the above-mentioned unsubstituted or substituted monovalent hydrocarbon group) R¹The content is preferably 0.0001 to 20 mol%, preferably 0.001 to 10 mol%, particularly about 0.01 to 5 mol%. This alkenyl group may be bonded to a silicon atom at the end of the molecular chain, or may be bonded to a silicon atom in the middle of the molecular chain, or may be bonded to both. Those containing bonded alkenyl groups are preferred.
[0013]
The degree of polymerization is not particularly limited and can be from liquid to raw rubber at normal temperature, but the average degree of polymerization is usually 50 to 20,000, preferably 100 to 10,000, more preferably 100 to 2. About 1,000 is preferably used.
[0014]
The structure of this organopolysiloxane basically has a main chain of diorganosiloxane units (R¹ ₂SiO_2/2), And both ends of the molecular chain are triorganosiloxy groups (R¹ _ThreeSiO_1/2), But may be partially branched or cyclic.
[0015]
The organohydrogenpolysiloxane of component (2) acts as a crosslinking agent for curing the composition by hydrosilylation addition reaction with the alkenyl group-containing organopolysiloxane of component (1), and the following average composition formula (ii)
R² _bH_cSiO_{(4-bc) / 2}          (Ii)
(Wherein R²Is a substituted or unsubstituted 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. )
It is necessary to have at least 2, preferably 3 or more (usually about 3 to 200), more preferably 3 to 100 silicon atom-bonded hydrogen atoms (SiH group) in one molecule. is there.
[0016]
Where R²As R in formula (i)¹The same groups as those mentioned above can be mentioned, but those having no aliphatic unsaturated bond are preferred.
[0017]
  Examples of the organohydrogenpolysiloxane include 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, trimethylsiloxy group-blocked methylhydrogenpolysiloxane, both ends Trimethylsiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane copolymer, both ends dimethylhydrogensiloxy group-blocked dimethylpolysiloxane, both ends dimethylhydrogensiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane copolymer, both ends trimethylsiloxy Blocked methylhydrogensiloxane / diphenylsiloxane copolymer, trimethylsiloxy group-blocked methylhydrogensiloxane / diphenylsiloxane / dimethylsiloxane copolymer on both ends Body, (CH_Three)₂HSiO_1/2Unit and SiO_4/2Copolymer consisting of units, (CH_Three)₂HSiO_1/2Unit and SiO_4/2Units and(C ₆ H _Five ) SiO _3/2 And a copolymer composed of units.
[0018]
The molecular structure of the organohydrogenpolysiloxane may be any of linear, cyclic, branched, and three-dimensional network structures, but the number of silicon atoms in one molecule (or the degree of polymerization) is 3 to 1. , Especially about 3 to 300 can be used.
[0019]
The compounding amount of the organohydrogenpolysiloxane is preferably 0.1 to 50 parts by weight, more preferably 0.3 to 30 parts by weight, based on 100 parts by weight of the organopolysiloxane (1).
[0020]
The organohydrogenpolysiloxane has a molar ratio of hydrogen atoms bonded to silicon atoms in the component (2) (that is, SiH groups) to alkenyl groups bonded to silicon atoms in the component (1) of 0.5. -5 mol / mol, preferably 0.8 to 4 mol / mol, more preferably 1 to 3 mol / mol.
[0021]
The addition reaction catalyst for component (3) is a catalyst for promoting the hydrosilylation addition reaction between the alkenyl group in component (1) and the SiH group in component (2). The addition reaction catalyst is platinum. Black, platinum chloride, chloroplatinic acid, reaction product of chloroplatinic acid and monohydric alcohol, complex of chloroplatinic acid and olefins, platinum catalyst such as platinum bisacetoacetate, palladium catalyst, rhodium catalyst Platinum group metal catalysts such as In addition, although the compounding quantity of this addition reaction catalyst can be made into a catalyst amount, 0.5-1,000 ppm with respect to the total weight of (1) and (2) component as a platinum group metal normally, especially 1-. It is preferable to blend about 500 ppm.
[0022]
On the other hand, the component (A), which is the main component (base polymer) of the organic peroxide-curable organopolysiloxane composition, has the following average composition formula (iii)
R^Three _dSiO_{(4-d) / 2}        (Iii)
(Wherein R^ThreeRepresents a substituted or unsubstituted monovalent hydrocarbon group, R^Three0.0001 to 10 mol% of the alkenyl group is an alkenyl group, and 80 mol% or more is a methyl group. d is a positive number of 1.9 to 2.4. )
Is an organopolysiloxane having an average of at least two alkenyl groups in one molecule.
[0023]
Where R^ThreeIs an unsubstituted or substituted monovalent hydrocarbon group having the same or different carbon number of 1 to 10, preferably 1 to 8, and d is 1.9 to 2.4, preferably 1.95 to 2.05, More preferably, it is a positive number in the range of 1.98 to 2.02. R above^ThreeAs the unsubstituted or substituted monovalent hydrocarbon group bonded to the silicon atom represented by the above formula, R in the above average composition formula (i)¹And the like, such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, cyclohexyl group, octyl group, nonyl group, decyl group, etc. Aryl group such as alkyl group, phenyl group, tolyl group, xylyl group, naphthyl group, aralkyl group such as benzyl group, phenylethyl group, phenylpropyl group, vinyl group, allyl group, propenyl group, isopropenyl group, butenyl group, Alkenyl groups such as hexenyl group, cyclohexenyl group, octenyl group, etc., and those in which part or all of hydrogen atoms of these groups are substituted with halogen atoms such as fluorine, bromine, chlorine, cyano groups, etc., such as chloromethyl group, Halogen-substituted alkyl groups such as chloropropyl group, bromoethyl group, and trifluoropropyl group Cyanoethyl group, and the like.
[0024]
In this case, R^ThreeAt least two of them must be alkenyl groups (preferably having 2 to 8 carbon atoms, more preferably 2 to 6). The content of the alkenyl group is the total organic group (that is, the above-mentioned unsubstituted or substituted monovalent hydrocarbon group) R^ThreeThe content is preferably 0.0001 to 10 mol%, particularly 0.001 to 5 mol%. 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.
[0025]
The degree of polymerization is not particularly limited and can be from liquid to raw rubber at normal temperature. Usually, the average degree of polymerization is from 50 to 20,000, preferably from 100 to 10,000, more preferably from 100 to 2 ,. About 000 is preferably used.
[0026]
The structure of this organopolysiloxane basically has a main chain of diorganosiloxane units (R^Three ₂SiO_2/2), And both ends of the molecular chain are triorganosiloxy groups (R^Three _ThreeSiO_1/2) Or hydroxydiorganosiloxy group ((HO) R^Three ₂SiO_1/2), But may be partially branched or cyclic.
[0027]
As the organic peroxide of the component (b), any organic peroxide can be used as long as it can be used as a catalyst for promoting the crosslinking reaction of the component (a) in the organic peroxide-curable organopolysiloxane composition. Can be used. For example, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, p-methylbenzoyl peroxide, o-methylbenzoyl peroxide, 2,4-dicumyl peroxide, 2,5-dimethyl-bis (2,5-t -Butylperoxy) hexane, di-t-butylperoxide, t-butylperbenzoate, 1,1-bis (t-butylperoxycarboxy) hexane and the like, but are not particularly limited thereto. .
[0028]
The addition amount of the organic peroxide is a catalyst amount and may be appropriately selected according to the curing rate. Usually, it is 0.1 to 10 parts by weight, preferably 0 with respect to 100 parts by weight of component (a). .2 to 2 parts by weight.
[0029]
In the present invention, the thermosetting organopolysiloxane composition of the above component (A) includes, as the component (B), an unexpanded organic resin micro hollow filler that can be expanded by heat or an already expanded organic resin micro hollow filler. Blend. This filler lowers the specific gravity like sponge rubber by giving a gas part in the cured rubber, and as an organic resin forming such a filler, vinylidene chloride, acrylonitrile, methacrylonitrile, acrylic acid Polymers of monomers selected from esters and methacrylates and those selected from two or more types of copolymers of these monomers are preferred. In this case, the non-expanded organic resin minute hollow filler that can be expanded by heat is an organic resin shell containing a volatile substance or a low-boiling substance.
[0030]
When blending the organic resin micro hollow filler of component (B) with the organopolysiloxane composition of component (A), after pre-expanded hollow filler is blended, it is cured or unexpanded. It may be expanded simultaneously with curing.
[0031]
Moreover, you may make an inorganic filler etc. adhere to those surfaces for reasons, such as improving the intensity | strength of a hollow filler. However, in order to provide functions such as a sufficient decrease in specific gravity and a decrease in thermal conductivity in the silicone rubber composition, the true specific gravity of the expanded hollow filler is 0.01 to 0.5, preferably 0.01. ~ 0.3. If the specific gravity is less than 0.01, not only is it difficult to mix and handle, but the pressure resistance of the hollow filler is insufficient, and it may be destroyed during molding, making it impossible to reduce the weight. On the other hand, if it is larger than 0.5, the specific gravity will not be sufficiently lowered.
[0032]
The average particle size of the hollow filler after expansion is 200 μm or less, usually 5 to 200 μm, preferably 10 to 150 μm. If it is larger than 200 μm, the hollow filler is destroyed by the pressure at the time of molding and the specific gravity may be increased, or the durability may be lowered.
[0033]
The blending amount of the component (B) is 0.1 to 30 parts by weight, preferably 0.2 to 20 parts by weight with respect to 100 parts by weight of the organopolysiloxane composition of the component (A). It is good to mix | blend so that it may become 10 to 80% with respect to (volume%, and the following similarly). If the blending amount is less than 10%, the decrease in specific gravity, the decrease in thermal conductivity, etc. will be insufficient, and if it exceeds 80%, not only molding and blending will be difficult, but the molded product will also be brittle without rubber elasticity. (However, in the case of an unexpanded hollow filler, it is volume% in the cured silicone rubber).
[0034]
In the present invention, an inorganic hollow filler is further blended as the component (C). Since the inorganic hollow filler of component (C) has a gas portion inside the inorganic powder, by blending it, the specific gravity of the resulting silicone rubber composition is decreased, the thermal conductivity is decreased, and the thermal expansion coefficient is decreased. It contributes to.
[0035]
  As such a material,Rica balloon, MosquitoThere are carbon balloon, alumina balloon, aluminosilicate balloon and zirconia balloon.
[0036]
  In this case, in order to reduce the thermal expansion coefficient without adversely affecting the weight reduction and low thermal conductivity due to the organic resin filler in the silicone rubber composition, the true specific gravity of the inorganic hollow filler is 0.1 to 0.8, Preferably0.1~ 0.7. If it is less than 0.1, the pressure resistance of the hollow filler is insufficient, and the filler may be destroyed during blending and molding, and its performance may not be brought out. Moreover, when specific gravity is larger than 0.8, not only the specific gravity fall by an organic resin filler will be impaired, but the shell part of a hollow filler will become thick and thermal conductivity will also rise. The average particle size of the inorganic hollow filler of component (C) is, ThroughAlways10It is -200 micrometers, Preferably it is 10-150 micrometers, and when it exceeds 200 micrometers, there exists a possibility that a hollow filler may be destroyed by the pressure at the time of a mixing | blending or a shaping | molding.
[0037]
(C) The compounding quantity of the inorganic hollow filler of a component is 2-70 weight part with respect to 100 weight part of organopolysiloxane composition of (A) component, Preferably it is 5-50 weight part. If it is less than 2 parts by weight, the effect of lowering the thermal expansion coefficient is insufficient, and if it exceeds 70 parts by weight, not only the blending is difficult, but the cured rubber may be hard and brittle.
[0038]
The silicone rubber composition of the present invention may contain fumed silica, precipitated silica, fused silica, calcined silica, sol-gel spherical silica, crystalline silica (quartz powder), diatomaceous earth, etc., if necessary, in addition to the above components. Silica fine particles, fillers such as calcium carbonate, silicone-based resin as reinforcing agent, carbon black, conductive zinc white, conductive agents such as metal powder, nitrogen-containing compounds, acetylene compounds, phosphorus compounds, nitriles Hydrosilylation reaction control agents such as compounds, carboxylates, tin compounds, mercury compounds, sulfur compounds, heat release agents such as iron oxide and cerium oxide, internal mold release agents such as dimethyl silicone oil, adhesion promoters, thixotropic properties An imparting agent and the like can be arbitrarily blended within a range not impairing the effects of the present invention.
[0039]
In the silicone rubber composition of the present invention, the above-mentioned components are uniformly mixed using a rubber kneader such as a planetary mixer, two rolls, a Banbury mixer, a dough mixer (kneader), and heat-treated as necessary. Can be obtained. In this case, for example, a part or all of the first component organopolysiloxane and an inorganic filler such as silica are mixed with a surface treatment agent as necessary to prepare a base compound, and the remaining second compound is then added. One component organopolysiloxane, second component organohydrogenpolysiloxane, third component addition reaction catalyst, organic resin hollow filler or inorganic hollow filler, and other optional components may be mixed.
[0040]
The silicone rubber composition thus obtained can be molded into silicone rubber required by various molding methods such as injection molding, cast molding, mold pressure molding, extrusion molding, etc. Injection molding can be suitably employed.
[0041]
In addition, although hardening conditions can be adjusted suitably, it is 80-200 degreeC, Preferably it is 100-180 degreeC, 5 seconds-60 minutes, Preferably it is about 20 seconds-30 minutes.
[0042]
【The invention's effect】
The silicone rubber composition of the present invention is a lightweight, low thermal conductivity, low thermal expansion coefficient, and provides a silicone rubber molded article excellent in dimensional stability. Because of these properties, it can be used for sealing materials, gasket materials, cushioning materials, etc. that are lightweight and require dimensional stability during heating, as well as heat insulation and dimensions during heating. It is also suitable as various sheet materials for electronic devices such as computers and mobile phones that require stability, and also has heat storage and dimensional stability when heated, so that it can be used for office work such as printers and copiers. Can be used as a fixing roll or belt coating material for industrial equipment.
[0043]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example. In the following examples, parts indicate parts by weight.
[0044]
    [Reference example 1]
  68 parts of dimethylpolysiloxane (1) having a viscosity of 10,000 poise, sealed at both ends with dimethylvinylsiloxy groups and having a viscosity at 25 ° C. of 10,000 poise, 200 m in specific surface area²/ G of fumed silica (Aerosil 200 manufactured by Nippon Aerosil Co., Ltd.) 32 parts, 5 parts of hexamethyldisilazane, and 2.0 parts of water were mixed at room temperature for 30 minutes, heated to 150 ° C. and stirred for 3 hours. Cooled to obtain a silicone rubber base. 50 parts of dimethylpolysiloxane (2) having a viscosity of 1000 poise at 25 ° C. sealed at both ends with dimethylvinylsiloxy groups on 100 parts of this silicone rubber base, a specific gravity of 0.04, and an average particle size of 40 μm 2 parts of hollow filler made of plastic resin (Expancel Company 551DE), 20 parts of glass hollow filler (Cel StarZ-39 Tokai Kogyo Co., Ltd.) having a specific gravity of 0.38 and an average particle size of 60 μm are placed in a planetary mixer for 30 minutes. After continuing the stirring, 3.5 parts of methyl hydrogen polysiloxane (3) having a SiH group at both ends and side chains (polymerization degree 17, SiH amount 0.0060 mol / g) as a crosslinking agent, reaction control agent And 0.05 part of ethynylcyclohexanol was added and stirring was continued for 15 minutes to obtain a silicone rubber composition. . This silicone rubber composition was mixed with 0.1 part of a platinum catalyst (Pt concentration: 1%), press-cured at 120 ° C. for 10 minutes, and further post-cured in an oven at 200 ° C. for 2 hours. The thermal conductivity and the thermal expansion coefficient (50 to 150 ° C.) were measured. The results are shown in Table 1. In addition, the volume ratio of the organic resin hollow filler in the composition and the total volume ratio of the organic resin hollow filler and the inorganic hollow filler are shown together in Table 1 (the same applies to the following examples and comparative examples).
[0045]
    [Example1]
  Reference example 1Dimethylpolysiloxane (1) 70 parts, specific surface area 200m²/ G of precipitated silica (Nippsil LP manufactured by Nippon Silica Industry Co., Ltd.), 30 parts of hexamethyldisilazane, 0.5 part of divinyltetramethyldisilazane, and 1.0 part of water are mixed at room temperature for 30 minutes, and then heated to 150 ° C. The temperature was raised, and stirring was continued for 3 hours, followed by cooling to obtain a silicone rubber base. To 100 parts of this silicone rubber base,Reference example 130 parts of dimethylpolysiloxane (2), a specific gravity of 0.02, 2.5 parts of an expanded thermoplastic resin hollow filler (Matsumoto Yushi Seiyaku Co., Ltd. Microsphere F-80ED), a specific gravity of 0.6, 30 parts of ceramic hollow filler with an average particle size of 60 μm (Yssphere BL100, manufactured by Chichibu Onoda Co., Ltd.) was placed in a planetary mixer and stirred for 30 minutes. 3.2 parts of hydrogen polysiloxane (3) (degree of polymerization 17, SiH amount 0.0060 mol / g), 0.05 part of ethynylcyclohexanol as a reaction control agent are added, and stirring is continued for 15 minutes to form a silicone rubber composition. I got a thing. This silicone rubber composition was mixed with 0.1 part of a platinum catalyst (Pt concentration: 1%), press-cured at 120 ° C. for 10 minutes, then further post-cured in an oven at 200 ° C. for 2 hours,Reference example 1In the same manner as above, specific gravity, thermal conductivity, and thermal expansion coefficient were measured. The results are shown in Table 1.
[0046]
    [Example2]
  100 parts of rubbery diorganopolysiloxane having 99.825 mol% of dimethylsiloxane units, 0.15 mol% of methylvinylsiloxane units and 0.025 mol% of dimethylvinylsiloxy units and having an average degree of polymerization of about 8,000 As a dispersant, 5 parts of a terminal silanol-blocked dimethylpolysiloxane (average polymerization degree 10), specific surface area of 200 m²A rubber compound was prepared by mixing 25 parts of fumed silica (manufactured by Nippon Aerosil Co., Ltd.). 125 parts of this compound, 15 parts of expanded thermoplastic resin hollow filler (Matsumoto Yushi Seiyaku Microsphere MFL-100CA) coated with calcium carbonate on the surface with a specific gravity of 0.13 and an average particle size of 100 μm, specific gravity of 0 7. After dispersing 40 parts of an aluminosilicate hollow filler having an average particle size of 100 μm (Philite 200/7, manufactured by Nippon Philite Co., Ltd.), 2,5-dimethyl-bis (2,5-t-butylperoxy) was further dispersed. ) 0.5 part of hexane was added and dispersed uniformly with two rolls. This silicone rubber composition was press-cured at 170 ° C. for 10 minutes, then post-cured in an oven at 200 ° C. for 2 hours, and thenReference example 1In the same manner as above, specific gravity, thermal conductivity, and thermal expansion coefficient were measured. The results are shown in Table 1.
[0047]
    [Comparative Example 1]
  Reference example 1Dimethylpolysiloxane (1) 68 parts, specific surface area 200m²/ G of fumed silica (Aerosil 200 manufactured by Nippon Aerosil Co., Ltd.) 32 parts, 5 parts of hexamethyldisilazane, and 2.0 parts of water were mixed at room temperature for 30 minutes, then heated to 150 ° C. and stirred for 3 hours. Cooled to obtain a silicone rubber base. To 50 parts of this silicone rubber base,Reference example 150 parts of dimethylpolysiloxane (2), a specific gravity of 0.04, and 4 parts of an expanded thermoplastic resin hollow filler (Expancel 551DE) having an average particle size of 40 μm were placed in a planetary mixer and stirred for 30 minutes. Furthermore, 3.5 parts of methyl hydrogen polysiloxane (3) having a SiH group at both ends and side chains (polymerization degree 17, SiH amount 0.0060 mol / g) as a crosslinking agent, and ethynylcyclohexanol 0 as a reaction control agent .05 parts was added and stirring was continued for 15 minutes to obtain a silicone rubber composition. This silicone rubber composition was mixed with 0.1 part of a platinum catalyst (Pt concentration: 1%), press cured at 120 ° C. for 10 minutes, then post-cured in an oven at 200 ° C. for 2 hours,Reference example 1In the same manner as above, specific gravity, thermal conductivity and thermal expansion coefficient (50 to 150 ° C.) were measured. The results are shown in Table 1.
[0048]
    [Comparative Example 2]
  Dispersed in 100 parts of rubbery diorganopolysiloxane having 99.825 mol% dimethylsiloxane units, 0.15 mol% methylvinylsiloxane units and 0.025 mol% dimethylvinylsiloxy units and having an average degree of polymerization of about 8,000. 5 parts of silanol-terminated dimethylpolysiloxane (average polymerization degree 10) as the agent, 200 m in specific surface area²A rubber compound was prepared by mixing 25 parts of fumed silica (manufactured by Nippon Aerosil Co., Ltd.). 100 parts of this compound was dispersed with 100 parts of an aluminosilicate hollow filler having a specific gravity of 0.7 and an average particle size of 100 μm (Philite 200/7, manufactured by Nippon Philite Co., Ltd.), and then 2,5-dimethyl-bis (2 , 5-t-butylperoxy) hexane 0.5 part was added and dispersed uniformly with two rolls. This silicone rubber composition was press-cured at 170 ° C. for 10 minutes, then post-cured in an oven at 200 ° C. for 2 hours, and thenReference example 1In the same manner as above, specific gravity, thermal conductivity, and thermal expansion coefficient were measured. The results are shown in Table 1.
[0049]
[Table 1]

Claims (5)

(A) As a thermosetting organopolysiloxane composition,
(1) Organopolysiloxane containing an alkenyl group bonded to at least two silicon atoms in one molecule: 100 parts by weight
(2) Organohydrogenpolysiloxane containing hydrogen atoms bonded to at least two silicon atoms in one molecule: 0.1 to 50 parts by weight
(3) Addition reaction catalyst: 100 parts by weight of an addition-curable organopolysiloxane composition comprising only a catalytic amount,
(B) 0.1-30 parts by weight of an unexpanded organic resin micro hollow filler or an expanded organic resin micro hollow filler that can be expanded by heat,
(C) Inorganic hollow filler 29.7 to 70 weight selected from silica balloon, carbon balloon, alumina balloon, aluminosilicate balloon and zirconia balloon, having a specific gravity of 0.1 to 0.8 and an average particle diameter of 10 to 200 μm A thermosetting silicone rubber composition comprising a part. (A) As a thermosetting organopolysiloxane composition,
(A) The following average composition formula (iii)
R ³ _d SiO _{(4-d) / 2} (iii)
(Wherein R ³ represents a substituted or unsubstituted monovalent hydrocarbon group, 0.0001 to 10 mol% of R ³ is an alkenyl group, and 80 mol% or more is a methyl group. D is 1) .9 to 2.4 is a positive number.)
100 parts by weight of an organopolysiloxane having an average of at least two alkenyl groups in one molecule represented by
(B) Organic peroxide: an organic peroxide curable organopolysiloxane composition consisting only of a catalyst amount
100 parts by weight,
(B) 0.1-30 parts by weight of an unexpanded organic resin micro hollow filler or an expanded organic resin micro hollow filler that can be expanded by heat,
(C) An inorganic hollow filler selected from silica balloon, carbon balloon, alumina balloon, aluminosilicate balloon and zirconia balloon, having a specific gravity of 0.1 to 0.8 and an average particle diameter of 10 to 200 μm, 2 to 70 parts by weight A thermosetting silicone rubber composition comprising:   The thermosetting silicone rubber composition according to claim 1 or 2, wherein the hollow filler made of an expanded organic resin as component (B) has a specific gravity of 0.01 to 0.2 and an average particle size of 5 to 200 µm.   The thermosetting silicone rubber composition according to claim 1 or 2, wherein the non-expandable organic resin micro hollow filler capable of being expanded by the heat of component (B) is an organic resin shell encapsulating a volatile substance or a low boiling point substance. object.   (B) The organic resin of the unexpanded organic resin micro hollow filler or the expanded organic resin micro hollow filler which can be expanded by the heat of the component is selected from vinylidene chloride, acrylonitrile, methacrylonitrile, acrylic acid ester and methacrylic acid ester The thermosetting silicone rubber composition according to any one of claims 1 to 4, wherein the thermosetting silicone rubber composition is selected from a polymer of monomers and a copolymer of two or more monomers.