JP2021109885A - Silicone rubber composition for cast molding die, and silicone rubber die - Google Patents

Abstract

To provide a silicone rubber composition for a cast molding die giving a silicone rubber die excellent in heat conductivity and heat radiation, and capable of rapidly performing a release work.SOLUTION: A silicone rubber composition for a cast molding die includes: (A) 100 pts.mass of organopolysiloxane having at least two alkenyl groups directly bonding to (a) silicone atom(s) in one molecule, and a viscosity at 25°C of 30-50,000 mPa s; (B) 100-400 pts.mass of crystalline silica having an average particle size of 0.1-50 μm; (C) 3-40 pts.mass of amorphous silica having a specific surface area by a BET method of 50 m2/g or greater; (D) organopolysiloxane having at least two hydrogen atoms bonding to (a) silicon atom(s) in one molecule by such an amount that the hydrogen atoms in constituent (D) to one alkenyl group bonding to a silicone atom in constituent (A) become 0.3-5; and (E) a platinum-based catalyst.SELECTED DRAWING: None

Description

The present invention relates to a silicone rubber composition for molding and a silicone rubber mold, and more specifically, to a heat conductive silicone rubber composition of an addition curing type and a silicone molding base mold (so-called female mold) obtained by curing the same. ..

Using a silicone rubber mold as an inversion master mold, filling it with resin, and curing it to manufacture multiple products is widely used, from miniature models for hobbies to prototype models for industry.
Silicone rubbers used for these have the advantage that they are liquid before curing and can be easily cured by mixing with a curing agent at room temperature or by heating to form an inverted mold. However, on the other hand, since it is rubber, there is a problem that the injection-molded resin and the rubber mold are in close contact with each other and it is difficult to release the mold.
A mold release agent has been generally used as a solution to this problem, but it has been a problem in shortening the process time.

As a means for solving this, Patent Document 1 proposes the addition of a non-crosslinkable silicone polymer having a chain length longer than that of the base polymer to be crosslinked, and has achieved great results in improving the releasability.
Further, in Patent Document 2, by adding an oily substance having a refractive index difference of 0.01 or more and a melting point of 100 ° C. or less from the base polymer, great results have been achieved in improving releasability.
However, in this method, when casting into a large master mold and heating and curing to make an inverted mold, or when making a resin model that crosslinks at a high temperature, the inverted mold becomes a workable temperature. There was a problem that it took a very long time.

Japanese Unexamined Patent Publication No. 7-118534 Japanese Unexamined Patent Publication No. 2000-289034

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a silicone rubber composition for molding, which provides a silicone rubber mold having excellent thermal conductivity and heat dissipation and capable of quick release work. ..

As a result of diligent studies to solve the above problems, the present inventors provide a silicone rubber mold in which a specific addition-curable silicone rubber composition has excellent thermal conductivity and heat dissipation and can be quickly released. We found that and completed the present invention.

That is, the present invention
1. 1. (A) Organopolysiloxane having at least two alkenyl groups bonded to a silicon atom in one molecule and having a viscosity at 25 ° C. of 30 to 50,000 mPa · s: 100 parts by mass,
(B) Crystalline silica having an average particle size of 0.1 to 50 μm: 100 to 400 parts by mass,
(C) Amorphous silica with a specific surface area of 50 m ² / g or more by the BET method: 3 to 40 parts by mass,
(D) Organopolysiloxane having at least two hydrogen atoms bonded to silicon atoms in one molecule: For one alkenyl group bonded to silicon atoms in component (A), to silicon atoms in component (D) A silicone rubber composition for molding, which contains an amount of 0.3 to 5 hydrogen atoms to be bonded and (E) a platinum-based catalyst.
2. 1. A silicone rubber composition for molding, wherein the crystalline silica has a spherical or irregular shape.
3. 3. 1 or 2 silicone rubber composition for molding, in which the crystalline silica is surface-treated with a surface treatment agent.
4. 3. A silicone rubber composition for molding, wherein the surface treatment agent is a siloxane compound having an alkoxysilyl group at the terminal.
5. Molding agent, which comprises any of 1 to 4 molding silicone rubber compositions.
6. A silicone rubber mold formed by curing any of the molding silicone rubber compositions 1 to 4.
7. 6 silicone rubber molds with thermal conductivity of 0.4 W / (m · K) or more,
8. Provided are 6 or 7 silicone rubber molds having a tear strength of 5 (kN / m) or more.

Since the silicone rubber mold obtained by curing the silicone rubber composition for molding of the present invention has excellent thermal conductivity and heat dissipation, it is possible to shorten the time required for cooling to a temperature at which the mold release work is possible. It can be made, and is particularly useful as a mold for resins having a high curing temperature such as nylon, and as a reversing mold for large members such as those for aircraft and automobiles.

Hereinafter, the present invention will be specifically described.
In the present invention, the silicone rubber composition for molding has fluidity in an uncured state, and is brought into contact with the entire surface or a part of the surface of the prototype by a method such as casting or coating. An uncured (liquid) composition that is cured in a state to form a mold (mother mold for molding) that is used for duplication with a resin or the like.

The silicone rubber composition for molding according to the present invention contains the following components (A) to (E).
(A) Organopolysiloxane (B) having at least two alkenyl groups bonded to a silicon atom and having a viscosity at 25 ° C. of 30 to 50,000 mPa · s has an average particle size of 0.1 to 50 μm. Organopolysiloxane (E) platinum-based having at least two hydrogen atoms bonded to amorphous silica (D) silicon atoms having ^{a specific surface area of 50 m 2} / g or more by the crystalline silica (C) BET method in one molecule. catalyst

[1] Component (A) The organopolysiloxane having at least two alkenyl groups bonded to silicon atoms in one molecule of the component (A) is crosslinked with the silicone rubber composition for molding of the present invention to form a rubber. It is the main component to become.
The viscosity of the component (A) is 30 to 50,000 mPa · s, preferably 50 to 10,000 mPa · s, and more preferably 100 to 1,000 mPa · s. If the viscosity exceeds 50,000 mPa · s, the packing property of crystalline silica, which will be described later, deteriorates, and if it is less than 30 mPa · s, the cured product becomes brittle. The viscosity in the present invention is a value measured at 25 ° C. using a rotational viscometer.

Such an organopolysiloxane is not particularly limited as long as it satisfies the above viscosity and alkenyl group content, and a known organopolysiloxane can be used, and the structure may be linear or branched, and is different. It may be a mixture of two or more kinds of organopolysiloxanes having a viscosity.

The alkenyl group bonded to the silicon atom is not particularly limited, but an alkenyl group having 2 to 10 carbon atoms is preferable, and an alkenyl group having 2 to 8 carbon atoms is more preferable.
Specific examples thereof include vinyl, allyl, 1-butenyl, 1-hexenyl groups and the like. Among these, a vinyl group is preferable from the viewpoint of ease of synthesis and cost.
The number of alkenyl groups is not particularly limited as long as it is 2 or more, but 2 to 10 is preferable.
The alkenyl group may be present at the end (both ends or one end) of the molecular chain of the organopolysiloxane or in the middle, but in terms of the flexibility of the obtained silicone rubber mold, only both ends are present. It is preferably present in.

The organic group other than the alkenyl group bonded to the silicon atom is not particularly limited, but a monovalent hydrocarbon group having 1 to 20 carbon atoms is preferable, and a monovalent hydrocarbon group having 1 to 10 carbon atoms is more preferable. ..
Specific examples thereof include alkyl groups such as methyl, ethyl, n-propyl, n-butyl, n-hexyl and n-dodecyl groups; aryl groups such as phenyl groups; 2-phenylethyl, 2-phenylpropyl groups and the like. Arylkill group and the like can be mentioned.
Further, a part or all of the hydrogen atoms of these hydrocarbon groups may be substituted with halogen atoms such as chlorine, fluorine and bromine, and specific examples thereof include fluoromethyl, bromoethyl, chloromethyl and 3, Examples thereof include halogen-substituted monovalent hydrocarbon groups such as 3,3-trifluoropropyl group.
Among these, an alkyl group having 1 to 5 carbon atoms is preferable, and 90 mol% or more is more preferably a methyl group from the viewpoint of ease of synthesis and cost.

Specific examples of the component (A) include a trimethylsiloxy group-blocking dimethylsiloxane / methylvinylsiloxane copolymer at both ends of the molecular chain, a trimethylsiloxy group-blocking methylvinylpolysiloxane at both ends of the molecular chain, and a trimethylsiloxy group-blocking methyl at both ends of the molecular chain. Vinylsiloxane / methylphenylsiloxane copolymer, trimethylsiloxy group-blocking at both ends of the molecular chain dimethylsiloxane / methylvinylsiloxane / methylphenylsiloxane copolymer, dimethylvinylsiloxy group-blocking at both ends of the molecular chain dimethylpolysiloxane, dimethyl at both ends of the molecular chain Vinylsiloxy group-blocked dimethylsiloxane / methylvinylsiloxane copolymer, molecular chain both-ended dimethylvinylsiloxy group-blocked methylvinylpolysiloxane, molecular chain double-ended dimethylvinylsiloxy group-blocked methylvinylsiloxane / methylphenylsiloxane copolymer, molecular chain Both-ended dimethylvinylsiloxy group-blocked dimethylsiloxane / methylvinylsiloxane / methylphenylsiloxane copolymer, molecular chain double-ended dimethylvinylsiloxy group-blocked dimethylsiloxane / methyl (3,3,3-trifluoropropyl) siloxane copolymer, Examples thereof include dimethylsiloxane, methylvinylsiloxane, methyl (3,3,3-trifluoropropyl) siloxane copolymer, etc., which block both ends of the molecular chain. Didimethylvinyl siloxy group block at both ends of the molecular chain. Siloxane is particularly preferred.
The component (A) may be used alone or in combination of two or more.

[2] Component (B) The crystalline silica of the component (B) is a component for improving the thermal conductivity of the silicone rubber mold obtained by curing the silicone rubber composition for molding of the present invention.
The shape of the component (B) is not limited, and may be spherical, plate-shaped, or indefinite.
The average particle size of the component (B) is in the range of 0.1 to 50 μm, but is preferably in the range of 0.1 to 20 μm in order to prevent sedimentation in the composition.
Further, the component (B) has a good thermal stability of the hardness of the obtained cured product by the ignition weight loss method specified in JIS H 1901 (heating temperature 1,100 ° C., heating time 1 hour). It is preferable that the ignition loss measured according to the above is 0.25% by mass or less.

The component (B) is preferably surface-treated with a surface treatment agent, which facilitates mixing with the component (A) and prevents separation and sedimentation of the component (B) from the composition. , The viscosity of the composition can be reduced.
Examples of the surface treatment agent include organoalkoxysilanes such as methyltrimethoxysilane, methyltriethoxysilane, vinyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and n-octyllimethoxysilane; tetramethoxysilane, tetrapropoxysilane, and the like. Tetraalkoxysilanes such as ethylpolysilicate or partial hydrolysis condensates thereof; organohalosilanes such as dimethyldichlorosilane and methyltrichlorosilane; organosilazanes such as hexamethyldisilazane; dimethylhydroxysiloxy group-blocking diorganosiloxane oligomers, cyclopolydi Organic silicon compounds such as organosiloxane and organopolysiloxane represented by the following formula (1); amine compounds such as tri-n-butylamine and tri-n-octylamine can be mentioned.
Of these, organoalkoxysilane, tetraalkoxysilane or a partially hydrolyzed condensate thereof, and organopolysiloxane represented by the following general formula (1) are preferable from the viewpoint of ease of surface treatment operation.

（式中、Ｒ¹は、それぞれ独立して、非置換または置換の一価炭化水素基を表し、Ｒ²は、それぞれ独立して、アルキル基、アルコキシアルキル基、アルケニル基またはアシル基を表し、ｎは、２〜１００の整数を表し、ａは、１〜３の整数を表す。）

(In the formula, R ¹ independently represents an unsubstituted or substituted monovalent hydrocarbon group, and R ² independently represents an alkyl group, an alkoxyalkyl group, an alkenyl group or an acyl group. n represents an integer of 2 to 100, and a represents an integer of 1 to 3).

The monovalent hydrocarbon group of R ¹ is not particularly limited, but a monovalent hydrocarbon group having 1 to 10 carbon atoms is preferable, a monovalent hydrocarbon group having 1 to 6 carbon atoms is more preferable, and a monovalent hydrocarbon group having 1 to 6 carbon atoms is more preferable. 1-3 monohydric hydrocarbon groups are more preferred.
Specific examples of the monovalent hydrocarbon group include an alkyl group, an alkenyl group, an aryl group, an aralkyl group, and some or all of the hydrogen atoms of these monovalent hydrocarbon groups are replaced with halogen atoms such as chlorine, fluorine and bromine. Examples thereof include a halogenated monovalent hydrocarbon group such as an alkyl halide group.

The alkyl group may be linear, branched or cyclic, and specific examples thereof include linear alkyl groups such as methyl, ethyl, n-propyl, n-hexyl and n-octyl groups; isopropyl, Branched chain alkyl groups such as isobutyl, tert-butyl and 2-ethylhexyl groups; cyclic alkyl groups such as cyclopentyl and cyclohexyl groups can be mentioned.
Specific examples of the alkenyl group include vinyl, allyl, 1-butenyl, 1-hexenyl group and the like.
Specific examples of the aryl group include a phenyl group and a tolyl group.
Specific examples of the aralkyl group include 2-phenylethyl, 2-methyl-2-phenylethyl group and the like.
Specific examples of the alkyl halide group include 3,3,3-trifluoropropyl, 2- (nonafluorobutyl) ethyl, 2- (heptadecafluorooctyl) ethyl group and the like.
Among these, R ¹ is preferably an alkyl group, more preferably an alkyl group having 1 to 6 carbon atoms, and even more preferably a methyl group.

Examples of the alkyl group and alkenyl group of R ^{2 include the same groups as those exemplified in R 1} above, examples of the alkoxyalkyl group include methoxyethyl and methoxypropyl groups, and examples of the acyl group include methoxyethyl and methoxypropyl groups. For example, acetyl, octanoyl group and the like can be mentioned.
Among these, R ² is preferably an alkyl group, more preferably a methyl group or an ethyl group.
n is an integer of 2 to 100, but an integer of 5 to 80 is preferable.
a is an integer of 1 to 3, but 3 is preferable.

The surface treatment may be performed in advance by adding a surface treatment agent to the component (B) and heating and stirring in a mixer. When the component (B) is blended with the component (A), the surface treatment agent is blended at the same time. Then, it may be heated and stirred with a mixer.
The blending amount of the surface treatment agent is not particularly limited, but is preferably 0.05 to 30% by mass with respect to the component (B).

The blending amount of the component (B) is in the range of 100 to 400 parts by mass with respect to 100 parts by mass of the component (A), but is preferably 140 to 300 parts by mass. If it is less than the lower limit of the above range, sufficient thermal conductivity cannot be imparted to the silicone rubber, and if it exceeds the upper limit of the above range, the viscosity and density of the composition are excessively increased and the workability is lowered.

[3] (C) Component (C) component has a specific surface area by the BET method of 50 m ² / g or more, preferably the 50 to 500 m ² / g, more preferably amorphous silica 150~350m ² / g , A component for imparting mechanical properties such as tensile strength, tear strength, and elongation at the time of cutting to a cured product obtained from the silicone rubber composition of the present invention.
Examples of the amorphous silica include fumed silica, precipitated silica, and silica whose surface is hydrophobized, and these may be used alone or in combination of two or more.

As such silica, as hydrophilic silica, Aerosil 130, 200, 300 (manufactured by Nippon Aerosil Co., Ltd.), Cabosil MS-5, MS-7 (manufactured by Cabot), Rheorosil QS-102,103 ((() Fumed silica such as Tokuyama Co., Ltd .; Precipitated silica such as Tokseal US-F (manufactured by Tokuyama Co., Ltd.) and Nippon Silica LP (manufactured by Nippon Silica Industry Co., Ltd.) can be mentioned as hydrophobic silica. Fumed silica such as Aerosil R-812, R-812S, R-972, R-974 (manufactured by Nippon Aerosil Co., Ltd.), Rheorosil MT-10 (manufactured by Tokuyama Co., Ltd.); Nippon Silica SS series (Nippon Silica Industry (Nippon Silica Industry) Precipitating silica and the like manufactured by Co., Ltd.) can be mentioned.

These amorphous silicas may be used as they are, but those which have been surface-hydrophobicized in advance with a surface treatment agent may be used, or the surface treatment agent may be added when the component (A) is kneaded to form amorphous silica. It is preferable that the surface is hydrophobized before use. Examples of the surface treatment agent include alkylalkoxysilane, alkylhydroxysilane, alkylchlorosilane, alkylsilazane, silane coupling agent, low molecular weight polysiloxane, titanate treatment agent, fatty acid ester and the like, preferably alkyldisilazane. Is hexamethyldisilazane. These surface treatment agents may be used alone or in combination of two or more at the same time or at different timings.
The amount of the surface treatment agent used is preferably 0.5 to 50 parts by mass, more preferably 1 to 40 parts by mass, and even more preferably 2 to 30 parts by mass with respect to 100 parts by mass of amorphous silica. When the amount of the surface treatment agent used is within the above range, the surface treatment agent or its decomposition products do not remain in the composition, fluidity can be obtained, and the increase in viscosity with time can be suppressed.

The blending amount of the component (C) is 3 to 40 parts by mass with respect to 100 parts by mass of the component (A) from the viewpoint of handleability of the composition and mechanical strength of the cured product, but 5 to 30 parts by mass is used. preferable. If the blending amount of the component (C) is less than 3 parts by mass, the mechanical properties of the obtained cured product are insufficient, and if it exceeds 50 parts by mass, the viscosity of the composition becomes high and it is difficult to cast it into the master mold. It becomes.

[4] Component (D) The component (D) is an organopolysiloxane having at least two hydrogen atoms (SiH groups) bonded to a silicon atom in one molecule, and is a hydrosilyl with an alkenyl group in the component (A). It is a component for curing the silicone rubber composition of the present invention by cross-linking by conversion.
The molecular structure of the component (D) is not particularly limited as long as it satisfies the content of the hydrogen atom bonded to the silicon atom, and is linear, linear with a partial branch, branched chain, or cyclic. In particular, a linear structure having a partial branch is preferable.

The weight average molecular weight of the component (D) is not particularly limited, but is preferably 1,000 to 30,000, preferably 1,500, in consideration of enhancing the workability of the composition and the mechanical properties of the cured product. ~ 10,000 is more preferable. The weight average molecular weight is a standard polystyrene-equivalent value in gel permeation chromatography (GPC).

Specific examples of the organohydrogenpolysiloxane of the component (D) include dimethylhydrogensiloxy group-blocked dimethylpolysiloxane at both ends of the molecular chain, dimethylhydrogensiloxy group-blocked methylhydrogenpolysiloxane at both ends of the molecular chain, and both ends of the molecular chain. Dimethylhydrogensiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane copolymer, molecular chain double-ended trimethylsiloxy group-blocked methylhydrogenpolysiloxane, molecular chain double-ended trimethylsiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane copolymer, Methylhydrogenpolysiloxane with silanol group-blocking at both ends of the molecular chain, dimethylsiloxane / methylhydrogensiloxane copolymer with silanol group-blocking at both ends of the molecular chain, formula: (CH ₃ ) ₃ siloxane unit and formula represented by SiO _1/2: (CH ₃ ) ₂ siloxane unit represented by HSiO _1/2 and formula: Organopolysiloxane consisting of siloxane unit represented by _{SiO 4/2 , formula: (CH 3} ) ₂ siloxane unit and formula represented by HSiO _1/2 : Organopolysiloxane consisting of siloxane unit represented by _{SiO 4/2 , formula: (CH 3} ) siloxane unit represented by _{HSiO 2/2 and formula: CH 3} siloxane unit represented by SiO _{3/2 or formula: HSiO 3 Examples thereof include an organopolysiloxane composed of a siloxane unit represented by / 2} , an organopolysiloxane in which a part of the methyl group of these organopolysiloxanes is replaced with a phenyl group, a 3,3,3-trifluoropropyl group or the like.

The blending amount of the component (D) is an amount in which the number of silicon atom-bonded hydrogen atoms in this component is in the range of 0.3 to 5 with respect to one alkenyl group in the component (A), and is preferable. , The amount of silicon atom-bonded hydrogen atoms in this component is in the range of 0.5 to 3 with respect to one alkenyl group in the component (A). If it is less than the lower limit of the above range, the cross-linking density of the cured product is insufficient and the heat resistance and mechanical properties are inferior. The rubber strength decreases due to the generation of voids inside the cured product.
The component (D) may be used alone or in combination of two or more.

[5] The platinum-based catalyst of the component (E) and the component (E) is a hydrosilylation reaction catalyst for promoting the hydrosilylation reaction between the alkenyl group in the component (A) and the SiH group in the component (B). ..
Specific examples thereof include fine particle platinum, chloroplatinic acid, alcohol-modified products of chloroplatinic acid, chelate compounds of platinum, complexes of platinum and diketone, coordination compounds of chloroplatinic acid and olefins, and chloroplatinic acid and alkenylsiloxane. Examples thereof include a complex and one in which these are supported on a carrier such as alumina, silica, or carbon black.
Among these, a complex of chloroplatinic acid and alkenylsiloxane is preferable because of its high activity as a catalyst for hydrosilylation reaction, and a platinum alkenylsiloxane complex as disclosed in Japanese Patent Publication No. 42-22924 is more preferable.
Further, a spherical fine particle catalyst composed of a thermoplastic resin containing a platinum-based catalyst as a platinum metal atom in an amount of 0.01% by mass or more can also be used.
The component (E) may be used alone or in combination of two or more.

The blending amount of the component (E) is not limited as long as it promotes the curing (hydrosilylation reaction) of the composition, and the metal atom in this component is 0 in terms of mass with respect to the mass of the component (A). The range of 0.01 to 500 ppm is preferable, and the range of 1 to 50 ppm is more preferable. Within this range, the reaction rate of the addition reaction is appropriate.

[6] (F) Ingredients The silicone rubber composition for molding of the present invention contains hydrosilyls so as not to cause thickening or gelation when the composition is prepared or before heat curing such as when molding. If necessary, the reaction control agent (F) may be added for the purpose of controlling the reactivity of the chemical reaction catalyst.
Specific examples of the reaction control agent include 3-methyl-1-butyne-3-ol, 3-methyl-1-pentyne-3-ol, 3,5-dimethyl-1-hexin-3-ol, and 1-ethynyl. -1-Cyclohexanol, ethynylmethyldecylcarbinol, 3-methyl-3-trimethylsiloxy-1-butyne, 3-methyl-3-trimethylsiloxy-1-pentyne, 3,5-dimethyl-3-trimethylsiloxy-1 -Hexin, 1-ethynyl-1-trimethylsiloxycyclohexane, bis (2,2-dimethyl-3-butynoxy) dimethylsilane, 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclo Examples thereof include tetrasiloxane, 1,1,3,3-tetramethyl-1,3-divinyldisiloxane, and these may be used alone or in combination of two or more.
Among these, 1-ethynylcyclohexanol, ethynylmethyldecylcarbinol, and 3-methyl-1-butyne-3-ol are preferable.

When the component (F) is used, the amount added is preferably 0.01 to 3.0 parts by mass, more preferably 0.01 to 1.5 parts by mass with respect to 100 parts by mass of the component (A). Within such a range, the effect of reaction control is fully exhibited.

[7] Other Ingredients In addition to the above components (A) to (F), the silicone rubber composition for molding of the present invention contains other components exemplified below as long as the object of the present invention is not impaired. You may.
Other components include conductive agents such as iron oxide, carbon black, conductive zinc oxide, and metal powder; heat resistant agents such as titanium oxide and cerium oxide; internal mold release agents such as dimethyl silicone oil; adhesive imparting agents; thixo. Sex-imparting agent; colorant and the like can be mentioned.

Specific examples of colorants include inorganic pigments such as ultramarine, iron oxide, titanium oxide, titanium yellow, carbon black, zinc white, and chrome green; anthraquinone violet, anthraquinone blue, induslen blue, allizanin green, perison red, etc. Organic pigments; metal powder pigments such as aluminum powder, copper powder, bronze powder, tin powder; phosphorescent pigments; fluorescent pigments, and dyes that do not inhibit curing. You can choose.

Further, an organopolysiloxane composed of a siloxane unit represented by the formula: (CH ₃ ) ₃ SiO _1/2 and a siloxane unit represented by the formula: SiO _{4/2 , the formula: CH 2} = CH (CH ₃ ) ₂ SiO _{1 /} siloxane units represented by the formula _2: (CH _{3) 3} siloxane units represented by the formula SiO _1/2: organopolysiloxane composed of siloxane units represented by SiO _4/2, wherein: CH ₂ = CH (CH ₃ ) ₂ Siloxane unit represented by SiO _1/2 and formula: (CH ₃ ) ₃ siloxane unit represented by SiO _1/2 and formula: Silicon atom bond such as organopolysiloxane consisting of siloxane unit represented by _{SiO 3/2} An organopolysiloxane resin that does not have a hydrogen atom and is solid at 25 ° C. may be used.
When an organopolysiloxane resin is used, the blending amount thereof is preferably 0.1 to 80 parts by mass, more preferably 1 to 50 parts by mass with respect to 100 parts by mass of the component (A).

The silicone rubber composition for molding of the present invention can be prepared by mixing the above components (A) to (E) and other components by a known method using a kneader, a planetary mixer or the like.
The silicone rubber composition for molding of the present invention comprises a first agent composed of a component (A), a component (B), a component (C), a component (E), and if necessary, other components, and (A). A second agent consisting of an ingredient, an ingredient (B), an ingredient (C), an ingredient (D) and, if necessary, other ingredients is prepared separately, and the first agent and the second agent are mixed before use. It may be a composition of a mold. In addition, there may be a component commonly used in the first agent and the second agent. By using such a two-dosage form for the composition, storage stability can be further ensured.

A silicone rubber mold can be obtained by casting the silicone rubber composition for molding of the present invention with a predetermined mold and curing it. In particular, it is preferable to cast using vacuum casting, and as curing conditions, for example, curing proceeds even at room temperature (5 to 35 ° C.), but curing can be accelerated by heating, and mass productivity is desired to be improved. This method is effective for.
When heat-curing, it can usually be carried out at a temperature of 40 to 60 ° C. for about 2 to 20 hours.

The silicone rubber mold obtained from the silicone rubber composition for molding of the present invention can be effectively used for molding resin molded products such as nylon resin, epoxy resin, and urethane resin. In particular, it is suitable for molding a nylon resin that requires a thermal deformation temperature of 50 to 200 ° C., preferably 70 to 180 ° C. for melting.

The thermal conductivity of the cured product of the silicone rubber composition for molding of the present invention is preferably 0.4 W / (m · K) or more, and more preferably 0.6 W / (m · K) or more. The upper limit of thermal conductivity is not particularly limited, but is usually 3.0 W / (m · K) or less.
Further, the tear strength of the cured product of the silicone rubber composition for molding of the present invention is preferably 5 kN / m or more, more preferably 10 kN / m or more. The upper limit of the tear strength is not particularly limited, but is usually 30 kN / m or less.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[Examples 1 to 4, Comparative Examples 1 to 3]
The following components were mixed at the compounding ratio (parts by mass) shown in Table 1 to prepare a silicone rubber composition. Specifically, first, the component (A), the component (B), the component (C), 4 parts by mass of hexamethyldisilazane, and 1.2 parts by mass of water are mixed at 25 ° C. for 1 hour using a kneader, and then 150. Mix at ° C. for 2 hours, add 1.2 parts by mass of organopolysiloxane represented by the following average formula (2), mix at 150 ° C. for 2 hours, cool to 25 ° C., and add the component (D) and (. After F) component was added and mixed, component (E) was added so as to be 10 ppm with respect to the entire composition in terms of mass of platinum, and after mixing, defoaming under reduced pressure was performed to obtain a silicone rubber composition. rice field.

(A) Ingredient:
(A-1) Didimethylpolysiloxane having a viscosity of 600 mPa · s at 25 ° C. with both ends sealed with a dimethylvinylsilyl group (vinyl value: 0.0124 mol / 100 g).
(A-2) Didimethylpolysiloxane having a viscosity of 30,000 mPa · s at 25 ° C. with both ends sealed with a dimethylvinylsilyl group (vinyl value: 0.00277 mol / 100 g).
(A-3) Didimethylpolysiloxane having a viscosity of 10,000 mPa · s at 25 ° C. with both ends sealed with a dimethylvinylsilyl group (vinyl value: 0.00430 mol / 100 g).

(B) Ingredient:
(B-1) Crystalline silica (manufactured by CBC Co., Ltd., KAIDA SP5, average particle size 5 μm, amorphous)

Ingredient (C):
(C-1) Fumed silica (manufactured by Nippon Aerosil Co., Ltd., Aerosil 200, BET specific surface area 200 m ² / g)

（式中、シロキサン単位の配列はランダムまたはブロックである。） Ingredient (D):
(D-1) Methylhydrogenpolysiloxane represented by the following average formula (3) (weight average molecular weight: 3,000)

(In the formula, the sequence of siloxane units is random or block.)

(D-2) Methylhydrogenpolysiloxane represented by the following average formula (4) (weight average molecular weight: 2,500)

（式中、シロキサン単位の配列はランダムまたはブロックである。） (D-3) Methylhydrogenpolysiloxane represented by the following average formula (5) (weight average molecular weight: 1,500)

(In the formula, the sequence of siloxane units is random or block.)

(E) Ingredient:
(E-1) Chloroplatinic acid octyl alcohol complex

(F) component:
(F-1) 1-ethynyl-1-cyclohexanol

¹⁾（Ａ）成分に対して白金が１０質量ｐｐｍとなる量
²⁾（Ａ）成分中の珪素原子に結合するアルケニル基１個に対する（Ｄ）成分中の珪素原子に結合する水素原子の数の比

¹⁾ Amount of platinum in 10 parts by mass with respect to the component (A)
²⁾ Ratio of the number of hydrogen atoms bonded to the silicon atom in the component (D) to one alkenyl group bonded to the silicon atom in the component (A)

Using the silicone rubber compositions prepared in Examples 1 to 4 and Comparative Examples 1 to 3, the following characteristics were evaluated. The results are shown in Table 2.
[Thermal conductivity]
For a cured product obtained by pouring a silicone rubber composition into a mold so as to have a size of 5 cm × 15 cm × 1 cm and curing it under the conditions of 60 ° C. for 2 hours, the thermal conductivity at an environmental temperature of 25 ° C. was measured by a hot disk method thermophysical property measuring device (a hot disk method thermophysical property measuring device). It was measured using TPA-501) manufactured by Kyoto Electronics Industry Co., Ltd.
[Arrival time at 30 ° C]
The cured product used for the thermal conductivity measurement was further exposed to an environment of 150 ° C. for 30 minutes, then taken out to an environment of 23 ° C., and the surface temperature of the cured product by a thermocouple (TR-W550, manufactured by KEYENCE CORPORATION). The time until the temperature reached 30 ° C. was measured.
[hardness]
The silicone rubber composition was poured into a mold so as to have a thickness of 2 mm, and the hardness (durometer A) of the cured product cured at 60 ° C. for 2 hours was measured according to JIS K 6253-: 2012. Further, the hardness of the similarly prepared cured product after being exposed to an environment of 180 ° C. for 150 hours was measured in the same manner as described above.
[Tensile strength, elongation at cutting]
A No. 2 dumbbell-shaped test piece in which the silicone rubber composition was poured into a mold to a thickness of 2 mm and cured at 60 ° C. for 2 hours was subjected to JIS K 6249: 2003, tensile strength (MPa), and tensile strength (MPa). Elongation (%) at the time of cutting was measured respectively.
Further, after exposing the similarly prepared dumbbell-shaped test piece to an environment of 180 ° C. for 150 hours, each of the above physical properties was measured.
[Tear strength]
A crescent-shaped test piece in which a silicone rubber composition was poured into a mold to a thickness of 2 mm and cured at 60 ° C. for 2 hours was subjected to a tear strength (kN / m) in accordance with JIS K 6252-1: 2015. It was measured.
Further, the tear strength of the similarly prepared crescent-shaped test piece after being exposed to an environment of 180 ° C. for 150 hours was measured in the same manner as described above.

As shown in Table 2, the cured product obtained from the silicone rubber composition for molding of the present invention prepared in Examples 1 to 4 has excellent heat conduction characteristics and heat dissipation, and has sufficient strength. It can be seen that it has excellent hardness stability even when it is held at a high temperature for a long period of time.
On the other hand, in Comparative Example 1 which does not contain the component (B) of the present invention and Comparative Example 3 in which the amount of the component (B) added is not sufficient, the thermal conductivity is low and it takes time to dissipate heat after heating. Further, it can be seen that Comparative Example 2 which does not contain the component (C) of the present invention is inferior in tensile strength, elongation at cutting, and tear strength, and is not suitable for molding.

Claims (8)

(A) Organopolysiloxane having at least two alkenyl groups bonded to a silicon atom in one molecule and having a viscosity at 25 ° C. of 30 to 50,000 mPa · s: 100 parts by mass,
(B) Crystalline silica having an average particle size of 0.1 to 50 μm: 100 to 400 parts by mass,
(C) Amorphous silica with a specific surface area of 50 m ² / g or more by the BET method: 3 to 40 parts by mass,
(D) Organopolysiloxane having at least two hydrogen atoms bonded to silicon atoms in one molecule: For one alkenyl group bonded to silicon atoms in component (A), to silicon atoms in component (D) A silicone rubber composition for molding containing an amount of 0.3 to 5 hydrogen atoms to be bonded and (E) a platinum-based catalyst. The silicone rubber composition for molding according to claim 1, wherein the crystalline silica has a spherical or irregular shape. The silicone rubber composition for molding according to claim 1 or 2, wherein the crystalline silica is surface-treated with a surface treatment agent. The silicone rubber composition for molding according to claim 3, wherein the surface treatment agent is a siloxane compound having an alkoxysilyl group at the terminal. A molding agent comprising the silicone rubber composition for molding according to any one of claims 1 to 4. A silicone rubber mold obtained by curing the silicone rubber composition for molding according to any one of claims 1 to 4. The silicone rubber mold according to claim 6, which has a thermal conductivity of 0.4 W / (m · K) or more. The silicone rubber mold according to claim 6 or 7, wherein the tear strength is 5 (kN / m) or more.