JP7106969B2 - Silicone rubber composition and silicone rubber - Google Patents

Description

TECHNICAL FIELD The present invention relates to a silicone rubber composition that gives a cured product having excellent light transmittance and excellent flame retardancy, and a cured product (silicone rubber) of the composition.

Silicone rubbers are widely used in various fields due to their properties such as excellent transparency, weather resistance, electrical properties, low compression set, heat resistance and cold resistance. In particular, materials used in home appliances are required to have excellent flame retardancy. Furthermore, transparent materials are required for light-transmitting materials such as lamp holders and liquid crystal blankets.

Silicone rubber has a backbone composed of siloxane bonds, and has a low organic component (hydrocarbon component) ratio compared to ordinary organic rubber, making it difficult to burn. However, under severe conditions such as direct contact with flame, the silicone rubber ignites and burns. In order to solve the above problems, it is known to add a triazole compound to a platinum compound or a reaction product of a platinum compound and a compound having an alkynyl group and an alcoholic hydroxyl group as a flame retardant imparting agent to a silicone rubber composition. (Patent Document 1).

A method of adding titanium dioxide having an average particle size of 0.10 to 0.50 μm has also been proposed (Patent Document 2). Flammability is also insufficient.
On the other hand, a silicone rubber composition containing an inorganic particle-polysiloxane composite, in which polysiloxane is grafted onto the surface of the inorganic particles, gives a silicone rubber cured product with excellent transparency, UV absorption performance, and heat resistance. (Patent Document 3), it could not be said that the flame retardancy was sufficient.

Furthermore, in epoxy resin compositions, there are descriptions that silicone powder is effective as a flame retardant agent and a flame retardant aid (Patent Documents 4 and 5). , it was not clear whether or not there is an effect of improving flame retardancy.

JP-A-11-140325 JP-A-9-194730 JP 2017-105895 A WO2012/029690 WO2017/022721

The present invention has been made in view of the above circumstances, and an object thereof is to provide a silicone rubber composition and a silicone rubber that become a silicone rubber (cured product) having excellent light transmittance and excellent flame retardancy.

The present inventors have conducted intensive studies to achieve the above objects, and found that titanium oxide is added to a silicone rubber composition containing an organopolysiloxane having at least two alkenyl groups in one molecule and reinforcing silica. Silica, a platinum-based compound, and a triazole that support metal oxide particles containing metal oxide particles, the surface of which is hydrophobized with a silicon atom-containing hydrophobizing agent, and have a primary particle diameter in the range of 5 to 50 nm before supporting the metal oxide particles. The inventors have found that the cured product of this silicone rubber composition has excellent light transmittance and excellent flame retardancy by blending the silicone rubber composition with the silicone rubber composition, and have completed the present invention.

Accordingly, the present invention provides the following silicone rubber composition and silicone rubber obtained by curing the composition.
1. (A) the following average composition formula (1)
RnSiO(4- _{n )/2} (1)
(Wherein, R is the same or different unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, and n is a positive number of 1.95 to 2.05.)
Organopolysiloxane represented by and having at least two alkenyl groups in one molecule
100 parts by mass,
(B) 5 to 100 parts by mass of reinforcing silica having a specific surface area of 50 m ² /g or more,
(C) Metal oxide particles containing titanium oxide are supported, the surface is hydrophobized with a silicon atom-containing hydrophobizing agent, and the primary particle size before supporting the metal oxide particles is in the range of 5 to 50 nm. Silica 0.01 to 50 parts by mass,
(D) silicone resin powder 0 to 50 parts by mass ,
(E) triazole compound 0.001 to 0.1 parts by mass,
(F) platinum compound
As platinum (in terms of mass), 16.3 to 1,000 ppm relative to the total mass of components (A) to (E) (However, if component (G) contains a platinum compound, the amount of platinum is also and (G ) a curing agent containing an effective amount for curing the component (A), and the average particle size of the metal oxide particles of the component (C) is determined by a dynamic light scattering method using a laser beam. A silicone rubber composition characterized by having a volume-based 50% cumulative distribution diameter (D ₅₀ ) of 1 to 50 nm as measured by .
2 . 2. The silicone rubber composition according to claim 1 , wherein the metal oxide particles are particles having a core-shell structure having a metal oxide nucleus and a silicon oxide shell formed on the outer surface thereof.
3 . 3. The silicone rubber composition according to 1 or 2 above, wherein the metal oxide particles are surface-modified with an organosilicon compound represented by the following general formula (2) and/or a (partial) hydrolysis condensate thereof.
^R1Si (Y) ₃ (2)
(In the formula, each R ¹ may be the same or different, and may be substituted with a (meth)acryl group, an oxiranyl group, an amino group, a mercapto group, an isocyanate group, or a fluorine atom. an alkyl group, an alkenyl group having 2 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, and a (poly)dimethylsiloxy group having 1 to 50 silicon atoms or is a hydrogen atom, and Y is a substituent selected from the group consisting of an alkoxy group, an acetoxy group, an enol group, and a chlorine atom.)
4 . 4. The silicone rubber composition as described in any one of 1 to 3 above, wherein the content of the metal oxide particles in the silica of component (C) is 1 to 30% by mass.
5 . 5. The silicone rubber composition as described in any one of 1 to 4 above, wherein the triazole compound of component (E) is benzotriazole.
6 . 6. The silicone rubber composition as described in any one of 1 to 5 above, wherein the curing agent of component (G) is an addition reaction curing type comprising a combination of an organohydrogenpolysiloxane and a hydrosilylation catalyst.
7 . 6. The silicone rubber composition as described in any one of 1 to 5 above, wherein the curing agent of component (G) is an organic peroxide.
8 . A silicone rubber comprising a cured product of the silicone rubber composition according to any one of 1 to 7 above.

The silicone rubber composition of the present invention can provide a silicone rubber (cured product) with excellent light transmittance and flame retardancy.

The present invention will be described in detail below.
The silicone rubber composition of the present invention comprises an organopolysiloxane (A) having at least two alkenyl groups in one molecule as a base polymer, an addition reaction curing agent (G-1) as a curing agent (G) and/or An organic peroxide curing agent (G-2) is used. The properties of the silicone rubber composition may be millable type or liquid type. Liquid silicone rubber compositions are self-fluid at room temperature (usually 25°C ± 10°C), whereas millable silicone rubber compositions have high viscosity and are self-fluid at room temperature. It means a raw rubber-like composition that is non-liquid (solid or highly viscous paste) and can be uniformly mixed under high shear stress by a kneading means such as a roll mill.

-(A) component-
In the present invention, component (A) is an organopolysiloxane represented by the following average compositional formula (1).
RnSiO(4- _{n )/2} (1)
(Wherein, R is the same or different unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, and n is a positive number of 1.95 to 2.05.)

In the above average composition formula (1), R is the same or different unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, preferably having 1 to 8 carbon atoms. Specifically, alkyl groups such as methyl group, ethyl group, propyl group, butyl group, hexyl group and octyl group; cycloalkyl groups such as cyclopentyl group and cyclohexyl group; and alkenyl groups such as vinyl group, allyl group and propenyl group. , an aryl group such as a cycloalkenyl group, a phenyl group and a tolyl group, and an aralkyl group such as a benzyl group and a 2-phenylethyl group. Also, some or all of the hydrogen atoms in these groups may be substituted with halogen atoms such as fluorine and chlorine, or with cyano groups. Among them, a methyl group, a vinyl group, a phenyl group and a trifluoropropyl group are preferred, and a methyl group and a vinyl group are particularly preferred.

In particular, the organopolysiloxane as the component (A) has 2 or more, usually 2 to 50, especially about 2 to 20 aliphatic unsaturated groups such as alkenyl groups and cycloalkenyl groups in one molecule. are preferred, and those having a vinyl group are particularly preferred. In this case, it is preferable that 0.01 to 20 mol %, particularly 0.02 to 10 mol % of all R are aliphatic unsaturated groups. The aliphatic unsaturated group may be bonded to a silicon atom at the terminal of the molecular chain, bonded to a silicon atom in the middle of the molecular chain (non-terminal of the molecular chain), or both. is preferably bonded to at least the silicon atom at the terminal of the molecular chain.
In addition, 80 mol% or more, preferably 90 mol% or more, more preferably 95 mol% or more, more preferably all R excluding aliphatic unsaturated groups in all R are alkyl groups, particularly methyl groups. is desirable.

In the above formula (1), n is a positive number of 1.95 to 2.05, preferably 1.98 to 2.02, more preferably 1.99 to 2.01.

The molecular structure of the component (A) organopolysiloxane is preferably linear or partially branched linear. Specifically, the repeating structure of the diorganosiloxane units (R ₂ SiO _2/2 , R is the same as above, the same applies hereinafter) constituting the main chain of the organopolysiloxane consists only of repeating dimethylsiloxane units. , or a diphenylsiloxane unit having a phenyl group, a vinyl group, a 3,3,3-trifluoropropyl group or the like as a substituent as part of the dimethylpolysiloxane structure consisting of repeating dimethylsiloxane units constituting the main chain, Those into which diorganosiloxane units such as methylphenylsiloxane units, methylvinylsiloxane units and methyl-3,3,3-trifluoropropylsiloxane units are introduced are suitable.

Both ends of the molecular chain are, for example, triorganosiloxy groups (R ₃ SiO _1/2 ) such as trimethylsiloxy group, dimethylphenylsiloxy group, vinyldimethylsiloxy group, divinylmethylsiloxy group and trivinylsiloxy group, or hydroxydimethyl It is preferably blocked with a hydroxydiorganosiloxy group (R ₂ (HO)SiO _1/2 ) such as a siloxy group.

As described above, the component (A) organopolysiloxane has triorganosiloxy groups (R ₃ SiO _1/2 ) or hydroxydiorganosiloxy groups (R ₂ (HO)SiO _1/2 ) at both ends of the molecular chain. Preferred examples include linear ones which are blocked and whose main chain consists of repeating diorganosiloxane units (R ₂ SiO _2/2 ). Particularly preferred types of substituents in the molecule (that is, unsubstituted or substituted monovalent hydrocarbon groups bonded to silicon atoms) include methylvinylpolysiloxane, methylphenylvinylpolysiloxane, and methyltrifluoropropylvinyl Polysiloxane, dimethylpolysiloxane and the like can be mentioned.

Such organopolysiloxanes can be prepared, for example, by (co)hydrolytic condensation of one or more organohalogenosilanes, or by using cyclic polysiloxanes (siloxane trimers, tetramers, etc.) in an alkaline or It can be obtained by ring-opening polymerization using an acidic catalyst.

The degree of polymerization of the organopolysiloxane is preferably 100 or more (usually 100 to 100,000), preferably 150 to 100,000. The degree of polymerization can be measured as a weight average degree of polymerization in terms of polystyrene by gel permeation chromatography (GPC) analysis.

Component (A) may be used singly or as a mixture of two or more different molecular weights (degrees of polymerization) and molecular structures.

-(B) component-
Component ⁽ B), the reinforcing silica, is a filler added to obtain a silicone rubber composition with excellent mechanical strength. and preferably 100 to 450 m ² /g, more preferably 100 to 300 m ² /g. If the specific surface area is less than 50 m ² /g, the mechanical strength of the cured product will be low.

Examples of such reinforcing silica include fumed silica, precipitated silica (wet silica), and the like, and the surfaces of these may be coated with organosilane compounds such as methylchlorosilane, hexamethyldisilazane, and the like. Hydrophobic treatment with a silazane compound or the like is also preferably used. Among these, fumed silica hydrophobized with a silazane compound or the like, which is excellent in transparency, is preferable.

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

The amount of the reinforcing silica of component (B) is 5 to 100 parts by mass, preferably 10 to 100 parts by mass, and 20 to 60 parts by mass based on 100 parts by mass of organopolysiloxane of component (A). is more preferable. If the amount of the component (B) is too small, no reinforcing effect can be obtained, and if it is too large, the workability will deteriorate, the mechanical strength will decrease, and the dynamic fatigue durability will also deteriorate. put away.

In the present invention, (B) a dispersant (wetter) for reinforcing silica can be blended as an optional component, if necessary. Examples of the wetter include silane compounds containing silanol groups (i.e., silicon-bonded hydroxyl groups) such as diphenylsilanediol, and linear dimethylsiloxane oligomers with silanol group-blocked at both ends of the molecular chain (e.g., degree of polymerization or One or two or more selected from silanol group-containing organosiloxane oligomers such as silanol group-containing organosiloxane oligomers, silazanes, etc. are used.

The wetter content is preferably 0 to 25 parts by mass, more preferably 3 to 20 parts by mass, per 100 parts by mass of the base polymer (component (A)). .

-(C) component-
Component (C) supports metal oxide particles containing titanium oxide, the surface is hydrophobized with a silicon atom-containing hydrophobizing agent, and the primary particle size before supporting the metal oxide particles is in the range of 5 to 50 nm. is silica (metal oxide-supported silica).

Examples of the metal oxide particles include those essentially containing titanium oxide and containing tin oxide and indium tin oxide. A solid solution of titanium oxide and tin and/or manganese may also be used.

Further, the metal oxide particles may be particles (core-shell particles) having a core-shell structure having a core of metal oxide and a shell of silicon oxide formed on the outer surface thereof.

As a method for forming a silicon oxide shell on the core of the metal oxide, a hydrolyzate/polymer obtained by a sol-gel method using a dispersion (sol) of metal oxide particles and an alkoxysilane can be used. A method of forming a condensate on the particle surface and the like can be mentioned. In this case, the concentration of the obtained core-shell particles in the sol is preferably 1 to 50% by mass, more preferably 10 to 40% by mass. If the content is 1% by mass or more, the amount of sol to be added is appropriate, and it is economical because it does not take much time to remove the dispersion medium of the sol from the silicone rubber composition of the present invention. On the other hand, if the content is 50% by mass or less, the core-shell particles can be easily dispersed.

The average particle size of the metal oxide particles is preferably 1 to 100 nm, particularly preferably 1 to 50 nm, because transparency in the visible region is important. If the average particle size of the metal oxide particles is 100 nm or less, it will be smaller than the wavelength of light in the visible region, and scattering will not be noticeable. Moreover, when the total surface area of the dispersoids is 1 nm or more, the total surface area of the dispersoids in the system does not become too large, and the handling of the dispersed liquid is facilitated, for example, aggregation is unlikely to occur.

In the present invention, the average particle size of metal oxide particles is a volume-based 50% cumulative distribution size ( _D50 ) measured by a dynamic light scattering method using a laser beam.

The metal oxide particles thus obtained are preferably surface-modified with an organosilicon compound represented by the following general formula (2) and/or its (partially) hydrolyzed condensate.
^R1Si (Y) ₃ (2)
(In the formula, each R ¹ may be the same or different, and may be substituted with a (meth)acryl group, an oxiranyl group, an amino group, a mercapto group, an isocyanate group, or a fluorine atom. an alkyl group, an alkenyl group having 2 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, and a (poly)dimethylsiloxy group having 1 to 50 silicon atoms or is a hydrogen atom, and Y is a substituent selected from the group consisting of an alkoxy group, an acetoxy group, an enol group, and a chlorine atom.)

Specific examples of the organosilicon compound represented by formula (2) include hydrogentrimethoxysilane, hydrogentriethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane, ethyltrimethoxysilane, ethyltrimethoxysilane, Ethoxysilane, ethyltriisopropoxysilane, propyltrimethoxysilane, propyltriethoxysilane, propyltriisopropoxysilane, vinyltrimethoxysilane, allyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltri Ethoxysilane, γ-acryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-chloro Propyltrimethoxysilane, 3,3,3-trifluoropropyltrimethoxysilane, 3,3,3-trifluoropropyltriethoxysilane, perfluorooctylethyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-amino propyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-(2-aminoethyl)aminopropyltrimethoxysilane, γ-isocyanatopropyltrimethoxysilane, γ-isocyanatopropyltriethoxysilane, phenyltrimethoxysilane, phenyltrimethoxysilane, Ethoxysilane, tris (3-trimethoxysilylpropyl) isocyanurate in which isocyanate groups are bonded to each other, tris (3-triethoxysilylpropyl) isocyanurate, partial hydrolysis condensate of methyltrimethoxysilane (trade name “KC-89S”) ”, “X-40-9220” manufactured by Shin-Etsu Chemical Co., Ltd.), a partial hydrolysis condensate of methyltrimethoxysilane and γ-glycidoxypropyltrimethoxysilane (trade name “X-41-1056” Shin-Etsu Chemical Kogyo Co., Ltd.) ; acetoxysilanes such as triacetoxymethylsilane, triacetoxyethylsilane, triacetoxypropylsilane, triacetoxyphenylsilane; trichloromethylsilane, trichloroethylsilane, trichloropropylsilane, Chlorosilanes such as trichlorophenylsilane; triisopropenyloxymethylsilane, ethyltriisopropenyloxysilane, triisopropenyloxysilane enol silanes such as propenyloxypropylsilane and phenyltriisopropenyloxysilane, among which hydrogentrimethoxysilane, hydrogentriethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane; , ethyltrimethoxysilane, ethyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-acryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ- Glycidoxypropyltriethoxysilane is preferred.

Fumed silica, for example, can be used as the silica on which the metal oxide particles containing titanium oxide are supported in the component (C). Component (C) silica has a primary particle size of 5 to 50 nm, preferably 5 to 15 nm, before supporting the metal oxide particles. That is, the component (C) of the present invention comprises silica having a primary particle size of 5 to 50 nm and metal oxide particles supported thereon. If the primary particle size is less than 5 nm, it becomes difficult to disperse in the silicone polymer. If it exceeds 50 nm, the transparency of the silicone polymer containing metal oxide-supported silica may deteriorate.

Batch equipment such as a Henschel mixer, an Eirich mixer, a high-speed mixer, or a continuous equipment such as a horizontal shaft rotating blade can be used as a method for supporting metal oxide particles on silica. In these facilities, it is possible to uniformly disperse titanium oxide sol having a core-shell structure by spraying while silica powder is being stirred and mixed at high speed. As a result, silica supporting titanium oxide having a core-shell structure can be obtained.

Component (C) silica may be granulated with a solvent such as water or alcohol. Granulation improves the handling of silica.

In the present invention, the metal oxide-supported silica is hydrophobized with a silicon atom-containing hydrophobizing agent when or after the metal oxide particles are supported on the silica.
In addition, the degree of hydrophobicity of the metal oxide-supporting silica is preferably 40 or more. If the degree of hydrophobicity is within this range, aggregation of silica can be prevented, and the resulting silicone rubber will have good transparency. A method for measuring the degree of hydrophobicity will be described in the examples below.

As the silicon atom-containing hydrophobizing agent, for example, one represented by the following general formula (3) can be used.
^R2Si (Y) ₃ (3)
(In the formula, each R ² may be the same or different, and may have 1 to 20 carbon atoms optionally substituted with a (meth)acryl group, oxiranyl group, amino group, mercapto group, isocyanate group or fluorine atom. an alkyl group, an alkenyl group having 2 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, and a (poly)dimethylsiloxy group having 50 or less silicon atoms or a hydrogen atom and Y is a substituent selected from the group consisting of an alkoxy group, an acetoxy group, an enol group and a chlorine atom.)

In this case, the alkyl group preferably includes an alkyl group having 1 to 6 carbon atoms, particularly a methyl group and an ethyl group, and the aryl group includes those having 6 to 10 carbon atoms, particularly a phenyl group. Furthermore, the number of silicon atoms in the (poly)dimethylsiloxy group is preferably 1-50, more preferably 1-30.

Specific examples of the silicon atom-containing hydrophobizing agent represented by formula (3) include hydrogentrimethoxysilane, hydrogentriethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane, and ethyltrimethoxysilane. , ethyltriethoxysilane, ethyltriisopropoxysilane, propyltrimethoxysilane, propyltriethoxysilane, propyltriisopropoxysilane, vinyltrimethoxysilane, allyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxysilane roxypropyltriethoxysilane, γ-acryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-chloropropyltrimethoxysilane, 3,3,3-trifluoropropyltrimethoxysilane, 3,3,3-trifluoropropyltriethoxysilane, perfluorooctylethyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-Aminopropyltrimethoxysilane, γ-Aminopropyltriethoxysilane, N-(2-Aminoethyl)aminopropyltrimethoxysilane, γ-Isocyanatopropyltrimethoxysilane, γ-Isocyanatopropyltriethoxysilane, Phenyltrimethoxysilane , phenyltriethoxysilane, tris (3-trimethoxysilylpropyl) isocyanurate in which isocyanate groups are bonded to each other, tris (3-triethoxysilylpropyl) isocyanurate, partial hydrolysis condensate of methyltrimethoxysilane (trade name " KC-89S”, “X-40-9220” manufactured by Shin-Etsu Chemical Co., Ltd.), partial hydrolysis condensate of methyltrimethoxysilane and γ-glycidoxypropyltrimethoxysilane (trade name “X-41-1056 Alkoxysilanes such as "Shin-Etsu Chemical Co., Ltd." ; acetoxysilanes such as triacetoxymethylsilane, triacetoxyethylsilane, triacetoxypropylsilane, triacetoxyphenylsilane; trichloromethylsilane, trichloroethylsilane, trichloro Chlorosilanes such as propylsilane and trichlorophenylsilane; triisopropenyloxymethylsilane, ethyltriisopropenyloxysilane, Examples include enol silanes such as lyisopropenyloxypropylsilane and phenyltriisopropenyloxysilane.

（式中、Ｍｅはメチル基であり、ｒは０～４９の整数である） Specific examples of silicon atom-containing hydrophobizing agents represented by formula (3) in which R ² is (poly)dimethylsiloxane include compounds represented by the following formula (4).

(wherein Me is a methyl group and r is an integer from 0 to 49)

In general formula (4), r is an integer of 0 or more and 49 or less, preferably 5 or more and 40 or less, and more preferably 10 or more and 30 or less. If r is 49 or less, the properties as a silicone oil will be appropriate, and the solubility of the surface-treated organosol in various resins will not be limited. In general formula (4), a compound having an average structure of r=30 is available under the trade name “X-24-9822” (manufactured by Shin-Etsu Chemical Co., Ltd.).

The amount of the silicon atom-containing hydrophobizing agent added is preferably 0.01 to 50 times, more preferably 1 to 25 times, the weight of silica as component (C), More preferably, it is 2 times or more and 10 times or less. If the amount added is 50 times or less with respect to the weight of silica, it does not form a slurry, the cohesive force of silica after drying becomes small, and the transparency when dispersed in a silicone polymer becomes good. If it is 0.01 times or more, the treatment of the silanol groups on the silica surface is sufficient, the cohesive force of the dried silica becomes small, and the transparency when dispersed in a silicone polymer becomes good.

In the silica of component (C), the content of the metal oxide particles is preferably 1 to 30% by mass, more preferably 1 to 10% by mass, based on the total mass of silica after supporting the metal oxide particles. %. If the content of the metal oxide particles is 1% by mass or more, there is no fear that the ultraviolet absorption effect will not be exhibited, and if the content is 30% by mass or less, the dispersibility of silica will be good.

The amount of component (C), metal oxide-supported silica, is 0.01 to 50 parts by mass per 100 parts by mass of component (A).

-(D) component-
Component (D) is not an essential component in the composition of the present invention, but it can be preferably used. Silicone resin powder which is polyorganosilsesquioxane fine powder, for example, JP-A-2-209927 The one described in the official gazette is used.
The silicone resin powder has a particle size (d ₅₀ ) at a cumulative frequency of 50% measured by a laser diffraction method of 1 to 50 μm, preferably 3 to 40 μm. When d50 is less than 1 μm, no flame retardant effect is observed, and when ₅₀ μm or more, transparency deteriorates.

The amount of the component (D) silicone resin powder to be blended is 0 to 50 parts by mass, preferably 0 to 40 parts by mass, per 100 parts by mass of the organopolysiloxane (A). By adding the component (D), the flame retardant effect is further improved. In addition, when blending, it is preferable to make it 1 mass part or more.

-(E) component-
The (E) component triazole compounds include, for example, 1,2,3-triazole, 1,2,4-triazole and derivatives thereof. Specifically, 1,2,3-triazole derivatives include benzotriazole, 4-hydroxy-1,2,3-triazole, 1,2,3-triazole-4-aldehyde, 4-cyano-1,2, 3-triazole and the like. Derivatives of 1,2,4-triazole include 5-amino-3-methyl-1,2,4-triazole, 3-mercapto-1,2,4-triazole, and the like. The most preferred of these are benzotriazole, 1,2,3-triazole and 1,2,4-triazole. These may be used alone or in combination of two or more.

Component (E) is added in an amount of 0.001 to 0.1 parts by mass, preferably 0.005 to 0.05 parts by mass, per 100 parts by mass of organopolysiloxane (A). If the amount is less than 0.001 part by mass, the flame retardancy is not improved, and if the amount is more than 0.1 part by mass, it is not economical and the cured product may yellow.

-(F) component-
(F) Platinum compounds include platinum black, diplatinum chloride, chloroplatinic acid, reactants of chloroplatinic acid and monohydric alcohols, complexes of chloroplatinic acid and olefins, platinum bisacetoacetate, and the like. of platinum-based compounds.

The amount of the platinum compound compounded is 0.5 to 1,000 ppm, particularly about 1 to 500 ppm, as platinum (in terms of mass), relative to the total mass of the components (A) to (E). If it is less than 0.5 ppm, the flame retardancy is insufficient, and if it exceeds 1,000 ppm, it is uneconomical and the flame retardancy may decrease.

-(G) component-
The curing agent is not particularly limited as long as it can cure the component (A), and includes the following (G-1) addition reaction curing agent and (G-2) organic peroxide curing agent.

(G-1) Addition Reaction Curing Agent (G-1) As the addition reaction curing agent, an organohydrogenpolysiloxane and a hydrosilylation catalyst are used in combination.

The organohydrogenpolysiloxane has 2 or more, preferably 3 or more, more preferably 3 to 200, and still more preferably about 4 to 100 silicon-bonded hydrogen atoms per molecule (that is, SiH group), it may have a linear, cyclic, branched, or three-dimensional network structure, and known organohydrogenpolysiloxanes are used as cross-linking agents for addition reaction-curable silicone rubber compositions. For example, an organohydrogenpolysiloxane represented by the following average compositional formula (5) can be used.
^R20pHqSiO ₍ 4- _{pq )/2} (5)

In the average composition formula (5), R ²⁰ represents an unsubstituted or substituted monovalent hydrocarbon group, which may be the same or different, and preferably excludes aliphatic unsaturated bonds. . Generally, those having 1 to 12 carbon atoms, particularly preferably 1 to 8 carbon atoms, are specifically exemplified by alkyl groups such as methyl group, ethyl group and propyl group, cycloalkyl groups such as cyclohexyl group, phenyl group and tolyl group. Aralkyl groups such as aryl groups, benzyl groups, 2-phenylethyl groups and 2-phenylpropyl groups, and groups in which some or all of the hydrogen atoms in these groups are substituted with halogen atoms, etc., e.g., 3, 3, 3 -trifluoropropyl group and the like.

Incidentally, p and q are 0<p<3, preferably 0.5≤p≤2.2, more preferably 1.0≤p≤2.0, 0<q≤3, preferably 0.002≤q. ≤1.1, more preferably 0.005≤q≤1, 0<p+q≤3, preferably 1≤p+q≤3, more preferably 1.002≤p+q≤2.7.

Organohydrogenpolysiloxane has 2 or more, preferably 3 or more SiH groups in one molecule. good too. The organohydrogenpolysiloxane preferably has a viscosity at 25° C. of 0.5 to 10,000 mPa·s, particularly 1 to 300 mPa·s.

Specific examples of such organohydrogenpolysiloxanes include 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, tris(hydrogendimethylsiloxy ) methylsilane, tris(hydrogendimethylsiloxy)phenylsilane, methylhydrogencyclopolysiloxane, methylhydrogensiloxane/dimethylsiloxane cyclic copolymer, both ends trimethylsiloxy group-blocked methylhydrogenpolysiloxane, both ends trimethylsiloxy group-blocked Dimethylsiloxane/methylhydrogensiloxane copolymer, dimethylpolysiloxane blocked at both ends with dimethylhydrogensiloxy groups, dimethylsiloxane/methylhydrogensiloxane copolymer blocked at both ends with dimethylhydrogensiloxy groups, methylhydrogenblocked with trimethylsiloxy groups at both ends gensiloxane/diphenylsiloxane copolymer, methylhydrogensiloxane/diphenylsiloxane/dimethylsiloxane copolymer blocked at both ends with trimethylsiloxy groups, methylhydrogensiloxane/methylphenylsiloxane/dimethylsiloxane copolymer blocked at both ends with trimethylsiloxy groups, dimethylhydrogensiloxy group-blocked methylhydrogensiloxane/dimethylsiloxane/diphenylsiloxane copolymer at both ends, dimethylhydrogensiloxy group-blocked methylhydrogensiloxane/dimethylsiloxane/methylphenylsiloxane copolymer at both ends, (CH ₃ ) ₂ Copolymers consisting of HSiO _1/2 units, (CH ₃ ) ₃ SiO _1/2 units and SiO _4/2 units, copolymers consisting of (CH ₃ ) ₂ HSiO _1/2 units and SiO _4/2 units coalescence, copolymers consisting of (CH ₃ ) ₂ HSiO _1/2 units, SiO _4/2 units and (C ₆ H ₅ ) ₃ SiO _1/2 units; Alternatively, all of them may be substituted with other alkyl groups, phenyl groups, or the like.

The amount of the organohydrogenpolysiloxane compounded is preferably 0.1 to 40 parts by weight per 100 parts by weight of component (A). In addition, the proportion of silicon-bonded hydrogen atoms (≡SiH groups) to one aliphatic unsaturated bond (alkenyl group, diene group, etc.) in component (A) is preferably in the range of 0.5 to 10. A range of 0.7 to 5 is preferable. If the number is less than 0.5, the cross-linking may be insufficient and sufficient mechanical strength may not be obtained. Compression set may increase.

The hydrosilylation catalyst is a catalyst for the hydrosilylation addition reaction between the alkenyl groups of the component (A) and the silicon-bonded hydrogen atoms (SiH groups) of the organohydrogenpolysiloxane. Examples of hydrosilylation catalysts include platinum group metal-based catalysts, including simple platinum group metals and compounds thereof, and conventionally known catalysts for addition reaction-curable silicone rubber compositions can be used. For example, particulate platinum metal adsorbed on a carrier such as silica, alumina or silica gel, platinum catalyst such as platinic chloride, chloroplatinic acid, alcoholic solution of chloroplatinic acid hexahydrate, palladium catalyst, rhodium catalyst, etc. platinum or platinum compounds (platinum catalysts) are preferred.

The amount of the catalyst to be added is sufficient as long as it can promote the addition reaction, and is usually used in the range of 1 ppm by mass to 1% by mass in terms of the amount of platinum group metal relative to the organopolysiloxane of the component (A). A range of -500 mass ppm is preferred. If the amount added is less than 1 mass ppm, the addition reaction may not be sufficiently accelerated, resulting in insufficient curing. It is small and may be uneconomical.

The platinum group metal-based catalyst used as the hydrosilylation catalyst of component (G-1) may be the same as or different from the platinum-based compound used in component (F) above. , it is necessary to set the desired blending amount for each, and be careful not to add too much or too little as a whole.

(G-2) Organic peroxide curing agent (G-2) Examples of the organic peroxide curing agent include benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, p-methylbenzoyl peroxide, o-methyl benzoyl peroxide, 2,4-dicumyl peroxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, di-t-butyl peroxide, t-butyl perbenzoate, 1,6 -hexanediol-bis-t-butyl peroxycarbonate and the like. The amount of the organic peroxide to be added is preferably 0.1 to 10 parts by weight, particularly 0.2 to 5 parts by weight, per 100 parts by weight of component (A). If the amount is too small, curing may be insufficient, and if it is too large, the cured product of the silicone rubber may turn yellow due to decomposition residues of the organic peroxide. In addition, addition reaction curing and organic peroxide curing were used in combination with component (A) by combining component (G-1) and component (G-2) within the ranges of the above amounts. It can also be a co-vulcanized silicone rubber composition.

[Other ingredients]
In addition to the above components, the silicone rubber composition of the present invention may optionally contain a filler such as crushed quartz, crystalline silica, diatomaceous earth, calcium carbonate, a coloring agent, and a tear strength. Various alkoxysilanes, especially phenyl group-containing alkoxysilanes and their hydrolysates, diphenylsilane diol, carbon It is optional to add known fillers and additives in thermosetting silicone rubber compositions such as functional silanes and silanol group-containing low-molecular-weight siloxanes.

As the method for molding and curing this silicone rubber composition, conventional methods can be adopted, but as the molding method, the most suitable means for the purpose can be selected from injection molding, transfer molding, injection molding, compression molding, and the like. It is possible. As the curing conditions, heat treatment (primary vulcanization) conditions at 40 to 230° C. for about 3 seconds to 160 minutes can be employed. Further, secondary vulcanization (post-curing) may optionally be performed at 40 to 230° C. for about 10 minutes to 24 hours, if necessary.

<Silicone rubber>
Furthermore, the present invention provides a silicone rubber comprising a cured product of the above silicone rubber composition. Such a silicone rubber is excellent in both optical transparency and flame retardancy. The silicone rubber obtained in this way has high transparency, and the total light transmittance of a 2 mm thick silicone rubber (cured product) measured by the method described in JIS K 7361-1:1997 is 75% or more (75 to 100 %), more preferably 85% or more (85 to 100%).

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples. In the following examples, "parts" means "mass parts". Further, the average degree of polymerization indicates the number average degree of polymerization in terms of polystyrene in gel permeation chromatography (GPC) analysis using toluene as a developing solvent.

[Preparation Examples 1 to 3 : Preparation of metal oxide particles]
(Preparation Example 1A: Preparation of aqueous dispersion (1) of core-shell particles)
An aqueous dispersion of a metal oxide was prepared by using water as a dispersion medium and core-shell particles having a titanium oxide-tin oxide composite oxide as a nucleus and a silicon oxide as a shell as a dispersoid. Specifically, according to the following procedure, first, a composite oxide dispersion liquid (i) containing titanium oxide-tin oxide particles serving as nuclei is produced, and then tetraethoxysilane is hydrolyzed and condensed to obtain a core-shell. An aqueous dispersion (1) containing particles was prepared.

(Preparation of composite oxide dispersion (i))
Tin (IV) chloride pentahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) was added to 66.0 g of a 36% by mass titanium (IV) chloride aqueous solution (manufactured by Ishihara Sangyo Co., Ltd., product name: TC-36)1. After adding 8 g and mixing well, this was diluted with 1,000 g of deionized water. 300 g of 5% by weight ammonia water (manufactured by Wako Pure Chemical Industries, Ltd.) was gradually added to this metal salt aqueous solution mixture for neutralization and hydrolysis to obtain a tin-containing titanium hydroxide precipitate. . The pH of the titanium hydroxide slurry at this time was 8. The obtained precipitate of titanium hydroxide was deionized by repeating addition of ion-exchanged water and decantation. 100 g of 30% by mass hydrogen peroxide solution (manufactured by Wako Pure Chemical Industries, Ltd.) was gradually added to the titanium hydroxide precipitate containing tin after the deionization treatment, and then stirred at 60° C. for 3 hours to obtain a sufficient mixture. reacted to Thereafter, pure water was added to adjust the concentration, thereby obtaining a translucent tin-containing peroxotitanic acid solution (solid concentration: 1% by mass). An autoclave with a volume of 500 mL (manufactured by Pressure Glass Industry Co., Ltd., product name: TEM-D500) was charged with 350 mL of the peroxotitanic acid solution synthesized as described above, and this was heated at 200 ° C. and 1.5 MPa for 240 minutes. hydrothermally treated. After that, the reaction mixture in the autoclave is discharged through a sampling tube into a container kept in a water bath at 25° C., and cooled rapidly to stop the reaction to obtain a composite oxide dispersion (i). rice field.

(Preparation of aqueous dispersion (1) of core-shell particles)
1,000 parts by mass of the composite oxide dispersion (i), 100 parts by mass of ethanol, and 2.0 parts by mass of ammonia were added to a separable flask equipped with a magnetic rotor and a thermometer at room temperature (25°C). Stirred magnetically. This separable flask was immersed in an ice bath and cooled until the content temperature reached 5°C. After adding 18 parts by mass of tetraethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBE-04"), a separable flask was placed in μReactorEx (manufactured by Shikoku Keisoku Kogyo Co., Ltd.). , a microwave with a frequency of 2.45 GHz and an output of 1,000 W was irradiated for 1 minute while magnetically stirring. In the meantime, it was confirmed that the content temperature reached 85°C by observing the thermometer. The resulting mixture was filtered through qualitative filter paper (Advantec 2B) to obtain a dilute colloidal solution. This dilute dispersion was passed through a Dynafilter (manufactured by Mitsubishi Kakoki Co., Ltd., product name “DyF152/S”, MgAl ₂ O disc having an average pore diameter of 7 nm [manufactured by ANDRITZ KMPT GmbH, product number 2065181, type φ152/7 nm]). was concentrated to a dispersoid concentration of 10% by mass by ultrafiltration using . The aqueous dispersion (1) of core-shell particles had a solid content concentration of 15.9% by mass and a particle size of 19.5 nm. At this time, the particle size is the value of the volume-based 50% cumulative distribution diameter (D ₅₀ ) measured by the dynamic light scattering method, which was measured using Nanotrac UPA-EX150 (manufactured by Nikkiso Co., Ltd.).

(Preparation Example 1B: Synthesis of ethanol dispersion (1) of surface-modified core-shell particles)
An aqueous dispersion of core-shell particles (1) (300 g, solid content concentration of 15.9% by mass) and 3 g of a sulfonic acid cationic ion exchange resin as a catalyst. Methyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., product name “KBM-13”, 230 g) was added as a surface modifier and vigorously stirred (250 rpm). It was observed that the dispersion liquid and the alkoxysilane reacted with each other by stirring and became uniform. At that time, it was observed that the temperature of the dispersion increased from 25°C to 52°C. After heating and stirring for 2 hours so that the temperature of the dispersion reached 50° C., the dispersion was diluted by adding ethanol (750 g) while stirring (250 rpm). The diluted dispersion was introduced into a Dynafilter (manufactured by Mitsubishi Kakoki Co., Ltd., product name “DyF152/S”, MgAl ₂ O disk with an average pore diameter of 7 nm [manufactured by ANDRITZ KMPT GmbH, product number 2065181, type φ152/7 nm]). did. A rotating shaft connected to the filter was rotated (1,000 rpm) while applying a static pressure of 0.2 MPa with compressed air. Exudation of the dispersion through the ceramic filter was observed. A receiver (5,000 mL) was provided at the outlet of the filter, and 800 g of exudate was collected. An organic solvent (ethanol) was continuously supplied under pressure (0.2 MPa) to the concentrated dispersion. A rotating shaft connected to the filter was rotated (1,000 rpm) while applying a static pressure of 0.2 MPa with compressed air. Exudation of the dispersion through the ceramic filter was observed. A receiver (5,000 mL) was provided at the filter outlet, and ethanol was supplied under pressure until the exudate reached 800 g. The dispersion liquid was taken out from the filtration chamber to obtain an ethanol dispersion liquid (1) of surface-modified core-shell particles. The ethanol dispersion (1) of surface-modified core-shell particles had a solid concentration of 17% by mass and a particle size of 19.2 nm. At this time, the particle size is the value of the volume-based 50% cumulative distribution diameter (D ₅₀ ) measured by the dynamic light scattering method, which was measured using Nanotrac UPA-EX150 (manufactured by Nikkiso Co., Ltd.).

(Preparation Example 1-C: Synthesis of polysiloxane-grafted core-shell particles (1))
A Dimroth condenser, a nitrogen inlet tube, a thermometer, a four-necked 2 L separable flask equipped with mechanical stirring blades, ethanol dispersion of core-shell particles (1) (258 g, solid content concentration 17% by mass), ethanol (634 g) , a cyclic siloxane (octamethylcyclotetrasiloxane [D4], 179 g) and trifluoromethanesulfonic acid (2 g) as a catalyst were added. After stirring at room temperature for 12 hours, ring-opening polymerization was performed by refluxing for 2 hours. Subsequently, ethanol was distilled off under normal pressure, and the mixture was further stirred at 110° C. for 2 hours while the ethanol was distilled off. After cooling to room temperature, toluene (300 g) and synthetic hydrotalcite (manufactured by Kyowa Chemical Industry Co., Ltd., "Kyoward 500", 8 g) were added to adsorb the acid catalyst. After Kyoward 500 was removed by filtration, toluene was removed by distillation under reduced pressure to obtain core-shell particles (1) grafted with liquid polysiloxane. As a result of thermogravimetric analysis, the content of the siloxane component in the resulting polysiloxane-grafted core-shell particles (1) was 72% by mass.

(Preparation Example 2: Synthesis of ethanol dispersion (2) of surface-modified core-shell particles)
Tin (IV) chloride pentahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) was added to 66.0 g of a 36% by mass titanium (IV) chloride aqueous solution (manufactured by Ishihara Sangyo Co., Ltd., product name: TC-36)1. Instead of adding 8 g, 36 mass% titanium (IV) chloride aqueous solution (manufactured by Ishihara Sangyo Co., Ltd., product name: TC-36) was added to 66.0 g of tin (IV) chloride pentahydrate (Wako Pure Chemical Industries, Ltd. Co., Ltd.) and 0.09 g of manganese (II) oxide (Kojundo Chemical Laboratory Co., Ltd.) were added, but an ethanol dispersion of core-shell particles surface-modified in the same manner as in Preparation Example 1B. (2) was obtained. The ethanol dispersion (2) of surface-modified core-shell particles had a solid concentration of 14.5% by mass and a particle size of 19.2 nm.

(Preparation Example 3: Synthesis of ethanol dispersion (3) of surface-modified core-shell particles)
γ-Acryloxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-5103", 230 g) was used to obtain an ethanol dispersion (3) of surface-modified core-shell particles in the same manner as in Preparation Example 1B. The ethanol dispersion (3) of surface-modified core-shell particles had a solid concentration of 15% by mass and a particle size of 19.5 nm.

[Preparation Examples I to X of Metal Oxide-Supported Silica]
(Preparation Example I: Preparation of metal oxide-supported silica (1))
200 g of fumed silica having a BET specific surface area of 200 m ² /g (Nippon Aerosil 200, primary particle diameter 12 nm) was charged into a high-speed mixer (10 L volume) and operated at 1500 rpm. When the rotation was stabilized, 70 g of dimethylpolysiloxane having an average degree of polymerization of 4 and a viscosity of 15 mPa s at 25°C as a silicon atom-containing hydrophobizing agent was sprayed for 20 seconds. 100 g of aqueous dispersion (1) and 200 g of pure water were sprayed for 60 seconds. This was heated at 250° C. for 2.5 hours after removing moisture with a dryer. The resulting metal oxide-supported silica (1) had a loose bulk density of 150 g/L measured by the following method, and a hydrophobicity of 60 by methanol titration.

<Method for measuring loose bulk density>
Multitester MT-1000 type manufactured by Seishin Enterprise Co., Ltd. is used. A funnel, a sieve (opening 150 μm), and a sieve spacer are stacked in this order on the top of the feeder unit and fixed with a stopper. A 100 ml cell is placed on the sample table, and the sample is put into the sample unit, while the feeder is vibrated to fill the cell with the sieved sample and scrape it off with a scraper. The loose bulk density ρ (g/l) is obtained by the following formula.
ρ = ((W1-W0)/100) x 1000
W0: Weight of cell container (g)
W1: cell container + sample weight (g)

<Method for measuring degree of hydrophobicity>
Put 50 ml of pure water into a 200 ml beaker, add 0.2 g of the sample, and stir with a magnetic stirrer. The tip of a burette filled with methanol is immersed in the liquid, methanol is added dropwise under stirring, and the amount of methanol added required for the sample to completely disperse in water is Zml, and is obtained by the following formula.
Hydrophobicity = (Z / (50 + Z)) x 100

(Preparation Example II: Preparation of metal oxide-supported silica (2))
200 g of fumed silica having a BET specific surface area of 200 m ² /g (Nippon Aerosil 200, primary particle diameter 12 nm) was charged into a high-speed mixer (10 L volume) and operated at 1500 rpm. When the rotation was stabilized, 70 g of dimethylpolysiloxane having an average degree of polymerization of 4 and a viscosity of 15 mPa s at 25°C as a silicon atom-containing hydrophobizing agent was sprayed for 20 seconds. 300 g of aqueous dispersion (1) was sprayed for 60 seconds. This was heated at 250° C. for 2.5 hours after removing moisture with a dryer. The resulting metal oxide-supported silica (2) had a loose bulk density of 210 g/L and a degree of hydrophobicity of 62 determined by methanol titration.

(Preparation Example III: Preparation of metal oxide-supported silica (3))
It was prepared in the same manner as in Preparation Example I, except that 50 g of dimethyldimethoxysilane was used instead of dimethylpolysiloxane having an average degree of polymerization of 4 and a viscosity of 15 mPa·s at 25° C. as the silicon atom-containing hydrophobizing agent. The resulting metal oxide-supported silica (3) had a loose bulk density of 160 g/L and a degree of hydrophobicity of 62 determined by methanol titration.

(Preparation Example IV: Preparation of metal oxide-supported silica (4))
Preparation Example I was repeated except that the ethanol dispersion (1) of core-shell particles obtained in Preparation Example 1B was used instead of the aqueous dispersion (1) of core-shell particles. The resulting metal oxide-supported silica (4) had a loose bulk density of 155 g/L and a degree of hydrophobicity of 58 determined by methanol titration.

(Preparation Example V: Preparation of metal oxide-supported silica (5))
It was prepared in the same manner as in Preparation Example I, except that pure water was not added. The resulting metal oxide-supported silica (5) had a loose bulk density of 70 g/L and a degree of hydrophobicity of 58 determined by methanol titration.

(Preparation Example VI: Preparation of metal oxide-supported silica (6))
It was prepared in the same manner as Preparation Example IV, except that 500 g of methanol was used instead of 200 g of pure water. The resulting metal oxide-supported silica (6) had a loose bulk density of 165 g/L and a degree of hydrophobicity of 62 determined by methanol titration.

(Preparation Example VII: Preparation of metal oxide-supported silica (7))
Preparation Example I was repeated except that the core-shell particle ethanol dispersion (2) obtained in Preparation Example 2 was used instead of the core-shell particle aqueous dispersion (1). The resulting metal oxide-supported silica (7) had a loose bulk density of 166 g/L and a degree of hydrophobicity of 61 determined by methanol titration.

(Preparation Example VIII: Preparation of metal oxide-supported silica (8))
It was prepared in the same manner as in Preparation Example I, except that the composite oxide dispersion (i) obtained in Preparation Example 1A was used instead of the core-shell particle aqueous dispersion (1). The resulting metal oxide-supported silica (8) had a loose bulk density of 160 g/L and a degree of hydrophobicity of 60 by methanol titration.

(Preparation Example IX: Preparation of metal oxide-supported silica (9))
It was prepared in the same manner as in Preparation Example I except that dimethylpolysiloxane having an average degree of polymerization of 4 and a viscosity at 25°C of 15 mPa·s was not added as a silicon atom-containing hydrophobizing agent. The resulting metal oxide-supported silica (9) had a loose bulk density of 140 g/L. This titanium oxide-supported silica was dissolved in water (hydrophobicity 0).

(Preparation Example X: Preparation of mixed liquid 1 of ethanol dispersion of core-shell particles and silanol group-containing siloxane)
10 g of the ethanol dispersion (1) of the core-shell particles obtained in Preparation Example 1B and 4 g of dimethylpolysiloxane having both terminal silanol groups, an average degree of polymerization of 3, and a viscosity at 25° C. of 15 mPa·s were mixed. , a "mixture 1" of an ethanol dispersion of core-shell particles and a silanol group-containing siloxane was prepared.

[ Preparation of Silicone Rubber Compositions of Examples 1 to 12 and Comparative Examples 1 to 7 ]
[Example 1]
Component (A) is an organopolysiloxane composed of 99.850 mol% of dimethylsiloxane units, 0.125 mol% of methylvinylsiloxane units, and 0.025 mol% of dimethylvinylsiloxy units, and having an average degree of polymerization of about 6,000. 50 parts by mass of raw rubber (indicated as "organopolysiloxane raw rubber I" in the table), 99.500 mol% of dimethylsiloxane units, 0.475 mol% of methylvinylsiloxane units, and 0.025 mol% of dimethylvinylsiloxy units 50 parts by mass of an organopolysiloxane raw rubber having an average degree of polymerization of about 6,000 (indicated as "organopolysiloxane raw rubber II" in the table); 4 parts by mass of hexamethyldisilazane was added to 50 parts by mass of fumed silica (Rheolosil DM30S, manufactured by Tokuyama Co., Ltd.) that had been surface-hydrophobized to ² /g and kneaded in a kneader at 170°C for 2 hours. A composition (base compound 1) was prepared by heating for a period of time.

Per 100 parts by mass of this composition (base compound 1), 5 parts by mass of the metal oxide-supported silica (1) obtained in Preparation Example I as the component (C), and an average particle size of 2.5 parts by mass as the component (D). 20 parts by mass of silicone resin powder (KMP-590, manufactured by Shin-Etsu Chemical Co., Ltd.) having a three-dimensional network crosslinked structure of 0 μm, 0.025 parts by mass of benzotriazole as component (E), and component (F) As a 2-ethylhexanol solution of chloroplatinic acid hexahydrate (platinum concentration 2% by mass) 0.1 parts by mass, (G-1) component C25A (platinum group metal hydrosilylation catalyst, platinum atom 0.1 part) 09% by mass, manufactured by Shin-Etsu Chemical Co., Ltd.) 0.5 parts by mass and C25B (containing 40% by mass of organohydrogenpolysiloxane, manufactured by Shin-Etsu Chemical Co., Ltd., organohydrogenpolysiloxane) 2.4 parts by mass was added, and the composition was press-cured for 10 minutes under the conditions of 120°C and 70 kgf/cm ² to prepare sheets of 2 mm thickness and 1 mm thickness. Then, post-curing was performed in an oven at 200° C. for 4 hours. These silicone rubber sheets were returned to room temperature (25° C.) and various physical properties, light transmittance and flame retardancy were measured.

[Example 2]
Various physical properties, light transmission, rate and flame retardancy were measured.

[Example 3]
Various physical properties, light transmission, rate and flame retardancy were measured.

[Example 4]
Various physical properties, light transmission, rate and flame retardancy were measured.

[Example 5]
Various physical properties, light transmission, rate and flame retardancy were measured.

[Example 6]
Various physical properties, light transmission, rate and flame retardancy were measured.

[Example 7]
Example 1 except that the metal oxide-supported silica (7) obtained in Preparation Example VII was used as the component (C) instead of the metal oxide-supported silica (1), and the component (D) was 10 parts by mass. Various physical properties, light transmittance and flame retardancy were measured in the same manner as above.

[Example 8]
Example 1 except that the metal oxide-supported silica (8) obtained in Preparation Example VIII was used as the component (C) instead of the metal oxide-supported silica (1), and the component (D) was 10 parts by mass. Various physical properties, light transmittance and flame retardancy were measured in the same manner as above.

[Example 9]
Component (A) is an organopolysiloxane composed of 99.850 mol% of dimethylsiloxane units, 0.125 mol% of methylvinylsiloxane units, and 0.025 mol% of dimethylvinylsiloxy units, and having an average degree of polymerization of about 6,000. 50 parts by mass of raw rubber (indicated as "organopolysiloxane raw rubber I" in the table), 99.500 mol% of dimethylsiloxane units, 0.475 mol% of methylvinylsiloxane units, and 0.025 mol% of dimethylvinylsiloxy units 50 parts by mass of an organopolysiloxane raw rubber having an average degree of polymerization of about 6,000 (indicated as "organopolysiloxane raw rubber II" in the table); ² /g surface-hydrophobicized fumed silica (Reolosil DM30S, manufactured by Tokuyama Co., Ltd.), 4 parts by weight of hexamethyldisilazane, 1,3-divinyl-1,1,3,3- 1.5 parts by mass of tetramethyldisilazane was added, kneaded with a kneader, and heat-treated at 170° C. for 2 hours to prepare a composition (base compound 2).

With respect to 100 parts by mass of this composition (base compound 2), 5 parts by mass of metal oxide-supported silica (1) as component (C), 0.025 parts by mass of benzotriazole as component (E), and component (F) As a 2-ethylhexanol solution of chloroplatinic acid hexahydrate (platinum concentration 2% by mass) 0.1 parts by mass, (G-1) component C25A (platinum group metal hydrosilylation catalyst, platinum atom 0.1 part) 09% by mass, manufactured by Shin-Etsu Chemical Co., Ltd.) 0.5 parts by mass and C25B (containing 40% by mass of organohydrogenpolysiloxane, manufactured by Shin-Etsu Chemical Co., Ltd., organohydrogenpolysiloxane) 2.4 parts by mass was added, and the composition was press-cured for 10 minutes under the conditions of 120°C and 70 kgf/cm ² to prepare sheets of 2 mm thickness and 1 mm thickness. Then, post-curing was performed in an oven at 200° C. for 4 hours. These silicone rubber sheets were returned to room temperature (25° C.) and various physical properties, light transmittance and flame retardancy were measured.

[Example 10]
Based on 100 parts by mass of the base compound (1), 5 parts by mass of the metal oxide-supported silica (1) obtained in Preparation Example I as the component (C), and a tertiary compound having an average particle size of 2.0 μm as the component (D) 20 parts by mass of silicone resin powder (KMP-590, manufactured by Shin-Etsu Chemical Co., Ltd.) having a structure crosslinked in the original network shape, 0.025 parts by mass of benzotriazole as component (E), chloride as component (F) 0.1 parts by mass of a 2-ethylhexanol solution of platinum acid hexahydrate (platinum concentration: 2% by mass) and 0.3 parts by mass of dicumyl peroxide as component (G-2) were added, and the composition was diluted to 170 parts by mass. C. and 70 kgf/ ^cm.sup.2 for 10 minutes to prepare sheets having a thickness of 2 mm and a thickness of 1 mm. Then, post-curing was performed in an oven at 200° C. for 4 hours. These silicone rubber sheets were returned to room temperature (25° C.) and various physical properties, light transmittance and flame retardancy were measured.

[Example 11]
Component (A) is an organopolysiloxane composed of 99.850 mol% of dimethylsiloxane units, 0.125 mol% of methylvinylsiloxane units, and 0.025 mol% of dimethylvinylsiloxy units, and having an average degree of polymerization of about 6,000. 50 parts by mass of raw rubber (indicated as "organopolysiloxane raw rubber I" in the table), 99.500 mol% of dimethylsiloxane units, 0.475 mol% of methylvinylsiloxane units, and 0.025 mol% of dimethylvinylsiloxy units 50 parts by mass of an organopolysiloxane raw rubber having an average degree of polymerization of about 6,000 (indicated as "organopolysiloxane raw rubber II" in the table); 50 parts by mass of fumed silica (Rheolosil DM30S, manufactured by Tokuyama Corp.) having a surface hydrophobized surface of ² /g; To 7 parts by mass, 4 parts by mass of hexamethyldisilazane was added, kneaded with a kneader, and heat-treated at 170° C. for 2 hours to prepare a composition (base compound 3).

Based on 100 parts by mass of this composition (base compound 3), as component (D), a silicone resin powder (KMP-590, Shin-Etsu Chemical Co., Ltd. ) 20 parts by mass, 0.025 parts by mass of benzotriazole as component (E), and 0.1 mass of a 2-ethylhexanol solution of chloroplatinic acid hexahydrate (platinum concentration: 2% by mass) as component (F) Part, as the (G-1) component, C25A (platinum group metal hydrosilylation catalyst, containing 0.09% by mass as platinum atoms, manufactured by Shin-Etsu Chemical Co., Ltd.) 0.5 parts by mass and C25B (organohydrogen poly 2.4 parts by mass of organohydrogenpolysiloxane (manufactured by Shin-Etsu Chemical Co., Ltd. containing 40% by mass of siloxane) was added, and the composition was press-cured for 10 minutes at 120° C. and 70 kgf/cm ² . Sheets with a thickness of 2 mm and a thickness of 1 mm were produced. Then, post-curing was performed in an oven at 200° C. for 4 hours. These silicone rubber sheets were returned to room temperature (25° C.) and various physical properties, light transmittance and flame retardancy were measured.

[Example 12]
In the same manner as in Example 1, various physical properties, Light transmittance and flame retardancy were measured.

[Comparative Example 1]
Various physical properties, light transmittance and flame retardancy were measured in the same manner as in Example 1, except that metal oxide-supported silica (1) was not added as component (C).

[Comparative Example 2]
The same as in Example 1 except that the metal oxide-supported silica (9) obtained in Preparation Example IX was used as the component (C') to be compared with the component (C) instead of the metal oxide-supported silica (1). Then, various physical properties, light transmittance and flame retardancy were measured.

[Comparative Example 3]
Various physical properties, light transmittance and flame retardancy were measured in the same manner as in Example 1, except that benzotriazole was not added as component (E).

[Comparative Example 4]
Various physical properties, light transmittance and flame retardancy were measured in the same manner as in Example 1, except that the 2-ethylhexanol solution of chloroplatinic acid hexahydrate was not added as component (F).

[Comparative Example 5]
Component (A) is an organopolysiloxane composed of 99.850 mol% of dimethylsiloxane units, 0.125 mol% of methylvinylsiloxane units, and 0.025 mol% of dimethylvinylsiloxy units, and having an average degree of polymerization of about 6,000. 50 parts by mass of raw rubber (indicated as "organopolysiloxane raw rubber I" in the table), 99.500 mol% of dimethylsiloxane units, 0.475 mol% of methylvinylsiloxane units, and 0.025 mol% of dimethylvinylsiloxy units 50 parts by mass of an organopolysiloxane raw rubber having an average degree of polymerization of about 6,000 (indicated as "organopolysiloxane raw rubber II" in the table); ² /g surface-hydrophobicized fumed silica (Rheolosil DM30S, manufactured by Tokuyama Co., Ltd.) was mixed with 50 parts by mass of an ethanol dispersion of the core-shell particles obtained in Preparation Example X and a silanol group-containing siloxane . 35.8 parts by mass of (1) was added, kneaded with a kneader, and heat-treated at 170° C. for 2 hours to prepare a composition (base compound 4).

Based on 100 parts by mass of this composition (base compound 4), as component (D), a silicone resin powder (KMP-590, Shin-Etsu Chemical Co., Ltd. ) 20 parts by mass, 0.025 parts by mass of benzotriazole as component (E), and 0.1 mass of a 2-ethylhexanol solution of chloroplatinic acid hexahydrate (platinum concentration: 2% by mass) as component (F) Part, as the (G-1) component, C25A (platinum group metal hydrosilylation catalyst, containing 0.09% by mass as platinum atoms, manufactured by Shin-Etsu Chemical Co., Ltd.) 0.5 parts by mass and C25B (organohydrogen poly 2.4 parts by mass of organohydrogenpolysiloxane (manufactured by Shin-Etsu Chemical Co., Ltd. containing 40% by mass of siloxane) was added, and the composition was press-cured for 10 minutes at 120° C. and 70 kgf/cm ² . Sheets with a thickness of 2 mm and a thickness of 1 mm were produced. Then, post-curing was performed in an oven at 200° C. for 4 hours. These silicone rubber sheets were returned to room temperature (25° C.) and various physical properties, light transmittance and flame retardancy were measured.

[Comparative Example 6]
Component (A) is an organopolysiloxane composed of 99.850 mol% of dimethylsiloxane units, 0.125 mol% of methylvinylsiloxane units, and 0.025 mol% of dimethylvinylsiloxy units, and having an average degree of polymerization of about 6,000. 50 parts by mass of raw rubber (indicated as "organopolysiloxane raw rubber I" in the table), 99.500 mol% of dimethylsiloxane units, 0.475 mol% of methylvinylsiloxane units, and 0.025 mol% of dimethylvinylsiloxy units 50 parts by mass of an organopolysiloxane raw rubber having an average degree of polymerization of about 6,000 (indicated as "organopolysiloxane raw rubber II" in the table); 50 parts by mass of fumed silica (Rheolosil DM30S, manufactured by Tokuyama Co., Ltd.) subjected to surface hydrophobization treatment of ² /g, 3 parts by mass of ethanol dispersion (1) of core-shell particles obtained in Preparation Example 1B, hexamethyl 4 parts by mass of disilazane were kneaded in a kneader and heat-treated at 170° C. for 2 hours to prepare a composition (base compound 5).

With respect to 100 parts by mass of this composition (base compound 5), 0.025 parts by mass of benzotriazole as component (E) and 2-ethylhexanol solution of chloroplatinic acid hexahydrate as component (F) (platinum concentration: 2 % by mass) 0.1 part by mass, and as component (G-1), C25A (platinum group metal hydrosilylation catalyst, containing 0.09% by mass as platinum atoms, manufactured by Shin-Etsu Chemical Co., Ltd.) 0.5 parts by mass and 2.4 parts by mass of C25B (containing 40% by mass of organohydrogenpolysiloxane, manufactured by Shin-Etsu Chemical Co., Ltd., organohydrogenpolysiloxane), and the composition was heated at 120° C. and 70 kgf/cm ² . Press curing was performed for 10 minutes to prepare sheets having a thickness of 2 mm and a thickness of 1 mm. Then, post-curing was performed in an oven at 200° C. for 4 hours. These silicone rubber sheets were returned to room temperature (25° C.) and various physical properties, light transmittance and flame retardancy were measured.

[Comparative Example 7]
Based on 100 parts by mass of base compound (1), 1.4 parts by mass of core-shell particles (1) grafted with polysiloxane obtained in Preparation Example 1-C as component (C') to be compared with component (C) , As the (G-1) component, C25A (platinum group metal hydrosilylation catalyst, containing 0.09% by mass as platinum atoms, manufactured by Shin-Etsu Chemical Co., Ltd.) 0.5 parts by mass and C25B (organohydrogenpolysiloxane 2.4 parts by mass of organohydrogenpolysiloxane (containing 40% by mass, manufactured by Shin-Etsu Chemical Co., Ltd.) is added, and the composition is press-cured for 10 minutes at 120° C. and 70 kgf/cm ² to obtain a thickness of 2 mm. Thick and 1 mm thick sheets were produced. Then, post-curing was performed in an oven at 200° C. for 4 hours. These silicone rubber sheets were returned to room temperature (25° C.) and various physical properties, light transmittance and flame retardancy were measured.

[Measurement of various physical properties]
Using a test sheet prepared in accordance with JIS K 6249: 2003, various physical properties [hardness (durometer A), tensile strength, elongation at break] were measured in accordance with JIS K 6249: 2003. . The results are shown in Table 1 (each example) and Table 2 (each comparative example) below.

[Measurement of light transmittance]
Using a haze meter (manufactured by Suga Test Instruments Co., Ltd., model: HGM-2), the light of a 2 mm thick silicone rubber sheet after post-curing at 200 ° C. for 4 hours according to the method described in JIS K 7361-1: 1997. Transmittance was measured. The results are shown in Table 1 (each example) and Table 2 (each comparative example) below.

[Measurement of flame retardancy]
Flame retardancy was measured using five silicone rubber sheets with a thickness of 1 mm according to the method specified in the 20 mm vertical burning test of UL94, afterflame time periods T1 and T2, and afterflame time for each set of all treatments. (total of T1 + T2 of the five silicone rubber sheets) was measured, and based on the results, the flame retardant classification of the material was performed. T1 represents the afterflame time after the first flame contact, and T2 represents the afterflame time after the second flame contact.

Claims (8)

(A) the following average composition formula (1)
R._nSiO_(4-n)/2 (1)
(Wherein, R is the same or different unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, and n is a positive number of 1.95 to 2.05.)
Organopolysiloxane represented by and having at least two alkenyl groups in one molecule
100 parts by mass,
(B) Specific surface area is 50m²/ g or more reinforcing silica 5 to 100 parts by mass,
(C) Metal oxide particles containing titanium oxide are supported, the surface is hydrophobized with a silicon atom-containing hydrophobizing agent, and the primary particle size before supporting the metal oxide particles is in the range of 5 to 50 nm. Silica 0.01 to 50 parts by mass,
(D) Silicone resin powder 0 to 50 parts by mass ,
(E) triazole compound 0.001 to 0.1 parts by mass,
(F) platinum compound
As platinum (mass conversion), 16.3 to 1,000 ppm with respect to the total mass of components (A) to (E)(However, if the component (G) contains a platinum-based compound, the amount of platinum is also included.),as well as
(G) Curing agent Effective amount for curing component (A)
and the average particle diameter of the metal oxide particles of the component (C) is a volume-based 50% cumulative distribution diameter (D₅₀) is 1 to 50 nm. 2. The silicone rubber composition according to claim 1 , wherein said metal oxide particles are particles having a core-shell structure having a metal oxide nucleus and a silicon oxide shell formed on the outer surface thereof. 3. The silicone rubber composition according to claim 1 or 2 , wherein the metal oxide particles are surface-modified with an organosilicon compound represented by the following general formula (2) and/or a (partial) hydrolysis condensate thereof. .
^R1Si (Y) ₃ (2)
(In the formula, each R ¹ may be the same or different, and may be substituted with a (meth)acryl group, an oxiranyl group, an amino group, a mercapto group, an isocyanate group, or a fluorine atom. an alkyl group, an alkenyl group having 2 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, and a (poly)dimethylsiloxy group having 1 to 50 silicon atoms or is a hydrogen atom, and Y is a substituent selected from the group consisting of an alkoxy group, an acetoxy group, an enol group, and a chlorine atom.) The silicone rubber composition according to any one of claims 1 to 3 , wherein the content of the metal oxide particles in the silica of component (C) is 1 to 30 mass%. The silicone rubber composition according to any one of claims 1 to 4 , wherein the triazole compound of component (E) is benzotriazole. The silicone rubber composition according to any one of claims 1 to 5 , wherein the curing agent of component (G) is an addition reaction curing type comprising a combination of an organohydrogenpolysiloxane and a hydrosilylation catalyst. The silicone rubber composition according to any one of claims 1 to 5 , wherein the curing agent of component (G) is an organic peroxide. A silicone rubber comprising a cured product of the silicone rubber composition according to any one of claims 1 to 7 .