JP6821535B2 - Silicone rubber composition and silicone rubber - Google Patents

Description

The present invention relates to a silicone rubber composition and a silicone rubber which is a cured product of the composition.

Silicone rubber has excellent weather resistance, electrical properties, low compression permanent strain resistance, heat resistance, cold resistance, etc., so it is used in various fields such as electrical equipment, automobiles, construction, medical care, and food. Widely used in. For example, keypads used as rubber contacts for remote controllers, typewriters, word processors, computer terminals, musical instruments, etc .; architectural gaskets; anti-vibration rubber for audio equipment, etc .; for automobile parts such as connector seals, spark plug boots, and computers. Examples include packing for compact discs used, molds for bread and cakes, and the like. At present, the demand for silicone rubber is increasing more and more, and the development of silicone rubber having excellent properties is desired.

Patent Document 1 and Patent Document 2 describe a room temperature curable silicone rubber composition to which an ultraviolet absorber is added as a building sealant. These compositions are a condensation-curing type, and a light stabilizer and an ultraviolet absorber are added in order to impart adhesive durability, and there is no description regarding transparency.

Patent Document 3 describes an ultraviolet-absorbing silicone coating composition, but since it is a coating agent, it is necessary to coat the molded product to exhibit ultraviolet-absorbing properties. Further, since this coating agent uses a benzotriazole group-containing silane as an ultraviolet absorber, the weather resistance is inferior. Patent Document 4 describes a coating agent for an ultraviolet-absorbing group-containing organopolysiloxane, but it needs to be applied to a base material. In addition, this coating agent has poor weather resistance. Patent Document 5 also describes that it contains a triazine-based ultraviolet absorber, but it is a room temperature curable coating agent.

On the other hand, it is widely known that the dispersion liquid containing titanium oxide particles is effective as an additive for imparting ultraviolet shielding performance, and is used in the fields of paints / cosmetics and hard coat agents, for example. It's being used.

In Patent Document 6 and Patent Document 7, rutile-type titanium dioxide particles are used, but they are used for paints, and when added to thermosetting silicone rubber, the transparency deteriorates. Patent Document 8 proposes a metal oxide-supported silica in which a metal oxide is supported on the pores and the surface of the spherical silica gel and the shape of the coated particles is also spherical. However, a silanol group of silica is used. Since it has not been treated, its transparency deteriorates when it is dispersed in a silicone polymer. Although Patent Document 9 describes a titanium-silica composite, it is used as a cosmetic and its transparency is evaluated even in a coating film. If this titanium-silica composite is dispersed in a silicone polymer, the transparency will deteriorate. Patent Document 10 describes a titanium oxide-silica composite fine particle, but since silica having a large particle size is used, if it is dispersed in a silicone polymer, the transparency will deteriorate. Patent Document 11 describes a composite material of an inorganic non-metal mineral supporting a titanium dioxide layer, but since the particle size of the inorganic non-metal mineral is large, the transparency deteriorates when dispersed in a silicone polymer. ..

JP-A-2002-302606 Japanese Unexamined Patent Publication No. 2000-212541 JP 2015-40223 Japanese Unexamined Patent Publication No. 2006-335855 Japanese Unexamined Patent Publication No. 2009-215521 Japanese Unexamined Patent Publication No. 2003-327430 Japanese Unexamined Patent Publication No. 2003-327431 Japanese Unexamined Patent Publication No. 6-12793 Japanese Unexamined Patent Publication No. 2000-344509 Japanese Unexamined Patent Publication No. 2004-231952 Japanese Patent Publication No. 2014-534141

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 which is a silicone rubber (cured product) having excellent transparency and ultraviolet absorption performance, and a cured product thereof.

In order to solve the above problems, the present invention
(A) Organopolysiloxane represented by the following average composition formula (1) and having at least two aliphatic unsaturated groups in one molecule: 100 parts by mass _RN SiO _{(4-n) / 2} (1)
(In the formula, 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.),
(B) Reinforcing silica with a specific surface area of 50 m ² / g or more: 5 to 100 parts by mass,
(C) Metal oxide particles containing titanium oxide are supported, the surface is made hydrophobic with a silicon atom-containing hydrophobic agent, and the primary particle diameter before supporting the metal oxide particles is in the range of 5 to 50 nm. Silica: 0.01 to 50 parts by mass,
(D) Hardener: 0.01 to 10 parts by mass,
To provide a silicone rubber composition containing.

Such a silicone rubber composition is a silicone rubber composition that can provide a silicone rubber having excellent transparency and ultraviolet absorption performance.

Further, it is preferable that the metal oxide particles are particles having a core-shell structure having a core of the metal oxide and a silicon oxide shell formed on the outer surface thereof.

With such metal oxide particles, the transparency of the silicone rubber can be further improved.

Further, it is preferable that 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.
R ¹ Si (Y) ₃ (2)
(In the formula, R ¹ may be the same or different, and may be substituted with a (meth) acrylic group, an oxylanyl group, an amino group, a mercapto group, an isocyanate group or a fluorine atom. The number of carbon atoms is 1 or more and 20 or less. A substituent selected from the group consisting of an alkyl group of 2 or more and 20 or less, an aryl group having 6 or more and 20 or less carbon atoms, and a (poly) dimethylsiloxy group having 1 or more and 50 or less silicon atoms. It 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.)

Such metal oxide particles can be suitably used for the silicone rubber composition of the present invention.

Further, in the silica of the component (C), the content of the metal oxide particles is preferably 1 to 30% by mass.

When the content of the metal oxide particles is within the above range, a sufficient ultraviolet absorbing effect can be obtained, and the dispersibility of silica becomes good.

Further, it is preferable that the component (D) is an addition reaction curing agent (D-1) composed of a combination of an organohydrogenpolysiloxane and a hydrosilylation catalyst.

Further, the component (D) may be an organic peroxide curing agent (D-2).

Such a component (D) can be suitably used for the silicone rubber composition of the present invention.

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

Such a silicone rubber has excellent transparency and ultraviolet absorption performance.

As described above, the silicone rubber composition of the present invention can provide a silicone rubber (cured product) having excellent transparency and ultraviolet absorption performance.

As described above, there has been a demand for the development of a silicone rubber composition which is a silicone rubber having excellent transparency and ultraviolet absorption performance.

As a result of diligent studies on the above problems, the present inventors supported metal oxide particles containing titanium oxide, the surface was made hydrophobic with a silicon atom-containing hydrophobizing agent, and before the metal oxide particles were supported. The present invention has been completed by finding that a silicone rubber having excellent transparency and ultraviolet absorption performance can be obtained by adding silica having a primary particle size in the range of 5 to 50 nm to the silicone rubber composition.

That is, the present invention (A) is represented by the following average composition formula (1), and is an organopolysiloxane having at least two aliphatic unsaturated groups in one molecule: 100 parts by mass R _n SiO _{(4-n). / 2} (1)
(In the formula, 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.),
(B) Reinforcing silica with a specific surface area of 50 m ² / g or more: 5 to 100 parts by mass,
(C) Metal oxide particles containing titanium oxide are supported, the surface is made hydrophobic with a silicon atom-containing hydrophobic agent, and the primary particle diameter before supporting the metal oxide particles is in the range of 5 to 50 nm. Silica: 0.01 to 50 parts by mass,
(D) Hardener: 0.01 to 10 parts by mass,
It is a silicone rubber composition containing.

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

<Silicone rubber composition>
The silicone rubber composition of the present invention contains the above components (A) to (D). The silicone rubber composition comprises an organopolysiloxane (A) having at least two aliphatic unsaturated groups in one molecule as a base polymer, an addition reaction curing agent (D-1) as a curing agent (D), and an addition reaction curing agent (D-1) as a curing agent (D). / Or, those using an organic peroxide curing agent (D-2) are preferable. The shape of the silicone rubber composition may be a mirrorable type or a liquid type. The liquid silicone rubber composition has self-fluidity at room temperature (usually 25 ° C. ± 10 ° C.), whereas the miraculous silicone rubber composition has high viscosity and self-fluidity at room temperature. It means a non-liquid (solid or highly viscous paste), raw rubber-like composition that can be uniformly mixed under high shear stress by a kneading means such as a roll mill.

Hereinafter, each component of the silicone rubber composition of the present invention will be described in detail.

-(A) component-
In the present invention, the component (A) is an organopolysiloxane represented by the following average composition formula (1) and having at least two aliphatic unsaturated groups in one molecule.
R _n SiO _{(4-n) / 2} (1)
(In the formula, 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 an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, and those having 1 to 8 carbon atoms are particularly preferable. 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, alkenyl groups such as vinyl group, allyl group and propenyl group. , Cycloalkenyl group, phenyl group, aryl group such as tolyl group, aralkyl group such as benzyl group, 2-phenylethyl group, or halogen atom such as fluorine, chlorine or cyano as part or all of hydrogen atom of these group. Examples thereof include a chloromethyl group, a trifluoropropyl group, a cyanoethyl group and the like substituted with a group, and a methyl group, a vinyl group, a phenyl group and a trifluoropropyl group are preferable, and a methyl group and a vinyl group are particularly preferable.

The organopolysiloxane of the component (A) has two or more aliphatic unsaturated groups in one molecule, but usually 2 to 50 groups, particularly about 2 to 20 alkenyl groups and cycloalkenyl groups. Those having an aliphatic unsaturated group such as the above are preferable, and those having a vinyl group are particularly preferable. In this case, 0.01 to 20 mol%, particularly 0.02 to 10 mol% of the total R is preferably an aliphatic unsaturated group. The aliphatic unsaturated group may be bonded to a silicon atom at the end of the molecular chain, to a silicon atom in the middle of the molecular chain (non-terminal of the molecular chain), or both. However, it is preferable that it is bonded to at least a silicon atom at the end of the molecular chain.

When the addition reaction curing agent (D-1) is used as the curing agent (D) described later, it is essential that the component (A) has two or more alkenyl groups in one molecule.

Further, 80 mol% or more, preferably 90 mol% or more, more preferably 95 mol% or more, and further preferably all R except an aliphatic unsaturated group in the total R may be an alkyl group, particularly a methyl group. desirable.

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

The molecular structure of the organopolysiloxane as the component (A) is preferably a linear structure or a linear structure having a partially branched structure. 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 of repeating only the 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 a part of a dimethylpolysiloxane structure composed of repeating dimethylsiloxane units constituting the main chain. Those introduced with diorganosiloxane units such as methylphenylsiloxane unit, methylvinylsiloxane unit, and methyl-3,3,3-trifluoropropylsiloxane unit are preferable.

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

As described above, the organopolysiloxane of the component (A) has a triorganosyloxy group (R ₃ SiO _1/2 ) or a hydroxydiorganosyloxy group (R ₂ (HO) SiO _1/2 ) at both ends of the molecular chain. A linear one in which the main chain is closed and the main chain consists of repeating diorganosiloxane units (R ₂ SiO _2/2 ) can be preferably mentioned. Particularly preferred are methylvinylpolysiloxane, methylphenylvinylpolysiloxane, and methyltrifluoropropylvinyl as the type of substituent in the molecule (ie, an unsubstituted or substituted monovalent hydrocarbon group attached to a silicon atom). Examples thereof include polysiloxane and dimethylpolysiloxane.

Such an organopolysiloxane can be obtained, for example, by (co) hydrolyzing and condensing one or more of organohalogenosilanes, or by making cyclic polysiloxanes (trimers of siloxanes, tetramers, etc.) 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), particularly preferably 150 to 100,000. This degree of polymerization can be measured as a polystyrene-equivalent weight average degree of polymerization by gel permeation chromatography (GPC) analysis.

The component (A) may be used alone or as a mixture of two or more kinds having different molecular weights (degrees of polymerization) and molecular structures.

-(B) component-
The reinforcing silica of the component (B) is a filler added to obtain a silicone rubber composition having excellent mechanical strength, and for this purpose, the specific surface area (BET adsorption method) is 50 m ² / g. The above is necessary, preferably 100 to 450 m ² / g, and 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 fumes silica (fumed silica) and precipitated silica (wet silica). Further, those whose surfaces are hydrophobized with an organosilane compound such as methylchlorosilane or a silazane compound such as hexamethyldisilazane are also preferably used, but silica as a component (C) described later is excluded. Of these, aerosol silica, which has excellent transparency, is preferable.

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

The blending amount of the reinforcing silica of the component (B) is 5 to 100 parts by mass, preferably 10 to 100 parts by mass, and 20 to 60 parts by mass with respect to 100 parts by mass of the organopolysiloxane of the component (A). Is more preferable. If the amount of the component (B) is less than 5 parts by mass, the reinforcing effect cannot be obtained, and if it is more than 100 parts by mass, the workability is deteriorated and the mechanical strength is lowered. Fatigue durability also deteriorates.

In the present invention, if necessary, a dispersant (wetter) is added as an optional component for the purpose of uniformly dispersing the reinforcing silica of the component (B) in the organopolysiloxane of the component (A). can do. Examples of this wetter include a silanol group (that is, a silicon atom-bonded hydroxyl group) -containing silane compound such as diphenylsilanediol, and a linear dimethylsiloxane oligomer having a silanol group block at both ends of the molecular chain (for example, the degree of polymerization or in the molecule). One or more selected from silanol group-containing organosiloxane oligomers such as (low polymerization degree polymers having 2 to 30 silicon atoms, particularly 3 to 20 silicon atoms), silazan, and the like are used.

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

-(C) component-
The component (C) supports metal oxide particles containing titanium oxide, has a surface hydrophobicized by a silicon atom-containing hydrophobic agent, and has a primary particle diameter in the range of 5 to 50 nm before supporting the metal oxide particles. Is silica (metal oxide-supported silica).

Examples of the metal oxide particles include those that require titanium oxide and contain tin oxide and indium tin oxide, and a solid solution of titanium oxide and tin and / or manganese may be used.

When a titanium oxide solid solution is used, the solid solution amount of the tin component is 10 to 1,000, preferably 15 to 300 in terms of the molar ratio (Ti / Sn) with titanium, and the solid solution amount of the manganese component is titanium. The molar ratio (Ti / Mn) with and to is 10 to 1,000, preferably 15 to 300. When the solid solution amount of the tin component is 10 or more, there is no possibility that the crystal system becomes anatase type and the absorption band is blue-shifted, so that a wide range of ultraviolet rays can be absorbed. When the solid solution amount of the tin component is 1,000 or less, the ultraviolet absorption performance is sufficient. Further, when the solid solution amount of the manganese component is 10 or more, the photocatalytic activity can be sufficiently suppressed and the weather resistance becomes good, and when it is 1,000 or less, the ultraviolet absorption performance becomes sufficient.

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

As a method for forming a silicon oxide shell on the core of a metal oxide, a hydrolyzate / weight obtained by a sol-gel method using a dispersion liquid (sol) of metal oxide particles and an alkoxysilane. Examples thereof include a method of forming a condensate on the surface of the particles. 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. When the content is 1% by mass or more, the amount of the sol added is appropriate, and it is economical because it does not take time to remove the dispersion medium of the sol from the silicone rubber composition of the present invention. On the contrary, when 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, and particularly preferably 1 to 50 nm, because transparency in the visible region is important. When the average particle size of the metal oxide particles is 100 nm or less, the particle size is smaller than the light wavelength in the visible region, and scattering is not remarkable. Further, if it is 1 nm or more, the total surface area of the dispersoid in the system does not become too large, and aggregation is unlikely to occur, so that the dispersion liquid can be easily handled.

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

The metal oxide particles thus obtained are preferably surface-modified with an organosilicon compound represented by the following general formula (2) and / or a (partial) hydrolysis condensate thereof.
R ¹ Si (Y) ₃ (2)
(In the formula, R ¹ may be the same or different, and may be substituted with a (meth) acrylic group, an oxylanyl group, an amino group, a mercapto group, an isocyanate group or a fluorine atom. The number of carbon atoms is 1 or more and 20 or less. A substituent selected from the group consisting of an alkyl group of 2 or more and 20 or less, an aryl group having 6 or more and 20 or less carbon atoms, and a (poly) dimethylsiloxy group having 1 or more and 50 or less silicon atoms. It 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 organic silicon compound represented by the general formula (2) include hydroxylentimethoxysilane, hydrogentriethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane, ethyltrimethoxysilane, and ethyltri. 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-isocyanuppropyltrimethoxysilane, γ-isocyanuppropyltriethoxysilane, phenyltrimethoxysilane, phenyltri Partial hydrolysis condensate of ethoxysilane, tris (3-trimethoxysilylpropyl) isocyanurate in which isocyanate groups are bonded, tris (3-triethoxysilylpropyl) isocyanurate, and methyltrimethoxysilane (trade name "KC-89S") , "X-40-9220" manufactured by Shinetsu Chemical Industry Co., Ltd.), Partial hydrolysis condensate of methyltrimethoxysilane and γ-glycidoxypropyltrimethoxysilane (trade name "X-41-1056" Shinetsu (Chemical Industry Co., Ltd.), etc. alkoxysilanes; allylsilanes such as triallylmethylsilane, triallylethylsilane, triallylisopropylsilane; triacetoxymethylsilane, triacetoxyethylsilane, triacetoxypropylsilane, triacetoxy Acetoxysilanes such as phenylsilane; such as trichloromethylsilane, trichloroethylsilane, trichloropropylsilane, trichlorophenylsilane, etc. Chlorosilanes; enolsilanes such as triisopropenyloxymethylsilane, ethyltriisopropenyloxysilane, triisopropenyloxypropylsilane, phenyltriisopropenyloxysilane, etc., among others, hydroxygentrimethoxysilane, hydrogenori Ethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-acry Loxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-glycidoxypropyltriethoxysilane are preferred.

In the component (C), for example, fumed silica can be used as the silica that supports the metal oxide particles containing titanium oxide. The silica of the component (C) has a primary particle diameter of 5 to 50 nm, preferably 5 to 15 nm, before supporting the metal oxide particles. That is, in the component (C) of the present invention, metal oxide particles are supported on silica having a primary particle diameter of 5 to 50 nm. 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 the metal oxide-supported silica may deteriorate.

As a method for supporting the metal oxide particles on the silica, batch equipment such as a Henschel mixer, an Erich mixer, and a high-speed mixer, and continuous equipment such as a horizontal axis rotary blade can be used. In these facilities, it is possible to spray a titanium oxide sol having a core-shell structure to uniformly disperse the silica powder while stirring and mixing it at high speed. Thereby, silica supporting titanium oxide having a core-shell structure can be obtained.

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

Another feature of the present invention is that the metal oxide-supported silica is made hydrophobic with a silicon atom-containing hydrophobizing agent when or after the metal oxide particles are supported on silica.
The degree of hydrophobicity of the metal oxide-supported silica is preferably 40 or more. When the degree of hydrophobization is within such a range, aggregation of silica can be prevented, and the transparency of the obtained silicone rubber becomes good. The method for measuring the degree of hydrophobicity will be described in the following examples.

As the silicon atom-containing hydrophobizing agent, for example, one represented by the following general formula (3) can be used.
R ² Si (Y) ₃ (3)
(In the formula, R ² may be the same or different, and may be substituted with a (meth) acrylic group, an oxylanyl group, an amino group, a mercapto group, an isocyanate group or a fluorine atom. The number of carbon atoms is 1 or more and 20 or less. Substituent or hydrogen atom selected from the group consisting of an alkyl group of 2 or more and 20 or less, an aryl group having 6 or more and 20 or less carbon atoms, and a (poly) dimethylsiloxy group having 50 or less silicon atoms. 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 an aryl group having 6 to 10 carbon atoms, particularly a phenyl group. Further, the number of silicon of the (poly) dimethylsiloxy group is preferably 1 to 50, particularly preferably 1 to 30.

Specific examples of the silicon atom-containing hydrophobizing agent represented by the general formula (3) include hydrogen trimethoxysilane, hydrogen triethoxysilane, methyl trimethoxysilane, methyl triethoxysilane, methyl triisopropoxysilane, and ethyl trimethoxysilane. , Ethyltriethoxysilane, ethyltriisopropoxysilane, propyltrimethoxysilane, propyltriethoxysilane, propyltriisopropoxysilane, vinyltrimethoxysilane, allyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacry Loxypropyltriethoxysilane, 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-isocyanuppropyltrimethoxysilane, γ-isocyanoxidetriethoxysilane, phenyltrimethoxysilane , Phenyltriethoxysilane, tris (3-trimethoxysilylpropyl) isocyanurate with isocyanate groups 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 Industry Co., Ltd.), Partial hydrolysis condensate of methyltrimethoxysilane and γ-glycidoxypropyltrimethoxysilane (trade name "X-41-" 1056 ”alkoxysilanes such as Shin-Etsu Chemical Industry Co., Ltd .; allylsilanes such as triallylmethylsilane, triallylethylsilane, and triallylisopropylsilane; triacetoxymethylsilane, triacetoxyethylsilane, triacetoxypropylsilane , Acetoxysilanes such as triacetoxyphenylsilane; trichloromethylsilane, trichloroethylsilane, trichloropropylsilane, trichlorophenylsila Chlorosilanes such as chlorosilanes; enolsilanes such as triisopropenyloxymethylsilane, ethyltriisopropenyloxysilane, triisopropenyloxypropylsilane, phenyltriisopropenyloxysilane and the like can be mentioned.

（式中、Ｍｅはメチル基であり、ｒは０〜４９の整数である） In the silicon atom-containing hydrophobizing agent represented by the general formula (3), as a specific example when R ² is (poly) dimethylsiloxane, a compound represented by the following general formula (4) can be mentioned.

(In the formula, Me is a methyl group and r is an integer from 0 to 49)

In the general formula (4), r is an integer of 0 or more and 49 or less, preferably an integer of 5 or more and 40 or less, and more preferably an integer of 10 or more and 30 or less. When r is 49 or less, the properties as a silicone oil are appropriate, and the solubility of the surface-treated organosol in various resins is not limited. In the general formula (4), the compound having an average structure of r = 30 can be obtained 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 times or more and 50 times or less, and more preferably 1 time or more and 25 times or less, based on the weight of silica as the component (C). More preferably, it is 2 times or more and 10 times or less. When the amount added is 50 times or less 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. When it is 0.01 times or more, the treatment of silanol groups on the silica surface is sufficient, the cohesive force of silica after drying is small, and the transparency when dispersed in the silicone polymer is good.

In the silica of the 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 the silica after supporting the metal oxide particles. %. If the content of the metal oxide particles is 1% by mass or more, there is no possibility that the ultraviolet absorbing effect will not be exhibited, and if it is 30% by mass or less, the dispersibility of silica will be good.

The blending amount of the metal oxide-supported silica of the component (C) is 0.01 to 50 parts by mass with respect to 100 parts by mass of the component (A).

-(D) component-
The component (D) is a curing agent. Examples of this curing agent include (D-1) addition reaction curing agent and (D-2) organic peroxide curing agent as described above.

The blending amount of the curing agent for the component (D) is 0.01 to 10 parts by mass with respect to 100 parts by mass for the component (A).

(D-1) Addition reaction curing agent (D-1) As the addition reaction curing agent, an organohydrogenpolysiloxane and a hydrosilylation catalyst are used in combination.
As the organohydrogenpolysiloxane, hydrogen atoms bonded to 2 or more, preferably 3 or more, more preferably 3 to 200, and further preferably about 4 to 100 silicon atoms in one molecule (that is, SiH). As long as it contains a group), it may have a linear, cyclic, branched, or three-dimensional network structure. As an example of the organohydrogenpolysiloxane, a known organohydrogenpolysiloxane as a cross-linking agent for the addition reaction curable silicone rubber composition can be used, and more specifically, it is represented by the following average composition formula (5). Organohydrogenpolysiloxane is used.
R ³ _p H _q SiO _{(4-p-q) / 2} (5)
(In the formula, R ³ may be the same or different and represents an unsubstituted or substituted monovalent hydrocarbon group, where p and q are 0 <p <3, 0 <q ≦ 3, 0 <p + q ≦. It is a positive number that satisfies 3.)

In the average composition formula (5), R ³ may be the same or different, and preferably shows an unsubstituted or substituted monovalent hydrocarbon group and excludes an aliphatic unsaturated bond. The monovalent hydrocarbon group of R ³ is usually preferably one having 1 to 12 carbon atoms, particularly 1 to 8 carbon atoms, and specifically, an alkyl group such as a methyl group, an ethyl group or a propyl group, or a cyclo such as a cyclohexyl group. Aryl groups such as alkyl groups, phenyl groups and trill groups, aralkyl groups such as benzyl groups, 2-phenylethyl groups and 2-phenylpropyl groups, and some or all of the hydrogen atoms of these groups are replaced with halogen atoms or the like. Examples thereof include 3,3,3-trifluoropropyl groups and the like.

In the average composition formula (5), 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. It is a positive number that satisfies.

The organohydrogenpolysiloxane has two or more, preferably three or more SiH groups in one molecule, and these SiH groups may be at the end of the molecular chain or in the middle of the molecular chain. It may be in both. Further, the organohydrogenpolysiloxane preferably has a viscosity at 25 ° C. of 0.5 to 10,000 mPa · s, particularly preferably 1 to 300 mPa · s.

Specific examples of such an organohydrogenpolysiloxane include 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, tris (hydrogendimethylsiloxy) methylsilane, and the like. Tris (hydrogendimethylsiloxy) phenylsilane, methylhydrogencyclopolysiloxane, methylhydrogensiloxane / dimethylsiloxane cyclic copolymer, both-terminal trimethylsiloxy group-blocked methylhydrogenpolysiloxane, both-terminal trimethylsiloxy group-blocked dimethylsiloxane Methylhydrogensiloxane copolymer, both-terminal dimethylhydrogensiloxy group-blocked dimethylpolysiloxane, both-terminal dimethylhydrogensiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane copolymer, both-terminal trimethylsiloxy group-blocked methylhydrogensiloxane Diphenylsiloxane copolymer, both-terminal trimethylsiloxy group-blocked methylhydrogensiloxane / diphenylsiloxane / dimethylsiloxane copolymer, both-terminal trimethylsiloxy group-blocked methylhydrogensiloxane / methylphenylsiloxane / dimethylsiloxane copolymer, both-terminal dimethyl Hydrogensiloxy group-blocked methylhydrogensiloxane / dimethylsiloxane / diphenylsiloxane copolymer, both-terminal dimethylhydrogensiloxy group-blocked methylhydrogensiloxane / dimethylsiloxane / methylphenylsiloxane copolymer, (CH ₃ ) ₂ HSiO _{1 / A} copolymer consisting of ₂ units and (CH ₃ ) ₃ SiO _1/2 unit and SiO _4/2 unit, (CH ₃ ) ₂ HSiO _1/2 unit and SiO _4/2 unit, (CH ₃ ) CH ₃ ) ₂ HSiO _1/2 unit, SiO _4/2 unit and (C ₆ H ₅ ) ₃ SiO _1/2 unit, etc., and some or all of the methyl groups in the above exemplified compounds. Examples thereof include those substituted with other alkyl groups and phenyl groups.

The blending amount of the organohydrogenpolysiloxane is preferably 0.1 to 40 parts by mass with respect to 100 parts by mass of the component (A). In addition, the ratio of hydrogen atoms (= SiH groups) bonded to silicon atoms in organohydrogenpolysiloxane is 0.5 to 10 per 1 aliphatic unsaturated bond (alkenyl group) of component (A). The range of is appropriate, and preferably the range of 0.7 to 5 is appropriate. When the above ratio is 0.5 or more, the cross-linking is sufficient and sufficient mechanical strength can be obtained. Further, when the above ratio is 10 or less, the physical characteristics after curing are not deteriorated, and there is no possibility that the heat resistance is particularly deteriorated or the compression set is increased.

The hydrosilylation catalyst is a catalyst in which the alkenyl group of the component (A) and the silicon atom-bonded hydrogen atom (SiH group) of the organohydrogenpolysiloxane are hydrosilylated and added. Examples of the hydrosilylation catalyst include platinum group metal-based catalysts, and examples thereof include simple substances of platinum group metals and their compounds. For this, conventionally known catalysts for addition reaction curable silicone rubber compositions can be used. For example, a platinum catalyst such as an alcohol solution of particulate platinum metal adsorbed on a carrier such as silica gel, alumina, or silica gel, secondary platinum chloride, platinum chloride acid, or hexahydrate of platinum chloride acid, a palladium catalyst, a rhodium catalyst, or the like. However, platinum or a platinum compound (platinum catalyst) is preferable.

The amount of the catalyst added may be such that the addition reaction can be promoted, and is usually used in the range of 1 mass ppm to 1 mass% with respect to the organopolysiloxane of the component (A) in terms of the amount of platinum group metal. The range of 10 to 500 mass ppm is preferable. When the addition amount is 1 mass ppm or more, the addition reaction is sufficiently promoted and the curing becomes sufficient. On the other hand, if the addition amount exceeds 1% by mass, even if a larger amount is added, the effect on the reactivity is small, so that the addition amount is economically 1% by mass or less.

(D-2) Organic peroxide curing agent (D-2) Organic peroxide curing agent includes, for example, 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-butylperbenzoate, 1,6 -Hexanediol-bis-t-butylperoxycarbonate and the like can be mentioned. The amount of the organic peroxide curing agent added is preferably 0.1 to 10 parts by mass, particularly 0.2 to 5 parts by mass, based on 100 parts by mass of the component (A). If the blending amount is 0.1 parts by mass or more, curing is sufficient, and if it is 10 parts by mass or less, there is no possibility that the cured silicone rubber product will turn yellow due to the decomposition residue of the organic peroxide. In addition, addition reaction curing and organic peroxide curing, in which the component (D-1) and the component (D-2) were combined and blended in the above-mentioned blending amount, were used in combination with the component (A). 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 contains, if necessary, a filler such as pulverized quartz, crystalline silica, diatomaceous earth, calcium carbonate, a colorant, an acid receiving agent, and heat such as alumina and boron nitride. Thermal curing of various alkoxysilanes such as conductivity improvers, mold release agents, and dispersants for fillers, especially phenyl group-containing alkoxysilanes and their hydrolysates, diphenylsilanediols, carbon functional silanes, and silanol group-containing low-molecular-weight siloxanes. It is optional to add known fillers and additives in the mold silicone rubber composition.

As a molding and curing method of this silicone rubber composition, a conventional method can be adopted, but as a molding method, an optimum means suitable 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 of about 3 seconds to 160 minutes at 40 to 230 ° C. can be adopted. Further, if necessary, secondary vulcanization (post-cure) may be performed at 40 to 230 ° C. for about 10 minutes to 24 hours.

<Silicone rubber>
Further, the present invention provides a silicone rubber made of a cured product of the above silicone rubber composition. Such a silicone rubber has excellent transparency and ultraviolet absorption performance.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples. In the following example, the part indicates the mass part. The average degree of polymerization indicates the polystyrene-equivalent number average degree of polymerization in gel permeation chromatography (GPC) analysis using toluene as a developing solvent.

[Preparation Examples 1 to 5: Preparation of Metal Oxide Particles]
(Preparation Example 1A: Preparation of aqueous dispersion of core-shell particles (1))
An aqueous dispersion of a metal oxide was prepared by using a titanium oxide-tin oxide composite oxide as a nucleus, core-shell particles having silicon oxide as a shell, and water as a dispersion medium. Specifically, the core shell is first produced by producing a composite oxide dispersion (i) containing titanium oxide-tin oxide particles as a core, and then hydrolyzed and condensed with tetraethoxysilane by the following procedure. The aqueous dispersion containing particles (1) was used.

(Preparation of composite oxide dispersion liquid (i))
36% by mass of titanium (IV) chloride aqueous solution (manufactured by Ishihara Sangyo Co., Ltd., product name: TC-36) to 66.0 g of tin (IV) chloride pentahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) 1. After adding 8 g and mixing well, this was diluted with 1,000 g of ion-exchanged water. A precipitate of titanium hydroxide containing tin was obtained by gradually adding 300 g of 5% by mass aqueous ammonia (manufactured by Wako Pure Chemical Industries, Ltd.) to this metal salt aqueous solution mixture for neutralization and hydrolysis. .. The pH of the titanium hydroxide slurry at this time was 8. The obtained titanium hydroxide precipitate was deionized by repeating addition of ion-exchanged water and decantation. To the tin-containing titanium hydroxide precipitate after the deionization treatment, 100 g of 30 mass% hydrogen peroxide solution (manufactured by Wako Pure Chemical Industries, Ltd.) is gradually added, and then the mixture is sufficiently stirred at 60 ° C. for 3 hours. Reacted to. Then, pure water was added to adjust the concentration to obtain a translucent tin-containing peroxotitanic acid solution (solid content concentration: 1% by mass). In an autoclave with a volume of 500 mL (manufactured by Pressure-Resistant Glass Industry Co., Ltd., product name: TEM-D500), 350 mL of the peroxotitanic acid solution synthesized as described above was charged, and this was placed at 200 ° C. and 1.5 MPa for 240 minutes. Hydro-heat treated. Then, the reaction mixture in the autoclave is discharged to a container held in a water bath at 25 ° C. via a sampling tube, and the reaction is stopped by rapid cooling to obtain a composite oxide dispersion liquid (i). It was.

(Preparation of aqueous dispersion of core-shell particles (1))
To a separable flask equipped with a magnetic rotor and a thermometer, 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 at room temperature (25 ° C.). It was magnetically stirred. The separable flask was immersed in an ice bath and cooled to a content temperature of 5 ° C. After adding 18 parts by mass of tetraethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBE-04"), a separable flask was installed in μReactorEx (manufactured by Shikoku Measurement Industry Co., Ltd.). Then, magnetic stirring was performed while irradiating a microwave with a frequency of 2.45 GHz and an output of 1,000 W for 1 minute. During that time, the thermometer was observed to confirm that the content temperature reached 85 ° C. The obtained mixture was filtered through a qualitative filter paper (Advantec 2B) to obtain a dilute colloidal solution. This dilute dispersion Dyna filter (Mitsubishikakoki Co., Ltd., product name "DyF152 / S", average pore diameter 7nm of MgAl ₂ O-made disk [ANDRITZ KMPT GmbH, Ltd., part number 2065181, type φ152 / 7nm]) The mixture was concentrated to a dispersoid concentration of 10% by mass by ultrafiltration using an aqueous dispersion (1) of core-shell particles having a titanium oxide-tin oxide composite oxide as a nucleus and silicon oxide as a shell. The solid content concentration of the aqueous dispersion (1) of the core-shell particles was 15.9% by mass, and the particle size was 19.5 nm. At this time, the particle size is a value of 50% cumulative distribution diameter (D ₅₀ ) based on the volume measured by the dynamic light scattering method, and was measured using Nanotrack UPA-EX150 (manufactured by Nikkiso Co., Ltd.).

(Preparation Example 1B: Synthesis of Ethanol Dispersion Solution (1) of Surface-Modified Core-Shell Particles)
In a 4-port 2L separable flask equipped with a Dimroth condenser, a nitrogen introduction tube, a thermometer, and a mechanical stirring blade, as an aqueous dispersion of metal oxide particles, an aqueous dispersion of core shell particles (1) (300 g, solid content) The concentration was 15.9% by mass) and 3 g of a sulfonic acid-based cationic ion exchange resin was added as a catalyst. Methyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-13", 230 g) was added thereto as a surface modifier, and the mixture was 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 liquid increased from 25 ° C. to 52 ° C. After heating and stirring for 2 hours so that the temperature of the dispersion was 50 ° C., ethanol (750 g) was added to the dispersion while stirring (250 rpm) to dilute the dispersion. Diluted dispersion Dyna filter (Mitsubishikakoki Co., Ltd., product name "DyF152 / S", average pore diameter 7nm of MgAl ₂ O-made disk [ANDRITZ KMPT GmbH, Ltd., part number 2065181, type φ152 / 7nm]) was introduced into the .. The rotating shaft connected to the filter was rotated (1,000 rpm) while applying a static pressure of 0.2 MPa with compressed air. It was observed that the dispersion liquid exuded through the ceramic filter. A receiver (5,000 mL) was provided at the filter outlet, and 800 g of exudate was collected. An organic solvent (ethanol) was continuously pressurized and supplied (0.2 MPa) to the concentrated dispersion. The rotating shaft connected to the filter was rotated (1,000 rpm) while applying a static pressure of 0.2 MPa with compressed air. It was observed that the dispersion liquid exuded through the ceramic filter. A receiver (5,000 mL) was provided at the filter outlet, and ethanol was pressurized and supplied until the exudate reached 800 g. The dispersion was taken out from the filtration chamber to obtain an ethanol dispersion (1) of surface-modified core-shell particles. The surface-modified core-shell particles in the ethanol dispersion (1) had a solid content concentration of 17% by mass and a particle size of 19.2 nm. At this time, the particle size is a value of 50% cumulative distribution diameter (D ₅₀ ) based on the volume measured by the dynamic light scattering method, and was measured using Nanotrack UPA-EX150 (manufactured by Nikkiso Co., Ltd.).

(Preparation Example 2: Synthesis of Ethanol Dispersion Solution (2) of Surface-Modified Core-Shell Particles)
36% by mass of titanium (IV) chloride aqueous solution (manufactured by Ishihara Sangyo Co., Ltd., product name: TC-36) to 66.0 g of tin (IV) chloride pentahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) 1. Instead of adding 8 g, tin (IV) chloride pentahydrate (Wako Pure Chemical Industries, Ltd.) to 66.0 g of a 36 mass% titanium (IV) chloride aqueous solution (manufactured by Ishihara Sangyo Co., Ltd., product name: TC-36) Ethanol dispersion of core-shell particles surface-modified in the same manner as in Preparation Example 1 except that 1.8 g (manufactured by Co., Ltd.) and 0.09 g of manganese oxide (II) (High Purity Chemical Laboratory Co., Ltd.) were added. (2) was obtained. The surface-modified core-shell particles in the ethanol dispersion (2) had a solid content concentration of 14.5% by mass and a particle size of 19.2 nm.

(Preparation Example 3: Synthesis of Ethanol Dispersion Solution (3) of Surface-Modified Core-Shell Particles)
An ethanol dispersion (3) of surface-modified core-shell particles was obtained in the same manner as in Preparation Example 1 except that tin (IV) chloride pentahydrate was not added. The solid content concentration of the ethanol dispersion liquid (3) of the surface-modified core-shell particles was 13% by mass, and the particle size was 17.2 nm.

(Preparation Example 4: Synthesis of Ethanol Dispersion Solution (4) of Surface-Modified Core-Shell Particles)
As a surface modifier, not methyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-13", 230 g), but γ-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM") An ethanol dispersion (4) of surface-modified core-shell particles was obtained in the same manner as in Preparation Example 1 except that −403 ”, 230 g) was used. The surface-modified core-shell particles ethanol dispersion (4) had a solid content concentration of 16% by mass and a particle size of 18.5 nm.

(Preparation Example 5: Synthesis of Ethanol Dispersion Solution (5) of Surface-Modified Core-Shell Particles)
As a surface modifier, not methyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-13", 230 g), but γ-acryloxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-") An ethanol dispersion (5) of surface-modified core-shell particles was obtained in the same manner as in Preparation Example 1 except that 5103 ”, 230 g) was used. The surface-modified core-shell particles in the ethanol dispersion (5) had a solid content concentration of 15% by mass and a particle size of 19.5 nm.

[Preparation Examples 6 to 17: Preparation of Metal Oxide-Supported Silica]
(Preparation Example 6: Preparation of Metal Oxide-Supported Silica (1))
200 g of fumed silica (manufactured by Nippon Aerosil Co., Ltd., Aerosil 200, primary particle diameter 12 nm) having a specific surface area of 200 m ² / g by the BET method was charged into a high-speed mixer (volume 10 L) and operated at a rotation speed of 1500 rpm. When the rotation was stable, 70 g of dimethylpolysiloxane having an average degree of polymerization of 4 and a viscosity of 15 mPa · s at 25 ° C. was sprayed as a silicon atom-containing hydrophobizing agent in 20 seconds, and then 100 g of an aqueous dispersion of core-shell particles (1). And 200 g of pure water were sprayed in 60 seconds. This was heated at 250 ° C. for 2.5 hours after removing water with a dryer. The obtained metal oxide-supported silica (1) had a loose bulk density of 150 g / L measured by the following method and a degree of hydrophobicity by the methanol titration method of 60.

<Measurement method of loose bulk density>
A multi-tester MT-1000 manufactured by Seishin Enterprise is used. Place the funnel, fluid (opening 150 μm), and fluid spacer in this order on the upper part of the feeder unit, and fix them with stoppers. A 100 ml cell is placed on a sample table, the sample is put into the sample unit, the feeder is vibrated, the cell is filled with the sifted sample, and the cell is scraped off with a fray plate. The loose bulk density ρ (g / l) is obtained by the following equation.
ρ = ((W1-W0) / 100) × 1000
W0: Weight of cell container (g)
W1: Cell container + sample weight (g)

<Measurement method of hydrophobicity>
Put 50 ml of pure water in a 200 ml beaker, add 0.2 g of a sample, and stir with a magnetic stirrer. When the tip of a burette containing methanol is put into a liquid, methanol is added dropwise with stirring, and the amount of methanol added until the sample is completely dispersed in water is Z ml, the following formula is obtained.
Degree of hydrophobization = (Z / (50 + Z)) x 100

(Preparation Example 7: Preparation of Metal Oxide-Supported Silica (2))
200 g of fumed silica (manufactured by Nippon Aerosil Co., Ltd., Aerosil 200, primary particle diameter 12 nm) having a specific surface area of 200 m ² / g by the BET method was charged into a high-speed mixer (volume 10 L) and operated at a rotation speed of 1500 rpm. When the rotation was stable, 70 g of dimethylpolysiloxane having an average degree of polymerization of 4 and a viscosity of 15 mPa · s at 25 ° C. was sprayed as a silicon atom-containing hydrophobizing agent in 20 seconds, and then 300 g of an aqueous dispersion of core-shell particles (1). Was sprayed in 60 seconds. This was heated at 250 ° C. for 2.5 hours after removing water with a dryer. The obtained metal oxide-supported silica (2) had a loose bulk density of 210 g / L and a degree of hydrophobization by the methanol titration method of 62.

(Preparation Example 8: Preparation of Metal Oxide-Supported Silica (3))
It was prepared in the same manner as in Preparation Example 6 except that 50 g of dimethyldimethoxysilane was used as the silicon atom-containing hydrophobizing agent instead of dimethylpolysiloxane having a viscosity of 15 mPa · s at an average degree of polymerization of 4 and 25 ° C. The obtained metal oxide-supported silica (3) had a loose bulk density of 160 g / L and a degree of hydrophobization by the methanol titration method of 62.

(Preparation Example 9: Preparation of Metal Oxide-Supported Silica (4))
It was prepared in the same manner as in Preparation Example 6 except that the ethanol dispersion of core-shell particles (1) was used instead of the aqueous dispersion of core-shell particles (1). The obtained metal oxide-supported silica (4) had a loose bulk density of 155 g / L and a degree of hydrophobization by the methanol titration method of 58.

(Preparation Example 10: Preparation of Metal Oxide-Supported Silica (5))
It was prepared in the same manner as in Preparation Example 6 except that pure water was not added. The obtained metal oxide-supported silica (5) had a loose bulk density of 70 g / L and a degree of hydrophobization by the methanol titration method of 58.

(Preparation Example 11: Preparation of Metal Oxide-Supported Silica (6))
It was prepared in the same manner as in Preparation Example 9 except that 500 g of methanol was used instead of 200 g of pure water. The obtained metal oxide-supported silica (6) had a loose bulk density of 165 g / L and a degree of hydrophobization by the methanol titration method of 62.

(Preparation Example 12: Preparation of Metal Oxide-Supported Silica (7))
It was prepared in the same manner as in Preparation Example 6 except that the ethanol dispersion of core-shell particles (2) was used instead of the aqueous dispersion of core-shell particles (1). The obtained metal oxide-supported silica (7) had a loose bulk density of 166 g / L and a degree of hydrophobization by the methanol titration method of 61.

(Preparation Example 13: Preparation of Metal Oxide-Supported Silica (8))
It was prepared in the same manner as in Preparation Example 6 except that the ethanol dispersion of core-shell particles (3) was used instead of the aqueous dispersion of core-shell particles (1). The obtained metal oxide-supported silica (8) had a loose bulk density of 164 g / L and a degree of hydrophobization by the methanol titration method of 61.

(Preparation Example 14: Preparation of Metal Oxide-Supported Silica (9))
It was prepared in the same manner as in Preparation Example 6 except that the ethanol dispersion of core-shell particles (4) was used instead of the aqueous dispersion of core-shell particles (1). The obtained metal oxide-supported silica (9) had a loose bulk density of 168 g / L and a degree of hydrophobization by the methanol titration method of 61.

(Preparation Example 15: Preparation of Metal Oxide-Supported Silica (10))
It was prepared in the same manner as in Preparation Example 6 except that the ethanol dispersion of core-shell particles (5) was used instead of the aqueous dispersion of core-shell particles (1). The obtained metal oxide-supported silica (10) had a loose bulk density of 170 g / L and a degree of hydrophobization by the methanol titration method of 61.

(Preparation Example 16: Preparation of Metal Oxide-Supported Silica (11))
It was prepared in the same manner as in Preparation Example 6 except that the composite oxide dispersion (i) was used instead of the aqueous dispersion (1) of the core-shell particles. The obtained metal oxide-supported silica (11) had a loose bulk density of 160 g / L and a degree of hydrophobization by the methanol titration method of 60.

(Preparation Example 17: Preparation of Metal Oxide-Supported Silica (12))
It was prepared in the same manner as in Preparation Example 6 except that dimethylpolysiloxane having a viscosity of 15 mPa · s at an average degree of polymerization of 4 and 25 ° C. was not added as a silicon atom-containing hydrophobizing agent. The obtained metal oxide-supported silica (12) had a loose bulk density of 140 g / L. This titanium oxide-supported silica was dissolved in water (hydrophobicity 0).

[Preparation Examples 18 and 19: Preparation of Metal Oxide-Supported Silica Paste]
(Preparation Example 18: Preparation of Metal Oxide-Supported Silica Paste (1))
After mixing 100 parts by mass of dimethylpolysiloxane having an average degree of polymerization of 180 with both ends of the molecular chain sealed with a dimethylvinylsiloxy group and 30 parts by mass of metal oxide-supported silica (1), three rolls were passed three times. A metal oxide-supported silica paste (1) was prepared.

(Preparation Example 19: Preparation of Metal Oxide-Supported Silica Paste (2))
After mixing 100 parts by mass of dimethylpolysiloxane having an average degree of polymerization of 180 with both ends of the molecular chain sealed with a dimethylvinylsiloxy group and 30 parts by mass of metal oxide-supported silica (12), three rolls were passed three times. A metal oxide-supported silica paste (2) was prepared.

[Examples 1 to 13, Comparative Examples 1 to 7: Synthesis of silicone rubber composition]
(Example 1)
Fumed silica (Japan) having 60 parts by mass of dimethylpolysiloxane (component (A)) having an average degree of polymerization of 750 and having a specific surface area of 300 m ² / g by the BET method, with both ends of the molecular chain sealed with dimethylvinylsiloxy groups. Aerosil 300) (component (B)) manufactured by Aerosil, 40 parts by mass, 8 parts by mass of hexamethyldisilazane, and 2.0 parts by mass of water are mixed at room temperature for 30 minutes, then heated to 150 ° C. and stirred for 3 hours. Was continued and cooled to obtain a silicone rubber base (1).
In 100 parts by mass of this silicone rubber base (1), 6 parts by mass of dimethylpolysiloxane (component (A)) having an average degree of polymerization of 750 in which both ends of the molecular chain are sealed with a dimethylvinylsiloxy group and both ends of the molecular chain are 5 parts by mass of dimethylpolysiloxane (component (A)) having an average degree of polymerization of 150, which is sealed with a trimethylsiloxy group and contains 10 mol% of vinylmethylsiloxane unit in the diorganosiloxane unit of the main chain, in Preparation Example 18. Metal oxide-supported silica paste (1) (component (C)) 4 parts by mass, platinum catalyst (Pt concentration 1% by mass) 0.1 parts by mass, and methylhydrogenpolysiloxane having a SiH group in the side chain as a cross-linking agent. (Dimethylsiloxane / Methylhydrogensiloxane copolymer with a degree of polymerization of 38 and a SiH group of 0.0074 mol% at both ends trimethylsiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane copolymer) 3 parts by mass (total amount of SiH group / vinyl group = 1.75 mol / mol) ( (Component)) and 0.05 parts by mass of ethynylcyclohexanol as a reaction control agent were added, and stirring was continued for 15 minutes to obtain a silicone rubber composition (1).
The silicone rubber composition (1) was press-cured (primary vulcanization) at 120 ° C. for 10 minutes and then post-cured (secondary vulcanization) at 150 ° C. for 1 hour in an oven to obtain a cured product. Various rubber physical characteristics and light transmittance were measured for the obtained cured product. The results are shown in Table 1.
Various rubber physical characteristics (hardness, tensile strength, elongation at cutting) were measured by the method described in JIS K 6249: 2003, and the light transmittance was measured by a spectrophotometer (manufactured by Hitachi, Ltd., model: Measurements were made using U-3310), and the light transmittances at wavelengths of 700 nm and 340 nm are also shown in Table 1.

(Example 2)
Fumed silica (Japan) having 60 parts by mass of dimethylpolysiloxane (component (A)) having an average degree of polymerization of 750 and having a specific surface area of 300 m ² / g by the BET method, with both ends of the molecular chain sealed with dimethylvinylsiloxy groups. Aerosil 300) (component (B)) 40 parts by mass, metal oxide-supported silica (1) (component (C)) of Preparation Example 6 by mass 1.4 parts, hexamethyldisilazane 8 parts by mass, and Aerosil After mixing 2.0 parts by mass of water at room temperature for 30 minutes, the temperature was raised to 150 ° C., stirring was continued for 3 hours, and the mixture was cooled to obtain a silicone rubber base (2).
In 100 parts by mass of this silicone rubber base (2), 6 parts by mass of dimethylpolysiloxane (component (A)) having an average degree of polymerization of 750, in which both ends of the molecular chain are sealed with a dimethylvinylsiloxy group, and both ends of the molecular chain are 5 parts by mass of dimethylpolysiloxane (component (A)), which is sealed with a trimethylsiloxy group and contains 10 mol% of vinylmethylsiloxane units in the diorganosiloxane units of the main chain and has an average degree of polymerization of 150, and a platinum catalyst (Pt). Concentration 1% by mass) 0.1 part by mass) Methylhydrogenpolysiloxane having SiH group in the side chain as a cross-linking agent (polymerization degree 38, SiH group 0.0074 mol%, both terminal trimethylsiloxy group-blocking dimethylsiloxane-methyl Add 3 parts by mass of (hydrogensiloxane copolymer) (total amount of SiH group / vinyl group = 1.81 mol / mol) (component (D)) and 0.05 part by mass of ethynylcyclohexanol as a reaction control agent, and add 15 parts. Minute stirring was continued to obtain a silicone rubber composition (2).
The silicone rubber composition (2) was press-cured (primary vulcanization) at 120 ° C. for 10 minutes and then post-cured (secondary vulcanization) at 150 ° C. for 1 hour in an oven to obtain a cured product. Various physical properties and light transmittance of the obtained cured product were measured. The results are shown in Table 1.

(Example 3)
A silicone rubber composition (3) was obtained in the same manner as in Example 2 except that the metal oxide-supported silica (2) of Preparation Example 7 was used instead of the metal oxide-supported silica (1). Various physical properties and light transmittance of the obtained composition were measured. The results are shown in Table 1.

(Example 4)
A silicone rubber composition (4) was obtained in the same manner as in Example 2 except that the metal oxide-supported silica (3) of Preparation Example 8 was used instead of the metal oxide-supported silica (1). Various physical properties and light transmittance of the obtained composition were measured. The results are shown in Table 1.

(Example 5)
A silicone rubber composition (5) was obtained in the same manner as in Example 2 except that the metal oxide-supported silica (4) of Preparation Example 9 was used instead of the metal oxide-supported silica (1). Various physical properties and light transmittance of the obtained composition were measured. The results are shown in Table 1.

(Example 6)
A silicone rubber composition (6) was obtained in the same manner as in Example 2 except that the metal oxide-supported silica (5) of Preparation Example 10 was used instead of the metal oxide-supported silica (1). Various physical properties and light transmittance of the obtained composition were measured. The results are shown in Table 1.

(Example 7)
A silicone rubber composition (7) was obtained in the same manner as in Example 2 except that the metal oxide-supported silica (6) of Preparation Example 11 was used instead of the metal oxide-supported silica (1). Various physical properties and light transmittance of the obtained composition were measured. The results are shown in Table 1.

(Example 8)
A silicone rubber composition (8) was obtained in the same manner as in Example 2 except that the metal oxide-supported silica (7) of Preparation Example 12 was used instead of the metal oxide-supported silica (1). Various physical properties and light transmittance of the obtained composition were measured. The results are shown in Table 1.

(Example 9)
A silicone rubber composition (9) was obtained in the same manner as in Example 2 except that the metal oxide-supported silica (8) of Preparation Example 13 was used instead of the metal oxide-supported silica (1). Various physical properties and light transmittance of the obtained composition were measured. The results are shown in Table 1.

(Example 10)
A silicone rubber composition (10) was obtained in the same manner as in Example 2 except that the metal oxide-supported silica (9) of Preparation Example 14 was used instead of the metal oxide-supported silica (1). Various physical properties and light transmittance of the obtained composition were measured. The results are shown in Table 1.

(Example 11)
A silicone rubber composition (11) was obtained in the same manner as in Example 2 except that the metal oxide-supported silica (10) of Preparation Example 15 was used instead of the metal oxide-supported silica (1). Various physical properties and light transmittance of the obtained composition were measured. The results are shown in Table 1.

(Example 12)
A silicone rubber composition (12) was obtained in the same manner as in Example 2 except that the metal oxide-supported silica (11) of Preparation Example 16 was used instead of the metal oxide-supported silica (1). Various physical properties and light transmittance of the obtained composition were measured. The results are shown in Table 1.

(Example 13)
Organopolysiloxane raw rubber ((A) component) consisting of 99.825 mol% of dimethylsiloxane unit, 0.15 mol% of methylvinylsiloxane unit, 0.025 mol% of dimethylvinylsiloxy unit, and an average degree of polymerization of about 6,000. ) 100 parts by mass, 40 parts by mass of fumed silica (Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) (component (B)) having a BET method specific surface area of 200 m ² / g, metal oxide-supported silica (1) of Preparation Example 6. ) (Component (C)) 1.4 parts by mass, 6 parts by mass of dimethylpolysiloxane having silanol groups at both ends and a viscosity of 15 mPa · s at an average degree of polymerization of 4, 25 ° C. was added, and 2 at 170 ° C. After heating under mixing with a kneader for hours, the base compound (1) was prepared.
Two 0.4 parts by mass of 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane (component (D)) as a curing agent with respect to 100 parts by mass of this composition (base compound 1). After adding with a roll and mixing uniformly to produce a raw rubber-like silicone rubber composition (13), the composition is press-cured at 165 ° C. and 70 kgf / cm ² for 10 minutes to a thickness of 2 mm. A sheet was prepared. Post-cure was then performed in an oven at 200 ° C. for 4 hours. Various physical properties and light transmittance of the obtained cured product were measured. The results are shown in Table 1.

(Comparative Example 1)
A comparative silicone rubber composition (1) containing no component (C) was obtained in the same manner as in Example 1 except that the metal oxide-supported silica paste (1) was not added. Various physical properties and light transmittance of the obtained composition were measured. The results are shown in Table 1.

(Comparative Example 2)
Silica is contained in the component (C) in the same manner as in Example 1 except that 5 parts by mass of the aqueous dispersion of core-shell particles (1) is added instead of the metal oxide-supported silica paste (1). No comparative silicone rubber composition (2) was obtained. Various physical properties and light transmittance of the obtained composition were measured. The results are shown in Table 1.

(Comparative Example 3)
Silica is contained in the component (C) in the same manner as in Example 2 except that 0.7 parts by mass of the aqueous dispersion of core-shell particles (1) was added instead of the metal oxide-supported silica (1). No comparative silicone rubber composition (3) was obtained. Various physical properties and light transmittance of the obtained composition were measured. The results are shown in Table 1.

(Comparative Example 4)
Silica is contained in the component (C) in the same manner as in Example 2 except that 0.7 parts by mass of the ethanol dispersion of core-shell particles (1) was added instead of the metal oxide-supported silica (1). No comparative silicone rubber composition (4) was obtained. Various physical properties and light transmittance of the obtained composition were measured. The results are shown in Table 1.

(Comparative Example 5)
Comparison in which the component (C) is not hydrophobic in the same manner as in Example 2 except that 1.4 parts by mass of the metal oxide-supported silica (12) was added instead of the metal oxide-supported silica (1). A silicone rubber composition (5) was obtained. Various physical properties and light transmittance of the obtained composition were measured. The results are shown in Table 1.

(Comparative Example 6)
The component (C) was hydrophobized in the same manner as in Example 1 except that the metal oxide-supported silica paste (2) of Preparation Example 19 was used instead of the metal oxide-supported silica paste (1). A comparative silicone rubber composition (6) was obtained. Various physical properties and light transmittance of the obtained composition were measured. The results are shown in Table 1.

(Comparative Example 7)
A comparative silicone rubber composition (7) containing no component (C) was obtained in the same manner as in Example 13 except that the metal oxide-supported silica (1) was not added. Various physical properties and light transmittance of the obtained composition were measured. The results are shown in Table 1.

As shown in Table 1, the silicone rubbers (Examples 1 to 13) made of a cured product of the silicone rubber composition of the present invention are all excellent in physical characteristics, transparency, and ultraviolet absorption performance of each rubber. It was. In particular, the silicone rubber composition in which the metal oxide particles form a core-shell structure is more transparent than the metal oxide particles having a core-shell structure (Examples 2 and 12). Further, both Examples 1 to 12 using the addition reaction curing agent (D-1) as the component (D) and Example 13 using the organic peroxide curing agent (D-2) are transparent. And it has excellent UV absorption performance.

On the other hand, in Comparative Examples 1 and 7 which did not contain the metal oxide-supported silica of the component (C), the ultraviolet absorption performance was inferior. Further, in Comparative Examples 2 to 4 in which only the metal oxide particles were added, and Comparative Examples 5 and 6 in which the metal oxide-supported silica was not hydrophobized, the transparency was deteriorated.

From the above, it has been clarified that the present invention can provide a silicone rubber composition which is a silicone rubber having excellent transparency and ultraviolet absorption performance.

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

Claims (6)

(A) Organopolysiloxane represented by the following average composition formula (1) and having at least two aliphatic unsaturated groups in one molecule: 100 parts by mass _RN SiO _{(4-n) / 2} (1)
(In the formula, 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.),
(B) Reinforcing silica with a specific surface area of 50 m ² / g or more: 5 to 100 parts by mass,
(C) Metal oxide particles containing titanium oxide are supported, the surface is made hydrophobic with a silicon atom-containing hydrophobic agent, and the primary particle diameter before supporting the metal oxide particles is in the range of 5 to 50 nm. Silica: 0.01 to 50 parts by mass,
(D) Hardener: 0.01 to 10 parts by mass,
The silicone is characterized in that the metal oxide particles are particles having a core-shell structure having a core of the metal oxide and a shell of silicon oxide formed on the outer surface thereof. Rubber composition. The metal oxide particles according to claim 1, characterized in that surface-modified with an organosilicon compound and / or its (partial) hydrolytic condensate represented by the following general formula (2) Silicone rubber composition.
R ¹ Si (Y) ₃ (2)
(In the formula, R ¹ may be the same or different, and may be substituted with a (meth) acrylic group, an oxylanyl group, an amino group, a mercapto group, an isocyanate group or a fluorine atom. The number of carbon atoms is 1 or more and 20 or less. A substituent selected from the group consisting of an alkyl group of 2 or more and 20 or less, an aryl group having 6 or more and 20 or less carbon atoms, and a (poly) dimethylsiloxy group having 1 or more and 50 or less silicon atoms. It 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 claim 1 or 2 , wherein the content of the metal oxide particles in the silica of the component (C) is 1 to 30% by mass. The present invention according to any one of claims 1 to 3 , wherein the component (D) is an addition reaction curing agent (D-1) composed of a combination of an organohydrogenpolysiloxane and a hydrosilylation catalyst. The silicone rubber composition according to the description. The silicone rubber composition according to any one of claims 1 to 3 , wherein the component (D) is an organic peroxide curing agent (D-2). A silicone rubber comprising a cured product of the silicone rubber composition according to any one of claims 1 to 5 .