Silicone composition and method for producing same

Abstract

The present invention is a silicone composition comprising: (A) 100 parts by mass of an organopolysiloxane having a viscosity of 0.01-100 Pa·s at 25°C and containing two or more alkenyl groups bonded to silicon atoms per molecule; (B) 10-500 parts by mass of hydrophobic silica particles having an average particle diameter ranging from 10-1,000 nm, having a hydrophobicity of 60% or more according to a methanol titration method, and having alkenyl groups bonded to silicon atoms on the surface; (C) organohydrogen polysiloxane having two or more hydrogen atoms bonded to silicon atoms per molecule, in an amount such that the hydrogen atoms bonded to silicon atoms in component (C) are 0.4-5.0 molar times the total alkenyl groups bonded to the total silicon atoms in the composition; and (D) a platinum group metal catalyst. A silicone composition is thus provided that has excellent handling properties and high tear strength after curing.

Description

Silicone composition and method for producing the same

[0001] The present invention relates to a silicone composition and a method for producing the same.

[0002] Silicone rubber has excellent heat resistance, cold resistance, and electrical insulation properties, and is widely used in various industries, including electrical and electronics, automobiles, and construction. Because the siloxane polymers that form silicone rubber have very weak intermolecular forces, silicone rubber formed by curing only the polymers results in very weak strength. When silicone rubber is used as an adhesive, sealant, or potting material for parts that generate high amounts of heat, thermal expansion due to the heat generated by the parts can cause stress and cracks in the silicone rubber material, requiring high mechanical strength. Furthermore, when used as a mold-making material or a lens material for ultrasound probes, both of these materials are used at room temperature, and high tear strength is required due to the stresses they experience during use. This results in materials with inadequate strength for practical use. To address this issue, reinforcing silica, such as fumed silica, is typically blended to improve mechanical strength. Silicone compositions incorporating reinforcing agents, such as silica particles or silicone resins, have also been proposed for the purpose of improving mechanical strength (Patent Documents 1 and 2). However, the use of silica particles with un- or insufficiently hydrophobicized surfaces results in high viscosity and thixotropy, reducing fluidity and making them difficult to handle. Furthermore, when only a silicone resin is used as a reinforcing agent, the degree of improvement in mechanical strength is low and sufficient strength cannot be obtained. Furthermore, although a silicone composition with high transparency has been proposed by using sol-gel silica with a hydrophobic surface, the mechanical strength is insufficient (Patent Documents 3 and 4).

[0003] JP 2000-351901 A JP 2013-64089 A JP 2012-144595 A JP 2019-1975 A

[0004] In recent years, there has been a demand for the development of a high-strength silicone rubber material that is easy to handle and does not crack even when subjected to stress.

[0005] The present invention has been made in view of the above circumstances, and has as its object to provide a silicone composition that is easy to handle (fluidity) and has high tear strength after curing, as well as a method for producing the same.

[0006] In order to solve the above-mentioned problems, the present invention provides a silicone composition comprising the following components (A) to (D): (A) 100 parts by mass of an organopolysiloxane having a viscosity at 25°C of 0.01 to 100 Pa s and having two or more silicon-bonded alkenyl groups per molecule, (B) 10 to 500 parts by mass of hydrophobic silica particles having a volume-based median diameter in the range of 10 nm to 1,000 nm, a hydrophobicity of 60% or more as measured by methanol titration, and having silicon-bonded alkenyl groups on their surfaces, (C) an organohydrogenpolysiloxane having two or more silicon-bonded hydrogen atoms per molecule, in an amount such that the number of silicon-bonded hydrogen atoms in component (C) is 0.4 to 5.0 times the molar ratio of all silicon-bonded alkenyl groups in the composition, and (D) an effective amount of a platinum group metal catalyst.

[0007] The silicone composition of the present invention is easy to handle and has high tear strength after curing.

[0008] At this time, the component (B) forms R on the silica surface. ２ SiO ３／２ Unit (R ２ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms; and R Ａ （ａ） R ３ （３－ａ） SiO １／２ Units (a is an integer of 1 to 3, R Ａ are the same or different, substituted or unsubstituted alkenyl groups having 2 to 8 carbon atoms, and R ３ are the same or different, substituted or unsubstituted alkyl groups having 1 to 6 carbon atoms. ３ ３ SiO １／２ Unit (R ３are the same or different, substituted or unsubstituted monovalent hydrocarbon groups having 1 to 6 carbon atoms.

[0009] Component (B) containing such units has an improved degree of hydrophobicity and can be suitably used in the silicone composition of the present invention.

[0010] Furthermore, it is preferable that the volume-based median diameter of component (B) is 10 nm to 200 nm.

[0011] A silicone composition containing such component (B) is easier to handle and has high tear strength after curing.

[0012] Furthermore, it is preferable that the blending amount of the component (B) is 100 to 300 parts by mass per 100 parts by mass of the component (A).

[0013] Such a silicone composition is easier to handle and has high tear strength after curing.

[0014] Furthermore, it is preferable that the composition contains 0.01 to 5.0 parts by mass of a reaction inhibitor (E) per 100 parts by mass of component (A).

[0015] The silicone composition of the present invention may contain such a reaction inhibitor.

[0016] The present invention also provides a method for producing the above-mentioned silicone composition, the method comprising the steps of: producing component (B) through steps including the following (α), (β), and (γ); and mixing at least component (B), (A), (C), and (D): (α) a step of hydrolyzing and condensing at least one of a tetrafunctional silane compound represented by the following general formula (i) and an alkyl silicate represented by the following general formula (ii) in a mixed liquid of a hydrophilic organic solvent and water in the presence of a basic substance to obtain a dispersion of hydrophilic silica particles: Si(OR ４ ) ４ (i) Si(OR ４ ) ３ -(-SiO(OR ４ )２ -) ｍ -Si(OR ４ ) ３ (ii) (wherein, R ４ are the same or different monovalent hydrocarbon groups having 1 to 6 carbon atoms, and m is 1 to 100. (β) A step of adding at least one of a trifunctional silane compound represented by the following general formula (iii) and its (partial) hydrolysis condensate (partial hydrolysis condensate or hydrolysis condensate) to the obtained dispersion of hydrophilic silica particles to treat the surfaces of the hydrophilic silica particles, thereby obtaining a dispersion of silica particles, which is an intermediate of component (B): R ２ Si(OR ５ ) ３ (iii) (wherein, R ２ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, and R ５ are the same or different monovalent hydrocarbon groups having 1 to 6 carbon atoms.) (γ) A step of adding a surface treatment agent containing at least one of a silazane compound represented by the following general formula (iv) and a monofunctional silane compound represented by the following general formula (v) to the obtained dispersion of silica particles, which are an intermediate of component (B), to treat the surfaces of the silica particles, which are an intermediate of component (B), thereby obtaining hydrophobic silica particles, which are component (B), having alkenyl groups bonded to silicon atoms on their surfaces: R Ａ （ａ） R ３ （３－ａ） SiNHSiR Ａ （ａ） R ３ （３－ａ） (iv) R Ａ （ａ） R ３ （３－ａ） SiX (v) (wherein a is an integer of 1 to 3, and R Ａ are the same or different substituted or unsubstituted alkenyl groups having 2 to 8 carbon atoms, R ３ are the same or different, substituted or unsubstituted alkyl groups having 1 to 6 carbon atoms, and X is an OH group or a hydrolyzable group.

[0017] A production method including such steps can easily produce a silicone composition that is easy to handle and has high tear strength.

[0018] Furthermore, it is preferable that the surface treatment agent in step (γ) further contains at least one of a silazane compound represented by the following general formula (vi) and a monofunctional silane compound represented by the following general formula (vii): ３ ３ SiNHSiR ３ ３ (vi) R ３ ３ SiX (vii) (wherein, R ３ are the same or different, substituted or unsubstituted alkyl groups having 1 to 6 carbon atoms, and X is an OH group or a hydrolyzable group.

[0019] A production method that includes such a step improves the degree of hydrophobicity of component (B), making it possible to easily produce a silicone composition that is easier to handle.

[0020] As described above, the silicone composition of the present invention is easy to handle and has high tear strength after curing. Such a silicone composition of the present invention can be used in applications requiring fluidity, transparency, and high tear strength. For example, it can be used as an adhesive, sealing material, or potting material for heat-generating components, which requires crack resistance. It can also be used as a molding material or ultrasonic probe material, which is used at room temperature but requires high tear strength. In other words, when the silicone composition of the present invention is used, it has mechanical strength that can suppress cracks that can occur due to thermal stress or external stress after curing.

[0021] As described above, there has been a demand for silicone compositions that are easy to handle and have high tear strength after curing.

[0022] As a result of extensive research conducted in order to achieve the above object, the inventors discovered that by including silica particles whose surfaces have been highly hydrophobized and which have alkenyl groups bonded to silicon atoms, a silicone composition can be obtained which is easy to handle and has high tear strength after curing, and this discovery led to the completion of the present invention.

[0023] That is, the present invention provides a silicone composition comprising the following components (A) to (D): (A) 100 parts by mass of an organopolysiloxane having a viscosity at 25°C of 0.01 to 100 Pa s and having two or more silicon-bonded alkenyl groups per molecule, (B) 10 to 500 parts by mass of hydrophobic silica particles having a volume-based median diameter in the range of 10 nm to 1,000 nm, a hydrophobicity of 60% or more as measured by methanol titration, and having silicon-bonded alkenyl groups on their surfaces, (C) an organohydrogenpolysiloxane having two or more silicon-bonded hydrogen atoms per molecule, in an amount such that the number of silicon-bonded hydrogen atoms in component (D) is 0.4 to 5.0 times the molar ratio of all silicon-bonded alkenyl groups in the composition, and (D) a platinum group metal catalyst.

[0024] The present invention will be described in detail below, but the present invention is not limited thereto.

[0025] The silicone composition of the present invention contains (A) an organopolysiloxane having two or more silicon-bonded alkenyl groups per molecule, (B) hydrophobic silica particles having a volume-based median diameter in the range of 10 nm to 1,000 nm, a hydrophobicity of 60% or more as measured by methanol titration, and having silicon-bonded alkenyl groups on their surfaces, (C) an organohydrogenpolysiloxane having two or more silicon-bonded hydrogen atoms per molecule, (D) a platinum group metal catalyst, and, optionally, (E) a reaction inhibitor.

[0026] [Component (A)] Component (A) is an organopolysiloxane having a viscosity at 25°C of 0.01 to 100 Pa·s, preferably 0.03 to 10 Pa·s, and containing two or more silicon-bonded alkenyl groups per molecule. If the viscosity at 25°C is less than 0.01 Pa·s, the cured product will have insufficient mechanical strength, while if it exceeds 100 Pa·s, the viscosity of the composition will be too high and its flowability will be poor. Note that the viscosity referred to in the present invention is a value measured using a B-type rotational viscometer (the same applies hereinafter).

[0027] There are no particular limitations on the organopolysiloxane (A), so long as it satisfies the above-mentioned viscosity and alkenyl group content requirements, and any known organopolysiloxane can be used. The structure of the organopolysiloxane may be either linear or branched, and the organopolysiloxane may also be a mixture of two or more organopolysiloxanes having different viscosities.

[0028] The alkenyl groups bonded to silicon atoms contained in component (A) of the present invention preferably have 2 to 10 carbon atoms, more preferably 2 to 8 carbon atoms, and examples include vinyl groups, allyl groups, 1-butenyl groups, and 1-hexenyl groups. Of these, vinyl groups are preferred in terms of ease of synthesis and cost. The alkenyl groups may be present either at the terminals or along the middle of the molecular chain of the organopolysiloxane, but from the perspective of flexibility, they are preferably present at both terminals. Furthermore, there is no particular upper limit to the number of alkenyl groups bonded to silicon atoms contained in one molecule of component (A), but it can be, for example, 50 or fewer.

[0029] The organic group other than an alkenyl group bonded to a silicon atom contained in component (A) of the present invention is preferably a monovalent hydrocarbon group having 1 to 20 carbon atoms, and more preferably 1 to 10 carbon atoms. Examples of such monovalent hydrocarbon groups include alkyl groups such as methyl, ethyl, propyl, butyl, hexyl, and dodecyl; aryl groups such as phenyl; aralkyl groups such as 2-phenylethyl and 2-phenylpropyl; and halogen-substituted monovalent hydrocarbon groups in which some or all of the hydrogen atoms of these hydrocarbon groups have been substituted with halogen atoms such as chlorine, fluorine, or bromine, such as fluoromethyl, bromoethyl, chloromethyl, and 3,3,3-trifluoropropyl. Of these, methyl groups accounting for 90 mol % or more are preferred from the standpoints of ease of synthesis and cost.

[0030] [Component (B)] Component (B) is hydrophobic silica particles having silicon-bonded alkenyl groups on the surface. By including component (B), the fluidity of the composition can be maintained while increasing the mechanical strength of the cured product.

[0031] Component (B) has a volume-based median diameter of 10 to 1,000 nm, preferably 10 to 500 nm, and particularly preferably 10 to 200 nm. If the particle diameter is smaller than 10 nm, aggregation becomes severe, resulting in a loss of fluidity and transparency. If the particle diameter is larger than 1,000 nm, transparency is lost and the effect of improving mechanical strength is small. The volume-based median diameter can be determined as the particle diameter corresponding to 50% of the cumulative distribution when the particle size distribution is expressed as a cumulative distribution using a laser analysis scattering particle size distribution analyzer.

[0032] The hydrophobicity of component (B) measured by methanol titration is 60% or more, preferably 64% or more. There is no particular upper limit to the hydrophobicity, but it is preferably 80% or less, more preferably 75% or less. Silica particles with a high hydrophobicity do not aggregate even when highly loaded in the composition, and the mechanical strength of the cured product can be increased without impairing the flowability.

[0033] The degree of hydrophobicity can be determined by the methanol titration method shown below. (1) A sample is suspended in a predetermined amount of ion-exchanged water, and methanol is added dropwise while stirring. (2) The amount of added methanol is read when the entire sample is suspended in ion-exchanged water. (3) The volume percentage calculated by [{amount of methanol added (mL)} / {amount of methanol added (mL) + amount of ion-exchanged water (mL)} x 100] is the degree of hydrophobicity.

[0034] The shape of the component (B) of the present invention is not particularly limited, but it is preferably spherical.

[0035] The blend amount of component (B) is 10 to 500 parts by mass, preferably 20 to 400 parts by mass, and more preferably 100 to 300 parts by mass, per 100 parts by mass of component (A). If the blend amount is less than 10 parts by mass, the effect of improving mechanical strength is small, and if the blend amount exceeds 500 parts by mass, the viscosity becomes too high and fluidity is poor.

[0036] In addition, component (B) is a compound having R ２ SiO ３／２ Unit (R ２ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms; and R Ａ （ａ） R ３ （３－ａ） SiO １／２ Units (a is an integer of 1 to 3, R Ａ are the same or different, substituted or unsubstituted alkenyl groups having 2 to 8 carbon atoms, and R ３ are the same or different, substituted or unsubstituted alkyl groups having 1 to 6 carbon atoms. ３ ３ SiO １／２ Unit (R ３ are the same or different, substituted or unsubstituted alkyl groups having 1 to 6 carbon atoms.

[0037] Such component (B) is, for example, a compound having R 1 on the surface of hydrophilic silica particles obtained by hydrolyzing and condensing a tetrafunctional silane compound, an alkyl silicate, or a mixture thereof. ２ SiO ３／２Units, then R Ａ （ａ） R ３ （３－ａ） SiO １／２ Units and R if necessary ３ ３ SiO １／２ It can be obtained by introducing units by hydrolysis condensation.

[0038] [Method for synthesizing component (B)] Specifically, the component (B) of the present invention is preferably synthesized through the following three steps: Step (α): a step of synthesizing hydrophilic silica particles, Step (β): a step of surface hydrophobizing treatment of the hydrophilic silica particles, and Step (γ): a step of surface hydrophobizing treatment of an intermediate for the component (B) and introducing an alkenyl group.

[0039] Each step will be explained below in order. Step (α): Synthesis of hydrophilic silica particles This step is to obtain a dispersion of hydrophilic silica particles by hydrolyzing and condensing at least one of a tetrafunctional silane compound represented by the following general formula (i) and an alkyl silicate represented by the following general formula (ii) in a mixed solution of a hydrophilic organic solvent and water in the presence of a basic substance. Si(OR ４ ) ４ (i) Si(OR ４ ) ３ -(-SiO(OR ４ ) ２ -) ｍ -Si(OR ４ ) ３ (ii) (wherein, R ４ are the same or different monovalent hydrocarbon groups having 1 to 6 carbon atoms; and m is 1 to 100.

[0040] In the above general formulas (i) and (ii), R ４ are the same or different monovalent hydrocarbon groups having 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, and particularly preferably 1 or 2 carbon atoms. ４Examples of the monovalent hydrocarbon group represented by the formula (I) include alkyl groups such as a methyl group, an ethyl group, a propyl group, and a butyl group; and aryl groups such as a phenyl group. Of these, a methyl group, an ethyl group, a propyl group, or a butyl group is preferred, and a methyl group or an ethyl group is particularly preferred.

[0041] In the above general formula (ii), m is 1 to 100, preferably 1 to 50, and particularly preferably 1 to 25.

[0042] Examples of the tetrafunctional silane compound represented by the general formula (i) include tetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane; and tetraphenoxysilane, preferably tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane, and particularly preferably tetramethoxysilane and tetraethoxysilane. Examples of the alkyl silicate represented by the general formula (ii) include methyl silicate and ethyl silicate, preferably methyl silicate.

[0043] These may be used alone or in combination of two or more.

[0044] The hydrophilic organic solvent used in step (α) is not particularly limited as long as it dissolves the tetrafunctional silane compound represented by general formula (i) or the alkyl silicate represented by general formula (ii) and water, and examples thereof include alcohols; cellosolves such as methyl cellosolve, ethyl cellosolve, butyl cellosolve, and cellosolve acetate; ketones such as acetone and methyl ethyl ketone; and ethers such as dioxane and tetrahydrofuran. Preferred are alcohols and cellosolves, and particularly preferred are alcohols. Examples of such alcohols include alcohols represented by the following general formula (xv). R ６ OH (xv) (wherein, R ６ is a monovalent hydrocarbon group having 1 to 6 carbon atoms.

[0045] In the above general formula (xv), R ６is a monovalent hydrocarbon group having 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, and particularly preferably 1 or 2 carbon atoms. ６ Examples of the monovalent hydrocarbon group represented by the formula (xv) include alkyl groups such as methyl, ethyl, propyl, isopropyl, and butyl, preferably methyl, ethyl, propyl, and isopropyl, and more preferably methyl and ethyl. Examples of the alcohol represented by the formula (xv) include methanol, ethanol, propanol, isopropanol, and butanol, preferably methanol and ethanol. As the number of carbon atoms in the alcohol increases, the particle size of the resulting silica particles increases. Therefore, methanol is preferred to obtain silica particles having the desired small particle size.

[0046] Examples of the basic substance used in step (α) include ammonia, dimethylamine, diethylamine, etc., preferably ammonia and diethylamine, and particularly preferably ammonia. These basic substances can be dissolved in a required amount in water, and then the resulting aqueous solution (basic) can be mixed with a hydrophilic organic solvent.

[0047] The amount of the basic substance used in step (α) is preferably 0.01 to 2 moles, more preferably 0.02 to 0.5 moles, and particularly preferably 0.04 to 0.12 moles, per mole of the total hydrocarbyloxy groups of the tetrafunctional silane compound represented by general formula (i) and / or the alkyl silicate represented by general formula (ii). The smaller the amount of basic substance, the more likely it is that the desired small-diameter silica particles will be obtained. The basic substance may also be added to the mixture of water and the hydrophilic organic solvent simultaneously with the addition of the tetrafunctional silane compound and / or the alkyl silicate and the hydrophilic organic solvent.

[0048] The amount of water used in the hydrolysis and condensation is preferably 0.5 to 5 moles, more preferably 0.6 to 2 moles, and particularly preferably 0.7 to 1 mole, per mole of the total of hydrocarbyloxy groups in the tetrafunctional silane compound represented by general formula (i) and / or the alkyl silicate represented by general formula (ii). The ratio of water to hydrophilic organic solvent is preferably 10 to 200 parts by mass of the hydrophilic organic solvent per 100 parts by mass of water.

[0049] The obtained dispersion containing hydrophilic silica particles may be used as is in step (β), but it is preferable to convert the dispersion containing hydrophilic silica particles into an aqueous dispersion by adding water to the dispersion containing hydrophilic silica particles, then evaporating off the hydrophilic organic solvent and converting the dispersion into an aqueous dispersion, since the remaining alkoxy groups are hydrolyzed by this.

[0050] The dispersion medium of the silica particle dispersion can be converted to water, for example, by adding water to the dispersion and distilling off the hydrophilic organic solvent (repeated as necessary). The amount of water added at this time is preferably 50 to 200 parts by mass, and more preferably 80 to 150 parts by mass, per 100 parts by mass of the combined total of the hydrophilic organic solvent used and the alcohol produced in the synthesis step of the hydrophilic silica particles.

[0051] Step (β): Surface Treatment Step of Hydrophilic Silica Particles This is a step in which at least one of a trifunctional silane compound represented by the following general formula (iii) and its (partial) hydrolysis condensate (partial hydrolysis condensate or hydrolysis condensate) is added to the dispersion of hydrophilic silica particles obtained in step (α) to treat the surfaces of the hydrophilic silica particles, thereby obtaining a dispersion of silica particles (hydrophobic silica particle intermediates) which are an intermediate of component (B). ２ Si(OR ５ ) ３ (iii) (wherein, R ２ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, and R ５ are the same or different monovalent hydrocarbon groups having 1 to 6 carbon atoms.

[0052] In the above general formula (iii), R ２ The monovalent hydrocarbon group represented by R is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, preferably 1 to 3 carbon atoms, and particularly preferably 1 or 2 carbon atoms. ２ Examples of the monovalent hydrocarbon group include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, butyl, and hexyl, preferably methyl, ethyl, n-propyl, or isopropyl, and particularly preferably methyl or ethyl. Some or all of the hydrogen atoms in these monovalent hydrocarbon groups may be substituted with halogen atoms such as fluorine, chlorine, or bromine, and preferably fluorine-substituted alkyl groups.

[0053] In the above general formula (iii), R ５ The monovalent hydrocarbon groups represented by R are the same or different monovalent hydrocarbon groups having 1 to 6 carbon atoms, preferably 1 to 3 carbon atoms, and particularly preferably 1 to 2 carbon atoms. ５ Examples of the alkyl group include alkyl groups such as methyl, ethyl, propyl and butyl groups, preferably methyl, ethyl or propyl groups, and particularly preferably methyl or ethyl groups.

[0054] Examples of the trifunctional silane compound represented by general formula (iii) include unsubstituted or halogen-substituted trialkoxysilanes such as methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, isopropyltrimethoxysilane, isopropyltriethoxysilane, butyltrimethoxysilane, butyltriethoxysilane, hexyltrimethoxysilane, trifluoropropyltrimethoxysilane, and heptadecafluorodecyltrimethoxysilane; preferably, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, and ethyltriethoxysilane; more preferably, methyltrimethoxysilane and methyltriethoxysilane.

[0055] The amount of the trifunctional silane compound represented by general formula (iii) added is preferably 0.001 to 1 mol, more preferably 0.01 to 0.4 mol, and particularly preferably 0.01 to 0.2 mol per mol of Si atoms in the hydrophilic silica particles used. If the amount added is 0.001 mol or more, the degree of hydrophobicity of the resulting component (B) is increased, resulting in excellent dispersibility, while if it is 1 mol or less, the risk of aggregation of component (B) can be suppressed.

[0056] Step (γ): Surface Treatment of Component (B) Intermediate and Alkenyl Group Introduction Step: To a dispersion of the obtained silica particles, which are an intermediate of component (B), a surface treatment agent containing at least one of a silazane compound represented by the following general formula (iv) and a monofunctional silane compound represented by the following general formula (v) is added to treat the surfaces of the silica particles, which are an intermediate of component (B), thereby obtaining hydrophobic silica particles, which are component (B), having alkenyl groups bonded to silicon atoms on their surfaces. This step converts the silanol groups remaining on the surfaces of the hydrophobic silica particle intermediate into triorganosilyl groups, thereby introducing R Ａ （ａ） R ３ （３－ａ） SiO １／２ Units are introduced to the surface. Ａ （ａ） R ３ （３－ａ） SiNHSiR Ａ （ａ） R ３ （３－ａ） (iv) R Ａ （ａ） R ３ （３－ａ） SiX (v) (wherein a is an integer of 1 to 3, and R Ａ are the same or different substituted or unsubstituted alkenyl groups having 2 to 8 carbon atoms, R ３ are the same or different, substituted or unsubstituted alkyl groups having 1 to 6 carbon atoms, and X is an OH group or a hydrolyzable group.

[0057] In the above general formulas (iv) and (v), R ＡThe alkenyl group represented by the formula (I) has 2 to 8 carbon atoms, preferably 2 to 6 carbon atoms, and examples thereof include a vinyl group, an allyl group, a 3-butenyl group, a 5-hexenyl group, etc. Among these, a vinyl group is particularly preferred from the standpoint of ease of synthesis and cost.

[0058] In the above general formulas (iv) and (v), R ３ The alkyl group represented by the formula (I) is preferably an alkyl group having 1 to 4 carbon atoms, particularly preferably 1 to 2 carbon atoms, and examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, etc., and a methyl group or an ethyl group is particularly preferred. Some or all of the hydrogen atoms of these monovalent hydrocarbon groups may be substituted with halogen atoms such as fluorine atoms, chlorine atoms, or bromine atoms, and a fluorine-substituted alkyl group is preferred.

[0059] In the general formula (v), X represents an OH group or a hydrolyzable group, and examples of the hydrolyzable group include a chlorine atom, an alkoxy group, an amino group, and an acyloxy group. An alkoxy group or an amino group is preferred, an alkoxy group is more preferred, and a methoxy group or an ethoxy group is particularly preferred.

[0060] Examples of the silazane compound represented by the general formula (iv) include hexavinyldisilazane, dimethyltetravinyldisilazane, and tetramethyldivinyldisilazane, with tetramethyldivinyldisilazane being preferred.

[0061] Examples of the monofunctional silane compound represented by general formula (v) include monosilanol compounds such as dimethylvinylsilanol and diethylvinylsilanol; monochlorosilanes such as dimethylvinylchlorosilane and diethylvinylchlorosilane; monoalkoxysilanes such as dimethylvinylmethoxysilane and dimethylvinylethoxysilane; monoaminosilanes such as dimethylvinylsilyldimethylamine and dimethylvinylsilyldiethylamine; and monoacyloxysilanes such as dimethylvinylacetoxysilane. Preferred are dimethylvinylsilanol, dimethylvinylmethoxysilane, and dimethylvinylsilyldiethylamine, and particularly preferred are dimethylvinylsilanol and dimethylvinylmethoxysilane.

[0062] In step (γ), it is preferable that the surface treatment agent further contains at least one of a silazane compound represented by the following general formula (vi) and a monofunctional silane compound represented by the following general formula (vii): ３ ３ SiNHSiR ３ ３ (vi) R ３ ３ SiX (vii) (wherein, R ３ are the same or different, substituted or unsubstituted alkyl groups having 1 to 6 carbon atoms, and X is an OH group or a hydrolyzable group.

[0063] In the above general formulas (vi) and (vii), R ３ The alkyl group represented by the formula (I) is preferably an alkyl group having 1 to 4 carbon atoms, particularly preferably 1 to 2 carbon atoms, and examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, etc., and a methyl group or an ethyl group is particularly preferred. Some or all of the hydrogen atoms of these monovalent hydrocarbon groups may be substituted with halogen atoms such as fluorine atoms, chlorine atoms, or bromine atoms, and a fluorine-substituted alkyl group is preferred.

[0064] The above X is an OH group or a hydrolyzable group, and examples of the hydrolyzable group include a chlorine atom, an alkoxy group, an amino group, and an acyloxy group, preferably an alkoxy group or an amino group, more preferably an alkoxy group, and particularly preferably a methoxy group or an ethoxy group.

[0065] Examples of the silazane compound represented by the general formula (vi) include hexamethyldisilazane and tetraethyldisilazane, with hexamethylsilazane being preferred.

[0066] Examples of the monofunctional silane compound represented by general formula (vii) include monosilanol compounds such as trimethylsilanol and triethylsilanol; monochlorosilanes such as trimethylchlorosilane and triethylchlorosilane; monoalkoxysilanes such as trimethylmethoxysilane and trimethylethoxysilane; monoaminosilanes such as trimethylsilyldimethylamine and trimethylsilyldiethylamine; and monoacyloxysilanes such as trimethylacetoxysilane. Of these, trimethylsilanol, trimethylmethoxysilane, or trimethylsilyldiethylamine is preferred, and trimethylsilanol or trimethylmethoxysilane is particularly preferred.

[0067] The amount of the silazane compound and / or monofunctional silane compound used is preferably 0.1 to 0.5 mol, more preferably 0.2 to 0.4 mol, and particularly preferably 0.25 to 0.35 mol, per mol of Si atoms in the hydrophilic silica particles used. If the amount used is 0.1 mol or more, the hydrophobicity of the resulting hydrophobic silica particles will be high and they will have excellent dispersibility, but if cost and other factors are taken into consideration, an amount used of 0.5 mol or less will be sufficient.

[0068] The dispersion medium of the mixed solvent dispersion of the hydrophobic silica particle intermediate obtained in step (β) can be converted from a mixture of water or a hydrophilic organic solvent and an alcohol produced during hydrolysis to a ketone-based solvent by adding a ketone-based solvent to the dispersion and then distilling off the water or the hydrophilic organic solvent and the alcohol mixture (this operation can be repeated as necessary). The amount of ketone-based solvent added in this case is preferably 50 to 500 parts by mass, and more preferably 100 to 300 parts by mass, per 100 parts by mass of the obtained hydrophobic silica particle intermediate. Specific examples of the ketone-based solvent used here include methyl ethyl ketone, methyl butyl ketone, and acetylacetone, with methyl isobutyl ketone being particularly preferred.

[0069] The component (B) obtained as described above can be dried under normal pressure, reduced pressure or other conventional methods to obtain a powder.

[0070] [Component (C)] Component (C) is an organohydrogenpolysiloxane having two or more silicon-bonded hydrogen atoms (Si—H groups) per molecule. It acts as a crosslinking agent that crosslinks with the alkenyl groups in components (A) and (B) via a hydrosilylation reaction. The upper limit of the number of silicon-bonded hydrogen atoms per molecule in component (C) is not particularly limited, but can be, for example, 50 or less. Component (C) is not particularly limited as long as it satisfies the above-mentioned amount of Si—H groups, but is preferably one represented by the following average composition formula (viii): R ７ ａ H ｂ SiO （４－ａ－ｂ）／２ (viii) (wherein, R ７ independently represent an unsubstituted or substituted monovalent hydrocarbon group containing no aliphatic unsaturated bonds, a is a number satisfying 0.7≦a≦2.1, b is a number satisfying 0.001≦b≦1.0, and a+b is a number satisfying 0.8≦a+b≦3.0.

[0071] In the above average composition formula (viii), R ７The unsubstituted or substituted monovalent hydrocarbon group containing no aliphatic unsaturated bond and represented by the formula (I) preferably includes a monovalent hydrocarbon group having 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms. Examples of such monovalent hydrocarbon groups include alkyl groups such as methyl, ethyl, propyl, butyl, hexyl, and dodecyl; aryl groups such as phenyl; aralkyl groups such as 2-phenylethyl and 2-phenylpropyl; and halogen-substituted monovalent hydrocarbon groups in which some or all of the hydrogen atoms of these hydrocarbon groups have been substituted with halogen atoms such as chlorine, fluorine, and bromine, such as fluoromethyl, bromoethyl, chloromethyl, and 3,3,3-trifluoropropyl, with a methyl group or a phenyl group being preferred.

[0072] In the above average composition formula (viii), a is a number that satisfies the conditions of 0.7 to 2.1, b is a number that satisfies the conditions of 0.001 to 1.0, and a+b is a number that satisfies the conditions of 0.8 to 3.0, and preferably, a is a number that satisfies the conditions of 1.0 to 2.0, b is a number that satisfies the conditions of 0.01 to 1.0, and a+b is a number that satisfies the conditions of 1.1 to 2.6.

[0073] The two or more silicon-bonded hydrogen atoms (Si—H groups) contained in each molecule of component (C) may be located at either the terminals or the middle of the molecular chain, or may be located at both locations. The molecular structure of this organohydrogenpolysiloxane may be linear, cyclic, branched, or a three-dimensional network structure, and the number of silicon atoms (or degree of polymerization) in each molecule is preferably 2 to 400, more preferably 3 to 200, and particularly preferably 4 to 100.

[0074] The organohydrogenpolysiloxane of component (C) preferably has a viscosity at 25°C of 1,000 mPa·s or less (usually 1 to 1,000 mPa·s), and more preferably 5 to 200 mPa·s.

[0075] Specific examples of the organohydrogenpolysiloxane of component (C) include 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, tris(hydrogendimethylsiloxy)methylsilane, tris(hydrogendimethylsiloxy)phenylsilane, methylhydrogencyclopolysiloxane, methylhydrogensiloxane-dimethylsiloxane cyclic copolymer, methylhydrogenpolysiloxane capped at both ends with trimethylsiloxy groups, dimethylsiloxane-methylhydrogensiloxane copolymer capped at both ends with trimethylsiloxy groups, dimethylpolysiloxane capped at both ends with dimethylhydrogensiloxy groups, copolymer of methylsiloxane and methylhydrogensiloxane, copolymer of methylhydrogensiloxane and diphenylsiloxane capped at both ends with trimethylsiloxy groups, copolymer of methylhydrogensiloxane, diphenylsiloxane and dimethylsiloxane capped at both ends with trimethylsiloxy groups, copolymer of methylhydrogensiloxane, methylphenylsiloxane and dimethylsiloxane capped at both ends with trimethylsiloxy groups, copolymer of methylhydrogensiloxane, dimethylsiloxane and diphenylsiloxane capped at both ends with dimethylhydrogensiloxy groups, copolymer of methylhydrogensiloxane, dimethylsiloxane and methylphenylsiloxane capped at both ends with dimethylhydrogensiloxy groups, (CH ３ ) ２ HSiO １／２ Units and (CH ３ ) ３ SiO １／２ Units and SiO ４／２ a copolymer consisting of (CH ３ ) ２ HSiO １／２ Units and SiO ４／２ a copolymer consisting of (CH ３ ) ２ HSiO １／２ Units and SiO ４／２ Units and (C ６ H ５ ) ３ SiO １／２In addition, copolymers consisting of the following general formulas (ix) to (xiv): R ７ ３ SiO[SiR ７ (H)O] ｔ SiR ７ ３ (ix) R ７ ３ SiO[SiR ７ (H)O] ｔ [SiR ７ ２ O] ｕ SiR ７ ３ (x) R ７ ２ (H)SiO[SiR ７ (H)O] ｔ Si(H)R ７ ２ (xi) R ７ ２ (H)SiO[SiR ７ ２ O] ｕ Si(H)R ７ ２ (xii) R ７ ２ (H)SiO[SiR ７ (H)O] ｔ [SiR ７ ２ O]Si(H)R ７ ２ (xiii) [SiR ７ (H)O] ｖ (cyclic compound) (xiv) (wherein R ７ is the same as above, t and u are integers of 1 to 100, preferably 2 to 25, and v is an integer of 4 to 8.

[0076] The component (C) may use either a single compound or a combination of two or more compounds.

[0077] The amount of component (C) to be blended is such that the silicon-bonded hydrogen atoms (Si—H groups) in component (C) are 0.4 to 5.0 times, preferably 0.5 to 5.0 times, and more preferably 0.7 to 3.5 times, the total of all silicon-bonded alkenyl groups in the composition, i.e., components (A), (B), etc. If the blending amount is less than 0.4 times or more than 5.0 times, the crosslinking balance will be inappropriate, and a cured product with the desired high tear strength will not be obtained.

[0078] [Component (D)] Component (D) is a platinum group metal catalyst. Any platinum group metal catalyst that promotes the addition reaction between the alkenyl groups contained in components (A), (B), etc., and the Si—H groups in component (C) can be used, and conventionally known catalysts can be used. Among these, catalysts selected from platinum and platinum compounds are preferred.

[0079] Examples of such catalysts include platinum group metals such as platinum (including platinum black), rhodium, and palladium; ２ PtCl ４ ・nH ２ O, H ２ PtCl ６ ・nH ２ O, NaHPtCl ６ ・nH ２ O, KHPtCl ６ ・nH ２ O, Na ２ PtCl ６ ・nH ２ O.K. ２ PtCl ４ ・nH ２ O, PtCl ４ ・nH ２ O, PtCl ２ , Na ２ HPtCl ４ ・nH ２0 (where n is an integer of 0 to 6, preferably 0 or 6), chloroplatinic acid and chloroplatinic acid salts, alcohol-modified chloroplatinic acid, complexes of chloroplatinic acid with olefins, platinum black, platinum group metals such as palladium supported on supports such as alumina, silica and carbon, rhodium-olefin complexes, chlorotris(triphenylphosphine)rhodium (Wilkinson's catalyst), complexes of platinum chloride, chloroplatinic acid or chloroplatinic acid salts with vinyl group-containing siloxanes, etc. These platinum group metal catalysts may be used alone or in combination of two or more.

[0080] The amount of component (D) blended is not particularly limited as long as it is an effective amount as a catalyst, and is an amount that can promote the reaction between components (A), (B), etc., and component (C), and can be adjusted appropriately depending on the desired curing rate. Preferably, the amount is 0.1 to 7,000 ppm, more preferably 1 to 6,000 ppm, calculated as platinum group metal atoms, relative to the mass of component (A). When the blending amount of component (D) is 0.1 ppm or more, the catalytic effect is adequate, and when taking into account costs, etc., a blending amount of 7,000 ppm or less is sufficient.

[0081] [Component (E)] The silicone composition of the present invention may further contain a reaction inhibitor as component (E). The reaction inhibitor inhibits the progress of the curing reaction at room temperature, thereby extending shelf life and pot life. The reaction inhibitor is not particularly limited as long as it is capable of inhibiting the catalytic activity of component (D), and known reaction inhibitors can be used. Examples include acetylene compounds such as 1-ethynyl-1-cyclohexanol and 3-butyn-1-ol, various nitrogen compounds, organic phosphorus compounds, oxime compounds, and organic chloro compounds. Among these, acetylene alcohols, which are not corrosive to metals, are preferred.

[0082] The amount of component (E) blended is 0.01 to 5 parts by mass, and preferably 0.05 to 1 part by mass, per 100 parts by mass of component (A). When the amount of reaction inhibitor blended is 0.01 part by mass or more, sufficient shelf life and pot life are obtained, and when the amount of reaction inhibitor blended is 5 parts by mass or less, the curability of the composition is not impaired. The reaction inhibitor may be diluted with an organic solvent such as toluene, xylene, or isopropyl alcohol to improve dispersibility in the silicone resin.

[0083] [Other Components] In addition to the above components (A) to (E), known additives may be added to the silicone composition of the present invention as needed. Examples of such additives include silane coupling agents, silicone resins, silicone / non-silicone adhesion promoters, hindered phenol antioxidants, reinforcing and non-reinforcing fillers such as calcium carbonate, and polyethers as thixotropy improvers. Furthermore, colorants such as pigments and dyes may be added as needed.

[0084] [Method for Producing Silicone Composition] The method for producing the silicone composition of the present invention is not particularly limited, and any conventionally known method can be used. That is, the silicone composition of the present invention can be obtained by mixing components (A) to (D) and, if necessary, other components.

[0085] The method for producing the silicone composition of the present invention preferably includes the steps of producing component (B) through the following steps (α), (β), and (γ), and mixing at least component (B), (A), (C), and (D): (α) a step of obtaining a dispersion of hydrophilic silica particles by hydrolyzing and condensing at least one of a tetrafunctional silane compound represented by the following general formula (i) and an alkyl silicate represented by the following general formula (ii) in a mixed solution of a hydrophilic organic solvent and water in the presence of a basic substance: Si(OR ４ ) ４ (i) Si(OR ４ ) ３ -(-SiO(OR ４ ) ２ -) ｍ -Si(OR４ ) ３ (ii) (wherein, R ４ are the same or different monovalent hydrocarbon groups having 1 to 6 carbon atoms, and m is 1 to 100. (β) A step of adding at least one of a trifunctional silane compound represented by the following general formula (iii) and its (partial) hydrolysis condensate (partial hydrolysis condensate or hydrolysis condensate) to the obtained dispersion of hydrophilic silica particles to treat the surfaces of the hydrophilic silica particles, thereby obtaining a dispersion of silica particles, which is an intermediate of component (B): R ２ Si(OR ５ ) ３ (iii) (wherein, R ２ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, and R ５ are the same or different monovalent hydrocarbon groups having 1 to 6 carbon atoms.) (γ) A step of adding at least one of a silazane compound represented by the following general formula (iv) and a monofunctional silane compound represented by the following general formula (v) to the obtained dispersion of silica particles, which are an intermediate of component (B), to treat the surfaces of the silica particles, which are an intermediate of component (B), thereby obtaining hydrophobic silica particles, which are component (B), having alkenyl groups bonded to silicon atoms on their surfaces: R Ａ （ａ） R ３ （３－ａ） SiNHSiR Ａ （ａ） R ３ （３－ａ） (iv) R Ａ （ａ） R ３ （３－ａ） SiX (v) (wherein a is an integer of 1 to 3, and R Ａ are the same or different substituted or unsubstituted alkenyl groups having 2 to 6 carbon atoms, R ３ are the same or different, substituted or unsubstituted alkyl groups having 1 to 6 carbon atoms, and X is an OH group or a hydrolyzable group.

[0086] The detailed method for producing component (B) has been described above and will not be described here.

[0087] The step of mixing components (A) to (D) is not particularly limited. For example, a one-component composition can be stored for a long period of time by refrigeration or freezing, and a two-component composition can be stored for a long period of time at room temperature.

[0088] A one-component composition can be obtained, for example, by placing components (A) and (B) in a Gate Mixer (manufactured by Inoue Seisakusho Co., Ltd., trade name: Planetary Mixer), heating and mixing for 3 hours at 150°C, adding component (E) after cooling the mixture, and mixing at room temperature for 30 minutes, followed by adding components (C) and (D), and mixing at room temperature for 30 minutes.

[0089] The two-component composition can be composed of any combination, as long as the combination of components (A), (C), and (D) and the combination of components (B), (C), and (D) do not coexist. For example, components (A) and (B) are placed in a gate mixer, heated and mixed at 150°C for 3 hours, and after cooling, component (D) is added and mixed at room temperature for 30 minutes, resulting in a composition designated as component A; components (A), (C), and (E) are placed in a gate mixer, mixed at room temperature for 1 hour, resulting in a composition designated as component B, resulting in a two-component composition of components A and B.

[0090] The viscosity of the silicone composition of the present invention at 25°C is preferably 0.1 to 100 Pa·s, and more preferably 1 to 50 Pa·s. A viscosity of 0.1 Pa·s or more at 25°C will enable the desired mechanical strength to be obtained, while a viscosity of 100 Pa·s or less will provide excellent handleability. The viscosity is measured using a B-type rotational viscometer.

[0091] The curing conditions for this silicone composition are not particularly limited and can be the same as those for known curable silicone compositions. Although the composition can be cured at room temperature, it can also be cured by heating, preferably at a temperature of 20°C to 180°C, more preferably 50 to 150°C, for a period of 0.1 to 3 hours, more preferably 0.5 to 2 hours.

[0092] The cured product of the silicone composition of the present invention preferably has a tear strength according to JIS K 6252-1:2015 of 15 kN / m or more, and more preferably 20 kN / m or more.

[0093] The present invention provides a silicone composition that is easy to handle and has high tear strength after curing. Such a silicone composition of the present invention can be used in applications requiring high tear strength because cracks can occur due to thermal stress or external stress after curing. For example, it can be used as an adhesive, sealant, or potting agent for heat-generating components that require crack resistance. It can also be used as a molding material or ultrasonic probe lens material that is subject to high external stress. That is, when the silicone composition of the present invention is used as an adhesive, sealant, or protective potting material around heat-generating components, or as a molding material or ultrasonic probe lens material, it will have mechanical strength after curing that can suppress cracks that can occur due to thermal stress or external stress.

[0094] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples. Each component used in the examples and comparative examples is described below.

[0095] Component (A) A-1: ​​an organopolysiloxane represented by the following formula, having a viscosity of 5 Pa·s at 25°C A-2: Organopolysiloxane represented by the following formula, having a viscosity of 5 Pa·s at 25°C

[0096] Component (B) Hydrophobic silica particles (B-1), (B-2), (B-3), and (B-4) were prepared according to the following procedure.

[0097] [Synthesis Example 1] Step (α): Synthesis of Hydrophilic Silica Particles 623.7 g of methanol, 41.4 g of water, and 49.8 g of 28% by weight aqueous ammonia were mixed in a 3-liter glass reactor equipped with a stirrer, a dropping funnel, and a thermometer. The solution was adjusted to 35°C, and while stirring, 1,163.7 g of tetramethoxysilane and 418.4 g of 5.4% aqueous ammonia were simultaneously added dropwise over 5 hours. After the dropwise addition was completed, stirring was continued for another 0.5 hours to carry out hydrolysis, thereby obtaining a suspension of hydrophilic spherical silica particles. The glass reactor was equipped with an ester adapter and a condenser, and heated to 60-70°C. After 649 g of methanol was distilled off, 1,600 g of water was added. The mixture was then further heated to 70-90°C, and 160 g of methanol was distilled off, obtaining an aqueous suspension of hydrophilic silica particles.

[0098] Step (β): Surface treatment step of hydrophilic silica particles 115.8 g of methyltrimethoxysilane (SiO ２ After the dropwise addition, the mixture was heated to 50° C. and aged for 1 hour. After the reaction was completed, the mixture was cooled to 25° C., and the surfaces of the hydrophilic silica particles were treated.

[0099] Step (γ): Surface Treatment of Component (C) Intermediate and Alkenyl Group Introduction Step. 1,000 g of methyl isobutyl ketone was added to the dispersion thus obtained, and then the dispersion was heated to 80-115°C while maintaining intense undulations at the liquid interface. 1,336 g of a mixture of methanol and water was distilled off over 11 hours. A mixture of 3.6 g of 1,3-divinyl-1,1,3,3-tetramethyldisilazane and 353.8 g of hexamethyldisilazane was added to the resulting dispersion at 25°C, and the dispersion was heated to 120°C and reacted for 3 hours. The silica particles were surface-treated to obtain a dispersion of hydrophobic silica particles bearing alkenyl groups bonded to silicon atoms on their surfaces. The dispersion medium was then distilled off under heating using an evaporator, yielding 477 g of hydrophobic silica particles (B-1).

[0100] Synthesis Example 2 470 g of hydrophobic silica particles (B-2) were obtained in the same manner as in Synthesis Example 1, except that 1,163.7 g of tetramethoxysilane was changed to 901.9 g of methyl silicate (Methyl Silicate 51 manufactured by Colcoat Co., Ltd.) in step (α).

[0101] Comparative Synthesis Example 1 470 g of hydrophobic silica particles (B-3) were obtained in the same manner as in Synthesis Example 1, except that in step (γ) a mixture of 3.6 g of 1,3-divinyl-1,1,3,3-tetramethyldisilazane and 353.8 g of hexamethyldisilazane was changed to 357.4 g of hexamethyldisilazane.

[0102] Comparative Synthesis Example 2 300 g of hydrophobic silica particles (B-4) were obtained in the same manner as in Synthesis Example 1, except that in step (γ) a mixture of 3.6 g of 1,3-divinyl-1,1,3,3-tetramethyldisilazane and 353.8 g of hexamethyldisilazane was replaced with 119.1 g of hexamethyldisilazane.

[0103] [Measurement Method] The obtained hydrophobic silica particles were measured according to the following measurement methods 1 and 2. The obtained results are shown in Table 1.

[0104] 1. Particle size measurement of hydrophobic silica particles (1) 0.1 g of sample was placed in a glass bottle, and 20 g of methanol was added and stirred. (2) The sample was dispersed for 10 minutes using an ultrasonic disperser to prepare a measurement sample. (3) The sample (2) was measured using a laser analysis scattering particle size distribution measuring device (Nanotra C150, manufactured by Nikkiso Co., Ltd.), and the volume-based median diameter (particle size corresponding to 50% of the cumulative distribution when the particle size distribution is expressed as a cumulative distribution) was taken as the particle size.

[0105] 2. Measurement of hydrophobicity of hydrophobic silica particles (methanol titration method) (1) 0.2 mg of sample was weighed into a 500 mL Erlenmeyer flask. (2) 50 mL of ion-exchanged water was added to (1) and stirred with a stirrer. (3) Methanol was added dropwise from a burette while stirring, and the amount added when the entire amount of the sample was suspended in ion-exchanged water was read. (4) The hydrophobicity was calculated using the following formula: Hydrophobicity (%) = {amount of methanol added (mL)} / {amount of methanol added (mL) + amount of ion-exchanged water (mL)} × 100

[0106]

[0107] Component (C) C-1: Organohydrogensiloxane represented by the following formula: C-2: Organohydrogensiloxane represented by the following formula:

[0108] Component (D) D-1: Dimethylpolysiloxane solution of platinum-divinyltetramethyldisiloxane complex (both ends of which are capped with dimethylvinylsilyl groups, and which has a viscosity of 0.6 Pa s at 25°C, dissolved in dimethylpolysiloxane. Contains 1% by mass of platinum atoms.)

[0109] Component (E) E-1: 1-ethynyl-1-cyclohexanol

[0110] Examples 1 to 3 and Comparative Examples 1 to 4 Preparation of Silicone Compositions Components (A) and (B) were added to a gate mixer (5L planetary mixer, manufactured by Inoue Seisakusho Co., Ltd.) in the amounts shown in Table 2, and mixed under heating at 150°C for 3 hours. Next, component (E) was added in the amount shown in Table 2, and mixed at 25°C for 30 minutes. Finally, components (C) and (D) were added in the amounts shown in Table 2, and mixed at 25°C for 30 minutes until uniform. The physical properties of each of the resulting compositions were measured using the methods shown below. The results are also shown in Table 2.

[0111] [Viscosity] The viscosity of each silicone composition at 25°C was measured using a Brookfield viscometer.

[0112] [Tear Strength] Each silicone composition was press-cured at 120° C. for 10 minutes and then heated for 20 minutes in an oven at 120° C. The tear strength of the resulting 2.0 mm thick silicone sheet was measured in accordance with JIS K 6252-1:2015.

[0113] [Hardness] Each silicone composition was press-cured at 120° C. for 10 minutes and then heated in an oven at 120° C. for 50 minutes. Three of the resulting 2.0 mm-thick silicone sheets were stacked, and the hardness was measured using a Type A durometer specified in JIS K 6253-3:2012.

[0114] [Tensile Strength, Elongation at Break] Each silicone composition was press-cured at 120° C. for 10 minutes and then heated in an oven at 120° C. for 50 minutes. The tensile strength and elongation at break of the resulting 2.0 mm thick silicone sheets were measured in accordance with JIS K 6251:2017.

[0115] [Density after curing] Each silicone composition was press-cured at 120° C. for 10 minutes and then heated for 20 minutes in an oven at 120° C. The density after curing of the resulting 2.0 mm thick silicone sheet was measured in accordance with JIS-K6249:2003.

[0116]

[0117] As shown in Table 2, the silicone compositions of the present invention prepared in Examples 1 to 3 had viscosities that allowed for easy handling, and the cured products had tear strengths of 22 kN / m or greater in accordance with JIS K 6252-1:2015.

[0118] On the other hand, Comparative Example 1, which did not contain component (B), and Comparative Examples 2 and 3, which replaced component (B) with hydrophobic silica having no alkenyl groups on the surface, exhibited insufficient tear strength and inferior mechanical properties. Furthermore, Comparative Example 4, which used component (B) with an insufficient hydrophobicity, produced a composition with too high a viscosity to be handled.

[0119] From the above, it is clear that the present invention provides a silicone composition that is easy to handle and has high tear strength after curing.

[0120] The present invention encompasses the following aspects. [1]: A silicone composition comprising the following components (A) to (D): (A) 100 parts by mass of an organopolysiloxane having a viscosity at 25°C of 0.01 to 100 Pa s and having two or more silicon-bonded alkenyl groups per molecule, (B) 10 to 500 parts by mass of hydrophobic silica particles having a volume-based median diameter of 10 to 1,000 nm, a hydrophobicity of 60% or more as measured by methanol titration, and having silicon-bonded alkenyl groups on their surfaces, (C) an organohydrogenpolysiloxane having two or more silicon-bonded hydrogen atoms per molecule, in an amount such that the number of silicon-bonded hydrogen atoms in component (C) is 0.4 to 5.0 times the molar ratio of all silicon-bonded alkenyl groups in the composition, and (D) a platinum group metal catalyst. [2]: A silicone composition comprising component (B) and a platinum group metal catalyst, wherein component (B) forms R groups on the silica surface. ２ SiO ３／２ Unit (R ２ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms; and R Ａ （ａ） R ３ （３－ａ） SiO １／２ Units (a is an integer of 1 to 3, R Ａ are the same or different, substituted or unsubstituted alkenyl groups having 2 to 8 carbon atoms, and R ３ are the same or different, substituted or unsubstituted alkyl groups having 1 to 6 carbon atoms. [3]: The silicone composition according to the above [1], characterized in that the component (B) further comprises R ３ ３ SiO １／２ Unit (R ３are the same or different, substituted or unsubstituted alkyl groups having 1 to 6 carbon atoms.) The silicone composition according to [2] above, characterized in that the silicone composition has a volume-based median diameter of component (B) of 10 nm to 200 nm. [5] The silicone composition according to any of [1] to [4] above, characterized in that the amount of component (B) blended per 100 parts by mass of component (A) is 100 parts by mass to 300 parts by mass. [6] The silicone composition according to any of [1] to [5] above, characterized in that the silicone composition further contains 0.01 to 5.0 parts by mass of (E) a reaction inhibitor per 100 parts by mass of component (A). [7]: A method for producing a silicone composition according to any one of [1] to [6] above, comprising the steps of: producing the component (B) through steps including the following (α), (β), and (γ); and mixing at least the component (B) with the components (A), (C), and (D): (α) a step of hydrolyzing and condensing at least one of a tetrafunctional silane compound represented by the following general formula (i) and an alkyl silicate represented by the following general formula (ii) in a mixed liquid of a hydrophilic organic solvent and water in the presence of a basic substance to obtain a dispersion of hydrophilic silica particles: Si(OR ４ ) ４ (i) Si(OR ４ ) ３ -(-SiO(OR ４ ) ２ -) ｍ -Si(OR ４ ) ３ (ii) (wherein, R ４ are the same or different monovalent hydrocarbon groups having 1 to 6 carbon atoms, and m is 1 to 100. (β) A step of adding at least one of a trifunctional silane compound represented by the following general formula (iii) and a (partial) hydrolysis condensate thereof to the obtained dispersion of hydrophilic silica particles to treat the surfaces of the hydrophilic silica particles, thereby obtaining a dispersion of silica particles, which is an intermediate of the component (B): R ２Si(OR ５ ) ３ (iii) (wherein, R ２ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, and R ５ are the same or different monovalent hydrocarbon groups having 1 to 6 carbon atoms.) (γ) A step of adding a surface treatment agent containing at least one of a silazane compound represented by the following general formula (iv) and a monofunctional silane compound represented by the following general formula (v) to the obtained dispersion of silica particles, which are an intermediate of component (B), to treat the surfaces of the silica particles, which are an intermediate of component (B), thereby obtaining hydrophobic silica particles, which are component (B), having alkenyl groups bonded to silicon atoms on their surfaces: R Ａ （ａ） R ３ （３－ａ） SiNHSiR Ａ （ａ） R ３ （３－ａ） (iv) R Ａ （ａ） R ３ （３－ａ） SiX (v) (wherein a is an integer of 1 to 3, and R Ａ are the same or different substituted or unsubstituted alkenyl groups having 2 to 8 carbon atoms, R ３ are the same or different, substituted or unsubstituted alkyl groups having 1 to 6 carbon atoms, and X is an OH group or a hydrolyzable group.) [8]: The method for producing a silicone composition according to claim 7, wherein the surface treatment agent in step (γ) further contains at least one of a silazane compound represented by the following general formula (vi) and a monofunctional silane compound represented by the following general formula (vii): ３ ３ SiNHSiR ３ ３ (vi) R ３ ３ SiX (vii) (wherein, R ３ are the same or different, substituted or unsubstituted alkyl groups having 1 to 6 carbon atoms, and X is an OH group or a hydrolyzable group.

[0121] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits similar effects is included within the technical scope of the present invention.

Claims

1. A silicone composition comprising the following components (A) to (D): (A) 100 parts by mass of an organopolysiloxane having a viscosity at 25°C of 0.01 to 100 Pa·s and having two or more alkenyl groups bonded to silicon atoms per molecule, (B) 10 to 500 parts by mass of hydrophobic silica particles having a volume-based median diameter in the range of 10 nm to 1,000 nm, a hydrophobicity degree of 60% or more as measured by a methanol titration method, and having alkenyl groups bonded to silicon atoms on their surfaces, (C) an organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms per molecule, in an amount such that the number of hydrogen atoms bonded to silicon atoms in component (C) is 0.4 to 5.0 times the molar amount of all alkenyl groups bonded to silicon atoms in the composition, and (D) a platinum group metal catalyst.

2. The component (B) forms R on the silica surface. ２ SiO ３／２ Unit (R ２ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms; and R Ａ （ａ） R ３ （３－ａ） SiO １／２ Units (a is an integer of 1 to 3, R Ａ are the same or different, substituted or unsubstituted alkenyl groups having 2 to 8 carbon atoms; R ３ and each of the groups represented by the formula (1) is an alkyl group having 1 to 6 carbon atoms, ....

3. The component (B) further provides R on the silica surface. ３ ３ SiO １／２ Unit (R ３ and each of the groups represented by the formula (1) is an alkyl group having 1 to 6 carbon atoms, ....

4. The silicone composition according to claim 1, wherein the volume-based median diameter of component (B) is 10 nm to 200 nm.

5. The silicone composition according to claim 1, characterized in that the blending amount of said component (B) is 100 to 300 parts by mass per 100 parts by mass of said component (A).

6. The silicone composition according to claim 1, further comprising (E) 0.01 to 5.0 parts by mass of a reaction inhibitor per 100 parts by mass of component (A).

7. A method for producing a silicone composition according to any one of claims 1 to 6, comprising the steps of producing the component (B) through the steps including the following (α), (β), and (γ), and mixing at least the component (B), the components (A), (C), and (D): (α) a step of obtaining a dispersion of hydrophilic silica particles by hydrolyzing and condensing at least one of a tetrafunctional silane compound represented by the following general formula (i) and an alkyl silicate represented by the following general formula (ii) in a mixed liquid of a hydrophilic organic solvent and water in the presence of a basic substance: Si(OR ４ ) ４ (i) Si(OR ４ ) ３ -(-SiO(OR ４ ) ２ -) ｍ -Si(OR ４ ) ３ (ii) (wherein, R ４ are the same or different monovalent hydrocarbon groups having 1 to 6 carbon atoms, and m is 1 to 100. (β) A step of adding at least one of a trifunctional silane compound represented by the following general formula (iii) and its (partial) hydrolysis condensate to the obtained dispersion of hydrophilic silica particles to treat the surfaces of the hydrophilic silica particles, thereby obtaining a dispersion of silica particles which is an intermediate of the component (B): ２ Si(OR ５ ) ３ (iii) (wherein, R ２ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, R ５ are the same or different monovalent hydrocarbon groups having 1 to 6 carbon atoms.) (γ) A step of adding a surface treatment agent containing at least one of a silazane compound represented by the following general formula (iv) and a monofunctional silane compound represented by the following general formula (v) to the obtained dispersion liquid of silica particles, which is an intermediate of the component (B), to treat the surfaces of the silica particles, which are an intermediate of the component (B), thereby obtaining hydrophobic silica particles, which are the component (B), having alkenyl groups bonded to silicon atoms on their surfaces: R Ａ （ａ） R ３ （３－ａ） SiNHSiR Ａ （ａ） R ３ （３－ａ） (iv) R Ａ （ａ） R ３ （３－ａ） SiX (v) (wherein a is an integer from 1 to 3; R Ａ are the same or different, substituted or unsubstituted alkenyl groups having 2 to 8 carbon atoms; R ３ are the same or different, substituted or unsubstituted alkyl groups having 1 to 6 carbon atoms, and X is an OH group or a hydrolyzable group.

8. The method for producing a silicone composition according to claim 7, wherein the surface treatment agent in step (γ) further comprises at least one of a silazane compound represented by the following general formula (vi) and a monofunctional silane compound represented by the following general formula (vii): ３ ３ SiNHSiR ３ ３ (vi) R ３ ３ SiX (vii) (wherein, R ３ are the same or different, substituted or unsubstituted alkyl groups having 1 to 6 carbon atoms, and X is an OH group or a hydrolyzable group.

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