Millable-type silicone rubber raw material mixture and compound, method for producing compound, and method for producing composition

Abstract

To provide: a millable-type silicone rubber raw material mixture, a compound and a composition that are able to be produced by simple methods and that do not contain crystalline components; and methods for producing them.SOLUTION: A millable-type silicone rubber raw material mixture contains the following components (A) to (E): (A) 100 pts.mass of an organopolysiloxane raw rubber having an average degree of polymerization of 1,000 to 100,000 and having two or more alkenyl groups bonded to silicon atoms in each molecule; (B) 5 to 100 pts.mass of reinforcing silica having a specific surface area of 50 to 450 m2 / g as measured by the BET adsorption method; (C) one or more dispersants selected from (C-1) and (C-2), where (C-1) is 1.0 to 50.0 pts.mass of an organosilane and / or siloxane having Si-OH groups at both ends, and (C-2) is 0.1 to 20 pts.mass of a partially hydrolyzed condensate of an alkoxysilane, the partially hydrolyzed condensate having a refractive index within the range of 1.39 to 1.41 and a kinematic viscosity of 1.0 to 1000 mm2 / s; (D') a solution obtained by dissolving a phosphite compound in a hydrocarbon-based organic solvent having a boiling point of 80°C or lower; and (E) one or more condensation-reaction catalysts selected from (E-1) to (E-3), where (E-1) is 0.0001 to 0.1 pt.mass of an amine compound that is liquid at 25°C and has a boiling point of 30 to 60°C at 1013 hPa, (E-2) is 0.001 to 1 pt.mass of a hexaorganodisilazane represented by general formula (4), and (E-3) is 0.001 to 1 pt.mass of aqueous ammonia having an ammonia concentration of 1.0 to 30.0 mass%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to millable silicone rubber raw material mixtures and compounds, as well as methods for producing the compounds and compositions. [Background technology]

[0002] In the prior art, addition reaction curable organopolysiloxane compositions contain an organohydrogenpolysiloxane having a hydrogen atom bonded to a silicon atom (i.e., a hydrosilyl group), an organopolysiloxane having an alkenyl group such as a vinyl group bonded to a silicon atom, and a platinum-based catalyst.

[0003] In the case of so-called one-component organopolysiloxane compositions that combine these three components, problems exist when exposed to high temperatures, such as changes in properties such as thickening and gelation, and changes in the physical properties of the organopolysiloxane cured product obtained after curing. To avoid these problems, several methods have been proposed: dividing the organopolysiloxane composition into two or more components and mixing them immediately before use to create a mixed organopolysiloxane composition; and transporting one-component organopolysiloxane compositions refrigerated or frozen. The former method poses the risk of changes in the physical properties of the resulting cured organopolysiloxane due to blending or mixing, requiring highly advanced blending and mixing techniques. The latter method, on the other hand, requires refrigeration or freezing from storage until use, significantly increasing transportation and storage costs and making it commercially unviable. Against this backdrop, there has been a growing demand in recent years for one-component organopolysiloxane compositions that maintain their properties and performance even after long-term storage at room temperature (here, 25°C).

[0004] Patent Documents 1 to 5 propose methods for improving storage stability using certain specific phosphite ester compounds. While these methods dramatically improve storage stability, they require the prior preparation of a platinum-phosphite ester complex-containing hydrosilylation catalyst, which poses challenges such as the labor, time, and cost required for producing the special platinum catalyst. Furthermore, because phosphite ester compounds are susceptible to reaction with oxygen, these methods suffer from poor storage stability in air, as well as the problem of catalyst recrystallization when the coordination number of the phosphite ester compound increases. Therefore, there has been a demand for one-component organopolysiloxane compositions with high storage stability. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2021 / 014970 [Patent Document 2] Japanese Patent Publication No. 2021-042323 [Patent Document 3] International Publication No. 2023 / 013443 [Patent Document 4] International Publication No. 2023 / 136259 [Patent Document 5] Japanese Patent Publication No. 2021-127373 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made to solve the above problems, and aims to provide a raw material mixture and compound for millable silicone rubber that can be produced by a simple method and does not contain crystalline components. It also aims to provide a method for producing a millable silicone rubber compound that does not contain crystalline components. It also aims to provide a method for producing a one-component organopolysiloxane composition that has high storage stability. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides: The present invention provides a millable silicone rubber raw material mixture containing the following components (A) to (E): (A) 100 parts by mass of organopolysiloxane gum having two or more silicon-bonded alkenyl groups per molecule and an average degree of polymerization of 1,000 to 100,000, (B) Specific surface area measured by BET adsorption method is 50 to 450 m 2 / g reinforcing silica: 5 to 100 parts by mass, (C) one or more dispersants selected from the following (C-1) and (C-2): (C-1) 1.0 to 50.0 parts by mass of an organosilane and / or siloxane having Si—OH groups at both ends, represented by the following general formula (1): [ka] (In the formula, R 1 are the same or different unsubstituted or substituted monovalent hydrocarbon groups having 1 to 8 carbon atoms, and m is an integer of 1 to 50. (C-2) A partial hydrolysis condensation product of an alkoxysilane represented by the following general formula (2): The refractive index of the partial hydrolysis condensate is in the range of 1.39 to 1.41, and the kinematic viscosity is in the range of 1.0 to 1000 mm 2 / s: 0.1 to 20 parts by mass, R 2 Si(OR 3 )3(2) (In the formula, R 2 are the same or different unsubstituted or substituted monovalent hydrocarbon groups having 1 to 12 carbon atoms, and R 3 represents a monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms. (D') a solution of a phosphite ester compound represented by the following general formula (3) dissolved in a hydrocarbon organic solvent having a boiling point of 80°C or less: [ka] (In the formula, R 4 are independently a hydrogen atom or a monovalent aliphatic hydrocarbon group having 1 to 3 carbon atoms. The amount of the phosphite ester compound is 0.0010 to 0.10 parts by mass per 100 parts by mass of the component (A), (E) one or more condensation reaction catalysts selected from the following (E-1) to (E-3): (E-1) an amine compound that is liquid at 25°C and has a boiling point of 30 to 60°C at 1013 hPa: 0.0001 to 0.1 parts by mass, (E-2) Hexaorganodisilazane represented by the following general formula (4): R 5 3SiNHSiR 5 3(4) (In the formula, R 5 represent the same or different monovalent hydrocarbon groups having 1 to 12 carbon atoms. :0.001~1 part by mass, (E-3) 1.0 to 30.0 mass% ammonia water: 0.001 to 1 part by mass.

[0008] Such a raw material mixture can provide a millable silicone rubber raw material mixture that does not contain crystalline components and can be produced by a simple method.

[0009] In addition, in the raw material mixture, the hydrocarbon organic solvent having a boiling point of 80°C or less is preferably an organic solvent selected from n-pentane, n-hexane, 2-methylbutane, 2,2-dimethylbutane, 2,3-dimethylbutane, 2-methylpentane, and 3-methylpentane.

[0010] Such solvents are easy to handle industrially, and if these solvents are used, the above-mentioned millable silicone rubber raw material mixture can be easily solvent-removed in the subsequent solvent removal process from the millable silicone rubber.As a result, the time it takes for component (D) to react with oxygen in the air is shortened, thereby suppressing the reaction that converts component (D) into a phosphate ester compound.

[0011] A method for producing a millable type silicone rubber compound, comprising: It is preferable to carry out a step of removing the hydrocarbon organic solvent having a boiling point of 80° C. or less from the above-described millable silicone rubber raw material mixture while blocking oxygen.

[0012] According to this production method, the reaction of component (D) with oxygen in the air during the solvent removal step to convert it into a phosphate ester compound is suppressed, the decrease in component (D) is suppressed, and the storage stability of the composition and the cured product derived therefrom is not impaired.

[0013] The present invention provides a method for producing a millable silicone rubber composition by producing a millable silicone rubber compound by the method described above, and then adding a curing agent (F) to the compound.

[0014] This production method preferably provides millable silicone rubber compositions with excellent storage stability and cured products derived therefrom.

[0015] As the (F) curing agent, it is preferable to use a curing agent for a hydrosilylation reaction, which is a combination of an organohydrogenpolysiloxane and a hydrosilylation catalyst.

[0016] The use of such a curing agent allows the production of a millable silicone rubber composition with excellent storage stability. Furthermore, the cured film derived from this composition exhibits minimal change in physical properties over time and is highly stable.

[0017] The present invention provides a millable silicone rubber compound containing the following components (A) to (E) but not containing any crystalline components. (A) 100 parts by mass of organopolysiloxane gum having two or more silicon-bonded alkenyl groups per molecule and an average degree of polymerization of 1,000 to 100,000, (B) Specific surface area measured by BET adsorption method is 50 to 450 m 2 / g reinforcing silica: 5 to 100 parts by mass, (C) one or more dispersants selected from the following (C-1) and (C-2): (C-1) 1.0 to 50.0 parts by mass of an organosilane and / or siloxane having Si—OH groups at both ends, represented by the following general formula (1): [ka] (In the formula, R 1 are the same or different unsubstituted or substituted monovalent hydrocarbon groups having 1 to 8 carbon atoms, and m is an integer of 1 to 50. (C-2) A partial hydrolysis condensation product of an alkoxysilane represented by the following general formula (2): The refractive index of the partial hydrolysis condensate is in the range of 1.39 to 1.41, and the kinematic viscosity is in the range of 1.0 to 1000 mm 2 / s: 0.1 to 20 parts by mass, R 2 Si(OR 3 )3(2) (In the formula, R 2 are the same or different unsubstituted or substituted monovalent hydrocarbon groups having 1 to 12 carbon atoms, and R 3 represents a monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms. (D) A phosphite compound represented by the following general formula (3): [ka] (In the formula, R 4 are independently a hydrogen atom or a monovalent aliphatic hydrocarbon group having 1 to 3 carbon atoms. :0.0010~0.10 parts by mass, (E) one or more condensation reaction catalysts selected from the following (E-1) to (E-3): (E-1) an amine compound that is liquid at 25°C and has a boiling point of 30 to 60°C at 1013 hPa: 0.0001 to 0.1 parts by mass, (E-2) Hexaorganodisilazane represented by the following general formula (4): R 5 3SiNHSiR 5 3(4) (In the formula, R 5represent the same or different monovalent hydrocarbon groups having 1 to 12 carbon atoms. :0.001~1 part by mass, (E-3) 1.0 to 30.0 mass% ammonia water: 0.001 to 1 part by mass.

[0018] Such a millable silicone rubber compound solves the problems of labor, time, and cost involved in its production, and provides a composition that is free of crystalline components and has high storage stability.

[0019] The millable silicone rubber compound of the present invention, which does not contain crystalline components, and the silicone rubber composition obtained by compounding said compound with a curing agent, do not produce crystalline components over the long term, even though the phosphite ester compound added to improve storage stability is solid.As a result, it is possible to obtain a one-component organopolysiloxane composition of stable quality over the long term using a simple method.

[0020] For this reason, the Millable-type silicone rubber raw material mixture of the present invention can provide a raw material mixture that does not contain crystalline components. It also provides a Millable-type silicone rubber raw material mixture that allows for easy removal of solvents when producing the compound. Furthermore, it can provide Millable-type silicone rubber compounds with high storage stability by suppressing decomposition due to the reaction of component (D) with oxygen during the process of producing the compound and composition, as well as compositions to which a hardener is added, and cured products derived from such compositions with high storage stability. These features contribute to supply stability, simplified inventory management, and products that achieve the Sustainable Development Goals, enabling a wide range of applications in fields such as electrical equipment, automobiles, construction, medicine, and food. DETAILED DESCRIPTION OF THE INVENTION

[0021] The present invention will be described in detail below, but the present invention is not limited thereto.

[0022] In the present invention, a mixture of the above components (A) to (E) is referred to as a silicone rubber raw material mixture, the product that undergoes the subsequent kneading step is referred to as a silicone rubber compound, and the compound to which the curing agent (F) is added is referred to as a silicone rubber composition.

[0023] As a result of extensive research into the above-mentioned problems, the inventors of the present invention have discovered that component (D), which has the effect of significantly improving the storage stability of silicone rubber compositions but is poorly soluble and generates crystalline components when added to silicone rubber compositions, can be added using a hydrocarbon organic solvent with a boiling point of 80°C or less, and then the solvent is removed in a subsequent step, thereby providing a silicone rubber composition containing component (D) without generating crystalline components, and have completed the present invention.

[0024] The millable silicone rubber raw material mixture of the present invention is a millable silicone rubber raw material mixture containing the following components (A) to (E): (A) 100 parts by mass of organopolysiloxane gum having two or more silicon-bonded alkenyl groups per molecule and an average degree of polymerization of 1,000 to 100,000, (B) Specific surface area measured by BET adsorption method is 50 to 450 m 2 / g reinforcing silica: 5 to 100 parts by mass, (C) one or more dispersants selected from the following (C-1) and (C-2): (C-1) 1.0 to 50.0 parts by mass of an organosilane and / or siloxane having Si—OH groups at both ends, represented by the following general formula (1): [ka] (In the formula, R 1 are the same or different unsubstituted or substituted monovalent hydrocarbon groups having 1 to 8 carbon atoms, and m is an integer of 1 to 50. (C-2) A partial hydrolysis condensation product of an alkoxysilane represented by the following general formula (2): The refractive index of the partial hydrolysis condensate is in the range of 1.39 to 1.41, and the kinematic viscosity is in the range of 1.0 to 1000 mm 2 / s: 0.1 to 20 parts by mass, R 2 Si(OR 3 )3(2) (In the formula, R 2 are the same or different unsubstituted or substituted monovalent hydrocarbon groups having 1 to 12 carbon atoms, and R 3 represents a monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms. (D') a solution of a phosphite ester compound represented by the following general formula (3) dissolved in a hydrocarbon organic solvent having a boiling point of 80°C or less: [ka] (In the formula, R 4 are independently a hydrogen atom or a monovalent aliphatic hydrocarbon group having 1 to 3 carbon atoms. The amount of the phosphite ester compound is 0.0010 to 0.10 parts by mass per 100 parts by mass of the component (A), (E) one or more condensation reaction catalysts selected from the following (E-1) to (E-3): (E-1) an amine compound that is liquid at 25°C and has a boiling point of 30 to 60°C at 1013 hPa: 0.0001 to 0.1 parts by mass, (E-2) Hexaorganodisilazane represented by the following general formula (4): R 5 3SiNHSiR 5 3(4) (In the formula, R 5 represent the same or different monovalent hydrocarbon groups having 1 to 12 carbon atoms. :0.001~1 part by mass, (E-3) 1.0 to 30.0 mass% ammonia water: 0.001 to 1 mass part

[0025] The millable-type silicone rubber compound of the present invention, which does not contain crystalline components, is produced by removing hydrocarbon organic solvents with a boiling point of 80°C or less from the millable-type silicone rubber raw material mixture. A millable-type silicone rubber composition can be obtained by adding a curing agent (F) to the millable-type silicone rubber compound. This curing agent (F) is preferably a hydrosilylation reaction curing agent consisting of a combination of an organohydrogenpolysiloxane and a hydrosilylation catalyst.

[0026] -Component (A)- In the present invention, component (A) is an organopolysiloxane gum having two or more silicon-bonded alkenyl groups per molecule and an average degree of polymerization of 1,000 to 100,000.

[0027] The alkenyl group bonded to a silicon atom is preferably an alkenyl group having 2 to 8 carbon atoms, and more preferably an alkenyl group having 2 to 6 carbon atoms. Specific examples include a vinyl group, an allyl group, a butenyl group, a pentenyl group, a hexenyl group, and a cyclohexenyl group. Of these, a vinyl group is preferred.

[0028] The substituents other than the alkenyl group preferably have 1 to 12 carbon atoms. Monovalent hydrocarbon groups having 1 to 8 carbon atoms are more preferred. Specific examples include alkyl groups such as methyl, ethyl, propyl, butyl, hexyl, and octyl; cycloalkyl groups such as cyclopentyl and cyclohexyl; aryl groups such as phenyl and tolyl; and aralkyl groups such as benzyl and 2-phenylethyl. Fluoroalkyl groups in which an alkyl group is partially substituted with a fluorine atom may also be used. The substituents other than the alkenyl group are preferably methyl and phenyl, with methyl being particularly preferred.

[0029] Furthermore, the number of alkenyl groups bonded to silicon atoms present in each molecule of component (A) is two or more, preferably 2 to 50, and more preferably 2 to 20. Of these, those containing vinyl groups are particularly preferred. In this case, it is preferred that 0.01 to 20 mol %, and particularly 0.02 to 10 mol %, of all siloxane units in the organopolysiloxane are siloxane units containing alkenyl groups. The alkenyl groups may be bonded to silicon atoms at the molecular chain terminals, or to silicon atoms in the middle of the molecular chain (non-terminal), or both, but it is preferred that they are bonded to silicon atoms at at least the molecular chain terminals.

[0030] It is also preferred that 80 mol % or more, preferably 90 mol % or more, more preferably 95 mol % or more of all siloxane units in the organopolysiloxane, and even more preferably all siloxane units except for siloxane units having alkenyl groups, are dialkylsiloxy groups, particularly dimethylsiloxy groups.

[0031] The molecular structure of the organopolysiloxane of component (A) is preferably linear or partially branched. Specifically, the repeating structure of the diorganosiloxane units constituting the main chain of the organopolysiloxane is preferably one consisting solely of repeating dimethylsiloxane units, or one in which diorganosiloxane units such as diphenylsiloxane units, methylphenylsiloxane units, methylvinylsiloxane units, or methyl-3,3,3-trifluoropropylsiloxane units have been introduced as part of the repeating structure.

[0032] Furthermore, both molecular chain terminals are preferably capped with a group selected from, for example, trimethylsiloxy groups, dimethylphenylsiloxy groups, vinyldimethylsiloxy groups, divinylmethylsiloxy groups, trivinylsiloxy groups, etc., and are particularly preferably capped with vinyldimethylsiloxy groups.

[0033] Examples of organopolysiloxanes of component (A) include methylvinylpolysiloxane, methylphenylvinylpolysiloxane, and methyltrifluoropropylvinylpolysiloxane.

[0034] Such organopolysiloxanes can be obtained, for example, by (co)hydrolytic condensation of one or more organohalogenosilanes, or by ring-opening polymerization of cyclic polysiloxanes (such as siloxane trimers and tetramers) using an alkaline or acidic catalyst.

[0035] The organopolysiloxane has an average degree of polymerization of 1,000 to 100,000, preferably 2,000 to 50,000, more preferably 2,500 to 30,000, and particularly preferably 3,000 to 20,000. The organopolysiloxane has no self-flowing properties at room temperature (25°C), and is thus in the form of a crude rubber (non-liquid). If the average degree of polymerization is too low, problems such as roll adhesion may occur when the compound is prepared, resulting in poor roll workability.

[0036] The degree of polymerization can be measured as a weight average degree of polymerization in terms of polystyrene by gel permeation chromatography (GPC) analysis. [Measurement conditions] Developing solvent: toluene Flow rate: 0.35mL / min Detector: Refractive index detector (RI) Column: TSK Guardcolumn SuperH-L TSKgel SuperH4000(6.0mmI.D.×15cm×1) TSKgel SuperH3000(6.0mmI.D.×15cm×1) TSKgel SuperH2000(6.0mmI.D.×15cm×2) (All manufactured by Tosoh Corporation) Column temperature: 40℃ Sample injection volume: 10 μL (toluene solution with a concentration of 0.5% by mass) The component (A) may be used alone or as a mixture of two or more species differing in molecular weight (degree of polymerization) or molecular structure.

[0037] -(B) Component- The reinforcing silica of component (B) is a filler added to obtain a silicone rubber composition with excellent mechanical strength. For this purpose, it is necessary to use a filler having a specific surface area (BET adsorption method) of 50 to 450 m 2 / g, and preferably 100 to 450 m 2 / g, more preferably 100 to 300m 2 / g. The specific surface area is 50m 2 If the specific surface area is less than 450 m / g, the mechanical strength of the cured product will be low. 2 If it is greater than / g, it will take a long time to compound, and there is a high possibility that the specified compounding amount will not be filled into component (A).

[0038] Examples of such reinforcing silica include fumed silica and precipitated silica, and those whose surfaces have been hydrophobized with chlorosilane or hexamethyldisilazane are also suitable. Of these, fumed silica is preferred because of its excellent dynamic fatigue properties. Component (B) may be used alone or in combination of two or more.

[0039] The amount of reinforcing silica (B) blended is 5 to 100 parts by mass, preferably 10 to 50 parts by mass, per 100 parts by mass of organopolysiloxane (A). If the amount of component (B) blended is less than 5 parts by mass, the reinforcing effect will not be obtained, while if it is more than 100 parts by mass, processability will be poor, mechanical strength will be reduced, and dynamic fatigue durability will also be impaired.

[0040] -(C) component- The purpose of the component (C) of the present invention is to use it as a dispersant for dispersing the reinforcing silica of the component (B) into the organopolysiloxane gum of the component (A).

[0041] (C) One or more dispersants selected from the following (C-1) and (C-2). (C-1) 1.0 to 50.0 parts by mass of an organosilane and / or siloxane having Si—OH groups at both ends, represented by the following general formula (1): [ka] (In the formula, R 1 are the same or different unsubstituted or substituted monovalent hydrocarbon groups having 1 to 8 carbon atoms, and m is an integer of 1 to 50.

[0042] (C-2) A partial hydrolysis condensation product of an alkoxysilane represented by the following general formula (2): The refractive index of the partial hydrolysis condensate is in the range of 1.39 to 1.41, and the kinematic viscosity is in the range of 1.0 to 1000 mm 2 / s: 0.1 to 20 parts by mass, R 2 Si(OR 3 )3(2) (In the formula, R 2 are the same or different unsubstituted or substituted monovalent hydrocarbon groups having 1 to 12 carbon atoms, and R 3 represents a monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms. Here, the components (C-1) and (C-2) may be used alone or in combination, and when used in combination, the amounts used are the same as when used alone.

[0043] (C-1) Component In general formula (1), R 1 are the same or different unsubstituted or substituted monovalent hydrocarbon groups having 1 to 8 carbon atoms, specifically alkyl groups having 1 to 8 carbon atoms such as methyl, ethyl, propyl, isopropyl, and butyl, alkenyl groups having 2 to 8 carbon atoms such as vinyl and allyl, and aryl groups having 6 to 8 carbon atoms such as phenyl and tolyl. 1 is preferably a methyl group or a vinyl group, and m is an integer of 1 to 50, preferably 2 to 20. When component (C-1) is used, the amount used is 1.0 to 50 parts by mass, and preferably 2.0 to 20 parts by mass, per 100 parts by mass of component (A). If the amount of organopolysiloxane endblocked with silanol groups is less than 1.0 part by mass, plastic reversion (creep hardening) becomes significant, while if it is more than 50 parts by mass, the plasticity of the compound becomes too low, causing roll stickiness in kneading means such as a roll mill, and reducing roll workability.

[0044] (C-2) Component In general formula (2), R 2 are the same or different unsubstituted or substituted monovalent hydrocarbon groups having 1 to 12 carbon atoms, and R 3 is a monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms. Specific examples of organoalkoxysilanes represented by general formula (2) include trimethoxy(methyl)silane, trimethoxy(ethyl)silane, trimethoxy(propyl)silane, trimethoxy(butyl)silane, trimethoxy(hexyl)silane, triethoxy(methyl)silane, tripropoxy(methyl)silane, and tributoxy(methyl)silane. Among these, trimethoxy(methyl)silane, trimethoxy(ethyl)silane, and triethoxy(methyl)silane are more preferred, and trimethoxy(methyl)silane is even more preferred. Partial hydrolysates of these organoalkoxysilanes are used as component (C). Note that, since component (C) is a partial hydrolyzate, the above R 2 Monovalent hydrocarbon groups derived from the above R 3 In addition to the alkoxy groups derived from the alkyl groups, some hydroxy groups (hydroxysilyl groups) are also present.

[0045] Here, the degree of polymerization of the partial hydrolyzate of organoalkoxysilane (C-2) is preferably 2 to 100, with those primarily composed of partial hydrolyzates with degrees of polymerization of 2 to 30 being particularly preferred. If component (C-2) is not a partial hydrolyzate, i.e., if a monomer is used, it will be more volatile and will evaporate during kneading, resulting in unstable plasticity of the resulting silicone rubber compound. Additionally, the increased amount of volatile components poses industrial hazards, such as inhalation of volatile vapors and ignition. Conversely, if the degree of polymerization of component (C-2) is 100 or less, the viscosity of component (C-2) will be appropriate, making it easier to compound, and the surface treatment ability of component (B) will also be favorable. This will also stabilize the compounding time and the plasticity of the resulting silicone rubber compound.

[0046] The refractive index of component (C-2) of the present invention is a value measured using an Abbe refractometer according to the method described in JIS K0062:1992. The refractive index of component (C-2) is preferably 1.39 to 1.41. A refractive index of 1.39 to 1.40 is particularly preferred. If the refractive index is less than 1.39, the purity of the partial hydrolyzate of the organoalkoxysilane of component (C-2) will be low, increasing industrial hazards such as inhalation of volatile vapors and ignition. Conversely, if the refractive index exceeds 1.41, the viscosity of the partial hydrolyzate of the organoalkoxysilane of component (C-2) will increase, and the self-condensation tendency of the partial hydrolyzate of the organoalkoxysilane of component (C-2) will also increase, making it prone to thickening and gelation, which may worsen blendability and is therefore undesirable.

[0047] The kinematic viscosity of the component (C-2) of the present invention at 25°C is 1.0 to 1,000 mm 2 / s range is preferable, and 1.5 to 500 mm 2 / s is more preferable, 1.5 to 300 mm 2 The kinematic viscosity of component (C-2) is a value measured using a Cannon-Fenske viscometer as described in JIS Z8803:2011. A viscosity within this range is preferred because it facilitates blending with other components and minimizes volatile components.

[0048] When component (C-2) is used, the amount used is preferably 0.1 to 20 parts by mass, and more preferably 0.5 to 10.0 parts by mass, per 100 parts by mass of component (A). If the amount of component (C) added is less than 0.1 part by mass, reversion may occur, resulting in poor processability, or in the worst case, the compound may not be obtainable. If the amount of component (C) added is more than 20 parts by mass, the resulting compound may become sticky, resulting in poor processability, or the mechanical properties of the silicone rubber obtained by curing the compound may be reduced.

[0049] -(D) Component- Component (D) of the present invention is a phosphite ester compound represented by the following formula (3). After producing a millable silicone rubber compound, component (D) is added to the millable silicone rubber composition to stabilize the hydrosilylation catalyst contained in the curing agent (F), which is used to obtain a one-component organopolysiloxane composition with high storage stability. [ka]

[0050] (In the formula, R 4 are independently a hydrogen atom or a monovalent aliphatic hydrocarbon group having 1 to 3 carbon atoms. In the above formula (3), R 4 are independently a hydrogen atom or a monovalent aliphatic hydrocarbon group having 1 to 3 carbon atoms, preferably 1 to 2 carbon atoms, more preferably 1 carbon atom, i.e., a methyl group. Specific examples of phosphite ester compounds include compounds in which R is methyl, such as tris(2,4-dimethylphenyl)phosphite, tris(2,4-di-tert-butylphenyl)phosphite, tris(2,4-bis(3-ethylpentan-3-yl)phenyl)phosphite, and tris(2,4-bis(4-propylheptan-4-yl)phenyl)phosphite. 4are the same aliphatic hydrocarbon groups, or R such as tris(4-(tert-butyl)-2-methylphenyl)phosphite, tris(4-(tert-butyl)-2-ethylphenyl)phosphite, tris(2-(tert-butyl)-4-(3-ethylpentan-3-yl)phenyl)phosphite, tris(2-(tert-butyl)-4-(3-methylhexan-3-yl)phenyl)phosphite, etc. 4 The phosphite ester compound used in the present invention is particularly preferably tris(2,4-di-tert-butylphenyl)phosphite, which is easily available and has excellent storage stability.

[0051] If component (D) is a solid at room temperature, it is highly likely that component (D) will exist in a crystalline state in the resulting millable silicone rubber compound, resulting in reduced mechanical strength and storage stability. Therefore, when component (D) is a solid at room temperature, a millable silicone rubber raw material mixture can be easily prepared by using a solution of component (D) dissolved in a hydrocarbon organic solvent. A millable silicone rubber compound free of crystalline components can be obtained by subjecting the raw material mixture to a solvent removal process. In the present invention, the solution in which component (D) is dissolved is designated component (D').

[0052] The hydrocarbon-based organic solvent used in the present invention is an aliphatic hydrocarbon-based solvent or an aromatic hydrocarbon-based solvent. It is preferable to remove the hydrocarbon-based organic solvent used from the resulting millable silicone rubber compound [step (a)]. This can suppress the reaction in which component (D) reacts with oxygen in the air to convert to a phosphate ester compound. Therefore, it is preferable that the hydrocarbon-based solvent has a relatively low boiling point. The hydrocarbon-based organic solvent used in the present invention is preferably an aliphatic hydrocarbon-based solvent rather than an aromatic hydrocarbon-based solvent.

[0053] Aliphatic hydrocarbon solvents having a boiling point of 80°C or less may have a linear or branched structure. Specific examples of hydrocarbon solvents having a boiling point of 80°C or less include n-pentane (boiling point: 36°C), n-hexane (boiling point: 68°C), 2-methylbutane (boiling point: 30°C), 2,2-dimethylbutane (boiling point: 50°C), 2,3-dimethylbutane (boiling point: 58°C), 2-methylpentane (boiling point: 62°C), and 3-methylpentane (boiling point: 63°C). Hydrocarbon solvents used in the present invention having a boiling point of 80°C or less are preferred because they are easily removed in the subsequent removal step. Among these, n-hexane (boiling point: 68°C) is particularly preferred because it is easy to handle for industrial use and is easily removed in the subsequent removal step.

[0054] The removal step is not particularly limited, but includes heat treatment with stirring, reduced pressure treatment, and treatment utilizing the heat of vaporization. Among these, a removal step involving heat treatment with stirring is preferred. In this step, component (D) reacts with oxygen and converts to a phosphate ester compound. Therefore, the step of removing the hydrocarbon-based organic solvent must be carried out while blocking oxygen [step (b)]. Here, "blocking" does not mean completely removing oxygen, but rather preventing oxygen from being mixed in. Examples of steps for removing the hydrocarbon-based organic solvent while blocking oxygen include an inert gas aeration method, a reduced pressure method, and a gas replacement method. Because it is necessary to block oxygen while efficiently removing the hydrocarbon-based organic solvent, it is preferable to carry out the step while passing a gas such as nitrogen or argon through the process. Among these, nitrogen is used as the gas for the step of removing the hydrocarbon-based organic solvent while blocking oxygen, which is preferred from both an industrial and safety standpoint.

[0055] The mixing temperature in the step of removing the hydrocarbon organic solvent used to dissolve the component (D) is preferably 20 to 200° C., more preferably 40 to 180° C., and even more preferably 80 to 170° C. The mixing time in the step of removing the hydrocarbon organic solvent used to dissolve the component (D) is not particularly limited, but in consideration of production efficiency, it is preferably 30 to 300 minutes, more preferably 60 to 120 minutes.

[0056] There are no particular restrictions on the amount of hydrocarbon solvent with a boiling point of 80°C or less used, since the amount of component (D) used is very small. There are also no particular restrictions on the dissolution time. It is preferable to select a container for dissolution that can block oxygen.

[0057] The amount of the phosphite compound used in the present invention is preferably 0.0010 to 0.10 parts by mass, and more preferably 0.0020 to 0.05 parts by mass, per 100 parts by mass of component (A). If the amount of component (D) added is less than 0.0010 parts by mass, a millable-type silicone rubber compound containing no crystalline components can be obtained, but the amount of effective component (D) required to stabilize the hydrosilylation catalyst contained in the subsequently added curing agent (F) will be too small, or component (D) will convert to a phosphate ester compound during production of the millable-type silicone rubber compound, making it impossible to obtain a one-component millable-type silicone rubber composition with the expected storage stability. Furthermore, if the amount of component (D) added exceeds 0.10 parts by mass, there is a high possibility that crystals of component (D) will form in the resulting millable silicone rubber compound. In addition, the amount of active component (D) required to stabilize the hydrosilylation catalyst contained in the subsequently added curing agent (F) will be too large, resulting in poor curability and a rubber with low mechanical strength after curing.

[0058] -(E) Component- Component (E) is a condensation reaction catalyst that induces a condensation reaction between the silanol groups present on the surface of the reinforcing silica of component (B), the silanol groups of component (C-1), and / or the alkoxy groups of component (C-2). Component (E) is one or more condensation reaction catalysts selected from the following (E-1) to (E-3):

[0059] Component (E-1) is an amine compound that is liquid at 25°C and has a boiling point of 30 to 60°C at 1013 hPa. Specific examples of component (E-1) include lower alkylamines such as propylamine (melting point: -83°C, boiling point: 48°C), isopropylamine (melting point: -95°C, boiling point: 33°C), and tert-butylamine (melting point: -67°C, boiling point: 45°C), and lower dialkylamines such as diethylamine (melting point: -50°C, boiling point: 56°C). The melting point and boiling point described above are the temperatures listed in the SDS issued by Fujifilm Wako Pure Chemical Industries, Ltd.

[0060] The amount of component (E-1) added is 0.0001 to 0.1 parts by mass, preferably 0.001 to 0.05 parts by mass, per 100 parts by mass of component (A). If the amount of component (E-1) used is less than 0.0001 parts by mass, the time required for surface treatment of the reinforcing silica may be prolonged, or the degree of surface treatment may be reduced, resulting in the failure to obtain a silicone rubber compound. Conversely, if the amount of component (E-1) used is more than 0.1 parts by mass, component (E-1) may not be removed from the silicone rubber compound, resulting in an increase in plasticity over time. Furthermore, when attempting to obtain a cured silicone rubber product by addition curing using a platinum catalyst, the physical properties of the cured product may be unstable, or the surface of the cured product may become tacky due to insufficient curing.

[0061] (E-2) Hexaorganodisilazane represented by the following general formula (4): R 5 3SiNHSiR 5 3(4) (In the formula, R 5 represent the same or different monovalent hydrocarbon groups having 1 to 12 carbon atoms. :0.001~1 part by mass,

[0062] In the above formula (4), R 5 As for R in the component (C-2), 2 Examples of the alkyl group include those similar to those listed above, but alkyl groups having 1 to 6 carbon atoms such as methyl and ethyl groups are particularly preferred. The molecule may also contain an alkenyl group such as a vinyl group. Specific examples of the component (E-2) include hexamethyldisilazane, 1-vinylpentamethyldisilazane, 1,3-divinyl-1,1,3,3-tetramethyldisilazane, and 1,3-dimethyl-1,1,3,3-tetravinyldisilazane. Of these, hexamethyldisilazane and 1,3-divinyl-1,1,3,3-tetramethyldisilazane are preferred, and hexamethyldisilazane is more preferred as the component (E-2).

[0063] The amount of component (E-2) blended is 0.001 to 1 part by weight, preferably 0.01 to 0.50 parts by weight, and more preferably 0.01 to 0.3 parts by weight, per 100 parts by weight of the organopolysiloxane (component (A)). If the amount of component (E-2) used is less than 0.001 part by weight, the time required for surface treatment of the reinforcing silica may be prolonged, or the degree of surface treatment may be reduced, resulting in the failure to obtain a silicone rubber compound. Conversely, if the amount of component (E-2) used is greater than 1 part by weight, component (E-2) may not be removed from the silicone rubber compound, resulting in an increase in plasticity over time. Furthermore, when attempting to obtain a silicone rubber cured product by addition curing using a platinum catalyst, the physical properties of the cured product may be unstable, or the surface of the cured product may become tacky due to insufficient curing. This is also economically undesirable.

[0064] The component (E-3) is 1.0 to 30.0% by mass of aqueous ammonia. The concentration of aqueous ammonia is 1.0 to 30.0% by mass, preferably 10.0 to 28.0% by mass, and more preferably about 15.0 to 28.0% by mass.

[0065] The amount of component (E-3) blended is 0.001 to 1 part by weight, preferably 0.005 to 1 part by weight, and more preferably 0.01 to 0.8 parts by weight, per 100 parts by weight of the organopolysiloxane (A). Using less than 0.001 parts by weight of component (E-3) can result in a longer surface treatment time for the reinforcing silica, or a lower level of surface treatment, potentially making it impossible to obtain a silicone rubber compound. Conversely, using more than 1 part by weight of component (E-3) can result in component (E-3) not being removed from the silicone rubber compound, resulting in increased plasticity over time. Furthermore, when attempting to obtain a cured silicone rubber product by addition curing using a platinum catalyst, the physical properties of the cured product may be unstable, or the surface of the cured product may become tacky due to insufficient curing. This is also economically undesirable. The millable type silicone rubber compound free of crystalline components obtained in the manner described above can be blended with (F) a curing agent to obtain a millable type silicone rubber composition free of crystalline components.

[0066] The millable silicone rubber compound of the present invention is preferably produced using equipment capable of uniformly kneading the predetermined amounts of the above-mentioned components (A) to (E). While there are no particular limitations on the equipment capable of uniformly kneading, it is preferable to use equipment that can perform the step of removing the hydrocarbon organic solvent with a boiling point of 80°C or less used to dissolve component (D) [step (a)], and the step of performing step (a) while blocking oxygen [step (b)]. Specifically, millable silicone rubber compounds can be obtained using kneading machines such as kneaders and Banbury mixers, but production using a kneader is particularly preferred. The mixing temperature of the components (A) to (E) is preferably in the range of 0 to 200° C., more preferably 10 to 180° C., and even more preferably 20 to 170° C. The mixing time of the components (A) to (E) is not particularly limited, but considering production efficiency, it is preferably 1 to 300 minutes, more preferably 10 to 120 minutes. The millable silicone rubber compound free of crystalline components obtained in the manner described above can be blended with (E) a curing agent to obtain a millable silicone rubber composition free of crystalline components.

[0067] -(F) Component- As the (F) curing agent, it is preferable to use an addition reaction (hydrosilylation reaction) type curing agent generally known as a rubber curing agent, that is, a hydrosilylation reaction curing agent consisting of a combination of an organohydrogenpolysiloxane (crosslinking agent) and a hydrosilylation catalyst.

[0068] The organohydrogenpolysiloxane used as the crosslinking agent for the addition reaction curing agent has two or more hydrosilyl groups in one molecule, and is particularly preferably an organohydrogenpolysiloxane represented by the following formula (5): (R 6 3SiO 1 / 2 )a(R 6 2SiO 2 / 2 )b(R 6 SiO 3 / 2 )c(SiO 4 / 2 )d (5) (In the formula, R 6 are independently a hydrogen atom or a group selected from an alkyl group having 1 to 8 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms, and two or more R 6 is a hydrogen atom. Note that two or more hydrogen atoms cannot exist on the same silicon atom. a is an integer of 2≦a≦30, b is an integer of 0≦b≦300, c is an integer of 0≦c≦10, and d is an integer of 0≦d≦30. Note that the bonding of each siloxane unit may be block or random.

[0069] where R 6 are independently a hydrogen atom, or a group selected from an alkyl group having 1 to 8 carbon atoms, preferably 1 to 6, an aryl group having 6 to 10 carbon atoms, preferably 6 to 8, and an aralkyl group having 7 to 10 carbon atoms, preferably 7 to 9. However, there are two or more, preferably 2 to 200, more preferably 2 to 130 R6 is a hydrogen atom. Examples of alkyl groups include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, and hexyl groups, and cycloalkyl groups such as cyclohexyl groups. Examples of aryl groups include phenyl and tolyl groups. Examples of aralkyl groups include benzyl and 2-phenylpropyl groups. Note that fluoroalkyl groups in which an alkyl group is partially substituted with a fluorine atom may also be used. Furthermore, a is an integer satisfying 2≦a≦30, preferably 2≦a≦20. b is an integer satisfying 0≦b≦300, preferably 3≦b≦200. c is an integer satisfying 0≦c≦10, preferably 0≦c≦5. and d are integers satisfying 0≦d≦30, preferably 0≦d≦20.

[0070] The molecular structure of the organohydrogenpolysiloxane may be linear, cyclic, branched, or three-dimensional network. In this case, the number of silicon atoms (or degree of polymerization) per molecule is preferably 2 to 300, particularly about 4 to 200, and is liquid at 25°C. The hydrosilyl group may be located at the molecular chain terminal, on a side chain (in the middle of the molecular chain), or both.

[0071] Examples of the organohydrogenpolysiloxane include 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, methylhydrogencyclopolysiloxane, methylhydrogensiloxane-dimethylsiloxane cyclic copolymer, tris(dimethylhydrogensiloxy)methylsilane, tris(dimethylhydrogensiloxy)phenylsilane, methylhydrogenpolysiloxane capped at both ends with trimethylsiloxy groups, dimethylsiloxane-methylhydrogensiloxane copolymer capped at both ends with trimethylsiloxy groups, and methylhydrogenpolysiloxane capped at both ends with dimethylsiloxy groups. Siloxy-group-blocked dimethylpolysiloxane, dimethylhydrogensiloxy-blocked dimethylsiloxane-methylhydrogensiloxane copolymer at both ends, trimethylsiloxy-blocked methylhydrogensiloxane-diphenylsiloxane copolymer at both ends, trimethylsiloxy-blocked methylhydrogensiloxane-diphenylsiloxane-dimethylsiloxane copolymer at both ends, cyclic methylhydrogenpolysiloxane, cyclic methylhydrogensiloxane-dimethylsiloxane copolymer, cyclic methylhydrogensiloxane-diphenylsiloxane-dimethylsiloxane copolymer, (CH3)2HSiO 1 / 2 Units and SiO 4 / 2 A copolymer consisting of (CH3)2HSiO units 1 / 2 Units and SiO 4 / 2 Units and (C6H5)SiO 3 / 2 and copolymers consisting of units, and the above-mentioned exemplary compounds in which some or all of the methyl groups have been substituted with other alkyl groups such as ethyl groups or propyl groups, or aryl groups such as phenyl groups. Specific examples of such organohydrogenpolysiloxanes include compounds of the following structural formula:

[0072] [ka] (In the formula, k is an integer of 2 to 10, and s and t are each an integer of 0 to 10.) The organohydrogenpolysiloxane preferably has a viscosity of 0.5 to 10,000 mPa·s, and particularly 1 to 300 mPa·s, at 25° C. The viscosity is a value measured using a rotational viscometer according to the method described in JIS K7117-1:1999.

[0073] The organohydrogenpolysiloxane is preferably blended in an amount such that the molar ratio of silicon-bonded hydrogen atoms (i.e., hydrosilyl groups) in the organohydrogenpolysiloxane to silicon-bonded alkenyl groups in component (A) (hydrosilyl groups / alkenyl groups) is 0.5 to 10, preferably 0.8 to 6, and more preferably 1 to 5. A ratio of 0.5 or greater ensures sufficient crosslinking and mechanical strength. A ratio of 10 or less ensures appropriate physical properties after curing, particularly in terms of heat resistance and compression set resistance.

[0074] The hydrosilylation catalyst used in the addition reaction curing agent promotes the addition reaction between the alkenyl groups in component (A) and the hydrosilyl groups in the organohydrogenpolysiloxane crosslinker. Examples of hydrosilylation catalysts include platinum group metal catalysts such as ruthenium and platinum. Platinum group metal catalysts include these platinum group metals and their compounds. These catalysts are conventionally known as catalysts for addition reaction curing silicone rubber compositions. Examples include particulate platinum metal adsorbed on a carrier such as silica, alumina, or silica gel; platinic chloride; chloroplatinic acid; reaction products of chloroplatinic acid with monohydric alcohols; complexes of chloroplatinic acid with olefins; complexes of chloroplatinic acid with vinyl group-containing (poly)siloxanes; complexes of chloroplatinic acid with phosphite esters; and complexes of these with vinyl group-containing (poly)siloxanes; palladium catalysts; rhodium catalysts; and ruthenium catalysts. The hydrosilylation catalyst used in the present invention is particularly preferably platinum or a platinum compound.

[0075] The amount of hydrosilylation catalyst added may be a catalytic amount sufficient to promote the addition reaction, and is typically used in a range of 1 ppm to 1 mass % calculated as the mass of platinum group metal relative to the amount of component (A), with a range of 10 to 500 ppm being preferred. Addition of 1 ppm or more sufficiently promotes the addition reaction, resulting in sufficient curing. On the other hand, an amount of 1 mass % or less is not excessive and is not uneconomical.

[0076] In addition to the above catalysts, an addition crosslinking inhibitor may be used to adjust the curing rate, specific examples of which include ethynylcyclohexanol and tetramethyltetravinylcyclotetrasiloxane.

[0077] In addition to the above components, the millable silicone rubber composition of the present invention, which does not contain crystalline components, may optionally contain conductive agents such as carbon black, flame retardant agents such as iron oxides and halogen compounds, antistatic agents, softeners, antioxidants, ultraviolet absorbers, colorants, etc.

[0078] A cured silicone rubber product can be obtained by curing the millable silicone rubber composition of the present invention, which does not contain a crystalline component. The curing temperature is preferably 60 to 300°C, and more preferably 80 to 200°C. The curing time is preferably 5 seconds to 1 hour, and more preferably 30 seconds to 30 minutes. [Example]

[0079] EXAMPLES The present invention will be specifically explained below using examples and comparative examples, but the present invention is not limited to these.

[0080] In the present examples, the melting point and boiling point are measured at 1013 hPa, and the average degree of polymerization is measured as a weight average degree of polymerization in terms of polystyrene by gel permeation chromatography (GPC). The viscosity is a value measured using a rotational viscometer according to the method described in JIS K7117-1:1999. The kinematic viscosity is a value measured using a Cannon-Fenske viscometer according to the method described in JIS Z8803:2011. The refractive index is a value measured using an Abbe refractometer according to the method described in JIS K0062:1992.

[0081] Specific examples of the components used in the examples and comparative examples of the present invention are shown below. (A) Organopolysiloxane raw rubber An organopolysiloxane gum consisting of 99.825 mol% dimethylsiloxane units, 0.15 mol% methylvinylsiloxane units, and 0.025 mol% dimethylvinylsiloxy units, with an average of 12 vinyl groups bonded to silicon atoms per molecule and an average degree of polymerization of 6,000.

[0082] (B) Reinforcing silica (B-1) BET specific surface area is 200m 2 / g of fumed silica (trade name: Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) (B-2) BET specific surface area is 130m 2 / g of surface-treated silica (product name: Aerosil R-972, manufactured by Nippon Aerosil Co., Ltd.)

[0083] (C) Dispersant (C-1) Dimethylpolysiloxane having silanol groups at both ends, an average degree of polymerization of 4, and a viscosity of 15 mPa·s at 25°C (C-2) Partial hydrolysis product of trimethoxy(methyl)silane (trade name: KC-89S, manufactured by Shin-Etsu Chemical Co., Ltd., kinematic viscosity [25°C]: 5 mm 2 / s, refractive index [25℃]: 1.394)

[0084] (D) Phosphite ester: Tris(2,4-di-tert-butylphenyl)phosphite (trade name: JP-650, manufactured by Johoku Chemical Industry Co., Ltd.) Hydrocarbon organic solvent used to dissolve component (D): n-hexane (boiling point: 68°C), component (D) was dissolved to a concentration of 10 wt% and used. (E) Catalyst (E-1) Amine compounds that are liquid at 25°C Isopropylamine (Melting point: -95°C, Boiling point: 33°C) (E-2) Hexaorganodisilazane Hexamethyldisilazane (trade name: SZ-31, manufactured by Shin-Etsu Chemical Co., Ltd.) (E-3) Ammonia water 28% by mass ammonia water The above components were mixed in the amounts shown in Table 1, and a silicone rubber compound was obtained through the following steps.

[0085] [Silicone rubber compound manufacturing process] A raw material mixture was prepared by adding 100 parts by mass of component (A) and 40 parts by mass of component (B) to a 3 L kneader and kneading them uniformly with components (C), (D), and (E) in the amounts listed in Table 1. This mixture was then kneaded further under the conditions of steps (a) and (b) listed in Table 1 to obtain a silicone rubber compound. In Table 1, "heat treatment mixing" refers to a method in which the mixture is heated externally to a set temperature and then mixed for a specified period of time.

[0086] Check for the presence of crystals The appearance of the silicone rubber raw material mixtures prepared in Examples 1 to 7 and Comparative Examples 1 to 3 was evaluated, as well as the appearance of the silicone rubber compounds at the initial stage of production and those stored for three months. The silicone rubber compounds at the initial stage of production and those stored at room temperature for three months were molded into approximately 1 mm thick silicone rubber compounds using two rolls, and the presence or absence of crystals was confirmed visually and microscopically (microscope used: Keyence Corporation, VHX-8000, magnification x100). Those in which crystals were not confirmed visually or microscopically were judged to pass, and those in which crystals were confirmed were judged to fail.

[0087] ○Measurement of physical properties and confirmation of storage stability For 100 parts by mass of the silicone rubber compounds prepared in Examples 1 to 7 and Comparative Examples 1 to 3, 0.01 parts by mass of a platinum catalyst (manufactured by Shin-Etsu Chemical Co., Ltd.) containing 1% by mass of a chloroplatinic acid-divinyldisiloxane complex in terms of platinum atomic mass as an addition reaction curing agent (F), and [(CH3)3SiO 1 / 2 ]2[H(CH3)SiO 2 / 2 ] 20 [(CH3)2SiO 2 / 2 ] 18 Then, 0.85 parts by mass of an organohydrogenpolysiloxane (manufactured by Shin-Etsu Chemical Co., Ltd.) represented by the following formula was added and mixed uniformly to prepare a millable type silicone rubber composition. This composition was used at the time of production and after 30 days of storage at 40°C, and test sheets were prepared by press curing at 120°C for 10 minutes and then post-curing at 200°C for 4 hours. The hardness (Durometer A), tensile strength, elongation at break, and compression set (150°C / 22 hours, 25% compression) of the prepared test sheets were measured according to the specifications of JIS K6249:2003.

[0088] The impact resilience was also measured according to the method described in JIS K6255: 2013. For all values, those whose physical property changes were within 1.2 times the initial value were judged to pass, and those whose physical property changes were 1.2 times or more the initial value or for which measurement of the physical property was impossible were judged to fail.

[0089] Furthermore, for the Millable-type silicone rubber composition after kneading, the Williams plasticity was measured 10 minutes later (initial) using the method described in JIS K6249:2003, and then the plasticity was measured after 30 days at 40°C, and the change in plasticity after 1 day at 40°C relative to the initial value was calculated to evaluate the change over time. Values ​​for the change over time within ±100 were judged to pass (equal to or better than the conventional product), and values ​​that deviated from this were judged to fail (worse than the conventional product).

[0090] [Table 1-1]

[0091] [Table 1-2]

[0092] [Table 1-3]

[0093] [Evaluation results]

[0094] In Comparative Example 1, the hardly soluble (D) component (phosphite ester compound) was not added, so a Millable-type silicone rubber compound containing no crystalline components was obtained, but the effect of (D) component, which has the effect of stabilizing the storage stability of the Millable-type silicone rubber composition, was not obtained, and the Millable-type silicone rubber composition using the compound turned into rubber when stored at 40°C for 30 days, and the target storage stability could not be achieved. In Comparative Example 2, when dispersing and blending component (D) (phosphite ester compound), it was dissolved in a hydrocarbon-based organic solvent with a boiling point of 80°C or less and blended as a solution, but the amount of component (D) blended exceeded the range required by the claimed invention. Test results showed no evidence of crystalline components in either the initial Millable silicone compound or the Millable silicone compound after 30 days of storage at 40°C. However, after 30 days of storage at 40°C, crystalline components consisting of the phosphite ester compound (component (D)) were generated in the Millable silicone rubber compound, resulting in an abnormal appearance. Furthermore, when the Millable silicone rubber composition produced from the Millable silicone rubber compound obtained in Comparative Example 2, which did not contain crystalline components, was cured, poor curing was confirmed by press curing, and the initial physical properties could not be measured. This is because the amount of component (D) added exceeded the required range.

[0095] In Comparative Example 3, when dispersing and blending component (D) (phosphite ester compound), the amount of component (D) added was within the required range, but a hydrocarbon-based organic solvent with a boiling point of 80°C or less was not used. As a result, dispersibility was poor, and crystals of the phosphite ester compound (component (D)) were confirmed visually and under a microscope in the millable-type silicone rubber compound after dispersion. Therefore, preparation of the millable-type silicone rubber composition was abandoned.

[0096] Example 7 is an embodiment that satisfies the requirements of claims (1) and (2). In Example 7, the amount of phosphite ester compound added is within the range required by the present invention. Furthermore, the phosphite ester compound, component (D), was dissolved in a hydrocarbon organic solvent with a boiling point of 80°C or less and dispersed as a solution. As a result, a Millable-type silicone rubber raw material mixture free of crystalline components was easily prepared. Furthermore, no crystalline components were observed in either the initial Millable-type silicone compound or the Millable-type silicone compound stored at 40°C for 30 days. This solves the problem of the present invention. However, since the compound was subsequently kneaded in the atmosphere, decomposition of component (D) occurred due to a reaction between component (D) and oxygen, resulting in failures in the plasticity and the change in physical properties of the cured product after 30 days at 40°C.

[0097] The silicone rubber compounds obtained in Examples 1 to 6 solved the problems and achieved the objects of the present invention. By blending component (D) in a solution dissolved in a hydrocarbon-based organic solvent, a silicone rubber compound raw material mixture free of crystalline components was easily obtained. By performing a solvent removal process in which oxygen was blocked, the compound could be prepared in a state where decomposition of component (D) due to reaction with oxygen was suppressed, allowing the production of a compound free of crystalline components. Furthermore, from this compound, a silicone rubber composition with excellent storage stability and a cured silicone rubber derived from this composition could be obtained. It can be seen that the physical properties of the molding test sheet of the millable silicone rubber composition of the present invention satisfied the target performance values.

[0098] From the above results, it can be seen that, according to the present invention, even if the phosphite ester compound, component (D), is solid, the resulting silicone rubber compound can stably produce a millable-type silicone rubber compound that does not contain crystal-forming components; in addition, the millable-type silicone rubber compound that does not contain crystal-forming components obtained according to the present invention can be used to produce a millable-type silicone rubber composition that does not contain crystal components; and that this composition makes it possible to obtain a silicone rubber cured product that has stable appearance and storage stability over the long term.

[0099] 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 millable type silicone rubber raw material mixture containing the following components (A) to (E): (A) 100 parts by mass of organopolysiloxane gum having two or more silicon-bonded alkenyl groups per molecule and an average degree of polymerization of 1,000 to 100,000; (B) A specific surface area measured by the BET adsorption method is 50 to 450 m ２ / g reinforcing silica: 5 to 100 parts by mass, (C) one or more dispersants selected from the following (C-1) and (C-2): (C-1) 1.0 to 50.0 parts by mass of an organosilane and / or siloxane having Si—OH groups at both ends, represented by the following general formula (1): 【Chemistry 1】 (In the formula, R １ are the same or different unsubstituted or substituted monovalent hydrocarbon groups having 1 to 8 carbon atoms, and m is an integer from 1 to 50. (C-2) A partial hydrolysis condensate of an alkoxysilane represented by the following general formula (2): The refractive index of the partial hydrolysis condensate is in the range of 1.39 to 1.41, and the kinematic viscosity is in the range of 1.0 to 1000 mm ２ / s: 0.1 to 20 parts by mass, R ２ Si(OR ３ ) 3 (2) (In the formula, R ２ are the same or different unsubstituted or substituted monovalent hydrocarbon groups having 1 to 12 carbon atoms, and R ３ represents a monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms. (D') a solution of a phosphite ester compound represented by the following general formula (3) dissolved in a hydrocarbon organic solvent having a boiling point of 80°C or less: 【Chemistry 2】 (In the formula, R ４ are independently a hydrogen atom or a monovalent aliphatic hydrocarbon group having 1 to 3 carbon atoms. The amount of the phosphite ester compound is 0.0010 to 0.10 parts by mass per 100 parts by mass of the component (A), (E) one or more condensation reaction catalysts selected from the following (E-1) to (E-3): (E-1) an amine compound that is liquid at 25°C and has a boiling point at 1013 hPa of 30 to 60°C: 0.0001 to 0.1 parts by mass, (E-2) Hexaorganodisilazanes represented by the following general formula (4): R ５ 3 SiNHSiR ５ 3 (4) (In the formula, R ５ represent the same or different monovalent hydrocarbon groups having 1 to 12 carbon atoms. : 0.001 to 1 part by mass, (E-3) 1.0 to 30.0 mass% ammonia water: 0.001 to 1 part by mass.

2. The millable silicone rubber raw material mixture according to claim 1, characterized in that the hydrocarbon organic solvent having a boiling point of 80°C or less is an organic solvent selected from n-pentane, n-hexane, 2-methylbutane, 2,2-dimethylbutane, 2,3-dimethylbutane, 2-methylpentane, and 3-methylpentane.

3. A method for producing a millable type silicone rubber compound, comprising: A method for producing a millable type silicone rubber compound, characterized by carrying out a process of removing the hydrocarbon-based organic solvent having a boiling point of 80°C or less from the millable type silicone rubber raw material mixture described in claim 1 or claim 2 while blocking oxygen.

4. A method for producing a millable silicone rubber composition, comprising: A method for producing a millable type silicone rubber composition, comprising the steps of: producing the compound by the method for producing a millable type silicone rubber compound according to claim 3; and then adding a curing agent (F) to the compound.

5. 5. The method for producing a millable silicone rubber composition according to claim 4, wherein the (F) curing agent is a hydrosilylation reaction curing agent comprising a combination of an organohydrogenpolysiloxane and a hydrosilylation catalyst.

6. A millable type silicone rubber compound containing the following components (A) to (E) but not containing any crystalline components. (A) 100 parts by mass of organopolysiloxane gum having two or more silicon-bonded alkenyl groups per molecule and an average degree of polymerization of 1,000 to 100,000; (B) A specific surface area measured by the BET adsorption method is 50 to 450 m ２ / g reinforcing silica: 5 to 100 parts by mass, (C) one or more dispersants selected from the following (C-1) and (C-2): (C-1) 1.0 to 50.0 parts by mass of an organosilane and / or siloxane having Si—OH groups at both ends, represented by the following general formula (1): 【Transformation 3】 (In the formula, R １ are the same or different unsubstituted or substituted monovalent hydrocarbon groups having 1 to 8 carbon atoms, and m is an integer from 1 to 50. (C-2) A partial hydrolysis condensate of an alkoxysilane represented by the following general formula (2): The refractive index of the partial hydrolysis condensate is in the range of 1.39 to 1.41, and the kinematic viscosity is in the range of 1.0 to 1000 mm ２ / s: 0.1 to 20 parts by mass, R ２ Si(OR ３ ) 3 (2) (In the formula, R ２ are the same or different unsubstituted or substituted monovalent hydrocarbon groups having 1 to 12 carbon atoms, and R ３ represents a monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms. (D) A phosphite ester compound represented by the following general formula (3): 【Chemistry 4】 (In the formula, R ４ are independently a hydrogen atom or a monovalent aliphatic hydrocarbon group having 1 to 3 carbon atoms. : 0.0010 to 0.10 parts by mass, (E) one or more condensation reaction catalysts selected from the following (E-1) to (E-3): (E-1) an amine compound that is liquid at 25°C and has a boiling point at 1013 hPa of 30 to 60°C: 0.0001 to 0.1 parts by mass, (E-2) Hexaorganodisilazanes represented by the following general formula (4): R ５ 3 SiNHSiR ５ 3 (4) (In the formula, R ５ represent the same or different monovalent hydrocarbon groups having 1 to 12 carbon atoms. : 0.001 to 1 part by mass, (E-3) 1.0 to 30.0 mass% ammonia water: 0.001 to 1 part by mass.

Images