Mirable-type silicone rubber compound, Mirable-type silicone rubber composition, and method for producing a Mirable-type silicone rubber composition

Abstract

To provide a millable silicone rubber compound having a high plasticity even if the millable silicone rubber compound has a relatively low hardness, a millable silicone rubber composition, and a production method for a millable silicone rubber composition.SOLUTION: The present invention provides a millable silicone rubber compound comprising (A) an organopolysiloxane crude rubber, (B) a reinforcing silica that has a specific surface area of 50-450 m2 / g, (C) a partial hydrolysate of an organoalkoxysilane represented by general formula (1), and (D) one or more condensation reaction catalysts selected from (D1)-(D3): (D1) an amine compound that is a liquid at 25°C and has a boiling point of 30-60°C at 1013 hPa; (D2) a hexaorganodisilazane represented by general formula (2); and (D3) aqueous ammonia at 1.0-30.0 mass%. Formula (1): RSi(OR1)3 and Formula (2): R23SiNHSiR23.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a millable-type silicone rubber compound, a millable-type silicone rubber composition, and a method for producing a millable-type silicone rubber composition. [Background technology]

[0002] Silicone rubber possesses excellent weather resistance, electrical properties, low compression set, heat resistance, and cold resistance, and is widely used in various fields such as electrical equipment, automobiles, construction, medical equipment, and food. The demand for silicone rubber is increasing, and there is a desire for the development of silicone rubber with further improved properties. These silicone rubbers are generally used in the form of millable-type silicone rubber compounds containing high-polymerization organopolysiloxane raw rubber and reinforcing fillers, and millable-type silicone rubber compositions in which a curing agent is added to this compound. These millable-type silicone rubber compounds and silicone rubber compositions are manufactured by mixing raw polymers with reinforcing fillers and various dispersants using kneading equipment such as a kneader or a double-roll kneader.

[0003] To manufacture Mirable-type silicone rubber compounds, as described above, it is necessary to knead reinforcing fillers such as fumed silica into organopolysiloxane. In this process, a surface treatment agent called a dispersant (wetter) is used for the reinforcing fillers. Typically, when dispersing reinforcing fillers such as silica in organopolysiloxane, organosilanes or siloxanes containing silanol groups are used as surface treatment agents. If the amount of surface treatment agent is too high, the plasticity of the silicone rubber compound decreases, and consequently, the plasticity of the silicone rubber composition also decreases. Using such a composition, depending on the molding method, such as extrusion molding, the uncured molded product may deform under its own weight, resulting in a defective product. In addition, there was the drawback of a sticky surface on the silicone rubber composition, which deteriorated processability. Conversely, if the amount of surface treatment agent added was insufficient, the plasticity increased, but crepe hardening, known as plasticity return, became excessive.

[0004] To address the problems described above, Patent Document 1 describes the addition of resin. Patent Document 2 describes that plasticity can be increased by adding a polycyclic aromatic compound having two or more phenyl groups. However, neither document mentions the problem of plasticity regression, and the additives are expensive. Patent Document 3 describes that plasticity regression can be suppressed by heating the silicone rubber compound at 200-250°C for 4-12 hours, but this is not economical. Patent Document 4 reports that plasticity can be increased by adding a catalyst for the condensation reaction of an organometallic compound selected from organotitanium compounds, organozirconium compounds, and organoaluminum compounds, and condensing silanol by heat treatment. While this method is indeed effective in increasing plasticity, it has been difficult to stably obtain the desired plasticity of the silicone rubber compound. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 06-256658 [Patent Document 2] Japanese Patent Application Publication No. 05-065415 [Patent Document 3] Japanese Patent Application Publication No. 07-133356 [Patent Document 4] Japanese Patent Publication No. 2014-109014 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The present invention has been made in view of the above circumstances, and aims to provide a millable-type silicone rubber compound, a millable-type silicone rubber composition, and a method for producing a millable-type silicone rubber composition that have high plasticity even in millable-type silicone rubber compounds with relatively low hardness. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides a millable silicone rubber compound, which is (A) 100 parts by 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 per molecule, (B) Reinforcing silica having a specific surface area of 50 to 450 m 2 / g as measured by the BET adsorption method, in an amount of 5 to 100 parts by mass, (C) 0.1 to 20 parts by mass of a partial hydrolyzate of an organoalkoxysilane represented by the following general formula (1), and RSi(OR 1 )3 (1) (In formula (1), R is a monovalent hydrocarbon group having 1 to 12 carbon atoms, and R 1 represents an alkyl group having 1 to 4 carbon atoms.) (D) one or more condensation reaction catalysts selected from the following (D1) to (D3) (D1) 0.0001 to 0.1 parts by mass of an amine compound that is liquid at 25°C and has a boiling point of 30 to 60°C at 1013 hPa, (D2) 0.001 to 1 part by mass of a hexaorganodisilazane represented by the following general formula (2), R 2 3SiNHSiR 2 3 (2) (In formula (2), R 2 are each independently an alkyl group having 1 to 12 carbon atoms.) (D3) 0.001 to 1 part by mass of 1.0 to 30.0 mass% aqueous ammonia, there is provided a millable silicone rubber compound comprising the above components.

[0008] Such a millable silicone rubber compound is a millable silicone rubber compound having high plasticity, even when it is a relatively low-hardness millable silicone rubber compound.

[0009] Further, in the present invention, R in formula (1) and R 1However, it is preferable that the group be independently one of a methyl group, an ethyl group, or a propyl group.

[0010] With such a millable-type silicone rubber compound, the effects of the present invention can be exhibited more effectively.

[0011] Furthermore, the present invention provides a millable-type silicone rubber composition comprising (E) a curing agent and a compound obtained by kneading the millable-type silicone rubber compound described above.

[0012] Such a millable-type silicone rubber composition will result in a millable-type silicone rubber composition with high plasticity, even in a millable-type silicone rubber compound with relatively low hardness.

[0013] In this case, it is preferable that component (E) is a curing agent for the hydrosilylation reaction, consisting of a combination of organohydrogenpolysiloxane and a hydrosilylation catalyst.

[0014] Such a (E) component is preferable because it contains fewer impurities that inhibit addition curing in the kneaded product of the millable-type silicone rubber compound of the present invention.

[0015] Furthermore, in this case, component (E) may be an organic peroxide.

[0016] Such curing agents can also be used in the millable-type silicone rubber composition of the present invention.

[0017] Furthermore, the present invention provides a method for producing a millable-type silicone rubber composition, which involves kneading the millable-type silicone rubber compound described above, removing component (D) by stirring heat while surface-treating component (B) with component (C) in the presence of component (D) which is a catalyst, and then adding a curing agent (E).

[0018] With this method of producing a millable-type silicone rubber composition, it is possible to produce a millable-type silicone rubber composition with high plasticity, even in millable-type silicone rubber compounds with relatively low hardness.

[0019] In this case, it is preferable to use a hydrosilylation reaction curing agent or organic peroxide consisting of a combination of organohydrogenpolysiloxane and a hydrosilylation catalyst as component (E).

[0020] Such curing agents can be used in the method for producing the millable-type silicone rubber composition of the present invention. [Effects of the Invention]

[0021] According to the method of the present invention, it is possible to provide a millable-type silicone rubber compound, a millable-type silicone rubber composition, and a method for producing a millable-type silicone rubber composition that can obtain high plasticity even in a millable-type silicone rubber compound with relatively low hardness. [Modes for carrying out the invention]

[0022] As described above, there has been a need to develop millable-type silicone rubber compounds, millable-type silicone rubber compositions, and methods for manufacturing millable-type silicone rubber compositions that possess high plasticity, even in millable-type silicone rubber compounds with relatively low hardness.

[0023] As a result of diligent research into the above-mentioned problems, the inventors of the present invention have found that the above-mentioned problems can be solved by a millable-type silicone rubber compound containing (A) a specific organopolysiloxane raw rubber, (B) reinforcing silica having a specific specific surface area, (C) a partially hydrolyzed organoalkoxysilane with a specific structure, and (D) a specific catalyst for a condensation reaction, and have completed the present invention.

[0024] In other words, the present invention is a millable type silicone rubber compound, (A) 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 per molecule: 100 parts by mass, (B) Reinforcing silica having a specific surface area of 50 to 450 m 2 / g measured by BET adsorption method: 5 to 100 parts by mass, (C) a partial hydrolyzate of an organoalkoxysilane represented by the following general formula (1): 0.1 to 20 parts by mass, and RSi(OR 1 )₃ (1) (In formula (1), R is a monovalent hydrocarbon group having 1 to 12 carbon atoms, and R 1 represents an alkyl group having 1 to 4 carbon atoms.) (D) one or more condensation reaction catalysts selected from the following (D1) to (D3) (D1) 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, (D2) a hexaorganodisilazane represented by the following general formula (2): 0.001 to 1 part by mass, R 2 ₃SiNHSiR 2 ₃ (2) (In formula (2), R 2 are each independently an alkyl group having 1 to 12 carbon atoms.) (D3) 1.0 to 30.0 mass% ammonia water: 0.001 to 1 part by mass, which is a millable silicone rubber compound comprising the above components.

[0025] Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.

[0026] [Millable Silicone Rubber Compound] The millable silicone rubber compound of the present invention is (A) 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 per molecule: 100 parts by mass, (B) Reinforcing silica having a specific surface area of 50 to 450 m 2Reinforcing silica per g: 5 to 100 parts by mass, (C) Partial hydrolysate of organoalkoxysilane represented by the following general formula (1): 0.1 to 20 parts by mass, and RSi(OR 1 )3(1) (In formula (1), R is a monovalent hydrocarbon group having 1 to 12 carbon atoms, 1 (This indicates an alkyl group with 1 to 4 carbon atoms.) (D) One or more condensation reaction catalysts selected from (D1) to (D3) below. (D1) Amine compound that is liquid at 25°C and has a boiling point of 30-60°C at 1013 hPa: 0.0001-0.1 parts by mass, (D2) Hexaorganodisilazane represented by the following general formula (2): 0.001 to 1 part by mass, R 2 3SiNHSiR 2 3(2) (In formula (2), R 2 (These are independently alkyl groups having 1 to 12 carbon atoms.) (D3) 1.0 to 30.0% by mass of aqueous ammonia: 0.001 to 1 part by mass, It includes. The following provides a detailed explanation of each component.

[0027] -(A) component- In the present invention, component (A) is 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 one molecule.

[0028] The above-mentioned alkenyl group is preferably an alkenyl group having 2 to 8 carbon atoms, and more preferably an alkenyl group having 2 to 6 carbon atoms. Specifically, examples include vinyl group, allyl group, butenyl group, pentenyl group, hexenyl group, and cyclohexenyl group. Among these, the vinyl group is preferred.

[0029] Other substituents besides the alkenyl group mentioned above include monovalent hydrocarbon groups having 1 to 12 carbon atoms, particularly 1 to 8 carbon atoms. Specifically, examples include alkyl groups such as methyl, ethyl, propyl, butyl, hexyl, and octyl groups; cycloalkyl groups such as cyclopentyl and cyclohexyl groups; aryl groups such as phenyl and tolyl groups; and aralkyl groups such as benzyl and 2-phenylethyl groups. Fluoroalkyl groups in which part of the alkyl group is substituted with fluorine atoms may also be used. Among these, methyl and phenyl groups are preferred, and methyl groups are particularly preferred.

[0030] Furthermore, component (A) is characterized by having alkenyl groups bonded to two or more silicon atoms in one molecule, preferably 2 to 50 alkenyl groups, more preferably 2 to 20 alkenyl groups. Among these, those having vinyl groups are particularly preferred. In this case, it is preferable that 0.01 to 20 mol%, and particularly 0.02 to 10 mol%, of the total siloxane units of the organopolysiloxane are siloxane units having alkenyl groups. These alkenyl groups may be bonded to silicon atoms at the end of the molecular chain, to silicon atoms in the middle of the molecular chain (non-terminal), or both, but it is preferable that they are bonded to silicon atoms at least at the end of the molecular chain.

[0031] Furthermore, it is desirable that 80 mol% or more, preferably 90 mol% or more, more preferably 95 mol% or more, of the total siloxane units in the organopolysiloxane, all siloxane units except for those having an alkenyl group are dialkylsiloxy groups, particularly dimethylsiloxy groups.

[0032] The molecular structure of the organopolysiloxane, which is component (A) above, is preferably linear or linear with a partially branched structure. Specifically, the repeating structure of the diorganosiloxane units constituting the main chain of the organopolysiloxane is preferably composed of repeating dimethylsiloxane units only, or it is preferable that diorganosiloxane units such as diphenylsiloxane units, methylphenylsiloxane units, methylvinylsiloxane units, or methyl-3,3,3-trifluoropropylsiloxane units are introduced as part of this structure.

[0033] Furthermore, it is preferable that both ends of the molecular chain are sealed with a group selected from, for example, a trimethylsiloxy group, a dimethylphenylsiloxy group, a vinyldimethylsiloxy group, a divinylmethylsiloxy group, or a trivinylsiloxy group, and it is particularly preferable that they be sealed with a vinyldimethylsiloxy group.

[0034] Examples of organopolysiloxanes of component (A) above include methylvinylpolysiloxane, methylphenylvinylpolysiloxane, and methyltrifluoropropylvinylpolysiloxane.

[0035] Such organopolysiloxanes can be obtained, for example, by (co)hydrolysis condensation of one or more organohalogenosilanes, or by ring-opening polymerization of cyclic polysiloxanes (such as trimers or tetramers of siloxanes) using an alkaline or acidic catalyst.

[0036] The average degree of polymerization of the above organopolysiloxane is 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. Furthermore, the properties of this organopolysiloxane are such that it does not self-flow at room temperature (25°C), resembling raw rubber (non-liquid). If the average degree of polymerization is too low, problems such as roll adhesion may occur when it is used as a compound, resulting in poor roll workability. If the average degree of polymerization is too high, when manufacturing the compound, the dispersion of reinforcing silica may be poor, the mixing time may be prolonged, or in the worst case, it may be impossible to obtain the desired compound. This degree of polymerization can be measured as the weight-average degree of polymerization in polystyrene terms by gel permeation chromatography (GPC) analysis.

[0037] (A) Component (A) may be used alone, or it may be a mixture of two or more components with different molecular weights (degrees of polymerization) or molecular structures.

[0038] -(B) Component- (B) The reinforcing silica of component (B) is a filler added to obtain a millable-type silicone rubber composition with excellent mechanical strength, and for this purpose, the specific surface area (BET adsorption method) is 50 to 450 m². 2 It must be / g, preferably 100-450m 2 / g, comfortable 100~300m 2 It is / g. The specific surface area is 50m². 2 A value less than / g is undesirable because it results in low mechanical strength of the cured product. Also, a specific surface area of ​​450 m² is desirable. 2 If the amount exceeds 450 m², it may lead to poor dispersion of reinforcing silica during compound manufacturing, increased mixing time, or in the worst case, failure to obtain the desired compound. 2 When reinforcing silica exceeding / g is used, the hardness of the cured product becomes extremely high, which also increases the likelihood of reduced flexibility.

[0039] Examples of such reinforcing silica include fumed silica and precipitated silica (wet silica). Furthermore, silica whose surfaces have been hydrophobized with chlorosilane or hexamethyldisilazane is also suitably used. Among these, fumed silica, which exhibits excellent dynamic fatigue properties, is preferred.

[0040] The above component (B) may be used alone or in combination of two or more types.

[0041] The amount of reinforcing silica in component (B) above is 5 to 100 parts by mass, preferably 10 to 50 parts by mass, per 100 parts by mass of organopolysiloxane raw rubber in component (A). If the amount of component (B) is too small, the reinforcing effect will not be obtained, and if it is too large, the processability will be poor, the mechanical strength will decrease, and the dynamic fatigue durability will also deteriorate.

[0042] -(C) component- In the present invention, as component (C), a partially hydrolyzed organoalkoxysilane represented by the following formula (1) is used. This component (C) reacts with the hydroxyl groups (hydroxysilyl groups) present on the surface of component (B) and is an essential component that acts as a surface treatment agent to rapidly and uniformly disperse component (B) in component (A). RSi(OR 1 )3(1) (In formula (1), R is a monovalent hydrocarbon group having 1 to 12 carbon atoms, 1 (This indicates an alkyl group with 1 to 4 carbon atoms.)

[0043] The R and R in formula (1) 1 However, it is preferable that the group be independently one of a methyl group, an ethyl group, or a propyl group.

[0044] Specific examples of the organoalkoxysilanes mentioned above 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 preferred, with trimethoxy(methyl)silane being more preferred. Partial hydrolysates of these organoalkoxysilanes are used as component (C). Since component (C) is a partial hydrolysate, it contains monovalent hydrocarbon groups derived from R and OR. 1 In addition to the alkoxy groups derived from the compound, some hydroxyl groups (hydroxysilyl groups) are also present.

[0045] Here, the degree of polymerization of the organoalkoxysilane partial hydrolysate of component (C) is preferably 2 to 100, and among these, a partial hydrolysate with a degree of polymerization of 2 to 30 as the main component is particularly preferred. If component (C) is not a partial hydrolysate, i.e., if a monomer is used, it becomes more volatile and volatilizes during mixing, resulting in unstable plasticity of the resulting silicone rubber compound. In addition, the amount of volatile components increases, which poses industrial hazards such as inhalation of volatile vapors and ignition. If the degree of polymerization of component (C) is 100 or less, the viscosity of component (C) does not increase, making it easier to blend and improving the surface treatment ability of component (B) above. Therefore, it contributes to shortening the blending time and stabilizing the plasticity of the resulting silicone rubber compound.

[0046] Furthermore, the kinematic viscosity of component (C) at 25°C is 1.0 to 1,000 mm². 2 A range of / s is preferred, and 1.5 to 500 mm 2 / s is more preferable, 1.5~300mm 2 A viscosity of / s is particularly preferred. This kinematic viscosity was measured using the Cannon-Fenske viscometer method described in JIS Z 8803:2011. This range is preferable because it facilitates blending with other components and suppresses volatile components.

[0047] Furthermore, the amount of the partially hydrolyzed organoalkoxysilane of component (C) added is preferably in the range of 0.1 to 20 parts by mass, 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 parts by mass, plasticity reversal may occur, resulting in problems with subsequent processability, or in the worst case, the compound may not be obtainable. Also, if the amount of component (C) added exceeds 20 parts by mass, the resulting compound may become sticky, resulting in poor subsequent processability, or the mechanical properties of the silicone rubber cured from this compound may decrease.

[0048] -(D) Component- Component (D) is a catalyst for the condensation reaction. It is intended to cause a condensation reaction between the hydroxysilyl groups present on the surface of the reinforcing silica of component (B) and the hydroxysilyl groups of component (C).

[0049] Furthermore, component (D) uses one or more condensation reaction catalysts selected from (D1) to (D3) below.

[0050] Component (D1) is a liquid amine compound at 25°C with a boiling point of 30-60°C at 1013 hPa. Specific examples of component (D1) include lower alkylamines such as propylamine (melting point: -83°C, boiling point: 49°C), isopropylamine (melting point: -101°C, boiling point: 33°C), and tert-butylamine (melting point: -72.65°C, boiling point: 46°C), as well as lower dialkylamines such as diethylamine (melting point: -50°C, boiling point: 56°C). The melting and boiling points mentioned above are those listed in the SDS issued by Fujifilm Wako Pure Chemical Industries, Ltd.

[0051] The amount of component (D1) 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 (D1) used is too small, the time required for surface treatment of the reinforcing silica may increase, or the degree of surface treatment may decrease, potentially resulting in the inability to obtain a mixed product of the millable-type silicone rubber compound. Conversely, if the amount of component (D1) used is too large, the component (D1) may not be removed from the mixed product of the millable-type silicone rubber compound, potentially leading to an increase in plasticity over time. Furthermore, if a cured silicone rubber product is obtained by addition curing using a platinum catalyst, the physical properties of the cured product may be unstable, or tack (adhesion) may occur on the surface of the cured product due to insufficient curing.

[0052] The (D2) component is a hexaorganodisilazane represented by the following general formula (2). R 2 3SiNHSiR 2 3(2) (In formula (2), R 2 (These are independently alkyl groups having 1 to 12 carbon atoms.)

[0053] In equation (2) above, R 2 Examples include those similar to R in component (A) above, but alkyl groups having 1 to 6 carbon atoms, such as methyl groups and ethyl groups, are particularly preferred. Furthermore, the molecule may also contain alkenyl groups such as vinyl groups.

[0054] Specific examples of component (D2) include hexamethyldisilazane, 1-vinylpentamethyldisilazane, 1,3-divinyl-1,1,3,3-tetramethyldisilazane, and 1,3-dimethyl-1,1,3,3-tetravinyldisilazane, but hexamethyldisilazane and 1,3-divinyl-1,1,3,3-tetramethyldisilazane are preferred, and hexamethyldisilazane is more preferred.

[0055] The amount of component (D2) added is 0.001 to 1 part by mass, preferably 0.01 to 0.50 parts by mass, and more preferably 0.01 to 0.3 parts by mass, per 100 parts by mass of component (A). If the amount of component (D2) used is too small, the time required for surface treatment of the reinforcing silica may increase, or the degree of surface treatment may decrease, potentially resulting in the inability to obtain a kneaded millable-type silicone rubber compound. Conversely, if the amount of component (D2) used is too large, the component (D2) may not be able to be removed from the kneaded millable-type silicone rubber compound, potentially leading to an increase in plasticity over time. Furthermore, if a cured silicone rubber product is obtained by addition curing using a platinum catalyst, the physical properties of the cured product may be unstable, or tack may occur on the surface of the cured product due to insufficient curing. This is also undesirable from an economic standpoint.

[0056] Component (D3) 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 15.0 to 28.0% by mass.

[0057] The amount of component (D3) added is 0.001 to 1 part by mass, preferably 0.005 to 1 part by mass, and more preferably 0.01 to 0.8 parts by mass, per 100 parts by mass of component (A). If the amount of component (D3) used is too small, the time required for surface treatment of the reinforcing silica may increase, or the degree of surface treatment may decrease, making it impossible to obtain a kneaded millable-type silicone rubber compound. Conversely, if the amount of component (D3) used is too large, the component (D3) may not be removed from the kneaded millable-type silicone rubber compound, leading to an increase in plasticity over time, or, if 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 tack may occur on the surface of the cured product due to insufficient curing. Furthermore, this is also undesirable from an economic standpoint.

[0058] There are no particular restrictions on the method of adding component (D) above, but it is preferable to add component (D) to component (C) above, and then quickly add it to the kettle containing component (B). This allows the condensation reaction between the hydroxysilyl group of component (B) and the hydroxysilyl group of component (C) to proceed efficiently. In addition, to make it easier to knead component (D) with a double roll or kneader, component (D) may be used in a paste form prepared in advance with an organopolysiloxane or the like.

[0059] The millable-type silicone rubber compound of the present invention is preferably manufactured using an apparatus capable of uniformly mixing predetermined amounts of the above-mentioned components (A) to (D). There are no particular restrictions on the apparatus capable of uniform mixing, but considering the reactivity of component (D) and its removal after the reaction is complete, it is preferable to use an apparatus that easily generates stirring heat. Specifically, the millable-type silicone rubber compound can be obtained by mixing using a kneader, Banbury mixer, roll mill, etc., but it is particularly preferable to manufacture it using a kneader.

[0060] When components (A) to (D) above are mixed, the partial hydrolysate of the organoalkoxysilane, component (C), acts as a wetter for the reinforcing silica, component (B). Adding the condensation reaction catalyst, component (D), is effective in promoting this wetting effect. In this case, water may be added as an optional component to further promote wetting. By adding this component, the partial hydrolysate of the organoalkoxysilane, component (C), rapidly acts as a wetter for the reinforcing silica, component (B). In order to effectively treat the hydroxysilyl groups present on the surface of component (B), it is essential that component (C) contains reactive groups that react rapidly with hydroxysilyl groups. For this reason, the partial hydrolysate of the organoalkoxysilane, which contains many reactive groups with hydroxysilyl groups in its molecule and hardly undergoes three-dimensional crosslinking, is effective.

[0061] Here, the preferred temperature for mixing components (A) to (D) is 0 to 200°C, more preferably 10 to 180°C, and even more preferably 20 to 170°C. Furthermore, while there are no particular restrictions on the mixing time of components (A) to (D), considering manufacturing efficiency, it is desirable to use conditions of 1 to 300 minutes, more preferably 10 to 120 minutes.

[0062] When components (A) to (D) are mixed using the method described above, stirring heat is generated. The amount of stirring heat generated varies depending on the degree of polymerization of component (A) used, the amount of reinforcing silica added to component (B), and the addition ratio of components (A) to (B). Specifically, if a composition suitable for millable-type silicone rubber compound is used, i.e., a composition similar to that of conventional millable-type silicone rubber compound, stirring heat of approximately 30 to 120°C is generated. Here, component (D) is liquid during compounding, making it easy to handle, and it also exhibits excellent reactivity with components (B) and (C). In particular, in the case of component (D1), since its boiling point at atmospheric pressure of 1013 hPa is 30 to 60°C, component (D) can be removed from the millable-type silicone rubber compound using only the stirring heat generated during compounding. Furthermore, when components (D2) or (D3) are added, ammonia is generated by water etc. present in the system, which further promotes the reaction between components (B) and (C). This ammonia can be removed from the millable-type silicone rubber compound solely by the heat generated during stirring during the compounding process.

[0063] Therefore, we can supply the market with the same type of millable silicone rubber compound as before, while contributing to environmental issues such as the recent trend towards a decarbonized society and reduction of CO2 emissions.

[0064] Furthermore, since the condensation reaction catalyst of component (D) used in this invention hardly remains in the mixture obtained by kneading the millable-type silicone rubber compound, there are no problems such as catalyst poisoning in the hydrosilylation reaction. For this reason, it can be suitably used even when an addition-type curing agent is used.

[0065] [Miracle-type silicone rubber composition] Furthermore, the Mirable-type silicone rubber composition of the present invention comprises (E) a curing agent and a kneaded mixture obtained by kneading the Mirable-type silicone rubber compound.

[0066] -(E) Component- (E) The curing agent is not particularly limited as long as it can cure the above-mentioned (A) component, but (E1) addition reaction (hydrosilylation reaction) type curing agents, which are generally known as rubber curing agents, i.e., hydrosilylation reaction curing agents consisting of a combination of organohydrogenpolysiloxane (crosslinking agent) and a hydrosilylation catalyst, or (E2) organic peroxides are preferred.

[0067] The organohydrogenpolysiloxane used as a crosslinking agent for the above (E1) addition reaction type curing agent has two or more hydrosilyl groups in one molecule. In particular, the organohydrogenpolysiloxane represented by the following formula (3) is preferred. [ka] (In formula (3), R 3 R is independently selected from a hydrogen atom, or 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, with two or more R groups in one molecule. 3 This represents a hydrogen atom. Note that there cannot be more than one hydrogen atom on the same silicon atom. a is an integer between 2 and 30, b is an integer between 0 and 300, c is an integer between 0 and 10, and d is an integer between 0 and 30. Note that the bonding of each siloxane unit may be block-based or random.

[0068] Here, R 3 R is independently selected from a hydrogen atom, or an alkyl group having 1 to 8 carbon atoms, preferably 1 to 6 carbon atoms, an aryl group having 6 to 10 carbon atoms, preferably 6 to 8 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms, preferably 7 to 9 carbon atoms. However, there are 2 or more R groups per molecule, preferably 2 to 200, more preferably 2 to 130. 3This is a hydrogen atom. Note that there cannot be two or more hydrogen atoms on the same silicon atom. Examples of alkyl groups include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, and hexyl groups, as well as cycloalkyl groups such as cyclohexyl. 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 part of the alkyl group is substituted with a fluorine atom may also be used. Furthermore, a is an integer between 2 ≤ a ≤ 30, preferably 2 ≤ a ≤ 20. b is an integer between 0 ≤ b ≤ 300, preferably 3 ≤ b ≤ 200. c is an integer between 0 ≤ c ≤ 10, preferably 0 ≤ c ≤ 5. and d are integers between 0 ≤ d ≤ 30, preferably 0 ≤ d ≤ 20.

[0069] Furthermore, the molecular structure of the organohydrogenpolysiloxane may be linear, cyclic, branched, or three-dimensional network structure. In this case, the number of silicon atoms (or degree of polymerization) in one molecule should be 2 to 300, and a liquid at 25°C with approximately 4 to 200 silicon atoms is particularly preferred. Note that the hydrosilyl group may be located at the end of the molecular chain, in the side chain (middle of the molecular chain), or both.

[0070] Examples of these organohydrogenpolysiloxanes include 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, methylhydrogencyclopolysiloxane, methylhydrogensiloxane-dimethylsiloxane cyclic copolymer, tris(dimethylhydrogensiloxy)methylsilane, tris(dimethylhydrogensiloxy)phenylsilane, methylhydrogenpolysiloxane with trimethylsiloxy groups sealed at both ends, dimethylsiloxane-methylhydrogensiloxane copolymer with trimethylsiloxy groups sealed at both ends, and dimethylhydrogen Siloxy group-sealed dimethylpolysiloxane, dimethylsiloxane-methylhydrogensiloxane copolymer with dimethylhydrogensiloxane at both ends, methylhydrogensiloxane-diphenylsiloxane copolymer with trimethylsiloxy groups at both ends, methylhydrogensiloxane-diphenylsiloxane-dimethylsiloxane copolymer with trimethylsiloxy groups at both ends, methylhydrogensiloxane-diphenylsiloxane-dimethylsiloxane copolymer, (CH3)2HSiO 1 / 2 Units and SiO 4 / 2 A copolymer consisting of units, (CH3)2HSiO 1 / 2 Units and SiO 4 / 2 Units and (C6H5)SiO 3 / 2 Examples include copolymers consisting of units, and in each of the above example compounds, some or all of the methyl groups are substituted with other alkyl groups such as ethyl groups and propyl groups, or aryl groups such as phenyl groups. Specifically, examples of such organohydrogenpolysiloxanes include compounds with the following structural formulas.

[0071] [ka] (In the formula, k is an integer between 2 and 10, and s and t are integers between 0 and 10.)

[0072] The organohydrogen polysiloxane is preferably one with a viscosity of 0.5 to 10,000 mPa·s, and particularly preferably 1 to 300 mPa·s, at 25°C. The viscosity is measured using a rotational viscometer according to the method described in JIS K 7117-1:1999.

[0073] Furthermore, it is desirable that the organohydrogenpolysiloxane be blended in an amount such that the molar ratio (hydrosilyl group / alkenyl group) of hydrogen atoms (i.e., hydrosilyl groups) bonded to silicon atoms in the organohydrogenpolysiloxane to the alkenyl groups bonded to silicon atoms in component (A) is 0.5 to 10, preferably 0.8 to 6, and more preferably 1 to 5. If the ratio is 0.5 or higher, sufficient crosslinking is achieved and sufficient mechanical strength is obtained, and if it is 10 or lower, the physical properties after curing do not deteriorate, and in particular, the heat resistance and compression set resistance do not deteriorate.

[0074] Furthermore, the hydrosilylation catalyst used in the (E1) addition reaction type curing agent is a catalyst that promotes the addition reaction between the alkenyl group in component (A) and the hydrosilyl group in the organohydrogenpolysiloxane used as a crosslinking agent. Examples of hydrosilylation catalysts include platinum group metal catalysts such as ruthenium and platinum. Platinum group metal catalysts include the elemental platinum metals and their compounds. For this, catalysts that have been conventionally known as catalysts for addition reaction curing type silicone rubber compositions can be used. Examples include particulate platinum metal adsorbed on a carrier such as silica, alumina, or silica gel, dic platinum chloride, chloroplatinic acid, reaction products of chloroplatinic acid and monohydric alcohols, complexes of chloroplatinic acid and olefins, complexes of chloroplatinic acid and vinyl group-containing (poly)siloxanes, complexes of chloroplatinic acid and phosphite esters, and complexes of these with vinyl group-containing (poly)siloxanes, as well as palladium catalysts, rhodium catalysts, ruthenium catalysts, etc. Among these, platinum or platinum compounds are particularly preferred.

[0075] The amount of hydrosilylation catalyst added should be a catalytic amount sufficient to promote the addition reaction. Typically, it is used in the range of 1 ppm to 1% by mass, calculated as the mass of platinum group metal relative to the amount of component (A) above, but a range of 10 to 500 ppm is preferred. If the amount added is 1 ppm or more, the addition reaction is sufficiently promoted and hardening is sufficient, while if it is 1% by mass or less, it is economical.

[0076] In addition to the catalysts mentioned above, an addition crosslinking control agent may be used to adjust the curing rate. Examples include ethinylcyclohexanol and tetramethyltetravinylcyclotetrasiloxane.

[0077] On the other hand, examples of the above (E2) organic peroxides include benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, p-methylbenzoyl peroxide, o-methylbenzoyl peroxide, 2,4-dicumyl peroxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, di-t-butyl peroxide, t-butyl perbenzoate, and 1,6-hexanediol-bis-t-butyl peroxycarbonate.

[0078] The amount of organic peroxide added is preferably 0.1 to 15 parts by mass, and particularly preferably 0.2 to 10 parts by mass, per 100 parts by mass of component (A). If the amount added is 0.1 parts by mass or more, the crosslinking reaction proceeds sufficiently, and deterioration of physical properties such as a decrease in hardness, insufficient rubber strength, and increased compression set does not occur. Furthermore, if the amount added is 15 parts by mass or less, it is economically preferable, as the amount of decomposition products of the curing agent is sufficiently small, and deterioration of physical properties such as increased compression set and discoloration of the obtained sheet do not increase.

[0079] In addition to the above components, the millable silicone rubber composition of the present invention may contain, depending on the purpose of the present invention, conductive agents such as carbon black, flame retardants such as iron oxide and halogen compounds, antistatic agents, softeners, anti-aging agents, ultraviolet absorbers, colorants, and the like.

[0080] The millable-type silicone rubber composition of the present invention obtained in this manner can be cured at 60 to 300°C, particularly 80 to 200°C, for 5 seconds to 1 hour, particularly 30 seconds to 30 minutes, to obtain a cured silicone rubber product.

[0081] [Method for producing a millable-type silicone rubber composition] The millable-type silicone rubber composition of the present invention can be obtained by kneading the millable-type silicone rubber compound described above, removing component (D) by stirring heat while surface treating component (B) with component (C) in the presence of component (D) which is a catalyst, and then adding the curing agent (E).

[0082] In this case, it is preferable to use a hydrosilylation reaction curing agent or organic peroxide consisting of a combination of organohydrogenpolysiloxane and a hydrosilylation catalyst as component (E). [Examples]

[0083] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples. The melting point and boiling point are given at 1013 hPa, the average degree of polymerization was measured as the weight-average degree of polymerization in polystyrene terms by gel permeation chromatography (GPC) analysis, the viscosity was measured using a rotational viscometer according to the method described in JIS K 7117-1:1999, the kinematic viscosity was measured using a Cannon-Fenske viscometer according to the method described in JIS Z 8803:2011, and the refractive index was measured using an Abbe refractometer according to the method described in JIS K 0062:1992.

[0084] The following are specific examples of the components used in the examples and comparative examples of the present invention.

[0085] (A) Organopolysiloxane raw rubber This organopolysiloxane raw rubber consists 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.

[0086] (B) Reinforced silica (B-1) Specific surface area of ​​200 m² obtained by BET adsorption method 2 / g of fumed silica (product name: Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) (B-2) Specific surface area of ​​130 m² obtained by BET adsorption method 2 / g of surface-treated silica (product name: Aerosil R-972, manufactured by Nippon Aerosil Co., Ltd.)

[0087] (C) Partial hydrolysate of organoalkoxysilane (C-1) Partial hydrolysate of trimethoxy(methyl)silane (product name: KC-89S, manufactured by Shin-Etsu Chemical Co., Ltd., kinematic viscosity [25℃]: 5 mm) 2 ( / s, refractive index [25℃]: 1.394) (C-2) Partial hydrolysate of trimethoxy(methyl)silane (Trade name: X-40-9225, manufactured by Shin-Etsu Chemical Co., Ltd., kinematic viscosity [25℃]: 100 mm) 2 ( / s, refractive index [25℃]: 1.407) (C-3) Trimethoxy(methyl)silane (Trade name: KBM-13, manufactured by Shin-Etsu Chemical Co., Ltd., kinematic viscosity [25℃]: 0.5 mm) 2 / s) [For comparative example] (C-4) Linear partial hydrolysate of tetramethoxysilane (product name: methyl silicate oligomer MKC silicate MS-51, manufactured by Mitsubishi Chemical Corporation, kinematic viscosity [25℃]: 7 mm) 2 / s) [For comparative example]

[0088] (D) Catalyst for condensation reaction (D1) Amine compounds that are liquid at 25°C (low boiling point amine compounds) Isopropylamine (melting point: -101°C, boiling point: 33°C) (D2) Hexaorganodisilazon Hexamethyldisilazane (product name: SZ-31, manufactured by Shin-Etsu Chemical Co., Ltd.) (D3) Ammonia water 28% by mass aqueous ammonia

[0089] Each of the above components was blended in the amounts listed in Table 1, and a mixture of Mirable-type silicone rubber compound was obtained through the following process.

[0090] [Manufacturing process for the mixed material of Mirable-type silicone rubber compound] In a 3L kneader, 100 parts by mass of component (A) and 40 parts by mass of component (B) were mixed with components (C) and (D) in the amounts shown in Table 1. After uniform mixing, the mixture was further kneaded for 2 hours at the temperature shown in Table 1 to obtain a compound of Mirable-type silicone rubber. In Table 1, "heat treatment mixing" refers to a method in which the mixture is heated from the outside to a set temperature and then mixed for a specified time, while "simple mixing" refers to mixing from room temperature for a specified time using only the heat of stirring, without external heating.

[0091] ○ Plasticity measurement The millable-type silicone rubber compounds prepared in Examples 1-6 and Comparative Examples 1-2 were kneaded 15 times using a three-roll milling machine. After 10 minutes (initial), the William plasticity was measured using the method described in JIS K6249:2003. Subsequently, the plasticity was measured again after 1 day at 40°C. The change over time was evaluated by calculating the change in plasticity from the initial value to the plasticity after 1 day at 40°C. Products with a change over time value within ±50 were judged as passing (equivalent to or better than conventional products), while those deviating from this range were judged as failing (worse than conventional products).

[0092] ○ Measurement of physical properties For 100 parts by mass of the millable-type silicone rubber compound kneaded in Examples 1-6 and Comparative Examples 1-2, 0.01 parts by mass of a platinum catalyst (manufactured by Shin-Etsu Chemical Co., Ltd.) containing 1% by mass of a chloroplatinate-divinyldisiloxane complex in terms of platinum atomic mass, and the following formula as an addition reaction type curing agent: (E1) [ka] 0.85 parts by mass of organohydrogen polysiloxane (manufactured by Shin-Etsu Chemical Co., Ltd.) was added and uniformly mixed to prepare a millable-type silicone rubber composition. This composition was then press-cured at 120°C for 10 minutes, followed by post-curing at 200°C for 4 hours to prepare test sheets. 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 description in JIS K 6249:2003. In addition, the rebound modulus was measured according to the method described in JIS K 6255:2013. Among these values, those with an elongation at break of 500% or less, or a compression set exceeding 30%, were judged to be unacceptable due to their inferior physical properties.

[0093] [Table 1]

[0094] [Evaluation Results] Each of the millable-type silicone rubber compounds obtained in Examples 1 to 6 satisfies the requirements of the present invention, and it can be seen that the physical properties of the kneaded mixtures of each millable-type silicone rubber compound, and the physical properties of the molded test sheets of the millable-type silicone rubber compositions prepared using them, satisfy the performance of the target values.

[0095] In contrast, in Comparative Example 1, although the structure of component (C), organoalkoxysilane, is the same, it is not a partial hydrolysate. As a result, the organoalkoxysilane added during kneading and heat treatment mixing volatilizes, reducing the surface treatment degree of component (B), reinforcing silica. Consequently, the initial plasticity is high, and the plasticity after 40°C × 24 hours is also high. In addition, the physical properties of the molded test sheet of the millable-type silicone rubber composition prepared using the kneaded product of the millable-type silicone rubber compound of Comparative Example 1 show that the elongation at break and compression set are worse compared to Examples 1 to 6. Therefore, the results deviate from the target values.

[0096] Furthermore, in Comparative Example 2, a partially hydrolyzed product with a different structure of the organoalkoxysilane, which is component (C), is used. Because this partially hydrolyzed product has a high ability to crosslink in three dimensions, the initial plasticity of the resulting millable-type silicone rubber compound mixture is very high, and an increase in plasticity can be confirmed after 24 hours at 40°C. However, a millable-type silicone rubber compound mixture with such a high initial plasticity also has reduced mixing uniformity. Therefore, the physical properties of the molded test sheet of the millable-type silicone rubber composition prepared using this millable-type silicone rubber compound mixture show that the elongation at break and compression set are worse compared to Examples 1 to 6.

[0097] From the above results, it was found that the millable-type silicone rubber compound of the present invention can produce a very stable millable-type silicone rubber compound mixture regardless of the mixing conditions, and that the millable-type silicone rubber composition made using it also exhibits very good physical properties.

[0098] [Industrial applicability] The millable-type silicone rubber compound of the present invention, and the millable-type silicone rubber composition obtained by blending a curing agent into the kneaded mixture of the compound, can provide a millable-type silicone rubber compound and a millable-type silicone rubber composition that can have high plasticity even in a relatively low-hardness millable-type silicone rubber compound. Therefore, it can contribute to the dimensional stability of low-hardness extruded materials and the like. Furthermore, a millable-type silicone rubber composition using the kneaded mixture of this millable-type silicone rubber compound can be expected to have a wide range of applications in fields such as electrical equipment, automobiles, construction, medical, and food.

[0099] It should be noted that the present invention is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the claims of the present invention and achieves similar effects is included within the technical scope of the present invention.

Claims

1. It is a Mirable-type silicone rubber compound, (A) Organopolysiloxane raw rubber having two or more alkenyl groups bonded to silicon atoms in one molecule and an average degree of polymerization of 1,000 to 100,000: 100 parts by mass, (B) Specific surface area of ​​50 to 450 m² by BET adsorption method ２ Reinforcing silica per g: 5 to 100 parts by mass, (C) Partial hydrolysis condensate of organoalkoxysilane represented by the following general formula (1): 0.1 to 20 parts by mass, and RSi(OR １ ) ３ (1) (In formula (1), R is a monovalent hydrocarbon group having 1 to 12 carbon atoms, R １ (This represents an alkyl group having 1 to 4 carbon atoms.) (D) One or more condensation reaction catalysts selected from (D1) to (D3) below (D1) Amine compound that is liquid at 25°C and has a boiling point of 30-60°C at 1013 hPa: 0.0001-0.1 parts by mass, (D2) Hexaorganodisilazane represented by the following general formula (2): 0.001 to 1 part by mass, R ２ ３ SiNHSiR ２ ３ (2) (In formula (2), R ２ are each independently an alkyl group having 1 to 12 carbon atoms.) (D3) 1.0 to 30.0% by mass of aqueous ammonia: 0.001 to 1 part by mass, A kneaded raw material composition containing the above, wherein the kinematic viscosity of component (C) at 25°C is 1.5 to 1,000 mm². ２ A Mirable-type silicone rubber compound characterized by being / s.

2. The R and R in formula (1) １ The millable-type silicone rubber compound according to claim 1, characterized in that the group is independently one of a methyl group, an ethyl group, and a propyl group.

3. A millable-type silicone rubber composition characterized by comprising (E) a millable-type silicone rubber compound according to claim 1 or claim 2 and a curing agent.

4. The millable-type silicone rubber composition according to claim 3, characterized in that the (E) component is a curing agent for a hydrosilylation reaction, comprising a combination of an organohydrogenpolysiloxane and a hydrosilylation catalyst.

5. The millable-type silicone rubber composition according to claim 3, characterized in that the (E) component is an organic peroxide.

6. A method for producing a millable-type silicone rubber composition, characterized in that, during the preparation of the millable-type silicone rubber compound according to claim 1 or claim 2, the (D) component is removed by stirring heat while surface treatment of the (B) component with the (C) component in the presence of the (D) component which is a catalyst during the kneading of the raw material composition, and the (E) curing agent is added to the prepared millable-type silicone rubber compound.

7. The method for producing a millable-type silicone rubber composition according to claim 6, characterized in that the (E) component is a hydrosilylation reaction curing agent or organic peroxide consisting of a combination of organohydrogenpolysiloxane and a hydrosilylation catalyst.

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