Mirable-type silicone rubber compound and Mirable-type silicone rubber composition

Abstract

Provided is a millable silicone rubber compound excellent in cold resistance, which can maintain rubber elasticity in an ultra-low temperature range without using various conventional techniques for improving cold resistance. 【Solution means】A millable silicone rubber compound containing the following components (A) to (E). (A) The following formula (1) M n M Vi (2-n) D γ D Vi δ (1) M:R 1 3SiO (1 / 2) M Vi :R 1 2RSiO (1 / 2) D:R 1 2SiO (2 / 2) D Vi :R 1 RSiO (2 / 2) (In the formula, R is independently an alkenyl group, R 1 is independently an unsubstituted or substituted monovalent hydrocarbon group not containing an aliphatic unsaturated bond. n is a positive number from 0 to 2. γ satisfies (γ / (γ + δ)) ≤ 0.98, δ satisfies (δ / (γ + δ)) ≥ 0.02, and (γ + δ) is a positive number such that (γ + δ) ≥ 6000.) raw rubber represented by (B) A compound having one hydrogen atom bonded to a silicon atom, (C) A specific dispersant, (D) Reinforcing silica having a specific specific surface area, (E) An addition reaction catalyst

Description

Technical Field

[0001] The present invention relates to a millable silicone rubber compound and a silicone rubber composition using the compound.

Background Art

[0002] Silicone rubber has properties such as 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, and food. The demand for silicone rubber is increasing day by day, and the development of silicone rubber with further improved these properties is desired. These silicone rubbers are generally used in the form of a millable silicone rubber compound containing a high-polymerization-degree organopolysiloxane raw rubber and a reinforcing filler, and a millable silicone rubber composition obtained by blending a curing agent with this compound. This millable silicone rubber compound and silicone rubber composition are used for electronic members such as in-vehicle electronic components and consumer electronic components because they are excellent in heat resistance, weather resistance, oil resistance, cold resistance, electrical insulation, etc. In recent years, due to requirements such as higher reliability of in-vehicle electronic components and consumer electronic components, the demand for a material that can maintain rubber elasticity even in a wide temperature range (especially in the ultra-low temperature range exceeding -40°C) for the silicone rubber material used as a member has been increasing.

[0003]

[0004] ​Due to the increasing demand for such properties, various cold resistance improvement technologies have been researched in recent years. For example, in the field of silicone gel compositions, Japanese Patent Publication No. 2000-169714 (Patent Document 1) describes how cold resistance can be improved by introducing phenyl groups into the base polymer. However, it has been found that using such phenyl group-containing base oils results in high costs, and when exposed to high temperatures exceeding 200°C for extended periods, the phenyl groups in the base polymer decompose, releasing benzene, which is a problem. Furthermore, introducing phenyl groups into the base polymer leaves behind phenyl group-containing low-molecular-weight impurities, which can adversely affect electronic substrates and components.

[0005] Furthermore, Japanese Patent Publication No. 2001-2922 (Patent Document 2) describes how improved cold resistance is achieved by incorporating a resin-structured organopolysiloxane. However, resin-structured organopolysiloxanes are expensive and have a high relative viscosity to the degree of polymerization, making them difficult to manufacture millable silicone rubber compounds and resulting in poor workability. In addition, the rubber hardens rapidly in the low-temperature range below -50°C, which means that the proposed technology cannot maintain rubber elasticity in the ultra-low temperature range.

[0006] Furthermore, International Publication No. 2012 / 50105 (Patent Document 3) reports a technology that suppresses changes in the rubber elasticity of cured products at low temperatures and improves cold resistance by using a large amount of branched polyorganosiloxane as the base polymer. However, since a large amount of branched polyorganosiloxane is essential, it is necessary to produce this branched polyorganosiloxane in large quantities. In addition, controlling the polymer structure during the production of branched polyorganosiloxane is extremely difficult, and increasing the number of branching points within a single molecule leads to unstable viscosity during production, and increases the risk of thickening or gelation, making it difficult to increase the number of branching points within a single molecule. Moreover, the need for a large amount of branched polyorganosiloxane also presents disadvantages in terms of raw material procurement and cost.

[0007] Furthermore, a method has been proposed for obtaining a cold-resistant silicone composition without having to procure the special raw materials mentioned above. For example, Japanese Patent Publication No. 08-32785 (Patent Document 4) is known. This proposal is a technique for obtaining a cold-resistant silicone gel composition by polymerizing a polymerizable polymer having alkenyl groups in its side chains with a monofunctional methylhydrogensiloxane and a bifunctional methylhydrogensiloxane in the presence of an addition reaction catalyst. However, although it is possible to obtain a cold-resistant silicone gel composition by this method, the problem of the rubber elasticity changing rapidly in the low-temperature range below -50°C has not been improved.

[0008] As a technology for improving the cold resistance of silicone rubber compositions, International Publication No. 2008 / 1625 (Patent Document 5) proposes a method using vinyl group-introduced methylfluoroalkyl vinyl silicone rubber obtained by copolymerizing dimethylsiloxane units, methylfluoroalkylsiloxane units, and methylvinylsiloxane units. Furthermore, International Publication No. 2007 / 145313 (Patent Document 6) reports on improving cold resistance by using vinyl group-introduced methylphenyl vinyl silicone rubber obtained by copolymerizing dimethylsiloxane units and methylphenylsiloxane units. However, since such special copolymerized raw rubbers are not used for general purposes, there were problems in terms of raw material procurement and cost. In addition, methylfluoroalkylsiloxane is classified as a PFAS (perfluoroalkyl and polyfluoroalkyl compound), which may cause environmental problems, and methylphenylsiloxane contains phenyl groups, so when exposed to high temperatures exceeding 200°C for a long time, the phenyl groups in the base polymer decompose, releasing benzene, which is a problem. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2000-169714 [Patent Document 2] Japanese Patent Publication No. 2001-2922 [Patent Document 3] International Publication No. 2012 / 50105 [Patent Document 4] Special Publication No. 08-32785 [Patent Document 5] International Publication No. 2008 / 1625 [Patent Document 6] International Publication No. 2007 / 145313 [Overview of the project] [Problems that the invention aims to solve]

[0010] The present invention has been made in view of the above circumstances, and aims to provide a millable-type silicone rubber compound with excellent cold resistance that can easily maintain rubber elasticity in the ultra-low temperature range without using various conventional techniques to improve cold resistance, and a silicone rubber composition using the compound. [Means for solving the problem]

[0011] The inventors of the present invention have conducted diligent studies to achieve the above objectives and have found that, as a base polymer used to obtain a millable-type silicone rubber compound, an organopolysiloxane having 2 mol% or more of alkenyl groups bonded to silicon atoms in the side chains of one molecular chain is used, and that by reacting this compound with a specific compound having one hydrogen atom bonded to a silicon atom in one molecule in the presence of an addition reaction catalyst to impart cold resistance to the compound, it is possible to easily obtain a millable-type silicone rubber compound with cold resistance. Furthermore, the inventors have found that by reacting this millable-type silicone rubber compound with an organohydrogenpolysiloxane containing a hydrogen atom, or by adding an organic peroxide and reacting it, a silicone rubber composition that can maintain rubber elasticity even in the ultra-low temperature range can be obtained, leading to the present invention.

[0012] Therefore, the present invention provides the following millable silicone rubber compound and a silicone rubber composition using the compound. 1. A millable silicone rubber compound comprising the following components (A) to (E). (A) The following average composition formula (1) M n M Vi (2-n) D γ D Vi δ (1) M:R 1 3SiO (1 / 2) M Vi :R 1 2RSiO (1 / 2) D:R 1 [[ID=3"2]]2SiO (2 / 2) D Vi :R 1 RSiO (2 / 2) (In the formula, M, M Vi , D, D Vi are the units shown above, respectively. R is independently an alkenyl group, and R 1 is independently an unsubstituted or substituted monovalent hydrocarbon group containing no aliphatic unsaturated bond. n is a positive number from 0 to 2. Also, γ satisfies (γ / (γ + δ)) ≤ 0.98, δ satisfies (δ / (γ + δ)) ≥ 0.02, and (γ + δ) ≥ 6000, where γ and δ are positive numbers.) Raw rubber represented by: 100 parts by mass, (B) The following general formula (2)

Chemical formula

Chemical formula

[0013] The present invention provides a millable-type silicone rubber compound that can easily maintain rubber elasticity even in ultra-low temperature ranges without using special raw materials, and a silicone rubber composition using the compound. [Modes for carrying out the invention]

[0014] The present invention will be described in more detail below, but the present invention is not limited to these details. The silicone rubber compound of the present invention contains the following components (A) to (E) as essential components. That is, in the present invention, "silicone rubber compound" means the mixture containing components (A) to (E) described below, before the addition of component (F). In the present invention, the compound to which component (F) has been added is referred to as a "silicone rubber composition".

[0015] -(A) component- Component (A) of the present invention is an organopolysiloxane raw rubber represented by the following average composition formula (1). M n M Vi (2-n) D γ D Vi δ (1) M:R 1 3SiO (1 / 2) M Vi :R 1 2RSiO (1 / 2) D:R 1 2SiO (2 / 2) D Vi :R 1 RSiO (2 / 2) (In the formula, M, M Vi , D, D Vi These are the units shown above, and R is independently an alkenyl group. 1γ is an unsubstituted or substituted monovalent hydrocarbon group that does not contain an aliphatic unsaturated bond. n is a positive number between 0 and 2. Furthermore, γ is a positive number satisfying (γ / (γ+δ)) ≤ 0.98, and δ is a positive number satisfying (δ / (γ+δ)) ≥ 0.02 and (γ+δ) ≥ 6000.

[0016] In formula (1) above, R is independently an alkenyl group, and is usually an alkenyl group having 2 to 6 carbon atoms, preferably 2 to 4 carbon atoms, and more preferably 2 to 3 carbon atoms. Specific examples include vinyl group, allyl group, propenyl group, isopropenyl group, butenyl group, isobutenyl group, etc., with vinyl group being preferred.

[0017] In the above equation (1), R 1 These are unsubstituted or substituted monovalent hydrocarbon groups that do not contain aliphatic unsaturated bonds, and their carbon number is usually 1 to 10, preferably 1 to 6. Specific examples include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, hexyl, cyclohexyl, octyl, and decyl groups; aryl groups such as phenyl and tolyl groups; aralkyl groups such as benzyl and phenylethyl groups; and chloromethyl groups, 3,3,3-trifluoropropyl groups, etc., in which some or all of the hydrogen atoms of these groups are substituted with halogen atoms such as chlorine, bromine, and fluorine. Among these, methyl, phenyl, or 3,3,3-trifluoropropyl groups are preferred because they are easy to synthesize.

[0018] Furthermore, in formula (1) above, n is 0 to 2, preferably 0 or 2, more preferably 0. γ is a positive number satisfying (γ / (γ+δ)) ≤ 0.98, and δ is a positive number satisfying (δ / (γ+δ)) ≥ 0.02 and (γ+δ) ≥ 6000. There is no restriction on positive numbers as long as the raw rubber composition satisfies this range. Here, the properties of this organopolysiloxane are so-called raw rubber-like (non-liquid) with no self-flow at room temperature (25°C). If the average degree of polymerization is too small, problems such as roll adhesion will occur when it is used as a compound, and the roll workability will deteriorate. The average degree of polymerization (for example, the n, γ, δ values ​​in the average composition formula (1) above) or molecular weight in this invention can be determined as the number average degree of polymerization (or number average molecular weight) in polystyrene terms in gel permeation chromatography (GPC) analysis measured under the conditions shown below.

[0019] [Measurement conditions] Developing solvent: Toluene Flow rate: 0.35mL / min Detector: Differential 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 (0.5% by mass toluene solution)

[0020] (A) Component (A) may be used alone, or it may be a mixture of two or more components with different molecular weights (average degree of polymerization) or molecular structures.

[0021] -(B) Component- Component (B) of the present invention reacts with component (A) and is an essential component for imparting cold resistance to the base polymer of component (A). Component (B) is given by the following general formula (2) [ka] (In the formula, R 1 R is independently a monovalent hydrocarbon group having 1 or 2 carbon atoms. 2 (This is the functional group shown in formula (3) or formula (4) below.) [ka] (In the formula, R 3 (These are independently monovalent hydrocarbon groups having 1 or 2 carbon atoms.) It is a compound represented by , which has one hydrogen atom bonded to a silicon atom in each molecule.

[0022] This is a compound R that has one hydrogen atom bonded to a silicon atom in one molecule. 1 R is independently selected from a monovalent hydrocarbon group having 1 or 2 carbon atoms, i.e., a methyl group and an ethyl group, with a methyl group being particularly preferred. Here, R 1 It doesn't matter if they are different or the same. Also, R 2 It is essential that the structure is represented by the general formula (3) or general formula (4) above. 2 Specific examples include phenyl group, trimethylsilyl group, triethylsilyl group, ethyldimethylsilyl group, and diethylmethylsilyl group. Among these, phenyl group and trimethylsilyl group are preferred, and trimethylsilyl group is more preferred. The compound (B), which has one hydrogen atom bonded to a silicon atom in one molecule, may be used alone or in combination of two or more types.

[0023] The amount of component (B) to be added is 1.0 to 20 parts by mass, more preferably 2.0 to 10 parts by mass, per 100 parts by mass of component (A). If the amount is less than 1.0 part by mass, the desired cold resistance cannot be obtained. If it exceeds 20 parts by mass, it becomes unfavorable in terms of cost, and most of the alkenyl groups of component (A) will react with component (B), making it impossible to obtain the desired cured product. The structure in which most of the alkenyl groups of component (A) have reacted with component (B) is shown in the average composition formula below. Mn M' (2-n) D γ D Vi (δ-Z) D' Z (M' and D' are M in equation (1) of component (A), respectively) Vi and D Vi This is the result of the alkenyl group reacting with the hydrogen atom bonded to the silicon atom of component (B). (Z is a positive number greater than or equal to 1.)

[0024] -(C) component- Component (C) of the present invention is a dispersant for dispersing the reinforcing silica of component (D), described later, into the organopolysiloxane raw rubber of component (A), and consists of the following components (C-1) and / or (C-2).

[0025] (C-1) Organosiloxanes having hydroxysilyl groups at both ends, represented by the following general formula (5) [ka] (In the formula, R 4 (where m is a positive number between 1 and 50, and is either the same or different unsubstituted or substituted monovalent hydrocarbon group having 1 to 8 carbon atoms.)

[0026] (C-2) A silane coupling agent which is a partial hydrolysate of an organoalkoxysilane represented by the following general formula (6), has a refractive index of 1.39 to 1.41, and a specific gravity of 1.0 or more: 0.1 to 20 parts by mass, R 5 Si(OR 6 )3(6) (In the formula, R 5 R is the same or different unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, 6 (This indicates a monovalent aliphatic hydrocarbon group with 1 to 10 carbon atoms.)

[0027] Here, components (C-1) and (C-2) may be used individually or in combination. When used in combination, the amount used should be such that the total number of moles of hydroxysilyl groups in component (C-1) and hydrolyzable groups in component (C-2) is the same as the number of moles when each component is used individually.

[0028] (C-1) Component In the above general formula (5), R 4 m is independently a monovalent hydrocarbon group having 1 to 8 carbon atoms, specifically an alkyl group having 1 to 8 carbon atoms such as a methyl group, ethyl group, propyl group, isopropyl group, or butyl group; an alkenyl group having 2 to 8 carbon atoms such as a vinyl group or allyl group; or an aryl group having 6 to 8 carbon atoms such as a phenyl group or tolyl group, preferably a methyl group or a vinyl group. Also, m is a positive number from 1 to 50, preferably from 2 to 20.

[0029] The amount of component (C-1) is 1.0 to 50 parts by mass, preferably 2.0 to 20 parts by mass, per 100 parts by mass of component (A). If the amount of component (C-1) is less than 1.0 part by mass, plasticity return (creep hardening) will be large, and if it is more than 50 parts by mass, the plasticity of the compound will be too low, causing roll stickiness in mixing means such as roll mills and worsening roll workability.

[0030] (C-2) Component In the above general formula (6), R 5 R is the same or different unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, 6C is a monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms. Specific examples of organoalkoxysilanes represented by the general formula (6) 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-2). Since component (C-2) is a partial hydrolysate, the above R 5 Derived monovalent hydrocarbon groups and the above R 6 In addition to the alkoxy groups derived from the compound, some hydroxyl groups (hydroxysilyl groups) are also present.

[0031] Here, the number-average degree of polymerization of component (C-2) is preferably in the range of 2 to 100, and more preferably 2 to 30. If the number-average degree of polymerization of component (C-2) is less than 2, i.e., if a monomer is used, component (C-2) becomes more volatile, volatilizing during mixing, and the plasticity of the resulting silicone rubber compound becomes unstable. In addition, the amount of volatile components increases, which poses industrial hazards such as inhalation of volatile vapors and ignition. On the other hand, if the number-average degree of polymerization of component (C-2) exceeds 100, the viscosity of component (C-2) becomes very high, making it difficult to blend and reducing the surface treatment ability of component (B) above. This can lead to an extension of the blending time and instability of the plasticity of the resulting silicone rubber compound, and in the worst case, it may become impossible to obtain a silicone rubber compound.

[0032] The kinematic viscosity of component (C-2) at 25°C is 1.0 to 1,000 mm². 2 A range of / s is preferred, and is 1.5 to 500 mm. 2 / s is more preferable, 1.5~300mm 2A viscosity of / s is particularly preferred. This kinematic viscosity was measured using the method described in JIS Z8803:2011 using a Cannon-Fenske viscometer. This range is preferable because it facilitates blending with other components and suppresses volatile components.

[0033] The specific gravity of component (C-2) at 25°C must be 1.0 or higher, preferably 1.00 to 1.20, and particularly preferably 1.00 to 1.19. This specific gravity was measured using a hydrometer under 25°C conditions in accordance with JIS B 7525-3:2018.

[0034] When using component (C-2), the amount to be blended is 0.1 to 20 parts by mass, preferably 1.0 to 10.0 parts by mass, per 100 parts by mass of component (A). If the amount of component (C-2) is 0.1 parts by mass or less, plasticity reversal may occur, resulting in problems with subsequent processability, or in the worst case, the compound may not be obtainable. On the other hand, if the amount of component (C-2) 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.

[0035] -(D) Component- (D) The reinforcing silica is a filler added to obtain a 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 The specific surface area of ​​this reinforcing silica is 50 m². 2 If the specific surface area is less than 450 m², the mechanical strength of the cured product will be low. 2 If the value exceeds / g, it may result in problems such as the compound being too hard, or in the worst case, the reinforcing filler not being able to be filled, and the desired silicone compound not being obtained.

[0036] Examples of such reinforcing silica include fumed silica and precipitated silica (wet silica). Those whose surfaces have been hydrophobized with chlorosilane or hexamethyldisilazane are also suitably used. Among these, fumed silica, which exhibits excellent dynamic fatigue properties, is preferred. Component (D) may be used alone or in combination of two or more.

[0037] The amount of reinforcing silica in component (D) of the present invention is 5 to 100 parts by mass, preferably 10 to 50 parts by mass, per 100 parts by mass of organopolysiloxane in component (A). If the amount of component (D) is less than 5 parts by mass, the reinforcing effect cannot be obtained, and if it is more than 100 parts by mass, the processability will be poor, the mechanical strength will decrease, and the dynamic fatigue durability will also deteriorate.

[0038] -(E) Component- The addition reaction catalyst of component (E) of the present invention is a catalyst for promoting the addition reaction between the alkenyl group contained in component (A) and the hydrogen atom bonded to the silicon atom contained in component (B) (i.e., the SiH group), and well-known catalysts such as platinum group metal catalysts can be used as catalysts for hydrosilylation reactions.

[0039] As for this platinum group metal catalyst, all known catalysts for hydrosilylation reactions can be used. For example, elemental platinum group metals such as platinum black, rhodium, and palladium; platinum chloride, chloroplatinic acid, and chloroplatinate salts such as H2PtCl4·yH2O, H2PtCl6·yH2O, NaHPtCl6·yH2O, KHPtCl6·yH2O, Na2PtCl6·yH2O, K2PtCl4·yH2O, PtCl4·yH2O, PtCl2, and Na2HPtCl4·yH2O (wherein y is an integer from 0 to 6, preferably 0 or 6); Examples include chol-modified chloroplatinic acid, complexes of chloroplatinic acid and olefins, platinum black, platinum group metals such as palladium supported on a carrier such as alumina, silica, or carbon; rhodium-olefin complex; chlorotris(triphenylphosphine)rhodium (Wilkinson catalyst); and complexes of platinum chloride, chloroplatinic acid or chloroplatinate salts with vinyl group-containing siloxanes, particularly vinyl group-containing cyclic siloxanes. Among these, preferred are those obtained by modifying chloroplatinic acid with silicone, from the viewpoint of compatibility and chlorine impurities. Specifically, for example, a platinum catalyst obtained by modifying chloroplatinic acid with tetramethyldivinyldisiloxane is a good example.

[0040] The amount of component (E) is 0.1 to 1,000 ppm, preferably 0.5 to 300 ppm, and more preferably 1 to 100 ppm, in terms of mass relative to the total amount of components (A) to (D) in terms of platinum atoms.

[0041] 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 (E). There are no particular restrictions on the apparatus capable of uniform mixing, but when mixing components (A), (C), and (D), it is preferable to use a sealed type such as a kneader or Banbury mixer, as well as a manufacturing apparatus that can suppress the scattering of component (D). It is preferable to obtain the millable-type silicone rubber compound by kneading components (B) and (E) into the masterbatch obtained using the above-mentioned apparatus using a kneader, roll mill, etc.

[0042] In this mixture of components (A), (C), and (D) described above, the dispersant component (C) acts as a wetter for the reinforcing silica component (D). To enhance this wetting effect, it is effective to add dispersion accelerators such as condensation catalysts or water as optional components. By adding these components, the dispersant component (C) can act as a wetter for the reinforcing silica component (D) more rapidly.

[0043] The mixing temperature of components (A), (C), and (D) above is preferably in the range of 0 to 200°C, more preferably 10 to 180°C, and even more preferably 20 to 170°C. While there are no particular restrictions on the mixing time of components (A) to (D), considering manufacturing efficiency, a range of 1 to 300 minutes, more preferably 10 to 120 minutes, is desirable.

[0044] Even if a masterbatch obtained by mixing components (A), (C), and (D) is cured by adding component (F), it is still not possible to obtain a silicone rubber with excellent cold resistance. In this invention, in order to obtain a millable-type silicone rubber compound with excellent cold resistance, which is the objective, components (B) and (E) are mixed into the masterbatch obtained by mixing components (A), (C), and (D), and these are reacted.

[0045] For mixing the masterbatch with components (B) and (E) as described above, the preferred temperature is in the range of 0 to 100°C, more preferably 10 to 50°C, and even more preferably 20 to 40°C. While there are no particular restrictions on the mixing time between the masterbatch and components (B) and (E), considering manufacturing efficiency, it is desirable to use conditions of 1 to 60 minutes, more preferably 3 to 30 minutes.

[0046] The millable-type silicone rubber compound obtained as described above can be combined with (F) a curing agent to obtain a millable-type silicone rubber composition.

[0047] -(F) component- (F) The curing agent is not particularly limited as long as it can cure the above component (A), but (F-1) addition reaction (hydrosilylation reaction) type curing agents, which are generally known as rubber curing agents, that is, hydrosilylation reaction curing agents consisting of a combination of organohydrogenpolysiloxane (crosslinking agent) and a hydrosilylation catalyst, or (F-2) organic peroxides are preferred.

[0048] The organohydrogenpolysiloxane used as a crosslinking agent for the above (F-1) addition reaction type curing agent has two or more hydrosilyl groups in one molecule. In particular, the organohydrogenpolysiloxane represented by the following formula (7) is preferred. [ka] (In the formula, R 7 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. 7 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.

[0049] Here, R 7 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. 7is a hydrogen 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. 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.

[0050] 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 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.

[0051] Examples of such organohydrogenpolysiloxanes include 1,1,3,3 - tetramethyldisiloxane, 1,3,5,7 - tetramethylcyclotetrasiloxane, methylhydrogen cyclopolysiloxane, methylhydrogen siloxane·dimethylsiloxane cyclic copolymer, tris(dimethylhydrogensiloxy)methylsilane, tris(dimethylhydrogensiloxy)phenylsilane, methylhydrogenpolysiloxane blocked at both ends with trimethylsiloxy groups, dimethylsiloxane·methylhydrogen siloxane copolymer blocked at both ends with trimethylsiloxy groups, dimethylpolysiloxane blocked at both ends with dimethylhydrogensiloxy groups, dimethylsiloxane·methylhydrogen siloxane copolymer blocked at both ends with dimethylhydrogensiloxy groups, methylhydrogen siloxane·diphenylsiloxane copolymer blocked at both ends with trimethylsiloxy groups, methylhydrogen siloxane·diphenylsiloxane·dimethylsiloxane copolymer blocked at both ends with trimethylsiloxy groups, cyclic methylhydrogenpolysiloxane, cyclic methylhydrogen siloxane·dimethylsiloxane copolymer, cyclic methylhydrogen siloxane·diphenylsiloxane·dimethylsiloxane copolymer, (CH3)2HSiO 1 / 2 units and SiO 4 / 2 units and copolymers composed of, (CH3)2HSiO 1 / 2 units and SiO 4 / 2 units and (C6H5)SiO 3 / 2 units and copolymers etc., and in each of the above - exemplified compounds, those in which part 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 can be mentioned. Also, as such organohydrogenpolysiloxanes, specifically, compounds having the following structural formulas can be exemplified.

[0052] [Chemical formula] (In the formula, k is an integer from 2 to 10, and s and t are each an integer from 0 to 10.)

[0053] 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 K7117-1:1999.

[0054] Furthermore, it is desirable that the above-mentioned 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 above molar ratio is less than 0.5, crosslinking may not be sufficient, and sufficient mechanical strength may not be obtained. On the other hand, if it exceeds 10, the physical properties after curing will deteriorate, and in particular, heat resistance and compression set resistance may deteriorate significantly.

[0055] Furthermore, the hydrosilylation catalyst used in the above-mentioned (F-1) addition reaction type curing agent is a catalyst that promotes the addition reaction of the hydrosilyl group in the above-mentioned organohydrogenpolysiloxane, which acts as a crosslinking agent, with the alkenyl group in component (A). Examples of hydrosilylation catalysts include platinum group metal catalysts such as ruthenium and platinum. Platinum group metal catalysts include these platinum group metals in their elemental form and compounds thereof. 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, palladium catalysts, rhodium catalysts, ruthenium catalysts, etc. Among these, platinum or platinum compounds are particularly preferred.

[0056] 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 mass% when converted to 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 less than 1 ppm, the addition reaction may not be sufficiently promoted, resulting in insufficient hardening. On the other hand, if it exceeds 1 mass%, adding more than this amount may have little effect on the reactivity and may be uneconomical.

[0057] 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.

[0058] On the other hand, examples of the above (F-2) 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.

[0059] 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 this amount is sufficient, the crosslinking reaction will proceed sufficiently, and deterioration of physical properties such as a decrease in hardness, insufficient rubber strength, and increased compression set will not occur. Furthermore, if the amount is not exceeded as described above, it is economically preferable, as the amount of decomposition products of the curing agent will be sufficiently small, and deterioration of physical properties such as increased compression set and discoloration of the obtained sheet will not increase.

[0060] In addition to the above components (A) to (F), the Mirable-type silicone rubber composition of the present invention may contain any other components as long as they do not impair the objectives of the present invention. Examples of such optional components include conductivity imparters such as carbon black, preservation stabilizers such as phosphite ester compounds, flame retardants such as iron oxide and halogen compounds, antistatic agents, softeners, anti-aging agents, ultraviolet absorbers, and colorants.

[0061] 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. [Examples]

[0062] 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 number-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 K7117-1:1999, the kinematic viscosity was measured using a Cannon-Fenske viscometer according to the method described in JIS Z8803:2011, and the refractive index was measured using an Abbe refractometer according to the method described in JIS K0062:1992. The following are specific examples of the components used in the examples and comparative examples of the present invention.

[0063] (A) Organopolysiloxane raw rubber This organopolysiloxane raw rubber consists of 97 mol% dimethylsiloxane units, 2.975 mol% methylvinylsiloxane units, and 0.025 mol% dimethylvinylsiloxy units, and has an average of 240 vinyl groups bonded to silicon atoms per molecule, with a number-average degree of polymerization of 8,000. (B) Compounds having one hydrogen atom bonded to a silicon atom in one molecule. (B-1) Phenyldimethylsilane (Tokyo Chemical Products) (B-2) 1,1,1,3,3-Pentamethyldisiloxane (Tokyo Chemical Products) (B-3) Heptamethyltrisiloxane (for comparison - Tokyo Chemical Products Co., Ltd.) (B-4) Tris(trimethylsilyloxy)silane (for comparison - Tokyo Chemical Products Co., Ltd.) (B-5) Triisopropylsilane (for comparison - Tokyo Chemical Co., Ltd.) (C) Dispersant (C-1) Dimethylpolysiloxane having hydroxysilyl groups at both ends, an average degree of polymerization of 4, and a viscosity of 15 mPa·s at 25°C. (C-2) 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, specific gravity [25℃]: 1.09) (D) Reinforced silica BET method specific surface area is 200m 2 / g of fumed silica (product name: Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) (E) Addition reaction catalyst Platinum catalyst containing 1% by mass of a chloroplatinate-divinyldisiloxane complex (based on platinum atomic mass) (manufactured by Shin-Etsu Chemical Co., Ltd.)

[0064] [Manufacturing process for silicone rubber compound] Components (A), (D), and (C) were added to a 3L kneader and uniformly mixed to create a masterbatch. Components (B) and (E) were then added to this masterbatch and uniformly mixed using a two-roll mill to obtain the desired silicone rubber compound. The amounts of each component added are shown in Table 1.

[0065] [Silicone rubber composition] To 100 parts by mass of the prepared silicone rubber compound described above, (F-1) As an addition reaction type curing agent, 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 on a platinum atomic mass basis, and the following formula (8) [ka] 0.85 parts by mass of organohydrogenpolysiloxane (manufactured by Shin-Etsu Chemical Co., Ltd.), or (F-2) 1.0 part by mass of 25% of 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane (manufactured by Shin-Etsu Chemical Co., Ltd.) The material was added and uniformly mixed to prepare a millable-type silicone rubber composition.

[0066] [Physical property measurement] For each of the compositions prepared above, For compositions using component (F-1), test sheets were prepared by press curing at 120°C for 10 minutes, followed by post-curing at 200°C for 4 hours. For compositions using component (F-2), test sheets were prepared by press curing at 165°C for 10 minutes, followed by post-curing at 200°C for 4 hours.

[0067] Furthermore, the hardness (durometer A), tensile strength, elongation at break, and compression set (180°C / 22 hours, 25% compression) of the above test sheets were measured based on the description in JIS K6249:2003. In addition, the rebound modulus was measured based on the method described in JIS K6255:2013.

[0068] Cold resistance was evaluated by performing a low-temperature elastic recovery test, which measures the ability of a silicone rubber composition to recover its elasticity and shrink as the temperature rises after being frozen at a low temperature after stretching. Specifically, using a TR tester (manufactured by Ueshima Seisakusho, part number: MODEL TM-3525) in accordance with JIS K6261-4:2017, the temperature at which 10% shrinkage occurs (TR10; embrittlement temperature) was measured. Silicone rubber compositions that were not detected (ND) or below -50℃ were judged as "pass," and those above -50℃ were judged as "fail." If a temperature at which 10% shrinkage could not be confirmed within the measurement range, it was indicated as "ND" (Not Detected).

[0069] [Table 1]

[0070] [Evaluation Results] As shown in Table 1, the silicone rubber compounds obtained in each of Examples 1 to 6 satisfy the requirements of the present invention. The physical properties of the moldable silicone rubber compositions prepared using these compounds show that even when the amount of component (B) is changed or the components are altered, there is no significant change in the mechanical properties of the rubber, and the low-temperature elastic recovery temperature can be lowered. In contrast, in Comparative Example 1, the low-temperature elastic recovery temperature is -45°C, which is worse, because the compound having one hydrogen atom bonded to a silicon atom in one molecule, which is component (B), is not added. Furthermore, in Comparative Examples 2 to 4, the compound having one hydrogen atom bonded to a silicon atom in one molecule, which is component (B), has a structure that does not satisfy the requirements of the present invention. Therefore, it can be seen that even if similar compounds having one hydrogen atom bonded to a silicon atom in one molecule are used in roughly the same amount, the low-temperature elastic recovery temperature cannot be made below -50°C.

[0071] From the evaluation results above, it is possible to obtain a silicone rubber compound obtained by the manufacturing method of the present invention that is no different from conventionally used silicone rubber compounds, and the physical properties of the silicone rubber composition created using it remain completely unchanged, while the low-temperature elastic recovery temperature can be lowered to a lower temperature. Therefore, the millable type silicone rubber compound and millable type silicone rubber composition of the present invention make it possible to improve low-temperature properties. [Industrial applicability]

[0072] As described above, the millable-type silicone rubber compound of the present invention, and the silicone rubber composition obtained by blending the compound with a curing agent, can provide a cured silicone rubber product with improved low-temperature properties while maintaining almost the same properties as conventionally used millable-type silicone rubber compounds and silicone rubber compositions. Therefore, this silicone rubber compound, and the silicone rubber obtained by curing the silicone rubber composition obtained by blending the compound with a curing agent, are expected to have a wide range of applications in fields such as electrical equipment, automobiles, construction, medical care, and food. In particular, it is a useful technology for the automotive and electronic equipment fields, and more specifically for in-vehicle electronic components and hydrogen gas sealing applications.

Claims

1. A Mirable-type silicone rubber compound characterized by containing the following components (A) to (E). (A) The following average composition formula (1) M n M Vi (2-n) D γ D Vi δ (1) M:R 1 3 SiO (1 / 2) M Vi :R 1 2 RSiO (1 / 2) D:R 1 2 SiO (2 / 2) D Vi :R 1 RSiO (2 / 2) (In the formula, M, M Vi , D, D Vi These are the units shown above, and R is independently an alkenyl group. 1 γ is an unsubstituted or substituted monovalent hydrocarbon group that does not contain an aliphatic unsaturated bond. n is a positive number between 0 and 2. Furthermore, γ is a positive number satisfying (γ / (γ+δ)) ≤ 0.98, and δ is a positive number satisfying (δ / (γ+δ)) ≥ 0.02 and (γ+δ) ≥ 6000. Raw rubber represented by: 100 parts by mass, (B) General formula (2) 【Chemistry 1】 (In the formula, R 1 R is independently a monovalent hydrocarbon group having 1 or 2 carbon atoms. 2 (This is the functional group shown in formula (3) or formula (4) below.) 【Chemistry 2】 (In the formula, R 3 (These are independently monovalent hydrocarbon groups having 1 or 2 carbon atoms.) A compound represented by having one hydrogen atom bonded to a silicon atom in one molecule: 1.0 to 20 parts by mass, (C) One or more dispersants selected from (C-1) and / or (C-2) below, (C-1) Organosilanes and / or siloxanes having hydroxysilyl groups at both ends, represented by the following average composition formula (5): 1.0 to 50.0 parts by mass, 【Transformation 3】 (In the formula, R 4 (where m is a positive number from 1 to 50, and is either the same or different unsubstituted or substituted monovalent hydrocarbon group having 1 to 8 carbon atoms.) (C-2) A silane coupling agent which is a partial hydrolysate of an organoalkoxysilane represented by the following general formula (6), having a refractive index of 1.39 to 1.41 and a specific gravity of 1.0 or more: 0.1 to 20 parts by mass, R 5 Si(OR 6 ) 3 (6) (In the formula, R 5 R is the same or different unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, 6 (This indicates a monovalent aliphatic hydrocarbon group with 1 to 10 carbon atoms.) (D) Specific surface area of ​​50 to 450 m² by BET adsorption method 2 Reinforcing silica per g: 5 to 100 parts by mass, and (E) Addition reaction catalyst: Effective amount

2. A millable-type silicone rubber composition characterized by comprising the millable-type silicone rubber compound described in claim 1 and (F) a curing agent.

3. The millable-type silicone rubber composition according to claim 2, wherein the curing agent (F) is a hydrosilylation reaction system curing agent consisting of a combination of organohydrogenpolysiloxane and a hydrosilylation catalyst.

4. The millable-type silicone rubber composition according to claim 2, wherein the curing agent (F) is an organic peroxide.

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