High heat-resistant silicone rubber composition and method for producing the same.

Abstract

This invention provides a highly heat-resistant silicone rubber composition that can be used even in high-temperature environments (e.g., 200°C or higher), a method for producing the same, and a method for improving the heat resistance of a silicone rubber composition and a heat resistance improver. [Solution] A high heat-resistant silicone rubber composition is prepared for use in environments with a temperature of 200°C or higher, satisfying either (A) or (B) below, in a silicone rubber composition containing a crosslinked silicone rubber component. (A): The silicone rubber component is a liquid or paste-like silicone rubber, and the inter-crosslinking molecular weight Me of the crosslinked product is 2.3 × 10 3 ~3.5×10 3 g / mol (B): The silicone rubber component is millable-type silicone rubber, and the inter-crosslinking molecular weight Me of the crosslinked product is 13.5 × 10 3 ~100×10 3 g / mol The high heat-resistant silicone rubber composition may or may not contain polysilane. The method for producing the high heat-resistant silicone rubber composition may include a crosslinking step in which the silicone rubber component is crosslinked in the presence of polysilane. The production method may also include a polysilane removal step in which the polysilane is removed from the crosslinked product obtained in the crosslinking step.

Description

[Technical Field]

[0001] This disclosure relates to a high heat-resistant silicone rubber composition and a method for producing the same, as well as a method for improving the heat resistance of a silicone rubber composition and a heat-resistant agent. [Background technology]

[0002] Silicone rubber is a type of rubber having a main chain formed by siloxane bonds (Si-O bonds). It has excellent heat and cold resistance and high chemical stability, and is therefore used in a wide range of fields such as automobiles, electrical and electronic equipment, and building materials (Patent Documents 1-4).

[0003] On the other hand, polysilanes are organic-inorganic composite compounds having a main chain formed by Si-Si bonds and organic groups in the side chains, and are used in a wide range of fields such as semiconductor process materials, coating raw materials for optical and electronic materials, and resin modifiers (adhesion improvers for polyolefin resins, etc.) (Non-Patent Literature 1). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2019-203092 [Patent Document 2] Japanese Patent Publication No. 2023-166880 [Patent Document 3] Japanese Patent Publication No. 2023-158594 [Patent Document 4] Special Publication No. 2017-523554 [Non-patent literature]

[0005] [Non-Patent Document 1] Molding and Processing, Vol. 32, No. 12, 2020, pp. 428-433 [Overview of the project] [Problems that the invention aims to solve]

[0006] Patent Document 4 discloses a method for manufacturing an optical conductor comprising an integrally molded optical element, which involves applying an adhesive aid mainly composed of silane or polysilane to at least a partial region of the end face of the optical conductor, and then integrally molding the optical element by covering this end face with a transparent synthetic resin selected from liquid silicone rubber.

[0007] However, polysilane is only listed as an adhesive aid, and there is no mention of its addition to silicone rubber or its effect on the heat resistance of silicone rubber.

[0008] Patent Document 2 discloses a heat-resistant silicone composition that utilizes gardenia pigment as a heat-resistant enhancer. Patent Document 3 discloses an addition-curing type silicone rubber composition that exhibits low compression set even under high-temperature conditions of 200°C or higher, and describes the use of titanium dioxide, iron oxide, and carbon black as heat-resistant enhancers in the examples.

[0009] However, these documents do not mention or suggest anything about adding polysilane to the composition (especially as a heat resistance improver).

[0010] Patent Document 1 discloses that a silicone rubber composition comprising a polyorganosiloxane, a polysilane, and a curing agent can improve surface properties and enhance adhesion to solids and ductility.

[0011] However, while Patent Document 1 describes how polysilane increases the molecular weight between crosslinking points, making the silicone rubber more flexible and improving its ductility, and how it increases the molecular mobility of the silicone rubber, leading to entanglement between intermolecular chains and improving surface properties such as adhesion to solids, it does not describe or suggest anything about its effect on heat resistance (especially heat resistance in applications exposed to high-temperature environments for extended periods).

[0012] Although Non-Patent Document 1 does not contain any description of silicone rubber, it suggests that polymethylphenylsilane (PMPS) has an effect of accelerating thermal and light degradation.

[0013] Therefore, the object of this disclosure is to provide a highly heat-resistant silicone rubber composition that can be used even in high-temperature environments (e.g., 200°C or higher), a method for producing the same, and a method for improving the heat resistance of a silicone rubber composition and a heat resistance improver. [Means for solving the problem]

[0014] The inventors have discovered that in crosslinked silicone rubber components, if the molecular weight between crosslinking points is within a specific range, the heat resistance of the crosslinked product can be improved even when using the same silicone rubber components, and have completed the present invention (or this disclosure). That is, this disclosure may include the following embodiments, etc.

[0015] Appearance [1]: A silicone rubber composition containing a crosslinked silicone rubber component, The following conditions (A) or (B) must be met: A high-temperature resistant silicone rubber composition for use in environments with temperatures above 200°C. (A): The silicone rubber component is a liquid or paste-like silicone rubber, and the inter-crosslinking molecular weight Me of the crosslinked product is 2.3 × 10 3 ~3.5×10 3 g / mol (B): The silicone rubber component is millable-type silicone rubber, and the inter-crosslinking molecular weight Me of the crosslinked product is 13.5 × 10 3 ~100×10 3 g / mol

[0016] Appearance [2]: A high heat-resistant silicone rubber composition according to embodiment [1], which does not contain polysilane.

[0017] Appearance [3]: A high heat-resistant silicone rubber composition according to embodiment [1], comprising polysilane.

[0018] Appearance [4]: Polysilane is given by the following formulas (1a) and (1b)

[0019] [ka]

[0020] (In the formula, R 1 ~R 3 (Each represents a hydrogen atom, a hydroxyl group, a halogen atom, or an organic group.) A high heat-resistant silicone rubber composition according to embodiment [3], comprising at least one structural unit selected from structural units represented by .

[0021] Appearance [5]: The polysilane is, in formula (1a), R 1 and R 2 The high heat-resistant silicone rubber composition according to embodiment [4], comprising at least one structural unit in which one is an alkyl group and the other is an aryl group.

[0022] Appearance [6]: The high heat-resistant silicone rubber composition according to embodiment [4] or [5], wherein the proportion of structural units represented by formula (1a) is 50 mol% or more with respect to the entire polysilane.

[0023] Appearance [7]: The high heat-resistant silicone rubber composition according to any one of embodiments [3] to [6], wherein the weight-average molecular weight Mw of the polysilane is 200 to 2000.

[0024] Appearance [8]: The high heat-resistant silicone rubber composition according to any one of embodiments [3] to [7], wherein the polysilane is a linear polysilane.

[0025] Appearance [9]: A high heat-resistant silicone rubber composition according to any one of embodiments [3] to [8], wherein the ratio of the polysilane to the silicone rubber component is the former / latter (mass ratio) = 0.1 / 99.9 to 30 / 70.

[0026] Appearance

[10] : The high heat-resistant silicone rubber composition according to any one of embodiments [1] to [9], wherein the silicone rubber component is a liquid or paste-like silicone rubber.

[0027] Appearance

[11] : The high heat-resistant silicone rubber composition according to any one of embodiments [1] to [9], wherein the silicone rubber component is a millable type silicone rubber.

[0028] Appearance

[12] : The high heat-resistant silicone rubber composition according to any one of embodiments [1] to

[11] , wherein the silicone rubber component is an addition-curing type or a radical-curing type silicone rubber.

[0029] Appearance

[13] : A high heat-resistant silicone rubber composition according to any one of embodiments [1] to

[12] for use in an environment with a temperature of 210 to 260°C.

[0030] Appearance

[14] : When heated at 240°C for 3 hours, The elongation at break after heating is 50-100% of the elongation at break before heating. A high heat-resistant silicone rubber composition according to any one of embodiments [1] to

[13] , wherein the tensile strength after heating is 50 to 120% of the tensile strength before heating.

[0031] Appearance

[15] : A method for producing a high heat-resistant silicone rubber composition according to any one of embodiments [1] to

[14] , comprising a crosslinking step of crosslinking the silicone rubber component in the presence of polysilane.

[0032] Appearance

[16] : The production method according to aspect

[15] , comprising a polysilane removal step of removing the polysilane from the crosslinked product obtained in the crosslinking step.

[0033] Aspect

[17] : A method for improving the heat resistance of a silicone rubber composition containing a crosslinked product of a silicone rubber component, the method comprising crosslinking the silicone rubber component in the presence of polysilane.

[0034] Aspect

[18] : The method for improving heat resistance according to aspect

[17] , wherein the polysilane is removed from the obtained crosslinked product after crosslinking.

[0035] Aspect

[19] : A heat resistance improver for a silicone rubber composition, the improver comprising polysilane.

[0036] Note that in the present disclosure, the following secondary objects may be achieved (the secondary problems may be solved).

[0037] That is, another object of the present disclosure is to provide a high heat resistance silicone rubber composition that can suppress deterioration of physical properties (increase in elastic modulus, decrease in tensile strength or elongation at break) even when exposed to a high temperature environment (for example, 200°C or higher) for a long time (for example, 10 minutes or longer), a production method thereof, as well as a method for improving the heat resistance of a silicone rubber composition and a heat resistance improver.

[0038] Note that in the present specification and claims, the number of carbon atoms may be represented by C1, C6, C 10 and the like. For example, an alkyl group having 1 carbon atom may be referred to as "C1 alkyl group", and an aryl group having 6 to 10 carbon atoms may be referred to as "C 6-10 aryl group" and the like.

[0039] Further, in the present specification and claims, "independently" means that a plurality of constituent elements are each independent constituent elements, and for example, R 1 to R 3In this case, it means that the groups may be the same or different.

[0040] In this specification and in the claims, the numerical range indicated by "X~Y" may include the numerical values ​​X and Y. [Effects of the Invention]

[0041] This disclosure provides a highly heat-resistant silicone rubber composition that can be used even in high-temperature environments (e.g., 200°C or higher), a method for producing the same, a method for improving the heat resistance of a silicone rubber composition, and a heat resistance improver. [Brief explanation of the drawing]

[0042] [Figure 1] Figure 1 is a graph showing the stress (σ)-elongation ratio (λ) curves of the rubber-like sheets obtained in (a) Example 1 or (b) Comparative Example 1 during tensile tests (before heating (25°C) and after heating at 240°C). [Figure 2] Figure 2 is a graph showing the stress (σ)-elongation ratio (λ) curves of the rubber-like sheets obtained in (a) Example 2 or (b) Comparative Example 2 during tensile tests (before heating (25°C) and after heating at 240°C). [Figure 3] Figure 3 is a graph showing the stress (σ)-elongation ratio (λ) curves of the rubber-like sheets obtained in (a) Example 3 or (b) Comparative Example 3 during tensile tests (before heating (25°C) and after heating at 240°C). [Figure 4] Figure 4 is a graph showing the stress (σ)-elongation ratio (λ) curves of the rubber-like sheet obtained in Comparative Example 4 during tensile tests (before heating (25°C) and after heating at 240°C). [Modes for carrying out the invention]

[0043] The high heat-resistant silicone rubber composition (high heat-resistant crosslinked silicone rubber composition) disclosed herein is a silicone rubber composition containing a crosslinked silicone rubber component, satisfying either (A) or (B) below, and is a composition for use in an environment with a temperature of 200°C or higher. (A): The silicone rubber component is a liquid or paste-like silicone rubber, and the inter-crosslinking molecular weight Me of the crosslinked product is 2.3 × 10 3 ~3.5×10 3 g / mol (B): The silicone rubber component is millable-type silicone rubber, and the inter-crosslinking molecular weight Me of the crosslinked product is 13.5 × 10 3 ~100×10 3 g / mol

[0044] The high heat-resistant silicone rubber composition of this disclosure may suppress deterioration of physical properties (increase in elastic modulus, decrease in tensile strength or elongation at break) even when exposed to high-temperature environments (e.g., 200°C or higher) for a long period of time (e.g., 10 minutes or more).

[0045] [Silicone rubber components] The silicone rubber component (uncrosslinked silicone rubber) is a component having siloxane bonds (Si-O bonds) as its main backbone, which form the main chain of the silicone rubber after crosslinking (curing), and conventional silicone rubber components can be used. Examples of conventional silicone rubber components include methyl silicone rubber (MQ), vinyl silicone rubber (VMQ), phenyl silicone rubber (PMQ), phenyl vinyl silicone rubber (PVMQ), and fluorinated silicone rubber (FVMQ), with VMQ being preferred. The silicone rubber component may be a combination of linear polyorganosiloxane (such as methyl silicone rubber) and branched or networked polyorganosiloxane (such as MQ resin), or it may be linear polyorganosiloxane alone.

[0046] Furthermore, the silicone rubber component (uncrosslinked silicone rubber) may be a polyorganosiloxane. The polyorganosiloxane is a compound (for example, a linear compound) having Si-O bonds (siloxane bonds) in a linear, branched, or network structure, and may be mainly formed of units (main units) represented by the following formula.

[0047] R Sa SiO (4-a) / 2 (In the formula, R S (where 'a' indicates a substituent, and 'a' indicates a number between 0 and 3.)

[0048] In the above formula, R S Examples of substituents represented by alkyl groups (such as methyl, ethyl, propyl, and butyl groups) 1-10 (Alkyl groups, etc.), halogenated alkyl groups (halogenated C such as 3-chloropropyl group, 3,3,3-trifluoropropyl group) 1-10 C(alkyl groups, etc.), alkenyl groups (vinyl groups, allyl groups, butenyl groups, etc.) 2-10 Alkenyl groups, etc., aryl groups (phenyl groups, tolyl groups, naphthyl groups, etc.) 6-20 (such as aryl groups), cycloalkyl groups (such as cyclopentyl groups and cyclohexyl groups) 3-10 Cycloalkyl groups (such as cycloalkyl groups), aralkyl groups (such as benzyl and phenethyl groups), etc. 6-12 Aryl-C 1-4 Examples include alkyl groups. These substituents may be used individually or in combination of two or more. Typical R S Examples include alkyl groups (such as methyl groups and C 1-4 Alkyl groups (such as alkyl groups), aryl groups (such as phenyl groups), alkenyl groups (such as vinyl groups), fluoroalkyl groups (such as 3,3,3-trifluoropropyl groups, etc.) 1-4 Examples include alkyl groups, etc., and methyl groups and vinyl groups (especially methyl groups) are preferred. If a is 2 or more, then 2 or more R S The types may be the same or different from each other.

[0049] The number of substitutions a may be, for example, 1 or 2 (in particular, 2). Therefore, the polyorganosiloxane may be linear (a linear chain formed of units where a is 1 at both ends and units where a is 2 inside).

[0050] Typical principal units represented by the above formula include, for example, when a is 2 and R SBoth are alkyl groups in a dialkylsiloxane unit [for example, a dimethylsiloxane unit, etc.]. 1-6 [Alkylsiloxane units, etc.]; a is 2, R S Alkylalkenylsiloxane units [such as methylvinylsiloxane units] are units in which one side is an alkyl group and the other side is an alkenyl group. 1-6 Alkyl C 2-6 [Alkenylsiloxane units, etc.]; a is 2, R S Alkylarylsiloxane units [such as methylphenylsiloxane units] are units in which one side is an alkyl group and the other side is an aryl group. 1-6 Alkyl C 6-10 [Arylsiloxane units, etc.]; a is 2, R S Diarylsiloxane units [such as diphenylsiloxane units] where both are aryl groups. 6-10 [Arylsiloxane units, etc.]; a is 2, R S One side is an alkyl group and the other side is a fluoroalkyl group, such as an alkylfluoroalkylsiloxane unit [methyl(3,3,3-trifluoropropyl)siloxane unit]. 1-6 AlkylfluoroC 1-6 Examples include alkylsiloxane units, etc.

[0051] The polyorganosiloxane may contain the main unit represented by the above formula alone or in combination of two or more types. The proportion of the main unit represented by the above formula may be, for example, 50 to 100 mol%, preferably in stages, 70 mol% or more, 80 mol% or more, and 90 mol% or more, relative to the total constituent units of the polyorganosiloxane.

[0052] Typical polyorganosiloxanes include polyorganosiloxanes (single or copolymer) containing the units described above as typical main units, either individually or in combination of two or more. For example, polydialkylsiloxanes (such as polydimethylsiloxane (PDMS)) 1-4 Alkylsiloxanes, polyalkylalkenylsiloxanes (such as polymethylvinylsiloxanes) 1-4 Alkyl C 2-4Alkenylsiloxanes, polyalkylarylsiloxanes (such as polymethylphenylsiloxanes) 1-4 Alkyl C 6-10 Arylsiloxanes, polydiarylsiloxanes (polydiphenylsiloxanes, etc.) 6-10 (arylsiloxane), dialkylsiloxane-alkylalkenylsiloxane copolymer [such as dimethylsiloxane-methylvinylsiloxane copolymer, etc.) 1-4 Alkylsiloxane-C 1-4 Alkyl C 2-4 [e.g., alkenylsiloxane copolymers], dialkylsiloxane-alkylarylsiloxane copolymers [e.g., diC C dimethylsiloxane-methylphenylsiloxane copolymers] 1-4 Alkylsiloxane-C 1-4 Alkyl C 6-10 [such as arylsiloxane copolymers], dialkylsiloxane-alkylalkenylsiloxane-alkylarylsiloxane copolymers [such as dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymers] 1-4 Alkylsiloxane-C 1-4 Alkyl C 2-4 Alkenylsiloxane-C 1-4 Alkyl C 6-10 [Arcylsiloxane copolymers, etc.], dialkylsiloxane-diarylsiloxane copolymers [Dimethylsiloxane-diphenylsiloxane copolymers, etc.] 1-4 Alkylsiloxane-diC 6-10 [such as arylsiloxane copolymers], dialkylsiloxane-alkylalkenylsiloxane-diarylsiloxane copolymers [such as dimethylsiloxane-methylvinylsiloxane-diphenylsiloxane copolymers] 1-4 Alkylsiloxane-C 1-4 Alkyl C 2-4 Alkenylsiloxane-C 6-10 [Arylsiloxane copolymers, etc.], dialkylsiloxane-alkylfluoroalkylsiloxane copolymers [Dimethylsiloxane-methyl(3,3,3-trifluoropropyl)siloxane copolymers, etc.] 1-4Alkylsiloxane-C 1-4 AlkylfluoroC 1-4 [Alkylsiloxane copolymers, etc.], alkylalkenylsiloxane-alkylfluoroalkylsiloxane copolymers [methylvinylsiloxane-methyl(3,3,3-trifluoropropyl)siloxane copolymers, etc.] 1-4 Alkyl C 2-4 Alkenylsiloxane-C 1-4 AlkylfluoroC 1-4 Examples include alkylsiloxane copolymers.

[0053] Furthermore, polyorganosiloxanes (for example, the representative polyorganosiloxanes mentioned above) may, if necessary, have one or more functional groups on any of the Si atoms constituting the polyorganosiloxane. For example, polyorganosiloxanes may have functional groups at the molecular ends and / or side chains (R in the main unit represented by the above formula). S They may have functional groups as follows: That is, in a polyorganosiloxane formed from the main unit represented by the above formula, at least one R S It may also be a functional group.

[0054] Examples of functional groups that may be bonded to the Si atom include hydrogen atoms (Si-H group or hydrosilyl group), hydroxyl groups (Si-OH group or silanol group), hydrolyzable groups [for example, alkoxy groups (methoxy group, ethoxy group, etc.)]. 1-4 Alkoxy groups, alkenyl groups (such as vinyl groups) 2-4 Alkenyl groups (such as alkenyl groups), alkenyloxy groups (such as isopropenoxy groups, etc.) 2-4 [such as alkenyloxy groups, halogen atoms, etc.], (meth)acryloyl groups, (meth)acryloyloxyalkyl groups (such as acryloyloxypropyl groups, etc. (meth)acryloyl C 2-4 Alkyl groups, etc.), mercaptoalkyl groups (mercaptoC groups such as mercaptopropyl groups) 2-4Examples include alkyl groups, epoxy groups, carboxyl groups, amino groups, or substituted amino groups (such as mono- or dialkylamino groups, mono- or diacylamino groups, etc.). These functional groups may be present individually or in combination of two or more.

[0055] The ends of polyorganosiloxanes (for example, both ends of a linear polyorganosiloxane) include, for example, trimethylsilyl groups, dimethylvinylsilyl groups, silanol groups, and tri-C 1-2 It may also be an alkoxysilyl group, etc.

[0056] The silicone rubber component (polyorganosiloxane) may be used alone or in combination of two or more types. A preferred silicone rubber component (polyorganosiloxane) is polydimethylsiloxane (PDMS), which may have one or more functional groups.

[0057] The silicone rubber component may be room temperature curing type, thermosetting type, or photocuring type (UV curing type), depending on the curing (crosslinking) method, with photocuring type (UV curing type) being preferred. Furthermore, the silicone rubber component may be radical curing type or peroxide curing type [crosslinking by radical reaction (radical polymerization, enthiol reaction, etc.) using organic peroxides, photoradical initiators, etc.]; addition curing type [crosslinking by hydrosilylation reaction between unsaturated bonds (such as vinyl groups or alkenyl groups) and hydrogen atoms (Si-H groups)]; condensation curing type (crosslinking by condensation reaction of silanol groups produced by hydrolysis of hydrolyzable groups); and combinations thereof (such as radical curing / condensation curing combined type), with radical curing type (or peroxide curing type) or addition curing type being preferred, and addition curing type silicone rubber being even more preferred because it is less prone to shrinkage during the curing reaction and has improved heat resistance.

[0058] The silicone rubber component may be millable silicone rubber or liquid or paste-type silicone rubber, depending on its properties or viscosity. Liquid or paste-type (especially liquid) silicone rubber is preferred because it is easy to mix with polysilane and allows for a good balance in improving heat resistance. If it is liquid or paste-type, it may be either a one-component curing type or a two-component curing type, with the two-component curing type being preferred.

[0059] The viscosity of liquid or paste-like silicone rubber at 23°C may be, for example, around 0.1 to 350 Pa·s, and preferably in the following increments: 0.3 to 100 Pa·s, 0.5 to 50 Pa·s, 1 to 10 Pa·s, 1.5 to 5 Pa·s, 2 to 4 Pa·s, and 2.5 to 3.5 Pa·s. In the case of a two-component curing type, the viscosity of each liquid before mixing may be within the above range, and the viscosity after mixing may also be within the above range.

[0060] In this specification and in the claims, viscosity can be measured in accordance with JIS K 6249.

[0061] Preferred silicone rubber components are radical-curing (or peroxide-curing) or addition-curing millable silicone rubber (e.g., VMQ), or photocuring (UV-curing) liquid or paste-type silicone rubber; more preferably, photocuring, particularly addition-curing, silicone rubber, and one-component or two-component curing (particularly two-component curing) liquid or paste-type (particularly liquid) silicone rubber, as they are less prone to shrinkage during the curing reaction and have easily improved heat resistance. Specifically, as photocuring liquid or paste-type silicone rubber, a combination of a polyorganosiloxane having an alkenyl group (such as a vinyl group) as a functional group and a polyorganosiloxane (or hydrogen polyorganosiloxane) having a hydrogen atom (Si-H group) as a functional group is preferred, and more preferably, a combination of polydimethylsiloxane (PDMS) having a vinyl group and polydimethylsiloxane (PDMS) having a hydrogen atom (Si-H group).

[0062] The ratio of the polyorganosiloxane having an alkenyl group (such as a vinyl group) to the polyorganosiloxane having a hydrogen atom (Si-H group) may be, for example, about 40 / 60 to 60 / 40 in terms of mass ratio (the former / the latter), preferably 45 / 55 to 55 / 45, and particularly 50 / 50.

[0063] The molecular weight Me between crosslinking points in the crosslinked product of the silicone rubber component may be within a predetermined range as shown below according to the type of the silicone rubber component.

[0064] (A): When the silicone rubber component is a liquid or paste-like silicone rubber, the molecular weight Me between crosslinking points in the crosslinked product of the silicone rubber component is, for example, 2×10 3 g / mol or more (e.g., 2.1×10 3 to 10×10 3 g / mol, among others 2.2×10 3 to 5×10 3 g / mol, particularly 2.3×10 3 to 3.7×10 3 g / mol) approximately, and preferably stepwise in the following ranges: 2.5×10 3 to 3.5×10 3 g / mol, 2.6×10 3 to 3.3×10 3 g / mol, 2.7×10 3 to 3.2×10 3 g / mol, 2.8×10 3 to 3.1×10 3 g / mol, 2.9×10 3 to 3×10 3 g / mol. When the molecular weight Me between crosslinking points is in an appropriate range that is not too low, the heat resistance tends to be easily improved effectively, and when it is in an appropriate range that is not too high, the deterioration of rubber-like properties (such as elasticity or shape recoverability) tends to be easily suppressed.

[0065] (B): When the silicone rubber component is a millable type silicone rubber, the molecular weight Me between crosslinking points in the crosslinked product of the silicone rubber component is, for example, 13.5×10 3 g / mol or more (e.g., 13.5×10 3~100×10 3 It may be around g / mol, preferably in the following steps: 20 × 10 3 ~95×10 3 g / mol, 22 × 10 3 ~93×10 3 g / mol, 23 × 10 3 ~92×10 3 g / mol, 24 × 10 3 ~91×10 3 g / mol, 25 × 10 3 ~90×10 3 g / mol, 30 × 10 3 ~80×10 3 g / mol, 40 × 10 3 ~75×10 3 g / mol, 50 × 10 3 ~70×10 3 g / mol, 52 × 10 3 ~65×10 3 g / mol, 53 × 10 3 ~64×10 3 g / mol, 54 × 10 3 ~63×10 3 g / mol, 55 × 10 3 ~62×10 3 g / mol, 56 × 10 3 ~61×10 3 g / mol, 57 × 10 3 ~60×10 3 g / mol, 58 × 10 3 ~59×10 3 The value is g / mol. When the molecular weight Me between crosslinking points is within a moderate range that is not too low, it is easier to effectively improve heat resistance, and when it is within a moderate range that is not too high, it tends to suppress the decrease in rubber-like properties (such as elasticity or shape recovery).

[0066] In this specification and in the claims, the molecular weight Me between crosslinking points can be measured by the method described in the examples below.

[0067] [Crosslinking agent] An uncrosslinked silicone rubber composition (a high-temperature resistant silicone rubber composition before crosslinking) for forming a high-temperature resistant silicone rubber composition may contain a crosslinking agent [vulcanizing agent, curing agent, or catalyst (curing catalyst)] for crosslinking (or curing) the silicone rubber components. The crosslinking agent [vulcanizing agent, curing agent, or catalyst (curing catalyst)] can be appropriately selected depending on the type of silicone rubber component (such as the form of curing (crosslinking)), and conventional crosslinking agents can be used.

[0068] Examples of crosslinking agents include organic peroxides [diasyl peroxides (p-methylbenzoyl peroxide, 2,4-dichlorobenzoyl peroxide), peroxyesters, dialkyl peroxides (dicumyl peroxide, t-butylcumyl peroxide, 1,1-di-butylperoxy-3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di(t-butylperoxy)-hexane, 1,3-bis(t-butylperoxy-isopropyl)benzene, di-t-butyl peroxide, etc.]; platinum group metal catalysts [for example, platinum catalysts (platinum or its compounds, e.g., platinum powder, platinum black, chloroplatinic acid, alcoholic solution of chloroplatinic acid (alcohol-modified chloroplatinic acid), platinum (chloroplatinic acid, etc.)-olefin complexes, platinum (chloroplatinic acid, etc.)-acetylene complexes, platinum (salts)]; platinum group metal catalysts [for example, platinum catalysts (platinum or its compounds, e.g., platinum fine powder, platinum black, chloroplatinic acid, alcoholic solution of chloroplatinic acid (alcohol-modified chloroplatinic acid), platinum (chloroplatinic acid, etc.)-olefin complexes, platinum (salts)]. Examples include: platinum-alkenylsiloxane (vinylsiloxane, etc.) complexes, platinum-phosphorus complexes, etc.; palladium-based catalysts (palladium or palladium compounds, e.g., tetrakis(triphenylphosphine)palladium, etc.); rhodium-based catalysts (rhodium or rhodium compounds, e.g., chlorotris(triphenylphosphine)rhodium, etc.); monosilanes with hydrolyzable groups [e.g., alkoxymonosilanes such as methyltri(methoxy)silane, alkenyloxymonosilanes such as methyltri(isopropenoxy)silane, acyloxymonosilanes such as methyltri(acetoxy)silane, oximemonosilanes such as methyltris(methylethylketoxime)silane, etc.]; tin compounds (tin salts (tin soap, etc.), etc.); titanium compounds; amine compounds, etc.

[0069] The crosslinking agent may be used alone or in combination of two or more types. For addition-curing type silicone rubber components, a platinum-based catalyst is preferred, and for radical-curing type (e.g., millable type) silicone rubber, an organic peroxide (e.g., acyl peroxide) is preferred.

[0070] The proportion of the crosslinking agent may be, for example, 0.01 to 10 parts by mass, preferably 0.1 to 5 parts by mass, and more preferably 0.5 to 3 parts by mass (particularly 1 to 2 parts by mass) per 100 parts by mass of the silicone rubber component.

[0071] [Polysilane] As described later in the section on manufacturing methods, the uncrosslinked silicone rubber composition (high heat-resistant silicone rubber composition before crosslinking) for forming a high heat-resistant silicone rubber composition contains at least polysilane. Crosslinking (curing) the silicone rubber component in the presence of polysilane effectively improves the heat resistance of the crosslinked silicone rubber composition. Therefore, this disclosure includes a heat-resistant improver containing polysilane (a heat-resistant improver for silicone rubber compositions).

[0072] Furthermore, the high heat-resistant silicone rubber composition after crosslinking may contain polysilane added during the crosslinking process, but it is preferable to substantially omit polysilane (remove polysilane) as this makes it easier to further improve heat resistance.

[0073] Polysilanes may be compounds having a linear, cyclic, branched, network-like (or lattice-like) shape (structure) with Si-Si bonds, or a combination of two or more of these. Examples of structural units (silane units) constituting polysilanes include structural units represented by the following formulas (1a) to (1d) (hereinafter also referred to as silane units (1a) to (1d) respectively), and it is preferable that polysilanes contain at least one structural unit selected from silane units (1a) and (1b).

[0074] [ka]

[0075] (In the formula, R 1 ~R 6 (Each represents a hydrogen atom, a hydroxyl group, a halogen atom, or an organic group.)

[0076] In the above formulas (1a), (1b), and (1d), the side chain R 1 ~R 6 Examples of organic groups represented by include hydrocarbon groups such as alkyl groups, alkenyl groups, cycloalkyl groups, cycloalkenyl groups, aryl groups, and aralkyl groups; and groups to which ether bonds are linked in correspondence with these hydrocarbon groups, such as alkoxy groups, cycloalkyloxy groups, aryloxy groups, and aralkyloxy groups.

[0077] Examples of alkyl groups (linear or branched alkyl groups) include methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, pentyl, and hexyl groups. 1-14 Examples include alkyl groups.

[0078] Examples of alkoxy groups include methoxy, ethoxy, propoxy, isopropoxy, n-butoxy, isobutoxy, s-butoxy, t-butoxy, and pentyloxy groups. 1-14 Examples include alkoxy groups.

[0079] Examples of alkenyl groups include vinyl, allyl, butenyl, and pentenyl groups. 2-14 Examples include alkenyl groups.

[0080] Examples of cycloalkyl groups include cyclopentyl, cyclohexyl, and methylcyclohexyl groups. 5-14 Examples include cycloalkyl groups.

[0081] Examples of cycloalkyloxy groups include cyclopentyloxy groups, cyclohexyloxy groups, and other C groups. 5-14Examples include cycloalkyloxy groups.

[0082] Examples of cycloalkenyl groups include cyclopentenyl groups, cyclohexenyl groups, and other C groups. 5-14 Examples include cycloalkenyl groups.

[0083] Examples of aryl groups include phenyl, methylphenyl (tolyl), dimethylphenyl (xylyl), and naphthyl groups. 6-20 Examples include aryl groups, preferably C 6-14 Aryl group, more preferably C 6-12 C such as an aryl group, more preferably a phenyl group. 6-10 It is an aryl group.

[0084] Examples of aryloxy groups include phenoxy groups, naphthyloxy groups, etc. 6-20 Examples include aryloxy groups.

[0085] Examples of aralkyl groups include benzyl groups, phenethyl groups, phenylpropyl groups, etc. 6-20 Aryl-C 1-6 Examples include alkyl groups.

[0086] Examples of aralkyloxy groups include benzyloxy, phenethyloxy, and phenylpropyloxy groups. 6-20 Aryl-C 1-6 Examples include alkyloxy groups.

[0087] These organic groups may be used individually or in combination of two or more. Of these organic groups, hydrocarbon groups such as alkyl groups, alkenyl groups, cycloalkyl groups, aryl groups, and aralkyl groups are preferred.

[0088] Note, R 1 ~R 6In this, the organic group (alkyl group, aryl group, etc.) may have substituents. Examples of such substituents (or functional groups) include groups similar to those exemplified above, such as hydroxyl groups, alkyl groups, aryl groups, and alkoxy groups, and the number of substituents is not particularly limited.

[0089] These R 1 ~R 6 Of these, hydrogen atoms, hydroxyl groups, alkoxy groups, halogen atoms, etc. are terminal, i.e., R of the structural unit represented by formula (1d). 4 ~R 6 Often, substitutions are made with R. 4 ~R 6 At least one of these may be a hydrogen atom, a hydroxyl group, an alkoxy group, or a halogen atom (such as a chlorine atom), and the remainder may be the aforementioned organic group (such as a methyl group or a phenyl group). Furthermore, the polysilane may be sealed, and if it is sealed, the terminal silane unit (1d) may contain R 4 ~R 6 All of them may be the aforementioned organic groups.

[0090] Polysilane is R 1 ~R 6 It may contain reactive groups such as radical polymerizable groups, or it may not contain them substantially.

[0091] Usually, R 1 ~R 6 (especially, R 1 ~R 3 ) is often an organic group, and preferred R 1 ~R 6 (especially, R 1 ~R 3 The group(s) are hydrocarbon groups such as alkyl groups, alkenyl groups, cycloalkyl groups, aryl groups, and aralkyl groups, and are more preferably alkyl groups and aryl groups.

[0092] Preferred alkyl groups (linear or branched alkyl groups) include C 1-10 Alkyl(C) 1-6 Examples include alkyl groups, and more preferably C 1-4 Alkyl(C) 1-3 These include alkyl groups, and among them, C groups such as methyl and ethyl groups. 1-2 It is an alkyl group, with a methyl group being the most preferred.

[0093] Preferred aryl groups include phenyl, tolyl, xylyl, naphthyl, and other C groups. 1-4 C may have alkyl groups. 6-12 It is an aryl group, and more preferably C 1-3 C may have alkyl groups. 6-10 It is an aryl group, and among them, C 1-2 A phenyl group which may have an alkyl group, and a phenyl group is most preferred.

[0094] In the silane unit (1a), R 1 and R 2 The types may be the same or different from each other, but it is preferable that they be different. In the silane unit (1a), R 1 and R 2 It is preferable that it contains at least one alkyl group and one aryl group. Typical silane units (1a) include, for example, R 1 ,R 2 Both are alkyl groups, such as dialkylsilane units (dimethylsilane units, etc.). 1-4 Alkylsilane units, etc.); R 1 ,R 2 Diarylsilane units (such as diphenylsilane units) are units in which both are aryl groups. 6-10 Arylsilane units, etc.); R 1 ,R 2 Alkylarylsilane units (such as methylphenylsilane units) are units in which one of the groups is an alkyl group and the other is an aryl group. 1-4 Alkyl C 6-10Examples include arylsilane units. Silane units (1a) may be included alone or in combination of two or more types.

[0095] In the silane unit (1b), R 3 It is preferably an alkyl group or an aryl group, and more preferably an aryl group (particularly a phenyl group). Typical silane units (1b) include, for example, R 3 The alkylsilane unit (such as the methylsilane unit) is an alkyl group. 1-4 Alkylsilane units, etc.); R 3 The aryl silane unit (such as the phenylsilane unit) is an aryl group. 6-10 Examples include arylsilane units. Silane units (1a) may be included alone or in combination of two or more types.

[0096] In the silane unit (1d), R 4 ,R 5 and R 6 The types may be the same or different from each other. The silane unit (1d) is located at the terminal in the chemical structure of the polysilane. At least some of the terminal groups of the polysilane may be alkyl groups or aryl groups, and silanol groups (R 4 ~R 6 At least one of them may be a hydroxyl group.

[0097] The polysilane preferably contains at least one structural unit selected from silane units (1a) and (1b), more preferably at least silane unit (1a), and even more preferably at least one selected from dialkylsilane units, diarylsilane units and alkylarylsilane units, in particular alkylarylsilane units (especially C such as methylphenylsilane units). 1-3 Alkyl C 6-8 Preferably, it contains at least arylsilane units.

[0098] The ratio of silane units (1a) to the total structural units of polysilane may be selected from a wide range of 10 to 100 mol%, preferably in stages as follows: 30 mol% or more, 50 mol% or more, 70 mol% or more, 80 mol% or more, 90 mol% or more, and especially may be substantially 100 mol%, and more preferably in stages as follows: 40 to 90 mol%, 50 to 80 mol%, 55 to 75 mol%, and 60 to 70 mol%.

[0099] The proportion of silane units (1b) to the total structural units of polysilane may be, for example, 0 to 20 mol% (e.g., 1 to 10 mol%, preferably 2 to 5 mol%), or it may not be substantially present at all.

[0100] The proportion of silane units (1c) to the total structural units of polysilane may be, for example, 0 to 20 mol% (e.g., 1 to 10 mol%, preferably 2 to 5 mol%), or it may not be substantially present at all.

[0101] Since silane units (1d) form the ends of the polysilane, the structure remaining after subtracting silane units (1a) to (1c) from the total structural units of the polysilane may consist of silane units (1d). The ratio of silane units (1d) to the total structural units of the polysilane is not particularly limited and may be, for example, around 0 to 50 mol% (e.g., 10 to 40 mol%), or 30 mol% or less (e.g., 10 mol% or less, substantially 0 mol%).

[0102] The polymerization form of polysilane is not particularly limited and may be a homopolymer or copolymer, such as a random copolymer, graft copolymer, block copolymer, or alternating copolymer.

[0103] Examples of typical polysilanes include linear or cyclic (especially linear) polysilanes having at least (especially predominantly) silane units (1a), and branched or network polysilanes (e.g., network polysilanes) having at least silane units (1b) and / or silane units (1c).

[0104] Examples of chain-like (especially linear) or cyclic polysilanes having silane units (1a) include polydialkylsilanes, polydiarylsilanes, polyalkylarylsilanes, dialkylsilane-diarylsilane copolymers, dialkylsilane-alkylarylsilane copolymers, and alkylarylsilane-diarylsilane copolymers.

[0105] Examples of polydialkylsilanes include polydimethylsilane, polymethylpropylsilane, polymethylbutylsilane, polymethylpentylsilane, polydibutylsilane, polydihexylsilane, and polydi-C dimethylsilane-methylhexylsilane copolymers. 1-8 Examples include alkylsilanes, preferably polydiC 1-4 Alkylsilanes, more preferably polydiC 1-2 It is an alkylsilane.

[0106] Examples of polydiarylsilanes include polydiphenylsilane and other polydiC 6-12 Examples include arylsilanes, preferably polydiC 6-10 The material is an arylsilane, more preferably a polydiphenylsilane.

[0107] Examples of polyalkylarylsilanes include polymethylphenylsilane, methylphenylsilane-phenylhexylsilane copolymers, and other poly(C) 1-8 Alkyl-C 6-12 Examples include arylsilanes, preferably poly(C) 1-4 Alkyl-C 6-10 Arylsilane), more preferably poly(C 1-2 It is an alkylphenylsilane.

[0108] Examples of dialkylsilane-diarylsilane copolymers include diC such as dimethylsilane-diphenylsilane copolymers. 1-8 Alkylsilane-diC 6-12 Examples include arylsilane copolymers, preferably diC 1-4 Alkylsilane-diC6-10 Arylsilane copolymer, more preferably diC 1-2 It is an alkylsilane-diphenylsilane copolymer.

[0109] Examples of dialkylsilane-alkylarylsilane copolymers include dimethylsilane-methylphenylsilane copolymer, dimethylsilane-(hexylphenylsilane) copolymer, dimethylsilane-(methylnaphthylsilane) copolymer, and other diC 1-8 Alkylsilane-(C 1-8 Alkyl-C 6-12 Examples include arylsilane copolymers, preferably diC 1-4 Alkylsilane-(C 1-4 Alkyl-C 6-10 Arylsilane copolymer, more preferably diC 1-2 Alkylsilane-(C 1-2 It is an alkyl-phenylsilane copolymer.

[0110] Examples of alkylarylsilane-diarylsilane copolymers include (methyl-phenylsilane)-diphenylsilane copolymers and other (C) 1-8 Alkyl-C 6-12 Arylsilane)-diC 6-12 Examples include arylsilane copolymers, preferably (C 1-4 Alkyl-C 6-10 Arylsilane)-diC 6-10 Arylsilane copolymer, more preferably (C 1-2 It is an alkyl-phenylsilane-diphenylsilane copolymer.

[0111] Examples of branched or network polysilanes (e.g., network polysilanes) having at least silane units (1b) and / or silane units (1c) include polyalkylsilanes and polyarylsilanes.

[0112] Examples of polyalkylsilanes include polymethylsilane, polypropylsilane, polybutylsilane, and polyhexylsilane. 1-8Examples include alkylsilanes, preferably polyC 1-4 Alkylsilane, more preferably polyC 1-2 It is an alkylsilane.

[0113] Examples of polyarylsilanes include polyphenylsilane and other poly-C 6-12 Examples include arylsilanes, preferably polyC 6-10 The arylsilane, more preferably polyphenylsilane, is used.

[0114] Polysilanes can be used alone or in combination of two or more. Linear or cyclic polysilanes having at least silane units (1a) [particularly having them mainly (for example, in a proportion of 50 mol% or more in the structural units)] are preferred, more preferably polyalkylarylsilanes, polydiarylsilanes, and even more preferably linear polyalkylarylsilanes, cyclic polydiarylsilanes (for example, cyclic polydi-C such as decaphenylcyclopentasilane). 6-10 These include arylsilanes, and among them, linear poly(C) 1-4 Alkyl-C 6-10 Linear polyalkylarylsilanes such as arylsilanes are preferred, and linear poly(C)methylphenylsilanes are particularly preferred. 1-2 It is an alkylphenylsilane.

[0115] It is preferable that polysilanes do not contain siloxane bonds (-Si-O-Si-), but they may inevitably contain trace amounts of siloxane bonds.

[0116] The average degree of polymerization of polysilane, in terms of silicon atoms (i.e., the average number of silicon atoms per molecule), is, for example, around 500 or less, specifically around 2 to 250, preferably 3 to 100, more preferably 3.5 to 50, even more preferably 4 to 20, and most preferably 4.5 to 10, with a particularly good preference of 5 to 7. When the average degree of polymerization is within a moderate range that is not too high, it tends to have excellent handling properties (fluidity or dispersibility), makes it easier to adjust the molecular weight Me between crosslinking points to a predetermined range, and, as will be described later, tends to make it easier to remove polysilane from the crosslinked product in the polysilane removal step after the crosslinking process.

[0117] The weight-average molecular weight Mw of polysilane can be measured by GPC (polystyrene equivalent) and can be selected from a range of approximately 150 to 50000, for example, 100 or more, specifically 200 to 30000 (e.g., 250 to 20000), preferably 300 to 15000 (e.g., 350 to 10000), and more preferably 400 to 5000 (e.g., 450 to 3000). Usually, it can be around 200 to 2000, with 500 to 1500 (e.g., 550 to 1000) being particularly preferred, and especially 600 to 800 (e.g., 650 to 750).

[0118] The number-average molecular weight Mn of polysilane is, for example, about 30,000 or less, and is, for example, 100 to 10,000, preferably 300 to 3,000, and more preferably 400 to 1,000 (particularly 500 to 700), according to the GPC (polystyrene equivalent) measurement method.

[0119] The dispersion degree Mw / Mn is, for example, 1 to 5, preferably 1 to 3, more preferably 1 to 2, and particularly 1 to 1.5.

[0120] When the weight-average molecular weight Mw and number-average molecular weight Mn are within a moderate range and not too large, the handling properties (fluidity or dispersibility) are excellent, and it tends to be easier to adjust the inter-crosslinking molecular weight Me to a predetermined range. Furthermore, as will be described later, it tends to be easier to remove polysilane from the crosslinked product in the polysilane removal process after the crosslinking process.

[0121] Furthermore, the weight-average molecular weight (Mw), number-average molecular weight (Mn), and dispersion degree (Mw / Mn) of polysilane can be measured using GPC (Geomorphic Spectroscopy) in terms of standard polystyrene equivalents.

[0122] Polysilane may be in a liquid (or viscous) or solid state at room temperature (for example, around 20°C) and 1 atmosphere, but it is preferable that it be in a liquid (or viscous) state from the viewpoint of dispersibility (or compatibility) with silicone rubber components and the like.

[0123] Polysilanes may be commercially available or prepared. When prepared, conventional methods such as preparation methods using halosilanes having structural units represented by formulas (1a) to (1d) may be used, for example, a method of dehalogenating halosilanes using magnesium as a reducing agent ("Magnesium Reduction Method", WO98 / 29476, etc.), a method of dehalogenating halosilanes in the presence of alkali metals ("Kipping Method", J.Am.Chem.Soc., 110,124 (1988), Macromolecules, 23,3423 (1990), etc.), or a method of dehalogenating halosilanes by electrode reduction (J.Chem.Soc., Chem.Commun., 1161 (1990), J.Chem.Soc., They can be obtained by methods such as dehydrogenation polymerization of hydrosilanes in the presence of a metal catalyst (e.g., Japanese Patent Publication No. 4-334551), anionic polymerization of disylene crosslinked with biphenyl (e.g., Macromolecules, 23, 4494 (1990)), or ring-opening polymerization of cyclic silanes.

[0124] The ratio of polysilane to the silicone rubber component (or the total amount of the silicone rubber component and the crosslinking agent) may be, for example, the former / latter (mass ratio) = approximately 0.1 / 99.9 to 30 / 70, and preferably, in stages, 1 / 99 to 20 / 80, 2 / 98 to 10 / 90, 3 / 97 to 8 / 92, and 4 / 96 to 6 / 94. This ratio may be the ratio in the uncrosslinked silicone rubber composition or the ratio in the crosslinked high heat-resistant silicone rubber composition. In the uncrosslinked silicone rubber composition, if the polysilane ratio is in a moderate range that is not too low, it is easier to effectively improve heat resistance, and if it is in a moderate range that is not too high, it is easier to suppress the decrease in rubber-like properties (such as elasticity or shape recovery), and it is also easier to suppress the decrease in heat resistance when polysilane remains in the crosslinked high heat-resistant silicone rubber composition.

[0125] In the crosslinked high heat-resistant silicone rubber composition, the ratio of polysilane to silicone rubber component (or the total amount of silicone rubber component and crosslinking agent) may be approximately 0 / 100 to 30 / 70 by mass ratio, preferably in the following increments: 0 / 100 to 25 / 75, 0 / 100 to 20 / 80, 0 / 100 to 15 / 85, 0 / 100 to 10 / 90, 0 / 100 to 5 / 95, 0 / 100 to 3 / 97, 0 / 100 to 2 / 98, and 0 / 100 to 1 / 99, with a substantially 0 / 100 ratio being particularly preferred. In the crosslinked high heat-resistant silicone rubber composition, a lower proportion of polysilane appears to more effectively improve heat resistance.

[0126] [Other ingredients] The uncrosslinked silicone rubber composition and the crosslinked high heat-resistant silicone rubber composition may or may not contain other components other than the silicone rubber component, crosslinking agent, and polysilane, as needed.

[0127] Other components are not particularly limited and may include conventional additives added to silicone rubber compositions. Examples of additives include fillers or fillers [e.g., reinforcing agents (dry silica, wet silica, etc.); bulking agents (crystalline silica, calcium carbonate, talc, etc.); thermally conductive fillers (ceramic fillers such as alumina, zinc oxide, magnesium oxide, anhydrous magnesium carbonate, crystalline silica, boron nitride, aluminum nitride, silicon nitride, etc.; metallic fillers such as aluminum, copper, silver, carbon fiber, graphite, etc.); fibers (organic or inorganic long or short fibers, etc.)], softeners, plasticizers, crosslinking aids (vulcanization aids), reaction regulators (vulcanization retarders, etc.), aging or antioxidants [e.g., rare earth metals, Group 4 of the periodic table (titanium, zirconium, etc.), Groups 7-10 of the periodic table (manganese, iron, carbon, etc.)], Examples of materials include metal compounds containing metal elements such as balt and nickel (oxides, hydroxides, carbonates, or fatty acid salts), stabilizers (ultraviolet absorbers, light stabilizers, heat stabilizers, etc.), heat resistance improvers or heat resistance imparters other than polysilanes (iron oxides, cerium oxide, titanium oxide, etc.), colorants (e.g., dyes and pigments), tackifiers, adhesion improvers (accelerators) or adhesion aids (silane coupling agents, organometallic compounds, etc.), surface modifiers, mold release agents, lubricants, flame retardants (phosphorus-based flame retardants, halogen-based flame retardants, inorganic flame retardants, etc.), flame retardant aids, antistatic agents, conductive agents, carbon materials, resin components (thermoplastic resins, thermosetting resins, etc.), solvents, dispersants, flow regulators, leveling agents, defoamers, stress reducers, antibacterial agents, and preservatives.

[0128] These other components can be used individually or in combination of two or more. The total proportion of the other components may be, for example, about 0.1 to 1000 parts by mass per 100 parts by mass of the silicone rubber component, preferably 0.1 to 100 parts by mass (for example, 0.5 to 50 parts by mass), and more preferably about 1 to 30 parts by mass (for example, 3 to 10 parts by mass).

[0129] [Method for producing a high heat-resistant silicone rubber composition, and method for improving heat resistance] The high heat-resistant silicone rubber composition of this disclosure can be produced by a method that includes a crosslinking (curing) step in which a silicone rubber component is crosslinked in the presence of polysilane.

[0130] (Crosslinking process) In the crosslinking process, an uncrosslinked silicone rubber composition prepared by mixing at least a silicone rubber component and polysilane (and optionally a crosslinking agent, other components, etc.) is subjected to a crosslinking (curing) reaction to form a crosslinked product of the silicone rubber component. When the silicone rubber component is crosslinked in the presence of polysilane, the molecular weight Me between crosslinking points in the crosslinked product can be increased (or easily adjusted to a predetermined range) compared to when it is crosslinked in the absence of polysilane, and the heat resistance can be effectively improved. Therefore, this disclosure includes a method for improving the heat resistance of a silicone rubber composition by crosslinking a silicone rubber component in the presence of polysilane, and a heat resistance improver containing polysilane (a heat resistance improver for silicone rubber compositions).

[0131] In the crosslinking (curing) process, depending on the type of silicone rubber component, the crosslinking (curing) reaction can be carried out using heat, light, and / or moisture (humidity). The crosslinking (curing) conditions (for example, heating temperature when using heat, wavelength and irradiation amount (integrated light amount) when using light (UV)) can be set appropriately according to the type of silicone rubber component and are not particularly limited.

[0132] (Polysilane removal process) Furthermore, the manufacturing method (and heat resistance improvement method) of the present disclosure may include a polysilane removal step in which the polysilane is removed from the crosslinked product (high heat-resistant silicone rubber composition) obtained through the crosslinking step. The high heat-resistant silicone rubber composition obtained through the polysilane removal step appears to have even greater heat resistance than the case in which the polysilane is not removed.

[0133] The method for removing polysilane is not particularly limited. Examples include extracting polysilane from the crosslinked material by washing and immersion using a solvent capable of dissolving polysilane (e.g., aromatic hydrocarbons such as toluene), vaporizing the polysilane in the crosslinked material by reduced pressure and / or heating, or a combination of these methods. The preferred removal method is washing and immersion using a solvent capable of dissolving polysilane, and the method of removing polysilane by Soxhlet extraction is even more preferred. The washing and immersion method with a solvent (especially Soxhlet extraction) seems to further improve heat resistance, possibly because other components such as unreacted silicone rubber components that did not participate in the crosslinking reaction are also removed along with the polysilane. The reason for this is not clear, but it is presumed that if unreacted silicone rubber components remain inside the crosslinked structure without being removed, the molecular chains forming the crosslinked structure become under tension, making them more susceptible to thermal degradation. Examples of solvents used in the Soxhlet extraction method include hydrocarbons (e.g., aromatic hydrocarbons such as toluene), ethers (e.g., cyclic ethers such as tetrahydrofuran (THF)), and ketones (e.g., dialkyl ketones such as methyl ethyl ketone).

[0134] In the polysilane removal step, it is sufficient to remove at least a portion of the polysilane in the crosslinked product obtained through the crosslinking step, and it is not necessary to remove all of the polysilane. However, from the standpoint of effectively improving heat resistance, it is preferable to remove substantially all of the polysilane (to the point where the composition substantially does not contain polysilane).

[0135] [Properties and applications of high heat-resistant silicone rubber compositions] The high heat-resistant silicone rubber composition of this disclosure has excellent heat resistance, and even when exposed to high-temperature environments (for example, when heated at 240°C for 3 hours), it can effectively suppress the decrease or deterioration of its physical properties (mechanical properties) and maintains the physical properties (mechanical properties) it had before heating (for example, at 25°C).

[0136] Therefore, when the high heat-resistant silicone rubber composition of this disclosure is heated at a temperature of 240°C for 3 hours, the elongation at break after heating may be, for example, 30% or more (for example, 50-100%) of the elongation at break before heating (at 25°C). If the silicone rubber component is liquid or paste-like silicone rubber, it is preferably in the following increments: 60-95%, 70-90%, 75-88%, and 80-85%; if the silicone rubber component is millable-type silicone rubber, it is preferably in the following increments: 50-85%, 55-80%, 58-75%, 60-70%, and 62-68%. When the elongation at break after heating is within a moderate range that is not too low, the rubbery properties are effectively maintained even when exposed to high-temperature environments, and the composition tends not to become brittle.

[0137] When the high heat-resistant silicone rubber composition of this disclosure is heated at a temperature of 240°C for 3 hours, the tensile strength after heating may be, for example, 30% or more (e.g., 50-120%) of the tensile strength before heating (at 25°C). If the silicone rubber component is liquid or paste-like silicone rubber, the preferred values ​​are, in stages, 60-110%, 70-100%, 80-98%, 85-95%, and 87-93%. If the silicone rubber component is millable-type silicone rubber, the preferred values ​​are, in stages, 55-110%, 60-100%, 70-95%, 75-90%, and 80-85%. When the tensile strength after heating is within a moderate range that is not too low, the rubbery properties are effectively maintained even when exposed to high-temperature environments, and the composition tends not to become brittle.

[0138] When the high heat-resistant silicone rubber composition of this disclosure is heated at a temperature of 240°C for 3 hours, the tensile modulus after heating may be, for example, 300% or less (for example, 100-250%) of the tensile modulus before heating (at 25°C). If the silicone rubber component is liquid or paste-like silicone rubber, it is preferably in the following increments: 120-230%, 130-210%, 140-200%, 150-190%, and 160-180%; if the silicone rubber component is millable-type silicone rubber, it is preferably in the following increments: 80-220%, 85-200%, 90-180%, 95-150%, 100-130%, and 105-120%. When the tensile modulus after heating is within a moderate range that is not too high, the rubbery properties are effectively maintained even when exposed to high-temperature environments, and it tends not to become brittle.

[0139] Furthermore, if the high heat-resistant silicone rubber composition of this disclosure is formed by at least a crosslinking step of crosslinking or curing an uncrosslinked silicone rubber composition containing polysilane (crosslinking or curing the silicone rubber component in the presence of polysilane), the high heat-resistant silicone rubber composition tends to exhibit better physical properties (mechanical properties) even after heating compared to a crosslinked product (cured product) of a composition obtained by removing polysilane from this uncrosslinked silicone rubber composition (a composition that does not contain polysilane), i.e., a polysilane-free crosslinked product obtained by crosslinking or curing the silicone rubber component in the absence of polysilane.

[0140] Therefore, when the high heat-resistant silicone rubber composition of this disclosure is heated at a temperature of 240°C for 3 hours, the elongation at break after heating may be, for example, 50% or more (for example, 70-120%) of the elongation at break at 25°C of the corresponding polysilane-free crosslinked product (unheated product not heated after crosslinking). If the silicone rubber component is liquid or paste-like silicone rubber, preferably the elongation is in the following increments: 75-115%, 80-110%, 85-105%, 90-100%, and 92-98%. If the silicone rubber component is millable-type silicone rubber, preferably the elongation is in the following increments: 100-550%, 200-530%, 300-500%, 350-480%, 400-460%, and 420-450%. When the elongation at break after heating is within a moderate range that is not too low, the rubbery properties are effectively maintained even when exposed to high-temperature environments, and the material tends not to become brittle.

[0141] When the high heat-resistant silicone rubber composition of this disclosure is heated at a temperature of 240°C for 3 hours, the tensile strength after heating may be, for example, 30% or more (e.g., 40-100%) of the tensile strength at 25°C of the corresponding polysilane-free crosslinked product (unheated product not heated after crosslinking). If the silicone rubber component is liquid or paste-like silicone rubber, the preferred values ​​are, in stages, 50-90%, 55-85%, 60-80%, and 65-75%; if the silicone rubber component is millable-type silicone rubber, the preferred values ​​are, in stages, 60-100%, 65-95%, 70-90%, and 75-85%. When the tensile strength after heating is within a moderate range that is not too low, the rubbery properties are effectively maintained even when exposed to high-temperature environments, and the material tends not to become brittle.

[0142] When the high heat-resistant silicone rubber composition of this disclosure is heated at a temperature of 240°C for 3 hours, the tensile modulus after heating may be, for example, 120% or less (for example, 50-115%) of the tensile modulus at 25°C of the corresponding polysilane-free crosslinked product (unheated product not heated after crosslinking). If the silicone rubber component is liquid or paste-like silicone rubber, the preferred values ​​are, in stages, 60-110%, 65-105%, 70-100%, 75-95%, and 80-90%; if the silicone rubber component is millable-type silicone rubber, the preferred values ​​are, in stages, 20-70%, 25-65%, 30-60%, 35-55%, and 40-50%. When the tensile modulus after heating is within a moderate range and not too high, the rubbery properties are effectively maintained and the material tends not to become brittle even when exposed to high-temperature environments.

[0143] The usage environment for the high heat-resistant silicone rubber composition disclosed herein is not particularly limited, but because of its excellent heat resistance, it may be a composition for use in environments with temperatures of 200°C or higher. The preferred usage temperature (e.g., the maximum temperature in the usage environment) is between 200°C and 270°C (e.g., 210-260°C), more preferably 220-255°C (e.g., 230-250°C), and particularly 235-245°C. The time of continuous exposure to the above maximum temperature environment may be, for example, 10 minutes or more (e.g., 30 minutes to 1000 hours), preferably 1 hour or more (e.g., 2-100 hours), and more preferably 3 hours or more (e.g., 3-10 hours). [Examples]

[0144] The present disclosure will be described in more detail below based on examples, but the present disclosure is not limited to these examples. The raw materials and evaluation methods used are as follows.

[0145] [Raw materials] (I) Two-component silicone rubber: "KER-4690-A / B" manufactured by Shin-Etsu Chemical Co., Ltd. [combination of a monomer having a vinyl group in the side chain of polydimethylsiloxane and a monomer having a hydrogen atom (Si-H group) in the side chain of polydimethylsiloxane], viscosity of monomer A (23℃) 2.9 Pa·s, viscosity of monomer B (23℃) 2.4 Pa·s, viscosity after mixing A:B (mass ratio) = 1:1 (23℃) 2.7 Pa·s, contains Pt catalyst. (II) Polymethylphenylsilane (PMPS): "OGSOL SI-10-40" manufactured by Osaka Gas Chemical Co., Ltd., weight-average molecular weight Mw700, soluble in toluene. (III) Silicone rubber: "BLUESIL GUM 751 / 753" manufactured by Elkem Silicones [dimethylsiloxane-methylvinylsiloxane rubber (VMQ)], with crosslinking agent (contains 1.5 parts by mass of acyl peroxide per 100 parts by mass of rubber component)

[0146] [Evaluation Method] (Molecular weight between crosslinking points Me) The molecular weight Me [g / mol] between crosslinking points was calculated according to the following formula.

[0147]

number

[0148] (In the formula, ρ is density [g / m³]) 3 ] indicates, R is the gas constant = 8.31 [J / K·mol]. T represents absolute temperature = 293.15 [K], E' represents the storage modulus [Pa].

[0149] The storage modulus E' was measured three times using a dynamic viscoelasticity measuring device [UBM Corporation's "Rheogel-E4000"] at a frequency of 5 Hz and a strain of 0.02%, and the median value of the E' values ​​obtained in the rubbery flat region at 20°C was adopted. The density ρ was measured three times using a densimeter [Shimadzu Corporation's "AccuPycII1345"] under a He gas atmosphere at 20°C, and the average value obtained was adopted.

[0150] (Tensile test: modulus of elasticity, tensile strength, and elongation at break) Tensile tests were performed five times on rubber-like sheets punched out onto a No. 7 dumbbell using a small benchtop testing machine [(Shimadzu Corporation "EZ-LX")] under the conditions of a tensile speed of 20 mm / min, a grip distance of 15 mm, a load cell of 500 N, and room temperature (approximately 25°C). The average values ​​of the measured elastic modulus, tensile strength, and elongation at break were adopted.

[0151] The punching performance of the aforementioned dumbbell was evaluated according to the following criteria.

[0152] ○...It was able to be punched out in a dumbbell shape without any problems. △...Brittle but punched through in a dumbbell shape ×...It was too brittle to be punched through in a dumbbell shape.

[0153] [Example 1] A liquid was prepared by uniformly mixing 95 parts by mass of raw material (I) with a monomer mixing ratio A:B (mass ratio) = 1:1 and 5 parts by mass of raw material (II). This liquid was cured by UV irradiation for 24 hours using a UV irradiation device with a peak wavelength of 387 nm [(BL1060) manufactured by Yazawa Corporation] to obtain a 0.5 mm thick rubber-like sheet. The obtained rubber-like sheet was subjected to Soxhlet extraction using toluene and dried under reduced pressure for 24 hours to remove the solvent and obtain a rubber-like sheet that was substantially free of raw material (II). The obtained rubber-like sheet was heated for 3 hours in an oven set to a predetermined temperature (25°C, 200°C, 220°C, 240°C, or 270°C) and then subjected to a tensile test.

[0154] [Example 2] A liquid was prepared by uniformly mixing 95 parts by mass of raw material (I) with a monomer mixing ratio A:B=1:1 and 5 parts by mass of raw material (II). This liquid was cured by UV irradiation for 24 hours using a UV irradiation device [BL1060 manufactured by Yazawa Corporation] to obtain a 0.5 mm thick rubber-like sheet. The obtained rubber-like sheet was heated for 3 hours in an oven set to a predetermined temperature (25°C, 200°C, 220°C, 240°C, or 270°C) and then subjected to a tensile test.

[0155] [Comparative Example 1] A liquid was prepared by uniformly mixing 100 parts by mass of raw material (I) with a monomer mixing ratio A:B=1:1. This liquid was cured by UV irradiation for 24 hours using a UV irradiation device with a peak wavelength of 387 nm [(BL1060) manufactured by Yazawa Corporation] to obtain a 0.5 mm thick rubber-like sheet. The obtained rubber-like sheet was subjected to Soxhlet extraction using toluene and dried under reduced pressure for 24 hours to remove the solvent. The obtained rubber-like sheet was heated in an oven set to a predetermined temperature (25°C, 200°C, 220°C, 240°C, or 270°C) for 3 hours and then subjected to a tensile test.

[0156] Furthermore, the rubber-like sheet heated to 270°C was quite brittle and could not be punched out in a dumbbell shape, making it impossible to conduct a tensile test.

[0157] [Comparative Example 2] A liquid was prepared by uniformly mixing 100 parts by mass of raw material (I) with a monomer mixing ratio A:B=1:1. This liquid was cured by UV irradiation for 24 hours using a UV irradiation device with a peak wavelength of 387 nm [(BL1060) manufactured by Yazawa Corporation] to obtain a 0.5 mm thick rubber-like sheet. The obtained rubber-like sheet was heated for 3 hours in an oven set to a predetermined temperature (25°C, 200°C, 220°C, 240°C, or 270°C) and then subjected to a tensile test.

[0158] Furthermore, the rubber-like sheet heated to 270°C was quite brittle and could not be punched out in a dumbbell shape, making it impossible to conduct a tensile test.

[0159] Table 1 shows the evaluation results of the rubber-like sheets obtained in the examples and comparative examples. Table 2 also shows the ratio of the tensile properties after heating to the pre-heating temperature (oven temperature 25°C) for each example (vs. 25°C) and the ratio of Comparative Example 2 to the oven temperature of 25°C (closest to the actual usage conditions for silicone rubber) (vs. Comparative Example 2 (25°C)). Figures 1 and 2 show the stress-elongation ratio curves obtained from the tensile tests of the rubber-like sheets (before heating (25°C) and after heating at 240°C).

[0160] [Table 1]

[0161] [Table 2]

[0162] As is clear from Tables 1 and 2, comparative examples 1 and 2, which were crosslinked (cured) in the absence of polysilane, tended to become brittle around 220-240°C, and after heating to 270°C they were too brittle to be punched out into a dumbbell shape. In contrast, examples 1 and 2, which were crosslinked (cured) in the presence of polysilane, retained sufficient physical properties to be punched out even after heating to 270°C, demonstrating excellent heat resistance.

[0163] Furthermore, as is clear from Tables 1-2 and Figures 1-2, Examples 1-2, compared to Comparative Examples 1-2, maintained their tensile strength and elongation at break at pre-heating (25°C) levels even after heating to over 200°C (especially 240°C), while suppressing an excessive increase in elastic modulus. This level was acceptable for practical use and demonstrated excellent heat resistance.

[0164] Furthermore, even when compared to Comparative Example 2 (25°C), which is closest to the actual usage conditions of conventional silicone rubber, Examples 1 and 2 (especially 240°C) were able to maintain values ​​relatively close to 1 for specific modulus of elasticity, specific tensile strength, and specific elongation at break (i.e., properties similar to those of Comparative Example 2 before heating), indicating that they can be used in the same way as conventional silicone rubber even in high-temperature environments.

[0165] Of Examples 1 and 2, Example 1, in which polysilane was removed by solvent extraction after crosslinking (curing), showed higher heat resistance.

[0166] Furthermore, in Examples 1 and 2, a slight tendency for tensile properties to decrease (increase in elastic modulus, decrease in tensile strength and elongation at break) was observed at 200°C, possibly because reformation of the silicone rubber main chain due to heating was more dominant. However, at temperatures higher than 200°C, the tensile properties that had decreased slightly at 200°C (recovery of rubber characteristics) were observed at 220°C and 240°C, possibly because the rupture of the silicone rubber main chain became more dominant. This was an unexpected behavior that differed from Comparative Examples 1 and 2.

[0167] [Example 3] A paste was prepared by uniformly mixing 95 parts by mass of raw material (III) and 5 parts by mass of raw material (II). A 1.0 mm thick rubber-like sheet was obtained by pressurizing the paste using a tabletop hot press [(Imoto Seisakusho Co., Ltd. "MH-10"] at 120°C, 30 MPa, and for 10 minutes. The obtained rubber-like sheet was left to stand at 200°C for 4 hours to obtain a cross-linked rubber-like sheet. Furthermore, the obtained cross-linked rubber-like sheet was subjected to Soxhlet extraction with toluene and dried under reduced pressure for 24 hours to obtain a cross-linked rubber-like sheet that was substantially free of raw material (II) after solvent removal. The obtained cross-linked rubber-like sheet was heated in an oven set to a predetermined temperature (25°C, 240°C, or 260°C) for 3 hours and then subjected to a tensile test.

[0168] [Comparative Example 3] A paste was prepared by uniformly mixing 100 parts by mass of raw material (III), and a 1.0 mm thick rubber-like sheet was obtained by pressurizing it at 120°C, 30 MPa, and for 10 minutes using a tabletop hot press [(Imoto Seisakusho Co., Ltd. "MH-10"]]. The obtained rubber-like sheet was left to stand at 200°C for 4 hours to obtain a cross-linked rubber-like sheet. Furthermore, the obtained cross-linked rubber-like sheet was subjected to Soxhlet extraction with toluene and dried under reduced pressure for 24 hours to obtain a cross-linked rubber-like sheet that was substantially free of raw material (II) after solvent removal. The obtained cross-linked rubber-like sheet was heated in an oven set to a predetermined temperature (25°C, 240°C, or 260°C) for 3 hours and then subjected to a tensile test.

[0169] [Comparative Example 4] A paste was prepared by uniformly mixing 100 parts by mass of raw material (III), and a 1.0 mm thick rubber-like sheet was obtained by pressurizing it at 120°C, 30 MPa, and for 10 minutes using a tabletop hot press [(Imoto Seisakusho Co., Ltd. "MH-10"]]. The obtained rubber-like sheet was left to stand at 200°C for 4 hours to obtain a cross-linked rubber-like sheet. The obtained cross-linked rubber-like sheet was heated in an oven set to a predetermined temperature (25°C, 240°C, or 260°C) for 3 hours and then subjected to a tensile test.

[0170] Table 3 shows the evaluation results of the rubber-like sheets obtained in the examples and comparative examples. Table 4 also shows the ratio of the tensile properties after heating to the pre-heating temperature (oven temperature 25°C) for each example (vs. 25°C) and the ratio of Comparative Example 4 to the oven temperature of 25°C (closest to the actual usage conditions for silicone rubber) (vs. Comparative Example 4 (25°C)). Figures 3 and 4 show the stress-elongation ratio curves obtained from the tensile tests of the rubber-like sheets (before heating (25°C) and after heating at 240°C).

[0171] [Table 3]

[0172] [Table 4]

[0173] As is clear from Tables 3 to 4, in Comparative Examples 3 to 4 which were crosslinked (cured) in the absence of polysilane, the elongation at break at 25°C was low, and the elongation at break tended to further decrease at 240°C and 260°C. In contrast, in Example 3 which was crosslinked (cured) in the presence of polysilane, the elongation at break at 25°C was more than twice that of Comparative Example 3, sufficient elongation at break was maintained even after heating at 240°C, and the heat resistance was excellent. Although the elongation at break decreased after heating at 260°C, the elastic modulus and tensile strength did not change significantly, which was at a level causing no practical problem.

[0174] Further, as is clear from Tables 3 to 4 and FIGS. 3 to 4, compared with Comparative Examples 3 to 4, Example 3 suppressed an excessive increase or decrease in the elastic modulus even after heating to 240°C or higher, while maintaining the tensile strength and elongation at break before heating (25°C), which was at a level causing no problem in practical use, and was excellent in heat resistance.

[0175] Furthermore, even when compared with Comparative Example 4 (25°C), which is closest to the actual use conditions of conventional silicone rubber, Example 3 (especially at 240°C) had a low specific elastic modulus, a high specific elongation at break, and a specific tensile strength that could be maintained at a value relatively close to 1 (that is, properties comparable to those of Comparative Example 4 before heating). Thus, it was found that even in a high-temperature environment, the material has higher flexibility than conventional silicone rubber and can be used in the same manner as conventional silicone rubber.

[0176] Regardless of the type of silicone rubber component and the presence or absence of polysilane, examples that were not subjected to solvent extraction showed a tendency to easily degrade in a high-temperature environment. Although the reason for this is not certain, it is presumed that in the examples not subjected to solvent extraction, unreacted silicone rubber components and the like that did not participate in the crosslinking reaction remain inside the crosslinked structure, causing the molecular chains forming the crosslinked structure to be in a strained state, making them more susceptible to thermal degradation. Industrial Applicability

[0177] The high heat-resistant silicone rubber composition of the present disclosure can be used in various fields and is not particularly limited, and examples thereof include various industrial members (such as conveyor belts, rubber cover rolls, gaskets, printing rolls, oil seals, packings, and hoses such as oil-resistant hoses), building members (such as window frame rubbers, vibration damping materials, carpet backing materials, and sealing materials), transport equipment members (automotive members, tires, power transmission belts, etc.), electric and electronic equipment members (electric wire coatings, sealing materials, potting materials, sealing materials, etc.), medical members (medical hoses and tubes, etc.), test and experiment members (hoses and tubes for solvents, hoses and tubes for reagents, etc.), adhesives, coating agents, vibration damping or vibration isolating materials, molding materials, and the like.

[0178] In addition, the high heat-resistant silicone rubber composition of the present disclosure can be effectively used as a heat dissipation member and / or a vibration damping member (or a buffer member) and the like, and for example, household or industrial power supplies and inverters / converters such as power conditioners [for example, heat dissipation members for choke coils, transformers, IGBT (insulated gate bipolar transistors), IPM (intelligent power module) substrates, MOS (metal oxide semiconductor) substrates, etc.]; lighting devices such as LEDs (light emitting diodes) (for example, heat dissipation members for substrates, light sources, etc.); wireless communication devices (for example, heat dissipation members for power supply substrates, communication modules, etc.); motors / drivers [for example, heat dissipation and / or vibration damping members for motor main bodies, heat dissipation members for control substrates (driver ICs), etc.]; air conditioning equipment such as air conditioners (for example, heat dissipation members for compressor control substrates, etc.); in-vehicle devices such as car navigation systems, back monitors, and back cameras (heat dissipation and / or vibration damping members for display devices such as liquid crystal displays, camera main bodies, etc.); action cameras (or wearable cameras) [for example, heat dissipation and / or vibration damping members for camera main bodies, substrates, etc.], construction machinery (construction equipment or heavy machinery) [heat dissipation and / or buffer members for batteries, etc.], and the like, and may be suitably used therein.

Claims

1. A silicone rubber composition containing a crosslinked silicone rubber component, The following conditions (A) or (B) must be met: A high-temperature resistant silicone rubber composition for use in environments with temperatures above 200°C. (A): The silicone rubber component is a liquid or paste-like silicone rubber, and the inter-crosslinking molecular weight Me of the crosslinked product is 2.3 × 10 ３ ~3.5 x 10 ３ g / mol (B): The silicone rubber component is millable-type silicone rubber, and the inter-crosslinking molecular weight Me of the crosslinked product is 13.5 × 10 ３ ~100 x 10 ３ g / mol

2. A high heat-resistant silicone rubber composition according to claim 1, which does not contain polysilane.

3. A high heat-resistant silicone rubber composition according to claim 1, comprising polysilane.

4. Polysilane is expressed in the following formulas (1a) and (1b) 【Chemistry 1】 (In the formula, R １ ~R ３ (Each represents a hydrogen atom, a hydroxyl group, a halogen atom, or an organic group.) The high heat-resistant silicone rubber composition according to claim 3, comprising at least one structural unit selected from structural units represented by .

5. The polysilane is R in formula (1a). １ and R ２ The high heat-resistant silicone rubber composition according to claim 4, comprising at least one structural unit in which one is an alkyl group and the other is an aryl group.

6. The high heat-resistant silicone rubber composition according to claim 4 or 5, wherein the proportion of structural units represented by formula (1a) is 50 mol% or more of the total polysilane.

7. The high heat-resistant silicone rubber composition according to any one of claims 3 to 5, wherein the weight-average molecular weight Mw of the polysilane is 200 to 2000.

8. The high heat-resistant silicone rubber composition according to any one of claims 3 to 5, wherein the polysilane is a linear polysilane.

9. The high heat-resistant silicone rubber composition according to any one of claims 3 to 5, wherein the ratio of the polysilane to the silicone rubber component is former / latter (mass ratio) = 0.1 / 99.9 to 30 / 70.

10. The high heat-resistant silicone rubber composition according to any one of claims 1 to 5, wherein the silicone rubber component is a liquid or paste-like silicone rubber.

11. The high heat-resistant silicone rubber composition according to any one of claims 1 to 5, wherein the silicone rubber component is a millable type silicone rubber.

12. The high heat-resistant silicone rubber composition according to any one of claims 1 to 5, wherein the silicone rubber component is an addition-curing type or a radical-curing type silicone rubber.

13. A high heat-resistant silicone rubber composition according to any one of claims 1 to 5, for use in an environment with a temperature of 210 to 260°C.

14. When heated at 240°C for 3 hours, The elongation at break after heating is 50-100% of the elongation at break before heating. A high heat-resistant silicone rubber composition according to any one of claims 1 to 5, wherein the tensile strength after heating is 50 to 120% of the tensile strength before heating.

15. A method for producing a high heat-resistant silicone rubber composition according to any one of claims 1 to 5, comprising a crosslinking step of crosslinking the silicone rubber component in the presence of polysilane.

16. The manufacturing method according to claim 15, comprising a polysilane removal step of removing the polysilane from the crosslinked product obtained in the crosslinking step.

17. A method for improving the heat resistance of a silicone rubber composition containing a crosslinked silicone rubber component, wherein the silicone rubber component is crosslinked in the presence of polysilane.

18. The method for improving heat resistance according to claim 17, wherein the polysilane is removed from the crosslinked product after crosslinking.

19. A heat-resistant agent for silicone rubber compositions, comprising polysilane.

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