Method for producing a silane-crosslinkable silicone rubber composition and method for producing a silane-crosslinkable silicone rubber molded article

Abstract

To provide a silane crosslinkable silicone rubber composition which enables production of a silane crosslinked silicone rubber molded body excellent in appearance, heat resistance and strength with excellent producibility even by a general-purpose extrusion molding machine for plastic, and a method for producing the same, and a silane crosslinked silicone rubber molded body exhibiting the excellent characteristics and a method for producing the same, and a silane crosslinked silicone rubber molded article.SOLUTION: There are provided a silane crosslinkable silicone rubber composition which contains, with respect to 100 pts.mass of a base rubber containing a millable type silicone rubber and an ethylene copolymer resin, 1-15 pts.mass of a silane coupling agent that is graft-bonded to the base rubber, 0.5-300 pts.mass of an inorganic filler, and 0.01-0.5 pts.mass of a silanol condensation catalyst and a method for producing the same; a silane crosslinked silicone rubber molded body using the silane crosslinkable silicone rubber composition and a method for producing the same; and a silane crosslinked silicone rubber molded article including the silane crosslinked silicone rubber molded body.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a silane-crosslinkable silicone rubber composition, a silane-crosslinkable silicone rubber molded article, a method for producing the same, and a silane-crosslinkable silicone rubber molded article using a silane-crosslinkable silicone rubber molded article. [Background technology]

[0002] Various resin or rubber molded materials are used as covering layers (insulators, sheaths, etc.) for wiring materials such as insulated wires, cables, cords, optical fiber cores, or optical fiber cords (optical fiber cables) used in the fields of electrical and electronic equipment and industrial applications, as well as for various molded products such as packings and sheets. Such molded products are required to have properties according to their application, such as appearance characteristics, strength (e.g., tensile strength), and heat resistance from the standpoint of safety and reliability. As a material for forming such molded articles, silicone rubber can be mentioned, which can exhibit excellent weather resistance, heat resistance, etc., through chemical crosslinking. Examples of molded articles using silicone rubber include, for example, Patent Document 1, which describes "an insulated wire in which the periphery of a conductor is covered with an insulating layer containing crosslinked silicone rubber, characterized in that the insulating layer contains an acid acceptor." Patent Document 2 also describes "an insulated wire in which the periphery of a conductor is covered with an insulating layer containing crosslinked silicone rubber, characterized in that the insulating layer has a Shore A hardness of 50 or higher as measured in accordance with JIS K6253, and contains an oxide of a transition metal." Furthermore, Patent Document 3 describes an insulating component for electrical cables obtained by molding a resin composition containing three types of antifungal agents in specific amounts and a specific total amount in a thermoplastic resin containing an ethylene copolymer and / or silicone rubber. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2016-091911 [Patent Document 2] Japanese Patent Publication No. 2015-090753 [Patent Document 3] Japanese Patent Publication No. 2007-287683 [Overview of the project] [Problems that the invention aims to solve]

[0004] The insulated wires described in Patent Documents 1 and 2 both have an insulating layer containing crosslinked silicone rubber. Furthermore, Patent Document 3 describes an insulating component for electrical cables in which radical-reactive silicone rubber may be crosslinked using a crosslinking agent (organic peroxide). Conventionally, the crosslinking method for silicone rubber (the final crosslinking method after molding) has been either a self-crosslinking method by heating or a chemical crosslinking method using a crosslinking agent. Therefore, crosslinking silicone rubber requires a high-temperature crosslinking reaction using crosslinking equipment such as a chemical crosslinking pipe. For example, in Patent Documents 1 and 2, the crosslinking reaction is carried out at 200°C for 4 hours. In Patent Document 3, the crosslinking reaction is carried out at 160°C. Thus, conventional methods for crosslinking silicone rubber have manufacturability problems in terms of preparation and maintenance of crosslinking equipment, as well as crosslinking conditions. In particular, in recent years, from the perspective of protecting and sustaining the global environment, there has been a growing demand for improved productivity and reduced manufacturing costs, and there is a need for a technology that enables the production of crosslinked silicone rubber molded articles exhibiting the desired characteristics with excellent manufacturability.

[0005] Incidentally, due to its bulk state and physical properties, silicone rubber is generally difficult to (extrude) mold using general-purpose plastic molding machines (hereinafter also referred to as general-purpose extrusion molding machines). In the example in Patent Document 3, the test sheet is manufactured by press molding after mixing with a stirrer. Among silicone rubbers, millable-type silicone rubber exhibits a pail-like (clay-like) state in its bulk state, and its mixing and molding require manufacturing equipment (mixers, extruders, etc.) specifically for silicone rubber. In particular, extrusion molding is an important molding method from the perspective of industrial manufacturing of various molded products, as it allows for co-extrusion molding with other parts and enables the molding of molded products that cannot be easily molded by other molding methods. Therefore, if the moldability problem of silicone rubber can be solved in addition to the above-mentioned manufacturability problem, and it becomes possible to mold it using general-purpose manufacturing equipment, especially extrusion molding machines, the limitations on handling and manufacturing equipment in the production of silicone rubber molded products can be overcome, and the benefits are significant.

[0006] The present invention aims to solve the above problems and provide a silane-crosslinkable silicone rubber composition and a method for producing the same, which can be manufactured with excellent manufacturability and even with a general-purpose extrusion molding machine, and which has excellent appearance, heat resistance, and strength. Furthermore, the present invention aims to provide a silane-crosslinkable silicone rubber molded article using a silane-crosslinkable silicone rubber molded article exhibiting the above excellent properties. [Means for solving the problem]

[0007] The inventors have found that a silane-crosslinkable silicone rubber composition containing 100 parts by mass of a base rubber containing millable-type silicone rubber (organopolysiloxane), 1 to 15 parts by mass of a silane coupling agent grafted to the base rubber, 0.5 to 300 parts by mass of an inorganic filler, and 0.01 to 0.5 parts by mass of a silanol condensation catalyst, undergoes a silane crosslinking reaction under relatively mild conditions without the use of special crosslinking equipment. As a result, it is possible to produce a silane-crosslinked body with excellent appearance, heat resistance, and strength, while resolving the issue of manufacturability. On the other hand, it was confirmed that this silane-crosslinkable silicone rubber composition also has a moldability problem, being difficult to extrude using general-purpose extrusion molding machines. Therefore, various studies were continued on the composition of the silane-crosslinkable silicone rubber composition. As a result, we discovered that in a silane-crosslinkable silicone rubber composition, by using a specific ethylene copolymer resin among various polymers as the base rubber in combination with millable-type silicone rubber, it is possible not only to resolve the moldability problems mentioned above, but also to realize a silane-crosslinkable silicone rubber molded article with even greater strength. Based on these findings, the inventors conducted further research and arrived at the present invention.

[0008] In other words, the objectives of the present invention were achieved by the following means. <1> A silane crosslinkable silicone rubber composition comprising 100 parts by mass of a base rubber containing millable-type silicone rubber and ethylene copolymer resin, 1 to 15 parts by mass of a silane coupling agent grafted to the base rubber, 0.5 to 300 parts by mass of an inorganic filler, and 0.01 to 0.5 parts by mass of a silanol condensation catalyst. <2> The ethylene copolymer resin is an ethylene-(meth)acrylic acid ester copolymer resin. <1> The silane crosslinkable silicone rubber composition described above. <3> The amount of the inorganic filler is 1 to 200 parts by mass per 100 parts by mass of the base rubber. <1> or <2> The silane crosslinkable silicone rubber composition described above. <4> The silane crosslinkable silicone rubber composition according to any one of <1> to <3>, wherein the inorganic filler is at least one selected from metal hydrates, talc, clay, silica, calcium carbonate, and carbon black. <5> The silane crosslinkable silicone rubber composition according to any one of <1> to <4>, wherein the content of the silane coupling agent is 3 to 15 parts by mass with respect to 100 parts by mass of the base rubber. <6> A silane crosslinked silicone rubber molded article obtained by bringing into contact with water after molding the silane crosslinkable silicone rubber composition according to any one of <1> to <5>. <7> A silane crosslinked silicone rubber molded product containing the silane crosslinked silicone rubber molded article according to <6>. <8> A method for producing a silane crosslinkable silicone rubber composition, comprising a step (1) of melt-mixing 1 to 15 parts by mass of a silane coupling agent having a grafting reaction site capable of grafting reaction to the base rubber, 0.5 to 300 parts by mass of an inorganic filler, 0.01 to 0.6 parts by mass of an organic peroxide, and 0.01 to 0.5 parts by mass of a silanol condensation catalyst with respect to 100 parts by mass of a base rubber containing a millable silicone rubber and an ethylene copolymer resin to obtain a silane crosslinkable silicone rubber composition. The method for producing a silane crosslinkable silicone rubber composition, wherein the step (1) has the following steps (a) and (c), provided that when a part of the base rubber is melt-mixed in the following step (a), the steps (a), (b), and (c) are included. Step (a): All or part of the base rubber, the silane coupling agent, the inorganic filler, and the organic peroxide are melt-mixed at a temperature above the decomposition temperature of the organic peroxide to prepare a silane masterbatch. Step (b): The remaining part of the base rubber and the silanol condensation catalyst are melt-mixed to prepare a catalyst masterbatch. Step (c): The silane masterbatch and the silanol condensation catalyst or the catalyst masterbatch Step (c): The silane masterbatch and the silanol condensation catalyst or the catalyst masterbatch are melt-mixed. Step (c): The silane masterbatch and the silanol condensation catalyst or the catalyst masterbatch A step of melt-mixing with a star batch <9> A method for producing a silane-crosslinked silicone rubber molded article having the following steps (1), (2), and (3): Step (1): A base rubber containing a millable silicone rubber and an ethylene copolymer resin Based on 100 parts by mass of the base rubber, 1 to 15 parts by mass of a silane coupling agent having a grafting reaction site capable of grafting reaction to the base rubber, an inorganic filler 0.5 to 300 parts by mass, 0.01 to 0.6 parts by mass of an organic peroxide And 0.01 to 0.5 parts by mass of a silanol condensation catalyst are melt-mixed to obtain a silane-crosslinkable silicone rubber composition Step To obtain a crosslinkable silicone rubber composition Step (2): A step of molding the silane-crosslinkable silicone rubber composition to obtain a molded article Step (3): A step of bringing the molded article into contact with water to obtain a silane-crosslinked silicone rubber molded article Process The method for producing a silane-crosslinked silicone rubber molded article, wherein the step (1) has the following steps (a) and (c), provided that when a part of the base rubber is melt-mixed in the following step (a), the following steps (a), (b), and (c) are included Step (a): All or part of the base rubber, the silane coupling agent, the Inorganic filler and the organic peroxide are melt-mixed at a temperature not lower than the decomposition temperature of the organic peroxide to prepare a silane masterbatch Step Step (b): The remaining part of the base rubber and the silanol condensation catalyst are melt-mixed to prepare a catalyst masterbatch Step Step (c): A step of melt-mixing the silane masterbatch with the silanol condensation catalyst or the catalyst masterbatch Star batch

[0009] In this invention, a numerical range represented using "~" means a range that includes the values ​​written before and after "~" as the lower and upper limits. In this invention, when multiple numerical ranges are set and explained for the content of components, physical properties, etc., the upper and lower limits that form the numerical range are not limited to the specific combinations written before and after "~" as a specific numerical range, but can be numerical ranges that are appropriately combined from the upper and lower limits of each numerical range. Furthermore, in the present invention, "(meth)acrylic acid" refers to either acrylic acid or methacrylic acid, or both, and "(meth)acrylic acid ester" refers to either acrylic acid ester or methacrylic acid ester, or both. [Effects of the Invention]

[0010] The present invention provides a silane-crosslinkable silicone rubber composition and a method for producing the same, which can be manufactured with excellent manufacturability and even using a general-purpose extrusion molding machine, and which exhibits excellent appearance, heat resistance, and strength. Furthermore, the present invention provides a silane-crosslinkable silicone rubber molded article exhibiting excellent appearance, heat resistance, and strength, and a method for producing this silane-crosslinkable silicone rubber molded article. Moreover, the present invention provides a silane-crosslinkable silicone rubber molded product using the silane-crosslinkable silicone rubber molded article exhibiting the above-mentioned excellent properties. [Modes for carrying out the invention]

[0011] [Silane-crosslinkable silicone rubber composition] The silane-crosslinkable silicone rubber composition of the present invention contains, per 100 parts by mass of a base rubber containing millable-type silicone rubber and ethylene copolymer resin, 1 to 15 parts by mass of a silane coupling agent grafted to the base rubber, 0.5 to 300 parts by mass of an inorganic filler, and 0.01 to 0.5 parts by mass of a silanol condensation catalyst. This silane-crosslinkable silicone rubber composition can be prepared by appropriately mixing the above components, but is preferably prepared by the method for producing the silane-crosslinkable silicone rubber composition of the present invention, as described later. The silane-crosslinkable silicone rubber composition can also be described as a molten mixture of a silane masterbatch and a silanol condensation catalyst or catalyst masterbatch, as described later.

[0012] As will be described in detail later, the silane crosslinkable silicone rubber composition of the present invention contains a silane crosslinkable silicone rubber in which a silane coupling agent, which is bonded or dissociated with an inorganic filler, is grafted onto a millable-type silicone rubber (organopolysiloxane) (grafting reaction).

[0013] This silane-crosslinkable silicone rubber composition does not require special crosslinking equipment such as chemical crosslinking tubes or electron beam crosslinking machines, and undergoes a silanol condensation reaction under mild conditions, resulting in excellent manufacturability. Moreover, it enables the production of silane-crosslinkable silicone rubber molded articles with excellent appearance, heat resistance, and tensile strength, even with general-purpose extrusion molding machines. Therefore, the silane-crosslinkable silicone rubber composition of the present invention is suitably used in the method for producing silane-crosslinkable silicone rubber molded articles or in the silane-crosslinkable silicone rubber molded articles of the present invention. When this silane-crosslinkable silicone rubber composition is applied to both of the above-mentioned production methods of the present invention (the embodiment for producing a catalyst masterbatch), both the silane masterbatch and the catalyst masterbatch, which are intermediate products of the silane-crosslinkable silicone rubber composition, can be prepared as pellets that are less prone to fusion.

[0014] [Silane-crosslinked silicone rubber molded product] The silane-crosslinked silicone rubber molded article of the present invention is a silane-crosslinked silicone rubber molded article obtained by molding the silane-crosslinkable silicone rubber composition of the present invention and then contacting it with water. More specifically, the silane-crosslinked silicone rubber molded article of the present invention is a silane-crosslinked silicone rubber molded article (a molded article consisting of a silanol condensate of the silane-crosslinkable silicone rubber composition) obtained by silane crosslinking (silanol condensation reaction) after molding the silane-crosslinkable silicone rubber composition of the present invention. The silane-crosslinked silicone rubber molded article of the present invention has a crosslinked structure that incorporates inorganic fillers in addition to the crosslinked structure at the crosslinking points (vinyl groups) of the millable-type silicone rubber (organopolysiloxane), while still being highly compatible with ethylene copolymer resin. Therefore, it exhibits an excellent appearance, sufficient heat resistance, and high strength.

[0015] As will be described in detail later, the silane-crosslinked silicone rubber molded article of the present invention has a crosslinked structure (a crosslinked structure via a silane coupling agent or its silanol condensate) in which millable-type silicone rubber is crosslinked with silane. It is believed that an inorganic filler is incorporated into a part of this crosslinked structure, as will be described later. The silane-crosslinked silicone rubber molded articles of the present invention are molded into appropriate shapes and dimensions depending on the application, for example, the application of the silane-crosslinked silicone rubber molded articles of the present invention as described later.

[0016] The components used in this invention are described below. Each component may be used in one or more forms. In this invention, the term "rubber" is used to include elastomers unless otherwise specified. <Base rubber> The base rubber used in the present invention comprises millable-type silicone rubber and ethylene copolymer resin as essential components, and may optionally contain other rubbers or various resins.

[0017] (Miracle-type silicone rubber) Mirable-type silicone rubber is used as a compound with linear organopolysiloxane (uncrosslinked) as the main raw material (raw silicone rubber), to which a reinforcing agent, usually silica, is added. The millable-type silicone rubber exhibits high thermal stability even above the decomposition temperature of organic peroxides (180°C), and can induce grafting reactions with silane coupling agents with good workability. According to the inventors' studies, even in the presence of a specific amount of inorganic filler, organopolysiloxanes without pre-added reinforcing agents, whether clay-like solids, gum-like substances, or liquids with crosslinking sites (vinyl groups), are less susceptible to grafting reactions with silane coupling agents, making the silane crosslinking method unsuitable. Furthermore, it has been found that organopolysiloxanes with pre-added reinforcing agents (millable-type silicone rubber), even in the presence of a specific amount of inorganic filler, exhibit increased fluidity of the reaction system due to the coexistence of ethylene copolymer resin, preferentially facilitating the grafting reaction of silane coupling agents over crosslinking reactions between organopolysiloxanes, thereby producing organopolysiloxanes with grafted silane coupling agents. Based on this finding, the present invention enables the application of a highly precise silane crosslinking method for the first time by grafting a silane coupling agent onto millable-type silicone rubber as a compound, while a specific amount of inorganic filler and ethylene-based copolymer resin are separately present.

[0018] The organopolysiloxanes mentioned above can be any organopolysiloxanes that can undergo a grafting reaction with a silane coupling agent. Examples include organopolysiloxanes containing vinyl groups as graftable sites (crosslinking sites), specifically methylvinylpolysiloxane, methylphenylvinylpolysiloxane, methylfluoroalkylpolysiloxane, etc. The fluoroalkyl group is not particularly limited, for example, a 3,3,3-trifluoropropyl group. The terminal groups of the organopolysiloxane are not particularly limited, for example, alkyl groups (methyl groups), vinyl groups, and hydroxyl groups. The content of vinyl groups in organopolysiloxane is not particularly limited and can be appropriately determined according to the degree of crosslinking, for example, it can be 0.025 to 1.0 (mol%). The content of vinyl groups can be determined by, for example, infrared absorption spectroscopy (FT-IR), proton NMR ( 1 It can be measured by 1H-NMR. The content of phenyl groups and fluoroalkyl groups in the organopolysiloxane is not particularly limited and can be appropriately determined according to the application, required properties, etc. Furthermore, the degree of polymerization of the organopolysiloxane is not particularly limited and can be, for example, 3,000 to 10,000.

[0019] Mirable-type silicone rubber contains a reinforcing agent (filler). The reinforcing agent is not particularly limited and includes, for example, various types of silica such as fumed silica (also called dry silica), precipitated silica, diatomaceous earth, and quartz powder, as well as surface-treated silica thereof. From the viewpoint of moldability, appearance of the molded product, and insulation resistance, fumed silica is preferred as the reinforcing agent. The BET specific surface area of ​​the reinforcing agent is not particularly limited, but for example, 50 to 300 m² is preferred. 2 It is preferable that the amount is approximately / g. The BET specific surface area can be measured by, for example, following the method specified in Japanese Industrial Standard (JIS) Z 8830 (2013), by adsorbing gas molecules with a known adsorption area, such as nitrogen gas, onto the surface of the powder particles, and determining the specific surface area of ​​the sample from the amount (BET method).

[0020] The specific gravity of the Mirable-type silicone rubber (before the silane coupling agent grafts) is not particularly limited and can be set appropriately according to the application, required characteristics, etc. A lower specific gravity in the Mirable-type silicone rubber reduces the amount of reinforcing agent it contains, improving the compatibility (fluidity) of the base rubber during molding of the silane-crosslinked silicone rubber composition. As a result, using a Mirable-type silicone rubber with a low specific gravity allows for molding with general-purpose extrusion molding machines without compromising excellent manufacturability, and achieves high heat resistance and tensile strength while maintaining a superior appearance. In terms of resolving moldability issues while achieving a good balance of high heat resistance and tensile strength, a specific gravity of 1.05 to 1.50 g / cm³ for Mirable-type silicone rubber is desirable. 3 It can be done as 1.05~1.25 g / cm³. 3 Preferably, it is 1.10 to 1.20 g / cm³. 3 It is more preferable that the concentration be 1.10 to 1.15 g / cm³. 3 It is even more preferable that the concentration be 1.11 to 1.14 g / cm³. 3 It is particularly preferable that this is the case. The specific gravity of the Mirable-type silicone rubber shall be the value measured by the method described in the examples below.

[0021] The amount of reinforcing agent in the Mirable-type silicone rubber is not particularly limited, as long as the specific gravity of the Mirable-type silicone rubber falls within the above range. In addition to specific gravity, it can be appropriately set according to the application, required characteristics, etc. For example, the amount of reinforcing agent in the Mirable-type silicone rubber can be 10 to 40% by mass, preferably 12 to 38% by mass, and more preferably 14 to 35% by mass, depending on the specific gravity of the reinforcing agent, etc. The Mirable-type silicone rubber may contain fillers other than reinforcing agents, dispersion accelerators, and other additives, for example, within a range that satisfies the above-mentioned specific gravity.

[0022] Mirable-type silicone rubber may be prepared by mixing organopolysiloxane and reinforcing agents, and the above additives as appropriate, or commercially available products (compounds that do not contain crosslinking agents (curing agents)) may be used. Examples of commercially available products include the ELASTSIL R401 series (manufactured by Asahi Kasei Wacker Corporation), the XIAMETER RBB6660 series (manufactured by Dow Corning Corporation), the KE series rubber compound (manufactured by Shin-Etsu Silicone Co., Ltd.), and the TSE series of Mirable-type silicone rubber (manufactured by Momentive Corporation).

[0023] (Ethylene copolymer resin) In the present invention, an ethylene copolymer resin refers to an ethylene copolymer resin that contains ethylene as a copolymer component and has an acid copolymer component or an acid ester copolymer component. In other words, even if a copolymer resin contains ethylene as a copolymer component, resins that do not have an acid copolymer component or an acid ester copolymer component are not included in the definition of an ethylene copolymer resin. In the present invention, if the base rubber contains an ethylene copolymer resin, it becomes possible to manufacture the product using general-purpose manufacturing equipment, particularly extrusion molding using general-purpose extrusion molding machines, and the strength of the silane-crosslinked silicone rubber molded article can be further increased. Although the details of the reason for this are not yet clear, it is thought that by coexisting with an ethylene copolymer resin in the silane crosslinking method, the fluidity of the reaction system can be increased during the grafting reaction without inhibiting the preferential and selective grafting reaction of the silane coupling agent to the millable silicone rubber, and as a result, the molten mixture during extrusion molding maintains high fluidity. Furthermore, in the method for manufacturing the silane-crosslinkable silicone rubber composition of the present invention (a method for manufacturing a catalyst masterbatch), the intermediate products, the silane masterbatch and the catalyst masterbatch, can be pelletized, and pellet fusion (blocking) can also be suppressed. In addition, heat resistance can be increased.

[0024] The compounds used to derive the acid copolymer component or acid ester copolymer component in the ethylene copolymer resin are not particularly limited and include carboxylic acid compounds such as (meth)acrylic acid, and acid ester compounds such as vinyl acetate and alkyl (meth)acrylate. The alkyl group of alkyl (meth)acrylate is preferably one with 1 to 12 carbon atoms. Examples of such ethylene copolymer resins include ethylene-vinyl acetate copolymer (EVA), ethylene-(meth)acrylic acid ester copolymer, and ethylene-(meth)acrylic acid copolymer. The resins comprising ethylene-(meth)acrylic acid ester copolymers and ethylene-(meth)acrylic acid copolymers are not particularly limited, and ordinary ones can be used. The (meth)acrylic acid ester that forms the ethylene-(meth)acrylic acid copolymer is not particularly limited, but examples include esters of (meth)acrylic acid with an alcohol having 1 to 12 carbon atoms. Specifically, examples include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. Examples of resins for the ethylene-(meth)acrylic acid copolymer include ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl acrylate copolymer (EEA), and ethylene-butyl acrylate copolymer (EBA). In particular, from the viewpoint of compatibility with silicone rubber, strength characteristics, and heat resistance, ethylene-vinyl acetate copolymer (EVA) and ethylene-(meth)acrylic acid ester copolymer resins are preferred, and ethylene-ethyl acrylate copolymer (EEA) resin is more preferred. The copolymer content in the ethylene copolymer resin is not particularly limited and can be set as appropriate, but it is preferable that the copolymer content be 15 to 45% by mass.

[0025] The base rubber may contain rubber, resin, etc., other than millable silicone rubber and ethylene copolymer resin. Examples of resins include polyolefin resins other than the ethylene copolymer resins mentioned above, and examples of rubbers include rubbers or elastomers such as polymers that form polyolefin resins. The present invention encompasses both embodiments in which the base rubber contains fluororubber and embodiments in which the base rubber does not contain fluororubber. It should be noted that the embodiment of the base rubber not containing fluororubber is not limited to embodiments in which the fluororubber content in the base rubber (rubber composition) is 0% by mass, but also includes embodiments in which the fluororubber content in the base rubber is less than 5% by mass, as long as the effects of the present invention are not impaired.

[0026] (Polyolefin resin) The polyolefin resin that the base rubber may contain refers to polyolefin resins other than the ethylene copolymer resins mentioned above. Such polyolefin resins are not particularly limited and include resins made from polymers obtained by homopolymerizing or copolymerizing olefin compounds. Examples include well-known resins used in various resin compositions. Specifically, examples include polyethylene (PE) and polypropylene (PP). Polyethylene resins and polypropylene resins are preferred as polyolefin resins. The polyolefin resin may also be acid-modified with commonly used unsaturated carboxylic acids or their derivatives.

[0027] - Polyethylene resin - Polyethylene resin (PE) is not particularly limited as long as it is a polymer resin mainly composed of ethylene. Examples include high-density polyethylene (HDPE), low-density polyethylene (LDPE), ultra-high molecular weight polyethylene (UHMW-PE), linear low-density polyethylene (LLDPE), and very low-density polyethylene (VLDPE).

[0028] - Polypropylene resin - Polypropylene resin (PP) is not particularly limited as long as it is a polymer resin mainly composed of propylene. Examples include propylene homopolymers, as well as random polypropylene and block polypropylene resins.

[0029] (Rubber other than Mirable-type silicone rubber) Other than Mirable-type silicone rubber, there are no particular limitations, and examples include known rubbers used in various rubber compositions. Specifically, these include ethylene-α-olefin copolymer rubber, styrene-based elastomer, fluororubber, acrylic rubber, and the like.

[0030] - Ethylene-α-olefin copolymer rubber - The ethylene-α-olefin copolymer rubber (also referred to as ethylene rubber in this invention) is not particularly limited as long as it is a copolymer rubber obtained by copolymerizing ethylene and α-olefin, and known types can be used. Preferred examples of ethylene-α-olefin copolymer rubber include binary copolymer rubber of ethylene and α-olefin, and ternary copolymer rubber of ethylene, α-olefin, and a diene compound. The α-olefin is not particularly limited, but each α-olefin having 3 to 12 carbon atoms is preferred. The diene compound constituting the ternary copolymer is not particularly limited, and examples include conjugated diene compounds such as butadiene, isoprene, 1,3-pentadiene, and 2,3-dimethyl-1,3-butadiene, and unconjugated diene compounds such as dicyclopentadiene (DCPD), ethylidene norbornene (ENB), and 1,4-hexadiene, with unconjugated diene compounds being preferred. As the binary copolymer rubber, ethylene-propylene rubber (EPM) is preferred, and as the ternary copolymer rubber, ethylene-propylene-diene rubber (EPDM) is preferred.

[0031] - Styrene-based elastomer - Styrene-based elastomers refer to elastomers composed of polymers having constituent components derived from aromatic vinyl compounds within their molecules. Examples of such styrene-based elastomers include block copolymers and random copolymers of conjugated diene compounds and aromatic vinyl compounds, or hydrogenated versions thereof. More specifically, examples include styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-isoprene-styrene block copolymer (SIS), hydrogenated SIS, styrene-butadiene-styrene block copolymer (SBS), hydrogenated SBS, styrene-ethylene-ethylene-propylene-styrene block copolymer (SEEPS), styrene-ethylene-propylene-styrene block copolymer (SEPS), styrene-butadiene rubber (SBR), and hydrogenated styrene-butadiene rubber (HSBR).

[0032] - Fluororubber - The fluororubber is not particularly limited; for example, conventional fluororubber used in heat-resistant rubber molded articles can be used. Examples of such fluororubbers are not limited to, but include copolymer rubbers of fluorine-containing monomers such as perfluorohydrocarbons like tetrafluoroethylene and hexafluoropropylene, and partially fluorinated hydrocarbons like vinylidene fluoride, as well as copolymer rubbers of these fluorine-containing monomers with hydrocarbons such as ethylene and / or propylene. Specifically, examples include tetrafluoroethylene-propylene copolymer rubber (FEPM), tetrafluoroethylene-fluorinated (e.g., hexafluoro)propylene copolymer rubber, tetrafluoroethylene-perfluorovinyl ether copolymer rubber (FFKM), and vinylidene fluoride rubber (FKM, e.g., vinylidene fluoride-hexafluoropropylene copolymer rubber). Furthermore, copolymer rubbers of the above-mentioned fluorine-containing monomers with chloroprene and / or chlorosulfonated polyethylene are also examples.

[0033] - Acrylic rubber - Acrylic rubber (also called ethylene-acrylic rubber) includes rubber obtained by copolymerizing at least ethylene with an alkyl acrylate as a constituent component. The alkyl acrylate is not particularly limited and examples include methyl acrylate and ethyl acrylate. As the acrylic rubber, various copolymer rubbers such as a binary copolymer of ethylene and alkyl acrylate, and a terpolymer obtained by copolymerizing these with a copolymer component containing a carboxyl group, can be suitably used. The copolymer component containing a carboxyl group is not particularly limited, but examples include (meth)acrylic acid and maleic acid.

[0034] (Mineral oil) The base rubber may also contain mineral oil. Examples of mineral oils include paraffin oil, naphthenic oil, and aromatic oil, with paraffin oil being preferred. It is particularly preferable that the mineral oil be included together with the elastomer.

[0035] (Composition of base rubber) The base rubber contains each component in the following proportions so that the total proportion is 100% by mass. If the base rubber contains multiple components, the proportion of each component shall be the sum of the proportions of all components combined. The content of millable silicone rubber in 100% by mass of base rubber is not particularly limited, but it is preferably 45 to 90% by mass in order to construct a sufficient cross-linked structure while resolving moldability issues, more preferably 50 to 80% by mass, even more preferably 55 to 75% by mass, and particularly preferably 55 to 70% by mass in order to achieve a higher level of balance between appearance, heat resistance, and tensile strength. The content of ethylene copolymer resin in 100% by mass of base rubber is not particularly limited, but it is preferably 5 to 30% by mass, more preferably 10 to 30% by mass, and even more preferably 15 to 25% by mass, in terms of tensile strength of the silane-crosslinked silicone rubber molded article while resolving moldability issues.

[0036] The total content of the polyolefin resin in 100% by mass of the base rubber is not particularly limited and can be determined as appropriate. For example, it is preferably 0 to 70% by mass, more preferably 5 to 50% by mass, and even more preferably 10 to 40% by mass. The polyethylene resin content in 100% by mass of the base rubber is not particularly limited and is set appropriately considering the total content of the polyolefin resin, for example, preferably 0 to 25% by mass, and more preferably 5 to 20% by mass. Similarly, the polypropylene resin content in 100% by mass of the base rubber is not particularly limited and is set appropriately considering the total content of the polyolefin resin, for example, preferably 0 to 25% by mass, and more preferably 2 to 20% by mass.

[0037] The total content of rubber other than millable-type silicone rubber in 100% by mass of base rubber is not particularly limited and can be determined as appropriate. For example, it is preferably 0 to 50% by mass, more preferably 5 to 45% by mass, and even more preferably 8 to 40% by mass. The content of ethylene-α-olefin copolymer rubber in 100% by mass of the base rubber is not particularly limited and is set appropriately considering the total content of the above rubber, for example, preferably 0 to 25% by mass, more preferably 0 to 20% by mass, and even more preferably 0 to 15% by mass. The content of styrene-based elastomer in 100% by mass of the base rubber is not particularly limited and is set appropriately considering the total content of the above rubber, for example, preferably 0 to 25% by mass, and more preferably 0 to 15% by mass. The content of fluororubber and acrylic rubber in 100% by mass of the base rubber is not particularly limited and is set appropriately considering the total content of the above rubber, for example, it can be 8 to 40% by mass.

[0038] The mineral oil content in 100% by mass of the base rubber is not particularly limited and can be determined as appropriate. For example, it is preferably 0 to 25% by mass, and more preferably 0 to 20% by mass.

[0039] <Silane coupling agent> The silane crosslinkable silicone rubber composition contains a silane coupling agent grafted onto a base rubber, particularly a millable-type silicone rubber. Preferably, the base rubber to which the silane coupling agent is grafted is prepared by a grafting reaction between the silane coupling agent and the base rubber in step (a) described later. The silane coupling agent used in the present invention (before the grafting reaction) has graft reaction sites (atoms or functional groups such as ethylenically unsaturated groups) that can graft onto graft-reactive sites of the base rubber in the presence of radicals generated by the decomposition of organic peroxides. Furthermore, it is preferable that it has hydrolyzable silyl groups as silanol condensation reaction sites and can react with chemically bondable sites of inorganic fillers. The silane coupling agent that can be used in the present invention is not particularly limited, and examples include silane coupling agents used in conventional silane crosslinking methods. Suitable silane coupling agents include those having an ethylenically unsaturated group and a hydrolyzable silyl group. Specifically, these include vinyl alkoxylanes such as vinyltrimethoxylane, vinyltriethoxylan, vinyltributoxylan, vinyldimethoxyethoxylan, vinyldimethoxybutoxylan, vinyldiethoxybutoxylan, allyltrimethoxylane, allyltriethoxylan, and vinyltriacetoxylan, as well as (meth)acryloxyalkoxylanes such as methacryloxypropyltrimethoxylane, methacryloxypropyltriethoxylan, and methacryloxypropylmethyldimethoxylane. Among these, vinyltrimethoxylane or vinyltriethoxylan are particularly preferred.

[0040] <Inorganic filler> While there are no particular limitations on the inorganic filler, it is preferable that it has sites on its surface that can chemically bond with the silanol condensation reaction sites of the silane coupling agent by hydrogen bonding, covalent bonding, or intermolecular bonding. The sites that can chemically bond with the reaction sites of the silane coupling agent are not particularly limited, but examples include OH groups (hydroxyl groups, water molecules in water or crystal water, carboxyl groups, etc.), amino groups, SH groups, etc. Examples of inorganic fillers include metal hydrates such as compounds having hydroxyl groups or crystal water, such as aluminum hydroxide, magnesium hydroxide, boehmite, calcium carbonate, magnesium carbonate, calcium silicate, magnesium silicate, calcium oxide, magnesium oxide, aluminum oxide, aluminum nitride, aluminum borate, whiskers, hydrated aluminum silicate, hydrated magnesium silicate, basic magnesium carbonate, hydrotalcite, and talc. Other examples include boron nitride, silica (crystalline silica, amorphous silica, etc.), carbon black, clay (calcined clay), zinc oxide, tin oxide, titanium oxide, molybdenum oxide, silicone compounds, quartz, zinc borate, white carbon, zinc borate, zinc hydroxystannate, and zinc stannate. The inorganic filler preferably contains at least one of metal hydrates, talc, clay, silica, calcium carbonate, and carbon black, with silica being more preferred in terms of heat resistance and tensile strength. For the inorganic filler, a surface-treated inorganic filler, such as one treated with a silane coupling agent, can be used. The amount of surface treatment is not particularly limited, but is preferably, for example, 3% by mass or less.

[0041] <Silanol condensation catalyst> The silanol condensation catalyst works by promoting the condensation reaction of the silanol condensation site of the silane coupling agent grafted onto the base rubber in the presence of water. Based on the action of this silanol condensation catalyst, the base rubber is crosslinked via the silane coupling agent. Such silanol condensation catalysts are not particularly limited and include, for example, organotin compounds, metal soaps, and platinum compounds. Examples of organotin compounds include dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin dioctiate, and dibutyltin diacetate.

[0042] <Additives> In the present invention, various additives commonly used in silicone rubber compositions may also be used. Examples of such additives include antioxidants, lubricants, metal deactivators, plasticizers, flame retardants, flame retardant aids, anti-plasticization agents, and (co)polymers other than those described for the base rubber. Examples of antioxidants include hindered phenol antioxidants, benzimidazole antioxidants, and hydrazine heavy metal deactivators. Examples of flame retardants (auxiliaries) include bromine-based flame retardants, chlorine-based flame retardants, and antimony trioxide. In the present invention, the silane crosslinkable silicone rubber composition and the silane crosslinkable silicone rubber molded article encompass both embodiments in which they contain any one or a combination of the above antioxidants, particularly a benzimidazole-based antioxidant, and embodiments in which they do not contain any one or a combination of the above antioxidants, particularly a benzimidazole-based antioxidant. In embodiments containing antioxidants, the total content of antioxidants is preferably less than 30 parts by mass, more preferably 0.2 to 19 parts by mass, and even more preferably 0.5 to 13 parts by mass, per 100 parts by mass of base rubber. The absence of antioxidants is not limited to embodiments in which the content of each antioxidant in the silane crosslinkable silicone rubber composition, etc., is 0% by mass, but includes embodiments in which they are contained within a range that does not impair the effects of the present invention. Within a range that does not impair the effects of the present invention, for example, the hindered phenol-based antioxidant and the hydrazine-based metal deactivator can be less than 0.2 parts by mass, and the benzimidazole-based antioxidant can be less than 1.5 parts by mass. In the present invention, the crosslinkable silicone rubber composition and the silane-crosslinked silicone rubber molded article include both embodiments: an embodiment containing a plasticization reversion inhibitor, for example, a silicone rubber containing no vinyl group, and an embodiment not containing it. When containing a plasticization reversion inhibitor, its content can be 0.5 to 10% by mass in the base rubber. On the other hand, not containing a plasticization reversion inhibitor is not limited to the embodiment where the content of the plasticization reversion inhibitor in the silane-crosslinkable silicone rubber composition etc. is 0% by mass, and includes embodiments containing less than 0.5 parts by mass, preferably 0.2 parts by mass or less, with respect to 100 parts by mass of the base rubber, within the range not impairing the effects of the present invention.

[0043] <Organic peroxide> In the present invention, an organic peroxide is used in the preparation of the silane-crosslinkable silicone rubber composition. The organic peroxide has a function of promoting the grafting reaction of the silane coupling agent to the base rubber (a covalent bond formation reaction between the grafting reaction site of the silane coupling agent and the graftable site of the base rubber, which is also called a (radical) addition reaction) by generating radicals through thermal decomposition. There is no particular limitation on the organic peroxide. For example, compounds represented by the general formula: R 1 -OO-R 2 、R 3 -OO-C(=O)R 4 、R 5 C(=O)-OO(C=O)R 6 are preferably used. Here, R 1 ~R 6 each independently represent an alkyl group, an aryl group or an acyl group. Among R 1 ~R 6 of each compound, those all being alkyl groups, or those in which any one is an alkyl group and the rest are acyl groups are preferred. The decomposition temperature of the organic peroxide is preferably 80 to 195 °C, particularly preferably 125 to 180 °C, as the decomposition temperature measured by the method described in JP-A-2016-121203. Examples of such organic peroxides include the organic peroxide described in paragraph

[0036] of Japanese Patent Publication No. 2016-121203, which is incorporated herein by reference as part of this specification. Among these, dicumyl peroxide, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane (perhexa 25B), and 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexyn-3 are preferred.

[0044] (Composition of silane-crosslinkable silicone rubber composition) In a silane crosslinkable silicone rubber composition, the content of the silane coupling agent grafted to the base rubber (calculated by mass before grafting reaction with the base rubber) is 1 to 15 parts by mass per 100 parts by mass of base rubber. This is preferable because it suppresses the formation of protruding aggregates (gel particles) caused by crosslinked gels, etc., and the volatilization of the silane coupling agent, thereby producing a silane crosslinkable silicone rubber molded article with excellent appearance, a sufficient crosslinked structure, and excellent heat resistance and mechanical properties (tensile strength, elongation at break). The silane coupling agent content is preferably 2 to 15 parts by mass, and more preferably 3 to 15 parts by mass, in order to produce a silane crosslinkable silicone rubber molded article that achieves a good balance between appearance, tensile strength, and heat resistance at a higher level. As an upper limit, it is also preferable to set it to 8 parts by mass, in order to suppress the volatilization or self-condensation of the silane coupling agent and achieve an excellent appearance. In the silane crosslinkable silicone rubber composition, the inorganic filler content is 0.5 to 300 parts by mass per 100 parts by mass of base rubber, in order to construct a crosslinked structure in which the inorganic filler is incorporated into the silane crosslinkable silicone rubber molded body, thereby achieving both heat resistance and tensile strength. The inorganic filler content is preferably set low in order to achieve a higher level of both heat resistance and tensile strength. Specifically, it is preferably 1 to 200 parts by mass, more preferably 1 to 100 parts by mass, even more preferably 3 to 50 parts by mass, particularly preferably 3 to 40 parts by mass, and most preferably 3 to 25 parts by mass. In embodiments in which the base rubber includes fluororubber, the inorganic filler content in the silane crosslinkable silicone rubber composition is preferably 1 to 100 parts by mass, more preferably 3 to 50 parts by mass, even more preferably 3 to 40 parts by mass, and particularly preferably 3 to 25 parts by mass, among the above contents. In the silane crosslinkable silicone rubber composition, the content of the silanol condensation catalyst is preferably 0.01 to 0.5 parts by mass, more preferably 0.03 to 0.3 parts by mass, and more preferably 0.05 to 0.15 parts by mass, per 100 parts by mass of base rubber, in order to achieve a good balance between appearance, heat resistance, and tensile strength.

[0045] The total content of additives (excluding antioxidants and anti-plasticization agents) in the silane crosslinkable silicone rubber composition is not particularly limited and can be appropriately set within a range that does not impair the effects of the present invention.

[0046] (Composition of silane-crosslinked silicone rubber molded articles) Since silane-crosslinked silicone rubber molded articles are formed by molding a silane-crosslinkable silicone rubber composition and then bringing it into contact with water to cause a silanol condensation reaction, the content of each component in the molded article is usually the same as the content in the silane-crosslinkable silicone rubber composition. However, in the case of silane-crosslinked silicone rubber molded articles, the content of the silane coupling agent is defined as the content before the silanol condensation reaction, and the content of the base rubber is defined as the content before crosslinking.

[0047] [Method for producing silane-crosslinkable silicone rubber compositions and silane-crosslinkable silicone rubber molded articles] The following describes the method for producing the silane-crosslinkable silicone rubber composition of the present invention and the method for producing the silane-crosslinkable silicone rubber molded article of the present invention. The silane-crosslinkable silicone rubber composition of the present invention is manufactured by performing the following step (1), and the silane-crosslinkable silicone rubber molded article of the present invention is manufactured by performing the following steps (1) to (3). The method for producing a silane-crosslinked silicone rubber molded article and the method for producing a silane-crosslinkable silicone rubber composition according to the present invention may be collectively referred to as the "production method of the present invention."

[0048] Step (1): Base rubber 10 containing millable-type silicone rubber and ethylene copolymer resin Per 0 parts by mass, graft reaction sites capable of grafting into the base rubber 1 to 15 parts by mass of a silane coupling agent having and 0.5 to 3 parts by mass of an inorganic filler 00 parts by mass, 0.01 to 0.6 parts by mass of organic peroxide, and silanol condensation Melt and mix with 0.01 to 0.5 parts by mass of a medium to produce silane crosslinkable silicone rubber. Process to obtain the composition This process (1) comprises the following steps (a) and (c). However, if a portion of the base rubber is melted and mixed in step (a), then the process comprises the following steps (a), (b), and (c). Process (a): All or part of the base rubber, a silane coupling agent, and an inorganic filler The organic peroxide and the mixture are melted and mixed at a temperature above the decomposition temperature of the organic peroxide. Then, the process of preparing the silane masterbatch. Step (b): The remaining base rubber and the silanol condensation catalyst are melt-mixed to form a catalyst master - Process of preparing a batch Step (c): Silane masterbatch and silanol condensation catalyst or catalyst masterbatch The process of melting and mixing Step (2): Step of molding a silane crosslinkable silicone rubber composition to obtain a molded article. Step (3): Step of bringing the molded body into contact with water to obtain a silane-crosslinked silicone rubber molded body.

[0049] In the manufacturing method of the present invention, the mixing amounts of each component used as the base rubber shall be the same as the content ratios described above as the composition of the base rubber. Furthermore, the mixing amounts of the silane coupling agent, inorganic filler, silanol condensation catalyst, and additives shall be the same as the content ratios in the silane crosslinkable silicone rubber composition described above. In the manufacturing method of the present invention, when a portion of the base rubber is mixed in step (a), the polymer component to be mixed may be a specific component or two or more components. The proportion of the base rubber mixed in step (a) is preferably 60 to 95% by mass of the 100% by mass of the base rubber mixed in steps (a) and (b), and more preferably 70 to 95% by mass, in which a sufficient cross-linked structure can be constructed to achieve a higher level of both heat resistance and mechanical properties. The remainder of the base rubber (carrier resin) mixed in step (b) is appropriately determined according to the portion of the base rubber mixed in step (a).

[0050] However, in the manufacturing method of the present invention, the base rubber used in step (a) contains at least millable silicone rubber from the above components, and an ethylene copolymer resin is used in at least one of step (a) or step (b). This solves the above-mentioned manufacturability problem and allows for the construction of a sufficient silane crosslinked structure in the silane crosslinked silicone rubber molded body, while also solving the above-mentioned moldability problem and achieving a good balance between heat resistance and tensile strength. It is preferable that the base rubber used in step (a) contains millable silicone rubber and an ethylene copolymer resin, as this solves the above-mentioned manufacturability problem and allows for a high level of both heat resistance and mechanical properties. On the other hand, it is also preferable that the base rubber (remainder) used in step (b) contains an ethylene copolymer resin. This improves the compatibility between the silane masterbatch and the catalyst masterbatch, thereby improving heat resistance and mechanical properties.

[0051] While inorganic fillers can be partially used in process (b), it is preferable to use them in process (a) because this allows for the construction of a cross-linked structure incorporating the inorganic fillers, thereby achieving a higher level of both heat resistance and mechanical properties. When inorganic fillers are used in process (b), the amount used is not particularly limited and can be determined as appropriate.

[0052] The various additives may be mixed in either step (a) or step (b). The antioxidant may be mixed in either step (a) or step (b), but mixing in step (b) is preferable because it allows the grafting reaction in step (a) to proceed more efficiently.

[0053] The amount of organic peroxide mixed in step (a) is 0.01 to 0.6 parts by mass per 100 parts by mass of base rubber. When organic peroxide is mixed in the above amount with millable-type silicone rubber containing the above content, competitive reactions (parallel reactions, side reactions), including crosslinking reactions between millable-type silicone rubbers, are suppressed during melt mixing, and the grafting reaction of the silane coupling agent to the millable-type silicone rubber can be preferentially and selectively promoted, while also suppressing the generation of gel particles. As a result, the appearance, heat resistance, and tensile strength of the silane-crosslinked silicone rubber molded article can be well-balanced. The amount of organic peroxide mixed is preferably 0.05 to 0.2 parts by mass.

[0054] <Process (a)> Step (a) is a step of preparing a silane masterbatch (silane MB) containing a silane crosslinkable silicone rubber in which the silane coupling agent is grafted onto the base rubber by grafting the base rubber with a silane coupling agent in the presence of an inorganic filler. In this process, the base rubber is heated and mixed with an inorganic filler and a silane coupling agent in the presence of an organic peroxide at a temperature above the decomposition temperature of the organic peroxide. This yields silane MB as a molten mixture.

[0055] In step (a), the mixing temperature for melting and mixing (also called melting and kneading) the above-mentioned components is above the decomposition temperature of the organic peroxide, preferably above the decomposition temperature of the organic peroxide + (25 to 110)°C, more preferably 150 to 230°C, and even more preferably 175 to 210°C. Mixing conditions such as the mixing time can be set as appropriate. For example, the mixing time can be 1 to 25 minutes, preferably 3 to 20 minutes. By melting and mixing at a temperature above the decomposition temperature of the organic peroxide, the organic peroxide undergoes thermal decomposition and generates radicals, thereby promoting the grafting reaction.

[0056] Any mixing method commonly used for mixing rubber, plastics, etc., is acceptable. Mixing equipment can include, for example, a single-screw extruder, twin-screw extruder, rolls, Banbury mixer, or various types of kneaders, with closed-type mixers such as Banbury mixers or various types of kneaders being preferred.

[0057] In this invention, the mixing order is not specified, and the above components may be mixed in any order. For example, the above components can be melted and mixed all at once. In the manufacturing method of the present invention, it is preferable to mix step (a) in the following order using steps (a-1) and (a-2) below. Step (a-1): A process to prepare a mixture by mixing an inorganic filler and a silane coupling agent. degree Step (a-2): The mixture obtained in step (a-1) and all or part of the base rubber are used. Dissolves in the presence of organic peroxides at temperatures above the decomposition temperature of organic peroxides. melting and mixing process

[0058] In step (a-1), pre-mixing the inorganic filler and silane coupling agent allows for a balanced formation of silane coupling agent weakly bonded or adsorbed to the inorganic filler and silane coupling agent strongly bonded or adsorbed to the inorganic filler. This effectively prevents volatilization of the silane coupling agent and condensation reactions between unadsorbed silane coupling agents during melt mixing in step (a-2). As a result, a silane-crosslinked silicone rubber molded article can be produced that exhibits a superior appearance while further improving the mechanical properties (tensile strength) and heat resistance caused by the silane crosslinking method. Examples of weak bonding with the inorganic filler include interactions via hydrogen bonding, interactions between ions, partial charges or dipoles, and adsorption. Examples of strong bonding with the inorganic filler include chemical bonding with chemically bondable sites on the inorganic filler surface.

[0059] The mixing method and conditions for step (a-1) are not particularly limited, but examples of mixing methods and conditions include using a known mixer, kneader, etc., and mixing by dry or wet method for several minutes to several hours at a temperature below the decomposition temperature of the organic peroxide, preferably 10 to 60°C, more preferably near room temperature (20 to 25°C). Among these, dry mixing (dry blending) at a temperature below the decomposition temperature of the organic peroxide is preferred. Other conditions for dry mixing can be determined as appropriate.

[0060] In process (a-1), the base rubber may also be mixed in, as long as the temperature below the above decomposition temperature is maintained. The organic peroxide only needs to be present during the melting and mixing in step (a-2), and may be mixed in step (a-2), but it is preferable that it be mixed in step (a-1).

[0061] Next, the mixture obtained in step (a-1) and all or part of the base rubber are melt-mixed in the presence of an organic peroxide at a temperature above the decomposition temperature of the organic peroxide to prepare silane MB (step (a-2)). This prepares a silane masterbatch containing silane crosslinkable silicone rubber. In this melt-mixing step, excessive crosslinking reaction (generation of gel particles) between the base rubbers can be prevented while suppressing the volatilization and self-condensation of the silane coupling agent mentioned above. The melting and mixing method and conditions for this step (a-2) are not particularly limited, and the melting and mixing method and conditions for step (a) described above can be applied.

[0062] In the melt mixing of steps (a) and (a-2), radicals generated from organic peroxides preferentially and selectively cause the grafting reaction of the silane coupling agent to the millable silicone rubber, rather than competitive reactions including crosslinking reactions between millable silicone rubbers. The detailed reasons for this are not yet clear, but are thought to be as follows: Since the vinyl group content in millable silicone rubber is usually not high, there are few reaction sites, and crosslinking reactions between millable silicone rubbers are unlikely to occur. On the other hand, because the molecular weight of the silane coupling agent is relatively small, the number of molecules per part by mass is large, and it has a high degree of freedom in the molten mixture, and since the content is set as described above, the opportunity to react with the millable silicone rubber is high. For this reason, it is thought that the grafting reaction of the silane coupling agent preferentially occurs over the crosslinking reaction between millable silicone rubbers. Furthermore, since ethylene copolymer resins are thought to have lower radical addition reactivity than silicone rubber, competitive reactions such as crosslinking reactions between these resins, crosslinking reactions between these resins and millable-type silicone rubber, and grafting reactions of silane coupling agents onto these resins are not expected to occur preferentially.

[0063] In steps (a) and (a-2), at least the following modes are possible for the silane coupling agent to graft onto the base rubber. Specifically, one mode involves the silane coupling agent, which is weakly bonded or adsorbed to the inorganic filler, detaching from the inorganic filler and grafting onto the base rubber. In this mode, the crosslinked structure formed in step (3), described later, does not incorporate the inorganic filler and is typically a crosslinked structure via silanol condensates of silane coupling agents. Another mode involves the silane coupling agent, which is strongly bonded or adsorbed to the inorganic filler, grafting onto the resin while maintaining its bond or adsorption to the inorganic filler. In this mode, the crosslinked structure formed in step (3), described later, incorporates the inorganic filler and is a crosslinked structure starting from the inorganic filler and mediated by the silane coupling agent bonded to it. By combining the crosslinked structures in both of the above modes, a highly developed crosslinked structure, including a crosslinked structure incorporating the inorganic filler, can be constructed in the silane crosslinked silicone rubber molded article.

[0064] In step (a), antioxidants, additives, etc., may also be mixed. However, it is preferable not to substantially mix the silanol condensation catalyst in step (a). This suppresses the occurrence of the silanol condensation reaction of the silane coupling agent. In the present invention, "substantially not mixed" does not mean that the unavoidably present silanol condensation catalyst is excluded, but rather that it may be present in a range that can suppress the silanol condensation reaction, for example, in a range of 0.01 parts by mass or less per 100 parts by mass of base rubber.

[0065] The silane MB prepared in step (a) contains a reaction mixture of base rubber, inorganic filler, and silane coupling agent, and contains a silane crosslinkable silicone rubber (silane graft polymer) in which the silane coupling agent is grafted onto the base rubber to a degree that allows for molding, as described in step (b) below. The silane coupling agent grafted onto the base rubber includes those that are bound to or adsorbed onto the inorganic filler at their silanol condensation-capable reaction sites. Silane MB may be in the form of clay, pellets, or powder.

[0066] <Process (b)> In the manufacturing method of the present invention, the remainder of the base rubber and the silanol condensation catalyst are melt-mixed to prepare a catalyst masterbatch (catalyst MB). The melting and mixing method and conditions in step (b) are not particularly limited, and the melting and mixing method and conditions of step (a) described above can be applied. For example, the melting and mixing temperature should be at or above the melting temperature of the base rubber, preferably 120 to 200°C, and more preferably 140 to 180°C. Catalyst MB may be in the form of clay, pellets, or powder.

[0067] <Process (c)> In the manufacturing method of the present invention, the silane masterbatch and the silanol condensation catalyst or catalyst masterbatch are then melt-mixed. The melt-mixing method is not particularly limited, but is basically the same as the melt-mixing in step (a), and is mixed at a temperature at which the base rubber melts. The mixing conditions in step (c) are not particularly limited, and the mixing conditions of step (a) above can be applied. For example, the mixing temperature is appropriately selected depending on the base rubber, for example, 80 to 250°C is preferred, 100 to 240°C is more preferred, and 120 to 200°C is even more preferred. In step (c), the melt mixing method and conditions are set to maintain the fluidity (moldability) of the silane crosslinkable silicone rubber composition. The silane crosslinkable silicone rubber in the silane crosslinkable silicone rubber composition is an uncrosslinked material in which the silane coupling agent has not undergone silanol condensation. In practice, some crosslinking may be unavoidable when melt mixing in step (c), but the moldability of the resulting silane crosslinkable silicone rubber composition is maintained. For example, in order to avoid the occurrence or progression of a silanol condensation reaction, it is preferable that the silane MB and silanol condensation catalyst are not kept at a high temperature for a long time in a mixed state. In step (c), it is preferable to dry blend the silane MB and the silanol condensation catalyst or catalyst masterbatch before melt-mixing them. The method and conditions for dry blending are not particularly limited and include, for example, the dry mixing in step (a-1) and the conditions therefor.

[0068] In this way, the silane crosslinkable silicone rubber composition of the present invention is produced as a molten mixture. This silane-crosslinkable silicone rubber composition contains the above-mentioned silane-crosslinkable silicone rubber, inorganic filler, silanol condensation catalyst, etc. In this silane-crosslinkable silicone rubber, the silanol-condensable reaction sites of the silane coupling agent may be bound to or adsorbed with the inorganic filler, but are not silanol-condensed. Therefore, the silane-crosslinkable silicone rubber includes a silane-crosslinkable silicone rubber in which the silane coupling agent bound to or adsorbed with the inorganic filler is grafted onto the base rubber, and a silane-crosslinkable silicone rubber in which the silane coupling agent not bound to or adsorbed with the inorganic filler is grafted onto the base rubber. Silane-crosslinkable silicone rubber compositions may also contain components based on various competitive reactions, depending on the selectivity of the grafting reaction of the silane coupling agent, in addition to the components mentioned above. Examples of such components include crosslinked organopolysiloxanes, crosslinked ethylene copolymer resins, crosslinked millable silicone rubber and ethylene copolymer resins, and ethylene copolymer resins to which the silane coupling agent is grafted.

[0069] <Process (2)> In the method for producing a silane-crosslinked silicone rubber molded article of the present invention, the silane-crosslinkable silicone rubber composition is then molded to obtain a molded article. Since the silane crosslinkable silicone rubber composition of the present invention has solved the above-mentioned moldability problems, the molding method is not particularly limited and can be appropriately selected according to the form of the target product. Examples of molding methods include press molding, molding using other general-purpose molding machines, and extrusion molding using a general-purpose extruder or injection molding machine. When manufacturing wiring materials, the extrusion molding method is preferred in terms of productivity and the ability to co-extrude with conductors. The molding conditions (melt mixing conditions) are not particularly limited as long as they allow the silane crosslinkable silicone rubber composition of the present invention to be molded and do not cause a silanol condensation reaction. For example, the melt mixing method and conditions of step (a) can be applied. More specifically, the molding (melt mixing) temperature in this step is above the temperature at which the base rubber melts, preferably 80 to 250°C, more preferably 100 to 240°C, and even more preferably 120 to 200°C. In this melt mixing, the melt mixing method and conditions are set while maintaining the moldability of the molten mixture of the silane crosslinkable silicone rubber composition. When co-extruding with a conductor using a general-purpose extrusion molding machine, it is preferable to set the temperature of the cylinder section to about 120 to 180°C and the temperature of the crosshead section to about 160 to 200°C, although this depends on various conditions such as the take speed of the conductor, etc. The molding speed (linear speed) in extrusion molding is not particularly limited and can be set appropriately according to the characteristics or performance of the extruder, the amount of extrusion (covering amount), etc. The linear velocity can typically be set to less than 1 to 20 m / min, preferably 1 to 10 mm / min. This linear velocity can also be suitably applied to the extruder used in the embodiments described later, as well as the amount of extrusion (coating thickness) onto the outer surface of the conductor. The silane-crosslinkable silicone rubber in the molded article obtained in step (2) is an uncrosslinked state in which the silane coupling agent has not undergone silanol condensation. In practice, partial crosslinking is unavoidable when melt-mixed in step (2), but the moldability of the resulting molded article is maintained. For example, to avoid the occurrence or progression of a silanol condensation reaction, it is preferable that the silane-crosslinkable silicone rubber composition is not held at high temperatures for a long time.

[0070] Step (2) can be carried out simultaneously with or immediately following step (c). For example, a series of steps can be employed in which silane MB and catalyst MB are mixed by dry blending or the like immediately before or inside the coating apparatus (extruder), then melt-mixed inside the coating apparatus (step (c)), and then (co-extruded) molded (step (2)) onto the outer surface of a conductor or the like.

[0071] <Process (3)> In the method for producing a silane-crosslinked silicone rubber molded article of the present invention, the molded article obtained in step (2) is then brought into contact with water to produce a silane-crosslinked silicone rubber molded article. Since the molded article obtained in step (2) is not crosslinked, this step causes and promotes (accelerates) a silanol condensation reaction at the silanol condensation-capable reaction sites of the silane coupling agent grafted to the base rubber, ultimately resulting in silane crosslinking. Contact between the uncrosslinked molded article and water can be carried out by conventional methods. The silanol condensation reaction proceeds even if left at room temperature, for example, at a temperature of around 20-25°C, but it is preferable to actively bring the article into contact with water to promote the silanol condensation reaction (crosslinking reaction). As for contact methods, those commonly applied to the silane crosslinking method can be listed, and various contact methods such as immersion in hot water, immersion in a humid heat bath, and exposure to high-temperature steam can be applied.

[0072] In this way, the silane-crosslinked silicone rubber molded article of the present invention is manufactured. This silane-crosslinked silicone rubber molded article contains a crosslinked silicone rubber formed by condensation of a base rubber (particularly an organopolysiloxane contained in millable-type silicone rubber) via siloxane bonds. Furthermore, the silane-crosslinked silicone rubber molded article contains an inorganic filler, which may be bonded to the silane coupling agent of the crosslinked silicone rubber. Therefore, it is considered that the crosslinked silicone rubber contains a crosslinked silicone rubber formed by the bonding or adsorption of multiple base rubbers to an inorganic filler via a silane coupling agent, and a crosslinked silicone rubber formed by the hydrolysis of the hydrolyzable groups of the silane coupling agent grafted to the base rubber and undergoing a silanol condensation reaction with each other, thereby crosslinking via the silane coupling agent (siloxane bonds) (without the involvement of the inorganic filler). Furthermore, the silane-crosslinked silicone rubber molded article of the present invention may also contain the above-mentioned components based on the competitive reaction described above, and the silanol condensate thereof.

[0073] As described above, the manufacturing method of the present invention allows the grafting reaction between the silane coupling agent and the base rubber in step (a) to be accelerated by increasing the fluidity of the reaction system even in the presence of inorganic fillers, while suppressing competitive reactions including the volatilization and self-condensation reactions of the silane coupling agent, as well as crosslinking reactions between organopolysiloxanes. Furthermore, the fluidity of the molten mixture is increased during molding (melt mixing), making it possible to mold it using a general-purpose extrusion molding machine without impairing excellent manufacturability. Therefore, by contacting the silane crosslinkable silicone rubber composition of the present invention with water under relatively mild conditions, a highly developed crosslinked structure including a crosslinked structure incorporating inorganic fillers can be constructed, and a silane crosslinked silicone rubber molded article exhibiting excellent appearance, heat resistance, and tensile strength can be produced.

[0074] [Silane-crosslinked silicone rubber molded product] The silane-crosslinked silicone rubber molded articles of the present invention are products that include the silane-crosslinked silicone rubber molded articles of the present invention and can be used as various rubber molded articles, preferably as substitutes for conventional silicone rubber molded articles. Examples include covering materials for wiring materials such as insulated wires, cables or optical fiber cables, materials for rubber substitute wires and cables, and other heat-resistant parts for microwave ovens or gas ranges, heat-resistant wire parts, heat-resistant sheets, heat-resistant films, etc. Furthermore, examples include power plugs, connectors, sleeves, boxes, tape substrates, tubes, sheets, packing materials, cushioning materials, vibration damping materials, wiring materials used for internal and external wiring of electrical and electronic equipment, especially electric wires and optical fiber cables, and the aforementioned wiring materials and tubular molded articles. The silane-crosslinked silicone rubber molded article of the present invention may be a molded article that includes the silane-crosslinked silicone rubber molded article of the present invention in part (the rubber molded portion), or it may be a molded article consisting only of the silane-crosslinked silicone rubber molded article of the present invention. The silane-crosslinked silicone rubber molded articles of the present invention exhibit excellent appearance, heat resistance, and tensile strength, similar to the silane-crosslinked silicone rubber molded articles of the present invention. Taking advantage of the above properties, the silane-crosslinked silicone rubber molded articles of the present invention are preferably applied to applications requiring high heat resistance, such as wiring covering materials, sheets, and gaskets, as well as applications requiring high heat resistance, such as gaskets around automobile engine compartments and gaskets around high-power motors. Furthermore, taking advantage of the abrasion resistance resulting from high strength, they are preferably applied to applications where general silicone rubber is difficult to use, such as applications prone to damage from repeated vibrations or applications involving repeated bending and stretching, such as insulated electric wires for automobiles, wiring materials for industrial robots, and industrial electric wires that are dragged outdoors.

[0075] The present invention describes a preferred sheet or packing as a silane-crosslinked silicone rubber molded product. Examples of sheets or packings include those obtained by molding the silane-crosslinkable silicone rubber composition of the present invention into a predetermined shape and then crosslinking it by contact with water. The shape and dimensions of the sheet or packing are determined as appropriate depending on the application.

[0076] The present invention describes preferred wiring materials (insulated wires for automobiles) as silane-crosslinked silicone rubber molded articles. Examples of wiring materials include wiring materials having a coating layer on the outer circumference of a conductor, wherein this coating layer is formed by molding and crosslinking the silane crosslinkable silicone rubber composition of the present invention into a tubular layer, and then forming it with a silane crosslinkable silicone rubber molded article of the present invention. The wiring material is the same as ordinary wiring materials used in various electrical and electronic equipment fields and industrial fields, except that the covering layer is formed from the silane-crosslinked silicone rubber molded article of the present invention. The covering layer formed from the silane-crosslinked silicone rubber molded article of the present invention is provided directly on the outer surface of the conductor or via other layers, and the presence or absence of other layers, materials, etc., are appropriately determined according to the type of wiring material, application, required characteristics, etc. Ordinary conductors can be used, such as single or stranded copper or aluminum wires (with tensile fibers attached longitudinally or twisted together). In addition to bare wires, tin-plated wires or wires with an enamel coating insulating layer can also be used. The thickness of the covering layer formed from the silane-crosslinked silicone rubber molded article of the present invention is not particularly limited, but is usually about 0.15 to 5 mm. The wiring material of the present invention can be manufactured by molding it using various molding methods in step (2) above, for example, a general-purpose extruder or injection molding machine, and then bringing it into contact with water. Preferably, it can be manufactured by arranging the silane crosslinkable silicone rubber composition of the present invention in a tubular shape around the outer circumference of a conductor and then subjecting it to a crosslinking reaction (silanol condensation reaction). For example, in the method for manufacturing a silane crosslinkable silicone rubber molded article of the present invention described above, the manufacturing process can be made by making molding step (2) a step of co-extruding the silane crosslinkable silicone rubber composition around the outer circumference of a conductor using a silicone rubber-specific or general-purpose coating device (extruder). The specific co-extrusion molding is as described above. [Examples]

[0077] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0078] The compounds used in the examples and comparative examples are shown below. <Base rubber> (1) Mirable-type silicone rubber: ELASTSIL R401 / 70S (product name, compound containing methyl vinyl silicone rubber and fuzzy silica (Part A), specific gravity 1.18 g / cm³) 3 (Manufactured by Asahi Kasei Wacker Co., Ltd.) (2) Mirable-type silicone rubber: ELASTSIL R401 / 80S (product name, compound containing methyl vinyl silicone rubber and atomized silica (Part A), specific gravity 1.20 g / cm³) 3 (Manufactured by Asahi Kasei Wacker Co., Ltd.) (3) Mirable-type silicone rubber: XIAMETER RBB6660-60 (product name, compound containing methyl vinyl silicone rubber and fuzzy silica (Part A), specific gravity 1.24 g / cm³) 3 (Manufactured by Dow Corning) (4) Ethylene-ethyl acrylate copolymer resin (EEA): NUC6510 (trade name, manufactured by ENEOS NUC Corporation) (5) Ethylene-vinyl acetate copolymer resin (EVA): VF120T (product name, manufactured by Ube Maruzen Polyethylene Co., Ltd.) (6) Linear low-density polyethylene (LLDPE): Evolu SP0510 (product name, manufactured by Prime Polymer Co., Ltd.) (7) Polypropylene resin (PP): PB222A (product name, Random PP, manufactured by Sun Allomer Co., Ltd.)

[0079] The specific gravity of the Mirable-type silicone rubber was measured according to JIS K 7112 (1999) Method A (water displacement method). Specifically, 20mm cube-shaped samples were prepared from each type of Mirable silicone rubber, and their mass was measured in air and liquid (distilled water). The specific gravity of the Mirable silicone rubber was defined as the value ρ calculated from the following formula using the obtained values ​​and the density (specific gravity) of the liquid. ρ = {Ma / Ma - Mw} × ρw In the above formula, Ma is the sample mass in air (g), Mw is the sample mass in liquid (g), and ρw is the density of the liquid (g / cm³).3 ) indicates.

[0080] <Inorganic filler> (1) Inorganic filler: Softon 1200 (product name, calcium carbonate, manufactured by Bihoku Powdering Industry Co., Ltd.) (2) Inorganic filler: Aerosil 200 (product name, dry silica, manufactured by Nippon Aerosil Co., Ltd.) (3) Inorganic filler: Crystallite 5X (product name, crystalline silica, manufactured by Takimori Co., Ltd.)

[0081] <Silane coupling agent> KBM-1003: Product name, vinyltrimethoxylane, manufactured by Shin-Etsu Chemical Co., Ltd. <Silanol condensation catalyst> Adeka Stab OT-1: Product name, dioctyl staghorn uraurylate, manufactured by ADEKA Corporation. <Organic peroxide> Perhexa 25B: Trade name, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, decomposition temperature 154℃, manufactured by NOF Corporation.

[0082] <Antioxidant> Irganox 1010 (product name, hindered phenol antioxidant, manufactured by BASF) Adeka Stab CDA-10 (product name, hydrazine-based heavy metal deactivator, manufactured by ADEKA Corporation)

[0083] (Examples 1-20 and Comparative Examples 3-8) Examples 1-20 and Comparative Examples 3-8 were carried out using the components shown in Tables 1-3. In Tables 1 to 3, the numerical values ​​for the blending amount (content) in each example are expressed in parts by mass unless otherwise specified. Furthermore, a blank space for each component indicates that the blending amount of that component is 0 parts by mass. In each example and comparative example, a portion of the base rubber (specifically, the millable-type silicone rubber, EEA, or LLDPE shown in the "Catalyst MB" column of Tables 1 to 3) was used as the carrier resin for the catalyst MB in the mass ratio shown in the same column.

[0084] First, the inorganic filler, silane coupling agent, and organic peroxide were added to a rotary blade mixer (Mazeler PM: trade name, manufactured by Mazeler Co., Ltd.) in the mass ratios shown in the "Silane MB" column of Tables 1 to 3, and stirred for 1 minute at a rotation speed of 10 rpm at room temperature (25°C) (pre-mixing) (step (a-1)). A powder mixture was thus obtained. Next, the powder mixture and the base rubber and antioxidant shown in the "Silane MB" column of Tables 1 to 3 were added to a Banbury mixer (capacity 2L) preheated to 80°C in the mass ratio shown in the same column. The mixture was mixed at 40 rpm for 5 minutes, followed by a final kneading (melt mixing) at 30 rpm for 3 minutes. After confirming that the temperature of the mixture reached 180-200°C, which is above the decomposition temperature of organic peroxides, the molten mixture was spread thinly to about 3 mm using an 8-inch open roll and pelletized using a square pelletizer to obtain silane MB (step (a-2), which together with step (a-1) constitutes step (a)).

[0085] Meanwhile, the base rubber, silanol condensation catalyst, and antioxidant shown in the "Catalyst MB" column of Tables 1 to 3 were sequentially added in the mass ratios shown in the same column to a Banbury mixer (capacity 2L) preheated to 80°C. After mixing at a rotation speed of 40 rpm for 5 minutes, finishing kneading (melt mixing) was performed at a rotation speed of 30 rpm for 3 minutes. After confirming that the temperature of the mixture reached approximately 160°C and that the carrier rubber was sufficiently melted, the molten mixture was spread thinly to approximately 3 mm using an 8-inch open roll, and the molten mixture was pelletized using a square pelletizer to obtain catalyst MB (step (b)).

[0086] Next, silane MB and catalyst MB were placed in a plastic bag in the mass ratios shown in the "Silane MB" and "Catalyst MB" columns of Tables 1 to 3, and dry-blended at room temperature (25°C) for 3 minutes to obtain a dry-blended product. Next, the obtained dry blend was introduced into an extruder equipped with an L / D ratio of 25 and a screw with a screw diameter of 25 mm (cylinder temperature 130°C, crosshead temperature 180°C). This extruder is a general-purpose plastic extrusion molding machine (model number: D2-1429, manufactured by Omiya Seiki Co., Ltd.). While melting and mixing the dry blend in the extruder (step (c)), the silane crosslinkable silicone rubber composition was extruded onto the outer surface of a 0.8 mm diameter copper conductor to a thickness of 0.8 mm at a linear speed of 10 m / min, obtaining a coated conductor with an outer diameter of 2.4 mm (step (2)). This coated conductor was left in an atmosphere of 60°C and 95% humidity for 24 hours to come into contact with water (step (3)). In this way, insulated wires were manufactured, each having a coating layer made of silane-crosslinked silicone rubber molded material on the outer surface of the conductor.

[0087] (Comparative Example 1) We attempted to obtain a pellet-shaped crosslinkable silicone rubber composition by placing each component shown in the "Silane MB" column of Table 3 into a Banbury mixer, melting and mixing at 60-100°C for 10 minutes, then discharging the material at a discharge temperature of 100°C, rolling it thinly to about 3 mm using an 8-inch open roll, and then using a square pelletizer, but we were unable to pelletize it. The resulting crosslinkable silicone rubber composition could not be extruded.

[0088] (Comparative Example 2) We attempted to produce silane MB pellets and catalyst MB pellets in the same manner as in Example 1, but in both cases, the pellets fused together significantly, making pelletization and extrusion impossible.

[0089] The manufactured insulated wires and other materials were evaluated as described below, and the results are shown in Tables 1 to 3. Note that blank spaces in the tensile test column indicate that a tensile test was not performed using the corresponding test specimen.

[0090] <Moldability Test> In this study, we evaluated whether silane MB and catalyst MB could be prepared as pellets that are not easily fused together in each example and comparative example (pellet preparation suitability), and further, whether the above-mentioned insulated wires could be manufactured by extrusion molding using these pellets. Specifically, the obtained silane MB pellets and catalyst MB pellets were held at a temperature of 40°C or 25°C (room temperature) for 24 hours. After 24 hours, the condition of each pellet was visually inspected, and whether or not extrusion molding using the pellets was possible was evaluated according to the evaluation criteria below. If there was a difference in evaluation of pellet preparation suitability between silane MB and catalyst MB, the lower evaluation was adopted. - Evaluation Criteria - "A" (Excellent, Pass): When the pellets do not fuse together (block) at either 40°C or 25°C, and there is no hindrance to extrusion molding (extrusion moldable). "B" (Good, Pass): When held at 40°C, the pellets fused together, hindering extrusion molding, but when held at 25°C, the pellets did not fuse together, and there were no problems with the extrusion molding process. "D" (Failure): The pelletized form could not be produced, and therefore could not be extruded.

[0091] <Extrusion Appearance Test> The appearance of each manufactured insulated wire was visually inspected and evaluated according to the following evaluation criteria. Furthermore, materials that failed the above moldability test were deemed unsuitable for extrusion molding, and therefore the results of the extrusion appearance test were evaluated as "D". - Evaluation Criteria - "A" (Good appearance, pass): The insulated wire surface is clean and no gel particles were observed. "B" (Acceptable appearance, Pass): An average of 1 to 5 gel particles were found per meter on the surface of the insulated wire, but the appearance of the insulated wire was not problematic. "D" (Appearance defects, failure): A large amount of gel-like particles or roughness can be observed on the surface of the insulated wire, resulting in a defective appearance for the insulated wire.

[0092] <Hot-set testing> (Preparation of test specimens) Conductors were extracted from each manufactured insulated wire to create tubular test specimens made from silane-crosslinked silicone rubber molded bodies. On the other hand, for Comparative Examples 1 and 2, in which insulated wires could not be manufactured, sheet-like molded bodies were formed as follows to obtain dumbbell test pieces. In Comparative Example 1, the crosslinkable silicone rubber composition was placed in an unpreheated press machine, then heating was started. When the temperature of the composition reached 120°C, a pressure of 10 MPa was applied and the mixture was pressed. This pressure was maintained for 3 minutes to perform press molding. For Comparative Example 2, silane MB and catalyst MB were kneaded together for 5 minutes at room temperature (25°C) using an 8-inch open roll. The resulting blend was placed in an unpreheated press and press-molded under the same conditions as in Comparative Example 1. The resulting molded body was left in an atmosphere of 60°C and 95% humidity for 24 hours to come into contact with water, similar to Example 1. In this manner, dumbbell-shaped test pieces were prepared by punching out dumbbell-shaped test pieces in the form of type 3 dumbbells as specified in JIS K 6251 (2017) from each of the prepared sheet-like molded bodies (2 mm thick). (test) At the lower end of this tubular test specimen, 83 gf (20 N / cm²) 2 A weight of 205 gf (20 N / cm²) was applied to the lower end of the dumbbell test piece. 2 Each of the weights was attached and suspended vertically, then left in a temperature environment of 150°C, 200°C, or 250°C for 15 minutes. After 15 minutes, the gauge length of each specimen was measured with the weight attached. A specimen was considered successful if the inter-gauge portion of the specimen was not broken and the gauge length was within 175% of the initial gauge length (before load application) (i.e., the gauge length increased by 2.75 times or less). The results of the hot-set test were evaluated according to the following evaluation criteria. This test evaluates both the heat resistance of the test specimen and the cross-linking state of the specimen. A higher evaluation criterion in this test indicates that a sufficient cross-linking structure has been established in the test specimen, resulting in high heat resistance and the property of not melting even at high temperatures. - Evaluation Criteria - "A" (Excellent, Passed): Passed at a temperature of 250℃. "B" (Good, Pass): Failed at 250°C but passed at 200°C. "C" (Acceptable, Pass): Failed at 200°C but passed at 150°C. "D" (Fail): Failed to pass at any temperature.

[0093] <Tensile Test> Each tubular test specimen and each dumbbell test specimen were prepared in the same manner as in the <hot-set test> described above (preparation of test specimens). In Example 1, in addition to the tubular test specimen, a dumbbell test specimen was also prepared, and tensile tests were performed on both test specimens. Tensile tests were performed on each prepared test specimen in accordance with JIS C 3005, under conditions of a gauge length of 20 mm and a speed of 200 mm / min, and the strength at fracture (MPa) and elongation at fracture (%) were measured. The measured strength at fracture (tensile strength) and elongation at fracture (elongation at fracture) were evaluated according to the following evaluation criteria. Of the tests conducted, the elongation at break is a reference test. - Criteria for evaluating tensile strength - "A" (Excellent, Pass): 10 MPa or higher "B" (Good, Pass): 7 MPa or more and less than 10 MPa "C" (Acceptable, Pass): 3 MPa or more and less than 7 MPa "D" (Fail): Less than 3 MPa - Criteria for evaluating elongation at break - "A" (Excellent, Pass): 400% or higher "B" (Good, Pass): 250% or more but less than 400% "C" (Acceptable, Pass): 100% or more but less than 250% "D" (Fail): Less than 100%

[0094] <Heat aging test> Each tubular test specimen and each dumbbell test specimen were prepared in the same manner as in the <hot set test> described above (preparation of test specimens). Each prepared test specimen was subjected to an aging treatment by being held at a temperature of 180°C for 168 hours. For each test specimen after aging treatment, the elongation at break was measured under the same conditions as the tensile test described above. The percentage of remaining elongation at break was calculated by dividing the elongation at break after aging treatment by the elongation at break before aging treatment (the elongation at break obtained in the tensile test described above). The remaining elongation at break was evaluated according to the following criteria. This test evaluates the heat resistance of the test specimen. - Evaluation Criteria - "A" (Excellent, Pass): The remaining elongation at break was 80% or more. "B" (Good, Pass): The remaining elongation at break was 65% or more but less than 80%. "C" (Pass): The remaining elongation at break was between 50% and 65%. "D" (Fail): The remaining elongation at break was less than 50%.

[0095] [Table 1]

[0096] [Table 2]

[0097] [Table 3]

[0098] The results in Tables 1 to 3 show the following: Comparative Example 1, which did not contain ethylene copolymer resin, could not be pelletized and therefore could not be extruded (the extruded appearance could not be evaluated). Furthermore, because a chemical crosslinking method was employed, the crosslinking reaction did not occur under the above press molding conditions, resulting in inferior hot-set test (heat resistance) and tensile strength. When a chemical crosslinking method is employed, high temperature and long heating are required to induce the crosslinking reaction, which is inferior in terms of productivity and production cost. Comparative Example 2, which did not contain ethylene copolymer resin, was similar to Comparative Example 1 in that the pellets fused together too much, making pelletization impossible and thus unsuitable for extrusion molding. Furthermore, although Comparative Example 2 used the silane crosslinking method, it failed the tensile strength test, which had a high acceptance standard. Comparative Example 3, which contained LLDPE in the base rubber, and Comparative Example 4, which contained PP, were both able to form pellets that did not fuse easily, but the extruded appearance was inferior. This is thought to be because the compatibility between LLDPE or PP and silicone rubber was insufficient due to the absence of ethylene copolymer resin. Comparative Example 5, which had too little inorganic filler, exhibited inferior extrusion appearance (resulting in the formation of gel particles). This is thought to be due to poor dispersion of the silane coupling agent and organic peroxide, leading to an uneven silane graft, i.e., crosslinked structure. On the other hand, Comparative Example 6, which had too much inorganic filler, exhibited inferior extrusion appearance, heat resistance, and mechanical properties. This is thought to be because the silane coupling agent was excessively adsorbed onto the inorganic filler, hindering the grafting reaction to the base rubber. Furthermore, Comparative Example 7, which had too little silanol condensation catalyst, failed to promote the silanol condensation reaction, resulting in insufficient construction of the crosslinked structure itself and thus inferior heat resistance and tensile strength. On the other hand, Comparative Example 8, which had too much silanol condensation catalyst, exhibited inferior extrusion appearance and elongation at break. Furthermore, when the components listed in the "Silane MB" column of Example 1, excluding the silane coupling agent, and the components listed in the "Catalyst MB" column were used and melt-mixed in the same manner as in Comparative Example 1, these components were not miscible, and a homogeneous mixture could not be obtained.

[0099] In contrast, Examples 1 to 20, which used a specific amount of silane coupling agent in the presence of a specific amount of silanol condensation catalyst and inorganic filler with a base rubber containing millable-type silicone rubber and ethylene copolymer resin, all demonstrated that silane crosslinking reactions could be initiated (promoted) under mild conditions without requiring special crosslinking equipment such as chemical crosslinking tubes or electron beam crosslinking machines. This showed that silane-crosslinked silicone rubber molded articles possessing excellent appearance, heat resistance, and tensile strength could be manufactured with superior manufacturability and using general-purpose plastic extrusion molding machines. Furthermore, the molded articles exhibited high heat resistance, with a residual tensile strength and elongation at break of 50% or more even after being held at 180°C for 168 hours, as well as excellent tensile strength. Furthermore, the method for producing a silane-crosslinkable silicone rubber composition having the above step (1) (a method for producing a catalyst masterbatch) allows for the preparation of intermediate products, namely pellets that are less likely to fuse with the silane masterbatch and the catalyst masterbatch. Combined with the effects of the silane-crosslinkable silicone rubber composition, it is possible to extrude a silane-crosslinkable silicone rubber molded body with good manufacturability using a general-purpose plastic extrusion molding machine.

Claims

1. A method for producing a silane crosslinkable silicone rubber composition, comprising the step (1) of melt-mixing 100 parts by mass of a base rubber containing a millable type silicone rubber and an ethylene copolymer resin having an acid copolymer component or an acid ester copolymer component with 1 to 15 parts by mass of a silane coupling agent having graft reaction sites capable of grafting into the base rubber, 0.5 to 300 parts by mass of an inorganic filler, 0.01 to 0.6 parts by mass of an organic peroxide, and 0.01 to 0.5 parts by mass of a silanol condensation catalyst to obtain a silane crosslinkable silicone rubber composition, wherein A method for producing a silane crosslinkable silicone rubber composition, wherein step (1) comprises the following steps (a) and (c), provided that if a portion of the base rubber is melted and mixed in step (a), then steps (a), (b), and (c) are also included. Step (a): All or part of the base rubber, the silane coupling agent, and the The inorganic filler and the organic peroxide are subjected to a decomposition temperature of the organic peroxide. The process involves melting and mixing at the above temperature to prepare a silane masterbatch. Step (b): The remaining portion of the base rubber and the silanol condensation catalyst are melted and mixed together. Process for preparing a master batch of the medium Step (c): The silane masterbatch and the silanol condensation catalyst or the catalyst masterbatch The process of melting and mixing the star batch.

2. A method for manufacturing a silane-crosslinked silicone rubber molded article comprising the following steps (1), (2), and (3): Step (1): Mix 100 parts by mass of base rubber containing millable-type silicone rubber and an ethylene copolymer resin having an acid copolymer component or an acid ester copolymer component with The base rubber has graft reaction sites that can undergo a graft reaction. 1 to 15 parts by mass of silane coupling agent and 0.5 to 3 parts by mass of inorganic filler 00 parts by mass, 0.01 to 0.6 parts by mass of organic peroxide, and silanol condensate. 0.01 to 0.5 parts by mass of the catalyst are melt-mixed to form a silane crosslinkable silica. Process for obtaining a rubber composition Step (2): A step of molding the silane crosslinkable silicone rubber composition to obtain a molded article. Step (3): The process of bringing the molded body into contact with water to obtain a silane-crosslinked silicone rubber molded body. degree A method for manufacturing a silane-crosslinked silicone rubber molded article, wherein step (1) comprises the following steps (a) and (c), provided that if a portion of the base rubber is melted and mixed in step (a), then steps (a), (b), and (c) are also included. Step (a): All or part of the base rubber, the silane coupling agent, and the The inorganic filler and the organic peroxide are subjected to a decomposition temperature of the organic peroxide. The process involves melting and mixing at the above temperature to prepare a silane masterbatch. Step (b): The remaining portion of the base rubber and the silanol condensation catalyst are melted and mixed together. Process for preparing a master batch of the medium Step (c): The silane masterbatch and the silanol condensation catalyst or the catalyst masterbatch The process of melting and mixing the star batch.

3. The manufacturing method according to claim 1 or 2, wherein the amount of millable silicone rubber mixed in 100% by mass of the base rubber is 45 to 90% by mass.

4. The manufacturing method according to any one of claims 1 to 3, wherein the ethylene copolymer resin having the acid copolymer component or the acid ester copolymer component is an ethylene-(meth)acrylic acid ester copolymer resin.

5. The manufacturing method according to any one of claims 1 to 4, wherein the amount of inorganic filler mixed is 1 to 200 parts by mass per 100 parts by mass of the base rubber.

6. The manufacturing method according to any one of claims 1 to 5, wherein the inorganic filler is at least one selected from metal hydrates, talc, clay, silica, calcium carbonate, and carbon black.

7. The manufacturing method according to any one of claims 1 to 6, wherein the amount of silane coupling agent mixed is 3 to 15 parts by mass per 100 parts by mass of the base rubber.

Images