JP7214677B2 - Crosslinked fluororubber composition, wiring material using the same, and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a crosslinked fluororubber composition, a wiring material using the same, and a method for producing the same.

Wiring materials for insulated wires, cables, cords, optical fiber core wires or optical fiber cords (optical fiber cables) used in electrical and electronic equipment fields, industrial fields, and automobiles have various properties such as heat resistance and mechanical properties (e.g., tensile properties). characteristics are required.

For applications that require heat resistance, wiring materials that have a coating layer formed of a resin such as cross-linked polyethylene on the outer peripheral surface of the conductor are usually used. , a wiring material having a coating layer formed of a crosslinked fluororubber composition has been used. For example, Patent Literature 1 discloses a wiring member having a coating layer made of a crosslinked fluororubber composition obtained by a silane crosslinking method on the outer peripheral surface of a conductor.

WO2017/138642

Depending on the mode of use, the wiring material may be bent or pulled around, which may cause friction between the wiring materials or against the installation part. A higher level of durability (abrasion resistance) is required against such rubbing. However, the wiring material (coating layer) having the coating layer made of the crosslinked fluororubber composition has insufficient abrasion resistance and there is room for improvement. The abrasion resistance of wiring materials can often be improved by blending an inorganic filler into a crosslinked fluororubber composition. / Or there was a case where the mechanical properties could not be maintained.
The present invention provides a crosslinked fluororubber composition that suppresses deterioration in heat resistance and mechanical properties and has excellent abrasion resistance, a wiring member having a coating layer formed from the fluororubber composition, and a method for producing the wiring member. The task is to provide

The present inventors have studied fillers and resins used in combination with fluororubber, including the crosslinking method, and as a result, for the tetrafluoroethylene-propylene copolymer fluororubber selected as the fluororubber, dry type After selecting silica, setting its BET specific surface area and usage amount to a specific range, and performing a cross-linking reaction treatment, the heat resistance and mechanical properties of the cross-linked fluororubber composition are not greatly reduced, and abrasion resistance is improved. I have found that I can improve my sexuality. Based on this knowledge, the present inventors have made further studies and completed the present invention.

That is, the objects of the present invention have been achieved by the following means.
[1]
A crosslinked fluororubber composition obtained by subjecting the following crosslinkable fluororubber composition to a crosslinking reaction.
[Crosslinkable fluororubber composition]
6 to 25 parts by mass of dry silica (X) having a BET specific surface area of 80 to 300 m ² /g is contained in 100 parts by mass of the base rubber containing the tetrafluoroethylene-propylene copolymer fluororubber, and the dry silica A crosslinkable fluororubber composition containing an inorganic filler other than (X) twice or less the content of the dry silica (X).
[2]
[1], wherein 60% by mass or more of the tetrafluoroethylene-propylene copolymer fluororubber and 3 to 40% by mass of the ethylene-vinyl acetate copolymer resin are contained in 100% by mass of the base rubber. A crosslinked fluororubber composition.
[3]
The crosslinked fluororubber composition according to [2], wherein the ethylene-vinyl acetate copolymer resin has a vinyl acetate content of 15 to 30% by mass.
[4]
The crosslinked fluororubber composition according to any one of [1] to [3], which contains a fluororesin in the base rubber.
[5]
The crosslinkable fluororubber composition was subjected to a grafting reaction with 6 to 25 parts by mass of dry silica (X) having a BET specific surface area of 80 to 300 m ² /g with respect to 100 parts by mass of the base rubber. The crosslinked fluororubber composition according to [1], which contains more than 2.0 parts by mass and 15.0 parts by mass or less of a silane coupling agent and a silanol condensation catalyst.
[6]
A wiring material having a coating layer made of the crosslinked fluororubber composition according to any one of [1] to [5] on the outer peripheral surface of the conductor.
[7]
A method for manufacturing a wiring material, comprising the following steps (A), (B) and (C).
Step (A): 0.003 to 0.5 parts by mass of an organic peroxide and a BET specific surface area of 80 to 300 m ² per 100 parts by mass of a base rubber containing a tetrafluoroethylene-propylene copolymer fluororubber. 6 to 25 parts by mass of dry silica (X) of /g and more than 2.0 parts by mass of a silane coupling agent having a graft reaction site capable of grafting reaction to the base rubber and a reaction site capable of silanol condensation. A crosslinkable fluororubber composition obtained by mixing an inorganic filler other than the dry-process silica (X), which is 0 parts by mass or less and twice or less the content of the dry-process silica (X), and a silanol condensation catalyst. Step (B): Step of coating the outer peripheral surface of the conductor with the crosslinkable fluororubber composition obtained in step (A) to obtain a coating layer precursor Step (C): Obtained in step (C) contacting the coated layer precursor with water to obtain a wiring material [8]
[7], wherein 60% by mass or more of the tetrafluoroethylene-propylene copolymer fluororubber and 3 to 40% by mass of the ethylene-vinyl acetate copolymer resin are contained in 100% by mass of the base rubber; The wiring material manufacturing method.
[9]
The method for producing a wiring member according to [8], wherein the ethylene-vinyl acetate copolymer resin has a vinyl acetate content of 15 to 30% by mass.
[10]
The method for producing a wiring material according to any one of [7] to [9], wherein the base rubber contains a fluororesin.
[11]
[7] A wiring material produced by the production method according to any one of [10].

According to the present invention, it is possible to provide a crosslinked fluororubber composition excellent in wear resistance while suppressing deterioration in heat resistance and tensile properties, and a wiring material using the same. Furthermore, it is possible to provide a method for manufacturing this wiring material.

The present invention will be described in detail below.
[Crosslinked fluororubber composition]
The crosslinked fluororubber composition of the present invention is a crosslinked product obtained by subjecting a crosslinkable fluororubber composition described later to a crosslinking reaction.
The crosslinked fluororubber composition of the present invention has a crosslinked structure in which at least the base rubber is crosslinked directly or via a crosslinking agent or the like, and exhibits mechanical properties, heat resistance, and abrasion resistance at a high level in a well-balanced manner. . The crosslinked structure differs depending on the type of crosslinking reaction (crosslinking method) for crosslinking the crosslinkable fluororubber composition, and cannot be defined clearly and unconditionally.

The cross-linking reaction (cross-linking method) for cross-linking the cross-linkable fluororubber composition is not particularly limited, and a known resin cross-linking method such as a cross-linking reaction for polyolefins can be applied. Examples thereof include an electron beam crosslinking method, an organic peroxide crosslinking method, and a silane crosslinking method. The silane cross-linking method is preferable in that the cross-linking reaction treatment can be performed with high productivity without requiring special equipment.
In the present invention, the organic peroxide cross-linking method is one of the chemical cross-linking methods, and is a method in which base rubbers are directly cross-linked by radicals generated by decomposing organic peroxides by applying heat (organic Peroxide cross-linking method). In addition, the silane crosslinking method is a chemical crosslinking method different from the organic peroxide crosslinking method, and in a crosslinkable fluororubber composition containing an organic peroxide as a crosslinking catalyst, the and a silane coupling agent as a cross-linking agent is grafted onto the base rubber by radicals generated from the organic peroxide to obtain a silane-grafted rubber. It refers to a method in which a silane coupling agent undergoes a silanol condensation reaction by bringing the silane graft rubber into contact with moisture in the presence of a catalyst.

Since the crosslinked fluororubber composition of the present invention is a crosslinked product of a fluororubber composition, it exhibits the heat resistance normally required for wiring materials.

[Crosslinkable fluororubber composition]
The crosslinkable fluororubber composition used in the present invention is dry silica (X) having a BET specific surface area of 80 to 300 m ² /g with respect to 100 parts by mass of the base rubber containing a tetrafluoroethylene-propylene copolymer fluororubber. Contains 6 to 25 parts by mass of (hereinafter sometimes referred to as dry silica (X)), contains inorganic fillers other than dry silica (X) twice or less than the content of dry silica (X), and is applied The composition may further contain essential or suitable components described later depending on the crosslinking method to be used.
The crosslinkable fluororubber composition may be a composition in which at least the base rubber can be crosslinked by the crosslinking reaction treatment described below. It is preferable to appropriately contain an agent, a cross-linking catalyst, a cross-linking accelerator, and the like.
In the present invention, a crosslinkable fluororubber composition suitably applicable to an electron beam crosslinkable method, an organic peroxide crosslinkable method or a silane crosslinkable method is defined as an electron beam crosslinkable fluororubber composition and an organic peroxide crosslinkable composition, respectively. It is sometimes called a fluororubber composition or a silane-crosslinkable fluororubber composition.
The electron beam crosslinkable fluororubber composition or the organic peroxide crosslinkable fluororubber composition contains the base rubber and dry silica (X) described above, and an inorganic filler other than dry silica (X), which is optionally contained. In addition, it preferably contains a cross-linking aid and/or an organic peroxide. Furthermore, it may contain a silane coupling agent.
The silane-crosslinkable fluororubber composition contains, in addition to the base rubber and the dry silica (X) described above, and optionally an inorganic filler other than the dry silica (X), a silane grafted onto the base rubber. It preferably contains a coupling agent and a silanol condensation catalyst. In the silane-crosslinkable fluororubber composition, at least a portion of the silane coupling agent may be grafted to the base rubber, and the rest may not be grafted.
A preferred embodiment of the silane-crosslinkable fluororubber composition is dry silica (X) having a BET specific surface area of 80 to 300 m ² /g for 100 parts by mass of the base rubber containing the tetrafluoroethylene-propylene copolymer fluororubber. 6 to 25 parts by mass, more than 2.0 parts by mass and 15.0 parts by mass or less of the silane coupling agent grafted to the base rubber, and twice or less the content of the dry silica (X). The silane-crosslinkable fluororubber composition contains an inorganic filler other than silica (X) and a silanol condensation catalyst.
Each component used in the present invention is described below.

<Base rubber>
The base rubber contains tetrafluoroethylene-propylene copolymer fluororubber (FEPM) (hereinafter sometimes referred to as fluororubber). When the base rubber contains a fluororubber, heat resistance can be imparted to the obtained crosslinked fluororubber composition.

- Tetrafluoroethylene-propylene copolymer fluororubber -
The tetrafluoroethylene-propylene copolymer fluororubber is not particularly limited as long as it is a copolymer rubber of tetrafluoroethylene and propylene and can be crosslinked. The third copolymerization component also includes fluororubbers obtained by copolymerizing various polymerizable components capable of polymerizing with tetrafluoroethylene and propylene.
Preferred examples of fluororubbers include rubbers having crosslinkable sites in the main chain or at the ends thereof. For example, when used in the silane cross-linking method, it is preferable to have a site capable of grafting reaction with a silane coupling agent and a site capable of grafting reaction in the presence of an organic peroxide. When used in the electron beam cross-linking method or the organic peroxide cross-linking method, those having sites capable of cross-linking reaction by electron beam irradiation or the presence of radicals generated from the organic peroxide are preferred. Such sites capable of cross-linking reaction and sites capable of grafting reaction are not particularly limited, but examples thereof include unsaturated bond sites in carbon chains and carbon atoms having hydrogen atoms. The tetrafluoroethylene-propylene copolymer fluororubber may be used alone or in combination of two or more.

- Other rubbers or resins -
The base rubber may contain other rubbers or resins in addition to the fluororubber.
Rubbers other than fluororubber and resins are not particularly limited, and those commonly used as covering materials for wiring materials can be used without particular limitations. As with fluororubber, when used in a silane cross-linking method, the presence of radicals when electron beam cross-linking or organic peroxide cross-linking has a site that can be grafted in the presence of an organic peroxide. Those having sites capable of undergoing a cross-linking reaction under the conditions are preferred. Examples of rubber include vinylidene fluoride-hexafluoropropylene copolymer rubber. Among them, ethylene-vinyl acetate copolymer resin, fluororesin, and ethylene-(meth)acrylic acid ester copolymer resin are preferable as the resin. These can be used alone or in combination of two or more.

The ethylene-vinyl acetate copolymer resin is not particularly limited as long as it can undergo a cross-linking reaction, and examples thereof include copolymer resins obtained by copolymerizing ethylene and vinyl acetate. When the base rubber contains an ethylene-vinyl acetate copolymer resin, the resulting crosslinked fluororubber composition can be imparted with excellent mechanical properties, heat resistance, and the like.

The ethylene-vinyl acetate copolymer resin preferably has a vinyl acetate content (VA) of 15 to 35% by mass, more preferably 15 to 30% by mass, and 15 to 25% by mass. is more preferred. When the vinyl acetate content in the ethylene-vinyl acetate copolymer resin is within the above range, abrasion resistance can be further enhanced. In addition, the compatibility between the fluororubber and the ethylene-vinyl acetate copolymer resin can be further enhanced. From the same point of view, even when two or more ethylene-vinyl acetate copolymer resins are used in combination, each ethylene-vinyl acetate copolymer resin preferably has a vinyl acetate content within the above range.
The vinyl acetate content in the ethylene-vinyl acetate copolymer resin can be determined according to JIS K7192.

Examples of fluororesins include homopolymer or copolymer resins containing fluorine atoms in the main chain or side chains. A fluororesin is usually obtained by (co)polymerizing a monomer containing a fluorine atom. When the base rubber contains a fluororesin, the obtained crosslinked fluororubber composition can be imparted with excellent wear resistance and the like.

Such a fluororesin is not particularly limited, but copolymerization of fluorine-containing monomers such as perfluorohydrocarbons such as tetrafluoroethylene and hexafluoropropylene, and partially fluorinated hydrocarbons such as vinylidene fluoride. Coalesced resins, and further resins of copolymers of these fluorine-containing monomers and hydrocarbons such as ethylene (excluding tetrafluoroethylene-propylene copolymer fluororubber) can be mentioned.
Specifically, tetrafluoroethylene-hexafluoropropylene copolymer resin, tetrafluoroethylene-perfluoroalkyl ether copolymer resin, ethylene-tetrafluoroethylene copolymer resin, ethylene-tetrafluoroethylene-hexafluoropropylene copolymer resin, Coalescent resins, chlorotrifluoroethylene resins, polyvinylidene fluoride resins, and the like can be mentioned. Among them, ethylene-tetrafluoroethylene-hexafluoropropylene copolymer resin, ethylene-tetrafluoroethylene copolymer resin, or a combination thereof is preferable.
The melting point of the fluororesin is preferably 240° C. or lower, more preferably 200° C. or lower. If the melting point is too high, foaming may occur in the compound or molding during kneading or extrusion. Melting points can be determined according to ASTM D3159.

The ethylene-(meth)acrylic acid ester copolymer resin is not particularly limited as long as it is a copolymer resin of ethylene and (meth)acrylic acid ester. When the base rubber contains an ethylene-(meth)acrylic acid ester copolymer resin, excellent wear resistance and the like can be imparted to the obtained crosslinked fluororubber composition. Ethylene-(meth)acrylate copolymer resins include ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-butyl acrylate copolymer and the like.

- Content of each component in the base rubber, etc. -
The base rubber may be 100% by mass of fluororubber, but may contain other rubbers or resins. When the base rubber contains other rubbers or resins in addition to the fluororubber, the total content of each component is appropriately adjusted to 100% by mass.
The content of the fluororubber in 100% by mass of the base rubber is not particularly limited, but from the viewpoint of imparting heat resistance, it is preferably 60% by mass or more, more preferably 60 to 90% by mass, and 65 to 85% by mass. Especially preferred.
The content of the ethylene-vinyl acetate copolymer resin in 100% by mass of the base rubber is not particularly limited, but is preferably 3 to 40% by mass, more preferably 5 to 25% by mass, and particularly preferably 7 to 20% by mass. . When the content of the ethylene-vinyl acetate copolymer resin is within the above range, both mechanical properties and heat resistance can be achieved.
The base rubber preferably contains an ethylene-vinyl acetate copolymer resin in addition to the fluororubber. It is preferable to contain 3 to 40% by mass.
The content of the fluororesin in 100% by mass of the base rubber is not particularly limited, but is preferably 5 to 30% by mass, more preferably 5 to 25% by mass, and particularly preferably 7 to 20% by mass. When the content of the fluororesin is within the above range, the abrasion resistance of the crosslinked fluororubber composition can be further improved.
The content of the ethylene-(meth)acrylic acid ester copolymer resin in 100% by mass of the base rubber is not particularly limited, but is preferably 5 to 25% by mass, more preferably 5 to 20% by mass, and 7 to 20% by mass. % by weight is particularly preferred. When the content of the ethylene-(meth)acrylate copolymer resin is within the above range, both mechanical properties and heat resistance can be achieved.
From the viewpoint of achieving both mechanical properties and heat resistance, the total content of the ethylene-(meth)acrylic acid ester copolymer resin and the content of the ethylene-vinyl acetate copolymer resin is 100% by mass of the base rubber. , 5 to 25% by mass.

<Dry silica having a BET specific surface area of 80 to 300 m ² /g>
The crosslinkable fluororubber composition contains dry silica having a BET specific surface area of 80 to 300 m ² /g. The dry silica (X) adheres closely to the base rubber having the above composition and contributes to the improvement of abrasion resistance.
Dry silica refers to silica produced by a dry method. As the dry silica (X), those produced by a dry method can be used without particular limitation. The fumed silica (X) can adhere to the surface of the base rubber by adsorption, bonding, or interaction (for example, interaction by hydrogen bonding, interaction between ions, partial charges, or dipoles, etc.). Especially when used in the silane cross-linking method described later, the dry silica (X) has, on its surface, a reaction site capable of silanol condensation of the silane coupling agent, a hydrogen bond or a covalent bond, etc. , or those having a site that can be chemically bonded through an intermolecular bond. The site that can be adhered is not particularly limited, and may function as the site that can be chemically bonded. OH groups such as groups), amino groups, SH groups, and the like. A commercially available product can be used as the dry silica. The dry silica (X) may be used singly or in combination of two or more. In addition, even when dry silica (X) and dry silica other than dry silica (X) described later are used in combination, each has a predetermined BET specific surface area.
The BET specific surface area of the dry silica (X) is 80 to 300 m ² /g, and from the viewpoint of imparting abrasion resistance and further excellent extrusion appearance quality without significantly impairing mechanical properties and heat resistance. , 90 to 250 m ² /g, more preferably 150 to 220 m ² /g.
The BET specific surface area (m ² /g) is a value measured using nitrogen gas as an adsorbate in accordance with JIS Z 8830:2013 "Carrier gas method". For example, it is a value measured using a specific surface area/pore size distribution measuring device “Flowsorb” (manufactured by Shimadzu Corporation).
The dry silica (X) content is 6 to 25 parts by mass, preferably 8 to 20 parts by mass, more preferably 8 to 15 parts by mass, based on 100 parts by mass of the base rubber.

<Inorganic filler other than dry silica having a BET specific surface area of 80 to 300 m ² /g>
As the inorganic filler other than dry-process silica having a BET specific surface area of 80 to 300 m ² /g (hereinafter referred to as inorganic filler other than dry-process silica (X)), those usually used for manufacturing wiring materials are used without particular limitation. be able to. Addition of an inorganic filler other than the dry silica (X) is preferable in that the amount can be increased and the cost can be suppressed. In addition, it is preferable in that heat resistance, tensile properties, flame retardancy, etc. can be adjusted. Hereinafter, dry silica (X) and inorganic fillers other than dry silica (X) may be simply referred to as "inorganic filler".
The inorganic filler other than the dry silica (X) preferably has a site capable of chemically bonding with the reaction site capable of silanol condensation of the silane coupling agent, similarly to the dry silica (X).
Examples of inorganic fillers other than dry silica (X) include aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, calcium silicate, magnesium silicate, calcium oxide, magnesium oxide, aluminum oxide, aluminum nitride, and aluminum borate. Whiskers, hydrated aluminum silicate, hydrated magnesium silicate, basic magnesium carbonate, metal hydrates such as compounds having hydroxyl groups or water of crystallization such as hydrotalcite, boron nitride, silica (dried silica Dry silica other than (X), wet silica), carbon, clay, zinc oxide, tin oxide, titanium oxide, molybdenum oxide, antimony trioxide, silicone compound, quartz, talc, zinc borate, white carbon, zinc borate, hydroxytin zinc acid and zinc stannate. One of the inorganic fillers other than the dry silica (X) may be used alone, or two or more of them may be used in combination. Among them, at least one selected from the group consisting of silica, calcium carbonate, clay and talc is preferable. From the viewpoint of suppressing foaming during (melt) mixing in the silane cross-linking method, it is preferable not to use wet silica. Inorganic fillers other than dry silica (X) may be surface-treated with a common surface-treating agent.
The inorganic filler other than the dry silica (X) is preferably particles, and the average particle size thereof is appropriately set.
The BET specific surface area (m ² /g) of inorganic fillers other than dry silica (X) is not particularly limited.
The content of inorganic fillers other than dry silica (X) is not more than twice the content of dry silica (X) with respect to 100 parts by mass of the base rubber, and is 1.7, from the viewpoint of reducing wear resistance deterioration. 1 times or less is preferable, 1.5 times or less is more preferable, and the same amount or less is still more preferable. From the viewpoint of the effect of adding an inorganic filler other than dry silica (X), it is practical that the lower limit of the content of the inorganic filler other than dry silica (X) is 0.1 parts by mass or more. From the viewpoint of improving wear resistance, it is preferable not to add inorganic fillers other than dry silica (X).

<Other ingredients>
The crosslinkable fluororubber composition may further contain the following components, if necessary.

- Crosslinking aid -
When the crosslinkable fluororubber composition is crosslinked by an electron beam crosslinking method, the crosslinkable fluororubber composition may contain a crosslinking aid. As the cross-linking aid, those commonly used in the electron beam cross-linking method can be used without particular limitation.
Examples of the cross-linking aid usually include polyfunctional compounds, for example, polypropylene glycol diacrylate, trimethylolpropane triacrylate (meth) acrylate compounds, triallyl cyanurate (TAC), triallyl isocyanurate ( TAIC), maleimide compounds, and divinyl compounds. Triallyl cyanurate and triallyl isocyanurate are preferred.
The content of the crosslinking aid in the crosslinkable fluororubber composition is appropriately set, and can be set, for example, to 3 to 15 parts by mass with respect to 100 parts by mass of the base polymer.

- Silane coupling agent -
When the crosslinkable fluororubber composition is crosslinked by an electron beam crosslinking method, the crosslinkable fluororubber composition may contain a silane coupling agent. When the crosslinkable fluororubber composition is crosslinked by a silane crosslinking method, the crosslinkable fluororubber composition contains a silane coupling agent.
The silane coupling agent used in the silane-crosslinkable fluororubber composition is a grafting reaction site that can undergo a grafting reaction on a site capable of grafting reaction in the base rubber in the presence of radicals generated by decomposition of the organic peroxide. (group or atom) and a reaction site capable of silanol condensation (including a site produced by hydrolysis, such as a silyl ester group) are preferred. Examples of such a silane coupling agent include silane coupling agents used in conventional silane cross-linking methods. The reactive site capable of silanol condensation functions as a reactive site capable of chemically bonding with dry silica (X) and/or an inorganic filler other than dry silica (X), if the site has a chemically bonding site. is preferred.
Silane coupling agents include silane coupling agents having an unsaturated group, specifically vinyltrimethoxysilane, vinyltriethoxysilane, vinyltributoxysilane, vinyldimethoxyethoxysilane, vinyldimethoxybutoxysilane, Examples thereof include vinylsilanes such as vinyldiethoxybutoxysilane, allyltrimethoxysilane, allyltriethoxysilane and vinyltriacetoxysilane, and (meth)acryloxysilane. Among them, vinyltrimethoxysilane or vinyltriethoxysilane is particularly preferred. One type of silane coupling agent may be used, or two or more types may be used.
The silane coupling agent may be used as it is or diluted with a solvent.
The content of the silane coupling agent is more than 2.0 parts by mass and 15.0 parts by mass with respect to 100 parts by mass of the base rubber, since it can further improve the wear resistance without significantly deteriorating the mechanical properties and heat resistance. Parts by mass or less is preferable, 3 to 12 parts by mass is more preferable, and 4 to 12 parts by mass is even more preferable.

- Organic peroxide -
When the crosslinkable fluororubber composition is crosslinked by an organic peroxide crosslinking method or a silane crosslinking method, the crosslinkable fluororubber composition contains an organic peroxide.
The organic peroxide generates radicals at least by thermal decomposition, and serves as a catalyst for the crosslinking reaction between the base rubbers or the radical reaction between the base rubber and the silane coupling agent in the organic peroxide crosslinking method, or the silane coupling agent. In the cross-linking method, the grafting reaction of the silane coupling agent to the base rubber by a radical reaction (a covalent bond forming reaction between the grafting reaction site of the silane coupling agent and the graftable site of the base rubber, ) is also called an addition reaction.).
As the organic peroxide, those having the above functions and used in radical polymerization or conventional silane cross-linking methods can be used without particular limitation. For example, benzoyl peroxide, dicumyl peroxide (DCP), 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane or 2,5-dimethyl-2,5-di-(tert-butylperoxy) Hexyne-3 is preferred. One type of organic peroxide may be used, or two or more types may be used.
The decomposition temperature of the organic peroxide is preferably 80 to 195°C, particularly preferably 125 to 180°C. In the present invention, the decomposition temperature of an organic peroxide refers to the temperature at which an organic peroxide of a single composition, when heated, causes itself to decompose into two or more compounds within a certain temperature or temperature range. means. Specifically, it refers to the temperature at which heat absorption or heat generation starts when heated from room temperature at a heating rate of 5° C./min in a nitrogen gas atmosphere by thermal analysis such as DSC method.

The content of the organic peroxide in the crosslinkable fluororubber composition is not particularly limited, and can be appropriately determined according to the crosslinking method.
In the present invention, in any cross-linking method, 0.003 to 0.5 parts by mass is preferable, 0.005 to 0.5 parts by mass is more preferable, and 0.005 to 0.005 parts by mass is preferable with respect to 100 parts by mass of the base rubber. 0.2 parts by mass is more preferable.
In the silane cross-linking method, by setting the content of the organic peroxide within the above range, the cross-linking reaction or grafting reaction can be performed in an appropriate range, and high heat resistance can be imparted to the cross-linked fluororubber composition. Furthermore, it is possible to suppress the generation of gel-like lumps (agglomerates).

- Silanol condensation catalyst -
When the crosslinkable fluororubber composition is crosslinked by a silane crosslinking method, the silane crosslinkable fluororubber composition preferably contains a silanol condensation catalyst.
The silanol condensation catalyst functions to cause (promote) the condensation reaction of the silanol-condensable reaction site of the silane coupling agent in the presence of moisture. Based on the action of this silanol condensation catalyst, the base rubbers are crosslinked via the silane coupling agent.
Such silanol condensation catalysts are not particularly limited, and examples thereof include organotin compounds, metallic soaps, platinum compounds and the like. Examples of organic tin compounds include organic tin compounds such as dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin dioctiate, and dibutyltin diacetate. One type of silanol condensation catalyst (X) may be used, or two or more types may be used.

The content of the silanol condensation catalyst in the silane-crosslinkable fluororubber composition is not particularly limited, but is preferably from 0.0001 to 0.5 parts by mass, more preferably from 0.001 to 0.001 part by mass, relative to 100 parts by mass of the base rubber. 2 parts by mass is more preferred. When the content of the silanol condensation catalyst is within the above range, the crosslinking reaction due to the condensation reaction of the silane coupling agent tends to proceed almost uniformly, physical properties such as appearance and heat resistance are improved, and productivity is also improved.

- Other additives (antioxidants, etc.) -
The crosslinkable fluororubber composition may contain various additives normally used in electric wires, electric cables, electric cords, etc., as long as they do not impair the effects of the present invention. Examples of such additives include antioxidants, lubricants, metal deactivators, or fillers (including flame retardants (auxiliaries)).
The antioxidant is not particularly limited, but includes, for example, an amine antioxidant, a phenol antioxidant, a sulfur antioxidant, etc., and a phenol antioxidant is preferred.
The antioxidant can be added in an amount of preferably 0.1 to 15.0 parts by mass, more preferably 0.1 to 10 parts by mass, per 100 parts by mass of the base rubber.

A crosslinked fluororubber composition is a crosslinked product of a crosslinkable fluororubber composition containing the above components.
When the crosslinked fluororubber composition is a crosslinked product obtained by an electron beam crosslinking method or an organic peroxide crosslinking method, the crosslinked fluororubber composition contains at least a crosslinked base rubber and dry silica (X). contains. The crosslinked fluororubber composition contains other optional components, for example, a crosslinked product of the base rubber via the silane coupling agent when used in combination with a silane coupling agent.
When the crosslinked fluororubber composition is a crosslinked product obtained by a silane crosslinking method, the crosslinked fluororubber composition contains at least a silane crosslinked base rubber in which the base rubber is condensed via silanol condensation (siloxane bond). One form of this silane-crosslinked base rubber includes a silane-crosslinked base rubber and fumed silica (X). The fumed silica (X) may be combined with the silane coupling agent of the silane-crosslinked base rubber. This silane-crosslinked base rubber is a crosslinked base in which a plurality of crosslinked base rubbers are bonded or adsorbed to dry silica (X) by a silane coupling agent and bonded (crosslinked) via dry silica (X) and the silane coupling agent. It contains at least a rubber and a crosslinked base rubber crosslinked via a silane coupling agent by hydrolysis of the reaction site of the silane coupling agent of the crosslinkable rubber and mutual silanol condensation reaction. In addition, the silane-crosslinked base rubber may have a mixture of bonding (crosslinking) via the dry silica (X) and the silane coupling agent and crosslinking via the silane coupling agent. Furthermore, it may contain a silane coupling agent and an unreacted rubber component and/or an uncrosslinked silane crosslinkable rubber. When an inorganic filler other than dry silica (X) is used in addition to dry silica (X), the silane-crosslinked base rubber has the form described above, and the dry silica (X) is dry silica (X ), except that inorganic fillers other than ) are substituted.

The crosslinked fluororubber composition exhibits excellent wear resistance while maintaining the heat resistance and mechanical properties normally required for the wiring material. Although the reason is not clear, it is considered as follows.
Heat resistance is enhanced by using a base rubber containing tetrafluoroethylene-propylene copolymer fluororubber.
A specific amount of the base rubber containing the tetrafluoroethylene-propylene copolymer fluororubber and the dry silica (X) having a BET specific surface area of 80 to 300 m ² /g are used in combination to form the base rubber and the dry silica (X). There is an increasing closeness between In addition, by cross-linking such a cross-linkable fluororubber composition, the dry silica (X) is involved in the base rubbers and uniformly cross-linked. As a result, it is considered that the abrasion resistance is improved while maintaining the heat resistance and mechanical properties of the fluororubber. In addition, by setting the amount of the inorganic filler other than the dry silica (X) to a ratio not more than twice the content of the dry silica (X), the amount of the base rubber is increased without significantly impairing the wear resistance. can reduce the amount used.

<Method for producing crosslinked fluororubber composition>
A method for producing a crosslinked fluororubber composition includes a step of mixing the above components to form a crosslinkable fluororubber composition and subjecting the mixture to a crosslinking reaction treatment.

- Preparation of crosslinkable fluororubber composition -
A crosslinkable fluororubber composition can usually be prepared by mixing the above components.
The crosslinkable fluororubber composition can be prepared by (melting) mixing the above components at once. The conditions for melt-mixing are not particularly limited, but the conditions for step (A1) described later can be employed. The crosslinkable fluororubber composition is preferably prepared by the step (A) in the wiring material manufacturing method described below. The silane-crosslinkable fluororubber composition prepared by melt-mixing the above components or by the step (A) contains a silane-crosslinkable rubber obtained by grafting a silane coupling agent to a base rubber, as described later. Furthermore, it may contain decomposition products of organic peroxides.
The mixing order of each component is not particularly limited, but premixing the inorganic filler containing the dry silica (X) and the silane coupling agent is preferable in that volatilization of the silane coupling agent can be suppressed.

The crosslinked fluororubber composition can be produced by subjecting the above-described crosslinkable fluororubber composition to a crosslinking reaction treatment. The cross-linking reaction (cross-linking method) is as described above.
The method for producing the crosslinked fluororubber composition is the same as the method for producing the wiring material described later, except that the step of forming a coating layer on the outer peripheral surface of the conductor is not included.

[Wiring material]
The wiring material of the present invention is a wiring material having a coating layer comprising the crosslinked fluororubber composition of the present invention on the outer peripheral surface of a conductor. A wiring material provided with this coating layer has well-balanced heat resistance, tensile properties, and wear resistance.
Examples of the wiring material include electric wires, cables, cords, optical fiber core wires, and optical fiber cords used for internal wiring or external wiring of electric/electronic devices, and electric wires or cables are preferred. Among others, the wiring material of the present invention can be preferably used as a wiring material that particularly requires wear resistance (for example, a heat-resistant automotive cable, a heat-resistant automotive electric wire (AFEX or EFFX), etc.).
The wiring member may have at least one coating layer made of the crosslinked fluororubber composition on the outer peripheral surface of the conductor, and the rest of the configuration may be the same as the ordinary configuration of the wiring member. For example, an electric wire having at least one coating layer on the outer peripheral surface of a conductor, at least one of which is a coating layer made of a crosslinked fluororubber composition. Alternatively, an electric wire having at least one coating layer or a cable in which a coating layer (sheath) is formed on the outer peripheral surface of a bundle in which a plurality of these are bundled, and at least one of these coating layers is made of a crosslinked fluororubber composition It can be a cable that is a different coating layer.
Usual conductors can be used as conductors, and may be single wires or twisted wires, and may be bare wires, tin-plated or enamel-coated wires. Examples of metal materials for forming conductors include annealed copper, copper alloys, and aluminum.
The coating layer made of the crosslinked fluororubber composition may be provided directly on the outer peripheral surface of the conductor, or may be provided indirectly via another member or layer. From the viewpoint of wear resistance, it is preferable that the coating layer made of the crosslinked fluororubber composition be the outermost layer.
The thickness (thickness) of the coating layer made of the crosslinked fluororubber composition is the same as that of ordinary wiring materials. Although the thickness of the coating layer formed around the conductor is not particularly limited, it is usually about 0.15 to 5 mm. Since the crosslinked fluororubber composition of the present invention exhibits high wear resistance as described above, it is not necessary to increase the thickness as in the case of using a conventional crosslinked fluororubber composition, and the coating layer has a low thickness. It is also possible to reduce costs by reducing the cost.

[Method for manufacturing wiring material]
The method for producing the wiring material preferably includes a step of mixing the above components to form a crosslinkable fluororubber composition, coating the outer peripheral surface of the conductor with this crosslinkable fluororubber composition, and subjecting it to a crosslinking reaction treatment.
A preferred embodiment of the wiring material manufacturing method will be described below.

In the present invention, mixing means obtaining a uniform mixture.
Mixing of the respective components can be carried out by adopting the conditions of the step (A1) described below, as in the above-described mixing in the method for producing a crosslinkable fluororubber composition.
The method of covering the outer peripheral surface of the conductor may be any method as long as the conductor can be covered with the crosslinkable fluororubber composition, and an appropriate molding method is applied. Examples of molding methods include extrusion molding using an extruder, injection molding using an injection molding machine, and molding using other molding machines. In the present invention, extrusion molding (extrusion coating) in which the conductor and the crosslinkable fluororubber composition are co-extruded is preferred.
Extrusion can be performed using a general-purpose extruder. The extrusion molding temperature is appropriately set according to various conditions such as the type of base rubber and extrusion speed (take-up speed), and is preferably set to 150 to 200°C, for example.

The method of cross-linking treatment is not particularly limited, and may be electron beam cross-linking, organic peroxide cross-linking or silane cross-linking. The silane cross-linking method is preferable because it does not require special machines such as a chemical cross-linking machine and an electron beam cross-linking machine. In addition, the silane cross-linking method can omit the organic peroxide cross-linking step, which usually takes a long time, and is therefore preferable in terms of productivity.

When the crosslinkable fluororubber composition is subjected to a cross-linking reaction treatment by an electron beam cross-linking method to produce a wiring material, an electron beam is irradiated as the cross-linking reaction treatment. The electron beam irradiation conditions are not particularly limited as long as the electron beam crosslinkable fluororubber composition (base rubber) can be crosslinked. For example, the electron beam irradiation dose can be 1 to 30 Mrad, more preferably 5 to 25 Mrad, and the acceleration voltage during irradiation can be 500 to 2000 keV.

An example of a method for manufacturing a wiring material by an electron beam crosslinking method is a manufacturing method having the following steps.
Step (E): 3 to 15 parts by mass of a cross-linking aid and dry silica having a BET specific surface area of 80 to 300 m ² /g per 100 parts by mass of a base rubber containing a tetrafluoroethylene-propylene copolymer fluororubber. (X) 6 to 25 parts by mass and an inorganic filler other than dry silica (X) that is twice or less the content of dry silica (X) are melt-kneaded to obtain a crosslinkable fluororubber composition. Steps Step (F): Step of coating the outer peripheral surface of the conductor with the crosslinkable fluororubber composition obtained in Step (E) to obtain a coating layer precursor Step (G): Coating obtained in Step (F) A step of subjecting the layer precursor to a cross-linking reaction treatment by irradiating it with an electron beam

The blending amount of each component in step (E) is the same as the content in the crosslinkable fluororubber composition described above, and the reason for setting the blending amount is also the same.

When a crosslinkable fluororubber composition is crosslinked by an organic peroxide crosslinking method to produce a wiring member, the composition is heated to a temperature higher than the decomposition temperature of the organic peroxide as the crosslinking reaction treatment. The heating condition is not particularly limited as long as it is equal to or higher than the decomposition temperature of the organic peroxide contained in the organic peroxide crosslinkable fluororubber composition, and the heating time is not particularly limited.
An example of a method for producing a wiring material by the organic peroxide method is a production method having the following steps.
Step (H): 0.5 to 2.0 parts by mass of an organic peroxide and 3 to 10 parts by mass of a cross-linking aid per 100 parts by mass of a base rubber containing a tetrafluoroethylene-propylene copolymer fluororubber. 6 to 25 parts by mass of dry silica (X) having a BET specific surface area of 80 to 300 m ² /g, and an inorganic filler other than dry silica (X) that is twice or less the content of dry silica (X). and a step of melt-kneading at a temperature at which the organic peroxide does not decompose (for example, 130 ° C. or less) to prepare an organic peroxide crosslinkable fluororubber composition;
Step (I): forming a coating layer precursor by molding the organic peroxide crosslinkable fluororubber composition obtained in step (H) on the outer peripheral surface of the conductor;
Step (J): A step of heating the coating layer precursor obtained in step (I) with a chemical cross-linking device at a temperature higher than the decomposition temperature of the organic peroxide (preferably 170° C. to 270° C.) to undergo a cross-linking reaction.

The blending amount of each component in the step (H) is the same as the content in the above-described crosslinkable fluororubber composition, and the reason for setting the blending amount is also the same.

When a wiring material is produced by subjecting a crosslinkable fluororubber composition to a crosslinking reaction treatment by a silane crosslinking method, it is brought into contact with moisture as the crosslinking reaction treatment. Conditions for contact with moisture will be described later.

As a method for producing a wiring material by the silane cross-linking method, a production method (sometimes referred to as the production method of the present invention) having the following steps (A), (B) and (C) is preferable.

Step (A): 0.003 to 0.5 parts by mass of an organic peroxide and a BET specific surface area of 80 to 300 m ² per 100 parts by mass of a base rubber containing a tetrafluoroethylene-propylene copolymer fluororubber. 6 to 25 parts by mass of dry silica (X) of /g and more than 2.0 parts by mass of a silane coupling agent having a graft reaction site capable of grafting reaction to the base rubber and a reaction site capable of silanol condensation. 0 parts by mass or less and 2 times or less of the content of dry silica (X), an inorganic filler other than dry silica (X) and a silanol condensation catalyst are mixed to obtain a crosslinkable fluororubber composition. Steps Step (B): Step of coating the outer peripheral surface of the conductor with the crosslinkable fluororubber composition obtained in Step (A) to obtain a coating layer precursor Step (C): Coating obtained in Step (C) A step of contacting the layer precursor with water to obtain a wiring material

The blending amount of each component in step (A) is the same as the content in the silane-crosslinkable fluororubber composition described above, and the reason for setting the blending amount is also the same.
When the amount of the organic peroxide compounded in the step (A) is within the above range, in addition to the above reason, the silane coupling agent can be effectively grafted onto the base rubber, and unreacted silane can be reduced. Condensation reaction between coupling agents and volatilization of unreacted silane coupling agents can be suppressed. Moreover, the cross-linking reaction between the base rubbers can be suppressed. As a result, as described above, the generation of pimples can be suppressed while imparting high heat resistance to the crosslinked fluororubber composition.

The mixing order of each component in step (A) is not particularly limited, but after (melting) mixing the base rubber, inorganic filler containing dry silica (X), silane coupling agent, and organic peroxide, Mixing the mixture (silane masterbatch) with a silanol condensation catalyst is preferable in that the silanol condensation reaction can be suppressed before the silane coupling agent is grafted onto the base rubber. At this time, "mixing the base rubber, the inorganic filler containing dry silica (X), the silane coupling agent and the organic peroxide" does not specify the mixing order when mixing, but what order It means that it can be mixed with The inorganic filler containing dry silica (X) is meant to include an aspect in which dry silica (X) is the only dry silica (X) and an aspect in which dry silica (X) and an inorganic filler other than dry silica (X) are included.
That is, in the present invention, when performing the step (A), when all the base rubber is used in the following step (A1), the following steps (A1) and (A3) are performed, and the following step (A1) is used to When using a part of, it is more preferable to perform the following steps (A1) to (A3).

Step (A1): All or part of the base rubber, dry silica (X), a silane coupling agent, and dry silica (X ) with an inorganic filler other than ) in the presence of an organic peroxide at a temperature equal to or higher than the decomposition temperature of the organic peroxide to allow a grafting reaction between the base rubber and the silane coupling agent. Step (A2) : A step of mixing the silanol condensation catalyst and the rest of the base rubber as a carrier rubber Step (A3): Mixing the molten mixture obtained in the step (A1) with the silanol condensation catalyst or the mixture obtained in the step (A2) process

More preferably, in step (A1), each component is mixed in the following two steps of steps (A1-1) and (A1-2).
Step (A1-1): Dry silica (X) and a silane coupling agent, and when inorganic filler other than dry silica (X) is used in step (A), inorganic filler other than dry silica (X) are mixed. Step (A1-2): The mixture obtained in Step (A1-1) and all or part of the base rubber are melted in the presence of an organic peroxide at a temperature equal to or higher than the decomposition temperature of the organic peroxide. A step of mixing to cause a grafting reaction between the base rubber and the silane coupling agent

The above step (A1) includes "an embodiment in which the entire amount (100 parts by mass) of the base rubber is blended" and "an embodiment in which a portion of the base rubber is blended". If part of the base rubber is blended in step (A1), the remainder of the base rubber is preferably blended in step (A2).
In the present invention, "a part of the base rubber" means the base rubber used in the step (A1) among the base rubbers, a part of the base rubber itself (having the same composition as the base rubber), It refers to a part of constituent components, a part of components constituting the base rubber (for example, the total amount of a specific component among a plurality of components).
In addition, the "remainder of the base rubber" is the remaining base rubber excluding a portion of the base rubber used in the step (A1). Specifically, the remainder of the base rubber itself constitutes the base rubber. The rest of the components that make up the base rubber.
When part of the base rubber is blended in step (A1), the blending amount of 100 parts by mass of the base rubber in step (A) includes steps (A1) to (A3), preferably steps (A1) and (A2). ) is the total amount of base rubber mixed in.
Here, when the balance of the base rubber is blended in the step (A2), the base rubber is preferably blended in the step (A1) in an amount of preferably 80 to 99% by mass, more preferably 85 to 95% by mass, and the step ( In A2), the content is preferably 1 to 20% by mass, more preferably 5 to 15% by mass.

In the production method of the present invention, the silane coupling agent is preferably premixed with dry silica (X) as described above (step (A1-1)). The premixed silane coupling agent exists so as to surround the surface of the dry silica (X), and part or all of it adheres or bonds to the dry silica (X). In this way, volatilization of the silane coupling agent can be reduced during subsequent melt-mixing, and the silane coupling agent that does not adhere to or bond to the dry silica (X) may condense, making melt-mixing difficult. can be prevented. Furthermore, the desired shape can be obtained during extrusion coating. When an inorganic filler other than the dry silica (X) is used in addition to the dry silica (X), the inorganic filler other than the dry silica (X) is preferably premixed. The silane coupling agent also adheres to or bonds to inorganic fillers other than dry silica (X) in the same manner as dry silica (X).

The method for pre-mixing the dry silica (X) and the silane coupling agent is not particularly limited, but includes a mixing method such as a wet treatment or a dry treatment. Preferably, the dry silica (X) and the silane coupling agent are heated at a temperature lower than the decomposition temperature of the organic peroxide, preferably 10 to 60° C., more preferably around room temperature (20 to 25° C.) for several minutes to several hours. A dry or wet mixing method may be mentioned, and a dry treatment in which a silane coupling agent is added to the dry silica (X) with or without heating and mixed is more preferred. In step (A1), a base rubber may be mixed as long as the temperature is maintained below the decomposition temperature. When using an inorganic filler other than dry silica (X) in addition to dry silica (X), pre-mixing can be performed in the same manner.

In the production method of the present invention, the mixture of the dry silica (X) and the silane coupling agent obtained in step (A1-1) and all or part of the base rubber, and optionally step (A1- The remaining components not mixed in 1) are melt-mixed in the presence of the organic peroxide while being heated to a temperature higher than the decomposition temperature of the organic peroxide (step (A1-2)). By doing so, excessive cross-linking reaction between the base rubber components can be prevented, and a cross-linked molded product with excellent appearance can be obtained.

In step (A1), the temperature for melt-mixing (also referred to as melt-kneading or kneading) the above components is the decomposition temperature of the organic peroxide or higher, preferably the decomposition temperature of the organic peroxide + (25 to 110) ° C. temperature. This decomposition temperature is preferably set after the base rubber component is melted. If it is the said mixing temperature, the said component will fuse|melt, and an organic peroxide will decompose and act, and a necessary silane grafting reaction will fully advance in a process (A1). Other conditions, such as mixing time, can be set as appropriate.
The mixing method is not particularly limited as long as it is a method commonly used for rubbers, plastics and the like. A single-screw extruder, a twin-screw extruder, a roll, a Banbury mixer, various kneaders, or the like is used as a kneading device. In terms of dispersibility of the base rubber component and stability of the cross-linking reaction, a closed mixer such as a Banbury mixer or various kneaders is preferred.

The organic peroxide may be present at the time of melt-mixing in step (A1), that is, at the time of melt-mixing the mixture obtained in step (A1-1) and the base rubber. The organic peroxide may be mixed in step (A1-1) or mixed in step (A1-2), for example.

In the production method of the present invention, the silanol condensation catalyst is preferably mixed in step (A3). It is preferable to mix each component of As a result, the silanol condensation reaction of the silane coupling agent can be suppressed, melt mixing is facilitated, and a desired shape can be obtained during extrusion coating. Here, "substantially not mixed" means that the silane coupling agent is present in an amount that does not cause the above-mentioned problem due to the silanol condensation reaction (for example, 0.01 parts by mass or less with respect to 100 parts by mass of the base rubber). It means that you may have

In the production method of the present invention, the above additives, especially the antioxidant, may be mixed in any step, but the step (A2) does not interfere with the grafting reaction of the silane coupling agent to the base rubber. should be mixed with

Thus, step (A1) (preferably step (A1-1) and step (A1-2)) is performed to prepare a silane masterbatch (also referred to as silane MB). This silane MB contains a silane crosslinkable rubber in which a silane coupling agent is grafted onto a base rubber to such an extent that it can be molded by the step (B) described later.

In the production method of the present invention, when part of the base rubber is melt-mixed in step (A1), the remainder of the base rubber and the silanol condensation catalyst are melt-mixed to prepare a catalyst masterbatch (also referred to as catalyst MB) ( Step (A2)).
Mixing may be performed by any method as long as it can be uniformly mixed, and examples thereof include mixing performed while the base rubber is molten (melt mixing). Melt-mixing can be performed in the same manner as the melt-mixing in step (A1) above. For example, the mixing temperature can be 80-250°C, more preferably 100-240°C. Other conditions, such as mixing time, can be set as appropriate.
The mixing ratio of the remainder of the base rubber as the carrier rubber and the silanol condensation catalyst is not particularly limited, but is preferably set so as to satisfy the above content in the silane-crosslinkable fluororubber composition.

In step (A2), an inorganic filler may be mixed. In this case, the amount of the inorganic filler compounded is not particularly limited, but is preferably 200 parts by mass or less with respect to 100 parts by mass of the carrier rubber. If the amount of the inorganic filler is too large, the silanol condensation catalyst may be difficult to disperse, and the cross-linking may be difficult to proceed.

In the production method of the present invention, the molten mixture (silane MB) obtained in step (A1) is then mixed with the silanol condensation catalyst or the mixture (catalyst MB) obtained in step (A2) (step (A3 )). Preferably, the silane MB and the catalyst MB are mixed.
When mixing the silanol condensation catalyst in step (A3), the silanol condensation catalyst can be mixed alone or as a mixture of the silanol condensation catalyst and other rubbers or resins.
The mixing method is not particularly limited, but is basically the same as the melt mixing in step (A1), and mixing is performed at least at a temperature at which the base rubber melts. The mixing temperature is appropriately selected depending on the base rubber, and is preferably 80 to 250°C, more preferably 100 to 240°C. Other conditions, such as mixing (kneading) time, can be appropriately set.
In step (A3), in order to avoid a silanol condensation reaction, it is preferable not to keep the silane MB and the silanol condensation catalyst in a mixed state at a high temperature for a long time.

In step (A3), it is preferable to dry blend the silane MB and the silanol condensation catalyst or the mixture obtained in step (A2) before melt mixing. The dry-blending method and conditions are not particularly limited, and examples thereof include dry-process mixing and its conditions in step (A1).

Thus, a silane-crosslinkable fluororubber composition containing a silane-crosslinkable rubber is prepared as a (melt) mixture of silane MB and a silanol condensation catalyst.

In the production method of the present invention, the step (B) of obtaining a coating layer precursor by coating the outer peripheral surface of the conductor with the silane-crosslinkable fluororubber composition obtained in step (A) is then carried out. The coating layer precursor obtained in step (B) is an uncrosslinked product in which the silane coupling agent has not undergone a silanol condensation reaction.
In this step (B), the outer peripheral surface of the conductor may be coated with the silane-crosslinkable fluororubber composition, and the above-described method for coating the outer peripheral surface of the conductor can be applied without particular limitation.

The coating of step (B) can be performed simultaneously with the mixing of step (A3) or consecutively. That is, during coating, for example, during or immediately before extrusion coating, the molten mixture obtained in step (A1) as a molding raw material and the silanol condensation catalyst or the mixture obtained in step (A2) are melt-mixed. aspects. For example, the melted mixture obtained in step (A1) and the mixture of the silanol condensation catalyst and the like are melt-mixed in a coating device, and then the outer peripheral surface of the conductor or the like is extrusion-coated to form a desired shape. process can be adopted.

In the production method of the present invention, the step (C) of bringing the coating layer precursor obtained in the step (B) into contact with water is then performed. As a result, the reaction sites of the silane coupling agent are hydrolyzed to form silanol, and the silanol condensation catalyst present in the coating layer precursor condenses the hydroxyl groups of the silanol to cause a cross-linking reaction. Thus, it is possible to obtain a wiring material having a coating layer made of a crosslinked fluororubber composition crosslinked by silanol condensation of the silane coupling agent grafted to the base rubber.
The treatment itself of this step (C) can be performed by a normal method. Condensation between silane coupling agents proceeds at room temperature. Therefore, in step (C), it is not necessary to actively bring the coating layer precursor into contact with water. In order to promote this cross-linking reaction, the coating layer precursor can be brought into contact with moisture. For example, a method of positively contacting with water, such as exposure to a high-humidity atmosphere, immersion in warm water, introduction into a moist heat bath, and exposure to high-temperature steam, can be adopted. Also, at that time, pressure may be applied to permeate the moisture inside.

Thus, a wiring material is manufactured. This wiring material contains a silane-crosslinked fluororubber obtained by cross-linking the above-described silane-crosslinkable rubber through a silanol condensation reaction at a reaction site capable of silanol condensation of a silane coupling agent.

The manufacturing method of the present invention can be expressed as follows.
A wiring material manufacturing method comprising the following steps (a), (b) and (c),
Step (a): 0.003 to 0.5 parts by mass of an organic peroxide and a BET specific surface area of 80 to 300 m ² per 100 parts by mass of a base rubber containing a tetrafluoroethylene-propylene copolymer fluororubber. / g of 6 to 25 parts by mass of dry silica (X), more than 2.0 parts by mass of the silane coupling agent and 15.0 parts by mass or less, and twice or less the content of dry silica (X), A step of melt-kneading an inorganic filler other than dry silica (X) at a temperature equal to or higher than the decomposition temperature of the organic peroxide to prepare a silane masterbatch Step (b): The silane masterbatch obtained in step (a) and a silanol condensation catalyst, and then coating the outer peripheral surface of the conductor with the resulting silane crosslinkable composition to form a coating layer precursor Step (c): The coating layer obtained in step (b) A manufacturing method comprising a step of contacting a precursor with water to carry out a silane cross-linking reaction treatment.
In the above method, the mixing step of steps (a) and (b) corresponds to step (A) above, the coating step of step (b) corresponds to step (B) above, and step (c) is the above step. Corresponds to (C).

EXAMPLES The present invention will be described in more detail below based on examples, but the present invention is not limited to these.
In addition, in Table 1, numerical values relating to formulation in each example represent parts by mass unless otherwise specified.

Examples 1 to 17 , Reference Examples 6, 15, 18 to 22, and Comparative Examples 1 to 11 were carried out using the following components under the conditions shown in Table 1, and evaluated as described later. are also shown.

Details of each compound shown in Table 1 are shown below.

<Base rubber>
Fluororubber 1: Afras 150P (trade name), manufactured by AGC Asahi Glass Co., Ltd., tetrafluoroethylene-propylene copolymer rubber Fluororubber 2: Aphras 400E (trade name), manufactured by AGC Asahi Glass Co., Ltd., tetrafluoroethylene-propylene copolymer rubber

Fluororesin 1: EP610 (trade name), manufactured by Daikin Industries, Ltd., ethylene-tetrafluoroethylene (ETFE) copolymer resin, melting point: 180°C
Fluororesin 2: RP4020 (trade name), manufactured by Daikin Industries, Ltd., ethylene-tetrafluoroethylene-hexafluoropropylene (ethylene-FEP) copolymer resin, melting point: 160°C

EVA1: EVAFLEX EV360 (trade name), manufactured by Mitsui Dow Polychemicals, ethylene-vinyl acetate copolymer resin, VA content: 25% by mass
EVA2: EVAFLEX EV180 (trade name), manufactured by Mitsui Dow Polychemicals, ethylene-vinyl acetate copolymer resin, VA content: 33% by mass

EEA1: NUC6510 (trade name), manufactured by Nihon Unicar Co., Ltd., ethylene-ethyl acrylate copolymer resin

<Organic Peroxide>
Organic peroxide 1: Perkadox 14 (trade name), manufactured by Kayaku Akzo Co., Ltd., 1,4-bis[(t-butylperoxy)isopropyl]benzene Organic peroxide 2: Perhexa 25B (trade name), Japan Yushisha, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, decomposition temperature 154°C

<Inorganic filler>
Silica 1: BET specific surface area = 200 m ² /g, Aerosil 200 (trade name), manufactured by Nippon Aerosil Co., Ltd., dry silica Silica 2: BET specific surface area = 90 m ² /g, Aerosil 90G (trade name), manufactured by Nippon Aerosil Co., Ltd. Dry silica Silica 3: BET specific surface area = 150 m ² /g, Aerosil 150 (trade name), manufactured by Nippon Aerosil Co., Ltd. Dry silica Silica 4: BET specific surface area = 300 m ² /g, Aerosil 300 (trade name), Nippon Aerosil Co., Ltd. Dry silica Silica 5: BET specific surface area = 450 m ² /g, Aerosil 450 (trade name), Nippon Aerosil Co., Ltd. Dry silica Silica 6: BET specific surface area = 50 m ² /g, Aerosil 50 (trade name), Japan Aerosil Co., Ltd., dry silica Silica 7: BET specific surface area = 12 m ² /g, Crystalite 5X (trade name), Tatsumori Co., Ltd., dry silica Calcium carbonate 1: Softon 1200 (trade name), Bihoku Funka Kogyo Co., Ltd. , calcium carbonate calcined clay 1: Satiton SP-33 (trade name), manufactured by Engelhard Co., Ltd., calcined clay talc 1: MV talc (trade name), manufactured by Nihon Mistron Co., Ltd., talc

<Crosslinking aid>
Crosslinking aid 1: TAIC (trade name), manufactured by Mitsubishi Chemical Corporation, triallyl cyanurate

<Silane coupling agent>
Silane coupling agent 1: KBM-1003 (trade name), manufactured by Shin-Etsu Chemical Co., Ltd., vinyltrimethoxysilane

<Silanol condensation catalyst>
Silanol condensation catalyst 1: ADEKA STAB OT-1 (trade name), manufactured by ADEKA, dioctyltin dilaurate

<Antioxidant>
Antioxidant 1: Irganox 1010 (trade name), manufactured by BASF, pentaerythritol tetrakis [3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate]

(Examples 1 to 17 , Reference Examples 6 and 15 and Comparative Examples 1 to 10)
In the present examples , reference examples and comparative examples, a wiring material having a coating layer formed by preparing a silane-crosslinkable fluororubber composition, extruding and coating it on the outer peripheral surface of a conductor, and then performing a silanol condensation reaction was produced. bottom.
First, among the components shown in the "Silane MB" column of Table 1, the inorganic filler, the silane coupling agent, and the organic peroxide are put into a 10 L Henschel mixer manufactured by Toyo Seiki at the mass ratio shown in Table 1. , and mixed at room temperature (25° C.) for 1 hour to obtain a powder mixture (step (A1)). Next, the powder mixture thus obtained and the base rubber among the components shown in Table 1 "Silane MB" were put into a 2L Banbury mixer manufactured by Nippon Roll Co., Ltd. at the mass ratio shown in Table 1. After kneading for 10 minutes at a temperature higher than the decomposition temperature of the organic peroxide, specifically at 190° C., the material was discharged at a discharge temperature of 200° C. to obtain silane MB (step (A1)). The resulting silane MB contains a silane-crosslinkable rubber obtained by grafting a silane coupling agent to a base rubber.

On the other hand, the carrier rubber, silanol condensation catalyst, and antioxidant shown in the "Catalyst MB" column of Table 1 were melt-mixed in a Banbury mixer at a mass ratio shown in Table 1 at 180 to 190 ° C., and the material discharge temperature It was discharged at 180-190° C. to obtain a catalyst MB (step (A2)).

Next, the silane MB and the catalyst MB were put into a closed ribbon blender and dry-blended at room temperature (25° C.) for 5 minutes to obtain a dry blend. At this time, the mixing ratio of the silane MB and the catalyst MB is the mass ratio shown in Table 1.

Next, the obtained dry blended product was extruded with an extruder equipped with a screw having an L/D (ratio of effective screw length L to diameter D) of 24 and a screw diameter of 30 mm (compression section screw temperature 170°C, head temperature 200°C ). While melt-mixing the dry blend in the extruder (step (A3)) (silane-crosslinkable fluororubber composition), the outer peripheral surface of the 1/0.8 TA conductor was covered with a thickness of 1 mm, and the outer diameter was 2.0 mm. An 8 mm coated conductor was obtained (step (B)). This covered conductor was left in an atmosphere of 40° C. and 95% humidity for one week (step (C)).
In this manner, electric wires, which are wiring materials, were produced, each having a coating layer made of the crosslinked fluororubber composition on the outer peripheral surface of the conductor.

( Reference Examples 18 to 20 and Comparative Example 11)
In the present reference examples and comparative examples, an electron beam crosslinkable fluororubber composition was prepared, extruded and coated on the outer peripheral surface of the conductor, and then subjected to a crosslinking reaction treatment by an electron beam crosslinking method to form a wiring having a coating layer. manufactured the material.
Each component shown in Table 1 is put into a 2L Banbury mixer manufactured by Nippon Roll Co., Ltd. at the mass ratio shown in Table 1. Specifically, after kneading at 190 ° C. for 10 minutes, the material is discharged at a temperature of 200 ° C., and electronic A linearly crosslinkable fluororubber composition was obtained (step (E)).
Next, the obtained electron beam crosslinkable fluororubber composition was put into an extruder equipped with a screw having an L/D (ratio of the effective screw length L to the diameter D) of 24 and a screw diameter of 30 mm (the screw temperature of the compression part was 170°C. , head temperature 200° C.). While melt-mixing the electron beam crosslinkable fluororubber composition in this extruder, the outer peripheral surface of the 1/0.8 TA conductor was coated with a thickness of 1 mm to obtain a coated conductor with an outer diameter of 2.8 mm (step (F)).
The coated conductor thus obtained was passed through an electron beam cross-linking facility and irradiated with an electron beam of 12 Mrad at an acceleration voltage of 750 keV to cause a cross-linking reaction, thereby obtaining a wiring material (step (G)).
In this manner, an electric wire was produced as a wiring material having a coating layer made of the crosslinked fluororubber composition on the outer peripheral surface of the conductor.

( Reference Examples 21 and 22)
In this reference example , an organic peroxide-crosslinkable fluororubber composition is prepared, the outer peripheral surface of the conductor is extrusion-coated with this, and then the coating layer is formed by a crosslinking reaction treatment by an organic peroxide crosslinking method. Manufactured wiring.
Each component shown in Table 1 is put into a 2L Banbury mixer manufactured by Nippon Roll Co., Ltd. at the mass ratio shown in Table 1. Specifically, after kneading at 100 ° C. for 10 minutes, the material is discharged at a material discharge temperature of 115 ° C., An organic peroxide crosslinkable fluororubber composition was obtained (step (H)).
Next, the obtained organic peroxide crosslinkable fluororubber composition was transferred to an extruder equipped with a screw having a screw diameter of 50 mm (L/D (ratio of screw effective length L to diameter D) = 20 (compression part screw temperature 115° C., head temperature 125° C.). While melt-mixing the dry blend in the extruder, the outer peripheral surface of the 1/0.8 TA conductor was covered with a thickness of 1 mm to obtain a covered conductor with an outer diameter of 2.8 mm (step (I)).
After the coating, the coated conductor was introduced into a pressurized cross-linking facility and subjected to a cross-linking reaction treatment by an organic peroxide cross-linking method. The cross-linking reaction treatment was performed at a cross-linking temperature of 220° C. for 10 minutes (step (J)).
In this manner, an electric wire was produced as a wiring material having a coating layer made of the crosslinked fluororubber composition on the outer peripheral surface of the conductor.

Each electric wire produced was subjected to the following tests, and the results are shown in Table 1.

<Tensile test>
Using a tubular test piece prepared by extracting a conductor from each electric wire, a tensile test was performed based on JIS C 3005 at a distance between gauge lines of 20 mm and a tensile speed of 200 mm / min. Tensile strength (MPa) and tensile elongation (%) was measured.
In this test, a tensile strength of 10 MPa or more is acceptable, and 12 MPa or more is preferable. Also, a tensile elongation of 150% or more is acceptable.

<Abrasion resistance test>
Each electric wire produced was tested based on the tape wear test of the wear resistance test of JASO D 618. The test was performed with a load of 567 g (additional load: 500 g). The number of times until the conductor was exposed was counted. This test was performed four times, and the average value of the four tests was obtained to evaluate the wear resistance.
The abrasion resistance test passes when the average value is 400 times or more. 600 times or more is preferable.

Furthermore, each electric wire was evaluated for the following preferable properties.

<Extrusion Appearance Test>
The extrusion appearance test was evaluated by observing the appearance of the coated conductor.
"A" indicates that the coated conductor was formed into an electric wire shape without any lumps. "C" was given when the wire shape could not be formed due to appearance defects. The extrusion appearance test is preferably evaluated as "B" or higher.

As is clear from the results shown in Table 1, a wiring member having a coating layer made of a crosslinked fluororubber composition obtained by subjecting a crosslinkable fluororubber composition not satisfying the composition specified in the present invention to a crosslinking reaction treatment (comparative example 1 to 11) failed either the tensile test or the abrasion resistance test regardless of whether the electron beam crosslinking method or the silane crosslinking method was adopted, and the mechanical properties, heat resistance, and resistance Abrasion resistance cannot be combined.
On the other hand, a wiring material having a coating layer composed of a crosslinked fluororubber molded article obtained by subjecting a crosslinkable fluororubber composition satisfying the composition specified in the present invention to a crosslinking reaction is performed by an electron beam crosslinking method as a crosslinking reaction treatment. and the silane cross-linking method, it passed both the tensile test and the wear resistance test. In addition, the wiring material having the crosslinked fluororubber composition of the present invention as a coating layer has a level of heat resistance normally required for wiring materials. For this reason, mechanical properties, heat resistance, and wear resistance are exhibited at a high level in a well-balanced manner. Thus, it can be seen that the crosslinked fluororubber composition is excellent in wear resistance while maintaining excellent mechanical properties and heat resistance.

Claims (12)

A crosslinked fluororubber composition obtained by subjecting the following crosslinkable fluororubber composition to a crosslinking reaction.
[Crosslinkable fluororubber composition]
With respect to 100 parts by mass of the base rubber, 6 to 25 parts by mass of dry silica (X 2 ) having a BET specific surface area of 80 to 300 m ² /g and twice or less the content of the dry silica (X) containing an inorganic filler other than dry silica (X), more than 2.0 parts by mass and not more than 15.0 parts by mass of a silane coupling agent grafted to the base rubber, and a silanol condensation catalyst ;
The base rubber is a tetrafluoroethylene-propylene copolymer fluororubber, a tetrafluoroethylene-hexafluoropropylene copolymer resin , an ethylene-tetrafluoroethylene copolymer resin, and an ethylene-tetrafluoroethylene-hexafluoropropylene copolymer. at least one fluororesin selected from a coalescent resin, a polychlorotrifluoroethylene resin and a polyvinylidene fluoride resin , the tetrafluoroethylene-propylene copolymer fluororubber having no melting point, and the fluororesin A crosslinkable fluororubber composition having a melting point of 240° C. or less . The base rubber contains an ethylene-vinyl acetate copolymer resin,
The content of the tetrafluoroethylene-propylene copolymer fluororubber in 100% by mass of the base rubber is 60 to 90% by mass, and the content of the ethylene-vinyl acetate copolymer resin is 3 to 30% by mass. The crosslinked fluororubber composition according to claim 1, wherein 3. The crosslinked fluororubber composition according to claim 2, wherein the ethylene-vinyl acetate copolymer resin has a vinyl acetate content of 15 to 30% by mass. The crosslinked fluororubber composition according to any one of claims 1 to 3, wherein the content of the fluororesin in 100% by mass of the base rubber is 5 to 30% by mass. The crosslinked fluororubber composition according to any one of claims 1 to 4, wherein the crosslinkable fluororubber composition contains 0.1 parts by mass or more of the inorganic filler with respect to 100 parts by mass of the base rubber. A wiring material having a coating layer comprising the crosslinked fluororubber composition according to any one of claims 1 to 5 on the outer peripheral surface of the conductor. A method for manufacturing a wiring material, comprising the following steps (A), (B) and (C).
Step (A): Tetrafluoroethylene-propylene copolymer fluororubber and tetrafluoro
Roethylene-hexafluoropropylene copolymer resin, ethylene-tetrafluoroethylene
Luoroethylene copolymer resin, ethylene-tetrafluoroethylene-hexa
Fluoropropylene copolymer resin, polychlorotrifluoroethylene resin and
and at least one fluororesin selected from polyvinylidene fluoride resin and
and the tetrafluoroethylene-propylene copolymer fluororubber contains
Base rubber 1 having no melting point and the fluororesin having a melting point of 240° C. or less
00 parts by weight, 0.003 to 0.5 parts by weight of organic peroxide and BET ratio
80-300m surface area ² / g dry silica (X) 6 to 25 parts by mass, and the
A grafting reaction site that can be grafted to the base rubber and a silanol condensation are possible
more than 2.0 parts by mass of a silane coupling agent having a reactive site and 15.0
Parts by mass or less and twice or less the content of the dry silica (X),
By mixing an inorganic filler other than the formula silica (X) and a silanol condensation catalyst,
Step of obtaining a crosslinkable fluororubber composition
Step (B): Coating the outer peripheral surface of the conductor with the crosslinkable fluororubber composition obtained in the step (A)
obtaining a coating layer precursor by
Step (C): A step of contacting the coating layer precursor obtained in the step (B) with water to obtain a wiring material.
about The base rubber contains an ethylene-vinyl acetate copolymer resin,
The content of the tetrafluoroethylene-propylene copolymer fluororubber in 100% by mass of the base rubber is 60 to 90% by mass, and the content of the ethylene-vinyl acetate copolymer resin is 3 to 30% by mass. The method for manufacturing the wiring material according to claim 7, wherein 9. The method for producing a wiring material according to claim 8, wherein the ethylene-vinyl acetate copolymer resin has a vinyl acetate content of 15 to 30% by mass. 10. The method for manufacturing a wiring material according to claim 7, wherein the content of said fluororesin in said base rubber is 5 to 30% by mass. The method for producing a wiring material according to any one of claims 7 to 10, wherein the crosslinkable fluororubber composition contains 0.1 parts by mass or more of the inorganic filler with respect to 100 parts by mass of the base rubber. A wiring material manufactured by the manufacturing method according to any one of claims 7 to 11 .