JP6688634B2 - SILANE CROSSLINKABLE RUBBER COMPOSITION, SILANE CROSSLINKED RUBBER MOLDED BODY, PROCESS FOR PRODUCING THEM, AND SILANE CROSSLINKED RUBBER MOLDED ARTICLE - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a silane-crosslinkable rubber composition, a silane-crosslinked rubber molded product, a method for producing them, and a silane-crosslinked rubber molded product.

Rubber products such as coating materials for various industrial cables (including electric wires) and rubber molding materials (for example, glass run channels for automobiles, weather strips, rubber hoses, wiper blade rubber, anti-vibration rubber) have a small compression set. Is required. Also, of the coating materials for various industrial cables, the sheath material (jacket material), etc. that covers the outer periphery is often rubbed because it is pulled in when laying the cable, preventing damage and damage. Therefore, high hardness and high tensile strength are also required. Further, from the economical point of view, a material excellent in high-speed moldability is required.
Conventionally, cross-linked EP rubber obtained by vulcanizing (cross-linking) ethylene-propylene rubber (EP rubber) has been used as a product used for applications requiring a small compression set. However, the crosslinked EP rubber needs to be vulcanized after molding the EP rubber.
For example, in Patent Document 1, in a method of injection molding a rubber composition containing ethylene-propylene rubber as a main component, the ethylene-propylene rubber has a propylene content of 30 to 55% by weight and a Mooney viscosity (ML (1 + 4)). It has been proposed to use one having a temperature of 100 ° C.) of 20 to 80 and add an organic peroxide as a vulcanizing agent. Patent Document 2 proposes that a vulcanized rubber product is further subjected to heat history treatment under atmospheric pressure or vacuum pressure. In Patent Document 3, 100 parts by mass of rubber and 30 parts by mass to 150 parts by mass of metal hydroxide are contained, and the rubber has an ethylene-propylene rubber 1 having an ethylene ratio of 60% to 64% and an ethylene ratio of 66%. A non-halogen flame-retardant rubber composition in which 70% of ethylene-propylene rubber 2 is mixed in a mass ratio of 70:30 to 30:70 has been proposed.

JP-A-8-66931 JP-A-11-302415 JP2012-241041A

In each of Patent Documents 1 to 3, since it is necessary to vulcanize the rubber in the production, vulcanization equipment is required. In addition to this, the vulcanization time was long and there was a problem in productivity.
In addition, when a molded product having a high hardness is obtained by using a general EP rubber, a material having a high ethylene content is often used. Furthermore, in order to impart high-speed moldability, a material having a low Mooney viscosity is often selected. However, the rubber material having such characteristics tends to have a large compression set.
Furthermore, when a crosslinked EP rubber product is produced by extrusion molding, the organic peroxide may decompose in the extruder to cause a crosslinking reaction of the EP rubber. The crosslinked EP rubber forms a gel that does not melt during molding, and becomes a lump-like substance (also referred to as lump) protruding on the surface of the obtained molded body. As a result, there is a problem in that the appearance of the manufactured rubber product is impaired.

The present invention overcomes the conventional problems described above, and has a small compression set (hereinafter sometimes referred to as an excellent compression set), high tensile strength, and high hardness even when extrusion-molded at a high linear velocity. An object is to provide a silane crosslinked rubber molded body. Another object is to provide a silane-crosslinked rubber molded article having a good appearance. An object of the present invention is to provide a method for producing a silane crosslinked rubber molded product having the above characteristics.
Further, the present invention provides a silane-crosslinked rubber composition having the above-mentioned properties, a silane-crosslinkable rubber composition which can be produced with high productivity without requiring vulcanization equipment, and a production method thereof. It is an issue.
Further, it is an object of the present invention to provide a silane crosslinked rubber molded article containing the silane crosslinked rubber molded article having the above-mentioned excellent properties.

The inventors of the present invention, in the production of a crosslinked rubber molding using an EP rubber, when a specific silane crosslinking method is applied to an EP rubber having a specific Mooney viscosity and an ethylene content, a vulcanization facility for the EP rubber becomes unnecessary, Even if an EP rubber having a low viscosity is used as a raw material rubber, a silane cross-linked rubber molded article having high tensile strength, small compression set, high hardness and appearance can be molded without impairing its moldability, even at high speed as necessary. I found that I could do it. The present inventors have conducted further research based on this finding and have completed the present invention.
Here, the silane cross-linking method of rubber means that after a hydrolyzable silane coupling agent having an unsaturated group is graft-reacted on the rubber in the presence of an organic peroxide to obtain a silane-grafted rubber, a silanol condensation catalyst is used. Is a method of obtaining a crosslinked rubber in which the silane graft rubber is crosslinked via a silane coupling agent by bringing the silane graft rubber into contact with water in the presence of.

That is, the object of the present invention was achieved by the following means.
[1] An ethylene-α olefin rubber having a Mooney viscosity (ML (1 + 4) 125 ° C.) of 15 to 40 and an ethylene content of 65 to 80% by mass, measured according to JIS K 6300-1: 2013, is 61 100 wt% including silane crosslinkable rubber silane coupling agent 1 to 15 parts by weight for the base rubber 100 parts by weight by grafting reaction in the presence of an organic peroxide 0.01 to 0.6 parts by weight A silane-crosslinkable rubber composition containing 0.3 to 400 parts by mass of dry silica and 0.0001 to 0.5 parts by mass of a silanol condensation catalyst based on 100 parts by mass of the base rubber.
[2] The silane crosslinkable rubber composition contains 0.3 to 400 parts by mass of dry silica , 1 to 15 parts by mass of a silane coupling agent, and 0.1. The silane-crosslinkable rubber composition according to [1], which is obtained by melt-mixing 01 to 0.6 parts by mass and silanol condensation catalyst 0.0001 to 0.5 parts by mass.
[ 3 ] The silane crosslinkable rubber composition according to [1] or [2], wherein the base rubber contains 1 to 30 mass% of a polypropylene resin.
[ 4 ] The silane crosslinkable rubber composition according to any one of [1] to [ 3 ], 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. object.
[ 5 ] A silane-crosslinked rubber molded product obtained by molding the silane-crosslinkable rubber composition according to any one of [1] to [ 4 ] and then contacting it with water.
[ 6 ] A silane-crosslinked rubber molded article containing the silane-crosslinked rubber molded article according to [ 5 ].
[ 7 ] An ethylene-α olefin rubber having a Mooney viscosity (ML (1 + 4) 125 ° C.) of 15 to 40 and an ethylene content of 65 to 80% by mass, measured according to JIS K 6300-1: 2013, is 61%. To 100 parts by mass of base rubber, 0.3 to 400 parts by mass of dry silica , 1 to 15 parts by mass of silane coupling agent, and 0.01 to 0.6 parts by mass of organic peroxide. A method for producing a silane crosslinkable rubber composition, comprising the step (1) of melt-mixing 0.0001 to 0.5 part by mass of a silanol condensation catalyst to obtain a silane crosslinkable rubber composition,
The step (1) includes 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) and (b) ) And the process (c), the manufacturing method of a silane crosslinkable rubber composition.
Step (a): All or part of the base rubber, the dry silica , the silane coupling agent, and the organic peroxide are melt-mixed at a temperature equal to or higher than the decomposition temperature of the organic peroxide, Step of preparing silane masterbatch Step (b): Step of preparing catalyst masterbatch by melting and mixing the rest of the base rubber and the silanol condensation catalyst Step (c): The silane masterbatch and the silanol A step of melt-mixing a condensation catalyst or the catalyst master batch [ 8 ] , which is a method for producing a silane-crosslinked rubber molded article having the following step (1), step (2) and step (3) ,
Step (1): An ethylene-α olefin rubber having a Mooney viscosity (ML (1 + 4) 125 ° C.) of 15 to 40 and an ethylene content of 65 to 80 mass% measured according to JIS K 6300-1: 2013. Of 100 to 100 parts by mass of the base rubber, 0.3 to 400 parts by mass of dry silica , and 1 to 15 parts of the silane coupling agent.
Parts by mass, 0.01 to 0.6 parts by mass of organic peroxide, and 0.000 of silanol condensation catalyst
Step of melt-mixing 1 to 0.5 parts by mass to obtain a silane-crosslinkable rubber composition Step (2): Molding the silane-crosslinkable rubber composition obtained in the step (1) to obtain a molded article Step Step (3): Step of contacting the molded body obtained in the step (2) with water to obtain a silane crosslinked rubber molded body The step (1) has the following steps (a) and (c). However, when a part of the base rubber is melt-mixed in the following step (a), a method for producing a silane crosslinked rubber molded product , which has the following steps (a), (b) and (c) .
Step (a): Melt-mixing all or part of the base rubber, the dry silica , the silane coupling agent, and the organic peroxide at a temperature equal to or higher than the decomposition temperature of the organic peroxide. A step of preparing a silane masterbatch step (b): a step of preparing a catalyst masterbatch by melt-mixing the rest of the base rubber with the silanol condensation catalyst step (c): the silane masterbatch and the above Melting and mixing with silanol condensation catalyst or the catalyst master batch

  In the present specification, the numerical range represented by using "to" means a range including the numerical values before and after "to" as the lower limit value and the upper limit value.

According to the present invention, a silane-crosslinked rubber molded body that overcomes the above-mentioned conventional problems and has a small compression set, high tensile strength, and high hardness, and a silane-crosslinked rubber molded body that has a good appearance are provided in EP rubber vulcanization equipment. Can be manufactured at high speed and with high productivity as required.
Therefore, according to the present invention, it is possible to provide a silane-crosslinked rubber molded product having a small compression set, a high tensile strength and a high hardness even when it is extrusion molded at a high linear velocity. Further, it is possible to provide a silane-crosslinked rubber molded product having a good appearance. It is possible to provide a method for producing a silane-crosslinked rubber molding having such excellent properties. It is also possible to provide a silane-crosslinkable rubber composition capable of producing a silane-crosslinked rubber molded product having the above-mentioned properties with high productivity without requiring vulcanization equipment and a method for producing the same. Further, it is possible to provide a silane-crosslinked rubber molded article including the silane-crosslinked rubber molded article having such excellent properties.

The silane crosslinkable rubber composition of the present invention has a Mooney viscosity (ML (1 + 4) 125 ° C.) of 15 to 40 and an ethylene content of 65 to 80% by mass, which are measured according to JIS K 6300-1: 2013. A silane crosslinkable rubber in which a silane coupling agent is grafted to a base rubber containing 61 to 100% by mass of an ethylene-α olefin rubber, and an inorganic filler 0.3 to 400 parts by mass with respect to 100 parts by mass of the base rubber, Silanol condensation catalyst 0.0001 to 0.5 parts by mass. The silane crosslinkable rubber composition is preferably 0.3 to 400 parts by mass of an inorganic filler, 1 to 15 parts by mass of a silane coupling agent, and 0.01% of an organic peroxide, based on 100 parts by mass of a base rubber. ˜0.6 parts by mass and silanol condensation catalyst 0.0001 to 0.5 parts by mass can be melt-mixed to prepare. Thereby, as described later, the silane coupling agent is graft-reacted with the base rubber to form a silane crosslinkable rubber.
The silane-crosslinked rubber molded product of the present invention can be obtained by molding the silane-crosslinkable rubber composition of the present invention and then contacting it with water. Thereby, as described later, the silane coupling agent of the silane crosslinkable rubber contained in the silane crosslinkable rubber composition undergoes a crosslinking reaction to form a silane crosslinked rubber molded body.

First, each component used in the present invention will be described.
<Base rubber>
The base rubber used in the present invention has a Mooney viscosity (ML (1 + 4) 125 ° C.) of 15 as measured according to JIS K 6300-1: 2013 as a rubber component having a site where a silane coupling agent can undergo a grafting reaction. And an ethylene-α olefin rubber having an ethylene content of 65 to 80% by mass.
The base rubber may further contain a polypropylene resin.
The base rubber may further contain a rubber component other than the ethylene-α-olefin rubber and a resin component other than the polypropylene resin. The rubber component other than the ethylene-α-olefin rubber is not particularly limited, and examples thereof include natural rubber (NR), styrene-butadiene rubber (SBR), chloroprene rubber (CR), acrylic rubber (ACM), silicone rubber (Q). Etc. The resin component other than the polypropylene resin is not particularly limited, and examples thereof include high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and ethylene-based copolymers. . When the base rubber contains these rubber components and resin components, the content of each of these rubber components and resin components is not particularly limited and is appropriately determined.
In this base rubber, the content of each rubber component and each resin component is appropriately determined so that the total of the rubber component and the resin component is 100% by mass, and preferably selected from the following range.

(Ethylene-α olefin rubber)
The ethylene-α olefin rubber used in the present invention has a Mooney viscosity (ML (1 + 4) 125 ° C.) of 15 to 40 measured according to JIS K 6300-1: 2013, and an ethylene content of 65 to 80% by mass. It is an ethylene-α olefin rubber. If the Mooney viscosity is too low, the high hardness and tensile strength required for the present invention may be insufficient. On the other hand, if the Mooney viscosity is too large, the moldability at high linear velocity (high-speed moldability) may be poor. If the ethylene content is less than 65% by mass, the high tensile strength required in the present invention may not be obtained. If the ethylene content exceeds 80% by mass, the compression set may become too large.
The Mooney viscosity of the ethylene-α olefin rubber is preferably 17 to 35 (ML1 + 4 (125 ° C), more preferably 20 to 30 (ML1 + 4 (125 ° C)) in terms of hardness, tensile strength and moldability.
The Mooney viscosity is measured based on the measuring method defined in JIS K 6300-1: 2013. The test is conducted as follows. As test pieces to be used, two sets of test samples each having a diameter of about 50 mm and a thickness of about 6 mm are prepared by the roll passing method described in JIS K 6300-1 5.3.1. A disc-shaped metal L-shaped rotor is mounted in a cylindrical hollow portion (cavity) composed of two dies, and the obtained rubber test piece is filled therein. After that, the rotor is rotated under constant conditions of a residual heat time of 1 minute, a rotor rotation time of 4 minutes, and a test temperature of 125 ° C., and the torque received by the rotor due to the resistance of the rubber at this time is measured in Mooney units as the Mooney viscosity of the rubber.

  The ethylene-α olefin rubber is preferably 67 to 78% by mass, and 67 to 75% by mass, in terms of tensile strength, compression set and hardness, the amount of ethylene constituent component (referred to as ethylene content) in the copolymer is 67% by mass. Is more preferable. The ethylene content is a value measured according to the method described in ASTM D3900.

The ethylene-α olefin rubber is a rubber composed of an ethylene-α olefin copolymer, preferably a rubber composed of a binary copolymer of ethylene and an α-olefin, and a rubber composed of ethylene, an α-olefin and a diene. A rubber made of a terpolymer may be used. The diene of the terpolymer may be a conjugated diene or a non-conjugated diene, preferably a non-conjugated diene. That is, examples of the terpolymer include a terpolymer of ethylene, an α-olefin and a conjugated diene, and a terpolymer of ethylene, an α-olefin and a non-conjugated diene. Binary copolymers of ethylene and α-olefins and terpolymers of ethylene, α-olefins and non-conjugated dienes are preferred.
Examples of the conjugated diene include butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene and the like, with butadiene being preferred. Examples of the non-conjugated diene include dicyclopentadiene (DCPD), ethylidene norbornene (ENB), and 1,4-hexadiene, and ethylidene norbornene is preferable. Each of the constituent components of the conjugated diene and the non-conjugated diene may be used alone or in combination of two or more.
Preferable examples of the α-olefin include α-olefins having 3 to 12 carbon atoms. The α-olefin is not particularly limited, and examples thereof include propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene and the like.

  Examples of the rubber composed of a binary copolymer of ethylene and α-olefin include ethylene-propylene rubber, ethylene-butene rubber, ethylene-octene rubber and the like. Examples of the rubber composed of a terpolymer of ethylene, α-olefin and diene include ethylene-propylene-diene rubber and ethylene-butene-diene rubber. Among them, ethylene-propylene rubber, ethylene-butene rubber, ethylene-propylene-diene rubber and ethylene-butene-diene rubber are preferable, ethylene-propylene rubber and ethylene-propylene-diene rubber are more preferable, ethylene-propylene rubber or ethylene-propylene-ethylidene rubber. Norbornene rubber is particularly preferred.

The ethylene-α olefin rubber has a diene component amount (referred to as a diene content) in the copolymer of preferably 0 to 10% by mass, more preferably 0 to 5% by mass, and further preferably 0 to 4% by mass. When the diene content is in the range of 0 to 10% by mass, the reactivity does not become too high and the moldability in the step (2) can be maintained. The diene content can be measured by, for example, infrared absorption spectroscopy (FT-IR), proton NMR ( ¹ H-NMR) method, or the like.

  The content of the ethylene-α olefin rubber is 61 to 100 parts by mass in 100 parts by mass of the base rubber. When the content of the ethylene-α-olefin rubber is 61 parts by mass or more, the above excellent properties can be imparted to the molded product. In the present invention, the lower limit of the content of the ethylene-α olefin rubber is preferably 70 parts by mass, more preferably 75 parts by mass, and further preferably 80 parts by mass. When the base rubber contains a polypropylene resin, the content of the ethylene-α-olefin rubber is preferably 70 to 99 parts by mass, and 75 to 95 parts by mass in 100 parts by mass of the base rubber in terms of moldability and compression set. Parts is more preferable, and 80 to 90 parts by mass is further preferable.

  The ethylene-α olefin rubber may be used alone or in combination of two or more.

(Polypropylene resin)
The polypropylene resin (PP) is not particularly limited as long as it is a resin made of a polymer containing a propylene component as a constituent component. The polypropylene resin includes homopolymer of propylene (h-PP), random polypropylene (r-PP) which is a copolymer with (preferably a small amount of) ethylene and / or 1-butene, and ethylene rubber. Block polypropylene (b-PP) in which the above rubber is dispersed in h-PP or r-PP is included. Of these, random polypropylene is preferable.
The melt flow rate (MFR, 230 ° C., 21.18N) of the polypropylene resin is not particularly limited, but is preferably 0.5 to 50 g / 10 minutes, particularly preferably 10 to 30 g / 10 minutes. By using a polypropylene resin having an MFR within this range, a high-speed moldability can be imparted and a molded product having an excellent appearance can be obtained. MFR (190 ° C., 21.18 N) is a value measured under the condition D of 190 ° C., 21.18 N based on “A method (manual cut-off method)” specified in JIS K 7210.
Examples of PP include Novatec (registered trademark) PP (manufactured by Japan Polypro), PM940M, PM921V (all are trade names, manufactured by Sun Allomer), Sumitomo Noblen (registered trademark, manufactured by Sumitomo Chemical Co., Ltd.), and Prime Polypro (registered). Trademark, manufactured by Prime Polymer Co., Ltd., and the like.
When the base rubber contains a polypropylene resin, the content of the polypropylene resin is not particularly limited, but is preferably 1 to 30 parts by mass, and 5 to 25 parts by mass in 100 parts by mass of the base rubber. Is more preferable and 10 to 20 parts by mass is more preferable.

  One type of polypropylene resin may be used alone, or two or more types may be used in combination.

<Inorganic filler>
The inorganic filler used in the present invention can be used without particular limitation as long as it has a site capable of being chemically bonded to the reaction site of the silane coupling agent by a hydrogen bond or a covalent bond on the surface thereof. In this inorganic filler, examples of the site capable of chemically bonding to the reaction site of the silane coupling agent include an OH group (hydroxyl group, water molecule of water containing or crystal water, OH group such as carboxy group), amino group, SH group and the like. To be

Examples of such inorganic fillers include metal hydrates such as water of hydration, compounds having a hydroxyl group or water of crystallization. Examples of the metal hydrate include metal hydroxides such as aluminum hydroxide, magnesium hydroxide and aluminum oxide hydrate, and further calcium carbonate, magnesium carbonate, calcium silicate, magnesium silicate, calcium oxide, magnesium oxide. In addition to aluminum oxide, aluminum nitride, aluminum borate whiskers, etc., inorganic acid salts or inorganic oxides such as hydrated aluminum silicate, hydrated magnesium silicate, basic magnesium carbonate, hydrotalcite, etc. having water of hydration, etc. Etc.
Examples of the inorganic fillers include, in addition to metal hydrates, boron nitride, silica (crystalline silica, amorphous silica, etc.), carbon black, clay, zinc oxide, tin oxide, titanium oxide, molybdenum oxide, and trihydrate. Examples thereof include antimony oxide, silicone compounds, quartz, talc, zinc borate, white carbon, zinc borate, zinc hydroxystannate, and zinc stannate.
Among these, the inorganic filler is preferably at least one selected from the group consisting of metal hydrate, talc, clay, silica and carbon black.
In particular, the silane-crosslinked rubber molded article of the present invention is an inorganic filler in that it can impart high insulating properties to the silane-crosslinked rubber molded article when it is used for an application that requires high insulating properties in water or in a wet environment, which will be described later. For this, dry silica (also called fumed silica) is preferable. Here, the dry silica is a kind of amorphous silica and is produced by a dry method (combustion method) of burning silicon tetrachloride in the presence of oxygen gas and hydrogen gas.
The inorganic filler may be used alone or in combination of two or more.

  The average primary particle size of the inorganic filler is preferably 0.001 to 10 μm, more preferably 0.005 to 5 μm, further preferably 0.01 to 2 μm, and particularly preferably 0.015 to 1 μm. When the average primary particle size is within the above range, the effect of retaining the silane coupling agent is high, and the tensile strength and compression set are excellent. In addition, the inorganic filler is less likely to be secondarily aggregated when mixed with the silane coupling agent, resulting in an excellent appearance. The average primary particle size is obtained by dispersing with alcohol or water and using an optical particle size measuring device such as a laser diffraction / scattering particle size distribution measuring device.

  As the inorganic filler, a surface-treated inorganic filler surface-treated with a silane coupling agent or the like can be used. Examples of the silane coupling agent surface-treated inorganic filler include Kisuma 5L and Kisuma 5P (all are trade names, magnesium hydroxide, manufactured by Kyowa Chemical Co., Ltd.) and the like. The surface treatment amount of the inorganic filler with the silane coupling agent is not particularly limited, but is, for example, 2% by mass or less.

<Silane coupling agent>
The silane coupling agent used in the present invention is a chemical bond between an inorganic filler and a grafting reaction site (group or atom) capable of undergoing a grafting reaction on a base rubber in the presence of a radical generated by decomposition of an organic peroxide. That has at least a reactive site capable of reacting with a reactive site and capable of silanol condensation (including a site formed by hydrolysis, such as a silyl ester group). As such a silane coupling agent, a hydrolyzable silane coupling agent having a hydrolyzable group at the terminal is preferable. The silane coupling agent is more preferably one having a group containing an amino group, a glycidyl group or an ethylenically unsaturated group and a group containing a hydrolyzable group at the terminal, and further preferably ethylene at the terminal. A silane coupling agent having a group containing a polymerizable unsaturated group and a group containing a hydrolyzable group. The group containing an ethylenically unsaturated group is not particularly limited, and examples thereof include a vinyl group, an allyl group, a (meth) acryloyloxy group, a (meth) acryloyloxyalkylene group, and a p-styryl group. Further, these silane coupling agents may be used in combination with other silane coupling agents having an end group.

  As such a silane coupling agent, for example, a compound represented by the following general formula (1) can be used.

In the general formula (1), R _a11 is a group containing an ethylenically unsaturated group, and R _b11 is an aliphatic hydrocarbon group, a hydrogen atom or Y ¹³ . Y ¹¹ , Y ¹² and Y ¹³ are hydrolyzable organic groups. Y ¹¹ , Y ¹² and Y ¹³ may be the same or different from each other.

R _a11 of the silane coupling agent represented by the general formula (1) is preferably a group containing an ethylenically unsaturated group, and the group containing an ethylenically unsaturated group is as described above, preferably vinyl. It is a base.

R _b11 is an aliphatic hydrocarbon group, a hydrogen atom or Y ¹³ described below, and the aliphatic hydrocarbon group is a monovalent aliphatic hydrocarbon group having 1 to 8 carbon atoms excluding an aliphatic unsaturated hydrocarbon group. Is mentioned. R _b11 is preferably Y ¹³ described later.

Y ¹¹ , Y ¹² and Y ¹³ are hydrolyzable organic groups, and examples thereof include an alkoxy group having 1 to 6 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, and an acyloxy group having 1 to 4 carbon atoms. Alkoxy groups are preferred. Specific examples of the hydrolyzable organic group include methoxy, ethoxy, butoxy, and acyloxy. Among these, methoxy or ethoxy is more preferable, and methoxy is particularly preferable, from the viewpoint of reactivity of the silane coupling agent.

The silane coupling agent is preferably a silane coupling agent having a high hydrolysis rate, more preferably a silane coupling agent in which R _b11 is Y ¹³ and Y ¹¹ , Y ¹² and Y ¹³ are the same as each other. Or a hydrolyzable silane coupling agent in which at least one of Y ¹¹ , Y ¹² and Y ¹³ is a methoxy group, and more preferably R _b11 is Y ¹³ and Y ¹¹ , Y ¹² and Y ¹³ are Silane coupling agents that are the same as each other. Particularly preferred is a hydrolyzable silane coupling agent having all methoxy groups.

As the silane coupling agent, specifically, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltributoxysilane, vinyldimethoxyethoxysilane, vinyldimethoxybutoxysilane, vinyldiethoxybutoxysilane, allyltrimethoxysilane, allyltrimethoxysilane. Examples thereof include vinylsilane such as ethoxysilane and vinyltriacetoxysilane, and (meth) acryloxysilane such as methacryloxypropyltrimethoxysilane, methacryloxypropyltriethoxysilane and methacryloxypropylmethyldimethoxysilane.
Those having a glycidyl group at the terminal include 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane. , 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane and the like.
Among the above silane coupling agents, a silane coupling agent having a vinyl group and an alkoxy group at the terminal is more preferable, and vinyltrimethoxysilane and vinyltriethoxysilane are particularly preferable.

  The silane coupling agent may be used alone or in combination of two or more. Further, it may be used as it is or diluted with a solvent or the like.

<Organic peroxide>
The organic peroxide generates radicals at least by thermal decomposition, and as a catalyst, undergoes a grafting reaction by a radical reaction (including a hydrogen radical abstraction reaction from the rubber) between the grafting reaction site of the silane coupling agent and the base rubber. It works to cause it.
The organic peroxide is not particularly limited as long as it can generate radicals, and examples thereof include general formulas: R ¹ —OO—R ² , R ³ —OO—C (═O) R ⁴ , and R ⁵ C. The compound represented by (= O) -OO (C = O) R ⁶ is preferable. Here, R ^{1 to} R ⁶ each independently represent an alkyl group, an aryl group, or an acyl group. Among R ^{1 to} R ⁶ of each compound, it is preferable that all are alkyl groups, or that one is an alkyl group and the rest is an acyl group.

  Examples of such organic peroxides include dicumyl peroxide (DCP), di-tert-butyl peroxide, 2,5-dimethyl-2,5-di- (tert-butylperoxy) hexane, and , 5-Dimethyl-2,5-di (tert-butylperoxy) hexyne-3,1,3-bis (tert-butylperoxyisopropyl) benzene, 1,1-bis (tert-butylperoxy) -3 , 3,5-Trimethylcyclohexane, n-butyl-4,4-bis (tert-butylperoxy) valerate, benzoyl peroxide, p-chlorobenzoyl peroxide, 2,4-dichlorobenzoyl peroxide, tert-butyl peroxide Oxybenzoate, tert-butyl peroxyisopropyl carbonate, diacetate Peroxide, lauroyl peroxide, it may be mentioned tert- butyl cumyl peroxide and the like. Among these, dicumyl peroxide, 2,5-dimethyl-2,5-di- (tert-butylperoxy) hexane, and 2,5-dimethyl-2 in terms of odor, colorability, and scorch stability. , 5-di- (tert-butylperoxy) hexyne-3 is preferred.

The decomposition temperature of the organic peroxide is preferably 130 to 195 ° C, and particularly preferably 150 to 185 ° C.
In the present invention, the decomposition temperature of an organic peroxide means that when an organic peroxide having a single composition is heated, it decomposes itself into two or more kinds of compounds at a certain temperature or temperature range for one minute. It means the temperature at which the reaction occurs (1 minute half-life temperature). Specifically, it refers to the temperature at which endothermic or exothermic starts when heated from room temperature in a nitrogen gas atmosphere at a rate of temperature increase of 5 ° C./min by thermal analysis such as DSC method.

<Silanol condensation catalyst>
The silanol condensation catalyst has a function of causing the silane coupling agent grafted on the base rubber to undergo a condensation reaction in the presence of water. Based on the function of this silanol condensation catalyst, the rubbers are crosslinked with each other via the silane coupling agent. As a result, it has a high tensile strength and a small compression set without using vulcanization equipment, and can be molded at a high temperature or at a high speed as necessary, and a silane crosslinked rubber molded body can be produced in a shorter time than the conventional method for producing a crosslinked EP rubber. Is obtained.

  Examples of the silanol condensation catalyst used in the present invention include organic tin compounds, metallic soaps, platinum compounds and the like. As a general silanol condensation catalyst, for example, dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin dioctiate, dibutyltin diacetate, zinc stearate, lead stearate, barium stearate, calcium stearate, sodium stearate, lead naphthenate, Lead sulfate, zinc sulfate, organic platinum compounds and the like are used. Among these, particularly preferable are organic tin compounds such as dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin dioctiate and dibutyltin diacetate.

<Carrier rubber>
The silanol condensation catalyst is used, optionally mixed with rubber. Such rubber (also referred to as carrier rubber) is not particularly limited, but each rubber component or each resin component described as the base rubber can be used.

<Additives>
The silane-crosslinked rubber molded product and the silane-crosslinkable rubber composition may contain various additives generally used in the above rubber products within a range that does not impair the effects of the present invention. Examples of such additives include crosslinking aids, antioxidants, lubricants, metal deactivators, colorants, and fillers (including flame retardant (auxiliary) agents) other than the above inorganic fillers. To be

Next, the method for producing the silane-crosslinkable rubber composition and the silane-crosslinked rubber molded product of the present invention will be specifically described.
In each of the “method for producing a silane-crosslinked rubber molded article” of the present invention and the “method for producing a silane-crosslinkable rubber composition” of the present invention, at least the following step (1) is performed. Therefore, the “method for producing a silane-crosslinked rubber molded article” of the present invention and the “method for producing a silane-crosslinkable rubber composition” of the present invention will be described below together (in the description common to both production methods, the present invention Sometimes called a manufacturing method.).

Step (1): With respect to 100 parts by mass of the base rubber, 0.3 to 400 parts by mass of the inorganic filler, 1 to 15 parts by mass of the silane coupling agent, and 0.01 to 0.6 parts by mass of the organic peroxide. And 0.0001 to 0.5 part by mass of silanol condensation catalyst are melt-mixed to obtain a silane-crosslinkable rubber composition as a molten mixture Step (2): Silane-crosslinkable rubber composition obtained in step (1) Step of molding article to obtain molded article Step (3): Step of contacting molded article obtained in step (2) with water to obtain silane crosslinked rubber molded article

This step (1) has steps (a) and (c) when the entire base rubber is melt mixed in the step (a), and a part of the base rubber is melt mixed in the following step (a). When it does, it has a process (a), a process (b), and a process (c).
Step (a): All or part of the base rubber, the inorganic filler, the silane coupling agent, and the organic peroxide are melt-mixed at a temperature equal to or higher than the decomposition temperature of the organic peroxide to form a silane masterbatch. Step of Preparing Step (b): Step of Preparing Catalyst Masterbatch by Melt Mixing Remainder of Base Rubber and Silanol Condensing Catalyst Step (c): Silane Masterbatch and Silanol Condensing Catalyst or the Catalyst Masterbatch Melting and mixing step Here, mixing means obtaining a uniform mixture.

  In the production method of the present invention, the “base rubber” is a base rubber for forming a silane crosslinked rubber molded product or a silane crosslinked rubber composition. Therefore, in the production method of the present invention, it is sufficient that the silane crosslinkable rubber composition obtained in the step (1) contains 100 parts by mass of the base rubber. For example, the step (a) includes "a mode in which the total amount (100 parts by mass) of the base rubber is mixed" and "a mode in which a part of the base rubber is mixed". In the "mode in which a part of the base rubber is mixed", the rest of the base rubber may be mixed as the carrier rubber in the step (b).

In the present invention, "a part of the base rubber" is a rubber used in the step (a) of the base rubber, and constitutes a part of the base rubber itself (having the same composition as the base rubber) and the base rubber. A part of the components (rubber component or resin component) to be used, or a part of the components that form the base rubber (for example, the total amount of a specific component of the plurality of components).
Further, the "remaining part of the base rubber" is the remaining rubber of the base rubber except a part used in the step (a), and specifically, the remaining part of the base rubber itself (having the same composition as the base rubber). ), The rest of the components that make up the base rubber, and the remaining components that make up the base rubber.

When a part of the base rubber is blended in the step (a), the content of the base rubber in the step (1) of 100 parts by mass is the total amount of the respective components mixed in the step (a) and the step (b). .
Here, when the balance of the base rubber is blended in the step (b), the base rubber is blended in the step (a) in an amount of preferably 80 to 99 parts by mass, more preferably 94 to 98 parts by mass. In b), preferably 1 to 20 parts by mass, more preferably 2 to 6 parts by mass are blended.

  In the step (1), the contents of the ethylene-α olefin rubber and the polypropylene resin in the base rubber are as described above. By adding a polypropylene resin, molding can be performed at a higher linear velocity while achieving excellent tensile strength and compression set.

  In the step (1), the content of the organic peroxide is 0.01 to 0.6 parts by mass, preferably 0.1 to 0.5 parts by mass with respect to 100 parts by mass of the base rubber. When the content of the organic peroxide is less than 0.01 parts by mass, the grafting reaction does not proceed during melt mixing, and the unreacted silane coupling agents are condensed with each other or the unreacted silane coupling agents are volatilized. In some cases, sufficient tensile strength and small compression set cannot be obtained. On the other hand, if the amount exceeds 0.6 parts by mass, many of the base rubbers are directly crosslinked due to a side reaction to form lumps, which may result in poor appearance. Thus, by setting the content of the organic peroxide within this range, it is possible to carry out the grafting reaction in an appropriate range, and to obtain a composition having excellent moldability without causing gel-like spots. Obtainable.

The content of the inorganic filler is 0.3 to 400 parts by mass, preferably 1 to 200 parts by mass, and more preferably 3 to 100 parts by mass with respect to 100 parts by mass of the base rubber. When the content of the inorganic filler is less than 0.3 parts by mass, the silane coupling agent is likely to volatilize, and the grafting reaction and the crosslinking reaction of the silane coupling agent may not proceed. As a result, a small compression set may not be obtained when the silane crosslinked rubber molded body is formed. On the other hand, when it exceeds 400 parts by mass, the interaction between the rubbers becomes small and the original properties of the rubber are impaired. Therefore, a small compression set and a high tensile strength cannot be obtained, and the maximum extrusion linear velocity may be slowed down because the load on the motor of the extrusion molding machine is increased.
When dry silica is used as an inorganic filler in order to obtain high insulating properties in water or in a wet environment, the content of dry silica is 0.3 to 10 parts by mass with respect to 100 parts by mass of the base resin. Is preferable, and 1-8 mass parts is more preferable.

The content of the silane coupling agent is 1 to 15 parts by mass, preferably 3 to 15 parts by mass, and more preferably more than 4 parts by mass and 15 parts by mass or less with respect to 100 parts by mass of the base rubber. And more preferably more than 4 parts by mass and 10 parts by mass or less.
If the content of the silane coupling agent is less than 1 part by mass, the crosslinking reaction may not proceed sufficiently and a small compression set may not be obtained. On the other hand, if the amount exceeds 15 parts by mass, the silane coupling agent cannot be completely adsorbed on the surface of the inorganic filler, and the silane coupling agent volatilizes during kneading, which is not economical. In addition, the silane coupling agent that does not adsorb may condense, and the molded article may be damaged or burned to deteriorate the appearance.

  When the content of the silane coupling agent is 3 to 15 parts by mass, particularly more than 4 parts by mass and 15 parts by mass or less, both the crosslinking reaction between the base rubbers and the condensation reaction between the silane coupling agents are caused. A silane-crosslinked rubber molded article that can be suppressed and has a beautiful appearance can be produced.

Although the details of the mechanism are not clear yet, it is considered as follows.
That is, in the step (a), the reaction due to the decomposition of the organic peroxide when the silane coupling agent is grafted on the base rubber is such that when the content of the silane coupling agent exceeds 4 parts by mass, the base rubbers are crosslinked. The reaction rate is faster than the reaction, the grafting reaction between the silane coupling agent and the base rubber, and the condensation reaction between the silane coupling agents become dominant. Therefore, the cross-linking reaction between the rubbers, which causes the appearance roughness and the spots, is unlikely to occur. In this way, the crosslinking reaction between the base rubbers is effectively suppressed depending on the content of the silane coupling agent. This gives a good appearance during molding. Further, since the above-mentioned defects due to the cross-linking reaction between the base rubbers are reduced, even if the extruder is restarted after being stopped, the appearance failure is less likely to occur. In this way, it is possible to suppress the cross-linking reaction between the base rubbers and manufacture a silane cross-linked rubber molded article having a good appearance.
On the other hand, in step (a), the reaction rate of the condensation reaction between the silane coupling agents is high. However, since many silane coupling agents are bonded or adsorbed to the inorganic filler and immobilized, the condensation reaction between the silane coupling agents bonded or adsorbed to the inorganic filler is less likely to occur. Although not bound or adsorbed to the inorganic filler, a condensation reaction between the free silane coupling agents may occur, but in the present invention, most of the silane coupling agents are bound or adsorbed to the inorganic filler, It does not lead to the formation of gel-like spots.
Thus, it is considered that a silane-crosslinked rubber molded article having a clean appearance can be manufactured by using a specific amount of the silane coupling agent.

  The content of the silanol condensation catalyst is 0.0001 to 0.5 part by mass, preferably 0.001 to 0.3 part by mass, based on 100 parts by mass of the base rubber. When the content of the silanol condensation catalyst is 0.0001 to 0.5 part by mass, the crosslinking reaction due to the condensation reaction of the silane coupling agent is likely to proceed almost uniformly, and the appearance, tensile strength and compression permanent of the silane crosslinked rubber molded body are improved. Distortion is excellent and productivity is improved. That is, if the content of the silanol condensation catalyst is too small, sufficient tensile strength or a small compression set may not be obtained. On the other hand, if the amount is too large, the crosslinking reaction due to the condensation reaction of the silane coupling agent becomes non-uniform, and the appearance and productivity may be poor.

  In the step (a), all or a part of the base rubber, the inorganic filler, the silane coupling agent, and the organic peroxide are charged into the mixer at the above contents, and the decomposition temperature of the organic peroxide. A silane masterbatch is prepared by melt-kneading while heating to the above temperature.

The temperature at which the above components are melt-mixed (also referred to as melt-kneading or kneading) is equal to or higher than the decomposition temperature of the organic peroxide, preferably the decomposition temperature of the organic peroxide + (1 to 80) ° C. Although it is difficult to uniquely determine the temperature of melt mixing, as an example, 80 to 250 ° C is preferable, and 100 to 240 ° C is more preferable. This mixing temperature is preferably set after the base rubber has melted. When the mixing temperature is within the above range, the above components are melted, the organic peroxide is decomposed, and acts so that the necessary grafting reaction proceeds sufficiently in step (a). Other conditions can be set as appropriate. For example, the mixing time may be a time at which the grafting reaction of the silane coupling agent onto the polyolefin resin at the melting temperature sufficiently proceeds, and for example, 5 minutes to 1 hour is preferable.
The mixing method is not particularly limited as long as it is a method usually used for rubber, plastics and the like. The mixing device is appropriately selected depending on the content of the inorganic filler, for example. As the kneading device, a single-screw extruder, a twin-screw extruder, a roll, a Banbury mixer, various kneaders, or the like is used. A closed mixer such as a Banbury mixer or various kneaders is preferable in terms of rubber dispersibility and stability of crosslinking reaction.
When the inorganic filler is mixed in an amount of more than 100 parts by mass with respect to 100 parts by mass of the base rubber, it is preferable to melt-mix with a continuous kneader, a pressure kneader, or a Banbury mixer.

In the present invention, "melt mixing of all or a part of the base rubber, the organic peroxide, the inorganic filler and the silane coupling agent" does not specify the mixing order at the time of melt mixing. It means that they may be mixed in order. That is, the order of mixing in step (a) is not particularly limited.
Also, the method of mixing the rubber is not particularly limited. For example, a base rubber prepared by mixing in advance may be used, or each rubber component or resin component may be mixed separately.

In the step (a), the above components can be melt-mixed at one time, but preferably the silane coupling agent is not mixed alone into the silane masterbatch, but is mixed with the inorganic filler in a premixed state or the like. It can also be done. The premixed silane coupling agent exists so as to surround the surface of the inorganic filler, and part or all of the silane coupling agent is adsorbed or bonded to the inorganic filler. This can reduce volatilization of the silane coupling agent during the subsequent melt mixing. Further, it is possible to prevent the silane coupling agent which is not adsorbed or bonded to the inorganic filler from condensing and making it difficult to melt-mix. Further, a desired shape can be obtained during extrusion molding.
As such a mixing method, the organic peroxide, the inorganic filler and the silane coupling agent are preferably added at a temperature lower than the decomposition temperature of the organic peroxide, preferably room temperature (25 ° C.), preferably for about 1 to 10 minutes. A method of pre-mixing (dispersing) and then melt-mixing the obtained mixture with the base rubber can be mentioned.

The method of mixing the inorganic filler, the silane coupling agent, and the organic peroxide is not particularly limited, and the organic peroxide may be mixed with the inorganic filler and the like at the same time, or the inorganic filler and the silane coupling agent may be mixed. May be mixed in any of the mixing stages with.
For example, the organic peroxide may be mixed with the inorganic filler after being mixed with the silane coupling agent, or may be separately mixed with the inorganic filler separately from the silane coupling agent. In the present invention, it is preferable that the organic peroxide and the silane coupling agent are substantially mixed together. On the other hand, depending on the production conditions, only the silane coupling agent may be mixed with the inorganic filler, and then the organic peroxide may be mixed. That is, in the step (1), the inorganic filler may be a mixture with the silane coupling agent in advance.
The organic peroxide may be a mixture with other components or may be a simple substance.
In the method of mixing the organic peroxide, the inorganic filler and the silane coupling agent, the rubber component or the resin component may be present as long as the temperature below the decomposition temperature is maintained.

Examples of the method for mixing the inorganic filler, the silane coupling agent, and the organic peroxide include a mixing method such as a wet treatment and a dry treatment. Specifically, a wet treatment in which a silane coupling agent is added in a state in which an inorganic filler is dispersed in a solvent such as alcohol or water, a dry treatment in which both are heated or unheated and mixed, and both of them are mentioned. In the present invention, a dry treatment is preferred in which a silane coupling agent is added to and mixed with an inorganic filler, preferably a dried inorganic filler, with or without heating.
This premixing is preferably performed with a mixer-type kneader such as a Banbury mixer or a kneader. By doing so, it is possible to prevent an excessive crosslinking reaction between the base rubbers, and the appearance becomes excellent. The pre-mixing may be performed using a mixer such as a Henschel mixer, or may be manually mixed.
In wet mixing, the binding force between the silane coupling agent and the inorganic filler becomes strong, so that volatilization of the silane coupling agent can be effectively suppressed, but the grafting reaction on the base rubber may be difficult to proceed. is there. On the other hand, in dry mixing, the binding force between the inorganic filler and the silane coupling agent becomes relatively weak, so that the grafting reaction proceeds efficiently and the silanol condensation reaction easily proceeds.

  In the premixing mixing method described above, then, the obtained mixture and all or part of the base rubber are melt-kneaded while being heated to a temperature equal to or higher than the decomposition temperature of the organic peroxide.

  In the step (a), it is preferable to knead the above-mentioned components without substantially mixing the silanol condensation catalyst. This makes it possible to suppress the condensation reaction of the silane coupling agent, facilitate melt mixing, and obtain a desired shape during extrusion molding. Here, "substantially not mixed" does not exclude the silanol condensation catalyst which is inevitably present, and is present to the extent that the above-mentioned problems due to silanol condensation of the silane coupling agent do not occur. Means good. For example, in step (a), the silanol condensation catalyst may be present in an amount of 0.01 parts by mass or less based on 100 parts by mass of the base rubber.

  In the step (1), the additives, particularly the antioxidant and the metal deactivator, may be mixed in any step or in the components, but are preferably mixed in the carrier rubber. For example, when an antioxidant is added to the silane masterbatch in a large amount (for example, 1 part by mass or more), crosslinking inhibition may occur due to a radical scavenging effect and the like, and as a result, the grafting reaction may not proceed sufficiently.

  In this way, step (a) is carried out to prepare a silane masterbatch (also referred to as silane MB). This silane MB is preferably used together with a silanol condensation catalyst or a catalyst masterbatch described below in the production of the molten mixture (silane crosslinkable rubber composition) prepared in step (1), as described below. The silane MB contains a silane crosslinkable rubber (silane graft rubber) in which a silane coupling agent is grafted onto a base rubber to such an extent that it can be molded in the step (2) described later.

  In the production method of the present invention, when a part of the base rubber is then melt-mixed in step (a), the rest of the base rubber and the silanol condensation catalyst are melt-mixed to form a catalyst masterbatch (also referred to as catalyst MB). ) Is performed. Therefore, when melt-mixing all of the base rubber in the step (a), the step (b) may not be performed, and another resin may be mixed with the silanol condensation catalyst.

The mixing ratio of the 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 step (1).
Any mixing method may be used as long as it can be uniformly mixed, and examples thereof include mixing (melt mixing) performed while the rubber is melted. The melt mixing can be performed in the same manner as the melt mixing in the above step (a). For example, the mixing temperature can be 80 to 250 ° C, more preferably 100 to 240 ° C. Other conditions, such as the mixing time, can be set appropriately.

In the step (b), other rubber component or resin component may be used as the carrier rubber instead of or in addition to the rest of the base rubber. That is, the step (b) is the rest of the base rubber when a part of the base rubber is melt-mixed in the step (a), or a rubber component or resin component other than the base rubber used in the step (a), and silanol. The catalyst MB may be prepared by melt mixing with a condensation catalyst.
When the carrier rubber is another rubber component or a resin component, the content of the other rubber component or the resin component is that the silane cross-linking can be promoted quickly in the step (a), and that no hard spots are formed during molding. Is preferably 1 to 50 parts by mass, more preferably 2 to 30 parts by mass, and still more preferably 4 to 20 parts by mass with respect to 100 parts by mass of the base rubber.

  Moreover, you may use an inorganic filler in a process (b). In this case, the content of the inorganic filler is not particularly limited, but is preferably 350 parts by mass or less with respect to 100 parts by mass of the carrier rubber. When the content of the inorganic filler is large, the silanol condensation catalyst is difficult to disperse, and the crosslinking reaction is difficult to proceed.

The catalyst MB thus prepared is a mixture of a silanol condensation catalyst, a carrier rubber, and an inorganic filler optionally added.
This catalyst MB is used as a master batch set in the production of the silane crosslinkable rubber composition prepared in the step (1) together with the silane MB.

In the production method of the present invention, next, step (c) of mixing the silane MB and the silanol condensation catalyst or the catalyst MB to obtain a molten mixture is performed.
Any mixing method may be used as long as a uniform molten mixture can be obtained as described above.

  The mixing is basically the same as the melt mixing in step (a). The mixing is carried out at a temperature at which the base rubber and other resin components melt. The mixing temperature is appropriately selected according to the melting temperature of the base rubber or the carrier rubber. In the step (c), the mixing temperature is, for example, preferably 100 to 250 ° C, more preferably 120 to 220 ° C. Other conditions, for example, mixing (kneading) time can be set appropriately.

  In the step (c), it is preferable that the silane MB and the silanol condensation catalyst are not kept at a high temperature for a long time in order to avoid the silanol condensation reaction.

  The step (c) may be a step of mixing the silane MB and the silanol condensation catalyst to obtain a molten mixture, and is a step of melting and mixing the catalyst MB containing the silanol condensation catalyst and the carrier rubber and the silane MB. Is preferred.

In this way, the steps (a) to (c) (step (1)), that is, the method for producing the silane-crosslinkable rubber composition of the present invention, is carried out, and the silane-crosslinkable rubber composition of the present invention is obtained as a molten mixture. Manufactured. This silane-crosslinkable rubber composition has a Mooney viscosity (ML (1 + 4) 125 ° C.) of 15 to 40 and an ethylene content of 65 to 80% by mass measured according to JIS K 6300-1: 2013. A silane crosslinkable rubber in which a silane coupling agent is grafted to a base rubber containing 61 to 100% by mass of α-olefin rubber, and 0.3 to 400 parts by mass of an inorganic filler, and silanol condensation with respect to 100 parts by mass of the base rubber. The catalyst contains 0.0001 to 0.5 parts by mass.
The silane crosslinkable rubber contained in this silane crosslinkable rubber composition is a silane crosslinkable rubber in which a silane coupling agent is grafted onto a base rubber. In this silane crosslinkable rubber, the reaction site of the silane coupling agent may be bonded or adsorbed to the inorganic filler, but is not silanol-condensed as described later. Therefore, a silane crosslinkable rubber is a crosslinkable rubber in which a silane coupling agent bound or adsorbed with an inorganic filler is grafted to a base rubber, and a silane coupling agent not bound or adsorbed with an inorganic filler is crosslinked in a base rubber. And at least a rubber. Further, the silane crosslinkable rubber may have a silane coupling agent having an inorganic filler bonded or adsorbed thereto and a silane coupling agent having no inorganic filler bonded or adsorbed thereto. Further, it may contain a rubber component which has not reacted with the silane coupling agent.

The silane crosslinkable rubber has an Mooney viscosity (ML (1 + 4) 125 ° C.) of 15 to 40 and an ethylene content of 65 to 80% by mass, which are measured according to JIS K 6300-1: 2013. It is preferable that 100 parts by mass of the base rubber containing 61 to 100% by mass of rubber be grafted with 1 to 15 parts by mass of the silane coupling agent at 70 to 100% by mass.
The reaction ratio of the silane coupling agent (also referred to as a grafting ratio) when the silane coupling agent is graft-reacted with the base rubber is not particularly limited as long as the effect of the present invention is not impaired. In the present invention, it is difficult to uniquely determine the grafting rate, but for example, the grafting rate according to the measuring method described in Examples described later is 70 to 100% by mass (the silane grafting amount is 0.7 to 15 parts by mass), more preferably 75 to 100% by mass (silane graft amount is 0.75 to 15 parts by mass), and 80 to 100% by mass (silane graft amount is 0.8 to 15). (Parts by mass) is more preferable. When the grafting ratio is 70 to 100% by mass, crosslinking of the base rubber will be sufficient, which is suitable for imparting the above excellent properties.
In the present invention, the grafting ratio can be set within a predetermined range depending on the type or content of organic peroxide, the type of silane coupling agent, the use of a closed mixer, and the like.

  The silane crosslinkable rubber obtained in the step (1) is an uncrosslinked body in which the silane coupling agent is not silanol condensed. Practically, when melt-mixed in the step (c), partial cross-linking (partial cross-linking) is unavoidable, but the obtained silane cross-linkable rubber composition is moldable at least in step (2). Shall be retained (uncrosslinked state or partially crosslinked state).

  In step (1), steps (a) to (c) can be performed simultaneously or successively.

In the method for producing a silane-crosslinked rubber molded product of the present invention, next, step (2) and step (3) are performed.
In the method for producing a silane-crosslinked rubber molded product of the present invention, the step (2) of molding the obtained molten mixture to obtain a molded product is performed. In this step (2), it is sufficient that the molten mixture can be molded, and the molding method and molding conditions are appropriately selected according to the form of the product of the present invention. Examples of the molding method include extrusion molding using an extruder, injection molding using an injection molding machine, press molding using a press molding machine, and molding using other molding machines. Extrusion is preferred when the product of the invention is a wire or fiber optic cable.
When the molding step (2) is carried out by extrusion molding, the molding speed (extrusion speed) of the silane crosslinkable rubber composition of the present invention is not particularly limited and is usually 1 to less than 20 m / min, preferably 1 in linear velocity. It can be set to 10 m / min. Further, in the present invention, the molding speed can be set to a high speed of 20 to 200 m / min in linear speed in order to further improve the productivity.
Also, extrusion molding can be performed at high temperature. When the molding temperature is set to a high temperature, extrusion molding at the above high extrusion speed becomes easy. In particular, the manufacturing method of the present invention can realize an excellent appearance. When the molding temperature is set to a high temperature, it can be set to, for example, 150 ° C. or higher, preferably 180 to 250 ° C.

In addition, step (2) can be performed simultaneously with step (c) or continuously. That is, as one embodiment of the melt mixing in the step (c), at the time of melt molding, for example, at the time of extrusion molding, or immediately before that, the molding raw materials such as the silane MB, the silanol condensation catalyst or the catalyst MB are melt mixed. The aspect which does is mentioned. For example, pellets such as dry blend may be mixed with each other at room temperature or high temperature and introduced into a molding machine (melt mixing), or they may be melt-mixed after mixing and pelletized again and introduced into a molding machine. Good. More specifically, a series of steps in which a molding material of silane MB and a silanol condensation catalyst or a catalyst MB is melt-kneaded in a coating device, and then the outer peripheral surface of a conductor or the like is extrusion-coated and molded into a desired shape. Can be adopted.
In this way, a molded product of the silane crosslinkable rubber composition is obtained. Like the silane-crosslinkable rubber composition, this molded article is inevitably partially crosslinked, but is in a partially crosslinked state that retains moldability that can be molded in step (2). Therefore, the silane-crosslinked rubber molded article of the present invention is made into a crosslinked or finally crosslinked molded article by carrying out the step (3).

In the method for producing a silane-crosslinked rubber molded body of the present invention, a step of bringing the molded body obtained in step (2) into contact with water is performed. As a result, the reaction sites of the silane coupling agent are condensed to cause a crosslinking reaction. Specifically, the reaction site is hydrolyzed to silanol, and the silanol hydroxyl groups are condensed with each other by the silanol condensation catalyst present in the molded body to cause a crosslinking reaction. In this way, a silane-crosslinked rubber molded product in which the silane coupling agent is silanol-condensed and crosslinked can be obtained.
The treatment itself of this step (3) can be performed by a usual method. Condensation of the silane coupling agents with each other proceeds only by leaving them at room temperature. Therefore, in the step (3), it is not necessary to positively contact the molded body with water. In order to accelerate this crosslinking reaction, the molded body can be brought into contact with water positively. For example, a method of actively contacting with water, such as immersion in warm water, introduction into a moist heat tank, exposure to high temperature steam, or the like, can be adopted. Further, at that time, pressure may be applied to permeate water into the inside. Such a method is effective in the case of an electric wire having a large coating thickness and other molded articles having a large volume.

  In this way, the method for producing a silane-crosslinked rubber molded article of the present invention is carried out, and a silane-crosslinked rubber molded article is produced from the silane-crosslinkable rubber composition of the present invention. This silane crosslinked rubber molded product contains a crosslinkable rubber obtained by crosslinking the silane crosslinkable rubber via a silane coupling agent, as described later. One form of this silane crosslinked rubber molded product contains a silane crosslinked rubber and an inorganic filler. Here, the inorganic filler may be bonded to the silane coupling agent of the silane crosslinked rubber. Therefore, this silane cross-linked rubber is a cross-linked rubber that is bonded (cross-linked) through the inorganic filler and the silane coupling agent by bonding or adsorbing a plurality of cross-linked rubbers to the inorganic filler by the silane coupling agent, and the above-mentioned cross-linking property. The rubber contains at least a cross-linked rubber that is cross-linked through a silane coupling agent by hydrolyzing the reaction site of the silane coupling agent and performing a silanol condensation reaction with each other. Further, the silane crosslinked rubber may have a mixture (crosslinking) through an inorganic filler and a silane coupling agent and a crosslink through a silane coupling agent. Further, a silane coupling agent and an unreacted rubber component and / or a non-crosslinked silane crosslinkable rubber may be contained.

The reason for grafting in the production method of the present invention is not yet clear, but it is considered as follows. That is, when the base rubber is heated and kneaded with the inorganic filler and the silane coupling agent at the decomposition temperature of the organic peroxide or higher in the presence of the organic peroxide, the organic peroxide is decomposed to generate radicals, and the base rubber is added. On the other hand, grafting of the silane coupling agent occurs.
Further, the heating in the melt mixing also causes a chemical bond forming reaction due to a covalent bond between the silane coupling agent and a group such as a hydroxyl group on the surface of the inorganic filler.
In the present invention, the final crosslinking reaction may be carried out in the step (3), and when a specific amount of the silane coupling agent is blended with the base rubber as described above, the extrusion workability (moldability) during molding is impaired. It becomes possible to mix a large amount of the inorganic filler without having to do so. As a result, it is possible to have an excellent appearance of the molded product and further mechanical properties while securing excellent moldability.

The method for producing a silane crosslinked rubber molded article of the present invention is a base rubber containing an ethylene-α olefin rubber having a low viscosity Mooney viscosity and an ethylene amount in the above range at the above content ratio by the above silane crosslinking method, Mix, mold and crosslink. Therefore, it is possible to produce a silane-crosslinked rubber molded article having excellent compression set, tensile strength, hardness and appearance.
Further, in the method for producing a silane-crosslinked rubber molded product of the present invention, since the above-mentioned base rubber is molded and crosslinked by the above-mentioned silane-crosslinking method, vulcanization equipment is not required for carrying out the crosslinking reaction, and EP rubber is added Productivity can be increased relative to the sulfurization method.
Furthermore, the method for producing a silane crosslinked rubber molded article of the present invention can suppress crosslinking of the base rubber during molding, and if necessary, the molding temperature can be set to a high temperature as described above, and the linear velocity can be increased. It can also be set.

Although the mechanism of action of the above process of the present invention is not yet clear, it is presumed as follows. That is, by using the inorganic filler and the silane coupling agent before and / or during the kneading with the base rubber, the silane coupling agent is bonded to the group capable of chemically bonding with the inorganic filler at the reaction site. , Retained. Alternatively, it is physically and chemically adsorbed and held in the holes and the surface of the inorganic filler without being bound to the inorganic filler. In this way, a silane coupling agent that binds to the inorganic filler with a strong bond (the reason is considered to be, for example, the formation of a chemical bond with a group capable of chemical bonding on the surface of the inorganic filler) and a weak bond. A silane coupling agent (which is considered to be, for example, an interaction due to a hydrogen bond, an interaction between ions, partial charges or dipoles, an action due to adsorption, etc.) can be formed. When kneading with the base rubber in this state in the presence of an organic peroxide, the silane coupling agent hardly volatilizes from the rubber composition (rubber kneading material) and the other end At the grafting reaction site existing in the base rubber, it is bonded to the site capable of grafting reaction of the base rubber. In this way, a silane cross-linking rubber in which the silane coupling agent has a different bond with the inorganic filler and is graft-reacted with the base rubber is formed.
In the step (1), it is considered that the diene components in the base rubber also crosslink with each other by radicals generated by decomposition of the organic peroxide. However, in the above preferred method, since the silane coupling agent, the organic peroxide and the inorganic filler are mixed, it is considered that the grafting reaction of the silane coupling agent proceeds preferentially.

  By the above-mentioned kneading, the silane coupling agent having a strong bond with the inorganic filler among the silane coupling agents, the bond with the inorganic filler is retained, and the grafting reaction site is a site where the grafting reaction of the base rubber is possible. Grafting reaction with (radical formation site of rubber produced by abstraction of hydrogen radical by radical produced by decomposition of organic peroxide). In particular, when a plurality of silane coupling agents are bonded to the surface of one inorganic filler particle via a strong bond, a plurality of rubbers are bonded via the inorganic filler particle. By these reactions or bonds, the cross-linked network via the inorganic filler spreads. That is, a silane cross-linking rubber formed by a graft reaction of the silane coupling agent bonded to the inorganic filler on the base rubber is formed.

In the case of the silane coupling agent having a strong bond with the inorganic filler, the condensation reaction in the presence of water by the silanol condensation catalyst is unlikely to occur, and the bond with the inorganic filler is retained. It is considered that the reason why the silanol condensation reaction is difficult to occur is that the binding energy between the inorganic filler and the silane coupling agent is so high that the condensation reaction does not occur even under the silanol condensation catalyst. In this way, the base rubber and the inorganic filler are bound to each other, and the rubber is crosslinked via the silane coupling agent. As a result, the adhesiveness between the base rubber and the inorganic filler becomes strong, and a molded product having high tensile strength and excellent compression set can be obtained.
Further, a plurality of silane coupling agents can be bonded to the surface of one inorganic filler particle, and high tensile strength can be obtained.
As described above, the silane coupling agent bonded to the inorganic filler with a strong bond is considered to contribute to the improvement of tensile strength and the suppression of compression set.

  On the other hand, among the silane coupling agents, the silane coupling agent having a weak bond with the inorganic filler is separated from the surface of the inorganic filler, and the grafting reaction site of the silane coupling agent is a site where the grafting reaction of the base rubber is possible. And a grafting reaction occurs. That is, the silane coupling agent separated from the inorganic filler is graft-reacted with the base rubber to form a silane crosslinkable rubber. The silane coupling agent in the graft portion thus produced is then mixed with a silanol condensation catalyst and brought into contact with water to cause a condensation reaction (crosslinking reaction). The silane-crosslinked rubber molded body obtained by this crosslinking reaction has a high tensile strength, and in addition to heat resistance, a silane-crosslinked rubber molded body having a small compression set can be obtained. Thus, it is considered that the silane coupling agent bonded to the inorganic filler by a weak bond contributes to the improvement of the degree of crosslinking, that is, the suppression of compression set.

  Particularly, in the present invention, the crosslinking reaction by condensation using the silanol condensation catalyst in the presence of water in the step (3) is performed after forming the molded body. As a result, the workability in the steps up to the formation of the molded body is excellent as compared with the method such as the method described in Patent Document 1 in which the extrusion molding and the crosslinking reaction are simultaneously performed. Moreover, since the condensation reaction using the silanol condensation catalyst does not proceed in the extruder in which almost no water is present, it becomes possible to perform extrusion molding at a high temperature in the step (2). Therefore, molding at high temperature and high speed is possible.

  Furthermore, when the silane coupling agent is mixed with the inorganic filler by the production method of the present invention, the appearance of the silane coupling agent is excellent because the condensation of the silane coupling agents is suppressed as described above. Moreover, in the present invention, when 3 to 15 parts by mass, particularly more than 4 parts by mass and 15 parts by mass or less of the silane coupling agent is mixed with the inorganic filler, as described above, the step (1), particularly the step ( It is possible to effectively suppress the crosslinking reaction between the rubbers at the time of melt-kneading in a). In addition, the silane coupling agent is bonded to the inorganic filler and is unlikely to volatilize during the melt kneading in the step (1), particularly the step (a), and the reaction between the released silane coupling agents is also effective. Can be suppressed to Therefore, even if the extruder is stopped and then restarted, a poor appearance hardly occurs, and a silane-crosslinked rubber molded article having a good appearance can be manufactured. Here, although it cannot be unequivocally stated that once stopped and then restarted depends on the composition of the base rubber, processing conditions, etc., it can be restarted at 190 ° C. for an interval of 30 minutes, preferably for 90 minutes. Say.

Further, the silane-crosslinked rubber molding of the present invention using dry silica as the inorganic filler can maintain high insulating properties even in water or in a wet environment.
For example, as the insulating property of the silane cross-linked rubber molding of the present invention, for example, the insulation resistance ρ _V1 when immersed in water at 20 ° C. for 1 hour is preferably 100,000 MΩ · km or more, and 120,000 MΩ · km or more. Is more preferable. The insulation resistance ρ _V24 when immersed in water at 20 ° C. for 24 hours is preferably 100,000 MΩ · km or more. Further, regarding the retention of the insulation characteristics in a wet environment, for example, the insulation resistance decrease rate Δρ, which is obtained from the insulation resistance ρ _V1 and the insulation resistance ρ _V24 by the following calculation formula, is preferably 50% or less, It is more preferably 35% or less. Here, the reduction rate of the insulation resistance is obtained from the following formula. The method for measuring the insulation resistance will be described later.

Calculation: reduction in the insulation resistance Δρ (%) = [(ρ V1 -ρ V24) / ρ V1] × 100

In the present invention in which dry silica is used as the inorganic filler and the silane crosslinked rubber molded article is prepared by the silane crosslinking method, as described above, the silane coupling agent is adsorbed and / or bonded to the surface of the dry silica. It is considered that this makes it difficult for moisture to be absorbed into the silane cross-linked rubber molded body, improves the initial (after manufacturing) insulating properties, and suppresses the deterioration of insulating properties even in water or in a wet environment. Here, the wet environment is an environment in which the silane-crosslinked rubber molded article of the present invention is used, for example, a temperature of 20 ° C. or higher and a relative humidity of 70% or higher at a specific temperature within this range. .
Further, in the above-mentioned conventional rubber composition, when dry silica is used as an inorganic filler, the obtained rubber composition exhibits high insulating properties under a dry environment, but has insulating properties under water or a wet environment. May be significantly reduced. It is considered that when the rubber composition contains dry silica having a large number of OH groups on the surface, it tends to absorb moisture.

The silane-crosslinked rubber molded product of the present invention has at least the following characteristics (the measuring method is the same as that of the example) and is excellent in appearance.
That is, the silane-crosslinked rubber molded product has a compression set of preferably 40% or less, more preferably 35% or less, and further preferably 30% or less. The lower limit is not particularly limited, but is 10%, for example.
The silane-crosslinked rubber molded product has a tensile strength of preferably 6 MPa or more, more preferably 8 MPa or more, still more preferably 10 MPa or more. The upper limit is not particularly limited, but is 15 MPa, for example.
The silane-crosslinked rubber molded body has a hardness of preferably 50 or more, more preferably 60 or more, and further preferably 70 or more. The upper limit is not particularly limited, but is 90, for example.

  The silane-crosslinkable rubber composition of the present invention can produce a silane-crosslinked rubber molded product having the above-mentioned excellent properties. Moreover, it excels in high-speed moldability and exhibits high productivity.

The silane-crosslinked rubber molded product of the present invention may be a product containing a silane-crosslinked rubber molded product or a product consisting of only a silane-crosslinked rubber molded product. Examples of the product including the silane-crosslinked rubber molded product include a product including the silane-crosslinked rubber molded product and other members such as a support and a support frame. In the present invention, the term "finished product" includes semi-finished products, parts, and members.
As the silane cross-linked rubber molded product of the present invention, a coating material for various industrial cables (including electric wires), a rubber molding material (for example, a glass run channel for automobiles, a weather strip, a rubber hose, a wiper blade rubber, a gasket, an anti-vibration rubber), etc. Is mentioned.
The silane-crosslinked rubber molded article of the present invention, when containing dry silica as an inorganic filler, is suitable for applications requiring high insulation properties, or long-term insulation properties, for example, applications used in water or in a wet environment. Suitable for Examples of such applications include, but are not limited to, high-voltage electric wires or cables, insulating rubber sheets in a power distribution chamber, grommets or packings, and rubber gloves for high-voltage work.

  The silane-crosslinked rubber molded product of the present invention is preferably a product that requires at least one of excellent compression set, high tensile strength, and high hardness. Such a product is not particularly limited. For example, a product requiring a compression set of 40% or less at 70 ° C., a product requiring a tensile strength of 6 MPa or more, a product requiring a hardness of 50 or more, or the compression set, the tensile strength, and the hardness described above. Required products are listed. Specifically, as the silane cross-linked rubber molded article of the present invention, preferably, a sheath material (jacket material) among coating materials for various industrial cables, and further, among rubber molding materials, a rubber molding material for automobiles, a weather Examples include strips and gaskets.

INDUSTRIAL APPLICABILITY The production method of the present invention is applied to the production of products requiring a small compression set (including semi-finished products, parts and members), products requiring high hardness, component parts of products such as rubber materials or members thereof. can do.
As described above, the production method of the present invention can produce a silane-crosslinked rubber molded product having the above excellent properties with high productivity without requiring vulcanization equipment. Therefore, the production method of the present invention can be particularly preferably applied to a product that requires at least one of characteristics such as small compression set, high tensile strength, and high hardness.

The production method of the present invention is preferably applied to the production of electric wires and optical cables among the above-mentioned products, and can form coating materials (insulators, sheaths) thereof.
When the product of the present invention is an extrusion molded article such as an electric wire or a cable, it is preferable that the molding material is melt-kneaded in an extruder (extrusion coating apparatus) while being extruded onto the outer periphery of the conductor or the like to coat the conductor or the like. Can be manufactured (step (c) and step (2)). Such a product is a special machine such as an electron beam cross-linking machine for a silane cross-linking rubber composition containing a large amount of an inorganic filler, using a general-purpose extrusion coating device without using rubber vulcanization equipment, It can be formed by extrusion coating around a conductor or around a conductor in which tensile strength fibers are laid vertically or twisted. For example, a single wire of copper or a stranded wire or the like can be used as the conductor. In addition to the bare wire, a conductor plated with tin or a conductor having an enamel coating insulating layer can be used as the conductor. The thickness of the insulating layer (a coating layer made of the silane-crosslinkable rubber composition or the silane-crosslinked rubber molded product of the present invention) formed around the conductor is not particularly limited, but is generally about 0.15 to 5 mm. Is.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.
In Table 1 and Table 2, the numerical value regarding the content of each example represents a mass part unless otherwise specified.

Examples 1 to 9, Reference Example 10 and Comparative Examples 1 to 10 were carried out by using the following components and setting the respective specifications to the conditions shown in Table 1 and Table 2.

Details of each compound (component) shown in Table 1 and Table 2 are shown below. The Mooney viscosity (ML (1 + 4) 125 ° C.), ethylene content and diene content (measured by infrared absorption spectroscopy) of ethylene-α-olefin rubber are shown in Tables 1 and 2.
<Rubber component>
(Ethylene-α olefin rubber, EP rubber)
"Nodell 3720P" (NORDEL (registered trademark), Dow Chemical Co., ethylene-propylene-ethylidene norbornene rubber)
"Nodell 3722P" (NORDEL (registered trademark), Dow Chemical Co., ethylene-propylene-ethylidene norbornene rubber)
"Nodel 4725P" (NORDEL (registered trademark), Dow Chemical Co., ethylene-propylene-ethylidene norbornene rubber)
"EP51" (trade name, manufactured by JSR, ethylene-propylene-ethylidene norbornene rubber)
"Vistalon 722" (Vistalon (registered trademark), manufactured by ExxonMobil, ethylene-propylene rubber)
"Vistalon 1703P" (Vistalon (registered trademark), manufactured by ExxonMobil, ethylene-propylene-ethylidenenorbornene rubber)
"Vistalon 8731" (Vistalon (registered trademark), ExxonMobil, ethylene-propylene-ethylidene norbornene rubber)
EPM-1, EPM-2, EPM-3, EPM-4 and EPM-5 were synthesized by the method described below.
<Resin component>
(Polypropylene resin)
"PM940M" (trade name, manufactured by Sun Allomer, r-PP, MFR (230 ° C, 21.18N) 30 g / 10 minutes)

<Inorganic filler>
"Aerosil 200" (Aerosil (registered trademark), Nippon Aerosil Co., Ltd., dry silica (hydrophilic fumed silica), average primary particle diameter 12 nm)
"Crystallite 5X" (trade name, manufactured by Tatsumori, crystalline silica, average primary particle size 1.4 μm)
"Kisuma 5L" (Kisuma (registered trademark), magnesium hydroxide, manufactured by Kyowa Chemical Co., Ltd., average primary particle size 0.8 μm)

<Silane coupling agent>
"KBM1003" (brand name, Shin-Etsu Silicone, vinyltrimethoxysilane)
<Organic peroxide>
"Perhexa 25B" (trade name, manufactured by NOF CORPORATION, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane, 1-minute half-life temperature 179.8 ° C)
<Silanol condensation catalyst>
"ADEKA STAB OT-1" (trade name, ADEKA, dioctyl tin dilaurate)

Synthesis of EPM-1, EPM-2, EPM-3, EPM-4, and EPM-5 EPM-1 to 5 have two types of Mooney viscosity and ethylene content shown in Table 1 and Table 2. The above EPM was melt-mixed at 150 ° C. for 10 minutes using a Banbury mixer in advance and obtained by pelletizing.
"EPM-1" (ethylene-propylene-rubber)
"EPM-2" (ethylene-propylene-rubber)
"EPM-3" (ethylene-propylene-rubber)
"EPM-4" (ethylene-propylene-rubber)
"EPM-5" (ethylene-propylene-rubber)

(Examples 1 to 9, Reference Example 10 and Comparative Examples 1 to 8)
In Examples 1 to 9, Reference Example 10 and Comparative Examples 1 to 8, a part of the EP rubber was used in the step (a), and the rest of the EP rubber (5 parts by mass) was used in the step (b) as the carrier rubber of the catalyst MB. Used as.
The inorganic filler, the silane coupling agent, and the organic peroxide were mixed at a mass ratio shown in Tables 1 and 2 at room temperature (25 ° C). The obtained mixture and the base rubber containing a part of the EP rubber are melt mixed for 5 minutes at a temperature (185 ° C.) higher than the decomposition temperature of the organic peroxide using a 2 L Banbury mixer (manufactured by Nippon Roll Co., Ltd.). After that, the material was discharged at a discharge temperature of 130 ° C. and pelletized to obtain silane MB (step (a)). The obtained silane MB contains a silane cross-linkable EP rubber obtained by graft-reacting an EP rubber with a silane coupling agent.

  Further, the rest of the EP rubber and 0.1 part by mass of the silanol condensation catalyst were melt mixed at 150 ° C. with a Banbury mixer (manufactured by Nippon Roll Co., Ltd.) and discharged at a material discharge temperature of 130 ° C. to obtain a catalyst MB ( Step (b)).

  The silane MB obtained in the step (a) and the catalyst MB obtained in the step (b) were prepared by using an electric wire coating extruder (L / D (ratio of effective screw length L and diameter D) of 25, and screw diameter of 25 mmφ). ) Was directly blended at 25 ° C. for about 1 minute to obtain a dry blended product.

-Manufacture of electric wires-
The obtained dry blended product was put into the above-mentioned electric wire coating extrusion molding machine, and a wire having a finished outer diameter of 1.2 mmφ was formed on the outer periphery of a 0.8 mmφ conductor (soft copper wire) under the following extrusion temperature conditions. A wire precursor was manufactured by extrusion coating at a speed of 10 m / min.
Extrusion temperature conditions are divided into 3 zones C1, C2 and C3 from the feeder side to the die side in the temperature control in the cylinder part of the wire coating extrusion molding machine. C1 zone is 150 ° C, C2 zone is 170 ° C and C3 zone. Was set to 190 ° C, and the die temperature (molding temperature) was set to 200 ° C.
A silane crosslinkable rubber composition was prepared by melt-mixing the above dry blend in an electric wire coating extruder before extrusion molding. This silane-crosslinkable rubber composition contains the above-mentioned silane-crosslinkable EP rubber, the inorganic filler and the silanol condensation catalyst in the contents shown in Tables 1 and 2.
The electric wire precursor thus obtained was left in an environment of 25 ° C. and 50% RH for 24 hours to be brought into contact with water to produce an electric wire. This electric wire had, as a coating material, a silane crosslinked molded product containing silane crosslinked EP rubber obtained by crosslinking EP rubber with a silane coupling agent and an inorganic filler having the content shown in Tables 1 and 2.

-Manufacture of columnar rubber moldings-
In the production of the above electric wire, a molten strand having a diameter of about 35 mm was obtained in the same manner as in the production of the above electric wire, except that a dry blend was extruded without using a conductor. The obtained molten strand was cut into pieces each having a length of about 15 mm, and while being kept in a molten state, they were pressed into a cylindrical mold having a diameter of 29.0 mm and a thickness of 12.5 mm, and preliminarily press-molded using a press molding machine.
Then, using a press molding machine, the cylindrical mold was preheated at 150 ° C. for 10 minutes, and then the press-preformed strand was put into the preheated cylindrical mold and press molded at 150 ° C. for 3 minutes at a pressure of 4 MPa. . As a result, a cylindrical rubber molded product having a diameter of 29.0 mm and a thickness of 12.5 mm was obtained.
The cylindrical rubber molded product thus obtained was left in an environment of 25 ° C. and 50% RH for 24 hours to be brought into contact with water to produce a cylindrical rubber molded product. This columnar rubber molded article was a silane crosslinked molded article containing the silane crosslinked EP rubber obtained by crosslinking the EP rubber with a silane coupling agent and the inorganic filler in the content shown in Tables 1 and 2.

(Comparative Examples 9 and 10)
-Manufacture of electric wires-
The organic peroxide in the proportion shown in Table 2 was kneaded into 100 parts by mass of the EP rubber shown in Table 2 at 100 ° C. using an 8-inch open roll to form a pellet. The obtained pellets were extrusion-coated on the conductor using the above-described electric wire coating extrusion molding machine in the same manner as in the production of the electric wire of Example 1 to produce an electric wire precursor.
Here, in Comparative Examples 9 and 10, when molded under the same extrusion temperature conditions as in Example 1, a cross-linking reaction occurred in the extruder and extrusion molding was not possible. The appearance of the precursor was impaired. Therefore, extrusion molding was performed by setting the C1 to C3 zones of the extruder to 90 ° C and the die temperature to 100 ° C.
The obtained electric wire precursor was crosslinked by passing through a chemically crosslinked pipe having a length of 20 m, which was set in a steam environment at a temperature of 200 ° C. and a pressure of 10 MPa, to produce an electric wire.

-Manufacture of columnar rubber moldings-
In the production of the above electric wire, a molten strand having a diameter of 35 mm was obtained in the same manner as in the production of the above electric wire except that a pellet was extruded without using a conductor. Then, the molten strand was cut into a length of 15 mm, pressed in a molten state into a cylindrical mold having a diameter of 29.0 mm and a thickness of 12.5 mm, and pre-press-molded using a press molding machine.
Then, using a press molding machine, the mold was preheated at 170 ° C. for 10 minutes, and then the press-preformed strand was put into the preheated mold and press-molded at 170 ° C. for 60 minutes at a pressure of 4 MPa. As a result, a cylindrical rubber molded product having a diameter of 29.0 mm and a thickness of 12.5 mm was manufactured.

<Measurement of grafting rate>
The grafting rate of each of the obtained electric wires was confirmed as follows, and the results are shown in Tables 1 and 2.
In the present invention, the grafting rate of the grafting reaction of the silane coupling agent to the rubber was measured as follows. First, a test piece obtained by sampling a coating at an arbitrary position from each obtained electric wire was dried under a vacuum environment of 80 ° C. for 24 hours, and then, by infrared absorption spectroscopy, from an absorption peak seen near 3750 cm ^−1. The mass of the isolated silanol (unreacted silane coupling agent) was quantified. Then, the grafting rate was calculated from the obtained value and the mass (content) of the silane coupling agent actually used by the following formula.
Grafting rate (mass%) = {(mass actually used-mass of isolated silanol by infrared absorption spectroscopy) / mass actually used) × 100

  The following tests were carried out on the obtained electric wires or cylindrical rubber molded products, and the results are shown in Tables 1 and 2.

<Appearance test>
The appearance of each manufactured electric wire was visually observed and evaluated. "A" was given when the appearance of the electric wire was excellent, and "B" was given when the electric wire had so many spots that there was a problem in the appearance of the product.

<Hardness A>
Based on JIS K 6253-3: 2012, the hardness of the cylindrical rubber molded product manufactured in each example was measured using a type A durometer. Data reading was performed 15 seconds after the push needle was pushed.
The hardness was 70 or more, "A", 60 or more and less than 70, "B", 50 or more and less than 60, "C", and less than 50, "D".
In the present invention, the hardness means that the evaluation “C” is the passing level of the test of the present invention.

<Tensile strength>
A tensile test was conducted based on JIS C 3005. Using a tubular piece obtained by pulling a conductor from the obtained electric wire, the tensile strength was measured at a gauge length of 20 mm and a tensile speed of 200 mm / min, and evaluated according to the following evaluation criteria.
When the tensile strength is 10 MPa or more, it is “A”, when it is 8 MPa or more and less than 10 MPa, it is “B”, when it is 6 MPa or more and less than 8 MPa, it is “C”, and when it is less than 6 MPa, it is “D”. "
In the present invention, as for the tensile strength, the evaluation “C” is the passing level of the test of the present invention.

<Compression set>
Based on JIS K 6262 A method, the compression set was measured using the cylindrical rubber molded product manufactured in each example. Using a compression device equipped with two compression plates and a spacer (thickness is 75% of the thickness of the cylindrical rubber molded product), the cylindrical rubber molded product is compressed by 25% in the thickness direction. (Compressibility: 25%), the state was heated to 70 ° C. and kept for 22 hours. Then, the compression was released at room temperature (23 ° C.), and after cooling for 30 minutes (final temperature is 23 ° C.), the thickness of the cylindrical rubber molded product was measured.
The compression set was calculated from the thickness of the cylindrical rubber molded product before and after compression by the following formula, and evaluated by the following evaluation criteria.

Formula: CS = [(t ₀ −t ₂ ) / (t ₀ −t ₁ )] × 100

In the formula, CS: compression set (%)
t ₀ : thickness of the cylindrical rubber molded product before compression (original thickness) (mm)
t ₁ : Spacer thickness (mm)
t ₂ Thickness of the cylindrical rubber molded product after compression (thickness after 30 minutes from removal from the compression device) (mm)
When the compression set was 30% or less, it was "A", when it was more than 30% and 35% or less, it was "B", and when it was more than 35% and 40% or less, it was "C", 40. When it exceeded%, it was designated as "D".
In the present invention, the compression set has a rating “C” which is a passing level of the test of the present invention.

<Extrudability>
Extrusion moldability (high-speed moldability) of the silane crosslinkable rubber composition (each dry-blended mixture mixed) prepared in each of the above examples was evaluated,
The dry blend prepared in each example was put into an electric wire extruder having an L / D of 25 and a screw diameter of 40 mmφ (motor load limit: 80 A), and a conductor of 0.8 mmφ was produced according to the following extrusion temperature conditions. The outer circumference of the (soft copper wire) was extrusion-coated while changing the wire speed so that the finished outer diameter was 2.4 mmφ.
Extrusion temperature conditions in Examples 1 to 9, Reference Example 10 and Comparative Examples 1 to 8 were set to 150 ° C. for the C1 zone, 170 ° C. for the C2 zone and 190 ° C. for the C3 zone, and a die temperature of 200 ° C. Set to. In Comparative Examples 9 and 10, the C1 to C3 zones were set to 90 ° C and the die temperature was set to 100 ° C.
In the extrusion coating, the high-speed moldability was evaluated according to the following evaluation criteria based on the maximum production speed (maximum linear speed) at which extrusion molding was possible. Here, the maximum production speed at which extrusion molding is possible is the linear speed at which the extruded coating does not break during extrusion (so-called resin breakage) and the motor load does not exceed the above-mentioned limit value. It is assumed that
"A" when the maximum linear velocity is 150 m / min or more, "B" when it is 100 m / min or more and less than 150 m / min, and "C" when it is 50 m / min or more and less than 100 m / min. ", And when it was less than 50 m / min.
In the present invention, the high-speed moldability is that the evaluation “C” is the passing level of the test of the present invention.

<Insulation resistance (reference test)>
The electric wire (50 m) manufactured in each of the above examples was immersed in water at 20 ° C. for 1 hour and 24 hours, and the insulation resistance values ρ _V1 and ρ _V24 (MΩ · km) were measured.
The insulation resistance was measured according to the method described in JIS C 3005, and the measurement voltage, charging time and measurement time were 500 V, 10 seconds and 50 seconds, respectively.
From the measured insulation resistances ρ _V1 and ρ _V24 , the reduction rate Δρ of insulation resistance was obtained by the above calculation formula.
In this test, the insulation resistance (ρ _V1 ) after one hour of immersion is 100,000 MΩ · km or more, and the reduction rate Δρ is preferably within 50%, which is particularly preferable as a covering material for the insulated wire.

As is clear from the results shown in Tables 1 and 2, the silane-crosslinked rubber molded products (electric wires or columnar rubber molded products) produced in Examples 1 to 9 and Reference Example 10 all had hardness and tensile strength. And the compression set was excellent, and the appearance was also good. Further, in each of the examples and the reference example 10 , extrusion molding was possible at a high temperature of 200 ° C. and at a maximum linear velocity of 50 m / min or more.
In particular, it was found that Examples 1 to 9 in which dry silica was used as the inorganic filler had a large insulation resistance ρ _V1 and a small decrease rate Δρ of the insulation resistance, and exhibited excellent insulation characteristics.

In contrast, Comparative Example 1 using EP rubber having a low Mooney viscosity (ML (1 + 4) 125 ° C.) had low hardness and tensile strength. On the other hand, Comparative Example 2 using EP rubber having a high Mooney viscosity (ML (1 + 4) 125 ° C.) had insufficient extrusion moldability.
Comparative Example 3 using EP rubber having a low ethylene content had low tensile strength. Comparative Example 4 using EP rubber having a high ethylene content had a large compression set.
Comparative Example 5 with a small content of the inorganic filler had a large compression set. In Comparative Example 6 in which the content of the inorganic filler was excessive, the tensile strength was low, the compression set was large, and the extrusion moldability was poor.
In addition, the compression set was large in Comparative Example 7 and Comparative Example 7 in which the content of the silane coupling agent was small. Comparative Example 8 containing a large amount of the silane coupling agent had a poor appearance.
Comparative Example 9, which is a rubber crosslinking method other than the silane crosslinking method, was inferior in extrusion moldability, and Comparative Example 10 was inferior in tensile strength and extrusion moldability.

  As described above, the present invention provides a silane-crosslinked rubber molded article and a silane-crosslinked rubber molded article having both small compression strain, high tensile strength and high hardness, and a silane-crosslinked rubber molded article and a silane-crosslinked rubber having a good appearance. Molded articles can be manufactured. Furthermore, the present invention can produce a silane-crosslinked rubber molded article and a silane-crosslinked rubber molded article having such excellent properties, at a high temperature and a high speed, if necessary, without the need for EP rubber vulcanizing equipment, and with good productivity. can do.

Claims (8)

61-100 mass of ethylene-α olefin rubber having a Mooney viscosity (ML (1 + 4) 125 ° C.) of 15-40 and an ethylene content of 65-80 mass% measured according to JIS K 6300-1: 2013. % silane crosslinkable rubber obtained by grafting reaction of the silane coupling agent of 1 to 15 parts by weight for the base rubber 100 parts by weight in the presence of an organic peroxide 0.01 to 0.6 parts by weight, including the A silane-crosslinkable rubber composition containing 0.3 to 400 parts by mass of dry silica and 0.0001 to 0.5 parts by mass of a silanol condensation catalyst with respect to 100 parts by mass of a base rubber. The silane crosslinkable rubber composition contains 0.3 to 400 parts by mass of dry silica , 1 to 15 parts by mass of silane coupling agent, and 0.01 to 0 parts of organic peroxide with respect to 100 parts by mass of the base rubber. The silane-crosslinkable rubber composition according to claim 1, which is obtained by melt mixing 6 parts by mass and 0.0001 to 0.5 parts by mass of the silanol condensation catalyst. The silane crosslinkable rubber composition according to claim 1 or 2 , wherein the base rubber contains 1 to 30% by mass of a polypropylene resin . The silane crosslinkable rubber composition according to any one of claims 1 to 3, 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 . A silane-crosslinked rubber molding obtained by molding the silane-crosslinkable rubber composition according to any one of claims 1 to 4 and then bringing the silane-crosslinked rubber composition into contact with water. A silane-crosslinked rubber molded article containing the silane-crosslinked rubber molded article according to claim 5. 61-100 mass of ethylene-α olefin rubber having a Mooney viscosity (ML (1 + 4) 125 ° C.) of 15-40 and an ethylene content of 65-80 mass% measured according to JIS K 6300-1: 2013. % To 100 parts by mass of base rubber, 0.3 to 400 parts by mass of dry silica, 1 to 15 parts by mass of silane coupling agent, 0.01 to 0.6 parts by mass of organic peroxide, and silanol condensation. A method for producing a silane-crosslinkable rubber composition, comprising the step (1) of melt-mixing a catalyst with 0.0001 to 0.5 part by mass to obtain a silane-crosslinkable rubber composition,
The step (1) includes 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) and (b) ) And the process (c), the manufacturing method of a silane crosslinkable rubber composition.
Step (a): All or part of the base rubber, the dry silica, and the silane cap.
A pulling agent and the organic peroxide are melted at a temperature equal to or higher than the decomposition temperature of the organic peroxide.
Mixing to prepare silane masterbatch
Step (b): The rest of the base rubber and the silanol condensation catalyst are melt-mixed and touched.
Process of preparing medium masterbatch
Step (c): the silane masterbatch and the silanol condensation catalyst or the catalyst master.
Process of melt mixing with star batch A method for producing a silane-crosslinked rubber molded article, comprising the following step (1), step (2) and step (3),
Step (1): Mooney viscosity measured based on JIS K 6300-1: 2013
(ML (1 + 4) 125 ° C.) is 15-40, and ethylene content is 65-80 mass.
% 100-base rubber containing 61-100% by mass of ethylene-α-olefin rubber
0.3 to 400 parts by mass of dry silica and 1 to 15 of silane coupling agent with respect to parts by weight.
Parts by mass, 0.01 to 0.6 parts by mass of organic peroxide, and 0.000 of silanol condensation catalyst
A step of obtaining a silane crosslinkable rubber composition by melt mixing 1 to 0.5 parts by mass.
Step (2): The silane crosslinkable rubber composition obtained in the above step (1) is molded into a molded body.
Process of obtaining
Step (3): molding the silane crosslinked rubber by contacting the molded body obtained in the above step (2) with water
The process of getting a body
The step (1) includes 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) and (b) ) And a process (c), the manufacturing method of a silane crosslinked rubber molded object.
Step (a): All or part of the base rubber, the dry silica, and the silane cap.
A pulling agent and the organic peroxide are melted at a temperature equal to or higher than the decomposition temperature of the organic peroxide.
Mixing to prepare silane masterbatch
Step (b): The rest of the base rubber and the silanol condensation catalyst are melt-mixed and touched.
Process of preparing medium masterbatch
Step (c): the silane masterbatch and the silanol condensation catalyst or the catalyst master.
Process of melt mixing with star batch