JP2022152948A - Silane-crosslinked rubber molding and method for manufacturing the same, silane-crosslinkable rubber composition, and silane-crosslinked rubber molded article - Google Patents

Abstract

To provide a manufacturing method in which a silane-crosslinked rubber molding having excellent appearance characteristics and reduced permanent compression set can be obtained by injection molding, a silane-crosslinked rubber molding obtained by the manufacturing method and a silane-crosslinked rubber molded article, and a silane-crosslinkable rubber composition that is suitable for forming the silane-crosslinked rubber molding.SOLUTION: Provided are a method for manufacturing silane-crosslinked rubber molding by silane crosslinking method that comprises a step of melt-mixing an organic peroxide by 0.01 to 0.6 pts.mass, an inorganic filler by 1 to 100 pts.mass, a silane coupling agent by 1 to 15 pts.mass, and a silanol condensation catalyst for 100 pts.mass of a base rubber containing an ethylene-α-olefin copolymer rubber having a diene component amount of 4.5 to 10 mass% by 5 to 35 mass%, an ethylene-α-olefin copolymer rubber having a diene component amount of 1.0 mass% or less by 5 to 50 mass%, an ethylene resin by 12 mass% or less, a propylene resin by 5 to 15 mass%, a styrene elastomer by 10 to 35 mass%, and a mineral oil by 20 to 40 mass%, a silane-crosslinked rubber molding and molded article manufactured using the same, and a silane-crosslinkable rubber composition that is used therefor.SELECTED DRAWING: None

Description

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

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, gaskets, anti-vibration rubber) have permanent compression set. Being small is one of the required characteristics.
Conventionally, crosslinked EP rubber obtained by vulcanizing (crosslinking) ethylene-propylene rubber (EP rubber) has been used for products used in applications requiring a small compression set. For example, Patent Literatures 1 to 3 disclose a method for producing a silane-crosslinked molded article by a silane-crosslinking method using a crosslinked EP rubber. In this case, the silane crosslinking method is obtained by grafting a hydrolyzable silane coupling agent having an unsaturated group to rubber in the presence of an organic peroxide to obtain a silane graft polymer, and then in the presence of a silanol condensation catalyst. is a method of cross-linking rubber by bringing the silane graft polymer into contact with moisture.

Patent No. 6706870 WO2015/046476 JP 2015-86385 A

Extrusion molding, injection molding, and the like are known as molding methods for producing crosslinked EP rubber. Injection molding has an advantage over extrusion molding in that it can be molded into complicated shapes.
In general, both the extrusion molding method and the injection molding method include a step of melt-mixing molding materials and molding, for example, a step of melt-mixing molding materials in a cylinder of a molding machine and molding. Assuming the silane cross-linking method, as the residence time in the cylinder increases in the manufacturing process, the heat of the cylinder partially causes the condensation reaction between the existing silane coupling agents and the silanol condensation reaction of the silane graft polymer. In some cases, gel spots and roughening may occur on the surface of the resulting molded product.
Among others, when producing crosslinked EP rubber, the injection molding method is more likely to cause defects in appearance characteristics such as gel spots, roughness, and flow marks (rubber composition flow traces) than the extrusion molding method. In the case of injection molding processes, intermittent retention of molding material in the cylinder occurs more frequently. In addition, there are many opportunities to stop the molding machine, such as when replacing the mold, and the retention time of the molding material in the cylinder tends to be longer. In addition, it is assumed that the work may be temporarily suspended during mass production. In that case, the residence time may be as long as one hour. Due to such intermittent retention and long-term retention, the above gel lumps and roughness are likely to occur in the case of the injection molding method. This retention in the cylinder becomes more pronounced when using a large injection molding machine. Furthermore, in the case of the injection molding method, the molding material may adhere to the walls inside the mold or inside the cylinder, etc., causing gel spots or flow marks on the surface of the molded product.
The production methods described in Patent Documents 1 to 3 are excellent in extrusion moldability, but are not suitable for injection molding of rubber moldings.

The present invention provides a production method for obtaining a silane-crosslinked rubber molded article having excellent appearance properties and reduced compression set by injection molding, a silane-crosslinked rubber molded article obtained by this production method, and a silane-crosslinked rubber. An object is to provide a molded product.
Another object of the present invention is to provide a silane-crosslinkable rubber composition suitable for producing the silane-crosslinked rubber molded article.

The present inventors have found that, in a method for producing a silane-crosslinked rubber molding by injection molding using a silane-crosslinking method, two types of ethylene-α-olefin copolymer rubbers having different amounts of diene components are used as base rubbers. When a silane-crosslinked rubber molded article is produced by using a propylene resin, a styrene elastomer, and a mineral oil together in specific amounts, the obtained silane-crosslinked rubber molded article can achieve excellent appearance characteristics and a reduction in compression set. Found it. Based on this knowledge, the present inventors have made further studies and completed the present invention.

That is, the objects of the present invention have been achieved by the following means.
[1]
A method for producing a silane-crosslinked rubber molding comprising the following steps (1), (2) and (3),
Step (1): In the presence of 0.01 to 0.6 parts by mass of an organic peroxide, 1 to 100 parts by mass of an inorganic filler, and radicals generated from the organic peroxide with respect to 100 parts by mass of the base rubber. 1 to 15 parts by mass of a silane coupling agent having a grafting reaction site capable of undergoing a grafting reaction with the base rubber and a silanol condensation catalyst are melt-mixed, and the grafting is performed by radicals generated from the organic peroxide. A step of obtaining a silane-crosslinkable rubber composition containing a silane-crosslinkable rubber by causing a grafting reaction between the reaction site and the graftable site of the base rubber. Step (2): The silane-crosslinkable rubber composition is Step (3): Contacting the molded article with water to obtain a silane-crosslinked rubber molded article The base rubber contains ethylene having a diene content of 4.5 to 10% by mass. - 5 to 35% by mass of α-olefin copolymer rubber, 5 to 50% by mass of ethylene-α-olefin copolymer rubber having a diene content of 1.0% by mass or less, 12% by mass or less of ethylene resin, 5 to 5% by mass of propylene resin 15% by weight, 10-35% by weight of styrene elastomer, and 20-40% by weight of mineral oil,
In performing the step (1),
When all of the base rubber is melt-mixed in the following step (a-2), the step (1) has the following steps (a-1), (a-2) and (c), and the following steps When part of the base rubber is melt-mixed in (a-2), step (1) has the following steps (a-1), (a-2), (b) and (c). and a method for producing a silane-crosslinked rubber molding.
Step (a-1): Step of mixing the inorganic filler and the silane coupling agent to prepare a mixture Step (a-2): The mixture and all or part of the base rubber are treated with the organic peroxide The graft reaction site and the graft reaction-capable site of the base rubber are separated by the radicals generated from the organic peroxide by melt-mixing in the presence of a substance at a temperature equal to or higher than the decomposition temperature of the organic peroxide. preparing a silane masterbatch containing a silane crosslinkable rubber by a grafting reaction step (b): melt-mixing the remainder of the base rubber and the silanol condensation catalyst to prepare a catalyst masterbatch; (c): A step of melt-mixing the silane masterbatch and the silanol condensation catalyst or the catalyst masterbatch to obtain the silane crosslinkable rubber composition.
[2]
The method for producing a silane-crosslinked rubber molding according to [1], wherein 10 to 60 parts by mass of the inorganic filler is blended with 100 parts by mass of the base rubber.
[3]
The method for producing a silane-crosslinked rubber molding according to [1] or [2], wherein the silanol condensation catalyst is blended in an amount of 0.03 to 0.5 parts by mass with respect to 100 parts by mass of the base rubber.
[4]
The method for producing a silane-crosslinkable rubber molding according to any one of [1] to [3], wherein the inorganic filler is metal hydrate, talc, clay, silica, carbon black, or a mixture thereof. .
[5]
In the step (1), 10 to 60 parts by mass of the inorganic filler, 1 to 15 parts by mass of the silane coupling agent, and 0.01 to 0.01 part by mass of the organic peroxide are added to 100 parts by mass of the base rubber. The method for producing a silane-crosslinked rubber molding according to any one of [1] to [4], wherein 6 parts by mass and 0.03 to 0.5 parts by mass of the silanol condensation catalyst are melt-mixed.
[6]
A silane-crosslinkable rubber composition produced by the step (1) of the production method according to any one of [1] to [5].
[7]
A silane-crosslinked rubber molded article produced by the method for producing a silane-crosslinked rubber molded article according to any one of [1] to [5].
[8]
A silane-crosslinked rubber molded article comprising the silane-crosslinked rubber molded article according to [7].

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

The present invention provides a production method for obtaining a silane-crosslinked rubber molded article having excellent appearance properties and reduced compression set by injection molding, a silane-crosslinked rubber molded article obtained by this production method, and a silane-crosslinked rubber. We can provide molded products. Moreover, it is possible to provide a silane-crosslinkable rubber composition suitable for producing a silane-crosslinked rubber molded article exhibiting such excellent properties.

The method for producing the silane-crosslinked rubber molding of the present invention will be described below.

First, each component used in the present invention will be explained.

<Base rubber>
The base rubber used in the present invention includes ethylene-α-olefin copolymer rubber having a diene content of 4.5 to 10% by mass, ethylene-α-olefin copolymer rubber having a diene content of 1.0% by mass or less, Contains propylene resin, styrene elastomer, and mineral oil. The base rubber may further contain an ethylene resin as an optional component. Any of these components, in the presence of a radical generated from an organic peroxide, a graft reaction site of the silane coupling agent and a site that can undergo a graft reaction, such as an unsaturated bond site of a carbon chain, a hydrogen atom in the main chain or at the end thereof.
The base rubber may contain rubbers or resins other than those described above as long as the properties are not impaired. Such a rubber or resin component includes a grafting reaction site of a silane coupling agent and a site capable of grafting reaction in the presence of an organic peroxide, such as an unsaturated bond site of a carbon chain or a carbon having a hydrogen bond. There is no particular limitation as long as it is a polymer resin or rubber having atoms in the main chain or at the end thereof.

- Ethylene-α-olefin copolymer rubber -
Ethylene-α-olefin copolymer rubber is a copolymer rubber of ethylene, α-olefin and diene.
The present invention uses, as an ethylene-α-olefin copolymer rubber, two types of ethylene-α-olefins having different amounts of diene components in the copolymer rubber (meaning the content of diene components constituting the copolymer rubber). Copolymer rubber is used. One is an ethylene-α-olefin copolymer rubber having a diene content of 4.5 to 10% by mass, and the other is an ethylene-α-olefin copolymer having a diene content of 1.0% by mass or less. is rubber. When the diene content is 0% by mass, the ethylene-α-olefin copolymer rubber is a copolymer rubber of ethylene and α-olefin.
The diene content of the ethylene-α-olefin copolymer rubber having a diene content of 4.5 to 10% by mass is preferably 4.6 to 9% by mass, more preferably 4.8 to 8% by mass.
The diene content of the ethylene-α-olefin copolymer rubber having a diene content of 1.0% by mass or less is preferably 0.9% by mass or less, more preferably 0.7% by mass or less.
The amount of diene component can be measured, for example, by infrared absorption spectroscopy (FT-IR), proton NMR ( ¹ H-NMR) method, or the like.
A diene content (D1) of an ethylene-α-olefin copolymer rubber having a diene content of 4.5 to 10% by mass and a diene of an ethylene-α-olefin copolymer rubber having a diene content of 1.0% by mass or less The difference (D1-D2) from the component amount (D2) is preferably 3 to 10% by mass, more preferably 4 to 8.5% by mass.

The ethylene content of the ethylene-α-olefin copolymer rubber having a diene content of 4.5 to 10% by mass (meaning the content of the ethylene component constituting the copolymer rubber) is not particularly limited, but is 50 to 80 mass. % is preferable, and 55 to 75% by mass is more preferable.
The ethylene content of the ethylene-α-olefin copolymer rubber having a diene content of 1.0% by mass or less is not particularly limited, but is preferably 50 to 80% by mass, more preferably 55 to 75% by mass.
The amount of ethylene component is a value measured according to the method described in ASTM D3900.

The Mooney viscosity of the ethylene-α-olefin copolymer rubber having a diene content of 4.5 to 10% by mass is not particularly limited, but is preferably 10 to 100 (ML1+4 (125° C.)), preferably 15 to 90 (ML1+4 (125° C.)) is more preferred, and 20 to 80 (ML1+4 (125° C.)) is even more preferred.
The Mooney viscosity of the ethylene-α-olefin copolymer rubber having a diene content of 1.0% by mass or less is not particularly limited, but is preferably 10 to 100 (ML1+4 (125° C.)), preferably 15 to 90 (ML1+4 ( 125° C.)) is more preferred, and 20 to 80 (ML1+4 (125° C.)) is even more preferred.
Mooney viscosity is measured based on the measurement method specified in JIS K 6300-1:2013. The test is performed as follows. As a test piece to be used, a set of two test samples having a diameter of about 50 mm and a thickness of about 6 mm is 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 the constant conditions of preheating time of 1 minute, rotor rotation time of 4 minutes, and test temperature of 125° C. The torque received by the rotor due to the resistance of the rubber at this time is measured as the Mooney viscosity of the rubber in Mooney units.

The ethylene-α-olefin copolymer rubber having a diene content of 4.5 to 10% by mass and the ethylene-α-olefin copolymer rubber having a diene content of 1.0% by mass or less are ethylene-α-olefin Copolymer rubbers each having a diene content within the above range can be used.
Examples of ethylene-α-olefin copolymer rubbers include rubbers composed of ethylene-α-olefin copolymers, and rubbers composed of binary copolymers of ethylene and α-olefins; ethylene, α-olefins and dienes; A rubber composed of a terpolymer with The diene of the terpolymer may be a conjugated diene or a non-conjugated diene, preferably a non-conjugated diene. That is, the terpolymer includes a terpolymer of ethylene, an α-olefin and a conjugated diene, a terpolymer of ethylene, an α-olefin and a non-conjugated diene, and the like. Binary copolymers of ethylene and α-olefins and terpolymers of ethylene, α-olefins and non-conjugated dienes are preferred.
Conjugated dienes include, for example, butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, etc., butadiene is preferred. Non-conjugated dienes include, for example, dicyclopentadiene (DCPD), ethylidenenorbornene (ENB), 1,4-hexadiene, etc. Ethylidenenorbornene is preferred. Each component of the conjugated diene compound and the non-conjugated diene can be used alone or in combination of two or more.
As α-olefins, α-olefins having 3 to 12 carbon atoms are preferably mentioned. The α-olefin is not particularly limited, and examples thereof include propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene and 1-dodecene.

Examples of rubbers composed of binary copolymers of ethylene and α-olefin include ethylene-propylene rubber, ethylene-butene rubber, ethylene-octene rubber and the like. Examples of rubbers composed of terpolymers of ethylene, α-olefins and dienes include ethylene-propylene-diene rubbers and ethylene-butene-diene rubbers. Among them, ethylene-propylene rubber, ethylene-butene rubber, ethylene-propylene-diene rubber and ethylene-butene-diene rubber are preferred, ethylene-propylene rubber and ethylene-propylene-diene rubber are more preferred, ethylene-propylene rubber or ethylene-propylene-ethylidene norbornene Rubber is particularly preferred.

- Propylene resin -
The propylene resin (PP resin) may be a resin whose main component is a polymer containing propylene, and resins such as propylene homopolymers, ethylene-propylene random copolymers, and ethylene-propylene block copolymers may be used. can be used.
The ethylene-propylene random copolymer is one in which the ethylene component content is about 1 to 10% by mass in the constituent components, and the ethylene component is randomly incorporated into the propylene chain. Further, the ethylene-propylene block copolymer refers to one having an ethylene or ethylene-propylene rubber (EPR) component content of about 5 to 20% by mass, and the ethylene and EPR components exist independently in the propylene component. It is a sea-island structure. A particularly preferred propylene resin is an ethylene-propylene random copolymer resin in terms of appearance. The ethylene component content is a value measured according to the method described in ASTM D3900.
The propylene resin may be used alone or in combination of two or more.

- Styrene elastomer -
The styrene elastomer used in the present invention is a copolymer block of constituent components derived from an aromatic vinyl compound and a conjugated diene compound, and/or a block copolymer or random block copolymer mainly composed of constituent components derived from the above compounds. It is a hydrogenated copolymer.
As the aromatic vinyl compound, for example, one or more of styrene, α-methylstyrene, vinyltoluene, p-tert-butylstyrene and the like can be selected, with styrene being preferred. As the conjugated diene compound, for example, one or more of butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, etc. can be selected. is preferred.
As styrene elastomers, it is possible to use binary or ternary copolymers composed of polystyrene blocks and elastomeric blocks of polyolefin structure.
The hydrogenated product of the above copolymer (hereinafter sometimes referred to as a hydrogenated copolymer) preferably contains 5 to 70% by mass, more preferably 10 to 60% by mass, of a constituent component derived from an aromatic vinyl compound. . This content is obtained by measuring the UV absorption spectrum, for example, with an ultraviolet spectrophotometer using a chloroform solution.
Styrene elastomers include, for example, SBS (styrene-butadiene-styrene block copolymer), SIS (styrene-isoprene-styrene block copolymer), SEBS (styrene-ethylene-butylene-styrene block copolymer: hydrogenated SBS), SEEPS (styrene- ethylene-ethylene-propylene-styrene block copolymer), SEPS (styrene-ethylene-propylene-styrene block copolymer: hydrogenated SIS), HSBR (hydrogenated styrene-butadiene random copolymer), and the like. One or two or more styrene elastomers may be used.
Examples of styrene elastomers include "Septon" (trade name, manufactured by Kuraray Co., Ltd.), "Tuftec" (trade name, manufactured by Asahi Kasei Chemicals Corp.), and "Dynaron" (trade name, manufactured by JSR Corporation).
The styrene elastomer preferably has a melt flow rate of less than 0.1 g/10 min at 190° C. and 2.16 kg. Here, the melt flow rate (hereinafter sometimes referred to as MFR) is a value measured in accordance with JIS K 7210 under conditions of a temperature of 190° C. and a load of 2.16 kg, unless otherwise specified. Say. The present invention has an embodiment in which the base rubber contains a styrene elastomer consisting of a styrene elastomer with an MFR of less than 0.1 g/10 min, and an embodiment in which the base rubber contains a styrene elastomer with an MFR of less than 0.1 g/10 min and other styrene elastomers.

- mineral oil -
The mineral oil used in the present invention is a mixed oil containing three of an oil having an aromatic ring, an oil having a naphthenic ring and an oil having a paraffin chain. Paraffin oil means that the carbon number (CP) of the paraffin chain is, for example, 50% or more and less than 75% of the total carbon number of the aromatic ring, naphthenic ring and paraffin chain, and the naphthenic chain carbon number (CN) is 20. 40% or more, and the number of carbon atoms in the aromatic ring (CA) is 3 or more and less than 10%. Naphthenic oil refers to those having CN of 40 to 60%, CP of 30% to 50%, and CA of 8% to 16%, based on the total number of carbon atoms. % or more.
Paraffin oil or naphthenic oil can be used as the mineral oil (rubber softener), and paraffin oil is preferred in terms of mechanical strength.
The paraffin oil preferably has a dynamic viscosity of 20 to 500 cSt at 40°C, a pour point of -10 to -15°C, and a flash point (COC) of 180 to 300°C.
Examples of mineral oils include "Diana Process Oil" (trade name, manufactured by Idemitsu Kosan Co., Ltd.), "Cosmo Neutral" (trade name, manufactured by Cosmo Oil Lubricants), and the like.

- Ethylene resin -
Ethylene resin is not particularly limited as long as it is a resin (excluding PP resin) composed of a polymer obtained by polymerizing or copolymerizing a compound having an ethylenically unsaturated bond. You can use what is used. Examples thereof include resins composed of polymers such as polyethylene, ethylene-α-olefin copolymers, and polyolefin copolymers having an acid copolymerization component or an acid ester copolymerization component. Among them, polyethylene resins and polyolefin copolymer resins having an acid copolymerization component or an acid ester copolymerization component are preferred.
The polyethylene resin may be a polymer resin containing an ethylene component, and may be a homopolymer consisting only of ethylene, or a copolymer of ethylene and α-olefin (preferably 5 mol % or less) (which corresponds to polypropylene). ), and resins composed of copolymers of ethylene and non-olefins (preferably 1 mol % or less) having only carbon, oxygen and hydrogen atoms in functional groups. As the α-olefins and non-olefins mentioned above, known ones conventionally used as copolymerization components of polyethylene can be used without particular limitation.
Examples of polyethylene resins include LDPE (low density polyethylene), LLDPE (linear low density polyethylene), MDPE (medium density polyethylene), and the like. The LLDPE may be LLDPE (Linear Low Density Polyethylene) synthesized in the presence of a metallocene catalyst. These polyethylenes may be used singly or in combination of two or more. Among these polyethylenes, it is preferable to use LLDPE synthesized in the presence of a metallocene catalyst.
Examples of ethylene-α-olefin copolymer resins include copolymer resins of ethylene and α-olefins having 4 to 12 carbon atoms. Examples of α-olefins include 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene and the like. These ethylene-α-olefin copolymer resins may be used singly or in combination of two or more.
The acid copolymerization component or the acid ester copolymerization component in the polyolefin copolymer resin having the acid copolymerization component or the acid ester copolymerization component is not particularly limited, but includes carboxylic acid compounds such as (meth)acrylic acid, vinyl acetate, Alternatively, acid ester compounds such as alkyl (meth)acrylates (preferably those having an alkyl group of 1 to 12 carbon atoms) can be mentioned. Polyolefin copolymer resins having an acid copolymer component or an acid ester copolymer component include, for example, ethylene-vinyl acetate copolymer (EVA), ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acryl Resins such as acid alkyl copolymers (preferably ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-butyl acrylate copolymer) can be mentioned.
The ethylene resin is preferably an ethylene-α-olefin copolymer resin, an ethylene-vinyl acetate copolymer resin, or a mixture thereof.
Examples of commercially available polyethylene resins and ethylene-α-olefin copolymer resins that can be used in the base rubber of the present invention include "Evolue" (trade name: manufactured by Prime Polymer Co., Ltd.). can be mentioned.

The ethylene resin may be acid-modified. The acid used for acid modification is not particularly limited, and commonly used unsaturated carboxylic acids and the like can be mentioned.

- Content in base rubber -
In the base rubber, the content of each component is preferably determined within the following range so that the total of each component is 100% by mass.
The content of the ethylene-α-olefin copolymer rubber having a diene content of 4.5 to 10% by mass is 5 to 35% by mass in 100% by mass of the base rubber. If this content is too high, it may not be possible to impart appearance properties when the residence time is long. On the other hand, if the content is too low, the compression set may not be sufficiently reduced.
The content of the ethylene-α-olefin copolymer rubber having a diene content of 4.5 to 10% by mass in the base rubber is preferably 7 to 32% by mass, more preferably 10 to 30% by mass, based on 100% by mass of the base rubber. is more preferred. Within this range, excellent appearance characteristics and reduction in compression set can be achieved in a well-balanced manner.

The content of the ethylene-α-olefin copolymer rubber having a diene content of 1.0% by mass or less is 5 to 50% by mass in 100% by mass of the base rubber. If this content is too high, the compression set may not be sufficiently reduced. On the other hand, if the content is too low, it may not be possible to impart excellent appearance properties when the residence time is long.
The content of the ethylene-α-olefin copolymer rubber having a diene content of 1.0% by mass or less in the base rubber is preferably 7 to 45% by mass, more preferably 10 to 35% by mass, based on 100% by mass of the base rubber. more preferred. Within this range, excellent appearance characteristics and reduction in compression set can be achieved in a well-balanced manner.

The content of the propylene resin is 5 to 15% by mass, preferably 7 to 13% by mass, more preferably 8 to 12% by mass, based on 100% by mass of the base rubber. Within this range, excellent appearance characteristics and reduction in compression set can be achieved in a well-balanced manner.

The content of the styrene elastomer is 10 to 35% by mass, preferably 12 to 32% by mass, more preferably 15 to 30% by mass, based on 100% by mass of the base rubber. Within this range, excellent appearance characteristics and reduction in compression set can be achieved in a well-balanced manner.

The mineral oil content is 20 to 40% by mass, preferably 23 to 38% by mass, more preferably 25 to 35% by mass, based on 100% by mass of the base rubber. Within this range, excellent appearance characteristics and reduction in compression set can be achieved in a well-balanced manner.

The ethylene resin content is 12% by mass or less, preferably 1 to 10% by mass, more preferably 3 to 8% by mass, based on 100% by mass of the base rubber. Within this range, excellent appearance characteristics and reduction in compression set can be achieved in a well-balanced manner.

The ratio of the styrene elastomer content to the mineral oil content (styrene elastomer content:mineral oil content) is 1:2.5 to 1:0.5 by mass, and 1:2 to 1:2. 1:0.8 is more preferred. Within this range, excellent appearance characteristics and reduction in compression set can be achieved in a well-balanced manner.

<Organic Peroxide>
The organic peroxide generates radicals by at least thermal decomposition, and serves as a catalyst for the grafting reaction of the silane coupling agent to the rubber component due to the radical reaction (grafting reaction site of the silane coupling agent and grafting of the rubber component). It is a covalent bond-forming reaction with a reactive site, which is also called a (radical) addition reaction.). In particular, when the silane coupling agent contains an ethylenically unsaturated group as a grafting reaction site, the grafting reaction is caused by a radical reaction between the ethylenically unsaturated group and the rubber component (including a hydrogen radical abstraction reaction from the rubber component). act to give rise to
^{The organic peroxide} is not particularly limited as long as it ^{generates radicals} . Compounds represented by (=O)-OO(C=O)R ⁶ are preferred. 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 of them are alkyl groups, or that one of them is an alkyl group and the rest are acyl groups.

Such organic peroxides include organic peroxides described in paragraph [0037] of WO 2015/046478, which description is hereby referred to and the contents of which are described herein. Take as part. In terms of odor, coloring and scorch stability, dicumyl peroxide, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di -(tert-butylperoxy)hexyne-3 is preferred.

The decomposition temperature of the organic peroxide is preferably 120-195°C, particularly preferably 125-180°C. The decomposition temperature of the organic peroxide is equal to or lower than the melt-mixing temperature in step (a-2) described later.
In the present invention, the decomposition temperature of an organic peroxide refers to the temperature at which an organic peroxide of a single composition, when heated, causes itself to decompose into two or more compounds within a certain temperature or temperature range. means. Specifically, it refers to the temperature at which heat absorption or heat generation starts when heated from room temperature at a heating rate of 5° C./min in a nitrogen gas atmosphere by thermal analysis such as DSC method.

<Inorganic filler>
In the present invention, the inorganic filler is used without particular limitation as long as it has, on its surface, a site capable of forming a hydrogen bond with a reactive site such as a silanol group of a silane coupling agent or a site capable of chemically bonding with a covalent bond. be able to. In this inorganic filler, the sites that can be chemically bonded to the reaction sites of the silane coupling agent include OH groups (hydroxyl groups, water molecules of water containing water or water of crystallization, OH groups such as carboxyl groups), amino groups, SH groups, and the like. be done.

Examples of inorganic fillers include aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, calcium silicate, magnesium silicate, calcium oxide, magnesium oxide, aluminum oxide, aluminum nitride, aluminum borate whiskers, and hydrated aluminum silicate. , hydrated magnesium silicate, basic magnesium carbonate, metal hydrates such as compounds having a hydroxyl group or water of crystallization such as hydrotalcite, boron nitride, silica (crystalline silica, amorphous silica, etc.), Carbon black, clay, zinc oxide, tin oxide, titanium oxide, molybdenum oxide, antimony trioxide, silicone compounds, quartz, talc, zinc borate, white carbon, zinc borate, zinc hydroxystannate, zinc stannate can be used. can. An inorganic filler may be mix|blended individually by 1 type, and may use 2 or more types together.
Among these, the inorganic filler is preferably metal hydrate (more preferably magnesium hydroxide), talc, clay, silica, carbon black, or a mixture thereof.

The average particle size of the inorganic filler is preferably 0.2-10 μm, more preferably 0.3-8 μm, even more preferably 0.4-5 μm, and particularly preferably 0.4-3 μm. The average particle size is obtained by dispersing the inorganic filler in alcohol or water and using an optical particle size measuring device such as a laser diffraction/scattering particle size distribution measuring device.

An inorganic filler surface-treated with a silane coupling agent or the like can be used as the inorganic filler. Examples of silane coupling agent surface-treated metal hydrates include KISUMA 5L and KISUMA 5P (both are trade names of magnesium hydroxide manufactured by Kyowa Kagaku Co., Ltd.). The surface treatment amount of the inorganic filler with the silane coupling agent is not particularly limited, but is, for example, 3% by mass or less.

<Silane coupling agent>
The silane coupling agent has a grafting reaction site (group or atom) capable of grafting to a graftable site of the base rubber in the presence of radicals generated by decomposition of the organic peroxide. there is In addition, it has a hydrolyzable silyl group as a site capable of silanol condensation by reacting with a chemically bonding site of the inorganic filler. Examples of such a silane coupling agent include silane coupling agents used in conventional silane cross-linking methods.
Silane coupling agents include silane coupling agents having an unsaturated group, specifically vinyltrimethoxysilane, vinyltriethoxysilane, vinyltributoxysilane, vinyldimethoxyethoxysilane, vinyldimethoxybutoxysilane, vinylalkoxysilanes such as vinyldiethoxybutoxysilane, allyltrimethoxysilane, allyltriethoxysilane and vinyltriacetoxysilane; ) acryloxyalkoxysilane and the like. Among them, vinyltrimethoxysilane or vinyltriethoxysilane is particularly preferred.
One type or two or more types of silane coupling agents may be used.
The silane coupling agent may be used as it is or diluted with a solvent.

<Silanol condensation catalyst>
The silanol condensation catalyst functions to cause (promote) the condensation reaction of the hydrolyzable silyl groups of the silane coupling agent grafted onto the base rubber in the presence of moisture. Based on the action of this silanol condensation catalyst, the base rubbers are crosslinked via the silane coupling agent.
Such silanol condensation catalysts are not particularly limited, and examples thereof include organotin compounds, metallic soaps, platinum compounds and the like. Examples of organic tin compounds include organic tin compounds such as dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin dioctiate, and dibutyltin diacetate.
One type or two or more types of silanol condensation catalysts may be used.

<Additive>
In the present invention, various additives commonly used in electric wires, electric cables, electric cords, automobile members, OA equipment, building members, miscellaneous goods, sheets, foams, tubes, pipes, etc. You may mix|blend suitably in the range which does not impair the effect which carries out. Examples of such additives include cross-linking aids, antioxidants, lubricants, metal deactivators, flame retardants (auxiliaries), and other resins.

A cross-linking aid refers to a compound that forms a partially cross-linked structure with a rubber component in the presence of an organic peroxide. Examples thereof include polyfunctional compounds.
Antioxidants are not particularly limited, but include, for example, amine antioxidants, phenol antioxidants, sulfur antioxidants, and the like.
Lubricants include hydrocarbons, siloxanes, fatty acids, fatty acid amides, esters, alcohols, metal soaps and the like.
Flame retardants include, but are not limited to, red phosphorus.

<Manufacturing method of silane-crosslinked rubber molding>
The method for producing the silane-crosslinked rubber molding of the present invention will be specifically described below.
The method for producing a silane-crosslinked rubber molded article of the present invention comprises the following steps (1), (2), and (3).
The silane-crosslinkable rubber composition of the present invention is produced by the following step (1).

Step (1): With respect to 100 parts by mass of base rubber, 0.01 to 0.6 parts by mass of organic peroxide, 1 to 100 parts by mass of inorganic filler, and in the presence of radicals generated from the organic peroxide 1 to 15 parts by mass of a silane coupling agent having a grafting reaction site capable of undergoing a grafting reaction with the base rubber and a silanol condensation catalyst are melt-mixed, and the grafting reaction site and the base are formed by radicals generated from the organic peroxide. A step of obtaining a silane-crosslinkable rubber composition containing a silane-crosslinkable rubber by causing a grafting reaction with a graftable site of rubber Step (2): Injection molding the silane-crosslinkable rubber composition into a mold Step of obtaining a body Step (3): A step of contacting the molded body with water to obtain a silane-crosslinked rubber molded body

The step (1) has the following steps depending on the mode of use of the base rubber.
When all of the base rubber is melt-mixed in the following step (a-2), the step (1) has the following steps (a-1), (a-2) and (c), and the following steps When part of the base rubber is melt-mixed in (a-2), step (1) has the following steps (a-1), (a-2), (b) and (c). .
Step (a-1): Step of mixing an inorganic filler and a silane coupling agent to prepare a mixture Step (a-2): Mixing the mixture and all or part of the base rubber in the presence of an organic peroxide Silane cross-linking is performed by melt-mixing at a temperature equal to or higher than the decomposition temperature of the organic peroxide, and causing a graft reaction between the graft reaction site and the graft-reactive site of the base rubber by radicals generated from the organic peroxide. Step (b): Melt-blending the rest of the base rubber and a silanol condensation catalyst to prepare a catalyst masterbatch and Step (c): Silane masterbatch and silanol condensation. A step of melt-mixing a catalyst or a catalyst masterbatch to obtain a silane-crosslinkable rubber composition.
Hereinafter, both steps (a-1) and (a-2) may be collectively referred to as step (a).

In the production method of the present invention, the "base rubber" is a rubber for forming a silane-crosslinked rubber molded article or a silane-crosslinkable rubber composition. Therefore, in the production method of the present invention, the reaction composition obtained in step (1) should contain 100 parts by mass of the base rubber. For example, in step (a-2), it includes "a mode in which the entire amount (100 parts by mass) of the base rubber is blended" and "a mode in which a part of the base rubber is blended".

When part of the base rubber is blended in step (a-2), the blending amount of 100 parts by mass of the base rubber in step (1) is equivalent to the base rubber mixed in steps (a-2) and (b). total amount.
Here, when the remainder of the base rubber (sometimes referred to as carrier) is blended in step (b), the base rubber is preferably 80 to 95% by mass, more preferably 85 to 95% by mass, in step (a-2). 92% by mass is blended, and in step (b), preferably 5 to 20% by mass, more preferably 8 to 15% by mass.

In the step (1), an ethylene-α-olefin copolymer rubber having a diene content of 4.5 to 10% by mass and an ethylene-α-olefin copolymer having a diene content of 1.0% by mass or less in the base rubber. Contents of rubber, ethylene resin, propylene resin, styrene elastomer, and mineral oil are as described above.
The ethylene-α-olefin copolymer rubber may be mixed in either step (a-2) or step (b), but is preferably mixed in step (a-2). . More preferably, in step (a-2), an ethylene-α-olefin copolymer rubber having a diene content of at least 4.5 to 10% by mass is mixed, and in step (a-2), the diene component It is preferable to mix an ethylene-α-olefin copolymer rubber with an amount of 4.5 to 10% by mass and an ethylene-α-olefin copolymer rubber with a diene content of 1.0% by mass or less. If these two types of ethylene-α-olefin copolymer rubbers are mixed in step (a-2), part of them may be mixed in step (b).
The ethylene resin may be mixed in either step (a-2) or step (b), but is preferably mixed in step (b).
The propylene resin may be mixed in either step (a-2) or step (b), but is preferably mixed in step (a-2).
Mineral oil may be mixed in either step (a-2) or step (b), but is preferably mixed in both step (a-2) and step (b). .
As the carrier, the rubber and/or resin components described for the base rubber can be used. As the carrier, ethylene-α-olefin copolymer rubber, propylene resin, styrene elastomer, mineral oil and ethylene resin are preferable, and styrene elastomer, mineral oil and ethylene resin are more preferable. LLDPE is preferred as the ethylene resin.

In step (1), the amount of the organic peroxide compounded is 0.01 to 0.6 parts by mass, preferably 0.01 to 0.5 parts by mass, and 0.01 to 0.6 parts by mass, preferably 0.01 to 0.5 parts by mass, based on 100 parts by mass of the base rubber. 05 to 0.2 parts by mass is more preferable. By setting the amount of the organic peroxide to be 0.01 to 0.6 parts by mass, the grafting reaction can be performed in an appropriate range, suppressing condensation between the silane coupling agents, and forming the molded product. It is possible to suppress deterioration of the appearance due to gel bumps and roughness.

In the step (1), the amount of the inorganic filler compounded is 1 to 100 parts by mass, preferably 10 to 60 parts by mass, more preferably 15 to 50 parts by mass, and 18 to 45 parts by mass with respect to 100 parts by mass of the base rubber. Parts by mass are more preferred. By setting the amount of the inorganic filler to be 1 to 100 parts by mass, it is possible to achieve excellent appearance characteristics and reduction in compression set.

In step (1), the amount of the silane coupling agent compounded is 1 to 15 parts by mass, preferably 1.5 to 7 parts by mass, more preferably 2 to 5 parts by mass with respect to 100 parts by mass of the base rubber. part by mass.
When the amount of the silane coupling agent is 1 to 15 parts by mass, the silane coupling agent is adsorbed on the surface of the inorganic filler, and volatilization of the silane coupling agent during kneading can be suppressed, which is economical. be. Moreover, it is possible to suppress the deterioration of the external appearance due to the condensation of the non-adsorbed silane coupling agent and the occurrence of gel spots and roughness in the molded article. Furthermore, if necessary, the compression set can be reduced by allowing the cross-linking reaction to proceed sufficiently.

In the step (1), the amount of the silanol condensation catalyst is not particularly limited, and is preferably 0.03 to 0.5 parts by mass, more preferably 0.05 to 0.3 parts by mass, based on 100 parts by mass of the base rubber. parts by mass, more preferably 0.07 to 0.25 parts by mass, particularly preferably 0.1 to 0.2 parts by mass. When the amount of the silanol condensation catalyst is within the above range, the formation of gel spots during molding can be suppressed, and cross-linking proceeds sufficiently to provide excellent compression set.

From the viewpoint of realizing a better balance between excellent appearance properties and reduction in compression set, in step (1), 10 to 60 parts by mass of an inorganic filler and 1 part of a silane coupling agent are added to 100 parts by mass of the base rubber. It is preferable to melt-mix to 15 parts by mass, 0.01 to 0.6 parts by mass of the organic peroxide, and 0.03 to 0.5 parts by mass of the silanol condensation catalyst.

When performing step (1), step (a-1) and step (a-2) are performed in sequence. That is, first, an inorganic filler and a silane coupling agent are mixed, and then the obtained mixture and all or part of the base rubber are mixed in the above-mentioned amount at a temperature equal to or higher than the decomposition temperature of the organic peroxide. By melt-kneading, the above-mentioned grafting reaction is caused to prepare a silane masterbatch.
In the present invention, "melting and mixing the mixture and all or part of the base rubber" does not specify the order of mixing (or compounding) during melt mixing, and may be mixed in any order. means good. That is, the mixing order in step (a-2) is not particularly limited.
Also, the method of mixing the base rubber is not particularly limited. For example, a premixed base rubber may be used, or each component, such as each rubber component, may be separately mixed.

In the present invention, the silane coupling agent is not introduced alone into the silane masterbatch, but is premixed with the inorganic filler. That is, an inorganic filler and a silane coupling agent are mixed to prepare a mixture (step (a-1)). It is believed that the premixed silane coupling agent exists so as to surround the surface of the inorganic filler, and part or all of it is adsorbed or bound to the inorganic filler. This can reduce volatilization of the silane coupling agent during subsequent melt-mixing. In addition, it is possible to prevent the silane coupling agent that is not adsorbed or bonded to the inorganic filler from condensing and making melt-kneading difficult.

A method for pre-mixing the inorganic filler and the silane coupling agent is not particularly limited, but includes a mixing method such as a wet process or a dry process. Specifically, the inorganic filler and the silane coupling agent are preferably heated at a temperature lower than the decomposition temperature of the organic peroxide, preferably 10 to 60° C., more preferably around room temperature (20 to 25° C.) for several minutes to A dry or wet mixing method for several hours may be mentioned, and a dry treatment in which a silane coupling agent is added to an inorganic filler, preferably a dried inorganic filler, with or without heating and mixed is more preferred. In step (a-1), the base rubber may be mixed as long as the temperature is maintained below the decomposition temperature.

In the production method of the present invention, the mixture of the inorganic filler and the silane coupling agent obtained in step (a-1) and all or part of the base rubber are then mixed in the presence of an organic peroxide. is melted and mixed at a temperature higher than the decomposition temperature of the organic peroxide (step (a-2)). By doing so, excessive cross-linking reaction between the base rubber components can be prevented, and a cross-linked molded product with excellent appearance can be obtained.
By the melt-mixing in step (a-2), radicals generated from the organic peroxide cause a grafting reaction between the grafting reaction sites of the silane coupling agent and the graftable sites of the base rubber. As a result, a silane crosslinkable rubber (silane graft polymer) in which the silane coupling agent is covalently bonded to the rubber component is synthesized, and a silane masterbatch containing this silane crosslinkable rubber is prepared. In the step (a-2), the silane coupling agent is grafted onto the base rubber at least as follows. That is, it is a mode in which the silane coupling agent bound or adsorbed to the inorganic filler by a weak bond desorbs from the inorganic filler and undergoes a grafting reaction with the base rubber. Also, in this mode, the silane coupling agent bonded or adsorbed to the inorganic filler by a strong bond undergoes a grafting reaction to the base rubber while maintaining the bond with the inorganic filler. The weak bond between the silane coupling agent and the inorganic filler includes interaction by hydrogen bonding, interaction between ions, partial charges or dipoles, action by adsorption, and the like. Further, examples of the strong bond with the inorganic filler include chemical bonding with a chemically bondable site on the surface of the inorganic filler. In the silane-crosslinkable rubber, the diene component-containing ethylene-α-olefin copolymer rubber is partially crosslinked at the diene component. The same applies when the styrene elastomer contains a diene component.

In step (a-2), the temperature for melt-mixing (also referred to as melt-kneading or kneading) the above components is the decomposition temperature of the organic peroxide or higher, preferably the decomposition temperature of the organic peroxide + (25 to 110 ) °C, more preferably 150-230 °C. It is preferable to set the decomposition temperature of the organic peroxide after the base rubber component is melted. At the above mixing temperature, the above components melt, the organic peroxide decomposes and acts, and the necessary silane grafting reaction proceeds sufficiently in step (a-2). The mixing time may be a time in which the reaction mixture is sufficiently mixed and the silane grafting reaction can be completed, and is appropriately set between 3 and 20 minutes, but is not limited thereto. Other conditions can be set as appropriate.
The mixing method is not particularly limited as long as it is a method commonly used for rubbers, plastics and the like. A single-screw extruder, a twin-screw extruder, a roll, a Banbury mixer, various kneaders, or the like is used as a kneading device. In terms of dispersibility of the base rubber component and stability of the cross-linking reaction, a closed mixer such as a Banbury mixer or various kneaders is preferred.

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

In steps (a-1) and (a-2), particularly in step (a-2), it is preferable to knead the above 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 injection molding. Here, the phrase "substantially not mixed" does not mean that the silanol condensation catalyst that is inevitably present is also excluded, 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-2), the silanol condensation catalyst may be present in an amount of 0.01 parts by mass or less with respect to 100 parts by mass of the base rubber.

In this way, the step (a) consisting of the steps (a-1) and (a-2) is performed, and the silane coupling agent and the base rubber are grafted to form a silane masterbatch (also called silane MB). ) is prepared. The silane MB thus obtained is preferably used together with a silanol condensation catalyst or a catalyst masterbatch described later in the production of the reaction composition (silane crosslinkable rubber composition) prepared in step (1), as described later. be done. Silane MB is a mixture containing silane-crosslinkable rubber in which a silane coupling agent is grafted to a rubber component to the extent that it can be molded by step (2) described later.

In the production method of the present invention, when part of the base rubber is melt-mixed in step (a-2), the remainder of the base rubber and the silanol condensation catalyst are melt-mixed to obtain a catalyst masterbatch (catalyst MB (also referred to as) is performed. Therefore, when all of the base rubber is melt-mixed in step (a-2), step (b) may be omitted, and other base rubber components and the silanol condensation catalyst may be mixed.

Although the mixing ratio of the base rubber as a carrier and the silanol condensation catalyst is not particularly limited, it is preferably set so as to satisfy the above-described compounding amount in step (1).
Mixing may be performed by any method as long as it can be uniformly mixed, and examples thereof include mixing performed while the base rubber is molten (melt mixing). Melt mixing can be performed in the same manner as the melt mixing in step (a-2) above. For example, the mixing temperature can be appropriately set at the melting temperature of the base rubber component or higher, preferably 120 to 200°C, more preferably 140 to 180°C. Other conditions, such as mixing time, can be set as appropriate.

In step (b), other resins can be used as carriers instead of or in addition to the rest of the base rubber. That is, in step (b), the remainder of the base rubber when part of the base rubber is melt-mixed in step (a-2), or a resin other than the rubber component used in step (a-2), and silanol A catalyst masterbatch may be prepared by melt mixing with a condensation catalyst.
When the carrier is another resin, the grafting reaction can be accelerated in the step (a-2), and the amount of the other resin is less than 100 parts by mass of the base rubber because it is less likely to cause lumps during molding. , preferably 1 to 60 parts by mass, more preferably 2 to 50 parts by mass, and even more preferably 3 to 40 parts by mass.

Moreover, an inorganic filler may be used in the step (b). In this case, the amount of the inorganic filler compounded in step (b) is not particularly limited, but is preferably 350 parts by mass or less with respect to 100 parts by mass of the carrier. By setting the amount of the inorganic filler to 350 parts by mass or less, the silanol condensation catalyst is appropriately dispersed and cross-linking is facilitated. Moreover, if necessary, sufficient heat resistance can be obtained.

The catalyst MB thus prepared is a (molten) mixture of silanol condensation catalyst and carrier, optionally added filler.
This catalyst MB is used together with the silane MB to produce the silane-crosslinkable rubber composition prepared in step (1).

In the production method of the present invention, the step (c) of obtaining a silane-crosslinkable rubber composition (reaction composition) by melt-mixing the silane MB and the silanol condensation catalyst or catalyst MB is then performed. This reaction composition is a composition containing the silane-crosslinkable rubber synthesized in the above step (a-2).
Any mixing method may be used as long as a uniform reaction composition can be obtained as described above.

Mixing is basically the same as melt mixing in step (a-2). Although there are rubber components such as elastomers whose melting points cannot be measured by DSC or the like, the kneading is performed at least at a temperature at which the rubber component or the like melts. The melt-mixing temperature is appropriately selected depending on the melting temperature of the base rubber or carrier, and is preferably 80 to 250°C, more preferably 100 to 240°C, still more preferably 120 to 200°C. Other conditions, such as mixing (kneading) time, can be appropriately set.

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

This step (c) may be a step of mixing a silane masterbatch and a silanol condensation catalyst or a catalyst masterbatch to obtain the reaction composition as a molten mixture thereof, and a catalyst containing a silanol condensation catalyst and a carrier. The step of melt mixing the masterbatch and the silane masterbatch is preferred.

In this manner, steps (a) to (c) (step (1)) are performed to produce a silane-crosslinkable rubber composition as a reaction composition. This silane-crosslinkable rubber composition comprises a silane-crosslinkable rubber obtained by grafting a silane coupling agent to a base rubber, 1 to 100 parts by mass of an inorganic filler per 100 parts by mass of the base rubber, a silanol condensation catalyst, contains
This silane-crosslinkable rubber composition contains silane-crosslinkable rubbers with different crosslinking methods. In this silane-crosslinkable rubber, the silanol-condensable 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, the silane cross-linkable rubber consists of cross-linkable rubber in which a silane coupling agent bound or adsorbed to an inorganic filler is grafted onto a base rubber, and cross-linkable rubber in which a silane coupling agent that is not bound or adsorbed to an inorganic filler is grafted onto a base rubber. and crosslinkable rubber. These crosslinkable rubbers may be further crosslinked at the diene component portion. Moreover, the silane crosslinkable rubber composition may have a silane coupling agent to which an inorganic filler is bound or adsorbed and a silane coupling agent to which an inorganic filler is not bound or adsorbed. Furthermore, it may contain a silane coupling agent and an unreacted rubber component.
As described above, the silane-crosslinkable rubber is an uncrosslinked product in which the silane coupling agent is not silanol-condensed. Practically, partial cross-linking (partial cross-linking) is unavoidable when melt-mixed in step (c), but the obtained silane-crosslinkable rubber composition has at least moldability in forming in step (2). shall be retained.

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

In step (1), the amounts of other base rubber components and additives that can be used in addition to the above components are appropriately set within a range that does not impair the object of the present invention.
In step (1), the additives, particularly antioxidants and flame retardants, may be mixed in any step or component, but are preferably mixed with the carrier.
In step (1), particularly in steps (a-1) and (a-2), it is preferred that the cross-linking aid is not substantially mixed. If the cross-linking aid is not substantially mixed, cross-linking between rubber components is unlikely to occur during melt-mixing, and the appearance of the silane cross-linked rubber molding is excellent. Here, "substantially not mixed" means that the cross-linking aid is not actively mixed, and does not exclude unavoidable mixing.

In the method for producing a silane-crosslinked rubber molded article according to the present invention, step (2) is then performed to obtain a molded article by injection molding the obtained reaction composition. In this step (2), it is sufficient that the reaction composition can be injection-molded, and the injection molding conditions are appropriately selected according to the form of the silane-crosslinked rubber molded article of the present invention or a silane-crosslinked rubber molded article containing the silane-crosslinked rubber molded article. be done.
The injection molding temperature cannot be uniquely determined depending on the type and amount of the base rubber component used, the type and amount of the inorganic filler, etc. 130 to 170°C at the center of the cylinder, about 140 to 180°C at the center of the cylinder, and about 160 to 210°C at the front of the cylinder (nozzle side).
Injection molding can be performed using a general-purpose injection molding machine for plastics. The mold is appropriately determined according to the shape, dimensions, etc. of the molded product.

In addition, step (2) can be performed simultaneously with step (c) or consecutively. That is, as one embodiment of melt-mixing in the step (c), there is a mode in which the raw materials are melt-mixed during or just before injection molding. For example, pellets such as dry blends may be mixed at room temperature or high temperature and introduced into the injection molding machine (melt mixing), or after being mixed, melt mixed, pelletized again and introduced into the injection molding machine. You may More specifically, a series of steps can be adopted in which a molding material comprising a silane MB and a silanol condensation catalyst or a catalyst MB is melt-kneaded in an injection molding machine and then injection-molded into a desired shape.
Thus, a molded article 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 capable of being molded in step (2). Therefore, the silane-crosslinked rubber molded article of the present invention is crosslinked or finally crosslinked by carrying out the step (3).

In the method for producing a silane-crosslinked rubber molded article of the present invention, the step (3) of bringing the molded article obtained in the step (2) into contact with water is carried out. As a result, the reactive sites of the silane coupling agent capable of silanol condensation are hydrolyzed to form silanol groups, and the hydroxyl groups of the silanol groups are condensed with each other by the silanol condensation catalyst present in the molded article, causing a cross-linking reaction. In this way, a silane-crosslinked rubber molding in which the silane coupling agent is silanol-condensed and crosslinked can be obtained.
The processing itself of this step (3) can be performed by a normal method. Condensation between silane coupling agents proceeds only by storage at room temperature. Therefore, it is not necessary to actively bring the compact into contact with water in step (3). In order to promote this cross-linking reaction, the molded article can be positively brought into contact with moisture. For example, a method of positively contacting with water such as immersion in warm water, introduction into a moist heat bath, exposure to high-temperature steam, or the like can be adopted. Also, at that time, pressure may be applied to permeate the moisture inside.

Thus, a silane-crosslinked rubber molding is produced from the silane-crosslinkable rubber composition of the present invention. This silane-crosslinked rubber molded article contains a crosslinked rubber obtained by condensing a silane-crosslinkable rubber via a siloxane bond, as will be described later. One form of this silane-crosslinked rubber molding 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 crosslinked rubber is composed of a crosslinked rubber in which a plurality of crosslinked rubbers are bonded or adsorbed to an inorganic filler by a silane coupling agent and bonded (crosslinked) via the inorganic filler and the silane coupling agent, and the crosslinkable rubber The reaction site of the silane coupling agent of (1) hydrolyzes and undergoes a silanol condensation reaction with each other, so that the crosslinked rubber is crosslinked via the silane coupling agent. In addition, the silane-crosslinked rubber may have a mixture of bonding (crosslinking) via the inorganic filler and the silane coupling agent and crosslinking via the silane coupling agent. Further, it may contain a silane coupling agent and an unreacted rubber component and/or a non-crosslinked silane-crosslinkable rubber, or a silane-crosslinkable rubber crosslinked at a diene component portion.

According to the manufacturing method of the present invention, it is possible to obtain a molded article having excellent appearance characteristics and reduced compression set by injection molding. ADVANTAGE OF THE INVENTION According to this invention, even if it resumes molding after stopping an injection molding machine temporarily, generation|occurence|production of poor appearance can be suppressed and the silane crosslinked-rubber molded object with favorable appearance can be manufactured. Here, restarting after a temporary stop depends on the composition of the base rubber, processing conditions, other necessary measures during the manufacturing process, etc., and cannot be stated unambiguously. It means that even if the molding material is retained in the injection molding machine in a molten state, preferably for up to 1.5 hours, and then the injection molding is restarted, molding can be performed while suppressing appearance defects. Although the details of the ability to produce a silane-crosslinked rubber molded article having such excellent properties are not yet clear, the following is considered.
According to the production method of the present invention, in the step (a-1), the inorganic filler and the silane coupling agent are premixed in a specific amount ratio, so that prior to the grafting reaction performed in the step (a-2), As a result, the silane coupling agent adsorbs or bonds to the inorganic filler. In this state, in the step (a-2), a grafting reaction occurs when melt-kneaded together with the base rubber in the presence of an organic peroxide. At that time, the silane coupling agent bonded or adsorbed with the weak bond with the inorganic filler desorbs from the inorganic filler, while the silane coupling agent bonded with the inorganic filler with a strong bond maintains the bond with the inorganic filler. . In this way, silane-crosslinkable rubbers having different inorganic filler adsorption states are formed. Furthermore, these silane-crosslinkable rubbers are brought into contact with moisture in step (3) to form crosslinked rubbers having a crosslinked structure via silanol bonds.
In the production method of the present invention, it is assumed that the crosslinked structure is formed by the above-mentioned silane crosslinking, and then, as the base rubber, an ethylene-α-olefin copolymer rubber 5 having a diene content of 4.5 to 10% by mass is used. 5 to 50% by mass of ethylene-α-olefin copolymer rubber with a diene content of 1.0% by mass or less, 12% by mass or less of ethylene resin, 5 to 15% by mass of propylene resin, 10 to 35% by mass of styrene elastomer % by weight, and 20-40% by weight of mineral oil.
In the step (a-2), the ethylene-α-olefin copolymer rubber having a large amount of diene component in the base rubber component undergoes not only a silane graft reaction but also crosslinks between the diene components. (However, since the inorganic filler and the silane coupling agent are pre-mixed, the silane graft reaction is thought to take precedence over the cross-linking of the diene components). On the other hand, an ethylene-α-olefin copolymer rubber containing a small amount of diene component undergoes a silane graft reaction, but the diene component does not form crosslinks or only a very small amount of crosslinks are formed. The same applies when the styrene elastomer or the like contains a diene component. In this way, silane-crosslinkable rubbers having different cross-linking states between the base rubber components are formed. Ethylene-α-olefin copolymer rubber, styrene elastomer, mineral oil, etc., which have a low diene component content, function as a fluidized bed in the base rubber, and during injection molding, the fluidity of the base rubber is adjusted to the appropriate range for injection molding. can. Due to this fluidity, gel lumps and the like generated in the cylinder can be efficiently discharged out of the cylinder of the molding machine, thereby reducing the influence on the external appearance of the molded product. Furthermore, flow marks can be suppressed. Moreover, in the finally obtained silane-crosslinked molded article, the compression set can be reduced by forming a crosslinked structure due to crosslinking of the diene component in addition to the crosslinked structure due to silanol condensation.

The production method of the present invention is applicable to the production of products (including semi-finished products, parts, and members) that require a small compression set and excellent appearance characteristics, and components of products such as rubber materials, or members thereof. be able to. Therefore, a silane-crosslinked rubber molded article or a silane-crosslinked rubber molded article containing a silane-crosslinked rubber molded article is regarded as such a product.
Examples of the silane-crosslinked rubber molded article of the present invention or a silane-crosslinked rubber molded article containing the silane-crosslinked rubber molded article include, for example, coating materials for wires such as flame-retardant insulated wires or flame-retardant cables, materials for rubber-substitute wires and cables, and others. , flame-retardant wire parts, flame-retardant heat-resistant sheets, flame-retardant films, and the like. Power plugs, connectors, sleeves, boxes, tape substrates, tubes, sheets, packing, cushioning materials, anti-vibration materials, wiring materials used for internal wiring and external wiring of electrical and electronic equipment, especially electric wires and optical cables. be done.

The silane-crosslinked rubber molded article of the present invention is suitable as a material for use in areas where small compression set and high moldability (especially injection moldability) are required. It can be used as a replacement for rubber materials that have undergone a vulcanization process.

EXAMPLES The present invention will be described in more detail below based on examples, but the present invention is not limited to these.
In Tables 1-1 to 1-3 (collectively referred to as Table 1), the numerical values relating to the compounding amounts in each example represent parts by mass unless otherwise specified. A blank column for each component means that the amount of the corresponding component is 0 parts by mass.

In Examples 1 to 27 and Comparative Examples 1 to 16, some of the components constituting the base rubber were used as carriers for the catalyst MB.

(Examples 1 to 27, Comparative Examples 1 to 6, 8 to 16)
First, an inorganic filler, a silane coupling agent, and an organic peroxide are put into a rotary blade mixer (trade name, Mazeler PM, manufactured by Mazeler) at a mass ratio shown in Table 1, and at room temperature (25°C), The mixture was stirred (pre-mixed) at 10 rpm for 1 minute to obtain a powder mixture (step (a-1)). Next, the obtained powder mixture and the base rubber were put into a kneader (capacity: 75 L) preheated to 100°C at the mass ratio shown in Table 1, mixed at 40 rpm for 5 minutes, and then mixed at 30 rpm for 3 minutes. Minutes, finish kneading was performed. After confirming that the temperature of the mixture reached 180 to 200° C., which is the decomposition temperature of the organic peroxide or higher, the mixture was pelletized using a feeder/ruder and a pelletizer to obtain a silane masterbatch (step (a -2)). The silane MB thus obtained contains a silane-crosslinkable rubber obtained by grafting a silane coupling agent to a base rubber component.

On the other hand, the base rubber, the inorganic filler, the antioxidant and the silanol condensation catalyst were sequentially added in the mass ratio shown in Table 1 into a kneader (capacity: 75 L) preheated to 80°C, and mixed at 30 rpm for 5 minutes. , 25 rpm for 3 minutes. After confirming that the temperature of the mixture reached about 160° C. and the base rubber was sufficiently melted, the mixture was pelletized using a feeder/ruder and a pelletizer to obtain a catalyst masterbatch (step (b)). This catalyst MB is a molten mixture of carrier and silanol condensation catalyst.

Next, the silane MB and the catalyst MB were placed in a plastic bag and dry blended at room temperature (25° C.) for about 3 minutes to obtain a dry blend. At this time, the mixing ratio of the silane MB and the catalyst MB is the mass ratio shown in Table 1. Specifically, in Examples 1 to 27 and Comparative Examples 1 to 6 and 8 to 16, the base rubber of the silane MB was 90 parts by mass and the carrier of the catalyst MB was 10 parts by mass.

Next, with a screw diameter of 26 mm and a 50-ton injection molding machine (Fanuc Corporation ROBOSHOT α-50iA), the nozzle temperature is 200 ° C., the front part is 200 ° C., the middle part is 160 ° C., the rear part is 150 ° C., and the mold temperature is 30 ° C. It was set to the injection temperature condition. The prepared dry blended product was charged into this injection molding machine and melt-mixed (step (c)).
Thus, a silane-crosslinkable rubber composition was prepared as a reaction composition. This silane-crosslinkable rubber composition is a molten mixture of silane MB and catalyst MB and contains the silane-crosslinkable rubber described above.
The molten mixture was injected into a mold under the following injection molding conditions (1) or (2) to obtain a sheet of A4 size and thickness of 2 mm (step (2)). As the mold, a mold having a cavity with a thickness of 2 mm and a size of “A4” (210 mm×297 mm) defined in the JIS standard was used.

Conditions common to the above injection molding conditions (1) and (2) Number of nozzles: 1 Gate shape: 4 x 3 mm
Filling pressure: 5MPa
Mold temperature: 30°C
Screw rotation speed: 100 rpm
Injection speed: 60 mm/sec Injection time: 10 sec Holding pressure: 20 MPa
Holding pressure time: 10 seconds Cooling time: 30 seconds

Injection molding conditions (1)
The molding was repeated 10 times in succession.

Injection molding conditions (2)
After the above injection molding condition (1), the injection molding machine was stopped (screw rotation speed 0 rpm), and the silane crosslinkable rubber composition was allowed to stay in the cylinder in a molten state while maintaining the injection temperature condition and left for 1 hour. After that, injection molding was resumed and molding was repeated 10 times.

The uncrosslinked sheet obtained by the 10th molding under the above injection molding conditions (1) and (2) was allowed to stand at room temperature (23°C) and 50% RH for 48 hours to allow silane crosslinking to proceed ( Step (3)). Thus, each sheet sample of "A4" size with a thickness of 2 mm was produced under the above injection molding conditions. A silane-crosslinked rubber molding as a sheet sample has the above-described silane-crosslinked rubber.

(Comparative Example 7)
When preparing the silane MB, without pre-mixing the inorganic filler, the silane coupling agent, and the organic peroxide (step (a-1)), the components shown in the silane MB column of Table 1 are added to Table 1 A sheet sample was produced in the same manner as in Example 1, except that the silane MB was obtained by putting it into a kneader at the mass ratio shown in .

In the production of the above examples and comparative examples, when the inorganic filler, the silane coupling agent and the organic peroxide were premixed (step (a-1)), the "premixing" column in Table 1 It was described as "yes", and when no pre-mixing was performed, it was described as "no".

As each component shown in Table 1, the following were used.
(1) Ethylene-α-olefin copolymer rubber 1A: Nodel 4770P (trade name, manufactured by Dow, ethylene-propylene-diene rubber)
(2) Ethylene-α-olefin copolymer rubber 1B: Nodel 6565XCF (trade name, manufactured by Dow, ethylene-propylene-diene rubber)
(3) Ethylene-α-olefin copolymer rubber 2A: Mitsui EPT0045 (trade name, manufactured by Mitsui Chemicals, ethylene-propylene rubber)
(4) Ethylene-α-olefin copolymer rubber 2B: Nodel 3745P (trade name, manufactured by Dow, ethylene-propylene-diene rubber)
(5) Styrene elastomer 1: Tuftec N504 (trade name, manufactured by Asahi Kasei Corporation, SEBS, MFR less than 0.1 g/10 min)
(6) Mineral oil 1: Diana process oil PW90 (trade name, manufactured by Idemitsu Kosan, paraffin oil)
(7) Propylene resin 1: PB222A (trade name, manufactured by SunAllomer, random polypropylene)
(8) Ethylene resin 1: Evolue SP0540 (trade name, manufactured by Prime Polymer, LLDPE)
(9) Ethylene resin 2: Sumikasen CU5003 (trade name, manufactured by Sumitomo Chemical Co., Ltd., LLDPE)
(10) Inorganic filler 1: Kisuma 5L (trade name, manufactured by Kyowa Kagaku Co., Ltd., magnesium hydroxide)
(11) Inorganic filler 2: Aerosil 200 (trade name, manufactured by Nippon Aerosil Co., Ltd., fumed silica)
(12) Inorganic filler 3: Crystalite 5X (trade name, manufactured by Takimori Co., Ltd., crystalline silica)
(13) Inorganic filler 4: Talc K-1 (trade name, manufactured by Nippon Talc Co., Ltd., talc)
(14) Inorganic filler 5: Softon 1200 (trade name, manufactured by Bihoku Funka Kogyo Co., Ltd., calcium carbonate)
(15) Inorganic filler 6: SATINTONE SP33 (trade name, manufactured by Toshin Kasei Co., Ltd., calcined kaolin)
(16) Silane coupling agent 1: KBM-1003 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd., vinyltrimethoxysilane)
(17) Organic peroxide 1: Perhexa 25B (trade name, manufactured by NOF Corporation, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane)
(18) Antioxidant 1: Irganox 1076 (trade name, manufactured by BASF, octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate)
(19) Silanol condensation catalyst 1: ADEKA STAB OT-1 (trade name, manufactured by ADEKA, dioctyltin dilaurate)

Various properties of each sheet sample obtained were evaluated by the test methods shown below.

1. Appearance test (1)
The surface of the sheet sample obtained by the tenth molding under the injection molding condition (1) was visually observed. When flow marks (flow traces of the rubber composition) were observed on the sheet surface, the area of the flow mark portions was obtained, and the flow mark ratio was calculated. Specifically, the boundary of the flow mark portion is enclosed with a line, the area of the enclosed flow mark portion is measured using a digital microscope VHX-1000 (trade name, manufactured by Keyence Corporation), and the flow is calculated according to the following formula. calculated the mark rate.
Flow mark rate (%) = flow mark area/sheet sample area x 100
Evaluation was performed according to the following criteria. "A (high surface quality)" indicates that flow marks, gel spots, and roughness are not observed on the sheet surface, and flow marks are observed, but the flow mark rate is less than 10%, and gel spots and roughness are not observed. was rated as "B (good surface property)", and those with a flow mark rate of 10% or more, gel bumps, and roughness were rated as "C (failed)". An evaluation of "B" or higher is the passing level of this test.

2. Appearance test (2)
The surface of the sheet sample obtained by the 10th molding after restarting the injection molding under the injection molding condition (2) was visually observed. When flow marks were observed on the sheet surface, the flow mark ratio was obtained in the same manner as in the appearance test (1).
Evaluation was performed according to the following criteria. "A (high surface quality)" indicates that flow marks, gel spots, and roughness are not observed on the sheet surface, and flow marks are observed, but the flow mark rate is less than 10%, and gel spots and roughness are not observed. was rated as "B (good surface property)", and those with a flow mark rate of 10% or more, gel bumps, and roughness were rated as "C (failed)". An evaluation of "B" or higher is the passing level of this test.

3. Compression Set Test Based on JIS K 6262 A method, the compression set was measured using a sheet sample obtained by the 10th molding under the above injection molding conditions (1). Using a compression device with two compression plates and a spacer (thickness is 75% of the thickness of the sheet sample), the sheet sample is compressed by 25% in the thickness direction (compression rate of 25%). , and then heated to 70° C. and held for 22 hours. After that, the compression was released at normal temperature (23°C), and after cooling for 30 minutes (final temperature was 23°C), the thickness of the sheet sample was measured.
From the thickness of the sheet sample before and after compression, the compression set was calculated according to the following formula and evaluated according to the following evaluation criteria.
Formula: CS = [(t0-t2)/(t0-t1)] x 100
During the ceremony,
CS: compression set (%)
t0: thickness of the sheet sample before compression (original thickness) (mm)
t1: spacer thickness (mm)
t2: Thickness after compression of sheet sample (thickness after 30 minutes after removal from compression device) (mm)
In this test, a compression set of less than 40% is a passing level.
When the compression set is less than 40%, it can be suitably used as a member for applications that are repeatedly opened and closed, such as weather strips for automobiles and window frame packings for building materials. Here, if the compression set differs by about 2%, the life of the member will be shortened accordingly.

If a base rubber that does not satisfy the composition specified in the present invention is mixed with the manufacturing method having each step specified in the present invention, any of appearance test (1), appearance test (2), and compression set test will be performed. It was not possible to obtain a sheet of silane-crosslinked rubber molded article that passed the test (Comparative Examples 1 to 2, 8 to 16). If the inorganic filler is mixed in a too small amount in the manufacturing method having each step specified in the present invention, the compression set test will fail, and the appearance test (1), the appearance test (2), and the compression A sheet of silane-crosslinked rubber molding that passed any of the permanent set tests could not be obtained (Comparative Example 3). If the inorganic filler is mixed in too large a compounding amount, the appearance test (2) and the compression set test are failed, and the appearance test (1), the appearance test (2), and the compression set test are both passed. A sheet of silane-crosslinked rubber molding could not be obtained (Comparative Example 4). When the silane coupling agent is mixed in an amount that is too small, the compression set test fails, and the silane crosslinked rubber molding passes both the appearance test (1), the appearance test (2), and the compression set test. A body sheet could not be obtained (Comparative Example 5). On the other hand, if the silane coupling agent and the organic peroxide are mixed in too large a compounding amount, both appearance test (1) and appearance test (2) will fail, and appearance test (1) and appearance test (2) will fail. ), and a sheet of a silane-crosslinked rubber molding that passed both the compression set test (Comparative Example 6). A silane that fails the compression set test without pre-mixing the inorganic filler and the silane coupling agent and passes both the appearance test (1), the appearance test (2), and the compression set test. A sheet of crosslinked rubber molding could not be obtained (Comparative Example 7).
On the other hand, in the manufacturing method having each step specified in the present invention, a base rubber satisfying the composition specified in the present invention is blended with an inorganic filler, an organic peroxide, etc. in specific amounts, and pre-mixed. As a result, it was possible to produce a silane-crosslinkable rubber molding excellent in appearance characteristics and compression set suppression, which passed all of appearance test (1), appearance test (2), and compression set test. (Examples 1-27). In particular, since it passed the appearance test (2), it can be seen that even if the residence time during injection molding is as long as one hour, it can be dealt with without causing poor appearance. Furthermore, according to the manufacturing method of the present invention, a molded article having excellent appearance characteristics can be obtained only by injection molding without performing post-treatments such as grinding and polishing.

Claims (8)

A method for producing a silane-crosslinked rubber molding comprising the following steps (1), (2) and (3),
Step (1): In the presence of 0.01 to 0.6 parts by mass of an organic peroxide, 1 to 100 parts by mass of an inorganic filler, and radicals generated from the organic peroxide with respect to 100 parts by mass of the base rubber. 1 to 15 parts by mass of a silane coupling agent having a grafting reaction site capable of undergoing a grafting reaction with the base rubber and a silanol condensation catalyst are melt-mixed, and the grafting is performed by radicals generated from the organic peroxide. A step of obtaining a silane-crosslinkable rubber composition containing a silane-crosslinkable rubber by causing a grafting reaction between the reaction site and the graftable site of the base rubber. Step (2): The silane-crosslinkable rubber composition is Step (3): Contacting the molded article with water to obtain a silane-crosslinked rubber molded article The base rubber contains ethylene having a diene content of 4.5 to 10% by mass. - 5 to 35% by mass of α-olefin copolymer rubber, 5 to 50% by mass of ethylene-α-olefin copolymer rubber having a diene content of 1.0% by mass or less, 12% by mass or less of ethylene resin, 5 to 5% by mass of propylene resin 15% by weight, 10-35% by weight of styrene elastomer, and 20-40% by weight of mineral oil,
In performing the step (1),
When all of the base rubber is melt-mixed in the following step (a-2), the step (1) has the following steps (a-1), (a-2) and (c), and the following steps When part of the base rubber is melt-mixed in (a-2), step (1) has the following steps (a-1), (a-2), (b) and (c). and a method for producing a silane-crosslinked rubber molding.
Step (a-1): Step of mixing the inorganic filler and the silane coupling agent to prepare a mixture Step (a-2): The mixture and all or part of the base rubber are treated with the organic peroxide The graft reaction site and the graft reaction-capable site of the base rubber are separated by the radicals generated from the organic peroxide by melt-mixing in the presence of a substance at a temperature equal to or higher than the decomposition temperature of the organic peroxide. preparing a silane masterbatch containing a silane crosslinkable rubber by a grafting reaction step (b): melt-mixing the remainder of the base rubber and the silanol condensation catalyst to prepare a catalyst masterbatch; (c): A step of melt-mixing the silane masterbatch and the silanol condensation catalyst or the catalyst masterbatch to obtain the silane crosslinkable rubber composition. 2. The method for producing a silane-crosslinked rubber molding according to claim 1, wherein 10 to 60 parts by mass of the inorganic filler is blended with 100 parts by mass of the base rubber. 3. The method for producing a silane-crosslinked rubber molding according to claim 1, wherein 0.03 to 0.5 parts by mass of said silanol condensation catalyst is compounded with respect to 100 parts by mass of said base rubber. The method for producing a silane-crosslinkable rubber molding according to any one of claims 1 to 3, wherein the inorganic filler is metal hydrate, talc, clay, silica, carbon black, or a mixture thereof. In the step (1), 10 to 60 parts by mass of the inorganic filler, 1 to 15 parts by mass of the silane coupling agent, and 0.01 to 0.01 part by mass of the organic peroxide are added to 100 parts by mass of the base rubber. The method for producing a silane-crosslinked rubber molding according to any one of claims 1 to 4, wherein 6 parts by mass and 0.03 to 0.5 parts by mass of the silanol condensation catalyst are melt-mixed. A silane-crosslinkable rubber composition produced by the step (1) of the production method according to any one of claims 1 to 5. A silane-crosslinked rubber molded article produced by the method for producing a silane-crosslinked rubber molded article according to any one of claims 1 to 5. A silane-crosslinked rubber molded article comprising the silane-crosslinked rubber molded article according to claim 7 .