JP2022155042A - Silane-crosslinked acrylic rubber molding and method for manufacturing the same, silane-crosslinkable acrylic rubber composition, and silane-crosslinked acrylic rubber molded article - Google Patents

Abstract

To provide a manufacturing method in which a silane-crosslinked acrylic rubber molding having excellent combination of appearance, high-temperature oil resistance, mechanical property and flexibility, and having suppressed bleeding can be obtained, a silane-crosslinked acrylic rubber molding and a molded article obtained by this method, and a silane-crosslinkable acrylic rubber composition that is suitable for manufacturing this molding.SOLUTION: Provided are a manufacturing method that has a step of melt-mixing a mixture of inorganic filler and silane coupling agent, and a base acrylic rubber containing an ethylene-acrylic rubber by 20 to 85 mass%, an ethylene resin by 60 mass% or less, a styrene elastomer by 1 to 20 mass%, and a mineral-based oil by 1 to 20 mass% in a ratio of styrene elastomer and mineral-based oil of 1:2.5 to 1:0.5, a silane-crosslinkable acrylic rubber composition and a silane-crosslinked acrylic rubber molding that are manufactured using the same, and a silane-crosslinked acrylic rubber molded article.SELECTED DRAWING: None

Description

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

Each wiring material such as insulated wires, cables, cords, optical fiber core wires or optical fiber cords used for internal wiring or external wiring of electrical and electronic equipment has mechanical properties (e.g., tensile strength, tensile elongation), flexibility Various properties such as toughness and appearance are required.

In order to improve the characteristics of the wiring material as described above, the resin or rubber forming the coating layer is often subjected to cross-linking treatment. As a method for cross-linking resins or rubbers, electron beam cross-linking methods or chemical cross-linking methods are generally used. For example, as a method for cross-linking a polyolefin resin such as polyethylene, an electron beam cross-linking method in which an electron beam is irradiated to cross-link, a cross-linking method in which an organic peroxide or the like is applied by applying heat after molding to cause a cross-linking reaction, and A chemical cross-linking method such as a silane cross-linking method can be used.
Here, the silane crosslinking method is a silane coupling agent having an unsaturated group in the presence of an organic peroxide to a resin or rubber to undergo a silane grafting reaction (simply referred to as a grafting reaction.) to a silane grafted resin. Alternatively, after obtaining a rubber, it is a method of obtaining a crosslinked resin by bringing the silane graft resin or rubber into contact with moisture in the presence of a silanol condensation catalyst.
Among the above methods, the silane cross-linking method in particular does not require special facilities for the cross-linking treatment, and can be used in a wide range of fields.

On the other hand, the wiring material may be used in a state where it can come into contact with oil. Wiring materials used for such applications are required to have oil resistance (characteristics in which changes in physical properties are small even when immersed in oil).

As an example of a method for producing an oil-resistant molded article by applying the silane crosslinking method, for example, Patent Document 1 describes a base resin containing specific amounts of acrylic rubber and polypropylene resin, an organic peroxide, a metal hydrate, A manufacturing method is described in which a silane coupling agent and a silanol condensation catalyst are melt-mixed, molded, and the obtained molded body is brought into contact with water. Patent Document 2 discloses a method of melting a base rubber containing specific amounts of ethylene-acrylic rubber and polyolefin resin modified with an unsaturated carboxylic acid component, an organic peroxide, an inorganic filler, a silane coupling agent, and a silanol condensation catalyst. A manufacturing method is described in which, after mixing, the mixture is molded and the resulting molding is brought into contact with water.

JP 2016-188307 A JP 2019-116582 A

The technique described in Patent Documents 1 and 2, which employ a base rubber containing a combination of acrylic rubber and specific components in the above-mentioned specific silane crosslinking method, has made it possible to improve oil resistance.
On the other hand, it is preferable that the method for manufacturing the wiring material can cope with a wide range of manufacturing conditions from the viewpoint of further increasing the productivity of industrial manufacturing. However, there is a problem that changes in manufacturing conditions naturally tend to affect product characteristics. For example, in the above silane cross-linking method, when silane cross-linking is performed after extrusion molding to produce a small-sized molded body or a thin-walled molded body, etc., the screw rotation speed of the extruder is increased while the extrusion speed (linear speed) is kept as it is. may decrease. Then, the silane-grafted resin or rubber stays in the cylinder of the extruder for a long time, and the heat of the cylinder tends to partially cause silane cross-linking there. As a result, there is a problem that gels, lumps, and the like are generated on the surface of the extruded body, causing poor appearance.
As a result of examination by the present inventors, it was found that the manufacturing methods described in Patent Documents 1 and 2 cannot sufficiently cope with changes in the screw rotation speed of resin or rubber (changes in coating film thickness, etc.). It's here. In addition, the molded article obtained by the manufacturing method described in Patent Document 2 is very hard and unsuitable as a wiring material for applications requiring flexibility.
Furthermore, it has been found that when oil is used to impart appearance and flexibility, there is a problem that it bleeds onto the surface of the wiring material.

The present invention provides a production method capable of obtaining a silane-crosslinked acrylic rubber molding having excellent appearance, high-temperature oil resistance, mechanical properties, and flexibility, and suppressing bleeding, and a silane-crosslinked acrylic obtained by this production method. An object of the present invention is to provide a rubber molded article and a silane-crosslinked acrylic rubber molded article.
Another object of the present invention is to provide a silane-crosslinkable acrylic rubber composition suitable for producing the silane-crosslinked acrylic rubber molded article.

The present inventors have found that, in the silane cross-linking method using ethylene-acrylic rubber, when a silane cross-linked acrylic rubber molding is produced by using a base acrylic rubber in combination with a styrene elastomer and mineral oil in a specific amount and in a specific ratio, high-temperature oil-resistant It has been found that the obtained silane-crosslinked acrylic rubber molded article can be imparted with an excellent appearance and flexibility while maintaining its properties and mechanical properties, and that bleeding can be suppressed. 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 acrylic rubber molding comprising the following steps (1), (2) and (3),
Step (1): With respect to 100 parts by mass of the base acrylic rubber, 0.01 to 0.6 parts by mass of an organic peroxide, 1 to 200 parts by mass of an inorganic filler, and 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 acrylic rubber and a silanol condensation catalyst are melt-mixed to form the radicals generated from the organic peroxide. A step of obtaining a silane-crosslinkable acrylic rubber composition containing a silane-crosslinkable acrylic rubber by subjecting a graftable reaction site and a graftable site of the base acrylic rubber to a graft reaction. Step (2): the silane-crosslinking. Step (3): Contacting the molded article with water to obtain a silane-crosslinked acrylic rubber molded article The base acrylic rubber is an ethylene-acrylic rubber 20 85% by mass, 60% by mass or less of ethylene resin, 1 to 20% by mass of styrene elastomer, and 1 to 20% by mass of mineral oil, the ratio of the content of the styrene elastomer to the content of the mineral oil (styrene Elastomer content: Mineral oil content) is contained so that the mass ratio is 1:2.5 to 1:0.5,
In performing the step (1),
When all of the base acrylic rubber is melt-mixed in step (a-2) below, step (1) includes step (a-1), step (a-2) and step (c) below, and When part of the base acrylic rubber is melt-mixed in step (a-2), step (1) is the following step (a-1), step (a-2), step (b) and step (c). A method for producing a silane-crosslinked acrylic rubber molded product.
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 acrylic rubber are mixed with the organic In the presence of an oxide, melt-mixing is performed at a temperature equal to or higher than the decomposition temperature of the organic peroxide, and the radicals generated from the organic peroxide form the grafting reaction site and the grafting reaction site of the base acrylic rubber. Step (b): Melt-mix the remainder of the base acrylic rubber and the silanol condensation catalyst to prepare a catalyst masterbatch. step (c): a step of melt-mixing the silane masterbatch and the silanol condensation catalyst or the catalyst masterbatch to obtain the silane-crosslinkable acrylic rubber composition [2]
[1], wherein the ethylene resin is an ethylene-α-olefin copolymer resin or an ethylene-vinyl acetate copolymer resin having a density of 0.910 to 0.940 g/cm ³ , or a mixture thereof; A method for producing the described silane-crosslinked acrylic rubber molding.
[3]
The method for producing a silane-crosslinked acrylic rubber molding according to [1] or [2], wherein the base acrylic rubber contains 1 to 6% by mass of a propylene resin per 100% by mass of the base acrylic rubber.
[4]
The method for producing a silane-crosslinked acrylic rubber molding according to any one of [1] to [3], wherein 30 to 200 parts by mass of the inorganic filler is blended with 100 parts by mass of the base acrylic rubber.
[5]
The silane-crosslinked acrylic rubber molded article according to any one of [1] to [4], wherein the silanol condensation catalyst is blended in an amount of 0.01 to 0.5 parts by mass with respect to 100 parts by mass of the base acrylic rubber. manufacturing method.
[6]
The ethylene-acrylic rubber is a binary copolymer of ethylene and an acrylic acid alkyl ester, or a terpolymer of ethylene, an acrylic acid alkyl ester and a copolymer component containing a carboxy group, or a mixture thereof. The method for producing a silane-crosslinked acrylic rubber molded article according to any one of [1] to [5].
[7]
The method for producing a silane-crosslinked acrylic rubber molded article according to any one of [1] to [6], wherein the inorganic filler is a metal hydrate.
[8]
In the step (1), 30 to 180 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 of the organic peroxide are added to 100 parts by mass of the base acrylic rubber. The method for producing a silane-crosslinked acrylic rubber molding according to any one of [1] to [7], wherein 6 parts by mass and 0.01 to 0.5 parts by mass of the silanol condensation catalyst are melt-mixed.
[9]
A silane-crosslinkable acrylic rubber composition produced by the step (1) of the production method according to any one of [1] to [8].
[10]
A silane-crosslinked acrylic rubber molded article produced by the method for producing a silane-crosslinked acrylic rubber molded article according to any one of [1] to [8].
[11]
A silane-crosslinked acrylic rubber molded article comprising the silane-crosslinked acrylic rubber molded article according to [10].

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 capable of obtaining a silane-crosslinked acrylic rubber molding having excellent appearance, high-temperature oil resistance, mechanical properties, and flexibility, and suppressing bleeding, and a silane-crosslinked acrylic obtained by this production method. Rubber moldings and silane-crosslinked acrylic rubber moldings can be provided. Moreover, it is possible to provide a silane-crosslinkable acrylic rubber composition suitable for producing a silane-crosslinkable acrylic rubber molded article exhibiting such excellent properties.

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

<Base acrylic rubber>
The base acrylic rubber used in the present invention contains ethylene-acrylic rubber, styrene elastomer, and paraffin oil as rubber components. The base acrylic 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 acrylic rubber component may contain rubbers or resins other than ethylene-acrylic rubber, styrene elastomer, paraffin oil, and ethylene resin 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-acrylic rubber -
In the present invention, ethylene-acrylic rubber refers to a rubber obtained by copolymerizing at least ethylene and alkyl acrylate as constituent components. The ethylene-acrylic rubber preferably contains 50% by mass or more of an acrylic acid alkyl ester component. The acrylic acid alkyl ester component is preferably 60% by mass or less. Those containing methyl acrylate and/or ethyl acrylate as monomer components are more preferred, and those containing methyl acrylate are particularly preferred.
Ethylene-acrylic rubbers include copolymers such as binary copolymers of ethylene and acrylic acid alkyl esters, and terpolymers obtained by further copolymerizing copolymer components containing carboxyl groups. rubber can be particularly preferably used. Examples of such a carboxy group-containing copolymer component include compounds having a carboxy group and an unsaturated group (usually an ethylenically unsaturated group) copolymerizable with ethylene or alkyl acrylate. Examples include (meth)acrylic acid and maleic acid. Terpolymers include, for example, ethylene-alkyl acrylate-acrylic acid copolymers and ethylene-alkyl acrylate-maleic acid copolymers, particularly ethylene-alkyl acrylate-acrylic acid copolymers. Polymers are preferred. The ethylene-acrylic rubber may be used alone or in combination of two or more.
Examples of the ethylene-acrylic rubber composed of a binary copolymer include Baymac DP and Baymac DLS. Examples of ethylene-acrylic rubbers composed of terpolymers include Baymac G, Baymac HG, Baymac LS, Baymac GLS, Baymac Ultra HT-OR (trade names, all manufactured by DuPont Mitsui Polychemicals). .

- Ethylene resin -
By incorporating an ethylene resin into the base acrylic rubber of the present invention, mechanical properties can be improved.
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 polyethylene resins may be used singly or in combination of two or more. Among these polyethylene resins, it is preferable to use LLDPE.
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 acrylic rubber of the present invention include "Evolue" (trade name: manufactured by Prime Polymer Co., Ltd.). etc. can be mentioned.

The density of the ethylene-α-olefin copolymer resin is preferably 0.910-0.940 g/cm ³ , more preferably 0.920-0.940 g/cm ³ . As a result, the inorganic filler receptivity is further increased, and excellent mechanical properties can be obtained, and high-temperature oil resistance can be maintained. The density of the ethylene-α-olefin copolymer resin can be measured by the method described in JIS K7112.

The ethylene resin is preferably an ethylene-α-olefin copolymer resin, an ethylene-vinyl acetate copolymer resin, or a mixture thereof having a density of 0.910 to 0.940 g/cm ³ .

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.

- 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).

- 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.

- Other base acrylic rubber components -
A propylene resin or the like can be used as long as the effects of the present invention are not impaired.

The propylene 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 can be used. can.
The ethylene-propylene random copolymer refers to one having an ethylene component content of about 1 to 10% by mass, and refers to a copolymer in which 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 preferable 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.

- Content in base acrylic rubber -
The base acrylic rubber contains 20 to 85% by mass of ethylene-acrylic rubber, 60% by mass or less of ethylene resin, 1 to 20% by mass of styrene elastomer, and 1 to 20% by mass of mineral oil. (content of styrene elastomer: content of mineral oil) is 1:2.5 to 1:0.5 by mass.
In the base acrylic 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 ethylene-acrylic rubber is 20 to 85% by mass in 100% by mass of the base acrylic rubber. If the content is too low, the heat-resistant silane-crosslinked acrylic rubber molded article may not be provided with sufficient high-temperature oil resistance and flexibility. On the other hand, if the content is too high, sufficient mechanical strength (tensile strength) may not be imparted. In addition, the resulting heat-resistant silane-crosslinked resin molding may tack and fuse together.
The content of ethylene-acrylic rubber in the base acrylic rubber is preferably 30 to 85% by mass. When the content of the ethylene-acrylic rubber is within the above range, the high-temperature oil resistance and flexibility of the heat-resistant silane-crosslinked resin molding can be further improved.

The ethylene resin content is 60% by mass or less, preferably 5 to 50% by mass, more preferably 15 to 40% by mass, based on 100% by mass of the base acrylic rubber, from the viewpoint of enhancing flexibility and high-temperature oil resistance. be.

The content of the styrene elastomer is 1 to 20% by mass, preferably 1 to 10% by mass, more preferably 2 to 8% by mass, based on 100% by mass of the base acrylic rubber. Within this range, high-temperature oil resistance and mechanical properties can be enhanced, and an excellent appearance can be imparted.

The content of mineral oil is 1 to 20% by mass, preferably 1 to 10% by mass, more preferably 2 to 8% by mass, based on 100% by mass of the base acrylic rubber. Within this range, high-temperature oil resistance and mechanical properties can be enhanced, and an excellent appearance can be imparted.

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, bleeding can be suppressed while imparting high-temperature oil resistance.

When the base acrylic rubber contains other base acrylic rubber components, the content of the other base acrylic rubber components is particularly limited when the amounts of ethylene-acrylic rubber, ethylene resin, styrene elastomer, and mineral oil are within the above ranges. Although not limited, it is preferably 40 to 75% by mass, more preferably 50 to 70% by mass, based on 100% by mass of the base acrylic rubber.
When the other base acrylic rubber component is a propylene resin, the content of the propylene resin in 100% by mass of the base acrylic rubber is preferably 1 to 6% by mass, preferably 1 to 5% by mass.

<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 particularly limited as long as it has a site on its surface that can be chemically bonded by a reactive site such as a silanol group of a silane coupling agent, a hydrogen bond, a covalent bond, or an intermolecular bond. can be used without 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 containing water or water of crystallization, OH groups such as carboxyl groups), amino groups, SH groups, and the like. be done.

The inorganic filler is not particularly limited, and examples thereof include aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, calcium silicate, magnesium silicate, calcium oxide, magnesium oxide, aluminum oxide, aluminum nitride, aluminum borate whisker, Metal hydrates such as compounds having a hydroxyl group or water of crystallization such as hydrated aluminum silicate, hydrated magnesium silicate, basic magnesium carbonate, hydrotalcite, and talc. Boron nitride, silica (crystalline silica, amorphous silica, etc.), carbon, clay, zinc oxide, tin oxide, titanium oxide, molybdenum oxide, antimony trioxide, silicone compounds, quartz, zinc borate, white carbon, zinc borate, zinc hydroxystannate, zinc stannate and the like. An inorganic filler may be used individually by 1 type, and may use 2 or more types together.
The inorganic filler is preferably at least one selected from metal hydrates (more preferably, aluminum hydroxide and magnesium hydroxide), silica, clay, talc, calcium carbonate, and more preferably metal hydrates.

A surface-treated 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 inorganic fillers include KISUMA 5L and KISUMA 5P (both are trade names of magnesium hydroxide manufactured by Kyowa Chemical Industry 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.

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.

<Silane coupling agent>
The silane coupling agent used in the present invention has a grafting reaction site (group or atom) capable of grafting reaction with the base acrylic rubber in the presence of radicals generated by decomposition of the organic peroxide. In addition, it has a reactive site (including a site formed by hydrolysis, such as a silyl ester group) capable of reacting with a chemically bonding site of the inorganic filler and capable of silanol condensation. Examples of such silane coupling agents include silane coupling agents conventionally used in silane cross-linking methods.
As the silane coupling agent, for example, a compound represented by the following general formula (1) can be used.

In general formula (1), R _a11 is a group containing an ethylenically unsaturated group, R _b11 is an aliphatic hydrocarbon group, a hydrogen atom or ^Y13 . Y ¹¹ , Y ¹² and Y ¹³ are hydrolyzable organic groups. Y ¹¹ , Y ¹² and Y ¹³ may be the same or different.

R _a11 is a grafting reaction site, preferably a group containing an ethylenically unsaturated group. Examples of groups containing an ethylenically unsaturated group include vinyl groups, (meth)acryloyloxyalkylene groups, and p-styryl groups. Among them, a vinyl group is preferred.
R _b11 represents an aliphatic hydrocarbon group, a hydrogen atom or Y ¹³ described later. The aliphatic hydrocarbon group includes monovalent aliphatic hydrocarbon groups having 1 to 8 carbon atoms, excluding aliphatic unsaturated hydrocarbon groups. R _b11 is preferably Y ¹³ described later.

Y ¹¹ , Y ¹² and Y ¹³ represent reactive sites (hydrolyzable organic groups) capable of silanol condensation. 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, and an alkoxy group is preferred. Specific examples of hydrolyzable organic groups include methoxy, ethoxy, butoxy, acyloxy and the like. Among these, methoxy or ethoxy is more 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. A ring agent or a silane coupling agent in which at least one of Y ¹¹ , Y ¹² and Y ¹³ is a methoxy group.

Specific examples of silane coupling agents include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltributoxysilane, vinyldimethoxyethoxysilane, vinyldimethoxybutoxysilane, vinyldiethoxybutoxysilane, allyltrimethoxysilane, allyltrimethoxysilane, and allyltrimethoxysilane. vinylalkoxysilanes such as ethoxysilane and vinyltriacetoxysilane; and (meth)acryloxyalkoxysilanes such as methacryloxypropyltrimethoxysilane, methacryloxypropyltriethoxysilane and methacryloxypropylmethyldimethoxysilane.

Among the above silane coupling agents, a silane coupling agent having a terminal vinyl group and an alkoxy group is more preferable, and vinyltrimethoxysilane or vinyltriethoxysilane is particularly preferable.

Silane coupling agents may be used alone or in combination of two or more. Moreover, it may be used as it is or after being diluted with a solvent or the like.

<Silanol condensation catalyst>
The silanol condensation catalyst functions to cause the silane coupling agent grafted onto the base acrylic rubber to undergo a condensation reaction in the presence of moisture. Based on the action of this silanol condensation catalyst, the rubber components are crosslinked via the silane coupling agent. As a result, a silane-crosslinked acrylic rubber molded article having excellent tensile strength can be obtained. In addition, a silane-crosslinked acrylic rubber molded article having excellent heat resistance can be obtained, if necessary.

The silanol condensation catalyst is not particularly limited, and examples thereof include organotin compounds, metallic soaps, platinum compounds and the like. Common silanol condensation catalysts include, 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, organoplatinum compounds, and the like are used. The silanol condensation catalyst may be used alone or in combination of two or more.

<Carrier>
A silanol condensation catalyst is optionally mixed with a resin or rubber and used. Such a resin or rubber (also referred to as a carrier) is not particularly limited, but the rubber and/or resin components described for the base acrylic rubber can be used. Ethylene-acrylic rubber and ethylene resin are preferred, and LLDPE and EVA are more preferred.

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

Step (1): In the presence of 0.01 to 0.5 parts by mass of an organic peroxide, 1 to 200 parts by mass of an inorganic filler, and radicals generated from the organic peroxide with respect to 100 parts by mass of the base acrylic 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 acrylic rubber and a silanol condensation catalyst are melt-mixed to obtain a grafting reaction site by radicals generated from the organic peroxide. and a graftable site of the base acrylic rubber to obtain a silane-crosslinkable acrylic rubber composition (reaction composition) containing a silane-crosslinkable acrylic rubber. Step (2): Silane-crosslinkable Molding the acrylic rubber composition to obtain a molded body Step (3): Contacting the molded body with water to obtain a silane-crosslinked acrylic rubber molded body

The above step (1) has the following steps depending on how the base acrylic rubber is used.
When all of the base acrylic rubber is melt-mixed in step (a-2) below, step (1) includes step (a-1), step (a-2) and step (c) below, and When part of the base acrylic rubber is melt-mixed in step (a-2), step (1) is the following step (a-1), step (a-2), step (b) and step (c). have

Step (a-1): Step of mixing an inorganic filler and a silane coupling agent to prepare a mixture Step (a-2): The mixture and all or part of the base acrylic rubber are combined in the presence of an organic peroxide. by melting and 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 sites and the graft-reactive sites of the base acrylic rubber by radicals generated from the organic peroxide. Step of preparing a silane masterbatch containing a silane crosslinkable acrylic rubber Step (b): Melting and mixing the remainder of the base acrylic rubber and a silanol condensation catalyst to prepare a catalyst masterbatch Step (c): With a silane masterbatch and a silanol condensation catalyst or a catalyst masterbatch to obtain a silane-crosslinkable acrylic rubber composition. That's what it means.

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

When part of the base acrylic rubber is blended in step (a-2), 100 parts by mass of the base acrylic rubber in step (1) is added to the base mixed in step (a-2) and step (b). It is the total amount of acrylic rubber.
Here, when the remainder of the base acrylic rubber is blended in step (b), the base acrylic rubber is preferably blended in step (a-2) in an amount of 80 to 95% by mass, more preferably 85 to 92% by mass. and, in step (b), preferably 5 to 20% by mass, more preferably 8 to 15% by mass.

In step (1), the amounts (contents) of the ethylene-acrylic rubber, ethylene resin, styrene elastomer, mineral oil, etc. in the base acrylic rubber are as described above. The ratio of the styrene elastomer content to the mineral oil content is also as described above.
The styrene elastomer and mineral oil may be mixed in either step (a-2) or step (b), but are preferably mixed in step (a-2).

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, based on 100 parts by mass of the base acrylic rubber. 0.05 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, improving mechanical properties, In some cases, sufficient heat resistance and reinforcing properties can be obtained, and since direct cross-linking of the rubber component due to side reactions is suppressed, it is possible to obtain a composition excellent in appearance without causing gel blisters. .

In step (1), the amount of the inorganic filler compounded is 1 to 200 parts by mass, preferably 30 to 200 parts by mass, more preferably 40 to 200 parts by mass, and 30 to 200 parts by mass with respect to 100 parts by mass of the base acrylic rubber. 180 parts by mass is more preferable. By adjusting the amount of the inorganic filler to be 1 to 200 parts by mass, the silane-crosslinked acrylic rubber molding can be imparted with flexibility and mechanical properties necessary for wiring materials. Furthermore, secondary molding can be made possible by suppressing an increase in load during molding and kneading.

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 15 parts by mass with respect to 100 parts by mass of the base acrylic rubber. 5 parts 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 roughness such as gel spots in the molded article. Furthermore, if necessary, the cross-linking reaction can be allowed to proceed sufficiently to exhibit excellent tensile strength.
When the amount of the silane coupling agent is more than 2.0 parts by mass and 15.0 parts by mass or less, it is possible to produce a silane-crosslinked acrylic rubber molded article having more excellent high-temperature oil resistance.

In step (1), the amount of the silanol condensation catalyst to be blended is not particularly limited, and is preferably 0.01 to 0.5 parts by mass, more preferably 0.02 to 0.5 parts by mass, relative to 100 parts by mass of the base acrylic rubber. 5 parts by mass, more preferably 0.05 to 0.4 parts by mass, particularly preferably 0.08 to 0.3 parts by mass. When the amount of the silanol condensation catalyst is within the above range, the formation of gel spots can be suppressed during molding, and cross-linking sufficiently progresses, resulting in excellent mechanical strength. Moreover, heat resistance can be imparted if necessary.

From the viewpoint of suppressing bleeding and imparting a superior level of appearance, high-temperature oil resistance, mechanical properties, and flexibility, in step (1), 30 to 30 parts of the inorganic filler is added to 100 parts by mass of the base acrylic rubber. 180 parts by mass, 1 to 15 parts by mass of a silane coupling agent, 0.01 to 0.6 parts by mass of an organic peroxide, and 0.01 to 0.5 parts by mass of a silanol condensation catalyst can be melt-mixed. preferable.

When performing step (1), step (a-1) and step (a-2) are performed in sequence. That is, first, the inorganic filler and the silane coupling agent are mixed, and then the obtained mixture and all or part of the base acrylic rubber are melted at a temperature equal to or higher than the decomposition temperature of the organic peroxide in the above-mentioned amount. By kneading, the above grafting reaction is caused to prepare a silane masterbatch.
The method of mixing the base acrylic rubber is not particularly limited. For example, a premixed base acrylic 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. Furthermore, the desired shape can be obtained during extrusion.

The method for pre-mixing the inorganic filler and the silane coupling agent is not particularly limited, but mixing methods such as wet processing and dry processing can be mentioned. Specifically, the inorganic filler and the silane coupling agent are heated at a temperature below the decomposition temperature of the organic peroxide, preferably 10 to 60°C, more preferably around room temperature (20 to 25°C) for several minutes to several hours. , dry or wet mixing, and more preferred is 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. In step (a-1), the base acrylic 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 acrylic rubber are then mixed with the presence of an organic peroxide. They are melt-mixed at a temperature equal to or higher than the decomposition temperature of the organic peroxide (step (a-2)). By doing so, excessive cross-linking reaction between the base acrylic rubber components can be prevented, and a cross-linked molded article having excellent appearance can be obtained.
By 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 acrylic rubber. As a result, a silane-crosslinkable acrylic rubber (silane graft polymer) is synthesized in which the silane coupling agent is covalently bonded to the rubber component, and a silane masterbatch containing this silane-crosslinkable acrylic rubber is prepared.

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 acrylic 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. A closed mixer such as a Banbury mixer or various kneaders is preferred in terms of the dispersibility of the base acrylic rubber component and the stability of the cross-linking reaction.

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 extrusion 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 acrylic 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 acrylic rubber are grafted to form a silane masterbatch (also known as silane MB). ) are prepared. The silane MB thus obtained is preferably used together with a silanol condensation catalyst or a catalyst masterbatch to be described later for the production of the reaction composition (silane-crosslinkable acrylic rubber composition) prepared in step (1), as described later. Used. Silane MB is a mixture containing silane-crosslinkable acrylic rubber in which a silane coupling agent is graft-reacted to a rubber component to the extent that it can be molded by the step (2) described later.

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

Although the mixing ratio of the base acrylic rubber as a carrier and the silanol condensation catalyst is not particularly limited, it is preferably set so as to satisfy the above-described blending 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 acrylic 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 or higher of the base acrylic rubber component, 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 in place of or in addition to the remainder of the base acrylic rubber. That is, in step (b), the remainder of the base acrylic rubber when part of the base acrylic rubber is melt-mixed in step (a-2), or the resin other than the rubber component used in step (a-2). , and a silanol condensation catalyst may be melt mixed to prepare a catalyst masterbatch.
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% by mass of the base acrylic rubber because it is less likely to cause lumps during molding. parts by weight, preferably 1 to 60 parts by weight, more preferably 2 to 50 parts by weight, and even more preferably 3 to 40 parts by weight.

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.

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 acrylic rubber composition prepared in step (1).

In the production method of the present invention, the step (c) of obtaining a silane-crosslinkable acrylic rubber composition (reaction composition) by melt-mixing the silane MB and the silanol condensation catalyst or catalyst MB is then carried out. This reaction composition is a composition containing the silane-crosslinkable acrylic 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 acrylic rubber or carrier, and is preferably 80 to 250°C, more preferably 100 to 240°C. Other conditions, such as mixing (kneading) time, can be appropriately set.

In step (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 acrylic rubber composition as a reaction composition. This silane-crosslinkable acrylic rubber composition contains 20 to 85% by mass of ethylene-acrylic rubber, 60% by mass or less of ethylene resin, 1 to 20% by mass of styrene elastomer, and 1 to 20% by mass of mineral oil. In the base acrylic rubber containing so that the ratio of the ratio to the content of mineral oil (content of styrene elastomer: content of mineral oil) is 1:2.5 to 1:0.5 by mass , a silane-crosslinkable acrylic rubber grafted with a silane coupling agent, 1 to 200 parts by mass of an inorganic filler per 100 parts by mass of the base acrylic rubber, and a silanol condensation catalyst.
This silane-crosslinkable acrylic rubber composition contains silane-crosslinkable acrylic rubbers with different crosslinking methods. In this silane-crosslinkable acrylic 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-crosslinkable acrylic rubber consists of a crosslinkable rubber in which a silane coupling agent bonded or adsorbed to an inorganic filler is grafted onto a base acrylic rubber, and a base acrylic rubber in which a silane coupling agent that is not bonded or adsorbed to an inorganic filler is grafted onto the base acrylic rubber. at least a crosslinkable rubber grafted onto. In addition, the silane-crosslinkable acrylic rubber 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 acrylic 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 melted and mixed in step (c), but for the resulting silane-crosslinkable acrylic rubber composition, at least the molding in step (2) It is assumed that gender is preserved.

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

In step (1), the amounts of other base acrylic 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 the rubber components is unlikely to occur during melt-mixing, and the appearance of the silane-crosslinked acrylic 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 acrylic rubber molded article of the present invention, step (2) and step (3) are then performed.
In the method for producing a silane-crosslinked acrylic rubber molded article of the present invention, the step (2) of molding the obtained reaction composition to obtain a molded article is carried out. In this step (2), it is sufficient that the reaction composition can be molded. Molding conditions are selected. The molding method includes extrusion molding using an extruder, extrusion molding using an injection molding machine, and molding using other molding machines. Extrusion molding is preferable when the silane-crosslinked acrylic rubber molded article of the present invention or a silane-crosslinked acrylic rubber molded article containing the silane-crosslinked acrylic rubber molded article is an electric wire or an optical fiber cable.
When step (2) is carried out by extrusion molding, the extrusion speed is not particularly limited, and can be preferably set to a linear speed of 5 to 100 m/min, particularly preferably 10 to 50 m/min.
Further, the screw rotation speed of the extruder is not particularly limited, and it can be set to usually 15 to 60 rpm, preferably 20 to 40 rpm, considering the thickness of the coating layer.
Further, in carrying out the production method of the present invention, the screw rotation speed set during extrusion molding can be appropriately set to a low rotation speed. Lowering the screw rotation speed is effective when molding thin wiring materials and the like. For example, the rotation speed can be set to 2 to 10 rpm, preferably 2 to 8 rpm.

In addition, step (2) can be performed simultaneously with step (c) or consecutively. That is, as one embodiment of the melt-mixing in the step (c), there is a mode in which the raw materials are melt-mixed during melt-molding, for example, during or immediately before extrusion molding. For example, pellets such as dry blends may be mixed at room temperature (for example, 20 to 25 ° C.) or at a high temperature and introduced into a molding machine (melt mixing), or may be melt mixed after mixing and pelletized again. can be introduced into the molding machine. More specifically, a molding material consisting of a silane MB and a silanol condensation catalyst or a catalyst MB is melt-kneaded in a coating device, and then extrusion-coated on the outer peripheral surface of a conductor or the like to form a desired shape. process can be adopted.
Thus, a molded article of the silane-crosslinkable acrylic rubber composition is obtained. Like the silane-crosslinkable acrylic 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 acrylic 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 acrylic rubber molded article of the present invention, the step (3) of contacting the molded article obtained in the step (2) 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 acrylic rubber molded article 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, eg, 20 to 25°C. 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 acrylic rubber molded article is produced from the silane-crosslinked acrylic rubber composition of the present invention. This silane-crosslinked acrylic rubber molded article contains a crosslinked rubber obtained by condensing a silane-crosslinkable acrylic rubber through a siloxane bond, as will be described later. One form of this silane-crosslinked acrylic 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. Furthermore, it may contain a silane coupling agent, an unreacted rubber component and/or an uncrosslinked silane-crosslinkable acrylic rubber.

The details of the reaction mechanism in the production method of the present invention are not yet clear, but are considered as follows. That is, when a rubber component is heated and kneaded together with an inorganic filler and a silane coupling agent in the presence of an organic peroxide at a temperature higher than the decomposition temperature of the organic peroxide, the organic peroxide decomposes to generate radicals, which are added to the rubber component. Grafting of the silane coupling agent to it occurs.

The heating in step (a-2) also partially causes a chemical bond formation reaction due to covalent bonding between the silane coupling agent and groups such as hydroxyl groups on the surface of the inorganic filler.
In the present invention, the final cross-linking reaction may be performed in step (3), and if the silane coupling agent is blended into the base acrylic rubber in a specific amount as described above, processability during molding (extrusion moldability is impaired). It is possible to mix a large amount of inorganic filler without any damage, and it is possible to have mechanical properties and the like while ensuring high-temperature oil resistance.

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 an inorganic filler and a silane coupling agent before and/or during kneading with the base acrylic rubber, the silane coupling agent can be added to the inorganic filler via a group capable of chemically bonding with its reaction site. , and a group capable of grafting reaction present at the other end binds to the uncrosslinked portion (site capable of grafting reaction) of the rubber component and is held. Alternatively, it is held by being physically or chemically adsorbed to the holes or surfaces of the inorganic filler without bonding to the inorganic filler. In this way, the silane coupling agent that binds to the inorganic filler with a strong bond (the reason for this is, for example, the formation of a chemical bond with the hydroxyl group on the surface of the inorganic filler, etc. can be considered) and the silane coupling agent that binds with a weak bond ( The reason for this may be, for example, interactions via hydrogen bonds, interactions between ions, partial charges or dipoles, effects due to adsorption, etc.). In this state, when the organic peroxide is added and kneaded, the silane coupling agent is hardly volatilized as described later, and the silane coupling agent having different bonds with the inorganic filler undergoes a grafting reaction to the rubber component. A silane-crosslinkable acrylic rubber is formed.

By the kneading described above, the silane coupling agent having a strong bond with the inorganic filler among the silane coupling agents retains the bond with the inorganic filler, and the cross-linking group capable of grafting reaction becomes the rubber component. Grafting reaction with the cross-linking site. In particular, when a plurality of silane coupling agents are bonded to the surface of one inorganic filler particle via strong bonding, a plurality of rubber components are bonded via this inorganic filler particle. These reactions or bonds spread the crosslinked network through the inorganic filler. That is, a silane-crosslinkable acrylic rubber is formed by grafting the silane coupling agent bonded to the inorganic filler to the rubber component.

In the case of a silane coupling agent having a strong bond with the inorganic filler, the silanol condensation catalyst hardly causes a condensation reaction in the presence of water, and the bond with the inorganic filler is maintained. The reason why the silanol condensation reaction hardly occurs is considered to be that the binding energy between the inorganic filler and the silane coupling agent is very high, and the condensation reaction does not occur even under the presence of the silanol condensation catalyst. Thus, the rubber component and the inorganic filler are bonded together, and the rubber component is crosslinked via the silane coupling agent. As a result, the adhesion between the rubber component and the inorganic filler is strengthened, and a molded article having good tensile strength can be obtained. In particular, a plurality of silane coupling agents can be bonded to the surface of one inorganic filler particle, and high tensile strength can be obtained. Thus, the silane coupling agent bonded to the inorganic filler with a strong bond is considered to contribute to high mechanical properties, wear resistance, scratch resistance and the like in some cases.

On the other hand, among the silane coupling agents, the silane coupling agent having a weak bond with the inorganic filler detaches from the surface of the inorganic filler, and the group capable of grafting reaction, which is the cross-linking group of the silane coupling agent, is organic peroxide. Grafting reaction occurs by reacting with the radicals of the rubber component generated by abstraction of hydrogen radicals by the radicals generated by the decomposition of the material. That is, a silane-crosslinkable acrylic rubber is formed in which the silane coupling agent separated from the inorganic filler is grafted to the rubber component. The silane coupling agent in the grafted portion produced in this manner is then mixed with a silanol condensation catalyst and brought into contact with moisture to cause a condensation reaction (crosslinking reaction). The high-temperature oil resistance of the silane-crosslinked acrylic rubber molded article obtained by this cross-linking reaction is enhanced, making it possible to obtain a silane-crosslinked acrylic rubber molded article having excellent high-temperature oil resistance. Furthermore, in some cases, it is also possible to impart heat resistance that does not melt even at high temperatures. Thus, it is considered that the silane coupling agent that is weakly bonded to the inorganic filler contributes to the improvement of the degree of cross-linking, that is, the improvement of heat resistance.

In particular, in the present invention, the cross-linking reaction by condensation using a silanol condensation catalyst in the presence of water in step (3) is carried out after forming the molded article. As a result, compared to the conventional method of forming a molded article after the final cross-linking reaction, workability in the steps up to formation of the molded article is excellent, and higher heat resistance than conventional methods can be obtained.

In the present invention, in addition to high temperature oil resistance and mechanical properties due to silane crosslinking, excellent appearance, mechanical properties, high temperature oil resistance and flexibility can be imparted to silane crosslinked acrylic rubber moldings, and bleeding can be suppressed. can.
Although the details of how such excellent properties can be imparted to the silane-crosslinked acrylic rubber molded article are not yet clear, it is believed that the base acrylic rubber components work together as follows.
In general, ethylene-acrylic rubber and mineral oil have very poor compatibility, so if they are simply used together, bleeding will occur. On the other hand, styrene elastomers are easily lubricated, and high-temperature oil resistance deteriorates when a large amount is blended.
However, in the present invention, ethylene-acrylic rubber is combined with a styrene elastomer and a mineral oil in a specific amount and in a specific ratio. bleed is suppressed. Furthermore, it is believed that these components have added a softening action and a formability improving action to achieve high-temperature oil resistance, mechanical properties, flexibility, and appearance in a well-balanced manner.

Furthermore, according to a preferred embodiment of the present invention, higher levels of high-temperature oil resistance, heat resistance that does not melt even at high temperatures, flame retardancy, wear resistance, and the like can be imparted. Here, the heat resistance that does not melt even at high temperatures refers to a property that does not melt at a temperature of preferably 200 ° C., more preferably at a temperature of 200 ° C. or higher, preferably a property that can maintain shape or strength. It means that the elongation after heating at 200° C. satisfies 100% or less and the elongation after heating and load removal is 25% or less in the set test.

The manufacturing method of the present invention can be applied to products requiring high-temperature oil resistance (including semi-finished products, parts, and members), products requiring strength in addition to high-temperature oil resistance, products requiring flexibility, and flame retardancy. It can be applied to the manufacture of components of products such as rubber materials and the like, which require good properties, or the members thereof. Therefore, a silane-crosslinked acrylic rubber molded article or a silane-crosslinked acrylic rubber molded article containing a silane-crosslinked acrylic rubber molded article is regarded as such a product.
Examples of the silane-crosslinked acrylic rubber molded article of the present invention or a silane-crosslinked acrylic rubber molded article containing the silane-crosslinked acrylic rubber molded article include, for example, coating materials for electric wires such as flame-retardant insulated wires or flame-retardant cables, and rubber-substituting electric wires and cables. Materials, flame-retardant electric 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.

Among the above oil-resistant products, the manufacturing method of the present invention is particularly suitable for manufacturing electric wires and optical cables, and can form coating materials (insulators, sheaths) thereof.

When the silane-crosslinked acrylic rubber molded article of the present invention or the silane-crosslinked acrylic rubber molded article containing the silane-crosslinked acrylic rubber molded article is an extruded article such as an electric wire or cable, the molding material is preferably extruded into an extruder (extrusion coating apparatus). ), the silane-crosslinkable acrylic rubber composition is prepared by melt-kneading and causing the above-mentioned grafting reaction, and the silane-crosslinkable acrylic rubber composition is extruded to the outer periphery of the conductor, etc., and the conductor is coated. , can be produced (step (c) and step (2)). At this time, the temperature of the extruder is preferably about 120 to 180°C at the cylinder part and about 160 to 210°C at the crosshead part, although it depends on various conditions such as the type of rubber and the take-up speed of the conductor. . Silane-crosslinked acrylic rubber moldings, or silane-crosslinked acrylic rubber molded articles containing silane-crosslinked acrylic rubber moldings, are obtained by using special machines such as electron beam crosslinking machines to prepare silane-crosslinkable acrylic rubber compositions to which a large amount of inorganic filler is added. It can be formed by extrusion coating around the conductor or around a conductor with tandem or twisted tensile strength fibers using conventional extrusion coating equipment. For example, the conductor is preferably a metal conductor, and a single wire or stranded wire of annealed copper, copper alloy, aluminum, or the like can be used. As the conductor, in addition to the bare wire, a tin-plated wire or a wire having an enamel-coated insulating layer can also be used. The thickness of the insulating layer (coating layer made of the silane-crosslinkable acrylic rubber composition of the present invention) formed around the conductor is not particularly limited, but is usually about 0.15 to 5 mm.

The silane-crosslinked acrylic rubber molded article of the present invention is suitable as a material for use in areas where oil resistance, particularly high-temperature oil resistance, is required. Furthermore, it can be used as a replacement for acrylic rubber materials, such as rubber molding materials, which have conventionally undergone cross-linking by electron beam irradiation or chemical vulcanization processes. Moreover, it is particularly effective for members that require flexibility, and can be used, for example, for cabtyre cables, electric wires for automobiles, electric wires for ships, cables for robots, and the like.

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 and 1-2 (together 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 18 and Comparative Examples 1 to 10, part of the rubber component constituting the base acrylic rubber was used as a carrier for the catalyst MB.

(Examples 1 to 18, Comparative Examples 1 to 7, 9)
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), Agitation (premixing) was carried out for 1 minute at 10 rpm to obtain a powder mixture (step (a-1)). Next, the obtained powder mixture, the base acrylic rubber, and the antioxidant are put into a kneader (capacity: 75 L) preheated to 100°C in the mass ratio shown in Table 1, and mixed at 30 rpm for 5 minutes. , 25 rpm for 3 minutes. 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 silane MB was obtained by pelletizing using a feeder ruder and a pelletizer (step (a- 2)). The silane MB thus obtained contains a silane-crosslinkable acrylic rubber obtained by grafting a silane coupling agent to a rubber component.

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

Next, the silane MB and the catalyst MB were put into a closed ribbon blender and dry-blended at room temperature (25° C.) for 5 minutes to obtain a dry blend. At this time, the mixing ratio of the silane MB and the catalyst MB is the mass ratio shown in Table 1. Specifically, in Examples 1 to 4 and 6 to 18 and Comparative Examples 1 and 4 to 7, the base acrylic rubber of the silane MB was 85 parts by mass and the carrier of the catalyst MB was 15 parts by mass. In Example 5, the proportion of the base acrylic rubber of the silane MB was 92 parts by mass and the carrier of the catalyst MB was 8 parts by mass. In Comparative Examples 2, 3, and 9, the proportion of the base acrylic rubber of the silane MB was 95 parts by mass and the carrier of the catalyst MB was 5 parts by mass.

Next, L / D (ratio of screw effective length L to diameter D) = 25, an extruder equipped with a screw with a screw diameter of 25 mm, a die temperature of 200 ° C., below to the feeder side, C3 = 180 ° C., C2 = The extrusion temperature conditions were set to 150°C and C1 = 130°C. The prepared dry blended product was put into this extruder and melt-mixed (step (c)), and an outer diameter of 1.4 mm and an insulating layer thickness of 0.8 mm were applied onto a bare annealed copper wire conductor having a diameter of 0.8 mm. 3 mm, a linear speed of 7 m / min and a screw rotation speed of 10 rpm (extrusion molding conditions (1), appearance test (1) conditions) or an outer diameter of 2.4 mm and an insulating layer thickness of 0.8 mm , and a linear speed of 7 m/min and a screw rotation speed of 35 rpm (extrusion conditions (2) and appearance test (2)) to obtain a coated conductor (step (2)).
A silane-crosslinkable acrylic rubber composition was prepared as a reaction composition by melt-mixing the above dry blend in an extruder before extrusion molding (step (c)). This silane-crosslinkable acrylic rubber composition is a molten mixture of silane MB and catalyst MB and contains the silane-crosslinkable acrylic rubber described above.

The resulting coated conductor is left under conditions of room temperature (23° C.) and 50% RH for 24 hours to hydrolyze the reaction site (trialkoxysilyl group) of the silane coupling agent, followed by silanol condensation reaction (silane cross-linking). (Step (3)). In this way, electric wires were produced by covering the conductor with the silane-crosslinked acrylic rubber molding under the extrusion molding conditions (1) and (2). The silane-crosslinked acrylic rubber molding as the coating layer has the above-mentioned silane-crosslinked acrylic rubber.

(Comparative Example 8)
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 An electric wire 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 .

(Comparative Example 10)
An electric wire was produced in the same manner as in Example 1, except that the components shown in the column of Silane MB in Table 1 were put into a kneader at the mass ratio shown in Table 1 to obtain Silane MB.

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-acrylic rubber 1: Baymac Ultra HT-OR (trade name, manufactured by DuPont, terpolymer)
(2) Ethylene-acrylic rubber 2: Baymac DP (trade name, manufactured by DuPont, binary copolymer)
(3) Ethylene resin 1: Evolue SP3010 (trade name, manufactured by Prime Polymer Co., Ltd., LLDPE, density 0.926 g/cm ³ )
(4) Ethylene resin 2: Evolue SP4020 (trade name, manufactured by Prime Polymer Co., Ltd., LLDPE, density 0.937 g/cm ³ )
(5) Ethylene resin 3: Levaprene 800 (trade name, manufactured by LANXESS, ethylene-vinyl acetate copolymer resin (EVA))
(6) Ethylene resin 4: Evolue SP1540 (trade name, manufactured by Prime Polymer Co., Ltd., LLDPE, density 0.913 g/cm ³ )
(7) Styrene elastomer 1: Tuftec N504 (trade name, manufactured by Asahi Kasei Corporation)
(8) Mineral oil 1: Cosmo Neutral 500 (trade name, Cosmo Oil Lubricants, paraffin oil)
(9) Propylene resin 1: PB222A (trade name, manufactured by SunAllomer, propylene resin)
(10) Modified polyethylene 1: Adtex L6100M (trade name, manufactured by Nippon Polyethylene Co., Ltd., unsaturated carboxylic acid-modified polyethylene (unsaturated carboxylic acid is maleic acid))
(11) Inorganic filler 1: Kisuma 5L (trade name, manufactured by Kyowa Kagaku Co., Ltd., magnesium hydroxide)
(12) Inorganic filler 2: Aerosil 200 (trade name, manufactured by Nippon Aerosil Co., Ltd., silica)
(13) Flame retardant 1: Novaled 120UFA (trade name, red phosphorus manufactured by Rin Kagaku Kogyo Co., Ltd.)
(14) Silane coupling agent 1: KBM-1003 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd., vinyltrimethoxysilane)
(15) Organic peroxide 1: Perhexa 25B (trade name, manufactured by NOF Corporation, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane)
(16) Antioxidant 1: Irganox 1076 (trade name, manufactured by BASF, octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate)
(17) Silanol condensation catalyst 1: ADEKA STAB OT-1 (trade name, manufactured by ADEKA, dioctyltin dilaurate)

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

1. Appearance test (1)
When the electric wire is manufactured by extrusion molding under the above-described extrusion molding conditions (1) (insulating layer thickness of 0.3 mm), "A (advanced)" indicates that no roughness such as gel bumps is observed on the surface of the electric wire, and the surface of the electric wire. "B (Good)" indicates that 1 to 5 rough spots such as gel bumps with a diameter of 1 mm or less are observed per 1 m on the surface of the wire, although there is no roughening such as large gel bumps exceeding 1 mm in diameter on the surface of the wire. A case where 1 or more rough spots such as large gel bumps exceeding 1 mm were observed per 1 m, or a case where 6 or more rough spots such as gel bumps with a diameter of 1 mm or less were observed per 1 m was evaluated as "D (failed)".
In this test, the screw rotation speed is slower than the screw rotation speed in the appearance test (2) to be described later, and the test is conducted under the condition that roughness such as gel bumps is likely to be formed.

2. Appearance test (2)
When the electric wire is manufactured by extrusion molding under the above-described extrusion molding conditions (2) (insulating layer thickness of 0.8 mm), "A (advanced)" indicates that no roughness such as gel bumps is observed on the surface of the electric wire, and the surface of the electric wire. "B (Good)" is when 1 to 5 rough spots such as gel bumps are found per 1 m, and "D (failed)" is when 6 or more rough spots such as gel bumps are seen per 1 m on the surface of the wire. "

3. Bleed test The wire obtained under the above extrusion molding conditions (2) was left in a constant temperature bath at 60°C for 14 days, then left at normal temperature (23°C) for 24 hours, and the appearance of the wire was visually observed. A sample in which no oil seepage (bleed) was observed was rated as "A (acceptable)", and a sample in which oil bleeding was observed was rated as "D (failed)".

4. Tensile properties (mechanical properties)
A tensile test was performed on the coating (tubular piece) extracted from each electric wire manufactured using the coated conductor obtained under the extrusion molding condition (2).
According to JIS C 3005, the tensile strength (MPa) and tensile elongation (%) were measured under the conditions of a gauge length of 25 mm and a tensile speed of 200 mm/min.
Tensile strength is represented by "A" as an excellent level when it is 8 MPa or more, and is represented by "B" as a passing level of this test when it is 6 MPa or more and less than 8 MPa. Those with a value of less than 4.5 MPa were indicated by "D" as a failing level of this test.
The tensile elongation is represented by "A" as an excellent level when it is 125% or more, and is represented by "B" as a passing level of this test when it is 100% or more and less than 125%, 80% or more and 100%. A value of less than 80% was indicated as "C" as the passing level of the main test, and a value of less than 80% was indicated as "D" as the failing level of the main test.

5. Flexibility test (100% modulus)
The tensile stress (100% modulus) at 100% elongation was measured by the tensile property test method.
100% modulus is less than 8 MPa as excellent level "A", 8 MPa or more and less than 9 MPa is good level "B", 9 MPa or more and less than 10 MPa is pass level "C", 10 MPa Those having the above were made into the failure level "D".

6-1. Oil resistance test A
"Oil resistance test" described in JIS C3005 was performed on each electric wire manufactured using the coated conductor obtained under the extrusion molding condition (2). In the oil resistance test A, the oil immersion temperature was 100° C., the oil immersion time was 24 hours, and IRM903 was used as the oil.
The tensile strength and tensile elongation after oil immersion were measured under the same conditions as the above tensile property test.
The tensile strength after oil immersion was divided by the tensile strength before oil immersion (the tensile strength obtained in the above-described tensile test) to calculate the residual percentage (%) of the tensile strength. Similarly, the residual rate of tensile elongation (%) was calculated.
In the evaluation of this test, the tensile strength retention rate and tensile elongation retention rate before and after oil immersion were both 80% or more as an excellent level of this test, "A", the tensile strength retention rate and A good level is "B" when both the tensile elongation retention rate is 70% or more and less than 80%, and the tensile strength retention rate and the tensile elongation retention rate are both 60% or more and less than 70%. was indicated as "C" as a passing level, and "D" as a failing level of this test when either one of the tensile strength retention rate and the tensile elongation retention rate was less than 60%.

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

6-2. Oil resistance test B
"Oil resistance test" described in JIS C3005 was performed on each electric wire manufactured using the coated conductor obtained under the extrusion molding condition (2). In the oil resistance test B, the oil immersion temperature was 100° C., the oil immersion time was 48 hours, and IRM903 was used as the oil.
The tensile strength and tensile elongation after oil immersion were measured under the same conditions as the above tensile property test.
The tensile strength after oil immersion was divided by the tensile strength before oil immersion (the tensile strength obtained in the above-described tensile test) to calculate the residual percentage (%) of the tensile strength. Similarly, the residual rate of tensile elongation (%) was calculated.
In the evaluation of this test, the tensile strength retention rate and tensile elongation retention rate before and after oil immersion were both 80% or more as an excellent level of this test, "A", the tensile strength retention rate and A good level is "B" when both the tensile elongation retention rate is 70% or more and less than 80%, and the tensile strength retention rate and the tensile elongation retention rate are both 60% or more and less than 70%. was indicated as "C" as a passing level, and "D" as a failing level of this test when either one of the tensile strength retention rate and the tensile elongation retention rate was less than 60%.

6-3. Oil resistance test C
"Oil resistance test" described in JIS C3005 was performed on each electric wire manufactured using the coated conductor obtained under the extrusion molding condition (2). In the oil resistance test C, the oil immersion temperature was 100° C., the oil immersion time was 72 hours, and IRM903 was used as the oil.
The tensile strength and tensile elongation after oil immersion were measured under the same conditions as the above tensile property test.
The tensile strength after oil immersion was divided by the tensile strength before oil immersion (the tensile strength obtained in the above-described tensile test) to calculate the residual percentage (%) of the tensile strength. Similarly, the residual rate of tensile elongation (%) was calculated.
In the evaluation of this test, the tensile strength retention rate and tensile elongation retention rate before and after oil immersion were both 80% or more as an excellent level of this test, "A", the tensile strength retention rate and A good level is "B" when both the tensile elongation retention rate is 70% or more and less than 80%, and the tensile strength retention rate and the tensile elongation retention rate are both 60% or more and less than 70%. was indicated as "C" as a passing level, and "D" as a failing level of this test when either one of the tensile strength retention rate and the tensile elongation retention rate was less than 60%.

6-4. Oil resistance test D
"Oil resistance test" described in JIS C3005 was performed on each electric wire manufactured using the coated conductor obtained under the extrusion molding condition (2). In the oil resistance test D, the oil immersion temperature was 100° C., the oil immersion time was 168 hours, and IRM903 was used as the oil.
The tensile strength and tensile elongation after oil immersion were measured under the same conditions as the above tensile property test.
The tensile strength after oil immersion was divided by the tensile strength before oil immersion (the tensile strength obtained in the above-described tensile test) to calculate the residual percentage (%) of the tensile strength. Similarly, the residual rate of tensile elongation (%) was calculated.
In the evaluation of this test, the tensile strength retention rate and tensile elongation retention rate before and after oil immersion were both 80% or more as an excellent level of this test, "A", the tensile strength retention rate and A good level is "B" when both the tensile elongation retention rate is 70% or more and less than 80%, and the tensile strength retention rate and the tensile elongation retention rate are both 60% or more and less than 70%. was indicated as "C" as a passing level, and "D" as a failing level of this test when either one of the tensile strength retention rate and the tensile elongation retention rate was less than 60%.

7. Hot Set Test A hot set test was performed using a tubular piece produced in the same manner as each electric wire produced using the coated conductor obtained under the above extrusion molding conditions (2).
The hot set test was performed according to the method described in IEC60811-2-1. The test conditions were 200° C., heating time was 15 minutes, and load was 20 N/cm ² . The length after heating was measured, and the elongation rate (%) relative to the length before heating was determined. Furthermore, the load was removed, the length after the load was removed was measured, and the elongation rate (%) with respect to the length before heating was obtained.
If the elongation after heating is 100% or less and the elongation after heating and removal of the load is 25% or less, the passing level of this test is indicated by "A", and other than that is the failing level of this test. is represented by "D".

8. Flame Retardancy Test A flame retardancy test was performed using each electric wire manufactured using the coated conductor obtained under the above extrusion molding condition (2). The test was conducted based on the first line combustion test described in IEC (International Electronic Commission) 60332-1-2.
A 600 mm long sample was cut from the wire, the sample was held vertically and a burner flame was applied to the lower end of the sample at an angle of 45 degrees and burned for 60 seconds. After the burner was removed and the flame was self-extinguished, the distance between the top end of the carbonized portion and the upper support member was 50 mm or more was rated as pass "A", and when less than 50 mm was rated as fail "D".

In the manufacturing method having each step defined in the present invention, when the base acrylic rubber not satisfying the composition defined in the present invention is mixed, the appearance test (1), bleeding test, mechanical property test, flexibility test, oil resistance test Any of A failed, and it was not possible to produce a silane-crosslinked acrylic rubber molded article with excellent appearance, mechanical properties, flexibility, and high-temperature oil resistance, and with suppressed bleeding (Comparative Example 1-8). Without pre-mixing the inorganic filler and the silane coupling agent, the mechanical properties test (tensile strength) and oil resistance test A failed, and excellent appearance, mechanical properties, flexibility, and high-temperature oil resistance were obtained. In addition, it was not possible to produce a silane-crosslinked acrylic rubber molding in which bleeding was suppressed (Comparative Example 9). Furthermore, if the components necessary for silane cross-linking are not blended, the oil resistance test A is not passed, and the silane-cross-linked acrylic rubber has excellent appearance, mechanical properties, flexibility, high-temperature oil resistance, and suppressed bleeding. A molding could not be produced (Comparative Example 10).
On the other hand, in the production method having each step specified in the present invention, when the base acrylic rubber satisfying the composition specified in the present invention is blended with the inorganic filler, organic peroxide, etc. in a specific amount, the appearance test ( 1) Passed all of the bleeding test, mechanical property test, flexibility test, and oil resistance test A, and had excellent appearance, mechanical properties, flexibility, high temperature oil resistance, and suppressed bleeding. Silane-crosslinked acrylic rubber moldings could be produced (Examples 1 to 18). Therefore, the electric wires of Examples 1 to 18 having these molded bodies as a coating layer all have excellent appearance, mechanical properties, flexibility, and high-temperature oil resistance, and bleeding is suppressed. . Furthermore, since it passed the appearance test (1) and the appearance test (2), it can be seen that it can cope with changes in the screw rotation speed.
Moreover, from the above, it can be seen that according to the present invention, it is possible to manufacture molded articles for various uses including thin-walled molded articles as well as electric wires.

Claims (11)

A method for producing a silane-crosslinked acrylic rubber molding comprising the following steps (1), (2) and (3),
Step (1): With respect to 100 parts by mass of the base acrylic rubber, 0.01 to 0.6 parts by mass of an organic peroxide, 1 to 200 parts by mass of an inorganic filler, and 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 acrylic rubber and a silanol condensation catalyst are melt-mixed to form the radicals generated from the organic peroxide. A step of obtaining a silane-crosslinkable acrylic rubber composition containing a silane-crosslinkable acrylic rubber by subjecting a graftable reaction site and a graftable site of the base acrylic rubber to a graft reaction. Step (2): the silane-crosslinking. Step (3): Contacting the molded article with water to obtain a silane-crosslinked acrylic rubber molded article The base acrylic rubber is an ethylene-acrylic rubber 20 85% by mass, 60% by mass or less of ethylene resin, 1 to 20% by mass of styrene elastomer, and 1 to 20% by mass of mineral oil, the ratio of the content of the styrene elastomer to the content of the mineral oil (styrene Elastomer content: Mineral oil content) is contained so that the mass ratio is 1:2.5 to 1:0.5,
In performing the step (1),
When all of the base acrylic rubber is melt-mixed in step (a-2) below, step (1) includes step (a-1), step (a-2) and step (c) below, and When part of the base acrylic rubber is melt-mixed in step (a-2), step (1) is the following step (a-1), step (a-2), step (b) and step (c). A method for producing a silane-crosslinked acrylic rubber molded product.
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 acrylic rubber are mixed with the organic In the presence of an oxide, melt-mixing is performed at a temperature equal to or higher than the decomposition temperature of the organic peroxide, and the radicals generated from the organic peroxide form the grafting reaction site and the grafting reaction site of the base acrylic rubber. Step (b): Melt-mix the remainder of the base acrylic rubber and the silanol condensation catalyst to prepare a catalyst masterbatch. Step (c): a step of melt-mixing the silane masterbatch and the silanol condensation catalyst or the catalyst masterbatch to obtain the silane-crosslinkable acrylic rubber composition 2. The method according to claim 1, wherein the ethylene resin is an ethylene-α-olefin copolymer resin or an ethylene-vinyl acetate copolymer resin having a density of 0.910 to 0.940 g/cm ³ or a mixture thereof. A method for producing the described silane-crosslinked acrylic rubber molding. 3. The method for producing a silane-crosslinked acrylic rubber molding according to claim 1, wherein the base acrylic rubber contains 1 to 6% by mass of propylene resin. The method for producing a silane-crosslinked acrylic rubber molding according to any one of claims 1 to 3, wherein 30 to 200 parts by mass of the inorganic filler is blended with 100 parts by mass of the base acrylic rubber. 5. The production of the silane-crosslinked acrylic rubber molding according to any one of claims 1 to 4, wherein the silanol condensation catalyst is blended in an amount of 0.01 to 0.5 parts by mass with respect to 100 parts by mass of the base acrylic rubber. Method. The ethylene-acrylic rubber is a binary copolymer of ethylene and an acrylic acid alkyl ester, or a terpolymer of ethylene, an acrylic acid alkyl ester and a copolymer component containing a carboxy group, or a mixture thereof. The method for producing a silane-crosslinked acrylic rubber molding according to any one of claims 1 to 5, comprising: The method for producing a silane-crosslinked acrylic rubber molding according to any one of claims 1 to 6, wherein the inorganic filler is a metal hydrate. In the step (1), 30 to 180 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 of the organic peroxide are added to 100 parts by mass of the base acrylic rubber. The method for producing a silane-crosslinked acrylic rubber molding according to any one of claims 1 to 7, wherein 0.01 to 0.5 parts by mass of the silanol condensation catalyst are melt-mixed with 0.01 to 0.5 parts by mass of the silanol condensation catalyst. A silane-crosslinkable acrylic rubber composition produced by the step (1) of the production method according to any one of claims 1 to 8. A silane-crosslinked acrylic rubber molded article produced by the method for producing a silane-crosslinked acrylic rubber molded article according to any one of claims 1 to 8. A silane-crosslinked acrylic rubber molded article comprising the silane-crosslinked acrylic rubber molded article according to claim 10 .