JP2022155043A - Flame-retardant silane-crosslinked acrylic rubber-molded body and method of producing the same, flame-retardant silane-crosslinked acrylic rubber composition, and flame-retardant silane-crosslinked acrylic rubber-molded article - Google Patents

Abstract

To provide: a method of producing a flame-retardant silane-crosslinked acrylic rubber-molded body with excellent high-temperature oil resistance, tensile properties, and flame retardancy while reducing the process load; a flame-retardant silane-crosslinked acrylic rubber-molded body and article obtained by the method; and a flame-retardant silane-crosslinked acrylic rubber composition suitable for producing the molded body.SOLUTION: Provided is a production method that comprises a process of obtaining a flame-retardant silane-crosslinked acrylic rubber composition, which contains: a silane-crosslinked acrylic rubber obtained by melt-mixing and graft-reacting, with a silane coupling agent, a mixture obtained by mixing a metal hydrate and the silane coupling agent, and 40 to 79 mass% of a base acrylic rubber containing specific amounts of ethylene-acrylic rubber and ethylene-vinyl acetate copolymer resin; and 21 to 60 mass% of a non-graft-reacted base acrylic rubber. Also provided are a flame-retardant silane-crosslinked acrylic rubber composition produced by the production method, and a molded body and molded article thereof.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a flame-retardant silane-crosslinked acrylic rubber molded article and its production method, a flame-retardant silane-crosslinked acrylic rubber composition, and a flame-retardant 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 various mechanical properties (e.g., tensile strength, tensile elongation). characteristics are required.

Furthermore, 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).

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, it is a method of obtaining a crosslinked resin by molding after obtaining a rubber and 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.

As an example of a method for producing an oil-resistant molded article by applying such a silane crosslinking method, for example, Patent Document 1 discloses a base resin containing specific amounts of acrylic rubber and polypropylene resin, an organic peroxide, and metal water. A manufacturing method is described in which a hydrated compound, 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

High-temperature oil resistance can be achieved to some extent by the techniques described in Patent Documents 1 and 2, which employ a base rubber containing a combination of acrylic rubber and specific components in the above-described specific silane crosslinking method.
However, wiring materials are generally required to have high tensile properties and flame retardancy in addition to high-temperature oil resistance. As a result of investigations by the present inventors, the molded articles obtained by the production methods described in Patent Documents 1 and 2 do not have sufficient tensile properties, and there is room for improvement in terms of compatibility with oil resistance. In addition, the production methods described in Patent Documents 1 and 2 further reduce the load during production during melt kneading, molding, etc. (for example, torque of the screw of the extruder in extrusion molding), and use a general-purpose molding machine. If a predetermined wiring material can be manufactured by using , a significant advantage can be expected from the actual manufacturing point of view.

The present invention provides a production method capable of obtaining a flame-retardant silane-crosslinked acrylic rubber molded article having excellent tensile properties and flame retardancy while maintaining high-temperature oil resistance while reducing the process load during production. An object of the present invention is to provide a flame-retardant silane-crosslinked acrylic rubber molded article and a flame-retardant silane-crosslinked acrylic rubber molded article obtained by a production method.
Another object of the present invention is to provide a flame-retardant silane-crosslinked acrylic rubber composition suitable for producing the flame-retardant silane-crosslinked acrylic rubber molded article.

In adopting the silane cross-linking method using ethylene-acrylic rubber, the present inventors have found that ethylene-acrylic rubber 10 does not necessarily require an ethylene resin other than an ethylene resin having a density of 0.910 to 0.940 g/cm ³ . to 70% by mass, and this content is in the range of 35 to 70% by mass as the total content of the ethylene-acrylic rubber and the ethylene-vinyl acetate copolymer resin. Above, 40 to 79% by mass of the total amount of the base acrylic rubber is used when preparing the silane masterbatch, and 21 to 60% by mass of the total amount is used when preparing the catalyst masterbatch to produce a flame-retardant silane-crosslinked acrylic rubber molding. The resulting flame-retardant silane-crosslinked acrylic rubber molded product has excellent tensile properties and flame retardancy while maintaining high-temperature oil resistance. I discovered what I have and what I can do. Based on these findings, the inventors of the present invention conducted further studies and completed the present invention.

The object of the present invention has been achieved by the following means.
[1]
A method for producing a flame-retardant silane-crosslinked acrylic rubber molding comprising the following steps (1), (2) and (3),
Step (1): 0.01 to 0.6 parts by mass of an organic peroxide, 75 to 200 parts by mass of a metal hydrate, 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 grafting reaction with the base acrylic rubber in the presence of a silanol condensation catalyst are melt-mixed to obtain radicals generated from the organic peroxide. a step (2 ): A step of molding the flame-retardant silane-crosslinked acrylic rubber composition to obtain a molded article. Step (3): A step of contacting the molded article with water to obtain a flame-retardant silane-crosslinked acrylic rubber molded article. The base acrylic rubber contains 10 to 70% by mass of ethylene-acrylic rubber, 45% by mass or less of ethylene-vinyl acetate copolymer resin, and 45% by mass or less of ethylene resin having a density of 0.910 to 0.940 g/cm ³ , The total content of the ethylene-acrylic rubber and the ethylene-vinyl acetate copolymer resin is contained in a mass ratio in the range of 35 to 70% by mass in 100% by mass of the base acrylic rubber, and the density is 0.910 to 0.910. Contains no ethylene resin other than 0.940 g/cm ³ of ethylene resin,
A method for producing a flame-retardant silane-crosslinked acrylic rubber molding, wherein the step (1) comprises the following steps (a-1), (a-2), (b), and (c).
Step (a-1): Step of mixing the metal hydrate and the silane coupling agent to prepare a mixture Step (a-2): 40 to 79% by mass of the total amount of the mixture and the base acrylic rubber are melt-mixed in the presence of the organic peroxide at a temperature equal to or higher than the decomposition temperature of the organic peroxide, and the radicals generated from the organic peroxide graft the grafting reaction site and the base acrylic rubber. Step (b): 21 to 60% by mass of the total amount of the base acrylic rubber and the silanol condensation catalyst Step (c): Melt-mixing the silane masterbatch and the catalyst masterbatch to obtain the flame-retardant silane-crosslinkable acrylic rubber composition [2 ]
The method for producing a flame-retardant silane-crosslinked acrylic rubber molding according to [1], wherein the base acrylic rubber contains 1 to 15% by mass of styrene elastomer and 1 to 15% by mass of mineral oil.
[3]
The method for producing a flame-retardant silane-crosslinked acrylic rubber molding according to [1] or [2], wherein the base acrylic rubber contains 1 to 10% by mass of a propylene resin and 1 to 10% by mass of an acid-modified ethylene resin.
[4]
The method for producing a flame-retardant silane-crosslinked acrylic rubber molding according to any one of [1] to [3], wherein 2.5 to 10 parts by mass of red phosphorus is melt-mixed with 100 parts by mass of the base acrylic rubber. .
[5]
The flame-retardant silane-crosslinked acrylic rubber molding according to any one of [1] to [4], wherein 100 to 200 parts by mass of the metal hydrate is melt-mixed with 100 parts by mass of the base acrylic rubber. body manufacturing method.
[6]
The flame-retardant silane crosslinker according to any one of [1] to [5], wherein 0.01 to 0.5 parts by mass of the silanol condensation catalyst is melt-mixed with respect to 100 parts by mass of the base acrylic rubber. A method for producing an acrylic rubber molding.
[7]
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 flame-retardant silane-crosslinked acrylic rubber molded article according to any one of [1] to [6].
[8]
In the step (1), 75 to 200 parts by mass of the metal hydrate, 1 to 15 parts by mass of the silane coupling agent, and 0.01 part of the organic peroxide are added to 100 parts by mass of the base acrylic rubber. 0.6 parts by mass and 0.01 to 0.5 parts by mass of the silanol condensation catalyst are melt-mixed, [1] to [4], [6] to [7]. A method for producing a flame-retardant silane-crosslinked acrylic rubber molding.
[9]
A flame-retardant silane-crosslinkable acrylic rubber composition produced by the step (1) of the production method according to any one of [1] to [8].
[10]
A flame-retardant silane-crosslinked acrylic rubber molded article produced by the method for producing a flame-retardant silane-crosslinked rubber molded article according to any one of [1] to [8].
[11]
A flame-retardant silane-crosslinked acrylic rubber molded article comprising the flame-retardant 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 producing a flame-retardant silane-crosslinked acrylic rubber molding having excellent high-temperature oil resistance, tensile properties, and flame retardancy while reducing process loads such as melt-kneading and molding. It is possible to provide a flame-retardant silane-crosslinked acrylic rubber molded article obtained by the method, and a flame-retardant silane-crosslinked acrylic rubber molded article containing this silane-crosslinked acrylic rubber molded article. Moreover, it is possible to provide a flame-retardant silane-crosslinked acrylic rubber composition suitable for producing a flame-retardant silane-crosslinked 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 as a rubber component. The base acrylic rubber further optionally includes ethylene-vinyl acetate copolymer resin and 0.910 to 0.940 g/cm ³ of ethylene resin, styrene elastomer, mineral oil, propylene resin, and acid-modified It can contain ethylene resin. 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.
Further, the base acrylic rubber does not contain ethylene resins other than ethylene resins with a density of 0.910-0.940 g/cm ³ .

- 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. Any rubber can be preferably used. Among them, a rubber made of a terpolymer is particularly preferable. 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-vinyl acetate copolymer resin -
Examples of ethylene-vinyl acetate copolymer resins include resins of copolymers obtained by copolymerizing ethylene and vinyl acetate. The ethylene-vinyl acetate copolymer resin may be used alone or in combination of two or more.

- Ethylene resin with a density of 0.910 to 0.940 g/cm ³ -
By incorporating an ethylene resin having a density of 0.910 to 0.940 g/cm ³ into the base acrylic rubber of the present invention, mechanical strength and elongation properties can be improved. The density of the ethylene resin having a density of 0.910 to 0.940 g/cm ³ is more preferably 0.920 to 0.940 g/cm ³ . By using an ethylene resin having such a density, the acceptability of metal hydrates is increased, excellent mechanical properties can be obtained, and high-temperature oil resistance can be maintained. The density of ethylene resin can be measured by the method described in JIS K 7112.
The ethylene resin having a density of 0.910 to 0.940 g/cm ³ can be selected from ethylene resins having the above density among the ethylene resins described later. In the present invention, when the term "ethylene resin" is used without specifying the density, it means that the density is not limited.

The ethylene resin is a resin (excluding ethylene-vinyl acetate copolymer resin and propylene resin) composed of a polymer obtained by polymerizing or copolymerizing a compound having an ethylenically unsaturated bond, and has the above density. The material is not particularly limited as long as it is a material, and those conventionally used as coating materials for electric wires can be used. Examples thereof include resins composed of polymers such as polyethylene and ethylene-α-olefin copolymers. Ethylene resins may be used singly or in combination of two or more.
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 HDPE (high density polyethylene), LDPE (low density polyethylene), UHMW-PE (ultra high molecular weight polyethylene), LLDPE (linear low density polyethylene), MDPE (medium density polyethylene), VLDPE ( ultra-low 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 individually by 1 type, and may be used in combination of 2 or more type. 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.

Commercially available ethylene resins include, for example, "Evolue" (trade name: manufactured by Prime Polymer Co., Ltd.).

- Ethylene resins other than ethylene resins having a density of 0.910 to 0.940 g/cm ³ -
The base acrylic rubber does not contain ethylene resin other than ethylene resin with a density of 0.910 to 0.940 g/cm ³ . Examples of such an ethylene resin include those having a density not in the range of 0.910 to 0.940 g/cm ³ among the above ethylene resins.

- 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 copolymer mainly composed of constituent components derived from the above compounds. It is a hydrogenated product of a polymer.
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. A styrene elastomer may be used individually by 1 type, and may be used in combination of 2 or more type.
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.

- Propylene resin -
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 preferred propylene resin is an ethylene-propylene random copolymer resin in terms of appearance. The ethylene component content is a value measured according to the method described in ASTM D3900.
The propylene resin may be used alone or in combination of two or more.

- Acid-modified ethylene resin -
As the acid-modified ethylene resin, a resin obtained by acid-modifying the above ethylene resin can be used. The density of the ethylene resin used for the acid-modified ethylene resin is not particularly limited. The acid used for acid modification is not particularly limited, and commonly used unsaturated carboxylic acids and the like can be mentioned.

- Other base acrylic rubber components -
Resins or rubbers other than those described above can be used as long as the effects of the present invention are not impaired.

- Content in base acrylic rubber -
The content of each component in the base acrylic rubber is determined within the following range so that the total of each component is 100% by mass.
The content of the ethylene-acrylic rubber is 10 to 70% by mass in 100% by mass of the base acrylic rubber. If the content is too low, the flame-retardant silane-crosslinked acrylic rubber molded article may not have sufficient flame retardancy and high-temperature oil resistance. On the other hand, if the content is too high, sufficient tensile properties may not be achieved.
The content of the ethylene-acrylic rubber in the base acrylic rubber is preferably 30-70% by mass, more preferably 32-70% by mass, and particularly preferably 35-55% by mass. When the content of the ethylene-acrylic rubber is within the above range, the flame retardancy or high-temperature oil resistance of the flame-retardant silane-crosslinked acrylic rubber molding can be further improved.
The content of the ethylene-vinyl acetate copolymer resin is 45% by mass or less in 100% by mass of the base acrylic rubber. If the content of the ethylene-vinyl acetate copolymer resin is too high, excellent high-temperature oil resistance may not be achieved. The content of the ethylene-vinyl acetate copolymer resin is preferably 10 to 40% by mass, more preferably 15 to 35% by mass.
Each of the ethylene-acrylic rubber and ethylene-vinyl acetate copolymer resin individually satisfies the content within the above range, and the total content of the ethylene-acrylic rubber and the ethylene-vinyl acetate copolymer resin is It is set in the range of 35 to 70% by mass based on 100% by mass of the base acrylic rubber. If the total content is too high, sufficient tensile properties may not be achieved. In addition, the load during manufacturing may become too high. If the total content is too low, sufficient flame retardancy may not be achieved. The total content is preferably 40 to 65% by mass, more preferably 45 to 60% by mass, and the lower limit can be 50% by mass or more. By making it 50% by mass or more, there is a tendency that higher flame retardancy can be achieved.

The content of the ethylene resin with a density of 0.910 to 0.940 g/cm ³ is 45% by mass or less, preferably 5 to 45% by mass, more preferably 15 to 40% by mass, based on 100% by mass of the base acrylic rubber. is. If this content is too high, sufficient flame retardancy may not be achieved.

In the present invention, "not containing an ethylene resin other than an ethylene resin having a density of 0.910 to 0.940 g/ ^cm3 " means that an ethylene resin other than an ethylene resin having a density of 0.910 to 0.940 g/ ^cm3 is It means that they may exist as long as they do not impair the effects of the present invention. For example, the content of the ethylene resin other than the ethylene resin having a density of 0.910 to 0.940 g/cm ³ is 5% by mass or less, preferably 1% by mass or less, based on 100% by mass of the base acrylic rubber.

The content of the styrene elastomer is not particularly limited, but is preferably 15% by mass or less, more preferably 1 to 15% by mass, even more preferably 1 to 10% by mass, and 2 to 8% by mass in 100% by mass of the base acrylic rubber. is particularly preferred. Within this range, high-temperature oil resistance and mechanical properties can be enhanced.

The mineral oil content is not particularly limited, but is preferably 15% by mass or less, more preferably 1 to 15% by mass, even more preferably 1 to 10% by mass, and 2 to 8% by mass based on 100% by mass of the base acrylic rubber. % is particularly preferred. Within this range, mechanical properties and flame retardancy can be enhanced while maintaining high-temperature oil resistance. Also, the load during manufacturing can be reduced.

The content of the propylene resin is not particularly limited, but is preferably 10% by mass or less, more preferably 1 to 10% by mass, even more preferably 1 to 6% by mass, and 1 to 5% by mass based on 100% by mass of the base acrylic rubber. is more preferred. Within this range, mechanical properties and flame retardancy can be enhanced while maintaining high-temperature oil resistance. Also, the load during manufacturing can be reduced.

The content of the acid-modified ethylene resin is not particularly limited, but is preferably 10% by mass or less, more preferably 1 to 10% by mass, even more preferably 1 to 6% by mass, and 1 to 5% by mass based on 100% by mass of the base acrylic rubber. % by mass is more preferred. Within this range, mechanical properties and flame retardancy can be enhanced while maintaining high-temperature oil resistance. Also, the load during manufacturing can be reduced.

The base acrylic rubber preferably contains 1 to 15% by weight of styrene elastomer and 1 to 15% by weight of mineral oil in 100% by weight of the base acrylic rubber.
The base acrylic rubber preferably contains 1 to 10% by mass of a propylene resin and 1 to 10% by mass of an acid-modified ethylene resin in 100% by mass of the base acrylic rubber.

<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.

<Metal hydrate>
In the present invention, the metal hydrate has a site on its surface that can be chemically bonded to a reactive site such as a silanol group of a silane coupling agent by a hydrogen bond, a covalent bond, or an intermolecular bond. It can be used without any particular limitation. Examples of the site of the metal hydrate that can be chemically bonded to the reaction site of the silane coupling agent include OH groups (hydroxyl groups, water molecules of hydrated or crystallized water, and OH groups such as carboxyl groups).

Metal hydrates include compounds having hydroxyl groups or water of crystallization. Metal hydrates are not particularly limited, and examples include aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, calcium silicate, magnesium silicate, calcium oxide, magnesium oxide, aluminum oxide, aluminum nitride, and aluminum borate. Whiskers, hydrated aluminum silicate, hydrated magnesium silicate, basic magnesium carbonate, hydrotalcite, talc and the like. One type of metal hydrate may be used alone, or two or more types may be used in combination.
As the metal hydrate, at least one selected from aluminum hydroxide, magnesium hydroxide and the like is preferable, and magnesium hydroxide is more preferable.

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

When the metal hydrate is powder, the average particle size of the metal hydrate is preferably 0.2 to 10 μm, more preferably 0.3 to 8 μm, even more preferably 0.4 to 5 μm, and 0.4 ~3 μm is particularly preferred. When the average particle size is within the above range, the effect of retaining the silane coupling agent is high and the tensile properties are excellent. In addition, secondary aggregation of the metal hydrate is less likely to occur when mixed with the silane coupling agent, resulting in an excellent appearance. The average particle size is obtained by dispersing the metal hydrate in alcohol or water and using an optical particle size analyzer such as a laser diffraction/scattering particle size distribution analyzer.

<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) that can react with a site that can chemically bond to a metal hydrate and that can be silanol-condensed. 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 flame-retardant silane-crosslinked acrylic rubber molded article having excellent tensile strength can be obtained. Also, if necessary, a flame-retardant silane-crosslinked acrylic rubber molded article having excellent heat resistance can be obtained.

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.

<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, and pipes are targeted. You may mix|blend suitably in the range which does not impair an effect. 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 red phosphorus in addition to the metal hydrates described above.
Although the amount of the flame retardant other than the metal hydrate is not particularly limited, it is preferably 2.5 to 10 parts by mass with respect to 100 parts by mass of the base acrylic rubber.

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

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, 75 to 200 parts by mass of a metal hydrate, and 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 in the presence thereof and a silanol condensation catalyst are melt-mixed and grafted by radicals generated from the organic peroxide. A step of obtaining a flame-retardant silane-crosslinkable acrylic rubber composition containing a silane-crosslinkable acrylic rubber by subjecting a reactive site and a graftable site of the base acrylic rubber to a graft reaction. Step (2): Flame retardancy Step of molding the silane-crosslinkable acrylic rubber composition to obtain a molded article Step (3): Contacting the molded article with water to obtain a flame-retardant silane-crosslinked acrylic rubber molded article

The step (1) includes the following steps.
Step (a-1): Step of mixing a metal hydrate and a silane coupling agent to prepare a mixture Step (a-2): Add 40 to 79% by mass of the mixture and the total amount of the base acrylic rubber to Melt-mixing is performed in the presence of an oxide at a temperature higher than the decomposition temperature of the organic peroxide, and the radicals generated from the organic peroxide graft the grafting reaction site and the grafting reaction-capable site of the base acrylic rubber. Process of preparing a silane masterbatch containing a silane crosslinkable acrylic rubber by reacting Step (b): 21-60% by weight of the total amount of the base acrylic rubber and a silanol condensation catalyst are melt mixed to prepare a catalyst masterbatch. Step (c): A step of melt-mixing a silane masterbatch and a catalyst masterbatch to obtain a flame-retardant silane-crosslinkable acrylic rubber composition Below, steps (a-1) and (a-2) Both steps may be collectively referred to as step (a).

In the production method of the present invention, the "base acrylic rubber" is a rubber for forming a flame-retardant silane-crosslinked acrylic rubber molded article or a flame-retardant silane-crosslinked acrylic rubber composition.

The amount of 100 parts by mass of the base acrylic rubber compounded in step (1) is the total amount of the base acrylic rubber mixed in steps (a-2) and (b).
40 to 79% by mass, preferably 45 to 70% by mass of 100% by mass of the base acrylic rubber is blended in step (a-2), and 21 to 60% by mass, Preferably 30 to 55 mass % is blended. By blending so as to fall within the above range, it is possible to improve mechanical properties and flame retardancy while maintaining high-temperature oil resistance. Also, the load during manufacturing can be reduced.

In step (1), the amount of ethylene-acrylic rubber, ethylene-vinyl acetate copolymer resin, and ethylene resin having a density of 0.910 to 0.940 g/cm ³ in the base acrylic rubber ( content) is as described above. The total amount of ethylene-acrylic rubber and ethylene-vinyl acetate copolymer resin is also as described above.
Furthermore, the amounts of ethylene resins other than styrene elastomer, mineral oil, propylene resin, acid-modified ethylene resin, and ethylene resin having a density of 0.910 to 0.940 g/cm ³ are also as described above.

As the base acrylic rubber component used in step (a-2), the base acrylic rubber component described above can be used without particular limitation. In step (a-2), ethylene-acrylic rubber, ethylene-vinyl acetate copolymer resin, ethylene resin having a density of 0.910 to 0.940 g/cm ³ , styrene elastomer, mineral oil, propylene resin, modified ethylene At least one kind of resin can be used. It is preferable to use ethylene-acrylic rubber, and it is more preferable to use ethylene resin, styrene elastomer and mineral oil having a density of 0.910 to 0.940 g/cm ³ in addition to ethylene-acrylic rubber.

As the base acrylic rubber (also referred to as carrier) component used to prepare the catalyst masterbatch in step (b), the base acrylic rubber component described above can be used without particular limitation. The carrier is preferably at least one of ethylene-acrylic rubber, ethylene-vinyl acetate copolymer resin, ethylene resin having a density of 0.910 to 0.940 g/cm ³ , propylene resin, and modified ethylene resin, and ethylene-vinyl acetate. At least one of copolymer resins, ethylene resins having a density of 0.910 to 0.940 g/cm ³ , propylene resins, and modified ethylene resins is more preferable.

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 and improving the mechanical properties. You can get enough.

In the step (1), the amount of the metal hydrate compounded is 75 to 200 parts by mass, preferably 100 to 200 parts by mass, more preferably 110 to 170 parts by mass, with respect to 100 parts by mass of the base acrylic rubber. 115 to 150 parts by mass is more preferable. By setting the content of the metal hydrate to 75 to 200 parts by mass, the flame-retardant silane-crosslinked acrylic rubber molded article can achieve tensile properties and flame retardancy necessary for wiring materials. Furthermore, molding can be made possible by suppressing an increase in load during molding and kneading. When the blending amount of the metal hydrate is 130 parts by mass or more, there is a tendency that higher flame retardancy can be achieved.

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 metal hydrate, and volatilization of the silane coupling agent during kneading can be suppressed. target. Moreover, it is possible to suppress the deterioration of the external appearance due to the condensation of the non-adsorbed silane coupling agent and the occurrence of gel spots and roughness in the molded article. Furthermore, if necessary, the 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 flame-retardant 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 cross-linking proceeds sufficiently and the mechanical strength is excellent. In addition, it is possible to achieve heat resistance as necessary and to suppress the occurrence of gel lumps during molding.

From the viewpoint of imparting excellent heat resistance, high-temperature oil resistance, and tensile strength, in step (1), 75 to 200 parts by mass of a metal hydrate and 1 part of a silane coupling agent are added to 100 parts by mass of the base acrylic rubber. It is preferable to melt-mix to 15 parts by mass, 0.01 to 0.6 parts by mass of the organic peroxide, and 0.01 to 0.5 parts by mass of the silanol condensation catalyst.

When performing step (1), step (a-1) and step (a-2) are performed in sequence. That is, first, the metal hydrate and the silane coupling agent are mixed, and then the obtained mixture and 40 to 79% by mass of the total amount of the base acrylic rubber are mixed in the above-mentioned amount at the decomposition temperature of the organic peroxide. By melt-kneading at the above temperature, the above-mentioned 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 metal hydrate. Specifically, a mixture is prepared by mixing a metal hydrate and a silane coupling agent (step (a-1)). It is believed that the premixed silane coupling agent exists so as to surround the surface of the metal hydrate, and some or all of it is adsorbed or bonded to the metal hydrate. This can reduce volatilization of the silane coupling agent during subsequent melt-mixing. It is also possible to prevent the silane coupling agent that does not adsorb or bond to the metal hydrate from condensing and making melt-kneading difficult. Furthermore, the desired shape can be obtained during extrusion.

A method for pre-mixing the metal hydrate and the silane coupling agent is not particularly limited, but includes a mixing method such as a wet treatment or a dry treatment. Specifically, the metal hydrate 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 minutes. A method of mixing by dry or wet for about an hour is more preferable, and a dry treatment in which a silane coupling agent is added to a metal hydrate, preferably a dried metal hydrate, with or without heating and mixed is preferred. preferable. 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 metal hydrate and the silane coupling agent obtained in step (a-1) and 40 to 79% by mass of the total amount of the base acrylic rubber are then combined with an organic Melt and mix while heating to a temperature higher than the decomposition temperature of the organic peroxide in the presence of the peroxide (step (a-2)).
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 150 to 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 usually set appropriately between 5 and 30 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.

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 acrylic 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 used in the production of the reaction composition (flame-retardant silane-crosslinkable acrylic rubber composition) prepared in step (1), together with the catalyst masterbatch described below. 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, the step (b) of preparing a catalyst masterbatch (also referred to as a catalyst MB) by melt-mixing 21 to 60% by mass of the total amount of the base acrylic rubber and a silanol condensation catalyst is then performed.

Mixing may be performed by any method as long as it can be uniformly mixed, and examples thereof include mixing performed under melting conditions of the base acrylic rubber (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 can be set as appropriate.

A metal hydrate may also be used in step (b). In this case, the amount of the metal hydrate compounded 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 metal hydrate to 350 parts by mass or less, the silanol condensation catalyst is appropriately dispersed and cross-linking is facilitated. Moreover, if necessary, sufficient heat resistance can be obtained.
In the step (b), it is preferable to use a metal hydrate from the viewpoint of imparting high flame retardancy and excellent appearance properties and reducing the production load. The amount of the metal hydrate compounded in step (b) is preferably 10 to 80% by mass, more preferably 25 to 70% by mass, of the total amount of metal hydrate in step (1).

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 flame-retardant silane-crosslinkable acrylic rubber composition prepared in step (1).

In the production method of the present invention, the silane MB and the catalyst MB are then melt-mixed to obtain a flame-retardant silane-crosslinkable acrylic rubber composition (reaction composition) (c). 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.

In this manner, steps (a) to (c) (step (1)) are performed to produce a flame-retardant silane-crosslinkable acrylic rubber composition as a reaction composition. This flame-retardant silane-crosslinkable acrylic rubber composition comprises a silane-crosslinkable acrylic rubber having a silane coupling agent grafted to 40 to 79% by mass of the base acrylic rubber, and 21 to 60% of the non-grafted base acrylic rubber. %, 75 to 200 parts by mass of metal hydrate and a silanol condensation catalyst with respect to 100 parts by mass of base acrylic rubber.
This flame-retardant 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 metal hydrate, but is not silanol-condensed as described later. Therefore, the silane-crosslinkable acrylic rubber is divided into a crosslinkable rubber in which a silane coupling agent bound or adsorbed to a metal hydrate is grafted onto a base acrylic rubber, and a silane coupling agent that is not bound or adsorbed to a metal hydrate. at least a crosslinkable rubber grafted onto the base acrylic rubber. Moreover, the silane-crosslinkable acrylic rubber may have a silane coupling agent to which a metal hydrate is bound or adsorbed and a silane coupling agent to which a metal hydrate 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 melt-mixed in step (c), but for the resulting flame-retardant silane-crosslinkable acrylic rubber composition, at least in step (2) It is assumed that the moldability in molding is maintained.

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 flame-retardant 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 flame-retardant silane-crosslinked acrylic rubber molded article of the present invention, step (2) and step (3) are then carried out.
In the method for producing a flame-retardant silane-crosslinked acrylic rubber molded article of the present invention, the step (2) is carried out to obtain a molded article by molding the obtained reaction composition. This step (2) only needs to be able to mold the reaction composition. The molding method and molding conditions are appropriately selected according to the requirements. 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 flame-retardant silane-crosslinked acrylic rubber molded article of the present invention or the flame-retardant silane-crosslinked acrylic rubber molded article containing the flame-retardant silane-crosslinked acrylic rubber molded article is an electric wire or an optical fiber cable.

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 flame-retardant silane-crosslinkable acrylic rubber composition is obtained. Like the flame-retardant 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 flame-retardant silane-crosslinked acrylic rubber molded article of the present invention is crosslinked or finally crosslinked by carrying out step (3).

In the method for producing a flame-retardant silane-crosslinked acrylic rubber molded article of the present invention, the step (3) is carried out in which the molded article obtained in the step (2) is brought into contact with water. 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 flame-retardant 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 flame-retardant silane-crosslinked acrylic rubber molded article is produced from the flame-retardant silane-crosslinked acrylic rubber composition of the present invention. This flame-retardant silane-crosslinked acrylic rubber molded article contains a crosslinked rubber obtained by condensing a silane-crosslinkable acrylic rubber via a siloxane bond, as will be described later. One form of this flame-retardant silane-crosslinked acrylic rubber molded article contains a flame-retardant silane-crosslinked rubber and a metal hydrate. Here, the metal hydrate may be bound to the silane coupling agent of the flame-retardant silane-crosslinked rubber. Therefore, this flame-retardant silane-crosslinked rubber is crosslinked by binding or adsorbing a plurality of crosslinked rubbers to a metal hydrate by a silane coupling agent and binding (crosslinking) via the metal hydrate and the silane coupling agent. It contains at least a rubber and a crosslinked rubber crosslinked via a silane coupling agent by hydrolysis of the reaction site of the silane coupling agent of the crosslinkable rubber and mutual silanol condensation reaction. The flame-retardant silane-crosslinked rubber may have a mixture of bonding (crosslinking) via the metal hydrate 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.

Although the action mechanism of the present invention is not yet clear, it is considered as follows.
According to the production method of the present invention, in the step (a-1), the metal hydrate and the silane coupling agent are premixed in a specific amount ratio, thereby performing the grafting reaction in the step (a-2). prior to the adsorption or bonding of the silane coupling agent to the metal hydrate. In this state, in the step (a-2), a grafting reaction occurs when melt-kneaded together with the base acrylic rubber in the presence of an organic peroxide. At that time, the silane coupling agent bound or adsorbed to the metal hydrate with a weak bond desorbs from the metal hydrate, while the silane coupling agent bound to the metal hydrate with a stronger bond than the former , remains bound to the metal hydrate. In this way, silane-crosslinkable rubbers having different metal hydrate adsorption states are formed. Furthermore, these silane-crosslinkable rubbers are brought into contact with moisture in step (3) to form crosslinked rubbers having a crosslinked structure via silanol bonds.
In the production method of the present invention, on the premise that a crosslinked structure is formed by the above-described silane crosslinking, a base acrylic rubber having a specific composition is added in a specific ratio together with other components, a silane masterbatch and a catalyst masterbatch. used for the preparation of By doing so, excessive cross-linking between the base acrylic rubber components can be suppressed. As a result, the extrusion load is reduced. Furthermore, by containing the base acrylic rubber that has undergone the grafting reaction and the base acrylic rubber that has not undergone the grafting reaction in an appropriate ratio, it is possible to suppress the reduction in tensile elongation due to excessive cross-linking, while maintaining sufficient tensile strength. can be increased, resulting in excellent tensile properties. In addition, it is possible to form crosslinks necessary for wiring materials. Thus, in the present invention, it is possible to obtain a molded article having excellent tensile properties and flame retardancy in addition to the high-temperature oil resistance inherent in ethylene-acrylic rubber.

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 flame-retardant silane-crosslinked acrylic rubber molded article or a flame-retardant silane-crosslinked acrylic rubber molded article containing a flame-retardant silane-crosslinked acrylic rubber molded article is regarded as such a product.
As the flame-retardant silane-crosslinked acrylic rubber molded article of the present invention or the flame-retardant silane-crosslinked acrylic rubber molded article containing the flame-retardant silane-crosslinked acrylic rubber molded article, for example, an electric wire such as a flame-retardant insulated wire or a flame-retardant Examples include cable coating materials, rubber substitute wire/cable materials, flame-retardant wire parts, flame-retardant heat-resistant sheets, and flame-retardant films. In addition, 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 insulated wires and optical cables. mentioned.

The flame-retardant silane-crosslinked acrylic rubber molded article of the present invention is particularly suitable as a material for use in areas where both excellent tensile properties and flame retardancy are required. However, it can be used as a substitute for acrylic rubber materials, such as hoses, tubes, rubber molding materials, etc., which have conventionally undergone cross-linking by electron beam irradiation and chemical vulcanization processes. Moreover, it can be used for electric wires for vehicles, electric wires for automobiles, and the like.

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 flame-retardant silane-crosslinked acrylic rubber molded article of the present invention or the flame-retardant silane-crosslinked acrylic rubber molded article containing the flame-retardant silane-crosslinked acrylic rubber molded article is an extruded article such as an electric wire or cable, preferably: While preparing a flame-retardant silane-crosslinkable acrylic rubber composition by melt-kneading the molding material in an extruder (extrusion coating device) and causing the grafting reaction, the flame-retardant silane-crosslinkable acrylic rubber composition is prepared. It can be manufactured by extruding the outer periphery of a conductor or the like to cover the conductor or the like (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. . Flame-retardant silane-crosslinked acrylic rubber moldings or flame-retardant silane-crosslinked acrylic rubber moldings containing flame-retardant silane-crosslinked acrylic rubber moldings are flame-retardant silane-crosslinked acrylic rubbers to which a large amount of metal hydrate is added. By extrusion coating the composition around a conductor or around a conductor in which tensile strength fibers are tandemly arranged or twisted using a general-purpose extrusion coating apparatus without using a special machine such as an electron beam cross-linking machine , can be molded. 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 flame-retardant 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.

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 21 and Comparative Examples 1 to 9, some of the components constituting the base acrylic rubber were used as carriers for the catalyst MB. The compounding ratio of the base acrylic rubber in the silane MB and the catalyst MB is shown in the "rubber ratio" column in the table.

(Examples 1 to 21, Comparative Examples 1 to 5, 7 to 9)
First, a metal hydrate, a silane coupling agent, and an organic peroxide are placed in a rotary blade mixer (trade name, MAZELLER PM, manufactured by MAZELLA CORPORATION) at a mass ratio shown in Table 1, and heated to room temperature (25°C). was stirred (premixed) 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, metal hydrate, flame retardant, antioxidant, and silanol condensation catalyst were sequentially added in the mass ratio shown in Table 1 to a kneader (capacity: 75 L) heated to 80°C in advance, and the kneader was stirred at 30 rpm. After mixing for 5 minutes at 25 rpm, final kneading was performed for 3 minutes. 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.

Next, the resulting dried blend was melt-mixed and molded under any one of the following extrusion molding conditions (1) to (3) to obtain coated conductors (steps (c) and (2)). A flame-retardant 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 flame-retardant silane-crosslinkable acrylic rubber composition is a molten mixture of silane MB and catalyst MB, and contains the silane-crosslinkable acrylic rubber described above.

(Extrusion molding conditions (1))
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 = 150 ° C., The extrusion temperature condition was set to C1=130°C. The prepared dry blended product is put into this extruder and melt-mixed (step (c)), and the outer diameter is 3.8 mm and the insulation layer thickness is 1 on a conductor with a diameter of 0.8 mm made of bare annealed copper wire. A coated conductor was obtained by extruding and covering at a line speed of 5 m/min (conditions of the extrusion load test) so that the thickness of the conductor was 0.5 mm (step (2)).

(Extrusion molding conditions (2))
An extruder equipped with a screw having an L/D ratio of 25 and a screw diameter of 90 mm was set to the same extrusion temperature conditions as the above extrusion molding conditions (1). The prepared dry blended product is put into this extruder and melt-mixed (step (c)), and five conductors with a diameter of 2.2 mm made of bare annealed copper wires are twisted and finished to a diameter of about 6.0 m. A covered conductor was obtained by extruding and covering at a line speed of 10 m/min so as to have an outer diameter of 9.0 mm and an insulating layer thickness of 1.5 mm (step (2)).

(Extrusion molding conditions (3))
An extruder equipped with a screw having an L/D ratio of 25 and a screw diameter of 70 mm was set to the same extrusion temperature conditions as the above extrusion molding conditions (1). The prepared dry blended product was put into this extruder and melt-mixed (step (c)), and an outer diameter of 5.0 mm and an insulating layer thickness of 1.0 mm were applied onto a conductor having a diameter of 2.0 mm made of bare annealed copper wire. A covered conductor was obtained by extruding and covering at a line speed of 20 m/min so as to have a thickness of 5 mm (step (2)).

The resulting coated conductor is left at room temperature (23° C.) and 50% relative humidity 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, each electric wire was produced by coating the above conductor with the flame-retardant silane-crosslinked acrylic rubber molding under any one of the above extrusion molding conditions (1) to (3). The flame-retardant silane-crosslinked acrylic rubber molding as the coating layer has the flame-retardant silane-crosslinked acrylic rubber described above.

(Comparative Example 6)
When preparing the silane MB, without premixing the metal hydrate, the silane coupling agent, and the organic peroxide (step (a-1)), the components shown in the silane MB column of Table 1 are 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 Table 1.

In the production of the above Examples and Comparative Examples, when premixing (step (a-1)) of the metal hydrate, the silane coupling agent and the organic peroxide was performed, the "premixing" in Table 1 was performed. "Yes" was written in the column, and "No" was written when premixing was not performed.

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) EVA1: EVAFLEX EV180 (trade name, manufactured by Mitsui DuPont Polychemicals, EVA)
(4) EVA2: Levaprene 800 (trade name, EVA manufactured by LANXESS)
(5) Ethylene resin 1: Evolue SP3010 (trade name, manufactured by Prime Polymer Co., Ltd., LLDPE, density 0.926 g/cm ³ )
(6) Ethylene resin 2: Evolue SP0540 (trade name, manufactured by Prime Polymer Co., Ltd., LLDPE, density 0.903 g/cm ³ )
(7) Ethylene resin 3: Hi-Zex 5100E (trade name, manufactured by Prime Polymer Co., Ltd., HDPE, density 0.943 g/cm ³ )
(8) Styrene elastomer 1: Tuftec N504 (trade name, manufactured by Asahi Kasei Corporation)
(9) Mineral oil 1: Cosmo Neutral 500 (trade name, Cosmo Oil Lubricants, paraffin oil)
(10) Propylene resin 1: PB222A (trade name, manufactured by SunAllomer, PP)
(11) Acid-modified ethylene resin 1: Adtex L6100M (trade name, manufactured by Nippon Polyethylene Co., Ltd., maleic acid-modified polyethylene)
(12) Metal hydrate 1: Kisuma 5L (trade name, manufactured by Kyowa Kagaku Co., Ltd., magnesium hydroxide)
(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. Extrusion load test The load during production was evaluated by the magnitude of the screw torque of the extruder.
The screw torque of the extruder was measured during the manufacture of the coated conductor under the extrusion molding conditions (1) described above. Those with a screw torque of less than 300 kg/cm ² are rated as "A" as particularly excellent levels, and those with a screw torque of 300 kg/cm ² or more and less than 450 kg/cm ² are rated as "B" as excellent levels, and 450 kg/cm ² or more. A value of less than 550 kg/cm ² was rated as “C” as the passing level of the final test, and a value of 550 kg/cm ² or more was rated as “D” as the failing level of the final test.
If the screw torque is less than 550 kg/cm ² , depending on the molding conditions, the extrusion load will be small, and generally extrusion molding can be performed using a general-purpose extruder. From the viewpoint of actual production using a general-purpose extruder by further reducing the extrusion load, it is preferably less than 300 kg/cm ² . When the screw torque is 550 kg/cm ² or more, it is usually necessary to modify the extruder.

2. Tensile property test (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 above extrusion molding conditions (1).
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.
The tensile strength was 12 MPa or more, represented by "A" as an extremely excellent level, 10 MPa or more and less than 12 MPa, represented by "B" as an excellent level, and 8 MPa or more and less than 10 MPa. The passing level is indicated by "C", and less than 8 MPa is indicated by "D" as the failing level of this test.
The tensile elongation is represented by "A" as an extremely excellent level of 250% or more, "B" as an excellent level of 200% or more and less than 250%, and 150% or more and less than 200%. The pass level of the final test is indicated by "C", and the level of less than 150% is indicated by "D" as the failing level of the main test.

3. Oil Resistance Test Each electric wire manufactured using the coated conductor obtained under the above extrusion molding conditions (1) was subjected to an "oil resistance test" described in JIS C3005. In the oil resistance test, the oil immersion temperature was 100° C., the oil immersion time was 24 hours, and IRM902 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%.

4. Hot Set Test A hot set test was performed using a tubular piece obtained by pulling out the conductor from each electric wire manufactured using the coated conductor obtained under the above extrusion molding conditions (1).
The hot set test was performed according to the method described in IEC60811-2-1.
The test conditions were 200° C. or 150° C., a heating time of 15 minutes, and a load of 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.
Even at a test temperature of 200° C., a case where the elongation after heating was 100% or less and the elongation after heating and load removal was 25% or less was indicated as "A" as an excellent level in this test.
At the test temperature of 200°C, the elongation after heating exceeds 100%, or the elongation after heating and unloading exceeds 25%, but when the test temperature is measured at 150°C, the elongation after heating exceeds 100%. % or less and the elongation rate after heating and removal of the load was 25% or less, the passing level of this test was indicated by "B". At a test temperature of 150° C., the case where the elongation after heating exceeded 100% or the elongation after heating and load removal exceeded 25% was represented by “D” and was regarded as unacceptable. Passing this exam is not mandatory.

5. Flame retardant test A
A flame retardancy test was conducted using an electric wire manufactured using the coated conductor obtained under the above extrusion molding conditions (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".
Passing the flame retardancy test A means that the coating layer has good flame retardancy, and high flame retardancy can be imparted to electric wires having an outer diameter of 9.0 mm or more.

6. Flame retardant test B
A flame retardancy test was conducted using an electric wire manufactured using the coated conductor obtained under the above extrusion molding condition (3). The test was performed according to IEC60332-1.
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". Passing this exam is not mandatory.
Passing the flame retardancy test B means that the coating layer has extremely high flame retardancy and can impart high flame retardancy to electric wires having an outer diameter of 5.0 mm or more and less than 9.0 mm. .
In the flame retardancy test B, a sample (outer diameter 5.0 mm) smaller than the sample (outer diameter 9.0 mm) in the flame retardancy test A is used. It can be said that this is a test under conditions that make it easier for flames to circulate due to the smaller outer diameter, making it easier to burn.

In the manufacturing method having each step defined in the present invention, if the base acrylic rubber not satisfying the composition defined in the present invention is mixed, any one of the extrusion load test, tensile property test, oil resistance test, and flame retardancy test A will be performed. failed, and it was not possible to produce a flame-retardant silane-crosslinked acrylic rubber molding that achieved excellent tensile properties and flame retardancy while maintaining high-temperature oil resistance by reducing the extrusion load (comparison Examples 1, 2, 5, 7, 8). If the ratio of the base acrylic rubber used in steps (a-2) and (b) does not satisfy the ratio specified in the present invention, any one of the extrusion load test, tensile property test, and oil resistance test will fail. Therefore, it was not possible to reduce the extrusion load to produce a flame-retardant silane-crosslinked acrylic rubber molded article that achieves excellent tensile properties and flame retardancy while maintaining high-temperature oil resistance (Comparative Examples 3 and 4). , 9). Without pre-mixing the metal hydrate and the silane coupling agent, the mechanical property test (tensile strength) and oil resistance test failed, and excellent tensile properties and resistance to heat were obtained while maintaining high-temperature oil resistance. A flame-retardant silane-crosslinked acrylic rubber molded article that achieves flame resistance could not be produced by reducing the extrusion load (Comparative Example 6).
On the other hand, in the manufacturing method having each step defined in the present invention, a base acrylic rubber satisfying the composition defined in the present invention is blended with a metal hydrate, an organic peroxide, etc. in specific amounts, and , When the ratio of the base acrylic rubber used in steps (a-2) and (b) satisfies the ratio specified in the present invention, extrusion load test, tensile property test, oil resistance test, flame retardancy test A We were able to produce a flame-retardant silane-crosslinked acrylic rubber molding that achieved excellent tensile properties and flame retardancy while maintaining high-temperature oil resistance while reducing the extrusion load (implementation Examples 1-21). Therefore, the electric wires of Examples 1 to 21 having these molded bodies as a coating layer can be manufactured with a reduced extrusion load, and have excellent tensile properties and flame retardancy while maintaining high-temperature oil resistance. have.

Claims (11)

A method for producing a flame-retardant silane-crosslinked acrylic rubber molding comprising the following steps (1), (2) and (3),
Step (1): 0.01 to 0.6 parts by mass of an organic peroxide, 75 to 200 parts by mass of a metal hydrate, 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 grafting reaction with the base acrylic rubber in the presence of a silanol condensation catalyst are melt-mixed to obtain radicals generated from the organic peroxide. a step (2 ): A step of molding the flame-retardant silane-crosslinked acrylic rubber composition to obtain a molded article. Step (3): A step of contacting the molded article with water to obtain a flame-retardant silane-crosslinked acrylic rubber molded article. The base acrylic rubber contains 10 to 70% by mass of ethylene-acrylic rubber, 45% by mass or less of ethylene-vinyl acetate copolymer resin, and 45% by mass or less of ethylene resin having a density of 0.910 to 0.940 g/cm ³ , The total content of the ethylene-acrylic rubber and the ethylene-vinyl acetate copolymer resin is contained in a mass ratio in the range of 35 to 70% by mass in 100% by mass of the base acrylic rubber, and the density is 0.910 to 0.910. Contains no ethylene resin other than 0.940 g/cm ³ of ethylene resin,
A method for producing a flame-retardant silane-crosslinked acrylic rubber molding, wherein the step (1) comprises the following steps (a-1), (a-2), (b), and (c).
Step (a-1): Step of mixing the metal hydrate and the silane coupling agent to prepare a mixture Step (a-2): 40 to 79% by mass of the total amount of the mixture and the base acrylic rubber are melt-mixed in the presence of the organic peroxide at a temperature equal to or higher than the decomposition temperature of the organic peroxide, and the radicals generated from the organic peroxide graft the grafting reaction site and the base acrylic rubber. Step (b): 21 to 60% by mass of the total amount of the base acrylic rubber and the silanol condensation catalyst Step (c): Melt-mixing the silane masterbatch and the catalyst masterbatch to obtain the flame-retardant silane-crosslinkable acrylic rubber composition 2. The method for producing a flame-retardant silane-crosslinked acrylic rubber molding according to claim 1, wherein the base acrylic rubber contains 1 to 15% by mass of styrene elastomer and 1 to 15% by mass of mineral oil. 3. The method for producing a flame-retardant silane-crosslinked acrylic rubber molding according to claim 1, wherein the base acrylic rubber contains 1 to 10% by mass of propylene resin and 1 to 10% by mass of acid-modified ethylene resin. The method for producing a flame-retardant silane-crosslinked acrylic rubber molding according to any one of claims 1 to 3, wherein 2.5 to 10 parts by mass of red phosphorus is melt-mixed with 100 parts by mass of the base acrylic rubber. The flame-retardant silane-crosslinked acrylic rubber molded article according to any one of claims 1 to 4, wherein 100 to 200 parts by mass of the metal hydrate is melt-mixed with 100 parts by mass of the base acrylic rubber. Production method. The flame-retardant silane-crosslinked acrylic rubber according to any one of claims 1 to 5, wherein 0.01 to 0.5 parts by mass of the silanol condensation catalyst is melt-mixed with 100 parts by mass of the base acrylic rubber. A method for producing a molded article. 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 flame-retardant silane-crosslinked acrylic rubber molded article according to any one of claims 1 to 6. In the step (1), 75 to 200 parts by mass of the metal hydrate, 1 to 15 parts by mass of the silane coupling agent, and 0.01 part of the organic peroxide are added to 100 parts by mass of the base acrylic rubber. The flame-retardant silane-crosslinked acrylic according to any one of claims 1 to 4 and 6 to 7, wherein ~0.6 parts by mass and 0.01 to 0.5 parts by mass of the silanol condensation catalyst are melt-mixed. A method for producing a rubber molding. A flame-retardant silane-crosslinkable acrylic rubber composition produced by the step (1) of the production method according to any one of claims 1 to 8. A flame-retardant silane-crosslinked acrylic rubber molded article produced by the method for producing a flame-retardant silane-crosslinked rubber molded article according to any one of claims 1 to 8. A flame-retardant silane-crosslinked acrylic rubber molded article comprising the flame-retardant silane-crosslinked acrylic rubber molding according to claim 10 .