CN110951147B - Flame-retardant resin composition and method for producing same, wire and method for producing same, cable and method for producing same - Google Patents

Flame-retardant resin composition and method for producing same, wire and method for producing same, cable and method for producing same Download PDF

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CN110951147B
CN110951147B CN201910731579.1A CN201910731579A CN110951147B CN 110951147 B CN110951147 B CN 110951147B CN 201910731579 A CN201910731579 A CN 201910731579A CN 110951147 B CN110951147 B CN 110951147B
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flame
resin composition
ethylene
retardant resin
vinyl acetate
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CN110951147A (en
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菊池龙太郎
黑泽芳宣
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Bomeilicheng Co ltd
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
    • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
    • C08L23/04—Homopolymers or copolymers of ethene
    • C08L23/08—Copolymers of ethene
    • C08L23/0846—Copolymers of ethene with unsaturated hydrocarbons containing other atoms than carbon or hydrogen atoms
    • C08L23/0853—Vinylacetate
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables
    • H01B13/06—Insulating conductors or cables
    • H01B13/14—Insulating conductors or cables by extrusion
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables
    • H01B13/22—Sheathing; Armouring; Screening; Applying other protective layers
    • H01B13/24—Sheathing; Armouring; Screening; Applying other protective layers by extrusion
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
    • H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
    • H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes
    • H01B3/44—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes vinyl resins; acrylic resins
    • H01B3/441—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes vinyl resins; acrylic resins from alkenes
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
    • C08K3/20—Oxides; Hydroxides
    • C08K3/22—Oxides; Hydroxides of metals
    • C08K2003/2217—Oxides; Hydroxides of metals of magnesium
    • C08K2003/2224—Magnesium hydroxide
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L2201/00—Properties
    • C08L2201/02—Flame or fire retardant/resistant
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L2203/00—Applications
    • C08L2203/20—Applications use in electrical or conductive gadgets
    • C08L2203/202—Applications use in electrical or conductive gadgets use in electrical wires or wirecoating

Abstract

The invention provides a flame-retardant resin composition with excellent low-temperature characteristics and fuel resistance characteristics, a manufacturing method thereof, an electric wire and manufacturing method thereof, and a cable and manufacturing method thereof. The method for producing the flame-retardant resin composition comprises: (S1) a 1 st kneading step of kneading the ethylene-vinyl acetate copolymer and the metal hydroxide to produce a 1 st kneaded product; (S2) a 2 nd kneading step of kneading the 1 st kneaded product and the maleic acid-modified ethylene- α -olefin copolymer to obtain a flame-retardant resin composition. The flame-retardant resin composition contains 150 to 300 parts by mass of the metal hydroxide per 100 parts by mass of the base polymer comprising the ethylene-vinyl acetate copolymer and the maleic acid-modified ethylene- α -olefin copolymer.

Description

Flame-retardant resin composition and method for producing same, wire and method for producing same, cable and method for producing same
Technical Field
The present invention relates to a flame retardant resin composition and a method for producing the same, an electric wire and a method for producing the same, and a cable and a method for producing the same.
Background
The electric wire has a conductor and an insulating layer as a coating material provided around the conductor. The cable includes the electric wire and a sheath (outer coating) as a coating material provided around the electric wire. The sheath is arranged around the insulating layer.
The insulating layer of the electric wire and the coating material such as the sheath of the cable are made of an electrically insulating material mainly composed of rubber or resin. The electrical insulating material has different characteristics required depending on the application. For example, an electrical insulating material used for a railway vehicle electric wire is required to have high flame retardancy, low temperature characteristics, fuel resistance, and the like.
As an example of such an electrically insulating material and an electric wire, patent document 1 describes a halogen-free flame retardant resin composition obtained by adding a metal hydroxide as a flame retardant to a polymer alloy containing an ethylene-vinyl acetate copolymer and a maleic acid-modified ethylene- α -olefin copolymer, an electric wire using the same, and the like.
The halogen-free flame retardant resin composition described in patent document 1 does not generate toxic gases such as hydrogen chloride and dioxin when burned, and therefore can prevent the generation of toxic gases and secondary disasters during a fire, and is also not problematic even when burned during disposal, and thus is useful as an insulating layer for electric wires for railway vehicles.
Prior art literature
Patent literature
Patent document 1: japanese patent application laid-open No. 2014-53247
Disclosure of Invention
Problems to be solved by the invention
However, according to the studies of the present inventors, it was found that the following cases exist: when the flame-retardant resin composition is intended to be produced, fuel resistant properties sufficient for use as a coating material such as an outer coating layer of the cable or an insulating layer of the electric wire cannot be obtained.
The present invention has been made in view of the above problems, and an object thereof is to provide a flame-retardant resin composition excellent in low-temperature characteristics and fuel resistance characteristics, and a wire and cable using the same.
Means for solving the problems
The following briefly describes an outline of a representative invention among the inventions disclosed in the present application.
[1] A method for producing a flame retardant resin composition, comprising: (a) A step of kneading the ethylene-vinyl acetate copolymer and the metal hydroxide to produce a 1 st kneaded product; (b) And (3) kneading the kneaded product 1 and the maleic acid-modified ethylene- α -olefin copolymer to obtain a flame-retardant resin composition. The flame-retardant resin composition contains 150 to 300 parts by mass of the metal hydroxide per 100 parts by mass of the base polymer comprising the ethylene-vinyl acetate copolymer and the maleic acid-modified ethylene- α -olefin copolymer.
[2] The method of producing a flame-retardant resin composition according to [1], wherein in the step (a), the metal hydroxide is added in multiple steps while kneading the ethylene-vinyl acetate copolymer after melting.
[3] The method for producing a flame-retardant resin composition according to [1], wherein the ethylene-vinyl acetate copolymer comprises a 1 st ethylene-vinyl acetate copolymer and a 2 nd ethylene-vinyl acetate copolymer having different vinyl acetate contents.
[4] A method of manufacturing an electric wire, comprising: (a) A step of kneading the ethylene-vinyl acetate copolymer and the metal hydroxide to produce a 1 st kneaded product; (b) And (3) kneading the kneaded product 1 and the maleic acid-modified ethylene- α -olefin copolymer to obtain a flame-retardant resin composition. The manufacturing method of the electric wire comprises the following steps: (c) Extruding the flame-retardant resin composition so as to cover the periphery of the conductor to form an insulating layer, thereby producing an electric wire; (d) And a step of irradiating the electric wire with an electron beam to crosslink the ethylene-vinyl acetate copolymer and the maleic acid-modified ethylene- α -olefin copolymer in the flame-retardant resin composition. The flame-retardant resin composition contains 150 to 300 parts by mass of the metal hydroxide per 100 parts by mass of the base polymer comprising the ethylene-vinyl acetate copolymer and the maleic acid-modified ethylene- α -olefin copolymer.
[5] A method of manufacturing a cable comprising: (a) A step of kneading the ethylene-vinyl acetate copolymer and the metal hydroxide to produce a 1 st kneaded product; (b) And a step of kneading the kneaded product 1 and the maleic acid-modified ethylene- α -olefin copolymer to produce a flame-retardant resin composition. The manufacturing method of the cable comprises the following steps: (c) Extruding the flame-retardant resin composition so as to cover the periphery of the conductor to form an insulating layer, thereby producing an electric wire; (d) And extruding the flame-retardant resin composition so as to cover the circumference of the electric wire, thereby forming a sheath. The flame-retardant resin composition contains 150 to 300 parts by mass of the metal hydroxide per 100 parts by mass of the base polymer comprising the ethylene-vinyl acetate copolymer and the maleic acid-modified ethylene- α -olefin copolymer.
[6] A flame retardant resin composition comprising an ethylene-vinyl acetate copolymer, a maleic acid-modified ethylene-alpha-olefin copolymer and a metal hydroxide. The ethylene-vinyl acetate copolymer contains a 1 st ethylene-vinyl acetate copolymer and a 2 nd ethylene-vinyl acetate copolymer having different vinyl acetate contents. The flame-retardant resin composition contains 150 to 300 parts by mass of the metal hydroxide per 100 parts by mass of the base polymer comprising the ethylene-vinyl acetate copolymer and the maleic acid-modified ethylene- α -olefin copolymer.
[7] An electric wire comprising an insulating layer formed of the flame-retardant resin composition according to [6 ].
[8] A cable comprising a sheath formed of the flame-retardant resin composition according to [6 ].
ADVANTAGEOUS EFFECTS OF INVENTION
According to the present invention, a flame-retardant resin composition having low-temperature characteristics and fuel resistance characteristics, and a wire and cable using the same can be provided.
Drawings
Fig. 1 is a flowchart showing a process for producing a flame retardant resin composition according to an embodiment.
Fig. 2 is a cross-sectional view showing a wire structure of one embodiment.
Fig. 3 is a cross-sectional view showing a cable structure of an embodiment.
Fig. 4 is a transmission electron microscope image of the insulating layer of the electric wire of example 1.
Fig. 5 is a transmission electron microscope image of the insulating layer of the wire of comparative example 2.
Fig. 6 is a transmission electron microscope image and a scanning electron microscope image of the insulating layer of the wire of comparative example 5.
Symbol description
1: a conductor; 2: an insulating layer; 3: an interlayer; 4: a sheath; 10: an electric wire; 11: and (3) a cable.
Detailed Description
(study item)
Before describing the embodiments, first, the matters studied by the present inventors will be described.
The present inventors studied: as a material used as a coating material such as an insulating layer of an electric wire or an outer coating layer of a cable, a halogen-free flame retardant resin composition obtained by adding a metal hydroxide as a flame retardant to a polymer alloy containing an ethylene-vinyl acetate copolymer and a maleic acid-modified ethylene- α -olefin copolymer is used.
Ethylene-vinyl acetate copolymers are thermoplastics that are excellent in flexibility and low-temperature characteristics. Flame retardancy can be improved by adding a metal hydroxide to an ethylene-vinyl acetate copolymer. However, in this case, it is known that the adhesion between the ethylene-vinyl acetate copolymer and the metal hydroxide is not high, and therefore the low-temperature characteristics are degraded.
Therefore, the ethylene-vinyl acetate copolymer is modified by adding a metal hydroxide and maleic acid to the ethylene- α -olefin copolymer. Since the maleic acid-modified ethylene- α -olefin copolymer forms a polymer alloy with the ethylene-vinyl acetate copolymer and has high adhesion to a metal hydroxide, the low temperature characteristics can be improved if the metal hydroxide is added to a polymer alloy (hereinafter referred to as a base polymer) containing the ethylene-vinyl acetate copolymer and the maleic acid-modified ethylene- α -olefin copolymer.
The method for producing the flame-retardant resin composition comprises the steps of: the ethylene-vinyl acetate copolymer (A), the maleic acid-modified ethylene- α -olefin copolymer (B) and the metal hydroxide (C) were simultaneously fed into a pressure kneader or the like, and kneaded (hereinafter referred to as "study example 1").
In study example 1, a base polymer comprising (a) an ethylene-vinyl acetate copolymer and (B) a maleic acid-modified ethylene- α -olefin copolymer was melted to form a liquid phase during kneading, while (C) a metal hydroxide was not melted, and a solid phase was maintained. Therefore, the metal hydroxide is difficult to mix with the base polymer.
In order to sufficiently exhibit the flame retardancy of the flame-retardant resin composition, the ratio of the metal hydroxide in the flame-retardant resin composition is preferably high. As described later, the amount of the metal hydroxide added is 150 to 300 parts by mass per 100 parts by mass of the base polymer comprising (a) the ethylene-vinyl acetate copolymer and (B) the maleic acid-modified ethylene- α -olefin copolymer.
Thus, the metal hydroxide is difficult to mix with the base polymer, and the ratio in the flame-retardant resin composition is high. Therefore, if the (a) ethylene-vinyl acetate copolymer, (B) maleic acid-modified ethylene- α -olefin copolymer and (C) metal hydroxide are simultaneously fed into a pressure kneader or the like and kneaded as in study example 1, there is a possibility that the metal hydroxide cannot be sufficiently dispersed in the flame-retardant resin composition.
Accordingly, the present inventors studied, as a method for producing a flame-retardant resin composition, a method for dispersing a metal hydroxide in a flame-retardant resin composition: the ethylene-vinyl acetate copolymer (A) and the maleic acid-modified ethylene- α -olefin copolymer (B) were kneaded by a pressure kneader or the like, and the metal hydroxide (C) was added to the kneaded mixture and kneaded in a plurality of times (hereinafter referred to as "study example 2"). According to study example 2, the metal hydroxide can be efficiently dispersed in the flame-retardant resin composition.
However, as described above, the inventors of the present invention have confirmed that the flame retardant resin composition of study example 2 may not have sufficient fuel resistance for use as a coating material such as an outer coating layer of the cable or an insulating layer of the electric wire. As a cause of this, it is known that, as described in comparative examples described later, a void is generated between the base polymer and the metal hydroxide, and the fuel enters the void.
Here, the inventors believe that the reason why the voids are generated between the base polymer and the metal hydroxide in the flame-retardant resin composition of study example 2 is that the adhesion between the maleic acid-modified ethylene- α -olefin copolymer and the metal hydroxide.
The maleic acid-modified ethylene- α -olefin copolymer has a carboxylic anhydride structure (derived from maleic anhydride) obtained by dehydration-condensation of 2 carboxyl groups (COOH), and a carboxyl group (derived from maleic acid) obtained by hydrolysis of the carboxylic anhydride. Thus, hydrogen bonds can be formed between the maleic acid-modified- α -olefin copolymer and the metal hydroxide. Therefore, the adhesion between the maleic acid-modified ethylene- α -olefin copolymer and the metal hydroxide is higher than the adhesion between the ethylene-vinyl acetate copolymer and the metal hydroxide. Due to such properties, the addition of the maleic acid-modified ethylene- α -olefin copolymer to the flame-retardant resin composition can improve the adhesion between the base polymer and the metal hydroxide, and can improve the low-temperature characteristics of the resulting flame-retardant resin composition.
However, the adhesion between the maleic acid-modified ethylene- α -olefin copolymer and the metal hydroxide is considered to be the opposite effect in kneading for the following reasons. That is, in the method for producing a flame-retardant resin composition of study example 2, if (C) a metal hydroxide is added and kneaded in the presence of (B) a maleic acid-modified ethylene- α -olefin copolymer, the (C) metal hydroxide is kneaded in a state of adhesion to (B) a maleic acid-modified ethylene- α -olefin copolymer by hydrogen bonding. As a result, in the kneading step after adding the metal hydroxide in study example 2, excessive stress was generated on the crystal of the metal hydroxide due to kneading of the maleic acid-modified ethylene- α -olefin copolymer, and a part of the metal hydroxide crystal was peeled off or the crystal of the metal hydroxide was finely pulverized. As a result, in study example 2, a void was generated between the base polymer and the metal hydroxide.
In particular, in the case of study example 2, since the metal hydroxide (C) was added to the base polymer in several portions, the kneading time was prolonged accordingly, and the crystals of the metal hydroxide were easily peeled off and easily broken.
As described above, in the method for producing a halogen-free flame-retardant resin composition in which a metal hydroxide is added as a flame retardant to a polymer alloy comprising an ethylene-vinyl acetate copolymer and a maleic acid-modified ethylene- α -olefin copolymer, it is expected that a flame-retardant resin composition having low-temperature characteristics and fuel resistance characteristics will be produced by examining the steps thereof.
(embodiment)
(1) Flame-retardant resin composition
Composition of flame-retardant resin composition
The flame-retardant resin composition according to one embodiment of the present invention comprises (A) an ethylene-vinyl acetate copolymer, (B) a maleic acid-modified ethylene-alpha-olefin copolymer, and (C) a metal hydroxide.
The ethylene-vinyl acetate copolymer (a) of the present embodiment may be a single ethylene-vinyl acetate copolymer, or 2 or more ethylene-vinyl acetate copolymers may be mixed as shown in examples described below. Here, if the content of vinyl acetate in the ethylene-vinyl acetate copolymer increases, the glass transition temperature increases and the low-temperature characteristics decrease. On the other hand, if the content of vinyl acetate in the ethylene-vinyl acetate copolymer is reduced, the polarity is reduced and the fuel resistance is reduced. Accordingly, by containing 2 or more ethylene-vinyl acetate copolymers having different vinyl acetate content, a flame-retardant resin composition having excellent balance between low-temperature characteristics and fuel resistance characteristics can be produced. Among them, an ethylene-vinyl acetate copolymer having a vinyl acetate content (VA amount) of 28 mass% and an ethylene-vinyl acetate copolymer having a vinyl acetate content (VA amount) of 41 mass% were used in examples described later.
The maleic acid-modified ethylene- α -olefin copolymer (B) of the present embodiment is obtained by graft polymerizing maleic anhydride to an ethylene- α -olefin copolymer such as an ethylene-propylene copolymer. The carbon number of the alpha-olefin is preferably 3 to 8.
The metal hydroxide (C) of the present embodiment may be magnesium hydroxide, aluminum hydroxide, calcium hydroxide, or a metal hydroxide having nickel dissolved therein. These metal hydroxides may be used in an amount of 1 kind or 2 or more kinds. The metal hydroxide is preferably a surface-treated metal salt of a fatty acid or fatty acid such as a silane coupling agent, a phthalate ester coupling agent, stearic acid, or calcium stearate. The surface treatment agent may be used in combination of a plurality of kinds of these surface treatment agents.
In addition, the flame retardant resin composition of the present embodiment may contain (D) a crosslinking auxiliary, (E) an antioxidant, (F) a colorant, or (G) a lubricant, if necessary, in addition to (a) the ethylene-vinyl acetate copolymer, (B) the maleic acid-modified ethylene- α -olefin copolymer, and (C) the metal hydroxide. Examples of the crosslinking assistant (D) include trimethylolpropane trimethacrylate (TMPT), triallyl isocyanurate, triallyl cyanurate, N' -m-phenylene bismaleimide, ethylene glycol dimethacrylate, zinc acrylate and zinc methacrylate. Examples of the antioxidant (E) include phenol antioxidants, phenol/thioester antioxidants, amine antioxidants, sulfur antioxidants, phosphite antioxidants, and the like. Examples of the colorant (F) include inorganic pigments, organic pigments, dyes, and carbon black. Examples of the lubricant (G) include zinc stearate, silicone, fatty acid amide-based, hydrocarbon-based, ester-based, alcohol-based, and metal soap-based lubricants.
In the present embodiment, the flame-retardant resin composition is crosslinked with (a) ethylene-vinyl acetate copolymers, (B) maleic acid-modified ethylene- α -olefin copolymers, or (a) ethylene-vinyl acetate copolymers and (B) maleic acid-modified ethylene- α -olefin copolymers. Such crosslinking is not necessary in the present embodiment, but is preferably performed because the mechanical properties of the flame-retardant resin composition are improved by the crosslinking. As the crosslinking method, an electron beam crosslinking method in which an electron beam is irradiated after molding, a chemical crosslinking method in which a crosslinking agent is added to a flame-retardant resin composition in advance and heat treatment is performed after molding, or the like can be used, and in this embodiment, an electron beam crosslinking method is used.
In this embodiment, the amount of the metal hydroxide to be added is 150 to 300 parts by mass, preferably 150 to 200 parts by mass, based on 100 parts by mass of the base polymer comprising (a) the ethylene-vinyl acetate copolymer and (B) the maleic acid-modified ethylene- α -olefin copolymer. When the amount of the metal hydroxide to be added is less than 150 parts by mass relative to 100 parts by mass of the base polymer, sufficient flame retardancy cannot be obtained. On the other hand, the mechanical properties are lowered when the amount of the metal hydroxide added is more than 300 parts by mass relative to 100 parts by mass of the base polymer. The flame retardant resin composition according to one embodiment of the present invention is preferably a halogen-free flame retardant resin composition.
In the present embodiment, the content of the (B) maleic acid-modified ethylene- α -olefin copolymer in the base polymer is not particularly limited, and it is preferable that the content of the (B) maleic acid-modified ethylene- α -olefin copolymer in 100 parts by weight of the base polymer is 1 to 30 parts by weight. The maleic acid-modified ethylene- α -olefin copolymer (B) in an amount of less than 1 part by weight based on 100 parts by weight of the base polymer has low adhesion between the base polymer and the metal hydroxide and low-temperature characteristics. On the other hand, in 100 parts by weight of the base polymer, the adhesion between the base polymer and the metal hydroxide is too high and the elongation is lowered when the amount of the maleic acid-modified ethylene- α -olefin copolymer (B) is more than 30 parts by weight.
Method for producing flame-retardant resin composition
Fig. 1 is a flowchart showing a process for producing the flame retardant resin composition according to the present embodiment. As shown in fig. 1, the method for producing the flame retardant resin composition of the present embodiment includes: (S1) a step of kneading (A) the ethylene-vinyl acetate copolymer and (C) the metal hydroxide (kneading step 1), and (S2) a step of kneading (kneading step 2) the 1 st kneaded product produced in the step (S1) and (B) the maleic acid-modified ethylene- α -olefin copolymer. Through these steps, the flame retardant resin composition of the present embodiment can be produced.
In order to easily knead the ethylene-vinyl acetate copolymer with the metal hydroxide and to sufficiently disperse the metal hydroxide in the flame-retardant resin composition, it is preferable to add the metal hydroxide (C) in multiple steps while kneading the molten (A) ethylene-vinyl acetate copolymer in the step (S1).
Although not shown, the step (S2) may be followed by the steps of: the flame-retardant resin composition produced in the step (S2) is irradiated with an electron beam to crosslink the ethylene-vinyl acetate copolymer (A) and the maleic acid-modified ethylene- α -olefin copolymer (B).
In the step (S1), a crosslinking assistant (D), an antioxidant (E), a colorant (F), a lubricant (G), or the like may be added as needed. These additives are preferably added before the addition of the (C) metal hydroxide, but are not limited thereto.
The temperature in the step (S1) is at least 70℃for example, at which the ethylene-vinyl acetate copolymer (A) is melt-continuous (molded). The temperature in the step (S2) is at least the melt-continuity temperature of the maleic acid-modified ethylene- α -olefin copolymer (B), for example, 120 to 170 ℃. As a result, the temperature in the step (S2) is higher than the temperature in the step (S1).
For example, a known kneading apparatus such as a batch kneader such as a Banbury mixer or a pressure kneader, or a continuous kneader such as a twin-screw extruder can be used as the kneading apparatus for producing the flame-retardant resin composition of the present embodiment.
The method for producing the flame-retardant resin composition according to the present embodiment is described as a method including the (S1) 1 st kneading step and the (S2) 2 nd kneading step, but the flame-retardant resin composition according to the present embodiment may be produced as 1 step obtained by continuing these steps. For example, in the case of a continuous kneading machine such as a twin screw extruder having a plurality of inlet ports in the extrusion direction, the step (S1) and the step (S2) can be performed as 1 continuous step in 1 kneading apparatus by charging (a) the ethylene-vinyl acetate copolymer and (C) the metal hydroxide through 1 inlet port and charging (B) the maleic acid-modified ethylene- α -olefin copolymer through another inlet port.
Features and effects of the present embodiment
One of the features of the method for producing a flame-retardant resin composition according to one embodiment of the present invention is that (a) an ethylene-vinyl acetate copolymer and (C) a metal hydroxide are kneaded in the absence of (B) a maleic acid-modified ethylene- α -olefin copolymer in the step (S1). Then, in the step (S2), the 1 st kneaded product produced in the step (S1) and (B) the maleic acid-modified ethylene- α -olefin copolymer are kneaded.
In this embodiment, by adopting such a step, in the method for producing a flame-retardant resin composition in which a metal hydroxide is added as a flame retardant to a polymer alloy containing an ethylene-vinyl acetate copolymer and a maleic acid-modified ethylene- α -olefin copolymer, a flame-retardant resin composition having low-temperature characteristics and fuel resistance characteristics can be produced. The reason for this will be specifically described below.
As described above, in the method for producing a flame-retardant resin composition of study example 2, (C) a metal hydroxide was added in a fraction in the presence of (B) a maleic acid-modified ethylene- α -olefin copolymer and kneaded, and as a result, a part of the metal hydroxide crystals was peeled off or the metal hydroxide crystals were finely pulverized. This results in the following: a void is generated between the base polymer and the metal hydroxide, and fuel resistance is lowered.
In the present embodiment, on the other hand, (B) a maleic acid-modified ethylene- α -olefin copolymer is not added in the step (S1), and (a) an ethylene-vinyl acetate copolymer and (C) a metal hydroxide are kneaded. In the step (S1), since the maleic acid-modified ethylene- α -olefin copolymer is not present in the kneaded material, excessive stress is not generated on the crystal of the metal hydroxide, and a part of the crystal of the metal hydroxide is not peeled off or the crystal of the metal hydroxide is finely pulverized. In order to sufficiently disperse the metal hydroxide in the flame-retardant resin composition, the metal hydroxide (C) is added and kneaded in a plurality of steps in the step (S1) similarly to the case of study example 2, and for the same reason, no problem occurs.
As a result, in the step (S1), the ethylene-vinyl acetate copolymer and the metal hydroxide can be sufficiently kneaded, and the metal hydroxide can be sufficiently dispersed in the kneaded material (1 st kneaded material).
Then, in the step (S2), the (B) maleic acid-modified ethylene- α -olefin copolymer is added and kneaded in a state where the (C) metal hydroxide is sufficiently dispersed in the 1 st kneaded product produced in the step (S1). By doing so, the kneading time of the maleic acid-modified ethylene- α -olefin copolymer (B) and the metal hydroxide (C) in the step (S2) can be made shorter than in the case of study example 2, and the possibility of peeling off a part of the metal hydroxide crystal or finely pulverizing the metal hydroxide crystal can be reduced.
As described above, in the present embodiment, in the flame-retardant resin composition in which the metal hydroxide as the flame retardant is added to the polymer alloy containing the ethylene-vinyl acetate copolymer and the maleic acid-modified ethylene- α -olefin copolymer, the occurrence of voids between the base polymer and the metal hydroxide can be prevented, and the low-temperature property and the fuel resistance property can be provided.
(2) Electric wire
Fig. 2 is a cross-sectional view showing an electric wire (insulated electric wire) according to an embodiment of the present invention. As shown in fig. 2, the electric wire 10 according to the present embodiment includes a conductor 1 and an insulating layer 2 covering around the conductor 1. The insulating layer 2 is formed of the aforementioned flame retardant resin composition.
As the conductor 1, a commonly used metal wire may be used, and for example, an aluminum wire, a gold wire, a silver wire, or the like may be used in addition to a copper wire and a copper alloy wire. As the conductor 1, a conductor plated with a metal such as tin or nickel around a metal wire may be used. Further, as the conductor 1, a twisted conductor obtained by twisting metal wires may be used.
The electric wire 10 of the present embodiment is manufactured, for example, as follows. First, a copper wire is prepared as the conductor 1. Then, the flame-retardant resin composition is extruded by an extruder so as to cover the circumference of the conductor 1, thereby forming the insulating layer 2 having a predetermined thickness. By doing so, the electric wire 10 of the present embodiment can be manufactured.
The flame-retardant resin composition used in the present embodiment is not limited to the electric wire produced in examples described later, and can be used for all applications and sizes, and can be used for insulating layers of electric wires for railway vehicles, automobiles, in-tray wiring, in-device wiring, and electric power.
In particular, as described above, the flame-retardant resin composition constituting the insulating layer 2 of the electric wire 10 of the present embodiment has good low-temperature characteristics and fuel resistance characteristics. Therefore, the electric wire 10 according to the present embodiment can be used as a flame-retardant resin-coated electric wire excellent in low-temperature characteristics and fuel resistance characteristics, and in particular, can be suitably used as an electric wire for a railway vehicle.
(3) Cable with improved cable characteristics
Fig. 3 is a cross-sectional view showing a cable 11 according to an embodiment of the present invention. As shown in fig. 3, the cable 11 according to the present embodiment includes: a two-core twisted wire formed by twisting 2 wires 10, an interlayer 3 arranged around the two-core twisted wire and a sheath 4 arranged around the interlayer 3. The sheath 4 is formed of the aforementioned flame retardant resin composition.
The cable 11 according to the present embodiment is manufactured, for example, as follows. First, 2 wires 10 were manufactured by the foregoing method. Then, the circumference of the electric wire 10 is covered with the interlayer 3, and then the aforementioned flame-retardant resin composition is extruded in such a manner as to cover the interlayer 3, thereby forming the sheath 4 of a predetermined thickness. By doing so, the cable 11 of the present embodiment can be manufactured.
As described above, the flame retardant resin composition constituting the sheath 4 of the cable 11 of the present embodiment has good low temperature characteristics and fuel resistance characteristics. Therefore, the cable 11 according to the present embodiment can be used as a flame-retardant resin cable having excellent low-temperature characteristics and fuel resistance characteristics, and is particularly suitable for use as a cable for a railway vehicle.
The cable 11 of the present embodiment has been described as an example in which the two-core twisted wire formed by twisting 2 wires 10 is used as the core wire, but the core wire may be a single core (1) or may be a multi-core twisted wire other than two cores. In addition, a multi-layer sheath structure in which another insulating layer (sheath) is formed between the electric wire 10 and the sheath 4 may be employed.
The cable 11 according to the present embodiment has been described by taking the case where the electric wire 10 is used as an example, but the present invention is not limited thereto, and an electric wire using a general-purpose material may be used.
Example (example)
The present invention will be described in further detail with reference to examples, but the present invention is not limited to these examples.
[ examples 1 to 8 and comparative examples 1 to 4]
Examples 1 to 8 and comparative examples 1 to 4 will be described below. Examples 1 to 8 and comparative examples 1 to 4 correspond to the electric wire 10 shown in fig. 2. As the conductor 1 shown in fig. 2, a tin-plated stranded conductor (core number 43, bare wire diameter 0.16 mm) having an outer diameter of 1.21mm was used. As the insulating layer 2, insulating layers formed of the flame-retardant resin composition produced by the production method of the present embodiment were used in examples 1 to 8. On the other hand, in comparative examples 1 to 4, insulating layers formed of the flame-retardant resin composition produced by the production method of study example 2 were used.
Example 1 to example 8 and comparative example 1 to comparative example 4
The raw materials used in examples 1 to 8 and comparative examples 1 to 4 were as follows.
(A) Ethylene vinyl acetate copolymer (EVA):
(A1) EV270 (manufactured by Mitsui DuPont polymerization chemical Co., ltd., MFR 1g/10min, vinyl acetate content 28, melting point 72 ℃)
(A2) V9000 (MFR 1g/10min, vinyl acetate content 41, melting point 50-60 ℃ C. Manufactured by Mitsui DuPont Polymer chemical Co., ltd.)
(B) Maleic acid-modified ethylene- α -olefin copolymer:
(B1) MH7020 (manufactured by Sanjing chemical Co., ltd., molding processing temperature (melt serialization temperature) 115 ℃ C.)
(B2) MH5040 (manufactured by Sanjing chemical Co., ltd., molding processing temperature (melt serialization temperature) 102 ℃ C.)
(C) Metal hydroxide: magseeds S4 (magnesium hydroxide surface-treated with silane coupling agent and stearic acid, manufactured by shendao chemical Co., ltd.)
(D) Crosslinking auxiliary agent: TMPT (trimethylolpropane trimethacrylate, new Zhongcun chemical Co., ltd.)
(E) Antioxidant:
(E1) AO18 (phenol/thioester antioxidant, manufactured by ADEKA)
(E2) Songnox1010 (phenol antioxidant, manufactured by Songyuan Co., ltd.)
(F) Coloring agent: FT carbon (carbon, manufactured by Xu carbon Co., ltd.)
(G) And (3) a lubricant:
(G1) Zn-St (Zinc stearate, manufactured by Ridong chemical industry Co., ltd.)
(G2) KE76S (organosilicon, manufactured by Xinyue chemical industry Co., ltd.)
Details of the material formulations used in examples 1 to 8 and comparative examples 1 to 4 are shown in table 1.
TABLE 1
Figure BDA0002160763130000131
As shown in table 1, the difference between the formulation 1 and the formulation 2 is that the molding processing temperature (melt-continuous temperature) was different only for the (B) maleic acid-modified ethylene- α -olefin copolymer, but the difference was the same.
Example 1 to example 8 manufacturing method
The samples of examples 1 to 8 were prepared by the following method. The kneading methods, formulations, kneaders, kneading conditions, and evaluation results of examples 1 to 8 are summarized in table 2.
TABLE 2
Figure BDA0002160763130000151
As described above, examples 1 to 8 correspond to the flame retardant resin composition produced by the production method of the present embodiment. Each condition is an example. As the formulation of the material, formulation 1 was used in examples 1 to 4, and formulation 2 was used in examples 5 to 8. Further, as the kneading machine, 3L pressure kneader was used in example 1, example 2, example 5 and example 6, and 6 inch rolls were used in example 3, example 4, example 7 and example 8. Examples 1 to 8 show the set temperature in the 1 st kneading step (S1), the input temperature of the (B) maleic acid-modified ethylene- α -olefin copolymer in the 2 nd kneading step (S2), and the final reached temperature in the 2 nd kneading step (S2), respectively, as kneading conditions.
(a) 1 st kneading step (S1)
The (A) ethylene-vinyl acetate copolymer, (D) crosslinking aid, (E) antioxidant, (F) colorant, and (G) lubricant were put into a 3L pressure kneader or 6-inch roll and kneaded. Then, the metal hydroxide (C) was charged into the 3L pressure kneader or 6-inch roll three times and kneaded.
(b) 2 nd kneading step (S2)
The maleic acid-modified ethylene- α -olefin copolymer (B) was charged into a 3L pressure kneader or a 6-inch roll, which had been subjected to the above-mentioned 1 st kneading step (S1), and kneaded. The product (flame-retardant resin composition) after kneading was sheeted with an 8-inch roll, cut with a square granulator, and molded into a plate shape.
(c) Extrusion process
Next, a tin-plated stranded conductor was inserted into a die of a 40mm single screw extruder. Then, the product of the kneading step (S2) of the above 2 was fed from a hopper of a single screw extruder, extruded into a tube shape, and pulled down in vacuum at a line speed of 30m/min while forming an insulating layer with a thickness of 0.7mm around the tin-plated stranded conductor, thereby producing an electric wire.
Wherein the ratio L/D of the screw diameter D to the screw length L was set to 24. The temperature of the 4 cylinders was 160℃and the temperature of the die was 180 ℃.
(d) Crosslinking step
The electric wire produced in the extrusion step was irradiated with an electron beam at 7.5Mrad to crosslink (a) the ethylene-vinyl acetate copolymer and (B) the maleic acid-modified ethylene- α -olefin copolymer in the flame-retardant resin composition. The electric wires of examples 1 to 8 were produced by the above steps.
Comparative examples 1 to 4
The samples of comparative examples 1 to 4 were prepared by the following methods. The kneading methods, formulations, kneaders, kneading conditions, and evaluation results of comparative examples 1 to 4 are summarized in Table 2.
As described above, comparative examples 1 to 4 correspond to the flame retardant resin compositions produced by the production method of study example 2. Each condition is an example. As the formulation of the material, formulation 1 was used in comparative example 1 and comparative example 2, and formulation 2 was used in comparative example 3 and comparative example 4. In addition, as the kneading machine, a 3L pressure kneader was used in comparative example 1 and comparative example 3, and a 6 inch roll was used in comparative example 2 and comparative example 4. As kneading conditions, comparative examples 1 to 4 show the set temperature in the kneading step and the final reached temperature in the kneading step, respectively.
(a) Mixing process
The (A) ethylene-vinyl acetate copolymer, (B) maleic acid-modified ethylene-alpha-olefin-based copolymer, (D) crosslinking aid, (E) antioxidant, (F) colorant, and (G) lubricant were put into a 3L pressure kneader or 6-inch roll and kneaded. Then, the metal hydroxide of (C) was fed into the 3L pressure kneader or 6-inch roll in three times and kneaded. The kneaded product was sheeted with an 8-inch roll, cut with a square granulator, and formed into a plate shape.
(b) Extrusion process
Next, a tin-plated stranded conductor was inserted into a die of a 40mm single screw extruder. Then, the product of the kneading step was fed into a hopper of a single screw extruder, extruded into a tube shape, pulled down in vacuum at a line speed of 30m/min, and an insulating layer having a thickness of 0.7mm was formed around the tin-plated stranded conductor, thereby producing an electric wire.
Wherein the ratio L/D of the screw diameter D to the screw length L was set to 24. The temperature of the 4 cylinders was 160℃and the temperature of the die was 180 ℃.
(c) Crosslinking step
The electric wire produced in the extrusion step was irradiated with an electron beam at 7.5Mrad to crosslink (a) the ethylene-vinyl acetate copolymer and (B) the maleic acid-modified ethylene- α -olefin copolymer in the flame-retardant resin composition. The electric wires of comparative examples 1 to 4 were produced by the above steps.
< evaluation methods of examples 1 to 8 and comparative examples 1 to 4 >
(1) Vertical flame retardant test (VFT)
For the produced wire, a burning test was performed in accordance with IEC 60332-1-2. The electric wires having the lengths of the charred portions after combustion satisfying the criteria were set to "o", and the electric wires not satisfying the criteria were set to "x".
(2) Flame-resistant material characteristics of
The conductor was pulled out from the produced wire, and a single insulating layer sample having a length of 120mm was prepared, and the sample was immersed in IRM903 oil (fuel) at 70 ℃ for 1 week, and the "change rate of elongation value" of the sample = (initial elongation value-elongation value after immersion)/initial elongation value was calculated. The result of the change rate of the elongation value being lower than 30% was "o", and the result of the change rate of the elongation value being 30% or more was "x".
(3) Low temperature characteristics
The conductor was pulled out from the produced wire, and a single insulating layer sample of 120mm in length was produced, which was kept at-40℃and then the elongation under the atmosphere was measured. The result of the elongation of this sample was "o" and the result of the elongation of this sample was less than 30% was "x".
(4) Phase structure
The conductor was pulled out from the produced wire to prepare an individual insulating layer having a length of 120mm, and the insulating layer was further prepared into a sample having a thickness of 0.1 to 0.2. Mu.m, and the sample was observed under conditions of an acceleration voltage of 100kV and a magnification of 10 ten thousand times by a transmission electron microscope (Transmission electron microscope: TEM).
For comparison, a scanning electron microscope (Scanning electron microscope: SEM) image was also measured in addition to the TEM image. Specifically, a conductor was pulled out from the prepared wire, a single insulating layer having a length of 120mm was prepared, and a sample having a thickness of about 1mm was prepared, and the sample was observed under conditions of an acceleration voltage of 5kV and a magnification of 2500 times by a scanning electron microscope (Scanning electron microscope: SEM).
< evaluation results of examples 1 to 8 and comparative examples 1 to 4 >
The above evaluation results are summarized in table 2, fig. 4 and fig. 5. Fig. 4 is a TEM image of the sample of example 1. Fig. 5 is a TEM image and an SEM image of a sample obtained by making the temperature condition of the 6-inch roller the same as in example 4 in comparative example 2. Fig. 6 is a TEM image of the sample of comparative example 2. In fig. 4, a corresponds to the sample before immersing the sample of example 1 in IRM903 oil, and b corresponds to the sample after immersing the sample of example 1 in IRM903 oil. In fig. 5, d and e are samples of comparative example 2, which had the same temperature conditions of the 6 inch roll as example 4, prior to immersion in IRM903 oil. FIG. 6 is a sample of comparative example 2 after soaking in IRM903 oil.
As is clear from the analysis of the inventors, in a, b in fig. 4, d in fig. 5, and c in fig. 6, the black oval portions are maleic acid-modified ethylene- α -olefin-based copolymer, the polygonal portions are crystals of magnesium hydroxide, the white portions are voids, and the other gray portions are ethylene-vinyl acetate copolymer. In fig. 5 e, it is understood that the white to gray portions are crystals of magnesium hydroxide, and the other dark gray to black portions are ethylene-vinyl acetate copolymer and maleic acid-modified ethylene- α -olefin copolymer.
As shown in table 2, in examples 1 to 8, (1) the vertical flame retardant test, (2) the fuel resistance property and (3) the low temperature property were all good.
In comparative examples 1 to 4, (1) the vertical flame retardant test and (3) the low temperature property were good, but (2) the fuel resistant property was poor.
As shown in a and B of fig. 4, in example 1, (4) the phase structure is an island-in-sea structure, that is, (a) the ethylene-vinyl acetate copolymer is a continuous phase (sea phase, matrix), and (B) the maleic acid-modified ethylene- α -olefin copolymer is a dispersed phase (island phase, domain). (B) The average particle diameter of the maleic acid-modified ethylene-alpha-olefin copolymer is 50-300 nm.
In comparative example 2, as shown by d in fig. 5, the temperature conditions of the 6-inch roll were set to be the same as those of example 4, and the (4) phase structure was also a sea-island structure, i.e., (a) an ethylene-vinyl acetate copolymer was a continuous phase and (B) a maleic acid-modified ethylene- α -olefin copolymer was a dispersed phase. The average particle diameter of the maleic acid-modified ethylene-alpha-olefin copolymer (B) is about 50 to 300 nm. Among these, the average particle diameter of the maleic acid-modified ethylene- α -olefin copolymer (B) is also known, and such a phase structure can be confirmed in the TEM image shown in fig. 5 d, but cannot be confirmed in the SEM image shown in fig. 5 e.
In addition, in comparative example 2 shown in fig. 5 d, in which the temperature condition of the 6-inch roller was set to be the same as that of example 4, the voids were more in the flame-retardant resin composition, and in example 1 shown in fig. 4 a, the voids were less in the flame-retardant resin composition, before immersing in the IRM903 oil.
Moreover, little change was observed in example 1 after immersion in IRM903 oil shown in fig. 4 b compared to example 1 before immersion in IRM903 oil shown in fig. 4 a. On the other hand, it is clear that in comparative example 2 after immersing in IRM903 oil shown in fig. 6 c, the voids in the flame-retardant resin composition are small, but a part of the maleic acid-modified ethylene- α -olefin copolymer is eluted.
In comparative example 2 shown in fig. 5 d, the temperature condition of the 6-inch roller was set to be the same as that of example 4, and in comparative example 2 shown in fig. 6 c, the magnesium hydroxide crystals were smaller than those of example 1 shown in fig. 4 a and b.
A detailed review of the above results is described in the summary of the examples below.
Example 9 and example 10
Examples 9 and 10 are described below. Example 9 and example 10 also correspond to the electric wire 10 shown in fig. 2. As the insulating layer 2, insulating layers made of the flame-retardant resin composition produced by the production method of the present embodiment were used in examples 9 and 10.
< constitution of example 9 and example 10 >
The raw materials used in example 9 and example 10 are the same as in example 1 and therefore omitted.
Example 9 and example 10 manufacturing method
The samples of examples 9 and 10 were prepared by the following method. The mixing methods, formulations, mixing rolls, mixing conditions and evaluation results of examples 1, 9 and 10 are summarized in Table 3.
TABLE 3
Figure BDA0002160763130000201
As described above, example 9 and example 10 correspond to the flame retardant resin composition manufactured by the manufacturing method of the present embodiment. Each condition is an example. The mixing rolls of example 9 and example 10 were 3L pressure kneaders similar to example 1. Among these, examples 9 and 10 were each different from example 1 in the clearance (interval) between the rotor and the kneading tank in the 3L pressure kneader. Specifically, as shown in Table 3, the clearance between the rotor kneading grooves was set to 2.5mm in example 1, 2mm in example 9, and 1.5mm in example 10.
Except for this, the material formulation and the like are the same as those of example 1, and thus the manufacturing process of example 9 and example 10 is omitted below.
< evaluation methods of example 9 and example 10 >)
The evaluation methods of example 9 and example 10 are basically the same as those of example 1, and therefore omitted.
< evaluation results of example 1, example 9 and example 10 >
The evaluation results of example 9 and example 10 are summarized in table 3 together with the evaluation results of example 1. As shown in table 3, in examples 9 and 10, (1) the vertical flame retardant test, (2) the fuel resistance property and (3) the low temperature property were all good.
Summary of examples ]
As shown in examples 1 to 10, according to the production method of the present embodiment, a flame retardant resin composition having low temperature characteristics and fuel resistance characteristics can be produced regardless of the type, the formulation ratio, the kneading machine, and the kneading conditions of the maleic acid-modified ethylene- α -olefin copolymer used.
Specifically, in the example shown in fig. 5 d in which the temperature condition of the 6-inch roll was the same as that of example 4 in comparative example 2, there was a large number of voids in the flame-retardant resin composition. This is considered to be the result of the method for producing the flame-retardant resin composition of study example 2, in which (C) a metal hydroxide was added and kneaded in a plurality of times in the presence of (B) a maleic acid-modified ethylene- α -olefin copolymer, and then (C) a part of the metal hydroxide crystals was peeled off.
Moreover, as shown in fig. 6 c, in comparative example 2, no voids were observed at first sight, which is considered to be the result of IRM903 oil entering voids generated in the flame-retardant resin composition. In comparative example 2, IRM903 oil entered the voids, and as a result, it was considered that a part of the maleic acid-modified ethylene- α -olefin copolymer eluted into the oil, and the fuel resistance was lowered.
In addition, in the example in which the temperature condition of the 6-inch roller is made the same as in example 4 in comparative example 2 shown in fig. 5 d and in comparative example 2 shown in fig. 6 c, the crystal size of magnesium hydroxide is smaller than in example 1 shown in fig. 4 a and b. This is considered to be the result of finely pulverizing the crystals of (C) metal hydroxide after the addition of (C) metal hydroxide in the presence of (B) maleic acid-modified ethylene- α -olefin copolymer and kneading in the method for producing a flame-retardant resin composition of research example 2. This is also considered to be one of the causes of the occurrence of voids between the base polymer and the metal hydroxide and the deterioration of fuel resistance.
On the other hand, in example 1 shown in fig. 4 a, the flame-retardant resin composition had little void prior to immersion in IRM903 oil. Therefore, even if the sample of example 1 is immersed in IRM903 oil, IRM903 oil does not enter the gap, and the fuel resistance is considered to be excellent. It can be said that the result confirms that: in this embodiment, in the step (S1) and the step (S2), the metal hydroxide crystal (C) is not partly peeled off or the metal hydroxide crystal is finely pulverized.
As shown in fig. 4 a and b, in example 1, magnesium hydroxide was sufficiently dispersed in the flame-retardant resin composition. It can be said that therefore, it is confirmed that: in the present embodiment, even if the kneading time of the (B) maleic acid-modified ethylene- α -olefin copolymer and the (C) metal hydroxide in the step (S2) is shortened, the (C) metal hydroxide can be sufficiently dispersed in the flame-retardant resin composition in the step (S1).
Further, as shown in examples 1, 9 and 10, according to the manufacturing method of the present embodiment, a flame-retardant resin composition having low temperature characteristics and fuel resistance characteristics can be produced regardless of whether there is a gap between the rotor and the kneading tank in the 3L pressure kneader. In general, if the gap between the rotor and the kneading tank is reduced, the shear stress applied to the kneaded material increases. However, in examples 1 to 9 and examples 9 to 10, good fuel resistance was obtained even when the gap between the rotor and the kneading tank was reduced. It can be said that therefore, it is confirmed that: in this embodiment, even when the stress applied to the kneaded material at the time of kneading in the step (S1) and the step (S2) is large, it is possible to prevent (C) the peeling of a part of the metal hydroxide crystal or the fine pulverization of the metal hydroxide crystal.
In the flame-retardant resin composition of the present embodiment, (B) the maleic acid-modified ethylene- α -olefin copolymer is a dispersed phase (island phase, domain), and (a) the ethylene-vinyl acetate copolymer is a continuous phase (sea phase, matrix), which is obtained by observation of a TEM image, not an SEM image.
The present invention is not limited to the foregoing embodiments and examples, and various modifications can be made without departing from the spirit and scope thereof.

Claims (5)

1. A method for producing a flame-retardant resin composition, comprising the steps of:
(a) A step of kneading an ethylene-vinyl acetate copolymer and a metal hydroxide in the absence of a maleic acid-modified ethylene- α -olefin copolymer to produce a 1 st kneaded product;
(b) A step of kneading the kneaded product 1 and a maleic acid-modified ethylene- α -olefin copolymer to produce a flame-retardant resin composition,
the flame retardant resin composition contains 150 to 300 parts by mass of the metal hydroxide per 100 parts by mass of a base polymer comprising the ethylene-vinyl acetate copolymer and the maleic acid-modified ethylene-alpha-olefin copolymer.
2. The method for producing a flame-retardant resin composition according to claim 1, wherein in the step (a), the metal hydroxide is added in multiple portions while kneading the molten ethylene-vinyl acetate copolymer.
3. The method for producing a flame-retardant resin composition according to claim 1, wherein the ethylene-vinyl acetate copolymer comprises a 1 st ethylene-vinyl acetate copolymer and a 2 nd ethylene-vinyl acetate copolymer having different content ratios of vinyl acetate from each other.
4. A method of manufacturing an electric wire, comprising the steps of:
(a) A step of kneading an ethylene-vinyl acetate copolymer and a metal hydroxide in the absence of a maleic acid-modified ethylene- α -olefin copolymer to produce a 1 st kneaded product;
(b) A step of kneading the 1 st kneaded product and a maleic acid-modified ethylene- α -olefin copolymer to produce a flame-retardant resin composition;
(c) Extruding the flame-retardant resin composition so as to cover the periphery of the conductor to form an insulating layer, thereby producing an electric wire;
(d) A step of irradiating the electric wire with an electron beam to crosslink the ethylene-vinyl acetate copolymer and the maleic acid-modified ethylene- α -olefin copolymer in the flame-retardant resin composition,
the flame retardant resin composition contains 150 to 300 parts by mass of the metal hydroxide per 100 parts by mass of a base polymer comprising the ethylene-vinyl acetate copolymer and the maleic acid-modified ethylene-alpha-olefin copolymer.
5. A method of manufacturing a cable comprising the steps of:
(a) A step of kneading an ethylene-vinyl acetate copolymer and a metal hydroxide in the absence of a maleic acid-modified ethylene- α -olefin copolymer to produce a 1 st kneaded product;
(b) A step of kneading the 1 st kneaded product and a maleic acid-modified ethylene- α -olefin copolymer to produce a flame-retardant resin composition;
(c) Extruding the flame-retardant resin composition so as to cover the periphery of the conductor to form an insulating layer, thereby producing an electric wire;
(d) Extruding the flame-retardant resin composition so as to cover the circumference of the electric wire to form a sheath,
the flame retardant resin composition contains 150 to 300 parts by mass of the metal hydroxide per 100 parts by mass of a base polymer comprising the ethylene-vinyl acetate copolymer and the maleic acid-modified ethylene-alpha-olefin copolymer.
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