JP7135661B2 - Flame-retardant resin composition, electric wire, cable, method for producing flame-retardant resin composition, method for producing electric wire, and method for producing cable - Google Patents

Description

TECHNICAL FIELD The present invention relates to a flame-retardant resin composition, an electric wire, a cable, a method for producing a flame-retardant resin composition, a method for producing an electric wire, and a method for producing a cable.

An electric wire has a conductor and an insulating layer as a covering material provided around the conductor. Also, the cable includes the electric wire and a sheath (covering layer) provided around the electric wire as a covering material. The sheath is provided around the insulating layer.

A covering material such as the insulating layer of the electric wire or the sheath of the cable is made of an electrically insulating material whose main raw material is rubber or resin. This electrically insulating material requires different properties depending on the application. For example, electrical insulating materials used for electric wires for railway vehicles are required to have high flame retardancy, low temperature properties, fuel resistance properties, and the like.

As an example of such an electrically insulating material and electric wire, Patent Document 1 discloses a polymer alloy composed of an ethylene-vinyl acetate copolymer and a maleic acid-modified ethylene-α-olefin copolymer, and a metal hydroxide as a flame retardant. and a non-halogen flame-retardant resin composition to which a compound is added and an electric wire using the same.

Since the non-halogen flame-retardant resin composition described in Patent Document 1 does not generate toxic gases such as hydrogen chloride and dioxin when burned, it is possible to prevent the generation of toxic gases and secondary disasters in the event of a fire, and to reduce waste. It is useful as an insulating layer for electric wires for railway vehicles because it does not pose a problem even if it is incinerated at the time of incineration.

JP 2014-53247 A

However, according to the studies of the present inventors, when attempting to produce the flame-retardant resin composition, it was found that the flame-retardant resin composition did not have sufficient resistance to be used as a covering material such as the jacket layer of the cable or the insulation layer of the electric wire. It has been found that the fuel characteristics may not be obtained in some cases.

The present invention has been made in view of such problems, and an object thereof is to provide a flame-retardant resin composition excellent in low-temperature characteristics and fuel resistance characteristics, and an electric wire and cable using the same. .

A brief outline of typical inventions disclosed in the present application is as follows.

[1] A method for producing a flame-retardant resin composition comprises: (a) a step of kneading an ethylene-vinyl acetate copolymer and a metal hydroxide to form a first kneaded product; and a step of kneading the kneaded product and the maleic acid-modified ethylene-α-olefin copolymer to produce a flame-retardant resin composition. The flame-retardant resin composition contains 150 parts by mass or more 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. Contains 300 parts by mass or less.

[2] In the method for producing a flame-retardant resin composition according to [1], in the step (a), the metal hydroxide is kneaded several times while the molten ethylene-vinyl acetate copolymer is kneaded. Add in portions.

[3] In the method for producing a flame-retardant resin composition according to [1], the ethylene-vinyl acetate copolymer is a first ethylene-vinyl acetate copolymer and a second ethylene having different vinyl acetate contents. - contains vinyl acetate copolymers;

[4] A method for producing an electric wire includes (a) a step of kneading an ethylene-vinyl acetate copolymer and a metal hydroxide to form a first kneaded product, (b) the first kneaded product and malein a step of kneading with an acid-modified ethylene-α-olefin copolymer to produce a flame-retardant resin composition. The method for producing an electric wire includes (c) extruding the flame-retardant resin composition so as to cover the periphery of a conductor to form an insulating layer to produce an electric wire, and (d) applying an electron beam to the electric wire. irradiation 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 parts by mass or more 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. Contains 300 parts by mass or less.

[5] A method for manufacturing a cable includes (a) a step of kneading an ethylene-vinyl acetate copolymer and a metal hydroxide to form a first kneaded product, (b) the first kneaded product and malein A step of kneading with an acid-modified ethylene-α-olefin copolymer to produce a flame-retardant resin composition. The method for producing a cable includes (c) extruding the flame-retardant resin composition so as to cover the circumference of a conductor to form an insulating layer to produce an electric wire, and (d) covering the circumference of the electric wire. extruding the flame retardant resin composition to form a sheath. The flame-retardant resin composition contains 150 parts by mass or more 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. Contains 300 parts by mass or less.

[6] The flame-retardant resin composition contains an ethylene-vinyl acetate copolymer, a maleic acid-modified ethylene-α-olefin copolymer, and a metal hydroxide. The ethylene-vinyl acetate copolymer includes a first ethylene-vinyl acetate copolymer and a second ethylene-vinyl acetate copolymer having different vinyl acetate contents. The flame-retardant resin composition contains 150 parts by mass or more 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. Contains 300 parts by mass or less.

[7] An electric wire comprising an insulating layer formed from the flame-retardant resin composition according to [6].

[8] A cable comprising a sheath formed from the flame-retardant resin composition according to [6].

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a flame-retardant resin composition having low temperature properties and fuel resistance properties, and electric wires and cables using the same.

It is a flow which shows the manufacturing process of the flame-retardant resin composition of one embodiment. It is a cross-sectional view showing the structure of the electric wire of one embodiment. It is a cross-sectional view showing the structure of the cable of one embodiment. 4 is a transmission electron microscope image of the insulating layer of the electric wire of Example 1. FIG. 4 is a transmission electron microscope image of the insulating layer of the electric wire of Comparative Example 2. FIG. 10A and 10B are a transmission electron microscope image and a scanning electron microscope image of the insulating layer of the electric wire of Comparative Example 5. FIG.

(to be considered)
First, before describing the embodiments, the matters studied by the inventors will be described.

The present inventor has developed a polymer alloy composed of an ethylene-vinyl acetate copolymer and a maleic acid-modified ethylene-α-olefin copolymer as a material to be used as a covering material such as an insulation layer of an electric wire or a jacket layer of a cable. The use of a non-halogen flame-retardant resin composition in which a metal hydroxide is added as a flame retardant was investigated.

Ethylene-vinyl acetate copolymers are thermoplastics with excellent flexibility and low-temperature properties. By adding a metal hydroxide to the ethylene-vinyl acetate copolymer, flame retardancy can be enhanced. However, in this case, it is known that the low-temperature properties deteriorate because the adhesion between the ethylene-vinyl acetate copolymer and the metal hydroxide is not high.

Therefore, a maleic acid-modified ethylene-α-olefin copolymer is added to an ethylene-vinyl acetate copolymer together with a metal hydroxide. Maleic acid-modified ethylene-α-olefin copolymers form polymer alloys with ethylene-vinyl acetate copolymers and have high adhesion to metal hydroxides. Addition of a metal hydroxide to a polymer alloy composed of an acid-modified ethylene-α-olefin copolymer (hereinafter referred to as a base polymer) can improve low-temperature properties.

A method for producing such a flame-retardant resin composition includes (A) an ethylene-vinyl acetate copolymer, (B) a maleic acid-modified ethylene-α-olefin copolymer, and (C) a metal hydroxide. are simultaneously put into a pressure kneader or the like and kneaded (hereinafter referred to as Examination Example 1).

However, in Investigation Example 1, the base polymer consisting of (A) the ethylene-vinyl acetate copolymer and (B) the maleic acid-modified ethylene-α-olefin copolymer melts into a liquid phase during kneading. Therefore, (C) the metal hydroxide does not melt and remains in a solid phase. Therefore, the metal hydroxide is difficult to mix with the base polymer.

Moreover, in order to sufficiently exhibit the flame retardancy of the flame-retardant resin composition, it is preferable that the proportion of the metal hydroxide in the flame-retardant resin composition is high. As will be described later, the amount of metal hydroxide (C) added to 100 parts by mass of a base polymer comprising (A) an ethylene-vinyl acetate copolymer and (B) a maleic acid-modified ethylene-α-olefin copolymer is , 150 to 300 parts by mass.

Thus, the metal hydroxide is difficult to mix with the base polymer and has a high proportion in the flame-retardant resin composition. Therefore, as in Study Example 1, (A) an ethylene-vinyl acetate copolymer, (B) a maleic acid-modified ethylene-α-olefin copolymer, and (C) a metal hydroxide are simultaneously mixed with a pressure kneader. etc., and kneading them, the metal hydroxide may not be sufficiently dispersed in the flame-retardant resin composition.

Therefore, the present inventors have found that (A) an ethylene-vinyl acetate copolymer and (B) A maleic acid-modified ethylene-α-olefin copolymer is kneaded with a pressure kneader or the like, and (C) metal hydroxide is added to the kneaded product in several batches and kneaded. Example 2). According to Examination Example 2, the metal hydroxide can be efficiently dispersed in the flame-retardant resin composition.

However, as described above, the present inventors have found that the flame-retardant resin composition of Study Example 2 has sufficient fuel resistance to be used as a coating material such as the jacket layer of the cable or the insulation layer of the electric wire. We have confirmed that there are cases where the characteristics cannot be obtained. It was found that the reason for this is that voids are formed between the base polymer and the metal hydroxide, and the fuel enters these voids, as will be described in Comparative Examples below.

Here, the inventors of the present invention found that in the flame-retardant resin composition of Investigation Example 2, the cause of the formation of voids between the base polymer and the metal hydroxide was the maleic acid-modified ethylene-α-olefin copolymer. It was thought that it was due to the adhesion with the metal hydroxide.

A maleic acid-modified ethylene-α-olefin copolymer has a carboxylic anhydride structure (derived from maleic anhydride) formed by dehydration condensation of two carboxyl groups (COOH) or a carboxylic anhydride hydrolyzed. It has a carboxyl group (derived from maleic acid). Therefore, the maleic acid-modified-α-olefin copolymer can form hydrogen bonds with metal hydroxides. 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, by adding a maleic acid-modified ethylene-α-olefin copolymer to the flame-retardant resin composition, the adhesion between the base polymer and the metal hydroxide is enhanced, The low-temperature properties of the flammable resin composition can be improved.

However, due to the following reasons, the adhesion between the maleic acid-modified ethylene-α-olefin copolymer and the metal hydroxide is thought to have an adverse effect during kneading. That is, in the method for producing a flame-retardant resin composition of Examination Example 2, (C) a metal hydroxide is added and kneaded in the presence of (B) a maleic acid-modified ethylene-α-olefin copolymer. Then, (C) the metal hydroxide is kneaded with the (B) maleic acid-modified ethylene-α-olefin copolymer in a state of being closely attached by hydrogen bonding. As a result, in Investigation Example 2, in the kneading step after adding the metal hydroxide, excessive stress was applied to the metal hydroxide crystals by kneading the maleic acid-modified ethylene-α-olefin copolymer, and the metal Part of the hydroxide crystals will peel off, and the metal hydroxide crystals will break into small pieces. As a result, in Study Example 2, voids are generated between the base polymer and the metal hydroxide.

In particular, in Investigation Example 2, (C) the metal hydroxide was added to the base polymer in several batches, so the kneading time became longer, and the crystals of the metal hydroxide peeled off and became fragile. Conceivable.

As described above, in the method for producing a non-halogen flame-retardant resin composition in which a metal hydroxide is added as a flame retardant to a polymer alloy composed of an ethylene-vinyl acetate copolymer and a maleic acid-modified ethylene-α-olefin copolymer, By devising the process, it is desired to produce a flame retardant resin composition with low temperature properties and fuel resistance properties.

(Embodiment)
(1) Flame-retardant resin composition <Configuration of flame-retardant resin composition>
A 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-α-olefin copolymer, and (C) a metal Hydroxide and

The ethylene-vinyl acetate copolymer (A) of the present embodiment may be a single ethylene-vinyl acetate copolymer, but two or more ethylene-vinyl acetate copolymers may be used as shown in Examples below. Coalescing may be mixed. Here, when the content of vinyl acetate in the ethylene-vinyl acetate copolymer increases, the glass transition temperature increases and the low-temperature properties deteriorate. On the other hand, when the content of vinyl acetate in the ethylene-vinyl acetate copolymer decreases, the polarity decreases and the fuel resistance deteriorates. Therefore, by including two or more types of ethylene-vinyl acetate copolymers having different vinyl acetate contents, it is possible to produce a flame-retardant resin composition having an excellent balance between low-temperature properties and fuel resistance properties. In Examples described later, an ethylene-vinyl acetate copolymer having a vinyl acetate content (VA amount) of 28% by mass and an ethylene-vinyl acetate copolymer having a vinyl acetate content (VA amount) of 41% by mass were used. and

Further, 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. It is. The α-olefin preferably has 3 to 8 carbon atoms.

Moreover, magnesium hydroxide, aluminum hydroxide, calcium hydroxide, or these metal hydroxides in which nickel is solid-dissolved can be used as the (C) metal hydroxide of the present embodiment. One of these metal hydroxides may be used, or two or more of them may be used in combination. In addition, it is preferable to use those metal hydroxides that have been surface-treated with a silane coupling agent, a titanate-based coupling agent, a fatty acid such as stearic acid or calcium stearate, or a fatty acid metal salt. A plurality of types of these surface treatment agents may be used in combination for treatment.

Further, the flame-retardant resin composition of the present embodiment includes (A) an ethylene-vinyl acetate copolymer, (B) a maleic acid-modified ethylene-α-olefin copolymer, and (C) a metal hydroxide. may also contain (D) a cross-linking aid, (E) an antioxidant, (F) a coloring agent, or (G) a lubricant, if necessary. (D) Crosslinking aids include trimethylolpropane trimethacrylate (TMPT), triallyl isocyanurate, triallyl cyanurate, N,N'-metaphenylene bismaleimide, ethylene glycol dimethacrylate, zinc acrylate, and zinc methacrylate. etc. (E) Antioxidants include phenol antioxidants, phenol/thioester antioxidants, amine antioxidants, sulfur antioxidants, and phosphite ester antioxidants. (F) Colorants include inorganic pigments, organic pigments, dyes, and carbon black. (G) Lubricants include zinc stearate, silicone, fatty acid amide-based, hydrocarbon-based, ester-based, alcohol-based, metal soap-based, and the like.

Further, in the present embodiment, in the flame-retardant resin composition, (A) ethylene-vinyl acetate copolymers, (B) maleic acid-modified ethylene-α-olefin copolymers, or ( A) an ethylene-vinyl acetate copolymer and (B) a maleic acid-modified ethylene-α-olefin copolymer are crosslinked. In the present embodiment, such cross-linking is not essential, but such cross-linking is preferable because cross-linking improves the mechanical properties of the flame-retardant resin composition. As a cross-linking method, an electron beam cross-linking method in which electron beams are irradiated after molding, a cross-linking agent is added in advance to the flame-retardant resin composition, and chemical cross-linking in which heat treatment is performed after molding can be used. form uses an electron beam cross-linking method.

In the present embodiment, the amount of metal hydroxide (C) added to 100 parts by mass of a base polymer comprising (A) an ethylene-vinyl acetate copolymer and (B) a maleic acid-modified ethylene-α-olefin copolymer. is 150 to 300 parts by mass, preferably 150 to 200 parts by mass. If the amount of metal hydroxide added to 100 parts by mass of the base polymer is less than 150 parts by mass, sufficient flame retardancy cannot be obtained. On the other hand, if the amount of metal hydroxide added to 100 parts by mass of the base polymer is more than 300 parts by mass, the mechanical properties deteriorate. Moreover, the flame-retardant resin composition according to one embodiment of the present invention is preferably a non-halogen flame-retardant resin composition.

Further, in the present embodiment, the content of (B) the maleic acid-modified ethylene-α-olefin copolymer in the base polymer is not particularly limited, but in 100 parts by weight of the base polymer, (B ) The content of the maleic acid-modified ethylene-α-olefin copolymer is preferably 1 to 30 parts by mass. If (B) the maleic acid-modified ethylene-α-olefin copolymer is less than 1 part by weight in 100 parts by weight of the base polymer, the adhesion between the base polymer and the metal hydroxide is low, resulting in poor low-temperature properties. On the other hand, if (B) the maleic acid-modified ethylene-α-olefin copolymer is more than 30 parts by weight in 100 parts by weight of the base polymer, the adhesion between the base polymer and the metal hydroxide becomes too high, resulting in elongation. decreases.

<Method for producing flame-retardant resin composition>
FIG. 1 is a flow showing the production steps of the flame-retardant resin composition of the present embodiment. As shown in FIG. 1, the method for producing a flame-retardant resin composition of the present embodiment includes (S1) a step of kneading (A) an ethylene-vinyl acetate copolymer and (C) a metal hydroxide ( first kneading step), (S2) a step of kneading the first kneaded product produced in the step (S1), and (B) the maleic acid-modified ethylene-α-olefin copolymer (second kneading step ) and Through these steps, the flame-retardant resin composition of the present embodiment can be produced.

In order to facilitate the kneading of the ethylene-vinyl acetate copolymer and the metal hydroxide and to sufficiently disperse the metal hydroxide in the flame-retardant resin composition, in the step (S1), the metal hydroxide was melted. It is preferable to add (C) the metal hydroxide in multiple portions while kneading (A) the ethylene-vinyl acetate copolymer.

Further, although not shown, after the step (S2), the flame-retardant resin composition produced in the step (S2) is irradiated with an electron beam to obtain (A) an ethylene-vinyl acetate copolymer and (B) A step of cross-linking the maleic acid-modified ethylene-α-olefin copolymer may be further included.

Moreover, in the step (S1), (D) a cross-linking aid, (E) an antioxidant, (F) a coloring agent, or (G) a lubricant may be added, if necessary. These additives are preferably added before adding (C) the metal hydroxide, but are not limited thereto.

The temperature in the step (S1) is equal to or higher than the melting continuous (molding) temperature of the ethylene-vinyl acetate copolymer (A), for example 70°C. The temperature in the step (S2) is equal to or higher than the melting continuous temperature of the (B) maleic acid-modified ethylene-α-olefin copolymer, and is, for example, 120 to 170°C. As a result, the temperature in the step (S2) is higher than the temperature in the step (S1).

The kneading device for producing the flame-retardant resin composition of the present embodiment is, for example, a known kneading machine such as a batch kneader such as a Banbury mixer or a pressure kneader, or a continuous kneader such as a twin-screw extruder. device can be employed.

The method for producing a flame-retardant resin composition of the present embodiment has been described as including (S1) the first kneading step and (S2) the second kneading step. The flame-retardant resin composition of the present embodiment can also be produced as one step. For example, in the case of a continuous kneader such as a twin-screw extruder having multiple inlets along the extrusion direction, (A) ethylene-vinyl acetate copolymer and (C) metal hydroxide are fed from one inlet. (B) the maleic acid-modified ethylene-α-olefin copolymer is introduced from another inlet, whereby the step (S1) and the step (S2) are continuously performed in one kneading device 1 can be performed as one step.

<Characteristics and effects of the present embodiment>
One of the characteristics of the method for producing a flame-retardant resin composition according to one embodiment of the present invention is that (B) the maleic acid-modified ethylene-α-olefin copolymer does not exist in the step (S1). (A) the ethylene-vinyl acetate copolymer and (C) the metal hydroxide are kneaded in this state. Then, in the (S2) step, the first kneaded product produced in the (S1) step and (B) the maleic acid-modified ethylene-α-olefin copolymer are kneaded.

In the present embodiment, by adopting such a process, a metal hydroxide is added as a flame retardant to a polymer alloy composed of an ethylene-vinyl acetate copolymer and a maleic acid-modified ethylene-α-olefin copolymer. In the flame-retardant resin composition manufacturing method described above, a flame-retardant resin composition having low temperature properties and fuel resistance properties can be produced. The reason for this will be specifically described below.

As described above, in the method for producing the flame-retardant resin composition of Investigation Example 2, (C) the metal hydroxide is added several times in the presence of (B) the maleic acid-modified ethylene-α-olefin copolymer. As a result of adding and kneading (C) a part of the metal hydroxide crystals, the metal hydroxide crystals were broken into small pieces. As a result, voids were formed between the base polymer and the metal hydroxide, resulting in deterioration in fuel resistance.

On the other hand, in the present embodiment, in the step (S1), (A) the ethylene-vinyl acetate copolymer and (C) It is kneaded with a metal hydroxide. In the step (S1), since the maleic acid-modified ethylene-α-olefin copolymer does not exist in the kneaded product, excessive stress is not applied to the metal hydroxide crystals. Part of the metal hydroxide does not peel off and the metal hydroxide crystals do not break finely. In addition, in order to sufficiently disperse the metal hydroxide in the flame-retardant resin composition, (C) the metal hydroxide was added in multiple portions and kneaded in the step (S1) in the same manner as in Examination Example 2. For the same reason, however, no problem arises.

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 product (first kneaded product). can be made

Then, in the (S2) step, (B) the maleic acid-modified ethylene-α-olefin-based co- A polymer is added and kneaded. By doing so, the kneading time of (B) the maleic acid-modified ethylene-α-olefin copolymer and (C) the metal hydroxide in the step (S2) can be shortened compared to Investigation Example 2. , it is possible to reduce the possibility that a part of the metal hydroxide crystals is peeled off or the metal hydroxide crystals are finely crushed.

As described above, in the present embodiment, a flame-retardant polymer alloy comprising an ethylene-vinyl acetate copolymer and a maleic acid-modified ethylene-α-olefin copolymer is added with a metal hydroxide as a flame retardant. In the resin composition, it is possible to prevent the formation of voids between the base polymer and the metal hydroxide, and to provide low temperature properties and fuel resistance properties.

(2) Electric Wire FIG. 2 is a cross-sectional view showing an electric wire (insulated electric wire) according to one embodiment of the present invention. As shown in FIG. 2, the electric wire 10 according to this embodiment has a conductor 1 and an insulating layer 2 covering the circumference of the conductor 1 . The insulating layer 2 is made of the flame-retardant resin composition described above.

As the conductor 1, a commonly used metal wire such as a copper wire, a copper alloy wire, an aluminum wire, a gold wire, a silver wire, or the like can be used. As the conductor 1, a metal wire plated with a metal such as tin or nickel may be used. Furthermore, as the conductor 1, a twisted conductor in which metal wires are twisted together can also be used.

The electric wire 10 of this embodiment is manufactured, for example, as follows. First, a copper wire is prepared as the conductor 1 . Then, an extruder is used to extrude the flame-retardant resin composition so as to cover the conductor 1, thereby forming an insulating layer 2 having a predetermined thickness. By carrying out like this, the electric wire 10 of this Embodiment can be manufactured.

The flame-retardant resin composition used in the present embodiment is not limited to the electric wires produced in the examples described later, and can be applied to all uses and sizes, such as railway vehicles, automobiles, wiring in the board, equipment It can be used for the insulation layer of each electric wire for internal wiring and electric power.

In particular, the flame-retardant resin composition forming the insulating layer 2 of the electric wire 10 of the present embodiment has good low-temperature properties and fuel resistance as described above. Therefore, the electric wire 10 of the present embodiment can be used as a flame-retardant resin-coated electric wire excellent in low-temperature characteristics and fuel resistance characteristics, and can be particularly suitably used as an electric wire for railway vehicles.

(3) Cable FIG. 3 is a cross-sectional view showing cable 11 according to one embodiment of the present invention. As shown in FIG. 3, the cable 11 according to the present embodiment includes a two-core stranded wire obtained by twisting two of the electric wires 10 described above, an interposition 3 provided around the two-core stranded wire, and an interposition 3 and a sheath 4 provided around the perimeter of the The sheath 4 is made of the flame-retardant resin composition described above.

Cable 11 of the present embodiment is manufactured, for example, as follows. First, two electric wires 10 are manufactured by the method described above. After that, the wire 10 is covered with the interposition 3, and then the aforementioned flame-retardant resin composition is extruded so as to cover the interposition 3 to form the sheath 4 with a predetermined thickness. By carrying out like this, the cable 11 of this Embodiment can be manufactured.

The flame-retardant resin composition forming the sheath 4 of the cable 11 of the present embodiment has good low-temperature properties and fuel resistance as described above. Therefore, the cable 11 of the present embodiment can be used as a flame-retardant resin cable excellent in low-temperature characteristics and fuel resistance characteristics, and can be particularly suitably used as a cable for railway vehicles.

Cable 11 of the present embodiment has a two-core twisted wire in which two electric wires 10 are twisted together as a core wire, but the core wire may be a single core (one), or a multi-core wire other than two cores. It may be a core stranded wire. A multi-layer sheath structure in which another insulating layer (sheath) is formed between the wire 10 and the sheath 4 can also be employed.

Moreover, although the cable 11 of the present embodiment uses the electric wire 10 described above as an example, it is not limited to this, and an electric wire using a general-purpose material can also be used.

(Example)
EXAMPLES The present invention will be described in more detail below based on 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 are described below. Examples 1 to 8 and Comparative Examples 1 to 4 correspond to the electric wire 10 shown in FIG. As the conductor 1 shown in FIG. 2, a tin-plated twisted conductor (43 cores, wire diameter 0.16 mm) having an outer diameter of 1.21 mm was used. As the insulating layer 2, in Examples 1 to 8, an insulating layer made of a flame-retardant resin composition produced by the production method of the present embodiment was used. On the other hand, in Comparative Examples 1 to 4, insulating layers made of the flame-retardant resin composition produced by the production method of Examination Example 2 were used.

<Structures of Examples 1 to 8 and Comparative Examples 1 to 4>
Raw materials used in Examples 1 to 8 and Comparative Examples 1 to 4 are as follows.

(A) ethylene-vinyl acetate copolymer (EVA):
(A1) EV270 (manufactured by DuPont Mitsui Polychemicals, MFR 1 g/10 min, vinyl acetate content 28, melting point 72°C)
(A2) V9000 (manufactured by DuPont Mitsui Polychemicals, MFR 1g/10min, vinyl acetate content 41, melting point 50-60°C)
(B) Maleic acid-modified ethylene-α-olefin copolymer:
(B1) MH7020 (manufactured by Mitsui Chemicals, molding processing temperature (melting continuous temperature) 115 ° C.)
(B2) MH5040 (manufactured by Mitsui Chemicals, molding processing temperature (melting continuous temperature) 102 ° C.)
(C) Metal hydroxide: Magshees S4 (manufactured by Kojima Kagaku, magnesium hydroxide surface-treated with a silane coupling agent and stearic acid)
(D) Cross-linking aid: TMPT (trimethylolpropane trimethacrylate, manufactured by Shin-Nakamura Chemical)
(E) Antioxidant:
(E1) AO18 (phenol/thioester antioxidant, manufactured by ADEKA)
(E2) songnox1010 (phenolic antioxidant, manufactured by Songwon)
(F) Coloring agent: FT carbon (carbon, manufactured by Asahi Carbon Co., Ltd.)
(G) Lubricant:
(G1) Zn-St (zinc stearate, manufactured by Nitto Kasei Kogyo Co., Ltd.)
(G2) KE76S (silicone, manufactured by Shin-Etsu Chemical Co., Ltd.)
Table 1 shows the details of the formulation of the materials used in Examples 1-8 and Comparative Examples 1-4.

As shown in Table 1, the only difference between Formulation 1 and Formulation 2 is the use of (B) a maleic acid-modified ethylene-α-olefin copolymer with a different molding temperature (melting continuous temperature). , and other points are the same.

<Manufacturing methods of Examples 1 to 8>
Samples of Examples 1 to 8 were produced by the following method. Table 2 summarizes the kneading methods, formulations, kneading machines, kneading conditions and evaluation results of Examples 1 to 8.

As described above, Examples 1 to 8 correspond to flame-retardant resin compositions produced by the production method of the present embodiment. Each condition is an example. As the composition of the materials, Examples 1 to 4 adopt Composition 1, and Examples 5 to 8 adopt Composition 2. As kneaders, 3L pressure kneaders are used in Examples 1, 2, 5 and 6, and 6-inch rolls are used in Examples 3, 4, 7 and 8. is doing. As the kneading conditions, in Examples 1 to 8, the set temperature in the first kneading step (S1) and the maleic acid-modified ethylene-α-olefin copolymer (B) in the second kneading step (S2) and the final temperature reached in the second kneading step (S2).

(a) First kneading step (S1)
(A) ethylene-vinyl acetate copolymer, (D) cross-linking aid, (E) antioxidant, (F) colorant and (G) lubricant are put into a 3L pressure kneader or 6 inch rolls and kneaded. rice field. After that, (C) metal hydroxide was put into this 3 L pressure kneader or 6 inch roll in 3 portions and kneaded.

(b) Second kneading step (S2)
The (B) maleic acid-modified ethylene-α-olefin copolymer was added to the 3-liter pressure kneader or 6-inch roll that had been subjected to the first kneading step (S1) and kneaded. The kneaded product (flame-retardant resin composition) was formed into a sheet by an 8-inch roll, then cut by a square pelletizer and formed into a plate.

(c) Extrusion Step Next, the tin-plated twisted conductor was passed through a die of a 40 mm single-screw extruder. After that, the product of the second kneading step (S2) is charged from the hopper of the single-screw extruder, extruded into a tube shape, drawn down at a line speed of 30 m / min while being vacuumed, and the tinned twist An electric wire was made by forming an insulating layer with a thickness of 0.7 mm around the conductor.

The ratio L/D between the screw diameter D and the screw length L was set to 24. The temperature of the four cylinders was 160°C, and the temperature of the head was 180°C.

(d) Cross-linking step The wire prepared in the extrusion step is irradiated with an electron beam at 7.5 Mrad, and (A) ethylene-vinyl acetate copolymer and (B) maleic acid-modified ethylene- The α-olefin copolymer was crosslinked. The electric wires of Examples 1 to 8 were produced by the above steps.

<Manufacturing methods of Comparative Examples 1 to 4>
The samples of Comparative Examples 1 to 4 were produced by the following method. Table 2 summarizes the kneading methods, formulations, kneaders, kneading conditions and evaluation results of Comparative Examples 1 to 4.

As described above, Comparative Examples 1 to 4 correspond to the flame-retardant resin composition produced by the production method of Study Example 2. Each condition is an example. Comparative Examples 1 and 2 employ Formulation 1, and Comparative Examples 3 and 4 employ Formulation 2 as the formulation of materials. As the kneader, Comparative Examples 1 and 3 employ a 3L pressure kneader, and Comparative Examples 2 and 4 employ a 6-inch roll. As the kneading conditions, in Comparative Examples 1 to 4, the set temperature in the kneading process and the final temperature reached in the kneading process are shown.

(a) kneading step (A) ethylene-vinyl acetate copolymer, (B) maleic acid-modified ethylene-α-olefin copolymer, (D) cross-linking aid, (E) antioxidant, (F) coloring The agent and (G) the lubricant were put into a 3 L pressure kneader or a 6 inch roll and kneaded. After that, (C) metal hydroxide was put into this 3 L pressure kneader or 6 inch roll in 3 portions and kneaded. The kneaded product was formed into a sheet by an 8-inch roll, and then cut by a square pelletizer to form a plate.

(b) Extrusion Step Next, the tin-plated twisted conductor was passed through a die of a 40 mm single-screw extruder. After that, the product of the kneading process was put into the hopper of a single-screw extruder, extruded into a tube shape, and drawn down at a line speed of 30 m/min while being vacuumed, and a thickness was applied around the tin-plated stranded conductor. An electric wire was produced by forming an insulating layer with a thickness of 0.7 mm.

The ratio L/D between the screw diameter D and the screw length L was set to 24. The temperature of the four cylinders was 160°C, and the temperature of the head was 180°C.

(c) Cross-linking step The wire prepared in the extrusion step is irradiated with an electron beam at 7.5 Mrad, and (A) ethylene-vinyl acetate copolymer and (B) maleic acid-modified ethylene- The α-olefin copolymer was crosslinked. Through the steps described above, electric wires of Comparative Examples 1 to 4 were produced.

<Evaluation methods for Examples 1 to 8 and Comparative Examples 1 to 4>
(1) Vertical flame resistance test (VFT)
The produced electric wire was subjected to a combustion test according to IEC60332-1-2. A case where the length of the carbonized portion after burning satisfies the standard was given as "○", and a case where it did not meet the standard was given as "x".

(2) Fuel resistance property A conductor was pulled out from the prepared electric wire to obtain a sample with only an insulating layer having a length of 120 mm, and this sample was immersed in IRM903 oil (fuel) at 70 ° C. for 1 week. Change rate of ”=(initial elongation value−elongation value after immersion)/initial elongation value was calculated. The rate of change in elongation value of less than 30% was rated as "◯", and the rate of change of 30% or more was rated as "x".

(3) Low-temperature characteristics A conductor was pulled out from the prepared electric wire to obtain a sample having only an insulating layer with a length of 120 mm. A sample with an elongation rate of 30% or more was rated as "◯", and a sample with a rate of less than 30% was rated as "x".

(4) Phase structure A conductor is pulled out from the prepared electric wire to form only an insulating layer with a length of 120 mm. : TEM) under the conditions of an acceleration voltage of 100 kV and a magnification of 100,000 times.

For comparison, a scanning electron microscope (SEM) image was also measured in addition to the TEM image. Specifically, the conductor was pulled out from the prepared electric wire to make only an insulating layer with a length of 120 mm, and this was further made into a sample with a thickness of about 1 mm. Observation was made under the conditions of 5 kV and a magnification of 2500 times.

<Evaluation Results of Examples 1 to 8 and Comparative Examples 1 to 4>
The above evaluation results are summarized in Table 2, FIGS. 4 and 5. 4 is a TEM image of the sample of Example 1. FIG. FIG. 5 is a TEM image and an SEM image of a sample in Comparative Example 2 in which the temperature conditions of the 6-inch roll were the same as in Example 4. FIG. 6 is a TEM image of the sample of Comparative Example 2. FIG. In FIG. 4, a corresponds to the sample of Example 1 before immersion in IRM903 oil, and b corresponds to the sample of Example 1 after immersion in IRM903 oil. In FIG. 5, both d and e are the samples before immersion in IRM903 oil in Comparative Example 2 with the temperature conditions of the 6-inch roll being the same as in Example 4. FIG. 6 is the sample of Comparative Example 2 after immersion in IRM903 oil.

According to the inventor's analysis, in a, b in FIG. 4, d in FIG. 5, and c in FIG. are magnesium hydroxide crystals, white portions are voids, and gray portions other than these are ethylene-vinyl acetate copolymers. In FIG. 5e, white to gray crystals are magnesium hydroxide crystals, and dark gray to black crystals are ethylene-vinyl acetate copolymer and maleic acid-modified ethylene-α-olefin copolymer. It was found to be polymeric.

As shown in Table 2, in Examples 1 to 8, (1) vertical flame resistance test, (2) fuel resistance and (3) low temperature properties were all good.

On the other hand, in Comparative Examples 1 to 4, (1) the vertical flame resistance test and (3) low temperature properties were good, but (2) the fuel resistance properties were poor.

As shown in FIGS. 4A and 4B, in Example 1, the (4) phase structure is a sea-island structure, that is, (A) the ethylene-vinyl acetate copolymer is the continuous phase (sea phase, matrix), (B) Maleic acid-modified ethylene-α-olefin copolymer was the dispersed phase (island phase, domain). (B) The average particle size of the maleic acid-modified ethylene-α-olefin copolymer was about 50 to 300 nm.

Further, as shown in d in FIG. 5, even when the temperature conditions of the 6-inch roll in Comparative Example 2 were the same as in Example 4, the (4) phase structure was a sea-island structure, that is, (A) ethylene-acetic acid The vinyl copolymer was the continuous phase, and the (B) maleic acid-modified ethylene-α-olefin copolymer was the dispersed phase. The average particle size of the (B) maleic acid-modified ethylene-α-olefin copolymer was about 50 to 300 nm. As can be seen from the average particle size of the maleic acid-modified ethylene-α-olefin copolymer (B), such a phase structure can be confirmed in the TEM image shown in d in FIG. It could not be confirmed in the SEM image shown in middle e.

In addition, before immersion in IRM903 oil, in Comparative Example 2 shown in d in FIG. , Example 1 shown in FIG. 4a has few voids in the flame-retardant resin composition.

In Example 1 after immersion in IRM903 oil shown in FIG. 4b, almost no change is observed compared to Example 1 before immersion in IRM903 oil shown in FIG. 4a. On the other hand, in Comparative Example 2 after immersion in IRM903 oil shown in FIG. I found out that

Further, in Comparative Example 2 shown in FIG. 5d, the temperature conditions of the 6-inch roll were the same as in Example 4, and in Comparative Example 2 shown in FIG. Magnesium hydroxide crystals are smaller than in Example 1.

A detailed discussion of the above results is provided in the Summary of Examples below.

[Example 9 and Example 10]
Examples 9 and 10 are described below. Examples 9 and 10 also correspond to the electric wire 10 shown in FIG. In Examples 9 and 10, as the insulating layer 2, an insulating layer made of a flame-retardant resin composition produced by the production method of the present embodiment was used.

<Structures of Examples 9 and 10>
The raw materials used in Examples 9 and 10 are the same as in Example 1, and therefore are omitted.

<Manufacturing methods of Examples 9 and 10>
Samples of Examples 9 and 10 were prepared by the following method. Table 3 summarizes the kneading methods, formulations, kneading machines, kneading conditions and evaluation results of Examples 1, 9 and 10.

As described above, Examples 9 and 10 correspond to flame-retardant resin compositions produced by the production method of the present embodiment. Each condition is an example. The kneaders in Examples 9 and 10 are the same 3L pressure kneaders as in Example 1. However, in Examples 9 and 10, the gap (distance) between the rotor and the kneading tank in the 3L pressure kneader is different from that in Example 1. Specifically, as shown in Table 3, in Example 1, the gap between the rotor and the kneading tank was 2.5 mm, whereas in Example 9 it was 2 mm, and in Example 10 it was 1.5 mm. and each.

Since the composition of other materials and the like are the same as in Example 1, the manufacturing steps of Examples 9 and 10 are omitted below.

<Evaluation method for Examples 9 and 10>
The evaluation methods of Examples 9 and 10 are basically the same as those of Example 1, and therefore are omitted.

<Evaluation Results of Examples 1, 9 and 10>
The evaluation results of Examples 9 and 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) vertical flame resistance test, (2) fuel resistance and (3) low temperature properties were all good.

[Summary of Examples]
As shown in Examples 1 to 10, according to the production method of the present embodiment, regardless of the type and blending ratio of the maleic acid-modified ethylene-α-olefin copolymer used, the kneader, and the kneading conditions, However, it is possible to produce a flame retardant resin composition with low temperature properties and fuel resistance properties.

Specifically, in Comparative Example 2 shown in d in FIG. 5, the temperature conditions of the 6-inch roll were the same as in Example 4, and there were many voids in the flame-retardant resin composition. This is because (C) the metal hydroxide is divided several times in the presence of (B) the maleic acid-modified ethylene-α-olefin copolymer in the method for producing the flame-retardant resin composition of Investigation Example 2. This is considered to be the result of part of the (C) metal hydroxide crystals peeling off when the metal hydroxide was added and kneaded.

As shown in Fig. 6c, in Comparative Example 2, it appears that there are no voids at first glance, but this is considered to be the result of IRM903 oil entering the voids generated in the flame-retardant resin composition. . In Comparative Example 2, as a result of the IRM903 oil entering the voids, part of the maleic acid-modified ethylene-α-olefin copolymer was eluted into this oil, and the fuel resistance was reduced. .

Further, in Comparative Example 2 shown in FIG. 5d, the temperature conditions of the 6-inch roll were the same as in Example 4, and in Comparative Example 2 shown in FIG. Magnesium hydroxide crystals are smaller than in Example 1. This is because (C) the metal hydroxide is divided several times in the presence of (B) the maleic acid-modified ethylene-α-olefin copolymer in the method for producing the flame-retardant resin composition of Investigation Example 2. It is thought that this is the result of fine crushing of the metal hydroxide crystals (C) when the metal hydroxide was added and kneaded. This is also considered to be one of the reasons why the fuel resistance is lowered due to the formation of voids between the base polymer and the metal hydroxide.

On the other hand, in Example 1 shown in FIG. 4a, there are few voids in the flame-retardant resin composition before being immersed in IRM903 oil. Therefore, even if the sample of Example 1 was immersed in the IRM903 oil, the IRM903 oil did not enter the voids, and the fuel resistance was good. As a result, in the present embodiment, in the steps (S1) and (S2), the (C) metal hydroxide crystals are partially peeled off or the metal hydroxide crystals are finely crushed. It has been proven that there is no such thing.

Moreover, as shown in a and b in FIG. 4, in Example 1, magnesium hydroxide is sufficiently dispersed in the flame-retardant resin composition. Therefore, in the present embodiment, even if the kneading time of (B) the maleic acid-modified ethylene-α-olefin copolymer and (C) the metal hydroxide is shortened in the step (S2), the (S1 ) process, it can be said that (C) the metal hydroxide can be sufficiently dispersed in the flame-retardant resin composition.

Further, as shown in Examples 1, 9 and 10, according to the manufacturing method of the present embodiment, regardless of the gap between the rotor and the kneading tank in the 3L pressure kneader, the low temperature characteristics and A flame retardant resin composition can be produced with fuel resistant properties. In general, the smaller the gap between the rotor and the kneading tank, the greater the shear stress applied to the kneaded material. However, even when the gap between the rotor and the kneading tank is reduced in Examples 1 to 9 and 9 to 10, good fuel resistance is obtained. Therefore, in the present embodiment, even when the stress applied to the kneaded product during kneading is large in the steps (S1) and (S2), the crystals of the (C) metal hydroxide are partly exfoliated. It can be said that it can be said that it is possible to prevent the metal hydroxide crystals from breaking into small pieces and from breaking into small pieces.

Further, in the flame-retardant resin composition of the present embodiment, (B) the maleic acid-modified ethylene-α-olefin copolymer is the dispersed phase (island phase, domain), and (A) the ethylene-vinyl acetate copolymer It became clear for the first time by observing a TEM image rather than an SEM image that the polymer is a continuous phase (sea phase, matrix).

The present invention is not limited to the above embodiments and examples, and can be modified in various ways without departing from the scope of the invention.

1 conductor 2 insulating layer 3 interposition 4 sheath 10 electric wire 11 cable

Claims (4)

(a) kneading an ethylene-vinyl acetate copolymer and a metal hydroxide to form a first kneaded product;
(b) kneading the first kneaded product and a maleic acid-modified ethylene-α-olefin copolymer to produce a flame-retardant resin composition;
and
The flame-retardant resin composition contains 150 parts by mass or more 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. Containing 300 parts by mass or less,
The method for producing a flame-retardant resin composition , wherein the ethylene-vinyl acetate copolymer includes a first ethylene-vinyl acetate copolymer and a second ethylene-vinyl acetate copolymer having different vinyl acetate contents . In the method for producing a flame-retardant resin composition according to claim 1,
In the step (a), the method for producing a flame-retardant resin composition, wherein the metal hydroxide is added in multiple portions while kneading the melted ethylene-vinyl acetate copolymer. (a) kneading an ethylene-vinyl acetate copolymer and a metal hydroxide to form a first kneaded product;
(b) kneading the first 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 to produce an electric wire;
(d) irradiating the 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;
including
The flame-retardant resin composition contains 150 parts by mass or more 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. A method for manufacturing an electric wire containing 300 parts by mass or less. (a) kneading an ethylene-vinyl acetate copolymer and a metal hydroxide to form a first kneaded product;
(b) kneading the first 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 to produce an electric wire;
(d) forming a sheath by extruding the flame-retardant resin composition so as to cover the wire;
including
The flame-retardant resin composition contains 150 parts by mass or more 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. A method for manufacturing a cable containing 300 parts by mass or less.

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