JP2024025002A - Non-halogen flame retardant resin compositions, electric wires and cables - Google Patents

Abstract

To provide a non-halogen fire retardant resin composition that can have high fire retardancy and further have excellent flexibility and breaking elongation as well as an electric wire using the non-halogen fire retardant resin composition and a cable.SOLUTION: A cable 20 constituted of a non-halogen fire retardant resin composition that includes: an electric wire 10, a shield layer 22 having a separator 21 provided on an outside thereof, and a coating layer 23 on an outside of the shield layer 22, wherein the coating layer 23 is constituted of a non-halogen fire retardant resin composition containing (a) a mixed resin of an ethylene acetic acid vinyl copolymer having a content of vinyl acetate of 60 mass% or more and an ethylenic polymer having a melting point of 115°C or more (excluding acid-modified polyolefin), and (b) a base polymer containing acid-modified polyolefin, and a fire retardant agent including aluminum hydroxide.SELECTED DRAWING: Figure 2

Description

The present invention relates to a non-halogen flame retardant resin composition that has high flame retardancy and can have excellent flexibility and elongation at break, as well as electric wires and cables using the non-halogen flame retardant resin composition.

Electric wires and cables used in vehicles such as railway vehicles and automobiles are required to have high flame retardancy, excellent flexibility, and elongation at break, depending on the environment in which they are used.

In order to impart high flame retardancy, it is known to add a halogen-based flame retardant or a phosphorus-based flame retardant such as red phosphorus. However, since halogen-based flame retardants generate halogen gas when burned, they lack consideration for environmental issues that are increasing worldwide. Furthermore, phosphorus-based flame retardants such as red phosphorus also have problems such as generating phosphine when burned and phosphoric acid when being disposed of, contaminating underground water veins.

On the other hand, metal hydroxides used as flame retardants do not cause the above-mentioned problems compared to halogen-based flame retardants and phosphorus-based flame retardants, but they must be highly charged in order to achieve the desired flame retardancy. In that case, there is a risk of deterioration of mechanical properties and low-temperature properties, as well as deterioration of electrical properties.

To solve this problem, electric wires and cables are known in which an insulating layer or a coating layer is formed using a resin composition containing a base polymer having a predetermined composition and a metal hydroxide as a flame retardant ( For example, see Patent Documents 1 and 2).

Japanese Patent Application Publication No. 2014-67657 Japanese Patent Application Publication No. 2021-125396

The present invention relates to a non-halogen flame-retardant resin composition that is non-halogen and has high flame retardancy, as well as superior flexibility and elongation at break, and electric wires and cables using the non-halogen flame-retardant resin composition. The purpose is to provide

Other objects and novel features will become apparent from the description of this specification and the accompanying drawings.

A non-halogen flame retardant resin composition according to one embodiment is made of (a) an ethylene-vinyl acetate copolymer having a vinyl acetate content of 60% by mass or more and an ethylene-based polymer (acid-modified (b) a base polymer containing an acid-modified polyolefin; and a flame retardant containing aluminum hydroxide; ) The mass ratio of the mixed resin and the polyolefin (b) is (a):(b) = 95:5 to 70:30, and the density of the ethylene polymer having a melting point of 115° C. or higher is 0.9 g. /cm ³ and contains 150 to 180 parts by mass of the flame retardant based on a total of 100 parts by mass of the mixed resin (a) and the polyolefin (b).

An electric wire according to one embodiment includes a conductor and an insulating layer provided around the conductor, the insulating layer including (a) a vinyl acetate content of 60% by mass or more; A base polymer containing a mixed resin of an ethylene vinyl acetate copolymer and an ethylene polymer having a melting point of 115° C. or higher (excluding acid-modified polyolefins), and (b) an acid-modified polyolefin, and aluminum hydroxide. A non-halogen flame retardant resin composition containing a flame retardant, wherein the mass ratio of the (a) mixed resin to the (b) polyolefin is (a):(b)=95:5 to 70: 30, and the density of the ethylene polymer having a melting point of 115° C. or higher is less than 0.9 g/cm ³ , based on a total of 100 parts by mass of the (a) mixed resin and the (b) polyolefin, It is composed of a non-halogen flame retardant resin composition containing 150 to 180 parts by mass of the flame retardant.

A cable according to an embodiment includes a single-core/multi-core stranded wire made by twisting one or more single-layer or multi-layer electric wires, a shield braid provided on the outside thereof with a shield braid or a separator, and a shield braid with a shield braid or a separator provided on the outside thereof. The cable is coated with a coating layer on the outside thereof, and the coating layer is made of (a) an ethylene-vinyl acetate copolymer having a vinyl acetate content of 60% by mass or more and an ethylene-based polymer having a melting point of 115° C. or higher ( (a) a base polymer containing a mixed resin (excluding acid-modified polyolefin); (b) a base polymer containing an acid-modified polyolefin; and a flame retardant containing aluminum hydroxide. , the mass ratio of the (a) mixed resin and the (b) polyolefin is (a):(b) = 95:5 to 70:30, and the density of the ethylene polymer having a melting point of 115 ° C. or higher is , less than 0.9 g/cm ³ and containing 150 to 180 parts by mass of the flame retardant based on a total of 100 parts by mass of the mixed resin (a) and the polyolefin (b). It consists of

According to one embodiment, a non-halogen flame-retardant resin composition that is non-halogen, has high flame retardancy, and has excellent oil resistance and low-temperature properties, and electric wires and cables using the same. Obtainable.

FIG. 1 is a cross-sectional view showing a structural example of an electric wire according to an embodiment. FIG. 1 is a cross-sectional view showing an example of the structure of a cable according to an embodiment.

An embodiment of the present invention will be described below with reference to the drawings. In addition, in all the drawings for explaining the embodiment, members having the same function are given the same reference numerals, and repeated explanation thereof will be omitted. Furthermore, in the following embodiments, descriptions of the same or similar parts will not be repeated in principle unless particularly necessary.

<Non-halogen flame retardant resin composition>
The non-halogen flame retardant resin composition of this embodiment will be described in detail below.

The non-halogen flame retardant resin composition according to the present embodiment includes (a) a mixed resin of an ethylene-vinyl acetate copolymer having a vinyl acetate content of 60% by mass or more and an ethylene polymer having a melting point of 115°C or more; b) A base polymer containing an acid-modified polyolefin and a flame retardant containing aluminum hydroxide.

First, the structure of the non-halogen flame retardant resin composition in this embodiment will be explained.

[Base polymer]
The base polymer used in this embodiment includes (a) a mixed resin of an ethylene-vinyl acetate copolymer with a vinyl acetate content of 60% by mass or more and an ethylene polymer with a melting point of 115°C or higher, and (b) acid-modified resin. containing a polyolefin. Each component will be explained below.

(a) Mixed resin The mixed resin used here includes (a1) an ethylene vinyl acetate copolymer (EVA) with a vinyl acetate content (VA amount) of 60% by mass or more, and (a2) a melting point of 115°C or more. It is a mixed resin containing an ethylene polymer. This mixed resin may also contain other polyolefins. However, it does not contain acid-modified polyolefin, which is component (b) described later.

(a1) EVA having a VA amount of 60% by mass or more can impart excellent oil resistance to the resin composition by setting the VA amount to 60% by mass or more. Furthermore, it has the effect of improving elongation properties by improving filler receptivity in the resin composition.

(a2) The ethylene polymer having a melting point of 115°C or higher has a melting point of 115°C or higher as described. By including an ethylene polymer having a melting point of 115° C. or higher, excellent oil resistance can be ensured. That is, for example, since the heating temperature of the test oil used in the oil resistance test is 70°C, an ethylene polymer with a melting point of 115°C or higher is used as a polymer with a melting point higher than the heating temperature of the test oil. This makes it possible to ensure excellent oil resistance. Here, the ethylene polymer may be any polymer containing ethylene as a monomer, and includes ethylene copolymers containing ethylene and other monomers in addition to polyethylene. The ethylene copolymer is preferably a copolymer containing ethylene and α-olefin as constituent units.

The blending ratio of the above components (a1) and (a2) is not particularly limited, but a ratio of (a1):(a2) = 1:2 to 2:1 is preferable, and 2:3 to 3:2 on a mass basis. is more preferable.

If the base polymer is composed only of EVA with a VA content of 60% by mass or more, the low-temperature properties will deteriorate, which is not preferable. Further, the amount of EVA added having a VA amount of 60% by mass or more should be 40% by mass or less when the total of the above (a) mixed resin and (b) polyolefin described below is 100% by mass. preferable. If the amount added is larger than this, there is a risk that the low temperature characteristics will deteriorate.

The above-mentioned ethylene polymers with a melting point of 115°C or higher include low density polyethylene (LDPE), high density polyethylene (HDPE), linear low density polyethylene (LLDPE), linear very low density polyethylene (VLDPE), and ethylene acetic acid. Vinyl copolymers (EVA, excluding those with a VA content of 60% by mass or more), ethylene-ethyl acrylate copolymers (EEA), ethylene-methyl acrylate copolymers (EMA), ethylene-glycidyl methacrylate copolymers (EGMA), ethylene-butene-hexene terpolymer, ethylene-propylene-diene terpolymer (EPDM), ethylene-octene copolymer (EOR), ethylene copolypropylene, ethylene-propylene copolymer (EPR), poly-4-methyl-pentene-1, maleic acid grafted low density polyethylene, hydrogenated styrene-butadiene copolymer (H-SBR), maleic acid grafted linear low density polyethylene, ethylene and carbon number Copolymers with 3 to 30 α-olefins, ethylene-styrene copolymers, maleic acid grafted ethylene-methyl acrylate copolymers, maleic acid grafted ethylene-vinyl acetate copolymers, ethylene-maleic anhydride copolymers, Ethylene-butene-1 copolymers such as ethylene-ethyl acrylate-maleic anhydride terpolymer, ethylene-propylene-butene-1 terpolymer containing butene-1 as the main component, ethylene-hexene-1 Examples include copolymers and olefin block copolymers.

The density of this (a2) ethylene polymer is preferably less than 0.9 g/cm ³ . When the density is less than 0.9 g/cm ³ , the resin composition has good flexibility and oil resistance.

Among them, specific examples of the olefin block copolymer include D9000, D9007, D9100, D9107, D9500, D9507, D9530, D9807, and D9817 manufactured by Dow Chemical Company under the trade name INFUSE series.

Further, EVA (excluding component (a1)) and one or more ethylene-α-olefin copolymers having a melting point of 115° C. or higher from among those described above can be mixed. In the case of mixing a plurality of EVA, it is preferable to use EVA because it has good compatibility with (a1) EVA with a VA content of 60% by mass or more, and in particular, EVA with a melting point of 85° C. or more is preferred because it also provides good oil resistance. At this time, since (a2) an ethylene-α-olefin copolymer having a temperature of 115° C. or higher is blended, the oil resistance of the resin composition can be further improved, which is preferable.

(b) Acid-modified polyolefin The (b) acid-modified polyolefin used here is a polyolefin modified with an acid. Ethylene-α-polyolefin is preferred as this polyolefin.Ethylene-α-polyolefin has excellent flexibility in low-temperature environments, and when modified with acid, can strengthen its adhesion to metal hydroxides. Therefore, the low-temperature properties of the resin composition can be improved.

Here, the polyolefin before modification includes low density polyethylene, linear low density polyethylene, ultra low density polyethylene, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-butene-1 copolymer. , ethylene-hexene-1 copolymer, ethylene-octene-1 copolymer, and the like. Among them, ethylene-butene-1 copolymer, ethylene-hexene-1 copolymer, and ethylene-octene-1 copolymer have few crystals and can accept fillers in resin compositions, improving flexibility at low temperatures. This is preferable because it can be applied. Examples of acids used for modification include maleic acid, maleic anhydride, fumaric acid, and the like.

The above (a) component and (b) component are contained to form a base polymer, and in these base polymers, the mass ratio of (a) mixed resin to (b) acid-modified polyolefin is (a):( b)=95:5 to 70:30 is preferable, and (a):(b)=90:10 to 80:20 is more preferable. For example, when the total of components (a) and (b) is 100 parts by mass, if component (b) is contained in 5 parts by mass or more, the low-temperature properties will be good, and if it is contained in 30 parts by mass or less, it will have a moderate relationship with the filler. Adhesion can be ensured and the elongation at break property of the resin composition can be improved.

[Flame retardants]
Aluminum hydroxide is used as the flame retardant used in this embodiment. Furthermore, other metal hydroxides can also be added, and examples of other metal hydroxides include magnesium hydroxide and calcium hydroxide.

Furthermore, in a cable structure using a shield braid constituting a cable to be described later, it is also important to prevent flame from propagating to the separator and electric wires directly under the braid. Aluminum hydroxide exhibits a dramatic flame retardant effect when applied to the sheath material of such cable structures. The mechanism is not clear, but when compared with magnesium hydroxide, it can be considered as follows.

The dehydration temperature of magnesium hydroxide is 340 to 420°C, with a peak near 400°C. The decomposition temperature of the base polymer is around 400°C, and high flame retardancy can be obtained. The dehydration temperature of aluminum hydroxide has three stages of dehydration reaction, existing at 245°C, 320°C, and 550°C, with the main temperature being 320°C. During dehydration of aluminum hydroxide, the base polymer has not reached its decomposition point and the coating layer expands significantly. It is estimated that this expansion produces a high heat insulating effect, suppresses the heat transmitted to the separator and the electric wire, and provides a high flame retardant effect.

The amount of this flame retardant added is preferably 150 to 180 parts by mass based on the total of 100 parts by mass of the mixed resin (a) and the polyolefin (b). When the content is 150 parts by mass or more, sufficient flame retardancy can be obtained, and when the content is 180 parts by mass or less, elongation at break and flexibility can be appropriately ensured.

This flame retardant can be surface-treated with a silane coupling agent, a titanate coupling agent, a fatty acid such as stearic acid, etc. in consideration of dispersibility, etc.; Hydroxide is preferable because it improves the reinforcing effect and low-temperature properties.

The metal hydroxide is added in the form of particles, and the particle size is preferably fine. For example, it is preferable to use particles having an average particle diameter D50 of 0.6 to 1.5 μm. In addition, in this specification, the average particle diameter means the particle diameter at 50% of the integrated value in the particle size distribution determined by laser diffraction/scattering method.

Further, when the specific surface area of the metal hydroxide particles is large, a reinforcing effect as a resin composition is expected, and high dynamic cut-through characteristics can be obtained. Specifically, it is preferable that the specific surface area measured by the BET method is 4 m ² /g or more.

A flame retardant aid may be added to the flame retardant to enhance the flame retardant effect. However, phosphorus-based flame retardants such as red phosphorus and triazine-based flame retardants such as melamine cyanurate are not suitable because they generate phosphine gas and cyan gas that are harmful to the human body. Other flame retardant aids can be used, such as clay, silica, zinc stannate, zinc borate, calcium borate, dolomide hydroxide, and silicone.

In addition to the components described above, the resin composition of this embodiment may optionally contain a crosslinking agent, a crosslinking aid, an ultraviolet absorber, a light stabilizer, a softener, a lubricant, a coloring agent, and a reinforcing agent. , surfactants, inorganic fillers, antioxidants, plasticizers, metal chelating agents, foaming agents, compatibilizers, processing aids, stabilizers, etc. can be added.

When the resin composition described above is used for an insulating layer of an electric wire or a coating layer of a cable, it is preferably crosslinked. Crosslinking is an important structure in ensuring oil resistance. The degree of crosslinking can be defined by the gel fraction. The gel fraction can be calculated, for example, as follows.

Before measuring the gel fraction, weigh the materials to be used in advance. The material is then immersed in xylene heated to 110°C for 24 hours. After immersion, the material was left at atmospheric pressure for 3 hours at 20°C and vacuum dried at 80°C for 4 hours, and the mass of the material after treatment was weighed. ) can be calculated by the ratio (percentage) of mass. If the gel fraction is not 80% or more, sufficient oil resistance cannot be obtained.

Crosslinking treatments include chemical crosslinking using organic peroxides, sulfur compounds, silane, etc., irradiation crosslinking with electron beams, radiation, etc., crosslinking using other chemical reactions, and are not particularly limited. Crosslinking methods are also applicable.

<Electric wire>
Next, an electric wire as one embodiment will be described using FIG. 1. FIG. 1 is a sectional view showing the structure of the electric wire according to the present embodiment.

As shown in FIG. 1, the electric wire 10 according to the present embodiment includes a conductor 11 and an insulating layer 12 coated around the conductor 11. The insulating layer 12 may have a single layer or a multilayer structure of two or more layers.

As the conductor 11, commonly used metal wires such as copper wires and copper alloy wires, as well as aluminum wires, gold wires, silver wires, etc. can be used. Further, as the conductor 11, a metal wire plated with a metal such as tin or nickel may be used. Further, the conductor 11 may have a single wire structure, or may be a twisted wire conductor made by twisting metal wires together. As the stranded wire conductor, concentric stranded wires, collective stranded wires, and composite stranded wires obtained by concentrically twisting these wires can be used. Further, a lightly compressed conductor obtained by compressing these stranded wires is preferable because the diameter of the electric wire can be reduced.

The insulating layer 12 is made of the resin composition described above. At this time, it is preferable to use a resin composition that has been crosslinked as described above. The thickness of this insulating layer 12 is not particularly limited, but is preferably 0.15 to 2 mm.

The electric wire 10 of this embodiment is manufactured, for example, as follows. First, materials containing (a) a mixed resin as a base polymer, (b) a polyolefin, and a metal hydroxide as a flame retardant are melt-kneaded to obtain the resin composition of this embodiment.

After that, the conductor 11 is prepared. Then, the resin composition of this embodiment is extruded using an extrusion molding machine so as to cover the periphery of the conductor 11, thereby forming an insulating layer 12 having a predetermined thickness. By doing so, the electric wire 10 can be manufactured.

Further, in this embodiment, after manufacturing the electric wire 10, the flame-retardant resin composition constituting the insulating layer 12 can be crosslinked by, for example, an electron beam crosslinking method or a chemical crosslinking method. Although it is not essential for the electric wire 10 of the present embodiment to be crosslinked, such crosslinking improves the oil resistance of the insulating layer 12 made of the flame retardant resin composition. It is preferable to perform crosslinking.

When using the electronic crosslinking method, after the resin composition is molded into the insulating layer 12 of the electric wire 10, it is crosslinked by irradiation with an electron beam of, for example, 1 to 30 MRad. When using a chemical crosslinking method, a crosslinking agent is added to the flame retardant resin composition in advance, and after this flame retardant resin composition is molded as the insulating layer 12 of the electric wire 10, it is heat treated and crosslinked.

<Cable>
A cable according to an embodiment of the present invention is a cable in which a shield braid is provided on the outside of a single or multi-core stranded wire made by twisting one or more insulated wires, and a coating layer is coated on the outside of the shield braid. . However, the separator can be installed freely and can be used both inside and outside in contact with the shield braid. The material of the separator is not particularly limited. Further, in the present invention, the separator may not be provided.

The cable according to this embodiment will be described in detail using FIG. 2. FIG. 2 is a sectional view showing the structure of the cable according to this embodiment.

As shown in FIG. 2, the cable 20 according to the present embodiment includes a stranded wire obtained by twisting two electric wires 10 together, and a separator 21 provided around the stranded wire. A braided shield layer 22 is provided on the outside. Here, there is a degree of freedom in the arrangement position of the separator 21, and for example, the separator 21 can be arranged in contact with the shield layer 22 regardless of whether it is inside or outside the shield layer 22. The material of this separator 21 is not particularly limited.

On the other hand, the shield layer 22 is made of a conductive material, typically a metal material, in order to exhibit a shielding effect. For example, the material of the shield layer 22 having a braided structure may be the same as the material of the conductor 11. At this time, the braid density is 50% to 99%. Further, the wire diameter is preferably 0.05 mm to 0.3 mm, preferably 0.1 mm to 0.2 mm. Subsequently, as shown in FIG. 2, a covering layer (sheath) 23 is provided on the outside of the shield layer 22. This coating layer 23 is made of the resin composition described above.

The cable 20 of this embodiment is manufactured, for example, as follows. First, two electric wires 10 are manufactured by the method described above. Thereafter, the two electric wires 10 are twisted together with intervening fibers, paper tape, jute, etc., and then a separator 21 and a shield layer 22 are formed in this order by a known method so as to cover this. Furthermore, the resin composition of this embodiment is extruded on the outer periphery of the shield layer 22 obtained in this way, similarly to the method for manufacturing the electric wire described above, to form a coating layer (sheath) 23 of a predetermined thickness. By doing so, the cable 20 of this embodiment can be manufactured.

The cable 20 of this embodiment has been described using as an example a case where the core wire is a two-core twisted wire made by twisting two electric wires 10 together, but the core wire may be a single core wire (one core wire) or a multi-core wire other than two core wires. It may also be a core strand. Moreover, there may be no interposition between the electric wire 10 and the coating layer 23.

Further, in the cable 20 of the present embodiment, the above-mentioned electric wire 10 is used as an example. However, the present invention is not limited to this, and it is also possible to use an electric wire using a general-purpose material for the insulating layer. .

When a general-purpose material is used for the insulating layer 12, it is preferable to add a flame retardant to the insulating layer 12 because higher flame retardance can be obtained. However, the flame retardant needs to be a non-halogen material, and even if it is a non-halogen flame retardant, it is preferable not to add a phosphorus-based flame retardant such as red phosphorus or a triazine-based flame retardant such as melamine cyanurate.

The polymer used for this insulating layer 12 is not particularly limited as long as it is non-halogen. Examples include polyolefins such as high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, very low-density polyethylene, and ethylene-acrylic acid ester copolymer.

Rubber materials are also applicable, including ethylene-propylene copolymer rubber, ethylene-propylene-diene terpolymer rubber, acrylic rubber, ethylene-acrylate copolymer rubber, and ethylene-octene copolymer rubber. , ethylene-acrylate copolymer rubber, ethylene-octene copolymer rubber, ethylene-vinyl acetate copolymer rubber, ethylene-butene-1 copolymer rubber, butadiene-styrene copolymer rubber, isobutylene-isoprene copolymer rubber Examples include polymer rubbers and block copolymer rubbers having polystyrene blocks.

Furthermore, engineering plastics can also be applied, such as polyethylene terephthalate, polybutylene terephthalate, polyphenylene ether, polycarbonate, polyamide, polyphenyl sulfide, polyether ether ketone, polyethylene naphthalate, polybutylene naphthalate, polyether sulfone, etc. These thermoplastic elastomers can also be used. The base polymer of this insulating layer 12 may be used alone or in a blend of two or more.

In the insulating layer 12, the resin composition composed of these materials may contain a crosslinking agent, a crosslinking aid, a flame retardant aid, an ultraviolet absorber, a light stabilizer, a softener, a lubricant, and a coloring agent, as necessary. , reinforcing agents, surfactants, inorganic fillers, plasticizers, metal chelating agents, foaming agents, compatibilizers, processing aids, stabilizers, etc. can be added.

Crosslinking should be done from the viewpoint of oil resistance, and crosslinking treatments include chemical crosslinking using organic peroxides or silane compounds, irradiation crosslinking with electron beams, radiation, etc., crosslinking using other chemical reactions, etc. However, any crosslinking method is applicable.

Note that the above-described insulating layer 12 and coating layer 23 need to be crosslinked in order to ensure oil resistance. At this time, the degree of crosslinking can be defined by the gel fraction. Crosslinking treatments include chemical crosslinking using organic peroxides, sulfur compounds, or silane, irradiation crosslinking with electron beams, radiation, etc., and crosslinking using other chemical reactions, but there are no particular limitations. Crosslinking methods are also applicable.

The thickness of the coating layer 23 is not particularly limited, but a thickness of 0.2 to 1.5 mm is particularly likely to exhibit the above effects.

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[Preparation of insulated wire]
First, as a conductor, a tin-plated conductor having a configuration of 19 wires/0.18 mm (wire diameter) was prepared. Next, 25 parts by mass of ethylene-methyl acrylate copolymer (Elvaloy 1125AC, manufactured by Japan Polyethylene Co., Ltd.), 10 parts by mass of high-density polyethylene (Hizex 5305E, manufactured by Prime Polymer Co., Ltd.), and maleic anhydride-modified high-density polyethylene ( 25 parts by mass of Fusabond E265 (manufactured by DuPont), 10 parts by mass of maleic anhydride-modified ethylene-α-olefin copolymer (Tafuma MH7020, manufactured by Mitsui Chemicals), ethylene-ethyl acrylate-maleic anhydride ternary copolymer. 30 parts by mass of a polymer (manufactured by Arkema, Bondine LX4110), 150 parts by mass of magnesium hydroxide (manufactured by Kyowa Chemical Co., Ltd., trade name: Kisuma 5L), and 2 parts by mass of Irganox 1010, manufactured by BASF as an antioxidant. , 8 parts by mass of TMPT (trimethylolpropane trimethacrylate) manufactured by Shin Nakamura Chemical Co. as a crosslinking aid, 1 part by mass of zinc stearate as a metal soap, Mg 12-hydroxythreaphosphate (manufactured by Katsuta Kako Co., Ltd., EMS-6) ) and 3 parts by mass of a metal chelating agent (manufactured by Adeka, CDA-6) were kneaded in a 25L kneader and pelletized in a granulator. The obtained pellets were extruded using a 65 mm extruder to cover the outer periphery of the conductor to produce a single-layer electric wire in which the conductor was covered with an insulating layer. Further, this electric wire was crosslinked by irradiating it with an electron beam of 10 Mrad.

(Examples 1-2, Comparative Examples 1-4)
A multicore stranded wire is prepared by twisting two of the resulting insulated wires together, a 32 μm polyethylene-terephthalate separator is wrapped around it, and a 0.11 mm tin-plated conductor is used to create a braid density of 80%. A core was obtained by applying a shield braid.

The obtained core was coated by extrusion using a 20 mm extruder using a resin composition having the composition shown in Table 1 so as to have a wall thickness of 0.7 mm. The obtained coating layer was irradiated with an electron beam to cause crosslinking, thereby producing a cable 20 having the configuration shown in FIG. 2.

The materials used to form the covering layer are as follows.

[material]
(base polymer)
・Ethylene vinyl acetate copolymer 1: Levaprene (trade name, manufactured by LANXESS, VA content 60% by mass)
・Ethylene vinyl acetate copolymer 2: Evaflex EV5274 (manufactured by DuPont Mitsui Chemical Co., Ltd., melting point: 89°C)
・Polyolefin: INFUSE9100 (manufactured by Dow, melting point: 120°C, density: 0.877g/cm ³ )
・Acid-modified ethylene-α-olefin copolymer: Tafuma MA7020 (manufactured by Mitsui Chemicals)

(Flame retardants)
・Aluminum hydroxide 1: OL104ZO (manufactured by HUBER, BET specific surface area: 4 m ² /g)
・Aluminum hydroxide 2: OL107ZO (manufactured by HUBER, BET specific surface area: 7m ² /g)
・Magnesium hydroxide: Mugsys S4 (manufactured by Kamishima Chemical Co., Ltd.)
・Others: Composition shown in Table 2

[Characteristics test]
Further, in order to obtain mechanical properties, each resin composition having the composition shown in Table 1 was prepared into a 1 mm sheet, and a crosslinked sheet was obtained by irradiation with an electron beam. Using this crosslinked sheet, the following various characteristic tests were conducted, and the results are also shown in Table 1.

(Tensile test)
As an initial tensile test, the resulting crosslinked sheet was punched out into a No. 6 dumbbell test piece, a tensile test was conducted at a displacement rate of 250 mm/min, and the tensile strength, 100% modulus, and elongation at break were measured. A tensile strength of 10 MPa or more was considered to be a pass, and a tensile strength of less than 10 MPa was a pass. Regarding 100% modulus, which is an index showing flexibility, less than 11 MPa was considered good (◎), 11 MPa or more and less than 14 MPa was good (○), and 14 MPa or more was bad (x). The elongation at break was evaluated as good (◎) if it was 150% or more, acceptable (◎) if it was 120% or more, and poor (x) if it was less than 110%.

(Oil resistance test)
As an oil resistance test, the resulting crosslinked sheet was punched out into a No. 6 dumbbell test piece, immersed in IRM903 test oil heated to 70°C for 168 hours, and then subjected to a tensile test at a displacement rate of 250 mm/min to determine the tensile strength. was measured. The rate of change with respect to the initial tensile strength was calculated, and if the rate of change in tensile strength was −30% or more, it was evaluated as acceptable (○), and if it was less than −30%, it was evaluated as not acceptable (×).

(Low temperature test)
For the low-temperature test (low-temperature elongation), the crosslinked sheet was punched out into a No. 6 dumbbell test piece, left in a -40°C low-temperature bath for 4 hours or more, and elongation at break was measured at a displacement rate of 25 mm/min. 30% or more was rated as good (◎), 20% or more and less than 30% was rated fair (○), and less than 20% was rated bad (x).

(Flame retardance)
As a flame retardant evaluation, hold a cable with a length of 600 mm vertically, apply it to the flame for 60 seconds, and after removing the flame, if the pass rate is 67% or more, it is acceptable (○), and if it is less than 67%, it is unacceptable. (x).

(comprehensive evaluation)
In the above test method, as a comprehensive evaluation, those with ◎ or 〇 in all evaluations were evaluated as acceptable (○), and those that included × were evaluated as unacceptable (x).

From the above results, Examples 1 and 2 were rated ◎ or ○ in all evaluations, so the overall evaluation was given as ○.

On the other hand, in Comparative Examples 1 and 2, no low-density polyolefin was added, and the 100% modulus was rejected. Furthermore, Comparative Example 3 was rejected because the amount of flame retardant added was large and the elongation at break was low. Comparative Example 4 failed the flame retardancy test because magnesium hydroxide was used as the flame retardant.

Although the present invention has been described with reference to the above-described embodiments and examples, the present invention is not limited to the above-described embodiments and examples, and can be modified in various ways without departing from the gist thereof.

The non-halogen flame-retardant resin composition of the present invention can be used not only for halogen-free and flame-retardant electric wires and cables, but also for sheets, films, panels, mats, pipes, protective materials, fillers, fibers, etc. that require halogen-free flame retardancy. It can be used for resin molded products, resin substrates, stationery, building materials, connectors, bushes, grommets, terminal blocks, terminal internal insulators, etc.

10 Electric wire 11 Conductor 12 Insulating layer 20 Cable 21 Separator 22 Shield layer 23 Covering layer

Claims (8)

(a) A mixed resin of an ethylene-vinyl acetate copolymer with a vinyl acetate content of 60% by mass or more and an ethylene polymer with a melting point of 115°C or higher (excluding acid-modified polyolefins) and (b) acid A non-halogen flame retardant resin composition containing a base polymer containing a modified polyolefin and a flame retardant containing aluminum hydroxide,
The mass ratio of the (a) mixed resin and the (b) polyolefin is (a):(b) = 95:5 to 70:30,
The density of the ethylene polymer having a melting point of 115° C. or higher is less than 0.9 g/cm ³ ,
A non-halogen flame retardant resin composition containing 150 to 180 parts by mass of the flame retardant based on a total of 100 parts by mass of the mixed resin (a) and the polyolefin (b). The non-halogen flame retardant resin composition according to claim 1,
A non-halogen flame retardant resin composition, wherein the content of the ethylene vinyl acetate copolymer is 40% by mass or less when the total of the mixed resin (a) and the polyolefin (b) is 100% by mass. In the non-halogen flame retardant resin composition according to claim 2,
A non-halogen flame retardant resin composition, wherein the aluminum hydroxide is silane-treated aluminum hydroxide. In the non-halogen flame retardant resin composition according to claim 3,
The silane-treated aluminum hydroxide is a non-halogen flame-retardant resin composition in which a BET indicating a specific surface area is 4 m ² /g or more. An electric wire comprising a conductor and an insulating layer provided around the conductor,
The insulating layer is made of (a) a mixed resin of an ethylene-vinyl acetate copolymer having a vinyl acetate content of 60% by mass or more and an ethylene polymer having a melting point of 115° C. or higher (excluding acid-modified polyolefin); and (b) a base polymer containing an acid-modified polyolefin, and a flame retardant containing aluminum hydroxide, the non-halogen flame retardant resin composition comprising:
The mass ratio of the (a) mixed resin and the (b) polyolefin is (a):(b) = 95:5 to 70:30,
The density of the ethylene polymer having a melting point of 115° C. or higher is less than 0.9 g/cm ³ ,
An electric wire made of a non-halogen flame retardant resin composition containing 150 to 180 parts by mass of the flame retardant based on a total of 100 parts by mass of the mixed resin (a) and the polyolefin (b). The electric wire according to claim 5,
An electric wire, wherein the insulating layer is a crosslinked product of the non-halogen flame-retardant composition. Single-core/multi-core stranded wire made by twisting one or more single-layer or multi-layer electric wires, a shield braid provided on the outside thereof with a shield braid or a separator, and a cable with a coating layer coated on the outside of the shield braid. And,
The coating layer is made of (a) a mixed resin of an ethylene-vinyl acetate copolymer having a vinyl acetate content of 60% by mass or more and an ethylene polymer having a melting point of 115° C. or higher (excluding acid-modified polyolefin); and (b) a base polymer containing an acid-modified polyolefin, and a flame retardant containing aluminum hydroxide, the non-halogen flame retardant resin composition comprising:
The mass ratio of the (a) mixed resin and the (b) polyolefin is (a):(b) = 95:5 to 70:30,
The density of the ethylene polymer having a melting point of 115° C. or higher is less than 0.9 g/cm ³ ,
A cable comprising a non-halogen flame retardant resin composition containing 150 to 180 parts by mass of the flame retardant based on a total of 100 parts by mass of the mixed resin (a) and the polyolefin (b). The cable according to claim 7,
The cable, wherein the coating layer is a crosslinked product of the non-halogen flame-retardant resin composition.

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