JP6868420B2 - Flame-retardant crosslinked resin composition and wiring material - Google Patents

Description

The present invention relates to a flame-retardant crosslinked resin composition and a wiring material. More specifically, the present invention relates to a flame-retardant crosslinked resin composition that exhibits a high degree of flame retardancy even when the content of the flame retardant is reduced, and a wiring material using the same as a coating material.

Insulated wires, cables, cords, optical fiber core wires, optical fiber cords, and other wiring materials used for internal wiring or external wiring of electrical and electronic equipment are required to have characteristics such as flame retardancy. As a flame-retardant standard, for example, a vertical combustion test (Vertical Flame) defined in Safety Organization (UL) 1581 (Related Standard for Electric Wires, Cables and Flexible Cords (Reference Standard for Electrical Wires, Cabres and Flexible Codes)). Test) (VW-1) or horizontal test or inclination test specified in Japanese Industrial Standards (JIS) C 3005 (rubber / plastic insulated wire test method) can be mentioned.

As a flame-retardant insulated electric wire, for example, a resin component mainly composed of an ethylene-based copolymer such as an ethylene-vinyl acetate copolymer or an ethylene-acrylic acid ester copolymer, a halogen-based flame retardant, and an antimony trioxide. An insulated wire coated with a resin composition containing a flame retardant in combination with the above (Patent Document 1).

Japanese Unexamined Patent Publication No. 2009-51918

Wiring materials used for various purposes are required to improve or improve their characteristics. In particular, in order to ensure higher safety, it is desired not only to clear the predetermined acceptance criteria but also to have higher flame retardancy. Further, depending on the application, properties such as mechanical properties, heat resistance, insulation properties or cold resistance (for example, properties in which the coating layer is not easily damaged in a low temperature environment of −40 ° C. or lower) are also required. On the other hand, weight reduction is also required. To reduce the weight of the wiring material, it is effective to reduce the mass of the coating layer.
However, if the content of the flame retardant in the coating material is reduced, the weight of the wiring material is reduced, but the flame retardancy of the coating layer and the wiring material may be impaired. Further, it was found that if the content of the flame retardant is increased in order to improve the flame retardancy, the weight reduction cannot be achieved and the mechanical properties as well as the properties such as heat resistance, insulation property or cold resistance are lowered. It was.

The present invention solves the above-mentioned problems and exhibits a flame-retardant crosslinked resin composition showing a high degree of flame retardancy even when the content of the flame retardant is reduced, and further, mechanical properties, heat resistance, cold resistance or An object of the present invention is to provide a flame-retardant crosslinked resin composition having insulating properties.
An object of the present invention is to provide a wiring material using the above flame-retardant crosslinked resin composition as a coating material.

As a result of diligent studies, the present inventors have found that in a flame retardant crosslinked resin composition containing a resin containing an ethylene-vinyl acetate copolymer and a flame retardant, at least a halogen-based flame retardant and a broom are used as the flame retardant. By using a combination of zinc acid acid and metal hydrate, it exhibits a high degree of flame retardancy even if the total content of the flame retardant is reduced, and further, this flame retardant crosslinked resin composition is used as a coating material for wiring materials. Found that it can be used as. Based on these findings, the present invention has been further studied and completed.

That is, the subject of the present invention has been achieved by the following means.
<1> 100 parts by mass of a resin containing (a1) 50 to 97% by mass of an ethylene-vinyl acetate copolymer and (a2) 3 to 50% by mass of at least one selected from a polypropylene-based resin and a polybutene-based resin, and a halogen-based resin. flame retardants 30-60 parts by weight, and contains a 20 to 50 parts by weight of zinc borate, a metal hydrate 20-50 parts by weight, and 0 to 50 parts by weight of antimony trioxide, in that case, the halogenated The total content of the flame retardant, the zinc borate, the metal hydrate and the antimony trioxide is 50 to 105 parts by mass with respect to 100 parts by mass of the resin, and the polypropylene resin contains an ethylene component. A flame retardant crosslinked resin composition which is at least one selected from an ethylene-propylene random copolymer having an amount of 1 to 10% by mass, a low stereoregular polypropylene having a mesopentad fraction of 30 to 60 mol%, and a propylene-based elastomer. ..
<2> The difficulty according to <1>, wherein the vinyl acetate content in the ethylene-vinyl acetate copolymer is 10 to 25% by mass, and the vinyl acetate content in the resin is 5 to 25% by mass. Flammable crosslinked resin composition.
<3> The polypropylene-based resin is at least one selected from an ethylene-propylene random copolymer having an ethylene component content of 6 to 10% by mass, low stereoregular polypropylene, and a propylene-based elastomer, and the polybutene-based resin is The flame-retardant crosslinked resin composition according to <1> or <2>, which is a butene-based elastomer.
<4> The flame-retardant crosslinked resin composition according to any one of <1> to <3>, wherein the halogen-based flame retardant contains at least one selected from a chlorine-based flame retardant and a bromine-based flame retardant.
<5> The flame-retardant crosslinked resin according to any one of <1> to <4>, wherein the metal hydrate contains magnesium hydroxide whose surface is treated with at least one of a fatty acid and a phosphoric acid ester. Composition.
<6> A wiring material having a coating layer of the flame-retardant crosslinked resin composition according to any one of <1> to <5> above.
<7> The wiring material according to <6>, wherein the wiring material is an insulated electric wire or a cable.

The numerical range represented by using "~" in the present specification means a range including the numerical values described before and after the numerical values as the lower limit value and the upper limit value.

According to the present invention, a flame-retardant crosslinked resin composition that exhibits a high degree of flame retardancy even when the content of the flame retardant is reduced, and further has mechanical properties, heat resistance, cold resistance, or insulating properties. A flame retardant crosslinked resin composition can be provided. Further, according to the present invention, it is possible to provide a wiring material using the flame-retardant crosslinked resin composition exhibiting the above-mentioned excellent properties as a coating material.

Hereinafter, preferred embodiments of the present invention will be described in detail.
<< Flame-retardant crosslinked resin composition >>
The flame retardant crosslinked resin composition of the present invention contains at least 1 type to 50% by mass selected from (a1) 50 to 100% by mass of an ethylene-vinyl acetate copolymer and (a2) a polypropylene-based resin and a polybutene-based resin. Contains 100 parts by mass of resin, 20 to 60 parts by mass of halogen-based flame retardant, 10 to 50 parts by mass of zinc borate, 5 to 50 parts by mass of metal hydrate, and 0 to 50 parts by mass of antimony trioxide. To do.

In the flame-retardant crosslinked resin composition of the present invention, at least a part of the ethylene-vinyl acetate copolymer is crosslinked. At this time, the cross-linking mode of the ethylene-vinyl acetate copolymer is not particularly limited, and the ethylene-vinyl acetate copolymers may be cross-linked with each other, including (in a state of including) a flame retardant or the like described later. It may be crosslinked (in this case, it forms a composite of the resin and the flame retardant).
Ethylene-vinyl acetate copolymers are usually crosslinked with an ethylene moiety. When the flame-retardant cross-linked resin composition of the present invention contains a cross-linking aid described later, the ethylene moiety of the ethylene-vinyl acetate copolymer and the functional group of the cross-linking aid described later undergo a cross-linking reaction. The ethylene-vinyl acetate copolymer is crosslinked via a crosslinking aid.
The degree of cross-linking of the ethylene-vinyl acetate copolymer (flame-retardant cross-linked resin composition) cannot be uniquely determined depending on the intended use, and examples thereof include the degree of cross-linking obtained by the cross-linking method and the cross-linking conditions described later. .. Specifically, as the degree of cross-linking, the gel fraction is preferably 50 to 90% by mass, and more preferably 60 to 80% by mass. When the degree of cross-linking of the ethylene-vinyl acetate copolymer is in the above range, excellent heat resistance, mechanical properties or heat deformation properties can be imparted to the flame-retardant cross-linked resin composition. The gel fraction can be measured by measuring the gel fraction using xylene heated to 105 ° C as a solvent.

In the present invention, the flame-retardant resin composition in which the ethylene-vinyl acetate copolymer is not crosslinked is referred to as a flame-retardant uncrosslinked resin composition or a flame-retardant non-crosslinked resin composition. Both are common in that the ethylene-vinyl acetate copolymer is not crosslinked, but the resin composition to be crosslinked is called a flame-retardant uncrosslinked resin composition and is not planned to be crosslinked ( The resin composition (without cross-linking treatment) is different in that it is a flame-retardant non-cross-linked resin composition. Therefore, the flame-retardant uncrosslinked resin composition can also be said to be a production intermediate (product) of the flame-retardant crosslinked resin composition of the present invention.
The fact that the ethylene-vinyl acetate copolymer is not cross-linked means that the ethylene-vinyl acetate copolymer is not completely cross-linked and a part of the ethylene-vinyl acetate copolymer is cross-linked. For example, the embodiment in which the gel fraction is less than 50% by mass is also included.

The flame-retardant crosslinked resin composition of the present invention exhibits a high degree of flame retardancy. Specifically, as the flame retardancy, as will be described later, in the vertical combustion test VW-1, the characteristic that the combustion does not occur for 30 seconds or more, the indicator flag and cotton do not burn, and the carbide drip does not occur. At least show.
Further, the flame-retardant crosslinked resin composition of the present invention has the above-mentioned high flame retardancy and mechanical properties, and also has heat resistance, cold resistance or insulating properties, if necessary. The mechanical properties, cold resistance, and insulating properties of the flame-retardant crosslinked resin composition of the present invention are each of high-level ones preferably satisfying the UL1581 standard. Further, the flame-retardant crosslinked resin composition of the present invention preferably has heat resistance of 150 ° C. class specified in UL3289 or UL3398.
Further, the flame-retardant crosslinked resin composition of the present invention is lightweight and preferably has a specific gravity of less than 1.50 in the underwater substitution method of JIS K 7112.

Hereinafter, the components contained in the flame-retardant crosslinked resin composition of the present invention will be described.
The flame-retardant crosslinked resin composition of the present invention contains a resin, a halogen-based flame retardant, a metal hydrate, zinc borate, preferably antimony trioxide as a flame retardant, and various additives and the like, if necessary. Contains.

<Resin>
The resin used in the present invention contains an ethylene-vinyl acetate copolymer, preferably at least one selected from polypropylene and polybutene, and may also contain a resin other than the ethylene-vinyl acetate copolymer, polypropylene and polybutene. it can.

(Ethylene-vinyl acetate copolymer)
The ethylene-vinyl acetate copolymer is not particularly limited, and examples thereof include a resin of a copolymer obtained by copolymerizing ethylene and vinyl acetate. The ethylene-vinyl acetate copolymer may be an alternating copolymer in which the ethylene component and the vinyl acetate component are alternately polymerized, or the ethylene component polymerization block and the vinyl acetate component polymerization block are bonded to each other. It may be a block copolymer obtained by the above, and further, it may be a random copolymer in which an ethylene component and a vinyl acetate component are randomly polymerized.
One type of ethylene-vinyl acetate copolymer may be used, or two or more types may be used in combination.

The ethylene-vinyl acetate copolymer preferably has a vinyl acetate content (Bi) of 10 to 25% by mass, preferably 15 to 20% by mass. When the vinyl acetate content in the ethylene-vinyl acetate copolymer is within the above range, it has the above-mentioned excellent properties. That is, if the vinyl acetate content in the copolymer is too high, the mechanical properties, cold resistance or insulating properties may deteriorate. If the vinyl acetate content is too low, the flame retardancy may decrease. From the same viewpoint, even when two or more kinds of ethylene-vinyl acetate copolymers are used in combination, it is preferable that each of the ethylene-vinyl acetate copolymers has a vinyl acetate content in the above range.
The vinyl acetate content in the ethylene-vinyl acetate copolymer can be determined in accordance with JIS K 7192.

Further, in the present invention, the vinyl acetate content (X) of the ethylene-vinyl acetate copolymer in the resin is preferably 5 to 25% by mass, preferably 10 to 20% by mass. When the vinyl acetate content in the resin is within the above range, a high degree of flame retardancy can be ensured. In addition, it has excellent insulation characteristics, tensile strength, and cold resistance.
The vinyl acetate content in the resin can be determined by the following formula (1).
X (mass%) = Σ (Ai × Bi) / 100 equation (1)
Ai = content of ethylene-vinyl acetate copolymer in resin (mass%)
Bi = Vinyl Acetate Content in Ethylene-Vinyl Acetate Copolymer (% by Mass)

The melt flow rate of the ethylene-vinyl acetate copolymer (hereinafter referred to as MFR, which means a value measured under the conditions of a temperature of 190 ° C. and a weight of 21.18 N in accordance with ASTM D-1238) is an insulated wire. From the viewpoint of moldability when producing a wiring material such as, 0.1 g / 10 minutes or more is preferable, and from the viewpoint of mechanical strength, it is preferably 10 g / 10 minutes or less.

Examples of the resin of the ethylene-vinyl acetate copolymer include Evaflex (trade name, manufactured by Mitsui-DuPont Polychemical) and Revaprene (trade name, manufactured by Bayer).

The content of the ethylene-vinyl acetate copolymer in the resin is 50 to 100% by mass. If this content is less than 50% by mass, it may not be possible to impart a high degree of flame retardancy to the flame-retardant crosslinked resin composition. In addition, sufficient flexibility (tensile elongation) and heat resistance may not be imparted. The upper limit of the content is preferably 99% by mass or less, and more preferably 97% by mass or less. On the other hand, the lower limit is preferably 65% by mass or more, and more preferably 75% by mass or more. In the present invention, the upper limit and the lower limit can be arbitrarily combined in the range of the content of the ethylene-vinyl acetate copolymer.

(Polypropylene resin and / or polybutene resin)
The resin used in the present invention preferably contains a polypropylene-based resin and / or a polybutene-based resin as described above. By containing such a resin, the flame retardancy of the flame-retardant crosslinked resin composition can be further enhanced in cooperation with zinc borate coexisting in the composition.

The polypropylene-based resin is not particularly limited, and examples thereof include a homopolymer or a copolymer resin or an elastomer containing a propylene component as a constituent component. Specific examples thereof include a propylene homopolymer and an ethylene-propylene random copolymer. Examples thereof include resins and elastomers such as coalesced or ethylene-propylene block copolymers, and ethylene-propylene random copolymers, low stereoregular polypropylene, propylene-based elastomers and the like are preferable. In the present invention, as a polypropylene-based resin, an ethylene-propylene random copolymer can impart good tensile properties, heat resistance, and heat deformation properties to the flame-retardant crosslinked resin composition in addition to flame retardancy. ,preferable. Further, as the polypropylene-based resin, at least one selected from an ethylene-propylene random copolymer having an ethylene component content of 6 to 10% by mass, a low stereoregular polypropylene, and a propylene-based elastomer, which will be described later, is flame-retardant crosslinked. In addition to flame retardancy, the resin composition is preferable in that it can impart good tensile properties, heat resistance, heat deformation properties, and flexibility.

Here, the ethylene-propylene random copolymer preferably has an ethylene component content of about 1 to 10% by mass (1 to 5% by mass and more than 5 to 10% by mass), and the ethylene component is a propylene chain. It means something that is randomly taken in. From the viewpoint of imparting flexibility to the flame-retardant crosslinked resin composition, an ethylene-propylene random copolymer having an ethylene component of 6 to 10% by mass is preferable. The ethylene-propylene block copolymer preferably has an ethylene or EPDM component content of about 5 to 15% by mass, and means that the ethylene or EPDM component and the propylene component are present as independent components.

The low stereoregular polypropylene preferably has a mesopentad fraction of 30 to 60 mol%. The mesopentad fraction indicates the abundance ratio of the isotactic chain in the polypropylene molecular chain. More specifically, it indicates the ratio of five consecutive methyl groups contained in the propylene monomer unit in polypropylene in the same direction, and is an index showing the stereoregularity of polypropylene. The larger this value is, the higher the stereoregularity is, and the higher the rigidity is. On the other hand, if this value is low, it becomes soft.
The mesopentad fraction is generally measured using, for example, ¹³ C-NMR. Specifically, the mesopentad fraction is the absorption intensity (A) derived from the methyl group at the center of the chain in which five consecutive mesobonds are formed in propylene units, and the absorption intensity derived from all the methyl groups in the propylene unit (absorption intensity). It is calculated as the ratio of B), that is, A / B.

The polypropylene MFR (meaning the value measured at a temperature of 230 ° C. and a weight of 21.18 N according to ASTM-D-1238) is preferably 0.1 to 60 g / 10 minutes, more preferably. Is 0.1 to 25 g / 10 minutes, more preferably 0.3 to 15 g / 10 minutes.

One type of polypropylene resin may be used, or two or more types may be used in combination.
Examples of polypropylene-based resins include SunAllomer PP (trade name, manufactured by SunAllomer Ltd.) and Prime Polypro (trade name, manufactured by Prime Polymer Co., Ltd.). Examples of the low stereoregular polypropylene include L-MODU (trade name, manufactured by Idemitsu Kosan Co., Ltd.). Examples of the propylene-based elastomer include Toughmer XM (trade name, manufactured by Mitsui Chemicals, Inc.).

The polybutene-based resin is not particularly limited, and examples thereof include a homopolymer or copolymer resin or elastomer containing a butene component as a constituent main component.
In the present invention, examples of the polybutene-based resin include polybutene (a homopolymer of butene, preferably 1-butene), butene-based elastomer, and the like. Butene-based elastomers are preferable because they can impart good tensile properties, heat resistance, heat deformation characteristics, and flexibility to the flame-retardant crosslinked resin composition in addition to flame retardancy.
The MFR of the polybutene resin (meaning the value measured under the conditions of a temperature of 190 ° C. and a weight of 21.18 N according to ASTM-D-1238) is preferably 0.1 to 60 g / 10 minutes. It is more preferably 0.1 to 20 g / 10 minutes, and even more preferably 0.3 to 10 g / 10 minutes.
One type of polybutene resin may be used, or two or more types may be used in combination.
Examples of the polybutene resin include buron (trade name, manufactured by Mitsui Chemicals, Inc.), and examples of the butene-based elastomer include Toughmer BL (trade name, manufactured by Mitsui Chemicals, Inc.).

The content of the polypropylene-based resin and the polybutene-based resin in the resin is 0 to 50% by mass in total. If this content exceeds 50% by mass, it may not be possible to impart a high degree of flame retardancy to the flame-retardant crosslinked resin composition. In addition, sufficient flexibility, heat resistance, and cold resistance may not be imparted. The upper limit of the content is preferably 20% by mass or less, and more preferably 10% by mass or less. On the other hand, the lower limit is preferably 1% by mass or more, and more preferably 3% by mass or more. In the present invention, the range of the content rates of the polypropylene-based resin and the polybutene-based resin can be arbitrarily combined with the above upper limit value and the above lower limit.
In particular, the resin contains 50 to 97% by mass of an ethylene-vinyl acetate copolymer having a vinyl acetate content of 10 to 25% by mass, and at least 3 to 50% by mass of at least one selected from polypropylene-based resins and polyvinyl acetate-based resins. When the vinyl acetate content in the resin is 5 to 25% by mass, the above-mentioned excellent properties can be imparted to the flame-retardant crosslinked resin composition.

The resin used in the present invention may also contain a resin component other than the ethylene-vinyl acetate copolymer, polypropylene-based resin and polybutene-based resin. Such resin components are not particularly limited, and examples thereof include resins and rubbers of various copolymers, and ethylene-α-olefin copolymers and unsaturated carboxylic acid-modified polyolefin (co) polymers are preferable. Be done.

(Ethylene-α-olefin copolymer)
When the resin used in the present invention contains an ethylene-α-olefin copolymer, the cold resistance and insulating properties of the flame-retardant crosslinked resin composition can be further improved.
Examples of the ethylene-α-olefin copolymer include a resin obtained from a copolymer of ethylene and an α-olefin having 4 to 12 carbon atoms. Examples of the α-olefin component include 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene and the like. In the present invention, the ethylene-α-olefin copolymer includes a copolymer containing a diene component, for example, an ethylene-propylene rubber (for example, ethylene-propylene-diene rubber).
Examples of the ethylene-α-olefin copolymer include LDPE (low density polyethylene), LLDPE (linear low density polyethylene), MDPE (medium density polyethylene), and polyethylene synthesized in the presence of a metallocene catalyst. Of these, LLDPE synthesized in the presence of a metallocene catalyst is preferable.
The density of the ethylene-α-olefin copolymer is not particularly limited, but is preferably ^{0.880 to 0.940 g / cm 3 , and more preferably 0.9000 to 0.930 g / cm 3} . As a result, the acceptability to inorganic fillers such as various flame retardants is improved, and excellent mechanical properties can be obtained. The density of the ethylene-α-olefin copolymer can be measured by the method described in JIS K 7112.
Examples of ethylene-α-olefin copolymers include "Kernel" (trade name, manufactured by Nippon Polyethylene), "Evolu" (trade name, manufactured by Prime Polymer Co., Ltd.), and "Sumikasen" (trade name, manufactured by Sumitomo Chemical Co., Ltd.). Can be mentioned.

One type of ethylene-α-olefin copolymer may be used, or two or more types may be used in combination.
When the resin contains an ethylene-α-olefin copolymer, the content of the ethylene-α-olefin copolymer in the resin is preferably 0 to 30% by mass, more preferably 5 to 20% by mass. If the content of the ethylene-α-olefin copolymer is too high, the flame retardancy and heat resistance of the flame-retardant crosslinked resin composition may decrease.

(Unsaturated carboxylic acid-modified polyolefin)
The resin used in the present invention can contain unsaturated carboxylic acid-modified polyolefins. The inclusion of unsaturated carboxylic acid-modified polyolefin can further improve the mechanical properties or abrasion resistance of the flame-retardant crosslinked resin composition.
The unsaturated carboxylic acid-modified polyolefin is not particularly limited, and examples thereof include a resin of a (co) polymer obtained by modifying the polyolefin with an unsaturated carboxylic acid. Examples of the polyolefin include polyethylene, polypropylene, polybutene, polymethylpentene and the like. Polyethylene or polypropylene is preferable in terms of the balance between strength characteristics and elongation characteristics. Examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, itaconic acid, fumaric acid, maleic anhydride, itaconic anhydride or fumaric acid anhydride.
The amount of modification of the unsaturated carboxylic acid-modified polyolefin with unsaturated carboxylic acid is preferably 0.5 to 15% by mass with respect to the polyolefin resin.

The unsaturated carboxylic acid-modified polyolefin may be appropriately synthesized or a commercially available product may be used. When synthesizing an unsaturated carboxylic acid-modified polyolefin, it can usually be obtained by a usual method of modifying the polyolefin with an unsaturated carboxylic acid. For example, it can be carried out by heating and kneading polyolefin and unsaturated carboxylic acid in the presence of an organic peroxide.
Commercially available unsaturated carboxylic acid-modified polyolefins include, for example, "Adtex" (trade name, manufactured by Japan Polyethylene Corporation), "Admer" (trade name, manufactured by Mitsui Chemicals, Inc.), and "Polybond" (trade name, manufactured by Chemtura). (Made) can be mentioned.

As the unsaturated carboxylic acid-modified polyolefin, one type may be used, or two or more types may be used in combination.
When the resin contains an unsaturated carboxylic acid-modified polyolefin, the content of the unsaturated carboxylic acid-modified polyolefin in the resin is preferably 0 to 30% by mass, more preferably 5 to 15% by mass. If this content is too high, the flexibility or elongation characteristics of the flame-retardant crosslinked resin composition may decrease.

<Flame retardant>
The flame-retardant crosslinked resin composition of the present invention contains at least a halogen-based flame retardant, zinc borate and a metal hydrate, and preferably further contains antimony trioxide. By using each of these flame retardants in combination, a high degree of flame retardancy can be imparted to the flame retardant crosslinked resin composition even if the total content of the flame retardants is reduced.

In the flame-retardant crosslinked resin composition of the present invention, the contents of the halogen-based flame retardant, zinc borate, metal hydrate and antimony trioxide are selected from the ranges described below, respectively. The total content of the flame retardant is 50 to 105 parts by mass with respect to 100 parts by mass of the resin. If the total content of the flame retardant is less than 50 parts by mass, it may not exhibit a high degree of flame retardancy. On the other hand, if it exceeds 105 parts by mass, at least one of mechanical properties, heat resistance, insulation and cold resistance, particularly tensile strength, may decrease. The total content of the flame retardant is such that a high degree of flame retardancy and mechanical properties, heat resistance, insulating property or cold resistance can be imparted to the flame retardant crosslinked resin composition with respect to 100 parts by mass of the resin. It is preferably 60 to 95 parts by mass, and more preferably 70 to 85 parts by mass.

(Halogen flame retardant)
The halogen-based flame retardant used in the present invention is not particularly limited as long as it is a flame retardant having a halogen atom, but a chlorine-based flame retardant containing a chlorine atom or a bromine-based flame retardant containing a bromine atom is preferably used. One kind of halogen-based flame retardant may be used, or two or more kinds may be used in combination.

Examples of the chlorine-based flame retardant include those usually used in flame-retardant resin compositions, and for example, decachlorododecahydrodimethanocyclooctene can be used. Examples of commercially available chlorine-based flame retardants include Declolan Plus (trade name, dodecachlorododecahydrodimethanodibenzocyclooctene, manufactured by Occidental Chemical Co., Ltd.).

The brominated flame retardant is not particularly limited as long as it excludes polybromophenyl ether and polybromophenyl, and examples thereof include those usually used in flame-retardant resin compositions. Examples thereof include organic bromine-containing flame retardants such as brominated ethylene bisphthalimide compounds, bisbrominated phenylterephthalamide compounds, brominated bisphenol compounds, and 1,2-bis (bromophenyl) ethane compounds. Among them, 1,2-bis (bromophenyl) ethane is preferable, and examples of commercially available products thereof include Cytex (trade name, manufactured by Albemarle Corporation) and Firemaster (trade name, manufactured by Chemtura Japan).

The halogen-based flame retardant preferably has a high content of halogen atoms (for example, in the flame retardant, preferably 65% by mass or more, more preferably 80% by mass or more), and the higher the content, the better the flame retardancy. The property can be imparted to the flame retardant crosslinked resin composition. The halogen atom content can be measured by, for example, energy dispersive X-ray fluorescence (EDX), combustion ion chromatograph, or the like.
The content of the halogen-based flame retardant is selected from the range of 20 to 60 parts by mass with respect to 100 parts by mass of the resin so as to satisfy the above-mentioned total content. If the content of the halogen-based flame retardant is less than 20 parts by mass, the effect of improving the flame retardancy may not be sufficient, while if it exceeds 60 parts by mass, the tensile strength may decrease. The content of the halogen-based flame retardant is preferably 25 to 50 parts by mass, more preferably 25 parts by mass, in that excellent flame retardancy can be imparted to the flame-retardant crosslinked resin composition without impairing mechanical properties (tensile strength). It is selected from the range of 28-40 parts by mass.

(Zinc borate)
The flame-retardant crosslinked resin composition of the present invention contains zinc borate. By further containing zinc borate in addition to the halogen-based flame retardant and metal hydrate, preferably antimony trioxide, the flame retardancy is further improved even if the content of the flame retardant is reduced. it can. More preferably, the mechanical properties, heat resistance, cold resistance and insulating properties can be maintained.

The zinc borate used in the present invention preferably has an average particle size of 10 μm or less, and more preferably 5 μm or less, in terms of appearance when the flame-retardant crosslinked resin composition is molded.
Here, the average particle size is a value measured by an optical particle size measuring device such as a laser diffraction / scattering type particle size distribution measuring device in which zinc borate is dispersed in alcohol or water.
Examples of zinc borate include Firebreak ZB, Firebreak ZB-Fine, Firebreak ZB-XF, Firebreak 415, Firebreak 500 (all trade names, manufactured by Borax), or SZB-2335 (trade name). , Sakai Chemical Co., Ltd.), and in particular, Firebreak ZB and SZB-2335, which have a large amount of water of crystallization in the structure, can be preferably used in terms of imparting flame retardancy.
One type of zinc borate may be used, or two or more types may be used in combination.
The content of zinc borate is selected from the range of 10 to 50 parts by mass with respect to 100 parts by mass of the resin so as to satisfy the above-mentioned total content. If the content of zinc borate is less than 10 parts by mass, the effect of improving flame retardancy may not be sufficient, while if it exceeds 50 parts by mass, any of tensile strength, heat resistance and insulating properties May decrease. Furthermore, the appearance when molded may be deteriorated. In this respect, zinc borate is preferably selected from the range of 12 to 40 parts by mass, more preferably 15 to 30 parts by mass with respect to 100 parts by mass of the resin.

(Metal hydrate)
Examples of the metal hydrate used in the present invention include compounds having a hydroxyl group or water of crystallization. For example, aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, calcium silicate, magnesium silicate, calcium oxide, magnesium oxide, aluminum oxide, aluminum nitride, aluminum borate whisker, hydrated aluminum silicate, hydrated silicic acid. Examples include magnesium, basic magnesium carbonate, hydrotalcite or talc.
Among the metal hydrates, aluminum hydroxide, magnesium hydroxide, calcium carbonate or magnesium carbonate are preferable, aluminum hydroxide or magnesium hydroxide is more preferable, and magnesium hydroxide is further preferable.

The metal hydrate is preferably surface-treated. Examples of the surface treatment include fatty acid treatment, phosphoric acid treatment, phosphoric acid ester treatment, titanate treatment, or treatment with a silane coupling agent. Among them, from the viewpoint of insulating properties, fatty acid treatment, phosphoric acid treatment or phosphoric acid ester treatment is preferable, fatty acid treatment or phosphoric acid ester treatment is more preferable, and phosphoric acid ester treatment is further preferable.
The fatty acid is not particularly limited as long as it is usually used for surface treatment of metal hydrates, and examples thereof include saturated fatty acids having 10 to 22 carbon atoms and unsaturated fatty acids having 10 to 22 carbon atoms. Specifically, examples of saturated fatty acids include capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, aragidic acid, and behenic acid, and examples of unsaturated fatty acids include oleic acid, linolenic acid, and linoleic acid. Can be mentioned.
The phosphoric acid ester is not particularly limited as long as it is usually used for surface treatment of metal hydrates, and examples thereof include stearyl alcohol phosphate ester and its metal salt, lauryl alcohol phosphate ester and its metal salt. Be done.
The titanate is not particularly limited as long as it is usually used for surface treatment of metal hydrates.
The silane coupling agent is not particularly limited as long as it has a vinyl group or an epoxy group at the end, which is usually used for surface treatment of metal hydrates. For example, vinyl trimethoxysilane, vinyl triethoxysilane, and glycid. Examples thereof include xypropyltrimethoxysilane, glycidoxypropyltriethoxysilane, glycidoxypropylmethyldimethoxysilane, methacryloxypropyltrimethoxysilane, methacryloxypropyltriethoxysilane, and methacryloxypropylmethyldimethoxysilane.
As the metal hydrate, magnesium hydroxide surface-treated with at least one selected from fatty acids and phosphoric acid esters is preferable.
The amount of the surface treatment of the metal hydrate is not particularly limited, but is preferably 0.05 to 3.0% by mass with respect to 100 of the metal hydrate, for example.
As the surface-treated metal hydrate, a metal hydrate surface-treated by a usual method can be used, or a commercially available product can also be used. For example, examples of magnesium hydroxide surface-treated with a phosphoric acid ester include Kisuma 5J (trade name, manufactured by Kyowa Chemical Industry Co., Ltd.).

One type of metal hydrate may be used, or two or more types may be used in combination.
The content of the metal hydrate is selected from the range of 5 to 50 parts by mass with respect to 100 parts by mass of the resin so as to satisfy the above-mentioned total content. If the content of the metal hydrate is less than 5 parts by mass, the effect of improving flame retardancy may not be sufficient, while if it exceeds 50 parts by mass, any one of tensile strength, heat resistance and insulating properties. May decrease. In this respect, the content of the metal hydrate is preferably selected from the range of 8 to 30 parts by mass, more preferably 10 to 25 parts by mass with respect to 100 parts by mass of the resin.

(Antimony trioxide)
The flame-retardant crosslinked resin composition of the present invention preferably further contains antimony trioxide. Antimony trioxide can be used in combination with a halogen-based flame retardant as a flame retardant aid for a halogen-based flame retardant. When the flame-retardant crosslinked resin composition of the present invention contains antimony trioxide, the flame retardancy of the flame-retardant crosslinked resin composition can be further improved.
Examples of antimony trioxide include PATOX-C, PATOX-M, PATOX-K (trade name, manufactured by Nihon Seiko Co., Ltd.), AT3, AT-3CN (trade name, manufactured by Suzuhiro Chemical Co., Ltd.), and the like. Antimony trioxide (manufactured by Toyota Tsusho Co., Ltd.) can be mentioned.
One type of antimony trioxide may be used, or two or more types may be used in combination.
The content of antimony trioxide is selected from the range of 0 to 50 parts by mass with respect to 100 parts by mass of the resin so as to satisfy the above-mentioned total content. When the content of antimony trioxide exceeds 50 parts by mass, the flame retardancy is not improved, and the tensile strength of the flame-retardant crosslinked resin composition may decrease or the specific gravity may increase. The content of antimony trioxide is preferably 18 to 30 parts by mass, and more preferably selected from the range of 20 to 25 parts by mass in these respects.

<Other ingredients>
In the present invention, the flame-retardant crosslinked resin composition is an object of the present invention, which comprises various additives generally used for electric wires, electric wire parts, electric cables, electric cords, sheets, foams, tubes, pipes and the like. Can be appropriately contained as long as the above is not impaired. Examples of such additives include antioxidants, metal deactivators, cross-linking aids, stabilizers, flame retardant (auxiliary) agents, fillers and lubricants.

(Antioxidant)
The antioxidant is not particularly limited, and examples thereof include amine antioxidants, phenolic antioxidants, sulfur antioxidants, and benzimidazole antioxidants. Examples of the amine antioxidant include polymers of 4,4'-dioctyldiphenylamine, N, N'-diphenyl-p-phenylenediamine, 2,2,4-trimethyl-1,2-dihydroquinoline and the like. .. Examples of the phenol antioxidant include pentaerythrityl-tetrax (3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate) and octadecyl-3- (3,5-di-tert-butyl). -4-Hydroxyphenyl) propionate, 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene and the like can be mentioned. Examples of the sulfur antioxidant include bis (2-methyl-4- (3-n-alkylthiopropionyloxy) -5-tert-butylphenyl) sulfide and pentaerythritol-tetrakis (3-lauryl-thiopropionate). And so on. Examples of the benzimidazole antioxidant include 2-mercaptobenzimidazole and a zinc salt thereof, and 2-methylmercaptobenzimidazole and a zinc salt thereof.

As the antioxidant, one type may be used, or two or more types may be used in combination.
In the present invention, it is preferable to use a phenol antioxidant and a benzimidazole antioxidant in combination in terms of heat resistance at a high temperature exceeding 150 ° C. and long-term heat resistance.

As the antioxidant, a commercially available product can be used. For example, examples of the phenolic antioxidant include Irganox 1010 (trade name, manufactured by BASF), Irganox 1076 (trade name, manufactured by BASF), and ADEKA STAB A-80 (trade name, manufactured by ADEKA). Examples of the benzimidazole antioxidant include Nocrack MB and Nocrack MBZ (trade name, manufactured by Ouchi Shinko Kagaku Co., Ltd.).

In the present invention, the content of the antioxidant is not particularly limited, but is preferably 5 to 30 parts by mass, and more preferably 8 to 20 parts by mass with respect to 100 parts by mass of the resin.
When a phenolic antioxidant is used among the antioxidants, the content thereof is not particularly limited as long as it is within the range of the content of the antioxidant, but is preferably 0.5 to 0.5 to 100 parts by mass of the resin. It is 10 parts by mass, more preferably 1 to 8 parts by mass, and even more preferably 2 to 6 parts by mass.
When a benzimidazole antioxidant is used among the antioxidants, its content is not particularly limited as long as it is within the range of the content of the antioxidant, but it is preferably 1 to 20 with respect to 100 parts by mass of the resin. It is by mass, more preferably 3 to 15 parts by mass, and even more preferably 5 to 12 parts by mass.

(Metal inactivating agent)
The metal inactivating agent is not particularly limited, and is, for example, N, N'-bis (3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyl) hydrazine, 3- (N-salicyloyl). Examples thereof include amino-1,2,4-triazole and 2,2'-oxamidbis (ethyl 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate).
As the metal inactivating agent, one type may be used, or two or more types may be used in combination.
The content of the metal deactivator is not particularly limited, but is preferably 0.3 to 5 parts by mass, and more preferably 0.5 to 3 parts by mass with respect to 100 parts by mass of the resin.

(Crosslinking aid)
The cross-linking aid is not particularly limited as long as it is at least a compound that forms or promotes cross-linking of an ethylene-vinyl acetate copolymer.
The functional group of the cross-linking aid is a group that reacts with the ethylene moiety of the ethylene-vinyl acetate copolymer, and various functional groups usually applied are selected depending on the ethylene moiety of the ethylene-vinyl acetate copolymer. To. Examples of such a functional group include an ethylenic double bond such as a (meth) acryloyl group and a vinyl group. In such a cross-linking aid having two or more functional groups, the functional group and the ethylene portion of the ethylene-vinyl acetate copolymer undergo a cross-linking reaction to form a cross-linked structure between the ethylene-vinyl acetate copolymer.
Examples of the cross-linking aid include bifunctional (meth) acrylates and trifunctional or higher functional polyfunctional (meth) acrylates. More specifically, such cross-linking aids include bifunctional (meth) acrylates such as polypropylene glycol di (meth) acrylates and trifunctional (meth) acrylates such as trimethylolpropane tri (meth) acrylates. Can be mentioned.
As the cross-linking aid, a commercially available product can be used, and examples thereof include Ogmont or NK ester (both trade names, manufactured by Shin-Nakamura Chemical Co., Ltd.).
As the cross-linking aid, one type may be used, or two or more types may be used in combination.
The content of the cross-linking aid is not particularly limited, but is preferably 1 to 10 parts by mass, and more preferably 2 to 6 parts by mass with respect to 100 parts by mass of the resin.

(Stabilizer)
Stabilizers are used to impart long-term heat resistance, especially long-term withstand voltage characteristics, to the flame-retardant crosslinked resin composition of the present invention. Examples of such stabilizers include zinc sulfide. As the stabilizer, one type may be used, or two or more types may be used in combination. The content of the stabilizer (particularly zinc sulfide) is not particularly limited, but is preferably 1 to 10 parts by mass, and more preferably 3 to 6 parts by mass with respect to 100 parts by mass of the resin.

(Flame-retardant (auxiliary) agent or filler)
The flame retardant (auxiliary) agent or filler may be any flame retardant (auxiliary) agent or filler other than the above flame retardant, and for example, carbon, clay, zinc oxide, tin oxide, titanium oxide, molybdenum oxide, and silicone. Examples include compounds, quartz and white carbon. One kind of flame-retardant (auxiliary) agent or filler may be used, or two or more kinds may be used in combination. The content of the flame-retardant (auxiliary) agent or filler is not particularly limited, but is preferably 1 to 20 parts by mass, and more preferably 3 to 15 parts by mass with respect to 100 parts by mass of the resin.

(Glidant)
The lubricant is not particularly limited, and examples thereof include hydrocarbon-based, siloxane-based, fatty acid-based, fatty acid amide-based, ester-based, alcohol-based, and metal soap-based lubricants. One type of lubricant may be used, or two or more types may be used in combination. The content of the lubricant is not particularly limited, but is preferably 0.1 to 5 parts by mass, and more preferably 0.3 to 2 parts by mass with respect to 100 parts by mass of the resin.

<< Wiring material >>
The wiring material of the present invention has a coating layer formed of the flame-retardant crosslinked resin composition of the present invention.
Examples of the wiring material include insulated wires, cables, cords, optical fiber core wires or optical fiber cords used for internal wiring or external wiring of electric / electronic devices, and insulated wires or cables are preferable.
As described above, the wiring material of the present invention exhibits a high degree of flame retardancy, and also has mechanical properties, heat resistance, cold resistance, or insulating properties. Specifically, it is the same as the flame-retardant, mechanical properties, heat resistance, cold resistance and insulating properties exhibited by the flame-retardant crosslinked resin composition of the present invention.
Therefore, the wiring material of the present invention is preferably used as a wiring material that requires a high degree of flame retardancy, and as a wiring material that requires heat resistance of 150 ° C. or higher.
Further, the wiring material of the present invention may exhibit a high degree of flame retardancy and further have mechanical properties (tensile strength) and flexibility. Such wiring materials are preferably used as wiring materials (for example, electric wires for electronic devices, wiring materials for automobiles, etc.) that are required to have both mechanical properties and flexibility.

<Insulated wire>
The insulated wire has a conductor and a coating layer formed of the flame-retardant crosslinked resin composition of the present invention around the conductor (outer peripheral surface).
The insulated wire is not particularly limited in other forms as long as it has the above configuration, and the number of conductors, the number of coating layers, and the like may be 1 or 2 or more, respectively. Further, the cross-sectional shape is not particularly limited, and examples thereof include a circular shape, an elliptical shape, a rectangular shape, and an eyeglass shape.
As the conductor, those usually used for insulated electric wires can be used without particular limitation. For example, annealed copper or a copper alloy, or a metal conductor such as a single wire or a stranded wire such as aluminum can be mentioned. Further, as the conductor, in addition to the bare wire, a conductor plated with tin, a conductor having an enamel coating layer, or the like can also be used. When the coating layer has a multi-layer structure, at least one layer may be formed of the flame-retardant crosslinked resin composition of the present invention. In this case, the other layer can be formed of a resin usually used for an insulated wire or a composition thereof.
The outer diameters of the insulated wire and the conductor are appropriately determined according to the application and the like. The thickness of the coating layer, particularly the coating layer formed of the flame-retardant crosslinked resin composition of the present invention, is appropriately determined depending on the application and the like, but the flame-retardant crosslinked resin composition of the present invention has. From the viewpoint of exhibiting excellent characteristics, 0.1 to 5.0 mm is preferable, and 0.4 to 1.0 mm is more preferable.

<Cable>
Examples of the cable include a conductor and a cable having a coating layer (sheath) in which a plurality of insulated electric wires having a coating layer around the conductor are laminated and the coating layers (sheath) are collectively coated. In such a cable, the coating layer (sheath) can be formed of the flame-retardant crosslinked resin composition of the present invention.

<< Manufacturing method of flame-retardant crosslinked resin composition and wiring material >>
The method for producing the flame-retardant crosslinked resin composition and the wiring material of the present invention will be described below.

The method for producing the flame-retardant crosslinked resin composition of the present invention is not particularly limited, but preferably, a flame-retardant uncrosslinked resin composition is prepared by mixing each of the above components, and the flame-retardant uncrosslinked resin composition is prepared. It is produced by cross-linking the resin composition.
The flame-retardant uncrosslinked resin composition is obtained by heating and kneading the above-mentioned resin, halogen-based flame retardant, zinc borate and metal hydrate, preferably antimony trioxide, and if necessary, other additives. , Prepared. The kneading conditions such as the kneading temperature and the kneading time are not particularly limited, and can be appropriately set within a temperature range equal to or higher than the melting temperature of the resin. The kneading temperature is preferably 120 to 220 ° C., for example. The kneading method is not particularly limited as long as it is a method usually used for kneading rubber or plastic. The apparatus to be used is not particularly limited, and examples thereof include a single-screw extruder, a twin-screw extruder, a roll, a Banbury mixer, and various kneaders.
By this heat kneading, a flame-retardant uncrosslinked resin composition in which each component is uniformly dispersed (mixed) can be obtained. The flame-retardant non-crosslinked resin composition described above can be prepared in the same manner.

In the above kneading, the ethylene-vinyl acetate copolymer may be partially crosslinked (partially crosslinked), but the obtained flame-retardant non-crosslinked resin composition and flame-retardant non-crosslinked resin composition can be molded. It is preferable that the property is maintained (for example, the degree of cross-linking is less than the above-mentioned degree of cross-linking of the flame-retardant cross-linked resin composition).

The flame-retardant crosslinked resin composition of the present invention is obtained by cross-linking a flame-retardant non-crosslinked resin composition. This cross-linking treatment may be performed before molding the flame-retardant uncross-linked resin composition or the like, or may be performed after molding. In the present invention, from the viewpoint of moldability, it is preferable to mold a flame-retardant uncrosslinked resin composition or the like and then carry out a cross-linking treatment. Therefore, when producing the wiring material of the present invention (method for producing the wiring material), a flame-retardant uncrosslinked resin composition is prepared as described above, and then this flame-retardant uncrosslinked resin composition is used as a conductor. It is placed on the outer circumference (extrusion molding) and crosslinked.

Extrusion molding of a flame-retardant uncrosslinked resin composition or the like can be performed by extrusion-coating the periphery of a conductor or the like using a general-purpose extrusion molding machine. The temperature of the extrusion molding machine cannot be uniquely determined depending on various conditions such as the type of resin and the take-up speed of the conductor. For example, it is preferable that the temperature of the cylinder portion is about 120 to 150 ° C. and that of the crosshead portion is about 160 to 180 ° C.

In the method for producing a wiring material, the flame-retardant uncrosslinked resin composition formed as described above is crosslinked. The cross-linking treatment is not particularly limited as long as it is a method capable of cross-linking the ethylene-α-olefin copolymer. For example, a chemical cross-linking method using a cross-linking aid, a cross-linking method by irradiation with radiation (electron beam or γ-ray), or a method in which these are used in combination can be mentioned. In the present invention, the radiation cross-linking method using a cross-linking aid is preferable from the viewpoint of efficient cross-linking reaction and mass productivity.
When an electron beam is used as the radiation in the radiation cross-linking method, the irradiation amount of the electron beam is not particularly limited as long as the ethylene-α-olefin copolymer can be cross-linked, but is preferably 1 to 30 Mrad, for example. .. If the irradiation amount is too small, the cross-linking reaction of the ethylene-α-olefin copolymer does not proceed sufficiently, and the above-mentioned excellent properties, particularly heat resistance, may not be imparted to the flame-retardant cross-linked resin composition. On the other hand, if the irradiation amount is too large, it may not be possible to impart sufficient tensile elongation or the like to the flame-retardant crosslinked resin composition. Further, the acceleration voltage in the irradiation of the electron beam is not particularly limited as long as the ethylene-α-olefin copolymer can be crosslinked, but is preferably 500 to 750 keV, for example. The reason is the same as the irradiation amount of the electron beam.

As described above, the flame-retardant crosslinked resin composition of the present invention is prepared, and the wiring material of the present invention is produced.
As described above, the wiring material of the present invention has a coating layer formed of the flame-retardant crosslinked resin composition of the present invention exhibiting the above-mentioned excellent properties. As described above, the flame-retardant crosslinked resin composition of the present invention exhibits high flame retardancy even when it contains a low flame retardant, and further has high mechanical properties, heat resistance, and cold resistance. It also has properties or insulating properties. Therefore, the wiring material of the present invention also exhibits a high degree of flame retardancy. This point is the same even if the coating layer has a wide range of thicknesses as described above. Further, as described above, the wiring material of the present invention also has a high degree of mechanical properties, heat resistance, cold resistance or insulation properties.

The reason why the flame-retardant crosslinked resin composition and wiring material (hereinafter, may be referred to as wiring material) of the present invention exhibit excellent vertical flame retardancy (VW-1) is not clear, but the following It can be thought of as.
That is, when the wiring material or the like is ignited, first, the shell (char) is rapidly formed by zinc borate (increased shell formation rate), the shell formation becomes stronger, and the coating layer (flame-retardant crosslinked resin) is formed. The drip of the composition) can be suppressed. Further, the combustion of the coating layer is suppressed by the synergistic effect of the halogen-based flame retardant and the preferably used antimony trioxide, specifically, the radical trapping effect and the oxygen blocking effect in the gas phase. In addition to this, it is considered that the metal hydrate exhibits higher flame retardancy due to the endothermic effect. The endothermic effect of this metal hydrate becomes remarkable especially when the thickness of the coating layer is 0.8 mm or more. Therefore, the wiring material or the like exhibits a high degree of flame retardancy, and the total content of the flame retardant can be reduced.
Further, even if a flame-retardant crosslinked resin composition containing polypropylene and / or polybutene as a resin is crosslinked by electron beam irradiation, polypropylene and / or polybutene is not crosslinked. Therefore, the shell formation of zinc borate at the time of ignition of the coating layer acts more efficiently, the flame-retardant action of zinc borate is effectively exhibited, and the flame-retardant crosslinked resin composition is more excellent in flame retardancy. Is considered to be possible. Further, in the case of polypropylene-based resin, since its melting point is generally 140 ° C. or higher, it also contributes to improvement of heat deformation characteristics.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.

In Tables 1 to 3, the numerical values of the compounding compositions in each Example and Comparative Example represent parts by mass unless otherwise specified, and blanks indicate that the corresponding component is not contained.
Tables 1 to 3 show the vinyl acetate content (X) in the resin calculated by the above formula.
The following components were used as the components shown in Tables 1 to 3.

<Resin>
(1) Polyethylene-vinyl acetate copolymer A: Evaflex V5274R (trade name), vinyl acetate content 17% by mass, MFR 0.8 g / 10 minutes, manufactured by Mitsui-Dupont Polychemical Co., Ltd. (2) Polyethylene-vinyl acetate Polymer B: Evaflex EV360 (trade name), vinyl acetate content 25% by mass, MFR 2.0 g / 10 minutes, manufactured by Mitsui-Dupont Polychemical Co., Ltd. (3) Polyethylene-propylene random copolymer: PB222A (trade name) , MFR 0.8 g / 10 minutes, manufactured by Sun Aromar (4) Ethylene-propylene random copolymer: PM940M (trade name), MFR 30 g / 10 minutes, manufactured by Sun Aromar (5) Low stereoregular polypropylene: L-MODU S901 ( Product name), MFR 50 g / 10 minutes, mesopentad fraction 45 mol%, manufactured by Idemitsu Kosan Co., Ltd. (6) Propylene elastomer: Toughmer XM5070 (trade name), MFR 7.0 g / 10 minutes, manufactured by Mitsui Chemicals Co., Ltd. (7) Polyethylene resin : Bureaun P5050N (trade name), MFR 0.5 g / 10 minutes, manufactured by Mitsui Kagaku Co., Ltd. (8) Butene-based elastomer: Toughmer BL3450 (trade name), MFR 4.0 g / 10 minutes, manufactured by Mitsui Kagaku Co., Ltd. (9) Polyethylene-α Olefin copolymer (LLDPE): Sumikasen CU5001 (trade name), density 923 kg / m ³ , manufactured by Sumitomo Chemical Co., Ltd. (10) Unsaturated carboxylic acid-modified polyethylene: Adtex L6100M (trade name), unsaturated carboxylic acid is maleic acid , 1.5% by mass of modification with unsaturated carboxylic acid, manufactured by Nippon Polyethylene Co., Ltd.

<Flame retardant>
(11) Bromine-based flame retardant: Firemaster 2100R (trade name), Compound name: Decabromodiphenylethane, bromine content 82% by mass, manufactured by Chemtura Japan Co., Ltd. (12) Chlorine-based flame retardant: Decloran Plus 25 (commodity) Name), Compound name: Dodecachlorododecahydrodimethanodibenzocyclooctene, chlorine content 65% by mass, manufactured by Occidental Chemical Co., Ltd. (13) Antimony trioxide: PATOX-C (trade name), manufactured by Nippon Seiko Co., Ltd. ( 14) Zinc borate: SZB-2335 (trade name), average particle size 3.9 μm, manufactured by Sakai Chemical Co., Ltd. (15) Magnesium hydroxide: Magnesium hydroxide FK621 (trade name), silane coupling agent: vinyl trimethoxy Silane, surface treatment amount 1.0% by mass, manufactured by Kamishima Chemical Co., Ltd. (16) Fatty acid surface treatment Magnesium hydroxide: Kisma 5A (trade name), fatty acid: stearic acid, surface treatment amount 3.0% by mass, manufactured by Kyowa Chemical Co., Ltd. (17) Phosphoric acid ester surface treatment Magnesium hydroxide: Kisuma 5J (trade name), Phosphoric acid ester: Stearyl phosphate, Surface treatment amount 2.3% by mass, manufactured by Kyowa Chemical Co., Ltd.

<Other additives>
(18) Hindered phenolic antioxidant: Irganox 1010 (trade name), compound name: pentaerythritol tetrakis [3- (3', 5'-di-tert-butyl-4'-hydroxyphenyl) propionate], BASF (19) benzimidazole antioxidant: Nocrack MBZ (trade name), compound name: 2-mercaptobenzimidazole, Ouchi Shinko Kagaku (20) cross-linking aid: Ogmont T200 (trade name), compound Name: Trimethylolpropane Trimethacrylate, manufactured by Shin-Nakamura Chemical Co., Ltd. (21) Stabilizer: Sactris HD-S (trade name), zinc sulfide, manufactured by Sactreben

<Examples 2 , 7 , 9, 11 to 20, Comparative Examples 1 to 12, and Reference Examples 1 to 7 >
Each component shown in Tables 1 to 3 is melt-kneaded (kneading temperature 200 ° C., kneading time 10 minutes) using a Banbury mixer at the ratio (parts by mass) shown in each table, pelletized, and compounded (flame retardant). Sexually uncrosslinked resin compositions) were obtained respectively.

Next, in a 40 mmφ extruder (L / D (ratio of effective screw length L to diameter D) = 25), the temperature of the crosshead and the die was set to 170 ° C., and thereafter, C3 zone = 150 toward the feeder side. The extrusion temperature conditions were set at ° C., C2 zone = 140 ° C., and C1 zone = 130 ° C.
Next, in Examples 2 , 7, 9, 11, 12, and 14 to 20, Comparative Examples 1 to 12, and Reference Examples 1 to 7 , tin-plated annealed copper wire, 21 wires / around a 0.18 mmφ conductor. Then, the flame-retardant uncrosslinked resin composition prepared by the above extruder was extruded so as to have the thickness of the coating layer shown in Tables 1 to 3.
On the other hand, in Example 13, a flame-retardant uncrosslinked resin composition prepared by the above extruder was applied around a tin-plated annealed copper wire, 7 wires / 0.08 mmφ conductor, in the coating layer shown in Table 2. It was extruded to a thickness.

The flame-retardant uncrosslinked resin composition extruded around the conductor in this manner is crosslinked by irradiating it with an acceleration voltage of 750 keV and an irradiation amount of 15 Mrad, and in Example 13, an acceleration voltage of 750 keV and an irradiation amount of 8 Mrad electron beam. I let you.
In this way, each of the insulated wires of Examples and Comparative Examples having a coating layer made of a flame-retardant crosslinked resin composition around the conductor was manufactured.
As a result of measuring the gel fraction of the coating layer in each example by the above method, all of them were in the range of 50 to 90% by mass.

<Characteristic evaluation of insulated wire>
The following characteristics specified in each standard were evaluated for each of the obtained insulated wires in accordance with UL1581 or UL3289 (or UL3398). The results are summarized in Tables 1 to 3.

1. 1. Vertical combustion test VW-1 (evaluation of flame retardancy)
After each of the manufactured insulated wires was stretched vertically without slack, an indicator flag was installed above the insulated wires and cotton was installed (laid) below the insulated wires. With the hood removed, ignition (flame contact) for 15 sec and extinguishing for 60 sec were repeated 5 times.
Flame retardancy was evaluated according to the following criteria. In this vertical combustion test VW-1, a high degree of flame retardancy is required, and ranks A and B are passed, and ranks C and D are rejected. However, according to the UL1581 standard, even rank C is acceptable.
A (especially highly flame-retardant): When all of the combustion of the insulated wire for 15 sec or more, the combustion of the indicator flag and cotton, and the drip of charcoal is not observed B (highly flame-retardant): 30 sec or more When all of the combustion of the insulated wire, the combustion of the indicator flag and the combustion of cotton, and the drip of charcoal were not observed C: The combustion of the indicator flag and the combustion of cotton were not observed, but the combustion of the insulated wire for 31 to 60 sec. Or when carbon dioxide drip is observed D: When combustion of 61 sec or more, combustion of indicator flag or combustion of cotton is observed

2. Tensile test (evaluation of mechanical properties (tensile strength and tensile elongation))
A tubular sample in which a conductor was extracted from each insulated wire was prepared, and breaking elongation (%), breaking strength (MPa), and 100% modulus were measured at a gauge point distance of 25 mm and a tensile speed of 500 mm / min. The evaluation of the elongation at break was evaluated as A (pass) when it was 300% or more, and AA (advanced) when it was 350% or more. The evaluation of breaking strength was given as A (pass) when it was 13.79 MPa or more, and AA (advanced) when it was 15.0 MPa or more. On the other hand, the case where the breaking elongation was less than 300% and the case where the breaking strength was less than 13.79 MPa were defined as D (failed), respectively.
100% Modulus is the tensile strength at 100% elongation, and the lower this value, the better the flexibility. The evaluation of 100% modulus was evaluated as AA (advanced) when it was 8 MPa or less, A (good) when it exceeded 8 MPa and 9 MPa or less, and B when it exceeded 9 MPa.

3. 3. Heat resistance test With respect to the tubular sample used in the above-mentioned tensile test, the initial breaking elongation (%) and the initial breaking strength (MPa) were measured at a gauge point distance of 25 mm and a tensile speed of 500 mm / min. Further, after holding the tubular sample at 180 ° C. for 7 days and 14 days, the breaking elongation (%) after holding and the breaking strength (MPa) after holding were measured in the same manner.
The residual elongation at break (%) was calculated by dividing the elongation at break after holding by the initial elongation at break. Similarly, the residual ratio (%) of tensile strength was calculated.
Regarding the evaluation of heat resistance, regarding the residual rate of elongation at break and the residual rate of tensile strength, those having a residual rate of 80% or more after holding for 7 days were rated as A (pass), and in particular, even after holding for 14 days. AA (advanced) was defined as the one in which the residual rate was maintained at 80% or more. On the other hand, when any one of the remaining rates after holding for 7 days was less than 80, it was defined as D (failed).

4. Thermal deformation test The thermal deformation test evaluates the lateral pressure characteristics of an insulated wire from the outside and the heat resistance during processing using solder.
The thermal deformation characteristics of each tubular sample were measured based on UL1581.
The test was carried out by applying a load of 400 gf (3.92 N) to a tubular sample having an outer diameter of 2.63 mm and 250 gf (2.45 N) to a tubular sample having an outer diameter of 1.08 mm.
When the heat deformation rate was 50% or less, it was designated as A (pass), and when it was 30% or less, it was designated as AA (advanced). On the other hand, when it exceeds 50%, it is defined as D (failure).

5. Insulation property test Each of the manufactured insulated wires (length 50 m) was immersed in a water tank at 20 ° C. for 24 hours, and the insulation resistance value was measured. At this time, the measurement voltage, charge time, and measurement time were set to 500 V, 10 seconds, and 50 seconds, respectively. Those having an insulation resistance value of 2500 MΩ · km or more were designated as A (pass), and those having an insulation resistance value of 10,000 MΩ · km or more were designated as AA (advanced). On the other hand, those having a value of less than 2500 MΩ · km were designated as D (failed).

6. Low temperature wrapping test (evaluation of cold resistance)
Based on UL1581, each of the manufactured insulated wires was left in an environment of -40, -50 and -60 ° C for 4 hours or more, respectively. After that, each cooled insulated wire is cooled to a metal mandrel having a diameter twice the outer diameter of the insulated wire (similar to the insulated wire to -40, -50 or -60 ° C, and cooled to the same temperature as the insulated wire to be wound. I wrapped it around the one I did. After cooling to -40 ° C and winding, no cracks were observed in the coating layer of the insulated wire as B (pass), and those in which no cracks were observed even at -50 ° C were designated as A (pass). Among them, AA (advanced one) was defined as one in which no crack was observed in the coating layer of the insulated wire even after cooling to -60 ° C. and winding. On the other hand, when cracks were observed in the coating layer of the insulated wire after cooling to −40 ° C. and winding, it was designated as D (failure).

7. Specific gravity (evaluation of lightness)
Based on JIS K 7112, a conductor was drawn from each of the manufactured insulated wires, and the specific gravity of the resin composition was measured from the tubular test piece by an underwater substitution method. The lower the specific gravity, the lighter the product, which is preferable. Specifically, it is preferably less than 1.50, and more preferably less than 1.45.

From the results in Tables 1 to 3, the following was found.
Insulated electric wires having a coating layer of a flame-retardant crosslinked resin composition containing a large amount of flame retardant showed a high degree of flame retardancy, but the breaking strength was small, and both mechanical properties and flame retardancy could not be achieved. .. On the other hand, the insulated electric wire having the coating layer of the crosslinked resin composition having the reduced content of the flame retardant did not have sufficient flame retardancy (Comparative Examples 1 to 11). Further, an insulated wire having a coating layer of a crosslinked resin composition that does not satisfy the composition specified in the present invention does not have sufficient heat resistance, insulating properties and cold resistance, and in addition to flame retardancy, the above It was not possible to combine the characteristics at a high level. An insulated wire having a coating layer of a crosslinked resin composition containing no ethylene-vinyl acetate copolymer was inferior in mechanical properties (tensile strength and tensile elongation) (Comparative Example 12).

On the other hand, the insulated electric wires (Examples 2 , 7 , 9, 11 to 20) having a coating layer of the flame-retardant crosslinked resin composition satisfying the composition specified in the present invention are all in 100 parts by mass of the resin. On the other hand, even if the content of the flame retardant was reduced to 50 parts by mass (even if the flame retardant was contained at a low content), high flame retardancy was exhibited. Specifically, the evaluation of the vertical combustion test VW-1 was rank B or higher, and it was possible to meet the demand for further improvement or improvement of flame retardancy. Moreover, all of the insulated wires were excellent in mechanical properties (tensile strength) in addition to high flame retardancy. Furthermore, it has a high level of flame retardancy, mechanical properties, heat resistance, cold resistance and insulation properties. Specifically, it has both high mechanical properties, flame retardancy, cold resistance and insulation properties that meet the UL1581 standard, and high heat resistance in the 150 ° C class specified in the UL3289 or UL3398 standard. Had had.
In particular, the resin contains 50 to 97% by mass of an ethylene-vinyl acetate copolymer having a vinyl acetate content of 10 to 25% by mass and at least 3 to 50% by mass of at least one selected from polypropylene-based resins and polybutene-based resins. When the vinyl acetate content in the resin was 5 to 25% by mass, the flame retardancy could be further improved while maintaining the above-mentioned excellent characteristics (Examples 2 and 19).
In addition, all of the insulated wires of Examples 2 , 7 , 9, 11 to 20 were also excellent in the heat deformation test (lateral pressure characteristics and heat resistance during processing using solder).

Claims (7)

100 parts by mass of a resin containing (a1) 50 to 97% by mass of an ethylene-vinyl acetate copolymer and (a2) 3 to 50% by mass of at least one selected from a polypropylene-based resin and a polybutene-based resin, and a halogen-based flame retardant 30. and 60 parts by weight, and contains a 20 to 50 parts by weight of zinc borate, a metal hydrate 20-50 parts by weight, and 0 to 50 parts by weight of antimony trioxide, in that case, the halogen-based flame retardant, The total content of the zinc borate, the metal hydrate and the antimony trioxide is 50 to 105 parts by mass with respect to 100 parts by mass of the resin, and the polypropylene resin has an ethylene component content of 1. A flame-retardant crosslinked resin composition which is at least one selected from an ethylene-propylene random copolymer of 10% by mass, a low stereoregular polypropylene having a mesopentad fraction of 30 to 60 mol%, and a propylene-based elastomer. The flame-retardant crosslink according to claim 1, wherein the vinyl acetate content in the ethylene-vinyl acetate copolymer is 10 to 25% by mass, and the vinyl acetate content in the resin is 5 to 25% by mass. Resin composition. The polypropylene-based resin is at least one selected from an ethylene-propylene random copolymer having an ethylene component content of 6 to 10% by mass, low stereoregular polypropylene, and a propylene-based elastomer, and the polybutene-based resin is a butene-based elastomer. The flame-retardant crosslinked resin composition according to claim 1 or 2. The flame-retardant crosslinked resin composition according to any one of claims 1 to 3, wherein the halogen-based flame retardant contains at least one selected from a chlorine-based flame retardant and a bromine-based flame retardant. The flame-retardant crosslinked resin composition according to any one of claims 1 to 4, wherein the metal hydrate contains magnesium hydroxide whose surface is treated with at least one selected from a fatty acid and a phosphoric acid ester. A wiring material having a coating layer of the flame-retardant crosslinked resin composition according to any one of claims 1 to 5. The wiring material according to claim 6, wherein the wiring material is an insulated electric wire or a cable.