CN114854118A

CN114854118A - Resin composition, electric wire and cable

Info

Publication number: CN114854118A
Application number: CN202210114804.9A
Authority: CN
Inventors: 中山明成; 木部有; 中村孔亮; 远藤正智
Original assignee: Hitachi Metals Ltd
Current assignee: Proterial Ltd
Priority date: 2021-02-04
Filing date: 2022-01-30
Publication date: 2022-08-05
Also published as: JP2022119412A

Abstract

Provided are a resin composition, a wire and a cable, wherein the resin composition has excellent flame retardancy and the change of tensile strength during heat aging is suppressed. A resin composition comprising (A) a vinyl polymer, (B) a metal hydroxide, and (C) at least one compound selected from the group consisting of a compound in which at least one of the three hydroxyl groups of gallic acid is substituted with an alkoxy group, a phenoxy group, or a silyl ether group, and a compound in which at least one of the three hydroxyl groups of gallic acid is substituted with an alkoxy group, a phenoxy group, or a silyl ether group.

Description

Resin composition, electric wire and cable

Technical Field

The present disclosure relates to a resin composition, a wire and a cable.

Background

The electric wire includes a conductor and a coating layer provided around the conductor. Further, the cable includes, for example, a stranded wire obtained by stranding such electric wires and a sheath provided around the stranded wire. The coating layer of the electric wire and the sheath of the cable are generally formed of an electrically insulating material mainly made of rubber, resin, or the like.

Various properties are required for the coating layer of the electric wire and the sheath of the cable according to the application. For example, wires and cables used for electronic equipment and railway vehicles are required to be formed of halogen-free materials in which generation of toxic gases, corrosive gases, and the like is suppressed during combustion, and to have high flame retardancy and the like.

As a material satisfying such a demand, patent document 1 describes a resin composition in which a metal hydroxide such as magnesium hydroxide is added as a flame retardant to a resin component containing a vinyl polymer as a base polymer.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2015-2062

Disclosure of Invention

Problems to be solved by the invention

However, according to the studies of the present inventors, the resin composition described in patent document 1 may be insufficient when higher flame retardancy is required.

On the other hand, the present inventors have found that the flame retardancy is greatly improved by adding a compound having a plurality of phenolic hydroxyl groups in a molecule such as gallic acid ester together due to the high radical trapping effect of the phenolic hydroxyl groups. The radical trapping effect means an effect of trapping a generated radical by a phenolic hydroxyl group. Thus, the flame retardant can trap radicals generated from a combustion product during combustion and suppress a reaction between the resin composition and oxygen.

However, the present inventors have further studied and, as a result, have newly shown that, if a resin composition containing a compound having a plurality of phenolic hydroxyl groups in the molecule is aged by heating, the tensile strength increases, and the rate of change in the tensile strength from the initial state increases.

An aspect of the present disclosure provides a resin composition that is excellent in flame retardancy while suppressing a change in tensile strength upon heat aging, and a wire and a cable formed using the resin composition.

Means for solving the problems

One embodiment of the present disclosure is a resin composition containing (a) a vinyl polymer, (B) a metal hydroxide, and (C) at least one compound of a compound in which at least one of three hydroxyl groups of gallic acid is substituted with an alkoxy group, a phenoxy group, or a silyl ether group, and a compound in which at least one of three hydroxyl groups of gallic acid is substituted with an alkoxy group, a phenoxy group, or a silyl ether group.

Effects of the invention

According to one embodiment of the present disclosure, a resin composition having excellent flame retardancy while suppressing a change in tensile strength upon heat aging, and a wire and a cable formed using the resin composition are provided.

Drawings

Fig. 1 is a cross-sectional view showing the structure of an electric wire according to a first embodiment.

Fig. 2 is a cross-sectional view showing the structure of an electric wire according to a second embodiment.

Fig. 3 is a cross-sectional view showing a structure of an example of the cable.

Description of the symbols

1: conductor, 2: insulating layer (coating layer), 2 a: insulating inner layer, 2 b: insulating outer layer (coating layer), 3, 6: a separator, 4: cable core, 4 a: three-core stranded wire, 4 b: interlayer, 5: sheath, 7: shielding braid, 10, 20: electric wire, 30: an electrical cable.

Detailed Description

The resin composition according to one embodiment of the present disclosure contains (a) a vinyl polymer, (B) a metal hydroxide, and (C) at least one compound selected from a compound in which at least one of three hydroxyl groups of gallic acid is substituted with an alkoxy group, a phenoxy group, or a silyl ether group, and a compound in which at least one of three hydroxyl groups of gallic acid is substituted with an alkoxy group, a phenoxy group, or a silyl ether group.

As described below, such a resin composition is excellent in flame retardancy and is suppressed in change in tensile strength during heat aging. Further, the elongation change during heat aging is also suppressed.

As described above, according to the studies of the present inventors, a compound having a plurality of phenolic hydroxyl groups in a molecule, such as gallic acid ester, can improve the flame retardancy of a resin composition. However, if a resin composition containing such a compound is heat-aged, the tensile strength is increased as compared with the initial state and the elongation is decreased, so that the rate of change thereof is increased. Such a case is not preferable because it is contrary to the design concept that the change in physical properties is small under heating conditions for a short time.

The reason why such a phenomenon occurs is considered to be that: the phenolic hydroxyl group captures a radical which may be generated when a coating layer of an electric wire and a sheath of a cable are manufactured, and the captured radical is emitted when heat aging is performed, thereby promoting a crosslinking reaction of a base polymer. For example, the resin composition may be crosslinked to improve the heat resistance of the wire coating layer and the cable sheath, but there is a possibility that radicals may be generated at the time of crosslinking.

The present inventors considered that, in order to achieve both the trapping of radicals during combustion and the suppression of the supply of radicals during thermal aging, it is effective to protect phenolic hydroxyl groups to temporarily reduce the reactivity of the phenolic hydroxyl groups and to restore the original hydroxyl groups during combustion. Namely, the following is considered: when oxygen in the phenolic hydroxyl group is left, only hydrogen is substituted with another structure, whereby reactivity of the phenolic hydroxyl group can be suppressed, and therefore, a change in tensile strength or the like during heat aging can be suppressed. Further, it is considered that if the substituted portion is released in a high-temperature environment during combustion and is restored to the original hydroxyl group to restore the radical trapping effect, high flame retardancy can be maintained. Therefore, the present inventors have conducted various studies on the protection of a hydroxyl group of a compound such as a gallic acid ester.

As a result, they have found that a change in tensile strength or the like upon heat aging can be suppressed while maintaining high flame retardancy by substituting at least one of the three hydroxyl groups of gallic acid or gallic acid ester with an alkoxy group, a phenoxy group, or a silyl ether group.

The resin composition, the electric wire and the cable according to one embodiment of the present disclosure will be described in detail below.

< resin composition >

The resin composition is a halogen-free flame-retardant resin composition.

The components contained in the resin composition will be described in detail below. Hereinafter, the component (B) and the component (C) may be described together as a flame retardant.

[ (A) component ]

Examples of the ethylene polymer as the component (a) include ethylene-vinyl acetate copolymers, ethylene-acrylic ester copolymers, and ethylene- α -olefin copolymers. The component (a) preferably contains an ethylene-vinyl acetate copolymer. The component (a) is preferably a base polymer of the resin composition.

[ (B) component ]

Examples of the metal hydroxide as the component (B) include magnesium hydroxide, aluminum hydroxide, hydrotalcite, boehmite, calcium hydroxide, iron (II) hydroxide, and iron (III) hydroxide. The component (B) preferably contains magnesium hydroxide.

Examples of the magnesium hydroxide include magnesium hydroxide without surface treatment and magnesium hydroxide with surface treatment. Examples of the magnesium hydroxide without surface treatment include natural magnesium hydroxide obtained by crushing brucite ore, synthetic magnesium hydroxide, and the like. Examples of the magnesium hydroxide subjected to surface treatment include magnesium hydroxide subjected to surface treatment with a silane coupling agent, a phosphate, a fatty acid (e.g., stearic acid, oleic acid, etc.), or a fatty acid salt.

The magnesium hydroxide is preferably surface-treated with a silane coupling agent. Since the magnesium hydroxide surface-treated with the silane coupling agent has high affinity with the component (a), the tensile properties of the resin composition are improved.

The content of the component (B) in the resin composition is preferably 50 to 300 parts by mass, more preferably 100 to 250 parts by mass, relative to 100 parts by mass of the component (a). (B) When the content of the component (A) is 50 parts by mass or more based on 100 parts by mass of the component (A), higher flame retardancy can be obtained in the resulting electric wire, cable or the like. When the content of the component (B) is 300 parts by mass or less based on 100 parts by mass of the component (a), the adhesion and aggregation of the metal hydroxide particles are suppressed, and the fluidity of the resin composition is hardly lowered, so that the processability of the resin composition, for example, the processability in extrusion molding, is good.

[ (C) ingredient ]

(C) The compound of component (A) is at least one compound of gallic acid having at least one of its three hydroxyl groups substituted by alkoxy, phenoxy or silyl ether group, and gallic acid ester having at least one of its three hydroxyl groups substituted by alkoxy, phenoxy or silyl ether group. The gallic acid is a compound represented by the following formula (1).

[ solution 1]

The carboxylic acid group in gallic acid may remain in a carboxylic acid structure or may be esterified as long as the hydroxyl group side is protected. The ester is preferably an alkyl ester having a small carbon number, for example, a lower alkyl ester having 1 to 4 carbon atoms. The gallic acid ester is particularly preferably at least one selected from methyl gallate represented by the following formula (2) and propyl gallate represented by the following formula (3).

[ solution 2]

[ solution 3]

(C) In the compound of component (a), at least one of the three hydroxyl groups may be substituted. The position of the substituent may be any of 3,4 and 5 positions. From the viewpoint of further suppressing the supply of radicals upon heat aging, it is preferable that a plurality of (i.e., two or three) hydroxyl groups are substituted, and it is more preferable that all hydroxyl groups are substituted. It is not known why the effect of inhibiting radicals from being supplied during heat aging is exhibited even if not all hydroxyl groups are protected, and the inventors of the present invention believe that the reason is that the radical trapping ability is decreased due to steric hindrance.

The alkoxy group as a substituent is preferably an alkoxy group having 1 to 4 carbon atoms such as a methoxy group, an ethoxy group, or a butoxy group, and more preferably a methoxy group from the viewpoint of availability. Examples of the alkoxy-substituted compound include 3,4, 5-trimethoxybenzoic acid (also known as eucalyptol acid) and alkyl esters thereof, and 3, 5-dimethoxy-4-hydroxybenzoic acid (also known as syringic acid) and alkyl esters thereof. Examples of the alkyl ester of eucalyptol include alkyl esters having 1 to 4 carbon atoms such as methyl eucalyptol and propyl eucalyptol. Examples of the alkyl ester of syringic acid include alkyl esters having 1 to 4 carbon atoms such as methyl syringate.

The compound substituted with an alkoxy group is preferably eucalyptol acid and alkyl esters thereof, and more preferably eucalyptol acid, from the viewpoint of further suppressing the supply of radicals upon heat aging.

Examples of the compound substituted with a phenoxy group include 3,4, 5-triphenoxybenzoic acid and alkyl esters thereof, 4-phenoxy-3, 5-dihydroxybenzoic acid and alkyl esters thereof, 3-phenoxy-4, 5-dihydroxybenzoic acid and alkyl esters thereof, and 3, 4-diphenoxy-5-dihydroxybenzoic acid and alkyl esters thereof. In this case, the alkyl ester is preferably an alkyl ester having 1 to 4 carbon atoms.

Examples of the silyl ether group as a substituent include a trialkylsilyloxy group having 1 to 4 carbon atoms such as a trimethylsilyloxy group, a triethylsilyloxy group, or a tri-tert-butylsilyloxy group. The silyl ether group is easily deprotected during combustion, and more preferably trimethylsilyloxy.

The silyl ether group can be introduced into a compound by silyl etherification of a hydroxyl group with a silane compound. Examples of the silane compound used for the silyl etherification include chlorosilane compounds such as trimethylchlorosilane, triethylchlorosilane and tri-t-butylchlorosilane. The protection of the silyl ether group can be easily achieved by, for example, adding a chlorosilane compound dropwise to a solution in which gallic acid or gallic acid ester is dissolved together with a base to carry out the reaction.

When an ethylene-vinyl acetate copolymer is used as the vinyl polymer of the component (a), the substituent is preferably a silyl ether group. In an environment which becomes acidic due to elimination of acetic acid during combustion, the silyl ether group rapidly deprotects the compound, and the compound is rapidly restored to the original gallic acid or gallic acid ester, so that the flame retardancy can be easily maintained.

Examples of the compound substituted with a silyl ether group include 3,4, 5-tris (trimethylsilyloxy) benzoic acid and its alkyl ester, 3, 5-bis (trimethylsilyloxy) -4-hydroxybenzoic acid and its alkyl ester, 3-trimethylsilyloxy-4, 5-dihydroxybenzoic acid and its alkyl ester, and 3,4, 5-tris (tri-t-butylsilyloxy) benzoic acid and its alkyl ester. Examples of the alkyl ester of 3,4, 5-tris (trimethylsilyloxy) benzoic acid include an alkyl ester having 1 to 4 carbon atoms such as

propyl

3,4, 5-tris (trimethylsilyloxy) benzoate. Examples of the alkyl ester of 3, 5-bis (trimethylsilyloxy) -4-hydroxybenzoic acid include alkyl esters having 1 to 4 carbon atoms such as propyl 3, 5-bis (trimethylsilyloxy) -4-hydroxybenzoate. Examples of the alkyl ester of 3-trimethylsilyloxy-4, 5-dihydroxybenzoic acid include alkyl esters having 1 to 4 carbon atoms, such as propyl 3- (trimethylsilyloxy) -4, 5-dihydroxybenzoate. Examples of the alkyl ester of 3,4, 5-tris (tri-tert-butylsilyloxy) benzoic acid include an alkyl ester having 1 to 4 carbon atoms such as

propyl

3,4, 5-tris (tri-tert-butylsilyloxy) benzoate.

Among the alkoxy group, phenoxy group and silyl ether group, the alkoxy group and silyl ether group are preferable, and the alkoxy group is more preferable, from the viewpoint of further suppressing the supply of radicals upon heat aging.

The content of the component (C) is preferably 1 to 50 parts by mass, more preferably 2 to 30 parts by mass, relative to 100 parts by mass of the component (a). (C) The content of the component (A) is 1 part by mass or more based on 100 parts by mass of the component (A), and thus a high flame retardancy can be obtained in the obtained electric wire, cable or the like. When the content of the component (C) is 50 parts by mass or less based on 100 parts by mass of the component (a), the tensile strength of the resin composition is improved.

[ other ingredients ]

In addition to the above components, the resin composition may contain other components as necessary within a range not affecting the above characteristics. Examples of the other components include flame retardants, flame retardant aids, crosslinking agents, crosslinking aids, processing aids, coupling agents, surface treatment agents, colorants, lubricants, compatibilizing agents, antioxidants, ozone inhibitors, ultraviolet absorbers, light stabilizers, metal chelating agents, softeners, and plasticizers other than the above-mentioned components.

< electric wire >

[ first embodiment ]

The electric wire 10 shown in fig. 1 is a halogen-free flame-retardant insulated electric wire according to the first embodiment. The electric wire 10 includes a conductor 1, an insulating layer 2 as a coating layer for covering the conductor 1, and a separator 3 provided between the conductor 1 and the insulating layer 2.

As the conductor 1, a commonly used metal wire, such as a copper wire, a copper alloy wire, an aluminum wire, a gold wire, a silver wire, or the like, can be used. As the conductor 1, a conductor plated with a metal such as tin or nickel around a metal wire can be used. As the conductor 1, a stranded wire obtained by stranding metal wires may be used. As the stranded wire, a concentric stranded wire, an aggregate stranded wire, a composite stranded wire obtained by concentrically twisting these, or the like can be used. As the conductor 1, a compressed conductor obtained by compressing a stranded wire may be used. The compressed conductor enables the wire diameter to be smaller, and is therefore preferable.

The insulating layer 2 is formed of the resin composition. The thickness of the insulating layer 2 is not particularly limited, but is preferably 0.15mm to 2 mm.

The separator 3 is formed of, for example, a polyester tape. By providing the separator 3, when a stranded conductor is used as the conductor 1, it is possible to suppress the resin composition from penetrating into the conductor 1 when the resin composition is extruded, that is, when the insulating layer 2 is formed. Note that the electric wire 10 may not have the separator 3.

The electric wire 10 can be manufactured, for example, as follows.

First, a resin composition is obtained by melt-kneading materials containing the above components (a) to (C) and other components. As the kneading apparatus, for example, a known kneading apparatus such as a batch kneader such as a banbury mixer and a pressure kneader, a continuous kneader such as a twin-screw extruder, and the like can be used.

Then, a conductor 1 is prepared, and a separator 3 is wound around the conductor 1. Then, the periphery of the separator 3 is covered with the resin composition by an extrusion molding machine. This enables the insulating layer 2 to be formed to a predetermined thickness.

Then, the insulating layer 2 is subjected to crosslinking treatment by, for example, electron beam crosslinking, chemical crosslinking, or the like. The crosslinking treatment is not essential, but the crosslinking treatment is preferably performed on the insulating layer 2 because the heat resistance of the insulating layer 2 is improved by performing the crosslinking treatment on the insulating layer 2. When the electron beam cross-linking method is used, the insulating layer 2 is irradiated with, for example, an electron beam of 1Mrad to 30Mrad (0.01MGy to 0.3 MGy). In the case of using the chemical crosslinking method, for example, a crosslinking agent is added to the resin composition in advance, and after the resin composition is molded as the insulating layer 2 of the electric wire 10, the insulating layer 2 is heat-treated. In the following examples, electron beam crosslinking is used.

[ second embodiment ]

The electric wire 20 shown in fig. 2 is a halogen-free flame-retardant insulated electric wire according to a second embodiment. The electric wire 20 is different from the electric wire 10 according to the first embodiment in that the insulating layer 2 is formed of two layers and in that the separator 3 is not provided. Specifically, the electric wire 20 includes a conductor 1, an insulating inner layer 2a provided around the conductor 1, and an insulating outer layer 2b provided around the insulating inner layer 2 a. The insulating inner layer 2a is formed of an insulating resin such as polyethylene. The insulating outer layer 2b is formed of the above resin composition. The insulating outer layer 2b corresponds to a coating layer. The wire 20 may be provided with the separator 3 in the same manner as the wire 10. Further, the insulating layer 2 may be 3 or more layers.

< Cable >

The cable 30 shown in fig. 3 is a halogen-free flame retardant cable. The cable 30 includes a cable core 4, a sheath 5 as a coating layer for coating the cable core 4, and a separator 6 and a shield braid 7 provided between the cable core 4 and the sheath 5.

The cable core 4 has a three-core stranded wire 4a formed by twisting 3 wires 10 and an interlayer 4b provided around the three-core stranded wire 4 a. The interlayer 4b is made of rayon, paper tape, jute, or the like. It should be noted that the cable core 4 may not have the interlayer 4 b.

The sheath 5 is formed of the resin composition. The separator 6 is the same as the separator 3 in the electric wire 10. The shielding braid 7 is provided around the separator 6, and has an electrical shielding function. The shield braid 7 is formed of, for example, a metal tape, a copper wire, or the like braided in a mesh shape. The shielding braid 7 may be provided inside the separator 6, and the cable 30 may not include the shielding braid 7.

The cable 30 can be manufactured, for example, as follows.

First, 3 wires 10 were manufactured by the same method as described above. Then, 3 wires 10 are twisted together with the interlayer 4b to form a cable core 4, and the separator 6 and the shielding braid 7 are provided around the cable core 4. Then, the periphery thereof was covered with the resin composition by an extrusion molding machine. This enables the sheath 5 to be formed to have a predetermined thickness.

Then, the sheath 5 is subjected to crosslinking treatment as needed in the same manner as described above. Thereby enabling the cable 30 to be manufactured. Note that other electric wires may be used instead of the electric wire 10. Instead of the three-core stranded wire 4a, a single core made of 1 wire may be used, or a multi-core stranded wire other than the three-core stranded wire may be used. Further, other layers, such as other insulating layers, may also be provided between the cable core 4 and the sheath 5.

< other uses of the resin composition >

The resin composition can be used for electric wires and cables of various applications and sizes. For example, the use of electric wires and cables includes electronic equipment use, railway vehicle use, automobile use, in-tray wiring use, in-machine wiring use, in-building wiring use, and the like. Particularly high flame retardancy is required for electric wires and cables used for electronic equipment or railway vehicles, and therefore the resin composition can be suitably used for electric wires and cables for electronic equipment or railway vehicles. The type of cable is not particularly limited, and may be, for example, a power cable, a signal cable, or the like.

Further, the above resin composition can be used not only for the above electric wire and cable but also for other uses. For example, the resin composition can be used for films, panels, mats, pipes, protective materials, fillers, fibers, resin molded articles, resin substrates, stationery, building materials, connectors, bushings, grommets, terminal blocks, terminal internal insulators, and the like.

Examples

One embodiment of the present disclosure will be described below with reference to examples, but the present disclosure is not limited to the following examples.

< production of resin composition for Cable sheath >

The respective materials of examples 1 to 8 and comparative examples 1 to 4 shown in table 1 below were dry-blended at room temperature, and the blended materials were melt-kneaded by a pressure kneader at a take-out temperature of 190 ℃. The unit of the content of each material in table 1 is part by mass.

In the resin compositions according to examples 1, 2, 6 to 8, (C1) cineole represented by the following formula (4) was used as the component (C). The resin compositions according to examples 1, 2, 6 to 8 were different in the content of (C1) cineole.

[ solution 4]

In the resin composition according to example 3, as the component (C), methyl syringate (C2) represented by the following formula (5) was used.

[ solution 5]

In the resin composition according to example 4, (C3) propyl gallate 1 (

propyl

3,4, 5-tris (trimethylsilyloxy) benzoate represented by the following formula (6)) was used as the component (C). Silyl-protected propyl gallate 1 was synthesized as follows. Propyl gallate was dissolved in acetone, 5 equivalents of triethylamine were added to 1 equivalent of hydroxyl groups of propyl gallate, and 5 equivalents of trimethylchlorosilane were added to 1 equivalent of hydroxyl groups of propyl gallate, and the mixture was reacted. Then, acetone and triethylamine were removed to obtain silyl-protected propyl gallate 1. It was confirmed that the original hydroxyl group in the obtained silyl-protected propyl gallate 1 was protected by using FT-IR.

[ solution 6]

In the resin composition according to example 5, (C4) propyl gallate 2 (

propyl

3,4, 5-tris (tri-t-butylsilyloxy) benzoate represented by the following formula (7)) was used as the component (C). Silyl-protected propyl gallate 2 was synthesized in the same manner as silyl-protected propyl gallate 1, using tri-tert-butylchlorosilane instead of trimethylchlorosilane.

[ solution 7]

Unlike the resin compositions of examples 1 to 8, the resin composition of comparative example 1 did not contain the component (C). In the resin compositions according to comparative examples 2 to 4, propyl gallate, the hydroxyl group of which is not protected at all, was used in place of the component (C).

< manufacture of Cable >

Extrusion molding was carried out using a 20mm single-screw extruder "Labo Plastomill (registered trademark)" manufactured by Toyo Seiki Seisaku-sho Ltd., as an extrusion coating apparatus for manufacturing an electric wire, so as to have a cross-sectional area of 0.5mm ² An insulating layer with a coating thickness of 0.2mm is formed around the compressed tin-plated copper stranded wire. The insulating layer was formed using a resin composition produced by melt-kneading the respective materials of comparative example 1 shown in table 1 in the same manner as the above-described resin composition for a sheath. The cylinder temperature was 160 ℃ and the wire drawing speed was 4.0 m/min. Then, the insulation layer of the produced electric wire was subjected to a crosslinking treatment by an electron beam crosslinking method under a condition of 7.5Mrad, thereby crosslinking the resin composition constituting the insulation layer.

The 3 wires obtained were twisted and wound with a polyester tape as a separator, and then a shield braid was provided around the wound tape. Then, a sheath made of the resin composition for sheaths according to examples 1 to 8 and comparative examples 1 to 4 was formed around the shield braid by extrusion molding using a 60mm single screw extruder so as to have a coating thickness of 0.45 mm. Then, the sheath was crosslinked by electron beam crosslinking under a condition of 7.5Mrad, thereby producing a cable having an outer diameter of 4.5 mm.

[ Table 1]

< evaluation method >

(1) Initial tensile test

The sheath was peeled off from the cable thus produced, and the dumbbell test piece was punched from the peeled sheath. Tensile tests were carried out using dumbbell test pieces in accordance with JIS C3005:2000, and the tensile strength and elongation were measured. Wherein the tensile test is carried out at a tensile rate of 250 mm/min.

(2) Heat aging test

The dumbbell test piece prepared in the same manner as in the initial tensile test of (1) was heated at 135 ℃ for 168 hours in a Gill oven. Then, using the heat-aged dumbbell test pieces, tensile tests were performed in the same manner as the initial tensile test, and the tensile strength and elongation were measured. For the tensile strength and elongation after heat aging, the rate of change from that before heat aging (i.e., at the time of the initial tensile test) was calculated.

(3) Cable burning test

The prepared cable was measured for 600mm in length and used as a test sample. A burning test was carried out in accordance with IEC60332-1 using the test specimen, and the distance from the upper support member to the burned portion was measured. The longer the distance from the upper support member to the burned portion, the shorter the burning distance, and the higher the flame retardancy. When the test specimen was completely burned, the distance from the upper support member to the burned portion was 0 mm.

(4) Comprehensive judgment

Regarding the tensile strength in the initial tensile test, a sample of 8MPa or more was judged as passed, and a sample of less than 8MPa was judged as failed. Regarding the elongation in the initial tensile test, a sample of 125% or more was judged as passed, and a sample of less than 125% was judged as failed.

Regarding the change rates of tensile strength and elongation in the heat aging test, samples having a tensile strength of. + -. 30% or less were judged as passed, and samples having a tensile strength of more than. + -. 30% were judged as failed. In the combustion test, a sample having a distance from the upper support member to the burned portion of 50mm or more was judged as a pass sample, and a sample having a distance of less than 50mm was judged as a fail sample, as in IEC 60332-1.

All samples that passed the tensile strength and elongation in the final initial tensile test, the change rate in the tensile strength and elongation in the heat aging test, and the combustion test were regarded as passed, and samples that failed any of these were regarded as failed. The evaluation results are shown in table 1. In Table 1, the acceptable samples are represented by good, and the unacceptable samples are represented by X.

< evaluation result >

As shown in Table 1, examples 1 to 8 were acceptable in all of the items of the initial tensile test, the heat aging test and the burning test.

On the other hand, comparative example 1 containing no component (C) failed in the burning test. In addition, comparative examples 2 to 3, which contained propyl gallate, the hydroxyl groups of which were not protected at all, instead of component (C), passed the initial tensile test and the burning test, but failed the heat aging test. In addition, comparative example 4 containing only a small amount of propyl gallate failed in the burning test, in addition to failing in the heat aging test.

< investigation >)

As shown in comparative examples 1 to 4, it is considered that the combination of gallic acid ester with the resin composition causes the composition to be compatible with each other in the burning test. However, as shown in comparative examples 2 to 4, the hydroxy group of the gallic acid ester was not protected, and thus the gallic acid ester failed the heat aging test.

It is considered that the gallic acid ester exerts the same flame retardancy effect as the component (C) by comparing the example 1 and the comparative example 2. That is, it is considered that whether or not the hydroxyl group of the gallic acid ester is protected has almost no influence on the flame retardancy. This indicates the possibility of substituent detachment upon combustion.

Further, in comparison of examples 1, 2, 6 and 7 with example 8, it is considered that the resin composition preferably contains the component (C) in an amount of 2 parts by mass or more and 30 parts by mass or less based on 100 parts by mass of the total amount of the component (a) from the viewpoint of improvement in tensile strength in the initial tensile test.

Claims

1. A resin composition comprising:

(A) a vinyl-based polymer,

(B) a metal hydroxide, and

(C) at least one compound selected from the group consisting of a compound in which at least one of the three hydroxyl groups of gallic acid is substituted with an alkoxy group, a phenoxy group, or a silyl ether group, and a compound in which at least one of the three hydroxyl groups of gallic acid ester is substituted with an alkoxy group, a phenoxy group, or a silyl ether group.

2. The resin composition according to claim 1, wherein,

the component (C) contains at least one compound selected from a compound in which at least one of the three hydroxyl groups of gallic acid is substituted with an alkoxy group or a silyl ether group, and a compound in which at least one of the three hydroxyl groups of gallic acid ester is substituted with an alkoxy group or a silyl ether group.

3. The resin composition according to claim 1 or 2, wherein,

the component (C) contains at least one compound selected from a compound in which at least one of the three hydroxyl groups of gallic acid is substituted by an alkoxy group and a compound in which at least one of the three hydroxyl groups of gallic acid ester is substituted by an alkoxy group.

4. The resin composition according to any one of claims 1 to 3, wherein,

the component (C) contains at least one compound selected from a compound in which two or three of the three hydroxyl groups of gallic acid are substituted with alkoxy groups and a compound in which two or three of the three hydroxyl groups of gallic acid ester are substituted with alkoxy groups.

5. The resin composition according to any one of claims 1 to 4,

the component (C) contains 3,4, 5-trimethoxybenzoic acid, i.e. at least one of eucalyptol acid and alkyl ester thereof.

6. The resin composition according to any one of claims 1 to 5, wherein,

the resin composition contains the component (C) in an amount of 2 to 30 parts by mass based on 100 parts by mass of the component (A).

7. A kind of electric wire is disclosed, which is composed of a wire core,

comprises a conductor and a coating layer for covering the conductor,

the coating layer is formed of the resin composition according to any one of claims 1 to 6.

8. A cable comprising a sheath made of the resin composition according to any one of claims 1 to 6.