JP2008305569A - Halogen-free fire-retardant cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a halogen-free fire retardant cable having characteristics superior in both flexibility and voltage resistance by optimizing a resin blending of an electric insulator consisting of an inner layer and an outer layer. <P>SOLUTION: This is the halogen-free fire retardant cable in which the outer circumference part of an electric conductor 2 is insulated by an electric insulator 5 consisting of two layers of an inner layer 3 and an outer layer 2. The inner layer 3 has a maleic anhydride denatured ethylene-ethyl-acrylate copolymer (maleic anhydride denaturation rate 25%) 5-40 pts.wt. against an ethylene vinyl acetate copolymer having vinyl acetate content of 60% or more and 80% or less 100 pts.wt. and a metal hydroxide added, and the outer layer 4 has a metal hydroxide added to an ethylene vinyl acetate copolymer of vinyl acetate content of 30% or more and less than 60%. Furthermore, the thickness of the outer layer 4 is formed thinner than that of the inner layer 3. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a halogen-free flame-retardant electric wire having flexibility and withstand voltage, using a halogen-free insulating resin composition used for internal wiring or the like of electrical equipment.

  In recent years, in order to cope with environmental problems, halogen-free flame-retardant resin compositions that do not generate harmful halogen gas such as dioxin at the time of combustion have been developed and used as insulating coating materials for electric wires and cables. Examples of the halogen-free flame retardant resin composition include copolymers such as ethylene vinyl acetate copolymer (EVA) and maleic anhydride modified ethylene ethyl acrylate copolymer (maleic anhydride modified EEA), and metal water as a flame retardant. The thing which mixed the oxide is known (for example, refer to patent documents 1).

  On the other hand, if the amount of the flame retardant mixed is increased in order to improve the flame retardancy, the mechanical properties and the electrical properties are lowered. Therefore, the insulating layer of the electric wire can be formed of two layers, an inner layer and an outer layer. Are known. However, even if 300 parts by weight of magnesium hydroxide is added to 100 parts by weight of polyolefin in order to make the outer layer more flame retardant, the layer thickness of the electrical insulator is increased in order to ensure mechanical and electrical characteristics. Then, polyolefin is fluidized at the time of combustion, and this is gasified and burned.

On the other hand, for example, in the technique disclosed in Patent Document 2, an ethylene ethyl acrylate copolymer (EEA) having an ethyl acrylate (EA) content of 9 to 35% by weight is used alone or as an inner layer of an electrical insulator. What contains 50-150 weight part of flame retardants, such as magnesium hydroxide, is used with respect to 100 weight part of base resin which mixed other polyolefin resin. As the outer layer of the electrical insulator, EEA having an EA content of 15 to 35% by weight or an ethylene vinyl acetate copolymer (EVA) having a vinyl acetate (VA) content of 15 to 45% by weight alone or other polyolefin What contains 150-300 weight part of flame retardants, such as magnesium hydroxide, is used with respect to 100 weight part of base resin which mixed the system resin.
JP 2003-160709 A JP 2006-286529 A

Although a halogen-free flame-retardant electric wire having flexibility and withstand voltage may be required, the addition of maleic anhydride-modified EEA to the base resin EVA lowers the elongation of the electrical insulator. That is, the flexibility as an insulated wire is lowered and hardened. On the other hand, by adding maleic anhydride-modified EEA to the base resin EVA, moisture absorption of the electrical insulator can be suppressed, and the withstand voltage of the insulated wire can be improved.
Moreover, if the VA content of EVA as the base resin is increased, it can be made flexible. However, when the VA content of EVA is increased, there is a problem in that when the insulated wire is wound, the wires stick to each other, the tensile strength is lowered, and the wire is easily broken.

  The present invention has been made in view of the above-described circumstances, and has an excellent characteristic in both flexibility and withstand voltage by optimizing the resin composition of the electric insulator composed of two layers of the inner layer and the outer layer. The purpose is to provide a halogen-free flame-retardant electric wire.

  The halogen-free flame-retardant electric wire according to the present invention is a halogen-free flame-retardant electric wire in which the outer periphery of an electric conductor is insulated with an electric insulator composed of two layers, an inner layer and an outer layer. The inner layer is a maleic anhydride modified ethylene ethyl acrylate copolymer (maleic anhydride modified rate of 25%) with respect to 100 parts by weight of ethylene vinyl acetate copolymer having a vinyl acetate content of 60% to 80% 5 ~ 40 parts by weight and a metal hydroxide are added, and the outer layer is characterized in that a metal hydroxide is added to an ethylene vinyl acetate copolymer having a vinyl acetate content of 30% to less than 60%. . In addition, it is desirable to form the outer layer thinner than the inner layer.

  According to the present invention, flexibility is ensured by increasing the vinyl acetate content of the ethylene vinyl acetate copolymer that is the base resin of the inner layer, and a terpolymer of polyethylene, maleic anhydride, and ethyl acrylate is added. Thus, the withstand voltage can be increased. In addition, by lowering the vinyl acetate content of the outer layer base resin ethylene vinyl acetate copolymer, the surface of the electrical insulator can be hardened to prevent the wires from adhering to each other and increase the tensile strength of the wires. And a halogen-free flame-retardant electric wire having both flexibility and withstand voltage.

  As shown in FIG. 1, the halogen-free flame-retardant electric wire 1 according to the present invention is intended for an electric wire or cable in which an outer side of an electric conductor 2 is covered with an electric insulator 5 composed of an inner layer 3 and an outer layer 4. The electrical conductor 2 is, for example, a tinned single-core annealed copper wire or a seven-strand annealed annealed copper wire having a circular cross section. Both the inner layer 3 and the outer layer 4 of the electrical insulator 5 are made of a polyolefin resin ethylene vinyl acetate copolymer (EVA) as a base resin, and a halogen-free flame retardant in which a metal hydroxide is added as a flame retardant. Resin is used.

  EVA used as a base resin has oxygen in the molecule, and therefore has high flame retardancy by itself and high affinity with metal hydroxide. Note that EVA is a thermoplastic resin obtained by copolymerizing ethylene and vinyl acetate (VA). However, as the content of VA increases, flexibility increases and rubber-like properties are exhibited. Those having a low VA content exhibit properties close to that of low-density polyethylene, but are tougher and have higher tensile strength. Therefore, in order to obtain the flexibility of the electric wire, if the electric insulator 5 is made of EVA having a large content of VA, the electric wire surface becomes sticky and the contact portions of the electric wire are likely to stick to each other, making it difficult to handle.

  In the present invention, the VA content in EVA of the inner layer 3 of the electrical insulator 5 is increased so that flexibility as an electric wire that can be easily wired in the device can be obtained, and the VA content of EVA in the outer layer 4 is obtained. And the surface of the electrical insulator 5 is hardened. Specifically, it is desirable that the inner layer 3 has a VA content of 60% or more and 80% or less to provide flexibility, and the outer layer 4 has a VA content of less than 60% and 30% or more and is hard. Thereby, the outer surface of the electrical insulator 5 is not sticky, the tensile strength can be secured to some extent, and the winding of the electric wire and the handling in the wiring can be facilitated.

  Further, maleic anhydride-modified ethylene ethyl acrylate copolymer (EEA) is added to EVA of the inner layer 3. This maleic anhydride-modified EEA increases heat resistance and mechanical strength, but decreases elongation. However, maleic anhydride-modified EEA has an action of suppressing the swelling of the electrical insulator with water. Therefore, the withstand voltage characteristic of the electrical insulator can be improved by adding this. In addition, EEA which is not modified with maleic anhydride does not have a swelling suppressing effect and does not have an ionic bond between acidic groups. Therefore, the bond with EVA is lowered and the required breaking strength cannot be obtained.

  Specifically, the maleic anhydride-modified EEA has a modification rate of 1 to 40%, and about 5 to 40 parts by weight, preferably 15 to 35 parts by weight is added to 100 parts by weight of EVA. If the amount is less than 5 parts by weight, the moisture absorption suppressing effect cannot be expected so much. If the amount exceeds 40 parts by weight, the amount of crystal components increases, resulting in poor flexibility and flexibility.

  In order to ensure the flexibility of the electric wire, it is desirable to make the thickness of the outer layer 4, which is less flexible than the inner layer 3, smaller than the thickness of the inner layer 3. The total thickness of the electrical insulator 5 varies depending on the required withstand voltage, the thickness of the electrical conductor, and the like. For example, the rated voltage is 6 kV (AC), and the electrical conductor thickness to be used is AWG 20 to 30 (diameter 0). .81 mm to 0.25 mm), the thickness of the inner layer 3 is 0.4 mm to 0.5 mm, the thickness of the outer layer 4 is 0.1 mm to 0.2 mm, and the total thickness of the inner layer and the outer layer is 0. It is desirable to set it as 0.5 mm-0.7 mm. If the thickness of the electrical insulator 5 is made too thick, it is difficult to bend and the flexibility is lowered and the handleability is deteriorated, so that a large wiring space is required in the device and the device is enlarged.

  Further, a metal hydroxide is added to each of the inner layer 3 and the outer layer 4 of the electrical insulator 5 as a flame retardant, as in the conventional case. As the metal hydroxide, for example, magnesium hydroxide, aluminum hydroxide, calcium hydroxide and the like are used. Among them, magnesium hydroxide is preferable because of its high flame retardant effect. In addition, these metal hydroxides have titanate coupling agents, silane coupling agents such as vinyl silane, epoxy silane, amino silane, and methacryl silane, stearic acid, oleic acid, lauric acid, in order to increase the affinity with the base resin. You may make it use what surface-treated using higher fatty acids, such as.

  The flame retardant composed of the metal hydroxide is added in an amount of 50 to 200 parts by weight with respect to 100 parts by weight of the base resin of the inner layer 3 and the outer layer 4 of the electrical insulator. The specific addition amount is determined according to the required flame retardance, but if it is less than 50 parts by weight, the flame retardancy is insufficient, and if it exceeds 200 parts by weight, the breaking strength and elongation of the electrical insulator are reduced. .

  In addition, in any of the inner layer 3 and the outer layer 4 of the electrical insulator 5 made of the above halogen-free flame retardant composition, the resin is weakened by thermal oxidation with respect to 100 parts by weight of the base resin as necessary. An antioxidant that suppresses 0.1 to 5.0 parts by weight can be added. In addition to these, various auxiliary agents such as a processing aid, a colorant, and a stabilizer that improve the moldability of the electrical insulator 5 can be added.

The halogen-free flame-retardant electric wire 1 in the present invention conforms to UL standard 758 (US standard) and satisfies the following results.
(1) About flame retardance, it has passed UL VW-1.
(2) Regarding flexibility (elongation), the breaking elongation of the electrical insulator (tube) remaining after pulling out the electrical conductor from the electric wire is 150% or more.
(3) Regarding the tensile strength, the breaking strength of the electric insulator (tube) is 10.3 MPa or more.
(4) Withstand voltage (when the rated voltage is AC 6 kV), apply a voltage of 13 kV for 1 minute between the water and the wire after putting the bundle of wires on the water for 24 hours (leave the end out). No voltage breakdown.

Example 1
・ Electric conductor: Tin-plated annealed copper wire (AWG24 conductor configuration 7 / 0.203 outer diameter 0.61 mm)
・ Electric insulator (inner layer): EVA with 70% VA content 100 parts by weight
Maleic anhydride modified EEA (modification rate 25%) 20 parts by weight
180 parts by weight of magnesium hydroxide
2 parts by weight of antioxidant
Layer thickness 0.42mm
-Electrical insulator (outer layer): EVA 100% by weight with 50% VA content
180 parts by weight of magnesium hydroxide
2 parts by weight of antioxidant
Layer thickness 0.13mm

  The wire of Example 1 clears the predetermined flame retardancy standard (UL VW-1), withstand voltage of 13 kV (1 minute), elongation of 170%, tensile strength of 11.5 MPa, predetermined Results satisfying the values were obtained.

(Example 2: the inner layer and the outer layer have the same thickness)
・ Electric conductor: Tin-plated annealed copper wire (AWG24 conductor configuration 7 / 0.203 outer diameter 0.61 mm)
・ Electric insulator (inner layer): EVA with 70% VA content 100 parts by weight
Maleic anhydride modified EEA (modification rate 25%) 20 parts by weight
180 parts by weight of magnesium hydroxide
2 parts by weight of antioxidant
Layer thickness 0.27mm
-Electrical insulator (outer layer): EVA 100% by weight with 50% VA content
180 parts by weight of magnesium hydroxide
2 parts by weight of antioxidant
Layer thickness 0.27mm

  The electric wire of the above Example 2 is an example in which the thickness of the inner layer and the outer layer in Example 1 is the same, clears a predetermined flame retardant standard (UL VW-1), and has a withstand voltage of 13 kV (1 minute) The elongation was 150%, the tensile strength was 10.5 MPa, and a result satisfying the predetermined value was obtained. However, the elongation and tensile strength were somewhat inferior to those of Example 1.

(Comparative Example 1: Maleic anhydride-modified EEA was not added to the inner layer)
・ Electric conductor: Tin-plated annealed copper wire (AWG24 conductor configuration 7 / 0.203 outer diameter 0.61 mm)
・ Electric insulator (inner layer): EVA with 70% VA content 100 parts by weight
180 parts by weight of magnesium hydroxide
2 parts by weight of antioxidant
Layer thickness 0.42mm
-Electrical insulator (outer layer): EVA 100% by weight with 50% VA content
180 parts by weight of magnesium hydroxide
2 parts by weight of antioxidant
Layer thickness 0.13mm

(Comparative Example 2: EEA of the inner layer is not modified with maleic anhydride)
・ Electric conductor: Tin-plated annealed copper wire (AWG24 conductor configuration 7 / 0.203 outer diameter 0.61 mm)
・ Electric insulator (inner layer): EVA with 70% VA content 100 parts by weight
20 parts by weight of EEA
180 parts by weight of magnesium hydroxide
2 parts by weight of antioxidant
Layer thickness 0.42mm
-Electrical insulator (outer layer): EVA 100% by weight with 50% VA content
180 parts by weight of magnesium hydroxide
2 parts by weight of antioxidant
Layer thickness 0.13mm

  Comparative Example 1 is an example in which the maleic anhydride-modified EEA (20 parts by weight) of the inner layer in Example 1 was not added. The flexibility and tensile strength were cleared, but the withstand voltage could not be satisfied. . Comparative Example 2 is an example in which maleic anhydride-modified EEA of the inner layer in Example 1 is added with simple EEA that is not modified with maleic anhydride. Like Comparative Example 1, the specified values for flexibility and tensile strength are cleared. However, the withstand voltage could not be satisfied.

From the above test results, by increasing the VA content of FVA which is the base resin of the inner layer, the flexibility of the halogen-free flame-retardant electric wire is ensured, and the maleic anhydride-modified ethylene ethyl acrylate copolymer is added. Withstand voltage can be increased. And by lowering the VA content of EVA, which is the base resin of the outer layer, the surface of the halogen-free flame-retardant electric wire is hardened to prevent the wires from adhering to each other, and the elongation and tensile strength of the electrical insulator are increased. The halogen-free flame-retardant electric wire having both flexibility and withstand voltage can be obtained.
Moreover, the above-mentioned effect can be further enhanced by making the thickness of the outer layer of the electrical insulator thinner than the thickness of the inner layer.

It is a figure explaining the outline of the halogen-free flame-retardant electric wire by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Halogen-free flame-retardant electric wire, 2 ... Electrical conductor, 3 ... Electrical insulator (inner layer), 3 ... Electrical insulator (outer layer), 5 ... Electrical insulator.

Claims (2)

A halogen-free flame-retardant electric wire in which the outer peripheral portion of the electric conductor is insulated with an electric insulator composed of two layers, an inner layer and an outer layer,
The inner layer is a maleic anhydride-modified ethylene ethyl acrylate copolymer (maleic anhydride modification rate 25%) 5-40 wt with respect to 100 parts by weight of ethylene vinyl acetate copolymer having a vinyl acetate content of 60-80%. Part and metal hydroxide are added,
The halogen-free flame-retardant electric wire according to claim 1, wherein the outer layer has a metal hydroxide added to an ethylene vinyl acetate copolymer having a vinyl acetate content of 30 to less than 60%.   The halogen-free flame-retardant electric wire according to claim 1, wherein the outer layer is thinner than the inner layer.

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