JP4174165B2 - Flame retardant wire - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to a flame-retardant electric wire, and more particularly to a flame-retardant electric wire that is suitably used for a power supply wire of a road vehicle using an internal combustion engine.
[0002]
[Prior art]
Cross-linked polyethylene resins obtained by cross-linking polyethylene, ethylene copolymers, or mixtures thereof are superior in heat resistance compared to vinyl chloride resins and do not have the problem of generation of harmful halogen-based gases during combustion as seen in vinyl chloride resins. For this reason, it is widely used as an electrically insulating resin material such as electric wires and cables. As an electric wire using such a crosslinked polyethylene resin as an electrically insulating resin material, for example, JP-A-10-106354 discloses that 90% or less of low-density polyethylene (hereinafter abbreviated as LDPE) and the remaining ethylene-ethyl acrylate. Household and residential electric wires are disclosed in which an insulating layer is an electrically insulating resin containing a resin component composed of an ethylene copolymer such as polymerization (hereinafter abbreviated as EEA) and a silane crosslinking agent. Also, examples of using cross-linked polyethylene resin insulating coating material for automotive wires, in JP-A-8-169991, EEA30 parts by weight (hereinafter abbreviated as LLDPE) linear low density polyethylene 70 parts by weight and the inorganic flame flame-retardant wire is disclosed comprising a skin made of retardant 80 parts by mass to cover the conductor. Insulating coating materials for electric wires for automobiles are required to have excellent flame retardancy, excellent heat resistance, excellent flexibility, and excellent wear resistance. However, the fact is that the cross-linked polyethylene resin having such a degree that all the properties can be sufficiently satisfied has not been obtained yet. In order to ensure satisfactory flame retardancy, it is necessary to make the thickness of the outer skin relatively large as 1 mm or more and to use a large amount of inorganic flame retardant. When the LDPF (or LLDPE): EAA mass ratio is 50:50 or more, the flexibility (flexibility) decreases and wiring becomes difficult, or the surface is whitened or cracked when the wire is forcibly bent. Cause problems. This problem can be solved by lowering the LDPE (or LLDPE): EEA ratio (increasing the amount of EEA), but in this case, a new problem arises that the wires are fused at this time. Since the electric wire for automobiles is exposed to a high temperature, it is necessary to withstand a high temperature standing test at 120 ° C. However, a skin having a high EEA content cannot withstand a high temperature standing test.
[0003]
[Problems to be solved by the invention]
An object of the present invention is to provide a flame-retardant electric wire that is suitably used as an electric wire for automobiles and has excellent heat resistance and good flexibility (flexibility).
[0004]
[Means for Solving the Problems]
According to the present invention, the flame retardant electric wire around the conductor was coated with an electrically insulating outer flame retardant, an outer skin, an ethylene - ethyl acrylate copolymer 70 to 90 wt% with linear low density polyethylene down trees an inner layer comprising the crosslinked product of the resin consisting of fat 30-10 wt%, provided around the inner layer, linear low density polyethylene emissions resins 90 to 70 wt% ethylene - ethyl acrylate copolymer 10 to 30 mass %, And the ratio of the thickness T ₂ of the inner layer to the thickness T ₃ of the outer layer, T ₂ : T ₃ is 50:50 to 90:10 A flame retardant electrical wire is provided.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will now be described in detail with reference to the drawings. In FIG. 1, 1 is a conductor, 2 is an inner layer, 3 is an outer layer, and 4 is an outer skin.
[0006]
Reference numeral 1 denotes a conductor such as a copper wire, which is composed of a plurality of stranded wires. Reference numeral 4 denotes a flame-retardant electrically insulating outer skin that covers the outer periphery of the conductor 1, and includes an inner layer 2 and an outer layer 3. When the flame-retardant electric wire of the present invention is used as an automobile electric wire, it is desirable that the outer skin 4 has a thickness of 1 to 2 mm. That is, the total thickness of the inner layer 2 and the outer layer 3 is desirably 1 to 2 mm. In this case, the ratio of the thickness _{T 2} of the inner layer 2 to the thickness _{T 3} of the outer layer _{3 (T} 2: T 3) of 50: 50-90: 10 and that is important in order to obtain the desired heat resistance and flexibility It is. This ratio (T ₂ : T ₃ ) is preferably in the range of 50:50 to 70:30.
[0007]
The inner layer 2 is an ethylene - including ethyl acrylate copolymer (EEA) 70 to 90 wt% with linear low density polyethylene emission resins (LLDPE) made of 30-10 wt% resin crosslinked. Conventionally used EEA can be used without limitation. EEA having an ethyl acrylate monomer unit content of 10 to 50% by mass , preferably 20 to 30% by mass , is generally used. The linear low density polyethylene emission resins (LLDPE) in the present invention, conventionally known ones can be used, its specific gravity is from 0.910 to 0.930. The inner layer 2, the case of the present invention, those containing a crosslinked product of a resin consisting of EEA70~90 wt% and LLDPE30~10 wt% (i.e., EEA: LLDPE weight ratio is 70: 30 to 90: 10 in the range of ) Is preferable in terms of flexibility.
[0008]
The outer layer 3 contains a crosslinked product of a resin consisting of LLDPE90~70 wt% and EEA10~30 mass%. The outer layer 3 preferably has an LLDPE: EEA mass ratio in the range of 90:10 to 70:30 in terms of heat resistance and flexibility.
[0009]
Each of the inner layer 2 and the outer layer 3 is made into a flame-retardant electric wire by containing a flame retardant. As the flame retardant, metal hydroxide flame retardants such as magnesium hydroxide, aluminum hydroxide and surface modified products thereof are usually used. The amount of the flame retardant used in the inner layer 2 and the outer layer 3 is usually 30 to 120 parts by mass , preferably 60 to 100 parts by mass , per 100 parts by mass of the resin of the inner layer 2 and the outer layer 3.
[0010]
Further, each of the inner layer 2 and the outer layer 3 can be added with various additives such as a colorant, an anti-aging agent, a lubricant, etc., as long as the purpose of the present invention is not impaired. 0 to 5 parts by weight per 100 parts by weight of the resin.
[0011]
The flame-retardant electric wire of the present invention can be easily obtained by extruding the resin composition of the inner layer 2 and the outer layer 3 around the conductor 1 and then crosslinking by electron beam irradiation. In this case, since the extruder can be co-extruded using two tandem extruders, a flame-retardant electric wire is manufactured without incurring a cost increase compared to the case of forming a single-layer skin. be able to. The inner layer 2 and the outer layer 3 can be cross-linked by adding a silane cross-linking agent to the composition constituting those layers in advance.
[0012]
The crosslinking rate of the inner layer 2 and the outer layer 3 is not particularly limited as long as it is a crosslinking rate at which the resin becomes insoluble and infusible, but is usually 50% or more, preferably expressed in gel fraction (JASO standard). 70% or more.
[0013]
【Example】
Next, the present invention will be described in further detail with reference to examples. In addition, the welding resistance and flexibility of the electric wires were measured by the following tests.
(1) Welding resistance test Two electric wire samples (length: 250 mm) are arranged, leaving 50 mm at each end, winding a tape for harness around the central portion of 150 mm, and leaving this at 120 ° C. for 120 hours. . Next, the tensile tester is used to pull the two electric wires protruding from one end of the electric wire so that the two electric wires are separated from each other, and the two electric wires are peeled off. Measure. In this case, the smaller the peeling force, the better the welding resistance.
(2) Flexibility test A wire sample having a length of 40π (mm) or more is bent until a semicircular shape with a bending radius of 40 mm is formed at one end thereof, and the maximum load at that time is measured. . In this case, the smaller the maximum load, the better the flexibility.
[0014]
Example 1
A flame-retardant electric wire having a structure shown in FIG. 1 was produced by forming a skin made of an inner layer and an outer layer on the outer periphery of the stranded wire. In this case, as the stranded wire 1, a wire having a diameter of 5.3 mm obtained by twisting 171 copper wires having a diameter of 0.32 mm was used. As the base resin composition for obtaining the inner layer 2, ethyl acrylate monomer content of 23 wt% ethylene - ethyl acrylate (EEA) 90 wt% and linear low density polyethylene emission resins (LLDPE) (Specific gravity: 0.92) What mixed 80 mass parts of aluminum hydroxide as a flame retardant with respect to 100 mass parts of mixed resin with 10 mass % was used. As the base resin composition for obtaining the outer layer 3, the same ethylene as above - resin mixture of ethylene acrylic (EEA) 30 wt% and the same linear 70 wt% low density polyethylene emission resins (LLDPE) and the 100 with respect to the weight unit used it was blended 80 parts by weight of aluminum hydroxide as a flame retardant. The flame-retardant electric wire in which the outer skin 4 was formed around the outer periphery of the stranded wire 1 was subjected to a crosslinking treatment by irradiation with an electron beam. In this case, the gel fraction of the outer layer 3 was 75%, and the gel fraction of the inner layer 2 was 80%.
[0015]
The outer skin 4 is formed on the outer periphery of the stranded wire 1 by using two tandem extruders, and the inner layer resin composition and the outer layer resin composition are mixed with each other with respect to the outer periphery of the stranded wire 1. It was produced by extruding by a coextrusion method. In this case, the thickness of the inner layer 2 is 0.9 mm, and the thickness of the outer layer 3 is 0.2 mm. The ratio of the thickness of the inner layer 2 to the thickness of the outer layer 3 is 82:18. As a result of the previous test, the flame-retardant electric wire thus obtained was not only flexible but also resistant to welding, and no welding occurred on its outer skin.
[0016]
Comparative Example 1
In Example 1, except for using EEA90 wt% and a mixed resin consisting of LLDPE10 wt% as a material of the outer layer 3 is conducted experiments in the same manner. In this case, the obtained flame-retardant electric wire was inferior in welding resistance as a result of the previous test.
[0017]
Comparative Example 2
In Example 1, the experiments were carried out in the same manner except for using EEA30 wt% and a mixed resin consisting of LLDPE70 wt% as a material of the inner layer 2. In this case, the obtained flame-retardant electric wire was inferior in flexibility as a result of the previous test.
[0018]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, while being excellent in flexibility (flexibility), it is excellent also in heat resistance, and the flame-retardant electric wire which does not produce weldability to the outer skin by heating to 90-120 degreeC is provided. .
[Brief description of the drawings]
FIG. 1 shows a cross-sectional view of an electric wire of the present invention.
[Explanation of symbols]
1 Conductor 2 Inner layer 3 Outer layer 4 Outer skin

Claims (2)

In the flame-retardant electric wire around coated with an electrically insulating outer sheath of flame-retardant conductors, the outer skin, ethylene - ethyl acrylate copolymer 70 to 90 wt% with linear low density polyethylene emissions resins 30 to 10 wt% an inner layer comprising the crosslinked product of the resin consisting of, provided around the inner layer, linear low density polyethylene emissions resins 90 to 70 wt% ethylene - resin consisting of ethyl acrylate copolymer 10 to 30 wt% crosslinking A flame retardant electric wire comprising an outer layer including a body and having a ratio T ₂ : T ₃ of 50:50 to 90:10 of a thickness T ₂ of the inner layer to a thickness T ₃ of the outer layer. The inner layer and each outer layer is flame-retardant wire according to claim 1 containing 30 to 120 parts by weight each of the resin per 100 parts by weight of a metal hydroxide flame retardant.

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