JPH0298005A - Flame-resisting electric wire/cable - Google Patents

Abstract

PURPOSE:To obtain an electric wire/cable having toughness and superior flame- resistance, by coating the surface of a conductor or the external circumference of the core of an insulated wire with a composition having a specified amount of metal hydroxide against 100 pts.wt. of a component containing an ethylene- alkylmethacrylate copolymer and polyolefin. CONSTITUTION:The wire/cable in the title are prepared by coating the external circumference of a conductor or an insulated wire-core with a composition having 50 to 150 pts.wt. of a metal hydroxide against 100 pts.wt. of a component containing an ehtylene-alkylmethacrylate copolymer and polyolefin contained therein. Hereupon, the ethylene-alkylmethacrylate copolymer is referred to a copolymer represented by a given formula in which (m) and (n) represent their respective integers while (X) represents alkyl radicals having the number of carbon up to 5. The use of this copolymer permits to improve the flame- resisting property of the composition prepared by mixing the metal hydroxide into the component.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a flame-retardant electric wire or cable that is unlikely to generate toxic gas when burned.

[Conventional technology] With the remarkable development of today's information society, the increase in demand for electricity in industrial and consumer settings, and the rise in the height of buildings and other structures, electric wires, cables, etc. are becoming more and more densely packed.
It has become highly integrated.

All of the materials conventionally used as insulation and sheaths for electric wires and cables are flammable, and in the event of a fire, the fire will travel through the wiring system of the highly integrated electric wires and cables. In many cases, the demand for flame-retardant electric wires and cables has suddenly increased. The standard for this flame retardancy is the VTFT (vertical tray combustion test) of IEEE (Institute of Electrical and Electronics Engineers) Standard 383, which requires passing a multi-strand combustion test that simulates the actual installation conditions of electric wires and cables. It has become common to adopt this as a condition for flame retardancy.

The flame retardant level specified by VTFT is quite strict, and conventionally, flame-retardant wires and cables that can meet these strict conditions have been made of materials such as vinyl, chloroprene rubber, or polyolefin mixed with halogen flame retardants. Covered materials have been proposed and used.

[Problem to be solved by the invention] Such flame-retardant wires and cables generate a large amount of nonflammable halogen gas in the event of a fire, thereby blocking oxygen around the wires and cables and preventing combustion. That is. Although the above-mentioned flame-retardant wires and cables exhibit sufficient flame-retardant properties, many of the halogen gases generated are toxic, such as hydrogen chloride, and a large amount of smoke containing such toxic gases is emitted. This creates a risk of poor visibility, impeding evacuation and fire extinguishing activities in the event of a fire, and there is a risk of secondary disasters as the toxic gases adversely affect the human body.Furthermore, halogen-based gases may be There is also a risk that it will react with the moisture inside, forming hydrohalic acid and corroding the switchboard.

The purpose of the present invention is to solve the problems of the prior art described above,
The present invention aims to provide flame-retardant wires and cables that have a high degree of flame retardancy that satisfies the V T F T and do not generate toxic halogen gases.

[Means for Solving the Problems 1] The present invention provides for 100 u parts of a component containing an ethylene-alkyl methacrylate copolymer and a polyolefin,
The outer periphery of a conductor or wire core is coated with a composition containing 50 to 150 parts by weight of metal hydroxide.

The ethylene-alkyl methacrylate copolymer referred to in the present invention is a copolymer represented by the general formula.

The reason why the present invention specifically selected this co-vertical is that it has a particularly great effect of improving flame retardant properties after being mixed with a metal hydroxide.

In the present invention, polyolefin is blended for the purpose of further improving toughness. Crystalline polymers with excellent toughness are desirable as polyolefins, such as ethylene vinyl acetate copolymer, ethylene methyl acrylate copolymer, ethylene ethyl acrylate copolymer, linear low density polyethylene, ultra low density polyethylene, ethylene butene copolymer, etc. is raised. These are 5 to 8 in the total polymer.
It is desirable to blend at a ratio of 0%, and 5'If
If 1 is less than the L amount%, the desired toughness cannot be imparted,
Moreover, if it exceeds 80% by weight, the flame retardant effect of the ethylene-alkyl methacrylate copolymer will not be exhibited.

The reason why metal hydroxides are mixed is that during combustion, the crystal water contained in the metal hydroxide decomposes and releases water vapor, which blocks oxygen around electric wires and cables and prevents combustion. This is for the sake of doing so.

Since what is released is harmless water vapor, the problems described above in the case of halogen-containing do not occur at all.

Such metal hydroxides include aluminum hydroxide,
Magnesium hydroxide, basic magnesium carbonate, hydrotalcites, etc. can be used. Ethylene-
50 to 1 part by weight of the metal hydroxide per 100 parts by weight of the component containing the alkyl methacrylate copolymer and polyolefin.
The reason why the content is 50 parts by weight is that if it is less than 50 parts by weight, the desired flame retardancy cannot be imparted, and if it exceeds 150 parts by weight, the toughness will be significantly reduced.

The molded product of the composition described above can be used either uncrosslinked or crosslinked. Crosslinking methods include crosslinking using organic peroxides, crosslinking using electron beam irradiation, and silane craft water crosslinking. For crosslinking using organic peroxides, organic peroxides such as dicumyl peroxide and 3-bis(t-butylperoxyisopropyl)benzene are suitable as crosslinking agents.

Further, in the case of crosslinking by electron beam irradiation, it is common to add a reactive monomer such as trimethylolglopant trimellitate or triallyl isocyanurate as a crosslinking aid. In addition to the above ingredients, antioxidants, lubricants,
Carne black etc. may be added.

[Example] The present invention will be described below with reference to Examples.

Samples having the compounding compositions shown in the Examples and Comparative Examples in Table 1 were prepared, and the tests shown in the evaluation items were conducted.

The compounding ingredients were kneaded using a 12-inch roll maintained at 120°C. Kneading tk 50 m maintained at 120°C
A cable was produced by forming an extrusion coating layer with a thickness of 1.5 cm on the outer periphery of three twisted ethylene propylene rubber insulated wire cores with an outer diameter of 3.0 mm using an extruder.

In Example 6, crosslinking was subsequently carried out by holding the sample in a steam atmosphere of 15 kf/- for 3 minutes.

Characteristics of each cable thus obtained were evaluated.

The tensile properties were determined by cutting out the extruded composite layer from the cable and polishing both sides with a grinder to a thickness of 1 inch.
A sample was prepared using dumbbell No. 3. This is pulled at a speed of 200
It was measured using a Schopper type tensile tester with mrr/1 lin.

For flame retardancy evaluation (vertical tray combustion test), eight 2m long cables are lined up vertically, and a 70,000 BTU flame is applied from below for 20 minutes.If the flame self-extinguishes, the cable passes the test, and burns completely without self-extinguishing. The item was rejected.

As is clear from Table 1, Examples 1 to 6 according to the present invention satisfy the polyethylene standards of the Electrical Appliance and Material Control Law, all have a tensile strength of 1 lqr/mi+" or more, an elongation of 350% or more, and vertical tray combustion. pass the exam.

On the other hand, Comparative Example 1.2 has insufficient flame retardancy, and Comparative Example 3.4 has significantly reduced tensile properties and does not meet the polyethylene standards of the Electrical Appliance and Material Control Law.

[Effects of the Invention] As explained above, the flame-retardant wire/cable according to the present invention has excellent toughness and high flame retardancy, generates little smoke when burned, and generates toxic halogen gas. This feature makes it very useful industrially.

Claims (1)

[Claims] (1) A composition containing 50 to 150 parts by weight of a metal hydroxide to 100 parts by weight of a component containing an ethylene-alkyl methacrylate copolymer and a polyolefin is coated on the conductor or around the insulated wire core. Flame-retardant wires and cables.