JPH04155710A - Fire retardant electric wire/cable - Google Patents

Abstract

PURPOSE:To provide high fire retardant characteristic without impairing required physical properties and prevent generation of harmful gas by coating the tape surface of an electric wire or cable with a certain thickness of mixture consisting of a resin in specific composition and a certain amount of inorganic pulverized substance having specified particle sizes. CONSTITUTION:On the periphery of a conductor are placed an insulation, interposition, fabric or glass tape, and fire retardant sheath one over another in the sequence as named. Either one or both sides of this tape are coated a mixture of max 200mum thick consisting of 10-30wt.% aqueous emulsion resin and 90-70wt.% inorganic pulverized substance having a mean particle size of no more than 50mum which is turned in glass state under 800 deg.C. The fire retardant sheath on the outside of the tape is formed from a material not containing halogen to which 100 parts by weight polyolefin and 50-250 parts by weight metal hydroxide are added, and thus a fire retardant electric wire or cable is accomplished free from risk of emitting any harmful halogen gas, without impairing its physical properties such as fiber properties, easy-to-shape characteristics and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to flame-retardant insulated wires and cables, and particularly to flame-retardant insulated wires and cables that do not generate toxic halogen gases when burned.

[Prior Art] Many polyolefins with excellent electrical insulation properties have been used as insulation materials and sheath materials for electric wires and cables. Recent trends include electric wires and cables for nuclear power plants,
IEEE (Institute of Electrical and Electronics Engineers) standard 383 V is used for vehicle wires and cables, marine wires and cables, etc.
A high level of flame retardancy is now required, which is required to pass a multi-strip combustion test that simulates the actual installation conditions stipulated in the TFT (Vertical Tray Combustion Test).

As a method of making polyolefin flame retardant, a method of incorporating a halogen-containing compound has generally been adopted.

However, these produce a large amount of smoke when burned, causing problems such as corrosiveness to equipment and toxicity to the human body. especially,
Recently, there has been a strong demand for not generating such halogen-based gases from the viewpoint of safety.

In light of this situation, metal hydroxides, which are extremely low in smoke generation and toxicity, are attracting attention.

[Problems to be Solved by the Invention] However, since metal hydroxides have a small flame retardant effect, it is necessary to add a large amount of metal hydroxides to provide a high degree of flame retardancy, and as a result, mechanical properties, Extrusion processability is significantly reduced. Therefore, by wrapping a thick glass tape around the outside of the conductor or the outside of the insulator, or wrapping a tape with a structure such as glass cloth or organic polymer film pasted on one side of soft or hard laminated mica, it is possible to create an insulator. There are methods to prevent flames from entering. However, the former makes it difficult to process the terminals, and the latter tape is not very flexible and is difficult to wrap around small-diameter wires and cables.

This invention was made in view of the above points, and has a high degree of flame retardancy without impairing the physical properties of the insulator and sheath material, and does not generate toxic halogen gas when flame retardant. The purpose is to provide flammable wires and cables.

[Means for Solving the Problems] As shown in FIG. 1, the present invention provides an insulator 2 and an intervening material 3 in sequence on the outside of a conductor 1, and furthermore, a cloth tape or a glass tape is provided on the outside of the insulator 2 and an intervening material 3, as shown in FIG. an aqueous emulsion with a composition of 10 to 30% by weight on both sides or one side;
Average particle size 50 μ which vitrifies at 800°C or less at 0% by weight
The maximum thickness of the mixture with inorganic particles is 200μm or less.
A flame-retardant sheath 5 that does not contain halogen and is made by adding 650 to 250 parts by weight of metal hydroxide to 100 parts by weight of polyolefin is coated on the outside. Electric wires and cables.

Here, the flame retardance improves as the content of metal hydroxide in the polyolefin increases, but mechanical properties and extrusion processability deteriorate accordingly. In this invention, good flame retardance is obtained by using a tape made by coating a cloth tape or a glass tape with a mixture of an aqueous emulsion resin and inorganic particles that vitrify at 800° C. or lower.

In the present invention, examples of the aqueous emulsion resin include polyvinyl acetate emulsion, vinyl acetate/ethylene copolymer emulsion, vinyl acetate/vinyl propionate copolymer emulsion, vinyl acetate/acrylate copolymer emulsion, acrylic ester copolymer emulsion, etc. Alternatively, two or more types can be used in combination.

These resins act as binders for coatings, but since they are generally flammable, their use is preferably minimal, and should be in the range of 10 to 30% by weight. If it is less than 10% by weight, its function as a binder is reduced and flexibility becomes poor, and if it exceeds 30% by weight, flame retardancy is reduced.

Inorganic particles with an average particle size of 50 μm or less that vitrify at 800°C or less include lead monoxide, as shown in Figure 2;
Examples include mixtures and single substances of lead carbonate, boron oxide, boric acid, silicon dioxide, zinc oxide, and aluminum oxide. The temperature at which an inorganic material turns into glass must be 800°C or lower, as the maximum sheath surface temperature during the flame retardancy test is 80θ°C, and anything that turns into glass at a temperature higher than this temperature must be , it does not become glassy and the flame retardancy is rejected. Compositions N001 to 1 shown in the same figure pass the flame retardant test.
4. In addition, the average particle size of the inorganic particles to be vitrified must be 50 μm or less; if this value is exceeded, cracks will appear on the surface when the tape is wound.
Flame retardancy becomes insufficient. The content of the inorganic particles to be vitrified must be 90 to 70% by weight; if it is less than 70% by weight, the flame retardance will be insufficient, and if it exceeds 90% by weight, the tape will not have flexibility. It disappears and cannot be wrapped outside the interposition. This mixture of inorganic fluid and aqueous emulsion resin must be applied to the tape to a maximum thickness of 200 μm; if the upper limit is exceeded, the tape loses its flexibility and cannot be wrapped outside the intervening area.

The content of metal hydroxide in the sheath layer is 50-250
If it is less than the lower limit, the desired flame retardance cannot be imparted, and if it exceeds the upper limit, the mechanical properties and extrusion processability will deteriorate.

As described above, according to the present invention, there is no need to add a large amount of metal hydroxide to impart a high degree of flame retardancy, and as a result, it is possible to prevent deterioration of mechanical properties and extrusion processability. In addition, there is no need to wrap a thick glass tape around the outside of the conductor or insulator, or wrap a tape with a structure such as glass cloth or organic polymer film pasted on one side of soft or hard laminated mica. So,
This eliminates the problems of difficulty in terminal processing and difficulty in wrapping small diameter wires and cables due to lack of flexibility.

In this invention, the polyolefins include ethylene propylene copolymer, ethylene brobylene dienther polymer, polyethylene, ethylene vinyl acetate copolymer, ethylene ethyl acrylate copolymer, ethylene butene copolymer, ethylene butene terpolymer, and ethylene methyl methacrylate copolymer. , these can be used alone or in combination of two or more.

Examples of metal hydroxides include aluminum hydroxide, magnesium hydroxide, salts, basic magnesium carbonate, calcium hydroxide, hydrotalcites, etc., and these may be used alone or in combination of two or more. .

Insulators used in this invention include polyethylene,
Commonly used insulating polyolefins such as crosslinked polyethylene or polyolefins mixed with an appropriate amount of metal hydroxide are used.

In this invention, in addition to the above components, crosslinking agents, antioxidants, lubricants, softeners, dispersants, etc. may be added as appropriate.

As a crosslinking agent, dicumyl peroxide, 3-bis(
An organic peroxide represented by t-butylperoxyisopropyl)benzene is suitable, and as a crosslinking agent,
Sulfur, ethylene dimethacrylate, diallyl phthalate, P-quinone dioxime, etc. may be used in combination. Further, in the case of crosslinking using ionizing radiation such as an electron beam, it is common to add a reactive monomer such as trimethylolpropane trimellitate or triallyl isocyanurate as a crosslinking aid. As an antioxidant, phenyl-α-
Examples include amine antioxidants such as naphthylamine, N9-di-β-naphthyl-p-phenylenediamine, and phenolic antioxidants such as 2,6-di-t-butyl-4-methylphenol and hindered phenol. It will be done.

[Examples] Next, the present invention will be described with reference to Examples and Comparative Examples.

Using sheaths and tapes made of the test components of Examples 1 to 4 and Comparative Examples 1 to 7 shown in the upper column of FIG.
．． A paper intervening layer was provided around the outer periphery of three 3 mm insulated wire cores twisted together, and a tape was further wrapped with 172 wraps, and each compounded component was placed on the outside of the tape into a 6 inch roll maintained at a temperature of 100°C. Roll kneading was performed, and after kneading, using a 40 m/m extruder (L/D = 25) maintained at a temperature of 120 ° C., various cables were produced by extrusion coating to a thickness of 2.0 mm. and each sample of Comparative Examples 1 to 7.

The evaluation results of the obtained cable are as shown in the lower column of FIG. Note that the evaluation was performed based on the following criteria.

Mechanical properties are JIS in accordance with Japan Electric Wire Industry Standard No. 391.
A sample punched with K7112 dumbbell No. 3 was subjected to a tensile test at 200 mm/min using a Schopper type tensile tester, and the tensile strength was 1.0 kg/mm or more and the elongation was 35.
A value of 0% or more was considered good, and a value less than this value was considered poor.

Processability was judged based on the condition and appearance during extrusion using a 40 m/m extruder.

Flame retardancy evaluation was performed as follows. Eight 2m long cables are lined up vertically, and 70,000B tu (
If the flame self-extinguished after being exposed to a flame (British thermal units) for 20 minutes, it passed; if it did not self-extinguish and completely burned down, it was rejected.

As is clear from FIG. 3, Example 1 according to the present invention
All of the samples No. 4 to 4 passed the flame retardant test and had excellent mechanical properties and extrusion processability.

On the other hand, Comparative Example 1, in which the aqueous emulsion content was less than the specified value, had poor flexibility and could not be wrapped with tape on the outside of the intervening layer, and Comparative Example 2, in which the content of the aqueous emulsion exceeded the specified value, failed in terms of flame retardancy. Comparative Example 3, in which the temperature at which it forms glass exceeds 800°C, failed in terms of flame retardancy. In addition, in Comparative Example 4, in which the average particle size of the inorganic particles used as glass exceeded the specified value, cracks appeared on the surface when the tape was wound, and the flame retardance was rejected. Comparative Example 2, in which the content of inorganic particles that become glass was less than the specified value, failed in terms of flame retardancy, and Comparative Example 1, in which the content of inorganic particles to become glass was less than the specified value, had poor flexibility and could not be wrapped with tape on the outside of the intervening area. In Comparative Example 5, in which the thickness of the mixture of aqueous emulsion resin and inorganic particles to become glass exceeded the specified value, the tape lacked flexibility and could not be wrapped outside the intervening area.

Comparative Example 6, in which the metal hydroxide content in the sheath layer was less than the specified value, failed in terms of flame retardancy, and Comparative Example 7, in which the content of metal hydroxide in the sheath layer exceeded the specified value, could not be extruded.

[Effects of the Invention] As explained above, the flame-retardant wire/cable of the present invention has good mechanical properties, moldability, and high flame retardancy, and does not generate toxic A-logen gas. You can get something excellent.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a flame-retardant electric wire showing an example of the present invention, and FIG. 2 is a composition diagram of an inorganic powder with an average particle size of 50 μm or less that vitrifies at 800° C. or less according to the present example. FIG. 3 is a characteristic diagram of flame-retardant cables of Examples 1 to 4 of the present invention and Comparative Examples 1 to 7.

Claims (1)

[Claims] An insulator and an intervening material are sequentially provided on the outside of the conductor, and a cloth tape or a glass tape is provided on the outside of the conductor, and a water-based emulsion resin having a composition of 10 to 30% by weight and a water-based emulsion resin of 90 to 70% by weight are coated on both or one side of the tape. Wrap a tape made by applying a mixture of inorganic powder with an average particle size of 50 μm or less that vitrifies at 800°C or less to a maximum thickness of 200 μm, and then coat the outside with metal hydroxide based on 100 parts by weight of polyolefin. 1. A flame-retardant electric wire/cable coated with a halogen-free flame-retardant sheath containing 50 to 250 parts by weight of halogen.