JPH0345637A - Flame-retardant electrical insulation composition - Google Patents

Abstract

PURPOSE:To prevent the generation of a halogen gas and improve the flame- retardant properties while maintaining the mechanical properties and extrusion moldability by compounding a polyolefin resin with an inorg. flame retardant and a specific polyacrylonitrile fiber. CONSTITUTION:100 pts.wt. polyolefin resin (e.g. ethylene-vinyl acetate copolymer) is compounded with 50-500 pts.wt. inorg. flame retardant (e.g. magnesium hydroxide), 1-50 pts.wt. polyacrylonitrile fiber having a diameter of 0.2-5mum and a length of 0.5-20mm, and if necessary a crosslinker, an antioxidant, a lubricant, a softener, a dispersant, etc.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to flame-retardant electrical insulation compositions that do not emit harmful halogen gases when burned, particularly to insulating materials and sheath materials for electric wires and cables. The present invention relates to a flame-retardant electrical insulation composition suitable for.

[Conventional technology] Materials traditionally used as insulators and sheaths for electric wires and cables, including polyolefin, which is widely used due to its excellent electrical insulation properties, are all flammable and can cause fires. When a fire occurs, there are many cases in which the fire spreads through the wiring system of electric wires and cables, and the demand for flame-retardant electric wires and cables has suddenly increased. In particular, as a recent trend, electric wires and cables for nuclear power plants,
IEEE (Institute of Electrical and Electronics Engineers) standard 383 V is used for electric wires and cables for vehicles, @ wires and cables for ships, etc.
A high degree of flame retardancy is now required, which is required to pass a multi-line installation combustion test that simulates the actual installation situation stipulated in i'F'I' (Vertical Tray Combustion Test). It's here.

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

However, such flame-retardant electrical insulation compositions generate a large amount of nonflammable halogen-based gas in the event of a fire, thereby blocking oxygen around electric wires and cables and preventing combustion. Although it exhibits sufficient flame retardant properties, many of the halogen gases generated are toxic, such as hydrogen chloride, and visibility is poor because a large amount of smoke containing such toxic gases is generated. i! in the event of a fire! There is a risk of secondary disasters such as making it difficult for people to take action or preventing firefighting, or the toxic gases mentioned above may have an adverse effect on the human body.Furthermore, halogen-based gases may react with moisture in the air and turn into hydrohalic acid. There is also the risk of corroding equipment, etc.

Therefore, a flame-retardant electrical insulating composition was proposed, in which an inorganic flame retardant such as aluminum hydroxide or magnesium hydroxide was mixed in place of the above-mentioned halogen-based compound, and which focused on safety in the event of a fire. ing.

[Problem to be solved by the invention] The flame retardant composition containing the above-mentioned inorganic flame retardant utilizes the maturation effect when the hydroxide releases crystal water during a fire as a flame retardant effect. , has very little fuming, toxicity or corrosiveness.

However, since inorganic flame retardants have a small flame retardant effect,
If it is simply mixed into a polymer, a drip phenomenon in which it melts and drips during combustion is observed, making it difficult to impart a high degree of flame retardancy.

Therefore, in order to impart a high degree of flame retardancy, it is necessary to add a large amount of inorganic flame retardant, which may result in a decrease in the tensile properties of the resulting insulator or sheath, and a decrease in extrusion processability. There is a problem with doing so.

The purpose of the present invention is to solve the problems of the prior art as described above, and to achieve high flame retardancy that passes the vertical tray combustion test level by incorporating an inorganic flame retardant that does not generate harmful halogen gases. The present invention also seeks to provide a flame-retardant electrical insulation composition that can maintain its mechanical properties and extrudability.

[Means for Solving the Problems] The present invention uses 50 to 500 parts by weight of an inorganic flame retardant to 100 parts by weight of polyolefin, and a polyacrylonitrile-based material having a diameter of 0.2 to 5 μm and a length of 0.5 to 20 mm. a fiber 1~
It contained 50 parts by weight.

In the present invention, examples of the polyolefin include ethylene propylene copolymer, ethylene propylene dienter polymer, polyethylene, ethylene vinyl acid copolymer, ethylene ethyl acrylate copolymer, ethylene butene copolymer, ethylene butene diene terpolymer, etc., which may be used alone or in combination. It is possible to use more than one species in combination.

! ! Examples of organic flame retardants include aluminum hydroxide, magnesium hydroxide, basic magnesium carbonate, calcium hydroxide, hydrotalcites, etc.6 The content of inorganic flame retardants is based on 100 parts by weight of polyolefin. If it is less than 50 parts by weight, the desired flame retardancy cannot be imparted, and if it exceeds 500 parts by weight, the processability will be significantly reduced and extrusion molding will become difficult.

In the present invention, in addition to the above-mentioned inorganic flame retardant,
The present invention was developed by focusing on containing 1 to 50 IIE parts of polyacrylonitrile fibers with a length of 2 to 5 μm and a length of 0.5 to 20 mm, thereby causing the cinders to expand and harden during combustion. It was discovered that dripping can be prevented and flame retardancy can be greatly improved.

When considering ease of kneading, expandability, extrudability, etc. described below, it is desirable to select polyacrylonitrile fibers within the above-mentioned range of diameter 0.2 to 5 μm and length 0.5 to 20 m. .

Polyacrylonitrile fiber is polyolefin 100
It is necessary to mix in the range of 1 to 502 parts by weight per 21 parts by weight.If it is less than 1 part by weight, the cinders will not expand and become hard during combustion, so dripping cannot be prevented, and if it exceeds 50 parts by weight, the admixture will deteriorate. This is not preferable since the viscosity increases and extrusion processability is impaired.

In the present 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(t
-butylperoxyiso-10vir) An organic peroxide represented by benzene is suitable, and as a crosslinking aid,
Sulfur, ethylene dimethacrylate, diallyl phthalate, p-quinone dioxime, etc. may be used in combination, and in the case of crosslinking using ionizing radiation such as electron beams, trimethylolpropane trimellitate, triallyl, etc. may be used as a crosslinking aid. It is common to add reactive monomers such as isocyanurates. #! As an I-forming inhibitor, phenyl-α
-naphthylamine, N,N--di-β-naphthyl-P-
Amine antioxidants such as phenylenediamine, 2,6-
Examples include phenolic antioxidants such as di-t-butyl-4-methylphenol and hindered phenol.

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

Using compositions consisting of the test ingredients of Examples 1 to 5 and Comparative Examples 1 to 7 shown in Table 1, an evaluation test was conducted on the evaluation items shown in the lower column of Table 1.

Each compounded component was put into a 6-inch roll kept at 100°C and kneaded by rolls, and after kneading, using a 40 m/m extrusion 11 (L/D = 25) kept at 120°C, an outer diameter of 5 .3- is attached to the outer circumference of three twisted insulated wire cores. O
Extrusion coating was performed to a thickness of n+s+.

In addition, in Examples 1, 3.4 and Comparative Example 1, following extrusion coating, crosslinking was carried out by holding in a steam atmosphere of 131 qr/aJ for 3 minutes.

The evaluation results for the insulated wires produced in each example are shown in the lower column of Table 1.

The hardness of ash during combustion is 20 x 20 x 2
After burning the rsm sample in a Bunsen burner for 20 minutes, the shape and hardness of the remaining ash were observed, and if it expanded and was hard, it was judged as good, and if it did not expand and was brittle, it was judged as poor.

Furthermore, flame retardancy evaluation was performed based on the following. Eight 2m long cables are lined up vertically, and two 70,000 BTU flames are placed from below.
If the odor is applied for 0 minutes and the odor self-extinguishes, the odor is passed; if the odor does not self-extinguish and the odor completely burns out, the odor is rejected.

As is clear from Table 1, Examples 1 to 5 according to the present invention
In both cases, the ash expands during combustion and becomes hard, passing the flame retardant test.
Excellent extrusion processability. On the other hand, Comparative Example 1, in which the content of the inorganic flame retardant was below the specified value, failed in terms of flame retardancy, and Comparative Example 2, in which the content of the inorganic flame retardant was above the specified value, had poor extrudability and could not be molded. In addition, in Comparative Example 3 where the diameter and length of polyacrylonitrile fibers were less than the specified values, and Comparative Example 5 where the content of polyacrylonitrile fibers was less than the specified values, the ash did not expand during combustion and was brittle and flame retardant. will fail. Furthermore, in Comparative Example 4 in which the diameter and length of the polyacrylonitrile fibers are greater than the specified value, or in Comparative Example 6 in which the content of the polyacrylonitrile fibers is greater than the specified value, extrudability deteriorates. Furthermore, in Comparative Example 7 in which an inorganic fibrous material such as potassium titanate whiskers was used, the ash during combustion did not expand and was brittle, resulting in a failure in flame retardancy.

[Effect of the invention] As explained above, according to the composition according to the present invention,
As a flame retardant, inorganic flame retardants and polyacrylonitrile fibers with a diameter of 0.2 to 5 μm and a length of 0.5 to 20 m+ are used in combination to prevent drips during combustion while maintaining good extrusion processability. It is possible to obtain an electrical insulating composition which can be imparted with flame retardancy and which does not generate toxic halogen gas when burned.

Claims (1)

[Claims] (1) Containing 50 to 500 parts by weight of an inorganic flame retardant and 1 to 50 parts by weight of polyacrylonitrile fibers having a diameter of 0.2 to 5 μm and a length of 0.5 to 20 mm per 100 parts by weight of polyolefin. A flame retardant electrically insulating composition.