JPH0143968B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a flame-retardant insulated wire, and particularly to an insulated wire coated with a flame-retardant insulating material that does not generate halogen gas when burned. Ethylene propylene copolymers and polyethylene-based polymers, which have excellent electrical insulation properties, are often used as insulating materials for electric wires and cables.
As a recent trend, there has been a strong demand for flame retardancy for electric wires and cables for nuclear power plants, and electric wires for wiring inside panels and inside machines. The methods used to make polymers flame retardant include mixing halogen-containing compounds, antimony trioxide, phosphorus-containing compounds, etc., but these produce a large amount of smoke in the event of a fire, and also emit gases harmful to the human body. There are problems such as . In light of this situation, inorganic hydrous compounds such as hydrated alumina, which generate very little smoke and do not emit harmful gases, have been attracting attention. However, in order to impart flame retardancy, it is necessary to add a large amount of inorganic water-containing compounds, and when ordinary inorganic water-containing compounds are used, there is a problem that the electrical properties deteriorate, especially due to water absorption and moisture absorption. Deterioration of characteristics has become a major problem. The present invention has been made in view of the above, and its purpose is to provide a flame-retardant insulated wire that has good electrical characteristics and flame retardancy, and does not generate harmful halogen gas when burned. It is about providing. The flame-retardant insulated wire of the present invention is made of ethylene polymer.
100 parts by weight or more of an inorganic hydrous compound and 0.1 part by weight of 2-mercaptobenzimidazole per 100 parts by weight
It is characterized by being coated with a flame-retardant electrical insulator made of a mixture containing at least part by weight. In the present invention, examples of the ethylene polymer include ethylene propylene copolymer, ethylene propylene diene terpolymer, polyethylene, ethylene vinyl acetate copolymer, ethylene ethyl acrylate copolymer, and ethylene butene copolymer, which may be used alone or in combination of two or more. It's possible. Examples of the inorganic hydrous compound include hydrated alumina, magnesium hydroxide, magnesium carbonate, and zinc borate. The inorganic hydrous compound must be contained in an amount of 100 parts by weight or more per 100 parts by weight of the ethylene polymer; anything less than this will result in flame retardancy (JIS horizontal).
becomes insufficient. 2-Mercaptobenzimidazole is added to prevent the hydroxyl groups on the surface of the hydrated inorganic compound from adsorbing a large amount of water and deteriorating the electrical properties.
It is necessary to make it 0.1 part by weight or more based on the weight part. In the present invention, in addition to the above components, a crosslinking agent,
Antioxidants, lubricants, softeners, dispersants, etc. may be added as appropriate. Suitable crosslinking agents include organic peroxides such as dicumyl peroxide and 1,3-bis(t-butylperoxyisopropyl)benzene, and sulfur, ethylene methacrylate, and dicumyl peroxide as crosslinking aids. acrylic phthalate,
p-quinone dioxime etc. may be used in combination. In addition, as antioxidants, amine antioxidants such as phenyl-α-naphthylamine, N,N′-di-β-naphthyl-p-phenylenediamine, 2,
Examples include phenolic antioxidants such as 6-di-t-butyl-4-methylphenol and hindered phenol. Examples of the present invention will be described below while comparing them with comparative examples. After kneading the mixture prepared according to the formulation shown in Table 1 with a roll, the outer diameter was
After coating the outer circumference of the 2.0mm copper wire with a thickness of 1mm,
Crosslinking was carried out by holding in steam at 13 atmospheres (temperature approximately 195°C) for 3 minutes. The results of evaluating the insulation resistance and flame retardance of the insulated wires of Examples and Comparative Examples are shown in the lower column of Table 1. The evaluation was based on the following. Insulation resistance: Insulation resistance was measured based on JISC3004 for the product immediately after drying at 80°C for 24 hours after crosslinking (initial stage) and after being left in a 93% atmosphere for one month after drying. Flame retardancy: If the flame is extinguished within 1 minute when burned with a burner, it is passed; if it burns for more than 1 minute, it is rejected.

[Table] As is clear from Table 1, in Examples 1 to 5 according to the present invention, the decrease in insulation resistance was small even after being left in an atmosphere with a humidity of 93%, and the flame retardance was JIS
Passed level. On the other hand, in Comparative Example 1, the content of inorganic hydrous compounds exceeds the specified value, so the flame retardance is rejected, and in Comparative Example 2, the amount of 2-mercaptobenzimidazole added is below the specified value. Therefore,
The insulation resistance decreases significantly after being left in an atmosphere with a humidity of 93%. As explained above, according to the present invention, it is possible to obtain an insulated wire that has good electrical properties and flame retardancy, and does not generate harmful halogen gas when burned.

Claims (1)

[Claims] 1. It is characterized by being coated with a flame-retardant electrical insulator made of a mixture containing 100 parts by weight or more of an inorganic hydrous compound and 0.1 parts by weight or more of 2-mercaptobenzimidazole per 100 parts by weight of an ethylene polymer. Flame-retardant insulated wire.