JPS60100302A - Flame resistant electrically insulating composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Background and Objects of the Invention] The present invention relates to a flame-retardant electrical insulation composition that does not generate halogen gas when burned.

For example, polyolefins with excellent electrical insulation properties are often used as insulation materials and sheath materials for electric wires and cables.

In recent years, there has been a strong demand for flame retardancy in electric wires and cables for nuclear power plants, electric wires for vehicles, and electric wires for wiring inside panels and machines. The method of making such polymers flame retardant has been to mix halogen-containing compounds, phosphorus-containing compounds, etc., but these produce a large amount of smoke in the event of a fire and also emit gases that are harmful to the human body. etc. are considered problematic.

In light of this situation, inorganic flame retardants with extremely low smoke generation and toxicity have been attracting attention. Among these, magnesium hydroxide is particularly effective in imparting flame retardancy, as it releases water of crystallization near the decomposition temperature of the polymer and absorbs a large amount of heat.

However, although it is necessary to add a large amount of magnesium hydroxide to impart a high degree of flame retardancy, the compatibility between the polymer and magnesium hydroxide is poor, leading to a decrease in mechanical properties. In addition, magnesium hydroxide reacts with water and carbon dioxide in the air and transforms into magnesium carbonate, which promotes water absorption, resulting in a significant decrease in electrical properties, which has limited its range of use. .

The present invention was made in order to solve the problems of the prior art described above, and it is possible to improve the compatibility between polyolefin and magnesium hydroxide, thereby improving the mechanical properties, electrical properties, and flame retardant properties. The object of the present invention is to provide a flame-retardant electrical insulation composition that does not generate scum.

[Summary of the Invention] The electrical insulating composition of the present invention has an average particle size of 6 μm or less and a BET specific surface area of 40 tons, based on 100 parts by weight of polyolefin.
+? /g or less, and contains 50 parts by weight or more of magnesium hydroxide surface-treated with either a fatty acid, a fatty acid metal salt, a titanate coupling agent, or a silane coupling agent.

Examples of the polyolefin in the present invention include ethylene propylene copolymer, ethylene propylene diene turbo polymer, polyethylene, ethylene vinyl acetate copolymer, ethylene ethyl acrylate copolymer, ethylene butene copolymer, polypropylene, polybutene, and polybentene, which may be used alone or Two or more types can be used in combination.

Since such polyolefin and magnesium hydroxide have poor compatibility, agglomeration occurs during roll or pan-burr kneading, resulting in deterioration of extrudability and tensile properties.

This is because magnesium hydroxide is an ionic crystal, whereas polyolefin is non-polar or only slightly polar, and has a small affinity with magnesium hydroxide.

In order to improve this, in the present invention, the average particle size is 5 μm or less,
Magnesium hydroxide having a BET specific surface area of 40 i/g or less is used; if it is outside this range, agglomeration occurs during roll or pan burr kneading, resulting in poor extrudability and tensile properties.

In addition, in order to prevent magnesium hydroxide from reacting with water and carbon dioxide in the air and changing into magnesium carbonate, magnesium hydroxide should be treated with fatty acids, fatty acid metal salts, titanate coupling agents, or silane coupling agents. The surface is treated with

Fatty acid is RCOOH, fatty acid metal salt is M(00CR)n
It is expressed as In addition, R is an alkyl group or an alkene group, M is an IA, nB, or mA group metal, and n is a natural number.

Examples of titanate coupling agents include isopropyl-tri(dioctylphosphate) titanate and titanium di(octylphosphate) oxyacetate, and examples of silane coupling agents include vinyltriethoxysilane and vinyltris(β-methoxyethoxy)silane. be.

The above-mentioned special magnesium hydroxide must be contained in an amount of 50 parts by weight or more per 100 parts by weight of the polyolefin. If it is less than 50 parts by weight, the desired flame retardancy cannot be imparted. The upper limit is determined depending on the purpose of use and is not particularly limited, but considering extrudability, it is 500
parts by weight, preferably 300 parts by weight.

In the present invention, the above composition can be used either uncrosslinked or crosslinked. Examples of crosslinking methods include crosslinking using organic peroxides, crosslinking using electron beam irradiation, and silane graft water crosslinking.

In the case of crosslinking using an organic peroxide, suitable organic peroxides include dicumyl peroxide and 3-bis(t-butylperoxyisopropyl)benzene.

Further, in the case of crosslinking by electron beam irradiation, a reactive monomer such as trimethylolpropane trimellitate or triallyl isocyanurate is generally added as a crosslinking aid.

In the present invention, in addition to the above components, antioxidants, lubricants, softeners, dispersants, etc. may be added.

As an antioxidant, phenyl-α-naphthylamine, N
, amine antioxidants such as N'-di-β-naphthyl-p-phenylenediamine, 2,6-di-t-butyl-4-
Examples include phenolic antioxidants such as methylphenol and hindered phenol.

[Examples and Comparative Examples] Various ingredients were mixed in the proportions shown in Table 1.
The material was placed in a 6-inch roll kept at 120°C and kneaded by rolls, and after kneading, a 40 m/m extruder (L/D = 25) kept at 120°C was used to place 1 on a copper wire with an outer diameter of 2.0 mm. ．． 'Omm thickness extrusion coating followed by 13kg
The wires were held in a water vapor atmosphere of /c for 3 minutes and cross-linked to produce various electric wires.

The evaluation results of the electric wires obtained on each side are as shown in the lower column of Table 1.

The dispersibility was measured by rolling out a sheet with a thickness of 0.5 mm after kneading,
Observation was made using a microscope with a magnification of 20 times.

In the flame retardancy evaluation, a wire held horizontally is burned in a burner for 30 seconds, and if the flame self-extinguishes after that, it passes, and if it does not self-extinguish, it fails.

The tensile properties were measured by pulling out the copper wire after steam crosslinking, leaving it in a constant temperature room at 20° C. for 1 day, and measuring the tensile properties using a Schopper type tensile tester at a tensile speed of 500 mm/min.

Insulation resistance was measured by drying an electric wire at 80°C for one day, immersing it in hot water at 85°C for one week, and then measuring it at 85°C.

As is clear from Table 1, Examples 1 to 6 according to the present invention
All wires made of the materials shown in the table have good dispersibility of magnesium hydroxide, pass the JIS flame retardant test for flame retardancy, and have a tensile strength of 0.4 kg/m2 or higher, which is the electrical appliance standard for ethylene propylene rubber. fully satisfied.

On the other hand, Comparative Example 1, in which the content of magnesium hydroxide was less than the specified value, failed in terms of flame retardancy. Average particle size and B
Comparative Examples 2 and 3 using magnesium hydroxide having an ET specific surface area other than the specified value had poor dispersibility, resulting in a significant decrease in tensile properties and insulation resistance. Furthermore, in Comparative Example 4 using magnesium hydroxide without surface treatment, the insulation resistance was significantly reduced.

[Effects of the Invention] As explained above, the present invention is a flame-retardant filler for polyolefin that has an average particle size and a BET specific surface area within a predetermined range, and that contains fatty acids, fatty acid metal salts, nathanate cutting agents, or silane cups. This product uses magnesium hydroxide that has been surface-treated with a ring agent, which improves the compatibility between the polymer and magnesium hydroxide.This results in excellent tensile properties, insulation resistance, and flame retardancy, and also eliminates toxic halogens during combustion. It becomes possible to obtain molded products that do not generate system gas.

Claims (2)

[Claims] (1) Average particle size 5 for 100 parts by weight of polyolefin
μm or less, BET specific surface area ILOd/g or less, and further contains 50 parts by weight or more of magnesium hydroxide that has been surface-treated with either a fatty acid, a fatty acid metal salt, a titanate coupling agent, or a silane coupling agent. Flammable electrical insulation composition. (2) The flame-retardant electrical insulation composition according to claim 1, wherein the composition contains a crosslinking agent.