JPH048884B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to improvements in flame-retardant insulated wires, and particularly to provide an improved flame-retardant insulated wire that effectively prevents the so-called sagging phenomenon during vertical combustion tests. Electric wires and cables for electrical equipment are required to have strict characteristics, but in recent years, particularly from the standpoint of disaster prevention, very strict characteristics such as UL Standard 62 VW-1 and CSA Standard C22.2 No. 3 have been adopted. It has become necessary to pass a strict vertical combustion test. In such tests, emphasis is placed not only on the spread of fire vertically upward of the cable, but also on the spread of fire below the cable due to falling combustible materials (so-called dripping). In general, polyethylene, ethylene vinyl acetate copolymer, and ethylene ethyl acrylate copolymer have excellent electrical properties and high mechanical strength at room temperature, and their crosslinked products also have excellent heat resistance. Due to its properties, it is widely used as an electrical insulator. However, since such resins are easily flammable, they are generally used after being blended with flame retardants such as halides and various inorganic compounds to make them flame retardant. In this case, polyethine, unlike other ethylene-vinyl acetate copolymers and ethylene-ethyl acrylate copolymers, has a low blendability with the above-mentioned flame retardant, and therefore is flame retardant as a blend with the copolymer. It is normal to become However, these copolymers become low-molecular and viscous liquefied under high temperatures during combustion, lowering the overall viscosity and becoming prone to dripping, which is a serious problem that causes the coating to droop, especially during the above-mentioned vertical combustion test for electric wires and cables. It was becoming the cause. Although many proposals have been made regarding the appropriate prevention of such dripping, the reality is that none of them are necessarily satisfactory. For example, measures such as increasing the degree of crosslinking of the resin used are not sufficient to prevent the dripping, and it is known that adding inorganic fillers such as clay and talc is effective in suppressing it. Regarding the above-mentioned polyethine, ethylene vinyl acetate copolymer or ethylene-ethyl acrylate copolymer,
The inhibitory effect is low, and it is necessary to add 50% by weight or more to the resin, which has the disadvantage of reducing the mechanical strength of the composition. Furthermore, according to the disclosure of Japanese Patent Publication No. 47-24455,
It is said that blending the desired amount of the above halogenated flame retardant is effective in preventing this dripping, but dripping is often observed in the case of resins such as polyethylene mentioned above during vertical combustion tests of cables, and the above strict requirements are not met. The reality is that it is impossible to respond to this. In view of these circumstances, the inventors have conducted extensive studies, and as a result have found a composition that surprisingly suppresses such dripping without degrading the above-mentioned mechanical properties, and has completed the present invention. That is, the present invention uses ethylene vinyl acetate copolymer or ethylene-ethyl acrylate copolymer alone or a blend resin of both, or a polyethine blend resin containing 30% by weight or more of the single or blend resin, based on 100 parts by weight of the polyethine blend resin, general formula, (However, in the formula, X is a halogen atom such as Cl, Br,
m is an integer of 3 to 4, n is an integer of 1 to 6, and Z represents an organic radical consisting of aliphatic carbon, aromatic carbon, nitrogen, carbon having an oxygen skeleton, hydrogen, oxygen, nitrogen, bromine, and chlorine. 20 to 70 parts by weight of a flame retardant represented by ), 3 to 30 parts by weight of a compound consisting of zinc and a Group A element of the periodic table excluding oxygen and having a melting point of 250°C or higher, and 10 to 70 parts by weight of antimony trioxide. A flame-retardant insulated wire is characterized in that a conductor is coated with a cross-linked ethylene-based flame-retardant resin composition comprising: In this invention, first, zinc sulfide (melting point 1850°C/
150 atm), zinc sulfate (decomposes above 740°C), zinc selenide (melting point 1100°C), zinc telluride (decomposes above 740°C),
1238.5℃), 2-mercaptobenzimidazole zinc salt (decomposes above 300℃), Methyl-2-mercaptobenzimidazole zinc salt (decomposes above 300℃), 2-mercaptobenzthiazole zinc salt (decomposes above 250℃) etc. are particularly suitable as they are easy to obtain. The zinc compound is blended in an amount of 3 to 30 parts by weight based on 100 parts by weight of the resin. If the blending amount is below the lower limit, the effect of preventing dripping during combustion cannot be obtained, and if the blending amount exceeds the upper limit, no improvement in the effect is observed, but rather leads to a decrease in mechanical properties. Next, the halogen flame retardant used in this invention has the general formula (However, in the formula, X is a halogen atom such as Cl, Br,
m is an integer of 3 to 4, n is an integer of 1 to 6, and Z represents an organic radical consisting of aliphatic carbon, aromatic carbon, nitrogen, carbon having an oxygen skeleton, hydrogen, oxygen, nitrogen, bromine, and chlorine. ), specifically, N,N'-(1,2-ethylene)-bis(3,4,5,6-tetrabromophthalimide), N,N'(1,4-phenylene) −
Bis(3,4,5,6-tetrabromophthalimide) and the like. In this invention, the halogen flame retardant and antimony trioxide are blended in an amount of 20 to 70 parts by weight and 10 to 70 parts by weight, respectively, per 100 parts by weight of the resin.
If the amount is less than these lower limits, the above-mentioned effect of preventing combustion in the vertical direction of the cable will be insufficient, and if the amount exceeds the upper limit, no improvement in the same effect will be observed, and on the contrary, the mechanical strength will decrease, which is undesirable. The ethylene resin used is ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer alone or a blend of both,
Or further add 30 of these individual resins or blended resins.
This is a polyethylene blend resin containing at least % by weight, and the reason for limiting it to such resins is that, as mentioned above, these resins have good crosslinking efficiency, excellent heat deterioration resistance, and electrical insulation properties, and blends within this range If so, it is possible to incorporate additives such as flame retardants without causing any disadvantages to various properties such as mechanical properties and processability. Examples of crosslinking methods for insulators using such compositions include ionizing radiation irradiation, chemical crosslinking using organic peroxides, and, for example, Japanese Patent Publication No. 48-1711
A silane crosslinking method using a silane compound represented by No. 1 is applicable. For the above-mentioned flame-retardant composition of the present invention, a halogen-based flame retardant other than those mentioned above or a hydrous inorganic flame retardant such as aluminum hydroxide may be used in combination without deteriorating other mechanical properties. ,
Furthermore, ultraviolet absorbers, metal deactivators, colorants, lubricants, reinforcing agents for rubber plastics, fillers, crosslinking agents, and crosslinking accelerators may be added as appropriate. As is clear from the Examples described later, the present invention is particularly applicable to
It is possible to provide an insulated wire that can withstand the above-mentioned severe combustion test without causing a decrease in mechanical properties, etc., and has great industrial utility value. The present invention will be specifically explained below using Examples. Flame retardant, N,N'(1,4-phenylene)-bis(3,4,5,6-tetrabromophthalimide)
Preparation Example The flask of 1 was equipped with a heating mantle and a reflux condenser, and in the flask, 1000 g of tetrabromo phthalic anhydride was completely dissolved in 0.5 ml of ethyl methyl ketone, and then 50 ml of ethyl 1.179 dissolved in methyl ketone
g of phenylenediamine was poured into this and reacted at 80° C. for 16 hours with stirring. The resulting precipitate was filtered and purified by dissolving unreacted substances twice at 80°C with ethyl methyl ketone. This precipitate was heated at 150°C for 1 hour to complete the condensation reaction. The resulting compound is a dark brown powder whose thermal properties are
It has no melting point up to 450℃, and decomposition begins at 450℃. The yield rate was 46%. Examples 1 to 10, Comparative Examples 1 to 13 Compositions having the composition ratios shown in Table 1 below were kneaded in a Banbury mixer to obtain kneaded products (mixer discharge material temperature: 145 to 160°C). The obtained kneaded material was made into a sheet using an open roll and then pelletized using a pelletizer. Using a small extruder, the above pellets were extruded onto a 18 AWG flexible twisted copper conductor to a thickness of 0.76 mm to obtain an insulated wire (material extrusion temperature: 160-170°C), and further coated on this.
Crosslinking was performed by irradiating 20 Mrad with a 1 MeV high-energy electron beam.

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[Table] Regarding each insulated wire above, the UL listed above
The results of the Subject758VW-1 combustion test and the tensile strength and elongation characteristics of the insulator are shown in Table 2 below. The above VW-1 test showed this by the number of passes per 10 tests.

【table】

[Table] According to the results shown in the above table, the following can be seen, and it is clear that the effects of the present invention are excellent. (i) Comparative Examples 1 and 2 and Examples 1, 2, 3, and 4 had approximately the same composition of base resin, flame retardant, etc., but the comparative example caused dripping with a probability of about 50%. In contrast, the present invention had no such problem. That is, in particular, the use of the zinc salt to prevent dripping was almost complete, and almost no deterioration in mechanical properties was observed. (ii) Even if a large amount of talc, which is a typical inorganic filler, is added as in Comparative Example 3, the above dripping cannot be prevented;
Furthermore, as in Comparative Example 4, silicon dioxide unnecessarily reduced the mechanical properties. (iii) According to Comparative Examples 5 and 6, zinc oxide has no effect and has a low melting point (200°C).
Other zinc salts were not sufficiently effective. (iv) Comparative Example 7 shows that with other commonly used flame retardants, even if the zinc salt used in the present invention is used in combination, the drip-preventing effect cannot be obtained. (v) In particular, Examples 5, 6 and 7 show that the base resins can be used alone or in blends. (vi) In Comparative Examples 8, 10, and 11, if the composition specified in the present invention is not met, the original effect of preventing dripping etc. cannot be obtained, and in Comparative Examples 9, 11, and 13, the blended amount is It has been clarified that an excess of 0.5% leads to a decrease in mechanical properties.

Claims (1)

[Claims] 1. Ethylene-vinyl acetate copolymer or ethylene-
For 100 parts by weight of a polyethylene blend resin containing 30% by weight or more of an ethyl acrylate copolymer alone or a blend of both, the general formula: (However, in the formula, X is a halogen atom such as Cl, Br,
m is an integer of 3 to 4, n is an integer of 1 to 6, and Z represents an organic radical consisting of aliphatic carbon, aromatic carbon, nitrogen, carbon having an oxygen skeleton, hydrogen, oxygen, nitrogen, bromine, and chlorine. 20 to 70 parts by weight of a flame retardant represented by ), 3 to 30 parts by weight of a compound consisting of zinc and a Group A element of the periodic table excluding oxygen and having a melting point of 250°C or higher, and 10 to 70 parts by weight of antimony trioxide. 1. A flame-retardant insulated wire, characterized in that a conductor is coated with a cross-linked ethylene-based flame-retardant resin composition.