JPS59160911A - Flame resistance, low smoke polyolefin resin coated wire - 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 [Technical Field of the Invention] The present invention relates to a flame-retardant, low-smoke polyolefin resin-coated electric wire that is flame-retardant, generates little smoke, and does not generate corrosive gases.

[Background of the invention]

In recent years, the requirements for flame retardancy for building wiring and equipment internal wiring have become increasingly strict, and it goes without saying that they must be flame retardant, emit less smoke, and, moreover, must be free of harmful gases that have an adverse effect on the human body and equipment. It is expected that this will not occur.

To meet these requirements, resins containing halogen in their molecular structure, such as polyvinyl chloride resin, cannot be used because they generate corrosive and harmful gases when burned. In addition, for resins that do not contain 9 halogens, such as polyolefin resins, flame retardants consisting of halogen compounds are generally added to make them flame retardant.
In this case, halogen gas is also generated during combustion. Therefore, a method of imparting flame retardance by adding so-called hydrated metal oxides that do not use norogens has become effective, and it is well known that aluminum hydroxide, magnesium hydroxide, etc. are used as hydrated metal oxides. ing.

Currently, the oxygen index method is one of the evaluation methods for flame retardancy.
The oxygen index of the polyolefin resin filled with metal carbonates and hydrated metal oxides was measured using the method (Ni-7201) and is shown in FIG. Figure 1 (1) shows the change in oxygen index with respect to the filler amount of m for magnesium carbonate, (2) for magnesium hydroxide, (3) for aluminum hydroxide, and (4) for zinc borate. Generally speaking, when flame retardancy is expressed as an oxygen index, the oxygen index is 22 to 25 at horizontal flame retardance level.
It is said that the vertical flame retardancy is 27-30 or higher. Now, when the amount of filler necessary to achieve an oxygen index of 30, which is the degree of flame retardance for vertical flame retardation, is determined from FIG. 1, it is found that 100 parts by weight or more is required to be added.

The smoke generation property was measured using an NBS smoke density chamber, and the maximum smoke density (Dm) at flaming is shown in Figure 2. The numbers in FIG. 2 indicate the same fillers as in FIG. As can be seen from this figure, it is necessary to increase the amount of filler in order to reduce the amount of smoke generated. However, in the case of crystalline polymers such as polyethylene, if 100 parts by weight or more of filler is added, the physical properties, processability, etc. will be significantly impaired and molding will not be possible.

Therefore, it is necessary to use a pace polymer that maintains its physical properties, processability, etc. to a certain extent even when a large amount of these fillers is added.

Examples of polymers to which a large amount of filler can be added include rubbers such as EP rubber, ethylene-vinyl acetate copolymers, and ethylene-α-olefin copolymers. Among these polymers, an ethylene-vinyl acetate copolymer having a vinyl acetate content of 50% or more can be molded even at a high filling of 200 to 300 parts by weight, and is suitable as a highly filled filler polymer. It is preferable to use ethylene-vinyl acetate copolymer alone as the base polymer, but depending on the required properties, other polymers such as polyethylene,
Polypropylene, ethylene-vinyl acetate copolymer (vinyl acetate content less than 5096), ethylene-ethyl acrylate copolymer, ethylene-α olefin copolymer, E
It is also possible to use it in a blend with P rubber (EPDM), butyl rubber, polybutadiene, polyurethane, etc.

In this way, it is already well known that hydrated metal oxides, metal carbonates, etc. are highly loaded into halogen-free polymers to achieve flame retardancy and low smoke without emitting corrosive gases. . However, from the viewpoint of physical properties such as mechanical properties and processability, it is preferable that the amount of filler to be filled is as small as possible.

From this perspective, the present invention was developed to achieve low smoke and flame retardancy with the same amount of filler or a smaller amount of filler.

[Summary of the invention]

The present invention was made based on the discovery that low smoke and flame retardance can be achieved at the same time by adding zinc borate to the hydrated metal oxide or metal carbonate mentioned above. The gist of this is that a hydrated metal oxide or metal carbonate is added as a filler to a polyolefin resin composition mainly composed of an ethylene-vinyl acetate copolymer with a vinyl acetate content of 50% by weight or more. and zinc borate in a total of 100 parts by weight or more, and the ratio of zinc borate in the filler was 0.25 to 0.75, and the composition was crosslinked with radiation and used as an insulation or sheath. It is a radiation-irradiated cross-linked, low-smoke, flame-retardant polyolefin resin coated electric wire.

[Detailed Description of the Invention] In the present invention, the polyolefin resin refers to an ethylene-vinyl acetate copolymer having a vinyl acetate content of 50% by weight or more, alone, or polyethylene, polypropylene, ethylene-vinyl acetate copolymer, It means a blend with ethylene-ethyl acrylate copolymer, ethylene-α olefin copolymer, EP rubber, butyl rubber, polybutadiene, polyurethane, etc.

Examples of hydrated metal oxides include aluminum hydroxide, magnesium hydroxide, calcium hydroxide, barium hydroxide, and the like.

Examples of metal carbonates include magnesium carbonate, calcium magnesium carbonate, calcium carbonate, zinc carbonate, and barium carbonate.

The reason why the combined amount of hydrated metal oxide or metal carbonate and zinc borate is 100 parts by weight or more is that if 100 parts by weight or more is not added, the oxygen index of the resin composition will be in the vertical flame retardant region of 30. This is because it does not exceed On the other hand, the maximum blending amount varies depending on the type of polyolefin resin, so
-Not prescribed by law.

For example, in the case of an ethylene-vinyl acetate copolymer alone having a vinyl acetate content exceeding 50% by weight, up to about 300 parts by weight can be blended.

In the present invention, the weight ratio of zinc borate in the filler is 0.
．． When it is 25 to 075, it exhibits excellent low smoke properties and flame retardancy. f
That is, when the weight ratio is less than 025, the effect of reducing the smoke amount is small, and when it exceeds 075, the oxygen index becomes less than 30.

In the present invention, the effect of radiation crosslinking is to improve the deterioration in physical properties caused by adding a large amount of filler to achieve low smoke and flame retardancy. For example, when 100 parts by weight of a hydrated metal oxide is added to an ethylene-vinyl acetate copolymer, the tensile strength is as small as 0.1 kg/mm 2 , which is not practical. By illuminating the electron beam at 20 Mrad,
The tensile strength is 0.6 kg/inm'', which is at the same level as ordinary cross-sulfurized rubber, and is sufficiently usable for practical use.

Further, the reason why radiation crosslinking is optimal is that crosslinking can be performed regardless of the molding temperature of the material.

That is, when attempting to chemically crosslink a material with a large amount of filler added as in the present invention using an organic peroxide, the torque during molding becomes high, the material temperature rises to around 200°C, and the decomposition temperature of the organic peroxide increases. (120~1
(approximately 80°C), crosslinking occurs in the molding machine, making molding impossible.

The present invention will be explained below using specific examples.

Using the composition shown in Table 1, wires with an insulation outer diameter of 2.4 mm and a conductor diameter of O8n1m were made, and after being irradiated with an electron beam of 20 Mrad, the wires were arranged in a predetermined size and the amount of smoke emitted from the coating layer (maximum smoke) was measured using an NBS smoke chamber. Density Dm) and oxygen index Table 1 1) Ethylene-vinyl acetate copolymer, (vinyl acetate content 60%) 2) Aluminum hydroxide number were measured. The results are shown in Figures 3 and 4, respectively. As is clear from FIG. 3, as zinc borate is added, the amount of smoke generation decreases, and when all the filler is placed in zinc borate, the flame retardance is not satisfied as shown in FIG. 44. From FIG. 3 and FIG. 4, it can be seen that the optimal ratio of zinc borate to the filler is 0.25 to 0.75. Regarding the combination of metal carbonate and zinc borate, an electric wire with an outer diameter of 2.4 mm and a conductor diameter of 0.8 M was prepared using the composition shown in Table 2, and after irradiating it with an electron beam of 20 Mrad, the amount of smoke and oxygen index were measured. The results were shown in FIGS. 5 and 6, respectively. In the combination of metal carbonate and zinc borate, the ratio of zinc borate to the filler is 0.25 to 0.75.
In the case of , it can be seen that both flame retardancy and low smoke properties are excellent.

As described above, according to the present invention, a coated electric wire having high flame retardance with an oxygen index of 30 or more and low smoke generation was obtained.

Table 2 1) Ethylene-vinyl acetate copolymer (Vinyl acetate content 60%) 2) Magnesium carbonate

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the amount of various fillers added and the oxygen index. FIG. 2 is a graph showing the relationship between the amount of various fillers added and the amount of smoke generated. FIG. 3 is a graph showing the relationship between the addition ratio of hydrated metal oxide and zinc borate and the amount of smoke generated. Figure 4 is a graph showing the relationship between the addition ratio of hydrated metal oxide and zinc borate and the oxygen index. FIG. 5 is a graph showing the relationship between the addition ratio of metal carbonate and zinc borate and the amount of smoke generated. FIG. 6 is a graph showing the relationship between the addition ratio of metal carbonate and zinc borate and the oxygen index. (1) is magnesium carbonate, (2) is magnesium hydroxide, (3) is aluminum hydroxide, and (4) is zinc borate. Full i41 amount (additional amount included)! 'yNt@/(ho,) Heibado 4 convex suni class late Ihiko naru) well 5

Claims (3)

[Claims] (1) A polyolefin resin composition mainly composed of an ethylene-vinyl acetate copolymer with a vinyl acetate content of 50% by weight or more is combined with a water-use metal oxide or metal carbonate and zinc borate as fillers. 100 parts by weight or more, and the ratio of zinc borate in the filler is 0.25-0.
75. A flame-retardant, low-smoke polyolefin resin-coated electric wire characterized in that a composition crosslinked by radiation irradiation is used as an insulator or a sheath. (2) Claim (1) characterized in that the water use metal oxide is selected from the group consisting of aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and norium hydroxide. flame-retardant, low-smoke polyolefin resin-coated wire. (3) The flame retardant according to claim (1), wherein the metal carbonate is selected from the group consisting of magnesium carbonate, magnesium calcium carbonate, calcium carbonate, zinc carbonate, and barium carbonate. , low smoke polyolefin resin coated wire.