JPH0952987A - Flame retardant covering material composition for electric wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition, capable of manifesting high flame retardance and heat resistance without containing a halogen and excellent in both physical properties and electric insulating properties. SOLUTION: This flame retardant resin composition for an electric wire comprises 150-200 pts.wt. metallic hydride, 1-5 pts.wt. 2-mercaptobenzimidazole- based compound and tetrakis[methylene-3(3',5'-di-t-butyl-4'-hydroxyphenyl) propionate]methane, 1-15 pts.wt. polymerizable organic acid metallic salt and 0.5-5 pts.wt. organic peroxide based on 100 pts.wt. base resin of 30-50 pts.wt. ethylene/vinyl acetate copolymer having 10-25wt.% vinyl acetate residue content and 70-50 pts.wt. ethylene/(meth)acrylate copolymer.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a flame-retardant coating material composition for electric wires, which can be used as a flame-retardant coating material for non-halogen flame-retardant cables and fire-resistant electric wires.
In particular, when crosslinked, a flame-retardant coating material composition for electric wires, which does not contain halogen, exhibits high flame retardancy and heat resistance, and is excellent in both physical properties and electrical insulation properties. Regarding things.

[0002]

2. Description of the Related Art Flame-retardant cables are generally used for distribution of electricity to buildings, factories, tunnels, vehicles, ships, etc. in order to prevent the spread of fire. In a conventional flame-retardant cable, a coating material such as a polymer-based electric insulator or sheath in which flammability is a problem is formed of a halogen-containing resin composition such as polyvinyl chloride or chloroprene rubber, and a coating material composition. A flame retardant such as a halogen-based flame retardant, antimony trioxide, and metal hydroxide may be mixed therein to enhance flame retardancy. However, from the viewpoint of suppressing the generation of harmful gases in actual fires, so-called non-halogen flame-retardant cables that do not contain halogen have recently been used as flame-retardant cables used in vehicles, ships, buildings, subways, underground malls, power plants, etc. It has been demanded. In addition, so-called fireproof electric wires are used for distribution of emergency equipment for fire fighting. Although an inorganic insulator such as mica is used as the fire resistant layer in this product, flame retardancy is also required for the polymer-based electric insulating layer and sheath.

In these non-halogen flame-retardant cables and fireproof electric wires, the composition used for forming an electric insulating layer, a sheath, etc. (hereinafter collectively referred to as "covering material") is usually
A polyolefin resin or copolymer is used as a base resin, which is mixed with metal hydrates such as aluminum hydroxide and magnesium hydroxide to suppress the generation of toxic gases during combustion and to reduce the amount of smoke emitted. In addition, a cross-linking agent is blended in order to cross-link the base resin to increase its heat resistance and prevent sagging at high temperatures.
In order to increase the flame retardancy of the base resin itself, a polyolefin having a polar residue in the molecule such as ethylene / vinyl acetate copolymer is used as the polyolefin.

[0004]

In the above halogen-free flame-retardant coating material composition, in order to enhance the flame retardancy, the content of polar components such as vinyl acetate residues in the base resin is first increased, In addition, it is necessary to increase the mixing ratio of the metal hydrate. However, if the content of the polar component in the base resin is increased, the electrical insulation properties such as volume resistivity are decreased, and if the mixing ratio of the metal hydrate is increased, the physical properties of the coating material such as tensile strength and elongation are decreased, It has been difficult to establish a good balance between flame retardancy, physical properties, and electrical insulation. The present invention has been made to solve the above problems, and therefore an object thereof is to provide a flame-retardant coating material composition for electric wires, which is a non-halogen type and is excellent in both physical properties and electrical insulation properties. Especially.

[0005]

[Means for Solving the Problems] The above-mentioned problem is a composition for forming a flame-retardant coating material for electric wires by crosslinking, wherein the content of vinyl acetate residue is in the range of 10% by weight to 25% by weight. Ethylene / vinyl acetate copolymer (hereinafter referred to as “EV
100 parts by weight of a base resin comprising 30 parts by weight to 50 parts by weight of A)) and 70 parts by weight to 50 parts by weight of an ethylene / (meth) acrylate copolymer (hereinafter referred to as “E / A”). 150 to 200 parts by weight of metal hydrate, 2-mercaptobenzimidazole compound (hereinafter referred to as "MBI"), and tetrakis [methylene-] which is a hindered phenol antioxidant.
3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate] methane (hereinafter, “HPA”)
For 1 to 5 parts by weight in total, 1 to 15 parts by weight of the polymerizable organic acid metal salt, and 0.5 to 5 parts by weight of organic peroxide. It can be solved by providing a flammable coating composition.
The above EVA has a melt index of 2.5 to 1
It is preferably within the range of 5. Further, it is preferable that the polymerizable organic acid metal salt is zinc (meth) acrylate.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The flame-retardant coating material composition for electric wire of the present invention (hereinafter, referred to as "the present composition") is basically composed of EVA and E / A, and a metal hydrate. Things and MB
I, HPA, a polymerizable organic acid metal salt, and an organic peroxide are blended. The present composition in which the blending ratio of each of these components is adjusted within a specific range is a flame-retardant coating material for electric wire, which is excellent in both physical properties and electric insulation, which is the object of the present invention, by molding and crosslinking. (Hereinafter, simply referred to as "covering material") is obtained.

Next, each component constituting the composition will be described. (Base Resin) EVA: A part of the base resin that constitutes the skeleton of the coating material, and the vinyl acetate residue contained therein enhances the flame retardancy of the composition. EVA containing vinyl acetate residues in the range of 10% to 25% by weight is used in the composition. If the vinyl acetate residue is less than 10% by weight, the flame retardancy when used as a coating material is not sufficient, and if it exceeds 25% by weight, the electrical insulating property (volume resistivity) decreases. From this viewpoint, it is more preferable that the vinyl acetate residue is contained in the range of 15% by weight to 20% by weight.

The EVA used in the present composition preferably has a melt index in the range of 2.5 to 15. Within this range, when the obtained composition is used to form a coating by extrusion, its flow characteristics can be suitably adjusted. This EVA base resin 1
The compounding ratio per 00 parts by weight is in the range of 30 to 50 parts by weight. This blending ratio is derived from the E / A blending ratio described below.

E / A: Examples of E / A which can be used as a part of the base resin of the present composition include, for example, ethylene / ethyl acrylate copolymer (EEA), ethylene / methyl acrylate copolymer. (EMA), ethylene /
Methyl methacrylate copolymer (EMMA), ethylene /
An ethyl methacrylate copolymer (EEMA) etc. can be mentioned.

The mixing ratio of E / A per 100 parts by weight of the base resin is in the range of 50 to 70 parts by weight. E / A controls the flow properties of the resulting composition as it is extruded from an extruder and coated onto a conductor. If the E / A is less than 50 parts by weight per 100 parts by weight of the base resin, the fluidity of the composition will be insufficient, and if it exceeds 70 parts by weight, the physical properties of the coating layer after crosslinking, such as tensile strength, will be reduced.

(Additive) Metal hydrate: Generally, aluminum hydroxide or magnesium hydroxide, or a mixture thereof is used. These are used as the flame retardant filler of the present composition. The mixing ratio is within the range of 150 to 200 parts by weight per 100 parts by weight of the base resin. If it is less than 150 parts by weight, the flame retardancy when used as a coating material is insufficient.
If it exceeds 100 parts by weight, the fluidity of the composition when coated becomes poor, and the physical properties of the coating layer after crosslinking, such as tensile strength and elongation, deteriorate.

MBI: 2-mercaptobenzimidazole represented by the following formula (1) and 2-mercaptomethylbenzimidazole represented by the formula (2) are included. M
BI is effective as a polyolefin antioxidant.

[0013]

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HPA: A compound generally used as an antioxidant for rubbers and plastics, which is commercially available under the trade name of "Irganox 1010" (manufactured by Ciba-Geigy).

In this composition, one of the above MBI and HPA is not blended alone, but
When both are used together, the heat aging resistance of the coating material is improved with a compounding amount that does not adversely affect the electrical characteristics and physical properties of the composition due to their synergistic effect. The mixing ratio is 100 parts by weight of the base resin, MBI and HP.
The total amount of A is in the range of 1 to 5 parts by weight. 1
If it is less than 5 parts by weight, the effect of preventing heat aging is not sufficient, and if it exceeds 5 parts by weight, the electrical properties and physical properties of the coating material may deteriorate. MBI and HPA are preferably blended in a weight ratio of about 1: 1.

Polymerizable organic acid metal salt: a salt of a polymerizable organic acid such as an organic acid having a polymerizable ethylene residue such as acrylic acid, methacrylic acid or maleic acid and a metal such as zinc, magnesium or aluminum. , Used as a cross-linking aid in organic peroxide cross-linking of polyolefin. The polymerizable organic acid metal salt serves as a coating material as compared with the case where other crosslinking aids such as triallyl isocyanurate and 2,4,6-triallyloxy-1,3,5-S-triazine are used. There is little decrease in the electrical insulation properties such as volume resistivity, and hardness, modulus,
Improves physical properties such as compression set.

The mixing ratio of the polymerizable organic acid metal salt is in the range of 1 part by weight to 15 parts by weight per 100 parts by weight of the base resin. If the amount is less than 1 part by weight, the effect as a crosslinking aid is insufficient, and if the amount exceeds 15 parts by weight, the hardness becomes excessive and the balance of physical properties is lost.

Organic peroxide: Generally, dicumyl peroxide (hereinafter referred to as "DCP") is used as a crosslinking agent for crosslinking the polyolefin coating material composition. Therefore, it is preferable to add DCP also in the present composition, but the present invention is not necessarily limited thereto. The mixing ratio is within the range of 0.5 to 5 parts by weight per 100 parts by weight of the base resin. The polyolefin composition containing DCP can be crosslinked by heating to, for example, 150 ° C. or higher.

[0019]

EXAMPLES Next, examples of the present invention will be described with reference to comparative examples. The temperature of each component shown in Table 1 below is 120 ° C.
And kneading with Example 1, Example 2 and Comparative Example 1 respectively.
~ The composition of Comparative Example 5 was obtained.

[0020]

[Table 1]

The components used in these Examples and Comparative Examples will be described below. (Component of Base Resin) EVA: One or two of three types were mixed and used. The three kinds used were 1 kind each having a vinyl acetate residue content of 19% by weight and a melt index (MI) of 15 and 2.5, and a vinyl acetate residue content of 2
It is 8% by weight and has a MI of 15. E / A: ethylene / ethyl acrylate (EEA),
One having an MI of 0.75 was used.

(Additive) Metal Hydrate: Aluminum Hydroxide ("Hidilite H-
42S "). MBI: 2-mercaptomethylbenzimidazole (of formula (2)) ("Nocrac MMB"). HPA: "Irganox 1010". Control anti-aging agent: As a control, a thiobisphenol-based anti-aging agent ("Nocrac 300") was used only in Comparative Example.

Polymerizable organic acid metal salt: Zinc methacrylate ("Actor ZMA" manufactured by Kawaguchi Chemical Industry Co., Ltd.). Control crosslinking aid: triallyl isocyanurate (manufactured by Nippon Kasei Co., Ltd., "TAIC") was used as a control only in Comparative Examples. Crosslinking agent: Dicumyl peroxide (DCP).

Using the compositions of Examples and Comparative Examples having the compositions shown in Table 1, a sheet having a thickness of 1.0 mm for measuring physical properties and electrical properties was cross-linked at a temperature of 200 ° C. and a flame retardance test. A sheet having a thickness of 3.0 mm was molded for use as a sample. The physical properties were measured with respect to tensile strength and elongation after molding, and tensile strength and elongation after heat aging at 135 ° C. for 7 days as heat aging resistance. For the electrical characteristics, the volume resistivity at 30 ° C. was measured. Flame retardancy is JIS K7
It evaluated by the oxygen index according to the test method of 201. Table 2 shows the test results.

[0025]

[Table 2]

With respect to the test results shown in Table 2, the quality levels required for the coating material of the flame-retardant cable are as follows. (Required quality level) Tensile properties: Tensile strength of 1.0 kgf / mm ² or more. Heat aging resistance: Strength residual rate is 100% or more. Volume resistivity: 1 × 10 ¹⁵ Ω · cm or more. Oxygen index: 30 or more.

Each sample in Table 1 was evaluated with reference to the above required quality level. The evaluation results are as follows. Example 1: This sample has a vinyl acetate residue content of 19
EVA (50 parts by weight) and EE with MI of 15% by weight
A base resin consisting of A (50 parts by weight) was used, and the additives were prepared from the composition obtained by using the additives within the scope of the present invention in an amount ratio within the scope of the present invention. The obtained sample is
The tensile properties, heat aging resistance, volume resistivity and oxygen index all exceeded the required quality level.

Example 2 A sample was prepared in the same manner as in Example 1, except that a base resin consisting of EVA (30 parts by weight) and EEA (70 parts by weight) was used. This sample is
The tensile properties, heat aging resistance, volume resistivity and oxygen index all exceeded the required quality level. From the results of Example 1 and Example 2, the blending ratio of EVA and EEA in the base resin was 50:50 to 3 by weight.
It can be seen that a coating material satisfying the required quality level was obtained within the range of 0:70.

In Comparative Example 1, EE was used as the base resin component.
EVA (50 parts by weight) having a vinyl acetate residue content of 19% by weight and an MI of 2.5 instead of A (50 parts by weight)
A sample was prepared in the same manner as in Example 1 except that was used.
In the case of Comparative Example 1 in which only EVA is used as the base resin and EEA is not used, it can be seen that the volume resistivity (electrical insulation) does not reach the required quality level.

In Comparative Example 2, a sample was prepared in the same manner as in Example 1 except that the base resin having a vinyl acetate residue content of 28% by weight was used alone. In the case of Comparative Example 2 in which EVA having a vinyl acetate residue content of more than 25% by weight was used as the base resin, the volume resistivity (electrical insulation) was lower than that of Comparative Example 1.

In Comparative Example 3, a sample was prepared in the same manner as in Example 1 except that a thiobisphenol-based antioxidant (2 parts by weight) was used instead of MBI and HPA. In this case, the volume resistivity (electrical insulation) of the sample did not reach the required quality level.

In Comparative Example 4, a sample was prepared in the same manner as in Example 1 except that triallyl isocyanurate (6 parts by weight) was used as the crosslinking aid instead of zinc methacrylate. In this case, the tensile strength, heat aging resistance (physical properties) and volume resistivity (electrical insulation) of the sample did not reach the required quality level.

Comparative Example 5 has a metal hydrate content of 150.
A sample was prepared in the same manner as in Example 1 except that the amount was less than parts by weight. In this case, the oxygen index (flame retardancy) of the sample did not reach the required quality level. From the results of Comparative Examples 1 to 5 described above, when the kind and amount of the additive are out of the range specified in the present invention, all are for electric wires in which physical properties, electrical characteristics and flame retardancy are balanced. A flame-retardant coating material could not be obtained.

[0034]

The flame-retardant coating material composition for electric wire of the present invention is
EVA and E / A within the specified range of vinyl acetate residue content
In addition to the base resin consisting of a specific range of the quantitative ratio of the metal hydrate, the MBI, HPA, the polymerizable organic acid metal salt and the organic peroxide in a specific range of the quantitative ratio, A flame-retardant coating material for electric wires in which physical properties, electrical characteristics, and flame retardance are well balanced is obtained.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location H01B 7/34 H01B 7/34 B

Claims (3)

[Claims] 1. A composition for cross-linking to form a flame-retardant coating material for electric wires, wherein the content of vinyl acetate residues is 10% by weight.
30 to 50 parts by weight of ethylene / vinyl acetate copolymer in the range of 25 to 25% by weight and ethylene /
150 parts by weight to 200 parts by weight of metal hydrate, 2-mercaptobenzimidazole compound and hindered phenol system based on 100 parts by weight of a base resin consisting of 70 parts by weight to 50 parts by weight of (meth) acrylate copolymer. Antioxidant tetrakis [methylene-
3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] methane in total of 1 part by weight to 5 parts by weight, and polymerizable organic acid metal salt in an amount of 1 part by weight to 15 parts by weight. And 0.5 parts by weight to 5 parts by weight of an organic peroxide, a flame-retardant coating material composition for electric wires. 2. The flame-retardant coating material composition for electric wires according to claim 1, wherein the melt index of the ethylene / vinyl acetate copolymer is in the range of 2.5 to 15. 3. The flame-retardant coating material composition for electric wire according to claim 1, wherein the polymerizable organic acid metal salt is zinc (meth) acrylate.