JPH04154852A - Flame retardant electrical insulating composition - Google Patents

Abstract

PURPOSE:To obtain an electrical insulating composition, containing a metallic hydroxide together with a polyphosphazene having a specific value or above of weight-average molecular weight as a polymer blend with a polyolefin, as a flame retarder. CONSTITUTION:A flame retardant electrically insulating composition is composed of (A) a polyolefin (e.g. ethylene vinyl acetate copolymer), (B) a polyphosphazene having >=2X10<5> weight-average molecular weight, e.g. a polypropoxyphosphazene expressed by the formula ((m) is an integer of >=2000) and (C) a metallic hydroxide, preferably hydroxide of a bi- to tetravalent metal having water of crystallization (e.g. magnesium hydroxide or hydrotalcite). The weight ratio of the components (B) to (A) is (10/90) to (50/50) and the amount of the component (C) is 50-200 pts.wt. based on 100 pts.wt. polymer blend of the components (A) and (B). The components (A) and (B) are preferably crosslinked by addition of an organic peroxide or irradiation with electron rays, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a flame-retardant electrical insulation composition, particularly a flame-retardant polyolefin electrical insulation composition useful as an insulator for electric wires and cables.

[Conventional technology]

As an insulator, polyolefins such as polyethylene have properties such as insulation resistance, dielectric strength, dielectric constant, water resistance, moisture resistance, solvent resistance,
It is widely used as an insulating coating for electric wires and cables because it is excellent in many aspects such as chemical resistance, but it is easily flammable.
Because fire often spreads from a fire source through electric wires and cables, they are required to be flame retardant. In particular, flame retardancy is strongly required for electric wires and cables used in aircraft, vehicles, ships, tunnels, factories, high-rise buildings, consumer electrical equipment, etc.

Polyolefin insulation materials are made flame retardant by adding flame retardants to polyolefins. Halogen-containing organic compounds are widely used as flame retardants, but because they generate toxic gas and large amounts of smoke in the event of a fire, recently metals such as aluminum hydroxide and magnesium hydroxide, which do not have these drawbacks, have been used. Inorganic flame retardants using hydroxides are now being used.

[Problem to be solved by the invention]

However, unless a large amount of metal hydroxide is added to polyolefin, it is necessary to
It is not possible to obtain the high degree of flame retardancy required by EEE Standard 383). However, when a large amount of metal hydroxide is added to polyolefin, the mechanical properties such as the tensile properties of the insulator are significantly deteriorated.

Therefore, an object of the present invention is to realize an electrical insulating composition that satisfies the mechanical properties required of an insulator and has excellent flame retardancy.

[Means to solve the problem]

The present invention satisfies the mechanical properties required for an insulator,
In order to realize an electrical insulation composition having excellent flame retardancy, polyphosphazene with a weight average molecular weight of 2x105 or more is contained as a polymer blend with a polyolefin together with a metal hydroxide as a flame retardant in the polyolefin electrical insulation composition. and the weight ratio of polyphosphazene to polyolefin is 10/90 to 50150,
The amount of metal hydroxide is 50 to 200 parts by weight per 100 parts by weight of the polymer blend of polyolefin and polyphosphazene.
Parts by weight.

Examples of polyolefins include polyethylene, ethylene propylene copolymer (which may contain other polymeric components), ethylene vinyl acetate copolymer, ethylene methyl acrylate copolymer, ethylene ethyl acrylate copolymer, ethylene butylene copolymer (and others). (may contain polymeric components)
etc. can be used. Two or more types of polyolefins may be used.

Polyphosphazene is a polymer having a bond between a phosphorus atom and a nitrogen atom in its main chain, and is represented by the following formula.

I 2 -(N=P), - In the formula, R' and R2 each represent an alkoxy group, an allyloxy group, or an amino group. The alkoxy group may be substituted with a halogen atom, an allyl group, an amino group, a hydroxy group, or the like. The allyloxy group may be substituted with a halogen atom, an alkyl group, an amino group, a hydroxy group, or the like. The amino group may be substituted with an alkyl group, an allyl group, or the like.

n is a positive integer. The polyphosphazene used in the present invention has a weight average molecular weight of 2×10 5 or more; if the molecular weight is smaller than this, satisfactory tensile properties cannot be obtained. A specific example of polyphosphazene used in the present invention is polypropoxyphosphazene-[N=P (QC,R7)ZllI- (m is 2000
(integer greater than or equal to) Polyphenoxyphosphazene-[N = P (OC6R5)2]--(p is 100
(an integer of 0 or more) polyaminophosphazene-[N=P (NH2)Z], - (q is an integer of 3,000 or more), and the like.

In the present invention, polyphosphazene is added such that the weight ratio of polyphosphazene to polyolefin is 10/90 to 50,150. If the amount of polyphosphazene relative to the polyolefin is less than this range, sufficient flame retardancy cannot be obtained, and if it is more than this range, the elongation of the insulator will be significantly reduced. The polyolefin and polyphosphazene form a polymer blend in the insulation composition.

Metal hydroxides can be divalent, trivalent, or tetravalent with water of crystallization.
Hydroxides of valent metals are preferred, and complexes with carbonates, silicates, etc. may also be used. For example, magnesium hydroxide, basic magnesium carbonate, hydrotalcite, and aluminum hydroxide can be used. It is desirable to add 50 parts by weight or more of the metal hydroxide to 100 parts by weight of the polymer blend of polyolefin and polyphosphazene. Otherwise, sufficient flame retardancy cannot be obtained. but,
As mentioned above, too much metal hydroxide impairs mechanical properties, so it is preferably 200 parts by weight or less.

Although the insulating composition of the present invention is thermoplastic and is used as a molded article, it is preferably crosslinked during or after molding in order to increase heat resistance and further improve mechanical properties. For crosslinking, any of the addition of an organic peroxide, electron beam irradiation, silane graft water crosslinking, etc. may be used. As an organic peroxide, dicumyl peroxide (dicumy
1 peroxide), 3-bis(1-butylperoxyisopropyl)benzene, and the like are preferred. When electron beam irradiation is used, a reactive monomer such as trimethylolpropane trimellitate or triallyl isocyanurate may be added as a crosslinking aid.

The insulating composition of the present invention may further contain an antioxidant, a slip agent, carbon black, and the like.

[Effect]

The electrical insulation composition of the present invention has a weight average molecular weight of 2×105 in addition to a metal hydroxide as a flame retardant in polyolefin.
By adding a predetermined amount of the above polyphosphazene,
It exhibits excellent flame retardancy even if the metal hydroxide is not added in such a large amount that it deteriorates mechanical properties.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

[Examples 1 to 4] Insulating compositions having the compositions shown in Table 1 were prepared (units are parts by weight). In Examples 1 and 2, poly(dimethoxyphosphazene) was used, and in Examples 3 and 4, poly(diaminophosphazene) was used.

In the compositions of Examples 2 and 4, the amount of polyphosphazene was increased and the amount of magnesium hydroxide was slightly decreased compared to the compositions of Examples 1 and 3.

The ethylene vinyl acetate copolymer used contained 25% by weight of vinyl acetate and had a melt index (190°C).
1.0, magnesium hydroxide has an average particle size of 1 μm
The one treated with stearic acid was used. The poly(
The molecular weight of dimethoxyphosphazene) is 8 x 105, and the molecular weight of poly(diaminophosphazene) is 1 x 106.

To prepare each composition, predetermined amounts of each component were kneaded in a Panbali mixer.

The tensile properties and flame retardance of each composition were evaluated as follows.

(1) Tensile properties Each composition was press-molded to a thickness of IIIllll at 180°C, and a test piece was punched out using a JIS dumbbell No. 3. Using a Schopper type tensile tester, a tensile speed of 500mm/
A tensile test was carried out at 10 minutes. The results, along with the composition, are
Shown in the table.

(2) 100 to 130 degrees after crosstalk with flame-retardant panbari mixer
Using an 80III11 extruder (screw L/D = 20) held at C, three ethylene propylene rubber insulated wires with an outer diameter of 4.0 mm were extruded and coated around the twisted wire core to a thickness of 2 holes. A cable was produced by crosslinking in water vapor at a pressure of 13 kg/cm2 for 3 minutes.

Ten cables with a length of 2.4 m are lined up vertically, and 7 cables are placed at the bottom end.
0. After applying a flame of 000 BTU/hr for 20 minutes,
If the flame is removed and the flame self-extinguishes within 1.8m, it passes, 1
．． If the fire spreads more than 8m, it will be rejected (this test method is
This is a vertical tray combustion test in accordance with EEE Standard 383). The results are shown in Table 1 along with the composition and tensile properties.

Table 1 As is clear from Table 1, each of the compositions of Examples 1 to 4 had a tensile strength of more than 1.0 kg/mm2 and a tensile strength of 350%.
It showed good elongation from front to back and passed all flame retardant test results.

[Example 5] The ethylene vinyl acetate copolymer used in Example 1 was replaced with ethylene ethyl acrylate copolymer, and poly(
dimethoxyphosphazene) was replaced with the same poly(diaminophosphazene) used in Example 3.4, and the amount of hydroxide was reduced slightly.

The ethylene ethyl acrylate copolymer contains 20% by weight of ethyl acrylate component and has a melt index (1
90°C) 1.0.

The preparation method and evaluation method are the same as Examples 1-4. The evaluation results are shown in Table 2 along with the composition.

Table 2 As is clear from Table 2, the composition of Example 5 was about 1.
It exhibited a tensile strength of 0 kg/mm2 and an elongation close to 350%, and passed the flame retardancy test.

[Comparative Examples 1 to 3] Insulating compositions having the compositions shown in Table 3 were prepared (units are parts by weight). The preparation method and evaluation method are the same as Examples 1-4. The evaluation results are shown in Table 3 together with the composition (* in the table indicates that measurement is not possible).

In Comparative Example 1 of Table 3, the amount of magnesium hydroxide was reduced to 10 parts by weight, and the tensile strength of the sheath was superior to Examples 3 and 4, but the flame retardance was rejected.

This result shows that 50 parts by weight or more of metal hydroxide is required to obtain sufficient flame retardancy.

In Comparative Example 2, the amount of magnesium hydroxide was increased to 300 parts by weight, and the flame retardance was passed, but the tensile strength was extremely low and unmeasurable, and the elongation did not reach 50%. It is shown that when more than 200 parts by weight of magnesium hydroxide is added to 100 parts by weight of the polymer blend (including 70 parts by weight of polyolefin), the tensile properties are significantly deteriorated.

In Comparative Example 3, all polyphosphazene was omitted, and the tensile strength of the sheath was superior to Examples 2 and 3, but the flame retardance was rejected. Comparing this result with the above example, It is understood that polyphosphazenes are effective in obtaining sufficient flame retardancy.

(Comparative Examples 4-5) Insulating compositions having the compositions shown in Table 4 were prepared (unit: parts by weight).The preparation method and evaluation method were the same as in Examples 1-4.

Comparative Example 4 in Table 4 shows that the composition of Example 4 contains 1 magnesium hydroxide.
The sheath using this composition was reduced from 10 parts by weight to 10 parts by weight, and the tensile strength and elongation of the sheath using this composition were similar to Comparative Example 1 and superior to Example 4, but the flame retardance was rejected. This result shows that 50 parts by weight or more of metal hydroxide is required to obtain sufficient flame retardancy.

In Comparative Example 5, 30 parts by weight of poly(diaminophosphazene) in the composition of Example 4 was omitted and replaced with the same weight of ethylene vinyl acetate copolymer.

The tensile strength and elongation of the sheath using this composition are shown in Comparative Example 3.
Although it was almost the same as that of Example 4 and was superior to Example 4, the flame retardance was rejected. Comparing this result with Example 4 shows that polyphosphazene is effective in obtaining sufficient flame retardancy.

The above Examples and Comparative Examples clearly demonstrate the excellent flame retardancy and mechanical properties of the insulating composition of the present invention, which contains metal hydroxide and polyphosphazene in a predetermined weight ratio to polyolefin.

〔Effect of the invention〕

The flame-retardant electrical insulation composition of the present invention has mechanical properties required for insulating materials such as electric wires and cables, and has excellent flame retardancy.

Claims (2)

[Claims] (1) Polyolefin and weight average molecular weight 2×10^5
The polyphosphazene is comprised of the above polyphosphazene and a metal hydroxide, the polyphosphazene is contained as a polymer blend with the polyolefin in an amount ranging from 10/90 to 50/50 in weight ratio to the polyolefin, and the metal hydroxide is contained in an amount of 50 to 200 parts by weight based on 100 parts by weight of the polymer blend. (2) The flame-retardant electrical insulation composition according to claim 1, wherein the polyolefin and the polyphosphazene are crosslinked.