JPH06329847A - Flame-retardant resin composition and molding therefrom - Google Patents

Abstract

(57) [Summary] [Structure] 95/5 of polyethylene and ethylene-propylene rubber having a density of 0.905 (g / cm ³ ) or less
A flame-retardant resin composition in which a resin mixture mixed at a ratio of 50/50 is flame-retarded. Insulated wire covered on the conductor. A shielded electric wire that is coated on a conductor and has an outer conductor layer formed on the outer periphery of the coating layer. A foamed shielded electric wire in which a conductor is covered with a foamed composition, and an outer conductor layer is formed on the outer periphery of the foamed coating layer. An insulated cable in which the outer circumference of a single-core or multiple-core insulated wire is covered.
A heat-shrinkable tube in which the composition is molded into a tube shape, the tube layer is crosslinked, and the diameter of the tube is fixed. [Effect] It has excellent extrusion processability, low dielectric constant, and excellent mechanical properties. It is useful as a flame retardant insulated wire for signal transmission, an insulator for flame retardant shielded wire, a sheath material for LAN UTP cables, and a heat shrink tube for terminal treatment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low dielectric constant, flame-retardant resin composition for electrical insulation, which is excellent in melt extrusion processability, and a molded article made from the same.

[0002]

2. Description of the Related Art Polyethylene resins such as high density polyethylene and low density polyethylene are excellent in electrical insulation and have a low dielectric constant of 2.1 to 2.2, so that they are suitable for computers, video equipment, office automation equipment, wireless equipment and the like. Widely used as an insulator for shielded wires and coaxial cables that transmit weak high-frequency signals.

If polyethylene resin is extruded and coated on the conductor while being foamed, the dielectric constant of the insulator is about 1.
Since it can be reduced to 3 to 1.6, it is possible to obtain a coaxial cable or a shielded electric wire with extremely low transmission loss of high frequency signals.

On the other hand, the flame-retardant property is also required for the shielded electric wire and the coaxial cable used in the above-mentioned electronic equipment, and the polyethylene insulator and the foamed polyethylene insulator are easily flammable, so that they are usually used in the outside. In many cases, the outer circumference of the conductor layer is covered with a flame-retardant sheath such as a polyvinyl chloride resin composition to ensure the flame-retardant property of the entire cable.

As an evaluation standard for flame retardancy of shielded electric wires and coaxial cables, for example, UL standard (Underwri) is used.
ters Laboratories Inc. ) Vertical combustion test (VW-1), in which the sample was installed vertically and the burner flame was set to 20 ° as shown in FIG.
When the ignition was repeated 5 times for 15 seconds at each angle,
It is a flame-retardant evaluation test that extinguishes the fire within 0 seconds, the kraft paper attached to the upper part does not burn, and the absorbent cotton laid on the lower part should not be ignited by burning falling objects.

Furthermore, depending on the application, there is a case where it is required to pass the vertical combustion test (VW-1SC) even with an insulator alone (with the sheath and outer conductor removed). In such a case, polyethylene is used. It is necessary to use, as an insulator, a polyethylene resin flame-retarded by a method of blending a halogen-based flame retardant or various fillers with the resin, or a foam thereof.

However, the resin composition obtained by making polyethylene flame-retardant by the above-mentioned method causes cracks when the tensile strength and the elongation at break are remarkably reduced or the embrittlement temperature rises, and in severe cases, bending at room temperature causes bending. There are cases where such problems occur, and there are problems that are not practical.

On the other hand, ethylene has 1-butene and 1-butene.
Copolymerizing α-olefins such as hexene, 1-octene, and 4-methyl-1-pentene, the density is about 0.905.
The crystallinity was controlled so as to be (g / cm ³ ) or less,
A method using so-called ultra-low density polyethylene has also been proposed.

Ultra-low density polyethylene has the same electrical insulation and dielectric constant as high density polyethylene and low density polyethylene, and is excellent in acceptability for various compounding agents such as flame retardants and fillers. Even with a resin composition containing a large amount of flame retardants and fillers and having improved flame retardancy to the extent that it passes the vertical combustion test, there is little deterioration in mechanical properties such as tensile strength and elongation at break, and it is brittle. There is an advantage that there is no problem such as an increase in oxidization temperature.

However, the resin composition obtained by flame-retarding ultra-low density polyethylene has a drawback that the melt extrusion processability is extremely poor. For example, when extrusion coating is performed on a conductor or extrusion coating is performed while foaming, extrusion is performed. When the linear velocity is increased, the appearance tends to be roughened, and there is a problem that the product cannot be efficiently manufactured at a high linear velocity.

On the other hand, EVA resin or E obtained by copolymerizing ethylene with α-olefin such as vinyl acetate or ethyl acrylate.
Since ethylene-based copolymers such as EA resins also have excellent receptivity to various fillers such as flame retardants and fillers, the mechanical properties of the flame-retarded resin composition are not significantly deteriorated, and Even in the melt extrusion coating at a high linear velocity, there is an advantage that there are few problems such as rough appearance.

However, since ethylene-based copolymers such as EVA resin and EEA resin have the drawback of having a higher dielectric constant than ultra-low density polyethylene, for example, in the case of flame-retardant ultra-low-density polyethylene foam insulation. It is necessary to increase the expansion ratio to obtain a dielectric constant equivalent to that of, which makes it difficult to control the outer diameter of the coating, and the larger the expansion ratio, the lower the tensile strength of the foam insulation and the mechanical strength. It is not preferable because there is a problem that the physical strength becomes small.

For these reasons, the flame-retardant resin has a low dielectric constant, is excellent in melt extrusion processability, and has no problem of deterioration in mechanical strength such as tensile strength even when it is used as a foamed insulator. The development of compositions has been desired.

[0014]

Means for Solving the Problems As a result of intensive studies made by the present inventor, the density of 0.905 (g / cm 2
³ ) The following so-called ultra-low density polyethylene with ethylene-
A flame-retardant resin composition whose flame retardancy is increased to the level of vertical flame retardancy by blending propylene rubber and adding a flame retardant, etc. Even in the case of melt extrusion or foam extrusion coating, it is possible to produce a flame-retardant insulated wire at a high linear velocity efficiently without causing problems such as rough appearance, and,
Even when the resin composition is extrusion coated while foaming, it was found that a flame-retardant foam insulated wire with a low dielectric constant can be produced without the problem of deterioration of mechanical strength, and the present invention was achieved based on such findings. It was

That is, the present invention is: 95/5 to 50/50 of polyethylene and ethylene-propylene rubber having a density of 0.905 (g / cm ³ ) or less.
A flame-retardant resin composition in which a resin mixture mixed in a weight ratio range of 1 is flame-retarded. Further, there is provided an insulated electric wire in which a conductor is coated with the flame-retardant resin composition described above. Further, there is provided a shielded electric wire in which the flame-retardant resin composition described above is coated on the conductor, and the outer conductor layer is formed on the outer periphery of the coating layer. Also,

There is provided a foamed shielded electric wire in which a foamed body of the flame-retardant resin composition described above is coated on a conductor, and an outer conductor layer is formed on the outer periphery of the foamed coating layer.
Further, the present invention provides an insulated cable in which the flame-retardant resin composition described above is coated on the outer periphery of a single-core or multi-core insulated wire. Further, there is provided a heat-shrinkable tube in which the flame-retardant resin composition described above is formed into a tube shape, and the tube layer is crosslinked and the diameter thereof is fixed. Also,

The present invention will be described in detail below. Density is 0.905 (g / cm ³ ) or less, preferably 0.902
The polyethylene of 0.870 (g / cm ³ ) means 1-butene, 1-hexene, 1-in addition to ethylene, as described above.
It is an ethylene-based copolymer obtained by copolymerizing α-olefins such as octene and 4-methyl-1-pentene.

Ethylene-propylene rubber is a random copolymer of ethylene and propylene, or ethylene and propylene containing dicyclopentadiene, ethylidene norbornene,
This is so-called EPDM obtained by copolymerizing a diene component such as 1,4-hexadiene as a third component.

Polyethylene having a density of 0.905 (g / cm ³ ) or less and ethylene-propylene rubber can be mixed in any composition ratio, but from the viewpoint of melt extrusion processability of the flame-retarded resin composition. From, the density is 0.905 (g / cm
³ ) The following mixing ratio of polyethylene / ethylene-propylene rubber is preferably set in a weight ratio range of 95/5 to 50/50.

As a compounding agent for flame retarding a mixture of polyethylene and ethylene-propylene rubber having a density of 0.905 (g / cm ³ ) or less, polybromodiphenyl ether, brominated bisphenol derivative, brominated ethylene bisphthalimide , Bis (brominated phenyl) ethane,
Halogen-based flame retardants such as bromine-based and chlorine-based bis (brominated phenyl) terephthalamides, perchloropentacyclodecane, and chlorinated paraffins;

Metal hydroxide flame retardants such as aluminum hydroxide, magnesium hydroxide and calcium hydroxide; phosphorus flame retardants such as trioctyl phosphate, antimony trioxide, antimony pentoxide, molybdenum oxide,
Examples thereof include metal oxides such as silica, clay, talc and zinc white; metal carbonates such as basic magnesium carbonate and calcium carbonate; metal borates such as zinc borate and barium metaborate.

The resin composition can be mixed by a known mixing device such as an open roll mixer, a Banbury mixer, a pressure kneader, a Henschel mixer, a biaxial mixer or the like. Various compounding chemicals such as antioxidants, processing stabilizers, lubricants, colorants, plasticizers, polyfunctional monomers, and vulcanizing agents can be compounded into the resin composition as needed, and a melt extruder or the like is used. If the conductor is coated with the resin composition, an insulated wire having a high linear velocity and a low dielectric constant and flame retardancy can be obtained efficiently.

In particular, polyfunctional monomers such as trimethylolpropane trimethacrylate and triallyl (iso) cyanurate can be used as crosslinking accelerators. Further, if a chemical foaming agent such as azodicarbonamide, p, p′-oxybis (benzenesulfonyl hydrazide), p-toluenesulfonyl semicarbazide, etc. is previously blended with the resin composition and foam extrusion coating is carried out, a further lower dielectric constant can be obtained. Since a flame-retardant foam insulated wire can be obtained, a shielded wire or a coaxial cable that requires VW-1SC can be manufactured.

After extrusion coating or foam extrusion coating, the coating layer is cross-linked by irradiating ionizing radiation such as accelerated electron beam or gamma ray to obtain an insulator or a foam insulator having excellent heat deformation resistance. You can also Instead of the electron beam crosslinking, it is also possible to preliminarily mix a crosslinking agent such as dicumyl peroxide into the base material and then heat the so-called chemical crosslinking.

Further, the resin composition was treated with LA as shown in FIG.
UTP cable for N (UTP: Unshielded)
When applied as a sheath material of Twist Pair, a UTP cable with a small transmission loss between twisted pairs can be manufactured. Further, the resin composition is extruded into a tube shape, and after cross-linking, a method such as sending compressed air to the inside of the tube-shaped molded article while heating is performed to expand the diameter and cool and fix it to obtain a heat shrinkable tube. Insulated wire or foam insulated wire with low dielectric constant and flame resistance,
A heat-shrinkable tube suitable for cable end processing is obtained.

Further, as the shield layer constituting the shielded electric wire, if a shield layer such as a horizontally wound conductor layer, a braided conductor layer or a metal foil provided with an adhesive layer or a metal filler-containing adhesive resin layer can be formed, Not limited.

The present invention will be described in more detail with reference to the following examples, which do not limit the scope of the present invention.

12 resin compositions shown in Tables 1 and 2 were used.
The mixture was kneaded with an open roll mixer heated to 0 to 140 ° C and pelletized. The resin compositions shown in Tables 1 and 2 contained 0.5 parts by weight of stearic acid, 50 parts by weight of decabromodiphenyl ether, and 2 parts of antimony trioxide.
0 parts by weight, basic magnesium carbonate 10 parts by weight, dry silica 10 parts by weight, pentaerythrityl tetrakis [3-
(3,5-di-t-butyl-4-hydroxyphenyl)
Propionate] 1 part by weight was commonly compounded.

The pellets of the resin composition obtained by the above method were melt-extruded (30 mmφ, L / D = 24, full flight screw, compression ratio 2.5) and the outer diameter was 0.8 mm.
Extrusion coating or foam extrusion coating to a thickness of 0.4 mm on a φ tin-plated annealed copper conductor, with an extrusion linear speed of 50
The appearance of the extrusion coating layer was examined under two conditions of m / min and 300 m / min.

Among the insulated wires manufactured by the above method, the insulated wire manufactured at an extrusion wire speed of 300 m / min has an accelerating voltage of 2M.
After irradiating the electron beam of V with 100 kGy, the tensile strength, the elongation at break, and the dielectric constant (measurement condition: 1 MHz) of the insulator were measured at n = 3, respectively, and the flame resistance of the insulated wire was measured by the vertical combustion test ( VW-1 method) and n = 3.

(Embodiments 1, 2, 5) Embodiments 1, 2, 5
Is polyethylene and ethylene-having a density of 0.905 or less.
An insulated wire using a resin composition obtained by flame-retarding a resin composition obtained by mixing propylene rubber in a weight ratio range of 95/5 to 60/40, and having an extruded appearance of a linear velocity of 50 m / min and 300 m.
/ Min is good, the dielectric constant is as low as 2.8 or less, the vertical combustion test has passed, and the tensile strength is 1.0 kg /
It can be seen that the mechanical properties are excellent at mm ² or more.

(Examples 3 to 4) In Examples 3 to 4, flame retardant resin compositions were prepared by mixing polyethylene having a density of 0.905 or less and ethylene-propylene rubber in the range of 95/5 to 60/40. A foamed insulated electric wire that is foamed and extruded using a resin composition in which an azobiscarbonamide foaming agent is kneaded and an extrusion die speed is set to 180 to 200 ° C. at an extrusion linear speed of 300 m / min. , Good appearance, low dielectric constant of 1.5 to 1.6, passed vertical combustion test, tensile strength of 1.0 kg / mm ² or more, and excellent mechanical properties. I understand.

Example 6 In Example 6, the density is 0.905.
The following polyethylene and ethylene-propylene rubber 50
An insulated wire using a resin composition obtained by flame-retarding a resin composition mixed at 50/50, which has a slightly poor appearance at an extrusion linear velocity of 300 m / min, but is good at an extrusion linear velocity of 50 m / min, It has a low dielectric constant of 2.7 and has passed the vertical combustion test.
It has excellent mechanical properties and flexibility.

[0033]

[Table 1] (* 1) ML _{1 + 4} (100 ° C): 55, ethylene ratio 6
5%, iodine value: 10 (* 2) ML _{1 + 4} (100 ° C): 43, ethylene ratio 5
5%, iodine value: 12

(Comparative Examples 1 to 3) Comparative Examples 1 to 3 use a resin composition in which a simple substance of polyethylene having a density of 0.905 or less is made flame-retardant, and the appearance is already poor at an extrusion linear velocity of 50 m / min. Is waking up.

(Comparative Example 4) In Comparative Example 4, the density was 0.918.
The resin composition obtained by flame-retarding the low-density polyethylene is used, and the appearance is good at an extrusion linear speed of 50 m / min, but the elongation of the insulator is less than 100%, making it insufficient as an insulated wire. Is.

Comparative Example 5 Comparative Example 5 has a density of 0.935.
The resin composition obtained by flame-retarding the high-density polyethylene is used, and the appearance is poor at the extrusion linear velocity of 50 m / min.

[0037]

[Table 2]

COMPARATIVE EXAMPLE 6 In Comparative Example 6, polyethylene / ethylene-propylene rubber having a density of 0.905 or less was used in 40 /
The resin composition obtained by flame-retarding the resin composition mixed in 60 is used, and there is a problem in that a defective appearance occurs at an extrusion linear velocity of 50 m / min.

COMPARATIVE EXAMPLE 7 In Comparative Example 7, polyethylene / ethylene-propylene rubber having a density of 0.905 or less was used in a ratio of 30 /.
The resin composition obtained by making the resin composition mixed in 70 flame-retardant is used, and there is a problem in that a defective appearance occurs at an extrusion linear velocity of 50 m / min.

Comparative Examples 8 and 9 In Comparative Examples 8 and 9, polyethylene having a density of 0.905 or less and a vinyl acetate content of 15 were used.
% Ethylene-vinyl acetate copolymer is used as the flame-retardant resin composition, and there is a problem in that a defective appearance occurs at an extrusion linear velocity of 50 m / min.

(Comparative Example 10) Comparative Example 10 is Comparative Examples 8 and 9.
A resin composition obtained by flame-retarding the ethylene-vinyl acetate copolymer used as a simple substance is used.
The appearance is good even at m / min, the mechanical properties are excellent, and the vertical combustion test and the low temperature winding test are passed, but the dielectric constant is 3.6, which is considerably higher than those of Examples 1 to 6.

(Comparative Example 11) Comparative Example 11 has a density of 0.90.
Polyethylene less than 5 and 25% ethyl acrylate content
The resin composition obtained by flame-retarding the resin composition obtained by mixing the ethylene-ethyl acrylate copolymer of No. 1 is used, and the appearance is poor at the extrusion linear velocity of 50 m / min.

(Comparative Example 12) Comparative Example 12 uses a resin composition obtained by flame-retarding the ethylene-ethyl acrylate copolymer used in Comparative Example 11 alone.
Even at 00m / min, the appearance is good and the mechanical properties are excellent.
It has passed the vertical combustion test and the low temperature winding test, and is excellent in flexibility, but has a dielectric constant of 4.0, which is higher than that of Comparative Example 10.

[0043]

[Table 3]

(* 1) ML _{1 + 4} (100 ° C.): 55, ethylene ratio 65%, iodine value: 10 (* 2) ML _{1 + 4} (100 ° C.): 43, ethylene ratio 5
5%, iodine value: 12 (* 3) vinyl acetate content: 15%, melt flow rate: 2 (190 ° C 2160g) (* 4) ethyl acrylate content: 25%, melt flow rate: 5 (190 ° C 2160g)

(Comparative Example 13) In Comparative Example 13, a resin composition prepared by kneading the ethylene-vinyl acetate copolymer used in Comparative Example 10 with a flame-retardant substance and an azobiscarbonamide foaming agent was used. Foam extrusion coating was performed under conditions of an extrusion linear velocity of 300 m / min and an extrusion die temperature of 170 to 200 ° C. Under foaming extrusion conditions in which the appearance is good and the outer diameter is stable, the dielectric constant is 2.4, which is considerably higher than in Examples 3 to 4, and the tensile strength is less than 1.0 kg / mm ² . In order to lower the dielectric constant, it was difficult to carry out stable extrusion under extrusion conditions in which the expansion ratio was further increased.

Comparative Example 14 In Comparative Example 14, a resin composition prepared by kneading an ethylene-vinyl acetate copolymer used in Comparative Example 12 with a flame-retardant single substance and an azobiscarbonamide foaming agent was used. Foam extrusion coating was performed under the conditions of an extrusion linear velocity of 300 m / min and an extruder die temperature of 170 to 200 ° C. Under foaming extrusion conditions in which the appearance is good and the outer diameter is stable, the dielectric constant is 2.7, which is considerably higher than in Examples 3 to 4, and the tensile strength is less than 1.0 kg / mm ² . In order to lower the dielectric constant, it was difficult to carry out stable extrusion under extrusion conditions in which the expansion ratio was further increased.

[0047]

[Table 4]

As described above, the densities of Examples 1 to 6 were 0.
905 (g / cm ³ ) or less polyethylene and ethylene-
When a resin composition obtained by flame-retarding a resin mixture obtained by mixing propylene rubber in a weight ratio range of 95/5 to 50/50 is used, the extrusion appearance at a high linear velocity is good, the dielectric constant is low, and the flame resistance is low. An insulated wire having excellent mechanical properties can be obtained. If a resin composition is preliminarily kneaded with a foaming agent such as azobiscarbonamide and foamed and extruded, a foamed insulated wire having a lower dielectric constant and excellent flame retardancy and no problem of reduction in tensile strength can be obtained. To be

On the other hand, the density is 0.905 (g / cm
³ ) Insulated wires with good extruded appearance cannot be obtained with the following resin compositions in which flame retardant polyethylene is used alone. Also,
Insulation with good extrusion appearance even when a resin composition in which a mixture of ethylene-vinyl acetate copolymer or ethylene-ethyl acrylate copolymer is flame-retarded is used in polyethylene of 0.905 (g / cm ³ ) or less I can't get an electric wire.

Further, with a resin composition obtained by flame-retarding an ethylene-vinyl acetate copolymer or an ethylene-ethyl acrylate copolymer alone, an insulated wire having a good extruded appearance can be obtained, but the dielectric constant becomes high. However, even if an attempt is made to lower the dielectric constant by foam extrusion, the dielectric constant becomes high and the tensile strength is 1.0 kg / mm ² under the condition that stable foam extrusion is possible.
There is a problem that the mechanical strength becomes insufficient below that.

(Example 7) Pellets of the resin composition of Example 1 were melt-extruded (30 mmφ, L / D = 24, full flight screw, compression ratio 2.5) and the outer diameter was 0.
A 7-strand conductor of 127 mmφ tin-plated annealed copper conductor was extrusion-coated at a linear velocity of 300 m / min so as to have a thickness of 0.3 mm to form an insulator, and then an electron beam with an accelerating voltage of 2 MV was irradiated with 100 kGy. A horizontal PVC shield layer is formed on the outer circumference of this insulated wire with a tin-plated annealed copper conductor having a wire diameter of 0.12 mmφ, and a soft PVC composition (Sumiflex K600SN-16, Sumitomo Bakelite Co., Ltd .; trade name) on the outer circumference thereof. Was coated by extrusion with a thickness of 0.30 mm to produce a shielded electric wire.

The insulator of this shielded wire has a tensile strength of 1.5 kg / mm ² , an elongation of 538%, which is excellent in mechanical strength, an electrostatic capacity of 160 pF / m (1 MHz), and a vertical combustion test (VW- 1) passed, the soft PVC coating layer and the horizontal winding shield layer were peeled off, and the vertical burning test (V
It was a shielded electric wire excellent in flame retardance that also passed W-1SC).

(Comparative Example 15) The resin composition of Comparative Example 10 was used as the resin composition of the insulator, and the outer diameter was 0.127 mm.
The thickness is 0.3 on the 7-stranded conductor of φ tin-plated annealed copper conductor.
After extrusion coating at a linear velocity of 300 m / min to form an insulator to form an insulator, an electron beam with an accelerating voltage of 2 MV is applied at 100 kG.
y irradiated. A horizontal winding shield layer and a soft PVC composition coating layer are formed on the outer periphery of this insulated wire in the same configuration as in Example 7,
A shielded electric wire was manufactured.

The insulator of this shielded wire had an excellent tensile strength of 1.3 kg / mm ² and an elongation of 623%, which was excellent in mechanical strength, passed the vertical combustion test (VW-1), and had a soft PVC coating layer and a lateral width. The winding shield layer was peeled off, and it passed the vertical combustion test (VW-1SC) with the insulator alone, and was excellent in flame retardancy, but the capacitance was 218 pF / m (1 MHz).
As compared with the shielded electric wire of Example 7, there was a defect that the electrostatic capacity was large.

Example 8 A resin composition of Example 3 was melt-extruded (30 mmφ, L / D = 24, full flight screw, compression) on a 7-strand conductor of tin-plated annealed copper conductor having an outer diameter of 0.127 mmφ. The ratio of 2.5) was used, the die temperature was set to 188 ° C., the extrusion linear velocity was 300 m / min, and foam extrusion was performed to a thickness of 0.3 mm and a capacitance of 90 pF / m. It was possible to form a foam insulation layer. This foamed insulated wire was irradiated with an electron beam with an accelerating voltage of 2 MV at 100 kGy, and then a horizontally wound shield layer and a soft PVC composition coating layer were formed on the outer periphery in the same configuration as in Example 7 to produce a shielded wire.

This shielded wire is subjected to a vertical burning test (VW-
Passing 1), the tensile strength of the foam insulation is 1.0 kg / m
m ² and elongation is 278%, which is excellent in mechanical strength. Moreover, the flexible PVC coating layer and the horizontal winding shield layer are peeled off, and a low static electricity that passes the vertical combustion test (VW-1SC) using the foam insulation alone. It was a shielded electric wire with excellent capacity and flame resistance.

(Comparative Example 16) The resin composition of Comparative Example 13 was used as the resin composition of the foamed insulation, and the melt extruder (3
0mmφ, L / D = 24, full flight screw, compression ratio 2.5), die temperature 170-200 ° C
The thickness is 0.3mm on the 7-strand conductor of tin-plated annealed copper conductor with an outer diameter of 0.127mmφ
Then, when an attempt was made to form a foamed insulating layer by foaming and extruding so that the electrostatic capacity was 95 pF / m (1 MHz), the outer diameter variation and the appearance roughness of the foamed insulating material were remarkable, and stable manufacturing could not be performed.

Example 9 1 part by weight of azobiscarbonamide was added to 100 parts by weight of Sumikasen E104 (low density polyethylene, trade name of Sumitomo Chemical Co., Ltd.) on an annealed copper wire having an outer diameter of 0.51 mmφ. The pellet of the material is melted using an extruder (30 mmφ, L / D = 24, full flight screw, compression ratio 2.5), and the die temperature is 1
The temperature was set to 90 ° C., and foam extrusion was performed so that the extrusion outer diameter was 0.87 mmφ to obtain a foam insulated electric wire having a capacitance of 203 pF / m.

This foam insulated wire was twisted in pairs at a pitch of 15 mm to form a twisted pair. Four pairs of this twisted pair were collected, and the pellets of Example 2 were used on the outer periphery thereof with a melt extruder (50 mmφ, L / D = 24, full flight screw, compression ratio 2.5) to have an outer diameter of 6.0 mmφ. ,
Extruded at a linear velocity of 50 m / min so that the wall thickness would be 0.7 mm,
A UTP cable was manufactured by forming a sheath layer.

When the transmission loss of the twisted pair of this UTP cable was measured at 100 MHz, the transmission loss per 100 m length was 18 dB, and this cable passed the vertical burning test (VW-1) and showed flame retardancy. It was also found that they are excellent and show sufficient characteristics as a UTP cable.

(Comparative Example 17) A soft PVC composition (Sumiflex K600SN-16, Sumitomo Bakelite Co., Ltd .; trade name) having an outer diameter of 6. was formed on the outer periphery of the assembly of 4 pairs of twisted pairs produced in Example 9. 0 mmφ, wall thickness 0.
Extrusion coating to 7 mm to form a sheath layer,
UTP (Unshielded Twist Pai
r) A cable was manufactured.

When the transmission loss of the twisted pair of this cable was measured at 100 MHz, the transmission loss per 100 m length was 24 dB, and the transmission loss was larger than that of the cable of Example 9 and there was a practical problem. all right.

Example 10 The pellets of Example 2 were melt-extruded (30 mmφ, L / D = 24, full flight screw, compression ratio 2.5) and the inner diameter was 6.4 mm.
2 MV after forming into a tube with φ and wall thickness of 0.6 mm
Was irradiated with 100 kGy.

The tubular molded product was placed in a constant temperature bath at 150 ° C., and compressed air was fed into the tubular molded product to expand the inner diameter to 13 mmφ, and immediately cooled with water to fix the shape. A heat shrink tube was manufactured.

The outer diameter of this heat-shrinkable tube is 8.0 mmφ.
When the aluminum pipe was covered with the aluminum pipe and left in a constant temperature bath of 150 ° C. for 5 minutes and then taken out, it was found that the aluminum pipe was fitted tightly to the outer periphery to cause heat shrinkage. Further, this tube passed a vertical combustion test (VW-1) using a nichrome wire having an outer diameter of 8.0 mmφ as a support, and it passed, and the dielectric constant was also low at 2.7 (1 MHz).
It was found that it has sufficient characteristics as a heat-shrinkable tube for terminal treatment of shielded wires and UTP cables.

[0066]

As described above, according to the present invention,
A flame-retardant resin composition with excellent extrusion processability, low dielectric constant, and excellent mechanical properties can be obtained. Therefore, flame-retardant insulated wires for signal transmission, insulators of flame-retarded shielded wires, and sheaths for UTP cables for LAN. It can be applied as a material and a material for these heat-shrinkable tubes for terminal treatment, and there is a very great utility value in the electric and electronic fields.

[Brief description of drawings]

FIG. 1 is a partially transparent schematic view of a UL standard vertical combustion test (VW-1) apparatus.

FIG. 2 shows a cross section of a UTP cable using the resin composition of the present invention as an insulator.

[Explanation of symbols]

 1 sheath 2 conductor 3 insulator 4 twisted pair 14 chamber 15 burner 16 kraft paper 17 absorbent cotton 18 sample

Claims (6)

[Claims] 1. A polyethylene and an ethylene-propylene rubber having a density of 0.905 (g / cm ³ ) or less is 95/5 to
A flame-retardant resin composition, wherein a resin mixture mixed in a weight ratio range of 50/50 is flame-retarded. 2. An insulated wire, characterized in that a conductor is coated with the flame-retardant resin composition according to claim 1. 3. A shielded electric wire comprising a conductor coated with the flame-retardant resin composition according to claim 1, and an outer conductor layer formed on the outer periphery of the coating layer. 4. A foam, characterized in that a conductor is covered with a foam of the flame-retardant resin composition according to claim 1, and an outer conductor layer is formed on the outer periphery of the foam covering layer. Shielded wire. 5. An insulated cable, characterized in that the flame-retardant resin composition according to claim 1 is coated on the outer circumference of a single-core or multi-core insulated wire. 6. The flame-retardant resin composition according to claim 1 is formed into a tube shape, and the tube layer is crosslinked,
A heat-shrinkable tube whose diameter is fixed.