JPH09227708A - Foamable resin composition for coating foamed insulating polyethylene and foamed insulating polyethylene-coated electric wire produced by coating with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a foamable resin composition for foamed insulating polyethylene coating and a foamed insulating polyethylene-coated e lectric wire. SOLUTION: This foamable resin composition is obtained by blending 100 pts.wt. of a polyethylene-based resin with 0.5-5 pts.wt. of an impurity-containing p,p'-oxy-bisbenzenesulfonylhydrazide (OBSH) and 0.005-0.5 pt.wt. of an impurity scavenger. The foamable resin composition is usable for producing a foamed insulating polyethylene and a foamed insulating polyethylene-coated coaxial cable. Even if an impurity-containing OBSH generally on the market is used, an inner electric conductor and an outer electric conductor of a prepared coaxial cable are not observed to cause rust development and a high-quality coaxial cable is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foamable resin composition for covering foamed insulated polyethylene, and a foamed insulated polyethylene-coated wire manufactured by coating the same. The electric wire manufactured by the present invention is used as a coaxial cable and a communication cable.

[0002]

2. Description of the Related Art In recent years, in the case of insulated wires, particularly coaxial cables used for high-frequency signal transmission, the dielectric constant and tan δ are reduced by increasing the foaming rate of an insulating film, thereby reducing the leakage attenuation rate of the cable and the like. In order to reduce the number of repeaters, sharpening of images and sounds is attempted.
In order to manufacture such an insulated wire having a high foaming rate, a chemical foaming method or a gas foaming method is generally performed.

[0003] In the chemical foaming method, a chemical foaming agent is mixed with a resin component at a temperature not higher than its decomposition temperature, and the resulting mixture is supplied to an extruder, and extruded on a metal conductor at a temperature higher than the decomposition temperature of the chemical foaming agent. Next, this is foamed in the air, and then cooled and solidified with water or the like. This chemical foaming method has lower equipment costs and is easier to operate than the gas foaming method.
Despite having a lower foaming rate than the gas foaming method and a lower mechanical strength of the foam, it has gained a certain share. However, the foaming degree of the foam by the chemical foaming method is limited to 70% in 7C-HFB and 7C-HFL even with the most advanced technology, and the resin that can be used is a high-pressure low-density polyethylene. Therefore, the mechanical strength was inferior, and it was insufficient for producing a high-quality coaxial cable.

On the other hand, in the gas foaming method, a freon gas such as monofluorotrichloromethane, difluorodichloromethane, trifluorotrichloroethane or tetrafluorodichloroethane is used as a foaming agent instead of a chemical foaming agent. The body is easily obtained,
In addition, high-density polyethylene having high mechanical strength can be used as a resin that can be used, so that a high-quality coaxial cable can be manufactured. However, Freon gas is considered to be a substance that causes the destruction of the ozone layer, and will be completely abolished in sequence according to the schedule based on the Montreal Protocol. Proposed.

Nitrogen gas was used in place of Freon gas, and when a coaxial cable was made by the gas foaming method using high density polyethylene which is a conventional material, a foam having a uniform and fine cell structure could not be obtained. . It is presumed that this is because the nitrogen gas does not have an affinity for polyethylene as much as the chlorofluorocarbon gas, the boiling point is low, and the specific heat is small, so that the above-mentioned insufficient results are obtained. Therefore, in the gas foaming method using nitrogen gas, by adopting a new resin composition in place of the high-density polyethylene that is usually used in the gas foaming method, a uniform and fine cell structure is obtained, and A foamable resin composition for coating a high-foaming insulating polyethylene capable of producing a high-foaming body having a high foaming degree close to 80% and excellent mechanical strength, and a method for producing a high-foaming insulating polyethylene-coated electric wire using the same The present inventors have proposed and filed a patent application as Japanese Patent Application No. 7-226118. In this invention, since a high foam cannot be obtained by nitrogen gas alone, the problem is solved by using a chemical foaming agent together.

[0006]

As described above, recently, the foam-insulated polyethylene-coated electric wire has been manufactured by the chemical foaming method or the gas foaming method using nitrogen gas. In either method, a chemical foaming agent is used, and as a typical one, p, p'-oxy-bis-benzenesulfonyl hydrazide (hereinafter sometimes abbreviated as OBSH) is used. The reason is that the decomposition temperature of OBSH is 130 to 1
The temperature is in the range of 60 ° C., which is the temperature range for producing a foamable resin composition using a polyethylene-based resin.
This is because it does not decompose at 130 ° C., but decomposes at 130 to 160 ° C., which is an appropriate temperature for foam-coating the electric wire with the resin composition. However, the foam-insulated polyethylene-coated electric wire produced by using OBSH has a problem of corroding the conductor metal in contact with the foam-insulated polyethylene and deteriorating the quality of images and sounds. Therefore, the present invention
It is an object of the present invention to prevent corrosion of a conductor metal due to OBSH, that is, to propose a foamable resin composition for coating a foamed insulating polyethylene that does not cause corrosion when the conductor metal is coated while containing OBSH. To do.

[0007]

The inventors of the present invention have found that OBSH
As a result of various experiments on the cause of metal corrosion caused by the above, it was proved that in the production of OBSH itself, a certain compound that was mixed with OBSH and was not removed was the cause, and a compound that eliminates the rusting action of this compound. Assuming that the problem can be solved by blending with the resin composition, a compounding experiment was conducted on many compounds, and it was found that the problem can be solved when a specific compound was compounded, and the present invention was completed.

[0008]

SUMMARY OF THE INVENTION That is, the present invention is: (1) 0.5 to 5 parts by weight of p, p'-oxy-bis-benzenesulfonyl hydrazide containing impurities in 100 parts by weight of a polyethylene resin and an impurity scavenger 0.005-
A foamable resin composition for coating foam insulating polyethylene, which is prepared by blending 0.5 part by weight, and (2) a foam insulating polyethylene coated electric wire produced by using the above foam resin composition (3) Impurity collection Relates to a foamable resin composition, wherein the agent is selected from the group consisting of hydrotalcite, higher fatty acid metal salt, magnesium oxide, calcium oxide, magnesium hydroxide, calcium hydroxide, zeolite, organotin compound, calcium phosphate .

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the polyethylene resin is a high-pressure low-density polyethylene, a high-density polyethylene, a medium-density polyethylene, a low-pressure ethylene-α-olefin copolymer, or the like. A small amount of another olefin-based resin may be blended as a main component.

The p, p'-oxy-bis-benzenesulfonyl hydrazide (OBSH) used as a chemical foaming agent in the present invention usually contains a certain compound as an impurity as described above. When a high-foam insulation polyethylene-coated electric wire is made by using it, the conductor metal may be corroded and rusted, but in the present invention, by using hydrotalcite in combination, it is possible to prevent corrosion and rusting action by these impurities. You can For example, when the highly foamed insulating polyethylene coating of the present invention was applied as an insulating layer of a coaxial cable, no rust was observed on the inner conductor and the outer conductor of the coaxial cable, and a good quality coaxial cable was obtained. Therefore, according to the present invention, normally commercially available OBSH containing impurities can be used as it is. In the present invention, in addition to OBSH, a chemical foaming agent such as azodicarbonamide or an inert gas such as argon or xenon may be used together. The amount of OBSH used is 0.5 to 5 parts by weight based on 100 parts by weight of the polyethylene resin.
If it is less than 0.5 part by weight, a high foam satisfying the properties of the coaxial cable cannot be obtained even if gas is used together, and if it exceeds 5 parts by weight, overfoaming occurs and a uniform foam cannot be obtained. The surface of the body is also non-uniform, and it is not desirable because images and sounds cannot be transmitted clearly.

In the present invention, the impurity scavenger means OB
Impurities existing in SH are physically and / or chemically adsorbed and / or collected by a reaction to suppress rusting caused by the impurities, and also to prevent the foaming inhibition of the polyethylene resin due to the impurities. Compounds that are expressed include hydrotalcite, higher fatty acid metal salts, magnesium oxide, calcium oxide, magnesium hydroxide, calcium hydroxide, zeolite, organotin compounds, calcium phosphate, and the like, with hydrotalcite being particularly preferable.
As the higher fatty acid metal salt, calcium stearate,
Zinc stearate, lithium stearate, magnesium stearate, aluminum stearate, lead stearate, barium stearate, cadmium stearate, calcium laurate, zinc laurate, cadmium laurate, barium ricinoleate, zinc 2-ethylhexoate, 2 -Lead ethylhexoate, zinc para-tertiary butyl benzoate, calcium 12-hydroxystearate, zinc 12-hydroxystearate, 12-
Examples thereof include magnesium hydroxystearate, barium 12-hydroxystearate, and lead 12-hydroxystearate. Of these, calcium stearate and zinc stearate are particularly desirable. In the present invention, hydrotalcite is a water-containing basic carbonate of magnesium or aluminum, which may be a natural product or a synthetic product. The natural product is Mg ₆ Al ₂ (OH) ₁₆ CO ₃
-Having a structure of 4H ₂ O, and the compound having a different ratio of Mg and Al, for example, Mg ₄ Al ₂ (OH) ₁₂ CO _{3
· 3H 2 O, Mg 5 Al} 2 (OH) 14 CO 3 · 4H 2
O, Mg ₁₀ Al ₂ (OH) ₂₂ CO ₃ .4H ₂ O, Mg _{8
Al 2 (OH) 20 CO 3} · 5H 2 O , and the like. The amount of the impurity scavenger used is in the range of 1 to 10% of OBSH,
That is, 0.005 to 0.5 part by weight. 0.005
If it is less than 0.5 parts by weight, the effect of preventing metal corrosion (anticorrosion effect) will not be exhibited, and if it exceeds 0.5 parts by weight, eye bleeding will occur in the vicinity of the extrusion die, resulting in poor productivity and uniform foam. Not be desirable.

The resin composition of the present invention may contain a foaming aid, a foaming uniformizing agent, a coloring agent, an antioxidant, a nucleating agent, a copper damage inhibitor, a processing aid, an eyelash generation inhibitor and the like. Good.

The expandable resin composition of the present invention is generally produced by kneading a polyethylene resin, OBSH, hydrotalcite and other additives with a suitable kneading means such as a Banbury mixer. According to a particularly preferable kneading method, a polyethylene resin, a predetermined amount of an impurity scavenger, and other additives (such as an antioxidant) are kneaded in a Banbury mixer by heating to a temperature equal to or higher than the melting point of the polyethylene resin, Next, a predetermined amount of OBSH is added to this kneaded product, and the OBSH decomposition temperature (130-
It is kneaded at a temperature lower than 160 ° C.) and cooled into a sheet. In this case, this sheet material may be pre-foamed. The sheet can then be cut into pellets.

The foamable polyethylene resin composition of the present invention can be coated as an insulating coating on a metal conductor such as copper or aluminum by a wire coating method well known in the art. According to a particularly preferred method, a pellet made as described above is fed to an extruder, brought to a predetermined temperature, and a highly foamed insulating polyethylene coating is formed by coaxial extrusion of the molten resin composition onto a preheated metal conductor. Can be formed. Various parameters in the wire coating method are:
It can be easily determined by those skilled in the art.

[0015]

Next, the present invention will be described in more detail by way of examples.

Example 1 Melt index 2.0 g / 10 minutes, density 0.917
Melt index of 3. with respect to 70 parts by weight of high-pressure low-density polyethylene having g / cm ³ and swelling ratio of 60%.
0 g / 10 min, density 0.960 g / cm ³ , swelling ratio 45%, melting point 135 ° C., 30 parts by weight of high-density polyethylene, antioxidant (butylated hydroxytoluene) 0.
2 parts by weight and hydrotalcite (Mg ₄ Al ₂ (O
0.3 parts by weight of H) ₁₂ CO ₃ .3H ₂ O) was kneaded with a Banbury mixer for 10 minutes at 140 ° C. to obtain a kneaded product having a melting point of 124 ° C. 5 parts by weight of impurities in 100 parts by weight of this kneaded material
1.3 parts by weight of p, p′-oxy-bis-benzenesulfonyl hydrazide containing was added and kneaded at 127 ° C. for 10 minutes using a Banbury mixer to obtain a sheet having a prefoaming degree of 4%. Cut this with a sheet cutter, thickness 3m
m, length 5 mm, width 4 mm pellets were obtained. Then
The pellets were fed to a 50 mmφ extruder (L / D = 24), the cylinder temperature in the feed zone was 130 ° C., the cylinder temperature in the compression zone was 140 ° C., the cylinder temperature in the metering zone was 147 ° C. A copper core wire preheated to 70 ° C. was extrusion-coated at a wire winding speed of 20 m / min to obtain a foam insulated coaxial cable core having an outer diameter of 5.1 mm. The obtained foam has a degree of foaming of 50% and a cell diameter of 5 to 15
A cylindrical test piece of a coaxial cable core having a length of 0 μm and a length of 20 mm was radially compressed at a speed of 10 mm / min, and the compressive strength was measured by Young's modulus calculated from the amount of compression (strain) and the force. However, it was 0.87 kg / mm ² , and it was found that the mechanical strength was sufficient. An external conduit (made of copper) is coated around this coaxial cable, and the temperature is 50 ° C and the humidity is 10
After moisturizing for 300 days under the condition of 0% RH, visual observation showed no rusting. Images and sounds were transmitted using this coaxial cable, but no abnormality was found.

Comparative Example 1 The same experiment as in Example 1 was carried out except that the amount of hydrotalcite was changed to 0, and rust was observed on the copper surface. When images and sounds were transmitted using this coaxial cable, the sharpness was poor.

Example 2 Melt index 2.3 g / 10 minutes, density 0.918
100 parts by weight of low-density polyethylene having a long chain branch produced by a high-pressure method with g / cm ³ and a swelling ratio of 54%, melting point 133 ° C., density 0.958 g / cm ³ , swelling ratio 48%, melt Index 3.5g / 10
80 parts by weight of high density polyethylene, melting point 155 ° C., density 0.90 g / cm ³ , melt flow rate 3 g / 10
5 parts by weight polypropylene, 0.2 parts by weight vinyltriethoxysilane, 0.3 parts by weight of antioxidant (butylated hydroxytoluene) and hydrotalcite (Mg ₁₀
0.05 part by weight of Al ₂ (OH) ₂₂ CO ₃ .4H ₂ O) was mixed and heated and kneaded at 140 ° C. for 10 minutes with a Banbury mixer to obtain a kneaded product having a melting point of 124 ° C. This kneaded product 10
OBSH (1.5 parts by weight) was added to 0 parts by weight, and the mixture was kneaded with a Banbury mixer at 127 ° C. for 10 minutes to obtain a pre-expansion degree of 4%.
Was manufactured and cut with a sheet cutter to obtain pellets having a thickness of 3 mm, a length of 5 mm and a width of 4 mm. Next, the pellets were supplied to a 50 mmφ extruder (L / D = 28), the cylinder temperature in the supply area was 132 ° C., the cylinder temperature in the compression area was 142 ° C., the cylinder temperature in the metering area was 148 ° C. In the region, 0.8 parts by weight of nitrogen was pressed into 100 parts by weight of the expandable resin composition (pellets), the pellets were sufficiently heated and kneaded, and the existing nitrogen was uniformly dispersed in the resin component, and the temperature was raised to 70 ° C. A preheated 2.0 mmφ copper core wire was extrusion coated at a wire winding speed of 20 m / min to obtain a foam insulated coaxial cable core having an outer diameter of 9.4 mm. The foam thus obtained has a foaming degree of 50.
%, A cylindrical test piece of a coaxial cable core having a cell diameter of 5 to 130 μ and a length of 20 mm was prepared, and was radially compressed at a speed of 10 mm / min, and the Young's modulus calculated from the compression amount (strain) and the force. The compressive strength was measured with 0.75kg /
mm ² and it was found that the mechanical strength was sufficient. Also, when the capacitance is measured, it is 54 F / km,
It was found that the electrical characteristics were good. An outer conduit (made of copper) was coated around the coaxial cable, humidified at a temperature of 50 ° C. and a humidity of 100% RH for 300 days, and rusting was not visually observed. Images and sounds were transmitted using this coaxial cable, but no abnormality was found.

Comparative Example 2 The same experiment as in Example 2 was carried out except that the blending amount of hydrotalcite was set to 0. As a result, rusting was recognized on the copper surface. When images and sounds were transmitted using this coaxial cable, the sharpness was poor.

Example 3 In Example 1, instead of hydrotalcite, calcium stearate, zinc stearate, magnesium oxide, calcium oxide, magnesium hydroxide, calcium hydroxide, zeolite, dibutyltin dilaurate, dioctyltin dilaurate, calcium phosphate. The same experiment as in Example 1 was performed except that each of the above was used. Foaming was also performed normally as in Example 1, no rusting was observed on the copper wire surface, and images and sounds were transmitted using these coaxial cables, but they were clear, and the effect of an impurity scavenger other than hydrotalcite was observed. Was confirmed.

[0021]

INDUSTRIAL APPLICABILITY In the present invention, even if OBSH which is a commercially available chemical blowing agent containing impurities is used,
No rust was observed on the inner conductor and the outer conductor of the manufactured coaxial cable, and there was an effect that a good quality coaxial cable could be obtained.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01B 7/02 H01B 7/02 G

Claims (3)

[Claims] 1. 0.5 to 5 parts by weight of p, p'-oxy-bis-benzenesulfonyl hydrazide containing impurities and 100 parts by weight of a polyethylene-based resin, and 0.0 as an impurity scavenger.
A foamable resin composition for coating foamed insulating polyethylene, which comprises 0.5 to 0.5 parts by weight. 2. A foam-insulated polyethylene-coated electric wire manufactured using the foamable resin composition according to claim 1. 3. The method according to claim 1, wherein the impurity trapping agent is hydrotalcite, a metal salt of a higher fatty acid, magnesium oxide, calcium oxide,
Magnesium hydroxide, calcium hydroxide, zeolite,
The foamable resin composition according to claim 1, wherein the foamable resin composition is selected from the group consisting of an organotin compound and calcium phosphate.