JP2001052537A - Non-halogen flame retardant shield cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce conversion dielectric constant to a specified value or less to obtain high flame resistance by covering a center conductor with a foam of a resin composition added with a non-halogen-based flame retardant material to a base polymer of a mixture of polyolefin and polyphenylene ether of a specified ratio, and sequentially forming an outer conductor layer and a jacket layer on the foamed body. SOLUTION: A center conductor is covered with the foam of a flame retardant resin composition, and an outer conductor layer and a jacket layer are sequentially formed on the foam to constitute a shield cable. The foam is made of a flame retardant resin composition prepared by adding a non-halogen-based flame retardant material to the base polymer of a mixture of polyolefin and polyphenylene ether having a weight ratio of 90/10-20/80. A non-halogen flame retardant shield cable is obtained with conversion dielectric constant of the formed insulator <=2.3, and the foamed insulating cable excluding the jacket layer and the outer conductor layer satisfying the VW-1 vertical firing test of the UL standard.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a non-halogen flame-retardant shielded electric wire used for internal wiring of electronic equipment.

[0002]

2. Description of the Related Art Insulated wires and shielded wires used for internal wiring of electronic devices are required to be flame-retardant so that fire does not spread along the wires in the event of a device accident. The standard for the flame retardancy of the internal wiring material is defined by, for example, the UL standard (Underwriters Laboratories Inc.) of the United States, and is evaluated by a vertical combustion test called a VW-1 test. Therefore, a flame retardant polymer such as polyvinyl chloride (PVC) or a chlorine-based or bromine-based flame retardant has been blended with a polyolefin resin such as polyethylene for the covering material of the insulated wire in the above field. Polyolefin-based resin compositions have been applied. However, in recent years, it has been desired to develop an electric wire in which a non-halogen-based flame-retardant resin composition containing no halogen-based substance is applied to a coating material in response to environmental problems.

[0003] On the other hand, as the performance of electronic equipment has become higher, the amount of information has increased and the density of wiring has been increasing, and the influence of external noise on insulated wires has been reduced, and high-frequency current transmitted to insulated wires has been reduced. In order to reduce the amount of electromagnetic waves radiated from the outside, an outer conductor layer such as a braided conductor layer or a horizontally wound conductor layer is provided on the outer periphery of the insulator, and the use of a shielded wire whose outer periphery is covered with a jacket is increasing. ing. As described above, these shielded wires are also required to have flame retardancy, but there are two types of required flame retardancy,
They are used differently according to the level of flame retardancy required for the equipment and the application. (1) The shielded wire only needs to pass the VW-1 test,
Non-flammable insulator is not required. (2) Not only does the shielded wire pass the VW-1 test, but the insulator also requires flame retardancy, and the sample with the jacket and outer conductive layer removed (only the center conductor and insulator) Are also required to pass the VW-1 test.

In a shielded electric wire, it is necessary to use a material having a small dielectric constant (dielectric constant) and a small dielectric loss for an insulator in order to increase a signal transmission speed and reduce a transmission loss.
Therefore, when the required level of flame retardancy is (1), polyethylene or foamed polyethylene is used for the insulator, and the flame retardancy has been ensured by the sheath. On the other hand, when the required level of flame retardancy is (2), if polyethylene or foamed polyethylene is applied as it is to the insulator, the flame retardancy will be rejected. Is added, the flame retardancy that passes the VW-1 test is ensured, and the foam is used to reduce the dielectric constant and dielectric loss to practically acceptable levels. I have been.

As a method for forming the foamed insulating layer, a resin composition in which a chemical foaming agent such as azobiscarbonamide which generates nitrogen gas or the like by heating is dispersed in a resin such as flame-retardant polyethylene is used. Using a melt extruder, etc., a chemical foaming extrusion method of foaming while extruding on a conductor,
There is a gas foaming extrusion method in which a resin such as flame-retardant polyethylene is injected into a molten resin with a high-pressure nitrogen gas using a gas foaming extruder to coat a conductor and simultaneously foam a dissolved nitrogen gas.

[0006]

Recently, as described above, it has been desired to develop an electric wire using a coating material that does not contain a halogen-based material in response to environmental problems. Electric wires are not an example. Non-halogen flame-retardant resin compositions containing no halogen-based substances include polyolefin resins such as polyethylene and metal hydroxide-based flame retardants such as aluminum hydroxide and magnesium hydroxide, and phosphate ester compounds. Resin compositions containing a phosphorus-based flame retardant such as described above are known. By applying a chemical foaming extrusion method or a gas foaming extrusion method to these non-halogen flame-retardant resin compositions to form a foam on a conductor and lowering the dielectric constant, flame retardancy and electrical properties are obtained. There is no problem as long as a flame-retardant shielded wire compatible with the above is obtained. However, the non-halogen flame-retardant resin composition has a problem that the foaming degree during the extrusion is not stable even when the chemical foaming extrusion method or the gas foaming extrusion method is applied.
It is difficult to increase the degree of foaming. And, if the non-halogen flame-retardant resin composition is not foamed, the dielectric constant is 3 to
5 which is relatively large. For this reason, it is difficult to reduce the dielectric constant to a level of 2.3 or less, which is practically no problem as a shielded wire, in a stable state, and it is a non-halogen type having both flame retardancy and electrical characteristics. No flame-retardant shielded wires were obtained.

[0007]

Means for Solving the Problems As a result of intensive studies on the above problems, the present inventors have made a mixture of a polyolefin resin and polyphenylene ether a base polymer,
If a resin composition to which a non-halogen flame retardant such as magnesium hydroxide is added is used, foam extrusion can be performed with good stability by chemical foaming extrusion or gas foaming extrusion. In addition, it is possible to stably obtain a foam having a dielectric constant reduced to a level of 2.3 or less, which has no practical problem, and to obtain a foamed insulated wire in which the jacket layer and the outer conductive layer have been removed.
The present inventors have found that high flame retardancy that passes the W-1 test can be obtained, and have completed the present invention.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Polyolefin resins used in the present invention include polypropylene, high density polyethylene,
Known propylene and ethylene such as linear low density polyethylene, low density polyethylene, ultra low density polyethylene, ethylene vinyl acetate copolymer, ethylene ethyl acrylate copolymer, ethylene methyl methacrylate copolymer, ethylene methyl acrylate A system polymer can be illustrated. Also,
In the present invention, as the polyphenylene ether, not only polyphenylene ether alone, but also a mixture containing polyphenylene ether as a main component, for example, a mixture of polyphenylene ether and polystyrene, a mixture of polyphenylene ether and polyamide resin, and a mixture of polyphenylene ether and PBT resin The mixture contains maleic anhydride-modified polyphenylene ether and the like. In the present invention, a mixture of the above-mentioned polyolefin resin and polyphenylene ether is used as a base polymer, and the mixing ratio of the polyolefin resin and the polyphenylene ether is controlled by chemical foaming extrusion or gas foaming extrusion. From the viewpoint, a weight ratio of 90/10 to 20/80 is preferable, and a range of 70/30 to 20/80 is more preferable.

For mixing the polyolefin resin and the polyphenylene ether, known mixing devices such as a Banbury mixer, a pressure kneader, and a twin-screw mixer can be applied. When the two components are melt-mixed, a block copolymer of polystyrene and polyethylene can be used. If a known compatibilizing agent such as a graft copolymer, a block copolymer of polystyrene and ethylene ethyl acrylate or a graft copolymer is added, the polyolefin resin and the polyphenylene ether can be finely dispersed and obtained. Preferred results can also be obtained in mechanical properties such as elongation and tensile strength of the resin mixture.

If a mixture of the above-mentioned polyolefin resin and polyphenylene ether is used as a base polymer and a non-halogen flame retardant is added thereto using the above-mentioned known mixing apparatus, the flame-retardant resin composition of the present invention can be obtained. . The mixing may be performed by mixing a base polymer in advance, adding a non-halogen flame retardant thereto, and mixing again.At the same time as mixing the base polymer, a non-halogen flame retardant is also added and mixed. Is also good. Non-halogen flame retardants include metal hydroxides such as aluminum hydroxide and magnesium hydroxide, inorganic flame retardants such as antimony trioxide, borates and molybdenum salts, phosphate ester compounds, phosphite ester compounds, phosphonate compounds, etc. Known non-halogen flame retardants such as phosphorus flame retardants, nitrogen flame retardants such as melamine compounds, and silicone flame retardants such as polysiloxane can be applied. These may be added alone or in combination. The amount of non-halogen flame retardant added is base polymer 1
The amount can be appropriately set within the range of 10 to 200 parts by weight, more preferably 20 to 150 parts by weight, with respect to 00 parts by weight.
If the amount is less than 10 parts by weight, sufficient flame retardancy cannot be obtained.
If it is added in excess of 0 parts by weight, not only does the flame retardancy level off, but it is also disadvantageous in terms of cost.

In applying the chemical extrusion foaming method to foam the above resin composition, an azo compound such as azobiscarbonamide, a hydrazide compound such as oxybis (benzenesulfonylhydrazide), a nitroso compound, A known chemical foaming agent such as sodium may be added to the resin composition and then extruded and foamed. The amount of the foaming agent can be appropriately set according to the required degree of foaming.
A range of from 5 to 5 parts by weight is preferred. Gas extrusion foaming can also be applied. In addition, if necessary, in addition to the above-described compatibilizer, known compounding chemicals such as a lubricant, a filler, an antioxidant, a stabilizer, and a plasticizer can be added to the resin composition. is there.

Further, the shielded electric wire of the present invention is an accelerating electron beam,
By irradiating ionizing radiation such as γ-rays or the like, if the foamed insulator and the jacket are crosslinked, heat resistance and chemical resistance are improved, and a more reliable flame-retardant shielded wire is obtained. In addition, even when the terminal is soldered, the foamed layer is not melted, and the processability of the terminal is improved. Further, a solid layer may be formed on the inner periphery or the outer periphery of the foamed insulator for the purpose of improving the dielectric breakdown voltage, and the solid layer may be formed of not only the resin composition of the present invention but also a polyethylene resin composition. It is also possible to apply a known resin composition such as

[0013]

The present invention will be described in more detail with reference to the following examples. Examples 1 to 4 Above Table 1, a part (characteristic portion) of the composition of the resin composition used in Examples 1 to 4 is shown. The resin compositions used in these examples were, in addition to those described above in Table 1, 0.5 parts by weight of stearic acid and 1 part by weight of Dolphinox 1010 (trade name, manufactured by Ciba Geigy) based on 100 parts by weight of the base polymer. , A graft copolymer of polystyrene and polyethylene (ratio of polystyrene and polyethylene 50/50, MI value 1 ＠ 190
℃ load 2160g) 10 parts by weight, azobiscarbonamide 1
Parts by weight were commonly added. Using a 30 mm melt extruder (L / D = 24), the resin composition was used to form a soft copper wire having a wire diameter of 0.127 mm.
Chemical foaming extrusion was performed on the stranded conductor so that the outer diameter was 1.20 mm and the capacitance was 100 ± 5 pF / m by an in-line capacitance monitor. As a result, any of the resin compositions of Examples 1 to 4 could be stably foamed and extruded, and a foamed insulated wire having a desired outer diameter and capacitance was obtained. As shown in the lower part of Table 1, the capacitance was within the range of 100 ± 5 pF / m of the target value, and the capacitance was converted to the dielectric constant (*). 1 to 4 are all 2.0 to
It was found that a low dielectric constant foam layer having a level of 2.3 or less, which is within the range of 2.1 and has no practical problem as a shielded wire, was formed. (*) Capacitance and dielectric constant conversion formula Dielectric constant ε = (C × log (Do / Di)) / 24.12 where C is the capacitance, Do is the outside diameter of the insulator, and Di is the outside of the conductor. Represents the diameter. In addition, in order to examine the flame retardancy of the obtained foamed insulated wire, a VW-1 combustion test was performed at five test points, and it was found that all passed. Subsequently, the outer diameter of each of the foamed insulated wires of Examples 1 to 4 was 0.127 mm.
A shield layer is formed by horizontally winding a tin-plated annealed copper wire, and an ethylene-vinyl acetate copolymer (vinyl acetate content: 33% by weight, MI value: 5 ＠ 190 ° C., load: 2,160 g) 100
A non-halogen flame-retardant resin composition containing 150 parts by weight of magnesium hydroxide as a main component was coated to a thickness of 0.38 mm with respect to parts by weight to form a jacket layer to obtain a shielded electric wire. When a VW-1 test was performed on these shielded wires with five test points, it was found that all passed. Next, as described above, the acceleration voltage of 3 Me was applied to each of the four types of shielded wires in which a shield layer and a jacket layer were sequentially provided on the outer periphery of the foamed insulated wire.
A V electron beam was irradiated at 200 kGy to crosslink the foamed insulating layer and the jacket layer. These shielded wires were entirely removed, and the jacket layer and the side-wound shield layer of the terminal 30 mm were removed to expose the foamed insulator layer.
It was immersed in a 300 ° C. molten solder bath, but it was found that each of them retained the shape and was a shielded wire having excellent heat resistance.

[0014]

[Table 1]

Comparative Examples 1 to 3 Above Table 2, a part (characteristic part) of the composition of the resin composition used in Comparative Examples 1 to 3 is shown. The resin compositions used in Comparative Examples 1 to 3 were, in addition to those described above in Table 2, in addition to 0.5 parts by weight of stearic acid and 1 part by weight of Dolphinox 1010 (trade name, manufactured by Ciba Geigy) based on 100 parts by weight of the base polymer. Parts and 2 parts by weight of azobiscarbonamide were commonly added. Using a 30 mm extruder (L / D = 24), the resin composition was coated on a soft copper wire having a strand diameter of 0.127 mm and stranded on a seven-stranded conductor in the same manner as in Examples 1 to 4.
Chemical foaming extrusion was studied with the aim of 1.20mm and capacitance of 100 ± 5pF / m. Comparative Example 1 uses a resin composition in which 50 parts by weight of magnesium hydroxide was added to 100 parts by weight of an ethylene-ethyl acrylate copolymer, and the capacitance of the obtained foamed electric wire was measured by a water immersion method. However, it was found that a foamed insulator having a low dielectric constant equivalent to 98 pF / m (dielectric constant 2.1) and polyethylene (dielectric constant 2.2) was obtained.
However, in order to investigate the flame retardancy of this foamed electric wire, VW-1
As a result of performing a combustion test, all of the five test points out of five were rejected, indicating that the flame retardancy was poor. In Comparative Example 2, magnesium hydroxide was added to an ethylene-vinyl acetate copolymer.
Chemical foaming extrusion was performed in the same manner using the resin composition added with 0 parts by weight, and various extrusion conditions were examined. As long as the resin composition was stably obtained, the capacitance was 162 pF even if the highest foaming degree was obtained. / m (3.3 in terms of dielectric constant), which proved to be problematic for use as a shielded wire. Further, even if an attempt was made to further increase the degree of foaming, not only did the extruded outer diameter of the insulator become unstable, but also the appearance deteriorated, and a good sample could not be obtained. However, when the VW-1 combustion test was performed, all of the five test points passed the test, and it was found that the flame retardancy was excellent. Comparative Example 3 uses a resin composition in which 100 parts by weight of magnesium hydroxide was added to linear low-density polyethylene, and was similarly subjected to chemical foaming extrusion to examine various extrusion conditions. Was obtained, the capacitance was 148 pF / m (3.0 in terms of dielectric constant), which proved to be insufficient electrical properties as a shielded wire. Moreover, VW-1
As a result of a combustion test, five out of five test points failed, and the flame retardancy was not good.

[0016]

[Table 2]

Comparative Example 4 In Comparative Example 4, a resin composition was prepared in the same composition as in Example 2 except that magnesium hydroxide was not added, and a 30 mm extruder (L / D = 2) was prepared in the same manner as in Examples 1 to 4.
Using 4), chemical foam extrusion was studied on a seven-stranded conductor of soft copper wire with a wire diameter of 0.127 mm, with an outer diameter of 1.20 mm and a capacitance of 100 ± 5 pF / m. As a result, foam extrusion could be performed stably, and a foamed insulated wire having a desired outer diameter and capacitance was obtained.
The capacitance was confirmed by the immersion method in water, and as a result, as shown in the lower part of Table 3, it was 99 pF / m.
It was found that the foam had a low dielectric constant equivalent to that of polyethylene. However, when the VW-1 combustion test was performed with five test points, it was found that all five points failed. Comparative Example 5 Comparative Example 5 used a 30 mm extruder (L / D =) as in Examples 1 to 4 in the same manner as in Examples 1 to 4 except that the base polymer was a simple substance of polyphenylene ether and magnesium hydroxide was added thereto.
This study examined chemical foam extrusion on a seven-stranded conductor made of soft copper wire with a strand diameter of 0.127 mm using the method described in 24) with the target of an outer diameter of 1.20 mm and a capacitance of 100 ± 5 pF / m. However, even if various extrusion conditions were examined, the value of the capacitance displayed on the capacitance monitor fluctuated extremely, and a sample with a stable capacitance could not be obtained. That is, it was found that this resin composition could not stabilize the degree of foaming and could not form a uniform low dielectric constant layer, and was not suitable for a shielded electric wire.

[0018]

[Table 3]

Embodiment 5 FIG. A resin composition was prepared by adding the chemical blowing agent azobiscarbonamide to the resin composition of Example 2, and using a 30 mmφ gas foaming extruder,
0.40m coating thickness on 7 strands of soft copper wire with strand diameter 0.127mm
The gas foaming extrusion was studied with the aim of m and electrostatic capacity of 100 ± 5 pF / m. Nitrogen gas injection pressure 280bar, resin pressure 210kg / cm2, barrel temperature 160 ° C, die temperature 160 ° C, screw rotation speed 22
When the gas foaming extrusion was studied under the conditions of rpm and a linear velocity of 200 m / min, a foamed insulated wire having a predetermined outer diameter and a capacitance of 103 pF / m (measured by an immersion method in water) was obtained. It was 2.1 in terms of the dielectric constant, and it was found that a foamed insulator having a low dielectric constant equivalent to that of polyethylene was obtained. A VW-1 combustion test was performed to examine the flame retardancy of this foamed electric wire. As a result, all of the five test points passed the test, and it was found that the flame retardancy was excellent. Comparative Example 6 A resin composition was prepared in the same manner as in Comparative Example 2 except that the chemical blowing agent azobiscarbonamide was not added.
Using a gas foaming extruder with a diameter of 0 mm, apply a coating thickness on a seven-stranded conductor of soft copper wire with a strand diameter of 0.127 mm in the same manner as in Example 5.
We studied gas foaming extrusion with a target of 0.40 mm and a capacitance of 100 ± 5 pF / m. However, even if the injection pressure of the nitrogen gas, the die temperature, the screw rotation speed, the linear velocity, etc. are variously examined, the foamed electric wire having the target capacitance cannot be obtained. 168 pF / m converted to a dielectric constant of 3.4
As a result, only shielded electric wires having problematic electrical characteristics were obtained. As described above, by using a resin composition in which a mixture of a polyolefin resin and polyphenylene ether is used as a base polymer and a non-halogen flame retardant is added thereto, foaming extrusion by chemical foaming extrusion or gas foaming extrusion is easily stabilized. It can be seen that there is no particular problem in that an electric characteristic such as a dielectric constant or the like suitable for a shielded electric wire and an electric wire satisfying high flame retardancy can be obtained without environmental problems.

[0020]

The shielded electric wire of the present invention is a shielded electric wire having no environmental problems, a high signal transmission speed, a small transmission loss, and a high degree of flame retardancy. Some of the utility values are very high.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masayo Uenoyama 1-3-1 Shimaya, Konohana-ku, Osaka-shi F-term in Osaka Works, Sumitomo Electric Industries, Ltd. 5G305 AA02 AB10 AB25 AB35 BA13 BA14 BA26 CA01 CA13 CA54 CC03 CD13 5G315 CA03 CB02 CD01 CD02 CD13 CD14

Claims (3)

[Claims] 1. A foamed insulated wire having a converted dielectric constant of 2.3 or less and having a jacket layer and an outer conductor layer removed, and passing a UL standard VW-1 vertical combustion test. Halogen flame-retardant shielded wires. 2. A shielded electric wire in which a foam of a flame-retardant resin composition is coated on the outer periphery of a center conductor and an outer conductor layer and a jacket layer are sequentially formed on the outer periphery, wherein the foam is a polyolefin. Non-halogen flame-retardant resin composition comprising a mixture of a polyphenylene ether and a polyphenylene ether in a weight ratio of 90/10 to 20/80 as a base polymer to which a non-halogen flame retardant is added. Shielded wire. 3. The halogen-free flame-retardant shielded electric wire according to claim 2, wherein a foam of the flame-retardant resin composition formed on the outer periphery of the center conductor is cross-linked.