JPH02195604A - Foam insulating electric wire - Google Patents

Abstract

PURPOSE:To suppress deterioration in stretching of an insulating film as time passes by, and to prevent deterioration in mechanical strength by providing the insulating film composed of a foaming body of a specified mixture. CONSTITUTION:There is provided a conductor, on which an insulating film is extrusively coated. The insulating film is formed out of a foaming body of a mixture of either single polypropylene(PP) or block copolymer of polypropylene(PP) and low density polyethylene(PE), or that of polypropylene(PP) and ethylene propylene rubber(EPR), and high density polyethylene(PE) whose melt index is larger than that of these materials. Since the high density polyethylene whose melt index is larger than that of polypropylene or of block copolymer is excellent in compatibility with polypropylene, polypropylene is disposed in the high density polyethylene while crystal of the polypropylene is dispersed as a whole, and crystallization of polypropylene is thus suppressed to further suppress deterioration in the stretching.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a foam insulated wire used, for example, in a coaxial cable for high-speed signal transmission used for wiring between or within a computer rack. .

(Prior Art) Among the characteristics required of this type of foam insulated wire are high-speed signal transmission characteristics and deformation resistance against external forces.In particular, high-speed signal transmission characteristics are becoming increasingly important due to the demand for further shortening of transmission time. For this reason, it is necessary to use a material with a low dielectric constant as the covering material for electric wires, and to increase the foaming rate. Polyethylene (PE) and polypropylene (PP) are usually used as materials that meet these requirements.
and fluororesins, etc.

[Problem to be solved by the invention]

Of these three materials, polyethylene has the worst properties, and especially when the foaming ratio exceeds approximately 50%, it cannot be used for cables that require a high degree of deformation resistance, such as undercarpet cables. In addition, fluororesin has an extremely high material cost, while polypropylene is most used as an inexpensive material that has high resistance to deformation against external forces even at a high foaming rate.

However, polypropylene is a typical crystalline resin, and when it is molded into the shape of a molten wire using an extruder, its elongation decreases over time, and this tendency decreases as the foaming rate increases. This becomes more noticeable as the wall thickness decreases. Low-density polyethylene and block copolymers of ethylene-propylene rubber (EPR) and polypropylene are known as materials that can improve these drawbacks, but even these have not been able to significantly improve the properties.

An object of the present invention is to provide an inexpensive foam insulated wire that avoids the above-mentioned drawbacks, can suppress a decrease in elongation, and has an insulation coating with excellent mechanical strength.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention combines a material consisting of polypropylene, a polypropylene/polyethylene block copolymer, and a polypropylene/ethylene-propylene rubber block copolymer, and a high-density polyethylene having a larger melt index than this material. The present invention provides a foam insulated wire characterized in that it has an insulation coating made of a foam of a mixture of.

[Effect] In this way, when high-density polyethylene, which has a higher melt index than this material, is mixed with polypropylene, a block copolymer of polypropylene/polyethylene, or a block copolymer of polypropylene/ethylene propylene rubber, the elongation of the insulation coating decreases over time. In addition to being able to suppress this, it also improves mechanical strength.

〔Example〕

Next, the foam insulated wire of the present invention will be explained in detail. The foam insulated wire of the present invention consists of a conductor and an insulating coating extruded on the conductor. As mentioned above, polypropylene (PP) alone or polypropylene (PP) and low density polyethylene (PE)
block copolymer or polypropylene (PP) with
and ethylene propylene rubber (EPR), and high-density polyethylene (PE), which has a higher melt index than these materials.

If the melt index of high-density polyethylene is smaller than the melt index of polypropylene alone or a block copolymer of polypropylene and low-density polyethylene or ethylene-propylene rubber, the mechanical strength may be good, or the compatibility between the resins may be poor, resulting in poor elongation. In addition to the uncontrollable deterioration over time, the appearance of the wires deteriorates significantly.

On the other hand, if the melt index of high-density polyethylene is larger than the index of materials such as polypropylene, the decline in elongation over time will be significantly suppressed, but mechanical strength, impact resistance, etc. will deteriorate significantly, so high-density polyethylene The appropriate melt index of polyethylene is 10 g, 710 minutes or less. Incidentally, the mixing ratio of polypropylene or its block copolymer with high density polyethylene is effective in any case.

Foamed materials used in the present invention include azodicarbonamide (ADCA), azobisisobutyronitrile (A
IBN), dinitrosopentamethylenetetramine (DP
T), p-) luenesulfonyl hydrazide (TSH),
p,p-oxybis(benzenesulfonylhydrazide)
A pyrolyzable organic foaming material such as (OBSH), gases such as nitrogen, carbon dioxide, chlorofluorocarbon (fluorocarbon), or a combination thereof can be used. Of course, during extrusion, a foaming core material, an anti-aging agent, a copper damage inhibitor, a coloring agent, etc. may also be added.

The decrease in elongation of polypropylene over time is due to the growth of crystals after the polypropylene melts and solidifies;
In foam insulated wires, crystals grow unevenly, and if the insulation coating is thin, it is thought that residual strain during processing is added, accelerating the decline in elongation.

On the other hand, high-density polyethylene, which has a higher melt index than polypropylene or block copolymers, has excellent compatibility with polypropylene, so if such high-density polyethylene is mixed with polypropylene, it will disperse into the polypropylene or high-density polyethylene. .

It is thought that since the polypropylene crystals are also dispersed throughout, crystallization of the polypropylene is suppressed and a decrease in elongation is suppressed.

Next, Table 1 shows specific examples and comparative examples of the foam insulated wire of the present invention.
The foam insulated wires shown in both examples have a diameter of 40 m.
The material shown in Table 1 was melt-kneaded in the extruder with a foaming nucleating agent, an anti-aging agent, and a copper damage inhibitor added, and the foaming agent was added from the middle of the extruder barrel. Chlorofluorocarbon 500 (commonly known as Freon 5)
00; CCl2F2/CH3-C) (F, = 73.8/
26.2 weight ratio), and an insulating coating with a foaming rate of about 55% was applied on a mild steel single wire conductor with a diameter of 0.226 mm so that the finished diameter was about 1.35 mm. In addition, the results of each elongation test are shown in Table 2, and this elongation test was conducted using a tubular sample according to J I 5C3005 using a Tensilon type tensile tester at a tensile speed of 50 mm/
The measurement was performed on the day of extrusion, on the 7th day, on the 300th day, and on the 100th day 0 after being left at room temperature. Further, the room temperature deformation rate was measured using the apparatus and method of a JISC3005 heating deformation tester, and the measurement temperature was only at room temperature (23° C.). Note that the load was 750 g.

Specific example 1.2 is Noblen BC8D (Mitsubishi Yuka P
Block copolymer of P and PE: melt index 1
．． 2g/lomin, density 0.89g/Cm''''), Lexron E750 (C) (Nisseki Chemical high density PE; melt index 5.3g/lomin, density 0.963g/
cm') (Example 1), Rexron E780 (C)
(High-density PE made by 0 Rock Chemical, melt index 8.0g
/10 minutes, density 0.963 g/cm') were mixed at a weight ratio of 80:20.

Further, in Specific Example 3.4, LEXRON E750 (C) (Specific Example 3) and Rexron E780 (C) (Specific Example 4) at a weight ratio of 80
: Materials mixed in step 20 were used.

On the other hand, Comparative Example 1 uses only Noblen BC8D, and Comparative Example 2.3 uses Noblen BC8D and Hizex5305.
E (high-density PE made by Mitsui Petrochemicals: melt index 0.8 g 710 minutes, density 0.945 g/cm') (Comparative Example 2) and Rexron M41 (low-density PE made by 0 Seki Kagaku)
: Melt index 6.0g/10min, density 0°92
2g/cm:l) were mixed at a weight ratio of 8020.

Comparative example 4 uses only UBE C211, and comparative example 5.6 uses Hizex5305E in UBE C211.
(Comparative Example 5) and UBE C180 (Comparative Example 6) were mixed at a weight ratio of 80:20.

Table 1 As is clear from Table 2, in Comparative Examples 1.2 and 4.5, the elongation of the insulation coating decreased as the E number increased, and after extrusion
On day OO, the absolute value was 100% or less, and the residual rate (ratio to the day of extrusion) was 20% or less. In addition, in Comparative Example 3.6, the decrease in elongation of the insulation coating with the passage of days was small, and 10
On the 0th day, the residual ratio is 90% or more, but the room temperature deformation rate becomes significantly worse and the mechanical strength decreases. On the other hand, in the specific example of the present invention, the initial elongation of the insulation coating on the day of extrusion is larger than that in Comparative Examples 1 to 6, and even after 100 days, the absolute value is 350% or more and the residual rate is 90% or more. Elongation is maintained,
It can also be seen that the deformation rate at room temperature is extremely small.

〔Effect of the invention〕

According to the present invention, as described above, insulation can be achieved by simply mixing polypropylene, a block copolymer of polypropylene/polyethylene, or a block copolymer of polypropylene/ethylene-propylene rubber with high-density polyethylene having a higher melt index than these materials. There is a practical benefit in that it is possible to suppress the deterioration of the elongation of the coating over time and to provide an inexpensive foam insulated wire that does not have a decrease in mechanical strength.

Ji-za f four tones.

Claims (1)

[Claims] having an insulating coating consisting of a foam of a mixture of polypropylene, a block copolymer of polypropylene/polyethylene, a block copolymer of polypropylene/ethylene-propylene rubber, and a high-density polyethylene having a higher melt index than this material; Features foam insulated wire.