JP2618464B2 - Foam insulated wire - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foamed insulated wire used for a high-speed signal transmission coaxial cable used for wiring between or within a computer, for example. .

[Conventional technology]

Among the characteristics required for this type of foamed insulated wire, there are high-speed signal transmission characteristics and resistance to deformation against external force. In particular, high-speed signal transmission characteristics are increasingly required from the demand for further reduction in transmission time. is there. For this reason, it is required to use a material having a small relative dielectric constant and to increase the foaming rate as a covering material of the electric wire. However, when the foaming rate is increased, the resistance to deformation against external force decreases. As materials satisfying these requirements, polyethylene (PE), polypropylene (PP), fluorine resin and the like are usually listed.

[Problems to be solved by the invention]

Of these three materials, polyethylene has the worst properties, especially if the foaming ratio exceeds about 50%, it cannot be used for cables requiring a high degree of deformation resistance, such as undercarpet cables. In addition, fluorine resin has an extremely high material cost, while polypropylene is most used as an inexpensive material having high deformation resistance against external force even at a high foaming ratio.

However, polypropylene is a typical crystalline resin, and has the property that elongation decreases with time when it is molded into an electric wire after melting with an extruder or the like. This becomes more pronounced as the wall thickness decreases.
Low density polyethylene and block copolymers of ethylene / propylene rubber (EPR) and polypropylene are known as materials for improving such disadvantages, but their characteristics have not been able to be remarkably improved.

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

[Means for solving the problem]

In order to solve the above-mentioned problems, the present invention provides a material having any one of a block copolymer of polypropylene and a polypropylene / polyethylene block copolymer and a block copolymer of a polypropylene / ethylene-propylene rubber, a melt index larger than this material and 10 g / 10 The present invention provides a foamed insulated wire characterized by having an insulating coating made of a foam of a mixture with a high-density polyethylene of not more than 10 minutes.

[Action]

As described above, when high-density polyethylene having a melt index greater than that of this material and 10 g / 10 minutes or less is mixed with polypropylene, a block copolymer of polypropylene / polyethylene, and a block copolymer of polypropylene / ethylene-propylene rubber, the elongation of the insulating coating increases. Over time can be suppressed, and the mechanical strength is improved. As the melt index of the high-density polyethylene is larger than the melt index of polypropylene or the like, the elongational decrease in elongation is remarkably suppressed, which is preferable. However, when this is too large, the mechanical strength and impact resistance are significantly reduced. . The maximum allowable melt index of 10 g / 10 min for high density polyethylene is a critical value that can maintain the mechanical strength and impact resistance of the insulating coating.

Further, even if the insulating coating material is a combination of polypropylene or the like and polyethylene and the melt index of the polyethylene is higher than that of the polypropylene or the like, if the polyethylene is a low-density polyethylene, the mechanical strength is significantly reduced and the insulating coating material is not suitable. Appropriate.

〔Example〕

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

If the melt index of the high-density polyethylene is smaller than that of the block copolymer of polypropylene alone or this polypropylene and the low-density polyethylene or ethylene-propylene rubber, the mechanical strength is improved, but the compatibility between the resins is poor and the elongation is poor. Cannot be suppressed, and the appearance of the electric wire is significantly deteriorated. Conversely, if the melt index of high-density polyethylene is too large than that of a material such as polypropylene, the decrease in elongation with time is significantly suppressed, but the mechanical strength, impact resistance, etc. are significantly deteriorated, so The melt index of polyethylene is required to be 10 g / 10 minutes or less. When the melt index of the high-density polyethylene is 10 g / 10 minutes or less, it is possible to maintain the mechanical strength and impact resistance required for the insulating coating of the foamed insulated wire. The mixing ratio of polypropylene and its block copolymer with high-density polyethylene is effective in any case.

The foaming materials used in the present invention include azodicarbonamide (ADCA) and azobisisobutyronitrile (AIB
N), dinitrosopentamethylenetetramine (DPT), p
-Toluenesulfonyl hydrazide (TSH), p, p'-
Oxybis (benzenesulfonyl hydrazide) (OBSH)
Or a gas such as nitrogen, carbon dioxide, chlorofluorocarbon (CFC), or a combination thereof. At the time of extrusion, a foaming nucleus material, an antioxidant, a copper damage inhibitor, a colorant, and the like may be added to the material.

The time-dependent decrease in the elongation of the polypropylene is due to the crystal growth after the polypropylene has melted and solidified.In the case of foamed insulated wires, the crystal growth method is not uniform, and when the insulating coating is thin, It is considered that the reduction of elongation is promoted by the addition of residual strain during processing.

On the other hand, high-density polyethylene having a melt index larger than polypropylene or a block copolymer has excellent compatibility with polypropylene,
It is considered that when such high-density polyethylene is mixed with polypropylene, the polypropylene is dispersed in the high-density polyethylene, and the crystals of the polypropylene are also entirely dispersed, so that the crystallization of polypropylene is suppressed and the decrease in elongation is suppressed.

Next, specific examples and comparative examples of the foamed insulated wire of the present invention are shown in Table 1. In each case, the foamed insulated wire was manufactured using an extruder having a diameter of 40 mm. In the extruder, a material obtained by adding a foam nucleating agent, an antioxidant, and a copper damage inhibitor to the materials shown in Table 1 was melt-kneaded. Further, chlorofluorocarbon 500 (commonly known as CFC 500; CCl ₂ F ₂ /
CH ₃ -CHF ₂ = 73.8 / 26.2 weight ratio), the diameter is 0.226m
An insulation coating having a foaming rate of about 55% was applied on the m. copper single-wire conductor so as to have a finished diameter of about 1.35 mm. Table 2 shows the results of the elongation test for each example.
Using a tubular sample based on SC3005, it was determined at a tensile speed of 50 mm / min by a Tensilon-type tensile tester, and the measurement was carried out at room temperature at the day of extrusion, on the 7th, 30th, and 100th days. Further, the room temperature deformation ratio was measured at room temperature (23 ° C.) only at the measurement temperature using the apparatus and method of a JIS C3005 heating deformation tester. The load was 750 g.

Examples 1 and 2 are Noblen BC8D (Mitsubishi Yuka PP and PE
Block copolymer; Melt index 1.2g / 10
Min, density 0.89 g / cm ³ ), Lexlon E750 (C) (high density PE manufactured by Nisseki Chemical; melt index 5.3 g / 10 min, density 0.
963 g / cm ³ ) (Specific Example 1), Lexlon E780 (C) (high density PE manufactured by Nisseki Chemical; melt index 8.0 g / 10 min, density 0.
963 g / cm ³ ) (Specific Example 2) was used at a weight ratio of 80:20.

Examples 3 and 4 are UBE C211 (Ube Industries PP and P
E block copolymer; melt index 2.7g / 10
And a density of 0.90 g / cm ³ ) with Lexlon E750 (C) (Specific Example 3) and Lexlon E780 (C) (Specific Example 4) mixed at a weight ratio of 80:20.

On the other hand, Comparative Example 1 uses Noblen BC8D alone, and Comparative Examples 2 and 3 use Hizex5305E (Mitsui Petrochemical's high-density PE; melt index 0.8 g / 10 min, density 0.945 g) for Noblene BC8D.
/ cm ³ ) (Comparative Example 2) and Lexlon M41 (low density PE manufactured by Nisseki Chemical; melt index 6.0 g / 10 min, density 0.922 g / c)
A material obtained by mixing m ³ ) (Comparative Example 3) at a weight ratio of 80:20 was used.

Comparative Example 4 used only UBE C211 and Comparative Example 5
No. 6 used a material obtained by mixing Hizex5305E (Comparative Example 5) and Lexlon M41 (Comparative Example 6) in a weight ratio of 80:20 with UBE C211.

As is clear from Table 2, in Comparative Examples 1, 2, 4 and 5, the elongation of the insulating coating decreased with the passage of days, and after extruding.
On the 100th day, the absolute value was 100% or less, and the residual ratio (compared to the day of extrusion) was 20% or less. In Comparative Examples 3 and 6, the decrease in elongation of the insulating coating with the passage of days was small, and the residual ratio was 90% or more even on the 100th day. However, the room-temperature deformation rate was significantly deteriorated, and the mechanical strength was reduced. On the other hand, in the specific example of the present invention, the elongation of the insulating coating on the day of the extrusion was comparatively 1 to 6
It can be seen that the elongation is maintained at 350% or more in absolute value and 100% or more in residual ratio even after 100 days, and the room-temperature deformation rate is extremely small. Comparative Examples 1 and 4 are examples using only a polypropylene / polyethylene block copolymer, and Comparative Examples 2 and 5 use a combination of a polypropylene / polyethylene block copolymer and high-density polyethylene. Comparative examples 3 and 6 are examples in which the melt index of the high-density polyethylene is lower than the melt index of the block copolymer, and Comparative Examples 3 and 6 are examples of the combination of the block copolymer of polypropylene / polyethylene and the low-density polyethylene. All of them are different from the materials targeted by the present invention, and as a result, as shown in Table 2, the elongation is greatly reduced with time or the mechanical strength is low.

〔The invention's effect〕

According to the present invention, as described above, polypropylene or a block copolymer of polypropylene / polyethylene or a block copolymer of polypropylene / ethylene-propylene rubber is mixed with high-density polyethylene having a higher melt index than these materials to form an insulating coating. There is a real advantage that an inexpensive foamed insulated wire that can suppress the elongation of elongation over time and that does not reduce the mechanical strength can be provided.

Claims (1)

(57) [Claims] 1. A material comprising a polypropylene, a block copolymer of polypropylene / polyethylene and a block copolymer of polypropylene / ethylene-propylene rubber, and a high-density polyethylene having a melt index greater than 10 g / 10 min. A foam insulated wire having an insulating coating made of a mixture foam.