JPH03102706A - Manufacture of high-forming polyolefin small-diameter wire - Google Patents

Abstract

PURPOSE:To improve compression resistant property in the vertical direction to the conductor direction by blending a surface active agent to a system consisting of base resin, a foaming nuclear agent and a foaming agent with specific concentration. CONSTITUTION:A surface active agent of 0.01-2phr is blended with a system consisting of base resin, a foaming nuclear agent and a foaming agent. When a blending amount of the surface active agent is less than 0.01phr, an effect to influence a foam construction is little, and when the blending amount exceeds 2phr, foam pushing out is not conveniently performed. Junction of bubbles with bubbles at a steep shear speed spot being generated at high linear speed in the gap between a die and a conductor is prevented by the surface active agent concerned so as to suppress bubble growth in the flow direction and to promote the growth of bubbles in the vertical direction to the longitudinal direction of the conductor while sharply improving the compression resistant strength in the vertical direction to the conductor of a foaming insulator layer.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is directed to a highly foamed state in which the foamed insulated wire has an extremely small diameter, for example, the outer diameter of the foamed insulator is 1.0 fi or less, and the foaming ratio is 3 times or more. The present invention relates to a method for producing a small-diameter highly foamed polyolefin electric wire that can be formed by extrusion, and in particular, the mechanical compressive strength at that time can be greatly improved compared to conventional examples. [Conventional technology 1] In cables for high-frequency transmission and cables for precision electronic devices such as computers, insulators are foamed to lower the dielectric constant, increase the speed of transmission signals, or reduce dielectric loss. Recently, high foaming ratios of more than 3 times have been achieved. Such highly foamed insulators can be formed relatively easily using almost established conventional techniques when the wire diameter is relatively large, such as for example in coaxial cables for CATV. In recent years, there has been a remarkable trend toward miniaturization and high-density packaging of communication equipment and precision electronic equipment. is l. Small diameter highly foamed insulated wires with a diameter of less than OAM have also come into use. [Problem to be solved by the invention 1 Reducing the diameter of electric wires is synonymous with reducing the thickness of foamed insulation, and such thin insulators are made with a foaming ratio of 3 times or more (
When trying to form a highly foamed layer (with a foaming degree of 67% or more), various problems that could not be considered with the above-mentioned conventional techniques were encountered. For example, as the insulator becomes thinner, it becomes difficult to achieve high foaming, and when the diameter of the insulator becomes thinner, coating breakage occurs when trying to increase the line speed and ensure productivity. These are the main problems, and the inventors have worked hard to solve these difficult problems, found a solution, and first proposed the details. (Patent application Hei 1-1041
92) However, an issue that remains unsolved in the above proposal is the problem of improving the compressive strength of the foamed insulator. ′′ at high linear speed by foam extrusion! MR foaming degree 70%
The above-mentioned highly foamed polyolefin small-diameter electric wires generally have a common drawback of low mechanical strength. This is thought to be caused by material factors, bubble structure factors, and core root remains factors. Among these, the uniqueness of cell elliptical structure can be mentioned as an essential factor common to the manufacturing method of foam extrusion using high linear speed.

．． In other words, if manufactured at a high linear velocity, the polymer melt in which the blowing agent gas is dissolved will be subjected to high shear at the die section, resulting in a parabolic velocity distribution of the flow in the cross section perpendicular to the flow direction. This results in the growth of bubbles that are elongated in the direction of flow. This unique bubble structure is
This is a major cause of decreasing the compressive strength in the direction perpendicular to the conductor direction of the core. The object of the present invention is to provide a novel highly foamed polyolefin small-diameter electric wire that can eliminate the above-mentioned drawbacks essentially inherent in the prior art and can greatly improve the compression resistance in the direction perpendicular to the conductor direction. The aim is to provide a manufacturing method for . [Means for Solving the Problems] The present invention provides an interface to a system consisting of a base resin, a foaming nucleating agent, and a foaming agent when forming and coating a thin conductor with a highly foamed polyolefin insulating layer by an extrusion method. The gist is to incorporate 0.01 to 2 phr of an active agent. The surfactants mentioned here include cationic surfactants (cationic) depending on the type of ions generated by ionization in aqueous solution φ.
There are three types of surfactants: anionic surfactants (anionic) and nonionic surfactants/fl (nonionic), which do not ionize, and which of them should be selected for use in the present invention. There is no thigh support. There are some substances, such as quaternary ammonium salts, that may deteriorate electrical properties, but within the range of the amount used in the present invention, there are few cases in which this actually becomes a problem. Therefore, setting the amount of surfactant to be in the range of 0.01 to 2 phr is zero.

This is because if it is less than ot phr, there will be little effect on the cell structure, and if it exceeds 2 phr, foam extrusion will not be carried out properly, which is not preferable. [Function] When a surfactant is added in the above formulation range and foaming extrusion is performed, the bonding between the bubbles in the severe IJI breaking velocity field that occurs in the gap between the die and the barrel due to high linear velocity is activated. The agent prevents and suppresses bubble growth in the direction of flow, promoting bubble growth in the direction perpendicular to the longitudinal direction of the barrel, thereby increasing the Compressive strength is greatly improved. [Examples] The present invention will be described below with reference to Examples. Example: An injection nozzle was installed in the center of a cylinder of 40 m + extrusion 111 (L/D = 29) for foam extrusion, and through this, liquid fluorocarbon (Freon 114) was injected under pressure as a foaming agent using a metering pump, and the fluorocarbon gas The melted polymer melt was extruded onto a running conductor using a crosshead section to fabricate a highly foamed polyolefin small-diameter electric wire.

The extrusion temperature was about 200°C, and the head part had a temperature gradient of about a't from the cylinder part in order to lower the die to near the melting point of the bolymer. To achieve high foaming and reducing the diameter, the die temperature was lowered and a part of the melt dross that expanded due to high foaming was controlled by the line speed to reduce the diameter.

Linear speed is approximately 50m/II! It was n. Shorex C4309 (density 0) as base resin
．． 944g/cs3. MI 0.9g/10iin;
Showa Denko products), powdered silica as a nucleating agent 0.51) hr
As a surfactant to be added in the present invention, nonionic alkylphenol type nonionic HS (NOF products) was used at O, 0.01, 0.05, 0.1, 0.5, 1.
0, 2.0, 3. The compound containing each Ophr was adjusted and finely granulated to prepare a test material. This compound was foamed and extruded into a conductor L with a conductor diameter of 0.18 mm using the extruder described above, and the core diameter was 0.8 m.
A highly foamed small diameter electric wire with a degree of foaming of approximately 80% was obtained. For this core sample, we investigated the core's crushing resistance, that is, its compression resistance perpendicular to the conductor direction. As a test machine,
Using a modified A-thickness gauge so that a load could be placed on the top, the deformation rate when the load was tooar and the permanent deformation rate 30 minutes after the load was removed were measured at room temperature. The results are shown in Table 1. As is clear from Table 1, N
0.1 shows large values for both the amount of deformation under load and the amount of permanent deformation. Addition of ON+hr (N
o. 2>, a remarkable change in the amount of deformation was observed, and from then on up to the addition of 2 phr (No. 7), the effect of compression deformation was remarkable as NO, 8, that is, 3. In the sample with Ollhr added, the amount of compressive deformation is even smaller, but the delay time is 4.2n.
s/m and increased to a large r1J, indicating that sufficient foaming was not performed in terms of foaming degree. The original reason for achieving high foaming, which is extremely difficult when using a III-type shuttle, is to shorten the delay time and increase the speed of the transmission signal (Td is 3.8 nS/m).
(below). Therefore, when considering this increase in delay time, it can be said that the upper limit of the amount of surfactant added is about 2 phr. [Effects of the invention 1

Claims (1)

[Claims] (1) When molding and coating a small-diameter conductor with a highly foamed polyolefin insulating layer by extrusion, 0.01 to 2 phr of a surfactant is added to the system consisting of the base resin, foaming nucleating agent, and foaming agent. A method for producing a highly foamed polyolefin small diameter electric wire.