JPH04319212A - Manufacture of extra-fine high forming wire - Google Patents

Abstract

PURPOSE:To stably manufacture a lengthy extra-fine high foaming wire. CONSTITUTION:When a foaming fluorinated carbon resin is extruded from an extruder and to the outer periphery of an extra-fine core wire, the diameter of which is no more than 0.3mm, and which is coated thereby, so as to manufacture an extra-fine high foaming wire, teh rotational number of a screw 2 of the extruder will be not les than 0.5rpm. The extra-fine high foaming wire is manufactured while the temperature of a cylinder 1 of an extruder in proximity of a hopper 3 of the extruder is maintained not more then the melting point of the fluovinated carbon resin.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention applies to core wires with an outer diameter of 0.3 mm.
The present invention relates to a method for producing an ultra-fine, highly foamed wire as described below.

0002

2. Description of the Related Art High-density electric wires with low information propagation delay time are required as information transmission paths for computers and the like because of the need to process a large amount of information at high speed. To meet this requirement, an ultra-fine highly foamed wire is used, in which the outer periphery of an ultra-fine core wire with an outer diameter of 0.3 mm or less is extruded from an extruder and coated with a foamed fluororesin such as foamed tetrafluoroethylene resin, which has a low dielectric constant. There is.

[0003] This ultra-fine foam wire is made by injecting a foaming gas such as chlorofluorocarbon into heat-meltable tetrafluoroethylene in an extruder, kneading it, and then extruding foamed fluororesin onto the ultra-fine core wire using a crosshead to coat the ultra-fine core wire, followed by foaming. Manufactured by In this case, if the core wire diameter is small, the amount of foamed fluororesin extruded from the extruder will also be small. Conventionally, an extruder with a cylinder inner diameter of 25 mm or a cylinder inner diameter of 30 mm was used.
The extruder was rotated at low speed to extrude and coat the ultra-fine core wire. In addition, when extruding tetrafluoroethylene, increasing the shear rate causes roughening of the coated surface.
There are limits to the shear rate.

0004

Problems to be Solved by the Invention The conventional method for producing ultra-fine, highly foamed wires has various problems as shown below.

(a) 0 in an extruder with a cylinder inner diameter of 25 mm
．． In order to obtain an extrusion rate of 35 g/min, the screw rotation speed needs to be 0.4 rpm or less. At this rotation speed, the extrusion amount is not stable, so the coating diameter becomes unstable.

(a) Tetrafluoroethylene and Freon react in the extruder, but since the extrusion rate is small, the residence time in the extruder becomes long, so the reaction progresses and the tetrafluoroethylene deteriorates before coating. For example, cylinder inner diameter 25
When extruding 0.35 g/min with a 1.0 mm extruder, the residence time of the extruded material from the hopper to the die will be more than 5 hours.

(c) If an extruder with a cylinder inner diameter of 10 mm or less is used, the strength of the screw shaft is low and the viscosity of tetrafluoroethylene changes rapidly near its melting point (300°C), so a large torsional moment is applied to the screw. The screw will be damaged.

An object of the present invention is to provide a method for producing an ultra-fine, highly foamed wire that can stably produce an ultra-fine, highly foamed wire having a core outer diameter of 0.3 mm or less over a long length.

[0009]

[Means for Solving the Problems] To explain the means of the present invention for achieving the above object, the present invention has an outer diameter of 0.3
In the method for producing an ultra-fine highly foamed wire, in which the outer periphery of an ultra-fine core wire of mm or less is coated with a foamed fluororesin by extrusion from an extruder to produce an ultra-fine, highly foamed wire, the screw rotation speed of the extruder is set to 0.5 rpm or more. Further, the ultrafine highly foamed wire is produced while maintaining the temperature of the cylinder of the extruder near the hopper of the extruder below the melting point of the fluororesin.

0010

[Operation] In this way, the screw rotation speed of the extruder is 0.
The screw can be rotated stably by manufacturing an ultra-fine, highly foamed wire at a speed of 5 rpm or more while maintaining the temperature of the extruder cylinder near the extruder hopper below the melting point of the fluororesin. This makes it possible to stably produce long lengths of ultra-fine, highly foamed wires that have the desired foaming rate, outer diameter, and good appearance.

[0011]

EXAMPLE FIG. 1(A) shows an extruder used in this example. In the figure, 1 is a cylinder, 2 is a screw that rotates within the cylinder 1, 3 is a hopper that supplies pellet-shaped extruded material 4 into the cylinder 1 on the base end side of the cylinder 1, and 5 is provided at the tip of the cylinder 1. 6 is a heater provided on the outer periphery of the cylinder 1, 7a to 7d are temperature measurement points of the cylinder 1, 8 is a foaming agent inlet provided in the cylinder 1, and 9 is a housing for storing the foaming agent. 10 is an injection pump for injecting the foaming agent from the tank 9 into the cylinder 1 through the foaming agent inlet 8, and 11 is a cooling jacket for cooling the cylinder 1 corresponding to the hopper 3.

FIG. 1(B) shows the temperature distribution of the feed zone, compression zone, and metering zone of the cylinder 1 in FIG. 1(A).

[0013] In order to determine the optimal manufacturing conditions for ultrafine, highly foamed wires with a core wire outer diameter of 0.3 mm or less, the present inventor conducted experiments on each wire type using tetrafluoroethylene (melting point: 300°C) as a coating material. As a result, the results shown in Table 1 were obtained.

[0014]

[Table 1]

Regarding the ultra-fine highly foamed wire with a wire type of 90Ω,
Initially, it was manufactured under the conditions shown in Table 1, but the surface had many irregularities.
Since the appearance was poor, a prototype was produced using an extruder with a cylinder inner diameter of 25 mm, and a good product was obtained. At this time, the screw rotation speed was 2 rpm, and the set temperature of the heater 6 near the bottom of the hopper 3 was 290°C.

[0016] Furthermore, the line type is 65Ω×3.8ns/m (
1) ,65Ω×3.8ns/m (2) ,65Ω×
When the ultrafine highly foamed wire of 3.8 ns/m (3) was manufactured under the conditions shown in Table 1, the desired foaming rate and outer diameter could be stably obtained over a long length. Furthermore, we were able to create a product with a good appearance.

The temperature of the heater 6 in the feed zone is heated to be below the melting point of the fluororesin, and in the compression zone (the point where the cross-sectional area ratio between the cylinder and the screw suddenly changes to the compression side), the melting point of the fluororesin is lowered. As a result, the temperature in the metering zone is 340°C or higher.

The blowing agent injection was carried out in the metering zone. The injection pressure at that time was 40 to 60 kg/cm.
It is 2.

[0019] Line type is 65Ω×3.8ns/m (3)
An extruder with a cylinder inner diameter of 15 mm was used as the extruder. From the hopper, the outer diameter is 1.5 mm and the length is 1.5 mm.
The following fine pellets were supplied. As the tetrafluoroethylene agent in the form of fine pellets, fully kneaded pellets mixed with a foaming nucleating agent were used. Screw rotation speed is 1.5
Coating was performed at rpm and extrusion rate of 2.2 g/min. As a result, the obtained ultra-fine highly foamed wire had a foaming rate of 73% and a propagation delay time of 3.8 ns/m ±0.12n.
Achieved s/m. A smooth appearance was obtained by directly cooling the ultra-fine, highly foamed wire with water immediately after it came out of the die. At this time, the temperature of the heater near the hopper was controlled at 280°C.

[0020]

Effects of the Invention As explained above, in the method for producing ultra-fine highly foamed wire according to the present invention, the screw rotation speed of the extruder is set to 0.5 rpm or more, and the The temperature of the extruder cylinder is maintained below the melting point of the fluororesin while producing ultra-fine, highly foamed wire.
The screw can be rotated stably, and it is possible to stably produce long lengths of ultra-fine, highly foamed wires that have the desired expansion rate and outer diameter and have a good appearance.

[Brief explanation of the drawing]

FIG. 1 (A) is a vertical cross-sectional view showing a schematic configuration of an extruder for carrying out the method for producing an ultra-fine, highly foamed wire according to the present invention, and (B) is a temperature distribution diagram of a cylinder of the extruder.

[Explanation of symbols]

1... Cylinder, 2... Screw, 3... Hopper, 4... Pellet-shaped extrusion material, 5... Crosshead, 6... Heater,
7a to 7d... Temperature measuring point of cylinder 1, 8... Foaming agent inlet, 9... Foaming agent storage tank, 10... Injection pump.

Claims (1)

[Claims] 1. A method for manufacturing an ultra-fine high-foam wire, in which the outer periphery of an ultra-fine core wire with an outer diameter of 0.3 mm or less is extruded and coated with a foamed fluororesin from an extruder to produce an ultra-fine high-foam wire, wherein the screw of the extruder The ultra-fine highly foamed wire is manufactured while maintaining the rotation speed at 0.5 rpm or more and the temperature of the cylinder of the extruder near the hopper of the extruder to be below the melting point of the fluororesin. A method for manufacturing ultra-fine, highly foamed wire.