JPH04123715A - Insulated wire and manufacture thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an insulated wire in which the dielectric constant of an insulating layer is lowered, and a method for manufacturing the same.

[Prior Art] Conventionally, foaming has been performed in insulated wires as a means of lowering the dielectric constant of an insulating layer.

A specific method for this is, for example, as disclosed in JP-A-58-178914 and JP-A-59-217906, a composition in which a chemical blowing agent such as azodicarbonamide is blended with a thermoplastic resin. Chemical foaming, in which a material is extruded onto a conductor in a molten state and foamed by the heat generated during the process, or gas foaming, in which an inert gas such as Freon is blown into a molten resin to foam it, is known.

However, in chemical foaming, does foaming occur in the resin? .

When the blending amount of the blowing agent is increased, a large amount of decomposition residue of the blowing agent is generated.
This poses a problem in that it causes deterioration of electrical characteristics such as an increase in dielectric voltage contact and an increase in damping in the high frequency range.Furthermore, in the case of gas foaming, a large amount of equipment costs are required, and the gas There is a problem in that the foaming agent becomes more likely to collect, and as a result, the air bubbles connect to form large cells, resulting in poor adhesion between the foamed insulating layer and the conductor.

In addition, as another method for improving the problems of these foam insulated wires, Japanese Patent Publication No. 56-43563 proposes hollow spheres made of glass or alumina-based inorganic materials with particle diameters of several μm to several mils. A method was proposed in which foamed spheres were mixed with a thermoplastic resin that could be extruded and coated on conductors by extrusion.
Furthermore, Japanese Patent Publication No. 56-43564 describes a method in which the surface of the hollow sphere is coated with a thermoplastic resin and is melt-extruded onto a conductor. It has also been proposed to dissolve a solvent-soluble resin and the hollow spheres in an organic solvent such as xylene, apply the solution onto a conductor, and then bake it to form an insulating layer.

[Problems to be Solved by the Invention] By the way, among the conventional techniques using the above-mentioned hollow spheres, Japanese Patent Publication No. 56-43563 discloses that the hollow spheres are mixed with a thermoplastic resin that can be extruded and coated on a conductor by extrusion. In the described method, when a large amount of hollow spheres is filled for the purpose of obtaining a high porosity, the viscosity of the molten resin composition increases significantly, and therefore the hollow spheres are destroyed inside the extruder, causing the insulation layer to deteriorate. The disadvantage is that the dielectric constant of the oxide cannot be lowered that much.

In addition, the surface of the hollow sphere is coated with a thermoplastic resin using an organic solvent and then melt-extruded.
564, and Japanese Patent Publication No. 57-39006, in which the hollow spheres are mixed in a solution of a resin such as polyvinyl chloride in an organic solvent such as xylene and then baked to form an insulating layer. In the method described, the resin that serves as the binder for the hollow spheres is limited to resins that are soluble in solvents. It cannot be applied to resins that do not. For this reason, there are restrictions on the resins that can be selected, and when trying to improve electrical properties such as dielectric constant, other properties required for insulated wires, such as flexibility and flame retardance, decrease. Until now, it has not been possible to improve various properties at the same time.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an insulated wire having a low dielectric constant and excellent other properties, and a method for manufacturing the same, which eliminates the drawbacks of the prior art.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an insulated wire in which the outer periphery of the conductor is coated with an insulating layer, and the insulating layer is coated with a resin dispersion in which micro hollow spheres are dispersed. The method for manufacturing it involves dispersing microscopic hollow spheres in a resin dispersion, applying this to the outer periphery of the conductor, and then heating it to remove the dispersion in the dispersion. The method is characterized in that the medium is removed and the resin and the micro hollow spheres are bonded and integrated to form an insulating layer.

Further, according to the present invention, in an insulated wire having an insulating layer coated on the outer periphery of the conductor, the insulating layer is coated with a dispersion liquid in which micro hollow spheres made of thermoplastic resin are dispersed and baked. In this case, a dispersion liquid in which micro hollow spheres made of thermoplastic resin are dispersed in a liquid is applied to the outer periphery of the conductor, and then the dispersion medium in the dispersion liquid is removed by heating. The above-mentioned insulated wire can be manufactured by fusing micro hollow spheres made of thermoplastic resin to each other on their surfaces to form an insulator layer.

In the present invention, the micro hollow spheres mixed into the resin to lower the dielectric constant of the insulating layer are glass, ceramic,
Made of insulating materials such as resins and elastomers, the particle size is 0.
A hollow sphere with a diameter of about 1 to 100 μm, preferably 20 μm or less, is used in view of the smoothness of the insulating layer. Here, examples of the material for the resin hollow spheres include thermoplastic resins such as vinylidene chloride, polyethylene, and fluorine resins, and thermosetting resins such as phenol resins, epoxy resins, and polyimides. , a homopolymer or a copolymer. Further, as the material for the ceramic hollow sphere, materials used as electrically insulating materials such as alumina can be used. Among these hollow spheres, glass hollow spheres with a silicon dioxide content of 80% or more are preferably used from the viewpoint of electrical properties. The hollow part is filled with gases such as nitrogen, carbon dioxide, argon, and isobutane, resulting in a low dielectric constant, low dielectric loss tangent, and low specific gravity. Note that the micro hollow spheres do not necessarily have to be completely sealed spheres, and foamed spheres with a large number of fine pores can also be used.

Furthermore, the resin dispersion that serves as the binding material for the micro hollow spheres is made of thermoplastic resins that have good electrical properties and have been traditionally used as insulating materials, such as polyethylene, polypropylene, polyethylene terephthalate, and fluorine resins. Fine particles are dispersed in a liquid such as water, and for example, an aqueous suspension of spherical hydrophobic colloidal particles obtained by a polymerization method such as emulsion polymerization can be used. Further, dispersions of precursors of thermosetting resins such as phenol resins and epoxy resins can also be used, and dispersions of these precursors are also included in the resin dispersion of the present invention. The mixing ratio of the micro hollow spheres to these resins is not particularly limited, but can be mixed in the shell in a range of 10 to 90% by weight, preferably 30 to 70% by weight, based on the resin. It is desirable that Note that the surfaces of these microscopic hollow spheres may be treated with a coupling agent in advance.

In addition, when forming an insulating layer by coating and baking a dispersion liquid in which micro hollow spheres are dispersed in a liquid without using a resin dispersion as a binder, the micro hollow spheres can be applied to the surface of the conductor. Since it is necessary to fuse the microscopic hollow spheres to each other, a thermoplastic resin having good electrical properties as described above is used as the material for the micro hollow spheres. When coating a conductor with these microscopic hollow spheres made of thermoplastic resin, they can be used in the form of a dispersion whose suspended state is stabilized with a surfactant or the like.

[Function] The insulator layer of the insulated wire according to the present invention is obtained by applying a resin dispersion in which micro hollow spheres are dispersed to the outer periphery of the conductor using a die or the like and baking it. If the resin is a precursor of a thermosetting resin, the thermoplastic resin particles melted by heating will bind and integrate a large number of 9 microscopic hollow spheres, and if the resin is a precursor of a thermosetting resin, the microscopic hollow particles will melt while being cured by heating. An insulating layer is formed by bonding and integrating the spheres. In addition, in the present invention, when forming the insulator layer, a large force is not applied to the micro hollow spheres as in extrusion molding, so the large number of micro hollow spheres interposed between the resins is substantially reduced. All of it remains undestroyed. Therefore, the insulated wire has a low dielectric constant and stable characteristics.

Furthermore, by selecting a resin with a low dielectric constant as the binder for the micro hollow spheres, the insulated wire can be made with an extremely low dielectric constant by making the insulator layer porous due to the micro hollow spheres. I can do it. Furthermore, since the resin serving as the binder is applied in the form of a dispersion obtained by emulsion polymerization, even resins that do not dissolve in solvents at all, such as fluororesins, can be used. The range of material selection is much wider than with traditional methods.

Furthermore, if the micro hollow spheres are made of a thermoplastic resin that can be heat-sealed, if the dispersion is applied to the conductor and then heated, the micro hollow spheres will bond to each other on the surface. Form an insulator layer. Therefore, since a binder is not required, the porosity increases accordingly, and an insulated wire with a lower dielectric constant can be obtained. Moreover, since the micro hollow spheres themselves have appropriate elasticity, the flexibility of the rim layer is maintained compared to those using micro hollow spheres made of inorganic materials such as glass or ceramics. It becomes an insulated wire with excellent properties.

"Example" Hereinafter, an example of the present invention will be described based on the drawings.
The figure is an enlarged partial cross-sectional view of an insulated wire according to the present invention. The illustrated insulated wire 10 consists of a conductor 11 and an insulator layer 12, where the insulator layer 12 includes low dielectric constant micro hollow spheres 12a such as glass micro hollow spheres, and micro hollow spheres 12a.
It is composed of a thermoplastic resin 12b having a low dielectric constant and a low dielectric loss tangent, such as a fluororesin, as a binding material.

This insulator layer 3 is formed by applying and baking a liquid in which the micro hollow spheres 12a are dispersed in a thermoplastic resin dispersion using the apparatus shown in FIG.

FIG. 2 shows an example of a coating device. In the illustrated device, a conductor 11 fed out from a feeder 1 passes through a container 2 that stores a dispersion liquid in which microscopic hollow spheres are dispersed in a thermoplastic resin dispersion. However, the dispersion liquid is applied here, and then, when passing through the hole of the die 3, the excess dispersion liquid adhering to the conductor is removed. Subsequently, the conductor 11 coated with a thermoplastic resin composition containing microscopic hollow spheres to a predetermined thickness is sent to the heating furnace 4 . Inside this heating furnace, the dispersion medium remaining in the composition is removed, and furthermore, the thermoplastic resin particles in the composition are melted to bind and integrate the micro hollow spheres, and an insulator layer 12 is formed on the conductor 11. Ru. The insulated wire 1 has an insulating layer 12 coated on the conductor 11.
0 is configured to be wound up by a winding machine 5.

The above embodiment will be explained in more detail using a specific example.

Example 1 Glass micro hollow spheres (manufactured by Emerson & Cumming Co., Ltd. GLASS l [IcROBALLOONS S
I, particle size: 20 μm passing product, relative dielectric constant 1.20) 50
Part by weight is 1 of an aqueous dispersion of tetrafluoroethylene-hexafluoropropylene copolymer resin (manufactured by DuPont Mitsui Fluorochemical Co., Ltd. 120J, solid content 50%).
00 parts by weight to prepare a dispersion for coating. Then, this dispersion was applied and baked on the outer periphery of a silver-plated annealed copper wire with an outer diameter of 0.481 TII11 using the above coating device, so that the insulator layer had a wall thickness of 0.2 mm and an outer diameter of 0.88 m.
An insulated wire of m according to the present invention was obtained. An aluminum polyester tape was wrapped around the outer circumference of this insulated wire to form a coaxial cable, and the propagation delay time was measured to be 3.80n.
s/m, and from this it can be estimated that the effective dielectric constant of the insulating layer is 1.30. Furthermore, even when this insulated wire was bent to a diameter twice the outer diameter, no cracks occurred in the insulator layer.

Example 2 Micro hollow spheres made of vinylidene chloride-acrylonitrile copolymer resin (EXPANCE manufactured by KemaNove1)
10 parts by weight of L WE-20 (average particle size: 15 μm) was added to an aqueous polyethylene dispersion (CHEI [IPEAL M-200, manufactured by Mitsui Petrochemical Industries, Ltd.).

90 parts by weight (solid content: 40%) was mixed to prepare a dispersion for coating. Then, this dispersion liquid was coated and baked on the outer circumference of a silver-plated annealed copper wire with an outer diameter of 0° and 48 mm using the above-mentioned coating device, so that the thickness of the insulating layer was 0. An insulated wire according to the present invention having a length of 2 mm and an outer diameter of 0.88 mm was obtained. In order to investigate the dielectric constant of this insulated wire, we made it into a coaxial cable as in Example 1 and measured its propagation delay time.
0 ns/m, and from this it can be estimated that the dielectric constant of the insulating layer is 1°51. Moreover, this insulated wire had improved flexibility compared to that of Example 1.

In addition, although the above example shows the case where the porosity of the insulator layer does not change in the radial direction, for example, several types of dispersion liquids with different contents of micro hollow spheres are prepared, The porosity of the insulating layer may be decreased from the conductor side toward the surface by coating the dispersion liquid in order of increasing amount.

FIG. 3 shows a different embodiment of an insulated wire according to the invention, the illustrated insulated wire 20 consisting of a conductor 21 and an insulating layer 22, the insulating layer 22 being made of thermoplastic resin. A large number of micro hollow spheres 22a are fused to each other on their surfaces while gas is sealed inside, forming a so-called independent pore porous structure. In this case, unlike the insulated wire 10 of the embodiment in FIG. 1, there is no need for a binder to bind the micro hollow spheres 22a together, so the gap can be increased accordingly. Therefore, the dielectric constant of the insulator layer 22 is further reduced. Furthermore, since the micro hollow spheres 22a made of thermoplastic resin are softer than micro hollow spheres made of glass or ceramic, the flexibility of the insulated wire is extremely good. This is effective in increasing the porosity of the insulator layer.

To manufacture such an insulated wire 20, first, micro hollow spheres 22a made of thermoplastic resin are dispersed in water containing a surfactant to form a suspension, and this suspension is coated with the coating shown in FIG. A predetermined thickness is applied to the outer periphery of the conductor 21 using a device. Then, the suspension applied onto the conductor 21 is heated in a heating furnace to such an extent that the thermoplastic resin minute hollow spheres retain their shape. Here, water as a dispersion medium is removed, and the surface portions of the micro hollow spheres are melted, so that they are fused and integrated with each other on the surface to form an insulating layer.

Next, the embodiment shown in FIG. 3 will be explained in more detail using a specific example.

Example 3 Micro hollow spheres made of vinylidene chloride-acrylonitrile copolymer resin (EXPANCE manufactured by KemaNove1)
LWE-20 (average particle size: 15 μm) was dispersed in water to which a surfactant was added to prepare a dispersion for coating. Then, this dispersion was coated and baked on the outer periphery of a silver-plated annealed copper wire with an outer diameter of 0.48 mm using the above coating device, so that the thickness of the insulator layer was 0.2 mm and the outer diameter was 0.
．． An 88 mm insulated wire according to the present invention was obtained. When this insulated wire was made into a coaxial cable and its propagation delay time was measured, it was found to be 4°1 Qns/m, and from this it can be estimated that the effective dielectric constant of the insulating layer is 1.51.

This insulated wire was extremely flexible.

[Effects of the Invention] As explained above, the insulated wire according to the present invention has the advantage that the size of the voids in the insulating layer can be freely controlled by selecting the diameter of the micro hollow spheres. By using micro hollow spheres with a small diameter, it is possible to make the insulator layer thinner than in the conventional insulated wire using a foaming agent, and it is possible to obtain a thinner diameter wire.

Furthermore, in contrast to the conventional method in which microscopic hollow spheres are bonded together using a resin dissolved in an organic solvent to form an insulating layer, the present invention uses a resin prepared in a dispersion state without being dissolved in an organic solvent. As a binder, it is possible to manufacture insulated wires using resins such as fluorine-based resins, which have excellent electrical properties but cannot be used because they do not dissolve in organic solvents. This makes it possible to obtain a material with a lower dielectric constant and better properties such as heat resistance and chemical resistance than before. Furthermore, if the micro hollow spheres are made of thermoplastic resin, it is possible to eliminate the need for a binder, and the insulated wire with such a structure has a low dielectric constant and is highly flexible. .

Furthermore, according to the method of the present invention, the resin used as the binder for the micro hollow spheres is in the form of a dispersion, so various resins can be used without considering solubility in organic solvents. The most suitable one can be selected depending on the usage conditions of the insulated wire.

[Brief explanation of drawings]

FIG. 1 is an enlarged partial cross-sectional view showing an embodiment of an insulated wire according to the present invention, FIG. 2 is a schematic explanatory diagram showing an example of a method for manufacturing an insulated wire according to the present invention, and FIG. 3 is an insulated wire according to the present invention. FIG. 3 is an enlarged partial cross-sectional view showing another embodiment of the invention. 11.21: Conductor, 12.22: Insulator layer, 12a, 2
2a: Microscopic hollow sphere. Patent applicant Junkosha Co., Ltd.

Claims (4)

[Claims] (1) An insulated wire in which the outer periphery of a conductor is coated with an insulating layer, characterized in that the insulating layer is made by coating and baking a resin dispersion in which minute hollow spheres are dispersed. (2) By dispersing the microscopic hollow spheres in a resin dispersion, applying this to the outer periphery of the conductor, and then heating it, the dispersion medium in the dispersion liquid is removed, and the resin and the microscopic hollow spheres are bound and integrated. 1. A method for manufacturing an insulated wire, comprising: forming an insulating layer by oxidizing the wire. (3) An insulated wire in which the outer periphery of the conductor is coated with an insulating layer, wherein the insulating layer is made by coating and baking a dispersion in which microscopic hollow spheres made of thermoplastic resin are dispersed. Electrical wire. (4) A dispersion in which micro hollow spheres made of thermoplastic resin are dispersed in a liquid is applied to the outer periphery of the conductor, and then heated to remove the dispersion medium in the dispersion and remove the dispersion liquid made of thermoplastic resin. A method for producing an insulated wire, which comprises fusing micro hollow spheres to each other on their surfaces to form an insulating layer.