JPS60220511A - Method of producing insulated wire - 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 The present invention applies powder coating of a powdered resin onto a conductor directly or through another insulating layer by an electrostatic dynamic dipping method, then heats it in a heating furnace, and then cools it. The present invention relates to a method of manufacturing an insulated wire by forming a uniform hardened film.

Conventionally, enameled wires have had many problems such as applying enamel varnish on the conductor, burning it out, and repeating such operations multiple times, and various studies have been conducted on other superior manufacturing methods.

By the way, it is already known that insulated wires can be manufactured by coating a continuous conductor using the so-called electrostatic powder coating method, in which finely powdered resin is electrostatically coated using air as a medium ( For example, Japanese Patent Application Laid-Open No. 55-152761).

The inventors have also conducted research on powder coating using the same method, but the insulated wire obtained by this method had considerably lower quality electrical properties than conventional enamelled wire. Specifically, the dielectric breakdown voltage of the powder-coated insulated wire and the corona onset voltage in insulating oil were about 1/3 to 1/4 of those of the enamelled wire obtained by the conventional method. .

The inventors thought that the main cause of these poor electrical characteristics was the voids (bubble-like voids) scattered in the insulation film, so they investigated various measures to suppress the occurrence of these voids as much as possible, and as a result they developed this book. This is an invention.

That is, the present invention applies a powder coating of powdered resin to a conductor directly or through another insulating layer using an electrostatic dynamic dipping method, and then heats and cools this in a heating furnace to form a uniform hardened coating. To form the resin powder layer, first, the resin powder layer applied to the conductor-1- is heated and melted at a temperature above the melting point of the resin and below the conditions that substantially cause gelation, and then heated in a furnace. This method of manufacturing an insulated wire is characterized by heating and hardening the wire in a heating furnace maintained at a pressure equal to or lower than normal pressure. According to this method, the powder that adheres uniformly around the object to be coated is first melted and then reheated at a pressure below normal pressure, which quickly removes the air trapped in the film and the gases generated during heat curing. Since the insulating film is baked while being emitted, there are almost no voids in the finished insulating film. As a result, the electrical properties of the insulating film were significantly improved compared to conventional methods, and properties close to those of conventional enamelled wire were obtained.

In addition, in the manufacturing method of the present invention, after heating and curing under reduced pressure, when passing through the pressure seal part, it is necessary to cool the resin to at least the heat deformation temperature of the cured resin or lower, and the refrigerant used for this purpose is the obtained insulated wire. It is best to use mineral oil, synthetic oil, or paraffin alone or in a mixture, which can finally give processability as a winding wire and have a high boiling point (stable under reduced pressure).

Furthermore, in order to prevent overheating, the cooling medium needs to be cooled by a heat exchanger with the outside of the vacuum system.

Examples of the present invention will be shown below.

The following examples were carried out using a production line as shown in FIG. 1 under the following common conditions.

Common conditions (1) Conductor: flat annealed copper wire with a thickness of 15 and a width of 5 and a rectangular cross section (2) Preheating furnace: length 2m, set furnace temperature 150°C (3) Curing furnace: length 5m, set furnace temperature 300 ~450℃ (4) Powder coating section; Air pressure 0. Bkg/cut, voltage 48~5 2
KV Example 1 While running the rectangular annealed copper wire at a line speed of 7 m/min, it was coated with epoxy powder based ASI (manufactured by 3M Company X) in the powder coating section.
After coating R-5256 (melting point approximately 80°C), the coated wire is passed through a preheating furnace, cooled with air, and then passed through a heat curing furnace in a reduced pressure chamber maintained at a pressure of approximately 0.8 atm to be heat cured. Then, this was immersed in mineral oil (high-voltage insulating oil manufactured by Showa Sekiyu), cooled, taken out of the system, and wound up. The surface temperature of the wire at the outlet of the preheating furnace is approximately 95°C, and the temperature of the mineral oil is approximately 50°C.
It was ℃.

Example 2 Approximately 1.
A polyamide-imide varnish (HI-405 manufactured by Hitachi Chemical Co., Ltd.) was coated and baked to a thickness of 0μ, and then an epoxy powder coating was applied and cured in the same manner as in Example 1 to form a double coat. Obtained insulated wire.

Example 3 The same rectangular annealed copper wire used in Example 1 was run at a linear speed of 7 m/min, and was coated with a polyester powder coating (terephthalic acid-ethylene glycol-glycerin-trimethylolpropane) in the powder coating section. The 3R form of tolylene diisocyanate was masked with flucol and Modaflow (Monsa
A mixture of NTO (manufactured by nto) was crushed and passed through a 200 Meson Co. sieve, and the melting point was approximately 85°C).The coated wire was passed through a preheating oven and air-cooled, then the pressure was approximately 0.
It was heated and cured by passing through a heating curing furnace in a vacuum chamber maintained at 6 atmospheres, and then immersed in a /% roughy / bath (Crystal 355 manufactured by Esso Standard Oil), cooled, and then taken out of the system. I wound it up.

As mentioned above, various characteristics were measured for each insulated wire obtained in Examples 1 to 3. The results obtained are shown in the table below.

In order to clarify the effects of the present invention, the characteristics of the insulated wires obtained by heating and curing the painted wires at normal pressure in Examples 1 and 3 are used as Comparative Examples 1 and 2, respectively. The characteristics of the formal rectangular copper wire obtained by this method are also listed in the table as Comparative Example 3.

As is clear from the above table, according to the method of the present invention, insulated wires having various properties comparable to those of conventional enamelled wires can be manufactured, and the industrial value thereof is extremely large.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the method of the present invention. FIG. 2 is an explanatory diagram of a test piece for measuring the corona onset voltage of an insulated wire. DESCRIPTION OF SYMBOLS 1... Conductor supply device, 2... Cleaning device, 3... Electrostatic dynamic immersion tank, 4... Preheating furnace, 5... Air cooling device, 6
... Decompression chamber, 7... Heat curing furnace, 8... Cooling tank,
9... Winding device, 10... Test loop.

Claims (1)

[Scope of Claims] 1. A method for producing an insulated wire, which comprises heating and melting the wire at a temperature below the conditions that substantially cause gelation, and then heating and hardening the wire in a heating furnace whose interior is maintained at a pressure below normal pressure. (2) The cured film after heat curing is made of mineral oil, synthetic oil, paraffin alone or a mixture of two or more of these.13) The heating furnace for heat curing and the cooling part are in the same vacuum chamber, and
The insulated wire according to claim 1, wherein the cooling medium in the cooling section is cooled by a heat exchanger with the outside.