JPS5846805B2 - Manufacturing method of polyester resin insulated wire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method for manufacturing a polyester resin insulated wire.

In recent years, in the manufacture of magnet wires, there has been a particular desire to develop coating methods such as resin powder coating and melt coating that do not use solvents, from the viewpoint of pollution, resource saving, and energy saving.

As one method, a method has been proposed in which an enameled wire-type insulated wire is manufactured by extrusion molding a crystalline thermoplastic resin such as polyethylene terephthalate onto a conductor.

(Japanese Unexamined Patent Publication No. 53-4875) However, when insulated wires coated with these resins by simply extrusion are used as magnet wires, the following drawbacks have been found.

In other words, since these resins are crystalline polymers, when the resin-coated wire is stretched or bent during coil processing, minute cracks, so-called crazing, occur in the coating, which deteriorates the electrical properties. Even when the film is heated to a temperature below its melting point for drying, etc., loss of flexibility due to crystallization of the film resin is observed.

Furthermore, as a test method for heat deterioration resistance of enameled wire, JIS
C3203, 3210, 3211, etc., the method of observing flexibility after heating for a predetermined period of time (for example, winding property after heating at 200°C for 6 hours for polyester enamel electric wires) also shows that the crystallization of the coating resin It completely loses its flexibility.

On the other hand, as an example of a technique for improving the characteristics of polyester resin insulated wires using the extrusion coating method, a polyester resin coating with a thickness of 100 μm or less is applied to the conductor, and then the coated wire is heated to a temperature 10 to 50 degrees Celsius higher than the glass transition point of the resin. By reheating the coating, the resin film deteriorates due to the residual strain generated during extrusion of the resin. Decrease in thermal properties such as wrapability and thermal shock resistance, and withstand voltage due to decrease in adhesion with conductors. A method for improving the deterioration of characteristics was proposed (Japanese Patent Publication No. 55-9767).

However, although the insulated wire manufactured by this method has improved the above-mentioned problems, it has problems such as loss of flexibility of the coating due to crystallization, which is a characteristic of linear polynisder resin, and crazing resistance.
No improvement effect was obtained with respect to drawbacks such as lack of chemical resistance, and depending on the heating conditions, the crystallinity of the resin film was promoted, which resulted in problems such as deterioration of the properties as an insulated wire.

The inventors continued intensive research into a method for obtaining polyester resin insulated wires without the use of solvents and without the above-mentioned drawbacks. After coating a linear polyester resin on a copper conductor, the inventors found that A method of heating at a temperature 50°C or more higher than the melting point of the linear polyester resin used was previously proposed (Japanese Patent Application No. 147,227/1982).

According to this method, three-dimensional network bonds occur in the resin film of the obtained polyester resin insulated wire, and the amount of three-dimensional network bonds (generally called gel content) is 9.
50 as the undissolved residual amount in m-cresol at 0°C
% or more, the above-mentioned property deterioration phenomenon no longer occurred and a magnet wire with sufficient properties could be obtained.

Based on the knowledge from As a result of studying various factors that affect the crosslinking rate and crosslinking density of polyester resins under the above-mentioned thermal crosslinking conditions in order to increase the size of polyester resins as much as possible, we have found that the most important factor is the rate of oxygen diffusion into polyester resins in the molten state. We found that the oxygen partial pressure of air, which is an oxygen-containing gas atmosphere in which it is easy to obtain the normal amount of oxygen partial pressure in oxygen-containing gas under heating conditions (
The present inventors have discovered that the crosslinking speed and crosslinking density of polyester resins can be dramatically improved by increasing the crosslinking temperature higher than the normal 159 mmHg (159 mmHg).

In oxidative thermal crosslinking of linear polyester resins, simply increasing the oxygen partial pressure in the oxygen-containing gas at a temperature higher than the melting point of the resin will cause the oxidative decomposition reaction of the resin, resulting in weight loss and physical property deterioration. It is expected that this will lead to encouraging
In fact, if an aluminum wire or the like with a surface outside the wind control is used as a conductor, and the oxygen partial pressure in the atmosphere is made higher than the oxygen partial pressure in the air, the oxidation of the coating resin and the scission of the main chain will be promoted. However, since the series of crosslinking reactions does not proceed smoothly,
Due to evaporation, sublimation, etc. of the produced low-molecular-weight substances, the properties of the resin film that has been significantly reduced in weight are also significantly reduced.

However, as shown in the method of the present invention, when the conductor has a copper surface, copper ions migrate from the conductor surface into the resin, and due to the presence of this copper, even if the oxygen partial pressure is increased, the resin Crosslinking speed and crosslinking density are significantly improved without promoting weight loss associated with oxidative decomposition reactions.
It was possible to simultaneously improve productivity and improve physical properties such as heat resistance, solvent resistance, and chemical resistance.

In other words, when the partial pressure of oxygen in the atmosphere is raised to a level higher than the oxygen partial pressure in normal air at a temperature higher than the melting point of the linear polyester resin, the rate of oxygen diffusion into the resin increases. The amount of oxygen taken into the resin increases, and before the oxygen taken into the resin is used for the oxidative decomposition reaction of the resin, the catalytic action of copper ions causes oxidation of the resin, scission of the main chain,
It is efficiently used in a series of oxidative thermal crosslinking reactions consisting of generation of free radicals and intermolecular crosslinking, and can significantly increase the oxygen partial pressure without promoting weight loss of the resin.

In the method of the present invention, the oxygen partial pressure in the oxygen-containing gas is 230
When it is more than agHg, the effect on improving the crosslinking rate is significant.

There is no particular limit on the upper limit, but from a safety perspective,
00 mmHg or less is desirable.

In addition, methods for increasing the oxygen partial pressure include, for example, blowing a predetermined amount of oxygen into the heating furnace at atmospheric pressure, or mixing oxygen and nitrogen, which is an inert gas to the crosslinking reaction, to the desired oxygen partial pressure. Conventional methods can be employed, such as using a premixed gas, or pressurizing air in a pressurizing device to increase the oxygen partial pressure, and then introducing the resin-coated conductor into the device and heating it.

Examples of aromatic dicarboxylic acids that are acid components constituting the linear polyester resin in the present invention include terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenoxyethanedicarboxylic acid, Examples include diphenyl ether dicarboxylic acid, methyl terephthalic acid, and methyl isophthalic acid.

Terephthalic acid is particularly preferred. Furthermore, aliphatic dicarboxylic acids such as co-phosphoric acid, adipic acid, and cepacic acid may be included in an amount of 30 mol% or less, preferably 20 mol% or less of the aromatic dicarboxylic acid that is the acid component. .

Furthermore, examples of the aliphatic diol constituting the linear polyester resin include ethylene glycol, propylene glycol, ethylene glycol, hexanediol, and decanediol.

In the method of the present invention, the reason why the heating temperature is limited to above the melting point of the resin used is that at lower temperatures, the resin may undergo crystallization, and the crosslinking rate is slow and the crosslinking density is difficult to increase. It's for a reason.

Also, if you increase the heating temperature. Although the rate of crosslinking increases, the possibility of thermal decomposition also increases, so the temperature is generally 450°C.
The following heating temperatures are preferred.

In addition, the gel fraction as used in the present invention refers to the insolubility in the sample resin when the resin film is peeled off from the obtained insulated wire and the resin film is heated and dissolved in m-cresol at 90°C for 5 hours as described above. This is the ratio of the remaining amount, and is a value indicating the degree of crosslinking of the resin.

The present invention will be explained below with reference to Examples.

Examples 1 to 3 ** Polyethylene terephthalate resin (manufactured by Kijinsha, trade name Tetron TR4550BH, hereinafter referred to as PBT.

A copper wire with a diameter of 9.85 myt is passed through a tank in which melting point 250-260°C, intrinsic viscosity in orthochlorophenol 0.7) is heated to 270°C, and the wire is squeezed with a die at the outlet to form a wire of 22-25μ. After forming a coating film, this coated line was then led into a furnace with a length of 5 m and a furnace temperature of 400° C., and heat treatment was performed under each condition shown in the table.

The atmosphere in the furnace was such that oxygen and nitrogen were mixed in advance so as to have the respective oxygen partial pressures shown in Table 1, and then introduced into the heating furnace.

The wire characteristics of the insulated wire thus obtained are also listed in Table 1 together with the wire characteristics of the coated wire before heating (Comparative Example 1).

Comparative Examples 2 to 3 Similarly to Example 1, the same PET used in Example 1 was used, the atmosphere in the furnace was changed to air, and heat treatment was performed under the conditions shown in Table 1 to obtain insulated wires.

Example 4 Using the same PET as in Example 1, the conductor was made with a diameter of 9.85 mm.
An insulated wire was obtained by heat treatment under the same conditions as in Example 2, except that the wire was replaced with a copper-clad aluminum wire of 1.0 mm thick.

Comparative Example 4 An insulated wire was obtained by heat treatment under the same conditions as in Example 4, except that the conductor was replaced with an aluminum wire of the same size.

Table 1 shows the properties of the insulated wires obtained in Example 4 and Comparative Examples 2 to 4, along with the gel content of each resin film.
Also listed in

Example 5 Fine pieces of polyethylene naphthalate film (manufactured by Kijinsha, trade name Q film, melting point 270-275°C) were
After heating and melting it to 0℃ and coating it to a thickness of 23μ on a copper wire with a diameter of 0.85mm, the coated wire was heated to a furnace length of 5m, a furnace temperature of 450℃, and an oxygen partial pressure of 460mmHg in the furnace atmosphere.
The insulated wire was then heated at a speed of 8 m/min by introducing the wire into a baking furnace filled with a gas mixed with oxygen and nitrogen so that the temperature would be as follows.

Table 2 shows the properties of the insulated wire thus obtained.

For comparison, a sample obtained under the same conditions except that it was heated in an air atmosphere is also listed in Table 2 as Comparative Example 5.

As is clear from the above Examples and Comparative Examples, when producing an insulated wire consisting of an electrical conductor coated with a linear polyester resin, the method of the present invention can be applied to a crosslinked polyester resin having good properties. System insulated wire greatly improves productivity (to obtain the same amount of gel, the wire speed is 1.5
3 times), which is extremely high.

Its industrial value is

Claims (1)

[Claims] 1. An acid component mainly consisting of an aromatic dicarboxylic acid or a dicarboxylic acid in which a part of the aromatic dicarboxylic acid is replaced with an aliphatic dicarboxylic acid;
After coating a substantially linear polyester resin consisting of an aliphatic diol without a solvent onto a conductor having at least a copper layer on the surface, the painted wire is placed in an oxygen-containing gas to form a linear polyester resin. In manufacturing a polyester resin insulated wire by heating the polyester resin to a temperature higher than the melting point and crosslinking it, the oxygen partial pressure in the oxygen-containing gas is made higher than the oxygen partial pressure in normal air. A method for manufacturing a polyester resin insulated wire.