JPH0136204B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing an insulated wire coated with a polyester resin. In recent years, in the manufacture of magnet wires, there has been a particular desire for the development of coating methods such as 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 enamelled wire-type insulated wire is manufactured by extrusion molding a crystalline thermoplastic resin such as polyethylene terephthalate (Japanese Patent Application Laid-Open No. 53-4875). However, when wires simply coated with these resins by extrusion are used as magnet wires, the following drawbacks have been found. In other words, since these resins are crystalline polymers, if they are stretched or bent during coil processing, microscopic cracks, or so-called crazing, will occur in the film, reducing electrical properties, and due to drying, etc. Even when the coating is heated to a temperature below its melting point, loss of flexibility due to crystallization of the coating resin is observed. Furthermore, as a test method for heat deterioration resistance of enameled wires, there is a method of observing the flexibility after heating for a predetermined time specified in JIS C3203, 3210, 3211, etc. (for example, for polyester enameled wires, 200
Regarding the wrapability after heating for 6 hours at ℃, the flexibility is completely lost due to crystallization of the coating resin. On the other hand, as an example of a technique for improving the characteristics of polyester insulated wires using the extrusion coating method, a layer of 100 μm thick was coated on the conductor.
After applying the following polyester resin coating, this painted line is reheated at a temperature 10 to 50°C higher than the glass transition point of the resin. A method has been proposed to improve thermal properties such as heat-degraded winding properties, thermal shock resistance, and voltage resistance properties due to reduced adhesion to conductors (Japanese Patent Publication No. 55-9767). but,
Although this method solves the above-mentioned problems,
No improvement effect was obtained for the disadvantages of linear polyester resins, such as loss of film flexibility due to crystallization, lack of crazing resistance, solvent resistance, chemical resistance, etc., and heating Depending on the conditions, the crystallinity of the resin film may be promoted, leading to problems such as deterioration of various properties as an electric wire. In order to obtain a polyester resin insulated wire without the use of solvents and without the above-mentioned drawbacks, the inventors have developed the characteristics of a linear polyester resin-coated insulated wire using aliphatic glycol as the diol component by heat crosslinking. We have previously proposed an improvement method (Japanese Patent Application No. 147227/1983), but now we have confirmed the same effect for linear polyester (polyarylate) using aromatic diol.
It has been discovered that the magnet wire obtained by this method is further superior in heat resistance. That is, a substantially linear aromatic polyester resin consisting of an acid component mainly consisting of an aromatic dicarboxylic acid or a dicarboxylic acid with a portion thereof replaced with an aliphatic dicarboxylic acid, and an aromatic diol is applied onto a conductor. A method for producing an insulated wire, which is characterized in that the coated wire is coated without a solvent and then heated in an oxygen-containing gas at a temperature of 50° to 250°C higher than the softening point of the polyester resin used to crosslink it. . Although the reason why crosslinks are formed in linear polyester resins by this method is unclear,
As mentioned in the patent application specification, heating above the melting point causes a series of crosslinking reactions, including oxidation of the resin, cleavage of the main chain, generation of free radicals, and intermolecular crosslinking, to occur due to oxygen and heat. It is thought that a three-dimensional network structure will be generated. By the way, in the above-mentioned patent application, it is essential to use a conductor having a copper layer on its surface, generally a copper wire. In other words, when aliphatic glycol is used as the diol component, copper ions migrate from the conductor surface into the resin when a copper wire is used, and the presence of this copper causes the crosslinking reaction to proceed efficiently in the resin. As expected, on the other hand, when a conductor with a surface other than copper, such as an aluminum wire, is used, thermal decomposition occurs first and crosslinking does not proceed smoothly. On the other hand, it has been found that when an aromatic diol is used as the linear polyester of the present invention, that is, the diol component, a crosslinking phenomenon occurs not only in a conductor having a copper layer on the surface but also in an aluminum wire. This is because the resin itself is aromatic, so it is presumed that it is relatively stable up to the crosslinking reaction temperature in the absence of copper ions. However, it was confirmed that as the heating temperature is relatively low and approaches the softening point of the resin, the crosslinking rate is faster when a conductor having a copper layer on the surface is used as the conductor. Aromatic diols constituting the linear polyester resin in the present invention include 4,4'-dihydroxydiphenyl ether, bis(4-hydroxyphenyl)sulfide, bis(4-hydroxyphenyl)sulfone, bis(4- Examples include hydroxyphenyl)methane, 1.1-bis(4-hydroxyphenyl)ethane, 2.2-bis(4-hydroxyphenyl)propane, and 2.2-bis(4-hydroxyphenyl)propane is particularly preferred. In addition, examples of aromatic dicarboxylic acids that are acid components constituting the linear polyester resin include terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenoxyethanedicarboxylic acid, Examples include diphenyl ether dicarboxylic acid, methyl terephthalic acid, methyl isophthalic acid, and terephthalic acid is particularly preferred. Furthermore, aliphatic dicarboxylic acids such as succinic acid, adipic acid, and sebacic acid may be contained in an amount of 30 mol % or less, particularly preferably 20 mol % or less, of the aromatic dicarboxylic acid that is the acid component. The reason why the heating temperature in the present invention is limited to 50° C. or higher than the softening point of the resin used is that at temperatures lower than this, the crosslinking rate of the resin is slow and the crosslinking density is difficult to increase. In addition, increasing the heating temperature increases the crosslinking rate of the resin, but on the other hand, it also significantly accelerates the thermal decomposition reaction of the resin, reducing the properties of the resulting resin film.
The atmospheric temperature of the heating furnace is particularly preferably set in a temperature range of 50 to 250° C. higher than the melting point of the coating resin used from the viewpoint of economy and physical properties. In the method of the present invention, oxygen plays the role of oxidizing the resin and generating free radicals, and the generated free radicals participate in intermolecular crosslinking. Therefore, heating in an oxygen-containing gas is essential to the present invention, and usually an air atmosphere is used because it is the easiest to obtain. Furthermore, increasing the oxygen partial pressure in the oxygen-containing atmosphere higher than the oxygen partial pressure of air in the normal state increases the oxygen diffusion rate into the resin and the oxygen concentration in the resin, so the crosslinking rate and crosslinking density can be improved. Therefore, it is of great significance from an industrial standpoint and physical properties. Regarding the degree of crosslinking of the resin film of the insulated wire obtained by the method of the present invention, the resin film was peeled off from the insulated wire and the original sample was dissolved by heating at 90°C for 5 hours in m-cresol. It is expressed as the ratio of undissolved residue to the weight of the resin film (gel fraction), and in order to improve the heat resistance, solvent resistance, and chemical resistance required for magnet wire, the gel fraction is 20%. The above is preferable. Hereinafter, the present invention will be explained with reference to Examples. Reference example 2.2-bisparaphenylenepropylidene terephthalate resin obtained from 2.2-bis(4-hydroxyphenyl)propane and terephthalic acid (manufactured by Unitika, trade name: U polymer, U-
4015, MI value at 300℃ approx. 5.4g/10min, specific gravity 1.24)
was extrusion coated onto a copper wire with a diameter of 0.85 mm using a melt extruder with cylinder temperature and die temperature of 310°C to form a resin film of 22 to 25 μm to obtain an insulated wire. The gel fraction of the resin film of the insulated wire thus obtained was 0%. Example 1 Using the insulated wire obtained in the reference example, the furnace length was 5.
The gel fraction of the resin film of the insulated wire obtained by heating and crosslinking the wire by passing it through an air atmosphere furnace at a furnace temperature of 470° C. at a speed of 7 m/min was 24.7%. Example 2 The resin film of an insulated wire obtained by heating and crosslinking under the same conditions as in Example 1 except that the speed was 5 m/min had a gel fraction of 84.5%. Example 3 A mixed gas of oxygen and nitrogen was introduced into the heating furnace in advance so that the oxygen partial pressure was 460 mmHg.
A coated wire was made under the same conditions as above, and the resin film was peeled off from the obtained insulated wire and the gel fraction was measured to be 91.6%. Example 4 An insulated wire using an aluminum wire with a diameter of 0.85 mm as a conductor and coated with the U polymer by extrusion using the same melt extruder as in the reference example was heat-treated under the same conditions as in Example 2. The gel fraction was 68.3%. Table 1 shows the characteristics of each insulated wire obtained in Examples 1 to 4 and Reference Example.

【table】

[Table] Example 5 The insulated wire obtained in the reference example was heated and crosslinked by passing it through an air atmosphere at a furnace temperature of 400°C at a speed of 3 m/min using the same furnace. When the film was peeled off and the gel fraction was measured, it was 73.0.
It was %. The heat softening temperature of the resin film of the insulated wire was 303°C. Example 6 As in Example 4, an insulated wire obtained by extrusion coating the U polymer onto an aluminum wire was heat-treated under the same conditions as in Example 5. The gel fraction of the resin film of the insulated wire thus obtained was 10.2%. Further, the heat softening temperature of the resin film of the insulated wire was 234°C. Comparing Examples 5 and 6 above, even though copper has a disadvantage in terms of the heat capacity of the conductor itself, when the furnace temperature decreases, the gel formation rate is clearly faster with copper wire than with aluminum wire. It can be seen that As is clear from the above examples, according to the present invention,
If an insulated wire is manufactured using a linear aromatic polyester resin, a polyester resin insulated wire with particularly improved heat resistance, solvent resistance, and chemical resistance can be manufactured, and its industrial value is great.

Claims (1)

[Scope of Claims] 1. A substantially linear aromatic polyester system consisting of an acid component mainly consisting of an aromatic dicarboxylic acid or a dicarboxylic acid in which a portion of the dicarboxylic acid is replaced with an aliphatic dicarboxylic acid, and an aromatic diol. An insulation characterized by coating a resin on a conductor without a solvent and then heating the coated wire in an oxygen-containing gas at a temperature 50° to 250°C higher than the softening point of the aromatic polyester resin to crosslink it. Method of manufacturing electric wire. 2. The method for producing an insulated wire according to claim 1, wherein the linear polyester resin is poly 2,2-bisparaphenylene propylidene terephthalate. 3. The method for manufacturing an insulated wire according to claim 1, wherein the electrical conductor is an electrical conductor having a copper layer on at least a surface thereof. 4. The method for manufacturing an insulated wire according to claim 1, wherein the oxygen-containing gas is a gas having an oxygen partial pressure that is at least higher than the oxygen partial pressure of air in a normal state. 5. A method for producing an insulated wire according to claim 1, which comprises heating and crosslinking the coated resin coated on the conductor so that the undissolved residual amount in m-cresol at 90°C becomes 20% by weight or more. .