JPS64764B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an insulated wire formed by extruding a resin and providing an insulating layer on an electric conductor. Conventionally, magnet wires have been manufactured by coating and baking a varnish dissolved in a phenolic solvent or the like onto an electrical conductor, but in recent years there has been a strong demand for pollution-free manufacturing processes and resource conservation.
Furthermore, in such conventional methods, the manufacturing speed is limited by the baking process, so that, with some exceptions, low manufacturing speeds are forced. Therefore, there is an urgent need to establish a new manufacturing method to replace the conventional manufacturing method. On the other hand, it is also common practice to use an extruder to produce plastic insulated wires. If this is applied to the magnet wire manufacturing process, the problems of the conventional magnet wire manufacturing process described above can be solved at once. However, with this method, it is difficult to stably extrude a thin film over a long length, and many thermoplastic resins do not meet the characteristics required as coatings for magnet wires. Its practical application was impossible. Recent advances in extrusion processing technology have made thin wall extrusion possible.
Although the production of magnet wire using the extrusion method has come one step closer to practical use, its practical use has not yet been realized. The present invention provides an insulated wire which is formed by extrusion coating an electric conductor with a composition mainly composed of polyethylene terephthalate resin, and which can be put to practical use as a magnet wire. Polyethylene terephthalate resin is generally used in large quantities for applications such as fibers, films, and containers due to its excellent mechanical properties, heat resistance, and chemical resistance. On the other hand, since the molecular structure is similar to the polyester resin that makes up the coating of polyester electric wires used as general-purpose magnet wires, it is possible to use this resin in electric wires by extrusion. However, polyethylene terephthalate resin exhibits its best properties only after undergoing some degree of orientation and crystallization treatment. However, when polyethylene terephthalate resin is used as an insulating coating, it is difficult to orient and crystallize it afterwards, so it is usually necessary to rapidly cool it after extrusion and use it in a state of low crystallinity. However, such low crystallinity polyethylene terephthalate resin begins to recrystallize at temperatures above the glass transition point, and especially at temperatures above 100°C, crystal embrittlement occurs in an extremely short period of time, and in the worst case The coating will peel off. Therefore, insulated wires using polyethylene terephthalate resin as an insulating coating must be used in a temperature range lower than the heat-resistant temperature range inherent to this resin. The present inventors conducted various studies to improve the above-mentioned drawbacks when polyethylene terephthalate resin is used alone as an insulation coating, and as a result, a polyethylene terephthalate resin was proposed for the purpose of improving impact resistance. It has been discovered that a composition containing a polycarbonate resin in a specific blending ratio can improve the above-mentioned drawbacks observed in a polyethylene terephthalate resin coating when used as a coating for a magnet wire, and the present invention has been made. This made it possible to develop an insulated wire. That is, the insulated wire of the present invention is provided with an extruded coating layer having a thickness of 100μ or less made of a composition containing 3 to 80 parts by weight of polycarbonate resin to 100 parts by weight of polyethylene terephthalate resin on the electrical conductor. This is a characteristic feature. In the present invention, all grades of commercially available polyethylene terephthalate resins can be used, but if the rate of thermal decomposition during molding is taken into account,
℃) A molecular weight of 0.6 or higher is desirable. Also,
All commercially available grades of polycarbonate resin can be used. What is important in the present invention is that the blending ratio of polyethylene terephthalate resin and polycarbonate resin is 3 to 80 parts by weight, preferably 20 to 30 parts by weight, per 100 parts by weight of the former, and the lower limit of this blending ratio is Polyethylene terephthalate resin
The reason why the amount of polycarbonate resin is limited to 3 parts by weight per 100 parts by weight is that if the blending ratio of polycarbonate resin is smaller than this, the effect of blending the polycarbonate resin cannot be obtained sufficiently. In addition, the reason why the upper limit of the blending ratio was limited to 80 parts by weight of polycarbonate resin per 100 parts by weight of polyethylene terephthalate resin is as follows. This is because the characteristics of the insulated wire obtained using this method include a low thermal softening temperature and poor solvent resistance, making it unsuitable for use as a magnet wire. When polycarbonate resin alone is used as the insulation coating for electric wires without using polyethylene terephthalate resin, the characteristics of this insulated wire are that its heat softening temperature is extremely low and its solvent resistance is also extremely poor, making it impossible to use as a magnet wire. It cannot be used. In order to eliminate such drawbacks of polycarbonate resin, it is necessary to limit the amount of this resin to 80 parts by weight or less per 100 parts by weight of polyethylene terephthalate resin. This is clear from the relationship between the blending ratio of both resins and the heat softening temperature of the composition containing both resins shown in FIG. That is,
In compositions containing approximately equal amounts of both resins and in compositions containing a larger amount of polycarbonate resin, the heat softening temperature is lower than when each is used alone, and this tendency shows that when polycarbonate resin is
It appears abruptly and discontinuously in compositions containing more than 100 parts by weight. The same applies to solvent resistance. Such a rapid change in the properties of a composition of polyethylene terephthalate resin and polycarbonate resin can be explained as a change in the compatibility of both resins in the normal molding temperature range of 270°C to 310°C for such compositions. . In other words, phase separation progresses rapidly in compositions containing more polycarbonate resin than equivalent formulations, but in compositions containing more polyethylene terephthalate resin than equivalent formulations, the composition becomes a single phase. Therefore, it is thought that in a composition containing a large amount of polyethylene terephthalate resin, defects as a magnet wire such as a decrease in the softening point due to the polycarbonate resin and swelling due to the solvent are suppressed. The behavior of such a composition of polyethylene terephthalate resin and polycarbonate resin is also supported by the viscoelastic measurement data described in JAPS 23 , 85-99 (1979). Compositions in which the amount of polycarbonate resin blended is from 80 parts by weight to 100 parts by weight are compositions that correspond to the so-called transition region of such phase change, and the use of compositions in this region should be avoided.
It is also necessary to avoid using compositions containing a larger amount of polycarbonate resin than in this range. Therefore, the amount of polycarbonate resin blended must be 80 parts by weight or less. The crystal embrittlement prevention effect of polyethylene terephthalate resin by polycarbonate resin is due to the fact that polycarbonate resin is a low-crystalline polymer, has a high glass transition point of 140 to 150°C, and has good compatibility with polyethylene terephthalate resin. This is thought to be due to this. However, the effect of preventing polyethylene terephthalate resin from crystal embrittlement cannot be achieved by any resin that satisfies the above conditions; for example, it is a non-crystalline polymer and its glass transition point is lower than that of polycarbonate resin. In a composition in which a polyarylate resin, which has high compatibility with polyethylene terephthalate resin, is blended instead of a polycarbonate resin, the effect of preventing crystal embrittlement as in a composition blended with a polycarbonate resin does not appear. The effect of preventing crystal embrittlement in a composition containing a polycarbonate resin is thought to be due to the unique effect of the polycarbonate resin on the crystallization behavior of the polyethylene terephthalate resin. In addition, this crystal embrittlement prevention effect is more pronounced as the coating is thinner, and if the coating is thicker, even a composition containing a polycarbonate resin will not have sufficient embrittlement prevention effect when used in electric wires. Therefore, the remarkable effects of the present invention can be obtained in the case of an insulated wire with a coating thickness of 100 μm or less. As described above, the present invention provides a composition in which a polycarbonate resin is blended with a polyethylene terephthalate resin, which exhibits a remarkable effect in preventing crystal embrittlement of the polyethylene terephthalate resin, and also has a thermal softening temperature that is a drawback of polycarbonate resin. This is based on the discovery that the decrease in the properties and the deterioration of the solvent resistance can be suppressed at a specific blending ratio. Heating the insulated wire of the present invention in an atmosphere of 300° C. or higher to remelt the coating resin and improve the adhesion between the coating resin and the conductor is highly effective in improving the characteristics. Further, mixing inorganic substances such as titanium oxide, talc, silica, and mica into the resin composition used in the present invention gives good results to the mechanical properties of the film.
Furthermore, additives such as heat stabilizers and flame retardants may be mixed as appropriate. Next, the present invention will be explained with reference to examples. Example 1 100 parts by weight of polyethylene terephthalate resin (manufactured by Teijin Ltd., grade number: TR-4550-BH) and 80 parts by weight of polycarbonate resin (manufactured by Teijin Ltd., trade name: Vanlite K-1300). , 30 for kneading
The mixture was mixed by kneading using a mm extruder.
This mixture was extruded onto a 1 mm diameter copper wire using an extruder with a screw diameter of 30 mm equipped with an extrusion coating crosshead to provide an extruded coating layer with a thickness of 30 μm, and then the coated wire was quenched with water. The characteristics of the insulated wire thus obtained were tested, and the results are shown in Table 1. Examples 2, 3 and 4 Same as Example 1 except that the blending ratio of polyethylene terephthalate resin and polycarbonate resin was 50 parts by weight, 10 parts by weight and 3 parts by weight of the latter to 100 parts by weight of the former. An insulated wire was obtained in the same manner. We tested the wire characteristics of this insulated wire,
The results are shown in Table 1. Comparative Example 1 An insulated wire was obtained in the same manner as in Example 1, except that the polyethylene terephthalate resin used in Example 1 was used alone without blending the polycarbonate resin. The wire characteristics of this insulated wire were tested and the results are shown in Table 1. Comparative Example 2 An insulated wire was obtained in the same manner as in Example 1, except that 100 parts by weight of polycarbonate resin was blended with 100 parts by weight of polyethylene terephthalate resin. The wire characteristics of this insulated wire were tested and the results are shown in Table 1. Comparative Example 3 An insulated wire was obtained in the same manner as in Example 1, except that the polycarbonate resin used in Example 1 was used alone without using the polyethylene terephthalate resin. The wire characteristics of this insulated wire were tested and the results are shown in Table 1. Example 5 100 parts by weight of polyethylene terephthalate resin (manufactured by Toyobo Co., Ltd., grade number: RT-540) and polycarbonate resin (manufactured by Mitsubishi Edogawa Chemical Co., Ltd.,
An insulated wire was obtained in the same manner as in Example 1, except that 30 parts by weight (trade name: Iupilon S-2000) was used. The wire characteristics of this insulated wire were tested and the results are shown in Table 1.

[Table] As shown in Table 1, the insulated wire of the present invention has excellent wire characteristics not found in insulated wires manufactured by conventional extrusion methods. As described above, the insulated wire of the present invention has excellent wire characteristics and is particularly useful as a polyester magnet wire as a substitute for conventional polyester enamelled wire.

[Brief explanation of drawings]

FIG. 1 is a thermal softening temperature curve of a composition depending on the blending ratio of polyethylene terephthalate resin and polycarbonate resin.

Claims (1)

[Claims] 1. On the electrical conductor, apply 3 parts of polycarbonate resin to 100 parts by weight of polyethylene terephthalate resin.
100μ thick consisting of a composition containing ~80 parts by weight
An insulated wire characterized by being provided with the following extruded coating layer.