JPH0336246B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improvement in an insulated wire for a magnet wire, and relates to an insulated wire formed by extruding a resin onto an electric conductor and providing a thin coating layer thereon. In recent years, it has been proposed to thinly coat a conductor with thermoplastic resin and use it as a magnet wire for the purpose of saving resources, saving energy, being pollution-free, and increasing productivity (Japanese Patent Laid-Open No. 53-4875). issue). Examples of resins used for this purpose include polyethylene terephthalate and polybutylene terephthalate resins, which have a proven track record as thin insulating materials and have excellent heat resistance and electrical properties.However, insulated wires coated with thin extruded resins include It turned out that it had a serious defect in practical use. That is, when an electric wire is stored in a temperature range of 30 to 50°C, its electric wire properties change over time, and when subjected to processing such as elongation, many crazes occur, and the covering voltage value, pinhole properties, etc. decrease. Such defects are considered to be caused by the fact that the rapidly cooled insulating layer undergoes volume relaxation during coating with the electric wire insulating layer, making the insulating layer susceptible to brittle coating during processing. Therefore, it is possible to prevent brittle fracture by mixing a polyolefin resin with a polyester resin, especially a polyolefin resin having a carboxylic acid in the side chain, which gives good dispersibility to the polyester resin. It has been found that this method is effective in reducing the breakdown voltage of polyester-coated wires. However, this was far from perfect, and when pinhole characteristics were measured after 3 to 5% elongation, it was found that fine crazing had occurred. The present inventors have arrived at the present invention as a result of studies aimed at improving the defects of insulated wires coated with polyester resin as described above. In order to achieve the above object, the present invention extrudes and coats a polyamide resin onto an electrical conductor, and then coats it with 100 parts by weight of a polyester resin and 1 to 15 parts by weight of a polyolefin resin having a carboxylic acid or carboxylate in the side chain. It is characterized by extrusion coating of a composition formed by mixing parts by weight. The polyamide resin used in the present invention includes nylon 6, 6, nylon 6, nylon 6, 10, nylon 11, nylon 12, etc., but the selection of these resins depends on the polyester resin of the upper coating layer. Determined by the selection. In addition, in the polyester resin used in the present invention, the dicarboxylic acid component is preferably an aromatic dicarboxylic acid in view of its heat resistance, examples of which include terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, diphenyl dicarboxylic acid, and diphenyl sulfone dicarboxylic acid. Acids include diphenyl ether dicarboxylic acid, methyl terephthalic acid, methyl isophthalic acid and the like, but terephthalic acid is particularly preferred. Examples of the diol component, which is the other component constituting the polyester resin, include ethylene glycol, propylene glycol, butanediol, hexanediol, and decanediol, with ethylene glycol and butanediol being particularly preferred. Some of the diol components are oxy(alkylene) glycols such as polyethylene glycol,
Polytetramethylene glycol may be substituted. Typical polyester resins obtained from these components include the aforementioned polyethylene terephthalate resin (PET) and polybutylene terephthalate resin (PBT). Examples of polyolefins having a carboxylic acid or carboxylic acid salt in the side chain used by kneading with the above polyester resin include unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid, or maleic acid, fumaric acid, and phthalic acid. Examples of copolymers of unsaturated dicarboxylic acids and ethylene polymers include copolymers of unsaturated dicarboxylic acids such as ) or EAA resin (trade name of Dow Corning, USA), which is an ethylene-acrylic copolymer. Similarly, the above unsaturated monocarboxylic acid or dicarboxylic acid can be used as polyethylene, polypropylene, polybutene,
An example is a graft polyolefin obtained by grafting onto an ethylene-propylene copolymer, and a typical commercially available product is Admer (trade name of Mitsui Petrochemicals). In the present invention, the kneading ratio of the polyolefin resin having carboxylic acid in the side chain to 100 parts by weight of the polyester resin of the upper layer coating composition is 1 to 15 parts by weight, preferably 5 to 10 parts by weight. If the kneading ratio is less than 1 part by weight, the effect of the present invention will not be achieved,
Moreover, if the amount exceeds 15 parts by weight, the heat resistance decreases and the wire cannot be used as a magnet wire. The upper layer kneaded composition and the lower layer polyamide according to the present invention may be used by adding a heat stabilizer, an antioxidant, a flame retardant, or an inorganic filler such as talc or titanium dioxide, etc., as necessary. The kneading composition of the present invention may be kneaded by any conventional method, such as mixing pellets of both resins in a mixer and then kneading in a twin-screw kneading extruder. The reason why a polyamide layer is used as the lower layer in the present invention is that polyamide has poor resistance to acids and alkalis, and is a resin that is susceptible to oxidative deterioration. This is because the disadvantages of resin can be overcome, and the deterioration of breakdown voltage and pinhole characteristics due to processing after aging, which are the disadvantages of the polyester resin coating layer described above, can be prevented. The conductor may be coated with the resin according to the present invention by a known extrusion coating method, and the thickness of the coating layer is preferably 100 μm or less, preferably 50 μm or less when used as a magnet wire. Further, the ratio of the coating thickness of the upper layer to the lower layer is preferably 1 or more since the upper layer maintains heat resistance. In addition, it is preferable that the temperature of the surface of the lower layer before applying the upper layer coating be below the melting point of the lower layer coating polyamide resin in order not to damage the surface of the lower layer coating layer, but if it is too low, the adhesion between the upper and lower coatings will deteriorate. To avoid this, the temperature should be maintained at a temperature range of 0 to 50°C lower than the temperature of the upper extruder head. In the present invention, it is also possible to improve the mechanical properties of the coating layer by performing double extrusion coating on the conductor and then crystallizing it by adjusting the cooling conditions. In this case, the crystallization temperature is 100℃ to maintain high-speed coating properties.
The above is desirable. The present invention will be explained below using examples. Example 1 Nylon 6,6 resin (Amiran manufactured by Toray Industries)
CM300IN) was extruded onto a mild steel wire with a diameter of 1.0mm using a 30mmφ extruder to a thickness of 10μ, and then
A mixture of 100 parts by weight of PET and 10 parts by weight of ionomer resin (Himilan 1855 manufactured by Mitsui Polychemicals) was extruded and coated on the above nylon coating layer to a thickness of 40μ using a 30mmφ extruder to form a double-covered electric wire. Obtained. Table 1 shows the wire characteristics of the obtained insulated wire. Examples 2 to 4, Comparative Examples 1 to 4 The same procedure as in Example 1 was carried out except that the resin compositions and coating thicknesses of the upper and lower layers were as shown in Table 1. The results are also listed in Table 1. The resins indicated by abbreviations in the table are as follows. PBT: Polybutylene terephthalate (FR-PMT G200A manufactured by Mitsui Petrochemicals) Nylon 6, 10: (Amiran CM2001 manufactured by Toray Industries) Nylon 12: (Diamide L2140 manufactured by Daicel Corporation) EAA: Ethylene acrylic copolymer (Dow Chemical Company) Admer: Ethylene graft polymer (manufactured by Mitsui Petrochemicals NEO-50)

[Table] As is clear from the above examples, the insulated wire of the present invention has various excellent properties, and its practical value is extremely large.

Claims (1)

[Claims] 1. A composition obtained by kneading a polyamide resin coating layer on an electrical conductor, 100 parts by weight of a polyester resin, and 1 to 15 parts by weight of a polyolefin resin having a carboxylic acid or carboxylate in the side chain. An insulated wire characterized by sequentially forming extruded coating layers. 2. The insulated wire according to claim 1, wherein the total coating thickness on the conductor is 100μ or less, and the ratio of the coating thickness of the upper layer to the lower layer is 1 or more. 3. The insulated wire according to claim 1, wherein a 6,6 nylon resin is used for the lower polyamide resin coating layer.