JPS6250926B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method of manufacturing an insulated wire without using a solvent, and particularly to a method of manufacturing an insulated wire coated with a polyester resin and having various properties comparable to those of conventional magnet wires. Conventionally, when manufacturing insulated wires used as magnet wires for motors, etc., it is common to apply an insulating paint obtained by dissolving a resin in an organic solvent onto a conductor and dry and solidify it. At this time, a large amount of solvent is used to adjust the viscosity of the paint in order to make it easier to coat the conductor with the paint, but due to the toxicity of the solvent used and incomplete recovery of the solvent, it is difficult to improve the working environment. Also, from the viewpoint of resource saving, there is a strong desire for a method of manufacturing insulated wires that does not use solvents. In response to this demand, a method has been proposed in which a resin having high strength and low melt viscosity, such as linear polyester, is melt-coated onto a conductor by extrusion molding (Japanese Patent Application Laid-Open No. 4875/1983). However, since the insulated wire obtained by this method is simply a conductor coated with thermoplastic resin, it has inferior abrasion resistance, mechanical strength, heat deterioration resistance, etc., and is inferior to magnet wire that passes JIS standards. It is impossible to obtain an insulated wire with the performance that would allow it to be used as such, and even if it could be used, it could only be used in extremely limited equipment. In other words, since resins such as linear polyester are crystalline polymers, if they are stretched or bent during coil processing,
In addition to the formation of minute cracks and deterioration of electrical properties, loss of flexibility due to crystallization is also observed when heated for drying or the like. JISC3203, 3210, as a test method for heat deterioration resistance of magnet wire.
3211, etc., which observes flexibility after heating for a predetermined period of time (e.g., for polyester enamelled copper wire, wrapability after heating at 200°C for 6 hours)
Also, the flexibility completely disappears due to crystallization. An object of the present invention is to provide a method for producing an insulated wire without the use of a solvent and having sufficient performance to be used as a magnet wire without the above-mentioned drawbacks. In order to achieve the above-mentioned object, the present inventors have conducted extensive research on a method for manufacturing insulated wires that does not use solvents, and as a result, first, a substantially linear polyester resin is coated on a linear conductor. Next, by heating this resin coating layer to a temperature higher than the melting point of the resin, it was possible to obtain properties as an insulated wire, but when compared with an insulated wire manufactured using a solvent-based paint, the thermal softening properties, etc. It was still inferior in terms of heat resistance. Further studies revealed that by applying a polyfunctional unsaturated monomer to the surface of the resin coating layer before heating it to a high temperature above the melting point, the crosslinking density of the coating layer increases and heat resistance increases. The present invention has been achieved based on the discovery that the thermal stability can be improved by increasing the bonding strength of crosslinks and eliminating the above-mentioned drawbacks. The present invention is directed to (a) a substantive substance whose main component is an ester bond consisting of an acid component mainly consisting of a dicarboxylic acid in which an aromatic group or a part thereof is replaced with an aliphatic group, and a diol component mainly consisting of an aliphatic diol. (b) Next, a polyfunctional unsaturated monomer is applied to the surface of this resin coating layer. (c) This coating layer is coated in an oxygen-containing atmosphere. The above object is achieved by heating the resin to a temperature higher than the melting point of the resin and crosslinking the coating layer until the gel fraction reaches 20% or more. The acid component constituting the linear polyester resin used in the present invention is an aromatic acid or a dicarboxylic acid in which a portion thereof is replaced with an aliphatic acid. Examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, diphenyl dicarboxylic acid, diphenylsulfone dicarboxylic acid, diphenoxyethane dicarboxylic acid, diphenyl ether dicarboxylic acid, methyl terephthalic acid, and methyl isophthalic acid. etc., with terephthalic acid being particularly preferred. Further, the aromatic dicarboxylic acid can contain an aliphatic dicarboxylic acid such as succinic acid, adipic acid, and sebacic acid in a proportion of 30 mol% or less, preferably 20 mol% or less. Further, examples of the aliphatic diol component constituting the linear polyester resin include ethylene glycol, trimethylene glycol, tetramethylene glycol, hexanediol, and decanediol. Particularly preferred are ethylene glycol and tetramethylene glycol. In addition, some of the aliphatic diols are oxy(alkylene) glycols,
For example, polyethylene glycol or polytetramethylene glycol can also be used. Various additives such as UV absorbers, stabilizers such as antioxidants, pigments, fillers such as glass fibers, etc. may be added to the polyester resin used in the present invention as required. can. The polyester resin can be easily coated onto the linear body by applying the polyester resin in a heated molten state, or by a conventional thermoplastic resin molding method such as extrusion molding. Polyfunctional unsaturated monomers used in the present invention include divinylbenzene, mono-, di-, tri- and tetra-ethylene glycol diacrylates, mono-, di-, tri- and tetra-ethylene glycol dimethacrylates. , vinyl acrylate, vinyl methacrylate, allyl acrylate, allyl methacrylate, divinyl ether of diethylene glycol, diallyl maleate, diallylitaconate, diallyl malonate, diallylbenzene phosphonate, triallyl phosphate, triallyl cyanurate, glycerin trimethacrylate and their corresponding close homologs and mixtures thereof. In the method of the present invention, after applying the polyfunctional monomer as described above, a step of heating it to a temperature higher than the melting point of the polyester resin is performed. It is desirable to have a high melting point,
In addition, cyanuric acid or derivatives of isocyanuric acid such as triallyl isocyanurate, triallyl cyanurate, diallylmethyl isocyanurate, etc. are particularly suitable, since an insulated wire with excellent heat resistance can be obtained by using one with a high melting point. It is. However, even with a low melting point, the heat resistance is improved compared to when it is not added, but the effect is smaller than that of a high melting point. The polyfunctional monomer does not need to be kneaded into the polyester resin, and exhibits sufficient properties simply by being applied to the surface of the polyester resin, which is advantageous in terms of cost and manufacturing process. The polyfunctional monomer can be applied by spraying it with a sprayer, by placing it in a tank or the like, and passing it through it. Heating after coating the polyfunctional monomer is performed in an oxygen-containing atmosphere. The reason for this is that when heated in an oxygen-free atmosphere, the degree of crosslinking is extremely low, and it is difficult to crosslink until the gel fraction of the coating layer reaches 20% or more. Air, which is industrially easiest to use, can be used as the oxygen atmosphere. Therefore, a conventional baking furnace for enamelled electric wires that uses a solvent can be used as is, and no new equipment is required, which is advantageous. The heating temperature must be above the melting point of the polyester resin used; if it is below the melting point, crystallization may proceed, resulting in loss of flexibility and the film falling off when folded or rolled up. There is a risk. The coating layer is heated to a gel fraction of 20
% or more. Here, the "gel fraction" is the ratio of the insoluble residue to the total coating layer when m-cresol is heated at 90°C. When the gel fraction is less than 20%, it is difficult to obtain the characteristics necessary for an insulated wire for a magnet wire. The mechanism by which the coating layer crosslinks when heated in an oxygen atmosphere above its melting point is not clear, but heating in an oxygen-containing atmosphere causes scission and oxidation of the main chain due to the action of oxygen and heat, resulting in the formation of free radicals. It is presumed that this causes cross-linking of the molecules, resulting in insolubility. It is thought that this polyfunctional monomer reacts not only with each other but also with free radicals generated during the course of thermal crosslinking of the polyester resin. It is thought that when a polyfunctional monomer coexists, a stronger crosslinked product is produced than when a polyester resin is used alone, and therefore superior heat resistance can be obtained than when the above-mentioned thermal crosslinking is used alone. Comparing the heat resistance with respect to the elevated heat softening temperature, which is an important characteristic of insulated wires for magnet wires, the heat resistance of only thermally crosslinked wires is around 280℃, while that of wires coated with polyfunctional monomers is about 280℃.
It shows a surprising improvement of about 350℃. In manufacturing an insulated wire according to the present invention,
The steps of coating with polyester resin, coating with polyfunctional monomer, and heating must be performed continuously using a running linear conductor. The coating layer is heated to a temperature higher than the melting point of the resin during the heating process and melts, becoming liquid like when applying conventional paint that uses a solvent. The coating layer may become uneven or fall off. Furthermore, if only a wire conductor is melted and coated with polyester resin, bending stress is applied when the wire is wound onto a bobbin, etc., which may cause crystallization and cracks. In carrying out the method of the present invention, it is necessary to carry out each step continuously using a running linear conductor. The insulated wire produced by the method of the present invention has an elevated heat softening temperature, which is a measure of its heat resistance, than an insulated wire produced using a solvent-based paint. In addition, traditional manufacturing methods that use solvents
The amount of coating per time in the coating and baking process for film formation is limited in order to volatilize the solvent and reaction products. For example, when using a conductor with a diameter of 1.0 mm, the coating and baking process must be applied at least three times. It is also an advantage of the present invention that a single coating, application and heating operation is sufficient for the method of the present invention, as opposed to the above-mentioned repeats. Next, the present invention will be explained with reference to examples. Example 1 Polyethylene terephthalate resin heated and melted at 270°C (manufactured by Teijin Ltd., trade name TR-4550BH, melting point
A copper wire with a diameter of 0.85 mm was passed through a tank containing a temperature of 250 to 260°C, and a die was squeezed at the exit to form a coating film with a thickness of 28 to 31 μm. Triallyl isocyanurate (manufactured by Nippon Kasei Co., Ltd.) is sprayed onto this coating film using a sprayer, and the resulting painted line is passed through a furnace with a length of 6 m and an air atmosphere at a furnace temperature of 400°C at a speed of 4 m/min. An insulated wire was obtained. When the rising heat softening temperature of this insulated wire was measured, it was 380°C. When the resin film was peeled off from this insulated wire and the gel fraction was measured, it was found to be 95%. The rising heat softening temperature is measured using the test method specified in JIS C-3003.
The test was carried out according to (2) heating method of 13.1.1 cross method (the load was 800 g). That is, take two test pieces approximately 10 cm long from the same roll, stack them at right angles, place them on a flat plate, place an 800 g weight on the overlapped part, place this in a thermostatic oven, and place the test pieces on a flat plate. between conductors
An AC voltage of 100 V with a waveform close to a 50 or 60 Hz sine wave was applied, the temperature was raised at a rate of about 2°C/min, and the temperature at which a short circuit occurred was measured. Comparative Example 1 A copper wire was coated with polyethylene terephthalate resin in the same manner as in Example 1, except that triallyl isocyanurate was not sprayed, and an insulated wire was obtained by baking. Regarding this insulated wire, Example 1
The elevated heat softening temperature and gel fraction were measured in the same manner as above. The heat softening temperature was 280°C and the gel fraction was 90%. Comparative Example 2 A copper wire with a diameter of 0.85 mm is passed through a tank containing the same polyethylene terephthalate resin as in Example 1 heated and melted at 270°C, and the die is squeezed at the outlet to determine the thickness.
A coating film of 28 to 31 μm was formed, and then the coated wire was immediately cooled with water to obtain an insulated wire. Regarding this insulated wire, the increased thermal softening temperature and gel fraction were measured in the same manner as in Example 1. Heat softening temperature is 250℃
The gel fraction was 0%. Example 2 An insulated wire was obtained under the same conditions as in Example 1, except that triallyl cyanurate (manufactured by Nippon Kasei Co., Ltd.) was used instead of triallyl isocyanurate.
The increased thermal softening temperature and gel fraction of this insulated wire were measured in the same manner as in Example 1. The rising heat softening temperature was 370°C and the gel fraction was 93%. Various properties of the insulated wires obtained in Examples 1 and 2 and Comparative Examples 1 and 2 were measured according to JIS3210. The measurement results are shown in Table 1.

[Table] From the measurement results of the elevated heat softening temperature, gel fraction, and wire characteristics shown in Examples 1 and 2 and Comparative Examples 1 and 2, the following can be found. Regarding the increased heat softening temperature, the insulated wire manufactured using conventional solvent-type paint has a softening temperature of 300°C, whereas that of Example 1 of the present invention has a softening temperature of 380°C, and that of Example 2 has a softening temperature of 370°C. Although it is superior to the solvent type, the temperature of Comparative Example 1 without triallyl isocyanurate is 280°C, which is lower than the conventional solvent type, indicating a problem. Moreover, the temperature of the wire without thermal crosslinking as shown in Comparative Example 2 was even lower at 250° C., which indicates that it does not satisfy the characteristics as an insulated wire for magnet wire. Regarding the gel fraction, Example 1 in which triallylisocyanurate was sprayed and Comparative Example 1 in which triallylisocyanurate was not sprayed had almost the same value; It is thought that the increased thermal softening temperature will be higher because these materials have a three-dimensional structure that is stronger than those that are thermally crosslinked alone. Moreover, the material of Example 2 in which triallyl cyanurate was used instead of triallyl isocyanurate had the same elevated heat softening temperature, gel fraction, and wire characteristics as the example in which triallyl isocyanurate was used. Examples 3 and 4 and Comparative Examples 3 and 4 The same polyethylene terephthalate as in Example 1 was melt-coated on a copper wire with a diameter of 0.85 mm, and various polyfunctional monomers were sprayed on it and then heated in a furnace. length 6m
An insulated wire was obtained by passing it through a baking furnace and heat-treating it under the conditions shown in Table 2. The thickness of the resin film of each insulated wire was 28 to 31 μm. Various properties of these insulated wires were measured according to JIS3210.
The measurement results are shown in Table 2.

[Table] From Example 1 in Table 1 and Examples 3 and 4 in Table 2, the gel fraction and wire properties are almost the same even if the type of polyfunctional monomer is changed, but the increase in thermal softening It can be seen that the temperature varies considerably. In addition, even when triallyl isocyanurate is sprayed, if the heating temperature is 200°C (Comparative Example 3), crosslinking is insufficient and crystallization progresses, resulting in poor electrical properties for magnet wires. Fails the JIS standard for polyester insulated wires. This shows that it is necessary to heat the polyester resin above its melting point in order to prevent crystallization. Furthermore, even when triallylisocyanurate was sprayed, the product heat-treated in nitrogen (Comparative Example 4) still had insufficient crosslinking, and its electrical properties failed the JIS standard. The effect of thermal crosslinking is as previously explained for Examples 1 and 2 and Comparative Example 2, and the effect of such thermal crosslinking is also clear from Example 1 and Comparative Examples 3 and 4.

Claims (1)

[Scope of Claims] 1 (a) The main component is an ester bond consisting of an acid component mainly consisting of a dicarboxylic acid in which an aromatic group or a part thereof is replaced with an aliphatic group, and a diol component mainly consisting of an aliphatic diol. (b) Next, a polyfunctional unsaturated monomer is applied to the surface of this resin coating layer. (c) This coating layer is exposed to oxygen. A method for producing an insulated wire, comprising heating the resin to a temperature higher than the melting point of the resin in an atmosphere containing the resin to crosslink the coating layer until the gel fraction reaches 20% or more.