JPS6286067A - Enameled wire varnish - Google Patents

Abstract

PURPOSE:To obtain the title varnish which has excellent appearance, inhibition of runaway and linear speed in baking and is inexpensive, by incorporating a monohydric alcohol into a specified enameled wire varnish. CONSTITUTION:An enameled wire varnish (A) containing a resin soluble in a cresol solvent (e.g., polyurethane) is mixed with a monohydric alcohol (B) having a boiling point of lower than those of the solvent s for component A, such as cresol or xylenol, and preferably of 165 deg.C or lower (e.g., isobutyl alcohol) in an amount of 1-30wt% based on the weight of the solvent in component A.

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial Field of Application" The present invention relates to an enamelled wire varnish used in the production of enameled wire.

"Prior Art" Various attempts have been made to improve the appearance of enameled wires, such as gloss and smoothness.

For example, ■ Adding a surfactant to the varnish lowers the surface tension of the varnish, increasing wettability, and increasing the dispersibility of the resin in the varnish, resulting in a uniform film thickness of 71/y? , fJ
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,, +NO+L A method of adding a leveling agent such as Teflon oil to obtain a smoothing effect on the surface of the film after applying and baking the varnish. (2) A method of reducing the baking temperature after varnish application and reducing the baking speed to eliminate unevenness in the enamel film.

"Problems to be Solved by the Invention" However, each of the above methods has the following problems. That is, in the method of adding a surfactant to the varnish and the method of adding a leveling agent to the varnish, these chemicals remain in the film after coating and baking, which may deteriorate the insulation properties of the enameled wire film.
There was a drawback that bleeding occurred in the film. Furthermore, in the case of varnishes containing the above-mentioned surfactants or leveling agents, when the varnish is baked after being applied,
This has been a problem because monovalent agents such as these can volatilize and become catalyst poisons that significantly interfere with the action of platinum-based solvent combustion catalysts installed in baking furnaces.

Furthermore, the method of reducing the baking speed naturally has the disadvantage of lowering the yield in the enamelled wire manufacturing process, leading to an increase in manufacturing costs.

Furthermore, regarding varnishes that have been commonly used,
In either case, if a desired film thickness was obtained by applying a small number of times, unevenness would occur on the film surface, so there was a complaint that it was not possible to reduce manufacturing costs by reducing the number of times of application. .

"Means for Solving the Problems" The varnish for enameled wire of the present invention is a varnish for enameled wire containing a resin soluble in a cresol solvent, in an amount of 1 to 30% (by weight %) based on the amount of solvent in the varnish. , the same applies hereinafter) is added.

"Example" As the varnish for enameled wire used in the present invention, a varnish for enameled wire containing a resin soluble in a cresol solvent such as polyester, polyesterimide, polyesteramideimide, polyurethane, etc. is preferably used. When a varnish containing a resin insoluble in cresol solvents is used, alcohol cannot be mixed uniformly.

The monohydric alcohol added to the above enamelled wire varnish is preferably one with a boiling point lower than that of the varnish solvent, such as cresol or quinlenol, particularly one with a boiling point of 165
When a solvent below 0.degree. C. is added, the volatility of the solvent in the varnish increases, and the time required for the baking process is shortened.

Table 1 shows such monohydric alcohols having a boiling point of 165° C. or lower.

Table 1 Alcohol name Boiling point (°C): Methanol 64.5: Ethanol
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97.2'' Isopropanol 82.3 n-butanol 117.7 iisobutanol 107.9 1□Sec-butanol 99.5'
The amount of alcohol added is 1 to 30% based on the solvent in the varnish. If the amount added is less than 1%, the resin dispersibility in the varnish will not be sufficient, and a satisfactory appearance improvement effect will not be obtained. In addition, the above addition ratio is 30%
If the amount is larger, the number of applications must be increased, and the effect of improving the appearance will be reduced, and depending on the varnish used, it may become cloudy or gel.

The varnish thus obtained can be applied and baked onto the conductive wire in exactly the same manner as in the production of ordinary enamelled wire.

In the case of such varnish for enameled wires, by adding -hydric alcohol, the cohesive force of the resin in the varnish can be relaxed and the dispersibility of the resin can be improved, which improves the appearance of the enamel film after application and baking. is possible. Furthermore, by increasing the dispersibility of +M in the varnish, a film of a predetermined thickness can be formed with fewer applications, and the manufacturing cost of enamelled wire can be reduced. Further, by adding alcohol, it is possible to improve the wettability of the copper wire, so that it is possible to prevent the varnish from being repelled during application.

In addition, when alcohol with a low boiling point (below 165°C) is used, the volatility of the solvent in the varnish can be increased by azeotropic action with other high-boiling point solvents, and the baking line speed in the baking process can be increased. Therefore, it is possible to reduce costs. Moreover, since the additive is alcohol, it does not remain in the film after baking, does not deteriorate the physical properties of the film, or acts as a catalyst poison on the combustion catalyst in the baking furnace.

``Experimental Example'' Next, an experimental example will be given to clarify the effects of the varnish for enameled wire of the present invention.

(Experimental example) In a polyurethane varnish with a resin content of 30% and consisting of 60% cresol solvent and 40% quinrole solvent, isobutyl alcohol was added in an amount of 1% based on the above amount of solvent (Experimental example 1) ) 1O%...(Experimental Example 2) 20%...(Experimental Example 3) 27%...(Experimental Example 4) After adding and thoroughly mixing, the resulting varnish was 0゜l.
Coating and baking were performed several times to obtain an insulation thickness of 20 μm after baking on the ml diameter line, and each experimental example was based on the minimum number of coatings and baking that was considered to give a good appearance of the enamel film.

(Comparative Example) - Isobutyl alcohol was added to the polyurethane varnish used in the experimental example at 0%... (Comparative Example 1) 0, 5%... (Comparative Example 2) 32%... (Comparative Example 3) was added, applied 7 times on a 0.1Rx diameter copper wire, and baked.

Next, regarding the obtained Experimental Examples 1 to 4 and Comparative Examples 1 to 3, the appearance quality, thickness unevenness ratio of the film, extensibility, softening resistance,
Soldering was compared based on gender. The results are shown in Table 2. In the table, ratios 1 to 4 represent experimental examples, and ratios 1 to 3 represent comparative examples.

As is clear from Table 2, the addition of 1 to 30% isobutyl alcohol had the effect of improving the appearance and was also able to reduce the number of applications.

"Effects of the Invention" The varnish for enameled wire of the present invention is obtained by adding 1 to 30% monohydric alcohol to the amount of the solvent in the varnish to the varnish for enameled wire containing a resin soluble in a cresol solvent. It has the following excellent effects.

■Since the cohesive force of the resin in the varnish can be relaxed and the dispersibility of the resin can be improved, it is possible to improve the appearance of the enamel film after coating and baking. (2) By increasing the dispersibility of the resin in the varnish, a film of a predetermined thickness can be formed with fewer applications, and the manufacturing cost of enamelled wire can be reduced. - By adding alcohol, it is possible to improve the wettability of the copper wire, so it is possible to prevent the varnish from splashing during application. ■It also has a low boiling point (16
When using alcohol (below 5°C), n-maI
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First, it is possible to increase the volatility of the solvent and increase the baking speed in the baking process, and in this respect, it is possible to reduce the manufacturing cost of enamelled wire.

Moreover, since the additive in the varnish of the present invention is alcohol, it will not remain in the enamel film after baking, and will not deteriorate the physical properties of the film or act as a catalyst poison for the combustion catalyst in the baking furnace. There is no need to act and f2.

Claims (1)

[Claims] A varnish for enameled wires, characterized in that 1 to 30% by weight of monohydric alcohol is added to the varnish for enameled wires containing a resin soluble in a cresol solvent.