JPH06899B2 - Varnish for enameled wire - Google Patents

Description

TECHNICAL FIELD The present invention relates to a varnish for an enameled wire used for producing an enameled wire.

"Prior Art" Various attempts have been made in the past as a method for improving the appearance of enameled wires such as gloss and smoothness. For example, a method in which a surfactant is added to the varnish to lower the surface tension of the varnish to improve the wettability and also to improve the dispersibility of the resin in the varnish to make the coating pressure uniform. A method in which a leveling agent such as silicon oil or Teflon oil is added to the varnish to obtain the surface smoothing effect of the coating after the coating and baking of the varnish. It is a method of reducing the baking temperature after applying the varnish and the baking speed to eliminate the unevenness of 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 in the varnish, and in the method of adding a leveling agent, after coating baking, all of these agents remain in the film, or lower the insulating properties of the enamel wire film,
There is a drawback that bleeding occurs in the film. Further, in the case of a varnish to which the above-mentioned surfactant or leveling agent is added, when the varnish is applied and then baked,
A part of these chemicals may radiate to become a catalyst poison that significantly interferes with the action of the platinum-based solvent combustion catalyst provided in the baking furnace, which has been a problem.

In addition, the method of decreasing the baking speed has a drawback that the yield in the enamel wire manufacturing process is naturally decreased and the manufacturing cost is increased.

Furthermore, in the varnish that has been commonly used in the past,
In both cases, if a predetermined film thickness was obtained by applying a few times, unevenness would be generated on the film surface, so there was also a complaint that the manufacturing cost could not be reduced by reducing the number of times of application. .

"Means for Solving Problems" The varnish for enamel wire of the present invention is a varnish for enamel wire containing a resin soluble in a cresol-based solvent, in an amount of 1 to 30% by weight (weight: %, The same shall apply hereinafter)).

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

The monohydric alcohol added to the varnish for enameled wire preferably has a boiling point lower than that of the solvent for the varnish, such as cresol or xylenol, and particularly has a boiling point of 165.
When a substance having a temperature of not higher than 0 ° C is added, the volatility of the solvent in the varnish becomes high 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.

The amount of this alcohol added is 1 to 30% with respect to the solvent in the varnish. If the amount added is less than 1%, the resin dispersibility in the varnish becomes insufficient, and a satisfactory appearance improving effect cannot be obtained. On the other hand, if the addition ratio is more than 30%, the number of coatings must be increased and the effect of improving the appearance becomes small, and depending on the varnish used, it may become cloudy or gel.

The coating and baking of the varnish thus obtained on the conductor wire may be performed in the same manner as in the usual production of enamel wire.

In such a varnish for enamel wire, by adding a monohydric alcohol, the cohesive force of the resin in the varnish can be relaxed and the dispersibility of the resin can be increased, so the appearance of the enamel film after coating and baking can be improved. Is possible. Further, by increasing the dispersibility of the resin in the varnish, a film having a predetermined thickness can be formed with a small number of coatings, and the manufacturing cost of the enameled wire can be reduced. Moreover, since the wettability with respect to the copper wire can be improved by adding alcohol, it is possible to prevent the varnish from being repelled at the time of application.

Also, when an alcohol having a low boiling point (165 ° C or lower) is used, the volatile property of the solvent in the varnish can be increased by the azeotropic action with another high boiling point solvent, and the baking linear velocity in the baking process can be increased. It is possible to increase the cost and thus reduce the cost. Moreover, since the additive is alcohol, it does not remain in the film after baking, does not deteriorate the physical properties of the film, and does not act as a catalyst poison on the combustion catalyst in the baking furnace.

"Experimental Example" Next, the working effect of the varnish for an enameled wire of the present invention will be clarified with reference to Examples.

(Experimental Example) In a polyurethane varnish containing a cresol-based solvent of 60% and a xylol-based solvent of 40% and having a resin content of 30%, isobutyl alcohol was used in an amount of 1% with respect to the amount of the solvent (Experimental Example 1). 10% ... (Experimental example 2) 20% ... (Experimental example 3) 27% ... (Experimental example 4) Add and sufficiently mix the resulting varnish with 0.1 mm.
Each experimental example was carried out by performing coating baking on a copper wire several times so that the insulation thickness after baking was 20 μm, and of the least number of times that the appearance of the enamel film was considered good.

(Comparative Example) Isobutyl alcohol was added to the polyurethane varnish used in the above experimental example with respect to the solvent amount of the varnish 0% (Comparative Example 1) 0.5% ... (Comparative Example 2) 32% ... (Comparative Example 3) After the addition, a copper wire having a diameter of 0.1 mm was coated 7 times and baked.

Then, with respect to the obtained Experimental Examples 1 to 4 and Comparative Examples 1 to 3, the quality of appearance, the uneven thickness ratio of the film, the extensibility, the softening property,
The handability was compared. The results are shown in Table 2. In the table, Examples 1 to 4 represent experimental examples, and Ratios 1 to 3 represent comparative examples.

As is apparent from Table 2, the addition of 1 to 30% of isobutyl alcohol provided the effect of improving the appearance and the number of coatings could be reduced.

"Effect of the invention" The varnish for enamel wire of the present invention is obtained by adding 1 to 30% of a monohydric alcohol to the amount of the solvent in the varnish for the varnish for enamel wire containing a resin soluble in a cresol size solvent. And 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 enhanced, the appearance of the enamel film after coating and baking can be improved. By increasing the dispersibility of the resin in the varnish, a coating having a predetermined thickness can be formed with a small number of coatings, and the manufacturing cost of the enameled wire can be reduced. The addition of alcohol can enhance the wettability with respect to the copper wire, so that the repelling of the varnish at the time of application can be prevented. In addition, low boiling point (16
When an alcohol of 5 ° C. or less) is used, it is possible to increase the volatility of the solvent by an azeotropic action with other high boiling point solvent in the varnish and to increase the baking linear velocity in the baking process, Therefore, also in this respect, the manufacturing cost of the enameled wire can be reduced.

Moreover, since the additive in the varnish of the present invention is alcohol, it does not remain in the enamel film after baking, and it reduces the physical properties of the film and acts as a catalyst poison on the combustion catalyst in the baking furnace. There is nothing to do.

Claims (1)

[Claims] 1. A varnish for an enameled wire containing a resin soluble in a cresol-based solvent, in an amount of 1 to 3 relative to the amount of the solvent in the varnish.
A varnish for an enamel wire, which is obtained by adding 0% by weight of a monohydric alcohol.