JPS61252276A - Powder paint for electrical insulation - Google Patents

Abstract

PURPOSE:To provide the titled paint having an excellent flowability which enables a thin film coating for electrical insulation and exhibits an excellent dielectric breakdown voltage, which comprises a mixture of specific thermosetting resin paint powder with a finely divided hydrophobic silica. CONSTITUTION:An insulating solid resin such as an epoxy resin and a polyester resin is mixed with a curing agent or a curing catalyst based on an acid anhydride, imidazole, dicyandiamide, etc. The mixture is optionally incorporated with additives such as a colorant and a flowability modifier, heat-melted and kneaded. The kneaded product is pulverized to obtain a thermosetting resin paint powder having volume-base accumulation of 50% and a particle diameter of 5-20mum. 100pts.wt. paint powder is dry mixed by means of a high-speed mixer with 0.05-2pts.wt. finely divided hydrophobic silica, the surface of which is optionally protected with a trimethylsilyl group.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an electrically insulating powder coating, and more particularly to an electrically insulating powder coating suitable for thin film coating used for insulation coating of electric wires for equipment.

<Prior art> Powder coatings are solid coatings that do not use organic solvents or water, and have recently attracted much attention as resource-saving and pollution-free coatings. Applications are being attempted. However, when trying to obtain a good coating film with conventional electrical insulation powder coatings, the coating thickness tends to be thicker (easier) than with solvent coatings, which is not only disadvantageous in terms of cost (insulating coatings). As an insulating material, it has a serious problem in that voids are generated therein, resulting in a decrease in dielectric breakdown voltage (hereinafter referred to as BDV).

There is a strong demand for thinner insulating coatings for electrical wires for equipment, that is, magnet wires.

This magnet wire has a volume standard integrated 50% diameter of 25
When applying a conventional powder coating of ~70u11 to obtain a good film using an electrostatic dynamic dipping method, etc., the film thickness becomes more than 80μI, and in addition to the above-mentioned problems, there is a decrease in curing speed due to the film thickness bath, and flexibility. Problems such as a decline in performance also occur. When conventional powders are used to form a thin film with a desired thickness of 50 um or less, the surface becomes noticeably uneven (the structure within the film is uneven, causing pinholes, and as a result, BDV
leading to a decrease in

As a countermeasure to this problem, it may be possible to simply reduce the particle size of the powder, but in this case, the fluidity of the powder in the fluidizing tank of the coating machine would be poor (powder coating would become impossible).

<Problems to be Solved by the Invention> The present invention has been made in view of the above-mentioned circumstances. The present invention provides an electrically insulating powder coating having D'V.

Means for Solving the Problems> The present invention is characterized in that in order to stably obtain a thin film of 50 μl or less, the volume-based integrated 50% diameter is 5 to 20 μ-
In order to ensure the fluidity of the powder, 0.05 to 2% of hydrophobic silica fine powder is added to 100 parts by weight of the powder. There is a particular thing.

The thermosetting resin powder as used in the present invention is a mixture of an insulating solid resin such as an epoxy resin or a polyester resin with a curing agent or curing catalyst such as an acid anhydride type, an acid dihydrazide type, an imidazole type, or a dicyandiamide type. Further, if necessary, additives such as a colorant and a fluidity regulator are suitably blended, and the mixture is mixed by hot melting and pulverized.

In this case, the particle size of the powder, that is, the volume-based integration using the particle analyzer Coulter Counter Model TA-II 5
It is necessary to control the 0% diameter in the range of 5 to 20 Ijm, preferably 8 to 15 Ijm.

If the particle size is 51 or less, problems occur in powder coating properties,
In addition, the productivity of powder is poor (cost is high, and on the other hand, 20um
The above causes problems when obtaining a thin film of 20 to 30 nm in thickness with a film thickness of 50 um or less.

The electrically insulating paint of the present invention can be obtained by dry mixing the thermosetting resin paint powder thus obtained and the hydrophobic silica fine powder at a predetermined mixing ratio in a high-speed mixer.

Examples of the silica in this case include, for example, HDK 112000, HD, whose surface is covered with trimethylsilyl groups.
K H2O, HDK H2O (all manufactured by Hoechst), and Aerosil R97, which is made hydrophobic by reacting the silanol groups on the surface with dimethyldichlorosilane.
2 (manufactured by Nippon Aerosil Co., Ltd.) is preferably used in the present invention.The above-mentioned hydrophobic silica is particularly effective in the present invention, but other than silica may also be used to improve the fluidity of the powder. It has been confirmed that fine powders that can improve the performance, such as alumina, polyvinylidene fluoride, metal soaps, and nonionic surfactants, are also effective in the present invention.

The electrically insulating powder coating of the present invention thus obtained is coated onto a conductor to a desired thickness using a coating device normally used in this field, such as electrostatic dynamic dipping, fluidized dipping, or electrostatic spraying. It is applied to the surface and put into practical use.

The electrically insulating powder coating of the present invention can be used not only for magnet wires, but also for insulating coatings on electronic components such as small motors, capacitors, and resistors, and for insulating coatings on a wide range of other electrical materials. Furthermore, it has been confirmed that the technology according to the present invention can be applied to powder coating for purposes other than electrical insulation.

<Example> The present invention will be described in detail below with reference to Examples and Comparative Examples.

Example 1 After dry mixing the above components in a Henschel mixer,
Heat-melt and knead with an extruder, cool the mixed material, coarsely crush it with a hammer crusher, and then finely crush it with a jet mill to obtain a thermosetting resin paint powder with a volume-based integrated 50% diameter of 10.7μ. Obtained. Next, 0.5 parts by weight of hydrophobic silica fine powder (HDK H2O00 manufactured by Hoechst) was added to 100 parts by weight of the powder and mixed in a Henschel mixer to produce the electrically insulating powder coating of the present invention. did.

The obtained powder of the present invention was 2×5
A rectangular steel wire having a cross-sectional dimension of m+ was coated to a desired coating thickness and cured by heating to form an insulating coating. In this case, the workability of painting was extremely good and the appearance of the painted surface was also good.

FIG. 1 shows the relationship between the coating thickness and BDV of the obtained insulated rectangular copper wire. According to this, an excellent BDV was observed with a thin film of 50μ or less, and in particular even with an ultra-thin film of 20 to 30μ, which was impossible with conventional technology.
A BDV of 3KV was observed.

Example 2 After dry mixing the above components in a Henschel mixer,
The mixture was hot-melted and kneaded in an extruder, cooled, and then coarsely and finely pulverized to obtain a thermosetting resin paint powder having a 50% integrated diameter based on body i of 9.6 μm. Next, 0.0% of hydrophobic silica fine powder (HDK H2O00) was added to 100 parts by weight of the powder.
5 parts by weight were mixed in a Henschel mixer to produce the electrically insulating powder coating of the present invention.

The obtained powder of the present invention was applied to 2×5 m by the electrostatic dynamic dipping method.
A rectangular copper wire having a cross-sectional dimension of was coated to a desired thickness and cured by heating to form an insulating coating. At this time, the workability of painting was extremely good, and the appearance of the painted surface was also good. Furthermore, the relationship between coating film thickness and BDV reproduced Example 1 shown in FIG. 1, and excellent practical characteristics were confirmed.

Comparative Example After dry mixing the above ingredients in a Henschel mixer,
The mixture was hot-melted and kneaded in an extruder, cooled, and then coarsely and finely pulverized to obtain a thermosetting resin coating powder having a volume-based integrated 50% diameter of 35 μI.

The obtained comparative powder was 2×5 m by electrostatic dynamic dipping method.
It was coated on a rectangular copper wire having a cross-sectional dimension of , and heated and cured to form an insulating coating. In this case, the workability of the painting was very good and there were no problems, but the unevenness of the painted surface was significant, especially in 5
For thin films of 0 μm or less, coating unevenness and pinholes were clearly observed on the coated surface.

FIG. 2 shows the relationship between the coating thickness and BDV of the comparative powder. According to this, the level of BDV of the comparative powder was lower than that of the present invention, and the variation in BDV at the same film thickness was large, causing a practical problem. And 40μ
- If the film thickness is below, the formation of the paint film itself will be incomplete due to the occurrence of many irregularities and pinholes, and the BD
It was not possible to measure V.

<Effects of the Invention> Since the present invention has the above-mentioned configuration, it becomes possible to apply a thin insulating coating film, and therefore, it becomes possible to arbitrarily obtain a high BDV by delicately controlling the coating film thickness, Thin film coating technology, which was not possible with other technologies, has made it possible to develop a wider range of applications for electrically insulating powder coatings.

[Brief explanation of drawings]

Figure 1 is a diagram showing the relationship between the coating thickness and BDV using the electrically insulating powder coating of the present invention, and Figure 2 is a diagram showing the relationship between the coating thickness and BDV using the powder coating according to the prior art. FIG.

Claims (1)

[Claims] 100 parts by weight of thermosetting resin paint powder with a volume-based integrated 50% diameter of 5 to 20 μm and 0.05 parts by weight of hydrophobic silica fine powder
A powder coating for electrical insulation, characterized in that it consists of a mixture with ~2%.