JPH01152169A - Epoxy resin powder coating composition - Google Patents

Abstract

PURPOSE:To provide the present compsn. having excellent moisture resistance and heat shock resistance, by incorporating a solid silicon resin having a hydroxyl group and a phenyl group into an epoxy resin powder coating comprising an epoxy resin, a curing agent, a filler, etc. CONSTITUTION:An epoxy resin powder coating compsn. comprising an epoxy resin (e.g., a bisphenol A epoxy resin), a curing agent of amine, acid anhydride or the like type, a filler such as silica or CaCO3, a pigment and an additive is blended with 0.1-3.0wt.% solid epoxy resin having a hydroxyl group and a phenyl group and having an MW of 500-1,000 and an m.p. of 50-150 deg.C [e.g., silanol-terminated poly(diphenylsiloxane)], followed by melt-kneading and pulverization.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is an epoxy resin powder coating that can be used as an insulating coating coating for electrical and electronic parts by incorporating a solid silicone resin as part of an additive. The present invention relates to a powder coating composition characterized by particularly excellent moisture resistance when used.

[Subject skill]

Powder coatings have been used as insulating coatings for electrical and electronic components, which have made remarkable progress in recent years. Electrical and electronic parts have been developed to be lighter, smaller, and more advanced in response to the demands of the era of power, such as becoming lighter, thinner, shorter, and smaller. Therefore, it is desired that the powder coating used for this purpose be one that can be applied thinly to match this direction, one that is effective in a small amount, and one that has better performance as an insulating coating, which is its original purpose. became.

The insulation properties of these coating resin coatings deteriorate over time because the resin itself has poor moisture resistance, the thermal expansion coefficients of the resin and the element are different, and the resin has a high elastic modulus. This may cause cranks to occur on the resin side, allowing moisture to enter there and reducing insulation. Therefore, in order to maintain high insulation properties, it is necessary to improve the moisture resistance and thermal shock resistance of the resin.

Epoxy resin powder coatings, which have traditionally been used as insulating coating materials for electrical and electronic components, consist of epoxy resin, curing agent,
Fillers, pigments, additives, etc. are uniformly kneaded and then ground into powder.

As the hardening agent, various amine hardening agents, dicyandiamide derivatives, imidazole derivatives, acid anhydrides, etc. are used, and as the filler, inorganic powders such as silica, alumina, hydrated alumina, and calcium carbonate are used. In addition, there is a method of adding a plastic resin for coloring (Japanese Unexamined Patent Publication No. 6O-4570), but this method is impractical due to decreased moisture resistance.

Furthermore, attempts have been made to raise the glass transition temperature of the cured product in order to improve its moisture resistance, but it has been difficult to reduce the stress of the resin.

As a result of extensive research, it was discovered that hydroxyl groups and phenicity can be dramatically improved.

[Structure of the invention]

The present invention is an epoxy resin powder coating in which a solid silicone resin having hydroxyl groups and phenyl groups is added to the epoxy resin, curing agent, filler, pigment, and additives that are the main components of conventional epoxy resin powder coatings. This is a resin powder coating composition, which can improve the desired moisture resistance.

In other words, this solid silicone resin with hydroxyl groups attacks the hydroxyl groups in the epoxy resin by applying heat, easily causing a dehydration condensation reaction, giving the epoxy resin water repellency and making it compatible with inorganic fillers. It has the effect of increasing sex. In addition, the presence of phenyl groups in the silicone resin makes the entire molecule bulky, which is presumed to contribute to stress relaxation between the epoxy resin and the inorganic filler.

The solid silicone resin to be added is 0.1~
It is desirable that the content be 3.0%; if it is less than 0.1%, it will not be able to function sufficiently as an additive; on the other hand, if it is more than 3.0%, it will not be effective during melt mixing or heat curing. This is because the water produced by the reaction becomes incompletely evaporated, and the remaining water accumulates in the resin, reducing its moisture resistance.

Epoxy resins include bisphenol A type, bisphenol F type, novolak type, and amine type epoxy resins, but in particular, epoxy resins such as bisphenol A type and bisphenol F type that have hydroxyl groups in the molecule are is preferred.

The curing agent may be of various amine type or acid anhydride type, and the filler may be any of the commonly used curing agents and fillers such as silica and calcium carbonate, and there are no particular limitations here. do not have.

Further, in the method for producing the composition of the present invention, kneading using a twin-screw extruder, rolls, etc., and pulverization using a hammer mill, ball mill, etc., as usual, are sufficient, and no special production method is necessary.

The solid silicone resin used in the present invention has a molecular weight of about 500 to 10,000, and its structure may be chain or cyclic, but the molecule contains (Ph-3
It has at least two (1-0H) groups. Here, it is preferable that this group be located at a non-adjacent position within the molecule.

Furthermore, as a solid silicone resin, the melting point is 50 to 150.
℃ is preferable 0 For example, chain-shaped ones include terminal silanol poly(diphenylsiloxane) and terminal diphenylsilanol poly(dimethyldiphenylsiloxane).
Among the cyclic ones, there is one with the following general formula. (
Ph represents a phenyl group).

m and n are positive integers [Effects of the Invention] Significant improvements can be made by using the epoxy resin powder coating composition of the present invention.

〔Example〕

Powder coatings were trial-produced using the blending ratios shown in Table 1 and designated as Compositions 1 and 2. The solid silicone resin content in this composition was 0.0.2.2.5 for both groups of acids.
It is 5.0%.

Soft coating is applied to ceramic capacitors using the fluidized dip coating method.
It was baked at 150°C for 1 hour.

Moisture resistance was determined by measuring the resistance change rate of a 100Ω resistor network after being treated with a pressure cooker at 120°C for 250 hours.The numbers in the table are the same as those of Kurushima because they were damaged by cranks, etc. after 100 and 200 cycles. A marked improvement in moisture resistance was observed, indicating that the epoxy resin powder coating composition of the present invention has excellent effects.

Claims (2)

[Claims] (1) An epoxy resin powder coating composition comprising an epoxy resin, a curing agent, a filler, etc., and containing a solid silicone resin having hydroxyl groups and phenyl groups as an essential component. (2) Add 0.1 to 3.0% of solid silicone resin to the composition.
Claim 1 characterized in that it contains 0% by weight.
The epoxy resin powder coating composition described in .