JPH0211667A - Epoxy resin powder coating composition - Google Patents

Abstract

PURPOSE:To obtain the title composition improved in flow and adhesion to substrate without detriment to its electrical properties, etc., by mixing an epoxy resin with a curing agent comprising bisphenol A, a filler, etc. CONSTITUTION:An epoxy resin (a) (e.g., o-cresol novolac epoxy resin) is mixed with a curing agent (b) comprising bisphenol A of a single MW of about 200 in an amount to give an equivalent ratio of the OH groups of component (b) to the epoxy groups of component (a) of 0.5-1.5, desirably, 0.9-1.1, a filler (c) such as an inorganic powder such as CaCO3, silica or Al(OH)3 and, optionally, a coupling agent, a pigment, a cure accelerator, etc., (d).

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides an epoxy resin powder coating material 4 that has excellent flowability and strong adhesion to elements (objects to be coated). The present invention relates to a composition.

[Conventional technology]

Epoxy resin powder coatings have various uses. For example, it has been put to practical use in motor insulation, electrical and electronic component insulation, and even as covers for electric wires and various electrical products.

Conventionally, these ↑5) body paints used a novolak type epoxy resin as part of the epoxy resin;
Novolank type epoxy resin and phenol novolac as a hardening agent, or TMA as a hardening agent
There were some that used trimellitic anhydride).

These powder coatings are powder-coated for the various uses mentioned above, and when they are fired, they retain flowability when melted. In particular, when used as a fixing agent for motor coils, conventionally used powder coatings have low flowability, so they do not impregnate the gaps between the coils, forming a coating layer on the coil surface, which hinders heat dissipation. There was a need for a powder coating with excellent flowability.

(Problems to be Solved by the Invention) As a result of various studies conducted by the present inventors in order to develop a powder coating that has excellent flowability during curing and melting and has strong adhesion to the coated object, the inventors have found that epoxy resin, By containing bisphenol 8 as a hardening agent in powder coatings consisting of hardeners, fillers, etc., it is possible to create coatings with extremely excellent flowability and adhesion without deteriorating electrical properties or other properties. It was found that four compositions were obtained.

[Means to solve the problem]

The present invention consists of an epoxy resin, a hardening agent, a filler, etc.
This is an epoxy resin powder coating composition characterized by containing bisphenol A as a curing agent.

As the epoxy resin, bisphenol A type epoxy resin, novolak epoxy resin, alicyclic epoxy resin, etc. can be used, but the present invention is not limited thereto.

Inorganic powders such as calcium carbonate, silica, and aluminum hydroxide are used as fillers, but the present invention is not limited to them. Coupling agents, pigments, etc. may be used as necessary.

The epoxy resin paint according to the present invention includes an epoxy resin,
It is obtained by kneading bisphenol A, a hardening accelerator, a pigment, and other additives using an extruder or roll, cooling, and then pulverizing to a desired particle size.

[For production]

This invention is characterized by the use of bisphenol 8 as a curing agent.

Although it is a known technique to use a phenol novolak resin as a curing agent, powder coatings using this resin have a drawback of poor flowability. The reason for this is that phenol novolak resin has a large molecular weight (average molecular weight 400-1000).
This is thought to be due to the wide molecular weight distribution. Therefore, bisphenol A with a molecular weight of 200 and a single molecular weight
It was only by using this that great flowability could be achieved.

The amount of bisphenol added as a curing agent is usually 0.5 to 1.5, preferably 0.5 to 1.5, based on the equivalent ratio of the hydroxyl group of bisphenol A to the epoxy group of the epoxy resin.
It is 9-1.1. When the amount of bisphenol is less than 0.5, the flowability becomes low and may not be practical.

If the amount is more than 1.5, the adhesion will decrease (there is a problem).

However, as a result of studies conducted by the present inventors, bisphenol A has a slow curing speed, so it is thought that its industrial use is limited. In order to improve this, it is preferable to use a curing accelerator in combination.

The type Il of the curing accelerator and its blending amount must be determined by considering the balance between gelation time, secondary transition point, etc., and flowability, but from the experimental results, in normal cases, the curing accelerator The blending ratio is preferably 15% by weight or less based on the epoxy resin.

This is because good flowability is often not obtained with 15 or more injection tubes.

Examples of curing accelerators include (11) aliphatic polyamines such as ethylenediamine and triethylenetetramine, aliphatic hydroxylamines such as monoethanolamine and propatoolamine, mekphenylenediamine, and 4,4'-diaminophenylmethane. Amine compounds such as aliphatic amines having a cyclic structure such as aromatic amines, piperazine, and 1-lyethylenediamine; (2) phthalic acid, maleic acid, tetrahydrofucuric acid, trimellitic acid, azelaic acid, benzophenonetetracarboxylic acid; Polyhydric carboxylic acids such as adipic acid or their anhydrides, (3) Other nitrogen-containing compounds such as dicyandiamide, carboxylic acids, dihydrazides, tertiary amines, imidazoles, and organic acid metal salts, but these are limited. It's not something you do.

〔Example〕

In each of the Examples and Comparative Examples shown in Table 1, the respective composition materials were melt-kneaded, cooled and pulverized, and the flowability and adhesion of the resulting powder coatings were measured.

Flowability is 13.40.5g powder coated using a 1φ mold.
is compressed at 200 kg/cd to obtain a tablet,
This tablet left was placed on a 10 degree inclined iron plate with a smooth surface in an electric heating furnace at 150° C. to melt it, and the length of flow after 30 minutes was measured.

Adhesion was determined using the JIS K6850r tensile shear adhesive strength test method, with powder coating applied to the iron-to-iron bonded area for $10,000.
A test piece was obtained by sandwiching 3 g of the sample and baking it for 30 minutes at 200°C in an electric heating furnace, and the tensile shear adhesive strength of this test piece was tested at 120°C.

〔Effect of the invention〕

Since the powder coating composition of the present invention contains bisphenol 8 as a curing agent, it has excellent flowability, and the resulting coating film has extremely excellent adhesion.

Because of these features, it is extremely suitable as a powder coating, particularly for applications that require great flowability, such as for fixing Morph coils.

Claims (1)

[Claims] (1) An epoxy resin powder coating composition comprising an epoxy resin, a curing agent, a filler, etc., and containing bisphenol A as the curing agent.