JPS62132974A - Powder coating composition - Google Patents

Abstract

PURPOSE:To provide the titled composition containing an epoxy resin modified with a specific butadiene-acrylonitrile copolymer, giving a coating film having excellent thermal aging resistance and sufficiently high flexibility and suitable for the insulation coating of electronic part, etc. CONSTITUTION:The objective composition can be produced by compounding (A) 100pts.(wt.) of an epoxy resin of usually a bisphenol A glycidyl ether type with (B) preferably 5-40pts. of a butadiene-acrylonitrile copolymer having carboxyl group at the terminal.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a powder coating composition suitable for insulation coating of electrical and electronic parts.

<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. Active efforts are also being made to apply it to painting.

Conventional powder coating compositions for electrical insulation use an epoxy resin as a base resin, and after uniformly melting and kneading additives such as acid anhydrides, curing agents such as dicyandiamide, pigments, fillers, and flow control agents, It can be obtained by crushing. Among these, the main component epoxy resin is often bisphenol A glycidyl ether type, but in addition to this, epoxy resins such as Talesol novolak glycidyl ether type and phenol novolac type to impart heat resistance, and flexible epoxy resins are used. Epoxy resins such as dimer acid glycidyl ester and diglycidyl ether of polyoxyalkylene glycol have been proposed for imparting the following properties.

On the other hand, quality requirements for electrical insulating coatings have recently become stricter, and powder coatings used to insulate magnet wires used in transformers and motors are required to have a high degree of heat resistance and flexibility. ing.

Among these, high heat resistance requires excellent heat deterioration resistance, resistance to heat softening, and high heat shock resistance, but conventional powder coating compositions do not meet these requirements. It is impossible to obtain insulating coatings that meet the requirements of heat resistance and sufficient flexibility. When heated for a long period of time, the resin undergoes oxidative decomposition and thermal decomposition reactions, and the side chains or main chains are cut, resulting in a decrease in thickness and weight, deterioration of properties, and finally dielectric breakdown. Although excellent thermal stability at high temperatures is a prerequisite for heat-resistant insulating materials, no powder coating composition that satisfies this requirement has yet been proposed.

<Problems to be Solved by the Invention> The present invention has been made in view of the above circumstances, and it is an object of the present invention to obtain an insulating coating film that has excellent heat deterioration resistance among heat resistance and sufficient flexibility. The present invention provides a powder coating composition that can be used.

Means for Solving the Problems The present invention is characterized by the use of an epoxy resin modified with a butadiene-acrylonitrile copolymer (CTBN) having a terminal carboxyl group in a powder coating composition.
(hereinafter referred to as CTBN-modified epoxy resin).

That is, in order to obtain the CTBN-modified epoxy resin referred to in the present invention, a bisphenol A diglycidyl ether type epoxy resin (DGEBA) that is liquid at room temperature, such as Epon 828 manufactured by Shell Chemical Co., Ltd., and, for example, Hyc
ar CT B N (Goodrich Chemica
It is obtained by reacting CTBN having the following structural formula (manufactured by 1 company) with a curing agent such as dicyandiamide.

However, x=5, y=1, and z=10 are average values, and in that case, the number average molecular weight (Mn) is 3300 and the acrylonitrile content is 18.8%.

The structure of the CTBN-modified epoxy resin obtained by the reaction between DGEBA and CTBN is thought to be as shown below, and commercially available products include Epomic 5R35K (
(manufactured by Mitsui Petrochemicals, epoxy equivalent: 985 g/eq).

The above CTBN-modified epoxy resin can be blended alone as a base resin, but due to heat softening properties and other properties, it is usually mixed with 100 parts by weight of a general-purpose bisphenol A glycidyl ether type epoxy resin. It is used in an amount of 5 to 40 parts by weight.

In order to obtain the powder coating composition of the present invention, a curing agent or curing catalyst such as an acid anhydride type, acid dihydrazide type, imidazole type, dicyandiamide type, etc. is mixed with the above-mentioned general-purpose and CTBN-modified epoxy resins, and if necessary, It can be obtained by appropriately blending additives such as a coloring agent and a flow control agent, and then hot-melting and pulverizing the mixture.

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

The powder coating composition of the present invention can be used not only for magnet wires, but also for insulation coatings of electronic parts such as small motors, capacitors, and resistors, insulation coatings for a wide range of electrical materials, and other general powder coatings such as decorative coatings. It encompasses various uses.

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 kneaded material, and then crush it with a bottle disc mill to obtain a volume-based integrated 50% diameter of 3.
A powder coating composition of 0 μm was obtained.

The obtained powder coating composition of the present invention was applied to a rectangular copper wire having a cross-sectional size of 2 x 5 m by an electrostatic dynamic dipping method to a desired coating thickness, and then heated and cured to form an insulating coating. .

Next, in order to examine the heat deterioration resistance of the insulating coating film, the rectangular copper wire with the above coating film was heat-treated at 200°C for 6 hours, and then tested at a tensile speed of 300 m using a Tensilon universal tensile tester.
/Iin, no cracks occurred in the coating film, and excellent heat deterioration resistance and flexibility were confirmed.
When the dielectric breakdown voltage (BDV) was measured before and after the heat treatment using the metal foil method specified in Jl5C3003, it was 60-75KV for a coating thickness of 100u+++.
An excellent BDV of /m was confirmed.

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 powder coating composition having a volume-based cumulative 50% diameter of 25 ua+.

The obtained powder of the present invention was transferred to 2×5M by 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.

Next, the practical characteristics of the insulating coating film were evaluated in the same manner as in Example 1, and the results showed that it had excellent heat deterioration resistance, flexibility, and B.
Domestic violence was 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 powder coating composition having a volume-based integrated 50% diameter of 35 μm.

The obtained powder of the present invention was immersed in 2×5I by electrostatic dynamic dipping method.
The coating was applied to a rectangular copper wire having a cross-sectional dimension of III11, and the coating was heated and cured to form an insulating coating film.

Next, when we examined the heat deterioration resistance of a rectangular copper wire with an insulating coating as in Example 1, we found that the coating had numerous cracks and peeled off from the steel wire, and the heat deterioration resistance was extremely poor. It was confirmed that this was sufficient.

<Effects of the Invention> Since the present invention has the above configuration, excellent heat deterioration resistance, which was impossible with conventional techniques, can be obtained, and BD
At the same time, it had excellent practical properties such as V and flexibility required as an electrically insulating powder coating.

Claims (1)

[Claims] A powder coating composition comprising an epoxy resin modified with a butadiene/acrylonitrile copolymer having a carboxyl group at the end.