JPS62252479A - Powder coating composition - Google Patents

Abstract

PURPOSE:To provide a powder coating compsn. which has a high crosslink density, has excellent adhesion, gives a cured coating film which hardly absorbs water, and is suitable for use in coating electrical and electronic components, containing an epoxy resin having a very high epoxy group content and a very low impurity content. CONSTITUTION:An epoxy resin having an epoxy group content of not lower than 90% expressed by the formula (wherein W is an epoxy equivalent in g/eq; A is an alpha-diol content in meq/100g; Cl is a hydrolyzable chlorine content in wt%; and P is a free phenol content in ppm) is prepd. by a two-step method comprising a polyaddition reaction between a low-molecular liquid resin and bisphenol A. The epoxy resin is blended with additives such as a curing agent (e.g., dicyandiamide), a curing accelerator (e.g., an imidazole catalyst), a filler, a pigment, etc., to obtain the desired powder coating compsn.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a powder coating assembly for insulating electric wires and impregnating solenoid P coils, and particularly to an epoxy resin powder coating assembly.

BACKGROUND OF THE INVENTION Conventionally, various resin paints including epoxy resin have been considered as resins used for electrical insulation, impregnation of coils, moisture-proof protection, etc. Among them, epoxy resin is used for electrical,
It is suitable for insulating coatings on electronic parts, and is used because it has moisture resistance and high-temperature electrical properties.

The epoxy resin used here is particularly good for health since powder coatings do not require the use of solvents, and there is no risk of fire, so they are evaluated as preferable from the standpoint of pollution prevention. Epoxy resin (fat powder coatings include epoxy resins such as bisphenol A type epoxy resin, Nozerak type epoxy resin, and alicyclic type epoxy resin, acid anhydrides, curing agents such as polyamines, curing accelerators such as tertiary amines, imidazole, etc.), It is composed of materials such as fillers and other additives, and is applied to electrical and electronic parts using methods such as fluidized dipping and electrostatic dipping.

Problems to be Solved by the Invention However, with the recent trend toward higher reliability in electrical and electronic components, there has been an increasing demand for improved moisture resistance of epoxy resin powder coatings and high-humidity adhesion to coated objects. Measures to deal with this are required. .

Means for Solving the Problems The present invention was developed as a result of various studies in view of the above circumstances, and in particular, focused on the structure of bisphenol-type epoxy resins, which are capable of producing water due to their chemical structure. The problems of the prior art described above are solved by using an epoxy resin with low adhesiveness and excellent adhesion as a powder coating.

In other words, the terminal chemical structure of this type of epoxy resin is considered to be as follows: 3] and [
4] has the risk of producing H20, so [1
) must be increased.

By the way, the method of synthesizing epoxy resins currently used as powder coatings is a method called a one-step method, and it has been found that the epoxy group content of epoxy resins is about 60 to less than 90%.

Here, the epoxy group content is calculated by the following formula.

1ooxto3 v::x poxy (9/eq) A: α-diol (meq/hoot) Cl:
Hydrolyzable chlorine (wt%) P: Free phenol (ppm) From this perspective, the inventor of the present invention solved the problems of the conventional technology by increasing the content of epoxy groups to 90 or more and using an epoxy fat powder paint. This is what I did.

The epoxy resin used in the present invention mentioned above is synthesized by a two-step CF'usion method in which a low molecular weight liquid resin and bisphenol A are subjected to a polyaddition reaction, and has a very high epoxy content. However, the amount of impurities such as α-diol is reduced, the adhesive strength, especially the shear adhesive strength at high temperatures, is increased, and the decrease in the number of hydroxyl groups in α-diol improves water resistance, making it difficult to apply even under severe heat cycles. No cracks will occur on the surface.

Specifically, when used for moisture-proof protection of solenoid coils, it provides a cured coating that has exceptional adhesion to the polymer such as polybutylene terephthalate that forms the coil's zepin, and has low water absorption. .

Examples Below, powder coatings of Examples and Comparative Examples of the present invention were made and applied to solenoid coils at 130°C and 15ml of lh4 + water.
0 cycle test t- performed.

For testing, polybutylene terephthalate (PBT) with a central hole was used. A yN bottle with a solenoid coil wound around it was used, and a powder coating was applied from the outside.

Example 1 Two-step epoxy resin with 95% epoxy group content 10
0 parts by weight (Epotote YD904.Tobu Kaishisha Exhibition) Dicyan, diamide
2 #imidazole catalyst
■l (2MZ-A, manufactured by Shikoku Fine Chemical Co., Ltd.) Pigment Pen 2 2.5
1 (R-550, Tone Sangyo Shari) Flow regulator
03I (Modaflow, 4 Uda I, manufactured by Sonsanto Co., Ltd.) The above ingredients were dry mixed in a Henschel mixer, then hot melt kneaded and extruded using an extruder, cooled, and then coarsely and finely crushed to give a volume-based integrated diameter of 50%. A powder coating composition having a diameter of 35 μm was obtained.

The obtained powder was sandwiched between two PBT test pieces and the %t
The bond was cured by heating at SO℃ for 30 seconds, and after cooling once, the shear adhesive strength was measured using Tensilon, and it was found that tiox7. It had a tosK9/2 at 2.125°C and 35 to 9/2 at 150°C, and had considerable adhesive strength even at high temperatures.

Next, the powder obtained above was applied to a solenoid coil using a fluidized dipping method to a coating thickness of 500 to 600 μm, left in air at 130°C for 1 hour, and then immersed in water for 15 minutes. After repeating 100 cycles,
There was no peeling of pBT or cracks on the coated surface, and the coating had sufficient properties for practical use.

Example 2 In place of dicyandiami P in the formulation of Example 1.

A powder coating composition of the present invention was obtained in the same manner as in Example 1 except that 10 parts by weight of trimellitic anhydride, which is an acid anhydride curing agent, was used.

The shear adhesive strength between the PBT and the test piece of the obtained powder of the present invention was 7.5% at ti3 in an atmosphere of 20°C. 'cm2,1
7 i Kg/cm2 at 00°C. 40 to 9/6n2 at 150°C. It exhibits considerable adhesive strength even at high temperatures.

The obtained powder of the present invention was then evaluated in the same manner as in Example 1, and was found to have practically sufficient properties.

Comparative example? One-step epoxy resin containing 1 [87%] 1
Part 00ii (Eporate YDO14, manufactured by Tobu Kasei Co., Ltd.)
Dicyandiamide
2.

Imidazole catalyst l
l (2MZ-A, 17c!r5377'(7'y Mikanishap) Pigment Red Garla
25# (R-550, Tone Sangyosha Rip) Flow regulator o
3゜(Modaflow Para/-1, Montsan) JJ [) The obtained powder was measured in the same manner as in Example 1, and the shear adhesion fr: between PBT and the test piece was measured. However, it showed no adhesion at all in an atmosphere of 15°C (9°C).

, Furthermore, when it was applied to a solenoid coil in the same manner as in Example 1 and a heating cycle test was performed, PBT y
Peeling from the j# bottle and cracks on the coated surface occurred, which caused problems in practical use.

Effects of the Invention According to the present invention, the epoxy resin powder coating provides a cured coating film with less temperature dependence of shear adhesive strength and less water absorption.

Agent Patent Attorney Mamoru Takeuchi Procedural Amendment (Voluntary) June 4, 1986 Director General of the Patent Office Michibe Uga 1, Indication of the Case 1986 Patent M No. 93398 2, Name of the Invention Powder Coating Composition Item 3: Relationship with the case of the person making the amendment Patent applicant address: 5-15 Kyobashi-chome, Chuo-ku, Tokyo Name:
Representative Takao Inoue 4, Tomoe Urashisho Co., Ltd. Address: 101 Address: Nanbu Building 5, 2-15-13 Uchikanda, Chiyoda-ku, Tokyo, "Claims" column of the specification to be amended and "Detailed Description of the Invention" Column (1) Amend the claims by adding a separate sheet.

(2) In the second line of page 8g3 of the specification, the phrase "subject to be coated" is amended to read "object to be coated."

(3) The denominator of the formula on page 4, line 12 is r355J.
Correct it to r 35.5 J.

(4) In the third line of page 7, the phrase “10 times” was replaced with “100 times.”
Correct it to "times".

(5) The 3rd line of page 7 says “30 seconds” r3
0 minutes”.

2. Claims: A powder coating composition 100XI O' characterized by containing an epoxy resin represented by the following formula and having an epoxy group content of 90% or more.

Claims (1)

[Scope of Claims] A powder coating composition characterized by containing an epoxy resin having an epoxy group content of 90% or more represented by the following formula: Epoxy content = {(100×10^3/W )/[(1
00×10^3/W)+A+(Cl×10^3/35.
5)+(P×10^-^4/114)]}×100(%
) However, w: epoxy equivalent (g/eq) A: α-diol (meg/100gr) Cl: hydrolase P: free phenol