JPS59226067A - Epoxy resin powder coating composition - Google Patents

Abstract

PURPOSE:To provide the titled compositon for the insulation coating of electrical and electronic parts, containing a specific bisphenol A-epoxy resin and a novolac phenolic resin as essential components, and having excellent moisture resistance, high-temperature electrical characteristics and heat-cycle resistance. CONSTITUTION:The objective composition is obtained by mixing (A) 40-80wt% of an epoxy resin (having an epoxy equivalent of 180-450 and a melting point of 40-150 deg.C) which is a glycidyl ether obtained by the condensation of (i) a phenolic compound composed of 50-100wt% of bisphenol A and 0-50wt% of a monohydric phenol and (ii) formaldehyde and (B) 20-60wt% of a novolac phenolic resin (having a hydroxyl equivalent of 100-250 and a melting point of 50-120 deg.C) as essential components.

Description

Detailed Description of the Invention The present invention provides an epoxy resin powder coating comprising as essential components an epoxy resin which is a glycidyl ether of a condensation product of a phenol containing at least a portion of bisphenol A and formaldehyde, and a novolak type phenol resin. The purpose of the present invention is to provide a powder coating composition that has excellent moisture resistance, high-temperature electrical properties, and heat cycle resistance and is suitable for insulating coatings on electrical and electronic parts.

Conventionally, bisphenol A type Evokin resin,
Powder coatings containing epoxy resins such as novolak epoxy resins and alicyclic epoxy resins, curing agents such as acid anhydrides and polyamines, curing accelerators such as tertiary amines and imidazole, fillers, and other additives. is well known. These powder coatings are applied to electrical and electronic components by methods such as fluidized dipping and electrostatic dynamic dipping, and have been widely used in recent years as an economical (= advantageous) insulation coating method for electrical and electronic components. It was two.

However, with the recent trend toward higher reliability of electrical and electronic components,
The epoxy resin powder coating used in this coating (2) is required to have minimal deterioration in electrical and mechanical properties due to high-temperature, high-humidity treatment (2). It is difficult to respond.

As a method of improving the moisture resistance and high-temperature electrical properties of the conventional epoxy resin powder coating mentioned above, it is known to use a part of bisphenol A type epoxy resin in combination with a novolak type epoxy resin. Although the high-temperature electrical properties are slightly improved, the heat cycle resistance of the painted parts is greatly reduced.

Furthermore, as a method of improving the heat cycle resistance of the conventional epoxy resin powder coating mentioned above, there is a known method of using fused silica as an inorganic filler, but with this method, the heat cycle resistance of the painted parts is quite low. Although it improves, moisture resistance is significantly reduced.

As described above, with conventional methods, it has not been possible to obtain a product that has both electrical properties at high temperatures and high humidity, such as humidity resistance and high-temperature electrical properties, and heat cycle resistance.

In order to solve the above problems, various researches have been carried out to reduce the hygroscopicity of the cured powder coating film and give it flexibility and toughness. The present inventors have discovered that a powder coating containing this as an essential component has extremely excellent moisture resistance, high-temperature electrical properties, and heat cycle resistance, leading to the completion of the present invention.

That is, the present invention provides an epoxy resin powder coating composition C2 which contains as essential components an epoxy resin which is a glycidyl ether of a condensation product of a phenol containing at least a portion of bisphenol A and formaldehyde, and a novolac type phenol resin. It is related to

C: Details of the present invention will be described below.

The epoxy resin used in the present invention contains 50 to 100% by weight of bisphenol A, -valent phenols such as phenol, cresol, quinlenol, ethylphenol, p-phenylphenol, p-tarnarypdelphenol, p-octylphenol. , p-nonylphenol phenols consisting of 0 to 50% by weight are added simultaneously or in portions and reacted with formaldehyde under an acidic catalyst. It is an epoxy resin that preferably has an epoxy equivalent of 180 to 450, a melting point of 40 to 150°C, and a preferable epoxy equivalent of 200 to 300, and a melting point of 60 to 8.
A temperature of 0°C is preferred (two are used).

In addition, epoxy resins other than those mentioned above 1 For example, novolanc type epoxy resin such as cresol or phenol, glycidyl ether type epoxy resin, grindyl ester type evoquin resin, grindylamine type epoxy resin, alicyclic epoxy resin, linear aliphatic epoxy It is also possible to use resins, heterocyclic epoxy resins, halogenated epoxy resins, etc. in an amount of 50]i' or less based on the above-mentioned epoxy resin.

Further, these epoxy resins preferably have a content of sodium and chloride ions of 30 ppm or less and a water-decomposable chlorine ion content of 0.1% by weight or less.

To obtain the epoxy resin of the present invention (= If the mixing ratio of bisphenol A and monohydric phenol to be used deviates from the above range, the coating obtained by heating, melting, and curing the powder coating composition) The flexibility of the membrane decreases,
The heat cycle resistance of the parts coated with the powder coating composition C2 decreases.

When the epoxy equivalent of the epoxy resin is lower than 180, the crosslinking density of the coating film obtained by heating, melting, and curing the powder coating composition becomes too high. The heat cycle resistance of the parts deteriorates.

If the epoxy equivalent exceeds 450, the crosslinking density of the coating film becomes too low and the moisture resistance and high temperature electrical properties of the coated parts deteriorate.

When the melting point of the epoxy resin is below 40°C, the powder coating composition tends to block, and when the melting point is above 150°C, the viscosity of the powder coating composition when melted becomes high. It becomes difficult to obtain a coating film with a smooth appearance.

The novolac-type phenolic resin used in the present invention is a monohydric phenol, such as phenol,
A resin obtained from the reaction of cresol, xylenol, ethylphenol, p-phenylphenol, p-9-sha9-j boolean phenol, p-octylphenol, p-nonylphenol and formaldehyde, preferably having a hydroxyl equivalent of 100 to 250. Melting point is 50-120
°C, more preferably those having a hydroxyl equivalent of 120 to 180 and a melting point of 60 to 90 °C, and those having a sodium ion and chloride ion content of 30 p'pm or less are preferably used.

When the hydroxyl equivalent of the novolac type phenolic resin is less than 100, the crosslinking density of the coating film obtained by heating, melting, and curing the powder coating composition becomes too high, and the powder coating composition C Second, the heat cycle resistance of the coated parts is reduced.

On the other hand, if the hydroxyl equivalent exceeds 250, the crosslinking density of the coating film becomes too low, and the moisture resistance and high-temperature electrical properties of the coated parts deteriorate.

When the melting point of the novolak type phenolic resin is below 50°C, the powder coating composition tends to block, and when the melting point is above 120°C, the viscosity of the powder coating composition when melted increases. Therefore, a coating film with a smooth appearance can be obtained.

As for the mixing ratio of the epoxy resin and the novolac type phenolic resin, the epoxy resin is preferably 40 to 80% by weight, more preferably 50 to 70% by weight, and the novolac type phenolic resin is preferably 20 to 60% by weight, even more preferably C1 is preferably used in a range of 30 to 50% by weight.

The reason for this is that if the mixing ratio of the epoxy resin and the novolac type phenolic resin deviates from the above range, the reaction will not occur sufficiently, and the powder coating composition will not be heated, melted, and cured (see step 2). This is because electrical properties and mechanical properties deteriorate.

The essential components of the powder coating composition of the present invention have been explained above. You may do so.

Examples of the curing accelerator include known curing accelerators, such as imidazoles and tertiary amines.

Examples of the inorganic filler include known inorganic fillers, such as zircon powder, quartz glass powder, talc powder, calcium carbonate powder, magnesia powder, calcium silicate powder, and lime powder.

The blending ratio of the inorganic filler is approximately 50 to 300 parts by weight per 100 parts by weight of the resin.

An example of a method for producing the powder coating composition of the present invention is a method in which the raw ingredients blended in a predetermined composition ratio are sufficiently mixed in a mixer, melt-kneaded, and then pulverized with aI (2). Ru.

As a method for insulating coating electrical and electronic parts with the powder coating composition C2 of the present invention, general powder coating methods such as fluidized dipping, hot spraying, electrostatic spraying, and electrostatic dynamic dipping can be used. used.

The powder coating composition of the present invention containing an epoxy resin and a novolac type phenol resin as essential components uses an epoxy resin having hydrophobicity, flexibility, and toughness as the resin. Heating, melting, hardening C
The coating film obtained from the second method has extremely excellent properties such as moisture resistance, high temperature electrical properties, and heat cycle resistance.

Furthermore, since the powder coating composition of the present invention uses an epoxy resin having a specific number of functional groups and a specific melting point and a novolac type phenol resin in a specific blending ratio, blocking performance is significantly reduced.
The epoxy resin powder coating composition of the present invention also has excellent properties required for powder coatings, such as good flowability when melted and a coating film with good smoothness. It is suitable for insulating coatings of electrical and electronic components such as capacitors, ceramic capacitors, multilayer ceramic capacitors, resistor networks, hybrid ICs, etc., and it is possible to obtain components with outstanding moisture resistance, heat cycle resistance, etc.

Next (2. The present invention will be further explained in detail by way of examples.

Examples 1 to 3 1) 228 parts of bisphenol A and 120 parts of a 37% formaldehyde aqueous solution were reacted over an acidic catalyst to produce a novolak type bisphenol resin, and then 280 parts of epichlorohydrin and 82 parts of caustic soda were added and reacted, and the mixture was reacted with hydrochloric acid. By soaking and washing with water, epoxy resin A having an epoxy equivalent of 220 and a melting point of 70°C was obtained.

2), 182 parts of bisphenol A and 3 parts of phenol added
A novolak-type bisphenol A1 phenol cocondensation resin was prepared by reacting with 105 parts of a 7% formaldehyde aqueous solution under an acidic catalyst, and then 280 parts of epichlorohydrin was added.
1 part and 82 parts of caustic soda were added and reacted, neutralized with hydrochloric acid and washed with water (from the second step, an epoxy resin B having an epoxy equivalent of 200 and a melting point of 68 DEG C. was obtained.

3), 94 parts of phenol and 60 parts of a 37% formaldehyde aqueous solution were reacted under an acidic catalyst to obtain a hydroxyl equivalent of 105
, Phenol resin A having a melting point of 65°C was obtained.

4) 108 parts of metacresol and 60 parts of a 37% formaldehyde aqueous solution were reacted under an acidic catalyst to obtain a phenol resin B having a hydroxyl equivalent of 124 and a melting point of 69°C.

Next, the obtained epoxy resin, phenol resin, inorganic filler, pigment, and hardening accelerator were blended in the composition ratio (N setting) shown in Table 1 (2), blended and melt-kneaded in a mixer, and then crushed in a crusher C2. (2) to obtain the epoxy resin powder coating composition of the present invention.

Table 1 Comparative Example 1 Bisphenol A type epoxy resin (Bikoat 100)
4. Manufactured by Yuka Shell ■) 320 parts Clay-Lunoporaku type Evokin resin (Evicron N-
670, manufactured by Dainippon Ink and Chemicals) 80 parts alumina powder 588 parts carbon plastic 10 parts imidazole 2 parts were blended in the above composition ratio,
Epoxy resin powder coating compositions were obtained in the same manner as in Examples 1 to 3.

Comparative Example 2 Bisphenol A epoxy resin (Epicote 1004
(manufactured by Yuka NEL) 400 parts Silica powder 588 parts Carbon black 10 parts Imidazole
2 parts were blended in the above composition ratio and Example 1
An epoxy resin powder coating composition was obtained in the same manner as in 3.

The volume resistivity (ρ) of the cured powder coating compositions of Examples 1 to 3 and Comparative Examples 1 to 2 was measured at room temperature and 150°C, and at 12
After vomiting after 300 hours of hygroscopic treatment (PCT) in water vapor at 5°C and 2.3 atm, the results are shown in Table 2 C.
It was as shown in Figure 2.

As is clear from Table 2, the cured product obtained from the powder coating composition of the present invention has significantly greater moisture resistance and high-temperature electrical properties than the conventionally known powder coating composition of Comparative Example 1.2. I can see that it is improving.

Next (=Examples 1 to 3. Powder coating compositions of Comparative Examples 1 to 2 (
2-way fluidized dipping method (60 pieces of Ω7 terminal resistance network are powder-coated on each side and left at 150℃ for a long time, and moisture absorption treatment (PCT) in water vapor at 125℃ and 2.3 atm). The rate of change in resistance over a long period of time, and repeated cooling and heating cycles at -50°C for 30 minutes and 50°C for 30 minutes, were examined to see if any cracks were observed in the powder coating film. The results shown in Table C2 were obtained.

Table 3 - 1 The values in the table are the average values of the resistance change rates of 20 test pieces.

2 The values in the table represent the number of defective pieces out of 20 pieces tested.

As is clear from No. 3&, the resistance network powder-coated with the epoxy resin powder coating composition of the present invention has better high-temperature electrical properties and moisture resistance than that of the resistance network powder-coated with the conventionally known comparative example 1.2. It can be seen that the heat cycle properties and heat cycle properties are extremely excellent.

Furthermore, when electrical and electronic components such as ceramic capacitors and hybrid ICs are powder-coated with the epoxy powder coating of the present invention, the high-temperature electrical Characteristics, moisture resistance,
The result was that the heat cycle resistance was significantly superior.

The obtained epoxy resin powder coating composition of the present invention can be easily powder coated by any coating method such as fluidized dipping, hot spraying, electrostatic dynamic dipping, or electrostatic spraying. The coating with good smoothness was changed to 11Q.

Claims (4)

[Claims] (1) An epoxy resin powder coating composition containing as essential components an epoxy resin which is a glycidyl ether of a condensation product of a phenol containing at least a portion of bisphenol A and formaldehyde, and a novolak type phenol resin. (2) the epoxy resin has an epoxy equivalent of 180 to 450;
Claim No. 1, characterized in that the novolac type phenolic resin has a hydroxyl equivalent of 100 to 250 and a melting point of 50 to 120°C.
The epoxy resin powder coating composition described in . (3) The phenol containing at least a portion of bisphenol A is 50 to 100% by weight of bisphenol A.
The epoxy resin powder coating composition according to claim 1 or 2, characterized in that it comprises 0 to 50% by weight of -valent phenols. (4) Claims (1) and (2) characterized in that the mixture is a mixture of 40 to 80% by weight of epoxy resin and 20 to 60% by weight of novolac type phenolic resin.
The epoxy resin powder coating composition according to item or item (3).