JPH06116514A - Flexible powder coating composition - Google Patents

Abstract

PURPOSE:To obtain a flexible powder coating composition having excellent coating film strength, wet-heat resistance, heat-resistance, chemical resistance, bonding strength and heat-cycling resistance and useful as an electrical insulating material, etc., by using an epoxy resin, a specific curing agent and a cure accelerator as essential components. CONSTITUTION:The composition contains, as essential components, (A) an epoxy resin such as a bisphenol A epoxy resin, (B) a curing agent obtained by mixing (i) a phenolic aralkyl resin of formula I (R1 is H or methyl; l is 1 or 2; p is 0-10) and (ii) a bisphenol compound of formula II (R2 is H, methyl, aryl, etc.; n is 1 or 2; X is methylene, propylidene, etc.) or formula III (R3 is H or methyl; n is 1 or 2) at an equivalent ratio (i/ii) of (10-100)/(90-0) and (C) preferably 0.5-3 pts.wt. (based on 100 pts.wt. of the component A) of a cure accelerator such as 2-methylimidazole. The amount of the component B is preferably 0.8-1.1 equivalent based on 1 equivalent of the component A.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is used as a powder coating, and particularly when a film capacitor coated with the coating is subjected to a safety test, the coating does not break, and the resistance to moisture and heat, heat resistance and chemical resistance are high. The present invention relates to a flexible powder coating composition which gives coating film properties excellent in properties, adhesive strength and heat cycle properties.

[0002]

2. Description of the Related Art Heretofore, as a powder coating material used as an electric insulating material for a ceramic capacitor, a film capacitor, a resistor network, a coil product such as an inductor, and an electronic / electrical component such as a hybrid IC, there has been disclosed, for example, Japanese Patent Laid-Open No.
As shown in No. 1-89271, (A) an epoxy resin having a melting point of 50 to 150 ° C. (B) one or more acids selected from trimellitic anhydride, pyromellitic dianhydride, and benzophenone tetracarboxylic anhydride An anhydride-based curing agent (C) triphenylphosphine (D) inorganic filler is known to be contained as an essential component. Electronic
Electrical parts are coated with the above powder coatings by a coating method such as fluidized-bed immersion method, electrostatic fluidized-bed immersion method, etc., and are widely used as an exterior method which is advantageous in terms of productivity, economy and pollution-free. I've been.

However, with the trend toward higher reliability of electronic / electrical parts, the powder coating used for the insulation coating is deteriorated or damaged in terms of electrical and mechanical characteristics in a pressure cooker test and a heat cycle test. What is not required is required. In the case of film capacitors, when charging and discharging are repeated under overvoltage, there is a phenomenon that the coating film expands and breaks, causing insulation failure. In Japan, JIS C 4901 "low voltage phase advance capacitor" is standardized in the safety test. There is. However, the powder coating having the above composition has a hard coating film, so that the coating film is destroyed when subjected to the safety test,
It is extremely difficult for the coating film not to be destroyed and to satisfy other electrical and mechanical characteristics as required for powder coating material in order to maintain safety.

On the other hand, in order to meet these requirements, it has been attempted to give flexibility by using a linear aliphatic epoxy resin, an aliphatic acid anhydride type curing agent, and a flexible phenol novolac resin. In the case of such a powder coating, although the heat cycle resistance is good, it is inferior in moist heat resistance and heat resistance, and at the same time, when the film capacitor is subjected to the safety test, the coating film may be destroyed. However, since it is inferior, there are many problems as an insulating material for electronic parts, and it has been difficult for conventional techniques to simultaneously satisfy the wet heat resistance, coating film strength, heat cycle resistance, and heat resistance 1.

[0005]

[Problems to be Solved by the Invention] Moisture and heat resistance, coating film strength,
Powder coating that satisfies heat cycle resistance and heat resistance at the same time, in particular, the coating film does not break when the film capacitor coated with this is subjected to the safety test, and the heat and humidity resistance is high.
A powder coating having excellent heat cycle property is desired.

[0006]

The inventors of the present invention have reached the present invention as a result of intensive studies to solve the above-mentioned problems. That is, the present invention relates to a powder coating containing an epoxy resin, a curing agent and a curing accelerator as essential components, and a phenol aralkyl resin represented by the formula (1) as a curing agent, and a formula (2) or a formula (3). There is provided a flexible powder coating composition using the indicated bisphenols in an equivalent ratio of 10-100 / 90-0.

[0007]

[Chemical 4]

(R ₁ represents a hydrogen atom or a methyl group,
Represents 1 or 2, and p represents an integer of 0 to 10. )

[0009]

[Chemical 5]

(R ₂ represents a hydrogen atom, a methyl group, an aryl group, or halogen, n represents 1 or 2. X represents a methylene group, a propylidene group, an isopropylidene group, a sulfonyl group, a cyclohexylidene group, or Represents an oxygen atom.)

[0011]

[Chemical 6]

(R ₃ represents a hydrogen atom or a methyl group, and n
Represents 1 or 2. ) The powder coating material of the present invention will be described in detail. The epoxy resin used in the present invention may be one having at least two epoxy groups in the molecule, and conventionally known epoxy resins can be used. Examples of such epoxy resin include bisphenol A type epoxy resin, halogenated bisphenol A type epoxy resin, bisphenol F type epoxy resin,
Phenol novolac type epoxy resin, cresol novolac type epoxy resin, halogenated phenol novolac type epoxy resin, biphenyl type epoxy resin, resorcin type epoxy resin, tetrahydrophenylethane type epoxy resin, polyolefin type epoxy resin, alicyclic epoxy resin, triglycidyl Isocyanate and the like can be mentioned. Particularly preferred are bisphenol A type epoxy resin, bisphenol F type epoxy resin, halogenated bisphenol A type epoxy resin and biphenyl type epoxy resin. This component may be used alone or in combination of two or more.

The phenol aralkyl represented by the formula (1) used in the present invention is obtained by linking phenol with a p-xylene structure. Usually, the phenols of the formula (4) and the aralkyl ether of the formula (5) are used as raw materials. (Α, α′-dimethoxyparaxylene) can be obtained by condensation by Friedel-Crafts reaction. Mirex XL-225 manufactured by Mitsui Toatsu is used as a raw material from phenol.

[0014]

[Chemical 7]

(R ₁ represents a hydrogen atom or a methyl group,
Represents 1 or 2. )

[0016]

[Chemical 8]

The bisphenols of the formula (2) used in the present invention include 4,4'-isopropylidenediphenol and di (4-hydroxy-3,5-dimethylphenyl).
Isopropane, di (4-hydroxy, 3,5-dibromophenyl) isopropane, 4,4'-propylidenediphenol, 4,4'-diphenolmethane, 1,1'-
Bis (p-hydroxyphenyl) cyclohexane, 4,
4'-dihydroxybiphenyl ether, 4,4'-diphenol sulfone, 3,3'-diallyl 4,4'-
Dihydroxydiphenyl sulfone, 3, 3 ', 5,
5'-tetramethyl 4,4'-dihydroxydiphenyl sulfone, 3,3 ', 5,5'-tetrabromo 4,
4'-dihydroxydiphenyl sulfone, 4,4'-
Dihydroxybiphenyl, 2,2 ', 6,6'-tetramethyl 4,4'-dihydroxybiphenyl and the like can be mentioned. Particularly preferred are 4,4'-isopropylidenediphenol, 4,4'-diphenolmethane, 4,
They are 4'-diphenol sulfone and 4,4'-dihydroxybiphenyl ether. The phenol aralkyl represented by the formula (1) and the bisphenol represented by the formula (2) or the formula (3) are used in an equivalent ratio of 100 to 10/0 to 90, preferably 100 to 20/0 to 80. To be done. When 90% or more of bisphenol is used, the cured product foams and cannot be used. The amount of the above phenols to be used with respect to the epoxy resin is such that the phenols are used in an equivalent ratio of 0.6 to 1.2, preferably 0.8 to 1.1, relative to the epoxy resin.

The curing accelerator used in the present invention includes:
2-methylimidazole, 2-phenylimidazole,
2,4-diamino (2-methylimidazole (1))-
Imidazoles such as s-ethyltriazine, amides such as dicyandiamide, 1,8-diazabicyclo (5,5)
4,0) diazas such as undecene-7 and salts thereof, phosphines such as triphenylphosphine, 2, 4,
6, and phenols such as trisaminomethylphenol can be mentioned, but phosphines and imidazoles are preferable. The mixing ratio of these curing accelerators is
0.2 to 5 parts by weight with respect to 100 parts by weight of the epoxy resin,
The proportion is preferably 0.5 to 3 parts by weight.

If necessary, an inorganic or organic filler is added to the composition of the present invention. Examples of the filler include conventional fillers such as silica, calcium carbonate, alumina, mica, talc, clay, aluminum hydroxide, calcium silicate, glass fiber and carbon fiber. The use of silica is preferred in order to obtain a powder coating having improved heat cycle resistance. The average particle size of the filler is 0.
It is 5 to 75 μ, preferably 2 to 50 μ. This filler is usually 0-10 with respect to 100 parts by weight of the epoxy resin.
It is used in an amount of 0 parts by weight, preferably 0 to 80 parts by weight. When it is used in an amount of 100 parts by weight or more, the flexibility is lost and the coating film is broken when it is subjected to the safety test. The filler may be surface-treated with a coupling agent.
As the coupling agent, a silane coupling agent, a titanate coupling agent, and an aluminum coupling agent are used, and a silane coupling agent and a titanate coupling agent are preferable. In addition to the purpose of the powder coating composition of the present invention,
A flame retardant, a coloring agent, a leveling agent, a defoaming agent, etc. can be added as appropriate.

To prepare the epoxy resin powder coating composition of the present invention, an epoxy resin of the formula (1) (2) or (3) is used.
The phenols and curing accelerators shown in 1 above are dry-mixed together with other compounding ingredients such as a filler using a Henschel mixer or the like, and then melt-mixed by a kneader or melt-mixed by an extruder. After that, the mixture may be solidified by cooling, finely pulverized and then classified. The particle size of the obtained powder coating composition is usually 10 to 150 µ.

The composition of the present invention can be electrically applied by various known coating methods such as a fluidized-bed method, an electrostatic fluidized-bed method, an electrostatic spray method, a sprinkling method, a rolling method, a spray method, a thermal spray method, and a fog box method. -Painted on electronic parts. Painting conditions are usually 8
It is 0 to 200 ° C. The powder coating composition of the present invention is excellent in coating film physical properties that do not break even when subjected to the safety test of film capacitors, moisture resistance, heat resistance, chemical resistance, adhesive strength, heat cycle property, and Although it is most suitable for coating electric parts (capacitors, hybrid ICs, varistors, thermistors, etc.), it can also be used for other coatings.

[0022]

EXAMPLES The present invention will be described in more detail by way of examples, but the present invention is not limited to these examples. In Examples and Reference Examples, "part" means part by weight.

Examples 1 to 7 and Comparative Examples Mixtures having the component composition (weight ratio, parts) shown in Table 1 were melt-mixed using a twin-screw kneader, and the obtained mixture was cooled, solidified, and then pulverized, The epoxy resin powder coating composition of the present invention was obtained through a 100-mesh sieve. Then, using those epoxy resin powder coating composition, 140 ℃
The film capacitor preheated to 60 is
After coating to a film thickness of 0 μ, it was cured under conditions of 105 ° C. for 2 hours, and its physical properties were evaluated. The results are shown in Table 1. The following products were used as the compounding ingredients shown in Table 1.

Epoxy resin (1): Epomic R-30
7 (Mitsui Petrochemical) Epoxy resin (2): Epotote YD-904 (Toto Kasei) Epoxy resin (3): Epomic R-302 (Mitsui Petrochemical) Epoxy resin (4): ESB-400T (Sumitomo Chemical) Phenol aralkyl: Millex XL-225 (manufactured by Mitsui Toatsu) Bisphenol (1): Bisphenol S Bisphenol (2): Bisphenol F Bisphenol (3): Bisphenol A Bisphenol (4): 4,4'-Dihydroxybiphenyl ether PAPA : Polyazelaic anhydride (manufactured by Shin Nippon Rika) PN-152: Phenol novolac resin (manufactured by Nippon Kayaku) TPP: Triphenylphosphine 2-MZ: Shikoku Kasei (2-methylimidazole) Silica: manufactured by Tatsumori ( RD-8) Leveling agent: Modaflow (Monsanto Made Michal)

The method of evaluating the performance of a coated product obtained by coating the epoxy resin powder coating composition of the present invention is as follows. The obtained results are shown in Table 1. (Safety test) JIS C 4901 8.17 using the film capacitors obtained in the respective examples and comparative examples.
The test was conducted according to the safety test, and those without cracks were marked with ◯, and those with cracks were marked with x. (Humidity and heat resistance) Using the film capacitors obtained in each of the examples and each of the comparative examples, it was measured at 85 ° C. and 95% relative humidity.
The change in the capacitance of the capacitor after standing for 00 hours was examined. 5%
If the following rate of change is ○, 5% or more rate of change is ×
And

[0026]

[Table 1] Actual examples Comparative examples 1 2 3 4 5 6 7 1 2 Epoxy resin (1) 40 40 40 Epoxy resin (2) 80 70 80 80 80 80 Epoxy resin (3) 40 40 40 Epoxy resin (4) 20 30 20 20 20 20 20 20 20 Phenol aralkyl 12.0 18.7 9.6 16.9 19.4 12.1 24.1 Bisphenol (1) 16.7 11.1 Bisphenol (2) 8.1 6.7 Bisphenol (3) 6.1 Bisphenol (4) 13.6 PAPA 16.1 PN-152 14.1 TPP 1 1 1 1 0.3 2-MZ 0.7 0.7 0.7 0.7 Antimony trioxide 6.7 6.7 6.7 6.7 6.7 6.7 6.7 6.7 6.7 Modaflow 1 1 1 1 1 1 1 1 1 1 Safety test results ○ ○ ○ ○ ○ ○ ○ × × Moisture and heat resistance ○ ○ ○ ○ ○ ○ ○ × ×

As is apparent from Table 1, the powder coating composition of the present invention has a coating film strength that can withstand the safety test and is also excellent in wet heat resistance.

[0028]

EFFECT OF THE INVENTION Having a coating film strength that can withstand a safety test,
Moreover, a flexible powder coating composition excellent in wet heat resistance was obtained.

Claims (1)

[Claims] 1. A powder coating comprising an epoxy resin, a curing agent and a curing accelerator as essential components, wherein the curing agent has the formula (1)
A phenol aralkyl resin represented by the formula (1) and a bisphenol represented by the formula (2) or the formula (3) in an amount of 10 to 100
Flexible powder coating composition used in an equivalent ratio of / 90 to 0 (R ₁ represents a hydrogen atom or a methyl group, l represents 1 or 2, and p represents an integer of 0 to 10.) (R ₂ represents a hydrogen atom, a methyl group, an aryl group, or halogen, n represents 1 or 2. X represents a methylene group, a propylidene group, an isopropylidene group, a sulfonyl group, a cyclohexylidene group, or an oxygen atom. It represents.) (R ₃ represents a hydrogen atom or a methyl group, and n represents 1 or 2.)