JP2639739B2 - Epoxy resin composition for powder coating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention has stable powder properties, and the obtained cured product has excellent heat resistance and electrical insulation properties. The present invention relates to an epoxy resin composition suitable for impregnating and fixing various coils by a powder coating method.

(Prior art)

Conventionally, amine curing agents such as aliphatic or aromatic polyamines and secondary or tertiary amines have been widely used as curing agents for epoxy resins. However, there is a problem that the amine-based curing agent is strongly irritating to human skin and is not preferable in terms of environmental hygiene. In addition to amine-based curing agents, novolak-based curing agents are also commonly used curing agents, but have the disadvantage that, even if they have good stability due to moisture absorption, their reactivity is slow and the cured products are brittle.

In recent years, acid anhydride-based curing agents such as maleic anhydride, phthalic anhydride, and hexahydrophthalic anhydride have been regarded as important and used. However, this acid anhydride-based curing agent has a large hygroscopic property, requires a high temperature for curing, requires a long time for curing, and evaporates when cured at a high temperature in the case of a low-melting solid acid anhydride. In some cases, high-melting solid acid anhydrides have problems such as insufficient compatibility with epoxy resins.

[Problem of the Invention]

An object of the present invention is to provide a new and improved epoxy resin composition which solves the above-mentioned conventional problems.

[Means for solving the problem]

In order to solve the above-described problems, the present inventors have demonstrated that the composition exhibits good stability during transportation and storage, has a suitable gelation time as a powder material when used, and has excellent adhesion to various adherends. After intensive research on epoxy resin powder compositions that show strength and give cured products with good impact resistance and heat resistance, epoxy resin, novolak resin, acid anhydride, curing accelerator, etc. It has been found that the above problem can be solved by using a composition consisting of the following, and the present invention has been completed.

According to the present invention, (A) 100 to 100 parts by weight of an epoxy resin composed of 40 to 90% by weight of a bisphenol A type epoxy resin and 60 to 10% by weight of a cresol novolac type epoxy resin or a phenol novolak type epoxy resin.
(B) 10-30 parts by weight of acid anhydride, 5-20 parts by weight of novolak resin, (C) 0.1-2 parts by weight of phenol salt of diazabicycloundecene or triphenolphosphine, (D)
20-80 parts by weight of calcium silicate, (E) calcium carbonate
80 to 20 parts by weight and (F) acrylate oligomer
Provided is an epoxy resin-based powder coating composition containing 0.1 to 0.5 part by weight.

That is, the epoxy resin powder coating composition of the present invention has a main feature that calcium silicate and calcium carbonate are used in combination as an inorganic filler to improve its properties.

[Means for solving the problem]

As the epoxy resin used in the present invention, bisphenol A type epoxy resin, bisphenol A type epoxy resin 40 to 90% by weight, novolak type epoxy resin
It is a mixed epoxy resin consisting of 10 to 60% by weight. The novolak type epoxy resin includes cresol novolak type, phenol novolak type and alkylphenol novolak type epoxy resins. When such a mixed epoxy resin of two types is used, a cured product having an appropriate crosslinking density, excellent heat resistance and excellent toughness can be obtained.

As the acid anhydride used as the curing agent, an aromatic acid anhydride is preferable, and specific examples thereof include phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic acid. Acid anhydride, ethylene glycol-anhydrotrimellitate, glycerol-trisanhydrotrimellitate, 5- (2,5-dioxotetrahydrofuryl) -3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride Things can be given.
In the present invention, aromatic carboxylic acid anhydrides are particularly useful among the aromatic acid anhydrides.

Novolak resin used in combination with acid anhydride is synthesized from phenols and formaldehyde,
It contains two or more OH groups in one molecule. Examples of such a resin include a phenol novolak resin, a cresol novolak resin, a t-butylphenol novolak resin, an octylphenol novolak resin, a nonylphenol novolak resin, and a bisphenol novolak resin. Further, the novolak resin used in the present invention, the various novolak resins may be a mixture of the various novolak resins, and in the production thereof, phenol and other phenols, for example, bisphenol A, bisphenol F, butylphenol, A material obtained by reacting formaldehyde with one or more phenols such as nonylphenol as a raw material may be used.

It is advantageous that the acid anhydride used in the present invention is melt-kneaded with the novolak resin in advance and mixed with the novolak resin in advance, whereby the moisture resistance of the composition can be improved.

In the present invention, the above-mentioned acid anhydride and novolak resin are used in combination as a curing agent. The proportion of acid anhydride and novolak resin used for the epoxy resin is 20 to 90% for the acid anhydride and 10 to 90% for the novolak resin, respectively, based on the theoretical addition amount of each.
It is preferable to use them together at a ratio of 80%. The single theoretical addition amount referred to herein means the acid anhydride addition amount obtained from the epoxy equivalent and the acid anhydride equivalent in the acid anhydride.
It is a numerical value multiplied by 85, and in the case of a novolak resin, means the amount of the novolak resin obtained from the epoxy equivalent and the OH equivalent. Specifically, for 100 parts by weight of epoxy resin,
The acid anhydride is used in an amount of 10 to 30 parts by weight, and the novolak resin is used in an amount of 5 to 20 parts by weight.

Further, as the curing accelerator, a phenol salt of diazabicycloundecene or triphenylphosphine is used, and a phenol resin salt of diazabicycloundecene, which is a basic compound, is preferable from the viewpoint of powder stability and reactivity. It is.

The amount of the curing accelerator used is 0.05 to 5.0 parts by weight, preferably 0.1 to 3.0 parts by weight, based on 100 parts by weight of the epoxy resin. If the amount is too small, it takes a high temperature or a long time for curing, which is not practical. Conversely, if the amount is too large, the storage stability of the obtained powder material deteriorates.

Further, an acrylate oligomer is blended as a leveling agent. The amount used is epoxy resin 10
0.1 to 0.5 parts by weight based on 0 parts by weight.

The composition of the present invention may optionally contain a reinforcing agent, a filler, a coupling agent, a flame retardant, a pigment, a colorant, and the like.

The composition of the present invention is prepared by uniformly mixing the above-mentioned essential components and, if necessary, fillers and other additives by a known method.

〔The invention's effect〕

The epoxy resin-based powder coating obtained from the composition of the present invention does not deteriorate due to moisture absorption during storage or transfer, has a suitable gelation time, and can be a coated or uncoated metal or ceramic. The cured product has excellent heat resistance and further excellent electrical insulation.

〔Example〕

 Next, the present invention will be described in more detail with reference to examples.

Examples 1 to 8 and Comparative Examples 1 to 5 A mixture of components (parts by weight) shown in Table 1 was melt-mixed with an extruder and pulverized so as to have a desired particle size distribution. Paint was obtained. Next, these powder coatings were examined for hygroscopicity and gelation time. Further, the cured product obtained by curing this powder coating material was examined for its adhesive strength to an adherend, glass transition temperature, impact strength, and thermal degradation at high temperatures.

In addition, the measurement of each physical property was performed as shown below.

Hygroscopicity (weight increase): 1kg of powder is put in a plastic bag, and the weight increase after standing at 40 ° C, RH80% for 7 days is checked. If the weight increase is 3% or more, × 1% or more and less than 3% , 0.5% or more and less than 1%, ○, and less than 0.5%, ◎.

Hygroscopicity (foaming property): Powder that has absorbed moisture under the above conditions is adhered to a coil preheated to 200 ° C by a flow immersion method and cured at 200 ° C. , Those that are not recognized are indicated by ○.

Gelation time: According to JIS C2104, about 0.1 to 0.2 g of the powder was placed in a circular concave portion of a hot plate kept at 200 ° C., and the time until the powder gelled was measured.

Adhesive strength: Prepare a 3.2 × 20 × 100mm iron plate, heat to 150-160 ° C, apply powder to the position about 12mm from one end in the longitudinal direction, and superimpose the two plates, then superimpose The mating part is sandwiched between pinch cocks and cured at 180 ° C. for 30 minutes to produce a test piece. This is pulled by a universal tensile tester at a pulling speed of 5 mm / min.
Was used to measure the shear bond strength.

Glass transition temperature: A cylindrical cured product having a diameter of 3 mm and a length of 10 mm is produced. The curing temperature is 180 ° C for 30 minutes. Test specimen at 5 ℃ with TMA
/ min, the thermal expansion curve was determined, and the inflection point of the curve was defined as the glass transition temperature. The compression load of TMA was 10 g.

Impact strength: An iron plate of 60 × 60 × 3.2 mm was coated by a fluid immersion method so that the thickness of the coating film was 0.5 mm. The preheating temperature is 160 ° C and the curing conditions are 180 ° C for 30 minutes. Using a DuPont impact tester, a test was conducted under the conditions of a load of 1 kg and a hammer head of 1/8 inch, and the maximum height at which the coating film did not crack was determined.

Heat resistance: A test piece similar to the impact test is left in an oven at 450 ° C. for 5 minutes, taken out, and gradually cooled to room temperature. The state of the coating film was visually observed and evaluated as follows. ：: no change (ignoring discoloration of the coating film), △: slightly cracked and blistered, ×: cracked, blistered and carbonized.

The specific contents of the components shown in Table 1 are as follows.

Epoxy resin (1): Bisphenol A type epoxy resin, epicoat trade name
1001, Yuka Shell Epoxy Co., Ltd. Epoxy resin (2): Bisphenol A type epoxy resin, trade name Epicoat
1002, Yuka Shell Epoxy Co., Ltd. Epoxy resin (3): Bisphenol A type epoxy resin, trade name Epicoat
1007, novolak epoxy resin manufactured by Yuka Shell Epoxy Co., Ltd .: o-cresol novolak epoxy resin, trade name E180
S90, manufactured by Yuka Shell Epoxy Co., Ltd. Calcium silicate: average particle size 5.5 to 8.9 μm, trade name SW-400: manufactured by Tatsumori Co., Ltd. Calcium carbonate: average particle size 6.2 μm, trade name KC-30A, Katakura Acrylic ester manufactured by Ticcarin Co., Ltd .: viscosity 1300 cp (25 ° C.), refractive index 1.464, trade name Nicalite XK-21, Nippon Carbide Industry Co., Ltd. Butyral resin: polyvinyl butyral resin, trade name Eslek BLS,
Sekisui Chemical Co., Ltd. Acid anhydride (1): benzophenonetetracarboxylic anhydride Acid anhydride (2): 5- (2,5-dioxotetrahydrofuryl) -3-methyl-3-cyclohexene-1,2 -Dicarboxylic anhydride, trade name EXB-4400, Dainippon Ink Co., Ltd. acid anhydride (3): reaction product of dicyclopentadiene and maleic anhydride, trade name Admarb DM-55, Idemitsu Petrochemical Co., Ltd. Novolak resin (1): Orthocresol novolak resin: trade name OCN-120,
Novolak resin (2) manufactured by Nippon Kayaku Co., Ltd .: Alkylphenol novolak resin: Trade name: Tamanoru
KP-757B, Arakawa Chemical Co., Ltd. Curing accelerator (1): Triphenylphosphine fin Curing accelerator (2): Phenolic resin salt of diazabicycloundecene, trade name Ucat-831, manufactured by San Avro Co., Ltd.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Seitaro Iwamoto 4-11-2 Ginza, Chuo-ku, Tokyo Inside Somaru Corporation (72) Inventor Kunimitsu Matsuzaki 4-11-2 Ginza, Chuo-ku, Tokyo (56) References JP-A-58-198524 (JP, A) JP-A-1-210419 (JP, A) JP-A-58-113267 (JP, A) JP-A-61-55113 (JP) JP, A) JP-A-61-89271 (JP, A) JP-A-63-161018 (JP, A) JP-A-51-73537 (JP, A) JP-A-58-198525 (JP, A)

Claims (1)

(57) [Claims] 1. A bisphenol A type epoxy resin (A)
(B) 10-30 parts by weight of an acid anhydride and 5-20 parts of a novolak resin per 100 parts by weight of an epoxy resin comprising -90% by weight and 60 to 10% by weight of a cresol novolak type epoxy resin or a phenol novolak type epoxy resin. Parts by weight, (C)
0.1 to 2 parts by weight of phenol salt of diazabicycloundecene or triphenylphosphine, 20 to 80 parts by weight of (D) calcium silicate, 80 to 20 parts by weight of (E) calcium carbonate, and 0.1 to 10 parts by weight of (F) acrylate oligomer An epoxy resin-based powder coating composition containing 0.5 part by weight.