JP2000191952A - Flame-retardant epoxy resin powder coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject powder coating not having a problem of discoloration, capable of effectively giving a flame-retardant property at an appropriate compounding of components and not deteriorating characteristics such as curing property by compounding a specific phosphor-containing compound as a flame- retardant in a specified ratio. SOLUTION: This flame-retardant epoxy resin powder coating contains (A) an epoxy resin, (B) a curing agent, (C) a filler and (D) a flame-retardant as essential components, wherein a phosphor-containing compound expressed by the formula (9-10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) is compounded as the component D in an amount of 1.5-3.5 wt.% converted to a phosphor content and based on the total weight of the component A and the component B. It is preferable that the main component of the component B is an acid anhydride curing agent such as an aromatic acid anhydride, especially preferably benzophenonetertacarboxylic acid, and further that the acid anhydride curing agent is compounded in an amount of 0.8-1.6 equivalent per equivalent of the component A.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flame-retardant epoxy resin powder coating having excellent flame retardancy without using a halogen-based flame retardant.

[0002]

2. Description of the Related Art Epoxy resin powder coatings used for insulating coating of electric and electronic parts are required to have high flame retardancy in order to ensure the safety of parts against fire. I have. For this reason, various compounds imparting flame retardancy are blended in the components of the powder coating.
A non-flammable inorganic filler that reduces the amount of flammable resin components, especially a filler that contains water of crystallization and emits fire during combustion to exhibit a flame-retardant effect, such as aluminum hydroxide and magnesium hydroxide A variety of methods have been proposed and implemented, such as a method of compounding a large amount of such a compound, or a method of modifying with a low flammable silicone resin or a cyanurate ring resin. This is a method of blending a flame retardant. Among these halogen compounds, aromatic bromine compounds exhibit a remarkable fire-extinguishing effect because hydrogen bromide generated during combustion shields the periphery of combustibles from oxygen with a heavy non-flammable gas and dilutes combustible gas. However, on the other hand, it has been pointed out that this hydrogen bromide is corrosive and, when thermally decomposed in the presence of oxygen, forms highly toxic polybromodibenzofuran and polydibromodibenzooxin similar to the highly toxic dioxin structure. Under such circumstances, a flame-retardant material agent containing no halogen compound has been desired.

[0003] For this reason, in recent years, as a flame retardant instead of a bromine compound, phosphorus compounds which exhibit a dehydrating action and a shielding effect by char formation during combustion have been widely studied, and inorganic red phosphorus and various organic phosphate esters have been used. ing.
However, since this red phosphorus compound has a dark reddish brown color, it is unsuitable for light colors such as blue, yellow and green, which are one of the features of epoxy resin powder coatings, when used in epoxy resin powder coatings. There is a disadvantage that it is limited to a dark color.In the case of various phosphoric acid ester blends, the curability is greatly reduced, and the phosphoric ester compound is decomposable under moisture absorption treatment. The moisture resistance of the film is greatly reduced, and it is difficult to say that the film is suitable for practical use.

[0004] As phosphorus compounds imparting flame retardancy, various compounds have been proposed in addition to red phosphorus and phosphate esters. For example, inorganic phosphates such as ammonium phosphate are said to have a flame retardant effect in some applications, but effective results can be obtained with powder coatings that require a high degree of flame retardancy. Can not. On the other hand, it has been proposed to synthesize various novel epoxy resins containing phosphorus in the structure and to apply this resin. However, since these resins all have a low phosphorus content of 3% or less, they are also flame-retardant. Is inadequate.

[0005]

The inventors of the present invention have intensively studied other phosphorus-containing compounds in order to solve the above-mentioned problems. The present inventors have found that 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide has no coloring problem, and that by adding an appropriate amount thereof, the effect of imparting flame retardancy is high, thereby achieving the present invention. An object of the present invention is to provide an epoxy resin powder coating which has high flame retardancy without blending a halogen compound and does not impair properties such as curability and moisture resistance.

[0006]

That is, the present invention relates to an epoxy resin composition containing an epoxy resin, a curing agent, a filler, and a flame retardant as essential components. A flame-retardant epoxy resin powder coating characterized in that the phosphorus content is 1.5 to 3.5% based on the total amount (weight ratio) of the resin and the curing agent.

[0007]

Embedded image

The compounding amount of this compound is 1.5 to 3.0 as a phosphorus content with respect to the total amount of the epoxy resin and the curing agent.
5%. If it is less than 1.5%, the flame retardancy is insufficient.
If it exceeds 5%, there is a problem that the curability is insufficient even if the measures described later are taken, and the moisture resistance is lowered.

The compound of the formula (1) has a highly reactive P in the molecule.
It has been found that the presence of the -H bond inhibits the curing reaction between the epoxy resin and the curing agent component and significantly reduces the curability of the epoxy resin powder coating. Therefore, as a result of intensive studies to solve this problem, a phosphorus-containing compound obtained by an addition reaction of the compound of Formula 1 with a compound having a double bond such as an unsaturated methylene group is used as a main component of the flame retardant. It has been confirmed that the curability and the properties of the cured product are not inferior to those of the conventional product while imparting a high degree of flame retardancy by application.

As the compound having an unsaturated methylene group suitable for this purpose, various vinyl compounds such as styrene and acrylic acid are suitable, and the desired compound can be easily prepared by mixing the compounds in an equivalent amount and subjecting them to an addition reaction by heating. Is obtained. However, in these reactions, it is necessary to carry out the reaction in an appropriate solvent in order to ensure a uniform reaction.After the reaction, the solvent is removed, unreacted components are removed, and only the reaction product is isolated with high purity. Must be purified. In addition, the reaction product is often a substance having a high melting point, and it is often difficult to blend this into a powder coating material to perform uniform melt mixing.

Accordingly, as a result of intensive studies on the use of the compound of the formula 1 having a large effect of imparting flame retardancy without performing the above-mentioned reaction, the curing agent, especially an aromatic compound, used for curing the epoxy resin is used. In the case of an acid anhydride, it has been found that the curability can be improved to a practical level by blending a larger amount than usual. This is presumed to be because the compound of Formula 1 undergoes an addition reaction with a part of the curing agent during the melt mixing process, but an appropriate amount of the curing agent remains, and the reaction between the epoxy resin and the curing agent proceeds normally. You. For this reason, it is considered that the amount of the curing agent to be added more than usual is generally proportional to the amount of the compound of formula 1, and good curability is realized by increasing the amount by 0.2 to 0.4 equivalents more than usual. it can. That is, the acid anhydride curing agent is usually added in an amount of 0.6 to 1.2 equivalents to the epoxy resin component, but when the compound of the formula 1 is added for imparting flame retardancy, 0.8 to 1.6 equivalents. It is appropriate to mix the equivalent amount.

As the epoxy resin in the present invention, 1
As long as it has at least two epoxy groups in the molecule and is a non-halogenated epoxy resin, it may be a solid at room temperature applied to a general epoxy resin powder coating, for example, bisphenol A type, Examples include bisphenol F type, bisphenol S type, phenol novolak type, cresol novolak type, biphenyl type, naphthalene type, and aromatic amine type, but are not particularly limited thereto. These can be used alone or in combination of two or more.

As the curing agent in the present invention, the main component is an acid anhydride, and an aromatic acid anhydride is particularly preferred. If this acid anhydride curing agent is blended in an amount of 50% or more, preferably 70% or more. Alternatively, one or more other curing agents may be used in combination. Specific examples are adipic acid, phthalic acid, maleic acid, trimellitic acid, benzophenone dicarboxylic acid, polydicarboxylic acids such as pyromellitic acid or acid anhydrides thereof, or phenol, cresol, and novolak resin containing xylenol as a phenol source. Illustrated. If necessary, a curing accelerator such as a tertiary amine, imidazole, or an organic phosphorus compound may be used for these curing agents.

Further, as a filler, calcium carbonate, calcium sulfate, barium sulfate, aluminum hydroxide, magnesium hydroxide, aluminum oxide, crystal or fused silica, talc, kaolin, clay, mica, dolomite,
In addition to using wollastonite, glass fiber or glass beads, zircon, titanium compounds, molybdenum compounds, etc., alone or in combination, various additives such as various pigments, leveling agents, coupling agents and defoaming agents are appropriately compounded. Further, in order to enhance the flame retardancy, a resin having a cyanurate ring skeleton such as a silicone resin or a melamine resin or a non-halogen flame retardant auxiliary such as antimony trioxide, zinc borate, or expandable graphite can be appropriately used. .

In the present invention, the method for producing these powder coating compositions is not particularly limited, and a general method may be used. As an example, a method in which the raw material components mixed in a predetermined composition ratio are sufficiently uniformly mixed by a mixer, then melt-mixed by an extruder or a twin-screw kneader, and then pulverized to an appropriate particle size by a pulverizer and classified. Is exemplified. The particle size distribution obtained by pulverization and classification is a very important item in order to obtain a coating workability and a uniform coating appearance of the powder coating, but the present invention is not particularly limited.

[0016]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples. The raw material components are blended by a mixer at a composition ratio (parts by weight) shown in Table 1, melt-kneaded, and pulverized by a pulverizer.
An epoxy resin powder coating having an average particle size of 40 to 60 μm was obtained.

[0017]

[Table 1]

(Materials Used) Epoxy resin ・ EP-1003 (made by Yuka Shell Epoxy) Bisphenol A type Epoxy equivalent 800 2. Curing agent-BTDA benzophenone tetracarboxylic anhydride-PMDA pyromellitic anhydride-Novolac resin PR-51470 (manufactured by Sumitomo Durez)-2MZ 2-methylimidazole Filler ・ Fused silica RD-8 (made by Tatsumori) Pigment ・ White pigment Titanium oxide (Ishihara Sangyo) ・ Blue pigment Cyanine blue (Sumitomo Seika) 5. Additives-Silane coupling agent A-187 (manufactured by Nippon Unicar) Flame retardant • 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide • Phosphate PX-200 (manufactured by Daihachi Chemical)

(Test Method) Gel time: hot plate method at 165 ° C (JIS C 21
61) 2. 2. Flame retardancy: UL94 method (test plate thickness 1 mm) Moisture resistance: A 0.6 mm thick powder-coated ceramic capacitor was treated at 121 ° C. for 2 hours, and then judged by insulation resistance. ：: over 10 ¹² Ω, Δ: 10 ¹² to 10 ¹¹ Ω, ×: 10
Less than ¹¹ Ω

In Examples 1 and 2, epoxy resin 1.
Example 3 in which 1.0 equivalent of an aromatic acid anhydride was blended with respect to 0 equivalent, and the compound of the formula 1 was further distributed at a phosphorus content of 2.7% with respect to the total amount of the epoxy resin and the curing agent. Is an acid anhydride and novolak as a curing agent in an equivalent ratio of 80/20.
The amount of the curing agent is 1.0 equivalent to 1.0 equivalent of the epoxy resin, which is higher than usual, and all of them have a high degree of flame retardancy. Various properties required for powder coatings such as moisture resistance are also excellent. In Example 4, the amount of the acid anhydride curing agent was as small as 0.7 equivalent, and the curability was slightly lowered, but there was no practical problem.

On the other hand, in the comparative example, there are problems in various items, and it is difficult to apply the present invention to a powder coating. Comparative Example 1 is a case where the phosphorus content is as small as 1.2%, and the flame retardancy is insufficient. Comparative Example 2 was a case where the phosphorus content was as high as 4.0%, and although the flame retardancy was high, the curing was slow and the moisture resistance was low. In Comparative Example 3, a phosphate ester having a high effect of imparting flame retardancy was blended, but the moisture resistance was significantly reduced.

[0022]

According to the present invention, a conventional epoxy resin powder coating for electric insulation uses a halogen-containing compound such as bromine or an antimony-based flame retardant, which has been pointed out as an environmental problem for imparting flame retardancy. An object of the present invention is to provide a flame-retardant epoxy resin powder coating which imparts excellent flame-retardant properties without having to do so and has excellent properties such as curability and moisture resistance.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09K 21/12 C09K 21/12 // C08L 63/00 C08L 63/00 CF Term (Reference) 4H028 AA35 AA42 BA06 4J002 CD031 CD051 CD061 DE077 DE147 DE237 DG057 DJ007 DJ017 DJ037 DJ047 DJ057 DL007 EF026 EF056 EF116 EF126 FA047 FA087 FD017 FD146 GH01 HA09 4J038 DB001 GA14 JA75 JC26 KA03 KA08 MA02 NA15

Claims (3)

[Claims] 1. An epoxy resin composition containing an epoxy resin, a curing agent, a filler, and a flame retardant as essential components, wherein a phosphorus-containing compound represented by the formula 1 is used as a flame retardant in a total amount (weight ratio) of the epoxy resin and the curing agent. A flame-retardant epoxy resin powder coating, characterized in that the composition contains 1.5 to 3.5% of a phosphorus content with respect to the above (1). Embedded image 2. The flame-retardant epoxy resin powder according to claim 1, wherein the main component of the curing agent is an acid anhydride curing agent, and the compounding amount thereof is 0.8 to 1.6 equivalents to the epoxy resin. paint. 3. The flame-retardant epoxy resin powder coating according to claim 1, wherein the acid anhydride curing agent is an aromatic acid anhydride.