JP2001002960A - Flame retardant epoxy resin powder coating material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject powder coating material enabling high grade flame retardancy to be exhibited without using a halogen-containing compound and also impairing hardenability, moisture resistance, etc., by compounding a specific phosphorus-containing compound in a solid state at normal temperature as a flame retarder. SOLUTION: This powder coating material comprises (A) an epoxy resin, (B) a curing agent, (C) a filler and (D) a flame retarder which is a phosphorus- containing compound of formula I [wherein Ys are each an epoxy group of formula II or the like; and X is a group of formula III (wherein R is H or methyl) or the like; and (n) is 1-3] as essential ingredients. The compound of formula I is easily obtained by the addition reaction of a compound having two or more epoxy groups at its end and an epoxy equivalent of <=250 and being in a liquid state at normal temperature with a compound of formula IV. The powder coating material preferably contains >=50 wt.% of the compound of formula I (wherein one or two of Ys are each terminal epoxy group). The powder coating material preferably comprises 1.5-3.5 wt.% of the ingredient D based on the total weight of ingredients A, B and D.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an 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 electrical and electronic parts are required to have a high degree of flame retardancy in order to ensure the safety of parts against fire. . For this reason, various compounds imparting flame retardancy are blended in the components of the powder coating. It contains a large amount of non-flammable inorganic fillers, especially aluminum hydroxide, magnesium hydroxide, etc., which contain a water of crystallization and emit this during combustion to exhibit a flame-retardant effect. Various methods have been proposed and implemented, such as a method and a method of modifying with a low flammable silicone resin or a cyanurate ring resin, but the most widely practiced is a method of blending various halogen-based flame retardants. .

Among these halogen compounds, aromatic bromine compounds exhibit a remarkable fire-extinguishing effect by diluting the combustible gas with hydrogen bromide generated during combustion, which is a non-flammable heavy gas that shields the periphery of combustibles from oxygen. However, on the other hand, it has been pointed out that this hydrogen bromide is corrosive, and that when thermally decomposed in the presence of oxygen, it forms highly toxic polybromodibenzofuran and polydibromodibenzooxin similar to a highly toxic dioxin structure. Under such circumstances, a flame-retardant system containing no halogen is desired.

[0004] For this reason, in recent years, as a flame retardant instead of a bromine compound, phosphorus compounds which exhibit a heat-shielding effect due to the formation of char as well as dehydration during combustion have been widely studied, and inorganic red phosphorus and various organic phosphate esters have been used. Have been. However, since the red phosphorus compound exhibits a dark reddish brown color, it is unsuitable for light colors such as blue, yellow, and green, one of the features of epoxy resin powder coatings, when used in epoxy resin powder coatings. There is an inconvenience limited to the dark color of the system. In any of the various phosphate ester formulations, the curability is greatly reduced, and the phosphate ester compound is decomposable under moisture absorption treatment. Therefore, the moisture resistance of the coating film in which the phosphate ester compound is blended is greatly reduced, which is not suitable for practical use.

[0005] 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 the same. However, since these resins all have a low phosphorus content of 3% or less, they are also flame-retardant. Is inadequate.

[0006]

The inventors of the present invention have intensively studied other phosphorus-containing compounds in order to solve the above-mentioned problems. As a result, 9,10-dihydro-9-oxa-1 represented by the formula (3) was obtained.
It has been found that 0-phosphaphenanthrene-10-oxide is highly effective in imparting flame retardancy. However, since this compound has a highly reactive PH bond in the molecule, it reacts with the epoxy resin, hinders the curing reaction between the epoxy resin and the curing agent component, and significantly reduces the curability of the epoxy resin powder coating. Let it. In order to remove this reaction activity, attempts have been made to mix a compound which has been previously subjected to an addition reaction with a novolak type epoxy resin as a flame retardant, but since this flame retardant has a high melting point and a high melt viscosity, powder coating products And the paintability is reduced.

The present inventors have conducted intensive studies to solve these problems, and as a result, have found that a compound containing an epoxy group, which is incompatible with powder coatings because it is liquid at room temperature, has the formula (3)
It is found that a phosphorus-containing compound which is solid at room temperature can be obtained by an addition reaction of the above compound, and when this phosphorus-containing compound is applied as a flame retardant in a powder coating, a high degree of flame retardancy is imparted with a small amount of addition. And found that the curability, paintability and cured product properties were comparable to those of conventional products.
The present invention has been completed based on these findings. An object of the present invention is to provide an epoxy resin powder coating which has high flame retardancy without blending a halogen-containing compound and does not impair properties such as curability and moisture resistance.

[0008]

SUMMARY OF THE INVENTION The present invention provides an epoxy resin composition containing an epoxy resin, a curing agent, a filler, and a flame retardant as essential components, and a phosphorus-containing flame retardant represented by the general formula (1). It is a flame-retardant epoxy resin powder coating characterized by containing a compound.

Embedded image However, in the formula (1), Y is an epoxy group represented by the formula (2) or a compound represented by the formula (4) in which a compound represented by the formula (3) is added to the epoxy group,

Embedded image Further, in the expression (1), X is the expression (5), (6),
This is represented by (7) or (8).

Embedded image

[0009] The phosphorus-containing compound of the general formula (1) can be easily obtained by adding a compound of the formula (3) to a compound having an epoxy group at a terminal. The compound having an epoxy group at the terminal may be a non-halogen type compound having a plurality of epoxy groups in one molecule and a liquid at room temperature, and examples thereof include bisphenol A type and bisphenol F type. However, the present invention is not particularly limited to these. However, in order to maintain the coatability of powder coating products by lowering the melting point and melt viscosity, it is necessary to increase the phosphorus content in order to impart higher flame retardancy. A compound having a small epoxy equivalent and a low molecular weight is desirable. The reaction is carried out by adding 0.5 to 1.0 equivalent of the compound of the formula (3) to 1 equivalent of the epoxy group,
It progresses easily by stirring while heating to 0 to 150 ° C. That is, the epoxy group at the terminal of the compound is opened to add the compound of the formula (3). As the addition reaction proceeds, the viscosity of the system increases, and after the reaction is completed, the cooled resin becomes solid.

It is preferable that the phosphorus-containing compound represented by the general formula (1) is imparted with sufficient flame retardancy, but as little as possible, so as to reduce the influence on the powder coating product characteristics. For this reason, the phosphorus-containing compound of the formula (1) may be blended at a phosphorus content of 1.5 to 3.5% with respect to the total amount (weight ratio) of the epoxy resin, the curing agent, and the compound of the formula (1). desirable. When one or more unreacted epoxy groups remain in the phosphorus-containing compound of the formula (1), the epoxy groups also react during the curing reaction of the powder coating product and are incorporated into the cured product. It is more preferable because the moisture resistance is improved.

[0011] The epoxy resin in the present invention includes 1
As long as the resin has at least two epoxy groups in the molecule and is a non-halogen epoxy resin, it may be a solid at room temperature which is applied to general epoxy powder coatings. For example, bisphenol A type, bisphenol F type , Bisphenol S type, phenol novolak type, cresol novolak type, biphenyl type, naphthalene type, aromatic amine type, etc., but are not particularly limited thereto. These can be used alone or in combination of two or more.

In the present invention, the curing agent is not particularly limited, either, and various curing agents may be used alone or in combination depending on the purpose to which the epoxy resin powder coating is applied. Examples include aromatic amines such as diaminodiphenylmethane and aniline resin, condensates of aliphatic amines with aliphatic dicarboxylic acids, dicyandiamide and its derivatives, various imidazole and imidazoline compounds, adipic acid, sebacic acid, phthalic acid, and maleic acid. acid,
Trimellitic acid, benzophenone dicarboxylic acid, polydicarboxylic acids such as pyromellitic acid or acid anhydrides thereof,
Examples include dihydrazides such as adipic acid and phthalic acid, novolaks such as phenol, cresol, xylenol, and bisphenol A, carboxylic acid amides, methylolated melamines, and block-type isocyanurates.

The ratio of the curing agent to the epoxy resin is appropriately determined depending on the type of the epoxy resin and the curing agent to be used. In consideration of the properties of the cured product, it is generally 0.6 to 1 equivalent of the epoxy resin. It is appropriate to use in the range of -1.2 equivalents. 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,
Wollastonite, glass fiber or glass beads, zircon, titanium compounds, molybdenum compounds, etc. are used alone or in combination. In addition, various pigments, additives such as a leveling agent, a coupling agent and an antifoaming agent are appropriately compounded. Also, silicone resin to enhance flame retardancy,
A resin having a cyanurate ring skeleton such as a melamine resin,
Alternatively, non-halogen flame-retardant auxiliaries such as zinc borate and expandable graphite can be used as appropriate.

In the present invention, the method for producing the powder coating is not particularly limited, and may be a general method. As an example, the raw material components blended 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. Can be

[0016]

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

[0017]

[Table 1]

(Materials Used) Epoxy resin EP-1003: Bisphenol A type, oiled shell epoxy 2. 2. Curing agent • BTDA: benzophenonetetracarboxylic anhydride • 2MZ: 2-methylimidazole Filler ・ Fused silica: Tatsumori, RD-8 ・ Aluminum hydroxide: Sumitomo Chemical, CL-310 Pigment-White pigment (titanium oxide): manufactured by Ishihara Sangyo, TTO-55-Blue pigment (cyanine blue): manufactured by Sumitomo Chemical, cyanine blue GH Additives-Silane coupling agent: manufactured by Nippon Unicar, A-187 Flame retardant Phosphate ester: PX-200 manufactured by Daihachi Chemical Co., Ltd. Compound of formula (3): 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide Phosphorus-containing compound A: Epikote 828 (Bisphenol A type epoxy resin, oiled shell epoxy) Compound obtained by reacting 1 equivalent of the compound of the formula (3) with 1 equivalent. Phosphorus-containing compound B: Epicoat 154 (phenol novolak type epoxy resin, oiled shell) A compound obtained by reacting one equivalent of the compound of formula (3) with one equivalent of an epoxy)

(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. ：: 10 ¹² Ω, Δ: 10 ¹² to 10 ¹¹ Ω, ×: 10 ¹¹
Less than Ω

In Example 1, 0.8 equivalent of an aromatic acid anhydride was added to 1.0 equivalent of an epoxy resin, and phosphorus-containing compound A was further added to the total amount of epoxy resin, curing agent and phosphorus-containing compound (weight Ratio) to the phosphorus content of 2.7%, and Example 2 of the formulation of Example 1
It applies 2-methylimidazole as a curing agent and aluminum hydroxide as a filler, all of which have high flame retardancy and are required for powder coatings such as curability, moisture resistance and paintability. Excellent in various properties.

On the other hand, each of the comparative examples has problems in several items, and is difficult to apply to powder coatings. In Comparative Example 1, a phosphate ester having a high effect of imparting flame retardancy was blended, but the moisture resistance was significantly reduced. Comparative Example 2 was prepared by blending the compound of the formula (3) as a flame retardant.
High flame retardancy but slow curing. In Comparative Example 3, the phosphorus-containing compound B was blended as a flame retardant, and the melt flowability was reduced and the paintability was poor. Comparative Example 4 used only aluminum hydroxide as a flame retardant and did not provide sufficient flame retardancy.
Furthermore, the moisture resistance is also reduced.

[0022]

The present invention uses a conventional epoxy powder coating for electrical insulation using a halogen-containing compound such as bromine or an antimony-based flame retardant, for which environmental problems have been pointed out for imparting flame retardancy. An object of the present invention is to provide a flame-retardant epoxy resin powder coating which imparts excellent flame-retardancy even without it and has excellent properties such as curability, moisture resistance, and heat discoloration resistance.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J002 CC03X CC15X CC18Y CD04W CD05W CD06W CD13W CD20Z CL03X CP03Y DA028 DE077 DE147 DE237 DG047 DG057 DJ007 DJ017 DJ037 DJ047 DJ057 DK008 DL007 EF066 EF076 EF116 FA076 EF116 EU076 EF116 EU076 EF116 FD13Y FD13Z FD138 FD139 FD14X FD146 FD150 GH01 HA09 4J038 DB001 DB061 DB071 DB151 HA196 HA216 HA286 HA376 HA446 HA486 HA526 HA536 JC24 KA03 KA08 KA11 NA15 PA02 PB09

Claims (3)

[Claims] 1. An epoxy resin composition comprising an epoxy resin, a curing agent, a filler, and a flame retardant as essential components, wherein a phosphorus-containing compound represented by the general formula (1) is blended as a flame retardant. Flame retardant epoxy resin powder coating. Embedded image However, in the formula (1), Y is an epoxy group represented by the formula (2) or a compound represented by the formula (4) obtained by adding a compound represented by the formula (3) to the epoxy group, Formula 2 Further, in the expression (1), X is the expression (5), (6),
This is represented by (7) or (8). Embedded image 2. A compound of the formula (1) obtained by a chemical reaction between a compound containing two or more epoxy groups at the terminal, having an epoxy equivalent of not more than 250, and being liquid at room temperature, and a compound of the formula (3). The flame-retardant epoxy resin powder according to claim 1, wherein the compound contains at least 50% of a compound in which one or two of Y in the formula (1) is a terminal epoxy group represented by the formula (2). Body paint. 3. The method according to claim 1, wherein the phosphorus-containing compound is blended in an amount of 1.5 to 3.5% in terms of phosphorus content based on the total amount (weight ratio) of the phosphorus-containing compound, epoxy resin and curing agent. Flame retardant epoxy resin powder coating.