JP6349836B2 - Epoxy resin powder coating for varistor and varistor - Google Patents

Description

  The present invention relates to an epoxy resin powder coating for varistors and a varistor.

  Epoxy resin powder coatings are conventionally used for the purpose of insulating and covering electrical and electronic parts. Such an epoxy resin powder coating is also required to have a high degree of flame retardancy in the insulating exterior coating film in order to ensure the safety of electrical and electronic parts against fire. For this reason, various compounds that impart flame retardancy are blended in the components of the powder coating.

  As a method for imparting flame retardancy, for example, the flame retardant resin component is reduced and the non-flammable inorganic filler, particularly crystal water, is contained and released at the time of combustion so as to exhibit the flame retardancy effect. Various methods have been proposed and implemented, such as a method of blending a large amount of inorganic fillers such as aluminum hydroxide and magnesium hydroxide, and a method of modifying an epoxy resin with a low-flammability silicone resin or a cyanurate ring-containing resin. However, the most widely practiced method is to blend various halogen-based flame retardants (for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 06-057101

The present invention provides an epoxy resin powder coating for varistors that has excellent flame retardancy and excellent moisture resistance without using a halogen material. Moreover, when the epoxy resin powder coating material for varistors is used for the exterior of a varistor, the varistor which has the outstanding combustion resistance and reliability is provided.

Such an object is achieved by the present invention described in items [1] to [7] below.
[1] A varistor epoxy resin powder coating used for exterior coating of a varistor, wherein the varistor epoxy resin powder coating contains an epoxy resin, a curing agent, a phosphate ester flame retardant, and a copper compound, When a varistor voltage test was performed on a varistor covered with an epoxy resin powder coating for a varistor before and after the pressure cooker treatment under conditions of 2 atm, 121 ° C., 100% RH, 24 hours, 1 mA The voltage change rate Δ1 (%) = (1−V1 / V ₀ 1) × 100 before and after the pressure cooker process is 5% or less when the voltage at which the current leaks is V ₀ 1 and V1, respectively. Epoxy resin powder coating for varistors.
[2] The epoxy resin powder coating for a varistor according to the above [1], wherein the copper compound is at least one copper compound selected from the group consisting of copper carbonate and copper oxalate.
[3] The epoxy for varistors according to [1] or [2], wherein the copper compound is 0.1 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the epoxy resin powder coating material for varistors. Resin powder paint.
[4] The varistor according to any one of [1] to [3], wherein the phosphate ester-based flame retardant is 5 to 100 parts by mass with respect to 100 parts by mass of the epoxy resin. Epoxy resin powder paint.
[5] The epoxy resin powder coating for varistors according to any one of [1] to [4], wherein the epoxy resin powder coating for varistor further contains a filler.
[6] The epoxy resin powder coating for varistors according to [5] above, wherein the filler is 40 to 80 parts by mass with respect to 100 parts by mass of the epoxy resin powder coating for varistors.
[7] A varistor which is covered with the epoxy resin powder coating for a varistor according to any one of [1] to [6] above.

  According to the present invention, there is provided an epoxy resin powder coating for varistors having excellent flame retardancy and improved moisture resistance. Moreover, when the epoxy resin powder coating material for varistors of the present invention is used as a varistor, a varistor having excellent combustion resistance and reliability is provided.

The epoxy resin powder coating for a varistor of the present invention is an epoxy resin powder coating for a varistor used for the exterior of a varistor, and the epoxy resin powder coating for a varistor is an epoxy resin, a curing agent, a phosphate ester type A varistor containing a flame retardant and a copper compound and coated with the epoxy resin powder coating for a varistor before and after pressure cooker treatment under conditions of 2 atm, 121 ° C., 100% RH, 24 hours When the voltage at which a current of 1 mA leaks during the voltage test is V ₀ 1 and V1, respectively, the voltage change rate Δ1 (%) before and after the pressure cooker process is (1−V1 / V ₀ 1) × 100. It is characterized by being 5% or less. Thereby, it is possible to obtain an epoxy resin powder coating for varistors having excellent flame retardancy and improved moisture resistance.
The varistor of the present invention is characterized in that it is covered with the epoxy resin powder coating material for varistors of the present invention. Accordingly, it is possible to obtain a varistor that is less likely to decrease the varistor voltage even after the humidification process and has excellent combustion resistance.
Below, the epoxy resin powder coating material and varistor for varistors of this invention are demonstrated.

First, the epoxy resin powder coating material for varistors of the present invention will be described.
The epoxy resin powder coating for a varistor of the present invention is an epoxy resin powder coating for a varistor used for the exterior of a varistor, and the epoxy resin powder coating for a varistor is an epoxy resin, a curing agent, a phosphate ester type A varistor containing a flame retardant and a copper compound and coated with the epoxy resin powder coating for a varistor before and after pressure cooker treatment under conditions of 2 atm, 121 ° C., 100% RH, 24 hours When the voltage at which a current of 1 mA leaks during the voltage test is V ₀ 1 and V1, respectively, the voltage change rate Δ1 (%) before and after the pressure cooker process is (1−V1 / V ₀ 1) × 100. It is characterized by being 5% or less. Thereby, it is possible to obtain an epoxy resin powder coating for varistors having excellent flame retardancy and improved moisture resistance.

  The epoxy resin used in the present invention has at least one epoxy group in the molecule, is a non-halogenated epoxy resin, and is solid at room temperature applied to general epoxy resin powder coatings. Can be used if present. Examples of such epoxy resins include, but are not limited to, bisphenol A type, bisphenol F type, bisphenol S type, phenol novolac type, cresol novolac type, biphenyl type, naphthalene type, and aromatic amine type. It is not something. These may be used alone or in combination. In particular, bisphenol A type epoxy resin and cresol novolac type are preferably used from the viewpoints of low cost, viscosity at melting, and heat resistance.

  As the curing agent used in the present invention, various kinds of curing agents can be used alone or in combination depending on the purpose to which the epoxy resin powder coating for varistor is applied. For example, aromatic amines such as diaminodiphenylmethane and aniline resins, condensates of aliphatic amines and aliphatic dicarboxylic acids, dicyandiamide and its derivatives, various imidazoles and imidazoline compounds, adipic acid, sebacic acid, phthalic acid, maleic acid, Polydicarboxylic acids such as merit acid, benzophenone dicarboxylic acid, pyromellitic acid or anhydrides thereof, dihydrazides such as adipic acid or phthalic acid, phenols, cresols, xylenol, bisphenol A and the like novolaks that are condensates of aldehydes, Examples thereof include carboxylic acid amides, methylolated melamines, and block type isocyanurates. Among these, an acid anhydride-based curing agent is preferable because it improves the curing characteristics of the obtained powder coating material.

  The ratio of the curing agent to the epoxy resin can be adjusted depending on the type of the epoxy resin and the curing agent used. Preferably, the functional group (number) of the curing agent is 0.6 mole equivalent to 1.2 mole equivalent, more preferably 0.9 mole equivalent to 1.1 mole equivalent to the epoxy group (number) of the epoxy resin. It is used in the range of the molar equivalent or less. When it is in the above range, good curing characteristics can be obtained. If necessary, curing accelerators such as tertiary amines and imidazoles may be used for these curing agents. Among them, the use of an organic phosphorus compound is desirable for further improving the flame retardancy.

  The total amount of the epoxy resin and the curing agent is preferably 10 parts by mass or more and 80 parts by mass or less, more preferably 20 parts by mass or more and 50 parts by mass or less, with respect to 100 parts by mass of the epoxy resin powder coating material for varistors. It is. When the blending amount is not less than the above lower limit value, the smoothness of the coating film is hardly lowered. On the other hand, when the blending amount is not more than the above upper limit value, it is difficult to cause appearance defects such as sagging or toggling during firing, which is a curing step after coating.

  The phosphate ester flame retardant is added to improve flame retardancy, and any organic phosphate ester generally used as a flame retardant can be used. Specific examples of the phosphate compound include triphenyl phosphate, trisnonylphenyl phosphate, resorcinol bis (diphenyl phosphate), resorcinol bis [di (2,6-dimethylphenyl) phosphate], 2,2-bis {4- [ Examples thereof include, but are not limited to, bis (phenoxy) phosphoryloxy] phenyl} propane, 2,2-bis {4- [bis (methylphenoxy) phosphoryloxy] phenyl} propane, and the like. In addition to the above, the phosphate ester compound is not particularly limited, but for example, trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, tributoxyethyl phosphate, tricresyl phosphate, cresyl phenyl phosphate, octyl diphenyl phosphate, Phosphate ester compounds such as diisopropylphenyl phosphate, diphenyl-4-hydroxy-2,3,5,6-tetrabromobenzyl phosphonate, dimethyl-4-hydroxy-3,5-dibromobenzyl phosphonate, diphenyl-4 -Hydroxy-3,5-dibromobenzyl phosphonate, tris (chloroethyl) phosphate, tris (dichloropropyl) phosphate, tris (chloropropyl) Phosphate, bis (2,3-dibromopropyl) -2,3-dichloropropyl phosphate, tris (2,3-dibromopropyl) phosphate, bis (chloropropyl) monooctyl phosphate hydroquinonyl diphenyl phosphate, phenylnonylphenyl hydroxide Examples thereof include monophosphate ester compounds such as nonyl phosphate and phenyl dinonylphenyl phosphate, and aromatic condensed phosphate esters. Phosphoric ester flame retardants may be used alone or in combination of two or more.

  Among these, the phosphate ester flame retardant used in the present invention preferably has a high phosphorus content and is solid at room temperature in order to impart sufficient flame retardancy, for example, triphenyl phosphate or aromatics. Condensed phosphate esters are preferably used.

  The amount of the phosphate ester flame retardant is 5 parts by mass or more and 100 parts by mass or less, preferably 20 parts by mass or more and 70 parts by mass or less, more preferably 40 parts by mass or more and 60 parts by mass with respect to 100 parts by mass of the epoxy resin. It is below mass parts. Thereby, the flame retardance of the epoxy resin powder coating material for varistors can be improved. In particular, when the epoxy resin powder coating material for varistors is used for the exterior of the varistor, the varistor can have excellent combustion resistance by being 20 parts by mass or more and 70 parts by mass or less. Furthermore, the varistor excellent in the balance of a flame retardance and hardened | cured material characteristic can be obtained by setting it as 40 to 60 mass parts.

  The copper compound used in the present invention is added to improve moisture resistance. The copper compound only needs to exclude halogen compounds, such as copper oxalate, copper stearate, copper formate, copper tartrate, copper oleate, copper acetate, copper gluconate, copper salicylate, and copper carbonate. Inorganic copper compounds such as natural minerals such as copper chloride, copper bromide, copper iodide, copper phosphate, hydrotalcite, stichite, and pyrolite can be used. In particular, from the viewpoints of compatibility with the epoxy resin, moldability of the epoxy resin powder coating material for varistors, and improvement of moisture resistance, copper carbonate and copper oxalate are preferably used.

  The compounding quantity of a copper compound is 0.1 to 20 mass parts with respect to 100 mass parts of said epoxy resin powder coating materials for varistors, More preferably, it is 3 to 10 mass parts. When the amount is more than 0.1 parts by mass, the effect of improving the moisture resistance by the copper compound is excellent. When the amount is less than 20 parts by mass, the curability becomes good, and a cured product having excellent characteristics can be obtained. Furthermore, when the epoxy resin powder coating for varistors is used as a varistor, the voltage change rate of the varistor after the pressure cooker (PCT) treatment is hardly lowered and the moisture resistance is excellent by setting the amount to 3 parts by mass or more and 10 parts by mass or less. In addition, the degree of cure of the epoxy resin powder coating for varistors is unlikely to vary, and the curability of the epoxy resin powder coating for varistors is excellent.

  The epoxy resin powder coating material for varistors of the present invention can further contain a filler. By containing the filler, the strength of the cured product can be improved and the viscosity at the time of melting can be adjusted to an optimum range. Fillers include calcium carbonate, calcium sulfate, barium sulfate, aluminum hydroxide, magnesium hydroxide, aluminum oxide, crystalline or fused silica, surface treated silica, talc, kaolin, clay, mica, dolomite, wollastonite, glass fiber , Glass beads, zircon, titanium compounds, molybdenum compounds and the like. These may be used alone or in combination. In particular, aluminum hydroxide, crystal, or fused silica is preferably used from the viewpoint of low cost and availability.

  The blending amount of the filler is preferably 40 parts by mass or more and 80 parts by mass or less, and more preferably 50 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of the epoxy resin powder coating material for varistors. When the blending amount is larger than the above lower limit value, it is difficult to cause appearance problems such as sagging or toggling during firing, and the mechanical strength of the coating film may be sufficient. On the other hand, if it is smaller than the above upper limit value, the smoothness of the coating film is hardly lowered.

  The particle diameter of the filler is not particularly limited, but usually an average particle diameter of 2 to 50 μm, more preferably 5 to 30 μm is used. Thereby, favorable fluidity | liquidity is provided to a powder coating material, coating property improves more, and also it can be made optimal about the mechanical strength of a coating film.

The epoxy resin powder paint for varistors of the present invention is a varistor covered with an epoxy resin powder paint for varistors before and after pressure cooker treatment under conditions of 2 atm, 121 ° C., 100% RH, 24 hours. , The voltage change rate Δ1 (%) before and after the pressure cooker process is (1−V1 / V ₀ 1), where V ₀ 1 and V1 are voltages at which a current of 1 mA leaks when the varistor voltage test is performed, respectively. X100 is 5% or less. When the voltage change rate Δ1 before and after the PCT treatment is 5% or less, and more preferably 2% or less, the reliability of the varistor is further improved. In addition, the PCT treatment can be performed under conditions of 2 atm, 121 ° C., 100% RH and 2 hours, but the above conditions (2 atm, 121 ° C., 100% RH, 24 hours) have a larger environmental load. As compared with other electronic components (ceramic capacitors or the like), high insulation is required at a reference voltage or lower, so that it can be used more suitably as a processing condition for indicating the performance of a varistor that requires more reliability.

  Further, instead of measuring the voltage at which a current of 1 mA leaks in the varistor voltage test, the voltage at which a current of 10 μA and 1 μA leaks can also be measured. When measuring the voltage at which a current of 10 μA and 1 μA leaks, the voltage change rate is likely to increase before and after the PCT process as compared with the voltage at which a current of 1 mA leaks, and the evaluation becomes more severe. When measuring the voltage at which a current of 10 μA leaks, the voltage change rate Δ2 before and after the PCT treatment is 30% or less, and preferably 20% or less. When measuring a voltage at which a current of 1 μA leaks, the voltage change rate Δ3 before and after the PCT process is 70% or less, and preferably 50% or less. When this numerical condition is satisfied, the moisture resistance of the varistor epoxy resin powder coating is excellent, and when the varistor epoxy resin powder coating is used with a varistor, the reliability of the varistor is excellent.

  Here, the varistor using the epoxy resin powder coating for varistor used in the test is a film thickness of the epoxy resin powder coating for varistor on a semiconductor ceramic (for example, diameter 9.5 mm × thickness 3.5 mm) which is not packaged. The varistor is packaged to have a thickness of 300 to 3000 μm. The apparatus used for the PCT process may be any apparatus that can create an environment that satisfies the above-described conditions. Examples thereof include a saturated pressure cooker processing apparatus (PC-362M manufactured by Hirayama Seisakusho Co., Ltd.). Examples of the device for measuring the voltage change rate include a constant current power supply device (AS508B, manufactured by Iwata High Voltage Research Institute). When measuring the voltage, it is performed at room temperature and in an atmosphere of 50% RH, and is processed as quickly as possible in order to avoid the influence of heat generation due to voltage application.

  The epoxy resin powder coating material for varistors of the present invention can contain additives such as pigments, leveling agents, coupling agents, and antifoaming agents, if necessary, in addition to the components described above. 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 aid such as zinc borate or expandable graphite may be used.

  In the present invention, the method for producing the powder coating material is not particularly limited, and a general method can be used. As an example, the raw material components blended in a predetermined composition ratio are sufficiently uniformly mixed with a mixer, then melt mixed with an extruder or a twin-screw kneader, and then pulverized and classified to an appropriate particle size with a pulverizer. be able to.

Next, the varistor of the present invention will be described.
The varistor of the present invention is characterized in that it is covered with the epoxy resin powder paint for varistors of the present invention. Accordingly, it is possible to obtain a varistor that is less likely to decrease the varistor voltage even after the humidification process and has excellent combustion resistance. A varistor having a structure in which a semiconductor ceramic having non-linear resistance characteristics is sandwiched between two electrodes can be used as a varistor before packaging. As the semiconductor ceramic, zinc oxide, strontium titanate, silicon carbide, or the like can be used. The part to be covered with the epoxy resin powder coating for varistors only needs to cover the entire outer periphery so as to be in contact with semiconductor ceramics having non-linear resistance characteristics, for example, sandwiching semiconductor ceramics having non-linear resistance characteristics. A part of the two electrodes may be covered. The thickness of the exterior is not particularly limited, but is preferably 300 μm or more and 3000 μm or less, and more preferably 500 μm or more and 2000 μm or less. In this range, a varistor having excellent moisture resistance can be obtained, the size of the coating apparatus can be reduced, and the cost of the varistor can be reduced.

  There are no particular restrictions on how to coat the varistor with the epoxy resin powder paint, but a varistor without an exterior is prepared, and the epoxy resin powder paint for the varistor is applied to the sealed part of the varistor using a coating device and heated. Thus, there is a method of curing the varistor epoxy resin powder coating material to produce the varistor. As the coating apparatus, a fluid immersion type apparatus is preferably used from the viewpoint of good adhesion of the epoxy resin powder coating material for varistors and easy operation.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these Examples.

The raw materials used in Examples and Comparative Examples are as follows.
1. Epoxy resin / bisphenol A type epoxy resin: Japan Epoxy Resin Mitsubishi Chemical Co., Ltd. “Epicoat 1003” (epoxy equivalent 720)
2. 2. Curing agent / TMA: trimellitic anhydride 3. Curing accelerator, TPP: Triphenylphosphine Filler / Aluminum hydroxide: Nippon Light Metal / BF083 (average particle size 10 μm)
5. 5. Pigment / carbon black Phosphate ester flame retardant / Phosphate ester flame retardant: PX-200, manufactured by Daihachi Chemical
7). 7. Copper compound, copper carbonate, copper oxalate Other metal compounds / magnesium oxalate

Example 1
(1) Preparation of Epoxy Resin Powder Coating for Varistor 28 parts by mass of bisphenol A type epoxy resin (Japan Epoxy Resin Mitsubishi Chemical Co., Ltd. “Epicoat 1003”), 4.4 parts by mass of trimellitic anhydride, triphenylphosphine 0 .1 part by mass, 57 parts by mass of aluminum hydroxide (Nippon Light Metal Co., Ltd., “BF083” (average particle size 10 μm)), 13 parts by mass of a phosphate ester flame retardant, and 0.1 parts by mass of copper carbonate were mixed with a mixer, After melt-kneading under 80 degreeC conditions, it grind | pulverized with the grinder and the epoxy resin powder coating material 1 for varistors with an average particle diameter of 40-60 micrometers was obtained.
(2) Production of varistor Semiconductor ceramic (diameter: 9.g) with fluidized dip coater (OPPC, model 0S), which is produced by using varistor epoxy resin powder coating 1 (1000 g) produced as described above. 5 mm × height 3.5 mm) so as to have a film thickness of 300 μm, and the epoxy resin powder coating material for varistors was cured for 30 minutes under the condition of 150 ° C. to produce varistor 1.

(Examples 2-7 and Comparative Examples 1-4)
A varistor epoxy resin powder coating and a varistor were prepared in the same manner as in Example 1 except that a varistor epoxy resin powder coating was prepared according to the blending types and blending amounts (parts by mass) shown in Table 1.
The following evaluations were made on the epoxy resin powder coating for varistors and the varistors obtained in the examples and comparative examples. The evaluation results are shown in Table 1.

(Evaluation method)
An evaluation method is shown below for each of the above evaluations.

(1) Gelation time Based on JIS C 2161, the time (seconds) until gelation was measured with respect to the obtained epoxy resin powder coating material for varistors using a 165 ° C. hot platen. A gelation time longer than 80 seconds and a gelation time close to 80 seconds is judged to have excellent moldability.

(2) Flame retardance The epoxy resin powder coating for varistors obtained using a heatable hand press device is melted at 120 ° C. and cured in a dryer at 150 ° C., and the length is 125 mm × width 13 mm × thickness. A 0.8 mm test plate was prepared and measured according to the UL94 vertical method. When the test result shows that the maximum value of the burning time after flame contact is 3 seconds or less, ◎ is shown when it is 10 seconds or less, and ○ is shown when it is longer than 10 seconds. When the result of the flame retardancy test is ◎, it is judged that the epoxy resin powder coating material for varistors has particularly excellent flame retardancy.

(3) Rate of change of varistor voltage before and after pressure cooker (PCT) treatment (%)
The obtained varistor was subjected to a varistor voltage test, and voltages V ₀ 1, V ₀ 2 and V ₀ 3 at which currents of 1 mA, 10 μA and 1 μA leaked were measured, respectively. After voltage measurement, pressure cooker (PCT) treatment was performed for 24 hours under the conditions of 2 atm, 121 ° C., and 100% RH. After the PCT treatment, the varistor was taken out, the varistor voltage test was performed again, and after the PCT treatment, 1 mA, 10 μA and Voltages V1, V2 and V3 at which a current of 1 μA leaks were measured, respectively. The rate of change of varistor voltage before and after the PCT treatment was calculated from the following equation.
1 mA leakage voltage change rate Δ1 (%) = (1−V1 / V ₀ 1) × 100
10 μA leakage voltage change rate Δ2 (%) = (1−V2 / V ₀ 2) × 100
1 μA leakage voltage change rate Δ3 (%) = (1−V3 / V ₀ 3) × 100
The lower the value of the varistor voltage change rate before and after the 1 mA, 10 μA, and 1 μA leakage voltage PCT, it is judged that the epoxy resin powder coating for varistors has better moisture resistance.
The apparatus for performing the PCT treatment is a saturated pressure cooker treatment apparatus (made by Hirayama Seisakusho, PC-362M), and the apparatus for measuring the voltage change rate is a constant current power supply (made by Iwata High Voltage Research Institute, AS508B). Was used.

(4) Reliability To evaluate the reliability of varistor exterior resin, melt the epoxy resin powder coating for varistors obtained using a heatable hand press device at 120 ° C and cure at 150 ° C with a dryer. Then, a test plate having a length of 100 mm × width of 100 mm × thickness of 1 mm was prepared, and the test piece was humidified for 1000 hours under the condition of 85 ° C. and 85%, and then volume resistivity was measured by a method based on JIS C2161. A sample having a density of 10 ¹³ Ω · cm or more was evaluated as ◯, and a sample having a value less than 10 ¹³ Ω · cm was evaluated as x. If it is ○, it is judged that the reliability of the varistor is excellent.

(5) Combustion resistance of varistor A voltage was applied to the obtained varistor using a voltage power supply device to cause overvoltage breakdown of the varistor, and the time from heat generation / ignition to fire extinguishing was measured. As the time from ignition to extinguishing at the time of overvoltage breakdown is shorter, it is judged that the varistor has better combustion resistance.

  From the evaluation results described in Table 1, the following can be understood.

  In the flame retardancy evaluation, the epoxy resin powder coatings of the present invention obtained in Examples 1 to 7 are compared with the epoxy resin powder coatings of Comparative Examples 3 and 4 that do not contain a phosphate ester flame retardant, It was found to have excellent flame retardancy.

In the varistor voltage change rate before and after the pressure cooker (PCT), the varistor using the epoxy resin powder coating of the present invention obtained in Examples 1 to 7 is the value of the varistor voltage change rate Δ1 before and after the pressure cooker (PCT). Was found to have low moisture and excellent moisture resistance.
On the other hand, the varistor using the epoxy resin powder coating obtained in Comparative Example 1 containing no copper compound and Comparative Example 2 containing a magnesium compound instead of a copper compound has a varistor voltage change rate Δ1 before and after the pressure cooker (PCT). This value was high and increased greatly from the initial value after the pressure cooker, and it was found that the moisture resistance was not excellent as compared with the varistors of the present invention obtained in Examples 1-7.

  In particular, the varistor using the epoxy resin powder coating of the present invention obtained in Examples 3 to 6 has a low varistor voltage change rate Δ2 value and Δ3 value before and after pressure cooker (PCT), and further excellent moisture resistance. It was found to have sex.

  In the reliability evaluation, the varistors using the epoxy resin powder coatings of the present invention obtained in Examples 1 to 7 are those of Comparative Examples 1 and 2 in which the voltage change rate Δ1 before and after the pressure cooker treatment is not less than 5%. Compared to varistors using epoxy resin powder coatings, the varistors were found to be more reliable.

  The varistors using the epoxy resin powder coatings of the present invention obtained in Examples 1 to 7 in the evaluation of the flame resistance of varistors were the epoxy resin powders of Comparative Examples 3 and 4 that did not contain a phosphate ester flame retardant. It was found that the varistor is superior in combustion resistance compared to a varistor using a paint.

  The present invention provides an epoxy resin powder coating material for varistors that has excellent flame resistance and excellent moisture resistance without using a halogen material, and also has an epoxy resin powder coating material for varistors. Is used for the exterior of a varistor, it provides a varistor having excellent combustion resistance, and can therefore be suitably used for industrial varistor production.

Claims (7)

An epoxy resin powder coating for a varistor used for the exterior of a varistor,
The epoxy resin powder coating for varistor includes an epoxy resin, a curing agent, a phosphate ester flame retardant, and a copper compound,
A varistor voltage test was performed on the varistor coated with the epoxy resin powder coating for varistors to a film thickness of 300 μm before and after the pressure cooker treatment at 2 atm, 121 ° C., 100% RH, 24 hours. when a 1mA current has a voltage from leaking and V ₀ 1 and V1 respectively during the voltage change rate before and after the pressure cooker treatment Δ1 (%) = (1- V1 / V 0 1) × 100 5% or less Epoxy resin powder coating for varistors, characterized in that   The epoxy resin powder coating material for varistors according to claim 1, wherein the copper compound is at least one copper compound selected from the group consisting of copper carbonate and copper oxalate. The epoxy resin powder paint for varistors according to claim 1 or 2, wherein the copper compound is 0.1 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the epoxy resin powder paint for varistors. 4. The epoxy resin powder coating for a varistor according to claim 1, wherein the phosphate ester flame retardant is 5 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the epoxy resin. The epoxy resin powder paint for varistors according to any one of claims 1 to 4, wherein the epoxy resin powder paint for varistors further contains a filler. The epoxy resin powder paint for varistors according to claim 5, wherein the filler is 40 parts by mass or more and 80 parts by mass or less with respect to 100 parts by mass of the epoxy resin powder paint for varistors. A varistor covered with an epoxy resin powder coating for a varistor,
A varistor, wherein the epoxy resin powder coating for varistor is the epoxy resin powder coating for varistor according to any one of claims 1 to 6.