JP2016035001A - Epoxy resin composition for coil cast molding and ignition coil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an epoxy resin composition for coil cast molding which has a high impregnation property and high thermal conductivity.SOLUTION: An epoxy resin composition for coil cast molding comprises (A) a bisphenol A type epoxy resin of 100 pts.mass, (B) an acid anhydride of 80-150 pts.mass, (C) a curing accelerator of 0.1-5 pts.mass, and (D) a crystal silica of 150-250 pts.mass as the essential components. The (D) crystal silica comprises 60 mass% or more of a crystal silica having undergone cyclone classification after jet mill pulverization.SELECTED DRAWING: None

Description

  The present invention relates to an epoxy resin composition for coil casting and an ignition coil.

  In an ignition coil for automobiles, components are casted and protected by a casting resin composition mainly composed of a thermosetting resin such as an epoxy resin or a polyester resin. In recent years, due to the multi-functionality and high functionality of coils, the resin composition for casting is required to have improved characteristics.

  For example, when the insulating property of the casting resin composition is insufficient, dielectric breakdown is likely to occur when a high voltage is applied. Moreover, when the mechanical properties and thermal properties of the casting resin composition are insufficient, cracks are likely to occur due to mechanical stress and thermal stress when a thermal cycle is applied. When a crack occurs, when a current flows through the coil, abnormal discharge may occur in the crack portion, and it may not operate normally.

  In order to solve such a problem, it is known to use silica particles having a specific particle size distribution (for example, see Patent Document 1). Further, it is known to use an acid anhydride, a curing accelerator, and an agent A composed of silica particles having a specific particle size distribution and an agent B composed of an epoxy resin (see, for example, Patent Document 2). .

  In addition, silica particles produced by the dry classification method contain fine particles, and impregnation properties are reduced by the fine particles, and therefore it is known to use silica particles produced by the wet classification method ( For example, see Patent Document 3.) Furthermore, since the wet classification method has lower productivity of silica particles than the dry classification method, it is known to use silica particles pulverized by the jet mill method (see, for example, Patent Document 4). In addition, it is known to use two types of crystalline silica particles and aluminum hydroxide particles having different particle size distributions in order to improve storage stability and workability and to suppress sedimentation of components during curing. (For example, refer to Patent Document 5).

JP 2008-195782 A JP-A-11-71503 JP 2004-346114 A JP 2011-201948 A JP 2009-114222 A

  As an ignition coil for automobiles, for example, a primary winding and a secondary winding are arranged concentrically in a cylindrical case, and a casting resin composition is injected and cured between them. Has been. Further, in recent years, with respect to such an ignition coil for an automobile, the amount of secondary winding accommodated in the case has been increased for higher output, and the amount of heat generated by the secondary winding has increased. .

  For such an ignition coil for automobiles, since the distance between the case and the component, the interval between the components is very narrow, and the secondary winding is increased, the resin for casting with high impregnation property There is a need for a composition. If the impregnating property of the casting resin composition is low, dielectric breakdown and cracks are likely to occur during use. In addition, the resin composition for casting is required to have high thermal conductivity in order to suppress the temperature rise of the ignition coil for automobiles. Further, the casting resin composition is required to have good productivity and low price. Conventional casting resin compositions have sufficient thermal conductivity, but do not necessarily have sufficient impregnation properties.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an epoxy resin composition for coil casting that has high impregnation and thermal conductivity. Another object of the present invention is to provide an ignition coil using such an epoxy resin composition for casting a coil.

  As a result of intensive investigations to achieve the above object, the present inventors have used impregnated resin composition for casting by reducing the viscosity of the resin composition for casting by using crystalline silica classified by cyclone after jet mill pulverization. Found to be higher. In addition, this can increase the content of crystalline silica in the casting resin composition, improve the thermal conductivity of the casting resin composition, and reduce the linear expansion coefficient and shrinkage ratio. And it discovered that generation | occurrence | production of the crack when a cooling-heat cycle was applied can be suppressed.

  That is, the epoxy resin composition for coil casting of the present invention comprises (A) 100 parts by mass of a bisphenol A type epoxy resin, (B) 80 to 150 parts by mass of an acid anhydride, and (C) 0.1 to 5 of a curing accelerator. It contains 150 parts by mass of (D) crystalline silica as an essential component. Further, (D) crystalline silica contains 60% by mass or more of crystalline silica classified by cyclone after jet mill pulverization.

  In the ignition coil of the present invention, a coil component is cast by the above-described epoxy resin composition for casting a coil.

  According to the present invention, it is possible to provide an epoxy resin composition for coil casting having high impregnation and thermal conductivity. In addition, according to the present invention, a highly reliable ignition coil can be provided.

It is a longitudinal cross-sectional view which shows one Embodiment of an ignition coil.

Hereinafter, the epoxy resin composition for coil casting of the present invention will be described in detail.
The epoxy resin composition for coil casting of the present invention comprises (A) 100 parts by mass of a bisphenol A type epoxy resin, (B) 80 to 150 parts by mass of an acid anhydride, and (C) 0.1 to 5 parts by mass of a curing accelerator. And (D) 150 to 250 parts by mass of crystalline silica are contained as essential components. Further, (D) crystalline silica contains 60% by mass or more of crystalline silica classified by cyclone after jet mill pulverization. Hereinafter, the epoxy resin composition for coil casting is simply described as an epoxy resin composition.

  (A) As the bisphenol A type epoxy resin, one having two or more epoxy groups in one molecule can be used. (A) The molecular weight and molecular structure of the bisphenol A type epoxy resin are not limited, but are preferably liquid at room temperature.

  In the epoxy resin composition, an epoxy resin other than the bisphenol A type epoxy resin can be used in addition to the (A) bisphenol A type epoxy resin as long as it is not contrary to the gist of the present invention. .

  Epoxy resins other than bisphenol A type epoxy resins include bisphenol type epoxy resins other than bisphenol A type epoxy resins, aromatic epoxy resins such as novolac type epoxy resins and biphenyl type epoxy resins, glycidyl ethers of polycarboxylic acids, and cyclohexane derivatives. An alicyclic epoxy resin obtained by epoxidation such as can be used. As the bisphenol type epoxy resin other than the bisphenol A type epoxy resin, a bisphenol F type epoxy resin, a bisphenol AD type epoxy resin, or the like can be used. Moreover, in order to provide flame retardancy, an epoxy resin modified with a phosphorus compound or the like can be used.

  One type of epoxy resin other than the bisphenol A type epoxy resin may be used, or two or more types may be mixed and used. Moreover, it is preferable that epoxy resins other than a bisphenol A type epoxy resin are liquid at normal temperature. When using an epoxy resin other than the bisphenol A type epoxy resin, the content of the epoxy resin other than the bisphenol A type epoxy resin is preferably 10 parts by mass or less with respect to 100 parts by mass of the bisphenol A type epoxy resin, and 5 parts by mass. The following is more preferable. The epoxy resin composition preferably contains substantially only a bisphenol A type epoxy resin as an epoxy resin.

  As the (B) acid anhydride, one having an acid anhydride group in the molecule and reacting with the (A) bisphenol A type epoxy resin to be cured can be used. (B) As the acid anhydride, methylhexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, pentadecenyl succinic anhydride, or the like can be used. These curing agents may be used alone or in combination of two or more.

  (B) Content of an acid anhydride is 80-150 mass parts with respect to 100 mass parts of (A) bisphenol A type epoxy resin. (B) When content of an acid anhydride is 80 mass parts or more, since the hardening time of an epoxy resin composition is shortened, it is preferable. (B) 85 mass parts or more are preferable with respect to 100 mass parts of (A) bisphenol A type epoxy resins, and, as for content of an acid anhydride, 90 mass parts or more are more preferable. Moreover, when content of (B) acid anhydride is 150 mass parts or less, since the characteristic fall of the hardened | cured material of an epoxy resin composition is suppressed, it is preferable. The content of (B) acid anhydride is preferably 140 parts by mass or less, more preferably 130 parts by mass or less, still more preferably 120 parts by mass or less, relative to 100 parts by mass of (A) bisphenol A type epoxy resin. Part by mass or less is particularly preferable.

  (C) The hardening accelerator can use what accelerates | stimulates reaction of (A) epoxy resins, or reaction of (A) epoxy resin and (B) acid anhydride. (C) Examples of the curing accelerator include imidazoles such as 2-ethyl-4-methylimidazole and 1-cyanoethyl-2-ethyl-4-methylimidazole, benzyldimethylamine, 2,4,6-tris (dimethyl). Aminomethyl) phenol, tertiary amines such as 1,8-diazabicyclo [5.4.0] undecene-7 (DBU) and its octyl salt, triethylphosphine, triphenylphosphine, diphenylphosphine and the like can be used. . These curing accelerators may be used alone or in combination of two or more.

  (C) Content of a hardening accelerator is 0.1-5 mass parts with respect to 100 mass parts of (A) bisphenol A type epoxy resin. (C) When content of a hardening accelerator is 0.1 mass part or more, since hardening reaction is accelerated | stimulated notably, it is preferable. (C) 0.3 mass part or more is preferable with respect to 100 mass parts of (A) bisphenol A type epoxy resins, and, as for content of a hardening accelerator, 0.5 mass part or more is more preferable. On the other hand, when the content of the (C) curing accelerator is 5 parts by mass or less, it is preferable because the properties such as impregnation are good. (C) 3 mass parts or less are preferable with respect to 100 mass parts of (A) bisphenol A type epoxy resins, and, as for content of a hardening accelerator, 1 mass part or less is more preferable.

  (D) Crystalline silica is added to improve the thermal conductivity and mechanical properties of the epoxy resin composition. (D) The crystalline silica contains at least part of crystalline silica classified after cyclone classification after jet milling.

  The jet mill pulverization method has a lower content of irregularly shaped particles and a higher content of rounded corner particles than the ball mill pulverization method, bead mill pulverization method, etc., so the content of crystalline silica in the epoxy resin composition Can be more. Also, the jet mill pulverization method is easy to adjust the particle size distribution because the content of fine particles is reduced. Further, the jet mill pulverization method is a dry pulverization method and does not use a liquid unlike the wet pulverization method, so that the cost of pulverization can be reduced.

  The cyclone classification method can reduce the content of fine particles by adjusting the suction force as compared with the conventional dry classification method. Further, the cyclone classification method is a dry pulverization method and does not use a liquid unlike the wet classification method, so that the cost of classification can be reduced and classification can be performed without changing the surface state of the particles. .

  Therefore, by carrying out cyclone classification after jet milling, the particle size distribution can be controlled without changing the surface state of the particles, and particles having a desired particle size distribution can be obtained. Further, by performing cyclone classification after jet mill pulverization, it is not necessary to use a liquid, so that the production cost of particles can be reduced.

  Jet mill pulverization can be performed by introducing crystalline silica particles into a jet stream. The jet air flow pressure during jet mill pulverization is preferably 0.15 to 1 MPa. A jet air flow pressure of 0.15 MPa or more is preferable because the grinding efficiency of crystalline silica is increased. The jet air flow pressure is more preferably 0.2 MPa or more. Moreover, when the jet airflow pressure is 1 MPa or less, it is preferable from the viewpoint of pressure resistance of the pulverizing equipment. The jet air flow pressure is more preferably 0.9 MPa or less.

  Such jet mill pulverization can be performed using a commercially available dry pulverizer. As such a dry pulverizer, for example, a supersonic jet pulverizer PJM-200SP (trade name) manufactured by Pneumatic Industry can be used. The pulverizer can perform pulverization by collision of particles at a theoretical flow velocity of Mach 2 or higher.

  The cyclone classification is preferably performed so that the average particle diameter of the crystalline silica is 4 to 10 μm. An average particle size of 4 μm or more is preferable because the viscosity of the epoxy resin composition is lowered and aggregation of crystalline silica is suppressed. In addition, when the average particle size is 10 μm or less, the content of coarse particles decreases, so that sedimentation when the epoxy resin composition is stored is suppressed and the impregnation property of the epoxy resin composition is also improved.

  The cyclone classification is preferably performed so that the content of particles of 1 μm or less is 8.0% by mass or less. When the content of particles of 1 μm or less is 8.0% by mass or less, the viscosity of the epoxy resin composition becomes low and the impregnation property of the epoxy resin composition becomes good. The content of particles of 1 μm or less may be reduced to, for example, about 3.0% by mass.

  Furthermore, the cyclone classification is preferably performed so that the content of particles of 34 μm or more is 1.0 mass% or less. When the content of particles of 34 μm or more is 1.0% by mass or less, the content of particles having a large particle size is reduced, so that sedimentation when storing the epoxy resin composition is suppressed, and the epoxy resin composition The impregnation property is also good. The content of particles of 34 μm or more is preferably 0.7% by mass or less, more preferably 0.5% by mass or less, and further preferably 0.3% by mass or less.

The particle size distribution can be determined using a laser diffraction particle size distribution measuring device. The average particle size is a particle size (50% particle size D ₅₀ ) at which the integrated volume in the particle size distribution is 50%.

  Cyclone classification can be performed using a commercially available dry classifier. As such a dry classifier, for example, a high-precision airflow classifier DXF-10 (trade name) manufactured by Pneumatic Kogyo Co., Ltd. can be used. The classifier can classify coarse particles and fine particles with high accuracy by a swirling airflow.

  The silica particles classified by cyclone after jet mill pulverization may be subjected to a surface treatment from the viewpoint of improving the adhesion with other components. Examples of the surface treatment agent include an organic silane compound, an organic titanate compound, and an organic aluminate compound, and these may be used alone or in combination of two or more.

  Examples of the organic silane compound include vinyltriethoxysilane, vinyl-tris- (2-methoxyethoxy) silane, γ-methacryloxypropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, and N-β- (aminoethyl). -Γ-aminopropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, and the like. May be used, or two or more kinds may be mixed and used.

  Examples of the organic titanate compound include tetra-i-propyl titanate, tetra-n-butyl titanate, butyl titanate dimer, tetrastearyl titanate, triethanolamine titanate, titanium acetylacetonate, titanium lactate, octylene glycol titanate, isopropyl ( N-aminoethylaminoethyl) titanate and the like may be mentioned, and these may be used alone or in combination of two or more.

  Examples of the organic aluminate compound include acetoalkoxyaluminum diisopropinate.

  (D) Crystalline silica contains 60% by mass or more of silica particles classified by cyclone after jet mill pulverization. When the silica particles classified by cyclone after jet mill pulverization are contained in an amount of 60% by mass or more, the viscosity of the epoxy resin composition is sufficiently low, and the impregnation property to an ignition coil or the like is also sufficient. (D) It is preferable that the crystalline silica contains 90% by mass or more of silica particles classified by cyclone after jet mill pulverization. The (D) crystalline silica may contain 100% by mass of silica particles classified by cyclone after jet mill pulverization, or may be composed of only silica particles classified by cyclone after jet mill pulverization.

  (D) Content of crystalline silica is 150-250 mass parts with respect to 100 mass parts of (A) epoxy resin. (D) When the content of crystalline silica is 150 parts by mass or more, the cured product of the epoxy resin composition has good mechanical strength, and the occurrence of cracks is suppressed when used in an ignition coil or the like. (D) As for content of crystalline silica, 160 mass parts or more are preferred to 100 mass parts of (A) epoxy resin. 170 parts by mass is more preferable. On the other hand, when the content of (D) crystalline silica is 250 parts by mass or less, workability is improved because the viscosity of the epoxy resin composition is lowered. (D) As for content of a crystalline silica, 240 mass parts or less are preferable with respect to 100 mass parts of (A) epoxy resins. More preferably, 230 parts by weight.

  The epoxy resin composition can contain, in addition to the above essential components, components that are generally blended in this type of epoxy resin composition as long as they do not impair the effects of the present invention. Examples of such components include inorganic fillers such as alumina, talc, calcium carbonate, titanium white, clay, bengara and carbon, coupling agents, antifoaming agents, pigments, and flame retardant aids such as antimony trioxide. It is done.

  In addition, it is preferable that an epoxy resin composition does not contain a fibrous filler substantially from the impregnation property to a coil falling. For this reason, in order to ensure the mechanical strength of the cured product, the epoxy resin composition contains 60% by mass or more of (D) crystalline silica in the epoxy resin composition and also contains an alicyclic epoxy resin. You may go out.

  The epoxy resin composition is prepared by thoroughly mixing (A) a bisphenol A type epoxy resin, (B) an acid anhydride, (C) a curing accelerator, (D) crystalline silica, and other components blended as necessary. And uniformly mixing.

The epoxy resin composition can impart excellent characteristics and reliability when applied to the sealing, covering, insulation, and the like of coils, particularly for the casting of ignition coils for automobiles. The impregnation property of the epoxy resin composition is preferably 90% or more, more preferably 95% or more, and further preferably 100%. Here, the impregnation property means an impregnation rate by a model coil described later. Moreover, 120 N / mm < ² > or more is preferable and, as for the bending strength of an epoxy resin composition, 130 N / mm < ² > or more is more preferable.

Next, an embodiment of the ignition coil will be described.
FIG. 1 is a longitudinal sectional view showing an embodiment of an ignition coil for an automobile.

  An ignition coil 10 for an automobile includes a central core 11, a primary bobbin 12, a primary coil 13, a secondary bobbin 14, a secondary coil 15, a case 16, and the like.

  The center core 11 has a columnar shape, and is configured by laminating sheets made of a magnetic material in layers. A cylindrical bobbin 14 having a cylindrical shape is disposed around the central core 11. A primary bobbin 12 having a cylindrical shape is disposed around the secondary bobbin 14. That is, the secondary bobbin 14 and the primary bobbin 12 are concentrically arranged in this order around the central core 11. On the primary bobbin 12, for example, an enameled wire having a diameter of about 0.5 mm is wound about 200 times and a primary coil 13 is provided. Further, the secondary bobbin 14 is provided with a secondary coil 15 in which, for example, an enamel thin wire having a diameter of about 0.05 mm is wound about 20,000 times.

  Coil components such as the above-described central core 11 are accommodated in the case 16. The case 16 is made of polyphenylene sulfide (PPS) or the like having good electrical insulation characteristics. The case 16 has a diameter of 2 mm or less, for example. The size of the case 16 can be set as appropriate according to the application.

  An epoxy resin composition 17 is injected and cured between the coil component and the case 16 and between the coil components. Further, the case 16 is provided with an input unit 18, an output unit 19, and the like. A battery (not shown) is connected to the input unit 18 to input a low voltage current. A spark plug (not shown) is fitted into the output unit 19 and outputs a high voltage to the spark plug.

  The ignition coil 10 operates as follows. First, a low-voltage current is input to the primary coil 13 from a battery (not shown) via the input unit 18. Thereafter, when the low voltage current is interrupted by the ignition timing adjusting electronic circuit component and the power switch, a high voltage of 20 to 40 KV is generated in the secondary coil 15 by the mutual induction action of the primary coil 13 and the secondary coil 15. Then, a high voltage is output from the secondary coil 15 to an ignition plug (not shown) via the output unit 19 to generate a spark discharge in the ignition plug.

  The ignition coil 10 is a pen type in which a primary coil 13 and a secondary coil 15 are concentrically arranged, and a part or all of the ignition coil 10 is accommodated in a plug hole of an engine head. By accommodating a part or all of the ignition coil 10 in the plug hole, it is possible to obtain effects such as, for example, a reduction in space on the engine head, a reduction in noise during ignition, and a reduction in ignition energy propagation loss. it can. In addition, since the epoxy resin composition 17 having good impregnation properties, thermal conductivity, etc. is used, the occurrence of cracks and temperature rise when a high voltage is repeatedly applied is suppressed, resulting in excellent reliability. ing.

Hereinafter, the present invention will be specifically described based on examples.
The present invention is not limited to these examples.

Example 1
100 parts by mass of R-140P (trade name) manufactured by Mitsui Chemicals as a bisphenol A type epoxy resin, 90 parts by mass of methylhexahydrophthalic anhydride and 10 parts by mass of tetrahedrophthalic anhydride as an acid anhydride, N, 0.5 parts by mass of N-dimethylbenzylamine, 180 parts by mass of AC-07 (1) (manufactured by Fukushima Ceramics Co., Ltd., prototype name) after pulverizing by jet mill as crystalline silica, 3-glycid as silane coupling agent An epoxy resin composition was produced by mixing 0.5 parts by mass of xylpropyltrimethoxysilane and 0.1 parts by mass of a silicone antifoam as an antifoam. The average particle diameter of AC-07 (1) is as shown in Table 1.

(Example 2)
An epoxy resin composition was produced in the same manner as in Example 1 except that AC-07 (2) (manufactured by Fukushima Ceramics Co., Ltd., prototype name) classified as cyclone after jet mill pulverization was used as crystalline silica. The average particle diameter of AC-07 (2) is as shown in Table 1.

(Example 3)
An epoxy resin composition was produced in the same manner as in Example 1 except that 216 parts by mass of AC-07 (1) (manufactured by Fukushima Ceramics Co., Ltd., prototype name) classified after cyclone jet milling as crystalline silica was used. The average particle diameter of AC-07 (1) is as shown in Table 1.

Example 4
An epoxy resin composition was produced in the same manner as in Example 1, except that 216 parts by mass of AC-07 (2) (manufactured by Fukushima Ceramics Co., Ltd., prototype name) classified as cyclone after jet mill pulverization was used as crystalline silica. The average particle diameter of AC-07 (2) is as shown in Table 1.

(Comparative Example 1)
An epoxy resin composition was produced in the same manner as in Example 1 except that 180 parts by mass of crystallite A-AC (trade name, manufactured by Tatsumori Co., Ltd.) wet-classified after ball milling was used as crystalline silica. The average particle size of A-AC is as shown in Table 1.

(Comparative Example 2)
An epoxy resin composition was produced in the same manner as in Example 1 except that 180 parts by mass of OC-07 (manufactured by Fukushima Ceramics Co., Ltd., prototype name) subjected to cyclone classification after ball milling was used as crystalline silica. The average particle size of OC-07 is as shown in Table 1.

(Comparative Example 3)
An epoxy resin composition was produced in the same manner as in Example 1, except that 216 parts by mass of OC-07 (manufactured by Fukushima Ceramics Co., Ltd., prototype name) classified as a cyclone after ball milling was used as crystalline silica. The average particle size of OC-07 is as shown in Table 1.

(Comparative Example 4)
An epoxy resin composition was produced in the same manner as in Example 1 except that 180 parts by mass of fused silica AF-07 (trade name, manufactured by Fukushima Ceramics Co., Ltd.), which was subjected to cyclone classification after jet mill grinding, was used instead of crystalline silica. did. The average particle size of AF-07 is as shown in Table 1.

  Next, for the epoxy resin compositions of Examples and Comparative Examples, evaluation of viscosity, impregnation property, bending strength, bending elastic modulus, bending elongation, dielectric breakdown strength, thermal conductivity, crack resistance was performed by the following methods. went. The results are shown in Tables 2 and 3.

Viscosity: measured at a temperature of 70 ° C. using a B-type viscometer.
Impregnation (Evaluation with Ignition Coil): An epoxy resin composition was vacuum injected into the winding of the ignition coil and cured under conditions of 100 ° C. × 3 hours and 150 ° C. × 3 hours to produce an ignition coil. The cross section of the ignition coil was observed to evaluate the length of the winding (the length of the unimpregnated portion of the secondary coil).
Impregnation (impregnation rate by model coil): A model coil produced by winding a bobbin (inner diameter 21 mm) with a polyesterimide-coated wire (50 μmφ) about 22,000 times was impregnated with an epoxy resin composition, and 100 ° C. × 3 hours and Curing was performed at 150 ° C. for 3 hours. The model coil was cut to observe the impregnation state, and the impregnation rate was calculated by the following formula.
Impregnation rate [%] = (impregnation area / total winding area) × 100
Flexural strength, flexural modulus, flexural elongation: The epoxy resin composition is cured under conditions of 100 ° C. × 3 hours and 150 ° C. × 3 hours, and a test piece (width 10 mm, height 4 mm, length 80 mm) is obtained. Produced. Using this test piece, it was measured at a temperature of 25 ° C. in accordance with JISK7171.
・ Dielectric breakdown strength: With respect to a cured product obtained by curing the epoxy resin composition at 100 ° C. × 3 hours and 150 ° C. × 3 hours, the dielectric breakdown voltage conforms to JISK6911 using a dielectric breakdown tester (manufactured by Tokyo Seiden). And it measured at the temperature of 25 degreeC.
-Thermal conductivity: About the hardened | cured material which hardened the epoxy resin composition on the conditions of 100 degreeC x 3 hours and 150 degreeC x 3 hours, it measured using Kyoto Electronics QTM-500.
-Crack resistance: An epoxy resin composition was vacuum injected into the winding of the ignition coil and cured under conditions of 100 ° C. × 3 hours and 150 ° C. × 3 hours to produce an ignition coil. About this ignition coil, after hold | maintaining at -40 degreeC for 30 minute (s), the heat cycle test which repeated 100 cycles of the temperature rising to 150 degreeC and hold | maintaining for 30 minutes was done. Such a thermal cycle test was conducted on 10 ignition coils to evaluate the occurrence rate of cracks.

  As can be seen from Tables 2 and 3, the epoxy resin compositions of the examples have good impregnation properties, and particularly when the content of crystalline silica is large, the impregnation properties are good. Moreover, it turns out that the epoxy resin composition of an Example becomes favorable also about heat conductivity and crack resistance.

  As mentioned above, although this invention was demonstrated in detail based on the Example, this invention is not limited to an Example, All modifications and changes are possible unless it deviates from the category of this invention.

  DESCRIPTION OF SYMBOLS 10 ... Ignition coil, 11 ... Central core, 12 ... Primary bobbin, 13 ... Primary coil, 14 ... Secondary bobbin, 15 ... Secondary coil, 16 ... Case, 17 ... Epoxy resin composition, 18 ... Input part, 19 ... Output part.

Claims (4)

(A) 100 parts by mass of bisphenol A type epoxy resin, (B) 80 to 150 parts by mass of acid anhydride, (C) 0.1 to 5 parts by mass of curing accelerator, and (D) 150 to 250 parts by mass of crystalline silica. As an essential ingredient,
The epoxy resin composition for coil casting, wherein the (D) crystalline silica contains 60% by mass or more of crystalline silica classified by cyclone after jet mill pulverization in the entire crystalline silica.   The coil casting according to claim 1, wherein the (D) crystalline silica has an average particle size of 4 to 10 µm and a content of particles having a particle size of 1.0 µm or less of 8.0 mass% or less. Epoxy resin composition.   3. The coil casting epoxy resin composition according to claim 1, wherein the (D) crystalline silica has a content of particles having a particle diameter of 34 μm or more of 1.0% by mass or less.   A coil component that is cast by the epoxy resin composition for coil casting according to any one of claims 1 to 3.

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