JP2015168687A - Resin composition for immersion of coil and coil device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin composition for immersion of coil having reduced hardening contraction, capable of suppressing occurrence of detachment from a crack and member, and to provide a coil device having excellent reliability with such resin composition for immersion of coil.SOLUTION: A resin composition for immersion of coil contains (A) epoxy resin, (B) anhydride hardening agent, (C) hardening facilitating agent, (D) thermally expandable balloon, and (E) inorganic fill up agent. The component (D) is one or more selected from thermally expandable balloons having expansion initiation temperature of 5 to 30°C lower than the gelling temperature of the resin composition and contained at 1 to 20 pts.mass per 100 pts.mass of the component (A). In addition, the coil device is thermally hardened by immersing the coil in the resin composition for immersion of coil.

Description

  The present invention relates to a resin composition for coil impregnation used as an insulating material such as an ignition coil, and a coil device using the same.

  For electrical and electronic parts, for example, coils such as transformers and stators, a resin composition mainly composed of a thermosetting resin such as an epoxy resin or a polyester resin is used for the purpose of protection or insulation. In particular, epoxy resin compositions are widely used because of their excellent impregnation properties, insulation properties, mechanical properties, moisture resistance, heat resistance, etc. Especially, epoxy resin compositions are generally used in automobile ignition coils. ing.

  However, the conventional epoxy resin composition has a large shrinkage at the time of curing, and when the epoxy resin composition is impregnated into a coil and cured, the cured product is cracked or peeled off from the member, resulting in a decrease in yield. In addition, the performance as a coil may not be maintained. For this reason, a technique for reducing the cure shrinkage of an epoxy resin, or an epoxy resin composition with little cure shrinkage is desired.

  As this type of technology, for example, a method of covering a wound body with a plastic film has been proposed in order to suppress component defects due to curing shrinkage (see, for example, Patent Document 1). However, this method requires a film coating process, which increases the number of processes. In addition, the effect of a small coil such as an ignition coil is limited, and the performance as a coil can be sufficiently maintained. It was difficult.

Japanese Patent Laid-Open No. 11-224824

  The present invention has been made to solve the above-described problems of the prior art, has little curing shrinkage, can suppress the occurrence of cracks and peeling from members, and has original excellent impregnation, insulation, mechanical properties, etc. An object of the present invention is to provide a resin composition for impregnating a coil and a coil device excellent in reliability using such a resin composition for impregnation of a coil.

  As a result of intensive studies to solve the above problems, the present inventors have reduced the curing shrinkage rate of the epoxy resin by using a thermally expandable balloon, and suppressed the occurrence of cracks and separation from the member. The present invention has been found out and the present invention has been completed.

  That is, the resin composition for coil impregnation according to one embodiment of the present invention includes (A) an epoxy resin, (B) an acid anhydride curing agent, (C) a curing accelerator, (D) a thermally expandable balloon, and (E ) A resin composition for coil impregnation containing an inorganic filler, wherein the component (D) is selected from thermally expandable balloons having an expansion start temperature 5-30 ° C. lower than the gelation temperature of the resin composition. It is characterized by being 1 or more types.

  A coil device according to another aspect of the present invention is characterized in that the coil impregnating resin composition is impregnated into a coil and cured by heating.

  According to the present invention, a resin composition for impregnating a coil with little cure shrinkage, capable of suppressing the occurrence of cracks and separation from a member, and having original excellent impregnation, insulation, mechanical properties, and the like, and A coil device having excellent reliability using a resin composition for impregnating a coil can be obtained.

Hereinafter, the present invention will be described in detail.
The resin composition for coil impregnation of the present invention contains (A) an epoxy resin, (B) an acid anhydride curing agent, (C) a curing accelerator, (D) a thermally expandable balloon, and (E) an inorganic filler. To do.

  The epoxy resin of component (A) used in the present invention is not particularly limited as long as it has two or more glycidyl groups (epoxy groups) in one molecule, and a known epoxy resin is used. be able to.

  Examples of usable epoxy resins include, for example, bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol AD type epoxy resins, bisphenol S type epoxy resins, tetramethylbisphenol A type epoxy resins, and tetramethylbisphenol F type epoxy resins. Resin, tetramethylbisphenol AD type epoxy resin, tetramethylbisphenol S type epoxy resin, tetrabromobisphenol A type epoxy resin, tetrachlorobisphenol A type epoxy resin, tetrafluorobisphenol A type epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy Resin, dicyclopentadiene type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, bisphenol A novo Type epoxy resin, hydrogenated bisphenol type epoxy resin, 1,4-cyclohexanedimethanol diglycidyl ether, 1,6-hexanediol diglycidyl ether, hexahydrophthalic acid diglycidyl ester, 3,4-epoxycyclohexylmethyl ( 3,4-epoxy) cyclohexanecarboxylate, triglycidyl isocyanurate and the like. These can be used individually by 1 type or in mixture of 2 or more types. Moreover, a liquid monoepoxy resin etc. can be used as a combined component as needed.

  As the epoxy resin as component (A), an epoxy resin that is liquid at room temperature is preferable from the viewpoints of moldability, reliability, coil impregnation, and the like. Specific examples of commercially available liquid epoxy resins suitable as the component (A) include, for example, R140P (trade name, manufactured by Mitsui Chemicals) of bisphenol A type epoxy resin, jER807 (Mitsubishi Chemical) of bisphenol F type epoxy resin. Product name), bis710 AD epoxy resin RD710 (Mitsui Chemicals product name), cycloaliphatic epoxy resin Celoxide 2021P (Daicel Chemical Industries, Ltd. product name), chain and fat Examples thereof include EP-4005 (trade name, manufactured by ADEKA Corporation) of a cyclic epoxy resin.

  The acid anhydride curing agent of component (B) used in the present invention can be used without particular limitation as long as it is conventionally used as a curing agent for epoxy resins.

  Examples of usable acid anhydride curing agents include tetrahydrophthalic anhydride (THPA), hexahydrophthalic anhydride (HHPA), methylhexahydrophthalic anhydride (ME-HHPA), and the like. . These can be used individually by 1 type or in mixture of 2 or more types.

  The blending amount of the acid anhydride curing agent of the component (C) has a range in which the acid anhydride group equivalent is 0.7 to 1.3 equivalent per equivalent of the epoxy group in the epoxy resin of the component (A). A range of 0.8 to 1.2 equivalents is more preferable. If it is less than 0.7 equivalent or exceeds 1.3 equivalent, the heat resistance, impact resistance, reliability, etc. of the cured product may be lowered.

  The curing accelerator for the component (C) used in the present invention can be used without any particular limitation as long as it can accelerate the curing of the component (A) and the component (B). .

  Examples of the curing accelerator that can be used include, for example, aromatic dimethylurea, aliphatic dimethylurea, 3- (3,4-dichlorophenyl) -1,1-dimethylurea (DCMU), 3- (3-chloro- Ureas such as 4-methylphenyl) -1,1-dimethylurea and 2,4-bis (3,3-dimethylureido) toluene; benzyldimethylamine, 1,8-diazabicyclo (5.4.0) undecene- 7. Tertiary amines such as triethylamine; 2-ethyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 2-methylimidazole, 2-ethylimidazole, 2-isopropylimidazole, 2-phenylimidazole, 2 -Imidazoles such as phenyl-4-methylimidazole and 2-methylimidazole borate salt, Phenylphosphine, organic phosphines such as tetraphenyl phosphine borate salts. These can be used individually by 1 type or in mixture of 2 or more types.

  The blending amount of the curing accelerator of component (C) is 0.1 to 10 parts by mass with respect to 100 parts by mass of the epoxy resin of component (A) from the viewpoint of balance between curing acceleration and physical properties of the cured product. Is preferable, and the range of 0.4 to 5 parts by mass is more preferable.

  The thermally expandable balloon of component (D) used in the present invention includes a foaming agent such as a low-boiling hydrocarbon in a shell made of a thermoplastic resin, and at the same time the foamed agent encapsulated by heating expands. When the thermoplastic resin constituting the shell is softened, it rapidly expands to form a hollow balloon. Examples of the thermoplastic resin constituting the shell include copolymers such as acrylonitrile, acrylic acid esters, methacrylic acid esters, and vinylidene chloride. Examples of the foaming gas to be encapsulated in the shell include low-boiling hydrocarbons such as isobutane and isopentane, low-boiling halogenated hydrocarbons, and methylsilane.

  For the purpose of the present invention, among such thermally expandable balloons, the expansion start temperature (softening point of the thermoplastic resin constituting the shell) is 5 to 5 from the gelation temperature of the coil impregnating resin composition. A material having a temperature lower by 30 ° C. is selected and used. By using such a heat-expandable balloon, the cure shrinkage rate of the resin composition for coil impregnation can be reduced, and the occurrence of cracks after peeling and peeling from the member can be suppressed. When the expansion start temperature of the heat-expandable balloon is higher than the above range, the resin composition for coil impregnation is cured before the heat-expandable balloon is sufficiently expanded, and the curing shrinkage rate cannot be sufficiently reduced. On the other hand, when the expansion start temperature of the thermally expandable balloon is lower than the above range, the thermally expandable balloon is excessively expanded, and the appearance of the cured product is deteriorated. The heat-expandable balloon preferably has an expansion start temperature 5 to 25 ° C. lower than the gelation temperature of the coil-impregnating resin composition, and more preferably has an expansion start temperature 5 to 20 ° C. lower. preferable.

  As the thermally expandable balloon of component (D), it is preferable to use a balloon having an average particle size of 5 to 50 μm when not expanded (before expansion). When the average particle diameter is 5 μm, the viscosity of the resin composition for coil impregnation increases, and when it exceeds 50 μm, the coil impregnation property may be lowered. The average particle size when not expanded (before expansion) is more preferably 5 to 30 μm, and even more preferably 5 to 20 μm. The average particle size of the thermally expandable balloon is an average measured by a dynamic light scattering method (DLS) by using a laser diffraction scattering type particle size distribution measuring device (product name: Microtrack) manufactured by Nikkiso Co., Ltd. The particle size.

  Examples of commercially available thermally expandable balloons having an average particle size in the above range include Matsumoto Microsphere F and FN series manufactured by Matsumoto Yushi Seiyaku Co., Ltd., EXPANCEL manufactured by Nippon Philite Co., Ltd. ADVANCEL manufactured by Sekisui Chemical Co., Ltd. (all are trade names). One of the thermally expandable balloons can be used alone, or two or more of them can be used in combination.

  The amount of the thermally expandable balloon as the component (D) is preferably in the range of 1 to 20 parts by mass, more preferably in the range of 2 to 15 parts by mass with respect to 100 parts by mass of the epoxy resin of the component (A). The range of 3 to 8 parts by mass is even more preferable. If it is less than 1 part by mass, the effect of addition cannot be obtained, and the curing shrinkage rate of the resin composition for coil impregnation becomes high. On the other hand, when the amount exceeds 20 parts by mass, the inflated balloon comes out on the surface of the cured product, the appearance becomes poor, and the mechanical strength also decreases.

  The inorganic filler of the component (E) used in the present invention is a component blended to improve the dielectric breakdown characteristics, mechanical strength, etc. of the resin composition for coil impregnation of the present invention, and this kind of resin composition If it is generally blended, it can be used without particular limitation. Examples of usable inorganic fillers include silica such as fused silica and crystalline silica, alumina, silicon nitride, boron nitride, magnesia, boehmite, calcium carbonate, aluminum hydroxide, talc, titanium white, clay, bengara, etc. Is mentioned. These may be used alone or in combination of two or more.

  The shape of these inorganic fillers is not particularly limited and may be any shape such as a spherical shape or a flake shape, but the viewpoint of reducing the viscosity of the resin composition for coil impregnation and improving the coil impregnation property. Is preferably spherical with no corners. As the inorganic filler, spherical fused silica is particularly preferable.

  The blending amount of the inorganic filler of the component (E) is preferably in the range of 100 to 850 parts by mass, more preferably in the range of 200 to 600 parts by mass with respect to 100 parts by mass of the epoxy resin of the component (A). If the amount is less than 100 parts by mass, the dielectric breakdown characteristics and mechanical strength may not be sufficiently improved. If the amount exceeds 850 parts by mass, the viscosity increases and the coil impregnation property decreases.

  Further, the inorganic filler of component (E) is preferably added in an amount of 40 to 85% by mass in the resin composition for coil impregnation in total with the thermally expandable balloon of component (D), and 50 to 80% by mass. % Is more preferable. If the amount is less than 40% by mass, the mechanical strength may not be sufficiently secured. If the amount exceeds 85% by mass, the viscosity may increase and the coil impregnation property may decrease.

The resin composition for coil impregnation of the present invention includes a coupling agent such as a silane coupling agent, a titanium coupling agent, and an aluminum coupling agent, a thixotropic agent, a release agent, and a colorant in addition to the above components. Moreover, a low stress imparting agent, an antifoaming agent, and other various additives can be blended within a range not impairing the effects of the present invention.
As the coupling agent, a silane coupling agent is preferable, and specific examples thereof include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3- (3,4-epoxy). (Cyclohexyl) ethyltrimethoxysilane, 3- (methacrylopropyl) trimethoxysilane and the like.

  Examples of the thixotropic agent include modified urea, and examples of the mold release agent include synthetic wax, natural wax, linear aliphatic metal salt, acid amide, ester, and the like. Furthermore, examples of the colorant include carbon black and cobalt blue, and examples of the low stress imparting agent include silicone oil and silicone rubber.

  The resin composition for coil impregnation of the present invention comprises (A) an epoxy resin, (B) an acid anhydride curing agent, (C) a curing accelerator, (D) a thermally expandable balloon, and (E) an inorganic material. It can be manufactured by thoroughly mixing the filler and various components blended as necessary, further kneading with a disperser, a kneader, etc., and then degassing under reduced pressure.

  The resin composition for coil impregnation of the present invention thus obtained can be used for impregnation casting of a coil such as an ignition coil. The resin composition for impregnating a coil of the present invention has little cure shrinkage and is excellent in impregnation, insulation, mechanical properties, etc., so it can be sufficiently applied to a small coil such as an ignition coil, such as a crack. It is possible to manufacture a coil device with excellent reliability.

  EXAMPLES Next, although an Example and a comparative example demonstrate this invention in detail, this invention is not limited by these examples. The materials used in the following examples and comparative examples are as shown in Table 1. Further, “part” means “part by mass” unless otherwise specified.

Example 1
69 parts of liquid epoxy resin (1), 24 parts of liquid epoxy resin (2), 7 parts of liquid epoxy resin (3), 100 parts of acid anhydride curing agent, 0.2 part of antifoaming agent, 1.2 parts of colorant, An epoxy resin composition is prepared by vacuum kneading 2 parts of a silane coupling agent, 548 parts of an inorganic filler, 0.6 part of a curing accelerator, and 5 parts of a heat-expandable balloon at 60 to 80 ° C. for 60 minutes using a kneader. did.

Examples 2-6, Comparative Examples 1-5
Except having changed the composition as shown in Tables 2 and 3, an epoxy resin composition was prepared in the same manner as in Example 1, and the obtained composition was further heat-cured to obtain a cured product.

  About the epoxy resin composition obtained by each said Example and each comparative example, various characteristics were evaluated by the method shown below, and the result was combined with Table 2, 3, and was shown.

(1) Gelation temperature A 10 mm diameter glass test tube containing 10 g of an epoxy resin composition and a glass rod is put into an oil bath, and the temperature of the oil bath is adjusted while raising and lowering the glass rod once a minute. The temperature when the glass rod could not be moved up and down was measured.
(2) Appearance of cured product The epoxy resin composition was heated at 75 ° C for 1.5 hours, heated from 75 ° C to 145 ° C over 3.5 hours, then heated at 145 ° C for 2 hours to be cured and cured. I got a thing. The surface of the cured product was visually observed, the number of bubbles was counted, the size was measured with an optical microscope, and evaluated according to the following criteria.
A: No bubbles having a diameter of 200 μm or more ○: 1 to 9 bubbles having a diameter of 200 μm to less than 400 μm Δ: 10 to 29 bubbles having a diameter of 200 μm to less than 400 μm ×: Bubbles having a diameter of 400 μm or more 30 bubbles or more (3) Curing shrinkage (specific gravity method)
The epoxy resin composition is heated and cured under the same conditions as in (2) to prepare a cured product sample piece, and the cured product specific gravity is measured in accordance with JIS K 6911. The specific gravity of the epoxy resin composition before curing ( (Specific gravity before curing) was measured according to JIS K 0061 and calculated from the following formula.
Curing shrinkage rate (%) = [(cured product specific gravity−specific gravity before curing) / specific gravity before curing] × 100
(4) Flexural strength / flexural modulus The epoxy resin composition was heated and cured under the same conditions as in (2) to produce a cured sample piece, which was measured at a temperature of 25 ° C. according to JIS K 6911. .
(5) Bending deformation amount The epoxy resin composition is heated and cured under the same conditions as in (2) to prepare a cured sample piece similar to (4), and the sample piece is obtained by the test method described in JIS K 6911. The amount of deformation (mm) until breakage was determined.
(6) Coil impregnation A model coil produced by winding a polyester imide-coated wire (50 μmφ) around a bobbin (21 mm inner diameter) about 22,000 times is impregnated with an epoxy resin composition and cured under the same conditions as in (2). It was. The model coil after the heat curing treatment was cut, the impregnation state was observed, and the following criteria were evaluated.
◎: Impregnation rate of 99% or more ○: Impregnation rate of 95% or more and less than 99% △: Impregnation rate of 90% or more and less than 95% ×: Impregnation rate of less than 90% (7) Crack resistance PPE (polyphenylene ether) plate spool material ( 40 mm x 20 mm x 1.5 mm) is placed on a rectangular copper conductor (40 mm x 5 mm x 1.5 mm), and both ends are connected with a copper wire (diameter 0.2 mm), and then covered with an epoxy resin composition. (2) And cured by heating under the same conditions as described above to obtain a 10 mm thick resin-attached plate. This sample was subjected to a thermal cycle test in which the sample was held at 140 ° C. for 20 minutes and then held at −40 ° C. for 10 minutes (temperature increase and temperature decrease rate: 6 ° C./min) for one cycle. The number of cycles until peeling occurred was measured.

  As is apparent from Tables 2 and 3, the resin composition for impregnating coils according to the examples has a curing shrinkage reduced to substantially zero, and such a resin composition for impregnating coils is used. Thus, it was confirmed that a coil device having excellent reliability can be obtained.

Claims (6)

A resin composition for coil impregnation comprising (A) an epoxy resin, (B) an acid anhydride curing agent, (C) a curing accelerator, (D) a thermally expandable balloon, and (E) an inorganic filler,
The component (D) is one or more selected from thermally expandable balloons having an expansion start temperature 5 to 30 ° C. lower than the gelation temperature of the resin composition, and per 100 parts by mass of the component (A) A resin composition for impregnating a coil, which is contained by 20 parts by mass.   2. The resin composition for coil impregnation according to claim 1, wherein the thermally expandable balloon of the component (D) is obtained by encapsulating a foaming agent in a shell made of a thermoplastic resin.   (A) 0.1-100 mass parts of hardening accelerators of (C) component and 100-850 mass parts of inorganic fillers of (E) component are contained per 100 mass parts of component (A). Or the resin composition for coil impregnation of 2.   The resin composition for coil impregnation according to any one of claims 1 to 3, wherein the thermally expandable balloon of component (D) has an average particle size of 5 to 50 µm when not inflated (before inflation). object.   The resin composition for coil impregnation according to any one of claims 1 to 4, wherein the inorganic filler of the component (E) is spherical silica.   A coil device comprising a coil impregnated with the resin composition for impregnating a coil according to any one of claims 1 to 5 and heat-cured.