JPS6144886B2 - - Google Patents

Description

[Detailed description of the invention]

Epoxy resins have excellent electrical properties, adhesive properties, and moisture resistance, and have a smaller shrinkage rate when cured than other resins, so they are widely used in casting and molding of electrical and electronic parts. Curing agents for curing epoxy resins generally include (1) polyamines, (2) polyamides, (3) organic dibasic acid anhydrides, (4) phenols, and (5) boron trifluoride amine complexes. Among them, when (3) organic dibasic acid anhydrides and (4) phenols are selected as curing agents, polyamines, tertiary amines, imidazoles, etc. are used to obtain the required properties. Depending on the situation, it is added as a curing accelerator. In recent years, electric and electronic parts used in automobile parts are increasingly being used in metal cases due to increased exhaust gas regulations and improvements in fuel efficiency, especially in the engine compartment, where metal cases are increasingly being used. Steel and aluminum, which have excellent properties, are often used. The casting material for these parts must have excellent adhesion to the case material, and must also be able to withstand severe thermal shock resistance. Epoxy resin has low shrinkage among thermosetting resins and has good adhesion to metals, so it is often selected as a material that meets the above requirements, but the physical properties of the cured product of epoxy resin depend on the type of curing agent. It varies markedly depending on the Among the curing agents for epoxy resin, polyamines are
Although it provides a cured product with excellent adhesion to metal cases and thermal shock resistance (heat cycle resistance), it has a short pot life and is highly irritating to the skin, making it less safe. On the other hand, when organic dibasic acid anhydrides are used alone or in combination with curing accelerators such as tertiary amines and imidazoles, they shrink more during curing than polyamines, and generate large internal stress, so heating Peeling or cracking from the case often occurs during curing. Furthermore, since the cured product has a high crosslinking density and is brittle, even if the cured product is good during heat curing, it will peel off from the case when subjected to thermal shock. Adding a plasticizing agent is generally used as a measure to prevent peeling and cracking, but in this case, the heat resistance and electrical properties often deteriorate significantly, making it difficult to impregnate high-voltage parts, etc. , it was not suitable for casting. On the other hand, methods have been used to reduce the shrinkage rate during curing by adding a filler, and to bring the coefficient of linear expansion closer to that of metal, thereby preventing peeling and cracking. In this case, the fluidity of the resin was impaired, and due to the settling of the filler, the cast material became uneven, often resulting in peeling from the case and cracks. The present invention consists of (1) an epoxy resin having at least one epoxy group in its molecule; (2) a silica-based filler having a particle size distribution of 1 to 100 microns and an average particle diameter of 15 to 35 microns; (3) an average particle size of 15 to 35 microns; Zirconium oxide (4) organic dibasic acid anhydride (5) having a particle size of 10 to 40 μ A cured epoxy resin product with excellent adhesion, adhesion, and thermal shock resistance (heat cycle resistance) can be obtained. Epoxy resins having at least one epoxy group in the molecule used in the present invention include diglycidyl ethers and derivatives thereof derived from bisphenol A and epichlorohydrin, and diglycidyl ethers and derivatives thereof derived from bisphenol F and epichlorohydrin. Commonly known as Epibis type liquid epoxy resin such as, diglycidyl ether derived from polyhydric alcohol and epichlorohydrin, glycidyl ester and its derivatives derived from polybasic acid and epichlorohydrin, diglycidyl derived from hydrogenated bisphenol A and epichlorohydrin. ether and its derivatives,
3,4-epoxy-6-methylcyclohexylmethyl-3,4-epoxy-6-methylcyclohexanecarboxylate, dicyclopentadiene oxide, vinylcyclohexene oxide, bis(2,3-epoxycyclopentyl) ether, 3,4-epoxy Alicyclic epoxy and derivatives thereof such as cyclohexylmethyl (3,4-epoxycyclohexane) carboxylate, bis(3,4-epoxy-6-methylcyclohexylmethyl) adipate, limonene dioxide, and methyl substitution derived from isobutylene Type epoxy or the like is used, and there are no restrictions on its type. The organic dibasic acid anhydrides used in the present invention include phthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, nadzic anhydride, Methylnadic acid, dodecenylsuccinic anhydride, maleic anhydride, chloreidic anhydride, and derivatives thereof are used, and the blending amount is 0.7 to 1 mole of epoxy resin from the viewpoint of heat deterioration resistance and hardness change over time. 1.3 mol is preferred, and 0.85 to 1.1 mol is more preferred. As the silica-based filler having a particle size distribution of 1 to 100μ and an average particle size of 15 to 35μ used in the present invention, for example, quartz powder, fused silica powder, talc, mica, etc. are used, and the cured product From the viewpoint of linear expansion coefficient and fluidity of the resin composition, it is preferable to mix 60 to 80% by weight of this into the mixed system of the epoxy resin and organic dibasic acid anhydride. The silica filler used in the present invention has a wide particle size distribution of 1 to 100μ.
It can be filled in a large amount without impairing the fluidity of the resin, and is extremely effective in reducing the coefficient of linear expansion. And it is necessary that the average particle diameter is 15 to 35μ. The average particle size of the filler used is 15
When it is less than μ, thixotropic properties are imparted to the resin, resulting in decreased workability and castability. If it exceeds 35μ, the filler will settle significantly and the linear expansion coefficient of the cured product will increase. A silica-based filler having a particle size distribution of 1 to 100 microns and an average particle size of 15 to 35 microns can also be obtained by blending commercially available fillers. for example
Fuse Rex RD-8 passed the 100μ sieve
(Tatsumorisha product name, average particle size 12~18μ) and glass grain 100~325 (manufactured by Toshiba Ceramics Co., Ltd., average particle size 70μ) that passed a 100μ sieve. /
Obtained by blending at a blending ratio (weight ratio) of 130-430-70. Zircon oxide is added to the present invention in order to improve fluidity, adhesion to the metal case, and thermal shock resistance. The average particle size of zircon oxide is 10-40
μ, and the blending amount is 3 to 10% by weight for the mixed system of epoxy resin, organic dibasic acid anhydride, and silica filler from the viewpoint of fluidity, adhesion to the metal case, and density of the resin composition. It is preferable to add. When the average particle diameter is less than 10μ, the effect of improving fluidity is small, and when it exceeds 40μ, the sedimentation of zircon oxide increases. In the present invention, an imidazole compound with excellent adhesion to the metal case and thermal shock resistance is used as a curing accelerator. 4 to 9 parts by weight is preferred. Imidazole compounds used in the present invention include 2-methylimidazole, 2-ethyl-4-methylimidazole, 1
-cyanoethyl-2-ethyl-4-methylimidazole, 1-benzyl-2-methylimidazole, etc. belong to this category. The epoxy resin composition of the present invention may contain colorants, coupling agents,
Other fillers and the like may also be included. The present invention will be explained with reference to Examples and Comparative Examples.
In Examples and Comparative Examples, parts refer to parts by weight. Table 1 shows the particle size distribution of the silica filler used, and Table 2 shows the particle size distribution of zirconium oxide. % in the table
% by weight is indicated.

【table】

[Table] Example 1 100 parts of an alicyclic epoxy resin with a molecular weight of 290 to 320 and an epoxy equivalent of 145 to 160 (Syodyne 540: brand name of Showa Denko KK), 520 parts of the above filler (A), 40 parts of zirconium oxide, anhydrous Methyltetrahydrophthalic acid 110
1 part and 5 parts of 1-cyanoethyl-2-ethyl-4-methylimidazole were stirred with a laboratory stirrer and then degassed to prepare a sample. Example 2 100 parts of an alicyclic epoxy resin with a molecular weight of 270 to 280 and an epoxy equivalent of 130 to 140 (ERL4221: trade name of Union Carbide Co., Ltd.), 480 parts of the above filler (A), 40 parts of zirconium oxide, 130 parts of methylnadic anhydride Part, 2
-Ethyl-4-methylimidazole (4 parts) was stirred with a laboratory stirrer and then degassed to prepare a sample. Comparative Example 1 100 parts of an alicyclic epoxy resin with a molecular weight of 270 to 280 and an epoxy equivalent of 130 to 140 (ERL4221: trade name of Union Carbide Co., Ltd.), 120 parts of methyltetrahydrophthalic anhydride, 520 parts of the above filler (B), oxidation 40 parts of zircon and 5 parts of 1-cyanoethyl-2-ethyl-4-methylimidazole were stirred with a lab stirrer and then degassed to prepare a sample. Comparative Example 2 100 parts of hexahydrophthalic acid diglycidyl ester with a molecular weight of 290 to 320 and an epoxy equivalent of 145 to 160 (Syodyne 540: Showa Denko Co., Ltd. brand name), 100 parts of methyltetrahydrophthalic anhydride, the above filler (C)
550 parts, 40 parts of zircon oxide, 1-cyanoethyl-
Six parts of 2-ethyl-4-methylimidazole was stirred with a lab stirrer and then degassed to prepare a sample. Comparative Example 3 100 parts of an alicyclic epoxy resin with a molecular weight of 270 to 280 and an epoxy equivalent of 130 to 140 (ERL4221: trade name of Union Carbide Co., Ltd.), 120 parts of methyltetrahydrophthalic anhydride, 520 parts of the above filler (A), 1 -cyanoethyl-2-ethyl-4-methylimidazole 5
The sample was stirred using a laboratory stirrer and then degassed. Comparative Example 4 100 parts of an alicyclic epoxy resin with a molecular weight of 270 to 280 and an epoxy equivalent of 130 to 140 (ERL4221: Union Carbide Co., Ltd. trade name), 130 parts of methylnadzic anhydride
parts, 520 parts of the above filler (A), 40 parts of zirconium oxide,
Two parts of 2-ethyl-4-methylimidazole were stirred with a lab stirrer and then degassed to prepare a sample. The fluidity of the samples of Examples 1 to 2 and Comparative Examples 1 to 4 was examined, and the samples were placed in an aluminum case and their adhesion (heat cycle resistance) with the aluminum case was compared. Figure 1 shows an outline of the fluidity test. FIG. 1a is a front view of the device used in the test, and FIG. 1b is a side view thereof. Fluidity is 5g placed in circle 2 of 40mmφ
The time (minutes) required for sample 1 to flow 50 mm down the 60° slope 3 of the tin plate is shown. FIG. 2 shows an outline of the aluminum case used in the adhesion test, with a being a top view and b being a cross-sectional view. The adhesion test was conducted by observing the presence or absence of peeling or cracking at the interface between the aluminum case and the hardened sample using a 50x microscope. Table 3 shows a comparison of characteristics. ◎ in the table
○ indicates that there is no cracking or cracking at the interface, ○ indicates that peeling of about 1 mm has occurred, and × indicates that cracking has occurred on one or more sides of the case.

[Table] The present invention greatly improves the heat cycle resistance of epoxy resins, which could not be achieved by conventional methods. In particular, the present invention can contribute to the reliability and long life of automobile parts, which have recently become smaller, more diverse, and more precise.

[Brief explanation of the drawing]

FIGS. 1a and 1b are diagrams showing an outline of the fluidity test conducted in the example, and FIGS. 2a and 2b are diagrams showing an outline of the aluminum case used in the adhesion test. Explanation of symbols: 1...Sample, 2...Circle, 3...Slope.

Claims (1)

[Scope of Claims] 1 (1) An epoxy resin having at least one epoxy group in its molecule (2) A silica filler having a particle size distribution of 1 to 100 μm and an average particle size of 15 to 35 μm (3) Zircon oxide having an average particle diameter of 10 to 40 μm (4) Organic dibasic acid anhydride (5) An epoxy resin composition containing an imidazole compound as a curing accelerator.