JPS6144109B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an epoxy resin composition for pressure molding, and particularly to an epoxy resin composition for pressure molding that provides a cured product having good molding fluidity and excellent heat resistance and thermal shock resistance. Since epoxy resins have excellent properties such as mechanical strength, dimensional stability, heat resistance, and electrical properties, demand for various insulating materials or sealing materials as molding materials is increasing significantly. However, since this type of material generally uses a solid resin, a melt blending method using heat kneading is used for manufacturing the material. Therefore, there were problems with temperature control, kneading time, etc., and mass production was difficult. Additionally, manufacturing steps such as crushing the material and forming tablets are required. Furthermore, during molding, in order to improve the fluidity of the molding material and increase molding efficiency, it was necessary to perform preheating such as high-frequency preheating before molding. Particularly in low-pressure transfer molding (applying pressure 200 kg/cm ² or less), when molding inserts with holes or narrow grooves, the fluidity of the material into the holes or grooves is poor, which poses a major limitation in terms of their use. receive. On the other hand, molding materials manufactured by kneading using liquid epoxy resin and curing agents have advantages such as being easy to mass produce and making it easy to adjust fluidity, but they do not cause cavities in molded products. There are disadvantages such as easy molding, extremely large amount of burrs on the parting surface of the mold even when molded at low pressure, and short storage stability of the molding material after kneading with a kneader. Furthermore, the cured product of liquid epoxy resin, which requires heat resistance, is generally brittle and it is difficult to blend a large amount of filler with kneader kneading, so there is a problem that the material has a large coefficient of linear expansion and poor thermal shock resistance. It is hardly used as a material for pressure molding. The present invention has been made in view of the current situation, and its purpose is to provide an epoxy resin composition for pressure molding that has good molding fluidity and has good heat resistance and thermal shock resistance of a cured product. That's true. To summarize the present invention, the epoxy resin composition for pressure molding of the present invention comprises (A) a liquid epoxy resin and
(B) (a) Inorganic filler containing about 90% by weight or more of SiO ₂ with a particle size of about 5 to 150 μm, (b) silica sand with a particle size of about 150 to 1000 μm, and (c) fine powder with a particle size of about 5 μm or less containing a filler consisting of a filler, and the total weight of the filler (B) is about 3.5 to 6 times the weight of the liquid epoxy resin (A),
Further, the blending weight ratio of the inorganic filler (a) to the silica sand (b) is about 1 to 6, and the blending amount of the fine powder filler (c) to the total weight of the filler (B). Approximately 1 to 20% by weight
It is characterized by: As a result of various studies, the inventors of the present invention have found that by blending a large amount of three types of fillers B with different particle sizes into liquid epoxy resin A and kneading them in a kneader, the resin can be cured with particularly excellent molding fluidity and good heat resistance. The present invention was completed based on the discovery that a pressure molding resin composition capable of producing a desired product can be obtained. Since a specific filler plays an important role in the present invention, it will first be explained in detail. The particle size of commonly used fillers is approximately 50~
It falls within the range of about 140μ. In addition, in the kneader kneading method, fillers with a particle size of about 5 to 150μ,
The blending amount is limited to about three times the amount of epoxy resin, which increases the cost of the material, increases the coefficient of linear expansion of the resulting cured product, reduces thermal shock resistance, and causes burrs on the parting surface of the mold. cannot be put to practical use because it becomes extremely large. According to the present invention, BiO ₂ with a particle size of about 5 to 150μ is
Inorganic filler a containing 90% by weight or more, particle size 150~
By using filler B, which is a mixture of 1000μ silica sand b and fine powder filler c with a particle size of about 5μ or less at a specific blending ratio, the blending amount of filler B can be increased and its effect can be effectively exhibited. I can do it. That is, by blending silica sand B with a particle size of about 150 to 1000 microns, it is possible to blend filler B in an amount up to 6 times the amount of liquid epoxy resin. In the present invention, the reason why the mixing ratio of the inorganic filler a and the silica sand b is limited to a weight ratio of 1 to 6 for the former is that if the weight ratio exceeds this range, the kneading property of the kneader deteriorates and a large amount of the filler must be used. This is because it is difficult to blend, and if the amount is less than this range, the filling properties of holes and grooves are poor, resulting in formation of cavities in the molded product and poor mold releasability. On the other hand, increasing the blending amount of the fine powder filler c with a particle size of 5μ or less can have the effect of suppressing the occurrence of burrs, but on the contrary, the molding fluidity tends to decrease, so the fine powder The amount of filler c to be blended is suitably within the range of about 1 to 20% by weight based on the total weight of filler B. The type of inorganic filler a above has a SiO ₂ content of approx.
There is no particular limitation as long as it is 90% by weight or more, and for example, fused silica powder, silica, silica sand, etc., or a mixture thereof can be used as appropriate. Note that if the content of SiO ₂ is less than about 90% by weight, the mold releasability during molding will be poor only when a liquid epoxy resin is used. Further, as the silica sand b, any of mountain sand, river sand, beach sand, natural silica sand, etc. can be used, and the particle size is preferably within the above range, but the particle size is about 150μ or less or 1000μ Even if the above components are contained in a total amount of about 5% by weight or less, the effects of the present invention will not be impaired. Note that calcium carbonate and the like are available as the filler due to its particle size, but this is not desirable because it tends to reduce the release agent. Further, the fine powder filler c is not particularly limited, and for example, fused quartz powder, silica, clay, barium sulfate, calcium sulfate, etc., or a mixture thereof can be appropriately selected and applied. The liquid epoxy resin A in the present invention is not particularly limited, and commercially available commercially available epoxy resins such as novolac type and/or cycloaliphatic epoxy resins can be suitably used. Furthermore, in the present invention, these liquid epoxy resins have an epoxy equivalent of about
By mixing and using 200 to 500% bisphenol A type epoxy resin, a cured product having particularly excellent heat resistance and thermal shock resistance can be obtained without reducing the molding fluidity of the resin composition.
If the epoxy equivalent of the bisphenol A type epoxy resin is less than about 200, the obtained cured product will be brittle, and if it is more than about 500, the melting point of the epoxy resin composition will become high and kneading with a kneader will become difficult.
Further, the amount of bisphenol A type epoxy resin blended is suitably within the range of about 20 to 60% by weight based on the total weight of the epoxy resin. This amount is approximately 20% by weight
If it is less than about 60% by weight, the resulting cured product will become brittle and its thermal shock resistance will be reduced, and if it exceeds about 60% by weight, its heat resistance will be significantly reduced. In the present invention, a curing agent for the epoxy resin and further a curing accelerator can be used in combination. There are many types of curing agents for epoxy resins, including the properties of the curing agent, pot life of the resin and curing agent mixture, viscosity,
Since the curing time, heat generation, etc. are very different, an appropriate curing agent must be selected depending on the purpose of use of the cured product, usage conditions, working conditions, etc. Curing agents include compounds with hydroxyl groups, carboxyl groups, amino groups, etc. that react with epoxy groups, and acid anhydrides.The main types include amines, acid anhydrides, polyamide resins, and synthetic resins for initial condensation. In particular, as curing agents for pressure molding materials, synthetic resin initial condensates (phenol resins, etc.) are generally used, and amines, acid anhydrides, etc. are also used in some cases. There is. In the present invention, the use of specific curing agents has been found to be desirable. When conventional liquid curing agents such as the above-mentioned acid anhydrides are used, there are problems such as poor storage stability of the epoxy resin composition and the tendency to generate burrs during molding. Anhydrides, phenolic resins, etc. have high melting points and cannot be completely dissolved by kneading with a kneader, which causes cavities in molded products. According to studies conducted by the present inventors, powdered hydroxy compounds have good dispersibility in materials and good curability, and among them, 4,4'-isopropylidene biphenol (bisphenol A) is particularly effective. By using this, it is possible to provide an epoxy resin composition that has excellent storage stability and provides a cured product with good properties. In addition, it is appropriate that the amount added is approximately 20 to 40 parts by weight per 100 parts by weight of the liquid epoxy resin B; if it is less than approximately 20 parts by weight, the thermal shock resistance of the cured product will deteriorate; If the amount is less than 40 parts by weight, the heat resistance will be significantly reduced. Further, the curing accelerator in the present invention is not particularly limited, and known Lewis acids, tertiary amines, organic acids, metal salts, borates, etc. can be used as appropriate.
Specifically, conventionally used nitrogen-containing compounds such as imidazole and amines, or organometallic compounds such as tetraphenylphosphonium tetraphenylborate, boron trifluoride and complexes thereof, etc. can be used. In the present invention, in addition to the above-mentioned components, mold release agents such as stearic acid, zinc stearate, calcium stearate, Hoechst wax and carnauba wax, and vinyl silane having a coupling effect between resin and filler, etc. Coupling agents such as , epoxy silane, amino silane and titanate compounds, or coloring agents such as titanium oxide, chromium oxide, ultramarine blue, pen color and carbon black can be incorporated. Next, the present invention and its effects will be explained by examples, but the present invention is not limited by these in any way. Examples 1 to 4 and Comparative Examples 1 to 7 100 parts by weight of liquid novolac type epoxy resin (manufactured by Ciel Chemical Co., Ltd., Epicoat 152, epoxy equivalent 175), 4,4'-isopropylidene bienol (Wako Pure Chemical Industries, Ltd.) as a curing agent (manufactured by Shikoku Fine Chemical Co., Ltd.) 20 parts by weight, 4 parts by weight of 2-undecylimidazole (manufactured by Shikoku Fine Chemical Co., Ltd., Imidazole C ₁₁ Z) as a curing accelerator,
3 parts by weight of Hoechstwax as a mold release agent, γ-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., KBM403) as a coupling agent, and silica (with a particle size of 5 to 150 μm and with a particle size of 5 μm or less) as a filler. ) and silica sand (with a particle size of 150 to 1000 μm) were blended in the amounts shown in Table 1 below. The blending was carried out by kneading at room temperature using a kneader with a capacity of 1, and the kneading properties were examined. Using this resin composition, 150°C, 30Kg/cm ² ,
Under the conditions of 3 minutes, pressurized transfer molding was carried out using an insert with a commutator attached to a flat electrical coil made by pressing a series of coils in a circular shape and fixing a fixing member in a circular shape, and in this case between the coils. The fluidity of the material and the amount of burr generation were investigated. For comparison, similar experiments were also conducted using fillers other than those in the present invention. The results obtained are shown in Table 1 below. Note that the evaluation was performed as follows. 〇Kneader kneading property: 〇...Good kneading property ×...Kneading not possible 〇Molding fluidity: Evaluated by spiral flow (S・F), which is a measure of fluidity, from the relationship with the material filling property of the insert material. . 〇...S/F 20 inches or more x...S/F 20 inches or less Amount of burr generation: Using a special mold, the amount of burr generation was evaluated based on the length of the material flowing out of a 100μ narrow groove. 〇……10mm or less △……10~30mm ×……30mm or more

[Table] Example 5 Using the same epoxy resin and curing agent as in Example 1, the relationship between the amount of curing agent and mechanical properties was measured at 150°C.
A comparative study was conducted based on the bending properties at . The blending ratio and amount of the filler was the same as in Example 2. The results obtained are shown in the drawings. That is, the drawing is a graph showing the relationship between the blending amount of the curing agent and the bending strength and breaking strain, where A shows the bending strength and B shows the breaking strain. As is clear from the drawings, good properties (flexural strength of 150 Kg/cm ² or more, rupture strain of 15% or more). Examples 6 to 9 and Comparative Examples 8 to 12 In the filler composition of Example 2, the amount of curing agent was kept constant at 30 parts by weight, and a liquid novolac type epoxy resin (manufactured by Ciel Chemical Co., Ltd., Epicoat) was used.
152, epoxy equivalent 175) and liquid cycloaliphatic epoxy resin (manufactured by Union Carbide, Bakelite
ERL-4221, epoxy equivalent weight 140) was used, and bisphenol A type epoxy resins (manufactured by Ciel Chemical Co., Ltd., Epicoat 834, epoxy equivalent weight 255, and Dow Chemical Company, Araldite CT-200, epoxy equivalent weight 370) were used. They were blended in the proportions shown in Table 2 below to obtain an epoxy resin composition. In addition, for comparison, we prepared products that did not contain bisphenol A type epoxy resin and products that contained a large amount of bisphenol A epoxy resin (70% by weight). Using these epoxy resins, inserts similar to those in Examples 1 to 4 were pressurized and transfer molded. The obtained molded product was heated at 150℃ for 1 hour←→-60℃, 1
A heat cycle was repeated 10 times, and the organic and heat resistance of cracks in the resin molded portion was investigated. The results obtained are shown in Table 2 below. In the evaluation of thermal shock resistance shown in the table, ◯ indicates that no cracks occur, and × indicates that cracks occur. In addition, heat distortion temperature was displayed as an evaluation method for heat resistance.

[Table] As is clear from Table 2, the molded products made from the epoxy resin of the present invention have better crack resistance and heat resistance than those of the comparative examples. As explained above, according to the present invention, it is possible to provide an epoxy resin composition for pressure molding that provides a cured product having good molding fluidity and excellent heat resistance and thermal shock resistance.

[Brief explanation of the drawing]

The drawing is a graph showing the relationship between the blending amount of the curing agent and the bending strength and breaking strain of the cured product in Example 5.

Claims (1)

[Claims] 1. (A) liquid epoxy resin and (B) (a) particle size of about 5 to 150
an inorganic filler containing approximately 90% by weight or more of SiO ₂ of μ; (b) silica sand with a particle size of approximately 150 to 1000 μ; and (c) a particle size of approximately 5
The total weight of the filler (B) is about 3.5 to 6 times the weight of the liquid epoxy resin (A), and the (b) ) The blending weight ratio of the inorganic filler (a) to the silica sand is about 1 to
6. An epoxy resin composition for pressure molding, wherein the amount of the fine powder filler (c) is about 1 to 20% by weight based on the total weight of the filler (B). 2 Liquid epoxy resin has an epoxy equivalent of approximately 200 to 500
The epoxy resin composition for pressure molding according to claim 1, containing about 20 to 60% by weight of bisphenol A type epoxy resin. 3. The epoxy resin composition for pressure molding according to claim 1, which contains about 20 to 40 parts by weight of 4,4'-isopropylidene biphenol as a curing agent based on 100 parts by weight of the liquid epoxy resin.