Epoxy resin composition and molded article of same

Abstract

An epoxy resin composition according to the present disclosure contains (A) an epoxy resin, (B) a phenolic resin, (C) a curing accelerator, (D) silica, and (E) alumina. The curing accelerator (C) has a reaction initiation temperature of the curing reaction of 125-150°C when the addition amount per 100 parts by mass of a mixture of a cresol novolac-type epoxy resin and a novolac-type phenolic resin (1 mol of a hydroxyl group of a novolac-type phenolic resin with respect to 1 mol of an epoxy group of a cresol novolac-type epoxy resin) is 1 part by mass. The silica (D) has a specific particle diameter, and the contents of the silica (D) and the alumina (E) are specific amounts.

Description

Epoxy resin composition and molded product thereof

[0001] The present disclosure relates to an epoxy resin composition and a molded article using the same.

[0002] Nozzles and ejection ports of a printer print head, liquid junctions of pH meters, etc. are formed with minute holes (hole diameter: 3 to 40 μm) through which ink liquid, sample liquid, etc. pass. Glass and ceramics have traditionally been used as materials for components having such minute holes, from the viewpoints of low linear expansion coefficient, good dimensional stability, chemical resistance, etc.

[0003] In recent years, the above-mentioned materials have been increasingly replaced by resins because they are lighter and easier to mold into complex shapes than glass or ceramics. Among resins, epoxy resins have a relatively low viscosity, can be filled with a large amount of filler, and tend to yield cured products with a low linear expansion coefficient and a high elastic modulus. From the viewpoint of balancing these characteristics with cost, cured products of epoxy resin compositions are used as the above-mentioned materials.

[0004] For example, Patent Document 1 describes the production of an inkjet recording head (print head) using a cured product of an epoxy resin composition and an alumina filler, and Patent Document 2 describes the use of alumina and silica as fillers.

[0005] JP 2019-142213 A JP 2023-10538 A

[0006] The epoxy resin composition disclosed herein is an epoxy resin composition for use in molded articles having pores with a diameter of 3 to 40 μm, and comprises (A) an epoxy resin, (B) a phenolic resin, (C) a curing accelerator, (D) silica, and (E) alumina. The curing accelerator (C) has a curing reaction initiation temperature of 125 to 150°C when added in an amount of 1 part by mass per 100 parts by mass of a mixture of a cresol novolac epoxy resin and a novolac phenolic resin (a mixing ratio in which 1 mole of epoxy groups in the cresol novolac epoxy resin corresponds to 1 mole of hydroxyl groups in the novolac phenolic resin). The silica (D) has a cumulative 10% volume particle diameter (D10) of 1.5 μm or more, a cumulative 50% volume particle diameter (D50) of 10.0 to 35.0 μm, and a cumulative 90% volume particle diameter (D90) of more than 35.0 μm and not more than 150.0 μm. The mass ratio of (E) alumina to (D) silica is 0.09 to 0.45.

[0007] The print head described in Patent Document 1 does not have a sufficiently low coefficient of linear expansion, and there is a risk of ink clogging due to deformation of the micropores or detachment of the alumina filler. Furthermore, even when alumina and silica are used in combination as fillers, the curing reaction of the epoxy resin composition described in Patent Document 2 proceeds quickly, making it difficult to accurately produce a cured molded product having micropores by injection molding or the like, and also making it difficult to use for continuous production.

[0008] The epoxy resin composition of the present disclosure has good flowability and moldability, and the curing reaction proceeds at an appropriate rate, making it suitable for obtaining a cured product of a molded article having micropores. Furthermore, according to the present disclosure, a molded article having micropores can be obtained that has a low linear expansion coefficient, high dimensional stability, and high alkali resistance.

[0009] The present disclosure will be described in detail below with reference to one embodiment. The meanings and definitions of terms used in the present disclosure are as follows. A numerical range expressed by "to" means a numerical range with the numerical values ​​before and after "to" as the lower and upper limits. A preferred numerical range can be any combination of preferred lower and upper limits. The upper and lower limits of a numerical range may be replaced with numerical values ​​described in the examples. The reaction initiation temperature is the temperature at the extrapolated intersection of the baseline of the DSC curve during the curing reaction and the tangent to the maximum slope of the peak in differential scanning calorimetry (DSC) (measurement conditions: heating rate 10°C / min). The exothermic peak temperature is the peak-top temperature of the DSC curve. The cumulative volume 10% particle size (D10), cumulative volume 50% particle size (D50), and cumulative volume 90% particle size (D90) are the particle sizes at which the cumulative volume from the small diameter side becomes 10%, 50%, and 90%, respectively, in a volume-based particle size distribution measured using a laser diffraction / scattering particle size analyzer. D10 is an index of the diameter of fine particles in the sample particles, D90 is an index of the diameter of coarse particles in the sample particles, and D50 is also called the median diameter.

[0010] [Epoxy Resin Composition] The epoxy resin composition of the present disclosure is an epoxy resin composition for use in molded articles having pores with a pore diameter of 3 to 40 μm, and comprises (A) an epoxy resin, (B) a phenolic resin, (C) a curing accelerator, (D) silica, and (E) alumina, wherein the curing accelerator (C) is a mixture of a cresol novolac epoxy resin and a novolac phenolic resin (1 mole of epoxy groups in the cresol novolac epoxy resin and 1 mole of hydroxyl groups in the novolac phenolic resin). The epoxy resin composition of the present disclosure has good flowability and moldability, and the curing reaction proceeds at an appropriate rate, and is suitable for obtaining a cured molded article having pores with a diameter of 3 to 40 μm (hereinafter also referred to as micropores).

[0011] ((A) Epoxy Resin) The (A) epoxy resin generally refers to a monomer, oligomer, or polymer having two or more epoxy groups in one molecule, and its molecular weight and molecular structure are not particularly limited. Examples of the (A) epoxy resin include crystalline epoxy resins such as biphenyl-type, bisphenol F-type, and stilbene-type; novolac-type epoxy resins such as phenol novolac-type and cresol novolac-type; multifunctional epoxy resins such as trisphenolmethane-type and alkyl-modified trisphenolmethane-type; aralkyl-type epoxy resins such as phenol aralkyl-type having a phenylene skeleton or biphenylene skeleton; naphthol-type epoxy resins such as dihydroxynaphthalene-type and epoxy resins obtained by glycidyl etherifying a dihydroxynaphthalene dimer; epoxy resins containing a triazine nucleus such as triglycidyl isocyanurate and monoallyl diglycidyl isocyanurate; and bridged cyclic hydrocarbon compound-modified phenol-type epoxy resins such as dicyclopentadiene-modified phenol-type. These may be used alone or in combination of two or more. Of these, the epoxy resin (A) may be a trisphenolmethane type epoxy resin from the viewpoint of reducing the molding shrinkage rate of the epoxy resin composition.

[0012] The content of the epoxy resin (A) in the epoxy resin composition may be 3.50 to 8.00% by mass, 4.00 to 7.10% by mass, or 4.50 to 6.50% by mass, from the viewpoints of ease of molding the epoxy resin composition and good dimensional stability of the cured product.

[0013] ((B) Phenolic Resin) The (B) phenolic resin generally refers to a monomer, oligomer, or polymer, and has two or more phenolic hydroxyl groups per molecule that can react with the epoxy groups of the (A) epoxy resin, and its molecular weight and molecular structure are not particularly limited. The (B) phenolic resin acts as a curing agent for the (A) epoxy resin, and can mainly improve the moldability of the epoxy resin composition. Examples of the (B) phenolic resin include novolac-type phenolic resins such as phenol novolac resin, cresol novolac resin, trisphenolmethane-type phenolic novolac resin, and naphthol novolac resin; polyfunctional phenolic resins such as trisphenolmethane-type phenolic resin; modified phenolic resins such as terpene-modified phenolic resin, triphenylmethane-type phenolic resin modified with formaldehyde, trihydroxyphenylmethane-type phenolic resin modified with formaldehyde, and dicyclopentadiene-modified phenolic resin; aralkyl-type phenolic resins such as phenol aralkyl resins having a phenylene skeleton and / or biphenylene skeleton, naphthol aralkyl resins having a phenylene and / or biphenylene skeleton, phenylaralkyl-type phenolic resins, and biphenylaralkyl-type phenolic resins; and bisphenols such as bisphenol A and bisphenol F. These may be used alone or in combination of two or more. Of these, the (B) phenolic resin may be one or more selected from the group consisting of novolac phenolic resins, polyfunctional phenolic resins, and aralkyl phenolic resins, or may be a phenol novolac resin, from the viewpoint of providing an epoxy resin composition with low viscosity and good moldability.

[0014] The content of the (B) phenolic resin in the epoxy resin composition may be 2.50 to 5.00 mass%, 2.70 to 4.70 mass%, or 2.90 to 4.20 mass%, from the viewpoints of ease of molding the epoxy resin composition and good dimensional stability of the cured product. In consideration of a balance between appropriate curability of the epoxy resin composition and the properties of the cured product, the content of the (B) phenolic resin may be an amount such that the number of hydroxyl groups in the (B) phenolic resin is 0.5 to 1.5 moles, or 0.9 to 1.2 moles, per mole of epoxy groups in the (A) epoxy resin.

[0015] (C) Curing Accelerator) From the viewpoint of a suitable curing acceleration effect and ease of molding of the epoxy resin composition, the (C) curing accelerator is one whose reaction initiation temperature (T1) of the curing reaction is 125 to 150°C when added in an amount of 1 part by mass per 100 parts by mass of a mixture of a cresol novolac epoxy resin and a novolac phenolic resin (a mixing ratio in which 1 mole of epoxy groups in the cresol novolac epoxy resin corresponds to 1 mole of hydroxyl groups in the novolac phenolic resin). The (C) curing accelerators may be used alone or in combination of two or more. In the present disclosure, the reaction initiation temperature is a temperature that serves as an indicator of the heating temperature suitable for application of the curing accelerator. By using a (C) curing accelerator having the above-described reaction initiation temperature (T1), the curing reaction initiation temperature of the epoxy resin composition is 125°C or higher, and the exothermic peak temperature is 150 to 170°C, allowing the curing reaction to proceed appropriately, and enabling the cured product to be suitably molded and having micropores.

[0016] When a curing accelerator having a reaction initiation temperature (T1) of less than 125°C is used, the curing reaction initiation temperature of the epoxy resin composition becomes low, and the curing reaction proceeds when the epoxy resin composition is poured into the cylinder of an injection molding machine, making it difficult to obtain a molded product of the desired shape by injection molding, etc. On the other hand, when a curing accelerator having a reaction initiation temperature (T1) of more than 150°C is used, the curing reaction initiation temperature of the epoxy resin composition becomes high, slowing down the curing reaction during molding of the epoxy resin composition and making it difficult to obtain a cured molded product with sufficient strength. The reaction initiation temperature (T1) may be 128 to 145°C or 130 to 140°C.

[0017] The curing accelerator (C) may have an exothermic peak temperature (T2) in the curing reaction of 150°C or higher, or may be 150 to 170°C, from the viewpoints of an appropriate curing-accelerating effect and ease of molding of the epoxy resin composition.

[0018] The melting point of the (C) curing accelerator may be 140 to 190°C, 145 to 188°C, or 150 to 185°C, from the viewpoints of an appropriate curing-accelerating effect and ease of molding of the epoxy resin composition.

[0019] The (C) curing accelerator may be a thermally latent curing catalyst having the above-mentioned reaction initiation temperature (T1), for example, a urea compound having a melting point of 140 to 190°C and two or more ureido groups per molecule, or may be either an aromatic dimethylurea or an aliphatic dimethylurea. Specifically, it may be 1,1'-(4-methyl-1,3-phenylene)bis(3,3-dimethylurea). If the melting point is 140°C or higher, the curing reaction does not proceed easily when the epoxy resin composition is introduced into the cylinder of an injection molding machine, making it easier to obtain a molded product with the desired shape. On the other hand, if the melting point is 190°C or lower, the curing reaction of the epoxy resin composition proceeds appropriately during molding, making it easier to obtain a cured molded product with sufficient strength.

[0020] The content of the (C) curing accelerator in the epoxy resin composition may be 0.05 to 1.00% by mass, 0.06 to 0.50% by mass, or 0.10 to 0.28% by mass, from the viewpoint of an appropriate curing-accelerating effect and ease of molding of the epoxy resin composition. When the content of the (C) curing accelerator is 0.05% by mass or more, the curing reaction of the epoxy resin composition proceeds appropriately during molding, making it easier to obtain a cured molded product with sufficient strength. On the other hand, when the content is 1.00% by mass or less, the curing reaction does not proceed easily when the epoxy resin composition is introduced into the cylinder of an injection molding machine, making it easier to obtain a molded product with the desired shape.

[0021] ((D) Silica) As the (D) silica, any silica generally used as a filler in epoxy resin compositions can be used, and silica having a D10 of 1.5 μm or more, a D50 of 10.0 to 35.0 μm, and a D90 of more than 35.0 μm and not more than 150.0 μm is used. As the (D) silica, one commercially available product may be used alone, or two or more types with different particle size distributions may be used in combination. By using silica with the particle size as described above, it is possible to effectively reduce the elution and detachment of silica from the surface of a molded article, which is a cured product of the epoxy resin composition, when the molded article comes into contact with an alkaline solution.

[0022] The D10 of (D) silica may be 1.6 μm or more and less than 10.0 μm, or may be 1.8 to 8.0 μm.

[0023] The D50 of the (D) silica may be 11.0 to 35.0 μm or 12.0 to 30.0 μm, from the viewpoints of the flowability of the epoxy resin composition and the ability to fill the periphery of micropores in a molded product.

[0024] (D) The D90 of the silica is greater than 35.0 μm and not greater than 150.0 μm, may be greater than 35.0 μm and not greater than 100.0 μm, or may be greater than 35.0 μm and not greater than 75.0 μm.

[0025] The silica (D) may be fused silica from the viewpoint of reducing the linear expansion coefficient of the cured product of the epoxy resin composition, or may be spherical particles from the viewpoint of improving the loading amount in the epoxy resin composition.

[0026] The content of (D) silica in the epoxy resin composition may be 62.0 to 85.0 mass %, 65.0 to 82.0 mass %, or 67.0 to 80.0 mass %, from the viewpoints of good flowability of the epoxy resin composition, reduction in molding shrinkage rate, reduction in the linear expansion coefficient of the molded product, and the like.

[0027] ((E) Alumina) Any alumina that is generally used as a filler in epoxy resin compositions can be used as the (E) alumina. When a molded article, which is a cured product of the epoxy resin composition, comes into contact with an alkaline solution, the combined use of the (E) alumina with the (D) silica can effectively reduce the elution and detachment of the (D) silica from the surface of the molded article.

[0028] From the viewpoint of providing good fluidity to the epoxy resin composition when used in combination with (D) silica, the (E) alumina may have a D50 of 0.1 to 2.0 μm, 0.2 to 1.8 μm, or 0.3 to 1.0 μm. As the (E) alumina, one commercially available product may be used alone, or two or more types with different particle size distributions may be used in combination. From the viewpoint of improving the loading amount in the epoxy resin composition, the (E) alumina may be in the form of spherical particles.

[0029] The total content of (D) silica and (E) alumina in the epoxy resin composition is 85.0 to 92.0 mass%, or alternatively 87.0 to 92.0 mass%, or alternatively 88.0 to 91.0 mass%, or alternatively 89.0 to 90.0 mass%, from the viewpoints of good fluidity of the epoxy resin composition, reduced molding shrinkage, and reduced linear expansion coefficient of the molded article. If the total content is less than 85.0 mass%, the molding shrinkage of the epoxy resin composition will be large and the linear thermal expansion coefficient of the molded article will be high. On the other hand, if the total content exceeds 92.0 mass%, the fluidity of the epoxy resin composition will be easily impaired.

[0030] The content of (E) alumina in the epoxy resin composition may be 5.0 to 27.0% by mass, 8.0 to 25.0% by mass, or 10.0 to 20.0% by mass, from the viewpoints of good moldability of the epoxy resin composition and good dimensional stability of the molded product.

[0031] The mass ratio of (E) alumina to (D) silica in the epoxy resin composition is 0.09 to 0.45, or alternatively 0.10 to 0.40, 0.15 to 0.35, or even 0.20 to 0.30, from the viewpoints of achieving a well-balanced particle size distribution of the two, good flowability of the epoxy resin composition, and good dimensional stability of the molded product. If the mass ratio is less than 0.09, the flowability of the epoxy resin composition is likely to decrease. On the other hand, if the mass ratio exceeds 0.45, it is difficult to reduce the linear expansion coefficient of the molded product.

[0032] ((F) Mold Release Agent) In addition to the above components (A) to (E), the epoxy resin composition of the present disclosure may contain a (F) mold release agent having a melting point of 70 to 180°C. By incorporating a (F) mold release agent, it is possible to prevent the moldability from being hindered by adhesion of the epoxy resin composition to the inside of the cylinder of the injection molding machine and to the mold during injection molding of the epoxy resin composition. From the viewpoint of ease of molding the epoxy resin composition, the (F) mold release agent may have a melting point of 75 to 175°C or 80 to 170°C. When the melting point is 75°C or higher, the (F) mold release agent adhering to the mold is less likely to oxidize, making it easier to remove the molded product from the mold. Furthermore, when the melting point is 175°C or lower, the (F) mold release agent is less likely to dissolve and remain in the molded product, making it easier to improve the dimensional stability of the molded product.

[0033] Examples of the (F) mold release agent include natural waxes such as carnauba wax and montan wax, synthetic waxes such as oxidized polyethylene wax, metal soaps such as calcium stearate, etc. The (F) mold release agent may be used alone or in combination of two or more types.

[0034] The (F) mold release agent may contain a natural wax and a metal soap. If the (F) mold release agent contains a natural wax with a melting point lower than 100°C, the natural wax melts during molding of the epoxy resin composition, making it easier to remove the molded product from the mold and more likely to produce a molded product with a smooth surface. Furthermore, if a metal soap with a melting point higher than that of the natural wax is used in combination as the (F) mold release agent, the metal soap will adhere to the inside of the cylinder of the injection molding machine, reducing adhesion of the epoxy resin composition and making injection easier.

[0035] The total content of the (F) mold release agent in the epoxy resin composition may be 0.05 to 1.0 mass%, 0.1 to 0.8 mass%, or 0.2 to 0.7 mass%, from the viewpoints of reducing adhesion during molding of the epoxy resin composition and achieving good mold releasability. When a natural wax and a metal soap are used as the (F) mold release agent, the mass ratio of the metal soap to the natural wax may be 0.2 to 1.4, 0.3 to 1.0, or 0.4 to 0.8, from the viewpoints of achieving a balance between reducing adhesion to a molding machine such as an injection molding machine and achieving good mold releasability from a mold.

[0036] (Other Components) The epoxy resin composition of the present disclosure may contain additives such as a silane coupling agent, a colorant such as carbon black, a stress-reducing agent such as rubber or silicone, a flame retardant, etc., as appropriate, depending on the desired physical properties of the molded article. The additives may be used alone, or two or more types may be used in combination. The total content of the additives in the epoxy resin composition may be within a range that does not inhibit the effects of the epoxy resin composition and molded article of the present disclosure, and may be 0 to 2.0% by mass, 0 to 1.5% by mass, or 0 to 1.0% by mass.

[0037] (Production Method) The epoxy resin composition of the present disclosure can be obtained by mixing the above-described components (A) to (E), and optionally (F) a mold release agent and other additives. For example, the components may be blended and thoroughly mixed (dry blended) using a mixer or the like, then melt-kneaded using a kneading device such as a heated roll or kneader, cooled, and then pulverized.

[0038] Examples of methods for obtaining molded articles having micropores using the epoxy resin composition of the present disclosure include molding methods such as injection molding, transfer molding, and compression molding. As described above, the epoxy resin composition of the present disclosure may be for injection molding. In injection molding, molded articles can be continuously produced under molding conditions such as an injection temperature of 85 to 110°C, a mold temperature of 120 to 200°C, and a pressure of 2 to 80 MPa.

[0039] The molded article of the present disclosure is a cured product of the epoxy resin composition described above, and has pores with a diameter of 3 to 40 μm. Examples of molded articles having such micropores include resin parts such as ink channels and print heads of printers such as inkjet printers, and electrode liquid junction members of pH meters.

[0040] The molded article of the present disclosure has a low linear expansion coefficient, high dimensional stability, and high alkali resistance. Furthermore, even when contacted with an alkaline solution, the filler components (D) silica and (E) alumina are less likely to leach out or fall off, and liquid contamination and clogging of micropores are unlikely to occur. Therefore, the molded article is suitable for use as the above-mentioned resin part having micropores through which ink liquid, sample liquid, etc. pass.

[0041] The present disclosure will now be described in detail with reference to examples, but the present disclosure is not limited to these examples in any way.

[0042] Table 1 shows the composition of each epoxy resin composition in the examples and comparative examples. Details of each component listed in Table 1 are as follows. <Epoxy resin> EPPN-502H: Trisphenolmethane type epoxy resin; manufactured by Nippon Kayaku Co., Ltd. <Phenol resin> BRG-555: Phenol novolac resin; manufactured by Aica Kogyo Co., Ltd. <Curing accelerator> U-CAT-3512T: 1,1'-(4-methyl-1,3-phenylene)bis(3,3-dimethylurea); aromatic dimethyl urea; manufactured by San-Apro Ltd.; reaction initiation temperature (T1) 131°C, melting point 184°C U-CAT-SA841: Phenol novolac resin salt of 1,8-diazabicyclo(5,4,0)-undecene-7 (DBU (registered trademark)) (30%); DBU type; manufactured by San-Apro Ltd.; reaction initiation temperature (T1) 124°C, melting point 137°C Hokuko TPP (registered trademark): triphenylphosphine; manufactured by Hokuko Chemical Industry Co., Ltd.; reaction initiation temperature (T1) 110°C, melting point 80°C <Silica> S-210: spherical fused silica; manufactured by Nippon Steel Chemical & Material Co., Ltd.; D10 = 2.1 μm, D50 = 15.0 μm, D90 = 40.0 μm FB-940A: spherical fused silica; manufactured by Denka Corporation; D10 = 1.1 μm, D50 = 15.0 μm, D90 = 59.0 μm <Alumina> AO-502: spherical alumina; manufactured by Admatechs Co., Ltd.; D50 = 0.8 μm <Mold release agent> Natural wax: Carvana wax No. 1 powder; manufactured by Toyochem Co., Ltd.; melting point 80 to 86°C Metal soap: calcium stearate GF-200; manufactured by NOF Corporation; melting point 145 to 150°C <Silane coupling agent> Y-9669: 3-(N-phenyl)aminopropyltrimethoxysilane; "SILQUEST (registered trademark) Y-9669 SILANE" manufactured by Momentive Performance Materials; aminosilane-based <Colorant> MA600: carbon black; manufactured by Mitsubishi Chemical Corporation

[0043] The reaction initiation temperature (T1) of the curing accelerator is a value measured using a differential scanning calorimeter (NEXTA (registered trademark) DSC600, manufactured by Hitachi High-Technologies Corporation; heating rate: 10°C / min) during the curing reaction when the curing accelerator is added in an amount of 1 part by mass per 100 parts by mass of a mixture of a cresol novolac epoxy resin and a novolac phenolic resin (a mixing ratio in which 1 mole of epoxy groups in the cresol novolac epoxy resin corresponds to 1 mole of hydroxyl groups in the novolac phenolic resin).

[0044] The particle sizes (D10, D50, and D90) of silica and alumina are values ​​measured using a laser diffraction / scattering particle size distribution measuring device "Mastersizer (registered trademark) 3000" (manufactured by Malvern Panalytical).

[0045] [Examples 1 to 7 and Comparative Examples 1 to 6] Each epoxy resin composition of the Examples and Comparative Examples was prepared by blending the components according to the formulations shown in Table 1 and kneading them in a twin-screw kneading extruder at 90°C for 3 minutes. The obtained epoxy resin composition was injected into a mold in an injection molding machine ("EC75SXR", manufactured by Shibaura Machine Co., Ltd.) at a mold temperature of 175°C and an injection pressure of 70 kgf / cm. ２ The mixture was poured into a molded body at 175°C for 8 hours, and held for 2 minutes to obtain a molded plate of 40 mm x 45 mm and 3 mm thick. The molded body obtained was heat-treated at 175°C for 8 hours to produce a molded sample of the cured product.

[0046] [Evaluation Methods] The prepared epoxy resin compositions and molded samples of their cured products were subjected to the following evaluations. The evaluation results are also shown in Table 1.

[0047] (Spiral flow) The length to the flow front of the molding material (spiral flow) was measured by injecting an epoxy resin composition (molding material) using a spiral flow measurement mold in accordance with ASTM D3123-09 (2017) under the following measurement conditions. <Measurement conditions> Mold temperature: 175°C Injection pressure: 9.8 MPa Molding time: 120 sec If the spiral flow is 50 cm or more, it can be said that the epoxy resin composition has good fluidity and good moldability. If the spiral flow is 80 cm or more, it can be said that the moldability is even better. On the other hand, if the spiral flow is 140 cm or more, the fluidity is too high and the molding material is less easy to handle.

[0048] (Gel Time) The gel time was measured by kneading 1 mL of an epoxy resin composition onto a flat plate at 175°C using a stainless steel spatula to spread the composition into a circle with a diameter of 4 to 5 cm at a rate of approximately one circle per second, and measuring the time until the epoxy resin composition thickened to the point where it could no longer be kneaded. If the gel time was 60 seconds or less, the epoxy resin composition could be said to have an adequate pot life (usable life). If the gel time was 20 seconds or more, the epoxy resin composition could be said to have a sufficient pot life.

[0049] (Mixing and Extruding Properties) A ​​mixing and extruding test of an epoxy resin composition was carried out under the following test conditions using a mixing and extruding property tester ("Labo Plastomill (registered trademark) 4C150", manufactured by Toyo Seiki Seisakusho, Ltd.). The mixing and extruding properties were evaluated based on the time it took for the torque of the roller mixer to reach its maximum (maximum torque arrival time) 60 seconds or more after the start of the test. <Test conditions> Sample amount: 50 g Mold temperature: 90°C Roller mixer rotation speed: 40 rpm If the maximum torque arrival time is 60 minutes or more, it can be said that injection molding of the epoxy resin composition can be carried out stably. From the viewpoint of more stable injection molding, the maximum torque arrival time may be 90 minutes or more.

[0050] (Curing reaction initiation temperature and exothermic peak temperature) The curing reaction initiation temperature and exothermic peak temperature of the epoxy resin composition were measured using a differential scanning calorimeter ("NEXTA (registered trademark) DSC600", manufactured by Hitachi High-Technologies Corporation; temperature rise rate: 10°C / min). If the curing reaction initiation temperature is 130°C or higher and the exothermic peak temperature is 150 to 170°C, it can be said that the curing reaction is progressing well.

[0051] (Molding Shrinkage) The epoxy resin composition was injected into a disk-shaped mold having an inner diameter of 80 mm and a thickness of 5 mm at room temperature (23°C) using an injection molding machine ("EC75SXR", manufactured by Shibaura Machine Co., Ltd.) at a mold temperature of 175°C and an injection pressure of 6.9 MPa. The molded product was held for 2 minutes and then heat-treated at 175°C for 8 hours to prepare a molded sample of the cured product. The molding shrinkage was calculated as the ratio of the shortest diameter L １ [mm] and longest diameter L ２ [mm] and the average value L (= (L １ +L ２ The molding shrinkage rate was calculated by dividing the average value L by the mold inner diameter L at room temperature (23°C). ０ (=80 mm), (L ０ -L) / L ０ × 100 [%]. If the molding shrinkage rate is 0.12% or less, it can be said that it is easy to set the control conditions for injection molding to obtain a molded product of the desired shape.

[0052] (Linear expansion coefficient) Linear expansion coefficient below the glass transition temperature (α １ The linear expansion coefficient (α) was determined for the molded product samples obtained in the examples and comparative examples by thermomechanical analysis (TMA) under the following measurement conditions. <Measurement conditions> Test piece: 3.54 mm x 3.54 mm x 15 mm Heating rate: 10°C / min Measurement temperature range: 40 to 280°C １ ) is 10 x 10 －６ / °C, the molded product can be said to have high dimensional stability. From the viewpoint of higher dimensional stability of the molded product, the linear expansion coefficient is 9 × 10 －６ / °C or less, and －６ / °C or less.

[0053] (Alkali Resistance) The alkali resistance of molded samples obtained in the Examples or Comparative Examples was evaluated by immersing them in a sodium hydroxide aqueous solution adjusted to pH 14 and performing a pressure cooker test (PCT) under the following test conditions. <Test Conditions> Test piece: 40 mm x 45 mm x 3 mm Temperature: 121°C Humidity: 100% RH Time: 10 hours After the test, the test piece was air-cooled to room temperature (23°C), and then quantitative analysis of silicon (dissolved Si) in the sodium hydroxide aqueous solution was performed using a high-frequency inductively coupled plasma (ICP) emission spectrometer ("ICPE-9820", manufactured by Shimadzu Corporation), to evaluate the degree of silica dissolution into the sodium hydroxide aqueous solution. In Table 1, cases where no silica was detected were indicated as "N.D." Furthermore, after the test, the test piece was air-cooled and left at room temperature (23°C) for one week, and the sodium hydroxide aqueous solution in which the test piece had been immersed was visually observed for the presence or absence of alumina detachment (precipitation) from the test piece. Furthermore, for test pieces in which no eluted Si or alumina loss was confirmed, PCT was carried out under the above test conditions for 250 hours, after which quantitative analysis of eluted Si and confirmation of the presence or absence of alumina loss were carried out in the same manner as above. If no eluted Si was detected and no alumina loss occurred, it can be said that the molded product has good alkali resistance.

[0054]

[0055] As can be seen from the evaluation results shown in Table 1, the epoxy resin composition of the present disclosure has good fluidity and moldability, and also has an appropriate pot life (usable time), making it suitable for injection molding and allowing continuous molding. Furthermore, molded articles of the epoxy resin composition of the present disclosure have high dimensional stability against heat and long-term alkali resistance, and are free from elution or shedding of the filler (silica and alumina), making them less likely to contaminate alkaline solutions that come into contact with them or to clog micropores.

Claims

1. An epoxy resin composition for a molded article having pores with a pore diameter of 3 to 40 μm, comprising (A) an epoxy resin, (B) a phenolic resin, (C) a curing accelerator, (D) silica, and (E) alumina, wherein the reaction start temperature of the curing reaction when the addition amount per 100 parts by mass of the mixture of a cresol novolak type epoxy resin and a novolak type phenolic resin (mixing ratio such that 1 mol of the hydroxyl group of the novolak type phenolic resin corresponds to 1 mol of the epoxy group of the cresol novolak type epoxy resin) is 125 to 150 °C for the (C) curing accelerator, the cumulative volume 10% particle diameter (D10) of the (D) silica is 1.5 μm or more, the cumulative volume 50% particle diameter (D50) is 10.0 to 35.0 μm, and the cumulative volume 90% particle diameter (D90) is more than 35.0 μm and 150.0 μm or less, the total content of the (D) silica and the (E) alumina is 85.0 to 92.0% by mass, and the mass ratio of the (E) alumina to the (D) silica is 0.09 to 0.

45. The epoxy resin composition.

2. The epoxy resin composition according to claim 1, wherein the content of the (D) silica is 62.0 to 85.0% by mass.

3. The epoxy resin composition according to claim 1 or 2, wherein the cumulative volume 50% particle diameter (D50) of the (E) alumina is 0.1 to 2.0 μm.

4. The epoxy resin composition according to any one of claims 1 to 3, wherein the (C) curing accelerator is a urea compound having a melting point of 140 to 190 °C and having two or more ureido groups in one molecule.

5. The epoxy resin composition according to any one of claims 1 to 4, wherein the (C) curing accelerator contains 1,1'-(4-methyl-1,3-phenylene)bis(3,3-dimethylurea).

6. The epoxy resin composition according to any one of claims 1 to 5, wherein the (D) silica is spherical particles.

7. The epoxy resin composition according to any one of claims 1 to 6, wherein the (E) alumina is spherical particles.

8. The epoxy resin composition according to any one of claims 1 to 7, wherein the (A) epoxy resin is a trisphenol methane type epoxy resin.

9. The epoxy resin composition according to any one of claims 1 to 8, further comprising (F) a release agent, and the melting point of the (F) release agent is 70 to 180 °C.

10. The epoxy resin composition according to claim 9, wherein the (F) release agent contains natural wax and metal soap.

11. The epoxy resin composition according to any one of claims 1 to 10, which is for injection molding.

12. A cured product of the epoxy resin composition according to any one of claims 1 to 11, which is a molded article having pores with a pore diameter of 3 to 40 μm.

13. The molded article according to claim 12, which is a print head.

14. The molded article according to claim 12, which is an electrode liquid junction member of a pH meter.

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