Curable resin composition and structure

Abstract

Disclosed is a curable resin composition. The curable resin composition contains an epoxy compound, an inorganic filler, a coupling agent, and a polymerization initiator. The epoxy compound includes an alicyclic epoxy compound. The alicyclic epoxy compound content is 60 mass% or more based on the total amount of the epoxy compound.

Description

Curable resin composition and structure

[0001] The present disclosure relates to a curable resin composition and a structure.

[0002] Curable resin compositions are widely used for sealing electronic component devices, bonding components together, protecting components, etc. For example, Patent Document 1 discloses a curable resin composition containing an epoxy resin or the like.

[0003] Japanese Patent Application Laid-Open No. 2008-179751

[0004] However, cured products formed from conventional curable resin compositions do not have sufficient resistance to solvents such as xylene (solvent resistance), and there is still room for improvement.

[0005] Therefore, a main object of the present disclosure is to provide a curable resin composition capable of forming a cured product having excellent solvent resistance.

[0006] The present disclosure provides curable resin compositions according to [1] to [3] and a structure according to [4]. [1] A curable resin composition comprising an epoxy compound, an inorganic filler, a coupling agent, and a polymerization initiator, wherein the epoxy compound comprises an alicyclic epoxy compound, and the content of the alicyclic epoxy compound is 60 mass% or more based on the total amount of the epoxy compounds. [2] The curable resin composition according to [1], wherein the content of the epoxy compound is 15 to 50 mass% based on the total amount of the curable resin composition. [3] The curable resin composition according to [2], wherein the content of the inorganic filler is 150 parts by mass or more based on 100 parts by mass of the total amount of the epoxy compounds. [4] A structure comprising a first adherend, a second adherend, and an adhesive joint that bonds the first adherend and the second adherend to each other, wherein the adhesive joint contains a cured product of the curable resin composition according to any one of [1] to [3].

[0007] According to the present disclosure, a curable resin composition capable of forming a cured product having excellent solvent resistance is provided. Some forms of the curable resin composition also tend to have excellent curability at low temperatures (e.g., 100°C or lower). Furthermore, according to the present disclosure, a structure using such a curable resin composition is provided.

[0008] Hereinafter, embodiments of the present disclosure will be described in detail, but the present disclosure is not limited to the following embodiments.

[0009] In this specification, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In numerical ranges described in stages in this specification, the upper or lower limit of a certain numerical range may be replaced with the upper or lower limit of another numerical range. Furthermore, in numerical ranges described in this specification, the upper or lower limit of that numerical range may be replaced with a value shown in the examples. Furthermore, individually described upper and lower limits can be arbitrarily combined. In a numerical range described as "A to B," the numerical values ​​A and B at both ends are included as the lower and upper limits, respectively, in the numerical range. In this specification, for example, the expression "10 or more" means "10" and "a number greater than 10," and this also applies when the numerical values ​​are different. Furthermore, for example, the expression "10 or less" means "10" and "a number less than 10," and this also applies when the numerical values ​​are different. In this specification, "A or B" may include either A or B, or may include both.

[0010] Unless otherwise specified, the materials exemplified below may be used alone or in combination of two or more. When a plurality of substances corresponding to each component are present in the composition, the content of each component in the composition means the total amount of the plurality of substances present in the composition unless otherwise specified.

[0011] [Curable Resin Composition] The curable resin composition of one embodiment contains an epoxy compound (hereinafter sometimes referred to as "component (A)"), an inorganic filler (hereinafter sometimes referred to as "component (B)"), a coupling agent (hereinafter sometimes referred to as "component (C)"), and a polymerization initiator (hereinafter sometimes referred to as "component (D)"). The curable resin composition of this embodiment may be a resin composition exhibiting thermosetting properties (thermosetting resin composition). The curable resin composition of this embodiment makes it possible to form a cured product with excellent solvent resistance. Furthermore, the curable resin composition of this embodiment also tends to have excellent curability at low temperatures (for example, 100°C or lower).

[0012] Component (A): Epoxy Compound Component (A) is a compound having one or more epoxy groups. Component (A) may be a compound having two or more epoxy groups. Component (A) contains an alicyclic epoxy compound (hereinafter, sometimes referred to as "component (A1)"). By including component (A) in component (A1), it is possible to form a cured product with excellent solvent resistance. Component (A) may contain an epoxy compound other than component (A1) (hereinafter, sometimes referred to as "component (A2)").

[0013] The component (A1) is a compound having an epoxy group (e.g., an epoxycyclohexyl group, an epoxycyclopentyl group, etc.) formed together with the two carbon atoms that constitute the alicyclic structure (alicyclic ring). The component (A1) can also be said to be a compound having a structure in which an alicyclic unsaturated hydrocarbon is epoxidized. Commercially available products of the component (A1) include, for example, Celloxide 8010, Celloxide 2021P, and Celloxide 2081 (trade names, all manufactured by Daicel Corporation). The component (A1) may be a compound having two or more epoxy groups formed together with the two carbon atoms that constitute the alicyclic structure (alicyclic ring), or may be a compound having two such epoxy groups. The component (A1) may also be an epoxy compound that does not have an aromatic ring.

[0014] The content of the (A1) component is 60% by mass or more, based on the total amount of the (A) component. When the content of the (A1) component is 60% by mass or more, based on the total amount of the (A) component, it is possible to form a cured product with excellent solvent resistance, and the shear strength when bonding adherends tends to be high. The content of the (A1) component may be 65% by mass or more, 70% by mass or more, 75% by mass or more, 80% by mass or more, 85% by mass or more, or 90% by mass or more, based on the total amount of the (A) component. The upper limit of the content of the (A1) component may be, for example, 100% by mass or less, 98% by mass or less, or 95% by mass or less.

[0015] Examples of the component (A2) include an aliphatic epoxy compound (hereinafter sometimes referred to as "component (A2a)") and an epoxy compound having an aromatic ring (hereinafter sometimes referred to as "component (A2b)"). The component (A2) may be, for example, the component (A2a).

[0016] The component (A2a) is an epoxy compound having an aliphatic group. The component (A2a) may be an epoxy compound having no aromatic ring. The component (A2a) may be an aliphatic diglycidyl ether having at least one aliphatic group (linking group) selected from the group consisting of an alkylene group, an oxyalkylene group, and a cycloalkylene group. The component (A2a) may also function as a solvent or dispersion medium.

[0017] Examples of aliphatic diglycidyl ethers include diglycidyl ethers having an alkylene group, such as ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, and 1,6-hexanediol diglycidyl ether; diglycidyl ethers having an oxyalkylene group, such as diethylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, and polyethylene glycol diglycidyl ether; and diglycidyl ethers having a cycloalkylene group, such as hydrogenated bisphenol A diglycidyl ether, 1,4-cyclohexanedimethanol diglycidyl ether, and diglycidyl-1,2-cyclohexanedicarboxylate.

[0018] Examples of the component (A2b) include phthalic acid diglycidyl ester, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AD ​​type epoxy resin, bisphenol S type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, biphenyl type epoxy resin, and biphenyl aralkyl type epoxy resin.

[0019] The content of the component (A2) may be 40% by mass or less, 35% by mass or less, 30% by mass or less, 25% by mass or less, 20% by mass or less, 15% by mass or less, or 10% by mass or less, or may be 0% by mass or more, 2% by mass or more, or 5% by mass or more, based on the total amount of the component (A).

[0020] The content of component (A) (total amount of component (A1) and component (A2)) may be 15 to 50 mass % based on the total amount of the curable resin composition. The content of component (A) may be 20 mass % or more or 25 mass % or more, and may be 45 mass % or less or 40 mass % or less, based on the total amount of the curable resin composition. Here, "the total amount of the curable resin composition" means the total solid content excluding the solvent or dispersion medium (excluding component (A2a)).

[0021] Component (B): Inorganic Filler Component (B) is not particularly limited, and conventionally known inorganic fillers can be used. Examples of component (B) include barium sulfate, barium titanate, amorphous silica, crystalline silica, fused silica, spherical silica, talc, clay, magnesium carbonate, calcium carbonate, aluminum oxide, aluminum hydroxide, silicon nitride, and aluminum nitride. Among these, component (B) may be silica, as it is easy to obtain the desired cured film properties. Component (B) may be surface-treated with a silane coupling agent or the like, as described below.

[0022] Component (B) may contain an inorganic filler with an average particle size of 0.01 to 50 μm. When component (B) contains an inorganic filler with an average particle size of 0.01 μm or more, component (B) tends to be less likely to aggregate and more easily dispersed. When component (B) contains an inorganic filler with an average particle size of 50 μm or less, component (B) tends to be less likely to settle in the resin varnish and more likely to form a homogeneous cured film. The average particle size may be 0.1 μm or more, 0.3 μm or more, or 0.5 μm or more, or may be 25 μm or less, 20 μm or less, 15 μm or less, 10 μm or less, 8 μm or less, 6 μm or less, 4 μm or less, or 2 μm or less. The average particle size is measured, for example, by laser diffraction / scattering.

[0023] Component (B) may contain an inorganic filler having an average primary particle size of 1 to 1,000 nm. When component (B) contains an inorganic filler having an average primary particle size of 1 nm or more, component (B) tends to be less prone to aggregation and more easily dispersed. When component (B) contains an inorganic filler having an average particle size of 1,000 nm or less, component (B) tends to be less prone to settling in the resin varnish and more easily produce a homogeneous cured film. The average primary particle size may be 3 nm or more, 5 nm or more, or 10 nm or more, or may be 500 nm or less, 300 nm or less, 100 nm or less, 50 nm or less, or 30 nm or less. The average primary particle size of component (B) is measured, for example, by image analysis using an electron microscope.

[0024] The content of component (B) may be 150 parts by mass or more, relative to 100 parts by mass of the total amount of component (A). When the content of component (B) is within this range, the solvent resistance of the resulting cured product tends to be further improved. The content of component (B) may be 160 parts by mass or more, 170 parts by mass or more, 180 parts by mass or more, 190 parts by mass or more, or 200 parts by mass or more, relative to 100 parts by mass of the total amount of component (A), and may be 500 parts by mass or less, 450 parts by mass or less, 400 parts by mass or less, 350 parts by mass or less, or 300 parts by mass or less.

[0025] Component (C): Coupling Agent Component (C) may be, for example, a silane coupling agent. The silane coupling agent may be, for example, a compound having a hydrolyzable silyl group and a functional group capable of reacting with either a (meth)acrylate compound or an epoxy compound. The hydrolyzable silyl group is, for example, a group having a silicon atom and an alkoxy group bonded to the silicon atom. The alkoxy group bonded to the silicon atom may have, for example, 1 to 4 carbon atoms. Examples of the functional group include amino groups such as primary amino groups and secondary amino groups, epoxy groups, mercapto groups, (meth)acryloyl groups, and isocyanate groups. The functional group may be, for example, an isocyanate group. In this specification, compounds having a hydrolyzable silyl group and an epoxy group are classified as silane coupling agents.

[0026] Commercially available silane coupling agents include, for example, KBM-303, KBM-402, KBM-403, KBE-402, KBE-403, KBM-4803, KBM-502, KBM-503, KBE-502, KBE-503, KBM-5103, KBM-5803, KBM-602, KBM-603, KBM-903, KBE-903, KBE-9103P, KBM-573, KBM-575, KBM-802, KBM-803, and KBE-9007N (trade names, manufactured by Shin-Etsu Chemical Co., Ltd.).

[0027] The content of component (C) may be 0.1 parts by mass or more, 0.3 parts by mass or more, or 0.5 parts by mass or more, and may be 10 parts by mass or less, 8 parts by mass or less, or 5 parts by mass or less, relative to 100 parts by mass of the total amount of component (A).

[0028] Component (D): Polymerization Initiator The component (D) may be, for example, an acid generator (cationic polymerization initiator). The acid generator is a compound that generates an acid upon at least one of heating and irradiation with active energy rays (e.g., ultraviolet rays) and promotes cationic polymerization of the component (A). A compound that generates an acid upon heating is also called a thermal acid generator (thermal cationic polymerization initiator). A compound that generates an acid upon irradiation with active energy rays is also called a photoacid generator (photocationic polymerization initiator). The component (D) may be a thermal acid generator. In addition to compounds that generate an acid upon heating and compounds that generate an acid upon irradiation with active energy rays, there are also compounds that generate an acid upon either heating or irradiation with active energy rays.

[0029] The thermal acid generator may be a salt compound composed of a cation and an anion. The thermal acid generator may be, for example, BF ４ － , B.R. ４ － (R represents a phenyl group substituted with two or more fluorine atoms or two or more trifluoromethyl groups), PF ６ － , SbF ６ － , AsF ６ － and onium salts such as sulfonium salts, phosphonium salts, ammonium salts, diazonium salts, iodonium salts, anilinium salts, and pyridinium salts having anions such as those mentioned above.

[0030] From the viewpoint of storage stability, the thermal acid generator is, for example, an anion containing boron as a constituent element, i.e., BF ４ － or BR ４ －(R represents a phenyl group substituted with two or more fluorine atoms or two or more trifluoromethyl groups). An anion containing boron as a constituent element may be a salt compound having BR ４ － and more specifically, tetrakis[tris(pentafluorophenyl)]borate.

[0031] The onium salt as the thermal acid generator may be, for example, a quaternary ammonium salt, since it has resistance to substances that can cause curing inhibition in cationic curing.

[0032] The thermal acid generator may contain a quaternary ammonium salt or a quaternary ammonium salt having an anion containing boron as a constituent element. Commercially available products of such salt compounds include CXC-1821 (trade name, manufactured by King Industries).

[0033] The content of the (D) component may be 0.1 parts by mass or more, 0.3 parts by mass or more, or 0.5 parts by mass or more, from the viewpoint of improving the curability, when the total amount of the (A) component is taken as 100 parts by mass, and may be 10 parts by mass or less, 8 parts by mass or less, or 5 parts by mass or less, from the viewpoint of improving the physical properties such as the mechanical properties of the cured product.

[0034] The curable resin composition may contain other components, such as a solvent or dispersion medium, a pigment, a dye, organic particles, a release agent, an antioxidant, and a surface tension adjuster.

[0035] Examples of the solvent or dispersion medium include aromatic hydrocarbons such as toluene, xylene, mesitylene, cumene, and p-cymene; aliphatic hydrocarbons such as hexane and heptane; cyclic alkanes such as methylcyclohexane; cyclic ethers such as tetrahydrofuran and 1,4-dioxane; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and 4-hydroxy-4-methyl-2-pentanone; esters such as methyl acetate, ethyl acetate, butyl acetate, methyl lactate, ethyl lactate, and γ-butyrolactone; and carbonates such as ethylene carbonate and propylene carbonate.

[0036] The curable resin composition can be prepared by mixing (or kneading) the components (A), (B), (C), and (D) and other components. Mixing can be performed using an appropriate combination of a conventional mixer and a dispersing machine such as a planetary mixer. During mixing, degassing treatment may be performed by vacuum degassing or the like.

[0037] The prepared curable resin composition is applied to a predetermined location on an adherend, and the solvent or dispersion medium is removed as needed to form a curable resin portion (curable resin layer). The formed curable resin portion (curable resin layer) is cured by heating or active energy ray irradiation, whereby the component (A) is polymerized and cured, forming an adhesive portion (adhesive layer) for bonding adherends together. In this case, the adhesive portion (adhesive layer) contains a cured product of the curable resin composition.

[0038] The coating method for the predetermined location can be a conventionally known method such as a method using a knife coater, a roll coater, an applicator, a comma coater, a die coater, a dispenser, or the like.

[0039] The conditions for curing the curable resin composition may be heating conditions. Since the curable resin composition of the present embodiment has excellent curability at low temperatures (for example, 100°C or lower), the heating conditions may be, for example, a heating temperature of 60 to 100°C or 70 to 90°C. The holding time may be, for example, 10 seconds to 12 hours or 1 minute to 6 hours.

[0040] [Structure] In one embodiment, the structure comprises a first adherend, a second adherend, and an adhesive joint that bonds the first adherend and the second adherend to each other. The adhesive joint contains a cured product of the curable resin composition described above.

[0041] Examples of the first and second adherends include organic materials such as polyolefin resins (polypropylene resins, etc.), polyamide resins, ABS (acrylonitrile butadiene styrene) resins, PC (polycarbonate) resins, PET (polyethylene terephthalate) resins, PPS (polyphenylene sulfide) resins, acrylic resins, and transparent resins; inorganic materials such as steel, stainless steel (SUS), metals (aluminum, copper, nickel, chromium, etc.) or alloys of these metals, glass, and silicon wafers; wood; rubber; etc. Examples of the first and second adherends include composites of the above organic and inorganic materials.

[0042] The structure can be obtained, for example, by a method including the steps of applying a curable resin composition onto a first adherend to form a curable resin part (curable resin layer) containing the curable resin composition, placing a second adherend on the curable resin part (curable resin layer) to produce a laminate, and heating the curable resin part (curable resin layer) of the laminate to form an adhesive part (adhesive layer) containing a cured product of the curable resin composition.

[0043] The curable resin composition can be applied using a knife coater, a roll coater, an applicator, a comma coater, a die coater, a dispenser, or the like.

[0044] The conditions for heating the adhesive portion of the laminate (heating temperature, holding time, etc.) may be the same as the conditions for curing the curable resin composition described above.

[0045] The thickness of the adhesive joint containing the cured product of the curable resin composition may be, for example, 0.01 to 1.0 mm, 0.01 to 0.5 mm, or 0.01 to 0.3 mm.

[0046] The present disclosure will be described in more detail below with reference to examples, although the present disclosure is not limited to these examples.

[0047] [Preparation of Curable Resin Composition] The amounts (parts by mass) of components (A), (B), and (E) shown in Table 1 were stirred in a planetary mixer at 2000 rpm for 5 minutes. Next, the amount (parts by mass) of component (C) shown in Table 1 was added to the stirred mixture, and the mixture was stirred in a planetary mixer at 2000 rpm for 5 minutes. Furthermore, the amount (parts by mass) of component (D) shown in Table 1 was added to the stirred mixture, and the mixture was stirred in a planetary mixer at 2000 rpm for 3 minutes, and further degassed at 2200 rpm for 2 minutes, thereby preparing the curable resin compositions of Examples 1 to 4 and Comparative Examples 1 and 2.

[0048] The details of each raw material are as follows: Component (A): Epoxy compound Component (A1): Alicyclic epoxy compound A1-1: 3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate (trade name: CELLOXIDE 2021P, manufactured by Daicel Corporation) Component (A2): Other epoxy compounds A2a-1: Neopentyl glycol diglycidyl ether (trade name: EPOGOSE NPG (D), manufactured by Yokkaichi Synthetic Co., Ltd.) A2b-1: Bisphenol A type epoxy resin (trade name: EPICLON 850, manufactured by DIC Corporation) Component (B): Inorganic filler B-1: Surface-modified silica (average particle size: 8.3 μm, silica having epoxy groups on the surface, manufactured by Admatechs Co., Ltd.) B-2: Fumed silica (average primary particle size: 16 nm, trade name: RY200S, manufactured by Nippon Aerosil Co., Ltd.) B-3: Surface-modified silica (average particle size: 1.5 μm, silica having epoxy groups on the surface, manufactured by Admatechs Co., Ltd.) B-4: Surface-modified silica (average particle size: 0.6 μm, silica having epoxy groups on the surface, manufactured by Admatechs Co., Ltd.) Component (C): Coupling agent C-1: 3-isocyanatepropyltriethoxysilane (trade name: KBE-9007N, manufactured by Shin-Etsu Chemical Co., Ltd.) Component (D): Polymerization initiator D-1: CXC-1821 (quaternary ammonium salt thermal acid generator, manufactured by King Industries) Component (E): Solvent E-1: Toluene

[0049] [Evaluation of Curable Resin Compositions] (Xylene Resistance Test) A xylene resistance test was conducted using the curable resin compositions of Examples 1 to 4 and Comparative Examples 1 and 2. Each curable resin composition was placed in an aluminum pan measuring 5.2 mm in diameter and 5 mm in height, and the pan was heated at 80°C for 5 hours to cure the curable resin composition. A container containing xylene was then prepared, and the heated aluminum pan was immersed in xylene and sealed. The sealed container was then kept at 60°C for one week, after which the aluminum pan was removed from the xylene and dried. The cured product of the curable resin composition in the dried aluminum pan was observed to evaluate for the presence or absence of cracks. The mass of the aluminum pan before immersion and the mass of the aluminum pan after immersion, wiping the surface, and air-drying for 10 minutes were defined as the mass of the aluminum pan before immersion and the mass of the aluminum pan after immersion, respectively. The mass change (%) after immersion was calculated based on the following formula. The results are shown in Table 1. In the xylene resistance test, it is presumed that phenomena such as the curable resin composition or its cured product flowing out into xylene or the xylene being taken up into the curable resin composition or its cured product occur during immersion, resulting in an increase or decrease in mass. Mass change rate after immersion (%) = [(mass of aluminum pan after immersion - mass of aluminum pan before immersion) / mass of aluminum pan before immersion] x 100

[0050] (Shear Strength Measurement) Shear strength measurements were performed using the curable resin compositions of Examples 1 to 4, which showed excellent results in the xylene resistance test. A spacer was placed on a SUS430 plate to achieve dimensions of 12.5 mm wide x 25 mm long and 200 μm thick, and the curable resin composition was applied to the SUS430 plate. Next, a SUS430 plate was placed on the applied curable resin composition, and the resulting laminate was heated at 80°C for 5 hours to obtain a measurement sample. Shear strength was determined by pulling the measurement sample in the longitudinal direction using a precision universal testing machine (Shimadzu Corporation, product name: Autograph AG-Xplus) at a shear rate of 50 mm / min. The results are shown in Table 1.

[0051]

[0052] As shown in Table 1, the curable resin compositions of Examples 1 to 4 had smaller absolute values ​​of the mass change rate after immersion than the curable resin compositions of Comparative Examples 1 and 2. Furthermore, it was also found that the absolute value of the mass change rate after immersion decreased as the content of the alicyclic epoxy compound increased, and the cured products of the curable resin compositions of Examples 1 to 4 had sufficient shear strength. These results confirmed that the curable resin composition of the present disclosure is capable of forming a cured product with excellent solvent resistance.

Claims

1. A curable resin composition comprising an epoxy compound, an inorganic filler, a coupling agent, and a polymerization initiator, wherein the epoxy compound comprises an alicyclic epoxy compound, and the content of the alicyclic epoxy compound is 60 mass% or more based on the total amount of the epoxy compounds.

2. The curable resin composition according to claim 1, wherein the content of the epoxy compound is 15 to 50 mass % based on the total amount of the curable resin composition.

3. The curable resin composition according to claim 2, wherein the content of the inorganic filler is 150 parts by mass or more when the total amount of the epoxy compounds is 100 parts by mass.

4. A structure comprising a first adherend, a second adherend, and an adhesive joint that bonds the first adherend and the second adherend to each other, wherein the adhesive joint contains a cured product of the curable resin composition according to any one of claims 1 to 3.

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