Method for producing cured product, and cured product

Abstract

To provide a method for satisfactorily producing a cured product by curing a curable resin composition containing a compound having a cationically curable functional group by heating at a relatively low temperature using a specific heat-latent cationic polymerization initiator, and to provide a cured product cured by the method.SOLUTION: A method for producing a cured product according to the present invention includes a step of preparing a curable resin composition by mixing a compound having a cationically curable functional group and a thermally latent cationic polymerization initiator, and a step of curing the curable resin composition by heating, wherein the thermally latent cationic polymerization initiator contains a specific Lewis acid-type cationic polymerization initiator and an amine compound, the Lewis acid-type cationic polymerization initiator and a part of the amine compound form a complex, and a remaining part of the amine compound is present in a state of being free from the Lewis acid-type cationic polymerization initiator, A molar ratio of an amino group contained in the free amine compound to 1 mol of a boron atom contained in the Lewis acid type cationic polymerization initiator is 0.15 or more and 1.70 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a good cured product by curing a curable resin composition containing a compound having a cationically curable functional group by heating at a relatively low temperature using a specific thermal latent cationic polymerization initiator, and to a cured product cured by the method. [Background technology]

[0002] Thermosetting epoxy resins are widely used in electronic products such as printed circuit boards, memory, and CPUs due to their high electrical insulation, water resistance, and chemical resistance. They are also used as an ingredient in anti-corrosion paints for automobiles and ships due to their high corrosion resistance. They are also used for coating the inside of beverage cans. They are also used as industrial adhesives, and in the construction industry as structural adhesives for concrete and steel plates. Recently, they have also been used as adhesives for lightweight, high-strength, high-performance materials such as carbon fiber and glass fiber.

[0003] Epoxy monomers are polymerized by cationic polymerization. Compared to radical polymerization, cationic polymerization has the advantage of not being inhibited by oxygen and of minimizing shrinkage during curing. However, if polymerization begins immediately after mixing the epoxy monomer with the cationic polymerization initiator, the product may harden before use.

[0004] Therefore, the inventor's research group has developed a thermally latent polymerization initiator composition containing the cationic polymerization initiator tris(pentafluorophenyl)borane and a specific amine compound, which does not initiate polymerization at room temperature but initiates polymerization at lower temperatures and has excellent catalytic activity (Patent Document 1). The group has also developed a curable resin composition containing a cationically curable compound having a cyclic ether group, a cationically curable compound having a double bond, and a specific boron compound, which has excellent storage stability and can efficiently produce cured products with high transparency and uniformity (Patent Document 2). Furthermore, the group has developed a polymerization initiator composition containing a triarylboron compound and a cyclic ether compound (Patent Document 3).

[0005] Additionally, a thermosetting epoxy resin composition is known that contains an epoxy resin, a specific aromatic amine compound, a specific boron-phosphorus complex, and a specific phosphorus compound and can form a cured film with excellent voltage resistance, adhesion, and heat resistance in a short curing time (Patent Document 4).Patent Document 5 discloses a curing catalyst that contains a Lewis acid and a monoamine or heterocyclic aromatic organic compound. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2012 / 036164 Brochure [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-152194 [Patent Document 3] Japanese Patent Application Publication No. 2019-218267 [Patent Document 4] Patent Publication No. 2021-66890 [Patent Document 5] Special Publication No. 2008-544067 Summary of the Invention [Problem to be solved by the invention]

[0007] As described above, thermally latent resin compositions that begin to cure when heated are known. However, unless heated to a high temperature, the resin may not cure, or the cured product may become discolored or crack. Therefore, an object of the present invention is to provide a method for satisfactorily producing a cured product by curing a curable resin composition containing a compound having a cationically curable functional group by heating at a relatively low temperature using a specific thermal latent cationic polymerization initiator, and to provide a cured product cured by this method. [Means for solving the problem]

[0008] The present inventors have conducted extensive research to solve the above problems, and as a result have found that a curable resin composition containing a compound having a cationically curable functional group can be satisfactorily cured at a relatively low temperature by using a thermally latent cationic polymerization initiator containing a complex of a specific Lewis acid-type cationic polymerization initiator and an amine compound, thereby completing the present invention. The present invention will now be described.

[0009] [1] A method for producing a cured product, A step of preparing a curable resin composition by mixing a compound having a cationically curable functional group and a thermal latent cationic polymerization initiator; a step of curing the curable resin composition by heating, the thermal latent cationic polymerization initiator contains a Lewis acid cationic polymerization initiator represented by the following formula (I) and an amine compound, the Lewis acid type cationic polymerization initiator and a part of the amine compound form a complex, the remainder of the amine compound is present free from the Lewis acid cationic polymerization initiator, a production method characterized in that the molar ratio of amino groups contained in the free amine compound to 1 mole of boron atoms contained in the Lewis acid type cationic polymerization initiator is 0.15 or more and 1.70 or less. [ka] [In the formula, F represents a fluoro group; R 1 represents a hydrocarbon group which may have a substituent, l represents an integer of 1 or more and 5 or less, m represents an integer of 1 to 3, n is an integer of 0 to 2, m+n=3, If n is 2, then two R 1 may be the same or different from each other. [2] The method according to [1], wherein the thermal latent cationic polymerization initiator further contains a solvent. [3] The method according to [2] above, wherein the solvent is an ether solvent having a boiling point of 80°C or higher and 160°C or lower. [4] The method according to any one of [1] to [3] above, wherein the heating temperature of the curable resin composition is 80°C or higher and 160°C or lower. [5] The method according to any one of [1] to [4] above, wherein the cationically curable functional group is an epoxy group and / or an oxetanyl group. [6] The method according to any one of [1] to [5], wherein the compound having a cationically curable functional group is one or more compounds selected from the group consisting of alicyclic epoxy compounds, aromatic epoxy compounds, and oxetane compounds. [7] The method according to any one of [1] to [6] above, further comprising the step of molding the curable resin composition. [8] The manufacturing method according to [7], wherein the curable resin composition is molded by a spin coating method, a solvent casting method, a dipping method, a spray coating method, or a dispenser method. [9] A cured product of a curable resin composition containing a Lewis acid type cationic polymerization initiator represented by the following formula (I), an amine compound, and a bisphenol epoxy compound represented by the following formula (III): [ka] [In the formula, F represents a fluoro group; R 1 represents a hydrocarbon group which may have a substituent, l represents an integer of 1 or more and 5 or less, m represents an integer of 1 to 3, n is an integer of 0 to 2, m+n=3, If n is 2, then two R 1 may be the same or different from each other] [ka] [In the formula, R 21 and R 22 are independently H, C 1-6 Alkyl groups, halogenated C 1-6 represents an alkyl group or a phenyl group, and R 21 and R 22 Let's get together and C 3-10 may form a cycloalkyl group, r is an integer between 0 and 100.

[10] The cured product according to [9], further containing rubber particles.

[11] The cured product according to [9] or

[10] above, which has a loss factor tanδ at 40°C of 0.01 or more. [Effects of the Invention]

[0010] The curable resin composition according to the present invention exhibits excellent thermal latency because the Lewis acid-type cationic polymerization initiator liberated by heating at a relatively low temperature can catalyze the polymerization reaction of a compound having a cationic curable functional group. Therefore, the curable resin composition containing the thermally latent cationic polymerization initiator according to the present invention does not cure at room temperature, but initiates curing upon heating at a relatively low temperature, making it possible to control curing by adjusting the temperature. Furthermore, the cured product produced by the present invention is suppressed from defects such as discoloration and cracking. Therefore, the present invention is industrially highly advantageous as it relates to a cured product and a method for producing the same that not only allow curing to be controlled but also have excellent quality after curing. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a photograph showing the appearance of the cured products of Examples 2 and 3 and Comparative Examples 1 and 2. DETAILED DESCRIPTION OF THE INVENTION

[0012] The method of the present invention will be described below step by step, but the present invention is not limited to the following specific examples. Note that hereinafter, "a compound represented by formula (x)" will be abbreviated as "compound (x)".

[0013] 1. Preparation of curable resin composition In this step, a compound having a cationically curable functional group and a thermally latent cationic polymerization initiator are mixed to prepare a curable resin composition. The thermally latent cationic polymerization initiator according to the present invention contains a Lewis acid-type cationic polymerization initiator (I) and an amine compound.

[0014] Thermal latent polymerization initiators are mainly divided into protonic acid type and Lewis acid type. Protonic acid type reacts with a compound having a cationic curable functional group to produce a strong acid as a by-product, whereas Lewis acid type does not. In addition, the ligand coordinated to the Lewis acid type cationic polymerization initiator functions as a stabilizer for the produced resin.

[0015] In the formula (I), examples of the hydrocarbon group include C 1-6 Alkyl group, C 2-6 Alkenyl groups, and C 2-6 Examples of aliphatic hydrocarbon groups include those selected from alkynyl groups. 1-6 Examples of the alkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, n-pentyl, and n-hexyl. 1-4 alkyl group, more preferably C 1-2 C is an alkyl group, and even more preferably methyl. 2-6 Examples of alkenyl groups include ethenyl (vinyl), 1-propenyl, 2-propenyl (allyl), isopropenyl, 2-butenyl, 3-butenyl, isobutenyl, pentenyl, and hexenyl. 2-4 C is an alkenyl group, more preferably ethenyl (vinyl) or 2-propenyl (allyl). 2-6 Examples of the alkynyl group include ethynyl, 1-propynyl, 2-propynyl, 2-butynyl, 3-butynyl, pentynyl, and hexynyl. 2-4 It is an alkynyl group, more preferably ethynyl or propynyl.

[0016] Examples of the substituent that the hydrocarbon group may have include C 1-6 Examples of the substituent include one or more selected from an alkoxy group, a halogeno group, a cyano group (-CN), and a nitro group (-NO2).

[0017] C 1-6 The alkoxy group refers to a linear or branched saturated aliphatic hydrocarbon oxy group having 1 to 6 carbon atoms. Examples include methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, t-butoxy, n-pentoxy, and n-hexoxy, and preferably C 1-4 is an alkoxy group, more preferably C 1-2 It is an alkoxy group, and even more preferably methoxy.

[0018] Examples of the halogeno group include fluoro, chloro, bromo and iodo, with chloro or bromo being preferred, and chloro being more preferred.

[0019] The number of substituents in the hydrocarbon group is not particularly limited as long as it is substitutable, but can be, for example, 1 to 8. The number is preferably 6 or 4 or less, more preferably 3 or 2 or less, and even more preferably 1.

[0020] The number l of fluoro groups on the phenyl group is preferably 2 or more, or 3 or more, more preferably 4 or more, and even more preferably 5.

[0021] The number m of phenyl groups is preferably 2 or more, and more preferably 3.

[0022] As the Lewis acid type cationic polymerization initiator, for example, tris(pentafluorophenyl)borane is preferable.

[0023] The amine compound according to the present invention refers to an organic compound having an amino group, and also includes ammonia (NH3). That is, the amine compound according to the present invention is classified into ammonia, primary amine compounds, secondary amine compounds, and tertiary amine compounds. In the present invention, the nitrogen atom of the amine compound coordinates with the boron atom of the Lewis acid cationic initiator (I) to suppress the catalytic activity of the Lewis acid cationic initiator (I). However, when the two atoms dissociate upon heating, the catalytic activity of the Lewis acid cationic initiator (I) is expressed. That is, the amine compound imparts thermal latency to the Lewis acid cationic initiator (I).

[0024] The primary amine compound is a compound (RNH2) in which one of the hydrogen atoms of ammonia is substituted with a hydrocarbon residue. 1 ) is an example of a compound represented by the formula: [ka] [In the formula, R 2 is C 1-6 represents an alkyl group, p represents an integer of 0 to 5, q represents an integer of 1 or more and 6 or less, p+q≦6, When p is an integer of 2 or more, R 2 may be the same or different from each other]

[0025] The secondary amine compound is a compound (R2NH) in which two of the hydrogen atoms of ammonia are substituted with a hydrocarbon residue or the like, and the tertiary amine compound is a compound (NR3) in which three of the hydrogen atoms of ammonia are substituted with a hydrocarbon residue or the like. The secondary amine compound and the tertiary amine compound include those represented by the following formula (II 2 ) is a compound having a piperidine structure represented by the formula: [ka] [In the formula, X represents an ether group (—O—) or a single bond; R 3 ~R 7 are independently H or C 1-6 indicates an alkyl group]

[0026] Examples of the secondary amine compound and the tertiary amine compound include compounds represented by the following formula (II 3 ) or (II 4 ) is an example of a compound represented by the formula: [ka] [In the formula, X and R 3 ~R 7 has the same meaning as above, Y represents a linker group or a single bond; R 8 is H, C 1-6 an alkyl group, or the piperidine structure (II 2 ) indicates

[0027] The linker group is the piperidine structure (II 2 ) and facilitates the synthesis of compounds. There are no particular limitations on the compounds as long as they exhibit such effects. For example, 1-10 Examples of such linked groups include an alkanediyl group, an ether group (-O-), a thioether group (-S-), a carbonyl group (-C(=O)-), a thionyl group (-C(=S)-), an ester group (-OC(=O)- or -C(=O)-O-), an amide group (-NH-C(=O)- or -C(=O)-NH-), a urea group (-NH-C(=O)-NH-), and a thiourea group (-NH-C(=S)-NH-); and groups in which two or more and five or less of these groups are linked together. Examples of such linked groups include C alkyl groups having at one or both ends a group selected from the group consisting of an ether group, a thioether group, a carbonyl group, a thionyl group, an ester group, an amide group, a urea group, and a thiourea group. 1-10 An alkanediyl group can be mentioned.

[0028] [ka] [In the formula, R 9 ~R 12 At least one of the piperidine structures (II 2 ) and the rest is C 1-20 indicates an alkyl group]

[0029] The amine compound is preferably a hindered amine compound. A hindered amine compound is an amine compound in which the nucleophilicity of the lone electron pair of the nitrogen atom is weakened by steric hindrance due to a substituent. For example, R 4 ~R 6 All are C 1-6 Piperidine structure (II) 2 ) is an amine compound having the formula:

[0030] Examples of the hindered amine compound include the following compounds: [ka]

[0031] [ka]

[0032] The amine compound may be an imidazole compound represented by the following formula: [ka] [In the formula, R 13 ~R 16 are independently a hydrogen atom (-H) or C 1-6 indicates an alkyl group] In imidazole compounds, R 16 is preferably a hydrogen atom.

[0033] In amine compounds, C 1-6The alkyl group refers to a linear or branched monovalent saturated aliphatic hydrocarbon group having 1 to 6 carbon atoms. Examples include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, n-pentyl, and n-hexyl. Preferably, C 1-4 alkyl group, more preferably C 1-2 It is an alkyl group, most preferably methyl.

[0034] Only one amine compound may be used, or a mixture of two or more amine compounds may be used. The mixture may be a mixture of amine compounds differing only in the number of carbon atoms in the alkyl group, or a mixture of different types of amine compounds. The number of amine compounds in the mixture is preferably 10 or less, more preferably 8 or less or 5 or less, and even more preferably 2. An example of a mixture of amine compounds is a mixture of a hindered amine compound and an imidazole compound.

[0035] The ratio of the two types of amine compounds may be adjusted appropriately depending on the thermal latent curability, corrosion resistance, etc. For example, the molar ratio of hindered amino groups to non-hindered amino groups may be set to 1 or more and 10 or less. The molar ratio is preferably 2 or more or 3 or more, and more preferably 8 or less or 5 or less.

[0036] The thermal latent cationic polymerization initiator according to the present invention may contain a solvent. If the initiator contains a solvent, it can be easily mixed with a compound having a cationically curable functional group, which increases convenience. On the other hand, from the viewpoint of storage stability, the initiator may not contain a solvent.

[0037] The solvent is not particularly limited as long as it can adequately dissolve the Lewis acid type cationic polymerization initiator (I), the amine compound, and a complex thereof. Examples of the solvent include alcohol solvents such as methanol, ethanol, and 2-propanol; ether solvents such as dimethyl ether, ethyl methyl ether, tetrahydrofuran, dioxane, and methoxycyclopentane; ketone solvents such as acetone and ethyl methyl ketone; ester solvents such as ethyl acetate and γ-butyrolactone; aliphatic hydrocarbon solvents such as n-pentane, n-hexane, cyclohexane, and methylcyclohexane; aromatic hydrocarbon solvents such as benzene and toluene; halogenated hydrocarbon solvents such as dichloroethane, chloroform, carbon tetrachloride, and chlorobenzene; and mixed solvents thereof, among which ether solvents are preferred.

[0038] The solvent preferably has a boiling point of 80°C or higher and 160°C or lower. If the boiling point is 80°C or higher, the curable resin composition can be sufficiently heated, and the curable resin composition can be sufficiently cured. If the boiling point is 160°C or lower, it is possible to prevent the curable resin composition from being excessively heated. As the solvent, an ether-based solvent having a boiling point of 80°C or higher and 160°C or lower is particularly preferred.

[0039] When the thermal latent cationic polymerization initiator according to the present invention contains a solvent, the concentration may be adjusted appropriately. For example, the total concentration of the Lewis acid type cationic polymerization initiator (I) and the amine compound can be adjusted to 10% by mass or more and 80% by mass or less, and preferably 25% by mass or more and 50% by mass or less.

[0040] Neutral tricoordinate boron compounds, known as boranes, exhibit electron-accepting properties, and amine compounds have a lone electron pair on the nitrogen atom, so it is believed that the Lewis acid cationic polymerization initiator (I) and the amine compound form a complex. However, the present inventors have discovered that even if the Lewis acid cationic polymerization initiator (I) and the amine compound are mixed so that the molar ratio of boron atoms to nitrogen atoms is 1:1, the two compounds do not necessarily form a complex in the exact amount, which is thought to depend mainly on the structure of the amine compound.

[0041] The present inventors have also found that by reacting a sufficient amount of an amine compound with the Lewis acid type cationic polymerization initiator (I) in a quantity greater than that required to form a complex with the Lewis acid type cationic polymerization initiator (I) and allowing a specific ratio of free amine compound to be present relative to the Lewis acid type cationic polymerization initiator (I), not only is thermal latency imparted to the Lewis acid type cationic polymerization initiator (I), but metal corrosion inhibitory action is also exhibited.

[0042] In addition to forming a complex with the Lewis acid type cationic polymerization initiator (I), the free amine compound present in liberation from the Lewis acid type cationic polymerization initiator (I) may exist alone in the thermal latent cationic polymerization initiator, or may form, for example, a salt with another anion.

[0043] Specifically, an amine compound is reacted with the Lewis acid cationic polymerization initiator (I) in a solvent so that the molar ratio of amino groups in the amine compound is greater than 1, thereby forming a complex between the Lewis acid cationic polymerization initiator (I) and the amine compound, and the molar ratio of amino groups in the free amine compound per mole of boron atoms in the Lewis acid cationic polymerization initiator is adjusted to 0.15 or more and 1.70 or less. A molar ratio of 0.15 or more ensures thermosetting properties. On the other hand, a molar ratio of 1.70 or less can suppress corrosion of the cured product and the metal, even when the cured product produced by the thermal latent cationic polymerization initiator comes into contact with the metal. The molar ratio is preferably 0.25 or more, more preferably 0.30 or more, and preferably 1.50 or less, more preferably 1.00 or less.

[0044] In the narrow sense, the amino group may refer to an -NH group, but in the present disclosure, the amino group is broadly defined to include not only an -NH group but also an -NH- group possessed by a secondary amine compound, an >N- group possessed by a tertiary amine compound, and, when ammonia is used as the amine compound, ammonia itself.

[0045] Because the amine compound complexed with the Lewis acid cationic polymerization initiator (I) loses its basicity, the concentration and amount of free amine compound liberated from the Lewis acid cationic polymerization initiator can be measured by acid titration. The concentration and amount of free amine compound are measured according to Section 3, Amine Value Determination Method (2), Method 2, of the Standards for Medical Drugs and Ingredients 2006. Specifically, the thermally latent cationic polymerization initiator and bromophenol blue are dissolved in ethanol and titrated with 0.5 mol / L hydrochloric acid until the solution turns green. The amount of free amine compound in the thermally latent cationic polymerization initiator can be determined from the amount and concentration of the acid added, and the molar ratio of amino groups in the free amine compound to one mole of boron atoms in the Lewis acid cationic polymerization initiator can then be calculated.

[0046] The thermally latent cationic polymerization initiator according to the present invention can be easily produced by simply mixing the Lewis acid cationic polymerization initiator (I) and an amine compound in a solvent. For example, the Lewis acid cationic polymerization initiator (I) and the amine compound may be mixed in a solvent at room temperature, more specifically, at a temperature of 10°C or higher and 40°C or lower. After mixing the Lewis acid cationic polymerization initiator (I) and the amine compound, the solvent may be distilled off. Post-reaction treatment may be carried out according to a conventional method.

[0047] The curable resin composition according to the present invention contains the thermal latent cationic polymerization initiator and a compound having a cationic curable functional group. The compound having the cationic curable functional group attacks a cation generated from the thermal latent cationic polymerization initiator with the cationic curable functional group to generate a cation, which then attacks the generated cation with another cationic curable functional group, thereby polymerizing.

[0048] Examples of the cationically curable functional group include a carbon-carbon double bond group and a cyclic ether group, such as a vinyl group, an epoxy group, and an oxetanyl group.

[0049] Examples of compounds having a cationically curable functional group include aliphatic unsaturated hydrocarbons, aromatic compounds having a vinyl group, and cationically curable heteroatom-containing compounds.

[0050] Examples of aliphatic unsaturated hydrocarbons include C olefins having one vinyl group, such as 1-butene, 2-butene, isobutene, 1-pentene, 3-methyl-1-butene, 1-hexene, 2-hexene, 3-methyl-1-pentene, 2,3-dimethyl-1-butene, 3,3-dimethyl-1-butene, vinylcyclopentane, 3,3-dimethyl-1-pentene, vinylcyclohexane, 1-octene, 2-octene, 2,4,4-trimethyl-1-pentene, vinylnorbornane, 1-decene, camphene, α-pinene, β-pinene, and vinyladamantane. 1-12 Aliphatic unsaturated hydrocarbon compounds: C compounds having two or more vinyl groups, such as butadiene, 1,4-pentadiene, cyclopentadiene, 1,5-hexadiene, 1,3-cyclohexadiene, 2,5-norbornadiene, dicyclopentadiene, 4-vinyl-cyclohexene, 5-vinyl-2-norbornene, and 5-ethylidene-2-norbornene. 1-12 Aliphatic unsaturated hydrocarbon compounds are included.

[0051] Examples of aromatic compounds that constitute aromatic compounds having a vinyl group include phenyl, naphthyl, anthryl, phenanthryl, pyrenyl, and the like. 6-18 Examples of aromatic compounds having a vinyl group include C aromatic compounds having one vinyl group, such as styrene, α-methylstyrene, 3-methylstyrene, 4-methylstyrene, 3-ethylstyrene, 4-ethylstyrene, 3-propylstyrene, 4-isopropylstyrene, 3-butylstyrene, 4-tert-butylstyrene, 4-hexylstyrene, 4-octylstyrene, 3-(2-ethylhexyl)styrene, 4-(2-ethylhexyl)styrene, 2,4-diphenyl-4-methyl-1-pentene, 1-vinylnaphthalene, 2-vinylnaphthalene, 2-isopropenylnaphthalene, 9-vinylanthracene, and 1-vinylanthracene. 6-18Aromatic compounds: C having two or more vinyl groups, such as 1,3-divinylbenzene, 1,4-divinylbenzene, 1,3-diisopropenylbenzene, 1,4-diisopropenylbenzene, 1,4-divinylnaphthalene, 1,5-divinylnaphthalene, 1,4-diisopropenylnaphthalene, 9,10-divinylanthracene, allylstyrene, isopropenylstyrene, butenylstyrene, and octenylstyrene. 6-18 Examples include aromatic compounds.

[0052] The cationically curable heteroatom-containing compound refers to a compound that contains a cationically curable functional group containing a heteroatom, such as an epoxy group or an oxetanyl group, and that polymerizes by cations. Examples of the cationically curable heteroatom-containing compound having an epoxy group include epoxy resins having a cyclohexane skeleton, alicyclic epoxy resins, aliphatic epoxy resins, and aromatic epoxy compounds.

[0053] Examples of epoxy resins having a cyclohexane skeleton include 1,2-epoxy-4-(2-oxiranyl)cyclohexane adducts of 2,2-bis(hydroxymethyl)-1-butanol.

[0054] Examples of alicyclic epoxy resins include vinylcyclohexene monoxide, 1,2-epoxy-4-vinylcyclohexane, 1,2:8,9 diepoxylimonene, 3,4-epoxycyclohexenylmethyl-3',4'-epoxycyclohexenecarboxylate, 3,4-epoxycyclohexenylmethyl-3',4'-epoxycyclohexenecarboxylate, and hydrogenated epoxy compounds.

[0055] Hydrogenated epoxy compounds are compounds obtained by reducing the aromatic ring of an aromatic epoxy compound. Examples of hydrogenated epoxy compounds include hydrogenated bisphenol A epoxy compounds, hydrogenated bisphenol F epoxy compounds, hydrogenated bisphenol E epoxy compounds, diglycidyl ethers of alkylene oxide adducts of hydrogenated bisphenol A, diglycidyl ethers of alkylene oxide adducts of hydrogenated bisphenol F, hydrogenated phenol novolac epoxy compounds, and hydrogenated cresol novolac epoxy compounds.

[0056] Examples of aliphatic epoxy resins include ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, trimethylolpropane diglycidyl ether, and polyethylene glycol diglycidyl ether.

[0057] Examples of aromatic epoxy compounds include aromatic bisphenol A type epoxy compounds, aromatic bisphenol F type epoxy compounds, aromatic bisphenol E type epoxy compounds, diglycidyl ethers of alkylene oxide adducts of aromatic bisphenol A type, diglycidyl ethers of alkylene oxide adducts of aromatic bisphenol F type, diglycidyl ethers of alkylene oxide adducts of aromatic bisphenol E type, aromatic novolac type epoxy compounds, urethane-modified aromatic epoxy compounds, nitrogen-containing aromatic epoxy compounds, rubber-modified aromatic epoxy resins containing polybutadiene or nitrile butadiene rubber (NBR), etc.

[0058] Examples of oxetane compounds, which are cationically curable heteroatom-containing compounds having an oxetanyl group, include 3-ethyl-3-(alkoxymethyl)oxetanes such as 3-ethyl-3-(hexyloxymethyl)oxetane, 3-ethyl-3-(heptyloxymethyl)oxetane, 3-ethyl-3-(2-ethylhexyloxymethyl)oxetane, 3-ethyl-3-(octyloxymethyl)oxetane, and 3-ethyl-3-(dodecyloxymethyl)oxetane.

[0059] The compound having a cationically curable functional group may be a bisphenol epoxy compound (III). Bisphenol epoxy compound (III) is a main component of some commercially available curable epoxy compound compositions, but curing with a cationic polymerization initiator requires high temperatures and may cause cracking or discoloration in the cured product. Examples of curable epoxy compound composition products containing bisphenol epoxy compound (III) include the Acryset (registered trademark) BR series manufactured by Nippon Shokubai Co., Ltd. and jER manufactured by Mitsubishi Chemical Corporation. TM There is a series.

[0060] [ka] [In the formula, R 21 and R 22 are independently H, C 1-6 Alkyl groups, halogenated C 1-6 represents an alkyl group or a phenyl group, and R 21 and R 22 Let's get together and C 3-10 may form a cycloalkyl group, r is an integer between 0 and 100.

[0061] r may be 0. The upper limit of r is preferably 50 or less, more preferably 10 or less, and even more preferably 5 or less or 3 or less.

[0062] The ratio of the compound having a cationically curable functional group to the thermal latent cationic polymerization initiator in the curable resin composition according to the present invention may be adjusted as appropriate within a range in which the compound having a cationically curable functional group can be satisfactorily cured, and for example, the mass ratio of the compound having a cationically curable functional group to 1 part by mass of the Lewis acid type cationic polymerization initiator (I) contained in the latent cationic polymerization initiator may be adjusted to about 50 to 200. The ratio is preferably 60 or more, more preferably 80 or more, and is preferably 150 or less, more preferably 120 or less.

[0063] In addition, the curable resin composition according to the present invention may contain additives such as an antistatic agent, a curing agent, a flame retardant, an antibacterial agent, an antioxidant, a pigment, etc. It is also preferable to contain particles such as silica particles in order to improve the linear expansion coefficient and electrical properties.

[0064] Furthermore, the incorporation of rubber particles can improve the impact resistance of the cured product. Examples of rubber particles include acrylic rubber particles, silicone rubber particles, and fluororubber particles. The particle size of the rubber particles is not particularly limited, but for example, rubber particles having a volume-based average particle size of 0.05 μm or more and 2 μm or less can be used. The amount of rubber particles incorporated into the curable resin composition is also not particularly limited, but can be, for example, 10 phr or more and 30 phr or less.

[0065] 2. Molding process In this step, the curable resin composition prepared in step 1 is molded. The molding method is not particularly limited and may be appropriately selected, and examples thereof include spin coating, solvent casting, dipping, spray coating, and dispenser methods. Spin coating is a method of coating a flat substrate with a liquid using centrifugal force, and this method can be used to form a thin film of a liquid curable resin composition. Solvent casting is a method of casting a liquid curable resin composition into a mold. Dipping is a method of immersing a mold or a core substrate in a liquid curable resin composition to form a coating of the liquid curable resin composition on the substrate surface. Spray coating is a method of spraying a liquid curable resin composition onto a substrate surface to form a coating of the liquid curable resin composition on the substrate surface. The dispenser method is a method of ejecting a fixed amount of liquid curable resin composition onto a substrate from a device called a dispenser to form a coating of the liquid curable resin composition on the substrate surface.

[0066] 3.Curing process In this step, the curable resin composition is cured by heating. The curable resin composition according to the present invention does not cure at room temperature due to the action of the thermal latent cationic polymerization initiator according to the present invention, which serves as a polymerization catalyst. However, when heated, the thermal latent cationic polymerization initiator according to the present invention exerts its polymerization catalytic ability, resulting in curing.

[0067] The curing initiation temperature of the thermal latent cationic polymerization initiator according to the present invention is preferably 50°C or higher. This is because if the curing initiation temperature is 50°C or higher, curing will hardly start at room temperature. The temperature is more preferably 60°C or higher or 80°C or higher, and even more preferably 100°C or higher. On the other hand, if the temperature is too high, there is a risk of the cured product decomposing, so the heating temperature is preferably 500°C or lower, more preferably 400°C or lower, even more preferably 300°C or lower, and even more preferably 200°C or lower.

[0068] It is believed that the thermal latent cationic polymerization initiator according to the present invention dissociates from the amine compound upon heating, thereby initiating a polymerization reaction. After the polymerization reaction, it is unclear whether the amine compound dissociated from the thermal latent cationic polymerization initiator forms a complex with the thermal latent cationic polymerization initiator again or remains free. However, amine compounds with low boiling points, such as ammonia, may evaporate from the cured product, potentially causing their concentration to fall below the detection limit.

[0069] When a cured product cured using a thermally latent cationic polymerization initiator comes into contact with metal, the cured product itself or the metal may discolor, especially under high-temperature or high-humidity conditions. The discolored metal parts can lead to deterioration of properties and corrosion, resulting in poor insulation. However, even when a cured product of the curable resin composition according to the present invention containing the thermally latent cationic polymerization initiator comes into contact with metal, discoloration of the cured product of the curable resin composition and the metal is suppressed, even under high-temperature and high-humidity conditions, presumably due to the presence of an appropriate amount of free amine compound relative to the Lewis acid-type cationic polymerization initiator (I).

[0070] The bonded structure according to the present invention includes a cured product of the curable resin composition and a metal, and the cured product and the metal are in contact with each other. As described above, the bonded structure according to the present invention has excellent corrosion resistance between the cured product and the metal.

[0071] The metal contained in the bonded body is not particularly limited, but examples thereof include copper, gold, silver, nickel, aluminum, and alloys of stainless steel, among which copper, silver, and nickel are preferred from the viewpoints of conductivity, ease of handling, cost, and the like.

[0072] The shape of the metal is not particularly limited and may be appropriately selected, for example, spherical, plate-like, tubular, bulk, linear, sponge-like, etc. The plate-like shape may be a foil of about 5 μm or more and 200 μm or less. The thickness is preferably 10 μm or more, and preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 20 μm or less.

[0073] The shape of the cured product is not particularly limited and can be, for example, spherical, plate-like, tubular, bulky, linear, or sponge-like. The thickness of the plate-like product can also be selected appropriately, and can be, for example, 10 μm or more and 500 μm or less. The thickness is preferably 15 μm or more, more preferably 20 μm or more, and preferably 200 μm or less, more preferably 150 μm or less, and even more preferably 50 μm.

[0074] Alternatively, a sheet of formed fibers such as carbon fibers may be impregnated with a solvent-containing curable resin composition to form a prepreg. The prepreg may be laminated with a metal foil and heated to cure the curable resin composition, thereby forming a metal-clad laminate.

[0075] In addition, the curable resin composition according to the present invention can also be used as an adhesive between metals or between a metal and another member, a conductive paste containing a conductive metal, an anisotropic conductive film (ACF) material, a sealant for circuit elements with exposed metal portions, and the like.

[0076] As described above, the combination of the Lewis acid type cationic polymerization initiator (I) and an amine compound can successfully polymerize and cure epoxy monomers at relatively low temperatures. For example, with conventional thermally latent cationic polymerization initiators, bisphenol epoxy resin (III) could not be polymerized unless at high temperatures, or even if polymerization was possible, defects such as discoloration and cracking could occur. However, with the combination of the Lewis acid type cationic polymerization initiator (I) and an amine compound according to the present invention, it is possible to polymerize and cure bisphenol epoxy resin (III) at relatively low temperatures while suppressing defects. The cured product produced by the method of the present invention can also be used as a protective layer for a printed wiring board. Specifically, a flexible printed wiring board having a conductor pattern formed by printing on a flexible and insulating plastic film such as polyester or polyimide is coated with the curable resin composition of the present invention so as to cover the conductor pattern, and the curable resin composition is cured by heating and pressing, thereby obtaining a flexible printed wiring board provided with a protective layer. The cured or semi-cured product of the present invention may be used as a resin film or prepreg. For example, the curable resin composition of the present invention may be applied to a release film, cured or semi-cured by heating, and formed into a film to form a resin film or prepreg. Semi-curing is, for example, B-staging. It is believed that the combination of the Lewis acid type cationic polymerization initiator (I) according to the present invention and an amine compound causes chain polymerization of epoxy monomers through the following reaction: In the following formula, R represents an unspecified hydrogen atom or an organic group, and multiple Rs may be the same or different. [ka] Since bisphenol epoxy resin (III) has two epoxy groups, its cured product may have a three-dimensional or higher-order structure. As a result, analysis of the chemical structure of a polymer is generally difficult, but analysis of the chemical structure of a cured product of bisphenol epoxy resin (III) is even more difficult. Since the present invention allows epoxy monomers to be polymerized at relatively low temperatures, it is believed that at least a portion of the Lewis acid type cationic polymerization initiator (I) remains in the cured product. On the other hand, since some amine compounds have low boiling points, such as ammonia, the content of the amine compound in the cured product may be below the detection limit. [Example]

[0077] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples, and it is possible to carry out the invention by making appropriate modifications within the scope of the above and below-described aims, and all such modifications are included in the technical scope of the present invention.

[0078] Catalyst Production Example 1: Production of cationic polymerization initiator Tris(pentafluorophenyl)borane (TPB) (10.556 g, 20.617 mmol) was added with 2,2,6,6-tetramethyl-4-piperidine ester of 1,2,3,4-butanetetracarboxylic acid having the following chemical structure ("ADK STAB LA57" manufactured by ADEKA Corporation, 4.077 g, 5.154 mmol) and methoxycyclopentane (14.000 g), and the mixture was stirred for 1 hour until dissolved.

[0079] [ka]

[0080] Test Example 1: Measurement of free amine value The free amine value of the produced cationic polymerization initiator was measured. Bromophenol blue was dissolved in ethanol to prepare a 0.1% by mass ethanol solution, hereafter referred to as BPB solution. A cationic polymerization initiator (1 g) and BPB solution (0.2 mL) were added to a vial containing ethanol (10 mL), then the vial was capped and stirred for approximately 5 seconds. 0.5 mol / L hydrochloric acid (Kishida Chemical Co., Ltd.) was slowly added dropwise to the resulting solution. The solution color was confirmed to change from blue to green to yellow, and the point at which it turned green was taken as the end point. The amine compound that forms a complex with TPB does not react with hydrochloric acid, and the number of moles of hydrochloric acid required to add dropwise corresponds to the number of moles of amino groups contained in the free amine. The number of moles of amino groups contained in free amines per mole of boron in the cationic polymerization initiator measured is taken as the free amine value, and is shown in Table 1 together with the molar ratio (N / B) of the amine compound to boron in the TPB used to produce the cationic polymerization initiator. The commercially available cationic polymerization initiator used for comparison (SAN-AID SI-80L, manufactured by Sanshin Chemical Industry Co., Ltd.) does not contain free amines in its structure, but when it was measured in the same way just to be sure, the color of the solution was yellow from the beginning, so it was determined that the free amine value was 0.

[0081] [ka]

[0082] [Table 1]

[0083] Production of curable resin composition The alicyclic epoxy compounds or aromatic epoxy compounds shown in Table 2 and the cationic polymerization initiators were mixed in the mass ratios shown in Table 3 to obtain resin compositions.

[0084] [Table 2]

[0085] [Table 3]

[0086] Test Example 2: Thermosetting Test The uncured resin compositions were molded onto substrates and thermally cured under the conditions shown in Table 4, and the state of cure and the appearance of the cured products were visually observed. The results are shown in Table 4. Photographs of the appearance of the cured products of Examples 2 and 3 and Comparative Examples 1 and 2 are shown in Figure 1.

[0087] [Table 4]

[0088] As shown in the results in Table 4 and FIG. 1, cracks and discoloration were observed in the cured products of the resin compositions of Comparative Examples 1 to 3, which contained an alicyclic epoxy resin and a commercially available cationic polymerization initiator. In Comparative Examples 4 and 5, which contained an aromatic epoxy resin and a commercially available cationic polymerization initiator, poor curing occurred and no cured product was obtained. In contrast, in Examples 1 to 6 according to the present invention, the curing reaction proceeded sufficiently with heating at 120 to 160°C for 1 hour for both the alicyclic epoxy resin and the aromatic resin, and cured products free from defects such as discoloration and cracks were obtained.

[0089] Test Example 3: Differential Scanning Calorimetry The heat generation characteristics of the curable resin composition were measured using a differential scanning calorimeter ("DSC 3500" manufactured by Netzsch Japan). The measurement conditions were a temperature rise rate of 10°C / min, and measurements were performed from 30°C to 250°C in a nitrogen atmosphere. The results are shown in Table 5.

[0090] [Table 5]

[0091] As shown in the results in Table 5, even with a commercially available initiator, the alicyclic epoxy compound could be polymerized (resin composition 7). However, in the case of aromatic epoxy compounds, when using commercially available initiators, the curing reaction either did not proceed at all (resin composition 9), or even if it did proceed, the heat generated was small and the curing was insufficient (resin composition 8). In contrast, in the case of resin compositions 1 to 6 according to the present invention, heat generation associated with the curing reaction was observed for both the alicyclic epoxy compound and the aromatic epoxy compound, and the amount of heat generated was large, indicating that curing had progressed sufficiently.

[0092] Test Example 4: Dynamic viscoelasticity measurement The storage modulus, loss modulus, and tan δ of the cured material were measured using a dynamic viscoelasticity measuring device ("DMA RSA-G2" manufactured by TA Instruments Japan). The measurement conditions were three-point bending, a heating rate of 5°C / min, measurement from 30°C to 250°C, a normal load of 10 g, and a sensitivity of 2 g. The sample size was 5 mm x 20 mm x 2 mm thick. The results are shown in Table 6.

[0093] [Table 6]

[0094] Dynamic modulus includes storage modulus (Pa) and loss modulus (Pa), with storage modulus being the component of energy generated by external force and strain that is stored inside the object, and loss modulus being the component that diffuses to the outside. Tan δ is called the loss factor and is expressed as loss modulus / storage modulus, and the larger this value, the higher the viscosity and the easier it is to diffuse energy generated by strain to the outside, making it more resistant to impact. As shown in Table 6, the cured products of Examples 4 to 6 according to the present invention not only have a high Tg of 100°C or higher, but also exhibit a higher tan δ than the cured product of Comparative Example 3, which was made with a commercially available initiator. This indicates that the cured products can diffuse external strain and have high impact resistance.

Claims

1. A method for producing a cured product, comprising: A step of preparing a curable resin composition by mixing a compound having a cationically curable functional group and a thermal latent cationic polymerization initiator; a step of curing the curable resin composition by heating, the thermal latent cationic polymerization initiator contains a Lewis acid type cationic polymerization initiator represented by the following formula (I) and an amine compound, the Lewis acid type cationic polymerization initiator and a part of the amine compound form a complex, the remainder of the amine compound is present free from the Lewis acid cationic polymerization initiator, a molar ratio of amino groups contained in the free amine compound to 1 mole of boron atoms contained in the Lewis acid type cationic polymerization initiator of 0.15 or more and 1.70 or less; 【Chemistry 1】 [In the formula, F represents a fluoro group; R 1 represents a hydrocarbon group which may have a substituent, l represents an integer of 1 or more and 5 or less, m represents an integer of 1 or more and 3 or less, n represents an integer of 0 to 2, m+n=3, When n is 2, two R 1 may be the same or different.]

2. The method according to claim 1, wherein the thermal latent cationic polymerization initiator further contains a solvent.

3. 3. The method according to claim 2, wherein the solvent is an ether solvent having a boiling point of 80°C or higher and 160°C or lower.

4. The method according to claim 1, wherein the curable resin composition is heated to a temperature of 80°C or higher and 160°C or lower.

5. The method according to claim 1, wherein the cationically curable functional group is an epoxy group and / or an oxetanyl group.

6. 2. The method according to claim 1, wherein the compound having a cationically curable functional group is one or more compounds selected from the group consisting of alicyclic epoxy compounds, aromatic epoxy compounds, and oxetane compounds.

7. The method according to claim 1 , further comprising the step of molding the curable resin composition.

8. The method according to claim 7 , wherein the curable resin composition is molded by a spin coating method, a solvent casting method, a dipping method, a spray coating method, or a dispenser method.

9. A cured product of a curable resin composition containing a Lewis acid type cationic polymerization initiator represented by the following formula (I), an amine compound, and a bisphenol epoxy compound represented by the following formula (III). 【Chemistry 2】 [In the formula, F represents a fluoro group; R 1 represents a hydrocarbon group which may have a substituent, l represents an integer of 1 or more and 5 or less, m represents an integer of 1 or more and 3 or less, n represents an integer of 0 to 2, m+n=3, When n is 2, two R 1 may be the same or different from each other. 【Transformation 3】 [In the formula, R 21 and R 22 are independently H, C 1-6 Alkyl group, halogenated C 1-6 represents an alkyl group or a phenyl group, and R 21 and R 22 Let's get together and C 3-10 may form a cycloalkyl group, and r represents an integer of 0 to 100.

10. The cured product according to claim 9, further comprising rubber particles.

11. The cured product according to claim 9, which has a loss factor tan δ at 40°C of 0.01 or more.

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