Thermosetting biscitraconimide resin composition

Abstract

To provide a thermosetting biscitraconimide resin composition which has a viscosity suitable for working and can give a cured product having both dielectric properties (a low relative dielectric constant and a low dielectric loss tangent) and heat resistance.SOLUTION: The thermosetting biscitraconimide resin composition comprises (A) a biscitraconimide compound, (B) a monocitraconimide compound having a melting point of ≤ 60 °C, (C) an epoxy resin, (D) an epoxy resin curing agent and (E) a curing accelerator.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a thermosetting biscitraconimide resin composition. [Background technology]

[0002] Electronic devices such as mobile communications equipment, network infrastructure equipment, and mainframe computers are increasingly using faster and larger signals every year. Furthermore, new systems that handle high-frequency wireless signals are being commercialized and planned for commercialization in the fields of ITS and indoor short-range communications. Accordingly, printed wiring boards used in these electronic devices must be capable of operating at frequencies in the 20 GHz range. Therefore, underfill materials are also required to have dielectric properties, such as low dielectric constant and low dielectric dissipation factor, which enable the reduction of transmission loss.

[0003] Known materials with low dielectric constants and low dielectric loss tangents include thermosetting resins such as modified polyphenylene ether resins and maleimide resins, and thermoplastic resins such as fluororesins, styrene resins, and liquid crystal polymers. However, these resins have high melt viscosities, and the resulting cured products are hard and brittle. In contrast, citraconic imide resins have lower melt viscosities than the above resins and produce cured products with excellent dielectric properties and heat resistance (Patent Documents 1 and 2). However, their viscosity at room temperature is higher than that of liquid epoxy resins, leaving issues with handling. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-018240 [Patent Document 2] Japanese Patent Publication No. 2022-147022 Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, an object of the present invention is to provide a thermosetting biscitraconimide resin composition that has a viscosity suitable for workability and can give a cured product that has both dielectric properties (low dielectric constant and low dielectric dissipation factor) and heat resistance. [Means for solving the problem]

[0006] As a result of intensive research aimed at solving the above problems, the present inventors have found that the following thermosetting biscitraconimide resin composition can achieve the above object, and have thus completed the present invention. That is, the present invention provides the following thermosetting biscitraconimide resin composition.

[0007] [1] (A) a biscitraconimide compound represented by the following formula (1): [ka] (In formula (1), B is a divalent organic group.) (B) a monocitraconimide compound represented by the following formula (2) and having a melting point of 60°C or less: [ka] (In formula (2), A is selected from hydrocarbon groups represented by the following structures.) [ka] (R is independently a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. Q is a linear or branched alkylene group having 1 to 10 carbon atoms. * indicates a bond to the nitrogen atom in the citraconic imide group.) (C) epoxy resin, (D) an epoxy resin curing agent, and (E) Curing accelerator A thermosetting biscitraconimide resin composition comprising: [2] The thermosetting biscitraconimide resin composition according to [1], wherein B in formula (1) is at least one group selected from the group represented by the following structure and a hydrocarbon group derived from a dimer acid skeleton: [ka] (* means a bond to the nitrogen atom in the citraconic imide group. n is 1 to 20.) [3] (A) The thermosetting biscitraconimide resin composition according to [1] or [2], wherein the melting point of the biscitraconimide compound is 25°C or lower. [4] (A) The thermosetting biscitraconimide resin composition according to any one of [1] to [3], wherein the biscitraconimide compound has a number average molecular weight of 200 to 10,000. [5] (C) The thermosetting biscitraconimide resin composition according to any one of [1] to [4], wherein the epoxy resin has two or more epoxy groups in one molecule. [6] The thermosetting biscitraconimide resin composition according to any one of [1] to [5], wherein (D) the epoxy resin curing agent is at least one selected from the group consisting of an amine compound, a phenol compound, an acid anhydride compound, and an active ester compound. [7] The thermosetting biscitraconimide resin composition according to any one of [1] to [6], wherein the curing accelerator (E) is at least one selected from the group consisting of imidazole curing accelerators, organophosphorus curing accelerators, and tertiary amine curing accelerators. [8] For a total of 100 parts by mass of component (A) and component (B), The component (B) is 1 to 30 parts by mass, The component (C) is 1 to 100 parts by mass, the molar equivalent ratio of functional groups reactive with epoxy groups in component (D) to 1 molar equivalent of epoxy groups in component (C) is 0.1 to 4.0; The thermosetting biscitraconimide resin composition according to any one of [1] to [7], wherein the component (E) is 0.01 to 20 parts by mass. [Effects of the Invention]

[0008] The thermosetting biscitraconimide resin composition of the present invention has a viscosity suitable for workability, and can give a cured product that has both dielectric properties (low relative dielectric constant and low dielectric dissipation factor) and heat resistance. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention will be described in detail below.

[0010] [(A) Biscitraconimide compound] Component (A) used in the present invention is a biscitraconimide compound represented by the following formula (1), which serves as the base component of the curable biscitraconimide resin composition of the present invention. The citraconic group is a maleimide group in which one hydrogen atom has been substituted with a methyl group. Due to the effect of the methyl group in the citraconic group, the biscitraconimide compound of component (A) not only exhibits a lower dielectric constant and lower dielectric dissipation factor than maleimide compounds with the same skeleton, but also a lower melting point and improved compatibility with other components. [ka] (In formula (1), B is a divalent organic group.) Such biscitraconimide compounds are preferred because the amine compounds used as raw materials are easily procured, have excellent solubility in solvents, and are easy to synthesize.

[0011] The biscitraconimide compound of component (A) is not particularly limited in terms of its properties or number-average molecular weight at room temperature, but is preferably liquid at 25° C. It also preferably has a number-average molecular weight of 200 to 10,000, more preferably 200 to 5,000, and even more preferably 200 to 2,000. In this specification, the number average molecular weight is measured under the following conditions: 1It was calculated from the results of H-NMR measurements. [Measurement conditions] Equipment: BURKER AVANCE III400 Solvent: CDCl3 Internal standard: tetramethylsilane (TMS)

[0012] Furthermore, in order to obtain low elasticity and excellent dielectric properties after curing (low relative dielectric constant and low dielectric dissipation factor), the divalent organic group represented by B in the biscitraconimide compound is more preferably at least one group selected from the group represented by the following structure and a hydrocarbon group derived from a dimer acid skeleton:

[0013] [ka] (* means a bond to the nitrogen atom in the citraconic imide group. n is 1 to 20.)

[0014] Dimer acid is a liquid dibasic acid whose main component is a 36-carbon dicarboxylic acid, produced by the dimerization of 18-carbon unsaturated fatty acids derived from natural sources such as vegetable oils. The dimer acid skeleton is not a single skeleton, but has multiple structures, and several types of isomers exist. Dimer acids are typically classified as linear (a), monocyclic (b), aromatic (c), and polycyclic (d). In this specification, the dimer acid skeleton refers to a group derived from a dimer diamine having a structure in which the carboxy group of such a dimer acid is substituted with a primary aminomethyl group. That is, the hydrocarbon group derived from the dimer acid skeleton possessed by the biscitraconimide compound of component (A) is preferably a branched divalent hydrocarbon group in which two carboxy groups in each of the dimer acids shown in (a) to (d) below are substituted with methylene groups. Furthermore, when the biscitraconimide compound of component (A) has a hydrocarbon group derived from a dimer acid skeleton, the hydrocarbon group derived from the dimer acid skeleton preferably has a structure in which the carbon-carbon double bond in the hydrocarbon group derived from the dimer acid skeleton is reduced by a hydrogenation reaction, from the viewpoint of the heat resistance and reliability of the cured product.

[0015] [ka]

[0016] The biscitraconimide compound of component (A) may be used alone or in combination of two or more.

[0017] In the thermosetting biscitraconimide resin composition of the present invention, the proportion of component (A) relative to the entire composition is preferably 50 to 90 mass %, more preferably 60 to 85 mass %, and even more preferably 70 to 80 mass %.

[0018] [(B) Monocitraconimide compound] The monocitraconimide compound, which is the component (B) of the present invention, is represented by the following formula (2). [ka] (In formula (2), A is selected from hydrocarbon groups represented by the following structures.)

[0019] [ka] In the above formula, R is independently a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. Examples of the monovalent hydrocarbon group include an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms. Of these, a hydrogen atom or a methyl group is preferred. In the above formula, Q is an alkylene group having 1 to 10 carbon atoms, which may be linear or branched. Among these, a methylene group, an ethylene group, etc. are preferred. Such monocitraconimide compounds are preferred because the amine compounds used as raw materials are easily procured, have excellent solubility in solvents, and are easy to synthesize. In the above formula, * represents a bond to the nitrogen atom in the citraconic imide group.

[0020] The monocitraconimide compound of component (B) is used as a reactive diluent. From the viewpoint of viscosity-reducing performance, component (B) has a melting point of 60°C or less, preferably 25°C or less. Even if the monocitraconimide compound is solid at room temperature (25°C), if it has a melting point of 60°C or less, when it is blended into a composition by heating and mixing, it becomes liquid in the composition even at 25°C due to a drop in the freezing point, thereby achieving a viscosity-reducing effect. In the present invention, by using a monocitraconimide compound as a reactive diluent, it is possible to obtain a cured product that not only has a viscosity-reducing effect but also has good dielectric properties (low relative dielectric constant and low dielectric dissipation factor) and heat resistance.

[0021] The blend amount of component (B) is preferably 1 to 30 parts by mass, and more preferably 10 to 20 parts by mass, per 100 parts by mass of the total of components (A) and (B).

[0022] [(C) Epoxy resin] The epoxy resin (C) is added for the purpose of promoting the reaction between the biscitraconimide compound (A) and the monocitraconimide compound (B).

[0023] The epoxy resin preferably has two or more epoxy groups in one molecule, and any conventionally known epoxy resin can be used. For example, bisphenol type epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, and bisphenol S type epoxy resin; novolac type epoxy resins such as phenol novolac type epoxy resin, cresol novolac type epoxy resin, bisphenol A novolac type epoxy resin, and bisphenol F novolac type epoxy resin; alicyclic epoxy resins such as dicyclopentadiene type epoxy resin and 3,4-epoxycyclohexenylmethyl-3',4'-epoxycyclohexenecarboxylate; amine compounds such as diaminodiphenylmethane, isocyanuric acid, and aminophenol. Examples of suitable epoxy resins include glycidylamine-type epoxy resins obtained by reaction with epichlorohydrin; polyfunctional phenol-type epoxy resins such as resorcinol-type epoxy resins and resorcinol novolac-type epoxy resins; stilbene-type epoxy resins, triazine-skeleton-containing epoxy resins, fluorene-skeleton-containing epoxy resins, triphenolalkane-type epoxy resins, biphenyl-type epoxy resins, xylylene-type epoxy resins, biphenylaralkyl-type epoxy resins, naphthalene-type epoxy resins, and diglycidyl ether compounds of polycyclic aromatics such as anthracene, as well as phosphorus-containing epoxy resins obtained by introducing phosphorus compounds into these epoxy resins. Among these, bisphenol A-type epoxy resins, dicyclopentadiene-type epoxy resins, glycidylamine-type epoxy resins, biphenylaralkyl-type epoxy resins, and naphthalene-type epoxy resins are preferred. These may be used alone or in combination of two or more.

[0024] When the total of components (A) and (B) is 100 parts by mass, the number of parts by mass of component (C) is preferably 1 to 100 parts by mass, more preferably 5 to 50 parts by mass, and particularly preferably 10 to 30. When the amount of epoxy resin (C) blended is within this range, a cured product with low dielectric properties (low dielectric constant and low dielectric dissipation factor) can be obtained.

[0025] [(D) Epoxy resin curing agent] The epoxy resin curing agent (D) is added for the purpose of reacting with the epoxy groups contained in the epoxy resin (C). The epoxy resin curing agent may have a functional group that reacts with the epoxy group, and among these, at least one selected from amine compounds, phenol compounds, acid anhydride compounds, and active ester compounds is preferred. Among these, phenol compounds are more preferred from the viewpoint of the dielectric properties of the composition.

[0026] Generally known amine compounds can be used. Aromatic amine compounds are preferred from the viewpoints of ease of handling and moisture resistance reliability. Examples of preferred amine compounds include aromatic diaminodiphenylmethane compounds such as 3,3'-diethyl-4,4'-diaminodiphenylmethane, 3,3',5,5'-tetramethyl-4,4'-diaminodiphenylmethane, and 3,3',5,5'-tetraethyl-4,4'-diaminodiphenylmethane; 2,4-diaminotoluene, 1,4-diaminobenzene, and 1,3-diaminobenzene; and more preferred amine compounds are aromatic diaminodiphenylmethane compounds such as 3,3'-diethyl-4,4'-diaminodiphenylmethane, 3,3',5,5'-tetramethyl-4,4'-diaminodiphenylmethane, and 3,3',5,5'-tetraethyl-4,4'-diaminodiphenylmethane. These compounds may be used alone or in combination of two or more.

[0027] The amine compound may be either liquid or solid at room temperature (20 to 30°C). While there is no problem with blending a liquid amine compound directly, blending a solid amine compound directly increases the viscosity of the resin composition, significantly reducing workability. Therefore, it is preferable to melt-mix the amine compound with the epoxy resin in advance, preferably at a specific blending ratio (described below) for 1 to 2 hours at a temperature range of 70 to 150°C. Mixing temperatures below 70°C may result in insufficient compatibility of the amine compound, whereas temperatures above 150°C may result in a reaction with the epoxy resin, increasing the viscosity. Mixing times shorter than 1 hour may result in insufficient compatibility of the amine compound, increasing the viscosity. Mixing times longer than 2 hours may result in a reaction with the epoxy resin, increasing the viscosity.

[0028] Generally known phenol compounds can be used. Examples include phenol novolac resins, naphthalene ring-containing phenol resins, aralkyl phenol resins, triphenolalkane phenol resins, biphenyl skeleton-containing aralkyl phenol resins, biphenyl phenol resins, alicyclic phenol resins, heterocyclic phenol resins, naphthalene ring-containing phenol resins, resorcinol phenol resins, allyl group-containing phenol resins such as novolac allyl phenol resins, and bisphenol phenol resins such as bisphenol A resins and bisphenol F resins. These compounds may be used alone or in combination of two or more.

[0029] Commonly known acid anhydride compounds can be used. Examples include 4-methylcyclohexane-1,2-dicarboxylic anhydride, 3,4-dimethyl-6-(2-methyl-1-propenyl)-1,2,3,6-tetrahydrophthalic anhydride, 1-isopropyl-4-methyl-bicyclo[2.2.2]oct-5-ene-2,3-dicarboxylic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, hexahydrophthalic anhydride, methylhimic anhydride, pyromellitic dianhydride, maleic alloocimene, benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetrabisbenzophenonetetracarboxylic dianhydride, (3,4-dicarboxyphenyl)ether dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, and 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride. These compounds may be used alone or in combination.

[0030] The active ester compound may be a generally known one. Examples thereof include active ester compounds having a dicyclopentadiene-type phenolic resin structure, active ester compounds having a phenol novolac structure, active ester compounds having a naphthalene ring structure, active ester compounds having an aralkyl-type phenolic resin structure, active ester compounds having a triphenolalkane-type phenolic resin structure, active ester compounds having a biphenyl skeleton-containing aralkyl-type phenolic resin structure, active ester compounds having a biphenyl-type phenolic resin structure, active ester compounds having an alicyclic phenolic resin structure, active ester compounds having a heterocyclic phenolic resin structure, active ester compounds having a naphthalene ring-containing phenolic resin structure, active ester compounds having a resorcinol-type phenolic resin structure, active ester compounds having an allyl group-containing phenolic resin structure, active ester compounds having a bisphenol A-type resin structure, and active ester compounds having a bisphenol-type phenolic resin structure such as bisphenol F-type resin. These may be used alone or in combination of two or more.

[0031] The amount of epoxy resin curing agent blended is such that the molar equivalent ratio of functional groups in the epoxy resin curing agent to 1 molar equivalent of epoxy groups in component (C) is preferably 0.1 to 4.0, more preferably 0.2 to 2.0. If the molar equivalent ratio is less than 0.1, unreacted epoxy groups may remain, potentially reducing adhesion, while if it exceeds 4.0, the moisture absorption rate of the cured product may increase, potentially causing cracks during reflow or temperature cycling. In the present invention, the term "equivalent" refers to the molecular weight per functional group.

[0032] [(E) Curing accelerator] The curing accelerator of component (E) may be any accelerator that accelerates the curing of the (A) biscitraconimide compound and (B) monocitraconimide compound, and may be any commonly known accelerator, such as an imidazole-based curing accelerator, an organic phosphorus-based curing accelerator, or a tertiary amine-based curing accelerator. Of these, it is preferable to use an imidazole-based curing accelerator in order to reduce the viscosity of the composition.

[0033] Examples of the imidazole curing accelerator include 2-methylimidazole, 2-phenylimidazole, 2-ethyl-4-methylimidazole, and 2-phenyl-4-methylimidazole. Examples of organic phosphorus curing accelerators include phosphines such as triphenylphosphine, tributylphosphine, tri(p-methylphenyl)phosphine, and tri(nonylphenyl)phosphine; phosphine-borane complexes such as triphenylphosphine-triphenylborane; phosphonium borate salts such as tetraphenylphosphonium tetraphenylborate, tetraphenylphosphonium tetra-p-tolylborate, p-tolyltriphenylphosphonium tetra-p-tolylborate, and tri-tert-butylphosphonium tetraphenylborate; and bis(tetrabutylphosphonium) dihydrogenpyromellitate. Examples of the tertiary amine curing accelerator include tertiary amine compounds such as triethylamine, benzyldimethylamine, α-methylbenzyldimethylamine, and 1,8-diazabicyclo[5.4.0]undecene-7; and 1,8-diazabicyclo[5.4.0]undecene-7. In addition to these, a curing accelerator may be used in combination, for example, Among these, salts of tertiary amine compounds and organic phosphorus compounds are preferred, and salts of 1,8-diazabicyclo[5.4.0]undecene-7 and tetraphenylphosphonium tetraphenylborate are more preferred.

[0034] The component (E) may be used alone or in combination of two or more.

[0035] When the total of components (A) and (B) is taken as 100 parts by mass, the number of parts by mass of component (E) is preferably 0.01 to 20 parts by mass, and more preferably 0.1 to 5 parts by mass.

[0036] [Other additives] In addition to the components (A) to (E), the thermosetting biscitraconimide resin composition of the present invention may contain other additives as needed within the range that does not impair the objects and effects of the present invention. Such additives include inorganic fillers, flame retardants, ion trapping agents, antioxidants, adhesion promoters, stress reducing agents, colorants, etc.

[0037] Examples of suitable inorganic fillers include silicas such as fused silica and crystalline silica, alumina, silicon nitride, aluminum nitride, boron nitride, barium sulfate, talc, clay, aluminum hydroxide, magnesium hydroxide, calcium carbonate, glass fibers, and glass particles. Furthermore, fluorine-containing resins, coating fillers, and / or hollow particles may be used to improve dielectric properties, and conductive fillers such as metal particles, metal-coated inorganic particles, carbon fibers, and carbon nanotubes may be added to provide electrical conductivity. The inorganic fillers may be used alone or in combination of two or more.

[0038] The flame retardant is added for the purpose of imparting flame retardancy. The flame retardant is not particularly limited, and any known flame retardant can be used, such as a phosphazene compound, a silicone compound, zinc molybdate-supported talc, zinc molybdate-supported zinc oxide, aluminum hydroxide, magnesium hydroxide, or molybdenum oxide.

[0039] The ion trapping agent is added for the purpose of capturing ionic impurities contained in the resin composition and preventing thermal degradation and moisture absorption degradation. The ion trapping agent is not particularly limited and any known agent can be used, such as hydrotalcites, bismuth hydroxide compounds, and rare earth oxides.

[0040] The antioxidant is not particularly limited, and examples thereof include n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)acetate, neododecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, dodecyl-2-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, ethyl Octadecyl-1-(4-hydroxy-3,5-di-t-butylphenyl)isobutyrate, Octadecyl-1-(4-hydroxy-3,5-di-t-butylphenyl)isobutyrate, Octadecyl-1-(4-hydroxy-3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2-(n-octylthio)ethyl-3,5-di-t-butyl-4-hydroxyphenylacetate, 2-(n-octadecylthio)ethyl-3, 5-Di-t-butyl-4-hydroxyphenyl acetate, 2-(n-octadecylthio)ethyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2-(2-stearoyloxyethylthio)ethyl-7-(3-methyl-5-t-butyl-4-hydroxyphenyl)heptanoate, 2-hydroxyethyl-7-(3-methyl-5-t-butyl-4-hydroxyphenyl)propionate, Pentaerythritol Phenolic antioxidants such as rhythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]; sulfur-based antioxidants such as dilauryl-3,3'-thiodipropionate, dimyristyl-3,3'-thiodipropionate, distearyl-3,3'-thiodipropionate, ditridecyl-3,3'-thiodipropionate, and pentaerythrityl tetrakis(3-laurylthiopropionate);Examples of phosphorus-based antioxidants include tridecyl phosphite, triphenyl phosphite, tris(2,4-di-t-butylphenyl)phosphite, 2-ethylhexyl diphenyl phosphite, diphenyl tridecyl phosphite, 2,2-methylenebis(4,6-di-t-butylphenyl)octyl phosphite, distearyl pentaerythritol diphosphite, bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol diphosphite, and 2-[[2,4,8,10-tetrakis(1,1-dimethylethyl)dibenzo[d,f][1,3,2]dioxaphosphepin-6-yl]oxy]-N,N-bis[2-[[2,4,8,10-tetrakis(1,1-dimethylethyl)dibenzo[d,f][1,3,2]dioxaphosphepin-6-yl]oxy]-ethyl]ethanamine;

[0041] The amount of other additives to be added varies depending on the purpose of the composition, but is generally 10% by mass or less of the total composition.

[0042] [Method of producing the composition] The liquid resin composition of the present invention can be produced by the following method. For example, components (A) to (E) are mixed, simultaneously or separately, with optional heating, followed by stirring, dissolving, and / or dispersing to obtain a mixture of components (A) to (E). Preferably, the mixture of components (A) to (E) may be obtained by adding epoxy resin curing agent (D) to a mixture of components (A), (B), (C), and (E), followed by stirring, dissolving, and / or dispersing. More preferably, the mixture of components (A) to (E) may be obtained by heating (B) above its melting point, adding epoxy resin curing agent (D) to a mixture of components (A), (B), (C), and (E), followed by stirring, dissolving, and / or dispersing. Depending on the intended use, at least one of a flame retardant, a polymerization initiator, and an ion-trapping agent may be added to and mixed with the mixture of components (A) to (E). Each component may be used alone, or two or more may be used in combination.

[0043] In the method for producing the composition, the apparatus for mixing, stirring, and dispersing is not particularly limited. Specifically, for example, a mortar and pestle mixer equipped with a stirring and heating device, a two-roll mill, a three-roll mill, a ball mill, a planetary mixer, or a mass colloider can be used, and these apparatuses may be used in appropriate combination.

[0044] The curing and molding method and conditions for the underfill composition of the present invention may be known, but preferably involve first performing a thermal oven cure at 100-120°C for at least 0.5 hours, followed by a thermal oven cure at 150-175°C for at least 2 hours. Heating at 100-120°C for at least 0.5 hours can suppress the formation of voids after curing. Furthermore, heating at 150-175°C for at least 2 hours can provide sufficient cured product properties. [Example]

[0045] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples. In Table 1, the blend amounts are in parts by mass.

[0046] The components used in the examples and comparative examples are shown below. Note that the number average molecular weight (Mn) was measured under the following conditions: 1 It was calculated from the results of H-NMR measurements. [Measurement conditions] Equipment: BURKER AVANCE III400 Solvent: CDCl3 Internal standard: tetramethylsilane (TMS)

[0047] The viscosities of components (A) and (B) were measured using an E-type viscometer (DV-III ULTRA, manufactured by Brookfield Corp.) Approximately 1.0 mL of sample was placed in a cup attached to the E-type viscometer, and the cup was placed in a thermostatic bath / liquid delivery device (KISS-K6, manufactured by Eiko Seiki Co., Ltd.) set at 25°C. Measurement of the rotational viscosity of the sample was started using the E-type viscometer, and the rotational viscosity value was read at the point where the rotational viscosity reading stabilized. The melting point of component (B) was measured using a differential scanning calorimeter (DSC3+ manufactured by METTLER TOLEDO).

[0048] (A) Biscitraconimide compound Synthesis Example 1 (Production of biscitraconimide compound) A 2 L glass four-neck flask equipped with a stirrer, Dean-Stark tube, cooling condenser, and thermometer was charged with 71.2 g (0.45 mol) of 2,2,4-trimethylhexamethylenediamine, 111.0 g (0.99 mol) of citraconic anhydride, and 150 g of toluene to prepare a reaction solution. The solution was stirred at 80 °C for 3 hours to synthesize the amic acid. After adding 40 g of methanesulfonic acid, the mixture was heated to 110 °C and stirred for 16 hours while distilling off the by-product water. The reaction solution was then washed five times with 200 g of ion-exchanged water. The product (A1), number-average molecular weight 590, viscosity at 25 °C 20 Pa·s, was obtained as a brown liquid (149.7 g, 96% yield) by vacuum stripping at 60 °C. 1 It was confirmed by 1 H-NMR that the compound was a biscitraconimide compound represented by the following formula (A1). [ka]

[0049] (A2) Biscitraconimide compounds A biscitraconimide compound represented by the following formula (trade name: BCI-1500, manufactured by Designer Molecules Inc.) (liquid at 25°C, number average molecular weight 2,300, Ci value = 0.095 mol / 100 g) [ka] -C 36 H 70 - indicates a structure derived from a dimer acid skeleton. m≒2 (average value)

[0050] (B) Monocitraconimide compound Synthesis Example 2 (Production of monocitraconimide compound) A 2 L glass four-neck flask equipped with a stirrer, Dean-Stark tube, cooling condenser, and thermometer was charged with 81.0 g (0.80 mol) of hexylamine, 98.6 g (0.88 mol) of citraconic anhydride, and 150 g of toluene to prepare a reaction solution. The mixture was stirred at 80 °C for 3 hours to synthesize the amic acid. 40 g of methanesulfonic acid was then added to the reaction solution, which was then heated to 110 °C and stirred for 16 hours while distilling off the by-product water. The reaction solution was then washed five times with 200 g of ion-exchanged water. The product was then vacuum stripped at 60 °C and cooled to room temperature (25 °C) to obtain 110.9 g (71% yield) of the desired product ((B1), viscosity 9 mPa s at 25 °C) as a brown liquid. 1 It was confirmed by 1 H-NMR that the compound was a monocitraconimide compound represented by the following formula (B1). [ka]

[0051] Synthesis Example 3 (Production of monocitraconimide compound) A 2 L glass four-neck flask equipped with a stirrer, Dean-Stark tube, cooling condenser, and thermometer was charged with 96.9 g (0.80 mol) of 1-phenylethylamine, 98.6 g (0.88 mol) of citraconic anhydride, and 150 g of toluene to prepare a reaction solution. The mixture was stirred at 80 °C for 3 hours to synthesize the amic acid. 40 g of methanesulfonic acid was then added to the reaction solution, which was then heated to 110 °C and stirred for 16 hours while distilling off the by-product water. The reaction solution was then washed five times with 200 g of ion-exchanged water. The product was then vacuum stripped at 60 °C and cooled to room temperature (25 °C) to obtain 141.2 g (82% yield) of the desired product ((B2), viscosity 92 mPa s at 25 °C) as a brown liquid. 1 It was confirmed by 1 H-NMR that the compound was a monocitraconimide compound represented by the following formula (B2). [ka]

[0052] Synthesis Example 4 (Production of monocitraconimide compound) A 2 L glass four-neck flask equipped with a stirrer, Dean-Stark tube, cooling condenser, and thermometer was charged with 96.9 g (0.80 mol) of 2-phenylethylamine, 98.6 g (0.88 mol) of citraconic anhydride, and 150 g of toluene to prepare a reaction solution. The mixture was stirred at 80 °C for 3 hours to synthesize an amic acid. 40 g of methanesulfonic acid was then added to the reaction solution, which was then heated to 110 °C and stirred for 16 hours while distilling off the by-product water. The reaction solution was then washed five times with 200 g of ion-exchanged water. The product was then vacuum stripped at 60 °C and cooled to room temperature (25 °C) to obtain 142.9 g (83% yield) of the desired product ((B3), melting point 52 °C) as a brown solid. 1 It was confirmed by 1 H-NMR that the compound was a monocitraconimide compound represented by the following formula (B3). [ka]

[0053] Synthesis Example 5 (Production of monocitraconimide compound) A 2 L glass four-neck flask equipped with a stirrer, Dean-Stark tube, cooling condenser, and thermometer was charged with 119.4 g (0.80 mol) of 3-amino-1-phenylbutane, 98.6 g (0.88 mol) of citraconic anhydride, and 150 g of toluene to prepare a reaction solution. The mixture was stirred at 80 °C for 3 hours to synthesize the amic acid. 40 g of methanesulfonic acid was then added to the reaction solution, which was then heated to 110 °C and stirred for 16 hours while distilling off the by-product water. The reaction solution was then washed five times with 200 g of ion-exchanged water. The product was then vacuum stripped at 60 °C and cooled to room temperature (25 °C) to obtain 134.3 g (69% yield) of the desired product (B4), a brown liquid with a viscosity of 141 mPa·s at 25 °C. 1 It was confirmed by 1 H-NMR that the compound was a monocitraconimide compound represented by the following formula (B4). [ka]

[0054] Synthesis Example 6 (Production of monocitraconimide compound) A 2 L glass four-neck flask equipped with a stirrer, Dean-Stark tube, cooling condenser, and thermometer was charged with 90.6 g (0.80 mol) of cyclohexanemethylamine, 98.6 g (0.88 mol) of citraconic anhydride, and 150 g of toluene to prepare a reaction solution. The mixture was stirred at 80 °C for 3 hours to synthesize an amic acid. 40 g of methanesulfonic acid was then added to the reaction solution, which was then heated to 110 °C and stirred for 16 hours while distilling off the by-product water. The reaction solution was then washed five times with 200 g of ion-exchanged water. The product was then vacuum stripped at 60 °C and cooled to room temperature (25 °C) to obtain 137.6 g (83% yield) of the desired product (B5), melting point 47 °C, as a brown solid. 1 It was confirmed by 1 H-NMR that the compound was a monocitraconimide compound represented by the following formula (B5). [ka]

[0055] Synthesis Example 7 (Production of monocitraconimide compound) A 2 L glass four-neck flask equipped with a stirrer, Dean-Stark tube, cooling condenser, and thermometer was charged with 137.0 g (0.80 mol) of 1-(1-naphthyl)ethylamine, 98.6 g (0.88 mol) of citraconic anhydride, and 150 g of toluene to prepare a reaction solution. The mixture was stirred at 80 °C for 3 hours to synthesize an amic acid. 40 g of methanesulfonic acid was then added to the reaction solution, which was then heated to 110 °C and stirred for 16 hours while distilling off the by-product water. The reaction solution was then washed five times with 200 g of ion-exchanged water. The product was then vacuum stripped at 60 °C and cooled to room temperature (25 °C) to obtain 176.2 g (83% yield) of the desired product ((B6), melting point 88 °C) as a brown solid. 1 It was confirmed by 1 H-NMR that the compound was a monocitraconimide compound represented by the following formula (B6). [ka]

[0056] (C) Epoxy resin (C1) Bisphenol A epoxy resin (jER828EL: manufactured by Mitsubishi Chemical Corporation, liquid at 25°C, epoxy group equivalent: 189)

[0057] (D) Epoxy resin hardener (D1) Novolac-type allylphenol resin (MEH-8000H: manufactured by Meiwa Kasei Co., Ltd., phenolic hydroxyl group equivalent: 141)

[0058] (E) Curing accelerator (E1) 2-Ethyl-4-methylimidazole (2E4MZ: manufactured by Shikoku Kasei Holdings Co., Ltd.)

[0059] The above components were mixed in the amounts (parts by mass) shown in Table 1 to obtain underfill compositions. Each composition and its cured product were evaluated for penetration, dielectric constant, dielectric dissipation factor, and adhesion using the methods described below. The results are shown in Table 1. The "equivalent ratio" shown in Table 1 refers to the ratio of the molar equivalent (active hydrogen equivalent) of the functional group of the epoxy resin curing agent in component (D) to 1 molar equivalent of the epoxy group contained in the epoxy resin in component (C).

[0060] 1.25℃ viscosity The viscosity of each thermosetting resin composition in the Examples and Comparative Examples was measured at 25°C using an E-type viscometer (DV-III ULTRA manufactured by Brookfield Corporation). Approximately 1.0 mL of the sample was placed in a cup attached to the E-type viscometer, and the cup was set in a thermostatic bath / liquid delivery device (KISS-K6 manufactured by Eiko Seiki Co., Ltd.) set at a temperature of 25°C. Measurement of the rotational viscosity of the sample was started using the E-type viscometer, and the rotational viscosity value was read at the point where the rotational viscosity reading stabilized.

[0061] 2. Dielectric constant and dielectric loss tangent A mold frame measuring 30 mm x 40 mm x 100 μm thick was prepared, and each thermosetting resin composition of the Examples and Comparative Examples was sandwiched between 50 μm thick release-treated PET films (E7006, manufactured by Toyobo) and molded using a vacuum press (manufactured by Nikko Materials) at 180°C for 5 minutes to obtain a cured product. The cured product was removed from the PET film and further cured at 165°C for 3 hours to obtain a cured resin film. Using the cured resin film, a network analyzer (E5063-2D5 manufactured by Keysight) and a strip line (manufactured by Keycom Corporation) were connected, and the relative dielectric constant and dielectric loss tangent of the cured resin film at a frequency of 10 GHz were measured.

[0062] 3. Measurement of Tg Each thermosetting resin composition of the Examples and Comparative Examples was molded using a 5 × 5 × 15 mm mold frame and cured at 165°C for 3 hours to obtain test specimens. The test specimens were placed in a thermal dilatometer (TMA8140C, manufactured by Rigaku Corporation). The heating program was set to a heating rate of 10°C / min and a constant load of 19.6 mN was applied. The dimensional change of the test specimens was measured between 25°C and 260°C. The relationship between this dimensional change and temperature was plotted. In the graph of dimensional change versus temperature obtained in this manner, the intersection of the tangent to the dimensional change versus temperature curve below the inflection point temperature and the tangent to the dimensional change versus temperature curve above the inflection point temperature was determined as the glass transition temperature (Tg).

[0063] [Table 1]

[0064] The results in Table 1 reveal that by using a monocitraconimide compound with a melting point of 60°C or less in combination with a biscitraconimide compound, the viscosity of the thermosetting biscitraconimide resin composition of the present invention is reduced, and the cured product exhibits excellent dielectric properties (low dielectric constant and low dielectric dissipation factor).

Claims

1. (A) a biscitraconimide compound represented by the following formula (1): 【Chemistry 1】 (In formula (1), B is a divalent organic group.) (B) a monocitraconimide compound represented by the following formula (2) and having a melting point of 60°C or less: 【Chemistry 2】 (In formula (2), A is selected from hydrocarbon groups represented by the following structures.) 【Transformation 3】 (R is independently a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. Q is a linear or branched alkylene group having 1 to 10 carbon atoms. * indicates a bond to the nitrogen atom in the citraconic imide group.) (C) an epoxy resin, (D) an epoxy resin curing agent, and (E) Curing accelerator A thermosetting biscitraconimide resin composition comprising:

2. 2. The thermosetting biscitraconimide resin composition according to claim 1, wherein B in formula (1) is at least one group selected from the group represented by the following structure and a hydrocarbon group derived from a dimer acid skeleton: 【Chemistry 4】 (* means a bond to the nitrogen atom in the citraconic imide group. n is 1 to 20.)

3. 2. The thermosetting biscitraconimide resin composition according to claim 1, wherein the melting point of the biscitraconimide compound (A) is 25° C. or lower.

4. 2. The thermosetting biscitraconimide resin composition according to claim 1, wherein the number average molecular weight of the biscitraconimide compound (A) is 200 to 10,000.

5. 2. The thermosetting biscitraconimide resin composition according to claim 1, wherein the epoxy resin (C) has two or more epoxy groups in one molecule.

6. 2. The thermosetting biscitraconimide resin composition according to claim 1, wherein the epoxy resin curing agent (D) is at least one selected from the group consisting of amine compounds, phenol compounds, acid anhydride compounds, and active ester compounds.

7. 2. The thermosetting biscitraconimide resin composition according to claim 1, wherein the curing accelerator (E) is at least one selected from the group consisting of imidazole curing accelerators, organophosphorus curing accelerators, and tertiary amine curing accelerators.

8. For a total of 100 parts by mass of component (A) and component (B), The component (B) is 1 to 30 parts by mass, The component (C) is 1 to 100 parts by mass, the molar equivalent ratio of functional groups reactive with epoxy groups in component (D) to 1 molar equivalent of epoxy groups in component (C) is 0.1 to 4.0; 2. The thermosetting biscitraconimide resin composition according to claim 1, wherein the component (E) is 0.01 to 20 parts by mass.

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