WO2024203425A1 - Mixture of cyclic acid anhydrides, method for producing same, curable resin composition, and cured products of these - Google Patents

Abstract

The present invention provides: a mixture of cyclic acid anhydrides having excellent heat resistance and dimensional stability; a curable resin composition; and a method for producing the mixture of cyclic acid anhydrides.　This mixture of cyclic acid anhydrides comprises a cyclic acid anhydride represented by formula (A-a), a cyclic acid anhydride represented by formula (A-b) and a cyclic acid anhydride represented by formula (A-c). If the total peak area for cyclic acid anhydrides represented by the formulae (A-a) to (A-c) is taken to be 100% when the mixture of cyclic acid anhydrides is analyzed using gas chromatography, the peak area of the cyclic acid anhydride represented by the formula (A-a) is 0.1-1.0%, the peak area of the cyclic acid anhydride represented by the formula (A-b) is 98.0-99.0%, and the peak area of the cyclic acid anhydride represented by the formula (A-c) is 0.1-1.0%.

Description

Cyclic acid anhydride mixture, its production method, curable resin composition, and cured product thereof

The present invention relates to a mixture of cyclic acid anhydrides, a curable resin composition, and a cured product thereof, and is suitable for use in electrical and electronic components such as semiconductor encapsulants, printed wiring boards, and build-up laminates, lightweight, high-strength materials such as carbon fiber reinforced plastics and glass fiber reinforced plastics, 3D printing applications, and adhesives.

Epoxy resins are widely used in a variety of fields due to their excellent mechanical strength, heat resistance, adhesiveness, and gas barrier properties. It has been well known that acid anhydrides are effective as curing agents for epoxy resins, and acid anhydrides have been used in applications such as small and large casting, impregnation molding, and powder coatings because they are less toxic and odorous than amine-based curing agents, and they generate less heat and shrink less during curing.

The raw materials used for hardeners such as epoxy resins and acid anhydrides are often petroleum-derived, but in recent years, concerns have arisen about the depletion of petroleum resources, and methods of recycling many materials using renewable resources such as plants or by decomposing the hardened materials are being considered.

Japanese Unexamined Patent Publication No. 55-118920 Japanese Patent Application Publication No. 01-167326 Japanese Patent Application Publication No. 07-018059 JP 2014-025036 A

Patent documents 1 to 4 describe 1-isopropyl-4-methyl-bicyclo[2.2.2]oct-5-ene-2,3-dicarboxylic anhydride, which is synthesized by the addition reaction of 1,3-p-menthadiene and maleic anhydride as a renewable resource such as plants. The applicant of the present application produced 1-isopropyl-4-methyl-bicyclo[2.2.2]oct-5-ene-2,3-dicarboxylic anhydride using the method described in these documents, and confirmed that the crystallization rate was slow.

When the crystallization rate is slow, the liquid is generally placed in a drum or other container and allowed to crystallize over time. After that, it is either crushed with a hammer from outside the drum or heated and melted in an oven before use. This makes it very difficult to handle.

On the other hand, if the crystallization rate is fast, it becomes possible to process the material into pellets, granules, or marble shapes, greatly improving handling. Also, if the crystallization rate is fast, when processing the material into granules or marble shapes, it becomes possible to use a manufacturing method in which droplets are dropped onto a conveyor and cooled during transport on the conveyor.

In addition, it was revealed that the curable resin composition containing the above-mentioned acid anhydride has a problem in that the heat resistance (Tg) of the cured product is low and the linear expansion coefficient is large, resulting in thermal shrinkage when the cured product is removed from the mold and cooled to room temperature. Therefore, in order to use it in carbon fiber reinforced composite materials, it was necessary to improve the thermal stability and dimensional stability.

The present invention has been made in consideration of the above problems, and aims to provide a cyclic acid anhydride mixture, a curable resin composition, and a method for producing the cyclic acid anhydride mixture, which are excellent in heat resistance and dimensional stability.

That is, the present invention is as shown in the following [1] to [7]. Note that in the present invention, "(Numerical value 1) to (Numerical value 2)" indicates that the upper and lower limits are included.
[1]
A mixture of cyclic acid anhydrides including a cyclic acid anhydride represented by the following formula (A-a), a cyclic acid anhydride represented by the following formula (A-b), and a cyclic acid anhydride represented by the following formula (A-c):
A mixture of cyclic acid anhydrides, in which, when the sum of the peak areas of the cyclic acid anhydrides represented by the formulas (A-a) to (A-c) is taken as 100% in a gas chromatographic analysis of the mixture of cyclic acid anhydrides, the peak area of the cyclic acid anhydride represented by the formula (A-a) is 0.1% or more and 1.0% or less, the peak area of the cyclic acid anhydride represented by the formula (A-b) is 98.0% or more and 99.0% or less, and the peak area of the cyclic acid anhydride represented by the formula (A-c) is 0.1% or more and 1.0% or less.

[2]
The mixture of cyclic acid anhydrides according to the above item [1], which is dissolved at 80° C., and then allowed to stand at 10° C. for 0.1 to 1.5 hours until crystallization.
[3]
The mixture of cyclic acid anhydrides according to the above item [1] or [2] is in the form of pellets, granules, or marbles.
[4]
A curable resin composition comprising the mixture of cyclic acid anhydrides according to any one of the above items [1] to [3], an epoxy resin, and a curing accelerator.
[5]
A cured product obtained by curing the curable resin composition described in the above item [4].
[6]
A carbon fiber reinforced composite material obtained by curing the curable resin composition according to item [4] above.
[7]
A method for producing a mixture of cyclic acid anhydrides according to any one of the above items [1] to [3], which is obtained by reacting 1,3-p-menthadiene, maleic anhydride, and a solvent at 40 to 80 ° C., and then concentrating the solvent.

The present invention provides a mixture of cyclic acid anhydrides and a curable resin composition that are excellent in heat resistance and dimensional stability. It also provides an inexpensive method for producing the mixture of cyclic acid anhydrides.

The mixture of cyclic acid anhydrides of this embodiment is composed of a cyclic acid anhydride represented by the following formula (A-a), a cyclic acid anhydride represented by the following formula (A-b), and a cyclic acid anhydride represented by the following formula (A-c). When the sum of the peak areas of the cyclic acid anhydrides represented by the formulas (A-a) to (A-c) in gas chromatography analysis is taken as 100%, the peak area of the cyclic acid anhydride represented by the formula (A-a) is 0.1% to 1.0%, the peak area of the cyclic acid anhydride represented by the formula (A-b) is 98.0% to 99.0%, and the peak area of the cyclic acid anhydride represented by the formula (A-c) is 0.1% to 1.0%. The mixture of cyclic acid anhydrides has a high crystallization rate and can be provided in the form of pellets, granules, or marbles. It can also be used for carbon fiber reinforced composite materials with high heat resistance and dimensional stability.

When the mixture of cyclic acid anhydrides is analyzed by gas chromatography, the sum of the peak areas of the cyclic acid anhydrides represented by the formulas (A-a) to (A-c) is taken as 100%, and the peak area of the cyclic acid anhydride represented by the formula (A-a) is preferably 0.1% to 1.0%, more preferably 0.1% to 0.8%, and particularly preferably 0.1% to 0.5%.

When the mixture of cyclic acid anhydrides is analyzed by gas chromatography, the sum of the peak areas of the cyclic acid anhydrides represented by the formulas (A-a) to (A-c) is taken as 100%, and the peak area of the cyclic acid anhydride represented by the formula (A-b) is preferably 98.0% or more and 99.0% or less, more preferably 98.5% or more and 99.0% or less, and particularly preferably 98.8% or more and 99.0% or less.

When the mixture of cyclic acid anhydrides is analyzed by gas chromatography, the sum of the peak areas of the cyclic acid anhydrides represented by the formulas (A-a) to (A-c) is taken as 100%, and the peak area of the cyclic acid anhydride represented by the formula (A-c) is preferably 0.1% to 1.0%, more preferably 0.1% to 0.8%, and particularly preferably 0.1% to 0.5%.

The gas chromatography analysis was carried out under the following conditions.
Gas chromatography (GC) measuring device: 8890GC System (manufactured by Agilent Technologies)
Column: HP-5MS (Agilent Technologies)
Column flow rate: 1.2 ml/min
Oven: 100 ° C (2 min) - 5 ° C/min - 300 ° C (3 min)
Inlet: 300℃, injection volume 1.0 μl
Detector: FID (300 ° C)

The mixture of cyclic acid anhydrides in this embodiment can be easily obtained by addition reaction of 1,3-p-menthadiene with maleic anhydride. The addition reaction conditions are the same as those of the normal Diels-Alder reaction. In other words, the reaction ratio is preferably approximately molar equivalent or slightly excess of maleic anhydride to 1,3-p-menthadiene.

The reaction may be carried out using an appropriate solvent, such as aromatic hydrocarbons and alicyclic hydrocarbons (e.g., n-heptane, benzene, toluene, xylene, cyclohexane, etc.), in the reaction system. The reaction temperature is preferably 40 to 80°C, more preferably 40 to 70°C, and particularly preferably 45 to 65°C.

The mixture of cyclic acid anhydrides in this embodiment may be in a solid state, a molten state, or a solution state, but is preferably in a solid state, and more preferably in a pellet, granular, or marbled state for uniform crystallization and ease of handling.

The method for forming into pellets, granules, or marbles is not particularly limited, but examples of pellet manufacturing equipment include a belt drum flaker manufactured by Nippon Coke & Engineering Co., Ltd., a steel belt conveyor manufactured by Nippon Steel Conveyor Co., Ltd., and a flaker manufactured by Mitsubishi Materials Techno Corporation. The size of the pellets, granules, and marbles is not particularly limited, but taking into consideration handling during the manufacturing process and handling during secondary molding, a size of 0.1 mm to 10 mm is preferable, and 1 mm to 5 mm is more preferable.

The melting point of the mixture of cyclic acid anhydrides in this embodiment is preferably 60 to 80°C, and more preferably 61.5 to 80°C. In addition, the crystallization rate measured under the following conditions is preferably 0.1 to 1.5 hours, and more preferably 0.5 to 1.5 hours.

The crystallization rate in this embodiment was measured under the following conditions.
<Crystallization rate measurement conditions>
The mixture of cyclic acid anhydrides was allowed to stand in an oven at 80°C for 1 hour to dissolve, and then 0.02 g of the solution of the mixture of dissolved cyclic acid anhydrides was dropped into a tray maintained at 10°C and allowed to stand, and the time until the transparent liquid crystallized and completely turned cloudy and solidified was measured.

The curable resin composition of this embodiment contains the mixture of cyclic acid anhydrides, an epoxy resin, and a curing accelerator. There are no particular limitations on the epoxy resin, and it can be appropriately selected from commonly used epoxy resins. Among them, an epoxy resin having two or more epoxy groups in one molecule is preferable. Examples of epoxy resins having two or more epoxy groups in one molecule include various polyfunctional epoxy resins such as naphthalene type, phenol novolac type, cresol novolac type, phenol aralkyl type, biphenyl type, hydroxybenzaldehyde type, dicyclopentadiene type, glycidyl ester type, glycidyl amine type, hydantoin type, and isocyanurate type. These epoxy resins may be used alone or in combination of two or more types.

The epoxy equivalent of the epoxy resin is not particularly limited. From the viewpoint of the heat resistance and water absorption of the cured product, it is preferably 100 to 350 (g/eq), and more preferably 150 to 300 (g/eq).

From the viewpoints of heat resistance, electrical properties and water absorption, the epoxy resin is preferably at least one type of multifunctional epoxy resin selected from the group consisting of dicyclopentadiene type, o-cresol novolac type, naphthalene type, biphenyl type, phenol aralkyl type and trisphenolmethane type, and has an epoxy equivalent of 100 to 350 (g/eq), and more preferably at least one type of multifunctional epoxy resin selected from the group consisting of dicyclopentadiene type, o-cresol novolac type, naphthalene type and trisphenolmethane type, and has an epoxy equivalent of 150 to 300 (g/eq).

The content of the epoxy resin in the curable resin composition is not particularly limited, but from the viewpoint of moldability and heat resistance, it is preferably 10% by weight to 80% by weight, and more preferably 40% by weight to 50% by weight, of the total weight of the curable resin composition.

In the curable resin composition of this embodiment, the amount of the cyclic acid anhydride mixture used is preferably 0.7 to 1.2 equivalents per equivalent of epoxy group in the epoxy resin. If the amount is less than 0.7 equivalents per equivalent of epoxy group or if it exceeds 1.2 equivalents, curing may be incomplete and good cured properties may not be obtained.

The curable resin composition may further contain other curing agents as necessary in addition to the mixture of cyclic acid anhydrides. The other curing agents can be appropriately selected from curing agents that are typically used in curable resin compositions. Examples of other curing agents include acid anhydride compounds other than the mixture of cyclic acid anhydrides, phenolic resins, etc.

Examples of acid anhydride compounds other than the mixture of cyclic acid anhydrides include phthalic anhydride, maleic anhydride, trimellitic anhydride, pyromellitic anhydride, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, methylnadic anhydride, nadic anhydride, glutaric anhydride, dimethylglutaric anhydride, diethylglutaric anhydride, succinic anhydride, methylhexahydrophthalic anhydride, and methyltetrahydrophthalic anhydride. Among these, at least one selected from the group consisting of phthalic anhydride, trimellitic anhydride, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, glutaric anhydride, dimethylglutaric anhydride, and diethylglutaric anhydride is preferred. From the viewpoint of handling and workability of the curable resin composition, an acid anhydride compound that is solid at room temperature is preferred.

The gel time of the curable resin composition of this embodiment can also be adjusted by using a curing accelerator. Examples of curing accelerators that can be used include imidazoles such as 2-methylimidazole, 2-ethylimidazole, and 2-ethyl-4-methylimidazole, tertiary amines such as 2-(dimethylaminomethyl)phenol and 1,8-diaza-bicyclo[5.4.0]undecene-7, phosphines such as triphenylphosphine, and metal compounds such as tin octoate. The curing accelerator is used in an amount of 0.01 to 5.0 parts by weight per 100 parts by weight of the epoxy resin, as necessary.

The curable resin composition of this embodiment may further contain various additives, such as those exemplified below, as necessary. However, the curable resin composition of this embodiment is not limited to the additives listed below, and may contain various additives well known in the art as necessary.

The curable resin composition of the present embodiment may further contain a flame retardant as necessary for the purpose of imparting flame retardancy. The flame retardant is not particularly limited, and examples thereof include phosphorus compounds such as red phosphorus coated with a thermosetting resin such as a phenolic resin, phosphoric acid esters, and triphenylphosphine oxide; nitrogen-containing compounds such as melamine, melamine derivatives, melamine-modified phenolic resins, compounds having a triazine ring, cyanuric acid derivatives, and isocyanuric acid derivatives; phosphorus and nitrogen-containing compounds such as cyclophosphazene; metal complex compounds such as dicyclopentadienyl iron; zinc compounds such as zinc oxide, zinc stannate, zinc borate, and zinc molybdate; metal oxides such as iron oxide and molybdenum oxide; and metal hydroxides such as aluminum hydroxide and magnesium hydroxide. Examples of the flame retardant include known organic or inorganic compounds and metal hydroxides containing halogen atoms, antimony atoms, nitrogen atoms, or phosphorus atoms.

The curable resin composition of this embodiment may further contain an inorganic filler as necessary. Specific examples of inorganic fillers include fine powders of fused silica, crystalline silica, glass, alumina, calcium carbonate, zirconium silicate, calcium silicate, silicon nitride, aluminum nitride, boron nitride, beryllia, zirconia, zircon, fosterite, steatite, spinel, mullite, titania, talc, clay, mica, etc., or beads obtained by spheronizing these.

Inorganic fillers that have a flame retardant effect may be used. Examples of inorganic fillers that have a flame retardant effect include aluminum hydroxide, magnesium hydroxide, composite metal hydroxides such as magnesium and zinc composite hydroxide, and zinc borate.

When the curable resin composition contains an inorganic filler, its content is not particularly limited as long as the effect of this embodiment can be obtained. The content of the inorganic filler is preferably 50% by weight or more of the total weight of the curable resin composition, and from the viewpoint of flame retardancy, 60% by weight to 95% by weight is more preferable, and 70% by weight to 90% by weight is even more preferable. By including an inorganic filler, it is possible to improve the thermal expansion coefficient, thermal conductivity, elastic modulus, etc. of the cured product to the desired properties. When the content of the inorganic filler is 50% by weight or more, the effect of improving these properties can be obtained more effectively. Furthermore, when it is 95% by weight or less, the increase in viscosity of the curable resin composition is further suppressed, sufficient fluidity is easily obtained, and moldability is further improved.

The curable resin composition of this embodiment can further contain an antioxidant as necessary. This can prevent oxidation of the cured product of the curable resin composition, and suppress weight loss of the cured product even when it is left in a high-temperature environment. Electrical properties are further improved.

Examples of antioxidants include phenol-based antioxidants, phosphite-based antioxidants, sulfur-based antioxidants, and hindered amine-based antioxidants. These antioxidants may be used alone or in combination of two or more.

When the curable resin composition contains an antioxidant, its content is not particularly limited as long as the weight loss suppression effect is achieved. From the viewpoint of the heat resistance (high Tg) of the curable resin composition, the antioxidant content is preferably 0.5 to 20 parts by weight, and more preferably 1 to 10 parts by weight, per 100 parts by weight of the epoxy resin. By making the antioxidant content 0.5 parts by weight or more, the weight loss suppression effect of the cured product can be sufficiently obtained, and by making the antioxidant content 20 parts by weight or less, the heat resistance (high Tg) of the cured product is suppressed from decreasing.

The curable resin composition of this embodiment may further contain a coupling agent as necessary. This further improves the adhesion between the resin component and the inorganic filler, and further improves the electrical properties. The coupling agent may be appropriately selected from compounds that are commonly used. Examples of coupling agents include known coupling agents such as various silane-based compounds, such as epoxy silane, mercapto silane, amino silane, alkyl silane, ureido silane, vinyl silane, styryl silane, methacryl silane, acrylic silane, and sulfido silane, titanium-based compounds, aluminum chelate compounds, and aluminum/zirconium-based compounds. Among these, silane-based compounds are preferred. These coupling agents may be used alone or in combination of two or more.

When the curable resin composition contains a coupling agent, the content is preferably 0.05 to 5.0 parts by weight, and more preferably 0.1 to 4.5 parts by weight, per 100 parts by weight of the inorganic filler. By making the content 0.05 parts by weight or more, the adhesion to the frame, etc. is further improved.

The method for preparing the curable resin composition of this embodiment is not particularly limited, but the components may be mixed uniformly or may be prepolymerized. For example, a mixture containing the compound of this embodiment is heated in the presence or absence of a curing accelerator or polymerization initiator, and in the presence or absence of a solvent, to form a prepolymer. Similarly, amine compounds, compounds having ethylenically unsaturated bonds, maleimide compounds, cyanate ester compounds, polybutadiene and modified products thereof, polystyrene and modified products thereof, inorganic fillers, and other additives may be added to form a prepolymer. The components may be mixed or prepolymerized using, for example, an extruder, kneader, rolls, etc. in the absence of a solvent, and a reaction kettle with a stirrer, etc. in the presence of a solvent.

The curable resin composition of this embodiment is obtained by uniformly mixing the above components. There are no particular limitations on the method for producing the curable resin composition of this embodiment, but it can be obtained, for example, by thoroughly mixing the epoxy resin with a curing agent, a curing accelerator, an inorganic filler, a release agent, a silane coupling agent, additives, etc., using an extruder, kneader, roll, planetary mixer, etc. until the mixture is uniform.

The obtained curable resin composition can be formed into various forms such as a resin sheet or a prepreg, depending on the molding method. A prepreg form can be obtained, for example, by heating and melting the curable resin composition and/or the resin sheet of this embodiment to reduce the viscosity and impregnating the composition into a fiber substrate.

The curable resin composition of this embodiment can be dissolved in a solvent such as toluene, xylene, acetone, methyl ethyl ketone, methyl isobutyl ketone, dimethylformamide, dimethylacetamide, or N-methylpyrrolidone as necessary to form a varnish-like composition (hereinafter simply referred to as varnish), which can then be impregnated into a substrate such as glass fiber, carbon fiber, polyester fiber, polyamide fiber, alumina fiber, or paper, and dried by heating to produce a prepreg. The solvent used in this case is in an amount that occupies 10 to 70% by weight, preferably 15 to 70% by weight, of the mixture of the curable resin composition of this embodiment and the solvent.

The above prepregs are cut into the desired shape and laminated, and then the laminate is subjected to pressure using a press molding method, autoclave molding method, sheet winding molding method, or other method while the epoxy resin composition is heated and cured to obtain carbon fiber reinforced plastic (CFRP). Copper foil or organic film can also be laminated when laminating the prepregs.

In addition to the above-mentioned methods, CFRP can also be obtained by molding using known methods. For example, resin transfer molding technology (RTM method) can be used, in which a carbon fiber substrate (usually woven carbon fiber fabric) is cut, laminated, and shaped to create a preform (a preliminary molded body before being impregnated with resin), the preform is placed in a mold and the mold is closed, resin is injected to impregnate the preform and harden it, and the mold is then opened to remove the molded product. In addition, it is also possible to use a type of RTM method, such as the VaRTM method, the SCRIMP (Seeman's Composite Resin Infusion Molding Process) method, or the CAPRI (Controlled Atmospheric Pressure Resin Infusion) method, which more appropriately controls the resin injection process, particularly the VaRTM method, by evacuating the resin supply tank described in JP-A-2005-527410 to a pressure lower than atmospheric pressure, using circulatory compression, and controlling the net molding pressure. In addition, other methods that can be used include the film stacking method, in which the fiber substrate is sandwiched between resin sheets (films), the method of attaching powdered resin to the reinforced fiber substrate to improve impregnation, the molding method (Powder Impregnated Yarn) that uses a fluidized bed or fluid slurry method in the process of mixing the resin into the fiber substrate, and the method of blending resin fibers into the fiber substrate.

Carbon fibers include acrylic, pitch, and rayon carbon fibers, with acrylic carbon fibers being preferred due to their high tensile strength. The carbon fibers can be in the form of twisted yarn, untwisted yarn, or non-twisted yarn, but untwisted yarn or non-twisted yarn is preferred due to the good balance between the formability and strength properties of the fiber-reinforced composite material.

The cured product of the curable resin composition of this embodiment can be used for various applications other than the above-mentioned applications such as CFRP, such as adhesives, paints, coating agents, molding materials (including sheets, films, CFRP, etc.), encapsulants for semiconductor elements, encapsulants for liquid crystal display elements, encapsulants for organic EL elements, printed wiring boards (BGA substrates, build-up substrates, etc.), and other electric and electronic parts, 3D printing, as well as additives for other resins, etc.

The adhesives include adhesives for civil engineering, construction, automotive, general office, and medical use, as well as adhesives for electronic materials. Among these, adhesives for electronic materials include interlayer adhesives for multilayer boards such as build-up boards, die bonding agents, semiconductor adhesives such as underfills, underfills for reinforcing BGAs, and mounting adhesives such as anisotropic conductive films (ACFs) and anisotropic conductive pastes (ACPs), and can be used for a variety of purposes.

When the curable resin composition of this embodiment is applied to an encapsulant for semiconductor elements, the curable resin composition of this embodiment is placed in a mold along with a lead frame equipped with a semiconductor element and a semiconductor package substrate, and molded by melt casting, transfer molding, injection molding, compression molding, or the like, and then heated at 80 to 200°C for 2 to 10 hours to obtain a cured product. Examples of semiconductor devices manufactured using this encapsulant include potting, dipping, and transfer mold encapsulation for capacitors, transistors, diodes, light-emitting diodes, ICs, and LSIs, potting encapsulation for COB, COF, TAB, and the like for ICs and LSIs, underfill for flip chips, and encapsulation (including reinforcing underfill) when mounting IC packages such as QFP, BGA, and CSP.

When the curable resin composition of this embodiment is applied to a printed wiring board application, a prepreg can be obtained by heating and melting the composition to reduce the viscosity and impregnating the composition into reinforcing fibers such as glass fibers and polyamide fibers. Specific examples of the composition include, but are not limited to, glass fibers such as E glass cloth, D glass cloth, S glass cloth, Q glass cloth, spherical glass cloth, NE glass cloth, and T glass cloth, and/or organic fibers. The shape of the substrate is not particularly limited, but examples include woven fabric, nonwoven fabric, roving, chopped strand mat, and the like. In addition, the weaving method of the woven fabric includes plain weave, saddle weave, twill weave, and the like, and these known methods can be appropriately selected and used depending on the intended application and performance. In addition, woven fabrics that have been opened and glass woven fabrics that have been surface-treated with a silane coupling agent are preferably used. The thickness of the substrate is not particularly limited, but is preferably about 0.01 to 0.4 mm. In addition, the varnish can be impregnated into reinforcing fibers and dried by heating to obtain a prepreg, which can then be used to create a copper clad laminate (CCL). The obtained prepreg and CCL can be hot-press molded to create a laminate using the curable resin composition of this embodiment. The laminate is not particularly limited as long as it has one or more prepregs, and may have any other layers. In addition, a sheet-like adhesive can be obtained by applying the varnish onto a release film, removing the solvent under heating, and performing B-stage formation. This sheet-like adhesive can be used as an interlayer insulating layer in a multilayer board or an adhesive sheet when mounting a semiconductor. The curable resin composition of this embodiment can also be used suitably for special board materials such as package boards (substrates) and HDIs (high density interconnects).

The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples. In the following, all parts are by weight unless otherwise specified.

Various analytical methods were carried out under the following conditions.
GC/MS measurement (EI, CI)
Equipment: GC-2020Plus/GCMS-QP2020 (Shimadzu Corporation)
Column: HP-5MS (Agilent Technologies)
Column flow rate: 1.2 ml/min
Oven: 50°C (2 min) - 10°C/min - 300°C (18 min)
Mass range: m/z 35-800
Ion source: 230° C.
Inlet: 320 ℃, injection volume 1.0 μl

GC measurement device: 8890GC System (manufactured by Agilent Technologies)
Column: HP-5MS (Agilent Technologies)
Column flow rate: 1.2 ml/min
Oven: 100 ° C (2 min) - 5 ° C/min - 300 ° C (3 min)
Injection port: 300℃, injection volume 1.0μl
Detector: FID (300 ° C)

[Synthesis Example 1]
A four-neck flask was charged with 49.1 parts of toluene and 25.8 parts of α-terpinene (1,3-p-menthadiene, manufactured by Guangxi Jie Xin Fragrance Co., Ltd.), which were then heated to 45°C and stirred. 16.7 parts of maleic anhydride manufactured by Junsei Chemical Co., Ltd. were added to this solution in four portions over one hour. After the addition was completed, the mixture was stirred at 45°C for one hour. After the reaction was completed, the mixture was concentrated under reduced pressure at 185°C to obtain 37 parts of a mixture of cyclic acid anhydrides (A-1).

[Synthesis Example 2]
The same procedure as in Synthesis Example 1 was repeated except that the reaction temperature was changed to 65° C., to obtain 35 parts of a cyclic acid anhydride mixture (A-2).

[Synthesis Example 3]
The same procedure as in Synthesis Example 1 was repeated except that the reaction temperature was changed to 85° C. and toluene was not used, to obtain 37 parts of a cyclic acid anhydride mixture (A-3).

[Synthesis Example 4]
The same procedure as in Synthesis Example 1 was repeated except that the reaction temperature was changed to 185° C. and toluene was not used, to obtain 34 parts of a cyclic acid anhydride mixture (A-4).

The structure of the mixture of cyclic acid anhydrides obtained in Synthesis Examples 1 to 4 was identified by GC/MS measurement, and the area percentage results when the sum of the peak areas of the cyclic acid anhydrides represented by formulas (A-a) to (A-c) measured by GC was taken as 100% are shown in Table 1.

The melting point and crystallization rate were measured under the following conditions.
<Melting point measurement conditions>
Differential scanning calorimeter: CHIP DSC manufactured by Linseis
Gas flow rate: _N2 gas 50 ml/min Heating rate: 20°C/min Measurement temperature range: 30°C-270°C

<Crystallization rate measurement conditions>
The mixtures of cyclic acid anhydrides obtained in Synthesis Examples 1 to 4 were allowed to stand in an oven at 80° C. for 1 hour to dissolve. 0.02 g of a solution in which the mixture of cyclic acid anhydrides was dissolved was dropped into a tray maintained at 10° C. and allowed to stand. The time until the transparent liquid crystallized and completely turned cloudy and solidified was measured.

[Example 1, Comparative Examples 1 and 2]
The mixtures of cyclic acid anhydrides obtained in Synthesis Examples 1 to 4, epoxy resins, and curing accelerators were mixed in the weight ratios shown in Table 2, and cured at 120°C for 2 hours and then at 160°C for 6 hours to produce cured products. Physical properties were evaluated under the following conditions.

<Conditions for measuring heat resistance (Tg) and linear expansion coefficient>
Thermomechanical analyzer: TMA Q400 (TA Instruments)
Measurement temperature range: 30 to 350°C
Heating rate: 2° C./min. Tg: change point of linear expansion coefficient
Coefficient of linear expansion (CTE): Unit dimensional change standard in each range of 50-90°C and 260-290°C: Compliant with JIS K-7244

RE-310S: Bisphenol A type epoxy resin (manufactured by Nippon Kayaku Co., Ltd.)
2E4MZ: 2-ethyl-4-methylimidazole (manufactured by Shikoku Chemical Industries, Ltd.)

As shown in Tables 1 and 2, the acid anhydride mixture of the present invention has a fast crystallization rate, and the curable resin composition thereof has excellent heat resistance and low linear expansion coefficient (dimensional stability), and therefore can be suitably used for carbon fiber reinforced composite materials.

Claims (7)

A mixture of cyclic acid anhydrides including a cyclic acid anhydride represented by the following formula (A-a), a cyclic acid anhydride represented by the following formula (A-b), and a cyclic acid anhydride represented by the following formula (A-c):
A mixture of cyclic acid anhydrides, in which, when the sum of the peak areas of the cyclic acid anhydrides represented by the formulas (A-a) to (A-c) is taken as 100% in a gas chromatographic analysis of the mixture of cyclic acid anhydrides, the peak area of the cyclic acid anhydride represented by the formula (A-a) is 0.1% or more and 1.0% or less, the peak area of the cyclic acid anhydride represented by the formula (A-b) is 98.0% or more and 99.0% or less, and the peak area of the cyclic acid anhydride represented by the formula (A-c) is 0.1% or more and 1.0% or less.
The mixture of cyclic acid anhydrides according to claim 1, which is dissolved at 80°C and then left to stand at 10°C for 0.1 to 1.5 hours until crystallization. The mixture of cyclic acid anhydrides according to claim 1, which is in the form of pellets, granules, or marbles. A curable resin composition comprising a mixture of cyclic acid anhydrides according to any one of claims 1 to 3, an epoxy resin, and a curing accelerator. A cured product obtained by curing the curable resin composition according to claim 4. A carbon fiber reinforced composite material obtained by curing the curable resin composition according to claim 4. The method for producing the cyclic acid anhydride mixture according to any one of claims 1 to 3, which is obtained by reacting 1,3-p-menthadiene, maleic anhydride and a solvent at 40 to 80 ° C., and then concentrating the solvent.