Maleimide resin solid, method for producing maleimide resin solid, maleimide resin composition and cured product thereof

Abstract

The present invention provides a novolac maleimide resin solid having repeating units with an average number of maleimide groups of 2 to 20, which has excellent solubility in solvents, and a method for producing the same. The novolac maleimide resin solid contains a novolac maleimide resin having repeating units with an average number of maleimide groups of 2 to 20, and a solvent A, wherein the content of the solvent A is 100 ppm or more and 30,000 ppm or less, and the Hildebrand solubility parameter of the solvent A is 12.0 or more and 18.0 or less.

Description

[Technical Field]

[0001] The present invention relates to a maleimide resin solid, a method for producing the maleimide resin solid, a maleimide resin composition, and a cured product thereof. More specifically, the present invention relates to a maleimide resin solid, a method for producing the maleimide resin solid, a maleimide resin composition, and a cured product thereof, which are used for highly reliable semiconductor encapsulants, insulating materials for electric and electronic components, various composite materials such as laminates (glass fiber reinforced composites for printed wiring) and CFRP (carbon fiber reinforced composites), various adhesives, various paints, structural members, etc. [Background technology]

[0002] Maleimide resins are compounds that have heat resistance exceeding that of epoxy resins, moldability equivalent to that of epoxy resins, and additional properties such as a low linear expansion coefficient and a high Tg. Polymaleimide compounds, whether crosslinked alone or reacted with various maleimide compounds or crosslinkers, can be made into materials with excellent heat resistance and flame retardancy, and have been used in a variety of applications, including encapsulation materials, circuit board materials, and insulating materials. They are particularly used in applications that require both extremely high heat resistance and moldability, such as high-heat-resistant circuit board materials, flexible circuit board materials, high-heat-resistant low-dielectric materials, high-heat-resistant CFRP materials (carbon fiber composite materials), and high-heat-resistant encapsulation materials for automotive SiC power devices.

[0003] Conventionally, maleimide resins have been commercially available as powdered crystalline materials obtained by recrystallization or reprecipitation due to their self-reactivity (see Patent Document 1). However, maleimide resins incorporate solvents and the like during crystallization and precipitation, creating the problem of not being able to completely remove the solvent. If acetic acids used as solvents during production are incorporated, the odor of acetic acid remains in the product, posing a safety risk to workers. Given this background, there is a demand for solid maleimide resins that are excellent in workability, productivity, and environmental safety.

[0004] Therefore, the applicant has filed an application for Patent Document 2, which aims to provide a novolac maleimide resin molded product that is easy to work with and highly productive, and that is less exposed to the solvent environment. Novolac maleimide resins are generally highly viscous, making it difficult to remove the solvent by distillation, and there is a high risk of polymerization or gelation when the resin is extracted as a solid. Patent Document 2 provides a novolac maleimide resin in the form of a film or flakes, which contains a predetermined amount or less of an organic solvent.

[0005] Furthermore, Patent Document 3 discloses a method of distilling off the solvent while reducing the pressure using an evaporator. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japan Special Publication No. 6-86425 [Patent Document 2] International Publication No. 2018 / 043380 [Patent Document 3] International Publication No. 2018 / 025921

[0007] The maleimide resin molded product of Patent Document 2 has a step of applying the maleimide resin to a support such as a film and then drying it, which poses a problem that it cannot be produced using ordinary synthesis equipment.

[0008] In Patent Document 3, although there was no significant change in the results when synthesized on a small scale, when the synthesis amount was increased, the solvent distillation required a long time, during which self-polymerization could occur. Therefore, in actual production, there is a significant risk of polymerization and gelation, and issues from the perspective of moldability and stable productivity, such as increased viscosity due to increased molecular weight and varying properties with each production run. Furthermore, if the temperature during solvent recovery is lowered to suppress this polymerization, it becomes difficult to remove the solvent, especially in the case of maleimide resins with softening points of 50°C or higher, resulting in a large amount of residual solvent. In particular, residual solvent levels exceeding 30,000 ppm pose safety issues, such as the risk of voids and cracks during molding and worker exposure. Furthermore, residual solvent is particularly problematic because the synthesis of these maleimide resins may involve substances that are harmful to the human body, such as acetic acid, toluene, and xylene. Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to provide a maleimide resin solid that has excellent solubility in solvents. [Means for solving the problem]

[0010] As a result of intensive investigations to solve the above problems, the present inventors established a method for isolating a novolac maleimide resin as a solid, and further found that the isolated novolac maleimide resin solid has excellent solubility in solvents, thereby completing the present invention.

[0011] That is, the present invention relates to the following [1] to

[11] . In the present invention, "(Numerical value 1) to (Numerical value 2)" indicates that the upper and lower limit values ​​are included. [1] A novolac maleimide resin solid comprising a novolac maleimide resin having a repeating unit and 2 to 20 maleimide groups in the molecule and a solvent A, wherein the content of the solvent A is 100 ppm or more and 30,000 ppm or less, and the Hildebrand solubility parameter of the solvent A is 12.0 or more and 18.0 or less. [2] The novolac maleimide resin solid according to the above item [1], which is porous. [3] A porous novolac-type maleimide resin solid having repeating units with an average number of functional groups of 2 to 20. [4] The novolac maleimide resin solid according to the above item [1] or [3], wherein the 90% by mass particle size (D90) is 10 μm or more and 200 μm or less. [5] BET specific surface area is 0.5m 2 / g or more 5.0m 2 / g or less of the novolac maleimide resin solid according to any one of [1] to [4] above. [6] 6. The novolac maleimide resin solid according to any one of items [1] to [5], wherein the softening point of the novolac maleimide resin is 40°C or higher and 100°C or lower. [7] The novolac maleimide resin solid according to any one of items [1] to [6] above, wherein the novolac maleimide resin has a structure represented by the following formula (1):

[0012] [ka] In the formula (1), each R independently represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or a phenyl group. X represents any one of the following structural formulae (A1) to (U1). n represents the average number of repetitions and is 1≦n≦5.

[0013] [ka]

[0014] In formulas (A1) to (V1), each of the multiple R's independently represents a hydrocarbon group having 1 to 5 carbon atoms. Each a' is independently an integer of 0 to 4, each b' is independently an integer of 0 to 3, and each p' is independently an integer of 1 to 20. * indicates a bonding position. [8] A maleimide resin composition comprising the maleimide resin solid material according to any one of the preceding items [1] to [7]. [9] A cured product of the maleimide resin composition according to the preceding item [8].

[10] A method for producing a novolac maleimide resin solid, comprising: a stirring step of adding a novolac maleimide resin having a repeating unit and 2 to 20 maleimide groups in a molecule, or a novolac maleimide resin solution comprising the novolac maleimide resin and a solvent B, to a solvent C and stirring the mixture; and a removal step of removing a precipitate obtained in the stirring step, A method for producing a novolac-type maleimide resin solid, wherein the solvent B has a Hildebrand solubility parameter of 9.0 or more and 10.0 or less, and the solvent C has a Hildebrand solubility parameter of 11.0 or more and 18.0 or less.

[11] The method for producing a maleimide resin solid according to item

[10] above, wherein the maleimide resin has a structure represented by the following formula (1):

[0015] [ka]

[0016] In the formula (1), each R independently represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or a phenyl group. X represents any one of the following structural formulae (A1) to (U1). n represents the average number of repetitions and is 1≦n≦5.

[0017] [ka]

[0018] In formulas (A1) to (V1), each of the multiple R's independently represents a hydrocarbon group having 1 to 5 carbon atoms. Each a' is independently an integer of 0 to 4, each b' is independently an integer of 0 to 3, and each p' is independently an integer of 1 to 20. * indicates a bonding position. [Effects of the Invention]

[0019] According to the present invention, a maleimide resin solid product having excellent solubility in solvents can be provided. [Brief explanation of the drawings]

[0020] [Figure 1] An electron microscope image of the maleimide resin solid (M1) is shown in FIG. [Figure 2] An electron microscope image of the maleimide resin solid (M2) is shown in FIG. [Figure 3] An electron microscope image of the maleimide resin solid (M3) is shown in FIG. [Figure 4] An electron microscope image of the maleimide resin solid (M4) is shown in FIG. [Figure 5] An electron microscope image of the maleimide resin solid (M5) is shown in FIG. [Figure 6] An electron microscope image of the maleimide resin solid (M6) is shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, an embodiment of the present invention (hereinafter also referred to as "the present embodiment") will be described in further detail.

[0022] The present embodiment relates to a solid (hereinafter also simply referred to as "maleimide resin solid") of a novolac-type maleimide resin (hereinafter also simply referred to as "maleimide resin") having repeating units and 2 to 20 maleimide groups in the molecule. The maleimide resin solid preferably contains a solvent A.

[0023] The content of solvent A in the maleimide resin solid is preferably 100 ppm to 30,000 ppm, more preferably 300 ppm to 10,000 ppm, even more preferably 500 ppm to 5,000 ppm, and particularly preferably 500 ppm to 2,000 ppm. The total amount of solvent contained in the maleimide resin solid is preferably 100 ppm to 100,000 ppm, more preferably 100 ppm to 50,000 ppm, and even more preferably 100 ppm to 30,000 ppm. The solvent content can be measured using a gas chromatograph GC-2010 manufactured by Shimadzu Corporation, as shown in the Examples below.

[0024] The Hildebrand solubility parameter (hereinafter also simply referred to as "solubility parameter") of the solvent A is preferably 12.0 or more and 18.0 or less, more preferably 14.0 or more and 16.0 or less. The definition of the Hildebrand solubility parameter can be found in CRC Handbook of Solubility Parameters and Other Cohesion Parameters, 2nd Edition, Allan F.M. Barton, CRC Press.

[0025] The solubility parameter of the solvent A is 12.0 or more and 18.0 or less. The solubility parameter range of 12.0 or more and 18.0 or less is a range in which the maleimide resin is difficult to dissolve, and corresponds to a so-called poor solvent. It is believed that the intermolecular forces between the maleimide resin molecules are weakened by the inclusion of a certain amount of this poor solvent, which reduces the crystallinity and thereby increases the solubility in the solvent. For this reason, it is particularly preferable that the content of solvent A in the maleimide resin solid is 100 ppm or more and 30,000 ppm or less.

[0026] The maleimide resin solid is preferably in a porous form, which provides excellent solubility in solvents compared to conventional maleimide resins supplied in a crystalline or powder form.

[0027] The BET specific surface area of ​​the maleimide resin solid is 0.5m 2 / g or more 10.0m 2 / g or less, and 0.5m 2 / g or more 5.0m 2 / g or less is more preferable, and 0.5m 2 / g or more 1.0m 2 If the BET specific surface area is greater than the upper limit, the solubility in solvents may be reduced. The BET specific surface area is determined by measuring the amount of physically adsorbed gas according to the Brunauer, Emmett, and Teller method (BET method). The BET specific surface area can be measured by the method described in JIS X8830:2013. For example, the BET specific surface area can be measured using a BELSORP-max II (MicrotracBEL) as shown in the Examples below.

[0028] The 90% by volume particle size (D90) of the maleimide resin solid is preferably 10 μm to 500 μm, more preferably 30 μm to 300 μm, and even more preferably 50 μm to 200 μm. The average particle size (volume-based median diameter D50) of the maleimide resin solid is preferably 1 μm to 200 μm, more preferably 10 μm to 100 μm, and even more preferably 20 μm to 80 μm. If the average particle size is greater than the upper limit, solubility in solvents may be impaired. If the average particle size is less than the lower limit, handling may be impaired or there may be a risk of dust exposure. The particle size distribution can be measured using a Microtrac MT3300 (manufactured by Microtrac Bell Co., Ltd.) as shown in the Examples below. D50 is the particle size at the point where the cumulative curve reaches 50% when the total volume of the particles is 100%. D90 is the particle size at the point where the cumulative curve reaches 90% when the total volume of the particles is 100%.

[0029] The maleimide resin that can be used in this embodiment may be any novolac-type maleimide resin having a repeating unit and having 2 to 20 maleimide groups in the molecule, and for example, one having a structure represented by the following formula (1) can be used.

[0030] [ka]

[0031] In the above formula (1), multiple Rs exist independently and represent a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or a phenyl group. X is represented by any of the following structural formulae (A1) to (V1). n is the average number of repetitions and is 1≦n≦5, preferably 1. <n≦5である。

[0032] [ka]

[0033] In the above formulas (A1) to (V1), each of the multiple R's independently represents a hydrocarbon group having 1 to 5 carbon atoms. Each a' is independently an integer of 0 to 4, each b' is independently an integer of 0 to 3, and each p' is independently an integer of 1 to 20. * indicates a bonding position.

[0034] X in the above formula (1) is preferably formula (H1), (U1), or (V1). In particular, from the viewpoint of solubility in a solvent, it is more preferably any of the following formulas (a) to (g), and particularly preferably formula (a), (c), or (g).

[0035] [ka]

[0036] The softening point of the maleimide resin is preferably 40° C. or higher and 100° C. or lower. A softening point of 40° C. or higher allows the shape of the maleimide resin solid to be maintained at room temperature, while a softening point of 100° C. or lower increases the fluidity of the resin solid and further improves its solubility in solvents. However, a lower softening point increases blocking tendency, so a more preferred range is 50° C. or higher and lower than 95° C., and even more preferably 60° C. or higher and lower than 90° C.

[0037] The method for producing the maleimide resin is not particularly limited, and the maleimide resin may be produced by any known method for synthesizing maleimide resins. As a specific production method, for example, the method described in JP 2009-001783 A is preferably used.

[0038] Next, a method for producing a maleimide resin solid material according to this embodiment will be described. The maleimide resin solid of the present embodiment can be obtained by a stirring step of adding a maleimide resin, or a maleimide resin solution comprising a maleimide resin and a solvent B having a solubility parameter of 9.0 or more and 10.0 or less, to a solvent C having a solubility parameter of 11.0 or more and 18.0 or less and stirring the mixture, and a removal step of removing the precipitate obtained in the stirring step.

[0039] The solubility parameter of the solvent B is more preferably 9.1 or more and 9.6 or less. The solubility parameter of the solvent C is more preferably 12.0 or more and 18.0 or less, and even more preferably 14.0 or more and 16.0 or less. A solubility parameter range of 9.0 or more and 10.0 or less is a range in which the maleimide resin is easily soluble, and corresponds to a so-called good solvent. A solubility parameter range of 11.0 or more and 18.0 or less is a range in which the maleimide resin is poorly soluble, and corresponds to a so-called poor solvent.

[0040] Solvent A in the maleimide resin mixture may be the same as solvent C having a solubility parameter of 12.0 or more and 18.0 or less, or may be a part of solvent C, which is a mixed solvent having a solubility parameter of 11.0 or more and 18.0 or less.

[0041] Examples of solvents having a solubility parameter of 9.0 or more and 10.0 or less include ethyl acetate, tetrahydrofuran, benzene, trichloroethyl, methyl ethyl ketone, chloroform, methylene chloride, acetone, methyl isobutyl ketone, vinyl acetate, 1,4-dioxane, 1,2-dichlorobenzene, 1-bromobutane, 2-methoxy-1-methylethyl acetate, acetophenone, amyl alcohol, isophorone, heptylene glycol, allyl acetate, chloroacetic acid, chlorostyrene, butyl formate, valeric acid, methyl chloride, diethylene glycol monobutyl ether, cyclohexanone, and dichloroethyl ether.

[0042] Examples of solvents having a solubility parameter of 11.0 or more and 18.0 or less include methanol, ethylene glycol, glycerol, ethanol, normal propanol, normal butanol, isopropyl alcohol, 1,4-butanediol, 2,3-butanediol, 2-acetylpyrrole, 4-acetylmorpholine, N,N,N',N'-tetramethylethanediamide, n-propyl alcohol, epsilon-caprolactam, acrylic acid, acetonitrile, allyl alcohol, and acetonitrile. Examples of the solvent A having a solubility parameter of 12.0 or more and 18.0 or less include methanol, ethylene glycol, glycerol, ethanol, and normal propanol.

[0043] Solvents B and C may be a mixed solvent consisting of multiple solvents. The solubility parameter of the mixed solvent is the sum of the solubility parameters of each solvent multiplied by the mixing ratio of each solvent. For example, the solubility parameter of a mixture of 93% by weight of methanol (solubility parameter 14.5) and 7% by weight of water (solubility parameter 23.4) is 15.1. Even when a mixed solvent is used for solvent C, it is preferable that at least one of the solvents is solvent A, which has a solubility parameter of 12.0 or more and 18.0 or less.

[0044] Next, the stirring step will be described, but the stirring step is not limited to the following description. The stirring step is a step in which a maleimide resin solution consisting of a maleimide resin and solvent B having a solubility parameter of 9.0 or more and 10.0 or less is added to solvent C having a solubility parameter of 11.0 or more and 18.0 or less and is stirred, and it is preferable to mix and stir the maleimide resin solution while adding it dropwise to solvent B. Thereafter, the precipitated maleimide resin is purified by washing with solvent C or another poor solvent. The maleimide resin solution may be prepared by mixing the maleimide resin with solvent B after synthesis, or by using solvent B during synthesis of the maleimide resin and allowing solvent B to remain after synthesis.

[0045] The amount of solvent B used is preferably 5 to 50% by weight, more preferably 10 to 40% by weight, and even more preferably 15 to 35% by weight, of the total amount of the maleimide resin solution.

[0046] The amount of solvent C used is preferably as large as possible relative to solvent B. On the other hand, in consideration of costs and environmental impact, the amount of solvent C used relative to solvent B is preferably not too large, and is preferably less than 100 times, more preferably less than 30 times, and even more preferably less than 20 times, the weight of solvent B.

[0047] Next, the removal step of removing the precipitate will be described, but the removal step is not limited to the following description. The removal step is a step of distilling off excess solvent from the maleimide resin precipitated in the stirring step using a reduced-pressure distillation apparatus such as an evaporator. For example, the maleimide resin precipitated in the stirring step is placed in an evaporator and left to stand at 85°C under reduced pressure for about 1 hour, thereby obtaining a maleimide resin solid from which excess solvent has been distilled off.

[0048] Next, the maleimide resin solid of this embodiment can be mixed with other materials to form a maleimide resin composition. The maleimide resin composition of this embodiment may contain a compound capable of crosslinking with the maleimide resin solid of this embodiment. The crosslinkable compound undergoes a crosslinking reaction with the maleimide resin solid and acts as a curing agent for the maleimide resin. Examples of the crosslinkable compound include compounds having an amino group, a cyanate group, a phenolic hydroxyl group, an alcoholic hydroxyl group, an allyl group, an acrylic group, a methacrylic group, a vinyl group, or a conjugated diene group. For example, it is preferable to blend an amine compound when heat resistance is required, or a cyanate ester compound when dielectric properties are required.

[0049] The maleimide resin composition of the present embodiment may contain a curing catalyst (curing accelerator) as needed. Examples of such catalysts include imidazoles such as 2-methylimidazole, 2-ethylimidazole, 2-phenylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole, and 1-cyanoethyl-2-ethyl-4-methylimidazole; amines such as triethylamine, triethylenediamine, 2-(dimethylaminomethyl)phenol, 1,8-diaza-bicyclo(5,4,0)-7-undecene, tris(dimethylaminomethyl)phenol, and benzyldimethylamine; triphenylphosphine, tributylphosphine, and trimethylisopropyl ... Examples of suitable curing catalysts include phosphines such as octylphosphine, organic metal salts such as tin octoate, zinc octoate, dibutyltin dimaleate, zinc naphthenate, cobalt naphthenate, and tin oleate, metal chlorides such as zinc chloride, aluminum chloride, and tin chloride, organic peroxides such as di-tert-butyl peroxide and dicumyl peroxide, azo compounds such as azobisisobutyronitrile and azobisdimethylvaleronitrile, mineral acids such as hydrochloric acid, sulfuric acid, and phosphoric acid, Lewis acids such as boron trifluoride, and salts such as sodium carbonate and lithium chloride. The amount of the curing catalyst is preferably 10 parts by weight or less, and more preferably 5 parts by weight or less, per 100 parts by weight of the maleimide resin solid matter of this embodiment.

[0050] An organic solvent can be added to the maleimide resin composition of this embodiment to form a varnish-like composition (hereinafter simply referred to as varnish). The maleimide resin composition of this embodiment can be dissolved as needed in a solvent such as toluene, xylene, acetone, methyl ethyl ketone, methyl isobutyl ketone, dimethylformamide, dimethylacetamide, or N-methylpyrrolidone to form an epoxy resin composition varnish, which can then be impregnated into a substrate such as carbon fiber, glass fiber, carbon fiber, polyester fiber, polyamide fiber, alumina fiber, or paper, and heated and dried to obtain a prepreg, which can then be hot-press molded to form a cured product of the maleimide resin composition of this embodiment. In this case, the solvent typically accounts for 10 to 70 wt %, and preferably 15 to 70 wt %, of the mixture of the maleimide resin composition of the present embodiment and the solvent. If the composition is in a liquid state, a cured product of the maleimide resin composition containing carbon fibers can be obtained as is, for example, by the RTM method.

[0051] The maleimide resin composition of this embodiment can also be used as a modifier for film-type compositions. Specifically, it can be used to improve flexibility and the like in the B-stage. Such a film-type resin composition can be obtained as a sheet-type adhesive by applying the maleimide resin composition of this embodiment as a maleimide resin composition varnish onto a release film, removing the solvent under heating, and then performing B-stage conversion. This sheet-type adhesive can be used as an interlayer insulating layer in a multilayer substrate or the like.

[0052] The maleimide resin composition of this embodiment can be heated and melted to reduce the viscosity, and then impregnated into reinforcing fibers such as glass fibers, carbon fibers, polyester fibers, polyamide fibers, and alumina fibers to obtain a prepreg. Alternatively, a prepreg can be obtained by impregnating reinforcing fibers with the varnish and drying the impregnated fibers by heating.

[0053] There are no particular limitations on the method for impregnating these reinforcing fibers with the maleimide resin composition of the present embodiment, but a method that does not use a solvent is preferred, and therefore a hot melt method is preferred in which the maleimide resin composition of the present embodiment is heated to 60 to 110°C and impregnated in a fluid state.

[0054] The proportion of the maleimide resin composition in the resulting prepreg (reinforcing fibers impregnated with the maleimide resin composition) depends on the form of the reinforcing fibers, but is usually 20% by weight to 80% by weight, preferably 25% by weight to 65% by weight, and more preferably 30% by weight to 50% by weight. If the proportion of the maleimide resin composition is higher than this range, the proportion of the reinforcing fibers will be relatively reduced, making it impossible to obtain a sufficient reinforcing effect. Conversely, if the proportion of the maleimide resin composition is low, moldability will be impaired.

[0055] This prepreg can be cured by a known method to form a final molded product. For example, the prepreg can be laminated and then heated in an autoclave at 2 to 10 kgf / cm. 2 The mixture can be pressed under pressure and heated at 150 to 200°C for 30 minutes to 3 hours to harden into a molded product. To further improve heat resistance, a post-cure step can be carried out at a temperature range of 180 to 280°C for 1 to 12 hours while increasing the temperature in steps, thereby producing a fiber-reinforced composite molded product. The prepreg is cut into a desired shape and laminated with copper foil or the like if necessary. The laminate can then be heated and cured while applying pressure to the laminate by press molding, autoclave molding, sheet winding molding, or the like, to obtain a laminate. Furthermore, a circuit can be formed on the laminated board by layering copper foil on the surface, and then prepreg, copper foil, etc. can be layered on top of that, and the above procedure can be repeated to obtain a multi-layer circuit board.

[0056] The cured product of the prepreg of this embodiment can be widely used in components that require light weight, high strength, and high heat resistance, such as robot hands for transporting liquid crystal glass substrates, disks for transporting silicon wafers, aerospace components, and automobile engine components.

[0057] Specific applications of the maleimide resin composition of this embodiment include adhesives, paints, coating agents, molding materials (including sheets, films, FRP, etc.), insulating materials for electronic materials (including printed circuit boards, electric wire coatings, etc., as well as cyanate resin compositions for sealing materials and substrates), and additives to other resins such as acrylate resins as resist curing agents. In particular, in FRP applications, solvent-free processes have become increasingly popular in recent years due to environmental considerations and the need to eliminate defects caused by voids. Furthermore, in semiconductor encapsulation applications, there are environments in which solvents cannot be introduced during the process. [Example]

[0058] The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto. In the text, "parts" and "%" represent "parts" and "%", respectively.

[0059] Example 1 A flask equipped with a thermometer, condenser, Dean-Stark azeotropic distillation trap, and stirrer was charged with 744 parts of aniline and 400 parts of toluene, and 292 parts of 35% hydrochloric acid was added dropwise at room temperature over 1 hour. After the dropwise addition, the mixture was heated to cool and separate the azeotropic water and toluene. The organic layer (toluene) was then returned to the system for dehydration. 250 parts of 4,4'-bis(chloromethyl)biphenyl were then added over 1 hour while maintaining the temperature at 60-70°C, and the reaction was continued for another 2 hours at the same temperature. After the reaction was completed, the toluene was distilled off while increasing the temperature to 195-200°C, and the reaction was continued at this temperature for 15 hours. 660 parts of 30% aqueous sodium hydroxide solution was then slowly added dropwise while cooling, avoiding vigorous reflux. The toluene that had distilled off during the temperature increase was returned to the system at below 80°C, and the system was allowed to stand at 70-80°C. The separated lower aqueous layer was removed, and the reaction mixture was repeatedly washed with water until the washings became neutral. Next, the oil layer was heated and reduced pressure (200°C, 0.6KPa) in a rotary evaporator to distill off excess aniline and toluene, yielding 346 parts of aromatic amine resin (a-1). The diphenylamine content in the aromatic amine resin (a-1) was 2.0%. The resulting resin was again heated and reduced pressure (200°C, 4KPa) in a rotary evaporator to distill off diphenylamine, yielding 332 parts of aromatic amine resin (A-1).

[0060] A flask equipped with a thermometer, condenser, Dean-Stark azeotropic distillation trap, and stirrer was charged with 147 parts maleic anhydride and 300 parts toluene. The resulting azeotropic water and toluene were cooled and separated, and the organic layer (toluene) was returned to the system for dehydration. Next, a resin solution prepared by dissolving 195 parts of aromatic amine resin (A-1) in 195 parts of N-methyl-2-pyrrolidone was added dropwise over 1 hour while maintaining the system at 80-85°C. After the dropwise addition, the reaction was continued at the same temperature for 2 hours. 3 parts of p-toluenesulfonic acid was added, and the azeotropic condensation water and toluene were cooled and separated under reflux conditions. The organic layer (toluene) was then returned to the system for dehydration. After the reaction was completed, 120 parts of toluene was added, and the mixture was repeatedly washed with water to remove p-toluenesulfonic acid and excess maleic anhydride. The water was then azeotropically removed from the system by heating. The reaction solution was then concentrated, and after confirming that the toluene content had reached 10% by gas chromatography, methyl ethyl ketone (MEK) was added to obtain a maleimide resin solution (A-2) containing 70% maleimide resin (toluene 7.8% / MEK 22.2%). The solubility parameter of the maleimide resin solution (A-2) in solvent B (a mixed solvent of toluene:MEK = 7.8:22.2) is 9.2.

[0061] Next, 363 parts of methanol and 27 parts of ion-exchanged water were placed in a flask equipped with a thermometer and a stirrer, and the mixture was stirred and cooled until the internal temperature reached 5° C. or below. The solubility parameter of the mixed solvent of methanol and ion-exchanged water (solvent C) prepared here was 15.1. Thereafter, 200 parts of the maleimide resin solution (A-2) was added dropwise to the mixed solvent (solvent C) in the flask over a period of 1 hour while stirring vigorously. After stirring for 1 hour after the dropwise addition, the precipitated resin powder was filtered under reduced pressure using a Buchner funnel. The resulting resin powder was placed in a flask equipped with a thermometer and stirrer, and 195 parts of methanol was added and stirred to wash. After washing with methanol multiple times, the resulting powder was vacuum dried at 95°C to obtain a porous maleimide resin solid (M1). An electron microscope image of the maleimide resin solid (M1) is shown in Figure 1.

[0062] Example 2 A flask equipped with a thermometer, condenser, Dean-Stark azeotropic distillation trap, and stirrer was charged with 192 parts of aniline, 112 parts of toluene, and 100 parts of 1,3-bis(2-hydroxy-2-propyl)benzene, and 21.5 parts of 35% hydrochloric acid was added dropwise over 10 minutes. The system was heated to 160°C, and the reaction was carried out at the same temperature for 17 hours while distilling off water and toluene. After cooling to 80°C, 124 parts of toluene was added, and 30 parts of 30% aqueous sodium hydroxide solution was added dropwise over 10 minutes. The mixture was then stirred at the same temperature for 2 hours and allowed to stand for 30 minutes. The separated lower aqueous layer was removed, and the reaction solution was repeatedly washed with water until the washings became neutral. Next, the excess aniline and toluene were distilled off from the oil layer using a rotary evaporator under reduced pressure and heating, yielding 158 parts of aromatic amine resin (B-1).

[0063] A flask equipped with a thermometer, condenser, Dean-Stark azeotropic distillation trap, and stirrer was charged with 73.5 parts maleic anhydride, 126 parts toluene, 1.86 parts methanesulfonic acid, and 12.6 parts N-methyl-2-pyrrolidone and heated to reflux. Next, a resin solution prepared by dissolving 93 parts of aromatic amine resin (B-1) in 55.8 parts toluene was added dropwise over 4 hours while maintaining reflux. During this time, the condensed water and toluene that formed azeotropically under reflux conditions were cooled and separated in the Dean-Stark azeotropic distillation trap. The organic layer, toluene, was returned to the system, and the water was discharged. After the resin solution was added dropwise, the reaction was continued for 10 hours while maintaining reflux and dehydration. After the reaction was completed, the mixture was washed with water four times to remove methanesulfonic acid and excess maleic anhydride. Water was then removed from the system by azeotroping toluene with water under reduced pressure and heating at 70°C or below. Next, 0.93 parts of methanesulfonic acid was added, and the reaction was carried out under reflux for 4 hours. After the reaction was complete, the mixture was washed four times until the wash water became neutral. Water was then removed from the system by azeotroping toluene with water under reduced pressure at 70°C or below. Toluene was then distilled off under reduced pressure until the resin concentration reached approximately 90%. Methyl ethyl ketone (MEK) was then added to adjust the resin concentration to 70% and the solvent to 30% (toluene 7.8% / MEK 22.2%). This yielded maleimide resin solution (B-2). The solubility parameter of solvent B (a mixed solvent of toluene:MEK = 7.8:22.2) for maleimide resin solution (B-2) was 9.2. Next, 363 parts of methanol and 27 parts of ion-exchanged water were placed in a flask equipped with a thermometer and a stirrer, and the mixture was stirred and cooled until the internal temperature reached 5° C. or below. The solubility parameter of the mixed solvent of methanol and ion-exchanged water (solvent C) prepared here was 15.1. Thereafter, 200 parts of the maleimide resin solution (B-2) was added dropwise to the mixed solvent (solvent C) in the flask over a period of 1 hour while stirring vigorously. After stirring for 1 hour after the dropwise addition, the precipitated resin powder was filtered under reduced pressure using a Buchner funnel. The resulting resin powder was placed in a flask equipped with a thermometer and stirrer, and 195 parts of methanol was added and stirred to wash. After washing with methanol multiple times, the resulting powder was vacuum dried at 95°C to obtain maleimide resin solid (M2). An electron microscope image of maleimide resin solid (M2) is shown in Figure 2.

[0064] Example 3 A flask equipped with a thermometer and stirrer was charged with 140 parts of the imidization reaction product of a polyamine obtained by polycondensation of aniline and formaldehyde with maleic anhydride (BMI-2300, manufactured by Daiwa Kasei Co., Ltd.), 44.4 parts of methyl ethyl ketone, and 15.6 parts of toluene, and dissolved to obtain maleimide resin solution (B-3). The solubility parameter of solvent B (a mixed solvent of toluene:MEK = 7.8:22.2) for maleimide resin solution (B-3) was 9.2. Next, 363 parts of methanol and 27 parts of ion-exchanged water were placed in a flask equipped with a thermometer and a stirrer, and the mixture was stirred and cooled until the internal temperature reached 5° C. or below. The solubility parameter of the mixed solvent of methanol and ion-exchanged water (solvent C) prepared here was 15.1. Thereafter, 200 parts of the maleimide resin solution (B-3) was added dropwise to the mixed solvent (solvent C) in the flask over a period of 1 hour while stirring vigorously. After stirring for 1 hour after the dropwise addition, the precipitated resin powder was filtered under reduced pressure using a Buchner funnel. The resulting resin powder was placed in a flask equipped with a thermometer and stirrer, and 195 parts of methanol was added and stirred to wash. After washing with methanol multiple times, the resulting powder was vacuum dried at 90°C to obtain maleimide resin solid (M3). An electron microscope image of maleimide resin solid (M3) is shown in Figure 3.

[0065] (Comparative Example 1) The maleimide resin solution (A-2) described in Example 1 was vacuum-dried at 130°C for 1 hour, and the resulting solid was crushed with a mortar and pestle to obtain maleimide resin solid (M4). An electron microscope image of the maleimide resin solid (M4) is shown in Figure 4.

[0066] (Comparative Example 2) The maleimide resin solution (B-2) described in Example 2 was vacuum-dried at 130°C for 1 hour, and the resulting solid was crushed with a mortar and pestle to obtain a maleimide resin solid (M5). An electron microscope image of the maleimide resin solid (M5) is shown in Figure 5.

[0067] (Comparative Example 3) The maleimide resin solution (B-3) described in Example 3 was vacuum-dried at 130°C for 1 hour, and the resulting solid was crushed with a mortar and pestle to obtain maleimide resin solid (M6). An electron microscope image of the maleimide resin solid (M6) is shown in Figure 6.

[0068] (Examples 1-1 to 1-5, Reference Examples 1-1 to 1-5) The maleimide resin solids obtained by replacing solvent B and solvent C in the maleimide resin solution of Example 1 with the solvents or mixed solvents shown in Table 1 were observed under an electron microscope (Miniscope, manufactured by Hitachi High-Technologies Corporation) to determine whether they were porous or not. As a result, those for which a porous solid was obtained were marked with an ◯, and those for which a porous solid was not obtained were marked with an ×.

[0069] [Table 1]

[0070] Toluene: Toluene, solubility parameter 8.9 (manufactured by Taishin Chemical Co., Ltd.) MEK: Methyl ethyl ketone, solubility parameter 9.3 (Kanto Chemical Co., Ltd.) THF: tetrahydrofuran, solubility parameter 9.1 (Mitsubishi Chemical Corporation) PEGMEA: propylene glycol monomethyl ether acetate, solubility parameter 9.2 (Kanto Chemical Co., Ltd.) MIBK: Methyl isobutyl ketone, solubility parameter 9.6 (Mitsubishi Chemical Corporation) Methanol: Solubility parameter 14.5 (Fujifilm Wako Pure Chemical Industries, Ltd.) Water: solubility parameter 23.4 Cyclohexane: solubility parameter 8.2 (manufactured by FUJIFILM Wako Pure Chemical Corporation) Acetone: solubility parameter 10.0 (manufactured by Nippon Oil Corporation) DMF: N,N-Dimethylformamide, solubility parameter 12.0 (manufactured by Kanto Chemical Co., Inc.)

[0071] The measurement results of the solvent content, particle size distribution, and BET specific surface area of the maleimide resin solids (M1 - M6) obtained in Examples 1 - 3 and Comparative Examples 1 - 3 are shown in Table 2. <Measurement of solvent content> Performed using a gas chromatograph GC - 2010 manufactured by Shimadzu Corporation, and as the column, DB - WAX (manufactured by Agilene Technologies) with a length of 30 m and an inner diameter of 0.25 mm was used. As the temperature - rising program, it was held at 70°C for 5 minutes, then heated to 140°C at a heating rate of 10°C / min, and then heated to 220°C at a heating rate of 20°C / min and held at 220°C for 5 minutes. <Measurement of particle size distribution> 0.1 g of the maleimide resin solids (M1 - M6) was put into 10 mL of isopropanol (manufactured by Junsei Chemical Co., Ltd.), and the dispersion liquid prepared by ultrasonic treatment for 3 minutes was used to measure the particle size distribution (D50, D90) by Microtrac MT3300 (manufactured by Microtrac BEL Co., Ltd.). <Measurement of BET specific surface area> The BET specific surface area was measured using a gas adsorption method specific surface area measurement device (BELSORP - maxII (manufactured by MicrotracBEL)). The maleimide resin solids (M1 - M6) were measured after vacuum degassing at 70°C for 4 hours as a pretreatment. Nitrogen was used as the adsorption gas.

[0072]

Table 2

[0073] Methanol: solubility parameter 14.5 MEK: Methyl ethyl ketone, solubility parameter 9.3 Toluene: Toluene, solubility parameter 8.9 NMP: N-methyl-2-pyrrolidone, solubility parameter 11.3

[0074] (Examples 4 and 5, Comparative Examples 4 and 5) The results of the solvent solubility test of the maleimide resin solids (M1, M2, M4, M5) obtained in Examples 1 and 2 and Comparative Examples 1 and 2 are shown in Table 2. <Solvent solubility test> The solubility of maleimide resin solids (M1, M2, M4, M5) in the solvents shown in Table 3 (acetone, MEK, NMP, DMF) was confirmed by the following procedure. (1) 0.50 g of maleimide resin solid, 1.16 g of solvent (adjusted to a solid content of 30%), and a stirrer were placed in a 10 mL glass bottle. (2) The mixture was stirred at 120 rpm and the time required for complete dissolution was measured. The upper limit of the measurement time was 600 seconds, and if the mixture did not dissolve within 600 seconds, it was deemed insoluble. The dissolution time was determined by visual observation of the glass bottle until it became transparent and no solid matter remained.

[0075] [Table 3]

[0076] From Table 3, it was confirmed that Examples 4 and 5 were superior to Comparative Examples 4 and 5 in solubility in solvents.

Claims

1. A novolac maleimide resin solid comprising a novolac maleimide resin having a repeating unit and 2 to 20 maleimide groups in the molecule and a solvent A, wherein the content of the solvent A is 100 ppm or more and 30,000 ppm or less, and the Hildebrand solubility parameter of the solvent A is 12.0 or more and 18.0 or less.

2. 2. The novolac maleimide resin solid according to claim 1, which is porous.

3. A porous novolac-type maleimide resin solid having repeating units and 2 to 20 maleimide groups in the molecule.

4. 4. The novolac maleimide resin solid according to claim 1, wherein the 90% by volume particle size (D90) is 10 μm or more and 200 μm or less.

5. BET specific surface area is 0.5m ２ / g or more 5.0m ２ 4. The novolac maleimide resin solid according to claim 1, wherein the molecular weight of the novolac maleimide resin is 1 / g or less.

6. 4. The novolac maleimide resin solid according to claim 1, wherein the softening point of the novolac maleimide resin is 40° C. or higher and 100° C. or lower.

7. The novolac maleimide resin solid according to claim 1 or 3, wherein the novolac maleimide resin has a structure represented by the following formula (1): 【Chemistry 1】 In the formula (1), each R independently represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or a phenyl group. X represents any one of the following structural formulae (A1) to (V1). n represents the average number of repetitions, and is 1≦n≦5. 【Chemistry 2】 In formulas (A1) to (V1), each of the multiple R's independently represents a hydrocarbon group having 1 to 5 carbon atoms. Each a' is independently an integer of 0 to 4, each b' is independently an integer of 0 to 3, and each p' is independently an integer of 1 to 20. * indicates a bonding position.

8. A maleimide resin composition comprising the maleimide resin solid according to claim 1 or 3.

9. A cured product of the maleimide resin composition according to claim 8.

10. A method for producing a novolac maleimide resin solid, comprising: a stirring step of adding a novolac maleimide resin having a repeating unit and 2 to 20 maleimide groups in a molecule, or a novolac maleimide resin solution comprising the novolac maleimide resin and a solvent B, to a solvent C different from the solvent B and stirring the mixture; and a removal step of removing a precipitate obtained in the stirring step, a Hildebrandt solubility parameter of the solvent B of from 9.0 to 10.0, and a Hildebrandt solubility parameter of the solvent C of from 11.0 to 18.

0.

11. The method for producing a maleimide resin solid according to claim 10, wherein the novolac-type maleimide resin has a structure represented by the following formula (1): 【Transformation 3】 In the formula (1), each R independently represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or a phenyl group. X represents any one of the following structural formulae (A1) to (V1). n represents the average number of repetitions, and is 1≦n≦5. 【Chemistry 4】 In formulas (A1) to (V1), each of the multiple R's independently represents a hydrocarbon group having 1 to 5 carbon atoms. Each a' is independently an integer of 0 to 4, each b' is independently an integer of 0 to 3, and each p' is independently an integer of 1 to 20. * indicates a bonding position.

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