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

Abstract

The present invention provides: a solid novolac-type maleimide resin material which exhibits excellent solubility in solvents and has a repeating unit in which the average number of maleimide groups is 2-20; and a method for producing same. The solid novolac-type maleimide resin material contains solvent A and a novolac-type maleimide resin having a repeating unit in which the average number of maleimide groups is 2-20. The content of the solvent A is 100-30,000 ppm. The Hildebrand solubility parameter of the solvent A is 12.0-18.0.

Description

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

[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 that is used in applications such as highly reliable semiconductor encapsulants, insulating materials for electric and electronic components, various composite materials including laminates (glass fiber reinforced composite materials for printed wiring) and CFRP (carbon fiber reinforced composite materials), various adhesives, various coating materials, and structural members, as well as a method for producing the maleimide resin solid, a maleimide resin composition, and a cured product thereof.

[0002] Maleimide resins are compounds that have heat resistance exceeding that of epoxy resins, moldability equivalent to that of epoxy resins, and furthermore, have the properties of a low linear expansion coefficient and a high Tg. Polymaleimide compounds can be crosslinked alone or reacted with various maleimide compounds or crosslinking agents to form materials with excellent heat resistance and flame retardancy, and have therefore been used in a variety of applications, including encapsulating materials, substrate materials, and insulating materials. In particular, they are used in applications that require both extremely high heat resistance and moldability, such as high-heat-resistant substrate materials, flexible substrate materials, high-heat-resistant low-dielectric materials, high-heat-resistant CFRP materials (carbon fiber composite materials), and high-heat-resistant encapsulating materials for automotive SiC power devices.

[0003] Conventionally, maleimide resins have been commercially available as crystalline powders obtained by recrystallization or as resin powders obtained by reprecipitation due to their self-reactivity (see Patent Document 1). However, maleimide resins incorporate solvents and the like during crystallization and precipitation, which poses a problem of inability 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. In light of this, there is a demand for maleimide resin solids that offer excellent 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 has excellent workability and productivity and is less exposed to the solvent environment. Generally, novolac maleimide resins are 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.

[0006] Japanese Patent Publication No. 6-86425 International Publication No. 2018 / 043380 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 may occur. Therefore, in actual production, there is a significant risk of polymerization and gelation, and there are issues from the perspective of moldability and stable productivity, such as increased viscosity due to increased molecular weight and variations in 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 exceeding 30,000 ppm poses 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.

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

[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 items [1] to

[11] . In the present invention, the terms "(numerical value 1) to (numerical value 2)" include the upper and lower limits. [1] A novolac maleimide resin solid product containing 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 product according to the above item [1], which is porous. [3] A novolac maleimide resin solid product having a repeating unit with an average number of functional groups of 2 to 20, which is porous. [4] The novolac maleimide resin solid product according to the above item [1] or [3], which has a 90% by mass particle size (D90) of 10 μm or more and 200 μm or less. [5] BET specific surface area is 0.5 m ２ / g or more 5.0m ２ [6] The novolac maleimide resin solid according to any one of items [1] to [5], wherein the novolac maleimide resin has a softening point of 40° C. or higher and 100° C. or lower. [7] The novolac maleimide resin solid according to any one of items [1] to [6], wherein the novolac maleimide resin has a structure represented by the following formula (1):

[0012] 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]

[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 items [1] to [7] above. [9] A cured product of the maleimide resin composition according to item [8] above.

[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 the molecule, or a novolac maleimide resin solution comprising the novolac maleimide resin and solvent B, to solvent C and stirring; and a recovery step of recovering the precipitate obtained in the stirring step, wherein solvent B has a Hildebrand solubility parameter of 9.0 or more and 10.0 or less, and solvent C has a Hildebrand solubility parameter of 11.0 or more and 18.0 or less.

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

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

[0015]

[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]

[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.

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

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

[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 a "maleimide resin solid") of a novolac-type maleimide resin (hereinafter also simply referred to as a "maleimide resin") having a repeating unit 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 described 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 reduced and the crystallinity is reduced, thereby increasing 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 0.5 m ２ / g or more 10.0m ２ / g or less, and 0.5m ２ / g or more 5.0m ２ / g or less, and more preferably 0.5m ２ / g or more 1.0m ２ / g or less is even more preferable. If the BET specific surface area is greater than the above upper limit, the solubility in solvents may be reduced. The BET specific surface area is determined by measuring the amount of physically adsorbed gas based on 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 (manufactured by MicrotracBEL) as shown in the examples described later.

[0028] The 90% by volume particle size (D90) of the maleimide resin solid is preferably 10 μm or more and 500 μm or less, more preferably 30 μm or more and 300 μm or less, and even more preferably 50 μm or more and 200 μm or less. The average particle size (volume-based median diameter D50) of the maleimide resin solid is preferably 1 μm or more and 200 μm or less, more preferably 10 μm or more and 100 μm or less, and even more preferably 20 μm or more and 80 μm or less. If the average particle size is greater than the upper limit, solubility in solvents may be impaired. If it is smaller 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 taken as 100%. D90 is the particle size at the point where the cumulative curve reaches 90% when the total volume of the particles is taken as 100%.

[0029] As the maleimide resin that can be used in the present embodiment, any novolac-type maleimide resin can be used as long as it has a repeating unit and the number of maleimide groups in the molecule is 2 to 20. For example, a maleimide resin having a structure represented by the following formula (1) can be used.

[0030]

[0031] In the above formula (1), multiple R's each independently 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 repeating units and is 1≦n≦5, preferably 1<n≦5.

[0032]

[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]

[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 any known method for synthesizing maleimide resins may be used. As a specific production method, it is preferable to use, for example, the method described in JP 2009-001783 A.

[0038] Next, a method for producing the maleimide resin solid of this embodiment will be described. The maleimide resin solid of this embodiment can be obtained by a stirring step of adding a maleimide resin or a maleimide resin solution composed of 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, acetonitrile, etc. Examples of solvent A having a solubility parameter of 12.0 or more and 18.0 or less include methanol, ethylene glycol, glycerol, ethanol, normal propanol, etc.

[0043] Solvents B and C may be mixed solvents composed of multiple solvents. The solubility parameter of the mixed solvent is the sum of the values ​​obtained by multiplying the solubility parameters of each solvent by the mixing ratio of each solvent. For example, the solubility parameter of a solvent obtained by mixing 93 wt % methanol (solubility parameter 14.5) and 7 wt % water (solubility parameter 23.4) is 15.1. Even when a mixed solvent is used as 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 is not limited to the following description. The stirring step is a step of adding a maleimide resin solution consisting of 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; the maleimide resin solution is preferably mixed and stirred while being added dropwise to the solvent B. The precipitated maleimide resin is then purified by washing with solvent C or another poor solvent. The maleimide resin solution may be one in which a maleimide resin is synthesized and then mixed with solvent B, or solvent B may be used during the synthesis of the maleimide resin and then left as is after the 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 can 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 the curing catalyst 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 to be added 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 in a solvent such as toluene, xylene, acetone, methyl ethyl ketone, methyl isobutyl ketone, dimethylformamide, dimethylacetamide, or N-methylpyrrolidone, as needed, to form an epoxy resin composition varnish. This varnish is then 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. This prepreg can then be hot-press molded to form a cured product of the maleimide resin composition of this embodiment. The solvent typically accounts for 10 to 70 wt %, preferably 15 to 70 wt %, of the mixture of the maleimide resin composition of this embodiment and the solvent. Furthermore, if the composition is in liquid form, a cured product of the maleimide resin composition containing carbon fiber can be obtained directly, 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-like 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 formation. This sheet-like adhesive can be used as an interlayer insulating layer in a multilayer substrate or the like.

[0052] A prepreg can be obtained by heating and melting the maleimide resin composition of this embodiment to reduce the viscosity and impregnating it into reinforcing fibers such as glass fibers, carbon fibers, polyester fibers, polyamide fibers, alumina fibers, etc. Alternatively, a prepreg can be obtained by impregnating reinforcing fibers with the varnish and drying them 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) varies depending 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 subjected to a pressure of 2 to 10 kgf / cm in an autoclave. ２ The prepreg can be pressurized to a desired shape and heat-cured at 150-200°C for 30 minutes to 3 hours to produce a molded product. To further improve heat resistance, a post-cure step of heating the prepreg in a temperature range of 180-280°C for 1-12 hours can be used to produce a fiber-reinforced composite molded product. The prepreg can be cut into a desired shape and, if necessary, laminated with copper foil or other materials. The laminate can then be heat-cured by applying pressure to the laminate using a press molding method, autoclave molding, sheet winding molding, or other method, to heat-cure the epoxy resin composition for laminates. Furthermore, a circuit can be formed on the resulting laminate by overlaying copper foil on the surface, and the above process can be repeated to produce a multilayer 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 common 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.

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

[0060] A flask equipped with a thermometer, a condenser, a Dean-Stark azeotropic distillation trap, and a stirrer was charged with 147 parts of maleic anhydride and 300 parts of toluene, and heated to cool and separate the azeotropic water and toluene. The organic layer, toluene, was then 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 completion of the dropwise addition, the reaction was carried out at the same temperature for 2 hours, and then 3 parts of p-toluenesulfonic acid was added. The azeotropic condensed water and toluene were cooled and separated under reflux conditions, and the organic layer, toluene, was returned to the system for dehydration. After completion of the reaction, 120 parts of toluene were added, and the mixture was repeatedly washed with water to remove p-toluenesulfonic acid and excess maleic anhydride. The mixture was then heated to remove water from the system by azeotropy. The reaction solution was then concentrated, and after confirming by gas chromatography that the toluene content after concentration was 10%, 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 solvent B (a mixed solvent of toluene:MEK=7.8:22.2) for maleimide resin solution (A-2) was 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, 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 maleimide resin solution (A-2) was added dropwise to the mixed solvent (solvent C) in the flask over one hour with vigorous stirring. After stirring for one hour after the dropwise addition, the precipitated resin powder was filtered under reduced pressure using a Buchner funnel, and the resulting resin powder was placed in a flask equipped with a thermometer and a 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, a condenser, a Dean-Stark azeotropic distillation trap, and a 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 temperature inside the system was raised 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 a 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 heating and reduced pressure, yielding 158 parts of aromatic amine resin (B-1).

[0063] A flask equipped with a thermometer, a condenser, a Dean-Stark azeotropic distillation trap, and a stirrer was charged with 73.5 parts of maleic anhydride, 126 parts of toluene, 1.86 parts of methanesulfonic acid, and 12.6 parts of 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 of toluene was added dropwise over 4 hours while maintaining reflux. During this time, the condensed water and toluene that formed an azeotropic distillation under reflux conditions were cooled and separated in the Dean-Stark azeotropic distillation trap, and the organic layer, toluene, was returned to the system, and the water was discharged outside. After completion of the dropwise addition of the resin solution, the reflux condition was maintained, and the reaction was carried out for 10 hours while performing a dehydration operation. After completion of the reaction, the mixture was washed with water four times to remove methanesulfonic acid and excess maleic anhydride, and water was removed from the system by azeotropic distillation of toluene and water under heating and reduced pressure at 70 ° C or less. Next, 0.93 parts of methanesulfonic acid was added, and the reaction was carried out under heated reflux for 4 hours. After the reaction was completed, the mixture was washed four times until the wash water became neutral. Water was then removed from the system by azeotropy of toluene and water under reduced pressure at 70°C or less. Toluene was then distilled off under reduced pressure at 70°C or less 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) in maleimide resin solution (B-2) was 9.2. Subsequently, 363 parts of methanol and 27 parts of ion-exchanged water were placed in a flask equipped with a thermometer and a stirrer, 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 one hour while stirring vigorously. After stirring for one hour after the dropwise addition, the precipitated resin powder was filtered under reduced pressure using a Buchner funnel, and the resulting resin powder was placed in a flask equipped with a thermometer and a stirrer, to which 195 parts of methanol was added and stirred for washing. After washing multiple times with methanol, the resulting powder was vacuum dried at 95°C to obtain a maleimide resin solid (M2). An electron microscope image of the maleimide resin solid (M2) is shown in Figure 2.

[0064] Example 3 In a flask equipped with a thermometer and a stirrer, 140 parts of an 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 were dissolved to obtain a maleimide resin solution (B-3). The solubility parameter of solvent B (a mixed solvent of toluene:MEK=7.8:22.2) in the maleimide resin solution (B-3) is 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, stirred, and cooled until the internal temperature was 5°C or below. The solubility parameter of the mixed solvent of methanol and ion-exchanged water (solvent C) prepared here is 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 1 hour with vigorous stirring. 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 a 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 a maleimide resin solid (M3). An electron microscope image of the 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 for 1 hour at 130°C, and the resulting solid was pulverized with a mortar and pestle to obtain a 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 for 1 hour at 130°C, and the resulting solid was pulverized 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 for 1 hour at 130°C, and the resulting solid was pulverized with a mortar and pestle to obtain a 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. 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]

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

[0071] The results of measuring the solvent content, particle size distribution, and BET specific surface area of ​​the maleimide resin solids (M1 to M6) obtained in Examples 1 to 3 and Comparative Examples 1 to 3 are shown in Table 2. <Solvent Content Measurement> Measurement was performed using a gas chromatograph GC-2010 manufactured by Shimadzu Corporation, and a DB-WAX (manufactured by Agilene Technologies) column with a length of 30 m and an inner diameter of 0.25 mm was used. The temperature-rising program used was to hold the temperature at 70°C for 5 minutes, raise the temperature to 140°C at a rate of 10°C / min, raise the temperature to 220°C at a rate of 20°C / min, and hold the temperature at 220°C for 5 minutes. <Particle size distribution measurement> 0.1 g of maleimide resin solids (M1 to M6) was placed in 10 mL of isopropanol (manufactured by Junsei Chemical Co., Ltd.), and the dispersion was dispersed by ultrasonic treatment for 3 minutes to prepare a dispersion, which was then used with a Microtrac MT3300 (manufactured by Microtrac BEL Co., Ltd.) to measure the particle size distribution (D50, D90). <BET specific surface area measurement> The BET specific surface area was measured using a gas adsorption specific surface area measurement device (BELSORP-max II (manufactured by Microtrac BEL Co., Ltd.)). The maleimide resin solids (M1 to M6) were subjected to vacuum degassing at 70°C for 4 hours as a pretreatment, followed by measurement. Nitrogen was used as the adsorption gas.

[0072]

[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 for the maleimide resin solids (M1, M2, M4, and M5) obtained in Examples 1 and 2 and Comparative Examples 1 and 2 are shown in Table 2. <Solvent Solubility Test> The solubility of the maleimide resin solids (M1, M2, M4, and M5) in the solvents listed in Table 3 (acetone, MEK, NMP, and DMF) was confirmed using the maleimide resin solids (M1, M2, M4, and M5) by the following procedure. (1) 0.50 g of maleimide resin solid, 1.16 g of solvent (adjusted to a solids 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 until complete dissolution was measured. The measurement time was limited to 600 seconds, and if the mixture did not dissolve within 600 seconds, it was considered insoluble. The dissolution time was determined by visual observation as the time until the glass bottle became transparent and no solids remained.

[0075]

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

3. A porous novolac-type maleimide resin solid having repeating units with an average number of maleimide groups of 2 to 20.

4. The novolac maleimide resin solid according to claim 1 or 3, 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. The novolac maleimide resin solid according to claim 1 or 3, 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): 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. 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 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 the molecule, or a novolac maleimide resin solution comprising said novolac maleimide resin and solvent B, to a solvent C different from said solvent B and stirring the mixture, and a removal step of removing the precipitate obtained in the stirring step, wherein the Hildebrand solubility parameter of said solvent B is 9.0 or more and 10.0 or less, and the Hildebrand solubility parameter of said solvent C is 11.0 or more and 18.0 or less.

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): 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. 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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