JP2022025527A - Maleimide resin, curable resin composition and cured product of the same - Google Patents

Abstract

To provide a maleimide resin, and a cured product which is obtained by curing a curable resin composition using the same and has excellent low hygroscopicity and dielectric characteristics.SOLUTION: A maleimide resin is represented by the following formula (1). In the formula (1), a plurality of R each independently represents an alkyl group having 1 to 5 carbon atoms, n is a repeating number, and its average value is 1<n<5.SELECTED DRAWING: Figure 1

Description

The present invention relates to a novel maleimide resin, a curable resin composition using the same, and a cured product thereof, and includes electric / electronic parts such as a semiconductor encapsulant, a printed wiring board, and a build-up laminated board, and carbon fiber. It is suitably used for lightweight and high-strength materials such as reinforced plastics and glass fiber reinforced plastics.

In recent years, the required characteristics of laminated boards on which electrical and electronic components are mounted have become widespread and sophisticated due to the expansion of their fields of use. For example, in the past, semiconductor chips were mainly mounted on metal lead frames, but semiconductor chips with high processing power such as CPUs are often mounted on laminated plates made of polymer materials. It has become. As the speed of elements such as CPUs increases and the clock frequency increases, signal propagation delay and transmission loss become problems, and the wiring board is required to have a low dielectric constant and a low dielectric loss tangent. At the same time, as the speed of the element increases, the heat generated by the chip increases, so that it is necessary to improve the heat resistance. In recent years, mobile electronic devices such as mobile phones have become widespread, and precision electronic devices have come to be used and carried in outdoor environments and in the immediate vicinity of the human body, so that the external environment (especially moisture-resistant heat-resistant environment) Tolerance is required.

Furthermore, in the field of automobiles, digitization has progressed rapidly, and precision electronic devices may be placed near the engine, and heat resistance and moisture resistance are required at a higher level. Safety such as flame retardancy is becoming more important in automobile applications and mobile devices, but halogens are used because the use of halogen-based flame retardants has been avoided due to the recent increase in awareness of environmental issues. There is an increasing need to impart flame retardancy without doing so.

Conventionally, a wiring board using BT resin, which is a resin in which a bisphenol A type cyanate ester compound and a bismaleimide compound are used in combination as in Patent Document 1, has excellent heat resistance, chemical resistance, electrical characteristics, etc., and therefore is a high-performance wiring board. However, in the situation where high performance is required as described above, further improvement is required.

In recent years, the weight of airplanes, automobiles, trains, ships, etc. has been reduced from the viewpoint of energy saving, and studies have been conducted to replace the conventional metal materials with lightweight and high-strength carbon fiber composite materials. ing. For example, in the Boeing 787, the weight is reduced by increasing the ratio of the composite material, and the fuel efficiency is greatly improved. In the aviation field, there is a movement to introduce carbon fiber composite materials to the parts around the engine in order to further reduce the weight, and naturally a high level of heat resistance is required. Although it is a part of the automobile field, it is equipped with a propeller shaft made of composite material, and there is also a movement to make the car body from composite material for luxury cars.

In the field of carbon fiber composite materials, composite materials using epoxy resins such as bisphenol A type diglycidyl ether and tetraglycidyl diaminodiphenylmethane and diaminodiphenylmethane and diaminodiphenyl sulfone as curing agents have been used. In order to promote weight reduction and high heat resistance, it is necessary to expand the application of composite materials, and maleimide resin is being studied as one means for that purpose.

Under these circumstances, the maleimide compound available on the market is often bismaleimide, and the cured product thereof has a drawback of high heat resistance but high hygroscopicity.

Japanese Unexamined Patent Publication No. 50-129700 Japanese Unexamined Patent Publication No. 61-0000041

An object of the present invention is to provide a novel maleimide resin and a cured product thereof that can realize low hygroscopicity, low dielectric property, and low dielectric loss tangent property.

As a result of diligent research to solve the above problems, the present inventors have completed the present invention.
That is, the present invention relates to the following [1] to [7].
[1]
Maleimide resin represented by the following formula (1).

(In equation (1), n is the average value of the number of repetitions, and 1 <n <5.)
[2]
The maleimide resin according to the preceding item [1], wherein n in the formula (1) is 1 <n <3.
[3]
The maleimide resin according to the preceding item [1] or [2], wherein the content of bismaleimide represented by n = 1 in the formula (1) is 98% or less.
[4]
The maleimide resin according to any one of the above items [1] to [3], which is obtained by reacting an amine resin represented by the following formula (2) with maleic acid or maleic anhydride.

(In equation (2), n is the average value of the number of repetitions, and 1 <n <5.)
[5]
The curable resin composition containing the maleimide resin according to any one of the above items [1] to [4].
[6]
A cured product obtained by curing the curable resin composition according to the preceding item [5].
[7]
Amine resin represented by the following formula (2).

(In equation (2), n is the average value of the number of repetitions, and 1 <n <5.)

The cured product obtained from the maleimide resin of the present invention can realize low hygroscopicity, low dielectric property, and low dielectric loss tangent property.

The GPC chart of the maleimide resin of Example 1 is shown.

The maleimide resin of the present invention is represented by the following formula (1).

(In equation (1), n is the average value of the number of repetitions, and 1 <n <5.)

In the formula (1), the value of n can be calculated from the value of the number average molecular weight obtained by the measurement of gel permeation chromatography (GPC, detector: RI) of the maleimide resin, but it is approximately a raw material. It can be considered that the value of n calculated from the measurement result of GPC of the amine resin is almost the same.

In the present invention, the content of the n = 1 component in the formula (1) can be determined by gel permeation chromatography (GPC, detector: RI) analysis.

The content of the maleimide resin represented by n = 1 in the maleimide resin of the present invention by GPC analysis (RI) is preferably 98 area% or less, more preferably 20 to 95 area%. It is more preferably in the range of 30 to 90 area%, and particularly preferably in the range of 50 to 90 area%. When the content of n = 1 bismaleimide in the formula (1) is 98 area% or less, the heat resistance is good and the solubility is also improved. In the formula (1), the lower limit of n = 1 bismaleimide may be 0 area%, but if it is 20 area% or more, the viscosity of the resin is not too high and the workability is good.

The maleimide resin represented by the formula (1) is an amine resin represented by the following formula (2), maleic acid or maleic anhydride (hereinafter, also referred to as "maleic anhydride") as a solvent, and the presence of a catalyst. It is obtained by adding or dehydrating and condensing the reaction underneath.

As the solvent used in the reaction, it is necessary to remove the water generated during the reaction from the system, so a water-insoluble solvent is used. For example, aromatic solvents such as toluene and xylene, aliphatic solvents such as cyclohexane and n-hexane, ethers such as diethyl ether and diisopropyl ether, ester solvents such as ethyl acetate and butyl acetate, methylisobutyl ketones and cyclopentanones and the like. However, the present invention is not limited to these, and two or more of them may be used in combination.

In addition to the water-insoluble solvent, an aprotic polar solvent can also be used in combination. For example, dimethyl sulfone, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone and the like can be mentioned, and two or more thereof may be used in combination. When an aprotic polar solvent is used, it is preferable to use a solvent having a boiling point higher than that of the water-insoluble solvent used in combination.

The catalyst used in the reaction is an acidic catalyst, and is not particularly limited, and examples thereof include p-toluenesulfonic acid, hydroxy-p-toluenesulfonic acid, methanesulfonic acid, sulfuric acid, and phosphoric acid. The amount of the acid catalyst used is usually 0.1 to 10% by weight, preferably 1 to 5% by weight, based on the aromatic amine resin.

For example, an aromatic amine resin represented by the above formula (2) is dissolved in toluene, maleic anhydride is added thereto to produce amic acid, and then p-toluenesulfonic acid is added to carry out reflux conditions. The reaction is carried out while removing the water generated in the above system from the system.

Alternatively, maleic anhydride is dissolved in toluene, and a toluene solution of the aromatic amine resin represented by the above formula (2) is added under stirring to generate amic acid, and then p-toluenesulfonic acid is added. Then, the reaction is carried out while removing the water generated under reflux conditions from the system.

Alternatively, the maleic acid anhydride is dissolved in toluene, p-toluenesulfonic acid is added, and the toluene solution of the aromatic amine resin represented by the above formula (2) is dropped in a stirred / refluxed state while azeotropically boiling in the middle. The reaction is carried out while the incoming water is removed from the system and the toluene is returned to the inside of the system (the above is the first stage reaction).

In either method, maleic anhydride is usually used in an amount of 1 to 3 times, preferably 1.2 to 2.0 times the amino group of the aromatic amine resin represented by the above formula (2). do.

In order to reduce the amount of unclosed ring amic acid, water is added to the reaction solution after the maleimidization reaction listed above to separate the resin solution layer and the aqueous layer, and excess maleic acid, maleic anhydride, and aprotic polarity. Since the solvent, catalyst, etc. are dissolved on the aqueous layer side, separate and remove them, and repeat the same operation to thoroughly remove excess maleic acid, maleic anhydride, aprotic polar solvent, and catalyst. .. The catalyst is added again to the maleimide resin solution of the organic layer from which excess maleic acid, maleic anhydride, aprotic polar solvent, and catalyst have been removed, and the dehydration ring closure reaction of the residual amic acid under heated reflux conditions is performed again. A maleic anhydride solution having a low acid value can be obtained (the above is the second stage reaction).

The time of the re-dehydration ring closure reaction is usually 1 to 5 hours, preferably 1 to 3 hours, and the above-mentioned aprotic polar solvent may be added if necessary. After the reaction is completed, the mixture is cooled and washed with water until the water is neutral. After that, water may be removed by azeotropic dehydration under heating and reduced pressure, and then the solvent may be distilled off or another solvent may be added to adjust the resin solution to a desired concentration, or the solvent may be completely retained. It may be removed and taken out as a solid resin.

Next, the curable resin composition of the present invention will be described.
The curable resin composition of the present invention can contain a compound capable of cross-linking with the maleimide resin of the present invention. Examples of the compound include functional groups (or functional groups) capable of cross-linking with a maleimide resin such as an amino group, a cyanate group, a phenolic hydroxyl group, an alcoholic hydroxyl group, an allyl group, a metallicyl group, an acrylic group, a methacrylic group, a vinyl group and a conjugated diene group. The amine compound and the maleimide compound are not particularly limited as long as they have a structure), and therefore, an aromatic amine resin represented by the above formula (2) may be used. Since the maleimide resin can be self-polymerized, it can be used alone. Further, an amine compound other than the aromatic amine resin represented by the formula (2) or a maleimide compound other than the maleimide resin represented by the formula (1) may be used in combination.

The content of the maleimide resin in the curable resin composition of the present invention is preferably 10% by weight or more, more preferably 15% by weight or more, still more preferably 20% by weight. In the above range, the mechanical strength of the cured product tends to be high, the peel strength is high, and the heat resistance tends to be high.

As the amine compound that can be blended in the curable resin composition of the present invention, a conventionally known amine compound can be used. Specific examples of the amine compound include diethylenetriamine, triethylenetetramine, tetraethylenepentamine, m-xylene diamine, trimethylhexamethylenediamine, 2-methylpentamethylenediamine, diethylaminopropylamine, isophoronediamine, and 1,3-bisaminomethyl. Cyclohexane, bis (4-aminocyclohexyl) methane, bis (4-amino-3-methylcyclohexyl) methane, norbornene diamine, 1,2-diaminocyclohexane, diaminodiphenylmethane, metaphenylenediamine, diaminodiphenylsulfone, dicyandiamide, polyoxypropylene Examples thereof include, but are not limited to, diamines, polyoxypropylene triamines, N-aminoethylpiperazines, and aniline / formarin resins. These may be used alone or in combination of two or more.

As the maleimide compound that can be blended in the curable resin composition of the present invention, a conventionally known maleimide compound can be used. Specific examples of the maleimide compound include 4,4'-diphenylmethanebismaleimide, polyphenylmethanemaleimide, m-phenylenebismaleimide, 2,2'-bis [4- (4-maleimidephenoxy) phenyl] propane, 3,3. '-Dimethyl-5,5'-diethyl-4,4'-diphenylmethanebismaleimide, 4-methyl-1,3-phenylene bismaleimide, 4,4'-diphenylether bismaleimide, 4,4'-diphenylsulphon bismaleimide , 1,3-Bis (3-maleimidephenoxy) benzene, 1,3-bis (4-maleimidephenoxy) benzene and the like, but are not limited thereto. These may be used alone or in combination of two or more. The blending amount of the maleimide compound is preferably in the range of 5 times or less, more preferably 2 times or less of the maleimide resin of the present invention in terms of weight ratio.

As the cyanate ester compound that can be blended in the curable resin composition of the present invention, a conventionally known cyanate ester compound can be used. Specific examples of cyanate ester compounds include polycondensates of phenols and various aldehydes, polymers of phenols and various diene compounds, polycondensates of phenols and ketones, and polycondensations of bisphenols and various aldehydes. Examples thereof include cyanate ester compounds obtained by reacting a substance with cyanogen halide, but the present invention is not limited thereto. These may be used alone or in combination of two or more.
Examples of the phenols include phenol, alkyl-substituted phenol, aromatic-substituted phenol, naphthol, alkyl-substituted naphthol, dihydroxybenzene, alkyl-substituted dihydroxybenzene, and dihydroxynaphthalene.
Examples of the various aldehydes include formaldehyde, acetaldehyde, alkylaldehyde, benzaldehyde, alkyl-substituted benzaldehyde, hydroxybenzaldehyde, naphthoaldehyde, glutaraldehyde, phthalaldehyde, crotonaldehyde, and cinnamaldehyde.
Examples of the various diene compounds include dicyclopentadiene, terpenes, vinylcyclohexene, norbornadiene, vinylnorbornene, tetrahydroindene, divinylbenzene, divinylbiphenyl, diisopropenylbiphenyl, butadiene, and isoprene.
Examples of the ketones include acetone, methyl ethyl ketone, methyl isobutyl ketone, acetophenone, benzophenone and the like.
Further, the cyanate ester compound whose synthesis method is described in JP-A-2005-264154 is particularly preferable as a cyanate ester compound because it is excellent in low hygroscopicity, flame retardancy and dielectric properties.

In the curable resin composition of the present invention, an epoxy resin can be further blended. As the epoxy resin that can be blended, any conventionally known epoxy resin can be used. Specific examples of the epoxy resin include a polycondensate of phenols and various aldehydes, a polymer of phenols and various diene compounds, a polycondensate of phenols and ketones, and a polycondensate of bisphenols and various aldehydes. Alicyclic epoxy represented by glycidyl ether-based epoxy resin obtained by glycidylizing alcohols, 4-vinyl-1-cyclohexene epoxide, 3,4-epoxycyclohexylmethyl-3,4'-epoxycyclohexanecarboxylate, etc. Examples thereof include, but are not limited to, resins, glycidylamine-based epoxy resins typified by tetraglycidyldiaminodiphenylmethane (TGDDM) and triglycidyl-p-aminophenol, and glycidyl ester-based epoxy resins. These may be used alone or in combination of two or more.
Further, the epoxy resin obtained by subjecting a phenol aralkyl resin obtained by a condensation reaction of phenols with a bishalogenomethyl aralkyl derivative or an aralkyl alcohol derivative as a raw material and reacting with epichlorohydrin by dehydrolysis is a low moisture absorption and flame retardant. It is particularly preferable as an epoxy resin because it has excellent properties and dielectric properties.

When the epoxy resin is blended, the blending amount is not particularly limited, but is preferably 0.1 to 10 times, more preferably 0.2 to 4 times, the weight ratio of the maleimide resin. If the blending amount of the epoxy resin is 0.1 times or less of that of the maleimide resin, the cured product may become brittle, and if it is 10 times or more, the dielectric properties may deteriorate.

In the curable resin composition of the present invention, a compound having a phenol resin can be further blended.
As the phenol resin that can be blended, any conventionally known phenol resin can be used. Specific examples of the phenol resin include bisphenols (bisphenol A, bisphenol F, bisphenol S, biphenol, bisphenol AD, etc.) and phenols (phenol, alkyl-substituted phenol, aromatic-substituted phenol, naphthol, alkyl-substituted naphthol, dihydroxybenzene, alkyl. Polycondensate of substituted dihydroxybenzene, dihydroxynaphthalene, etc.) and various aldehydes (formaldehyde, acetaldehyde, alkylaldehyde, benzaldehyde, alkyl substituted benzaldehyde, hydroxybenzaldehyde, naphthoaldehyde, glutaaldehyde, phthalaldehyde, crotonaldehyde, cinnamaldehyde, etc.), Polymers of phenols and various diene compounds (dicyclopentadiene, terpenes, vinylcyclohexene, norbornadiene, vinylnorbornene, tetrahydroinden, divinylbenzene, divinylbiphenyl, diisopropenylbiphenyl, butadiene, isoprene, etc.), phenols and ketones. Polycondensates with other species (acetone, methyl ethyl ketone, methyl isobutyl ketone, acetophenone, benzophenone, etc.), phenols and aromatic dimethanols (benzenedimethanol, α, α, α', α'-benzenedimethanol, biphenyldi. Polycondensation with methanol, α, α, α', α'-biphenyldimethanol, etc., and polycondensation of phenols with aromatic dichloromethyls (α, α'-dichloroxylene, bischloromethylbiphenyl, etc.) Examples include, but are not limited to, bisphenols and polycondensates of various aldehydes, and modified products thereof. These may be used alone or in combination of two or more.
Further, the phenol aralkyl resin obtained by subjecting phenols to a condensation reaction with the above-mentioned bishalogenomethyl aralkyl derivative or aralkyl alcohol derivative is particularly preferable as a phenol resin because it is excellent in low moisture absorption, flame retardancy and dielectric properties. ..
Further, when the above-mentioned phenol resin has an allyl group or a metalyl group, the reactivity with the maleimide group is better than that of the hydroxyl group, so that the curing rate is increased and the cross-linking points are increased, so that the strength and heat resistance are increased. Therefore, it is preferable.
Further, an allyl ether body obtained by allylating the hydroxyl group of the above-mentioned phenol resin or a metallyl ether body obtained by metallizing the hydroxyl group can also be blended, and the water absorption is lowered because the hydroxyl group is etherified.

In the curable resin composition of the present invention, a compound having an acid anhydride group can be further blended.
As the compound having an acid anhydride group that can be blended, any conventionally known compound can be used. Specific examples of the compound having an acid anhydride group include 1,2,3,4-butanetetracarboxylic acid dianhydride, 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride, 1,2,3. 4-Cyclopentanetetracarboxylic acid dianhydride, 1,2,4,5-cyclohexanetetracarboxylic acid dianhydride, pyromellitic acid anhydride, 5- (2,5-dioxotetrahydrofuryl) -3-methyl- 3-Cyclohexene-1,2-dicarboxylic acid anhydride, 4- (2,5-dioxotetratetra-3-yl) -1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic acid anhydride, etc. Can be mentioned.
The compound having an acid anhydride group can be used alone or in combination of two or more. Further, as a result of the reaction between the acid anhydride group and the amine, it becomes an amic acid, but when it is further heated at 200 ° C. to 300 ° C., it becomes an imide structure by a dehydration reaction, and becomes a material having very excellent heat resistance.

A catalyst for curing (curing accelerator) can be added to the curable resin composition of the present invention, if necessary. For example, imidazoles such as 2-methylimidazole, 2-ethyl imidazole, 2-phenyl imidazole, 2-ethyl-4-methyl imidazole, 2-undecyl imidazole, 1-cyanoethyl-2-ethyl-4-methyl imidazole, triethylamine, Amines such as triethylenediamine, 2- (dimethylaminomethyl) phenol, 1,8-diaza-bicyclo (5,4,0) undecene-7, tris (dimethylaminomethyl) phenol, benzyldimethylamine, triphenylphosphine, Hosphins such as tributylphosphine and trioctylphosphine, organic metal salts such as tin octylate, zinc octylate, dibutyltin dimaleate, zinc naphthenate, cobalt naphthenate, tin oleate, zinc chloride, aluminum chloride, tin chloride, etc. Metal chlorides, organic peroxides such as di-tert-butyl peroxide and dicumyl peroxide, azo compounds such as azobisisobutyronitrile and azobisdimethylvaleronitrile, ores such as hydrochloric acid, sulfuric acid and phosphoric acid. Examples thereof include acids, Lewis acids such as boron trifluoride, and salts such as sodium carbonate and lithium chloride. The blending amount of the curing catalyst is preferably in the range of 10 parts by weight or less, more preferably 5 parts by weight or less, based on 100 parts by weight of the total of the curable resin composition.

An organic solvent can be added to the curable resin composition of the present invention to obtain a varnish-like composition (hereinafter, simply referred to as varnish). Examples of the solvent used include γ-butyrolactones, N-methylpyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, N, N-dimethylimidazolidinone and other amide solvents, tetramethylene sulfone and the like. Ethereal solvents such as sulfones, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, propylene glycol, propylene glycol monomethyl ether, propylene glycol monomethyl ether monoacetate, propylene glycol monobutyl ether, and ketones such as methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, and cyclohexanone. Examples include solvents, aromatic solvents such as toluene and xylene. The solvent is used in a range in which the solid content concentration of the obtained varnish excluding the solvent is usually 10 to 80% by weight, preferably 20 to 70% by weight.

Further, a known additive can be added to the curable resin composition of the present invention, if necessary. Specific examples of the additives that can be used include curing agents for epoxy resins, polybutadienes and modified products thereof, modified products of acrylonitrile copolymers, polyphenylene ethers, polystyrenes, polyethylenes, polyimides, fluororesins, maleimide compounds, and cyanate ester compounds. , Silicone gel, silicone oil, and inorganic fillers such as silica, alumina, calcium carbonate, quartz powder, aluminum powder, graphite, talc, clay, iron oxide, titanium oxide, aluminum nitride, asbestos, mica, glass powder, silane cups, Examples thereof include surface treatment agents for fillers such as ring agents, mold release agents, and colorants such as carbon black, phthalocyanine blue, and phthalocyanine green. The blending amount of these additives is preferably in the range of 1,000 parts by weight or less, more preferably 700 parts by weight or less, based on 100 parts by weight of the curable resin composition.

The method for preparing the curable resin composition of the present invention is not particularly limited, but each component may be uniformly mixed or prepolymerized. For example, the maleimide resin and the cyanate ester compound are prepolymerized by heating in the presence or absence of a catalyst and in the presence or absence of a solvent. Similarly, the maleimide resin of the present invention and, if necessary, an epoxy resin, an amine compound, a maleimide-based compound, a cyanate ester compound, a phenol resin, an acid anhydride compound and other additives may be added to form a prepolymer. For mixing or prepolymerizing each component, for example, an extruder, kneader, roll or the like is used in the absence of a solvent, and a reaction kettle with a stirrer is used in the presence of a solvent.

A prepreg can be obtained by heating and melting the curable resin composition of the present invention to reduce the viscosity and impregnating it with reinforcing fibers such as glass fiber, carbon fiber, polyester fiber, polyamide fiber and alumina fiber.
Further, the prepreg can also be obtained by impregnating the reinforcing fibers with the varnish and heating and drying the varnish.
The above prepreg is cut into a desired shape, laminated with copper foil or the like if necessary, and then the curable resin composition is heat-cured while applying pressure to the laminate by a press molding method, an autoclave molding method, a sheet winding molding method, or the like. This makes it possible to obtain a laminated board for electrical and electronic use (printed wiring board) and a carbon fiber reinforced material.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. In the text, "part" and "%" represent "parts by weight" and "% by weight", respectively. The softening point and the melt viscosity were measured by the following methods.

[Analysis method]
・ Melting point: Measured by DSC ・ GPC (Gel Permeation Chromatography) Analysis Manufacturer: Waters
Column: Guard column SHODEX GPC KF-601 (2), KF-602, KF-602.5, KF-603
Flow rate: 0.5 ml / min.
Column temperature: 25 ° C
Solvent used: THF (tetrahydrofuran)
Detector: RI (Differential Refractometer)

[Example 1]
73.6 parts of maleic anhydride and 100 parts of toluene, 10 parts of N-methyl-2-pyrrolidone, 1.2 parts of methanesulfonic acid in a flask equipped with a thermometer, a cooling tube, a Dean-Stark azeotropic distillation trap, and a stirrer. It was charged and heated to reflux. Next, a resin solution prepared by dissolving 63.6 parts of the aromatic amine resin (A1) (Kayahard AA manufactured by Nippon Kayaku Co., Ltd.) represented by the formula (1) in 50 parts of toluene was added while maintaining a reflux state. It was dropped over 2 hours. During this period, the condensed water and toluene that azeotrope under reflux conditions were cooled and separated in the Dean-Stark azeotropic distillation trap, then the toluene, which is an organic layer, was returned to the inside of the system, and the water was discharged to the outside of the system. After the completion of the dropping of the resin solution, the reaction was carried out for 4 hours while maintaining the reflux state and performing the dehydration operation.
After completion of the reaction, washing with water was repeated 3 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 of 70 ° C. or lower. Then, when toluene was gradually distilled off under heating and reduced pressure of 70 ° C. or lower, crystals were precipitated. The crystals were filtered off by filtration and dried under heating and reduced pressure to obtain 68 parts of a maleimide resin (M1) represented by the formula (1). The melting point of the obtained maleimide resin (M1) was 212 ° C. By GPC analysis (RI), n = 1 bismaleimide in formula (1) was 93%. The GPC chart of the maleimide resin (M1) is shown in FIG.

[Example 2]
The reaction was carried out in the same manner as in Example 1, and after the reaction was completed, washing with water was repeated 3 times to remove methanesulfonic acid and excess maleic anhydride. Then, toluene was distilled off from the oil layer with a rotary evaporator to obtain 101 parts of a resin-like maleimide resin (M2) represented by the formula (1). By GPC analysis (RI), n = 1 bismaleimide in formula (1) was 76%.

[Example 3, Comparative Example 1]
Using the maleimide resin (M1) obtained in Example 1 and the maleimide resin (M3) of aniline novolac (BMI-2300 manufactured by Daiwa Kasei Kogyo Co., Ltd.), various epoxy resins, curing agents, and curing accelerators are listed in Table 1. (Part by weight), kneaded with a mixing roll, made into a tablet, and then a resin molded product was prepared by transfer molding and cured at 200 ° C. for 2 hours. Table 1 shows the results of measuring the physical characteristics of the cured product thus obtained for the following items.

[evaluation]
-Td5 (5% thermogravimetric reduction temperature): The obtained cured product was crushed into powder, and the thermal decomposition temperature was measured by TG-DTA using a sample of 100 mesh pass and 200 mesh on. The temperature at which the weight was reduced by 5% as measured at a sample amount of 10 mg, a heating rate of 10 ° C./min, and an air amount of 200 ml / hr.
Water absorption rate: Weight increase rate (%) before and after boiling a disk-shaped test piece having a diameter of 5 cm and a thickness of 4 mm in water at 100 ° C. for 24 hours.
Hygroscopicity: Weight gain after 24 hours at 85 ° C / 85% and 121 ° C / 100%. The test piece is a disk with a diameter of 50 mm and a thickness of 4 mm.
Permittivity and dielectric loss tangent: Measured at 1 GHz according to K6991 (Cavity Resonator Agilent Technologies).

E1: NC-3000-L (Nippon Kayaku Epoxy Equivalent 270g / eq)
P1: Kayahard GPH-65 (Nippon Kayaku Co., Ltd. hydroxyl group equivalent 200 g / eq)
2E4MZ: 2-Ethyl-4-methylimidazole (manufactured by Tokyo Chemical Industry Co., Ltd.)

From the results in Table 1, Example 3 showed better results in many properties such as heat resistance, low hygroscopicity, and dielectric properties as compared with Comparative Example 1.

The maleimide resin of the present invention has high workability due to its excellent solution stability, and has excellent heat resistance, low moisture absorption, and dielectric properties. Therefore, it is an electrical / electronic component such as a semiconductor encapsulant, a printed wiring board, and a build-up laminated board. It is suitably used for lightweight and high-strength materials such as carbon fiber reinforced plastic and glass fiber reinforced plastic.

Claims (7)

Maleimide resin represented by the following formula (1).

(In equation (1), n is the average value of the number of repetitions, and 1 <n <5.) The maleimide resin according to claim 1, wherein n in the formula (1) is 1 <n <3. The maleimide resin according to claim 1 or 2, wherein the content of bismaleimide represented by n = 1 in the formula (1) is 98% or less. The maleimide resin according to any one of claims 1 to 3, which is obtained by reacting an amine resin represented by the following formula (2) with maleic acid or maleic anhydride.

(In equation (2), n is the average value of the number of repetitions, and 1 <n <5.) A curable resin composition containing the maleimide resin according to any one of claims 1 to 4. A cured product obtained by curing the curable resin composition according to claim 5. Amine resin represented by the following formula (2).

(In equation (2), n is the average value of the number of repetitions, and 1 <n <5.)

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