Thermosetting resin and cured product thereof

Abstract

The present application provides a thermosetting resin which can obtain a cured product having excellent dielectric properties. The thermosetting resin of the embodiment has a repeating unit corresponding to a monovinyl aromatic compound and a repeating unit corresponding to a divinyl aromatic compound, the number average molecular weight Mn and the weight average molecular weight Mw are each 10,000 or more and 100,000 or less, and the content of the repeating unit corresponding to the divinyl aromatic compound is 5 to 20 mol%.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to a thermosetting resin and a cured product thereof, and a thermosetting composition containing the thermosetting resin. BACKGROUND

[0002] In recent years, miniaturization and high performance of electronic devices are progressing, and the required properties of various materials used therewith are increasing. For example, a printed board material capable of coping with high frequency communication with low dielectric loss tangent is required.

[0003] In Patent Literature 1, as a thermosetting resin material excellent in heat resistance and electrical properties, a vinyl compound in which the terminals of a di-functional polyphenylene ether (PPE)-based oligomer are converted into vinyl groups is disclosed.

[0004] In Patent Literature 2, as a curable resin composition excellent in dielectric properties, long-term environmental reliability, heat resistance, and adhesiveness, a curable resin composition containing a multi-functional vinyl aromatic copolymer containing 2 to 95 mol% of a repeating unit derived from a divinyl aromatic compound and 5 to 98 mol% of a repeating unit derived from a monovinyl aromatic compound; a thermoplastic resin; and a thermosetting crosslinking agent is disclosed.

[0005] PRIOR ART DOCUMENTS

[0006] PATENT LITERATURE

[0007] Patent Literature 1: Japanese Patent Application Laid-Open No. 2004-067727

[0008] Patent Literature 2: Japanese Patent Application Laid-Open No. 2019-178310 SUMMARY

[0009] PROBLEMS TO BE SOLVED BY THE INVENTION

[0010] In Patent Literature 1, a PPE-based resin having low dielectric loss tangent and good reactivity is used, but the dielectric loss tangent is not sufficient. In Patent Literature 2, a styrene-based thermosetting resin is disclosed, but the number average molecular weight Mn of the specifically disclosed thermosetting resin is low, and in addition, the content of the repeating unit derived from a divinyl aromatic compound is high, so it is found that the dielectric loss tangent is not sufficient, and in addition, cracks caused by curing shrinkage occur, and moldability deteriorates.

[0011] Embodiments of the present application aim to provide a thermosetting resin capable of suppressing deterioration of moldability and obtaining a cured product having excellent dielectric properties.

[0012] MEANS FOR SOLVING THE PROBLEMS

[0013] The present invention includes the embodiments shown below.

[0014] [1] A thermosetting resin having repeating units corresponding to monovinyl aromatic compounds and repeating units corresponding to divinyl aromatic compounds, having a number-average molecular weight Mn and a weight-average molecular weight Mw of 10,000 or more and 100,000 or less, wherein the content of the repeating units corresponding to the divinyl aromatic compounds is 5 mol% to 20 mol%.

[0015] [2] The thermosetting resin as described in [1] is a linear vinyl copolymer.

[0016] [3] The thermosetting resin as described in [1] or [2] is obtained by reacting a copolymer of vinyl benzyl phosphonium halide and monovinyl aromatic compound with formaldehyde.

[0017] [4] A cured product formed by curing a thermosetting resin as described in any one of [1] to [3].

[0018] [5] A thermosetting composition comprising any one of [1] to [3] thermosetting resins.

[0019] [6] The thermosetting composition as described in [5] is a printed substrate material.

[0020] Invention Effects

[0021] If the resin used in the embodiments of the present invention is a thermosetting resin, then the deterioration of formability can be suppressed, and a cured product with excellent dielectric properties can be obtained. Detailed Implementation

[0022] The thermosetting resin of this embodiment is a vinyl copolymer having repeating units corresponding to monovinyl aromatic compounds and repeating units corresponding to divinyl aromatic compounds, with a number-average molecular weight (Mn) and a weight-average molecular weight (Mw) of 10,000 or more and 100,000 or less, and the content of repeating units corresponding to the aforementioned divinyl aromatic compounds is 5 mol% to 20 mol%. According to this embodiment, the dielectric loss tangent of the cured product can be reduced. In addition, since the increase in crosslinking density can be suppressed, the generation of cracks caused by curing shrinkage can be suppressed, thus suppressing the deterioration of formability.

[0023] The repeating unit corresponding to the monovinyl aromatic compound is a structural unit of a vinyl copolymer, and is a structural unit having a structure formed by addition polymerization of the monovinyl aromatic compound as a monomer. If it has a structure corresponding to the monovinyl aromatic compound, it is not necessarily limited to being polymerized using the monovinyl aromatic compound, but can also be a structure corresponding to the monovinyl aromatic compound prepared by further reaction after polymerization.

[0024] As the repeating unit corresponding to the monovinyl aromatic compound, a repeating unit having a structure obtained by making the vinyl group of the monovinyl aromatic compound a single bond by addition polymerization represented by the following general formula (1) can be exemplified.

[0025] [Chem. 1]

[0026]

[0027] In formula (1), R 1 represents a monovalent aromatic hydrocarbon group having 6 to 30 carbon atoms, and more specifically, a monovalent aromatic hydrocarbon group having 6 to 30 carbon atoms selected from the group consisting of a phenyl group which can have a substituent, a biphenyl group which can have a substituent, a naphthyl group which can have a substituent, and a terphenyl group which can have a substituent.

[0028] As the monovinyl aromatic compound forming such a repeating unit, it is only necessary to be an aromatic compound having one vinyl group, and for example, a vinyl aromatic compound such as styrene, vinyl naphthalene, vinyl biphenyl, an alkylstyrene (for example, o-methylstyrene, m-methylstyrene, p-methylstyrene, o-ethylstyrene, m-ethylstyrene, p-ethylstyrene), a dialkylstyrene (for example, 3,5-dimethylstyrene, 2,5-dimethylstyrene, 2,5-diethylstyrene), an alkylvinyl biphenyl (for example, ethylvinyl biphenyl), an alkylvinyl naphthalene (for example, ethylvinyl naphthalene), and the like, a core alkyl-substituted vinyl aromatic compound, and the like can be exemplified, and any one of these or two or more of these can be used in combination. Among these, styrene is preferred.

[0029] The repeating unit corresponding to the divinyl aromatic compound is a structural unit of a vinyl copolymer, and is a structural unit having a structure formed by addition polymerization using the divinyl aromatic compound as a monomer, and if it is a structure corresponding to the divinyl aromatic compound, it is not necessarily limited to one formed by polymerization using the divinyl aromatic compound, but can also be one formed by further reacting after polymerization to form a structure corresponding to the divinyl aromatic compound.

[0030] As the repeating unit corresponding to the divinyl aromatic compound, a repeating unit having a structure obtained by making one vinyl group of the divinyl aromatic compound a single bond by addition polymerization represented by the following general formula (2) can be exemplified.

[0031] [Chem. 2]

[0032]

[0033] In formula (2), R 2a divalent aromatic hydrocarbon group having 6 to 30 carbon atoms, more specifically, a divalent aromatic hydrocarbon group having 6 to 30 carbon atoms selected from the group consisting of a phenylene group which can have a substituent, a biphenylene group which can have a substituent, a naphthylene group which can have a substituent, and a terphenylene group which can have a substituent.

[0034] As the divinyl aromatic compound forming such a repeating unit, it is only necessary to be an aromatic compound having two vinyl groups, and for example, divinylbenzene (including each positional isomer or a mixture thereof), divinyl naphthalene (including each positional isomer or a mixture thereof), divinyl biphenyl (including each positional isomer or a mixture thereof) can be exemplified, and any one of these or two or more of these in combination can be used. Among these, divinylbenzene (meta, para, or a positional isomer mixture thereof) is preferred.

[0035] In the thermosetting resin of the present embodiment, the arrangement order of the repeating unit corresponding to the monovinyl aromatic compound and the repeating unit corresponding to the divinyl aromatic compound can be regularly arranged, or can be randomly arranged. A random copolymer in which the arrangement is random is preferred.

[0036] In addition, the thermosetting resin can contain a repeating unit corresponding to another monomer in addition to the repeating unit corresponding to the monovinyl aromatic compound and the repeating unit corresponding to the divinyl aromatic compound, within a range not impairing the effects thereof. As such another monomer, for example, a trivinyl aromatic compound, a trivinyl aliphatic compound, a divinyl aliphatic compound, a monovinyl aliphatic compound, and the like can be exemplified.

[0037] The number average molecular weight Mn of the thermosetting resin of the present embodiment is 10,000 or more and 100,000 or less. By making the number average molecular weight Mn 10,000 or more, it is possible to reduce the concentration of terminal groups derived from the polymerization initiator and improve the dielectric properties. In addition, by making the number average molecular weight Mn 100,000 or less, it is possible to suppress the increase in viscosity when the thermosetting resin is made into a solution and improve the handleability. The number average molecular weight Mn is preferably 15,000 or more, more preferably 20,000 or more, and is preferably 50,000 or less, more preferably 40,000 or less, and further preferably 30,000 or less.

[0038] The weight average molecular weight Mw of the thermosetting resin of the present embodiment is 10,000 or more and 100,000 or less. By making the weight average molecular weight Mw 10,000 or more, the concentration of terminal groups derived from the polymerization initiator can be reduced and the dielectric properties can be improved. Also, by making the weight average molecular weight Mw 100,000 or less, the high viscosity when the thermosetting resin is made into a solution can be suppressed and the handleability can be improved. The weight average molecular weight Mw is preferably 20,000 or more, more preferably 25,000 or more, further preferably 30,000 or more, and still further preferably 40,000 or more, and is preferably 70,000 or less, more preferably 60,000 or less, and further preferably 50,000 or less.

[0039] In the thermosetting resin of the present embodiment, the ratio of the weight average molecular weight Mw to the number average molecular weight Mn, that is, the molecular weight distribution Mw / Mn is not particularly limited and is preferably 4.0 or less, more preferably 1.2 to 3.0, and further preferably 1.5 to 1.9.

[0040] Here, the number average molecular weight Mn and the weight average molecular weight Mw are the number average molecular weight and the weight average molecular weight in terms of polystyrene, which are measured by gel permeation chromatography (GPC).

[0041] In the thermosetting resin of the present embodiment, the content of the repeating unit corresponding to the divinyl aromatic compound is 5 mol% to 20 mol%. That is, when all of the repeating units constituting the vinyl copolymer are taken as 100 mol%, the content of the repeating unit corresponding to the divinyl aromatic compound is 5 mol% or more and 20 mol% or less. By making the content of the repeating unit corresponding to the divinyl aromatic compound 5 mol% or more, the thermosetting can be improved and a good cured product can be obtained, and also, by making the content 20 mol% or less, the generation of cracks due to curing shrinkage can be suppressed and the moldability can be improved. The content of the repeating unit corresponding to the divinyl aromatic compound is preferably 7 mol% or more and also preferably 15 mol% or less.

[0042] In the thermosetting resin of the present embodiment, when all of the repeating units constituting the vinyl copolymer are taken as 100 mol%, the content of the repeating unit corresponding to the monovinyl aromatic compound is preferably 80 mol% to 95 mol%. The content of the repeating unit corresponding to the monovinyl aromatic compound is preferably 85 mol% or more and also preferably 93 mol% or less.

[0043] The method for producing the thermosetting resin of the present embodiment is not particularly limited and, for example, it can be obtained by polymerizing monomers containing a monovinyl aromatic compound and a divinyl aromatic compound in the presence of a polymerization initiator.

[0044] As a preferable production method, a method in which a vinylbenzylphosphonium halide is copolymerized with a monovinyl aromatic compound, and the obtained copolymer is reacted with formaldehyde, thereby obtaining a thermosetting resin, can be exemplified. Based on this, a linear vinyl copolymer having no branch can be synthesized as a thermosetting resin, and thus the concentration of terminal groups derived from a polymerization initiator can be reduced and the dielectric properties can be improved. In addition, the moldability is improved by generating entanglement of molecular chains using the linear structure.

[0045] As the phosphonium group in the above-described vinylbenzylphosphonium halide, a quaternary phosphonium group such as a trialkylphosphonium group, a triarylphosphonium group, a triarylalkylphosphonium group, and the like can be exemplified. In addition, as the halogen forming a salt with the phosphonium group, chlorine, bromine, and the like can be exemplified.

[0046] As the method of copolymerizing the vinylbenzylphosphonium halide with the monovinyl aromatic compound, a publicly known vinyl polymerization method can be used, and there is no particular limitation. For example, copolymerization is performed using a radical polymerization initiator such as an azo compound such as azobisisobutyronitrile (AIBN), an organic peroxide such as benzoyl peroxide, and the like, and thus a copolymer having a repeating unit derived from the vinylbenzylphosphonium halide and a repeating unit derived from the monovinyl aromatic compound is obtained.

[0047] Further, as the method of reacting the obtained copolymer with formaldehyde, a publicly known Wittig reaction can be used, and the copolymer is reacted with formaldehyde by being treated with a base, thereby causing the phosphonium group to fall off and introducing a vinyl group.

[0048] If this production method is used, in the copolymerization step, the vinylbenzylphosphonium halide is monovinyl, and thus a copolymer having no branch is obtained, and a vinyl group is introduced into the repeating unit derived from the vinylbenzylphosphonium halide after the copolymerization, and thus a linear vinyl copolymer having a repeating unit corresponding to a divinyl aromatic compound and having no branch can be obtained.

[0049] The thermosetting composition of the present embodiment contains the above-described thermosetting resin. As for the content of the thermosetting resin in the thermosetting composition, there is no particular limitation as long as the composition has a property of being cured by heat. For example, it can be 1 to 99 mass% or 10 to 95 mass% with respect to 100 mass% of the solid content of the thermosetting composition (in the case of containing an organic solvent described later, the amount excluding the organic solvent, and in the case of not containing an organic solvent, the amount of the entire composition).

[0050] In the thermosetting composition, in addition to the above-mentioned thermosetting resin, for example, other thermosetting resins (thermosetting crosslinking agents), thermoplastic resins, fillers, flame retardants, curing accelerators, polymerization initiators, defoaming agents, heat stabilizers, antistatic agents, ultraviolet absorbers, colorants such as dyes or pigments, lubricants, dispersants, and the like can be contained.

[0051] In addition, the thermosetting composition can contain an organic solvent to adjust the viscosity thereof, and the thermosetting composition can be a solution containing the above-mentioned thermosetting resin. As the organic solvent, those which can dissolve the above-mentioned thermosetting resin can be used, and for example, acetone, methyl ethyl ketone, methyl isobutyl ketone, and the like can be exemplified as ketones, ethyl acetate, propyl acetate, butyl acetate, and the like can be exemplified as esters, dimethylacetamide, dimethylformamide, and the like can be exemplified as amides, toluene, xylene, and the like can be exemplified as aromatic hydrocarbons, and the like can be used, and any one of these or two or more kinds thereof can be used in combination.

[0052] The thermosetting resin or the thermosetting composition of the present embodiment can be crosslinked by polymerization because it has a vinyl group in the molecular chain of the vinyl copolymer, and a cured product can be obtained by thermal curing. Because the dielectric loss tangent of the cured product is low, the dielectric properties are excellent, and therefore, for example, it can be used for electronic material applications such as printed board materials, semiconductor sealing materials, and the like.

[0053] As the printed board material, rigid printed board materials such as single-sided boards, double-sided boards, multilayer boards, build-up boards, and the like, or flexible printed board materials in the form of films or sheets, and the like can be exemplified. In addition, because the dielectric loss tangent is low, it can be appropriately used as a high-frequency board material used in high-frequency communication equipment.

[0054] [Example]

[0055] Hereinafter, the present application will be more specifically described using examples, but the present application is not limited to the following examples.

[0056] <Measurement, Evaluation Method>

[0057] [Molar ratio of styrene / divinylbenzene, divinylbenzene ratio]

[0058] Regarding the products obtained in Examples 1 to 2 and Comparative Examples 1 to 3, they were dissolved in deuterated chloroform, and the molar ratio of the repeating units corresponding to styrene and the repeating units corresponding to divinylbenzene were found using a nuclear magnetic resonance device (manufactured by JEOL). 1 H-NMR measurement, the molar ratio of the repeating units corresponding to styrene and the repeating units corresponding to divinylbenzene were found, and the content of the repeating units corresponding to styrene (styrene ratio) and the content of the repeating units corresponding to divinylbenzene (divinylbenzene ratio) were calculated with respect to 100 mol% of all the repeating units.

[0059] [Number average molecular weight, weight average molecular weight]

[0060] The products obtained in Examples 1 to 2 and Comparative Examples 1 to 4 were dissolved in tetrahydrofuran, and the number average molecular weight Mn and the weight average molecular weight Mw in terms of polystyrene were measured by gel permeation chromatography (GPC) (Prominence, Shimadzu Corporation) using four columns (Shodex GPC columns KF-601, KF-602, KF-603, KF-604, manufactured by Showa Denko) connected in series with polystyrene-based gel as a filler. The column oven temperature was set to 40°C, and the THF flow rate was set to 0.6 mL / min, and a differential refractive index detector (Shodex RI-504, manufactured by Showa Denko) was used.

[0061] [Dielectric constant, dielectric loss tangent]

[0062] The products obtained in Examples 1 to 2 and Comparative Examples 1 to 4 were used as samples. Using a test single-action compression molding machine (manufactured by Yasuda Seiki Mfg. Co., Ltd.), 1.5 g of the sample was pressed for 15 minutes at a pressure of 10 Pa and a temperature of 220°C to produce a flat plate of 30 mm x 30 mm x 1 mm in thickness. The obtained flat plate was cut to produce a test piece of 2 mm in width, 1 mm in thickness, and 30 mm in length, and a hollow resonator method dielectric constant measuring device (manufactured by KEYSIGHT) was used to measure the dielectric constant and the dielectric loss tangent at 10 GHz.

[0063] [Thermosetting]

[0064] The products obtained in Examples 1 to 2 and Comparative Examples 1 to 4 were used as samples, and a differential scanning calorimeter (manufactured by Rigaku) was used to heat the samples at a rate of 10°C / min from room temperature to 350°C. A sample having a heat generation of 40 J / g or more at the heat generation peak was regarded as “◎” (good thermosetting), a sample having a heat generation of 20 J / g to 40 J / g was regarded as “O”, and a sample having a heat generation of less than 20 J / g was regarded as “X” (poor thermosetting).

[0065] [Formability]

[0066] The products obtained in Examples 1 to 2 and Comparative Examples 1 to 4 were used as samples, and a test single-action compression molding machine (manufactured by Yasuda Seiki Mfg. Co., Ltd.) was used to press 7.0 g of the sample at a pressure of 10 Pa and a temperature of 220°C for 10 minutes. A sample that produced a self-supporting plate of 110 mm x 60 mm x 1 mm in thickness was regarded as “O” (good formability), and a sample that could not produce a self-supporting plate due to breakage of the cured product or the like was regarded as “X” (poor formability).

[0067] (Synthesis Example 1) Synthesis of Compound 1: Triphenylvinylbenzylphosphonium chloride

[0068] Vinylbenzyl chloride (trade name: CMS-14, manufactured by AGC Seimi Chemical Co., Ltd.) 1.5 moles (228.9 g), triphenylphosphine 1.8 moles (472.1 g), and dimethylformamide 622.4 g were charged into a 2.0-L reactor, and reacted at 70°C for 3 hours under nitrogen to precipitate a white solid. After the solid was sufficiently washed with acetone, it was dried under reduced pressure at 92°C to recover 490 g of Compound 1.

[0069] (Synthetic Example 2) Synthesis of Copolymer A

[0070] Styrene 552.12 g, Compound 1 169.2 g, azobisisobutyronitrile 3.27 g, and dimethylformamide 1682.68 g were charged into a 3.0-L reactor, and reacted at 70°C for 9 hours under nitrogen. The reaction solution was concentrated under reduced pressure, dissolved in dichloromethane, and then precipitated in a large excess of isopropanol. Next, the supernatant was decanted, and the residual solid was dried under reduced pressure at 92°C to recover 285.0 g of Copolymer A.

[0071] (Synthetic Example 3) Synthesis of Copolymer B

[0072] Styrene 110 g, Compound 1 62.6 g, azobisisobutyronitrile 0.78 g, and dimethylformamide 258.9 g were charged into a 1.0-L reactor, and reacted at 70°C for 9 hours under nitrogen to obtain Copolymer B as a dimethylformamide solution.

[0073] (Comparative Synthetic Example 1) Synthesis of Copolymer C

[0074] Styrene 1.37 moles (142.7 g), Compound 1 0.051 moles (21.2 g), azobisisobutyronitrile 0.75 g, and dimethylformamide 245.9 g were charged into a 1.0-L reactor, and reacted at 70°C for 9 hours under nitrogen. The reaction solution was concentrated under reduced pressure, dissolved in dichloromethane, and then precipitated in a large excess of isopropanol. Next, the supernatant was decanted, and the residual solid was dried under reduced pressure at 92°C to recover 102.4 g of Copolymer C.

[0075] (Comparative Synthetic Example 2) Synthesis of Copolymer D

[0076] Styrene 0.53 moles (55.2 g), Compound 1 0.041 moles (16.9 g), azobisisobutyronitrile 3.24 g, and dimethylformamide 108.17 g were charged into a 500-mL reactor, and reacted at 70°C for 5 hours under nitrogen to obtain Copolymer D as a dimethylformamide solution.

[0077] (Comparative Synthesis Example 3) Synthesis of Copolymer E

[0078] Styrene 0.48 mole (50.2 g), 0.12 mole (50.0 g) of Compound 1, azobisisobutyronitrile 0.45 g, and dimethylformamide 186.09 g were charged into a 500 mL reactor, and reacted at 68°C for 8.5 hours under nitrogen to obtain Copolymer E as a dimethylformamide solution.

[0079] (Example 1)

[0080] Copolymer A obtained in Synthesis Example 2, 37% formalin 169.83 g, 28% aqueous potassium hydroxide 209.66 g, and tetrahydrofuran 665.0 g were charged into a 3 L reactor, and reacted at room temperature for 4 hours. The reaction solution was reprecipitated in a large excess of methanol, and the solid was removed by filtration, dissolved in dichloromethane, washed with distilled water, and reprecipitated in a large excess of methanol / water = 7 / 3. Next, the solid was removed by filtration, and dried under reduced pressure at 92°C to recover Product 1. Product 1 had Mn of 24700, Mw of 39800, a styrene ratio of 92.1 mole%, and a divinylbenzene ratio of 7.9 mole%.

[0081] (Example 2)

[0082] Copolymer B obtained in Synthesis Example 3, dimethylformamide solution 20 g, 37% formalin 3.8 g, 28% aqueous potassium hydroxide 9.4 g, and dimethylformamide 24 g were charged into a 50 mL reactor, and reacted at room temperature for 1 hour. The precipitated solid was dissolved in dichloromethane, reprecipitated in isopropanol, and the solid was removed by filtration. It was again dissolved in dichloromethane, washed with distilled water, and reprecipitated in methanol / water = 7 / 3. Next, the solid was removed by filtration, and dried under reduced pressure at 92°C to recover Product 2. Product 2 had Mn of 26600, Mw of 48900, a styrene ratio of 85.3 mole%, and a divinylbenzene ratio of 14.7 mole%.

[0083] (Comparative Example 1)

[0084] A solution of 6.00 g of the copolymer C obtained in Comparative Synthesis Example 1, 5.47 g of 37% formalin, 6.00 g of 28% aqueous potassium hydroxide solution, and 150 g of tetrahydrofuran was put into a 500 mL reactor and allowed to react at room temperature for 4 hours. The reaction solution was reprecipitated in methanol, and the solid was removed by filtration, and then dried under reduced pressure at 92°C to recover the product 3. The product 3 had an Mn of 24300, an Mw of 39200, a styrene ratio of 95.7 mol%, and a divinylbenzene ratio of 4.3 mol%.

[0085] (Comparative Example 2)

[0086] A solution of 29.7 g of the copolymer D obtained in Comparative Synthesis Example 2 in dimethylformamide, 6.1 g of 37% formalin, 7.6 g of 28% aqueous potassium hydroxide solution, and 70 g of tetrahydrofuran was put into a 300 mL reactor and allowed to react at room temperature for 2.5 hours. The reaction solution was reprecipitated in methanol, and the solid was removed by filtration, dissolved in dichloromethane, washed with distilled water, and reprecipitated in methanol / water = 7 / 3. Then, the solid was removed by filtration, and dried under reduced pressure at 92°C to recover the product 4. The product 4 had an Mn of 3400, an Mw of 8400, a styrene ratio of 91.9 mol%, and a divinylbenzene ratio of 8.1 mol%.

[0087] (Comparative Example 3)

[0088] A solution of 280.0 g of the copolymer E obtained in Comparative Synthesis Example 3 in dimethylformamide, 48.5 g of 37% formalin, 59.5 g of 28% aqueous potassium hydroxide solution, and 93.8 g of tetrahydrofuran was put into a 1 L reactor and allowed to react at room temperature for 7 hours. The reaction solution was reprecipitated in methanol after adding dichloromethane, and the solid was removed by filtration, dissolved in dichloromethane, washed with distilled water, and reprecipitated in methanol / water = 7 / 3. Then, the solid was removed by filtration, and dried under reduced pressure at 92°C to recover the product 5. The product 5 had an Mn of 24200, an Mw of 43300, a styrene ratio of 75.0 mol%, and a divinylbenzene ratio of 25.0 mol%.

[0089] (Comparative Example 4) Synthesis of a vinylbenzylated polyphenylene ether compound

[0090] A 2L four-necked flask including a temperature regulator, a stirring device, a cooling condenser, a dropping funnel was charged with 158g (0.1 mol) of a reactive low-molecular-weight polyphenylene ether (trade name: Noryl SA-90, manufactured by SABIC Japan LLC), toluene 221g, isopropyl alcohol 94.8g, and a uniform solution was prepared. Subsequently, tetra-n-butylammonium bromide 0.96g, vinylbenzyl chloride (meta body / para body = 50 / 50, trade name: CMSP, manufactured by AGC Chemicals Americas, Inc.) 33.6g (0.22 mol) were added, and the temperature was raised to 75°C. To this, 48% sodium hydroxide aqueous solution 53.3g (0.64 mol) was added dropwise in 1 / 4 amounts each for 30 minutes over 2 hours, and a reaction was performed at 75°C for a total of 8 hours. As a result, the reaction rate was 98% or more. Thereafter, the temperature was cooled to 50°C, toluene 295g, isopropyl alcohol 31.6g, and water 79g were added, and neutralization was performed using 35 mass% hydrochloric acid aqueous solution 66.7g. The reaction solution was left to stand until the two layers were separated, and the lower aqueous layer was removed. Further, isopropyl alcohol 15.8g and water 63.2g were used for five washings. The organic layer was removed at 70°C and 50mmHg until the moisture content was 0.05% or less, and the solution was filtered to obtain a 50% toluene solution of the vinylbenzylated polyphenylene ether compound 345g (yield 95% based on the polyphenylene ether). The solution was reprecipitated in a large excess of methanol, and the solid taken out by filtration was dried under reduced pressure at 92°C. The number average molecular weight of the obtained vinylbenzylated polyphenylene ether compound was 2200, and the weight average molecular weight was 4000.

[0091] The products obtained in Examples 1 to 2 and Comparative Examples 1 to 4 were evaluated for dielectric constant, dielectric loss tangent, thermosetting property, and moldability. The results are shown in Table 1 and Table 2 below.

[0092] [Table 1]

[0093] Example 1 Example 2 Styrene / divinylbenzene molar ratio 11.7 / 1 5.8 / 1 Divinylbenzene ratio (mole %) 7.9 14.7 Number average molecular weight Mn 24700 26600 Weight average molecular weight Mw 39800 48900 Dielectric constant (10 GHz) 2.34 2.30 Dielectric loss tangent (10 GHz) 0.0015 0.0013 Thermosetting ○ ◎ Moldability ○ ○

[0094] [Table 2]

[0095]

[0096] As shown in Table 1, in Comparative Example 1, the di-vinylbenzene ratio was low, and the thermosetting property was insufficient, and a test piece for evaluation of dielectric constant and dielectric loss tangent could not be produced. Therefore, the dielectric constant and dielectric loss tangent were not measured, and the moldability was not evaluated.

[0097] In Comparative Example 2, the number average molecular weight Mn and the weight average molecular weight Mw were small, and therefore the dielectric loss tangent was greatly deteriorated. In addition, since the dielectric loss tangent was poor, the evaluation of moldability was not performed.

[0098] In Comparative Example 3, the divinylbenzene ratio is high, and thus the dielectric loss tangent difference is caused due to the presence of unreacted vinyl groups. In addition, the test piece for evaluation of the dielectric constant and the dielectric loss tangent could be formed, but in the evaluation of the formability in which the size of the test piece is large, the test piece was cracked, and the formability was poor. It is considered that the number of functional groups is large, and thus the formability is decreased due to curing shrinkage.

[0099] On the other hand, in Comparative Example 4 which is a PPE-based thermosetting resin, the dielectric loss tangent is high, and the dielectric properties are poor.

[0100] In contrast, in Example 1 and Example 2 in which the number average molecular weight Mn and the weight average molecular weight Mw are within the prescribed range, and the divinylbenzene ratio is within the prescribed range, even if a thermoplastic resin or a crosslinking agent is not used, a self-supporting test piece can be formed, the formability is excellent, and the dielectric loss tangent is low as compared with the PPE-based thermosetting resin of Comparative Example 4, and the dielectric properties are excellent.

[0101] The above describes several embodiments of the present application, but these embodiments are presented as examples, and are not intended to limit the scope of the application. These embodiments can be implemented in various other ways, and various omissions, substitutions, and modifications can be made within the scope of the gist of the application. These embodiments or omissions, substitutions, and modifications, and the like are included in the scope or gist of the application, and are included in the scope of the application described in the claims and the equivalent thereof.

Claims

1. A thermosetting resin characterized in that, the thermosetting resin is a random copolymer having a repeating unit corresponding to a monovinyl aromatic compound represented by the following general formula (1) and a repeating unit corresponding to a divinyl aromatic compound represented by the following general formula (2), the number average molecular weight Mn and the weight average molecular weight Mw of the thermosetting resin are each 10,000 or more and 100,000 or less, the content of the repeating unit corresponding to the divinyl aromatic compound is 5 to 20 mol%, the thermosetting resin is a linear vinyl copolymer, the thermosetting resin is obtained by reacting a copolymer obtained by copolymerizing a vinylbenzyl phosphonium halide and a monovinyl aromatic compound with formaldehyde, [Chemical Formula 1] In formula (1), R 1 represents a monovalent aromatic hydrocarbon group having 6 to 30 carbon atoms, [Chemical Formula 2] In formula (2), R 2 represents a divalent aromatic hydrocarbon group having 6 to 30 carbon atoms.

2. A cured product characterized in that, the cured product is obtained by curing the thermosetting resin according to claim 1.

3. A thermosetting composition characterized in that, the thermosetting composition comprises the thermosetting resin according to claim 1.

4. The thermosetting composition according to claim 3, wherein, the thermosetting composition is a printed board material.

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