Cyclic olefin ring-opening copolymer, composition for insulating material, and insulating material

Abstract

This copolymer formed by ring-opening copolymerization of a cycloolefin comprises structural units derived from a norbornene compound including a heteroelement-containing hydrocarbon group and structural units derived from a norbornene compound including a hydrocarbon group containing no heteroelement. The copolymer has a content of the structural units derived from a norbornene compound including a heteroelement-containing hydrocarbon group of 0.01-15.00 mol% with respect to all the structural units contained in the copolymer, which are taken as 100 mol%.

Description

[Technical field]

[0001] The present invention relates to a cyclic olefin ring-opening copolymer, an insulating material composition containing the cyclic olefin ring-opening copolymer, and an insulating material containing the insulating material composition. [Background technology]

[0002] It is known that polymers containing units having a norbornene skeleton (hereinafter, sometimes referred to as "norbornene-based polymers") can exhibit various beneficial properties. Taking advantage of such properties, norbornene-based polymers are suitably used in a variety of applications. In recent years, attempts have been made to improve norbornene-based polymers in order to further improve their adaptability to various applications.

[0003] Specifically, for example, Patent Document 1 discloses a norbornene-based crosslinked polymer containing 50% by mass or more of one or more selected from the group consisting of dicyclopentadiene-based monomer units, tetracyclododecene-based monomer units, and tricyclopentadiene-based monomer units, and having a glass transition temperature of 240° C. or higher. Furthermore, for example, Patent Document 2 discloses an addition polymer containing a unit having a norbornene skeleton and a unit having a norbornene skeleton and having a maleimide-containing group. Furthermore, for example, Patent Document 3 discloses an addition polymer and a ring-opening polymer containing at least a unit having a norbornene skeleton containing a radical. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-104934 A [Patent Document 2] International Publication No. 2008 / 070774 [Patent Document 3] JP 2012-197440 A Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, norbornene-based polymers have been attracting attention for use as insulating materials due to their high heat resistance, which is one of their characteristics. In order to be used as insulating materials, the norbornene-based polymer must have a high dielectric breakdown voltage. However, the above-mentioned conventional compositions of norbornene-based polymers have not been able to sufficiently increase the dielectric breakdown voltage.

[0006] Therefore, an object of the present invention is to provide a cyclic olefin ring-opening copolymer having a sufficiently high dielectric breakdown voltage. Another object of the present invention is to provide a composition for insulating materials that can be advantageously used when forming insulating materials. A further object of the present invention is to provide an insulating material capable of exhibiting excellent performance. [Means for solving the problem]

[0007] The present inventors have conducted extensive research to solve the above problems, and have newly discovered that in a cyclic olefin ring-opening copolymer containing a structural unit derived from a norbornene compound having a hetero element-containing hydrocarbon group and a structural unit derived from a norbornene compound having a non-hetero element-containing hydrocarbon group, when the content of the structural unit derived from a norbornene compound having a hetero element-containing hydrocarbon group is 0.01 mol % or more and 15.00 mol % or less, the dielectric breakdown voltage can be sufficiently increased, and have completed the present invention.

[0008] That is, the present invention aims to advantageously solve the above-mentioned problems, and the cyclic olefin ring-opening copolymer of the present invention is a cyclic olefin ring-opening copolymer containing a structural unit derived from a norbornene compound having a hetero element-containing hydrocarbon group and a structural unit derived from a norbornene compound having a hetero element-free hydrocarbon group, characterized in that the content ratio of the structural unit derived from the norbornene compound having the hetero element-containing hydrocarbon group is 0.01 mol% or more and 15.00 mol% or less, with the total structural units of the cyclic olefin ring-opening copolymer being 100 mol%. Thus, in the cyclic olefin ring-opening copolymer containing a predetermined structural unit, if the content ratio of the structural unit derived from the norbornene compound having a hetero element-containing hydrocarbon group is 0.01 mol% or more and 15.00 mol% or less, the dielectric breakdown voltage can be sufficiently increased. Here, the "structural unit" in the copolymer means a unit that can form a copolymer by repeating it. And the "content ratio of the structural unit" is 1 H-NMR and 13 It can be measured using nuclear magnetic resonance (NMR) techniques such as C-NMR.

[0009] Here, the cyclic olefin ring-opening copolymer of the present invention preferably has a content ratio of the structural unit derived from the norbornene compound having a non-heteroelement-containing hydrocarbon group of 85.00 mol % or more and 99.99 mol % or less, where the total structural units of the cyclic olefin ring-opening copolymer are taken as 100 mol %. In the cyclic olefin ring-opening copolymer containing a predetermined structural unit, if the content ratio of the structural unit derived from the norbornene compound having a non-heteroelement-containing hydrocarbon group is 85.00 mol % or more and 99.99 mol % or less, the dielectric breakdown voltage of the cyclic olefin ring-opening copolymer can be further increased.

[0010] In the cyclic olefin ring-opening copolymer of the present invention, the hetero element-containing hydrocarbon group preferably has a cyclic structure. If the hetero element-containing hydrocarbon group of the structural unit derived from the norbornene compound having a hetero element-containing hydrocarbon group has a cyclic structure, the dielectric breakdown voltage of the cyclic olefin ring-opening copolymer can be further increased.

[0011] In the cyclic olefin ring-opening copolymer of the present invention, the structural unit derived from the norbornene compound having a hetero element-free hydrocarbon group preferably contains a structural unit derived from a norbornene compound having a hetero element-free hydrocarbon group with an aromatic ring. If the structural unit derived from the norbornene compound having a hetero element-free hydrocarbon group contains a structural unit derived from a norbornene compound having a hetero element-free hydrocarbon group with an aromatic ring, the dielectric breakdown voltage of the cyclic olefin ring-opening copolymer can be further increased.

[0012] The present invention also aims to advantageously solve the above problems, and the insulating material composition of the present invention is characterized by containing any one of the above-mentioned cyclic olefin ring-opening copolymers. The insulating material composition containing the above-mentioned cyclic olefin ring-opening copolymer can be advantageously used when forming an insulating material.

[0013] Furthermore, the present invention aims to advantageously solve the above problems, and an insulating material of the present invention is characterized in that it is formed using the above-mentioned insulating material composition. The insulating material formed using the above-mentioned insulating material composition can exhibit excellent performance. Effect of the Invention

[0014] According to the present invention, it is possible to provide a cyclic olefin ring-opening copolymer having a sufficiently high dielectric breakdown voltage. Furthermore, according to the present invention, it is possible to provide a composition for insulating materials that can be advantageously used when forming an insulating material. Furthermore, according to the present invention, it is possible to provide an insulating material capable of exhibiting excellent performance. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the present invention will be described in detail. Here, the cyclic olefin ring-opening copolymer of the present invention has a sufficiently high dielectric breakdown voltage and can therefore be suitably used when forming an insulating material.

[0016] (Cyclic olefin ring-opening copolymer) The cyclic olefin ring-opening copolymer can be obtained, for example, by ring-opening polymerization of a monomer composition containing a norbornene compound having a hetero element-containing hydrocarbon group and a norbornene compound having a non-hetero element-containing hydrocarbon group in the presence of a polymerization catalyst. The cyclic olefin ring-opening copolymer of the present invention contains a structural unit derived from a norbornene compound having a non-hetero element-containing hydrocarbon group, and the content ratio of the structural unit derived from a norbornene compound having a hetero element-containing hydrocarbon group is 0.01 mol% or more and 15.00 mol% or less.

[0017] <Structural unit derived from norbornene compound having a hetero element-containing hydrocarbon group> Norbornene compounds capable of forming structural units derived from norbornene compounds having a hetero element-containing hydrocarbon group (hereinafter sometimes referred to as "hetero element-containing norbornene compounds") include norbornene compounds represented by the following formula (1). [ka] In the above formula (1), p is an integer of 0 to 4, and R 1 ~R 4 are each independently a hydrogen atom, a single bond, a non-heteroatom-containing hydrocarbon group, or a heteroatom-containing hydrocarbon group; R 1 ~R 4 At least one of R is a heteroatom-containing hydrocarbon group, 1 ~R 4 Two or more of these may be bonded to each other to form a monocyclic or polycyclic ring.

[0018] More specifically, R 1 ~R 4 Examples of the heteroatom-containing hydrocarbon group that may be include a substituted or unsubstituted imido group, a substituted or unsubstituted maleimido group, a substituted or unsubstituted carbonyl group, and a substituted or unsubstituted epoxy group. In this specification, "substituted or unsubstituted" means having one or more substituents or having no substituents.

[0019] R 1 ~R 4 Examples of the non-heteroelement-containing hydrocarbon group that may be include a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, and a substituted or unsubstituted aryl group having 1 to 40 carbon atoms.

[0020] When the various groups described above have a substituent, the substituent is not particularly limited, and examples thereof include a linear or branched alkyl group having 1 to 20 carbon atoms and an aryl group having 6 to 40 carbon atoms.

[0021] Among them, in formula (1), p is 0 and R 1 ~R 4 It is preferable that one of R is a substituted or unsubstituted imido group, and the imido group and one of the other three form a cyclic structure, and the cyclic structure forms a condensed ring structure together with the norbornene ring. 1 ~R 4 The remaining two of these are preferably hydrogen atoms, and the heteroelement-containing norbornene compound is preferably a maleimide-modified norbornene compound satisfying the following formula (2): [ka] In the above formula, R is hydrogen or a linear or branched alkyl group having 1 to 10 carbon atoms. Of these, R is preferably a linear or branched alkyl group having 1 to 6 carbon atoms, such as a methyl group, an ethyl group, an n-butyl group, a t-butyl group, an n-propyl group, or an i-propyl group, and of these, R is more preferably an n-butyl group, a t-butyl group, or an i-propyl group.

[0022] The above-mentioned hetero element-containing norbornene compounds may be used alone or in combination of two or more.

[0023] The content of structural units derived from a norbornene compound having a hetero element-containing hydrocarbon group in the total structural units (100 mol%) contained in the cyclic olefin ring-opening copolymer is preferably 0.10 mol% or more and 10.00 mol% or less, and more preferably 0.50 mol% or more and 5.00 mol% or less. When the copolymer contains structural units derived from a norbornene compound having a hetero element-containing hydrocarbon group within this range, the dielectric breakdown voltage can be further increased.

[0024] <Structural unit derived from norbornene compound having non-hetero element-containing hydrocarbon group> Examples of norbornene compounds capable of forming structural units derived from norbornene compounds having a non-heteroelement-containing hydrocarbon group (hereinafter, sometimes referred to as "non-heteroelement-containing norbornene compounds") include norbornene compounds represented by the following formula (3). [ka] In the above formula (3), q is an integer of 0 to 4, and R 5 ~R 8 is a hydrogen atom or a substituted or unsubstituted hydrocarbon group. 5 ~R 8 When the hydrocarbon group, which may be any of the following, has a substituent, the substituent is also a group not containing a hetero element.

[0025] Among them, as the heteroelement-free norbornene compound, it is preferable to use at least a heteroelement-free norbornene compound having an aromatic ring.Furthermore, as the heteroelement-free norbornene compound, it is more preferable to use a heteroelement-free norbornene compound having an aromatic ring and a heteroelement-free norbornene compound not having an aromatic ring in combination.In other words, it is preferable that the structural unit derived from the norbornene compound having a heteroelement-free hydrocarbon group contains at least a structural unit derived from the heteroelement-free norbornene compound having an aromatic ring, and it is more preferable to contain a structural unit derived from the heteroelement-free norbornene compound having an aromatic ring and a structural unit derived from the heteroelement-free norbornene compound not having an aromatic ring.

[0026] <<Structural units derived from norbornene compounds having aromatic rings and no heteroelement>> Examples of norbornene compounds having an aromatic ring and no heteroelement that can be used to form a structural unit derived from a norbornene compound having an aromatic ring include compounds having an aromatic ring and a norbornene ring in the molecule. The aromatic ring and the norbornene ring may exist separately as a single ring or may form a condensed ring. From the viewpoint of further increasing the dielectric breakdown voltage, it is preferable that the aromatic ring and the norbornene ring form a condensed ring.

[0027] Here, the aromatic ring is not particularly limited, and examples thereof include aromatic hydrocarbon rings such as a benzene ring, a naphthalene ring, and an anthracene ring.

[0028] In addition, examples of compounds having an aromatic ring and a norbornene ring in the molecule (heteroelement-free norbornene compounds having an aromatic ring) are not particularly limited, and include, for example, phenylnorbornenes such as 5-phenyl-2-norbornene, 5-methyl-5-phenyl-bicyclo[2.2.1]hept-2-ene, 5-benzyl-bicyclo[2.2.1]hept-2-ene, 5-tolyl-bicyclo[2.2.1]hept-2-ene [i.e., 5-(4-methylphenyl)-2-norbornene], 5-(ethylphenyl)-bicyclo[2.2.1]hept-2-ene, 5-(isopropylphenyl)-bicyclo[2.2.1]hept-2-ene, 8-phenyl-tetracyclo[4.4.0.1 2,5 .1 7,10 ]-3-dodecene, 8-methyl-8-phenyl-tetracyclo[4.4.0.1 2,5 .1 7,10 ]-3-dodecene, 8-benzyl-tetracyclo[4.4.0.1 2,5 .1 7,10 ]-3-dodecene, 8-tolyl-tetracyclo[4.4.0.1 2,5 .1 7,10 ]-3-dodecene, 8-(ethylphenyl)-tetracyclo[4.4.0.12,5 .1 7,10 ]-3-dodecene, 8-(isopropylphenyl)-tetracyclo[4.4.0.1 2,5 .1 7,10 ]-3-dodecene, 8,9-diphenyl-tetracyclo[4.4.0.1 2,5 .1 7,10 ]-3-dodecene, 8-(biphenyl)-tetracyclo[4.4.0.1 2,5 .1 7,10 ]-3-dodecene, 8-(β-naphthyl)-tetracyclo[4.4.0.1 2,5 .1 7,10 ]-3-dodecene, 8-(α-naphthyl)-tetracyclo[4.4.0.1 2,5 .1 7,10 ]-3-dodecene, 8-(anthracenyl)-tetracyclo[4.4.0.1 2,5 .1 7,10 ]-3-dodecene, 11-phenyl-hexacyclo[6.6.1.1 3,6 .1 10,13 .0 2,7 .0 9,14 ]-4-heptadecene, 6-(α-naphthyl)-bicyclo[2.2.1]-hept-2-ene, 5-(anthracenyl)-bicyclo[2.2.1]-hept-2-ene, 5-(biphenyl)-bicyclo[2.2.1]-hept-2-ene, 5-(β-naphthyl)-bicyclo[2.2.1]-hept-2-ene, 5,6-diphenyl-bicyclo[2.2.1]-hept-2-ene, 1,4-methano-1,4,4a,4b,5,8,8a,9a-octahydrofluorene, 1,4-methano-1,4,4a,9a-tetrahydrofluorene 1,4-methano-8-methyl-1,4,4a,9a-tetrahydrofluorene, 1,4-methano-1,4,4a,9a-tetrahydrodibenzofuran, 1,4-methano-1,4,4a,5,10,10a-hexahydroanthracene, 7,10-methano-6b,7,10,10a-tetrahydrofluoranthene, cyclopentadiene-acenaphthylene adduct, cyclopentadiene-acenaphthylene adduct with further addition of cyclopentadiene, 11,12-benzo-pentacyclo[6.5.1.1 3,6 .0 2,7 .0 9,13]-4-pentadecene, 11,12-benzo-pentacyclo[6.6.1.1 3,6 .0 2,7 .0 9,14 ]-4-Hexadecene, 14,15-Benzo-heptacyclo[8.7.0.1 2,9 .1 4,7 .1 11,17 .0 3,8 .0 12,16 ]-5-eicosene, etc. The above-mentioned heteroelement-free norbornene compounds having an aromatic ring may be used alone or in combination of two or more. Among these, 1,4-methano-1,4,4a,9a-tetrahydrofluorene is more preferable from the viewpoint of further increasing the dielectric breakdown voltage.

[0029] <<Structural units derived from norbornene compounds that do not contain aromatic rings and do not contain heteroelements>> The norbornene compound capable of forming a structural unit derived from a norbornene compound not having an aromatic ring (a norbornene compound not having an aromatic ring) is not particularly limited, and examples thereof include norbornene; norbornenes having an alkyl group such as 5-methylnorbornene, 5-ethylnorbornene, 5-butylnorbornene, 5-hexylnorbornene, 5-decylnorbornene, 5-cyclohexylnorbornene, and 5-cyclopentylnorbornene; norbornenes having an alkenyl group such as 5-ethylidenenorbornene, 5-vinylnorbornene, 5-propenylnorbornene, 5-cyclohexenylnorbornene, and 5-cyclopentenylnorbornene; dicyclopentadiene, tricyclo[4.3.0.1 2,5 ]dec-3-ene, tricyclo[4.4.1 2,5 dicyclopentadienes such as tetracyclo[6.2.1.1]und-3-ene; 3,6 .0 2,7]dodec-4-ene); tetracyclododecenes having an alkyl group such as 8-methyltetracyclododecene, 8-ethyltetracyclododecene, 8-cyclohexyltetracyclododecene, 8-cyclopentyltetracyclododecene; tetracyclododecenes having an exocyclic double bond such as 8-methylidenetetracyclododecene, 8-ethylidenetetracyclododecene, 8-vinyltetracyclododecene, 8-propenyltetracyclododecene, 8-cyclohexenyltetracyclododecene, 8-cyclopentenyltetracyclododecene; hexacycloheptadecene; 12-methylhexa hexacycloheptadecenes having an alkyl group such as cycloheptadecene, 12-ethylhexacycloheptadecene, 12-cyclohexylhexacycloheptadecene, and 12-cyclopentylhexacycloheptadecene; hexacycloheptadecenes having a double bond outside the ring such as 12-methylidenehexacycloheptadecene, 12-ethylidenehexacycloheptadecene, 12-vinylhexacycloheptadecene, 12-propenylhexacycloheptadecene, 12-cyclohexenylhexacycloheptadecene, and 12-cyclopentenylhexacycloheptadecene; etc. These may be used alone or in combination of two or more. Among them, from the viewpoint of further increasing the dielectric breakdown voltage, dicyclopentadiene and tetracyclododecene (tetracyclo[6.2.1.1 3,6 .0 2,7 ]dodec-4-ene) is preferred.

[0030] The proportion of the structural units derived from the norbornene compound having a non-heteroelement-containing hydrocarbon group in the total structural units (100 mol%) of the cyclic olefin ring-opening copolymer must be 99.99 mol% or less, preferably 85.00 mol% or more, and more preferably 99.50 mol% or less. If the proportion of the structural units derived from the norbornene compound having a non-heteroelement-containing hydrocarbon group is within the above range, the dielectric breakdown voltage can be further increased.

[0031] Furthermore, when the structural units derived from the norbornene compound having a non-heteroelement-containing hydrocarbon group are taken as 100 mol %, the ratio of units having an aromatic ring is preferably 10 mol % or more, more preferably 25 mol % or more, preferably 90 mol % or less, and more preferably 75 mol % or less. If the ratio of units having an aromatic ring is within the above range when the structural units derived from the norbornene compound having a non-heteroelement-containing hydrocarbon group are taken as 100 mol %, the dielectric breakdown voltage can be further increased.

[0032] The cyclic olefin ring-opening copolymer may optionally have, as a unit not having a norbornene structure, a ring-opening polymerization unit derived from a cyclic olefin monomer not having a norbornene structure. However, the proportion of units not having a norbornene structure in all structural units (100 mol%) contained in the cyclic olefin ring-opening copolymer is preferably 10% or less, more preferably 5% or less, and even more preferably 0%.

[0033] Examples of cyclic olefin monomers not having a norbornene structure that can be used to introduce units not having a norbornene structure into the cyclic olefin ring-opening copolymer include monocyclic olefin monomers. Examples of monocyclic olefins include cyclic monoolefins or cyclic diolefins having a carbon number of usually 4 to 20, preferably 4 to 10. Specific examples of cyclic monoolefins include cyclobutene, cyclopentene, methylcyclopentene, cyclohexene, methylcyclohexene, cycloheptene, and cyclooctene. Specific examples of cyclic diolefins include cyclohexadiene, methylcyclohexadiene, cyclooctadiene, methylcyclooctadiene, and phenylcyclooctadiene. These can be used alone or in combination.

[0034] <Method of producing cyclic olefin ring-opening copolymer> The cyclic olefin ring-opening copolymer of the present invention can be prepared by using a known ring-opening polymerization method such as ring-opening polymerization using a metathesis polymerization catalyst.

[0035] Here, the metathesis polymerization catalyst and the additives that can be used in combination are not particularly limited, and known ones such as ruthenium carbene complexes are used (for example, see JP-A-2019-104934 and JP-A-6104263). The amount of the catalyst and additives used may be appropriately selected depending on the polymerization conditions, etc.

[0036] The polymerization reaction may be carried out by bulk polymerization, in which case the polymerization conditions such as the polymerization temperature, polymerization pressure, and polymerization time may be appropriately adjusted.

[0037] (Insulating material composition) The insulating material composition of the present invention contains the above-mentioned cyclic olefin ring-opening copolymer of the present invention, and optionally further contains various additives. Furthermore, since the insulating material composition of the present invention contains a copolymer having a high dielectric breakdown voltage, it can be used particularly advantageously when forming an insulating material.

[0038] Here, additives that may be contained in the insulating material composition are not particularly limited, and examples thereof include fillers described in JP 2019-104934 A. The addition ratio of the additives can be appropriately adjusted according to the application as long as the effect of improving the dielectric breakdown voltage is not impaired.

[0039] (Insulating materials) The insulating material of the present invention is formed using the insulating material composition of the present invention and contains the cyclic olefin ring-opening copolymer of the present invention, and therefore can exhibit excellent performance.

[0040] Here, the molding method for obtaining the insulating material is not particularly limited, and examples thereof include the RIM (Reaction Injection Molding) molding method, the RTM (Resin Transfer Molding) method, the potting method, the (solid, liquid) transfer molding method, the compression molding method, the print molding method, the vacuum molding method, etc. Among them, the insulating material of the present invention can be suitably produced by the RIM molding method in which a compound containing a norbornene compound having a hetero element-containing hydrocarbon group, a norbornene compound having a non-hetero element-containing hydrocarbon group, and a metathesis polymerization catalyst is subjected to bulk ring-opening polymerization in a molding die. EXAMPLES

[0041] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples in any way. Measurements and evaluations in each example were performed by the following methods. In the following description, the units "parts" and "%" that represent amounts are by weight unless otherwise specified.

[0042] (Measurement of dielectric breakdown voltage) In accordance with JIS-C2110-1 (2010), the test samples obtained in the examples and comparative examples were sandwiched and fixed between two spherical electrodes in Fluorinert, an insulating liquid. After increasing the voltage to 10 kV, a voltage was applied to the test samples by a stepwise voltage increase method in which the voltage was increased by 1 kV every 10 seconds. The voltage one step before the test sample was shorted was recorded as the breakdown voltage of the test sample. In addition, the breakdown voltage value V was recorded for each test sample. i is the breakdown voltage value V recorded for the test specimen obtained using the base monomer mixture of the same composition. o Compared to, improvement rate (%) = V i / V o Got ×100-100.

[0043] Example 1 <Preparation of catalyst solution> A catalyst solution was obtained by dissolving 0.6 parts of a ruthenium catalyst (Zhan 1N) represented by the following formula as a metathesis polymerization catalyst and 15 parts of 2,6-di-t-butyl-p-cresol (BHT) as an antiaging agent in 82 parts of cyclopentanone. [ka] In the above formula, Mes represents a mesityl group.

[0044] <Molding of sample plate> As a norbornene compound not containing a heteroatom having no aromatic ring, tetracyclo[6.2.1.1 3,6 .0 2,7 6.43 g (about 0.04 mol) of 1,4-methano-1,4,4a,9a-tetrahydrofluorene (hereinafter sometimes abbreviated as "MTF"; molecular weight: 182.95 g / mol) as a heteroelement-free norbornene compound having an aromatic ring was weighed out and mixed to obtain a base monomer mixture. 0.41 g (about 0.002 mol) of a maleimide-modified norbornene monomer as a norbornene compound having a heteroelement-containing hydrocarbon group represented by the following formula was dissolved in the base monomer mixture at room temperature to obtain a resin solution. 0.41 g of the catalyst solution prepared above was added to the obtained resin solution and mixed by stirring to obtain a polymerizable composition. [ka] In the above formula, R is an isopropyl group.

[0045] A stainless steel male mold having a space of 100 mm in length × 100 mm in width × 0.15 mm in thickness was prepared as a mold, and the polymerizable composition obtained above was poured into the space. Another flat, smooth stainless steel plate was placed on top of the mold, taking care not to create any voids. The mixture was then heated in a press molding machine at a temperature of 80°C and a pressure of 10 MPa for 10 minutes, and further heated at 120°C and a pressure of 10 MPa for 10 minutes to carry out a bulk ring-opening polymerization reaction, thereby obtaining a sample plate. A 40 mm×40 mm piece was cut out from the obtained sample plate as a test sample, and the dielectric breakdown voltage was measured at 23° C. according to the above-mentioned method. The results are shown in Table 1.

[0046] Example 2 A sample plate was molded in the same manner as in Example 1, except that 0.69 g (about 0.003 mol) of the maleimide-modified norbornene monomer was added to the base monomer mixture and dissolved at room temperature, and the dielectric breakdown voltage was measured. The results are shown in Table 1.

[0047] Example 3 A sample plate was molded in the same manner as in Example 1, except that 0.14 g (approximately 0.0007 mol) of maleimide-modified norbornene monomer was added to the base monomer mixture and dissolved at room temperature, and the dielectric breakdown voltage was measured. The results are shown in Table 1.

[0048] Example 4 In preparing the base monomer mixture, 2.78 g (approximately 0.02 mol) of dicyclopentadiene (hereinafter sometimes abbreviated as "DCP"; molecular weight: 132.2 g / mol) as a heteroelement-free norbornene compound having no aromatic ring and 9.65 g (approximately 0.06 mol) of TCD were weighed and mixed to obtain a base monomer mixture. 0.12 g (approximately 0.0006 mol) of maleimide-modified norbornene monomer was added to the obtained base monomer mixture and dissolved at room temperature. Using the obtained resin liquid, a sample plate was molded in the same manner as in Example 1, and the dielectric breakdown voltage was measured. The results are shown in Table 1.

[0049] Example 5 0.62 g (about 0.003 mol) of maleimide-modified norbornene monomer was added to the same base monomer mixture as in Example 4 and dissolved at room temperature. The obtained resin liquid was used to mold a sample plate in the same manner as in Example 1, and the dielectric breakdown voltage was measured. The results are shown in Table 1.

[0050] Comparative Example 1 The same base monomer mixture as in Example 4 was prepared, and the maleimide-modified norbornene was not added to make a resin solution containing only the base monomer mixture. The obtained resin solution was used to mold a sample plate in the same manner as in Example 1, and the dielectric breakdown voltage was measured. The results are shown in Table 1.

[0051] Comparative Example 2 When preparing the base monomer mixture, 8.33 g (about 0.06 mol) of DCP and 3.66 g (about 0.02 mol) of MTF were mixed, and no maleimide-modified norbornene monomer was added to make a resin solution containing only the base monomer mixture. Using the obtained resin solution, a sample plate was molded in the same manner as in Example 1, and the dielectric breakdown voltage was measured. The results are shown in Table 1.

[0052] Comparative Example 3 The same base monomer mixture as in Example 1 was prepared, and the maleimide-modified norbornene was not added to make a resin solution containing only the base monomer mixture. The obtained resin solution was used to mold a sample plate in the same manner as in Example 1, and the dielectric breakdown voltage was measured. The results are shown in Table 1.

[0053] Comparative Example 4 A resin solution was obtained by dissolving 3.36 g (about 0.016 mol) of maleimide-modified norbornene monomer at room temperature in the same base monomer mixture as in Example 1. A sample plate was molded using the obtained resin solution in the same manner as in Example 1, and the dielectric breakdown voltage was measured. The results are shown in Table 1.

[0054] In Table 1, "NB" stands for norbornene compound. "TCD" is a tetracyclo[6.2.1.1 3,6 .0 2,7 ]dodec-4-ene, "MTF" stands for 1,4-methano-1,4,4a,9a-tetrahydrofluorene. "DCP" stands for dicyclopentadiene. "NBNiPr" is an isopropyl-substituted maleimide-modified norbornene compound, Each is shown.

[0055] [Table 1]

[0056] From Table 1, it can be seen that the cyclic olefin ring-opening copolymers obtained in Examples 1 to 5, in which the amount of maleimide-modified norbornene monomer added was within a specified range (0.01 mol % or more and 15.00 mol % or less), had improved breakdown voltages compared to copolymers obtained using the same base monomer. Moreover, from Comparative Example 4 in Table 1, it is seen that when the amount of the maleimide-modified norbornene monomer added was more than 15.00 mol %, the effect of improving the dielectric breakdown voltage could not be achieved. [Industrial Applicability]

[0057] According to the present invention, it is possible to provide a cyclic olefin ring-opening copolymer having a sufficiently high dielectric breakdown voltage. Furthermore, according to the present invention, it is possible to provide a composition for insulating materials that can be advantageously used when forming an insulating material. Furthermore, according to the present invention, it is possible to provide an insulating material capable of exhibiting excellent performance.

Claims

1. A cyclic olefin ring-opening copolymer containing a structural unit derived from a norbornene compound having a hetero element-containing hydrocarbon group and a structural unit derived from a norbornene compound having a non-hetero element-containing hydrocarbon group, the content of the structural unit derived from the norbornene compound having a heteroatom-containing hydrocarbon group is 0.01 mol % or more and 15.00 mol % or less, based on 100 mol % of all structural units contained in the cyclic olefin ring-opening copolymer; The structural unit derived from a norbornene compound having a heteroatom-containing hydrocarbon group is a structural unit derived from a maleimide-modified norbornene compound that satisfies the following formula (2): 【Chemistry 1】 ・・・（２） (In the above formula (2), R is hydrogen or a linear or branched alkyl group having 1 to 10 carbon atoms.) Cyclic olefin ring-opening copolymer.

2. The cyclic olefin ring-opening copolymer according to claim 1, wherein the content of the structural unit derived from the norbornene compound having the hetero element-free hydrocarbon group is 85.00 mol % or more and 99.99 mol % or less, based on 100 mol % of all structural units possessed by the cyclic olefin ring-opening copolymer.

3. 3. The cyclic olefin ring-opening copolymer according to claim 1, wherein the structural unit derived from a norbornene compound having a heteroelement-free hydrocarbon group comprises a structural unit derived from a norbornene compound having a heteroelement-free hydrocarbon group and having an aromatic ring.

4. An insulating material composition comprising the cyclic olefin ring-opening copolymer according to any one of claims 1 to 3.

5. An insulating material comprising the insulating material composition of claim 4.

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