Method for producing cyclic olefin copolymer

Abstract

To provide a method for producing a cyclic olefin copolymer, capable of suppressing generation of polyethylene-like impurities.SOLUTION: The present invention provides a method for producing a cyclic olefin copolymer, the production method involving addition polymerization of a norbornene monomer and ethylene, wherein the addition polymerization is performed under prescribed conditions in the presence of a borate compound, alkylaluminium, and a catalyst.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing a cyclic olefin copolymer. [Background technology]

[0002] Cyclic olefin copolymers are resins that have high transparency and are used in a wide range of fields such as optical materials.

[0003] Known methods for producing cyclic olefin copolymers include addition polymerization of various monomers in the presence of a catalyst and a cocatalyst (such as a borate compound) (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2020 / 204187 Summary of the Invention [Problem to be solved by the invention]

[0005] On the other hand, the present inventors have found a new problem in the production method of a cyclic olefin copolymer, that is, when the polymerization temperature exceeds 90°C, particularly during the reaction process of addition polymerization of a norbornene monomer and ethylene, polyethylene-like impurities are likely to be produced, and the impurities may impair the transparency of the cyclic olefin copolymer.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing a cyclic olefin copolymer, which can suppress the production of polyethylene-like impurities. [Means for solving the problem]

[0007] The present inventors have found that the above problems can be solved by using a specific amount of a borate compound in addition polymerization of a norbornene monomer and ethylene, and have completed the present invention. More specifically, the present invention provides the following.

[0008] (1) A method for producing a cyclic olefin copolymer, comprising the steps of: The method includes addition polymerizing norbornene monomer and ethylene, the addition polymerization is carried out in the presence of a borate compound, an alkylaluminum, and a catalyst; the borate compound is a salt composed of a boron-containing anion and a nitrogen-containing cation, The temperature condition of the addition polymerization is more than 90° C., the acid dissociation constant (pKa) of the conjugate acid of the tertiary amine constituting the nitrogen-containing cation is greater than 5.0; The amount (molar ratio) of the borate compound to the catalyst is 1.0 to 1.7. Manufacturing method.

[0009] (2) The boron-containing anion is a tetraaryl boron anion, The method according to (1), wherein the nitrogen-containing cation is a tertiary ammonium cation.

[0010] (3) The method according to (2), wherein the tertiary ammonium cation has an aliphatic hydrocarbon group having 6 to 20 carbon atoms.

[0011] (4) The method according to (2) or (3), wherein the tertiary ammonium cation is a didecylmethylammonium ion.

[0012] (5) The method according to any one of (1) to (4), wherein the alkylaluminum is at least one selected from the group consisting of triisobutylaluminum, trimethylaluminum, and octylaluminum. Effect of the Invention

[0013] According to the present invention, there is provided a method for producing a cyclic olefin copolymer, which can suppress the formation of polyethylene-like impurities. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, a method for producing a cyclic olefin copolymer will be described. However, the method for producing the cyclic olefin copolymer is not limited to the specific embodiments described below, and may be appropriately modified as long as the desired effects are not impaired.

[0015] <Method of Producing Cyclic Olefin Copolymer> The process for producing a cyclic olefin copolymer satisfies the following requirements. The method of manufacture includes addition polymerization of norbornene monomer and ethylene. The addition polymerization is carried out in the presence of a borate compound, an alkylaluminum, and a catalyst. The borate compound is a salt composed of a boron-containing anion and a nitrogen-containing cation. The temperature condition for addition polymerization is above 90°C. The acid dissociation constant (pKa) of the conjugate acid of the tertiary amine that constitutes the nitrogen-containing cation is greater than 5.0. The amount (molar ratio) of the borate compound to the catalyst is 1.0 to 1.7.

[0016] The cyclic olefin copolymer is produced by addition polymerization of various monomers. In such a production process, the present inventors have found that, particularly when norbornene monomer and ethylene are addition polymerized, polyethylene-like impurities are generated and the impurities can impair the transparency of the cyclic olefin copolymer.

[0017] Therefore, the present inventors have conducted extensive research into conditions under which the generation of such impurities can be suppressed. As a result, it was unexpectedly discovered that the formation of polyethylene-like impurities can be suppressed by adjusting the conditions of the co-catalyst (i.e., a specific borate compound and an alkylaluminum) used together with the catalyst in the addition polymerization. This suppression effect was stably observed even when the temperature condition of the addition polymerization was over 90°C.

[0018] In the specification of this application, the term "polyethylene-like impurities" refers to by-products having a polyethylene structure or a structure similar thereto that are produced during the addition polymerization of norbornene monomer and ethylene.

[0019] Whether or not polyethylene-like impurities are produced during the addition polymerization and the extent of the production can be determined by subjecting the produced cyclic olefin copolymer to a thermal analysis of impurities based on the glass transition temperature and / or a turbidity test. For both the thermal analysis of impurities based on the glass transition temperature and the turbidity test, the methods shown in the examples can be preferably employed. For example, if no peaks derived from polyethylene-like impurities are detected in an impurity thermal analysis, or no turbidity is observed in a turbidity test, it can be determined that the production of polyethylene-like impurities is suppressed.

[0020] The process for producing the cyclic olefin copolymer will be described in detail below.

[0021] (1) Components used in addition polymerization The addition polymerization is carried out in the presence of a borate compound, an alkylaluminum, and a catalyst. The borate compound, the alkylaluminum, and the catalyst may each be used alone or in combination of two or more kinds.

[0022] (1-1) Borate compounds The borate compound corresponds to a promoter. The borate compound is a salt consisting of a boron-containing anion and a nitrogen-containing cation.

[0023] (1-1-1) Boron-containing anions The boron-containing anion that constitutes the borate compound is [B(Org)4] - " is an anion represented by the formula (I). Here, "Org" is an organic group. In the boron-containing anion, a carbon atom in Org is bonded to a boron atom.

[0024] From the viewpoint of easily enhancing the effect of suppressing the production of polyethylene-like impurities, the boron-containing anion preferably contains a tetraaryl boron anion, and more preferably consists of a tetraaryl boron anion.

[0025] The tetraarylboron anion is tetrakisphenylborate ([B(C6H5)4] - ), tetrakistryl borate ([B(C6H4CH3)4] - ), tetrakis(pentafluorophenyl)borate ([B(C6F5)4] - ), tetrakis[(trifluoromethyl)phenyl]borate ([B(C6H4CF3)4] - ), and tetrakis(difluorophenyl)borate ([B(C6H3F2)4] - ) etc.

[0026] (1-1-2) Nitrogen-containing cations The nitrogen-containing cation constituting the borate compound is not particularly limited as long as the acid dissociation constant (pKa) of the conjugate acid of the tertiary amine constituting the nitrogen-containing cation exceeds 5.0. Here, the above acid dissociation constant is the value of the conjugate acid of the tertiary amine in water at 300K.

[0027] As a result of investigations by the present inventors, the unexpected finding was made that polyethylene-like impurities can be stably suppressed by using a nitrogen-containing cation in which the conjugate acid of a tertiary amine has an acid dissociation constant of more than 5.0. From this viewpoint, the acid dissociation constant of the conjugate acid of the tertiary amine constituting the nitrogen-containing cation is more than 5.0, preferably 7.0 or more, and more preferably 9.0 or more. The upper limit of the acid dissociation constant is not particularly limited, but is usually 12.0 or less.

[0028] The acid dissociation constant of the conjugate acid of a tertiary amine is preferably determined by neutralization titration.

[0029] From the viewpoint of easily enhancing the effect of suppressing the production of polyethylene-like impurities, the nitrogen-containing cation preferably contains a tertiary ammonium cation, and more preferably consists of a tertiary ammonium cation. Tertiary ammonium cation is "(Org)3N + It is a cation represented by "H". "Org" is an organic group. In a tertiary ammonium cation, the carbon atom in Org is bonded to the nitrogen atom.

[0030] The tertiary ammonium cation has an aliphatic hydrocarbon group preferably having a carbon number of 6 to 20, more preferably 8 to 18. The structure of the aliphatic hydrocarbon group may be linear, branched, or cyclic, or may be a combination of these structures.

[0031] Furthermore, the aliphatic hydrocarbon group constituting the tertiary ammonium cation may have one or more unsaturated bonds selected from a carbon-carbon double bond and a carbon-carbon triple bond. Examples of the aliphatic hydrocarbon group include alkyl groups such as n-hexyl, isohexyl, n-heptyl, n-octyl, isooctyl, 2-ethylhexyl, n-nonyl, isononyl, n-decyl, isodecyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, n-octadecyl, n-nonadecyl, and n-icosyl groups; and cycloalkyl groups such as cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, and cyclodecyl groups.

[0032] The tertiary ammonium ion may have an aliphatic hydrocarbon group having 1 to 5 carbon atoms in addition to the aliphatic hydrocarbon group having 6 to 20 carbon atoms. Examples of the aliphatic hydrocarbon group having 1 to 5 carbon atoms include alkyl groups (such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, sec-pentyl, and tert-pentyl groups), and cycloalkyl groups (such as cyclopropyl, cyclobutyl, and cyclopentyl groups).

[0033] The most preferred tertiary ammonium cation is the didecylmethylammonium ion.

[0034] (1-1-3) Preferred borate compounds Preferable borate compounds include "borate-3" and "borate-4" used in the examples.

[0035] (1-1-4) Amount of borate compound used In the addition polymerization, the amount (molar ratio) of the borate compound to be charged relative to the catalyst is 1.0 to 1.7, preferably 1.0 to 1.5, and more preferably 1.0 to 1.2. As a result of investigations by the present inventors, it has been found that polyethylene-like impurities can be stably suppressed by using the above-mentioned borate compound in such an amount.

[0036] (1-2) Alkyl aluminum The alkylaluminum corresponds to a promoter. By using the above-mentioned borate compound in combination with an alkyl aluminum, polyethylene-like impurities can be stably suppressed.

[0037] The alkylaluminum is not particularly limited as long as it is used in the synthesis of a polymer (particularly, a cyclic olefin copolymer). The alkylaluminum may be one or more selected from the group consisting of triisobutylaluminum, trimethylaluminum, and octylaluminum. Of these, triisobutylaluminum is preferred because it is widely used industrially.

[0038] In the addition polymerization, the amount of alkylaluminum used is not particularly limited, but from the viewpoint that the activity (yield) of the cyclic olefin copolymer is likely to be good, the amount is preferably 1 to 1000 (molar ratio), more preferably 1 to 500 (molar ratio), and even more preferably 1 to 250 (molar ratio) relative to the borate compound.

[0039] (1-3) Catalyst The catalyst is not particularly limited as long as it is used in the synthesis of a polymer (particularly, a cyclic olefin copolymer).

[0040] Examples of the catalyst include a titanocene catalyst, a zirconocene catalyst, and a hafnocene catalyst. Preferred catalysts include "Catalyst-1," "Catalyst-2," and "Catalyst-3" used in the examples.

[0041] The amount of the catalyst in the addition polymerization is not particularly limited as long as the addition polymerization reaction proceeds smoothly. The amount of the catalyst in the addition polymerization may be, for example, 0.00001 to 0.1 mmol.

[0042] (1-4) Norbornene monomer and ethylene Norbornene monomer and ethylene are polymerization targets (monomers) in addition polymerization.

[0043] (1-4-1) Norbornene monomer Norbornene (CAS registration number: 498-66-8, chemical formula: C7H 10 ) is a type of cyclic olefin monomer. Norbornene monomers also include substituted norbornenes, which are norbornenes having a substituent. The norbornene monomers may be used alone or in combination of two or more.

[0044] The substituted norbornene is not particularly limited. Examples of the substituents of the substituted norbornene include halogen atoms and monovalent or divalent hydrocarbon groups. Specific examples of the substituted norbornene include the compound represented by the following formula (I).

[0045] [ka]

[0046] In formula (I), R a1 ~R a12 may be the same or different and are atoms or groups selected from the group consisting of hydrogen atoms, halogen atoms, and hydrocarbon groups. R a9 and R a10 , R a11 and R 12 may combine together to form a divalent hydrocarbon group. R a9 or R a10 And, R a11 or R a12 may be bonded to each other to form a ring. n is 0 or a positive integer. If n is 2 or more, R a5 ~R a8 may be the same or different in each repeating unit. However, if n is 0, then R a1 ~R a4 and R a9 ~R a12 At least one of is not a hydrogen atom.

[0047] R a1 ~R a8 Specific examples of R include a hydrogen atom; halogen atoms such as fluorine, chlorine, and bromine; and alkyl groups having 1 to 20 carbon atoms. a1 ~R a8 may all consist of different atoms or groups. a1 ~R a8 Some or all of these may be the same atom or group.

[0048] R a9 ~R a12 Specific examples of R include a hydrogen atom; halogen atoms such as fluorine, chlorine, and bromine; alkyl groups having 1 to 20 carbon atoms; cycloalkyl groups such as a cyclohexyl group; substituted or unsubstituted aromatic hydrocarbon groups such as a phenyl group, a tolyl group, an ethylphenyl group, an isopropylphenyl group, a naphthyl group, and an anthryl group; and aralkyl groups such as a benzyl group and a phenethyl group. a9 ~R a12 may all consist of different atoms or groups. a9 ~R a12 Some or all of these may be the same atom or group.

[0049] R a9 and R a10 , or R a11 and R a12 Specific examples of divalent hydrocarbon groups that can be formed by combining the above include alkylidene groups such as an ethylidene group, a propylidene group, and an isopropylidene group.

[0050] R a9 or R a10 And, R a11 or R a12 When they are bonded to each other to form a ring, the ring formed may be a monocyclic ring or a polycyclic ring. The ring formed may be a polycyclic ring having a bridge. The ring formed may have a double bond. The ring formed may have a substituent such as a methyl group.

[0051] Specific examples of the substituted norbornene represented by formula (I) include 5-methyl-bicyclo[2.2.1]hept-2-ene, 5,5-dimethyl-bicyclo[2.2.1]hept-2-ene, 5-ethyl-bicyclo[2.2.1]hept-2-ene, 5-butyl-bicyclo[2.2.1]hept-2-ene, 5-ethylidene-bicyclo[2.2.1]hept-2-ene, 5-hexyl-bicyclo[2.2.1]hept-2-ene, 5-methyl-bicyclo[2.2.1]hept-2-ene, 5,5-dimethyl-bicyclo[2.2.1]hept-2-ene, 5-ethyl-bicyclo[2.2.1]hept-2-ene, 5-hexyl ... Bicyclic olefins such as cyclo[2.2.1]hept-2-ene, 5-octyl-bicyclo[2.2.1]hept-2-ene, 5-octadecyl-bicyclo[2.2.1]hept-2-ene, 5-methylidene-bicyclo[2.2.1]hept-2-ene, 5-vinyl-bicyclo[2.2.1]hept-2-ene, and 5-propenyl-bicyclo[2.2.1]hept-2-ene; Tricyclo[4.3.0.1 2,5 ]Deca-3,7-diene (common name: dicyclopentadiene), tricyclo[4.3.0.1 2,5 ]dec-3-ene; tricyclo[4.4.0.1 2,5 ]Undeca-3,7-diene or tricyclo[4.4.0.1 2,5 ]Undeca-3,8-diene or partially hydrogenated products thereof (or an adduct of cyclopentadiene and cyclohexene) 2,5 ]undec-3-ene; three-ring cyclic olefins such as 5-cyclopentyl-bicyclo[2.2.1]hept-2-ene, 5-cyclohexyl-bicyclo[2.2.1]hept-2-ene, 5-cyclohexenyl-bicyclo[2.2.1]hept-2-ene, and 5-phenyl-bicyclo[2.2.1]hept-2-ene; Tetracyclo[4.4.0.1 2,5 .1 7,10 ]dodec-3-ene (also called tetracyclododecene), 8-methyltetracyclo[4.4.0.1 2,5 .1 7,10 ]dodec-3-ene, 8-ethyltetracyclo[4.4.0.1 2,5 .1 7,10 ]dodec-3-ene, 8-methylidenetetracyclo[4.4.0.1 2,5 .1 7,10]dodec-3-ene, 8-ethylidenetetracyclo[4.4.0.1 2,5 .1 7,10 ]dodec-3-ene, 8-vinyltetracyclo[4,4.0.1 2,5 .1 7,10 ]dodec-3-ene, 8-propenyl-tetracyclo[4.4.0.1 2,5 .1 7,10 ] 4-ring cyclic olefins such as dodec-3-ene; 8-Cyclopentyl-tetracyclo[4.4.0.1 2,5 .1 7,10 ]dodec-3-ene, 8-cyclohexyl-tetracyclo[4.4.0.1 2,5 .1 7,10 ]dodec-3-ene, 8-cyclohexenyl-tetracyclo[4.4.0.1 2,5 .1 7,10 ]dodec-3-ene, 8-phenyl-cyclopentyl-tetracyclo[4.4.0.1 2,5 .1 7,10 ]dodec-3-ene;tetracyclo[7.4.1 3,6 .0 1,9 .0 2,7 ]tetradeca-4,9,11,13-tetraene (also called 1,4-methano-1,4,4a,9a-tetrahydrofluorene), tetracyclo[8.4.1 4,7 .0 1,10 .0 3,8 ]Pentadeca-5,10,12,14-tetraene (also called 1,4-methano-1,4,4a,5,10,10a-hexahydroanthracene); Pentacyclo[6.6.1.1 3,6 .0 2,7 .0 9,14 ]-4-Hexadecene, Pentacyclo[6.5.1.1 3,6 .0 2,7 .0 9,13 ]-4-Pentadecene, Pentacyclo[7.4.0.0 2,7 .1 3,6 .1 10,13 ]-4-Pentadecene;Heptacyclo[8.7.0.1 2,9 .1 4,7 .1 11,17 .0 3,8 .0 12,16]-5-Eicosene, heptacyclo[8.7.0.1 2,9 .0 3,8 .1 4,7 .0 12,17 .1 13,l6 ]-14-eicosene; and polycyclic olefins such as a tetramer of cyclopentadiene.

[0052] Among these, for example, alkyl-substituted norbornenes such as bicyclo[2.2.1]hept-2-ene substituted with one or more alkyl groups, and alkylidene-substituted norbornenes such as bicyclo[2.2.1]hept-2-ene substituted with one or more alkylidene groups are preferred. 5-Ethylidene-bicyclo[2.2.1]hept-2-ene (common name: 5-ethylidene-2-norbornene, or simply ethylidenenorbornene) is particularly preferred.

[0053] (1-4-2) Ethylene Ethylene (C2H4) is an α-olefin with two carbon atoms.

[0054] (1-4-3) Amount of monomer used, etc. The amount of the monomer used is not particularly limited, but may satisfy any of the following requirements.

[0055] The amount of norbornene monomer charged per part by mass of the catalyst is preferably 1 to 300,000 parts by mass, and more preferably 10 to 200,000 parts by mass.

[0056] The method of feeding ethylene is not particularly limited as long as the desired amount of ethylene can be charged into the polymerization vessel. Typically, ethylene is preferably charged into the polymerization vessel so that the charging pressure of ethylene in the polymerization vessel is 0.5 MPa or more. The charging pressure of ethylene is more preferably 0.55 MPa or more, and even more preferably 0.6 MPa or more. By increasing the charging pressure of ethylene, the amount of catalyst used per polymer produced can be reduced. As for the upper limit, the charging pressure of ethylene is, for example, preferably 10 MPa or less, more preferably 5 MPa or less, and even more preferably 3 MPa or less. In view of the above, the feeding pressure of ethylene is preferably from 0.5 to 10 MPa, more preferably from 0.55 to 5 MPa, and further preferably from 0.6 to 3 MPa. The ethylene charging pressure is a gauge pressure.

[0057] (2) Addition polymerization conditions The conditions for the addition polymerization of norbornene monomer and ethylene are not particularly limited, except that the temperature condition is more than 90°C.

[0058] By carrying out the addition polymerization under the above-mentioned conditions, even if the temperature condition of the addition polymerization is above 90°C at which polyethylene-like impurities are likely to be produced, the production of polyethylene-like impurities can be stably suppressed. The temperature condition for the addition polymerization is more than 90°C, and may be 100°C or higher, or 110°C or higher. The upper limit of the temperature condition for the addition polymerization is not particularly limited, but is usually 180° C. or lower.

[0059] Other addition polymerization conditions are not particularly limited as long as the addition polymerization reaction proceeds smoothly and the desired cyclic olefin copolymer is obtained.

[0060] In the addition polymerization, the components to be reacted (norbornene monomer, ethylene, etc.) may be added to a reaction vessel simultaneously or separately.

[0061] The addition polymerization may be carried out in the presence of a solvent. The solvent is not particularly limited as long as it does not inhibit the polymerization reaction. Preferred solvents include, for example, hydrocarbon solvents and halogenated hydrocarbon solvents. When a solvent is used, the amount of the solvent used is not particularly limited and is appropriately set depending on the amount of the monomer, etc.

[0062] The time for the addition polymerization is not particularly limited. The addition polymerization time can be, for example, 0.1 to 10 hours.

[0063] The atmosphere in which the addition polymerization reaction is carried out is not particularly limited as long as the reaction is not inhibited. The atmosphere in which the addition polymerization reaction is carried out is preferably an inert gas atmosphere (nitrogen gas, helium gas, etc.).

[0064] After the addition polymerization is completed, the cyclic olefin copolymer can be recovered from the reaction vessel in a conventional manner.

[0065] The yield in the method for producing the cyclic olefin copolymer is not particularly limited, but for example, the yield of the cyclic olefin copolymer per 1 g of catalyst may be 10 to 100 kg / g.

[0066] <Cyclic olefin copolymer> The cyclic olefin copolymer includes any cyclic olefin copolymer obtained from the above-mentioned production method. In a preferred embodiment, the cyclic olefin copolymer may satisfy, for example, the following requirements:

[0067] (1) Polyethylene-like impurities The cyclic olefin copolymer obtained by the above-mentioned production method is suppressed in the production of polyethylene-like impurities, and therefore the cyclic olefin copolymer has a low content of polyethylene-like impurities or does not contain any polyethylene-like impurities.

[0068] In a preferred embodiment, the cyclic olefin copolymer has no detectable peak when subjected to the following detection test.

[0069] [Detection test] A sample of the cyclic olefin copolymer is measured by a differential scanning calorimeter (DSC) in a nitrogen atmosphere at a heating rate of 20° C. / min according to the method described in JIS K7121 to obtain a DSC curve. Next, the presence or absence of a melting point (melting enthalpy) peak due to polyethylene-like impurities is confirmed in the obtained DSC curve. The melting point peak due to polyethylene-like impurities is generally detected within the range of 100°C to 140°C. If no peak is detected, it means that the cyclic olefin copolymer does not contain any polyethylene-like impurities or contains only a very small amount of such impurities. If a peak is detected, it means that polyethylene-like impurities are present in the cyclic olefin copolymer.

[0070] (2) Ratio of constituent monomers In the cyclic olefin copolymer, the ratio of the number of moles of structural units derived from ethylene to the number of moles of all structural units is preferably 1 to 99 mol %, more preferably 5 to 90 mol %.

[0071] In the cyclic olefin copolymer, the ratio of the number of moles of structural units derived from norbornene monomer to the number of moles of all structural units is preferably 1 to 99 mol %, more preferably 5 to 90 mol %, and further preferably 10 to 80 mol %.

[0072] The ratio of the number of moles of structural units derived from ethylene or norbornene monomers to the number of moles of all structural units is 13 It is calculated by measuring the C-NMR spectrum.

[0073] The cyclic olefin copolymer includes copolymers containing structural units derived from a norbornene monomer and a monomer other than ethylene. That is, the cyclic olefin copolymer may have structural units other than the structural units derived from a norbornene monomer and the structural units derived from ethylene. However, from the viewpoint of stably realizing the effect of suppressing the production of polyethylene-like impurities, the cyclic olefin copolymer preferably consists only of structural units derived from norbornene monomers and structural units derived from ethylene.

[0074] (3) Glass transition temperature The glass transition temperature (also referred to as "Tg") of the cyclic olefin copolymer is not particularly limited, but from the viewpoint of easily achieving good processability of the cyclic olefin copolymer, it is preferably 185°C or less, more preferably 170°C or less, even more preferably 160°C or less, even more preferably 150°C or less, even more preferably 130°C or less, even more preferably 120°C or less, and even more preferably 100°C or less.

[0075] In the present specification, the term "glass transition temperature (of a cyclic olefin copolymer)" refers to a value determined by the DSC method (the method described in JIS K7121).

[0076] (4) Uses of cyclic olefin copolymers The cyclic olefin copolymer can be used in any application. For example, it can be used in place of or in conjunction with conventional cyclic olefin copolymers. EXAMPLES

[0077] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0078] <Preparation and evaluation of cyclic olefin copolymers> Cyclic olefin copolymers according to the Examples and Comparative Examples were produced by the following method, and the presence or absence of polyethylene-like impurities produced during the process was evaluated.

[0079] (1) Production of cyclic olefin copolymers First, a 150 mL stainless steel autoclave including a stirrer was thoroughly dried, and a polymerization solvent (decalin) and a norbornene monomer (2-norbornene) were added thereto so that the total solution volume was 70 mL. Next, a toluene solution (1 mol / L, 200 μL) of alkylaluminum (triisobutylaluminum) was added, followed by a toluene solution of a borate compound, and the autoclave was heated until the polymerization temperature was reached, after which the catalyst solution (0.5 μmol) was added. After the catalyst solution was added, ethylene pressure (gauge pressure 0.9 MPa) was applied, and the polymerization initiation point of the addition polymerization was set to 30 seconds after the start of the pressure. The total amount of the monomer solution immediately before the application of ethylene pressure was set to 80 mL. 15 minutes after the polymerization initiation point, the ethylene supply was stopped, and the pressure was carefully returned to normal pressure, and then isopropyl alcohol was added to the reaction solution to terminate the reaction, obtaining a polymerization solution. The polymerization solution was poured into a mixed solvent to precipitate the copolymer. The resulting copolymer was collected by suction filtration, washed with acetone and methanol, and then vacuum dried (110° C., 12 hours) to obtain a copolymer of norbornene and ethylene (cyclic olefin copolymer).

[0080] In this example, the amount of norbornene monomer used is as shown in Table 3 under "Charged amount of norbornene."

[0081] The polymerization temperature for the addition polymerization is as shown in Table 3 under "Polymerization temperature."

[0082] The catalysts used in this example are as shown in "Catalyst" in Table 3, and each number corresponds to the three types of catalysts shown in Table 1 below.

[0083] [Table 1]

[0084] In this example, the amount (molar ratio) of the borate compound charged relative to the catalyst is as shown in Table 3 under "Borate / Catalyst."

[0085] The borate compounds used in this example are as shown in "Borate Compounds" in Table 3, and each number corresponds to the four types of borate compounds shown in Table 2 below. Both "borate-3" and "borate-4" are salts consisting of a boron-containing anion and a nitrogen-containing cation. In these salts, the boron-containing anion is a tetraaryl boron anion, and the nitrogen-containing cation is a tertiary ammonium cation.

[0086] [Table 2]

[0087] In this example, the amount (molar ratio) of alkylaluminum (triisobutylaluminum, TIBA) charged relative to the borate compound is as shown in Table 3 under "TIBA / borate."

[0088] The mixed solvent used for precipitating the copolymer was a solvent consisting of acetone (300 mL), methanol or isopropyl alcohol (200 mL), and hydrochloric acid (5 mL).

[0089] The mass of each copolymer obtained was used to calculate the yield per 1 g of catalyst. The results are shown in Table 3 under "Copolymer yield per 1 g of catalyst."

[0090] (2) Evaluation of cyclic olefin copolymers Each of the cyclic olefin copolymers obtained in the above (1) was evaluated for the presence or absence of polyethylene-like impurities by the following method.

[0091] (2-1) Glass transition temperature (Tg) The Tg of the cyclic olefin copolymer was measured by a DSC method (method described in JIS K7121) under the following conditions. The results are shown in "Tg" in Table 3. DSC equipment: Differential scanning calorimeter (TA Instruments DSC-Q1000) Measurement atmosphere: Nitrogen Heating condition: 20℃ / min

[0092] (2-2) Impurity thermal analysis In the DSC curve obtained by measuring the glass transition temperature, the presence or absence of a melting point peak derived from polyethylene-like impurities observed within the range of 100° C. to 140° C. was judged from the shape of the curve. The results are shown in Table 3 under "Tm peak." The term "undetected" indicates that no peak derived from a polyethylene-like impurity was detected on the DSC curve, and the term "detected" indicates that the peak was detected.

[0093] (2-3) Turbidity test The obtained cyclic olefin copolymer (0.1 g) was dissolved in toluene (10 g), and the obtained solution was visually observed for the presence or absence of turbidity (polyethylene-like impurities). When turbidity was observed, it was judged as "present", and when no turbidity was observed, it was judged as "absent". The results are shown in Table 3 under "Turbidity Test."

[0094] [Table 3]

[0095] As can be seen from the comparison between Example 1 and Comparative Example 1, even when a borate compound was used, if the acid dissociation constant of the conjugate acid of the tertiary amine constituting the nitrogen-containing cation was 5 or less, polyethylene-like impurities were generated.

[0096] As can be seen from a comparison between Example 1 and Comparative Example 2 or Comparative Example 3, even when a borate compound in which the conjugate acid of the tertiary amine constituting the nitrogen-containing cation has an acid dissociation constant of more than 5 was used, polyethylene-like impurities were generated unless the amount (molar ratio) of the borate compound to the catalyst was within the range of 1.0 to 1.7.

[0097] As can be seen from a comparison between Example 7 and Comparative Example 4, when a borate compound, which is a salt composed of a boron-containing anion and a nitrogen-containing cation, was not used, polyethylene-like impurities were generated.

Claims

1. A method for producing a cyclic olefin copolymer, The production method includes addition polymerization of a norbornene monomer and ethylene, The addition polymerization is carried out in the presence of a borate compound, an alkylaluminum, and a catalyst, The borate compound is a salt composed of a boron-containing anion and a nitrogen-containing cation, The temperature condition of the addition polymerization is above 90°C, The acid dissociation constant (pKa) of the conjugate acid of the tertiary amine constituting the nitrogen-containing cation is greater than 5.0, The charged amount (molar ratio) of the borate compound to the catalyst is 1.0 to 1.5, Production method.

2. The boron-containing anion is a tetraarylboron anion, The nitrogen-containing cation is a tertiary ammonium cation. The production method according to claim 1.

3. The tertiary ammonium cation has an aliphatic hydrocarbon group having 6 to 20 carbon atoms. The production method according to claim 2.

4. The tertiary ammonium cation is a didecylmethylammonium ion. The production method according to claim 3.

5. The alkylaluminum is one or more selected from the group consisting of triisobutylaluminum, trimethylaluminum, and octylaluminum. The production method according to any one of claims 1 to 4.