WO2025047583A1 - Method for producing cyclic olefin copolymer - Google Patents

Abstract

The present invention provides a method for producing a cyclic olefin copolymer, the method making it possible to produce a cyclic olefin copolymer that has a low glass transition temperature and contains a structural unit derived from a norbornene monomer and a structural unit derived from an olefin selected from ethylene and α-olefins. A metal-containing catalyst that satisfies specific parameters and has a structure in which one or more ligands are coordinated to a central metal is used when producing a norbornene copolymer by polymerizing monomers including a norbornene monomer and an olefin selected from ethylene and α-olefins while the norbornene monomer is in a molten state.

Description

Method for producing cyclic olefin copolymer

The present invention relates to a method for producing a cyclic olefin copolymer that contains structural units derived from norbornene monomer and structural units derived from an olefin selected from ethylene and α-olefins.

Cyclic olefin copolymers have low moisture absorption and high transparency and are used in a variety of applications including optical materials such as optical disk substrates, optical films, and optical fibers.
A representative cyclic olefin copolymer is a copolymer of cyclic olefin and ethylene, which is widely used as a transparent resin. The glass transition temperature (Tg) of the copolymer of cyclic olefin and ethylene can be changed depending on the copolymerization composition of the cyclic olefin and ethylene, so that a copolymer having a glass transition temperature adjusted in a wide temperature range can be produced (see, for example, Non-Patent Document 1).

In recent years, various industries, particularly the manufacturing industry, have been increasingly required to be sustainable. As a method for producing the above-mentioned cyclic olefin copolymer that can meet the demand for sustainability, a method for producing the cyclic olefin copolymer by polymerization using a molten cyclic olefin monomer as a solvent has been proposed (see, for example, Patent Document 1).
Cyclic olefin copolymers are generally produced by polymerization in an organic solvent, but the method described in Patent Document 1 does not require energy for recycling the organic solvent by a method such as distillation, and can reduce the amount of organic solvent to be discarded.

JP 04-268312 A

Incoronatta, Tritto et al., Coordination Chemistry Reviews, 2006, Vol. 250, pp. 212-241

However, as described in Patent Document 1, when producing a cyclic olefin copolymer by carrying out polymerization in a molten cyclic olefin, it is difficult to obtain a cyclic olefin copolymer having a low glass transition temperature.

The present invention has been made in consideration of the above problems, and aims to provide a method for producing a cyclic olefin copolymer that contains constituent units derived from norbornene monomer and constituent units derived from an olefin selected from ethylene and an α-olefin, and that can produce a cyclic olefin copolymer having a low glass transition temperature.

The present inventors have discovered that the above problems can be solved by using a metal-containing catalyst that has a structure in which one or more ligands are coordinated to a central metal and satisfies specific parameters when producing a norbornene copolymer by polymerizing a monomer containing a norbornene monomer and an olefin selected from ethylene and an α-olefin while the norbornene monomer is in a molten state, and have thus completed the present invention. More specifically, the present invention provides the following.

(1) A method for producing a cyclic olefin copolymer containing a constituent unit derived from a norbornene monomer and a constituent unit derived from an olefin selected from ethylene and an α-olefin, comprising the steps of:
Charging at least a norbornene monomer and an olefin as monomers into a polymerization vessel;
and polymerizing the monomers in the polymerization vessel in a molten state of norbornene monomer in the presence of a metal-containing catalyst having a structure in which one or more ligands are coordinated to a central metal,
The ratio of the mass of the norbornene monomer to the mass of the polymerization solution in the polymerization vessel at the start of polymerization is 80 mass% or more,
The monomer reactivity ratio _rN of the metal-containing catalyst at 1 atmosphere and a reaction temperature of 363.15 K is 1.0 × ^10-4 or less;
The value of _rN is the ratio _kNN / _kNE of the insertion rate constant _kNN of norbornene into norbornene bound to a metal-containing catalyst to the insertion rate constant _kNE of ethylene into norbornene bound to a metal-containing catalyst,
_rN is represented by the following formula (r1):
r _N = exp(-(G ^‡ _NN -G ^‡ _NE )/RT)...(r1)
(In formula (r1), G ^‡ _NN is the Gibbs free energy of activation of the insertion reaction of norbornene into norbornene having a metal-containing catalyst bound thereto, G ^‡ _NE is the Gibbs free energy of activation of the insertion reaction of ethylene into norbornene having a metal-containing catalyst bound thereto, R is the gas constant, and T is the reaction temperature of 363.15 K.)
It is calculated by
G ^‡ _NN and G ^‡ _NE are calculated by the density functional method based on the DFT theory M06-2X and the basis set cc-pVDZ-(PP),
A production method, wherein the metal-containing catalyst contains Ti, Zr, Hf, Ni, Pd, or Pt as a central metal.

(2) The method for producing a cyclic olefin copolymer according to (1), wherein the polymerization solution in the polymerization vessel does not contain an organic solvent at the start of polymerization.

(3) The method for producing a cyclic olefin copolymer according to (1) or (2), wherein the polymerization pressure is 1 to 25 atm as a gauge pressure when the metal-containing catalyst is added to the polymerization vessel.

(4) A method for producing a cyclic olefin copolymer according to any one of (1) to (3), in which the polymerization of the monomers is carried out at 50 to 150°C.

(5) A method for producing a cyclic olefin copolymer according to any one of (1) to (4), in which the polymerization of the monomers is carried out in the presence of one or more cocatalysts selected from aluminoxanes, alkyl metal compounds, borate compounds, and organic phosphine compounds.

(6) A method for producing a cyclic olefin copolymer according to any one of (1) to (5), in which the polymerization of the monomer is carried out in the presence of a chain transfer agent.

(7) The method for producing a cyclic olefin copolymer according to (6), wherein the chain transfer agent is hydrogen or an amine.

The present invention provides a method for producing a cyclic olefin copolymer that contains constituent units derived from norbornene monomer and constituent units derived from an olefin selected from ethylene and an α-olefin, and that has a low glass transition temperature.

<Method for producing cyclic olefin copolymer>
The method for producing a cyclic olefin copolymer is a method for producing a cyclic olefin copolymer containing a constituent unit derived from a norbornene monomer and a constituent unit derived from an olefin selected from ethylene and an α-olefin.

The method for producing a cyclic olefin copolymer comprises the steps of:
Charging at least a norbornene monomer and an olefin as monomers into a polymerization vessel;
The method includes polymerizing the monomers in a polymerization vessel in a molten state of norbornene monomer in the presence of a metal-containing catalyst having a structure in which one or more ligands are coordinated to a central metal.

The ratio of the mass of norbornene monomer to the mass of the polymerization solution in the polymerization vessel at the start of polymerization is 80 mass% or more.

<Metal-containing catalyst>
The monomer reactivity ratio _rN of the metal-containing catalyst at 1 atmospheric pressure and a reaction temperature of 363.15 K is 1.0×10 ⁻⁴ or less.
The value of _rN is the ratio _kNN / _kNE of the insertion rate constant _kNN of norbornene into norbornene bound to a metal-containing catalyst to the insertion rate constant _kNE of ethylene into norbornene bound to a metal-containing catalyst.
_rN is represented by the following formula (r1):
r _N = exp(-(G ^‡ _NN -G ^‡ _NE )/RT)...(r1)
(In formula (r1), G ^‡ _NN is the Gibbs free energy of activation of the insertion reaction of norbornene into norbornene having a metal-containing catalyst bound thereto, G ^‡ _NE is the Gibbs free energy of activation of the insertion reaction of ethylene into norbornene having a metal-containing catalyst bound thereto, R is the gas constant, and T is the reaction temperature of 363.15 K (90° C.).)
It is calculated as follows.
G ^‡ _NN and G ^‡ _NE are calculated by the density functional method based on the DFT theory M06-2X and the basis set cc-pVDZ-(PP).
The metal-containing catalyst contains Ti, Zr, Hf, Ni, Pd, or Pt as a central metal.

The above manufacturing method makes it possible to produce a cyclic olefin copolymer with a low glass transition temperature. Specifically, the glass transition temperature of the resulting cyclic olefin copolymer is preferably 130°C or lower, more preferably 120°C or lower, and even more preferably 100°C or lower.

As described above, in the above production method, a metal-containing catalyst is used having a monomer reactivity ratio _rN of 1.0×10 ⁻⁴ or less at 1 atmosphere and a reaction temperature of 363.15 K. The value of _rN is the ratio _kNN / _kNE of the insertion rate constant _kNN of norbornene into norbornene bound to the metal-containing catalyst to the insertion rate constant _kNE of ethylene into norbornene bound to the metal-containing catalyst.
By setting the value of the monomer reactivity ratio _rN to 1.0×10 ⁻⁴ or less, continuous bonding of constitutional units derived from norbornene monomers during polymerization is suppressed, and a cyclic olefin copolymer having a low glass transition temperature can be produced.

The metal-containing catalyst is selected from various metal-containing catalysts having a structure in which one or more ligands are coordinated to a central metal by calculating the above _rN based on the structure of the catalyst.
The metal-containing catalyst is preferably selected from the group of metallocene catalysts represented by the following formula (C).
(Cp) (ZR ⁰¹ _m ) _n (A) _r ML _p (C)

In formula (C), (ZR ⁰¹ _n1 ) _n2 is a divalent group that bonds Cp and A.
Z is C, Si, Ge, N, or P.
R ⁰¹ is a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, a cycloalkenyl group having 3 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an alkylaryl group having 7 to 20 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms.
Cp is a cyclopentadienyl group which may have a substituent and which may be condensed with an aromatic ring.
A is -O-, -S-, -N(R ⁰² )-, or the above-mentioned Cp. R ⁰² is a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, a cycloalkenyl group having 3 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an alkylaryl group having 7 to 20 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms.
M is Ti, Zr, or Hf.
L is an anionic sigma ligand selected from the group consisting of a halogen atom, -OR ⁰³ , an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, a cycloalkenyl group having 3 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an alkylaryl group having 7 to 20 carbon atoms, and an aralkyl group having 7 to 20 carbon atoms. The anionic sigma ligand as L may contain one or more Si or Ge. ^{R 03} is a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, a cycloalkenyl group having 3 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an alkylaryl group having 7 to 20 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms.
n1 is 1 or 2. However, when Z is N or P, n1 is 1. When Z is C, Si, or Ge, n1 is 2.
n2 is an integer from 0 to 4.
r is 0 or 1. When r is 0, n2 is 0.
p is an integer of 2 to 3.
When r is 1, p is equal to (the oxidation state of metal M minus 2). When r is 0, p is equal to (the oxidation state of metal M minus 1).

Suitable examples of the divalent bridging group (ZR ⁰¹ _n1 ) _n2 include -C(R ⁰¹ ) ₂ -, -(C(R ⁰¹ ) ₂ ) ₂ -, -(C(R ⁰¹ ) ₂ ) ₃ -, -Si(R ⁰¹ ) ₂ -, -Ge(R ⁰¹ ) ₂ -, -NR ⁰¹ -, and -PR ⁰¹ -.

Preferred specific examples of the divalent bridging group (ZR ⁰¹ _n1 ) _n2 include -Si(CH ₃ ) ₂ -, -Si(Ph) ₂ -, -CH ₂ -, -CH ₂ CH ₂ -, -CH ₂ CH ₂ CH ₂ -, and -C(CH ₃ ) ₂ -.

Preferred examples of the ligand Cp that is π-bonded to the metal M include a cyclopentadienyl group, a methylcyclopentadienyl group, a dimethylcyclopentadienyl group, a trimethylcyclopentadienyl group, and a tetramethylcyclopentadienyl group; a 4-tert-butylcyclopentadienyl group; a 4-adamantylcyclopentadienyl group; an indenyl group, a monomethylindenyl group, a dimethylindenyl group, a trimethylindenyl group, and a tetramethylindenyl group; a 4,5,6,7-tetrahydroindenyl group; a fluorenyl group; a 5,10-dihydroindeno[1,2-b]indol-10-yl group; an N-methyl-5,10-dihydroindeno[ 1,2-b]indol-10-yl group, and N-phenyl-5,10-dihydroindeno[1,2-b]indol-10-yl group; 5,6-dihydroindeno[2,1-b]indol-6-yl group; N-methyl-5,6-dihydroindeno[2,1-b]indol-6-yl group, and N-phenyl-5,6-dihydroindeno[2,1-b]indol-6-yl group; azapentalen-4-yl group; thiapentalen-4-yl group; azapentalen-6-yl group; thiapentalen-6-yl group; monomethylazapentalen-4-yl group, dimethylazapentalen-4-yl group, and trimethylazapentalen-4-yl group.
A is preferably Cp as defined above.

For example, in a metal-containing catalyst, the value of _rN tends to be smaller when a bulky group is present near the central metal. In addition, the value of rN tends to be smaller when Cp has a substituent on a cyclopentadiene ring or a condensed ring containing a cyclopentadiene ring than when Cp does not have a substituent on the cyclopentadiene ring or a condensed ring containing a cyclopentadiene ring. Furthermore, when Cp has a substituent on a cyclopentadiene ring or a condensed ring containing a cyclopentadiene ring, the value _{of rN} tends to be smaller when the number of substituents is large.

Specific examples of metal-containing catalysts having a structure corresponding to the structure of the above formula (C) and having an _rN value of 1.0×10 ⁻⁴ or less include the following C1 and C2.
On the other hand, specific examples of metal-containing catalysts having a structure corresponding to the structure of the above formula (C) but having an _rN value of more than 1.0×10 ⁻⁴ include the following C′1 and C′2.
The structures of C2 and C'1 are similar. However, the _rN values of the two are significantly different. This is believed to be due to the fact that in C2, an electron-donating isopropyl group (iPr) is bonded to the cyclopentadiene ring, resulting in Zr being rich in electrons. In C2, which has electron-rich Zr, it is presumed that norbornene is weakly coordinated, making it difficult for an insertion reaction following coordination to occur.

（Ｃ１：ｒ_Ｎ＝２．８×１０^－７）
（Ｃ２：ｒ_Ｎ＝６．４×１０^－５）

(C1: r _N =2.8×10 ⁻⁷ )
(C2: r _N =6.4×10 ⁻⁵ )

（Ｃ’１：ｒ_Ｎ＝３．３×１０^－４）
（Ｃ’２：ｒ_Ｎ＝３．３×１０^－２）

(C'1: r _N =3.3×10 ^-4 )
(C'2: r _N =3.3×10 ^-2 )

<Monomer>
In the above-mentioned method for producing a cyclic olefin copolymer, a monomer containing a norbornene monomer and an olefin selected from ethylene and an α-olefin is used.

[Norbornene Monomer]
The norbornene monomer will now be described.

Norbornene monomers include, for example, norbornene and substituted norbornene, with norbornene being preferred. Norbornene monomers can be used alone or in combination of two or more.

The above-mentioned substituted norbornene is not particularly limited, and 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 compounds represented by the following general formula (I).

（式中、Ｒ^１～Ｒ^１２は、それぞれ同一でも異なっていてもよく、水素原子、ハロゲン原子、及び、炭化水素基からなる群より選ばれるものであり、
　Ｒ^９とＲ^１０、Ｒ^１１とＲ^１２は、一体化して２価の炭化水素基を形成してもよく、
　Ｒ^９又はＲ^１０と、Ｒ^１１又はＲ^１２とは、互いに環を形成していてもよい。
　また、ｎは、０又は正の整数を示し、
　ｎが２以上の場合には、Ｒ^５～Ｒ^８は、それぞれの繰り返し単位の中で、それぞれ同一でも異なっていてもよい。
　ただし、ｎ＝０の場合、Ｒ^１～Ｒ^４及びＲ^９～Ｒ^１２の少なくとも１個は、水素原子ではない。）

(In the formula, R ¹ to R ¹² may be the same or different and are each selected from the group consisting of a hydrogen atom, a halogen atom, and a hydrocarbon group;
R ⁹ and R ¹⁰ , and R ¹¹ and R ¹² may combine together to form a divalent hydrocarbon group;
R ⁹ or R ¹⁰ and R ¹¹ or R ¹² may be joined to form a ring.
In addition, n represents 0 or a positive integer,
When n is 2 or more, R ⁵ to R ⁸ may be the same or different in each repeating unit.
However, when n=0, at least one of R ¹ to R ⁴ and R ⁹ to R ¹² is not a hydrogen atom.

The substituted norbornene represented by the general formula (I) will be described below. R ¹ to R ¹² in the general formula (I) may be the same or different and are each selected from the group consisting of a hydrogen atom, a halogen atom, and a hydrocarbon group.

Specific examples of R ¹ to R ⁸ include a hydrogen atom; a halogen atom such as fluorine, chlorine, or bromine; and an alkyl group having 1 to 20 carbon atoms, and these may be different from each other, may be partially different, or may all be the same.

Specific examples of R ⁹ to R ¹² include a hydrogen atom; a halogen atom such as fluorine, chlorine, or bromine; an alkyl group having 1 to 20 carbon atoms; a cycloalkyl group such as a cyclohexyl group; a substituted or unsubstituted aromatic hydrocarbon group such as a phenyl group, a tolyl group, an ethylphenyl group, an isopropylphenyl group, a naphthyl group, or an anthryl group; a benzyl group, a phenethyl group, or an aralkyl group in which an aryl group is substituted on an alkyl group; and the like. These may be different from each other, may be partially different, or may all be the same.

Specific examples of the divalent hydrocarbon group formed by combining R ⁹ and R ¹⁰ , or R ¹¹ and R ¹² together, include alkylidene groups such as an ethylidene group, a propylidene group, and an isopropylidene group.

When ^R9 or ^R10 and ^R11 or ^R12 form a ring together, the ring formed may be a monocyclic or polycyclic ring, a polycyclic ring having a bridge, a ring having a double bond, or a ring consisting of a combination of these rings. These rings may have a substituent such as a methyl group.

Specific examples of the substituted norbornene represented by the general 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- Bicyclic olefins such as bicyclo[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 ]deca-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 their partial hydrogenated products (or adducts of cyclopentadiene and cyclohexene), tricyclo[4.4.0.1 ^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 simply 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 . 4-ring cyclic olefins such as ^17,10 ]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 . ^cyclo [ ^{8.7.0.12,9.03,8.14,7.012,17.113,16} ]-5-eicosene, heptacyclo[ ^{8.7.0.12,9.03,8.14,7.012,17.113,16 ]} -14 ^- eicosene ^; and polycyclic olefins such as a tetramer of cyclopentadiene.

Among these, alkyl-substituted norbornenes (e.g., bicyclo[2.2.1]hept-2-ene substituted with one or more alkyl groups) and alkylidene-substituted norbornenes (e.g., bicyclo[2.2.1]hept-2-ene substituted with one or more alkylidene groups) are preferred, with 5-ethylidene-bicyclo[2.2.1]hept-2-ene (common name: 5-ethylidene-2-norbornene, or simply ethylidenenorbornene) being particularly preferred.

[Olefin]
The olefin is selected from ethylene and α-olefins.
Ethylene and α-olefins will be described below. As the α-olefin, any known α-olefin can be used without any particular limitation. The α-olefin may be substituted with at least one substituent such as a halogen atom.

As the α-olefin, C3 to C12 α-olefins are preferred. There are no particular limitations on the C3 to C12 α-olefins, but examples include propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene, 3-methyl-1-pentene, 3-ethyl-1-pentene, 4-methyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1-hexene, 3-ethyl-1-hexene, 1-octene, 1-decene, and 1-dodecene. Of these, 1-hexene, 1-octene, and 1-decene are preferred.

As the cyclic olefin copolymer obtained by polymerizing the monomers described above, a norbornene monomer/ethylene copolymer, a norbornene monomer/α-olefin copolymer, and a norbornene monomer/ethylene/α-olefin copolymer are preferred, and a norbornene monomer/ethylene copolymer and a norbornene monomer/α-olefin copolymer are more preferred.
As the norbornene monomer/ethylene/α-olefin copolymer, a copolymer of a diene type norbornene monomer such as 5-ethylidene-2-norbornene, ethylene, and propylene is preferred. The 5-ethylidene-2-norbornene/ethylene/propylene copolymer is known as EPDM.

The polymerization reaction is carried out without using a solvent or with a small amount of a solvent. Specifically, the polymerization is carried out under the condition that the ratio of the mass of the norbornene monomer to the mass of the polymerization solution in the polymerization vessel at the start of the polymerization is 80 mass% or more.
At the start of polymerization, the ratio of the mass of the norbornene monomer to the mass of the polymerization solution in the polymerization vessel may be 85% by mass or more, or may be 90% by mass or more.

The polymerization pressure is preferably 1 to 25 atm as a gauge pressure when the metal-containing catalyst is added to the polymerization vessel.
In particular, when the olefin is in a gaseous state under the feeding conditions, the feeding pressure of the olefin into the polymerization vessel is preferably 1 to 25 atm as the pressure when the catalyst is added into the polymerization vessel. The feeding pressure is a gauge pressure.

The temperature at which the monomers are polymerized in the polymerization vessel is preferably from 50 to 150°C, more preferably from 50 to 130°C.
The polymerization time is not particularly limited, and the polymerization is carried out until a desired yield is reached or the molecular weight of the cyclic olefin copolymer increases to a desired level.
The polymerization time varies depending on the polymerization temperature, the catalyst composition, and the monomer composition, but is typically 0.01 to 120 hours, preferably 0.1 to 80 hours, and more preferably 0.2 to 10 hours.

In general, when ethylene charged at high pressure and norbornene monomer are copolymerized at a high temperature, such as 50° C. or higher, in the presence of a highly active catalyst, polymerization of ethylene units tends to proceed, and polyethylene-like impurities are likely to be produced.
If the cyclic olefin copolymer contains polyethylene-like impurities, turbidity occurs when the cyclic olefin copolymer is dissolved in a solvent.
Therefore, whether or not the cyclic olefin copolymer contains polyethylene-like impurities can be confirmed by visually observing a solution in which the cyclic olefin copolymer is dissolved in toluene at a concentration of 1% by mass. If the solution is cloudy, it can be said that the cyclic olefin copolymer contains polyethylene-like impurities.
As can be understood from such a phenomenon, when a cyclic olefin copolymer contains polyethylene-like impurities, there is a concern that the transparency of the cyclic olefin copolymer may decrease. Therefore, when polyethylene-like impurities are generated during the production of a cyclic olefin copolymer, a process is required to filter and remove the unnecessary polyethylene-like impurities, which increases the production cost.
However, when ethylene is used as the olefin, the production of polyethylene-like impurities can be suppressed by copolymerizing norbornene monomer with ethylene by the above-mentioned method.

Furthermore, the presence of polyethylene-like impurities can also be confirmed by measuring the cyclic olefin copolymer with a differential scanning calorimeter (DSC).
Specifically, the cyclic olefin copolymer is measured by DSC under a nitrogen atmosphere at a temperature increase rate of 20°C/min according to the method described in JIS K7121 to obtain a DSC curve. Then, the presence or absence of a melting point (melting enthalpy) peak due to polyethylene-like impurities is confirmed in the obtained DSC curve. When the cyclic olefin copolymer contains polyethylene-like impurities, the melting point peak due to polyethylene-like impurities on the DSC curve is generally detected within the range of 100°C to 140°C.

A solvent may be charged into the polymerization vessel together with the norbornene monomer and the olefin, as long as the desired effect is not impaired. There are no particular limitations on the solvent, so long as it does not inhibit the polymerization reaction. Examples of solvents include hydrocarbon solvents such as pentane, hexane, heptane, octane, cyclohexane, mineral oil, benzene, toluene, and xylene, and halogenated hydrocarbon solvents such as chloroform, methylene chloride, dichloroethane, and chlorobenzene.

The polymerization of the monomers is preferably carried out in the presence of one or more cocatalysts selected from aluminoxanes, alkyl metal compounds, borate compounds, and organic phosphine compounds.

[Aluminoxane]
As the aluminoxane, various aluminoxanes that have been conventionally used as cocatalysts in the polymerization of various olefins can be used without any particular limitation. Typically, the aluminoxane is an organic aluminoxane.
In producing the catalyst composition, the aluminoxane may be used alone or in combination of two or more kinds.

As the aluminoxane, alkylaluminoxanes are preferably used. Examples of alkylaluminoxanes include compounds represented by the following formula (b1-1) or (b1-2). The alkylaluminoxanes represented by the following formula (b1-1) or (b1-2) are products obtained by reacting trialkylaluminum with water.

（式（ｂ１－１）及び式（ｂ１－２）中、Ｒは炭素原子数１～４のアルキル基、ｎは０～４０、好ましくは２～３０の整数を示す。）

(In formula (b1-1) and formula (b1-2), R represents an alkyl group having 1 to 4 carbon atoms, and n represents an integer of 0 to 40, preferably 2 to 30.)

Examples of alkylaluminoxanes include methylaluminoxane and modified methylaluminoxanes in which some of the methyl groups of methylaluminoxane are replaced with other alkyl groups. For example, modified methylaluminoxanes having an alkyl group with 2 to 4 carbon atoms such as an ethyl group, a propyl group, an isopropyl group, a butyl group, or an isobutyl group as the alkyl group after substitution are preferred, and modified methylaluminoxanes in which some of the methyl groups are replaced with isobutyl groups are more preferred. Specific examples of alkylaluminoxanes include methylaluminoxane, ethylaluminoxane, propylaluminoxane, butylaluminoxane, isobutylaluminoxane, methylethylaluminoxane, methylbutylaluminoxane, and methylisobutylaluminoxane, and among these, methylaluminoxane and methylisobutylaluminoxane are preferred.

Alkyl aluminoxanes can be prepared by known methods. Commercially available alkyl aluminoxanes may also be used. Commercially available alkyl aluminoxanes include, for example, MMAO-3A, TMAO-200 series, TMAO-340 series (all manufactured by Tosoh Finechem Co., Ltd.) and methyl aluminoxane solution (manufactured by Albemarle Corporation).

The amount of aluminoxane used together with the metal-containing catalyst is preferably 10 to 100,000 moles, and more preferably 100 to 10,000 moles, in terms of the number of moles of aluminum atoms per mole of the metal-containing catalyst.

[Alkyl metal compound]
As the alkyl metal compound, various alkyl metal compounds which have been conventionally used as cocatalysts or the like in the polymerization of various olefins can be used without any particular limitation.
As the alkyl metal compound, it is preferable to use at least one of an alkyl aluminum compound having at least one alkyl group bonded to an Al atom and an alkyl zinc compound having at least one alkyl group bonded to a Zn atom.
The alkyl metal compounds may be used alone or in combination of two or more.

As the alkylaluminum compound, any compound that has been conventionally used for the polymerization of olefins, etc., can be used without any particular limitation. As the alkylaluminum compound, for example, a compound represented by the following general formula (II) can be mentioned.
(R ¹¹ ) _z1 AlX _3-z1 (II)
(In formula (II), R ¹¹ is an alkyl group having 1 to 15 carbon atoms, X is a halogen atom or a hydrogen atom, and z1 is an integer of 1 to 3.)

The number of carbon atoms in the alkyl group represented by R ¹¹ is 1 to 15, and from the viewpoint of easily obtaining the desired effect, is preferably 1 to 8, and is further preferably 2 to 8. Specific preferred examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, and an n-octyl group.

Specific examples of alkylaluminum compounds include trialkylaluminums such as trimethylaluminum, triethylaluminum, tri-n-propylaluminum, triisopropylaluminum, tri-n-butylaluminum, triisobutylaluminum, trisec-butylaluminum, tri-n-pentylaluminum, tri-n-hexylaluminum, tri-n-heptylaluminum, and tri-n-octylaluminum; dialkylaluminum halides such as dimethylaluminum chloride, diethylaluminum chloride, and diisobutylaluminum chloride; dialkylaluminum hydrides such as dimethylaluminum hydride, diethylaluminum hydride, di-n-propylaluminum hydride, diisopropylaluminum hydride, di-n-butylaluminum hydride, diisobutylaluminum hydride, disec-butylaluminum hydride, di-n-pentylaluminum hydride, di-n-hexylaluminum hydride, di-n-heptylaluminum hydride, and di-n-octylaluminum hydride; and dialkylaluminum alkoxides such as dimethylaluminum methoxide.

As the alkylzinc compound, any compound that has been conventionally used for the polymerization of olefins, etc., can be used without any particular limitation. As the alkylzinc compound, for example, a compound represented by the following general formula (III) can be mentioned.
(R ¹² ) _z2 ZnX _2-z2 (III)
(In formula (III), R ¹² is an alkyl group having 1 to 15, preferably 1 to 8, carbon atoms, X is a halogen atom or a hydrogen atom, and z2 is an integer of 1 to 3.)

The number of carbon atoms in the alkyl group represented by R ¹² is 1 to 15, and from the viewpoint of easily obtaining the desired effect, 1 to 8 is more preferable, and 2 to 8 is even more preferable. Specific preferred examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, and an n-octyl group.

Specific examples of alkyl zinc compounds include dialkyl zincs such as dimethyl zinc, diethyl zinc, di-n-propyl zinc, diisopropyl zinc, di-n-butyl zinc, diisobutyl zinc, di-sec-butyl zinc, di-n-pentyl zinc, di-n-hexyl zinc, di-n-heptyl zinc, and di-n-octyl zinc; alkyl zinc halides such as methyl zinc chloride, ethyl zinc chloride, and isobutyl zinc chloride; and alkyl zinc hydrides such as methyl zinc hydride, ethyl zinc hydride, and isobutyl zinc hydride.

Among the alkyl metal compounds, one or more selected from the group consisting of trialkylaluminum, dialkylaluminum hydride, and dialkylzinc are preferred, with trialkylaluminum and/or dialkylaluminum hydride being more preferred.

The amount of alkyl metal compound used together with the metal-containing catalyst is preferably 10 to 100,000 moles, and more preferably 100 to 10,000 moles, in terms of the number of moles of metal contained in the alkyl metal compound per mole of the metal-containing catalyst.

[Borate compounds]
As the borate compound, various borate compounds that have been conventionally used as cocatalysts or the like in the polymerization of various olefins can be used without any particular limitation.
Preferred specific examples of the borate compound include tetrakis(pentafluorophenyl)trityl borate, dimethylphenylammonium tetrakis(pentafluorophenyl)borate, and N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate.
The amount of the borate compound used together with the metal-containing catalyst is preferably 1 to 3 mol, more preferably 1 to 2 mol, per 1 mol of the metal-containing catalyst.

The polymerization of the monomers is also preferably carried out in the presence of a chain transfer agent. Examples of chain transfer agents include alcohols, thiols, ketones, aldehydes, amines, and hydrogen. Among these, amines and hydrogen are preferred as chain transfer agents.

Specific examples of chain transfer agents include alcohols such as methanol, ethanol, propanol, isopropanol, butanol, and pentanol; thiols such as ethanethiol, n-propanethiol, 2-propanethiol, n-butanethiol, 1,1-dimethylethanethiol, 2-butanethiol, 2-methyl-2-propanethiol, n-pentanethiol, 2-pentanethiol, 3-pentanethiol, 2-methyl-2-butanethiol, 3-methyl-2-butanethiol, and n-hexanethiol; ketones such as acetone, methyl ethyl ketone, diethyl ketone, and diamyl ketone; aldehydes such as acetaldehyde, propionaldehyde, butanal, and pentanal; ethylamine, diethylamine, triethylamine, propylamine, tripropylamine, dipropylamine, butylamine, dibutylamine, and tributylamine; and hydrogen.

The amount of the chain transfer agent used is preferably 1 to 100,000 mol, and more preferably 10 to 10,000 mol, per mol of the metal-containing catalyst.
When the chain transfer agent is hydrogen, the amount of hydrogen used is preferably 0.0001 to 1 atm, more preferably 0.001 to 0.1 atm, in terms of the partial pressure of hydrogen in the polymerization vessel at the time of adding the catalyst.

<Cyclic olefin copolymer>
The cyclic olefin copolymer obtained by the above production method contains constitutional units derived from a norbornene monomer and constitutional units derived from an olefin selected from ethylene and an α-olefin.
Hereinafter, the cyclic olefin copolymer obtained by the above-mentioned production method will be simply referred to as "cyclic olefin copolymer".
Furthermore, a structural unit derived from a norbornene monomer is designated as "N", and is also referred to as a "structural unit N derived from a norbornene monomer" or "structural unit N". Further, a structural unit derived from an olefin is designated as "O", and is also referred to as an "olefin-derived structural unit O" or "structural unit O".
The cyclic olefin copolymer may or may not contain a diad moiety in which two structural units N derived from a norbornene monomer are bonded together.
The biadjacent moiety is a meso biadjacent moiety and/or a racemo biadjacent moiety.
The cyclic olefin copolymer may or may not contain a triad moiety in which three structural units N derived from norbornene monomers are bonded together.
The ratio of the number of moles of the structural unit N constituting the diad moiety to the number of moles of all structural units in the cyclic olefin copolymer is preferably 10 mol % or less.
When the cyclic olefin copolymer contains a diad moiety, the ratio Mm/Mr of the number of moles of the racemo diad moiety Mr to the number of moles of the meso diad moiety Mm is preferably 0.01-30.
The ratio of the number of moles of the structural unit N constituting a triad to the number of moles of all structural units in the cyclic olefin copolymer is preferably 1.0 mol % or less.

When the norbornene monomer is norbornene, the meso type dyad structure is represented by the following formula (A), and the racemo type dyad structure is represented by the following formula (B).

The cyclic olefin copolymer contains little or no diad moieties in which two structural units N derived from norbornene monomers are bonded. The cyclic olefin copolymer contains little or no triad moieties in which three structural units N derived from norbornene monomers are bonded.
That is, in the molecular chain of the cyclic olefin copolymer, there are few sites where the structural units N derived from norbornene monomer are consecutively present, or there are no consecutive structural units N. For this reason, the cyclic olefin copolymer has few or no norbornene monomer blocks with consecutive structural units N, and therefore has a smaller free volume than conventional cyclic olefin copolymers containing many norbornene monomer blocks.
As a result, the cyclic olefin copolymer exhibits excellent water vapor barrier properties.

Furthermore, norbornene monomer blocks with consecutive N structural units have a negative effect on the impact resistance of the cyclic olefin copolymer. For this reason, when norbornene monomer blocks with consecutive N structural units are present in a small amount or are absent in a cyclic olefin copolymer, the cyclic olefin copolymer exhibits excellent impact resistance.

Furthermore, cyclic olefin copolymers are less likely to discolor or crack when exposed to high temperatures for long periods of time.

The ratio of the number of moles of the structural unit N constituting the diad moiety to the number of moles of all structural units of the cyclic olefin copolymer is preferably 10 mol % or less, more preferably 7 mol % or less, even more preferably 5 mol % or less, and particularly preferably 3 mol % or less.
The lower limit of the ratio of the number of moles of the structural unit N constituting the diad moiety to the number of moles of all the structural units of the cyclic olefin copolymer is not particularly limited as long as the desired effect is not impaired. The lower limit of the ratio of the number of moles of the structural unit N constituting the diad moiety to the number of moles of all the structural units of the cyclic olefin copolymer may be, for example, 0 mol% or more, 0.1 mol% or more, 0.3 mol% or more, or 0.5 mol% or more.
Therefore, for example, the ratio of the number of moles of the structural unit N constituting the diad moiety to the number of moles of all structural units of the cyclic olefin copolymer may be 0 to 10 mol%, 0.1 to 10 mol%, 0.3 to 10 mol%, 0.5 to 10 mol%, 0 to 7 mol%, 0.1 to 7 mol%, 0.3 to 7 mol%, 0.5 to 7 mol%, 0 to 5 mol%, 0.1 to 5 mol%, 0.3 to 5 mol%, 0.5 to 5 mol%, 0 to 3 mol%, 0.1 to 3 mol%, 0.3 to 3 mol%, or 0.5 to 3 mol%.

The ratio of the number of moles of the structural unit N constituting the triad moiety to the number of moles of all structural units of the cyclic olefin copolymer is preferably 1.0 mol % or less, more preferably 0.5 mol % or less, even more preferably 0.3 mol % or less, particularly preferably 0.1 mol % or less, and most preferably 0 mol %.
The lower limit of the ratio of the number of moles of the structural unit N constituting the triad moiety to the number of moles of all the structural units of the cyclic olefin copolymer is not particularly limited as long as the desired effect is not impaired. The lower limit of the ratio of the number of moles of the structural unit N constituting the triad moiety to the number of moles of all the structural units of the cyclic olefin copolymer may be, for example, 0 mol% or more, 0.01 mol% or more, 0.03 mol% or more, or 0.05 mol% or more.
Therefore, the ratio of the number of moles of the structural unit N constituting the triad portion to the number of moles of all structural units of the cyclic olefin copolymer is 0 to 1.0 mol%, 0.01 to 1.0 mol%, 0.03 to 1.0 mol%, 0.05 to 1.0 mol%, 0 to 0.5 mol%, 0.01 to 0.5 mol%.
, 0.03 to 0.5 mol%, 0.05 to 0.5 mol%, 0 to 0.3 mol%, 0.01 to 0.3 mol%, 0.03 to 0.3 mol%, 0.05 to 0.3 mol%, 0 to 0.1 mol%, 0.01 to 0.1 mol%, 0.03 to 0.1 mol%, or 0.05 to 0.1 mol%.

In the cyclic olefin copolymer, the ratio Mm/Mr of the number of moles of the racemo-type diad sites Mr to the number of moles of the meso-type diad sites Mm is preferably 0.01 to 30, more preferably 0.1 to 27, and even more preferably 0.5 to 25. When the above ratio Mm/Mr is 0.01 to 30, the cyclic olefin copolymer has excellent water vapor barrier properties.

The cyclic olefin copolymer may contain other structural units in addition to the structural unit N derived from a norbornene monomer and the structural unit O derived from an olefin selected from ethylene and an α-olefin.
The monomers which provide the other structural units are not particularly limited as long as they are monomers which are copolymerizable with norbornene monomer, ethylene, and α-olefin.
The content of other structural units in the cyclic olefin copolymer is not particularly limited as long as the desired effects are not impaired, but is preferably 10 mol % or less, more preferably 5 mol % or less, even more preferably 3 mol % or less, particularly preferably 1 mol % or less, and most preferably 0 mol %, based on the number of moles of all structural units in the cyclic olefin copolymer.

The content of the structural unit N derived from the norbornene monomer in the cyclic olefin copolymer is not particularly limited as long as the desired effects are not impaired.
The content of the structural unit N is preferably 50 mol% or less, more preferably 20 to 50 mol%, further preferably 25 to 50 mol%, and particularly preferably 30 to 50 mol%, based on the number of moles of all structural units in the cyclic olefin copolymer. When the content of the structural unit N is 50 mol% or less based on the number of moles of all structural units in the cyclic olefin copolymer, the cyclic olefin copolymer tends to exhibit a low glass transition point, which is preferable.

In the cyclic olefin copolymer, the content of the structural unit O derived from an olefin selected from ethylene and α-olefins is not particularly limited as long as the desired effects are not impaired.
The content of the structural unit O is preferably 50 mol % or more, more preferably 50 to 80 mol %, further preferably 50 to 75 mol %, particularly preferably 50 to 70 mol %, based on the number of moles of all structural units in the cyclic olefin copolymer.

The cyclic olefin copolymer produced by the above method has a low glass transition temperature and is therefore excellent in processability. In addition, the cyclic olefin copolymer produced by the above method has excellent water vapor barrier properties and transparency. For this reason, the cyclic olefin copolymer produced by the above method is particularly preferably used as a material for optical films or optical sheets, films or sheets for packaging materials, etc., which require high water vapor barrier properties and high transparency.

The present invention will be explained in detail below with examples, but the present invention is not limited to these examples.

[Examples 1 to 9, Comparative Example 1, and Comparative Example 2]
In producing the cyclic olefin copolymer, the following metal-containing catalysts C1 and C2 were used in the examples, and the following metal-containing catalysts C'1 and C'2 were used in the comparative examples.

（Ｃ１：ｒ_Ｎ＝２．８×１０^－７）
（Ｃ２：ｒ_Ｎ＝６．４×１０^－５）

(C1: r _N =2.8×10 ⁻⁷ )
(C2: r _N =6.4×10 ⁻⁵ )

（Ｃ’１：ｒ_Ｎ＝３．３×１０^－４）
（Ｃ’２：ｒ_Ｎ＝３．３×１０^－２）

(C'1: r _N =3.3×10 ^-4 )
(C'2: r _N =3.3×10 ^-2 )

In the examples and comparative examples, the following cocatalysts CC1 to CC4 were used.
CC1: N-methyldialkylammonium tetrakis(pentafluorophenyl)borate (alkyl: C14 to C18 (average: C17.5) (manufactured by Tosoh Finechem Co., Ltd.)
CC2: Triisobutylaluminum (manufactured by Tosoh Finechem Co., Ltd.)
CC3: TMAO-211 toluene solution (methylaluminoxane solution, manufactured by Tosoh Finechem Co., Ltd.)
CC4: 40.6 mass% (as the content of Al atoms) solid MAO toluene solution (average particle size d(0.5) 5.6 μm (measurement dispersion medium: toluene), slurry concentration 12.2 wt%, manufactured by Tosoh Finechem Co., Ltd.)

All operations were carried out under an inert gas atmosphere. Two well-dried 20 mL Schlenk flasks were prepared. A metal-containing catalyst and triisobutylaluminum shown in Table 1 were added to one Schlenk flask so that the substance ratio was 1:1000. A cocatalyst shown in Table 1 was added to the other Schlenk flask. Toluene was added to each Schlenk flask to obtain a metal-containing catalyst solution and a cocatalyst solution. A well-dried 150 mL stainless steel autoclave including a stirrer was heated to the polymerization temperature (60 to 90°C) shown in Table 1, and 20 mL of a melt of norbornene at 80°C was added using a pre-warmed syringe. The norbornene in the autoclave was stirred for 5 minutes, and then a metal-containing catalyst solution containing 0.1 μmol of the metal-containing catalyst was added to the autoclave. Thereafter, the cocatalyst solution prepared by the above method was added to the autoclave so that the molar ratio of the amount of cocatalyst to the amount of metal-containing catalyst was the molar ratio shown in Table 1. Next, ethylene pressure was applied to the autoclave to initiate polymerization so that the gauge pressure was 0.9 MPa. The polymerization initiation point was 30 seconds after the pressurization. The total amount of the monomer solution immediately before the application of ethylene pressure was 21 mL. 15 minutes after the start of polymerization, the ethylene supply was stopped, and the pressure was carefully returned to normal pressure. Then, the polymerization solution was immediately poured into a mixed solvent consisting of 50 mL of acetone, 50 mL of methanol, and 1.5 mL of hydrochloric acid to precipitate the cyclic olefin copolymer. The precipitate was collected by suction filtration. The collected precipitate was washed with acetone and methanol, and the washed precipitate was vacuum dried at 110 ° C. for 12 hours to obtain a copolymer of norbornene and ethylene as a cyclic olefin copolymer.
The copolymer yield (g) per 1 μg of catalyst, calculated from the amount of catalyst used and the amount of cyclic olefin copolymer obtained, is shown in Table 1.
In Example 4, 200 mol of triethylamine was used as a chain transfer agent relative to 1 mol of the metal-containing catalyst. In Example 5, 500 mol of triethylamine was used as a chain transfer agent relative to 1 mol of the metal-containing catalyst. In Examples 7 and 9, hydrogen gas equivalent to a partial pressure of 0.01 atm was added to the polymerization vessel as a chain transfer agent.

The cyclic olefin copolymers obtained in each of the Examples and Comparative Examples were subjected to the following methods: glass transition temperature, molecular weight measurement by gel permeation chromatography, impurity thermal analysis, and turbidity test. The measurement and test results are shown in Table 1.

<Glass transition temperature (Tg)>
The Tg of the cyclic olefin copolymer was measured by a DSC method (the method described in JIS K7121).
DSC device: differential scanning calorimeter (DSC-Q1000 manufactured by TA Instruments)
Measurement atmosphere: nitrogen Temperature rise condition: 20°C/min

<Impurity Thermal Analysis>
In the DSC curve obtained by measuring the glass transition temperature, the calorific value (mJ/mg) was calculated from the peak area of the melting point derived from the polyethylene-like impurity observed in the range of 100° C. to 140° C. The larger the calculated calorific value, the higher the content of the polyethylene-like impurity.
In Table 1, ND indicates that no peak derived from polyethylene-like impurities was detected on the DSC curve.

<Turbidity test>
0.5 g of the obtained cyclic olefin copolymer was dissolved in 45 g of toluene, and the presence or absence of turbidity in the solution was observed. When turbidity was observed, it was judged as ×, and when no turbidity was observed, it was judged as ◯.

＊触媒１μｇ当たりの環状オレフィン共重合体収量（ｇ）

*Cyclic olefin copolymer yield (g) per 1 μg of catalyst

From Table 1, it can be seen that the cyclic olefin copolymer of the embodiment produced by the above-mentioned specified method has a low glass transition temperature (Tg) and excellent processability.

For the cyclic olefin copolymers obtained in Example 1, Example 6, Comparative Example 1, and Comparative Example 2, the ratio of the structural unit N derived from a norbornene monomer, the ratio of the structural unit N constituting a diad moiety in which two structural units N are bonded, and the ratio of the structural unit N constituting a triad moiety in which three structural units N are bonded, relative to the total structural units of the cyclic olefin copolymer, and the meso/racemo ratio for the diad moiety were calculated from the integral values of the spectra observed by ^13C -NMR according to the following method.

The primary structures of the polymers identified by each spectrum are described in "Macromol. Chem. Phs. 1999, Vol. 200, Page 1340", "Macromolecules 2004, Vol. 37, Page 9681", "Macromolecules 2000, Vol. 33, Page 8931", etc.

This section explains how to calculate specific parameters when the norbornene monomer is norbornene and the olefin is ethylene.

First, the calculation of the composition will be described.
The composition is determined from the integrals observed at chemical shift values of 44.5-56.0 ppm in a spectrum chart obtained by ¹³ C-NMR: I _C2,C3 (derived from the 2nd and 3rd positions of the norbornene ring), I _C1,C4 (derived from the 1st and 4th carbons of the norbornene ring), I _C7 (derived from the 7th carbon of the norbornene ring) and I _C5,C6 +I _E (derived from the 5th and 6th carbons of the norbornene ring and the carbon of the ethylene moiety).
Composition of structural unit N (mol %)=1/3×(I _C2,C3 +I _C1,C4 +2×I _C7 )÷(I _C5,C6 +I _E )×100
From this, the proportion of the structural unit N derived from the norbornene monomer can be calculated.
In addition, the proportion of the structural unit O derived from an olefin can be calculated by subtracting the composition of the structural unit N from 100%.

The ratio of the amount of the diad moiety (NN dyad) and the amount of the triad moiety (NN triad) can be calculated from the distribution of the six triads (EEE, EEN, NEN, NNN, NNE, ENE) described in "Maclomol. Chem. Phs. 1999, Vol. 200, Page 1340" using the following formula: N represents a structural unit derived from a norbornene monomer, and E represents a structural unit derived from ethylene.
The ratio of the amount of the diad moiety (NN dyad) is the ratio of the number of constituent units N derived from norbornene monomers constituting the diad moiety to the total number of constituent units of the cyclic olefin copolymer.
The ratio of the amount of triad moieties (NN triads) is the ratio of the number of constituent units N derived from norbornene monomers constituting the triad moieties to the total number of constituent units of the cyclic olefin copolymer.
NN dyad (mol%)=(2×NNN+ENN)÷(2×ENN+2×ENE+2×NNN)×100
NN triad (mol%)=NNN÷(ENN+ENE+NNN)×100

The mole fraction of the meso form of the NN dyad is calculated from the average value of the sum of the integral of the C5 ENNE-meso peak (28.0-28.5 ppm) and the C6 ENNE-meso peak (31.5-31.8 ppm) divided by the peak of the C5, C6, and ethylene regions (29.4-32.5 ppm) and the integral of the C7 ENNE-meso peak (33.1-33.2 ppm) divided by the composition of the structural unit N derived from norbornene monomer and the integral of the C7 region (32.6-39 ppm).

Similarly, the mole fraction of the racemo species of the NN dyad is calculated from the average of the sum of the integral of the C5 ENNE-racemo species peak (28.0-28.5 ppm) and the C6 ENNE-racemo species peak (31.2-31.4 ppm) divided by the peak in the C5, C6, and ethylene regions (28-32.5 ppm) and the integral of the C7 ENNE-racemo species peak (33.4-33.8 ppm) divided by the norbornene composition and the integral of the C7 region (32.6-39 ppm).

An example of sample preparation conditions and measurement conditions is as follows.
Solvent: 1,1,2,2-tetrachloroethane-d2 (containing 10% by volume of hexamethyldisilane)
Concentration: 70mg/mL
Apparatus: Bruker AVANCE600 (resonance frequency of hydrogen atoms: 600 MHz)
Sample tube diameter: 10 mm
Measurement method: Power gate type Pulse width: 15 μsec
Delay time: 2.089 sec
Data acquisition time: 0.911 sec
Observation frequency range: 35971.22Hz
Decoupling: complete decoupling Number of integrations: 18,000 Chemical shift reference: the peak of hexamethyldisilane is set at −2.43 ppm.

The ratio of the structural units N derived from norbornene monomer to the total structural units of the cyclic olefin copolymer, the ratio Mr of the structural units N constituting the racemo-type diadjunction portion, the ratio Mm of the structural units N constituting the meso-type diadjunction portion, and Mm/Mr, determined by the above measurements, are shown in Table 2.

In addition, the cyclic olefin copolymers obtained in Example 1, Example 6, Comparative Example 1, and Comparative Example 2 were subjected to impact resistance tests and water vapor barrier property tests according to the following methods.

<Impact resistance test>
The obtained cyclic olefin copolymer was melted. The molten cyclic olefin copolymer was formed into a film on a glass substrate and then cooled to prepare a film sample having a thickness of 50 μm. The impact resistance of a specimen cut out from the obtained film sample was evaluated according to ASTM-D3420 using a film impact tester. The results are shown in Table 2. When the measured value of the impact resistance was 0.35 J or less, it was evaluated as ×, and when the measured value of the impact resistance was more than 0.35 J, it was evaluated as ◯.

<Water vapor barrier test>
The obtained cyclic olefin copolymer was melted. The melted cyclic olefin copolymer was formed into a film on a glass substrate and then cooled to prepare a film sample having a thickness of 100 μm. The obtained film sample was used to evaluate the water vapor barrier property under conditions of 40° C. and 90% RH according to the method of JIS Z0208. The water vapor barrier property was evaluated in units of g/m ² /24h. When the measured value of the water vapor barrier property was 4 g/m ² /24h or less, it was evaluated as ○, and when the measured value of the water vapor barrier property was more than 4 g/m ² /24h, it was evaluated as ×. The results are shown in Table 2.

[0113] Table 2 shows that the cyclic olefin copolymers obtained in Examples 1 and 6, which were produced by the above-mentioned method and had a small amount of diads formed from the constituent unit N derived from a norbornene monomer and a small amount of triads formed from the constituent unit N derived from a norbornene monomer, not only had excellent water vapor barrier properties but also excellent impact resistance.
On the other hand, the cyclic olefin copolymers obtained in Comparative Example 1 and Comparative Example 2, in which the amount of diads composed of the structural unit N derived from a norbornene monomer and the amount of triads composed of the structural unit N derived from a norbornene monomer are large, are inferior in water vapor barrier property and impact resistance.

In addition, according to Tables 1 and 2, the cyclic olefin copolymers obtained in Examples 1 and 6, which have a small amount of diads composed of the structural unit N derived from norbornene monomer and a small amount of triads composed of the structural unit N derived from norbornene monomer, have a low glass transition temperature (Tg) and excellent processability.

Claims (7)

A method for producing a cyclic olefin copolymer comprising a norbornene monomer-derived structural unit and an olefin-derived structural unit selected from ethylene and an α-olefin, comprising the steps of:
charging at least the norbornene monomer and the olefin as monomers into a polymerization vessel;
and polymerizing the monomer in the polymerization vessel in a molten state of the norbornene monomer in the presence of a metal-containing catalyst having a structure in which one or more ligands are coordinated to a central metal,
A ratio of the mass of the norbornene monomer to the mass of the polymerization solution in the polymerization vessel at the start of polymerization is 80 mass% or more;
The metal-containing catalyst has a monomer reactivity ratio _rN of 1.0× ^10-4 or less at 1 atmosphere and a reaction temperature of 363.15 K;
The value of _rN is a ratio kNN/kNE of the insertion rate constant _kNN of norbornene into norbornene bound to the metal-containing catalyst to the insertion rate constant _kNE of ethylene into _norbornene bound to _{the metal-} containing catalyst,
The _rN is represented by the following formula (r1):
r _N = exp(-(G ^‡ _NN -G ^‡ _NE )/RT)...(r1)
(In formula (r1), G ^‡ _NN is the Gibbs free energy of activation of the insertion reaction of norbornene into the norbornene bound to the metal catalyst, G ^‡ _NE is the Gibbs free energy of activation of the insertion reaction of ethylene into the norbornene bound to the metal catalyst, R is the gas constant, and T is the reaction temperature of 363.15 K.)
It is calculated by
The G ^‡ _NN and the G ^‡ _NE are calculated by a density functional method based on the DFT theory M06-2X and the basis set cc-pVDZ-(PP);
The production method, wherein the metal-containing catalyst contains Ti, Zr, Hf, Ni, Pd, or Pt as the central metal. The method for producing a cyclic olefin copolymer according to claim 1, wherein the polymerization solution in the polymerization vessel does not contain an organic solvent at the start of polymerization. The method for producing a cyclic olefin copolymer according to claim 1 or 2, wherein the polymerization pressure is 1 to 25 atm as a gauge pressure when the metal-containing catalyst is added to the polymerization vessel. The method for producing a cyclic olefin copolymer according to claim 1 or 2, wherein the polymerization of the monomer is carried out at 50 to 150°C. The method for producing a cyclic olefin copolymer according to claim 1 or 2, wherein the polymerization of the monomer is carried out in the presence of one or more cocatalysts selected from aluminoxanes, alkyl metal compounds, borate compounds, and organic phosphine compounds. The method for producing a cyclic olefin copolymer according to claim 1 or 2, wherein the polymerization of the monomer is carried out in the presence of a chain transfer agent. The method for producing a cyclic olefin copolymer according to claim 6, wherein the chain transfer agent is hydrogen or an amine.