Resin composition for injection molding and injection molded article

Abstract

To provide a resin composition for injection molding comprising a cyclic olefin copolymer which gives an injection moded body which has excellent breaking strain and toughness and having hardly causes cracks even when placed in a high temperature and high humidity environment and to provide an injection molded body comprising the resin composition for injection molding.SOLUTION: There is provided a resin composition for injection molding comprising (A) a cyclic olefin copolymer and a specific amount of (B) a hindered phenol-based antioxidant, wherein the amount of the structural unit derived from the α-olefin is adjusted to be 10 mol% or more and 40 mol% or less based on the total structural units and the cyclic olefin copolymer (A) is adjusted to have two or more glass transition temperatures in the range of 0°C to 300°C as determined by solid viscoelasticity measurement in the cyclic olefin copolymer (A) by using a copolymer of a cyclic olefin monomer and an α-olefin having 3 or more and 20 or less carbon atoms as the cyclic olefin copolymer (A).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an injection molding resin composition containing a cyclic olefin copolymer, and an injection molded article. [Background technology]

[0002] Cyclic olefin polymers and cyclic olefin copolymers (also referred to as "COP" and "COC," respectively) have low moisture absorption and high transparency. For this reason, COPs and COCs are used in a variety of applications, including optical materials such as optical disk substrates, optical films, and optical fibers. A typical COC is a copolymer of cyclic olefin and ethylene. The glass transition temperature of such a copolymer can be changed by the copolymerization composition of the cyclic olefin and ethylene. Therefore, a copolymer of cyclic olefin and ethylene can be produced as a copolymer with a higher glass transition temperature (Tg) than COPs, and it is even possible to achieve a Tg of over 200°C, which is difficult to achieve with COPs. However, such copolymers are hard and brittle. Therefore, such copolymers have problems such as low mechanical strength and poor handling and processability.

[0003] One method for improving the mechanical strength of high TgCOC is to copolymerize cyclic olefins with α-olefins other than ethylene (hereinafter referred to as "specific α-olefins"). Various studies have been conducted on the copolymerization of cyclic olefins with specific α-olefins.

[0004] The copolymerization of a cyclic olefin and a specific α-olefin is significantly different from the copolymerization of a cyclic olefin and ethylene. Under the conditions under which a high molecular weight material can be obtained by copolymerization of a cyclic olefin and ethylene, a chain transfer reaction caused by the specific α-olefin occurs in the copolymerization of a cyclic olefin and a specific α-olefin, making it difficult to obtain a high molecular weight material. Therefore, copolymers of a cyclic olefin and a specific α-olefin have been considered unsuitable for use as molding materials (see, for example, Non-Patent Document 1).

[0005] For this reason, various studies have been conducted to improve the molding processability of copolymers of cyclic olefins and specific α-olefins.For example, as a method for producing a copolymer of cyclic olefins and specific α-olefins that has a relatively high molecular weight and can be molded into a film, a method has been proposed in which a cyclic olefin and a specific α-olefin are copolymerized in the presence of a titanocene catalyst having a specific structure and triphenylmethylium tetrakis(pentafluorophenyl)borate (see Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-56275 [Non-patent literature]

[0007] [Non-Patent Document 1] Jung, HY et al., Polyhedron, 2005, Vol. 24, pp. 1269-1273 Summary of the Invention [Problem to be solved by the invention]

[0008] However, even when injection molding is performed using a copolymer of a cyclic olefin and a specific α-olefin obtained by the method described in Patent Document 1, there are problems such as the inability to obtain an injection-molded article that has both excellent fracture strain and toughness, and the injection-molded article that is obtained is prone to cracking when placed in a high-temperature, high-humidity environment.

[0009] The present invention has been made in view of the above circumstances, and has an object to provide a resin composition for injection molding containing a cyclic olefin copolymer, which gives an injection-molded article that has both excellent fracture strain and excellent toughness and is less likely to crack even when placed in a high-temperature, high-humidity environment, and an injection-molded article made from the resin composition for injection molding. [Means for solving the problem]

[0010] The present inventors have discovered that the above-mentioned problems can be solved by using, as the (A) cyclic olefin copolymer, a copolymer of a cyclic olefin monomer and an α-olefin having from 3 to 20 carbon atoms in a resin composition for injection molding, comprising (A) a cyclic olefin copolymer and a specific amount of (B) a hindered phenol-based antioxidant, and by controlling the amount of structural units derived from the α-olefin in the (A) cyclic olefin copolymer to be from 10 mol % to 40 mol % of the total structural units, and by making the (A) cyclic olefin copolymer have two or more glass transition temperatures within the range of 0°C to 300°C as determined by solid viscoelasticity measurement, thereby completing the present invention. More specifically, the present invention provides the following.

[0011] (I) A resin composition for injection molding comprising (A) a cyclic olefin copolymer and (B) a hindered phenol-based antioxidant, (A) The cyclic olefin copolymer is an addition polymer of a cyclic olefin monomer and an α-olefin having 3 to 20 carbon atoms, (A) the ratio of the number of moles of structural units derived from α-olefin to the number of moles of all structural units of the cyclic olefin copolymer is 10 mol % or more and 40 mol % or less, (A) the cyclic olefin copolymer has two or more glass transition temperatures determined by viscoelasticity measurement within a range of 0°C to 300°C; A resin composition for injection molding, wherein the content of the (B) hindered phenol-based antioxidant is 0.1 to 2.0 parts by mass per 100 parts by mass of the (A) cyclic olefin copolymer.

[0012] (II) The injection molding resin composition according to (I), wherein the cyclic olefin copolymer (A) has at least one glass transition temperature within the range of 0°C to 100°C and at least one glass transition temperature within the range of 160°C to 300°C.

[0013] (III) The injection molding resin composition according to (I) or (II), wherein the cyclic olefin copolymer (A) has at least one glass transition temperature below 0°C, at least one glass transition temperature between 0°C and 100°C, and at least one glass transition temperature between 160°C and 300°C.

[0014] (VI) An injection-molded article made from the resin composition for injection molding according to any one of (I) to (III).

[0015] (V) The injection-molded article according to (VI), which has a tensile strength of 30 MPa or more and a tensile breaking strain of 8% or more, as measured in accordance with ISO 527-1. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a resin composition for injection molding containing a cyclic olefin copolymer, which gives an injection-molded article that has both excellent fracture strain and excellent toughness and is less likely to crack even when placed in a high-temperature, high-humidity environment, and an injection-molded article made from the resin composition for injection molding. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments.

[0018] ≪Resin composition for injection molding≫ The resin composition for injection molding contains (A) a cyclic olefin copolymer and (B) a hindered phenol-based antioxidant. The content of the (B) hindered phenol-based antioxidant in the resin composition for injection molding is 0.1 to 2.0 parts by mass relative to 100 parts by mass of the (A) cyclic olefin copolymer. By using the above-mentioned resin composition for injection molding, it is possible to obtain an injection-molded article that has both excellent breaking strain and excellent toughness and is less likely to crack even when placed in a high-temperature, high-humidity environment.

[0019] Essential and optional components contained in the resin composition for injection molding will be described below.

[0020] <(A) Cyclic olefin copolymer> (A) Cyclic olefin copolymer is an addition polymer of a cyclic olefin monomer and an α-olefin having 3 to 20 carbon atoms. In (A) cyclic olefin copolymer, the ratio of the number of moles of structural units derived from α-olefin to the number of moles of all structural units is 10 to 40 mol %. In addition, (A) cyclic olefin copolymer has two or more glass transition temperatures within the range of 0 to 300°C as determined by viscoelasticity measurement.

[0021] Although the detailed mechanism is unknown, the cyclic olefin copolymer (A) has both excellent breaking strain and excellent toughness. Specifically, the (A) cyclic olefin copolymer exhibits a tensile strength of preferably 25 MPa or more, more preferably 27.5 MPa or more, and even more preferably 30 MPa or more, as measured in a tensile test performed at 23°C using a 2 mm-thick 1BA dumbbell test piece according to a method in accordance with ISO 527-1. Furthermore, the cyclic olefin copolymer (A) preferably exhibits a tensile strain at break of 4% or more, more preferably 6% or more, and even more preferably 8% or more, as measured by the tensile test according to the above method. Furthermore, the cyclic olefin copolymer (A) preferably exhibits a tensile modulus of elasticity of 1000 MPa or more, more preferably 1100 MPa or more, and even more preferably 1500 MPa or more, as measured by the tensile test according to the above method.

[0022] In the (A) cyclic olefin copolymer, the ratio of the number of moles of structural units derived from α-olefin to the number of moles of all structural units is 10 mol% or more and 40 mol% or less, and preferably 20 mol% or more and 30 mol% or less. If the ratio of the number of moles of structural units derived from α-olefin is too high, it is difficult to obtain a (A) cyclic olefin copolymer with high tensile strength and tensile modulus. If the ratio of the number of moles of structural units derived from α-olefin is too high, it is difficult to obtain a (A) cyclic olefin copolymer with high glass transition temperature and excellent heat resistance. The ratio of the number of moles of structural units derived from α-olefins is 13 It can be calculated by measuring the C-NMR spectrum.

[0023] (A) The cyclic olefin copolymer may contain structural units other than the structural units derived from the cyclic olefin monomer and the structural units derived from an α-olefin having from 3 to 20 carbon atoms, provided that the object of the present invention is not impaired. As the other structural units, structural units derived from a compound copolymerizable with the cyclic olefin monomer and the α-olefin having from 3 to 20 carbon atoms and having a carbon-carbon unsaturated double bond may be used. Typically, structural units derived from ethylene are preferred as the other structural units.

[0024] In the (A) cyclic olefin copolymer, the sum of the ratio of the number of moles of structural units derived from cyclic olefin monomers and the ratio of the number of moles of structural units derived from α-olefins to the number of moles of all structural units is preferably 80 mol% or more, more preferably 90 mol% or more, even more preferably 95 mol% or more, and most preferably 100 mol%.

[0025] (A) The cyclic olefin copolymer has two or more glass transition temperatures within the range of 0°C to 300°C as determined by viscoelasticity measurement. The glass transition temperature can be measured by observing the viscoelastic behavior of a 50 μm-thick film-shaped molded product with a solid rheometer at −100° C. to 300° C. Specifically, the glass transition temperature is determined as the peak top temperature in the tan δ chart obtained by the above-mentioned measurement.

[0026] The (A) cyclic olefin copolymer preferably has at least one glass transition temperature within the range of 0°C to 100°C and at least one glass transition temperature within the range of 160°C to 300°C, as this provides good mechanical properties measured by the above tensile test. In particular, since the breaking strain measured by the above-mentioned tensile test is large, it is preferable that (A) cyclic olefin copolymer has at least one glass transition temperature in the range below 0°C, in the range of 0°C to 100°C, and in the range of 160°C to 300°C. Within the above range of 0°C to 100°C, the range of 30°C to 80°C is preferred, and the range of 40°C to 70°C is more preferred. Within the above range of 160°C to 300°C, 170°C to 280°C is preferred, and 180°C to 270°C is more preferred. Within the above range of less than 0°C, -50°C to 0°C is preferred, and -40°C to -10°C is more preferred.

[0027] Typically, the (A) cyclic olefin copolymer has one glass transition temperature in the range of 0°C to 100°C and one glass transition temperature in the range of 160°C to 300°C, or has one glass transition temperature in the range below 0°C, one glass transition temperature in the range of 0°C to 100°C, and one glass transition temperature in the range of 160°C to 300°C.

[0028] The molecular weight of the (A) cyclic olefin copolymer is not particularly limited. The weight average molecular weight (Mw) of the (A) cyclic olefin copolymer is preferably 5,000 or more and 200,000 or less, and more preferably 10,000 or more and 100,000 or less, as a polystyrene-equivalent value measured by gel permeation chromatography (GPC). The number average molecular weight (Mn) of the (A) cyclic olefin copolymer is preferably 5,000 or more and 200,000 or less, more preferably 10,000 or more and 100,000 or less, in terms of polystyrene, measured by gel permeation chromatography (GPC). The dispersion ratio (Mw / Mn) is preferably 1.2 or more, and more preferably 1.3 or more.

[0029] [Cyclic olefin monomer] The cyclic olefin monomer is not particularly limited as long as it does not impair the object of the present invention. Typically, norbornene and substituted norbornene are preferably used as the cyclic olefin monomer. Norbornene is particularly preferred as the cyclic olefin monomer in terms of a good balance between cost, polymerizability, and the physical properties of the resulting cyclic olefin copolymer (A). The cyclic olefin monomer may be used alone or in combination of two or more.

[0030] The substituted norbornene is not particularly limited. Examples of the substituents on the substituted norbornene include halogen atoms and monovalent or divalent hydrocarbon groups. Specific examples of the substituted norbornene include compounds represented by the following formula (I):

[0031] [ka]

[0032] In formula (I), R a1 ~R a12 may be the same or different and each represents an atom or group selected from the group consisting of a hydrogen atom, a halogen atom, and a hydrocarbon group. R a9 and R a10 , R a11 and R 12 may combine 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, R a1 ~R a4 and R a9 ~R a12 At least one of the is not a hydrogen atom.

[0033] R a1 ~R a8 Specific examples of R include a hydrogen atom; a halogen atom such as fluorine, chlorine, and bromine; and an alkyl group having 1 to 20 carbon atoms. a1 ~R a8 R may all consist of different atoms or groups. a1 ~R a8 Some or all of these may be the same atom or group.

[0034] 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 R may all consist of different atoms or groups. a9 ~R a12 Some or all of these may be the same atom or group.

[0035] 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 groups include alkylidene groups such as an ethylidene group, a propylidene group, and an isopropylidene group.

[0036] R a9 or R a10 and R a11 or R a12 When these bond to each other to form a ring, the ring formed may be a monocyclic or 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.

[0037] 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-bicyclo[2.2.1]hept-2-ene, 5-methyl ... 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 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-cyclohexenylbicyclo[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 .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 known as 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 known as 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.

[0038] Among these, 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.

[0039] [α-Olefin] The α-olefin is an α-olefin having 3 to 20 carbon atoms. As such an α-olefin, not only unsubstituted α-olefins but also substituted α-olefins having a substituent such as a halogen atom can be used. The number of carbon atoms in the α-olefin is 3 to 20, preferably 4 to 12, and more preferably 6 to 10.

[0040] Specific examples of α-olefins having 3 to 12 carbon atoms 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. Among these, 1-hexene, 1-octene, and 1-decene are preferred.

[0041] [(A) Method for producing cyclic olefin copolymer] The method for producing the cyclic olefin copolymer (A) will be described below. (A) A method for producing a cyclic olefin copolymer includes addition polymerizing a cyclic olefin monomer and an α-olefin in the presence of a titanocene catalyst represented by the following formula (1) and a co-catalyst, wherein the co-catalyst includes a borate compound and a hindered phenol. In the above production method, the cyclic olefin monomer and the α-olefin are each added in two or more batches to the reaction system where addition polymerization is carried out. [ka] (In formula (1), R 1 ~R 3 are each independently an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, and R 4 and R 5 are each independently an alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or a halogen atom; R 6 ~R 13 are each independently a hydrogen atom, an alkyl group having from 1 to 12 carbon atoms, an aryl group having from 6 to 12 carbon atoms, or a silyl group which may have, as a substituent, a monovalent hydrocarbon group having from 1 to 12 carbon atoms.

[0042] According to this method, it is possible to provide a cyclic olefin copolymer (A) that satisfies any one of the above-mentioned requirements (I) to (III). Hereinafter, this method will also be referred to as the "first production method."

[0043] The following production method is also preferred as a method for producing the cyclic olefin copolymer (A). This method can provide the cyclic olefin copolymer (A) that satisfies the constituent requirements described in (I) or (II) above. Specifically, this method involves addition polymerizing a cyclic olefin monomer and an α-olefin in the presence of a titanocene catalyst represented by formula (1) and a co-catalyst. The co-catalyst includes a borate compound and a hindered phenol. The addition polymerization is carried out at a temperature ranging from 10°C to 60°C. The titanocene catalyst represented by formula (1) is the same as the titanocene catalyst described above for the first production method. Hereinafter, this method will also be referred to as the "second manufacturing method."

[0044] (First manufacturing method) In the first production method, a monomer containing the above-mentioned cyclic olefin monomer and α-olefin is used. The types of cyclic olefin monomer, α-olefin, and copolymerization ratio thereof are the same as those described for (A) cyclic olefin copolymer.

[0045] In the first production method, the cyclic olefin monomer and the α-olefin are each added in two or more batches to a reaction system where addition polymerization is carried out. By adding the cyclic olefin monomer and the α-olefin in this way, it is easy to obtain a cyclic olefin copolymer (A) having good mechanical properties, and also, by adding the cyclic olefin monomer and the α-olefin in this way, it is easy to obtain a cyclic olefin copolymer (A) having a glass transition temperature in the range of less than 0°C.

[0046] When adding in portions, the number of portions is not particularly limited. For example, the number of portions is preferably 2 or more and 5 or less, more preferably 2 or 3, and even more preferably 2. When adding in portions, the amount of cyclic olefin monomer or α-olefin added per portion is preferably TA / N×0.5 or more and TA / N×1.5 or less, more preferably TA / N×0.7 or more and TA / N×1.3 or less, and even more preferably TA / N×0.9 or more and TA / N×1.1 or less, where TA is the mass of the total amount added and N is the number of portions added.

[0047] When the number of divisions is two, the amount of cyclic olefin monomer or α-olefin added per division is preferably 25% by mass or more and 75% by mass or less, more preferably 35% by mass or more and 65% by mass or more, and even more preferably 45% by mass or more and 55% by mass or less, based on the total mass of the addition amount.

[0048] When the divided addition is carried out, at least one of the cycloolefin monomer and the α-olefin is added to the reaction vessel at or before the start of the addition polymerization, and then, at any timing after the start of the addition polymerization, the second or subsequent addition of the cycloolefin monomer or the α-olefin is carried out. When adding the components in portions, the time between each addition is preferably 3 minutes or more and 20 minutes or less, more preferably 5 minutes or more and 15 minutes or less. When the divided additions are carried out, the timing of addition of the cyclic olefin monomer and the timing of addition of the α-olefin may be simultaneous or different. The number of times the cyclic olefin monomer is added may be different from the number of times the α-olefin is added.

[0049] As described above, when producing the cyclic olefin copolymer (A), a titanocene catalyst represented by the above formula (1) is used. In formula (1), R 1 ~R 3 are each independently an alkyl group having from 1 to 6 carbon atoms or an aryl group having from 6 to 12 carbon atoms. Specific examples thereof include alkyl groups such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a t-butyl group, a pentyl group, a hexyl group, a cyclopentyl group, and a cyclohexyl group; and aryl groups such as a phenyl group, a biphenyl group, a phenyl group or a biphenyl group having the above alkyl group as a substituent, a naphthyl group, and a naphthyl group having the above alkyl group as a substituent.

[0050] R 4 and R 5are each independently an alkyl group having from 1 to 12 carbon atoms, an aryl group having from 6 to 12 carbon atoms, or a halogen atom, and specific examples thereof include a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom; a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a t-butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a cyclopentyl group, a cyclohexyl group, or any of these alkyl groups having the above-mentioned halogen atom as a substituent; a phenyl group, a biphenyl group, a naphthyl group, or any of these aryl groups having the above-mentioned halogen atom or alkyl group as a substituent.

[0051] R 6 ~R 13 are each independently a hydrogen atom, an alkyl group having from 1 to 12 carbon atoms, an aryl group having from 6 to 12 carbon atoms, or a silyl group which may have a monovalent hydrocarbon group having from 1 to 12 carbon atoms as a substituent. Specific examples of alkyl groups having from 1 to 12 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl, hexyl, heptyl, octyl, cyclopentyl, and cyclohexyl. Specific examples of aryl groups having from 6 to 12 carbon atoms include phenyl, biphenyl, naphthyl, and these aryl groups having the above alkyl groups as a substituent. Furthermore, specific examples of silyl groups having a monovalent hydrocarbon group having from 1 to 12 carbon atoms as a substituent include silyl groups having an alkyl group having from 1 to 12 carbon atoms as a substituent, such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a t-butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a cyclopentyl group, or a cyclohexyl group.

[0052] Specific examples of the titanocene catalyst represented by general formula (1) include (isopropylamido)dimethyl-9-fluorenylsilanetitanium dimethyl, (isobutylamido)dimethyl-9-fluorenylsilanetitanium dimethyl, (t-butylamido)dimethyl-9-fluorenylsilanetitanium dimethyl, (isopropylamido)dimethyl-9-fluorenylsilanetitanium dichloride, (isobutylamido)dimethyl-9-(3,6-dimethylfluorenyl)silanetitanium dichloride, (t-butylamido)dimethyl-9-fluorenylsilanetitanium dichloride, ( (Isopropylamido)dimethyl-9-(3,6-dimethylfluorenyl)silanetitanium dichloride, (isobutylamido)dimethyl-9-(3,6-dimethylfluorenyl)silanetitanium dichloride, (t-butylamido)dimethyl-9-(3,6-dimethylfluorenyl)silanetitanium dimethyl, (isopropylamido)dimethyl-9-[3,6-di(i-propyl)fluorenyl]silanetitanium dichloride, (isobutylamido)dimethyl-9-[3,6-di(i-propyl)fluorenyl]silanetitanium dichloride, (t-butylamido)dimethyl methyl-9-[3,6-di(i-propyl)fluorenyl]silanetitanium dimethyl, (isopropylamido)dimethyl-9-[3,6-di(t-butyl)fluorenyl]silanetitanium dichloride, (isobutylamido)dimethyl-9-[3,6-di(t-butyl)fluorenyl]silanetitanium dichloride, (t-butylamido)dimethyl-9-[3,6-di(t-butyl)fluorenyl]silanetitanium dimethyl, (isopropylamido)dimethyl-9-[2,7-di(t-butyl)fluorenyl]silanetitanium dichloride, (isobutylamido)dimethyl

[0033] Examples of the silane titanium dichloride include (t-butylamido)dimethyl-9-[2,7-di(t-butyl)fluorenyl]silanetitanium dichloride, (t-butylamido)dimethyl-9-[2,7-di(t-butyl)fluorenyl]silanetitanium dimethyl, (isopropylamido)dimethyl-9-(2,3,6,7-tetramethylfluorenyl)silanetitanium dichloride, (isobutylamido)dimethyl-9-(2,3,6,7-tetramethylfluorenyl)silanetitanium dichloride, and (t-butylamido)dimethyl-9-(2,3,6,7-tetramethylfluorenyl)silanetitanium dimethyl.Preferred is (t-butylamido)dimethyl-9-fluorenylsilanetitanium dimethyl ((t-BuNSiMe2Flu)TiMe2). (t-BuNSiMe2Flu)TiMe2 is a titanium complex represented by the following formula (2), and can be easily synthesized, for example, based on the description in "Macromolecules, Vol. 31, p. 3184, 1998."

[0053] [ka] (In the formula, Me represents a methyl group, and t-Bu represents a tert-butyl group.)

[0054] The amount of the titanocene catalyst used is not particularly limited as long as the addition polymerization reaction proceeds smoothly. The amount of the titanocene catalyst used is preferably 0.001 parts by mass or more and 10 parts by mass or less, more preferably 0.01 parts by mass or more and 5 parts by mass or less, and even more preferably 0.1 parts by mass or more and 1 part by mass or less, relative to 100 parts by mass of the total amount of the cyclic olefin monomer and the α-olefin.

[0055] The addition polymerization of a cyclic olefin monomer and a monomer containing an α-olefin is carried out in the presence of the titanocene catalyst and a co-catalyst, which includes a borate compound and a hindered phenol. By carrying out addition polymerization in the presence of the titanocene catalyst and a cocatalyst so as to satisfy the above-mentioned predetermined conditions, a cyclic olefin copolymer (A) having both excellent breaking strain and excellent toughness can be obtained.

[0056] As the borate compound, any borate compound that has been conventionally used as a co-catalyst in the homopolymerization or copolymerization of cyclic olefin monomers can be used without any particular limitation. Specific preferred examples of the borate compound include triphenylmethylium tetrakis(pentafluorophenyl)borate, dimethylphenylammonium tetrakis(pentafluorophenyl)borate, N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate, and N-methyldin-normal-decylammonium tetrakis(pentafluorophenyl)borate.

[0057] As the hindered phenol, any hindered phenol that has been used as a co-catalyst in the homopolymerization or copolymerization of a cyclic olefin monomer can be used without any particular limitation. Here, the hindered phenol is a phenol having a bulky substituent at at least one of the two adjacent positions to the phenolic hydroxyl group, such as an alkyl group other than a methyl group (e.g., isopropyl, isobutyl, sec-butyl, or tert-butyl group), an alkenyl group, an alkynyl group, an aryl group, a heterocyclic group, an alkoxy group, an aryloxy group, a substituted amino group, an alkylthio group, or an arylthio group.

[0058] Specific examples of hindered phenols include 2,6-di-tert-butyl-4-hydroxytoluene (BHT), 2,6-di-tert-butylphenol, 2-tert-butylphenol, 2-tert-butyl-p-cresol, 3,3',5,5'-tetra-tert-butyl-4,4'-dihydroxybiphenyl, 3,3',5,5'-tetra-tert-butyl-2,2'-dihydroxybiphenyl, 4,4'-butylidenebis(3-methyl-6-tert-butylphenol), 2,2'-methylenebis(6-tert-butyl-4-methylphenol), 4,4',4"-(1-methylpropanyl-3-ylidene)tris(6-tert-butyl-m-cresol), and 1,3,5-tris(3,5-di-tert-butyl-4-hydroxyphenylmethyl)2,4,6-trimethylbenzene. Among these, 2,6-di-tert-butyl-4-hydroxytoluene (BHT) and 2,6-di-tert-butylphenol are preferred because they have a small molecular weight and the desired effect of using a hindered phenol can be easily obtained by using a small amount.

[0059] Furthermore, the hindered phenol can increase the yield of the cyclic olefin copolymer by reacting with the alkylaluminum compound in the polymerization system, and therefore it is preferred that the co-catalyst further contains an alkylaluminum compound. Specific examples of alkylaluminum compounds include trialkylaluminums such as trimethylaluminum, triethylaluminum, triisopropylaluminum, tri-n-butylaluminum, triisobutylaluminum, tri-sec-butylaluminum, and tri-n-octylaluminum; dialkylaluminum halides such as dimethylaluminum chloride and diisobutylaluminum chloride; dialkylaluminum hydrides such as diisobutylaluminum hydride; and dialkylaluminum alkoxides such as dimethylaluminum methoxide.

[0060] The amount of the borate compound used is not particularly limited as long as the addition polymerization reaction proceeds smoothly and a cyclic olefin copolymer having the desired properties is obtained. The amount of the borate compound used is preferably 0.01 to 100 parts by mass, more preferably 0.1 to 10 parts by mass, and even more preferably 1 to 5 parts by mass, relative to 100 parts by mass of the total amount of the cyclic olefin monomer and the α-olefin.

[0061] The amount of the hindered phenol used is not particularly limited as long as the addition polymerization reaction proceeds smoothly and a cyclic olefin copolymer having the desired properties is obtained. The amount of the hindered phenol used is preferably 0.001 to 100 parts by mass, more preferably 0.01 to 10 parts by mass, and even more preferably 0.1 to 1 part by mass, relative to 100 parts by mass of the total amount of the cyclic olefin monomer and the α-olefin.

[0062] The amount of the alkylaluminum compound used is not particularly limited as long as the addition polymerization reaction proceeds smoothly and a cyclic olefin copolymer having the desired properties is obtained. The amount of the alkylaluminum compound used is preferably 0.001 to 10 parts by mass, more preferably 0.01 to 5 parts by mass, and even more preferably 0.1 to 1 part by mass, relative to 100 parts by mass of the total amount of the cyclic olefin monomer and the α-olefin.

[0063] 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, with hydrocarbon solvents being preferred due to their ease of handling, thermal stability, and chemical stability. Specific examples of preferred solvents include hydrocarbon solvents such as pentane, hexane, heptane, octane, isooctane, isododecane, mineral oil, cyclohexane, methylcyclohexane, decahydronaphthalene (decalin), benzene, toluene, and xylene, and halogenated hydrocarbon solvents such as chloroform, methylene chloride, dichloromethane, dichloroethane, and chlorobenzene.

[0064] The solvent may be charged into the polymerization vessel alone, or may be charged into the polymerization vessel in the form of a monomer solution, a catalyst solution, or a cocatalyst solution.

[0065] When a solvent is used, the amount thereof is not particularly limited, and the amount of the solvent used is preferably 100 parts by mass or more and 100,000 parts by mass or less, more preferably 500 parts by mass or more and 10,000 parts by mass or less, and even more preferably 1,000 parts by mass or more and 5,000 parts by mass or less, relative to 100 parts by mass of the total amount of the cyclic olefin monomer and the α-olefin.

[0066] The temperature of the addition polymerization is not particularly limited and is, for example, preferably from -20°C to 200°C, more preferably from -10°C to 10°C, and even more preferably from -5°C to 5°C. When producing a cyclic olefin copolymer having a glass transition temperature in the range of less than 0°C, in the range of 0°C to 100°C, or in the range of 160°C to 300°C, the temperature of the addition polymerization is preferably -20°C or higher and lower than 10°C. The time for addition polymerization is not particularly limited and is, for example, preferably from 5 minutes to 30 minutes, more preferably from 8 minutes to 20 minutes, and even more preferably from 10 minutes to 15 minutes.

[0067] The atmosphere in which the addition polymerization reaction is carried out is not particularly limited, but an inert gas atmosphere is preferred, and examples of the inert gas that can be used include nitrogen gas and helium gas.

[0068] After the addition polymerization is carried out as described above to produce the cyclic olefin copolymer (A), the cyclic olefin copolymer (A) is recovered from the reaction vessel in a conventional manner.

[0069] (Second manufacturing method) The second production method is similar to the first production method, except that the method for charging the cyclic olefin monomer and the α-olefin is not particularly limited, and the addition polymerization is carried out at a temperature in the range of 10°C or higher and 60°C or lower.

[0070] In the second production method, the method for charging the cyclic olefin monomer and the α-olefin may be the same as in the first production method. Because the charging operation is simple, the method for charging the cyclic olefin monomer and the α-olefin in the second production method is preferably a method in which the cyclic olefin monomer and the α-olefin are charged all at once into a reaction vessel at or before the start of the addition polymerization reaction.

[0071] <(B) Hindered phenol antioxidant> As the (B) hindered phenol-based antioxidant, any hindered phenol-based antioxidant that has conventionally been blended in various resin compositions can be used without any particular limitation. Here, the definition of the hindered phenol is the same as the definition of the hindered phenol explained in the first production method above.

[0072] Specific examples of (B) hindered phenol-based antioxidants include 2,2'-methylenebis(4-methyl-6-tert-butylphenol), hexamethylene glycol-bis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate), pentaerythritol-tetrakis-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, triethylene glycol-bis-3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate, 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, n-octadecyl-3-(4'-hydroxy-3',5 4,4'-di-tert-butylphenol)propionate, 4,4'-methylenebis(2,6-di-tert-butylphenol), 4,4'-butylidene-bis(6-tert-butyl-3-methyl-phenol), di-stearyl-3,5-di-tert-butyl-4-hydroxybenzylphosphonate, 2-t-butyl-6-(3-tert-butyl-5-methyl-2-hydroxybenzyl)-4-methylphenyl acrylate, and 3,9-bis{2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl}-2,4,8,10-tetraoxaspiro[5,5]undecane.

[0073] As described above, the content of the (B) hindered phenol-based antioxidant is 0.1 to 2.0 parts by mass relative to 100 parts by mass of the (A) cyclic olefin copolymer. The content of the (B) hindered phenol-based antioxidant is preferably 0.1 to 1.0 part by mass, and more preferably 0.1 to 0.5 part by mass, relative to 100 parts by mass of the (A) cyclic olefin copolymer, because this reduces adverse effects due to volatilization or sublimation of the (B) hindered phenol-based antioxidant itself or decomposition products of the (B) hindered phenol-based antioxidant during continuous production of injection-molded articles.

[0074] <Other additives> The resin composition for injection molding may contain additives other than (A) the cyclic olefin copolymer and (B) the hindered phenol antioxidant, as long as the desired effects are not impaired. Examples of other additives include antioxidants other than the (B) hindered phenol-based antioxidant, weather stabilizers, ultraviolet absorbers, antibacterial agents, flame retardants, colorants, reinforcing materials, fillers, etc. These additives are added to the resin composition for injection molding in amounts taking into account the typical amounts used depending on the type of additive. As the other additives, one kind may be used alone, or two or more kinds may be used in combination.

[0075] When the resin composition for injection molding contains the other additives described above, the ratio of the mass of the other additives to the mass of the resin composition for injection molding is not particularly limited as long as the desired effect is not impaired. The mass ratio of the other additives to the mass of the resin composition for injection molding can be adjusted appropriately depending on the effect to be obtained.

[0076] <Method for producing resin composition for injection molding> The method for producing the resin composition for injection molding is not particularly limited as long as it is a method that can uniformly mix (A) the cyclic olefin copolymer, (B) the hindered phenol antioxidant, and, if necessary, other additives. A preferred method for producing the resin composition for injection molding includes melt-kneading (A) the cyclic olefin copolymer, (B) the hindered phenol antioxidant, and, if necessary, other additives, using a melt-kneading device such as a single-screw extruder or a multi-screw extruder having two or more screws.

[0077] The form of the resin composition for injection molding is not particularly limited. The resin composition for injection molding may be in the form of powder, flakes, or pellets. Typically, the resin composition for injection molding is discharged in the form of strands from a melt kneading device. The strand-shaped resin composition for injection molding is cooled and solidified, and then cut into pellets.

[0078] ≪Injection molded body≫ The injection molded article is a molded article obtained by injection molding the above-mentioned resin composition for injection molding. Injection molded articles have both excellent fracture strain and excellent toughness, and are less likely to crack even when placed in a high-temperature, high-humidity environment, and are therefore suitable for use as molding materials for optical lenses, for example.

[0079] Furthermore, since the injection-molded article exhibits a low relative permittivity and a low dielectric loss tangent in the high-frequency band, it is suitable for use as a component or substrate material for electric or electronic devices used in the high-frequency band. Specifically, the injection molded body has a relative dielectric constant of 2.2 or less and a dielectric constant of 3.0 × 10 at 40 GHz. -4 The dielectric loss tangent is shown below.

[0080] The injection molded article preferably has a tensile strength of 30 MPa or more and a tensile breaking strain of 8% or more, as measured by the tensile test according to the above-mentioned method.

[0081] The injection molding method is not particularly limited, and any well-known injection molding method can be used without any particular limitation. The size and shape of the injection molded article are appropriately selected depending on the application of the injection molded article. [Example]

[0082] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[0083] [Examples 1 to 3] In Examples 1 to 3, 2-norbornene (Nb) and 1-octene (Oct) were used in the ratios shown in Table 1, with the total amount of 2-norbornene and 1-octene being 118.8 mmol. A 500 mL eggplant-shaped flask purged with nitrogen was charged with half of the 2-norbornene and 1-octene, 0.198 mmol of tri-n-octylaluminum, and 0.396 mmol of 2,6-di-tert-butyl-4-hydroxytoluene. The contents of the flask were then diluted with toluene to a volume of 258 mL. The contents of the flask were then cooled to 0°C. After cooling, a toluene solution containing a titanocene catalyst at a concentration of 0.04 mmol / L was added to the reaction mixture to adjust the titanocene catalyst amount to 0.22 mmol. The titanocene catalyst used was a compound represented by the aforementioned formula (2). Next, a toluene solution containing a borate compound at a concentration of 0.008 mmol / L was added to the reaction solution to adjust the amount of borate compound to 0.22 mmol. Triphenylmethylium tetrakis(pentafluorophenyl)borate was used as the borate compound. After adding the titanocene catalyst and the borate compound to initiate addition polymerization, the reaction solution was stirred with a magnetic stirrer at 0°C for 10 minutes. After the 10-minute reaction, the remaining half of the amounts of 2-norbornene and 1-octene, along with 0.022 mmol of tri-n-octylaluminum and 0.044 mmol of 2,6-di-tert-butyl-4-hydroxytoluene, were added to the eggplant-shaped flask. The addition polymerization reaction was then continued for 15 minutes. After a total of 25 minutes of reaction, a small amount of 2-propanol was added to the reaction solution to terminate the addition polymerization reaction. Hydrochloric acid was added to the reaction solution and stirred for 10 minutes, after which the organic layer was washed with ion-exchanged water. Repeated washing with ion-exchanged water was performed until the aqueous layer became neutral, and the washed organic layer was recovered. The recovered organic layer was added dropwise to a large amount of acetone to precipitate the resulting cyclic olefin copolymer. The precipitated copolymer was recovered by filtration, and then washed twice or more with methanol and acetone. The washed copolymer was dried under reduced pressure at 110°C for 16 hours or more to obtain a dried cyclic olefin copolymer.

[0084] For the resulting cyclic olefin copolymer, the ratio of the number of moles of structural units derived from α-olefin (1-octene) (α-olefin ratio) was determined by the following method. Approximately 50 mg of the obtained cyclic olefin copolymer was dissolved in 0.6 mL of chloroform-d, and the 13C-NMR spectrum was measured using a BRUKER AVANCE III 400+ cryoprobe under the conditions of 300 K, 90° pulse, repetition time 30 seconds, and accumulation 1000 times. From the obtained spectrum, the ratio of α-olefin was calculated based on the following formula in accordance with the method described in Macromolecules 2010, 43, 4527-4531. The results are shown in Table 1 as the Oct ratio in the resin. α-olefin ratio (mol%) = [integral value of carbon derived from α-olefin / (integral value of carbon derived from α-olefin + integral value of carbon derived from cyclic olefin monomer)] × 100

[0085] The molecular weight of the resulting cyclic olefin copolymer was measured by gel permeation chromatography, and the glass transition temperature was measured by the method described above. The results are shown in Table 1.

[0086] The film used as the sample in the measurement of the glass transition temperature was prepared by the following method. A mold with a depth of 50 μm was prepared using Kapton (registered trademark) film measuring 10 cm × 10 cm × 50 μm. The mold was filled with the obtained cyclic olefin copolymer, and then vacuum-pressed using a hot vacuum press under conditions of a pressure of 15 MPa, a temperature of 320 to 340°C, and a time of 15 minutes. After pressing, the pressed cyclic olefin copolymer was rapidly cooled by sandwiching it between metal plates at room temperature. After cooling, the metal plates were removed, yielding a cyclic olefin copolymer film with a thickness of approximately 50 μm.

[0087] 100 parts by mass of the cyclic olefin copolymer obtained according to the method described above and 0.15 parts by mass of a hindered phenol-based antioxidant (pentaerythritol-tetrakis-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate) were melt-kneaded under the following extrusion conditions using an extruder (tabletop extruder AS-1, manufactured by Apex Japan Co., Ltd.), and the molten mixture was then pelletized to obtain a resin composition for injection molding. [Extrusion conditions] (cylinder temperature) Example 1: 310°C Example 2: 300°C Example 3: 290°C

[0088] The obtained resin composition for injection molding was injection molded under the following injection molding conditions using a molding machine (Shinko Selvic Co., Ltd., small injection molding machine C, Mobile-0813) to obtain a 1BA type dumbbell test piece with a thickness of 2 mm as an injection molded article. In Examples 1 to 3, injection molding was carried out at the following cylinder temperatures and mold temperatures. [Molding conditions] (cylinder temperature) Example 1: 330°C Example 2: 320°C Example 3: 310°C (mold temperature) Example 1: 150°C Example 2: 130°C Example 3: 120°C

[0089] The injection-molded articles thus obtained were subjected to a high-temperature, high-humidity test according to the following method, and the occurrence of moisture cracks during the high-temperature, high-humidity test was evaluated. The evaluation results are shown in Table 2. <High temperature and humidity test> The resulting injection-molded articles were treated for 168 hours at a temperature of 60°C and a humidity of 90% using an environmental tester (Espec Corporation, small environmental tester SH-241), and then left to stand at room temperature for 3 hours. After standing at room temperature, the interior of the injection-molded test pieces was photographed using a laser microscope (Keyence Corporation, ultra-deep color 3D shape measuring microscope VK-9510), and the occurrence of moisture cracks was evaluated according to the following criteria. ○: No cracks (spherical particles) in the image ×: Cracks (spherical particles) present in the image

[0090] The injection-molded articles (1BA dumbbell test pieces) were subjected to tensile tests according to the following method. The results of the tensile tests are shown in Table 2. <Tensile test> The obtained injection molded article was subjected to a tensile test in accordance with ISO527-1 using a tensile tester (Shimadzu Corporation, Autograph AG-Xplus) at a temperature of 23°C, a chuck distance of 58 mm, and a tensile speed of 25 mm / min.

[0091] [Comparative Example 1] A cyclic olefin copolymer was obtained in the same manner as in Example 1, except that the norbornene and 1-octene were all charged at once before the start of the addition polymerization reaction, the reaction temperature was changed to 40°C, and the reaction time was changed to 4 hours. The charging ratio of norbornene and 1-octene is as shown in Table 1. The obtained cyclic olefin copolymer was subjected to measurement of the Oct ratio in the resin, measurement of the molecular weight by gel permeation chromatography, and measurement of the glass transition temperature by the above-mentioned method in the same manner as in Example 1. The measurement results are shown in Table 1.

[0092] Using 100 parts by mass of the cyclic olefin copolymer obtained according to the method described above and 0.15 parts by mass of a hindered phenol-based antioxidant (pentaerythritol-tetrakis-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate), pellets of a resin composition for injection molding were obtained in the same manner as in Example 1, except that the cylinder temperature of the extruder was changed to 310°C.

[0093] The obtained resin composition for injection molding was used to obtain an injection-molded article by injection molding in the same manner as in Example 1, except that the cylinder temperature was changed to 290°C and the mold temperature was changed to 100°C. The obtained injection-molded article was evaluated for moisture cracking during a high-temperature, high-humidity test and subjected to a tensile test in the same manner as in Example 1. The evaluation results are shown in Table 2.

[0094] Comparative Example 2 A cyclic olefin copolymer was obtained in the same manner as in Example 1, except that 0.97 mmol of CC1 below and 0.68 mmol of CC2 below were used as cocatalysts, the reaction temperature was changed to 40°C, and the polymerization time was changed to 4 hours. The charging ratios and charging methods of norbornene and 1-octene are as shown in Table 1. The obtained cyclic olefin copolymer was subjected to measurement of the Oct ratio in the resin, measurement of the molecular weight by gel permeation chromatography, and measurement of the glass transition temperature by the above-mentioned method in the same manner as in Example 1. The measurement results are shown in Table 1. CC1: 6.5 mass% (as Al atom content) MMAO-3A toluene solution ([(CH3) 0.7 (iso-C4H9) 0.3 AlO] n (Tosoh Finechem Co., Ltd., containing 6 mol% trimethylaluminum based on the total aluminum) CC2: 9.0 mass% (as Al atom content) TMAO-211 toluene solution (methylaluminoxane solution, manufactured by Tosoh Finechem Co., Ltd., containing 26 mol% trimethylaluminum based on the total Al)

[0095] Using 100 parts by mass of the cyclic olefin copolymer obtained according to the method described above and 0.15 parts by mass of a hindered phenol-based antioxidant (pentaerythritol-tetrakis-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate), pellets of a resin composition for injection molding were obtained in the same manner as in Example 1, except that the cylinder temperature of the extruder was changed to 340°C.

[0096] An attempt was made to perform injection molding using the resulting resin composition for injection molding, but injection molding was not possible because the resin composition for injection molding did not flow to an extent that would allow injection molding at a temperature lower than the decomposition temperature of the resin.

[0097] Comparative Example 3 A cyclic olefin copolymer was obtained in the same manner as in Comparative Example 1, except that only 0.22 mmol of triphenylmethylium tetrakis(pentafluorophenyl)borate was used as the co-catalyst, the reaction temperature was changed to 25°C, and the reaction time was changed to 2 hours. The charging ratios of norbornene and 1-octene are as shown in Table 1. The obtained cyclic olefin copolymer was subjected to measurement of the Oct ratio in the resin, measurement of the molecular weight by gel permeation chromatography, and measurement of the glass transition temperature by the above-mentioned method in the same manner as in Example 1. The measurement results are shown in Table 1.

[0098] Using 100 parts by mass of the cyclic olefin copolymer obtained according to the method described above and 0.15 parts by mass of a hindered phenol-based antioxidant (pentaerythritol-tetrakis-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate), pellets of a resin composition for injection molding were obtained in the same manner as in Example 1, except that the cylinder temperature of the extruder was changed to 270°C.

[0099] The obtained resin composition for injection molding was used to obtain an injection-molded article by injection molding in the same manner as in Example 1, except that the cylinder temperature was changed to 310°C and the mold temperature was changed to 140°C. The obtained injection-molded article was evaluated for moisture cracking during a high-temperature, high-humidity test and subjected to a tensile test in the same manner as in Example 1. The evaluation results are shown in Table 2.

[0100] [Table 1]

[0101] [Table 2]

[0102] Tables 1 and 2 show that the (A) cyclic olefin copolymers prepared in Examples 1 to 3, in which the ratio of the number of moles of structural units derived from α-olefins to the number of moles of all structural units is 10 mol % or more and 40 mol % or less, and which have two or more glass transition temperatures determined by viscoelasticity measurement within the range of 0°C to 300°C, exhibit excellent tensile properties and combine excellent breaking strain with excellent toughness. Therefore, the injection-molded articles obtained using the injection-molding compositions containing the cyclic olefin copolymers (A) prepared in Examples 1 to 3 also have excellent breaking strain and excellent toughness. Furthermore, the injection-molded articles obtained using the resin compositions for injection molding of Examples 1 to 3, which contained (B) a hindered phenol-based antioxidant, were less likely to crack even when placed in a high-temperature, high-humidity environment. On the other hand, the injection molding resin compositions of Comparative Examples 1 to 3 containing (A) cyclic olefin copolymers prepared in Comparative Examples 1 to 3, which had only one glass transition temperature within the range of 0°C to 300°C as determined by viscoelasticity measurement, were prone to moisture cracking, were inferior in at least one of tensile strength, breaking strain, and tensile modulus, and did not flow below their decomposition temperature and could not be injection molded, making it impossible to evaluate the occurrence of moisture cracking, even though they contained (B) hindered phenol-based antioxidant.

Claims

1. A resin composition for injection molding comprising (A) a cyclic olefin copolymer and (B) a hindered phenol-based antioxidant, The cyclic olefin copolymer (A) is an addition polymer of a cyclic olefin monomer and an α-olefin having 3 to 20 carbon atoms, the ratio of the number of moles of structural units derived from the α-olefin to the number of moles of all structural units of the cyclic olefin copolymer (A) is 10 mol % or more and 40 mol % or less, the cyclic olefin copolymer (A) has at least one glass transition temperature measured by viscoelasticity measurement in the range of less than 0°C, at least one glass transition temperature in the range of 0°C to 100°C, and at least one glass transition temperature in the range of 160°C to 300°C; The resin composition for injection molding, wherein the content of the hindered phenol-based antioxidant (B) is 0.1 to 2.0 parts by mass per 100 parts by mass of the cyclic olefin copolymer (A).

2. An injection-molded article made from the resin composition for injection molding according to claim 1.

3. 3. The injection molded article according to claim 2, which has a tensile strength of 30 MPa or more and a tensile breaking strain of 8% or more, as measured in accordance with ISO 527-1.

Images