Rubber composition and its uses

Abstract

To obtain a rubber composition suitable for obtaining a rubber material for a tire which can improve tear resistance while maintaining rupture properties at a practically sufficient level.SOLUTION: There is provided a rubber composition which comprises a diene-based rubber (Z) and 0.5 to 50 pts.mass of an ethylene-non-conjugated polyene copolymer (X) satisfying all of the following (1) to (%) based on 100 pts.mass of the diene-based rubber (Z). (1) The content of the constituent unit derived from a non-conjugated polyene is in the range of 0.01 to 10 mol% [provided that the total of (A) and (B) is defined as 100 mol%]. (2) The intrinsic viscosity [η] measured in decalin at 135°C is in the range of 1.0 to 2.0 dl / g. (3) The density is in the range of 920 to 950 kg / m3. (4) The melting point (Tm) measured by DSC is in the range of 100 to 130°C. (5) P value [η*(ω=0.1) / η*(ω=100)] determined by melt viscoelasticity measurement is in the range of 5 to 100.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a rubber composition suitable for obtaining a rubber material for tires and to applications such as tires using the same. [Background technology]

[0002] Rubber (vulcanized rubber) has excellent elasticity and heat resistance, and is widely used in automobile tires, vibration-proof rubber, and various sealing materials. The raw rubbers used include natural rubber, styrene-butadiene rubber, butadiene rubber, and ethylene-propylene rubber. Synthetic rubber such as rubber is used.

[0003] Proposed rubber compositions for use in tires include a rubber composition for tire treads (Patent Document 1) that can provide tire treads with an excellent balance between durability such as abrasion resistance, cut resistance, and tear resistance, and reduced rolling resistance, and a rubber composition for use in tire treads (Patent Document 2) that contains a rubber component consisting of at least one of natural rubber and synthetic diene rubber, and also contains a specific bismaleimide and a functionalized polyolefin. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-99746 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-121326 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to obtain a rubber composition suitable for obtaining a rubber material for tires which can improve tear resistance while maintaining break properties at a practically sufficient level. [Means for solving the problem]

[0006] The present invention relates to a diene rubber (Z), and a composition comprising, per 100 parts by mass of the diene rubber (Z), It contains a structural unit (A) derived from ethylene and a structural unit (B) derived from a non-conjugated polyene, The present invention relates to a rubber composition characterized by containing 0.5 to 50 parts by mass of an ethylene-non-conjugated polyene copolymer (X) that satisfies all of the following (1) to (5):

[0007] Ethylene-non-conjugated polyene copolymer (X) (1) The content of structural units derived from non-conjugated polyenes is in the range of 0.01 to 10 mol % (where the total of (A) and (B) is taken as 100 mol %). (2) The intrinsic viscosity [η] measured in decalin at 135°C is in the range of 1.0 to 2.0 dl / g. (3) Density: 920 to 950 kg / m 3 is in the range. (4) The melting point (Tm) measured by DSC is in the range of 100 to 130°C. (5) The P value [η*(ω=0.1) / η*(ω=100)] determined by melt viscoelasticity measurement is in the range of 5 to 100. [Effects of the Invention]

[0008] The rubber composition of the present invention contains an ethylene-non-conjugated polyene copolymer that is crystalline and can be co-crosslinked with a diene rubber. Therefore, a molded article made from the rubber composition has tensile properties (tensile stress at break and tensile elongation at break) that are sufficient for practical use, and also has improved tear resistance (excellent tear strength), making it particularly suitable as a rubber material for tires. DETAILED DESCRIPTION OF THE INVENTION

[0009] <Diene rubber (Z)] The diene rubber (Z), which is one of the components constituting the rubber composition of the present invention, is a rubber having units derived from a conjugated diene in the molecule, and any known diene rubber having a double bond in the molecule can be used without limitation, and these may be used alone or in combination of two or more.

[0010] As the diene rubber (Z) according to the present invention, a polymer or copolymer rubber containing a conjugated diene compound as a main monomer is preferably used. In the present invention, the diene rubber also includes natural rubber (NR) and hydrogenated rubber. As the diene rubber (Z), an uncrosslinked one can usually be used, and it is desirable that the iodine value be 100 or more, preferably 200 or more, and more preferably 250 or more.

[0011] Specific examples of the diene rubber (Z) according to the present invention include natural rubber (NR), isoprene rubber (IR), styrene-butadiene rubber (SBR), butadiene rubber (BR), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), nitrile rubber, and hydrogenated nitrile rubber.

[0012] In the present invention, the diene rubber (Z) is preferably natural rubber (NR), isoprene rubber (IR), styrene-butadiene rubber (SBR), or butadiene rubber (BR), and particularly preferably styrene-butadiene rubber (SBR), butadiene rubber (BR), or a mixture of styrene-butadiene rubber (SBR) and butadiene rubber (BR). These diene rubbers (Z) can be used alone or in combination of two or more.

[0013] As natural rubber (NR), natural rubber standardized by the Green Book (International Quality Packaging Standard for Various Grades of Natural Rubber) can be used. As isoprene rubber (IR), rubber with a specific gravity of 0.91 to 0.94 and a Mooney viscosity [ML(1+4)(100°C), JIS K6300] of 30 to 120 is preferably used.

[0014] As the styrene-butadiene rubber (SBR), one having a specific gravity of 0.91 to 0.98 and a Mooney viscosity [ML(1+4)(100°C), JIS K6300] of 20 to 120 is preferably used.

[0015] The butadiene rubber (BR) preferably has a specific gravity of 0.90 to 0.95 and a Mooney viscosity [ML(1+4)(100°C), JIS K6300] of 20 to 120.

[0016] <Ethylene-non-conjugated polyene copolymer (X)> The ethylene-non-conjugated polyene copolymer (X) (hereinafter, sometimes referred to as "copolymer (X)"), which is one of the components constituting the rubber composition of the present invention, is an ethylene-non-conjugated polyene copolymer (X) characterized by containing a structural unit (A) derived from ethylene and a structural unit (B) derived from a non-conjugated polyene, and satisfying all of the following requirements (1) to (5):

[0017] <Requirement (1)> The content of structural units derived from non-conjugated polyenes is in the range of 0.01 to 10 mol %, preferably 0.05 to 8 mol % (where the total of (A) and (B) is taken as 100 mol %).

[0018] The non-conjugated polyene constituting the copolymer (X) of the present invention may be a cyclic or linear non-conjugated polyene. Examples of cyclic non-conjugated polyenes include 5-ethylidene-2-norbornene (ENB), dicyclopentadiene, 5-vinyl-2-norbornene (VNB), norbornadiene, and methyltetrahydroindene. Examples of linear non-conjugated polyenes include 1,4-hexadiene, 7-methyl-1,6-octadiene, 8-methyl-4-ethylidene-1,7-nonadiene, and 4-ethylidene-1,7-undecadiene. These non-conjugated polyenes may be used alone or in combination.

[0019] Among these non-conjugated polyenes, ENB and VNB are preferred. Specific examples of the copolymer (X) of the present invention include ethylene-ENB copolymer, ethylene-VNB copolymer, ethylene-ENB-VNB copolymer, and the like.

[0020] The molar amount (mol %) of the copolymer (X) of the present invention is1 The intensity was determined by measuring the intensity using a H-NMR spectrometer. Details of the measurement conditions are described in WO 2015 / 122415.

[0021] <Requirement (2)> The intrinsic viscosity [η] measured in decalin at 135° C. is in the range of 1.0 to 2.0 dl / g, preferably 1.4 to 1.7 dl / g.

[0022] By using a copolymer (X) having an intrinsic viscosity within this range, the diene rubber and copolymer (X) constituting the rubber composition have good compatibility, and when a rubber composition containing these is used, a crosslinked molded article can be produced without phase separation.

[0023] <Requirement (3)> Density: 920-950 kg / m 3 , preferably 930 to 940 kg / m 3 is in the range. When the density of the copolymer (X) is within this range, the breaking properties and tear resistance of the rubber composition can be improved without impairing the kneading processability due to the crystallinity of the copolymer (X). The density of the copolymer (X) was measured in water at 23°C by a liquid weighing method in accordance with JIS Z8807:2012.

[0024] <Requirement (4)> The melting point (Tm) measured by DSC is in the range of 100 to 130°C, preferably 110 to 125°C.

[0025] When the melting point of the copolymer (X) is within this range, it melts during processing in a kneader, and therefore poor dispersion in the rubber composition does not occur. The melting point (Tm) of the copolymer (X) was measured by the following method.

[0026] Using a differential scanning calorimeter (DSC), approximately 5 mg of sample was sealed in an aluminum pan and heated from room temperature to 200°C at 10°C / min. The sample was then held at 200°C for 3 minutes to completely melt it. The sample was then cooled to 30°C at 10°C / min and held at 30°C for 3 minutes. The sample was then heated again to 230°C at 10°C / min. The peak temperature detected in the second heating test was taken as the melting point (Tm).

[0027] Requirement (5) The P value [η*(ω=0.1) / η*(ω=100)] determined by melt viscoelasticity measurement is in the range of 5-100, preferably 6-50, and more preferably 6-30.

[0028] When the P value of the copolymer (X) is within this range, the branched structure formed by the structural unit (B) derived from the non-conjugated polyene does not impair the crystallinity of the copolymer (X) to a great extent, and the break properties of the rubber composition can be maintained.

[0029] The P value of the copolymer (X) was measured by the following method. Using an Ares rheometer (Rheometric Scientific), complex viscosities η*(ω=0.01), η*(ω=0.1), η*(ω=10), and η*(ω=100) were measured at 190°C and 1.0% strain. The complex viscosities η*(ω=0.01), η*(ω=0.1), η*(ω=10), and η*(ω=100) were measured (all in Pa·sec). The P value (η*(ω=0.1) / η*(ω=100)), which is the ratio of the complex viscosities η*(ω=0.1) to η*(ω=100), was calculated from the results.

[0030] The copolymer (X) of the present invention satisfies all of the above requirements (1) to (5), and therefore when made into a rubber composition, it has good kneading processability and can improve tear resistance while maintaining break properties at a practically sufficient level.

[0031] <Method for producing ethylene-non-conjugated polyene copolymer (X)> The copolymer (X) of the present invention is a copolymer of ethylene and a non-conjugated polyene, which is a kind of metallocene compound, and bis(4-methylphenyl)methylene (η 5 -cyclopentadienyl)(η 5 -octamethyloctahydrodibenzofluorenyl)]zirconium dichloride (metallocene compound (a)) in the presence of a polymerization catalyst system containing the compound (a).

[0032] <Polymerization catalyst containing metallocene compound (a)> Polymerization catalysts that can be suitably used in producing the copolymer (X) of the present invention include those that contain the above metallocene compound (a) and are capable of copolymerizing monomers.

[0033] A preferred polymerization catalyst is one that is composed of (a) a metallocene compound, (b) at least one compound selected from (b-1) an organometallic compound, (b-2) an organoaluminum oxy compound, and (b-3) a compound that reacts with the metallocene compound (a) to form an ion pair (hereinafter also referred to as "ionizing ionic compound"), and, if necessary, (c) a particulate carrier. Each component will be specifically described below.

[0034] ≪Compound (b)≫ The compound (b) is at least one compound selected from (b-1) organometallic compounds, (b-2) organoaluminum oxy-compounds, and (b-3) ionizing ionic compounds, and preferably contains at least the organometallic compound (b-1).

[0035] (b-1) Organometallic compound As the organometallic compound (b-1), for example, organometallic compounds of Groups 1, 2, 12 and 13 of the periodic table, such as those represented by the following general formulae [VII] to [IX], are used.

[0036] (b-1a) General formula: R a m Al(OR b ) n H p Xq ···[VII] (In formula [VII], R a and R b may be the same as or different from each other, and represent a hydrocarbon group having 1 to 15 carbon atoms, preferably 1 to 4 carbon atoms. X represents a halogen atom, m is a number where 0 < m ≦ 3, n is a number where 0 ≦ n < 3, p is a number where 0 ≦ p < 3, q is a number where 0 ≦ q < 3, and m + n + p + q = 3.) An organoaluminum compound represented by

[0037] Examples of such compounds include trialkylaluminums such as trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-octylaluminum, tricycloalkylaluminum, isobutylaluminum dichloride, diethylaluminum chloride, ethylaluminum dichloride, ethylaluminum sesquichloride, methylaluminum dichloride, dimethylaluminum chloride, diisobutylaluminum hydride.

[0038] (b-1b) General formula: M 2 AlR a 4···[VIII] (In formula [VIII], M 2 represents Li, Na or K, and R a is a hydrocarbon group having 1 to 15 carbon atoms, preferably 1 to 4 carbon atoms.) A complex alkyl compound of a Group 1 metal of the periodic table and aluminum represented by Examples of such compounds include LiAl(C2H5)4, LiAl(C7H 15 )4, etc. <00002​​​​​​​​​​​​​​​is Mg, Zn or Cd. Dialkyl compounds containing a metal of Group 2 or 12 of the periodic table represented by

[0040] Among the above organometallic compounds (b-1), organoaluminum compounds such as triethylaluminum, triisobutylaluminum, tri-n-octylaluminum, etc. are preferred. These organometallic compounds (b-1) may be used singly or in combination of two or more.

[0041] (b-2) Organoaluminum oxy compounds The organoaluminum oxy compound (b-2) may be a conventionally known aluminoxane, or may be a benzene-insoluble organoaluminum oxy compound such as those exemplified in JP-A No. 2-78687.

[0042] Conventionally known aluminoxanes can be produced, for example, by the following method, and are usually obtained as a solution in a hydrocarbon solvent. (1) A method in which an organoaluminum compound such as trialkylaluminum is added to a hydrocarbon medium suspension of a compound containing adsorbed water or a salt containing water of crystallization, such as magnesium chloride hydrate, copper sulfate hydrate, aluminum sulfate hydrate, nickel sulfate hydrate, or cerous chloride hydrate, to react the adsorbed water or water of crystallization with the organoaluminum compound. (2) A method in which water, ice, or water vapor is directly applied to an organoaluminum compound such as trialkylaluminum in a medium such as benzene, toluene, ethyl ether, or tetrahydrofuran. (3) A method in which an organoaluminum compound such as trialkylaluminum is reacted with an organotin oxide such as dimethyltin oxide or dibutyltin oxide in a medium such as decane, benzene, or toluene.

[0043] The aluminoxane may contain a small amount of an organometallic component. After the solvent or unreacted organoaluminum compound is removed by distillation from the recovered aluminoxane solution, the aluminoxane may be redissolved in a solvent or suspended in a poor solvent for the aluminoxane.

[0044] Examples of organoaluminum compounds used in preparing aluminoxane include the same organoaluminum compounds as those exemplified as organoaluminum compounds belonging to the above (b-1a).

[0045] Of these, trialkylaluminum and tricycloalkylaluminum are preferred, and among these, trimethylaluminum and triisobutylaluminum are particularly preferred. The organoaluminum compounds as described above may be used singly or in combination of two or more.

[0046] The benzene-insoluble organoaluminum oxy-compound (b-2) used in the present invention is preferably one in which the Al component dissolved in benzene at 60°C is usually 10% by weight or less, preferably 5% by weight or less, and particularly preferably 2% by weight or less, calculated as Al atoms, relative to 100% by weight of benzene. In other words, the benzene-insoluble organoaluminum oxy-compound is preferably one which is insoluble or poorly soluble in benzene.

[0047] The organoaluminum oxy compound (b-2) used in the present invention may also include boron-containing organoaluminum oxy compounds represented by the following general formula [X].

[0048] [ka] (In formula [X], R 1 represents a hydrocarbon group having 1 to 10 carbon atoms, and R 2 ~R 5 may be the same or different and represent a hydrogen atom, a halogen atom, or a hydrocarbon group having 1 to 10 carbon atoms.)

[0049] The boron-containing organoaluminum oxy compound represented by the general formula [X] is General formula: R 1 -B(OH)2 [XI] (In formula [XI], R 1 is R in the general formula [X] 1 The alkylboronic acid represented by the formula (I) is the same group as that represented by the formula (I). The alkylboronic acid can be produced by reacting an alkylboronic acid represented by the formula (I) with an organoaluminum compound in an inert solvent under an inert gas atmosphere at a temperature of −80° C. to room temperature for 1 minute to 24 hours.

[0050] Examples of the alkylboronic acid represented by the general formula [XI] include methylboronic acid, ethylboronic acid, isopropylboronic acid, n-propylboronic acid, n-butylboronic acid, isobutylboronic acid, n-hexylboronic acid, cyclohexylboronic acid, phenylboronic acid, 3,5-difluorophenylboronic acid, pentafluorophenylboronic acid, and 3,5-bis(trifluoromethyl)phenylboronic acid.

[0051] Among these, methylboronic acid, n-butylboronic acid, isobutylboronic acid, 3,5-difluorophenylboronic acid, and pentafluorophenylboronic acid are preferred, and these may be used singly or in combination of two or more.

[0052] Examples of organoaluminum compounds to be reacted with such alkylboronic acids include the same organoaluminum compounds as those exemplified as the organoaluminum compounds belonging to the above (b-1a). Among these, trialkylaluminum and tricycloalkylaluminum are preferred, and trimethylaluminum, triethylaluminum, and triisobutylaluminum are particularly preferred. The organoaluminum oxy compounds (b-2) as described above may be used singly or in combination of two or more.

[0053] (b-3) Ionized ionic compounds Examples of the ionizable ionic compound (b-3) include Lewis acids, ionic compounds, borane compounds, and carborane compounds described in JP-T-1-501950, JP-T-1-502036, JP-A-3-179005, JP-A-3-179006, JP-A-3-207703, JP-A-3-207704, and US Pat. No. 5,321,106. Further examples include heteropoly compounds and isopoly compounds. Such ionizable ionic compounds (b-3) can be used singly or in combination of two or more.

[0054] Specific examples of Lewis acids include compounds represented by BR3 (R is fluorine or a phenyl group which may have a substituent such as fluorine, a methyl group, or a trifluoromethyl group), such as trifluoroboron, triphenylboron, tris(4-fluorophenyl)boron, tris(3,5-difluorophenyl)boron, tris(4-fluoromethylphenyl)boron, tris(pentafluorophenyl)boron, tris(p-tolyl)boron, tris(o-tolyl)boron, and tris(3,5-dimethylphenyl)boron.

[0055] The ionic compound may, for example, be a compound represented by the following general formula [XII].

[0056] [ka] (In formula [XII], R 1+ As for H + , carbonium cation, oxonium cation, ammonium cation, phosphonium cation, cycloheptyltrienyl cation, ferrocenium cation containing a transition metal, etc. 2 ~R 5 may be the same or different and are organic groups, preferably aryl groups or substituted aryl groups.

[0057] Specific examples of the carbonium cation include tri-substituted carbonium cations such as triphenylcarbonium cation, tri(methylphenyl)carbonium cation, and tri(dimethylphenyl)carbonium cation.

[0058] Specific examples of the ammonium cation include trialkylammonium cations such as trimethylammonium cation, triethylammonium cation, tripropylammonium cation, tributylammonium cation, and tri(n-butyl)ammonium cation; N,N-dialkylanilinium cations such as N,N-dimethylanilinium cation, N,N-diethylanilinium cation, and N,N,2,4,6-pentamethylanilinium cation; Examples include dialkylammonium cations such as di(isopropyl)ammonium cation and dicyclohexylammonium cation.

[0059] Specific examples of the phosphonium cation include triarylphosphonium cations such as triphenylphosphonium cation, tri(methylphenyl)phosphonium cation, and tri(dimethylphenyl)phosphonium cation.

[0060] R 1+ As the cation, a carbonium cation, an ammonium cation, etc. are preferred, and a triphenylcarbonium cation, an N,N-dimethylanilinium cation, and an N,N-diethylanilinium cation are particularly preferred.

[0061] Examples of the ionic compound include trialkyl-substituted ammonium salts, N,N-dialkylanilinium salts, dialkylammonium salts, and triarylphosphonium salts.

[0062] Specific examples of trialkyl-substituted ammonium salts include triethylammonium tetra(phenyl)boron, tripropylammonium tetra(phenyl)boron, tri(n-butyl)ammonium tetra(phenyl)boron, trimethylammonium tetra(p-tolyl)boron, trimethylammonium tetra(o-tolyl)boron, tri(n-butyl)ammonium tetra(pentafluorophenyl)boron, tripropylammonium tetra(o,p-dimethylphenyl)boron, tri(n-butyl)ammonium tetra(N,N-dimethylphenyl)boron, tri(n-butyl)ammonium tetra(p-trifluoromethylphenyl)boron, tri(n-butyl)ammonium tetra(3,5-ditrifluoromethylphenyl)boron, and tri(n-butyl)ammonium tetra(o-tolyl)boron.

[0063] Specific examples of N,N-dialkylanilinium salts include N,N-dimethylanilinium tetra(phenyl)boron, N,N-diethylanilinium tetra(phenyl)boron, and N,N,2,4,6-pentamethylanilinium tetra(phenyl)boron.

[0064] Specific examples of dialkylammonium salts include di(1-propyl)ammonium tetra(pentafluorophenyl)boron, dicyclohexylammonium tetra(phenyl)boron, and the like.

[0065] Further examples of ionic compounds include triphenylcarbenium tetrakis(pentafluorophenyl)borate, N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate, ferrocenium tetra(pentafluorophenyl)borate, triphenylcarbenium pentaphenylcyclopentadienyl complex, N,N-diethylanilinium pentaphenylcyclopentadienyl complex, and boron compounds represented by the following formula [XIII] or [XIV]: In the following formulas, Et represents an ethyl group.

[0066] [ka]

[0067] [ka]

[0068] Specific examples of the borane compound include decaborane; salts of anions such as bis[tri(n-butyl)ammonium]nonaborate, bis[tri(n-butyl)ammonium]decaborate, bis[tri(n-butyl)ammonium]undecaborate, bis[tri(n-butyl)ammonium]dodecaborate, bis[tri(n-butyl)ammonium]decachlorodecaborate, and bis[tri(n-butyl)ammonium]dodecachlorododecaborate; and salts of metal borane anions such as tri(n-butyl)ammonium bis(dodecahydridedodecaborate)cobaltate(III) and bis[tri(n-butyl)ammonium]bis(dodecahydridedodecaborate)nickelate(III).

[0069] Specific examples of the carborane compound include 4-carbanonaborane, 1,3-dicarbanonaborane, 6,9-dicarbadecaborane, dodecahydride-1-phenyl-1,3-dicarbanonaborane, dodecahydride-1-methyl-1,3-dicarbanonaborane, undecahydride-1,3-dimethyl-1,3-dicarbanonaborane, 7,8-dicarbaundecaborane, 2,7-dicarbaundecaborane, and undecahydride-7,8-dimethyl-7,8 -Dicarbaundecaborane, Dodecahydride-11-methyl-2,7-dicarbaundecaborane, Tri(n-butyl)ammonium 1-carbadecaborate, Tri(n-butyl)ammonium-1-carbaundecaborate, Tri(n-butyl)ammonium-1-carbadodecaborate, Tri(n-butyl)ammonium-1-trimethylsilyl-1-carbadecaborate, Tri(n-butyl)ammonium bromo-1-carbadodecaborate, Tri(n-butyl)ammonium ) ammonium-6-carbadecaborate, tri(n-butyl)ammonium-7-carbaundecaborate, tri(n-butyl)ammonium-7,8-dicarbaundecaborate, tri(n-butyl)ammonium-2,9-dicarbaundecaborate, tri(n-butyl)ammonium dodecahydride-8-methyl-7,9-dicarbaundecaborate, tri(n-butyl)ammonium undecahydride-8-ethyl-7,9-dicarbaundecaborate salts of anions such as tri(n-butyl)ammonium undecahydride-8-butyl-7,9-dicarboxundecaborate, tri(n-butyl)ammonium undecahydride-8-allyl-7,9-dicarboxundecaborate, tri(n-butyl)ammonium undecahydride-9-trimethylsilyl-7,8-dicarboxundecaborate, and tri(n-butyl)ammonium undecahydride-4,6-dibromo-7-carbaundecaborate; Tri(n-butyl)ammonium bis(nonahydride-1,3-dicarbanonaborate)cobaltate(III), tri(n-butyl)ammonium bis(undecahydride-7,8-dicarbandecaborate)ferrate(III), tri(n-butyl)ammonium bis(undecahydride-7,8-dicarbandecaborate)cobaltate(III), tri(n-butyl)ammonium bis(undecahydride-7,8-dicarbandecaborate)nickelate(III), tri(n-butyl)ammonium bis(undecahydride-7,8-dicarbandecaborate)cuprate(III), tri(n-butyl)ammonium bis(undecahydride-7,8-dicarbandecaborate)aurate(III), tri(n-butyl)ammonium bis(nonahydride-7,8-dimethyl-7,8-dicarbandecaborate)ferrate salts of metal carborane anions such as salt (III), tri(n-butyl)ammonium bis(nonahydride-7,8-dimethyl-7,8-dicarboxundecaborate)chromate(III), tri(n-butyl)ammonium bis(tribromooctahydride-7,8-dicarboxundecaborate)cobaltate(III), tris[tri(n-butyl)ammonium]bis(undecahydride-7-carbowndecaborate)chromate(III), bis[tri(n-butyl)ammonium]bis(undecahydride-7-carbowndecaborate)manganate(IV), bis[tri(n-butyl)ammonium]bis(undecahydride-7-carbowndecaborate)cobaltate(III), and bis[tri(n-butyl)ammonium]bis(undecahydride-7-carbowndecaborate)nickelate(IV).

[0070] The heteropoly compound is composed of an atom selected from silicon, phosphorus, titanium, germanium, arsenic, and tin, and one or more atoms selected from vanadium, niobium, molybdenum, and tungsten. Specifically, usable examples include phosphovanadic acid, germanovanadic acid, arsenic vanadic acid, phosphoniobic acid, germanoniobic acid, siliconomolybdic acid, phosphomolybdic acid, titanomolybdic acid, germanomolybdic acid, arsenic molybdic acid, tinmolybdic acid, phosphotungstic acid, germanotungstic acid, tintungstic acid, phosphomolybdovanadic acid, phosphotungstovanadic acid, germanotungstovanadic acid, phosphomolybdotungstovanadic acid, germanomolybdotungstovanadic acid, phosphomolybdotungstic acid, phosphomolybdoniobic acid, and salts of these acids, such as salts with metals of Group 1 or 2 of the periodic table, specifically, lithium, sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium, barium, etc., and organic salts such as triphenylethyl salts.

[0071] Among the ionizing ionic compounds (b-3), the above-mentioned ionic compounds are preferred, and among them, triphenylcarbenium tetrakis(pentafluorophenyl)borate and N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate are more preferred.

[0072] In the present invention, when a metallocene catalyst containing the above metallocene compound (a), an organometallic compound (b-1) such as triisobutylaluminum, an organoaluminum oxy compound (b-2) such as methylaluminoxane, and an ionizing ionic compound (b-3) such as triphenylcarbenium tetrakis(pentafluorophenyl)borate is used as the polymerization catalyst, extremely high polymerization activity can be exhibited in the production of the copolymer (X).

[0073] (c) Particulate carrier In the present invention, the particulate carrier (c) used as needed is an inorganic or organic compound, and is a granular or fine particle solid.

[0074] The inorganic compound is preferably a porous oxide, an inorganic halide, a clay, a clay mineral, or an ion-exchangeable layered compound, specific examples of which include those described in WO2015 / 122495.

[0075] The clay, clay mineral, and ion-exchangeable layered compound used in the present invention may be used as is, or may be used after treatment such as ball milling or sieving. They may also be used after newly adding and adsorbing water or after heat dehydration treatment. Furthermore, they may be used alone or in combination of two or more.

[0076] Of these, clay or clay minerals are preferred, and montmorillonite, vermiculite, hectorite, taeniolite and synthetic mica are particularly preferred. Examples of organic compounds include granular or particulate solids with particle sizes in the range of 10 to 300 μm. Specific examples include (co)polymers mainly composed of α-olefins having 2 to 14 carbon atoms, such as ethylene, propylene, 1-butene, and 4-methyl-1-pentene, and (co)polymers mainly composed of vinylcyclohexane and styrene, and modified products thereof.

[0077] The polymerization catalyst used in the present invention comprises a metallocene compound (a), at least one compound (b) selected from an organometallic compound (b-1), an organoaluminum oxy compound (b-2), and an ionizing ionic compound (b-3), a carrier (c) used as needed, and may further contain a specific organic compound component (d) as needed.

[0078] (d) Organic compound component In the present invention, the organic compound component (d) is used as needed to improve the polymerization performance and the physical properties of the resulting polymer. Examples of such organic compounds include, but are not limited to, alcohols, phenolic compounds, carboxylic acids, phosphorus compounds, and sulfonates.

[0079] <Production method and conditions for copolymer (X)> The copolymer (X) of the present invention is produced by copolymerizing ethylene and a non-conjugated polyene. When copolymerizing such monomers, the method of use and order of addition of the components constituting the polymerization catalyst described above can be selected arbitrarily, and examples thereof include the following methods (1) to (5). (1) A method in which the metallocene compound (a) is added alone to a polymerization reactor. (2) A method in which the metallocene compound (a) and the compound (b) are added to a polymerization reactor in any order. (3) A method in which a catalyst component in which a metallocene compound (a) is supported on a carrier (c) and a compound (b) are added to a polymerization reactor in any order. (4) A method in which the catalyst component in which the compound (b) is supported on the carrier (c) and the metallocene compound (a) are added to a polymerization reactor in any order. (5) A method in which a catalyst component in which a metallocene compound (a) and a compound (b) are supported on a carrier (c) is added to a polymerization reactor.

[0080] In each of the above methods (2) to (5), at least two of the metallocene compound (a), the compound (b) and the support (c) may be contacted in advance. In the above methods (4) and (5) in which the compound (b) is supported, an unsupported compound (b) may be added in any order, if necessary. In this case, the compound (b) may be the same as or different from the compound (b) supported on the support (c).

[0081] In addition, the solid catalyst component in which the metallocene compound (a) is supported on the support (c) and the solid catalyst component in which the metallocene compound (a) and the compound (b) are supported on the support (c) may be prepolymerized with an olefin, or the prepolymerized solid catalyst component may further have a catalyst component supported thereon.

[0082] The copolymer (X) of the present invention can be suitably obtained by copolymerizing ethylene and a non-conjugated polyene in the presence of the above-mentioned polymerization catalyst. When polymerizing ethylene and a non-conjugated polyene using the above polymerization catalyst, the metallocene compound (a) is usually used in an amount of 10 -12 ~10 -2 moles, preferably 10 -10 ~10 -8 It is used in molar amounts.

[0083] Compound (b-1) is used in an amount such that the molar ratio of compound (b-1) to the total transition metal atoms (M) in metallocene compound (a) [(b-1) / M] is usually 0.01 to 50,000, preferably 0.05 to 10,000. Compound (b-2) is used in an amount such that the molar ratio of aluminum atoms in compound (b-2) to the total transition metal atoms (M) in metallocene compound (a) [(b-2) / M] is usually 10 to 50,000, preferably 20 to 10,000. Compound (b-3) is used in an amount such that the molar ratio of compound (b-3) to the transition metal atoms (M) in metallocene compound (a) [(b-3) / M] is usually 1 to 20, preferably 1 to 15.

[0084] In the present invention, the method for producing the copolymer (X) can be carried out by any of a liquid phase polymerization method such as solution (dissolution) polymerization or suspension polymerization, or a gas phase polymerization method, and is not particularly limited, but preferably includes a step of obtaining the following polymerization reaction liquid.

[0085] The step of obtaining a polymerization reaction liquid is a step of copolymerizing ethylene and a non-conjugated polyene in the presence of the metallocene compound (a) using an aliphatic hydrocarbon as a polymerization solvent to obtain a polymerization reaction liquid of copolymer (X).

[0086] Examples of polymerization solvents include aliphatic hydrocarbons and aromatic hydrocarbons. Specific examples include aliphatic hydrocarbons such as propane, butane, pentane, hexane, heptane, octane, decane, dodecane, and kerosene; alicyclic hydrocarbons such as cyclopentane, cyclohexane, and methylcyclopentane; aromatic hydrocarbons such as benzene, toluene, and xylene; and halogenated hydrocarbons such as ethylene chloride, chlorobenzene, and dichloromethane. These solvents can be used alone or in combination of two or more. Olefins themselves can also be used as solvents. Among these, hexane is preferred from the viewpoint of separation and purification from the resulting copolymer (A).

[0087] The polymerization temperature is usually −50 to +200° C., preferably in the range of 0 to +150° C., and more preferably in the range of +70 to +110° C. Although it depends on the attained molecular weight and polymerization activity of the metallocene catalyst system used, a higher temperature (+70° C. or higher) is desirable from the viewpoints of catalytic activity, copolymerizability, and productivity.

[0088] The polymerization pressure is usually normal pressure to 10 MPa gauge pressure, preferably 1.1 to 5 MPa gauge pressure, more preferably 1.2 to 2.0 MPa gauge pressure, and the polymerization reaction can be carried out by any of batch, semi-continuous, and continuous methods. Furthermore, the polymerization can be carried out in two or more stages with different reaction conditions. Among these, in the present invention, it is preferable to adopt a method in which ethylene and a non-conjugated polyene are continuously supplied to a reactor to carry out copolymerization.

[0089] The reaction time (average residence time when copolymerization is carried out by a continuous method) varies depending on conditions such as catalyst concentration and polymerization temperature, but is usually 0.5 minutes to 5 hours, preferably 5 minutes to 3 hours, and more preferably 10 minutes to 2 hours.

[0090] The molecular weight of the resulting copolymer (X) can be adjusted by adding hydrogen to the polymerization system or by changing the polymerization temperature. Furthermore, it can also be adjusted by the amount of compound (b) used. Specific examples include triisobutylaluminum, methylaluminoxane, and diethylzinc. When hydrogen is added, the amount is preferably about 0.001 to 100 nL per kg of olefin.

[0091] The present invention preferably comprises, after the step (1) of copolymerizing in the presence of the polymerization catalyst, a step (2) of deactivating the polymerization catalyst by adding a catalyst deactivator. As the catalyst deactivator, alcohols can be used, and methanol or ethanol is preferred, with ethanol being particularly preferred.

[0092] In step (2), the catalyst deactivator is preferably added in an amount of 0.05 to 3.0 mol times, more preferably 0.06 to 2.5 mol times, and even more preferably 0.08 to 2.0 mol times the amount of the organometallic compound (b-1). This allows for the generation of a small amount of catalyst denatured by the catalyst deactivator, such as ethanol, and moderate polymerization of low molecular weight components, resulting in a copolymer (X) with a moderately broad molecular weight distribution. On the other hand, if too much catalyst deactivator is added, almost no denatured catalyst is generated, and almost no polymerization of low molecular weight components occurs, resulting in a narrow molecular weight distribution of the resulting copolymer (X). Furthermore, if no catalyst deactivator is added, or if too little is added, a large amount of denatured catalyst is generated, resulting in the polymerization of a large amount of low molecular weight components, resulting in a copolymer (X) with an excessively high content of low molecular weight components.

[0093] <Rubber composition> The rubber composition of the present invention is a composition containing the diene rubber (Z) and the ethylene-non-conjugated polyene copolymer (X) in an amount of 0.5 to 50 parts by mass, preferably 1 to 40 parts by mass, and more preferably 2.5 to 20 parts by mass, per 100 parts by mass of the diene rubber (Z).

[0094] The rubber material for tires and tire tread obtained from the rubber composition of the present invention containing the copolymer (X) in the above range have good tear strength and excellent chipping resistance. The rubber composition of the present invention contains, in addition to the copolymer (X), preferably 0.2 to 15 parts by mass, preferably 0.5 to 10 parts by mass, more preferably 1.0 to 5 parts by mass of the vulcanizing agent (C) described below, 5 to 100 parts by mass, preferably 10 to 80 parts by mass, more preferably 20 to 60 parts by mass of the carbon black (D) described below, 5 to 150 parts by mass, preferably 10 to 100 parts by mass, more preferably 15 to 60 parts by mass of the white filler (E) described below, and 0.2 to 10 parts by mass, preferably 1.0 to 8 parts by mass, more preferably 2 to 6 parts by mass of the silane coupling agent (F) described below, relative to 100 parts by mass of the diene rubber (Z).

[0095] <Vulcanizing agent (C)> The vulcanizing agent (C) to be compounded in the rubber composition of the present invention is not particularly limited as long as it is capable of vulcanizing the diene rubber (Z) and the copolymer (A), and may be any of various vulcanizing agents commonly used in the field of rubber, such as sulfur-based compounds and peroxide-based crosslinking agents.

[0096] In the present invention, a suitable vulcanizing agent (C) is a sulfur-based compound. By crosslinking the rubber composition with a sulfur-based compound, it is possible to impart to the molded article the same low-temperature properties as when a peroxide-based crosslinking agent such as dicumyl peroxide is used, while imparting significantly superior flexibility and mechanical properties.

[0097] Examples of sulfur compounds include sulfur, sulfur chloride, sulfur dichloride, morpholine disulfide, alkylphenol disulfide, tetramethylthiuram disulfide, selenium dithiocarbamate, etc. Among these, sulfur and tetramethylthiuram disulfide are preferred.

[0098] On the other hand, depending on the type of diene rubber (Z), a peroxide-based crosslinking agent can also be used as a vulcanizing agent. Peroxide-based crosslinking agents include: Peroxyketals such as 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclohexane, 2,2-bis(t-butylperoxy)octane, and 1,1-bis(t-butylperoxy)cyclododecane, as well as Examples of the peroxide include dialkyl peroxides such as di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, α,α'-bis(t-butylperoxy-m-isopropyl)benzene, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, t-butylperoxy-2-ethylhexanoate, t-butylperoxy-3,5,5-trimethylhexanoate, and 2,5-dimethyl-2,5-di(benzoylperoxy)hexane.

[0099] <Carbon Black (D)> The carbon black (D) blended in the rubber composition of the present invention is a type of compounding agent that is blended with rubber to improve physical properties such as mechanical strength, impact resilience, and abrasion resistance of a molded article.

[0100] As the carbon black (D), known carbon blacks such as Asahi #55G, Asahi #60G, and Asahi #80 (all manufactured by Asahi Carbon Co., Ltd.) and Seast (SRF, GPF, FEF, MAF, HAF, ISAF, SAF, FT, MT, G-SO, etc.) (all manufactured by Tokai Carbon Co., Ltd.) can be used. These can be used alone or in combination. Carbon blacks that have been surface-treated with a silane coupling agent or the like can also be used.

[0101] <White filler (E)> Examples of the white filler (E) to be compounded in the rubber composition of the present invention include silica such as hydrophobic silica, hydrophilic silica, and amphiphilic silica, silicic acid and silicate fine powder, activated calcium carbonate, light calcium carbonate, heavy calcium carbonate, talc, clay, etc. These fillers may be used alone or in combination of two or more.

[0102] The average particle size of the white filler (E) is preferably in the range of 1 to 50 nm, more preferably 2 to 45 nm, and even more preferably 5 to 40 nm. The white filler (E) according to the present invention may be surface-treated.

[0103] <Silane coupling agent (F)> Examples of the silane coupling agent (F) to be compounded in the rubber composition of the present invention include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, vinyltrichlorosilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, Ethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, N-(1,3-dimethylbutylidene)-3-(triethoxysilyl)-1-propanamine, N,N'-bis(3-(trimethoxysilyl)propyl)ethylenediamine, polyoxyethylenepropyltrialkoxysilane, polyethoxydimethylsiloxane, p-styryltrimethoxysilane, and 3-acryloxypropyltrimethoxysilane.

[0104] The rubber composition of the present invention contains the diene rubber (Z), the copolymer (X), the vulcanizing agent (C), the carbon black (D), the white filler (E), and the silane coupling agent (F), as well as other components, such as various additives, including plasticizers, vulcanization accelerators, co-crosslinking agents, vulcanization aids, processing aids, antioxidants, and activators. Furthermore, known foaming agents, foaming aids, colorants, dispersants, flame retardants, heat stabilizers, weather stabilizers, antistatic agents, colorants, lubricants, and thickeners may also be used as other components, as needed.

[0105] Other ingredients <Plasticizer> The rubber composition of the present invention may further contain a plasticizer, specifically a known plasticizer generally used as a softener in the field of rubber, depending on its application.

[0106] Specific examples of such plasticizers include petroleum-based softeners such as process oil, lubricating oil, paraffin oil, liquid paraffin, petroleum asphalt, and Vaseline; coal tar-based softeners such as coal tar and coal tar pitch; fatty oil-based softeners such as castor oil, linseed oil, rapeseed oil, soybean oil, and coconut oil; waxes such as beeswax, carnauba wax, and lanolin; and ricinoleic acid, palmitic acid, stearic acid, barium stearate, calcium stearate, and zinc laurate. Examples of softeners include fatty acids or their salts; naphthenic acid, pine oil, and rosin or their derivatives; synthetic polymers such as terpene resins, petroleum resins, atactic polypropylene, and coumarone-indene resins; ester-based softeners such as dioctyl phthalate, dioctyl adipate, and dioctyl sebacate; and other softeners such as microcrystalline wax, liquid polybutadiene, modified liquid polybutadiene, liquid thiokol, hydrocarbon-based synthetic lubricating oils, tall oil, and sub(factice). Among these, petroleum-based softeners are preferred. Among petroleum-based softeners, petroleum-based process oils are preferred, with paraffin-based process oils, naphthenic process oils, and aromatic process oils being more preferred.

[0107] The content of the plasticizer can be appropriately selected depending on the application, and is usually at most 200 parts by mass, preferably at most 150 parts by mass, and more preferably at most 130 parts by mass per 100 parts by mass of the diene rubber (Z).

[0108] <Vulcanization accelerator> The rubber composition according to the present invention may further contain a vulcanization accelerator in addition to the above components. Specific examples of the vulcanization accelerator include thiazole-based accelerators such as N-cyclohexyl-2-benzothiazole sulfenamide (e.g., "Suncerer CM" (trade name; manufactured by Sanshin Chemical Industry Co., Ltd.)), N-oxydiethylene-2-benzothiazole sulfenamide, N,N'-diisopropyl-2-benzothiazole sulfenamide, 2-mercaptobenzothiazole (e.g., "Suncerer M" (trade name; manufactured by Sanshin Chemical Industry Co., Ltd.)), 2-(4-morpholinodithio)benzothiazole (e.g., "Noccelaer MDB-P" (trade name; manufactured by Sanshin Chemical Industry Co., Ltd.)), 2-(2,4-dinitrophenyl)mercaptobenzothiazole, 2-(2,6-diethyl-4-morpholinothio)benzothiazole, and dibenzothiazyl disulfide; guanidine-based accelerators such as diphenylguanidine, triphenylguanidine, and diorthotolylguanidine; acetaldehyde-aniline condensates, butylalcohols, and the like. aldehyde-aniline condensates, aldehyde amines; imidazoline-based compounds such as 2-mercaptoimidazoline; thiourea-based compounds such as diethylthiourea and dibutylthiourea; thiuram-based compounds such as tetramethylthiuram monosulfide and tetramethylthiuram disulfide (for example, "Suncerer TT" (trade name; manufactured by Sanshin Chemical Industry Co., Ltd.)); zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate (for example, Examples include dithioacid salts such as "Suncerer BZ" (trade name, manufactured by Sanshin Chemical Industry Co., Ltd.) and tellurium diethyldithiocarbamate; thioureas such as ethylenethiourea (for example, "Suncerer 22-C" (trade name, manufactured by Sanshin Chemical Industry Co., Ltd.) and N,N'-diethylthiourea; xanthates such as zinc dibutylxatogenate; and zinc oxides such as "META-Z102" (trade name, manufactured by Inoue Lime Industry Co., Ltd.).

[0109] When the rubber composition of the present invention contains a vulcanization accelerator, the content thereof is preferably 0.1 to 15 parts by mass, more preferably 0.5 to 10 parts by mass, per 100 parts by mass of the diene rubber (Z). When the rubber composition contains the vulcanization accelerator in such an amount, the rubber composition has excellent crosslinking properties, and the occurrence of blooming from the obtained molded article is further reduced.

[0110] <Co-crosslinking agent> When a peroxide-based crosslinking agent is used as the crosslinking agent, an appropriate co-crosslinking agent may be further contained as necessary for the purpose of improving the vulcanization rate of the rubber composition and the physical properties of the resulting molded article.

[0111] Examples of the co-crosslinking agent include polyethylene glycol dimethacrylate (PEGDM) such as Blemmer PDE-100 (trade name, manufactured by Nippon Oil & Fats Co., Ltd.), diallyl phthalate (DAP), triallyl isocyanurate (TAIC) such as Taik (trade name, manufactured by Nippon Kasei Co., Ltd.), triallyl cyanurate (TAC) such as Tack (trade name, manufactured by Musashino Chemical Laboratory Co., Ltd.), tetrahydrofurfuryl methacrylate (THFMA) such as Acryester THF (trade name, manufactured by Mitsubishi Rayon Co., Ltd.), Sanester EG ( Examples of suitable methacrylates include ethylene dimethacrylate (EDMA) such as Acrylate ED (product name, manufactured by Mitsubishi Rayon Co., Ltd.), 1,3-butylene dimethacrylate (BDMA) such as Acrylate BD (product name, manufactured by Mitsubishi Rayon Co., Ltd.), and trimethylolpropane trimethacrylate (TMPMA) such as Sunester TMPMA (product name, manufactured by Sanshin Chemical Industry Co., Ltd.), Acrylate TMP (product name, manufactured by Mitsubishi Rayon Co., Ltd.), and Hicross M (product name, manufactured by Seiko Chemical Co., Ltd.).

[0112] When the rubber composition of the present invention contains a co-crosslinking agent, the amount thereof is suitably about 1 to 10 parts by mass per 100 parts by mass of the diene rubber (Z). In addition, in the rubber composition of this embodiment, when crosslinking is performed using a peroxide-based crosslinking agent, a vulcanization aid such as methacrylic acid ester or triallyl isocyanurate (TAIC) such as TAIC (Nippon Kasei Co., Ltd.) may be further added.

[0113] <Vulcanization aid> Specific examples of the vulcanization aid include magnesium oxide and zinc oxide (for example, zinc oxide such as "META-Z102" (trade name; manufactured by Inoue Lime Industry Co., Ltd.)). When the rubber composition of the present invention contains a vulcanization aid, the amount thereof is usually 1 to 20 parts by mass per 100 parts by mass of the diene rubber (Z).

[0114] <Processing aids> The rubber composition of the present invention may further contain a processing aid. The processing aid may be a compound typically used in rubber processing, including higher fatty acids such as ricinoleic acid, stearic acid, palmitic acid, and lauric acid; salts of higher fatty acids such as barium stearate, zinc stearate, and calcium stearate; and esters of higher fatty acids such as ricinoleic acid, stearic acid, palmitic acid, and lauric acid.

[0115] When the rubber composition of the present invention contains a processing aid, the amount thereof is 10 parts by mass or less, preferably 5 parts by mass or less, per 100 parts by mass of the diene rubber (Z). However, it is desirable to determine the optimum amount appropriately depending on the required physical property values.

[0116] <Anti-aging agent> The rubber composition of the present invention may contain an antioxidant to extend the product life of the molded article obtained by crosslinking. Examples of the antioxidant include conventionally known antioxidants such as amine-based antioxidants, phenol-based antioxidants, and sulfur-based antioxidants.

[0117] Specific examples of antioxidants include aromatic secondary amine antioxidants such as phenylbutylamine and N,N-di-2-naphthyl-p-phenylenediamine, phenolic antioxidants such as dibutylhydroxytoluene and tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, thioether antioxidants such as bis[2-methyl-4-(3-n-alkylthiopropionyloxy)-5-t-butylphenyl]sulfide, dithiocarbamate antioxidants such as nickel dibutyldithiocarbamate, and sulfur-based antioxidants such as 2-mercaptobenzoylimidazole, zinc salt of 2-mercaptobenzimidazole, dilaurylthiodipropionate, and distearylthiodipropionate. These antioxidants can be used alone or in combination of two or more.

[0118] When the rubber composition of the present invention contains an antioxidant, the amount thereof is usually 0.3 to 10 parts by mass, preferably 0.5 to 7.0 parts by mass, and more preferably 0.7 to 5.0 parts by mass, relative to 100 parts by mass of the diene rubber (Z). When the amount of the antioxidant is within the above range, inhibition of vulcanization when crosslinking (vulcanizing) the rubber composition can be reduced, and the occurrence of blooming in the obtained molded article can be reduced.

[0119] <Activator> The rubber composition of the present invention may contain one or more activators, if necessary.

[0120] Specific examples of surfactants include amines such as di-n-butylamine, dicyclohexylamine, monoethanolamine, "Acting B" (trade name; manufactured by Yoshitomi Pharmaceutical Co., Ltd.), and "Acting SL" (trade name; manufactured by Yoshitomi Pharmaceutical Co., Ltd.); amine-based surfactants such as diethylene glycol, polyethylene glycol, lecithin, triallyl trimellitate, and zinc compounds of aliphatic and aromatic carboxylic acids (e.g., "Struktol activator 73," "Struktol IB 531," and "Struktol FA541" (trade names; manufactured by Schill & Seilacher); zinc peroxide preparations such as "ZEONET ZP" (trade name; manufactured by Zeon Corporation); octadecyltrimethylammonium bromide, synthetic hydrotalcite, and special quaternary ammonium compounds (e.g., "Arcade 2HF" (trade name; manufactured by Lion-Akzo Co., Ltd.)).

[0121] When the rubber composition of the present invention contains an activator, the amount thereof is usually 0.2 to 10 parts by mass, preferably 0.3 to 5 parts by mass, and more preferably 0.5 to 4 parts by mass, per 100 parts by mass of the diene rubber (Z).

[0122] <Rubber materials for tires> The rubber composition of the present invention can be suitably used as a rubber material for tires. The rubber material for tires of the present invention achieves excellent tear resistance without deteriorating fuel economy and wet grip performance. Furthermore, the rubber material is also excellent in rubber elasticity, weather resistance, and ozone resistance, and is particularly excellent in mechanical properties and fatigue resistance. Therefore, by applying the rubber material for tires of the present invention, it is possible to obtain tires that maintain fuel economy and wet grip performance, and are also excellent in rubber elasticity, weather resistance, and ozone resistance, and are particularly excellent in tear resistance and fatigue resistance (long life performance).

[0123] Specific applications of the rubber material for tires include tire innerliners, tire innertubes, tire flaps, tire shoulders, tire beads, tire treads, tire sidewalls, etc. Among these, the rubber material can be suitably used for tire treads and tire sidewalls, and can be particularly suitably used for tire treads.

[0124] <Method for preparing rubber composition> Examples of methods for preparing the rubber composition include a method of mixing the components contained in the rubber composition using a conventional kneading machine such as a mixer, kneader, or roll, or a continuous kneading machine such as a twin-screw extruder, and a method of preparing a solution in which the components contained in the rubber composition are dissolved or dispersed, and then removing the solvent.

[0125] The rubber composition according to the present invention can be prepared by simultaneously or sequentially blending the diene rubber (Z) and the copolymer (X), and, if necessary, any optional components. The method for preparing the rubber composition is not particularly limited, and a general method for preparing a rubber compound can be used without any particular limitation. For example, when the rubber composition of the present invention contains optional components, at least a part of the optional components may be mixed in advance with the diene rubber (Z) or the copolymer (X) and then the remaining optional components may be compounded, or the optional components may be added and compounded after compounding the diene rubber (Z) and the copolymer (X).

[0126] For example, the diene rubber (Z), copolymer (X), and other optional components are kneaded for 3 to 10 minutes at a temperature of 80 to 170°C using an internal mixer such as a Banbury mixer, kneader, or intermix, and then a crosslinking agent, and optionally a crosslinking accelerator, crosslinking aid, or foaming agent, are added. The mixture is then kneaded for 5 to 30 minutes at a roll temperature of 40 to 80°C using rolls such as open rolls or a kneader, followed by dispensing. This typically results in a ribbon- or sheet-shaped rubber composition. When the kneading temperature in the internal mixer is low, the crosslinking agent, crosslinking accelerator, foaming agent, etc. can also be kneaded simultaneously.

[0127] <Molded body> The molded article of the present invention can be obtained by vulcanizing (also referred to as crosslinking) the rubber composition of the present invention. The vulcanization may or may not involve the use of a mold. When a mold is not used, the rubber composition is usually molded and crosslinked continuously.

[0128] Examples of methods for vulcanizing a rubber composition include (a) a method in which a rubber composition containing a vulcanizing agent is preformed into a desired shape, usually by a molding method such as extrusion molding, press molding, or injection molding, or by roll processing, and then heated either simultaneously with molding or by introducing the molded product into a crosslinking tank; and (b) a method in which a rubber composition containing a vulcanizing agent is preformed in the same manner as method (a), and then irradiated with an electron beam.

[0129] In method (a), a crosslinking reaction occurs due to heating with the crosslinking agent in the rubber composition, resulting in a molded article. In method (b), a crosslinking reaction occurs due to electron beam irradiation, resulting in a molded article. In method (b), a preformed rubber composition is typically irradiated with an electron beam having an energy of 0.1 to 10 MeV so that the absorbed dose of the rubber composition is typically 0.5 to 36 Mrad, preferably 0.5 to 20 Mrad, and more preferably 1 to 10 Mrad.

[0130] Furthermore, vulcanization (crosslinking) of rubber compositions can be carried out by preforming an uncrosslinked rubber composition into a desired shape using various molding methods, typically with a molding machine such as an extruder, calendar roll, press, injection molding machine, or transfer molding machine, and then either simultaneously with molding or by introducing the molded product into a crosslinking tank and heating it, or by irradiating it with radiation such as electron beams, X-rays, gamma rays, alpha rays, or beta rays. As molding or preforming methods, known molding methods for molding into a desired shape, such as extrusion molding, injection molding, inflation molding, blow molding, extrusion blow molding, press molding, vacuum molding, calendar molding, and foam molding, can be appropriately employed. Furthermore, when the crosslinked molded product is a foam, it can be produced by foam-molding an uncrosslinked rubber composition containing a foaming agent, followed by crosslinking by electron beam irradiation or heating, or by promoting crosslinking simultaneously with foam molding. Furthermore, the step of crosslinking the rubber composition may be carried out by combining crosslinking by heating and electron beam crosslinking.

[0131] When the rubber composition is crosslinked by heating, it is generally preferable to use a rubber composition containing a vulcanizing agent such as sulfur, a sulfur-based compound, or peroxide, and heat the rubber composition for 1 to 30 minutes at a temperature of 150 to 270°C in a crosslinking bath using a heating method such as hot air, a glass bead fluidized bed, UHF (ultra-high frequency electromagnetic waves), steam, or an LCM (molten salt bath). Sulfur crosslinking or peroxide crosslinking has the advantage of not requiring special equipment for the crosslinking step, and has therefore been widely used in the crosslinking step of rubber compositions.

[0132] In addition, when crosslinking is performed by electron beam crosslinking, it is usually preferable to use a rubber composition that does not contain a crosslinking agent, and irradiate the preformed rubber composition with electron beams to produce a crosslinked molded product. Crosslinking by electron beam irradiation can be performed without using a crosslinking agent, and has the advantage of generating less volatile matter during the crosslinking process.

[0133] Specifically, the production of crosslinked molded articles involving a crosslinking step using electron beam irradiation can be carried out, for example, as follows. First, using a mixer such as a Banbury mixer, the diene rubber (Z), and, if necessary, various additives and crosslinking aids, etc., are kneaded for 3 to 10 minutes at a temperature of 80 to 170°C. Then, using rolls such as open rolls, the mixture is kneaded for 5 to 30 minutes at a roll temperature of 40 to 80°C, and then separated to prepare a ribbon-shaped or sheet-shaped rubber composition. Alternatively, the rubber composition is prepared by blending the various components in a container or the like. The rubber composition thus prepared is either molded into the desired shape, such as a sheet, using an extruder, calendar roll, injection molding machine, or press, or extruded into strands from an extruder and pulverized into pellets using a cutter or the like, and then irradiated with an electron beam. Alternatively, a crosslinked product of the rubber composition may be prepared by directly irradiating powder of the diene rubber (Z) and copolymer (X) impregnated with a compound such as a crosslinking aid, with an electron beam. The electron beam irradiation is carried out using an electron beam having an energy of usually 0.1 to 10 MeV (megaelectronvolts), preferably 0.3 to 5 MeV, so that the absorbed dose is usually 0.5 to 100 kGy (kilograys), preferably 0.5 to 70 kGy.

[0134] Gamma ray irradiation has a higher penetration rate into a rubber composition than electron beam irradiation, and in particular, when irradiating a rubber composition in the form of pellets, direct irradiation with a small amount of radiation can sufficiently crosslink the rubber composition to the inside of the pellets. Gamma ray irradiation can be carried out so that the dose of gamma rays applied to the rubber composition is usually 0.1 to 50 kGy, preferably 0.3 to 50 kGy.

[0135] The degree of crosslinking of a molded article can be expressed by its gel fraction. Typically, the gel fraction of a crosslinked article is 1 to 80%. However, the degree of crosslinking of the crosslinked molded article of the present invention is not limited to this range. Even a crosslinked article with a low degree of crosslinking, that is, a crosslinked article with a gel fraction of less than 10%, particularly less than 0.5%, can achieve the same excellent surface appearance effect as the crosslinked molded article of the present invention with a high degree of crosslinking.

[0136] The molded article according to the present invention can be used without limitation in the application of various products having rubber properties. The crosslinked molded article according to the present invention may constitute at least a part of the product, and it is preferable that the entire product is constituted by the molded article according to the present invention. It is also preferable that the molded article according to the present invention is a laminate or composite that constitutes at least a part of the product. Examples of laminates include multilayer laminates having two or more layers, at least one of which is the molded article according to the present invention, and include forms such as multilayer films and sheets, multilayer containers, multilayer tubes, and multilayer coating film laminates contained as a component of water-based paints.

[0137] The molded article according to the present invention has particularly excellent weather resistance and can therefore be suitably used in applications that are used outdoors for a long period of time, such as tires and electric wire covering materials, and can be particularly suitably used as tire components that constitute at least a part of various tires.

[0138] The molded article of the present invention retains the excellent mechanical strength and fatigue resistance (long life performance) inherent to diene rubber and also exhibits excellent tear resistance. Tire components such as tire treads and tire sidewalls using the crosslinked molded article of the present invention have excellent weather resistance and tear resistance.

[0139] <Foam> The rubber composition of the present invention can also be used as a foam, which can be obtained by crosslinking and foaming the rubber composition of the present invention containing a foaming agent.

[0140] Since the rubber composition contains a foaming agent, heating the rubber composition causes a crosslinking reaction by the crosslinking agent and decomposes the foaming agent to generate carbon dioxide gas and nitrogen gas, thereby producing a foam having a cellular structure.

[0141] <Application> The rubber composition of the present invention is extremely excellent in low-temperature properties, mechanical properties, moldability such as extrusion moldability, press moldability, and injection moldability, and roll processability, and from the rubber composition of the present invention, molded articles excellent in low-temperature properties (flexibility at low temperatures, rubber elasticity, etc.), mechanical properties, etc. can be suitably obtained.

[0142] Furthermore, the rubber composition of the present invention has excellent processability, moldability, and crosslinking properties, and can be used to produce molded articles that are excellent in heat resistance stability, long life performance, and tear resistance. Therefore, molded articles obtained from the rubber composition of the present invention can be suitably used in applications where long-term use at high temperatures is expected, or where a large tear force is expected to be applied during use.

[0143] The rubber composition of the present invention and molded articles obtained from the composition, such as crosslinked articles and foamed articles, can be used in a variety of applications. Specifically, they are suitable for use in rubber materials for tires, O-rings, industrial rolls, packings (e.g., condenser packings), gaskets, belts (e.g., heat-insulating belts, copier belts, and conveyor belts), hoses such as automotive hoses (e.g., turbocharger hoses, water hoses, brake reservoir hoses, radiator hoses, and air hoses), vibration-isolating rubber, vibration-insulating or vibration-damping materials (e.g., engine mounts and motor mounts), muffler hangers, sponges (e.g., weatherstrip sponges, heat-insulating sponges, protective sponges, and micro-foam sponges), cables (ignition cables, cab-tire cables, and high-tension cables), electric wire coating materials (high-voltage electric wire coating materials, low-voltage electric wire coating materials, and marine electric wire coating materials), glass run channels, colored skin materials, paper feed rolls, and roofing sheets. Among these, it is preferably used for interior and exterior parts of automobiles and for applications requiring heat resistance, and is also suitable as a rubber material for tires such as tire treads.

[0144] <Tire tread> The tire tread according to the present invention is formed using the rubber material for a tire according to the present invention. By using a tire tread obtained by vulcanizing the rubber material for a tire according to the present invention, it is possible to obtain a tire which has excellent breaking properties and excellent tear resistance while maintaining fuel economy and wet grip performance, and which is also excellent in rubber elasticity, weather resistance, and ozone resistance, and which is particularly excellent in mechanical properties and fatigue resistance (long life performance).

[0145] <Tires> The tire according to the present invention includes the tire tread described above. The tire according to the present invention achieves both excellent breaking properties and excellent tear resistance while maintaining fuel economy and wet grip performance, and is also excellent in rubber elasticity, weather resistance, and ozone resistance, and is particularly excellent in mechanical properties and fatigue resistance (long life performance). [Example]

[0146] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The methods for evaluating the various properties in the examples and comparative examples are as follows.

[0147] The diene rubbers (Z) and ethylene-non-conjugated polyene copolymers (X) used in the examples and comparative examples are shown below. (1) Diene rubber (Z) (1-1)SBR As the diene rubber (Z-1), SBR, trade name Nipol NS116R manufactured by ZS Elastomers, bound styrene content: 21 mass %, Mooney viscosity [ML(1+4)(100°C): 45] was used. (1-2) Butadiene rubber As the diene rubber (Z-2), a butadiene rubber, trade name: Nipol BR12200, manufactured by Nippon Zeon Co., Ltd., Mooney viscosity [ML(1+4)(100°C): 43] was used. (2) Ethylene-non-conjugated polyene copolymer (X) As the copolymer (X), the copolymers produced in the following Polymerization Examples 1 to 3 were used. The symbols (a) to (w) shown in Polymerization Examples 1 to 3 represent the amounts of each unit shown in Table 1 below.

[0148] [Polymerization Examples 1 to 3] Dehydrated and purified n-hexane (C6) was fed into one feed port of a 136 L continuous polymerization reactor at a rate of (a) L / h, and [bis(4-methylphenyl)methylene (η 5 -cyclopentadienyl)(η 5 A hexane solution of (b) mmol / L (4 mmol / L) of [(2-octamethyloctahydrodibenzofluorenyl)]zirconium dichloride (ZD) was continuously fed at a rate of (c) L / h, a hexane solution of triisobutylaluminum (4 mmol / L) was continuously fed at a rate of (d) L / h, a hexane slurry of triphenylcarbenium tetrakis(pentafluorophenyl)borate (CB-3) was continuously fed at a rate of (e) mmol / L (f) L / h, VNB was continuously fed at a rate of (g) g / h, and ENB was continuously fed at a rate of (h) g / h [total hexane (T-C6): (i) L / h]. Simultaneously, ethylene (C2") was continuously fed at a rate of (j) kg / h and hydrogen was continuously fed at a rate of (k) NL / h to another feed inlet of the polymerization reactor. Continuous solution polymerization was carried out under the conditions of a polymerization temperature of 1°C, a total pressure of (m) MPaG, and a residence time of (n) min.

[0149] The hexane solution of ethylene-non-conjugated polyene copolymer (X) produced in the polymerization reactor was continuously discharged through an outlet provided on the side wall of the polymerization reactor, and the pressure in the jacket was 8 kg / cm 2 The hexane solution of ethylene-non-conjugated polyene copolymer (X) heated to about 170°C in the steam-jacketed connecting pipe was maintained at a liquid level of 10 kg / cm by adjusting the opening of the liquid level control valve installed at the end of the connecting pipe so as to maintain the solution volume in the polymerization vessel at about 28 L. 2The liquid was continuously fed to the flash tank through the inner pipe of a double pipe heated with steam. A supply port for injecting methanol, a catalyst deactivator, was attached immediately after the liquid level control valve, and methanol was injected as a 1.0 vol% diluted hexane solution at a rate of 12 L / h to join the hexane solution. During transfer to the flash tank, the solution temperature and the pressure control valve opening were set so that the pressure inside the flash tank was maintained at 0.05 MPaG and the temperature of the vapor in the flash tank was maintained at 180°C.

[0150] As a result, ethylene-non-conjugated polyene copolymer (X) was obtained at a production rate of (p) kg / h. The polymerization mileage of ethylene-non-conjugated polyene copolymer (X) was (q) kg / mmol-Zr, the [η] of ethylene-non-conjugated polyene copolymer (X) was (r) dl / g, the MFR was (s) g / 10 min, the melting point (Tm) was (t) °C, and the density was (u) kg / m 3 The content of VNB was (v) mol% (mol %), and the content of ENB was (w) mol% (mol %).

[0151] [Table 1]

[0152] <Physical properties of unvulcanized rubber composition> (1) Coach Mooney The minimum viscosity (Vm) and scorch time (t5) at 125°C were measured in accordance with JIS K6300 using a Mooney viscometer (Model SMV202 manufactured by Shimadzu Corporation) at 125°C.

[0153] (2) Vulcanization speed Using the unvulcanized rubber compositions of the Examples and Comparative Examples, the vulcanization rate (tc90) was measured as follows using a measuring device: MDR2000 (manufactured by ALPHA TECHNOLOGIES) under measurement conditions of a temperature of 170°C and a time of 20 minutes.

[0154] The change in torque obtained under conditions of a constant temperature and a constant shear rate was measured. The time required to reach 90% of the difference between the maximum and minimum torque values ​​was defined as the vulcanization rate (tc90; min).

[0155] <Physical properties of vulcanized rubber composition> (1) Hardness test (Duro-A hardness) In accordance with JIS K 6253, the hardness (Type A durometer, HA) of the crosslinked sheet was measured using six 2mm sheet-shaped rubber molded pieces with smooth surfaces, stacked on their flat surfaces to a thickness of approximately 12mm. However, specimens with foreign matter, bubbles, or scratches were not used. The dimensions of the measurement surface of the specimen were such that measurements could be taken with the tip of the indenter at least 12mm away from the edge of the specimen. Lower hardness is an indicator of better braking performance.

[0156] (2) Tensile test According to JIS K 6251, a tensile test was conducted at a temperature of 23°C and a tensile speed of 500 mm / min to measure the breaking strength (TB) [MPa] and elongation at break (EB) [%] of the sheet. Specifically, a No. 3 dumbbell test piece described in JIS K 6251 (2001) was prepared by punching out the crosslinked molded sheet. Using this test piece, a tensile test was conducted according to the method specified in JIS K 6251 at a temperature of 25°C and a tensile speed of 500 mm / min to measure the tensile stress at break (TB) and the tensile elongation at break (EB). Larger TB and EB are indicators of better fatigue resistance (long-life performance).

[0157] (3) Tear strength The tear strength of the crosslinked sheet was measured by preparing a 2 mm thick angle-shaped test piece under the same conditions as for preparing the vulcanized molded body, pulling the test piece at a speed of 500 mm / sec, and measuring the maximum stress value (tear strength) (measurement temperature: 25°C).

[0158] (4) Tensile viscoelasticity test Storage modulus E': Dynamic viscoelasticity was measured under nitrogen using a TA-Instruments RSA-G2 for 1 mm thick vulcanized rubber sheets obtained in the Examples and Comparative Examples. Here, storage modulus (E') is a component of the complex modulus, which expresses the relationship between stress and strain when a sinusoidal oscillatory strain is applied to a viscoelastic material, and is the value measured using the TA-Instruments RSA-G2 in tension mode (1% strain) at a temperature range of -70°C to 100°C, at a heating rate of 4°C / min, and at a frequency of 10 Hz.

[0159] Tan δ: Dynamic viscoelasticity was measured under nitrogen using a TA-Instruments RSA-G2 for 1 mm thick sheets of vulcanized rubber obtained in the Examples and Comparative Examples. Here, tan δ is the value calculated by the formula tan δ (0°C, 60°C) = E" / E'. A larger tan δ0°C indicates better wet grip, and a smaller tan δ60°C indicates better fuel economy.

[0160] Example 1 <Preparation of Rubber Composition and Production of Molded Article> The diene rubber (Z-1) was 75 parts by mass of the SBR and the diene rubber (Z-2) was 25 parts by mass of the butadiene rubber (total: 100 parts by mass), and the copolymer (X-1) was 20 parts by mass, zinc oxide (ZnO#1 / zinc oxide type 2, manufactured by Hakusui Tech Co., Ltd.) was used as a crosslinking aid, 3 parts by mass of zinc oxide, stearic acid (Camellia stearate series, manufactured by NOF Corporation) was used as a processing aid, 2 parts by mass of carbon black (trade name Asahi #80 A rubber compound was obtained by kneading 40 parts by mass of silica (Nipsil VN3, Tosoh Silica Corporation) as a white filler, 4 parts by mass of a silane coupling agent (Si-69, EVONIK), 50 parts by mass of aromatic oil (AH-16, Idemitsu Kosan Co., Ltd.) as a softener, 1.4 parts by mass of sulfur as a vulcanizing agent, and 1.7 parts by mass of Suncerer CM (Sanshin Chemical Co., Ltd.) and 2.0 parts by mass of Noccelaer D (Ouchi Shinko Chemical Co., Ltd.) as vulcanization accelerators using a BB-4 Banbury mixer (Kobe Steel, Ltd.).

[0161] In the kneading, the silica / coupling agent / polymer was masticated for 2 minutes, then zinc oxide, stearic acid, carbon black, and aromatic oil were added and kneaded for 2 minutes, after which the ram was raised and cleaned, and kneaded for another 1 minute to obtain an unvulcanized rubber compound (G-1).

[0162] The rubber compound (G-1) was kneaded by winding it around an 8-inch roll (manufactured by Nippon Roll Co., Ltd.) with the surface temperature of the front roll at 50°C, the surface temperature of the rear roll at 50°C, the rotation speed of the front roll at 18 rpm, and the rotation speed of the rear roll at 16 rpm.

[0163] The kneading was carried out by cutting the mixture three times and rolling it six times to obtain a rubber composition in the form of a sheet with a thickness of 2.2 to 2.5 mm. The obtained rubber composition was used to evaluate the properties of the unvulcanized rubber compound (G-1). The results are shown in Table 2.

[0164] The crosslinked product (G-2) was then pressed at 170°C for 10 minutes using a press molding machine to produce crosslinked product (G-2) sheets with thicknesses of 2 mm and 1 mm. The resulting crosslinked product (G-2) sheets were subjected to hardness tests, tensile tests, tear strength tests, and tensile viscoelasticity tests. The evaluation results of the rubber composition and the crosslinked product are shown in Table 2.

[0165] Examples 2 to 12 The rubber compositions were obtained in the same manner as in Example 1, except that the amount of copolymer (X-1) was changed to the amount shown in Table 2, and that copolymer (X-1) was changed to the amount shown in Table 2 and copolymer (X-2) and copolymer (X-3) were changed to the amounts shown in Table 2 and Table 3, respectively. The rubber compositions and crosslinked products obtained were evaluated by the methods described above. The evaluation results are shown in Tables 2 and 3.

[0166] Comparative Example 1 A rubber composition was obtained in the same manner as in Example 1, except that the copolymer (X-1) was not used instead of the rubber composition used in Example 1. The rubber compositions and crosslinked products obtained were evaluated by the methods described above. The evaluation results are shown in Table 3.

[0167] [Table 2]

[0168] [Table 3]

Claims

1. A rubber composition comprising: a diene rubber (Z); and an ethylene-non-conjugated polyene copolymer (X) in an amount of 0.5 to 50 parts by mass per 100 parts by mass of the diene rubber (Z), the ethylene-non-conjugated polyene copolymer (X) comprising a structural unit (A) derived from ethylene and a structural unit (B) derived from a non-conjugated polyene, and satisfying all of the following (1) to (5): Ethylene-non-conjugated polyene copolymer (X) (1) The content of structural units derived from non-conjugated polyenes is in the range of 0.01 to 10 mol % (where the total of (A) and (B) is taken as 100 mol %). (2) The intrinsic viscosity [η] measured in decalin at 135°C is in the range of 1.0 to 2.0 dl / g. (3) Density is 920 to 950 kg / m 3 is in the range. (4) The melting point (Tm) measured by DSC is in the range of 100 to 130°C. (5) The P value [η*(ω=0.1) / η*(ω=100)] determined by melt viscoelasticity measurement at 190°C is in the range of 5 to 100.

2. The rubber composition according to claim 1, characterized in that it contains 1 to 40 parts by mass of the ethylene-non-conjugated polyene copolymer (X) per 100 parts by mass of the diene rubber (Z).

3. 3. The rubber composition according to claim 1, further comprising, per 100 parts by mass of the diene rubber (Z), 0.2 to 15 parts by mass of a vulcanizing agent (C), 5 to 100 parts by mass of carbon black (D), 5 to 150 parts by mass of a white filler (E), and 0.2 to 10 parts by mass of a silane coupling agent (F).

4. A rubber material for tires, comprising the rubber composition according to any one of claims 1 to 3.

5. A tire tread formed using the rubber material for a tire according to claim 4.

6. A tire comprising the tire tread of claim 5.

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