JP4433910B2 - High hardness compounded rubber composition - Google Patents

Description

  The present invention relates to a high-hardness blended rubber composition. More specifically, the present invention relates to a tire bead that has improved dimensional stability during extrusion (small die swell) and tire durability while maintaining high hardness. And a rubber composition suitable for a chafer. The present invention can also be used for tire members such as cap treads, base treads, sidewalls, carcass, and belts in tires, and industrial products such as hoses, belts, rubber rolls, rubber coolers, and shoe rubbers.

  The polybutadiene has a so-called microstructure that includes a bond portion (1,4-structure) formed by polymerization at the 1,4-position and a bond portion (1,2-structure) formed by polymerization at the 1,2-position. Coexist in the molecular chain. The 1,4-structure is further divided into two types, a cis structure and a trans structure. On the other hand, the 1,2-structure has a structure in which a vinyl group is a side chain.

  Conventionally, a method for producing a vinyl-cis polybutadiene rubber composition has been carried out with an aromatic hydrocarbon solvent such as benzene, toluene or xylene. When these solvents were used, the viscosity of the polymerization solution was high, and there were problems with stirring, heat transfer, transfer, etc., and excessive energy was required to recover the solvent. In addition, the solvent is extremely toxic to the environment due to its carcinogenic effect due to its toxicity.

As the method of production, the water in an inert organic solvent, soluble cobalt compound of the general formula AlR _n X _3-n (where R is an alkyl group, a phenyl group or a cycloalkyl group having 1 to 6 carbon atoms , X is a halogen element, n is a number from 1.5 to 2), and BR is produced by cis 1,4 polymerization of 1,3-butadiene using a catalyst obtained from an organoaluminum chloride. Then, a soluble cobalt compound and a general formula AlR ₃ (wherein R is an alkyl group having 1 to 6 carbon atoms, a phenyl group or a cycloalkyl group) with or without the addition of 1,3-butadiene and / or the solvent to the polymerization system. 1,3-butadiene is synthesized in syndiotactic 1,2 polymerization (hereinafter abbreviated as 1,2 polymerization) in the presence of a catalyst obtained from an organoaluminum compound and carbon disulfide. That method (e.g., JP-B-49-17666 (Patent Document 1), see JP-B-49-17667 (Patent Document 2)) are known.

  Also, for example, Japanese Patent Publication No. Sho 62-171 (Patent Document 3), Japanese Patent Publication No. Sho 63-36324 (Patent Document 4), Japanese Patent Publication No. 2-337927 (Patent Document 5), Japanese Patent Publication No. 2-38081 (Patent Document 6), Japanese Patent Publication No. 3-63566 (Patent Document 7), or manufactured by cis 1,4 polymerization of 1,3-butadiene in the presence or absence of carbon disulfide Later, 1,3-butadiene and carbon disulfide are separated and recovered, and 1,3-butadiene substantially free of carbon disulfide and a method of circulating the inert organic solvent are described. Further, Japanese Patent Publication No. 4-48815 (Patent Document 8) discloses a rubber composition having a small die swell ratio and a vulcanized product excellent in tensile stress and bending crack growth resistance suitable as a tire sidewall. Is described.

  JP-A-2000-44633 (Patent Document 9) discloses an inert organic solvent mainly composed of a C4 fraction such as n-butane, cis 2-butene, trans-2-butene, and butene-1. The method of manufacturing in is described. 1,2-polybutadiene contained in the rubber composition in this method is a short fiber crystal, and the distribution of the major axis length of the short fiber crystal is 98% or more of the fiber length is less than 0.6 μm, 70% It is described that the above is less than 0.2 μm, and the resulting rubber composition has the moldability, tensile stress, tensile strength, flex crack growth resistance of cis 1,4 polybutadiene rubber (hereinafter abbreviated as BR), etc. Is described as being improved.

  The rubber member disposed around the bead of the tire is made of high-hardness rubber. A rubber composition containing a large amount of carbon black and a rubber composition containing a novolac type phenol resin (Japanese Patent Publication No. 57-30856) ), A rubber composition (Japanese Patent Laid-Open No. 7-315014) containing short fibers and an olefin resin.

  As a method of obtaining a hard rubber composition, it is common to increase the carbon black and mix fibers / resins, etc., but when the heat generation during repeated deformation increases, the durability / fatigue resistance decreases. There is a need for improvement.

Japanese Patent Publication No.49-17666 Japanese Patent Publication No.49-17667 Japanese Patent Publication No.62-171 Japanese Examined Patent Publication No. 63-36324 JP-B-2-37927 JP-B-2-38081 Japanese Examined Patent Publication No. 3-63566 Japanese Patent Publication No. 4-48815 JP 2000-44633 A

  An object of this invention is to provide the rubber composition which can improve the dimensional stability at the time of extrusion, and the durability of a tire, maintaining high hardness.

The present invention relates to a vinyl cis polybutadiene rubber (a) comprising 1,2-polybutadiene crystal fiber and a rubber component, wherein (а-1) 1,3-butadiene and a solubility parameter of 8.5 to 7.0 are carbonized. (A-2) Next, as a catalyst for cis-1,4 polymerization, the general formula AlRnX _3-n (where R is a carbon number of 1 to 4) is adjusted. 6 is an alkyl group, a phenyl group or a cycloalkyl group, X is a halogen element, and n is 1.5 to 2.) 1,3-butadiene is added to perform cis-1,4 polymerization. (A-3) Then, a soluble cobalt compound and a general formula AlR ₃ (wherein R is 1 to 6 carbon atoms) in the obtained polymerization reaction mixture. The Archi In the presence of a catalyst obtained from an organoaluminum compound and carbon disulfide represented by a group, a phenyl group or a cycloalkyl group, Rubber component (a) + (b) 100 parts by weight and rubber reinforcing agent (c) 60-100 in an amount of 20-80% by weight and diene rubber (b) other than (a) 80-20% by weight a rubber composition comprising a weight part, the minor axis length of monodispersed fiber crystals having an average 1,2-polybutadiene crystal fiber which is contained in the vinyl-cis-polybutadiene rubber (a) is be 0.2μm or less The present invention relates to a high-hardness blended rubber composition having an aspect ratio of 10 or less, a short fiber shape having 10 or more monodisperse fiber crystals, and a melting point of 170 ° C. or more.

In the present invention, the vinyl cis polybutadiene rubber (a)
(1) adjusting the water concentration of a mixture mainly composed of 1,3-butadiene and a hydrocarbon organic solvent having a solubility parameter of 8.5 or less,
(2) Next, as a catalyst for cis-1,4 polymerization, the general formula AlRnX3-n (wherein R is an alkyl group having 1 to 6 carbon atoms, a phenyl group or a cycloalkyl group, X is a halogen element, n is 1.5 to 2.) A halogen-containing organoaluminum compound represented by (2) and a soluble cobalt compound are added to the mixture to polymerize 1,3-butadiene in cis-1,4,
(3) The organoaluminum compound represented by the soluble cobalt compound and the general formula AlR3 (wherein R is an alkyl group having 1 to 6 carbon atoms, a phenyl group or a cycloalkyl group) in the resulting polymerization reaction mixture. The present invention relates to a high-hardness blended rubber composition characterized in that it is produced by 1,2-butadiene polymerization of 1,3-butadiene in the presence of a catalyst obtained from carbon disulfide.

Further, the present invention is high-hardness compounded rubber composition according to claim 1 wherein said vinyl-cis-polybutadiene rubber (a) is characterized by having the following characteristics.
(1) The molecular weight index η sp / c (reduced viscosity measured at 135 ° C. from an orthodichlorobenzene solution ) in the boiling n-hexane insoluble content of the vinyl cis-polybutadiene rubber is in the range of 0.5-4. .
(2) The polystyrene-converted weight average molecular weight of the boiling n-hexane soluble content of the vinyl cis-polybutadiene rubber is in the range of 300,000 to 800,000.
(3) The cis structure content in the microstructure of the boiling n-hexane soluble part of the vinyl cis-polybutadiene rubber is 90% or more.
(4) The relationship between the viscosity of the 5 wt% toluene solution at 25 ° C. and the Mooney viscosity at 100 ° C. of the boiling n-hexane soluble content of the vinyl cis-polybutadiene rubber is T-cp / ML ≧ 1.

  The present invention also relates to a high hardness compounded rubber composition wherein the diene rubber (b) other than (a) is natural rubber and / or polyisoprene.

  The present invention also relates to a high hardness compounded rubber composition characterized in that the rubber reinforcing agent is carbon black.

  The rubber composition for a sidewall in the present invention is a short fiber having an average monodisperse fiber crystal minor axis length of 0.2 μm or less, an aspect ratio of 10 or less, and an average number of monodisperse fiber crystals of 10 or more. Because it contains vinyl cis-polybutadiene containing 1,2-polybutadiene crystal fiber with a melting point of 170 ° C or higher, it maintains dimensional stability and durability of the tire while maintaining high hardness. It can be improved at the same time, and both performances can be balanced.

The vinyl cis polybutadiene rubber comprising (a) a specific 1,2-polybutadiene crystal fiber and a rubber component of the present invention,
(1) An average monodisperse fiber crystal short axis length of 1,2-polybutadiene crystal fiber is 0.2 μm or less, an aspect ratio is 10 or less, and an average number of monodisperse fiber crystals is 10 or more. 1 and 50 parts by weight of 1,2-polybutadiene crystal fiber having a melting point of 170 ° C. or higher, and (2) 100 parts by weight of rubber.

  The 1,2-polybutadiene crystal fiber of the above component (1) has an average monodisperse fiber crystal minor axis length of 0.2 μm or less, preferably 0.1 μm or less, and an aspect ratio of 10 or less, preferably 8 or less, the average number of monodisperse fiber crystals is 10 or more, preferably 15 or more, and the melting point is 170 ° C. or more, preferably 190 to 220 ° C.

  (2) The rubber component is preferably cis 1,4-polybutadiene having the following characteristics.

  Cis 1,4-structure content is generally 90% or more, especially 95% or more, Mooney viscosity is 10 to 130, preferably 15 to 80, toluene solution viscosity is 30 to 200, preferably 30 to 100, Contains substantially no gel content.

  The proportion of (1) component 1,2-polybutadiene crystal fiber and (2) rubber component is 1 to 50 weight of (1) component 1,2-polybutadiene crystal fiber with respect to 100 parts by weight of (2) rubber component. Parts, preferably 1 to 30 parts by weight. If it is out of the above range, the short fiber crystal of 1,2-polybutadiene crystal fiber in BR becomes large, and the low die swell, high hardness, etc., which are features, are difficult to be exhibited, and there are problems such as deterioration of workability. .

  The vinyl cis-polybutadiene is preferably obtained by the following production method, for example.

  It is produced by polymerization using a hydrocarbon solvent having a solubility parameter (hereinafter referred to as SP value) of 8.5 or less. For hydrocarbon solvents with a solubility parameter of 8.5 or less:

  For example, n-hexane (SP value: 7.2), n-pentane (SP value: 7.0), n-octane (SP value: 7.5), cyclohexane (aliphatic hydrocarbon, alicyclic hydrocarbon) SP value: 8.1), n-butane (SP value: 6.6), etc. are mentioned. Of these, cyclohexane and the like are preferable.

  The SP values of these solvents are known in documents such as the Rubber Industry Handbook (Fourth Edition, Japan Rubber Association, published on January 20, 1994; page 721).

  If a solvent having an SP value greater than 8.5 is used, the dispersion state of the short fiber crystals of 1,2 polybutadiene in the polybutadiene rubber is difficult to be formed as in the present invention, so that excellent die swell characteristics and low heat generation characteristics can be obtained. Since it does not express, it is not preferable.

  Next, the concentration of water in the mixed medium obtained by mixing 1,3-butadiene and the solvent is adjusted. The water content is preferably in the range of 0.1 to 1.0 mol, particularly preferably 0.2 to 1.0 mol, per mol of organoaluminum chloride in the medium. Outside this range, the catalytic activity is decreased, the cis 1,4 structure content is decreased, the molecular weight is abnormally decreased or increased, and the generation of gel during polymerization cannot be suppressed. This is not preferable because gel adheres to the tank and the continuous polymerization time cannot be extended. A known method can be applied as a method of adjusting the moisture concentration. A method of adding and dispersing through a porous filter medium (Japanese Patent Laid-Open No. 4-85304) is also effective.

Organoaluminum chloride is added to the solution obtained by adjusting the water concentration. Specific examples of the organoaluminum chloride represented by the general formula AlR _n X _3-n include diethylaluminum monochloride, diethylaluminum monobromide, diisobutylaluminum monochloride, dicyclohexylaluminum monochloride, diphenylaluminum monochloride, diethylaluminum sesquichloride. Etc. can be preferably mentioned. As a specific example of the amount of the organoaluminum chloride used, 0.1 mmol or more, particularly 0.5 to 50 mmol is preferable per 1 mol of the total amount of 1,3-butadiene.

  Subsequently, a soluble cobalt compound is added to the mixed medium to which the organoaluminum chloride is added, and cis 1,4 polymerization is performed. The soluble cobalt compound is soluble in an inert medium or liquid 1,3-butadiene mainly composed of a hydrocarbon solvent having an SP value of 8.5 or less, or can be uniformly dispersed, for example, cobalt ( II) Cobalt β-diketone complexes such as acetylacetonate and cobalt (III) acetylacetonate, β-keto acid ester complexes of cobalt such as cobalt acetoacetate ethyl ester complex, cobalt octoate, cobalt naphthenate, cobalt benzoate, etc. And cobalt halides such as cobalt salts of organic carboxylic acids having 6 or more carbon atoms, cobalt chloride pyridine complexes, and cobalt chloride ethyl alcohol complexes. The amount of the soluble cobalt compound used is preferably 0.001 mmol or more, more preferably 0.005 mmol or more, per mol of 1,3-butadiene. The molar ratio (Al / Co) of the organoaluminum chloride to the soluble cobalt compound is 10 or more, and particularly preferably 50 or more. In addition to soluble cobalt compounds, nickel organic carboxylates, nickel organic complexes, organolithium compounds, neodymium organic carboxylates, and neodymium organic complexes can also be used.

  The temperature at which cis 1,4 polymerization is carried out is such that 1,3-butadiene is cis 1,4 polymerized in a temperature range of more than 0 ° C. to 100 ° C., preferably 10 to 100 ° C., more preferably 20 to 100 ° C. The polymerization time (average residence time) is preferably in the range of 10 minutes to 2 hours. The cis 1,4 polymerization is preferably carried out so that the polymer concentration after the cis 1,4 polymerization is 5 to 26% by weight. The polymerization tank is performed by connecting one tank or two or more tanks. The polymerization is carried out by stirring and mixing the solution in a polymerization tank (polymerizer). As a polymerization tank used for polymerization, a polymerization tank equipped with a high-viscosity liquid stirring apparatus, for example, an apparatus described in JP-B-40-2645 can be used.

  Known molecular weight regulators in the cis 1,4 polymerization of the present invention, for example, non-conjugated dienes such as cyclooctadiene, allene, and methylallene (1,2-butadiene), or α- such as ethylene, propylene, and butene-1. Olefins can be used. In order to further suppress the formation of gel during polymerization, a known gelation inhibitor can be used. The cis 1,4-structure content is generally 90% or more, particularly 95% or more, and has a Mooney viscosity of 10 to 130, preferably 15 to 80, and contains substantially no gel content.

1,3-butadiene may or may not be added to the cis 1,4 polymerization reaction mixture obtained as described above. Then, an organoaluminum compound represented by the general formula AlR ₃ and carbon disulfide, and if necessary, the above-mentioned soluble cobalt compound is added, and 1,3-butadiene is polymerized 1,2 to obtain a boiling n-hexane soluble content of 99 to 50 wt. % And H.V. A vinyl cis polybutadiene rubber having I of 1 to 50% by weight is produced. Preferred examples of the organic aluminum compound represented by the general formula AlR3 include trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-hexylaluminum, and triphenylaluminum. The organoaluminum compound is at least 0.1 mmol, especially 0.5 to 50 mmol, per mole of 1,3-butadiene. The carbon disulfide is not particularly limited, but is preferably one that does not contain moisture. The concentration of carbon disulfide is 20 mmol / L or less, particularly preferably 0.01 to 10 mmol / L. A known phenyl isothiocyanate or xanthate compound may be used as an alternative to carbon disulfide.

  The temperature for 1,2 polymerization is 100 ° C. or less, preferably -50 to 80 ° C., more preferably -20 to 70 ° C., and 1,3-butadiene is subjected to 1,2 polymerization. 1 to 50 parts by weight, preferably 1 to 20 parts by weight of 1,3-butadiene per 100 parts by weight of the cis polymerization solution is added to the polymerization system for the 1,2 polymerization. The yield of 1,2-polybutadiene can be increased. The polymerization time (average residence time) is preferably in the range of 10 minutes to 2 hours. The 1,2 polymerization is preferably performed so that the polymer concentration after the 1,2 polymerization is 9 to 29% by weight. The polymerization tank is performed by connecting one tank or two or more tanks. The polymerization is carried out by stirring and mixing the polymerization solution in a polymerization tank (polymerizer). As a polymerization tank used for 1,2 polymerization, a higher viscosity is obtained during the 1,2 polymerization, and the polymer easily adheres, so a polymerization tank equipped with a high-viscosity liquid stirring device, for example, an apparatus described in JP-B-40-2645 Can be used.

  After the polymerization reaction reaches a predetermined polymerization rate, a known anti-aging agent can be added according to a conventional method. Representative of the antioxidants are phenol-based 2,6-di-t-butyl-p-cresol (BHT), phosphorus-based trinonylphenyl phosphite (TNP), sulfur-based 4.6-bis (octylthio). Methyl) -o-cresol, dilauryl-3,3′-thiodipropionate (TPL) and the like. They may be used alone or in combination of two or more, and the addition of the antioxidant is 0.001 to 5 parts by weight based on 100 parts by weight of the vinyl cis polybutadiene rubber. Next, a polymerization terminator is added to the polymerization system and stopped. For example, after the polymerization reaction is completed, the polymer is supplied to a polymerization stop tank, and a large amount of a polar solvent such as alcohol such as methanol or ethanol or water is added to the polymerization solution, or an inorganic acid such as hydrochloric acid or sulfuric acid, acetic acid, benzoic acid, etc. This is a method known per se, such as a method of introducing an organic acid or hydrogen chloride gas into the polymerization solution. Next, the vinyl cis polybutadiene rubber produced according to the usual method is separated, washed and dried.

  The vinyl cis-polybutadiene thus obtained has a Mooney viscosity of 20 to 150, preferably 25 to 100, (1) 1 to 50 parts by weight of 1,2 polybutadiene, and a melting point of 170 to 220 ° C. (2) A cis 1,4-polybutadiene having a rubber content of 100 parts by weight and a microstructure of cis 90% or more.

  1,2-polybutadiene crystal fiber dispersed in vinyl cis polybutadiene is partially dispersed in the form of monodisperse as fine crystals in vinyl cis polybutadiene matrix rubber, coexisting with large fiber crystals having an agglomerated structure is doing. The monodispersed fine fiber crystals improve the interface affinity with the matrix rubber component. This monodisperse fiber crystal has a short fiber shape having an average minor axis length of 0.2 μm or less, an aspect ratio of 10 or less, and an average number of monodisperse fiber crystals of 10 or more. On the other hand, most of the conventional vinyl cis-polybutadiene has a fiber crystal having a large aggregate structure, and the number of monodisperse fiber crystals is 5 or less.

  1,3-butadiene, inert medium obtained by distillation from the mixture containing the remaining unreacted 1,3-butadiene, inert medium and carbon disulfide obtained by separating the vinyl cis-polybutadiene rubber thus obtained. On the other hand, carbon disulfide is separated and removed by adsorption separation treatment of carbon disulfide or carbon disulfide adduct separation treatment, and 1,3-butadiene substantially free of carbon disulfide is inert. Collect the medium. Also, carbon disulfide is substantially contained by recovering three components from the mixture by distillation and separating and removing carbon disulfide from the distillation by the adsorption separation or carbon disulfide deposit separation treatment. Unrecovered 1,3-butadiene and inert media can also be recovered. The carbon disulfide recovered as described above and the inert medium are used by mixing freshly replenished 1,3-butadiene.

  When continuously operated by the method of the present invention, the vinyl cis-polybutadiene rubber can be produced continuously for a long time with excellent catalyst component operability and industrially advantageous with high catalyst efficiency. In particular, it can be continuously produced industrially advantageously at a high conversion without adhering to the inner wall of the polymerization tank, the stirring blade, and other parts where the stirring is slow.

  However, the polymerization method is not particularly limited, and it can be produced by continuous polymerization or batch polymerization.

  Next, the rubber composition for sidewalls used in the present invention comprises the vinyl cis polybutadiene (a), a diene rubber (b) other than (a), and a rubber reinforcing agent (c). .

  Examples of the diene rubber (b) include high cis polybutadiene rubber, low cis polybutadiene rubber (BR), natural rubber, polyisoprene rubber, emulsion polymerization or solution polymerization styrene butadiene rubber (SBR), ethylene propylene diene rubber (EPDM). , Nitrile rubber (NBR), butyl rubber (IIR), chloroprene rubber (CR) and the like.

  In addition, derivatives of these rubbers such as polybutadiene rubber modified with tin compounds and the above-mentioned rubbers modified with epoxy, silane, and maleic acid can be used. These rubbers can be used alone or in combination of two or more. May be.

  As the rubber reinforcing agent of component (c) of the present invention, in addition to various carbon blacks, inorganic reinforcing agents such as white carbon, activated calcium carbonate, and ultrafine magnesium silicate, syndiotactic 1,2 polybutadiene resin, polyethylene resin And organic reinforcing agents such as polypropylene resin, high styrene resin, phenol resin, lignin, modified melamine resin, coumarone indene resin and petroleum resin, and particularly preferably, the particle diameter is 90 nm or less and the dibutyl phthalate (DBP) oil absorption is Carbon black of 70 ml / 100 g or more, and examples thereof include FEF, FF, GPF, SAF, ISAF, SRF, HAF and the like.

  100 parts by weight of the rubber component (a) + (b) composed of 20 to 80% by weight of vinyl cis polybutadiene (a) and diene rubber (b) other than (a) (80 to 20% by weight). And a rubber reinforcing agent (c) in an amount of 40 to 100 parts by weight.

  If the amount of vinyl cis polybutadiene is less than the lower limit, a rubber composition having a large die swell and low exothermic property of the vulcanizate cannot be obtained, and if the amount of vinyl cis polybutadiene is larger than the upper limit, the composition The Mooney viscosity becomes too high, and the moldability deteriorates. When the amount of the rubber reinforcing agent is less than the lower limit, the die swell becomes large. Conversely, when the amount is larger than the upper limit, the Mooney viscosity becomes excessively high and kneading becomes difficult.

  The high-hardness blended rubber composition of the present invention can be obtained by kneading the above components using a conventional Banbury, open roll, kneader, biaxial kneader or the like. The kneading temperature needs to be lower than the melting point of the 1,2 polybutadiene crystal fiber contained in the vinyl cis polybutadiene. Kneading at a temperature higher than the melting point of the 1,2 polybutadiene crystal fibers is not preferable because fine short fibers in the vinyl-cis polybutadiene are melted and deformed into spherical particles.

  If necessary, the rubber composition of the present invention is kneaded with compounding agents usually used in the rubber industry, such as vulcanizing agents, vulcanization aids, anti-aging agents, fillers, process oils, zinc white, and stearic acid. May be.

  As the vulcanizing agent, known vulcanizing agents such as sulfur, organic peroxides, resin vulcanizing agents, and metal oxides such as magnesium oxide are used.

  As the vulcanization aid, known vulcanization aids such as aldehydes, ammonia, amines, guanidines, thioureas, thiazoles, thiurams, dithiocarbamates, xanthates and the like are used.

  Examples of the anti-aging agent include amine / ketone series, imidazole series, amine series, phenol series, sulfur series and phosphorus series.

  Examples of the filler include inorganic fillers such as calcium carbonate, basic magnesium carbonate, clay, Lissajous and diatomaceous earth, and organic fillers such as recycled rubber and powder rubber.

  The process oil may be any of aromatic, naphthenic, and paraffinic.

  The high hardness compounded rubber composition of the present invention has a small die swell and a low heat generation characteristic of the vulcanizate. , Belts, beads, etc.).

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. In the examples and comparative examples, the physical properties of the vinyl cis polybutadiene rubber, the physical properties of the resulting high-hardness blended rubber composition, and the physical properties of the vulcanizate were measured as follows.
(1) Content of 1,2 polybutadiene crystal fiber : The remainder of the extraction by boiling 2 g of vinyl cis polybutadiene with 200 ml of n-hexane for 4 hours by a Soxhlet extractor is shown in parts by weight.
(2) Melting point of 1,2 polybutadiene crystal fiber : The boiling n-hexane extraction remainder was determined by the peak temperature of the endothermic curve by a differential scanning calorimeter (DSC).
(3) ηsp / C : As a measure of the molecular weight of 1,2 polybutadiene crystal fiber, the reduced viscosity was measured at 135 ° C. from an orthodichlorobenzene solution.
(4) Crystal fiber form : Vinyl cis polybutadiene is vulcanized with sulfur monochloride and carbon disulfide, and the vulcanized product is cut into ultra-thin sections and double bond of rubber of vinyl cis polybutadiene with osmium tetrachloride vapor. Was obtained by observing with a transmission electron microscope.
(5) Microstructure of rubber in vinyl cis polybutadiene ; the analysis was performed by infrared absorption spectrum analysis. The microstructure was calculated from the absorption intensity ratio of cis 740 cm ⁻¹ , trans 967 cm ⁻¹ and vinyl 910 cm ⁻¹ .
(6) Viscosity of toluene solution of rubber in vinyl cis polybutadiene : The viscosity of a 5 wt% toluene solution at 25 ° C. was measured and expressed in centipoise (cp).
(7) [η] of rubber content in vinyl cis-polybutadiene rubber ; The boiling n-hexane soluble content was collected by drying and measured with a toluene solution at a temperature of 30 ° C.
(8) Weight average molecular weight of rubber content in vinyl cis-polybutadiene rubber ; boiled n-hexane soluble content was collected by drying and converted into a tetrahydrofuran solution by gel permeation chromatography (GPC, manufactured by Tosoh Corporation, HCL-802A). The weight average molecular weight (Mw) was determined from a calibration curve using standard polystyrene at 40 ° C.
(9) Mooney viscosity ; a value measured at 100 ° C. according to JIS K6300.
(10) Die swell : The diameter of the compound and the die orifice diameter at the time of extrusion at 100 ° C. and a shear rate of 100 sec-1 as an indication of the extrudability of the compound using a processability measuring device (Monsanto, MPT) (However, the ratio L / D = 1.5 mm / 1.5 mm) was measured to obtain. The smaller the index, the better the workability.
(11) Hardness : Measured at room temperature using a type A durometer according to JIS K6253.
(12) Low exothermic tan δ : Measured at a temperature of 60 ° C., a frequency of 10 Hz, and a dynamic strain of 2% using a rheometric viscoelasticity measuring device. The smaller the index, the better the heat generation.

(Manufacture of vinyl cis polybutadiene sample 1)
In a 30-liter stainless steel reactor equipped with a stirrer that was replaced with nitrogen gas, a solution of 1.6-butadiene dissolved in 1.8 kg of dehydrated cyclohexane was placed and 4 mmol of cobalt octoate, 84 mmol of diethylaluminum chloride and 1.5- Cyclopolymerization was carried out by mixing 70 mmol of cyclooctadiene and stirring at 25 ° C. for 30 minutes. Immediately after cis polymerization, 90 mmol of triethylaluminum and 50 mmol of carbon disulfide were added to the polymerization solution, and the mixture was stirred at 25 ° C. for 60 minutes to carry out 1,2 polymerization. After completion of the polymerization, the polymerization product solution is added to 18 L of methanol containing 1% by weight of 4,6-bis (octylthiomethyl) -O-cresol to precipitate a rubbery polymer, and the rubbery polymer is separated. After washing with methanol, it was vacuum dried at room temperature. The yield of the vinyl-cis polybutadiene rubber thus obtained was 82%.
(Manufacture of vinyl cis polybutadiene sample 2)
Vinyl cis polybutadiene was obtained in the same manner as in the production method of Sample 1, except that dehydrated benzene was used as the polymerization solvent. The yield of the vinyl-cis polybutadiene rubber thus obtained was 80%.
Table 1 shows the physical properties of Sample 1 and Sample 2.

(Examples 1-5) (Comparative Examples 1-4)
Using Sample 1 and Sample 2, among the compounding formulations shown in Table 2, a vulcanization accelerator and a compounding agent excluding sulfur were kneaded using a 1.7 L test Banbury mixer, and a high hardness compounded rubber composition A kneaded product was obtained. At this time, the maximum kneading temperature was adjusted to 170 to 180 ° C. Next, the kneaded product was kneaded with a vulcanization accelerator and sulfur on a 10-inch roll, rolled out into a sheet, and then vulcanized in a mold to obtain a vulcanized product. Vulcanization was performed at 150 ° C. for 30 minutes. The results are summarized in Table 2.
The compositions of the examples have greatly improved elastic moduli and a high balance between die swell and fuel efficiency. On the other hand, in the composition of the comparative example, when commercially available BR is used, the die swell becomes large, and when the amount of carbon black is large, the heat generation characteristics deteriorate. Further, when a vinyl cis polybutadiene that does not satisfy the present invention is used or the amount of the vinyl cis polybutadiene of the present invention is small, the improvement effect does not reach the expected level.

（注１）NR；RSS#1
（注２）BR；ポリブタジエン（UBEPOL-BR150、宇部興産（株）製）
（注３）老化防止剤；アンテージＡＳ（アミンとケトンの反応物）
（注４）加硫促進剤；ノクセラーＣＺ（Ｎ−シクロヘキシル−２−ベンゾチアゾールスルフェンアミド

(Note 1) NR; RSS # 1
(Note 2) BR: Polybutadiene (UBEPOL-BR150, manufactured by Ube Industries)
(Note 3) Anti-aging agent; Antage AS (reaction product of amine and ketone)
(Note 4) Vulcanization accelerator; Noxeller CZ (N-cyclohexyl-2-benzothiazolesulfenamide

Claims (5)

A vinyl-cis polybutadiene rubber (a) comprising 1,2-polybutadiene crystal fiber and a rubber component is a hydrocarbon organic solvent having (а-1) 1,3-butadiene and a solubility parameter of 8.5 to 7.0. (A-2) Then, as a catalyst for cis-1,4 polymerization, the general formula AlRnX _3-n (where R is an alkyl group having 1 to 6 carbon atoms) , A phenyl group or a cycloalkyl group, X is a halogen element, and n is 1.5 to 2.) A halogen-containing organoaluminum compound represented by , 3-butadiene is subjected to cis-1,4 polymerization. (A-3) Then, a soluble cobalt compound and a general formula AlR ₃ (wherein R is an alkyl group having 1 to 6 carbon atoms, and Feni In the presence of a catalyst obtained from carbon disulfide and an organoaluminum compound represented by the following formula: ~ 80 wt% and
In (a) non-diene rubber (b) 80 to 20% by weight of rubber component (a) + (b) 100 parts by weight of a rubber reinforcing agent (c) a rubber composition comprising 60 to 100 parts by weight There,
The average monodisperse fiber crystal short axis length of 1,2-polybutadiene crystal fibers contained in the vinyl-cis polybutadiene rubber (a) is 0.2 μm or less, the aspect ratio is 10 or less, and the monodisperse fibers A high-hardness blended rubber composition having a short fiber shape with 10 or more crystals and a melting point of 170 ° C or higher. The high-hardness blended rubber composition according to claim 1, wherein the vinyl-cis polybutadiene rubber (a) has the following characteristics.
(1) The molecular weight index η sp / c (reduced viscosity measured at 135 ° C. from an orthodichlorobenzene solution) of the boiling n-hexane insoluble matter of the vinyl cis-polybutadiene rubber is in the range of 0.5-4. .
(2) The polystyrene-converted weight average molecular weight of the boiling n-hexane soluble content of the vinyl cis-polybutadiene rubber is in the range of 300,000 to 800,000.
(3) The cis structure content in the microstructure of the boiling n-hexane soluble part of the vinyl cis-polybutadiene rubber is 90% or more.
(4) The relationship between the viscosity of the 5 wt% toluene solution at 25 ° C. and the Mooney viscosity at 100 ° C. of the boiling n-hexane soluble content of the vinyl cis-polybutadiene rubber is T-cp / ML ≧ 1. 3. The high-hardness blended rubber composition according to claim 1, wherein the diene rubber (b) other than (a) is natural rubber and / or polyisoprene.   The rubber compounding composition according to any one of claims 1 to 3, wherein the rubber reinforcing agent (c) is carbon black.   The high-hardness blended rubber composition according to any one of claims 1 to 4, wherein the hydrocarbon-based organic solvent having a solubility parameter of (а-1) of 8.5 to 7.0 is cyclohexane.