WO2020054707A1

WO2020054707A1 - Rubber composition and tire

Info

Publication number: WO2020054707A1
Application number: PCT/JP2019/035520
Authority: WO
Inventors: 遼大曽根; 和宏秋川; 春田　淳; 雅大田中; 孝一ノ瀬; 勇人茶野木
Original assignee: 株式会社ブリヂストン; 宇部興産株式会社
Priority date: 2018-09-14
Filing date: 2019-09-10
Publication date: 2020-03-19
Also published as: JP7031003B2; JPWO2020054707A1

Abstract

This rubber composition is characterized by containing: 100 parts by mass of a rubber component (A)+(B) that includes 1-50 parts by mass of a vinyl cis-polybutadiene rubber (A) containing 35-99 mass% of 1,2-polybutadiene having a melting point of 150-195°C and 50-99 parts by mass of a diene-based rubber (B) excluding (A); and 1-150 parts by mass of a rubber reinforcing agent (C). This tire is obtained by using said rubber composition.

Description

Rubber composition and tire

The present invention relates to a rubber composition and a tire using the same. More specifically, the present invention relates to a rubber composition using a vinyl cis-polybutadiene rubber and a tire using the same.

Conventionally, vinyl cis-polybutadiene rubber has been produced by converting 1,3-butadiene into cis-1,1-butadiene using a predetermined catalyst in an inert organic solvent mainly containing a hydrocarbon such as benzene, toluene and xylene. It is carried out by a method of polymerizing 4 followed by syndiotactic-1,2 polymerization (hereinafter sometimes simply referred to as “1,2 polymerization”).

ビニル Vinyl cis-polybutadiene rubber is desired to have various improved properties depending on the use of the rubber composition. For example, Patent Literature 1 describes a vinyl-cis-polybutadiene rubber in which SPB is finely divided into fine particles of SPB using a solvent as a C4 fraction to improve tensile properties and crack resistance. Patent Literature 2 discloses a vinyl cis-metal having improved fatigue resistance by setting the ratio of the number of moles of a halogen atom in a halogen-containing organoaluminum compound to the number of moles of an organoaluminum compound (AlR3) to an optimum value. Polybutadiene rubber is described. Patent Literature 3 describes a vinyl cis-polybutadiene rubber in which the amount of a catalyst used is adjusted to impart excellent productivity and suitable rigidity. Patent Documents 4 and 5 disclose a vinyl cis-polybutadiene rubber having a boiling n-hexane insoluble matter (HI), a long chain branching index and a degree of branching within a specific range, and imparting excellent cold flow and rigidity. Has been described.

Japanese Patent No. 0385480 Japanese Patent No. 05287436 Japanese Patent No. 0544708 Patent No. 0544707 Japanese Patent No. 0558710

However, the vinyl cis-polybutadiene rubbers described in Patent Literatures 1 to 5, which are various improved vinyl cis-polybutadiene rubbers, also have other properties such as steering stability and low loss when formed into a rubber composition. There is still room for improvement with regard to the physical properties of.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a rubber composition excellent in balance between steering stability and low loss property, and a tire using the same.

Means for Solving the Problems The present inventors have conducted intensive studies in order to achieve the above object, and have found that 1,2-polybutadiene having a specific melting point is contained in a specific concentration in vinyl-cis-polybutadiene rubber compounded in a rubber composition. The present inventors have found that a rubber composition having excellent steering stability can be produced by containing the rubber composition, and have led to the present invention.

That is, the present invention provides 1 to 50 parts by mass of a vinyl cis-polybutadiene rubber (A) containing 35 to 99% by mass of 1,2-polybutadiene having a melting point of 150 to 195 ° C., and a diene system other than (A). Rubber composition comprising 100 parts by mass of rubber component (A) + (B) containing 50 to 99 parts by mass of rubber (B) and 1 to 150 parts by mass of rubber reinforcing agent (C), and rubber composition A tire using the same.

As described above, according to the present invention, it is possible to provide a rubber composition excellent in balance between low loss properties and steering stability, and a tire using the same.

<Vinyl cis-polybutadiene rubber (A)>
The vinyl cis-polybutadiene rubber (A) used in the rubber composition of the present invention contains 35 to 99% by mass of 1,2-polybutadiene having a melting point of 150 to 195 ° C in 1,4-polybutadiene.

(1,2-polybutadiene)
In the vinyl cis-polybutadiene rubber (A) used in the present invention, 1,2-polybutadiene has a melting point of 150 to 195 ° C, preferably 160 to 190 ° C, more preferably 170 to 185 ° C. preferable. If the melting point of 1,2-polybutadiene (B) is lower than 150 ° C., the die swell is deteriorated, and if it is higher than 195 ° C., the fuel efficiency is deteriorated, which is not preferable.

Here, let the peak temperature of the endothermic peak derived from 1,2-polybutadiene measured by a differential scanning calorimeter be the melting point of 1,2-polybutadiene. When there are a plurality of endothermic peaks derived from 1,2-polybutadiene, peak separation is performed, and the peak top of the peak having the largest area is determined as the melting point of 1,2-polybutadiene.

The content of 1,2-polybutadiene is 35 to 99% by mass, preferably 35 to 90% by mass, more preferably 40 to 80% by mass, based on the vinyl-cis-polybutadiene rubber. If the content is more than 99% by mass, for example, the dispersibility of 1,2-polybutadiene after compounding is insufficient and the effect of the vinyl-cis-polybutadiene rubber is small, which is not preferable. When the amount is less than 35% by mass, the effect of improving the elastic modulus of 1,2-polybutadiene is not sufficiently exhibited, which is not preferable. Here, the concentration of the crystal part of 1,2-polybutadiene is defined as the concentration of 1,2-polybutadiene.

The concentration of the 1,2-polybutadiene crystal part is calculated from the heat of fusion of the 1,2-polybutadiene crystal part measured by a differential scanning calorimeter.
Specifically, first, the vinyl-cis-polybutadiene rubber is heated at a heating rate of 10 ° C./min, and the heat of fusion is calculated from an endothermic peak derived from the melting of 1,2-polybutadiene. Next, the concentration (% by mass) of the crystal part of 1,2-polybutadiene contained in the vinyl-cis-polybutadiene rubber can be calculated from the known heat of fusion of 1,2-polybutadiene per unit mass.

The vinyl-cis-polybutadiene rubber may contain an amorphous portion of 1,2-polybutadiene, and the content of the amorphous portion of 1,2-polybutadiene is 0 to 30 with respect to the vinyl-cis-polybutadiene rubber. % By mass, more preferably 0 to 25% by mass, and particularly preferably 0 to 10% by mass. It is possible to obtain a vinyl-cis-polybutadiene rubber capable of providing a rubber composition having a lower loss property and a more excellent handling stability.

The content of 1,2-polybutadiene in the vinyl-cis-polybutadiene rubber (A) is determined by synthesizing 1,3-butadiene in the third step of the method for producing the vinyl-cis-polybutadiene rubber (A) described below. -1, adjusted in polymerization.

は Further, the peak top molecular weight (Mp) of 1,2-polybutadiene is preferably from 1,000 to 300,000, more preferably from 5,000 to 150,000. When the peak top molecular weight (Mp) is larger than 300,000, elongation tends to be deteriorated, and when it is smaller than 1,000, the elastic modulus tends to be deteriorated. In the present invention, the peak top molecular weight (Mp) is a molecular weight of a peak top in an elution curve obtained by gel permeation chromatography (GPC) measurement, and can be calculated from a calibration curve obtained using polystyrene as a standard substance. .

(1,4-polybutadiene)
In the vinyl cis-polybutadiene rubber (A) used in the present invention, 1,4-polybutadiene is converted to 1,3-butadiene in the second step of the method for producing the vinyl cis-polybutadiene rubber (A) described below. It is obtained by 1,4 polymerization. The Mooney viscosity (ML _{1 + 4} , 100 ° C.) of polybutadiene is preferably from 20 to 60, and more preferably from 25 to 45. If the Mooney viscosity (ML _{1 + 4} , 100 ° C.) is smaller than 20, the low loss property is reduced, and if it is larger than 60, the workability is reduced.
The cis-1,4 structure content of polybutadiene is preferably at least 90%, particularly preferably at least 95%.

The weight average molecular weight (Mw) of 1,4-polybutadiene is preferably from 200,000 to 800,000, more preferably from 400,000 to 650,000. If the weight average molecular weight (Mw) is smaller than 200,000, the low loss property is reduced, and if it is larger than 800,000, the processability is reduced.
Further, the ratio (Mw / Mn) between the weight average molecular weight (Mw) and the number average molecular weight (Mn) is preferably 2.00 to 5.00, more preferably 2.20 to 3.50.

１， 1,4-polybutadiene obtained by cis-1,4 polymerization contains substantially no gel component.

<Method for producing vinyl cis-polybutadiene rubber (A)>
The method for producing a vinyl-cis-polybutadiene rubber according to the present invention comprises a first step of preparing a mixture of 1,3-butadiene and an inert organic solvent containing a hydrocarbon as a main component, and a first step. (A) a catalyst composed of water, an organoaluminum compound and a soluble cobalt compound, or (b) a catalyst composed of an organoaluminum compound, a nickel compound and a fluorine compound, to convert 1,3-butadiene into cis-1,1. 4) a second step of polymerizing, and a third step of syndiotactic-1,2 polymerization of 1,3-butadiene in the polymerization reaction mixture obtained in the second step, obtained in the third step It is characterized by adding a melting point depressant for lowering the melting point of 1,2-polybutadiene.

(First step)
Examples of the inert organic solvent containing a hydrocarbon as a main component used in the method for producing the vinyl-cis-polybutadiene rubber (A) according to the present invention include aromatic hydrocarbons such as toluene, benzene and xylene, n-hexane and butane. , Hydrocarbons such as heptane and pentane, alicyclic hydrocarbons such as cyclohexane and cyclopentane, the above-mentioned olefin compounds and olefinic hydrocarbons such as cis-2-butene and trans-2-butene, mineral spirits and solvents Examples include hydrocarbon solvents such as naphtha and kerosene, and halogenated hydrocarbon solvents such as methylene chloride. Further, the 1,3-butadiene monomer itself may be used as the polymerization solvent.

中でも Among the above-mentioned inert organic solvents, toluene, cyclohexane, a mixture of cis-2-butene and trans-2-butene, and the like are preferably used.

(2nd process)
Next, (a) a catalyst comprising water, an organoaluminum compound and a soluble cobalt compound is added to the mixture prepared in the first step, and 1,3-butadiene is subjected to cis-1,4 polymerization. That is, first, water is added to the mixture prepared in the first step to adjust the concentration of water. The concentration of water is preferably in the range of 0.1 to 1.4 mol, particularly preferably 0.2 to 1.2 mol, per 1 mol of the organic aluminum compound used in the cis-1,4 polymerization. Outside this range, the catalytic activity is reduced, the cis-1,4 structure content is reduced, and the molecular weight is unusually low or high, which is not preferable. If the amount is outside the above range, the generation of gel during polymerization cannot be suppressed, so that the gel adheres to a polymerization tank or the like, and the continuous polymerization time cannot be extended, which is not preferable. A known method can be applied as a method for adjusting the concentration of water. A method of adding and dispersing through a porous filter medium (JP-A-4-85304) is also effective.

Next, the organoaluminum compound is added to the mixture obtained by adjusting the concentration of water as described above. Examples of the organoaluminum compound include trialkylaluminum, dialkylaluminum chloride, dialkylaluminum bromide, alkylaluminum sesquichloride, alkylaluminum sesquibromide, and alkylaluminum dichloride.

Among the above-mentioned organoaluminum compounds, a trialkylaluminum represented by the general formula AlR ₃ (where R is a hydrocarbon group having 1 to 10 carbon atoms) can be preferably used. Examples of trialkyl aluminum include trimethyl aluminum, triethyl aluminum, tri-n-propyl aluminum, triisopropyl aluminum, tri-n-butyl aluminum, triisobutyl aluminum, tripentyl aluminum, trihexyl aluminum, tricyclohexyl aluminum, trioctyl Aluminum, triphenylaluminum, tri-p-tolylaluminum, and tribenzylaluminum can be mentioned. The alkyl groups in the trialkylaluminum may be the same or different.

In addition to the above organoaluminum compounds, dialkylaluminum chlorides such as dimethylaluminum chloride and diethylaluminum chloride, organoaluminum halides such as sesquiethylaluminum chloride and ethylaluminum dichloride, diethylaluminum hydride, diisobutylaluminum hydride and sesquiethylaluminum hydride and the like Can also be used.

Two or more of these organoaluminum compounds can be used in combination.

The amount of the organoaluminum compound used is: (a) in the case of cis-1,4 polymerization using a catalyst comprising water, an organoaluminum compound and a soluble cobalt compound, at least 0.1 mmol per mol of 1,3-butadiene; In particular, it is preferably from 0.5 to 50 mmol. When cis-1,4 polymerization is carried out using (b) a catalyst comprising an organoaluminum compound, a nickel compound and a fluorine compound, 1 × 10 ⁻⁵ to 1 × 10 ⁻¹ mol per mol of 1,3-butadiene is used. It is preferred that

Next, a soluble cobalt compound is added to the mixture to which the organoaluminum compound has been added, and 1,3-butadiene is subjected to cis-1,4 polymerization. Examples of the soluble cobalt compound include those which are soluble in an inert organic solvent containing hydrocarbon as a main component or liquid 1,3-butadiene, or which can be uniformly dispersed, for example, cobalt (II) acetylacetonate and cobalt (III) Organic compounds having 6 or more carbon atoms such as β-diketone complex of cobalt such as acetylacetonate, β-keto acid ester complex of cobalt such as ethyl acetoacetate complex, cobalt octoate, cobalt naphthenate and cobalt benzoate. Cobalt salts of carboxylic acids, cobalt halide complexes such as cobalt chloride pyridine complexes and cobalt chloride ethyl alcohol complexes are used. The amount of the soluble cobalt compound used is preferably at least 0.001 micromol, particularly preferably at least 0.005 micromol, per mole of 1,3-butadiene. Further, the molar ratio of the organic aluminum compound to the soluble cobalt compound (Al / Co) is 10 or more, and particularly preferably 50 or more.

Further, instead of (a) a catalyst comprising water, an organoaluminum compound and a soluble cobalt compound, (b) a catalyst comprising an organoaluminum compound, a nickel compound and a fluorine compound is added to convert 1,3-butadiene into cis-1, Four polymerization may be carried out. In this case, water may or may not be added as a component of the cis-1,4 polymerization catalyst.

As the nickel compound, a salt or complex of nickel is preferably used. Particularly preferred are nickel halides such as nickel chloride and nickel bromide, nickel salts of inorganic acids such as nickel nitrate, nickel carboxylate having 1 to 18 carbon atoms such as nickel octylate, nickel acetate and nickel octoate; Nickel complexes such as nickel naphthenate, nickel malonate, nickel bisacetylacetonate and trisacetylacetonate, acetoacetate ethyl ester, nickel halide triarylphosphine complex, trialkylphosphine complex, pyridine complex and picoline complex Various complexes such as an organic base complex and an ethyl alcohol complex can be exemplified. The use amount of the nickel compound is preferably 1 × 10 ⁻⁷ to 1 × 10 ⁻³ mol per mol of 1,3-butadiene.

As the fluorine compound, a boron trifluoride ether, an alcohol, or a complex of a mixture thereof, or a hydrogen fluoride ether, an alcohol, or a mixture of these complexes is preferably used. Particularly preferred are boron trifluoride diethyl etherate, boron trifluoride dibutyl etherate, hydrogen fluoride diethyl etherate, and hydrogen hydrogen dibutyl etherate. The use amount of the fluorine compound is preferably 1 × 10 ⁻⁴ to 1 mol per 1 mol of 1,3-butadiene.

The temperature at which cis-1,4 polymerization of 1,3-butadiene is performed is more than 0 ° C. and 100 ° C. or less, preferably 10 to 100 ° C., and more preferably 20 to 100 ° C. The polymerization time is preferably in the range of 10 minutes to 2 hours. The cis-1,4 polymerization is preferably performed so that the polymer concentration after the cis-1,4 polymerization is 5 to 26% by mass. The polymerization is carried out by stirring and mixing the solution in a polymerization tank (polymerization vessel). As a polymerization tank used for the polymerization, a polymerization tank equipped with a high-viscosity liquid stirring device, for example, an apparatus described in Japanese Patent Publication No. 40-2645 can be used.

During cis-1,4 polymerization, known molecular weight regulators, for example, non-conjugated dienes such as cyclooctadiene, arene and methylarene (1,2-butadiene), or α-olefins such as ethylene, propylene and butene-1 Kinds can be used. In order to further suppress the formation of a gel at the time of polymerization, a known gelling inhibitor can be used.

(3rd step)
Next, 1,3-butadiene in the polymerization reaction mixture obtained in the second step is subjected to syndiotactic-1,2 polymerization. At that time, 1,3-butadiene may or may not be added to the obtained cis-1,4 polymer. The method of polymerizing 1,2 is not particularly limited, but the polymerization of 1,2 is represented by the general formula AlR ₃ (where R is a hydrocarbon group having 1 to 10 carbon atoms). It is preferable that 1,3-butadiene is polymerized into 1,2 by adding an organic aluminum compound and carbon disulfide, and a soluble cobalt compound may be further added as necessary. Further, water may be added to the polymerization system during the polymerization of 1,2.

As the organoaluminum compound represented by the general formula AlR ₃ , trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-hexylaluminum, triphenylaluminum and the like are preferable. The amount of the organoaluminum compound is preferably 0.1 mmol or more, especially 0.5 to 50 mmol, per 1 mol of 1,3-butadiene. The concentration of carbon disulfide is 20 mmol / L or less, particularly preferably 0.01 to 10 mmol / L. As a substitute for carbon disulfide, known phenyl isothiocyanate or xanthate compound may be used. Water is preferably added to the polymerization system after bringing 1,3-butadiene into contact with the organoaluminum compound. The addition amount of water is preferably 0.1 to 1.5 mol per 1 mol of the organic aluminum compound. As the soluble cobalt compound, the same compounds as those described in the second step can be used.

方法 The method for producing a vinyl-cis-polybutadiene rubber according to the present invention is characterized in that in the third step, a melting point depressant for lowering the melting point of the obtained 1,2-polybutadiene is added. Examples of the melting point depressant include dimethyl sulfoxide (DMSO) and acetone. From the viewpoint of separation and purification from unreacted 1,3-butadiene, dimethyl sulfoxide (DMSO) is particularly preferable.

添加 The amount of the melting point depressant added is preferably from 0.01 to 10, more preferably from 0.05 to 5, and particularly preferably from 0.1 to 3, based on the organoaluminum compound added in the third step. By adding the above-mentioned melting point depressant, the melting point of 1,2-polybutadiene obtained in the third step can be adjusted to 150 to 195 ° C. If the molar ratio of the added amount is more than 10, the melting point will be excessively lowered, and the effect of improving the elastic modulus of 1,2-polybutadiene tends to be small, and if it is less than 0.1, the effect of improving the fuel efficiency tends to be small. Therefore, it is not preferable.

The temperature for polymerization of # 1 and # 2 is preferably from -5 to 100 ° C, more preferably from -5 to 80 ° C. By adding 1,3-butadiene during the 1,2 polymerization, the yield of 1,2-polybutadiene during the 1,2 polymerization can be increased. The polymerization time is preferably in the range of 2 minutes to 2 hours. The 1,2 polymerization is preferably performed so that the polymer concentration after the 1,2 polymerization is 3 to 30% by mass. The polymerization is carried out by stirring and mixing the polymerization solution in a polymerization tank (polymerization vessel). The polymerization tank used for the polymerization of 1, 2 has a higher viscosity during the polymerization of 1, 2 and the polymer is liable to be adhered. Therefore, a polymerization tank equipped with a high-viscosity liquid stirring device, for example, described in Japanese Patent Publication No. 40-2645. Can be used.

後 After the polymerization reaction reaches a predetermined polymerization rate, a known antioxidant can be added according to a conventional method. Examples of anti-aging agents include phenolic 2,6-di-t-butyl-p-cresol (BHT), phosphorus-based trinonylphenyl phosphite (TNP), and sulfur-based 4,6-bis (octylthio). Methyl) -o-cresol and dilauryl-3,3′-thiodipropionate (TPL). These may be used alone or in combination of two or more kinds. The addition of the antioxidant is 0.001 to 5 parts by mass based on 100 parts by mass of the vinyl cis-polybutadiene rubber.

The polymerization reaction is a method of introducing a large amount of a polar solvent such as alcohol or water such as methanol or ethanol into the polymerization solution, an inorganic acid such as hydrochloric acid and sulfuric acid, an organic acid such as acetic acid and benzoic acid, a phosphite, or Stopping is performed by a method known per se, such as a method of introducing hydrogen chloride gas into the polymerization solution. The resulting vinyl cis-polybutadiene rubber is then separated, washed and subsequently dried according to conventional methods.

The concentration of the crystal part of 1,2-polybutadiene contained in the vinyl-cis-polybutadiene rubber can be arbitrarily changed according to, for example, a required function. As a specific method, for example, by heating the produced vinyl cis-polybutadiene rubber before or after drying in a liquid, in nitrogen, in the air, or in an atmosphere other than these, a part of the crystal is formed. Alternatively, all can be amorphized.

<Rubber composition>
The rubber composition of the present invention comprises a rubber component (A) + (B) containing 1 to 50 parts by mass of the vinyl-cis-polybutadiene rubber (A) and 50 to 99 parts by mass of a diene rubber (B) other than (A). B) 100 parts by mass and 1 to 150 parts by mass of a rubber reinforcing agent (C).

(Diene rubber other than (A) (B))
In the present invention, as the diene rubber other than (A) as the component (B), for example, at least one or more selected from natural rubber, isoprene rubber, butadiene rubber, emulsion-polymerized or solution-polymerized styrene-butadiene rubber, and butyl rubber Diene rubber can be used. It preferably contains natural rubber and / or butadiene rubber. When used for a base tread, the rubber composition preferably contains natural rubber and butadiene rubber, and more preferably contains 30 parts by mass or more of natural rubber. When the component (B) is mixed with the component (A), it may be mixed during the usual kneading of a Banbury, a roll, or the like, or may be used by previously mixing and drying in a solution state after polymerization. You may.

The ratio of the component (A) to the component (B) is 5 to 45 parts by mass for the component (A) and 65 to 95 parts by mass for 100 parts by mass of the rubber component (A) + (B). The component (A) is more preferably 10 to 40 parts by mass, the component (B) more preferably 60 to 90 parts by mass, particularly the component (A) 15 to 35 parts by mass, and the component (B) When the component is 65 to 85 parts by mass, it is most suitable as a rubber composition for a tire.

(Rubber reinforcement (C))
In the present invention, the rubber reinforcing agent of the component (C) includes various fillers such as carbon black and silica, inorganic reinforcing agents such as activated calcium carbonate and ultrafine magnesium silicate, and syndiotactic-1,2-polybutadiene. Organic reinforcing agents such as resin, polyethylene resin, polypropylene resin, high styrene resin, phenol resin, lignin, and modified melamine resin. The syndiotactic-1,2-polybutadiene in the vinyl cis-polybutadiene rubber (A) is not included in the rubber reinforcing agent (C).
Examples of the carbon black include, but are not particularly limited to, FEF, FF, GPF, SAF, ISAF, SRF, and HAF. The content of carbon black is preferably at least 20 parts by mass from the viewpoint of steering stability, and is preferably at most 100 parts by mass from the viewpoint of fuel economy.
It is preferable that the particle diameter is 15 nm or more and 90 nm or less, the nitrogen adsorption specific surface area is 15 to 135 m ² / g, and the dibutyl phthalate (DBP) oil absorption is 60 ml / 100 g or more and 180 ml / 100 g or less.
In the present invention, silica can be used as a rubber reinforcing agent. The type of silica is not particularly limited, and can be used according to the intended use, such as general-grade silica and special silica surface-treated with a silane coupling agent.
The silica is not particularly limited, and examples thereof include wet silica (hydrous silicic acid), dry silica (silicic anhydride), calcium silicate, and aluminum silicate. Of these, wet silica is preferable. These silicas may be used alone or in combination of two or more.

配合 The compounding ratio of the component (C) is preferably from 10 to 150 parts by mass, more preferably from 20 to 120 parts by mass, per 100 parts by mass of the rubber component (A) + (B). When the amount of the component (C) is less than 10 parts by mass, the tensile stress tends to decrease, and when the amount is more than 150 parts by mass, the workability tends to deteriorate.

From the viewpoint of improving the elastic modulus, it is preferable that the component (C) contains a total of 30 parts by mass or more of a filler such as carbon black and silica. It is preferably 150 parts by mass or less from the viewpoint of processability. Although the detailed mechanism is unknown, it is assumed that 1,2-polybutadiene and a filler such as carbon black and silica form a network, thereby improving the elastic modulus.

(Other components)
The rubber composition of the present invention may contain, if necessary, petroleum resin, coumarone indene resin, vulcanizing agent, vulcanization aid, antioxidant, filler, process oil, zinc white, stearic acid, which are other components. For example, it may contain chemicals commonly used in the rubber industry.

Examples of the petroleum resin include C ₅ resin, C ₅ -C ₉ resin, C ₉ resin, terpene resin, terpene-aromatic compound resin, rosin resin, dicyclopentadiene resin, and alkylphenol resin. Is raised.

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 accelerator, known vulcanization accelerators such as aldehydes, ammonias, amines, guanidines, thioureas, thiazoles, thiurams, dithiocarbamates, xanthates and the like are used.

Examples of the filler include calcium carbonate, basic magnesium carbonate, clay, Lissajous, diatomaceous earth, recycled rubber, powdered rubber, and the like.

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

Aromatic, naphthenic, and paraffinic process oils may be used.

ゴム The rubber composition of the present invention can be obtained by kneading the above-mentioned components using a conventional Banbury, open roll, kneader, twin-screw kneader or the like.

The vulcanized rubber composition obtained by vulcanizing the rubber composition of the present invention can be used for tires for passenger cars and competitions, and for large and heavy tires by utilizing the improved steering stability and low loss balance. It is also applicable to heavy tire applications.

The rubber composition according to the present invention can be used for each part of a tire such as a cap tread, a base tread, a side reinforcing rubber, a carcass, a belt, a chafer, a bead, a stiffener, and an inner liner. It is preferably used for a base tread.

The tire using the rubber composition according to the present invention is preferably a pneumatic tire, and as the filling gas, normal or oxygen partial pressure-adjusted air, nitrogen, and inert gas such as argon and helium are used. There are gas and the like.

When the rubber composition according to the present invention is used for each member of a tire, the rubber composition according to the present invention containing each component is processed in an unvulcanized stage, and attached by a normal method on a tire molding machine. The molded tire can be obtained. The green tire can be heated and pressurized by a vulcanizer to obtain a tire.

ゴム In addition, the rubber composition according to the present invention can be used for anti-vibration rubber, seismic isolation rubber, belts (belt conveyors), rubber crawlers, various hoses, and moran, in addition to tire applications.

Hereinafter, the present invention will be specifically described based on examples, but these do not limit the purpose of the present invention. The physical properties of the vinyl cis-polybutadiene rubber (A) and the rubber composition were measured as follows.

<Vinyl cis-polybutadiene rubber (A)>
1.1 Concentration of Crystalline Part of 1,2-Polybutadiene The concentration of the crystal part of 1,2-polybutadiene contained in the vinyl cis-polybutadiene rubber was measured by a differential scanning calorimeter (DSC-50, manufactured by Shimadzu Corporation). It was calculated from the heat of fusion of the 1,2-polybutadiene crystal part. Specifically, first, about 10 mg of vinyl-cis-polybutadiene rubber was heated at a heating rate of 10 ° C./min, and the heat of fusion was calculated from an endothermic peak derived from the melting of 1,2-polybutadiene. Next, the concentration (% by mass) of the crystal part of 1,2-polybutadiene contained in the vinyl-cis-polybutadiene rubber was calculated from the known heat of fusion per unit mass of 1,2-polybutadiene.

2.1 Concentration of Amorphous Part of 1,2-Polybutadiene The concentration of the amorphous part of 1,2-polybutadiene contained in the vinyl-cis-polybutadiene rubber is defined as the concentration of the crystalline part of 1,2-polybutadiene and 1,4-polybutadiene. It was calculated from the concentration of polybutadiene by the following equation (1).
(Concentration of amorphous portion of 1,2-polybutadiene (% by mass)) = 100− (Concentration of crystal portion of 1,2-polybutadiene after amorphization treatment (% by mass)) − (concentration of 1,4-polybutadiene Concentration (% by mass)) Formula (1)
The 1,4-polybutadiene concentration (% by mass) was calculated by the following equation (2).
(Concentration of 1,4-polybutadiene (% by mass)) = 100− (Concentration of 1,2-polybutadiene crystal part before amorphization treatment (% by mass))
Here, “after the amorphization treatment” means a part of the crystal part of 1,2-polybutadiene performed to adjust the concentration of the crystal part of 1,2-polybutadiene contained in the vinyl-cis-polybutadiene rubber. Means before the amorphization treatment, and "before the amorphization treatment" means before the amorphization treatment.

3. Melting point of 1,2-polybutadiene The melting point of 1,2-polybutadiene was measured with a differential scanning calorimeter (DSC-50, manufactured by Shimadzu Corporation) at a temperature of about 10 mg at a heating rate of 10 ° C./min. did. The temperature at the peak top of the endothermic peak derived from 1,2-polybutadiene was defined as the melting point. When there were a plurality of endothermic peaks derived from 1,2-polybutadiene, peak separation was performed, and the peak top temperature of the peak having the largest area was defined as the melting point.

4. Weight average molecular weight (Mw)
GPC (manufactured by Shimadzu Corporation) was carried out at a temperature of 40 ° C. using polystyrene as a standard substance and tetrahydrofuran as a solvent, and the weight average molecular weight (Mw) was calculated by using a calibration curve obtained from the obtained molecular weight distribution curve. .

5. Mooney viscosity (ML _{1 + 4} , 100 ° C)
According to JIS-K6300-1, preheating was performed at 100 ° C. for 1 minute using a Mooney viscometer manufactured by Shimadzu Corporation, and measurement was performed for 4 minutes to determine the Mooney viscosity (ML _{1 + 4} , 100 ° C.) of the rubber.

<Rubber composition>
1. Low loss (tan δ)
After vulcanizing the obtained rubber composition at 160 ° C. for 20 minutes, it was measured at a temperature of 50 ° C., a dynamic strain of 0.1%, and a frequency of 15 Hz using a viscoelasticity measuring device ARES (manufactured by TA Instruments). The index was calculated for each reciprocal of Comparative Example 1 and Examples 1 to 4 with tan δ of Comparative Example 2 set to 100. The larger the index is, the smaller the tan δ is and the lower the loss is.
As a reference example, the rubber composition was vulcanized at 150 ° C. for 25 minutes, and then measured at a temperature of 50 ° C., a dynamic strain of 0.2%, and a frequency of 16 Hz using a viscoelasticity measuring device EPLEXOR (manufactured by GABO). Then, the tan δ of Reference Example 1 was set to 100, and an index was calculated for the reciprocal of Reference Example 2. The larger the index is, the smaller the tan δ is and the lower the loss is.

2. Driving stability (storage modulus)
After vulcanizing the obtained rubber composition at 160 ° C. for 20 minutes, in a dynamic viscoelasticity test using a viscoelasticity measuring device ARES (manufactured by TA Instruments), the temperature was 30 ° C., the dynamic strain was 0.1%, and the frequency was 15 Hz. Was used to measure the storage modulus G ′. The index was calculated for each of Comparative Example 1 and Examples 1 to 4, with G ′ of Comparative Example 2 being 100. The larger the index, the larger G ', indicating that the steering stability is excellent.
As a reference example, the rubber composition was vulcanized at 150 ° C. for 25 minutes, and then measured at a temperature of 50 ° C., a dynamic strain of 0.2%, and a frequency of 16 Hz using a viscoelasticity measuring device EPLEXOR (manufactured by GABO). Then, the index was calculated for Reference Example 2, with the storage elastic modulus E 'of Reference Example 1 being 100. The larger the index, the larger the E ', indicating that the steering stability is more excellent.

3. Balance between Low Loss Property and Driving Stability The value obtained by adding the Low Loss Property Index and the Driving Stability Index and dividing by 2 was used as a balance index between the Low Loss Property and Driving Stability. The larger the index, the better the balance between low loss and steering stability. When the balance index is 108 or more, it can be said that the balance between the low loss property and the steering stability is excellent.

(Synthesis example 1)
Cyclohexane (450 mL) is charged into a 1.5 L stainless steel autoclave equipped with helical blades and replaced with nitrogen, and the autoclave is sealed. Was prepared. Water (H ₂ O) was added to the raw material solution using a syringe so as to have a concentration of 2.47 mmol / L, and then the autoclave was heated to 30 ° C. and stirred at 500 rpm for 30 minutes. After cooling the autoclave to 25 ° C., diethyl aluminum chloride and triethyl aluminum (molar ratio 3: 1) were added using a syringe so as to have a concentration of 3.0 mmol / L, followed by stirring for 5 minutes. Next, 1,5-cyclooctadiene (COD) was added using a syringe to a concentration of 28.5 mmol / L, and the temperature was raised to 35 ° C. Cobalt octoate (Co (Oct) ₂ ) was added using a syringe to a concentration of 6.18 μmol / L, and cis-1,4 polymerization was performed at 35 ° C. for 12 minutes. To the obtained polymerization reaction mixture, triethylaluminum (TEA) was added using a syringe so as to have a concentration of 3.91 mmol / L, and the mixture was maintained for 2 minutes. Then, cobalt octoate (Co (Oct) ₂ ) was added to 0.1%. The solution was added using a syringe to a concentration of 800 mmol / L, kept for 2 minutes, and dimethylsulfoxide (DMSO) was added using a syringe to a concentration of 0.98 mmol / L. Finally, carbon disulfide (CS ₂ ) was added using a syringe to a concentration of 1.17 mmol / L, and syndiotactic-1,2 polymerization was performed at 35 ° C. for 25 minutes. Trisnonylphenyl phosphite was added to the resulting polymerization reaction mixture to terminate the syndiotactic-1,2 polymerization. Thereafter, the autoclave was cooled and depressurized to obtain a polymerization reaction mixture. Next, the polymerization reaction product was poured into water at 80 ° C. to precipitate vinyl-cis-polybutadiene rubber. The precipitated vinyl-cis-polybutadiene rubber was recovered, placed in a stainless steel autoclave together with water, sealed, and kept at 130 ° C. for 10 minutes. After cooling, the vinyl cis-polybutadiene rubber was taken out of the stainless steel autoclave and dried at 100 ° C. for 1 hour. Table 1 shows the composition and melting point of the vinyl cis-polybutadiene rubber according to Synthesis Example 1. The weight average molecular weight (Mw) of the vinyl cis-polybutadiene rubber of Synthesis Example 1 was 404,000, and the Mooney viscosity (ML _{1 + 4} , 100 ° C.) was 38.6.

(Synthesis example 2)
10 L / h of a cyclohexane solution containing 44.5 mass% of 1,3-butadiene and 248 mass ppm of carbon disulfide and 0.41 ml / h of water are mixed at a temperature of 60 ° C., and the mixture is kept at 30 ° C. And supplied to a 5.0 L stainless aging tank equipped with a stirrer. In addition, a mixture of a 10% by mass cyclohexane solution of diethylaluminum chloride and a 10% by mass cyclohexane solution of triethylaluminum (Al molar ratio: 3: 1) was supplied to the same aging tank at a rate of 57 ml / h. The obtained aging solution was supplied to a 5.3 L stainless steel cis polymerization tank equipped with a stirrer and maintained at 35 ° C. Cis-1,4 polymerization was carried out by supplying a cyclohexane-toluene solution of COD 34 ml / h and 0.03 mass% of cobalt octoate (Co (Oct) ₂ ) to the polymerization tank. The obtained cis-1,4 polymerization solution was supplied to a 5.3 L, 1,2-polybutadiene polymerization tank made of stainless steel equipped with a ribbon-type stirrer, and polymerized at 35 ° C. in syndiotactic-1,2. In this polymerization tank, 80 ml / h of a 10% by mass solution of triethylaluminum in cyclohexane and 36 ml / h of a 7.5% by mass solution of cobalt octoate (Co (Oct) ₂ ) in cyclohexane and 5% by mass of DMSO were added. 36 ml / h of a toluene solution and 1 L / h of a cyclohexane solution containing 1.0% by mass of 1,3-butadiene were also supplied at the same time. The obtained syndiotactic-1,2 polymer solution was supplied to a 1.0 L stainless steel mixing tank equipped with a stirrer, and 100 ml / h of water, 4,6-bis (octylthioethyl) -o-cresol and tris Nonylphenyl phosphite was added in an amount of 1% by mass with respect to 100 parts by mass of the vinyl cis-polybutadiene rubber. After terminating the polymerization, the mixture was poured into hot water maintained at 130 ° C. to precipitate the vinyl cis-polybutadiene rubber. I let it. The precipitate was dried at 100 ° C. for 1 hour. Table 1 shows the composition of the vinyl-cis-polybutadiene rubber according to Synthesis Example 2 and the melting point of 1,2-polybutadiene. The weight average molecular weight (Mw) of the vinyl cis-polybutadiene rubber of Synthesis Example 2 was 411,000.

(Synthesis example 3)
Cyclohexane (450 mL) is charged into a 1.5 L stainless steel autoclave equipped with helical blades and replaced with nitrogen, and the autoclave is sealed. Was prepared. Water (H ₂ O) was added to the raw material solution using a syringe so as to have a concentration of 1.85 mmol / L, and then the autoclave was heated to 60 ° C. and stirred at 500 rpm for 30 minutes. After cooling the autoclave to 25 ° C., diethyl aluminum chloride and triethyl aluminum (molar ratio 3: 1) were added using a syringe so as to have a concentration of 3.0 mmol / L, followed by stirring for 5 minutes. Next, 1,5-cyclooctadiene (COD) was added using a syringe to a concentration of 21.7 mmol / L, and the temperature was raised to 35 ° C. Cobalt octoate (Co (Oct) ₂ ) was added using a syringe to a concentration of 5.02 μmol / L, and cis-1,4 polymerization was carried out at 35 ° C. for 12 minutes. To the obtained polymerization reaction mixture, triethylaluminum (TEA) was added using a syringe so as to have a concentration of 3.91 mmol / L, and the mixture was maintained for 2 minutes. Then, cobalt octoate (Co (Oct) ₂ ) was added to 0.1%. The solution was added using a syringe to a concentration of 756 mmol / L, kept for 2 minutes, and dimethyl sulfoxide (DMSO) was added using a syringe to a concentration of 0.94 mmol / L. Finally, carbon disulfide (CS ₂ ) was added using a syringe to a concentration of 1.17 mmol / L, and syndiotactic-1,2 polymerization was performed at 35 ° C. for 25 minutes. Trisnonylphenyl phosphite was added to the resulting polymerization reaction mixture to terminate the syndiotactic-1,2 polymerization. Thereafter, the autoclave was cooled and depressurized, and the polymerization reaction mixture was taken out into a vat. The vat was put into a vacuum drier heated to 100 ° C., and the unreacted butadiene and solvent were removed to obtain a vinyl-cis-polybutadiene rubber according to Synthesis Example 3. Table 1 shows the composition of the vinyl cis-polybutadiene rubber according to Synthesis Example 3 and the melting point of 1,2-polybutadiene. The weight average molecular weight (Mw) of the vinyl cis-polybutadiene rubber of Synthesis Example 3 was 404,000, and the Mooney viscosity (ML _{1 + 4} , 100 ° C.) was 38.6.

(Synthesis example 4)
In the cis-1,4 polymerization, the concentration of water was set to 1.60 mmol / L, the concentration of 1,5-cyclooctadiene (COD) was set to 16.3 mmol / L, and the concentration of cobalt octoate (Co (Oct) ₂ ) was set. In the same manner as in Synthesis Example 3, except that the concentration of cobalt octoate (Co (Oct) ₂ ) was changed to 1.500 μmol / L and the concentration of cobalt octoate (Co (Oct) ₂ ) was changed to 0.800 mmol / L in the syndiotactic-1,2 polymerization. A cis-polybutadiene rubber was produced. Table 1 shows the composition of the vinyl cis-polybutadiene rubber according to Synthesis Example 4 and the melting point of 1,2-polybutadiene. The weight average molecular weight (Mw) of the vinyl cis-polybutadiene rubber of Synthesis Example 4 was 484,000.

(Reference synthesis example)
Cyclohexane (360 mL) was charged into a 1.5 L stainless steel autoclave equipped with helical blades and replaced with nitrogen, and the autoclave was sealed. Was prepared. Water (H ₂ O) was added to the raw material solution using a syringe so as to have a concentration of 1.76 mmol / L, and then the autoclave was heated to 60 ° C. and stirred at 500 rpm for 30 minutes. After cooling the autoclave to 25 ° C., diethylaluminum chloride and triethylaluminum (molar ratio 3: 1) were added using a syringe such that the concentration became 3.6 mmol / L, and the mixture was stirred for 5 minutes. Next, 1,5-cyclooctadiene (COD) was added using a syringe so as to have a concentration of 18.3 mmol / L, and the temperature was raised to 45 ° C. Cobalt octoate (Co (Oct) ₂ ) was added using a syringe to a concentration of 12.5 μmol / L, and cis-1,4 polymerization was carried out at 45 ° C. for 20 minutes. To the obtained polymerization reaction mixture, triethylaluminum (TEA) was added using a syringe so as to have a concentration of 5.40 mmol / L, and the mixture was maintained for 2 minutes. Then, cobalt octoate (Co (Oct) ₂ ) was added to a concentration of 0.10 mmol / L. The solution was added using a syringe so as to have a concentration of 150 mmol / L, kept for 2 minutes, and dimethyl sulfoxide (DMSO) was added using a syringe so as to have a concentration of 5.40 mmol / L. Finally, carbon disulfide (CS ₂ ) was added using a syringe to a concentration of 0.54 mmol / L, and syndiotactic-1,2 polymerization was carried out at 45 ° C. for 20 minutes. 1,4-Naphthoquinone was added to the resulting polymerization reaction mixture to terminate the syndiotactic-1,2 polymerization. Thereafter, the autoclave was cooled and depressurized, and the polymerization reaction mixture was taken out into a vat. The vat was put into a vacuum dryer heated to 100 ° C., and the unreacted butadiene and the solvent were removed to obtain a vinyl cis-polybutadiene rubber. Table 1 shows the composition of the vinyl-cis-polybutadiene rubber and the melting point of 1,2-polybutadiene according to the reference synthesis example. The weight average molecular weight (Mw) of the vinyl cis-polybutadiene rubber of Reference Synthesis Example was 490,000, and the Mooney viscosity (ML _{1 + 4} , 100 ° C.) was 41.7.

According to Table 2, carbon black, natural rubber, process oil, zinc white, stearic acid, and an antioxidant (each by mass, hereinafter the same) were added to the vinyl-cis-polybutadiene rubber obtained in Synthesis Examples 1 to 4 according to Table 2 using a plastmill. A primary blending was performed, followed by a secondary blending with the addition of a vulcanization accelerator and sulfur to produce a blend. Further, after molding this compound and press vulcanizing to obtain a rubber composition, the low loss property (tan δ) and the steering stability (storage modulus) were measured, and the balance between the low loss property and the steering stability was measured. Was calculated. Table 2 also shows the measurement results of the physical properties of these rubber compositions.

Comparative Example 1 contained no vinyl-cis-polybutadiene rubber, and Comparative Example 2 contained a commercially available vinyl-cis-polybutadiene rubber (VCR412: 12% concentration of 1,2-polybutadiene and a melting point of 200 ° C.). Prepared specimens were measured for physical properties in the same manner as in Examples 1-4. Table 2 shows the results.

Further, the vinyl-cis-polybutadiene rubber according to the reference synthesis example was kneaded by adding carbon black, natural rubber, process oil, zinc white, stearic acid and an antioxidant according to Table 3, and then primary kneading was performed. A blend (Reference Example 2) was prepared by performing a secondary blend in which an agent and sulfur were added. Further, after molding this compound and press vulcanizing to obtain a rubber composition, the low loss property (tan δ) and the steering stability (storage modulus) were measured, and the balance between the low loss property and the steering stability was measured. Was calculated. Table 3 also shows the measurement results of the physical properties of these rubber compositions. Further, as Reference Example 1, one prepared by blending VCR412 was prepared.

(Note 1) Natural rubber (RSS No. 3) (Note 2) Butadiene rubber; "UBEPOL 150L" manufactured by Ube Industries, Ltd. (Note 3) "UBEPOL VCR412" manufactured by Ube Industries, Ltd. (Note 4) Asahi Carbon Co., Ltd. # 80 "(Note 5)" Diana Process NH-70S "manufactured by Idemitsu Kosan Co., Ltd. (Note 6)" Nocrack 6C "manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (Note 7)" Noxeller D "manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

(Note 1) Natural rubber (RSS # 1) (Note 2) "UBEPOL VCR412" manufactured by Ube Industries, Ltd. (Note 3) "Diablack I" manufactured by Mitsubishi Chemical Corporation (Note 4) "Viva Tec 400" manufactured by H & R (Note 5) Sumitomo Chemical Co., Ltd. "Antigen 6C" (Note 6) Ouchi Shinko Chemical Co., Ltd. "Noxeller NS"

From the above, it can be seen that the rubber compositions according to Examples 1 to 4 achieve a better balance between low loss and steering stability than the rubber compositions of Comparative Examples 1 and 2. Further, by comparing Example 1 with Examples 2 to 4, it was found that the rubber composition using vinyl cis-polybutadiene rubber having a low concentration of the amorphous portion of 1,2-polybutadiene had lower loss and steering stability. It can be seen that the balance of sex is improved.

Claims

1 to 50 parts by mass of a vinyl cis-polybutadiene rubber (A) containing 35 to 99% by mass of 1,2-polybutadiene having a melting point of 150 to 195 ° C., and 50 to 50% of a diene rubber (B) other than (A) A rubber composition comprising 100 parts by mass of a rubber component (A) + (B) containing 99 parts by mass, and 1 to 150 parts by mass of a rubber reinforcing agent (C).
The vinyl cis-polybutadiene rubber (A) is
A first step of preparing a mixture of 1,3-butadiene and a hydrocarbon-based inert organic solvent;
The mixture prepared in the first step is added with (a) a catalyst comprising water, an organoaluminum compound and a soluble cobalt compound, or (b) a catalyst comprising an organoaluminum compound, a nickel compound and a fluorine compound to give 1,3- A second step of cis-1,4 polymerization of butadiene;
A third step of syndiotactic-1,2 polymerization of 1,3-butadiene in the polymerization reaction mixture obtained in the second step,
2. The rubber composition according to claim 1, obtained in the third step by a production method in which a melting point depressant for lowering the melting point of the obtained 1,2-polybutadiene is added.
3. The rubber composition according to claim 1, wherein the melting point depressant is dimethyl sulfoxide.
A tire using the rubber composition according to any one of claims 1 to 3.
A tire using the rubber composition according to any one of claims 1 to 3 for a cap tread.
A tire using the rubber composition according to any one of claims 1 to 3 for a base tread.