JP2020100697A - Method for producing rubber composition for tire, rubber composition for tire and tire - Google Patents

Abstract

To provide a method for producing a rubber composition for a tire having excellent various physical properties, especially having excellent tensile characteristics with less carbon fiber content.SOLUTION: There is provided a method for producing a rubber composition for a tire which comprises: a 1-1 step of preparing a mixture of a carbon fiber (a), 1,3-butadiene and an inactive organic solvent; a 1-2 step of adding a catalyst comprising water, an organoaluminium compound and a soluble cobalt compound or a catalyst comprising an organoaluminium compound, a nickel compound and a fluorine compound to the mixture prepared in the 1-1 step, followed by subjecting the 1,3-butadiene to cis-1,4-polymerization; a 1-3 step of subjecting the 1,3-butadiene in the polymerization reaction mixture obtained in the 1-2 step to syndiotactic-1,2-polymerization; and a step of mixing a carbon fiber-containing polybutadiene composition obtained through the 1-3 step, other diene-based rubber and a rubber-reinforcing material.SELECTED DRAWING: None

Description

The present invention relates to a method for producing a rubber composition for tires, a rubber composition for tires, and a tire.

Carbon black has been conventionally used as a compounding agent for reinforcing a rubber composition for tires. However, in recent years, tires are required to have a high level of performance, and it has become impossible to sufficiently support carbon black for reinforcement. Therefore, various studies have been made so far on the performance improvement of the rubber composition for tires reinforced by the micro organic short fibers. Recently, a rubber composition containing a vapor-grown carbon fiber has been proposed as a filler capable of exhibiting a high effect even when added in a relatively small amount (see Patent Documents 1 to 8).

Regarding a rubber composition containing a vapor-grown carbon fiber, for example, Patent Document 1 discloses that a rubber material as a base material is blended with a vapor-grown carbon fiber having an average aspect ratio of less than 10 as a filler. Discloses a rubber composition having improved tan δ value at 40° C. or higher and modulus at 80° C. or higher. Further, in order to improve mechanical properties such as workability and fatigue resistance of a vulcanized rubber containing a vapor grown carbon fiber, a softening agent (oil) is also added.

In Patent Document 2, in order to increase the affinity between the rubber matrix and the carbon fiber, by using carbon fiber synthesized by the vapor phase growth method whose surface is modified by acid or plasma treatment, tensile stress of the vulcanized product and Improves impact resilience.

In Patent Documents 3 to 5, by adding fine carbon fibers synthesized by the vapor phase growth method at the time of preparing a composition, a high effect is exhibited even with a relatively small amount of addition, and other performances such as mechanical properties are obtained. A method for producing a vulcanized product which does not adversely affect the above is disclosed.

In Patent Document 6, by adding a polycyclic aromatic compound having a crosslinkable functional group in addition to the carbon fiber, the low loss property is improved while maintaining the breaking strength.

In Patent Document 7, carbon fibers having a fiber diameter before crushing treatment of more than 0.1 μm are subjected to crushing treatment when used, thereby improving low loss property and tensile property.

In Patent Document 8, by containing 20 to 60 parts by weight of carbon nanotubes or carbon nanofibers having an average outer diameter of 4 to 50 nm and an average aspect ratio of 10 to 3000 in a rubber composition for a tire, the elastic modulus is reduced even at high temperatures. A rubber composition for a run flat tire is proposed.

JP, 2003-327753, A JP-A-1-289844 JP, 2006-298946, A JP, 2006-124459, A JP, 2010-235376, A JP, 2007-238933, A JP, 2009-144131, A JP, 2009-46547, A

Here, when a generally known method is used, it is considered that the effect of adding the carbon fiber is recognized when the carbon fiber content is 2 parts by weight or more based on 100 parts by weight of the rubber component. Furthermore, carbon fibers are known to be very expensive, and for example, when a carbon fiber-containing vulcanizate is used as a tire material, the content of the carbon material can be adjusted from the viewpoint of reducing the manufacturing cost of the tire. It is desirable to reduce as much as possible. That is, it is desired to develop a technique for producing excellent effects with a low carbon fiber content.

Therefore, the present invention aims to provide various physical properties with a small carbon fiber content, a method for producing a rubber composition for a tire having particularly excellent tensile properties, a rubber composition for a tire, and a tire using the same. And

In order to achieve the above object, the inventors of the present invention have conducted extensive studies on a rubber composition for tires having excellent physical properties while having a low carbon fiber content. As a result, when a specific amount of carbon fiber, 1,2-polybutadiene and cis-polybutadiene rubber is contained, a rubber composition having excellent physical properties is obtained even if the carbon fiber content is small. The inventors have found that particularly excellent tensile properties can be imparted to the present invention.

That is, the present invention is
Step 1-1 for preparing a mixture of carbon fiber (a), 1,3-butadiene, and an inert organic solvent, and water, an organoaluminum compound, and a solubility in the mixture prepared in the step 1-1. A 1-2 step of adding a catalyst composed of a cobalt compound or a catalyst composed of an organoaluminum compound, a nickel compound and a fluorine compound to polymerize the 1,3-butadiene with cis-1,4;
A first to third step of polymerizing the 1,3-butadiene in the polymerization reaction mixture obtained in the first to second step with syndiotactic-1,2;
A step of blending the carbon fiber-containing polybutadiene composition obtained through the first to third steps, another diene rubber, and a rubber reinforcing material,
A method for producing a rubber composition for a tire, comprising:

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the rubber composition for tires which has various physical properties with a small carbon fiber content, and has especially outstanding tensile property can be provided.

(A) It is a figure which shows typically the minimum structural unit (bell-shaped structural unit) which comprises a fine carbon fiber. (B) It is a figure which shows typically the aggregate|stack which stacked 2-30 bell-shaped structural units. (A) It is a figure which shows typically a mode that an aggregate is connected at intervals and constitutes a fiber. (B) It is a figure which shows typically the mode that it bent and was connected, when the aggregate|assembly was connected at intervals.

Hereinafter, preferred embodiments of the present invention will be described.
<Method for producing tire rubber composition>
Hereinafter, the method for producing the rubber composition for a tire of the present invention will be described in detail.
The rubber composition for a tire of the present invention is prepared by the 1-1 step of preparing a mixture of carbon fiber (a), 1,3-butadiene and an inert organic solvent, and the 1-1 step. Further, water, a catalyst composed of an organoaluminum compound and a soluble cobalt compound, or a catalyst composed of an organoaluminum compound, a nickel compound and a fluorine compound is added to the mixture to polymerize the 1,3-butadiene with cis-1,4. Step 1-2, Step 1-3 of polymerizing the 1,3-butadiene in the polymerization reaction mixture obtained in the Step 1-2 by syndiotactic-1,2, and Step 1-3 It is characterized by including a carbon fiber-containing polybutadiene composition obtained through the steps, another diene rubber, and a step of blending a rubber reinforcing material.

By having such characteristics, it is possible to provide a method for producing a rubber composition for a tire, which has excellent physical properties with a low carbon fiber content, and particularly excellent tensile properties.

Hereinafter, each step will be described.
[Step 1-1]
In this step, a mixture of carbon fiber (a), 1,3-butadiene and an inert organic solvent is prepared.

(Carbon fiber (a))
The carbon fiber (a) may be one synthesized by any method including, for example, a vapor phase growth method, and may have high crystallinity, fiber length, fiber diameter, particle size, and other physical properties of the fiber itself. It can be preferably used regardless of its chemical properties. For example, carbon fiber AMC (registered trademark) manufactured by Ube Industries, Ltd. can be used.
In particular, the carbon fiber (a) is a fine carbon fiber in which a graphite mesh surface composed only of carbon atoms is composed of a bell-shaped structural unit having a closed top and a body with an open lower part. Preferably. That is, it is preferable that the fine carbon fibers have a bell-shaped structure as shown in FIG. 1A as a minimum structural unit.

The temple bell, found in Japanese temples, has a relatively cylindrical body, which is different from the conical Christmas bell.
As shown in FIG. 1( a ), the structural unit 11 has a crown 12 and a body 13 having an open end like a bell, and has a shape of a rotating body that is rotated about a central axis. Has become. The structural unit 11 is formed of a graphite net surface composed only of carbon atoms, and the circumferential portion of the open end of the body portion becomes the open end of the graphite net surface. In addition, in FIG. 1A, the center axis and the body portion 13 are shown as straight lines for convenience, but they are not necessarily straight lines and may be curved lines.
The body 13 is gradually expanded toward the open end, so that the generatrix of the body 13 is slightly inclined with respect to the central axis of the bell-shaped structural unit, and the angle θ between them is smaller than 15°. , More preferably 1°<θ<15°, further preferably 2°<θ<10°.

There are defects and irregular disturbances in the fine carbon fiber, but if such irregularities are eliminated and the overall shape is captured, the bell 13 with the body 13 gently spreading toward the open end side It can be said that it has a shape-like structure. This fine carbon fiber does not mean that θ shows the above range in all parts, but when the structural unit 11 is grasped as a whole while eliminating defective parts and irregular parts. In total, it means that θ satisfies the above range. Therefore, in the measurement of θ, it is preferable to exclude the vicinity of the crown 12 where the thickness of the body may change irregularly. More specifically, for example, if the length of the bell-shaped structural unit aggregate 21 is L as shown in FIG. 1B, (1/4)L, (1/2)L and ( It is also possible to measure θ at three points of 3/4) L and obtain the average thereof, and use that value as the overall θ for the structural unit 11. Further, it is ideal to measure L with a straight line, but in reality, since the body 13 is often a curve, it may be closer to the actual value when measured along the curve of the body 13. ..

The shape of the crown is smoothly continuous with the trunk, and has a curved surface that is convex upward (in the figure). The length of the crown is typically about D (FIG. 1(b)) or less, which describes the bell-shaped structural unit aggregate, and may be about d (FIG. 1(b)) or less.
Furthermore, as described later, since active nitrogen is not used as a raw material, other atoms such as nitrogen are not included in the graphite network plane of the bell-shaped structural unit. Therefore, the crystallinity of the fiber is good.

As shown in FIG. 1(b), the fine carbon fiber used in the present invention is formed by stacking 2 to 30 such bell-shaped structural units with the central axis in common and stacking the bell-shaped structural unit aggregates 21 (hereinafter , Sometimes referred to simply as an aggregate). The number of layers is preferably 2 to 25, and more preferably 2 to 15.

The outer diameter D of the body of the aggregate 21 is 5 to 40 nm, preferably 5 to 30 nm, more preferably 5 to 20 nm. The outer diameter D of the body is preferably measured at three points (1/4)L, (1/2)L and (3/4)L from the top of the aggregate and averaged. Although the outer diameter D of the body portion is shown for convenience in FIG. 1B, the actual value of D is preferably the average value of the above three points.

The inner diameter d of the body of the aggregate is 3 to 30 nm, preferably 3 to 20 nm, and more preferably 3 to 10 nm. Also for the measurement of the inner diameter d of the trunk, measure from the crown side of the bell-shaped structural unit aggregate at three points of (1/4)L, (1/2)L and (3/4)L and average them. Is preferred. In addition, although the body part inner diameter d is shown in FIG. 1B for convenience, the actual value of d is preferably the average value of the above three points.
The aspect ratio (L/D) calculated from the length L of the aggregate 21 and the outer diameter D of the body is 2 to 150, preferably 2 to 30, more preferably 2 to 20, and even more preferably 2 to 10. is there.
The bell-shaped structural unit and the bell-shaped structural unit aggregate in the fine carbon fiber used in the present invention have essentially the same structure, but the fiber lengths are different as described below.

The fine carbon fibers used in the present invention are formed by further connecting the aggregates in a Head-to-Tail manner, as shown in FIG. 2(a). The head-to-tail mode means that, in a fine carbon fiber structure, a joint portion between adjacent aggregates has a top portion (Head) of one aggregate and a lower end portion (Tail) of the other aggregate. ) Means that it is formed. The specific shape of the joining portion is as follows: in the lower end opening of the first aggregate 21a, further inside the bell-shaped structural unit of the innermost layer, and on the crown of the bell-shaped structural unit of the outermost layer of the second aggregate 21b. Is further inserted, the top of the third aggregate 21c is inserted into the lower end opening of the second aggregate 21b, and the fibers are formed by further continuing this.

Each joining portion forming one fine fiber of the fine carbon fibers used in the present invention has no structural regularity, and for example, the joining of the first aggregate and the second aggregate is performed. The length of the portion in the fiber axis direction is not necessarily the same as the length of the joint portion between the second aggregate and the third aggregate. In addition, as shown in FIG. 2A, two aggregates to be joined may share a central axis and may be linearly connected, but the bell-shaped structural unit aggregates 21b and 21c of FIG. As described above, they may be joined without sharing the central axis, and as a result, a bending structure may occur at the joined portion. The length L of the bell-shaped structural unit aggregate is generally constant for each fiber. However, in the vapor phase growth method, the gas components of the raw materials and by-products and the solid components of the catalyst and the products coexist, so in carrying out the exothermic carbon deposition reaction, the heterogeneous reaction consisting of the gas and the solid mentioned above. A temperature distribution may occur in the reactor, such as temporary formation of locally high temperature due to the flow state of the mixture, and as a result, the length L may vary to some extent.

In the fine carbon fiber thus configured, at least a part of the open end of the graphite net surface at the lower end of the bell-shaped structural unit is exposed on the outer peripheral surface of the fiber according to the connection interval of the aggregate. The fine carbon fiber structure as described above can be observed by a TEM image. Further, it is considered that the effect of the fine carbon fiber of the present invention has almost no effect even if the assembly itself is bent or the connection portion of the assembly is bent. Therefore, in the TEM image, an aggregate having a shape relatively close to a straight line may be observed to obtain each parameter related to the structure, and the structure parameters (θ, D, d, L) for the fiber may be obtained.

In XRD of the fine carbon fiber used in the present invention by the Gakushin method, the peak half-value width W (unit: degree) of the 002 plane measured is in the range of 2 to 4.
The graphite spacing d002 of the fine carbon fibers used in the present invention determined by XRD measurement by the Gakushin method is 0.350 nm or less, and preferably 0.341 to 0.348 nm.
The ash content contained in the fine carbon fibers used in the present invention is 4% by weight or less, and no purification is required for ordinary use. Usually, it is 0.3% by weight or more and 4% by weight or less, more preferably 0.3% by weight or more and 3% by weight or less. The ash content is determined from the weight of the oxide remaining after burning 0.1 g or more of the fiber.

Carbon fiber-containing polybutadiene composition obtained through steps 1-3 described below The carbon fiber (a) content in the carbon fiber-containing polybutadiene composition is not particularly limited, but the polybutadiene in the carbon fiber-containing polybutadiene composition is not limited. The amount is preferably 0.0001 to 99 parts by weight, more preferably 0.001 to 50 parts by weight, based on 100 parts by weight. When the content of the carbon fiber (a) is less than the lower limit value, a sufficient effect cannot be expected, and when the content of the carbon fiber exceeds the upper limit value, further improvement of the addition effect cannot be expected and the polymerization reaction proceeds. Hard to do.

(Inert organic solvent)
Examples of the inert organic solvent include aromatic hydrocarbons such as toluene, benzene and xylene, aliphatic hydrocarbons such as n-hexane, butane, heptane and pentane, alicyclic hydrocarbons such as cyclohexane and cyclopentane, and the above. Olefin compounds and olefinic hydrocarbons such as cis-2-butene and trans-2-butene, mineral spirits, hydrocarbon solvents such as solvent naphtha and kerosene, and halogenated hydrocarbon solvents such as methylene chloride. To be Further, the 1,3-butadiene monomer itself may be used as a polymerization solvent.

Among the above-mentioned inert organic solvents, toluene, cyclohexane, and a mixture of cis-2-butene and trans-2-butene are preferably used.
The content of 1,3-butadiene in the mixture is preferably 1 to 99% by weight, more preferably 10 to 80% by weight.
In this step, it is preferable to add 1,2-polybutadiene (d) having a melting point of 95 to 110° C. in addition to the carbon fibers (a), 1,3-butadiene and the inert organic solvent.

1,2-polybutadiene (d) having a melting point of 95 to 110° C. is a cobalt compound, an organoaluminum compound represented by the general formula AlR ₃ (wherein R is a hydrocarbon group having 1 to 10 carbon atoms), and Using a catalyst comprising carbon disulfide and, if necessary, one or more compounds selected from the group consisting of alcohols, aldehydes, ketones, esters, nitriles, sulfoxides, amides and phosphoric acid esters, 1,3 -Made by polymerizing butadiene. The 1,2-structure content of the 1,2-polybutadiene (d) is preferably 40 to 99%, particularly preferably 50 to 95%. The 1,2-polybutadiene (d) is preferably syndiotactic-1,2-polybutadiene.

The addition amount of 1,2-polybutadiene (d) is determined by adding 1,2-polybutadiene (b) described later, cis-polybutadiene rubber (c) described later, and 1,2-polybutadiene (d) in a polybutadiene composition. It is 4 to 20% by weight, preferably 4 to 10% by weight, more preferably 4 to 8% by weight. If the addition amount is more than 20% by weight, the workability tends to deteriorate, and if it is less than 4% by weight, the tensile stress tends to deteriorate, which is not preferable.
The melting point of 1,2-polybutadiene (d) is 95 to 110°C, preferably 95 to 105°C. When the melting point of 1,2-polybutadiene (d) is less than the lower limit value, the tensile stress tends to decrease, and when the melting point of 1,2-polybutadiene (d) exceeds the upper limit value, crack resistance is increased. It tends to decrease, which is not preferable.

[Step 1-2]
In this step, water, a catalyst composed of an organoaluminum compound and a soluble cobalt compound, or a catalyst composed of an organoaluminum compound, a nickel compound and a fluorine compound is added to the mixture prepared in the 1-1 step to prepare 1,3 -Polymerize butadiene with cis-1,4.
More specifically, first, water is added to the mixture to adjust the water concentration of the mixture.

The concentration of water is preferably 0.1 to 1.4 mol, particularly preferably 0.2 to 1.2 mol, per mol of the organoaluminum compound used in cis-1,4 polymerization. Outside of this range, the catalytic activity decreases, the cis-1,4 structure content decreases, and the molecular weight becomes abnormally low or high, which is not preferable. Further, if the amount is out of the above range, it is not possible to suppress the generation of gel during the polymerization, so that the gel may adhere to the polymerization tank or the like and the continuous polymerization time cannot be extended, which is not preferable. A known method can be applied to the method for adjusting the water concentration. A method of adding and dispersing through a porous filter material (Japanese Patent Laid-Open No. 4-85304) is also effective.

Next, an organoaluminum compound is added to the mixture obtained by adjusting the water concentration as described above. Examples of the organic aluminum compound include trialkyl aluminum, dialkyl aluminum chloride, dialkyl aluminum bromide, alkyl aluminum sesquichloride, alkyl aluminum sesquibromide, and alkyl aluminum dichloride.

Among the above organoaluminum compounds, trialkylaluminum represented by the general formula AlR ₃ (wherein R is a hydrocarbon group having 1 to 10 carbon atoms) can be preferably used.
Examples of the trialkylaluminum include trimethylaluminum, triethylaluminum, tri-n-propylaluminum, triisopropylaluminum, tri-n-butylaluminum, triisobutylaluminum, tripentylaluminum, trihexylaluminum, tricyclohexylaluminum, trioctyl. Aluminum, triphenyl aluminum, tri-p-tolyl aluminum, and tribenzyl aluminum can be mentioned. The alkyl groups in the trialkylaluminum may be the same or different from each other.

In addition to the above organoaluminum compounds, dialkylaluminum chlorides such as dimethylaluminum chloride and diethylaluminum chloride, organoaluminum halogen compounds such as sesquiethylaluminum chloride and ethylaluminum dichloride, diethylaluminum hydride, diisobutylaluminum hydride and sesquiethylaluminum hydride, etc. It is also possible to use the organoaluminum hydride compound.
Two or more kinds of these organoaluminum compounds may be used in combination.

When the cis-1,4 polymerization is carried out using a catalyst system composed of water, an organoaluminum compound and a soluble cobalt compound, the amount of the organoaluminum compound used is 0.1 mmol or more, and particularly 0 mol/mol of 1,3-butadiene. It is preferably 0.5 to 50 mmol. When cis-1,4 polymerization is carried out using a catalyst system composed of an organoaluminum compound, a nickel compound and a fluorine compound, it is 1×10 ⁻⁵ to 1×10 ⁻¹ mol per mol of 1,3-butadiene. It is preferable.

Next, a soluble cobalt compound is added to the mixture containing the organoaluminum compound to polymerize 1,3-butadiene with cis-1,4.
The soluble cobalt compound is soluble in an inert organic solvent or liquid 1,3-butadiene, or can be uniformly dispersed, for example, cobalt (II) acetylacetonate and cobalt (III) acetylacetonate. Cobalt β-diketone complex, cobalt β-keto acid ester complex such as cobalt acetoacetic acid ethyl ester complex, cobalt octoate, cobalt naphthenate, cobalt benzoate and the like, cobalt salts of organic carboxylic acids having 6 or more carbon atoms, chloride A cobalt halide complex such as a cobalt pyridine complex and a cobalt chloride ethyl alcohol complex is used. The amount of the soluble cobalt compound used is preferably 0.0005 mmol or more, and particularly preferably 0.001 mmol or more per 1 mol of 1,3-butadiene. Further, the molar ratio (Al/Co) of the organoaluminum compound to the soluble cobalt compound is 10 or more, and particularly preferably 50 or more.

Further, instead of the soluble cobalt compound, a nickel compound and a fluorine compound may be added to a mixture containing an organoaluminum compound to polymerize 1,3-butadiene with cis-1,4. In this case, water may or may not be added as a component of the cis-1,4 polymerization catalyst.

As the nickel compound, nickel salts or complexes are preferably used.
Examples of the salt or complex of nickel include nickel halides such as nickel chloride and nickel bromide, nickel salts of inorganic acids such as nickel nitrate, nickel octylate, nickel acetate, and nickel octoate having 1 to 18 carbon atoms. Nickel carboxylates, nickel naphthenates, nickel malonates, nickel bisacetylacetonates and trisacetylacetonates, nickel complexes such as acetoacetic acid ethyl ester, nickel halide triarylphosphine complexes, trialkylphosphine complexes, pyridine complexes And organic base complexes such as picoline complex, and various complexes such as ethyl alcohol complex.
The amount of the nickel compound used is preferably 1×10 ⁻⁷ to 1×10 ⁻³ mol per mol of 1,3-butadiene.

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

The temperature for cis-1,4 polymerization of 1,3-butadiene 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. It is preferable to carry out cis-1,4 polymerization so that the polymer concentration after cis-1,4 polymerization becomes 5 to 26% by weight. Polymerization is performed by stirring and mixing the solution in a polymerization tank (polymerizer). As the polymerization tank used for the polymerization, a polymerization tank equipped with a high-viscosity liquid stirring device, for example, the device described in JP-B-40-2645 can be used.

At the time of cis-1,4 polymerization, known molecular weight regulators, 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. Further, in order to further suppress the formation of gel during polymerization, a known gelation inhibitor can be used.
The Mooney viscosity (ML ₁₊₄ , 100° C.) of the cis-polybutadiene rubber (c) obtained by polymerizing 1,3-butadiene with cis-1,4 is preferably from 20 to 60, more preferably from 20 to 35. Further, the cis-1,4 structure content of cis-polybutadiene is preferably 90% or more, and particularly preferably 95% or more.
The weight average molecular weight of the cis-polybutadiene rubber (c) is preferably 200,000 to 800,000, more preferably 400,000 to 650,000. Moreover, the ratio (Mw/Mn) of the weight average molecular weight and the number average molecular weight is preferably 2.00 to 5.00, and more preferably (2.20 to 3.50).
The polybutadiene obtained by cis-1,4 polymerization contains substantially no gel component.

[Step 1-3]
In this step, 1,3-butadiene in the polymerization reaction mixture obtained in Step 1-2 is polymerized with syndiotactic-1,2.
In this step, 1,3-butadiene may or may not be added separately to the obtained cis-1,4 polymer.
In addition, during the 1, 2 polymerization, an organoaluminum compound and carbon disulfide represented by the general formula AlR ₃ (wherein R is a hydrocarbon group having 1 to 10 carbon atoms), and a soluble cobalt compound 1,3-butadiene may be polymerized by 1,2 addition, or water may be added to the polymerization system to perform 1,2 polymerization.
Further, carbon disulfide has a small influence on the cis-1,4 polymerization and remains in the solution after the polymerization is completed, and thus it may be added in the step 1-1 or the step 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 used in this step is preferably 0.1 mmol or more, and more preferably 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 an alternative to carbon disulfide, known phenyl isothiocyanate or xanthogenic acid compounds may be used. Water is preferably added to the polymerization system after contacting 1,3-butadiene with the organoaluminum compound. The amount of water added is preferably 0.1 to 1.5 mol per mol of the organoaluminum compound.

In the first to third steps, the content (HI) of the 1,2-polybutadiene (b) obtained in this step can be adjusted by adjusting the addition amount of the soluble cobalt compound. The amount of the soluble cobalt compound added in the 1-3 step is preferably 0.005 mmol or more per 1 mol of the residual 1,3-butadiene after the 1-2 step. Moreover, as the soluble cobalt compound, the same compounds as those described in the above-mentioned step 1-2 can be used. When the polymerization activity is low, the soluble cobalt compound may be added more than usual.

The content (HI) of 1,2-polybutadiene (b) is 10 to 15% by weight in the polybutadiene composition obtained by combining 1,2-polybutadiene (b) and cis-polybutadiene rubber (c). , 12 to 14% by weight is preferable. If the content is more than 15% by weight, the workability, crack resistance and fuel economy will tend to decrease, and if it is less than 10% by weight, the tensile stress and crack resistance will tend to decrease, such being undesirable.
Further, the melting point of 1,2-polybutadiene (b) produced in this step is preferably 160 to 197°C.

Further, in this step, it is preferable to add a melting point depressant that lowers the melting point of the 1,2-polybutadiene (b).
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.

The addition amount of the melting point depressant is preferably 0.1 to 10, more preferably 0.3 to 5, and still more preferably 0.5 to 3, in molar ratio with respect to the organoaluminum compound added in the first to third steps. .. By adding the above-mentioned amount of the melting point depressant, the melting point of the 1,2-polybutadiene (b) obtained in the first to third steps can be adjusted to 160 to 197°C. If the molar ratio of the added amount is more than 10, the melting point tends to be excessively lowered and die swell tends to be deteriorated, and if it is less than 0.1, the effect of improving fuel economy tends to be small, which is not preferable.

The temperature of 1,2 polymerization is preferably -5 to 100°C, more preferably -5 to 80°C.
Further, 1 to 50 parts by weight of 1,3-butadiene is added to 100 parts by weight of the cis-1,4 polymer obtained in the step 1-2 in the polymerization system for 1,2 polymerization. Is preferable, and it is more preferable to add 1 to 20 parts by weight of 1,3-butadiene. Thereby, the yield of 1,2-polybutadiene (b) synthesized by 1,2 polymerization can be increased.
The polymerization time is preferably in the range of 10 minutes to 2 hours.
Further, it is preferable to carry out 1,2 polymerization so that the polymer concentration after 1,2 polymerization is 9 to 29% by weight.
The polymerization is performed by stirring and mixing the polymerization solution in a polymerization tank (polymerization vessel). As the polymerization tank used for the 1,2 polymerization, the viscosity becomes higher during the 1,2 polymerization, and the polymer is easily attached, so that the polymerization tank is equipped with a high-viscosity liquid stirring device, for example, it is described in JP-B-40-2645. Different devices can be used.

After the polymerization reaction reaches a predetermined polymerization rate, a known antioxidant can be added according to a conventional method. As the antioxidant, phenol-based 2,6-di-t-butyl-p-cresol (BHT), phosphorus-based trinonylphenyl phosphite (TNP), and sulfur-based 4,6-bis(octylthio) are used. Methyl)-o-cresol and dilauryl-3,3'-thiodipropionate (TPL). These may be used alone or in combination of two or more, and the addition amount of the antioxidant is 0.001 to 5 parts by weight with respect to 100 parts by weight of vinyl cis-polybutadiene.

The polymerization reaction is carried out by adding a large amount of an alcohol such as methanol and ethanol or a polar solvent such as water to the polymerization solution, an inorganic acid such as hydrochloric acid and sulfuric acid, an organic acid such as acetic acid and benzoic acid, or hydrogen chloride gas. Stop using a method known per se, such as a method of introducing into a solution. Then, if necessary, the produced polybutadiene composition is separated from the polymerization reaction mixture, washed, and then dried according to a conventional method.

[Step 1-4]
In this step, the polybutadiene composition obtained through the first to third steps, the rubber reinforcing material, and another diene rubber are mixed. The mixing can be performed using a Banbury, an open roll, a kneader, a twin-screw kneader, or the like.

As the rubber reinforcing material, carbon black or the like which is usually used in tires and the like is used. As the carbon black, particularly preferably, the particle diameter is 90 nm or less and the dibutyl phthalate (DBP) oil absorption amount is 70 mL/100 g or more, and for example, FEF, FF, GPF, SAF, ISAF, SRF, HAF and the like are used.

Here, the other diene rubber refers to a rubber component other than the diene rubber contained in the polybutadiene composition obtained through the first to third steps.
As such a diene rubber, a polymer of a diene monomer such as natural rubber, syndiotactic-1,2-polybutadiene-containing butadiene rubber (VCR), isoprene rubber, butyl rubber or chloroprene rubber; acrylonitrile butadiene rubber (NBR) Acrylonitrile-diene copolymer rubber such as nitrile chloroprene rubber and nitrile isoprene rubber; emulsion polymerization or solution polymerization styrene butadiene rubber (SBR), styrene-diene copolymer rubber such as styrene chloroprene rubber, styrene isoprene rubber; ethylene propylene diene rubber ( EPDM) and the like.

Among these, butadiene rubber, natural rubber, butadiene rubber containing syndiotactic-1,2-polybutadiene, isoprene rubber, acrylonitrile butadiene rubber, and styrene butadiene rubber are preferable.
In particular, solution-polymerized styrene-butadiene rubber (s-SBR), natural rubber, or isoprene rubber is suitable. The other rubber components may be used alone or in combination of two or more.

The content of the carbon fiber (a) in the obtained rubber composition for tire is preferably 0.00001 to 99 parts by weight based on 100 parts by weight of the rubber component in the rubber composition for tire. It is more preferably 0.0001 to 30 parts by weight. When the content of the carbon fiber (a) is less than the lower limit value, a sufficient effect cannot be expected, and when the content of the carbon fiber exceeds the upper limit value, further improvement of the addition effect cannot be expected and the polymerization reaction proceeds. Hard to do.

Further, in this step, in the rubber composition for a tire, if necessary, a silane coupling agent, a vulcanizing agent, a vulcanization accelerator, an antioxidant, a filler, a process oil, zinc white, stearic acid, etc. Compounding agents used in the rubber industry may be kneaded.

As the silane coupling agent, a silane coupling agent having a functional group capable of reacting with polybutadiene and other rubber components is preferable. The silane coupling agents may be used alone or in combination of two or more.

As the vulcanizing agent, known vulcanizing agents such as sulfur, organic peroxides, resin vulcanizing agents, and metal oxides such as magnesium oxide are used. The vulcanizing agents may be used alone or in combination of two or more.

As the vulcanization accelerator, known vulcanization aids such as aldehydes, ammonias, amines, guanidines, thioureas, thiazoles, thiurams, dithiocarbamates, xanthates and the like can be used. The vulcanization accelerators may be used alone or in combination of two or more.

Examples of the antiaging agent include amine/ketone antiaging agents, imidazole antiaging agents, amine antiaging agents, phenol antiaging agents, sulfur antiaging agents, phosphorus antiaging agents, and the like. The antioxidants may be used alone or in combination of two or more.

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. As the filler, one kind may be used alone, or two or more kinds may be used in combination.

As the process oil, any of an aromatic type process oil, a naphthene type process oil and a paraffin type process oil may be used. Alternatively, low molecular weight liquid polybutadiene or tackifier may be used. The process oil may be used alone or in combination of two or more.

The rubber composition for a tire obtained as described above can be used for manufacturing a tire.
This tire rubber composition is used not only for tire applications such as a cap tread, a side reinforcement layer of a run flat tire, a carcass, a belt, a chafer, a base tread, a bead, a stiffener and an inner liner, but also an anti-vibration rubber, a hose, an insulating material. It can also be used for applications other than tires such as seismic rubber and footwear members.
Further, a tire using the above rubber composition for a tire is particularly excellent in tensile properties and the like.

Although the preferred embodiment of the present invention has been described above, the present invention is not limited to this.

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 carbon fiber-containing polybutadiene composition and the physical properties of the tire rubber composition were measured as follows. The physical properties of the carbon fiber-containing rubber composition for tires were evaluated by calculating an index with Comparative Example being 100.

[Evaluation of carbon fiber-containing polybutadiene composition]
Mooney viscosity (ML _{1+4,100° C.} ) of carbon fiber-containing polybutadiene composition:
According to JIS K6300, a Mooney viscometer manufactured by Shimadzu Corporation was used for preheating at 100° C. for 1 minute, and then measured for 4 minutes, and the Mooney viscosity of rubber (ML _{1+4,100° C.} ) was displayed.

High melting point SPB (1,2-polybutadiene (b)) content (HI):
The heat of fusion measured by a differential scanning calorimeter (manufactured by Shimadzu Corporation, trade name: DSC-50) and the measured H.V. I. The H. I. It was calculated from the calibration curve. Measured H. I. 2 parts of vinyl cis-polybutadiene rubber was extracted by boiling with 200 mL of n-hexane for 4 hours using a Soxhlet extractor, and the rest of the extraction was shown in parts by weight.

High melting point SPB (1,2-polybutadiene (b)) melting point:
The melting point of the high-melting point SPB (1,2-polybutadiene (b)) was measured with a differential scanning calorimeter (manufactured by Shimadzu Corporation, DSC-50) when the sample was about 10 mg and the heating rate was 10° C./min. ..

Low melting point SPB (1,2-polybutadiene (d)) content:
The content of low melting point SPB (1,2-polybutadiene (d)) was calculated using the following formula (1).
Content of low melting point SPB (1,2-polybutadiene (d))=amount of low melting point SPB added to polymerization system/amount of obtained carbon fiber-containing polybutadiene composition×100 (1)

[Evaluation of rubber composition for tire]
Tensile properties:
According to JIS K6251, 100%, 200%, 300% tensile stress and breaking strength (TB) were measured. The comparative example was set to 100 and displayed as an index. The larger the index, the better the tensile properties.

(Example)
<Synthesis of carbon fiber-containing polybutadiene composition>
A autoclave having an internal capacity of 1.5 L was charged with 0.1 g of AMC (registered trademark), which is a carbon fiber manufactured by Ube Industries, Ltd., and 10 mL of octane, and the inside of the autoclave was replaced with nitrogen. Then, 2.7 g of low-melting point SPB (1,2-polybutadiene (c) component, manufactured by JSR, trade name: RB830) and 450 mL of cyclohexane were charged to seal the autoclave, and then 450 mL of 1,3-butadiene was charged. .. Next, 40 μL of distilled water was added using a syringe, the temperature of the autoclave was raised to 60° C., and the low melting point SPB was completely dissolved by stirring at 500 rpm for 1 hour. After cooling the autoclave to 30° C., 4.8 mL of a cyclohexane solution (aluminum content is 0.568 mol/L) having a molar ratio of diethylaluminum chloride and triethylaluminum of 3:1 and 3.15 mL of 1,5-cyclooctadiene. After adding, the temperature was raised to 45°C. Then, 0.8 mL of a toluene solution of cobalt octenoate (3.4 mmol/L) was added, and cis-1,4 polymerization was carried out at 45° C. for 20 minutes. To the obtained polymerization reaction mixture, 6.0 mL of triethylaluminum (aluminum content: 0.586 mol/L) was added using a syringe and held for 2 minutes. Then, 1.35 mL of a toluene solution of cobalt octenoate (100 mmol/L) was added and held for 2 minutes, 2.0 mL of dimethyl sulfoxide was added and held for 5 minutes. Then, 1.35 mL of a cyclohexane solution of carbon disulfide (250 mmol/L) was added, and syndiotactic-1,2 polymerization was carried out at 45° C. for 9 minutes. 2.0 mL of a toluene solution of naphthoquinone (150 mmol/L) and 1.5 mL of an ethanol solution of an antioxidant were added, and the autoclave was cooled and depressurized.

Then, the carbon fiber-containing polymerization reaction mixture was taken out in a vat and vacuum dried at 100° C. for 1 hour to obtain a carbon fiber-containing polybutadiene composition. The carbon fiber content in the carbon fiber-containing polybutadiene composition was 0.16 parts by weight. The results of measuring the physical properties of this carbon fiber-containing polybutadiene composition are shown in Table 1.

<Preparation of tire rubber composition>
Using the carbon fiber-containing polybutadiene composition, a rubber composition for tires was prepared based on the formulation shown in Table 2. First, plastomill was used to add rubber, carbon black, process oil, zinc white, stearic acid, and antioxidant, and the primary compounding was carried out.Next, roll was used to carry out the secondary compounding to add vulcanization accelerator and sulfur. Then, a compounded rubber was prepared. This compounded rubber was press-vulcanized at 150° C. to obtain a tire rubber composition, and then physical properties were measured. The compounding recipe is shown in Table 2, and the physical property measurement results are shown in Table 3.

(Comparative Example 1)
<Synthesis of 1,4-polybutadiene>
The inside of the autoclave having an internal capacity of 1.5 L was replaced with nitrogen. Next, a solution consisting of 300 mL of cyclohexane solvent and 300 mL of butadiene was charged. Then, after adding 31 μL of distilled water, 3.2 mL of a cyclohexane solution (aluminum content is 0.568 mol/L) in which the molar ratio of diethylaluminum chloride and triethylaluminum was 3:1 (2.0 mL of 1,5-cyclooctadiene), was added. , 0.9 mL of a toluene solution of cobalt octenoate (3.4 mmol/L) was added. After polymerization at 65° C. for 20 minutes, 1.5 mL of an ethanol solution containing an antioxidant was added, the pressure inside the autoclave was released, and then ethanol was added to the polymerization solution to recover a carbon fiber-containing polybutadiene composition. Then, the recovered 1,4-polybutadiene was vacuum dried at 100° C. for 1 hour. The results of measuring the physical properties of this 1,4-polybutadiene are shown in Table 1.

<Preparation of tire rubber composition>
A rubber composition containing no carbon fiber was prepared in the same manner as in Example except that the carbon fiber-containing polybutadiene composition was replaced with 1,4-polybutadiene. The compounding recipe is shown in Table 2, and the physical property measurement result of the tire rubber composition containing no carbon fiber is shown in Table 3.

(Comparative example 2)
<Synthesis of 1,4-polybutadiene>
1,4-Polybutadiene was prepared in the same manner as in Comparative Example 1. The results of measuring the physical properties of this 1,4-polybutadiene are shown in Table 1.

<Preparation of tire rubber composition>
A rubber composition for tires was prepared in the same manner as in Comparative Example 1 except that carbon fiber was added in an amount of 0.05 part by weight based on 100 parts by weight of the rubber component in the compounded rubber. The compounding recipe is shown in Table 2, and the physical property measurement results of the rubber composition are shown in Table 3.

The numerical values in Table 3 are indexed for each item when each characteristic value of Comparative Example 1 is used as a reference (100). The larger the value, the better the characteristics.
As described above, it is understood that the examples are rubber compositions for tires having excellent tensile properties as compared with the comparative examples.

11 structural unit 12 crown 13 trunk 21, 21a, 21b, 21c bell-shaped structural unit aggregate

Claims (11)

Step 1-1 for preparing a mixture of carbon fiber (a), 1,3-butadiene and an inert organic solvent,
Water, a catalyst composed of an organoaluminum compound and a soluble cobalt compound, or a catalyst composed of an organoaluminum compound, a nickel compound and a fluorine compound is added to the mixture prepared in the step 1-1 to prepare the 1,3- A 1-2 step of cis-1,4 polymerization of butadiene;
A first to third step of polymerizing the 1,3-butadiene in the polymerization reaction mixture obtained in the first to second step with syndiotactic-1,2;
A step of blending the carbon fiber-containing polybutadiene composition obtained through the first to third steps, another diene rubber, and a rubber reinforcing material,
A method for producing a rubber composition for a tire, comprising: The method for producing a rubber composition for a tire according to claim 1, wherein in the 1-1 step, 1,2-polybutadiene (d) having a melting point of 95 to 110° C. is further added. The method for producing a tire rubber composition according to claim 1 or 2, wherein the 1,2-polybutadiene (b) produced in the first to third steps has a melting point of 160 to 197°C. A melting point depressant that lowers the melting point of the 1,2-polybutadiene (b) produced in the first to third steps is added in the first to third steps or the second to third steps. A method for producing the tire rubber composition according to any one of 1. The method for producing a rubber composition for a tire according to claim 4, wherein the melting point depressant is dimethyl sulfoxide. Content of the said carbon fiber (a) is 0.0001-99 weight part with respect to 100 weight part of polybutadiene in a carbon fiber containing polybutadiene composition, In any one of Claim 1 thru|or 5 characterized by the above-mentioned. A method for producing the rubber composition for a tire as described. The tire according to any one of claims 1 to 6, wherein the content of the carbon fiber (a) is 0.00001 to 99 parts by weight with respect to 100 parts by weight of the rubber component in the tire rubber composition. For producing a rubber composition for a car. The fine carbon fiber composed of a bell-shaped structural unit having a closed top portion and a trunk portion with an open lower portion, wherein the graphite fiber surface composed of only carbon atoms is used as the carbon fiber. A method for producing the tire rubber composition according to any one of 1. The method for producing a rubber composition for a tire according to any one of claims 1 to 8, wherein the rubber reinforcing material is carbon black. A rubber composition for a tire manufactured by the method for manufacturing a rubber composition for a tire according to any one of claims 1 to 9. A tire using the rubber composition for a tire according to claim 10.

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