WO2020184675A1 - Rubber composition for tire, and pneumatic tire using this - Google Patents

Abstract

In order to provide a rubber composition for a tire with excellent filler dispersibility, which achieves higher strength, lower heat generation and a higher elastic modulus and which has excellent electric conductivity, 1-150 parts by mass of carbon black and/or silica, and 0.1-10 parts by mass of a carbon nanotube-polymer composite obtained by adding a polymer to at least one part of the carbon nanotubes are blended per 100 parts by mass of a diene rubber.

Description

Rubber composition for tires and pneumatic tires using it

The present invention relates to a rubber composition for a tire and a pneumatic tire using the same. Specifically, the present invention is excellent in dispersibility of a filler, achieves high strength, low heat generation and high elastic modulus, and is electric. The present invention relates to a rubber composition for a tire having excellent conductivity and a pneumatic tire using the same.
The present invention also relates to a rubber composition for a tire and a pneumatic tire using the same. Specifically, the rubber composition for a tire having excellent filler dispersibility, wear resistance and electrical conductivity and the like. It relates to a pneumatic tire using.

Pneumatic tires are mainly composed of a pair of left and right bead parts and sidewall parts, and a tread part that is connected to both sidewall parts and consists of a cap tread and an under tread. A carcass layer is provided on the inside of the tire, and both ends of the carcass layer are folded back so as to wrap the bead core from the inside to the outside of the tire.

The compound for tire under tread is required to have the following characteristics.
(1) To improve durability by increasing strength while maintaining tire manufacturing workability.
(2) To reduce tire rolling resistance by reducing heat generation.
(3) To improve tire steering stability by increasing the elastic modulus.

However, in (1) above, in order to increase the strength, there are methods such as increasing the blending amount of natural rubber and using carbon black having a high specific surface area, but there is a problem in achieving both low heat generation. is there.
Further, in the above (2), in order to reduce heat generation, there are methods such as blending a filler such as silica or using carbon black having a low specific surface area, but there is a problem in achieving both high strength. .. In addition, there is a problem in the dispersibility of the filler.
Further, in the above (3), in order to increase the elastic modulus, there are methods such as using carbon black having a high specific surface area or using a high Tg polymer, but there is a problem in achieving both low heat generation. is there.

On the other hand, especially for tires with high silica content, Earth Red may be used to improve electrical conductivity. Earth red is conductive rubber that is embedded in tread rubber and exposed to the tire contact patch. However, since installing an earth red on a tire causes an increase in tire manufacturing man-hours, an under tread may be used instead of the earth red. In such a form, it is necessary for the undertread compound to maintain a certain level of electrical conductivity or higher.

At present, tire cap tread compounds containing high silica are widely used in order to improve wet performance and low rolling performance.
On the other hand, a compound for a tire cap tread containing a high silica content is required to have the following characteristics.
(4) Excellent wear resistance.
(5) To improve electrical conductivity.

However, in the above (4), in order to improve the wear resistance, for example, a method of adjusting the particle size and the specific surface area of silica has been studied, but sufficient wear resistance has not been obtained yet.
Further, in the above (5), in order to improve the electrical conductivity, the adoption of an earth red structure can be mentioned. Earth red is conductive rubber that is embedded in tread rubber and exposed to the tire contact patch. However, installing an earth red on a tire has a problem that it causes an increase in tire manufacturing man-hours.

Although Patent Documents 1 to 3 disclose rubber compositions for tires using carbon nanotubes, neither disclosure nor suggestion is made of the carbon nanotube-polymer composite of the present invention described below.

Japanese Patent No. 5376966 JP-A-2009-179809 Japanese Unexamined Patent Publication No. 2011-126729

Therefore, an object of the present invention is a rubber composition for a tire which has excellent filler dispersibility, high strength, low heat generation and high elastic modulus, and excellent electrical conductivity, and a pneumatic tire using the same. Is to provide.
Another object of the present invention is to provide a rubber composition for a tire having excellent dispersibility of a filler, excellent wear resistance and electrical conductivity, and a pneumatic tire using the same.

The present invention comprises 0.1 to 150 parts by mass of carbon black and / or silica and 0.1 to 0.1 to 150 parts by mass of carbon nanotube-polymer composite in which a polymer is adhered to at least one part of carbon nanotubes with respect to 100 parts by mass of diene rubber. Provided is a rubber composition for a tire, which is characterized by blending 10 parts by mass.
The present invention also provides the rubber composition for a tire, which comprises 40 to 150 parts by mass of silica blended with 100 parts by mass of a diene rubber.
The present invention also provides the rubber composition for a tire, wherein the amount of the polymer attached to the carbon nanotube-polymer composite is 5 to 20% by mass.
The present invention also provides the rubber composition for a tire, characterized in that the average particle size of the carbon nanotube-polymer composite is 0.1 mm to 3 mm.
The present invention also provides the rubber composition for a tire, wherein the carbon black has a nitrogen adsorption specific surface area (N ₂ SA) of 30 to 140 m ² / g.
The present invention also provides the rubber composition for tires, characterized in that the average glass transition temperature (Tg) of the rubber composition for tires is −20 ° C. or lower.
The present invention also provides the rubber composition for a tire, characterized in that the CTAB specific surface area (N ₂ SA) of the silica is 100 to 300 m ² / g.
The present invention also provides a pneumatic tire using the rubber composition for a tire as an under tread.
The present invention also provides a pneumatic tire using the rubber composition for a tire as a cap tread.
The present invention also provides a method of use characterized in that the rubber composition for a tire is used as a tire cap tread earth.

In the present invention, 1 to 150 parts by mass of carbon black and 0.1 to 10 parts by mass of a carbon nanotube-polymer composite in which a polymer is attached to at least one part of carbon nanotubes are blended with respect to 100 parts by mass of diene rubber. Therefore, it has excellent dispersibility of the filler, achieves high strength, low heat generation and high elastic modulus, and has excellent electrical conductivity and a rubber composition for tires. Pneumatic tires can be provided.
Further, the present invention provides a carbon nanotube-polymer composite in which 1 to 150 parts by mass of silica, preferably 40 to 150 parts by mass, and at least one part of carbon nanotubes are adhered with a polymer with respect to 100 parts by mass of diene rubber. Since it is characterized by blending 0.1 to 10 parts by mass, a rubber composition for tires having excellent filler dispersibility, excellent wear resistance and electrical conductivity, and pneumatic tires having the same characteristics can be obtained. Can be provided.

Hereinafter, the present invention will be described in more detail.

(Diene rubber)
As the diene rubber used in the present invention, any diene rubber that can be blended in a normal rubber composition can be used, and for example, natural rubber (NR), isoprene rubber (IR), and butadiene rubber ( BR), styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR) and the like. These may be used alone or in combination of two or more. Further, its molecular weight and microstructure are not particularly limited, and may be terminal-modified with an amine, amide, silyl, alkoxysilyl, carboxyl, hydroxyl group or the like, or may be epoxidized.
When the diene rubber of the present invention is used for the undertread, it is preferable that the natural rubber is 40 parts by mass or more and the styrene-butadiene copolymer rubber is 50 parts by mass or less in 100 parts by mass of the diene rubber.

(Carbon black)
The carbon black used in the present invention preferably has a nitrogen adsorption specific surface area (N ₂ SA) of 30 to 140 m ² / g. When the nitrogen adsorption specific surface area (N ₂ SA) is 30 m ² / g or more, the strength can be increased. Further, when the nitrogen adsorption specific surface area (N ₂ SA) is 140 m ² / g or less, good dispersibility of the filler and low heat generation can be achieved. Further, from the viewpoint of improving the effect of the present invention, the nitrogen adsorption specific surface area (N ₂ SA) is preferably 30 to 100 m ² / g. The nitrogen adsorption specific surface area (N ₂ SA) is a value obtained in accordance with JIS K6217-2.

(silica)
The silica used in the present invention is not particularly limited, and for example, any conventionally known silica blended in a rubber composition for tire applications can be used.
Specific examples of silica include wet silica, dry silica, fumed silica and the like. As the silica, one type of silica may be used alone, or two or more types of silica may be used in combination.
From the viewpoint of improving the effect of the present invention, particularly from the viewpoint of improving wear resistance, the CTAB specific surface area of silica is preferably 100 to 300 m ² / g, and more preferably 150 to 260 m ² / g. .. The CTAB specific surface area of silica is measured according to ISO5794 / 1.

(Carbon nanotube-polymer composite)
The carbon nanotube-polymer composite used in the present invention is obtained by adhering a polymer to at least one part of carbon nanotubes.

Examples of the polymer include diene rubbers such as NR and SBR; olefin resins such as polyethylene and poly α-olefins; silicone resins; fluororesins such as polyvinylidene fluoride; silicone resins; oils such as liquid paraffins; poly Examples include vinyl chloride; polyvinyl acetate; polystyrene and the like.

Further, in the carbon nanotube-polymer composite, the amount of the polymer attached is preferably, for example, 5 to 20% by mass from the viewpoint of improving the effect of the present invention.
A more preferable amount of the attachment is 5 to 15% by mass.

The carbon nanotube-polymer composite used in the present invention has high electrical conductivity and high strength. In addition, the dispersibility in the diene rubber is also good, and from these facts, the rubber composition has excellent dispersibility of the filler, achieves high strength, low heat generation and high elastic modulus, and has excellent electrical conductivity. Can be provided.

In the carbon nanotube-polymer composite used in the present invention, a plurality of single carbon nanotubes (primary structure) are assembled (secondary structure), and the secondary structured carbon nanotubes are further assembled (tertiary structure). The polymer can be adhered to at least one or all of the tertiary-structured carbon nanotubes to form beads. Here, "adhesion" can be a state in which the polymer is usually attached to at least one part of the cubicly structured carbon nanotubes, or the polymer is coated on the whole, and the carbon nanotubes can be referred to. The polymer may be fixed, and it does not matter whether the bond between the two is a mechanical bond or a chemical bond. The average particle size of the beads is, for example, 0.1 mm to 3 mm. The average particle size can be grasped by, for example, observing the carbon nanotube-polymer composite under a microscope and calculating the average particle size of the composites per 100 pieces. Such a carbon nanotube-polymer composite can be prepared by a known means. For example, a single carbon nanotube (primary structure) is dispersed in water to prepare a dispersion solution, and the polymer is separately dissolved in a solvent. A carbon nanotube-polymer composite can be obtained by preparing a solution, stirring the dispersion and the solution in the same container, granulating, and drying. Such a carbon nanotube-polymer composite has electrical conductivity equivalent to that of a single carbon nanotube (primary structure).

The method for producing a carbon nanotube-polymer composite will be described in more detail.
The carbon nanotube-polymer composite can be produced, for example, according to the methods disclosed in Japanese Patent No. 4787892 and Japanese Patent No. 5767466.

When the polymer is a thermoplastic resin other than rubber, (1) a dissolution step of dissolving the thermoplastic resin in a water-insoluble solvent to prepare a resin binder solution, and (2) a dissolution step in the resin binder solution. Obtained in the suspension step of adding 100 to 1500 parts by mass of carbon nanotubes to water with respect to 100 parts by mass of the thermoplastic resin and uniformly suspending the suspension to obtain a suspension, and (3) the dissolution step. The resin binder solution was added to the suspension obtained in the suspension step to prepare a mixed solution, and (4) the mixed solution obtained in the mixing step was stirred. The carbon nanotube height is increased by a stirring step of transferring the carbon nanotubes from the aqueous phase to the resin phase, and (5) separation and removal of the aqueous phase and the resin phase from the mixed solution obtained in the stirring step, and drying of the resin phase. A carbon nanotube-polymer composite can be obtained by going through a separation / drying step of obtaining a compounded resin granule.

The raw material carbon nanotube (CNT) is not particularly limited, but for example, one having a fiber diameter of 1 to 200 nm and a fiber length of 1 to 100 μm can be used.

The (1) dissolution step is a step of dissolving the thermoplastic resin in a water-insoluble solvent. As the solvent used here, a water-soluble solvent can be used in addition to the water-insoluble solvent.
As the solvent, any kind of water-insoluble solvent capable of dissolving the thermoplastic resin can be used. As a simple method for checking the degree of dissolution, the extent to which all the liquid can be filtered with the circular filter paper # 5C manufactured by Advantech Co., Ltd. is a guide, and if there is even a small amount of filtration residue, it is necessary to change the solvent.
Examples of water-insoluble solvents include organic solvents such as toluene, xylene, hexane, tetrohydrofuran, benzene and cyclohexane.

In the (2) suspension step, CNT corresponding to 100 to 1500 parts by mass, preferably 200 to 1000 parts by mass is added to water with respect to 100 parts by mass of the thermoplastic resin, and the mixture is uniformly suspended. The CNT concentration in the suspension is preferably 0.1 to 10% by mass, more preferably 0.5 to 5% by mass.
To determine the degree of dispersion of CNTs in water, take the suspension on a glass plate with a dropper, spread the color with a spatula, visually and finger-inspect the undispersed mass, and suspend until the texture and feel are no longer rough. Let me. By this treatment, the CNTs are sufficiently loosened from the agglomerate state.
The suspension method is preferably carried out by mechanically stirring CNTs in a dispersion medium such as water. Moreover, ultrasonic irradiation may be used together.

In the mixing step (3), it is necessary to add the resin-dissolving solvent under a uniform addition rate such as 60 cc / min, and if the resin-dissolving solvent is mixed non-uniformly, the adsorption of the thermoplastic resin to the CNT becomes non-uniform. This adversely affects the final performance.
Further, the dropping is preferably performed by a tube pump, a diagram pump, a gear pump or the like, and the temperature of the suspension of CNT and water is 50 ° C. or lower, preferably 25 ° C. or lower.
Regarding the dropping situation, the droplet shape does not necessarily have to be granular. Depending on the stirring speed, a thin liquid column may be continuously dropped.
At this time, the temperature of the additive liquid is not particularly limited and may be in the temperature range near room temperature.

In the (4) stirring step, it is preferable to complete the stirring within 30 minutes, although it depends on the liquid temperature of the suspension solution. If stirring is continued for 30 minutes or more, the produced resin granules tend to be crushed into a slurry.
When the resin binder solution is added in the form of droplets or thin liquid columns during stirring of a uniform suspension of CNT and water, two phases, a resin phase and an aqueous phase, are formed. Initially, CNTs are mainly present in the aqueous phase, but when stirring is continued, the CNTs in the aqueous phase move into the resin phase (flushing action). At this time, if a solvent is present, resin granules composed of CNT and resin can be obtained under stirring.

In the above (5) separation / drying step, the separation operation can be easily performed using a sieve. Drying can be performed by a method such as steam drying or vacuum drying. The temperature at this time is preferably 200 ° C. or lower in the case of a steam dryer or 150 ° C. or lower in the case of vacuum drying.

When the polymer is rubber, (A) a dissolution step of dissolving solid rubber in a solvent to prepare a rubber binder solution, and (B) 100 parts by mass of the solid rubber in the rubber binder solution. A suspension step in which 100 to 1500 parts by mass of carbon nanotubes is added to water and uniformly suspended to obtain a suspension, and (C) the rubber binder solution obtained in the dissolution step is subjected to the suspension step. A mixing step of adding to the suspension obtained in (1) to prepare a mixed solution, and (D) a transition step of transferring the carbon nanotubes from the aqueous phase to the rubber phase by stirring the mixed solution, and (E). ) After that, the aqueous phase and the rubber phase are separated and removed from the mixed solution, and the rubber phase is dried to obtain carbon nanotube-rich rubber granules. The carbon nanotube-polymer composite is obtained through a separation / drying step. Can be obtained.

(A) In the dissolution step, various arbitrary solvents capable of dissolving solid rubber can be used. As a simple method for checking the degree of dissolution, the extent to which all the liquid can be filtered with the circular filter paper # 5C manufactured by Advantech Co., Ltd. is a guide, and if there is even a small amount of filtration residue, it is necessary to change the solvent.
Examples of solvents include toluene, xylene, hexane, tetrahydrofuran, benzene, cyclohexane, naphthylamine, isooctane, isopropyl ether, ethylbenzene, cresol, chlorosulfonic acid, chlorotoluene, chloronaphthalene, chloroform, diethyl ether, dioxane, cyclohexane, dichlorobenzene. , Dibutyl phthalate, dibenzyl ether, dipentene, tetraline, terpineol, trichloroethylene, dichloromethane, dichloroethane, nitrobenzene, carbon disulfide, tetrachloroethylene, pinene, piperidine, pyridine, furan, benzine, thiol, monochlorobenzene, methyl methacrylate, tetrachloride There is an organic solvent such as carbon. The amount of the solvent added is preferably 0.8 to 1.5 times the amount of the carbon nanotube (CNT) absorbed by DBP. The amount of DBP absorbed by carbon nanotubes was measured by the JIS K 6221A method.

The (B) suspension step, the (C) separation / drying step, the (D) transition step, and the (E) separation / drying step are the (2) suspension step and the (3), respectively. It can be carried out in the same manner as the mixing step, the (4) stirring step and the above (5) separation / drying step (“resin” is read as “rubber”).

As the carbon nanotube-polymer composite used in the present invention, a commercially available one can also be used. For example, Durobeads manufactured by Mitsubishi Corporation, product number = DP5210 (polymer used = NR, amount of polymer adhered = 10 mass). %, Average particle size = 0.5 mm to 2 mm),
Durobeads manufactured by Mitsubishi Corporation, product number = DP4210 (polymer used = SBR, polymer adhesion amount = 10% by mass, average particle size = 0.5 mm to 2 mm),
Durobeads manufactured by Mitsubishi Corporation, product number = DP1210 (polymer used = polyethylene, amount of polymer adhered = 10% by mass, average particle size = 0.5 mm to 2 mm),
Durobeads manufactured by Mitsubishi Corporation, product number = DP7210 (polymer used = polyvinylidene fluoride, amount of polymer adhered = 10% by mass, average particle size = 0.5 mm to 2 mm),
Durobeads manufactured by Mitsubishi Corporation, product number = DR3110 (polymer used = silicone resin, amount of polymer adhered = 10% by mass, average particle size = 0.5 mm to 2 mm),
Durobeads manufactured by Mitsubishi Corporation, product number = DP2210 (polymer used = liquid paraffin oil, polymer adhesion amount = 10% by mass, average particle size = 0.5 mm to 2 mm),
And so on.

(Mixing ratio of rubber composition for tires)
In the embodiment (A) of the rubber composition for a tire of the present invention, 1 to 150 parts by mass of carbon black and 0.1 to 10 parts by mass of the carbon nanotube-polymer composite are used with respect to 100 parts by mass of the diene rubber. It is characterized by being blended in parts by mass.
If the blending amount of carbon black is less than 1 part by mass, the reinforcing performance is not exhibited, and conversely, if it exceeds 150 parts by mass, the rolling resistance deteriorates.
If the blending amount of the carbon nanotube-polymer composite is less than 0.1 parts by mass, the addition amount is too small to achieve the effect of the present invention. On the contrary, if it exceeds 10 parts by mass, the filler dispersibility, strength and heat generation property deteriorate.

In the embodiment (A), the amount of the carbon black blended is more preferably 30 to 100 parts by mass with respect to 100 parts by mass of the diene rubber.
In the embodiment (A), a more preferable amount of the carbon nanotube-polymer composite is 0.5 to 7 parts by mass with respect to 100 parts by mass of the diene rubber.
Further, in the embodiment (A), silica can be used in combination in the range of 1 to 150 parts by mass, if necessary, as described below.

In another embodiment (B) of the rubber composition for a tire of the present invention, 1 to 150 parts by mass of silica and 0.1 to 0.1 to 100 parts by mass of the carbon nanotube-polymer composite are used with respect to 100 parts by mass of the diene rubber. It is characterized by blending 10 parts by mass.
If the blending amount of silica is less than 1 part by mass, the addition amount is too small to achieve the effect of the present invention. On the contrary, if it exceeds 150 parts by mass, the wear resistance deteriorates.
If the blending amount of the carbon nanotube-polymer composite is less than 0.1 parts by mass, the addition amount is too small to achieve the effect of the present invention. On the contrary, if it exceeds 10 parts by mass, the filler dispersibility deteriorates, and there is a concern that the rolling resistance deteriorates.

In the embodiment (B), the blending amount of the silica is more preferably 40 to 150 parts by mass, particularly preferably 60 to 130 parts by mass with respect to 100 parts by mass of the diene rubber. When the amount of the silica compounded is 40 parts by mass or more, many of the merits of the silica compounding system can be enjoyed (for example, rolling resistance is improved).
In the embodiment (B), the blending amount of the carbon nanotube-polymer composite is more preferably 0.5 to 7 parts by mass with respect to 100 parts by mass of the diene rubber.

In addition to the above-mentioned components, the rubber composition for tires of the present invention includes rubber compositions such as vulcanization or cross-linking agents, vulcanization or cross-linking accelerators, various fillers, various oils, anti-aging agents, and plasticizers. Various commonly blended additives can be blended, and such additives can be kneaded by a general method to form a composition, which can be used for vulcanization or cross-linking. The blending amount of these additives can also be a conventional general blending amount as long as it does not contradict the object of the present invention.

Further, in the embodiment (A), the rubber composition for a tire of the present invention has excellent filler dispersibility, achieves high strength, low heat generation and high elastic modulus, and is excellent in electrical conductivity. Therefore, it is particularly preferable to use it for under tread. In this form, the composition of the diene-based rubber is 10 to 100 parts by mass, preferably 40 to 80 parts by mass, and 0 to 70 parts by mass of the styrene-butadiene rubber, when the entire diene-based rubber is 100 parts by mass. It is preferably 20 to 50 parts by mass, and butadiene rubber is preferably 0 to 40 parts by mass, preferably 5 to 30 parts by mass. When silica is used, it is preferably less than 40 parts by mass with respect to 100 parts by mass of the diene rubber. It is also a preferable form to use the rubber composition for a tire of the present invention as a tire cap tread ground in which a part of the underdread is penetrated through the cap tread and exposed on the outer surface of the cap tread.

Further, in the embodiment (B), the tire rubber composition of the present invention preferably has an average glass transition temperature (average Tg) of −20 ° C. or lower.
The average Tg referred to in the present specification is a value calculated based on the total product of the glass transition temperature of each component multiplied by the weight fraction of each component, that is, a weighted average. At the time of calculation, the total weight fraction of each component is 1.0. The glass transition temperature is set to the midpoint temperature of the transition region by measuring the thermogram under the condition of a heating rate of 20 ° C./min by differential scanning calorimetry (DSC).
In addition, each of the above-mentioned components means a diene-based rubber, an oil, and a resin. The oil and resin may not be contained in the rubber composition.
A more preferable average Tg is, for example, −20 ° C. to −80 ° C.

Further, the rubber composition for a tire of the present invention is particularly preferable to be used for a cap tread because it has excellent filler dispersibility, wear resistance and electrical conductivity. In this form, the composition of the diene-based rubber is such that the styrene-butadiene copolymer rubber is 30 to 100 parts by mass, preferably 50 to 80 parts by mass, and the butadiene rubber is 0, when the entire diene-based rubber is 100 parts by mass. It is preferably about 60 parts by mass, preferably 10 to 50 parts by mass, and 0 to 100 parts by mass, preferably 0 to 50 parts by mass of natural rubber or isoprene rubber.

Further, the rubber composition for a tire of the present invention can manufacture a pneumatic tire according to a conventional method for manufacturing a pneumatic tire.

Hereinafter, the present invention will be further described with reference to Examples and Comparative Examples, but the present invention is not limited to the following examples.

Standard Examples 1-2, Examples 1-6, Comparative Examples 1-2
In the formulation (parts by mass) shown in Table 1, the vulcanization accelerator and the components excluding sulfur were kneaded with a 1.7 liter sealed Banbury mixer for 5 minutes, and the rubber was discharged to the outside of the mixer and cooled to room temperature. Then, the rubber was put into the same mixer again, a vulcanization accelerator and sulfur were added, and the mixture was further kneaded to obtain a rubber composition. Next, the obtained rubber composition was press-vulcanized in a predetermined mold at 160 ° C. for 20 minutes to obtain a vulcanized rubber test piece, and the unvulcanized rubber composition and the vulcanized rubber were obtained by the test method shown below. The physical properties of the test piece were measured.

Filler dispersibility ΔG': Vulcanization was performed at 160 ° C. for 20 minutes using an unvulcanized rubber composition, and strain shear stress G'with a strain ratio of 0.28% to 30.0% was measured (unit: unit: MPa). A viscoelasticity measuring device RPA2000 (manufactured by Alpha Technologies) was used for the measurement. Difference between G'(G'0.28) at a strain rate of 0.28% and G'(G'30.0) at a strain of 30.0% ΔG'= (G'0.28-G'30) .0) was calculated. The results were expressed exponentially with the value of Standard Example 1 or 2 as 100. The smaller the index, the better the dispersibility of the filler (carbon black, carbon nanotube-polymer composite, silica).
Tensile strength (TB): A tensile test was carried out at 100 ° C. based on JIS K6251 (JIS No. 3 dumbbell). The results were expressed exponentially with the value of Standard Example 1 or 2 as 100. The larger the index, the higher the strength.
Storage modulus E': Based on JIS K6394, using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho, the storage modulus (E') at 20 ° C. under the conditions of initial strain 10%, amplitude ± 2%, and frequency 20 Hz. Asked. The results were expressed exponentially with the value of Standard Example 1 or 2 as 100. The larger the index, the higher the elastic modulus.
Electrical conductivity: The electrical resistance value was measured according to JIS K6911. The results were exponentially displayed with the value of Standard Example 1 as 100. The smaller the index, the higher the electrical conductivity.
Tan δ (60 ° C.): Using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho Co., Ltd., tan δ (60 ° C.) was measured under the conditions of initial strain of 10%, amplitude of ± 2%, frequency of 20 Hz, and temperature of 60 ° C. The results were expressed exponentially with the value of Standard Example 1 or 2 as 100. The smaller the index, the lower the heat generation.
The results are also shown in Table 1. The results of Examples 1 to 4 and Comparative Examples 1 and 2 are compared with the results of Standard Example 1, and the results of Examples 5 to 6 are compared with the results of Standard Example 2.

* 1: NR (PT. KIRANA SAPTA SIR20)
* 2: SBR (Nippon Zeon Co., Ltd. Nipol 1502)
* 3: BR (Nippon Zeon Co., Ltd. Nipol BR 1220)
* 4: Carbon black (Cabot Japan's Shiyo Black N339, N ₂ SA = 90m ² / g)
* 5: Carbon nanotubes (VGCF manufactured by Showa Denko KK, vapor phase carbon fiber synthesized by CVD method (with graphitization treatment), fiber diameter = 150 nm, fiber length = 10 to 20 μm, bulk density = 0.04 g / Cm ³ )
* 6: Carbon nanotube-polymer composite 1 (Durobeads manufactured by Mitsubishi Corporation, product number = DP2210, polymer used = liquid paraffin oil)
* 7: Carbon nanotube-polymer composite 2 (Durobeads manufactured by Mitsubishi Corporation, product number = DP4210, polymer used = SBR)
* 8: Carbon nanotube-polymer composite 3 (Durobeads manufactured by Mitsubishi Corporation, product number = DP5210, polymer used = NR)
* 9: Zinc oxide (3 types of zinc oxide manufactured by Shodo Chemical Industry Co., Ltd.)
* 10: Stearic acid (bead stearic acid YR manufactured by NOF CORPORATION)
* 11: Anti-aging agent (6PPD made by EASTMAN)
* 12: Oil (Extract No. 4 S manufactured by Showa Shell Co., Ltd.)
* 13: Sulfur (Muclon OT-20 manufactured by Shikoku Chemicals Corporation)
* 14: Vulcanization accelerator (Suncellor CM-G manufactured by Sanshin Chemical Industry Co., Ltd.)
* 15: Silica (ULTRASIL VN3GR manufactured by EVONIK)
* 16: Silane coupling agent (Si69 manufactured by EVONIK)

As is clear from Table 1 above, the rubber compositions prepared in Examples 1 to 6 have 1 to 150 parts by mass of carbon black and at least 1 part of carbon nanotubes with respect to 100 parts by mass of diene rubber. Since 0.1 to 10 parts by mass of a carbon nanotube-polymer composite in which a polymer is impregnated is blended, the dispersibility of the filler is excellent as compared with Standard Example 1 or 2, and the strength is increased, the heat generation is reduced, and the elastic modulus is increased. Achieves rate and has excellent electrical conductivity.
Since Comparative Example 1 did not contain a carbon nanotube or a carbon nanotube-polymer composite, the results were inferior in breaking strength, storage elastic modulus, and electrical conductivity as compared with Standard Example 1.
In Comparative Example 2, since the blending amount of the carbon nanotube-polymer composite exceeded the upper limit specified in the present invention, the dispersibility, breaking strength, and tan δ (60 ° C.) of the filler were deteriorated as compared with Standard Example 1.

Standard Example 3, Examples 7 to 13, Comparative Examples 3 to 5
In the formulation (parts by mass) shown in Table 2, the vulcanization accelerator and the components excluding sulfur were kneaded with a 1.7 liter sealed Banbury mixer for 5 minutes, and the rubber was discharged to the outside of the mixer and cooled to room temperature. Then, the rubber was put into the same mixer again, a vulcanization accelerator and sulfur were added, and the mixture was further kneaded to obtain a rubber composition. Next, the obtained rubber composition was press-vulcanized in a predetermined mold at 160 ° C. for 20 minutes to obtain a vulcanized rubber test piece, and the unvulcanized rubber composition and the vulcanized rubber were obtained by the test method shown below. The physical properties of the test piece were measured.

Filler dispersibility ΔG': Vulcanization was performed at 160 ° C. for 20 minutes using an unvulcanized rubber composition, and strain shear stress G'with a strain ratio of 0.28% to 30.0% was measured (unit: unit: MPa). A viscoelasticity measuring device RPA2000 (manufactured by Alpha Technologies) was used for the measurement. Difference between G'(G'0.28) at a strain rate of 0.28% and G'(G'30.0) at a strain of 30.0% ΔG'= (G'0.28-G'30) .0) was calculated. The results were exponentially displayed with the value of Standard Example 3 as 100. The smaller the index, the better the dispersibility of the filler (carbon black, carbon nanotube-polymer composite, silica).
Abrasion resistance: The abrasion resistance of the vulcanized rubber test piece was evaluated using a lambourn abrasion tester in accordance with JIS K6264. The results obtained were expressed as an index with the value of Standard Example 3 as 100. The larger the index, the better the wear resistance.
Electrical conductivity: The electrical resistance value was measured according to JIS K6911. The results were exponentially displayed with the value of Standard Example 3 as 100. The smaller the index, the higher the electrical conductivity.
The results are also shown in Table 2.

* 17: SBR1 (Nipol 1739 manufactured by Nippon Zeon Corporation, oil spread = 37.5 parts by mass per 100 parts by mass of SBR)
* 18: SBR2 (HP755B manufactured by JSR Corporation, oil spread = 37.5 parts by mass per 100 parts by mass of SBR)
* 19: BR (Nipol BR 1220 manufactured by Nippon Zeon Corporation)
* 20: Silica 1 (ZEOSIL1165MP manufactured by Solvay, CTAB specific surface area = 155m ² / g)
* 21: Silica 2 (ZEOSIL1115MP manufactured by Solvay, CTAB specific surface area = 110 m ² / g)
* 22: Silica 3 (Solvay ZEOSIL Premium 200MP, CTAB specific surface area = 200m ² / g)
* 23: Carbon nanotubes (VGCF manufactured by Showa Denko KK, vapor phase carbon fiber synthesized by CVD method (with graphitization treatment), fiber diameter = 150 nm, fiber length = 10 to 20 μm, bulk density = 0.04 g / Cm ³ )
* 24: Carbon nanotube-polymer composite 1 (Durobeads manufactured by Mitsubishi Corporation, product number = DP2210, polymer used = liquid paraffin oil)
* 25: Carbon nanotube-polymer composite 2 (Durobeads manufactured by Mitsubishi Corporation, product number = DP4210, polymer used = SBR)
* 26: Carbon nanotube-polymer composite 3 (Durobeads manufactured by Mitsubishi Corporation, product number = DP5210, polymer used = NR)
* 27: Carbon black (Cabot Japan's Shiyo Black N339)
* 28: Silane coupling agent (Si69 manufactured by Evonik Industries)
* 29: Zinc oxide (3 types of zinc oxide manufactured by Shodo Chemical Industry Co., Ltd.)
* 30: Stearic acid (bead stearic acid YR manufactured by NOF CORPORATION)
* 31: Anti-aging agent (6PPD made by EASTMAN)
* 32: Wax (paraffin wax manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)
* 33: Oil (Extract No. 4 S manufactured by Showa Shell Co., Ltd.)
* 34: Sulfur (oil-treated sulfur from Hosoi Chemical Industry Co., Ltd.)
* 35: Vulcanization accelerator CBS (Suncellor CM-G manufactured by Sanshin Chemical Industry Co., Ltd.)
* 36: Vulcanization accelerator DPG (Sulfur DG manufactured by Sumitomo Chemical Co., Ltd.)

As is clear from Table 2 above, the rubber compositions prepared in Examples 7 to 13 contain 40 to 150 parts by mass of silica and at least one part of carbon nanotubes with respect to 100 parts by mass of diene rubber. Since 0.1 to 10 parts by mass of the carbon nanotube-polymer composite impregnated with the polymer is blended, the dispersibility of the filler is excellent, and the abrasion resistance and the electric conductivity are excellent as compared with Standard Example 3.
Since Comparative Example 3 did not contain a carbon nanotube or a carbon nanotube-polymer composite, no improvement in wear resistance was observed as compared with Standard Example 3, and the result was that the electrical conductivity was inferior.
In Comparative Example 4, since the blending amount of the carbon nanotube-polymer composite exceeds the upper limit specified in the present invention, the dispersibility of the filler is deteriorated as compared with Standard Example 3, and there is a concern that the rolling resistance may be deteriorated. ..
In Comparative Example 5, since the blending amount of silica exceeded the upper limit specified in the present invention, the dispersibility of the filler was deteriorated and the wear resistance was deteriorated as compared with Standard Example 3.

Claims (10)

1. 1 to 150 parts by mass of carbon black and / or silica and 0.1 to 10 parts by mass of a carbon nanotube-polymer composite in which a polymer is adhered to at least one part of carbon nanotubes are blended with respect to 100 parts by mass of diene rubber. A rubber composition for tires, which is characterized by being made of.
2. The rubber composition for a tire according to claim 1, wherein 40 to 150 parts by mass of silica is blended with respect to 100 parts by mass of diene-based rubber.
3. The rubber composition for a tire according to claim 1, wherein the amount of the polymer attached to the carbon nanotube-polymer composite is 5 to 20% by mass.
4. The rubber composition for a tire according to claim 1, wherein the average particle size of the carbon nanotube-polymer composite is 0.1 mm to 3 mm.
5. The rubber composition for a tire according to claim 1, wherein the carbon black has a nitrogen adsorption specific surface area (N ₂ SA) of 30 to 140 m ² / g.
6. The tire rubber composition according to claim 1, wherein the average glass transition temperature (Tg) of the tire rubber composition is −20 ° C. or lower.
7. The rubber composition for a tire according to claim 1, wherein the CTAB specific surface area (N ₂ SA) of the silica is 100 to 300 m ² / g.
8. A pneumatic tire using the rubber composition for a tire according to claim 1 for an under tread.
9. A pneumatic tire using the rubber composition for a tire according to claim 1 for a cap tread.
10. A method of use characterized in that the rubber composition for a tire according to claim 1 is used as a tire cap tread earth.