JP6042398B2 - Pneumatic tire - Google Patents

Description

The present invention relates to a pneumatic tire.

Carbon black has a great influence on the performance of the rubber composition when blended in the rubber composition due to physical properties such as specific surface area, structure and surface properties. For this reason, carbon black having different characteristics is selectively used depending on the required performance of the rubber composition, the environmental conditions in which the rubber composition is used, and the like (for example, Patent Document 1).

The tread rubber that is in contact with the ground is required to have excellent resistance to wear during running (wear resistance), low hysteresis loss that occurs when the rubber is running, and low heat build-up. In order to achieve both wear resistance and low heat build-up, methods such as a high filling method of carbon black, a high specific surface area (small particle size), or a method using carbon black having a high structure are being studied. However, when these carbon blacks are used, although the wear resistance is improved, the low heat build-up may not be sufficient.

In addition, as a technique for improving the wear resistance of a tire with characteristics other than the specific surface area and structure of carbon black, a technique for increasing the sharpness of the aggregate diameter distribution of carbon black has been proposed. However, the rubber composition in which the carbon black is blended has reduced heat generation, and the low heat generation of a tire using the rubber composition in a tread may not be sufficient. Further, if the sharpness of the aggregate diameter distribution is lowered (increases the broadness), the low heat buildup of the tire can be improved, but at the same time, the wear resistance tends to be lowered. Thus, the method of adjusting only the aggregate diameter distribution of carbon black is not an effective means for achieving both wear resistance and low heat build-up of the tire.

Thus, wear resistance and low heat build-up are in a trade-off relationship, and developments are being made to achieve both performances at a high level, but it is currently difficult.

JP 2001-081239 A

An object of the present invention is to solve the above-mentioned problems and to provide a pneumatic tire that can achieve both wear resistance and low heat build-up.

As a result of intensive studies, the present inventors have blended carbon black having a specific aggregate characteristic, such as carbon black obtained by using a specific raw material oil, as a filler in a tread containing a specific rubber component and sulfur. Thus, the present inventors have found that the performance balance between wear resistance and low heat buildup can be remarkably and synergistically improved, and the present invention has been completed.

The present invention relates to a pneumatic tire having a tread composed of a rubber composition containing isoprene-based rubber and a high-cis butadiene rubber having a cis content of 90% by mass or more, one or more carbon blacks, and sulfur. And at least one of the carbon blacks has a specific gravity D (60/60) when compared with water having an average boiling point T (° C) and 60 ° F as a raw material oil for producing the carbon black. The pneumatic tire is carbon black obtained using a feedstock oil having a BMCI value of 150 or less and an aliphatic hydrocarbon ratio of 30% by mass or more calculated from
BMCI = 48640 / (T + 273) + 473.7D-456.8

Carbon obtained by using at least one of the carbon blacks as a raw material oil for producing the carbon black, a raw material oil having a BMCI value of 95 or more and an aliphatic hydrocarbon ratio of 60% by mass or less Black is preferred.

In 100% by mass of aliphatic hydrocarbons contained in the raw material oil, 10% by mass or more is preferably an aliphatic hydrocarbon derived from animal or vegetable oils or modified products thereof.

The raw material oil preferably contains tall oil.

The carbon black is preferably carbon black produced by a furnace method.

The present invention also includes a pneumatic component having a tread composed of a rubber composition containing a rubber component containing an isoprene-based rubber and a high-cis butadiene rubber having a cis content of 90% by mass or more, one or more carbon blacks, and sulfur. In the tire, at least one of the above carbon blacks has a maximum frequency diameter (Dmod) of a distribution curve having a Stokes equivalent diameter as an aggregate characteristic of 79 nm or less, and a ratio of a half value width (ΔD50) of the distribution curve to Dmod ( ΔD50 / Dmod) relates to a pneumatic tire that is carbon black having a value of 0.78 or more.

In 100% by mass of the rubber component, the content of the isoprene-based rubber is 35 to 95% by mass, and the content of the high-cis butadiene rubber is 5 to 65% by mass. In the rubber composition, the rubber component is 100% by mass. The sulfur content is preferably 0.5 to 1.6 parts by mass with respect to parts.

The high-cis butadiene rubber is preferably a high-cis butadiene rubber synthesized using a rare earth element-based catalyst and having a vinyl content of 1.0% by mass or less and a cis content of 95% by mass or more.

In the rubber composition, the total content of stearic acid, calcium stearate and zinc fatty acid is preferably 2 to 6 parts by mass with respect to 100 parts by mass of the rubber component.

In the rubber composition, the oil content is preferably 7 parts by mass or less and the zinc oxide content is 1.5 to 3.99 parts by mass with respect to 100 parts by mass of the rubber component.

According to the present invention, an air having a tread composed of a rubber composition containing a rubber component containing isoprene-based rubber and a high-cis butadiene rubber having a cis content of 90% by mass or more, one or more carbon blacks, and sulfur. Since a specific type of carbon black is used in the entering tire, the performance balance of wear resistance and low heat generation is remarkably improved.

1st this invention has the tread which consists of a rubber composition containing the rubber component containing the isoprene-type rubber | gum and the high cis-butadiene rubber whose cis content is 90 mass% or more, 1 or more types of carbon black, and sulfur. A pneumatic tire, wherein at least one of the carbon blacks has a specific gravity D (compared with water having an average boiling point T (° C.) and 60 ° F. as a raw material oil for producing the carbon black. 60/60 ° F) is a carbon black (1) obtained by using a feedstock oil having a BMCI value calculated by the following formula of 150 or less and an aliphatic hydrocarbon ratio of 30% by mass or more. Regarding tires.
BMCI = 48640 / (T + 273) + 473.7D-456.8

The second aspect of the present invention has a tread comprising a rubber composition containing a rubber component containing isoprene-based rubber and a high-cis butadiene rubber having a cis content of 90% by mass or more, one or more carbon blacks, and sulfur. In the pneumatic tire, at least one of the carbon blacks has a maximum frequency diameter (Dmod) of a distribution curve of Stokes equivalent diameter as an aggregate characteristic of 79 nm or less, and a half-value width (ΔD50) of the distribution curve with respect to Dmod. The present invention relates to a pneumatic tire that is carbon black (1) having a ratio (ΔD50 / Dmod) of 0.78 or more.

In the present invention, in a tread containing isoprene-based rubber, high-cis butadiene rubber, and sulfur, as a raw material oil for producing carbon black, a BMCI value is equal to or less than a specific value and an aliphatic hydrocarbon ratio is Carbon black (1) obtained by using raw material oil having a specific value or more, carbon black (1) having a specific aggregate characteristic that Dmod is a specific value or less and ΔD50 / Dmod is a specific value or more are used as a tread. By blending, it is possible to improve wear resistance while maintaining or improving good low heat build-up, and to achieve both the wear resistance and performance balance of low heat build-up. In particular, the performance balance is remarkably and synergistically improved as compared with the case of using other rubber components (only isoprene-based rubber, only styrene-butadiene rubber, etc.) in place of the blend rubber of isoprene-based rubber and high-cis butadiene rubber. It becomes possible.

In the following, first, the first and second rubber compositions used in the first and second inventions will be described.

The first and second rubber compositions contain isoprene-based rubber as a rubber component. Examples of the isoprene-based rubber include natural rubber (NR), isoprene rubber (IR), epoxidized natural rubber (ENR), and the like. Among these, NR can be preferably used because of its excellent wear resistance, low heat build-up, and the like. As the NR, for example, those commonly used in the tire industry such as SIR20, RSS # 3, TSR20 and the like can be used. The IR is not particularly limited, and those commonly used in the tire industry can be used.

In the first and second rubber compositions, the content of the isoprene-based rubber in 100% by mass of the rubber component is usually 35% by mass or more, preferably 55% by mass or more, and more preferably 75% by mass or more. If it is less than 35% by mass, the fuel economy may not be sufficiently improved. The content of isoprene-based rubber is usually 95% by mass or less, preferably 85% by mass or less. If it exceeds 95% by mass, sufficient wear resistance cannot be secured, and there is a possibility that low fuel consumption and wear resistance cannot be obtained in a well-balanced manner.

The first and second rubber compositions also contain a high cis butadiene rubber (high cis BR) having a cis content of 90% by mass or more as a rubber component. The high cis BR is not particularly limited, and those commonly used in the tire industry can be used. However, the high cis BR is synthesized using a rare earth element-based catalyst and has a vinyl content of 1.0% by mass or less (preferably 0.8% by mass or less). ), High cis BR having a cis content of 95% by mass or more (preferably, rare earth butadiene rubber [rare earth BR]) can be suitably used.
In the present invention, the vinyl content (1,2-bonded butadiene unit amount) and the cis content (cis-1,4-bonded butadiene unit amount) are values measured by infrared absorption spectrum analysis.

In the first and second rubber compositions, the content of the high cis BR in 100% by mass of the rubber component is usually 5% by mass or more, preferably 15% by mass or more. If it is less than 5% by mass, sufficient wear resistance cannot be ensured. The content of the high cis BR is usually 65% by mass or less, preferably 45% by mass or less, and more preferably 25% by mass or less. If it exceeds 65% by mass, fuel economy and wear resistance may not be sufficiently improved.

In the first rubber composition, carbon black (1) obtained by using a raw material oil having a BMCI value of a specific value or less and an aliphatic hydrocarbon ratio of a specific value or more, and in the second rubber composition, Dmod is A carbon black (1) having a specific aggregate characteristic of a specific value or less and ΔD50 / Dmod of a specific value or more is used. By blending the carbon black (1), both wear resistance and low heat build-up can be achieved.

In the second rubber composition, the maximum frequency diameter (Dmod) of the Stokes equivalent diameter distribution curve as an aggregate characteristic of the carbon black (1) is 79 nm or less, preferably 69 nm or less, more preferably 63 nm or less. If it exceeds 79 nm, the effect of the present invention (particularly, the effect of improving wear resistance) cannot be obtained sufficiently. Although the minimum of this Dmod is not specifically limited, Preferably it is 50 nm or more, More preferably, it is 56 nm or more. If it is less than 50 nm, the dispersibility is inferior, and the fracture characteristics and wear resistance tend to decrease.

In the second rubber composition, the ratio (ΔD50 / Dmod) of the half-value width (ΔD50) of the distribution curve to Dmod as an aggregate characteristic of carbon black (1) is 0.78 or more, preferably 0.8. 90 or more, more preferably 1.0 or more, still more preferably 1.1 or more. If it is less than 0.78, the effect of the present invention (particularly, the effect of improving low heat build-up) cannot be obtained sufficiently. The upper limit of ΔD50 / Dmod is not particularly limited, but is preferably 2.5 or less, more preferably 2.0 or less. If it exceeds 2.5, the wear resistance is deteriorated and the desired effect may not be obtained.

In this specification, Dmod and ΔD50 of carbon black are values measured by the following method.
A carbon black sample precisely weighed in a 20% aqueous ethanol solution to which a surfactant (“NONIDET P-40” manufactured by SIGMA CHEMICAL) is added is added to prepare a sample solution having a carbon black concentration of 0.01% by weight. A carbon black slurry is prepared by dispersing the sample solution for 5 minutes using an ultrasonic disperser (“Ultrasonic Generator USV-500V” manufactured by Ultrasonic Industry Co., Ltd.) with a vibration frequency of 200 kHz and an output of 100 W. On the other hand, 10 ml of spin solution (pure water) was injected into a centrifugal sedimentation type particle size distribution measuring device (“BI-DCP PARTIC LSIZ” manufactured by BROOK HAVEN INSTRUMENTS), and 1 ml of buffer solution (20 vol% ethanol aqueous solution) was further injected. Thereafter, 1 ml of each of the prepared carbon black slurries is injected, and the Stokes equivalent diameter is measured by centrifugal sedimentation at a rotational speed of 8000 rpm, and a histogram of the occurrence frequency relative to the Stokes equivalent diameter is prepared. Let C be the intersection of a straight line passing through the peak (A) of the histogram and parallel to the Y axis and the X axis of the histogram. The Stokes diameter at C is the maximum frequency Stokes equivalent diameter (Dmod). Further, an intermediate point (D, E) between a straight line G passing through F and parallel to the X axis and a histogram distribution curve (D, E) is obtained with the midpoint of the line segment AC as F, and the difference between the D and E Stokes diameters The absolute value is defined as the Stokes equivalent diameter half-width value (half-value width of distribution curve (ΔD50)).

The carbon black (1) has a cetyltrimethylammonium bromide adsorption specific surface area (CTAB) of preferably 60 to 150 m ² / g, more preferably 80 to 145 m ² / g, still more preferably 100 to 140 m ² / g, and particularly preferably. Is 105 to 135 m ² / g. The effect of this invention is acquired more suitably as CTAB is in the said range.
In the present specification, the cetyltrimethylammonium bromide adsorption specific surface area (CTAB) of carbon black is a value measured in accordance with JIS K6217-3: 2001.

The iodine adsorption amount (IA) (mg / g) of carbon black (1) is preferably 100 to 400 mg / g, more preferably 110 to 300 mg / g, and still more preferably 120 to 250 mg / g. When the iodine adsorption amount (IA) is within the above range, the effect of improving the wear resistance is more suitably obtained, and the effect of the present invention is more suitably obtained.

The ratio (CTAB / IA) of the cetyltrimethylammonium bromide adsorption specific surface area (CTAB) to the iodine adsorption amount (IA) (mg / g) of the carbon black (1) is preferably 0.8 to 1.2 m ² / mg. More preferably, it is 0.85-1.15 m < ² > / mg, More preferably, it is 0.9-1.1 m < ² > / mg. When CTAB / IA is within the above range, the effect of the present invention can be more suitably obtained.
In the present specification, the iodine adsorption amount (IA) of carbon black is a value measured according to JIS K6217-1: 2008.

The surface activity index represented by CTAB / IA can be considered as an index of the crystallinity (graphitization rate) of carbon black. That is, as CTAB / IA is higher, crystallization is less advanced, and the interaction between carbon black and the rubber component tends to increase.
CTAB / IA is also positioned as a parameter for evaluating the amount of acidic functional groups present on the carbon black surface. The acidic functional group on the surface of carbon black contributes to the interaction with the rubber component, but the higher the CTAB / IA, the more acidic functional groups are present on the surface of the carbon black. Therefore, when CTAB / IA is within the above range, a more remarkable reinforcing effect can be exerted on the rubber component, and the effect of the present invention can be obtained more suitably.

24M4 dibutyl phthalate oil absorption of carbon black (1) (24M4DBP) is preferably 50~120cm ³ / 100g, more preferably 70~120cm ³ / 100g, more preferably 90~115cm ³ / 100g, particularly preferably 95 to 110cm is a ³ / 100g. When 24M4DBP is within the above range, the effect of the present invention can be more suitably obtained.
In the present specification, the 24M4 dibutyl phthalate oil absorption (24M4DBP) of carbon black is a value measured according to ASTM D3493-85a.

Carbon black (1) may be acidic, neutral or basic, but preferably has a pH of 2.0 to 10.0 as measured according to JIS K6220-1. More preferably, it is 9.5. When the pH of the carbon black (1) is within the above range, the mechanical strength and wear resistance of the rubber composition can be improved more suitably, and the effects of the present invention can be obtained more suitably.

As a method for producing carbon black (1), for example, a method characterized in that a raw material oil having a BMCI value of 150 or less and an aliphatic hydrocarbon ratio of 30% by mass or more is used as a raw material oil (raw material hydrocarbon). Is preferably adopted. Thereby, carbon black (1) which has the said characteristic is obtained suitably. Further, according to this method, carbon black is prepared in one pot, that is, using the above-mentioned raw material oil, without mixing a plurality of prepared carbon blacks or performing post-treatment such as surface treatment on the prepared carbon black. The carbon black (1) having the above characteristics can be easily prepared simply by preparing the above.

Here, in this specification, the BMCI value is a value calculated from the average boiling point T (° C.) and specific gravity D (60/60 ° F.) when compared with water at 60 ° F. is there.
The average boiling point T is the temperature at which 50% of the raw material oil is distilled off on a mass basis.
BMCI = 48640 / (T + 273) + 473.7D-456.8

In the first rubber composition, the BMCI value of the raw oil is 150 or less, preferably 140 or less, more preferably 130 or less, still more preferably 120 or less, and particularly preferably 110 or less. If it exceeds 150, the particle size distribution of carbon black becomes too sharp, the above-mentioned specific aggregate characteristics cannot be obtained, and it becomes impossible to achieve both wear resistance and low heat build-up. The lower limit of the BMCI value of the feedstock is not particularly limited, but is preferably 95 or more. If it is less than 95, the yield may be deteriorated (a sufficient amount of carbon black cannot be obtained).

In the first rubber composition, the aliphatic hydrocarbon ratio (the content of the aliphatic hydrocarbon in 100% by mass of the raw material oil) is 30% by mass or more, and preferably 40% by mass or more. If it is less than 30% by mass, the above-mentioned specific aggregate characteristics cannot be obtained, and it becomes impossible to achieve both wear resistance and low heat build-up. The upper limit of the aliphatic hydrocarbon ratio is not particularly limited, but is preferably 60% by mass or less. If it exceeds 60% by mass, the yield may be deteriorated (a sufficient amount of carbon black cannot be obtained).

The content of aliphatic hydrocarbons derived from animal and vegetable oils or modified products thereof in 100% by mass of aliphatic hydrocarbons contained in the feedstock oil is preferably 10% by mass or more, more preferably 20% by mass or more, and still more preferably. 30% by mass or more. The upper limit of this content is not specifically limited, 100 mass% may be sufficient. When the content is within the above range, not only the effect of the present invention can be obtained more suitably, but also the above effect can be achieved using a non-depleted resource as a raw material, so that resource depletion and the environment can be considered.

As the feedstock satisfying the above characteristics, one satisfying the above characteristics may be used alone, or a mixture of two or more kinds so as to satisfy the above characteristics may be used.

Specific examples of raw material oils include: (1) aromatic hydrocarbons such as anthracene; coal-based hydrocarbons such as creosote oil; EHE oil (replicated oil during ethylene production), FCC oil (fluid catalytic cracking residue oil) And a raw material mixture of at least one selected from the group consisting of petroleum heavy oils such as ()) and (2) aliphatic hydrocarbons. These may be modified. Among these, a mixed raw material oil of coal-based hydrocarbon and aliphatic hydrocarbon is preferable.

As the aliphatic hydrocarbon, for example, petroleum-based aliphatic hydrocarbons typified by process oil, and animal and vegetable oils typified by fatty acids such as soybean oil, rapeseed oil, and palm oil can be used.
Here, animal and vegetable oils include fish oil (liver oil) obtained from fish liver, marine animal oil such as sea animal oil obtained from whales, and land animal oil such as beef tallow and pork fat, as well as plant seeds, fruits, and nuclei. It contains fats and oils and the like containing fatty acid glycerides collected from the above.

Further, as the raw material oil, a mixed raw material oil of coal-based hydrocarbons and petroleum-based aliphatic hydrocarbons, a mixed raw material oil of coal-based hydrocarbons and animal and vegetable oils are preferable, creosote oil and petroleum-based aliphatic hydrocarbons and Of these, a mixed raw material oil of creosote oil and soybean oil is more preferable. Furthermore, tall oil containing aliphatic hydrocarbons can also be suitably used as a raw material oil. In addition, as said coal-type hydrocarbon, coal-type aromatic hydrocarbon is preferable.

Carbon black (1) can be produced by a known production method except that the above-mentioned raw material oil is used, and its production method is not particularly limited. Specifically, carbon black (1) is carbonized by spraying raw material oil into combustion gas. A method for producing black is preferably employed, and conventionally known methods such as a furnace method and a channel method are used. Among these, the furnace method shown below is preferable because the above-mentioned specific aggregate characteristics can be suitably obtained.

The furnace method (oil furnace method) is, for example, as disclosed in Japanese Patent Application Laid-Open No. 2004-43598 and Japanese Patent Application Laid-Open No. 2004-277443. A process using a device having a reaction zone for introducing hydrocarbons and converting raw material hydrocarbons to carbon black by a pyrolysis reaction, and a reaction stop zone for quenching reaction gas to stop the reaction, combustion conditions, high temperature Carbon blacks having various characteristics can be produced by controlling various conditions such as the combustion gas flow rate, the conditions for introducing the raw material oil into the reaction furnace, and the time from the conversion of carbon black to the termination of the reaction.

In the combustion zone, air, oxygen or a mixture thereof and a gaseous or liquid fuel hydrocarbon are mixed and burned as an oxygen-containing gas to form a high-temperature combustion gas. As the fuel hydrocarbon, petroleum-based liquid fuel such as carbon monoxide, natural gas, coal gas, petroleum gas, heavy oil, and coal-based liquid fuel such as creosote oil are used. The combustion is preferably controlled so that the combustion temperature is in the range of 1400 ° C to 2000 ° C.

In the reaction zone, the raw material hydrocarbon is sprayed and introduced into the high-temperature combustion gas flow obtained in the combustion zone in a co-current flow or in a lateral direction, and the raw material hydrocarbon is thermally decomposed and converted to carbon black. Preferably, the feedstock oil is introduced by one or more burners into a high temperature combustion gas stream having a gas flow rate in the range of 100 to 1000 m / s. The feedstock oil is preferably divided and introduced by two or more burners. In order to improve the reaction efficiency, it is preferable to provide a throttle part in the reaction zone. The ratio of the diameter of the throttle part / the diameter of the upstream area of the throttle part is preferably 0.1 to 0.8.

In the reaction stop zone, water spray or the like is performed to cool the high temperature reaction gas to 1000 to 800 ° C. or less. The time from the introduction of the feedstock to the reaction stop is preferably 2 to 100 milliseconds. The cooled carbon black can be separated and recovered from the gas and then subjected to a known process such as granulation and drying.

In the first and second rubber compositions, the content of carbon black (1) is preferably 20 parts by mass or more, more preferably 40 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 20 parts by mass, the effects of the present invention tend not to be sufficiently obtained. Content of this carbon black (1) becomes like this. Preferably it is 70 mass parts or less, More preferably, it is 60 mass parts or less. If it exceeds 70 parts by mass, low heat build-up and wear resistance may be deteriorated.

In the present invention, carbon black other than carbon black (1) may be blended together with carbon black (1).

The first and second rubber compositions contain sulfur. The sulfur is not particularly limited, and those commonly used in the tire industry can be used. Examples thereof include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur. The sulfur in the present invention includes sulfur in a sulfur-containing compound having crosslinkability such as a sulfur-containing coupling agent.

The sulfur content is preferably 0.5 parts by mass or more, and more preferably 0.6 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 0.5 parts by mass, the vulcanization is not sufficiently performed, and a desired strength may not be obtained. The sulfur content is preferably 1.6 parts by mass or less, more preferably 1.1 parts by mass or less. If it exceeds 1.6 parts by mass, the wear resistance may be reduced.

In addition, in this specification, content of sulfur means the total amount of the pure sulfur content of the vulcanizing agent mix | blended with a rubber composition. For example, when a sulfur-containing coupling agent such as oil-containing sulfur or Vulcuren KA9188 manufactured by LANXESS or DURALINK HTS manufactured by Flexis is used as the vulcanizing agent, the sulfur content or sulfur-containing coupling contained in the oil-containing sulfur is used. This is the total amount of sulfur in the agent.

（式（Ｉ）において、Ａは炭素数２〜１０のアルキレン基、Ｒ^１及びＲ^２は、同一若しくは異なって、窒素原子を含む１価の有機基を表す。） The first and second rubber compositions may use a compound represented by the following formula (I) as a crosslinking agent (sulfur-containing coupling agent). Thereby, a CC bond with high binding energy and high thermal stability can be retained in the rubber composition.

(In formula (I), A represents an alkylene group having 2 to 10 carbon atoms, and R ¹ and R ² are the same or different and each represents a monovalent organic group containing a nitrogen atom.)

The alkylene group for A (having 2 to 10 carbon atoms) is not particularly limited, and includes linear, branched, and cyclic groups. A linear alkylene group is preferable, and a hexamethylene group is more preferable. R ¹ and R ² are not particularly limited as long as they are monovalent organic groups containing a nitrogen atom, but those containing at least one aromatic ring are preferred, and N—C (═S) in which a carbon atom is bonded to a dithio group. )-Is more preferable.

When the first and second rubber compositions contain the compound represented by the formula (I), the content thereof is preferably 0.5 to 5 parts by mass, more preferably 100 parts by mass of the rubber component. Is 1 to 3 parts by mass.

The first and second rubber compositions preferably contain at least one selected from the group consisting of stearic acid, calcium stearate, and fatty acid zinc. As fatty acid zinc, the saturated fatty acid zinc which consists of several C14-C20 carbon number can be used conveniently.

In the first and second rubber compositions, the total content of stearic acid, calcium stearate and fatty acid zinc is preferably 2 parts by mass or more, more preferably 3 parts by mass or more, with respect to 100 parts by mass of the rubber component. Preferably it is 3.5 parts by mass or more. If the total content is less than 2 parts by mass, sufficient processability (Mooney viscosity, extrusion processability) may not be ensured. The total content is preferably 6 parts by mass or less, more preferably 4 parts by mass or less. If the total content exceeds 6 parts by mass, the wear resistance and elongation at break may be reduced.

The first and second rubber compositions preferably contain zinc oxide. It does not specifically limit as a zinc oxide, A thing common in a tire industry can be used.

The content of zinc oxide is preferably 1.5 parts by mass or more, more preferably 2 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 1.5 parts by mass, the fuel efficiency may be lowered. The content of zinc oxide is preferably 3.99 parts by mass or less, preferably 3 parts by mass or less. If it exceeds 3.99 parts by mass, the wear resistance may be reduced.

In addition to the above components, the first and second rubber compositions include compounding agents commonly used in the production of rubber compositions, for example, reinforcing fillers such as silica, silane coupling agents, anti-aging agents, Oils, waxes, vulcanization accelerators and the like can be appropriately blended.

The oil content is preferably 7.0 parts by mass or less, more preferably 3.0 parts by mass or less, still more preferably 1.0 parts by mass or less, even with 0 parts by mass with respect to 100 parts by mass of the rubber component. Good.

As a method for producing the first and second rubber compositions, a known method, for example, a method of kneading each component with a known mixer such as a roll or Banbury can be used.

The first and second rubber compositions preferably contain a master batch obtained by kneading isoprene-based rubber and carbon black (1). That is, it is preferable to prepare a master batch by kneading isoprene-based rubber and carbon black (1), and then kneading the obtained master batch and another compounding agent. Thus, the dispersibility of carbon black (1) can be improved by kneading isoprene-based rubber and carbon black (1) in advance.

When carbon black (1) is used in combination with fine particle carbon black, carbon black (1) having a large nitrogen adsorption specific surface area (N ₂ SA) is kneaded in the masterbatch preparation step. It is preferable. In this case, the carbon black is efficiently dispersed by kneading the master batch and carbon black, which has fine particles and poor dispersibility, together with other compounding agents in a later step.

In the preparation process of the masterbatch, when rubber components other than isoprene rubber, oil, processing aid, stearic acid, and anti-aging agent are kneaded, the viscosity of the rubber decreases and the dispersibility of the carbon black (1) decreases. There is a risk. Therefore, it is preferable to knead rubber components other than isoprene-based rubber, oil, processing aids, stearic acid, and anti-aging agent in a later step. That is, it is preferable to knead only the isoprene-based rubber and carbon black (1) in the masterbatch preparation process.

In the preparation process of the master batch, the discharge temperature is preferably 130 to 170 ° C. Moreover, although kneading | mixing time changes with the magnitude | sizes of the kneading machine to be used, etc., it may usually be about 2 to 5 minutes.

In the master batch, the blending amount of the carbon black (1) with respect to 100 parts by mass of the isoprene-based rubber is preferably 30 to 80 parts by mass, more preferably 45 to 65 parts by mass.

The first and second rubber compositions can be used for tire treads.

The pneumatic tire of the present invention is produced by a usual method using the rubber composition. That is, a rubber composition containing various additives as necessary is extruded in accordance with the shape of the tread of the tire at an unvulcanized stage, molded by a normal method on a tire molding machine, etc. The tire members are bonded together to form an unvulcanized tire. This unvulcanized tire can be heated and pressurized in a vulcanizer to produce the pneumatic tire of the present invention.

The pneumatic tire of the present invention can be used for passenger car tires, heavy load tires and the like, and in particular, can be suitably used for heavy load tires containing a large amount of isoprene-based rubber.

The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

[Carbon black production equipment]
A raw material introduction zone comprising an inner diameter of 500 mm having an air introduction duct and a combustion burner, a length of 1750 mm, a combustion zone having a length of 1750 mm, an inner diameter of 55 mm having a raw material nozzle penetrating from the periphery, and a narrow diameter portion having a length of 700 mm, A carbon black production facility in which a rear reaction zone having an inner diameter of 200 mm and a length of 2700 mm equipped with a quench device was sequentially joined was used.
[Production conditions] (Furnace method)
Using this production facility, carbon black was produced using natural gas as a fuel, using oils and petroleum hydrocarbons whose characteristics are shown in Table 1 as raw material oils, and other conditions shown in Table 2 as other conditions. Table 2 shows the yield and various characteristics of the carbon black obtained in each production example. Incidentally, various characteristics of carbon black were measured by the above-described methods. Further, the carbon blacks obtained in Production Examples 2-5 and 7-14 correspond to the carbon black (1). Note that the carbon black obtained by Production Example 12-14 had a poor yield, and carbon black that could be evaluated was not obtained. Therefore, the value of the amount of the raw material oil in the production conditions could not be confirmed. The measurement of various characteristics of black and the test for blending carbon black described later into the rubber composition were not performed.

Hereinafter, various chemicals used in Examples and Comparative Examples will be described together.
NR: TSR20 (natural rubber)
High cis BR: BUNA-CB25 manufactured by LANXESS Co., Ltd. (rare earth BR synthesized using Nd catalyst, vinyl content: 0.7 mass%, cis content: 97 mass%)
Carbon black: Carbon black wax obtained by Production Examples 1 to 11: Ozoace 355 manufactured by Nippon Seiwa Co., Ltd.
Anti-aging agent 1: Antigen 6C (N-phenyl-N '-(1,3-dimethylbutyl) -p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd.
Anti-aging agent 2: Nocrack 224 (poly (2,2,4-trimethyl-1,2-dihydroquinoline)) manufactured by Ouchi Shinsei Chemical Co., Ltd.
Stearic acid: Stearic acid “椿” manufactured by NOF Corporation
Zinc oxide: Silver candy R made by Toho Zinc Co., Ltd.
5% oil-containing powder sulfur: HK-200-5 manufactured by Hosoi Chemical Co., Ltd. (vulcanizing agent, oil content 5% by mass)
Crosslinking agent: Vulcuren KA9188 (1,6-bis (N, N′-dibenzylthiocarbamoyldithio) hexane, LANXESS Co., Ltd., sulfur element content 28% by mass)
Vulcanization accelerator: Noxeller NS-G manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

[Examples and Comparative Examples]
[Production Method A]
(Base kneading process 1)
Using a 1.7 L Banbury mixer manufactured by Kobe Steel, the entire amount of NR and carbon black was kneaded for 4 minutes and discharged at 150 ° C. to obtain a master batch.
(Base kneading process 2)
To the obtained master batch, high cis BR and materials other than sulfur, vulcanization accelerator and KA9188 were added, kneaded for 4 minutes with the above Banbury mixer, and discharged at 150 ° C. to obtain a kneaded product. .
(Finish kneading process)
Sulfur, a vulcanization accelerator and KA9188 were added to the obtained kneaded product, kneaded with an open roll for 2 minutes, and discharged at 105 ° C. to obtain an unvulcanized rubber composition.
(Vulcanization process)
The obtained unvulcanized rubber composition was press vulcanized at 150 ° C. for 30 minutes to obtain a vulcanized rubber composition.

[Production Method B]
A vulcanized rubber composition was prepared in the same manner as in Production Method A, except that in the base kneading step 1, all the rubber components and carbon black were added.

The following evaluation was performed using the obtained vulcanized rubber composition. Each test result is shown in Tables 3-4.

(Abrasion resistance)
Using a Lambourn abrasion tester, the Lambourn abrasion amount was measured under the conditions of a temperature of 20 ° C., a slip ratio of 20% and a test time of 2 minutes. Further, the volume loss amount was calculated from the measured amount of lambourne wear, and the lamborn wear index of Comparative Example 1 or 4 was set to 100, and the volume loss amount of each formulation was displayed as an index according to the following formula (Lambourn wear index). It shows that it is excellent in abrasion resistance, so that a Lambourn abrasion index is large.
(Abrasion resistance index) = (Volume loss amount of Comparative Example 1 or 4) / (Volume loss amount of each formulation) × 100

(Low heat generation)
Using a viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho Co., Ltd.), the loss tangent (tan δ) of each formulation was measured under the conditions of a temperature of 50 ° C., an initial strain of 10%, and a dynamic strain of 2%. The tan δ of 4 was set to 100, and other blends were indexed by the following formula (rolling resistance index). The larger the index, the better the rolling resistance characteristics (low heat generation). A good index was determined when the index was 95 or higher.
(Rolling resistance index) = (tan δ of Comparative Example 1 or 4) / (tan δ of each formulation) × 100

From Tables 3 to 4, in the examples in which the specific carbon black of the present invention was blended with NR, high cis BR, and sulfur, the wear resistance could be improved while maintaining or improving the good low heat build-up. While low heat build-up can be achieved at high order, the performance was inferior when carbon black other than specified was used.

In particular, for example, in comparison with Comparative Example 1 and Example 1 and Comparative Examples 2 to 3, the rubber component is added to the blend of NR and Hicis BR compared to the addition of the specific carbon black to the blend of only NR. It has been clarified that the performance balance of wear resistance and rolling resistance (low exothermic property) is remarkably improved, and synergistically improved.

Claims (14)

A step of kneading a rubber component containing isoprene-based rubber and a high-cis butadiene rubber having a cis content of 90% by mass or more, one or more carbon blacks, and sulfur ; and
Using the rubber composition obtained by the step, including a step of producing a tread ,
At least one of the carbon blacks has an average boiling point T (° C.) and a specific gravity D (60/60 ° F.) when compared with water of 60 ° F. as a raw material oil for producing the carbon black. The manufacturing method of the pneumatic tire which has the said tread which is carbon black obtained using the raw material oil whose BMCI value calculated by the following formula | equation is 150 or less and whose aliphatic hydrocarbon ratio is 30 mass% or more.
BMCI = 48640 / (T + 273) + 473.7D-456.8 Carbon obtained by using at least one of the carbon blacks as a raw material oil for producing the carbon black having a BMCI value of 95 or more and an aliphatic hydrocarbon ratio of 60% by mass or less The method for producing a pneumatic tire according to claim 1, wherein the pneumatic tire is black. 3. The method for producing a pneumatic tire according to claim 1, wherein 10% by mass or more of the aliphatic hydrocarbon contained in the raw material oil is 10% by mass or more of an aliphatic hydrocarbon derived from an animal or vegetable oil or a modified product thereof. The method for producing a pneumatic tire according to claim 1, wherein the raw material oil contains tall oil. The method for producing a pneumatic tire according to claim 1, wherein the carbon black is carbon black produced by a furnace method . A pneumatic tire having a tread composed of a rubber composition containing isoprene-based rubber and a high-cis butadiene rubber having a cis content of 90% by mass or more, one or more carbon blacks, and sulfur,
At least one of the carbon blacks has a maximum frequency diameter (Dmod) of the distribution curve of the Stokes equivalent diameter as an aggregate characteristic of 43 to 79 nm, and the ratio of the half width ( ΔD50 ) of the distribution curve to Dmod ( ΔD50 / A pneumatic tire which is carbon black having a Dmod) of 0.78 to 2.5 . In 100% by mass of the rubber component, the content of the isoprene-based rubber is 35 to 95% by mass, and the content of the high-cis butadiene rubber is 5 to 65% by mass,
The method for producing a pneumatic tire according to any one of claims 1 to 5 , wherein the sulfur content is 0.5 to 1.6 parts by mass with respect to 100 parts by mass of the rubber component in the rubber composition. . The high-cis butadiene rubber, synthesized using a rare earth element-containing catalyst, a vinyl content of 1.0 mass% or less, more of claims 1 to 5 and 7 cis content is high cis-butadiene rubber least 95 mass% A method for producing a pneumatic tire according to claim 1 . In the rubber composition, described for 100 parts by mass of the rubber component, stearate, to any one of claims 1 to 5, 7 and 8 the total content of calcium stearate and fatty acid zinc is 2 to 6 parts by weight Method of manufacturing a pneumatic tire. Wherein the rubber composition, wherein the rubber component 100 parts by weight, oil content 7 parts by mass or less, claims the content of zinc oxide is from 1.5 to 3.99 parts by weight 1-5 and 7 the method of manufacturing a pneumatic tire according to any one of 1-9. In 100% by mass of the rubber component, the content of the isoprene-based rubber is 35 to 95% by mass, and the content of the high-cis butadiene rubber is 5 to 65% by mass,
The pneumatic tire according to claim 6, wherein the sulfur content is 0.5 to 1.6 parts by mass with respect to 100 parts by mass of the rubber component in the rubber composition. The pneumatic tire according to claim 6 or 11, wherein the high-cis butadiene rubber is a high-cis butadiene rubber having a vinyl content of 1.0 mass% or less and a cis content of 95 mass% or more. The air according to any one of claims 6, 11 and 12, wherein in the rubber composition, the total content of stearic acid, calcium stearate and fatty acid zinc is 2 to 6 parts by mass with respect to 100 parts by mass of the rubber component. Enter tire. In the rubber composition, the oil content is 7 parts by mass or less and the zinc oxide content is 1.5 to 3.99 parts by mass with respect to 100 parts by mass of the rubber component. The pneumatic tire according to any one of the above.