JP2012180447A - Rubber composition and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition in which fracture resistance, fatigue resistance, and cut resistance are improved with well balance while maintaining low heat buildup, and which is useful as a raw material of at least one place of a bead filler and a chafer pad, and to provide a pneumatic tire.SOLUTION: The rubber composition includes carbon black that satisfies the following (1)-(4): (1) the dibutyl phthalate (DBP) absorbed amount (ml/100g) is 90-180; (2) the difference between a BET specific surface area (BET5) (m/g) and an outer specific surface area (STSA) (m/g) is 5≤(BET5)-(STSA)≤12; (3) the ratio of a Stokes diameter (Dst) to a Stokes diameter distribution (ΔD-50 (half value width)) of the carbon black is 0.70≤(ΔD-50)/(Dst)≤1.10, and (4) the ratio of the BET specific surface area (BET5) (m/g) to an iodine absorbed amount (IA) (mg/g) is 1.05≤(BET5)/(IA)≤1.35.

Description

  The present invention is a rubber composition that contains a rubber component and carbon black and is useful as a raw material for at least one of a bead filler and a chacher pad of a pneumatic tire, and is resistant to breakage while maintaining low heat buildup. The present invention relates to a rubber composition and a pneumatic tire that have improved properties and fatigue resistance in a well-balanced manner and are excellent in durability.

  As shown in FIG. 1, a bead filler 2 disposed on the outer side in the tire radial direction of the bead wire 1 and a chacher pad 9 disposed on the outer side in the tire radial direction of the bead filler 2 are members disposed inside the tire. Therefore, it is easy to store heat during tire travel. For this reason, considering durability, it is indispensable for the bead filler and the chacher pad to reduce the heat generation of the rubber itself.

  As a general method for improving the low exothermic property of rubber, there is a method of reducing the amount of carbon black compounded in rubber as a reinforcing material. However, when the amount of carbon black is reduced, the fracture resistance and elastic modulus of the rubber are lowered, and the amount of deformation during tire running increases. For this reason, the fatigue deterioration of rubber tends to proceed, and as a result, the durability of the pneumatic tire tends to deteriorate. As for bead fillers, as a general method for improving bead durability, there is a method of blending an adhesive resin such as methylene acceptor such as resorcin, methylene donor such as hexamethylenetetramine, which forms strong adhesiveness. is there. However, when such an adhesive resin is blended in a large amount, the fracture resistance of the rubber decreases, and as a result, the durability of the pneumatic tire tends to deteriorate. Therefore, bead fillers and chacher pads are strongly required to improve in a balanced manner with fracture resistance and fatigue resistance while maintaining low heat generation.

In the following Patent Document 1, the loss on heating from 150 ° C. to 450 ° C. is 0.87% by mass or more, the toluene coloring permeability is 90% or more, and the nitrogen adsorption specific surface area (N ₂ SA) (m ² / g) and iodine A rubber composition containing carbon black having a ratio of 1.10 to 1.30 with the amount of adsorption (IA) (mg / g) and a processing aid that is at least one of a fatty acid ester and a fatty acid metal salt. It describes that both wear resistance and reduction of rolling resistance can be achieved. In Patent Document 2 below, the specific surface area (m ² / g) of cetyltriammonium (CTAB) is 115 to 145, and the ratio of DBP absorption (24M4DBP) (ml / 100 g) to CTAB is 0.75 to 0.00. 92, a rubber composition containing carbon black having a ratio of CTAB to IA of 0.97 to 1.25 and a specific coloring amount TINT (%) ≧ −46.787 (24M4DBP / CTAB) +168 It describes the point that it is possible to achieve both low temperature and low heat generation. In Patent Document 3 below, a rubber composition containing carbon black in which the ratio of N ₂ SA to IA is 1.20 to 1.30 and the difference between N ₂ SA and CTAB is adjusted to 5 or less is It describes that both wear and low heat build-up can be achieved. Further, in Patent Document 4 below, carbon having a CTAB of 120 or more, a compressed DBP absorption amount of 90 (ml / 100 g) or more, and a pore volume of 25 to 30 nm in the pore volume between aggregates is 30 ml / 100 g or more. It describes that the rubber composition containing black can achieve both wear resistance and low heat build-up.

  However, as a result of intensive studies by the present inventor, it is difficult to accurately grasp the degree of pores on the surface of the carbon black aggregate only by optimizing each index of carbon black noted in the above document. found. The degree of pores on the surface of the carbon black aggregate has a great influence on the low heat buildup and fracture resistance, so the carbon black used in the above documents has a particularly low heat buildup in bead fillers and chacher pads. It has been found that there is room for further improvement when attempting to achieve both the fracture resistance and the fracture resistance.

  In the following Patent Document 5, in the rubber portion of the upper soft bead filler, by replacing a part of carbon black with a bituminous coal pulverized product, an increase in viscosity of the raw rubber composition is suppressed, and processability is maintained. It is described that the low exothermic property of the upper soft bead filler is improved. Further, in Patent Document 6 below, in the rubber part of the belt cushion, by adding carbon black, zinc monomethacrylate and cyclic polysulfide without using silica together, an increase in the viscosity of the rubber composition as a raw material is suppressed. Further, it is described that the low exothermic property of the upper soft bead filler is improved while maintaining the workability. However, in these rubber compositions, it has been found that there is room for further improvement in the bead filler and the chacher pad, particularly when achieving both low heat buildup and fracture resistance.

JP 2009-40904 A JP 2000-344945 A JP 2007-231179 A JP-A-2005-334063 JP 2009-155483 A JP 2009-242581 A

  The present invention has been made in view of the above circumstances, and its purpose is to maintain a low exothermic property while improving fracture resistance, fatigue resistance, and cut resistance in a well-balanced manner. An object of the present invention is to provide a rubber composition useful as a raw material in at least one place, and a pneumatic tire including the rubber composition as a constituent member and having improved durability.

  In order to solve the above-mentioned problems, the present inventors diligently studied a method for accurately grasping the degree of pores on the surface of the carbon black aggregate. As a result, in the carbon black in which the difference between the BET specific surface area (BET5) and the external specific surface area (STSA) is within a specific range, the degree of pores on the surface of the carbon black aggregate is reduced in fracture resistance, fatigue resistance, and It has been found that it is particularly preferable for achieving both cut resistance and low heat generation. Further, in addition to BET5 and STSA, dibutyl phthalate (DBP) absorption amount, iodine adsorption amount (IA), and Stokes diameter (Dst) of carbon black, which have been conventionally used as indicators of carbon black characteristics, and By using a rubber composition that contains carbon black that is optimal in relation to the Stokes diameter distribution (ΔD-50 (half-value width)), the low heat build-up of the bead filler and the chacher pad is maintained and the fracture resistance is maintained. The present inventors have found that fatigue resistance and cut resistance can be improved in a balanced manner. The present invention has been made as a result of the above-described studies, and achieves the above-described object with the following configuration.

That is, the present invention is a rubber composition containing a rubber component and carbon black and serving as a raw material for at least one of a bead filler and a chacher pad, wherein the carbon black comprises the following (1) to (4): A rubber composition characterized by satisfying:
(1) Dibutyl phthalate (DBP) absorption (ml / 100 g) is 90 to 180,
(2) The difference between the BET specific surface area (BET5) (m ² / g) and the external specific surface area (STSA) (m ² / g) is 5 ≦ (BET5) − (STSA) ≦ 12,
(3) The ratio between the Stokes diameter (Dst) of the carbon black and the Stokes diameter distribution (ΔD-50 (half-value width)) is 0.70 ≦ (ΔD-50) / (Dst) ≦ 1.10. 4) The ratio between the BET specific surface area (BET5) (m ² / g) and the iodine adsorption amount (IA) (mg / g) relates to 1.05 ≦ (BET5) / (IA) ≦ 1.35.

  The rubber composition according to the present invention has (1) dibutyl phthalate (DBP) absorption (ml / 100 g) of carbon black of 90 to 180, so that it has fracture resistance, fatigue resistance, cut resistance and low heat generation. It is possible to balance the sex with a good balance. The DBP absorption amount is an index of the structure of the carbon black aggregate, and if the DBP absorption amount is below the range described in (1), the structure of the carbon black aggregate is too low, so that the rubber reinforcement is It tends to decrease and durability deteriorates. On the other hand, when the DBP absorption amount exceeds the range described in (1), the structure of the carbon black aggregate is too high, and thus the low heat build-up tends to deteriorate.

Further, the rubber composition according to the present invention has a difference between the carbon black (2) BET specific surface area (BET5) (m ² / g) and the external specific surface area (STSA) (m ² / g) of 5 ≦ ( BET5) − (STSA) ≦ 12. Since the BET specific surface area (BET5) and the external specific surface area (STSA) are both indices related to the specific surface area calculated based on the nitrogen absorption amount, the difference between the two is calculated, so that the carbon black aggregate surface The degree of pores can be accurately grasped.

  Since rubber molecules cannot enter the pores on the surface of the carbon black aggregate, the more pores, the weaker the bond between carbon black and rubber molecules. In the present invention, since the (BET5)-(STSA) relationship of carbon black satisfies the above (2), the degree of bonding between carbon black and rubber molecules is optimized, and as a result, fracture resistance, fatigue resistance and Cut resistance and low heat build-up can be achieved in a well-balanced manner.

  In the rubber composition according to the present invention, (3) the ratio of the Stokes diameter (Dst) of carbon black to the Stokes diameter distribution (ΔD-50 (half width)) is 0.70 ≦ (ΔD-50) / Since (Dst) ≦ 1.10, the fracture resistance, fatigue resistance, cut resistance and low heat build-up can be improved in a well-balanced manner. When (ΔD-50) / (Dst) is less than the range described in (3), the low heat build-up tends to deteriorate. On the other hand, when (ΔD-50) / (Dst) exceeds the range described in (3), any of the fracture resistance, fatigue resistance and cut resistance tends to deteriorate.

Furthermore, in the rubber composition according to the present invention, the ratio of (4) BET specific surface area (BET5) (m ² / g) and iodine adsorption amount (IA) (mg / g) of carbon black is 1.05 ≦ Since (BET5) / (IA) ≦ 1.35, the degree of bonding between carbon black and rubber molecules is optimized, and the fracture resistance, fatigue resistance, cut resistance and low heat build-up are improved in a well-balanced manner. be able to. (BET5) / (IA) is an index of the surface activity of the carbon black particles. When (BET5) / (IA) is below the range described in (4), the low heat build-up tends to deteriorate. is there. On the other hand, when (BET5) / (IA) exceeds the range described in (4), any of the fracture resistance, fatigue resistance and cut resistance tends to deteriorate.

In the rubber composition, the carbon black preferably has an external specific surface area (STSA) (m ² / g) of 75 to 170. STSA is an index of the specific surface area (particle size) of carbon black particles, and when STSA is less than 75, any of fracture resistance, fatigue resistance, and cut resistance tends to deteriorate. If it exceeds 1, the low exothermicity tends to deteriorate.

  The said rubber composition WHEREIN: It is preferable that the compounding quantity of the said carbon black is 30-70 mass parts with respect to 100 mass parts of said rubber components. In the rubber composition, the amount of the reinforcing filler other than the carbon black is preferably 0 to 10 parts by mass with respect to 100 parts by mass of the rubber component. When the blending amount of the filler other than carbon black and carbon black is below the above range, any of the fracture resistance, fatigue resistance and cut resistance tends to deteriorate. There is a tendency to get worse.

  The present invention also relates to a pneumatic tire using any one of the above rubber compositions in at least one of a bead filler and a chacher pad. As described above, the rubber composition according to the present invention has improved fracture resistance, fatigue resistance, cut resistance, and low heat build-up in a well-balanced manner. Therefore, a pneumatic tire provided with a bead filler and / or a chacher pad manufactured using such a rubber composition as a raw material is excellent in durability.

Tire meridian cross-sectional view showing an example of a pneumatic tire according to the present invention For each carbon black, a graph in which (BET5) / (IA) is plotted on the horizontal axis and (BET5)-(STSA) is plotted on the vertical axis.

  The rubber composition according to the present invention contains a rubber component and carbon black. In the present invention, it is preferable to contain a diene rubber as a rubber component.

  Examples of the diene rubber include natural rubber (NR), polyisoprene rubber (IR), styrene butadiene rubber (SBR), polybutadiene rubber (BR), butadiene rubber (SPB) containing syndiotactic-1,2-polybutadiene, A chloroprene rubber (CR), a nitrile rubber (NBR), etc. are mentioned, These can each be used individually or as a 2 or more types of blend. These exemplified diene rubbers are those having terminal modified as required (for example, terminal modified BR, terminal modified SBR, etc.), or modified to give desired characteristics (for example, modified). NR) can also be used. Regarding polybutadiene rubber (BR), in addition to those synthesized using a cobalt (Co) catalyst, a neodymium (Nd) catalyst, a nickel (Ni) catalyst, a titanium (Ti) catalyst, and a lithium (Li) catalyst, WO2007 What was synthesize | combined using the polymerization catalyst composition containing the metallocene complex as described in -129670 can also be used. In order to improve the fracture resistance, fatigue resistance and cut resistance in a well-balanced manner while maintaining the low exothermic property of the vulcanized rubber, it is preferable to use natural rubber as a main component among the diene rubbers. . Specifically, when the total amount of the rubber component is 100 parts by mass, the natural rubber is preferably contained in an amount of 90 parts by mass or more, more preferably 95 parts by mass or more. Is particularly preferably 100 parts by mass.

In the present invention, the greatest feature is that the carbon black to be used satisfies the following (1) to (4).
(1) Dibutyl phthalate (DBP) absorption (ml / 100 g) is 90 to 180,
(2) The difference between the BET specific surface area (BET5) (m ² / g) and the external specific surface area (STSA) (m ² / g) is 5 ≦ (BET5) − (STSA) ≦ 12,
(3) The ratio between the Stokes diameter (Dst) of the carbon black and the Stokes diameter distribution (ΔD-50 (half-value width)) is 0.70 ≦ (ΔD-50) / (Dst) ≦ 1.10. 4) The ratio of the BET specific surface area (BET5) (m ² / g) to the iodine adsorption amount (IA) (mg / g) is 1.05 ≦ (BET5) / (IA) ≦ 1.35.

  The carbon black satisfying the above (1) to (4) has a smaller degree of pores on the surface of the carbon black aggregate than the ISAF class (ASTM grade) carbon black usually used in the tire industry. The carbon black has a special aggregate distribution. In the present invention, by using such a rubber composition containing carbon black as a raw material, the fracture resistance, fatigue resistance, cut resistance and low heat build-up can be improved in a well-balanced manner. More specifically, fracture resistance, fatigue resistance and cut resistance comparable to rubber compositions containing ISAF class carbon black, and low heat buildup comparable to rubber compositions containing HAF class carbon black And can be realized.

The rubber composition according to the present invention preferably contains carbon black having an external specific surface area (STSA) (m ² / g) of 75 to 170. In this case, both wear resistance and low heat generation can be achieved in a balanced manner.

In particular, in the present invention, the carbon black dibutyl phthalate (DBP) absorption (ml / 100 g) is preferably 120 to 150, and the BET specific surface area (BET 5) (m ² / g) and the external specific surface area ( STSA) (m ² / g) is preferably 7 ≦ (BET5) − (STSA) ≦ 10, and the Stokes diameter (Dst) and Stokes diameter distribution (ΔD-50 (half width)) of carbon black )) Is preferably 0.75 ≦ (ΔD-50) / (Dst) ≦ 0.95, or the BET specific surface area (BET5) (m ² / g) and iodine adsorption amount (IA) ( mg / g) is preferably 1.10 ≦ (BET5) / (IA) ≦ 1.30. Moreover, in this invention, it is preferable that the external specific surface area (STSA) (m < ² > / g) of carbon black is 90-120.

Among the characteristic evaluation items of the carbon black, dibutyl phthalate (DBP) absorption (ml / 100 g) is JIS K6217-4, BET specific surface area (BET5) (m ² / g) and external specific surface area (STSA) (m ² / G) is JIS K6217-7, Stokes diameter (Dst) and Stokes diameter distribution (ΔD-50 (half-value width)) is JIS K6217-6, and iodine adsorption amount (IA) (mg / g) is JIS K6217-1. Measured according to the above.

  The rubber composition according to the present invention contains 30 to 70 parts by mass of carbon black satisfying the above (1) to (4) as an essential component with respect to 100 parts by mass of the rubber component. Moreover, 0-10 mass parts of reinforcing fillers other than carbon black are contained as an optional component with respect to 100 mass parts of the rubber component. In order to improve the fracture resistance, fatigue resistance, cut resistance, and low heat build-up in a well-balanced manner, the blending amount of carbon black is preferably 40 to 60 parts by mass, and reinforcing filling other than carbon black It is preferable that the compounding quantity of a material is 0-20 mass parts, and it is more preferable that it is 0-10 mass parts.

  In the present invention, silica, calcium carbonate, magnesium carbonate, magnesium oxide, titanium oxide, talc, clay, alumina, sericite, or the like can be used as a filler other than carbon black. In addition, when using a silica, it is preferable to use a silane coupling agent together.

  In the rubber composition according to the present invention, a methylene acceptor and a methylene donor may be blended in order to improve the adhesion with the carcass ply, the chacher, and the sidewall. Adhesiveness with the carcass ply, the chacher, and the sidewall can be enhanced by the curing reaction between the hydroxyl group of the methylene acceptor and the methylene group of the methylene donor.

  As the methylene acceptor, a phenolic compound or a phenolic resin obtained by condensing a phenolic compound with formaldehyde is used. Such phenolic compounds include phenol, resorcin or alkyl derivatives thereof. Alkyl derivatives include methyl group derivatives such as cresol and xylenol, and derivatives with long chain alkyl groups such as nonylphenol and octylphenol. The phenol compound may contain an acyl group such as an acetyl group as a substituent.

  In addition, phenolic resins obtained by condensing phenolic compounds with formaldehyde include resorcin-formaldehyde resins, phenolic resins (phenol-formaldehyde resins), cresol resins (cresol-formaldehyde resins), and formaldehyde composed of a plurality of phenolic compounds. Resin etc. are included. These are uncured resins that have liquid or heat fluidity.

  Among these, from the viewpoint of compatibility with the rubber component and other components, the density of the resin after curing, and the reliability, the methylene acceptor is preferably resorcin or a resorcin derivative, and in particular, resorcin or resorcin Alkylphenol-formalin resins are preferred. As a compounding quantity of these phenol compounds or phenol-type resin, it is preferable that it is 0.1-10 mass parts with respect to 100 mass parts of rubber components, More preferably, it is 0.5-5 mass parts.

  As the methylene donor, hexamethylenetetramine or a melamine derivative is used. As such a melamine derivative, for example, methylol melamine, a partially etherified product of methylol melamine, a condensate of melamine, formaldehyde, and methanol is used, and among them, hexamethoxymethyl melamine is particularly preferable. As a compounding quantity of a hexamethylenetetramine or a melamine derivative, it is preferable that it is 0.1-10 mass parts with respect to 100 mass parts of rubber components, More preferably, it is 0.5-5 mass parts.

  The rubber composition according to the present invention includes sulfur, a silane coupling agent, zinc white, stearic acid, a vulcanization accelerator, a vulcanization accelerator, a vulcanization together with the rubber component, fillers such as carbon black and silica. A compounding agent usually used in the rubber industry such as a retarder, an anti-aging agent, a softening agent such as wax or oil, or a processing aid can be appropriately blended and used within a range not impairing the effects of the present invention.

  Sulfur should just be normal sulfur for rubber | gum, For example, powder sulfur, precipitated sulfur, insoluble sulfur, highly dispersible sulfur etc. can be used. When the rubber physical properties and durability after vulcanization are taken into consideration, the compounding amount of sulfur with respect to 100 parts by mass of the rubber component is preferably 2 to 7 parts by mass in terms of sulfur content.

  As the vulcanization accelerator, sulfenamide vulcanization accelerator, thiuram vulcanization accelerator, thiazole vulcanization accelerator, thiourea vulcanization accelerator, guanidine vulcanization, which are usually used for rubber vulcanization. Vulcanization accelerators such as accelerators and dithiocarbamate vulcanization accelerators may be used alone or in admixture as appropriate. When the rubber physical properties and durability after vulcanization are taken into consideration, the blending amount of the vulcanization accelerator with respect to 100 parts by mass of the rubber component is preferably 0.1 to 5 parts by mass.

  As an anti-aging agent, an aromatic amine-based anti-aging agent, an amine-ketone anti-aging agent, a monophenol anti-aging agent, a bisphenol anti-aging agent, a polyphenol anti-aging agent, dithiocarbamic acid, which are usually used for rubber Anti-aging agents such as a salt-based anti-aging agent and a thiourea-based anti-aging agent may be used alone or in an appropriate mixture. In consideration of rubber physical properties and durability, the blending amount of the anti-aging agent with respect to 100 parts by mass of the rubber component is preferably 0.1 to 5 parts by mass.

  The rubber composition according to the present invention comprises the above rubber component, fillers such as carbon black and silica, and optionally sulfur, silane coupling agent, zinc white, stearic acid, vulcanization accelerator, and vulcanization accelerator. Additives usually used in the rubber industry such as vulcanization retarders, anti-aging agents, softeners such as waxes and oils, processing aids, etc. are used in the normal rubber industry such as Banbury mixers, kneaders, rolls, etc. It can be obtained by kneading using a kneader.

  In addition, the blending method of each of the above components is not particularly limited, and a blending component other than a vulcanizing component such as sulfur and a vulcanization accelerator is previously kneaded to obtain a master batch, and the remaining components are added and further kneaded. , Rubber component and carbon black only in advance as a kneading masterbatch, the remaining components are added and further kneaded, each component is added in any order and kneaded, all components are added simultaneously and kneaded, etc. Either of these may be used. In addition, when making a rubber component and carbon black into a masterbatch beforehand, you may use the wet masterbatch obtained by mixing carbon black in rubber latex.

  The rubber composition according to the present invention is useful as a raw material for at least one of a bead filler and a chacher pad of a pneumatic tire. As shown in FIG. 1, the pneumatic tire according to the present invention includes a pair of bead wires 1, a bead filler 2 disposed on the outer side of the bead wire 1 in the tire radial direction, a bead wire 1 and a bead filler 2. A sidewall 3 extending radially outward; a tread 4 connected to each tire radial outer end of the sidewall 3; and a carcass ply 5 whose ends are wound up from the inner side in the tire width direction by a pair of bead wires 1; And a belt 6 composed of a plurality of belt plies arranged on the outer peripheral side (outer in the tire radial direction) of the carcass ply 5. The tread 4 may be composed of a single rubber portion, or may be composed of two layers of a cap tread on the ground contact surface side and a base tread on the inner side in the tire radial direction. In the example shown in FIG. 1, the bead filler 2 has a two-layer structure of an upper bead filler 2 a and a lower bead filler 2 b that is harder than the bead filler 2 a and is in contact with the bead wire 1. The rubber composition according to the present invention is useful as a raw material for the upper bead filler when the bead filler has a two-layer structure, and is useful as a raw material for the entire one-layer structure when the bead filler has a single-layer structure. .

  On the inner side in the tire radial direction of the bead wire 1 and the bead filler 2, a chacher 7 and a rim strip 8 are arranged via a carcass ply 5, and the rim strip 8 sits in contact with a tire rim (not shown). On the outer side of the bead filler 2 in the tire radial direction, a chacher pad 9 is disposed so as to sandwich the chacher 7. On the other hand, an inner liner 10 for maintaining air pressure is disposed on the inner peripheral side of the carcass ply 5. A shoulder pad 11 is disposed on the end side of the belt 6 in the tire radial direction, and a belt edge filler 12 is disposed between a plurality of belt ply end portions.

  The rubber composition according to the present invention is used to manufacture at least one of the bead filler 2 and the chacher 7 by a known facility such as a rubber extruder, and after molding an unvulcanized tire including these, it is known. By vulcanizing according to the above method, it is possible to produce a pneumatic tire including a bead filler and / or a chacher in which fracture resistance, fatigue resistance and cut resistance are improved in a well-balanced manner while maintaining low heat generation. it can.

  Hereinafter, examples and the like specifically showing the configuration and effects of the present invention will be described. The evaluation items in Examples and the like were evaluated based on the following evaluation conditions for rubber samples obtained by heating and vulcanizing each rubber composition at 150 ° C. for 30 minutes.

(1) Rubber hardness Based on JIS K6253, it evaluated by the rubber hardness (durometer A type) in 23 degreeC.

(2) Breaking strength (breaking resistance)
In accordance with JIS K6251, a sample was prepared using dumbbell No. 3 and subjected to a tensile test, and the breaking strength at the time of breaking the sample was measured. The larger the breaking strength, the better the fracture resistance.

(3) Tear strength (cut resistance)
Evaluation was performed in accordance with JIS K6252. The measured value of Comparative Example 1 is set to 100 and displayed by index evaluation, and the larger the value, the better the cut resistance.

(4) Low exothermic property (tan δ)
Evaluation was performed based on tan δ values measured at an initial strain of 15%, a dynamic strain of ± 2.5%, a frequency of 10 Hz, and a temperature of 60 ° C. using a viscoelastic spectrometer manufactured by UBM. It means that it is excellent in low exothermic property, so that a numerical value is small.

(Preparation of rubber composition)
In accordance with the formulation of Table 1, the rubber compositions of Examples 1 to 9 and Comparative Examples 1 and 2 were blended and kneaded using a normal Banbury mixer to prepare a rubber composition. Each compounding agent described in Table 1 is shown below (in Table 1, the compounding amounts of carbon black and each compounding agent are shown in terms of parts by mass with respect to 100 parts by mass of the rubber component). Carbon black was produced by the following production method.

a) Rubber component Natural rubber (NR) "RSS # 3"
b) Zinc Hana “Zinc Hana 3” (Mitsui Mining & Mining)
c) Anti-aging agent “Sant Flex 6PPD” (manufactured by Flexis)
d) Insoluble sulfur “Christex HS OT-20” (manufactured by Flexis)
e) Vulcanization accelerator “Noxeller NS-P (NS)” (manufactured by Ouchi Shinsei Chemical Co., Ltd.)
f) Silica “Nipseal AQ” (made by Nippon Silica Kogyo Co., Ltd.)
g) Resorcin-alkylphenol-formalin resin “SUMIKANOL 620” (manufactured by Sumitomo Chemical Co., Ltd.)
h) Hexamethoxymethylmelamine “Cylettes 963L” (Mitsui Cytec)
i) Oil (made by Japan Energy)

(Method for producing carbon black)
A combustion chamber having a tangential air supply port at the furnace head and a combustion burner mounted in the furnace axis direction, a multistage narrow-diameter reaction chamber having a feed oil injection nozzle coaxially connected to the combustion chamber, and a wide chamber The carbon black mixed gas temperature is 1000 to 2200 ° C., and the ratio of the air amount (Nm ³ / h) to the raw material introduction amount (kg / h) is 2.0 using an oil furnace having a diameter reaction chamber. ~ 6.0, the ratio of the air amount and the fuel introduction amount (kg / h) is appropriately adjusted within the range of 15.0 to 30.0, and the ratio of the raw material introduction amount and the fuel introduction amount is within the range of 3.0 to 8.0. In order to obtain carbon black having a specified specific surface area, structure, surface activity, aggregate distribution, and degree of pores, the following i) to iv):
i) Split introduction of feedstock,
ii) oxygen gas addition,
iii) reaction time 0.002 to 0.05 (seconds),
iv) Drying temperature 180-250 (° C),
Were used alone or in combination to produce carbon blacks (A) to (E) shown in Table 1. Table 2 shows the carbon black characteristics of the carbon blacks (A) to (E). Moreover, about carbon black (A)-(E), the graph which plotted (BET5) / (IA) on the horizontal axis and (BET5)-(STSA) on the vertical axis | shaft is shown in FIG.

Moreover, the carbon black commercial item as described below was used as carbon black (F)-(G). Table 2 shows the carbon black characteristics of carbon blacks (F) to (G). Moreover, about carbon black (F)-(G), the graph which plotted (BET5) / (IA) on the horizontal axis and (BET5)-(STSA) on the vertical axis | shaft is shown in FIG.
g) Carbon Black (F) “Seast KH (HAF)” manufactured by Tokai Carbon Co., Ltd. h) Carbon Black (G) “Seast 6 (ISAF)” manufactured by Tokai Carbon Co., Ltd.

  From the results of Table 1, in Examples 1 to 9 containing any one of carbon blacks (A) to (E), the fracture resistance, fatigue resistance, and cut resistance are improved while maintaining low heat generation. You can see that On the other hand, in Comparative Examples 1 and 2 containing carbon black (F) or (G), since the used carbon black does not satisfy any of the above conditions (1) to (4), fracture resistance, fatigue resistance It turns out that it deteriorates in any of a characteristic, cut resistance, and low exothermic property.

Claims (5)

A rubber composition containing a rubber component and carbon black and serving as a raw material for at least one of a bead filler and a chacher pad,
A rubber composition characterized in that the carbon black satisfies the following (1) to (4):
(1) Dibutyl phthalate (DBP) absorption (ml / 100 g) is 90 to 180,
(2) The difference between the BET specific surface area (BET5) (m ² / g) and the external specific surface area (STSA) (m ² / g) is 5 ≦ (BET5) − (STSA) ≦ 12,
(3) The ratio between the Stokes diameter (Dst) of the carbon black and the Stokes diameter distribution (ΔD-50 (half-value width)) is 0.70 ≦ (ΔD-50) / (Dst) ≦ 1.10. 4) The ratio of the BET specific surface area (BET5) (m ² / g) to the iodine adsorption amount (IA) (mg / g) is 1.05 ≦ (BET5) / (IA) ≦ 1.35. ^2. The rubber composition according to claim 1, wherein the carbon black has an external specific surface area (STSA) (m ² / g) of 75 to 170. 3.   The rubber composition according to claim 1 or 2, wherein a blending amount of the carbon black is 30 to 70 parts by mass with respect to 100 parts by mass of the rubber component.   The rubber composition according to any one of claims 1 to 3, wherein a compounding amount of the reinforcing filler other than the carbon black is 0 to 10 parts by mass with respect to 100 parts by mass of the rubber component.   A pneumatic tire using the rubber composition according to any one of claims 1 to 4 in at least one of a bead filler and a chacher pad.

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