JP6011152B2 - Rubber composition for tire - Google Patents

Description

  The present invention provides a rubber composition for a tire that improves the handling stability when used in a tire to a level higher than the conventional level while blending carbon black with controlled colloidal characteristics to reduce rolling resistance.

  In recent years, as a required performance for pneumatic tires, it is required to have excellent steering stability and excellent fuel efficiency. In particular, improving fuel efficiency is becoming more and more important with increasing interest in global environmental issues. In order to improve fuel efficiency, it is known to reduce rolling resistance. For this reason, heat generation of the rubber composition constituting the pneumatic tire is suppressed to reduce the rolling resistance when the tire is formed. Generally, 60 ° C. tan δ by dynamic viscoelasticity measurement is used as an index of exothermic property of the rubber composition. The smaller the tan δ (60 ° C.) of the rubber composition, the smaller the exothermic property.

  As a method for reducing the tan δ (60 ° C.) of the rubber composition, Patent Document 1 proposes blending silica and a silane coupling agent with a rubber component containing a modified butadiene. However, there is a strong demand for further reducing rolling resistance in recent years and a high balance between low rolling resistance, steering stability, and wear resistance, and the above-mentioned performance is improved not only from silica-containing systems but also from carbon black. It is hoped that.

  As a method for reducing the tan δ (60 ° C.) of the rubber composition with carbon black, for example, the amount of carbon black is reduced, the specific surface area of carbon black is increased, or the size of the aggregate (aggregate) is reduced. Can be mentioned. However, such a method has a problem that mechanical properties such as rubber hardness and elastic modulus are lowered, and steering stability is lowered when the tire is formed.

  Patent Document 2 mainly reduces the heat generation of a rubber composition by blending carbon black with adjusted specific surface area (BET specific surface area, CTAB specific surface area, iodine adsorption index IA), DBP structure value, Stokes diameter Dst, etc. Propose to do. However, in this rubber composition, the effect of achieving both low exothermic property and steering stability of the rubber composition is not always sufficient, and further improvement has been demanded.

  On the other hand, Patent Document 3 proposes that a cashew modified phenolic resin and a methylene donor are blended with a diene rubber to reduce the temperature dependence of the rubber elastic modulus and suppress the change in steering stability performance. However, although this rubber composition is effective in suppressing changes in steering stability performance when used as a tire, the effect of reducing rolling resistance is not always sufficient, and further improvement has been demanded.

JP 2010-132872 A Special table 2004-519552 gazette Japanese Patent No. 4458186

  An object of the present invention is to provide a rubber composition for a tire that improves the handling stability when it is made into a tire, while reducing rolling resistance by blending carbon black with controlled colloidal characteristics. It is in.

In the tire rubber composition of the present invention that achieves the above object, a total of 1 to 50 parts by weight of a novolac type phenol resin and a methylene donor is blended with 100 parts by weight of a diene rubber, and 30 to 100 parts by weight of carbon black. A rubber composition for a tire containing 60 to 100 parts by weight of a reinforcing filler containing a part, wherein a mode diameter Dst in a mass distribution curve of the Stokes diameter of the carbon black aggregate is 145 nm or more, a nitrogen adsorption specific surface area N ₂ SA is 45~70m ² / g, the ratio N ₂ SA / IA of the nitrogen adsorption specific surface area N ₂ SA for iodine adsorption amount IA (units mg / g) is Ri der 1.00 to 1.40, the carbon when black N ₂ SA is less than 55m ² / g, the mode diameter Dst Stokes diameter is not more 180nm or less, of the carbon black N ₂ SA When more than 55m ² / g, the mode diameter Dst of the Stokes diameter is characterized by satisfying the relation of the following equation (1).
Dst <1979 × (N ₂ SA) ^−0.61 (1)
(In the formula, Dst is the mode diameter (nm) in the mass distribution curve of the Stokes diameter of the aggregate, and N ₂ SA is the nitrogen adsorption specific surface area (m ² / g).)

The rubber composition for tires of the present invention contains 1 to 50 parts by weight of a novolac type phenol resin and a methylene donor in total with 100 parts by weight of a diene rubber, and a mass distribution of Stokes diameters of carbon black aggregates. mode diameter Dst in the curve is above 145 nm, a nitrogen adsorption specific surface area N ₂ SA is 45~70m ² / g, the ratio N ₂ SA / IA of the nitrogen adsorption specific surface area N ₂ SA for iodine adsorption amount IA (units mg / g) 60 to 100 parts by weight of reinforcing filler containing 30 to 100 parts by weight of carbon black having a 1.00 to 1.40 is blended, so that tan δ (60 ° C.) of the rubber composition is reduced and rolled. While reducing the resistance, the handling stability when the tire is made can be improved to a level higher than the conventional level.

In the present invention, the upper limit of the mode diameter Dst Stokes diameter of the carbon black, as described above, it is Dst is 180nm or less when N ₂ SA is less than 55m ² / g, N ₂ SA is 55m ² / Dst when more than g is to satisfy the relationship of equation (1) below.
Dst <1979 × (N ₂ SA) ^−0.61 (1)
(In the formula, Dst is the mode diameter (nm) in the mass distribution curve of the Stokes diameter of the aggregate, and N ₂ SA is the nitrogen adsorption specific surface area (m ² / g).)

  The novolac phenol resin is preferably a resin modified with cashew oil.

  The pneumatic tire in which the bead filler is constituted by the tire rubber composition of the present invention can improve steering stability to a level higher than the conventional level while reducing rolling resistance and improving fuel efficiency.

  A pneumatic tire comprising a rubber reinforcing layer having a crescent-shaped cross section of the left and right sidewall portions of a run-flat tire with the rubber composition for tires of the present invention, while reducing rolling resistance during normal running and improving fuel economy performance, Steering stability can be improved beyond the conventional level. Further, during run flat running, the run flat running performance is excellent and the durability of the rubber reinforcing layer having a crescent-shaped cross section in the sidewall portion is suppressed.

It is sectional drawing of the tire meridian direction which shows an example of embodiment of the pneumatic tire using the rubber composition for tires of this invention.

  The tire to which the rubber composition for a tire of the present invention is applied is not particularly limited as long as it is a pneumatic tire. For example, a pneumatic tire for passenger cars, a pneumatic tire for trucks and buses, a pneumatic run flat tire, etc. Can be used. Examples of the pneumatic run-flat tire include a side-reinforced run-flat tire in which a crescent-shaped rubber reinforcement layer in the left and right sidewall portions is formed. FIG. 1 is a half cross-sectional view in the tire meridian direction showing an example of a side reinforcing type run-flat tire.

  In FIG. 1, the run flat tire has a tread portion 1, a sidewall portion 2, and a bead portion 3, and a two-ply carcass 6 is interposed between a pair of left and right bead cores 4 and 4, and a bead core 4 and a bead filler 5. A radial structure in which a belt layer 7 composed of a plurality of plies (2 plies in the figure) is disposed over the circumference of the tire on the outer peripheral side of the carcass 6 of the tread portion 1 so as to be folded back from the inside to wrap the tire It has become. An inner liner layer 9 is disposed on the innermost peripheral side of the tire. In addition, rubber reinforcing layers 8 and 8 having a crescent-shaped cross section are inserted inside the carcass 6 in the left and right sidewall portions 2 and 2, respectively. The position where the rubber reinforcing layer having a crescent-shaped cross section is inserted is not limited to the illustrated example, and may be inserted between the two carcass 6.

  The rubber composition for tires of the present invention can be suitably used for the bead filler 5 and / or the rubber reinforcing layer 8 having a crescent-shaped cross section. In addition, it can use suitably also for the bead filler of pneumatic tires other than a run flat tire.

  In the rubber composition for tires of the present invention, examples of the diene rubber include natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber and the like that are usually used in tire rubber compositions. Of these, natural rubber, isoprene rubber, butadiene rubber, and styrene-butadiene rubber are preferable. These diene rubbers can be used alone or as any blend.

  The rubber composition for tires of the present invention necessarily contains a novolac type phenol resin and a methylene donor. By including the novolac type phenol resin and the methylene donor, the rubber hardness and elastic modulus of the rubber composition can be increased, and the steering stability when the tire is formed can be maintained and improved.

  In the present invention, as the novolac type phenolic resin, those usually compounded in a tire rubber composition can be used. Examples thereof include those produced by a condensation reaction of phenol, cresol, resorcin, tert-butylphenol phenols or a mixture thereof with formaldehyde in the presence of an acid catalyst such as hydrochloric acid or oxalic acid. In addition, novolak-type modified phenol resins obtained by modifying novolak-type phenol resins with oils can be mentioned. Examples of the oils used for the modification of novolak-type phenol resins include rosin oil, tall oil, cashew oil, and linol. Examples include acids, oleic acid, and linolenic acid. Of these, phenol resins and cashew-modified phenol resins are preferable. These novolac-type phenol resins can be used alone or in any mixture.

  A commercial item can be used for these novolak type phenol resins. Examples of the phenol resin include Sumikalol 620 manufactured by Sumitomo Chemical Co., Ltd. Examples of cashew-modified phenolic resins include Sumitomo Resin PR-YR-170 and PR-150 manufactured by Sumitomo Bakelite Co., Ltd., Phenolite A4-1419 manufactured by Dainippon Ink & Chemicals, Inc., and the like.

  In the present invention, a methylene donor is used as a curing agent for the above-described novolak type phenol resin. Examples of methylene donors include hexamethylenetetramine and methylolated melamine derivatives. Examples of methylolated melamine derivatives include hexamethoxymethylol melamine, pentamethoxymethylol melamine, hexamethoxymethyl melamine, pentamethoxymethyl melamine, hexaethoxymethyl melamine, hexakis- (methoxymethyl) melamine, N, N ', N "-trimethyl- N, N ', N "-trimethylolmelamine, N, N', N" -trimethylolmelamine, N-methylolmelamine N, N '-(methoxymethyl) melamine, N, N', N "-tributyl-N , N ′, N ″ -trimethylolmelamine, etc. Among them, hexamethylenetetramine, hexamethoxymethylolmelamine, pentamethoxymethylolmelamine, hexamethoxymethylmelamine, and pentamethoxymethylmelamine are preferable. These can be used alone or in combination.

  Examples of hexamethylenetetramine include Sunseller HT-PO manufactured by Sanshin Chemical Industry Co., Ltd. Examples of hexamethoxymethylmelamine (HMMM) include CYREZ 964RPC manufactured by CYTEC INDUSTRIES. Examples of pentamethoxymethylmelamine (PMMM) include BARA CHEMICAL Co. , LTD. An example is Sumikanol 507A manufactured by the company.

  In the present invention, the compounding amount of the novolac phenol resin and the methylene donor is 1 to 50 parts by weight, preferably 3 to 35 parts by weight, based on 100 parts by weight of the diene rubber. To. In particular, when used as a bead filler in a pneumatic tire, the amount is preferably 10 to 35 parts by weight. When the total amount of the novolak type phenol resin and the methylene donor is less than 1 part by weight, the rubber hardness and elastic modulus of the rubber composition cannot be sufficiently increased. On the other hand, when the total amount of the novolak type phenolic resin and the methylene donor exceeds 50 parts by weight, the exothermic property of the rubber composition increases, and the rolling resistance when the tire is formed deteriorates.

  The weight ratio of the novolak type phenolic resin and the methylene donor used in the present invention is preferably 3/1 to 30/1, more preferably 5/1 to 20/1, for the novolak type phenolic resin / methylene donor. Good. If the weight ratio of novolak type phenol resin / methylene donor is less than 3/1, the amount of methylene donor is too much than the amount of phenol resin, so that the methylene donor remains and the crosslink density of the phenol resin becomes too high and brittle. Destruction is likely to occur. On the other hand, if the weight ratio of novolak type phenol resin / methylene donor is larger than 30/1, the amount of methylene donor is insufficient, and the crosslinking density of the resin is too low to be effective.

In the tire rubber composition of the present invention, the ratio N of the nitrogen adsorption specific surface area to the mode diameter Dst, DBP absorption, nitrogen adsorption specific surface area N ₂ SA and iodine adsorption IA in the Stokes diameter mass distribution curve of a specific aggregate. ₂ By blending a new carbon black with limited SA / IA, maintaining the steering stability when used as a tire while reducing the tan δ (60 ° C) of the rubber composition using carbon black with a large particle size・ I can improve. The compounding amount of the carbon black is 30 to 100 parts by weight, preferably 50 to 100 parts by weight with respect to 100 parts by weight of the diene rubber. When the blending amount of the carbon black is less than 30 parts by weight, steering stability when used as a tire is deteriorated. On the other hand, when the blending amount of the carbon black exceeds 100 parts by weight, tan δ (60 ° C.) is increased, and steering stability when the tire is formed is deteriorated.

The carbon black that is always used in the present invention has a nitrogen adsorption specific surface area N ₂ SA of 45 to 70 m ² / g, preferably 48 to 62 m ² / g. When N ₂ SA is less than 45 m ² / g, steering stability when used as a tire is lowered. When N ₂ SA exceeds 70 m ² / g, tan δ (60 ° C.) increases. N ₂ SA shall be measured according to JIS K6217-2.

The ratio N ₂ SA / IA of the nitrogen adsorption specific surface area N ₂ SA to the iodine adsorption amount IA (unit: mg / g) of the carbon black is 1.00 to 1.40, preferably 1.01 to 1.27. To do. When the colloidal characteristic ratio N ₂ SA / IA is less than 1.00, tan δ (60 ° C.) of the rubber composition cannot be reduced. On the other hand, if the ratio N ₂ SA / IA exceeds 1.40, the surface activity is too high and the mixing property is deteriorated. The iodine adsorption amount IA is measured according to JIS K6217-1.

  The DBP absorption amount of this carbon black is preferably 100 to 160 ml / 100 g, more preferably 110 to 150 ml / 100 g. When the DBP absorption amount is less than 100 ml / 100 g, the reinforcing property is excessively lowered, so that the steering stability when the tire is made is lowered. Further, since the mixing processability of the rubber composition is lowered and the dispersibility of the carbon black is deteriorated, the reinforcing performance of the carbon black cannot be sufficiently obtained. If the DBP absorption amount exceeds 160 ml / 100 g, the steering stability when the tire is made deteriorates. In addition, workability deteriorates due to an increase in viscosity. The DBP absorption amount shall be measured according to JIS K6217-4 oil absorption amount A method.

  The carbon black used in the present invention has a mode diameter Dst (hereinafter sometimes referred to as “Stokes diameter Dst”) in the mass distribution curve of the Stokes diameter of the aggregates of 145 nm or more, preferably 150 nm or more. By setting the Stokes diameter Dst to 145 nm or more, it is possible to maintain and improve the steering stability when the tire is made while reducing the tan δ (60 ° C.) of the rubber composition. In the present invention, the mode diameter Dst in the mass distribution curve of the Stokes diameter of the aggregate refers to the mode diameter of the maximum frequency in the mass distribution curve of the Stokes diameter of the aggregate obtained by centrifugal sedimentation of carbon black. In the present invention, Dst is measured according to the method for obtaining the aggregate distribution by JIS K6217-6 disc centrifugal light sedimentation method.

The upper limit of the Stokes diameter Dst is determined in relation to the nitrogen adsorption specific surface area N ₂ SA of carbon black. That is, when the N ₂ SA of the carbon black is less than 45 m ² / g or more 55m ² / g, the Stokes diameter Dst is Ru der 1 80 nm or less. And when the N ₂ SA of the carbon black is less than 55m ² / g to greater than 70m ² / g, the Stokes diameter Dst is satisfying a relation of the following Symbol formula (1).
Dst <1979 × (N ₂ SA) ^−0.61 (1)
(In Formula (1), Dst is the mode diameter (nm) in the mass distribution curve of the Stokes diameter of the aggregate, and N ₂ SA is the nitrogen adsorption specific surface area (m ² / g).)

  By making the upper limit of the Stokes diameter Dst of carbon black within the above-described range, both productivity and cost of carbon black can be achieved.

That is, in the present invention, specific carbon black having a ratio N ₂ SA / IA of 1.00 to 1.40 and a Stokes Dst of 145 nm or more is used in a range of N ₂ SA of 45 to 70 m ² / g. Such carbon black has a large Stokes diameter of the aggregate, reduces the tan δ (60 ° C.) of the rubber composition, and enhances the reinforcing performance against the rubber. Can be improved.

  Carbon black having the colloidal characteristics described above is, for example, feedstock introduction conditions, fuel oil and feedstock supply rate, fuel oil combustion rate, reaction time (combustion from the last feedstock introduction position to reaction stoppage) in the carbon black production furnace. The production conditions such as gas residence time) can be adjusted.

  In the tire rubber composition of the present invention, 60-100 parts by weight of the reinforcing filler containing carbon black described above is blended with respect to 100 parts by weight of the diene rubber. When the compounding amount of the reinforcing filler is less than 60 parts by weight, the reinforcing property of the rubber composition cannot be sufficiently obtained. Moreover, when the compounding quantity of a reinforcing filler exceeds 100 weight part, rolling resistance when it is set as a tire will become large.

  As the reinforcing filler, in addition to the above-mentioned specific carbon black, for example, carbon black other than the above-mentioned specific carbon black, silica, clay, mica, talc, calcium carbonate, aluminum oxide, titanium oxide, activated zinc white, etc. It can be illustrated. Of these, carbon black, silica, and clay other than the specific carbon black described above are preferable. Carbon blacks other than the specific carbon black described above do not satisfy at least one of the specific requirements for the specific carbon black described above.

  In the rubber composition of the present invention, when silica is compounded as a reinforcing filler, the compounding amount of silica is 0 to 70 parts by weight, more preferably 0 to 50 parts by weight with respect to 100 parts by weight of the rubber component. By setting the blending amount of silica in such a range, the low exothermic property of the rubber composition and the handling stability when made into a tire are compatible. When the compounding amount of silica exceeds 70 parts by weight, durability when used as a tire is lowered.

Silica preferably has a CTAB specific surface area of 80 to 300 m ² / g. If the CTAB of silica is less than 80 m ² / g, the reinforcing property to the rubber composition is insufficient, and the durability when the tire is made is insufficient. On the other hand, if the CTAB of silica exceeds 300 m ² / g, the heat generation is deteriorated and the rolling resistance is increased when the tire is formed. Note that the CTAB specific surface area of silica is determined according to ISO 9277.

  The silica used in the present invention is not limited as long as it has the above-described characteristics, and may be appropriately selected from those manufactured, or may be manufactured to have the above-described characteristics by a normal method. . As the type of silica, for example, wet method silica, dry method silica, or surface-treated silica can be used.

  In the rubber composition of the present invention, when silica is used, a silane coupling agent may be blended together with silica, so that the dispersibility of silica can be improved and the reinforcement with the rubber component can be further enhanced. When mix | blending a silane coupling agent, Preferably it is 3-20 weight% with respect to a silica compounding quantity, More preferably, it is good to mix | blend 5-15 weight%. When the compounding amount of the silane coupling agent is less than 3% by weight of the silica weight, the effect of improving the dispersibility of the silica cannot be sufficiently obtained. Moreover, when the compounding quantity of a silane coupling agent exceeds 20 weight%, silane coupling agents will condense and it will become impossible to acquire a desired effect.

  The silane coupling agent is not particularly limited, but a sulfur-containing silane coupling agent is preferable, for example, bis- (3-triethoxysilylpropyl) tetrasulfide, bis- (3-triethoxysilylpropyl) disulfide. Examples thereof include sulfide, 3-trimethoxy 9510 silylpropylbenzothiazole tetrasulfide, γ-mercaptopropyltriethoxysilane, 3-octanoylthiopropyltriethoxysilane, and the like.

  Various additives commonly used in tire rubber compositions, such as vulcanization or crosslinking agents, vulcanization accelerators, various inorganic fillers, various oils, anti-aging agents, and plasticizers, for tire rubber compositions These additives can be kneaded by a general method to form a rubber composition, which can be used for vulcanization or crosslinking. As long as the amount of these additives is not contrary to the object of the present invention, a conventional general amount can be used. The rubber composition for tires of the present invention can be produced by mixing the above components using a normal rubber kneading machine such as a Banbury mixer, a kneader, or a roll.

  The rubber composition for a tire of the present invention can be suitably used for a bead filler of a pneumatic tire and a side reinforcing rubber layer having a crescent cross section in a run flat tire. Since the pneumatic tire using the rubber composition of the present invention for these members has low heat generation during running, it can reduce rolling resistance and improve fuel efficiency. At the same time, by improving the rubber hardness and elastic modulus of the rubber composition, the handling stability when the tire is made can be improved to a level higher than the conventional level. In addition, when used in a crescent-shaped rubber reinforcement layer on the left and right sidewalls of run-flat tires, the driving stability can be improved to a level higher than conventional levels while reducing rolling resistance and improving fuel efficiency during normal driving. it can. Further, during run flat running, the run flat running performance is excellent and the durability of the rubber reinforcing layer having a crescent-shaped cross section in the sidewall portion is suppressed.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, the scope of the present invention is not limited to these Examples.

  20 types of rubber compositions (Examples 1 to 10 and Comparative Examples 1 to 10) were prepared using 9 types of carbon black (CB1 to CB9). Of these, four types of carbon black (CB1 to CB4) are commercial grades, and five types of carbon black (CB5 to CB9) are prototypes. The colloidal characteristics of each type are shown in Table 1.

In Table 1, each abbreviation represents the following colloidal characteristics.
N ₂ SA: Nitrogen adsorption specific surface area measured based on JIS K6217-2 IA: Iodine adsorption amount measured based on JIS K6217-1 CTAB: CTAB adsorption measured based on JIS K6217-3 Specific surface area DBP: DBP absorption measured based on JIS K6217-4 (uncompressed sample) 24M4: 24M4-DBP absorption measured based on JIS K6217-4 (compressed sample) Dst: JIS K6217 Mode diameter which is the maximum value of the mass distribution curve of the Stokes diameter of the aggregate by the disc centrifugal photoprecipitation method measured based on -6. ΔD50: by the disc centrifugal photoprecipitation method measured based on JIS K6217-6 In the mass distribution curve of the Stokes diameter of the aggregate, the distribution width when the mass frequency is half the maximum point (Half width)
Α: Coefficient α when Dst and N ₂ SA described above are applied to the relationship of the following formula (2)
Dst = α × (N ₂ SA) ^−0.61 (2)
(In the formula, Dst is the mode diameter (nm) in the mass distribution curve of the Stokes diameter of the aggregate, and N ₂ SA is the nitrogen adsorption specific surface area (m ² / g).)
N ₂ SA / IA: Ratio of nitrogen adsorption specific surface area N ₂ SA and iodine adsorption amount IA

In Table 1, carbon blacks CB1 to CB4 represent the following commercial grades, respectively. Carbon blacks CB5 to CB9 were prepared by the following manufacturing method.
・ CB1: Seest KH made by Tokai Carbon Co., Ltd.
・ CB2: Tokai Carbon Co., Ltd. Seest NH
・ CB3: Toast Carbon Co., Ltd. Seest 116HM
・ CB4: Toast Carbon Co., Ltd. Seast F

Production of carbon black CB5 to CB9 Using a cylindrical reactor, carbon black CB5 was changed by changing the total air supply amount, fuel oil introduction amount, fuel oil combustion rate, raw material oil introduction amount, reaction time as shown in Table 2. -CB9 was produced.

Preparation and Evaluation of Tire Rubber Composition 20 types of rubber compositions (Examples 1 to 10 and Comparative Example 1) having the composition shown in Tables 3 and 4 using the above-mentioned 9 types of carbon blacks (CB1 to CB9). 10) to 10), the components excluding sulfur and the vulcanization accelerator were weighed and kneaded in a 55 L kneader for 15 minutes, and then the master batch was discharged and cooled to room temperature. This master batch was subjected to a 55 L kneader, and sulfur and a vulcanization accelerator were added and mixed to obtain a tire rubber composition.

  A pneumatic tire having a tire size of 195 / 65R15 was vulcanized and molded so as to constitute a bead filler of a pneumatic tire using the obtained 20 kinds of rubber compositions. The rolling resistance and wear resistance of the 20 types of pneumatic tires obtained were evaluated by the methods shown below.

  In Table 4, for the example of using two types of carbon black (Comparative Example 5 and Example 7), two columns of “type and blending amount of carbon black” are provided.

Rolling resistance The obtained tire is assembled to a standard rim (size 15 × 6J wheel) and attached to an indoor drum tester (drum diameter 1707 mm) compliant with JIS D4230, which is compliant with “6.4 High-Speed Performance Test A” of JIS D4230. A high-speed durability test was carried out in accordance with the described high-speed durability test, and the resistance force at a test load of 2.94 kN and a speed of 50 km / hour was measured to obtain a rolling resistance. The obtained results are shown in the “Rolling resistance” column of Tables 4 and 5 as an index with the reciprocal of the value of Comparative Example 1 as 100. The larger this index, the smaller the rolling resistance and the better the fuel efficiency.

Steering stability The tires obtained were assembled on a standard rim (size 15 x 6J wheel) and mounted on a domestic 2.0 liter class test vehicle. The course was run on a real vehicle, and the handling stability at that time was scored by a sensitive evaluation by three expert panelists. The obtained results are shown in the “Steering stability” column of Tables 4 and 5 as an index with the value of Comparative Example 1 as 100. The larger this index, the better the steering stability performance.

The types of raw materials used in Tables 3 and 4 are shown below.
NR: natural rubber, RSS # 3
SBR: styrene-butadiene rubber, Nipol 1502 manufactured by Nippon Zeon
Phenol resin 1: Cashew modified phenolic resin, Sumitomo Bakelite Sumilite resin phenolic resin 2: Octylphenol resin, DIC DIC-POP
Methylene donor: Hexamethylenetetramine, Noxeller H-PO manufactured by Ouchi Shinsei Chemical Co., Ltd.
CB1 to CB9: Carbon black aroma oil shown in Table 1 described above: Process X-140 manufactured by Japan Energy
Zinc Hana: Zinc Oxide 3 types manufactured by Shodo Chemical Industry Co., Ltd. Stearic acid: Beads manufactured by NOF Co., Ltd. Stearate anti-aging agent: SANTOFLEX 6PPD manufactured by Flexis
Vulcanization accelerator: Noxeller NS-G manufactured by Ouchi Shinsei Chemical Co., Ltd.
Sulfur: Insoluble sulfur, Shikoku Kasei Co., Ltd. Mukuron OT-20, sulfur content 80%

  As is clear from Tables 3 and 4, it was confirmed that the tire rubber compositions of Examples 1 to 10 were improved in the low rolling resistance and the steering stability to the conventional level (Comparative Example 1) or more.

As is apparent from Table 3, the rubber composition of Comparative Example 2 has poor steering stability because the Stokes diameter Dst of the carbon black CB2 is less than 145 nm. In the rubber composition of Comparative Example 3, since the Stokes diameter Dst of the carbon black CB3 is less than 145 nm and the ratio N ₂ SA / IA is less than 1.00, the steering stability is deteriorated. In the rubber composition of Comparative Example 4, since the N ₂ SA of the carbon black CB4 is less than 45 m ² / g and the ratio N ₂ SA / IA is less than 1.00, the steering stability is deteriorated.

  As is apparent from Table 4, the rubber composition of Comparative Example 5 has a large effect on rolling resistance because the blending amount of the carbon black of the present invention is smaller than 30 parts by weight, but the steering stability performance deteriorates. In the rubber composition of Comparative Example 6, the rolling resistance is deteriorated because the blending amount of carbon black is larger than 100 parts by weight.

  Since the rubber composition of Comparative Example 7 does not contain a methylene donor, steering stability is deteriorated. Since the rubber composition of Comparative Example 8 does not contain a phenol resin, steering stability is deteriorated.

  In the rubber composition of Comparative Example 9, the handling stability deteriorates because the sum of the phenol resin and the methylene donor is less than 1 part by weight. In the rubber composition of Comparative Example 10, the rolling resistance is deteriorated because the sum of the phenol resin and the methylene donor is larger than 50 parts by weight. In addition, the amount of the methylene donor is too large, the reaction with the phenol resin is difficult to proceed, and the steering stability is also deteriorated.

Claims (4)

A total of 1-50 parts by weight of a novolac-type phenolic resin and a methylene donor is blended with 100 parts by weight of the diene rubber, and 60-100 parts by weight of a reinforcing filler containing 30-100 parts by weight of carbon black is blended. A rubber composition for a tire, wherein the mode diameter Dst in the mass distribution curve of the Stokes diameter of the carbon black aggregate is 145 nm or more, the nitrogen adsorption specific surface area N ₂ SA is 45 to 70 m ² / g, and the iodine adsorption amount IA ( Ri ratio N ₂ SA / IA is 1.00 to 1.40 der of the nitrogen adsorption specific surface area N ₂ SA for the unit mg / g), when N ₂ SA of the carbon black is less than 55m ² / g, the mode diameter Dst Stokes diameter is not more 180nm or less, when the N ₂ SA of the carbon black exceeds 55m ² / g, mode of the Stokes diameter De diameter Dst tire rubber composition characterized by satisfying the relation of the following equation (1).
Dst <1979 × (N ₂ SA) ^−0.61 (1)
(In the formula, Dst is the mode diameter (nm) in the mass distribution curve of the Stokes diameter of the aggregate, and N ₂ SA is the nitrogen adsorption specific surface area (m ² / g).) The rubber composition for a tire according to claim 1 , wherein the novolac type phenol resin is a resin modified with cashew oil. A pneumatic tire comprising a bead filler made of the tire rubber composition according to claim 1 . A pneumatic tire comprising a rubber reinforcing layer having a crescent-shaped cross section in left and right sidewall portions of a run-flat tire using the tire rubber composition according to claim 1 .

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