JP2008138140A - Rubber composition for tire tread and pneumatic tire using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for a tire tread for easily and certainly producing a pneumatic tire sustaining excellent grip performance and wear resistance in a long time use, and to provide a pneumatic tire using the same. <P>SOLUTION: The invention relates to the rubber composition for a tire tread at least composed of a rubber component and carbon black, wherein a part of the carbon particle constituting the carbon black is acidic carbon particle which has ≤4.0 of pH by having acidic groups in the particle and the content of the acidic particle is 5-50 pts.mass per 100 pts.mass of the rubber component, and the content of the acidic carbon particle is 3-30 mass% to the carbon black. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rubber composition for a tire tread that maintains good grip performance even when the rubber temperature rises during traveling, and a pneumatic tire using the same.

  In a pneumatic tire, grip performance and wear resistance after long-term use are required. On the other hand, workability at the time of tire manufacture must also be secured.

  In Patent Document 1, as a method for producing a rubber composition for a tire tread for obtaining a pneumatic tire that maintains good grip performance and wear resistance even when used over a long period of time, a rubber component is ion-bonded. A method for producing a tire tread rubber composition comprising a step of kneading together with a compound to obtain an unvulcanized rubber composition, and a vulcanization step, wherein the tire tread rubber composition is within the range of 80 to 120 ° C. A method for producing a rubber composition for a tire tread in which tan δ (loss tangent) is set to be 0.2 or more and 0.6 or less has been proposed.

  However, in the technique of Patent Document 1, when an acidic compound is used for the preparation of an ion-binding compound, if the acidic compound remains, vulcanization in the vulcanization process is inhibited, and the wear resistance of the pneumatic tire is reduced. There's a problem.

  In Patent Document 2, for the purpose of providing a tire rubber composition exhibiting high grip performance, (B) 2,2,6,6-tetramethylpiperidine and (B) with respect to 100 parts by weight of a diene rubber 0.1 to 30 parts by weight of at least one compound selected from the group consisting of derivatives thereof, (C) 0.1 to 30 parts by weight of at least one compound selected from the group consisting of protonic acids and phenol derivatives, and ( D) A rubber composition for tires containing 10 to 200 parts by weight of carbon black has been proposed.

However, in the technique of Patent Document 2, there is a problem that vulcanization may be inhibited by an acid component such as a protonic acid, and a problem that workability is deteriorated due to the compounding component adhering to the mixer or roll during rubber mixing. There is.
JP 2005-263831 A JP-A-2005-112922

  The present invention solves the above-mentioned problems, and a rubber composition for a tire tread for obtaining a pneumatic tire that maintains good grip performance and wear resistance even when used over a long period of time, and pneumatic using the same The purpose is to provide tires.

  The present invention relates to a tire tread rubber composition containing at least a rubber component and carbon black, wherein some of the carbon particles constituting the carbon black are acidic carbon particles, and the acidic carbon particles are contained in the particles. Particles having a pH of 4.0 or less by having an acidic group, and the content of the acidic carbon particles is in the range of 5 to 50 parts by mass with respect to 100 parts by mass of the rubber component, And it is related with the rubber composition for tire treads in which the ratio for which an acidic carbon particle accounts in carbon black exists in the range of 3-30 mass%.

  In the tire tread rubber composition of the present invention, the acidic group is preferably at least one selected from a hydroxyl group, a carboxyl group, a phenyl group, a phenolic hydroxyl group, and a quinonyl group.

In the tire tread rubber composition of the present invention, the amount of acidic groups contained in the acidic carbon particles is preferably in the range of 1 to 50 μmol / m ² .

  In the tire tread rubber composition of the present invention, tan δ (loss tangent) in the range of 80 ° C. to 120 ° C. is preferably in the range of 0.2 to 0.6.

  The present invention also relates to a pneumatic tire using any one of the above-described rubber compositions for a tire tread in a tread portion.

  According to the rubber composition for a tire tread of the present invention, it is possible to obtain a pneumatic tire that maintains good grip performance and wear resistance even when used for a long period of time.

  In the present invention, carbon black containing acidic carbon particles is contained in the tire tread rubber composition. In general, the grip performance of a tire can be improved by setting the tan δ (loss tangent) of the rubber composition constituting the tire, that is, the energy loss of the rubber composition to be a certain level or more. As a method for improving the tan δ of the polymer material at a certain temperature, a method of setting the Tg (glass transition temperature) of the polymer to be relatively high can be adopted. In this case, at a temperature equal to or higher than the Tg of the polymer, E ′ ( There is a risk that the storage modulus) and tan δ (loss tangent) are drastically lowered and brittle fracture occurs. Therefore, in a tire blended with a polymer in which only Tg is taken into account, there is a problem that grip performance is greatly reduced as the rubber temperature increases during running.

  The acidic carbon particles blended in the present invention are particles having a pH of 4.0 or less by having acidic groups in the particles. Acidic carbon particles form ionic aggregates having a relatively large binding energy in the rubber composition due to the presence of acidic groups in the particles, and therefore, tan δ (loss tangent) is increased without significantly increasing Tg (glass transition temperature). Has the effect of improving.

  As a result, the effect of preventing the decrease in tan δ at a high temperature of the tire tread rubber composition can be obtained. Therefore, according to the pneumatic tire using the rubber composition for a tire tread of the present invention, the grip performance is not deteriorated even when the rubber temperature is increased during traveling, and good steering stability is obtained. In addition, since the effect of preventing tan δ from being lowered at a high temperature according to the present invention is brought about by the formation of the above-mentioned ion aggregates, the wear resistance of the tire tread rubber composition is well maintained.

  The acidic groups that contribute to the formation of ion aggregates are typically contained in the carbon particles by introducing acidic groups into the carbon particles. That is, in the present invention, bulky carbon particles are associated, so that even if the content of acidic groups in the rubber composition is relatively low, the effect of preventing tan δ from being reduced at high temperatures can be obtained remarkably. A good effect of preventing tan δ from being lowered at high temperatures can be obtained without inhibiting the vulcanization of the rubber component during the production of the tire tread rubber composition.

  The pH of the acidic carbon particles used in the present invention is 4.0 or less. When the pH is 4.0 or less, since the acidic carbon particles contain a relatively large amount of acidic groups, the effect of preventing tan δ from being lowered at a high temperature due to the formation of ion aggregates is good. The pH of the acidic carbon particles is preferably 3.5 or less, more preferably 3.0 or less. On the other hand, the pH of the acidic carbon particles is preferably 2.0 or more, more preferably 2.5 or more, from the viewpoint that the vulcanization of the rubber component during the production of the tire tread rubber composition can be favorably progressed. .

  The pH of the acidic carbon particles is a value measured based on, for example, JIS K6221.

  The acidic carbon particles are a part of the carbon particles constituting the carbon black. That is, in the present invention, acidic carbon particles into which acidic groups are introduced and carbon particles into which acidic groups are not introduced are used in combination. If the carbon black is entirely composed of acidic carbon particles, the amount of acidic groups contained in the carbon black will increase and vulcanization will occur if an attempt is made to form ion aggregates to the extent necessary to obtain the desired tan δ reduction prevention effect. May be disturbed. However, in the present invention, only a part of the carbon black is made into acidic carbon particles, so that a relatively large amount of acidic groups are introduced into the acidic carbon particles, so that the formation of ion aggregates by the acidic carbon particles is favorably performed. By suppressing the content of acidic groups in the entire black relatively low, the rubber component can be vulcanized well. Therefore, the pneumatic tire using the rubber composition for a tire tread of the present invention in the tread portion is excellent in grip performance and wear resistance even during long-term use.

  Content of acidic carbon particle shall be in the range of 5-50 mass parts with respect to 100 mass parts of a rubber component. When the content is 5 parts by mass or more, the grip performance of the pneumatic tire can be improved to a desired degree by the effect of preventing the tan δ decrease at a high temperature of the tire tread rubber composition, and when the content is 50 parts by mass or less. Further, the rubber component is prevented from being inhibited from being vulcanized during the production of the tire tread rubber composition, and good wear resistance is imparted to the pneumatic tire. The content is more preferably 10 parts by mass or more, more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less.

  The carbon black content is preferably in the range of 60 to 120 parts by mass with respect to 100 parts by mass of the rubber component. When the content is 60 parts by mass or more, the rubber composition for the tire tread has a high rubber hardness and can impart excellent wear resistance to the pneumatic tire. When the content is 120 parts by mass or less, when running Good durability can be imparted to the pneumatic tire by keeping the heat generation of the pneumatic tire low. The content is more preferably 70 parts by mass or more, and more preferably 90 parts by mass or less.

  The proportion of the carbon black in the acidic carbon particles is in the range of 3 to 30% by mass. When the proportion is 3% by mass or more, the effect of improving the grip performance according to the present invention can be favorably obtained, and when it is 30% by mass or less, the mechanical strength is excellent without inhibiting the vulcanization of the rubber component. A rubber composition for a tire tread can be obtained. The ratio is more preferably 5% by mass or more, and further preferably 10% by mass or more, and more preferably 20% by mass or less, and further preferably 15% by mass or less.

  Examples of the acidic group contained in the acidic carbon particles include one or more selected from a hydroxyl group, a carboxyl group, a phenyl group, a phenolic hydroxyl group, a quinonyl group, and the like. Among these, at least one of a hydroxyl group and a carboxyl group is preferable in terms of availability.

In the present invention, by controlling the amount of acidic groups contained in the acidic carbon particles within a predetermined range, it is possible to achieve a good tan δ reduction preventing effect particularly at high temperatures and a good progress of vulcanization of the rubber component during production. Both can be achieved. That is, in the rubber composition for a tire tread of the present invention, the amount of acidic groups contained in the acidic carbon particles is preferably in the range of 1 to 50 μmol / m ² . When the amount of acidic groups contained in the acidic carbon particles is 1 μmol / m ² or more, a tan δ reduction preventing effect at a high temperature is better obtained, and when it is 50 μmol / m ² or less, the rubber component at the time of production The vulcanization can proceed more favorably. The amount of acid groups contained in the acid carbon particles, 2.mu. mol / m ² or more, still more preferably 5μ mol / m ² or more, also, 30.mu. mol / m ² or less, further 20μ mol / m ² or less More preferably.

  In the tire tread rubber composition of the present invention, tan δ (loss tangent) in the range of 80 ° C. to 120 ° C. is preferably in the range of 0.2 to 0.6. When the tan δ is 0.2 or more, the tire tread rubber composition has a large tan δ even in a high temperature region of, for example, Tg or more, and has a good grip on a pneumatic tire even under running conditions where the rubber temperature is high. Performance can be imparted. Further, when the tan δ is 0.6 or less, there is little risk of impairing the workability during the production of the tire tread rubber composition, and the excessive increase in the rolling resistance of the pneumatic tire is prevented to prevent It is preferable because the fuel consumption can be maintained well. The tan δ is more preferably 0.25 or more, further 0.3 or more, and more preferably 0.5 or less, and further preferably 0.4 or less.

  The tan δ is a value measured using a viscoelastic spectrometer, giving an initial strain of 10%, and giving a dynamic strain of 2% at 80 to 120 ° C.

  The rubber hardness of the rubber composition for a tire tread of the present invention is preferably in the range of 20-50. When the rubber hardness is 20 or more, good abrasion resistance is imparted by the pneumatic tire, and when it is 50 or less, good grip performance is imparted by the pneumatic tire. The rubber hardness is more preferably 25 or more and further 30 or more, and more preferably 45 or less and further 40 or less.

  The rubber hardness is a value of type A durometer measured by the method of JIS K6253 “Hardness test of vulcanized rubber and thermoplastic rubber”.

The nitrogen adsorption specific surface area (N ₂ SA) of the acidic carbon particles is preferably in the range of 25 to 400 m ² / g. When the nitrogen adsorption specific surface area is 25 m ² / g or more, the rubber composition for tire tread has good wear resistance and processability at the time of manufacture, and when it is 400 m ² / g or less, it is pneumatic when traveling. Tire heat generation can be suppressed satisfactorily. The nitrogen adsorption specific surface area is more preferably 100 m ² / g or more, further preferably 200 m ² / g or more, more preferably 370 m ² / g or less, and further preferably 300 m ² / g or less.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon particles other than the acidic carbon particles constituting the carbon black is preferably in the range of 100 to 200 m ² / g. When the nitrogen adsorption specific surface area is 100 m ² / g or more, the wear resistance and processability of the rubber composition for tire tread are good. When the nitrogen adsorption specific surface area is 200 m ² / g or less, it is pneumatic when traveling. Tire heat generation can be suppressed satisfactorily. The nitrogen adsorption specific surface area is preferably 130 m ² / g or more, more preferably 150 m ² / g or more, more preferably 180 m ² / g or less, and further preferably 160 m ² / g or less.

  The pH of the carbon particles other than the acidic carbon particles constituting the carbon black can be set within a range of 6.0 to 8.0, for example.

  The acidic carbon particles can be prepared by introducing a target acidic group into the carbon particles, and specific examples include a heat treatment method.

  Examples of rubber components used in the rubber composition for tire treads of the present invention include polybutadiene rubber (BR), styrene-butadiene rubber (SBR), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR), and acrylonitrile-butadiene rubber. (NBR), butyl rubber (IIR) and the like can be preferably used as one kind or a mixture of two or more kinds. The ethylene-propylene-diene rubber (EPDM) contains a third diene component in the ethylene-propylene rubber (EPM). Here, as the third diene component, a non-conjugated diene having 5 to 20 carbon atoms, such as 1, In addition to 4-pentadiene, 1,4-hexadiene, 1,5-hexadiene, 2,5-dimethyl-1,5-hexadiene and 1,4-octadiene, 1,4-cyclohexadiene, cyclooctadiene, dicyclopentadiene In addition, cyclic dienes such as 5-ethylidene-2-norbornene, 5-butylidene-2-norbornene, 2-methallyl-5-norbornene and 2-isopropenyl-5-norbornene can be used.

  In the present invention, after carbon black containing acidic carbon particles is kneaded together with a rubber component to prepare an unvulcanized rubber composition, a rubber composition for a tire tread is manufactured through a vulcanization step. The acidic carbon particles dispersed in the unvulcanized rubber composition by being kneaded with the rubber component form an ion aggregate. Thereby, a rubber composition for a tire tread having a high tan δ particularly in a high temperature region is obtained.

  In the present invention, in addition to the rubber component and carbon black, compounding components generally used in the manufacture of rubber products can be appropriately blended. The compounding component may be added at the time of kneading the rubber component and carbon black, or may be added to the kneaded product obtained after kneading the rubber component and carbon black in advance.

  For example, an oil component can be blended in the rubber composition produced in the present invention. When an oil component is blended, the grip performance of the tire can be improved by imparting flexibility to the rubber composition. However, when a large amount of the oil component is added, physical properties such as tan δ at a high temperature are lowered, and the oil component may bleed on the tire surface. Therefore, the compounding quantity of an oil component can be set in the range of 0-300 mass parts, for example with respect to 100 mass parts of rubber components.

  Oil components that can be blended include process oils such as paraffinic, olefinic, and aroma oils, petroleum oils such as liquid paraffin, petroleum asphalt, and petroleum jelly, and fatty oils such as castor oil, linseed oil, rapeseed oil, and palm oil Examples of such oils include, for example, Process X-260 (aromatic oil) manufactured by Japan Energy.

  An ionomer resin or the like can be blended in the rubber composition produced in the present invention. The ionomer resin has an ionic bond in the molecule. The ionomer resin may be added during kneading with the rubber component, or may be added as a co-crosslinking agent after kneading. As a specific example of the ionomer resin, for example, it is obtained by neutralizing at least a part of a carboxyl group in a copolymer of an α-olefin and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms with a metal ion. At least a carboxyl group in a terpolymer of an α-olefin, an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and an α, β-unsaturated carboxylic acid ester having 2 to 22 carbon atoms Examples thereof include those obtained by neutralizing a part with metal ions. As said alpha olefin, ethylene, propylene, 1-butene, 1-pentene etc. can be used, for example, ethylene is preferable, As C3-C8 alpha, beta-unsaturated carboxylic acid, for example, Acrylic acid, methacrylic acid, fumaric acid, maleic acid, crotonic acid and the like can be used, among which acrylic acid and methacrylic acid are preferred. Examples of the unsaturated carboxylic acid ester having 2 to 22 carbon atoms include methyl, ethyl, propyl, n-butyl and isobutyl esters such as acrylic acid, methacrylic acid, fumaric acid and maleic acid. Acid esters and methacrylic acid esters are preferred.

  Copolymer of the α-olefin and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms or an α-olefin and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and a carbon number of 2 to 22 Examples of the metal ion that neutralizes at least a part of the carboxyl group in the terpolymer with the α, β-unsaturated carboxylic acid ester include sodium ion, lithium ion, zinc ion, magnesium ion, potassium ion, and the like. Is mentioned.

  Specific examples of the ionomer resin are exemplified by trade names. As the ionomer resin of a binary copolymer commercially available from Mitsui DuPont Chemical Co., Ltd., Himiran 1555 (Na), Himiran 1557 (Zn), Himiran 1605 (Na), HiMilan 1706 (Zn), HiMilan 1707 (Na), and ternary copolymer ionomer resins include HiMilan 1856 (Na), HiMilan 1855 (Zn), and HiMilan AM7316 (Zn). Further, as ionomer resins commercially available from DuPont, Surlyn 8940 (Na), Surlyn 8945 (Na), Surlyn 9910 (Zn), and Terpolymeric ionomer resins, Surlyn AD8265 (Na), Surlyn AD8269 (Na )and so on. Note that Na, Zn, K, Li, Mg, and the like described in parentheses after the trade name of the ionomer resin indicate the metal species of these neutralized metal ions. The ionomer resin used in the present invention may be a mixture of two or more of those exemplified above, or neutralized with an ionomer resin neutralized with a monovalent metal ion exemplified above and a divalent metal ion. Two or more ionomer resins may be mixed and used.

  Furthermore, the following compounding components can be appropriately blended in the tire tread rubber composition of the present invention.

  As the vulcanizing agent, either an organic peroxide-based vulcanizing agent or a sulfur-based vulcanizing agent can be used, and a mixture thereof may be used. Examples of the organic peroxide vulcanizing agent include benzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, t-butyl cumyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide, 2,5- Dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, 2,5-dimethyl-2,5-di (t-butylperoxy) Oxy) hexyne-3 or 1,3-bis (t-butylperoxypropyl) benzene, di-t-butylperoxy-diisopropylbenzene, t-butylperoxybenzene, 2,4-dichlorobenzoyl peroxide, 1, 1-di-t-butylperoxy-3,3,5-trimethylsiloxane, n-butyl And the like can be used 4,4--t- butyl peroxy valerate. Of these, dicumyl peroxide, t-butylperoxybenzene and di-t-butylperoxy-diisopropylbenzene are preferred. Moreover, as a sulfur type vulcanizing agent, sulfur, morpholine disulfide, etc. can be used, for example. Of these, sulfur is preferred.

  Vulcanization accelerators include sulfenamide, thiazole, thiuram, thiourea, guanidine, dithiocarbamic acid, aldehyde-amine, aldehyde-ammonia, imidazoline, or xanthate vulcanization accelerators. It is possible to use one containing at least one of them. Specifically, for example, CBS (N-cyclohexyl-2-benzothiazylsulfenamide), TBBS (N-tert-butyl-2-benzothiazylsulfenamide), N, N-dicyclohexyl-2-benzothia Sulfenamide compounds such as dilsulfenamide, N-oxydiethylene-2-benzothiazylsulfenamide, N, N-diisopropyl-2-benzothiazole sulfenamide, MBT (2-mercaptobenzothiazole), MBTS (Dibenzothiazyl disulfide), sodium salt of 2-mercaptobenzothiazole, zinc salt, copper salt, cyclohexylamine salt, 2- (2,4-dinitrophenyl) mercaptobenzothiazole, 2- (2,6-diethyl-4 -Morpholinothio) thiazoles such as benzothiazole Compounds, TMTD (tetramethyl thiuram disulfide), tetraethyl thiuram disulfide, tetramethyl thiuram monosulfide, dipentamethylene thiuram disulfide and other thyllium compounds, diethylthiourea, dibutylthiourea, trimethylthiourea, diortolylthiourea and other thiols Guanidine compounds such as urea compounds, diphenylguanidine, diortolylguanidine, triphenylguanidine, orthotolylbiguanide, diphenylguanidine phthalate, zinc ethylphenyldithiocarbamate, zinc butylphenyldithiocarbamate, sodium dimethyldithiocarbamate, zinc dimethyldithiocarbamate, Zinc diamyldithiocarbamate, zinc dipropyldithiocarbamate, pentamethylenedithiocarbamate Complex salts of zinc acid and piperidine, zinc hexadecyl (or octadecyl) isopropyl dithiocarbamate, sodium diethyldithiocarbamate, selenium dimethyldithiocarbamate, dithiocarbamate compounds such as tellurium diethyldithiocarbamate, acetaldehyde-aniline reactant, butyraldehyde-aniline condensation Aldehyde-amine compounds or aldehyde-ammonia compounds such as hexamethylenetetramine, acetaldehyde-ammonia reactant, imidazoline compounds such as 2-mercaptoimidazoline, xanthate compounds such as zinc dibutylxanthate, and the like.

  The rubber composition for a tire tread of the present invention may contain additives such as short fibers, resin powder, vegetable cellulose powder, inorganic powder and the like alone or as a mixture of two or more. These additives can be mix | blended within the range of 0.5-5 mass parts with respect to 100 mass parts of rubber components of the rubber composition for tire treads, for example.

In the rubber composition for a tire tread produced in the present invention, silica can be blended within a range of, for example, 60 parts by mass or less with respect to 100 parts by mass of the rubber component. As the silica, a precipitated silica having a nitrogen adsorption specific surface area of about 150 to ²⁰⁰ m ² / g can usually be used. When the nitrogen adsorption specific surface area is within the above range, the wear resistance of the tire tread and the processability of the unvulcanized rubber can be satisfied at the same time. In addition, when mix | blending a silica, it is preferable to mix | blend a coupling agent together. The content of the coupling agent can be appropriately adjusted within a range that does not deteriorate the workability of the pneumatic tire. Examples of coupling agents include aluminate coupling agents such as acetoalkoxyaluminum diisopropylate, vinyltrichlorosilane, vinyltris (2-methoxyethoxy) silane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloxypropyltri Silane coupling agents such as methoxysilane, isopropyl triisostearoyl titanate, isopropyl tridecylbenzenesulfonyl titanate, isopropyl tris (dioctylpyrophosphate) titanate, tetra (2,2-diallyloxymethyl-1-butyl) bis (di -Titanium couplings such as tridecyl) phosphite titanate, bis (dioctylpyrophosphate) ethylene titanate, isopropyl trioctanoyl titanate Agents, etc. can be used.

  The rubber composition for a tire tread of the present invention can appropriately contain compounding agents such as zinc oxide, stearic acid, anti-aging agent, wax, pressure-sensitive adhesive, inorganic filler, and plasticizer.

  As the antioxidant, amine-based, phenol-based, and imidazole-based compounds, carbamic acid metal salts, waxes, and the like can be used. As the adhesive, adhesives such as rosin resin, terpene resin, terpene phenol resin, phenol resin, coumarone indene resin, petroleum resin and the like can be used.

  As plasticizers, DMP (dimethyl phthalate), DEP (diethyl phthalate), DBP (dibutyl phthalate), DHP (diheptyl phthalate), DOP (dioctyl phthalate), DINP (diisononyl phthalate), DIDP (phthalate) Diisodecyl acid), BBP (butylbenzyl phthalate), DLP (dilauryl phthalate), DCHP (dicyclohexyl phthalate), hydrophthalic anhydride ester, TCP (tricresyl phosphate), TEP (triethyl phosphate), TBP (tributyl phosphate), TOP (trioctyl phosphate), TCEP (tri (chloroethyl phosphate)), TDCPP (tris dichloropropyl phosphate), TBXP (tosibutoxyethyl phosphate), TCPP (tris (β-chloropropyl) phosphate) G), TPP (triphenyl phosphate), octyl diphenyl phosphate, phosphoric acid (trisisopropylphenyl), DOA (dioctyl adipate), DINA (diisononyl adipate), DIDA (diisodecyl adipate), D610A (dialkyl adipate 610), BXA (dibutyl diglycol adipate), DOZ (di-2-ethylhexyl azelate), DBS (dibutyl sebacate), DOS (dioctyl sebacate), acetyl triethyl citrate, acetyl tributyl citrate, DBM (dibutyl maleate), DOM (2-ethylhexyl maleate), DBF (dibutyl fumarate), or the like can be used.

  The rubber composition for tire treads of the present invention can be suitably used for pneumatic tires for passenger cars, buses, trucks and the like. FIG. 1 is a cross-sectional view showing the right half of a pneumatic tire to which the present invention is applied. In FIG. 1, a pneumatic tire T has a pair of bead portions 1, a pair of sidewall portions 2, and a tread portion 3 that is continuous with both sidewall portions, and a bead core 4 embedded in the pair of bead portions 1. A carcass 5 extending between each other and a belt 6 that reinforces the tread portion 3 on the outer periphery of the carcass 5 are provided. The carcass 5 has a carcass main body portion extending between the pair of bead cores 4 and a turn-up portion 5a wound around the bead core 4 from the inner side to the outer side in the tire radial direction. The carcass 5 is composed of a ply in which a radial arrangement cord such as a steel cord or an ultrahigh strength organic fiber cord such as aramid is covered with rubber. The rubber composition for a tire tread of the present invention is suitably used for the tread portion 3 of the pneumatic tire having the basic structure as described above.

[Example]
EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

  Among the components shown in Table 1, components other than sulfur and vulcanization accelerator were kneaded for 3 minutes at 150 ° C. in a BP-type banbury, added with sulfur and vulcanization accelerator, and about 5 minutes in an open roll. Kneaded. A sheet was prepared from the obtained rubber composition and vulcanized at 170 ° C. for 12 minutes using a predetermined mold to obtain a vulcanized sheet.

(1) Viscoelasticity evaluation The vulcanized sheet obtained above was used as a measurement sample, and an initial strain of 10% was given using a viscoelasticity spectrometer manufactured by Iwamoto Seisakusho, and a dynamic strain of 2% was given at 100 ° C. Tan δ (loss tangent) was measured. The larger tan δ, the better the physical properties. The results are shown in Table 1.

(2) T95
Among the components shown in Table 1, when components other than sulfur and a vulcanization accelerator are kneaded with a BP type Banbury at 150 ° C. for 3 minutes and then added with sulfur and a vulcanization accelerator, they are kneaded with an open roll. The time until the vulcanization degree of the rubber component reached 95% was measured. The results are shown in Table 1.

(3) Grip performance The vulcanized sheet obtained above was bonded to a tire to produce an 11X 7.10-5 size cart tire. The cart tire was mounted on the cart, and the grip performance was evaluated by sensory evaluation. The results were expressed as 3 points on the basis of the following criteria, with Comparative Example 1 as 3 points. The results are shown in Table 1.
(Grip evaluation and wear resistance evaluation criteria)
3: Good.
2: Moderate.
1: Bad.

Note 1: SBR is “Toughden 4350” (styrene butadiene rubber: bound styrene content 39%) manufactured by Asahi Kasei Corporation.
Note 2: Carbon particles (A) are carbon black “Dia Black A” (N110) manufactured by Mitsubishi Chemical Corporation.
Note 3: The acidic carbon particles (B) are carbon black “Dia Black # 2400B” (pH = 2.5, nitrogen adsorption specific surface area: 320) manufactured by Mitsubishi Chemical Corporation.
Note 4: Carbon particles (C) are carbon black “Dia Black # 2300B” (pH = 8.0, nitrogen adsorption specific surface area: 320) manufactured by Mitsubishi Chemical Corporation.
Note 5: Methacrylic acid is “Methacrylic acid (MMA)” manufactured by Nippon Shokubai Co., Ltd.
Note 6: The nitrogen compound is Curesol “1,2DMZ” manufactured by Shikoku Chemicals.
Note 7: Oil is “Process X-260” manufactured by Japan Energy.
Note 8: Stearic acid is stearic acid manufactured by NOF Corporation.
Note 9: Anti-aging agent 6C is “Sant Flex 13” manufactured by Flexis.
Note 10: Anti-aging agent 224 is “NOCRACK 224” manufactured by Flexis.
Note 11: Zinc flower is "Zinc oxide 2 types" manufactured by Mitsui Kinzoku Kogyo.
Note 12: Sulfur is “powder sulfur” manufactured by Tsurumi Chemical Co., Ltd.
Note 13: The vulcanization accelerator is “Noxeller NS” manufactured by Ouchi Shinsei Chemical Co., Ltd.

  First, when Comparative Example 1 and Comparative Example 2 are compared, it can be seen that the effect of improving grip performance can be obtained by blending an acidic component such as methacrylic acid, but at the same time, vulcanization inhibition has occurred. On the other hand, compared with Comparative Example 1 in which methacrylic acid was blended, Comparative Example 2 in which methacrylic acid was not blended, and Comparative Examples 3 and 4 in which carbon particles of pH = 8.0 and methacrylic acid were blended, an acidic carbon component was blended. In Examples 1 and 2, the value of T95 and the evaluation results of grip performance were both good. That is, when the tire tread rubber composition of the present invention containing acidic carbon particles is used, the grip performance of the pneumatic tire can be remarkably improved without causing vulcanization inhibition of the rubber component during production. I understand.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the pneumatic tire which can maintain grip performance and abrasion resistance over a long period of time by using the rubber composition for tire treads containing acidic carbon particles.

It is sectional drawing which shows the right half of the pneumatic tire with which this invention is applied.

Explanation of symbols

  1 bead part, 2 side wall part, 3 tread part, 4 bead core, 5 carcass, 5a folded part, 6 belt.

Claims (5)

A rubber composition for a tire tread containing at least a rubber component and carbon black,
Some of the carbon particles constituting the carbon black are acidic carbon particles,
The acidic carbon particles are particles having a pH of 4.0 or less by having acidic groups in the particles,
The content of the acidic carbon particles is in the range of 5 to 50 parts by mass with respect to 100 parts by mass of the rubber component,
A rubber composition for a tire tread, wherein the proportion of the acidic carbon particles in the carbon black is in the range of 3 to 30% by mass.   The rubber composition for a tire tread according to claim 1, wherein the acidic group is at least one selected from a hydroxyl group, a carboxyl group, a phenyl group, a phenolic hydroxyl group, and a quinonyl group. The rubber composition for a tire tread according to claim 1 or 2, wherein an amount of acidic groups contained in the acidic carbon particles is within a range of 1 to 50 µmol / m ² .   The rubber composition for a tire tread according to any one of claims 1 to 3, wherein tan δ (loss tangent) within a range of 80 ° C to 120 ° C is within a range of 0.2 to 0.6.   The pneumatic tire which used the rubber composition for tire treads in any one of Claims 1-4 for the tread part.

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