JP2009263511A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire having excellent abrasion resistance and durability while securing low heat build-up. <P>SOLUTION: The pneumatic tire is obtained by using a rubber composition that comprises a synthetic rubber and a natural rubber as rubber components in which at least one kind of the synthetic rubber is an amine-based functional group-modified styrene-butadiene copolymer as a base rubber of tread. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a pneumatic tire using a predetermined rubber composition as a base rubber of a tread portion.

  The performance required for the base rubber of the tire tread portion is required to have low heat buildup and excellent wear resistance and cut resistance. As means for improving wear resistance and cut resistance, the main filler (for example, carbon black) of tire rubber is increased, or the filler is made finer (upgrade of carbon black). (For example, refer to Patent Document 1). However, when such a means is employed, it becomes difficult to ensure heat generation. That is, it can be said that it is very difficult to ensure heat generation while improving wear resistance and cut resistance.

  In addition, silica has been blended as a conventional technique. By blending silica, the hysteresis loss was increased, and the effect on the rough road chipping and the like could be exhibited. However, it has been difficult in factories to blend a large amount of silica due to a decrease in elastic modulus, a decrease in heat generation due to reversion during long-term vulcanization, and a significant deterioration in workability.

Japanese Patent Laid-Open No. 10-195249

  An object of the present invention is to provide a pneumatic tire having good wear resistance and durability while ensuring low heat build-up.

  As a result of intensive studies to achieve the above object, the present inventor has obtained a rubber composition comprising a styrene-butadiene copolymer modified with a specific amine functional group and a natural rubber, and a base of the tread portion. It has been found that its purpose can be achieved when used in rubber. The present invention has been completed based on such findings.

That is, the present invention
(1) Pneumatic in which a rubber composition containing a synthetic rubber and a natural rubber as a rubber component and at least one of the synthetic rubbers is an amine functional group-modified styrene-butadiene copolymer is used as a base rubber of a tread. Tire.
(2) The pneumatic tire according to (1), wherein the amine functional group-modified styrene-butadiene copolymer has a protic amino group and / or a protected amino group as the amine functional group.
(3) The pneumatic tire according to (1) or (2), which includes 30 to 65 parts by mass of a filler with respect to 100 parts by mass of the rubber component.

  According to the present invention, it is possible to provide a pneumatic tire having good wear resistance and durability while ensuring low heat generation.

  The pneumatic tire of the present invention is obtained by using a predetermined rubber composition for base rubber as a base rubber of a tread. Hereinafter, the components of the rubber composition for the base rubber will be described.

[Rubber composition for base rubber]
The rubber composition for a base rubber according to the present invention includes a synthetic rubber and a natural rubber as rubber components, and at least one of the synthetic rubbers is an amine-based functional group-modified styrene-butadiene copolymer (hereinafter referred to as a modified SBR). There is.)
First, the modified styrene-butadiene copolymer in the present invention will be described.

(Modified SBR)
In the modified SBR modified with an amine functional group, the position of the polymer into which the amine functional group is introduced is not particularly limited, and may be a polymerization terminal or a side chain of the polymer chain. However, from the viewpoint of ease of introduction of an amine functional group and suppression of energy loss from the polymer terminal to improve low heat buildup, the polymerization terminal is preferable.

  Examples of the amine functional group include a protic amino group and / or a protected amino group. In the modified SBR, those having a hydrocarbyloxysilane group in the polymer together with the protic amino group and / or protected amino group are preferable. These functional groups are preferably introduced at the polymerization terminal for the above reasons, and particularly preferably introduced at the same polymerization terminal.

  Compounds having these functional groups used for modification of the above-mentioned protic amino group, protected amino group and hydrocarbyloxysilane group, and base SBR (hereinafter referred to as SBR or unmodified SBR) (hereinafter referred to as modifier) Etc.) will be described in detail later.

  As a method for producing a modified SBR according to the present invention, a method of producing a modified SBR by obtaining an SBR having an active end and reacting the active end with a modifying agent can be employed.

(Manufacture of SBR)
In the present invention, SBR having an active terminal is obtained by copolymerizing styrene and butadiene, and the production method is not particularly limited, and may be a solution polymerization method, a gas phase polymerization method, or a bulk polymerization method. Either can be used, but the solution polymerization method is particularly preferable. Moreover, any of a batch type and a continuous type may be sufficient as the superposition | polymerization form.
The active site metal present in the SBR molecule is preferably one selected from alkali metals and alkaline earth metals, more preferably alkali metals, and particularly preferably lithium metal.

In the solution polymerization method, for example, the target polymer can be produced by anionic polymerization of styrene and butadiene using an organic alkali metal compound, particularly a lithium compound as a polymerization initiator.
When the solution polymerization method is used, the monomer concentration in the solvent is preferably 5 to 50% by mass, more preferably 10 to 30% by mass. The amount of styrene is preferably in the range of 20 to 45% by mass with respect to the total amount with butadiene.

  The lithium compound of the polymerization initiator is not particularly limited, but hydrocarbyl lithium and lithium amide compounds are preferably used. When the former hydrocarbyl lithium is used, it has a hydrocarbyl group at the polymerization initiation terminal and the other terminal. SBR in which is a polymerization active site is obtained. When the latter lithium amide compound is used, SBR having a nitrogen-containing group at the polymerization start terminal and the other terminal being a polymerization active site is obtained.

  As the hydrocarbyl lithium, those having a hydrocarbyl group having 2 to 20 carbon atoms are preferable, for example, ethyl lithium, n-propyl lithium, isopropyl lithium, n-butyl lithium, sec-butyl lithium, tert-octyl lithium, n-decyl. Examples include lithium, phenyllithium, 2-naphthyllithium, 2-butyl-phenyllithium, 4-phenyl-butyllithium, cyclohexyllithium, cyclobenchyllithium, and reactive organisms of diisopropenylbenzene and butyllithium. Of these, n-butyllithium is particularly preferred.

  On the other hand, examples of the lithium amide compound include lithium hexamethylene imide, lithium pyrrolidide, lithium piperide, lithium heptamethylene imide, lithium dodecamethylene imide, lithium dimethyl amide, lithium diethyl amide, lithium dibutyl amide, lithium dipropyl amide, and lithium disulfide. Heptylamide, lithium dihexylamide, lithium dioctylamide, lithium di-2-ethylhexylamide, lithium didecylamide, lithium-N-methylpiperazide, lithium ethylpropylamide, lithium ethylbutyramide, lithium ethylbenzylamide, lithium methylphenethyl Examples include amides. Among these, in view of the interaction effect on carbon black and the ability to initiate polymerization, cyclic lithium amides such as lithium hexamethylene imide, lithium pyrrolidide, lithium piperide, lithium heptamethylene imide, and lithium dodecamethylene imide are preferable, In particular, lithium hexamethylene imide and lithium pyrrolidide are suitable.

In general, these lithium amide compounds prepared from a secondary amine and a lithium compound can be used for the polymerization, but they can also be prepared in-polymerization in situ. The amount of the polymerization initiator used is preferably selected in the range of 0.2 to 20 mmol per 100 g of monomer.
There is no restriction | limiting in particular as a method of manufacturing SBR by anionic polymerization using the said lithium compound as a polymerization initiator, A conventionally well-known method can be used.
Specifically, in an organic solvent inert to the reaction, for example, a hydrocarbon solvent such as an aliphatic, alicyclic, or aromatic hydrocarbon compound, styrene and butadiene are used as a polymerization initiator, and the lithium compound is used as a polymerization initiator. If desired, the desired SBR can be obtained by anionic polymerization in the presence of the potassium compound or randomizer used.
Thus, content of all the styrene units of SBR obtained is 0.5-55 mass%, and 20-45 are more preferable. The vinyl bond amount in the butadiene portion is preferably 10 mol% or more.
When the vinyl bond content in the butadiene portion is 10 mol% or more, the hysteresis loss can be improved.
By setting the content of all styrene units in SBR and the vinyl bond content in the butadiene part within the above ranges, the object of the present invention can be effectively achieved.

The randomizer used as desired is control of the microstructure of the SBR, for example, increasing the 1,2 bond of the butadiene moiety, or control of the composition distribution of the monomer unit, for example, randomization of the butadiene unit, styrene unit, etc. It is a compound having the action of The randomizer is not particularly limited, and any one of known compounds generally used as a conventional randomizer can be appropriately selected and used. Specifically, dimethoxybenzene, tetrahydrofuran, dimethoxyethane, diethylene glycol dibutyl ether, diethylene glycol dimethyl ether, 2,2-bis (2-tetrahydrofuryl) -propane, triethylamine, pyridine, N-methylmorpholine, N, N, N ′, Examples thereof include ethers such as N′-tetramethylethylenediamine and 1,2-dipiperidinoethane, and tertiary amines. Further, potassium salts such as potassium-t-amylate and potassium-t-butoxide, and sodium salts such as sodium-t-amylate can also be used.
One of these randomizers may be used alone, or two or more thereof may be used in combination. The amount used is preferably selected in the range of 0.01 to 1000 molar equivalents per mole of the lithium compound.

  The temperature in this polymerization reaction is preferably selected in the range of 0 to 150 ° C, more preferably 20 to 130 ° C. The polymerization reaction can be carried out under generated pressure, but it is usually desirable to operate at a pressure sufficient to keep the monomer in a substantially liquid phase. That is, the pressure depends on the particular material being polymerized, the polymerization medium used and the polymerization temperature, but higher pressures can be used if desired, such pressure being a gas that is inert with respect to the polymerization reaction. Can be obtained by an appropriate method such as pressurizing.

In this polymerization, all raw materials involved in the polymerization, such as polymerization initiators, potassium compounds, randomizers, solvents, and monomers, are obtained by removing reaction inhibitors such as water, oxygen, carbon dioxide, and protic compounds. It is desirable to use
In addition, it is preferable that the obtained SBR has a glass transition temperature (Tg) determined by a differential thermal analysis method of −95 ° C. to −15 ° C. By setting the glass transition temperature within the above range, it is possible to suppress the increase in viscosity and obtain an SBR that is easy to handle.

(SBR denaturation)
In the present invention, a predetermined modifier is reacted with the active terminal of the SBR having the active terminal thus obtained, and an amine functional group such as a protic amino group and / or a protected group is formed at the polymerization terminal. An amino group, preferably a protic amino group and / or a protected amino group and a hydrocarbyloxysilane group are introduced. More preferably, the protic amino group and / or the protected amino group and the hydrocarbyloxysilane group are introduced into the same polymerization terminal.
Examples of the protic amino group and / or protected amino group include —NH ₂ , —NHR ^a , —NL ¹ L ^2, and —NR ^b L ³ (wherein R ^a and R ^b each represent a hydrocarbon group. , L ¹ , L ^2, and L ³ each represents a hydrogen atom or a dissociable protecting group).
Examples of the hydrocarbon group represented by R ^a and R ^b include various alkyl groups, alkenyl groups, aryl groups, and aralkyl groups. L ¹ , L ² , and L ³ may be any protecting group that can be easily dissociated, and are not particularly limited, and examples thereof include groups described below.

<Modifier>
In the present invention, the modified SBR preferably has a protic amino group and / or a protected amino group and a hydrocarbyloxysilane group at the same polymerization terminal. It is preferable to use a bifunctional silicon compound having a secondary amino group.
Examples of the bifunctional silicon compound having a protected primary amino group in the same molecule include compounds represented by formula (I), formula (II) and formula (III).

Wherein R ¹ and R ² are each independently a hydrocarbon group having 1 to 20 carbon atoms, R ^{3 to} R ⁵ are each independently a hydrocarbon group having 1 to 20 carbon atoms, and R ⁶ is a carbon number 1 To 12 divalent hydrocarbon groups, A represents a reactive group, and f represents an integer of 1 to 10.)

(In the formula, R ^{7 to} R ¹¹ each independently represent a hydrocarbon group having 1 to 20 carbon atoms, and R ¹² represents a divalent hydrocarbon group having 1 to 12 carbon atoms.)

Wherein R ¹ and R ² are each independently a hydrocarbon group having 1 to 20 carbon atoms, R ^{3 to} R ⁵ are each independently a hydrocarbon group having 1 to 20 carbon atoms, and R ⁶ is a carbon number 1 12 divalent hydrocarbon group, R ¹³ is a divalent hydrocarbon group having 1 to 12 carbon atoms, a represents a reactive group, f is an integer from 1 to 10.)

  In the above formulas (I) to (III), specific examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms are, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl. Group, isobutyl group, sec-butyl group, tert-butyl group, various pentyl groups, various hexyl groups, various octyl groups, various decyl groups, various dodecyl groups, various tetradecyl groups, various hexadecyl groups, various octadecyl groups, various icosyl groups , Cyclopentyl group, cyclohexyl group, vinyl group, propenyl group, allyl group, hexenyl group, octenyl group, cyclopentenyl group, cyclohexenyl group, phenyl group, tolyl group, xylyl group, naphthyl group, benzyl group, phenethyl group, A naphthylmethyl group etc. are mentioned. Of these, a methyl group having 1 to 4 carbon atoms, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, and the like are preferable. A butyl group is more preferred.

Examples of the divalent hydrocarbon group having 1 to 12 carbon atoms include an alkylene group having 1 to 12 carbon atoms, an arylene group having 6 to 12 carbon atoms, and an arylene alkylene group having 7 to 12 carbon atoms.
The alkylene group having 1 to 12 carbon atoms may be linear or branched, and specifically includes a methylene group, an ethylene group, a trimethylene group, a tetramethylene group, a hexamethylene group, and an octamethylene group. Linear alkylene groups such as decamethylene group, propylene group, isopropylene group, isobutylene group, 2-methyltrimethylene group, isopentylene group, isohexylene group, isooctylene group, 2-ethylhexylene group, isodecylene group, etc. A branched alkylene group may be mentioned.
Examples of the arylene group having 6 to 12 carbon atoms include phenylene group, methylphenylene group, dimethylphenylene group, and naphthylene group. Examples of the arylene alkylene group having 7 to 12 carbon atoms include phenylenemethylene group and phenyleneethylene. Group, xylylene group and the like. Among them, an alkylene group having 1 to 4 carbon atoms is preferable, and a trimethylene group is particularly preferable.

The reactive group of A is preferably a halogen atom, a hydrocarbyloxy group having 1 to 20 carbon atoms, or a hydroxy group. Examples of the halogen atom include fluorine, chlorine, bromine, and iodine. Among them, chlorine is preferable.
Examples of the hydrocarbyloxy group having 1 to 20 carbon atoms include an alkoxy group having 1 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, and an aralkyloxy group having 7 to 20 carbon atoms.
Examples of the alkoxy group having 1 to 20 carbon atoms include methoxy group, ethoxy group, n-propoxy group, n-butoxy group, isobutoxy group, sec-butoxy group, tert-butoxy group, various hexoxy groups, various octoxy groups, and various types. Examples include decyloxy groups, various dodecyloxy groups, various tetradecyloxy groups, various hexadecyloxy groups, various octadecyloxy groups, and various icosyloxy groups. Examples of the aryloxy group having 6 to 20 carbon atoms include phenoxy group, methylphenoxy group, dimethylphenoxy group, and naphthoxy group. Examples of the aralkyloxy group having 7 to 20 carbon atoms include benzyloxy group, phenethyloxy group, A naphthyl methoxy group etc. are mentioned. Among these, 1-4 alkoxy groups are preferable, and an ethoxy group is particularly preferable.

  In addition, when the hydroxy group bonded to the silicon atom obtained by hydrolysis in advance reacts with a reinforcing filler, particularly silica, compared with the alkoxy group, the reactivity with silica is higher, and the rubber composition contains There is a great effect that the dispersibility of silica is improved and the low heat build-up of the rubber composition is improved. Furthermore, when the characteristic group that generates a hydroxy group by hydrolysis is an alkoxy group, a volatile organic compound (VOC, particularly alcohol) is generated, but a hydroxy group is not generated.

Examples of other reactive groups include groups containing a carbonyl group, an acid anhydride residue, each dihydroimidazolinyl group, an N-methylpyrrolidonyl group, an isocyanate group, and the like.
Further, two of R ³ , R ⁴ and R ⁵ in formula (I) may be bonded to form a 4- to 7-membered ring together with the silicon atom to which they are bonded. Two of R ⁹ , R ¹⁰ and R ¹¹ in (II) may be bonded to form a 4- to 7-membered ring together with the silicon atom to which they are bonded. Examples of the 4- to 7-membered ring include those having a methylene group having 4 to 7 carbon atoms.

  Examples of the compound containing a protected primary amino group and a bifunctional silicon atom having at least an alkoxy group bonded to a silicon atom include N, N-bis (trimethylsilyl) aminopropylmethyldimethoxysilane, N, N-bis ( Trimethylsilyl) aminopropylmethyldiethoxysilane, N, N-bis (trimethylsilyl) aminoethylmethyldimethoxysilane, N, N-bis (trimethylsilyl) aminoethylmethyldiethoxysilane, and 1-trimethylsilyl-2-ethoxy-2-methyl Examples thereof include -1-aza-2-silacyclopentane.

Examples of the compound in which A is a halogen atom include N, N-bis (trimethylsilyl) aminopropylmethylmethoxychlorosilane, N, N-bis (trimethylsilyl) aminopropylmethylethoxychlorosilane, and N, N-bis (trimethylsilyl) aminoethyl. Examples include methylmethoxychlorosilane and N, N-bis (trimethylsilyl) aminoethylmethylethoxychlorosilane.
Preferably, N, N-bis (trimethylsilyl) aminopropylmethyldimethoxysilane, N, N-bis (trimethylsilyl) aminopropylmethyldiethoxysilane, 1-trimethylsilyl-2-ethoxy-2-methyl-1-aza-2- Silacyclopentane.

These modifiers may be used alone or in combination of two or more. The modifier may be a partial condensate.
Here, the partial condensate means a product in which a part (not all) of the modifier SiOR is SiOSi bonded by condensation.
In the above modification reaction, it is preferable that the polymer to be used has at least 10% of the polymer chain having a living property.

  In the denaturing reaction with the denaturing agent, the amount of the denaturing agent is preferably 0.5 to 200 mmol / kg · SBR. The content is more preferably 1 to 100 mmol / kg · SBR, and particularly preferably 2 to 50 mmol / kg · SBR. Here, SBR means the mass of only a polymer that does not contain an additive such as an anti-aging agent added during or after production. By making the usage-amount of a modifier into the said range, it is excellent in the dispersibility of a filler and the fracture | rupture characteristic after vulcanization | cure, an abrasion characteristic, and low exothermic property are improved.

  The method for adding the modifier is not particularly limited, and examples thereof include a batch addition method, a division addition method, and a continuous addition method. preferable. Further, the modifier may be bonded to any of the polymerization initiation terminal, the polymerization termination terminal, the polymer main chain, and the side chain, but it can improve the low heat build-up by suppressing energy loss from the polymer terminal. Therefore, it is preferably introduced at the polymerization initiation terminal or the polymerization termination terminal.

<Condensation accelerator>
In the present invention, it is preferable to use a condensation accelerator in order to accelerate the condensation reaction involving the alkoxysilane compound having a protected primary amino group used as the modifier.
Examples of such a condensation accelerator include a compound containing a tertiary amino group, or among group 3, 4, 5, 12, 13, 14, and 15 of the periodic table (long period type). An organic compound containing one or more elements belonging to any of the above can be used. Further, as a condensation accelerator, an alkoxide, carboxylate, or acetyl containing at least one metal selected from the group consisting of titanium (Ti), zirconium (Zr), bismuth (Bi), and aluminum (Al). An acetonate complex salt is preferred.

The condensation accelerator used here can be added before the modification reaction, but is preferably added to the modification reaction system during and / or after the modification reaction. When added before the denaturation reaction, a direct reaction with the active end may occur, and a hydrocarbyloxy group having a protected primary amino group at the active end may not be introduced.
The addition time of the condensation accelerator is usually 5 minutes to 5 hours after the start of the modification reaction, preferably 15 minutes to 1 hour after the start of the modification reaction.

  Specific condensation accelerators include tetrakis (2-ethyl-1,3-hexanediolato) titanium, tetrakis (2-methyl-1,3-hexanediolato) titanium, tetrakis (2-propyl-1,3). -Hexanediolato) titanium, tetrakis (2-butyl-1,3-hexanediolato) titanium, tetrakis (1,3-hexanediolato) titanium, tetrakis (1,3-pentanediolato) titanium, tetrakis (2 -Methyl-1,3-pentanediolato) titanium, tetrakis (2-ethyl-1,3-pentanediolato) titanium, tetrakis (2-propyl-1,3-pentanediolato) titanium, tetrakis (2-butyl) -1,3-pentanediolato) titanium, tetrakis (1,3-heptanediolato) titanium, tetrakis (2-methyl-1,3- Butanediolato) titanium, tetrakis (2-ethyl-1,3-heptanediolato) titanium, tetrakis (2-propyl-1,3-heptanediolato) titanium, tetrakis (2-butyl-1,3-heptanediolato) titanium, tetrakis (2- Ethylhexoxy) titanium, tetramethoxy titanium, tetraethoxy titanium, tetra-n-propoxy titanium, tetraisopropoxy titanium, tetra-n-butoxy titanium, tetra-n-butoxy titanium oligomer, tetraisobutoxy titanium, tetra-sec-butoxy titanium , Tetra-tert-butoxytitanium, bis (oleate) bis (2-ethylhexanoate) titanium, titanium dipropoxybis (triethanolamate), titanium dibutoxybis (triethanolamate), tita Tributoxy systemate, titanium tripropoxy systemate, titanium tripropoxyacetylacetonate, titanium dipropoxybis (acetylacetonate), titanium tripropoxy (ethylacetoacetate), titanium propoxyacetylacetonatebis (ethylacetoacetate), titanium Tributoxyacetylacetonate, titanium dibutoxybis (acetylacetonate), titanium tributoxyethylacetoacetate, titaniumbutoxyacetylacetonatebis (ethylacetoacetate), titanium tetrakis (acetylacetonate), titanium diacetylacetonatebis (ethyl) Acetoacetate), bis (2-ethylhexanoate) titanium oxide, bis (laurate) titanium oxide, bis (naphthate) Titanium oxide, bis (stearate) titanium oxide, bis (oleate) titanium oxide, bis (linoleate) titanium oxide, tetrakis (2-ethylhexanoate) titanium, tetrakis (laurate) titanium, tetrakis (naphthate) titanium, tetrakis ( Stearate) titanium, tetrakis (oleate) titanium, tetrakis (linoleate) titanium, titanium di-n-butoxide (bis-2,4-pentanedionate), titanium oxide bis (stearate), titanium oxide bis (tetramethylheptanedio) Nate), titanium oxide bis (pentanedionate), titanium tetra (lactate) and the like. Among these, tetrakis (2-ethyl-1,3-hexanediolato) titanium, tetrakis (2-ethylhexoxy) titanium, and titanium di-n-butoxide (bis-2,4-pentanedionate) are preferable.

  Examples of the condensation accelerator include tris (2-ethylhexanoate) bismuth, tris (laurate) bismuth, tris (naphthate) bismuth, tris (stearate) bismuth, tris (oleate) bismuth, and tris (linoleate). Bismuth, tetraethoxyzirconium, tetra-n-propoxyzirconium, tetraisopropoxyzirconium, tetra-n-butoxyzirconium, tetra-sec-butoxyzirconium, tetra-tert-butoxyzirconium, tetra (2-ethylhexoxy) zirconium, zirconium tributoxy Stearate, zirconium tributoxyacetylacetonate, zirconium dibutoxybis (acetylacetonate), zirconium tributoxyethylacetoacetate Zirconium butoxyacetylacetonate bis (ethylacetoacetate), zirconium tetrakis (acetylacetonate), zirconium diacetylacetonate bis (ethylacetoacetate), bis (2-ethylhexanoate) zirconium oxide, bis (laurate) zirconium oxide, Bis (naphthate) zirconium oxide, bis (stearate) zirconium oxide, bis (oleate) zirconium oxide, bis (linoleate) zirconium oxide, tetrakis (2-ethylhexanoate) zirconium, tetrakis (laurate) zirconium, tetrakis (naphthate) Zirconium, Tetrakis (stearate) zirconium, Tetrakis (oleate) zirconium, Tet Mention may be made of a kiss (linoleate) zirconium and the like.

  Also, triethoxyaluminum, tri-n-propoxyaluminum, triisopropoxyaluminum, tri-n-butoxyaluminum, tri-sec-butoxyaluminum, tri-tert-butoxyaluminum, tri (2-ethylhexoxy) aluminum, aluminum dibutoxy Stearate, aluminum dibutoxyacetylacetonate, aluminum butoxybis (acetylacetonate), aluminum dibutoxyethylacetoacetate, aluminum tris (acetylacetonate), aluminum tris (ethylacetoacetate), tris (2-ethylhexanoate) ) Aluminum, Tris (laurate) aluminum, Tris (naphthate) aluminum, Tris (stearate) aluminum, To Scan (oleate) aluminum, tris (linolate) aluminum, and the like.

  Of the above-mentioned condensation accelerators, titanium-based condensation accelerators are preferred, and titanium metal alkoxides, titanium metal carboxylates, or titanium metal acetylacetonate complex salts are particularly preferred. The amount of the condensation accelerator used is preferably such that the number of moles of the compound is 0.1 to 10 as the molar ratio to the total amount of hydrocarbyloxy groups present in the reaction system, and 0.5 to 5 Particularly preferred. By setting the use amount of the condensation accelerator within the above range, the condensation reaction proceeds efficiently.

The condensation reaction in the present invention proceeds in the presence of the above-described condensation accelerator and water vapor or water. An example of the presence of water vapor is a solvent removal treatment by steam stripping, and the condensation reaction proceeds during steam stripping. The condensation reaction may be carried out in an aqueous solution, and the condensation reaction temperature is preferably 85 to 180 ° C, more preferably 100 to 170 ° C, and particularly preferably 110 to 150 ° C.
By setting the temperature during the condensation reaction within the above range, the condensation reaction can be efficiently progressed and completed, and deterioration in quality due to the aging reaction of the polymer due to the change over time of the modified SBR obtained can be suppressed.

The condensation reaction time is usually about 5 minutes to 10 hours, preferably about 15 minutes to 5 hours. By setting the condensation reaction time within the above range, the condensation reaction can be completed smoothly.
Moreover, the pressure of the reaction system at the time of the condensation reaction is usually 0.01 to 20 MPa, preferably 0.05 to 10 MPa.
There is no restriction | limiting in particular about the format in the case of performing a condensation reaction in aqueous solution, You may carry out by a continuous type using apparatuses, such as a batch type reactor and a multistage continuous type reactor. Moreover, you may perform this condensation reaction and desolvent simultaneously.

The primary amino group derived from the modifying agent of the modified SBR is generated by performing a deprotection treatment as described above. Specific examples of suitable deprotection treatments other than the solvent removal treatment using steam such as steam stripping described above will be described in detail below.
That is, the protecting group on the primary amino group is converted to a free primary amino group by hydrolysis. By removing the solvent, a modified SBR having a primary amino group can be obtained. In addition, the deprotection treatment of the protected primary amino group derived from the modifier can be performed as necessary in any step from the step including the condensation treatment to the solvent removal to the dry polymer.

The Mooney viscosity (ML _{1 + 4} , 100 ° C.) of the modified SBR according to the present invention is preferably 10 to 150, more preferably _{15 to} 100. By setting the Mooney viscosity value within the above range, a rubber composition having excellent kneading workability and mechanical properties after vulcanization can be obtained.

The modified SBR according to the present invention has a protic amino group and / or a protected amino group, preferably these amine functional groups and a hydrocarbyloxysilane group, in the polymer. The group dissociation group has a good interaction with carbon black and silica, while the hydrocarbyloxysilane group has a particularly excellent interaction with silica.
The rubber composition containing the modified SBR can provide a pneumatic tire (for example, a heavy-duty tire) having excellent fracture characteristics and wear characteristics and ensuring low heat build-up.

As described above, the rubber composition for a base rubber according to the present invention contains a synthetic rubber and a natural rubber as rubber components, and at least one of the synthetic rubbers is an amine functional group-modified styrene-butadiene as described above. It is a copolymer. Moreover, a filler etc. are mix | blended suitably.
Hereinafter, the rubber component and the like will be described.

(Rubber component)
The content of the modified SBR in the rubber component is preferably 10% by mass or more, and more preferably 40% by mass or more. By setting the modified SBR in the rubber component in the above range, a rubber composition having desired physical properties can be obtained.

  This modified SBR may be used singly or in combination of two or more. As other rubber components used in combination with the modified SBR and natural rubber within the scope of the effects of the present invention, synthetic isoprene rubber, butadiene rubber, styrene-butadiene rubber, ethylene-α-olefin copolymer rubber, ethylene- Examples include α-olefin-diene copolymer rubber, acrylonitrile-butadiene copolymer rubber, chlorobrene rubber, halogenated butyl rubber, and mixtures thereof. Further, some of them may have a branched structure by using a polyfunctional type, for example, a modifier such as tin tetrachloride or silicon tetrachloride. Of these, natural rubber and synthetic isoprene rubber are preferable, and natural rubber is particularly preferable.

(filler)
The rubber composition according to the present invention can contain a reinforcing filler as the filler. Examples of the reinforcing filler include carbon black and silica.
As long as carbon black enhances the mechanical performance of the base rubber and improves processability, etc., a known range in which the ranges of I ₂ adsorption amount, CTAB specific surface area, N ₂ adsorption amount, DBP adsorption amount, etc. are appropriately selected Carbon black can be used. As the type of carbon black, for example, known ones such as SAF, ISAF-LS, HAF, HAF-HS can be appropriately selected and used.

Silica does not represent only silicon dioxide in a narrow sense, but means a silicate-based filler. Specifically, in addition to anhydrous silicic acid, hydrous silicic acid, calcium silicate, aluminum silicate, etc. Contains silicate. Of these, wet silica having excellent wear resistance is preferred. Examples of such silica include “Nipseal AQ” (BET specific surface area: 195 m ² / g) manufactured by Tosoh Silica.

  The filler is preferably 30 to 65 parts by mass and more preferably 35 to 55 parts by mass per 100 parts by mass of the rubber component. By setting it as 30-65 mass parts, a destructive characteristic can be maintained and the fall of the kneading | mixing workability | operativity of a composition can be suppressed.

(Silane coupling agent)
In the rubber composition according to the present invention, when silica is used as the reinforcing filler, a silane coupling agent can be blended for the purpose of further improving the reinforcing property and low heat build-up. The blending amount of the preferred silane coupling agent varies depending on the kind of the silane coupling agent, but is preferably selected in the range of 2 to 20% by mass with respect to silica.
By setting it as 2 mass% or more, it becomes difficult to fully exhibit the effect as a coupling agent, and by setting it as 20 mass% or less, gelatinization of a rubber component can be prevented. From the viewpoint of the effect as a coupling agent and the prevention of gelation, the preferred amount of the silane coupling agent is in the range of 5 to 15% by mass.

  Preferred silane coupling agents include the following general formula (IV)

A silane coupling agent comprising a protected mercaptosilane represented by the formula:
In the general formula (IV), R ¹⁴ represents R ¹⁹ O—, R ¹⁹ C (═O) O—, R ¹⁹ R ²⁰ C═NO—, R ¹⁹ R ²⁰ N— or — (OSiR ¹⁹ R ²⁰ ) _m ( OSiR ¹⁸ R ¹⁹ R ²⁰ ) (wherein R ¹⁹ and R ²⁰ are each independently a hydrogen atom or a monovalent hydrocarbon group having 1 to 18 carbon atoms), R ¹⁵ is the substituent mentioned in R ¹⁴ A group, a hydrogen atom or a monovalent hydrocarbon group having 1 to 18 carbon atoms, R ¹⁶ is the substituent described in R ¹⁴ and R ¹⁵ , or a — [O (R ²¹ O) _a ] _0.5 — group (provided that R ²¹ is an alkylene group having 1 to 18 carbon atoms, a is an integer of 1 to 4), R ¹⁷ is a divalent hydrocarbon group having 1 to ¹⁸ carbon atoms, and R ¹⁸ is one having 1 to ¹⁸ carbon atoms. And x, y, and z are numbers satisfying the relationship of x + y + 2z = 3, 0 ≦ x ≦ 3, 0 ≦ y ≦ 2, and 0 ≦ z ≦ 1.

  In the general formula (IV), examples of the monovalent hydrocarbon group having 1 to 18 carbon atoms include an alkyl group having 1 to 18 carbon atoms, an alkenyl group having 2 to 18 carbon atoms, and an aryl group having 6 to 18 carbon atoms, Examples thereof include aralkyl groups having 7 to 18 carbon atoms. Here, the alkyl group and alkenyl group may be linear, branched or cyclic, and the aryl group and aralkyl group may have a substituent such as a lower alkyl group on the aromatic ring. Good.

  Specific examples of the monovalent hydrocarbon group having 1 to 18 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, Pentyl group, hexyl group, octyl group, decyl group, dodecyl group, cyclopentyl group, cyclohexyl group, vinyl group, propenyl group, allyl group, hexenyl group, octenyl group, cyclopentenyl group, cyclohexenyl group, phenyl group, tolyl Group, xylyl group, naphthyl group, benzyl group, phenethyl group, naphthylmethyl group and the like.

In the general formula (IV), the alkylene group having 1 to 18 carbon atoms represented by R ²¹ may be linear, branched or cyclic, and is particularly preferably linear. . Examples of the linear alkylene group include a methylene group, an ethylene group, a trimethylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group, an octamethylene group, a decamethylene group, and a dodecamethylene group.

Examples of the divalent hydrocarbon group having 1 to 18 carbon atoms represented by R ¹⁷ include an alkylene group having 1 to 18 carbon atoms, an alkenylene group having 2 to 18 carbon atoms, and a cycloalkylene having 5 to 18 carbon atoms. Groups, cycloalkylalkylene groups having 6 to 18 carbon atoms, arylene groups having 6 to 18 carbon atoms, and aralkylene groups having 7 to 18 carbon atoms. The alkylene group and alkenylene group may be linear or branched, and the cycloalkylene group, cycloalkylalkylene group, arylene group, and aralkylene group may have a substituent such as a lower alkyl group on the ring. You may have.
R ¹⁷ is preferably an alkylene group having 1 to 6 carbon atoms, particularly preferably a linear alkylene group such as a methylene group, an ethylene group, a trimethylene group, a tetramethylene group, a pentamethylene group, or a hexamethylene group. it can.

  Examples of the silane coupling agent represented by the general formula (IV) include 3-hexanoylthiopropyltriethoxysilane, 3-octanoylthiopropyltriethoxysilane, 3-decanoylthiopropyltriethoxysilane, 3- Lauroylthiopropyltriethoxysilane, 2-hexanoylthioethyltriethoxysilane, 2-octanoylthioethyltriethoxysilane, 2-decanoylthioethyltriethoxysilane, 2-lauroylthioethyltriethoxysilane, 3-hexanoyl Ruthiopropyltrimethoxysilane, 3-octanoylthiopropyltrimethoxysilane, 3-decanoylthiopropyltrimethoxysilane, 3-lauroylthiopropyltrimethoxysilane, 2-hexanoylthioethyltrimethoxysilane, 2-o Motor noise Lucio ethyltrimethoxysilane, 2- deca Neu thio ethyltrimethoxysilane, and the like of 2-lauroyl thio ethyltrimethoxysilane.

  By using such a silane coupling agent, the rubber composition according to the present invention can be kneaded for a long time by increasing the time until the occurrence of burns due to the decrease in the viscosity of the unvulcanized rubber. Thus, the workability at the time of kneading and processing of the rubber composition is excellent, the dispersion of silica into the rubber component is improved, and the reactivity between silica and the polymer is improved, so that hysteresis loss can be reduced. Utilizing this improvement, it becomes possible to increase the blending amount of the reinforcing filler, and as a result, it is possible to obtain a heavy duty tire with good wear resistance.

In this invention, the said silane coupling agent may be used individually by 1 type, and may be used in combination of 2 or more type.
Furthermore, in order to couple the silane coupling agent and the polymer, it is preferable to add a proton donor typified by DPG (diphenylguanidine) or the like as a deprotecting agent in the final kneading step. The amount used is preferably from 0.1 to 5.0 parts by weight, more preferably from 0.2 to 3.0 parts by weight, per 100 parts by weight of the rubber component.

  In addition, a sulfur-containing silane compound having a specific structure having an organooxysilyl group at both ends of a molecule described in the WO 2004/000930 pamphlet published by the present applicant and having a sulfide or polysulfide at the center of the molecule is disclosed in the present invention. When used as a silane coupling agent according to the present invention, the rubber composition has a low unvulcanized viscosity and a high dispersibility of silica. High, suppresses the temperature rise of the running base rubber.

Furthermore, conventionally used silane coupling agents can also be applied.
Examples of the silane coupling agent include bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, and bis (2-triethoxy). Silylethyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyl Trimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N, N-dimethylthiocarba Yl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxy Ethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis (3-diethoxymethylsilylpropyl) tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N, N-dimethylthiocarbamoyl Tetrasulfide, dimethoxymethylsilylpropyl benzothiazolyl tetrasulfide, etc. are mentioned. Of these, bis 3-triethoxysilylpropyl) polysulfide and 3-trimethoxysilylpropyl benzothiazolyl tetrasulfide are preferable.
One of these silane coupling agents may be used alone, or two or more thereof may be used in combination.

(Preparation of rubber composition)
In the rubber composition according to the present invention, various chemicals usually used in the rubber industry, for example, a vulcanizing agent, a vulcanization accelerator, a process oil, and an anti-aging agent, as long as the object of the present invention is not impaired. Further, a scorch inhibitor, zinc white, stearic acid, and the like can be contained.

  As said vulcanizing agent, sulfur etc. are mentioned, The usage-amount is 0.1-10.0 mass parts as sulfur content with respect to 100 mass parts of (A) rubber components, More preferably, it is 1.0. -5.0 parts by mass. When it is 0.1 part by mass or more, it is possible to prevent the vulcanized rubber from being deteriorated in breaking strength, abrasion resistance, and low heat build-up, and when it is 10.0 parts by mass or less, rubber elasticity is lost. Can be prevented.

  The vulcanization accelerator that can be used in the present invention is not particularly limited, and examples thereof include M (2-mercaptobenzothiazole), DM (dibenzothiazyl disulfide), and CZ (N-cyclohexyl-2-benzothiazyl). Sulfenamide) and other guanidine vulcanization accelerators such as DPG (diphenylguanidine) can be mentioned, and the amount used is 0.1 with respect to 100 parts by mass of (A) rubber component. -5.0 mass parts is preferable, More preferably, it is 0.2-3.0 mass parts.

  Examples of the process oil that can be used in the rubber composition of the present invention include paraffinic, naphthenic, and aromatic oils. Aromatics are used for applications that emphasize tensile strength and wear resistance, and naphthenic or paraffinic systems are used for applications that emphasize hysteresis loss and low-temperature characteristics. The amount of use is preferably 0 to 100 parts by mass with respect to 100 parts by mass of the rubber component (A), and by setting it to 100 parts by mass or less, the tensile strength and low heat build-up of the vulcanized rubber are prevented from decreasing. be able to.

  The rubber composition in the present invention is obtained by kneading using a kneading machine such as a roll or an internal mixer, and is vulcanized after molding and used as a base rubber in a tire tread portion.

[Pneumatic tire]
The pneumatic tire of the present invention includes a tread portion having a cap / base structure, and is manufactured by a normal method using the rubber composition according to the present invention as a base rubber of the tread portion. That is, if necessary, a rubber composition containing various chemicals as described above is processed into a base rubber at an unvulcanized stage, and is pasted and molded by a normal method on a tire molding machine. Molded. The green tire is heated and pressurized in a vulcanizer to obtain a pneumatic tire. The pneumatic tire has good wear resistance and durability while ensuring low heat build-up, and can be applied to, for example, a heavy duty tire.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.

The physical properties of unmodified or modified SBR were measured according to the following methods.
<Microstructure analysis method>
The vinyl bond content (%) was measured by an infrared method (Morero method).
<Bound styrene content (mass% in polymer)>
It was determined by 270 MHz 1H-NMR.
<Measurement of Mooney viscosity (ML _{1 + 4} , 100 ° C.)>
According to JIS K6300, L rotor, preheating 1 minute, rotor operating time 4 minutes, temperature 100 ° C.

Example 1
<Synthesis of modifier>
In a nitrogen atmosphere, 36 g of 3-aminopropylmethyldiethoxysilane (manufactured by Gelest) was added as an aminosilane site to 400 ml of dichloromethane solvent in a glass flask equipped with a stirrer, and trimethylsilane chloride (Aldrich) was further added as a protective site. 48 ml and triethylamine 53 ml were added to the solution, and the mixture was stirred at room temperature for 17 hours, and then the solvent was removed by applying the reaction solution to an evaporator to obtain a reaction mixture. The obtained reaction mixture was further decompressed under conditions of 665 Pa. By distillation, 40 g of N, N-bis (trimethylsilyl) aminopropylmethyldiethoxysilane (modifier) was obtained as a 130-135 ° C. fraction.

<Synthesis of primary amine-modified styrene-butadiene rubber>
An autoclave reactor with an internal volume of 5 liters purged with nitrogen was charged with 2,750 g of cyclohexane, 41.3 g of tetrahydrofuran, 125 g of styrene, and 375 g of 1,3-butadiene. After adjusting the temperature of the reactor contents to 10 ° C., 215 mg of n-butyllithium was added to initiate polymerization. The polymerization was carried out under adiabatic conditions and the maximum temperature reached 85 ° C.
When the polymerization conversion rate reached 99%, 10 g of butadiene was added, and polymerization was further performed for 5 minutes. The polymer solution from the reactor was sampled in a small amount in 30 g of a cyclohexane solution to which 1 g of methanol was added, and then 1129 mg of N, N-bis (trimethylsilyl) aminopropylmethyldiethoxysilane obtained in Synthesis Example 1 was added to perform the modification reaction. I went for 15 minutes. Thereafter, 8.11 g of tetrakis (2-ethyl-1,3-hexanediolato) titanium as a condensation accelerator was added, and the mixture was further stirred for 15 minutes to conduct a condensation reaction. Finally, 2.6-di-tert-butyl-p-cresol was added to the polymer solution after the reaction. Next, the solvent is removed by steam stripping and the protected primary amino group is deprotected, and the rubber is dried with a ripening roll adjusted to 110 ° C. to give a primary amine-modified styrene-butadiene rubber (amine functional group). Modified styrene-butadiene copolymer SBR (A) in Table 1) was obtained. The obtained primary amine-modified styrene-butadiene rubber had a bound styrene content of 24.5% by mass, a vinyl content in the conjugated diene part of 56 mol%, and a Mooney viscosity of 32.

<Preparation of rubber composition>
The above primary amine-modified styrene-butadiene rubber, NR, carbon black (HAF N330), silica, stearic acid, zinc white, anti-aging agent, accelerator, and sulfur are mixed in the formulation shown in Table 1 below to obtain a base. A rubber composition for rubber was prepared.

<Production of pneumatic tire>
The produced rubber composition for base rubber was applied to a tread base rubber member to produce a pneumatic tire having a tire size of 180R33.

Examples 2, 3 and Comparative Examples 1-6
A rubber composition for a base rubber and a pneumatic tire were produced in the same manner as in Example 1 except that the formulation was as shown in Table 1 below.

  In addition, S-SBR used in Comparative Example 6 is an emulsion polymerization SBR of “SL552” manufactured by JSR Corporation.

Example 4
A primary amine-modified styrene-like compound as in Example 1 except that N, N-bis (trimethylsilyl) aminopropylmethyltriethoxysilane was used instead of N, N-bis (trimethylsilyl) aminopropylmethyldiethoxysilane. A butadiene rubber (an amine functional group-modified styrene-butadiene copolymer, corresponding to SBR (B) in Table 1) was produced, and a rubber composition for a base rubber and a pneumatic tire were further produced.

Example 5
Primary amine-modified styrene-butadiene in the same manner as in Example 1 except that N, N-bis (trimethylsilyl) aminopropyldimethylethoxysilane was used instead of N, N-bis (trimethylsilyl) aminopropylmethyldiethoxysilane. Rubber (amine functional group-modified styrene-butadiene copolymer, corresponding to SBR (C) in Table 1) was prepared, and further, a rubber composition for a base rubber and a pneumatic tire were prepared.

  The following evaluations were performed on the rubber composition for a base rubber or the pneumatic tire produced in each example and comparative example. The results are shown in Table 1 below.

<Evaluation>
<Low heat generation>
(1) Rebound resilience Measured according to JIS K 6301 under vulcanization conditions at 145 ° C. for 30 minutes.
(2) Equivalent tire temperature A test tire of 1800R13 was made with each base rubber, a drum test was conducted at a constant speed of 10 km / hr, an initial internal pressure of 700 kPa and a load of 10.9 ton, and a constant depth after running for 24 hours. The temperature was measured at the position. The value of Comparative Example 1 was set to 100, and the values of Examples and Comparative Examples were displayed as indices. The larger the index, the greater the effect of reducing heat generation.

<Abrasion resistance>
In accordance with JIS K 6264-2: 2005, a rubber sample vulcanized under vulcanization conditions at 145 ° C. for 30 minutes was worn at a slip rate of 25% and indexed with the value of the reciprocal of the wear amount being 100. It shows that abrasion resistance is excellent, so that a numerical value is large.

<Cut resistance>
After buffing to 10 mm of the remaining groove of the pneumatic tire produced in each example and comparative example and running for 500 Hrs, the appearance of the tire base portion was visually evaluated. Cut scratches per 10 lag (thickness of 30 mm or more) were counted, and the value of each example and comparative example was displayed as an index with the value of comparative example 1 being 100. The larger the index, the greater the effect of cut resistance.

［注］
ＨＡＦ Ｎ３３０：旭カーボン社製「＃７０」
ＩＳＡＦ Ｎ２２０：旭カーボン社製「＃８０」
シリカ：東ソー・シリカ株式会社製「ニプシルＡＱ」
老化防止剤：大内新興化学工業社製「ノクセラー６Ｃ」
促進剤：大内新興化学工業社製「ノクセラーＣＺ」

[note]
HAF N330: “# 70” manufactured by Asahi Carbon Co.
ISAF N220: “# 80” manufactured by Asahi Carbon Co., Ltd.
Silica: “Nipsil AQ” manufactured by Tosoh Silica Corporation
Anti-aging agent: “Noxeller 6C” manufactured by Ouchi Shinsei Chemical Co., Ltd.
Accelerator: “Noxeller CZ” manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

In Comparative Example 2, although the heat generation was reduced due to the increase in the crosslinking density, the cut resistance was markedly reduced. In Comparative Example 3, the cut resistance was improved by upgrading the carbon black, but the exothermic deterioration was great. In Comparative Example 4, the cut resistance was improved by applying silica, but as with Comparative Example 3, the exothermic deterioration was accompanied. Therefore, when it was attempted to ensure low heat build-up by reducing the amount of filler as in Comparative Example 5, it was difficult to ensure cut resistance. When S-SBR is applied as in Comparative Example 6, the cut resistance is greatly improved, but the function as a base rubber cannot be achieved because the low heat build-up is greatly deteriorated.
On the other hand, in Example 1, since the first amine-modified SBR was applied, it was possible to improve the cut resistance while ensuring low heat generation. In Example 2, since the primary amine-modified SBR was applied and the amount of the filler was further reduced, low exothermic property and cut resistance could be achieved at a high level. In Example 3, by increasing the blending amount of the primary amine-modified SBR, similarly to Example 2, low exothermic property and cut resistance could be achieved at the next highest level. In Examples 4 and 5, it was found that even when the modifier was changed, good low heat build-up and wear resistance were obtained, and the modifier was able to improve cut resistance.

Claims (3)

  A pneumatic tire comprising a rubber composition containing a synthetic rubber and a natural rubber as a rubber component, wherein at least one of the synthetic rubbers is an amine functional group-modified styrene-butadiene copolymer as a base rubber of a tread.   The pneumatic tire according to claim 1, wherein the amine functional group-modified styrene-butadiene copolymer has a protic amino group and / or a protected amino group as the amine functional group.   The pneumatic tire according to claim 1 or 2, comprising 30 to 65 parts by mass of a filler with respect to 100 parts by mass of the rubber component.