JP4467248B2 - Pneumatic tire - Google Patents

Description

（式中、Ａはエチレン性結合によって重合されたエチレン性不飽和化合物由来の部分であり、各繰り返し単位において同一でも異なっていてもよい）
で表される繰り返し単位から実質的になるポリケトンの繊維で構成したコードを適用したことを特徴とする。
【０００９】
本発明の空気入りタイヤの好適例においては、前記式(I)中のＡがエチレン基である。
【００１０】
【発明の実施の形態】
以下に、本発明を詳細に説明する。本発明の空気入りタイヤは、一対のビード部及び一対のサイドウォール部と、両サイドウォール部に連なるトレッド部とを有し、前記一対のビード部間にトロイド状に延在して、これら各部を補強するラジアルカーカスと、前記ビード部内に夫々埋設したビードコアのタイヤ半径方向外側に配置したビードフィラーと、前記サイドウォール部の前記カーカスの最内側面に配置した一対のサイド補強ゴム層とを具え、前記サイド補強ゴム層及び前記ビードフィラーの少なくとも一方を構成するゴム組成物は、20〜80℃における1％歪時の損失正接(tanδ)の最大値が0.08以上で、150〜250℃における1％歪時の損失正接(tanδ)の最大値が0.05以下であって、且つ、前記サイド補強ゴム層及び前記ビードフィラーの少なくとも一方を構成するゴム組成物のゴム成分は、ビニル結合量が25％以上、重量平均分子量(Ｍw)が20万〜90万、重量平均分子量(Ｍw)と数平均分子量(Ｍn)との比で表わされる分子量分布(Ｍw／Ｍn）が１〜４であるポリブタジエンゴムと天然ゴムとからなり、該ポリブタジエンゴムをゴム成分中に50〜70質量％含み、前記カーカスに上記式(I)で表される繰り返し単位から実質的になるポリケトンの繊維で構成したコードを適用したことを特徴とする。上記ゴム組成物は、通常走行時の温度領域でのtanδが高く、且つランフラット走行時の温度領域でのtanδが低いので、通常走行時の振動や衝撃を熱エネルギーとして充分に拡散できるため、タイヤの乗り心地が向上しており、更に、ランフラット走行時の発熱を充分に抑制することができるため、タイヤのランフラット耐久性の低下が抑制されている。なお、上記ゴム組成物をサイド補強ゴム層又はビードフィラーに用いることにより、ランフラット耐久性と乗り心地とを高度にバランスさせることができるが、サイド補強ゴム層とビードフィラーの両方に用いることにより、ランフラット耐久性と乗り心地とを更に高度にバランスさせることができる。
【００１１】
加硫後の物性として20〜80℃における1％歪時の損失正接(tanδ)の最大値が0.08未満であるゴム組成物を、サイド補強ゴム層及びビードフィラーに用いたタイヤは、通常走行時の振動や衝撃を熱エネルギーとして拡散することが充分にできず、タイヤの乗り心地が悪化する。一方、加硫後の物性として150〜250℃における1％歪時の損失正接(tanδ)の最大値が0.05を超えるゴム組成物を、サイド補強ゴム層及びビードフィラーに用いたタイヤは、ランフラット走行時の発熱を充分に抑制することができず、サイドウォール部の発熱が過度に進み、結果として、タイヤのランフラット耐久性が低下してしまう。
【００１２】
上記サイド補強ゴム層及びビードフィラーに用いるゴム組成物は、ゴム成分として、ビニル結合量が25％以上で、重量平均分子量(Ｍw)が20万〜90万で、重量平均分子量(Ｍw)と数平均分子量(Ｍn)との比で表わされる分子量分布(Ｍw／Ｍn）が１〜４であるポリブタジエンゴムと天然ゴムとからなり、該ポリブタジエンゴムの含有量がゴム成分中50〜70質量％である。
【００１３】
上記ポリブタジエンゴムのビニル結合量が25％未満では、150℃以上の高温下での硫黄架橋切断に伴なう弾性率低下が支配的となるため、温度上昇による弾性率の低下を抑制できず、ランフラット耐久性が低下する。この観点から、上記ポリブタジエンゴムのビニル結合量は、30％以上であるのが好ましく、35％以上であるのが更に好ましく、40〜60％であるのが特に好ましい。また、上記ポリブタジエンゴムの重量平均分子量(Ｍw)が20万未満では、ゴム組成物の引張り特性及び転がり抵抗性が劣り、90万を超えると加工性が劣る傾向がある。この観点から、上記ポリブタジエンゴムの重量平均分子量(Ｍw)は、30万〜80万であるのが更に好ましい。更に、上記ポリブタジエンゴムの分子量分布(Ｍw／Ｍn)が4を超えると、発熱性の低下及び150℃以上の温度領域での弾性率維持が困難となる傾向がある。
【００１４】
上記サイド補強ゴム層及びビードフィラーに用いられるゴム組成物は、ゴム成分の50質量％以上が前述したポリブタジエンゴムである必要がある。ゴム成分における前記ポリブタジエンゴムの含有量が50質量％未満では、ランフラット走行時、即ち、150℃以上での発熱抑制効果が小さく、ランフラット耐久性が低下する。この観点から、前記ポリブタジエンゴムの含有量は、60質量％以上であるのが更に好ましい。
【００１５】
上記ポリブタジエンゴムに用いる単量体は、１,３-ブタジエンである。
【００１６】
上記ポリブタジエンゴムは種々の方法で製造することができ、重合方式としては、バッチ重合方式及び連続重合方式の何れでもよい。好ましい製造方法としては、次のようなものが挙げられる。即ち、１,３-ブタジエンを不活性溶媒、好ましくは炭化水素溶媒中で、有機金属化合物等の開始剤、好ましくは有機リチウム化合物開始剤の存在下で重合して得られる。上記炭化水素溶媒としては特に制限はないが、例えばｎ-ペンタン、ｎ-ヘキサン、ｎ-ヘプタン、シクロヘキサン、ベンゼン、トルエン等が挙げられ、これらの中でも、シクロヘキサン及びｎ-ヘキサンが好ましい。これらの炭化水素溶媒は、単独で用いてもよいし、２種以上を混合して用いてもよい。開始剤として用いられる有機リチウムとしては、少なくとも１個のリチウム原子が結合しており且つ炭素数２〜２０の炭化水素リチウム化合物が好ましく、例えば、ｎ-ブチルリチウム、sec-ブチルリチウム、エチルリチウム、ｎ-プロピルリチウム、ｔ-オクチルリチウム、フェニルリチウム等が挙げられ、これらの中でも、ｎ-ブチルリチウムが特に好ましい。これらの有機リチウム開始剤は、単独で用いてもよいし、２種以上を混合して用いてもよい。ポリブタジエンゴムのビニル結合量は、ジテトラヒドロフリルプロパン、テトラヒドロフラン、ジエチルエーテル、ジメトキシベンゼン、ジメトキシエタン、エチレングリコールジブチルエーテル、トリエチルアミン、ピリジン、Ｎ,Ｎ,Ｎ',Ｎ'-テトラメチルエチレンジアミン、ジピペリジノエタン等のエーテル及び第３級アミン化合物を重合系に適当量添加することにより、適宜変えることができる。
【００１７】
上記ポリブタジエンゴムとしては、分子中にスズ原子及び／又は窒素原子を含む変性ポリブタジエンゴムを用いることができる。分子鎖中にスズ原子や窒素原子などを導入した変性ポリブタジエンゴムは、温度上昇による弾性率の低下を抑制すると共に、カーボンブラック配合ゴム組成物における低発熱性を改良することもできる。該変性ポリブタジエンゴムとしては、多官能変性剤を用いることにより得られる分岐構造を有するものが特に好ましい。上記変性ポリブタジエンゴムは、公知の方法により製造され、通常、有機リチウム開始剤によって重合を開始させ、リチウム活性末端を有する重合体の溶液に各種変性剤を添加することによって得られる（特公平６−８９１８３号公報、特開平１１−２９６５９号公報等参照）。例えば、スズ原子は、四塩化スズ，トリブチルスズクロリド，ジオクチルスズジクロリド，ジブチルスズジクロリド，塩化トリフェニルスズ等のスズ化合物を用いて導入し、窒素原子は、ジイソシアナートジフェニルメタン等のイソシアネート系化合物，４-(ジメチルアミノ)ベンゾフェノン等のアミノベンゾフェノン化合物，４-ジメチルアミノベンジリデンアニリン，ジメチルイミダゾリジノン，Ｎ-メチルピロリドン等の窒素含有化合物を用いて導入することができる。また、例えば、ジエチルアミンのような２級アミン化合物又はヘキサメチレンイミンのようなイミン化合物と有機リチウム化合物とから得られるリチウムアミド開始剤を用いて重合させることにより、変性ポリブタジエンゴムを得ることもできる。
【００１８】
また、上記サイド補強ゴム層及びビードフィラーに用いるゴム組成物は、更にフェノール樹脂及びその硬化剤を含むのが好ましい。ここで、フェノール樹脂としては、フェノール・ホルムアルデヒド樹脂、レゾルシン・ホルムアルデヒド樹脂、クレゾール樹脂などが挙げられ、これらの中でも、フェノール・ホルムアルデヒド樹脂が特に好ましい。フェノール樹脂は100％フェノール樹脂の他、天然樹脂変性フェノール樹脂、油変性フェノール樹脂等を用いることができる。
【００１９】
また、上記フェノール樹脂の硬化剤としては、ヘキサメチレンテトラミン、ヘキサメトキシメチルメラミンなどが挙げられる。これらの組み合わせは自由に選ぶことができ、樹脂及びその硬化剤はそれぞれ複数選択してもよい。また、硬化剤が内添された樹脂を用いてもよい。
【００２０】
上記ゴム組成物には、前述のゴム成分、フェノール樹脂及びその硬化剤の他に、通常ゴム業界で用いられる硫黄、過酸化物等の加硫剤、加硫促進剤、老化防止剤、軟化剤、補強用充填材、無機充填材等の各種配合剤を、適宜配合することができる。また、該ゴム組成物は、更に、各種材質の粒子、繊維、布等との複合体としてもよい。上記ゴム組成物の各物性は、使用するゴム成分及び配合剤の種類、並びにその配合比を適宜選択することにより、前述の範囲内に調整することができる。
【００２１】
本発明の空気入りタイヤのカーカスに用いるコードは、上記式(I)で表される繰り返し単位から実質的になるポリケトン製の繊維よりなる。該ポリケトンは、分子中にＣＯ単位（カルボニル基）とエチレン性不飽和化合物由来の単位とが配列された交互共重合体、即ち、高分子鎖中で各ＣＯ単位の隣に、例えばエチレン単位等のオレフィン単位が一つずつ位置する構造である。また、該ポリケトンは、一酸化炭素と特定のエチレン性不飽和化合物一種との共重合体であってもよく、一酸化炭素とエチレン性不飽和化合物二種以上との共重合体であってもよい。式(I)中のＡを形成するエチレン性不飽和化合物としては、エチレン，プロピレン，ブテン，ペンテン，ヘキセン，ヘプテン，オクテン，ノネン，デセン，ドデセン，スチレン等の不飽和炭化水素化合物、メチルアクリレート，メチルメタクリレート，ビニルアセテート，ウンデセン酸等の不飽和カルボン酸又はその誘導体、更にはウンデセノール，６-クロロヘキセン，Ｎ-ビニルピロリドン，及びスルニルホスホン酸のジエチルエステル等が挙げられる。これらは単独で用いてもよく、二種以上を組み合わせて用いてもよいが、特にポリマーの力学特性や耐熱性等の点から、エチレン性不飽和化合物としてエチレンを主体とするものを用いたポリケトンが好ましい。
【００２２】
エチレンと他のエチレン性不飽和化合物とを併用する場合、エチレンは、全エチレン性不飽和化合物に対し、80モル％以上になるように用いるのが好ましい。80モル％未満では得られるポリマーの融点が200℃以下になり、得られるポリケトン繊維コードの耐熱性が不充分となる場合がある。ポリケトン繊維コードの力学特性や耐熱性の点から、エチレンの使用量は、特に全エチレン性不飽和化合物に対し90モル％以上が好ましい。前記のポリケトンは、公知の方法、例えばヨーロッパ特許公開第１２１９６５号，同第２１３６７１号，同第２２９４０８号及び米国特許第３９１４３９１号明細書に記載された方法に従って製造することができる。
【００２３】
上記ポリケトンの重合度は、ｍ-クレゾール中、60℃で測定した溶液粘度が1.0〜10.0dL/gの範囲にあるのが好ましい。溶液粘度が1.0dL/g未満では、得られるポリケトン繊維コードの力学強度が不充分となる場合があり、コードの力学強度の観点から、溶液粘度が1.2dL/g以上であるのが更に好ましい。一方、溶液粘度が10.0dL/gを超えると、繊維化時の溶融粘度や溶液粘度が高くなりすぎて紡糸性が不良となる場合があり、紡糸性の観点から、溶液粘度が5.0dL/g以下であるのが更に好ましい。繊維の力学強度及び紡糸性などを考慮すると、溶液粘度は1.3〜4.0dL/gの範囲が特に好ましい。
【００２４】
上記ポリケトンの繊維化方法は、特に限定されないが、一般的には溶融紡糸法又は溶液紡糸法が採用される。溶融紡糸法を採用する場合には、例えば特開平１−１２４６１７号公報に記載の方法に従って、ポリマーを通常、融点より20℃以上高い温度、好ましくは融点より40℃程度高い温度で溶融紡糸し、次いで、通常、融点より10℃以下低い温度、好ましくは融点より40℃程度低い温度において、好ましくは3倍以上の延伸比で、更に好ましくは7倍以上の延伸比で延伸処理することにより、容易に所望の繊維を得ることができる。
【００２５】
一方、溶液紡糸法を採用する場合、例えば特開平２−１１２４１３号公報に記載の方法に従って、ポリマーを例えばヘキサフルオロイソプロパノール，ｍ-クレゾール等に0.25〜20質量％、好ましくは0.5〜10質量％の濃度で溶解させ、紡糸ノズルより押し出して繊維化し、次いでトルエン，エタノール，イソプロパノール，ｎ-ヘキサン，イソオクタン，アセトン，メチルエチルケトン等の非溶剤浴、好ましくはアセトン浴中で溶剤を除去、洗浄して紡糸原糸を得、さらに(融点−100℃)〜(融点＋10℃)、好ましくは(融点−50℃)〜(融点)の範囲の温度で延伸処理することにより、所望のフィラメントを得ることができる。また、このポリケトンには、熱，酸素等に対して十分な耐久性を付与する目的で酸化防止剤を加えることが好ましく、また必要に応じて艶消し剤，顔料，帯電防止剤等も配合することができる。
【００２６】
本発明のタイヤに用いるカーカスは、高弾性なポリケトン繊維（ＰＫ繊維）よりなるコードを含むため、通常のレーヨンよりなるコードを適用したカーカスに比べ、通常走行時のタイヤの縦バネを維持しつつ、ランフラット走行時のタイヤの縦バネを向上させることができる。そのため、ＰＫ繊維よりなるコードを適用したカーカスをタイヤに用いることで、通常走行時のタイヤの乗り心地を維持しつつ、ランフラット耐久性を向上させることができる。これは、タイヤに空気が充填された状態でコードに発生する引張り歪よりも、ランフラット走行時にコードに発生する引っ張り歪みの方が大幅に大きいことを利用した作用である。また、上記ポリケトン繊維よりなるコードは、レーヨンよりなるコードに比べ高強度であるため、カーカスにおけるコードの配列本数を減少させても、ランフラット走行時のタイヤの縦バネを維持してランフラット耐久性を維持することができる一方、コードの配列本数を減少させることで、通常走行時のタイヤの縦バネを低下させて乗り心地を改善することができる。
【００２７】
本発明の空気入りタイヤは、ビードフィラー及びサイド補強ゴム層の少なくとも一方に前述の物性を有するゴム組成物を適用し、常法により製造することができる。なお、本発明の空気入りタイヤにおいて、タイヤ内に充填する気体としては、通常の或いは酸素分圧を変えた空気、又は窒素等の不活性ガスを用いることができる。
【００２８】
次に、本発明のタイヤの実施態様を図面に基づき説明する。図１は、本発明の空気入りタイヤの一実施態様を示す断面図である。図１に示すタイヤは、左右一対の一対のビード部１及び一対のサイドウォール部２と、両サイドウォール部２に連なるトレッド部３とを有し、前記一対のビード部１間にトロイド状に延在して、これら各部１，２，３を補強するラジアルカーカス４と、該カーカス４のタイヤ半径方向外側に配置された少なくとも２枚のベルト層からなるベルト５と、前記ビード部１内に夫々埋設したリング状のビードコア６のタイヤ半径方向外側に配置したビードフィラー７と、前記サイドウォール部２の前記カーカス４の最内側面に配置した一対のサイド補強ゴム層８とを具える。
【００２９】
図示例のタイヤにおいて、ラジアルカーカス４は、折り返しカーカスプライ４ａ及びダウンカーカスプライ４ｂとからなり、折り返しカーカスプライ４ａの両端部は、ビードコア６の周りに折り返され、折り返し端部を形成している。なお、ラジアルカーカス４の構造及びプライ数は、これに限られるものではない。ビードフィラー７は、折り返しカーカスプライ４ａとその折り返し端部との間に位置しており、また、ダウンカーカスプライ４ｂは、サイドウォール部２と折り返しカーカスプライ４ａの折り返し端部との間に配置されている。サイド補強ゴム層８は、サイドウォール部２の折り返しカーカスプライ４ａの内側に配置されている。ここで、サイド補強ゴム層８の最大厚さは6〜13mmが好ましい。図示例のサイド補強ゴム層８の形状は、断面三日月状であるが、その断面形状はサイド補強の機能を有するものであれば特に限定されない。
【００３０】
本発明の空気入りタイヤにおいては、上記のビードフィラー７及びサイド補強ゴム層８の少なくとも一方を、前述の物性を有し且特定のゴム成分を所定量含むゴム組成物を用いて形成し、更に、上記ラジアルカーカス４に上述のポリケトン繊維コードを適用することによって、タイヤの通常走行時における乗り心地性とランフラット耐久性とを高度にバランスさせることが出来る。
【００３１】
【実施例】
以下に、実施例を挙げて本発明を更に詳しく説明するが、 本発明は下記の実施例に何ら限定されるものではない。
【００３２】
ポリケトン繊維（ＰＫ繊維、式(I)中のＡがエチレン基のもの）又はレーヨンを用い、表１に示す構造及び撚り数のコードを試作した。更に、該コードをエポキシ水溶液接着剤に浸漬し、乾燥、熱処理を行い、次いで、ＲＦＬ（レゾルシン-ホルムアルデヒド-ラテックス）水溶液接着剤に浸漬し、乾燥、熱処理してディップコードとした。ここで、乾燥ゾーンの処理温度は150℃、処理時間は120秒間とし、また熱処理ゾーンの処理温度は210℃、処理時間は80秒間とした。また、ヒートセット時のコード張力は1.0g/dとした。次に、上記ディップコードを表１に示す打ち込み数で用い、上下よりコーティングゴムをトッピングしてカーカスを作製した。
【００３３】
また、表１に示す配合処方のゴム組成物を調製し、その損失正接（tanδ）を下記の方法に従い測定した。結果を表１に示す。
【００３４】
（１）損失正接(tanδ)
ゴム組成物を160℃、12分間の条件で加硫して得られた厚さ2mmのスラブシートから、幅5mm、長さ40mmのシートを切り出し、試料とした。この試料について、上島製作所(株)製スペクトロメーターを用い、チャック間距離10mm、初期歪み200マイクロメートル（ミクロン）、動的歪1％、周波数52Hz、測定開始温度20℃、昇温速度3℃/分，測定終了温度250℃の条件で、損失正接(tanδ)を測定した。
【００３５】
次に、上記ゴム組成物をサイド補強ゴム層に適用し、上記カーカスを用いて、図１に示す構造を有し且つサイズ２１５／４５ＺＲ１７の乗用車用ラジアルタイヤを定法に従って製造し、下記に示す方法で乗り心地性及びランフラット耐久性を評価した。
【００３６】
（２）乗り心地性
各試作タイヤを乗用車に装着し、専門のドライバー２名により乗心地性のフィーリングテストを行い、1〜10の評点をつけその平均値を求めた。該値が大きい程、乗り心地が良好であることを示す。
【００３７】
（３）ランフラット耐久性
各試作タイヤを常圧でリム組みし、空気を内圧230kPaで封入してから38℃の室温中に24時間放置後、バルブのコアを抜き内圧を大気圧として、荷重4.17kN(425kgf)、速度89km/h、室温38℃の条件でドラム走行テストを行った。この際の故障発生までの走行距離を測定し、比較例１を100として指数表示し、ランフラット耐久性の指標とした。指数値が大きい程、ランフラット耐久性が良好であることを示す。
【００３８】
なお、表１中の共役ジエン系重合体Ａは、次のようにして製造した。乾燥し、窒素置換された温度調節ジャケットつき８リットルの耐圧反応装置に、連続的に乾燥された１,３-ブタジエンの15質量％シクロへキサン溶液を毎分200gの速度で導入した。また同じ位置より、ジテトラヒドロフリルプロパン(ＤＴＨＦＰ)の1mol/Lシクロヘキサン溶液0.15mmol/minとｎ-ブチルリチウムのｎ-ヘキサン溶液0.2mmol/minを連続的に導入した。重合系は、常に80℃に保ち、連続的に反応装置上部より生成したポリマーを取り出し、２,６-ジ-ｔ-ブチル-ｐ-クレゾール(ＢＨＴ)の1質量％イソプロパノール溶液に投入して重合体を得た。重合体は重合開始から終了まで、全く沈殿は見られず均一で且つ透明であった。重合転化率は、ほぼ100％であった。更に固形物を乾燥して、共役ジエン系重合体Ａを得た。
【００３９】
得られた共役ジエン系重合体Ａのミクロ構造を赤外法（モレロ法）によって分析したところ、ビニル結合（１,２-結合）量が50％であった。また、共役ジエン系重合体Ａの分子量(Ｍw)及び分子量分布(Ｍw／Ｍn)を、ゲルパーミエーションクロマトグラフィ［ＧＰＣ；東ソー製ＨＬＣ-８０２０, カラム；東ソー製ＧＭＸ-ＸＬ（２本直列）, 検出器；示差屈折率計(ＲＩ)］により分析したところ、単分散ポリスチレンを標準としたポリスチレン換算で重量平均分子量(Ｍw)が30万であり、分子量分布(Ｍw／Ｍn)が2.1であった。
【００４０】
【表１】

【００４１】
比較例１及び２と、比較例３及び４との比較から、20〜80℃での損失正接が小さいゴム組成物を用いたタイヤは、通常走行時の乗り心地が悪いことが分かる。
【００４２】
また、比較例１及び２と、実施例１及び２との比較から、レーヨンからなるコードに代えてＰＫ繊維からなるコードをカーカスに適用することにより、サイド部の剛性が向上して、ランフラット走行時のタイヤ耐久性が向上することが分かる。
【００４３】
更に、実施例３及び４から、レーヨンコードに代えてＰＫ繊維コードをカーカスに用いることにより、コードの打ち込み数を減少させても、比較例１と同等のランフラット耐久性を維持することができ、通常走行時の乗り心地を改善できることが分かる。
【００４４】
【発明の効果】
本発明によれば、サイド補強ゴム層とビードフィラーとを備えたタイヤにおいて、特定の物性を有し且特定のゴム成分を所定量含むゴム組成物を該サイド補強ゴム層及びビードフィラーの少なくとも一方に適用することに加え、ポリケトン繊維コードをカーカスに適用することより、タイヤのランフラット耐久性と乗り心地とが高度にバランスされた空気入りタイヤを提供することができる。
【図面の簡単な説明】
【図１】 本発明の空気入りタイヤの一実施態様を示す断面図である。
【符号の説明】
１ ビード部
２ サイドウォール部
３ トレッド部
４ ラジアルカーカス
４ａ 折り返しカーカスプライ
４ｂ ダウンカーカスプライ
５ ベルト
６ ビードコア
７ ビードフィラー
８ サイド補強ゴム層[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire in which run-flat durability and ride comfort are highly balanced.
[0002]
[Prior art]
Conventionally, even in a state where the internal pressure of the tire is reduced due to puncture or the like, a tire that can travel safely over a certain distance, a so-called run-flat tire, has a crescent cross section on the innermost side of the carcass in the sidewall portion of the tire. A side-reinforcement type run-flat tire is known in which a side-reinforcing rubber layer is disposed to improve the rigidity of the sidewall portion. However, in the so-called run-flat running in a state where the internal pressure of the tire is reduced, the deformation of the side reinforcing rubber layer increases as the deformation of the sidewall portion of the tire increases. Heat generation proceeds and in some cases reaches a high temperature of 200 ° C. or higher. In such a state, the side reinforcing rubber layer exceeds its failure limit, and there is a risk that the tire will break down.
[0003]
As a means for delaying the time to failure, there is a means for increasing the volume of the side reinforcing rubber layer by increasing the maximum thickness of the side reinforcing rubber layer. If adopted, problems such as deterioration in ride comfort, increase in weight, and increase in noise occur. In addition, there is a means of increasing the maximum thickness of the bead filler by arranging a bead filler on the outer side in the tire radial direction of the bead part. In this case, however, the ride quality is deteriorated, the weight is increased, and the noise is increased. Such problems arise.
[0004]
On the other hand, in order to avoid deterioration in ride comfort, the composition of the rubber composition used for the side reinforcing rubber layer and the bead filler is changed, the elastic modulus of the rubber composition is lowered, and the loss tangent of the rubber composition is further reduced. There is also a method to improve the (tanδ) and diffuse the impact as thermal energy, but in this case, the sidewall part cannot support the load applied to the tire during run flat running, and the deformation of the sidewall part becomes very large, The actual situation is that the heat generation in the side wall portion proceeds excessively, and as a result, the tires fail early.
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 2000-264012
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide a pneumatic tire that solves the above-described problems of the prior art and highly balances run-flat durability and ride comfort.
[0007]
[Means for Solving the Problems]
As a result of intensive studies to achieve the above object, the present inventor has obtained a rubber composition having a specific physical property and a specific amount of a specific rubber component in a tire including a side reinforcing rubber layer and a bead filler. In addition to being applied to at least one of the side reinforcing rubber layer and the bead filler, it has been found that the run-flat durability and the ride comfort of the tire can be highly balanced by applying a polyketone fiber cord to the carcass. The present invention has been completed.
[0008]
That is, the pneumatic tire of the present invention has a pair of bead portions and a pair of sidewall portions, and a tread portion connected to both sidewall portions, and extends in a toroidal shape between the pair of bead portions, A radial carcass that reinforces each of these parts, a bead filler that is disposed radially outside the bead core in each bead part, and a pair of side reinforcing rubber layers that are disposed on the innermost side surface of the carcass in the sidewall part In the pneumatic tire comprising the rubber composition constituting at least one of the side reinforcing rubber layer and the bead filler, the maximum value of the loss tangent (tan δ) at 1% strain at 20 to 80 ° C. is 0.08 or more. The maximum value of the loss tangent (tan δ) at 1% strain at 150 to 250 ° C. is 0.05 or less, and at least one of the side reinforcing rubber layer and the bead filler. The rubber component of the rubber composition is composed of a vinyl bond amount of 25% or more, a weight average molecular weight (Mw) of 200,000 to 900,000, and a ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn). It consists of a polybutadiene rubber having a molecular weight distribution (Mw / Mn) of 1 to 4 and a natural rubber, and the polybutadiene rubber is contained in the rubber component in an amount of 50 to 70% by mass. The carcass has the following formula (I):
[Formula 4]

(In the formula, A is a portion derived from an ethylenically unsaturated compound polymerized by an ethylenic bond, and may be the same or different in each repeating unit)
A cord composed of a polyketone fiber consisting essentially of repeating units represented by the formula is applied.
[0009]
In a preferred example of the pneumatic tire of the present invention, A in the formula (I) is an ethylene group.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below. The pneumatic tire of the present invention has a pair of bead portions and a pair of sidewall portions, and a tread portion connected to both sidewall portions, and extends in a toroidal shape between the pair of bead portions. A radial carcass that reinforces a bead core, a bead filler that is disposed outside the bead core in the tire radial direction, and a pair of side reinforcing rubber layers that are disposed on the innermost side surface of the carcass in the sidewall portion. The rubber composition constituting at least one of the side reinforcing rubber layer and the bead filler has a maximum loss tangent (tan δ) at 1% strain at 20 to 80 ° C. of 0.08 or more, and 1 at 150 to 250 ° C. The rubber composition of a rubber composition having a maximum value of loss tangent (tan δ) at% strain of 0.05 or less and constituting at least one of the side reinforcing rubber layer and the bead filler. The molecular weight distribution (Mw / Mn) represented by the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), with a vinyl bond amount of 25% or more, a weight average molecular weight (Mw) of 200,000 to 900,000 A polyketone comprising a polybutadiene rubber having a rubber content of 1 to 4 and a natural rubber, the polybutadiene rubber being contained in a rubber component in an amount of 50 to 70% by mass , and substantially comprising the repeating unit represented by the above formula (I) in the carcass. It is characterized by applying a cord composed of the above fiber. The rubber composition has a high tan δ in the temperature range during normal running and a low tan δ in the temperature range during run flat running, so that vibration and impact during normal running can be sufficiently diffused as thermal energy. Since the riding comfort of the tire is improved and the heat generation during the run-flat running can be sufficiently suppressed, the decrease in the run-flat durability of the tire is suppressed. By using the rubber composition in the side reinforcing rubber layer or the bead filler, run flat durability and riding comfort can be highly balanced, but by using both the side reinforcing rubber layer and the bead filler. The run-flat durability and ride comfort can be further balanced.
[0011]
Tires using a rubber composition with a maximum loss tangent (tan δ) at 1% strain at 20-80 ° C of less than 0.08 as the physical properties after vulcanization for side reinforcing rubber layers and bead fillers The vibration and impact of the tire cannot be sufficiently diffused as thermal energy, resulting in a deterioration in tire riding comfort. On the other hand, as a physical property after vulcanization, a tire using a rubber composition having a maximum value of a loss tangent (tan δ) at 1% strain at 150 to 250 ° C. exceeding 0.05 as a side reinforcing rubber layer and a bead filler is run flat. Heat generation during traveling cannot be sufficiently suppressed, and heat generation in the sidewall portion proceeds excessively, resulting in a decrease in tire run-flat durability.
[0012]
The rubber composition used for the side reinforcing rubber layer and the bead filler has, as a rubber component, a vinyl bond amount of 25% or more, a weight average molecular weight (Mw) of 200,000 to 900,000, a weight average molecular weight (Mw) and a number. It consists of a polybutadiene rubber and a natural rubber having a molecular weight distribution (Mw / Mn) represented by a ratio to the average molecular weight (Mn) of 1 to 4, and the content of the polybutadiene rubber is 50 to 70% by mass in the rubber component. .
[0013]
If the amount of vinyl bonds in the polybutadiene rubber is less than 25%, the elastic modulus decrease due to sulfur cross-linking breakage at a high temperature of 150 ° C. or higher is dominant, so the decrease in elastic modulus due to temperature rise cannot be suppressed, Run-flat durability is reduced. From this viewpoint, the vinyl bond amount of the polybutadiene rubber is preferably 30% or more, more preferably 35% or more, and particularly preferably 40 to 60%. Further, when the weight average molecular weight (Mw) of the polybutadiene rubber is less than 200,000, the tensile properties and rolling resistance of the rubber composition are inferior, and when it exceeds 900,000, the workability tends to be inferior. In this respect, the polybutadiene rubber preferably has a weight average molecular weight (Mw) of 300,000 to 800,000. Further, when the molecular weight distribution (Mw / Mn) of the polybutadiene rubber exceeds 4, there is a tendency that the exothermic property is lowered and it is difficult to maintain the elastic modulus in a temperature range of 150 ° C. or higher.
[0014]
In the rubber composition used for the side reinforcing rubber layer and the bead filler, 50% by mass or more of the rubber component needs to be the polybutadiene rubber described above. When the content of the polybutadiene rubber in the rubber component is less than 50% by mass, the effect of suppressing heat generation during run flat running, that is, at 150 ° C. or higher is small, and run flat durability is reduced. In this respect, the content of the polybutadiene rubber is more preferably 60% by mass or more.
[0015]
Monomers used in the polybutadiene rubber is 1,3-butadiene.
[0016]
The polybutadiene rubber can be produced by various methods, and the polymerization method may be either a batch polymerization method or a continuous polymerization method. The following are mentioned as a preferable manufacturing method. That is, it is obtained by polymerizing 1,3-butadiene in an inert solvent, preferably a hydrocarbon solvent, in the presence of an initiator such as an organometallic compound, preferably an organic lithium compound initiator. Although there is no restriction | limiting in particular as said hydrocarbon solvent, For example, n-pentane, n-hexane, n-heptane, cyclohexane, benzene, toluene etc. are mentioned, Among these, cyclohexane and n-hexane are preferable. These hydrocarbon solvents may be used alone or in combination of two or more. The organic lithium used as the initiator is preferably a hydrocarbon lithium compound having at least one lithium atom bonded thereto and having 2 to 20 carbon atoms, such as n-butyllithium, sec-butyllithium, ethyllithium, Examples include n-propyllithium, t-octyllithium, phenyllithium and the like. Among these, n-butyllithium is particularly preferable. These organolithium initiators may be used alone or in combination of two or more. The vinyl bond amount of polybutadiene rubber is ditetrahydrofurylpropane, tetrahydrofuran, diethyl ether, dimethoxybenzene, dimethoxyethane, ethylene glycol dibutyl ether, triethylamine, pyridine, N, N, N ′, N′-tetramethylethylenediamine, dipiperidi It can be changed as appropriate by adding an appropriate amount of ether such as noethane and a tertiary amine compound to the polymerization system.
[0017]
As said polybutadiene rubber , the modified polybutadiene rubber which contains a tin atom and / or a nitrogen atom in a molecule | numerator can be used. The modified polybutadiene rubber in which tin atoms, nitrogen atoms, etc. are introduced into the molecular chain can suppress the decrease in elastic modulus due to temperature rise and can also improve the low heat buildup in the carbon black compounded rubber composition. As the modified polybutadiene rubber , those having a branched structure obtained by using a polyfunctional modifier are particularly preferable. The modified polybutadiene rubber is produced by a known method and is usually obtained by initiating polymerization with an organolithium initiator and adding various modifiers to a polymer solution having an active lithium end (Japanese Patent Publication No. 6-6). 89183, JP-A-11-29659, etc.). For example, a tin atom is introduced using a tin compound such as tin tetrachloride, tributyltin chloride, dioctyltin dichloride, dibutyltin dichloride, triphenyltin chloride, and a nitrogen atom is an isocyanate compound such as diisocyanate diphenylmethane, 4- It can be introduced using an aminobenzophenone compound such as (dimethylamino) benzophenone, a nitrogen-containing compound such as 4-dimethylaminobenzylideneaniline, dimethylimidazolidinone, N-methylpyrrolidone. Further, for example, a modified polybutadiene rubber can be obtained by polymerizing using a secondary amide compound such as diethylamine or a lithium amide initiator obtained from an imine compound such as hexamethyleneimine and an organic lithium compound.
[0018]
The rubber composition used for the side reinforcing rubber layer and the bead filler preferably further contains a phenol resin and a curing agent thereof. Here, examples of the phenol resin include a phenol / formaldehyde resin, a resorcin / formaldehyde resin, and a cresol resin. Among these, a phenol / formaldehyde resin is particularly preferable. As the phenolic resin, natural resin-modified phenolic resin, oil-modified phenolic resin, etc. can be used in addition to 100% phenolic resin.
[0019]
Examples of the phenol resin curing agent include hexamethylenetetramine and hexamethoxymethylmelamine. These combinations can be freely selected, and a plurality of resins and their curing agents may be selected. Further, a resin in which a curing agent is internally added may be used.
[0020]
In addition to the rubber component, phenolic resin and its curing agent, the rubber composition includes vulcanizing agents such as sulfur and peroxides, vulcanization accelerators, anti-aging agents, and softening agents that are usually used in the rubber industry. Various compounding agents such as reinforcing fillers and inorganic fillers can be appropriately blended. Further, the rubber composition may be a composite with particles, fibers, cloths and the like of various materials. Each physical property of the rubber composition can be adjusted within the aforementioned range by appropriately selecting the types of rubber components and compounding agents to be used and the compounding ratio thereof.
[0021]
The cord used for the carcass of the pneumatic tire of the present invention is made of a polyketone fiber substantially composed of a repeating unit represented by the above formula (I). The polyketone is an alternating copolymer in which CO units (carbonyl group) and units derived from an ethylenically unsaturated compound are arranged in a molecule, that is, an ethylene unit, for example, next to each CO unit in a polymer chain. This structure has one olefin unit. Further, the polyketone may be a copolymer of carbon monoxide and one specific ethylenically unsaturated compound, or may be a copolymer of carbon monoxide and two or more ethylenically unsaturated compounds. Good. Examples of the ethylenically unsaturated compound forming A in the formula (I) include unsaturated hydrocarbon compounds such as ethylene, propylene, butene, pentene, hexene, heptene, octene, nonene, decene, dodecene, styrene, methyl acrylate, Examples thereof include unsaturated carboxylic acids such as methyl methacrylate, vinyl acetate, and undecenoic acid or derivatives thereof, as well as undecenol, 6-chlorohexene, N-vinylpyrrolidone, and diethyl ester of sulphonylphosphonic acid. These may be used alone or in combination of two or more, but in particular from the viewpoint of the mechanical properties and heat resistance of the polymer, polyketone using ethylenically unsaturated compounds mainly composed of ethylene Is preferred.
[0022]
When ethylene and other ethylenically unsaturated compounds are used in combination, it is preferable to use ethylene at 80 mol% or more based on the total ethylenically unsaturated compounds. If it is less than 80 mol%, the melting point of the resulting polymer will be 200 ° C. or less, and the resulting polyketone fiber cord may have insufficient heat resistance. In view of the mechanical properties and heat resistance of the polyketone fiber cord, the amount of ethylene used is preferably 90 mol% or more with respect to the total ethylenically unsaturated compound. The polyketone can be produced according to a known method, for example, a method described in European Patent Publication Nos. 121965, 213671, 229408 and US Pat. No. 3,914,391.
[0023]
The degree of polymerization of the polyketone is preferably such that the solution viscosity measured in m-cresol at 60 ° C. is in the range of 1.0 to 10.0 dL / g. When the solution viscosity is less than 1.0 dL / g, the resulting polyketone fiber cord may have insufficient mechanical strength. From the viewpoint of the cord mechanical strength, the solution viscosity is more preferably 1.2 dL / g or more. On the other hand, if the solution viscosity exceeds 10.0 dL / g, the melt viscosity at the time of fiberization and the solution viscosity may become too high, resulting in poor spinnability. From the viewpoint of spinnability, the solution viscosity is 5.0 dL / g. More preferably, it is as follows. Considering the mechanical strength and spinnability of the fiber, the solution viscosity is particularly preferably in the range of 1.3 to 4.0 dL / g.
[0024]
The method for fiberizing the polyketone is not particularly limited, but generally a melt spinning method or a solution spinning method is adopted. When adopting the melt spinning method, for example, according to the method described in JP-A-1-124617, the polymer is usually melt-spun at a temperature higher than the melting point by 20 ° C. or more, preferably about 40 ° C. higher than the melting point, Then, usually at a temperature lower than the melting point by 10 ° C. or less, preferably about 40 ° C. lower than the melting point, preferably by stretching at a stretch ratio of preferably 3 times or more, more preferably at a stretch ratio of 7 times or more. Desired fibers can be obtained.
[0025]
On the other hand, when adopting the solution spinning method, the polymer is added to, for example, hexafluoroisopropanol, m-cresol, etc. in an amount of 0.25 to 20% by mass, preferably 0.5 to 10% by mass, for example, according to the method described in JP-A-2-112413. The solution is dissolved at a concentration, extruded from a spinning nozzle to form a fiber, and then the solvent is removed and washed in a non-solvent bath such as toluene, ethanol, isopropanol, n-hexane, isooctane, acetone, methyl ethyl ketone, and preferably in an acetone bath. A desired filament can be obtained by obtaining a yarn and further drawing at a temperature in the range of (melting point−100 ° C.) to (melting point + 10 ° C.), preferably (melting point−50 ° C.) to (melting point). In addition, it is preferable to add an antioxidant to the polyketone for the purpose of imparting sufficient durability against heat, oxygen and the like, and if necessary, a matting agent, a pigment, an antistatic agent and the like are also blended. be able to.
[0026]
Since the carcass used in the tire of the present invention includes a cord made of highly elastic polyketone fiber (PK fiber), the carcass using a cord made of ordinary rayon maintains a longitudinal spring of the tire during normal running. The longitudinal spring of the tire during run flat running can be improved. Therefore, by using a carcass to which a cord made of PK fiber is applied for a tire, run-flat durability can be improved while maintaining the riding comfort of the tire during normal running. This is an action utilizing the fact that the tensile strain generated in the cord during run-flat traveling is significantly larger than the tensile strain generated in the cord when the tire is filled with air. The cord made of the polyketone fiber is stronger than the cord made of rayon, so even if the number of cords arranged in the carcass is reduced, the longitudinal spring of the tire during run-flat running is maintained and the run-flat durability is maintained. On the other hand, by reducing the number of cords arranged, it is possible to improve the ride comfort by reducing the vertical spring of the tire during normal running.
[0027]
The pneumatic tire of the present invention can be produced by a conventional method by applying the rubber composition having the above-described properties to at least one of the bead filler and the side reinforcing rubber layer. In the pneumatic tire of the present invention, as the gas filled in the tire, normal or air with a changed oxygen partial pressure, or an inert gas such as nitrogen can be used.
[0028]
Next, embodiments of the tire of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing one embodiment of the pneumatic tire of the present invention. The tire shown in FIG. 1 has a pair of left and right bead portions 1 and a pair of sidewall portions 2, and a tread portion 3 connected to both sidewall portions 2, and has a toroidal shape between the pair of bead portions 1. A radial carcass 4 extending to reinforce each of these parts 1, 2, 3, a belt 5 composed of at least two belt layers arranged on the outer side in the tire radial direction of the carcass 4, and the bead part 1 A bead filler 7 disposed on the outer side in the tire radial direction of each of the ring-shaped bead cores 6 embedded therein and a pair of side reinforcing rubber layers 8 disposed on the innermost side surface of the carcass 4 of the sidewall portion 2 are provided.
[0029]
In the illustrated tire, the radial carcass 4 includes a folded carcass ply 4a and a down carcass ply 4b, and both end portions of the folded carcass ply 4a are folded around the bead core 6 to form folded ends. The structure and the number of plies of the radial carcass 4 are not limited to this. The bead filler 7 is located between the folded carcass ply 4a and its folded end, and the down carcass ply 4b is disposed between the sidewall portion 2 and the folded end of the folded carcass ply 4a. ing. The side reinforcing rubber layer 8 is disposed inside the folded carcass ply 4 a of the sidewall portion 2. Here, the maximum thickness of the side reinforcing rubber layer 8 is preferably 6 to 13 mm. The shape of the side reinforcing rubber layer 8 in the illustrated example has a crescent-shaped cross section, but the cross-sectional shape is not particularly limited as long as it has a side reinforcing function.
[0030]
In the pneumatic tire of the present invention, at least one of the bead filler 7 and the side reinforcing rubber layer 8 is formed using a rubber composition having the aforementioned physical properties and containing a predetermined amount of a specific rubber component, By applying the above-mentioned polyketone fiber cord to the radial carcass 4, it is possible to highly balance the riding comfort and run-flat durability during normal running of the tire.
[0031]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.
[0032]
Using the polyketone fiber (PK fiber, A in the formula (I) is an ethylene group) or rayon, a cord having the structure and twist number shown in Table 1 was produced. Further, the cord was dipped in an epoxy aqueous solution, dried and heat-treated, and then dipped in an RFL (resorcin-formaldehyde-latex) aqueous solution adhesive, dried and heat-treated to obtain a dip cord. Here, the treatment temperature in the drying zone was 150 ° C., the treatment time was 120 seconds, the treatment temperature in the heat treatment zone was 210 ° C., and the treatment time was 80 seconds. The cord tension during heat setting was 1.0 g / d. Next, the dip cord was used in the number of drivings shown in Table 1, and a coating rubber was topped from above and below to prepare a carcass.
[0033]
Moreover, the rubber composition of the mixing | blending prescription shown in Table 1 was prepared, and the loss tangent (tan-delta) was measured in accordance with the following method. The results are shown in Table 1.
[0034]
(1) Loss tangent (tanδ)
A sheet having a width of 5 mm and a length of 40 mm was cut out from a slab sheet having a thickness of 2 mm obtained by vulcanizing the rubber composition at 160 ° C. for 12 minutes, and used as a sample. Using a spectrometer made by Ueshima Seisakusho Co., Ltd., the distance between chucks was 10 mm, the initial strain was 200 micrometers (microns), the dynamic strain was 1%, the frequency was 52 Hz, the measurement start temperature was 20 ° C., and the heating rate was 3 ° C. / The loss tangent (tan δ) was measured under the conditions of minute and measurement end temperature of 250 ° C.
[0035]
Next, the rubber composition is applied to a side reinforcing rubber layer, and a radial tire for a passenger car having the structure shown in FIG. 1 and having a size of 215 / 45ZR17 is manufactured according to a conventional method using the carcass. The ride comfort and run-flat durability were evaluated.
[0036]
(2) Ride comfort Each prototype tire was mounted on a passenger car, a feeling test of ride comfort was conducted by two specialized drivers, and an average value of 1-10 was obtained. It shows that riding comfort is so favorable that this value is large.
[0037]
(3) Run flat durability Each prototype tire is assembled with rims at normal pressure, air is sealed at an internal pressure of 230 kPa, and then left at room temperature of 38 ° C. for 24 hours, then the valve core is removed and the internal pressure is set to atmospheric pressure. A drum running test was conducted under the conditions of 4.17 kN (425 kgf), speed 89 km / h, and room temperature 38 ° C. The distance traveled until the failure occurred at this time was measured, and the index was displayed with Comparative Example 1 as 100, which was used as an indicator of run-flat durability. The larger the index value, the better the run flat durability.
[0038]
The conjugated diene polymer A in Table 1 was produced as follows. A continuously dried 15 mass% cyclohexane solution of 1,3-butadiene was introduced at a rate of 200 g / min into an 8-liter pressure-resistant reactor equipped with a temperature-controlled jacket that was dried and purged with nitrogen. From the same position, 0.15 mmol / min of a 1 mol / L cyclohexane solution of ditetrahydrofurylpropane (DTHP) and 0.2 mmol / min of an n-butyllithium n-hexane solution were continuously introduced. The polymerization system is always kept at 80 ° C., the polymer formed continuously is taken out from the upper part of the reaction apparatus, taken into a 1% by mass isopropanol solution of 2,6-di-t-butyl-p-cresol (BHT), Coalescence was obtained. The polymer was uniform and transparent with no precipitation observed from the beginning to the end of the polymerization. The polymerization conversion rate was almost 100%. Further, the solid was dried to obtain a conjugated diene polymer A.
[0039]
When the microstructure of the obtained conjugated diene polymer A was analyzed by an infrared method (morero method), the amount of vinyl bonds (1,2-bonds) was 50%. Further, the molecular weight (Mw) and molecular weight distribution (Mw / Mn) of the conjugated diene polymer A are determined by gel permeation chromatography [GPC; Tosoh HLC-8020, column; Tosoh GMX-XL (two in series), detection. Instrument; differential refractometer (RI)], the weight average molecular weight (Mw) was 300,000 in terms of polystyrene with a monodisperse polystyrene as a standard, and the molecular weight distribution (Mw / Mn) was 2.1.
[0040]
[Table 1]

[0041]
From comparison between Comparative Examples 1 and 2 and Comparative Examples 3 and 4, it can be seen that a tire using a rubber composition having a small loss tangent at 20 to 80 ° C. has poor riding comfort during normal running.
[0042]
Further, from the comparison between Comparative Examples 1 and 2 and Examples 1 and 2, by applying the cord made of PK fiber to the carcass instead of the cord made of rayon, the rigidity of the side portion is improved, and the run flat It can be seen that the tire durability during running is improved.
[0043]
Furthermore, from Examples 3 and 4, by using PK fiber cords in the carcass instead of rayon cords, the run-flat durability equivalent to Comparative Example 1 can be maintained even if the number of cords to be driven is reduced. It can be seen that the ride comfort during normal driving can be improved.
[0044]
【The invention's effect】
According to the present invention, in a tire including a side reinforcing rubber layer and a bead filler, a rubber composition having specific physical properties and containing a predetermined amount of a specific rubber component is added to at least one of the side reinforcing rubber layer and the bead filler. In addition to being applied to the above, by applying the polyketone fiber cord to the carcass, it is possible to provide a pneumatic tire in which the run-flat durability and the ride comfort of the tire are highly balanced.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of a pneumatic tire according to the present invention.
[Explanation of symbols]
1 Bead part 2 Side wall part 3 Tread part 4 Radial carcass 4a Folded carcass ply 4b Down carcass ply 5 Belt 6 Bead core 7 Bead filler 8 Side reinforcing rubber layer

Claims (4)

A radial carcass having a pair of bead portions and a pair of sidewall portions, and a tread portion connected to both sidewall portions, extending in a toroidal shape between the pair of bead portions, and reinforcing the respective portions; In a pneumatic tire comprising a bead filler disposed on the outer side in the tire radial direction of a bead core embedded in each bead portion, and a pair of side reinforcing rubber layers disposed on the innermost side surface of the carcass of the sidewall portion,
The rubber composition constituting the side reinforcing rubber layer has a maximum loss tangent (tan δ) at 1% strain at 20 to 80 ° C. of 0.08 or more, and a loss tangent (tan δ at 1% strain at 150 to 250 ° C. ) And the rubber component of the rubber composition constituting the side reinforcing rubber layer has a vinyl bond content of 25% or more, a weight average molecular weight (Mw) of 200,000 to 900,000, consists of a molecular weight distribution (Mw / Mn) of polybutadiene rubber and natural rubber is 1 to 4 represented by the ratio of the weight average molecular weight (Mw) to number average molecular weight (Mn), 50 the polybutadiene rubber in the rubber component Containing ~ 70% by mass ,
The carcass has the following formula (I):

(In the formula, A is a portion derived from an ethylenically unsaturated compound polymerized by an ethylenic bond, and may be the same or different in each repeating unit)
A pneumatic tire characterized by applying a cord composed of a polyketone fiber substantially composed of a repeating unit represented by: A radial carcass having a pair of bead portions and a pair of sidewall portions, and a tread portion connected to both sidewall portions, extending in a toroidal shape between the pair of bead portions, and reinforcing the respective portions; In a pneumatic tire comprising a bead filler disposed on the outer side in the tire radial direction of a bead core embedded in each bead portion, and a pair of side reinforcing rubber layers disposed on the innermost side surface of the carcass of the sidewall portion,
The rubber composition constituting the bead filler has a maximum loss tangent (tan δ) at 1% strain at 20 to 80 ° C. of 0.08 or more and a loss tangent (tan δ) at 1% strain at 150 to 250 ° C. The rubber component of the rubber composition constituting the bead filler having a maximum value of 0.05 or less has a vinyl bond content of 25% or more, a weight average molecular weight (Mw) of 200,000 to 900,000, a weight average molecular weight ( Mw) and a polybutadiene rubber having a molecular weight distribution (Mw / Mn) represented by a ratio of the number average molecular weight (Mn) of 1 to 4 and natural rubber, and the polybutadiene rubber is contained in a rubber component in an amount of 50 to 70% by mass. Including
The carcass has the following formula (I):

(In the formula, A is a portion derived from an ethylenically unsaturated compound polymerized by an ethylenic bond, and may be the same or different in each repeating unit)
A pneumatic tire characterized by applying a cord composed of a polyketone fiber substantially composed of a repeating unit represented by: A radial carcass having a pair of bead portions and a pair of sidewall portions, and a tread portion connected to both sidewall portions, extending in a toroidal shape between the pair of bead portions, and reinforcing the respective portions; In a pneumatic tire comprising a bead filler disposed on the outer side in the tire radial direction of a bead core embedded in each bead portion, and a pair of side reinforcing rubber layers disposed on the innermost side surface of the carcass of the sidewall portion,
The rubber composition constituting the side reinforcing rubber layer and the bead filler has a maximum loss tangent (tan δ) at 1% strain at 20 to 80 ° C. of 0.08 or more, and at 1% strain at 150 to 250 ° C. The maximum value of the loss tangent (tan δ) is 0.05 or less, and the rubber component of the rubber composition constituting the side reinforcing rubber layer and the bead filler has a vinyl bond content of 25% or more, a weight average molecular weight (Mw ) Having a molecular weight distribution (Mw / Mn) of 1 to 4 expressed by a ratio of 200,000 to 900,000 and a weight average molecular weight (Mw) and a number average molecular weight (Mn), and natural rubber, Containing 50 to 70% by mass of polybutadiene rubber in the rubber component;
The carcass has the following formula (I):

(In the formula, A is a portion derived from an ethylenically unsaturated compound polymerized by an ethylenic bond, and may be the same or different in each repeating unit)
A pneumatic tire characterized by applying a cord composed of a polyketone fiber substantially composed of a repeating unit represented by:   The pneumatic tire according to claim 1, wherein A in the formula (I) is an ethylene group.

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