JP4266116B2 - Heavy duty pneumatic radial tire for aircraft - Google Patents

Description

〔式（Ｉ）中、Ｒ¹とＲ²は炭素数１〜２０の脂肪族、脂環族、芳香族の炭化水素基から選ばれる基を表し、該基は同一であっても異なっていてもよい。〕
【００２６】
【化２】

〔式（II）中、Ｘは次の構造基から選ばれる。Ｘ−Ｉ：（ＣＲ³Ｒ⁴）_nからなる飽和型環状構造基、Ｘ−II：（Ｒ⁵Ｒ⁶）_m−Ｙ−（Ｒ⁵Ｒ⁶）_l（但し、該ＹはＮＲ⁷、Ｏ、又は炭素−炭素２重結合を有するイミン化合物である）。ここで、Ｒ³〜Ｒ⁶は水素及び炭素数１〜１０の脂肪族、炭素数３〜１０の脂環族、炭素数６〜１０の芳香族の炭化水素基から選ばれる基を表し、また、Ｒ⁷は炭素数１〜１０の脂肪族、炭素数３〜１０の脂環族、炭素数５〜１０の芳香族の炭化水素基から選ばれる基を表し、該基は同一であっても異なっていてもよい。ｎは３〜１０の整数を表し、ｍとｌの合計は２〜９の整数である。〕
【００２７】
これらの中でも、好ましいトリオルガノアミドスズリチウムとしては、例えば、トリピロリジドスズリチウム、トリヘキサメチレンイミドスズリチウム、トリジエチルアミドスズリチウム、及びトリ（ジプロピルアミド）スズリチウム等が挙げられる。
【００２８】
尚、上記において、トリオルガノアミドスズリチウムについては米国特許第５５０２１２９号明細書に記載されており、トリオルガノアミドスズリチウム及びトリオルガノイミドスズリチウムについては米国特許第５４６３００３号明細書に記載されている。また、前記第５の方法として、目的とするスチレン−ブタジエン共重合体は、スズ原子を有する第３モノマーを導入することによっても得ることができる。ここで、スチレンやブタジエンと共重合される第３モノマーとしては、下記の一般式（III）又は（IV）で表される化合物が好適に用いられる。
【００２９】
【化３】

〔式（III）中、Ｒ⁸〜Ｒ¹⁰は炭素数１〜３０の脂肪族、脂環族又は芳香族の炭化水素基を表し、該基は同一であっても異なっていてもよい。〕
【００３０】
【化４】

〔式（IV）中、Ｒ¹¹（Ｒ¹²）Ｃ＝ＣＲ¹³−、Ｒ¹⁴〜Ｒ¹⁷はベンゼン環に結合する基であり、Ｒ¹¹〜Ｒ²²は、水素原子又は炭素数１〜３０の脂肪族、脂環族又は芳香族の炭化水素基を表し、該基は同一であっても異なっていてもよい。但し、Ｒ²⁰〜Ｒ²²は水素原子を含まない。〕
【００３１】
具体的には、前記一般式（III）で表される化合物としては、２−トリブチルスタニル−１，３−ブタジエン、２−トリオクチルスタニル−１，３−ブタジエン、２−トリシクロヘキシルスタニル−１，３−ブタジエン、２−トリフェニルスタニル−１，３−ブタジエン、２−ジブチルフェニルスタニル−１，３−ブタジエン、２−ジフェニルオクチルスタニル−１，３−ブタジエン等が挙げらる。また、前記一般式（IV）で表わされる化合物としては、ｍ−ビニルベンジルトリブチルスズ、ｍ−ビニルベンジルトリオクチルスズ、ｍ−ビニルベンジルトリフェニルスズ、ｍ−（１−フェニルビニル）ベンジルトリブチルスズ、及びこれらのｐ−体、ｍ−体／ｐ−体の混合物などが好適に挙げられる。
【００３２】
前記リチウム化合物を重合開始剤として用い、アニオン重合によってスチレン−ブタジエン共重合体（スチレン又はブタジエンのモノマー単位中にスズ原子を導入した共重合体を含む）を製造する方法としては特に制限はなく、従来より公知の方法を用いることができる。具体的には、反応に不活性な有機溶剤、例えば脂肪族、脂環族、芳香族炭化水素化合物などの炭化水素系溶剤中において、スチレンと１，３−ブタジエンを、前記有機リチウム化合物を重合開始剤として、所望により、用いられるランダマイザーの存在下にアニオン重合させることにより、目的のスチレン−ブタジエン共重合体が得られる。この重合反応における温度は、通常−８０〜１５０℃、好ましくは−２０〜１００℃の範囲で適宜に選定される。上記重合反応は、発生圧力下で行うことができるが、通常は単量体を実質的に液相に保つ十分な圧力で操作することが望ましい。所望ならば更に高い圧力を用いることができ、この様な圧力は重合反応に関して不活性なガスで反応器を加圧する等の適当な方法で得られる。
【００３３】
この様にして得られた、重合開始末端にヒドロカルビル基又は窒素含有基を有し、且つ他方の末端が重合活性である変性前のスチレン−ブタジエン共重合体（スチレン又はブタジエンのモノマー単位中にスズ原子を導入した共重合体を含む）の該重合活性末端に、スズ化合物を反応させることにより、所望の変性スチレン−ブタジエン共重合体ゴムが得られる。
上記のスズ化合物としては、例えば、四塩化スズ、トリブチルスズクロリド、トリオクチルスズクロリド、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などが挙げられる。また、変性剤を使用せず反応を停止しても分子中にスズ原子が導入されている。
【００３４】
本発明のゴム組成物に用いられる溶液重合ＳＢＲは、分子内に少なくとも１個のスズ原子を有し、分子内の結合スチレン含量が２０〜４０質量％であり、且つポリブタジエン鎖部の１，２−ビニル結合量が３０モル％以下である変性スチレン−ブタジエン共重合体ゴムである。結合スチレン含量が上記範囲未満では、制動（スキッド）性能の水準が不足し、一方、上記範囲を越えると発熱特性が低下する。また、ビニル結合量が上記範囲を越えると破壊強度や発熱特性が低下する。
【００３５】
本発明のゴム組成物には、ゴム成分（ｂ）として、天然ゴム及び／又は合成イソプレンゴムが用いられる。上記天然ゴムとしては、シートゴムでもブロックゴムでもよく、ＲＳＳ＃１〜＃５の総て及びＴＳＲの総てのグレードを用いることができる。上記合成イソプレンゴム（ＩＲ）は、イソプレンモノマーの重合により得られたものであり、中でもシス１，４−結合が９８％前後のＩＲは、天然ゴムに極めて類似の分子構造を有するため、天然ゴムに近い基本的な特性を有し好ましい。
【００３６】
また、本発明のゴム組成物（Ｂ）には、ゴム成分（ｃ）として、シス−１，４−ポリブタジエンゴム（ＢＲ）が用いられる。該ポリブタジエンゴム（ＢＲ）は高シスＢＲゴムと呼ばれるもので、通常、シス１，４−結合が９６％以上のものが好ましく用いられる。
【００３７】
尚、本発明のゴム成分１００質量部の組成としては、制動性能と破壊物性及び転動抵抗等を高度に鼎立させて向上させる観点より、前述した（ａ）成分の１０〜７０質量部、（ｂ）成分の２０〜８０質量部、及び（ｃ）成分の０〜３０質量部、の範囲から選ばれる任意組成からなるものが好ましい。
【００３８】
本発明のゴム組成物には、補強剤ないし充填剤としてカーボンブラックを配合することが好ましい。このカーボンブラックは、窒素吸着比表面積（Ｎ₂ＳＡ）が５０ｍ²／ｇ以上のものが好ましい。この（Ｎ₂ＳＡ）が５０ｍ²／ｇ未満では充分な耐摩耗性が得られ難い。また、（Ｎ₂ＳＡ）が大きすぎると低発熱性能が低下する原因となることがある。耐摩耗性及び低発熱性能のバランスなどの面から、より好ましい（Ｎ₂ＳＡ）は８０〜１６０ｍ²／ｇの範囲である。ここで、該（Ｎ₂ＳＡ）はＡＳＴＭ Ｄ３０３７−８８に準拠して測定した値である。
【００３９】
上記カーボンブラックとしては特に制限はなく、従来ゴムの補強用充填材として慣用されているものの中から任意のものを適宜選択して用いることができる。好適なカーボンブラックの例としては、ＦＥＦ、ＳＲＦ、ＨＡＦ、ＩＳＡＦ、ＳＡＦ等が挙げられるが、これらの中でも、耐摩耗性に優れるＨＡＦ、ＩＳＡＦ、及びＳＡＦカーボンが特に好適である。本発明においては、このカーボンブラックは、前記（Ａ）或いは（Ｂ）のゴム成分１００質量部に対し、２０〜７０質量部の範囲で配合することが好ましい。この配合量が２０質量部未満では耐摩耗性が充分に発揮されない恐れがあり、７０質量部を超えると低発熱性能が低下したり、分散不良をもたらし、耐摩耗性などが悪化する原因となることがある。耐摩耗性、低発熱性能及び分散性などを考慮すると、このカーボンブラックの配合量は３０〜６０質量部の範囲がより好ましい。
【００４０】
本発明のゴム組成物においては、所望により、更にシリカを配合することができる。このシリカは、窒素吸着比表面積（Ｎ₂ＳＡ）が１６０〜２６０ｍ²／ｇの範囲にあり、且つジブチルフタレート吸油量（ＤＢＰ）が１８０〜２６０ｍL／１００ｇの範囲にあるものが好適である。この（Ｎ₂ＳＡ）が１６０ｍ²／ｇ未満や（ＤＢＰ）が１８０ｍL／１００ｇ未満では耐摩耗性が不充分になる恐れがあり、一方、（Ｎ₂ＳＡ）が２６０ｍ²／ｇを超えたり、（ＤＢＰ）が２６０ｍL／１００ｇを超えると分散不良を引き起こし、低発熱性能及び耐摩耗性が低下する原因となることがある。ここで、上記（Ｎ₂ＳＡ）は、３００℃で１時間乾燥した後、ＡＳＴＭ Ｄ４８２０−９３に準拠して測定した値であり、（ＤＢＰ）は、ＡＳＴＭ Ｄ２４１４−９３に準拠して測定した値である。
【００４１】
上記シリカとしては、例えば湿式シリカ（含水ケイ酸）、乾式シリカ（無水ケイ酸）、ケイ酸カルシウム、ケイ酸アルミニウムなどが挙げられるが、これらの中で、特に湿式シリカが好適である。本発明においては、このシリカは、前記（Ａ）或いは（Ａ）のゴム成分１００質量部に対し、３０質量部以下の範囲で配合されることが好ましい。この配合量が３０質量部を超えると低発熱性能が低下する恐れがある。更に好ましいシリカの配合量は２０質量部以下の範囲である。
【００４２】
本発明のゴム組成物は、前記（Ａ）或いは（Ｂ）成分であるゴム成分、好ましくはカーボンブラック及びシリカの他に、通常の工業用ゴム配合に常用される加硫剤、加硫促進剤、加硫助剤、老化防止剤、プロセス油、軟化剤、その他ゴム配合剤を適宜に含有することができる。本発明の重荷重用空気入りラジアルタイヤは、この様なゴム組成物をトレッドゴムとして用い、通常の加硫条件に従って加硫成形することにより、製造することができる。また、本発明の上記タイヤに充填される気体には、空気或いは窒素などの不活性なガスが用いられる。
【００４３】
（航空機用重荷重用ラジアルタイヤ）
上述したゴム組成物をタイヤのトレッドゴムに適用した、本発明の航空機用重荷重用空気入りラジアルタイヤについて、以下に詳細に説明する。
本発明者等が、ベルト層の張力負担を詳細に調べた結果、図３のグラフに示すように、１００％内圧（ＴＲＡ規定内圧）の無負荷状態では１点鎖線の様な分布になっていた。尚、図３において、縦軸は張力、横軸はベルト幅方向の位置、ＳＢＷはベルト層の最大幅を示す。
ところで、航空機用タイヤの場合、無負荷状態において、規定内圧の４００％の耐圧性が必要である。該４００％内圧充填時の張力分布を調べた結果、実線の様になることが分かった。一方、荷重負荷状態では、ベルト層の張力分布は２点鎖線のようになることが分かった。このことから、該ベルト層は、両方の条件を満たす強度を有することが必要となることが分かる。
発明者等は種々の実験、調査から、無負荷時の張力に対し、赤道面の強力をベルト層の最大幅の２／３の位置の強力よりも大きく規定することで、径成長の抑制と質量減の両立を達成できることを見出した。
請求項１に記載の発明は上記事実に鑑みてなされたものであって、一対のビードコアと、一方ビードコアから他方のビードコアに向けてトロイド状に延びる少なくとも１枚以上のカーカスプライからなるカーカス層と、前記カーカス層のタイヤ半径方向外側のクラウン域外周面に、有機繊維コードを含む少なくとも１枚以上のベルトプライからなるベルト層と、該ベルト層のタイヤ半径方向外側に踏面部を構成するトレッドゴム層と、を備えた空気入りラジアルタイヤであって、タイヤ赤道面位置Ｐ０での単位幅当りにおける前記ベルト層のタイヤ周方向の総強力をＫ０、タイヤ赤道面を中心として前記ベルト層の最大幅の２／３の幅位置Ｐ２での単位幅当りにおける前記ベルト層のタイヤ周方向の総強力をＫ２としたときに、Ｋ２＜Ｋ０を満足する、ことを特徴としている。
次に、請求項１に記載の空気入りラジアルタイヤの作用を説明する。
請求項１に記載の空気入りラジアルタイヤでは、タイヤ赤道面位置Ｐ０での単位幅当りにおけるベルト層のタイヤ周方向の総強力Ｋ０を、タイヤ赤道面を中心としてベルト層の最大幅の２／３の幅位置Ｐ２での単位幅当りにおけるベルト層のタイヤ周方向の総強力より大きく設定したので、ベルト層の材料使用量を抑えつつ、標準内圧の充填時及び高速回転時に、トレッド中央域でのトレッドゴムの周方向伸張量を抑制し、タイヤの径成長を抑制することができる。トレッドゴムの周方向伸張量が抑制されることでゴムの緊張度合いが低下するので、異物の進入に対する抵抗力が増大し、また、万一異物が刺さり込んだ場合であっても、亀裂の成長を抑えることが出来る。
尚、請求項１に記載の空気入りラジアルタイヤにおいて、前述した本発明のゴム組成物は、ベルト層のタイヤ半径方向外側に配置されたトレッドゴム層の全体に適用されてもよく、少なくともショルダーリブ領域に適用されてもよい。
【００４４】
（総強力の定義）ここでいう総強力とは、ベルト層の周方向の強力を指しており、１本のコードの強力に単位幅当り（ここでは１０ｍｍ）の本数を掛けて算出したものである。なお、コードが周方向に対して角度θで傾斜している場合の総強力は、上記単位幅当りの総強力にｃｏｓθを掛けて算出してものとする。また、タイヤ内のコードがタイヤ周方向に波型（ジグザグ状）に伸びている場合は、真っ直ぐに伸ばして強力を算出するのではなく、タイヤに埋設されている形状、即ち、波状に型付けされたものを周方向に伸ばした時の強力を算出する。
【００４５】
請求項４に記載の発明は、請求項１に記載の空気入りラジアルタイヤにおいて、０．２≦Ｋ２／Ｋ０≦０．８を満足する、ことを特徴としている。
次に、請求項５に記載の空気入りラジアルタイヤの作用を説明する。
強力の比（Ｋ２／Ｋ０）が０．２を下回ると、ショルダー部付近に位置する有機繊維コードに過大な張力が負担されることによる耐圧性能の低下を引き起こす虞がある。一方、強力の比（Ｋ２／Ｋ０）が０．８を上回ると、２／３点に配置したベルトプライの有機繊維コードが有効に活用されず、空気入りラジアルタイヤの質量増につながる。従って、強力の比（Ｋ２／Ｋ０）は、０．２≦Ｋ２／Ｋ０≦０．８を満足することが好ましい。
【００４６】
請求項５に記載の発明は、請求項１または請求項４に記載の空気入りラジアルタイヤにおいて、前記ベルト層において、前記有機繊維コードの積層厚みを前記タイヤ赤道面位置Ｐ０で最も厚くし、前記タイヤ赤道面位置Ｐ０での前記有機繊維コードの積層厚みをＧ０、前記ベルト層の最大幅の２／３の幅位置Ｐ２での前記有機繊維コードの積層厚みをＧ２としたときに、Ｇ２＜Ｇ０を満足する、ことを特徴としている。
次に、請求項５に記載の空気入りラジアルタイヤの作用を説明する。
ベルト層の最大幅の２／３の幅位置Ｐ２での有機繊維コードの積層厚みＧ２を、タイヤ赤道面位置Ｐ０での有機繊維コードの積層厚みＧ０よりも大きく設定することで、Ｋ２＜Ｋ０を容易に達成することができる。尚、有機繊維コードの積層厚みとは、ベルト層をタイヤ径方向断面で見たときのタイヤ径方向に積層されている有機繊維コードの総径寸法である。例えば、直径がＡの有機繊維コードが１２本積層されている場合には、積層厚みはＡ×１２となる。
【００４７】
請求項６に記載の発明は、請求項５に記載の空気入りラジアルタイヤにおいて、０．３５≦Ｇ２／Ｇ０≦０．８５を満足することを特徴としている。
次に、請求項６に記載の空気入りラジアルタイヤの作用を説明する。
有機繊維コードの積層厚みの比Ｇ２／Ｇ０が、０．３５を下回ると、ショルダー部付近に位置する有機繊維コードに過大な張力が負担されることによる耐圧性能の低下を引き起こす虞がある。一方、有機繊維コードの積層厚みの比Ｇ２／Ｇ０が０．８５を上回ると、２／３点に配置したベルトプライの有機繊維コードが有効に活用されず、空気入りラジアルタイヤの質量増につながる。従って、有機繊維コードの積層厚みの比Ｇ２／Ｇ０は、０．３５≦Ｇ２／Ｇ０≦０．８５を満足することが好ましい。
【００４８】
請求項７に記載の発明は、請求項１〜請求項６の何れか１項に記載の空気入りラジアルタイヤにおいて、前記ベルト層において、前記ベルト層の最大幅の２／３の幅位置Ｐ２での前記有機繊維コードの積層厚みをＧ２とした時に、前記ベルト層には、前記ベルト層の最大幅の２／３の幅位置Ｐ２よりもタイヤ幅方向外側の領域において、前記積層厚みＧ２よりも積層厚みの厚い部分が設けられている、ことを特徴としている。
次に、請求項７に記載の空気入りラジアルタイヤの作用を説明する。
ベルト層の最大幅の２／３の幅位置Ｐ２よりもタイヤ幅方向外側の領域において、積層厚みＧ２よりも積層厚みの厚い部分を設けると、高速走行時、特にタイヤ幅方向の外力に晒される様な場合に、タイヤ両側部の大きな張力変動を柔軟に吸収せしめることが可能となり、空気入りラジアルタイヤの寿命を著しく低下させ得るスタンディングウエーブの発生を効果的に抑制することができる。
【００４９】
請求項８に記載の発明は、請求項１〜請求項７の何れか１項に記載の空気入りラジアルタイヤにおいて、前記ベルト層は、引張破断強度が６．３ｃＮ／ｄｔｅｘ以上、伸張方向に０．３ｃＮ／ｄｔｅｘ荷重時の伸び率が０．２〜２．０％、伸張方向に２．１ｃＮ／ｄｔｅｘ荷重時の伸び率が１．５〜７．０％、伸張方向に３．２ｃＮ／ｄｔｅｘ荷重時の伸び率が２．２〜９．３％とされた有機繊維コードを含むベルトプライの少なくとも２枚以上で構成された主ベルト層を有する、ことを特徴としている。
次に、請求項８に記載の空気入りラジアルタイヤの作用を説明する。
本発明の様に、ベルト層の強度分布を規定することで、径成長抑制と質量減の両立を達成できるが、ナイロンの様な低弾性のコードを用いると、径成長を抑えるために多層にする必要があり、タイヤの質量増につながる。
【００５０】
請求項８に記載の空気入りラジアルタイヤでは、主ベルト層を、引張破断強度が６．３ｃＮ／ｄｔｅｘ以上とされた高弾性の有機繊維コードを含む少なくとも２枚以上のベルトプライで構成することにより、必要な耐圧性能を満足することができる。ここで、有機繊維コードの伸張方向に２．１ｃＮ／ｄｔｅｘ荷重時の伸び率を１．５〜７．０％、伸張方向に３．２ｃＮ／ｄｔｅｘ荷重時の伸び率を２．２〜９．３％とすることにより、目標の径成長の抑制を容易に達成することができた。
その理由は、航空機用の空気入りラジアルタイヤでは、標準状態の内圧負荷時におよそ２．１ｃＮ／ｄｔｅｘのコード張力が加わり、高速走行時におよそ３．２ｃＮ／ｄｔｅｘのコード張力が加わるが、有機繊維コードの伸び率が上記範囲を上回る場合、タイヤ内圧充填時においてタイヤ径方向の膨出を効果的に抑えられず、異物の刺さり込みに対する性能を期待できなくなるからである。
一方、有機繊維コードの伸び率が上記範囲を下回る場合、ベルトプライのタガ効果が大き過ぎるため、カーカスプライが必要以上にタイヤ幅方向に膨出する結果となり好ましくない。
更に、有機繊維コードの伸張方向に０．３ｃＮ／ｄｔｅｘ荷重時の伸び率を０．２〜２．０％とした理由は、以下に述べる通りである。先ず、空気入りラジアルタイヤを加硫するに当り、航空機用空気入りラジアルタイヤの場合、通常タイヤモールド内にて生タイヤが０．２〜２．０％ほど伸張する様にタイヤ外径が設定される。これは、加硫時に生タイヤ内部より負荷される圧力によってタイヤを均等に伸張せしめることによってコードの方向を揃え、コード打込みのばらつきを是正するためのものである。然る該工程においては、０．３ｃＮ／ｄｔｅｘ程度の比較的小さい張力が有機繊維コードに作用するが、この時の有機繊維コードの伸び率が２．０％より大きいと、コード性状是正の効果が薄く、また、伸び率が０．２％より小さい場合には、加硫時の膨張時にコード張力が大となり、有機繊維コードがタイヤ径方向内側のゴムに食い込むなどの不都合が生じるからである。
【００５１】
（標準状態の内圧負荷時の定義）ここでの内圧及び荷重は、ＴＲＡ ＹＥＡＲＢＯＯＫ（２００２年度版）に規定されている内圧、及び荷重を採用している。例えば、航空機用ラジアルタイヤ１２７０×４５５Ｒ２２ ３２ＰＲの場合、規定内圧は１６２０ｋＰａ、規定荷重は２４８６０ｋｇである。
尚、有機繊維コードは、伸張方向に０．３ｃＮ／ｄｔｅｘ荷重時の伸び率が０．２〜１．５％、伸張方向に２．１ｃＮ／ｄｔｅｘ荷重時の伸び率が１．５〜６．５％、伸張方向に３．２ｃＮ／ｄｔｅｘ荷重時の伸び率が２．２〜８．３％のものがより好ましい。
【００５２】
請求項９に記載の発明は、請求項８に記載の空気入りラジアルタイヤにおいて、前記主ベルト層のタイヤ幅方向端部では、少なくとも前記ベルトプライが２層以上積層されている、ことを特徴としている。
次に、請求項９に記載の空気入りラジアルタイヤの作用を説明する。
主ベルト層のタイヤ幅方向端部において、ベルトプライを２層以上積層することで、タイヤ走行時、特に、タイヤ幅方向に外力が作用する場合のように、タイヤ接地面の幅方向両端付近の有機繊維コードに激しい張力変動を伴う様な条件下においても、その弾力性を持って衝撃を効果的に分散することが可能となり、苛酷な使用条件下におけるタイヤの信頼性向上に効果的である。
【００５３】
請求項１０に記載の発明は、請求項８又は請求項９に記載の空気入りラジアルタイヤにおいて、前記主ベルト層は、芳香族ポリアミド系の繊維から構成され、下撚り係数が０．１２〜０．８５、上撚り係数が０．４０〜０．８０とされた有機繊維コードを含むベルトプライを有する、ことを特徴としている。
次に、請求項１０に記載の空気入りラジアルタイヤの作用を説明する。
主ベルト層を構成する有機繊維コードを芳香族ポリアミド系の繊維から構成し、下撚り係数を０．１２〜０．８５、好ましくは０．１７〜０．５１、上撚り係数を０．４０〜０．８０とすることで、有機繊維コードを請求項６に規定の物性、即ち、引張破断強度を６．３ｃＮ／ｄｔｅｘ以上、伸張方向に０．３ｃＮ／ｄｔｅｘ荷重時の伸び率を０．２〜２．０％、伸張方向に２．１ｃＮ／ｄｔｅｘ荷重時の伸び率を１．５〜７．０％、伸張方向に３．２ｃＮ／ｄｔｅｘ荷重時の伸び率を２．２〜９．３％に設定することができる。
【００５４】
（撚り係数の定義）ここでいう撚り係数とは、以下の式から算出されるものである。
ＮＴ＝Ｎ×（０．１３９×Ｄ／ρ）^1/2×１０^-3
Ｎ：有機繊維コード１００mm当りの撚り数
Ｄ：総表示デシテックス（ｄｔｅｘ）
ρ：有機繊維コードの比重（ｇ／ｃｍ³）
【００５５】
請求項１１に記載の発明は、請求項８〜請求項１０の何れか１項に記載の空気入りラジアルタイヤにおいて、前記主ベルト層は、芳香族ポリアミド系の繊維と脂肪族ポリアミド系の繊維とを含み、芳香族ポリアミド系の繊維と脂肪族ポリアミド系の繊維との質量比が１００：１０〜１７０とされた有機繊維コードを含むベルトプライを有する、ことを特徴としている。
次に、請求項１１に記載の空気入りラジアルタイヤの作用を説明する。
主ベルト層を構成する有機繊維コードを芳香族ポリアミド系の繊維と脂肪族ポリアミド系の繊維とから構成し、かつ芳香族ポリアミド系の繊維と脂肪族ポリアミド系の繊維との質量比を１００：１０〜１７０とすることで、有機繊維コードを請求項８に規定の物性、即ち、引張破断強度が６．３ｃＮ／ｄｔｅｘ以上、伸張方向に０．３ｃＮ／ｄｔｅｘ荷重時の伸び率が０．２〜２．０％、伸張方向に２．１ｃＮ／ｄｔｅｘ荷重時の伸び率が１．５〜７．０％、伸張方向に３．２ｃＮ／ｄｔｅｘ荷重時の伸び率が２．２〜９．３％に設定することができる。
ここで、芳香族ポリアミド系の繊維の質量１００に対して脂肪族ポリアミド系の繊維の質量が１０を下回ると、上記荷重を負荷したときに、コード伸張が小さくなるため請求項８に規定の物性を達成することが困難となる。一方、芳香族ポリアミド系の繊維の質量１００に対して脂肪族ポリアミド系の繊維の質量が１７０を上回ると、上記荷重を負荷したときに、コード伸張が大きくなるため請求項９に規定の物性を達成することが困難となる。
【００５６】
尚、芳香族ポリアミド系の繊維と脂肪族ポリアミド系の繊維との質量比は、より好ましくは１００：１７〜８６である。ここで、脂肪族ポリアミド系の繊維とは、例えば、６−ナイロン、６，６−ナイロン、４，６−ナイロン繊維等である。ここで、有機繊維コードは、芳香族ポリアミド系の繊維と脂肪族ポリアミド系の繊維とから構成されていればよく、芳香族ポリアミド系有機繊維コードと脂肪族ポリアミド系有機繊維コードとを撚り合わせてもよく、芳香族ポリアミド系の繊維と脂肪族ポリアミド系の繊維とを合わせてから撚りをかけてもよい。
また、芳香族ポリアミド系有機繊維コードをＡ、脂肪族ポリアミド系有機繊維コードをＢとした場合、ＡまたはＢを下撚り（Ｚ撚り）後、引き揃えて、下撚りと逆方向に上撚り（Ｓ撚り）をかけることで主ベルト層を構成する有機繊維コードを得ることができる。尚、下撚り時は、ＡまたはＢをそれぞれ単独で撚ってもよいし、ＡとＢを併せた後撚ってもよい。下撚り又は上撚り時のＡ、Ｂ又はＡＢ（合糸）の本数は１本ずつでも複数本ずつでもよい。Ａ又はＢ原糸の太さは同じでもよいし異なっていてもよい。混撚糸の形態は、芯となる糸の回りにループを作ったものなどでもよい。
【００５７】
請求項１２に記載の発明は、請求項１１に記載の空気入りラジアルタイヤにおいて、前記主ベルト層は、芳香族ポリアミド系のコードと脂肪族ポリアミド系のコードとが撚り合わされ、且つ前記芳香族ポリアミド系のコードの下撚り係数が０．１２〜０．８５とされた有機繊維コードを含むベルトプライを有する、ことを特徴としている。
次に、請求項１２に記載の空気入りラジアルタイヤの作用を説明する。
芳香族ポリアミド系のコードの下撚り係数を０．１２〜０．８５とすることにより、請求項８に規定の物性を達成することが容易になる。尚、芳香族ポリアミド系のコードの下撚り係数を０．１７〜０．５１とすることが更に好ましい。
【００５８】
請求項１３に記載の発明は、請求項８〜請求項１２の何れか１項に記載の空気入りラジアルタイヤにおいて、前記主ベルト層は、タイヤ赤道面に対して略０°の角度で螺旋状に巻回された有機繊維コードを含むベルトプライを有する、ことを特徴としている。
次に、請求項１３に記載の空気入りラジアルタイヤの作用を説明する。
有機繊維コードのタイヤ赤道面に対する角度が略０°に設定することで、主ベルト層の周方向剛性を確保するために使用する有機繊維コードの強力を最大限に活用することが可能となり、空気入りラジアルタイヤの軽量化を図ることが出来る。尚、ここでいう略０°とは、２．０°以下を含むものとする。
【００５９】
請求項１４に記載の発明は、請求項８〜請求項１３の何れか１項に記載の空気入りラジアルタイヤにおいて、前記主ベルト層は、タイヤ赤道面に対して２〜２５°の角度で傾斜し、それぞれのプライ端で反対方向に傾斜するように同一面内で屈曲されてタイヤ周方向にジグザグ状に延びる有機繊維コードを含むベルトプライを有する、ことを特徴としている。
次に、請求項１４に記載の空気入りラジアルタイヤの作用を説明する。
タイヤ赤道面に対して２〜２５°の角度で傾斜し、それぞれのプライ端で反対方向に傾斜するように同一面内で屈曲されてタイヤ周方向にジグザグ状に延びる有機繊維コードを含むベルトプライを用いることで、主ベルト層の周方向剛性を大きく低下させることなくしてタイヤ幅方向の剛性を確保することができ、その結果、優れた耐摩耗性を実現することが可能となる。
【００６０】
タイヤ幅方向の剛性を確保することで、優れた耐摩耗性が実現される理由は以下の通りである。一般に、内圧充填時のタイヤ形状において、クラウンセンター部とショルダー部との径差が大きいと、いわゆる「引きずり摩耗」を起こす可能性が高くなる。タイヤ回転中に接地したセンター部とショルダー部は、接地長の分だけ回転するが、一定の周長に対応するタイヤ回転角度は径の小さいショルダー部の方が大きくなる。このため、路面を離れるまでにショルダー部は回転方向後方に拘束された状態となり、トレッド接地面内にてセンター部とショルダー部とが剪断変形する。この変形を是正するためにショルダー部が路面に対して相対的に滑る現象が「引きずり摩耗」である。
上記周方向位置のずれの大きさは、上記センター部とショルダー部との径差、及びトレッド面内の周方向剪断剛性に依存し、径差が大きく剪断剛性が小さいほど引きずり摩耗の程度が大きくなる。スパイラルベルトは、コードがほぼ周方向を向いているため、上記剪断剛性が小さく、引きずり摩耗に関しては有効ではない。これを補うため、タイヤ周方向に対する角度が大きいコードを有するベルトを追加することで、タイヤ幅方向剛性を確保でき、摩耗特性の改善が図られる。ここで、有機繊維コードのタイヤ赤道面に対する角度が２°を下回ると、幾何学的にジグザグ状にベルトを巻回することが困難となる（即ち、スパイラル状になってしまう。）。一方、有機繊維コードのタイヤ赤道面に対する角度が２５°を上回ると、有機繊維コードがタイヤ周方向に発揮し得る張力が相対的に減少し、空気入りラジアルタイヤの内圧を負担する効率が悪化する。
【００６１】
（１つの実施形態）
以下、本発明の航空機用空気入りラジアルタイヤの１つの実施形態を、添付した図１に基づいて説明する。
図１に示す様に、本実施形態の航空機用の空気入りラジアルタイヤ１０１（タイヤサイズ：１２７０×４５５Ｒ２２ ３２ＰＲ）は、ビード部１２に丸型断面を有するビードコア１４を備えていて、ゴム被覆された有機繊維コードがラジアル方向に配列された６枚のカーカスプライよりなるカーカス層１６がこのビードコア１４に係留されている。
カーカス層１６のタイヤ半径方向外側のクラウン域外周面には、ベルト層２０、ベルト層２０のタイヤ径方向外側にはトレッド部を構成するトレッドゴム層（３１、３２、３３）が設けられている。また、カーカス層のタイヤ幅方向外側には、サイドウォール部２５を構成するサイドゴム層２７が設けられている。尚、本実施の形態では、ベルト層２０は、タイヤ径方向内側の主ベルト層２６と、主ベルト層２６のタイヤ径方向外側に設けられる副ベルト層２８、副ベルト層２８のタイヤ径方向外側に設けられる保護ベルト層２２とから構成されている。
ここで、前述した本発明のゴム組成物は上記トレッドゴム層に適用されるが、トレッドゴムの全体（図１の３１、３２、３３で示す。）に用いてもよく、トレッドゴムの一部（例えば、図１の３１、３２、３３のいずれか。）に用いてもよい。特に、耐偏磨耗性を改良するためには、トレッドゴム層の少なくともショルダー領域（図１の３３で示す。）に適用することが好ましい。
【００６２】
主ベルト層２６は、複数枚のベルトプライ、本実施形態では、８枚のベルトプライから構成されている。主ベルト層２６を構成するこれらプライは、複数本の有機繊維コードをゴム被覆することにより形成されている。これらの有機繊維コードは、引張破断強度を６．３ｃＮ／ｄｔｅｘ以上とすることが好ましく、伸張方向に０．３ｃＮ／ｄｔｅｘ荷重時の伸び率が０．２〜２．０％、伸張方向に２．１ｃＮ／ｄｔｅｘ荷重時の伸び率が１．５〜７．０％、伸張方向に３．２ｃＮ／ｄｔｅｘ荷重時の伸び率が２．２〜９．３％であることが好ましい。
本実施形態の有機繊維コードは、芳香族ポリアミド系の繊維から構成されている。有機繊維コードを芳香族ポリアミド系の繊維から構成した場合、下撚り係数は０．１２〜０．８５、好ましくは０．１７〜０．５１、上撚り係数は０．４０〜０．８０に設定することが好ましい。本実施形態では、芳香族ポリアミド系の繊維、具体的にはデュポン社製ポリアミド繊維（商品タイプ名：ＫＥＶＬＡＲ（Ｒ）２９、公称繊度３０００デニール。以後、適宜ケブラーと呼ぶ。）からなる有機繊維コードを用いている。なお、本実施形態では、有機繊維コードの傾斜角度はタイヤ赤道面ＣＬに対して略０°である。なお、ベルトプライにおいて、有機繊維コードの打込み数は、４〜１０本／１０ｍｍの範囲内が好ましい。本実施形態では、ベルトプライ２６において、有機繊維コードの打込み数が６．３本／１０ｍｍである。
【００６３】
本実施形態のように副ベルト層２８を設ける場合、その範囲は、タイヤ赤道面ＣＬから主ベルト層２６の幅ＢＷの１４０％位置までの範囲内に設けることが好ましい。本実施形態では、副ベルト層２８の幅ＳＢＷは主ベルト層２６の幅ＢＷの１０３％である。副ベルト層２８は、本実施形態では１枚のベルトプライから構成されている。本実施形態のベルトプライは、１又は複数本の有機繊維コードをゴム被覆して構成した帯状の細長体を準備し、この細長体をほぼ１周する毎に両プライ端間を１度だけ往復させながらタイヤ赤道面に対して２〜２５°の角度で傾斜させて周方向に巻き付けると共に、このような巻付けを細長体間に隙間が生じないよう周方向にほぼ細長体の幅だけずらして多数回巻回することで形成している（以後、適宜無端ジグザグ巻きベルトと呼ぶ。）。この結果、ベルトプライ内には両プライ端において折り曲げ方向を変えることによりジグザグしながらほぼ周方向に延びる有機繊維コードが、該ベルトプライの全領域においてほぼ均一に埋設されることになる。
【００６４】
このベルトプライには、主ベルト層２６に含まれる有機繊維コードに対して弾性率が同等、あるいは小さい有機繊維コード（主ベルト層２６の有機繊維コードに対して２．１ｃＮ／ｄｔｅｘ荷重時の伸び率が略同等以上である有機繊維コード）を用いることが好ましい。副ベルト層２８を構成するベルトプライに用いる有機繊維コードとしては、ナイロン等の脂肪族ポリアミド系の繊維からなるコード、アラミド等の芳香族ポリアミド系の繊維とナイロン等の脂肪族ポリアミド系の繊維とを含むコード等が好ましく、本実施形態では、ナイロンコード（撚り数：１２６０Ｄ／／２／３、打込み数７．３本／１０ｍｍ）を用いている。また、無端ジグザグ巻きベルトである本実施形態のベルトプライにおいて、その有機繊維コードの傾斜角度はタイヤ赤道面ＣＬに対して２〜４５°の範囲内が好ましく、本実施形態では８°に設定されている。
【００６５】
【実施例】
以下に、本発明を実施例により更に具体的に説明するが、本発明はこれらの実施例により限定されるものではない。ここで、実施例において用いたカーボンブラック、ワックス、老化防止剤、加硫促進剤等のゴム用配合剤は一例を示すものであって、目的に応じて他の任意の配合剤を使用することができる。尚、本実施例中の「部数」及び「％」は全て、「質量部」及び「質量％」を表す。
【００６６】
［実施例１〜３及び比較例１〜３］
下記の表１に示す配合処方に従って、実施例１〜３及び比較例１〜３のゴム組成物を調合して、２５０ｍLのラボプラストミル（（株）東洋精機製作所製）を用いて混練した後、３インチロールで各ゴム組成物のシート物を作製した。次いで、温度１５０℃で、加硫反応によるトルクの上昇が最高値の９０％に達するまでの時間（ｔ₉₀）の１．５倍にあたる加硫時間で加硫して、下記の物性測定用の供試サンプルを得た。
【００６７】
【表１】

【００６８】
上記の表１に記載のＳＢＲゴムは、下記の仕様（スペック）のものである。
・Ｅ−ＳＢＲ………ＪＳＲ（株）製の乳化重合ＳＢＲ「＃１５００」
・Ｓ−ＳＢＲ（１）………ＦＳＰＣ（ファイアストン・ケミカル）社製の溶液重合ＳＢＲ「ＨＸ７６５」（スチレン含量：２５％、ビニル結合量：２８モル％）
・Ｓ−ＳＢＲ（２）………ＪＳＲ（株）製の溶液重合ＳＢＲ（スチレン含量：３５％、ビニル結合量：２３モル％）
また、使用した老化防止剤と加硫促進剤は下記のものである。
・６ＰＰＤ………Ｎ−（１，３−ジメチルブチル）−Ｎ’−フェニル−ｐ−フェニレンジアミン
・ＴＢＢＳ………Ｎ−ｔ−ブチル−２−ベンゾチアゾリルスルフェンアミド
【００６９】
上記で得られた各加硫ゴム試料につき、以下の様に評価試験を実施して、その結果を下記の表３に記入した。
（１）発熱特性
（米国）レオメトリックス社製の動的粘弾性測定試験機「ＡＲＥＳ」を使用して、温度５０℃、測定周波数１５Ｈｚ、及び動的せん断歪１％における損失正接（ｔａｎδ）を測定した。このｔａｎδ値の逆数を、比較例１のものを１００として指数で表示した。この指数の値が大きい程、低発熱性であることを意味する。
【００７０】
（２）ランボーン摩耗試験
ＪＩＳ Ｋ ６２６４に準拠して、岩本製作所（株）製のランボーン摩耗試験機を用いて、温度３０℃、スリップ率６０％の条件で摩耗量を測定した。この摩耗量の逆数を、比較例１のものを１００として指数で表示した。この指数の値が大きい程、耐摩耗性は良好であることを意味する。
【００７１】
（３）偏摩耗性の試験
［実施例１〜４及び比較例１〜３］
前記表１の実施例１〜３及び比較例１〜３に示す各配合のゴム組成物を、図１に示す航空機用空気入りラジアルタイヤ（サイズ：ＡＰＲ １２７０×４５５Ｒ２２ ３２ＰＲ）のトレッド部全体（図１の３１、３２、３３で示す。）に適用して、通常の航空機用ラジアルタイヤの製造プロセスに従って、供試用タイヤを作製した。尚、実施例４の供試用タイヤは、トレッド部のショルダーリブ（図１の３３で示す。）のみに実施例２のゴム組成物を適用し、その他の部分（図１の３１、３２で示す。）には比較例１のゴム組成物を適用したこと以外は、上記と同様にして作製したものである。
【００７２】
この様にして得られた各供試タイヤにつき、４６×１７Ｒ２０／３０をリムに用い内圧１２．７ｋｇ／ｃｍ²で組み付けたリム組立体を、セーフティウォークを貼り付けたドラム上でＴａｘｉ模擬走行を行った。このＴａｘｉ模擬走行は、下記の表２に記載のＡ〜Ｃの試験条件を、Ａ→Ｂ→Ｃを１サイクルとして６０分間隔で該サイクルを繰り返して行うものである。試験タイヤのショルダーリブのブレーカーコードが露出した時点を試験終了時として、該時点までの繰返しサイクル数を測定した。表３に記入の値は、比較例１の供試タイヤの上記試験サイクル数を１００として、各々の値を指数化した値であり、その数値が大きい程、耐偏摩耗性が優れていることを意味している。
【００７３】
【表２】

【００７４】
【表３】

【００７５】
上記の表３の結果から明らかな様に、本発明のトレッド用ゴム組成物（実施例１〜３）は、比較例のものに比べて、低発熱性及び耐摩耗性に優れていることが判明した。また、これらのゴム組成物をトレッドに適用した本発明の航空機用ラジアルタイヤ（実施例１〜４）は、比較例のタイヤに比べて、Ｔａｘｉ模擬走行において、耐偏摩耗性において優れていることが実証された。
【００７６】
【発明の効果】
本発明のゴム組成物及びタイヤ構造を適用することに依って、耐摩耗性、特に耐偏摩耗性と抗破壊性及び低発熱性の鼎立がバランス良く高いレベルで達成された重荷重用空気入りラジアルタイヤ、特に航空機用ラジアルタイヤを提供することが可能になった。
【図面の簡単な説明】
【図１】第１の実施形態に係る本発明の航空機用空気入りラジアルタイヤ（１０１）の断面図である。
【図２】従来例に係る空気入りラジアルタイヤ（１０２）の断面図である。
【図３】ベルト層にかかる張力を示すグラフである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a radial tire for high-speed heavy loads, and more particularly, to a pneumatic radial tire suitable for aircraft having improved uneven wear resistance and improved durability life.
[0002]
[Prior art]
Conventional high-speed heavy-duty radial tires, particularly aircraft radial tires, have a large tread surface radial protrusion due to the effects of high internal pressure and centrifugal force during high-speed rotation. When the tread surface protrudes in the radial direction as described above, the tread rubber is stretched in the tire circumferential direction accordingly. In particular, the difference in diameter that occurs when the protruding amount in the center in the tire width direction is larger than the vicinity of both ends (shoulders) in the tire width direction causes a drag phenomenon on the ground contact surface of the rotating tire, and the vicinity of the shoulder is in the center of the tire. There is a problem that a so-called “uneven wear phenomenon” occurs, which wears faster than the part and shortens the life of the tire.
[0003]
In addition, since radial tires for aircraft are used under conditions of high internal pressure and high load, the property of the tire not to damage the tread when riding over the foreign matter when passing over the foreign matter, so-called “envelope” In particular, when the tire tread rubber is stretched in the tire circumferential direction, the damage resistance against foreign matter is weakened, and the stepped foreign matter can easily enter the rubber and easily damage the tire. is there.
[0004]
As a conventional method for improving the wear characteristics of the tread by suppressing the bulging deformation of the tread and improving the envelope property, as illustrated in the cross-sectional view of FIG. A belt layer 20 disposed between the tread rubber layer 30 and a conventional general main belt layer 26 made of a wide belt ply and a sub belt made of a narrow belt ply added to the outer peripheral side of the main belt layer 26. The belt layer 28 is used to increase the belt rigidity with the sub belt layer 28 disposed in the central portion of the main belt layer 26, and in particular, the air born from the technology for restraining the bulging deformation in the central region of the tread. A entering radial tire (102) is conceivable.
[0005]
Further, in order to suppress the protrusion due to the internal pressure in the center portion in the width direction of the tire, a conventionally used method is to replace the ply cord with an aromatic polyamide cord having a relatively high elastic modulus (for example, a patent Reference 1). This aromatic polyamide-based cord exhibits high tension and maintains internal pressure even in a low elongation region compared to aliphatic polyamides that have been generally used for aircraft tires so far, and therefore effective for the tire to stick out. Can be suppressed.
[0006]
In addition, as a conventional method for suppressing the protrusion of the center portion in the width direction of the tire, for example, a pneumatic radial tire in which a narrow reinforcing layer (cord is steel) is added to a belt has been proposed (for example, Patent Document 2). As another conventional example, a pneumatic radial tire is proposed in which a reinforcing layer composed of a cord reinforced with a high-strength cord such as glass, metal, or aramid is provided on the outermost layer of a belt made of organic fibers. (For example, refer to Patent Document 3).
[0007]
In these conventional inventions, a belt having a high tension is further added. However, according to the prior art shown in FIG. 2, the tread is secured by ensuring the required rubber thickness H (thickness of rubber only, excluding cords) in the tread central region where the total thickness of the belt layer is the thickest. Side area rubber thickness H₀Since the tire becomes too thick, the tire weight is inevitably increased, and the amount of heat generated in the tread side region increases, resulting in a problem that the high-speed durability decreases.
[0008]
In addition, in the conventional belt structure, if a cord with relatively high elasticity is used only for the belt ply, the performance utilizing the cord characteristics cannot be fully exhibited, and the amount of members to be used must be minimized. It was difficult to achieve a balance with the weight reduction problem. In the first place, since aircraft tires originally have a large number of belts, it is not desirable to increase the number of belts, and since a large centrifugal force is applied when rolling, there is a demand to reduce the mass of the tread portion.
[0009]
Therefore, in order to overcome these problems, it is necessary to adopt a new belt arrangement and structure that can utilize the characteristics of the cord without waste. In consideration of the above facts, the present invention is a pneumatic radial tire belt suitable for an aircraft capable of suppressing radial growth of a tread surface, improving durability against cutting of foreign matters, and at the same time achieving weight reduction. The purpose is to provide an arrangement structure.
[0010]
Furthermore, in heavy-duty pneumatic tires used in aircraft, in order to improve wear resistance and extend the life of the tire, it is possible to improve the tread rigidity, suppress the decrease in the life due to trauma, It is also important to suppress the temperature rise of the tread rubber due to repeated strain. Conventionally, in order to improve the rigidity, for example, treatments such as an increase in the filling amount of carbon black, an increase in the addition amount of resin, and an increase in the amount of a vulcanizing agent such as sulfur or a vulcanization accelerator have been adopted. However, when the carbon black filling amount is increased, the wear resistance is improved, but the low heat generation performance and the anti-destructive property are unavoidable. In addition, increasing the amount of vulcanizing agents such as sulfur and vulcanization accelerators does not change the low heat generation performance and wear resistance, but rather decreases the anti-destructive properties. Increasing the amount of resin added improves the anti-destructive properties. However, there was a problem that the wear resistance and the low heat generation performance were lowered.
[0011]
Therefore, tread rubber for heavy duty pneumatic tires is generally based on isoprene-based rubbers such as natural rubber to achieve both high wear resistance and low heat generation performance, and carbon black / Mixing a silica combined system is performed. However, the rubber component mainly composed of isoprene-based rubber is not preferable because the elastic modulus is lowered due to reversion by overvulcanization, low heat generation performance is easily deteriorated, and wear resistance is also lowered. Invite the situation.
In addition, in order to improve the low heat generation performance of the heavy load tire, a low loss agent (low heat generation imparting agent) represented by 5-nitroso-8-hydroxyquinoline is further added to the above-mentioned composition. Yes. However, these low-loss agents have a vulcanization degree dependency, and there is a problem that due to the generated overvulcanization, the elastic modulus is lowered and the effect of improving the low heat generation performance is not sufficiently exhibited.
[0012]
As a technique for solving the above problems, a rubber composition for a tread comprising a rubber component made of natural rubber or isoprene rubber and a modified styrene-butadiene copolymer rubber obtained by solution polymerization and a hydrazide compound is disclosed. In tires for trucks and buses, it is described that the effect of improving wear resistance, low heat generation performance, and anti-destructive properties was obtained (see, for example, Patent Document 4). However, particularly in heavy-duty radial tires for aircraft, there is a limit to the improvement effect of the rubber composition alone, and there is a strong demand for the development of further high performance materials and belt layer structures that take advantage of the characteristics of the materials. Has been.
[0013]
[Patent Document 1]
JP-A-61-178204
[Patent Document 2]
JP-A-8-58310
[Patent Document 3]
USP 4216813 specification
[Patent Document 4]
JP 2002-146102 A
[0014]
[Problems to be solved by the invention]
  Under such circumstances, the present invention is applied with a rubber composition suitable as a tread rubber which has improved anti-destructive properties and low heat generation performance, and further improved wear resistance, particularly uneven wear resistance.For aircraftAn object is to provide a heavy-duty pneumatic radial tire.
[0015]
[Means for Solving the Problems]
As a result of intensive studies to achieve the above object, the present inventors have obtained a specific modified styrene-butadiene copolymer obtained as a rubber component by solution polymerization and having at least one tin atom in the molecule. The present invention has been completed by finding that rubber and a rubber composition containing natural rubber or synthetic isoprene rubber can meet the purpose. That is, the present invention
[0016]
<1> A pair of bead cores, a carcass layer composed of at least one carcass ply extending in a toroidal shape from one bead core to the other bead core, and an organic layer on the outer circumferential surface of the crown region of the carcass layer in the tire radial direction A pneumatic radial tire comprising: a belt layer comprising at least one belt ply including a fiber cord; and a tread rubber layer constituting a tread surface portion on the outer side in the tire radial direction of the belt layer.,
  The tread rubber layerThe component (A) (a) obtained by solution polymerization has at least one tin atom in the molecule, the bound styrene content in the molecule is 20 to 40% by mass, and 1, Modified styrene-butadiene copolymer rubber having a 2-vinyl bond content of 30 mol% or less and (b) natural rubber and / or synthetic isoprene rubber, or (B) (a), (b) and (c) cis A rubber composition containing -1,4-polybutadiene rubberObtained by applying
  TThe total strength in the tire circumferential direction of the belt layer per unit width at the ear equator plane position P0 is K0, and the unit strength at the width position P2 is 2/3 of the maximum width of the belt layer around the tire equator plane. When the total strength of the belt layer in the tire circumferential direction is K2, K2 <K0 is satisfied.For aircraftHeavy duty pneumatic radial tire.
<2> 100 parts by mass of the rubber component is selected from a range of 10 to 70 parts by mass of the component (a), 20 to 80 parts by mass of the component (b), and 0 to 30 parts by mass of the component (c). The composition according to <1>, wherein the composition is an arbitrary compositionFor aircraftHeavy duty pneumatic radial tire.
<3> The above-mentioned <1> or <2>, wherein the rubber composition is applied to at least a shoulder rib region of the tread rubber layer.For aircraftHeavy duty pneumatic radial tire.
<4> The belt layer satisfies 0.2 ≦ K2 / K0 ≦ 0.8.1 > ~ < 3 > Any one ofDescribed inFor aircraftHeavy duty pneumatic radial tire.
<5> In the belt layer, the laminated thickness of the organic fiber cord is the thickest at the tire equatorial plane position P0, the laminated thickness of the organic fiber cord at the tire equatorial plane position P0 is G0, and the maximum width of the belt layer <2> where G2 <G0 is satisfied when the laminated thickness of the organic fiber cord at the 2/3 width position P2 is G2.1 > ~<4>Any one ofDescribed inFor aircraftHeavy duty pneumatic radial tire.
<6> In the belt layer, 0.35 ≦ G2 / G0 ≦ 0.85 is satisfied,5>For aircraftHeavy duty pneumatic radial tire.
<7> In the belt layer, when the laminated thickness of the organic fiber cord at the width position P2 that is 2/3 of the maximum width of the belt layer is G2, the belt layer includes 2/2 of the maximum width of the belt layer. In the region outside in the tire width direction from the width position P2 of No. 3, a portion having a thickness greater than the thickness G2 is provided.1> ~ <6Any of>OneDescribed inFor aircraftHeavy duty pneumatic radial tire.
<8> The belt layer has a tensile breaking strength of 6.3 cN / dtex or more, an elongation rate of 0.2 to 2.0% in the stretching direction at a load of 0.3 cN / dtex, and a load of 2.1 cN / dtex in the stretching direction. At least two belt plies including an organic fiber cord having an elongation ratio of 1.5 to 7.0% and an elongation ratio of 2.2 to 9.3% when loaded with 3.2 cN / dtex in the stretching direction. A main belt layer composed of: <1> ~ <7Any of>OneDescribed inFor aircraftHeavy duty pneumatic radial tire.
<9> At least two belt plies are laminated at the end in the tire width direction of the main belt layer.8>For aircraftHeavy duty pneumatic radial tire.
<10> The main belt layer is composed of aromatic polyamide fibers, and includes a belt ply including an organic fiber cord having a lower twist coefficient of 0.12 to 0.85 and an upper twist coefficient of 0.40 to 0.80. Characterized by having the above <8> Or <9>For aircraftHeavy duty pneumatic radial tire.
<11The main belt layer includes an aromatic polyamide fiber and an aliphatic polyamide fiber, and a mass ratio of the aromatic polyamide fiber to the aliphatic polyamide fiber is 100: 10 to 170. It has a belt ply containing an organic fiber cord, and the above <8> ~ <10Any of>OneDescribed inFor aircraftHeavy duty pneumatic radial tire.
<12> The main belt layer is an organic fiber in which an aromatic polyamide-based cord and an aliphatic polyamide-based cord are twisted, and a lower twist coefficient of the aromatic polyamide-based cord is 0.12 to 0.85. <1 characterized in that it has a belt ply including a cord1>For aircraftHeavy duty pneumatic radial tire.
<13The main belt layer has a belt ply including an organic fiber cord spirally wound at an angle of approximately 0 ° with respect to the tire equatorial plane.8> ~ <12Any of>OneDescribed inFor aircraftHeavy duty pneumatic radial tire.
<14> The main belt layer is inclined at an angle of 2 to 25 ° with respect to the tire equatorial plane, is bent in the same plane so as to be inclined in the opposite direction at each ply end, and extends in a zigzag shape in the tire circumferential direction. It has a belt ply containing an organic fiber cord, and the above <8> ~ <13Any of>OneDescribed inFor aircraftHeavy duty pneumatic radial tire.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
  (Rubber composition)
  Of the present inventionFor aircraftThe rubber composition applied to the tread rubber layer of the heavy-duty pneumatic radial tire has (a) at least one tin atom in the molecule obtained by solution polymerization, and the bound styrene content in the molecule is 20 to 40 mass. %, And the modified styrene-butadiene copolymer rubber having a 1,2-vinyl bond content of the polybutadiene chain portion of 30 mol% or less and (b) natural rubber and / or synthetic isoprene rubber are contained as rubber components. The rubber composition (A) or the rubber composition (B) containing the rubber component (a), the rubber (b), and the (c) cis-1,4-polybutadiene rubber as rubber components. .
[0018]
The modified styrene-butadiene copolymer rubber (a) is obtained by solution polymerization, and is modified by introducing a tin atom into at least one of the polymerization initiation terminal or polymerization active terminal of the molecular chain, or the molecular chain. SBR rubber. Such a modified styrene-butadiene copolymer rubber can be preferably produced by, for example, the following method. That is,
In the first and second methods, 1,3-butadiene and styrene are used as raw materials, and an alkali metal compound, preferably a lithium compound is used as a polymerization initiator, and solution polymerization (anionic polymerization) is performed, so that the terminal is a polymerization active terminal. A base polymer comprising a styrene-butadiene copolymer is obtained. The base polymer thus obtained can be modified with a tin compound to obtain a desired modified styrene-butadiene copolymer.
[0019]
In the third method, 1,3-butadiene and styrene are used as raw materials, an alkali metal compound having a tin atom, preferably a lithium compound, is used as a polymerization initiator, and solution polymerization (anionic polymerization) is performed, whereby the terminal is a polymerization active terminal. A base polymer comprising a styrene-butadiene copolymer is obtained. Subsequently, the active terminal is modified with a modifying agent such as a tin compound, an alkoxysilane compound, or a nitrogen-containing compound. In this case, the reaction may be stopped without using a modifier.
[0020]
In the fourth method, 1,3-butadiene and styrene are used as raw materials, an alkali metal compound having a tin atom and a nitrogen atom, preferably a lithium compound is used as a polymerization initiator, and a solution polymerization (anionic polymerization) is carried out to form a molecule. A styrene-butadiene copolymer having tin atoms and nitrogen atoms introduced therein is obtained.
The fifth method uses 1,3-butadiene, styrene, and a tin atom-containing compound (monomer) as raw materials, and an alkali metal compound, preferably a lithium compound, as a polymerization initiator, and is subjected to solution polymerization (anionic polymerization), thereby forming a terminal. A base polymer composed of a styrene-butadiene copolymer having a polymerization active terminal is obtained. Subsequently, the active terminal is modified with a modifying agent such as a tin compound, an alkoxysilane compound, or a nitrogen-containing compound. In this case, the reaction may be stopped without using a modifier.
The above methods can be combined as appropriate. In the third to fifth methods, a copolymer into which tin atoms are introduced can be obtained without performing a terminal modification step with a modifier.
[0021]
In the first, second and fifth methods, as the polymerization initiator lithium compound, hydrocarbyl lithium and lithium amide compound are preferably used. When the former hydrocarbyl lithium is used, the polymerization initiation terminal is a hydrocarbyl group. A base polymer of a certain styrene-butadiene copolymer (including a copolymer in which a tin atom is introduced into a monomer unit of styrene or butadiene) is obtained. When the latter lithium amide compound is used, a base of a styrene-butadiene copolymer having a nitrogen-containing group at the polymerization initiation terminal (including a copolymer in which a tin atom is introduced into a styrene or butadiene monomer unit) is used. A polymer is obtained. Here, the base polymer means a copolymer having an active terminal before the reaction is stopped.
[0022]
As said hydrocarbyl lithium, what has a C2-C20 hydrocarbyl group is preferable, for example, ethyl lithium, n-propyl lithium, isopropyl lithium, n-butyl lithium, sec-butyl lithium, t-butyl lithium, tert-octyl Lithium, n-decyl lithium, phenyl lithium, 2-naphthyl lithium, 2-butyl-phenyl lithium, 4-phenyl-butyl lithium, cyclohexyl lithium, cyclopentyl lithium, reaction products of diisopropenylbenzene and butyl lithium, etc. Among these, n-butyl lithium is preferable.
[0023]
On the other hand, as the lithium amide compound, for example, lithium hexamethylene imide, lithium pyrrolidide, lithium piperidide, lithium heptamethylene imide, lithium dodecamethylene imide, lithium dimethylamide, lithium diethylamide, lithium dibutylamide, lithium dipropylamide, Lithium diheptylamide, lithium dihexylamide, lithium dioctylamide, lithium bis-2-ethylhexylamide, lithium didecylamide, lithium-N-methylpiperazide, lithium ethylpropylamide, lithium ethylbutyramide, lithium methylbutyramide, lithium ethylbenzyl Examples include amide and lithium methylphenethyl amide. Among these, cyclic lithium amides such as lithium hexamethylene imide, lithium pyrrolidide, lithium piperidide, lithium heptamethylene imide, and lithium dodecamethylene imide are preferable, and lithium hexamethylene imide and lithium pyrrolidide are particularly preferable.
[0024]
In the third method, as the lithium compound used for the polymerization initiator, triorganotin lithium compounds such as tributyltin lithium and trioctyltin lithium are preferably used. Furthermore, in the fourth method, as the lithium compound having a tin atom and a nitrogen atom used as a polymerization initiator, triorganoamidotin lithium represented by the following general formula (I), or the following general formula (II) ) Is preferably used.
[0025]
[Chemical 1]

[In formula (I), R¹And R²Represents a group selected from aliphatic, alicyclic and aromatic hydrocarbon groups having 1 to 20 carbon atoms, and these groups may be the same or different. ]
[0026]
[Chemical formula 2]

[In formula (II), X is selected from the following structural groups. XI: (CR^ThreeR^Four)_nA saturated cyclic structure group consisting of: X-II: (R^FiveR⁶)_m-Y- (R^FiveR⁶)_l(However, Y is NR⁷, O, or an imine compound having a carbon-carbon double bond. Where R^Three~ R⁶Represents a group selected from hydrogen and an aliphatic hydrocarbon group having 1 to 10 carbon atoms, an alicyclic group having 3 to 10 carbon atoms, and an aromatic hydrocarbon group having 6 to 10 carbon atoms, and R⁷Represents a group selected from an aliphatic hydrocarbon group having 1 to 10 carbon atoms, an alicyclic group having 3 to 10 carbon atoms, and an aromatic hydrocarbon group having 5 to 10 carbon atoms, and these groups may be the same or different. Also good. n represents an integer of 3 to 10, and the sum of m and l is an integer of 2 to 9. ]
[0027]
Among these, preferable triorganamidotin lithium includes, for example, tripyrrolididotin lithium, trihexamethyleneimidotin lithium, tridiethylamidotin lithium, and tri (dipropylamido) tin lithium.
[0028]
In the above, triorganamidotin lithium is described in US Pat. No. 5,502,129, and triorganamidotin lithium and triorganimidotin lithium are described in US Pat. No. 5,463,003. . As the fifth method, the target styrene-butadiene copolymer can also be obtained by introducing a third monomer having a tin atom. Here, as the third monomer copolymerized with styrene or butadiene, a compound represented by the following general formula (III) or (IV) is preferably used.
[0029]
[Chemical 3]

[In formula (III), R⁸~ R^TenRepresents an aliphatic, alicyclic or aromatic hydrocarbon group having 1 to 30 carbon atoms, and the groups may be the same or different. ]
[0030]
[Formula 4]

[In formula (IV), R¹¹(R¹²) C = CR¹³-, R¹⁴~ R¹⁷Is a group bonded to the benzene ring, R¹¹~ R^{twenty two}Represents a hydrogen atom or an aliphatic, alicyclic or aromatic hydrocarbon group having 1 to 30 carbon atoms, and the groups may be the same or different. However, R²⁰~ R^{twenty two}Does not contain a hydrogen atom. ]
[0031]
Specifically, the compound represented by the general formula (III) includes 2-tributylstannyl-1,3-butadiene, 2-trioctylstannyl-1,3-butadiene, 2-tricyclohexylstannyl. -1,3-butadiene, 2-triphenylstannyl-1,3-butadiene, 2-dibutylphenylstannyl-1,3-butadiene, 2-diphenyloctylstannyl-1,3-butadiene, etc. . Examples of the compound represented by the general formula (IV) include m-vinylbenzyltributyltin, m-vinylbenzyltrioctyltin, m-vinylbenzyltriphenyltin, m- (1-phenylvinyl) benzyltributyltin, and these Preferred examples include p-isomers, m-isomers / p-isomers, and the like.
[0032]
As a method for producing a styrene-butadiene copolymer (including a copolymer in which a tin atom is introduced into a monomer unit of styrene or butadiene) by anionic polymerization using the lithium compound as a polymerization initiator, there is no particular limitation. Conventionally known methods can be used. Specifically, styrene and 1,3-butadiene are polymerized with the organolithium compound in an organic solvent inert to the reaction, for example, a hydrocarbon solvent such as an aliphatic, alicyclic or aromatic hydrocarbon compound. If desired, the desired styrene-butadiene copolymer can be obtained by anionic polymerization in the presence of a randomizer used as desired. The temperature in this polymerization reaction is appropriately selected in the range of usually -80 to 150 ° C, preferably -20 to 100 ° C. The polymerization reaction can be carried out under generated pressure, but it is usually desirable to operate at a sufficient pressure to keep the monomer in a substantially liquid phase. Higher pressures can be used if desired, and such pressures can be obtained by any suitable method such as pressurizing the reactor with a gas inert to the polymerization reaction.
[0033]
The styrene-butadiene copolymer before modification having a hydrocarbyl group or a nitrogen-containing group at the polymerization initiation terminal and having polymerization activity at the other terminal (tin in the monomer unit of styrene or butadiene) thus obtained. A desired modified styrene-butadiene copolymer rubber is obtained by reacting a tin compound with the polymerization active terminal (including a copolymer having atoms introduced therein).
Examples of the tin compound include tin tetrachloride, tributyltin chloride, trioctyltin chloride, dioctyltin dichloride, dibutyltin dichloride, and triphenyltin chloride. Even if the reaction is stopped without using a modifier, tin atoms are introduced into the molecule.
[0034]
The solution-polymerized SBR used in the rubber composition of the present invention has at least one tin atom in the molecule, a bound styrene content in the molecule of 20 to 40% by mass, and 1, 2 of polybutadiene chain part. -A modified styrene-butadiene copolymer rubber having a vinyl bond content of 30 mol% or less. If the bound styrene content is less than the above range, the level of braking (skid) performance is insufficient. On the other hand, if the bound styrene content exceeds the above range, the heat generation characteristics deteriorate. On the other hand, if the vinyl bond amount exceeds the above range, the breaking strength and heat generation characteristics are lowered.
[0035]
In the rubber composition of the present invention, natural rubber and / or synthetic isoprene rubber is used as the rubber component (b). The natural rubber may be sheet rubber or block rubber, and all grades of RSS # 1 to # 5 and all grades of TSR can be used. The synthetic isoprene rubber (IR) is obtained by polymerization of an isoprene monomer. Among them, the IR having about 98% cis 1,4-bond has a molecular structure very similar to that of natural rubber. It is preferable because it has basic characteristics close to.
[0036]
In the rubber composition (B) of the present invention, cis-1,4-polybutadiene rubber (BR) is used as the rubber component (c). The polybutadiene rubber (BR) is called a high cis BR rubber, and those having a cis 1,4-bond of 96% or more are preferably used.
[0037]
The composition of 100 parts by mass of the rubber component of the present invention is 10 to 70 parts by mass of the component (a) described above from the viewpoint of enhancing and improving braking performance, fracture physical properties, rolling resistance and the like. What consists of arbitrary compositions chosen from the range of 20-80 mass parts of b) component, and 0-30 mass parts of (c) component is preferable.
[0038]
The rubber composition of the present invention preferably contains carbon black as a reinforcing agent or filler. This carbon black has a nitrogen adsorption specific surface area (N₂SA) is 50m²/ G or more is preferable. This (N₂SA) is 50m²If it is less than / g, it is difficult to obtain sufficient wear resistance. Also, (N₂If SA) is too large, the low heat generation performance may be reduced. More preferable in terms of balance between wear resistance and low heat generation performance (N₂SA) 80-160m²/ G. Where the (N₂SA) is a value measured according to ASTM D3037-88.
[0039]
There is no restriction | limiting in particular as said carbon black, Arbitrary things can be suitably selected and used from what is conventionally used as a reinforcing filler of rubber | gum. Examples of suitable carbon black include FEF, SRF, HAF, ISAF, and SAF. Among these, HAF, ISAF, and SAF carbon, which are excellent in wear resistance, are particularly suitable. In the present invention, the carbon black is preferably blended in the range of 20 to 70 parts by mass with respect to 100 parts by mass of the rubber component (A) or (B). If the blending amount is less than 20 parts by mass, the wear resistance may not be sufficiently exhibited. If the blending amount exceeds 70 parts by mass, the low heat generation performance may be deteriorated or the dispersion may be deteriorated, resulting in deterioration of the wear resistance. Sometimes. In consideration of wear resistance, low heat generation performance, dispersibility, and the like, the blending amount of the carbon black is more preferably in the range of 30 to 60 parts by mass.
[0040]
In the rubber composition of the present invention, silica can be further blended if desired. This silica has a nitrogen adsorption specific surface area (N₂SA) is 160-260m²In the range of 180 g / g and dibutyl phthalate oil absorption (DBP) in the range of 180 to 260 mL / 100 g. This (N₂SA) is 160m²If less than / g or (DBP) is less than 180 mL / 100 g, the wear resistance may be insufficient.₂SA) is 260m²When exceeding / g or (DBP) exceeding 260 mL / 100 g, poor dispersion may be caused, resulting in a decrease in low heat generation performance and wear resistance. Here, the above (N₂SA) is a value measured according to ASTM D4820-93 after drying at 300 ° C. for 1 hour, and (DBP) is a value measured according to ASTM D2414-93.
[0041]
Examples of the silica include wet silica (hydrous silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, and the like. Among these, wet silica is particularly preferable. In this invention, it is preferable that this silica is mix | blended in 30 mass parts or less with respect to 100 mass parts of said rubber components of (A) or (A). When this compounding quantity exceeds 30 mass parts, there exists a possibility that the low heat generation performance may fall. A more preferable amount of silica is in the range of 20 parts by mass or less.
[0042]
The rubber composition of the present invention comprises a rubber component that is the component (A) or (B), preferably carbon black and silica, as well as a vulcanizing agent and a vulcanization accelerator that are commonly used in normal industrial rubber compounding. , Vulcanization aids, anti-aging agents, process oils, softeners, and other rubber compounding agents can be appropriately contained. The heavy-duty pneumatic radial tire of the present invention can be produced by using such a rubber composition as a tread rubber and vulcanizing and molding it under normal vulcanization conditions. In addition, an inert gas such as air or nitrogen is used as the gas filled in the tire of the present invention.
[0043]
  (For aircraft(Radial tires for heavy loads)
  The rubber composition described above is applied to a tread rubber of a tire.For aircraftThe heavy duty pneumatic radial tire will be described in detail below.
  As a result of detailed examination of the tension load of the belt layer by the present inventors, as shown in the graph of FIG. 3, the distribution is like a one-dot chain line in a no-load state at 100% internal pressure (TRA specified internal pressure). It was. In FIG. 3, the vertical axis represents the tension, the horizontal axis represents the position in the belt width direction, and SBW represents the maximum width of the belt layer.
  By the way, in the case of aircraft tires, a pressure resistance of 400% of the specified internal pressure is required in a no-load state. As a result of examining the tension distribution at the time of filling with 400% internal pressure, it was found that a solid line was obtained. On the other hand, it was found that the tension distribution of the belt layer becomes like a two-dot chain line in a load application state. From this, it can be seen that the belt layer is required to have strength satisfying both conditions.
  From various experiments and investigations, the inventors have determined that the strength of the equator plane is greater than the strength at the position 2/3 of the maximum width of the belt layer with respect to the tension under no load, thereby suppressing the radial growth. It has been found that a balance between weight loss can be achieved.
  Claim1The invention described in the above is made in view of the above-described fact, and includes a pair of bead cores, a carcass layer including at least one carcass ply extending in a toroidal shape from one bead core to the other bead core, and the carcass A belt layer composed of at least one belt ply containing an organic fiber cord on the outer peripheral surface of the crown region on the outer side in the tire radial direction of the layer, and a tread rubber layer constituting a tread surface part on the outer side in the tire radial direction of the belt layer; The total radial strength of the belt layer per unit width at the tire equatorial plane position P0 is K0, and the maximum width of the belt layer around the tire equatorial plane is 2 / When the total strength in the tire circumferential direction of the belt layer per unit width at the width position P2 of 3 is defined as K2, K2 <K0 is satisfied. It is characterized in that.
  Next, the claim1The operation of the pneumatic radial tire described in 1 will be described.
  Claim1In the pneumatic radial tire described in the above, the total strength K0 of the belt layer in the tire circumferential direction per unit width at the tire equatorial plane position P0 is 2/3 of the maximum width of the belt layer centered on the tire equatorial plane. Since the belt layer is set to be larger than the total strength in the tire circumferential direction per unit width at P2, the amount of the tread rubber in the central region of the tread is reduced at the time of filling with standard internal pressure and at high speed rotation while suppressing the material usage of the belt layer. The amount of circumferential expansion can be suppressed, and the tire diameter growth can be suppressed. Suppressing the amount of stretch in the circumferential direction of the tread rubber reduces the degree of rubber tension, increasing the resistance to entry of foreign matter, and even if foreign matter is stuck, crack growth Can be suppressed.
  Claims1In the pneumatic radial tire described above, the rubber composition of the present invention described above may be applied to the entire tread rubber layer disposed on the outer side in the tire radial direction of the belt layer, and at least applied to the shoulder rib region. Also good.
[0044]
(Definition of total strength) The total strength here refers to the strength in the circumferential direction of the belt layer, calculated by multiplying the strength of one cord by the number per unit width (here 10 mm). is there. The total strength when the cord is inclined at an angle θ with respect to the circumferential direction is calculated by multiplying the total strength per unit width by cos θ. In addition, when the cord in the tire extends in a wavy shape (zigzag shape) in the tire circumferential direction, it is not stretched straight and the strength is calculated, but the shape embedded in the tire, that is, in a wavy shape. Calculates the strength when the object is stretched in the circumferential direction.
[0045]
  Claim4The invention described in claim1The pneumatic radial tire described in 1 is characterized by satisfying 0.2 ≦ K2 / K0 ≦ 0.8.
  Next, the operation of the pneumatic radial tire according to claim 5 will be described.
  If the strength ratio (K2 / K0) is less than 0.2, there is a risk that pressure resistance is lowered due to excessive tension being applied to the organic fiber cord located near the shoulder portion. On the other hand, when the strength ratio (K2 / K0) exceeds 0.8, the organic fiber cord of the belt ply disposed at 2/3 points is not effectively used, leading to an increase in the mass of the pneumatic radial tire. Therefore, the strength ratio (K2 / K0) preferably satisfies 0.2 ≦ K2 / K0 ≦ 0.8.
[0046]
  Claim5The invention described in claim1Or claims4In the pneumatic radial tire according to claim 1, in the belt layer, the laminated thickness of the organic fiber cord is the thickest at the tire equatorial plane position P0, and the laminated thickness of the organic fiber cord at the tire equatorial plane position P0 is G0. When the laminated thickness of the organic fiber cord at the width position P2 that is 2/3 of the maximum width of the belt layer is G2, G2 <G0 is satisfied.
  Next, the claim5The operation of the pneumatic radial tire described in 1 will be described.
  By setting the laminated thickness G2 of the organic fiber cord at the width position P2 of 2/3 of the maximum width of the belt layer to be larger than the laminated thickness G0 of the organic fiber cord at the tire equatorial plane position P0, K2 <K0 Can be easily achieved. In addition, the lamination | stacking thickness of an organic fiber cord is a total diameter dimension of the organic fiber cord laminated | stacked on the tire radial direction when a belt layer is seen in a tire radial direction cross section. For example, when twelve organic fiber cords having a diameter A are laminated, the lamination thickness is A × 12.
[0047]
  Claim6The invention described in claim5The pneumatic radial tire described in 1 is characterized by satisfying 0.35 ≦ G2 / G0 ≦ 0.85.
  Next, the claim6The operation of the pneumatic radial tire described in 1 will be described.
  When the ratio G2 / G0 of the laminated thickness of the organic fiber cords is less than 0.35, there is a possibility that pressure resistance performance is lowered due to excessive tension being applied to the organic fiber cords located near the shoulder portion. On the other hand, if the ratio G2 / G0 of the laminated thickness of the organic fiber cord exceeds 0.85, the organic fiber cord of the belt ply disposed at 2/3 points is not effectively used, leading to an increase in the mass of the pneumatic radial tire. . Therefore, it is preferable that the ratio G2 / G0 of the laminated thickness of the organic fiber cords satisfies 0.35 ≦ G2 / G0 ≦ 0.85.
[0048]
  Claim7The invention described in claim1~ Claim6In the pneumatic radial tire according to any one of the above, when the laminated thickness of the organic fiber cord is G2 in the belt layer at the width position P2 that is 2/3 of the maximum width of the belt layer, the belt The layer is characterized in that a portion having a thickness greater than the thickness G2 is provided in a region outside the width position P2 that is 2/3 of the maximum width of the belt layer in the tire width direction. .
  Next, the claim7The operation of the pneumatic radial tire described in 1 will be described.
  In the region outside the width direction P2 that is 2/3 of the maximum width of the belt layer in the tire width direction, if a portion thicker than the stack thickness G2 is provided, the belt layer is exposed to an external force, particularly in the tire width direction. In such a case, it is possible to flexibly absorb large tension fluctuations on both sides of the tire, and it is possible to effectively suppress the occurrence of a standing wave that can significantly reduce the life of the pneumatic radial tire.
[0049]
  Claim8The invention described in claim1~ Claim7In the pneumatic radial tire according to any one of the above, the belt layer has a tensile breaking strength of 6.3 cN / dtex or more, and an elongation rate at a load of 0.3 cN / dtex in the extension direction is 0.2 to 2. 0%, the elongation at 2.1cN / dtex load in the stretching direction is 1.5 to 7.0%, and the elongation at 3.2cN / dtex load in the stretching direction is 2.2 to 9.3%. The main belt layer is composed of at least two belt plies including organic fiber cords.
  Next, the claim8The operation of the pneumatic radial tire described in 1 will be described.
  By specifying the strength distribution of the belt layer as in the present invention, it is possible to achieve both suppression of diameter growth and mass reduction, but using a low-elasticity cord such as nylon can reduce the growth of the diameter in multiple layers. Need to lead to increased tire mass.
[0050]
  Claim8In the pneumatic radial tire described in the above, it is necessary to configure the main belt layer with at least two belt plies including a highly elastic organic fiber cord having a tensile breaking strength of 6.3 cN / dtex or more. It can satisfy the pressure resistance performance. Here, the elongation at the time of 2.1 cN / dtex load in the stretching direction of the organic fiber cord is 1.5 to 7.0%, and the elongation at the load of 3.2 cN / dtex in the stretching direction is 2.2 to 9.9. By setting the ratio to 3%, it was possible to easily achieve the target diameter growth suppression.
  The reason for this is that in a pneumatic radial tire for an aircraft, a cord tension of about 2.1 cN / dtex is applied when an internal pressure is loaded in a standard state, and a cord tension of about 3.2 cN / dtex is applied during high-speed driving. This is because, when the elongation percentage of the tire exceeds the above range, bulging in the tire radial direction cannot be effectively suppressed during filling of the tire internal pressure, and the performance against the penetration of foreign matter cannot be expected.
  On the other hand, when the elongation percentage of the organic fiber cord is less than the above range, the hoop effect of the belt ply is too large, and the carcass ply bulges more than necessary in the tire width direction, which is not preferable.
  Furthermore, the reason why the elongation at the time of 0.3 cN / dtex load is 0.2 to 2.0% in the stretching direction of the organic fiber cord is as described below. First, when vulcanizing a pneumatic radial tire, in the case of an aircraft pneumatic radial tire, the outer diameter of the tire is usually set so that the raw tire expands by 0.2 to 2.0% in the tire mold. The This is for correcting the variation of the cord driving by aligning the direction of the cord by uniformly stretching the tire by the pressure applied from the inside of the green tire during vulcanization. In this process, a relatively small tension of about 0.3 cN / dtex acts on the organic fiber cord. If the elongation rate of the organic fiber cord at this time is greater than 2.0%, the effect of correcting the cord properties If the elongation is less than 0.2%, the cord tension becomes large during expansion during vulcanization, and the organic fiber cord bites into the rubber inside the tire in the radial direction. .
[0051]
(Definition at the time of internal pressure load in the standard state) The internal pressure and load defined in TRA YEARBOOK (2002 edition) are adopted here. For example, in the case of a radial tire for aircraft 1270 × 455R22 32PR, the specified internal pressure is 1620 kPa and the specified load is 24860 kg.
The organic fiber cord has an elongation rate of 0.2 to 1.5% when loaded with 0.3 cN / dtex in the stretching direction and an elongation rate of 1.5 to 6.5 when loaded with 2.1 cN / dtex in the stretching direction. More preferably, the elongation is 5% and the elongation at the time of 3.2 cN / dtex in the stretching direction is 2.2 to 8.3%.
[0052]
  Claim9The invention described in claim8The pneumatic radial tire described in 1 is characterized in that at least two layers of the belt ply are laminated at the tire width direction end of the main belt layer.
  Next, the claim9The operation of the pneumatic radial tire described in 1 will be described.
  By laminating two or more belt plies at the tire width direction end of the main belt layer, when the tire is running, especially when an external force is applied in the tire width direction, the vicinity of both ends in the width direction of the tire ground contact surface Even under conditions with severe tension fluctuations in organic fiber cords, it is possible to effectively disperse impact with its elasticity, which is effective in improving tire reliability under severe use conditions. .
[0053]
  Claim 10The invention described in claim8Or claim9In the pneumatic radial tire according to claim 1, the main belt layer is made of an aromatic polyamide fiber, and has a lower twist coefficient of 0.12 to 0.85 and an upper twist coefficient of 0.40 to 0.80. And a belt ply including an organic fiber cord.
  Next, claim 10The operation of the pneumatic radial tire described in 1 will be described.
  The organic fiber cord constituting the main belt layer is composed of an aromatic polyamide fiber, the lower twist coefficient is 0.12 to 0.85, preferably 0.17 to 0.51, and the upper twist coefficient is 0.40. By setting the organic fiber cord to 0.80, the physical properties of the organic fiber cord as defined in claim 6, that is, the tensile breaking strength is 6.3 cN / dtex or more, and the elongation rate at the time of 0.3 cN / dtex load in the stretching direction is 0.2. ~ 2.0%, elongation at 2.1 cN / dtex load in the stretching direction is 1.5 to 7.0%, and elongation at 3.2 cN / dtex load in the stretching direction is 2.2 to 9.3. % Can be set.
[0054]
(Definition of twist coefficient) The twist coefficient referred to here is calculated from the following equation.
NT = N × (0.139 × D / ρ)^1/2× 10^-3
N: Number of twists per 100 mm of organic fiber cord
D: Total display decitex (dtex)
ρ: Specific gravity of organic fiber cord (g / cm^Three)
[0055]
  Claim 11The invention described in claim8-Claim 10The pneumatic radial tire according to any one of the above, wherein the main belt layer includes an aromatic polyamide fiber and an aliphatic polyamide fiber, and the aromatic polyamide fiber and the aliphatic polyamide fiber. And a belt ply including an organic fiber cord having a mass ratio of 100: 10 to 170.
  Next, claim 11The operation of the pneumatic radial tire described in 1 will be described.
  The organic fiber cord constituting the main belt layer is composed of an aromatic polyamide fiber and an aliphatic polyamide fiber, and the mass ratio of the aromatic polyamide fiber and the aliphatic polyamide fiber is 100: 10. ˜170 to claim the organic fiber cord8The tensile physical strength is 6.3 cN / dtex or more, the elongation at the time of 0.3 cN / dtex is 0.2 to 2.0% in the stretching direction, and the load is 2.1 cN / dtex in the stretching direction. The elongation at the time can be set to 1.5 to 7.0%, and the elongation at the time of 3.2 cN / dtex in the stretching direction can be set to 2.2 to 9.3%.
  Here, when the mass of the aliphatic polyamide fiber is less than 10 with respect to 100 mass of the aromatic polyamide fiber, the cord elongation becomes small when the load is applied.8It is difficult to achieve specified physical properties. On the other hand, if the mass of the aliphatic polyamide fiber exceeds 170 with respect to 100 mass of the aromatic polyamide fiber, the cord elongation increases when the load is applied, so that the physical properties specified in claim 9 are obtained. It becomes difficult to achieve.
[0056]
The mass ratio of the aromatic polyamide fiber and the aliphatic polyamide fiber is more preferably 100: 17 to 86. Here, the aliphatic polyamide fibers include, for example, 6-nylon, 6,6-nylon, 4,6-nylon fiber, and the like. Here, the organic fiber cord only needs to be composed of an aromatic polyamide fiber and an aliphatic polyamide fiber, and the aromatic polyamide organic fiber cord and the aliphatic polyamide organic fiber cord are twisted together. Alternatively, twisting may be performed after combining the aromatic polyamide fiber and the aliphatic polyamide fiber.
In addition, when the aromatic polyamide organic fiber cord is A and the aliphatic polyamide organic fiber cord is B, A or B is twisted (Z twist) and then aligned and twisted in the direction opposite to the twist ( An organic fiber cord constituting the main belt layer can be obtained by applying (S twist). In addition, at the time of under twisting, A or B may be twisted individually, or after A and B may be twisted together. The number of A, B or AB (combined yarn) at the time of the lower twist or the upper twist may be one by one or plural. The thickness of the A or B raw yarn may be the same or different. The form of the mixed twisted yarn may be one in which a loop is formed around the core yarn.
[0057]
  Claim 12The invention described in claim 11In the pneumatic radial tire according to claim 1, in the main belt layer, an aromatic polyamide cord and an aliphatic polyamide cord are twisted together, and a lower twist coefficient of the aromatic polyamide cord is 0.12 to 0.12. It has a belt ply including an organic fiber cord set to 0.85.
  Next, claim 12The operation of the pneumatic radial tire described in 1 will be described.
  By setting the twisting coefficient of the aromatic polyamide cord to 0.12 to 0.85,8It is easy to achieve specified physical properties. In addition, it is more preferable that the lower twist coefficient of the aromatic polyamide cord is 0.17 to 0.51.
[0058]
  Claim 13The invention described in claim8-Claim 12The pneumatic radial tire according to any one of the above, wherein the main belt layer has a belt ply including an organic fiber cord spirally wound at an angle of approximately 0 ° with respect to the tire equatorial plane. It is characterized by.
  Next, claim 13The operation of the pneumatic radial tire described in 1 will be described.
  By setting the angle of the organic fiber cord to the tire equatorial plane to be approximately 0 °, the strength of the organic fiber cord used to secure the circumferential rigidity of the main belt layer can be utilized to the maximum, It is possible to reduce the weight of the incoming radial tire. Here, the term “substantially 0 °” includes 2.0 ° or less.
[0059]
  Claim 14The invention described in claim8-Claim 13The pneumatic radial tire according to any one of claims 1 to 3, wherein the main belt layer is inclined at an angle of 2 to 25 ° with respect to the tire equatorial plane and is inclined in the opposite direction at each ply end. And a belt ply including an organic fiber cord bent in a zigzag shape in the tire circumferential direction.
  Next, claim 14The operation of the pneumatic radial tire described in 1 will be described.
  Belt ply including an organic fiber cord that is inclined at an angle of 2 to 25 ° with respect to the tire equatorial plane and is bent in the same plane so as to be inclined in the opposite direction at each ply end and extends in a zigzag shape in the tire circumferential direction By using, the rigidity in the tire width direction can be ensured without greatly reducing the circumferential rigidity of the main belt layer, and as a result, excellent wear resistance can be realized.
[0060]
The reason why excellent wear resistance is achieved by ensuring the rigidity in the tire width direction is as follows. In general, if the diameter difference between the crown center portion and the shoulder portion is large in the tire shape at the time of internal pressure filling, there is a high possibility that so-called “drag wear” will occur. The center portion and the shoulder portion that are grounded during the rotation of the tire rotate by the length of the ground contact length, but the tire rotation angle corresponding to a certain circumferential length is larger in the shoulder portion having a smaller diameter. For this reason, before leaving the road surface, the shoulder portion is constrained rearward in the rotational direction, and the center portion and the shoulder portion are shear-deformed in the tread contact surface. A phenomenon in which the shoulder portion slides relative to the road surface in order to correct this deformation is “drag wear”.
The magnitude of the displacement in the circumferential direction depends on the diameter difference between the center portion and the shoulder portion and the circumferential shear rigidity in the tread surface. The greater the diameter difference and the smaller the shear rigidity, the greater the degree of drag wear. Become. In the spiral belt, since the cord is oriented substantially in the circumferential direction, the shear rigidity is small, and the drag wear is not effective. In order to compensate for this, by adding a belt having a cord having a large angle with respect to the tire circumferential direction, rigidity in the tire width direction can be secured, and wear characteristics can be improved. Here, when the angle of the organic fiber cord with respect to the tire equatorial plane is less than 2 °, it becomes difficult to wind the belt geometrically in a zigzag shape (that is, a spiral shape). On the other hand, when the angle of the organic fiber cord to the tire equatorial plane exceeds 25 °, the tension that the organic fiber cord can exert in the tire circumferential direction is relatively reduced, and the efficiency of bearing the internal pressure of the pneumatic radial tire is deteriorated. .
[0061]
(One embodiment)
Hereinafter, one embodiment of a pneumatic radial tire for aircraft according to the present invention will be described with reference to FIG.
As shown in FIG. 1, a pneumatic radial tire 101 (tire size: 1270 × 455R22 32PR) for an aircraft according to the present embodiment includes a bead core 14 having a round cross section in a bead portion 12 and is covered with rubber. A carcass layer 16 composed of six carcass plies in which organic fiber cords are arranged in the radial direction is anchored to the bead core 14.
The outer circumferential surface of the carcass layer 16 in the tire radial direction is provided with a belt layer 20 and a tread rubber layer (31, 32, 33) constituting a tread portion on the outer side in the tire radial direction of the belt layer 20. . A side rubber layer 27 constituting the sidewall portion 25 is provided on the outer side in the tire width direction of the carcass layer. In the present embodiment, the belt layer 20 includes a main belt layer 26 on the inner side in the tire radial direction, a sub belt layer 28 provided on the outer side in the tire radial direction of the main belt layer 26, and an outer side in the tire radial direction of the sub belt layer 28. And a protective belt layer 22 provided on the belt.
Here, although the rubber composition of the present invention described above is applied to the tread rubber layer, it may be used for the entire tread rubber (shown by 31, 32, 33 in FIG. 1), or a part of the tread rubber. (For example, any one of 31, 32, and 33 in FIG. 1) may be used. In particular, in order to improve uneven wear resistance, it is preferably applied to at least a shoulder region (shown by 33 in FIG. 1) of the tread rubber layer.
[0062]
The main belt layer 26 is composed of a plurality of belt plies, in this embodiment, eight belt plies. These plies constituting the main belt layer 26 are formed by rubber coating a plurality of organic fiber cords. These organic fiber cords preferably have a tensile breaking strength of 6.3 cN / dtex or more, an elongation rate of 0.2 to 2.0% at a load of 0.3 cN / dtex in the stretching direction, and 2 in the stretching direction. It is preferable that the elongation rate at a load of 1 cN / dtex is 1.5 to 7.0%, and the elongation rate at a load of 3.2 cN / dtex in the stretching direction is 2.2 to 9.3%.
The organic fiber cord of this embodiment is composed of aromatic polyamide fibers. When the organic fiber cord is composed of an aromatic polyamide fiber, the lower twist coefficient is set to 0.12 to 0.85, preferably 0.17 to 0.51, and the upper twist coefficient is set to 0.40 to 0.80. It is preferable to do. In the present embodiment, an organic fiber cord made of an aromatic polyamide fiber, specifically, a polyamide fiber manufactured by DuPont (product type name: KEVLAR® 29, nominal fineness of 3000 denier, hereinafter referred to as Kevlar as appropriate). Is used. In the present embodiment, the inclination angle of the organic fiber cord is approximately 0 ° with respect to the tire equatorial plane CL. In the belt ply, the number of organic fiber cords to be driven is preferably in the range of 4 to 10/10 mm. In the present embodiment, in the belt ply 26, the number of driving organic fiber cords is 6.3 / 10 mm.
[0063]
When the sub belt layer 28 is provided as in the present embodiment, the range is preferably provided within a range from the tire equatorial plane CL to a position of 140% of the width BW of the main belt layer 26. In the present embodiment, the width SBW of the sub belt layer 28 is 103% of the width BW of the main belt layer 26. The sub belt layer 28 is composed of one belt ply in this embodiment. The belt ply of the present embodiment prepares a strip-like elongated body constituted by coating one or a plurality of organic fiber cords with rubber, and reciprocates between the ends of both plies only once every round of the elongated body. In this way, the tire is tilted at an angle of 2 to 25 ° with respect to the tire equatorial plane and wound in the circumferential direction, and such winding is shifted by approximately the width of the elongated body in the circumferential direction so that no gap is generated between the elongated bodies. It is formed by winding many times (hereinafter, referred to as an endless zigzag winding belt as appropriate). As a result, in the belt ply, the organic fiber cord extending in the circumferential direction while being zigzag by changing the bending direction at both ply ends is embedded substantially uniformly in the entire region of the belt ply.
[0064]
In this belt ply, an organic fiber cord having an elastic modulus equal to or smaller than that of the organic fiber cord included in the main belt layer 26 (elongation to the organic fiber cord of the main belt layer 26 at a load of 2.1 cN / dtex). It is preferable to use an organic fiber cord whose rate is substantially equal or higher. The organic fiber cord used for the belt ply constituting the sub belt layer 28 includes a cord made of an aliphatic polyamide fiber such as nylon, an aromatic polyamide fiber such as aramid, and an aliphatic polyamide fiber such as nylon. In this embodiment, a nylon cord (twisting number: 1260 D // 2/3, driving number: 7.3 / 10 mm) is used. Further, in the belt ply of the present embodiment which is an endless zigzag wound belt, the inclination angle of the organic fiber cord is preferably within a range of 2 to 45 ° with respect to the tire equatorial plane CL, and is set to 8 ° in the present embodiment. ing.
[0065]
【Example】
EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. Here, the rubber compounding agents such as carbon black, wax, anti-aging agent, and vulcanization accelerator used in the examples are examples, and other arbitrary compounding agents may be used depending on the purpose. Can do. In this example, “parts” and “%” all represent “parts by mass” and “% by mass”.
[0066]
[Examples 1-3 and Comparative Examples 1-3]
After the rubber compositions of Examples 1 to 3 and Comparative Examples 1 to 3 were prepared according to the formulation shown in Table 1 below and kneaded using a 250 mL lab plast mill (manufactured by Toyo Seiki Seisakusho). A sheet of each rubber composition was prepared with a 3-inch roll. Next, at a temperature of 150 ° C., the time until the torque increase due to the vulcanization reaction reaches 90% of the maximum value (t₉₀) Was vulcanized for 1.5 times the vulcanization time to obtain the following test samples for measuring physical properties.
[0067]
[Table 1]

[0068]
The SBR rubber described in Table 1 has the following specifications.
E-SBR: Emulsion polymerization SBR “# 1500” manufactured by JSR Corporation
S-SBR (1): Solution polymerization SBR “HX765” manufactured by FSPC (Firestone Chemical) (styrene content: 25%, vinyl bond content: 28 mol%)
-S-SBR (2) .... Solution polymerization SBR manufactured by JSR Corporation (styrene content: 35%, vinyl bond content: 23 mol%)
Moreover, the used anti-aging agent and vulcanization accelerator are as follows.
・ 6PPD ............ N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine
・ TBBS: Nt-butyl-2-benzothiazolylsulfenamide
[0069]
Each vulcanized rubber sample obtained above was subjected to an evaluation test as follows, and the results were entered in Table 3 below.
(1) Heat generation characteristics
Loss tangent (tan δ) at a temperature of 50 ° C., a measurement frequency of 15 Hz, and a dynamic shear strain of 1% was measured using a dynamic viscoelasticity measurement tester “ARES” manufactured by Rheometrics (USA). The reciprocal of this tan δ value was expressed as an index with the value of Comparative Example 1 as 100. A larger value of this index means lower heat generation.
[0070]
(2) Lambourne wear test
In accordance with JIS K 6264, the amount of wear was measured under the conditions of a temperature of 30 ° C. and a slip rate of 60% using a Lambone abrasion tester manufactured by Iwamoto Seisakusho Co., Ltd. The reciprocal of the amount of wear was expressed as an index with the value of Comparative Example 1 as 100. A larger index value means better wear resistance.
[0071]
(3) Uneven wear test
[Examples 1-4 and Comparative Examples 1-3]
The rubber composition of each compounding shown in Examples 1 to 3 and Comparative Examples 1 to 3 in Table 1 above is the entire tread portion of the pneumatic radial tire for aircraft (size: APR 1270 × 455R22 32PR) shown in FIG. 1, 31, 32, and 33), and a test tire was manufactured according to a normal aircraft radial tire manufacturing process. In the test tire of Example 4, the rubber composition of Example 2 was applied only to the shoulder rib (shown by 33 in FIG. 1) of the tread portion, and the other parts (shown by 31 and 32 in FIG. 1). .) Was produced in the same manner as above except that the rubber composition of Comparative Example 1 was applied.
[0072]
For each test tire thus obtained, 46 × 17R20 / 30 was used for the rim and the internal pressure was 12.7 kg / cm.²The rim assembly assembled in (1) was simulated for taxi on the drum with the safety walk attached. This Taxi simulation running is performed by repeating the test conditions A to C shown in Table 2 below at intervals of 60 minutes with A → B → C as one cycle. The time when the breaker cord of the shoulder rib of the test tire was exposed was regarded as the end of the test, and the number of repeated cycles up to that time was measured. The values entered in Table 3 are values obtained by indexing each value with the test cycle number of the test tire of Comparative Example 1 being 100, and the larger the value, the better the uneven wear resistance. Means.
[0073]
[Table 2]

[0074]
[Table 3]

[0075]
As is clear from the results in Table 3 above, the rubber compositions for treads of the present invention (Examples 1 to 3) are superior in low heat buildup and wear resistance as compared with the comparative examples. found. In addition, the radial tires for aircraft of the present invention (Examples 1 to 4) in which these rubber compositions are applied to the tread are superior in uneven wear resistance in simulated taxi running compared to the tires of the comparative examples. Has been demonstrated.
[0076]
【The invention's effect】
By applying the rubber composition and the tire structure of the present invention, a pneumatic radial for heavy loads in which the wear resistance, in particular the uneven wear resistance, the anti-destructive property and the low heat build-up is achieved at a high level in a balanced manner. It has become possible to provide tires, in particular radial aircraft tires.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an aircraft pneumatic radial tire (101) of the present invention according to a first embodiment.
FIG. 2 is a cross-sectional view of a pneumatic radial tire (102) according to a conventional example.
FIG. 3 is a graph showing tension applied to a belt layer.

Claims (14)

A pair of bead cores, a carcass layer composed of at least one carcass ply extending in a toroidal shape from one bead core to the other bead core, and an organic fiber cord on the outer circumferential surface of the crown region of the carcass layer in the tire radial direction A pneumatic radial tire comprising: a belt layer including at least one belt ply including a tread rubber layer constituting a tread portion on the outer side in the tire radial direction of the belt layer ;
The tread rubber layer as rubber component, at least one tin atom in the obtained molecule by (A) (a) a solution polymerization, a bound styrene content in the molecule is 20 to 40 wt%, And a modified styrene-butadiene copolymer rubber having a polybutadiene chain portion with a 1,2-vinyl bond content of 30 mol% or less and (b) natural rubber and / or synthetic isoprene rubber, or (B) (a) and ( obtained by applying a rubber composition containing b) and (c) cis-1,4-polybutadiene rubber ,
Other tire equatorial plane position the belt layer in a unit width per at P0 tire circumferential direction of the total strength K0, unit width per a width position P2 2/3 of the maximum width of the belt layer around the tire equatorial plane A heavy-duty pneumatic radial tire for aircraft , wherein K2 <K0 is satisfied when the total strength in the tire circumferential direction of the belt layer is K2. 100 parts by weight of the rubber component is selected from an arbitrary composition selected from the range of 10 to 70 parts by weight of the component (a), 20 to 80 parts by weight of the component (b), and 0 to 30 parts by weight of the component (c). The heavy-duty pneumatic radial tire for aircraft according to claim 1, wherein The heavy-duty pneumatic radial tire for aircraft according to claim 1 or 2, wherein the rubber composition is applied to at least a shoulder rib region of a tread rubber layer. The heavy-duty pneumatic radial tire for an aircraft according to any one of claims 1 to 3, wherein the belt layer satisfies 0.2≤K2 / K0≤0.8. In the belt layer, the laminated thickness of the organic fiber cord is the thickest at the tire equatorial plane position P0, the laminated thickness of the organic fiber cord at the tire equatorial plane position P0 is G0, and the maximum width of the belt layer is 2 The aircraft heavy load according to any one of claims 1 to 4 , wherein G2 <G0 is satisfied, where G2 is a laminated thickness of the organic fiber cord at a width position P2 of ／. Heavy duty pneumatic radial tire. 6. The heavy radial pneumatic tire for aircraft according to claim 5 , wherein the belt layer satisfies 0.35 ≦ G2 / G0 ≦ 0.85. In the belt layer, when the lamination thickness of the organic fiber cord at the width position P2 that is 2/3 of the maximum width of the belt layer is G2, the belt layer includes 2/3 of the maximum width of the belt layer. in the region of the tire width direction outside than the width position P2 of the aircraft according to any one of claims 1 to 6, wherein the laminated layer thickness thick portion of the laminated layer thickness than G2 is provided, it is characterized by Pneumatic radial tire for heavy loads. The belt layer has a tensile breaking strength of 6.3 cN / dtex or more, an elongation rate of 0.2 to 2.0% in a stretching direction at a load of 0.3 cN / dtex, and a load of 2.1 cN / dtex in a stretching direction. At least two belt plies including an organic fiber cord having an elongation of 1.5 to 7.0% and an elongation of 2.2 to 9.3% when loaded with a load of 3.2 cN / dtex in the stretching direction. having configured the main belt layer, aircraft heavy duty pneumatic radial tire according to claim 1, characterized in that. The heavy-duty pneumatic radial tire for aircraft according to claim 8 , wherein at least two layers of the belt ply are laminated at an end of the main belt layer in the tire width direction. The main belt layer is made of an aromatic polyamide fiber, and includes a belt ply including an organic fiber cord having a lower twist coefficient of 0.12 to 0.85 and an upper twist coefficient of 0.40 to 0.80. The heavy-duty pneumatic radial tire for an aircraft according to claim 8 or 9 , characterized by comprising: The main belt layer includes an aromatic polyamide-based fiber and an aliphatic polyamide-based fiber, and an organic material in which the mass ratio of the aromatic polyamide-based fiber to the aliphatic polyamide-based fiber is 100: 10 to 170. having a belt ply including a fiber cord, aircraft heavy duty pneumatic radial tire according to any one of claims 8 to 10, characterized in that. The main belt layer is an organic fiber cord in which an aromatic polyamide-based cord and an aliphatic polyamide-based cord are twisted, and a lower twist coefficient of the aromatic polyamide-based cord is 0.12 to 0.85. The heavy-duty pneumatic radial tire for aircraft according to claim 11 , further comprising a belt ply including Said main belt layer is any one of claims 8 to 12 having a belt ply including an organic fiber cord wound helically at an angle of approximately 0 ° to the tire equatorial plane, characterized in that Heavy duty pneumatic radial tire for aircraft described in 1. The main belt layer is inclined at an angle of 2 to 25 ° with respect to the tire equatorial plane, is bent in the same plane so as to be inclined in the opposite direction at each ply end, and extends in a zigzag manner in the tire circumferential direction. having a belt ply including a fiber cord, aircraft heavy duty pneumatic radial tire according to any one of claims 8 to 13, characterized in that.

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