JP2004306635A - Pneumatic radial tire for aircraft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial tire for an aircraft capable of improving durability against a cut of a foreign matter, etc. by suppressing the radial growth of a tread surface and attaining the reduction of weight. <P>SOLUTION: As organic fiber cords making a carcass ply and/or a belt layer of this tire, polyketone fiber cords made of repeating units shown in a formula (I) are used. The A in the formula (I) may be the same or different in each of the repeating units in a part derived from an ethylenically unsaturated compound polymerized by ethylenic bonding. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

（式中の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、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なるポリケトン繊維のコードであることを特徴とする。
【０００６】
ベルト層に用いるポリケトン繊維のコードは、５．０ｃＮ／ｄｔｅｘ以上の引張破断強度と、伸長方向に０．３ｃＮ／ｄｔｅｘ荷重時の伸び率が０．２−２．０％、伸長方向に２．１ｃＮ／ｄｔｅｘ荷重時の伸び率が１．５−７．０％、伸長方向に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。この場合、該ベルト層に用いるポリケトン繊維のコードは、０．１２−０．８５の下撚り係数と、０．３５−０．７５の上撚り係数とを有することが好ましい。
【０００７】
カーカスプライに用いるポリケトン繊維のコードは、５．０ｃＮ／ｄｔｅｘ以上の引張破断強度と、伸長方向に０．２ｃＮ／ｄｔｅｘ荷重時の伸び率が０．２−１．８％、伸長方向に１．９ｃＮ／ｄｔｅｘ荷重時の伸び率が１．４−６．４％、伸長方向に２．９ｃＮ／ｄｔｅｘ荷重時の伸び率が２．１−８．６％であることが好ましい。この場合、該カーカスプライに用いるポリケトン繊維のコードは、０．１２−０．８５の下撚り係数と、０．３５−０．７５の上撚り係数とを有することが好ましい。
【０００８】
さらに。式（Ｉ）中のＡはエチレンであることが好ましい。
【０００９】
【発明の実施の形態】
以下に、本発明を詳細に説明する。本発明の航空機用空気入りラジアルタイヤは、一対のビードコアと、該ビードコア間にトロイド状に延在する少なくとも１枚の有機繊維コードを含むカーカスプライよりなるラジアルカーカスと、該カーカスのクラウン部外周に配した少なくとも１枚の有機繊維コードを含むベルト層よりなるベルトとを備え、該カーカスプライおよび／またはベルト層を構成する有機繊維コードに下記の式（Ｉ）：
【化３】

（式中の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、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なるポリケトン繊維のコードを用いる。
【００１０】
式（Ｉ）で表されるポリケトンは、分子中にＣＯ単位（カルボニル基）とオレフィン由来の単位とが配列された交互共重合体、すなわち、高分子鎖中で各ＣＯ単位の隣に、たと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、このポリケトンは、一酸化炭素と特定のオレフィン一種との共重合体であってもよく、一酸化炭素と特定のオレフィン二種以上との共重合体であってもよい。式（Ｉ）におけるＡを形成するオレフィンの例としては、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。ドデセン等の不飽和炭化水素化合物、スチレン、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またはその誘導体、およびウンデセノール、６−クロロヘキセン、Ｎ−ビニルピロリドン、およびスルホニルスル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、二種以上を組合せて用いてもよい。特に、重合体の力学特性や耐熱性等の点から、Ａはエチレンが好ましい。
【００１１】
エチレンと他のオレフィンとを併用する場合、エチレンは全オレフィンに対し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、得られる重合体の融点が２００℃以下になり、該重合体から得られる繊維のコードの耐熱性が不十分となる場合がある。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、特に全オレフィンに対し９０モル％以上が好ましい。
【００１２】
式（Ｉ）のポリケトンは、公知の方法、たとえばヨーロッパ特許公開第１２１９６５号、同第２１３６７１号、同第２２９４０８号、および米国特許第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。
【００１３】
本発明に係る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１．０−１０．０デシリットル／ｇの範囲、さらに１．２−５．０デシリットル／ｇの範囲にあるのが好ましい。溶液粘度が１．０デシリットル／ｇ未満の場合、得られる繊維コードの強度が不十分となり、一方１０．０デシリットル／ｇを越えると、繊維形成時の溶融粘度や溶液粘度が高くなりすぎ、紡糸性が劣化する。
【００１４】
このポリケトン繊維の形成方法は、特に制限されず、一般的な溶融紡糸法や溶液紡糸法が採用される。溶融紡糸法の場合、たとえば特開平１−１２４６１７号公報に記載の方法に従って、重合体をその融点より２０℃以上高い温度、好ましくは４０℃程度高い温度で溶融紡糸し、次いで融点より１０℃以下低い温度、好ましくは４０℃程度低い温度で、３倍以上、好ましくは７倍以上の延伸比にて延伸処理を施すことにより所望の繊維を容易に得ることができる。一方、溶液紡糸法の場合、たとえば特開平２−１１２４１３号公報に記載の方法に従って、重合体をヘキサフルオロイソプロパノールやｍ−クレゾールに０．２５−２０質量％、好ましくは０．５−１０質量％の濃度で溶解し、紡糸ノズルより押し出し、溶剤を除去して紡糸原糸を得、さらに融点−１００℃から融点＋１０℃、好ましくは融点−５０℃から融点の範囲の温度で延伸処理することにより、所望の繊維を得ることができる。なお、ポリケトン繊維を形成する際に、所要に応じて、酸化防止剤、艶消し剤、顔料、帯電防止剤等を配合することができる。
【００１５】
このようにして形成したポリケトン繊維を用いてカーカスプライやベルト層用のコードを形成する場合、該コードは５．０ｃＮ／ｄｔｅｘ以上の引張破断強度を有するのが好ましい。コードの引張破断強度が０．５ｃＮ／ｄｔｅｘ未満になると、必要な耐圧性能を満足することができない。
【００１６】
ポリケトン繊維コードをベルト層に用いる場合、該コードは、伸長方向に０．３ｃＮ／ｄｔｅｘ荷重時の伸び率が０．２−２．０％、伸長方向に２．１ｃＮ／ｄｔｅｘ荷重時の伸び率が１．５−７．０％、伸長方向に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。また、ポリケトン繊維コードをカーカスプライに用いる場合、該コードは、伸長方向に０．２ｃＮ／ｄｔｅｘ荷重時の伸び率が０．２−１．８％、伸長方向に１．９ｃＮ／ｄｔｅｘ荷重時の伸び率が１．４−６．４％、伸長方向に２．９ｃＮ／ｄｔｅｘ荷重時の伸び率が２．１−８．６％であることが好ましい。
【００１７】
ポリケトン繊維コードの伸び率を伸長方向に０．３ｃＮ／ｄｔｅｘ荷重時０．２−２．０％、または伸長方向に０．２ｃＮ／ｄｔｅｘ荷重時０．２−１．８％とする理由は以下のとおりである。すなわち、航空機用空気入りラジアルタイヤを加硫するにあたり、通常生タイヤが加硫モールド内にて０．２−２．０％程度伸長するようにタイヤ外径を設定する。これは、加硫時に生タイヤ内部に負荷される圧力によってタイヤを均等に伸長せしめてコードの方向を揃え、コードの打ち込みバラツキを是正するためである。該加硫工程では、ベルト層のコードにおよそ０．３ｃＮ／ｄｔｅｘ、カーカスプライのコードにおよそ０．２ｃＮ／ｄｔｅｘの比較的小さい張力が作用するので、このときポリケトン繊維コードの伸び率がベルト層で２．０％より大きく、カーカスプライで１．８％より大きいと、コード性状是正の効果がなくなり、一方０．２％未満になると、コード張力が加硫中の生タイヤの膨満時に大きくなり、該コードがタイヤ径方向内側のゴム中に食い込む等の不都合が生ずる。
【００１８】
一方、ポリケトン繊維コードの伸び率を伸長方向に２．１ｃＮ／ｄｔｅｘ荷重時１．５−７．０％、３．２ｃＮ／ｄｔｅｘ荷重時２．２−９．３％、または伸長方向に１．９ｃＮ／ｄｔｅｘ荷重時１．４−６．４％、２．９ｃＮ／ｄｔｅｘ荷重時２．１−８．６％とする理由は以下のとおりである。すなわち、航空機用空気入りラジアルタイヤでは、標準状態の内圧負荷時にベルト層のコードにおよそ２．１ｃＮ／ｄｔｅｘまたカーカスプライのコードにおよそ１．９ｃＮ／ｄｔｅｘの張力が加わり、走行時にベルト層のコードにおよそ３．２ｃＮ／ｄｔｅｘまたカーカスプライのコードにおよそ２．９ｃＮ／ｄｔｅｘの張力が加わるので、このときコードの伸び率が上記範囲を上回ると、タイヤ径方向の膨出を効果的に抑制することができず、異物に対する抵抗力が小さくなる。また、伸び率が逆に上記範囲を下回ると、ベルト層のタガ効果が著しく大きくなり、カーカスプライが必要以上にタイヤ幅方向に膨出することになり、好ましくない。
【００１９】
さらに、カーカスプライやベルト層に用いるポリケトン繊維コードは、ポリケトン繊維の原糸を下撚りし、次いで上撚りすることにより形成されたもので、下撚り係数が０．１２−０．８５、上撚り係数が０．３５−０．７５であるのが好ましい。各撚り係数が上記範囲を下回ると、コードの引き揃え効果が悪くなり、段切れを生じてコード強力の低下を招き、逆に上回ると、繊維を拘束する力が大きくなりすぎ、コード強力の不足につながり、好ましくない。
【００２０】
ここで言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
上撚りの“Ｄ”：下撚りをかける糸束のデニール数
下撚りの“Ｄ”：コード全体のデニール数÷２
ρ：有機繊維コードの比重（ｇ／ｃｍ^３）
【００２１】
本発明に係る航空機用空気入りラジアルタイヤは、上述したポリケトン繊維のコードを含むカーカスプライを少なくとも一枚および／または該ポリケトン繊維のコードを含むベルト層を少なくとも一層備えるもので、特にカーカスプライ枚数およびベルト層数に制限はないが、カーカスプライ数は６枚、ベルト層数は６枚が好ましい。
【００２２】
ナイロンコードをカーカスプライおよびベルト層に用いる従来の航空機用空気入りラジアルタイヤでは、通常カーカスプライ数は７枚、ベルト層数は８枚であるので、本発明では使用カーカスプライ枚数やベルト層数を従来のものよりはるかに減ずることができ、タイヤの軽量化になる。
【００２３】
【実施例】
次に、本発明を実施例につき説明するが、これら実施例によってなんら限定されるものではない。
【００２４】
タイヤサイズ：１２７０ｘ４４５Ｒ２２ ３２ＰＲを有する実施例１，２および３ならびに従来例の航空機用空気入りラジアルタイヤを作成する。これらタイヤは、表１に示すようなナイロンコードおよびポリエチレンケトン繊維コードをカーカスプライおよび／またはベルト層にベルト層のコード打込み数が６．３本／１０ｍｍ、カーカスプライのコード打込み数が７．８本／１０ｍｍとして用いる以外、すべて同一のタイヤ構造を有する。なお、使用したナイロンコードと、ポリエチレンケトン繊維コードの物性を表２に示す。これらタイヤに対し、後述する方法により耐カット性を測定し、結果を表１に示す。
【００２５】
従来例：カーカスプライおよびベルト層にナイロンコードを使用しており、カーカスプライ枚数は７枚、ベルト層数は８枚である。
実施例１：ベルト層のナイロンコードをポリエチレンケトン繊維コードに変更しており、またベルト層数を６枚に変更している。
実施例２：ベルト層およびカーカスプライのナイロンコードをポリエチレンケトン繊維コードに変更しており、またベルト層数を６枚、カーカスプライ枚数を６枚に変更している。
実施例３：カーカスプライのナイロンコードをポリエチレンケトン繊維コードに変更しており、またカーカスプライ枚数を６枚に変更している。
【００２６】
耐カット性は、幅４０ｍｍ，刃先角度３０度のカッターを１６２０ｋＰａの内圧充填下の供試タイヤのトレッドセンター部にその幅方向に向けて規定荷重（２４８６０ｋｇ）の５％に相当する力で垂直に押し付けた際に生ずるカット深さを測定することにより評価し、従来例タイヤのカット深さの逆数を１００として指数表示する。この場合、数値が大きいほど、耐カット性に優れていることを示す。
【００２７】
タイヤ重量は、従来例タイヤを１００として指数表示する。この場合、数値が小さいほど、軽量であることを示す。
【００２８】
【表１】

【００２９】
【表２】

【００３０】
表１の結果から、すべての実施例タイヤは、ポリケトン繊維のコードをカーカスプライおよび／またはベルト層に使用しているので、従来例タイヤに比べて耐カット性に優れ、タイヤ重量も軽量化されていることが分かる。
【００３１】
【発明の効果】
以上説明したように、本発明によれば、ポリケトン繊維よりなるコードをカーカスプライおよび／またはベルト層に用いることにより、航空機用空気入りラジアルタイヤの耐カット性を大幅に向上させることができ、またタイヤ重量を低減することができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a pneumatic radial tire for an aircraft, particularly to a pneumatic radial tire for an aircraft having excellent cut resistance and reduced weight.
[0002]
[Prior art]
In a conventional aircraft radial tire, a nylon cord is used for a carcass ply and a belt layer, so that the number of carcass plies and the number of belt layers are increased and the weight is increased. Recently, it has been a requirement of OEMs to reduce the weight of members used as much as possible, but it is difficult for conventional aircraft radial tires to achieve such OEM requirements.
[0003]
In addition, since radial tires for aircraft are used under conditions of high internal pressure and high load, the tread surface protrudes radially outward due to the high internal pressure and the action of centrifugal force during high-speed rotation. As a result, the tread rubber is stretched in the tire circumferential direction. In particular, when passing over a foreign object on the runway during takeoff and landing, the resistance of the tread to the foreign object becomes weaker, and the tread rubber causes a cut scar on the tread rubber. There is a problem that can cause damage.
[0004]
[Problems to be solved by the invention]
The present invention solves the above-mentioned problems of the prior art, and suppresses the radial growth of the tread surface by using a specific organic fiber cord described later to improve the durability against cutting of foreign matters and the like, and also reduces the weight. It is an object of the present invention to provide a pneumatic radial tire for an aircraft which can also be achieved.
[0005]
[Means for Solving the Problems]
The pneumatic radial tire for an aircraft according to the present invention includes a radial carcass including a pair of bead cores, a carcass ply including at least one organic fiber cord extending in a toroidal shape between the bead cores, and a crown portion outer periphery of the carcass A belt comprising a belt layer including at least one organic fiber cord disposed in the carcass ply and / or the belt layer, wherein the organic fiber cord constituting the carcass ply and / or the belt layer has the following formula (I):
Embedded image

(A in the formula 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.) It is characterized by.
[0006]
The cord of the polyketone fiber used for the belt layer has a tensile breaking strength of 5.0 cN / dtex or more, an elongation of 0.2 to 2.0% under a 0.3 cN / dtex load in the elongation direction, and 2. It is preferable that the elongation percentage under a 1 cN / dtex load is 1.5-7.0% and the elongation percentage under a 3.2 cN / dtex load in the elongation direction is 2.2-9.3%. In this case, the polyketone fiber cord used for the belt layer preferably has a lower twist coefficient of 0.12 to 0.85 and a lower twist coefficient of 0.35 to 0.75.
[0007]
The cord of the polyketone fiber used for the carcass ply has a tensile breaking strength of 5.0 cN / dtex or more, an elongation rate of 0.2-1.8% under a load of 0.2 cN / dtex in the elongation direction, and 1. It is preferable that the elongation percentage under a 9 cN / dtex load is 1.4-6.4% and the elongation percentage under a 2.9 cN / dtex load in the elongation direction is 2.1-8.6%. In this case, the polyketone fiber cord used for the carcass ply preferably has a lower twist coefficient of 0.12 to 0.85 and a lower twist coefficient of 0.35 to 0.75.
[0008]
further. A in the formula (I) is preferably ethylene.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail. The pneumatic radial tire for aircraft according to the present invention includes a radial carcass including a pair of bead cores, a carcass ply including at least one organic fiber cord extending in a toroidal shape between the bead cores, and a crown outer periphery of the carcass. A belt comprising a belt layer containing at least one organic fiber cord disposed therein, wherein the organic fiber cord constituting the carcass ply and / or the belt layer has the following formula (I):
Embedded image

(A in the formula is a portion derived from an ethylenically unsaturated compound polymerized by an ethylenic bond, and each repeating unit may be the same or different.) A polyketone fiber cord comprising a repeating unit represented by the following formula is used.
[0010]
The polyketone represented by the formula (I) is an alternating copolymer in which CO units (carbonyl groups) and olefin-derived units are arranged in a molecule, that is, next to each CO unit in a polymer chain, for example, In this structure, olefin units such as ethylene units are located one by one. Further, the polyketone may be a copolymer of carbon monoxide and a specific olefin, or a copolymer of carbon monoxide and two or more specific olefins. Examples of the olefin forming A in the formula (I) include ethylene, propylene, butene, pentene, hexene, heptene, octene, nonene and decene. Unsaturated hydrocarbon compounds such as dodecene, styrene, methyl acrylate, methyl methacrylate; Examples include unsaturated carboxylic acids such as vinyl acetate and undecenoic acid and derivatives thereof, and undecenol, 6-chlorohexene, N-vinylpyrrolidone, and diethyl ester of sulfonylsulfonic acid. These may be used alone or in combination of two or more. Particularly, A is preferably ethylene from the viewpoint of the mechanical properties and heat resistance of the polymer.
[0011]
When ethylene and another olefin are used in combination, it is preferable to use ethylene so as to be at least 80 mol% based on all olefins. If it is less than 80 mol%, the melting point of the obtained polymer will be 200 ° C. or lower, and the heat resistance of the fiber cord obtained from the polymer may be insufficient. From the viewpoint of the mechanical properties and heat resistance of the fiber cord, the amount of ethylene used is particularly preferably 90 mol% or more based on all olefins.
[0012]
The polyketones of formula (I) can be prepared according to known methods, for example, those described in EP-A-121965, EP-A-213671, EP-A-229408, and US Pat. No. 3,914,391.
[0013]
The polymerization degree of the polyketone according to the present invention is such that the solution viscosity measured at 60 ° C. in m-cresol is in the range of 1.0 to 10.0 deciliter / g, and further in the range of 1.2 to 5.0 deciliter / g. Is preferred. When the solution viscosity is less than 1.0 deciliter / g, the strength of the obtained fiber cord becomes insufficient. On the other hand, when the solution viscosity exceeds 10.0 deciliter / g, the melt viscosity and the solution viscosity during fiber formation become too high, and Deteriorates.
[0014]
The method for forming the polyketone fiber is not particularly limited, and a general melt spinning method or a solution spinning method is employed. In the case of the melt spinning method, the polymer is melt-spun at a temperature higher than its melting point by 20 ° C. or more, preferably by about 40 ° C., and then at 10 ° C. or lower than its melting point according to the method described in JP-A-1-124617. A desired fiber can be easily obtained by performing a stretching treatment at a low temperature, preferably about 40 ° C., at a stretching ratio of 3 times or more, preferably 7 times or more. On the other hand, in the case of the solution spinning method, the polymer is added to hexafluoroisopropanol or m-cresol in an amount of 0.25 to 20% by mass, preferably 0.5 to 10% by mass according to the method described in JP-A-2-112413. And then extruded from a spinning nozzle to remove the solvent to obtain a spun yarn, and further subjected to a drawing treatment at a temperature in the range of from -100 ° C to + 10 ° C, preferably from -50 ° C to mp. Thus, a desired fiber can be obtained. When forming the polyketone fiber, an antioxidant, a matting agent, a pigment, an antistatic agent and the like can be blended as required.
[0015]
When a cord for a carcass ply or a belt layer is formed using the polyketone fiber thus formed, the cord preferably has a tensile breaking strength of 5.0 cN / dtex or more. If the tensile strength at break of the cord is less than 0.5 cN / dtex, the required pressure resistance cannot be satisfied.
[0016]
When a polyketone fiber cord is used for the belt layer, the cord has an elongation of 0.2-2.0% under a load of 0.3 cN / dtex in the elongation direction and an elongation of 2.1 cN / dtex in the elongation direction. Is preferably 1.5 to 7.0%, and the elongation at the time of 3.2 cN / dtex load in the elongation direction is preferably 2.2 to 9.3%. When a polyketone fiber cord is used for a carcass ply, the cord has an elongation of 0.2-1.8% under a load of 0.2 cN / dtex in the elongation direction, and an elongation of 1.9 cN / dtex in the elongation direction. It is preferable that the elongation percentage is 1.4 to 6.4% and the elongation percentage under a 2.9 cN / dtex load in the elongation direction is 2.1 to 8.6%.
[0017]
The reason for setting the elongation percentage of the polyketone fiber cord in the elongation direction to 0.2-2.0% under a load of 0.3 cN / dtex, or 0.2-1.8% in the elongation direction under a load of 0.2 cN / dtex is as follows. It is as follows. That is, when vulcanizing an aircraft pneumatic radial tire, the outer diameter of the tire is usually set such that the green tire extends about 0.2 to 2.0% in the vulcanization mold. The reason for this is to uniformly expand the tire by the pressure applied to the inside of the green tire during vulcanization, align the cords, and correct the variation in cord driving. In the vulcanization step, a relatively small tension of about 0.3 cN / dtex acts on the cord of the belt layer and about 0.2 cN / dtex acts on the cord of the carcass ply. If it is greater than 2.0% and the carcass ply is greater than 1.8%, the effect of correcting the cord properties is lost, while if it is less than 0.2%, the cord tension increases when the green tire is inflated during vulcanization. Inconveniences such as the biting of the cord into rubber inside the tire in the radial direction occur.
[0018]
On the other hand, the elongation percentage of the polyketone fiber cord in the elongation direction is 1.5-7.0% under a 2.1 cN / dtex load, 2.2-9.3% under a 3.2 cN / dtex load, or 1. The reason for setting 1.4-6.4% under a 9 cN / dtex load and 2.1-8.6% under a 2.9 cN / dtex load is as follows. That is, in the pneumatic radial tire for an aircraft, a tension of about 2.1 cN / dtex is applied to the cord of the belt layer and about 1.9 cN / dtex to the cord of the carcass ply when the internal pressure is loaded in a standard state. Since a tension of about 3.2 cN / dtex or about 2.9 cN / dtex is applied to the cord of the carcass ply, if the elongation of the cord at this time exceeds the above range, bulging in the tire radial direction is effectively suppressed. And the resistance to foreign matter is reduced. On the other hand, if the elongation is less than the above range, the slack effect of the belt layer becomes extremely large, and the carcass ply swells more than necessary in the tire width direction, which is not preferable.
[0019]
Furthermore, the polyketone fiber cord used for the carcass ply or the belt layer is formed by twisting the raw yarn of the polyketone fiber and then twisting the twisted yarn. The twisting coefficient is 0.12-0.85, and the twisting is performed. Preferably, the coefficient is between 0.35 and 0.75. If each twist coefficient is less than the above range, the effect of aligning the cords is deteriorated, causing breakage of the cords, resulting in a decrease in the cord strength. Leads to undesirable.
[0020]
Here, the twist coefficient 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 Upper twist “D”: Denier number of yarn bundle to be twisted Lower twist “D”: Denier number of entire cord ÷ 2
ρ: Specific gravity of organic fiber cord (g / cm ³ )
[0021]
The pneumatic radial tire for aircraft according to the present invention includes at least one carcass ply including the above-described polyketone fiber cord and / or at least one belt layer including the polyketone fiber cord. Although the number of belt layers is not limited, the number of carcass plies is preferably six and the number of belt layers is preferably six.
[0022]
In a conventional aircraft pneumatic radial tire using a nylon cord for a carcass ply and a belt layer, the number of carcass plies and the number of belt layers are usually seven and eight, respectively. It can be reduced much more than the conventional one, resulting in a lighter tire.
[0023]
【Example】
Next, the present invention will be described with reference to examples, but the present invention is not limited to these examples.
[0024]
Pneumatic radial tires for aircraft of Examples 1, 2 and 3 having a tire size of 1270 × 445R22 32PR and conventional examples are prepared. In these tires, as shown in Table 1, a nylon cord and a polyethylene ketone fiber cord have a carcass ply and / or a belt layer with a cord number of 6.3 cords / 10 mm and a carcass ply with a cord number of 7.8. All have the same tire structure except that they are used as a book / 10 mm. Table 2 shows the physical properties of the used nylon cord and polyethylene ketone fiber cord. For these tires, cut resistance was measured by the method described below, and the results are shown in Table 1.
[0025]
Conventional example: Nylon cords are used for the carcass ply and the belt layer, the number of carcass plies is 7, and the number of belt layers is 8.
Example 1: The nylon cord of the belt layer was changed to a polyethylene ketone fiber cord, and the number of belt layers was changed to six.
Example 2: The nylon cord of the belt layer and the carcass ply was changed to a polyethylene ketone fiber cord, the number of belt layers was changed to 6, and the number of carcass plies was changed to 6.
Example 3: The nylon cord of the carcass ply was changed to a polyethylene ketone fiber cord, and the number of carcass plies was changed to six.
[0026]
The cut resistance is as follows. A cutter having a width of 40 mm and a cutting edge angle of 30 degrees is vertically applied to the tread center portion of the test tire filled with an internal pressure of 1620 kPa with a force equivalent to 5% of a specified load (24860 kg) in the width direction. The evaluation is performed by measuring the cut depth generated when the tire is pressed, and the reciprocal of the cut depth of the conventional tire is represented as an index. In this case, the larger the value, the better the cut resistance.
[0027]
The tire weight is indicated as an index with the conventional tire set as 100. In this case, the smaller the numerical value, the lighter the weight.
[0028]
[Table 1]

[0029]
[Table 2]

[0030]
From the results shown in Table 1, all of the example tires have a polyketone fiber cord used for the carcass ply and / or the belt layer, and therefore have excellent cut resistance and a reduced tire weight as compared with the conventional example tire. You can see that.
[0031]
【The invention's effect】
As described above, according to the present invention, the cut resistance of a pneumatic radial tire for aircraft can be significantly improved by using a cord made of polyketone fibers for a carcass ply and / or a belt layer, Tire weight can be reduced.

Claims (6)

A radial carcass comprising a pair of bead cores, a carcass ply including at least one organic fiber cord extending in a toroidal shape between the bead cores, and at least one organic fiber cord disposed on the outer periphery of a crown portion of the carcass. In the pneumatic radial tire for an aircraft provided with a belt having a belt layer, the organic fiber cord constituting the carcass ply and / or the belt layer has the following formula (I):

(A in the formula 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 radial tire for aircraft characterized by the following. The cord of the polyketone fiber used for the belt layer has a tensile breaking strength of 5.0 cN / dtex or more, an elongation of 0.2 to 2.0% under a 0.3 cN / dtex load in the elongation direction, and 2% in the elongation direction. The elongation at 1.5 cN / dtex load is 1.5-7.0%, and the elongation at 3.2 cN / dtex load in the elongation direction is 2.2-9.3%. 2. The pneumatic radial tire for aircraft according to 1. 3. The aircraft according to claim 2, wherein the cord of the polyketone fiber used for the belt layer has a lower twist coefficient of 0.12-0.85 and a lower twist coefficient of 0.35-0.75. Pneumatic radial tire. The polyketone fiber cord used for the carcass ply has a tensile breaking strength of 5.0 cN / dtex or more, an elongation of 0.2-1.8% under a 0.2 cN / dtex load in the elongation direction, and 1% in the elongation direction. The elongation percentage under a 2.9 cN / dtex load is 1.4-6.4%, and the elongation percentage under a 2.9 cN / dtex load in the elongation direction is 2.1-8.6%. 2. The pneumatic radial tire for aircraft according to 1. The aircraft cord according to claim 4, wherein the cord of the polyketone fiber used for the carcass ply has a lower twist coefficient of 0.12-0.85 and a lower twist coefficient of 0.35-0.75. Pneumatic radial tire. The pneumatic radial tire for an aircraft according to claim 1, wherein A in the formula (I) is ethylene.