JP4475883B2 - Pneumatic radial tire - Google Patents

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であることを特徴とする。
【００１０】
本発明の空気入りラジアルタイヤにおいて、ショルダー領域のポリケトンのコードが、少なくともベルト端からタイヤ幅方向で中央領域の方に存在するのが好ましい。
【００１１】
また、式（Ｉ）中のＡがエチレンであるのが好ましい。
【００１２】
【発明の実施の形態】
以下に、本発明を詳細に説明する。本発明の空気入りラジアルタイヤは、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上に配した少なくとも２つのベルト層よりなるベルトと、該ベルトの外周上に配したベルト補強層とを備え、該ベルト補強層に用いるコード材質を同一タイヤ内でタイヤ中央領域とショルダー領域とで変え、タイヤ中央領域にナイロンコードを用い、ショルダー領域に下記の式（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。
【００１３】
ショルダー領域に用いる式（Ｉ）で表されたポリケトンは、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。
【００１４】
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。
【００１５】
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。
【００１６】
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。
【００１７】
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。
【００１８】
本発明においては、上述したポリケトン繊維コードをベルト補強層のショルダー領域、すなわちキャッププライのショルダー領域またはキャッププライとエッジカバーとの組合せ体におけるエッジカバーに配設し、キャッププライの中央領域または組合せ体のキャッププライ部分にナイロンコードを配設しているので、従来の高弾性かつ高Ｔｇのコードを全領域にわたって配設してなるベルト補強層に比べてコストを低減することができ、一方ナイロンコードを全領域にわたって配設したものと比べてロードノイズおよびフラットスポットを低減し、ベルト層端部の迫り出し性を改善することができる。
【００１９】
本発明に係るベルト補強層においては、ナイロンコードを周方向に延在させて螺旋状にタイヤ中央領域に巻回配置し、ポリケトン繊維のコードをショルダー領域のみに周方向に延在させて螺旋状に巻回配置する。この場合、一本のポリケトン繊維コードまたは複数本のポリケトン繊維コードよりなるストリップをべルトの各側端部（ショルダー領域）でタイヤの幅方向にその中央領域に向けて螺旋状に巻回し、一本のナイロンコードまたは複数本のナイロンコードよりなるストリップをタイヤ中央領域で一方側から他方側に向けて螺旋状に巻回することにより、キャッププライまたはキャッププライとエッジカバーとの組合せ体よりなるベルト補強層を形成する。
【００２０】
ベルト補強層がキャッププライのみの場合、各ショルダー領域の幅は該キャッププライの幅の５−１５％の範囲にあるのが好ましく、一方キャッププライとエッジカバーとの組合せ体の場合、該エッジカバーの幅はキャッププライの幅の５−１５％の範囲にあるのが好ましい。
【００２１】
【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。
【００２２】
タイヤサイズ:１９５／６５Ｒ１４を有する実施例１および２ならびに比較例１−４の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、アラミドコードおよびポリエチレンケトン繊維コードをベルト補強層に用いる以外、すべて従来の空気入りラジアルタイヤと同一のタイヤ構造を有する。これらタイヤに対し、後述する方法により高速耐久性、ベルト層端部の迫出し量、ロードノイズおよびフラットスポットを測定し、結果を表１に示す。
【００２３】
高速耐久性は、供試タイヤを２００ｋＰａの内圧充填下６Ｊ−１４のリムサイズを有するリムに組み付け、１５０ｋｍ／ｈの速度で３０分間走行させ、故障がなければ速度を６ｋｍ／ｈずつ上げていき、故障発生時の速度を測定することにより評価し、比較例１の故障発生速度を１００として指数表示する。この場合、指数値が大きくなるほど、耐久限界速度が上がり、高速耐久性に優れる。
【００２４】
ベルト層端部の迫出し量は、上記高速耐久性試験で１５０ｋｍ／ｈの速度で走行後にショルダー領域の迫出し量（高速変形）を測定することにより評価し、比較例１の迫出し量を１００として指数表示する。この場合、指数値が大きくなるほど、迫出し量が低減する。
【００２５】
ロードノイズは、供試タイヤを２００ｋＰａの内圧充填下６Ｊ−１４のリムサイズを有するリムに組み付け、２０００ｃｃの排気量を有するセダンタイプの乗用車の４輪すべてに装着し、２名乗車の荷重下テストコースを６０ｋｍ／ｈの速度で走行させながら、運転席の背もたれの中央部分に取り付けた集音マイクを介して周波数：１００−５００Ｈｚおよび３００−５００Ｈｚの全音圧（デシベル）を測定することにより評価し、比較例１のロードノイズを１００として指数表示する。この場合、指数値が大きくなるほど、ロードノイズが低減する。
【００２６】
フラットスポットは、供試タイヤを実車に装着し、一定時間走行させて十分高温となったタイヤに負荷をかけて完全に冷えるまで放置した後のタイヤの変形を、真円度の変化として測定することにより評価する。すなわち、負荷の前後における真円度をそれぞれ測定して、その差をフラットスポット量として求め、比較例１のフラットスポット量を１００として指数表示する。この場合、指数値が大きくなるほど、フラットスポット量が低減する。
【００２７】
【表１】

【００２８】
【発明の効果】
以上説明したように、本発明によれば、ベルト補強層のタイヤ中央領域にナイロンコードを、ショルダー領域にポリケトン繊維コードを使用することにより、従来のナイロンコードをベルト補強層に用いた場合に比べて空気入りラジアルタイヤの高速耐久性を大幅に向上させ、ロードノイズおよびフラットスポットも低減することができ、またこれら特性は従来のアラミドコードをベルト補強層に用いる場合とほぼ同等になる一方、コストを大幅に低減することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic radial tire, and more particularly to a pneumatic radial tire excellent in high-speed durability and having reduced road noise and flat spots.
[0002]
[Prior art]
Radial tires for passenger cars use at least two belt layers mainly including steel cords inclined at an angle with respect to the equator plane of the tire, such that the cords in these layers intersect each other, and In order to ensure stability during tire running, especially in the radial direction of the belt in order to prevent belt layer separation (particularly significant peeling at the belt layer end) during high speed running and improve durability. A cap ply made of nylon cord or the like, or a combination of a cap ply and an edge cover is arranged on the outside as a belt reinforcing layer.
[0003]
At present, in order to improve high-speed durability, a cap ply and an edge cover are generally used as a belt reinforcing layer, and a low heat generation and low cost nylon is mainly used as a cord material in the belt reinforcing layer. However, in recent years, as OEM requirements, further reduction of road noise, reduction of flat spots, or improvement of the protruding property of the belt layer end at the time of high speed running is further demanded.
[0004]
As such improvement measures, any material such as aramid, a composite material comprising aramid (eg, aramid / nylon hybrid), which has higher elasticity and higher glass transition point (Tg) than nylon and is effective in reducing flat spots. The cord which consists of is applied to the belt reinforcement layer. However, it is a well-known fact that all of these materials are high in cost and inferior to nylon in comparison with nylon. It does not lead to improvement of high-speed durability.
[0005]
In recent years, it has been proposed to use a cord made of an aliphatic polyolefin ketone fiber for a belt reinforcing layer instead of an aramid or an aramid composite material. Such a fiber cord has better heat-resistant adhesion than an aramid cord or the like. However, since the belt reinforcing layer is composed of only this fiber cord, the cost becomes higher than that of a case composed of only a nylon cord.
[0006]
[Patent Document 1]
Japanese Patent Laid-Open No. 2000-142025
[Patent Document 2]
JP 2001-334811 A
[Problems to be solved by the invention]
The present invention eliminates the above-mentioned problems of the prior art, and uses a specific organic fiber cord, which will be described later, only in the shoulder region of the belt reinforcing layer, and uses nylon cord in the remaining central region. An object of the present invention is to provide a pneumatic radial tire that is excellent in performance, road noise and flat spots are reduced, and costs are reduced.
[0009]
[Means for Solving the Problems]
A pneumatic radial tire according to the present invention includes a pair of bead cores, a radial carcass made of at least one carcass ply extending in a toroidal shape between the bead cores, and at least two arranged on the outer periphery of the crown portion of the carcass A belt composed of a belt layer and a belt reinforcing layer disposed on the outer periphery of the belt, and a cord material used for the belt reinforcing layer is changed between a tire central region and a shoulder region in the same tire, and a cord in the tire central region The material is nylon, the cord material of the shoulder region is the following formula (I):
[Chemical formula 2]

(Wherein A is a portion derived from an ethylenically unsaturated compound polymerized by an ethylenic bond, and each repeating unit may be the same or different) and is a polyketone comprising repeating units represented by To do.
[0010]
In the pneumatic radial tire of the present invention, it is preferable that the cord of the polyketone in the shoulder region exists at least in the center region in the tire width direction from the belt end.
[0011]
Moreover, it is preferable that A in Formula (I) is ethylene.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below. The pneumatic radial tire of the present invention includes a pair of bead cores, a radial carcass formed of at least one carcass ply extending in a toroidal shape between the bead cores, and at least two belts disposed on the outer periphery of the crown portion of the carcass. And a belt reinforcing layer disposed on the outer periphery of the belt, and a cord material used for the belt reinforcing layer is changed between a tire central region and a shoulder region in the same tire, and a nylon cord is formed in the tire central region. And the shoulder region has the following formula (I):
[Chemical 3]

(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).
[0013]
The polyketone represented by the formula (I) used for the shoulder region is an alternating copolymer in which CO units (carbonyl groups) and olefin-derived units are arranged in the molecule, that is, each CO unit in the polymer chain. Next, for example, an olefin unit such as an ethylene unit is located one by one. The polyketone may be a copolymer of carbon monoxide and one specific olefin, or may be a copolymer of carbon monoxide and two or more specific olefins. Examples of olefins forming A in formula (I) are ethylene, propylene, butene, pentene, hexene, heptene, octene, nonene, decene. Unsaturated hydrocarbon compounds such as dodecene, styrene, methyl acrylate, methyl methacrylate. Examples thereof include unsaturated carboxylic acids such as vinyl acetate and undecenoic acid or 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. In particular, A is preferably ethylene from the viewpoint of the mechanical properties and heat resistance of the polymer.
[0014]
When ethylene and other olefins are used in combination, ethylene is preferably used in an amount of 80 mol% or more based on the total olefins. If it is less than 80 mol%, the melting point of the resulting polymer will be 200 ° C. or lower, and the heat resistance of the fiber cord obtained from the polymer may be insufficient. In view 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 the total olefin.
[0015]
The polyketone of formula (I) can be prepared according to known methods, for example, those described in European Patent Publication Nos. 121965, 213671, 229408, and US Pat. No. 3,914,391.
[0016]
The polymerization degree of the polyketone according to the present invention is such that the solution viscosity measured in m-cresol at 60 ° C. is in the range of 1.0-10.0 deciliter / g, and further in the range of 1.2-5.0 deciliter / g. Is preferred. If the solution viscosity is less than 1.0 deciliter / g, the strength of the resulting fiber cord is insufficient, while if it exceeds 10.0 deciliter / g, the melt viscosity or solution viscosity at the time of fiber formation becomes too high, and spinning. Deteriorates.
[0017]
The method for forming the polyketone fiber is not particularly limited, and a general melt spinning method or solution spinning method is adopted. In the case of the melt spinning method, for example, according to the method described in JP-A-1-124617, the polymer is melt-spun at a temperature 20 ° C. or higher, preferably about 40 ° C. higher than its melting point, and then 10 ° C. or lower than the melting point. A desired fiber can be easily obtained by performing a stretching treatment at a low temperature, preferably a temperature as low as about 40 ° C., at a draw ratio of 3 times or more, preferably 7 times or more. On the other hand, in the case of the solution spinning method, for example, according to the method described in JP-A-2-112413, 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. By spinning out from the spinning nozzle, removing the solvent to obtain a spinning yarn, and further drawing at a temperature in the range of melting point-100 ° C to melting point + 10 ° C, preferably melting point-50 ° C to melting point. The desired fiber can be obtained. In forming the polyketone fiber, an antioxidant, a matting agent, a pigment, an antistatic agent, and the like can be blended as necessary.
[0018]
In the present invention, the polyketone fiber cord described above is disposed in the shoulder region of the belt reinforcing layer, that is, the shoulder region of the cap ply or the edge cover in the combined body of the cap ply and the edge cover, and the central region or combined body of the cap ply. Nylon cords are arranged on the cap ply part of the belt, so the cost can be reduced compared to the conventional belt reinforcement layer in which high elastic and high Tg cords are arranged over the entire area. The road noise and the flat spot can be reduced as compared with the case where the belt is disposed over the entire region, and the protruding property of the belt layer end can be improved.
[0019]
In the belt reinforcing layer according to the present invention, the nylon cord extends in the circumferential direction and is spirally wound around the tire center region, and the cord of the polyketone fiber extends in the circumferential direction only in the shoulder region and spirals. Winding around. In this case, a strip made of one polyketone fiber cord or a plurality of polyketone fiber cords is spirally wound in the width direction of the tire toward the central region at each side end (shoulder region) of the belt. A belt made of a cap ply or a combination of a cap ply and an edge cover by winding a strip of nylon cord or a plurality of nylon cords spirally from one side to the other side in the tire central region A reinforcing layer is formed.
[0020]
When the belt reinforcing layer is only the cap ply, the width of each shoulder region is preferably in the range of 5 to 15% of the width of the cap ply, whereas in the case of the combination of the cap ply and the edge cover, the edge cover Is preferably in the range of 5-15% of the cap ply width.
[0021]
【Example】
EXAMPLES Next, although an Example demonstrates this invention, it is not limited at all by these Examples.
[0022]
Pneumatic radial tires of Examples 1 and 2 and Comparative Example 1-4 having tire size: 195 / 65R14 are prepared. These tires all have the same tire structure as conventional pneumatic radial tires except that nylon cords, aramid cords and polyethylene ketone fiber cords as shown in Table 1 are used for the belt reinforcing layer. For these tires, high-speed durability, the amount of protrusion at the end of the belt layer, road noise and flat spots were measured by the method described later, and the results are shown in Table 1.
[0023]
For high-speed durability, the test tire is assembled to a rim having a rim size of 6J-14 under an internal pressure of 200 kPa, and is run for 30 minutes at a speed of 150 km / h. If there is no failure, the speed is increased by 6 km / h. Evaluation is made by measuring the speed at the time of failure occurrence, and the failure occurrence speed of Comparative Example 1 is set as 100 and displayed as an index. In this case, the larger the index value, the higher the durability limit speed and the higher the high speed durability.
[0024]
The amount of protrusion at the end of the belt layer was evaluated by measuring the amount of protrusion (high-speed deformation) in the shoulder region after running at a speed of 150 km / h in the high-speed durability test. The index is displayed as 100. In this case, the amount of protrusion decreases as the index value increases.
[0025]
For road noise, the test tire is assembled on a rim having a rim size of 6J-14 under 200kPa internal pressure filling, and is mounted on all four wheels of a sedan type passenger car having a displacement of 2000cc. Is measured by measuring the total sound pressure (decibel) of frequencies: 100-500 Hz and 300-500 Hz through a sound collecting microphone attached to the center part of the backrest of the driver's seat while traveling at a speed of 60 km / h. The road noise of Comparative Example 1 is displayed as an index with 100 as the road noise. In this case, the road noise decreases as the exponent value increases.
[0026]
The flat spot measures the deformation of a tire as a change in roundness after the test tire is mounted on a real vehicle, left running until it has been fully cooled by applying a load to a tire that has been sufficiently hot after running for a certain period of time. To evaluate. That is, the roundness before and after the load is measured, the difference is obtained as a flat spot amount, and the flat spot amount of Comparative Example 1 is displayed as an index as 100. In this case, the flat spot amount decreases as the exponent value increases.
[0027]
[Table 1]

[0028]
【The invention's effect】
As described above, according to the present invention, the nylon cord is used in the tire central region of the belt reinforcing layer and the polyketone fiber cord is used in the shoulder region, so that the conventional nylon cord is used for the belt reinforcing layer. The high-speed durability of pneumatic radial tires can be greatly improved, road noise and flat spots can be reduced, and these characteristics are almost the same as when conventional aramid cords are used for the belt reinforcement layer. Can be greatly reduced.

Claims (3)

A pair of bead cores, a radial carcass composed of at least one carcass ply extending in a toroidal shape between the bead cores, a belt composed of at least two belt layers disposed on the outer periphery of the crown portion of the carcass, In a pneumatic radial tire provided with a belt reinforcing layer disposed on the outer periphery, the cord material used for the belt reinforcing layer is changed between the tire central region and the shoulder region in the same tire, and the cord material in the tire central region is nylon. The cord material of the shoulder region is represented by the following formula (I):

(Wherein A is a portion derived from an ethylenically unsaturated compound polymerized by an ethylenic bond, and each repeating unit may be the same or different) and is a polyketone comprising repeating units represented by Pneumatic radial tire. 2. The pneumatic radial tire according to claim 1, wherein the cord of the polyketone in the shoulder region is present at least in the center region in the tire width direction from the belt end. The pneumatic radial tire according to claim 1, wherein A in the formula (I) is ethylene.