JP2004238420A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire having high and stabilized durability in addition to excellent processability during production of the tire. <P>SOLUTION: The pneumatic tire comprises a layer in which at least either one of a carcass 4 and a belt 6 is composed of steel cords coated with a coating rubber. In the pneumatic tire, a rubber composition prepared by compounding a compound represented by formula (I) (wherein, (n) is an integer of 0-100; R<SP>1</SP>s are each independently hydrogen, a halogen or a 1-6C straight-chain or branched alkyl group; R<SP>2</SP>s are each independently hydrogen, hydroxy group, a halogen or a 1-6C straight-chain or branched alkyl group; and R<SP>3</SP>s are each independently a 1-12C straight-chain or branched alkylene group) in an amount of 0.1-10 pts. mass based on 100 pts. mass of a rubber component is used in the coating rubber coating the steel cords in at least either one of the carcass 4 and the belt 6. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

（式中、ｎは０〜１００の整数で；Ｒ^１は、夫々独立して水素、ハロゲン、又は炭素数１〜６の直鎖若しくは分岐のアルキル基で；Ｒ^２は、夫々独立して水素、水酸基、ハロゲン、又は炭素数１〜６の直鎖若しくは分岐のアルキル基で；Ｒ^３は、夫々独立して炭素数１〜１２の直鎖若しくは分岐のアルキレン基である。）
【０００９】
本発明の空気入りタイヤの好適例においては、前記式（Ｉ）で表される化合物において、Ｒ^１が水素で、Ｒ^２が水素又は水酸基で、Ｒ^３がエチレン基、プロピレン基及びブチレン基の何れかである。
【００１０】
本発明の空気入りタイヤの他の好適例においては、前記式（Ｉ）で表される化合物において、ｎが０である。
【００１１】
本発明の空気入りタイヤの他の好適例においては、上記コーティングゴムに用いるゴム組成物は、更に有機酸コバルト化合物を前記ゴム成分１００質量部に対しコバルト量として０．０３〜１質量部配合してなる。
【００１２】
本発明の空気入りタイヤの他の好適例においては、前記ゴム成分は、７５質量％以上の天然ゴム（ＮＲ）及び残部合成ゴムよりなる。
【００１３】
本発明の空気入りタイヤの他の好適例においては、前記ゴム成分は、天然ゴム及びポリイソプレンゴム（ＩＲ）の少なくとも一方よりなる。
【００１４】
【発明の実施の形態】
以下に、本発明を詳細に説明する。図１は本発明の実施形態を示す横断面図であり、図中１はトレッド部を、２は、トレッド部１の側部から半径方向内方へ延びる一対のサイドウォール部を、そして３は、サイドウォール部２の半径方向内端に連なるビード部をそれぞれ示す。
【００１５】
ここでは、タイヤの骨格構造をなし、タイヤの上記各部１，２，３を補強するカーカス４を、一枚以上のカーカスプライにて構成するとともに、それぞれのビード部３に配設したそれぞれのビードコア５間にトロイダルに延びる本体部と、各ビードコア５の周りで、タイヤ幅方向の内側から外側に向けて半径方向外方に巻上げた折り返し部を有するものとする。図中のカーカス４は、一枚のカーカスプライよりなるが、本発明のタイヤにおいては、カーカスプライの枚数は複数であってもよい。
【００１６】
また、図中６はベルトを示し、ベルト６は、カーカス４のクラウン部のタイヤ半径方向外側に配設した一枚以上のベルト層からなる。図中のベルト６は、二枚のベルト層よりなるが、本発明のタイヤにおいては、ベルト層の枚数はこれに限られるものではない。
【００１７】
この空気入りタイヤは、カーカス４及びベルト６の少なくとも一方がコーティングゴムで被覆したスチールコードの層を含む。即ち、カーカス４のカーカスプライの少なくとも一枚及び／又はベルト６のベルト層の少なくとも一層が、スチールコードの層であればよく、一枚以上のカーカスプライ及び一層以上のベルト層がスチールコードの層であってもよい。
【００１８】
そしてここでは、カーカス４及びベルト６の少なくとも一方で、スチールコードを被覆するコーティングゴムに、ゴム成分１００質量部に対し上記式（Ｉ）で表される化合物０．１〜１０質量部を配合してなるゴム組成物を用いる。式（Ｉ）で表される化合物は、レゾルシンやＲＦ樹脂よりも極性が低いため、極性の低いゴム成分と混ざり易い。そのため、式（Ｉ）の化合物を配合したゴム組成物は、レゾルシンやＲＦ樹脂を配合したゴム組成物よりも粘度が低く、ブルームし難く、経時変化が少なく、貯蔵期間に関わらず安定した接着性を発現することができる。本発明の空気入りタイヤを構成するカーカス及びベルトの少なくとも一方のスチールコードの層のコーティングゴムには、かかる低粘度で且つ接着安定性に優れたゴム組成物が用いられているため、該タイヤは製造時の加工性が高いことに加え、耐久性が高く且つ安定している。
【００１９】
上記式（Ｉ）において、ｎは０〜１００の整数であり、好ましくは０である。
【００２０】
また、Ｒ^１は、夫々独立して水素、ハロゲン、又は炭素数１〜６の直鎖若しくは分岐のアルキル基である。具体的に、炭素数１〜６のアルキル基としては、メチル基、エチル基、ｎ−プロピル基、ｉ−プロピル基、ｎ−ブチル基、ｉ−ブチル基、ｔ−ブチル基、ペンチル基（異性体を含む）、ヘキシル基（異性体を含む）等を例示することができる。これらの中でも、Ｒ^１としては水素が好ましい。
【００２１】
更に、Ｒ^２は、夫々独立して水素、水酸基、ハロゲン、又は炭素数１〜６の直鎖若しくは分岐のアルキル基である。具体的に、炭素数１〜６のアルキル基としては、メチル基、エチル基、ｎ−プロピル基、ｉ−プロピル基、ｎ−ブチル基、ｉ−ブチル基、ｔ−ブチル基、ペンチル基（異性体を含む）、ヘキシル基（異性体を含む）等を例示することができる。これらの中でも、Ｒ^２としては水素及び水酸基が好ましく、水素がより好ましい。
【００２２】
また更に、Ｒ^３は、夫々独立して炭素数１〜１２の直鎖若しくは分岐のアルキレン基である。具体的に、炭素数１〜１２のアルキレン基としては、メチレン基、エチレン基の他、プロピレン基、ブチレン基、ヘキサメチレン基、オクタメチレン基及びそれらの異性体等を例示することができる。これらの中でも、Ｒ^３としては、メチレン基、エチレン基、プロピレン基（異性体を含む）、ブチレン基（異性体を含む）が好ましい。
【００２３】
上記式（Ｉ）で表される化合物は、 １種単独で使用してもよく、２種以上を併用してもよい。
【００２４】
式（Ｉ）で表される化合物の配合量は、ゴム成分１００質量部に対し０．１〜１０質量部であり、０．３〜６質量部が好ましい。式（Ｉ）で表される化合物の配合量が０．１質量部未満では、耐湿熱接着性を向上させる効果が低く、１０質量部を超えると、該化合物がブルームし、接着性が低下する。
【００２５】
上記コーティングゴムに用いられるゴム組成物のゴム成分には、天然ゴムの他；ビニル芳香族炭化水素／共役ジエン共重合体、ポリイソプレンゴム、ブタジエンゴム、ブチルゴム、ハロゲン化ブチルゴム、エチレン−プロピレンゴム等の合成ゴム等、通常タイヤに用いられるゴム成分の少なくとも１種を、本発明の効果を損なわない範囲で適宜用いることができるが、スチールコードのコーティングゴムには耐破壊性が要求されるため、耐破壊性の観点から、該ゴム成分は、７５質量％以上の天然ゴムを含むのが好ましい。また、前記合成ゴムの中では、ポリイソプレンゴムが好ましい。
【００２６】
上記コーティングゴムに用いられるゴム組成物は、更に接着促進剤として有機酸コバルト塩を前記ゴム成分１００質量部に対しコバルト量として０．０３〜１質量部配合してなるのが好ましい。有機酸コバルト塩の配合量が０．０３質量部未満では、ゴム組成物とスチールコードとの接着性が充分でなく、１質量部を超えると、ゴム組成物の老化特性が悪化し過ぎる。該有機酸コバルト塩としては、ナフテン酸コバルト、ステアリン酸コバルト、ネオデカン酸コバルト、ロジン酸コバルト、バーサチック酸コバルト、トール油酸コバルト等が挙げられる。該有機酸コバルト塩は、有機酸の一部をホウ酸等で置き換えた複合塩でもよい。具体的には、マノボンド（商標：ＯＭＧ製）が挙げられる。
【００２７】
また、上記ゴム組成物には、加硫剤としての硫黄がゴム成分１００質量部に対し１〜１０質量部、好ましくは３〜８質量部配合される。硫黄の配合量が１質量部未満では、スチールコードとの接着性が不十分であり、１０質量部を超えると、過加硫となり接着性が低下する。
【００２８】
上記コーティングゴムに用いられるゴム組成物には、上記式（Ｉ）の化合物、ゴム成分、有機酸コバルト塩、硫黄の他、カーボンブラック及びシリカ等の充填剤、シリカ用のシランカップリング剤、加硫促進剤、軟化剤、酸化亜鉛、ステアリン酸、老化防止剤としての酸化防止剤、オゾン劣化防止剤等のゴム業界で通常使用される配合剤を本発明の効果を損なわない範囲で適宜配合することができる。
【００２９】
なお、本発明の空気入りタイヤのカーカス及びベルトの少なくとも一方に用いられるスチールコードは、ゴムとの接着を良好にするために黄銅、亜鉛或いはこれらにニッケルやコバルトを含有する金属でメッキ処理されているのが好ましく、黄銅メッキ処理されているのが特に好ましい。また、該コードのサイズ、撚り数、撚り条件等は、タイヤの要求性能に応じて適宜選択される。
【００３０】
上記ゴム組成物は、インターナルミキサー等の混練り機を用いて混練りされ、ロール等でシート状に加工され、更に加工されたゴムシート２枚がスチールコードを挟んだ状態に成形加工されて、カーカスプライやベルト層が形成される。形成されたベルト層は常法に従ってカーカスのタイヤ半径方向外側に積層され、その他の部材と共に本発明の空気入りタイヤを構成する。本発明の空気入りタイヤのトレッド踏面部、サイドウォール部及びビード部等には、通常のタイヤのそれらの部分に使用される材料、形状、配置を適宜採用することができる。
【００３１】
【実施例】
以下に、実施例を挙げて本発明を更に詳しく説明するが、 本発明は下記の実施例に何ら限定されるものではない。
【００３２】
表１に示す配合処方のゴム組成物を常法により調製し、以下に示す方法で加工性、耐湿熱接着性及び接着安定性を評価した。結果を表１に示す。
【００３３】
（１）加工性評価
ＪＩＳ Ｋ６３００−１：２００１に準拠して、上記ゴム組成物のムーニー粘度ＭＬ_１＋４（１３０℃）を測定し、比較例１を１００として指数表示した。指数値が小さい程、粘度が低く加工性が良好であることを示す。
【００３４】
（２）耐湿熱接着性評価
スチールコードを上記ゴム組成物で被覆してベルト層を形成し、該ベルト層を備え、サイズ１８５／７０ Ｒ １４のラジアルタイヤを常法により試作した。これらの試作タイヤを、１００℃、９５％ＲＨに保持した恒温恒湿槽中に５週間放置した後、タイヤからベルト層を取り出し、ベルト層中のスチールコードを引張試験機により５０ｍｍ／ｍｉｎの速度で引張り、露出したスチールコードのゴムの被覆状態を目視で観察し、その被覆率を０〜１００％で表示して耐湿熱接着性の指標とした。数値が大きい程、接着性が高く良好であることを示す。
【００３５】
（３）接着安定性評価
前記成形後のグリーンタイヤを４０℃、８０％ＲＨで７日間放置した後、加硫したタイヤからベルト層を取り出し、ベルト層中のスチールコードを引張試験機により５０ｍｍ／ｍｉｎの速度で引張り、露出したスチールコードのゴムの被覆状態を目視で観察し、その被覆率を０〜１００％で表示して接着安定性の指標とした。
【００３６】
【表１】

【００３７】
比較例１に比べて、レゾルシン又はＲＦ樹脂を配合したゴム組成物をベルト層のコーティングゴムに用いた比較例２又は３のタイヤは、スチールコードとコーティングゴムとの耐湿熱接着性が向上するものの、コーティングゴムに用いたゴム組成物のムーニー粘度が著しく上昇し、更に接着安定性が低下していた。
【００３８】
一方、式（Ｉ）の化合物を配合したゴム組成物をベルト層のコーティングゴムに用いた実施例１〜４のタイヤは、比較例１に比べてスチールコードとコーティングゴムとの耐湿熱接着性及び接着安定性が向上しており、且つコーティングゴムに用いたゴム組成物のムーニー粘度の上昇が抑制されていた。
【００３９】
但し、実施例１〜３及び比較例４の結果から、式（Ｉ）の化合物の配合量が増えるに従い、ゴム組成物のムーニー粘度が上昇し、且つ接着安定性が低下する傾向があるので、式（Ｉ）の化合物の配合量は、ゴム成分１００質量部に対し１０質量部以下である必要がある。
【００４０】
【発明の効果】
以上に説明したように、本発明によれば、カーカス及びベルトの少なくとも一方がコーティングゴムで被覆したスチールコードの層を含む空気入りタイヤにおいて、カーカス及びベルトの少なくとも一方で、スチールコードを被覆するコーティングゴムに、式（Ｉ）の化合物を所定量配合してなるゴム組成物を適用することにより、該ゴム組成物の粘度が低いためタイヤ製造時の加工性が高いことに加え、スチールコードとコーティングゴムとの耐湿熱接着性及び接着安定性が高いため、高く且つ安定した耐久性を有する空気入りタイヤを提供することができる。
【図面の簡単な説明】
【図１】本発明の実施の形態を示す横断面図である。
【符号の説明】
１ トレッド部
２ サイドウォール部
３ ビード部
４ カーカス
５ ビードコア
６ ベルト[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention improves durability by suppressing wet heat deterioration of at least one of a carcass and a belt in which at least one of a pneumatic tire and, in particular, at least one carcass ply and / or at least one belt layer is formed of a steel cord layer. The present invention relates to an improved pneumatic tire. More specifically, a rubber composition which is excellent in processability, is not influenced by standing conditions in a manufacturing process, has little change over time, and has a stable and good initial adhesion to a steel cord and a moisture and heat resistant adhesion to a steel cord coating rubber. It relates to the pneumatic tire used.
[0002]
[Prior art]
Since the development of steel radial tires by Michelin in the late 1940's, steel cord reinforced pneumatic tires using steel cord as a reinforcing material for at least one of a carcass and a belt have been steadily increasing their share. In particular, in recent years, with the shift to belted bias tires and radial tires, the steel cord reinforced pneumatic tires have remarkably increased their share, and also have rapidly increased their share for trucks.
[0003]
On the other hand, in recent years, the performance required for automobile tires has become increasingly severe, and further improvement in tire durability is desired. In the above steel cord reinforced pneumatic tire, it is important to ensure the adhesion between the steel cord and the coating rubber covering the cord, and if this adhesion is reduced, the durability of at least one of the carcass and the belt is reduced. Further, it is known that a problem is caused in the durability of the tire. Therefore, various studies have been made to improve the adhesion between the steel cord and the coating rubber.
[0004]
For example, there is a technique (see Patent Document 1) for blending resorcinol or a resorcinol-formaldehyde resin (hereinafter referred to as “RF resin”) obtained by condensing resorcinol and formaldehyde into a rubber composition. By blending, the wet heat resistance between the steel cord and the rubber is dramatically improved. However, the rubber composition containing resorcinol and RF resin has high viscosity and has a problem in processability. In addition, since resorcinol and RF resin have high polarity and poor compatibility with a rubber component having low polarity, in a rubber composition containing the resorcinol and RF resin, mixing, storage, and leaving conditions in a tire manufacturing process are not considered. This causes a so-called bloom in which the resorcin and the RF resin are deposited. Therefore, the rubber composition has a large change with time and has a problem in stability of adhesiveness.
[0005]
[Patent Document 1]
JP 2001-234140 A
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to have high wet heat resistance as high as a rubber composition containing resorcinol or RF resin, and suppress the increase in viscosity and bloom seen when resorcinol or RF resin is added. By applying a rubber composition capable of expressing stable adhesion with a small change with time to the coating rubber of the steel cord layer of at least one of the carcass and the belt, in addition to being excellent in workability during tire production, An object of the present invention is to provide a highly durable and stable pneumatic tire.
[0007]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to achieve the above object, and as a result, applied a rubber composition obtained by compounding a predetermined amount of a compound having a specific structure to a coating rubber of a steel cord layer of at least one of a carcass and a belt. By doing so, the processability during tire production is improved as compared with the case where a rubber composition containing resorcinol or RF resin is applied, and the wet heat resistance between the steel cord and the coating rubber is high and the adhesion is high. Since the properties are stable, the inventors have found that the manufactured tire has high and stable durability, and have completed the present invention.
[0008]
That is, the pneumatic tire of the present invention includes a carcass composed of one or more carcass plies, and a belt composed of one or more belt layers disposed outside the carcass in the tire radial direction. In a pneumatic tire including a layer of a steel cord at least one of which is coated with a coating rubber, at least one of a carcass and a belt is coated on a coating rubber coating a steel cord with the following formula (I) based on 100 parts by mass of a rubber component. It is characterized by using a rubber composition containing 0.1 to 10 parts by mass of a compound represented by the formula.
Embedded image

Wherein n is an integer of 0 to 100; R ¹ is each independently hydrogen, halogen, or a linear or branched alkyl group having 1 to 6 carbon atoms; R ² is each independently hydrogen A hydroxyl group, a halogen, or a linear or branched alkyl group having 1 to 6 carbon atoms; R ³ is each independently a linear or branched alkylene group having 1 to 12 carbon atoms.)
[0009]
In a preferred example of the pneumatic tire of the present invention, in the compound represented by the formula (I), R ¹ is hydrogen, R ² is hydrogen or a hydroxyl group, and R ³ is an ethylene group, a propylene group and a butylene group. Either.
[0010]
In another preferable example of the pneumatic tire of the present invention, n is 0 in the compound represented by the formula (I).
[0011]
In another preferred embodiment of the pneumatic tire of the present invention, the rubber composition used for the coating rubber further contains an organic acid cobalt compound in an amount of 0.03 to 1 part by mass as a cobalt amount based on 100 parts by mass of the rubber component. It becomes.
[0012]
In another preferred embodiment of the pneumatic tire of the present invention, the rubber component comprises at least 75% by mass of natural rubber (NR) and the balance is synthetic rubber.
[0013]
In another preferred embodiment of the pneumatic tire of the present invention, the rubber component comprises at least one of a natural rubber and a polyisoprene rubber (IR).
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail. FIG. 1 is a cross-sectional view showing an embodiment of the present invention, in which 1 is a tread portion, 2 is a pair of sidewall portions extending radially inward from a side portion of the tread portion 1, and 3 is And a bead portion connected to the radially inner end of the sidewall portion 2.
[0015]
Here, the carcass 4 which forms the skeleton structure of the tire and reinforces the above-mentioned parts 1, 2, 3 of the tire is constituted by one or more carcass plies, and the respective bead cores arranged on the respective bead parts 3 It has a body portion extending toroidally between the five, and a folded portion wound around each bead core 5 radially outward from the inside to the outside in the tire width direction. Although the carcass 4 in the figure is composed of one carcass ply, the number of carcass plies may be plural in the tire of the present invention.
[0016]
In the figure, reference numeral 6 denotes a belt, and the belt 6 is composed of one or more belt layers disposed radially outside the crown portion of the carcass 4 in the tire radial direction. Although the belt 6 in the figure includes two belt layers, the number of belt layers in the tire of the present invention is not limited to this.
[0017]
The pneumatic tire includes a steel cord layer in which at least one of the carcass 4 and the belt 6 is coated with a coating rubber. That is, at least one of the carcass plies of the carcass 4 and / or at least one of the belt layers of the belt 6 may be a steel cord layer, and one or more of the carcass plies and one or more belt layers may be a steel cord layer. It may be.
[0018]
Here, at least one of the carcass 4 and the belt 6 is mixed with 0.1 to 10 parts by mass of the compound represented by the above formula (I) per 100 parts by mass of the rubber component in the coating rubber covering the steel cord. A rubber composition is used. Since the compound represented by the formula (I) has lower polarity than resorcinol and RF resin, it is easy to mix with the rubber component having low polarity. Therefore, the rubber composition containing the compound of the formula (I) has a lower viscosity than the rubber composition containing the resorcinol or RF resin, is less likely to bloom, has less change with time, and has stable adhesiveness regardless of the storage period. Can be expressed. Since the rubber composition having low viscosity and excellent adhesion stability is used for the coating rubber of the steel cord layer of at least one of the carcass and the belt constituting the pneumatic tire of the present invention, the tire is In addition to high workability at the time of manufacturing, durability is high and stable.
[0019]
In the above formula (I), n is an integer of 0 to 100, preferably 0.
[0020]
R ¹ is independently hydrogen, halogen, or a linear or branched alkyl group having 1 to 6 carbon atoms. Specifically, examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an i-butyl group, a t-butyl group, a pentyl group (isomer Hexyl group (including isomers) and the like. Among them, hydrogen is preferable as R ¹ .
[0021]
Further, R ² is each independently hydrogen, a hydroxyl group, a halogen, or a linear or branched alkyl group having 1 to 6 carbon atoms. Specifically, examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an i-butyl group, a t-butyl group, a pentyl group (isomer Hexyl group (including isomers) and the like. Among them, R ² is preferably hydrogen and a hydroxyl group, and more preferably hydrogen.
[0022]
Further, R ³ is each independently a linear or branched alkylene group having 1 to 12 carbon atoms. Specifically, examples of the C1-C12 alkylene group include a methylene group, an ethylene group, a propylene group, a butylene group, a hexamethylene group, an octamethylene group, and isomers thereof. Among them, R ³ is preferably a methylene group, an ethylene group, a propylene group (including isomers), and a butylene group (including isomers).
[0023]
The compounds represented by the above formula (I) may be used alone or in combination of two or more.
[0024]
The compounding amount of the compound represented by the formula (I) is 0.1 to 10 parts by mass, preferably 0.3 to 6 parts by mass, per 100 parts by mass of the rubber component. When the compounding amount of the compound represented by the formula (I) is less than 0.1 part by mass, the effect of improving the wet heat resistance is low, and when it exceeds 10 parts by mass, the compound blooms and the adhesiveness decreases. .
[0025]
The rubber component of the rubber composition used in the above coating rubber includes natural rubber in addition to vinyl aromatic hydrocarbon / conjugated diene copolymer, polyisoprene rubber, butadiene rubber, butyl rubber, halogenated butyl rubber, ethylene-propylene rubber, and the like. At least one kind of rubber component usually used for tires, such as synthetic rubber, can be appropriately used within a range that does not impair the effects of the present invention. However, since coating rubber of steel cord is required to have fracture resistance, From the viewpoint of fracture resistance, the rubber component preferably contains 75% by mass or more of natural rubber. Further, among the synthetic rubbers, polyisoprene rubber is preferable.
[0026]
It is preferable that the rubber composition used for the coating rubber further contains an organic acid cobalt salt as an adhesion promoter in an amount of 0.03 to 1 part by mass as a cobalt amount based on 100 parts by mass of the rubber component. If the amount of the organic acid cobalt salt is less than 0.03 parts by mass, the adhesion between the rubber composition and the steel cord is not sufficient. If the amount exceeds 1 part by mass, the aging characteristics of the rubber composition are excessively deteriorated. Examples of the organic acid cobalt salt include cobalt naphthenate, cobalt stearate, cobalt neodecanoate, cobalt rosinate, cobalt versatate, and cobalt tall oil. The organic acid cobalt salt may be a complex salt in which a part of the organic acid is replaced with boric acid or the like. Specific examples include Manobond (trademark: manufactured by OMG).
[0027]
Further, the rubber composition contains 1 to 10 parts by mass, preferably 3 to 8 parts by mass of sulfur as a vulcanizing agent per 100 parts by mass of the rubber component. If the amount of sulfur is less than 1 part by mass, the adhesion to the steel cord is insufficient. If the amount exceeds 10 parts by mass, the composition becomes over-vulcanized and the adhesion decreases.
[0028]
The rubber composition used in the coating rubber includes a compound of the formula (I), a rubber component, an organic acid cobalt salt, sulfur, a filler such as carbon black and silica, a silane coupling agent for silica, Compounding agents commonly used in the rubber industry, such as a sulfur accelerator, a softener, zinc oxide, stearic acid, an antioxidant as an antioxidant, and an antiozonant, are appropriately compounded within a range that does not impair the effects of the present invention. be able to.
[0029]
The steel cord used for at least one of the carcass and the belt of the pneumatic tire of the present invention is plated with brass, zinc or a metal containing nickel or cobalt in these in order to improve adhesion with rubber. And it is particularly preferable that it is subjected to a brass plating treatment. The size, number of twists, twisting conditions, etc. of the cord are appropriately selected according to the required performance of the tire.
[0030]
The rubber composition is kneaded using a kneading machine such as an internal mixer, processed into a sheet shape by a roll or the like, and further processed into two rubber sheets sandwiching a steel cord. , A carcass ply and a belt layer are formed. The formed belt layer is laminated on the outside of the carcass in the tire radial direction according to a conventional method, and constitutes the pneumatic tire of the present invention together with other members. Materials, shapes, and arrangements used for those portions of a normal tire can be appropriately adopted for the tread tread portion, the sidewall portion, the bead portion, and the like of the pneumatic tire of the present invention.
[0031]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples.
[0032]
A rubber composition having the compounding formulation shown in Table 1 was prepared by a conventional method, and the processability, wet heat and heat resistance and adhesion stability were evaluated by the following methods. Table 1 shows the results.
[0033]
(1) Evaluation of processability The Mooney viscosity ML _{1 + 4} (130 ° C.) of the rubber composition was measured in accordance with JIS K6300-1: 2001, and the index was indicated as an index with Comparative Example 1 being 100. The smaller the index value, the lower the viscosity and the better the processability.
[0034]
(2) Evaluation of Wet and Heat Adhesion Resistance A steel cord was coated with the above rubber composition to form a belt layer, and a radial tire having the belt layer and having a size of 185/70 R14 was prototyped by an ordinary method. After leaving these prototype tires in a thermo-hygrostat kept at 100 ° C. and 95% RH for 5 weeks, the belt layer was taken out from the tire, and the steel cord in the belt layer was subjected to a tensile tester at a speed of 50 mm / min. The coated state of the rubber of the exposed steel cord was visually observed, and the coating rate was indicated as 0 to 100%, which was used as an index of wet heat and heat resistance. The higher the value, the higher the adhesion and the better.
[0035]
(3) Evaluation of adhesion stability After the molded green tire was allowed to stand at 40 ° C. and 80% RH for 7 days, the belt layer was taken out from the vulcanized tire, and the steel cord in the belt layer was removed by a tensile tester at 50 mm / mm. The steel cord was pulled at a speed of min, and the exposed state of the steel cord covered with rubber was visually observed, and the coverage was indicated as 0 to 100%, which was used as an index of adhesion stability.
[0036]
[Table 1]

[0037]
Compared to Comparative Example 1, the tire of Comparative Example 2 or 3 using a rubber composition containing resorcinol or RF resin for the coating rubber of the belt layer has improved wet-heat resistance between the steel cord and the coating rubber. In addition, the Mooney viscosity of the rubber composition used for the coating rubber was significantly increased, and the adhesion stability was further decreased.
[0038]
On the other hand, the tires of Examples 1 to 4 in which the rubber composition containing the compound of the formula (I) was used as the coating rubber for the belt layer showed better wet-heat adhesion between the steel cord and the coating rubber than Comparative Example 1. The adhesion stability was improved, and the rise in Mooney viscosity of the rubber composition used for the coating rubber was suppressed.
[0039]
However, from the results of Examples 1 to 3 and Comparative Example 4, as the amount of the compound of the formula (I) increases, the Mooney viscosity of the rubber composition tends to increase, and the adhesive stability tends to decrease. The compounding amount of the compound of the formula (I) needs to be 10 parts by mass or less based on 100 parts by mass of the rubber component.
[0040]
【The invention's effect】
As described above, according to the present invention, in a pneumatic tire including a steel cord layer in which at least one of the carcass and the belt is coated with a coating rubber, the coating that covers the steel cord in at least one of the carcass and the belt By applying a rubber composition obtained by compounding a predetermined amount of the compound of the formula (I) to rubber, the viscosity of the rubber composition is low, so that the workability during tire production is high, and the steel cord and the coating are coated. Since the wet heat resistance and the adhesion stability to rubber are high, a pneumatic tire having high and stable durability can be provided.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass 5 Bead core 6 Belt

Claims (6)

A steel cord comprising: a carcass comprising one or more carcass plies; and a belt comprising one or more belt layers disposed radially outside the carcass in a tire direction, wherein at least one of the carcass and the belt is coated with a coating rubber. In a pneumatic tire including a layer comprising
A rubber composition obtained by compounding 0.1 to 10 parts by mass of a compound represented by the following formula (I) with respect to 100 parts by mass of a rubber component to a coating rubber for covering a steel cord with at least one of a carcass and a belt. A pneumatic tire characterized by being used.

Wherein n is an integer of 0 to 100; R ¹ is each independently hydrogen, halogen, or a linear or branched alkyl group having 1 to 6 carbon atoms; R ² is each independently hydrogen A hydroxyl group, a halogen, or a linear or branched alkyl group having 1 to 6 carbon atoms; R ³ is each independently a linear or branched alkylene group having 1 to 12 carbon atoms.) In the compound represented by the formula (I), R ¹ is hydrogen, R ² is hydrogen or a hydroxyl group, and R ³ is any one of an ethylene group, a propylene group and a butylene group. A pneumatic tire according to claim 1. 3. The pneumatic tire according to claim 1, wherein n is 0 in the compound represented by the formula (I). The rubber composition according to any one of claims 1 to 3, wherein the organic acid cobalt salt is further compounded in an amount of 0.03 to 1 part by mass as a cobalt amount based on 100 parts by mass of the rubber component. Pneumatic tire. The pneumatic tire according to any one of claims 1 to 4, wherein the rubber component comprises 75% by mass or more of natural rubber and the balance is synthetic rubber. The pneumatic tire according to any one of claims 1 to 4, wherein the rubber component comprises at least one of a natural rubber and a polyisoprene rubber.

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