JP2005343301A - Pneumatic radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial tire having a cap ply improving high-speed durability and uniformity. <P>SOLUTION: The cap ply 1 of the pneumatic radial tire T aligns a primary twisted yarn 9a twisting rayon filament bundle and a primary twisted yarn 9b twisting nylon filament bundle in the same direction of the primary twisted yarn, and is formed by a complex cord 9 which is twisted in the opposite direction to the twisting direction of the primary yarns 9a, 9b. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pneumatic radial tire, and more particularly to a pneumatic radial tire excellent in high speed durability and uniformity.

  In recent years, in pneumatic radial tires, in order to further improve high-speed performance and driving stability, a tire in which a reinforcing layer is formed by continuously winding a cord substantially parallel to the tire circumferential direction on the outer side of a belt layer of a tread portion. It is used to improve the durability of the tire by suppressing the separation of the belt edge due to the rising phenomenon of the belt layer end during high-speed running, the growth of the outer periphery of the tire, and the like.

  In such radial tires, it is common to provide a belt reinforcement layer called a cap ply in which a low elastic modulus cord such as nylon is continuously wound substantially parallel to the tire circumferential direction on the outer side of the belt layer. there were. However, since the nylon cord has a small tensile elastic modulus, it is difficult to secure the tensile rigidity in the tire circumferential direction to cope with the increase in load on the belt portion accompanying the recent super flattening.

  For this reason, it is conceivable to use a high modulus organic fiber such as an aramid fiber having a high tensile modulus for the cap ply. The belt part cannot follow and lacks adhesion to the vulcanizing kiln, not only lowering the vulcanization formability of the tire and worsening the uniformity, but also said that the belt layer is unevenly disturbed and the durability is lowered. There's a problem.

In order to solve such a problem of high elastic modulus fibers, proposals have been made to use a high elastic modulus filament and a low elastic modulus filament, or a composite cord obtained by twisting those yarns (Patent Documents 1 and 2). ).
JP-A-1-247204 JP-A-4-2832

  However, in the composite cord in which the high elastic modulus filament of the aramid fiber or the aromatic polyester fiber described in the above-mentioned literature 1 and the low elastic modulus filament such as nylon fiber are twisted together, the adhesion with the rubber is ensured and the high-speed durability or In order to improve uniformity, a special bonding treatment solution for aramid fibers must be used, and special materials such as aramid fibers are expensive, so they are applied to general-purpose radial tires from a cost standpoint. There is a problem that it is difficult.

  Moreover, although it is disclosed by literature 2 that the nylon fiber extended | stretched by high magnification is used as a high elastic modulus code | cord | chord, the complexity that an extending | stretching process increases at the time of code | cord manufacture is accompanied.

  Accordingly, an object of the present invention is to vulcanize a high elastic modulus fiber by applying a composite cord that can be bonded with a general RFL processing solution and is not accompanied by an increase in the number of steps to a cap ply. An object of the present invention is to provide a pneumatic radial tire that can solve the problem of lifting at the time and can improve high-speed durability and uniformity.

  The invention according to claim 1 is arranged in a radial arrangement of the carcass layer folded around the bead core of the bead part from the tread part through the sidewall part, and arranged inside the tread part and radially outside the carcass layer. In a pneumatic radial tire having a belt layer and a reinforcing layer formed by winding a cord around the belt layer substantially parallel to the tire circumferential direction, the cord of the reinforcing layer includes a rayon filament bundle and a nylon filament bundle. And the total fineness of the rayon filament is 2600 dtex or less, and the composition ratio of the rayon filament comprises 50 to 70% of the total fineness of the cord. A pneumatic radial tire that is subjected to RFL treatment and heat treatment.

  The invention according to claim 2 is characterized in that the composite cord comprises at least one twisted yarn in which a rayon filament bundle is twisted, and at least one twisted yarn in which a nylon filament bundle is twisted in the same direction as the twisted yarn. 2. The pneumatic radial tire according to claim 1, wherein the pneumatic radial tire according to claim 1 is formed by aligning and twisting in a direction opposite to a twisting direction of these lower twisted yarns.

  The invention according to claim 3 is the pneumatic radial tire according to claim 1 or 2, wherein a treatment temperature in the heat treatment is 170 to 180 ° C.

  According to the pneumatic radial tire of the present invention, since the composite cord constituting the cap ply is constituted by the rayon filament and the nylon filament as described above, the nylon is used at a low load in order to correspond to the lift rate at the time of tire vulcanization. Increases elongation to improve tire accuracy and improve uniformity and durability, and the high modulus of rayon and high shrinkage of nylon act on the centrifugal force and heat generation during high-speed driving, and the belt layer circumference The above-mentioned tensile rigidity can be secured, and the durability of the tire can be improved by suppressing the separation of the edge portion and the growth of the tire outer periphery due to the rising phenomenon of the belt layer end portion. Further, since the composite cord is composed of rayon and nylon, high adhesion to rubber can be obtained with a general RFL treatment liquid.

  According to the present invention, by applying a composite cord composed of rayon and nylon to the cap ply, air that improves high-speed durability and uniformity without the need for additional cord manufacturing processes or special bonding treatment An input radial tire can be provided.

  Hereinafter, embodiments of the present invention will be described.

  FIG. 1 is a tire sectional view showing a pneumatic radial tire for passenger cars (hereinafter referred to as a radial tire) T according to an embodiment of the present invention, and FIG. 2 is a development view of a cap ply portion of a tread portion.

  The radial tire T has a tread portion 2, sidewall portions 3 that extend inward in the tire radial direction from both ends thereof, and bead portions 4 that are positioned at the inner ends of both sidewall portions 3. Each bead portion 4 has an annular bead core 5 embedded therein, and a carcass layer 6 is mounted between the bead cores 5 and 5, and two belt layers 7 are provided on the outer peripheral side of the carcass layer 6 in the tread portion 2. Are arranged so that the cords cross each other. The carcass layer 6 is made of an organic fiber cord such as polyester, rayon or nylon, and the belt layer 7 is made of a high elastic modulus cord such as a steel cord or an aramid fiber.

  Further, a cap ply 1 made of one reinforcing layer is disposed on the tread portion 2 outside the belt layer 7. As shown in FIG. 2, this cap ply 1 has a reinforcing cord 9 or a ribbon-like continuous strip having a width of 5 to 15 mm in which about 2 to 10 cords 9 are arranged and covered with rubber in the tire circumferential direction. On the other hand, the belt layer 7 is continuously wound at a cord angle of 0 to 10 °.

  The number of layers constituting the cap ply 1 is not particularly limited, and may be one layer as shown in the figure, or may be two layers or three or more layers. Further, the reinforcing layer of the belt layer 7 may be provided like the cap ply 1 covering the entire width of the belt layer 7 as shown in the figure, or only the end of the belt layer 7 as shown in FIG. The edge ply 8 may be formed, or both the cap ply 1 and the edge ply 8 may be provided.

  The reinforcing cords constituting the cap ply 1 and the edge ply 8 are composed of a composite cord 9 as shown in FIG. The composite cord 9 is formed by drawing two lower twisted yarns 9a and 9b that are twisted in the same direction and applying an upper twist in a direction opposite to the twisted direction of the lower twisted yarns 9a and 9b. . As the number of the lower twisted yarns constituting the composite cord 9, two lower twisted yarns 9a and 9b are preferable from the viewpoint of productivity as shown in the figure, but may be configured by three or more.

  The lower twisted yarn 9a constituting the composite cord 9 is obtained by twisting a rayon filament bundle in the Z direction, and the lower twisted yarn 9b is obtained by twisting a nylon filament bundle such as nylon 6, 66, 46 in the same Z direction as the lower twisted yarn 9a. The composite cord 9 is formed by aligning the lower twisted yarns 9a and 9b and twisting them in the S direction opposite to the twisted direction of the lower twisted yarns 9a and 9b.

  The composite cord 9 is obtained by twisting together a rayon filament bundle and a nylon filament bundle that are arranged together without using the lower twisted yarns 9a and 9b subjected to the lower twist as described above. Alternatively, a cord obtained by randomly arranging and twisting a small bundle of filaments of rayon and nylon may be used. The rayon used for the composite cord 9 is preferably a super 2 having a high strength level, and is preferably a super 3 having a higher grade.

  Here, it is preferable that the total fineness of the rayon filament constituting the composite cord 9 is 2600 dtex or less. It is disadvantageous to the properties, making it difficult to use the cap ply 1 as a reinforcing cord, and the cord diameter becomes larger in order to achieve both the high modulus of rayon and the low-load elongation property of nylon.

  The composition ratio of the rayon filament and the nylon filament of the composite cord 9 is preferably such that the ratio of the rayon filament constitutes 50 to 70% of the total fineness of the composite cord 9. When the rayon ratio is less than 50%, the cord layer lacks the restraint effect of the belt layer and the belt layer cannot be sufficiently raised during high speed running, resulting in insufficient durability. Nylon cannot exert the effect of elongation at low load, and it becomes difficult to follow lifting during vulcanization.

  The adhesive treatment of the composite cord 9 used in the present invention can be performed using a general known RFL treatment liquid used for nylon cord treatment. This RFL treatment liquid is obtained, for example, by adding a solution obtained by reacting resorcin and formalin in an alkaline aqueous solution to natural rubber or synthetic rubber latex and aging. The RFL treatment is performed by dipping the cord into the RFL liquid by a dipping treatment apparatus normally used in the rubber industry and then drying the cord.

  The heat treatment of the composite cord 9 is usually performed by a dipping processing apparatus continuously after the RFL processing. That is, after the composite cord 9 is dipped in the RFL treatment liquid and subjected to dipping treatment, the RFL treatment liquid is dried in the drying treatment (dry) zone at a predetermined temperature, and then the tension heat treatment ( The cord physical properties are adjusted by sequentially passing through a heat stretch) zone and a tension relaxation heat treatment (heat relax) zone under a predetermined tension, heat treatment and heat setting, and then cooled to form a dip cord.

  In the present invention, the heat treatment temperature in the heat stretch zone and the heat relaxation zone is set to 170 to 180 ° C., thereby preventing the heat degradation of the rayon without impairing various physical properties such as high modulus, strength, adhesiveness, The properties of nylon such as low-load elongation characteristics and adhesiveness can be obtained, and cord properties useful as a cap ply reinforcement cord are provided.

  If the heat treatment temperature is less than 170 ° C, the heat treatment of nylon is insufficient, and the desired elongation, shrinkage and adhesion at low load cannot be obtained. If the heat treatment temperature exceeds 180 ° C, the modulus and strength are deteriorated due to rayon deterioration. The high-speed durability becomes insufficient.

  That is, the composite cord 9 used in the present invention exhibits a high elongation due to the characteristics of nylon in the low load region, and easily follows the lifting during vulcanization to make the belt layer uniform and uniform. Steering stability can be improved. In addition, after the composite cord is stretched morphologically by the lift during vulcanization, the elongation decreases and the high modulus of rayon acts, and the shrinkage stress of the nylon increases and the belt contracts due to contraction stress due to heat generation during running. The effect of tightening the layers is also synergistic, and it is possible to suppress the rising of the belt layer end and the growth of the outer periphery during high-speed running, thereby improving the high-speed durability of the tire.

  Hereinafter, the present invention will be described in more detail based on examples.

  Using the lower twisted yarns (A) and (B) made of rayon filaments and nylon 66 filaments according to the specifications listed in Table 1, each composite cord is prepared by twisting them together and twisting them together. After dipping using a general RFL treatment solution for nylon with a commonly used dipping treatment apparatus and drying in a dry zone, heat treatment was performed under the heat treatment conditions (temperature x time) described in the table to create a dip code. . In the heat treatment condition column of the table, the dry zone is abbreviated as 1Z, the heat stretch zone is 2Z, and the heat relaxation zone is abbreviated as 3Z.

  The cord strength of each of the obtained dip cords, the 2% elongation load and adhesive strength were measured in accordance with “Tensile test, T test (Method A)” described in JIS L1017, and are shown in the table.

  Using this dip cord, a ribbon-like continuous strip having a width of 10 mm is prepared from a topping sheet that has been stretched and covered with rubber according to the number of ends shown in the table, and this strip is continuously wound on the belt layer to form a one-ply cap. A test tire having a tire size of 195 / 50R15 82V shown in FIG. 1 and formed with a ply was manufactured, and the high-speed durability performance and uniformity of the tire were evaluated by the following methods. The carcass layer of the test tire is polyester 1670 dtex / 2 (end number 23/25 mm) 2-ply, and the belt layer is a steel cord 2 + 2 × 0.25 (end number 20.5 / 25 mm) with an intersection angle of 23 degrees. Two plies were used.

[High-speed durability]
After assembling the test tire on the standard rim, using a rotating drum with a drum diameter of 1707 mm under conditions of air pressure 300 kPa and load 3.4 kN, and running for a specified time in accordance with the high-speed durability test method of ECE-R30 Every 10 minutes, the speed was increased by 10 km / h, and the vehicle was run until the tire broke down. The distance traveled until the failure occurred is shown in the table as an index with Comparative Example 1 taken as 100. The larger the value, the better.

[Uniformity]
Radial force variation (RFV) was measured in accordance with JASO C607 automotive tire uniformity test method, and evaluation was performed based on Comparative Example 1. The results are shown in the table as “◯” for “same” or “excellent” as Comparative Example 1 and “x” for inferior 5% or more.

  As is clear from the results shown in Table 1, the tires of Examples 1 and 2 according to the present invention are greatly improved in high-speed durability with respect to the tire having the cap ply of the conventional configuration of Comparative Example 1, and the uniformity is Steering stability is stable at the same level or higher. Compared to the examples, Comparative Example 2 has a low rayon composition ratio and lacks modulus, so the high-speed durability is not improved as much as the Examples, and Comparative Example 3 is inferior in lifting tracking during vulcanization because the rayon ratio is too high. The belt accuracy decreased and the uniformity and durability deteriorated. In Comparative Example 4 in which the total fineness of the rayon was large, the cord diameter was increased, the tread volume was increased, the heat generation was high, and the blowout was performed early. Further, Comparative Example 5 having a high heat treatment temperature has a lower durability due to insufficient cord strength, and Comparative Example 6 having a lower processing temperature also results in a decrease in durability due to poor adhesion of nylon.

  As described above, the pneumatic radial tire of the present invention has excellent high-speed durability and at the same time improves uniformity, and various tires that require durability performance and steering stability, particularly flatness Suitable for large high-speed tires.

It is sectional drawing of the pneumatic radial tire of embodiment. FIG. 2 is a development view of a cap ply in a tread portion of the tire of FIG. 1. It is a side view of the composite cord of an embodiment. It is sectional drawing of the pneumatic radial tire provided with the edge ply.

Explanation of symbols

1 …… Cap ply 2 …… Tread part 3 …… Side wall part 4 …… Bead part 5 …… Bead core 6 …… Carcass layer 7 …… Belt layer 8 …… Edge ply 9 …… Composite cord T …… Pneumatic Radial tire

Claims (3)

A radial carcass layer folded from the tread portion through the sidewall portion around the bead core of the bead portion; and a belt layer disposed inside the tread portion and radially outside the carcass layer, and the belt In a pneumatic radial tire in which a reinforcing layer is formed by winding a cord substantially parallel to the tire circumferential direction on the outside of the layer,
The cord of the reinforcing layer is formed by twisting a rayon filament bundle and a nylon filament bundle, the total fineness of the rayon filament is 2600 dtex or less, and the composition ratio of the rayon filament is 50 to 50 of the total fineness of the cord. A pneumatic radial tire comprising a composite cord constituting 70%, wherein the composite cord is subjected to RFL treatment and heat treatment. The composite cord draws at least one primary twisted yarn obtained by twisting rayon filament bundles and at least one primary twisted yarn obtained by twisting a nylon filament bundle in the same direction as the primary twisted yarn, and twisting these primary twisted yarns The pneumatic radial tire according to claim 1, wherein the pneumatic radial tire is twisted in a direction opposite to the direction. The processing temperature in the said heat processing is 170-180 degreeC. The pneumatic radial tire of Claim 1 or 2 characterized by the above-mentioned.

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