JP2008223200A - Reinforcing cord and pneumatic radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reinforcing cord capable of giving a lightweight pneumatic radial tire low in rolling resistance, high in steering stability and high in durability as well, and to provide such a pneumatic radial tire enabling the performance of the reinforcing cords to be fully exhibited. <P>SOLUTION: The reinforcing cord to be used for tire reinforcement consists of such a cord that three or more first-twisted cords are arranged in parallel and then final-twisted in the opposite direction of the first twist, wherein among the three or more first-twisted cords, at least one of them differs in constituent fiber from the other(s). The pneumatic radial tire comprises a pair of left and right beads, a pair of left and right sidewalls joining to the beads respectively, and a tread situated in between these sidewalls. In this radial tire, there are carcass plies 75-90° in cord angle relative to both the directions of the tire in between the pair of beads and there are such one or more belt-reinforcing plies that cords cross one another at 10-35° relative to both the directions of the tire on the carcass plies at the tread, wherein at least one of the belt-reinforcing plies is composed of the reinforcing cords. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic radial tire that can be suitably employed as a pneumatic radial tire and is excellent in durability of a belt reinforcing layer.

  At present, steel belt radial tires that are generally used can provide much higher belt rigidity than when organic fiber cords such as rayon and polyester are used for the belt, so that they are extremely superior in terms of handling stability and wear resistance. Although it is excellent, on the other hand, the specific gravity of steel is high, so the rolling resistance is inferior, the belt weight is large, the centrifugal force during running is large, standing waves are likely to occur, and high-speed durability is poor, There are several problems such as the occurrence of rust due to the entry of rainwater and the like, leading to tire destruction.

  However, when using aramid fiber or carbon fiber twisted cord with high tensile elastic modulus as a belt reinforcement layer to solve these problems, steering stability and durability are improved compared to when rayon or polyester is used. Still, steel is not enough. Moreover, since the tensile modulus is high, it is difficult to improve the finishing accuracy during vulcanization molding.

On the other hand, as a belt reinforcement layer that is lightweight, excellent in rolling resistance and has sufficient steering stability, it is proposed in Patent Document 1 to use a hybrid cord in which a high elastic filament and a low elastic filament are twisted. However, a tire using the above-described hybrid cord as a belt reinforcing layer has a problem that durability inherent to a high elastic filament is low.
Japanese Patent Laid-Open No. 7-276913

  An object of the present invention is to provide a reinforcing cord capable of obtaining a pneumatic radial tire that is lightweight and has low rolling resistance, excellent steering stability, and excellent durability, and air capable of sufficiently exhibiting the performance of the reinforcing cord. The purpose is to provide a radial tire.

  The inventors of the present invention have reached the present invention as a result of intensive studies in order to solve the above problems. That is, the present invention relates to a reinforcing cord used for reinforcing a tire, and the reinforcing cord is arranged so that three or more lower twisted cords each having a lower twist are aligned and an upper twist is applied in a direction opposite to the lower twist. And at least one of the three or more lower twisted cords is a cord made of a fiber of a different type from the other lower twisted cords. .

  Another embodiment of the present invention includes a pair of left and right bead portions, a pair of left and right side wall portions respectively connected to the bead portion, and a tread portion positioned between the side wall portions. A carcass layer having a cord angle of 75 to 90 ° between two beat portions of the tire and a belt reinforcing layer of one or more layers in which a cord with respect to both directions of the tire intersects at 10 to 35 ° on the carcass layer in the tread portion A pneumatic radial tire having at least one of the belt reinforcing layers made of the above-described reinforcing cord.

  ADVANTAGE OF THE INVENTION According to this invention, the reinforcement cord from which the pneumatic radial tire which is lightweight, has small rolling resistance, is excellent in steering stability, and is excellent in durability can be provided. Moreover, according to the pneumatic radial tire of the present invention, the performance of the reinforcing cord can be sufficiently exhibited.

  The reinforcing cord of the present invention is a reinforcing cord used for reinforcing a tire. In the present invention, the reinforcing cord is composed of a cord in which three or more lower twisted cords each having a lower twist are aligned and subjected to an upper twist in a direction opposite to the lower twist, and the three or more lower twisted cords. Of the twisted cords, it is important that at least one of the lower twisted cords is a cord made of a different kind of fiber from the other lower twisted cords.

The present inventors have found that when a reinforcing cord having the above-described configuration is used for a pneumatic tire, a pneumatic tire that is light in weight, has low rolling resistance, is excellent in handling stability, and is excellent in durability.
Furthermore, the present inventors have found that when the above reinforcing cord is used in a pneumatic radial tire described below, the effect appears remarkably.

That is, a pair of left and right bead portions, a pair of left and right side wall portions respectively connected to the bead portion, and a tread portion located between the side wall portions, and a tire in both directions between the pair of bead portions. A carcass layer with a cord angle of 75 to 90 °, preferably 80 to 90 °, and a cord with respect to the tire circumferential direction intersects with the carcass layer in the tread portion at 10 to 35 °, preferably 12 to 35 ° 1 In a pneumatic radial tire having at least a belt reinforcing layer, when the belt reinforcing layer is composed of at least the above reinforcing cord, it is remarkable that it is light and has low rolling resistance, excellent driving stability and durability. It has been found that various effects can be obtained.
Therefore, the above-mentioned effect cannot be obtained with a cord obtained by simply twisting two lower twisted cords made of different types of fibers, and it is difficult to achieve both steering stability and durability.

  In the present invention, at least one of the above-mentioned three or more under-twist cords is carbon fiber, aromatic polyamide fiber, wholly aromatic polyester fiber, polyvinyl alcohol fiber having a strength of 13 cN / dtex or more, nylon 6 One or more kinds selected from polyamide fibers such as fibers and nylon 66 fibers, polyester fibers such as polyethylene terephthalate fibers and polyethylene naphthalate fibers, or vinylon fibers are preferable.

  The other lower twisted cord is different from the above-described fibers selected from polyamide fibers such as nylon 6 fibers and nylon 66 fibers, polyester fibers such as polyethylene terephthalate fibers and polyethylene naphthalate fibers, vinylon, and the like. It is preferable that the fibers are of more than one type.

  In particular, in the present invention, at least one lower twisted cord comprising one or more types of fibers selected from carbon fibers, aromatic polyamide fibers, wholly aromatic polyester fibers, or polyvinyl alcohol fibers having a strength of 13 cN / dtex or more. And lower elastic modulus made of one or more kinds of fibers selected from polyamide fibers such as nylon 6 fibers and nylon 66 fibers, polyester fibers such as polyethylene terephthalate fibers and polyethylene naphthalate fibers, or vinylon fibers. A combination with a twisted cord is preferred.

  The number of lower twisted cords constituting the reinforcing cord of the present invention is preferably 3-5, more preferably 3-4, and even more preferably 3. Further, when the reinforcing cord is a cord obtained by twisting three lower twisted cords, one lower twisted cord made of a fiber having a higher elastic modulus and two lower twisted cords made of a fiber having a lower elastic modulus. The combination of is preferable.

  In addition, as an elastic modulus of the fiber constituting the lower twisted cord, an initial elastic modulus obtained by measurement in accordance with JIS L1017 (2002) 8.8 is 300 cN / dtex or more for a fiber having a high elastic modulus. The fiber having a low elastic modulus is preferably 500 cN / dtex or more, and less than 300 cN / dtex, preferably 250 cN / dtex or less.

The twist number of the lower twist is preferably 10 to 60 times / 10 cm, more preferably 20 to 50 times / 10 cm. When the number of lower twists is less than 10 times / 10 cm, the durability of the pneumatic radial tire tends to be low. On the other hand, when the number of lower twists exceeds 60 times / 10 cm, the rigidity of the cord is lowered, and as a result, the steering stability of the pneumatic radial tire tends to be lowered.
Further, the number of twists of the upper twist is preferably 10 to 60 times / 10 cm, more preferably 20 to 50 times / 10 cm, similarly to the lower twist from the same viewpoint.

The twisted cord is most preferably used after being immersed in a normal RFL (resorcin / formalin / latex) aqueous solution and thermally dried for adhesion to rubber, but rubber cement is used as an adhesive with rubber. May be. Depending on the type of fibers to be twisted, pretreatment with an aqueous epoxy solution or the like may be performed before the RFL adhesive treatment, or surface adhesion activity may be imparted by plasma treatment, corona discharge treatment or acid treatment. Further, as a bonding system, a dry bonding system in which a resorcinol, a formaldehyde generator such as hexamethylenetetramine, silica, etc., is blended in a rubber compound for coating a twisted cord may be used. On the other hand, the cord adhesive treatment step can be omitted.
The pneumatic radial tire of the present invention has the above-described configuration, and the radial tire can be manufactured by a conventionally known manufacturing method.

EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, an Example is an example to the last and does not limit this invention. In the examples, each measured value was measured by the following method.
(1) 1% initial elastic modulus Measured according to JIS L1017 (2002) 8.8 to obtain an initial elastic modulus of 1%.
(2) Steering stability The prototype tires are mounted on a car, run on a round course at a speed of 180 km / h or higher, and the degree of convergence of the disturbance when the test driver gives a disturbance is evaluated by feeling. The higher the index, the better.
(3) Durability (drum test)
The drum was run for 50,000 km under the conditions of a tire internal pressure of 3.0 kg / cm ² , a load of 990 kg, and a speed of 60 km / h, and the strength retention rate of the cord before and after running was determined and compared.

[Example 1]
1680 dtex aramid fiber (Twaron 1000 manufactured by Teijin Twaron Co., Ltd., 1% initial elasticity 620 cN / dtex) was subjected to a twist of 33/10 cm by a ring twisting machine manufactured by Kaji Tech Co., Ltd. One cord (under twisted cord 1 in Table 1) was obtained. In addition, 940 dtex nylon 66 fiber (Asahi Kasei Fibers Co., Ltd. T-5, 1% initial elastic modulus 48 cN / dtex) was subjected to 40 twists / 10 cm twist (Z direction) with the above-mentioned ring twisting machine, Two lower twisted cords (lower twisted cords 2 and 3 in Table 1) were obtained. The obtained aramid fiber and a nylon 66 fiber were combined together and subjected to 30 times / 10 cm of upper twisting (S direction) with the above ring twisting machine to obtain an upper twisting cord. . Furthermore, after applying an aqueous dispersion of epoxy and blocked isocyanate to this cord, heat treatment was performed at 150 ° C. for 90 seconds and 220 ° C. for 60 seconds, followed by application of RFL adhesive, and heat treatment at 150 ° C. for 90 seconds and 230 ° C. for 60 seconds. Did. The adhesion amount of the adhesive was 8% by weight based on the weight of the upper twisted cord. The upper twisted cord provided with the adhesive was used as a cord for a belt reinforcing layer.

  On the other hand, the same 940 dtex nylon 66 fibers (T-5 manufactured by Asahi Kasei Fibers Co., Ltd.) were drawn together and twisted 40 times / 10 cm (Z direction) with the above ring twisting machine. Further, in the same manner as described above, an aqueous dispersion of epoxy and blocked isocyanate was applied, followed by heat treatment, and subsequently, an RFL adhesive was applied to perform heat treatment. The adhesion amount of the adhesive was 8% by weight with respect to the cord weight. The cord provided with this adhesive was used as a cord for the carcass layer.

  Using the belt reinforcing layer cord and the carcass layer cord, a pair of left and right bead portions, a pair of left and right sidewall portions respectively connected to the bead portion, and a tread positioned between the sidewall portions And two carcass layers having a cord angle with respect to both directions of the tire of 85 ° between the pair of bead portions, and a cord with respect to the tire circumferential direction intersecting at 35 ° on the carcass layer in the tread portion. A pneumatic tire with a tire size of 170 / 60ZR17 having a belt reinforcement layer of layers was produced. The results are shown in Table 1.

[Example 2]
Instead of one lower twisted cord made of 1680 dtex aramid fiber, 1100 dtex aramid fiber (Twaron 1000 manufactured by Teijin Twaron Co., Ltd., 1% initial elasticity 627 cN / dtex) is twisted 40 times / 10 cm by the above ring twisting machine. One stranded cord (under laid cord 1 in Table 1) subjected to (Z direction) was used. Further, the upper twist was changed from 40 times / 10 cm upper twist (S direction) to 33 times / 10 cm upper twist (S direction). Except for these, the same procedure as in Example 1 was performed. The results are shown in Table 1.

[Comparative Example 1]
940 dtex nylon 66 fiber (T-5 manufactured by Asahi Kasei Fibers Co., Ltd.) is replaced with two lower twisted cords with a lower twist, and two 940 dtex nylon 66 fibers (T-5 manufactured by Asahi Kasei Fibers Co., Ltd.) are aligned. One twisted cord (twisted cord 2 in Table 1) subjected to 28 twists / 10 cm twist (Z direction) was used. This nylon 66 fiber one twisted cord and the 1680 dtex aramid fiber made in Example 1 (1 twisted cord 1 in Table 1) were combined and used 30 times with the above ring twisting machine. Example 10 was carried out in the same manner as Example 1 except that an upper twisted cord (S direction) was applied and an upper twisted cord was obtained. The results are shown in Table 1.

[Comparative Example 2]
In place of one lower twist cord made of 1680 dtex aramid fiber, 1100 dtex aramid fiber (Twaron 1000 manufactured by Teijin Twaron Co., Ltd.) was subjected to 40 twists / 10 cm of lower twist (Z direction) by the above ring twisting machine. One cord (under twisted cord 1 in Table 1) was used. Further, the upper twist was changed from 40 times / 10 cm upper twist (S direction) to 33 times / 10 cm upper twist (S direction). Except for these, the same procedure as in Comparative Example 1 was performed. The results are shown in Table 1.

  A tire using the reinforcing cord of the present invention is lightweight, has a small rolling resistance, is excellent in steering stability, and is excellent in durability. In addition, the pneumatic radial tire of the present invention can sufficiently exhibit the performance of the reinforcing cord. For this reason, the said reinforcement cord and radial tire can be widely used for the various tire use as which high performance is requested | required.

Claims (3)

  A reinforcing cord used for reinforcing a tire, wherein the reinforcing cord is made of a cord in which three or more lower twisted cords each having a lower twist are aligned and subjected to an upper twist in a direction opposite to the lower twist; and Among the three or more under-twist cords, at least one of the under-twist cords is a cord made of a fiber different from other under-twist cords.   At least one lower twisted cord is composed of one or more kinds selected from carbon fiber, aromatic polyamide fiber, wholly aromatic polyester fiber, or polyvinyl alcohol fiber having a strength of 13 cN / dtex or more. The reinforcing cord according to claim 1, comprising at least one selected from nylon fiber, polyethylene terephthalate fiber, polyethylene naphthalate fiber, or vinylon fiber.   A pair of left and right bead portions, a pair of left and right sidewall portions connected to the bead portion, and a tread portion located between the sidewall portions, and a cord for both directions of the tire between the pair of beat portions A pneumatic radial tire having a carcass layer having an angle of 75 to 90 ° and one or more belt reinforcing layers intersecting at 10 to 35 ° with cords in both directions on the carcass layer in the tread portion, A pneumatic radial tire characterized in that at least one of the belt reinforcing layers comprises the reinforcing cord according to claim 1 or 2.