JPH07310251A - Pneumatic radial tire reinforced with organic fiber cord - Google Patents

Abstract

PURPOSE:To produce a pneumatic radial tire excellent in vibration properties and useful for a car comfortable to ride in and excellent in steering stability by using respectively specified organic fiber cords for a carcass ply and a cap belt. CONSTITUTION:Primary twist treatment is applied to a raw yarn composed of polyethylene naphthalate and a pair of the treated raw yarns are subsequently intertwisted to form a cord having 3.0 to 6.2% elongation at 170+ or -2 deg.C under 0.5g/dl load. The resultant cord is used as a carcass ply. On the other hand, a nylon 66 cord having >=0.40g/dl heat shrinkage stress at 170 deg.C is used for a cap belt arranged in a belt-reinforcing layer of the outermost layer of a tire. The objective pneumatic radial tire having a tube-less structure is produced by using this carcass ply and this cap belt.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire reinforced with an organic fiber cord, and more particularly to a pneumatic radial tire characterized by a reinforcing cord for carcass plies and cap belts.

[0002]

2. Description of the Related Art Conventionally, in order to improve the vibration riding comfort performance and the steering stability performance, there are those that specify the physical properties of the carcass ply of the tire. For example, if you want to emphasize vibration comfort, use a low modulus cord such as nylon cord to reduce the modulus to absorb vibrations from the road surface, while if you want to emphasize driving stability, use polyester cord. A high modulus cord is used to increase the modulus to increase the tire rigidity. With such a method, it is not possible to achieve both vibration riding comfort performance and steering stability performance. Therefore, to achieve both of these,
There is also an attempt to design the shape of the stress-elongation curve of the carcass ply cord.

[0003]

However, in the above-mentioned attempt, since attention is paid only to the carcass ply cord, there is a limit to improving both vibration riding comfort performance and steering stability performance. there were. An object of the present invention is to further improve both the vibration riding comfort performance and the steering stability performance by examining the combination of both the carcass ply cord and the cap belt cord.

[0004]

To achieve the above object, the present invention has the following constitution. That is, the elongation at 170 ± 2 ° C. under a load of 0.5 g / de is 3.0 to 6.2%.
Reinforced with a carcass ply reinforced with a fiber cord made of polyethylene naphthalate in the range of 1 and an organic fiber cord disposed in the outermost belt reinforcing layer of the tire and having a heat shrinkage stress at 170 ± 2 ° C of 0.40 g / de or more. A pneumatic radial tire reinforced with an organic fiber cord, which is characterized by having the above cap belt.

That is, according to the present invention, in the carcass ply, a specific polyethylene naphthalate cord whose tire shape can be easily controlled and whose modulus after vulcanization is kept high is used for reinforcement, and its cord characteristics are Is defined by the heat applied to the tire during tire production and the elongation at heat corresponding to the tension, and for the cap belt,
In order to optimize the tire shape and increase the circumferential tension of the tire, we decided to use cords with high heat shrinkage stress for reinforcement, and by this combination, high level vibration that could not be obtained by single use was obtained. It is intended to provide a pneumatic radial tire having both ride comfort performance and steering stability performance.

In other words, conventionally, since the carcass ply cord was focused only on the physical properties and the like, the cord could not be sufficiently exhibited, but the cap belt was used in combination with a cord having a high heat shrinkage stress. By doing so, the true value of the carcass ply cord is exhibited, and the level of vibration riding comfort performance and steering stability performance is dramatically improved.

[0007]

In the constitution of the present invention, the polyethylene naphthalate cord applied to the carcass ply is 170 ± 2 ° C.
The elongation under a 0.5 g / de load is 3.0-
The range is 6.2%, but if it is less than 3.0%, the steering stability performance is improved, but the vibration riding comfort performance remains at the conventional level, while if it exceeds 6.2%, the vibration riding comfort is improved. This is because only the performance is improved and the steering stability performance is at the conventional level. Further, it is preferably 3.4 to 5.8%, but this makes it possible to achieve the above performance at a higher level.

The technical reason for this is that in the tire manufacturing process, the change in modulus due to heat applied to the carcass ply,
That is, the change in the elongation of the cord at a high temperature has a large effect on the tire shape, and this is because when it is out of the above range, the antinomy between the vibration riding comfort performance and the steering stability performance becomes stronger.

[0009] The use of polyethylene naphthalate cord for reinforcing the carcass ply means that the modulus of the carcass ply cord in the tire after the tire is manufactured, that is, the product, is more than that of the conventional product (for example, polyethylene terephthalate). This is to keep it high, and by using this, the rigidity of the tire is dramatically improved, especially the level of response and linearity in the evaluation of the steering stability performance of the tire is improved, and in the vibration riding comfort performance, This is because the level of vibration and shock is improved.

The cord used for the cap belt has a heat shrinkage stress at 170 ± 2 ° C. of 0.40 g / d.
When it is less than e, the tire performance cannot be improved even if the polyethylene naphthalate cord according to the present invention is used for the carcass ply. Tire performance is dramatically improved only by using organic fiber cords such as polyamide cords, which have large heat shrinkage stress, for the cap belt.

This is because by using a cap belt having a high heat shrinkage stress, a force for tightening in the circumferential direction is exerted on the entire tire tread portion at the time of tire production, and the contact surface shape is flattened. It is considered that this flatness simultaneously satisfies the effect on the vibration riding comfort performance and the effect on the steering stability performance due to the improvement in the circumferential rigidity of the tread portion of the finished tire at the same time.

In this case, the upper limit value for the heat shrinkage stress of the cap belt reinforcing cord is not particularly specified, but when a polyamide cord is used as the cap belt, it is usually raised to about 0.65 g / de. However, if the tire is manufactured more than that, the tire is distorted during tire manufacturing, and the tire uniformity is impaired in a general tire manufacturing method. Therefore, it is preferably 0.40 to 0.65 g / de, more preferably 0.
It is in the range of 43 to 0.60 g / de.

Further, the cord type of the cap belt may be one having a high heat shrinkage stress and an adhesive force which can endure the temperature rise of the tread portion for durability, such as polyamide cord, polyester cord and polyaramid cord. ,
Examples thereof include hybrid cords of polyester and polyamide (twisted), conjugated cords of polyester and polyamide (core-shell structure), and the like.

Test method (a) Elongation measurement method under a load of 0.5 g / de at 170 ± 2 ° C. Using a tensile tester equipped with a thermostatic chamber at an atmospheric temperature of 170 ± 2 ° C., it is performed according to JIS L1017. A stress (g / de) -elongation (%) curve is drawn on an autograph and the elongation at a stress of 0.5 g / de is read. Where 0.
5 g / de assumes the tension applied to one ply cord during vulcanization.

(B) Method of measuring heat shrinkage stress at 170 ± 2 ° C. At room temperature (25 ± 2 ° C.), the cord was subjected to an initial load of 1/60 g (0.0167 g / de) of the total denier of the cord. After fixing in that state, the ambient temperature of the cord is raised to 170 ± 2 ° C. at a rate of 5 ° C./min. The stress (g / de) generated by the heat shrinkage of the cord at 170 ± 2 ° C. was defined as the heat shrinkage stress (g / de) at 170 ± 2 ° C.

The measuring and testing machine has a thermostatic chamber capable of raising the temperature at a rate of 5 ° C./min within a range of about 20 to 200 ° C. and the stress applied to the cord is within a range of 20 to 5000 g. It is necessary to be able to measure at.

Method for Producing Polyethylene Naphthalate Cord According to the Present Invention A raw yarn made of polyethylene-2,6-naphthalate is twisted into a lower twist, and these two yarns are combined and further twisted. The twisting coefficient α at this time is 0.30 <α <
The optimum value is selected within the range of 0.60.

[Equation 1] (In the formula, N represents the number of twists per 10 cm of cord, D represents 1/2 of the total denier of the cord, and P represents the specific gravity of the fiber.)

The cord thus obtained is subjected to an adhesive heat treatment under the following conditions. First, it is dipped in a resorcin-formaldehyde-latex adhesive, the treatment temperature in the drying zone is 170 ° C., the treatment time is 60 to 160 seconds, and the treatment temperature in the heat setting zone and the normalizing zone is 250 to 260, respectively. ℃, treatment time 60 each
To 160 seconds, further set the cord tension in the heat setting zone to 0.10 to 1.20 g / de and the cord tension in the normalizing zone to 0.03 to 0.50 g / de, and dry the cord. Heat treatment. As a result, a code having desired physical properties can be obtained.

Further, the cord type of the cap belt may be any one as long as it has a high heat shrinkage stress and has an adhesive force to endure the temperature rise of the tread portion for durability.
6,6-Nylon and the like are suitable as the material.

For example, when 6,6-nylon is used,
It is obtained by the following manufacturing method. That is, a 6,6-nylon original yarn produced by a usual production method is twisted into a ply, and two of these yarns are combined and further plied. At this time, the optimum twisting coefficient α is selected to be an optimum value within the range of 0.30 <α <0.60 (α satisfies the relationship of the above-mentioned expression 1).

The cord thus obtained is subjected to an adhesive heat treatment under the following conditions. First, it is dipped in a resorcin-formaldehyde-latex adhesive and the treatment temperature in the drying zone is 170 ° C., the treatment time is 60 to 120 seconds, and the treatment temperature in the heat setting zone and the normalizing zone are 230 to 245 °, respectively. Processing time is 60 to 12 each
The cord tension in the heat setting zone is set to 0 seconds, the cord tension in the heat setting zone is set to 0.70 to 1.90 g / de, and the cord tension in the normalizing zone is set to 0.35 to 0.90 g / de, and the cord is dried and heat treated. .

The feature of the cap belt cord in the present invention is that the heat shrinkage stress is high. Therefore, in order for the feature to be exhibited, the temperature is slightly lower than that of the conventional dry heat treatment method, and It is necessary to process with high tension.

[0023]

EXAMPLES The present invention will be described below based on examples. The tire size used was a tubeless structure of 205 / 65R15, and the tire was manufactured in a factory under normal conditions.

Regarding the carcass ply, 1500 D /
2 (1500 denier 2 twists), 2 pieces of lower twist x number of upper twists 39 × 39 (times / 10 cm), the driving angle is 80 to 90 ° with respect to the circumferential direction (both are 90
°), the number of shots is 50 lines / 5 cm.

As for the belt layer, two steel cord belts having a structure of 1 × 5 × 0.23 are arranged, and the driving angles are 26 ° to the left and right with respect to the circumferential direction, and the driving number is 55 lines / 5 cm.

Regarding the cap belt, 1260D /
2 (1260 denier 2 twists), 1 piece of lower twist x number of upper twists 39 × 39 (turns / 10 cm), driving angle is 0 to 15 ° with respect to the circumferential direction (0 ° for implementation) The number of shots is 55 pieces / 5 cm.

Table 1 shows each cord type and physical properties used for the tire, and the tire performance. That is, Comparative Examples 1 to 3 are examples using polyethylene terephthalate (PET) as carcass ply reinforcing cords, and Comparative Examples 4 to 6 are used.
And Examples 1 to 8 are polyethylene naphthalate (PE
It is an example using N). The cords for reinforcing the cap belt were all made of nylon 6,6 throughout the comparative examples and examples.
Code (NY66) was used.

The tire performance test method is as follows. Steering stability test Each prototype tire was mounted on a passenger car, and 60 to 200km / h
The actual vehicle feeling test was conducted at the speed of (1)
Straight running stability, (2) turning stability, (3) sense of rigidity, (4)
For items such as handling, 1 to 10 points are evaluated, and the average score of all items is calculated. The test was carried out by two professional drivers respectively, and the average of the average scores of both the drivers was calculated, and the result was displayed as an index using Comparative Example 1 as a control (100). The larger the number, the better.

Vibration Riding Comfort Test Each prototype tire was mounted on a passenger car, and a feeling test of vibration riding comfort performance was conducted by two specialized drivers, and a score of 1 to 10 was given, and the average of both riders was evaluated. In the same manner as above, Comparative Example 1 was used as a control (100),
Displayed as an index. The larger the number, the better.

[0030]

[Table 1]

From the results shown in Table 1, when polyethylene terephthalate was used for the carcass ply, the steering stability was low even when the elongation at heat and the cap belt cord were within the range of the present invention (Comparative Example 3). Even if polyethylene naphthalate is used, if the hot elongation is out of the specified range, the vibration riding comfort performance (Comparative Example 4) or the steering stability performance (Comparative Example 5) is inferior, and even if only the carcass ply cord is within the specified range. If the cap belt does not satisfy the conditions, the steering stability is not favorable (Comparative Example 6). On the other hand, Example 1
In both cases, both performances are good.

[0032]

According to the present invention, when the cord according to the present invention is used for both the carcass ply and the cap belt, both vibration riding comfort performance and steering stability performance can be maintained at a high level.

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location // D01F 6/62 302 C 306 T

Claims (1)

[Claims] 1. A carcass ply reinforced with a fiber cord made of polyethylene naphthalate having an elongation at 170 ± 2 ° C. under a load of 0.5 g / de of 3.0 to 6.2%, and a tire outermost layer. Placed on the belt reinforcement layer of
A pneumatic radial tire reinforced with an organic fiber cord, comprising a cap belt reinforced with an organic fiber cord having a heat shrinkage stress of 0.40 g / de or more at 0 ± 2 ° C.