JPS6045401A - Pneumatic tyre reinforced with composite polyester cord - Google Patents

Abstract

PURPOSE:To improve the uniformity and the driving stability of a radial tyre by using a composite cord comprising a polyester yarn having specified properties, spun at high speeds, and an aromatic polyamide yarn in a carcass ply of the tyre. CONSTITUTION:A polyester yarn is formed by bundling a number of polyester filaments having an intrinsic viscosity of at least 0.8, which filaments are obtained by cold drawing and heat treating spun filaments prepared from a molten polyester by cooling to solidify extruded polyester while being drafted. The polyester yarn is specified by a dimensional variation coefficient, which is defined by a sum of an intermediate elongation (%) at a load of 4.5g/d and a dry heat shrinkage percentage (%) when heated at 150 deg.C for 30min, of not more than 14%. A cord formed by twisting at least one of the polyester yarns and at least one of aromatic polyamide yarns together is used in a carcass ply, whereby the unevenness of a side wall is reduced, as well as the uniformity and the driving stability of a tyre are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pneumatic radial tire that has a carcass ply made of a novel polyester cord and has excellent uniformity and handling stability. This invention relates to a tire equipped with a carcass ply made of composite polyester cord.

Polyester cord has high strength and rigidity, and is widely used as a carcass ply for tires with a radial structure. In the manufacturing process of radial tires, a large number of cords are arranged in parallel, made into a blind weave, coated with rubber, and then cut at right angles to the length of the cord. 1 to 5 cords on the edges are overlapped, and each cut piece is sequentially joined to form a long strip of constant width with the cords arranged in the width direction, and this strip is made into a cord. A cylindrical carcass ply is formed by cutting the carcass ply to a predetermined length along the same direction and joining the cut ends together to form a cylindrical carcass ply. Bead assembly, belt,
A green tire is formed by sequentially laminating sidewall rubber, tread rubber, etc., and is vulcanized and molded in a vulcanization mold while applying internal pressure to manufacture the tire. Therefore, a carcass ply always includes some seams of blind weave pieces. The density of the cord at this seam is twice that of other parts, making the carcass locally more rigid. In the vulcanization process of tire manufacturing, internal pressure and temperature are applied during vulcanization of the tire, so the tension applied to each cord due to the internal pressure during vulcanization is smaller at the lap joint than at other parts.
Therefore, the cord at the overlapped portion experiences a large amount of heat shrinkage during vulcanization.

Furthermore, when the tire is filled with internally pressurized air after the tire is completed, the carcass' overlapping joints have high rigidity, so the expansion is small. That is, the overlapping portion has a large vulcanization shrinkage and also has a small expansion upon filling with internal pressure, so this portion appears as a recess on the tire side surface. Since this recess causes tire non-uniformity, it is necessary to use a cord that exhibits little heat shrinkage during vulcanization and has a low intermediate elongation. Recently, there has been a trend to reduce the number of carcass plies as much as possible in order to manufacture tires with fewer man-hours, but the influence of the seam becomes even greater. Therefore, in order to reduce the number of carcass plies, a polyester cord with low dry heat shrinkage and intermediate elongation is desired.

However, the dry heat anti-shrinkage and intermediate elongation of conventional polyester cords have a mutually beneficial relationship, and if the dry heat shrinkage rate is decreased by changing the number of cord twists and heat treatment conditions, the intermediate elongation can be increased. On the other hand, if an attempt is made to reduce the intermediate elongation, the dry heat shrinkage rate increases, making it difficult to reduce both the dry heat shrinkage rate and the intermediate elongation.

In view of the above-mentioned drawbacks of conventional pneumatic radial tires, the present invention has developed a tire that uses a new composite polyester cord with low dry heat shrinkage and low intermediate elongation, which has uniformity, excellent handling stability, and fewer side unevenness defects. The aim is to provide quality tires.

As a result of repeated research to achieve the above objectives, we found that during melt spinning of polyester filaments, the filaments are drawn out at high speed and solidified while being stretched, and then subjected to appropriate cold stretching, hot stretching, and heat treatment to achieve intermediate elongation and dry heat shrinkage. Polyester filaments with a low modulus are obtained, and a composite cord made by twisting the bundled polyester yarn with an aromatic polyamide yarn has particularly low intermediate elongation and dry heat shrinkage, and this polyester composite cord can be used for carcass plies. The inventors have discovered that a pneumatic radial tire with excellent uniformity and handling stability and no unevenness on the tire side can be obtained by doing so, and have completed the present invention.

That is, the present invention produces a dimensional change coefficient that is made by spinning a molten polyester, cooling and solidifying the spun yarn while drawing it, and then cold-drawing and heat-treating it. The gist of the present invention is to provide a composite polyester cord-reinforced pneumatic tire in which a carcass ply is made of a cord made by twisting together at least one polyester yarn having a diameter of 14 inches or less and at least one aromatic polyamide yarn.

Here, the dimensional change coefficient is a coefficient defined as the sum at a load of 4.5 g/d.

Generally, polyester yarn is produced by cooling and solidifying molten polyester extruded from a spinning nozzle to form a spun yarn, which is then pre-stretched, hot-stretched and heat-treated to form filaments.
The filaments are bundled to form yarn. Conventional polyester yarn has a winding speed of approximately 400 m1.
As the tension that acts in the process of cooling and solidifying the molten polyester extruded from the nozzle is small, the degree of orientation of the molecular chains in the spun yarn is small, which is an indicator of the degree of orientation of the molecular chains in the spun yarn. The birefringence index was 5×10 2 or less, and as a result, the dimensional change coefficient of the filament after cooling after spinning and further cold stretching, hot stretching, and heat treatment was over 14%.

The polyester yarn used in the present invention is produced by spinning molten polyester and cooling it to solidify it.
By winding at a high speed of ~4000772/min, a large tension is applied to the spun yarn, the spun yarn is cooled and solidified, and the winding speed is adjusted so that the birefringence of the spun yarn is 10XIO~40x10, It consists of filaments obtained by further cold-stretching, hot-stretching, and heat-treating the spun yarn obtained by adjusting the stretching ratio in the same manner as ordinary polyester yarn. In this way, the polyester yarn used in the present invention is produced by applying tension to the filaments during the spinning and solidifying process by taking off the spun yarn at a much faster speed than when spinning conventional polyester yarns. As the filament is stretched and cooled, the molecular chains in the filament become oriented along its length. The degree of orientation of the molecular chains is detected by measuring the birefringence, and the winding speed of the spun yarn is adjusted from 1000 to 4000 so that the birefringence is in the range of 10xlO- to 40x10-.
Adjust within the range of m1 minute. The spun yarn thus obtained is further subjected to cold stretching, hot stretching, and heat treatment in the same manner as in the conventional method, but the stretching ratio at this time may be slightly lower than in the conventional method.

The polyester yarn produced as described above has a dimensional change coefficient of 8.5 to 14 inches, making it a polyester yarn suitable for use in the tire of the present invention.

If the dimensional change coefficient of this polyester yarn is thicker than 14, tires manufactured using a composite cord made by twisting this polyester yarn and aromatic polyamide yarn will tend to have side unevenness defects; If it is less than 8.5%, the breaking energy becomes extremely small, so the polyester yarn produced by the above method and having a dimensional change coefficient of 8.5 to 14% is used in the tire of the present invention.

The polyethylene filament constituting the carcass cord in the present invention is a polyester containing ethylene terephthalate as a main monomer component, and is a copolymerized polyester containing 15 moles or less of other monomer components such as ethylene isophthalate and ethylene benzoate in addition to ethylene terephthalate. But that's fine. If the raw material polyester has an intrinsic viscosity [η] of less than 0.8 when spun filaments are dissolved in orthochlorophenol, the strength of the cord will be weakened.

At least one of the above-mentioned polyester yarns and at least one aromatic polyamide yarn are first twisted, respectively, and then twisted together in a direction opposite to the first twisting to form a cord. In order to further improve adhesion to rubber, a three-component cord may be constructed using nylon 66 yarn produced by a high-speed spinning method and having a dimensional change coefficient of 13 inches or less.

A carcass ply is formed using the above-mentioned composite polyester cord, and a pneumatic radial tire is manufactured by a method completely similar to a conventional tire manufacturing method.

Next, the content of the present invention will be explained in more detail with reference to Examples.

Example 1 A yarn was formed from a polyester filament with a birefringence index of 20×10 obtained by spinning molten polyethylene terephthalate from a spinning nozzle and cooling and solidifying it while stretching at a winding speed of 1000 m/min. Intermediate elongation 4
A 1500 denier yarn with a dry heat shrinkage rate of 9% and a dimensional change coefficient of 13 inches was obtained. On the other hand, the aromatic polyamide filament bundled yarns are pre-twisted and then twisted together to form a polyester composite cord, and this cord is used as a carcass ply cord to manufacture a radial tire with a tire size of 1658R13 according to the usual method. did. The cord manufacturing conditions and tire performance are shown in Table 1.

Examples 2 and 3 and Comparative Examples 1 to 3 The results when the winding speed of the polyester filament in Example 1 was set to 130 (1/min and 1800???!/min) were taken as Examples 2 and 3, respectively. The same is shown in Table 1. Also, the case where the winding speed of the polyester filament in Example 1 is 400 m7 minutes is shown in Table 1 as Comparative Example 1. Table 1 shows the results of Comparative Examples 2 and 3, in which cords made only of polyester filaments were used, and Comparative Example 4, in which cords made only of aromatic polyamide filaments were used.

Comparative Example 3 is a radial tire with carcass ply made of polyester cord, which has been commonly used in the past.

In Table 1, "drum durability" is US automobile safety standard F.
According to WSS109 regulations, the internal pressure is 17kg/c-
I ran it with the specified load applied at specified intervals, and since there were no abnormalities, I added 1/2 of the specified load every 12 hours.
IO (46 kg) was added and the vehicle was run until a failure occurred, and the measured values of each tire were expressed as an index, with the conventional tire of Comparative Example 3 set as 100.

“Side unevenness” is caused by 2. ,．． 2 kg/cd
Measure the depth of the groove-like recess in the radial direction on the sidewall part that is formed when filled with internal pressure air, and for those without four parts...Depth of the part between five points Q, short of 3 ays or less Things...4
Long with a point recess depth of 0.3 fl or less ...Short with a 3 point recess depth of 0.311 or more ...Long with a 2 point recess depth of 0.3 ff or more ...1 point It was shown as

"Uniformity" conforms to the automobile standard JASO-0607 established by the Society of Automotive Engineers of Japan, with an internal pressure of 2 kg/c-
60 tires are pressed against the drum with a load of 387 kq.
The tire was rotated at rpm, the magnitude of the change in force in the radial direction of the tire was measured, and the reciprocal was expressed as an index with Comparative Example 3 set as 100.

"Drivability" was determined by pressing a tire filled with 1.9 kg/aA of internal pressure air into a drum testing machine with a load of 450 kQ.
The drum is rotated at a speed of 10 km/hr, and the lateral force acting on the tire is measured (while the tire's axis of rotation is gradually shifted from a direction parallel to the drum's axis of rotation at a slip angle), and the slip angle is The value obtained by dividing the lateral force by the angle at 2 degrees (cornering power) is 10 for Comparative Example 3.
It is expressed as an index as 0.

It should be noted that the larger the values of the uniformity and maneuverability indexes, the better the performance.

All of the tires of the above examples are superior to the conventional tire of Comparative Example 3. Among the examples, the tire of Example 3, in which the winding speed of the polyester filament is high, has excellent durability, uniformity, and maneuverability. By increasing the birefringence of the yarn, it is possible to improve the performance of the tire.

According to the composite polyester cord reinforced pneumatic tire of the present invention, by using a composite cord of high speed spun polyester yarn and aromatic polyamide yarn in the carcass ply of the radial tire, a cord using polyester yarn/or aromatic polyamide yarn alone can be used. Compared to tires using the carcass ply, the tire has superior uniformity, handling stability, and durability, and a tire with fewer sidewall irregularities can be obtained.

In the above description, a radial tire was described in which the composite polyester cords were arranged in a direction perpendicular to the equator direction of the tire to form a carcass ply. The present invention can be carried out in exactly the same manner as a semi-radial tire having a carcass ply.

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Claims (2)

[Claims] (1) The intrinsic viscosity is 0, which is made by spinning molten polyester, cooling and solidifying the spun yarn while stretching, and then cold-stretching and heat-treating the spun yarn.
．． A large number of polyester filaments of 8 or more are bundled together.
Intermediate elongation (%) at 4.5 f/d load and 150°C3
At least one polyester yarn having a dimensional change coefficient of 14 inches or less, defined as the sum of dry heat shrinkage rates (%) for 0 minutes, and at least one aromatic polyamide yarn are twisted together. (2) The composite polyester cord reinforced pneumatic tire according to claim 1, wherein the cords of the carcass ply have a radial structure in which the cords are arranged perpendicular to the tire equator.