JP2642616B2 - Pneumatic radial tire with improved durability - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The technical contents described in this specification with respect to a pneumatic radial tire show a development result of improvement in durability of a tire particularly when a polyester cord is used as a carcass ply. There is a suggestion.

(Prior Art) Conventionally known pneumatic radial tires using an organic fiber cord, particularly a polyester cord for a ply of a carcass, have excellent handling stability and abrasion resistance, but the separation at which the interface between the cord and rubber is broken. Resistance to,
This also has the disadvantage that the separation performance is particularly poor at the bead portion.

The cause is that the carcass cord itself is likely to generate heat due to the repeated vibration load and stress strain applied to the polyester carcass cord, which is considerably higher than when a nylon cord is used for the carcass ply. It has been considered that the adhesive strength with the rubber part is relatively low.

(Problems to be Solved by the Invention) To provide a pneumatic radial tire having improved bead portion durability by eliminating the above-mentioned drawbacks of a pneumatic tire using a polyester cord for a carcass ply, which is inferior in separation resistance, to a carcass ply. Is the object of the present invention.

(Means for Solving the Problems) As a result of diligent research, the inventors have found that by reducing defects at the adhesive interface between the heat-treated polyester cord and the rubber, the interface between the cord and the rubber per cord can be reduced. It has been determined as follows that the permeability of air, which is mainly composed of, can be reduced and the separation resistance can be significantly improved.

In other words, using a polyester cord for the carcass ply and trying to elucidate in detail the pneumatic tire with poor separation resistance, it can be said that the tube is used for inner liner rubber applied to the inner surface of tubeless tires or tires with tubes. However, when used under high internal pressure air filling, a phenomenon was observed in which a very small amount of air permeated, and this air reached the cord of the carcass ply and accumulated.

Therefore, when a polyester cord is used for a carcass ply, there are originally many defects on the surface of the treated cord. When the pressure of the accumulated air at the interface between the cord of the carcass ply and the rubber reaches a certain level or more, the part having the largest input during the tire running, that is, usually the upper part of the bead core, Interfacial cracks occur in parts and sometimes shoulders, which eventually leads to separation.

Therefore, conversely, if the air that accumulates at the interface between the cord and the rubber is prevented from moving to the portion where the input is large, or if the accumulation of air at the interface can be eliminated, the separation resistance will be greatly improved. .

Here, the pneumatic radial tire with improved durability according to the present invention comprises a pair of bead cores, and at least one rubber coating of a polyester cord arranged at an angle of approximately 90 ° to the tire equatorial plane between the bead cores. A carcass ply, and a belt for reinforcing a crown portion of the carcass ply. The polyester cord of the carcass ply is subjected to a dip treatment by passing a raw cord weave cord through an adhesive solution, and subsequently the cord cord is woven. After the drying treatment in the drying zone, and heat treatment to adjust the elastic modulus and heat shrinkage characteristics in the heat setting zone and the normalizing zone in order, the rubber is coated on the opposite side of the cord to form a carcass ply member. Pneumatic radial tire obtained by applying a member to an unvulcanized tire and subjecting it to vulcanization molding In the above, the polyester cord of the carcass ply was subjected to means for applying a high tension of 0.3 gr / D or more of each cord opposite to the cord or the dip treatment in both the dip treatment and the drying treatment in the drying zone. Immediately increase the amount of adhesive adhering to each of the cords opposite the cord, and reduce the drying temperature in the drying zone.
After applying a quick-drying treatment of the adhesive to a temperature of more than 170 ° C. and 180 ° C. or less, the adhesive adhesion rate of each cord is adjusted to 5.5 to 6.5% by applying one of the means. The above-mentioned object is assumed assuming that the polyester cord of the carcass ply in the above consists of cords having an air permeability of 1.10 × 10 ^-3 kg / cm ² / h or less including the interface between the cord and rubber per cord. Can be satisfied.

The pneumatic radial tire according to the present invention has a bead core buried in a pair of bead portions (not shown) and a tire equatorial plane substantially extending between the bead cores.
It is customary to provide at least one carcass ply which is to be a rubber coating of polyester cords arranged at an angle of 90 ° and a belt which reinforces the crown of the carcass ply.

Furthermore, the polyester cord of the above carcass ply,
The raw (untreated) polyester cord is woven into a long cord, and the dip is passed through an adhesive solution to ensure adhesion to the coated rubber, and then the cord attached to the adhesive is dried. , Heat-setting zone, and normalizing zone. In the drying zone, the adhesive adhering to each cord is first dried. Then, in the heat-setting zone and the normalizing zone, a relatively low cord tension (g / g) is used. D) For example, the elastic modulus and heat shrinkage of each cord opposite to the cord are adjusted under a treatment condition of heating at a high temperature, for example, about 250 ° C. under the action of 0.1 to 0.2 g / D.

The carcass ply member is formed by coating a rubber on the opposite side of the cord which has undergone these treatments, and this member is subjected to tire molding to obtain an unvulcanized tire, which is subjected to ordinary vulcanization molding to obtain a pneumatic radial tire.

Here, the feature of the present invention resides in the first half of the above-mentioned various code counter-processing steps, namely, the dip processing step and the following drying zone processing step. Conversely, the air permeability of the carcass ply polyester cord for tires, including the interface between the cord and rubber per cord, should be 1.1 × 10 ^-3 kg / cm ² / h or less. It is.

(Means 1) In order to move a long cord in the adhesive solution at a predetermined feed rate and apply a predetermined amount of adhesive to each cord over the entire width of the cord, and then to sufficiently dry the adhesive. The code is sent to the next drying zone. At this time, a high tension of 0.3 gr / D or more is applied to each cord from the position where the untreated winding cord is pulled out to the drying zone through the adhesive solution and the conventional cord tension of 0.1 to 0.2 gr / D. This is one of the means. It is necessary to maintain the tension of 0.3 gr / D or more from at least the position immediately before immersion in the adhesive solution to the position immediately after the end of the drying zone. In particular, it is important to maintain the tension immediately before and immediately after the application of the adhesive (afterwards). Codes No. 1, 2 and N of Table 1 listed
o.5, 6).

(Means 2) Use an oil agent with excellent affinity for the adhesive in the adhesive solution in the dip treatment step,
Alternatively, dip treatment is performed by reducing or adjusting the suction pressure of the vacuum acting on the opposite side of the cord immediately after passing through the adhesive solution, or by increasing the adhesive concentration in the adhesive solution to 1.3 to 1.5 times the conventional concentration. Immediately after passing through, the amount of adhesive applied per cord opposite to the cord is increased from the conventional amount, and the drying temperature in the drying zone is also reduced to the conventional value of 15%.
After increasing the temperature from 170 ° C to 180 ° C or less, which is higher than the temperature of 0 ° C or less, accelerate the viscosity increase rate and drying rate in the thickness direction of the thick and wet adhesive part in the drying zone, and after solidifying the adhesive The adhesive adhesion rate of each cord of the conventional 1.
The second means is to make it 5.5% to 6.5%, which is 1 to 1.3 times. Here, the adhesive adhesion rate is expressed as a percentage obtained by dividing the difference between the treated cord weight per unit length after passing through the drying zone and the raw cord weight having the same length by the raw cord weight. These two processing elements are fundamental, but also the cord tension (gr / D)
Although it is not necessary to follow one of the means, it is preferable to set the conventional cord tension to 0.1 to 0.2 gr / D or more if possible (see the code counter Nos. 9 and 10 in Table 2 below). If the adhesive concentration is too high, a film of the adhesive solution is formed between adjacent cords opposite to the cord woven in the form of a cord, and even if a vacuum device is applied to the cord just after passing through the adhesive solution, the film is not removed. The removal is not sufficient, and the inconvenience that rubber is difficult to enter later occurs.
The limit is 1.3 times 6.5%.

The air permeability of the polyester cord in the carcass ply is increased to 1.10 × 10 ⁻³ kg / c by any of the above-described means.
The reason why it can be set to m ² / h or less will be described below.

First, as mentioned above, the relationship between the cord of the carcass ply that becomes the conventional rubber-coated polyester cord and the surrounding rubber, as a result of microscopic observation on a filament basis,
The filaments forming the outside of the cord along the cord's axial direction, together with the rubber that surrounds it, have a completely bonded part and a part that does not adhere and have a gap. all right.

On the outside of the cord, the filament group naturally forms many peaks and valleys, and it has been found that the above-mentioned void portions are generated in particularly deep valleys (a kind of depression) among the peaks and valleys. Then, a conventional carcass ply was cut out to produce a test piece, and when pressurized air was applied to one end of the test piece, it was confirmed that a large amount of air leaked from the cord at the other end. That is, the pressurized air easily flows from one end of the cord to the other end through the gap, which is the actual condition of the defect that deteriorates the air permeability. It has been clarified that when the depression between the filaments forming the outer side of the filaments constituting the cord is extremely deep, even if the high pressure is applied during the vulcanization molding, the inflow of the rubber is significantly inhibited, resulting in elucidation. .

As for the polyester cord, about 190 to 250 filaments of 5 to 8 D (denier) are bundled and twisted, and two to three of the twisted original yarns are combined and twisted to give a raw polyester cord, for example, 1000D / 2. , 1000D / 3 to 1600D / 2 and 1600D / 3 are well known. However,
The outer surface of the cord is a microscopic view of a cylindrical side surface aggregate of filaments. If the outer envelope (surface) is substantially circular (cylindrical), the remarkably deep depression does not exist. The outer surface of the cord has extremely large irregularities around the outer periphery, and this state is maintained even to the tire.

Next, in one of the above-mentioned means, in the bonding treatment step for the long cord, in the bonding treatment step, each cord from the position where the winding cord is pulled out to the drying zone through the adhesive solution is passed.
By applying a tension of 0.3 gr / D or more, the filaments are remarkably improved in mutual adhesion and are evenly aligned, and small irregularities that cause no inconvenience on the outer surface of the cord (adjacent filaments There are irregularities between each other), but the envelope surface of the outer filament group has a substantially cylindrical shape. Since this cylindrical outer surface is fixed in the drying zone of the cord, subsequent heat treatment of the cord ~
Until after the vulcanization molding of the unvulcanized tire, the above-mentioned void portion (defect portion) can be prevented from being generated outside the cord.
The tension gr / D is a value obtained by dividing the tension (gr) applied to one cord by the total denier number (D).

The air permeability of the carcass ply cord cannot be neglected by the amount of air flowing along the filament group inside the cord, but especially in the case of polyester cord, it flows through the void formed at the interface between the cord and rubber. Since the absolute amount of air is predominantly large, by preventing the generation of voids (defects) as described above, the air permeability can be reduced to the value described above.

Further, in the second means, even if the depression between the filament groups in the cord passing through the adhesive solution is formed deeper than the first means, the adhesive adhesion rate is reduced to 1.1 times the conventional adhesion rate. A large amount of (thick) wet adhesive that fills the deep depression, while filling the depression as 1.3 to 5.5% to 6.5%, permeates inside the filament under the conventional temperature of 150 ° C or less in the drying zone. It re-creates the deep depressions, but at the same time increases the temperature of the drying zone to 17
By raising the temperature above 0 ° C to 180 ° C or less and immediately drying the wet adhesive, it is possible to prevent the re-formation of deep depressions and smooth the outer surface of the cord, and the cord that has passed through the drying zone is It is possible to keep the envelope surface of the outer surface cylindrical, and it is possible to achieve a low air permeability similar to one of the measures.

Further, the air permeability is defined by a numerical value obtained by the following measuring method.

The sidewall rubber of the radial tire is scraped with a grinder over an area of about 1 cm square, and part of this is scraped off to the cord surface to expose the three cords.

If the carcass ply is wound around the bead core and turned back in the radially outward direction of the tire, and the carcass ply cord end reaches a position that is at least 2 cm higher than the reim contact part, the cut-off position is So that the cord of the outermost ply (the innermost ply in the inside of the tire) is exposed, and the carcass ply is folded in the same manner, and the carcass folded ply cord end is located below the rim contact portion, that is, closer to the bead core. In the case of a tire or a structure in which an additional ply is wound around the bead core from the outside of the carcass ply to the outside of the carcass ply, the outermost ply cord of the cutting portion should be between the outer edge of the rim flange and the tire shoulder. Exposed at any position and additional plies are code examples other than polyester cord For example, when reinforced with nylon cord, this additional ply is also cut and removed to expose the outermost cord of the polyester carcass ply.

This is because nylon cord plies are generally highly air impermeable.

Volume of recessed portion scraping over substantially 1cm square is adjusted to about 0.5cm ³ ~1.0cm ^3.

To this part, a plate material having a thickness of about 1 cm and an air-impermeable rubber having a size of about 2 cm square is bonded using a strong adhesive so as to cover the recess.

A pressure gauge is inserted in the center of the rubber plate in advance, and after the bonding, the pressure in the recess due to the cutting is measured.

After this preparation is completed, the internal pressure of the tire is increased to a pressure suitable for the tire. Test internal pressure is 3.0kg / cm for passenger car tires
^2, small light trucks (8 ply rating below) tires 4.5 kg / cm ^2, large light truck (10 ply rating or higher) is 7.0 kg / cm ^2, and truck, bus tires at 9.0 kg / cm ² carry out.

Check that there is no air leakage from the adhesive part of the rubber plate,
Leave the tire in a room at 25 ° C ± 3 ° C.

In this test, it is observed that the needle of the pressure gauge rises relatively quickly in a tire whose carcass ply is made of a cord having a high air permeability.

Pressure gauge value after 24 hours (hereinafter referred to as carcass built-in pressure)
Read the following formula Calculate the air permeability according to

For the tires manufactured according to one to three of the above-mentioned means, the tires obtained by approaching these means to the conventional means, and the conventional tire, the air permeability obtained by such a test method and the separation durability by the drum test FIG. 1 shows the results of the investigation of the gender relationships.

The tires used in this test and the test conditions were a steel belt pneumatic radial tire for light trucks (for vans), tire size 205 R14, and a drum endurance test was performed with a tire air pressure of 6 kg / cm ² , a load of 1630 kg, and a running speed of 60 km / hr
It was carried out in. These test conditions are particularly suitable for evaluating bead durability, and indicate that a running life of 10,000 km or more is acceptable.

The internal air pressure in the air permeability test is 4.5 kg / cm ^{2 of the} standard internal pressure.
And

If a polyester cord ply with an air permeability of 1.1 × 10 ^-3 kg / cm ² / h or less in this test is used for the carcass, most tires do not cause separation between the bead cord and rubber. The separation resistance has been greatly improved, and the driving life is at a pass level of 1.
Only when the distance exceeded 10,000 km, failures other than the bead separation, especially the belt end separation, occurred, ending the driving life.

Here, the heat set zone, the normalizing zone (hereinafter referred to as "norma zone") and the high elastic modulus property and heat shrinkage property (thermal dimensional stability) of the polyester cord after the drying zone treatment are maintained almost equal to those of the conventional case. The physical properties such as the elastic modulus and the heat shrinkage property are adjusted according to the conventional 3T conditions (temperature, time, tension). As described in detail above, when a polyester cord having a reduced number of defects at the interface between the cord and the rubber is arranged in the carcass ply, the handling stability and abrasion resistance are disadvantageously increased, and accordingly, the beads are particularly required. This is advantageous because the separation resistance of the part can be improved.

By the way, generally, the conditions for heat treatment of a polyester cord are under a low tension with emphasis on dimensional stability and adhesiveness so that the polyester fiber itself exhibits a high elastic modulus as compared with nylon fibers which are other general-purpose fibers. The usual method is to treat at a high temperature. At this time, there is no contact with reported cases that consider the occurrence of void defects at the rubber-cord interface due to deep depressions on the treated cord surface. .

The pneumatic radial tire according to the present invention will be further described later with reference to examples, but the present invention is not limited to these examples. It includes all tires used and defined by the air permeability measured by the above method.

The twist structure of the used polyester cord is 10
00D / 2,1000D / 3,1100D / 2,1100D / 3,1500D / 2,1500D / 3,1600
D / 2,1600D / 3 etc., and as a belt cord material of a pneumatic radial tire using the carcass ply of the present invention, not only steel, but also polyester, rayon, aramid, glass, carbon fiber, etc. .

(Examples) For Examples 1 to 6, Examples 1, 2 and Examples 5, 6
Is a pneumatic radial tire for a light truck (van) having a size of 205R14. Examples 3 and 4 are HR78-size tires.
15 pneumatic radial tires for passenger cars. Each tire has two ply carcass plies, each ply is a rubber coating of polyester cord arranged at an angle of about 90 ° to the tire equatorial plane, and these two ply carcass plies are turned up around each bead core. Has,
The higher edge of the fold is about 6 cm higher for the van tire and about 5 cm higher for the car tire when the tire is mounted on a standard rim.

Example 1 and 2
Is 1500 D / 2, and Examples 3 to 6 are 1000 D / 2. Further, the belt for reinforcing the crown portion of the carcass ply has two steel cord cross layers. In addition, tires of Comparative Examples 1 to 6 were prepared in order to confirm the superiority of separation resistance in each Example, Comparative Examples 1 and 2 were Examples 1 and 2, Comparative Examples 3 and 4 were Examples 3 and 4, Comparative Examples 5 and 6 corresponded to Examples 5 and 6, respectively, and were matched to the size and structure of the corresponding Example tire.

The polyester cords applied to the carcass plies of the tires of Examples 1 to 6 and Comparative Examples 1 to 6 were prepared as follows.

Regarding the cords applied to Examples 1 and 2 and Comparative Examples 1 and 2, first, a 1500D polyester filament bundle (192 filaments) was twisted, and the two twisted yarns were combined and twisted to 1500D. / 2 polyester raw cord (twisted number per 10 cm × twist direction 40S × 40Z) was made, and a long cord was woven with 53/5 cm of the raw cord. Example 3 As for the cords to be applied to Nos. To 6 and Comparative Examples 3 to 6, a raw polyester cord of 1000D / 2 (number of twists per 10 cm × the direction of twist is 49S × 49Z) was prepared in the same manner as above, and 54 of these raw cords were used. A long cord weaving cord counter was manufactured with the number of insertions of / 5 cm.

Next, these cords are dipped in an adhesive solution of RFL to apply the adhesive to each cord, and then the adhesive attached to each cord is dried in a drying zone. And a series of cord reverse treatments in which each cord was heat treated through a quota zone.

At that time, first, the tension applied to each cord 1500D / 2, 1000D / 2 opposite to the cord at the time of dipping and in the drying zone was divided into a group of 0.3 g / D or more and a group of less than 0.3 g / D. Nos. 1 to 8 are attached to the eight types of cords, and in addition to this tension, a series of remaining conventional processing conditions (tension, temperature,
The processing time), the physical properties of the cord after the processing and the adhesive adhesion rate are shown together in Table 1.

Next, assuming the same code denier number of 1000D / 2 and the same dipping treatment tension and drying zone tension of 0.23 g / D as the code No. 7 shown in Table 1, the affinity of the oil of the polyester raw yarn with the adhesive RFL was changed. No. 9 is the code opposite to the code that has increased the amount of adhesive applied using a high oil agent, and the suction pressure of the squeezing vacuum device that passes immediately after the adhesive is applied is reduced, and the surface of the adhesive code that is wet is reduced. No. 10 was used to increase the retention rate of the cords at No. 10, and on the other hand, the adhesive drying temperature in the drying zone of Nos. 9 and 10 was set to 180 ° C., which is 10 ° C. higher than the codes shown in Table 1, and these measures were taken. Tables 2 and 3 show the treatment conditions of these cords, the physical properties of the cords after treatment, and the adhesive adhering rate, similarly to Table 1 assuming that the conventional cords not subjected to the treatment are Nos. 11 and 12.

The strength (kg) of the processing code in Tables 1 and 2 is JIS L101
It is the value obtained according to 7. The heat shrinkage (%) is the initial load 5
It is the value of the dry heat shrinkage at 177 ° C. × 80 minutes at 0 g / piece, and the same applies hereinafter.

First, in the carcass ply of the tires of Examples 1 to 4,
Rubber-coated ply members were applied to the cords No. 1 and No. 2 and Nos. 5 and 6 shown in Table 1. That is, the polyester cord used for the carcass ply of the tire of Example 1 was 0.5 g / D at the time of dipping at the adhesive adhering stage of the cord of the weaving cord before rubber coating and in the drying zone. (Corresponding to No. 1, 1 g). The polyester cord used for the carcass ply of the tire of Example 2 has a tension of 0.37 g / D (each cord). The polyester cord used for the carcass ply of the tire of Example 3 had a tension of 0.38 g / D (a tension of 760 g per cord). The polyester cord used for the carcass ply of the tire of Example 4 was applied with a tension of 0.30 g / D (a tension of 600 g per cord) (cord reversal No. 5). No,
6), which have undergone the respective processes, and other than these processes follow conventional processing conditions.

On the other hand, for the carcass plies of the tires of Comparative Examples 1 to 4, the members covered with the rubber coated Nos. 3, 4 and Nos. 7, 8 shown in Table 1 were applied. Each of the polyester cords had the same value as described in Table 1 in the same processing steps as in the above Examples, as shown in Table 1.
A tension of less than 3 g / D was applied.

Examples 1-4 and Comparative Examples 1-4 as carcass plies coated with rubber on the opposite side of the cord weaving cord after the above treatment
Using the tires as test tires, an air permeability test and a separation durability test using a drum were performed indoors, and further, driving stability and ride comfort were tested using a real vehicle on a test course. Examples 1 and 2 and Comparative Examples 1 and 2 are shown in Table 3 and Examples 3 and 4 and Comparative Examples 3 and 4 are shown in Table 4 together with the code counter No. applied to the carcass ply.
Are shown below. The results of the drum test include the distance traveled (km) up to the occurrence of the failure, the details of the failure and the degree of the failure, and the steering stability and ride comfort were determined by comparing the results of Comparative Example 2 with 100 based on the feeling evaluation results by the test driver. The index value is described. The larger the value, the better.

The air permeability (kg / cm ² / h) described in Tables 3 and 4 was determined according to the measurement method and the calculation formula described above, and the tires of Examples 1 and 2 and Comparative Examples 1 and 2 had an internal pressure of 4.5 kg / h. cm ² in Examples 3, 4
And the tires of Comparative Examples 3 and 4 are each filled with an internal pressure of 3.0 kg / cm ^2, and about 1 c from the folded edge of the carcass ply toward the bead core until the outermost cord of the folded portion is exposed.
It is the pressure increase per hour in an enclosed space where rubber was scraped over m squares.

In addition, the drum separation test employs test conditions suitable for generating separation in the bead portion. The tires of Examples 1 and 2 and Comparative Examples 1 and 2 have an internal pressure of 6 kg / hour on a drum rotating at a surface speed of 60 km / h. Fill cm ² and load 1630k
g, the tires of Examples 3 and 4 and Comparative Examples 3 and 4 were filled with an internal pressure of 3.0 kg / cm ² and pressed and run with a load of 1370 kg, and the running distance when the tire failed was measured. The test was terminated at 15,000 km even if no failure was found on the appearance, and the failure contents of the belt part and the bead part were examined by dissection in each case.

Finally, in the carcass plies of the tires of Examples 5 and 6,
A ply member coated with rubber was applied to the cords No. 9 and 10 shown in Table 2. That is, while increasing the amount of adhesive applied during the dipping process, the drying temperature of the
At 0 ° C, the adhesive solidifies rapidly in the cord surface area,
In addition, the adhesion rate of the adhesive was set at 6.0% for the carcass ply cord of Example 9 and 6.5% at the maximum for the carcass ply cord of Example 10.

On the other hand, Table 2 shows the carcass ply of the tires of Comparative Examples 5 and 6.
This is a carcass ply cord similar to Comparative Example 3 in which a ply member coated with rubber is applied to cords Nos. 11 and 12 shown in FIG.

In Examples 5 and 6 and Comparative Examples 5 and 6, only the air permeability test and the drum separation test were performed by the same evaluation method according to the same conditions as in Examples 1 and 2 and Comparative Examples 1 and 2. Table 5 shows the test results.

Referring to Tables 1 to 5, a polyester cord to which a tension of 0.3 g / D or more has been applied from the dipping treatment opposite to the cord weaving cord before rubber coating to the adhesive drying treatment in the drying zone is used for the carcass ply. Examples 1 to 4 and the selection of an appropriate oil agent for the polyester cord or the suction force adjustment by vacuum increased the amount of adhesive adhered, and the adhesion rate of the solidified adhesive mainly on the cord surface by drying at 180 ° C. at a high temperature was 6.0%. In each of Examples 5 and 6 in which the carcass ply had a polyester cord of 1.1 × 10 ⁻³ kg / cm ² / h
0.3g / D while the following air permeability can be achieved
The polyester cords of the carcass plies of Comparative Examples 1 to 4 in which the application of a cord tension of less than Comparative Examples 1 to 4 and Comparative Examples 5 and 6 in which the drying temperature was low and the adhesive adhesion rate was the same as that of the conventional example were the same as those in Examples except for other processing conditions. Too high air permeability exceeding 1.1 × 10 ^-3 kg / cm ² / h, and as a result, the tires of Examples 1 to 6 exhibited sufficient separation resistance over a drum test mileage of over 10,000 km. In contrast, Comparative Examples 1 to
It can be seen that the tire of No. 6 had a separation failure at a low level far less than 10,000 km, that is, the tires of Examples 1 to 6 achieved a sufficient level of durability of the bead portion and the belt respectively on the market. You can see that it is.

(Effects of the Invention) According to the present invention, the durability of a pneumatic radial tire, which tends to be a problem when a polyester cord is used for a carcass ply, and particularly the improvement of separation resistance of a bead portion can be advantageously achieved. .

[Brief description of the drawings]

FIG. 1 is a graph showing the effect of air permeability on running life.

Claims (1)

(57) [Claims] 1. A pair of bead cores, at least one carcass ply which is a rubber coating of a polyester cord arranged at an angle of about 90 ° with respect to the tire equatorial plane between the bead cores, and a crown portion of the carcass ply. A belt to reinforce the polyester cord of the carcass ply, the raw cord weaving cord is passed through an adhesive solution and subjected to a dipping treatment, followed by a drying treatment in a drying zone, and a heat setting zone. And after the heat treatment for adjusting the elastic modulus and the heat shrinkage property in the normalizing zone is sequentially applied, the rubber is coated on the opposite side of the cord to form a carcass ply member, and the member is applied to an unvulcanized tire. In the pneumatic radial tire obtained by performing the vulcanization molding, the polyester cord of the carcass ply, A means of applying a high tension of 0.3gr / D or more to each of the cords in the dipping process and the drying process in the drying zone, or an adhesive for each of the cords immediately after the dipping process. Increase the amount of coating and increase the drying temperature in the drying zone to 17
After applying the adhesive at a rate of 5.5 to 6.5% after the quick drying and solidification treatment of the adhesive at a temperature exceeding 0 ° C and 180 ° C or less, the tire is applied through one of the means. The polyester cord of the carcass ply is made of a cord having an air permeability of not more than 1.10 × 10 ^-3 kg / cm ² / h including an interface between the cord and the rubber per cord. Pneumatic radial tire with improved performance.