JPH11263102A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide such a steel radial tire that reduces generation of bead crack. SOLUTION: This tire has a radial structure wherein a reinforcing layer 5 of organic fibers formed by covering both the ends of a basket fabric of organic fiber cords with topping rubber is positioned on the outside of an outwardly bent-up part 4 which is formed by bending an end up of a carcass ply 2 of a steel cord from the inside of a bend core 6 toward the outside thereof. In this case, the topping rubber is formed of a rubber composition wherein 10-40 wt.% of butadiene rubber and 90-60 wt.% of diene rubber other than butadiene rubber are compounded with 3-20 pts.wt. silica and 0.5-2 pts.wt. resorcin derivative composed by reaction of resorcin or resorcin and aldehyde, in addition melamine derivative composed by condensation addition reaction of formaldehyde to hexamethylenetetramine or melamine is added 0.8-2 times as much wt. as resorcin or resorcin derivative, and also the storage elastic modulus of vulcanized substance measured at 30 deg.C is 7-11 MPa and the loss elastic mudulus thereof measured at 30 deg.C is 1.5-2.5 MPa.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a pneumatic tire having a radial structure in which a carcass ply is made of a steel cord.
Particularly, the present invention relates to a pneumatic tire used for a large vehicle.

[0002]

2. Description of the Related Art A pneumatic tire having a radial structure in which a carcass is formed by a carcass ply in which a number of steel cords are arranged, or a pneumatic tire in which a steel cord reinforcing layer is disposed outside the carcass ply, is formed by winding a carcass ply. The rigidity changes greatly at the tip of the raised portion or at the tip of the steel cord reinforcement layer, so during use of the tire, stress is concentrated on the tip of the carcass ply roll-up portion or the tip of the steel cord reinforcement layer, and separation is likely to occur. . To prevent separation,
As shown in FIG. 1 or FIG. 2, an organic fiber strong layer 5 having topping rubber coated on both sides of the organic fiber cord fabric is arranged outside the top of the rolled-up portion or over the top end of the steel cord reinforcing layer. I was

[0003] In general, as a topping rubber, adhesiveness,
Excellent in fatigue resistance, high tear strength, low heat generation Small amount of styrene-butadiene rubber blended with a small amount of styrene butadiene rubber to improve rolling processability A rubber composition containing sulfur, a vulcanization accelerator, zinc white, stearic acid and the like has been used.

[0004]

However, in a tire in which a carcass ply is formed of a steel cord, a so-called steel radial tire, as described above, the tip of the rolled-up portion or the upper end of the steel cord reinforcing layer is coated with an organic fiber reinforcing layer. Even when reinforced, when used under severe conditions such as use at a load equal to or higher than the design load, use at an internal pressure equal to or lower than the design internal pressure, cracks occur near the upper end of the organic fiber reinforcing layer, and the cracks are adjacent In some cases, it propagates to the rubber member and expands, causing a failure called a bead crack and being removed early.

[0005] It is an object of the present invention to provide a steel radial tire with reduced occurrence of bead cracks.

[0006]

Means for Solving the Problems The inventors disassembled a tire in which a bead crack occurred and a tire in which a sign of bead crack was observed, and observed the upper end of the organic fiber reinforcing layer. It has been found that a fracture occurs, which is initiated and causes a crack to occur and propagate to an adjacent rubber member, which spreads and causes a failure called a bead crack. Therefore, in order to prevent bead cracks, it is better to improve the topping rubber so that micro-destruction in the topping rubber layer, which is the initiation of cracks, does not occur, rather than improving the rubber member in which bead cracks occur. The present invention was thought to be effective and repeated trial and error to arrive at the present invention.

According to the present invention, the carcass is formed by a carcass ply in which a number of steel cords are arranged at right angles to the tire circumferential direction, and the ends of the carcass ply extend from inside to outside around a bead core arranged in a bead portion. Pneumatic tire having a radial structure in which an organic fiber reinforcing layer formed by covering both sides of an organic fiber cord fabric with topping rubber is arranged outside the wound part to form a wound part; In a pneumatic tire having a radial structure in which a steel cord reinforcing layer is disposed outside the raised portion, and an organic fiber reinforcing layer formed by coating both sides of the organic fiber cord fabric with topping rubber is disposed outside the steel cord reinforcing layer. The topping rubber is butadiene rubber 10
40% by weight, diene rubber other than butadiene rubber 90 to 90%
3 to 20 parts by weight of silica, 0.5 to 3 parts by weight of resorcinol or a resorcinol derivative obtained by reacting resorcinol with aldehyde are mixed with 100 parts by weight of a rubber component of 60% by weight, and further mixed with hexamethylenetetramine or melamine. A rubber composition comprising a melamine derivative obtained by reacting formaldehyde with resorcinol or 0.8 to 2 times by weight of the resorcinol derivative, having a storage elastic modulus (E ') of 7 to 11 MPa measured at a temperature of 30 ° C., and a loss elastic modulus. (E ″) is 1.5 to 2.5 MPa.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A pneumatic tire according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view of the right half of one embodiment of the pneumatic tire of the present invention. Reference numeral 1 denotes a carcass. The end portion 3 of the carcass ply 2 that reinforces the carcass 1 is wound up from the inside to the outside around the bead core 6 to form a rolled-up portion 4, and terminates in a lower region of the side portion S. The organic fiber reinforcing layer 5 is disposed adjacent to the outer surface of the wound portion 4 so as to straddle the tip 4 ′ of the wound portion 4. The organic fiber reinforcing layer 5 covers both sides of the cord of the organic fiber cord with a topping rubber, and has a predetermined shape such that the cord direction is inclined with respect to the tire radial direction when the topping rubber-coated cord is incorporated into a tire. It is formed by cutting.

FIG. 2 is a partial sectional view showing a bead of another embodiment of the pneumatic tire of the present invention. Similarly to the above embodiment, the end portion 3 of the carcass ply 2 is wound up along the bead core 6 to form a wound-up portion 4. A steel cord reinforcing layer 7 is arranged adjacent to the outer surface of the rolled-up portion 4, and an organic fiber reinforcing layer 5 is arranged adjacent to the outer surface of the steel cord reinforcing layer 7 across the upper end 7 ′ of the steel cord reinforcing layer. .

The rubber component of the rubber composition used for the topping rubber of the organic fiber reinforcing layer of the tire of the present invention (hereinafter, the comb composition used for the topping rubber is simply referred to as a rubber composition) is 10 to 40% by weight of butadiene rubber. And 90 to 60% by weight of a diene rubber other than butadiene rubber. When the blending ratio of butadiene rubber is less than 10% by weight, the effect of butadiene rubber is not exhibited, so that the object of the present invention cannot be achieved. When it is more than 40% by weight, the tear strength decreases,
Not preferred. Examples of the diene rubber other than butadiene rubber include natural rubber, isoprene rubber and styrene butadiene rubber. Among them, natural rubber which generates a small amount of heat and has high tear strength is preferable.

The rubber composition of the present invention contains silica as a reinforcing agent in addition to carbon black in an amount of 3 to 20 parts by weight per 100 parts by weight of the rubber component. If the amount of silica is less than 3 parts by weight, the effect of the silica is not exhibited, so that the object of the present invention cannot be achieved. If the amount is more than 20 parts by weight, the fatigue resistance decreases. When silica is used as a reinforcing agent, a silane coupling agent that is usually blended is not blended.

The rubber composition of the present invention contains resorcinol or a resorcinol derivative in an amount of 0.1 to 100 parts by weight of the rubber component.
5 to 3 parts by weight are blended. The resorcinol derivative is a condensation polymer of resorcinol and an aldehyde, preferably formaldehyde, and if a methylene donor is added,
Further, it was adjusted so as to undergo a condensation polymerization reaction with a methylene donor.
0 and 620 are available. If the amount of resorcinol or resorcinol compound is less than 0.5 part by weight, the object of the present invention cannot be achieved. If the amount is more than 3 parts by weight, the fatigue resistance is reduced. As a methylene donor of resorcinol or a resorcinol derivative, hexamethylenetetramine or melamine obtained by reacting melamine with formaldehyde, or a melamine derivative which is a mixture thereof is 0.8 to 2 times the weight of the resorcinol or resorcinol derivative. Be blended. Hexamethylenetetramine or melamine derivative compounding amount,
If the amount of resorcinol or resorcinol derivative is less than 0.8 times, the unreacted product of resorcinol or resorcinol derivative with hexamethylenetetramine or melamine derivative remains, and if it is more than twice, resorcinol or resorcinol derivative of hexamethylenetetramine or melamine derivative. Unreacted material remains. These unreacted substances act as foreign substances and reduce the fatigue resistance of the rubber composition.

The rubber composition of the present invention has a storage elasticity measured at a temperature of 30 ° C., an elongation of 15%, an amplitude of 1% and a frequency of 50 Hz by adjusting the amount of a compounding agent such as carbon black, a softening agent and sulfur. Modulus is 7-11MPa, loss modulus is 1.5
２．５2.5 MPa. Storage elastic modulus is 7MPa
If it is smaller, the difference in storage modulus between the topping rubber of the steel cord ply adjacent to the organic fiber reinforcing layer and the topping rubber is large, and the object of the present invention cannot be achieved. If it is larger than 11 MPa, the fatigue resistance is reduced. . Loss modulus is 1.5
If the pressure is lower than MPa, the effect of converting mechanical energy into heat energy to attenuate the stress acting on the tip of the hoisting portion is reduced, and cracks are likely to occur.
If it is larger than a, the fatigue resistance will decrease.

[0014]

EXAMPLES The rubber components shown in Table 1 or Table 2 were blended with carbon black and silica in the proportions shown in Table 1 or Table 2 (parts by weight, hereinafter, parts by weight are simply referred to as "parts"). 3 parts, 1 part of stearic acid, 2 parts of oil, 1 part of antioxidant (trade name: Nocrack 6C manufactured by Ouchi Shinko Chemical Co., Ltd.) are mixed, mixed using a Banbury mixer according to a general method, and once discharged and cooled. After that, resorcinol in the amount shown in Table 1 or Table 2 was additionally mixed and discharged and cooled.
Alternatively, a mixed rubber was obtained by additionally mixing hexamethylenetetramine, 2 parts of sulfur and 1 part of a vulcanization accelerator CBS in the amounts shown in Table 2.

A sample was taken from the above mixed rubber, and the storage modulus and the loss modulus were measured by the methods described below. The results are shown in Table 1 or Table 2.

Further, each of the above mixed rubbers has a fineness of 12
A 60D / 2 nylon 66 cord cord weave is cut into a predetermined shape by topping on both sides with a rubber composition of 0.3 mm on one side, and this is used as an organic fiber reinforcing layer member. The size 11R22. Five tires were prototyped. A durability test was performed on each prototype tire by the method described below. The results are shown in Table 1 or Table 2.

[0017]

[Table 1]

[0018]

[Table 2]

Storage elastic modulus and loss elastic modulus: The mixed rubber was put into a mold and vulcanized at a temperature of 150 ° C. for 30 minutes to produce a test piece, and a viscoelastic spectrometer manufactured by Iwamoto Seisakusho was used. Extension rate 15%, amplitude 1%, frequency 50Hz
It measured on condition of. Endurance: The prototype tire is assembled on a rim, filled with 0.9MPa internal pressure air, set on a drum tester, and run on a drum at a load of 5400 kg at a speed of 40 km / hr until a failure occurs. did. The durability is 10 compared to Comparative Example C1.
%, An improvement of less than ± 10% is indicated by Δ, and a decrease of 10% or more is indicated by X.

Each of the prototype tires of the examples is a comparative example C1 having an organic fiber reinforcing layer topped with a conventional rubber composition.
The durability improved more than 10%. C2 having a butadiene rubber blend ratio of more than 40% by weight has lower durability than C1. C3 containing no silica and C4 containing more than 20 parts of silica and having a storage modulus of less than 7 MPa have reduced fatigue resistance and no improvement in durability. C5 in which the amount of hexamethylenetetramine is less than 0.8 times the amount of resorcinol and C6 in which the amount of hexamethylenetetramine is more than 2.0 times do not show improvement in durability. C7 containing no hexamethylenetetramine has lower durability than C1. C8 having a storage modulus of more than 11 MPa has lower durability than C1.

[0021]

The topping rubber of the organic fiber reinforcing layer comprises butadiene rubber in an amount of 10 to 40% by weight of the rubber component, and 3 to 20 parts of silica, resorcin or resorcin derivative 1.5 to 3. The bead durability is improved by forming a rubber composition in which 0 parts are blended and resorcin hexamethylenetetramine or a melamine derivative is added in an amount of 1.5 to 2.5 times the weight of resorcin or resorcin derivative.

[Brief description of the drawings]

FIG. 1 is a sectional view of a right half of an embodiment of a pneumatic tire according to the present invention.

FIG. 2 is a partial sectional view of a bead portion of another embodiment of the pneumatic tire of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 carcass 2 carcass ply 3 end of carcass ply 4 rolled-up portion 4 ′ tip of rolled-up portion 5 organic fiber reinforcing layer 6 bead core 7 steel cord reinforcing layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI B60C 9/04 B60C 9/04 C 9/08 9/08 E 9/20 9/20 C 15/00 15/00 A 15 / 06 15/06 N // C08K 3/36 C08K 3/36 C08L 9/00 C08L 9/00 (C08L 9/00 61:12 61:28)

Claims (1)

[Claims] A carcass is formed of a carcass ply in which a number of steel cords are arranged at right angles to the tire circumferential direction, and the end of the carcass ply is wound from inside to outside around a bead core arranged in a bead portion. A pneumatic tire having a radial structure in which an organic fiber reinforcing layer formed by covering both sides of an organic fiber cord fabric with topping rubber is disposed outside the wound part to form a wound part; In a radial structure pneumatic tire in which an organic fiber reinforcing layer formed by coating both sides of an organic fiber cord woven fabric with topping rubber is disposed outside the steel cord reinforcing layer.
The above-mentioned topping rubber is 100 parts by weight of a rubber component consisting of 10 to 40% by weight of butadiene rubber and 90 to 60% by weight of a diene rubber other than butadiene rubber, and 3 to 20 parts by weight of silica.
Parts by weight, 0.5 to 3 parts by weight of resorcinol or a resorcinol derivative obtained by reacting resorcinol and aldehyde,
Furthermore, the melamine derivative obtained by condensation addition of formaldehyde to hexamethylenetetramine or melamine contains 0.8 to 2.0 times the weight of resorcinol or resorcinol derivative, and the storage modulus (E ′) of the vulcanizate measured at a temperature of 30 ° C.
Is 7 to 11 MPa, and the loss elastic modulus (E ″) is 1.5 to 2.5.
A pneumatic tire formed of a rubber composition having a pressure of MPa.