LU100828B1 - TOP FLOOR BAND COMPRISING NYLON 6.6 AND PET CABLE ALTERNATE CABLES - Google Patents

Abstract

Woven or woven fabric for pneumatic tires, made from PET and nylon 6,6 warp yarns, alternately arranged with a different cable twist coefficient, which is used as reinforcement for a pneumatic tire. Such a cable stripe or such a woven fabric for a tire improves high-speed durability, tread separation resistance, and impact resistance when used in the form of a web. spirally wound vertex forming a zero degree angle in pneumatic tires of the radial web type.

Description

TOP FLOOR BAND COMPRISING NYLON CABLES

6,6 AND PET ALTERNATELY DISPOSED

DESCRIPTION FIELD OF THE INVENTION

The present invention relates to a novel strand of cord or a new woven fabric for a pneumatic tire comprising alternately arranged PET and nylon 6,6 warp strands, which are used as reinforcement for a pneumatic tire. A new strand of cable or a new woven fabric of this type for a pneumatic tire can improve high-speed durability, tread separation resistance and impact resistance when used under the shape of a spirally wound crown ply forming an angle equal to zero degrees on a bunch of belts in pneumatic tires of the radial ply type.

BASIS OF THE INVENTION

In high speed conditions, the outer diameter of the tire increases under the influence of the centrifugal forces generated by the tread and the bundle of belts formed by steel cords. Such an increase in the diameter or such expansion of the tire increases the pantographic movements of the cords at the edges of the belts, which gives rise to crack initiation, crack propagation and separations of the terminal edges to the belts.

On the other hand, raising the temperature at the belt edges under high speed conditions can trigger a degradation of the local adhesion of the textile crown ply strip and give rise to local separations between the tread and the summit plies, which can ultimately result in belt edge separations in a very short time based on non-uniform distributions of constraints.

The crown ply layer which wraps circumferentially around the belt package prevents excessive expansion of the tire under high speed conditions by exerting compressive forces (restriction forces) on a thick belt package consisting of layers of diagonal-ply type steel cords. In order to increase the force of restriction, webs of crowns having cords of the type with a high number of cords (high epdm value) (such as nylon, 1400 × 2, 110 epdm or nylon 1400x1, 140 epdm, etc.). At present, the most widely used materials for crown plies are nylon 6.6 cords and hybrid aramid / nylon cords that spiral into a package of belts at 0 to 5 degrees from the equatorial plane of the tire.

Nylon cords have excellent fatigue resistance when subjected to axial flexion and compression, as well as bielastic tensile strength characteristics, making it easy to handle during the course of the process. making the tire. In addition, the generation of a thermal shrinkage force as a result of a rise in operating temperature under high speed conditions improves the resistance to belt edge separation, as well as the high speed durability.

It is well known that hybrid cords comprising high modulus and low modulus yarns having a bielastic tensile strength behavior are also used to act as crown plies in high velocity tires. The low modulus component of the hybrid cable allows for easy lifting of the belt package in the absence of excessive formation of tightly bound cords due to its high extensibility and the high modulus component proves effective under service conditions. When using hybrid cords to act as a crown ply, the total thickness of the crown ply layer as well as the rubber content can be reduced, and the high modulus component of the hybrid cord can increase the thickness of the crown ply. Restricting force and improve high speed durability.

U.S. Patent 4,284,117 discloses a nylon crown ply which is formed from individual yarns rather than from cords. The crown ply is thinner than conventional crown plies in that it has superior flexibility characteristics and superior heat dissipation. However, the limited fatigue resistance exhibited by individual ground cords represents the major disadvantage of said application. Increasing the twist to improve fatigue strength results in a dramatic drop in the modulus and the force of restriction.

U.S. Patent No. 5,115,853 discloses a radial ply type tire having a crown ply structure which is radially disposed outside of the belt reinforcing structure. The crown ply structure comprises side-by-side 420x2 nylon cords having a cord twist of not more than 280 rpm. The limited torsion, in this case the low torsion (low helical angle), has negative effects on the fatigue resistance and on the impact resistance.

In U.S. Patent No. 7,584,774, a polyethylene terephthalate (PET) cord is described as a belt-reinforcing layer (crown ply) spirally wound on a belt pack in the circumferential direction. Said PET cord has a modulus of elasticity of not less than 2.5 mN / dtex.% Under a load of 29.4 N at 160 ° C. The high module drop of PET cords at high speed temperatures limits durability performance.

SUMMARY OF THE INVENTION

The present invention relates to a novel strand of cord or a new woven fabric for a pneumatic tire, made from alternately arranged PET and nylon 6,6 warp yarns, which is used as reinforcement for a bandage. pneumatic. Such a new strand of cords or such a new woven fabric for a tire makes it possible to improve high-speed durability, tread separation resistance and impact resistance when used in the form a spiral-shaped crown ply forming a zero-degree angle in radial-ply type pneumatic tires.

As is well known, nylon 6,6 has excellent fatigue resistance and a bielastic tensile strength, which makes possible the lifting process in the absence of tightly formed cords and which makes it possible to obtain a sufficient restriction force under high speed conditions. However, because of the low initial modulus of the nylon 6,6 cords, it is necessary to use bands or fabrics with a high epdm value (high number of cords per decimeter) in order to obtain the restraining force. sufficient for the package of belts (as can be seen in Figure 1). On the other hand, PET cords have a modulus of elasticity and a glass transition temperature (Tg) that are higher than those of nylon 6,6, which is why they reduce the phenomenon of bandage flattening. pneumatic due to inadequate parking of the vehicle (in English: "flatspotting"), to reduce the generation of noise and increase durability when traveling at a speed ranging from a low speed to a medium speed. However, the low level of surface activity of PET implies lower static and dynamic adhesion than those obtained with nylon 6,6.

In addition, the distance from cord to rivet in such strips or fabrics is too narrow, making it difficult for the rubber to penetrate between the cords without premature vulcanization. Based on the short distance from cord to cord due to a high number of wire ends (high epdm value), cracks in the rubber can easily be triggered between cords under dynamic conditions based on high shear stresses. . It is well known that the distance from hard-wired to hard-wired (rivet zone) is an important parameter for controlling crack initiation as well as tire failure.

The present invention combines the advantage of a high initial modulus and a high Tg value manifested by the PET cord as well as the properties of bielastic characteristic, high fatigue resistance, better adhesion and generation. a high resistance to thermal shrinkage that manifests nylon 6,6.

According to the invention, in the webs of crown plies, the nylon 6.6 and PET cords have different moduli or different LASE values, and different values of resistance to thermal shrinkage. During lifting (during expansion) during the vulcanization process, high modulus type PET cords (wired slightly stretchy) are subjected to a load far superior to that of nylon 6,6 cords (wired highly extensible). Based on a higher cord load, PET cords penetrate better than nylon 6,6 cords through the scrubbing compound. Given the different penetration levels of the PET and nylon 6,6 cords, the single-web type web-edge layer is transformed into a bilayer-type vertex web (as can be seen in Figure 2).

DEFINITIONS Wired: reinforcing element obtained by reciprocal twisting of wires of the type with two or more layers.

Denier: the weight in grams of a thread with a length of 9000 m.

Dtex: the weight in grams of a thread with a length of 10,000 m.

Flatspotting: temporary fixation of the footprint configuration when parking after high speed driving. LASE: the load at a specified elongation. LASE 7%: the load at an elongation of 7%.

Linear density: the weight per unit length expressed in g / dtex or g / d (denier).

Restriction force: The force exerted by the crown ply on the belt pack when driving to prevent expansion of the tire.

Total Linear Density: The sum of the nominal linear densities of the strand wires of the cord. Wired type of two layers: wired that is prepared by twisting reciprocal son of two-ply type. Wired three-ply type: wired that is prepared by reciprocal twisting son of three-ply type.

Twist: the number of turns per meter (t / m or rpm).

Chain: The group of threads or cords in all woven fabrics, which extend longitudinally and parallel to the selvedge and intertwine with the filling material.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a cross-sectional view of a conventional nylon crown ply (of the prior art) on a bundle of belts made of diagonal-ply type steel cords after the vulcanization process. a represents a bundle of belts constituted by steel cords of the diagonal web type; b represents a conventional crown ply on a package of belts; c represents a tread.

FIG. 2 is a cross-sectional view of a crown ply according to the invention comprising nylon 6.6 and PET cords arranged alternately on a bundle of belts consisting of diagonal-ply type steel cords, after the vulcanization process. a represents a bundle of belts constituted by steel cords of the diagonal web type; b represents a crown ply on a pack of belts according to the invention; c represents a tread.

Figure 3a is a cross-sectional view of the crown ply according to the invention on a bundle of belts consisting of diagonal-ply type steel cords, (1) before the vulcanization process; (2) after the vulcanization process. A: represents a nylon cord 6.6 having a low initial modulus; B: represents a PET cable having a high initial modulus; H: represents the difference in penetration of the cords in a rubber matrix.

Fig. 3b is a top view of the crown ply web made from cords A (nylon 6,6, low modulus, low tensile strength) and B (PET, high modulus, high tensile strength) .

Fig. 4a is a cross-sectional view of the crown ply comprising cords arranged in pairs side by side (nylon 6,6 / PET) in accordance with the invention on a bundle of diagonal web type steel cord belts. , (1) before the vulcanization process; (2) after the vulcanization process.

Figure 4b is a top view of cords arranged side by side (in pairs) A (nylon 6.6, low modulus, low resistance to voltage) and B (PET, high modulus, high voltage resistance) in a Summit tablecloth band.

Figure 5 shows the changes in the distance between one cord and another cord after the vulcanization process, (1) before the vulcanization process; (2) after the vulcanization process: 51: cable to cable distance between A and B before the expansion and vulcanization process; 52: cable to cable distance between A and B after the expansion and vulcanization process; 53: cable to cable distance between A and A after the expansion and vulcanization process; 54: cable distance to wired between B and B after the expansion and vulcanization process;

Fig. 6 shows 1 + 2 + 1 arrangements of cords, (1) before vulcanization process, (2) after curing process: (1) cabling arrangement A + B + B + A + B + B + A + ... before the expansion and vulcanization process; (2) arrangement of cords A + B + B + A + B + B + A + ... after the expansion and vulcanization process.

Figure 7 shows 2 + 1 + 2 cable arrangements: (1) wire arrangement A + A + B + A + A + B + A + A + ... before the expansion and vulcanization process; (2) arrangement of cords A + A + B + A + A + B + A + A + ... after the expansion and vulcanization process.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the invention, webs of summit webs or crown webs spirally wound on packets of circumferentially circumferential radial tire belts having nylon 6.6 and PET cords arranged in alternation, in the form of a chain: improve high-speed durability based on the high modulus of PET cords, the high thermal shrink resistance of nylon 6,6 cords and on the basis of longer distances from hard-wired to hard-wired (by decreasing the shear stresses) between the cords (shifting the cords vertically, forming two layers or zigzag pattern) (as can be seen in Figures 3a, 3b and 5); improve the shock resistance of the belt package based on superior energy absorption by nylon 6.6 cords and high torsion type PET cords; and improve the resistance to separation between the tread and the crown plies by virtue of the corrugated surface structure of the crown ply. The zigzag configuration of the surface also improves the mechanical bond between the crown ply compound and the tread compound; and reduce the phenomenon of tire flattening due to inadequate vehicle parking (in English: "flatspotting") due to the lower nylon 6.6 content and the presence of PET cords having a higher Tg value.

The nylon 6,6 cords and the PET cords in a crown ply strip represent two-ply and / or three-ply type cords. The angle formed by the strips of crown plies spirally wound with respect to the medial circumferential line (or with respect to the equatorial plane of the tire) rises from 0 to 5 °.

In order to achieve an effective combination of fatigue strength and nylon 6.6 modulus, the tensile strength of nylon 6,6 cords is at least 10,000 and at most 15,000, according to the formula indicated below:

Coefficient of torsion = twist of the cord x (total linear density of the cord) 1/2 (1)

Twist expressed in rpm.

Linear density expressed in dtex.

In order to obtain the advantages mentioned above, the twist of the PET cord is at least 50 rpm greater than that of the nylon cord 6.6 (for example woven nylon 6.6, 1400x2, Z / S, 250/250 rpm, and wired in PET 1440x2, Z / S, 300/300 rpm or 350/350 rpm).

When the cable twist difference is less than 50 rpm between the first and second cords, the LASE value, the modulus, or the difference in extensibility between the first and second cords become insignificant. Under these conditions, the corrugated surface of the crown ply can not be obtained on the tire belt package.

The total linear density of the cords is at least 500 dtex and at most 5,000 dtex. Summit ply cords that have a value of less than 500 dtex are too thin and LASE values are too low and do not provide sufficient restrictive force, even with very high numbers of cords (high epdm value ). Apart from this disadvantage, during the process of lifting and curing, they can cause cuts in the compound serving as a scrub layer of the belt layer and come into contact with the steel cords. Topwrap cords with a value greater than 5,000 dtex are too thick and require too much rubber for the coating. The potential disadvantage associated with such cords in pneumatic tires is the increase in rolling resistance and greater heat accumulation in the crown area.

The difference in total linear density between the first and second cords is less than 15%. Preferably, the total linear densities of the first and second cables will be identical.

In accordance with the invention, the sequence of the nylon 6.6 and PET cords, which are parallel to each other in a crown web strip, represents an alternate form as follows: A + B + A + B + A + B + ... etc., wherein A represents the nylon cord 6.6 having a low torsion and B represents the PET cord whose torsion is greater than that of A. Such a band of crown ply provides a uniform corrugated surface after the vulcanization process, which strongly binds to the tread compound by improving the tread separation resistance under high speed conditions.

In accordance with the invention, the sequence of the nylon 6.6 and PET cords, which are parallel to each other in a crown web strip, represents an alternate form as follows: AB + AB + AB +. etc., in the form of cords arranged in pairs, where A is the low-torsion nylon cord 6.6 and B is the PET cord whose twist is greater than that of A.

In accordance with the invention, the sequence of the nylon 6.6 and PET cords, which are parallel to one another in a crown ply band, represents an alternating shape as indicated below A + B + B + A + B + B + A + B + B + ... etc., where A is the nylon cord 6.6 with a low twist and B is the PET cord whose twist is greater than that of A .

In accordance with the invention, the sequence of the nylon 6.6 and PET cords, which are parallel to each other in a crown ply strip, represents an alternating shape as indicated below A + A + B + A + A + B + A + A + B + ... etc., wherein A is the nylon cord 6.6 having a low twist and B is the PET cord whose twist is greater than that of A .

According to the invention, the number of cable ends in the strip amounts to at least 70 epdm (ends per decimeter). In the case of numbers of cable ends with a value of less than 70 epdm, the effectiveness of the surface corrugation is not sufficient to obtain a mechanical connection to the tread.

According to the invention, the difference between the 7% LASE values of the first and second nylon cords is at least 15% and preferably at 25% (7% LASE values determined according to ASTM D885). -16).

According to the invention, the width of the strips of crown plies is between 8 and 25 mm, preferably between 10 and 15 mm.

Claims (16)

A crown ply web made from alternately woven, alternately woven nylon 6.6 and PET yarns, which is wrapped circumferentially around a bunch of belts of a radial ply tire, characterized in that the twist coefficient of said PET cord which is determined according to the formula given below: torsion coefficient = twist of the cord x (total linear density of the cord) 1/2; is at least 15% greater than the torsion coefficient of said nylon cord 6.6. The crown ply web of claim 1, wherein the torsion coefficient of said nylon cord 6.6 is at least 10,000 and at most 15,000. The crown ply web of claim 1, wherein the twist coefficient of said PET cord is less than 20,000. The crown ply web of claim 1 wherein said nylon cords 6.6 and said PET cords are two-ply type cords. The crown ply web of claim 1, wherein said nylon cords 6.6 and said PET cords are three-ply cords. The crown ply web of claim 1, wherein the linear density of said nylon 6,6 cords and said PET cords is at least 500 dtex and at most 5,000 dtex. The crown ply web of claim 1, wherein the difference between the linear densities of said nylon cords 6.6 and said PET cords is less than 15%. A crown ply web according to claim 1, wherein the arrangement of said nylon 6,6 (A) cords and said PET cords (B) in said web is as indicated below A + B + A + B + A + B etc. The crown ply web of claim 1, wherein the arrangement of said nylon 6,6 (A) cords and said PET cords (B) in said web is as follows AB + AB + AB etc., in the form of cords arranged in pairs. The crown ply web of claim 1, wherein the arrangement of said nylon 6,6 (A) cords and said PET cords (B) in said web is as indicated below A + B + B + A + B + B + A + B + B + A etc. The crown ply web of claim 1, wherein the arrangement of said nylon 6,6 (A) cords and said PET cords (B) in said web is as indicated below A + A + B + A + A + B + A + A + B etc. The crown ply web of claim 1, wherein the number of ends of cords in said web is at least 70 epdm (ends per decimeter). The crown ply web of claim 1, wherein the difference of the 7% LASE values (determined in accordance with ASTM D885-16) between said PET cords and said nylon 6,6 cords amounts to at least 25%. The crown ply web of claim 1, wherein the difference of 7% LASE values between said PET cords and said nylon 6,6 cords is at least 35%. The crown ply web of claim 1, wherein the width of said crown ply band is at least 8 mm and at most 25 mm. The crown ply web of claim 1, wherein the width of said crown ply band is at least 10 mm and at most 15 mm.