LU100827B1 - Polyester Summit Tablecloth - Google Patents

Abstract

A strip or fabric of tows for a tire comprising parallel, alternately arranged polyethylene terephthalate (PET) cords having different lengths of twist is disclosed. Such a web or cable fabric for a tire improves high-speed durability, tread separation resistance, and impact resistance when used in the form of a crown ply spiral wound at zero degree angle in radial-ply type pneumatic tires.

Description

POLYESTER TOP TABLECLOTH

DESCRIPTION FIELD OF THE INVENTION

The present invention relates to a novel tire web or tire fabric comprising alternating polyester parallel cords having different twists. A new strip or fabric of such cords for a tire improves durability at high speed, tread separation resistance and impact resistance when used in the form of a tire. a spirally wound crown ply forming an angle equal to zero degrees on a belt pack in radial ply type pneumatic tires.

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 PET, 1100x2, 110 epdm, etc.) are usually used. ). 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.

PET (polyethylene terephthalate) cords have a higher modulus and higher voltages between the cords inside the tire compared to reinforcements in the form of nylon top plies 6,6. Due to a smaller number of active sites (functional groups) on the fiber surface compared to nylon 6,6, PET is more sensitive to thermal degradation with respect to adhesion with rubber to high temperatures. This is why the resistance to separation between the tread and the crown plies, which the PET shows is lower than that of the nylon 6,6.

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.

In U.S. Patent No. 7,584,774, a polyethylene terephthalate (PET) cord is disclosed as a belt-reinforcing layer (crown ply) that spirals around the package of belts 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 major disadvantage with conventional PET web plies in high velocity radial web tires is the need for robust dynamic adhesion to retard crack formation between the cords (due to shear forces). ). In high speed conditions, the temperature at the edges of the belts also becomes higher and the modulus of the cords of the crown plies of PET decreases. For this reason, it is preferred to use strips having a high number of cable ends as a single layer top sheet. Nevertheless, crown plies having a high number of cords show a greater tendency to crack formation, which may lead to separation of plies.

SUMMARY OF THE INVENTION

The present invention relates to a novel band or a new woven fabric for a pneumatic tire made from alternately woven (woven) cords having different twists. A new tire band or fabric for a tire improves the high-speed durability, tread separation resistance, and impact resistance when used in the form of a tire. a spiral-shaped crown ply forming a zero degree angle in pneumatic tires of the radial ply type.

Because of the lower dynamic adhesion that polyester (PET) exhibits, it is preferable to use it as a monolayer-type crown ply having a high number of cords and a narrow rivet on packages. belts in pneumatic tires with radial ply for high speeds (as can be seen in Figure 1). On the other hand, the distance from cord to cord (rivet zone) in such strips or fabrics is too narrow, which makes it difficult for the rubber to penetrate between the cords without premature vulcanization. In addition, cracks in the rubber can easily be triggered between cords having a narrow rivet under dynamic conditions based on high shear stresses.

According to the invention, in the webs of crown plies, the PET cords having different twists have different moduli or LASE values and different values of thermal shrinkage. During lifting (during expansion) during the vulcanization process, PET cords of the low twist type (high modulus, wired slightly expandable) are subjected to a load far superior to that of torsion type cords high (low module, highly scalable wired). In addition to superior stress resistance of the cord, the low twist type nylon cords subjected to higher loads generate a higher heat shrinkage value (greater contraction force) than the vulcanization temperature. Based on a higher cord load and a higher heat shrinkage value, low torsion type nylon cords penetrate better than high torsion type cords through the scrubbing compound. Due to the different penetration levels of the low torsion type and high torsion type PET cords, the single web type vertex band layer is transformed into a bilayer-type vertex band (as can be seen from FIG. 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.

Equatorial plane: the plane passing through the circumferential median line in the tire. LASE: the load at a specified elongation. LASE 7%: the load at an elongation of 7% in the load / elongation curve.

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

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 polyester (PET) top ply on a package 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 polyester web (PET) according to the invention on a belt pack consisting of diagonal web 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.

Fig. 3a is a cross-sectional view of a nylon crown ply according to the invention on a belt pack consisting of diagonal web type steel cords, (1) prior to the vulcanization process; (2) after the vulcanization process. A: represents a first polyester cord (PET) having a high torsion or a high torsion coefficient, having a modulus lower than that of the cord B; B: represents a second polyester cord (PET) having a low twist or a low torsion coefficient, having a modulus higher than that of the cord A; H: represents the difference in penetration of the cords in a rubber matrix.

Fig. 3b is a top view of a PET web ply web constituted by A (high twist, low modulus, low tensile strength) and B (low twist, high modulus, high tensile strength).

Fig. 4a is a cross-sectional view of a PET web ply comprising cords arranged in side-by-side pairs according to the invention on a diagonal web-type steel cord belt package, (1) before the vulcanization process; (2) after the vulcanization process.

Figure 4b is an elevation view of cords A (high torsion, low modulus, low tensile strength) and B (low torsion, high modulus, high tensile strength) in a crown ply band.

Figure 5 shows the changes in the distance from cord to 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;

Figure 6 shows 1 + 2 + 1 cable arrangements. (1) arrangement of cords 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) cord 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, crown ply webs or crown ply fabrics spirally wound on circumferentially circumferential radial ply tire belt packages having alternately arranged polyester warp (PET) cords. , having different torsion coefficients: improve the high speed durability based on the high modulus of the low twist type PET cords and on the basis of the greater distances from cord to cord (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 exhibited by the belts package based on superior energy absorption by high torsion and highly extensible PET-type cords; and also improve the separation resistance 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.

The first PET cords (A) and the second PET cords (B) in a crown ply strip represent two-ply and / or three-ply 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 the above-mentioned advantages, the torsion coefficient of a PET cord (A) having a high torsion coefficient, which is determined according to the formula (1) indicated above. below is at least 13,000 and below 17,000. The

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

According to the invention, the torsion coefficient of the second PET cord (B) (of the low twist type) is at least 15% and preferably 25% less than the torsion coefficient of the first PET cord (A). ) (of the high torsion type).

When the twist coefficient of the second PET cord (B) (of the low twist type) is less than 15% of the twist coefficient of the first PET cord (A) (of the high twist type), the LASE value, the module or the difference in extensibility between the first and the second wired become insignificant. Under these conditions, the corrugated surface of the crown ply can not be obtained in the tire.

The total linear density of the cords is at least 1,000 dtex and at most 5,000 dtex. Topwrap cords that have a value less than 1000 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 PET cord (A) and the second PET cord (B) is less than 15%. Preferably, the total linear densities of the first PET cord (A) and the second PET cord will be identical.

According to the invention, the sequence of the first PET cord (A) and the second PET cord (B), which are parallel to each other in a crown ply strip, represents an alternate form as shown below. : A + B + A + B + A + B + ..., etc., in which A represents the first cord having a high twist and B represents the second cord whose twist is smaller than that of A. Such top sheet web 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 (as can be seen in Figure 3a).

According to the invention, the sequence of the first PET cord (A) and the second PET cord (B), which are parallel to each other in a crown ply strip, represents an alternate form as shown below. : AB + AB + AB + ..., etc., in the form of cords arranged in pairs, where A is the first cord having a high twist and B is the second cord having a smaller twist than that of A (as can be seen in Figure 4a).

According to the invention, the sequence of the first PET cord (A) and the second PET cord (B), which are parallel to each other in a crown ply strip, represents an alternate form as shown below. : A + B + B + A + B + B + A + B + B + ..., etc., in which A represents the first cord having a high twist and B represents the second cord whose twist is lower compared to that of A (as can be seen in Figure 6).

According to the invention, the sequence of the first PET cord (A) and the second PET cord (B), which are parallel to each other in a crown ply strip, represents an alternate form as shown below. : A + A + B + A + A + B + A + A + B + ..., etc., where A is the first cord having a high twist and B is the second cord having a lower twist with respect to that of A (as can be seen in Figure 7).

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

Claims (12)

1. Summit web tape made from alternately woven, alternately woven, polyethylene terephthalate (PET) first and second cords having the same linear densities and wrapping circumferentially around a bunch of belts a radial ply tire, characterized in that the torsion coefficient of the first PET cord (A), which is determined according to the formula given below torsion coefficient = cord twist (rpm) x ( total linear density of the cord expressed in dtex) 1/2; is at least 13,000 and is less than 17,000; and the twist coefficient of the second PET cord (B) is at least 15% and preferably 25% less than the twist coefficient of the first PET cord (A). The crown ply web of claim 1, wherein the first and second PET cords are two ply type cords. The crown ply web of claim 1, wherein the first and second PET cords are three ply cords. The crown ply web of claim 1, wherein the linear density of said PET cords is at least 1,000 dtex and at most 5,000 dtex. The crown ply web of claim 1, wherein the difference between the linear densities of the first and second PET cords is less than 15%. The crown ply web of claim 1, wherein the arrangement of the first and second PET cords 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 the first and second PET cords in said web is as indicated below AB + AB + AB, etc., in the form of cords. arranged in pairs. The crown ply web of claim 1 wherein the arrangement of the first and second PET cords in said web is as follows: A + B + B + A + B + B + A + B + B + A, etc. The crown ply web of claim 1, wherein the arrangement of the first and second PET cords 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 cords ends in said web is at least 70 epdm (ends per decimeter). 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 strip is at least 10 mm and at most 15 mm.