LU100713B1 - NEW ARAMIDE BIELASTIC CABLE FOR PNEUMATIC BANDAGE AS A TOP MATCH - Google Patents

Abstract

The present invention relates to a novel tire cord reinforcement made from ultra-modulus aramid fibers which has bielastic tensile properties. Such a new tire bielastic cord improves durability at high speed and eliminates planarization when used as a crown ply in radial web type pneumatic tires.

Description

NEW ARAMIDE BIELASTIC CABLE FOR PNEUMATIC BANDAGE AS A TOP MATCH

FIELD OF THE INVENTION

The present invention relates to a novel tire cord reinforcement made from ultra-modulus aramid fibers, which has bielastic tensile properties. A new tire bielastic cord of this type improves durability at high speed and eliminates planarization when used as a crown ply in radial tire type tires.

DESCRIPTION OF THE PRIOR ART

Under high speed conditions, the outer diameter of the tire increases due to the centrifugal forces generated by the package of steel cord belts and the tread. Such an increase in the diameter or such a broadening of the tire increases pantograph movements of the tires. wired from the edge of the belt giving rise to crack initiation, crack propagation and finally to belt edge separations.

The crown ply layer wound spirally on the belt package prevents excessive expansion of the tire under high speed conditions by exerting compressive forces (holding force) on a thick belt package made from wired steel diagonal structure. At present, the most widely used materials for crown plies are multi-ply nylon 6.6 layers or single-ply hybrid cords which are spirally wound on the belt package at an angle of 0 to 5 degrees from the equatorial plane of the tire.

Nylon cords have excellent fatigue resistance under bending and axial compression conditions and a bielastic tensile strength characteristic for easy processing during tire building. In addition, the generation of a shrinkage or shrinkage force proportionally to the elevation of the operating temperature under high speed conditions improves the belt edge separation resistance as well as the high speed durability. However, the low glass transition temperature of the nylon poses problems of flattening in the tire during parking after a high speed movement. Another potential disadvantage associated with a multilayer type nylon lap ply assembly is its high rubber content which results in an increase in the rolling resistance of the tire by hysteresis (heat accumulation).

It is well known that hybrid cords comprising high modulus yarns and low modulus yarns having a bielastic tensile strength behavior are also used as a crown ply in high speed type pneumatic tires. The low modulus component of the hybrid cable allows for easy lifting of the belt package in the absence of tight cable formation due to its high expansion capability and the high modulus component becomes effective under service conditions. By using hybrid cords 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 increases the holding force and improves durability at high speed. But the presence of nylon also causes some flattening.

In addition, cords made from high torsion modulus yarns are also used to reinforce a tire in order to eliminate planarization and improve high speed performance, but a high degree of twisting of the cord gives rise to drastic module losses and breaking strength.

U.S. Patent No. 4,893,665 discloses a hybrid cord comprising at least two yarns, each of which consists solely of aramid filaments, and a single central yarn which is formed solely by filaments selected from the group consisting of polyamides whose structure is at least partially oriented and by polyesters whose structure is at least partially oriented.

U.S. Patent No. 5,558,144 discloses a hybrid cord having high modulus aramid and low modulus nylon, spirally wound and continuously on a belt package in the circumferential direction of the tire at an angle of 0 to 3 degrees from the equatorial plane.

U.S. Patent No. 6,799,618 discloses a textile crown ply structure which is superimposed radially outwardly to the seat belt assembly, which is reinforced with cords. made from materials that include nylon and aramid. In the initial extension of the cords, the yarns supporting the main load are nylon yarns and after appreciable elongation, the yarns supporting the main load are the aramid yarns.

U.S. Patent No. 2013/0025758 discloses a high performance radial tire tire for passenger vehicles, which utilizes a hybrid cord which consists of a two-type aramid yarn. webs and a single web-type nylon yarn having different torsional coefficients for the first twist and different torsion coefficients for the second twist, as a crown ply, and which thus has better durability at high speed and better directional stability.

SUMMARY OF THE INVENTION The invention relates to a reinforcement of two or more ply-type cords made from an aramid yarn having bielastic properties of tensile strength. Specifically, a low initial modulus and a high modulus after the initial elongation. In order to prevent excessive losses in terms of modulus and tensile strength, a high rate of twisting of the cord was avoided

The production principle of transforming the linear tensile behavior of the aramid cord into a bielastic characteristic is based on the opening of the cord plies and the insertion of an RFL adhesive into said opening. The aramid cord which contains RFL between its open plies exhibits a bielastic behavior of tensile strength under tension. Definitions Wired: The product that is obtained by twisting together two or more type of wire.

Wire Strand: Single-ply type wire within the wire.

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

Flattening: the cords in a tire having a low Tg value and a high heat shrinkage force are subjected to impression removal. When cooled in this position, the cord maintains planarization until it regains its value Tg during use. Unbleached wired: twisted wire before immersion and heat curing.

Heat curing; the process of imparting deformation resistance and heat resistance to yarns, cords or fabrics using either moisture or heat. Wired after heat curing; wired exposed to a high temperature (e.g. from 120 ° C to 260 ° C under tension).

Linear density: weight per unit length expressed in g / dtex or g / d (denier). Spacing (s): reciprocal distance of web to ply within a multi-ply-type twisted cord. TASE at an elongation of 2%; strain at an elongation of 2% expressed in cN / dtex. Toughness: tensile strength (N) divided by the linear density (dtex).

Tg: glass transition temperature of a polymer.

Total nominal dtex of a cable: sum of the nominal linear densities of a wire (3340 dtex for a 1670x2 cable).

Torsion; number of turns around its axis per meter of wire or cable (t / m or rpm).

Ultrahigh modulus wire: tensile modulus of elasticity greater than 100 GPa.

BRIEF DESCRIPTION OF THE DRAWINGS

Figures 1 and 2 are cross-sectional views of conventional (prior art) aramid yarns of the two-ply and three-ply type, respectively.

Fig. 3 is a cross-sectional view of a conventional two-ply hybrid type prior art cord, wherein A is an aram web (yarn), B is a nylon ply (yarn).

Fig. 4 is a cross-sectional view of a conventional three-ply conventional hybrid cord (in the prior art) in which A is an aram web (yarn), and B is a nylon ply (yarn).

Figures 5 and 6 are cross-sectional views of conventional (prior art) nylon (nylon 6 or nylon 6.6) cords of the two-ply and three-ply type, respectively.

Fig. 7 shows the opening of the cross-sections of the cord and the subsequent penetration of the dip solution between the cord plies for two-ply and three-ply aramid cords, wherein A is a sectional view. cross-section of two-ply and three-ply type aramid cords, in the form of closed plies, B is a cross-sectional view of two-ply and three-ply aramid cords in the form of open plies, C is a cross-sectional view of the two-ply and three-ply type aramid cords, in a dip-impregnated form according to the invention, D represents the immersion solution containing an adhesive (RFL) filling the openings between tablecloths and covering the surface of the cords.

Figure 8a is a cross-sectional side view of a conventional two-ply type aramid cord.

Figure 8b is a cross-sectional side view of a two-ply type aramid cord in open form in accordance with the invention (prior to the immersion step).

Figure 9a is a cross-sectional side view of a conventional three-ply type aramid cord.

Figure 9b is a cross-sectional side view of a three-ply type aramid cord in the open form according to the invention (before the immersion step).

Figures 10a, 10b, 10c and 10d show cross-sectional views of closed and open forms of cable plies. D represents the diameter of the cord and s represents the spacing (the opening) between the plies of cords.

Fig. 11 shows stress-strain curves of aramid cords, in which 1 represents a 1670 dtex / 3 aramid wire having a Z / S twist, 320/320 rpm (prior art) having a linear resistance characteristic 2 shows a 1670 dtex / 3 aramid yarn having a Z / S twist, 320/280 rpm (subjected to 40 rpm in the Z direction) and after immersion having a bielastic resistance characteristic in traction according to the invention.

DETAILED DESCRIPTION OF THE INVENTION Aramid with its ultra-high modulus and high strength is a material which is very resistant to deformation. Due to its highly crystalline microstructure, it exhibits no significant heat shrinkage when exposed to high temperature. In its twisted form as a two-ply or three-ply type cord, it can be used as reinforcement in pneumatic tires and in mechanical rubber articles such as V-belts (as can be seen in the figures). 1 and 2).

The twisting of the cord improves the fatigue strength of the aramid in flexion and compression, but at the same time reduces the modulus as well as the resistance.

In applications involving zero degree type crowns in radial-ply tires, the high modulus for the retaining force is required to prevent belt edge separations under high speed conditions. also an initial ability to expand at low forces (low initial modulus) for processability during lifting of the belt package in the tire making and vulcanizing processes is needed in order to avoid cuts of cords through the gum compound of the belt.

Hybrid aramid / nylon cords solve this problem, but the presence of nylon creates flattening problems and asymmetric cabling structures (as can be seen in Figures 3 and 4).

Six-ply or three-ply nylon 6 or nylon 6.6 cords (as can be seen in FIGS. 5 and 6) represent well-known reinforcements as crown plies in tablecloth type pneumatic tires. radial designed for passenger vehicles and vans, but flattening and a low level of module are their major drawbacks.

In accordance with the present invention, two or more web type aramid yarns can be obtained in the absence of any low modulus component web, such as nylon, with bielastic properties of tensile strength. (as can be seen in Figure 7). New aramid bielastic cords of this type can be used as a zero degree top ply in radial ply tires to improve durability at high speed and exhibit no flattening.

According to the invention, the basic production principle of the aramid bielastic cord is to open the cable plies and to insert the immersion solution containing an adhesive between the plies. The aramid yarn containing a high percentage of adhesive such as the RFL between its webs becomes extensible at low forces, and during this extension the aramid web plies exert compressive forces on the adhesive material (RFL). and compress it. During this compression process, the cord is elongated with low forces. Once the aramid cord plies have moved closer to each other, the aramid cord resists elongation and becomes an ultra-high modulus wire (as can be seen in Figure 11).

In order to obtain a bielastic tensile strength characteristic, the aramid cord plies can be opened by a variety of methods: a) two or more layer type aramid gray cords are heat-cured at a temperature between 120 ° C and 260 ° C and after cooling, they are subjected to partial torsion back in the opposite direction to the twist of the cord. During this back-twisting process, the cable plies are open (as can be seen in FIGS. 8a, 8b, 9a, 9b, 10a, 10b, 10c and 10d). The aramid yarns with their open plies are again subjected to immersion and heat curing and, during these processes, the voids between the plies of cords are filled with the immersion solution and the outer surface of the plies. Cable plies are also covered by the immersion solution. (b) Unbleached aramid type cord of the two or more-ply type are subjected to immersion and heat-setting at a temperature between 120 ° C and 260 ° C and after cooling they are subjected to partial twisting in return in the opposite direction to the twisting of the cord. During this process of twisting back, the cable plies are open. The aramid yarns with their open plies are again subjected to immersion and heat curing and, during these processes, the voids between the plies of cords are filled with the immersion solution and the outer surface of the plies. Cable plies are also covered with an additional amount of the immersion solution. c) aramid yarns of two or more ply type are axially compressed during the immersion process and the cord with its open plies under compression absorbs the immersion solution between the open plies of cords. After the immersion process, the aramid cord, into which the immersion solution has penetrated between the plies, is dried and heat set at 120 ° to 260 ° C.

The tensile strength bielasticity characteristic of the aramid cord can be varied with the opening degree (s) of the plies (as can be seen in FIGS. 10b and 10d), with the type of solution of immersion, with the content of immersion solution between the layers and with the degree of hardening of the immersion solution at high temperatures (hardness of the immersion solution).

According to the invention, the aramid cord of the two or more-ply type has a TASE value of less than 2.0 cN / dtex at an elongation of 2%, determined according to ASTM D885-16 and the spacing ( the spacings) between the plies of cords, which is (are) filled with the immersion solution containing an adhesive is (are) greater than 0.1 x D and less than 0.8 x D.

A TASE value at 2% greater than 2.0 cN / dtex gives tight cords when applied as a crown ply during the tire lift process.

Preferably, s is greater than 0.2xD and less than 0.5xD.

According to the invention, the absorption of the immersion solution containing an adhesive (DPU) of the cord after immersion is greater than 10% and less than 50%, preferably greater than 15% and less than 35%, by weight. .

A DPU less than 10% does not completely fill the openings between the layers of cords and a DPU greater than 50% gives rise to diameters of cords too thick.

According to the invention, the twist coefficient of the cord is greater than 10,000 and less than 25,000, as determined based on the following formula:

Coefficient of torsion = cable twist (rpm) x square root of the total nominal dtex value of the cord (1).

Cables with a torsion coefficient of less than 10,000 have insufficient flexural fatigue strength and cords with a torsion coefficient greater than 25,000 have significant modulus reductions.

According to the invention, the total nominal linear density of the cord is greater than 200 dtex and less than 6,000 dtex. Cables with a value of less than 200 dtex are not efficient enough and cords with a value greater than 6,000 dtex are too thick.

Claims (8)

1. An aramid and heat-cured aramid having at least two plies and having a spacing (s) between said plies of cords, whose TASE value is less than 2.0 cN / dtex at an elongation of 2.0%, characterized in that the spacing (s) between the plies of cords is more than 10% and less than 80% of the diameter (D) of the cord. An aramid-wired, heat-cured aramid cable according to claim 1, wherein the spacing (s) between the cord plies of said cord is preferably more than 20% to less than 50%. the diameter (D) of the cord. The aramid-wired, heat-cured wired fabric of claim 1, wherein the absorption value of the dip solution containing an adhesive (DPU) of said cord is greater than 10% and less than 50% by weight . 4. The aramid-wired, heat-cured cable of claim 1, wherein the absorption value of the dip solution containing an adhesive of said cord is greater than 15% and less than 35% by weight. The aramid-wired, dipping and heat-cured cable of claim 1, wherein the torsion coefficient is between 10,000 and 25,000, which is calculated with reference to formula (1). The aramid-wired, dipping and heat-cured wiring of claim 1, wherein the total nominal linear density is between 200 dtex and 6,000 dtex. The aramid-wired and heat-cured aramid cable of claim 1 which is used as a circumferentially wound crown ply on the belt package in radial-ply type pneumatic tires. The aramid-wired, heat-cured wire as claimed in claim 1, which is used as a reinforcement for mechanical rubber articles.