[go: up one dir, main page]

EP3512719A1 - Polyester cap ply cord - Google Patents

Polyester cap ply cord

Info

Publication number
EP3512719A1
EP3512719A1 EP16836128.5A EP16836128A EP3512719A1 EP 3512719 A1 EP3512719 A1 EP 3512719A1 EP 16836128 A EP16836128 A EP 16836128A EP 3512719 A1 EP3512719 A1 EP 3512719A1
Authority
EP
European Patent Office
Prior art keywords
cord
polyester
cap ply
ply cord
ply
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP16836128.5A
Other languages
German (de)
French (fr)
Inventor
Mehmet Sadettin Fidan
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Kordsa Teknik Tekstil AS
Original Assignee
Kordsa Teknik Tekstil AS
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Kordsa Teknik Tekstil AS filed Critical Kordsa Teknik Tekstil AS
Publication of EP3512719A1 publication Critical patent/EP3512719A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
    • B60C9/00—Reinforcements or ply arrangement of pneumatic tyres
    • B60C9/0042—Reinforcements made of synthetic materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
    • B60C9/00—Reinforcements or ply arrangement of pneumatic tyres
    • B60C9/18—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers
    • B60C9/20—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers built-up from rubberised plies each having all cords arranged substantially parallel
    • B60C9/22—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers built-up from rubberised plies each having all cords arranged substantially parallel the plies being arranged with all cords disposed along the circumference of the tyre
    • B60C9/2204—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers built-up from rubberised plies each having all cords arranged substantially parallel the plies being arranged with all cords disposed along the circumference of the tyre obtained by circumferentially narrow strip winding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
    • B60C9/00—Reinforcements or ply arrangement of pneumatic tyres
    • B60C9/18—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers
    • B60C9/20—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers built-up from rubberised plies each having all cords arranged substantially parallel
    • B60C2009/2074—Physical properties or dimension of the belt cord
    • B60C2009/208—Modulus of the cords
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
    • B60C9/00—Reinforcements or ply arrangement of pneumatic tyres
    • B60C9/18—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers
    • B60C9/20—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers built-up from rubberised plies each having all cords arranged substantially parallel
    • B60C9/22—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers built-up from rubberised plies each having all cords arranged substantially parallel the plies being arranged with all cords disposed along the circumference of the tyre
    • B60C2009/2252—Physical properties or dimension of the zero degree ply cords
    • B60C2009/2257—Diameters of the cords; Linear density thereof
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
    • B60C9/00—Reinforcements or ply arrangement of pneumatic tyres
    • B60C9/18—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers
    • B60C9/20—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers built-up from rubberised plies each having all cords arranged substantially parallel
    • B60C9/22—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers built-up from rubberised plies each having all cords arranged substantially parallel the plies being arranged with all cords disposed along the circumference of the tyre
    • B60C2009/2252—Physical properties or dimension of the zero degree ply cords
    • B60C2009/2261—Modulus of the cords
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
    • B60C9/00—Reinforcements or ply arrangement of pneumatic tyres
    • B60C9/18—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers
    • B60C9/20—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers built-up from rubberised plies each having all cords arranged substantially parallel
    • B60C9/22—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers built-up from rubberised plies each having all cords arranged substantially parallel the plies being arranged with all cords disposed along the circumference of the tyre
    • B60C2009/2252—Physical properties or dimension of the zero degree ply cords
    • B60C2009/2276—Tensile strength
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
    • B60C9/00—Reinforcements or ply arrangement of pneumatic tyres
    • B60C9/18—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers
    • B60C9/20—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers built-up from rubberised plies each having all cords arranged substantially parallel
    • B60C9/22—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers built-up from rubberised plies each having all cords arranged substantially parallel the plies being arranged with all cords disposed along the circumference of the tyre
    • B60C2009/2252—Physical properties or dimension of the zero degree ply cords
    • B60C2009/2285—Twist structures

Definitions

  • the present invention relates to a novel polyester tire cord which has different tensile and thermal properties at top and bottom side of the cord.
  • a novel bi- elastic polyester tire cord improves processability, high speed durability, eliminates flatspotting and enables high liftings during tire building and curing processes when used as spirally wound zero degree cap strip in pneumatic radial tires.
  • the outer diameter of the tire increases due to centrifugal forces generated by steel cord belt package and tread.
  • Such a diameter increase or tire growth increases the pantographic movements of the belt edge cords leading to the crack initiations, crack propagations and at the end belt edge separations.
  • the cap ply layer which is circumferentially wound on belt package prevents excessive tire growth under high speed conditions by applying compressive forces (restraining force) on heavy belt package made of cross ply steel cord layers.
  • cap ply materials are nylon 6.6 and hybrid cords which are spirally wound on belt package at 0 to 5 degrees to equatorial plane of the tire.
  • nylon 6.6 and aramid/nylon 6.6 hybrid cords there are also some polyester (polyethylene terephthalate, PET) applications as cap ply.
  • PET polyethylene terephthalate
  • Nylon cords have excellent fatigue resistance under bending and axial compression, and bi-elastic tensile characteristic enabling easy processing during tire building. Additionally, shrink force generation with increasing service temperature under high speed conditions improves belt edge separation resistance and high speed durability. But low glass transition temperature of nylon causes flatspot problems in tire during parking after high speed driving. Other potential drawback of multilayer nylon cap ply assembly is its high rubber gauge which cause to increase the rolling resistance of the tire by hysteresis (heat build up). As mentioned above, the hybrid cords comprising high and low modulus yarns having bi-elastic tensile behaviour are also used as cap ply in high speed tires.
  • hybrid cord enables easy belt package lifting without tight cord formation due to its high extensibility and the high modulus component becomes effective in service conditions.
  • hybrid cords as cap ply, the total thickness of the cap ply layer and rubber content can be reduced, and the high modulus component of the hybrid cord enhances the restraining force and improves the high speed durability. But existence of nylon causes also some flatspot. As cap ply, hybrid cord containing aramid is an expensive solution.
  • cap ply cords made of ultra high modulus yarns having high twist have been also used as tire reinforcement to eliminate flatspot and improve high speed performance, but high level of cord twist results in drastic modulus and breaking strength (tenacity) losses.
  • US Patent No. 6,799,618 describes a textile cap ply structure which is superimposed radially outwardly to the belt assembly is reinforced with cords being made of materials including nylon and aramid.
  • cords being made of materials including nylon and aramid.
  • the primary load bearing yarns are nylon yarns, and after appreciable elongation the primary load bearing yarns are the aramid yarns.
  • US Patent No. 7,584,774 describes a belt reinforcing layer (cap ply) disposed outside the belt in the radial direction, characterized in that the belt reinforcing layer is formed by continuously and spirally winding a polyethylene terephthalate (PET) cord in a circumferential direction of the tire, and this cord has an elastic modulus of not less than 2.5mN/dtex.% under a load of 29.4N measured at 160°C. Due to high initial modulus of the PET cord, lifting must be less than 2% in this applications to prevent excessive tight cord formations.
  • PET polyethylene terephthalate
  • US Patent No. 2013/0025758 describes a high performance pneumatic radial tire for passenger cars which uses a hybrid cord composed of two ply aramid yarn and single ply nylon yarn having different twist counts for the first twist and different twist counts for the second twist, as a cap ply, and thereby has improved high speed durability and steering stability.
  • the invention provides a two or more ply polyester cord reinforcement having different tensile and thermal properties at top and bottom side of the cord.
  • Such cords show bi-elastic tensile properties, because each ply within this cord comprises alternately high and low modulus parts.
  • the production principle of the transformation of more or less linear tensile behaviour of the polyester cord to bi-elastic characteristic is based on the thermal relaxation of one side of the pre-stretched polyester cord along its axis. That means, the polyester cord according to the invention comprises high modulus top side and low modulus bottom side (or vice versa) along its axis.
  • Each of the single plies of such a polyester cord contains intermittent zones (parts) having high and low modulus with bi-elastic tensile behaviour.
  • Cord ply Plied single yarns within cord.
  • Dtex The gramm weight of yarn having lO.OOOmeter length.
  • Greige cord Twisted cord before dipping and heat- setting
  • Heat-setting The process of conferring dimensional stability and heat resistance to the
  • Heat-set cord Cord exposed to high temperature(e.g. 120°C to 260°C under tension)
  • Linear density Weight per unit length as g/dtex or g/d(denier)
  • Total nominal cord dtex Sum of nominal yarn linear densities (3340 dtex for 1670x2 cord)
  • Twist Number of turns about its axis per meter of a yarn or cord (t/m or tpm) BRIEF DESCRIPTION OF THE DRAWINGS
  • Figure- 1 is a lateral view of conventional (prior art) two ply polyester cords and its individual plies in which,
  • Figure-2 is a lateral view of a two-ply polyester cord under tension during heat- setting process (prior art process)
  • Figure-3 is a lateral view of a pre-stretched two-ply polyester cord under tension during heat- setting process according to invention
  • Figure-4 is a lateral view of partially relaxed two-ply polyester cord
  • PET with its high modulus and low thermal shrinkage is a dimensionally stable material. In twisted form as two or three-ply cord, it can be used as carcass and cap ply reinforcement in radial passenger and light truck tires.
  • the cord twisting improves bending and compression fatigue resistance of the PET, but at the same time reduces the modulus and strength too.
  • the current tire process technology for radial passenger, SUV and light truck tires requires bi-elastic cap ply for zero degree belt reinforcement applications.
  • the high modulus is needed for restraining force to prevent belt edge separations under high speed conditions, but initial extensibility with low forces (initial low modulus) is also needed for processability during lifting of belt package in tire building and curing processes to avoid cord cuttings through the belt skim compound.
  • Nylon and aramid/nylon hybrid cords fulfill bi-elasticity requirement which is needed due to high lifting ratios during tire building process.
  • the conventional polyester cords are uniformly heat-set in high temperature ovens having constant temperature along the oven (Tl) under a given tension (F) ( Figure 1 and 2).
  • Such cords have uniform and constant physical properties in radial and axial directions.
  • two or more ply polyester cords without any low modulus component ply like nylon can be produced with bi-elastic tensile properties.
  • Such a novel bi-elastic polyester cords can be used as zero degree cap ply in radial tires to improve high speed durability and do not show any significant flatspotting.
  • the basic production principle of the bi-elastic polyester cord is to relax one side (e.g. bottom side) of the cord at high temperature while maintaining the original high modulus at another side (e.g. top side).
  • the relaxed parts of the polyester cord become more extensible under a given force, and the rest of the cord maintaining the original high modulus keeps its low extensibility (Figure- 3)
  • a polyester cord having relaxed side means, the individual cord plies comprise high and low modulus parts (zones) as repeated units alternately along its length axis.
  • Such a cord elongates initially more than the original non-relaxed high modulus cord upon subjecting to a load. That means it has bi-elastic tensile behaviour.
  • the already hot-stretched (pre- hot stretched) polyester cord is exposed to high temperature from the bottom side under a tension which is lower than the thermal shrink force at that temperature which leads to partial relaxation at the bottom side of the polyester cord.
  • each of the cords plies are relaxed (lowered modulus) at the bottom side, while maintaining non-relaxed state (high modulus) at the top side.
  • the polyester cord comprising plies with high and low modulus parts shows bi-elastic tensile behaviour which is required for cap ply applications ( Figure-4 and 5)
  • the tensile bielasticity characteristic of the polyester cord can be changed with the degree of relaxation.
  • the 3% TASE value is measured in accordance with ASTM D885-16 and this value for the polyester cord according to the invention is less than 1.5cN/dtex.
  • the twist factor of the cord is higher than 10,000 and less than 20,000 which is determined based on the following formula
  • Twist factor cord twist (tpm)x square root of total nominal cord dtex (1)
  • the cords with lower than 10,000 twist factor have insufficient fatigue resistance under bending and the cords with higher than 20,000 twist factor have significant modulus reductions.
  • the total nominal cord linear density is higher than 3000dtex and less than 8,000 dtex.
  • the cords having less than 3000 dtex can not be partially relaxed and the cords having higher than 8,000 dtex are too thick.
  • the preferable polyester polymer types are polyethylene terephthalate and polyethylene naphthlate.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Tires In General (AREA)
  • Yarns And Mechanical Finishing Of Yarns Or Ropes (AREA)

Abstract

The present invention relates to a novel polyester tire cord which has different tensile and thermal properties at top and bottom side of the the cord. Such a novel bi-elastic polyester tire cord improves processability, high speed durability, eliminates flatspotting and enables high liftings during tire building and curing processes when used as spirally wound zero degree cap strip in pneumatic radial tires.

Description

POLYESTER CAP PLY CORD
FIELD OF THE INVENTION
The present invention relates to a novel polyester tire cord which has different tensile and thermal properties at top and bottom side of the cord. Such a novel bi- elastic polyester tire cord improves processability, high speed durability, eliminates flatspotting and enables high liftings during tire building and curing processes when used as spirally wound zero degree cap strip in pneumatic radial tires.
BACKGROUND OF THE INVENTION
Under high speed conditions, the outer diameter of the tire increases due to centrifugal forces generated by steel cord belt package and tread. Such a diameter increase or tire growth increases the pantographic movements of the belt edge cords leading to the crack initiations, crack propagations and at the end belt edge separations.
The cap ply layer which is circumferentially wound on belt package prevents excessive tire growth under high speed conditions by applying compressive forces (restraining force) on heavy belt package made of cross ply steel cord layers.
Currently, most widely used cap ply materials are nylon 6.6 and hybrid cords which are spirally wound on belt package at 0 to 5 degrees to equatorial plane of the tire. In addition to nylon 6.6 and aramid/nylon 6.6 hybrid cords, there are also some polyester (polyethylene terephthalate, PET) applications as cap ply. But due to high initial modulus of PET, there is a risk of tight cord formation after lifting which means contact with steel cords of the top belt layer leading to cord breaks under dynamic conditions.
Nylon cords have excellent fatigue resistance under bending and axial compression, and bi-elastic tensile characteristic enabling easy processing during tire building. Additionally, shrink force generation with increasing service temperature under high speed conditions improves belt edge separation resistance and high speed durability. But low glass transition temperature of nylon causes flatspot problems in tire during parking after high speed driving. Other potential drawback of multilayer nylon cap ply assembly is its high rubber gauge which cause to increase the rolling resistance of the tire by hysteresis (heat build up). As mentioned above, the hybrid cords comprising high and low modulus yarns having bi-elastic tensile behaviour are also used as cap ply in high speed tires. The low modulus component of hybrid cord enables easy belt package lifting without tight cord formation due to its high extensibility and the high modulus component becomes effective in service conditions. By using hybrid cords as cap ply, the total thickness of the cap ply layer and rubber content can be reduced, and the high modulus component of the hybrid cord enhances the restraining force and improves the high speed durability. But existence of nylon causes also some flatspot. As cap ply, hybrid cord containing aramid is an expensive solution.
On the other hand, cap ply cords made of ultra high modulus yarns having high twist have been also used as tire reinforcement to eliminate flatspot and improve high speed performance, but high level of cord twist results in drastic modulus and breaking strength (tenacity) losses.
US Patent No. 6,799,618 describes a textile cap ply structure which is superimposed radially outwardly to the belt assembly is reinforced with cords being made of materials including nylon and aramid. At initial elongation of the cords, the primary load bearing yarns are nylon yarns, and after appreciable elongation the primary load bearing yarns are the aramid yarns.
US Patent No. 7,584,774 describes a belt reinforcing layer (cap ply) disposed outside the belt in the radial direction, characterized in that the belt reinforcing layer is formed by continuously and spirally winding a polyethylene terephthalate (PET) cord in a circumferential direction of the tire, and this cord has an elastic modulus of not less than 2.5mN/dtex.% under a load of 29.4N measured at 160°C. Due to high initial modulus of the PET cord, lifting must be less than 2% in this applications to prevent excessive tight cord formations.
US Patent No. 2013/0025758 describes a high performance pneumatic radial tire for passenger cars which uses a hybrid cord composed of two ply aramid yarn and single ply nylon yarn having different twist counts for the first twist and different twist counts for the second twist, as a cap ply, and thereby has improved high speed durability and steering stability.
SUMMARY OF THE INVENTION
The invention provides a two or more ply polyester cord reinforcement having different tensile and thermal properties at top and bottom side of the cord. Such cords show bi-elastic tensile properties, because each ply within this cord comprises alternately high and low modulus parts. The production principle of the transformation of more or less linear tensile behaviour of the polyester cord to bi-elastic characteristic (initial modulus reduction and enhancing initial extensibility with low forces) is based on the thermal relaxation of one side of the pre-stretched polyester cord along its axis. That means, the polyester cord according to the invention comprises high modulus top side and low modulus bottom side (or vice versa) along its axis. Each of the single plies of such a polyester cord contains intermittent zones (parts) having high and low modulus with bi-elastic tensile behaviour.
Definitions:
Cord: The product formed by twisting together two or more plied yarns
Cord ply: Plied single yarns within cord.
Dtex: The gramm weight of yarn having lO.OOOmeter length.
Flatspotting: Cords in tire having low Tg and high thermal shrikforce is subjected to shrinkage at footprint. When cooled in this position, the cord maintains flatspot until it again reaches its Tg in use.
Greige cord: Twisted cord before dipping and heat- setting
Heat-setting: The process of conferring dimensional stability and heat resistance to the
yarns, cords or fabrics by means of either moist or heat.
Heat-set cord: Cord exposed to high temperature(e.g. 120°C to 260°C under tension)
Linear density: Weight per unit length as g/dtex or g/d(denier)
TASE at 3% elongation: Stress at 3% elongation as cN/dtex
Tenacity: Breaking force(N) divided by linear density(dtex)
Tg: Glass transition point of polymer
Thermal relaxation: Thermal shrinkage causing modulus reduction
Total nominal cord dtex: Sum of nominal yarn linear densities (3340 dtex for 1670x2 cord)
Twist: Number of turns about its axis per meter of a yarn or cord (t/m or tpm) BRIEF DESCRIPTION OF THE DRAWINGS
Figure- 1 is a lateral view of conventional (prior art) two ply polyester cords and its individual plies in which,
1- Lateral view of the conventional two-ply polyester cord
2- First ply of polyester cord in separated(isolated) form
3- Second ply of polyester cord in separated(isolated) form
Figure-2 is a lateral view of a two-ply polyester cord under tension during heat- setting process (prior art process),
4- Cord tension(F) applied to polyester cord during heat-setting process 5- Oven temperature (Tl) to which polyester cord exposed uniformly from all directions during heat-setting process.
Figure-3 is a lateral view of a pre-stretched two-ply polyester cord under tension during heat- setting process according to invention
4- Cord tension (F) applied to polyester cord during heat-setting process 5-Oven temperature (T2) to which the polyester cord exposed at the bottom side
6-Oven temperature (Tl) to which the polyester cord exposed at the top side
Figure-4 is a lateral view of partially relaxed two-ply polyester cord
2a- The top part of the first ply of the polyester cord exposed to the temperature Tl during
heat- setting process
3a- The top part of the second ply of the polyester cord exposed to the temperature Tl
during heat-setting process
2b-The bottom part of the first ply of the polyester cord exposed to the temperature T2
during heat-setting process. 3b-The bottom part of the second ply of the polyester cord exposed to the temperature
T2 during heat-setting process
Figure-5 The separated plies of the polyester cord heat-set according to the invention
2a-The top part of the first ply of the polyester cord exposed to the temperature
Tl during
heat-setting process having high modulus (3% TASE)
3a- The top part of the second ply of the polyester cord exposed to the temperature Tl
during heat-setting process having high modulus (3% TASE)
2b-The bottom part of the first ply of the polyester cord exposed to the temperature T2
during heat-setting process having lower modulus (3% TASE), relaxed part of the ply
with higher extensibility
3b-The bottom part of the second ply of the polyester cord exposed to the temperature
T2 during heat-setting process having lower modulus (3% TASE), relaxed part of the
ply with higher extensibility.
DETAILED DESCRIPTION OF THE INVENTION
PET with its high modulus and low thermal shrinkage is a dimensionally stable material. In twisted form as two or three-ply cord, it can be used as carcass and cap ply reinforcement in radial passenger and light truck tires.
The cord twisting improves bending and compression fatigue resistance of the PET, but at the same time reduces the modulus and strength too. The current tire process technology for radial passenger, SUV and light truck tires requires bi-elastic cap ply for zero degree belt reinforcement applications.
In zero degree cap ply applications in pneumatic radial tires, the high modulus is needed for restraining force to prevent belt edge separations under high speed conditions, but initial extensibility with low forces (initial low modulus) is also needed for processability during lifting of belt package in tire building and curing processes to avoid cord cuttings through the belt skim compound.
Nylon and aramid/nylon hybrid cords fulfill bi-elasticity requirement which is needed due to high lifting ratios during tire building process.
As well-known aramid/nylon hybrid cords are expensive and their transition points from low modulus to high modulus should conform with lifting process parameters. Otherwise the hybrid cords may cause tight or loose cords in cap ply.
Two or three-ply nylon 6.6 cords are well known reinforcements as cap ply in radial passenger car and light truck tires, but flatspot and low level of modulus are their major drawbacks.
The conventional polyester cords are uniformly heat-set in high temperature ovens having constant temperature along the oven (Tl) under a given tension (F) (Figure 1 and 2). Such cords have uniform and constant physical properties in radial and axial directions.
According to the present invention, two or more ply polyester cords without any low modulus component ply like nylon, can be produced with bi-elastic tensile properties. Such a novel bi-elastic polyester cords can be used as zero degree cap ply in radial tires to improve high speed durability and do not show any significant flatspotting.
According to invention, the basic production principle of the bi-elastic polyester cord is to relax one side (e.g. bottom side) of the cord at high temperature while maintaining the original high modulus at another side (e.g. top side). The relaxed parts of the polyester cord become more extensible under a given force, and the rest of the cord maintaining the original high modulus keeps its low extensibility (Figure- 3)
According to invention, , a polyester cord having relaxed side (e.g. bottom side) means, the individual cord plies comprise high and low modulus parts (zones) as repeated units alternately along its length axis. Such a cord elongates initially more than the original non-relaxed high modulus cord upon subjecting to a load. That means it has bi-elastic tensile behaviour. In order to obtain a bielastic tensile characteristics, the already hot-stretched (pre- hot stretched) polyester cord is exposed to high temperature from the bottom side under a tension which is lower than the thermal shrink force at that temperature which leads to partial relaxation at the bottom side of the polyester cord. In another words, each of the cords plies are relaxed (lowered modulus) at the bottom side, while maintaining non-relaxed state (high modulus) at the top side. The polyester cord comprising plies with high and low modulus parts shows bi-elastic tensile behaviour which is required for cap ply applications (Figure-4 and 5)
The tensile bielasticity characteristic of the polyester cord can be changed with the degree of relaxation.
The 3% TASE value is measured in accordance with ASTM D885-16 and this value for the polyester cord according to the invention is less than 1.5cN/dtex.
According to invention, the twist factor of the cord is higher than 10,000 and less than 20,000 which is determined based on the following formula;
Twist factor = cord twist (tpm)x square root of total nominal cord dtex (1) The cords with lower than 10,000 twist factor have insufficient fatigue resistance under bending and the cords with higher than 20,000 twist factor have significant modulus reductions.
According to invention, the total nominal cord linear density is higher than 3000dtex and less than 8,000 dtex.
The cords having less than 3000 dtex can not be partially relaxed and the cords having higher than 8,000 dtex are too thick.
The preferable polyester polymer types are polyethylene terephthalate and polyethylene naphthlate.

Claims

1- At least two ply, dipped and heat- set polyester cap ply cord which is spirally wound on the top belt layer of a radial pneumatic tire is characterized in that,
- said polyester cap ply cord has 3% TASE value less than 1.5cN/dtex,
- each of the said polyester cap ply cord comprises alternately repeated parts having different 3% TASE values
- and the ratio of lower 3% TASE/higher 3%TASE is less than 0.70 and higher than 0.30.
2- A polyester cap ply cord according to claim 1 which is characterized in that, twist factor of the said polyester cap ply cord is higher than 10,000 and lower than 20,000 which is calculated according to the following formula (1);
Twist factor = cord twist (tpm)x square root of total nominal cord dtex.
3- A polyester cap ply cord according to claim 1 which is characterized in that, total nominal linear density of the said polyester cap ply cord is higher than 3000dtex and lower than 8,000dtex.
4- A polyester cap ply cord according to claim 1 which is characterized in that the said polyester is polyethylene terephthalate.
5- A polyester cap ply cord according to claim 1 which is characterized in that the said polyester is polyethylene naphthalate.
EP16836128.5A 2016-12-28 2016-12-28 Polyester cap ply cord Withdrawn EP3512719A1 (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/TR2016/050552 WO2018124985A1 (en) 2016-12-28 2016-12-28 Polyester cap ply cord

Publications (1)

Publication Number Publication Date
EP3512719A1 true EP3512719A1 (en) 2019-07-24

Family

ID=58016770

Family Applications (1)

Application Number Title Priority Date Filing Date
EP16836128.5A Withdrawn EP3512719A1 (en) 2016-12-28 2016-12-28 Polyester cap ply cord

Country Status (2)

Country Link
EP (1) EP3512719A1 (en)
WO (1) WO2018124985A1 (en)

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6799618B2 (en) 2002-12-18 2004-10-05 The Goodyear Tire & Rubber Company Pneumatic tire having an overlay reinforcement
JP4397207B2 (en) 2003-10-06 2010-01-13 株式会社ブリヂストン Pneumatic radial tire
WO2005111297A1 (en) * 2004-05-18 2005-11-24 Toyo Boseki Kabushiki Kaisha Reinforcement polyester cords for rubbers and process for production thereof
KR101260390B1 (en) 2011-07-25 2013-05-21 한국타이어 주식회사 Hybride cord comprised of Aramid cord and Nylon 66, and Pneumatic Tire Using it as a Reinforcing Cord
US10046603B2 (en) * 2013-12-25 2018-08-14 Kordsa Global Endüstriyel Iplik Ve Kord Bezi Sanayi Ve Ticaret Anonim Sirketi Pneumatic radial tire
LU92867B1 (en) * 2014-03-12 2016-03-10 Kordsa Global Endustriyel Iplik Ve Kord Bezi Sanay RADIAL INFLATABLE PNEUMATIC WITH HYBRID CABLE REINFORCEMENT

Also Published As

Publication number Publication date
WO2018124985A1 (en) 2018-07-05

Similar Documents

Publication Publication Date Title
EP1431076B1 (en) Pneumatic tire having an overlay reinforcement
KR101869147B1 (en) Hybrid cord and tire using the same
EP2261059B1 (en) Pneumatic tire with an overlay reinforcement
WO2015137901A1 (en) A pneumatic radial tire with hybrid cord reinforcement
EP2380754A2 (en) Hybrid cord in a belt ply for a pneumatic tire
US6267165B1 (en) Pneumatic tire with specified aramid belt
EP3478511B1 (en) Novel bielastic carbon fiber cord as cap ply
US10369844B2 (en) Bielastic polyester tire cord as cap ply
CN107531095B (en) Hybrid reinforcement elements with different twists
US10472743B2 (en) Bielastic aramid tire cord as cap ply
US5906693A (en) Pneumatic radial tire with specified organic fiber carcass cords
WO2017048208A1 (en) A plied twisted cap ply reinforcement hybrid yarn
WO2018124985A1 (en) Polyester cap ply cord
EP3478513B1 (en) A novel bielastic aramid tire cord as carcass reinforcement
WO2018124982A1 (en) Bi-elastic polyester cap ply cord
US20190375240A1 (en) A novel nylon 6.6 cap ply
JP2000127710A (en) Pneumatic radial tire
JPH0930208A (en) Pneumatic radial tire

Legal Events

Date Code Title Description
STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: UNKNOWN

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE INTERNATIONAL PUBLICATION HAS BEEN MADE

PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: REQUEST FOR EXAMINATION WAS MADE

17P Request for examination filed

Effective date: 20190418

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

AX Request for extension of the european patent

Extension state: BA ME

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION HAS BEEN WITHDRAWN

18W Application withdrawn

Effective date: 20191022