Bielastic Polyester Tire Cord for Flatspotting

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Solution Overview

Problem

Current tire reinforcement materials, such as nylon and aramid hybrid cords, face issues with high initial modulus leading to tight cord formation and flatspotting, while ultra-high modulus yarns result in modulus and strength losses, and existing polyester tire cords have high thermal shrinkage and high rubber gauge, increasing rolling resistance.

Innovation Solution

Development of a bi-elastic polyester tire cord with low initial modulus and high modulus after elongation, achieved by opening the cord plies and inserting RFL adhesive between them, which reduces initial modulus and enhances extensibility with low forces, preventing modulus and strength loss, and eliminating flatspotting.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If high modulus polyester cord is used as cap ply, then restraining force is improved, but initial extensibility deteriorates causing tight cord formation

Engineering Contradiction:

Improverestraining forceVSAvoidinitial extensibility

Core Design Contradiction:

StrengthVSEase of operation

Solution Approach 1:

The cord structure is segmented into multiple plies (typically 2-4 plies) that can independently deform. Each ply contains polyester filaments that can slide relative to each other, enabling the cord to extend in stages rather than as a rigid unit, thus providing initial extensibility while maintaining high restraining force

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The cord construction parameters are optimized to achieve bi-elastic behavior: twist levels are controlled (typically 200-400 turns per meter), ply spacing is regulated, and polyester filament denier and count are selected to provide appropriate initial modulus followed by high restraining force at elevated elongations

Inventive Principle:

Principle #35Parameter changes

2Strength

If ultra high modulus yarns with high twist are used, then restraining force is improved, but modulus and breaking strength are lost

Engineering Contradiction:

Improverestraining forceVSAvoidmodulus and breaking strength

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The twist level is carefully controlled within an optimal range (200-400 turns per meter) rather than using high twist. This parameter optimization ensures that the polyester filaments remain sufficiently aligned to maintain high modulus and breaking strength, while still providing the necessary restraining force for high speed durability

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If nylon cords are used as cap ply, then bielastic tensile characteristic is improved, but flatspotting occurs due to low glass transition temperature

Engineering Contradiction:

Improvebielastic tensile characteristicVSAvoidflatspotting

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The invention uses polyester material that inherently provides bielastic tensile characteristics without relying on nylon's low glass transition temperature. The polyester cord structure itself (through ply configuration and twist control) enables the desired elasticity, eliminating the flatspotting issue associated with nylon while maintaining processing benefits

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The cap ply uses composite construction with multiple polyester plies arranged to achieve bielastic behavior. This composite structure of multiple polyester layers provides the necessary tensile characteristics without the thermal limitations of nylon, preventing flatspotting while maintaining ease of processing

Inventive Principle:

Principle #40Composite materials

4Reliability

If multi-ply nylon or hybrid cords are used as cap ply, then high speed durability is improved, but rolling resistance increases due to high rubber gauge

Engineering Contradiction:

Improvehigh speed durabilityVSAvoidrolling resistance

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

The cord construction parameters are optimized to achieve the required restraining force with reduced cord thickness. By controlling twist levels and ply configuration, the invention provides high speed durability through efficient force distribution while minimizing the rubber gauge, thereby reducing rolling resistance and heat build-up

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The bi-elastic polyester tire cord improves high-speed durability and processability during tire building and curing, while maintaining high modulus for restraining forces, reducing flatspotting and rolling resistance.

Implementation Method 1

opening the cord plies and inserting RFL adhesive between them, which reduces initial modulus and enhances extensibility with low forces

Methodology Applied

Scientific EffectAdhesive bonding: Adhesive

Implementation Method 2

shrinkforce generation with increasing service temperature under high speed conditions improves belt edge separation resistance and high speed durability

Methodology Applied

Scientific EffectThermal shrinkage: Thermal Contraction

Data Source

PatentEP3478512B1Novel bielastic polyester tire cord as cap ply

Publication Date: 2020.04.01 KORDSA TEKNIK TEKSTIL AS

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AI summary

The present invention relates to a novel polyester tire cord reinforcement which has bi-elastic tensile properties. Such a novel bi-elastic polyester tire cord improves high speed durability and significantly eliminates flatspotting when used as cap ply in pneumatic radial tires.