Chemically Recycled PET Fiber Crystallinity for Durable Tire Cords

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Solution Overview

Problem

Chemically-recycled PET fibers face issues with degradation and insufficient strength due to impurities inhibiting crystallization, which limits their application in demanding products like tire cords.

Innovation Solution

The chemically-recycled PET fiber is produced by controlling the carboxyl end group concentration to 15 eq/ton or less and maintaining a degree of crystallinity of 40% or more, using depolymerized terephthalic acid and bis(2-hydroxyethyl) terephthalate, to suppress degradation and enhance strength and durability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If chemically-recycled PET is produced by depolymerization and re-polymerization, then PET recycling is achieved, but impurities inhibit crystallization and facilitate degradation

Engineering Contradiction:

ImprovePET fiber durabilityVSAvoidimpurity-induced degradation

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The invention changes critical parameters of the PET fiber: controlling carboxyl end group concentration to 15 eq/ton or less and maintaining degree of crystallinity at 40% or more. These parameter changes suppress degradation reactions and overcome the harmful effects of impurities, achieving reliable durable PET fibers from chemically-recycled material

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention creates a composite structure within the PET fiber by maintaining high crystallinity regions that resist degradation. The crystalline phases act as a protective matrix that limits the impact of impurities and carboxyl end groups, effectively creating a composite material system with enhanced durability

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If impurities such as IPA and DEG are present in PET raw material, then chemical recycling is feasible, but crystallization is inhibited and amorphous regions expand

Engineering Contradiction:

Improvechemical recycling feasibilityVSAvoidcrystallization stability

Core Design Contradiction:

Ease of manufactureVSStability of the object's composition

Solution Approach 1:

The invention compensates for the destabilizing effect of impurities by precisely controlling key parameters: maintaining carboxyl end group concentration at 15 eq/ton or less and degree of crystallinity at 40% or more. This parameter control stabilizes the crystalline structure despite the presence of impurities from chemical recycling

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention converts the presence of impurities from a harmful factor into an acceptable condition by demonstrating that with proper parameter control (low CEG and high crystallinity), chemically-recycled PET can achieve the same durability as virgin PET. The impurities are tolerated through controlled crystallization that prevents their harmful effects

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Ease of manufacture

If carboxyl end group concentration is high, then polymerization is easier, but degradation reaction is accelerated

Engineering Contradiction:

Improvepolymerization easeVSAvoidfiber strength

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The invention identifies and controls the carboxyl end group concentration as a critical parameter, setting it at 15 eq/ton or less. This parameter control suppresses the autocatalytic degradation reaction while maintaining sufficient polymerization, achieving both manufacturability and high fiber strength

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention implements feedback control by measuring and adjusting carboxyl end group concentration during production. By monitoring this parameter and making adjustments to maintain it at or below 15 eq/ton, the process ensures consistent suppression of degradation and reliable fiber strength

Inventive Principle:

Principle #23Feedback

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

This approach results in PET fibers with reduced degradation and improved strength and durability, suitable for applications in rubber-fiber composites, conveyor belts, hoses, and tires.

Implementation Method 1

impurities inhibit the crystallization of PET at the time of re-polymerization, resulting in the expansion of amorphous regions

Methodology Applied

Scientific EffectCrystallization: Crystallisation

Data Source

PatentUS20240344242A1Chemically-recycled pet fiber, rubber-fiber composite, conveyor belt, hose and tire

Publication Date: 2024.10.17 BRIDGESTONE CORP

AI summary

Provided is a chemically-recycled PET fiber with reduced degradation and superior strength and durability, and rubber-fiber composite products, such as tires, using the chemically-recycled PET fiber. The chemically-recycled PET fiber is made by polymerizing a raw material containing at least one of a monomer and an intermediate that are obtained by depolymerization of a PET product, the monomer including terephthalic acid (TPA) and/or dimethyl terephthalate (DMT) and the intermediate including bis(2-hydroxyethyl) terephthalate (BHET). The chemically-recycled PET fiber has a carboxyl end group (CEG) concentration of 15 eq/ton or less and a degree of crystallinity of 40% or more.