Polyester Fabric Depolymerization Using Recoverable Solid Ionic Catalysts

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Solution Overview

Problem

Conventional chemical recycling methods for polyester fabrics using organic metal catalysts face issues such as poor quality recycled polyester pellets, high recycling costs, and difficulty in catalyst recovery, while methods using organic substances with low boiling points suffer from low purity and high costs.

Innovation Solution

A method utilizing an ionic liquid catalyst in a solid state for de-polymerizing polyester fabrics, followed by centrifugal and filtering separation to recover the catalyst, and subsequent purification and pelletizing processes to enhance recycling quality and reduce costs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If organic metal catalysts are used to catalyze de-polymerization reaction, then de-polymerization efficiency is improved, but catalyst recovery becomes difficult and side reactions increase

Engineering Contradiction:

Improvede-polymerization efficiencyVSAvoidcatalyst recovery

Core Design Contradiction:

ProductivityVSEase of operation

Solution Approach 1:

The patent changes the physical state parameter of the catalyst from liquid/dissolved (conventional organic metal catalysts) to solid (ionic liquid catalyst in solid state), enabling easy separation and recovery through filtration while maintaining catalytic efficiency

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses composite ionic liquid catalysts that combine the catalytic properties of ionic liquids with the solid-state characteristics of support materials, achieving both high de-polymerization efficiency and easy catalyst recovery

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If conventional chemical de-polymerization method is used, then polyester fabrics can be de-polymerized, but purification process becomes complicated and recycling costs increase

Engineering Contradiction:

Improvede-polymerization capabilityVSAvoidpurification process complexity

Core Design Contradiction:

Ease of manufactureVSDevice complexity

Solution Approach 1:

The patent changes the chemical state parameter by using ionic liquid catalysts that remain in solid state during reaction, allowing simple filtration to remove catalyst and impurities simultaneously, thus simplifying the purification process

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent extracts the catalyst in solid state from the reaction mixture through simple filtration, removing both the catalyst and most impurities in one step, thereby simplifying the overall purification process

Inventive Principle:

Principle #2Taking out (Extraction)

3Ease of operation

If organic substance with low boiling point is used as catalyst, then catalyst can be recovered by evaporation, but BHET purity remains low and recycling costs are high

Engineering Contradiction:

Improvecatalyst recoverabilityVSAvoidBHET purity

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The patent changes the physical state parameter of the catalyst from volatile liquid to non-volatile solid, eliminating the need for evaporation and enabling simple filtration for recovery, while also improving BHET purity through effective catalyst separation

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the thermal evaporation process with a mechanical filtration process, using solid-liquid separation instead of phase change, which is more efficient and maintains higher product purity

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 method achieves high-quality recycled polyester pellets with a recovery rate of not less than 90% and low recycling costs, with a catalyst recovery rate of not less than 95%, addressing the limitations of existing technologies.

Implementation Method 1

using a chemical de-polymerization liquid to chemically de-polymerize the recycled polyester fabric to form a de-polymerization product, in which the de-polymerization product mainly includes bis-2-hydroxylethyl terephthalate (BHET), the de-polymerization operation is to chemically de-polymerize the recycled polyester fabric in an environment where a de-polymerization catalyst exists, and the de-polymerization catalyst is the ionic liquid catalyst in a solid state

Methodology Applied

Scientific EffectCatalysis: Catalysis

Implementation Method 2

separating the ionic liquid catalyst from the de-polymerization product by a centrifugal method

Methodology Applied

Scientific EffectCentrifugal separation: Centrifugal Separation

Implementation Method 3

separating the ionic liquid catalyst from the de-polymerization product by a centrifugal method and/or a filtering method

Methodology Applied

Scientific EffectFiltration: Filter (physical)

Data Source

PatentUS12466934B2Method for recycling polyester fabrics with use of ionic liquid catalyst

Publication Date: 2025.11.11 NANYA PLASTICS CORP

AI summary

A method for recycling polyester fabrics with use of an ionic liquid catalyst is provided, which includes: providing a recycled polyester fabric; and using a chemical de-polymerization liquid to chemically de-polymerize the recycled polyester fabric and form a de-polymerization product that includes bis-2-hydroxylethyl terephthalate (BHET). The chemical de-polymerization liquid is used to chemically de-polymerize the recycled polyester fabric in an environment where a de-polymerization catalyst exists, and the de-polymerization catalyst is the ionic liquid catalyst in a solid state.