Polyester Depolymerization via Low-Temperature Transesterification

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Solution Overview

Problem

Existing methods fail to decompose polyesters or polyester-containing materials into monomers at low temperatures of 150°C or lower in a simple process.

Innovation Solution

A method involving mixing a base, a monohydric alcohol, and a carbonic acid diester is used to decompose polyesters, with a reaction temperature range of 20°C to 150°C, utilizing a mechanochemical reaction device like a ball mill, which allows for high-purity dicarboxylic acid diester production without excess solvents or bases.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional depolymerization methods (water or supercritical alcohol) are used, then polyester can be decomposed into monomers, but high temperature (300°C or higher) is required

Engineering Contradiction:

Improvemonomer purityVSAvoidreaction temperature

Core Design Contradiction:

Manufacturing precisionVSTemperature

Solution Approach 1:

The invention changes the chemical parameters by introducing a base catalyst (alkali metal carbonate, hydroxide, or alkoxide) and a specific alcohol solvent system, enabling depolymerization to proceed at low temperatures (20-150°C) while maintaining high monomer purity through controlled transesterification reactions

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention uses an intermediary alcohol solvent (methanol, ethanol, or propanol) that facilitates the depolymerization process at low temperatures by acting as a medium for the base-catalyzed transesterification reaction, avoiding the need for high-temperature water or supercritical conditions

Inventive Principle:

Principle #24Intermediary (Mediator)

2Temperature

If base catalyst and alcohol are used for low-temperature depolymerization, then reaction temperature is reduced to 20-150°C, but the method is limited to high-purity PET from bottles

Engineering Contradiction:

Improvereaction temperatureVSAvoidapplicability to polyester materials

Core Design Contradiction:

TemperatureVSAdaptability or versatility

Solution Approach 1:

The invention achieves universality by demonstrating that the base-catalyzed transesterification method using alcohol solvents can effectively depolymerize various polyester materials including PET bottles, polyester fibers, and film materials, making the process applicable to diverse polyester-containing materials regardless of their initial purity or form

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Adaptability or versatility

If excessive base catalyst and ethylene glycol are used for colored polyester fibers, then depolymerization can proceed, but high temperature (200°C) and additional decoloring steps are required

Engineering Contradiction:

Improveprocessing of colored polyesterVSAvoidreaction temperature

Core Design Contradiction:

Adaptability or versatilityVSTemperature

Solution Approach 1:

The invention extracts or removes the problematic high-temperature and excessive-catalyst requirements by using a controlled amount of base catalyst combined with alcohol solvents that enable low-temperature depolymerization, eliminating the need for additional high-temperature decoloring steps while effectively processing colored polyester materials

Inventive Principle:

Principle #2Taking out (Extraction)

4Ease of manufacture

If high-purity PET from bottles is used, then simple depolymerization methods work, but the method cannot be applied to polyester-containing materials like fibers and films

Engineering Contradiction:

Improvesimplicity of processVSAvoidapplicability to polyester materials

Core Design Contradiction:

Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 effectively decomposes polyesters into high-purity monomers at low temperatures, producing dicarboxylic acid diesters with purities of 99% or more, even in complex materials like polyester fibers and films, without the need for halogenated solvents or excessive bases.

Implementation Method 1

a transesterification method using a base catalyst and an alcohol can achieve depolymerization at a relatively low temperature

Methodology Applied

Scientific EffectTransesterification: Chemical Bonding

Implementation Method 2

utilizing a mechanochemical reaction device like a ball mill

Methodology Applied

Scientific EffectMechanochemical reaction: Mechanical Force

Data Source

PatentUS20260042895A1Polyester decomposition method, polyester production method, and polyester decomposition product recovery method

Publication Date: 2026.02.12 NATIONAL INSTITUTE OF ADVANCED INDUSTRIAL SCIENCE & TECHNOLOGY

AI summary

Provided are: a polyester decomposition method capable of decomposing a polyester or polyester contained in various polyester-containing materials into monomers at a low temperature of 150° C. or lower in a simple process; a polyester production method for producing a polyester from the monomers obtained by the decomposition method; and a polyester decomposition product recovery method for recovering a predetermined polyester decomposition product from polyester decomposition products obtained by the polyester decomposition method. The polyester decomposition method of a polyester contained in a polyester-containing material includes a decomposition step of mixing a base, a monohydric alcohol, and a carbonic acid diester to decompose the polyester.