Recycled Polyester Composition via Density-Controlled Depolymerization
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Solution Overview
Problem
Existing chemical recycling methods for waste polyester are limited by the varying degrees of contamination, shape, and apparent density, leading to reduced yield and purity of recycled raw materials.
Innovation Solution
A process involving pretreatment to adjust the apparent density of waste polyester to 0.5 kg/L or more, followed by depolymerization and purification, including specific conditions for melt extrusion, glycolysis reactions, and purification steps such as pressurized filtration, ion-exchange resin treatment, and crystallization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If chemical recycling methods are used to depolymerize waste polyester, then the ester bond is severed to obtain recycled raw materials, but the varying apparent density and contamination of waste polyester limit the yield to below required levels
Solution Approach 1:
The patent changes the physical parameter of apparent density through pretreatment. By adjusting the apparent density of waste polyester to 0.5 kg/L or more before depolymerization, the process achieves high yield (95% or more) while accommodating heterogeneous waste materials with varying initial densities, contamination levels, and shapes.
2Productivity
If waste polyester with low apparent density (0.1 kg/L or less) is directly depolymerized, then the process is simple, but the yield of recycled raw materials remains below required levels
Solution Approach 1:
The patent applies preliminary action by performing pretreatment on waste polyester before depolymerization. This pretreatment adjusts the apparent density to 0.5 kg/L or more, ensuring high yield (95% or more) of recycled raw materials. The preliminary density adjustment step enables subsequent high-efficiency depolymerization while maintaining process simplicity.
3Manufacturing precision
If physical recycling methods are used for waste polyester, then the process is simple, but purity cannot be guaranteed
Solution Approach 1:
The patent replaces physical/mechanical recycling methods with chemical recycling through depolymerization. By severing ester bonds chemically and controlling the reaction conditions, the process achieves high purity (95% or more) of recycled raw materials such as BHET, while maintaining ease of manufacture through a straightforward chemical process.
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 process enables the production of a recycled raw material composition with high purity and yield, suitable for preparing recycled polyester resin with excellent thermal resistance and weatherability.
Implementation Method 1
Glycolysis among them is to decompose a waste polyester by adding a glycol such as ethylene glycol or diethylene glycol
Implementation Method 2
pretreating a waste polyester with an apparent density of 0.1 kg/L or less to have an apparent density of 0.5 kg/L or more
Data Source
AI summary
The present invention relates to a process for preparing a recycled raw material composition using depolymerization of waste polyester. The preparation process comprises (1) pretreating a waste polyester with an apparent density of 0.1 kg/L or less to have an apparent density of 0.5 kg/L or more; (2) depolymerizing the pretreated waste polyester; and (3) purifying the reactant obtained through the depolymerization.