PET Oligomer Recycling with Hunter Lab b-Value Color Control
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Solution Overview
Problem
Current chemical recycling methods for polyethylene terephthalate (PET) are energy inefficient, ecologically unfriendly, have low throughput, and produce degradation products that are difficult to remove, often requiring mixing with virgin PET to achieve high-quality recycled products.
Innovation Solution
A method involving the use of specific organic compounds, such as ethylene glycol, to adjust the Hunter Lab colour coordinates of PET oligomers, reducing impurities and caustic content, and optimizing processing conditions to enhance purity and throughput, while minimizing energy consumption and carbon footprint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If chemical recycling methods are used to depolymerize PET into monomers, then recycled PET can be produced, but the process is energy inefficient and produces large amounts of degradation products that cannot be removed
Solution Approach 1:
The patent changes the depolymerization parameters by using oligomers (intermediate molecular weight products) instead of complete monomer depolymerization, and controls the intrinsic viscosity to be between 0.03-0.45 dL/g to optimize the balance between recycling efficiency and energy consumption while avoiding excessive degradation products
Solution Approach 2:
The patent extracts and removes degradation products through specific filtration steps using filter aids and activated carbon, and removes caustic through washing steps, thereby separating harmful byproducts from the recycled PET product stream
2Productivity
If PET is depolymerised to monomers, then chemical recycling is achieved, but long depolymerisation times are required and large amounts of degradation products are produced
Solution Approach 1:
The patent applies partial depolymerization to produce oligomers with intrinsic viscosity of 0.03-0.45 dL/g rather than complete depolymerization to monomers, which reduces the required processing time while still achieving effective recycling and allows for easier removal of degradation products
3Productivity
If chemical recycling methods are used, then PET can be recycled, but the process is ecologically unfriendly and has low throughput
Solution Approach 1:
The patent converts the potentially harmful oligomers and degradation products into beneficial intermediates for recycling by controlling their formation and then using them as feedstock for producing new PET with controlled intrinsic viscosity, thereby transforming waste products into valuable materials and improving ecological sustainability
4Manufacturing precision
If PET is chemically recycled, then recycled PET can be produced, but mixing with virgin PET is required to obtain sufficiently high quality product
Solution Approach 1:
The patent performs preliminary purification steps including filtration through filter aids and activated carbon, and washing to remove caustic, before the recycled PET is combined with virgin PET, thereby pre-treating the recycled material to achieve higher quality output and reducing the amount of virgin PET needed
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 improves the purity and quality of PET oligomers and polymers, increases production efficiency, reduces energy and carbon footprint, and enhances the throughput of the recycling process.
Implementation Method 1
contacting the first polyester with a further organic compound, preferably in a volume section V3, to obtain a further initial mixture; wherein the Hunter Lab colour coordinates of the first intermediate mixture are adjusted
Implementation Method 2
The invention also pertains to a method for producing a first intermediate product, wherein the method can remove more impurities during the production of the first intermediate product. Sources of impurities include the feedstock
Implementation Method 3
the method can remove more caustic during the production of the first intermediate product. Caustic may be present due to, e.g., the feedstock having been subjected to a caustic wash
Implementation Method 4
reducing a weight average molar mass of the first polyester, preferably in the volume section V3, to obtain a first intermediate mixture
Data Source
AI summary
One aspect is a method for producing a first intermediate product. A feedstock is provided that comprises a first polyester. The first polyester is contacted with a further organic compound in a volume section V3 to obtain a further initial mixture. A weight average molar mass of the first polyester is reduced in the volume section V3 to obtain a first intermediate mixture. The first intermediate mixture comprises a first intermediate product and, the further organic compound. A b value of the Hunter Lab colour coordinates of the first intermediate mixture is adjusted in a volume section V5. The b value of the Hunter Lab colour coordinates of the first intermediate mixture is adjusted so that b≤0.