Bis(Glycol) Terephthalate Oligomer Process for High-Recycled Polyester
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Solution Overview
Problem
Existing methods for recycling waste polyester into high-quality polyester products face challenges due to low purity of recycled bis(2-hydroxyethyl) terephthalate (BHET), formation of excessive glycol by-products, and increased costs from additional glycol monomers, which hinder the increase of recycled raw material content in the final resin.
Innovation Solution
A process involving a transesterification reaction of bis(2-hydroxyethyl) terephthalate with a glycol having 3 or more carbon atoms to form bis(glycol) terephthalate oligomer, followed by collecting and removing ethylene glycol by-products, and then conducting polymerization to enhance the content of recycled raw materials and improve resin purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If an excessive amount of BHET is added to the polymerization reaction to increase the content of recycled raw materials, then the content of recycled raw materials is improved, but glycol by-products increase
Solution Approach 1:
The invention performs a preliminary transesterification reaction between BHET and glycol having 3 or more carbon atoms before the main polymerization reaction. This preliminary action converts BHET into bis(glycol) terephthalate oligomer, which then participates in polymerization with reduced glycol by-product formation. The reaction conditions are specifically controlled (temperature 100-200°C, time 1-24 hours, molar ratio BHET:glycol 1:(0.5-2.0)) to optimize this preliminary conversion and minimize harmful by-products while maintaining high recycled material content.
2Manufacturing precision
If separate processes such as ion exchange or recrystallization are used to purify recycled BHET, then purity is improved, but costs increase
Solution Approach 1:
The invention extracts and removes impurities from recycled BHET during the transesterification reaction process itself, rather than requiring separate purification steps. The reaction conditions and subsequent processing enable removal of contaminants while forming the desired bis(glycol) terephthalate oligomer, thereby achieving purification as an integrated part of the manufacturing process rather than as an additional costly step.
Solution Approach 2:
The invention merges the purification function with the transesterification reaction function. Instead of performing purification and reaction as separate sequential steps, the process combines impurity removal and oligomer formation into a single integrated operation, reducing both cost and process complexity while maintaining product purity.
3Manufacturing precision
If glycol monomers are used in addition to BHET to produce copolyester resin, then resin quality is improved, but it becomes difficult to increase the content of recycled raw materials
Solution Approach 1:
The invention makes the glycol having 3 or more carbon atoms serve multiple functions: it acts as both a quality-enhancing comonomer in the copolyester resin and as a reagent in the preliminary transesterification reaction with BHET. This multi-functionality allows the same substance to simultaneously improve resin quality and enable high recycled material content, resolving the contradiction between these two objectives.
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 increases the recycled raw material content in the polyester resin, reduces glycol by-products, and improves resin quality by removing impurities, leading to environmentally friendly polyester products with reduced costs.
Implementation Method 1
subjecting bis(2-hydroxyethyl) terephthalate to a transesterification reaction with a glycol having 3 or more carbon atoms; obtaining a bis(glycol) terephthalate oligomer as a product of the transesterification reaction
Implementation Method 2
collecting and removing ethylene glycol as a by-product formed during the transesterification reaction
Implementation Method 3
conducting a polymerization using the bis(glycol) terephthalate oligomer
Data Source
AI summary
According to the present invention, bis(glycol)terephthalate can be prepared by a transesterification reaction of glycol and bis(2-hydroxyethyl)terephthalate and then introduced to a polymerization reaction to increase the content of recycled raw materials in a polyester resin. In addition, purity is improved through the removal of impurities by extracting glycol byproducts during the transesterification reaction, and thus the quality of the final resin can be improved while reducing the amount of byproducts from the polymerization reaction.