Crystallizable Polyester Catalyst Composition for Recycled PET Color Control
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Solution Overview
Problem
Existing polyester compositions containing neopentyl glycol (NPG) require extreme reaction conditions and specialized catalysts, leading to high glycol degradation, poor color, and reduced polymerization rates, making them unsuitable for recyclable PET streams.
Innovation Solution
A titanium-antimony catalyst system combined with a phosphorus compound is used to produce crystallizable polyester compositions with improved color and polymerization rates, allowing for recyclability in PET streams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a titanium-only catalyst system is used to produce polyester compositions containing neopentyl glycol, then the polyester can be produced, but the color becomes very yellow (high b* values) and polymerization rate decreases
Solution Approach 1:
The patent applies composite catalysis by combining titanium compounds with antimony compounds and phosphorus compounds to create a multi-component catalyst system. This composite approach allows the system to overcome the limitations of titanium-only catalysts, specifically the high yellow color (high b* values) and reduced polymerization rates, by leveraging the synergistic effects of multiple catalyst components working together.
Solution Approach 2:
The patent modifies the catalyst system parameters by introducing antimony and phosphorus compounds in specific concentrations (antimony: 1-50 ppm, phosphorus: 1-100 ppm) alongside titanium compounds. These parameter changes transform the catalyst system from a single-component titanium catalyst to a multi-component system that achieves both acceptable color quality and maintained polymerization rates.
2Object-affected harmful factors
If phosphorus loading is increased to reduce yellow color, then color improves slightly, but polymerization rate decreases significantly
Solution Approach 1:
The patent optimizes the concentration parameters of all catalyst components simultaneously, specifying titanium compounds at 1-10 ppm, antimony compounds at 1-50 ppm, and phosphorus compounds at 1-100 ppm. This multi-parameter optimization allows achieving color improvement without the severe polymerization rate reduction that occurs when phosphorus loading is increased alone in titanium-only systems.
Solution Approach 2:
By creating a composite catalyst system where antimony and phosphorus compounds work synergistically with titanium compounds, the patent achieves color improvement through the combined effect of multiple catalysts rather than relying on high phosphorus loading alone, thus maintaining polymerization rates.
3Object-affected harmful factors
If titanium level is decreased to improve color, then yellow color reduces slightly, but polymerization rate is reduced
Solution Approach 1:
The patent compensates for reduced titanium levels by introducing antimony and phosphorus compounds that work synergistically with the lower titanium concentration. This composite approach maintains polymerization rates even when titanium is reduced from typical levels (20-25 ppm) to lower levels (1-10 ppm), while achieving improved color quality.
4Quantity of substance
If extreme reaction conditions are used to incorporate neopentyl glycol, then glycol incorporation increases, but glycol degradation and color deterioration worsen
Solution Approach 1:
The patent modifies the reaction parameters by using a multi-component catalyst system (titanium, antimony, and phosphorus compounds in specific concentrations) that enables neopentyl glycol incorporation under milder conditions. This approach achieves adequate NPG incorporation (1-30 mole percent) without the extreme reaction conditions that cause glycol degradation and color deterioration.
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 new catalyst system produces polyesters with better color and equivalent reaction rates, enabling them to be processed with PET without forming clumps during recycling, thus maintaining the integrity of the PET flake.
Implementation Method 1
A catalyst system comprising 2-15 ppm of a titanium compound, 50-150 ppm of an antimony compound and 0-90 ppm of a phosphorus compound
Data Source
AI summary
A process for producing a polyester composition from recycled polyesters comprising: (a) introducing terephthalic acid (TPA); and ethylene glycol (EG); and recycled polyesters (b) passing the paste tank slurry to a first reaction zone; (c) introducing at least one additional glycol; (d) reacting the TPA and EG and the recycled polyesters with the at least one additional glycol in the first reaction zone at a melt temperature of at least 200° C.; (e) passing the first esterification product to a second reaction zone; (f) reacting further the first esterification product; (g) passing the second esterification product to a third reaction zone; (h) polycondensing the second esterification product in the third reaction zone to form a polymerization product.