PET Melt-Phase Composition with Naphthalene and Titanium
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Solution Overview
Problem
Polyethylene terephthalate (PET) produced by a melt-phase only process lacks oxidative stability, leading to molecular weight breakdown when exposed to air at temperatures above 165°C, which is problematic for drying and subsequent processing, and results in hazy, dark-colored bottles due to the use of antimony catalysts.
Innovation Solution
Incorporating residues of 2,6-naphthalenedicarboxylic acid (0.5-2.5 mole%) and titanium (3-100 ppm) into the melt-phase polyethylene terephthalate polyester, produced in the presence of titanium, to enhance oxidative stability and eliminate the need for antimony catalysts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If antimony catalyst is used in melt-phase process, then polymerization is efficient, but product becomes hazy and dark-colored
Solution Approach 1:
The patent removes antimony catalyst from the melt-phase process and replaces it with titanium catalyst. This extraction of the harmful catalyst eliminates the haze and dark coloration while maintaining polymerization efficiency through the alternative catalyst system.
Solution Approach 2:
The patent changes the catalyst parameter from antimony to titanium, which has different chemical properties that do not cause discoloration. This parameter change resolves the contradiction between maintaining productivity and eliminating harmful visual effects.
2Object-affected harmful factors
If melt-phase only process is used, then antimony catalyst is eliminated, but oxidative stability is reduced
Solution Approach 1:
The patent changes the catalyst parameter from antimony to titanium, which provides both antimony-free production and maintained oxidative stability. The titanium catalyst enables the melt-phase only process to produce stable PET without compromising reliability.
Solution Approach 2:
The patent uses a composite approach by incorporating titanium catalyst with specific dicarboxylic acid residues (naphthalenedicarboxylic acid, isophthalic acid, cyclohexane dimethanol) to create a stable PET composition that maintains oxidative stability without antimony.
3Ease of operation
If PET is dried at high temperature to remove moisture, then processing is enabled, but molecular weight breaks down
Solution Approach 1:
The patent changes the chemical composition parameters by incorporating stable dicarboxylic acid residues and titanium catalyst, which raises the thermal stability threshold. This allows drying at higher temperatures (165-180°C) without molecular weight breakdown, enabling ease of operation while maintaining composition stability.
Solution Approach 2:
The patent builds thermal stability into the polymer structure beforehand through the selection of stable monomers and catalyst system. This prior cushioning of thermal stability prevents molecular weight breakdown during subsequent high-temperature drying operations.
4Strength
If higher molecular weight PET is produced to compensate for breakdown, then initial strength is improved, but processing complexity increases
Solution Approach 1:
The patent performs the preliminary action of producing PET with inherently high thermal stability through careful selection of monomers and catalyst during synthesis. This eliminates the need for subsequent solid-state polymerization or other complex processes to achieve desired molecular weight, simplifying overall processing.
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 inclusion of 2,6-naphthalenedicarboxylic acid and titanium significantly improves the thermo-oxidative stability of PET, allowing for higher temperature drying without molecular weight loss and eliminating the need for subsequent molecular weight increase, resulting in clear and stable PET products.
Implementation Method 1
reacting the mixture in the presence of titanium to obtain the melt-phase polyethylene terephthalate polyester
Implementation Method 2
residues of a monomer having two or more fused aromatic rings... significantly improves the thermo-oxidative stability of PET
Data Source
AI summary
Polyester compositions are disclosed that include a melt-phase polyethylene terephthalate polyester having incorporated therein residues of a monomer having two or more fused aromatic rings, and that also include titanium. Also disclosed are articles that include the disclosed polyester compositions, and processes for producing such polyester compositions, that include the steps of forming a mixture comprising ethylene glycol, at least one acid chosen from terephthalic acid and derivatives of terephthalic acid, and a monomer having two or more fused aromatic rings; and reacting the mixture in the presence of titanium to obtain the melt-phase polyethylene terephthalate polyester.