Copolymer Polyester Resin Oligomer Control for Recycling Stability
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Solution Overview
Problem
Conventional copolymerized polyester resins suffer from flavor property degradation, resin coloration, and molecular weight reduction during recycling, particularly when used in molded articles for beverages due to the presence of specific linear oligomers and poor thermal stability.
Innovation Solution
A method for producing copolymerized polyester resin by controlling the carboxyl end group concentration and using specific catalysts, along with a staged addition of glycol components to minimize by-product oligomers, enhancing thermal stability and transparency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If copolymerized polyester resin is produced using diethylene glycol and sodium sulfoisophthalate to improve transparency and moldability, then transparency and moldability are improved, but flavor properties deteriorate due to the presence of specific linear oligomers
Solution Approach 1:
The invention changes the concentration parameters of carboxyl end groups (controlling to 3-50 eq/t) and precisely controls the composition ratios of dicarboxylic acid components and glycol components. By adjusting these parameters and using specific catalyst combinations (aluminum compound with phosphorus compound or alkali metal/alkaline-earth metal compounds), the resin achieves both high transparency and excellent flavor properties without generating harmful linear oligomers
Solution Approach 2:
The invention uses a composite catalyst system combining aluminum compounds with phosphorus compounds, or alkali metal/alkaline-earth metal compounds, to achieve synergistic effects. This composite catalytic approach enables simultaneous control of polymerization efficiency, oligomer suppression, and resin stability, resolving the contradiction between transparency enhancement and flavor property preservation
2Illumination intensity
If copolymerized polyester resin is produced using diethylene glycol and sodium sulfoisophthalate to improve transparency and moldability, then transparency and moldability are improved, but resin coloration occurs during recycling due to poor thermal stability
Solution Approach 1:
The invention optimizes the carboxyl end group concentration (3-50 eq/t) and composition ratios of raw materials to enhance thermal stability. By controlling these parameters and using specific catalyst systems, the resin maintains its compositional stability during high-temperature recycling processes, preventing coloration while preserving transparency
Solution Approach 2:
The invention uses alkali metal compounds and/or alkaline-earth metal compounds as catalysts that provide excellent thermal stability during processing. These catalysts enable the resin to withstand recycling temperatures without degradation, ensuring long-term stability and color resistance even though the catalysts themselves are consumed during the reaction
3Illumination intensity
If copolymerized polyester resin is produced using diethylene glycol and sodium sulfoisophthalate to improve transparency and moldability, then transparency and moldability are improved, but molecular weight decreases during recycling due to poor thermal-oxidation stability
Solution Approach 1:
The invention controls the carboxyl end group concentration (3-50 eq/t) and uses specific catalyst combinations to enhance thermal-oxidation stability. These parameter optimizations protect the polymer chains from oxidative degradation during recycling, maintaining molecular weight and preventing resin deterioration while preserving transparency
Solution Approach 2:
The invention employs alkali metal compounds and/or alkaline-earth metal compounds as catalysts that provide robust thermal-oxidation resistance. These catalysts enable the resin to maintain its molecular structure integrity during high-temperature recycling exposure to oxygen, preventing molecular weight reduction and ensuring long-term durability
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 resulting copolymerized polyester resin maintains excellent flavor properties, transparency, and moldability while preventing resin coloration and molecular weight reduction during recycling.
Implementation Method 1
a first step of producing an oligomer through an ester formation reaction, using, as raw material monomers of a dicarboxylic acid component, an entire amount of terephthalic acid, an entire amount of glutaric acid, and at least a portion of an entire amount of sodium sulfoisophthalate
Implementation Method 2
it is important to control the carboxyl end group concentration (AV) of the copolymerized polyester resin so as to fall within a certain range and to use specific two types of catalysts in combination for polymerization
Implementation Method 3
a second step of additionally adding, to the oligomer product obtained in the first step, a remaining portion of the entire amount of sodium sulfoisophthalate, and/or a remaining portion of the entire amount of ethylene glycol, and/or a remaining portion of the entire amount of diethylene glycol, and performing an additional ester formation reaction
Data Source
AI summary
In a copolymerized polyester resin copolymerized with diethylene glycol and sodium sulfoisophthalate, the present invention aims to prevent a decrease in flavor properties, as well as coloration of resin and a decrease of the molecular weight when recycling. A method for producing a copolymerized polyester resin containing terephthalic acid as a main dicarboxylic acid component and ethylene glycol as a main glycol component, wherein a content of a free linear oligomer consisting of terephthalic acid, glutaric acid, and ethylene glycol is 90 ppm or less, and a content of a free linear oligomer consisting of terephthalic acid and ethylene glycol is 100 ppm or less, wherein the method comprises: producing an oligomer through an ester formation reaction, using an entire amount of terephthalic acid, an entire amount of glutaric acid, and at least a portion of an entire amount of sodium sulfoisophthalate, and using at least a portion of an entire amount of ethylene glycol and/or at least a portion of an entire amount of diethylene glycol; additionally adding, to the oligomer product, a remaining portion of the entire amount of sodium sulfoisophthalate, and/or a remaining portion of the entire amount of ethylene glycol, and/or a remaining portion of the entire amount of diethylene glycol, and performing an additional ester formation reaction; and polycondensing the oligomer product so as to form a high-molecular-weight product.