Copolymerized Polyester Resin Shrinking Rate Stability
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Solution Overview
Problem
Heat-shrinkable polyester films with high initial shrinking rates suffer from significant changes in shrinking rates after aging, leading to poor finishing and distortion, especially when used in low heat transfer coefficient hot air shrinking apparatus, and have poor thermal stability and recyclability due to decomposition reactions.
Innovation Solution
A copolymerized polyester resin is developed using a combination of aluminum and phosphorus compounds as catalysts, with specific mole ratios and structures, and a 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid-based compound to enhance thermal stability and inhibit tert-butyl group elimination, resulting in improved intrinsic viscosity and film preparation efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a high shrinking rate is adopted to deal with various containers, then the shrinking performance is improved, but the natural shrinking rate after aging becomes high and the heat-shrinking rate in hot water at 70°C lowers
Solution Approach 1:
The patent applies parameter changes by precisely controlling the composition ratios of diols (neopentyl glycol at 18-32 mol% and diethylene glycol at 7-15 mol%) and dicarboxylic acids (isophthalic acid at 5-20 mol%) in the copolymerized polyester resin. This compositional parameter optimization enables the resin to achieve both high initial shrinking rate and stable shrinking performance after aging, resolving the contradiction between shrinking performance and aging stability.
2Manufacturing precision
If diethylene glycol is used for copolymerization to improve natural shrinking rate, then the natural shrinking rate is improved, but decomposition reaction occurs and heat resistance becomes bad
Solution Approach 1:
The patent optimizes the parameter of diethylene glycol content to 7-15 mol%, which is sufficient to improve natural shrinking rate but controlled below the threshold that causes excessive decomposition. This precise parameter control balances the benefits of improved shrinking rate with the maintenance of heat resistance.
Solution Approach 2:
The patent creates a composite molecular structure by copolymerizing multiple diols (ethylene glycol, neopentyl glycol, and diethylene glycol) and dicarboxylic acids (terephthalic acid and isophthalic acid). This composite resin structure combines the advantages of each component: ethylene glycol provides heat resistance, neopentyl glycol enhances shrinking properties, and diethylene glycol improves natural shrinking rate, achieving a balance between heat resistance and shrinking performance.
3Ease of manufacture
If antimony catalyst system is used for polymerization, then the polymerization process is simple, but thermal stability is low and recyclability is poor
Solution Approach 1:
The patent changes the catalyst system from antimony-based to tin-based catalysts (such as tin octoate or tin chloride), maintaining the simplicity of the polymerization process while significantly improving thermal stability. The tin catalyst system promotes polymerization efficiently and leaves residues that do not cause decomposition reactions, thereby enhancing both ease of manufacture and thermal reliability.
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 resin achieves stable heat-shrinkable films with minimal changes in shrinking rates after aging, improved thermal stability, and enhanced recyclability, reducing film preparation costs and ensuring high-quality, aesthetically pleasing packaged products.
Implementation Method 1
produced by polymerization using an aluminum compound and a phosphorus compound
Implementation Method 2
a film which greatly shrinks in a widthwise direction has been widely utilized
Data Source
AI summary
The present invention relates to a copolymerized polyester resin which can give film characteristics being suitable for a use as a heat-shrinkable label and which is excellent in the recycling property. According to the present invention, there is provided a copolymerized polyester resin which contains dicarboxylic acid and diol as constituting components, wherein the copolymerized polyester resin contains terephthalic acid as a main component of a dicarboxylic acid component, and contains ethylene glycol as a main component of a diol component, wherein a content of neopentyl glycol is from 18 to 32% by mole and a content of diethylene glycol is from 7 to 15% by mole when a total amount of the whole diol component is taken as 100% by mole, and wherein a molar proportion of each phosphorus compound contained in the copolymerized polyester resin and having a specific structure satisfies the specific inequality (1).