Polyester Film Isosorbide Diethylene Glycol Heat Resistance Transparency
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Solution Overview
Problem
Polyethylene terephthalate (PET) films face issues with low heat resistance, high crystallinity, and poor heat sealability, leading to transparency and surface defects, especially when exposed to high temperatures, and require improvements in chemical resistance and manufacturing processes.
Innovation Solution
A polyester film with a resin layer formed from a polyester resin containing 1-30 mol % isosorbide and 2-5 mol % diethylene glycol, biaxially drawn, and having an oligomer content of 1.3% by weight or less, which maintains low haze values even after heat treatment, enhancing heat resistance, chemical resistance, and heat sealability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the heat setting step is performed at high temperature to increase heat resistance of PET film, then heat resistance is improved, but oligomers precipitate and crystallize on the film surface, lowering transparency
Solution Approach 1:
The patent changes the chemical composition parameters of the polyester resin by incorporating isosorbide (1-30 mol%) and diethylene glycol (2-5 mol%) to modify the polymer structure. This compositional parameter change allows the resin to maintain low oligomer content and high transparency even after heat treatment at elevated temperatures, resolving the contradiction between heat resistance and transparency
Solution Approach 2:
The patent creates a composite polyester resin system combining isosorbide-derived diol moieties, diethylene glycol-derived diol moieties, and conventional diols. This composite material approach synergistically improves heat resistance through the rigid isosorbide structure while maintaining transparency by controlling oligomer formation, thus resolving the technical contradiction
2Productivity
If molding processes such as printing are performed at high temperature to improve productivity, then productivity is improved, but the probability of occurrence of defects remarkably increases
Solution Approach 1:
The patent modifies the resin composition parameters to include specific amounts of isosorbide and diethylene glycol, which change the thermal and chemical properties of the polyester film. This enables the film to withstand higher molding temperatures without defects, thus improving productivity while maintaining manufacturing precision
3Strength
If PET film has high crystallinity to improve mechanical strength, then strength is improved, but heat sealability becomes poor
Solution Approach 1:
The patent applies local quality by incorporating isosorbide units at specific positions in the polymer chain (1-30 mol%) rather than uniformly throughout. This localized structural modification allows certain regions to maintain crystallinity for strength while other regions provide amorphous characteristics for heat sealability, resolving the contradiction between strength and heat sealability
Data Source
AI summary
The present invention relates to a polyester film and a preparation method thereof. The polyester film is formed of a polyester resin having a specific content of isosorbide and diethylene glycol introduced therein, containing a low content of oligomer, and exhibiting a specific intrinsic viscosity, thereby exhibiting excellent mechanical properties, heat resistance and chemical resistance, and good heat sealability.