Antimony-free Polyester Films for High-Temperature Food Packaging
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Solution Overview
Problem
Current polyester films used for food packaging, especially for high-temperature applications like oven cooking, face challenges with mechanical stability, antimony migration, and brittleness due to the use of antimony-containing catalysts, which pose health risks and exceed migration limits.
Innovation Solution
Development of biaxially oriented polyester films with less than 30 ppm antimony and germanium, incorporating a copolyester layer with radical scavengers, produced using titanium or aluminum catalysts, ensuring high temperature resistance and low antimony migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If antimony-containing catalysts are used for polyester production, then temperature resistance and mechanical stability are improved, but health safety deteriorates due to antimony migration exceeding limits
Solution Approach 1:
The patent removes the harmful antimony catalyst from the polyester production process, replacing it with alternative catalysts that do not migrate into food. This extraction of the harmful substance while maintaining the essential catalytic function resolves the contradiction between temperature resistance and health safety.
Solution Approach 2:
The patent changes the chemical composition parameters by using different catalyst systems (tin, zinc, or aluminum-based) instead of antimony. This parameter change maintains the polyester's structural integrity and temperature resistance while eliminating the harmful migration issue.
2Object-affected harmful factors
If antimony-free catalysts are used for polyester production, then health safety is improved, but temperature resistance deteriorates causing brittleness at high temperatures
Solution Approach 1:
The patent introduces intermediary substances (radical scavengers and stabilizers) that mediate between the antimony-free catalyst system and the polyester structure. These intermediaries protect the polyester chains from thermal degradation, maintaining temperature resistance without requiring antimony.
Solution Approach 2:
The patent creates a composite material system combining antimony-free polyester with specific stabilizer packages. This composite approach achieves both health safety (no antimony migration) and temperature resistance through synergistic interactions between the polyester matrix and stabilizing additives.
3Temperature
If radical scavengers are added to antimony-free polyester, then temperature resistance is improved, but the risk of migration increases
Solution Approach 1:
The patent employs stabilizers that are designed to be consumed during processing and initial use, protecting the polyester during its critical early life. These stabilizers sacrificially degrade or crosslink to protect the main polymer structure, providing temporary protection without requiring long-term persistence that would increase migration risk.
Solution Approach 2:
The patent optimizes the concentration and type of radical scavengers to achieve sufficient temperature resistance while minimizing migration. By carefully adjusting these parameters, the patent finds the optimal balance between protective function and migration control.
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 films maintain mechanical stability and transparency at high temperatures, preventing brittleness and antimony migration, allowing safe handling and cooking without leakage or microcracks, while adhering to safety standards.
Implementation Method 1
The film contains a radical scavenger in amounts of 50-10000 ppm, in particular up to 5000 ppm and preferably up to 1200 ppm
Implementation Method 2
The polyesters are produced using a suitable titanium or aluminum compound as a polycondensation catalyst
Data Source
AI summary
The invention relates to the selection and production of temperature-resistant polyester films for metal lamination (can liners) and for packaging food, for example, to cook food in an oven, such as a microwave oven, without first removing the food from the packaging. Polyester films made from antimony-free polyesters containing radical scavengers are suitable for this purpose. Such films exhibit high temperature resistance, so that packaging made from them (e.g., roasting bags) can remain in an oven at temperatures above 180 °C for more than an hour without becoming brittle.