Cross-linked Polyester Coatings for Food Containers
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Solution Overview
Problem
Current protective coatings for metal food and beverage containers contain undesirable compounds like Bisphenol A (BPA), Bisphenol F (BPF), Bisphenol A diglycidyl ether (BADGE), and Bisphenol F diglycidyl ether (BFDGE), which are not ideal for food storage due to concerns over chemical resistance and adhesion, especially with acidic products, and there is a need for coatings that are free from these mobile compounds while maintaining corrosion protection and flexibility.
Innovation Solution
A hardenable packaging coating composition comprising a hydroxyl-functional polyester resin, a carboxyl-functional polyester resin, a blocked-isocyanate cross-linker, and a phenol-formaldehyde resin, which are applied in a multi-coat system to provide a hardened composite coating that is substantially free of BPA, BPF, BADGE, and BFDGE, ensuring excellent chemical and physical properties, including corrosion inhibition and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If epoxy-based coatings containing mobile BPA, BPF, BADGE and BFDGE are used, then adhesion and corrosion protection are improved, but health safety and chemical resistance deteriorate
Solution Approach 1:
The patent removes harmful epoxy-based compounds (BPA, BPF, BADGE, BFDGE) from the coating formulation while retaining the desired performance characteristics through alternative resin chemistry
Solution Approach 2:
The invention creates a composite coating system combining phenolic resin with polyester resin and cross-linking agents to achieve both safety (free from harmful compounds) and performance (adhesion and corrosion protection)
2Reliability
If conventional thermoset coatings are applied to protect metal from acidic contents, then corrosion protection is improved, but chemical resistance to foodstuffs deteriorates
Solution Approach 1:
The patent eliminates conventional thermoset coatings that may leach chemicals into foodstuffs while maintaining corrosion protection through phenolic-polyester composite chemistry
Solution Approach 2:
The coating creates a chemically inert barrier that protects metal from acidic contents while preventing chemical migration into foodstuffs, ensuring both corrosion protection and food safety
3Reliability
If multi-coat systems with epoxy resin are used, then adhesion is improved, but flexibility and processability deteriorate
Solution Approach 1:
The patent formulates a composite coating combining phenolic resin with polyester resin and cross-linking agents to achieve both strong adhesion and flexibility, eliminating the need for complex multi-coat epoxy systems
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 coating composition achieves effective corrosion protection, chemical resistance, and adhesion to metal substrates, particularly suitable for containers with 'easy-open' end closures, while being free from undesirable compounds, thus addressing the limitations of existing coatings.
Implementation Method 1
a blocked-isocyanate cross-linker
Implementation Method 2
a phenol-formaldehyde resin
Implementation Method 3
hardenable packaging coating composition
Data Source
AI summary
The invention relates to protective coating systems derived from a functional polyester resin, a cross-linker and a phenol-formaldehyde resin. Also provided is a method of coating a metal substrate using the protective coating systems to produce a cross-linked protective coating. Further provided is a composite material prepared with the coating system and, in certain embodiments, useful in fabricating metal foodstuffs storage containers. The composite material may be particularly useful in fabricating foodstuffs storage containers and "easy-open" end closures wherein the cross-linked protective coating contacts the foodstuffs.