BADGE-Free Metal Can Coating Composition
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Solution Overview
Problem
Current metal can coatings for food and beverages contain harmful substances like BADGE and BPA, require additional primer layers, and include undesirable metal stabilizers, failing to meet food law compliance and processing requirements.
Innovation Solution
A BADGE- and BPA-free coating composition for metal cans, comprising PVC polymer, acrylic resin, a crosslinking agent derived from phenol and formaldehyde, and optional additives, applied directly without a primer, providing flexibility, scratch resistance, and sterilization resistance up to 135°C without the need for pigments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If BADGE-containing epoxy phenolic coatings are used, then good resistance to aggressive filled products and metal adhesion are achieved, but the coating fails to comply with food law restrictions on harmful substances
Solution Approach 1:
The patent removes the harmful BADGE component from the coating formulation while retaining the essential epoxy phenolic coating structure and performance characteristics, creating a BADGE-free alternative that complies with food law restrictions
Solution Approach 2:
The invention uses a composite coating formulation combining epoxy phenolic resins with polyester resins and crosslinking agents to achieve the desired performance properties without relying on BADGE-containing formulations
2Reliability
If bisphenol-A (BPA) is used in polyester type coatings, then sterilization resistance is achieved, but the coating contains harmful substances that may lead to reproduction disorders
Solution Approach 1:
The patent eliminates BPA from the coating formulation while maintaining sterilization resistance through alternative crosslinking mechanisms using amino-type or isocyanate-type resins that do not rely on BPA
Solution Approach 2:
The invention changes the chemical composition parameters by substituting BPA with alternative resin systems and crosslinking agents, achieving the same functional performance (sterilization resistance) through different chemical pathways
3Stability of the object's composition
If metal stabilizers such as lead- or tin-based stabilizers are added to coating compositions, then processing stability is improved, but the coating contains undesirable substances that do not comply with food laws
Solution Approach 1:
The patent removes harmful metal stabilizers from the coating formulation and replaces them with alternative stabilizing mechanisms that do not involve lead or tin compounds, ensuring compliance with food law restrictions on heavy metals
4Reliability
If a primer composition is applied before the coating composition, then adhesion to metal surface is improved, but an additional costly processing step is required and many primers do not comply with food laws
Solution Approach 1:
The patent combines the primer and topcoat functions into a single coating composition that provides both adhesion to the metal surface and the required protective and aesthetic properties, eliminating the need for separate primer application
Solution Approach 2:
The coating composition is designed to perform multiple functions simultaneously: providing metal adhesion, offering protection against corrosion and aggressive filled products, and ensuring compliance with food laws, thereby replacing the traditional multi-layer primer-coat system
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 offers enhanced flexibility, scratch resistance, and sterilization resistance at elevated temperatures, eliminating the need for pigments and primers, while adhering to food law standards by being free from toxic substances like BADGE and BPA.
Implementation Method 1
The term 'cross-links', as used within the context of the present invention, designates covalent bonds linking one polymer chain to another and the term 'crosslinking agents' designates monomers or polymers that are able to react or co-react with the polymer chains linking them together to form a duroplastic network
Implementation Method 2
This is to prevent or minimize corrosion to the metal by the product and any disadvantageous influences on the quality of the product
Data Source
AI summary
The present invention relates to a composition, which is useful for producing coatings for metal sheet substrates of metal cans for storing and/or transporting food or beverages or a lid thereof, and which comprises the following components:(a) 30 to 90 wt. % of a polyvinylchloride-(PVC)-polymer,(b) 7 to 25 wt. % of an acrylic resin,(c) 3 to 40 wt. % of a crosslinking agent, which is produced from phenol, para-tert.-butylphenol, xylenol or a mixture thereof, and formaldehyde,(d) 0 to 8 wt. % additive,(e) 0 to 50 wt. % pigment and(f) a solvent-component,where all weight percentages are on the basis of the total dry weight of the coating composition (without solvents) and the composition is substantially free of bisphenol-A-diglycidyl-ether (“BADGE”) and also substantially free of bisphenol-A-resins. The composition provides metal can coatings that have suitable flexibility, scratch resistance, adherence and sterilization resistance when processed in contact with food. The coatings are suitable for three-piece cans as well as deep-drawn metal cans. In particular they are, however, useful for lids that are to be torn open due to their extraordinary flexibility and sterilization resistance.