Aqueous Can Coating Composition Without BPA or Isocyanates
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Solution Overview
Problem
Existing coating compositions for food and beverage cans contain substances like Bisphenol A, formaldehyde, and isocyanates, which are harmful and require aqueous systems with reduced solvent content, while maintaining performance standards such as solvent resistance, substrate adhesion, and flexibility.
Innovation Solution
An aqueous coating composition comprising anionic salt groups derived from unsaturated and saturated polyesters and acid functional vinyl copolymers, formed through specific reaction products and neutralization, ensuring adhesion and flexibility without harmful substances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional coating compositions containing Bisphenol A, formaldehyde, and isocyanates are used, then solvent resistance and substrate adhesion are achieved, but harmful substances are present that require avoidance for food contact applications
Solution Approach 1:
The patent removes harmful substances (Bisphenol A, formaldehyde, isocyanates) from the coating composition while retaining the essential protective functions. The aqueous coating composition uses alternative safe components that provide solvent resistance and adhesion without the toxic crosslinkers and resins traditionally used in food contact coatings.
Solution Approach 2:
The patent changes the chemical composition parameters by using water as the primary solvent instead of organic solvents, and by employing safe polyesters and copolymers with controlled molecular weights and functional groups. This parameter change eliminates harmful substances while maintaining coating performance through carefully selected alternative化学成分.
2Object-affected harmful factors
If aqueous coating systems with reduced solvent content are developed, then harmful substances are avoided, but maintaining performance standards such as solvent resistance, substrate adhesion, and flexibility becomes difficult
Solution Approach 1:
The patent uses composite material strategies by combining water-soluble polyesters with specific copolymers containing carboxyl groups. This composite approach creates a synergistic system where the aqueous-based binder provides adhesion and flexibility, while the copolymer components enhance solvent resistance, achieving all performance standards without organic solvents or harmful crosslinkers.
Solution Approach 2:
The patent employs intermediaries in the form of carboxyl-containing copolymers that act as bridging components between the aqueous binder and the substrate. These copolymer intermediaries provide both water solubility for easy application and sufficient crosslinking capability for solvent resistance, mediating between the conflicting requirements of aqueous formulation and performance.
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 composition achieves solvent resistance, substrate adhesion, and flexibility comparable to traditional systems, while avoiding Bisphenol A, formaldehyde, and isocyanates, suitable for food and beverage can coatings.
Implementation Method 1
anionic salt groups comprising unsaturated polyester, or a salt comprising blend of an unsaturated polyester and a saturated polyester, or a salt comprising blend of an unsaturated polyester, optionally a saturated polyester, and a copolymer of polymerized alpha, beta ethylenically unsaturated monomers
Data Source
AI summary
The present invention relates to an aqueous coating composition comprising: - one or more anionic salt group(s) comprising unsaturated polyester(s); or - an anionic salt groups comprising blend of one or more unsaturated polyester(s) and one or more saturated polyester(s); or - an anionic salt groups comprising blend of one or more unsaturated polyester(s) and one or more acid functional vinyl copolymers(s), wherein said blend is a physical blend and/or a reaction product, preferably a reaction product; or - an anionic salt groups comprising blend of one or more unsaturated polyester(s), one or more saturated polyester(s), and one or more acid functional vinyl copolymers(s), wherein said blend is a physical blend and/or a reaction product, preferably a reaction product. The present invention also relates to the use of said aqueous coating composition for coating a metal substrate, to a method for producing a coated metal substrate and to a method for producing coated can bodies and can ends.