Multi-Stage Polymeric Latex for Food Can Coatings
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Solution Overview
Problem
There is a need for improved coating compositions that do not use bisphenol A but still exhibit the stringent balance of coating properties required for food or beverage container coatings, including corrosion resistance, flexibility, and toughness.
Innovation Solution
An aqueous coating composition comprising a multi-stage polymeric latex with two or more emulsion polymerized stages, where the latex has a lower glass transition temperature (Tg) stage and a higher Tg stage, or a gradient Tg, to achieve the desired coating properties when applied to food or beverage containers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If replacement coating compositions are made without bisphenol A, then health safety is improved, but coating properties such as corrosion resistance, flexibility, and toughness deteriorate
Solution Approach 1:
The patent uses a composite resin system combining multiple polymers (acrylic, polyether, polyester, vinyl) with different properties to achieve both health safety and coating performance. This composite approach allows the coating to exhibit corrosion resistance, flexibility, and toughness without relying on bisphenol A-derived polymers.
Solution Approach 2:
The patent adjusts key parameters including resin composition ratios, curing conditions (temperature and time), and coating weight to optimize performance. By controlling these parameters, the coating achieves adequate protection without bisphenol A while maintaining required coating properties for food and beverage containers.
2Strength
If coating is made more flexible to prevent cracking during flexure, then coating integrity is improved, but corrosion resistance may deteriorate
Solution Approach 1:
The patent employs a multi-component resin system where each polymer contributes specific properties: acrylic provides flexibility, polyether provides toughness, and polyester provides corrosion resistance. This composite structure enables the coating to simultaneously achieve flexibility for crack prevention and corrosion resistance for metal protection.
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 provides excellent corrosion resistance, flexibility, and toughness, as evidenced by global extraction results of less than 50 ppm and metal exposure of less than 3 mA when tested with 1% NaCl in deionized water.
Implementation Method 1
a multi-stage polymeric latex having two or more emulsion polymerized stages in an aqueous carrier liquid
Implementation Method 2
cured at 188° C. to 199° C. (measured at the can dome) for 55 seconds
Data Source
AI summary
An aqueous coating composition is provided that is useful in coating a variety of substrates, including interior or exterior portions of food or beverage cans. The coating composition includes a resin system that includes a multi-stage latex. In some embodiments, the multi-stage latex is formed using a process that includes emulsion polymerizing two or more stages in the presence of an aqueous dispersion including a water-dispersible polymer. In certain preferred embodiments, the water-dispersible polymer is a polyether polymer.