Modified Epoxy Resin Coating for Extractable BADGE Reduction
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Solution Overview
Problem
Existing epoxy resin coatings for metal food and drink containers contain low molecular weight components like BADGE, which are extractable and pose health concerns, making it difficult to achieve low levels while maintaining flexibility, sterilization resistance, and other required properties.
Innovation Solution
A crosslinkable coating composition comprising modified epoxy resin formed from the reaction of bis phenol A diglycidyl ether and bis phenol A, with a reactive material that includes a mono-functional organic compound and dicarboxylic acid, reducing the amount of low molecular weight resin components extractable from the coating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If epoxy resin is formed from the reaction of bis phenol A diglycidyl ether with bis phenol A, then the coating provides good flexibility and adhesion, but low molecular weight components like BADGE are extracted and contaminate the contents
Solution Approach 1:
The invention removes the harmful low molecular weight components (BADGE and other extractables) from the coating system by using a pre-polymerized epoxy resin with controlled molecular weight, eliminating the source of contamination while preserving the desired flexibility and adhesion properties
Solution Approach 2:
The invention changes the molecular weight parameter of the epoxy resin by using a pre-polymerized resin with average molecular weight of 1000-5000 g/mol, which significantly reduces extractable components while maintaining the necessary mechanical properties for can coating applications
2Reliability
If the coating is sterilized by heating to 130°C for 1-2 hours, then the contents are sterilized, but the coating integrity must be maintained to prevent corrosion and metal migration
Solution Approach 1:
The invention uses a composite coating system comprising a pre-polymerized epoxy resin combined with a crosslinking agent, creating a network structure that provides both sterilization resistance and maintains coating integrity under heating conditions
Solution Approach 2:
The epoxy resin is pre-polymerized to a controlled molecular weight before application, which establishes a stable base structure that resists degradation during subsequent sterilization heating, preventing coating failure and metal contamination
3Ease of manufacture
If low molecular weight resin components are present in the coating, then the coating can be applied and cured, but these components are easily extracted and pose health concerns
Solution Approach 1:
The invention extracts and eliminates the harmful low molecular weight components by using a pre-polymerized epoxy resin with controlled molecular weight, while retaining the necessary reactivity for coating application and curing through the incorporation of crosslinking agents
Solution Approach 2:
The invention introduces a crosslinking agent as an intermediary that reacts with the pre-polymerized epoxy resin to form a crosslinked network, enabling the coating to be applied and cured while preventing the extraction of harmful components
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 modified epoxy resin composition achieves low levels of extractable BADGE and other low molecular weight components, improving safety and maintaining the required properties of flexibility, sterilization resistance, and flavor integrity.
Implementation Method 1
epoxy resin formed from the reaction of bis phenol A diglycidyl ether (subsequently referred to as BADGE) with bis phenol A
Implementation Method 2
The coating is often applied to the flat metal by roller coating before the can is formed and then dried and/or cured in a stoving operation. Typical oven temperatures used are about 200° C. for 6 to 12 minutes
Implementation Method 3
crosslinkable coating composition comprising modified epoxy resin and crosslinker
Data Source
AI summary
A protective crosslinkable coating composition comprising modified epoxy resin and crosslinker the modified epoxy resin being the reaction product, by weight, of i) from 80 to 99.9 parts of di-epoxy resin of epoxy equivalent weight from 500 to 5000 and formed from the reaction of bis phenol A diglycidyl ether and bis phenol A and ii) from 0.1 to 20 parts of reactive material characterised in that a) the di-epoxy resin contains minor amounts of resin components of molecular weight less than 1000 Daltons, and the reactive material comprises b) mono-functional organic material of molecular weight at: least 100 Daltons having one moiety capable of reacting with the epoxy moieties of the di-epoxy resin and c) dicarboxylic acid of molecular weight less than 300 Daltons having two moieties capable of reacting with the epoxy moieties of the di-epoxy resin.