Resin-Coated Container Sheet With Low Hot Friction and Print Adhesion
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Solution Overview
Problem
Existing resin-coated metal sheets for containers face issues with breaking or scraping during high-degree processing and inadequate ink adhesiveness, which conventional techniques fail to address simultaneously.
Innovation Solution
A resin-coated metal sheet with controlled static friction coefficient and polar component of surface free energy, using a polyester resin with specific properties and a lubricant component, achieves both inhibition of breaking/scraping and good appearance after printing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a resin-coated metal sheet is used for high-degree processing to manufacture two-piece cans, then formability is improved, but the resin coating layer is prone to breaking or scraping
Solution Approach 1:
The patent changes the physical-chemical parameters of the resin coating layer by controlling the water contact angle to 40° or more, which modifies the surface properties to reduce friction and prevent breaking during high-degree processing while maintaining formability
Solution Approach 2:
The resin coating layer acts as an intermediary between the metal substrate and the external environment, with its surface properties specifically engineered to provide lubrication during forming operations, preventing direct contact and damage between processing tools and the metal surface
2Ease of manufacture
If the water contact angle of the resin coating layer is increased to prevent breaking during processing, then formability is improved, but ink adhesiveness deteriorates
Solution Approach 1:
The patent optimizes the water contact angle parameter to a specific range (40° or more) that balances two opposing requirements: high enough to provide slip during forming, but controlled to maintain sufficient surface energy for ink adhesion, thus resolving the contradiction between formability and printing quality
3Reliability
If conventional coating techniques are used to improve corrosion resistance and weatherability, then protection is improved, but processing time increases and solvent discharge increases
Solution Approach 1:
The patent replaces conventional multi-step coating and baking processes with a thermoplastic film lamination process, substituting complex chemical coating mechanisms with a simpler thermal bonding process that reduces processing time and eliminates solvent discharge while maintaining corrosion resistance
Solution Approach 2:
The patent utilizes the phase transition properties of thermoplastic resins, which become soft and adhesive at elevated temperatures during lamination, then solidify upon cooling to form a protective coating, eliminating the need for solvent-based coatings and complex baking processes
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 solution ensures the resin coating layer withstands high-degree processing without breaking or scraping and maintains effective ink adhesiveness, enhancing the overall quality of the container.
Implementation Method 1
a polar component of surface free energy of a resin coating layer to be positioned on an outer face side of the container is 3.5 mN/m or more, after the resin coating layer to be positioned on the outer face side of the container after forming is subjected to heat treatment at a melting point of the resin coating layer plus 8° C. for 2 minutes
Implementation Method 2
a static friction coefficient of the resin coating layer to be positioned on an outer face side of the container after forming, at 145° C., is 0.16 or less
Data Source
AI summary
A resin-coated metal sheet for a container includes: a metal sheet; a first resin coating layer provided on an inner face of the metal sheet after forming; and a second resin coating layer provided on an outer face of the metal sheet after forming, wherein a polar component of surface free energy of the second resin coating layer is 3.5 mN/m or more, after the second resin coating layer is subjected to heat treatment at a melting point of the second resin coating layer plus 8° C. for 2 minutes, and a static friction coefficient of the second resin coating layer, at 145° C., is 0.16 or less.