Polyester Resin-Coated Metal Sheet for Forming and Print Adhesion
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Solution Overview
Problem
Resin-coated metal sheets for containers face issues with the resin coat layer breaking or scraping off during high-degree processing, and the adhesion property with printing ink is impaired, leading to poor design quality and printing durability.
Innovation Solution
A resin-coated metal sheet with a polyester resin coat layer having a specific melting point, controlled arithmetic average roughness, crystallization temperature, and surface properties, including inorganic particles and titanium oxide, to enhance processing and printing quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If the degree of processing is increased to obtain the same can body shape using thinned material, then material cost is reduced, but the resin coat layer is broken or scraped off
Solution Approach 1:
The patent changes the chemical composition parameters of the resin coat layer by introducing a specific copolymer structure with controlled ratios of components (A) and (B), where component (A) contains ester groups and component (B) contains hydroxyl groups. This compositional parameter change enables the resin to maintain both processability during high-degree forming operations and adhesion quality for printing, resolving the contradiction between material thinning and resin layer integrity.
2Ease of manufacture
If a lubricant is applied onto the resin coat layer to enable high-degree processing, then processability is improved, but the adhesion property with printing ink is impaired
Solution Approach 1:
The patent applies local quality by creating a resin coat layer with spatially differentiated properties: the bulk resin provides lubricity for forming operations, while the surface maintains hydroxyl group-rich composition for ink adhesion. This is achieved through the specific copolymer structure where component (B) with hydroxyl groups segregates to the surface, ensuring printing quality is not impaired even when lubricants are applied during manufacturing.
3Loss of substance
If the resin coat layer is made thinner to reduce material cost, then material usage is reduced, but the breaking strength decreases
Solution Approach 1:
The patent employs composite material principles by creating a copolymer resin system combining component (A) with ester groups and component (B) with hydroxyl groups in specific ratios. This composite structure provides synergistic effects where the ester groups contribute to molecular chain flexibility and the hydroxyl groups provide intermolecular bonding, enabling thin resin layers to maintain sufficient breaking strength while reducing overall material usage.
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 prevents breakage or scrape-off of the resin coat layer during high-degree processing and ensures superior printing quality by balancing breaking strength, elongation, and adhesion properties.
Implementation Method 1
a crystallization temperature of 110° C. to 160° C. in a state that the resin coat layers coat the metal sheet
Implementation Method 2
a water contact angle of 55 degrees to 80 degrees in a state that the resin coat layers have been heated at 240° C. for 90 seconds
Data Source
AI summary
A resin-coated metal sheet for a container, the metal sheet including: a first resin coat layer provided on a first surface of the metal sheet; a second resin coat layer provided on a second surface of the metal sheet, wherein each of the first and the second resin coat layers is composed mainly of a polyester resin having a melting point of 230° C. to 254° C., and the first resin coat layer, in a state that the resin coat layers coat the metal sheet, is formed of a resin material having: an arithmetic average roughness (Ra) of 0.10 μm to 1.0 μm; a crystallization temperature of 110° C. to 160° C.; and a water contact angle of 55 degrees to 80 degrees in a state that the resin coat layers have been heated at 240° C. for 90 seconds after the resin coat layers coat the metal sheet.