Wax-Modified Polyester Film for Metal Container Lamination
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Solution Overview
Problem
The existing methods for manufacturing metal sheets for containers, which involve laminating a thermoplastic resin film, face challenges such as difficult food release, productivity degradation due to wax adhesion, and economic inefficiency from excessive wax usage, especially when used as food containers.
Innovation Solution
A metal sheet with a polyester film laminated on its inner surface, containing 0.010 to 2.000% wax and a dipole-dipole force of 40 mN/m or less, is developed, using polyethylene wax or sodium stearate, and manufactured using specific lamination and cooling processes to ensure easy food release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a thermoplastic resin film is laminated on a heated metal sheet to replace painting treatment, then productivity is improved and solvent discharge is reduced, but food strongly adheres to the inner surface and release becomes difficult
Solution Approach 1:
The patent applies parameter changes by controlling the lamination temperature to be within a specific range (50°C to 100°C) and managing the lamination time to achieve optimal conditions. This temperature and time control allows the polyester film to adhere properly to the metal sheet while preventing excessive adhesion that would cause food sticking, thus resolving the contradiction between productivity improvement and food release ease.
Solution Approach 2:
The patent uses a composite material structure consisting of a polyester film (containing 0.01-5 mass% wax) laminated on a metal sheet. This composite structure combines the productivity benefits of film lamination with the food release properties of the wax-containing polyester, solving the contradiction between ease of manufacture and food release.
2Ease of operation
If wax is added to a thermoplastic resin film to facilitate food release, then food release becomes easier, but productivity degrades due to wax adhesion to the lamination roll
Solution Approach 1:
The patent resolves this contradiction by precisely controlling the lamination temperature parameter within 50°C to 100°C. This temperature range is high enough to prevent wax adhesion to the lamination roll (maintaining productivity) but low enough to allow the wax to remain effective for food release. The patent also controls lamination time to achieve the same effect.
Solution Approach 2:
The patent applies local quality by ensuring the wax is distributed specifically in the polyester film layer that contacts the food, rather than throughout the entire metal sheet structure. This localized wax placement provides food release functionality without causing widespread adhesion issues during lamination, thus maintaining productivity.
3Ease of operation
If the amount of wax added to the thermoplastic resin film is increased to ensure easy food release, then food release improves, but economic efficiency deteriorates due to excessive wax usage
Solution Approach 1:
The patent resolves this contradiction by optimizing the wax content parameter in the polyester film to a specific range of 0.01-5 mass%. This optimized concentration provides sufficient food release functionality while minimizing wax usage, thereby achieving economic efficiency. The patent further refines this by controlling lamination temperature and time parameters to maximize the effectiveness of the minimal wax amount used.
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 provides excellent content release properties and maintains productivity while being economically efficient by minimizing wax usage and preventing wax adhesion to lamination rolls.
Implementation Method 1
has a dipole-dipole force of 40 mN/m or less
Implementation Method 2
a laminating step of passing a metal sheet and a polyester film containing polyester and 0.010 to 2.000 mass % of a wax through a pair of lamination rolls in a sandwiched state to laminate the polyester film on a surface of the metal sheet
Implementation Method 3
a cooling step of cooling the metal sheet having the polyester film laminated on the surface after the laminating step
Data Source
AI summary
A metal sheet for containers includes a metal sheet and a polyester film which is laminated on a surface of the metal sheet to be an inner surface side of containers. The polyester film contains a wax in an amount of 0.010 to 2.000 mass %, and has a dipole-dipole force of 40 mN/m or less.