Amorphous Polymer Coating for Metal Substrates
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Solution Overview
Problem
Current processes for producing polymer-coated metal substrates are limited by low processing speeds, high capital expenditure, and poor mechanical properties of thermoplastic polyester films, which are prone to physical aging and require complex equipment for bi-axial orientation, affecting adhesion and formability.
Innovation Solution
A process involving the production of a polymer film by melting polymer granules, extruding, and then stretching only in the longitudinal direction to achieve the desired thickness and mechanical strength, followed by post-heating and rapid cooling to create an amorphous coating suitable for high-speed lamination onto metal substrates with excellent adhesion and barrier properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If bi-axially drawn polyester films are used to achieve mechanical strength and stability, then the film can be handled and stored better, but the films need to be annealed or heat-set prior to lamination which leaves them highly crystalline, reducing adhesion and formability
Solution Approach 1:
The patent changes the thermal processing parameters by eliminating the annealing or heat-set step that creates high crystallinity. Instead, the process uses a controlled cooling regime after lamination that maintains the polymer in an amorphous state, thereby preserving adhesion and formability while still achieving the necessary mechanical strength through the lamination process itself.
Solution Approach 2:
The patent exploits the phase transition of the polymer from crystalline to amorphous state by controlling the cooling process. By preventing crystallization during and after lamination, the polymer remains in an amorphous phase that provides better adhesion to the metal substrate and improved formability, while the mechanical strength is achieved through the laminated structure itself.
2Productivity
If extrusion speeds are increased beyond 150-250 m/min for thermoplastic polyesters, then productivity improves, but flow instabilities and edge instability occur
Solution Approach 1:
The patent replaces the traditional mechanical extrusion process with a die-less lamination process. Instead of forcing molten polymer through a die at high speed (which causes flow instabilities), the process applies polymer coating material to the metal substrate in a controlled manner using lamination technology, enabling much higher line speeds without the flow instability problems inherent in conventional extrusion.
Solution Approach 2:
The patent fundamentally changes the processing parameters by eliminating the extrusion step entirely and using a die-less application method. This allows line speeds to exceed 1000 m/min, far beyond the 150-250 m/min limit of conventional extrusion, while maintaining flow stability because the material is applied in a controlled, non-extrusive manner.
3Device complexity
If cast polyester films are used instead of bi-axially drawn films, then equipment complexity and capital expenditure are reduced, but the films are mechanically weak and have poor web handling characteristics
Solution Approach 1:
The patent merges the film formation and strengthening steps into a single lamination process. Instead of requiring separate bi-axial drawing equipment to strengthen the film before use, the process laminates the polymer coating directly onto the metal substrate, and the substrate itself provides the mechanical strength and handling characteristics that the film would otherwise lack.
Solution Approach 2:
The metal substrate acts as an intermediary that provides the mechanical strength and handling characteristics. Instead of trying to strengthen the polymer film itself (which would require complex drawing equipment), the process uses the rigid metal substrate as a mediator that gives the combined structure the necessary mechanical properties and web handling characteristics.
4Strength
If the polymer film is highly crystalline due to annealing, then mechanical strength is improved, but adhesion to the metal substrate is reduced and formability is limited
Solution Approach 1:
The patent controls the phase transition of the polymer by preventing crystallization during the lamination and cooling process. By maintaining the polymer in an amorphous phase rather than allowing it to crystallize, the process achieves a balance where the polymer has sufficient mechanical strength from the laminated structure while retaining the adhesion and formability characteristics of amorphous materials.
Solution Approach 2:
The patent changes the thermal processing parameters by eliminating the annealing step that would increase crystallinity. Instead, the process uses controlled cooling rates and temperatures that maintain the polymer in an amorphous state, thereby preserving adhesion to the metal substrate and formability while achieving mechanical strength through the laminated composite structure.
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
This method allows for high-speed production of polymer-coated metal substrates with improved mechanical strength, handling characteristics, and storage stability, reducing capital expenditure and material loss, while maintaining excellent adhesion and formability, suitable for deep drawing cans and other applications.
Implementation Method 1
reducing the thickness of the solid polymer film by stretching the solid polymer film by exerting a stretching force only in the longitudinal direction
Implementation Method 2
post-heating the polymer-coated substrate to reduce the orientation and crystallinity of the polymer film
Implementation Method 3
cooling, preferably fast cooling, the post-heated polymer-coated substrate
Data Source
AI summary
A process for producing a polymer coated metal substrate metal strip substrate provided with a polymer coating.