PBT Packaging Material for Power Storage Sealing
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Solution Overview
Problem
The heat-sealing process for power storage device packaging materials requires high temperature and pressure, leading to sealing defects due to low molecular weight compound deposits on the seal bar, which reduces productivity and increases cleaning frequency, and using a heat fusible resin layer with a lower melting point may compromise insulation and formability.
Innovation Solution
A molding packaging material comprising a polybutylene terephthalate layer as the outer layer, a heat fusible resin layer as the inner layer, and a metal foil layer in between, bonded with a urethane adhesive containing polyester polyol, polyfunctional isocyanate, and polyhydric alcohol, with a specific dicarboxylic acid content and molecular weight range to enhance adhesion and formability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high temperature and pressure heat-sealing is performed to seal the packaging material, then sealing strength is improved, but low molecular weight compound deposits on the seal bar causing sealing defects and reduced productivity
Solution Approach 1:
The patent introduces a polyester resin layer as an intermediary between the polyamide resin layer and the seal bar. This intermediary layer prevents direct contact and adhesion of low molecular weight compounds from the polyamide resin to the seal bar, while still allowing effective heat and pressure transmission for sealing. The polyester layer acts as a barrier that mediates the heat-sealing process, preventing deposit formation on the seal bar surface.
Solution Approach 2:
The patent changes the chemical composition parameters of the outer layer from conventional polyamide resin to polyester resin. This parameter change alters the molecular weight distribution and reduces the presence of low molecular weight compounds that cause deposits. The polyester resin has different thermal and chemical properties that prevent adhesion to the seal bar while maintaining sealing effectiveness at high temperature and pressure.
2Reliability
If a polyester resin layer is laminated on the outer surface of the polyamide resin layer to prevent sealing defects, then sealing quality is improved, but costs increase and formability decreases
Solution Approach 1:
The patent changes the resin type parameter from polyamide to polyester, which fundamentally alters the material properties. Polyester resin provides both the desired sealing quality (preventing deposits) and maintains good formability for deep-drawing and stretch forming processes. The chemical structure of polyester allows for better balance between sealing performance and manufacturing ease compared to polyamide.
3Temperature
If a heat fusible resin layer with lower melting point is used to lower heat-sealing temperature, then sealing temperature is reduced, but thickness after sealing is reduced compromising insulation
Solution Approach 1:
The polyester resin layer serves as a thermal intermediary that enables effective heat transfer for sealing without requiring excessive temperature. The layer facilitates the heat-sealing process at moderate temperatures while its position and properties ensure that the inner heat fusible resin layer maintains sufficient thickness for insulation. The polyester layer mediates between the sealing requirement and insulation requirement.
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 configuration significantly reduces seal bar cleaning frequency, improves electrolyte resistance, and prevents delamination, while maintaining sufficient insulation and formability, thereby enhancing productivity and sealing efficiency.
Implementation Method 1
the polybutylene terephthalate layer and the metal foil layer are bonded via an outer adhesive layer, wherein the outer adhesive layer is formed of a cured film of a urethane adhesive containing polyester polyol, a polyfunctional isocyanate compound, and a polyhydric alcohol
Implementation Method 2
When a heat fusible resin layer having a low melting point is used, however, there is a concern that the thickness after sealing will be reduced, which is hard to achieve sufficient insulation
Data Source
AI summary
Provided is a molding packaging material capable of sealing without causing sealing failure, significantly reducing cleaning frequency of a seal bar to improve productivity, and preventing occurrence of delamination. The molding packaging material includes a PBT terephthalate (PBT) layer 2, a heat fusible resin layer 3, and a metal foil layer 4 between the two layers. The PBT layer 2 and the metal foil layer 4 are bonded via an outer adhesive layer 5. The outer adhesive layer 5 is formed of a urethane adhesive cured film composed of a polyester polyol, a polyfunctional isocyanate compound, and polyhydric alcohol. The polyester polyol contains a dicarboxylic acid component, the dicarboxylic acid component includes an aromatic dicarboxylic acid. The dicarboxylic acid component contains an aromatic dicarboxylic acid. The content rate of the aromatic dicarboxylic acid in the dicarboxylic acid component is 40 mol % to 80 mol %. The Young's modulus of the cured film of the urethane adhesive is 70 MPa to 400 MPa. The PBT layer has tensile strength of 100 MPa to 300 MPa.