Sharp-Edged Plastic Containers via Copolyester Blow Molding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing blow molding methods are unable to produce plastic containers with sharp-edged geometries due to the tendency of plastic materials to tear or burst when inflated, and strain hardening of polyester-based plastics during stretching prevents the formation of sharp contours.
Innovation Solution
A 2-stage stretch blow molding method using a copolyester with specific monomer composition and intrinsic viscosity, allowing for the production of plastic containers with sharp edges by slowing down stretch-setting and crystallization, and enabling the formation of edges with radii of curvature less than 0.5 mm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If blow molding method is used to manufacture plastic containers, then production efficiency and cost-effectiveness are improved, but sharp-edged geometries cannot be achieved due to material tearing and strain hardening
Solution Approach 1:
The patent changes the chemical composition parameters of the polyester material by incorporating specific comonomers (cyclohexanedimethanol and/or 1,4-cyclohexanedimethanol) in controlled amounts (0.1-10 mol% based on total diols). This compositional parameter change modifies the material's strain hardening characteristics, allowing it to form sharp edges during blow molding without tearing or bursting, thus resolving the contradiction between production efficiency and manufacturing precision for sharp-edged geometries
Solution Approach 2:
The patent creates a composite polyester material system by combining different diol comonomers (ethylene glycol, 1,4-cyclohexanedimethanol, cyclohexanedimethanol) with controlled ratios. This composite material approach allows tuning of the polymer's mechanical properties during processing, enabling the material to simultaneously maintain processability for blow molding and achieve sharp-edged geometries that would otherwise be impossible with conventional polyesters
2Strength
If polyester material is used for plastic containers, then mechanical strength and barrier characteristics are improved, but strain hardening during stretching prevents formation of sharp contours
Solution Approach 1:
The patent modifies the polyester's chemical structure parameters by controlling the type and amount of diol comonomers. Specifically, incorporating 0.1-10 mol% of cyclohexanedimethanol and/or 1,4-cyclohexanedimethanol relative to total diols changes the polymer chain flexibility and crystallization behavior. This parameter change reduces strain hardening during stretching while maintaining adequate mechanical strength, enabling the formation of sharp contours (edges with radii < 0.5 mm) that preserve both strength and geometric precision
3Productivity
If conventional blow molding is used, then basic container shapes are produced efficiently, but sharp edges with radius less than 0.5 mm cannot be formed due to material tearing
Solution Approach 1:
The patent changes the material's intrinsic viscosity and compositional parameters to enable sharp edge formation. By controlling the copolyester's intrinsic viscosity ([η] in dL/g) and incorporating specific comonomer ratios, the material achieves optimal balance between ductility during inflation and edge definition. This allows conventional blow molding processes to produce sharp edges with radii < 0.5 mm without material tearing, maintaining high productivity while achieving previously unattainable precision
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
Enables the manufacture of plastic containers with sharp-edged structures that are mechanically strong and have good barrier characteristics, while maintaining the basic course of the blow molding process, and allows for the production of containers with sharp edges that were previously unattainable.
Implementation Method 1
A 2-stage stretch blow molding method using a copolyester with specific monomer composition and intrinsic viscosity, allowing for the production of plastic containers with sharp edges by slowing down stretch-setting and crystallization
Data Source
AI summary
A plastic container manufactured from a preform with a mass share of at least 80% polyester and possibly an additive from the group consisting of dyes, fillers, catalysers, additives and lubricative additives. The plastic container comprises a container neck and a container shoulder which connects with the container neck and merges into a container body closed by a container base. The container shoulder, the container base and the container body are exclusively reshaped by a 2-stage stretch blow moulding method. The polyester is a copolyester and comprises groups which originate from the monomers cyclohexanedimethanol (CHDM) and/or monoethylene glycol (MEG), terephthalic acid (TPA) or its derivatives and isophthalic acid (IPA) or its derivatives. At least a part-region of the container body and/or of the container shoulder comprises a sharp edge with a radius of less than 0.5 mm. A method of manufacturing the plastic container is also described.