HDPE Bottle Cap Composition Eliminating Inner Liners
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Solution Overview
Problem
Current methods for manufacturing closure devices, such as bottle caps, using polymeric materials face challenges in achieving the necessary strength, seal integrity, and environmental stress crack resistance without the need for inner liners, while also addressing issues of shrinkage consistency and cost.
Innovation Solution
A high-density polyethylene composition comprising a high molecular weight ethylene alpha-olefin copolymer and a low molecular weight ethylene polymer, with specific density and melt index ranges, is developed for injection molding, which eliminates the need for inner liners and improves shrinkage consistency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a two-part construction with inner liner is used to achieve seal integrity and strength, then seal quality and strength are improved, but manufacturing cost and device complexity increase
Solution Approach 1:
The patent merges the sealing function and structural function into a single polypropylene component, eliminating the need for separate inner liner and outer cap parts. The polypropylene material is selected to provide both the sealing properties previously requiring an inner liner and the structural strength previously requiring an outer cap, thereby reducing device complexity while maintaining reliability.
Solution Approach 2:
The polypropylene closure device is designed to perform multiple functions simultaneously: providing sealing against carbonated beverages, withstanding internal pressure, and enabling easy opening by consumers. This multi-functional single-part design replaces the specialized division of labor between inner liner and outer cap in traditional two-part constructions.
2Device complexity
If polymer blend formulations are used to eliminate inner liner, then device complexity is reduced, but manufacturing precision and property consistency remain insufficient
Solution Approach 1:
The patent specifies precise parameter ranges for the polypropylene material including density (0.90-0.97 g/cm³), melt flow rate (0.5-5.0 decigrams per 10 minutes), and tensile strength (minimum 15,000 psi). These controlled parameters ensure consistent manufacturing properties while maintaining the simplified single-part construction.
3Ease of manufacture
If conventional polymers are used for closure devices, then manufacturing is simple, but shrinkage consistency and tolerance control are poor
Solution Approach 1:
The patent controls the density parameter within a specific range (0.90-0.97 g/cm³) and specifies melt flow rate parameters to optimize shrinkage behavior. These parameter specifications enable consistent shrinkage control during injection molding while maintaining ease of manufacture through standard processing techniques.
Data Source
AI summary
A high-density polyethylene composition that is formulated for being injection molded into an injection-molded bottle cap closure comprising a skirt that axially extends from the periphery of a base, and internal screw threads for securing the cap to a container, and method of producing the same.