Polyethylene Resin Composition for Injection Molding
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Solution Overview
Problem
Current polyethylene resin compositions for injection-molding used in food and drug containers or stoppers face issues with low ductile properties, poor impact resistance, high molecular weight migration, and inadequate environmental stress crack resistance, leading to poor performance and safety concerns.
Innovation Solution
A resin composition is developed by melt-mixing 80-90 wt% linear low density polyethylene resin with 10-20 wt% ethylene-alpha-olefin copolymer resin, where the alpha-olefin is 1-hexene or 1-octene, and the ethylene content is 70-90 mol%, resulting in improved ductility, impact resistance, and reduced migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If high flow linear low density polyethylene or high flow low density polyethylene is used, then moldability is improved, but ductile property deteriorates leading to poor impact resistance and low environmental stress crack resistance
Solution Approach 1:
The patent uses a composite resin composition consisting of linear low density polyethylene (80-95 wt%) and ethylene-alpha olefin copolymer (5-20 wt%). This composite structure combines the excellent moldability of high flow polyethylene with the superior ductility and environmental stress crack resistance of the copolymer component, resolving the contradiction between ease of manufacture and strength.
2Ease of manufacture
If physical mixing of resin materials is used, then manufacturing process is simple, but dispersibility deteriorates leading to low product uniformity
Solution Approach 1:
The patent specifies precise compositional parameters: linear low density polyethylene (80-95 wt%) with density 0.915-0.930 g/cm³ and melt flow index 15-30 g/10min, combined with ethylene-alpha olefin copolymer (5-20 wt%) with density 0.860-0.880 g/cm³ and melt flow index 30-35 g/10min. These controlled parameter ranges ensure optimal dispersibility and product uniformity while maintaining manufacturing simplicity.
3Strength
If ethylene-alpha-olefin copolymer is used in high amount, then ductile property is improved, but moldability deteriorates
Solution Approach 1:
The patent optimizes the balance between ductile property and moldability by controlling the ethylene-alpha olefin copolymer content at 5-20 wt% with a specific melt flow index of 30-35 g/10min. This parameter control ensures sufficient ductility improvement without excessive compromise to moldability, as the copolymer's flow characteristics are carefully selected to maintain processability.
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 composition exhibits high flowability, excellent ductile properties, and high environmental stress crack resistance, ensuring long-term performance and safety in severe environments with low molecular weight material migration, meeting European Commission Regulation standards.
Implementation Method 1
a resin composition for injection-molding in which an ethylene-based resin is melt-mixed
Data Source
Figure 1
AI summary
Disclosed herein is a resin composition for injection-molding in which an ethylene-based resin is melt-mixed to be excellent in ductile property and impact property, excellent in environmental stress crack resistance, and low in an overall migration, and thus may be widely used as a food and drug container or a stopper. The present invention provides a resin composition for injection-molding formed by melt-mixing 80-90 wt% of a linear low density polyethylene having a melt flow index of 15-30 dg/min (190°C, 2.16 kg) and 10-20 wt% of an ethylene-alpha-olefin copolymer resin having a melt flow index of 10-20 wt%.