Propylene 1-Hexene Copolymer Containers for Low Migration
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Solution Overview
Problem
Existing microwavable containers made from propylene polymers do not meet the stringent requirements for low overall migration limits when used for food, particularly under condition 5 (OM5), which is a concern for safety and regulatory compliance.
Innovation Solution
The use of a propylene 1-hexene copolymer with specific characteristics, such as a 1-hexene derived units content between 0.5 and 3.1% by weight, a molecular weight distribution greater than 4.0, and a melt flow rate between 5 to 75 g/10 min, produced using a stereospecific heterogeneous Ziegler-Natta catalyst system, to create injection molded containers that exhibit low overall migration values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If propylene polymers are used for microwavable food containers, then the containers can be processed and used in microwave ovens, but the overall migration limit under condition 5 (OM5) exceeds the stringent safety requirements
Solution Approach 1:
The patent applies parameter changes by precisely controlling the 1-hexene content (0.5-3.1% by weight), molecular weight distribution (Mw/Mn > 4.0), and melt flow rate (5-75 g/10min) of the propylene copolymer. These parameter optimizations result in containers with OM5 values below 4.0 mg/dm², meeting the stringent migration limits while maintaining microwave usability.
2Ease of manufacture
If the 1-hexene content is increased to improve polymer properties, then the processability and mechanical properties improve, but the overall migration limit increases beyond acceptable levels
Solution Approach 1:
The patent identifies and optimizes the critical parameter of 1-hexene content, establishing the narrow range of 0.5-3.1% by weight. Within this range, the copolymer achieves adequate processability and mechanical properties while maintaining OM5 values below 4.0 mg/dm², thus balancing manufacturability with migration compliance.
Solution Approach 2:
The patent applies local quality by creating specific microstructural characteristics through controlled copolymer composition. The optimized 1-hexene content and molecular weight distribution create a polymer structure with reduced extractable substances while maintaining necessary processing and mechanical qualities in specific regions of the material.
Data Source
AI summary
The use of a propylene 1-hexene copolymer for producing an injection molded container to be used in a microwave oven wherein the propylene 1-hexene copolymer characterized by the following features: - an 1-hexene content of between 0.5 and 3.1 % by weight; - a molecular weight distribution (MWD), expressed in terms of Mw/Mn, of greater than 4.0; - a melt flow rate (MFR; 230°C, 2.16 kg) of between 5 to 75 g/10 min; and - a fraction soluble in xylene at 25°C of lower than 2.5 wt%.