Propylene/1-Hexene Copolymer for Faster Thin-Wall Container Molding
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Solution Overview
Problem
Existing propylene homopolymers and propylene/1-hexene copolymers used in injection molding have insufficient crystallization temperatures (Tc) and optical and impact resistance properties, leading to prolonged cooling times and reduced productivity in the production of injection molded containers.
Innovation Solution
A propylene/1-hexene copolymer with specific compositional and structural characteristics, including 1.5-2.5 wt% 1-hexene content, high xylene insolubility, and controlled melt flow rate, is developed using a Ziegler-Natta catalyst system, enabling faster crystallization and improved mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If propylene homopolymer is used to achieve high crystallization temperature, then cooling time is reduced, but optical and impact resistance properties deteriorate
Solution Approach 1:
The patent changes the chemical composition parameters of the polymer by incorporating 1-hexene comonomer at specific levels (0.5-2.5 wt%) and controlling comonomer distribution. This parameter change allows achieving a balance between crystallization temperature (maintaining short cooling time) and mechanical/optical properties (improving reliability), resolving the contradiction between speed and quality
Solution Approach 2:
The patent creates a composite polymer structure by combining propylene homopolymer segments with propylene-1-hexene copolymer segments in a single resin system. This composite structure enables the material to exhibit both the high crystallization temperature of homopolymer (for fast cooling) and the improved optical/impact properties of copolymer, simultaneously addressing both requirements
2Reliability
If propylene/1-hexene copolymer with low Tc is used to improve mechanical properties, then optical and impact resistance properties are improved, but cooling time increases
Solution Approach 1:
The patent precisely controls the comonomer content parameter (0.5-2.5 wt% 1-hexene) and comonomer distribution to optimize the crystallization temperature. By maintaining Tc above 110°C while incorporating enough 1-hexene for improved mechanics, the patent resolves the contradiction between mechanical reliability and production speed
Solution Approach 2:
The patent creates local variations in comonomer distribution within the polymer structure, allowing different regions to have different properties. Some regions maintain high crystallinity for fast cooling while other regions provide mechanical toughness, enabling simultaneous optimization of both cooling time and mechanical properties
3Reliability
If 1-hexene content is increased to improve mechanical properties, then optical resistance is improved, but crystallization temperature decreases
Solution Approach 1:
The patent optimizes the 1-hexene content parameter to a specific range (0.5-2.5 wt%) where optical resistance is significantly improved but crystallization temperature remains above 110°C. This precise parameter control resolves the contradiction between optical quality and crystallization speed
Solution Approach 2:
The patent applies partial action by incorporating a small but sufficient amount of 1-hexene (0.5-2.5 wt%) to achieve the necessary optical and mechanical improvements without excessively reducing crystallization temperature. This moderate comonomer level provides just enough property enhancement while maintaining fast cooling capability
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 copolymer allows for a 30% reduction in cycle time in thin wall injection molding, enhancing productivity and maintaining excellent mechanical and optical properties.
Implementation Method 1
A propylene/1-hexene copolymer with specific compositional and structural characteristics, including 1.5-2.5 wt% 1-hexene content, high xylene insolubility, and controlled melt flow rate, is developed using a Ziegler-Natta catalyst system
Implementation Method 2
polymers having higher crystallization temperatures (Tc) require less time to reach said Tc from the melted state
Data Source
AI summary
A propylene/ 1-hexene copolymer in which: i) the content of 1-hexene derived units, measured by C13-NMR, ranges from 1.5 wt% to 2.5 wt% and the content of propylene derived units ranges from 97.5 to 98.5 wt. %; ii) melting temperature measured by DSC in the range 148-153°C; iii) the amount of fraction insoluble in xylene at 25°C is higher than 97.0%; iv) has a melt flow rate (MFR) measured according to ISO 1133, 230°C, 2.16 kg ranging from 35 to 65 g/10 min. The copolymer is useful for the production of injection molded articles in particular Twin- Wall injection molding articles.