Propylene Copolymer Microstructure for Thin-Wall Packaging
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Solution Overview
Problem
Existing polypropylene copolymers face challenges in achieving a balance between high flowability, impact strength, and optical properties, with increased melt flow rate often compromising impact properties and high crystallinity leading to increased haze.
Innovation Solution
A propylene copolymer with a high melt flow rate and moderate to low randomness, characterized by a comonomer content of 2.0 to 11.0 mol-%, a melt flow rate of 25.0 to 100 g/10min, and a relative content of isolated to block ethylene sequences of 55.0 to 70.0%, ensuring monophasic structure and specific microstructural features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the melt flow rate is increased to improve flowability and processability, then the stiffness is improved, but the impact properties significantly drop
Solution Approach 1:
The invention changes the microstructural parameters of the polypropylene copolymer by controlling the comonomer content (2.0-11.0 mol-%) and specifically the relative content of isolated to block ethylene sequences (I(E)) in the range of 55.0-70.0%. This parameter optimization allows achieving high melt flow rate (25.0-100 g/10min) while maintaining good impact properties, resolving the contradiction between flowability and impact strength
Solution Approach 2:
The invention creates a composite microstructure within the polypropylene copolymer by combining propylene sequences with specifically controlled ethylene sequences (isolated and block). This composite molecular architecture at the microstructural level enables the material to simultaneously achieve high flowability and maintain impact resistance, as the different sequence types contribute different properties to the overall material performance
2Strength
If the degree of crystallinity is increased to improve stiffness, then the material becomes stiffer, but the haze increases
Solution Approach 1:
The invention optimizes the crystallinity parameter within a specific range (30-70%) by controlling the comonomer content and ethylene sequence distribution. This parameter optimization allows achieving sufficient stiffness for thin-wall packaging while maintaining acceptable optical properties and low haze, resolving the contradiction between stiffness and transparency
Data Source
AI summary
Propylene copolymer having a comonomer content in the range of 2.0 to 11.0 mol.-% and a melt flow rate MFR2 (230 °C) in the range of 25.0 to 100 g/10min, wherein said propylene copolymer is featured by good toughness.