Propylene Copolymer Balance Impact Resistance and Optical Clarity
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Solution Overview
Problem
Current propylene copolymers fail to achieve a balance between good optical properties and impact resistance, particularly in blow molded articles, which are crucial for applications like bottles that require both optical clarity and durability in drop tests.
Innovation Solution
A propylene copolymer with a high overall comonomer content and a high propylene content in the xylene cold soluble fraction, characterized by specific ranges of melt flow rate, comonomer content, and intrinsic viscosity, which enhances its optical and mechanical properties, including a high melting temperature and low flexural modulus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a heterophasic propylene copolymer with dispersed elastomeric copolymer inclusions is used to improve impact behavior, then impact resistance is improved, but optical properties deteriorate
Solution Approach 1:
The patent applies parameter changes by precisely controlling the comonomer content (7.5-12.0 wt.-%) and the comonomer content in the XCS fraction (16.0-28.0 wt.-%), along with specific melt flow rate (0.5-2.5 g/10 min) and XCS content (30.0-40.0 wt.-%). These parameter optimizations enable the polymer to achieve both good optical properties and impact resistance without the need for traditional heterophasic structures with dispersed inclusions.
2Strength
If comonomer content is increased to improve impact behavior, then impact resistance is improved, but melting temperature decreases
Solution Approach 1:
The patent resolves this contradiction through optimized parameter changes: maintaining comonomer content in the range of 7.5-12.0 wt.-% (which improves impact behavior) while simultaneously achieving a melting temperature of at least 160°C. This is accomplished by controlling the comonomer distribution, particularly with 16.0-28.0 wt.-% comonomer content in the XCS fraction, and optimizing the melt flow rate to 0.5-2.5 g/10 min.
3Illumination intensity
If overall comonomer content is increased to improve optical properties, then optical properties are improved, but stiffness increases
Solution Approach 1:
The patent applies parameter changes by optimizing the comonomer content to 7.5-12.0 wt.-% and the comonomer content in the XCS fraction to 16.0-28.0 wt.-%, which achieves good optical properties while maintaining a flexural modulus (stiffness) of at most 600 MPa. The specific melt flow rate range of 0.5-2.5 g/10 min and XCS content of 30.0-40.0 wt.-% further fine-tune the balance between optical properties and mechanical stiffness.
Data Source
AI summary
Propylene copolymer having a melt flow rate MFR2 (230° C.) in the range of more than 0.5 to below 2.5 g/10 min, a xylene cold soluble content (XCS) in the range of 30.0 to 40.0 wt-%, a comonomer content in the range of more than 7.5 to 12.0 wt.-%, wherein further the comonomer content of xylene cold soluble (XCS) fraction of the propylene copolymer is in the range of 16.0 to 28.0 wt.-%.