Multimodal Propylene-Hexene Copolymers for Flexural Modulus
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Solution Overview
Problem
Copolymers of propylene and hexene-1 with low 1-hexene content lack improved mechanical properties, particularly in flexural modulus, which is essential for industrial sheet production.
Innovation Solution
Development of propylene-hexene copolymers with a multimodal molecular weight distribution, characterized by a 1-hexene content ranging from 0.6 wt% to 3.0 wt%, specific melt flow rate, polydispersity, and melting point, achieved through stereospecific heterogeneous Ziegler-Natta catalysis and a gas-phase polymerization process in interconnected reactor zones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If copolymers of propylene and hexene-1 with low 1-hexene content are used, then the polymer exhibits broad molecular weight distribution of monomodal type, but the mechanical properties particularly flexural modulus are not improved
Solution Approach 1:
The patent applies segmentation by dividing the molecular weight distribution into multiple modes (multimodal distribution) rather than a single mode. This is achieved by using a multi-stage polymerization process with different catalysts and conditions in each stage, creating distinct polymer fractions with different molecular weights that combine to produce superior mechanical properties including enhanced flexural modulus
Solution Approach 2:
The patent changes the molecular weight distribution parameter from monomodal to multimodal through controlled variation of polymerization conditions across multiple stages. By adjusting catalyst types, monomer ratios, and reaction conditions in each stage, the process generates a tailored multimodal distribution that optimizes both processability and mechanical performance
2Strength
If propylene-hexene copolymers are produced with specific multimodal distribution characteristics, then enhanced flexural modulus and impact strength are achieved, but the polymerization process complexity increases
Solution Approach 1:
The polymerization process is segmented into multiple sequential stages, each with specific catalyst systems and reaction conditions. This segmentation allows independent optimization of each stage to produce polymer fractions with targeted properties, ultimately combining them into a multimodal distribution that delivers enhanced impact strength while maintaining manageable process complexity through modular design
Solution Approach 2:
The patent creates a composite polymer structure by combining different polymer fractions with distinct molecular weight characteristics into a single multimodal copolymer material. This composite approach at the molecular level integrates the advantages of different polymer types, achieving superior impact strength and flexural modulus while the process complexity is managed through systematic process design
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 resulting copolymers exhibit enhanced flexural modulus and impact strength, making them suitable for industrial sheets with thicknesses above 0.1 mm, outperforming monomodal distribution counterparts.
Implementation Method 1
The propylene-hexene-1 copolymers of the present invention can be prepared by polymerizing propylene and 1-hexene in the presence of highly stereospecific heterogeneous Ziegler-Natta catalyst
Data Source
AI summary
A propylene-1-hexene copolymer having: i) a content of 1-hexene derived units ranging from 0.6 wt% to 3.0 wt%; ii) melt flow rate (MFR) measured according to the method ISO 1133 (230° C, 5 kg) ranging from 0.5 g/10 min to 5.0 g/10 min iii) the polydispersity (PI) ranges from 4.5 to 10 and the distribution of molecular weight is of multimodal type; iv) the melting point ranges from 160°C to 145°C; v) the DSC curve (temperature/heat of fusion) shows at least two peaks.