Polymer Blends Bimodal Distribution via Catalyst Merging
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Solution Overview
Problem
Existing polymer blends using single site catalysts and phenoxide ligand-containing catalysts do not achieve optimal physical properties for various applications, such as pipe applications, due to limitations in molecular weight distribution and density range.
Innovation Solution
A post-reactor polyolefin blend is created using a supported catalyst system with specific transition metal and ligand configurations, combining polymers with different molecular weights and densities, prepared through gas phase, slurry, or solution polymerization, to achieve a broad molecular weight distribution and suitable density for diverse applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single site catalyst is used to produce polymer, then the polymer has narrow polydispersity (Mw/Mn typically 2.5 to 3.5), but the blend lacks sufficient breadth in molecular weight distribution for optimal processability and physical properties
Solution Approach 1:
The patent combines two different single-site catalyst systems (metallocene and phenoxide ligand catalysts) in a single reactor to produce a bimodal resin blend. Each catalyst maintains its narrow polydispersity characteristic while the combination creates the desired broad molecular weight distribution, resolving the contradiction between precision control and distribution breadth.
Solution Approach 2:
The invention creates a composite polymer blend consisting of two distinct polymer components with different molecular weight characteristics. The first component (from metallocene catalyst) and second component (from phenoxide catalyst) are combined in situ to form a bimodal resin with composite properties that neither component alone could achieve.
2Stability of the object's composition
If polymer is produced with uniform comonomer incorporation, then the resin has consistent properties, but the blend lacks the density range needed for diverse applications
Solution Approach 1:
The patent applies local quality by allowing different comonomer incorporation levels in different polymer components. The phenoxide ligand catalyst produces a component with higher comonomer content and lower density, while the metallocene catalyst produces a component with lower comonomer content and higher density. This localized variation in composition creates the desired density range while each component maintains its own compositional consistency.
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 polymer blend exhibits improved physical properties, including broad molecular weight distribution and suitable density, making it suitable for applications like films, pipes, and injection molding, with enhanced processability and mechanical strength.
Implementation Method 1
a supported catalyst of the formula: wherein M is a group 4 transition metal; R1 and R6 are independently selected from the group consisting of C1-6 alkyl or C6-10 aryl radicals; R2 and R7 are independently selected from the group consisting of C3-5 secondary or tertiary alkyl radicals
Data Source
AI summary
A blend of polymers comprising from 5 to 95 weight % of a polymer having a high molecular weight made using a single site type catalyst and from 95 to 5 weight % of a polymer having a lower molecular weight made using a catalyst containing a phenoxide, preferably a salicylaldimine ligand, has an excellent toughness and would be suitable for use in applications such as polyolefin pipes.