Long Chain Branched Propylene Interpolymers
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Solution Overview
Problem
Current propylene polymers lack effective methods for introducing long chain branching during polymerization without using dienes or chain extenders, limiting their processability and commercial applications due to issues with shear thinning behavior and melt strength.
Innovation Solution
The development of a propylene interpolymer with long chain branching achieved through continuous solution polymerization using a catalyst composition comprising a hafnium complex of a polyvalent aryloxyether, which does not require dienes or chain extenders, and is characterized by specific molecular weight and branching properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If long chain branching is introduced through post-polymerization modification (e-beam radiation, azide coupling), then the polymer structure gains long chain branching, but the process complexity and cost increase significantly
Solution Approach 1:
The patent incorporates long chain branching directly during the polymerization process rather than as a post-processing step. The catalyst system enables branching to form preliminarily as the polymer chain grows, eliminating the need for subsequent modification steps involving e-beam radiation or azide coupling.
Solution Approach 2:
The patent removes the need for external chain extenders and dienes from the process. By using a specialized catalyst system, the long chain branching is achieved through the polymerization of simple propylene and alpha-olefin monomers alone, extracting out the unnecessary additional chemicals and steps.
2Shape
If long chain branching is introduced using dienes or chain extenders, then the polymer gains long chain branching, but the manufacturing cost and process complexity increase
Solution Approach 1:
The patent extracts out the need for dienes and chain extenders from the polymerization process. The catalyst system is designed to produce long chain branching through the copolymerization of propylene with small amounts of alpha-olefin, eliminating the requirement for additional chain extenders or diene monomers.
Solution Approach 2:
The patent changes the compositional parameters by using very low levels of alpha-olefin (0.1-40 wt%) compared to traditional methods that require higher levels of dienes or chain extenders. This parameter change enables branching without the need for substantial amounts of additional chemicals.
3Productivity
If conventional propylene polymers are used without long chain branching, then the manufacturing process is simple, but the shear thinning behavior and melt strength are insufficient for improved processing rates
Solution Approach 1:
The patent creates a balanced polymer structure where long chain branching provides both improved melt strength and shear thinning behavior simultaneously. The branching architecture creates equipotential improvement in both rheological properties, enabling high processing rates without sacrificing melt strength.
Solution Approach 2:
The patent creates a composite molecular architecture within the polymer itself, combining linear propylene chains with long chain branches formed during copolymerization. This internal composite structure provides both the strength and flow characteristics needed for high-speed processing.
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
This approach enhances the shear thinning behavior and melt strength of propylene polymers, enabling improved processing rates and commercial applications in various extruded articles, films, fibers, and blends, with reduced surface melt fracture and improved shape retention.
Implementation Method 1
polymerization of propylene and at least one of ethylene and a C 4-30 alpha-olefin under continuous solution polymerization conditions in the presence of a catalyst composition comprising a hafnium complex of a polyvalent aryloxyether
Data Source
Figure 1~2
Figure 3~4A
Figure 4B~5
AI summary
Substantially isotaclic propylene interpolyraets comprise (A) at least 60 weight percent (wt%) units derived from propylene, and (B) between greater than zero and 40 wt% units derived from ethylene, the propylene interpolyrner further characterized by at least one of the following properties: (1 ) a ratio of less than 1 measured at interpolyraer nurnbcr average molecular weight (Mn), (2) a relative compositional drift of less than 50%, arid (3) propylene chain segments having a chain isotacticity triad index of at least 70 mole percent.