Heterophasic Polypropylene Resin Low-Temperature Impact Flowability
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Solution Overview
Problem
Current heterophasic polypropylene resins face challenges in achieving a balance between high flowability and low-temperature impact properties, with existing methods often resulting in inhomogeneous mixing and high production costs, while also limiting flowability due to the need for high matrix viscosity.
Innovation Solution
A heterophasic polypropylene resin comprising a crystalline propylene homopolymer matrix and an amorphous propylene/ethylene or propylene/alpha olefin copolymer phase, with specific fractions insoluble and soluble in p-xylene, optimized for improved impact properties and flowability through a multi-stage production process using asymmetric single-site catalysts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If in-reactor production is used to improve homogeneity and reduce production cost, then manufacturing precision and productivity are improved, but flowability deteriorates due to high matrix viscosity requirements
Solution Approach 1:
The patent changes the molecular weight parameter of the matrix phase by using asymmetric single-site catalysts that produce polymers with tailored molecular weight distributions. Specifically, the matrix phase is designed with lower molecular weight (intrinsic viscosity < 1.1 dl/g) compared to conventional high molecular weight matrices, which reduces viscosity while maintaining homogeneity through in-reactor production
Solution Approach 2:
The patent creates a composite material system with two distinct phases: a crystalline propylene homopolymer matrix phase and an amorphous propylene copolymer dispersed phase. This composite structure allows the matrix to provide structural integrity while the dispersed phase provides impact modification, and the specific phase composition enables both good homogeneity and acceptable flowability
2Manufacturing precision
If matrix viscosity is increased to achieve high homogeneity, then manufacturing precision is improved, but flowability deteriorates
Solution Approach 1:
The patent fundamentally changes the viscosity parameter by controlling molecular weight through catalyst selection. The asymmetric single-site catalyst produces matrix polymers with intrinsic viscosity specifically controlled to be less than 1.1 dl/g, which is lower than conventional matrices. This parameter change allows the material to flow better while still achieving homogeneous mixing during in-reactor production
3Ease of operation
If melt flow rate is increased to improve flowability, then ease of operation is improved, but impact properties deteriorate due to coarse morphology
Solution Approach 1:
The patent uses a composite material approach where a dispersed amorphous propylene copolymer phase (containing 40-70 wt% ethylene/alpha olefin) is distributed within the crystalline propylene homopolymer matrix. This composite structure provides impact modification at the micro level, maintaining fine morphology and good impact properties even when the matrix has lower molecular weight for improved flowability
Solution Approach 2:
The patent applies local quality by creating regions with different properties: the matrix phase provides structural continuity and flow characteristics, while the dispersed copolymer particles provide localized impact energy absorption. This local differentiation allows the material to have good overall flowability while maintaining excellent impact properties through the distributed rubber phase
Data Source
AI summary
The present invention relates to a heterophasic polypropylene resin comprising a crystalline propylene homopolymer matrix (A) and an amorphous propylene copolymer phase (B) dispersed within the matrix having excellent mechanical properties, in particular at low temperatures, and at the same time high flowability. Further, the invention relates to a production process of the heterophasic polypropylene resin, the use of such a resin in a polypropylene composition and to articles made of the heterophasic polypropylene resin.