Heterophasic Polypropylene Composition Eliminates Flow Marks
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Solution Overview
Problem
Heterophasic polypropylene copolymer compositions used in automotive applications often suffer from surface defects like 'Tigerstripes' or flow marks, which affect the optical quality and consistency, and previous solutions have either compromised impact strength/stiffness balance or introduced other undesirable properties.
Innovation Solution
A polypropylene polymer composition comprising 45 to 70 wt% of a propylene homo- or copolymer matrix with high melt flow rate, 25 to 40 wt% of an elastomeric propylene-ethylene copolymer with high intrinsic viscosity, and 0 to 15 wt% of an elastomeric ethylene/alpha-olefin random copolymer, combined with inorganic filler, produced through a multistage process using a Ziegler-Natta catalyst system, ensuring excellent surface quality and absence of flow marks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If bimodal rubber compositions are used to improve surface toughness and scratch resistance, then scratch resistance is improved, but product consistency deteriorates due to migration leading to surface deposits
Solution Approach 1:
The patent changes the molecular weight distribution parameter from bimodal to unimodal rubber composition, eliminating the low IV fraction that causes migration and surface deposits while maintaining scratch resistance through controlled rubber particle size and distribution
Solution Approach 2:
The patent uses unimodal rubber composition with uniform molecular weight distribution to ensure homogeneous material properties throughout the composition, preventing migration and surface deposits while maintaining consistent performance
2Strength
If low IV rubber fraction is used to improve impact strength, then impact strength is improved, but steam jet performance deteriorates due to easy delamination
Solution Approach 1:
The patent changes the molecular weight distribution from bimodal to unimodal, removing the low IV fraction that provides impact strength but causes delamination, while compensating through optimized rubber content and composition
3Ease of manufacture
If Reactor-grade Thermoplastic Olefins are used to improve flowability, then flowability is improved, but flow marks appear on the surface
Solution Approach 1:
The patent optimizes the MFR parameter to achieve the right balance between flowability and surface quality, using controlled melt flow rate that prevents flow marks while maintaining adequate processing capability
Solution Approach 2:
The patent creates a composite material system combining propylene matrix with unimodal rubber composition that achieves synergistic effects: the rubber phase prevents flow marks while the optimized MFR maintains flowability
4Volume of moving object
If long flow paths are used for large articles, then article size is increased, but optical irregularity appears due to flow marks
Solution Approach 1:
The patent optimizes MFR and rubber content parameters to achieve a composition that maintains flowability over long distances without developing flow marks, enabling large article production with excellent surface quality
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 composition achieves a balance of high impact strength, stiffness, and flowability while eliminating flow marks, resulting in injection-molded parts with excellent surface quality suitable for large automotive components.
Implementation Method 1
produced through a multistage process using a Ziegler-Natta catalyst system
Data Source
AI summary
Heterophasic polypropylene composition comprising(A) 45 to 70 wt % of a propylene homo- or copolymer matrix with an MFR2 in accordance with ISO 1133 (230° C., 2.16 kg load) of ≧80 g/10 min and(B) 25 to 40 wt % of an elastomeric propylene-ethylene copolymer, having an intrinsic viscosity IV (ISO 1628, with decalin as solvent) of ≧3.3 dl/g and an ethylene content of 20 to 50 wt %,(C) 0-15 wt % of an elastomeric ethylene/alpha-olefin random copolymer(D) 3-25 parts per weight of inorganic filler,the heterophasic polypropylene compositions having a total MFR2 (230° C./2.16 kg) in accordance with ISO 1133 of ≧5 g/10 min, a Charpy notched impact strength according to ISO 179/1eA at +23° C. of ≧15.0 kJ/m2, preferably ≧25.0 kJ/m2, a minimum value for the Charpy notched impact strength according to ISO 179/1eA at −20° C. of ≧7.0 kJ/m2, preferably ≧10.0 kJ/m2 and a tensile modulus according to ISO 527-3 of ≧1200 MPa; their preparation and use for producing injection moulded articles being free of flow marks.