Heterophasic Polypropylene Impact Resistance Hexane Extractables
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Solution Overview
Problem
Heterophasic polypropylene copolymers face challenges in achieving a balance of high impact resistance at low temperatures while maintaining low hexane extractables content, which is crucial for compliance with food and medical packaging regulations, as existing materials often exceed the FDA-approved hexane-solubles limit.
Innovation Solution
A polypropylene homo- or copolymer matrix combined with a dispersed phase comprising an ethylene or C4-C10-alpha olefin-propylene copolymer with high propylene monomer units and intrinsic viscosity, resulting in heterophasic polypropylene copolymers with improved impact properties and reduced hexane extractables.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If existing heterophasic polypropylene copolymers are used to achieve high impact resistance, then impact properties are improved, but hexane extractables content increases and exceeds FDA limits
Solution Approach 1:
The patent applies parameter changes by precisely controlling the intrinsic viscosity of the XCS fraction (2.1-3.5 dl/g) and the propylene monomer unit content (50-90 wt%), along with adjusting the glass transition temperature of the rubber phase (-42 to -30°C). These parameter optimizations enable the material to achieve both high impact resistance and low hexane extractables content, resolving the contradiction between impact properties and harmful extractables.
Solution Approach 2:
The patent uses composite materials by creating a heterophasic structure with a propylene matrix phase and an elastomeric copolymer disperse phase. The specific composition of the rubber phase (ethylene and/or C4-C20 alpha-olefin with propylene) and its controlled properties create a composite system that simultaneously provides impact resistance while maintaining low hexane extractables, satisfying both contradictory requirements.
2Object-generated harmful factors
If heterophasic copolymers are designed for low hexane extractables, then purity is improved, but impact resistance deteriorates
Solution Approach 1:
The patent resolves this contradiction by optimizing multiple parameters simultaneously: the intrinsic viscosity of the XCS fraction is controlled within 2.1-3.5 dl/g, the rubber phase glass transition temperature is set between -42 to -30°C, and the propylene monomer unit content is maintained at 50-90 wt%. This multi-parameter optimization ensures that even with reduced hexane extractables, the impact resistance remains high.
Solution Approach 2:
The patent applies local quality by creating distinct phases with specific properties: the matrix phase provides structural integrity while the disperse elastomeric phase (with specific Tg and composition) provides impact resistance. This localized functional distribution allows the material to achieve both low hexane extractables and high impact resistance through phase-specific property optimization.
3Strength
If the rubber phase intrinsic viscosity is increased to improve impact properties, then impact resistance is improved, but the material complexity increases
Solution Approach 1:
The patent manages material complexity by establishing clear parameter ranges for the rubber phase: intrinsic viscosity of 2.4-4.5 dl/g, glass transition temperature of -42 to -30°C, and specific comonomer composition. By defining these precise parameter boundaries, the patent simplifies the characterization and manufacturing control of complex heterophasic materials while maintaining high impact resistance.
Data Source
AI summary
Heterophasic polypropylene copolymers having an MFR (2.16 kg, 230°C) of 15 to 200 g/10 min, determined according to ISO 1133 comprising a propylene homo- or copolymer matrix with an MFR (2.16 kg, 230°C) of 80 to 500 g/10 min, determined according to ISO 1133 (A) and an ethylene or C4-C10-alpha-olefin propylene rubber phase (B) dispersed within the matrix, wherein the heterophasic polypropylene resin has a fraction soluble in p-xylene at 25°C (XCS), having an intrinsic viscosity of 2.85 to 4.00 dl/g, determined according to DIN EN ISO 1628-1 and -3 and being composed of propylene monomer units in an amount of 70 wt% to 90 wt%, with optimum balance of impact resistance and low amount of hexane extractables; a process for their preparation and their use.