Soft Polypropylene Composition for Medical Packaging
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Solution Overview
Problem
Existing random heterophasic propylene copolymers used in medical packaging suffer from significant changes in optical and mechanical properties after sterilization, particularly in terms of stiffness and haze, which are undesirable for medical applications.
Innovation Solution
A random heterophasic propylene copolymer (RAHECO) is developed with a low comonomer content and specific relative content of isolated to block ethylene sequences, produced using a Ziegler-Natta catalyst that does not include phthalic acid ester derivatives, maintaining improved optical and mechanical properties before and after sterilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a rubber phase is dispersed within the polypropylene matrix to improve impact strength, then impact strength is improved, but the material becomes stiffer and less soft
Solution Approach 1:
The invention changes the parameters of the rubber phase by controlling the comonomer content (below 36.0 mol-%) and the relative content of isolated to block ethylene sequences (below 55.0%) in the elastomeric propylene copolymer. This optimization allows achieving high impact strength while maintaining softness and flexibility, resolving the contradiction between strength improvement and softness preservation.
2Strength
If standard heterophasic systems are used to provide mechanical strength, then impact strength is improved, but optical properties such as haze are significantly impaired after sterilization
Solution Approach 1:
The invention optimizes specific parameters of the elastomeric propylene copolymer including comonomer content (below 36.0 mol-%) and ethylene sequence distribution (isolated to block ratio below 55.0%). These parameter changes result in a heterophasic propylene copolymer that maintains excellent optical clarity (low haze) even after sterilization, while providing the necessary impact strength.
3Productivity
If phthalic acid ester derivatives are used as internal donors in the catalyst system, then the polymerization process is effective, but health and environmental compliance is compromised
Solution Approach 1:
The invention extracts and removes the harmful phthalic acid ester derivatives from the catalyst system while replacing them with safe alternative internal donors. This substitution maintains the effectiveness of the polymerization process and the quality of the resulting heterophasic propylene copolymer, while ensuring compliance with health and environmental regulations such as REACH.
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 RAHECO exhibits a balanced combination of mechanical strength and optical clarity that is preserved post-sterilization, making it suitable for medical packaging and cable insulation applications without the use of harmful phthalic acid ester derivatives.
Implementation Method 1
the random heterophasic propylene copolymer (RAHECO) must be produced in the presence of a Ziegler-Natta catalyst containing an internal donor (D) not belonging to the class of phthalic acid ester derivatives
Data Source
Figure 1
AI summary
The present invention is directed to a new heterophasic propylene copolymer (RAHECO), a process for obtaining said heterophasic propylene copolymer (RAHECO) and a film or a cable insulation comprising the heterophasic propylene copolymer (RAHECO).