Polyolefin Composition for Steam Sterilization Clarity
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Solution Overview
Problem
Polypropylene compositions used in packaging and medical applications face challenges with opacity and mechanical property degradation due to sterilization methods, particularly steam sterilization, which increases crystallinity and brittleness, and affects optical and mechanical properties.
Innovation Solution
A polyolefin composition comprising a propylene-based polymer, a terpolymer of propylene, an α-olefin, and an ethylene copolymer, with a propylene content of at least 60 wt%, which maintains good optical and mechanical properties and is suitable for steam sterilization, including medical applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If elastomeric olefin copolymer (EPR) is added to polypropylene to improve flexibility and impact resistance, then mechanical properties are improved, but the composition becomes opaque due to refraction index mismatch
Solution Approach 1:
The patent changes the chemical composition parameters by introducing a terpolymer containing cycloolefin units, which have a refraction index closer to polypropylene. This parameter change in composition resolves the transparency issue while maintaining the mechanical benefits of elastomeric modifiers.
Solution Approach 2:
The patent creates a composite material system combining polypropylene, elastomeric olefin copolymer, and a specific terpolymer with cycloolefin units. This composite approach allows the system to simultaneously achieve transparency (from the refraction-matched terpolymer) and impact resistance (from the elastomeric copolymer).
2Reliability
If steam sterilization is applied to propylene copolymer films to ensure medical sterility, then reliability is improved, but the material becomes stiffer, more brittle, and develops increased haze
Solution Approach 1:
The patent incorporates a hydrophobic acid scavenger into the composition before sterilization. This preliminary action prevents acid formation during steam sterilization that would otherwise cause crystallization and embrittlement, allowing the material to withstand sterilization without losing mechanical properties.
Solution Approach 2:
The acid scavenger acts as a protective buffer against acid formation during sterilization. This beforehand cushioning neutralizes potential harmful effects before they can damage the polymer structure, preserving impact strength and flexibility after sterilization.
3Illumination intensity
If comonomers are incorporated into propylene polymer chain to improve transparency and softness, then optical properties are improved, but stereo defects concentrate and increase intermolecular heterogeneity, leading to embrittlement after sterilization
Solution Approach 1:
The patent introduces a specific terpolymer composition with cycloolefin units as a new parameter variable. This compositional change allows the system to achieve transparency benefits from comonomer incorporation while the unique cycloolefin structure prevents the concentration of stereo defects that lead to embrittlement.
Data Source
AI summary
The invention relates to acomposition comprising: (A) a propylene-based polymer which is a propylene homopolymer or a propylene copolymer consisting of at least 90 wt% of propylene monomer units and at most 10 wt% of ethylene monomer units and/or an α-olefin monomer units having 4 to 10 carbon atoms, (B) a terpolymer of propylene, an α-olefin having 4 to 10 carbon atoms and ethylene and (C) a copolymer of ethylene and an α-olefin having 4 to 10 carbon atoms,wherein the copolymer (C) has a density of at least 0.880 g/cm3, wherein the amount of the propylene-based polymer (A) is at least 60 wt% with respect to the total composition.