Three-Component Propylene Polymer Composition for Impact and Transparency
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Solution Overview
Problem
Isotactic polypropylene copolymers with ethylene and α-olefins do not sufficiently improve impact resistance without compromising transparency, especially after sterilization processes.
Innovation Solution
A propylene polymer composition comprising specific weight percentages of propylene homopolymer, low ethylene copolymer, and high ethylene copolymer, with controlled melt flow rate and xylene solubility, produced using Ziegler-Natta catalysts and tailored polymerization techniques, ensuring improved impact resistance and transparency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If propylene is copolymerized with ethylene and/or α-olefins to decrease crystallinity, then flexibility and transparency are improved, but impact resistance is insufficient
Solution Approach 1:
The invention uses a composite material system consisting of three distinct propylene copolymers with different ethylene contents (first copolymer with 1-10 wt% ethylene, second copolymer with 10-20 wt% ethylene, third copolymer with 20-40 wt% ethylene). This multi-component composite approach allows simultaneous achievement of transparency (through the first copolymer), flexibility (through the second copolymer), and impact resistance (through the third copolymer with higher elastomeric content), resolving the contradiction between transparency and impact resistance that cannot be achieved with single copolymers or conventional two-component blends.
2Strength
If an elastomeric propylene-ethylene copolymer is added to improve impact resistance, then impact resistance is improved, but transparency is detrimental
Solution Approach 1:
The invention segments the elastomeric function across three different copolymers with progressively increasing ethylene content rather than using a single high-ethylene copolymer. The third copolymer (20-40 wt% ethylene) provides the necessary elastomeric properties for impact resistance, while the first two copolymers with lower ethylene content maintain transparency and flexibility. This segmentation allows each component to optimize its specific function while contributing to the overall performance, resolving the transparency-impact resistance trade-off.
Solution Approach 2:
Different regions of the polymer composition have different local qualities: the first copolymer (1-10 wt% ethylene) provides transparent crystalline regions, the second copolymer (10-20 wt% ethylene) provides flexible intermediate regions, and the third copolymer (20-40 wt% ethylene) provides elastomeric impact-absorbing regions. This local quality differentiation allows the material to exhibit multiple properties simultaneously in different phases, resolving the contradiction between transparency and impact resistance.
3Ease of operation
If propylene copolymers are used to improve flexibility, then flexibility is improved, but impact resistance at low temperatures is insufficient
Solution Approach 1:
The invention creates a composite system where the third copolymer with high ethylene content (20-40 wt%) provides low-temperature impact resistance through its elastomeric properties, while the first two copolymers with lower ethylene content maintain flexibility and processability. The synergistic interaction between these three components with different glass transition temperatures and crystallinity levels allows the material to remain flexible at operating temperatures while providing enhanced impact resistance at low temperatures, resolving the contradiction between flexibility and low-temperature impact resistance.
Data Source
AI summary
Propylene polymer composition made from or containing:A) from 30 wt % to 50 wt % of a propylene homopolymer having a melting point, measured by DSC, between 152° C. and 162° C.;B) from 35 wt % to 55 wt % of a copolymer of propylene with ethylene containing from 2.5 wt % to 5.8 wt % of ethylene derived units, based upon the total weight of the propylene/ethylene copolymer; andC) from 5 wt % to 24 wt % of a copolymer of propylene with ethylene containing from 6.0 wt % to 8.0 wt %, of ethylene derived units, based upon the total weight of the propylene/ethylene copolymer;the sum of the amount of A, B, and C being 100 wt %.