Multimodal Polyethylene Composition for Pipe Pressure and Processability
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Solution Overview
Problem
Current polyethylene compositions for pipes lack a combination of high pressure resistance, high impact strength, and high processability while maintaining good surface appearance, which is essential for various applications.
Innovation Solution
A multimodal ethylene copolymer comprising 55 to 80 wt% ethylene homopolymer component A and 20 to 45 wt% ethylene copolymer component B, with specific density, melt flow index, and viscosity ranges, allowing for improved pressure resistance, impact strength, and processability, and enabling the production of products with a good surface appearance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polyethylene composition uses base resin with density of 950.0-962.0 kg/m3 and MFR21 of 1.0-9.0 g/10 min, then processability is improved, but pressure resistance deteriorates (only 2000 hours at 12.9 MPa, 20°C)
Solution Approach 1:
The patent divides the polyethylene composition into multiple distinct components with specific molecular weight ranges (very high molecular weight component ≥10^6 g/mol, high molecular weight component 10^5-10^6 g/mol, low molecular weight component <10^5 g/mol). Each component contributes different properties: very high molecular weight provides pressure resistance, high molecular weight provides impact strength, and low molecular weight provides processability. This segmentation allows simultaneous achievement of contradictory properties.
Solution Approach 2:
The patent creates a composite polyethylene system by combining multiple polyethylene components with different molecular weight characteristics. The composition specifies precise weight ratios (very high molecular weight: 10-40 wt%, high molecular weight: 30-60 wt%, low molecular weight: 10-40 wt%) to achieve synergistic effects that satisfy both pressure resistance (≥5000 hours at 12.9 MPa) and processability requirements.
2Ease of manufacture
If polyethylene composition uses base resin with density of 952.0-960.0 kg/m3, MFR21 of 1.0-7.5 g/10 min, and complex viscosity η0.05 of 750-1900 kPa·s, then processability is improved, but pressure resistance deteriorates (6-70 hours at 7.0 MPa, 80°C)
Solution Approach 1:
The patent segments the polyethylene into distinct molecular weight fractions, where the very high molecular weight component (≥10^6 g/mol, 10-40 wt%) and high molecular weight component (10^5-10^6 g/mol, 30-60 wt%) provide enhanced high-temperature pressure resistance through their molecular structure, while the low molecular weight component (<10^5 g/mol, 10-40 wt%) ensures adequate processability. This segmentation enables the composition to achieve ≥5000 hours pressure resistance at 80°C while maintaining processability.
3Reliability
If polyethylene composition uses base resin with density of 950-965 kg/m3 and MFR5 of ≤0.1 g/10 min, then pressure resistance is improved, but impact strength and processability deteriorate
Solution Approach 1:
The patent divides the polyethylene composition into three molecular weight segments: very high molecular weight (≥10^6 g/mol, 10-40 wt%) for pressure resistance, high molecular weight (10^5-10^6 g/mol, 30-60 wt%) for impact strength, and low molecular weight (<10^5 g/mol, 10-40 wt%) for processability. This segmentation resolves the contradiction by assigning different functional roles to different molecular weight fractions.
Solution Approach 2:
The patent creates a composite polyethylene system combining multiple molecular weight components in specific ratios. The very high molecular weight component provides exceptional pressure resistance (≥5000 hours at 12.9 MPa), the high molecular weight component contributes impact strength, and the low molecular weight component ensures processability. The composite structure achieves all three properties simultaneously.
4Reliability
If polyethylene composition uses very high molecular weight polyethylene component, then pressure resistance is improved, but processability and surface appearance deteriorate
Solution Approach 1:
The patent segments the polyethylene into very high molecular weight (≥10^6 g/mol, 10-40 wt%) for pressure resistance, high molecular weight (10^5-10^6 g/mol, 30-60 wt%), and low molecular weight (<10^5 g/mol, 10-40 wt%) for processability and surface appearance. The low molecular weight component acts as a lubricant during processing, improving flow and surface finish, while the very high molecular weight component maintains pressure resistance.
Solution Approach 2:
The patent creates a composite polyethylene system where the very high molecular weight component (≥10^6 g/mol) provides pressure resistance (≥5000 hours at 12.9 MPa), the high molecular weight component (10^5-10^6 g/mol) provides impact strength, and the low molecular weight component (<10^5 g/mol) ensures processability and surface appearance. The synergistic combination achieves all properties simultaneously.
Data Source
AI summary
An ethylene copolymer includes or consists of 55 to 80 wt % of an ethylene homopolymer component A and 20 to 45 wt % of an ethylene copolymer component B of ethylene and an olefin comonomer, wherein the component A has a melt flow index as measured according to ISO1133-1:2011 at 190° C., 1.2 kg of 80 to 400 dg/min and a density of at least 968 kg/m3, and the ethylene copolymer has a melt flow index as measured according to ISO1133-1:2011 at 190° C., 5 kg of 0.05 to 0.3 dg/min, a density of 956 to 962 kg/m3, a comonomer content of 0.03 to 0.30 mol %, a viscosity value η0.05 at a temperature of 190° C. and a shear rate of 0.05 rad/s of 200 to 1000 kPa·s and a viscosity value η300 at a temperature of 190° C. and a shear rate of 300 rad/s of 700 to 1500 Pa·s.