PE-RT Pellet Resin Composition for Large-Diameter Pipe Extrusion
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Solution Overview
Problem
Polyethylene of Raised Temperature resistance (PE-RT) type II pipes with large diameters face challenges in maintaining pressure resistance, dimensional stability, and processability due to high resin viscosity, which leads to increased processing loads and decreased line speed.
Innovation Solution
A pellet-type polyethylene resin composition is developed, comprising an ethylene/1-hexene copolymer with specific properties such as a melt index of 0.40 g/10 min to 0.80 g/10 min, density of 0.945 g/cm3 to 0.950 g/cm3, and a bimodal molecular weight distribution, achieved through a polymerization process using a hybrid supported catalyst, to enhance viscosity and reduce melt fracture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If high resin viscosity is used for large diameter pipes, then dimensional stability is improved, but processing load increases and line speed decreases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the melt index (MI) within 0.40-0.80 g/10min and density within 0.945-0.950 g/cm³, along with implementing a bimodal molecular weight distribution. These parameter optimizations enable the resin to achieve appropriate viscosity that simultaneously provides dimensional stability for large diameter pipes and maintains acceptable processing speed, resolving the contradiction between stability and productivity
Solution Approach 2:
The patent employs composite material strategies through the bimodal molecular weight distribution, which combines low molecular weight fractions (improving flow and processability) with high molecular weight fractions (providing strength and dimensional stability). This composite approach at the molecular level allows the resin to exhibit both stability and processability required for large diameter pipe production
2Stability of the object's composition
If high resin viscosity is used for large diameter pipes, then dimensional stability is improved, but processing load increases
Solution Approach 1:
The patent optimizes the melt index to 0.40-0.80 g/10min, which represents a parameter change that reduces resin viscosity to an optimal range. This reduction in viscosity directly decreases the processing load and energy consumption during extrusion, while the controlled density (0.945-0.950 g/cm³) and bimodal molecular weight distribution ensure dimensional stability is maintained, thus resolving the contradiction between stability and energy use
3Productivity
If low molecular weight fraction is increased, then processability is improved, but pressure resistance may be reduced
Solution Approach 1:
The patent implements a bimodal molecular weight distribution that acts as a composite material strategy at the molecular level. The low molecular weight fraction (peak A) enhances processability by improving flow characteristics and reducing processing loads, while the high molecular weight fraction (peak B) maintains pressure resistance and mechanical strength. The synergistic combination of these two fractions resolves the contradiction between processability and strength
Solution Approach 2:
The patent applies local quality by assigning different functional roles to different molecular weight fractions within the same resin system. The low molecular weight fraction specifically addresses processability requirements, while the high molecular weight fraction specifically addresses strength requirements. This functional differentiation within the composite resin system allows simultaneous optimization of both processability and pressure resistance
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 composition improves pipe pressure resistance, dimensional stability, and processability by balancing viscosity and fluidity, making it suitable for large-diameter PE-RT pipes with enhanced production efficiency.
Implementation Method 1
performing a polymerization reaction of an ethylene monomer and a 1-hexene comonomer in the presence of a hybrid supported catalyst
Data Source
AI summary
Provided are a pellet-type polyethylene resin composition capable of improving pipe pressure resistance property, dimensional stability, and processability at the same time, and a method of preparing the same.