Polyethylene Copolymer Composition for Pipe Processability and Durability
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Solution Overview
Problem
Polyolefin resins used in large-diameter high-pressure pipes face challenges in balancing long-term pressure resistance stability and processability, with high density leading to brittle fracture and processing difficulties, while high molecular weight resins increase extrusion load and reduce pipe processability.
Innovation Solution
A polyethylene copolymer is developed with a specific molecular structure, including an ethylene-derived and an alpha-olefin-derived repeating unit, satisfying a slow crack growth index condition, which is achieved through polymerization using a hybrid supported catalyst, optimizing molecular weight distribution and comonomer content for improved processability and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the density of polyolefin resin is increased to improve high pressure resistance, then the modulus and ability to withstand high pressure are improved, but resistance to brittle fracture is degraded and long term pressure resistance characteristic is deteriorated
Solution Approach 1:
The patent applies parameter changes by precisely controlling the density of the polyolefin resin within a specific range of 0.935-0.945 g/cm³, and controlling the molecular weight distribution with Mw/Mn ratio of 3.0-8.0. This optimized parameter range resolves the contradiction by finding the optimal balance point where high pressure resistance and long term durability are both satisfied.
Solution Approach 2:
The patent uses a composite approach by combining polyolefin resin with specific additives including antioxidants (0.1-5.0 parts by weight) and UV absorbers (0.1-5.0 parts by weight) per 100 parts by weight of resin. This composite formulation enhances both the immediate high pressure resistance and the long term reliability by protecting against oxidative and UV degradation.
2Reliability
If the molecular weight of polyolefin resin is increased to improve long term pressure resistance, then the processability is improved, but the extrusion load is increased and pipe processability declines
Solution Approach 1:
The patent applies parameter changes by controlling the molecular weight distribution within a specific range (Mw/Mn ratio of 3.0-8.0) and density (0.935-0.945 g/cm³). This optimized parameter range resolves the contradiction by finding the optimal balance point where long term durability is achieved while maintaining acceptable processability.
Solution Approach 2:
The patent applies dynamics by optimizing the molecular weight distribution to create a balanced polymer structure that exhibits appropriate flow characteristics during extrusion while maintaining long term strength. The controlled polydispersity index allows the material to be processed at reasonable extrusion loads while still achieving the desired long term pressure resistance.
3Ease of manufacture
If the molecular weight of polyolefin resin is decreased to improve processability, then the extrusion load is reduced, but a sagging phenomenon occurs and processing becomes difficult
Solution Approach 1:
The patent applies parameter changes by controlling the molecular weight distribution with Mw/Mn ratio of 3.0-8.0 and density of 0.935-0.945 g/cm³. This optimized parameter range provides sufficient molecular weight to prevent sagging during processing while maintaining good processability through appropriate molecular weight distribution.
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 polyethylene copolymer exhibits excellent processability and long-term durability, enhancing mechanical strength and maintaining high pressure resistance, suitable for hollow molding of pipes and other applications.
Implementation Method 1
achieved through polymerization using a hybrid supported catalyst
Data Source
AI summary
The present invention relates to a polyethylene copolymer which has excellent processability and long-term durability, and thus is useful for hollow molding of a pipe or the like.