Multimodal Ethylene Copolymer for Flexible High-Pressure Pipes
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Solution Overview
Problem
Pipes made of high-density polyethylene lack flexibility and sufficient mechanical properties for high-pressure fluid transportation applications, such as water or gas distribution, where they need to be coiled and meet PE100 qualifications.
Innovation Solution
A multimodal ethylene copolymer composition comprising a blend of low and high molecular weight components, produced through a multistage polymerization process using a single-site catalyst, offering a balance of flexibility and mechanical strength, allowing the pipes to be coiled and meet PE100 standards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high-density polyethylene is used for pipes, then mechanical strength and pressure resistance are improved, but flexibility is worsened
Solution Approach 1:
The patent applies composite materials by combining HDPE with LLDPE in a specific ratio (60-90% HDPE and 10-40% LLDPE). This creates a composite polymer material that integrates the high mechanical strength of HDPE with the flexibility of LLDPE, resolving the contradiction between strength and flexibility for pressure pipes.
Solution Approach 2:
The patent changes the compositional parameters of the polymer material by controlling the density range (0.940-0.960 g/cm³) and molecular weight distribution (bimodal or multimodal). By adjusting these parameters, the material achieves both sufficient mechanical strength for pressure resistance and adequate flexibility for installation.
2Stress or pressure
If HDPE pipes are made rigid for pressure resistance, then pressure resistance is improved, but coilability is worsened
Solution Approach 1:
The composite of HDPE and LLDPE creates a material with balanced properties where the LLDPE component provides the necessary flexibility for coiling while the HDPE component maintains pressure resistance capability, enabling pipes to meet both coilability and pressure resistance requirements.
Solution Approach 2:
By controlling the density parameter within 0.940-0.960 g/cm³ and using bimodal/multimodal molecular weight distribution, the material achieves optimal balance between rigidity for pressure resistance and flexibility for coilability, allowing pipes to be wound into coils while maintaining structural integrity under pressure.
3Ease of operation
If LLDPE is used for flexibility, then flexibility is improved, but mechanical strength is worsened
Solution Approach 1:
The patent uses a composite material system where LLDPE (providing flexibility) is combined with HDPE (providing mechanical strength) in controlled ratios. This composite approach allows the final pipe material to exhibit both flexibility for installation and sufficient mechanical strength for pressure applications.
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 polymer composition enables pipes that are flexible enough to be coiled while maintaining the necessary mechanical strength for high-pressure applications, adhering to PE100 standards, thus addressing the limitations of existing HDPE pipes.
Implementation Method 1
polymerising, in a first polymerisation step in a first polymerisation zone, in the presence of a single site polymerisation catalyst, ethylene, hydrogen and optionally one or more alpha-olefins having 4 to 10 carbon atoms to form the low molecular weight component (A)
Data Source
Figure 1
AI summary
The present invention deals with polymer compositions suitable for making pipes. The compositions comprise a multimodal copolymer of ethylene and one or more alpha-olefins having from 4 to 10 carbon atoms wherein the multimodal ethylene copolymer has a density of from 937 to 950 kg/m3, a melt index MFR5 of from 0.3 to 3.0 g/10 min, a melt index MFR2 of from 0.1 to 2.0 g/10 min and a shear thinning index SHI2.7/210 of from 2 to 30. In addition the multimodal copolymer comprises: (A) from 30 to 70 % by weight, based on the combined amount of components (A) and (B), of a low molecular weight ethylene polymer selected from ethylene homopolymer and a copolymer of ethylene and one or more alpha-olefins having from 4 to 10 carbon atoms and having a weight average molecular weight of from 5000 to 100000 g/mol and a density of from 960 to 977 kg/m3; and (B) from 30 to 70 % by weight, based on the combined amount of components (A) and (B), of a high molecular weight copolymer of ethylene and one or more alpha-olefins having from 4 to 10 carbon atoms and having a weight average molecular weight of from 100000 to 1000000 g/mol and a density of from 890 to 929 kg/m3.