Multimodal Polyethylene Pipe Coating Neck-In Control
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Solution Overview
Problem
Existing methods for coating metal pipes with bimodal or multimodal ethylene polymers face challenges in achieving high throughput and processability, particularly in reducing neck-in and improving production economy.
Innovation Solution
A method involving a coating composition of multimodal ethylene copolymers with specific molecular weight ranges, molecular weight distribution, and additives, applied in a two-stage polymerization process to produce pipes with improved mechanical properties and high throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If bimodal or multimodal ethylene polymers are used for coating steel pipes, then the coating has good processability, but the throughput and neck-in control remain insufficient
Solution Approach 1:
The patent applies parameter changes by precisely controlling the molecular weight distribution (Mw/Mn ratio of 15-50) and composition of the multimodal ethylene copolymer. The coating composition uses a specific blend of low molecular weight (5000-35000 g/mol) and high molecular weight (100000-700000 g/mol) components, which optimizes both processability and throughput by adjusting the rheological parameters of the coating material.
Solution Approach 2:
The patent employs composite materials by creating a multimodal copolymer system that combines ethylene with alpha-olefin comonomers (4-10 carbon atoms). This composite polymer structure, consisting of multiple molecular weight fractions and comonomer types, provides synergistic effects that improve both ease of manufacture and productivity simultaneously.
2Strength
If higher molecular weight polymers are used to improve mechanical strength, then the coating strength increases, but the processing throughput decreases
Solution Approach 1:
The patent applies segmentation by dividing the polymer into distinct molecular weight segments: low molecular weight component (5000-35000 g/mol) for processability and high molecular weight component (100000-700000 g/mol) for mechanical strength. This segmented approach allows each segment to fulfill its specific function, resolving the contradiction between strength and throughput.
Solution Approach 2:
The patent utilizes dynamics by creating a multimodal distribution where different molecular weight fractions respond dynamically to processing conditions. The low molecular weight fraction provides fluidity during processing for high throughput, while the high molecular weight fraction maintains structural integrity for mechanical strength, allowing the system to adapt to different process stages.
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 solution enables the production of coated metal pipes with enhanced mechanical properties and high throughput, reducing operational issues like neck-in and improving production efficiency.
Implementation Method 1
a coating composition (B-2) comprising a multimodal copolymer of ethylene and one or more alpha-olefin comonomers
Data Source
AI summary
Coated pipes have a layer of multimodal polyethylene. The multimodal ethylene copolymer is a copolymer of ethylene with one or more alpha-olefin comonomers having from 4 to 10 carbon atoms and has a weight average molecular weight of from 70000 g/mol to 250000 g/mol, the ratio of the weight average molecular weight to the number average molecular weight, Mw/Mn, of from 15 to 50, a melt index MFR2 of from 0.05 g/10 min to 5 g/10 min, a melt index MFR5 of from 0.5 to 10 g/10 min and a density of from 930 kg/m3 to 955 kg/m3.