Ethylene Polymer Composition Azide Coupling for Pipe Extrusion
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Solution Overview
Problem
Conventional ethylene-based polymer resins for pipe production with Ziegler-Natta catalysts have low melt strength and sag resistance, making them difficult to process under high shear conditions, resulting in rough pipe surfaces and lower production rates.
Innovation Solution
A composition comprising a combination of two ethylene-based polymers with a high load melt index ratio greater than 40 and azide compounds present at least 50 ppm, which improves melt strength and sag resistance, allowing for high shear processing without surface roughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If azide coupling is used to improve melt strength and sag resistance, then pipe surface roughness increases under high shear conditions, but if azide content is decreased to eliminate surface roughness, then melt strength and sag resistance are reduced
Solution Approach 1:
The patent changes the chemical structure parameters of the azide compound by introducing fluorinated alkyl groups with specific chain lengths and branching patterns. This modifies the azide's reactivity and coupling behavior, allowing sufficient melt strength while reducing surface roughness under high shear conditions.
Solution Approach 2:
The patent creates a composite effect by combining the azide-coupled polyethylene with a specific polymer blend system (including metallocene polyethylene and conventional polyethylene) in precise ratios. This composite approach distributes the mechanical strength requirements across multiple components, reducing the azide's burden while maintaining overall melt strength.
2Strength
If conventional Ziegler-Natta catalyst resins are used, then mechanical properties are excellent, but melt strength and sag resistance are low making processing difficult
Solution Approach 1:
The patent merges three distinct polyethylene components with different molecular weight distributions and branching characteristics, along with azide coupling, to achieve a synergistic effect. The metallocene polyethylene provides narrow MWD and consistent structure, the conventional polyethylene provides bulk mechanical properties, and the azide coupling provides melt strength enhancement without sacrificing processability.
Solution Approach 2:
The patent performs preliminary azide coupling on the polyethylene before final pipe extrusion processing. This pre-modification ensures that the melt strength enhancement is already in place during the extrusion process, eliminating sagging issues and enabling high shear rate processing without surface defects.
3Productivity
If pipe is extruded at high shear rates to increase production rate, then surface roughness increases on pipe, but if shear rate is decreased to eliminate roughness, then production rate decreases
Solution Approach 1:
The patent modifies the rheological parameters of the polyethylene melt through azide coupling and polymer blending, changing the shear thinning behavior. This allows the material to maintain stability at high shear rates during extrusion, preventing surface roughness while enabling high production rates.
Data Source
AI summary
The invention provides a composition comprising the following components: A) a first composition, wherein the first composition comprises a first ethylene-based polymer and a second ethylene-based polymer, and wherein the ratio of the “high load melt index (I21) of the first composition” to the “high load melt index (I21) of the first ethylene-based polymer” is greater than, or equal to, 40, and B) one or more azide compounds present in an amount greater than, or equal to, 50 ppm, based on the weight of the first composition.