Peroxide-Treated Metallocene Polyolefins for Blown Film Melt Strength
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Solution Overview
Problem
In thick gauge film applications for linear low density polyethylene (LLDPE) resins, such as geomembranes, achieving good melt strength and flexibility while maintaining maximum use temperature and stiffness is challenging, as reducing density for flexibility adversely affects stiffness and use temperature.
Innovation Solution
Ethylene polymers with specific molecular weight ratios, zero-shear viscosity, and long chain branching are developed, produced using a metallocene-based catalyst system and treated with a peroxide compound to enhance melt strength and stability, allowing for the production of films with improved mechanical properties without compromising temperature resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the density of LLDPE resin is reduced to improve flexibility, then flexibility is improved, but stiffness and maximum use temperature deteriorate
Solution Approach 1:
The patent changes the molecular weight distribution parameters (Mw/Mn ratio ≤ 5, Mz/Mw ratio ≤ 2.3) and introduces specific long chain branching (0.01-0.1 per 1000 carbon atoms) to achieve a unique combination of flexibility and temperature resistance that cannot be obtained by simple density adjustment alone
Solution Approach 2:
The patent creates a composite molecular structure within the polymer by combining narrow molecular weight distribution with controlled long chain branching, resulting in a material that exhibits both flexibility (from lower density) and temperature resistance (from the structured molecular architecture)
2Ease of operation
If the density of LLDPE resin is reduced to improve flexibility, then flexibility is improved, but stiffness deteriorates
Solution Approach 1:
The patent modifies the molecular weight distribution parameters (Mw/Mn ≤ 5, Mz/Mw ≤ 2.3) and introduces controlled long chain branching to achieve a balance between flexibility and stiffness that is not attainable through density reduction alone
Solution Approach 2:
The patent introduces long chain branching (LCB) which creates curved/branched structures in the polymer chains, affecting the packing and crystallinity to achieve both flexibility and maintained stiffness
3Reliability
If melt strength is improved for blown film processing, then bubble stability is improved, but processing complexity increases
Solution Approach 1:
The patent achieves improved bubble stability by controlling molecular weight distribution (Mw/Mn ≤ 5, Mz/Mw ≤ 2.3) and introducing specific long chain branching (0.01-0.1 per 1000 carbon atoms), which enhances melt strength without requiring complex processing equipment or multi-component blends
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 resulting ethylene polymers exhibit improved melt strength, stability, and flexibility, maintaining high temperature resistance and stiffness, suitable for various applications including geomembranes and blown films.
Implementation Method 1
Processes for producing these ethylene polymers using a base resin and a peroxide compound also are disclosed herein
Data Source
AI summary
Disclosed herein are ethylene-based polymers having low densities and narrow molecular weight distributions, but high melt strengths for blown film processing. Such polymers can be produced by peroxide-treating a metallocene-catalyzed resin.