Polyethylene Film Composition for Lower Oxygen and Moisture Transmission
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Solution Overview
Problem
Existing nucleating agents for thermoplastic polymers face challenges in identifying optimal pairings with polymers to achieve desirable physical properties such as lower water vapor and oxygen transmission rates, particularly in processes like blow molding and blown film production.
Innovation Solution
A thermoplastic polymer composition comprising a polyethylene polymer with a Melt Relaxation Index of 2 or greater and a salt of bicyclo[2.2.1]heptane-2,3-dicarboxylic acid is used, where the polyethylene polymer is selected to ensure sufficient melt relaxation to maximize heterogeneous nucleation, reducing self-nucleation and improving film properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional nucleating agents are used with polyethylene polymers, then crystallization can occur at higher temperatures and faster rates, but it is difficult to identify optimal pairings to achieve desirable physical properties such as lower water vapor and oxygen transmission rates
Solution Approach 1:
The patent applies parameter changes by specifying a Melt Relaxation Index threshold (≥2) for the polyethylene polymer and using a specific nucleating agent (salt of bicyclo[2.2.1]heptane-2,3-dicarboxylic acid). This quantitative parameter specification resolves the difficulty of identifying optimal pairings by establishing clear criteria for selecting polymers that will achieve both fast crystallization and desirable physical properties like lower water vapor and oxygen transmission rates.
Solution Approach 2:
The patent uses the Melt Relaxation Index as an intermediary parameter to bridge the gap between polymer selection and nucleating agent effectiveness. By measuring and specifying this intermediate property, the patent enables systematic identification of polymer-nucleating agent pairings that simultaneously achieve high crystallization rates and desirable barrier properties, eliminating the trial-and-error approach.
2Productivity
If self-nucleation occurs in the polymer, then processing can proceed, but the physical properties of the resulting articles are inferior compared to heterogeneously nucleated polymers
Solution Approach 1:
The patent introduces the Melt Relaxation Index as an intermediary parameter to predict and control nucleation behavior. By selecting polymers with MRI ≥2, the patent ensures heterogeneous nucleation dominates over self-nucleation, thereby achieving both processing capability and superior physical properties including lower water vapor and oxygen transmission rates.
Solution Approach 2:
The patent changes the nucleation mechanism from self-nucleation to heterogeneous nucleation by specifying particular parameters: using a salt of bicyclo[2.2.1]heptane-2,3-dicarboxylic acid as the nucleating agent and selecting polyethylene with Melt Relaxation Index ≥2. This parameter specification transforms the nucleation process to achieve both productivity and reliability.
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 composition achieves significantly lower water vapor and oxygen transmission rates in blown films, making it suitable for extrusion blow molding and film blowing processes.
Implementation Method 1
These nucleating agents generally function by forming nuclei or providing sites for the formation and/or growth of crystals in the thermoplastic polymer as it solidifies from a molten state
Implementation Method 2
a polyethylene polymer composition having a Melt Relaxation Index of 2 or greater; and a salt of bicyclo[2.2.1]heptane-2,3-dicarboxylic acid, where the polyethylene polymer is selected to ensure sufficient melt relaxation to maximize heterogeneous nucleation
Data Source
AI summary
A thermoplastic polymer composition comprises a polyethylene polymer composition and a salt of bicyclo[2.2.1]heptane-2,3-dicarboxylic acid. The polyethylene polymer composition can have a Melt Relaxation Index of 2 or greater. A method for molding a thermoplastic polymer composition comprises the steps of (a) providing an apparatus comprising a die with an annular orifice, a means for blowing pressurized fluid into a tube exiting the die orifice, and a means for drawing and collecting the tube; (b) providing the thermoplastic polymer composition described above; (c) heating the thermoplastic polymer composition to melt the thermoplastic polymer composition; (d) extruding the molten thermoplastic polymer composition through the die to form a tube; (e) blowing a pressurized fluid into the tube to inflate the tube while simultaneously drawing it; (f) allowing the film to cool; and (g) collecting the film.