Polypropylene composition containing a new charge-stabilizing agent for electret melt blown webs
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Solution Overview
Problem
Current charge-stabilizing additives for polypropylene-based electrets often have limitations, such as additional functionalities that restrict the choice of polypropylene base materials and provide inadequate long-term charge retention, impacting filtration efficiency and pressure drop in applications like facemasks.
Innovation Solution
A polypropylene composition incorporating a specific charge-stabilizing agent, where polypropylene is combined with a compound according to Formula (I), allowing for improved charge stabilization and retention, thereby enhancing filtration efficiency and maintaining performance over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional charge-stabilizing additives are used, then charge stabilization is provided, but additional functionalities (such as visbreaking) restrict the choice of polypropylene base material
Solution Approach 1:
The invention extracts and separates the charge-stabilizing function from other functionalities (such as visbreaking) that were previously combined in single additives. By using a dedicated charge-stabilizing agent according to Formula (I), the patent eliminates the restriction on polypropylene base material selection that arose from multi-functional additives, while maintaining effective charge stabilization.
2Duration of action of stationary object
If conventional charge-stabilizing additives are used, then initial charge is achieved, but long-term charge retention is inadequate
Solution Approach 1:
The invention changes the chemical parameters of the charge-stabilizing agent by specifying a particular chemical structure (Formula (I)) with defined functional groups and molecular weight range. This parameter optimization enables the additive to effectively scavenge radicals and stabilize charges over extended periods, maintaining filtration efficiency without the inadequate long-term retention experienced with conventional additives.
3Ease of manufacture
If polypropylene with high melt flow rate is used, then processing is improved, but charge retention over time deteriorates
Solution Approach 1:
The charge-stabilizing agent according to Formula (I) acts as an intermediary substance that bridges the contradiction between high melt flow rate polypropylene and charge retention. The additive scavenges radicals generated during processing of high MFR polypropylene and stabilizes the electrostatic charges, enabling both easy processing and long-term charge retention to coexist.
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 described composition achieves high filtration efficiency and stable charge retention, maintaining performance for extended periods without significant pressure drop, making it suitable for critical applications like facemasks.
Implementation Method 1
a compound according to Formula (I) ... for stabilizing the charge of an electret material
Implementation Method 2
Polypropylene is a natural electret, meaning that it is able to support a permanent electric dipole due to its dielectric properties
Data Source
AI summary
A polypropylene composition (PC) comprising: a. from 95.0 to 99.99 wt.-%, of a polypropylene (PP), preferably a propylene homopolymer (HPP); and b. from 0.01 to 5.0 wt.-%, of a compound according to Formula (I) wherein each R is independently selected from C1 to C6 alkylene, C2 to C6 alkenylene and a single bond, each R' is independently selected from H and C1 to C6 alkyl, each R" is independently selected from H and C1 to C22 alkyl, wherein each alkylene, alkenylene and alkyl group may optionally be substituted by deuterium or fluorine, and the two substituents on the central benzene ring may be either positioned in an ortho, meta or para relationship; wherein the polypropylene composition (PC) has an MFR2 of from 400 to 5000 g/10 min and a melting temperature Tm of from 140 to 170 °C.