Multi-Stage Emulsion Processing Aid for Foamable Halogenated Polymers
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Solution Overview
Problem
Current methods for producing foamed halogenated polymers like PVC face challenges in recycling scrap material due to cross-linking processes that result in thermoset materials, making it difficult to reprocess and limiting their use in extrusion foaming processes.
Innovation Solution
A multi-stage emulsion processing aid polymer is developed, where functionalized ethylenically unsaturated monomers are staged in polymerization to increase molecular weight and incorporate functional groups such as β-keto esters and sulfonazides, allowing for higher melt strength and preventing foam collapse, while maintaining the material as a thermoplastic for easier recycling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If cross-linking agents are used to increase melt strength and prevent foam collapse, then foam structure stability is improved, but the material becomes a thermoset that cannot be reprocessed
Solution Approach 1:
The patent changes the chemical parameter of the processing aid polymer by incorporating functionalized ethylenically unsaturated monomers (containing β-keto ester, β-diketone, cyanoacetic ester, malonate, nitro, or sulfonazide groups) into the polymer structure. These functional groups enable cross-linking reactions with the halogenated polymer during processing, providing the necessary melt strength and foam structure stability while maintaining thermoplasticity for reprocessing.
Solution Approach 2:
The patent creates a composite system by combining the halogenated polymer with a specifically designed processing aid polymer that contains multiple functional groups. This composite approach allows the processing aid to provide cross-linking functionality without converting the entire system into a thermoset, as the functionalized monomers are incorporated at controlled levels (0.1-10 mole%) within the polymer structure.
2Shape
If high molecular weight processing aids are used to increase polymer expansion and melt strength, then foam cell uniformity is improved, but the complexity of polymerization process increases
Solution Approach 1:
The patent divides the polymerization process into multiple stages, with functionalized ethylenically unsaturated monomers introduced at specific stages during emulsion polymerization. This segmented approach allows control over the distribution and concentration of functional groups within the polymer, enabling high molecular weight (≥700,000) while managing process complexity through structured monomer addition sequences.
Solution Approach 2:
The functionalized ethylenically unsaturated monomers are incorporated into the processing aid polymer structure during the polymerization process itself, before the actual foaming application. This preliminary incorporation ensures that the cross-linking functionality is already present in the polymer chains, eliminating the need for separate cross-linking steps and simplifying the overall manufacturing process.
3Reliability
If functionalized monomers are incorporated to enable cross-linking, then foam structure stability is improved, but the molecular weight control becomes more difficult
Solution Approach 1:
The patent carefully controls the concentration parameter of functionalized monomers, limiting them to 0.1-10 mole% of the total monomer composition. This parameter control ensures that enough functional groups are present for cross-linking and foam structure stability, while maintaining the majority of the polymer as high molecular weight chains (Mw ≥ 700,000) for proper processing and extrusion characteristics.
Solution Approach 2:
The functionalized monomers are distributed locally within the polymer structure rather than uniformly throughout. This local incorporation allows specific regions of the polymer to provide cross-linking functionality while the overall polymer maintains high molecular weight and thermoplastic properties. The functional groups are embedded within the polymer chains at controlled intervals, providing localized cross-linking points that stabilize foam structure without compromising molecular weight control.
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 enhances the molecular weight of the polymer, improving melt strength and preventing foam collapse, allowing for the reuse of scrap material and maintaining the material as a thermoplastic, thus addressing the limitations of existing cross-linking methods.
Implementation Method 1
A multi-stage emulsion processing aid polymer is developed, where functionalized ethylenically unsaturated monomers are staged in polymerization to increase molecular weight
Implementation Method 2
functionalized ethylenically unsaturated monomers are staged in polymerization to increase molecular weight and incorporate functional groups such as β-keto esters and sulfonazides, allowing for higher melt strength and preventing foam collapse
Data Source
AI summary
A multi-stage emulsion processing aid polymer comprising one or more functionalized ethylenically unsaturated monomer into the emulsion polymerization reactor, wherein the functionality is selected from the group consisting of β-keto esters, β-keto amides, β-diketones, cyanoacetic esters, malonates, nitroalkanes, β-nitro esters, sulfonazides, thiols, thiol-s-triazines, and amine, where the functionality is incorporated into polymers by polymerizing, ethylenically unsaturated monomers containing these functionalities or by post functionalization of a polymer with additional reactions after polymerization in one of the first or second stages. Foamable halogenated polymers comprising the multi-stage emulsion processing aid polymer is also provided. Also provided are methods for making the multi-stage emulsion processing aid polymer and foamable halogenated polymers.