Polyolefin Powder Formation via Melt Blending and Phase Transition
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Solution Overview
Problem
Current methods for producing polyolefin powders with small mean volume average particle size for 3D-printing techniques result in powders with agglomerates, voids, and irregular shapes, affecting mechanical properties and particle size distribution.
Innovation Solution
A process involving melt blending of a polyolefin phase and an aqueous phase in the presence of dispersants like acrylic and poloxamer dispersants, controlling interfacial tension, and forming a polyolefin aqueous dispersion with specific solids content, followed by water removal to produce powders with desired particle size, sphericity, and density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If spray drying or coagulating is used to produce small particle size polyolefin powder, then the mean volume average particle size is reduced, but the powder contains agglomerates with voids that are not fully dense
Solution Approach 1:
The patent utilizes phase transition by melt-blending the polyolefin with aqueous phase at elevated temperatures to form a homogeneous mixture, then rapidly cooling to quench and freeze the morphology. This phase transition approach creates fully dense spherical particles without voids, resolving the contradiction between small particle size and full density.
Solution Approach 2:
The patent introduces an aqueous phase as an intermediary medium during melt-blending, which acts as a heat transfer medium and structure-forming agent. The aqueous phase enables controlled cooling and freezing that produces dense spherical particles, eliminating the voids that occur in conventional spray drying or coagulation processes.
2Length of moving object
If mechanical grinding is used to reduce particle size, then the mean volume average particle size is reduced, but the particles have irregular shapes and broad particle size distribution
Solution Approach 1:
The patent performs preliminary action by melt-blending the polyolefin with aqueous phase before solidification, establishing a homogeneous molten state with uniform distribution. This preliminary mixing ensures that when the material solidifies, it forms regular spherical particles rather than irregular fragmented shapes from mechanical grinding.
Solution Approach 2:
The patent explicitly employs spheroidality by controlling the freeze-drying process to form spherical particles. The aqueous phase acts as a spherical template during freezing, and the subsequent lyophilization preserves this spherical morphology, producing particles with sphericity greater than 0.9, in contrast to the irregular shapes from mechanical grinding.
3Ease of manufacture
If spray drying or coagulating is used to produce polyolefin powder, then the process is relatively simple, but the resulting powder contains agglomerates with voids that deteriorate mechanical properties
Solution Approach 1:
The patent uses phase transitions (melting, freezing, and lyophilization) to transform the polyolefin-aqueous mixture into fully dense spherical particles. This phase transition approach, while adding steps, eliminates voids and agglomerates, significantly improving mechanical properties and sintering behavior despite the increased process complexity.
4Quantity of substance
If conventional methods are used to produce polyolefin powder, then production cost is controlled, but the powder has broad particle size distribution and irregular shapes
Solution Approach 1:
The patent performs preliminary melt-blending of polyolefin with aqueous phase to create a homogeneous mixture before solidification. This preliminary action ensures uniform distribution and consistent freezing behavior, resulting in narrow particle size distribution and regular spherical shapes, contrasting with the broad distribution from mechanical grinding.
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 process yields powders with narrow particle size distribution, high sphericity, and full density, enhancing mechanical properties and flowability, suitable for 3D-printing and other applications like rotomolding and powder coatings.
Implementation Method 1
producing an interfacial tension from 0.1 dynes/cm to 25 dynes/cm
Implementation Method 2
removing the water from the polyolefin aqueous dispersion to form a powder
Data Source
Figure 1
AI summary
The present disclosure provides a process. The process includes (i) melt blending, in an extruder, (a) a polyolefin phase and (b) an aqueous phase in the presence of (c) at least one dispersant selected from an acrylic dispersant, a poloxamer dispersant, and combinations thereof; (ii) producing an interfacial tension from 0.1 dynes/cm to 25 dynes/cm; (iii) forming a polyolefin aqueous dispersion having from 25 wt% to 90 wt% solids content of dispersion; and (iv) removing the water from the polyolefin aqueous dispersion to form a powder. The powder has a mean volume average particle size from 10 μm to 300 μm, a sphericity from 0.92 to 1.0, a particle size distribution from 1 to less than 2, and a particle density from 98% to 100%.