Process for forming a powder

Abstract

The present disclosure provides a process including providing a polyolefin aqueous dispersion having (50) to (90) wt% solids content of dispersion, the polyolefin aqueous dispersion containing solid particles containing a polyolefin including an ethylene-based polymer having a melting temperature from greater than (115) to (140) deg C, polyolefin wax, acrylic dispersant; and an aqueous phase including excess acrylic dispersant; adding diluting water to form a diluted polyolefin aqueous dispersion having (5) to less than (50) wt% solids content; collecting the solid particles; washing the solidparticles with a washing agent to remove the excess acrylic dispersant; and removing the washing agent to form a powder having a mean volume average particle size from (10) to (300) um, a sphericityfrom (0.92) to (1.0), a particle size distribution from (1) to less than (2), a particle density from (98) % to (100) %, and a flow rate in a large funnel from (1) to (5) seconds.

Description

Background technique [0001] The present disclosure relates to a method for forming a powder. [0002] Polyolefin powders with a very small average volume average particle size can be used in 3D printing techniques such as powder bed fusion, where successive layers of powder are laid down and sintered to form a 3D final product. Powder bed fusion requires a flowable powder so that the powder can be easily transported and loaded. Powder bed fusion also requires a powder with a very small average volume average particle size. Polyolefin powders with a very small average volume average particle size are typically formed in one of three ways: (i) spray drying an aqueous polyolefin dispersion of small particle size to remove water and obtain an aggregated dry powder; ( ii) coagulating or agglomerating the small particle size aqueous polyolefin dispersion and filtering the aggregate to remove water; or (iii) mechanically grinding the polyolefin to the desired size, such as by cryog...

AI Technical Summary

Problems solved by technology

When produced via spray-drying and / or coagulation or agglomeration methods, the resulting powder contains not fully dense agglomerates with voids, which deteriorate the mechanical properties of the final product formed from said powder

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