4 Insights Into Prilling, Shaping, and Particle Coating

Justin Klinger, Feb 25, 2021 6:45:00 AM

Prilling, Shaping, & Coating Particles

Prilling, melt spraying, spheronization, and other particle shaping and surface treatments are all about improving control over the way a material behaves. The effect can be as simple as reducing dust, preventing agglomeration, or mitigating other handling challenges. 

Particle shaping, coating, and conditioning can also offer advanced effects, optimizing how a material behaves in a dispersion or blend, or a host of other functional improvements.

A well-equipped, experienced toll processor can perform a broad range of particle shaping, coating, and surface treatments on just as broad a range of materials and particle sizes.

The technologies used for these processes run from centuries-old prilling to state-of-the-art nano coatings that can optimize the function and behavior of incredibly fine particles in environments ranging from harsh weather conditions to the human digestive tract.

In this article, we’ll take a look at some of the applications and methods involved in important particle finishing processes that go beyond size reduction to enhance your control over particle morphology and surface characteristics — expanding your definition of what’s possible.

1. Material behavior drives coatings & surfacing innovations.

Driving every innovation in particle technologies is a need. Prilling and spray-melting, for example, answer a need for a solid state material to flow freely.

A prill is a free-flowing bead or spherical pellet of material. Materials are often prilled to make them easier to handle. Agricultural chemicals, fertilizers, detergents, waxes, polymers, fats, and other materials, typically with a melt point below 200°C, can be prilled. Prilled materials can be useful in a broad range of industries, from industrial chemicals to pharmaceuticals and food.

Prilling is an old process, modeled on the first lead shot tower, built in Bristol, England, and patented in 1782. In a shot tower, molten lead is dropped through a sieve. Droplets fall, cool and harden into spheres. The size of shot produced in a tower was limited by tower height, because to maintain a spherical shape, droplets had to cool completely before hitting the tower floor.

Later, the introduction of cold air allowed the spheres to cool faster, enabling the production of larger gauges of lead shot. Over time, process innovations have expanded prilling’s range of materials and sizes. Larger prilled materials range in size from 100 microns to a millimeter.

Melt spraying, or melt atomization, works the same way at a finer gauge. Molten material is sprayed into a chamber, where droplets quickly cool into round beads less than 100 microns in size. Prilled and melt-sprayed products can be screened for classification. Out-of-spec material is often reprocessed.

Not sure about what service is needed? Contact your toll processor’s material experts
to discuss your goal. They can guide you to your most efficient processing options.

2. Particle shaping and conditioning prepare materials for complex processes.

While prilling and melt spraying create spherical particle shapes, particles that result from other processes — like granulation and extrusion — can also be reshaped and surface-conditioned through the spheronization process.

Spheronization applies centrifugal, gravitational, and friction forces to quickly and efficiently round granulated or extruded material into consistent, smooth-surfaced spheres. The uniform shape and surface of the resulting particles and their freshly receptive surfaces prepare them for subsequent processes, including various coating methods.

Particle surface treatments can also include tumbling with abrasives for a desired effect, whether that’s a smoother or rougher particle surface, depending on what’s needed for the next step in a process.

3. Particle coatings expand possibilities like never before.

Particles have long been subject to coating processes, and have long since transcended the sugar-coating of medicines in the 1800s to mask bitter flavors. Particle coatings can include:

  • Fillers
  • Colorants
  • Lubricants
  • Binders
  • Flavors
  • Stabilizers
  • And more 

In addition to creating very fine prills, melt spraying can be used to deposit a thin layer of a coating material — such as pharmaceutical polymers or waxes — on a particle’s surface to mask flavor or odor, or to achieve time-release or delayed-release effects. 

Other particle coatings may include dyes or pigments that can alter a product’s color, or even an active ingredient applied as a coating on an inert carrier particle. But melt spraying isn’t the only way to apply coatings on small particles, and surface coatings’ benefits extend well beyond pharmaceuticals and food.

Fluid bed microencapsulation allows tight control over the thickness of coatings on very finely milled particles. This technology can allow fine particles to be coated to prevent agglomeration, improve wettability, distribute fillers, and much more.

Particle coatings can change a particle’s surface from hydrophobic to hydrophilic, facilitating dispersibility — an in-demand characteristic for paints, pigments, and dyes. Surfactant coatings can alter the hue or brightness of a pigment. Other coatings can prevent or modify interaction with another ingredient in a blend, for anything from industrial chemicals to specialty polymers. The key is tapping into the right expertise to harness the potential of specialty coating technologies.

4. Trust your toll processing partner to recommend the right process to meet your material needs.

Say you aren’t sure which process is right for your material, but you know what you need to achieve. That’s where your toll processor’s team of experts comes in. Material scientists, engineers, and specialized equipment operators with decades of experience — and the certifications needed to meet regulatory requirements in your industry — can help you determine the most efficient and cost-effective process for meeting your material objectives.

In fact, the benefits of working with a trusted toll processing partner include more than technical expertise. Working with a toll processor, you can access advanced equipment without the massive capital investment, not to mention the time to install and get up and running. Your toll processing team’s combined process knowledge also delivers optimization and efficiencies that you might otherwise take years to achieve.

There’s a lot more to the benefits of taking your particle shaping, conditioning, and coating challenges to a toll processor. You can learn more about the potential benefits when you download our guide, Comparing the Benefits of Toll Processing and In-House Manufacturing. Just click the link below. And if you’ve got a question, you can send it straight to our team using our contact form.Toll processing vs In-House manufacturing. Which is better for you? Use this quick-comparison guide. Get it now!

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