Solid isolates of CBD may be created in a number of different forms. They may be created as a non-homogenous “cake” of material, or they may be created as a mixture of granules that are loosely associated and comprising a wide distribution in terms of particle size.
Typically, particle size reduction and/or homogenization are required to create material that is suitable for consumption or subsequent formulation in other products. Traditional sieving methods or a particle size analyzer may help to achieve confirmation of particle size distribution of a given sample.
Universal Cutting Mill PULVERISETTE 19. Image Credit: FRITSCH GmbH - Milling and Sizing
Laser Particle Sizer ANALYSETTE 22 NeXT. Image Credit: FRITSCH GmbH - Milling and Sizing
Variable Speed Rotor Mill PULVERISETTE 14 classic line. Image Credit: FRITSCH GmbH - Milling and Sizing
Some of the primary considerations when selecting a milling system for CBD homogenization are as follows:
- The size of the batch (throughput requirement kg/batch/day)
- A drive to minimize losses (physical and/or chemical)
- The final particle size range that is desired
- The ease of cleaning (to prevent batch cross-contamination)
Small Scale Homogenization
Low energy ball milling may be used to achieve small-scale homogenization of CBD isolate. Alternatively, this can be achieved by using an automated mortar and pestle. The FRITSCH Variable Speed Rotor Mill PULVERISETTE 14 classic line with Cyclone separator may be used to process larger batches in a continuous manner.
The PULVERISETTE 14 classic line with Cyclone is configured as a continuous milling system and facilitates a continuous feeding of material as well as active removal of material from the rotor area.
These processes typically take place in a fraction of a second; therefore, there is no time for frictional temperature increase, given the speed with which the homogenization occurs and material is removed.
Such temperature changes could (if allowed) potentially cause chemical degradation. To reduce the likelihood of cross-contamination, all product contact surfaces can be cleaned thoroughly between batches – and all are stainless steel (or food-grade plastic vacuum hose for the Cyclone).
Control of particle size output is provided thanks to its range of sieve rings and variable speed motor.
The PUVERISETTE 14 classic line and Cyclone separator, when used together with collection vessel, allow for continuous feeding and homogenization of CBD material into the low micron range (similar approximate consistency of talcum powder).
Figure 1. Inside of a Variable Speed Rotor Mill PULVERISETTE 14 classic line, showing fixed collection vessel, rotor and sieve ring. The high-performance Cyclone separator made of stainless steel is shown on the right. Image Credit: FRITSCH GmbH - Milling and Sizing
Large Scale Homogenization
The FRITSCH Universal Cutting Mill PULVERISETTE 19 is ideal for the production-scale homogenization of CBD isolate into a uniform powder.
This cutting mill can be configured to facilitate large-scale continuous processing of isolate material, in addition to already being considered the premier precision-milling solution for the preparation of cannabis biomass for extractions or pre-roll products.
Figure 2. Left side shows the PULVERISETTE 19 cutting mill system, shown with high-performance Cyclone separator mounted to 60 L collection vessel. Right side shows image CBD isolate homogenized into the low-mid micron range using the Universal Cutting Mill PULVERISETTE 19. Image Credit: FRITSCH GmbH - Milling and Sizing
Suggested System Settings
- Machine set between 2000 – 3000 rpm
- Rotor with fixed knives and notched edges
- Gap setting between cutting rotor & fixed knives should be 1 – 2 mm
- Sieve cassette: 1, 2 or 4 mm (depending on the desired fineness and the nature of the sample material)
- High-performance stainless-steel Cyclone separator
Analysis of Particle Size
The following reasons may contribute to characterizing the particle size distribution of a sample:
- To verify that a milling system has achieved particles within an established range
- In quality control: As a criterion for release into the manufacturing process (raw material testing) or for the sale of a product
- In R&D: To study the efficacy of a compound based on its particle size, and/or for reports on the perceived quality of a formulated product
The process of using traditional sieving methods to undertake particle size analysis involves using a series of sieve pans with progressively smaller openings, passing the material through the plans and subsequently observing and calculating the weight of material left in each pan.
Using this method, the number of different sieves that are used limits the data that can be obtained. Such data can be thwarted if and when particles stick to the metal surfaces.
Particle Sizer ANALYSETTE 22 NeXT. Image Credit: FRITSCH GmbH - Milling and Sizing
Using FRITSCH Instruments to Size Particles
FRITSCH pioneered laser particle size analyzers with a reverse Fourier optical system over three and a half decades ago. Since their inception, these analyzers have become a worldwide standard across a huge variety of industries for precise size characterization of materials down into the low nanometer range.
Figure 3. The ANALYSETTE 22 was used to measure CBD isolate before & after homogenization. Starting CBD sample (orange) contained a mixture of loose granules with a wide particle size distribution. Material homogenized using the Variable Speed Rotor Mill PULVERISETTE 14 classic line (purple) resulted in a particle size consistency similar to talcum powder. Image Credit: FRITSCH GmbH - Milling and Sizing
Where CBD isolates are being characterized, the Laser Particle Sizer ANALYSETTE 22 has been very effective, using either a dry or a wet dispersion method.
This information has been sourced, reviewed and adapted from materials provided by FRITSCH GmbH - Milling and Sizing.
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