Oxford Catalysts advances microchannel emulsification

Oxford, UK – Emulsions play an essential role in many personal care and over-the-counter drug products. But development of emulsion-based products is often a long process because formulators must deal with issues such as product efficacy, phase stability and non-uniform process conditions on scale up.

In a talk to be presented 28 June at the HBA Global Expo in New York, Mark Grace, president, Smooth, within Oxford Catalysts, will discuss how microchannel emulsification technology can be used to produce emulsions made up of smaller droplets, resulting in higher quality emulsion-based products.

Smooth is a technology developed by Velocys, Inc. of Columbus, Ohio, which specialises in the design and development of microchannel process technology for the production of synthetic fuels.

The US company claims to own, or have licences to, the largest microchannel patent portfolio in the world, with over 550 patent filings, and supports a large microchannel development team. Velocys, Inc. was acquired by Oxford Catalysts in 2008.

Emulsions are a mixture of immiscible fluids, in which droplets of a dispersed phase are distributed within a continuous phase. In general, the smaller the droplets, the more stable the mixture, eliminating or reducing the need to add surfactants.

Traditionally emulsions are produced in batches using different types of mixer. In contrast, Velocys Inc.’s microchannel emulsification technology, called Smooth, is said to use laminar shearing - also known as laminar flow emulsification - to produce emulsified mixtures in a continuous stream.

Research carried out by Velocys now shows that by controlling the flow rate of the continuous phase, and cooling the resulting emulsion very quickly, microchannel emulsification makes it possible to produce stable emulsions containing very small droplets.

As a rule of thumb, the faster the flow of the continuous phase, and the colder and faster the quenching, the smaller the droplets produced.

Optimum droplet sizes can be achieved by controlling flow rates and the speed and temperature of quenching to produce consistent products to tight specifications while reducing or eliminating the need to use surfactants.

Developing new formulations using traditional emulsification technology can be very time consuming because you need to test each formulation individually and wait for the results, according to Grace.

“One advantage of the Smooth technology is that it allows you to run multiple formulations quickly. You can change conditions such as viscosity, flow speeds, heating and cooling rates as well as quenching conditions on the fly and realise new properties nearly instantaneously - thus cutting development times,” he noted.

Emulsions are conventionally formed in batches under high shear conditions using static mixers, ultrasound devices, homogenisers, or rotor/stator mixers. Ensuring consistent product quality using traditional methods can be problematic because the high speed mixing process is difficult to control, leading to over shearing of sensitive materials and the need to use expensive surfactants.

Microchannel emulsification takes advantage of a process known as laminar shearing - also known as laminar flow emulsification – to produce stable and uniform emulsified mixtures in a continuous stream, often without the need for surfactants.

In the Smooth microchannel emulsifier module a continuous stream flows through the microchannel, with the dispersed phase introduced perpendicular to it after passing through a plate containing specifically sized pores. These range from 0.1 microns to 100 microns in diameter. Individual modules have a footprint of just 25.4 cm long x 7.6 cm wide x 10 cm high.

The pore size and channel depths can be altered to enable precise control of process parameters and resultant end product characteristics. The process can be scaled up by simply adding in additional modules.