Cosmetic creams and lotions are used for many purposes such as cleansing and moisturizing. The ingredients will vary depending on the desired use, but to some extent the basic manufacturing process is the same.

Products can be oil-in-water or water-in-oil emulsions, consisting of emollients and lubricants dispersed in an oil phase, and an aqueous phase containing emulsifiers and thickeners, fragrances, colors, and preservatives. The active ingredient is dispersed in either phase, depending on the raw material and the desired properties of the final product. 

A typical manufacturing process is as follows:

1. Flake/powder ingredients, such as cetyl alcohol and stearic acid, are sometimes pre-dried and dispersed into the oil phase. Heat may be required to melt some ingredients.

2. The active ingredient is dispersed in the appropriate phase.

3. Separately prepare an aqueous phase containing emulsifiers and stabilizers such as Veegum® or Carbopol®.

The two phases are then mixed to form an emulsion. This can be aided by heating to 110 - 185°F (45 - 85°C) depending on formulation and viscosity.

4. Continue mixing until the final product is homogeneous.

There are a number of problems that can be encountered with traditional mixers:

1. Some ingredients can form clumps that regular blenders cannot break up.

2. Hydration of thickeners and suspending agents is one of the most difficult of all mixing operations. Agglomerates are easy to form, and some ingredients require shearing to develop their desired properties.

3. When powdered ingredients are added to the container, some hydrated material will build up on the walls of the container and some parts of the agitator.

4. Even if the oil phase and the water phase have been heated, the stirrer does not easily form a stable emulsion.

5. Obtaining a homogeneous product usually requires longer processing times and additional equipment.

Solution

Using Silverson high shear mixers can eliminate intermediate stages of production, improve product quality and significantly reduce processing time. The benefits of Silverson high shear mixers stem from the 3-stage mixing/shearing action created by the precision machined workhead.

1. The boat is charged in a "continuous" phase. Start the Silverson mixer and add the solid/powdered ingredients. The powerful suction created by the high-speed rotation of the rotor blades draws liquid and solid components into the workhead, where they are rapidly mixed.

2. Solids break down in precision machined rotor/stator work heads. The micronized powder and other ingredients are completely dispersed into the liquid before being extruded through the stator and recycled into the mixed mass. At the same time fresh material is sucked into the working head.

3. Once the powder ingredients are completely dispersed in the "continuous" liquid phase, the "dispersed" phase can be added to form an emulsion. The high shear mixing action of the rotor/stator workhead ensures a uniform and stable emulsion.