Emulsion processing methods – how are emulsions made
của NiuShangshen
To create an emulsion, the ingredients are first combined to form a crude premix emulsion. This premix can be created in several ways:
The emulsifier is dissolved in the continuous phase, and then the internal phase is slowly added with good agitation (most common method).
The emulsifier can be dissolved in the internal phase before slowly adding that blend to the continuous phase under agitation.
The emulsifier can be dissolved in the internal phase before slowly adding the continuous phase to form the premix. This means usually produces the best results but it requires a lot of time and vigorous mixing because it involves bringing a preliminary W/O emulsion through the inversion stage to eventually form the desired O/W type.
Another method is using a mix-order control method specifically developed. This technique permits the injection of the product components directly into the product stream at different steps along a multistage mixing chamber.
The first method produces good results if a mechanical shearing device such as a colloid mill or an in-line mixer is used in the finishing step, the first premix method usually produces good results.
Having assured a well-formulated and stable premix, the colloid mill or in-line mixer can finish the job of emulsifying. The zone of intense hydraulic shear forces within the colloid mill or in-line mixer head breaks the internal phase droplets apart and creates the small particle size that is generally desired. If sufficient emulsifier is used for the enormous increase in surface area generated by this process, the final product should exhibit enhanced stability.
In some cases, a good emulsion can be produced with a moderate level of applied mechanical energy, but a poor emulsion results if the energy level is increased. The increase in applied energy causes additional particle size reduction, but without adjustment to the emulsifier concentration, the smaller particles are not stable. This is known as overworking the emulsion. Processing equipment, such as in-line mixers that offer Shear Zone Management (multiple, customizable, high-shear action zones) and Mix Order Control (adaptable mixing chambers to introduce process material at different positions in the shear zone), provides critical advantages for commercial emulsion development and processing.
Reduction in dispersed phase viscosity enhances emulsion formation, but what effects can be expected from changes in the continuous-phase viscosity? A reduction in viscosity should lead to easier emulsion formation because of a reduced interfacial tension. While this is true, another factor must be considered. An increase in continuous-phase viscosity will greatly improve emulsion stability by retarding the inevitable rise of the oil droplets to the top. In most circumstances, this more stable finished product is the overriding concern, and a decision to gain this advantage at the expense of overcoming a higher interfacial tension in the mechanical processing step is gladly accepted.
Monitoring and controlling the viscosity of the emulsification process becomes critical to achieving a repeatable, efficient process.
The emulsifier is dissolved in the continuous phase, and then the internal phase is slowly added with good agitation (most common method).
The emulsifier can be dissolved in the internal phase before slowly adding that blend to the continuous phase under agitation.
The emulsifier can be dissolved in the internal phase before slowly adding the continuous phase to form the premix. This means usually produces the best results but it requires a lot of time and vigorous mixing because it involves bringing a preliminary W/O emulsion through the inversion stage to eventually form the desired O/W type.
Another method is using a mix-order control method specifically developed. This technique permits the injection of the product components directly into the product stream at different steps along a multistage mixing chamber.
The first method produces good results if a mechanical shearing device such as a colloid mill or an in-line mixer is used in the finishing step, the first premix method usually produces good results.
Having assured a well-formulated and stable premix, the colloid mill or in-line mixer can finish the job of emulsifying. The zone of intense hydraulic shear forces within the colloid mill or in-line mixer head breaks the internal phase droplets apart and creates the small particle size that is generally desired. If sufficient emulsifier is used for the enormous increase in surface area generated by this process, the final product should exhibit enhanced stability.
In some cases, a good emulsion can be produced with a moderate level of applied mechanical energy, but a poor emulsion results if the energy level is increased. The increase in applied energy causes additional particle size reduction, but without adjustment to the emulsifier concentration, the smaller particles are not stable. This is known as overworking the emulsion. Processing equipment, such as in-line mixers that offer Shear Zone Management (multiple, customizable, high-shear action zones) and Mix Order Control (adaptable mixing chambers to introduce process material at different positions in the shear zone), provides critical advantages for commercial emulsion development and processing.
Reduction in dispersed phase viscosity enhances emulsion formation, but what effects can be expected from changes in the continuous-phase viscosity? A reduction in viscosity should lead to easier emulsion formation because of a reduced interfacial tension. While this is true, another factor must be considered. An increase in continuous-phase viscosity will greatly improve emulsion stability by retarding the inevitable rise of the oil droplets to the top. In most circumstances, this more stable finished product is the overriding concern, and a decision to gain this advantage at the expense of overcoming a higher interfacial tension in the mechanical processing step is gladly accepted.
Monitoring and controlling the viscosity of the emulsification process becomes critical to achieving a repeatable, efficient process.