What are the factors affecting the emulsification result of a vacuum emulsifier?

A vacuum emulsifier is equipment that emulsifies and shears materials under a vacuum state. Utilizing the high-shear homogenizing head within the emulsification tank, it performs high-speed shearing to efficiently, rapidly, and uniformly disperse multiple phases of materials into another phase. By harnessing the powerful kinetic energy generated mechanically, the processed material is subjected to comprehensive actions including hundreds of thousands of hydraulic shearing, centrifugal extrusion, impact, and tearing per minute within the narrow gap between the stator and rotor, achieving uniform emulsification and dispersion. Through high-frequency cyclic processing, it produces high-quality products that are bubble-free, stable, and fine.

Vacuum emulsifier applicable industries:

It is suitable for industries such as daily chemicals, fine chemicals, pharmaceuticals, and bio-chemicals, used for homogenizing, emulsifying, preparing, and producing ointments. Examples include toothpaste, hair dye, ointments, shampoo, shoe polish, dermatitis cream, facial cleanser, cosmetics, etc.

Based on over 20 years of production and R&D experience in emulsification equipment, JINZONG Enterprise summarizes the factors affecting the emulsification results of vacuum emulsifiers as follows:

1. Type of Emulsification Head (batch type vs. continuous type; continuous type generally yields better results).

2. Shearing Rate of the Emulsification Head (higher rates generally improve effectiveness).

3. Tooth Structure of the Emulsification Head (classified as coarse, medium, fine, and ultra-fine teeth; finer teeth typically yield better results).

4. Residence Time of Materials in the Dispersion Wall & Emulsification/Dispersion Duration (with the same motor power, smaller flow rates generally improve results).

5. Number of Cycles in the Vacuum Emulsifier (more cycles improve results up to the equipment's limit).

Temperature in Vacuum Emulsification
Temperature significantly impacts emulsification quality, though there are no strict limits. If both oil and water phases are liquid, emulsification can often be achieved at room temperature with stirring. Generally, the emulsification temperature depends on the melting point of high-melting-point substances in the two phases, as well as the type of emulsifier and the solubility of the oil and water phases. Additionally, the temperatures of the two phases should be kept similar, especially when emulsifying oil phases containing high-melting-point (above 70°C) waxes or lipids. Adding a low-temperature water phase should be avoided to prevent the crystallization of waxes or lipids, which could result in lumpy or coarse emulsions. Typically, the temperatures of both oil and water phases during emulsification are controlled between 75°C and 85°C. If the oil phase contains high-melting-point components like wax, the emulsification temperature should be higher. If viscosity increases significantly during emulsification, making stirring difficult, the temperature can be appropriately raised. If the emulsifier has a specific phase inversion temperature, the emulsification temperature should be set near this point. Emulsification temperature can also affect particle size. For instance, when using fatty acid soap anionic emulsifiers with the nascent soap method, emulsifying at 80°C yields particle sizes of about 1.8–2.0 μm, while at 60°C, particle sizes increase to about 6 μm. Nonionic emulsifiers, however, show less sensitivity to temperature in terms of particle size.

Emulsification Time in Vacuum Emulsifiers
Emulsification time significantly impacts emulsion quality. The optimal time depends on the oil-to-water phase volume ratio, the viscosities of the phases and the resulting emulsion, the type and amount of emulsifier used, and the emulsification temperature. The emulsification time should ensure thorough mixing and is closely related to the efficiency of the emulsification equipment. It can be determined empirically or through experimentation. For example, when using a homogenizer (3000 rpm), emulsification may only require 3–10 minutes.

Stirring Speed in Vacuum Emulsifiers
The emulsification equipment, particularly stirring speed, plays a critical role. Moderate stirring ensures thorough mixing of the oil and water phases. If the speed is too low, insufficient mixing occurs. If too high, air may be incorporated, creating a three-phase system and destabilizing the emulsion. Thus, avoiding air entrainment during stirring is essential, and vacuum emulsifiers excel in this regard.

Selection of Emulsifiers
(1) Choose emulsifiers with hydrophobic groups similar to the material being emulsified.
(2) Opt for a blend of several emulsifiers.
(3) Select emulsifiers that dissolve easily.
(4) Combine hydrophilic and lipophilic emulsifiers for balanced performance.
(5) Use composite emulsifiers from the same hydrophobic base but with varying hydrophilicities.
(6) For O/W emulsions, prioritize water-soluble emulsifiers, with other emulsifiers decreasing in usage on both sides of the main emulsifier according to HLB sequence.
(7) The HLB value of the composite emulsifier should roughly match that of the oil phase being emulsified.