The oxidized MARCUS 3400 or 3500 and oleic acid are mixed and melted together the temperature being adjusted to within the range 125-130ºC. The amine is stirred in and the blend well mixed for a short time in order to allow the amine to react with the fatty acid and oxidized polyethylene. It can be advantageous during this step to let the melt cool somewhat in order that the amine does not volatilize too much. While the wax melt is being processed, soft or demineralised water is heated to a temperature of 95-98ºC. The temperature of the wax melt is again adjusted to 125-130ºC and then poured in a slow steady stream into the well stirred water. In effecting this, it is not necessary to have high speed or high shear mixing and an ordinary propellor or turbine design is perfectly adequate providing, that it is so placed as to give a thorough mixing and circulation action. It is also beneficial to place it so that a small vortex is created at the surface and the wax melt added at this point is very efficiently and rapidly dispersed.
Following the wax melt addition, the emulsion is cooled ( under continuous stirring ) as quickly as possible to room temperature. Cooling may be made through use of a double jacketed vessel or, more preferably by passage through an external heat exchanger. It is important that rapid cooling is applied with stirring since if left to cool slowly and without stirring, a “crust” is formed and also, in addition, the emulsion has a pronounced tendency to display instability and creaming.
After cooling, the addition of a bactericide is made to protect the emulsion from subsequent contamination and bacteriological attack which can cause discoloration, gelling, separation and high odor to develop.
As a final step the emulsion is filtered as it is inevitable that some foreign matter and over sized particles are present.
The maximum solids content which can be comfortably attained is 25%.
The procedure is essentially the same as for anionic. The oxidized wax and surfactant are mixed and melted together and the temperature adjusted to 125-130ºC.
Whie this is being done, a potassium hydroxide solution in monoethylene glycol is prepared. This is done by heating 1 part of the KOH with 2 parts of glycol ( the dissolution process is violent and consequently heating should be gentle ). This solution is dark yellow brown and becomes viscous upon cooling. Therefore, for addition to the wax melt it is recommended that it is added hot. An alternative means of adding the KOH is as a solution in water. However, this is not advised as there is a real risk that when added, and too quickly, boiling occurs and the wax melt overflows the vessel.
As for anionic preparation, water is heated to 95-98ºC. The KOH solution is stirred into the wax melt and mixed well for a short time to ensure that the wax is correctly saponified. Following this the emulsion is prepared as described above.
The maximum solids content which can be attained is slightly higher than with anionics and is 30%.
The same procedure is basically followed as for those above. However, cationics are difficult to prepare by this technique due to the low boiling point of acetic acid ( 118ºC ) and much is lost during the mixing stage and this results in poor quality emulsions. The pressure method is advised as this is carried out in a closed vessel.