Updated: Sep 8, 2020
Rosin emulsions are produced by the emulsification of a resinous phase into an aqueous medium using a surfactant system that uses firstly a primary surfactant selected to offer an optimum HLB (Hydrophobic-Lipophilic Balance) and then towards the end of the process a stabilising surfactant is added.
This process does away with the old requirement of producing emulsions under very high shear such as homogenisation whilst under pressure. This process in comparison is more cost-effective and simpler to achieve good emulsions.
Rosin emulsions find applications as sizing agents and as tackifiers in adhesives systems.
Sizing agents are used in paper production to produce good water resistance and to enhance the surface strength; both of which will improve printability. In adhesive applications, the rosin acts as a tackifier and can be used in both hot melt and aqueous based adhesives.
The process to produce good emulsions are as follows:
· Melt rosin and agitate, add TEA (TEA to be added at levels to neutralise the acid value of the Rosin in some instances this is not always necessary)
· Agitate using a bladed paddle stirrer or high shear mixer - do not homogenise
· Add Lanphos PET22 (primary emulsifier) and heat to 100°C
· Add water slowly and reflux
· The emulsion will form and invert to an O/W emulsion
· Cool to 40-50°C and add Lansurf AE35 (stabiliser)