DISPERAL and DISPAL are the trademarked names of Sasol’s high-purity boehmite powder solutions for industrial applications.
These boehmites, which are nano-sized in the dispersed phase, exhibit a unique combination of purity, consistency and dispersibility that make them excellent materials for use in colloidal applications.
The Sasol range of dispersible boehmites has traditionally been used in applications such as sol-gel ceramics, catalysis, refractory materials, rheology control and surface frictionising.
Other applications include surface coating as well as paint detackification, polymeradditives and functional fillers.
Features of Sasol dispersible boehmites
The unique product characteristics of Sasol dispersible boehmites can lead to many
advantages for use in different systems. Some key features are:
- The high-purity boehmites are produced under careful control to yield products with consistent quality and reliable performance
- The powders are highly dispersible. Low-viscosity nano-sized particle sols can be prepared at room temperature in ten to 30 minutes with concentrations of 10wt.%–40wt.% AlOOH
- The boehmites are versatile. They can be employed under a variety of application conditions, including low or high pH and low or high shear
- Sasol also offers boehmites which are dispersible in polar and non-polar organic media
Advantages of DISPERAL and DISPAL
Sasol pioneered processes utilising alkoxide chemistry to convert primary aluminium metal into synthetic boehmite of exceptional purity.
Unlike other alumina manufacturing processes that start with less pure materials, Sasol’s processes yield aluminas with significantly lower levels of common impurities such as iron, sodium and silica.
Additionally, our 50 years of experience, in combination with other proprietary production techniques, allow us to produce highly dispersible boehmites with a wide range of physical properties such as dispersed particle size, resulting in translucent to opaque dispersions.
Thus, our customers are not limited in their thinking for possible uses for the aluminas.
To form a colloidal sol or dispersion from a water dispersible DISPERAL or DISPAL powder, simply stir the powder in deionised water with moderate to intense agitation at room temperature for 20–30 minutes.
The maximum achievable solids loading will vary according to the specific boehmite selected.
For most applications, the boehmites perform best when completely dispersed prior to further formulation. The resulting pH will be between three and five.
DISPAL 11 N7-80 that is modified with 0.1wt.% nitric acid can be dispersed at pH six or seven as well.
Dispersions of acid dispersible products may be formed in a similar fashion by dispersing in dilute aqueous monovalent acids such as nitric, hydrochloric, formic or acetic (typically < 1 wt.% acid) at pH three to five.
Neutral to alkaline dispersible boehmites
By changing the surface chemistry Sasol boehmites can also be stabilized under neutral and alkaline conditions.
By modification with lanthanum the iso-electric point can be shifted to higher pH values, providing stability at pH six / seven.
DISPERAL HP14/7 and DISPAL 18C9 are surface modified with citric acid to provide colloidal stability at pH eight to ten.