Alkyl Ketene Dimmer (AKD) also called AKD wax and Alkenyl Succinic Anhydride (ASA) are
wax like chemicals. Both AKD and ASA are used as sizing chemicals for paper.
Traditionally Rosin (Acidic sizing) was used as paper sizing material.
Due to changes in paper manufacturing technologies the sizing process is changed to alkaline/neutral sizing from acidic sizing. AKD and ASA are the main neutral sizing chemicals.