Alkyl ketene dimer (AKD) was industrialized in 1956 and was only used in special papers requiring heavy sizing. In recent years, cultural paper has been basically changed to AKD neutral sizing, making it more widely used. Applications.
Mode of action
Alkyl ketene dimer (AKD) is a water-insoluble solid with a melting temperature between 40 and 60 °C. It is a widely used neutral-sizing chemical in the papermaking industry, as the compound decreases the rate of aqueous liquid penetration into papers. The compound possesses one unsaturated β-lactone ring and 16–18 carbons of the alkyl groups. Its β-lactone ring can readily react with hydroxyl groups of cellulose to form a β-ketoester bond, enabling its hydrophobic tails to arrange into hydrophobic domains. In the presence of water, however, the reactivity of AKD with water is faster than with hydroxyl groups, generating dialkylketone with no or low internal sizing ability, i.e., the ability of additives to facilitate the water-resistant protection of a paper’s surface. Ordinary sizing with AKD involves a complex series of processes, including emulsification of the waxy AKD material; measures to avoid the agglomeration of the emulsified AKD particles; addition of a stabilized AKD dispersion to the papermaking furnish; interactions with various retention aid chemicals to fix the material onto solid surfaces; and various spreading and curing processes that take place during the drying and cooling of the paper product[1-2].
