Alkenylsuccinic anhydride

Alkenyl succinic anhydrides (ASA) are modified five-membered succinic anhydrides bearing a branched iso-alkenyl chain (C14 to C22). They are colorless, and usually viscous liquids. They are widely used, especially in surface sizing of paper, paperboard, and cardboard, as well as in the hydrophobicization of cellulose fibers. Products treated with it show reduced penetration of aqueous media, such as inks or drinks (like milk or fruit juices). Alkenyl succinic anhydrides (ASA) are modified five-membered succinic anhydrides bearing a branched iso-alkenyl chain (C14 to C22). They are colorless, and usually viscous liquids. They are widely used, especially in surface sizing of paper, paperboard, and cardboard, as well as in the hydrophobicization of cellulose fibers. Products treated with it show reduced penetration of aqueous media, such as inks or drinks (like milk or fruit juices). In terms of their mode of action, the anhydride is proposed to react with the hydroxyl groups on the cellulose, forming an ester. The alkenyl side-chain modifies the surface properties of the paper product. The application is similar to that for alkyl ketene dimers. In the United States alkenylsuccinic anhydrides are the preferred paper sizing agents, whereas in Europe, alkyl ketene dimers (AKDs) predominate. The reaction of maleic anhydride (MAN) with aliphatic monounsaturated n- and iso-alkenes was described as early as 1936 in a patent. The alkenes are obtained from the so-called 'cracked distillate', a distillate fraction with a high content of unsaturation formed by cracking of petroleum. The patent describes the reaction of the olefins with excess maleic anhydride at 200 °C in an autoclave. The excess alkene is removed by distillation in vacuo, the resulting alkenyl succinic anhydride hydrolyzed with dilute sodium hydroxide solution and the disodium salt reacted with an acid to achieve an alkenebutanedioic acid. However, under the 'many useful applications' described for the products obtained, the use as a size has not yet been mentioned. 30% higher reaction yields were achieved with a pre-cleaned cracked petroleum distillate in an autoclave at 210 °C and it was found that the hydrolysis of the succinic anhydride can already be carried out with steam.