Hot extended press nips as gas-phase reactors : hydrophobation with ASA

Hot extended nips could be used as self-sealing reaction vessels for gas-phase modification of dry paper webs. This possibility is illustrated by the gas-phase redistribution of an ASA (alkenyl succinic anhydride) and an AKD (alkyl ketene dimer) sprayed onto one side of of an unsized paper before the nip. This method can become an alternative to wet-end sizing for specialty papers. A simultaneous auto-crosslinking of paper polymers also occurs.