Preparation of solvent-based fluorine–silicon modified acrylate and its application in specialty paper

Conventional starch and polyvinyl alcohol sizing agents rely on hydrogen bonding, but are susceptible to temperature and humidity, limiting their use in specialty papers such as banknotes. To address this, we synthesized a fluorine–silicon modified acrylate via radical copolymerization of hexafluorobutyl methacrylate (HFBMA) and silane coupling agents (KH570 and KH560) with common acrylate monomers, using ethanol as solvent. HFBMA lowers surface energy through C–F bond surface segregation, while the silane components form Si–O–Si networks and silanol groups that strengthen hydrogen bonding with cellulose fibers. Upon drying, the fluorinated and siloxane segments migrate to the paper surface and assemble into a hydrophobic barrier. Among three systems (F3, Si 570 -F3, and Si 560 -F3), the optimized Si 560 -F3 at 5% dosage increased tensile strength from 28.1 to 47.8 MPa (+70.1%), reduced water absorption from 29.1% to 5.5% (−81.1%), and raised water contact angle from 85° to 122°. These results confirm that this sizing agent effectively enhances both mechanical strength and water resistance for specialty paper.