Abstract

Diisobutylene-maleic anhydride polymeric fatliquoring agents (DMPF) are a class of high-performance synthetic fatliquoring agents. To investigate the mass transfer behaviour of DMPF during fatliquoring, 5-Aminofluorescein (5-AF) was grafted onto the DMPF molecular chain to prepare a fluorescent tracer, designated F-DMPF. At a 5-AF dosage of 0.065 wt‰ relative to the polymer mass, a grafting efficiency of 87.1% was achieved. The structure of F-DMPF was verified by FTIR, 1H-NMR, GPC and fluorescence spectroscopy. The fluorescent tracer exhibited a molecular weight comparable to that of the unmodified polymeric fatliquoring agent. F-DMPF displayed high fluorescence intensity along with pH-responsive behaviour, producing the strongest signal at pH 9–10. F-DMPF was used to monitor the mass transfer behaviour of DMPF in bovine wet-blue leather. The findings revealed that the penetration of polymeric fatliquors can be accelerated by increasing the fatliquor dosage, extending the fatliquoring time, or applying anionic retanning agents. At a fatliquoring temperature of 40°C and a fatliquoring agent dosage of 10 wt%, complete penetration was attained after 90 min of fatliquoring. Based on the principles of mass transfer equilibrium and mass conservation, a kinetic equation describing the mass transfer process was established. The fluorescent labeling technique developed in this study enables visualization and quantitative analysis of the mass transfer of polymeric fatliquoring agents, offering a scientific foundation for optimizing their application conditions and molecular design.