Temperature-Responsive Microemulsion for Efficient Recyclable Degreasing of Fatty Pickled Sheepskin

In the leather production process, emulsification degreasing can effectively remove grease. However, the direct discharge of emulsifiers often leads to substantial pollution. With the aim of addressing this issue and realizing the recycling of degreasing agents, temperature-responsive microemulsions were proposed for the leather degreasing process in this research. First, a series of polyether surfactants (MAOAPEG-m, mm = 600, 800, 2000, 4000) were designed and synthesized. Subsequently, the temperature-responsive microemulsion system was constructed with MAOAPEG-m, SDS, E-1300 (isotridecyl alcohol polyoxyethylene ether), n-butanol, D-limonene, and NaCl. Then, the influence of the polyether segment length on the microemulsion region, conductivity, droplet size, and absorbance was systematically investigated. Finally, the microemulsion was applied in the degreasing experiment of fatty pickled sheepskin. The results showed that the degreasing rate of the microemulsion could reach 76.7%, which was higher than that of the commercial degreasing agent. Furthermore, after five cycles, the degreasing rate of the microemulsion still remained above 60%. These results indicated that the microemulsion had superior performance in leather degreasing and oil separation, thereby providing an effective method for the recyclable degreasing process of leather.