Leather degreasing via microemulsions

The large-scale application of micro emulsions in leather degreasing was motivated by questioning current industrial processes for degreasing due to potentially environmental concerns. Of relevance for leather degreasing were mainly two processes, a solvent-based one and a water-based one. The surfactants showing the best performance in the latter 

However, the La-phase in both systems extends over a wide y -range below the lower phase boundary. The most suitable of the characterised surfactants regarding the degreasing process is Eusapon OD. Although less efficient than Lutensol A07 and Lutensol A08 no La-phase can be observed and the X-point is located near the degreasing temperature, T = 48.13°C. 

Sheep skins were degreased using Eusapon OD following the above presented procedure in the beam house. Samples were taken from every float and the phase behaviour was directly characterised by visual inspection. The results are presented in the following beginning with the short float. 

Because of the small amount of water in the short float, samples had to be taken by wringing out the sheep skins. A three-phase state at T = 37°C could be observed, where a microemulsion phase coexisted with a fat-excess phase and a water-excess phase as presented in Fig. 10.6. At this point, the occurrence of the three-phase state in the short float was a first evidence for the good performance of Eusapon OD. The three-phase state is closely connected to the interfacial tension between water and oil, in this case water and grease (crab) which becomes ultra-low for efficient microemulsion systems. At this point the low interfacial tension ensures a good degreasing performance of the system. More 

Samples were also taken from the diluted and the long float. The characterisation of the phase behaviour resulted for both floats in a three-phase state, which, in contrast to the short float, is not located at T = 37°C, but at T = 60°C as shown in Fig. 10.7. At the degreasing temperature T = 30°C now a fat-in-water microemulsion coexists with a fat-excess phase, which is turned into a stable fat-in-water emulsion via shearing. 

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