New Chrome Tanning Method Assisted by Wringing and Ultrasound

Abstract

A new chrome tanning method was designed using wringing (10 kg/cm2) and ultrasound (28 kHz, 300W). The grain down pickled skin was put into the penetration tank to let the chrome tanning agent penetrate for 3min. After penetration, the skin was transferred into the fixation tank to basify for 3min. Then the skin was again penetrated and fixated to finish the tanning process as is described above. During the penetration and fixation stage, an ultrasound field was used and the skin was transported with belts one by one. Before each stage skins were wrung to recover the penetration solution or fixation solution and lower the water content of the leathers to about 55%. The results showed that tanning time was obviously shorted compared with a conventional method because of the mechanical extrusion formation of the micro vacuum and ultrasonic cavitationsf effect. The wet blue obtained by the new method remained the same properties compared with conventional wet blue, such as shrinkage temperature, chrome content in leather, and physical properties after retanning, fatliquoring and finishing in a normal shoe upper leather process. Furthermore, collagen structure and cross section of the leathers maintained integrity during the tanning processCproved by SEM. In short, this new chrome tanning method assisted by wringing and ultrasound could be used in future tanning industry.