关键词: 铬鞣剂, 粒径, 铬鞣过程, 鞣革湿热稳定性

Abstract: Taking chromium tannage as the study object, the effects of pH and temperature on particle size of chrome tanning agents were investigated. Based on this, the influence of their particle size on the tanning process and hydrothermal stability of tanned leather was further explored. The results indicated that for chrome solution with 7% chrome powder (1.7% Cr2O3) , when the pH value was raised from 2.5 to 3.8, the average particle size of chrome tanning agent varied from 982 nm to 2899 nm at 25 ℃, from 1265 nm to 3384 nm at 30  and from 1289 nm to 3630 nm at 35 ℃, respectively, showing an increasing tendency. At the same temperature, the higher the pH value, the lager the particle size was. What’s more, at the same pH, the particle size of chrome tanning agent increased with the increase of temperature. Chrome tanning experiments showed that as the average particle size of the chrome tanning agent increases, the chromium absorption rate increased gradually. When the particle size was less than 2000 nm, the chrome tanning agent had better permeability and the distribution of chromium in leather was relatively uniform. When the particle size of chrome tanning agent was in a range of 2000 to 3000 nm, the uniformity of chromium distribution in leather decreased and the shrinkage temperature (Ts) of wet blue leather showed a trend of increasing first and then decreasing with the increase of particle size of chrome tanning agent, and reached a maximum value when particle size was 2700 nm or so, Further increased the particle size to 3000-4000 nm which results in the Ts decrease due to the overtanned surface and the insufficient tanned inner layer. At the same pH, with the increase of temperature, the particle size of chrome tanning agent increased, while the absorption rate of chromium and hydrothermal stability of crust leather were improved.

Key words: chrome tanning agent, particle size, chrome tanning process, tanned leather hydrothermal stability