The Relationship Between the Structure of Hyper-branched Polymer and its Effect on High Exhaust Chrome in Reduced Chrome Tanning

Abstract

Hyper-branched polymer (HBP) has been widely used aspretanning, tanning auxiliary and retanning agent in chrometanning industry. However the effect of the structure of HBPincluding the degree of branching (DB) and molecular weight(Mw), on chrome tanning has seldom been studied. In this studya series of carboxyl-terminated hyper-branched oligomer (HBP)with different DB and Mw have been prepared and characterizedby GPC and 1H-NMR for determining their molecular weightand its distribution, as well the DB. The effect of DB and Mw onthe chrome uptake and shrinkage temperature (Ts) of hide wasinvestigated. Experimental results showed that the chromeuptake was affected by both DB and Mw of developed HBP. HBPthat possesses high DB and the Mw closed to 2000 Da, hasendowed the obtained leather with higher Ts and chrome uptake.Moreover, the leather tanned with 3% chrome and 1.5% HBPpossesses similar properties to the traditional tanning processusing 6-8% chrome. Therefore, the carboxyl-terminated HBPpresents a potential application as a tanning auxiliary in reducedchrome tanning due to it’s improving the absorption of chrome.