| Résumé : |
The unhairing process is the most significant contributor to pollution load in the beamhouse. This has made unhairing one of most investigated areas over the past few decades, where the focus has been to reduce the amount of sulfur-based chemistry used during processing. In a country like Brazil, with 36 million hides processed every year, the amount of sodium sulfide applied during unhairing is around 10.800 tons/year, which represents approximately 2.200* ton of sulfur added to the process.
A conventional unhairing process for bovine hides normally uses sulfide, sulfhydrate, lime, surfactants, and one or more auxiliaries based on mercaptans, thioglycolate, amines, urea, enzymes, or combination of these. The use of such auxiliaries was introduced many years ago with the purpose of reducing the amount of sulfide/sulfhydrate applied, while improving the efficiency of hair removal and helping to control swelling. Since then, many types of unhairing auxiliaries have come to the market, with different chemical compositions, for different purposes and with different efficiencies. Nevertheless, when the amount of sulfide/sulfhydrate needs to be reduced to very low levels without diminishing the quality of the unhairing and at reasonable cost, enzymatic auxiliaries are the preferred and logical choices.
In this paper we will present the results from an enzymatic unhairing process developed by Buckman that allowed the reduction of Na2S offer to half of the normal levels. In addition to reducing the environmental impact of unhairing - and the whole beamhouse operation - the process also produced significant benefits in terms of increased area yield (from raw hide to wetblue), improved flatness, and less drawing while maintaining the same characteristics of grain integrity and tightness. |
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Advances in understanding of enzymatic unhairing of bovine hides in JOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA), Vol. CIX, N° 8 (08/2014)
