Abstract: The purpose of this study is to modify tannin extract used as a neutralizer for leather.In the experiment myrtan(Myrica esculenta)tannin extract was subjected to a treatment with much more sulfite and at higher temperature compared to ordinary method.A modified product was obtained when a mixture of 100 part myrtan tannin extract,30 part NaHSO₃,36 part Na₂SO₃ and 1 part aluminum compound was heated and reacted at 129℃ and 165 kPa for 10 h.The modified extract has pH value 7.15 at 5% solution,7.0 at 10% solution and 20%-30% tannin content by hide powder method.It has improved buffer property to maintain stable pH value between pH volute 3.5-5.5.Tanning experiment showed that it has milder astringency and tanning properties compared with ordinary extract.Modified product at 3%-5% is enough to neutralize leather thoroughly with good leather quality.In conclusion,modified myrtan tannin extract is a new material applicable as a neutralizer for leather.

Key words: Myrica esculenta extract, tannin, sulfitation, leather making, retanning