Half-Degumming of Raw Silk Yarns Degummed after Fixing Sericin with Formaldehyde

To obtain the half-degummed silk yarns of 5~10% degumming losses, raw silk yarns were degummed with alkaline detergent after fixing sericin with formaldehyde. Adding above 5 g/l acetic acid or tartaric acid in 1% and 5% formaldehyde fixing baths created a lot of sericin loss during degumming with 3 g/l alkaline detergent and 2 g/l sodium carbonate after fixing sericin due to alkaline hydrolysis of sericin cross-linkage. When sericin was degummed with 3 g/l alkaline detergent after fixing with 0.1% formaldehyde at or for 15 min, the degumming temperature necessary to obtain satisfactory half-degumming was . Also, fixing sericin at resulted in stronger sericin fixation than fixing at . However, the softener of cationic surfactant added in sericin fixing baths did not prevent the attachment of degummed silk yarns. Approximately 6.5% degumming loss was obtained when sericin was degummed at for 30 min with 3 g/l alkaline detergent after fixing with 0.1% formaldehyde at for 15 min and 30 min, and in case of adding 2 g/l acetic acid in fixing baths the half-degummed silk yarns of about 10% degumming losses, which were severely attached to each other, were obtained.