| 摘要 |
Finely powdered high-purity fibroin and a process for producing the same are disclosed. The fibroin is a fine powder of regenerated fibroin in nonfibrous and particulate form which has an average molecular weight of not less than 50,000 particle diameters of from 1 to 100 mu , and a bulk density of from 0.1 to 0.7 g/cm<3> as measured in the dry state and which contains at least 50% by weight of hot-water-insoluble fibroin having the beta -configuration. The process comprises dissolving a degummed silk material in at least one solvent selected from the group consisting of an aqueous cupriethylenediamine solution, an aqueous ammoniacal solution of cupric hydroxide, an aqueous alkaline solution of cupric hydroxide and glycerol, an aqueous lithium bromide solution, an aqueous solution of the chloride, nitrate or thiocyanate of calcium, magnesium or zinc, and an aqueous sodium thiocyanate solution; adding a coagulating salt to the resulting aqueous fihroin solution having a fibroin concentration of 3 to 20% by weight to coagulate and precipitate the fibroin; dehydrating and drying the gel so formed; and then pulverizing the resulting powder. Alternatively, the process comprises dissolving a degummed silk material in a solvent as defined above; dialyzing the resulting aqueous fibroin solution; subjecting the dialyzed aqueous fibroin solution having a fibroin concentration of from 3 to 20% by weight to at least one treatment for coagulating and precipitating the fibroin, the treatment being selected from the group consisting of the addition of an alcohol, the addition of a coagulating salt, aeration, coagulation at the isoelectric point, exposure to ultrasonic waves, and agitation at high shear rate; dehydrating and frying the gel so formed; and then pulverizing the resulting powder. The fine powder of fibroin thus obtained is particularly useful as an additive for cosmetic preparations. |
