| abstract |
A process for producing a fine powder of high-purity silk fibroin in nonfibrous and particulate form is disclosed. The process comprises dissolving a degummed silk material in at least one solvent selected from the group consisting of an aqueous cupri-ethylenediamine 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 silk fibroin solution having a silk fibroin concentration of from 3 to 20% by weight to coagulate and precipitate the silk 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 silk fibroin solution; subjecting the dialyzed aqueous silk fibroin solution having a silk fibroin concentration of from 3 to 20% weight to at least one treatment for coagulating and precipitating the silk fibroin, the treatment being selected from the group consisting of the addition of a coagulating salt, aeration, coagulation at the isoelectric point, exposure to ultrasonic waves, and agitation at high shear rate; dehydrating and drying the gel so formed; and then pulverizing the resulting powder. The fine powder of silk fibroin thus obtained is particularly useful as an additive for cosmetic preparations. |