Fibroin-coated pigment and processes for producing same.

摘要

A fibroin-coated pigment and two processes for producing the same are disclosed. The fibroin-coated pigment comprises a carrier pigment in the form of finely divided particles whose surfaces are substantially coated with a film of regenerated fibroin and is characterized in that at least 50% by weight of the regenerated fibroin is constituted of hot-water-insoluble fibroin having the P-config u ration. One of the processes comprises the steps of 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; dispersing a carrier pigment in the resulting fibroin solution having a fibroin concentration of from 3 to 20% by weight; adding a coagulating salt to the pigment-loaded fibroin solution to coagulate and precipitate the fibroin; dehydrating and drying the resulting coagulum and then pulverizing the dried product. The other process comprises the steps of dissolving a degummed silk material in a solvent as defined above; dialyzIng the resulting fibroin solution; dispersing a carrier pigment in the resulting aqueous fibroin solution having a fibroin concentration of from 3 to 20% by weight; subjecting the pigment-loaded aqueous fibroin solution to at least one treatment for coagulating and precipitating the fibroin, the treatment being selected from the group consisting of the addition of the coagulating salt, aeration, coagulation at the isoelectric point, exposure to ultrasonic waves, and agitation at high shear rate; dehydrating and drying the resulting coagulum; and then pulverizing the dried product. The fibroin-coated pigment thus obtained is particularly useful as a pigment or additive for cosmetic preparations and coating compositions.