THERMOPLASTIC FILM COMPRISING A FINE POWDER OF A NATURAL ORGANIC SUBSTANCE

摘要

An ultrafine silk fibroin powder contained in the invention product containing fine powder of natural organic substance is produced by a process comprising the step 1 of pulverizing silk fibroin into a coarse powder by a dry mechanical pulverizing means, the step 2 of pulverizing the coarse powder thus obtained into a fine powder by a dry mechanical pulverizing means, and the step 3 of pulverizing the fine powder thus obtained into an ultrafine powder having an average particle diameter of 10 mu m or less by a dry mechanical pulverizing means, while treating the fibroin powder to assume the beta -arrangement in or after at least one of the steps 1 to 3. Examples of the title product include film, sheet, coating material and fiber treatment.