Process for preparing fine powder of silk fibroin

Details Process for preparing fine powder of silk fibroin Process for preparing fine powder of silk fibroin

1996-09-26

1998-12-29

Elliott, George C.

Drug, bio-affecting and body treating compositions

Preparations characterized by special physical form

Particulate form

424 63, 424 69, 81281, A61K 7021, A61K 7035, A61K 950, D06M 1100

Patent

active

058537643

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to a process for preparing fine powder of silk fibroin from a silk substance.


BACKGROUND ART

Fine powder of silk fibroin is useful as an additive to food products, beverages and cosmetic products.
Heretofore, as a process for preparing fine powder of silk fibroin, it is known a process comprising dissolving a silk substance in an aqueous solution containing a neutral salt, removing the neutral salt from the solution to yield an aqueous fibroin solution, adding a precipitating agent to the resulting aqueous solution to cause the silk fibroin to precipitate therein, and separating the precipitate from the solution and drying the precipitate or lyophilizing the aqueous solution, thereby yielding fine powder of silk fibroin.
This process, however, cannot be said to be satisfactory from the point of view of industrial application because it requires the silk substance to be dissolved in water forming an aqueous solution.
On the other hand, a silk substance cannot be pulverized into finely divided crystalline powder with high efficiency by mechanically dividing the silk substance directly into fine powder because the silk substance is so high in mechanical strength that it is very hard to divide it into fine powder.
It is an object of the present invention to provide a process for preparing fine powder of crystalline silk fibroin from a silk substance, which can offer industrial advantages.


DISCLOSURE OF INVENTION

As a result of extensive studies and research to achieve the object as described hereinabove, the present inventors have completed this invention.
The present invention provides a process for the preparation of fine powder of silk fibroin, characterized in that a silk substance is contacted with an alkaline aqueous solution at a temperature of 95.degree. C. or higher to deteriorate the strength of said silk substance, that the resulting silk substance is then subjected dealkalinization and drying, and that the resulting dried silk substance is thereafter finely pulverized.
The silk substance to be used for the present invention may include, for example, cocoons, cocoon thread, silk yarn, silk cloth and waste.
The process according to the present invention may be preferably carried out first by treating a silk substance by bringing it into contact with an alkaline aqueous solution at a temperature of 95.degree. C. or higher, preferably approximately 100.degree. C. As an alkaline substance for the alkaline aqueous solution, there may be employed sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide or the like. The extent of alkalinity of the alkaline aqueous solution may be pH 11.5 or higher, preferably pH 12 or higher.
The treatment of the silk substance with the alkaline aqueous solution may be carried out by immersing the silk substance in the alkaline aqueous solution.
The period of time (treatment time) during which the silk substance is kept in contact with the alkaline aqueous solution is a period of time long enough to cause a strength of the silk substance, whichever threads produced by sericulture or wild silkworms, to deteriorate to such a suitable extent to which the silk substance can be pulverized into finely divided powder. For silk threads, for example, it is such that they may come in contact with the alkaline aqueous solution until their tensile strength becomes approximately 0.05 g/d or less. Generally, the treatment time may be in the range of from 1 to 4 hours; however, additional 2 or 3 hours or longer hours are required when the raw silk thread is large in fineness or when attachment of siren can be recognized thereon or when a silk substance such as wild silk thread is difficult to deteriorate. The specific period of time required for allowing the silk substance to come in contact with the alkaline aqueous solution, however, can be determined readily by a simple preliminary experiment for investigating the relationship between the readiness of pulverizing the silk substance with its strength deteriorated

REFERENCES:
patent: 4233211 (1980-11-01), Ohtomo
patent: 4233212 (1980-11-01), Otoi

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