Solid material comminution or disintegration – Processes – Plural successive comminuting operations
Reexamination Certificate
2000-03-28
2002-08-06
Ostrager, Allen (Department: 3725)
Solid material comminution or disintegration
Processes
Plural successive comminuting operations
C241S021000, C241S025000
Reexamination Certificate
active
06427933
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method for manufacturing silk fibroin powder below 3 &mgr;m in an average particle diameter from silk substances.
BACKGROUND ART
Silk powder is used as an additive for food, beverages, cosmetics, and paints. Conventionally known methods for manufacturing silk powder, particularly, crystalline silk fibroin powder, include:
1) a mechanical method for comminuting silk yarn into powder, and 2) a chemical method in which, for example, a silk substance is dissolved in an aqueous solution containing an acid or neutral salt or the like; thereafter salt produced by neutralization is removed to form a fibroin aqueous solution; a precipitant is added into this aqueous solution to allow silk fibroin to be precipitated; and then this precipitate is dried by separation or the aforementioned aqueous solution is dried by freezing or by spraying.
As an example of powdering according to the aforementioned mechanical method, an example for obtaining 300-mesh silk powder (approximately 30 through 50 &mgr;m in an average particle diameter) for use in cosmetics (Japanese Patent Publication No. Sho 27-3650) has been formerly reported and an example of obtaining silk fibroin superfine powder 3.25 &mgr;m in an average particle diameter for use in paints (Japanese Laid-Open Patent Publication No. Hei 6-339924) has been reported.
However, the chemical method produces powder of a low crystalline level and thus is not available for producing crystalline silk fibroin powder having a property intrinsically provided in silk.
Silk substances have a property in that moisture absorbency and water absorbency increase as crystallinity becomes lower, so that silk absorbs moisture or water to become softened and easily transformed.
If silk powder having such low crystallinity is dried after absorption of moisture or water, the powder tightly coagulates to form very hard lumps and thus provides no value for use. Therefore, in order to hold the property intrinsically provided in silk, the powder is required to be a crystalline powder in which the structure intrinsically provided in silk yarn remains. Therefore, it can be said that the mechanical comminuting method is desirably employed as an industrial manufacturing method of crystalline powder. On the other hand, as described above, the prior art is limited to obtaining powder approximately 3 &mgr;m in an average particle diameter even by the mechanical comminuting method.
That is, various types of mechanical pulverizers provide a limited size of particles by comminuting depending on the property of a raw material to be pulverized so long as the same type of pulverizers are used, whereby powder with a limitlessly small particle diameter cannot be obtained.
In general, pulverizers employing a higher impact speed provide powder having a smaller diameter, however, smaller powder diameters provide lower probability of collision of particles. This provides lower probability for particles to be applied with stress beyond the fracture speed, so that the energy efficiency of the pulverizer decreases acceleratedly with the diameter of particles equal to or less than a specific value.
Therefore, approximately 3 &mgr;m is thought to be the limit in an average particle diameter provided by means of the prior art method for obtaining fine powder by comminuting silk yarn.
Concerning the application of silk substances, the present inventors formerly made it clear that silk substances match skin whereby the powder thereof is useful as an epidermal cell growth activating raw material (Japanese Patent Application No. Hei 9-333560). In addition, the fine powder of silk substances has also been expected to be useful as a raw material filler, a coating material, a raw material for cosmetics, etc. The present inventors formerly developed a method for obtaining crystalline silk fibroin powder 3 through 6 &mgr;m in an average particle diameter by deteriorating a silk substance in strength through the exposure thereof to an aqueous solution of an alkali meal compound under atmospheric pressure at temperatures of 95° C. or higher, and thereafter by performing dealkalization and drying of the resultant silk substance, and then by comminuting (U.S. Pat. No.2,615,440). Thereafter, intensive research lead us to a result in that crystalline silk fibroin powder, the powder being a superfine powder below 3 &mgr;m in an average particle diameter with the structure intrinsically provided in silk, exerts a property unique thereto so as to be useful for various applications.
That is, such findings have been obtained in that the crystalline silk fibroin powder which is a superfine powder below 3 &mgr;m in an average particle diameter provides excellent formability, improved adhesive property to the skin or the like, improved extensibility, and an improved sense of touch and the like, and is outstandingly suitable for applications to raw materials for use in cosmetics such as lip sticks, eyebrow paints, hair dyes, eyeliners, powder blushes, and foundations, and for applications to ink additives, resin composite raw materials, and raw materials for paints.
The present invention has been developed in view of the technical background mentioned above. Its object is to provide a method for manufacturing industrially, by mechanically comminuting silk yarn, crystalline silk fibroin powder below 3 &mgr;m in an average particle diameter, which can be used for each of the aforementioned applications.
DISCLOSURE OF INVENTION
In order to achieve the aforementioned object, the present invention employs technical items as shown below. That is, the present invention lies in (1) a method for manufacturing crystalline silk fibroin powder, in which the structure of silk yarn remains, below 3 &mgr;m in an average particle diameter, which is obtained by bringing a silk substance such as cocoon filaments, silk yarn, and raw silk into contact with an alkali aqueous solution under a pressure above 1 atmospheric pressure to reduce the strength of the silk substance, then by dealkalizing and drying the silk substance after that, and by comminuting the resultant silk substance thereafter.
Furthermore, the present invention lies in (2) a method for manufacturing crystalline silk fibroin powder below 3 &mgr;m in an average particle diameter by bringing a silk substance such as cocoon filaments, silk yarn, and raw silk into contact with an alkali aqueous solution under a pressure of 1 through 5 atmospheric pressure at a temperature of 100° C. through 150° C. to reduce the tensile strength of the silk substance to around 0.02 g/d or less, then dealkalizing and drying the resultant silk substance after that, and by comminuting the dried resultant silk substance thereafter.
Still furthermore, the present invention lies in (3) the method for manufacturing crystalline silk fibroin powder below 3 &mgr;m in an average particle diameter according to the aforementioned (2) in which alkalinity of said alkali aqueous solution is pH 9 through pH 12.5.
Still furthermore, the present invention lies in (4) the method for manufacturing crystalline silk fibroin powder below 3 &mgr;m in an average particle diameter according to the aforementioned (2) in which impact and frictional comminution are combined in order to comminute said dried silk substance.
Still furthermore, the present invention lies in (5) the method for manufacturing crystalline silk fibroin powder below 3 &mgr;m in an average particle diameter according to the aforementioned (2) in which impact and frictional comminution are combined in order to comminute said dried silk substance whereby particle sizes are classified.
Still furthermore, the present invention lies in (6) the method for manufacturing crystalline silk fibroin powder below 3 &mgr;m in an average particle diameter according to the aforementioned (4) in which in order to perform comminution by combining impact and frictional comminutions; impact comminution—frictional comminution, frictional-comminution—impact comminution, or frictional comminution—impact comminution—fr
Flynn ,Thiel, Boutell & Tanis, P.C.
Hong William
Japan as represented by Director General of National Institute o
Ostrager Allen
LandOfFree
Method for manufacturing crystalline superfine silk powder does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for manufacturing crystalline superfine silk powder, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for manufacturing crystalline superfine silk powder will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2952600