Coating processes – Particles – flakes – or granules coated or encapsulated – Inorganic base
Reexamination Certificate
2000-10-26
2002-07-30
Beck, Shrive P. (Department: 1762)
Coating processes
Particles, flakes, or granules coated or encapsulated
Inorganic base
C427S212000, C427S215000, C427S213000, C427S216000
Reexamination Certificate
active
06426116
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the uniform coating or encapsulation of energetic materials that are suitable for controlled release particulate applications, including air bags, gas generators, solid propellants, ordnance and time release drugs. In another aspect, the invention relates to a green technology.
2. Description of Related Art
The development of advanced, coated, particulate materials with tailored characteristics of release onset and rate control has direct application to air bags, gas generators, solid propellants, ordnance and time release drugs. These goals have been a long-lasting challenge to the propellant, ordnance and pharmaceutical industries. Until the advent and development of supercritical-fluid-aided material processing, the effort to identify successful techniques for achieving the required microns-thin, high-quality particle coatings was unsuccessful.
In the last ten years or so, there has been an influx of new supercritical-fluid-aided material processing options for a variety of materials. These processing applications include impregnation of porous matrices, formation of controlled porosity materials, coating/spraying of two-dimensional flat surfaces, macro-encapsulation, extrusion, nucleation of particles with narrow and controlled particle size, and drying.
Micro-encapsulation using supercritical fluids (SCF) has been tried by Tom et al. [1993] for drug-polymer systems with very limited success due to poor understanding of complex phenomena involved in co-nucleation of chemically diverse components. The RESS (Rapid Expansion of Supercritical Fluid Solutions) process used in these trials (first introduced by Krukonis [1984]) for micro-encapsulation has major limitations. Not only do particles with desired particle size and shape have to be nucleated, but also a uniform encapsulating material has to be formed simultaneously. The alternatives to SCF micro-encapsulation processes are spray chilling, standard fluidized bed coating, centrifugal extrusion, coacervation, and co-crystallization. These alternative processes often require the use of surfactants and thermally sensitive compounds that should be avoided because of their potential for contamination and disruption of the desired thin films.
There are many techniques, including SCF nucleation, which result in formation of particles with desired shape and particle size distribution. However, there are no processes other than SCF techniques that permit coating of particles with high quality of thin films. This invention permits coating and micro-encapsulation of particles in an environment fluidized by a supercritical fluid.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided a method for forming thin films on particles, the method including the steps of suspending particles to be coated in a supercritical fluid containing dissolved coating material therein and then simultaneously nucleating and depositing the dissolved coating material onto the surface of the particles forming the desired thin films.
REFERENCES:
patent: 4092187 (1978-05-01), Hildebrant et al.
patent: 4678684 (1987-07-01), Sand
patent: 4689250 (1987-08-01), Quella et al.
patent: 4859493 (1989-08-01), Lemelson
patent: 5399597 (1995-03-01), Mandel et al.
patent: 5472712 (1995-12-01), Oshlack et al.
patent: 5620751 (1997-04-01), Brindoepke et al.
patent: 5766637 (1998-06-01), Shine et al.
patent: 5833891 (1998-11-01), Subramaniam et al.
Beck Shrive P.
Blanton Rebecca A.
Kohn & Associates
University of South Florida
LandOfFree
Supercritical fluid aided coating of particulate material does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Supercritical fluid aided coating of particulate material, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Supercritical fluid aided coating of particulate material will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2886421