Drying and gas or vapor contact with solids – Process – Freeze-drying
Patent
1996-11-04
1998-03-17
Bennett, Henry A.
Drying and gas or vapor contact with solids
Process
Freeze-drying
34288, 34 92, F26B 506
Patent
active
057273332
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a process for obtaining a solid or semi-solid material by drying a solution thereof.
BACKGROUND ART
In many processes used in industry and research facilities involving areas such as pharmaceuticals, healthcare, food and cosmetics, there is a requirement to extract, modify or synthesize a product or products in solution. Following these activities there is frequently a requirement to dry the product(s) by removal from the solution. The drying processes used can be either single step or multiple step processes involving, inter alia, precipitation, centrifugation, evaporation, increased temperature, hot airstreams or fluidised bed vibration. The resulting solid material is in the form of a powder or cake, the particle size of which is largely dependent upon the chosen technique. The particle size influences the further processing, storage, handling, transport and application of the material. Many applications require mean particle diameters of less than 100 .mu.m. Since great care is needed to achieve such a particle size, milling or grinding of the dried powder is frequently used to reduce mean particle diameter.
Control of the particle size is vital for many applications in the pharmaceutical industry, where the size of the particle of an active drug substance or excipient can influence the efficacy of a medication. For example, in a metered dose inhaler which is used to treat asthmatic attacks, a modified aerosol system is used to deliver an aerosol of finely dispersed drug substance to the upper respiratory tract. In order to penetrate to the bronchi it is known that the particle size of the drug substance in the aerosol should be in the region of 2 .mu.m.
The optimum release profiles for many formulations for both oral and parenteral administration require the use of delayed, controlled or sustained release particles. This is frequently achieved using some form of micro-encapsulation, wherein finely dispersed particles of the active substance are coated with a biodegradable coating which facilitates slow or sustained release of the active substance. In order to inject a suspension of microcapsules in a carrier liquid, the microcapsules must be sufficiently small to travel through a small bore needle without blocking it. This may require drug particles of 10 .mu.m or less.
The transdermal administration of many drugs is also facilitated by the provision of reduced particle size. Transdermal migration of an active substance is heavily dependent on the concentration gradient of the active substance across the skin. The greatest concentration at the surface of the skin is achieved by a solid in close proximity thereto. A smaller particle size results in a greater surface area of solid in contact with the skin. In addition, finer particles are more closely associated with the pores of the skin, facilitating faster dissolution and transdermal migration.
Ointments, lotions and creams designed for topical application may contain a suspension of a solid active substance. The particle size of a suspended solid dictates the "feel" of the preparation. Coarse or gritty particles which are detectable by feel on application reduce the desirability of the preparation and hence reduced particle size is a requirement.
In a suspension, reduced particle size of a suspended solid will cause a delay in settling out and will facilitate rapid re-dispersion on shaking, thereby enhancing the homogeneity of the preparation.
Similar considerations apply in the cosmetics and food industries as in the case of the pharmaceutical industry, particularly in the applications of flavours, fragrances and colourings. Again, it is frequently desirable to provide a very finely dispersed solid or even to achieve a micro-encapsulation of such ingredients.
A large number of substances used in the pharmaceutical, healthcare, food and cosmetics industries are thermolabile, i.e. susceptible to denaturation by heat. Particular care is required in drying these substances: the method most frequently chosen
REFERENCES:
patent: 2471035 (1949-05-01), Hurd
patent: 3313032 (1967-04-01), Malecki
patent: 3319344 (1967-05-01), Sachsel et al.
patent: 3362835 (1968-01-01), Thuse et al.
patent: 3621587 (1971-11-01), Smith, Jr.
patent: 3633283 (1972-01-01), Mishkin et al.
patent: 3909957 (1975-10-01), Passey
patent: 3932943 (1976-01-01), Briggs et al.
patent: 4033048 (1977-07-01), Van Ike
patent: 4823478 (1989-04-01), Thompson, Sr.
patent: 4848094 (1989-07-01), Davis et al.
patent: 5208998 (1993-05-01), Oyler, Jr.
patent: 5230162 (1993-07-01), Oyler, Jr.
patent: 5248905 (1993-09-01), Beurel et al.
patent: 5257657 (1993-11-01), Gore
Bennett Henry A.
Gravini Steve
Kinerton Limited
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