Coating processes – Medical or dental purpose product; parts; subcombinations;... – Particulate or unit-dosage-article base
Patent
1998-08-18
2000-04-04
Parker, Fred J.
Coating processes
Medical or dental purpose product; parts; subcombinations;...
Particulate or unit-dosage-article base
427475, 427477, 427478, 427479, 427483, 427485, 42721331, 118629, 118636, 118638, B05D 106, B05B 5025
Patent
active
060458550
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND AND SUMMARY
The present invention relates to a process and a device for electrostatic surface coating of small objects that are not earthed. More particularly, the invention relates to a process for forming an even and homogeneous coating of liquids or powder on small, free falling objects. The process and the device according to the present invention are mainly intended for coating of medicinal products and for surface coating of foodstuffs.
Surface coating of medicinal products in tablet form, is made for both medical, practical and aestethical reasons. Coating is made for example to facilitate administration, to hide unpleasant taste or smell, to improve mechanical properties of the medicine, to protect the active agents of the medicine from being destroyed by e.g. saliva or gastric juices or to protect the tablet in storage. Coating can also be used to bring about a controlled release of the medicine in the human body.
The processes which are used at present for coating of medicinal products involve rotating a large number of tablets in a slanting drum, known as a coating pan, or in horizontally mounted perforated cylinders, while at the same time the surface coating material, dissolved in a suitable substance, is poured or sprayed into the pan. The rotation of the tablets causes a tablet to move upwards in the coating pan along the side of the pan and then fall downwards in the middle of the pan on top of the bed formed by the tablets that are moving upwards. As the solvent of the coating material evaporates, the material will be deposited on the tablets.
A large problem with the current technology is that the tablets preferably should be spherical or at least be made by convex-shaped rounded dies. The reason therefor is that the existence of edges on the tablets may cause the coating applied thereon not to be even and homogeneous. However, tablets produced today usually have a flat, circular form, that is, they have a special edge surface to avoid problems with for instance caping of the tablet or increasing demands on the tablet-producing machine (deep concave dies, etc). The coating processes used today are batchwise and each batch goes through a large number of steps involving a large amount of manual work as well. The energy consumption is relatively high and the noise level is considerable. Space requirements are large, ventilation demands are stringent. These processes are time consuming as well.
Coating of confectionary, for example, the chocolate sweets known as "NON-STOP", is often performed in a similar manner.
In recent times, so called high speed methods for medicinal product coating have been developed, but in spite of this, the time needed to get finished dragees is about one to two working days. The cost of the substances the tablets are coated with often is fairly low, accounting for only a small amount of the total cost of the coating.
It is likewise known to perform the coating in a fluidizing bed. The tablets are made to move upwards through the bed propelled by a gas, preferably air, while the coating is being sprayed on.
Processes for electrostatic coating of small objects have been known for some time. A feature often common in earlier known technologies is that the objects to be coated are earthed, see for example U.S. Pat. No. 4,774,102, wherein a process for electrostatic spray coating of a not earthed object is described.
Electrostatic coating of medicinal products is also previously known; for example in WO 92/14451, such a process is described. According to the process of that publication, medicinal products are coated with a dry powder by using a procedure according to which the medicinal products are placed on a transportation device on which they are coated with a powder. The potential difference between the medicinal product and the powder or between the transportation device and the powder is used to attract the powder to the medicinal products. In this way those parts of the medicinal products that are in contact with the transportation device receive no
REFERENCES:
patent: 2270341 (1942-01-01), Ransburg
patent: 4510170 (1985-04-01), Cosentino et al.
patent: 4774102 (1988-09-01), Kiefer et al.
patent: 5470603 (1995-11-01), Staniforth et al.
patent: 5520754 (1996-05-01), Yaney et al.
Johansson Hasse
Lewinsky Nils
Lindqvist Anders
Parker Fred J.
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