Fishing – trapping – and vermin destroying
Patent
1994-11-04
1996-03-12
Beck, Shrive
Fishing, trapping, and vermin destroying
427220, 118303, B05D 700
Patent
active
054984475
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL BACKGROUND
The present invention relates to a coating method of a wax on the solid particles, More particularly, the present invention relates to a coating method which can make it available a simple and easy spray-coating of a thermally melted wax on the surfaces of solid particles kept flowing without using any organic solvent.
PRIOR ART
There have been well known some methods for preparing sustained release preparations which control the release of an active ingredient therefrom, or preparations for masking materials of unpleasant and bitter tastes, which comprise coating a wax on the surfaces of solid particles containing an active ingredient.
For example, there are disclosed a method of coating solid particles containing an active ingredient with a wax, which comprises dissolving a wax in an organic solvent and spraying the resultant solution on the surfaces of solid particles containing an active ingredient, and drying them (Japanese Patent Second Publication (Kokoku) No. 26837/1965), a method of coating solid particles containing an active ingredient with a wax, which comprises pulverizing a wax to fine powder, depositing said fine powder on the surfaces of solid particles containing an active ingredient, further thermally melting thereof (Japanese Patent Second Publication (Kokoku) No. 3789/1965), and the like. Recently, it has been tried to effect the coating by thermally melting a wax and directly spraying the resultant (cf. PHARM TECH JAPAN, 7, 711-718 ( 1991)).
However, in the coating method which comprises dissolving a wax in an organic solvent and spraying the resultant solution, there are used as an organic solvent, for example, halogenated hydrocarbons such as carbon tetrachloride, chloroform. trichloroethane, etc., hydrocarbons such as hexane, benzene, etc., lower alcohols such as methanol, ethanol, propanol, etc., ketones such as acetone, methyl ethyl ketone, etc., and the use of these solvents has many problems, for example, bad effects on human beings, air pollution, and causes of disasters, etc. Besides, in order to avoid these problems, the method should be carried out in a closed system, and needs a large equipment such as an equipment for recovering organic solvents. Moreover, it has some problems in view of industrial efficiency, because the large amount of organic solvents are used and hence, it takes a lot of time to remove these solvents from the resulting preparations after coating.
In the method which comprises pulverizing a wax to fine powder, depositing said fine powder on solid particles and then thermally melting thereof, the process of pulverization of a wax to fine powder is very complicated, and it should be usually carried out after cooling the wax with liquid nitrogen or dry ice so that a special equipment is needed therefor, and it is difficult to control the size of the powder thus obtained. Further, in this method, it is essential to thermally melt the fine powder alter depositing on the solid particles, and if the temperature of thermal melting is not high enough to melt the wax, the resulting coating is not sufficiently uniform. On the contrary, if the temperature of thermal melting is too high, the wax fuses to cause forming of agglomerated solid particles. Besides, the temperature range at which a wax starts melting and completes melting is usually wide, and hence, it is very difficult to melt the wax at the optimum temperature thereof.
On the other hand, these problems can be solved in the method comprising directly spray-coating a thermally melted wax onto solid particles containing an active ingredient. However, this method includes other problems, for example, clogging of spray nozzle caused by cooling of the thermally melted wax when spraying, powdering of the melted wax caused by finely dividing of spray mist, or forming of agglomerated solid particles caused by coarse particles of spray mist, and hence, it can still not achieve the sufficient coating. That is, in the conventional method, the thermally melted wax is sprayed from the central
REFERENCES:
Jozwiakowski et al., "Characterization of a Hot-Melt Fluid Bed Coating Process for Fine Granules", Pharmaceutical Research, vol. 7, No. 11, 1990 pp. 1119-1126 (no month).
Kobayashi Masaru
Nishii Hiroyuki
Toya Kazutoshi
Uchiyama Nobuo
Beck Shrive
Maiorana David
Sumitomo Pharmaceuticals Company Limited
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