Plastic and nonmetallic article shaping or treating: processes – With severing – removing material from preform mechanically,... – To form particulate product
Patent
1997-06-20
2000-10-17
Theisen, Mary Lynn
Plastic and nonmetallic article shaping or treating: processes
With severing, removing material from preform mechanically,...
To form particulate product
264141, 425363, B29B 910
Patent
active
061326593
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for the production of lenticular tablets by molding a melt which contains an active ingredient in a calender with counter-rotating molding rolls which have on their surface depressions for receiving and molding the melt (melt calendering).
The production of tablets by calendering a melt containing an active ingredient is disclosed in DE-A 1 766 546 and U.S. Pat. No. 4,880,585. The basis of this process is the embedding of an active ingredient in a melt of a carrier, eg. fatty substances or water-soluble thermoplastic polymers. The melt is produced by melting the mixture of active ingredient, polymer and, where appropriate, other ancillary substances, for example in an extruder, and molding the melt in a downstream molding calender to give tablets which harden on cooling. The molding calender comprises a pair of counter-rotating molding rolls which have on their surface engravings (depressions) which correspond to the shape of one half of the required tablet. The tablet molding takes place in the region of contact of the two rolls by combination of the tablet composition in one depression on one roll with that in the opposite depression on the other roll. Both DE-A 1 766 546 and U.S. Pat. No. 4,880,585 describe the production of rod-shaped tablets (oblong tablets).
The production of tablets by the melt calendering process usually results, as a consequence of the compression process, in an encircling burr consisting of melt residues. This burr must be removed by deflashing techniques after the tablets have cooled. In the case of hard, brittle tablet formulations and thin burrs, this can take place in a simple manner, for example, by placing the tablets in rotating vessels in which deflashing takes place due to mutual abrasion of the tablets against one another. In the case of thick burrs or formulations capable of plastic deformation, simple deflashing is impossible. For example, deflashing of the oblong tablets described in U.S. Pat. No. 4,880,585 is not satisfactorily possible by the mentioned simple process in rotating vessels. In order to ensure adequate deflashing in such cases it is necessary to have recourse to other deflashing techniques which increase the production costs.
Because of inaccuracies in the production of the molding rolls or non-uniform rotation of the molding rolls, the depressions necessary to mold a tablet are frequently not exactly opposite to one another. The consequence of this is that the two halves of the tablet are displaced with respect to one another.
Such a displacement between the upper half and lower half of the tablet in the case of oblong tablets disclosed in U.S. Pat. No. 4,880,585 is shown in FIG. 2. In order to obtain usable tablets it is necessary to abrade the protruding tablet residues. It is evident from FIG. 2 that large amounts of tablet material must be abraded in the case of prior art oblong tablets, which is extremely time-consuming and, as a rule, associated with loss of material. DE-A 38 30 355 proposes a way of avoiding the abovementioned difficulties by molding the tablets not by calendering but after the extrusion in a conventional tableting machine at 25.degree. C.
It is an object of the present invention to provide a process for the production of tablets in which the deflashing of the tablets and the removal of the protruding parts owing to a displacement between the tablet halves is possible in a simple way.
We have found that this object is achieved by producing tablets by melt calendering in a mold in which the angle between the plane of the burr and the tablet body is greater than 90.degree.. Tablets of this type are lenticular in shape.
The present invention therefore relates to a process for the production of lenticular tablets by molding a melt which contains an active ingredient in a calender with two counter-rotating molding rolls which have on their surface depressions for receiving and molding the melt, wherein at least one molding roll which has depressions in the shape of segments of an ellipsoid
REFERENCES:
patent: 3927194 (1975-12-01), Geller
patent: 4880585 (1989-11-01), Klimesch et al.
patent: 5009896 (1991-04-01), Becker
patent: 5073379 (1991-12-01), Klimesch et al.
patent: 5626874 (1997-05-01), Conte et al.
Breitenbach Jorg
Maier Werner
Rosenberg Joerg
BASF - Aktiengesellschaft
Theisen Mary Lynn
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