Cover foil as a push-through foil for a blister pack

Abstract

A cover foil as a push-through foil for a blister pack for packaging moisture-sensitive products has an aluminum foil as the barrier layer against the penetration of water vapor and gases and a sealing layer for sealing against a blister base part. A plastics material layer containing moisture-adsorbing drying agent is arranged on the side of the aluminum foil provided with the sealing layer.

Claims

1. A push-through cover foil for a blister pack having a collapsible blister base part for packaging a moisture-sensitive product, the push-through cover foil comprising: an aluminium foil as the barrier layer against the penetration of water vapour and gases, a sealing layer for sealing against the blister base part, a plastics material layer containing a moisture-adsorbing drying agent arranged on the side of the aluminium foil provided with the sealing layer, and a buffer layer made of plastic material arranged between the aluminum foil and the plastics material layer comprising the drying agent, wherein the plastics material layer containing the moisture-adsorbing drying agent has a weight per area in the range of 30 g/m.sup.2 to 38 g/m.sup.2, and wherein the cover foil is configured to rupture upon collapsing the blister base part containing the moisture-sensitive product.

2. A cover foil according to claim 1, wherein the drying agent comprises at least one oxide selected from the group consisting of alkaline oxides and alkaline-earth metal oxides.

3. A cover according to claim 2, wherein the plastics material layer comprising drying agent comprises, as the drying agent, calcium oxide (CaO).

4. A cover foil according to claim 1, wherein the drying agent is selected from the group consisting of silicates, silica gels, aluminosilicates, physically drying substances, substances taking in water of crystallisation, compounds carrying sugar and hydroxyl groups.

5. A cover foil according to claim 1, wherein at least one of the plastics material layer containing the drying agent, the buffer layer, or the sealing layer is comprised of polyolefin.

6. A cover foil according to claim 1, wherein the buffer layer, the plastics material layer containing the drying agent and the sealing layer are formed from a coextrusion layer applied to the aluminium foil.

7. A cover foil according to claim 5, wherein the polyolefin is selected from the group consisting of polyethylenes and polypropylenes.

8. A cover foil according to claim 1, wherein the aluminium foil is coated on the side provided with the sealing layer with an adhesion promoter.

9. A blister pack comprising a blister base part and a cover foil according to claim 1, wherein the sealing layer is sealed against the blister base part.

10. A packaged pharmaceutical product, comprising a moisture-sensitive tablet or powder packaged in a blister pack comprised of a blister base part and a cover foil according to claim 1, wherein the sealing layer is sealed against the blister base part.

11. A cover foil according to claim 1, wherein the plastics material layer is comprised of 0.5 to 95% by weight CaO.

12. A cover foil according to claim 1, wherein the plastics material layer is comprised of 10 to 65% by weight CaO.

13. A cover foil according to claim 5, wherein the polyolefin is selected from the group consisting of high density polyethylene (HDPE), linear low density polyethylene (LLDPE), and low density polyethylene (LDPE).

14. A cover foil according to claim 5, wherein the plastics material layer is additionally comprised of at least one acid-modified polyolefin.

15. A cover foil according to claim 8, wherein the adhesion promoter is selected from the group consisting of water-based primers, solvent-based primers, and polymeric adhesion promoters.

16. A cover foil according to claim 1, having a structure: a). lacquer; b). aluminium foil as the barrier layer; c). primer; d). LDPE as a buffer layer; e). PE and drying agent as the plastics material layer; and f). LDPE as the sealing layer.

17. A cover foil according to claim 16, wherein the plastics material layer is comprised of 10 to 65% by weight CaO.

18. A blister pack comprising a blister base part and a cover foil according to claim 16, wherein the sealing layer is sealed against the blister base part.

19. A packaged pharmaceutical product, comprising a moisture-sensitive tablet or powder packaged in a blister pack comprised of a blister base part and a cover foil according to claim 16, wherein the sealing layer is sealed against the blister base part.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) The invention utilises knowledge obtained in general from packaging foils and packagings produced therefrom in accordance with WO-A-2004/080808 and from blister base parts in accordance with WO-A-2007/104344.

(2) It has surprisingly been found that the inner layer, i.e. the plastics material layer which is arranged on the side of the aluminium foil provided for sealing against a blister base part and containing drying agent, may have a double to triple thickness compared to the sealable inner layers which are conventional in push-through foils according to the prior art, without reducing the push-through capacity of the foil. The reason for this is that the layer carrying the drying agent has a much higher brittleness in comparison to layers without drying agent. This recognition cleared the way for the first time for the development of the cover foil according to the invention with a substantial and therefore economically sensible content of drying agent.

(3) The plastics material layer containing drying agent preferably contains as the drying agent at least one oxide from the group of alkaline and earth-alkaline metals. A particularly preferred plastics material layer containing drying agent contains, as the drying agent, calcium oxide (CaO), in particular 0.5 to 95% by weight CaO, preferably 10 to 65% by weight.

(4) However, other substances which are suitable as drying agents can also be used, such as, for example, silicates, silica gels, aluminosilicates, physically drying substances, substances taking in water of crystallisation, compounds carrying sugar and hydroxyl groups.

(5) As drying agents are generally present as powders in granular form, care has to be taken that the grains of the drying agent do not press into the aluminium foil and push through these, as holes thus produced in the aluminium foil would destroy the integrity of the blister pack and eliminate the high moisture protection aimed for. Drying agents are generally applied in the form of a master batch carrying drying agent to the aluminium foil by an extrusion or coextrusion method. In this case, the layer thickness of the layer carrying the drying agent may not be too great as otherwise the relatively low expenditure of force, which is above all important for elderly people, is exceeded when a tablet is pushed out and the push-through capacity of the cover foil is lost. In the master batches carrying drying agent and which are commercially available, made, for example, of polyethylene (PE) and CaO, the drying agent has particle sizes (d.sub.100)>10 to 20 μm. Particle sizes of this type are in a position to push through aluminium foils with a thickness of, for example, 20 μm, which are generally used for push-through foils in the “hard” state.

(6) For this reason, it may prove to be expedient to arrange a buffer layer made of plastics material between the aluminium foil and the plastics material layer containing the drying agent.

(7) The plastics material layer containing the drying agent and/or the buffer layer and/or the sealing layer preferably consist of polyolefin, preferably of polyethylene (PE), in particular of a high density polyethylene (HDPE) and/or a linear low density polyethylene (LLDPE) and/or a low density polyethylene (LDPE) and/or polypropylene (PP) and optionally contain components of acid-modified polyolefins, such as ionomers, EAA or PP-MSA. These acid-modified polyolefins act as adhesion promoters, so that in certain cases a separate primer can be dispensed with.

(8) The buffer layer, the plastics material layer containing the drying agent and the sealing layer are preferably formed from a coextrusion layer applied to the aluminium foil.

(9) The aluminium foil may be coated, on the side provided with the sealing layer, with an adhesion promoter, in particular with a water-based or solvent-based primer or with a polymeric adhesion promoter.

(10) A typical structure of a cover foil is, for example:

(11) Lacquer, 1 to 2 g/m.sup.2

(12) Aluminium foil 20 μm, hard

(13) Primer, 1 g/m.sup.2

(14) LDPE, 12 g/m.sup.2 as the buffer layer

(15) PE+drying agent 30 g/m.sup.2

(16) LDPE, 4 g/m.sup.2 as the sealing layer.

(17) In addition, the cover foil may be printed and the printing may optionally be over-lacquered.

(18) Measurements show that in a plastics material layer containing drying agent, up to a weight per unit area of about 38 g/m.sup.2, no impairment of the push-through capacity is ascertained in comparison to a standard push-through foil with the layer structure

(19) Lacquer, 1 to 2 g/m.sup.2

(20) Aluminium foil 20 μm, hard

(21) Primer, 1 g/m.sup.2

(22) LDPE, 15 g/m.sup.2 as the sealing layer.