AU2007100655A4

AU2007100655A4 - Improvements in Blister Backing Strips

Info

Publication number: AU2007100655A4
Application number: AU2007100655A
Authority: AU
Inventors: Gerard Stevens
Original assignee: Manrex Pty Ltd
Current assignee: Manrex Pty Ltd
Priority date: 2007-07-18
Filing date: 2007-07-18
Publication date: 2007-08-16
Anticipated expiration: 2015-07-18
Also published as: CN101347383B; CN101347383A; HK1124755A1; ZA200710186B

Description

IMPROVEMENTS IN BLISTER BACKING STRIPS THIS INVENTION relates to the manufacture of foil backing strips used to seal blisters of a blister sheet so that medication doses prescribed by a doctor are retained in the 0_ blisters until required by a patient.

tV 5 A blister package comprises a combination of a blister sheet having depressible blisters IDwhich contain medication doses to be administered to a patient at different times of the day. The position of each blister signifies the time and day at which the medication in the blister is to be administered. The blister sheet has its blisters loaded with the medication Sdoses by a pharmacist in accordance with a medical prescription provided by a doctor. A flexible foil backing strip is then placed over the cavities of the blisters and adhesively secured to the back of the blister sheet.

Currently it is preferred to cold seal the backing strip to the blister sheet rather than use a hot sealing process, as there is less risk of the medication doses in the blisters being adversely affected by heat. Foil backing strips have been developed which have a multilayer sandwich structure. The exposed layer of the strip comprises a paper web which will accept printing to identify the medication doses in the associated blister beneath. The strip is secured over one face of a metal foil by a first layer of a relatively strong adhesive. The opposite face of the foil is covered with a second layer of a relatively weak adhesive which hold a cover sheet in place. The cover sheet is formed at the position of each blister with a blank which covers the cavity of the blister and holds the medication doses in place in the blister. To use the backing strip the cover sheet is peeled off its surface and it is then positioned so that each blister cavity is closed by a blank. Cold rolling pressure is then used to anchor the backing strip to the blister sheet by means of the exposed portions of the relatively weak adhesive layer.

It has been discovered that a blister package constructed as described above may suffer from a premature partial detachment of the backing strip from the blister sheet, such detachment commencing as a curling away of the marginal portions of the backing strip 2 from the blister sheet with the risk that the medication doses in the blister cavities may be exposed to ambient air before they are required to be administered.

An object of this invention is to provide an improved backing strip.

00 In accordance with the present invention a multi-layer flexible backing strip has a first 5 layer of adhesive securing a paper web to one face of a metal foil, a second layer of IN adhesive securing the opposite face of the foil to a removable cover strip, and an array of

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0 spaced blanks adhering to the second layer and shaped and positioned to cover mouths of rrespective cavities of a blister sheet with which the backing strip is to be used; in which Sbacking strip the adhesive strength of the second layer is greater than the adhesive strength of the first layer.

The backing strip of the invention resists curling of the combination of the foil and web away from the blister sheet. Such curling is believed to be caused by differential expansion of the web with respect to the foil as a result of contraction of the web in dry ambient conditions when the ambient temperature is sufficiently high to cause thermal expansion of the foil.

Preferably one or more air-venting means are provided in the vicinity of the edge portions of the blanks and suitably such means extend through the thickness of the blank, the second layer of adhesive, the foil, the first layer of adhesive and the web. Such airventing means may take the form of perforations or other forms of air passageways.

The purpose of the air-venting means is to ensure that when a blister is depressed by finger pressure to eject its contents out through the backing strip, the air-venting means enable air in the blister to escape when the blister is being depressed. The air in the blister does not then act as a cushion tending to obstruct further depression of the blister.

The invention will now be described in more detail, by way of example, with reference to the accompanying diagrammatic drawings, in which:- O FIGURE 1 shows to a greatly enlarged scale, an exploded vertical section through a multi-layer backing sheet and underlying blister sheet; and, 00 FIGURE 2 is an under plan view of a part of a blister sheet shown to a reduced scale as compared with figure 1 and provided with blister, cavities containing medication doses prescribed by a doctor and closed by blanks provided on a backing sheet of the form Idescribed in figure 1.

A backing strip 1 shown in figure 1, has a flexible, laminated, multi-layer structure comprising a paper web 2 on the exposed surface 3 of which can be printed information relating to the contents of blisters 13 of a blister sheet 14 located beneath the strip 1. A layer 4 of adhesive secures the web 3 to a thin aluminium foil 5 having an undersurface 6.

A second layer 7 of adhesive covers the undersurface 6 of the foil 5 and has an adhesive tenacity greater than that of the layer 4. An array of flat paper blanks 8 adheres to the layer 7 at positions corresponding to the locations of the open sides or mouths 15 of the cavities of the blisters 13. Each blank 8 is shaped to nearly fit the mouth of a blister cavity beneath, to prevent medication doses within the cavity of the blister from contacting the adhesive layer 7. The blanks 8 are individually formed by respective parts of a removable cover sheet 9, such parts being each delineated by an oblong slit extending through the cover sheet and arranged around the edge of each blank 8. The cover sheet 9 totally covers the adhesive layer 7 when the strip is not in use, and is peeled off the strip when it is required to be used to leave the blanks 8 adhering to the adhesive layer 7. The cover sheet 9 is coated with a substance which enables it to be manually peeled off the adhesive layer 7.

Figure 2 shows an oblong line of perforations 10 spaced outwardly of the peripheral edge of each blister cavity by about one millimeter. The perforations 10 extend through the adhesive layer 7, the aluminium foil 5, the first adhesive layer 4 and the paper web 3.

The backing strip shown in the figures is used as follows: SAn empty blister sheet is inverted so that its blister cavities can be filled from above with medication doses prescribed by a doctor. The flexible backing strip 1 has its cover sheet 9 peeled off manually. The severance slit surrounding each blister enables it to remain in

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0position on the adhesive layer 7 after peeling off of the surrounding portions of the cover sheet 9. The planar upper surface of the blister sheet 14 is then exposed to the array of blanks 8 and the intervening and surrounding portions of the adhesive layer 7. The Ibacking sheet 1 is then carefully positioned so that each of the blanks 8 is located over a respective blister cavity. The strip is then pressed firmly down on the planar upper surface of the blister sheet. This process is carried out without the application of heat to N 10 the backing strip 1, pressure alone being used to cold seal the backing strip 1 to the blister sheet 14.

In certain atmospheric conditions such as when the ambient air is hot and dry, the differential expansion occurring between the thin and flexible aluminium foil 5 which expands, and the paper web 2 which contracts, can cause the backing strip 1 to tend to arch away and then detach itself from the blister sheet 14 unless steps are taken to prevent this. In the present case, the increased adhesive tenacity of the layer 7 in contact with the blister sheet with respect to the weaker tenacity of the adhesive layer 4 securing the foil to the paper web 2, resists the tendency of the foil to curl away from the blister sheet 14.

Such curling would otherwise occur if the adhesive tenacity of the two layers 5 and 7 was the same or if the tenacity of the layer 7 was not carefully chosen to be strong enough to resist this curling tendency.

In order to eject the medication doses from a particular blister, its convex upper surface is depressed by finger pressure. This pushes the medication doses against the blank 8 while simultaneously increasing the air pressure inside the cavity 13 of the blister. This increased air pressure would normally provide a pneumatic cushion inside the blister, thus making ejection of the medication doses from the blister harder. However the increased air pressure inside the blister causes the blank 8 to lift slightly with respect to the plane of the blister sheet 14, and thus to ease the surrounding portion of the adhesive t layer 7 away from the blister sheet. This exposes one or more of the perforations which provides a vent through which excess pressure inside the blister cavity can leak away to atmosphere. The formation of an air cushion inside the blister which would otherwise oppose the compression of the blister by finger pressure, is thus prevented.

00 Variations to the above-described example of the invention are possible. For example, the t blank 8 may be shaped to to have its marginal edge portion extending beyond the edge of IND the mouth of the cavity so as to eliminate altogether the risk of medication doses inside _the cavity from coming into contact with the adhesive layer 7. The line of perforations can then be provided in the marginal edge portion of the blank and about one millimeter 10 outwardly of the periphery of the mouth of the blister cavity so that the venting openings are not established until the air pressure inside the blister cavity exceeds atmospheric pressure by a chosen amount.

Claims

3. A backing strip as claimed in claim 2, in which the air-venting means are formed by perforations arranged around the marginal edge of each blank.
4. A backing strip as claimed in claim 4, arranged and adapted to be used substantially as described with reference to the accompanying drawing. Dated this 14th day of July 2007. MANREX PTY. LTD. By:..