Extrusion-Coated Lidding Foil For Push-Through Blister Packaging

Abstract

An extrusion-coated lidding foil for blister packaging particularly suitable for push-through pharmaceutical and food blister packaging. The lidding foil includes a foil layer on which one or more tie layer and one or more sealant layer, one or both of which include an embrittling agent mixed therein, are extrusion coated resulting in a lidding foil having push-through ability. The push-through ability of the lidding foil is characterized by a Mullen burst strength of about 10 psi to about 30 psi and an MD tear strength of about 30 to about 100 grams-force.

Description

FIELD OF THE INVENTION

The present invention relates to packaging having a lidding foil. The invention is particularly useful for push-through blister packaging and is directed to an extrusion-coated lidding foil useful for such packaging.

BACKGROUND OF THE INVENTION

“Blister packaging” is a common term used for packaging having a bottom part, typically referred to as the “blister film”, with a plurality of recesses formed therein (e.g., through vacuum forming or pressure forming) wherein a respective product piece (e.g., a consumable tablet or pill) is positioned and held therein. A cover, typically referred to as a “lidding foil” is placed over and sealed to the blister film about the perimeter of each recess.

There are basically three different types of blister packaging which relate to how the consumer is meant to retrieve the consumable from its respective recess within the sealed package: push-through type, peel-push type and lock type. In the “push-through” type of blister package, the consumer must use a finger to push against the malleable blister film at the location of a recess and continue pushing until the consumable in the recess is pressed against and breaks through the covering lidding foil. In the “peel-push” type of blister package, the consumer must first peel away an upper layer of a two layer lid stock to reveal the lower layer, and then push against the malleable blister film at the location of a recess and continue pushing until the consumable in the recess is pressed against and breaks through the lower layer of the lidding foil. The “peel-push” type package is considered more child-proof than the strictly push-through type due to the extra layer of the lidding foil. In the “lock” type of blister package, the consumer can only get access to the recess content by destructing the lidding material using a tool like a pair of scissors, a knife, nails, etc. The present invention is primarily directed to the push-through or peel-push blister packaging, although it is noted that push-through is considered an integral part of a peel-push package. The push-through type of blister packaging is the most common package type for consumables in pill or tablet form such as chewing gum or pharmaceuticals.

Present day push-through blister packaging is manufactured with a lidding foil (typically aluminum foil) to which a heat seal lacquer is applied using gravure coating process. In the gravure coating process, the lacquer adhesive (e.g., vinyl acrylic lacquer) is dissolved in a solvent and applied to a steel roll engraved with a pattern of micro dimples or “cells”. As the steel roll rotates, the cells on the surface pick up the lacquer either by passing through a bath of lacquer or by direct application of the lacquer to the steel roll. A roll of aluminum foil rolls a sheet of foil between the rotating steel roll and a rubber roll whereby a thin layer of the lacquer is transferred from the steel roll to the foil. The use of the gravure coating process thus allows a relatively thin layer of the lacquer to be applied to the lidding foil. The use of this process on push-through blister packaging lidding foils has therefore been the industry standard for many years since, if the foil sheet and/or the lacquer layer are too thick, the consumer would not be able to readily push and cleanly break through the lidding foil.

In an extrusion coating process, the adhesive is extruded through a die in the form of a molten polymer curtain that is applied to the continuously moving aluminum foil. If extruded too thinly, breaks within the curtain could cause voids, which could leads to breaches in the package seal. Present day peelable lidstock (e.g., as used in single serve food containers having a peel-away foil lid) is typically manufactured using either extrusion coating process, extrusion lamination process or gravure coating process. Extrusion coating/lamination employs different adhesives than are used in a gravure coating process, and the peel-away type of lidding foil is sufficiently thick to prevent inadvertent puncturing of the lid prior to opening the container. A thicker layer of sealant (as one gets with an extrusion coating process as compared to the gravure coating process) may therefore be used for peel-away lidding foils to ensure complete sealing, but is inadequate for push-through blister packaging application.

In present day push-through blister packaging, the blister film is typically formed from a polymeric material such as, for example, polyvinyl chloride (PVC), polyvinylidene dichloride (PVdC), a PVC/PVdC-combination, a PVC/PCTFE-combination or polystyrene (PS). During the packaging process, the consumables are placed in their respective recesses in the blister film and the lidding foil is positioned thereover. A heat press is then applied to seal the lidding foil to the blister film about the periphery of each recess to thereby seal the consumable within the package.

The polymers presently used for the blister film of the package either do not create a complete barrier to moisture and air, and/or they may contain plasticizers that are subject to blooming and can contaminate the consumable. Insufficient barrier properties allow moisture and air seepage into the package over time which shortens package shelf life. Also, contamination of the consumable by additive blooming may be harmful to human health. Some states such as California have recognized the potentially harmful effects of PVC in packaging for consumables and is considering enacting legislation prohibiting the use of PVC in food and pharmaceutical packaging. There is thus presently a trend in the pharmaceutical industry toward the use of blister films made of materials which have better moisture and air barrier properties and are more inert than presently used polymeric blister films. Polychlorotrifluoroethylene (PCTFE), available from Honeywell under the trademark Aclar®, is one example of a material having these desirable properties. Cyclic olefin copolymers (COC) available from Topas Advanced Polymers represent another class of similarly suitable materials.

Unfortunately, for push-through type lidding foils, the heat seal lacquers presently used for push-through blister lidding foils exhibit difficulty adhering efficiently directly to PCTFE (Aclar®), COC, and other similar materials having the above beneficial properties. As such, it has been a practice in the industry, when making push-through blister packaging, to laminate the more beneficial PCTFE (Aclar®), COC, etc. to the less beneficial (and less expensive) PVC (or some other polymers such as polypropylene (PP), high density polyethylene (HDPE), linear low density polyethylene (LLDPE), and polystyrene (PS), for example) to form the blister film. One present day industry manufacturing method then takes the conventionally manufactured push-through lidding foil with heat seal lacquer and seals it to the PVC side of the blister film to which the heat seal lacquer can efficiently adhere. This of course means the PVC side of the blister film must face the lidding foil and thus be in contact with the consumable. While this practice provides the benefit of the barrier properties of the PCTFE (Aclar®), COC, etc., the possibility of additive blooming is still present since it is the PVC layer which is in contact with the consumable inside the package. The ability to seal a push-through lidding foil directly to PCTFE (Aclar®), COC, etc. or similarly beneficial material would thus provide both an improved barrier and contact of the consumable with an inert material.

Sealant materials useful for peel-away lidstock are described in US Patent Application Serial Nos. 2005/0159549, 2005/0249903, and 2006/00104022, the disclosures of which are incorporated herein by reference, such materials including polymeric compositions that consist essentially of: about 10 to about 80 weight % of at least one ethylene/alkyl (meth)acrylate copolymer; about 5 to about 60 weight % of at least one polyolefin; 0 to about 35 weight % of at least one tackifying resin; and 0 to about 35 weight % of a filler such as, for example, talc.

The sealant materials described in the referenced patent applications are asserted to be useful to the pharmaceutical industry in user-friendly blister packaging for drugs in the form of pills, tablets, capsules and the like, and also for non-drugs such as poisons, catalysts, cleaning compositions, batteries, and various other goods. They may also be employed to seal lidded containers containing products such as yogurts, puddings, custards, gelatins, fruit sauces, cheese spreads and dips, meats, frozen or refrigerated meals, and dry foods such as noodle and snacks. The described sealant materials employed in various packaging applications are also asserted to provide a good heat seal that can be easily peeled.

U.S. Pat. No. 4,211,326, the disclosure of which is incorporated herein by reference, describes a push-through blister package that comprises a metal foil and a sheet provided with thermoformed pockets that comprises, prior to thermoforming, a laminate structure having outer layers of polyvinyl chloride (PVC) and an intermediate layer of fluid compression rolled, partially oriented polymeric material, for example, high density polyethylene (HDPE).

U.S. Pat. No. 6,010,784, the disclosure of which is incorporated herein by reference, describes a paperboard laminate for pharmaceutical blister packaging that employs a blend of a hot melt adhesive such as ethylene vinyl acetate (EVA) and calcium carbonate that is capable of sealing to Aclar®.

US Patent Application Serial No. 2007/0224379, the disclosure of which is incorporated herein by reference, describes a peelable child-resistant pharmaceutical blister lidstock for peel-push blister packaging that comprises a first layer of white polyester, a second layer of adhesive, a third layer of foil, and a fourth layer of a coating of a heat sealant such as a vinyl acrylic.

US Patent Application Serial No. 2002/0193031, the disclosure of which is incorporated herein by reference, describes a laminate for blisters and pouches that comprises a metal foil having an uncoated surface which has been directly heat sealed to the surface of a polymeric web by an outer surface of the web, wherein the outer surface comprises a blend of an EVA copolymer and an additive that embrittles the copolymer at room temperature. The polymeric web may be a laminate that includes a polyolefin core and a second outer surface that may be a polychlorotrifluoroethylene. The laminate is asserted to be useful in producing press-through packages, where it will not peel open when tablets are pushed through it, and also in producing pouches, where it will peel.

US Patent Application Serial No. 2005/0058793, the disclosure of which is incorporated herein by reference, describes a coextruded multilayer heat sealant structure that comprises a first layer of a thermoplastic polymeric material, a second layer of low density polyethylene, and a third layer of a single site catalyzed polyethylene for use as a heat sealant layer, the heat sealant structure being laminated to a substrate such as aluminum foil.

U.S. Pat. No. 7,316,317, the disclosure of which is incorporated herein by reference, describes a package that comprises a polymeric base sheet such as PVC containing recesses and a sealing web that includes a metal foil adhered to a polymeric web, for example, polyethylene terephthalate (PET). The sealing web has strength sufficient to prevent a packaged item in a recess from being pushed through by pressure applied to the recess. A portion of the package where the base web is sealed to the sealing web includes lines of weakness that allow the packaged item to be pushed through the sealing web.

US Patent Application Serial No. 2006/0199022, the disclosure of which is incorporated herein by reference, describes a blister pack that includes a laminate of a metal foil adhered to a water permeable layer by an adhesive that can be softened on exposure to water. A packaged item cannot be pushed through the foil until the adhesive is softened by water, thereby allowing removal of the water permeable layer from the foil.

While the above patents and applications describe various lidding foils, blister films and sealants for blister packaging, neither the industry nor the prior patent publications above have provided an extrusion-coated lidding foil for push-through blister packaging. Furthermore, the prior art fails to disclose or teach an extrusion-coated lidding foil for push-through blister packaging which may be sealed directly to PCTFE (Aclar®), COC, or similarly a beneficial material having enhanced barrier and inert properties.

SUMMARY OF THE INVENTION

The present invention successfully addresses the above deficiencies of the prior art by providing an extrusion-coated lidding foil for blister packaging particularly suitable for push-through pharmaceutical and food blister packaging. The lidding foil includes a foil layer on which one or more tie layer and one or more sealant layer, one or both of which include an embrittling agent mixed therein, are extrusion coated resulting in a lidding foil having push-through ability. The push-through ability of the lidding foil is characterized by a Mullen burst strength of about 10 psi to about 30 psi and an MD tear strength of about 30 to about 100 grams-force. The lidding foil of the present invention may be heat sealed to a polymeric bottom blister film to form a push-through blister pack although the lidding foil may of course be used in other types of blister packaging as desired (e.g., peel-push type or lock type).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a prior art heat seal lacquered lidding foil (Structure type 1);

FIG. 2 is a schematic representation of a prior art extrusion-coated lidding foil containing prior art sealant resin (C) (Structure type 2);

FIG. 3 is a schematic representation of an extrusion-coated lidding foil containing sealant resin with embrittling agent (I) of the present invention (Structure type 3);

FIG. 4 is a schematic representation of an extrusion-coated lidding foil containing sealant resin (I) of the present invention, with additional embrittling agent incorporation in only a portion of the sealant layer (Structure type 4);

FIG. 5 is a photograph of three foil lidding samples (G, H & I) following Mullen burst test;

FIGS. 6A-H are plots depicting the results of dart puncture tests for samples G, H, I, J, K,& L;

FIG. 7 is a graph of the sealing force as a function of temperature of a lidding foil of the present invention on PCTFE (Aclar®)-containing blister film;

FIG. 8 depicts a blister pack that includes a lidding foil of the present invention sealed to a bottom blister film; and

FIG. 9 is a photograph of a blister package according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a lidding foil particularly suitable for push-through type pharmaceutical and food blister packaging although it is envisioned the lidding foil may be useful in other packaging applications.

In one embodiment, a lidding foil comprises aluminum foil, a tie layer extrusion coated on the aluminum foil, and a sealant layer extrusion coated on the tie layer. The foil is of a thickness of about 20 μm to about 25 μm and may be soft (i.e. annealed) or hard tempered (i.e. unannealed). The tie and sealant layers are extrusion coated either simultaneously or sequentially onto the aluminum foil. An embrittling agent is mixed into one or both of the tie and sealant layers in an amount of about 5 to about 50% by weight, and more preferably in an amount of about 10 to about 30% by weight. The embrittling agent is preferably a mineral and may be one or more of calcium carbonate, calcium sulfate, glass fiber, kaolin, mica, silica, talc, and wollastonite, for example. The embrittling agent may be equally or non-equally distributed in one or both of the tie and sealant layers. For example, the embrittling agent may be non-equally distributed in the sealant layers with a higher concentration in one sealant layer toward the tie layer.

In the preferred embodiment, the tie layer is extrusion coated to a coatweight of about 2 to about 5 pounds per ream and the sealant layer is extrusion coated to a coatweight of about 4 to about 10 pounds per ream.

The resultant lidding foil is characterized by a Mullen burst strength of about 10 psi to about 30 psi and an MD tear strength of about 30 to about 100 grams-force.

The tie layer may be a polymer selected from the group consisting of:

a) polyethylene;

b) ethylene acid copolymer;

c) ethylene acetate copolymer;

d) ethylene acrylate copolymer

e) ethylene anhydride copolymer

f) modified ethylene acrylate copolymer;

g) ionomer;

h) polypropylene;

i) anhydride-grafted polypropylene; and

j) a mixture of two or more of a-i.

The sealant layer may be a polymer selected from the group consisting of:

a) polyethylene;

b) polypropylene;

c) ethylene acrylate copolymer;

d) ethylene acetate copolymer;

e) modified ethylene acrylate copolymer;

f) modified ethylene acetate copolymer;

g) ionomer; and

h) a mixture of two or more of a-g.

FIG. 1 depicts a prior art lidding foil structure (structure type 1) that includes a thin layer of a heat seal lacquer applied to aluminum foil.

FIG. 2 depicts a prior art die-cuttable lidding foil structure (structure type 2) intended for peel-away lidding (e.g., as used on single-serve packages for yogurts, fruit sauces, juices, puddings . . . ) that includes relatively thick layers of tie and sealant resins applied to aluminum foil.

FIG. 3 depicts a push-through lidding foil structure (structure type 3) according to the present invention that includes a tie and sealant layer that are substantially thinner than that of the prior art structure and a sealant layer that contains an embrittling agent.

FIG. 4 depicts a push-through lidding foil structure (structure type 4) according to the present invention in which a portion of the sealant layer adjacent the tie layer contains a higher embrittling agent concentration.

A print primer layer, depicted in FIGS. 1-4, may be used to promote adhesion of inks to the outer surface of the aluminum foil.

Samples of prior art lidding foils in comparison with lidding foils according to the present invention were prepared as follows:

TABLE 1
Lidding foil description for samples A to N:
	MANUFACTURING
SAMPLE	PROCESS	STRUCTURE DESCRIPTION
A	gravure coating	37 μm soft foil/5.5 μm HS FP1-1015
B	extrusion-coating	37 μm soft foil/6 μm Nucrel 3990E/9 μm Lotryl EDA XY 0303
C	extrusion-coating	37 μm soft foil/6 μm Nucrel 3990E/17 μm Lotryl EDA XY 0303
D	extrusion-coating	37 μm soft foil/6 μm Lotader 3210/9 μm Lotryl EDA XY 0303
E	extrusion-coating	37 μm soft foil/6 μm Lotader 3210/17 μm Lotryl EDA XY 0303
F	extrusion-coating	37 μm soft foil/5 μm Nucrel 0910HS/25 μm blend 50:50 HDPE/MB
		10012-089
G	gravure coating	25 μm soft foil/5.5 μm HS FP1-1015
H	extrusion-coating	25 μm soft foil/7 μm Nucrel 0910HS/19 μm Appeel 20D828
I	extrusion-coating	25 μm soft foil/6 μm Nucrel 0910HS/10 μm Appeel 20D828
J	gravure coating	20 μm hard foil/6 μm HS FP1-1015
K	extrusion-coating	20 μm hard foil/5 μm Nucrel 0910HS/7 μm Appeel 20D828
L	extrusion-coating	20 μm hard foil/5 μm Nucrel 0910HS/4 μm blend 50:50 Appeel
		20D828/MB 10012-089/3 μm Appeel 20D828
M	extrusion-coating	20 μm hard foil/5 μm Nucrel 0910HS/4 μm blend 50:50 Appeel
		20D828/MB 10012-089/4 μm Appeel 20D828
N	extrusion-coating	20 μm hard foil/5 μm Nucrel 0910HS/8 μm blend 50:50 Appeel
		20D828/MB 10012-089
Robond ® HS FP1-1015, available from Rohm & Haas, was employed as the heat seal lacquer in prior art samples A, G and J.
Nucrel ® 0910HS, available from DuPont, was used in the tie layers of samples B, C, F, H, I, and K-N.
Lotader ® 3210, available from Arkema France Corporation, was used in the tie layers of samples D and E.
Appeel ® 20D828, available from DuPont, was used in the sealant layers of samples H, I, and K-N.
Lotryl ® EDA XY 0303, available from Arkema France Corporation, was used in the sealant layers of samples B-E.
Antiblock masterbatch 10012-089, available from Colortech Inc., was used in the sealant layers of samples L-N.

Samples A-F use foil having a thickness of 37 μm which is too thick for push-through ability. However, testing was only conducted to illustrate the effect of the embrittling agent on mechanical performance as shown in Table 2 below.

TABLE 2
test conditions	SAMPLE A	SAMPLE B	SAMPLE C	SAMPLE D	SAMPLE E	SAMPLE F
Foil thickness (μm)	37	37	37	37	37	37
Tie & sealant layer	3.25	9.2	14.2	9.2	14.2	18
coatweight (lb/ream)
Embrittling agent in	not	NO	NO	NO	NO	YES
the extrusion-coating	applicable
composition
Mullen burst strength	42.13	50.33	50.83	48.17	50.50	46.67
(psi)
MD tear strength	32.9	111.3	135.4	123.5	166.9	58.5
(gram-force)

As seen, sample F illustrates that despite having a thicker tie and sealant coatweight, use of an embrittling agent is important for increasing brittleness of an extrusion-coated lidding foil to make it more suitable for push-through blister packaging applications. The embrittling agent could be added in the formulation via use of a mineral-loaded masterbatch or in-situ in the composition of the selected sealant resin. Adequate embrittling agent content is between 5 to 50% and preferably between 10 and 30% of the sealant layer composition by weight.

Below is a comparison Table 3 with 25 μm soft-tempered foil regarding mechanical performance.

TABLE 3
Test conditions	SAMPLE G	SAMPLE H	SAMPLE I
Foil thickness (μm)	25	25	25
Temper foil type	Soft (“O”)	Soft (“O”)	Soft (“O”)
Tie & sealant layers	3.25	15.6	9
coatweight (lb/ream)
Embrittling agent in the	not	YES	YES
extrusion-coating composition	applicable
Mullen burst strength (psi)	25.67	16.50	13.33
MD tear strength (gram-force)	16.7	132.4	64.2

Heat seal lacquered structure (sample G) exhibits slightly higher Mullen burst strength but much lower tear strength than extrusion-coated structures. However, as illustrated in FIG. 5, the heat seal lacquered lidding foil (sample G) shows a more brittle fracture mode (i.e., it is less ductile) during Mullen burst test than extrusion-coated structures H and I. Therefore, one can postulate that a good lidding foil for a push-through blister package would be a structure that does not exhibit too high puncture or burst strength and that is accompanied with the lowest tear strength possible. Thus, improved extrusion-coated structure type 3 (sample I) shows these improved characteristics since tear and burst strengths are significantly lower than conventional extrusion-coated structure (sample H).

As shown in FIG. 5, sample I with reduced resin coatweight exhibits much more brittle rupture mode than conventional extrusion-coated structure sample H. A more brittle rupture mode, as seen with the conventional heat lacquered structure of sample G, is preferred for blister packaging applications.

Additional foil lidding puncture testing was carried out to fully understand the foil rupture mechanism. Spherical dart puncture tests were conducted at 5 inch/min perforation speed with the graphed results shown in FIGS. 6A-C for three specimens of sample G, H and I. FIG. 6D is a comparison chart of these three samples. The energy corresponds to the work, i.e., force times displacement or also area under the curve. The closer the total energy is to the energy at peak, the more brittle is the tested structure. Energy at peak and total energy of the samples G, H and I are set forth below in Table 4.

	TABLE 4
	Structure	Energy @ peak (lb · in)	Total energy (lb · in)
	G	1.542	1.745
	H	0.932	2.107
	I	0.712	1.293

Contrary to the Mullen burst test, dart puncture test provides not only energy at peak but also total energy to break the entire lidding foil structure. Mullen burst strengths correlate very well with energy at peak. However, it is in fact the total energy that represents better ease of rupturing the entire lidding foil structure, i.e., simulating push-through and release of the goods from inside the blister package. Thus, although it is more ductile, sample I requires less energy to break the structure than a conventional heat seal lacquer lidding foil. This is a totally unexpected result and it is this characteristic as to why such a structure becomes suitable for push-through blister application as illustrated in FIG. 9. Conversely, sample H is not adequate for the push-through application because of excessive plastic elongation when pushing-through, meaning it is too ductile.

Regarding sealability of the lidding foil to the blister film material, as a reference, typical minimum sealing force required for blister packaging applications is on the order of 2.0 lbs/in. However, sealing force above 2.5 lbs./in. is by far preferable to ensure good impermeability and integrity of the whole packaging.

Appeel® 20D828 from Dupont used in developed extrusion-coated lidding foils of this invention (ref Table 1 above) is a modified ethylene acrylate copolymer that contained talc in-situ in its composition. This resin provides significantly good sealing performance on most polymeric material including PCTFE (Aclar®), for example.

Table 5 presents sealing results for sample I (structure type 3) at several temperatures for COC-based blister films containing various outer layers,

	TABLE 5
	Sealing force as function of temperature *
Polymer	275° F.	300° F.	325° F.	350° F.	375° F.
HDPE	5.45	5.92	5.19	4.19	5.15
PETG	3.55	4.11	3.89	3.66	4.11
PP	3.39	3.60	3.33	3.44	3.99
LLDPE	5.39	4.62	5.13	5.26	4.79
SBC	2.76	3.15	3.29	5.02	5.69
COC/LLDPE	4.00	4.04	3.78	3.96	4.23
COC	4.68	4.62	4.38	4.24	4.30
* 1″ strip sealed at 40 psi for 0.7 second

As shown by the data in Table 5, regardless of the polymeric nature of the blister film skin layer or the sealing temperature, excellent sealability of sample I is observed.

Thus, the present innovative extrusion-coated structure is not only adequate for push-through blister packaging applications but, contrary to heat seal lacquered structure, may also exhibit very universal sealing characteristics since it seals to most of the typical commercial blister films made of PVC, PVdC, PS, PCTFE (Aclar®), HDPE, LLDPE, LDPE, PP, PETG, SBC or even COC, for example.

Below is another comparison table with 20 μm hard-tempered foil regarding mechanical performance.

TABLE 6
mechanical & sealing properties	J	K	L	M	N
Foil thickness (μm)	20	20	20	20	20
Temper foil type	Hard	Hard	Hard	Hard	Hard
	(‘’H19”)	(‘’H19”)	(‘’H19”)	(‘’H19”)	(‘’H19”)
Tie & sealant layers coatweight	3.8	7.16	7.15	7.94	8.1
(lb/ream)
Embrittling agent in the	not	YES	YES	YES	YES
extrusion-coating composition	applicable
Mullen burst strength (psi)	26	19.8	21.2	22.5	21.7
MD tear strength (gram-force)	13.8	56.1	69.1	53.2	53.1

Additional embrittling agent incorporation in the sealant layer (or in a portion of it) for samples L, M and N leads to a very slight increase of Mullen burst strength as compared to sample K and no appreciable effect on tear strength. It is therefore reasonable to conclude that the embrittling effect of additional mineral incorporation in the composition of the sealant layer (or a portion of it) reaches a plateau but is not necessarily detrimental to the end-use blister packaging application and may be seen as another embodiment of the present invention for enhancing sealing properties.

FIGS. 6E-G show the graphs for three specimens of samples J, K and L with their peak and total energy provided in below Table 7. FIG. 6H is a comparison chart of these three samples.

TABLE 7
structure	Energy @ peak (lb · in)	Total energy (lb · in)
J	0.704	0.724
K	0.411	0.45
L	0.46	0.494

As with samples J, K and L, the data again shows the unexpected result that the innovative extrusion-coated lidding foil of the present invention is even easier to push-through than a conventional heat-seal lacquered lidding foil.

Additional testing was conducted to manufacture push-through blister packaging with sample I lidding foil and a PVC/PCTFE (Aclar®) blister film on an Ulhmann machine to evaluate its processability and its ease of pill release. Ten-cavity blister packs were manufactured at different sealing temperatures. FIG. 8 shows a photograph of the overall blister pack filled with smarties®.

Sealing performance of sample I was tested directly on the blister pack. FIG. 7 shows a graph of the sealing curve of innovative structure sample I on PCTFE (Aclar®)/PVC blister film. The data shows again excellent sealing ability of sample I on PCTFE (Aclar®) blister film. As illustrated in FIG. 7, the sealing temperature window is very broad. Optimum sealing temperature would be in the range of 160-180° C. as for COC-based blister films. In this processing window, sealing force is around 550-600 g/0.375″, which corresponds to approximately 3.25 lbf/in.

The sample blister packs were then submitted to leakage test consisting of immerging blister pack in pigmented water under 15″ Hg vacuum for 3 minutes. No leakage was observed at all for any sealing temperature varying from 120 to 190° C.

Release of a pill from its respective blister cavity was very good. Contrary to the heavier coatweight such as in sample H, no sealant layer elongation occurs during the releasing process of the pill with sample I. And, despite its heavier coatweight versus heat seal lacquer, ease of release with sample I is very comparable to heat seal lacquered lidding foil products as depicted in FIG. 9.

The present invention thus provides an innovative extrusion-coated lidding foil structure suitable for push-through blister packaging application. A further benefit is that the lidding foil of the present invention seals universally on most blister films including those made of PCTFE (Aclar®) or COC. Of course, this technological platform can be not only utilized for push-through blister packs, but can be also used for other packaging having lidding foils such as peel-push type and lock type requiring cutting.

While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but will have full scope defined by the language of the following claims.

Claims

1. A push-through blister packaging comprising:

a. a lidding foil comprising: i. an aluminum foil; and ii. one or more tie layer comprising ethylene acid copolymer extrusion coated on said aluminum foil and one or more sealant layer comprising modified ethylene acrylate copolymer extrusion coated on said tie layer, one or both of said tie and sealant layers having an embrittling agent mixed therein in an amount of about 5 to about 50% by weight;

wherein said lidding foil is characterized by a Mullen burst strength of about 50 kPa to about 250 kPa and a MD tear strength of about 0.25 N to about 1.0 N; and

b. a polymeric blister film,

wherein said lidding foil is heat sealed to said blister film to form said push-through blister packaging containing a substance which may be retrieved from said packaging by pushing the substance against and breaking said lidding foil.

2. The lidding foil of claim 1 wherein said embrittling agent is mixed in one or both of said tie and sealant layers in an amount of about 10 to about 30% by weight.

3. The lidding foil of claim 1 wherein said embrittling agent is a mineral.

4. The lidding foil of claim 3 wherein said embrittling agent is one or more of:

a. calcium carbonate;

b. calcium sulfate;

c. glass fiber;

d. kaolin;

e. mica;

f. silica

g. talc

h. wollastonite; and

i. a mixture of two or more of a-h.

5. The lidding foil of claim 1 wherein said embrittling agent is equally distributed within said sealant layer.

6. The lidding foil of claim 1 wherein said embrittling agent is non-equally distributed within said sealant layer, said embrittling agent being more concentrated within a portion of said sealant layer that is adjacent to said tie layer.

7. The lidding foil of claim 1 wherein said aluminum foil has a thickness of about 20 μm to about 25 μm.

8. The lidding foil of claim 1 wherein said aluminum foil is hard tempered (unannealed).

9. The lidding foil of claim 1 wherein said aluminum foil is soft tempered (annealed).

10. The lidding foil of claim 1 wherein said one or more tic layer is coated on said foil in an amount of about 3 to about 8 g/m2, and said one or more sealant layer is coated on said tie layer in an amount of about 6 to about 16 g/m2.

11. A push-through blister packaging comprising:

a. a lidding foil comprising: i. an aluminum foil; ii. one or more tie layer comprising ethylene acid copolymer extrusion coated on said aluminum foil and one or more sealant layer comprising modified ethylene acrylate copolymer extrusion coated on said tie layer, one or both of said tie and sealant layers having an embrittling agent mixed therein in an amount of about 5 to about 50% by weight;

wherein said tie layer is extrusion coated to a coatweight of about 3 to about 8 g/m2 and said sealant layer is extrusion coated to a coatweight of about 6 to about 16 g/m2.; and

b. a polymeric blister film,

wherein said lidding foil is heat sealed to said blister film to form said push-through blister packaging containing a substance which may be retrieved from said packaging by pushing the substance against and breaking said lidding foil.

12. The lidding foil of claim 11 wherein said lidding foil is characterized by a Mullen burst strength of about 50 kPa to about 250 kPa and a MD tear strength of about 0.25 N to about 1.0 N.

13. The lidding foil of claim 11 wherein said embrittling agent is mixed in one or both of said tie and sealant layers in an mount of about 10 to about 30% by weight.

14. The lidding foil of claim 11 wherein said embrittling agent is a mineral.

15. The lidding foil of claim 14 wherein said embrittling agent is one or more of:

a. calcium carbonate;

b. calcium sulfate;

c. glass fiber;

d. kaolin;

e. mica;

f. silica

g. talc

h. wollastonite; and

i. a mixture of two or more of a-h.

16. The lidding foil of claim 11 wherein said embrittling agent is equally distributed within said sealant layer.

17. The lidding foil of claim 11 wherein said embrittling agent is non-equally distributed within said sealant layer, said embrittling agent being more concentrated within a portion of said sealant layer that is adjacent to said tie layer.

18. The lidding foil of claim 11 wherein said aluminum foil has a thickness of about 20 μm to about 25 μm.

19. The lidding foil of claim 11 wherein said aluminum foil is hard tempered (i.e. unannealed).

20. The lidding foil of claim 11 wherein said aluminum foil is soft tempered (i.e. annealed).

21. A method of making a push-through blister packaging comprising the steps of:

a. making a lidding foil comprising the steps of: i. providing an extrusion coating machine; ii. providing a roll of aluminum foil on the extrusion coating machine; iii. extrusion coating a tie layer comprising ethylene acid copolymer having a coatweight of about 3 to about 8 g/m2 onto said aluminum foil; iv. extrusion coating a sealant layer comprising modified ethylene acrylate copolymer having a coatweight of about 6 to about 16 g/m2 onto said tie resin, one or both of said tie and sealant layers having an embrittling agent mixed therein in an amount of about 5 to about 50% by weight;

b. providing a polymeric blister film; and

c. sealing said lidding foil to said blister film containing a consumable substance and thereby forming said push-through blister packaging,

whereby said consumable substance may be retrieved from said blister packaging by pushing the consumable substance against and breaking said lidding foil open.

22. The method of claim 21 wherein said blister film comprises a polymer selected from the group consisting or PVC, PVDC, PS, HIPS, PCTFE, HDPE, LLDPE, LDPE, PP, PETG, SBC, COC, and combinations thereof.

23. The method of claim 22 wherein said blister film comprises polychlorotrifluoroethylene (PCTFE)

24. The method of claim 22 wherein said blister film comprises a cyclic olefin copolymer (COC).

25. The method of claim 21 further comprising the step of adding an embrittling agent mixed into one or both of said tie and sealant layers in an amount of about 5 to about 50% by weight.

26. The method of claim 25 wherein said embrittling agent is one or more of:

a. calcium carbonate;

b. calcium sulfate;

c. glass fiber;

d. kaolin;

e. mica;

f. silica

g. talc

h. wollastonite; and

i. a mixture of two or more of a-h.

27. The method of claim 25 wherein said embrittling agent is equally distributed within said sealant layer.

28. The method of claim 25 wherein said embrittling agent is non-equally distributed within said sealant layer, said embrittling agent being more concentrated within a portion of said sealant layer that is adjacent to said tie layer.

29. The method of claim 21 wherein said tie layer and said sealant layer are simultaneously co-extruded onto the aluminum foil.

30. The method of claim 21 wherein said tie layer and said sealant layer are sequentially extrusion-coated onto the aluminum foil.

31. The method of claim 21 wherein said aluminum foil has a thickness of about 20 μm to about 25 μm.