Abstract:
Multi-layer web and mechanical scoring process for forming lidding film for push through blister packages. The web is configured to resist the tensile forces encountered during manufacturing processes, including slitting, rewinding and heat sealing processes. A simplified web conversion process for creating mechanically scored lidding film for blister packages is provided at reduced investment and operational costs compared to prior art systems.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to lidding film for a blister package and more particularly to a multi-layer web and mechanical scoring process for forming such lidding film. 
       BACKGROUND OF THE INVENTION 
       [0002]    Blister packaging is known for receiving a product, e.g., in tablet or powder form, wherein each of the individual recesses or compartments of the base substrate can be provided with one product or the like and the packaging can then be sealed with a cover, e.g., in the form of a lidding film. The lidding film is sealed to the base substrate on plane surfaces provided between the recesses and along recesses outer edges of the base. As a result, the packaged material is sealed tight against the exterior environment and each individual product in the various compartments is mutually separated from one another. Packaging of this type is known as “push-through” blister packaging when the product in an individual recess can be removed by manually pressing on the base substrate (below the recess) and pushing the product through the lidding film. 
         [0003]    Blister packages are known having a base section made of plastic and a cover that includes an aluminum foil or an aluminum foil containing composite. When such packaging material is recycled, waste products from the different materials are obtained, some of which are still adhesively or weld bonded to one another. This poses difficulty in recycling of such packaging materials. 
         [0004]    One type of all-plastic blister package has a peelable (as opposed to push through) heat seal lid. The opening action (removing the peelable film) is generally considered less user friendly (e.g., more difficult for seniors) compared to the push-through lidding films. Also, the peelable heat seal formulations are generally of different materials than the base, which impacts recyclability. 
         [0005]    Another type of lidding film for blister packages, consisting of mineral filled thermoplastic polymer components, is described in U.S. Pat. Nos. 5,932,338 and 6,006,913. One lidding film of this type is commercially available from Etimex GMBH (http://www.etimex-pp.com/), under the “Purelay” brand. These films are devoid of metal foils, and possess frangible push-through characteristics. However, these mineral based films are known to be rigid or brittle, and difficult to process during slitting, rewinding and heat sealing. While the push-through force for a given package design can theoretically be tailored by altering the mineral filler content, the range for such adjustments is limited. At low mineral filler content an excessive push-through force is generally required to allow the contents to break through the film. At higher mineral filler content, the film may be too brittle to handle during the slitting, rewinding and heat sealing processes and may prematurely fracture during such handling and conversion processes. 
         [0006]    An all-polymer lidding film, devoid of metal foils typically requires scoring of the film to enable the push-through characteristic. Scoring can be performed either mechanically or by laser scoring. Laser scoring is significantly more expensive and typically costs multiple times per unit cost of a mechanical scoring process. 
         [0007]    Thus there is an ongoing need for materials and processes for making push through blister packaging that overcome the limitations of the prior art. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention provides a multi-layer web and mechanical scoring process for forming lidding film for push through blister packages. The web is configured to resist the tensile forces encountered during manufacturing processes, including slitting, rewinding and heat sealing processes. A simplified web conversion process for creating mechanically scored lidding film for blister packages is provided at reduced investment and operational costs compared to prior art systems. These and other advantages of the invention are described below with respect to various embodiments of the invention. 
         [0009]    In one embodiment of the present invention a multi-layer web is provided comprising: a multi-layer web of film windable on a core and adapted to be scored and slit to form scored lidding film for blister packages, the film being formed without a metal layer and including an inner seal layer and an outer layer comprising different thermoplastic polymer materials, 
         [0000]    the inner seal layer configured to form a thermal weld seal with a base substrate of a blister package, while the outer layer has a central scored area configured to rupture and release a product contained in a recess of a base substrate without breaking the weld seal,
 
the web being unwound from the core in a machine M direction transverse to a central longitudinal axis CL of the core on which the web is wound,
 
the central scored area extending between opposing first and second non-scored edge grip areas aligned in the M direction, the central scored area being sized to cover a plurality of recesses in a base substrate of a blister package without the need for registering the scored area with individual recesses,
 
the central scored area being formed by passing the web against a scoring roller to mechanically score fully or partially through the outer layer without scoring the inner seal layer,
 
the opposing first and second edge grip areas being non-scored and each of a minimum width configured to provide structural integrity to the web during winding and unwinding of the web onto or from the core, and
 
the non-scored edge grip areas being slit to form a scored lidding film for blister packages, wherein the central scored area comprises 75% to 99% of a total width of the slit lidding film and the non-scored edge grip areas together comprise 1% to 25% of the total width of the slit lidding film.
 
         [0010]    In another embodiment of the present invention, a multi-layer web is provided, wherein the central scored area comprises 80% to 99% of the total width of the slit lidding film. 
         [0011]    In another embodiment of the present invention a multi-layer web is provided, wherein the central scored area comprises 85% to 99% of the total width of the slit lidding film. 
         [0012]    In another embodiment of the present invention a multi-layer web is provided, wherein the scoring depth is between and 10% and 90% of the outer layer thickness. 
         [0013]    In another embodiment of the present invention a multi-layer web is provided, wherein the scoring depth is between 20% and 80% of the outer layer thickness. 
         [0014]    In another embodiment of the present invention a multi-layer web is provided, wherein the scoring depth is between 30% and 70% of the outer layer thickness. 
         [0015]    In another embodiment of the present invention a multi-layer web is provided, wherein the scoring comprises spaced apart arrow shaped scored formations aligned in the M direction. 
         [0016]    In another embodiment of the present invention a multi-layer web is provided, wherein the inner layer comprises 5% to 50% of the total lidding film thickness and the outer layer comprises 50% to 95% of the total lidding film thickness. 
         [0017]    In another embodiment of the present invention a multi-layer web is provided, wherein the inner layer comprises 5% to 40% of the total lidding film thickness and the outer layer comprises 60% to 95% of the total lidding film thickness. 
         [0018]    In another embodiment of the present invention a multi-layer web is provided, wherein the inner layer comprises 5% to 30% of the total lidding film thickness and the outer layer comprises 70% to 95% of the total lidding film thickness. 
         [0019]    In another embodiment of the present invention a multi-layer web is provided, wherein the lidding film is from 10 to 100 micron in thickness. 
         [0020]    In another embodiment of the present invention a multi-layer web is provided, wherein the lidding film is from 15 to 90 micron in thickness. 
         [0021]    In another embodiment of the present invention a multi-layer web is provided, wherein the lidding film is from 20 to 80 micron in thickness. 
         [0022]    In another embodiment of the present invention a multi-layer web is provided, wherein the scoring is uniformly distributed in the central area. 
         [0023]    In another embodiment of the present invention a multi-layer web is provided, wherein the scoring width is from 5 to 100 microns. 
         [0024]    In another embodiment of the present invention a lidding film is formed from the multi-layer web, combined with a thermoformed base substrate, the inner layer being weld sealed to the base substrate. 
         [0025]    In another embodiment of the present invention a lidding film and base substrate is cut to form a single blister package. 
         [0026]    In another embodiment of the present invention a lidding film and base substrate is made from materials compatible in recycling. 
         [0027]    In another embodiment of the present invention a multi-layer web is provided, wherein the multi-layer web is formed by co-extrusion of the inner seal layer and outer layer, extrusion coating of the inner seal layer onto the outer layer, or coating of the inner seal layer onto the outer layer via solvent, water or solventless coating processes or by wet or dry bond lamination of the inner seal layer to the outer layer. 
         [0028]    In another embodiment of the present invention a multi-layer web is provided, wherein the outer layer comprises polyester or polyolefin. 
         [0029]    In another embodiment of the present invention a multi-layer web is provided, wherein the outer layer comprises polyethylene terephthalate or polypropylene, including homopolymers, copolymers and blends thereof. 
         [0030]    In another embodiment of the present invention a multi-layer web is provided, wherein the inner layer comprises ethylene vinyl acetate copolymers, polyester, polyethylene, polypropylene, or acrylic, including homopolymers, copolymers and blends thereof. 
         [0031]    In another embodiment of the present invention a multi-layer web is provided, wherein the outer layer comprises a semi crystalline polyethylene terephthalate polymer or copolymer and the inner layer comprises an amorphous polyethylene terephthalate copolymer. 
         [0032]    In another embodiment of the present invention, a method of forming blister packages is provided comprising steps of: 
         [0000]    providing a master roll of the multi-layer web wound on a core, the master roll configured to form scored lidding film for multiple blister packages across a width W of the master roll transverse to the machine M direction,
 
unwinding a length of the master roll from the core in the M direction, passing the length of the master roll against a rotating scoring roller to mechanically score only the outer layer of the film, wherein multiple central scored areas are formed across the width of the master roll between non-scored areas,
 
slitting the master roll along the M direction in the non-scored areas between central scored areas to form multiple slit rolls of scored lidding film, each slit roll being wound onto a core unwinding a slit roll of lidding film from the core and attaching a series of base substrates along a length of the unwound slit roll to form a series of blister packages.
 
         [0033]    In another embodiment of the present invention, the method of forming blister packages, further comprises cutting individual blister packages from the series of blister packages. 
         [0034]    In another embodiment of the present invention an apparatus for forming blister packages is provided including a plurality of stations for in-line forming of a series of blister packages, the stations comprising: 
         [0000]    a base forming station for unwinding a roll of base film from a core in a machine direction M, followed by heating and thermoforming the base film to form a series of thermoformed base substrates with product recesses in the base film aligned along the M direction,
 
a filling station for dispensing product into the recesses of the series of base substrates,
 
a roll of scored lidding film on a core having a series of central scored areas between nonscored areas aligned along a machine direction M, a thermal sealing station, receiving the series of filled base substrates and a length of the scored lidding film unwound from the core in the M direction wherein the inner layer of the scored lidding film is sealed to each filled base substrate with the central scored area over the recesses of the substrate to form a series of sealed blister packages, and
 
a cutting station for cutting individual blister packages from the series.
 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0035]    The following figures illustrate various embodiments of the invention in more detail. 
           [0036]      FIG. 1  is a schematic view of a blister package assembly apparatus and process according to one embodiment of the invention; 
           [0037]      FIG. 2A  is an exploded perspective view of a base substrate and scored lidding film for forming a push through blister package according to one embodiment; 
           [0038]      FIG. 2B  is a cross sectional view of an assembled blister package from the components of  FIG. 2A , showing an individual product in each recess of the base substrate and the scored lidding film attached to the base substrate; 
           [0039]      FIG. 3  is a schematic view of a scoring, slitting, and rewinding conversion process according to one embodiment; 
           [0040]      FIG. 4  is a top plan view of a master web of the lidding film prior to and after scoring and slitting to create multiple slit rows of scored lidding film according to one embodiment; 
           [0041]      FIG. 5A  is top plan view of a section of one slit roll of scored lidding film having a central scored area with an array of scored arrow-shaped formations, extending between opposing first and second edge grip areas that are not scored, and  FIG. 5B  is a cross sectional view of the scored lidding film of  FIG. 5A ; 
           [0042]      FIG. 6A  is a perspective view of an assembled blister package of the type shown in  FIGS. 2A-2B , prior to cutting (removing) the unscored edge areas of the lidding film and substrate below, and 
           [0043]      FIG. 6B  is the final package (with the unscored edge areas removed) 
           [0044]      FIG. 7A  is a perspective view of a first pair of scoring rollers for forming a scored lidding film according to one embodiment, and  FIG. 7B  is a perspective view of a second pair of scoring rollers for forming three scored central areas (for three blister packages) across the width of the scoring rollers. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0045]      FIG. 1  illustrates one embodiment of a process for making a push through blister package, of the type illustrated in  FIGS. 2 and 5-6 , according to one embodiment of the invention. 
         [0046]    In  FIG. 1  there is schematically shown an inline forming and assembly apparatus for making a series of blister packages, A final blister package  10  is shown exiting the final cutting station  7 . The packages are formed by unwinding a base film (web  12 W) from a roll  48  on a core, forming and then filing recesses in the base film at stations  2 - 5  and then attaching a lidding film (web  14 W), unwound from roll  40  on a core, to the formed and filled base substrate film at station  6 , followed by cutting the final package at station  7 . The final cut package, comprising a base substrate  12  and a scored lidding film  14  is shown in  FIGS. 2A-2B  and  FIG. 6B .  FIG. 6A  shows the attached lidding film and base substrate prior to cutting. 
         [0047]    More specifically, beginning at the bottom left hand side of  FIG. 1 , a web  12 W of base film is unwound from roll  48  on a core and heated at pre-heat station  2 ; the base film is then thermoformed at forming station  3  to form recesses or hollows  16  in a series of base substrates (along machine direction M). The formed series of base substrates is then fed around rollers  9  to a filling station  5  where each recess  16  is filled with product  20 . The filled base film  12 W is then aligned with the web  14 W of lidding film, being unwound from roll  40  on a core, wherein the open end of each filled recess  16  is brought into alignment with the lidding film web  12 W at a thermal sealing station  6  (or similar station) for securing the lidding film to the base substrate. The lidding film is sealed to top planar areas  15  in between and around the recesses of the base to close each recess  16  and seal the product  20  therein (see  FIG. 2 ). The combined lidding film and base substrate is then cut and separated as desired at cutting station  7  to define individual blister packages  10  each having a desired number of products in the thermoformed recesses (e.g., as shown in  FIGS. 2A-2B and 6B ). Thus at station  7  there are edge trim areas of both the lidding film and underlying base substrate removed to form the final cut blister package  10 . 
         [0048]    The schematic of  FIG. 1  is provided to show the steps of an assembly process for a finished package according to one embodiment. The steps may be performed together or as part of separate operations. For example, the lidding film  14  may be printed, coated or die cut as part of one operation or separate operations. As described further in regard to  FIGS. 3-4 and 7 , each roll of lidding film  40  may be slit from a master web roll  30  that has been scored, and then slit into individual slit lidding film rolls (such as roll  40  in  FIG. 1 ). Other operations may be performed within the conversion process as known to the skilled person. 
         [0049]      FIG. 2A  illustrates, in exploded view, the components of a blister package  10  according to one embodiment. The package  10  includes a base substrate  12  and a scored lidding film  14 . The base  12  includes a plurality of recesses  16  that are arranged in an aligned pattern or array (e.g., rectangular array of rows and columns), with each recess  16  separated by a top planar sealing flange  15 . Each recess  16  retains product  20 . The blister package may be formed with any number of recesses, and each recess may hold an individual product or multiple products or a quantity of loose product, such as a powder or granular material. A series of separation lines (not shown) may be provided within the sealing flange  15 , between adjacent recesses, or group of multiple recesses, as desired, to permit separation of a portion of the base substrate from the remainder. 
         [0050]    The lidding film  14  is joined to the base substrate  12  of a package as shown in the cross sectional view of  FIG. 2B . The lidding film  14  is joined to the sealing flange  15  by a thermal weld seal, such that each individual recess  16  containing product  20  is covered and closed. A score pattern  22  of scored formations  23  ( FIGS. 2A-2B ) is formed only in an outer layer  18  of the multi-layer lidding film  14 . The score pattern  22  is provided for the initiation and propagation of the tear within the lidding film  14  overlying the recess  16 , upon application of a force against the base material forming the recess  16 , and the product  20  retained therein. In  FIG. 2B , the force is represented by the arrow F, with the resulting tear in the lidding film  14  occurring in an area of the scored lidding film  14  over the recess  16 , for releasing the previously sealed product  20 . As such, the lidding film is designed to tear above a recess, without breaking the weld seal between the lidding film and base substrate. 
         [0051]    As shown in  FIGS. 2, 5 and 6 , the score pattern  22  in the disclosed embodiment includes a plurality of individual scored formations  23 , separated by non-scored areas  25  surrounding each scored formation. Each scored formation in this example is shaped like an arrow head, including two generally straight lines  23 A and  23 B, joined at an apex  23 C ( FIG. 5A ). The apexes of the scored formations  23  all point in the machine direction M in this example (same as the lengthwise package direction L). The individual scored formations may be aligned in rows and columns, which are equidistantly spaced from one another, where each row is offset with respect to the adjacent rows. Other patterns (e.g., irregular spacing between scored formations) may be used. The shape of the scored formation  23  and the size, depth, width of scoring lines  23 A,  23 B and number of scored formations across the width of the blister package, and/or across the width of each recess, can be varied for purposes of customizing the package based on the materials used for the base film and lidding film, the contents (product enclosed), and the desired push-through force. 
         [0052]    As described in greater detail below, the scored formations  23  extend across all of the recesses  16  of the lidding film in the final package  10  such that no registration (alignment) of the scored formations of the lidding film and the recesses is required. This greatly simplifies production and assembly. 
         [0053]    As shown in cross section in  FIGS. 2B and 5B , the lidding film  14  is a multi-layer film comprising inner and outer film layers of different thermoplastic polymer materials, and without a metal layer. An inner seal layer  17  of the lidding film  14  forms a weld seal bond to the top surface (the sealing flange  15 ) of the base substrate  12 . The inner seal layer  17  is formed of a thermoplastic polymer material that softens at a lower melt temperature than the outer layer  18 , in order to bond the inner layer to the base substrate. The inner layer material for forming the weld (non-peelable) seal may comprise any of various known sealing materials based on, for example, ethylene vinyl acetate (EVA), polyester, polyolefin, acrylic, and others, including co-polymers, homopolymers and blends thereof. The outer layer  18  of the lidding film is a heat resistant layer, compared to the inner layer. The outer layer resists softening and maintains structural integrity for handling of the lidding film composite when the inner layer is softened for weld sealing to the base substrate. The outer layer may comprise any of various thermoplastic polymer materials, such as polyester, (e.g., polyethylene terephthalate PET), polyolefin (e.g., polypropylene or polyethylene), including homopolymers, co-polymers, and blends thereof. As used herein, the different thermoplastic polymer materials of the inner and outer film layers  17 ,  18  includes polymers of different chemistry or polymers of the same chemistry (thermoplastic family, such as polyester) but having different characteristics (e.g., crystalline, semi-crystalline, or amorphous) and/or comprising homopolymers, copolymers of blends thereof. In one example the outer layer comprises homopolymer polypropylene and the inner layer comprises polypropylene copolymer. In another example the outer layer comprises semi-crystalline polyethylene terephthatlate (PET) and the inner layer comprises an amorphous polyethylene terephthalate copolymer. 
         [0054]    Also, the lidding film materials and base substrate materials are preferably compatible in commercial recycling streams. For example, both the base substrate and lidding film materials may be from the same thermoplastic family (e.g., polypropylene, or polyester). Materials that are compatible in recycling means materials of the same thermoplastic family that are melt compatible. 
         [0055]      FIG. 3  illustrates a schematic view of one apparatus and process for scoring and slitting a master web  30  of lidding film being unwound from a master roll unwound unit  50  in order to generate multiple individual scored and slit rolls of lidding film.  FIG. 4  illustrates a length of the master web  30  during the scoring and slitting process illustrated in  FIG. 3 . The master web of lidding film  30  has an initial width W 1  in a direction transverse T to the machine direction M (the machine direction being the direction in which the web  30  is advanced through the scoring and slitting apparatus). In this example, the master web  30  (shown moving to the left in  FIGS. 3-4 ) will be first scored by scoring unit  52  ( FIG. 3 .). The scored web is then slit by slitting station  54  ( FIG. 3 ). The result is six individual scored and slit rolls  14 A-F of lidding film. Each scored and slit roll is then rewound onto a separate core at rewind station  56  (only two of six cores are shown in cross section). 
         [0056]    The film from the master web  30  after passing through the scoring and slitting stations  52 ,  54  includes non-scored outermost opposing edge trim areas  31 ,  32  ( FIG. 4 ) along the length of the roll (in the M direction), and between those non-scored edges  31 , 32 , six (6) equally sized individual lidding films  14 A,  14 B,  14 C,  14 D,  14 E,  14 F. Each individual lidding film  14 A-F of width W 2  has a central scored area  40  of width B for forming the scored lidding film of a blister package, and opposing non-scored edge grip areas  41 ,  42 , each of width A. The edge grip areas  41 ,  42  extend along the longitudinal length L (same as machine direction M) of the film from the master web  30  that has been scored and split into individual rolls  14 . 
         [0057]      FIG. 5A  is a top view of a length of one slit roll of lidding film (e.g.  14 C), of width A+B+A, including central scored area  40  of width B, and two opposing non-scored edge grip areas  41 ,  42  each of width A.  FIG. 5B  shows a cross section of the slit roll, including outer layer  18  of thickness t 1  and inner seal layer  17  of thickness t 2 . The total film thickness t 3  is the sum of t 1 +t 2 . The scoring depth (SD) of the scored formations is also shown, extending only partially through the thickness t 1  of the outer layer  18 . The inner seal layer  17  is not scored. 
         [0058]    As shown in  FIG. 3 , the master web  30  of lidding film is unrolled from a master roll unwind unit  50 , and fed to a scoring station  52 , where the web  30  is fed between two opposing rollers  53 ,  55 , one roller  53  having formed thereon scoring surfaces  57  (see  FIGS. 7A and 7B ) for scoring the outer layer  18  of the web film  30  to form the scored central area  40  of width B, between two non-scored areas  41 ,  42  each of width A. After scoring, the scored web  30 A advances in line to a slitting station  54  where the scored web  30 A is slit into multiple slit rolls  30 B, in this example into six individual slit rolls  14 A-F, each slit roll  14  then being wound on a separate core as a separate roll  58 ,  59  at rewind station  56 . The outermost non-scored trim edges  31 ,  32  of the master roll  30  are removed during the slitting process (at station  54 ), such that each of the six individual film rolls has the same width W 2 , including the central scored area  40  of width B and two opposing non-scored edges  41 ,  42  each of width A. The non-scored edges  41 ,  42  of each individual slit roll  30 B provide structural integrity to prevent tearing of the rolls during the scoring, slitting, and winding/rewinding steps. 
         [0059]    The scored formations  23  are preferably formed on a continuous basis by a rotary die cut roller, such as scoring roller  53  shown in  FIG. 7A . The scoring roller may have only a single width B of scoring to form lidding film for a single blister package  10 , of width A+B+A. Alternatively as shown in  FIG. 7B , the scoring roller may include multiple scoring areas, each of width B, for simultaneously forming multiple scored lidding films that are later slit to form multiple slit rolls of scored lidding film. 
         [0060]    In the example of  FIG. 3  showing a scoring station  52 , the film is passed through the nip of a pair of opposing rollers  53 ,  55 , one of which is a scoring roller  53 . The opposing non-scoring roller  55  supports the web film as it passes against the scoring roller  53 . Thus, as used herein passing against a scoring roller includes the use of one or multiple rollers. 
         [0061]    After rewinding, each individual scored lidding film roll  58 ,  59 , can be unwound from its core and aligned with a formed base substrate (filled with product) as shown in  FIG. 1 , for weld sealing the lidding film to the substrate to form the filled blister packages. In the present embodiment, the individual slit rolls form narrow rolls  14 A- 14 F, each having a width adapted for a blister package. The slit rolls are then separately sealed to a series of base substrates during the inline forming and sealing operations, with the individual (or multiple) packages  10  then being cut from the series of sealed base substrates and lidding film formed inline in the machine direction. The non-scored edge areas  41 ,  42  of the lidding film and underlying base substrate are removed during the final die cutting of the individual blister packages as shown in the final step (cutting station  7 ) of  FIG. 1 . 
         [0062]    In alternative embodiments, a scored and slit roll of lidding film may be wide enough to form multiple packages across the width of the lidding film. The drawings and specification have set forth a number of embodiments of the invention, which are intended to be descriptive only and not for the purpose of limitation. Variations will be apparent to those skilled in the art and are intended to be included in the scope of the present invention.