WO2016071685A1

WO2016071685A1 - Packaging system and process for sealing a packaging system

Info

Publication number: WO2016071685A1
Application number: PCT/GB2015/053308
Authority: WO
Inventors: Alan Davey; David Parker
Original assignee: Linpac Packaging Limited
Priority date: 2014-11-03
Filing date: 2015-11-03
Publication date: 2016-05-12
Also published as: GB201419532D0

Abstract

The present invention relates to a packaging system comprising a thermoformed blister shell (2) and a lidding sheet (3), wherein the blister shell (2) consists essentially of polyethylene terephthalate (PET) and the lidding sheet (3) comprises a layer of glycol-modified polyethylene terephthalate (PET-G) and/or a layer amorphous polyethylene terephthalate (APET). The present invention also relates to a process for sealing the packaging system.

Description

PACKAGING SYSTEM AND PROCESS FOR SEALING A PACKAGING SYSTEM

The present invention relates to a packaging system. More particularly, the invention relates to a blister packaging system comprising a polyethylene terephthalate (PET) blister shell and a glycol-modified polyethylene terephthalate (PET-G) and/or amorphous polyethylene terephthalate (APET) backing.

Blister packs are a popular packaging means for consumer packaged goods (CPG) such as toiletries and cosmetics, housekeeping products, toys, batteries and the like. Other industries, for instance the pharmaceutical industry, have adopted aluminium-covered blister packs to protect tablets and other contamination-sensitive products.

Conventional blister packaging systems for consumer goods comprise a molded plastics pack shaped so as to receive the product to be packaged. The pack is affixed to a cardboard or paperboard backing to protect the product. A transparent pack is favoured for display purposes. The cardboard backing is inexpensive and provides a support for product information to be printed thereon. However, the cardboard backing suffers the disadvantages of being sensitive to moisture and damage. In addition, because the backing is often glued directly onto the blister pack, the seal thereby obtained is weak and the backing can be accidentally peeled off.

For more robustness, the cardboard backing can be replaced with a lid made of a plastics material. However, efficient plastics-to-plastics seal is difficult to achieve and control. Thus, instead of using an adhesive, the rim of the blister pack and the plastics lid are fused with each other by application of heat (for example by ultrasonic welding) to become inseparable. This produces a secure, tamper-proof seal. However, these blister packs are extremely difficult, if not impossible, to open without strong scissors or a sharp knife since the edges of the packaging are fused. The other disadvantage of this type of packaging is that high temperatures are required to melt and fuse the materials of the blister pack and the lid, so that there is a risk that the whole packaging becomes deformed. Also, higher sealing temperatures mean higher energy consumption and thus, higher manufacturing costs. Lower seal temperatures result in partial or incomplete sealing of the pack with the lid and in order to improve the seal, longer seal times are required, which in turn result in lower productivity. It is an object of the invention to at least alleviate the above-mentioned disadvantages.

According to a first aspect of the invention, there is provided a packaging system comprising a blister shell and a lidding sheet for sealing thereon, wherein the shell consists essentially of polyethylene terephthalate (PET) and the lidding sheet comprises a layer of glycol- modified polyethylene terephthalate (PET-G) and/or a layer amorphous polyethylene terephthalate (APET). The packaging system provides a safe alternative to fused blister packs, whilst providing improved protection of the packaged product when compared with conventional cardboard covered blisters. This is primarily due to the specific materials chosen for the lidding sheet and the blister shell as will be explained in further details below. Plastics-to-plastics sealing is notoriously difficult to achieve and control. However, the inventors have developed a packaging system in which the lid can be easily removed from the blister shell to access the packaged product, without compromising the sealing efficiency, the condition of the packaged product or the safety of the user.

In addition, the packaging system of the present invention was found to be particularly advantageous when used in combination with the process as described in the Applicant's own publication WO2011/083342, in which adhesive is applied only on the flange of the container so that a lidding film can be sealed on the flange. The materials selected for the present invention in combination with this process, result in a packaging with improved peelability and resealability, and is particularly useful for "easy open" applications. The consistent peeling and resealing properties make the invention an ideal for packaging multiple items such as laundry tablets, razor blades, where the user opens and closes the packaging repeatedly.

Preferably, the lidding sheet comprises a first outer surface layer of PET-G and a second outer surface layer of PET-G and a third inner layer of APET between the first and second surface layers. Alternatively, the lidding sheet consists essentially of PET-G or of APET. PET-G is a thermoplastic polymer resulting from the copolymerisation of polyethylene terephthalate and ethylene glycol. The glycol in PET-G imparts high impact and chemical resistance characteristics to the lidding sheet and renders it generally less breakable. Another advantage in using a PET-G layer is that its surface is well suited for printing. Thus product information can be directly printed onto the lidding sheet without the need for an additional cardboard or paper insert or more complex printing techniques such as corona plasma treatment.

APET (or "aPET") is amorphous polyethylene terephthalate. APET also has excellent impact resistance and mechanical stability. It is widely used in the packaging industry for its good transparency and both PET-G and APET are suitable and approved for food packaging.

A PET-G/APET/PET-G multilayer structure is known as a "GAG" structure. The GAG sheet may comprise an inner surface layer of PET-G facing the packaged product and blister shell, an intermediary layer of APET and an outer surface layer of PET-G facing away from the packaged product and blister shell. GAG sheets are easy to handle and combine the qualities of both PET-G and APET. The added advantage is that APET is relatively inexpensive and provides a cost-effective alternative to PET-G-only lids.

Specifically within the context of this invention, it has been observed that GAG sheets were particularly well suited for the present application, in particular in terms of thermal and heat transfer properties. As will be explained in further details below, the lidding sheet is positioned onto a sealing surface of the blister shell and heat is conducted through the lidding sheet to soften an adhesive composition located between the lidding sheet and the sealing surface of the blister shell.

Preferably, the thickness of the lidding sheet is from 100 micrometers to 500 micrometers, preferably from 250 micrometers to 350 micrometers. This thickness range is advantageous in that it achieves an optimum balance between robustness, flexibility and heat transfer. Preferably, the shell forms a cavity for comprising one or more objects to be packaged. The blister shell is the container part of the packaging system. Preferably, the shell is a sheet of PET that has been thermoformed or cold-formed so as to comprise a cavity or pocket to receive a product to be packaged therein. The dimensions and/or shape of the cavity may be adjusted to match the contour of the product to be packaged so that the product is tightly and safely packaged. Preferably, the shell comprises a sealing surface for sealing the lidding sheet thereon. The sealing surface is the surface of the shell onto which the lidding sheet will be sealed. The sealing surface is preferably a substantially flat portion of the blister shell. In a preferred embodiment, the blister shell comprises a cavity for receiving the product to be packaged and a substantially flat sealing surface surrounding the mouth of the cavity.

It is also envisaged, within the context of the invention, that the packaging system comprises two blister shells, in other words, the lidding sheet is another blister shell. For example, the present invention may be applied to partly or wholly complementary male and female blisters.

In an embodiment, the blister shell comprises a peripheral flange surrounding the mouth of the blister shell and the sealing surface is located on the peripheral flange. Preferably, the adhesive is applied onto the sealing surface by means of one or more rollers to ensure the application of an even layer of adhesive. The use of rollers is also preferred to apply the adhesive onto the sealing surface only, i.e. not in the cavity of the blister shell and/or to the surface of the lidding film.

In another embodiment, the blister shell comprises a peripheral platform offset from the mouth of the shell and the sealing surface is located on the peripheral platform. The blister shell may or may not comprise an additional peripheral flange. For example, the blister shell may be a skirted blister shell (i.e. with a peripheral flange) with a peripheral platform offset from the mouth and therefore flange. A preferred offset distance is from 3 to 10 mm. Preferably, the adhesive is applied using a nozzle, such as an automated nozzle system, programmed to apply the adhesive on the sealing surface. Preferably, the adhesive is applied as one or more drops or beads of adhesive or as one or more lines of adhesive. The blister shell consists essentially of PET, preferably amorphous PET, recycled PET (rPET) or recyclable PET. A preferred embodiment is a packaging system in which both the blister shell and the lidding sheet are made of recycled or recyclable PET. The advantages of PET for food packaging applications are well known. However, despite being widely used, the industry still experiences difficulties in achieving efficient adhesion of PET to other lidding materials. The specific materials used in the present invention and the inventive sealing process overcome these difficulties.

Preferably, the sealing surface of the shell comprises an adhesive composition, preferably holt-melt adhesive. More preferably, only the sealing surface of the shell comprises an adhesive composition, i.e. the remainder of the shell and the lidding sheet are both free of adhesive composition. This improves the recyclability of the product and prevents the packaged product from being contaminated with adhesive. Preferably the adhesive composition is applied as a layer of adhesive composition with a thickness of from 20μιη to ΙΟΟμιη. This range has been found to be the best compromise between efficient adhesion and setting time during the sealing process.

Preferably, the adhesive composition has a softening temperature which is lower than the softening temperature of the lidding sheet or of material of the outer surface layer of the lidding sheet. Thus, an efficient seal can be achieved without affecting the integrity of the lidding sheet. Preferably, the adhesive composition has a softening temperature of from 80°C to 120°C, more preferably from 95°C to 105°C, most preferably 100°C. In another embodiment, the adhesive composition is a composition which can be cold sealed, with or without the application of pressure.

In a preferred embodiment, the blister shell comprises one or more denesting features. Preferably, the blister shell comprises a denesting platform offset from the sealing surface, said denesting platform comprising one or more denesting recesses. Conventional containers are partly or fully coated with adhesive. Adhesive compositions have low tack, which increases as temperature increases. Therefore, when the flanges are coated with adhesive, the containers will have a tendency to stick to each other. It is therefore advantageous to have denesting features offset from the flange, in an area devoid of adhesive. A preferred offset distance is around 1mm. These features are particularly advantageous when the blister shell are pre-formed, and may be nested for transport and storage.

According to a second aspect of the invention, there is provided a process for sealing a packaging system as described above. The process comprises the steps of:

(a) providing a blister shell consisting essentially of PET, the shell comprising a surface for sealing a lidding sheet thereon;

(b) applying an adhesive composition onto the sealing surface;

(c) applying a lidding sheet comprising a layer of PET-G and/or a layer of APET onto the sealing surface;

(d) applying heat to seal the lidding sheet onto the sealing surface of the shell. Preferably, the process further comprises the step of obtaining a shell comprising a cavity and/or a sealing surface through thermoforming or cold forming. Preferably, the blister shell comprises a cavity for receiving the product to be packaged and a sealing surface surrounding the mouth of the cavity. In step (b), the adhesive composition may be applied onto the sealing surface by means of rollers to obtain a homogeneous layer of adhesive across the sealing surface or by other automated means. Alternatively, one or more drops of adhesive composition may be deposited onto the sealing surface. In this embodiment, the adhesive composition may be spread across the sealing surface during the sealing step (d) through application of pressure. Preferably, the adhesive composition is applied onto the sealing surface only.

The sealing surface may be a peripheral flange formed around the mouth of the blister shell. When the flange is located at the upmost position of the blister, then the adhesive can be applied for example as a layer using one or more rollers. In the case of a skirted blister, the sealing surface may be offset from the mouth of the blister shell, in which case, the adhesive is preferably applied as drops, beads or lines of adhesive. Preferably, the sealing surface is provided with an area devoid of adhesive so as to facilitate the initiation of the opening/peeling of the lid. This may be an area devoid of adhesive, for example an adhesive-free recess in the sealing surface. Preferably, the lidding sheet or the material of the outer surface layer of the lidding sheet has a melting temperature greater than the sealing temperature in step (d). Preferably, the lidding sheet or the material of the outer surface layer of the lidding sheet has a melting temperature greater than the softening temperature of the adhesive composition.

Preferably, the sealing temperature (i.e. the temperature of the sealing bar or heating means) is from 130°C to 200°C, more preferably from 170°C to 190°C. The sealing temperature is chosen so as to activate the adhesive composition without damaging the lidding sheet and/or the blister. It has been observed that the lidding sheet used in the present invention has excellent heat transfer characteristics thereby allowing the use of lower sealing temperatures to activate the adhesive. In prior sealing processes, low sealing temperatures are undesirable because longer sealing times would be required to compensate for the low temperatures so that the productivity (i.e. the number of blister packs sealed per unit time) would be decreased. This is particularly relevant in the present invention in which the blister shell is made of PET. PET has insulating properties; therefore the packaging must be heated fast enough to ensure suitable seal without melting or distorting the PET blister shell.

Heat and/or pressure is applied onto the lidding sheet by means of a sealing bar or other sealing surface. However, other heating processes are envisaged, including processes based on radiofrequency and RF welding technologies. In the present invention, the sealing time in step (d) is preferably from 0.1 second to 3.0 seconds. This is the time period during which heat is applied to seal the lidding sheet onto the sealing surface.

Preferably, the sealing pressure is from 1 bar to 6 bar. Within this pressure range, the integrity of the packaging system and in particular of the blister shell is preserved. The use of a blister shell support may be envisaged at higher sealing pressures. Conventional sealing pressures range from 2bar to 12 bar with a sealing time of between 0.5 to 5 seconds. As explained above, the process according to the present invention allows the use of lower sealing temperatures to activate the adhesive, without compromising the sealing time. It has also been found that lower sealing pressures are required so that the risk of deforming the blister shell during the sealing step is minimised. In another embodiment, the adhesive composition is applied and cold sealed. This step may be carried out with or without the application of pressure.

The packaging system according to the present invention may be used in MAP and/or CAP applications (i.e. modified atmosphere or controlled atmosphere packaging) and the process preferably comprises the step of modifying and/or controlling the atmosphere of the sealed system. The sealing process described herein is particularly advantageous when used in combination with MAP/CAP, as it results in higher burst pressures and improved sealing with lower sealing temperatures and shorter sealing times than conventional sealing processes. The blister shell may be pre-formed, and subsequently filled with one or more products, then closed by means of a lidding sheet or blister shell. However, the packaging system may be produced through a continuous process, such as a form-fill-seal process. The process may be a continuous process, including a continuous blister shell supply and/or a continuous application of adhesive. However, the process may also be applied to a batch process, for example where a robot is used to apply the adhesive on the sealing surface.

Numerical ranges provided within the context of this invention include the lowest and highest values of the range. The invention will be further described with reference to the drawings and figures, in which

Figure 1 is a schematic representation of a cross section of a first packaging system according to the present invention, in an unsealed configuration and a sealed configuration;

Figure 2 is a schematic representation of a cross section of a second packaging system according to the present invention, in an unsealed configuration and a sealed configuration;

Figure 3 is a schematic representation a cross section of a third packaging system according to the present invention, in an unsealed configuration and a sealed configuration; Figure 4 is a schematic representation a cross section of a fourth packaging system according to the present invention, in an unsealed configuration and a sealed configuration;

Figure 5 is a schematic representation a cross section of a fifth packaging system according to the present invention, in an unsealed configuration and a sealed configuration;

Figure 6 is a schematic representation a cross section of a sixth packaging system according to the present invention, in an unsealed configuration and a sealed configuration.

Referring to figure 1, there is illustrated a packaging system 1 comprising a blister shell 2 and a lidding sheet 3 for sealing to the blister shell 2, wherein the shell 2 consists essentially of polyethylene terephthalate (PET) and the lidding sheet 3 comprises a layer of glycol-modified polyethylene terephthalate (PET-G) and/or a layer amorphous polyethylene terephthalate (APET).

The blister shell 2 comprises a cavity 2a for receiving the product to be packaged (not shown) and a sealing surface 2b. The blister shell 2 is made of PET and is transparent for display purposes, although coloured or opaque shells are also envisaged. The cavity 2a has a contour, shape and dimensions suitable for receiving the product. The cavity 2a is molded from PET and comprises a mouth or opening through which the product is introduced. The blister shell 2 also comprises a sealing surface 2b onto which an adhesive composition

4 is applied. The sealing surface 2b surrounds the mouth of the cavity 2a so that once the lidding sheet 3 is sealed onto the sealing surface 2b, the cavity 2a is closed and sealed. Since the lidding sheet 3 is substantially flat, the sealing surface 2b is also substantially flat for optimum seal. The adhesive composition 4 is a hot melt polymer-based adhesive with a softening temperature between 80°C to 120°C, preferably 95°C to 105°C, most preferably 100°C. The adhesive composition 4 is applied onto the sealing surface 2b of the blister shell 2 only so that the lidding sheet and the remainder of the blister shell is devoid of adhesive. Preferred adhesives for use in the present invention are listed in the Table below: Application Lock seal Easy peel Peel / reclose

Polyolefin based Copolymer based Thermoplastic rubber

Specific Description adhesive to provide a adhesive to provide a based adhesive to permanent bond removable bond provide a re-closable bond

Softening range (°C) 80 - 120 81 - 121 80 - 111

Preferred softening range 95 - 105 96 - 106 86 - 96 (°C)

Most preferred softening 100 101 91 range (°C)

Adhesive grade BAM2041* BAM2291* BAM2301*

Supplied by Beardow & Adams (Adhesives) Ltd

The lidding sheet 3 comprises an outer surface layer made of PET-G, an intermediate layer 3b made of APET and an inner surface layer made of PET-G. The inner surface layer is the layer facing the blister shell 2 and its sealing surface 2b. The outer surface layer is the layer facing away from the blister shell 2 and its sealing surface 2b. The lidding sheet 3 has a total thickness of 100 micrometers to 500 micrometers, preferably 250 micrometers to 350 micrometers. In use, a blister shell 2 comprising cavity 2a and sealing surface 2b is thermoformed from a

PET sheet or PET roll by application. An adhesive composition 4 with a softening temperature of from 80°C to 120°C is applied onto the sealing surface 2b of the blister shell 2. Rollers can accurately apply the adhesive composition as a homogeneous layer across the sealing surface 2b but not on the surface of the cavity 2a.

The lidding sheet 3 is positioned with its PET-G inner surface layer facing the sealing surface 2b of the blister shell 2. Heat and pressure are applied onto the PET-G outer surface layer of the lidding sheet 3 by means of a sealing machine or sealing bar. The GAG lidding sheet 3 efficiently conduct heats so that the adhesive composition 4 reaches its softening point. The sealing temperature (i.e. the applied temperature) range is between 130°C to 200°C. The sealing pressure range is between 1 bar and 6 bar. The sealing time range is between 0.1 second to 3 seconds.

The sealing temperature is higher than the softening point of the adhesive composition 4, but lower than the softening point of the material of the outer surface layer of the lidding sheet 3 or of the lidding sheet 3. Owing to the heat transfer capacity of the lidding sheet 3, the temperature of the sealing bar or machine can be adjusted to a value closer to that of the softening temperature of the adhesive composition 4 so that the sealing process is energy efficient. This also means that the risk of deforming the lidding sheet 3 and blister shell 2 is minimised. The sealing temperature can be lowered without increasing the sealing time so that productivity is maintained or increased.

Where the seal temperature is close to the softening temperature of the material of the outer surface layer, then the outer surface layer has a tendency to become sticky and stick to the sealing bar. To prevent the outer surface layer from sticking to the seal bar, the outer surface layer of the lidding sheet can be heat treated and/or lacquered. Alternatively, a protective sheet with minimal heat resistance can be placed between the seal bar and the outer surface layer during the sealing step and removed after sealing.

The adhesive composition 4 cools down and sets so as to seal the lidding sheet 3 onto the sealing surface 2b of the blister shell 2.

Figure 2 shows a second embodiment of the present invention, in which the blister shell is a so-called skirted blister shell. The sealing surface 2b is offset from the upmost part or flange of the blister shell, i.e. offset from the mouth of cavity 2a. As with the first embodiment, the adhesive 4 is applied onto the sealing surface 2b. In the case of a skirted blister with an offset sealing surface 2b, it is preferred to apply the adhesive 4 as drops or beads of adhesive.

Figure 3 shows a third embodiment of the present invention, in which the packaging system comprises two partly complementary blister shells 2,5. The lidding sheet 3 has been replaced with a blister shell according to the present invention or is a lidding sheet according to the present invention shaped as a blister shell. In this embodiment, the adhesive 4 is applied on the sealing surface 5 a of the second blister shell 5.

Figure 4 shows a fourth embodiment of the present invention, similar to that shown in figure 3. In this embodiment, the adhesive is applied on the sealing surface 2b of the first blister shell 2. Figure 5 shows a fifth embodiment of the present invention, in which the packaging system comprises two partly complementary female and male blister shells 2,5. In this embodiment, the adhesive may be applied on the sealing surface 2b of the female blister shell 2 and/or the sealing surface 5a of the male blister shell 5.

Figure 6 shows a sixth embodiment of the present invention, similar to that shown in figure 5. In this embodiment, the two blister shells 2,5 are of similar shape and dimensions and the adhesive may be applied on the sealing surface 2b of the first blister shell 2 and/or the sealing surface 5a of the second blister shell 5.

EXAMPLES

BAM2041 (Beardow Adams), softening temperature 100°C Thus, from the above description, it can be seen that the present invention provides clear improvements on commercially available blister packaging with a cardboard backing and fused blister packaging such as clamshell packaging. In the present invention, the packaged product is better protected and the lid is easily peeled off. There is no need for scissors or a knife and therefore no risk of injury. The packaging system according to the present invention can be easily manufactured and sealed. The inventive sealing process results in improved productivity and product quality.

Claims

1. A packaging system comprising a blister shell and a lidding sheet for sealing thereon, wherein the shell consists essentially of polyethylene terephthalate (PET) and the lidding sheet comprises a layer of glycol-modified polyethylene terephthalate (PET-G) and/or a layer amorphous polyethylene terephthalate (APET).

2. The packaging system according to claim 1, wherein the blister shell comprises an adhesive composition applied solely on a sealing surface of the blister shell.

3. The packaging system according to claim 1 or 2, wherein the lidding sheet comprises a first outer surface layer of PET-G and a second outer surface layer of PET-G and a third inner layer of APET between the first and second surface layers.

4. The packaging system according to claim 1 or 2, wherein the lidding sheet consists essentially of PET-G.

5. The packaging system according to claim 1 or 2, wherein the lidding sheet consists essentially of APET.

6. The packaging system according to any preceding claim, wherein the thickness of the lidding sheet is from 100 micrometers to 500 micrometers, preferably from 250 micrometers to 350 micrometers.

7. The packaging system according to any preceding claim, wherein the shell consists essentially of amorphous PET.

8. The packaging system according to any preceding claim, wherein, when assembled, the shell and the lidding sheet form an inner cavity for comprising one or more objects to be packaged.

9. The packaging system according to any preceding claim, wherein the shell comprises a sealing surface for sealing the lidding sheet thereon.

10. The packaging system according to claim 9, wherein the shell comprises a peripheral flange surrounding the mouth of the shell and the sealing surface is located on the peripheral flange.

11. The process according to claim 9, wherein the shell comprises a peripheral platform offset from the mouth of the shell and the sealing surface is located on the peripheral platform.

12. The packaging system according to any one of claims 9 to 11, wherein the sealing surface of the shell comprises an adhesive composition.

13. The packaging system according to claim 12, wherein only the sealing surface of the shell comprises an adhesive composition.

14. The packaging system according to claim 12 or 13, wherein the adhesive composition has a softening temperature of from 80°C to 120°C.

15. The packaging system according to any preceding claim, wherein the blister shell comprises a denesting platform offset from the sealing surface, said denesting platform comprising one or more denesting recesses.

16. A process for sealing a packaging system according to any preceding claim comprising the steps of:

(b) applying an adhesive composition onto the sealing surface only;

(d) applying heat to seal the lidding sheet onto the sealing surface of the shell.

17. The process according to claim 16, wherein the blister shell comprises a peripheral flange surrounding the mouth of the blister shell and the adhesive composition is applied onto the peripheral flange only.

18. The process according to claim 16, wherein the blister shell comprises a peripheral platform offset from the mouth of the blister shell and the adhesive composition is applied onto the peripheral platform only.

19. The process according to any one of claims 16 to 18 wherein the adhesive is applied as a layer, as drops or beads, or as one or more lines of adhesive.

20. The process according to claim 19, wherein a layer of adhesive is applied with a thickness of from 20μιη to ΙΟΟμιη.

21. The process according to any one of claims 16 to 20, wherein the sealing temperature is from 130°C to 200°C.

22. The process according to any one of claims 16 to 21, wherein the sealing time is from 0.1 second to 3.0 seconds.

23. The process according to any one of claims 16 to 22, wherein the sealing pressure is from 1 bar to 6 bar.

24. The process according to any one of claims 16 to 23, wherein the shell is obtained through thermoforming or cold forming.

25. The process according to any one of claims 16 to 23 comprising the step of modifying and/or controlling the atmosphere within the sealed packaging system.

26. A packaging system as described herein with reference to the accompanying drawings and/or examples.

27. A sealing process as described herein with reference to the accompanying drawings and/or examples.