CZ28307U1 - Package - Google Patents

Abstract

The present application relates to a sealable container comprising a base and a continuous side wall extending substantially perpendicular to the base with a peripheral flange formed along the upper, in use, edge of the continuous side wall, wherein a layer of adhesive is located on an upper, in use, surface of the peripheral flange such that a lidding film may be sealed to the peripheral flange to create a sealed space between the base, continuous side wall and lidding film. The present application further relates to a process for making said sealed container.

Description

Technical field

The present invention relates to packaging suitable for use in the packaging, storage, transport and / or offering of a product, such as a fresh food product or a medicament, and to a method for producing such packaging.

BACKGROUND OF THE INVENTION

It is known to use plastic containers for packaging, storing, transporting and offering fresh food. These packages may be sealed with a cover film to protect the food in the package against the environment. In addition, the atmosphere in the package may be modified to improve the shelf life and / or appearance of the fresh food in the package.

Transparent containers can be made of polyethylene terephthalate (PET). The use of PET provides a highly clear product that allows the user to easily see the contents of the packaging (recycled PET can also be used, providing environmental and sometimes economic benefits). However, as explained above, it is desirable to seal the transparent wrapper with a cover sheet, but it is difficult to attach the cover sheet to PET and the seal of the cover sheet is particularly susceptible to contamination.

A known solution to the problem described above is to provide PET packages coated with a polyethylene (PE) layer and an intermediate layer of ethylene vinyl acetate (EVA). PE provides a surface to which the cover film adheres readily, thereby facilitating the formation of sealed packages. Generally, PET is substantially thicker than the EVA and PE layers, and the PET / EVA / PE product can be made by coextrusion, lamination, extrusion coating or any other suitable technique. Although the PET / EVA / PE product provides a package with high clarity. EVA and PE have different refractive indices than PET and thus the PET / EVA / PE product has a somewhat lower clarity than the uncoated PET product. In addition, the use of EVA and PE causes increased costs for two reasons; firstly, because the laminate or co-extruded layer is expensive in itself, and secondly, because, as described below, the internal recycling of the production and "skeletal waste" trays is negatively affected by the presence of EVA and PE in otherwise pure PET material. Thus, compared to a PET product, the PET / EVA / PE product has less clarity, is more expensive, less recyclable, and less user friendly at the production facility.

Therefore, there are also environmental consequences of using a PET / EVA / PE product. During the production of PET / EVA / PE packages by thermoforming, a plurality of packages are formed from large and often continuous sheets of PET / EVA / PE material, and individual packages are cut from these large sheets. Waste material is produced from those parts of large sheets that are not used in individual packages. This waste material, known as 'skeletal waste', contains a mixture of PET, EVA and PE, which, when recycled, produces a cloudy product that cannot be used to produce transparent plastic packaging. Because transparent plastic packaging is much more desirable than opaque plastic packaging, recycling this waste is uneconomical.

An alternative method of producing the food trays described above is by injection molding. There is no skeletal waste as in the thermoforming described above, but there is also no easy and cost effective way of applying the PE layer to the tray, which would help to easily seal the topsheet.

Therefore, it is an object of the present invention to provide a package that overcomes some or all of the disadvantages described above.

The essence of the technical solution

According to a first aspect of the present invention, there is provided a sealable container comprising a base and a continuous sidewall extending substantially perpendicular to the base with a peripheral edge

U1 formed along, using, the upper edge of the continuous sidewall, wherein, using the upper surface of the peripheral edge, a layer of adhesive is placed such that the cover film can be adhered to the peripheral edge to form a sealed space between the base, continuous side wall and cover foil. The adhesive layer disposed on the top surface of the peripheral edge does not extend on the vertical surfaces of the continuous side wall or extend on the base.

The term "adhesive" is used herein to denote any material that allows the covering film to adhere to the peripheral edge. The glue may be a traditional glue, it may be a PE-based material or a PE copolymer, or any other suitable material applied separately to the peripheral edge.

As explained above, transparent plastic containers are more desirable than opaque plastic containers, and thus the base and the continuous sidewall may be transparent. A suitable material for making the transparent base and transparent continuous wall is PET, the base and continuous side wall may consist essentially of PET, optionally recycled PET.

Adhesives suitable for use in the present invention include polymer substrate adhesives, for example hot melt adhesives. The thickness of the adhesive may vary. We have found that a thickness of 20 pm to 100 pm is effective, and a thickness of 50 pm is most effective.

The sealable containers of the present invention may be sealed to form sealed containers. Thus, according to a second aspect of the present invention, the sealed packages are provided with a cover film adhered to the sealable package described above.

The atmosphere within the sealed package may be modified to extend shelf life and / or improve the appearance of the products packaged within the sealed package. Modified atmosphere packaging (MAP) may contain increased concentrations of oxygen or other gases. For example, for packaging red meat, the modified atmosphere may contain elevated oxygen concentrations, for example 25% to 90% oxygen, preferably 80% oxygen. Alternatively, the modified atmosphere package may contain increased concentrations of carbon dioxide as used for poultry packaging. These are just examples; there are a large number of commercially available gaseous mixtures used for a wide range of food and non-food products. There are also significant commercial volumes of controlled atmosphere packages where the gas mixture within the sealed package is initially air, but the product consumes and also generates gases, so that the atmosphere is modified by the choice of carefully designed and targeted foil material and packaging material. This package is known as Controlled atmosphere packaging (CAP). Reliable and efficient sealing between the liner and the sealable package, which must be effective despite contamination of the sealing surface, is the key to the efficiency of modified atmosphere packaging and controlled atmosphere packaging.

The liner suitable for use in the manufacture of the sealed packages of the present invention may include polypropylene (PP) and / or PE. These materials may function as a sealing layer in a multilayer film, which may be formed by coextrusion or lamination. Other layers in the multilayer structure may be selected to impart special properties such as strength, flexibility, gas and / or water vapor barrier properties, shrinkage properties and UV filter properties. The thickness of the sealing film of the cover film may vary. The inventors have found that a sealing layer thickness of 15 µm to 50 µm is effective, and a thickness of 20 µm is most effective. The total thickness of the cover film is typically 20 µm to 60 µm.

According to a third aspect of the present invention, there is provided a method of manufacturing a sealable container as described above, the method comprising:

(a) providing a container comprising a base and a continuous sidewall protruding from the base with a peripheral edge formed along the upper edge of the continuous sidewall; and

b) applying an adhesive layer to the upper surface of the peripheral edge to form a sealable package.

Between steps a) and b), the sheath may be treated with a corona discharge or plasma to improve the adhesion of the adhesive to the peripheral edge.

-2GB 28307 U1

The adhesive layer may be applied to the upper surface of the peripheral edge by a roller, for example a silicone roller or a heated chrome roller. Alternatively, the adhesive layer may be applied by spray coating, hot melt glue gun or printing techniques.

The inventors have found that supporting the package during application of the adhesive layer helps to transfer a uniform thickness of the adhesive to the peripheral edge. In particular, the inventors have found that supporting the peripheral edge helps to produce an excellent sealed package.

The method of manufacturing a sealable container according to the present invention may be carried out in a continuous process. For example, the packages may be fed continuously to a production line for continuous application of the adhesive layer. The method of manufacturing a sealable container according to the present invention can also be carried out in a batch process. Alternatively, the method of manufacturing a sealable container according to the present invention may be performed as a combination of the steps of a continuous and batch process. For example, the containers may be fed in a batch process step, and the glue layer may be applied in a continuous process step.

According to a fourth aspect of the present invention, there is provided a method of manufacturing the sealed package described above, the method comprising:

(a) providing a sealable container prepared by the sealable container manufacturing method described above;

b) applying a cover film to the peripheral edge of the sealable container; and

c) applying pressure to the peripheral edge to adhere the cover film to the sealable package.

The pressure serves to fuse the cover film to the adhesive layer applied on the peripheral edge and thereby seal the package. Preferably, heat is applied simultaneously with the pressure.

The pressure applied to the peripheral edge and the time for which the pressure is applied may vary. The inventors have found that a pressure of 30 psi to 180 psi and a time interval of 0.5 seconds to 5 seconds is effective, and the most effective is a pressure of 110 psi and a time interval of 1 second.

The heat applied to the peripheral edge may also be different. The inventors have found that a temperature of 105 ° C to 170 ° C is effective and a temperature of 150 ° C is most effective.

The pressure itself or the pressure and heat may be applied to the peripheral edge in any manner suitable for adhering the cover film to the sealable package. Typically, a sealing agent corresponding to the shape of the peripheral edge serves to adhere the cover film to the sealable container.

Like the method of manufacturing a sealable package, the method of making a sealed package according to the present invention can also be performed as a continuous process. For example, sealable packages may be fed to a production line to arrange the cover film layer and apply heat to the peripheral edge. The method of manufacturing the sealed package of the present invention can be carried out as a batch process. Alternatively, the method of manufacturing a sealed package according to the present invention may be performed as a combination of continuous and batch process steps.

The sealed package manufacturing process can be performed after the sealable package has been manufactured and the product has been placed in the sealable package, or the sealed package manufacturing process can be performed separately from the sealable package manufacturing process.

BRIEF DESCRIPTION OF THE DRAWINGS

The technical solution will be further described with the help of drawings in which:

Fig. 1 is a cross-sectional view of a prior art tray;

Figure 2 is a flow chart of a typical prior art thermoforming process;

Fig. 3 is a perspective view of a cup according to the invention;

Fig. 4 is a cross-sectional view of a cup according to the invention;

Fig. 5 is a flow chart of a typical thermoforming process according to the present invention;

Fig. 6 shows schematically a detail of the rim of the prior art dish; 7A-7E schematically show details of trays according to the invention;

Figures 8A, 8B and 8C show schematically, in plan, side and elevation views, a cup according to the invention, including a modified release arrangement;

Figure 9A is a schematic representation of a prior art tray inserted in a similar tray; and Fig. 9B is a schematic representation of a tray according to the present invention including a modified release assembly inserted into a similar tray.

Giant. 1 shows a cross-section of a prior art container zahrnující comprising a base 2 [with ribs 6 ', side walls T and a peripheral edge Ψ. The casing Γ is made of PET and has a thickness of, for example, 400 to 500 µm. The surface of the package is coated with a PE foil having a thickness of, for example, 30 to 50 µm. The bowl generally contains 1 gram of PE (5.8% by weight) and 16.8 grams of PET (94.2% by weight).

Giant. 2 is a simplified illustration of a thermoforming process for the production of PET / PE packaging in which PET is introduced into a system for producing trays and pellets. The flakes and pellets are melted to form sheets that are coated with PE foil. The sheets are then formed to form bowls. About 6% of PET / PE waste is recovered from the extrusion of these trays.

At this stage, the extruded trays are connected to each other by a lamella 7, which is cut to form individual trays with an edge bent back. The separation process generates about 40% of the waste from the splice plates. Finally, about 2% of the waste from the trays is generated during the end of the process of trimming the trays. Extrusion waste, splice waste and tray waste are contaminated with PE and cannot be recycled to form transparent products. Based on the production of 100,000,000 trays, this represents a total of about 888 tonnes of waste per year (ie 148 tonnes of extrusion waste, 705 tonnes of connecting slat waste and 35 tonnes of dish waste per year).

Giant. 3 shows a sealable container 1 according to the invention comprising a base 2 and a continuous side wall 3 protruding from the base 1. A peripheral edge 4 is formed along the upper edge of the continuous side wall 3. An adhesive layer 5 is disposed on the upper surface of the peripheral edge 4 so that (not shown) can be glued to the edge. Thereby a sealed space can be formed between the base 1, the continuous side wall 3 and the cover foil.

Giant. 4 shows a cross-section of a sealable container 1 according to the invention comprising a base 2 and a continuous side wall 3 projecting from the base 1. The container is preferably made of PET and has a thickness of, for example, 400 to 500 µm. The peripheral edge 4 is formed along the upper edge of the continuous side wall 3 and may include a bent back edge. The cover is not coated with PE foil as in Fig. 2, but instead an adhesive foil 5 is applied to the upper surface of the peripheral edge 4 so that a cover foil can be adhered to the edge. The thickness of the adhesive film is preferably about 50 µm. In the base 2 are placed ribs 6 for strengthening the base of the cup.

Giant. 5 is a simplified illustration of a thermoforming process for the production of PET packaging according to the present invention in which PET is introduced into a bowl production system in the form of flakes and pellets. The flakes and pellets are first melted to form sheets of pure PET. Thus, the process of the present invention generates, after extrusion, PET waste that can be recycled to the production of a transparent product because the waste is substantially free of glue or PE. The trays are then formed in a PET sheet, and then the glue applicator 8 is applied to the edge and the trays are cut and separated. The waste from the splice plates is also substantially free of glue and can be recycled to the process. At the end of the production line, bowl waste is produced that contains PET and glue. Accordingly, the process of the present invention generates substantially less adhesive or PE contaminated waste and, as a result, is more cost effective by allowing the production of transparent products from the collected recycled waste. In the example of 100,000,000 trays, 888 tons of collected waste can again be envisaged, but only 35 tons are affected by PE and / or glue. This waste can be recycled to the extrusion process

-430 28307 U1 without loss of clarity, or at worst, collected and used for products (such as color products) where clarity is not important.

As explained above, it is difficult to attach the topsheet to PET surfaces, and in the past it has been suggested to coat the entire top surface of the wrapper with a PE layer and an intermediate EVA layer since PE provides a surface to which the topsheet easily adheres. The resulting trays were heavier and more difficult to recycle than PET trays due to the presence of additional layers.

In the packaging according to the present invention, an adhesive layer is placed on the upper surface of the peripheral edge so that, at a later stage, if necessary, a cover film can be adhered to the peripheral edge to form a sealed space between the base, the continuous side wall and the cover film. Thus, no changes are made to the top sealing film (which may be a conventional covering film used in industry) and only the packaging is modified. Other solutions would require expensive and complicated modifications to the housing and / or cup. The resulting wrapper is better recyclable and trays that are up to 3% lighter than prior art trays can be obtained.

Another advantage of the present invention is that the adhesive layer disposed on the upper edge surface provides a means for visually identifying the presence of the adhesive layer prior to adhering, since the adhesive surface is visually different from the PET surface. In addition, after sealing, the adhesive layer provides a means for visually checking the integrity of the seal by forming a "strip" of adhesive that is visible through the cover sheet.

When the dishes are inserted into each other, their separation can often be difficult due to the adhesive properties of the PET (ie, due to the tendency of the PET surfaces to adhere to other PET surfaces). Giant. 6 is a schematic representation of a corner of a known cup structure. Because of the bowl design, the edge at the corners is wider than along the sides of the bowl. In known trays, this additional surface can be used to create a release treatment to assist in separating the trays. This is achieved by providing a recess in the cup, the recess abutting the upper edge of the intermediate cup. The position of the recesses is alternated in such a sequence that they do not correspond to the next dish inserted.

In the present invention, the upper surface of the peripheral edge is coated with an adhesive. Some adhesives have low tack at room temperature; however, as the temperature rises, the level of tack also increases. As a result, the bowls (or partial sticking) of the bowls will become interlocked when the underside of the releasing recess of the (upper) bowl comes into contact with the upper edge of the bowl (lower) into which it is inserted.

To solve this problem, the tray according to the present invention may comprise at least one release recess located in the release region, the release region being deepened relative to the upper surface of the edge, i.e. arranged below the edge level by a distance of preferably 1 mm. The depressed region extends partially (e.g., as crescents adjacent the corners of the dish) or completely (i.e. both adjacent the corners of the dish and along the sides of the dish) along the inner periphery of the edge so that when adhesive is applied to the dish povlečen. For example, in Figures 7A, 7B and 7C, the depressed area is located in the corners of a crescent-shaped dish and the release recess is located in the depressed area. In Figs. 7D, 7E, and 7F (as well as Figs. 8A, 8B, and 8C), the depressed region extends along the entire inner periphery of the rim such that the tray has an adhesive-coated outer peripheral edge and an adhesive-free inner peripheral edge.

The release recesses are located in the recessed area such that when the adhesive material is applied to the tray, the top surface of the release recess and the area surrounding the recess is not coated. This eliminates the possibility of interlocking. The step height can be varied to adjust the separation gap between the trays. A typical gap in this area is 7 mm.

In these embodiments, the distance between the upper surface of the recessed region and the base of the cup is less than the distance between the upper surface of the edge and the base. Preferably, the distance between the upper surface of the rim and the upper surface of the depression is about 1 mm. Preferably, the width of the depression region is about 1 mm. As is apparent from Figs. 9A and 9B, the distance between the adhesive coated with the edge of the lower tray and the adjacent wall of the upper tray may typically be increased by approximately 1 mm (e.g., 0.84 mm for standard trays and 1.71 mm). for trays according to the present invention). The recessed area is therefore advantageous in preventing the first tray of the present invention from adhering to the second, intermediate tray due to the distance formed between the adhesive and the top surface of the first tray edge and the adjacent wall of the second tray.

Examples

LINPAC rfresh R2-45 meat trays were prepared and tested to demonstrate the suitability of a technical solution for packaging fresh meat in a modified atmosphere.

The dishes were made from a 500 µm thick single-layer sheet of amorphous PET. The dishes were coated with an adhesive available from Beardow and Adams (Adhesives) Ltd. (designation BAM 2041). The glue was applied to the rim of the tray using a Diemme Fin Model SC4 roller. The glue was melted on a 177 ° C chrome roller and was applied to the rim of the dish via a 125 ° C silicone rubber roller. The coating device had a line speed of 10 m / min and the dishes were coated in batches of four using an aluminum carrier adapted to support the edge of each tray while passing under the coating roller. The device was adjusted to apply the adhesive uniformly to the edge at coating thicknesses of 50 µm, 60 µm, 80 µm and 90 µm. The remaining tray surfaces were free of glue contamination.

The dishes were sealed using a 35 µm thick commercially available cover film. The film was supplied by LINPAC Packaging Limited (designation THB 267110). The dishes were filled with a gas atmosphere of 80% oxygen and 20% carbon dioxide using a World Class Packaging model T200. Various bonding conditions were used, with bonding times of 1 to 3 seconds, sealing pressures of 30 psi to 180 psi, and sealant temperatures of 130 ° C to 170 ° C.

The plates were stored for 10 days at 4 ° C to simulate the package delivery chain. The residual oxygen was then measured using a HiTec MAP 4050 gas analyzer. There was no appreciable loss of oxygen concentration indicating that the packages were leaking. Tightness tests were conducted at room temperature using the Lippke 4000 Package Test System. The leak test pressure was 50 mbar, the exposure phase lasted 30 seconds and the leak detection time was 30 seconds. Again, the containers were found to be leak free since the observed pressure drop was <2 mbar. The burst tests were performed using the Lippke 4000 Package Test System. The pressure increase rate was 5 mbar / s. Failure occurred by rupture of the topsheet, indicating that the adhesive bond between the tray and the topsheet was good.

The attempt number Adhesive thickness Bonding temperature (CC) Bonding time (s) Gluing pressure (dogs) Average leakage (mbar) Average burst (mbar) 1 50 130 1 110 on 216 2 50 130 3 110 on 225 3 50 170 1 110 on 175 4 50 170 3 110 on 126 6 50 130 3 110 4,5 230 7 90 130 3 110 2.9 274 8 50 130 1 65 on 233 9 50 130 1 110 on 247 10 50 150 1 65 on 159 11 50 150 1 110 on 186 12 50 170 1 65 on 175 13 50 170 1 110 on 207 14 50 130 1 110 1.7 260 15 Dec 60 130 1 110 2.1 315 16 80 130 1 110 2J 270

Claims (14)

A container comprising a base (2) and a continuous sidewall (3) extending substantially perpendicular to the base (2), with a peripheral rim (4) formed along the upper edge of the continuous sidewall (3), the base (2) and the continuous side wall (3) consists essentially of polyethylene terephthalate PET, wherein an adhesive layer (5) is disposed on the upper surface of the peripheral rim (4) and said adhesive layer (5) does not interfere with the vertical surface of the continuous side wall (3) and 2), wherein the package (1) further comprises a cover film that can be sealed to the peripheral rim (4) to form a sealed space between the base (2), the continuous side wall (3) and the cover film; and wherein the cover film is a multilayer film comprising a sealing layer and the sealing layer comprises polypropylene PP and / or polyethylene PE. Packaging according to claim 1, characterized in that the base (2) and the continuous side wall (3) are transparent. Packaging according to claim 2, characterized in that the base (2) and the continuous side wall (3) consist essentially of recycled PET. Packaging according to claim 1, 2 or 3, characterized in that the adhesive (5) is an adhesive based on a polymer substrate or on the basis of polyethylene PE or a copolymer of PE. Packaging according to one of the preceding claims, characterized in that the thickness of the adhesive layer (5) is from 20 µm to 100 µm, preferably 50 µm. Packaging according to any one of the preceding claims, characterized in that it further comprises at least an adhesive-free recess (5) adjacent the corner of the packaging (1). Packaging according to one of the preceding claims, characterized in that it further comprises an adhesive-free release region (5) which extends partially or completely along the inner periphery of the rim (4). Packaging according to claim 7, characterized in that the distance between the upper surface of the release region and the base (2) of the cup is less than the distance between the upper surface of the skirt (4) and the base (2). Packaging according to claim 7 or 8, characterized in that said at least one recess is located in the release region. Packaging according to one of Claims 1 to 9, characterized in that a cover foil is sealed to the packaging (1). Packaging according to claim 10, characterized in that inside the sealed packaging (1) there is a modified or controlled atmosphere. The container of claim 11, wherein the modified atmosphere comprises an increased oxygen or carbon dioxide content. Packaging according to claim 1, characterized in that the thickness of the sealing layer is 15 to 50 µm, preferably 20 µm. Packaging according to one of Claims 10 to 14, characterized in that the thickness of the covering film is 20 to 60 µm.