DK201400135Y3 - Container - Google Patents

Abstract

The present application relates to a sealable container comprising a bottom and a through sidewall; extending substantially perpendicular to the bottom, with a circumferential flange formed along the upper edge of the through-going side wall in use, wherein a layer of adhesive is placed on an upper surface of the peripheral flange in use such that a cover film can be sealed to the peripheral flange to create a sealed space between the bottom, the through-side wall and the cover foil. The present application further relates to a process for making the sealed container.

Description

in DK 2014 00135 Y3

Container

The invention relates to containers suitable for use in the packaging, storage, transport and / or display of a product, such as a fresh product or a medical product, and to processes for the manufacture of such containers.

It is known to use plastic containers for packaging, storing, transporting and displaying fresh foods. These containers may be sealed with a cover foil to protect the food in the container from the surrounding environment. Furthermore, the atmosphere inside such containers can be modified to improve the shelf life and / or appearance of the fresh food inside the container.

Clear plastic containers can be made of polyethylene terephthalate (PET). Using PET provides a high-clarity product that makes it easy for a user to see the contents of the container. (Recycled PET can also be used, providing environmental and sometimes economic benefits.) However, as explained above, it is desirable to seal clear plastic containers with a cover film, but it is difficult to attach a cover film to PET and the seal of a cover film to PET is particularly sensitive to pollution.

20

A known solution to the problem described above is to make the containers of PET coated with a layer of polyethylene (PE) and an intermediate layer of ethylene vinyl acetate (EVA). PE provides a surface to which a cover film is easily adhered, thereby facilitating the manufacture of sealed containers. PET is typically substantially thicker than the EVA and 25 PE layers, and the PET / EVA / PE product can be made by co-extrusion, lamination, extrusion coating or any other suitable technique. Although the PET / EVA / PE product provides containers with high clarity, EVA and PE have different light refraction compared to PET, and therefore the PET / EVA / PE product has slightly less clarity than an uncoated PET product. The use of EVA and PE also incurs an additional 30 costs for two main reasons: firstly, because the laminate or co-extruded layer has an inherent cost, and secondly, as described below, the internal reprocessing of factory trays and "skeletal waste" is damaged by the presence of EVA and PE in an otherwise pure PET stream. Compared to a PET-2 DK 2014 00135 Y3 product, the PET / EVA / PE product has poorer clarity, is more expensive, less reusable and less user-friendly in the production plant.

There are also environmental consequences of using a PET / EVA / PE product. During the manufacture of PET / EVA / PE containers by thermoforming, several containers are formed of large and often continuous sheets or sheets of PET / EVA / PE material, and individual containers are cut out of these large plates. Waste material is formed from the parts of the large sheets that are not used in the individual containers. This waste material, known as "skeletal waste", contains a mixture of PET, EVA and PE, which upon recycling forms a foggy product which cannot be used to produce clear plastic containers. Since clear plastic containers are more desirable than opaque containers, waste * is uneconomical to recycle.

An alternative way to prepare food trays described above is by using 15 injection molding. Then, in thermoforming, there will be no skeletal waste as described above, but there is also no easy and cost-effective way to apply the PE layer to the tray, which will promote easy sealing to a top foil.

It is therefore an object of the present invention to provide containers which overcome some or all of the problems described above.

According to a first aspect of the invention, there is provided a sealable container comprising a bottom and a through-side wall extending substantially perpendicular to the bottom with a peripheral flange formed along the upper edge of the through-through side during use, wherein a layer of adhesive is placed on an upper surface of the peripheral flange in use, such that a cover film can be sealed to the peripheral flange to create a sealed space between the bottom, the through-side wall and the cover film. The adhesive layer located on the upper surface of the peripheral flange does not extend on the vertical side surfaces of the through-side wall and does not extend to the bottom.

The term "adhesive" is used herein to refer to any material which enables adhesion of the cover film to the peripheral flange. The adhesive may be a traditional adhesive, it may be a PE-based or a PE-copolymer-based material or indeed any other suitable material which is applied discretely to the peripheral flange.

As explained above, clear plastic containers are more desirable than opaque plastic containers, and therefore the bottom and the through side wall may be clear. A suitable material for making the clear bottom and the clear through side wall is PET, and therefore the bottom and the through side wall may consist essentially of PET, possibly recycled PET.

Suitable adhesives for use in the present invention include adhesives based on a polymeric substrate, such as a hollow adhesive. The thickness of the adhesive layer may vary. The inventors have found that a thickness of 20 µm to 100 µm is effective and a thickness of 50 µm is most effective.

Sealed containers according to the present invention can be sealed to produce sealed containers. According to another aspect of the present invention, sealed containers are therefore provided with a cover film which is sealed to a sealable container as described above.

The atmosphere inside the sealed container can be modified to improve the durability and / or appearance of products packed in the container. Modified Atmospheré Packaging (MAP) may contain elevated levels of oxygen or other gases. For example, to pack red meat, the modified atmosphere may contain elevated levels of oxygen, such as from 25% to 90% oxygen, preferably 80% oxygen. Alternatively, MAP may contain increased levels of carbon dioxide used in poultry packaging. These are just examples; There are a wide variety of commercially available gas mixtures used across a wide range of foods and non-foods. There are also significant commercial quantities of controlled atmosphere packaging where the gas mixture inside a sealed package is originally air but where the product consumes and in addition generates gases such that the atmosphere is modified by carefully designed and targeted foil material and container material selection. This is known as Controlled Atmosphere Packaging (CAP). A reliable and effective seal between cover film and sealable container that is able to work despite contamination of the sealing surface is the key to MAP and CAP being effective.

Cover foils suitable for making sealed containers according to the present invention may comprise polypropylene PP and / or PE. These materials can act as a sealing layer in a multilayer film which can be formed by co-extrusion or lamination. The other layers in a multilayer structure can be selected to impart special properties such as strength, elasticity, gas and / or water barrier properties, shrinkage characteristics and UV shielding. The thickness of the adhesive layer of the film can vary. The inventors have found that a seal layer thickness from 15 µm to 50 µm is effective and a thickness of 20 µm is most effective. The total thickness of the cover film is from 20 µm to 60 µm.

According to a third aspect of the present invention, there is provided a process for producing a sealable container as described above, wherein the process comprises: a) providing one container comprising a bottom and a through-side wall which rises from the bottom with a peripheral flange formed along the upper edge of the through-going side wall in use, and b) applying a layer of adhesive to an upper surface of the peripheral flange to produce a sealable container.

The container may be corona or plasma treated between steps a) and b) to improve adhesion of the adhesive to the peripheral flange.

The adhesive layer may be applied to the upper surface of the peripheral flange with a roller such as a silicone roller or a heated chrome roller. Alternatively, the adhesive layer may be applied by spraying, with a hot melt gun or by a printing technique.

The inventors have found that supporting the container during application of the adhesive layer helps to transfer an even thickness of the adhesive to the peripheral flange. In particular, the inventors have found that it is conducive to support the peripheral flange in the manufacture of an exceptionally good sealable container.

5 DK 2014 00135 Y3

The process of making a sealable container according to the present invention can be operated as a continuous process. For example, the containers may be continuously fed to a production line for continuous application of the adhesive layer. The process of making a sealable container according to the present invention may also be operated as a batch process. Alternatively, the process for producing a sealable container of the present invention can be operated as a combination of continuous process steps and batch process steps. For example, the containers can be fed in batch process steps and application of the adhesive layer acts as a continuous process step.

10

According to a fourth aspect of the present invention, there is provided a process for manufacturing a sealed container as described above, wherein the process comprises: a) providing a sealable container made according to the process for manufacturing a sealed container described above; b) applying a layer of cover film to the peripheral flange of the sealable container; and c) applying pressure to the peripheral flange to seal the cover film to the sealable container.

The pressure is applied to fuse the cover film with the adhesive layer applied to the peripheral flange, thereby sealing the container. Preferably, heat is used simultaneously with the pressure.

The pressure applied to the peripheral flange and the time over which the pressure is applied may vary. The inventors have found that a pressure of 30 psi to 180 psi and a time period of 0.5 s to 5 s is effective, and a pressure of 110 psi and a time period of 1 s is most effective.

The heat applied to the peripheral flange may also vary. The inventors have found that a temperature of 105 ° C to 170 ° C is effective and a temperature of 150 ° C is most effective. 30

Pressure alone or pressure and heat can be applied to the peripheral flange with any process suitable for sealing the cover film to the sealable container. Typically, a sealing shoe suitable for the shape of the peripheral flange is used to seal the cover foil to the sealable container.

As with the process of making a sealed container, the process of making a sealed container according to the present invention can be operated as a continuous process. For example, the sealable containers may be provided with a production line for providing a layer of cover film and applying heat to the peripheral flange. The process of making a sealed container according to the present invention can be operated as a batch process. Alternatively, the process for making a sealed container according to the present invention can be operated as a combination of continuous process steps and batch process steps.

The process of making a sealed container can be carried out after the sealed container is made and a product is placed inside the sealed container, or the process of manufacturing the sealed container can be carried out separately from the process of manufacturing the sealed container.

The invention will be further explained with reference to the drawings and figures, in which fig. 1 is a cross-section of a known tray; FIG. 2 is a flow diagram of a typical known thermoforming process; FIG. 3 is a perspective view of a tray according to the invention; FIG. 4 is a cross-sectional view of a tray according to the invention; FIG. 5 is a flow diagram of a thermoforming process according to the invention; FIG. 6 is a schematic partial view of a flange on a known tray; FIG. 7A to 7E are schematic partial views of trays according to the invention; Figures 8A, 8B and 8C are schematic top, side and front views of a tray according to the invention, including a modified release detail; 9A is a schematic representation of a known tray assembled with a similar tray; and FIG. 9B is a schematic representation of a tray according to the invention comprising a modified release detail and assembled with a similar tray.

7 DK 2014 00135 Y3

FIG. 1 shows a cross section of a known container Γ comprising a bottom 2 'with ribs 6', side walls 3 'with a peripheral flange 4'. The container Γ is made of PET and has a thickness of e.g. 400-500 pm. The surface of the container is coated with PE film having a thickness of e.g. 30 to 50 pm. The tray typically comprises 1 g PE (i.e. 5.8 wt%) and 16.8 g PET (i.e. 94.2 wt%).

FIG. 2 is a simplified illustration of a thermoforming process for the production of PET / PE containers, in which PET in the form of flakes and granules is introduced into the system for making the trays. The flakes and granules are melted into sheets coated with a film of PE. The sheets are then shaped into trays. Approximately 6% PET / PE waste is phased out by the extension of the trays.

In this step, the extruded trays are attached to each other by a web 7 which is cut to produce individual trays with a return flange. This separation process produces about 40% web waste. Finally, 2% tray waste is generated by cleaning the trays at the end of the process. Extrusion waste, web waste and ground waste are contaminated with PE and cannot be recycled to produce clear products. Based on the production of 100,000,000 trays, it gives a total of approx. 888 tonnes of waste per year (ie 148 tonnes of extrusion waste, 705 tonnes of railway waste and 35 tonnes of ground waste).

FIG. 3 shows a sealable container 1 according to the invention, comprising a base 2 and a continuous or continuous side wall 3, which stands up to the bottom 1. A peripheral flange 4 is formed along the upper edge of the through side wall 3. A layer of adhesive 5 is placed on a upper surface of the peripheral flange 4 such that a cover film (not shown) can be sealed to the flange. Thereby a sealed space can be created between the bottom 1, through-side wall 3 and cover foil.

FIG. 4 shows a cross-section through a sealable container 1 according to the invention, comprising a bottom 2 and a through-side wall 3 which is raised from the bottom 1. The container is preferably made of PET and has a thickness of e.g. 400-500 pm. A peripheral flange 4 is formed along the upper edge of the through-side wall 3 and may comprise a return flange. The container is not coated with a PE film as in FIG. 2, but in place, an adhesive film 5 is applied to an upper surface of the peripheral flange 4 so that a cover film can be sealed to the flange. The thickness of the adhesive foil is preferably approx. 50 pm. Ribs 6 are located at the bottom 2 to reinforce the bottom of the tray.

FIG. 5 is a simplified illustration of a thermoforming process for the production of PET / PE containers according to the present invention, in which PET in the form of flakes and granules is introduced into the system for making the trays. The flakes and granules are first melted into sheets of pure PET. Therefore, a process according to the present invention produces waste after PET extrusion which can be recycled to give a clear product, since the waste is substantially free of adhesive or PE. Trays are then formed in the PET plate, and subsequently the adhesive is applied to the flange using an adhesive applicator 8, and the trays are cleaned and separated. The web waste is also substantially free of adhesive and can be recycled in the process. At the end of the production line, trash waste is produced which includes PET and adhesive. Therefore, the process sought produces substantially less waste, which is contaminated with adhesive or PE and is therefore more cost effective as it enables the production of clear products of the accumulated recycled waste. Using the example of producing 100,000,000 trays, we can again predict the same 888 tonnes of accumulated waste, but only 35 tonnes are affected by PE / adhesive. This can be traced back to the extrusion processP without the current negative effects on clarity, or at worst be excreted and applied to products (eg colored products) where clarity is unimportant.

As explained above, it is difficult to attach a cover film to PET surfaces, and a previously proposed solution has been to coat the entire upper surface of the container with a layer of PE and an intermediate layer of EVA, since PE provides a surface like a cover film easily are liable to. However, the resulting trays were heavier and less recyclable than the PET trays due to the presence of the additional layers.

In the container of the present invention, a layer of adhesive is placed on an upper surface of the peripheral flange, so that a later film, when needed, can be sealed to the peripheral flange to create a sealed space between the bottom, the bottom and the bottom. DK 2014 00135 Y3 through sidewall and lid foil. Therefore, no changes have been made to the top seal foil (which may be a conventional cover foil used in the industry) and only the container is modified. Other solutions would require expensive and complex modifications to the lid and / or tray. The resulting container has better option 5 to be recycled and trays can be obtained which are up to 3% lighter than known trays.

A further advantage of the present invention is that the adhesive layer located on the upper surface of the flange provides means for visually identifying the presence 10 of a sealing layer prior to sealing because the adhesive surface is visually different from the PET surface. In addition, the adhesive layer after sealing provides means for visually checking the integrity of the seal by forming an adhesive "tape" visible through the cover film.

15 When the trays are inserted, they are often difficult to separate due to the blocking properties of PET (i.e., the propensity of PET to adhere to other PET surfaces). FIG. 6 is a schematic representation of a corner of a known tray configuration. Due to the shape of the tray, the flange is wider at the corners than along the sides of the tray. On known trays, this additional area may be utilized to create a release detail 20 to assist in the separation of the composite trays. It is accomplished by forming a recess in the tray where this recess sits on the upper flange of the composite tray. The recess is arranged alternately in order that it does not match the tray with which it is set.

In the present invention, the upper surface of the peripheral flange is coated with an adhesive. Some adhesives have a low adhesion at room temperature, but as the temperature rises, the adhesive level also increases. The result of this will be the interlocking (or partial gluing) of trays, since the underside of the release recess of an (upper) tray is in contact with the upper flange of the 30 composite (lower) tray.

To address this, the tray of the present invention may comprise at least one release recess located in a release area, thereby releasing the release area in relation to the upper surface of the flange, i. E. set lower than the flange level with a distance of preferably 1 mm. The released area extends partially (e.g., as crescents adjacent to the corners of the tray) or completely (i.e. both adjacent corners of the tray and along the sides of the tray) along the inner periphery of the flange such that when 5 adhesive material is applied to the tray, the upper surface of the freed area not. For example, in FIG. 7A, 7B and 7C, the released area is located at the corners of the tray in the form of a crescent and the release recess is located in the released area. In FIG. 7D, 7E and 7F (and also in Figures 8A, 8B and 8C), the released area extends along the entire inner periphery of the flange, such that the tray comprises an outer peripheral flange 10 coated with adhesive and an inner peripheral flange without adhesive.

The release recesses are located in the released areas so that when the adhesive material is applied to the tray, the upper surface of the release recess and the area surrounding the recess are not coated. As such, the possibility of interlocking the 15 trays is eliminated. The height of the step can be adjusted to adjust the space between the trays. A typical gap is in the range of 7 mm.

In these embodiments, the distance between the upper surface of the released area and the bottom of the tray is shorter than the distance between the upper surface of the flange and the bottom. Preferably, the distance between the upper surface of the flange and the upper surface of the released area is approx. 1 mm. Preferably, the width of the released area is about 1 mm. As can be seen in FIG. 9A and 9B, the distance between the adhesive coated flange of a bottom tray and the adjacent wall of an upper tray can typically be increased by approx. 1 mm (e.g., 0.84 mm for standard trays and 1.71 for trays 25 of the present invention). Therefore, the released area is advantageous in that it prevents a first tray of the present invention from hanging from a second composite tray because of the distance created between the adhesive on the upper surface of the first tray flange and the adjacent wall of the tray. second hill.

30 Examples LINPAC rfresh R2-45 meat trays were prepared and tested to demonstrate the suitability of the invention for packing fresh meat using a MAP system.

11 DK 2014 00135 Y3

The trays were made from a 500 μπι thick single layer, amorphous PET plate. The formed trays were coated with an adhesive (reference BAM 2041) provided by Beardow and Adams (Adhesives) Ltd. The adhesive was applied to the flange of the tray using a Diemme Fin model SC4 glue roll spreading machine. The adhesive was melted against a chrome roller with a temperature of 177 ° C and applied to the tray flange via a silicone rubber roller with a temperature of 125 ° C. The coating equipment had a line speed of 10 m / min and the trays were coated in batches of four using an aluminum support designed to support each tray's flange as they passed under the coating roll. The equipment was adjusted to apply the adhesive 10 uniformly to the flange with coating thicknesses of 50 µm, 60 µm, 80 µm and 90 µm. The remaining tray surfaces were free of adhesive contamination.

The trays were sealed using a 35 µm commercially available cover film. This was provided by LINPAC Packaging Limited (reference THB 267110).

15 The trays were filled with an atmosphere of 80% oxygen and 20% carbon dioxide gas using a World Class Packaging model T200 tray sealing machine. Various sealing conditions were used with sealing times from 1 to 3 s, sealing pressures from 30 psi to 180 psi, and sealing beam temperatures from 130 ° C to 170 ° C.

The trays were stored for 10 days at 4 ° C to simulate the packaging supply chain. Residual oxygen was then measured using a HiTec MAP 4050 gas analyzer. No reduction in the oxygen concentration of significance was noted, indicating that the packages were leaking. Leak tests were performed at room temperature using a Lippke 4000 Package Test System.

The leakage test pressure was 50 mbar with a set period of 30 s and a leak detection time of 30 s. Package was again shown to be leaky as the observed pressure drop was <2 mbar. Failure tests were performed using the Lippke 4000 Package Test System. The pressure increase rate was 5 mbar / s. The mode of failure was failure of the top web foil, which showed that the adhesive bond between tray and top web was good.

30 12DK 2014 00135 Y3

Sample no. Adhesive thickness Seal temp (° C) Seal temp (sec) Seal pressure (psi) Average leakage (mbar) Average burst (mbar) 1 50 130 1 110 Not applicable 216 2 50 130 3 110 Not applicable 225 3 50 170 1 110 Not applicable 175 4 50 170 3 110 Not applicable 126 6 50 130 3 110 4,5 230 7 90 130 3 /. / 110 2.9 274 8 50 130 1 65 Not applicable 233 9 50 130 1 110 Not applicable 247 10 50 150 1 65 Not applicable 159 11 50 150 1 110 Not applicable 186 12 50 170 1 65 Not applicable 175 13 50 170 1 110 Not applicable 207 14 50 130 1 110 1.7 260 15 60 130 1 110 2.1 315 16 80 130 1 110 2.1 270

Claims (14)

A container comprising a bottom and a through-side wall extending substantially perpendicular to the bottom with a peripheral flange formed along the upper edge of the through-through side wall in use, wherein the bottom and the through-side wall consist essentially of polyethylene terephthalate (PET), wherein a layer of adhesive is applied to an upper surface of the peripheral flange in use, and wherein the adhesive layer does not extend to the vertical surfaces of the through-side sidewall in use and does not extend to the bottom, wherein the container further comprises a cover film. , which can be sealed to the peripheral flange to create a sealed space between the bottom, the through-wall 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 PE. Container according to claim 1, wherein the dog and the through side wall are clear. Container according to claim 2, wherein the bottom and the through side wall of the Essential consists of recycled PET. The container of claim 1, 2 or 3, wherein the adhesive is an adhesive based on a polymer substrate or a polyethylene (PE) or PE copolymer based material. A container according to any one of the preceding claims, wherein the thickness of the adhesive layer is from 20 µm to 100 µm, preferably 50 µm. Container according to any preceding claim, further comprising at least one adhesive-free recess and adjoining a corner of the container. The container of any preceding claim, further comprising at least one adhesive-free release area extending partially or completely along the inner periphery of the flange. 14 DK 2014 00135 Y3 The container of claim 7, wherein the distance between the upper surface of the release area and the bottom of the tray is shorter than the distance between the upper surface of the flange and the bottom. 5 The container of claim 7 or 8, wherein the at least one recess is located in the release area. A container according to any one of claims 1 to 9, wherein the cover film is sealed thereto. 10 The container of claim 10, wherein the atmosphere inside the sealed container has been modified or controlled. The container of claim 11, wherein the modified atmosphere contains increased levels of oxygen or carbon dioxide. The container of claim 1, wherein the thickness of the sealing layer is from 15 µm to 50 µm, preferably 20 µm. 13 DK 2014 00135 Y3 A container according to any one of claims 10 to 14, wherein the thickness of the cover film is from 20 µm to 60 µm.