EP2500292A1

EP2500292A1 - Method for making a container, such container, a method of filling a container and the filled container

Info

Publication number: EP2500292A1
Application number: EP11158532A
Authority: EP
Inventors: Wim Vierhouten
Original assignee: Ardagh MP Group Netherlands BV
Current assignee: Trivium Packaging Group Netherlands BV
Priority date: 2011-03-16
Filing date: 2011-03-16
Publication date: 2012-09-19

Abstract

The present invention relates to a method for making a container comprising the steps of:
i) providing a metal container body having an opening;
ii) applying a foil over the opening;
iii) mounting a cap onto the container body thereby pressing the foil onto an edge of the opening; and
iv) induction heat sealing the foil to the edge, to the container obtainable, to a method for filling such container and to the filled container.

Description

The present invention relates to a method for making a container, to a container which can be made with this method, to a method of filling a container and to a filled container.
The present invention relates to containers of which a container opening is closed off with a foil which is adhered to an edge of the opening. Although the foil is relatively vulnerable, an closure provides a very effective closure of a container with a high resistance to hydraulic shock and may counter relatively high internal pressures during a retortable process. Still, the consumer may open the container by applying relatively low opening force. Such container may comprise retortable products such as vegetables, soup, sauces, meat and pate, pet food, sea food and salads. On the other hand, such containers may comprise dry products such as baby food, specialty coffee, milk powder, nutritional products, snacks, non-processed dry products, and paint or pigments.
The container is produced generally either by sealing or by contact heating.
During the heating step a foil is contacted and pressed onto an opening edge of the container body by a heating tool and due to the applied heat a heat sensitive adhesive is melted and contacted with the container edge. Upon cooling the foil has become adhered to the edge. Dependent on the type and quality of the adhesive the foil is permanently of reclosably contacted to the opening edge.
Another option for making an opening is by sealing. During sealing, a container is provided with a foil which foil is pressed onto an opening edge and subjected to an electromagnetic field resulting in an induced heating of the adhesive which is then adhered to the container edge. The electromagnetic field varies slightly and is typically within the range of 30-100 kHz. Lower frequencies give a more uniform heating across the diameter of the seal and help wax to melt on large containers. Higher frequencies give a greater heating effect and therefore a sealing at higher rates on smaller diameters.
The present invention has for its object to improve the heat sealing and make it suitable for other type of containers, in particular metal containers. It is up to today that sealing is restricted to heat sealing by induction of a foil, in particular a metal or aluminum foil, onto a glass or plastic container.
Intensive and long investigations by the applicant has turned out that also a metal container body may be used for a product wherein the foil is adhered to the container edge by induction heat sealing, that is without any direct contact between the container and a induction element. Such contactless heat sealing has for its major object that the processing and transport of the container is not hindered by any contact whereas the transport speed may be relatively high. In addition heat sealing by induction is also relatively independent of the type, form and particular height of the container to be heat sealed.
Accordingly the present invention provides a method for making a container comprising the steps of:

i) providing a metal container body having an opening;
ii) applying a foil over the opening;
iii) mounting a cap onto the container body thereby pressing the foil onto an edge of the opening; and
iv) induction heat sealing the foil to the edge.

As indicated above the present invention is based on the insight and on experimental confirmation thereafter that a metal container body may be provided with a foil which is adhered to an edge of the opening by induction heat sealing.
The container body may be made of any type of metal but in particular of steel such as tin plated steel, aluminum. The diameter of the metal container body may be any relevant practical diameter such as 36-190mm. The height of the metal container is not relevant because the induction heat sealing apparatus may be adjusted in height to the height of the metal container. Also the volume of the metal container body is not of relevance or is not critical and any practical volume may be used for a metal container body to be induction heat sealed. Basically dependent on the diameter, height and volume of the container the electromagnetic field may be vary in strength such that the foil is correctly adhered to the edge of the container body by induction heat sealing.
The foil to be heat sealed by induction to the edge of the opening may be made of any relevant material which provides sufficient strength to form a barrier in between the content of the metal container and its surroundings. The foil may be preferably made of metal, such as aluminum. However, the foil may also be made of plastic or paper or cardboard material provided that is comprises the desired strength. For the adherence and contact of the foil to the opening edge, it is relevant, that the foil is provided with an adhesive or a wax which is melted due to the induction heat sealing, makes contact with the edge of the opening in its melted stage and upon cooling forms a reliable bond between the foil on the one hand and the edge of the opening on the other. The thickness of the foil may be dependent on the material of which the foil is made. When the foil is made of metal, such as aluminum, the thickness may vary between 0.05-0.3 mm. when made of plastic or paper or cardboard, than is it likely that the foil is thicker such as in the range of 0.2 - 0.8mm.
The cap may be made of any suitable material that protects (partly) the vulnerable foil and when mounted on the container body can press the foil to the opening edge of the container. Examples are plastics, such as polypropylene, polyethylene and mixtures or copolymers thereof, metals, such as steel, aluminium, and combinations thereof. The cap may cover the foil completely or only partly, such as along the circumference of the opening edge.
For providing a reliable and strong bond in between the foil and the edge of the opening, it is necessary that the foil is pressed onto the edge of the opening. Such pressing is accomplished with the cap mounted on the container body. Such mounting may be by screwing the cap onto the container body, or by clamping the cap onto the container body and/or by forming a snapping connection between the cap and the container body. In essence, any suitable form of pressing the foil onto the edge of the opening by the container is suitable within the present invention, as long as there remains no contact with the surroundings other than to support and transport the container.
Obviously the foil and the cap may be applied one after the other onto the opening of the container and wherein the foil is contacted with the edge of the opening. However, it is advantageous that the foil is combined with the cap and the combination of the cap and the foil is mounted onto the container. By combining the foil with the cap, it is only necessary that the combination of both is in one process step mounted onto the container body and by that mounting the foil is brought into a pressed contact with the edge of the opening. For a reliable contact of the foil with the cap, it is preferred that the cap is adhered to the cup by using an adhesive, or a wax. Such adhesive or wax should have a bonding strength which is substantially smaller than the ultimate bonding strength of the heat sealed foil onto the opening edge. Under circumstances it may occur that there are irregularities over the circumference of the container edge and/or that the thickness of the edge is not constant over the area in which the foil contacts the cap. Then it is advantageous if the foil is in contact with a foam layer and that in turn the foam layer is connected to the cap. Such foam layer than compensates for any irregularities and for differences in thickness. Obviously the bonding strength of the foam layer to the cap is higher than the bonding strength of the foil to the foam layer. Accordingly, after induction heat sealing the cap may be removed in combination with the foam layer while maintaining mounted and heat sealed the foil on the edge of the container.
Although, the foils on a container provides a reliable closure of the content of the container and that undesired or unauthorized opening of the container making access to the content of the container is almost always visible from the outside, it is still possible and advantageous in order to lower further the risks of undesired or unauthorized opening of the container when temper proof means are applied to the cap mounted onto the container.
Another aspect of the invention relates to a container makeable with the method described above for heat sealing foil onto a metal container body.
Such container body is preferably characterized by comprising a metal container body having an opening, a foil applied over the opening and induction heat sealed onto an edge of the opening, and a cap mounted onto the container pressing the foil onto the opening edge.
As indicated as above, it is preferred when the foil is connected to the cap and the combination of cap and foil is applied onto the container and pressing via the cap the foil onto the edge which can then be induction heat sealed onto that edge. For reasons as indicated above, it is advantageous when the foil is connected to a foam layer which is adhered to the cap.
A further aspect of the present invention relates to a method of filling a container comprising the steps of:

i) providing a metal container body having an opening;
ii) filling the metal container body via the opening;
iii) applying a foil and a cap as defined in any of the claims 1-9, so that the foil is pressed against an opening edge; and
iv) induction heat sealing the foil onto the edge of the opening.

The present invention makes is possible that a customer is provided with empty metal container bodies which are filled by the customer and after filling the foil and the cap and/or the combination of foil and cap is applied onto the container thereby pressing the foil onto the edge of the container. By applying the combination it is very reliable and predictable that the cap with the foil is applied in the correct manner because the cap is dictating the mounting and positioning of the foil onto the edge of the container. After the reliable and correct mounting and positioning of the foil onto the container edge which is thereby pressed onto the edge by the cap, the heat seal induction is then reliable for adhering and bonding an foil onto a metal container.
Finally another aspect of the present invention relates to a container obtainable by the method of the invention for filling and induction heat sealing foil onto a metal container body.
Mentioned and other features of the present invention will be further discussed and illustrated by the following description of several embodiments of the present invention without the intention to restrict the invention to these embodiments. In this respect reference will be made to the annex drawings wherein:

Figure 1 is an exploded perspective view of a container according to the invention to be subjected to induction heat sealing according to the invention;
Figures 1a-1c are cross sections over the line I - I of figure 1 showing various steps in the method of the present invention;
Figures 2a-2c, 3a-3c and 8a-8c show other variants of this method;
Figures 4 and 5 show other container edges provided by induction heat sealing with a foil according to the invention;
Figure 6 shows schematically a method according to the invention for filling a container; and
Figure 7 shows a container to be provided with a screw cap for induction heat sealing according to the invention.

Figure 1 shows a metal container 1. The container 1 comprises a metal container body 2 provided with a necked portion 3 and an edge 4 defining an opening 5 of the container 1. The opening 5 is to be closed of by a foil 6 provided with a tab 7. The foil 6 is covered and closed off by a plastic or metal cap 8 which is pressed onto the necked portion 3 of the container body 2.
Figure 1a shows in detail and in cross section the application of the foil 6 onto the edge 4 following the arrow 9. Subsequently the cap 8 is applied following arrow 10.
As shown in figure 1a, is the foil 6 a laminate having a middle card board layer 11 and an adhesive layer 12 facing the edge 4 and an imprint layer 13 facing the cap 8 and ultimately the consumer using the container.
As shown in figure 1b, the cap 8 presses the foil 6 onto the edge 4 of the container body 2. Heat sealing by using electromagnetic radiation 14 results in a temporary melting of the adhesive layer 12 and combining of the melted adhesive to the edge 4 and upon cooling the adherence of the foil 6 to the edge 4. Accordingly, as shown in figure 1c, the subsequent release of the cap 8 following arrow 15 is possible and the foil 6 remains adhered to the edge 4 of the metal container body 2.
Figure 2a shows a container body 16 provided with a necked portion 17 having an elongated and curled edge 18 of a metal foil 19 provided with an adhesive layer (not shown) is applied following the arrow 20 onto the upper edge part 21 of the edge 18. Thereafter a foam layer 22 made of an open cell or closed cell foam structure, such as PET and pvc, following the arrow 23. Finally the plastic cap 24 is applied following the arrow 25. The skirt 26 of the cap 24 is clamped onto the lateral wall 27 of the edge 18. This results in a pressing of the foil 19 onto the edge part 21 so that by induction heat sealing the foil 19 is adhered to the edge part 21. According to a preferred embodiment a temper proof band 28 is applied over the lower part 29 of the curl 18 and partly over the cap 24 (see figure 2b). After the induction heat sealing and the bonding of the foil 19 to the upper edge part 21 of the curl 18, the cap 24 inclusive the foam layer 22 may be released following the arrow 30 thereby providing access to the foil 19 and after its removal to the content of the container.
Figures 3a-3c show an alternative to the container as shown in figures 2a-2c. As shown in figure 3a, the metal container body 31 has a curl 32 onto which is applied a metal foil 33 having a tab 34. Thereafter a foam layer 35 is applied and finally a metal cap 36 carrying on its skirt 37 an inward projection 28 which forms with the curl 32 a snapping connection 39 (see figure 3b). After induction heating sealing the foil 33 is adhered to an upper region 40 of the curl 32 so that the cap 36 and the foam 35 may be released. Due to the induction heat sealing the foam layer 35 became bound to the cap 36 so that they can be removed in combination.
Figure 4 shows an alternative to the container shown in figure 3b, in that the curl 32 is formed in a necked portion 41 and the plastic cap 36 having a snap fitting 39 on the curl 32 is provided with a temper proof band 28. Accordingly the cap and temper proof means fall within the imaginary envelop of the container body because they reside in the necked portion 41.
Figure 5 shows another metal container 42 according to the invention comprising in a necked portion 34 an elongated curl 44 provided with an extended and downwardly directed upper edge portion 45. It is in this extended upper portion 45 that a metal foil 46 is adhered by induction heat sealing of an adhesive present initially only on the extended upper portion instead of being applied on the lower side of the metal foil. Obviously the lower side of the metal foil 46 alone or as well as on the extended upper portion the adhesive may have been applied.
Figure 6 shows a method of filling a metal container body 2 and induction sealing a foil 49 onto the container opening. A metal container body having a necked portion 3 is filled with a product 47 via arrow 48. Subsequently a metal foil 49 is applied on the edge 4 of the metal container body 2. Subsequently a metal cap 50 is applied over the metal foil 49 onto the metal container body 2 in the necked portion where it forms a clamp fitting. Transported following the arrow 51, the filled and closed container 52 is subjected to induction heat sealing in an induction heat sealing unit 35 wherein the container 52 is exposed to electromagnetic radiation dependent on the volume, height and diameter of the container 52. Leaving the induction heat sealing unit 53 the closed container 54 is provided with an foil 49 which is tightly closing of the food 47 from the outside.
Figure 7 shows another metal container body 55 according to the invention comprising an edge provided with a screw thread 57 onto which a metal cap 61 may be screwed. Figure 8a shows in cross section the edge 56 comprising the screw thread 57. Onto the upper portion 58 of the edge 57 is provided the metal foil 59 and subsequently the foam layer 60. Thereafter a metal cap 61 is screwed onto the edge 65 and thereto a skirt 62 of the cap 51 is provided with screwing flanks 63. Figure 8b shows the cap 61 screwed onto the edge 56 thereby pressing the foil 59 with inserted the height compensating foam layer 60. After heat sealing the foil 59 is permanently adhered to the upper part 58 of the edge 56 so that the cap 61 inclusive the foam layer 60 may be screwed of following the arrow 64.
Hereinbefore is described the inventive induction heat sealing of a foil onto the edge of a metal container body thereby forming a tightly closed container providing traditional retortable or dry products. A cap is applied by snapping, pressing or screwing onto the metal container body whereby the foil is brought in intimate pressed contact with the edge thereby it is possible with induction heat sealing to reliably and permanently or releasably connecting the foil to the edge. Upon release of the cap the foil is exposed to the consumer and may be opened and released thereby making available the content to the consumer.

Claims

Method for making a container comprising the steps of:
i) providing a metal container body having an opening;

ii) applying a foil over the opening;

iii) mounting a cap onto the container body thereby pressing the foil onto an edge of the opening; and

iv) induction heat sealing the foil to the edge.
Method as claimed in claim 1, wherein the cap is mounted by screwing, clamping and/or snapping onto the container body.
Method according to claim 1 or 2, wherein the foil is combined with the cap and the combination of the cap and the foil is mounted onto the container body.
Method as claimed in claim 3, wherein the foil is adhered to the cap, preferably via a foam layer.
Method as claimed in any of the claims 1-4, wherein temper proof means are applied to the cap mounted onto the container body.
Metal container makeable with the method according to any of the claims 1-5.
Container according to claim 6 comprising a metal container body having an opening, a foil applied over the opening and induction heat sealed onto an edge of the opening, and a cap mounted onto the container by pressing the foil onto the opening edge.
Container according to any of the claims 6 or 7, wherein the foil is connected to the cap.
Container according to claim 8, wherein the foil is connected to a foam layer adhered to the cap.
Method of filling a container according to claim 6-9, comprising the steps of:
i) providing a metal container body having an opening;

ii) filling the metal container body via the opening;

iii) applying a foil and a cap as defined in any of the claims 1-9, so that the foil is pressed against an opening edge; and

iv) induction heat sealing the foil onto the edge of the opening.
Filled metal container obtainable with claim 10.