EP1582477A1

EP1582477A1 - Container closure and method of its manufacture

Info

Publication number: EP1582477A1
Application number: EP04007594A
Authority: EP
Inventors: Arno Hohmann; Mathias Bertl; Kerstin Janz
Original assignee: 3M Espe AG
Current assignee: 3M Deutschland GmbH
Priority date: 2004-03-29
Filing date: 2004-03-29
Publication date: 2005-10-05

Abstract

The present invention relates to a sealing assembly, particularly for sealing container openings, a sealing cap assembly using such sealing assembly, a container being sealed by such sealing assembly or being closed by such a sealing cap assembly, respectively, and a method for manufacturing a sealing assembly. The sealing assembly according to the present invention comprises at least a first film (2) and a second film (3). The at least first and second films are adjacent to each other. The film comprises an aperture (5) forming a through-hole, and at least a portion (6) of the edge of the aperture forms a wiping edge.

Description

Field of the present invention

The present invention relates to a sealing assembly, particularly for sealing container openings, a sealing cap assembly using such sealing assembly, a container being sealed by such sealing assembly or being closed by such a sealing cap assembly, respectively, and a method for manufacturing a sealing assembly.

Background of the present invention

Pulverulant or granular materials, for example dental powder such as glass ionomer, are usually stored and delivered in containers such as bottles, preferably glass bottles. In order to prepare a glass ionomer cement, usually some amount of a glass ionomer powder is mixed with a liquid by hand. The powder dosage used therefor is obtained or discharged from the bottle using a spoon. In order to achieve acceptable dosing reproducibility, conventional bottles contain a plastic insert at the bottle opening with a "wiping edge" to wipe excess powder off the spoon.
In case humidity sensitive powders are used, it is necessary that the container has a moisture-proof seal. Conventionally, a suitable seal is achieved by using an aluminium multi-layer film that is sealed to the opening or lip, respectively, of the bottle. A variety of solutions are actually available in the prior art for sealing glass bottles. However, these conventional methods are not suitable for bottles containing such glass ionomer cements as the required plastic insert covers the lip of the bottle (at least in part), thus making it difficult to seal the aluminium foil to the top of the bottle. Sealing the film directly upon the plastic insert is also not possible because existing gaps between the insert and the bottle lip would not ensure an appropriate moisture-proof sealing. Furthermore, the conventional assembly is disadvantageous because the separate plastic insert adds cost to the product.

Summary of the invention

A first object of the present invention is to provide a simple and cost-effective sealing assembly.
A further object of the present invention is to provide a simple and cost-effective sealing cap assembly.
Another object of the present invention is to provide an improved container at low costs that is relatively simple in design.
Finally, another object of the present invention is to provide a method for manufacturing a sealing assembly.
These objects are achieved with the features of the claims.
According to a first aspect of the present invention, a sealing assembly is provided. The sealing assembly according to the first aspect of the present invention comprises at least a first film and a second film. Preferably, the first and second film are provided in a sandwich construction, i.e. the first film and the second film are adjacent to each other. Furthermore, the first film (forming a "dosing film" or "dosing wiper") comprises an aperture forming a through-hole through the first film. At least a portion of the edge of the aperture forms a wiping edge. In comparison to conventional assemblies, this first film replaces the commonly used plastic insert. The second film is provided to cover the first film/wiper film, and thus to form a closure film for a container being sealed with the sealing assembly according to the first aspect of the present invention.
Preferably, in order to form the wiping edge, the aperture provided in the first film is not a circular aperture but only a partial circular aperture that comprises a straight edge portion that forms the wiping edge. The aperture is preferably provided in line with the opening of the container so that, for example, a spoon can be inserted through the aperture into the interior of the container in order to take some amount of the material contained in the container; upon taking out the spoon from the container, the wiping edge of the first film is used to wipe excess powder of the spoon. Alternatively, the wiping edge does not have a straight edge portion but rather a zig-zag shape, sinusoidial shape or other meandering shape.
The second film covers the first film such that a moisture-proof sealing is achieved between the first film and the second film. Preferably, the closure film comprises several layers of plastic film, i.e. is of a multi-layer construction, and preferably comprises at least one metal foil, for example aluminium.
The first film preferably comprises several layers of plastic and/or metal films.
Preferably, the first film and/or the second film are coated films.
According to a preferred embodiment, the first and second films are laminated to form a semifinished wiper/closure element. In order to provide adhesion between the first film and the container, the first film comprises an adhesion area on the surface that is opposite to the second film, i.e. on the surface facing the container. The adhesion area is provided with a first adhesive. Preferably, the first adhesive is a heat-sealable adhesive so that the first film is heat-sealable upon a container opening or lip. Alternatively, in case the container is made out of plastic it is possible to directly bond the film onto it. Preferably, if polyethylene or polypropylene is used for both parts, i.e. container and first film, sealing can easily be made without the use of an adhesive. According to an alternative embodiment, pressure sensitive glue (activation of glue by just pressing two surfaces onto each other) is used for attaching the first film to the container instead of a heat-sealable adhesive. However, further alternatives are within the scope of the present invention. For example, a further method would be the usage of ultrasonics. In this case the lip of the container facing the first film preferably forms a sharp edge in order to provide homogeneous welding. Alternatively, micro-replicated surfaces could be used since micro-replication provides very tight sealing. Further alternatively, use wet glue coating (glue with solvents or hot-melts) is used. In this case the film and container are free of glue. The glue is coated onto the container lip, the film or onto both parts. A variety of glue types are available for this, e.g., Pioloform with a solvent, or polyurethane types (hot-melt). Instead of heat sealing using hot tools in general it is envisaged to use laser, induction or ultrasonics. Finally, it is furthermore possible to use so-called "self-adhesives".
The adhesion area on the first film is preferably sized and shaped such that it corresponds to the lip or opening of the container, i.e. the first adhesive is present in that area of the first film that is in direct contact with the container.
It is preferred that the adhesion between the first film and the container is stronger than the adhesion between the first and the second films, respectively, so that it is possible to peal the second film/cover film from the first film/wiper film while the wiper film remains on the container. In other words, the first film is basically permanently sealed to the container and remains on the container even after the second film, i.e. the closure, is removed from the container in order to take out material from the container.
As regards bonding of the second film to the first film, all concepts described above for adhesion between the first film and the container are applicable if the second film is not a metal film. Is furthermore preferred to use a modified plastic for the first film which provides adhesion - when heat sealed - directly to the metal surface of the second film. In this case no glue has to be used for bonding the first and second films, e.g., a Surlyn(R)™ plastic type providing those characteristics.
Materials with different adhesion properties to provide both the required permanent and temporary seal are well-known in the art (for example polyvinylbutyral, like Pioloform (R) BL 18™ manufactured by Wacker Chemie, Germany, or Surlyn (R)™ manufactured by DuPont). Furthermore, different adhesion technologies, like those utilizing light-curing, thermal setting, chemical cure reaction etc. are preferably used in the present invention.
In a preferred embodiment of the present invention, the sandwich structure is obtained by laminating Surlyn/tie layer (or bonding agent, respectively)/PET (high stiffness)/separation layer to PET on a plastic film/tie layer (or bonding agent, respectively)/aluminium/tie layer (or bonding agent, respectively)/PET (thin).
Thus, the sealing assembly according to the first aspect of the present invention provides a gas-proof and also moisture-proof sealing using cost effective and market-available components.
According to a second aspect of the present invention, a sealing cap assembly is provided. The sealing cap assembly comprises a cap, for example a screw cap and a sealing assembly according to the first aspect of the present invention. The sealing assembly is provided in the interior of the cap.
Such a sealing cap assembly is preferably used in order to seal the wiper/closure assembly to the container. Preferably, an induction sealing method is used. According to the induction sealing method, the container is first closed with the screw cap (with the sealing assembly accommodated therein). As a next step, electromagnetic induction is applied to the container. Due to the induced energy, the temperature of the metal part of the sealing assembly increases which causes the first film of the sealing assembly to adhere to the container. For example, in case a hot-melt glue layer is used as first adhesive, the glue layer will start to melt owing to the temperature increase. The screw cap provides the necessary force to ensure that the sealing assembly is completely secured and adhered to the container. Upon removal of the screw cap, the second film can be removed from the first film, and material contained in the container can be dispensed.
Preferably, the sealing cap assembly comprises an additional elastic layer, for example, a foamed plastic layer. Such an additional elastic layer is advantageous because it provides a homogenous pressure contact between the sealing assembly and the container. The elastic layer is preferably arranged between the sealing assembly and the bottom of the cap, and is connected to the second film of the sealing assembly such that the elastic member remains in the screw cap when the screw cap is unscrewed from the container. After the closure film has been removed from the container, the elastic layer operates as a seal when the screw cap is again screwed onto the container. Alternatively, the elastic layer is connected to the second film by a tie layer. This alternative is advantageous because all layers can then be manufactured in a single in-line process. This tie layer would provide just a marginal adhesion in order to allow handling during manufacturing. Thus, after assembly into the screw cap the elastic layer would easily separate from the other films. To facilitate separation and to fix the elastic layer in the cap, the elastic layer could additionally be coated with sticky glue on the side facing the inner surface of the cap.
Instead of using a sticky glue on the elastic layer facing the inner side of the cap, the elastic layer is preferably mechanically held in the cap. In this case, the elastic layer has a larger diameter relative to the first and second film, and is, for example, clamped into the cap. Alternatively, it is preferred to use micro-replication structures on the elastic layer and the inner surface of the cap. These structures can be directly manufactured on the elastic film and the cap during film and cap manufacturing, or, alternatively, separate elements with micro-replication structures are used.
According to a third aspect of the present invention, an improved container is provided. The container comprises an opening that is sealed with a sealing assembly according to the first aspect of the present invention, or is closed by a sealing cap assembly according to the second aspect of the present invention. Preferably, the container is a bottle, and more preferably a glass bottle.
The fourth aspect of the present invention is related to the manufacturing process for manufacturing a sealing assembly according to the present invention. Preferably the manufacturing of the sealing assembly is done in an "endless" or "reel-to-reel" process as is standard in the film manufacturing industry.
According to the present invention, the manufacturing of a sealing assembly comprising a first layer, a second layer, and an additional elastic layer is preferably as follows.
In a first step, the first film (wiper film) is coated with an adhesion layer, i.e., the first adhesive for providing adhesion between the first film and the container. It is preferred herein that the first film comprises a PET film and the container is a glass bottle. The adhesion layer is preferably a co-extruded layer out of two Surlyn™ materials, one designed for optimum adhesion to PET and the other designed for optimum adhesion to glass, both Surlyn™ types compatible to be co-extruded so as to form a strong adhesion to each other. However, Surlyn™ types which provide optimum adhesion to glass and PET which are preferred to coextrusion of two materials. In this case, extrusion of one material only would be sufficient.
In a second step, the first and second films are laminated together. Preferably the second film (closure film) comprises an aluminium foil. The aluminium foil is coated via extrusion with a tie layer preferably comprising Surlyn™. The tie layer provides a temporary adhesion between the first and second films. Therefore, it is preferred to coat the aluminium foil with a Surlyn™ material which provides permanent adhesion to the aluminium foil (second film) but temporary adhesion only to the PET film (first film). The PET film (first film) is laminated onto the still warm coat of the aluminium foil (second film). Preferably, lamination is done shortly after the aluminium foil (second film) has been coated but while it is still, for example, on the chill roll in order to allow the coat to cool down to a temperature that prevents the aperture, already present in PET film (first film), from being closed by the coating material.
At the same time, the temperature has to be sufficient to achieve sufficient bond strength between the two films.
Finally, in a third step, an elastic film is laminated to the film assembly formed by the first and second film. Therefore, the elastic layer is preferably coated by a material providing a relatively low level of adhesion, e.g. a wax, between the film assembly and the elastic layer. Preferably, this material, e.g. the wax, is coated via a thermo glue application system and the film assembly is laminated to the still hot coat shortly after the coating step.
It is preferred to arrange all processes in-line. Alternatively, all processes are performed separately. Furthermore, the order of processes or process steps may be changed.
According to the present invention, for manufacturing of a sealing assembly for mechanical retention in the cap, the final film assembly comprising a first film, a second film, and an additional elastic film is preferably punched in two steps. For this process it is preferred to use sharp-edged cutting tools which penetrate the film assembly only partially. In a first step, the elastic layer is punched with a first cutting tool. Penetration of the first cutting tool is limited so as to not punch through the whole film assembly but only through the elastic film. The cutting edge of the first cutting tool is such that the elastic layer punched out has a desired size or diameter. In a second step, the other layers are punched from the opposite side with a second cutting tool. The depth of the cut is limited to end up close to or within the elastic layer. The cutting edge of the second cutting tool is such that the punched areas of the first and second films are smaller in size or diameter than the size or diameter of the elastic layer. Finally, the punched sealing assembly (i.e., punched final film assembly and elastic film) is pushed out of the film assembly and inserted into the screw cap.
According to another aspect of the present invention, a kit is provided comprising a container, a sealing assembly according to the first aspect of the present invention or a sealing cap assembly according to the second aspect of the present invention.

Brief description of the drawings

Other features and advantages of the present invention will be seen as the following description of particular embodiments progresses in conjunction with the drawings in which:

Fig. 1: shows a preferred embodiment of the first and third aspects of the present invention;
Figs. 2a, b: alternative wiping edges;
Fig. 3: shows an alternative solution to hold the elastic layer in the cap; and
Fig. 4: shows a preferred manufacturing process.

Detailed description of the invention

The following description is meant to be illustrative only and not limiting. Other embodiments of this invention will be apparent to those of ordinary skill in the art in view of this description.
The sealing assembly 1 shown in Fig. 1 comprises a wiper film 2 and a closure film 3. The wiper 2 comprises an aperture 4 forming a through-hole through the wiper film. As shown in Fig. 1, the aperture is not a circular aperture, but comprises a straight edge 6 in addition to the partial-circular edge 5. Edge 6 functions as a wiping edge. Alternative shapes of the wiping edge are shown in Figs. 2a and 2b. Fig. 2a shows a zig-zag shape of the wiping edge, and Fig. 2b shows a meandering wiping edge.
As shown in the cross-sectional view of the Fig. 1, the closure film 3 is located adjacent to the wiper film 2 so that the closure film fully covers the aperture 4 provided in the wiper film 2. The wiper 2 is attached to the lip of the bottle 10 by means of a seal 7. The closure film 3 is connected to the wiper film 2 by means of another seal 8. Seal 8 is a peelable seal, whereas seal 7 provides a permanent seal.
As shown in the top left part of Fig. 1, the seal container is opened in that the closure film with the peelable seal is removed.
Fig. 3 shows a preferred embodiment for holding an elastic layer 11 in a cap 13 for a container. The elastic layer 11 comprises a diameter that is larger than the diameter of the wiper film/closure film so that in can be mechanically fixed to the cap. As shown in Fig. 3. cap 13 comprises an inner annular flange 12 that provides that the elastic layer 11 is kept in the cap 13 once the cap 13 is unscrewed from the container.
Fig. 4 shows a preferred method of manufacturing a sealing assembly from a film assembly comprising a first film 2, a second film 3, and an elastic layer 11. In step I, a first cutting tool 20 is used to punch through the elastic layer 11 (here from above). During this step, the film assembly is supported by support structure 21. In the following step II, a second cutting tool 22 is used to punch through the first and second films 2, 3 (here from below). A support structure 23 is provided on the opposite side to support the film assembly during the punching step. As can be clearly seen in Fig. 4, the diameter of the first cutting tool 20 is larger than the diameter of the second cutting tool 22 so that the resulting sealing assembly comprises a T-like cross-sectional shape. The elastic layer 11 with its larger diameter can be mechanically attached to the cap, as shown in Fig. 3.

Claims

Sealing assembly comprising
at least a first film and a second film;
said at least first and second films being adjacent to each other;
said first film comprising an aperture forming a through-hole through the first film, at least a portion of the edge of said aperture forming a wiping edge.
The sealing assembly of claim 1, said first film further comprising an adhesion area on the surface being opposite to the second film, wherein a first adhesive is provided in said adhesion area.
The sealing assembly of claim 3, said adhesion area being sized and shaped for adhering said sealing assembly to an opening of a container.
The sealing assembly of claim 1, 2 or 3, wherein said first and second films are laminated.
The sealing assembly of claim 1, 2 or 3, wherein said first and second films are connected by means of a second adhesive.
The sealing assembly of any of claims 2 to 5, wherein said first adhesive provides a stronger adhesion than the adhesion between said first and second films.
The sealing assembly of any of claims 1 to 6, said first film being a multi-layer film comprising plastic and/or metal layers.
The sealing assembly of any of claims 1 to 7, said second film being a multi-layer film comprising plastic layers and preferably at least one metal layer.
The sealing assembly of any of claims 1 to 8, wherein said first and/or second films is/are coated.
The sealing assembly of any of claims 3 to 9, wherein said sealing assembly is heat-sealable upon a container opening.
The sealing assembly of any of claims 1 to 10, further comprising an elastic layer releaseably connected to said second film on the surface being opposite to said first film.
The sealing assembly of claim 11, said elastic layer comprising an adhesive area on the surface being opposite to the second film.
The sealing assembly of claim 11, said elastic layer comprising micro-replication structures on the surface being opposite to the second film.
The sealing assembly of claim 11, 12 or 13, said elastic layer having a first diameter and said first and second films having a second diameter, said first diameter being larger than said second diameter.
The sealing assembly of any of claims 11 to 14, said elastic layer being a foamed elastic layer.
Sealing cap assembly comprising
a cap; and
a sealing assembly according to any of claims 1 to 15, said sealing assembly being provided in the interior of said cap.
The sealing cap assembly of claim 16, wherein said elastic layer is facing the bottom of said cap.
The sealing cap assembly of claim 16 or 17, wherein said elastic layer is connected to the bottom of said cap such that it remains in said cap once said cap is removed from a container, whereas said sealing assembly remains on said container.
The sealing cap assembly of any of claims 16, 17, or 18, said cap being a screw-cap.
Container comprising a container opening being sealed with a sealing assembly of any of claims 1 to 15.
The container of claim 20, comprising a sealing cap assembly of any of claims 16 to 19.
The container of claim 20 or 21 being a bottle, preferably a glass bottle.
The container of claim 20, 21, or 22, wherein the container contains a glass ionomer cement.
A kit comprising a container, a sealing assembly according to any of claims 1 to 15, or a sealing cap assembly according to any of claims 16 to 19.
The kit of claim 24, wherein the container contains a glass ionomer cement.
A method for manufacturing a sealing assembly from a film assembly comprising at least a first film and a second film, said at least first and second films being adjacent to each other, said first film comprising an aperture forming a through-hole through the first film, at least a portion of the edge of said aperture forming a wiping edge, and an elastic layer releaseably connected to said second film on the surface being opposite to said first film, said method comprising the steps of:

punching only said elastic layer by means of a first cutting tool;

punching said first film and second film from the opposite side by means of a second cutting tool.
The method of claim 26, wherein the diameter of the cutting edge of the first cutting tool is larger than the diameter of the cutting edge of the second cutting tool.