Receptacles – Closures – Removable closure retained by adhesive or fusion means
Reexamination Certificate
1999-04-19
2001-10-16
Shoap, Allan N. (Department: 3727)
Receptacles
Closures
Removable closure retained by adhesive or fusion means
C220S359100, C220S359300, C220S062130, C220S062120, C156S069000, C156S580000
Reexamination Certificate
active
06302290
ABSTRACT:
The invention relates to a sealing structure for a container provided with an opening, this structure being of the same kind as those which comprise a sheet welded around the edge of the opening of the container.
For economic and recycling reasons, products are being packaged in increasingly large amounts in the same container, in particular in the same package. This is a source of problems for the consumer who does not wish to use the packaged product at one time. After having opened the container in order to remove part of the contents, the consumer wants to be able to reseal the container easily and effectively and to restore part of its initial integrity which it possessed before it was opened. For example, in the case of foodstuffs, the consumer wants to be able to reseal the package before putting it back into his refrigerator in order to avoid the problem of an unpleasant smell, the problem of the packaged product drying out and the problem of loss of space, and to avoid other drawbacks.
This is also true for products other than foodstuffs, for example for industrial products packaged in large number, such as screws, nails and washers, as well as for pharmaceutical products, for example those in the form of pills or tablets.
These non-limiting examples show that there is a considerable demand, in very varied fields, for a sealing structure for containers which allows easy opening and effective and simple resealing of the container after part of its contents has been removed.
The object of the invention is therefore to provide a sealing structure which satisfies these requirements.
The object of the invention is also to provide a sealing structure which is relatively simple and inexpensive to manufacture and to fit onto the container.
According to the invention, a sealing structure for a container provided with an opening, comprising a sheet welded around the edge of the opening of the container, is characterized in that the sheet consists of at least three layers, namely a welding layer pressed against and welded as a bead to the edge of the opening, a barrier-forming exterior layer and an intermediate adhesive layer, the weld between the bead of the welding layer and the edge of the opening having a tear strength greater than the strength of adhesion between the welding layer and the adhesive layer so that, at the first occasion of exposing the opening, the welded bead of the welding layer remains in place around the edge of the opening and separates from the rest of the welding layer and from the adhesive layer, which adhesive layer is thus uncovered over an area corresponding to the said bead, it being possible for the container to be sealed again by pressing the uncovered area of the adhesive layer against the bead of the welding layer that has remained in place.
The exterior layer may consist of a flexible film; its thickness may be approximately 50 micrometers. Advantageously, the exterior layer is made of biaxially oriented polyester.
As a variant, the exterior layer may consist of a rigid film.
The welding layer consists of a thin film, the thickness being, in particular, about 20 micrometers, which is easy to tear, or of a thicker film having easy-tear properties obtained by adjusting the extrusion parameters or by adding mineral fillers.
By way of example, the welding layer may consist of a film of high-density polyethylene.
The adhesive layer is preferably formed by depositing a material to a thickness at least equal to 10 micrometers. This adhesive layer is formed, in particular, by a permanently tacky acrylic polymer, which is a solid at room temperature, or by a hot-melt adhesive based on a thermoplastic elastomer.
Advantageously, the materials of which the layers are composed comply with the legislation defining the use of adhesives in the context of food packaging. The layers may be transparent so that the structures sheet itself is transparent.
The invention also relates to a container sealed by such a sealing structure. The container may be formed by a rigid film or by a flexible film. In one embodiment, the container is made of a film of rigid PVC (polyvinyl chloride) covered on the inside by a film of linear polyethylene with a layer of polyurethane adhesive interposed between the two films.
The invention also relates to a method of sealing a container having an opening by a sheet welded around the edge of the opening, characterized in that, for the sealing process, a sheet is used which consists of at least three layers, namely a welding layer, a barrier-forming exterior layer and an intermediate adhesive layer and in that the sheet is joined to the edge of the container, in particular using a welding tool, by welding around a bead the weld being produced so as to cause the welding layer and the adhesive layer to waken and so as to establish a bond between the bead of the welding layer and the edge of the opening, having a tear strength greater than the strength of adhesion between the welding layer and the adhesive layer so that, at the first occasion of exposing the opening bead, the welded bead of the welding layer remains in place around the edge of the opening and separates from the rest of the welding layer and from the adhesive layer.
The sheet consisting of at least three layers may be produced by depositing the adhesive layer between the exterior and welding layers by the hot extrusion of an adhesive resin between these layers.
According to another option, the adhesive resin is deposited hot on the exterior layer before calendering the welding layer to the latter.
The sheet thus produced can be stored in reeled form since the welding layer protects the adhesive layer and prevents problems of blocking between turns in the reels of sheet.
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Atofina
Eloshway Niki M.
Pennie & Edmonds LLP
Shoap Allan N.
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