CONTAINER FOR EMANATING VOLATILE SUBSTANCES

Abstract: A container for volatile substances, which has at least one region closed by a multi-ply mated film in which a plurality of outer plies (1-5) can be identified which constitute an impermeable barrier for the volatile substance, and which is detachable from the permeable ply (6). In order to allow the separation of the barrier layer from the permeable ply (6) a coextruded element, which is substantially composed of three plies, is provided: respectively, an outer polyethylene (4), an intermediate EVOH ply (5), and an inner polyethylene ply (6), which acts as a permeable ply. In order to be sure that separation always occurs between the EVOH and the inner polyethylene layer, a bonding resin (9) is interposed between the outer polyethylene ply (4) and the EVOH ply (5), while a peelable resin (10) is extruded between the EVOH ply (5) and the inner polyethylene ply (6).

Description: CONTAINER FOR EMANATING VOLATILE SUBSTANCES Technical Field The present invention relates to a container for emanating volatile substances. Background Art The container according to the present invention is of the kind that contains aromatic substances and is closed with a multi-ply film in which two groups of detachable plies can be identified. Multiple outer plies constitute a barrier for the aromatic substance, while a single inner ply, placed so as to close the containment compartment, is permeable to the volatile substance. In order to emanate the substance, the entire set of barrier plies is removed and only the permeable ply remains on the container. Several problems arise in these containers. On the one hand, when the container is in store (storage before use), the contained substance must not be able to escape in any way; on the other hand, separation of the barrier ply must occur without damaging the permeable ply. Several kinds of container, manufactured in order to achieve these purposes, are known. In a conventional solution, the permeable ply is constituted by paper, but this solution has the drawback that the substance permeates the paper and escapes through the edges even while the barrier ply is still coupled (i.e., before use) . This entails the drawback that the containers empty themselves even without being used. Containers are also known wherein there is provided a film made of a foamed material opening along its thickness when the multi-ply layer that constitutes the barrier is removed. In this case, the foamed ply does not break uniformly and therefore the emanation of the contained product is unpredictable and therefore uncontrollable. A solution is also known in which the plies that separate are obtained by coextruding polyethylene (or other permeable resins) with polypropylene or polypropylene copolymers, or nylon and polyethylene. This coextrusion operation, however, is very critical, since the strength of the connection between the two plies that must subsequently separate is highly influenced by the extrusion temperature. Disclosure of the Invention The aim of the present invention is to overcome the problems found in conventional containers. An important object is to provide a container which before separating the barrier ply is impermeable to the volatile product, so that it can be stored even for very long periods. Another important object is to achieve cohesion between the plies of the container in a manner which can be scarcely affected by the process temperature. Another object is to provide a container by using conventional components and conventional production methods. This aim, these objects and others which will become apparent hereinafter are achieved by a container for emanating volatile " substances which is closed by a film formed by multiple outer plies, at least one of which constitutes a barrier for the volatile substance and at least one is a membrane which is permeable to the volatile substance, said outermost plies (with respect to the container) being detachable from said permeable membrane, wherein said permeable membrane is made of polyethylene and is part of a coextruded element composed of at least three plies which are, sequentially, polyethy 1 ene-EVOH- polyethylene, with a peelable resin interposed between the EVOH ply and said permeable membrane. EVOH is an ethylene-vinyl alcohol copolymer. Brief Description of the Drawings Further characteristics and advantages of the present invention will become apparent from the following detailed description of an embodiment, which is given only by way of non-limitative example and is illustrated with the aid of the accompanying drawings, wherein: figure 1 is a sectional view of a container according to the invention; figure 2 is another sectional view, taken along the plane II-II of figure 1. Ways of carrying out the Invention With reference to the above figures, the container is composed of a lower body, designated by the reference letter A, which is closed at the top by a film, generally designated by the reference letter B. The lower body A forms a tray-like compartment C, in which the volatile product D is to be contained. The film B is provided by means of a sequence of plies which, starting from" the outside, are: — a paper ply 1; — an aluminum ply 2; — a polyester ply 3; — a polyethylene ply 4; — an EVOH ply 5; — a polyethylene ply 6. The lower body A is obtained by means of a polyethylene ply 7 and a polyacrylonitrile ply 8. The aluminum ply 2 is substantially the barrier element, while the polyethylene ply 6 is the permeable membrane . In order to separate the group of plies 1, 2, 3, 4 and 5 from the permeable ply 6, which during use is the element for closing the compartment C, the plies 4, 5 and 6 are first obtained by coextrusion. More particularly, as shown in figure 2, coextrusion occurs by interposing a bonding resin 9 between the polyethylene ply 4 and the EVOH ply 5 and a peelable resin ιo between the EVOH ply 5 and the polyethylene ply 6 that constitutes the permeable membrane. In these conditions, coextrusion is not critical, particularly in terms of temperature, and the bond between the EVOH ply 5 and the polyethylene ply 6 is weaker than the bond between the polyethylene ply 4 and the EVOH ply 5. The separation region is therefore always located at the peelable resin 10 and the polyethylene ply 6 is in any case not damaged by this operation. As regards the connection among the other plies, it is convenient to interpose a layer of glue 11 between the paper ply 1 and the aluminum ply 2, while an adhesive 12 is provided between the aluminum ply 2 and the polyethylene ply 3; likewise, a similar adhesive 13 is interposed between the polyester ply 3 and the polyethylene ply 4. The advantages of a film of this kind are linked to the easy manufacture of the coextruded element, in which it is possible to perfectly control the resistance to ply separation between the EVOH and the polyethylene. The aluminum barrier, which is known to be much weaker than polyethylene and polyester, is arranged so that it is not affected by mechanical stresses. From the above description and from the illustrations it is evident that the intended aim and objects have been achieved by adopting a new combination of plies which ensures separation as well as perfect tightness and impermeability to volatile substances when the container is intact . In order to facilitate separation, a small already- separated region 14 is provided which allows easy grip and guides separation of the plies in the chosen point.

Claims: CLAIMS 1. A container for emanating volatile substances, closed by a film formed by multiple plies, at least one of the outer said plies constituting a barrier for the volatile substance and at least one being a membrane which is permeable to the volatile substance, said outermost plies being detachable from said permeable membrane, characterized in that said permeable membrane is made of polyethylene and is part of a coextruded element composed of at least three plies which are, sequentially, polyethy lene-EVOH- polyethylene, with a peelable resin interposed between the EVOH ply and said permeable membrane. 2. A container according to claim 1, characterized in that said coextruded element is composed of a polyethylene ply which is firmly coupled, also with the aid of a bonding resin, to the EVOH ply, which is more weakly coupled, also by means of the interposition of a peelable resin, to the polyethylene ply which acts as permeable membrane. 3. A container according to claim 1, characterized in that said coextruded element is firmly coupled, on the opposite side with respect to said peelable membrane, to an additional triple ply which has a barrier function. 4. A container according to claim 3, characterized in that said triple ply is composed externally of a paper ply which is coupled to an aluminum sheet which is in turn coupled to a polyester ply. 5. A container according to claim 1, characterized in that the weakest coupling among the various plies is between the EVOH ply of the coextruded element and the polyethylene ply that constitutes " the permeable membrane. 6. A container according to claim 5, characterized in that the closure of the various plies is hermetic along the edges and constitutes a barrier to the volatile substance. 7. A container according to claim 1, characterized in that it has a small separated region between the EVOH and the permeable membrane which constitutes a grip tab for separating the two parts of the film at this coupling.

Inventors: VISONA SERGIO, VISONA', SERGIO
Applicants: BURGOPACK STAMPA TRASFORMAZION, VISONA SERGIO, BURGOPACK STAMPA, TRASFORMAZIONE, IMBALLAGI S.P.A., VISONA', SERGIO
Application year: 1997
Main classification: A61L9
IPC codes: A61L9