Patent Application
20140305939
The invention relates to the field of packaging, and, more particularly, to that of the multilayer structures forming at least a part of the wall of a package.
Many products degrade when they are in contact with oxygen molecules. The packaged products can come into contact with the oxygen for two main reasons.
The first reason is linked to the air captive in the package at the time of the packaging operation when the product does not completely fill the cavity of the container. The second is linked to the migration through the wall of the packaging of the oxygen molecules present in the ambient air.
A number of approaches have been proposed to mitigate these difficulties, such as substituting the air captive in the package with an inert gas, like the use of multilayer structures or like the use of oxygen absorbers that are captive in the wall of the package.
There are numerous packagings or parts of packagings which are manufactured by injection molding or by compression molding. Improving the barrier properties of these molded packages has been the subject of numerous developments in recent years. The patent applications WO2007111857 and WO2008096290 describe improving the molded objects by multilayer injection or compression.
The development of oxygen absorbers has made it possible, in some cases, to replace the more complex multilayer structures to be manufactured with single-layer packaging walls comprising oxygen absorbers.
However, this solution can be used only when the conservation time of the product is time-reduced.
Unlike the packagings manufactured from films for which it is possible to obtain an almost total oxygen barrier—that is to say, for example, when the structure comprises an aluminum film—it is not possible today to obtain as high a barrier level for packages or parts of packages manufactured by injection or compression molding.
Some packagings comprise only a part that is molded. Such is the case, for example, of the flexible tubes for which the head is manufactured by molding. These packagings exhibit an oxygen permeability that is generally higher in the molded part despite the efforts made to improve the barrier properties. These packagings also exhibit a greatly reduced oxygen impermeability at the area of transition between the molded part and the film forming the flexible part. For these reasons, it is difficult to use packagings comprising a molded part to conserve products that are very sensitive to oxygen or to conserve products that degrade with oxygen for a long period.
The object of the invention is to remedy the abovementioned problems using a significant improvement of the oxygen barrier properties of the molded packagings.
The invention consists of a multilayer structure having a very weak oxygen permeability through an unexpected synergy between at least one passive barrier layer and one active barrier layer. A “passive barrier layer” is defined as a layer of oxygen barrier resin having a weak oxygen permeability and an “active barrier layer” is defined as a layer of oxygen permeable resin comprising oxygen absorbers.
The invention results from a synergy between the passive and active barrier layers as well as their relative position in the multilayer structure.
The invention also makes it possible to significantly improve the oxygen impermeability of packagings comprising a molded part linked to a flexible part composed of films.
Hereinafter in the explanation, multilayer structures obtained by molding are presented. In order to simplify their understanding, the same convention will always be used, consisting in describing the multilayer structure from the outer surface of the packaging which is generally the visible part, to the inner surface of the packaging which is in contact with the packaged product. The following references will be used for clarity of the explanation:
The invention consists in using at least two distinct resins for which the oxygen permeability ratio is greater than or equal to 50. The first resin with the lower oxygen permeability forms the passive oxygen barrier layer 1. Oxygen absorbers are dispersed in the second resin for which the oxygen permeability is at least 50 times greater and forms the active oxygen barrier layer 2. The association of the layers 1 and 2 results in considerably improved conservation times.
The invention also consists in producing a multilayer structure by injection or compression molding, said structure comprising at least one passive barrier layer and one active barrier layer; the active barrier layer being situated between the passive barrier layer and the packaged product.
In order to better understand the unexpected effect of the invention, let us consider the following three examples:
Take a multilayer structure of overall thickness denoted E forming a package. The multilayer structure is composed of a first, strongly oxygen permeable resin and a second resin with oxygen permeability at least 50 times lower and forming a thin passive barrier layer denoted Ep. This multilayer structure leads to a product conservation time denoted Dp. It is known to those skilled in the art that, by doubling the thickness of the passive barrier layer, or by adding a second passive barrier layer of identical thickness, the product conservation time is roughly doubled.
Take the packaging considered in example 1 in which the wall of thickness E is composed only of said first, strongly oxygen permeable resin containing 15% oxygen absorber. The conservation time of said product in this packaging is denoted Da. It is also known to those skilled in the art that by doubling the quantity of oxygen absorber in the wall of packaging the product conservation time is roughly doubled.
The third example illustrates the unexpected effect of the invention. Take the packaging considered in the examples 1 and 2 in which the wall of thickness E is composed of said first, strongly permeable resin and containing 15% oxygen absorbers and said second resin forming a passive barrier layer of thickness Ep. The product conservation time in the packaging is very much greater than the sum of Dp and Da.
A first embodiment of the invention consists of a multilayer structure comprising an active barrier layer and a passive barrier layer.
A second embodiment of the invention consists of a structure comprising at least one active barrier layer 2 captive between two passive barrier layers 1; said active barrier layer 2 being composed of oxygen absorbers dispersed in a first resin and the passive barrier layer 1 being composed of a second resin of oxygen permeability at least 50 times lower than that of said first resin.
A fourth example relating to the first embodiment of the invention is illustrated in
A fifth example relative to the first embodiment of the invention is illustrated in
The addition of thin layers of binder between the layers in order to improve the cohesion of the structure is not described systematically in this explanation. This variant is difficult to obtain by injection in multi-impression molds because of the large number of layers. However, this variant can be obtained easily by compression molding using a co-extruded multilayer dose. In order to avoid complicating the explanation, the layers of binder are not described systematically, bearing in mind that a person skilled in the art knows when these layers have to be added.
A third embodiment of the invention consists of a structure comprising at least one passive barrier layer captive between two active barrier layers 2; said active barrier layer 2 being composed of oxygen absorbers dispersed in a first resin and the passive barrier layer 1 being composed of a second resin of oxygen permeability at least 50 times lower than that of said first resin.
A sixth example related to the second embodiment of the invention leads to a multilayer structure of the 2/1/2 type illustrated in
A seventh example relating to the second embodiment of the invention is illustrated in
An eighth example is a combination of the first and second embodiments of the invention. This example illustrated in
Several versions of the bottle 4 have been produced by varying the multilayer structure of the neck 6 and of the bottom 7 and correspond to the examples respectively denoted 9 to 13. The multilayer structure of the neck 6 and of the bottom 7 has been produced with the following materials:
The oxygen barrier properties of the bottles are compared by measuring the time it takes for the liquid contained by the bottle to receive 5 ppm (parts per million) of oxygen. These measurements are conducted in a laboratory according to a rigorous measurement protocol. A Presens laboratory appliance is used to quantify the quantity of oxygen which migrates in the packaging. The results of these measurements are summarized in the table below:
The examples 9 and 10 correspond to the prior art and serve as a reference.
The example 9 illustrates the properties of the bottle when the neck 6 and the bottom 7 comprise a multilayer structure with only a passive barrier. The time for 5 ppm of oxygen to migrate into the packaging is 7 days.
The example 10 corresponds to the properties of the bottle 4 when the neck 6 and the bottom 7 are composed of a single layer containing oxygen absorbers. The time for 5 ppm of oxygen to migrate into the bottle is 32 days.
The example 11 corresponds to the properties of the bottle 4 when the neck 6 and the bottom 7 comprise a passive barrier layer captive between two active barrier layers. This multilayer structure is illustrated in
The example 12 illustrates the properties of the bottle 4 when the neck 6 and the bottom 7 comprise the five-layer structure illustrated in
The example 13 describes the properties of the bottle 4 when the neck 6 and the bottom 7 comprise a passive barrier layer 1 and an active barrier layer 2, the active barrier layer being situated inside the packaging. The time for 5 ppm of oxygen to migrate into this bottle is 619 days. The product conservation time in this bottle is increased by a factor of 19 compared to the prior art bottle described in the example 10, and by a factor of 88 compared to the prior art bottle described in the example 9.
The multilayer structure described in the example 13 is particularly powerful but, however, difficult to produce by multi-material molding. In practice, for economic reasons it is important to reduce the thickness of the passive barrier layer 1, which is difficult when the layer 1 is produced by injection or compression molding. There are, however, alternative techniques that make it possible to obtain this two-layer structure economically. A first alternative consists in overmolding a film containing the passive barrier with a resin comprising oxygen absorbers. This technology is limited to relatively simple object geometries. A second alternative consists in molding a multilayer object with a resin containing oxygen absorbers and then subsequently depositing a coating which adds a passive barrier to the surface of the molded object. Numerous coatings are known in the prior art such as, for example, the thin layers obtained by plasma deposition or gaseous phase evaporation. According to these methods, the passive barrier layer is generally either of the silicon or aluminum oxide type, or of amorphous carbon type.
The invention is not limited to the abovementioned examples and materials listed. There are a wide variety of resins or materials that can be used to form the passive barrier layer. In general, it is considered that the material can be used as passive barrier when its oxygen permeability value is at least 50 times lower than that of the material in which oxygen absorbers are added to form an active barrier layer.
Similarly, there are a wide variety of oxygen absorbers. The oxygen absorbers can, for example, be organic polymers which operate through iron oxidation, ascorbic acid or a polyamide catalyzed by cobalt; these products are standard on the market. In the invention, the term active layer is used for a layer containing at least elements which react with oxygen in order to limit the migration of the oxygen molecules into the packaging. In some products, the oxygen absorbers are associated with a barrier material which is dispersed in the form of slivers in order to increase the effectiveness by increasing the tortuousness.
As explained previously, the invention makes it possible to considerably improve the barrier properties of the parts molded by injection or compression molding. However, while working on developing the invention, the inventors observed that the oxygen impermeability of the packaging could be further improved by also applying the invention to other parts of the packaging.
When the packaging is a flexible tube, the inventors observed that the oxygen impermeability of the packaging was improved by applying the invention not only to the head of the tube as explained previously, but also to the tubular body. When the tubular body is co-extruded, oxygen absorbers can be incorporated in the most permeable layer in order to obtain multilayer structures as described in the invention. Other flexible tubes are obtained from a multilayer film which is welded on itself to form the cylindrical body. While this multilayer film is being manufactured by lamination or by co-extrusion, oxygen absorbers are added in order to obtain a multilayer structure as described in the invention.
It was observed that, when the packaging is formed from several parts, including at least one molded part, it is advantageous to apply the invention not only to the molded part but also to the other parts of the packaging. Such is the case in particular with packagings formed from films and including a neck, blown extruded packagings comprising a stopper, or even packagings having a cardboard-based multilayer structure and comprising a molded neck.
It should finally be pointed out that the invention can also be used in packagings formed from multilayer films or formed from any other multilayer structure not necessarily comprising one or more molded parts.
| Number | Date | Country | Kind |
|---|---|---|---|
| 11162559.6 | Apr 2011 | EP | regional |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IB2012/051816 | 4/13/2012 | WO | 00 | 12/9/2013 |
