EP3025977A1 - Method for producing a container in the form of a can with an inner protection layer - Google Patents

Abstract

The present invention relates to a method for the manufacture of a container, which method comprises a step for obtaining a protective layer (10) comprising, distributed over at least a portion of its surface, a plurality of pores (11). ) through each of which an area facing (7a) of an inner surface of tin (7) is accessible from the inner volume of container (6). The protective layer (10) consists of a protective varnish, which is applied on the inner surface of tin (7) so as to obtain, before filling, said protective layer (10) comprising the pores (11) of access to said inner surface of tin (7). The protective varnish applied consists of an emulsion or dispersion comprising (i) the protective varnish itself and (ii) a fluid dispersed in said varnish and which is capable of being removed after the application operation on the body of box (1) so as to form the pores (11).

Description

The present invention relates to a method for the manufacture of a container of the kind can, intended to receive a product to be packaged, the inner surface is at least partially made of tin coated with a protective layer.

Certain foodstuffs, such as fruit or products containing tomato, are advantageously packaged in cans containing a can body whose inner surface is made at least partially of tin.

Indeed, thus conditioned, the product takes a certain amount of tin on the inner surface of the can body, which ensures the preservation of its organoleptic and visual properties by a limitation, or even a suppression, of oxidation phenomena.

To control the amount of tin made available of the packaged product, it is known to partially coat the tinned inner surface of the can body with a layer of protective varnish.

Such canisters partially partially painted internally are for example described in the documents EP-0 492 870 or EP-0 688 615 .

In these documents, the box body, comprising a bottom element which is extended by a side wall whose upper edge delimits an upper opening intended to receive a shutter element, is made from a shaped tin plate by a stamping operation.

The body of this can consists of a single, varnished cylindrical surface that extends continuously and uniformly over a portion of the height of the inner surface of its side wall from its top edge. The remaining cylindrical portion of the height of this side wall (here on the side of its bottom element) constitutes an exposed area of the inner surface of tin (devoid of protective layer).

The removal of tin is of some interest for the packaged product, but the contact between the product and the tinned surface of the can body causes a corrosion reaction which is accompanied by a slight darkening phenomenon.

Thus, the aforementioned type of box, partially painted, is not completely satisfactory in that the inner surface of its side wall has a contrast with two different color zones, which are unsightly (the upper varnished , rather clear, and the other lower devoid of varnish, darker).

In view of this drawback, the Applicant has developed a process for the manufacture of a tin-type container, particularly suitable for the packaging of foodstuffs, whose inner surface of tin is coated with a protective layer which is adapted to limit or even eliminate the aesthetic impact of the chemical reaction of the product on the exposed tin, while allowing an optimal provision of tin to preserve the qualitative characteristics of the packaged foodstuff.

More generally, such a container can be used for the packaging of any product for which it would be interesting to take tin directly on the can body.

For this, the method, according to the invention, is suitable for the manufacture of a container comprising a box body (for example in one or two pieces) defining an interior volume of packaging and having an inner surface formed at least partially of tin which is coated with a protective layer to resist the chemical action of the product to be packaged.

This protective layer comprises, distributed over at least a portion of its surface, a plurality of pores (or otherwise called orifices or openings) through each of which an area facing the inner surface of tin is accessible from the inner volume of packaging.

The protective layer consists of a protective varnish, which is applied to the inner surface of tin so as to obtain, before filling, said protective layer comprising the access pores to said inner surface of tin.

This protective varnish applied consists of an emulsion or dispersion comprising (i) the protective varnish itself and (ii) a fluid dispersed in said varnish and which is capable of being removed after the application operation on the body of box so as to form the pores.

This particular tin can thus divides the exposed tin inner surface (accessible through the pores) into a plurality or multiplicity of distinct areas; this allows the desired exposed tinned surface to be distributed over a larger portion of the inner packaging surface, and thus to limit the visual impact resulting from the chemical reaction between the tin and the packaged product.

• le fluide dispersé dans le vernis consiste par exemple en un liquide destiné à être éliminé par évaporation naturelle ou active ;
• le fluide dispersé dans le vernis consiste en un gaz ;
• le pourcentage de fluide dispersé dans le vernis de protection varie au cours de l'application ;
• les pores de la couche de protection sont répartis uniformément, ou au moins approximativement uniformément, sur la surface intérieure d'étain ; ils peuvent de manière alternative être regroupés sur une partie de la surface intérieure d'étain, par exemple dans la largeur d'une bande située au niveau de la paroi latérale, située de préférence à distance de la bordure supérieure et en-dessous du niveau de surface des produits destinés à être conditionnés dans le corps de boîte de sorte à obtenir une bande supérieure de ladite paroi latérale munie d'une couche de protection uniforme et dépourvue de tels pores ;
• les pores de la couche de protection sont ménagés aléatoirement ou non-aléatoirement, au niveau de tout ou partie de la couche de protection ;
• les pores de la couche de protection ont une dimension maximale supérieure à 0,1 µm, et de préférence inférieure à 5 mm ;
• les pores de la couche de protection ont de préférence une surface comprise entre 100 µm² et 9 mm² (et avantageusement encore de 2 et 9 mm²) ;
• les pores de la couche de protection représentent ensemble une surface comprise entre 10 % et 70%, et de préférence encore entre 17 % et 50 %, par rapport à la surface intérieure du corps de boîte ;
• la couche de protection consiste en un vernis de protection, choisi par exemple parmi le polyester et l'époxy-acrylate, et comportant avantageusement une épaisseur comprise entre 2 et 80 µm (et de préférence entre 4 et 30 µm).

Other advantageous characteristics, which can be taken independently or in combination, are developed below:

• the fluid dispersed in the varnish consists for example of a liquid intended to be removed by natural or active evaporation;
• the fluid dispersed in the varnish consists of a gas;
• the percentage of fluid dispersed in the protective varnish varies during the application;
• the pores of the protective layer are distributed uniformly, or at least approximately uniformly, on the inner surface of tin; they may alternatively be grouped together on a part of the inner surface of tin, for example in the width of a strip located at the level of the side wall, preferably located at a distance from the upper edge and below the level surface products intended to be packaged in the can body so as to obtain an upper band of said side wall provided with a uniform protective layer and devoid of such pores;
• the pores of the protective layer are formed randomly or non-randomly, at all or part of the protective layer;
• the pores of the protective layer have a maximum dimension greater than 0.1 μm, and preferably less than 5 mm;
• the pores of the protective layer preferably have a surface area of between 100 μm ² and 9 mm ² (and advantageously still 2 and 9 mm ² );
• the pores of the protective layer together represent an area of between 10% and 70%, and more preferably between 17% and 50%, with respect to the inner surface of the can body;
• the protective layer consists of a protective varnish, chosen for example from polyester and epoxy acrylate, and advantageously having a thickness of between 2 and 80 μm (and preferably between 4 and 30 μm).

This layer of protective varnish is advantageously applied (i) to a metal part intended to be shaped to form at least a part of the box body and / or (ii) on a metal part already shaped.

• la figure 1 est une vue générale et schématique d'un contenant, avec un plan de coupe vertical diamétral ;
• la figure 2 est une vue agrandie du détail Il de la figure 1, de sorte à montrer schématiquement la structure de la couche de protection revêtant le corps de contenant.

The invention will be further illustrated, without being limited in any way, by the following description of a particular embodiment, given solely by way of example, illustrated by the appended drawings in which:

• the figure 1 is a general and schematic view of a container, with a diametral vertical section plane;
• the figure 2 is an enlarged view of the detail He of the figure 1 , so as to show schematically the structure of the protective layer coating the container body.

The container, as shown on the Figures 1 and 2 here consists of a can, for the packaging of a foodstuff for example (not shown).

This container comprises a can body 1 composed of a bottom member 2 whose periphery is extended upwards by a side wall 3 (preferably in one or two rooms).

The side wall 3 is preferably devoid of moldings, or mostly devoid of such moldings.

The upper edge 4 of the side wall 2 delimits an upper opening 5 through which the foodstuff to be conditioned is brought. This upper edge 4 is intended to receive a shutter member (not shown), which may be chosen by those skilled in the art (for example a peelable membrane or a metal disc with rupture initiation line).

This can body 1 defines an interior volume 6 for the packaging of the product of interest (for example a food product based on tomato or fruit).

The bottom element 2 and the side wall 3 of the can body 1 can be made in one piece (for example by stamping).

These two parts 2, 3 can also be manufactured independently of one another and then secured together by any suitable operation (for example by crimping or welding).

The bottom element 2 and the side wall 3 of this box body 1 are advantageously made of a steel matrix.

Moreover, as illustrated by the figure 2 at least a part of the inner surface 7 of this can body 1 (oriented towards the inner volume side 6), and preferably at least the inner surface 3 a of its side wall 3, is made of tin coating and / or a tin-based alloy.

The bottom element 2 may or may not be coated with such a layer of tin.

The inner surface of tin 7 is itself coated with an inner protective layer 10 which is made of a product resistant to the chemical action of the product to be packaged.

The protective layer 10 of the surface tinned 7 comprises, distributed over at least part of its surface, a plurality of pores 11 through each of which a facing 7 in area of the inner surface 7 of tin is accessible from the interior volume of container 6.

The bottom element 2 is itself coated here with a continuous protective layer; alternatively, this element 2 may be (i) devoid of protection, (ii) partially protected or (iii) provided with a protective layer 10 also provided with pores 11 (in particular if the bottom element 2 also comprises an inner surface of tin 7).

This multi-pore protective layer 10, 11 allows the contacting zones 7 a of the inner tin underlying surface 7 with the packaged product, so as to deliver a certain amount of tin in the product by oxidation-reduction chemical reaction.

This particular distribution of the exposed tin zones 7 has the advantage of limiting their aesthetic impact (blackening, darkening due to oxidation by the foodstuff), but also possibly of ensuring a delivery of tin well. distributed over the entire height of the conditioned foodstuff (to allow at least approximately uniform distribution of the tin).

For this purpose, the pores 11 of the protective layer 10 are advantageously uniformly distributed, or at least approximately uniformly, over the entire inner surface of tin 7.

Alternatively, these pores 11 of the protective layer 10 can be distributed and / or grouped only on the side wall 3: over its entire height or only a portion of the height of this side wall 3, for example in the width one or more annular bands.

In the case of a side wall 3 with pores 11 on only a part of its height, these pores 11 are then advantageously arranged at a distance from the upper edge 4 and below the surface level of the products packaged in this body. box 1; an upper band of the side wall 3 provided with a uniform protective layer 10 and free of such pores 11 is thus obtained, which is particularly useful for preventing any negative visual appearance of the protective layer 10.

In all these embodiments, these pores 11 may be distributed and arranged randomly, or non-randomly (that is to say in a predetermined manner and predetermined to form, together, a particular pattern and / or regular).

Still for an optimal compromise between aesthetics and the desired release of tin, the pores 11 advantageously have a maximum dimension d greater than 0.1 μm, and preferably less than 5 mm; these pores 11 preferably have a maximum dimension d of between 10 μm and 2.5 mm.

Also preferably, the pores 11 each have an area of between 100 μm ² and 9 mm ² .

By "dimension" of a pore is meant preferably the largest dimension of this pore 11, as illustrated by the dimensional dimension d on the figure 2 .

These pores 11 may have a regular contour, or at least approximately regular, for example of generally circular or oval shape as shown in FIG. figure 2 . Alternatively, this contour may also be irregular.

In addition, the pores 11 advantageously together represent an area of between 10% and 70% (preferably between 17% and 50%) of the inner surface of the box body 1, preferably of the inner surface of the side wall 3 and more preferably the inner surface of tin 7.

According to a preferred embodiment, the protective layer 10 advantageously consists of a layer of varnish, the composition and thickness of which are chosen by those skilled in the art depending on the conditioned foodstuff.

This protective varnish is preferably chosen from polyester and epoxy acrylate. It can be applied in liquid or powder form.

Its thickness is advantageously between 2 microns and 80 microns, and more preferably between 4 microns and 30 microns.

The layer of multi-porous protective varnish 10, 11 is obtained by means of a process comprising, before the step of filling with the product to be packaged, a step of applying the protective varnish to the inner surface of tin 7 so as to obtain directly said protective layer 10 provided with pores 11.

The protective varnish applied consists of an emulsion or dispersion comprising (i) the protective varnish itself and (ii) a fluid (gas or liquid) dispersed in this varnish and which is capable of being removed after the operation of application to the can body 1 so as to form the pores 11 (in practice, this dispersed fluid is advantageously immiscible or poorly miscible with the protective varnish).

In the case of a liquid emulsified in the protective varnish, this liquid is intended to be removed by natural or active evaporation. The liquid removed consists for example of water.

To adjust the release of tin on the height of the box, it may be envisaged to vary the percentage of fluid dispersed in the protective varnish during the application.

• le vernis de protection appliqué au-dessus du niveau de surface soit dépourvu du fluide dispersé, et
• le vernis de protection appliqué au-dessous du niveau de surface contient une quantité appropriée de ce fluide dispersé.

For example, to keep the pores 11 away from the upper edge 4 of the side wall 3 and below the surface level of the products intended to be packaged in the can body 1, it can be provided that:

• the protective varnish applied above the surface level is devoid of the dispersed fluid, and
• the protective varnish applied below the surface level contains an appropriate amount of this dispersed fluid.

In general, the protective varnish may be applied by means of a spray nozzle, a brush, a sponge and / or a roller, these application means being suitably controlled so as to obtain the special protective layer as described above.

Once the box body obtained, with its multi-porous protective layer 10, 11 constituted, the container can be filled with the product to be packaged, and the filling opening 5 can then be closed with a second bottom element reported. .

As illustrated on Figures 1 and 2 , the side wall 3 is of generally cylindrical tubular shape; it could alternatively have any other configuration and desired section: it could have for example a radial section oval, rectangular or square, oblong, etc.

Similarly, it may have on its height a set of ribs or grooves, dents, necking, etc.

The container according to the invention has an inner surface which is partially protected. The free zones 7 a of the inner surface of tin 7 are arranged to limit the visual impact of the chemical reaction with the packaged product. Moreover, the exposed tin zones are distributed 7 has here the height of the side wall 3, which allows a better distribution of tin into the packed product.

Claims (11)

A method of manufacturing a container comprising a can body (1) composed of a bottom member (2) which is extended by a side wall (3) whose upper edge (4) delimits an upper opening (5) for receiving a closure member, which can body (1) delimits an interior conditioning volume (6) and has an inner surface (7) at least partially made of tin which is coated with a protective layer (10). ) intended to resist the chemical action of said product to be conditioned,
which method comprises, before the step of filling with the product to be packaged, a step for obtaining said protective layer (10) comprising, distributed over at least a part of its surface, a plurality of pores (11) at through each of which a facing zone (7a) of said inner surface of tin (7) is accessible from said inner volume of container (6),
characterized in that the protective layer (10) consists of a protective varnish, which is applied to the inner surface of tin (7) so as to obtain, before filling, said protective layer (10) comprising the pores ( 11) of access to said inner surface of tin (7),
which protective varnish applied consists of an emulsion or dispersion comprising (i) the protective varnish itself and (ii) a fluid dispersed in said varnish and which is capable of being removed after the application operation on the body of box (1) so as to form the pores (11). Production method according to claim 1, characterized in that the fluid dispersed in the varnish consists of a liquid intended to be removed by natural or active evaporation. Production method according to claim 1, characterized in that the fluid dispersed in the varnish consists of a gas. Manufacturing method according to any one of claims 1 to 3, characterized in that the percentage of fluid dispersed in the protective varnish varies during the application. Production method according to one of Claims 1 to 4, characterized in that the pores (11) of the protective layer (10) are distributed evenly or at least approximately uniformly over the inner surface of tin (7). ). Manufacturing method according to any one of claims 1 to 5, characterized in that the pores (11) of the protective layer (10) are grouped on a portion of the inner surface of tin (7). Production method according to one of Claims 1 to 6, characterized in that the pores (11) are arranged at a distance from the upper edge (4) of the side wall (3) and below the surface level of the products intended for being packaged in the box body (1), so as to obtain an upper band of said side wall (3) provided with a protective layer (10) uniform and devoid of such pores (11). Manufacturing method according to any one of claims 1 to 7, characterized in that the pores (11) of the protective layer (10) are formed randomly or non-randomly. Manufacturing method according to any one of claims 1 to 8, characterized in that the pores (11) of the protective layer (10) have a maximum dimension ( d ) greater than 0.1 microns. Manufacturing method according to any one of claims 1 to 9, characterized in that the pores (11) of the protective layer (10) each have a surface between 100 microns ² and 9 mm ² . Manufacturing method according to any one of claims 1 to 10, characterized in that the pores (11) of the protective layer (10) together represent an area of between 10% and 70% relative to the inner surface of the body of box (1).

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