A can whose lid is connected to the can body by a flange connection is known. A packaging of this type is suitable for sterilization. To open a packaging of this type, it is usual for the lid to be cut off the can body, for example with the aid of a can opener.

One drawback of the known can is that after it has been opened the original lid cannot readily be used to close the packaging again.

It is an object of the invention to provide a metal packaging which can be sterilized and, moreover, can be reclosed after it has been opened.

In particular, it is an object of the invention to provide a metal packaging which can be sterilized in the closed and filled state and can be reclosed after it has been opened.

Yet another object of the invention is to provide a metal packaging which can be sterilized in the closed and filled state and has an improved shelf life of its filling after the packaging has first been opened.

Yet another object of the invention is to provide a packaging of this type in which the filling can be successfully removed from the packaging without the filling becoming caught behind edges or ridges.

Another object of the invention is to provide a packaging which is efficient to produce.

One or more objects are achieved, according to the invention, by a metal packaging comprising a can body and a lid, each formed from a metal plate coated with a plastic coating layer, the shapes of which can body and lid are matched to one another in such a manner that the can body can be closed off in a clamping manner by the lid, and in a sterilization state of the packaging there is a hermetically sealed, breakable join between the two plastic coating layers.

The creation of the hermetically sealed join between the plastic coating layer of the can body and the plastic coating layer of the lid, which join is characteristic of the packaging in the sterilization state, allows the packaging to be sterilized in the filled state and the product inside the can to be kept sterilized. In the context of the present patent application, a join is understood as meaning a join by which the plastic coating layers are bonded to one another.

Since the hermetically sealed, breakable join is breakable, it can be broken when the packaging is first opened, for example, although without imposing any limitation, by the lid being twisted, peeled or lifted off the can body.

Since the shapes of the can body and the lid are, moreover, matched to one another in such a manner that the can body can be closed off in a clamping manner by

the lid, the packaging can then be reclosed. Since, during normal use, the packaging is not resterilized after it has been opened, it is then no longer necessary to form a hermetically sealed join during reclosure.

The packaging according to the invention meets a long-standing need. The packaging according to the invention is eminently suitable for product which is to be sold in the sterilized state, such as foodstuffs, in which instance, since the packaging is recloseable, the shelf life of the product after the hermetically sealed, breakable join has been broken is also improved compared to the known can.

In one embodiment, the hermetically sealed, breakable join is formed by at least one seal.

In the context of the present application, a seal is understood as meaning a join between two layers of plastic which has been formed by fusing the layers together. The seal can be obtained by bringing components which are to be joined to one another, for example the can body and the lid, into contact with one another at the location where the seal is to be formed and heating them in such a manner that the plastic surfaces melt at that location.

The creation of the at least one seal which characterizes the packaging, at least in this embodiment, in the sterilization state allows the packaging to be sterilized in the filled state. When the packaging according to the invention is first opened in the sterilization state, the seal is broken, for example, although without constituting any restriction, by the lid being twisted, peeled or lifted off the can body.

A good-quality seal is hermetic with regard to the sterilizability of the filling and can preferably be opened without the use of a tool and without there being any possibility of it tending to open spontaneously.

A good quality seal can be achieved if the plastics which are to be sealed to one another are miscible. This can easily be achieved if the lid and the can body are coated with the same type of coating layer plastic or at least comprise similar plastics. In certain cases, however, it is also possible to mix different types of plastics.

In one embodiment, the hermetically sealed, breakable join comprises an interlayer which comprises at least one plastic layer. This interlayer ensures that any manufacturing inaccuracies with regard to the planarity of the lid and the can body can easily be compensated for at the location of the hermetically sealed, breakable join without the coating layers having to be very thick. This is favourable with a view to forming the hermetically sealed, breakable join.

The interlayer makes it possible to adapt any properties of the hermetically sealed, breakable join to the use, simply by selecting a material which provides the desired property for the interlayer.

In an embodiment in which the hermetically sealed, breakable join is provided with an interlayer which comprises a layer of plastic, the plastic layer comprises an interlayer plastic type which is similar to a coating layer plastic type which is present in at least one of the plastic coating layers. Since at least parts of the interlayer and the at least one plastic coating layer can be mixed with one another as a result of this measure, it is possible to achieve a good-quality seal.

In an advantageous embodiment, the interlayer can be removed separately from the lid. This is advantageous with a view to enhancing the breakability of the hermetically sealed, breakable join. The breaking of the hermetically sealed, breakable join and the removal of the lid are then operations which can be carried out separately, with the result that the matching shapes of the can body and the lid and the hermetically sealed, breakable join can each be optimized independently of one another.

The metal packaging according to the invention can be opened by using an auxiliary means, for example by using a spoon or the like to lever the lid off the can body, or the hermetically sealed, breakable join can be cut open with the aid of a knife, for example.

However, it is preferable for the hermetically sealed join to be breakable by hand, so that there is no need for a separate tool or means to open the packaging.

This can be promoted, inter alia, by providing the packaging with a peelable hermetically sealed join. When the packaging is first opened in its sterilization state, the peelable join is broken as a result of the plastic layers in this join being torn off one another. Since the plastic layers are torn off one another, the metal below is prevented from being exposed, with the result that no corrosion problems occur at the location.

A"peelable"join can be broken by exerting a force of between 10 and 20 N on the lid.

A seal may be suitable for this purpose. The peelability of a seal is determined by the bulk mechanical properties of the plastic in the seal.

The peelability of the hermetically sealed, breakable join is promoted in an embodiment in which the hermetically sealed join comprises a plastic filled with a filler. A filler of this type, for example in powder form, such as talc powder, clay powder, soot powder or a powder of a ceramic material, such as for example titanium dioxide, locally reduces the tearing force in the join.

In a simple embodiment, the filler is included in an interlayer.

The breakability and/or the possibility of manual removal of the lid from the packaging is favourably promoted by providing the lid with auxiliary means for opening the packaging. In this context, consideration may be given, for example, to a tab which is connected to the lid and/or forms an integral part of the lid.

In one embodiment, matching shapes of the can body and the lid comprise local clamping regions which are distributed over the periphery. The result of this is that the overall clamping force is reduced and therefore the packaging is easier to open by hand.

In this case, there is no clamping region at the location of the auxiliary means for opening the packaging, so that the initial force required to open the packaging is not unnecessarily high.

In one embodiment, the lid is round. The result of this is that the seal can easily be broken by means of a twisting movement. This also makes it easier to open the packaging by hand. Since the hermetically sealed, breakable join is subject to shear loads by means of the twisting movement, which usually involves a lower breaking threshold than when tensile loads are applied. In one embodiment, the can body comprises a beaded edge, over which the lid can be placed. This creates a reinforced rim over which the lid can be fitted in a clamping manner. The beaded edge provides a plurality of surfaces for producing the sealed join to the lid. The beaded edge is preferably, although not necessarily, beaded outwards in order to facilitate removal of the filling and to keep the inner surface of the packaging clean.

The width of the hermetic seal is preferably at least 1.0 mm, more preferably at least 1.5 mm. More than 2.0 mm is not necessary for most applications.

In one embodiment, the plastic coating layer comprises a plastic type selected from the group consisting of polyolefins. Plastic types of this type are suitable for forming a seal, since they can generally be successfully fused together. If desired, the plastic may comprise a modified polymer or a copolymer or a mixture of different polymers in order to improve the fusability and/or peelability properties.

In one embodiment, the plastic comprises polypropylene (PP). PP, optionally modified, and copolymers with PP, or PP mixed with, for example, polyethylene PE (or, for example, polybutylene, readily form a good seal and, moreover, can be successfully sterilized and have a good stability with respect to acids. With the aid of an interlayer or in the modified state, this plastic can be successfully bonded to metal, and the seal can be broken without difficulty when desired.

Some other suitable materials based on packaging steel provided with a PET- comprising coating are described in WO 00/53665 and are also suitable for the purpose.

In one embodiment, the metal is packaging steel. The mechanical properties of packaging steel make it possible to achieve a good clamping action.

In a following aspect, the invention relates to a method for provided a filled metal packaging.

According to the invention, this method is characterized in that a can body and a lid are provided, which can body and lid are each provided with a plastic coating layer, the can body is filled with a product, and the packaging is converted into a sterilization

state, in which the can body is closed off in a clamping manner by the lid, and then a hermetically sealed, breakable join is formed between the two plastic coating layers.

The formation of the hermetically sealed join between the plastic coating layer of the lid and the plastic coating layer of the can body ensures that the packaging can be sterilized in the filled state. Since the join is breakable, it is broken the first time the packaging is opened, for example, although without this constituting any restriction, by the lid being twisted, peeled or lifted off the can body. Since the can body is closed in a clamping manner by the lid, the packaging can then be reclosed. Since the packaging is not normally resterilized after it has been opened, it is not usually necessary to form another hermetic seal during reclosure.

Preferred embodiments of the method according to the invention are given in the embodiments of the packaging according to the invention which are described in the present patent application.

The invention will now be explained with reference to the drawing, in which: FIG. 1, parts a to d, show a longitudinal section through part of a packaging provided with a surrounding lid; FIG. 2, parts a to c, shows longitudinal sections through parts of packaging provided with an enclosed lid; FIG. 3, parts a and b, shows an embodiment similar to FIG. 2 but provided with an interlayer; FIG. 4, parts a and b, shows variations on the embodiment shown in FIG. 3; FIG. 5 shows an embodiment which is similar to FIG. 1 but is provided with an interlayer; FIG. 6 shows another embodiment which is provided with an interlayer; FIG. 7, parts a to c, shows a variation on the embodiment shown in FIG. 2; FIG. 8, parts a to d, show a variation on the embodiment shown in FIG. 7; FIG. 9, parts a to c, shows an embodiment which is not circular in cross section.

FIG. 1 of the drawing shows a can body 1 which is provided with an outwardly beaded edge 2 and is closed off by means of a lid 3, which is fitted in a clamping manner onto the can body 1. The lid is arranged so as to surround the can body. In this example, the clamping action is achieved by means of a clamping geometry which is promoted by the interaction between the beaded-over edges of the can body and the lid.

The lid 3 is also provided with a beaded edge 5, from which the lid derives strength and so that the lid can be fitted with a better clamping action to the can edge. The lid as shown in the drawing also has an edge which is inclined inwards, which also contributes to the clamping interaction between lid 3 and can body 1.

The lid is preferably resilient and dimensionally stable, so that a good clamping action on the can body is achieved, the shape of the lid being retained, so that the lid is suitable for reclosure.

The lid and the can body are made from metal coated with plastic (for example polypropylene, PP), such as plastic-coated aluminium or plastic-coated packaging steel, preferably the latter. The plastic coating layers are joined to one another by a hermetically sealed, breakable join 4, so that the packaging can be sterilized.

The hermetically sealed, breakable join 4 may be located on the top side of the beaded edge on the can body (FIG. la) or on the side of the beaded edge (FIG. lb), or both (FIG. lc). The join may be formed as a seal using exclusively the plastic coating layers of the lid 3 and the can body 1, or alternatively the hermetically sealed, breakable join may, as shown in FIG. ld, comprise an interlayer 6 which comprises a plastic layer and is hermetically joined, by means of its sides facing away from one another (24,24'), to the plastic coating layers of both the lid 3 and the can body 1.

FIG. 2 of the drawing shows part of a can body 11 which is provided with a flanged edge 12 and is closed off by means of a lid 13 which is arranged in a clamping manner inside the can body 11.

The lid and the can body are formed from metal coated with plastic (for example polypropylene, PP), such as plastic-coated aluminium or plastic-coated packaging steel, preferably the latter. The plastic coating layers are joined to one another by a hermetically sealed, breakable join 4, so that the packaging can be sterilized.

The join 4 may be located on the top side of the flanged edge 12 on the can body (FIG. 2a) or on the side of the flanged edge 12 (FIG. 2b), or both (FIG. 2c). The join may be formed as a seal comprising exclusively the plastic coating layers of the lid 13 and the can body 11 or, in a similar manner to the embodiment shown in FIG. ld, may comprise an interlayer which comprises a plastic layer and is hermetically joined to both the lid 13 and the can body 11.

The interlayer is particularly preferably present in embodiments as shown in FIG. lb and FIG. 2b, the hermetically sealed, breakable join extending around the periphery of the lid or can body, since the manufacturing inaccuracies which have to be compensated for by the interlayer are greatest in the diameter dimension. An interlayer of this type may consist entirely of plastic or may, for example, comprise a layer of metal foil. The interlayer is preferably easy to break in order for the packaging to be opened from its sterilization state.

The lid is arranged inside the can body. In this example, the clamping action is achieved by means of a clamping geometry which is promoted by the slightly obliquely shaped side wall (s) of the can body 11 and/or the lid 13.

FIG. 3A of the drawing shows another embodiment, in which the interlayer 6 is not joined to the lid and the can body on opposite sides, but rather in which the joins 14 and 14'to the can body 11 and the lid 13 are provided next to one another on one side of the interlayer 6. An interlayer of this type may consist entirely of plastic or may, for example, comprise metal foil and can easily be peeled off in order for the packaging to be opened from its sterilization state. To promote manual peeling, the interlayer may, for example, be provided with a tab 7, as shown in FIG. 3b.

As with the embodiment shown in FIG. 2, the exemplary embodiment shown in FIG. 3 has a can body 11 which is formed from plastic-coated metal and is provided with a flanged edge 12, a lid 13 which is formed from plastic-coated metal and is arranged in a clamping manner in the can body 11. The joins 14 and 14'may be formed as seals between the plastic layer of the interlayer 6 and of the plastic coating layers of the lid 13 and the can body 11.

FIG. 4a and FIG. 4b show variations of the embodiment shown in FIG. 3, with the lid 23 flanged over in the other direction. Since the flanged edge 25 of the lid 23 is directed away from the can body 21, the flanged edge 22 on the can body 21 may be of flat design, contrary to the recessed design of the flanged edge 12 used in the embodiment shown in FIG. 3.

In FIG. 4b, the can body 31 is designed conically in the vicinity of its end, and the lid 33 fits into the conical section. The clamping closure feature is achieved by provided the can body with at least an inwardly directed clamping edge 38 along the periphery in a transition between the conical section of the can body 31 and the flanged edge 32.

FIG. 5 of the drawing shows a part of a can body 81 which is provided with a beaded edge 82 and is closed off by a lid 83 which is arranged in a clamping manner on the can body 81. The lid is arranged so as to surround the can body.

In this example, the clamping action is achieved by means of a clamping geometry which is promoted by the interaction between the beaded edges of the can body and the lid. The lid 83 is also provided with a beaded edge 85, from which the lid derives strength and which facilitates clamping fitting of the lid to the edge of the can.

The lid 83 as shown in the drawing also has an edge which is inclined inwards.

The lid and the can body are formed from metal coated with plastic (for example polypropylene, PP), for example plastic-coated aluminium or plastic-coated packaging steel, preferably the latter. The plastic coating layers are joined to one another by a hermetically sealed, breakable join, comprising an interlayer 86. This interlayer is not joined to the lid and the can body on opposite sides, but rather the joins 84 and 84'to the can body 81 and the lid 83 are provided adjacent to one another on one side of the interlayer 86, in a similar manner to the embodiments shown in FIG. 3 and FIG. 4.

The interlayer may consist entirely of plastic or may, for example, comprise metal foil. The joins 84 and 84'may be formed as seals between the plastic layer of the interlayer 86 and the plastic coating layers of the lid 83 and the can body 81.

FIG. 6 shows an embodiment in which the interlayer 96 has a tab 97 which, optionally locally, projects between the lid 93 and the can body 91 and with the aid of which the interlayer can be pulled off first, with the result that the hermetic join between the lid 93 and the can body 91 is broken before the lid 93 itself is removed.

The embodiment of the interlayer as shown in FIG. 3 and/or FIG. 4 and/or FIG. 5 and/or FIG. 6, with the aid of which the hermetically sealed, breakable join is formed, has the advantage that the join can easily be broken by this interlayer being removed separately from the packaging, for example by peeling and/or pulling, before the lid is removed from the packaging. Since the breaking of the hermetically sealed breakable join and the removal of the lid are actions which are to be carried out separately, the matching shapes of the can body and the lid and the hermetically sealed, breakable join can each be optimized independently of one another.

If, as in embodiments as shown in FIG. 1 and FIG. 2, the hermetically sealed, breakable join is to be broken at the same time as the removal of the lid from the can body, the hermetically sealed, breakable join and the matching shapes of the can body and lid will have to satisfy the additional demand that this be possible. This can be achieved, inter alia, by providing the lid with auxiliary means in order to make it easier to remove, making the lid less flexurally rigid, so that it can be peeled off the can body, or selecting a lid which is flexurally rigid but can be twisted off, by clamping the lid less firmly into or onto the can body, for example by provided individual, interrupted clamping regions, or by provided the hermetically sealed, breakable join with a filler, so that it can be torn off more easily.

FIG. 7 shows, by way of example, an embodiment in which the enclosing lid 43 is not provided with a clamping form for interaction with a corresponding form 48 in the can body 4 over the entire periphery, but rather only in individual clamping regions 47 which are distributed over the periphery. The lid 43, which is shown separately in FIG. 7c, is locally provided with a tab 50.

FIG. 7a shows the packaging in longitudinal section at the location of the tab 50.

Since at the location of the tab 50 the edge 49 does not latch into the clamping edge 48 arranged in the can body 41, at that location there is no or scarcely any clamping action between the lid 43 and can body 41. Consequently, the hermetically sealed, breakable join can be broken relatively easily, since it is not initially necessary to overcome the clamping force. FIG. 7b shows the packaging in another longitudinal section, where the lid 43 is provided with a region 47 which is provided with a clamping shape.

The hermetically sealed, breakable join 4 in FIG. 7 extends continuously over the entire periphery on the top side of the flanged edge 42 on the can body. Obviously, the join may in addition or as an alternative be located between the upright edge of the lid and the can body. The join may be formed as a seal comprising exclusively the plastic coating layers of the lid 43 and the can body 41 or may comprise an interlayer which comprises a plastic layer and is hermetically joined to both the lid 43 and the can body 41. Obviously, the flanged edge may be provided with a beaded edge and/or may be designed as a beaded edge in a similar manner to the embodiment shown in FIG. 1.

The embodiment shown in FIG. 8 has a lid 53 (shown in plan view in FIG. 8c) which is less dimensionally stable than the lid shown in FIG. 7, since the lid is virtually flat, apart from a number of clamping regions 57 distributed locally over the periphery.

FIG. 8a shows the packaging in longitudinal section at the location of a tab 60 locally provided on the lid 53. The hermetically sealed, breakable join 4 extends over the entire periphery between a relatively flat part of the flanged edge 52 of the can body 51 and the lid 53. The join 4 may be formed as a seal comprising exclusively the plastic coating layers of the lid 53 and the can body 51 or may comprise an interlayer which comprises a plastic layer and is hermetically joined to both the lid 53 and the can body 51.

Since there is no clamping region at the location of the tab 60, as indicated by a flat flange part 59 of the lid 53, at that location there is no or scarcely any clamping action between lid 53 and can body 51. Consequently, the hermetically sealed, breakable join can be broken relatively easily since it is initially not necessary to overcome the clamping force. Moreover, the relatively flat lid 53 has a minimal resistance to bending, so that the join 4 can continue to be broken off more or less by peeling.

FIG. 8b shows the packaging in another longitudinal section, where the lid 53 is provided with a region 57 which is provided with a clamping shape. This region can interact with a clamping groove 58 provided for this purpose in the flanged edge 52.

Of course, the clamping regions may also be arranged on or in the edge of the lid, as shown by clamping means 67 in FIG. 8d. In that case, it is possible to make do with a can body which is provided with a beaded edge, in a similar manner to the can body shown in FIG. 1.

FIG. 9 of the drawing shows an exemplary embodiment with a cross section which is substantially not round. FIG. 9b shows the can body 71 in a straight can body part, which can body is provided in the vicinity of its end with a conical part and a beaded edge 72. The shapes of the edge of the lid 73 and the edge of the can body are matched to one another in such a way that in the straight sections of the can body 71 there is a clamping action between the lid 73 and the can body 71. The lid is subject to

a clamping action as a result of it being clamped beneath the beaded edge 72 of the can body 71.

In the corners, the can body 71 and the lid 73 are subject to no or scarcely any clamping action. This means that the packaging is not unnecessarily difficult to open. A longitudinal section through one of the corners is shown in FIG. 9a.

The join 4 in FIG. 9 extends without interruption over the entire periphery between the can body 71 and the lid 73. The join may be formed as a seal comprising exclusively the plastic coating layers of the lid 73 and the can body 71, or may comprise an interlayer which comprises a plastic layer and is hermetically joined to both the lid 73 and the can body 71.

The seals which may form part of the exemplary embodiments of the invention which have been illustrated may be formed by fitting the lid to the can body and heating the plastic layers to above their melting point at least at the locations where the seal is to be formed. A heated press ram can be used for this purpose, but it is also possible to use other heating techniques, such as for example pulse heating, heating by means of a hot wire or hot knives, ultrasonic heating, frictional heating, hot-air heating, contact heating, induction heating, dielectric heating, magnetic hysteresis heating, laser heating.

The miscibility is generally good between two plastics of the same type. In certain cases, it is also possible for the desired miscibility to be achieved between plastic layers of different types.

It has been found that the strength of the seal is generally not particularly sensitive to the pressure which is exerted during heating, provided that the plastic layers are sufficiently fused together. A pressure which is typically used is between 10 and 100 N/cm2, but it is possible to deviate from these pressures. A reduction in the joint thickness of the plastic layers in the seal which is typically suitable is approximately 50%. This achieves a considerable degree of certainty that the plastic layer in the seal has in fact been melted sufficiently while at the same time there is still a reasonable quantity of plastic present at the location at the seal.

The width of a hermetic seal is at least 1.0 mm and more preferably at least 1.5 mm. However, more than 2.0 mm is not necessary for most applications.

The seal properties are primarily determined by the bulk properties of the plastic used.