HK1078838B - Method and device for improving adhesion of the individual layers of a composite material - Google Patents

Description

Method and device for improving the adhesion of layers of composite materials

Technical Field

The invention relates to a method for improving the adhesion of the layers of a composite material made of plastic-coated cardboard, in particular for producing composite beverage/food packages, wherein the composite material has a metal layer if required and the composite material is reheated in the region of the opening of the subsequent package.

Background

Such multilayer composite packages are known in many supply forms, for example as flat-top composite packages. It is mainly used in the field of liquid composite packages together with cold, cold-aseptic, hot and aseptic filling.

In order to improve the operability of the composite packages described in detail previously, and in particular to make it reclosable, one increasingly turns to composite packages provided with reclosable pouring elements. Such pouring elements can be designed in one or more parts and usually have an opening element and a lid. The packages with reclosable pouring elements are available on the market today almost without exception.

A multilayer composite package provided with a pouring element for the first opening of the package and provided with a corresponding closing element for enabling reclosing is known, for example, from EP 0580593B 1. In the area of the cardboard layer and the outer polyethylene layer of the composite material of the package there is a score for weakening the side wall material, and for opening the package an opening member, which is integral with the pouring member, is pressed into the packaging material at the score.

Another known multilayer composite package with a pouring element is described in DE 19727996C 2. This known pouring element has a pouring tube which simultaneously serves as an opening element for rupturing the package wall. Furthermore, packages provided with a pouring element closed with a screw thread are also known.

Regardless of whether the pouring element used for this purpose is screw-closed or closed by a flap, the opening element of the pouring element must first break through the wall of the package. In order to easily do this, the package in question is provided in the region of the opening with a material weakening, wherein the parts of the composite layer, i.e. the cardboard layer and the outer polyethylene layer, are destroyed in the region of the desired opening contour by punching or punching.

To burst the package wall, the opening member of the pourer only needs to burst the remaining layers, usually an oxygen barrier layer (e.g. aluminium foil) and an inner layer (product side) of polyethylene. The adhesion-promoting layer arranged in the middle thereof serves to bond the paperboard layer and the aluminum foil comprehensively. Although the aluminum foil tears relatively quickly upon opening, the polyethylene inner layer partially does not significantly elongate until it reaches the desired failure. Since the opening member of the used pourer has only a certain insertion depth, attempts have been made to solve this problem by using an opening member with a cutting edge or the like, which allows a better break through the packaging material.

It has also been found that reheating in the area of the opening of the subsequent package improves the adhesion between the polyethylene inner layer and the paperboard layer or the aluminium film layer. This reheating is in the prior art to apply hot air to the respective areas. This hot air flow blows only more or less onto the package from above and thus does not reach regular and certain activation.

For better understanding, the opening area of one package is schematically depicted in fig. 7A. In which a line of weakness 20 is shown by mechanically breaking the polyethylene outer layer and the base material in the region where the pouring element is to be fitted. To improve the adhesion, the material is heated in this region point by point with hot air, as can be seen from fig. 7B, wherein a hot air beam 21 heats the opening region with hot air in the vicinity of the weakening line 20.

For various reasons, no reproducible good activation results are obtained in this way. Too strong or too weak an activation effect under the same preconditions, too large an area, or in the wrong region, etc. This results in the inner polyethylene layer bulging in the separation region from the paperboard layer or aluminum foil layer in the regions which are not activated or are insufficiently activated and can be stretched relatively strongly during opening and tear without certainty.

Disclosure of Invention

The object of the invention is therefore to design and further develop the method mentioned at the outset in such a way that the adhesion between the layers in the region of the opening of the subsequent package is greatly improved, so that a defined rupture occurs on the rupture of the package wall by applying the used pouring spout.

The method according to the invention for improving the adhesion of the layers of a composite material made of plastic-coated cardboard for producing composite packages, wherein the composite material is reheated in the opening region of a subsequent package, is characterized in that the composite material is compressed at least in the opening region of the subsequent package by a certain energy input and subsequent pressing.

This object is achieved in that the composite material is compressed at least in the region of the subsequent pouring element by a certain energy input and subsequent pressing. The degree of compression is determined so as to ensure that the inner polyethylene layer does not stretch excessively upon opening and the walls of the package are cleanly breached. "cracking" of a material can be almost more of a concern than "tearing".

According to the invention, the subsequent targeted and defined activation of the opening region of the package results in a reinforced connection between the cardboard, the adhesion promoter (HV), the aluminum foil and the polyethylene inner layer in the opening region. Heating at the contact point produces another melting and thus a better adhesion. The inner layer of plasticized polyethylene is compressed by the pressing device, forming a smaller residual thickness in the region of the opening contour. The "tear thickness" of the polyethylene layer is reduced to a minimum size according to the invention. Due to this reduced thickness, which the polyethylene layer can stretch, this layer can be torn off relatively quickly (positively).

The invention also recognizes that the composite material is compressed (plastically deformed) in the opening region of the subsequent package by a certain energy input and subsequent pressing, at least in the region of the subsequent dispenser, so that it can be ensured that the package wall is torn cleanly without the inner polyethylene layer being stretched too much.

According to another teaching of the present invention, the composite material, while still in tape form, is reheated prior to application of the overlying (bonding) polyethylene inner layer. This applies if the blanks are arranged transversely on the composite material web and the subsequent heating in the area of the openings of the packages takes place in strips. This is particularly true if the entire tape is heated, and the relatively high temperature of the polyethylene can adversely affect the taste of the product located within the composite package.

Another teaching of the invention provides that the composite material, which is still in the form of a tape, is reheated after perforation/weakening in the opening region of the subsequent package. In this case, it is particularly advantageous if the compression takes place only in the region of the perforation/weakening line profile in the subsequent opening region of the package.

Heating can also be carried out according to the invention continuously or only in sections. For this purpose, the energy input during heating takes place in a clocked manner, depending on the speed of the plate and the length of the heating.

In a further embodiment of the invention, it is also possible to reheat the blank after the production of the package or even after the formation of the package. In the latter case, the heating can also be carried out in the filling machine, either on the mandrel wheel of the filling machine during the formation of the packages or directly before the sterilisation unit of the filling machine with a separate activation device.

According to a further teaching of the present invention, the composite material is heated to an elevated temperature Δ T of from 40 ℃ to 140 ° without causing the range defined by the open area of the subsequent package to adversely affect the taste of the product. The actual temperature applied will depend on many different factors, such as the respective heating location, the type and thickness of the layer sequence of the composite, the actual temperature of the area of the composite to be heated, the belt speed, the ambient temperature, and so forth. For example, in a composite containing aluminum foil, if the adhesion-promoting layer between the base materials also consists of Polyethylene (PE), then it is necessary to reach at least the melting point of PE, approximately 110 ℃, when heating the subsequent opening region in order to be able to soften these layers. Only then is plastic deformation achieved upon subsequent pressing.

Depending on whether the composite material used contains a metal layer or not, high-frequency coils (only in the case of a composite material containing metal) or ultrasonic welding means and infrared means (in the case of no metal or a composite material containing metal) can be used as options for heating. If no tools are used for pressing the layers during the production of the composite material or the composite package, a further teaching of the invention provides that a separate processing device is provided with not only means for reheating but also means for pressing. However, it is also possible to fit corresponding pressure means matching the opening contour of the subsequent package into an existing rotary tool, such as a scoring tool or a rotary punch.

If the heating and pressing of the composite material takes place only in the filling machine, i.e. intermittently, a free station in the mandrel wheel or a separate processing device can be used for this purpose if necessary, directly before the sterilization unit.

Drawings

The invention is explained in detail below with the aid of the drawings, which show only one preferred embodiment. In the drawings:

figure 1 is a schematic cross-sectional view of a first embodiment of the invention,

figure 2 a schematic top view of the embodiment of figure 1,

figure 3 is a schematic cross-sectional view of a second embodiment of the invention,

figure 4A is a schematic cross-sectional view of another embodiment of the present invention,

figure 4B is a functional view of the embodiment of figure 4,

figure 5A shows a cross-section of a conventional composite material in the area of the opening of a subsequent package,

figure 5B the conventional composite of figure 5A in an open state,

figure 6A shows a cross-section of a composite according to the invention in the area of the opening of a subsequent package,

figure 6B the composite material according to the invention of figure 6A in an open state,

FIG. 7A is a perspective view of the location of the opening area of the package after; and

fig. 7B is a schematic cross-sectional view of the conventional melting of the opening region thereafter.

Detailed Description

In the first embodiment of the invention shown in fig. 1, the reheating of the composite material tape 1 is also carried out before the coating with the inner layer 2 of Polyethylene (PE) by means of the extruder 3. The composite material web 1 consists of a cardboard layer 4 as a base material, on which cardboard layer 4 an outer layer 5 of polyethylene and a layer 7 of aluminium foil in combination with an adhesion-promoting layer 6 have been applied. The compound 1 is heated to a higher temperature level by means of an additional activation device, in the present illustration and in the embodiment preferred so far a high-frequency coil 8. This first softens the adhesion promoter layer 6 between the cardboard layer 4 and the aluminum foil 7, with the advantage that less water vapour a condenses on the heated aluminum when the polyethylene inner layer 2 is subsequently bonded thereto. The formation of condensed water vapour A, B on both sides of the still liquid polyethylene inner layer 2 cannot be completely avoided. The "as-manufactured" composite material 9 has better adhesion due to the preheating by the high-frequency coil 8 and the resulting less condensation of water vapor a.

In fig. 2, which schematically shows the arrangement of fig. 1 in a top view, the pressure roller 10 and the cooling roller 11 can be seen without the extrusion unit located thereon. As is clear from fig. 2, not the entire composite material web 1, but only the strip-shaped portions 1 ', 1 ", 1'" are heated by the three high-frequency coils 8 in the exemplary embodiment shown. It is expedient if a blank of a subsequent package, not shown, is arranged transversely on the composite material web 1 and the high-frequency coil 8 is located in the region of the subsequent opening.

Fig. 3 shows another possible embodiment according to the invention. In this configuration the high frequency coil 8' is arranged below the composite band 9 after perforation/weakening in the area of the opening of the subsequent package. For example, the laser 12 may be used to create the lines of weakness. In this alternative configuration, the reheated strip-like portions are compressed by means of respective pressing members 13 provided in scoring tool 14 before longitudinal cutting device 15 and transverse cutting device 16. The pressure member 13 may have a shape that exactly matches the profile of the opening later.

Although a continuous process for reheating has been described above, the present invention is directed to a batch process. In fig. 4A and 4B an activation process is shown, wherein the reheating is performed after the formation of the package, i.e. directly before the sterilisation unit in the filling machine.

Fig. 4A shows a clamping jaw 17, in the base body 18 of which an activation device, schematically indicated as a high-frequency coil 8', is present. A pivotable pressure bow 19 is adapted to the subsequent opening contour in such a way that the contour is exactly subjected to a certain reheating and subsequent compression in the region of the weakening line 20. The correspondingly formed transverse webs 21 are thus compressed during the engagement, in particular, by the polyethylene inner layer 2, so that excessive elongation is reliably prevented during the subsequent opening process.

The function of the press jaw 17 is also schematically depicted in fig. 4B. The pressure jaw is closed from above or from the side onto an opening region of a packaging P, which is then activated by a radio-frequency coil, not shown here, and the pressure bow 19 is moved from its rest position, indicated by a dash-dotted line, into the pressing position shown.

In order to illustrate the invention more clearly, a comparison of a composite material according to the invention and a conventional composite material is shown in fig. 5 and 6.

First, fig. 5A schematically shows a cross-section of a conventional composite material in the area of the opening of the subsequent package, as can be seen at the weakening line 20. The conventional opening process is shown in fig. 5B. When the composite material is pressed in the direction of the arrow O in the region of the weakening line 20, the inner polyethylene layer 2 is considerably stretched before it breaks, although the aluminum layer 7 is undoubtedly destroyed. Imperfect adhesion between the aluminium foil 7 and the inner polyethylene layer 2 results in the two layers separating close to the weakening line 20 during opening, as indicated by the arrow L. In extreme cases, it can result that the opening part of the not-shown pouring device cannot open a sufficiently large pouring opening.

In fig. 6A is shown a composite material 9 pretreated according to the method of the invention in the area of the package opening. It can clearly be seen therein that the inner polyethylene layer 2 has been deformed so strongly in the region below the weakening lines 20 that two thickenings 22 have been formed. Fig. 6B finally shows that all layers below the weakening line 20 are definitely broken after the application of the opening force O in the composite material according to the invention. Excessive elongation of the polyethylene inner layer 2 is thus reliably excluded.

Claims (14)

1. Method for improving the adhesion of the layers of a composite material made of plastic-coated cardboard for the production of composite packages, wherein the composite material is reheated in the opening region of a subsequent package, characterized in that the composite material is compressed at least in the opening region of the subsequent package by a certain energy input and subsequent compression.

2. The method of claim 1, wherein the composite material has a metal layer.

3. The method of claim 1, wherein the composite material, while still in tape form, is reheated prior to applying the inner polyethylene layer.

4. A method according to claim 3, characterized in that the package blanks are arranged transversely on the composite material web and are heated in strips in the opening areas of subsequent packages.

5. A method according to claim 3, characterized in that the package blanks are arranged longitudinally on the composite material web and are heated in sections in the area of the subsequent opening of the package.

6. Method according to claim 1, characterized in that the composite material, which is still in the form of a tape, is reheated after perforation/weakening in the area of the opening of the subsequent package.

7. Method according to claim 6, characterized in that the compression is carried out only in the area of the perforation/weakening line profile in the opening area of the subsequent package.

8. A method according to any one of claims 1 to 7, wherein the heating is carried out continuously.

9. Method according to one of claims 1 to 7, characterized in that the heating is carried out in sections.

10. A method according to claim 1, wherein reheating is performed after the formation of the package blank.

11. The method of claim 1, wherein reheating is performed in a filling machine.

12. A method according to claim 11, wherein reheating is performed on a mandrel wheel of the filling machine.

13. Method according to claim 11, characterized in that reheating is performed before the sterilization unit of the filling machine.

14. A method according to any of claims 1 to 7, wherein the composite material is heated to an elevated temperature Δ T of from 40 ℃ to 140 ℃ in the area of the opening of a subsequent package.