WO2021043908A1

WO2021043908A1 - Cross bottom bag made of coated paper and method for producing a cross bottom bag

Info

Publication number: WO2021043908A1
Application number: PCT/EP2020/074608
Authority: WO
Inventors: Andreas Kleemann; Andreas Lamkemeyer
Original assignee: Windmöller & Hölscher Kg
Priority date: 2019-09-05
Filing date: 2020-09-03
Publication date: 2021-03-11
Also published as: DE102019213476A1

Abstract

The invention relates to a cross bottom bag comprising a first and a second outer ply which are connected by means of a first and a second longitudinal edge. The two outer plies delimit an interior. The first and the second outer ply each comprise, at least in some regions, at least two layers, with a first layer comprising paper and a second layer, which is provided at least in some regions, comprising a plastic layer. The first and the second outer ply are connected by means of at least one bottom; this bottom comprises two triangular pouches and two tabs placed one on top of the other in some regions. A bottom cover sheet is provided and is connected to both triangular pouches and both tabs. The bottom cover sheet comprises a first layer made of paper and preferably a plastic layer as an at least second layer provided. The bottom cover sheet, at least in some regions, is non-releasably connected to regions of the plastic layers of the triangular pouches and of the tabs without the use of adhesive.

Description

Cross-bottom sack made of coated paper and a method for producing a cross-bottom sack

The invention relates to a cross-bottom sack and a method for its production.

For the transport of loose goods, packaging materials are usually necessary, which make these loose goods movable in individual portions, for example by hand. The packaging should also protect the goods filled in them, for example from moisture. Cross-bottom sacks have proven particularly useful in the field of powdery or granular goods. Such bags are prefabricated and then filled. The weight of such bags after they have been filled is usually 10 kg to 50 kg.

With such large transport weights, cross-bottom bags must also be very stable, in particular tear-resistant. For this purpose, a kraft paper is generally used which comprises at least predominantly long-fiber cellulose fibers, the proportion of waste paper and / or fillers being very low (<1%).

Since such a Kraft paper is permeable to moisture and air, at least one separate layer of plastic film is provided for the production of cross-bottom bags. The paper web and the plastic web are placed one on top of the other, glued together if necessary, processed into tubes and separated into tube pieces; furthermore, at least one Molded floor and its individual parts glued together for a permanent connection.

This procedure is comparatively expensive, since the adhesive used for bonding is consumed in large quantities. In addition, the applied adhesive has to dry, so that the production of such cross-bottom bags takes some time.

The object of the present invention is therefore to propose a cross-bottom sack and a production method, such a sack being cheaper and faster to produce.

The object is achieved by a cross-bottom sack with the features according to claim 1. Accordingly, a cross-bottom sack according to the invention comprises a first and a second outer layer, which are connected by means of a first and a second longitudinal edge, the two outer layers delimiting an interior space, the first and the The second outer layer comprises at least two layers, at least in some areas, a first layer comprising paper and a second layer provided at least in some areas comprising a plastic layer, the first and second outer layers being connected by means of at least one bottom, which has two triangular pockets and two tabs placed one on top of the other in some areas comprises, wherein a bottom cover sheet is provided which is connected to both triangular pockets and both tabs, wherein the bottom cover sheet comprises a first layer of paper and preferably a second layer provided at least in regions, a plastic layer, wherein the bottom cover sheet with areas of the plastic layers of the triangular pockets and the tabs is permanently and adhesive-free connected. In the present invention, therefore, a separate plastic film web is primarily dispensed with. In contrast, it is provided that the paper layers of the cross-bottom sack are at least partially provided with a plastic coating before processing and in particular in the area of the later bottoms. Due to these features alone, a more cost-effective production of cross-bottom sacks is possible. In addition, a coating on a substrate, in this case on paper, usually requires a smaller layer thickness compared to the layer thickness of a separately supplied plastic film.

A non-detachable connection is understood to mean that the base cover sheet is materially connected to areas of the plastic layers and the tabs. In particular, this means that no adhesive is applied. This also means that no heat-activatable adhesive (“hot-melt”) is used. As a result, there is no need to add a consumable during the production of the cross-bottom sack, so that further cost savings can be achieved. The plastic layer cannot be removed from the flaps, the triangular pockets and the bottom cover sheets without also pulling paper fibers along with it.

The bottom cover sheet is therefore directly connected to the plastic layers of the triangular pockets and the tabs, the plastic layer being connected in particular to the fibers of the bottom cover sheet. This can be achieved, for example, in that the plastic coating is strongly heated in a manufacturing process and becomes very soft to almost liquid in the process. In this state, the base cover sheet can be pressed on or pressed on, so that the plastic comes into strong contact with the paper of the base cover sheet or even partially penetrates the paper. As a result, the plastic is firmly connected not only to the triangular pockets and / or the tabs, but also to the bottom cover sheet.

In a further embodiment of the invention, the base cover sheet likewise comprises - at least in some areas - a plastic coating. In this case, as described with reference to the above exemplary embodiment, the plastic coating is connected to the paper fibers. If the plastic coatings of the tabs and / or the triangular pockets and the plastic coating of the bottom cover sheet are heated to the liquefaction limit or even beyond, the two plastic coatings can combine with one another after these components have been brought into contact and pressed together. After a cooling period, the two plastic coatings are consequently only perceptible as a single plastic layer. It should be emphasized that, if you look closely, there is no liquefaction limit, as a plastic coating usually does not go through a phase transition. As a rule, only a small proportion of the plastic coating has crystallized out. “Heating up to the liquefaction limit” thus means that, on a microscopic basis, a sufficient number of molecular connections have subsequently been broken so that the corresponding molecules can form new connections with molecules of other coatings or other paper layers. Such new connections can be comparatively strong after a renewed cooling.

In a preferred embodiment of the invention it is provided that the paper-encompassing layer of the first outer layer and the second outer layer is directed towards the interior. The paper-encompassing layer provides capillarity for water molecules. The paper thus has a certain blotting-sheet function and can absorb moisture that has either got onto the paper from the outside or has been entered with the filling material. In principle, an inner layer made of paper is also permeable to gases, in particular air. In this way, the air can pass through the paper and, if other conditions are met, escape into the environment. A prerequisite is, for example, that the plastic coating is only applied over part of the area and not over the entire area.

In a further advantageous embodiment of the invention it is provided that the degree of shrinkage of the paper-encompassing layer is less than 1% per 100 degrees of temperature increase. This shrinkage allows a Sufficient format stability if, for the purpose of heating, parts of a plastic layer are exposed to heat and also cooled again later. If this format stability were not present to the specified extent, the paper material could warp during heating and / or cooling, so that a later sack would have quality defects such as a bottom cover sheet that was not applied in the correct position.

It is also advantageous if, in a cross-bottom sack according to the invention, parts of the outer surfaces of the outer layers are uncoated and provide a higher flaft coefficient than the coated areas. In particular, it is provided in this embodiment that the outer surfaces of the outer layers are at most partially coated with plastic. If, for example, two sacks are placed one on top of the other, as is the case in particular on a pallet, the aforementioned features prevent or even prevent the two sacks from being displaced relative to one another. This greatly restricts slipping, for example on a pallet, so that the pallet is very stable. This enables safer transport. As an alternative or in addition to the above embodiment of the invention, it can advantageously be provided that parts of the outer surfaces are embossed. Embossings are, for example, bulges of the outer layers, the bulges being directed outwards. If a sack now rests on another sack, this other sack comprising embossings, this reduces the contact surface and thus increases the contact pressure. This also reduces the possibility of the two bags slipping against one another. The embossing is done by pushing the ram into the inside of the outer layers, avoiding the penetration of the layers. This can result in elevations on the outsides which are, for example, hemispherical.

In a further, advantageous embodiment of the invention it is provided that the first layer and the second layer of the first and / or the second outer layer and / or the bottom cover sheet are partially detachable from one another are connected. It can be provided that first areas of the connection between the bottom cover sheet and the first and / or the second outer layer are non-detachable with one another, but second areas are releasably connected with one another. In particular, it is provided in this case that these second areas can be manually detached from one another. For example, areas of the bottom cover sheet can be peeled off, with the paper in particular remaining free of damage. This can create an opening through which the interior of the cross-bottom bag is accessible or through which the contents of the cross-bottom bag can be poured out. Since the paper remains free of damage through this measure, trickle losses can be avoided, especially when pouring out.

Another embodiment of the invention provides that the first layer of the bottom cover sheet has a greater density and / or a greater weight per unit area than the first layer of the first and / or the second outer layer. The first layer of the bottom cover sheet thus provides a greater specific load capacity than the first layer of the first and / or second outer layer. In this way it is possible to produce a bottom of the sack with greater stability. In particular, folded edges in the base, which are indispensable for the lowering of a sack according to the invention, represent weaknesses in the material. If the base cover sheet is now made more stable, these weaknesses can be compensated for.

Furthermore, in one embodiment of the invention, perforations can be provided in regions of the outer layers which comprise a first layer and a second layer. Perforations are to be understood as an area with a plurality of through openings, i. H,. the perforations provide unobstructed passages for air or other gases so that these can pass through the outer layers. Such perforations are particularly important during the filling process, in which air or other gases are usually also introduced into the interior of the sack with the filling material. However, it is usually desired that the air is released again from the interior of the sack to the environment after the filling process. Since the perforations are now provided in an area in which one Plastic layer is arranged, the perforations can now be closed by, for example, the plastic is heated in the area of these perforations and flows into the perforation holes. After the plastic has cooled down again, the perforations are permanently closed, so that complete tightness, which also prevents moisture penetration, can almost be achieved.

It is also advantageous that the tear strength according to ISO 1974 (Elmendorf) of the first and / or the second outer layer is at least 3000 mN. In this case, with the usual filling weights of bags in the range from 5 kg to 50 kg, sufficient strength is provided even if, for example, an outer layer has damage such as a small tear.

The above-mentioned object is also achieved by a method for producing a cross-bottom sack, comprising a first and a second outer layer, which are connected by means of a first and a second longitudinal edge, according to claim 10,

• where the two outer layers delimit an interior space,

• the first and second outer layers each comprising at least two layers at least in some areas, a first layer comprising paper and a second layer provided at least in some areas comprising a plastic layer,

• wherein the first and the second outer layer are connected by means of at least one base, whereby a base rectangle is drawn out with the formation of two triangular pockets, which comprises two flaps,

• whereby the flaps are folded back in order to at least partially cover the triangular pockets,

• where a bottom cover sheet is connected to both triangular pockets and both flaps,

• wherein the bottom cover sheet comprises a first layer made of paper and preferably a second layer provided at least in some areas, a plastic layer, The plastic layer of the bottom cover sheet with areas of the plastic layers of the triangular pockets and the tabs are connected to one another without adhesive by means of direct heating. The same advantages can be achieved with this method as have already been described in connection with the cross-bottom sack according to the invention. Features of the cross-bottom sack can therefore also be associated with the method according to the invention. The method according to the invention can advantageously be further developed in that the first and the second outer layer are produced from a paper web, the paper web being turned over along the longitudinal edges, the edge regions of the paper web overlapping along a longitudinal strip in an overlap region, so that the paper web then forms a tube. In this way, a tube can be produced in a simple manner from a flat paper web. One of the two outer layers will then encompass the overlap area.

According to an advantageous development of the method according to the invention, it is provided that at least one of the two mutually facing sides of the overlap area is provided with parts of the second layer. It is therefore provided that in the overlap area at least one of the two sides facing each other is provided with a plastic layer in order to be able to produce a tube from a flat web, in which the two sides facing each other are connected to one another by means of a sealing process, in particular by means of a hot air sealing process can. A flat web made of paper, which is suitable for carrying out the method according to the invention, can partially comprise a second layer on one side and also have a second layer on the other side in its edge region. In this exemplary embodiment, the second layer is provided in the overlap area on both sides facing one another, which enables a sealed connection in a simple manner. Furthermore, it is advantageous if the paper web and / or the tube is needled, in particular by means of a needle roller, which is preferably switched on and off the paper web in cycles. By performing needling, openings are thus created which, as has already been described in connection with a cross-bottom sack according to the invention, convey an escape of air, which has been brought in in particular during the filling process, out of the interior of the sack. A simple way of producing such needles is to use a needle roller that carries a large number of needles on its outer circumference, which penetrate into the paper web or into the paper tube and thus pierce the first and / or the second outer layer. It can be advantageous that the needle roller is brought out of engagement with the paper web at time, in particular at regular time intervals, in order not to generate any needling, particularly at points on the paper web where the bottom folds will later occur. Since folds often weaken the material, additional weakening of the material by needling can be avoided.

Further advantages, features and details of the invention emerge from the following description, in which various exemplary embodiments are explained in detail with reference to the figures. The features mentioned in the claims and in the description can be essential to the invention individually or in any combination of the features mentioned. In the context of the entire disclosure, features and details that are described in connection with the cross-bottom sack according to the invention naturally also apply in connection with the method according to the invention and in each case vice versa, so that with regard to the disclosure of the individual aspects of the invention, reference is or will always be made to each other can. The individual figures show:

Fig. 1 Schematic representation of the tube formation. Fig. 2 Processing steps for the production of sacks. Fig. 3 Schematic representation of the production of sacks Fig. 1 shows a schematic diagram for tube formation from a paper material. This tube formation takes place in a tube formation station 1. A flat web material 2, which is provided in the form of a roll 3, is fed to the tube formation station 1. This lap 3 can rotate on or with a lap carrier 4, which is mounted, for example, in the machine frame of the tube-forming station or in the frame of an unwinding station.

In the embodiment shown, to which the present invention is not restricted, the flat web material 2 comprises at least regionally two layers. The first layer is a layer comprising paper and is marked with the letter I, since this layer is directed inwards after the tube formation. The second layer, which faces outwards after the tube formation, is identified with the letter A. In the present example, however, this layer comprises, in particular, only a line 7 made of a plastic material and is close to an edge or directly on the edge of the outside.

The flat web material 2 is transported in the transport direction z by one or more pulling and / or advancing devices. Preference or feed devices, which can include pairs of transport rollers, are not shown in FIG. After unwinding, one side of the flat web material 2 is first turned over onto itself by means of a guide plate 5. Further guide elements can also be provided for the simultaneous formation of side folds, which, however, are not shown.

Shortly after the first side of the flat web material 2 has started to be turned over, its second side is also turned over. Both sides are folded in so far that the side edges are then on top of each other. The second page is turned over again with a guide element, which can be designed like the guide plate 5. This guide element is not shown for the sake of clarity. Immediately before the two side edges touch, the first side edge on the outside that comes into contact with the second side edge is subjected to a treatment which serves to join the two side edges. In the figure 1 a hot air device 6 is shown, with which a hot air stream is given approximately in the direction of the edge of the first side. In this way the second layer is heated up to or slightly below its liquefaction. Immediately afterwards, the inside of the second side is applied to the first side. Here, the inside of the first layer - or more precisely its edge - is brought into connection with the second layer, whereby the melted plastic can connect to the fibers of the paper-encompassing layer, so that a very firm connection is brought about.

The hot air device 6 comprises a hot air nozzle 8, to which a hot air stream can be fed via a feed line which is not explained in detail. The hot air nozzle 8 can be mounted displaceably in the direction of the double arrow B transversely to the transport direction of the flat web material 2. A traverse 9, which can be fastened in the machine frame of the hose-forming station 1, is used for this purpose.

After hot air has been introduced into the space between the two edges and the second side has been brought together, the joint seam can be pressed with a pressing device 10 in order to connect the inside of the first layer and the melted plastic well together. This pressing device advantageously comprises a pressing roller 11, which can be part of a pair of pressing rollers. The pressure roller 11 can be rotated relative to the machine frame via an axis or shaft 12. The pressure roller 11 can also be used to cool the joint seam. For this purpose, the roller 11 can be designed in such a way that a cooling medium can flow through it. When the roller 11 comes into contact, it can then dissipate heat from the joint seam, so that the joint seam has sufficient durability more quickly.

However, other cooling methods and devices are also conceivable, such as, for example, a device for inflating cooling air. After the joint seam has been pressed, the resulting tube 13 can be wound onto a new winding 14 of a winding station 15. Ventilation openings must be provided to ensure that the sack is vented later during or after it is filled. For this purpose, a perforating device 28 is provided which can comprise a perforating roller 29 which rotates relative to the machine frame and can carry needles 30 on its outer circumference, which can penetrate into the hose material and thus produce ventilation holes. Other types of perforating devices, for example contactless, are also conceivable. The arrangement of the perforating device is also not limited to the arrangement shown. The perforating device can also be arranged in front of the actual tube forming device. An arrangement directly in front of the separating device is also conceivable. In any case, however, the perforation must have taken place before the hose is separated into hose pieces.

The processing steps for forming individual sacks from the tube 13 are now shown in FIG. This tube, which was transported as a lap 14 from the tube-forming station 1 into the unwinding device 16, is separated into individual tube pieces 18 by means of a separating device 17, which comprises, for example, a cutting blade that can be displaced transversely to the initial transport direction y. The transport direction of the tube pieces 18 is then changed so that they are now transported further in the direction z transversely to their direction of extension, which points in the direction y. For this purpose, a transport device 19 is provided, which can be configured, for example, as a double belt conveyor.

In the first processing step a for forming the bag bottoms, which takes place in the bottom pulling station, the ends of the tube pieces are first pulled open. This step can be done with the help of suction cups, which pull the two layers apart at the ends. With spreaders you can now the layers are brought into one plane and spread out, the bottom being folded over along the so-called bottom center line 20. The ends drawn up in this way now form a bottom rectangle 21 with lateral triangular pockets 22. In FIG. 2, only the corresponding elements of the lower end of the hose section 18 are provided with reference numerals. However, these also apply mutatis mutandis to the other end of the hose section.

In processing step b, a valve label 23 can now be applied to an open end of the tube piece 18 and fastened there. The fastening is advantageously carried out by means of hot air welding, the valve label 23 being fastened at least to the triangular pocket 22.

In processing step c, the outer flaps 24 of the bottom rectangle 21 are now folded back so far that the outer edge of a flap 24 is moved over the bottom center line 20. The folding back takes place, for example, with guide elements, such as with guide plates. The areas of the triangular pockets, which are also folded back during this process, can be connected to one another. Instead of the outer flaps 24, the inner flaps 25 can also be folded back.

The inner flaps 25 are, however, preferably folded back in method step d, the inner flap 25 now covering the outer flap 24 in an overlapping area. In this overlap area, both flaps can be connected to one another, so that a usable sack bottom has already been created. Since the valve label 23 was also tucked in, a valve hose was created in this way, which enables the bag to be filled, but prevents the material to be filled from escaping after filling.

In a particularly preferred embodiment of the invention, a further processing step e takes place, in which a base cover sheet 26 is applied to each of the already closed bases and is preferably fastened using a hot air welding process. The bottom cover sheet 26 is included preferably dimensioned so that it covers areas of the tabs 24 and 25 and areas of the triangular pockets 22. It is also placed on the floor with its plastic layer so that the plastic layers face each other. This enables a very durable connection which can be produced by hot air welding. In the area of the overlap of the tabs 24 and 25, the tab 25 can be provided with cutouts so that the bottom cover sheet 25 also has direct contact with the tab 24 in the area of this overlap. In a similar manner, direct contact of the bottom cover sheet 26 with the valve label 23 can be made.

FIG. 3 again shows, in a schematic representation, the individual method steps for producing sacks from a flat web material. In this embodiment, however, the winding of the hose, the transport of the roll and the renewed unwinding of the hose are dispensed with. Instead of these devices, a deflection device 27 is provided which deflects the finished tube 13 from the transport direction z into the transport direction y. This deflection device can be displaced along the double arrow C in or against the direction z, so that the position of the side edge can be changed after the deflection in or against the direction z.

FIG. 3 also shows a method step f in which several bags are stacked before they are packed in a transport container, for example.

Claims

1. Cross-bottom sack, comprising a first and a second outer layer, which are connected by means of a first and a second longitudinal edge,

• where the two outer layers delimit an interior space,

• wherein the first and the second outer layer are connected by means of at least one base, which comprises two triangular pockets and two tabs placed one on top of the other in some areas,

• A bottom cover sheet is provided, which is connected to both triangular pockets and both tabs,

• wherein the bottom cover sheet comprises a first layer of paper and preferably a second layer provided at least in some areas, a plastic layer,

• wherein the bottom cover sheet is connected to areas of the plastic layers of the triangular pockets and the tabs, at least in some areas, in a non-detachable and adhesive-free manner.

2. Cross bottom sack according to claim 1, characterized in that the paper-comprising layer is directed towards the interior, the paper-comprising layer providing capillarity for water molecules.

3. Cross-bottom sack according to one of the preceding claims, characterized in that the shrinkage of the paper-enclosing layer is less than 1% per 100 degrees of temperature increase.

4. Cross bottom sack according to one of the preceding claims, characterized in that

Parts of the outer surfaces of the outer layers are uncoated and provide a higher coefficient of adhesion than the coated areas.

5. Cross bottom sack according to one of the preceding claims, characterized in that

Parts of the outer surfaces are embossed.

6. Cross bottom sack according to one of the preceding claims, characterized in that the first layer and the second layer of the first and / or the second outer layer and / or the bottom cover sheet are partially detachably connected to one another.

7. Cross bottom sack according to one of the preceding claims, characterized in that the first layer of the bottom cover sheet has a greater density and / or a larger area weight than the first layer of the first and / or the second outer layer.

8. Cross bottom sack according to one of the preceding claims, characterized in that in areas of the outer layers, a first layer and a second layer include, perforations are provided.

9. Cross bottom sack according to one of the preceding claims, characterized in that the tear strength according to ISO 1974 (Elmendorf) of the first and / or the second outer layer is at least 3000 mN.

10. A method for producing a cross-bottom sack, comprising a first and a second outer layer, which are connected by means of a first and a second longitudinal edge,

• where the two outer layers delimit an interior space,

• whereby the flaps are folded back in order to at least partially cover the triangular pockets

• where a bottom cover sheet is connected to both triangular pockets and both tabs,

• the plastic layer of the bottom cover sheet with areas of the plastic layers of the triangular pockets and the tabs being connected to one another without adhesive by means of direct heating.

11. The method according to the preceding claim, characterized in that the first and the second outer layer are produced from a paper web, wherein the paper web is turned over along the longitudinal edges, wherein the edge areas of the paper web overlap along a longitudinal strip in an overlapping area, so that the paper web then forms a tube.

12. The method according to any one of the preceding claims, characterized in that at least one of the two mutually facing sides of the overlapping area is provided with parts of the second layer.

13. The method according to any one of the preceding claims, characterized in that the paper web and / or the tube is needled, in particular by means of a needle roller, which is preferably switched on and off the paper web in cycles.

14. The method according to any one of the preceding claims, characterized in that the paper web and / or the tube is needled, wherein the side of the paper web from which the paper web is needled can be selected.

15. The method according to any one of the preceding claims, characterized in that the paper web and / or the tube is needled, wherein the depth of penetration of the needles into the paper is adjusted.

16. The method according to any one of the two preceding claims, characterized in that the first layer of the first outer layer and / or the second outer layer is printed and / or is imprinted and then the second layer is applied.

17. The method according to any one of the three preceding claims, characterized in that the second layer is applied to the first layer of the first outer layer and / or the second outer layer and then the second layer is printed.