Side-gusset bag made of a plastic fabric composite, and method for the production thereof

The invention relates to a flat-lying side-gusset bag made of a plastic fabric composite (2) and to a method for the production thereof. The side-gusset bag has opposing front walls (3a, 3b), side gussets (4a, 4b) introduced in between said front walls (3a, 3b), and folding edges (5) between the front walls (3a, 3b) and the side gussets (4a, 4b). Peripheral sections of the plastic fabric composite (2) are connected together in an overlapping region (10) at a longitudinal seam, wherein the plastic fabric composite (2) has a plastic fabric (7) and at least one closed plastic layer. The side gussets (5) extend, in the case of the flat-lying side-gusset bag, in each case over at most ⅓ of the width of the front walls. According to the invention, the overlapping region (10) is arranged off-center on one of the front walls (3a, 3b) at least partially over one of the side gussets (4a, 4b) or at one of the side gussets (4a, 4b). In order to be able to form such a side-gusset bag, in the production method, first of all a closed, two-layer tube (12) is formed, from which a side-gusset tube (1) is subsequently formed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the US-national stage of PCT application PCT/EP2013/052899 filed 13 Feb. 2013 and claiming the priority of German patent application 102012101932.0 itself filed 7 Mar. 2012.

FIELD OF THE INVENTION

The present invention relates to a method of making a gusset bag made of a plastic/fabric laminate and a corresponding flat gusset bag. The flat side-gusset bag is cut from a gusseted tube and typically closed only at one of its two ends in order to be filled and ultimately completely closed at the other end. The filled side-gusset bag is provided as a package, in particular, for free-flowing bulk materials such as pelletized animal feed, litter for animals, or similar materials. Due to the use of the plastic/fabric laminate, the side-gusset bag is especially suitable for large bags that have a significant fill volume and a significant filling weight. In practice, corresponding side-gusset bags are also described as side-gusset sacks, although these terms will not be differentiated in the present invention.

The present invention relates to side-gusset bags made of a plastic/fabric laminate that has opposite front and back panels when flat, gussets between them and longitudinal-edge folds between the front and back panels and the gussets. The plastic/fabric laminate comprises a plastic fabric and at least one closed plastic layer with the plastic fabric normally on the inside of the packaging bag.

Even though the plastic fabric typically consists of a material that can be thermally welded, a tight seal is not possible as a result of the fabric structure or at best, with limitations. Unlike typical plastic bags, it is therefore not possible or practical to close the side-gusset bag produced from a plastic/fabric laminate continuous web on its periphery, that is at both edges where the inner surface formed by the plastic fabric is welded with itself. Rather, in side-gusset bags made of a plastic fabric, a gusseted tube is shaped such that edge strips of the continuous web overlap, with a first face of the continuous web at the respective outer edge strip being connected with the inner edge strip of a second face by an adhesive in order to peripherally close the gusseted tube.

A generic flat side-gusset bag is known from EP 1 899 235 [US 2006/029173] and DE 101 06 289 [U.S. Pat. No. 6,800,051]. The gussets extend over a maximum of one third of the width of the front and back panels, i.e. over a maximum of one third of the width of the flat side-gusset bag. In making such a side-gusset bag, a continuous web is first shaped into a gusseted tube with the edges of the continuous web overlapping in the region between the gussets and there, after forming the gusseted tube, they are fixed together with an adhesive. For the adhesive, conventional adhesives can be used such as adhesives containing solvent or hot-melt adhesives. However, within the scope of the invention, an application of a fusible polymer is also suitable as an adhesive, having the effect of a bonding upon the application of force to the overlap.

In known embodiments, in order to first form the gusseted tube and to subsequently be able to peripherally close it, the overlap is always located approximately in the center on one of the front and back panels between the two gussets. Because of the resultant poor appearance, this panel typically forms the back of the side-gusset bag. In spite of that, the overlap extending on the back approximately in the middle can be found to be objectionable, particularly when printed matter is to be located there as well. Finally, in known side-gusset bags made of a plastic/fabric laminate, the design possibilities are significantly limited.

OBJECT OF THE INVENTION

Given this background, the object of invention is to provide a method of making a side-gusset bag and a side-gusset bag in which the disadvantages that have been described above are avoided.

SUMMARY OF THE INVENTION

The subject matter of the invention and the solution of the problem consist of a method of making a side-gusset bag of a plastic/fabric laminate in which a continuous web with a plastic fabric is applied to at least one closed plastic layer and shaped into a tube such that edge strips of the continuous web overlap and a first face of the continuous web form the inner surface and the second continuous web forms the outer surface. At the overlap, the first face of the continuous web at the respective outer edge strip is fixed with the inner edge strip of the second face by an adhesive in order to peripherally close the tube. As adhesives, conventional adhesives are suitable such as solvent-containing adhesives or hot-melt adhesives. Furthermore, a fusible plastic can also be provided as adhesive. Within the scope of the invention, the term adhesive thus includes conventional adhesives, but is not limited to them.

According to the invention, first a simple tube is formed. In flat condition, this simple tube is formed out of two layers of the continuous web at least outside of the overlap.

According to the invention, the tube is first closed and subsequently fed into a folder that shapes it into a flat gusseted tube with opposite front and back panels having gussets inserted between them and edge folds between the front and back panels and the gussets, so that the gusseted tube, at least outside the overlap, has four layers at the gussets and two layers of the continuous web between the gussets.

According to the invention, because of the connection at the overlap, first a closed tube is formed and only then is a flat gusseted tube formed, so the overlap can be freely positioned to a large extent. Thus, the overlap is located at least partly in a section of the gusseted tube that is formed by four layers of continuous web. The overlap is thus either on one of the gussets or on a front panel over one of the gussets.

However, advantageously, it should be avoided that the overlap extends beyond one of the longitudinal-edge folds. But the overlap can easily be placed directly up to one of the longitudinal-edge folds.

Finally, pieces are cut from the gusseted tube to form individual side-gusset bags. Within the scope of the invention, the separation is typically performed without any prior coiling of the gusseted tube. As a result of the location of the overlap in the area of one of the gussets, coiling is disadvantageous, because coiling would produce a coil with uneven thickness.

Preferably, the continuous web is formed by laminating the plastic fabric with a film so that the plastic fabric forms the first face, and the film forms the second face of the continuous web. Within the scope of such an embodiment, lamination with adhesive or preferably an extrusion lamination is possible where a fusible polymer film is inserted between the film and the plastic fabric. Such a polymer film can have one layer or several layers. When inserting a multilayer film, it is created by coextrusion, as a result of which an optimal bonding with the plastic fabric can be achieved on the one hand, and also with the outer film on the other hand.

Lamination also provides the advantage that the outer films of the side-gusset bag can be provided with printed matter even prior to lamination. This printed matter is then advantageously located on the side that is laminated with the plastic fabric. In the plastic/fabric laminate formed in this way, the printed matter is then positioned in a way that is protected on an inner face.

In place of laminating with a film, the plastic fabric can also be coated with a fusible plastic layer to form the plastic/fabric laminate. Even in such an embodiment, the plastic fabric can provide a high degree of stability, while the plastic layer that is applied has the effect of a tight closure and forms a largely homogeneous, printable outer surface. However, within the scope of such an embodiment there is the disadvantage that the plastic coating formed in this way can only be provided with an printed matter on an outer face. But if necessary, such printed matter can also be provided with a protective lacquer to achieve a high degree of resistance against abrasion.

Beyond that, the protective lacquer can also be provided for achieving a flat, nonslip surface. A flat, nonslip surface is preferred in order to avoid shifting while stacking the filled side-gusset bags. For the same reason, when laminating with a film as the outer layer, preferably a flat polymer material that has a nonslip surface consistency is provided for the outer layer.

At the overlap, the outer edge of the continuous web is visible at the outer edge strip. The overlap is therefore advantageously formed such that the outer edge of the continuous web is on that side of the overlap adjacent the closest edge fold. In such an embodiment, the outer edge of the continuous web can be placed directly up to the closest edge fold.

Preferably, the spacing from the outer edge to the closest edge fold is less than 80 mm.

Within the scope of an alternate embodiment of the invention it is also possible to locate the overlap on one of the gussets. Both the front and the back panel are then free of any impediment and can be provided with printed matter on their entire surface.

Advantageously, the plastic fabric is formed by strips or ribbons of a stretched film, with a first group of ribbons and a second group of ribbons extending perpendicular to one another. It is known to produce corresponding plastic fabrics on circular knitting machines. The width of the ribbons crossing each other is typically between 2 mm and 4 mm, in particular, between 2.5 mm and 3.2 mm. The plastic ribbons that are longitudinally stretched are typically produced made of polyolefin, in particular, polypropylene. For the side-gusset bag according to the invention, in particular, plastic fabrics with a weight per unit of area between 50 g/m2and 100 g/m2, are suitable, for example, with a weight by unit of area of approximately 72 g/m2.

Even though polyolefins and, in particular, polypropylene are generally thermoplastic, the plastic fabric cannot easily be thermally welded because of its fabric structure. In order to be able to provide functional elements such as reclosable seals or the like at the inner side of the side-gusset bag, the plastic fabric can optionally also be provided with a hot-seal coating in sections or over its entire surface, or be provided with glued-on hot-sealable film patches.

The side-gusset bag according to the invention is particularly well-suited for a large fill volume and a heavy weight. Given this background, it can be advantageous to provide the side-gusset bag with a carry handle. Because of the difficult of welding to the inner plastic fabric, a carry handle that is glued onto the outer surface of the side-gusset bag must be considered. As has already been explained, the inner face can be provided with individual hot-sealable film patches at which a carrying handle can then also be fastened.

According to a preferred embodiment of the invention the side-gusset bag consists entirely of polyolefin and especially preferred, entirely out of polypropylene (PP). Within the scope of such an embodiment, the side-gusset bag can be recycled easily or incinerated with no ash.

In a plastic/fabric laminate formed by extrusion lamination, the film located on the outside of the side-gusset bag can consist of, for example, polypropylene, in particular, a biaxially oriented polypropylene (BO-PP). The layer thickness of such a film is preferably between 10 and 40 μm, especially preferred between 15 and 30 μm.

In extrusion lamination, a fusible film is inserted between the outer film and the plastic fabric, and this film must have a sufficient thickness in order to form a secure bond in spite of a structure of the plastic fabric that is irregular to a certain degree. Thus, the film that is provided for the bonding preferably has a weight per unit of area of between 25 g/m2and 40 g/m2. The fusible film can be extruded in one layer as well as coextruded in multilayers. In a multilayered coextrusion, advantageously, a thin adhesion-promoting layer is provided against the outer film on the side-gusset bags. In principle, the outer film and the plastic fabric can be provided with a primer prior to lamination to increase the bonding strength. Especially in the case of a one-layer extrusion, the application of primer to the film is advantageous if the film is printed. Then, an adequate adhesion of the fusible film must be achieved on the printed matter.

Within the scope of the method according to the invention, first a simple tube is formed that is peripherally closed at an overlap. Preferably, the tube is formed flat with two lateral outer web edges, then the tube is formed into a gusseted tube such that the outer web edges are located at one of the longitudinal-edge folds of the gusseted tube. The finished side-gusset bag then has diagonally opposite longitudinal-edge folds.

The formation of the tube out of the continuous web, the peripheral closing of the continuous web in the overlap and the formation of the gusseted tube preferably takes place on a continuous strand in successive method steps. Within the scope of such an embodiment, mass production is possible, with an advance rate of the strand equal, for example, to at least 70 m/min, preferably 100 m/min (meters per minute).

The length of the individual tube pieces cut from the gusseted tube preferably ranges between 700 mm and 1200 mm. By taking the previously cited advance rate into consideration, this results in a typical production-cycle rate of approximately 100 tube pieces and thus 100 side-gusset bags per minute.

The separated tube pieces are first open at their two ends. But advantageously, the tube pieces will be closed at one of their ends directly after separation. Thus, one of the open ends of the tubular pieces can be rolled in and fixed together in rolled-in condition. When rolling in, based on the open end, typically a first strip of the tubular piece is folded by 180° and then a second strip having the first strip located on it is also folded in by 180°. The strips can, for example, have a width of approximately 20 mm. The fixation can, for example, be accomplished by an adhesive strip, by an adhesive or by hot air. When the end that is closed in this way forms the bottom of the side-gusset bag, the side-gusset bag is subsequently filled in a filling system at its upper end and then closed at its upper end. As is the case in typical paper sacks, closure can be accomplished, for example, by sewing or welding together.

According to an alternative design, the end of the side-gusset bag that is directly closed during production is intended to be the upper edge of the side-gusset bag. The rolled-in end can thereby be fixed together by an adhesive strip that can be pulled off again. As a result of the adhesive strip that can be pulled off, an especially easy opening of the filled side-gusset bag can be achieved. Within the scope of such an embodiment, the bag that is prepared in this way can then be filled from the lower end and closed there. In particular, it is also known to provide an adhesive strip in the center that can then be pulled off laterally in both directions.

For practical reasons, the rolling in for flat tubular pieces is typically done on that edge at which the overlap is also provided. According to the prior art, the front panel with the clearly visible overlap and the rolled-in end is typically located on the back of the bag. An adhesive strip that can be pulled off is then, however, not directly noticeable by the user. Within the scope of the present invention, the advantage results that the overlap is located far toward the outer edge at one of the gussets and in this way, the visual appearance is less disturbing. The corresponding front panel of the side-gusset bag can therefore also be provided as the front so that then a removable adhesive strip on a rolled-in end is likewise on the front side and is visible directly.

The weight per unit of area of the plastic/fabric laminate is preferably between 100 g/m2and 150 g/m2.

SPECIFIC DESCRIPTION OF THE INVENTION

FIG. 1shows a gusseted tube1made of plastic/fabric laminate2, from which individual flat side-gusset bags can be cut. The gusseted tube1or the individual side-gusset bags have opposite front and back panels3aand3bwith gussets4aand4binserted between them, as well as longitudinal-edge folds5between the front and back panels3aand3band the gussets4aand4b.

According to the enlarged sectional view ofFIG. 1, the plastic/fabric laminate2is formed by extrusion lamination of a film6forming the outer surface of the gusseted tube1and a plastic fabric7that lies on the inner surface of the gusseted tube1. The film6and the plastic fabric7are connected by an intermediate layer8inserted as a fusible film during the extrusion lamination. According toFIG. 1, the plastic fabric7is formed by film strips crossing each other and typically having a width of approximately 3 mm.

The weight by unit of area of the plastic fabric7is 72 g/m2, and the strips consist of polypropylene and are axially stretched. Typically, the strips are arrayed with a first group of strips extending longitudinally of the gusseted tube1and a crossing second group of strips extending transversely. Since the stretched strips crossing each other, a particularly high degree of stability of the side-gusset bag is achieved. In particular, local damage such as punctures, cracks or the like cannot expand in the plastic/fabric laminate2.

The film6that on the outside of the gusseted tube1can, for example, consist of a biaxially oriented polypropylene (BO-PP) having a typical thickness of 18 μm. Preferably, a comparable nonslip material is used to avoided shifting while stacking the filled side-gusset bags15. The fusible intermediate layer8in the laminate also consists of polypropylene, so that the entire the plastic/fabric laminate2consists of polypropylene and can thus be easily recycled. The weight per unit of area of the intermediate layer8is, for example, 30 g/m2.

FIG. 1further shows that the film6is printed on its outer face adjacent to intermediate layer8. This gives the advantage that this printed matter9is optimally protected against any external influences because of its location inside the laminate.

Overall, the plastic fabric7cannot be welded well, for which reason for the purpose of closing the gusseted tube1, an overlap10is provided at which edge strips of the plastic/fabric laminate2overlie each other. At the overlap10, the outer face of an edge strip of the plastic fabric7engages an inner face of an opposite edge strip of the film6to close the gusseted tube1. Not only conventional adhesives such as solvent-containing adhesives and hot-melt adhesives come into consideration as an adhesive11, but also fusible plastics. Within the scope of the present invention, an application of fusible polypropylene is particularly preferred.

According to the invention, the overlap10is located on a gusset4aand4b, or off-center on one of the front and back panels3aand3b, at least partly over one of the gussets4aand4b. For this reason, it is not easy to first form the gusseted tube1and then make the bond with the adhesive11in the overlap10.

According to the invention, in the method of making a side-gusset bag according toFIG. 4aout of the plastic/fabric laminate2that is extends as a continuous web, a simple, flat tube12is formed that is closed at the overlap10by adhesive11.

As shown inFIG. 4b, the closed tube12is subsequently fed into a folder13that shapes the previously described flat tube into the flat gusseted tube1. The flat tube12is advantageously fed into the folder13such that two of the longitudinally extending edge folds5are formed at each of the two outer edges14of the flat tube12.

Since according to the invention the gussets4aand4bare made only after making the closed flat tube12, the overlap10can also easily be formed in a section of one of the gussets4aand4b, i.e. on one of the gussets4aand4b, or on one of the front and back panels3aand3bat least partly over one of the gussets4aand4b.

The formation of the flat tube12from the plastic/fabric laminate2as a continuous web, the closing of the continuous web at the overlap10, as well as the formation of the gusseted tube1take place continuously as a continuously running strand that is preferably advanced at a rate of at least 70 m/min (meters per minute).

To be able to form individual side-gusset bags, individual tubular pieces are cut from the gusseted tube1, typically having a length of between 700 mm and 1200 mm.

In order to close one end of the tubular pieces, the end can be rolled in by a method that is known per se and can be fixed in the rolled-in position. An end that is closed in this way can form the lower edge as well as also the upper edge of the side-gusset bag.

FIG. 3shows a possible embodiment of a filled side-gusset bag15in which one end is rolled in onto itself by double folding and is fixed in this rolled-in condition by an adhesive strip16.

The adhesive strip16can be pulled off so that the filled side-gusset bag15can be opened easily. Furthermore, the outer edge17of the plastic/fabric laminate2visible at the overlap10is set at a small spacing to one of the longitudinal edges5. For this reason, the overlap10can also be on the front of the filled side-gusset bag15where the adhesive strip16is also provided. The visual appearance of the printed front side of the filled side-gusset bag15is not significantly impaired by the overlap10set at the edge.

The side-gusset bag15shown inFIG. 3was filled from its bottom side and was closed there, for example, by a stitched seam as is typical for sacks made of paper or cloth.