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

Abstract

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.

Claims

1. A method of making a side-gusset bag from a plastic/fabric laminate, the method comprising the steps of: providing a longitudinally extending and continuous web having opposite first and second faces and made of a plastic fabric forming one of the faces and at least one closed plastic layer forming the other of the faces; shaping the continuous web into a continuous tube such that longitudinal edge strips of the continuous web overlap and that the first face of the continuous web forms an inner surface and the second face of the continuous web forms an outer surface of the tube and the inner surface confronts the outer surface at the overlap; inserting an adhesive at the overlap between the confronting inner and outer surfaces and thereby bonding at the overlap the inner surface of the tube with the outer surface of the tube to peripherally close the tube; flattening the closed tube with the edge strips bonded at the overlap by the adhesive between the inner and outer surfaces of the tube such that the flattened tube has two longitudinally extending outer edges; feeding the flattened closed tube into a folder that shapes it into a flat gusseted tube with opposite front and back panels having gussets at longitudinal-edge folds formed by the longitudinally extending outer edges between the front and back panels so that the gusseted tube has longitudinal edge regions formed by four layers of the continuous web at the gussets and two layers between the gussets; forming the gusseted tube such that the overlap is at least partly in one of the longitudinal edge regions of the gusseted tube formed by four layers of the continuous web; and cutting tubular pieces from the gusseted tube to form individual side-gusset bags.

2. The method defined in claim 1, wherein the continuous web is formed by laminating the plastic fabric with a film forming the closed plastic layer such that the plastic fabric forms the first face and the film forms the second face of the continuous web.

3. The method defined in claim 2, wherein the film and the plastic fabric are laminated together by coextrusion.

4. The method defined in claim 2, further comprising the step of: providing the film with printed matter lamination with the plastic fabric on its printed face.

5. The method defined in claim 4, further comprising the step of: covering the printed matter by the at least one transparent outer layer of the plastic/fabric laminate.

6. The method defined in claim 1, further comprising the step of: rolling in an open end of the tubular pieces and fixing the open end together in rolled-in condition.

7. The method defined in claim 5, further comprising the step of: fixing together the rolled-in end by a removable adhesive strip.

8. The method defined in claim 1, wherein the overlap is formed on one of the front and back panels such that an outer edge of the continuous web that forms one of the outer edge strips is spaced by less than 80 mm to the closest edge fold.

9. The method defined in claim 1, wherein the overlap is on one of the gussets.

10. The method defined in claim 1, wherein the side-gusset bag consists entirely of olefin.

11. The method defined in claim 1, wherein the formation of the closed tube out of the continuous web, the closing of the continuous web at the overlap, and the formation of the gusseted tube take place while continuously displacing the web.

12. The method defined in claim 10, wherein the web is advanced at at least 70 m/min.

13. The method defined in claim 1, further comprising the step of: cutting tubular pieces having at least a length ranging between 700 mm and 1200 mm from the gusseted tube.

14. The method defined in claim 1, wherein the plastic/fabric laminate has a weight by unit of area of between 100 g/m.sup.2 and 150 g/m.sup.2.

15. The method defined in claim 1, further comprising the step of: forming the plastic fabric from strips with a strip width of between 2 mm and 4 mm.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) In the following, the invention will be explained in more detail reference to a drawing showing only one embodiment. Therein:

(2) FIG. 1 is a perspective sectional view of a gusseted tube.

(3) FIG. 2 is a top view of a gusseted tube according to FIG. 1.

(4) FIG. 3 is a view like FIG. 1 showing a side-gusset bag formed of the tube of FIG. 1.

(5) FIGS. 4a and 4b are schematic views showing the method steps for making the gusseted tube according to FIG. 1.

SPECIFIC DESCRIPTION OF THE INVENTION

(6) FIG. 1 shows a gusseted tube 1 made of plastic/fabric laminate 2, from which individual flat side-gusset bags can be cut. The gusseted tube 1 or the individual side-gusset bags have opposite front and back panels 3a and 3b with gussets 4a and 4b inserted between them, as well as longitudinal-edge folds 5 between the front and back panels 3a and 3b and the gussets 4a and 4b.

(7) According to the enlarged sectional view of FIG. 1, the plastic/fabric laminate 2 is formed by extrusion lamination of a film 6 forming the outer surface of the gusseted tube 1 and a plastic fabric 7 that lies on the inner surface of the gusseted tube 1. The film 6 and the plastic fabric 7 are connected by an intermediate layer 8 inserted as a fusible film during the extrusion lamination. According to FIG. 1, the plastic fabric 7 is formed by film strips crossing each other and typically having a width of approximately 3 mm.

(8) The weight by unit of area of the plastic fabric 7 is 72 g/m.sup.2, 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 tube 1 and 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 laminate 2.

(9) The film 6 that on the outside of the gusseted tube 1 can, 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 bags 15. The fusible intermediate layer 8 in the laminate also consists of polypropylene, so that the entire the plastic/fabric laminate 2 consists of polypropylene and can thus be easily recycled. The weight per unit of area of the intermediate layer 8 is, for example, 30 g/m.sup.2.

(10) FIG. 1 further shows that the film 6 is printed on its outer face adjacent to intermediate layer 8. This gives the advantage that this printed matter 9 is optimally protected against any external influences because of its location inside the laminate.

(11) Overall, the plastic fabric 7 cannot be welded well, for which reason for the purpose of closing the gusseted tube 1, an overlap 10 is provided at which edge strips of the plastic/fabric laminate 2 overlie each other. At the overlap 10, the outer face of an edge strip of the plastic fabric 7 engages an inner face of an opposite edge strip of the film 6 to close the gusseted tube 1. Not only conventional adhesives such as solvent-containing adhesives and hot-melt adhesives come into consideration as an adhesive 11, but also fusible plastics. Within the scope of the present invention, an application of fusible polypropylene is particularly preferred.

(12) According to the invention, the overlap 10 is located on a gusset 4a and 4b, or off-center on one of the front and back panels 3a and 3b, at least partly over one of the gussets 4a and 4b. For this reason, it is not easy to first form the gusseted tube 1 and then make the bond with the adhesive 11 in the overlap 10.

(13) According to the invention, in the method of making a side-gusset bag according to FIG. 4a out of the plastic/fabric laminate 2 that is extends as a continuous web, a simple, flat tube 12 is formed that is closed at the overlap 10 by adhesive 11.

(14) As shown in FIG. 4b, the closed tube 12 is subsequently fed into a folder 13 that shapes the previously described flat tube into the flat gusseted tube 1. The flat tube 12 is advantageously fed into the folder 13 such that two of the longitudinally extending edge folds 5 are formed at each of the two outer edges 14 of the flat tube 12.

(15) Since according to the invention the gussets 4a and 4b are made only after making the closed flat tube 12, the overlap 10 can also easily be formed in a section of one of the gussets 4a and 4b, i.e. on one of the gussets 4a and 4b, or on one of the front and back panels 3a and 3b at least partly over one of the gussets 4a and 4b.

(16) The formation of the flat tube 12 from the plastic/fabric laminate 2 as a continuous web, the closing of the continuous web at the overlap 10, as well as the formation of the gusseted tube 1 take place continuously as a continuously running strand that is preferably advanced at a rate of at least 70 m/min (meters per minute).

(17) To be able to form individual side-gusset bags, individual tubular pieces are cut from the gusseted tube 1, typically having a length of between 700 mm and 1200 mm.

(18) 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.

(19) FIG. 3 shows a possible embodiment of a filled side-gusset bag 15 in which one end is rolled in onto itself by double folding and is fixed in this rolled-in condition by an adhesive strip 16.

(20) The adhesive strip 16 can be pulled off so that the filled side-gusset bag 15 can be opened easily. Furthermore, the outer edge 17 of the plastic/fabric laminate 2 visible at the overlap 10 is set at a small spacing to one of the longitudinal edges 5. For this reason, the overlap 10 can also be on the front of the filled side-gusset bag 15 where the adhesive strip 16 is also provided. The visual appearance of the printed front side of the filled side-gusset bag 15 is not significantly impaired by the overlap 10 set at the edge.

(21) The side-gusset bag 15 shown in FIG. 3 was 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.