Abstract
A bag wall is designed for producing a bag open on a top side by means of at least a connection seam and for closing said bag by means of at least one further connecting seam after being filled with bulk material and is characterized by at least one Kraft paper layer forming a Kraft paper core (1) and essentially determining the load capacity of the bag which core (1) is provided with fine openings (2) in two-dimensional regions covering at least half of the surface of said core (1) and is directly coated on both sides with a plastic layer (3, 4) each wherein both plastic layers consist of plastic material being miscible in liquid states and wherein the plastic layers (3, 4) are connected to each other by material fit through said openings (2) during the coating.
Claims
1. A bag wall designed for producing a bag open on a top side by means of at least a connection seam and for closing said bag by means of at least one further connecting seam after being filled with bulk material, wherein at least one Kraft paper layer forming a Kraft paper core and essentially determining the load capacity of the bag which core is provided with fine openings in two-dimensional regions covering at least half of the surface of said core and is directly coated on both sides with a plastic layer each wherein both plastic layers consist of plastic material being miscible in liquid states and wherein the plastic layers are connected to each other by material fit through said openings during the coating.
2. The bag wall according to claim 1, wherein the openings are distributed over the whole surface of the Kraft paper core.
3. The bag wall according to claim 1, wherein the openings are distributed uniformly over the surface of the Kraft paper core.
4. The bag wall according to claim 1, wherein the openings form a pattern wherein a distance between an opening and an adjacent opening is between 3 and 100 mm, especially between 5 and 50 mm.
5. The bag wall according to claim 1, wherein the openings form a regular pattern which repeats within the two-dimensional region of the surface of the core.
6. The bag wall according to claim 1, wherein the Kraft paper core has a grammage of 70 to 120 g/m.sup.2 and the plastic layers each have a coating weight per unit area of 10 to 30 g/m.sup.2.
7. The bag wall according to claim 1, wherein the plastic layer designed for the inner side of the bag has a higher coating weight per unit area than the plastic layer designed for the outer side of the bag.
8. The bag wall according to claim 1, wherein at least one plastic layer, preferably both plastic layers, consists of polyethylene.
9. The bag wall according to claim 1, wherein the largest dimension of each opening is between 0.5 and 2 mm.
10. A method for producing a bag wall wherein a Kraft paper core essentially determining the stability of the bag wall is provided on its whole surface with numerous openings and that the Kraft paper layer is coated on both sides with a plastic layer each in liquid states of the plastics so that the plastic layers are connected with each other through the openings by material fit.
11. A bag tube formed from a bag wall according to claim 1 by means of at least one longitudinal seam connecting together longitudinal end portions of the flat bag wall so as to form the tube.
12. The bag tube according to claim 11, wherein the longitudinal seam is a weld seam.
13. A use of a bag wall according to claim 1, wherein a web of the bag wall is formed by means of a longitudinal seam or a folding, a bag open at a top is formed from the web by means of at least one seam and a bag section is separated by a cutting line, the bag open at the top is then filled with bulk material and closed after filling by means of at least one further seam.
14. The use according to claim 13, wherein at least one seam is a weld seam and positioned in a region having openings.
Description
[0021] Embodiments of the present invention are illustrated in the accompanying drawings and will be described herein after.
[0022] FIG. 1 shows a schematic longitudinal section through a bag wall according to the present invention;
[0023] FIG. 2 shows a pattern of openings which may be repeated over the whole surface of a Kraft paper core;
[0024] FIG. 3 shows a schematic top view on a bag wall wound on a supply reel as a closed tube with dewinding steps as performed by the user;
[0025] FIG. 4 shows a side view corresponding to FIG. 3;
[0026] FIG. 5 shows a schematic perspective view on a filled and closed bag;
[0027] FIG. 6 shows a schematic representation of a bag wall formed as a closed tube by means of a longitudinal seam, the tube having gussets, as may be delivered by the bag manufacturer;
[0028] FIG. 7 shows a schematic representation of different seams applied to the delivered bag by the user before and after filling the bag.
[0029] The bag wall a section of which is illustrated in FIG. 1 in a schematic enlarged view consists of a paper layer 1 having a multitude of openings 2 and being provided with a first coating 3 and a second coating 4. The first coating 3 is designed for the inner side of a bag formed by the bag wall whereas the second coating 4 is designed for the outer layer. The paper layer 1 is a Kraft paper layer which essentially determines the stability or load capacity of the bag wall. The paper layer 1 is directly coated with the first coating 3 and the second coating 4 which both are of plastic material like e. g. polyethylene. The coating is performed by applying the plastic material in a liquid state so that the plastic material of both coatings 3 and 4 migrate into the openings 2. Since the plastic material of both coatings are miscible they will completely fill the openings 2 so that both coatings 3, 4 are connected by material fit through said openings 2. The plastic material of both coatings 3, 4 is preferably thermoplastic material so that the plastic material in the liquid state is applied during lamination of the paper layer will become solid with the connection between both coatings 3, 4 through the openings 2. FIG. 2 shows a possible pattern of five openings 2, four of them being arranged in the corners of a square and the fifth opening 2 in the center of the square. This pattern may be repeated over the whole surface of the bag wall. In an embodiment of the invention the largest dimension of the opening 2 lies between 0.5 and 2 mm and the distance a between 2 adjacent openings 2 may lie between 3 and 100 mm, preferably between 5 and 50 mm. The illustrated example of FIG. 2 shows a side length a of the square of 5 mm so that the pattern is characterized by aa (5), where (5) means the number of openings 2 and aa means the distance of the holes within the squares. It is noted that the distance between the openings 2 at the corners of the square and the central opening 2 is somewhat smaller than the distance a.
[0030] FIGS. 3 and 4 illustrate the arrangement of the bag wall of FIG. 1 formed as a tube with gussets and wound on a core so as to form a supply reel 6 from which a web 7 of a continuous bag tube is decoiled at the user's premises. In FIG. 3 the fold lines 8 defining the gussets of the bag tube is shown in dotted lines. During the unwinding process a first transverse seam 9, especially a weld seam, is applied defining the length of the bag formed from the tube 7. Furthermore, diagonal bottom seams 10 are applied as known in the art. In the next step a length of the web 7 is cut along a cutting line 11 so that now a bag open at the right end in FIGS. 3 and 4 is produced. In the next step the bag is filled with bulk material as indicated by filling contour 12 in FIG. 3. The open end 13 of the filled bag is now closed by a final seam corresponding to bottom seam 9. The closed and filled bag is schematically illustrated in FIG. 5, where the height of the bag is determined by the defolded gussets. The folding line 8 of which is shown in FIG. 5.
[0031] It should be noted that FIGS. 3 and 4 only show an embodiment of the production of an open bag from a bag wall according to the present invention. In the embodiment of FIGS. 3 and 4 a web 7 of a bag tube is illustrated. As an alternative the web 7 may consist of a bag wall folded at one side edge so as to form a U shape. The free ends of both flaps of the bag wall are not connected and will establish the opening at the top when seams corresponding to seam 9 in FIG. 3 define side walls of the bag and the fold at the edge of the web 7 establishes a bottom of the bag. In this embodiment there is no gusset so that a shape of the filled bag will occur which may not be preferred in any case.
[0032] FIG. 6 shows a section of the web 7 produced by the bag manufacturer when the bag wall forms the web 7 as a tube. There is a longitudinal seam 14 by which overlapping ends of the bag wall are connected. In this case a weld seam may be produced by connecting the second (outer) coating 4 with the first (inner) coating 3 along the longitudinal seam 14. FIG. 6 illustrates the folding lines 8 for gussets formed in the wall tube as wound on the supply reel by the bag manufacturer. Only for the purpose of illustration the openings 2 are shown as an enlarged view. They form sections leaving a sector along the length of the tube without openings.
[0033] As shown in FIG. 7 at user's premises further seams 9, 10 and 13 are produced in the sections of the bag tube where openings 2 exist. Thereby, the seams 9, 10 and 13 are stabilized through the connections between the coatings 3, 4 through the openings 2, as described above.
