Method of producing paper sack involves forming intermediate layer and paper layer with perforations or breaks

The present invention relates to a method for producing a multi-layer, partially air-permeable paper sack, which has at least between two paper layers an intermediate layer consisting in particular of a plastic film or coating, at least the intermediate layer and one paper layer connected or connectable therewith having a plurality is formed by perforations or breakthroughs. The invention further relates to a paper sack which has at least between two paper layers an intermediate layer consisting in particular of a plastic film or coating, the intermediate layer and a paper layer connected or connectable therewith being formed with a plurality of perforations or openings.

From EP-A 0 867 379 and DE-A 25 27 453 processes for the production of perforated sacks and multi-layer sacks or bags are known, with perforation taking place through all the layers of a sack. Such sacks are used, for example, for chunky foodstuffs in order to keep them fresh for a longer period of time, while fine-grained or powdery materials cannot be picked up with such sacks.

A method for producing a multi-layer, partially air-permeable paper sack and a paper sack of the type mentioned at the outset are, for example, WO 98/57861 or WO 98/57861

See U.S. Patent 5,988,881. In this known paper sack, this has on its broad sides a plurality of perforations or openings in tape or strip form at least in an intermediate layer consisting of a plastic film, with areas without perforations or areas between the strip-like arrangement of the plurality of perforations or openings . Breakthroughs are formed. In order to achieve a desired air permeability, these holes or openings have a correspondingly large diameter due to the fact that openings are each provided in a strip or band-like manner, with large portions of the surface of the sack being formed without openings Holes or perforations having a diameter reduce the strength of the manufactured

Paper sack is reduced accordingly. This is particularly disadvantageous when such paper sacks are used to hold goods, some of which are heavy, such as, for example, in the cement industry.

The present invention aims, starting from a method for the production of a multi-layer, partially air-permeable paper sack and a paper sack of the type mentioned to enable a further development to the effect that in such a multi-layer paper sack with a between two paper layers arranged between two paper layers, in particular made of plastic film or . -coating existing intermediate layer an improvement of the air permeability with a simultaneous increase of the water vapor density can be achieved.

To achieve these objects, a method of the type mentioned at the outset is essentially characterized in that the perforations are introduced or formed, starting from the paper layer connected or connectable to the intermediate layer, through the intermediate layers in the direction of the second paper layer. The fact that according to the invention

Openings starting from the paper layer connected to the intermediate layer are subsequently introduced or formed through the intermediate layer, it is ensured in particular that for the holes in the, for example, made of a plastic film or -coating existing intermediate layer, which is crucial for the definition of a desired air permeability while maintaining the water vapor permeability, a precisely defined size of the openings can be achieved in order to be able to adapt the properties of the paper sack produced subsequently to the conditions of use. To cover the perforations or Paper layer provided with openings and the intermediate layer connected to it, an additional paper layer without openings can be provided on both sides of the perforated composite.

AT41I3 273B

The connection between the intermediate layer, in particular made of plastic, and the

The paper layer can be essentially full-surface and / or the intermediate layer can be applied to the paper layer as a coating. Alternatively, the intermediate layer and the

For example, paper ply can be produced separately and connected to one another via areal or at least point-wise adhesion.

According to a particularly preferred embodiment, it is proposed in this context that the second paper layer be brought into contact with the perforated intermediate layer under pressure, especially after the paper sack has been filled, which ensures that when the perforations are made, when the first paper layer and the intermediate layer has a bead or bead, particularly in the area of ​​the intermediate layer. Edge at the edge of the respective opening is again smoothed by the pressing or application of pressure by means of the second paper layer, which is provided in particular after the filling of the paper sack, so that the desired, precisely defined size of the opening can be achieved. As a result of the application of pressure or pressing by the second paper layer, which is additionally proposed according to the invention, the edge or edge that forms during the production of the perforation is removed. Bead in turn compressed, which leads to a defined reduction in the clear cross-section of the individual openings, so that overall a substantial increase or improvement in the water vapor density can be achieved, with sufficient air permeability being ensured during the filling process even with small, clear cross-sections of the openings.

It should be noted here that the preferably proposed application of pressure or pressing results in a direct connection between the second paper layer and the intermediate one

Intermediate layer does not take place, but that the pressing results in the desired shape for the openings or holes. The proposed application of pressure to the second paper layer in contact with the perforated intermediate layer can take place by a corresponding pressing or pressure application of the finished and in particular filled paper sack or it can only be done by the weight of stacked or stacked paper bags. stacked, filled paper sacks, the desired compression and thus the change in cross-section can be achieved.

While it is essential according to the invention that the perforations are made first through the paper layer connected to the intermediate layer and subsequently through the intermediate layer connected to it, the paper layer likewise provided with perforations or perforations can either be on the outside, depending on the intended use or be provided on the inside facing the material to be picked up. For a first filtering through the inner paper layer, it is proposed according to a preferred embodiment that the outer paper layer and the intermediate layer connected to it are perforated.

To form the openings or perforations, in particular in a method for producing a particularly multi-layer, partially air-permeable paper sack, which preferably has an intermediate layer between two paper layers, in particular consisting of a plastic film or coating, at least the intermediate layer and / or one connected to it or connectable paper layer with a plurality of perforations or Breakthroughs is formed, it is proposed that the perforations are formed by a needle roller or the like. Which is driven to rotate in accordance with the feed movement of the paper layer and / or the intermediate layer connected to it. When using needle rollers, it is known to store them freely, for example, so that a dragging movement of a web or web to be perforated of a material to be perforated, the needle roller is immediately subjected to a rotary movement. A disadvantage of such an automatic entrainment of the needle roller, however, is that the drive energy required for a rotational movement of the needle roller is caused by the one to be perforated

Web itself must be applied, so that a tear or an irregular formation

ÄT413 273B fertilize the openings or perforations to be produced. It is therefore proposed according to the invention that the needle roller is driven to rotate, the peripheral speed of the needle roller being dependent on the feed movement or speed of the paper layer to be perforated and the intermediate layer connected therewith is coordinated, so that no impairment of the shape of the perforations to be produced by the needle roller is to be feared by the entrainment of the perforating elements. With such a drive of the needle roller, taking into account the feed movement or speed of the material web to be perforated, in particular exact openings or Produce holes with correspondingly small dimensions, whereby it is preferably proposed that the conveying speed of the layer to be perforated and the peripheral speed of the rotating needle roller are chosen to be the same.

For a simple control of the drive movement of the needle roller, it is proposed according to a further preferred embodiment that the feed speed of the paper layer and / or the intermediate layer connected to it is scanned and a control of the rotary drive of the needle roller is input.

As already indicated above, the method according to the invention aims in particular at improving the air permeability and, in the case of a subsequent pressing, at increasing or optimizing the water vapor density, so that especially small dimensions of the openings or holes are favorable. It is therefore proposed, according to a further preferred embodiment, that the size, in particular the diameter, of the preferably essentially circular openings be selected between 0.05 and 1.5 mm, in particular 0.1 to 0.8 mm. In addition to the desired adjustment to the air permeability or The water vapor density is ensured by such small holes that even with a high perforation density a minimal loss of strength of the resulting paper sack due to the negligible impairment or damage to the paper or cellulose fibers can be achieved, so that correspondingly heavy goods can be picked up in this way.

In order to adapt the paper sack that can be produced with the method according to the invention to different purposes, it is proposed according to a further preferred embodiment that the size or shape of the perforations be determined by the selection of the puncture depth of essentially different cross-sectional shapes, especially conical needles of the Needle roller is selected. A suitably adapted or modified design and, in particular, the size or shape of the openings or holes can thus be achieved simply by choosing the puncture depth without costly retooling or conversion work.

To achieve the most uniform possible air permeability over large areas of the paper sack to be produced while maintaining the desired water vapor density and to avoid excessive loss of strength of the resulting paper sack, it is proposed according to a further preferred embodiment that a hole density of at least 100 perforations / dm², in particular at least 1000 perforations / dm², is chosen. In particular when using holes having correspondingly small dimensions, the desired air permeability can be made possible with the high hole density proposed according to the invention, while achieving a correspondingly high water vapor density. In order, for example, to enable the air to be expelled quickly and reliably when the material to be accommodated in the paper sack is introduced, it is proposed according to a further preferred embodiment that the perforations are designed to be distributed essentially uniformly over at least one broad side of the paper sack, the formation of perforations over predominant areas of the paper sack to be produced also, for example in the case of subsequent stacking, facilitate the handling of the filled paper sack.

ÄT 413 273 B

To solve the problems set out above, there is also a paper sack which has an intermediate layer between at least two paper layers, in particular consisting of a plastic film or coating, the intermediate layer and an associated or connectable paper layer with a plurality of perforations or openings is formed, essentially characterized in that the perforations proceeding from the connected or connected to the intermediate layer. connectable paper layer are introduced or formed through the intermediate layer in the direction of the second paper layer. In this way, a sack with the desired properties, in particular with regard to air permeability and water vapor density, can be achieved.

According to a preferred embodiment it is proposed that the paper layer and the intermediate layer connected or connectable therewith have a hole density of at least 100 perforations / dm², in particular at least 1000 perforations / dm², exhibit. With such a high hole density, with correspondingly good air permeability and increased

Achieve a suitably easy-to-handle paper sack adapted to the intended use. According to a particularly preferred embodiment, it is proposed that the perforations are designed to be distributed essentially uniformly over at least one broad side of the paper sack.

In order to avoid an excessive loss of strength in the paper sack to be produced, it is also preferably proposed that the size, in particular the diameter, of the preferably essentially circular openings be selected between 0.05 and 1.5 mm, in particular 0.1 to 0.8 mm .

According to a preferred embodiment it is proposed that the outer paper layer and the intermediate layer connected to it are perforated. It is particularly preferably provided that the size or shape of the perforations is selected by selecting the puncture depth of needles of the needle roller which have essentially different cross-sectional shapes, in particular conical needles.

The invention is explained in more detail below with reference to the exemplary embodiments shown schematically in the accompanying drawing. In this show:

1 shows a schematic representation of a device for carrying out the method according to the invention for producing a paper sack according to the invention:

2 shows, in an enlarged illustration, a partial section through a paper sack according to the invention; FIG. 3, in a representation similar to FIG. 2, likewise a partial section through a modified embodiment of a paper sack according to the invention; FIG. and

4 shows, in a view similar to FIGS. 2 and 3, a detailed view for carrying out the method according to the invention for producing holes or perforations with an adjustable hole size.

In Fig. 1, 1 denotes a roll from which a material web, schematically designated 2, is unrolled, which, as can be clearly seen from FIG an intermediate layer 4 consisting of a plastic film or coating. The material web 2 is fed via a feed roller or roller 5 is fed to a needle roller 6 for the formation of a plurality of openings or perforations to be produced essentially over the width of the material web 2, a pressure or counter roller in the area of ​​the needle roller 6 being indicated by 7. The perforated or Material web 2 provided with perforations is subsequently brought together in the area of ​​a subsequent station with a material web consisting of only one paper layer 8 via a roller 11, which is supported by a feed roller 9, in order to form a multi-layer structure, which is subsequently used to produce a multi-layer paper sack is removed.

AT413 273B

In particular, after the paper sack to be produced subsequently has been filled, pressure is applied or pressed either by a separate device or, in the case of a stack, under the dead weight of the filled sacks, so that the protruding edge or bead 14 formed when the perforations 13 are formed the ends 15, the

The stitching direction is indicated in FIG. 2 by the arrow 16, and the application of pressure to the paper web or sheet 8 results in a depression or pressing of the edges or ends 15 of the perforations 13, as indicated by 15 in FIG. 2 'is indicated. The in Fig. 2 at a distance from the web 2 forming layers 3 and 4 shown paper web 8 is pressed by the application of pressure in contact with the intermediate layer 4, so that the rising edges 15, which result from the penetration of the needles of the needle roller 6, corresponding to the reduction of the clear cross-section of the openings 13 are pressed.

By setting a desired pressing force or pressing force, in addition to the for

Adjustment of the size of the holes 13 by using appropriately dimensioned needles of the needle roller 6 by pressing the edges 15 as desired to achieve a corresponding air permeability while maintaining a high water vapor density and adjustment of the clear cross section of the openings 13.

In Fig. 2, the stitch direction 16 is chosen so that after a paper sack has been completed by joining two multi-layer material webs, which consist altogether of the paper layers 3 and 8 and the intermediate layer 4, the perforated paper layer 3 on the inside of the paper sack to be produced Paper sack lies.

It is further proposed that to achieve the desired air permeability and while minimizing the influence on the strength of the paper sack to be produced, small holes or perforations 13 with a diameter of less than 1.5 mm and in particular less than 0.8 mm are formed. In order to achieve such small openings with a correspondingly precise shape, it is further proposed, as shown in FIG. 1 It is indicated that the feed speed or movement of the material web 2, which consists of a paper layer 3 and the intermediate layer 4 connected to it, is determined via a sensor 17, the sensor signal being fed to a schematically indicated controller 18 which in turn has a motor 19 for the needle roller 6 controls or regulates. By coordinating the drive or the rotational movement of the needle roller 6 on the feed speed of the multi-layer material web 2 is prevented that by a relative movement between the surface of the needle roller 6 and the material web to be perforated 2 to be produced, in particular holes with a small diameter or small dimensions are torn or badly have a defined outer shape.

In Fig. 3 a modified embodiment is shown, either by reversing the arrangement of the needle roller 6 and the feed direction of the paper layer 8 or by reversing the use of the multi-layer sandwich structure consisting of the paper layer 3, the intermediate layer 4 connected to it and the separate paper layer 8 subsequently a paper sack is obtained in which the outer paper layer 3 and the one connected to it

Intermediate layer 4 are perforated or provided with openings 13, while the paper layer 8 facing the interior is designed without openings or holes in order to achieve a first filtering. Also in the illustration according to FIG. 3 it is indicated that a corresponding pressing or application of pressure when bringing together the multilayer sandwich structure or if necessary, after the production and in particular the filling of the paper sack by pressing the entire paper sack, the protruding ends 15 are again pressed while reducing the free passage cross-section of the openings 13.

In the illustration according to FIG. 4, there is the possibility of setting or selecting the size of the openings 13 to be produced using, in particular, a conical one

Needles 20 having the outer circumference in the needle roller, not shown in detail, are indicated

AT 413 273 Β tet, whereby by appropriate selection of the penetration or puncture depth of the needle 20 in the puncture direction again denoted by 16, the paper layer 3 and in particular the intermediate layer 4 connected to it can be formed with appropriately dimensioned openings 13. In adaptation to the desired application and / or the one used

Composition of the paper layer 3 and the intermediate layer 4 can be determined by the choice of

Penetration depth and thus the choice of the size of the holes 13 to be produced that can be achieved thereby achieve an adaptation to the desired air permeability and the water vapor density to be maintained while at the same time minimizing a loss of strength in a paper sack to be produced subsequently. Particularly when forming openings or openings with small dimensions. Holes 13, damage to the fibers of the paper layer 3 is largely avoided, so that the desired strength, especially for holding heavy goods, can be easily maintained.

For special purposes, one can on both sides of the structure consisting of the paper layer 3 and the intermediate layer 4 with the openings or holes 13

Paper layer 8 can be provided so that a total of three paper layers are provided, of which the paper layer 3 connected to the intermediate layer 4 is correspondingly perforated.