EP2836358A2

EP2836358A2 - Perforated film

Info

Publication number: EP2836358A2
Application number: EP13728927.8A
Authority: EP
Inventors: Thomas Gahleitner; Harald Katzinger
Original assignee: Teufelberger GmbH
Current assignee: Teufelberger GmbH
Priority date: 2012-04-12
Filing date: 2013-04-08
Publication date: 2015-02-18
Also published as: WO2013152375A3; WO2013152375A2

Abstract

The invention relates to a method for producing a perforated film (1), wherein a film body (2) is produced from a plastic melt, in which film body (2) slits (6) and/or thin points are made, or which film body (2) is produced at least approximately in a lattice-shaped manner or is provided with a lattice-shaped structure, and subsequently the film body (2) is stretched, in particular biaxially in a longitudinal direction and in a transverse direction, to produce a structure with longitudinal slats (3) which are connected to one another by transverse slats (4), with the formation of apertures (5), wherein the proportion of the material of the plastic is distributed non-uniformly to the longitudinal direction and the transverse direction of the film body (2). Furthermore, the invention relates to a corresponding perforated film.

Description

perforated foil

The invention relates to a method for producing a perforated film wherein a film body is produced from a plastic melt, are introduced into the thin areas and / or slots or at least approximately produced lattice-shaped and then the film body to a structure with longitudinal bars, which by cross bars with each other are connected, is stretched, in particular biaxially in a longitudinal direction and in a transverse direction, and a perforated foil with a plastic film body of longitudinal bars and transverse bars is formed, wherein the longitudinal bars are interconnected by the transverse bars, wherein between the longitudinal bars and the transverse bars Breakthroughs are formed.

By the term at least approximately lattice-like is meant a set of lattice cells which are defined by a set of lattice points interconnected by a set of lattice lines. At least approximately indicates that the grid cells, due to the manufacturing process, do not necessarily have to be all the same size and shape. The latticed structure may be symmetrical or asymmetrical. The term "thin spot" is understood to mean a region of the film body which has a reduced layer thickness with respect to a maximum layer thickness of the perforated film, in particular a layer thickness reduced by at least 50% of the maximum layer thickness of the perforated film To produce hole foils by the introduction of slots in a film and then stretching the film.

Thus, for example, DE 19 19 876 B1 describes a method in which a thermoplastic film is provided with slots which lie in substantially parallel rows, which are staggered with respect to one another, and this slit film is then heated until softening. The film is stretched prior to slitting the slits to produce a shrinkage stress substantially transverse to the slits. Further, the heating is carried out after cutting the slits to a degree of softening in which the Plastic film shrinks in the area of the slots to form openings automatically thickened webs and knots.

JP 10-072837 A describes a method in which a plastic melt is introduced between embossing rollers, wherein the embossing rollers produce a plastic layer which has raised and recessed areas. On the recessed areas a color of a metal powder is printed, so that the absorption of heat radiation is increased in these areas. By subsequent biaxial stretching under heat, the breakthroughs are finally produced in the plastic layer.

DE 27 41 591 A1 describes a method for the continuous production of three-dimensional lattices from a sheet of thermoplastic material, after which rows of parallel cuts are made, each row being separated from the adjacent row by an uncut portion, and then the foil is stretched at a draw ratio of 1.1 to 3 in the transverse direction.

From DE 22 32 758 A a method for slitting thermoplastic films is known, after which the film is mechanically stressed and pressed with the tip of a heated blade against a support member while the film is stretched, the upper part of the Blade is heated to a temperature which is higher than the softening temperature of the film, and the tip is removed after penetrating the film. The blades may be arranged on a slot roll. The film is stretched longitudinally and, alternatively, may additionally be stretched in a different direction. It is thus obtained an apertured film.

GB 1,083,847 A describes a process for producing a thermoplastic film of plastic having an open structure, after which the film is perforated at an elevated temperature and then biaxially stretched.

The present invention has for its object to provide a method for producing a perforated film, after which the perforated film can be easily adapted to a wide variety of applications. This object of the invention is achieved by the aforementioned method and by the above-mentioned perforated foil, wherein provided by the method that the proportion of the material of the plastic is unevenly divided on the longitudinal bars and the cross bars and in the perforated film, the material content of the plastic on the film body is unevenly divided on the longitudinal bars and the cross bars.

The advantage here is that the elasticity of the perforated film in this direction can be reduced by the higher proportion of material in one direction, this reduction also affects the elasticity in the direction orthogonal to the first direction, so that a total of a perforated film is obtained with reduced elasticity. The perforated film also has in the direction of the higher proportion of material also improved mechanical strength, in particular by train on. By adjusting the higher proportion of material in one direction, the force flow direction in the perforated film can be positively influenced so that thinner hole foils can be made available overall with the same load-bearing capacity as with prior art perforated foils, or with the same film thickness the perforated foil higher loads can be exposed. This, in turn, has an advantageous effect on the winding of the perforated foil, since in comparison with products from the prior art, winding cores with more linear perforated foil can be provided with a constant diameter, in particular if the perforated foil is wound in an offset manner.

Preferably, the plastic melt is processed to divide the plastic on the longitudinal bars and the cross bars with a profiled molding tool before the stretching is performed. So it is the profiling before drawing. This has the advantage that in the case of extrusion of the plastic melt, the extruder die can remain unchanged. Moreover, this has the advantage that when changing the geometry of the perforated film, for example a change in the cross sections and / or size of the apertures, only the forming roll (s) must be replaced (must), the rest of the plant for producing the perforated film remain unchanged can. The plastic melt can be distributed such that a higher proportion of the plastic melt is present in a longitudinal direction of the film body than in a transverse direction of the film body, in other words the longitudinal bars have a higher proportion of material to the plastic than the transverse bars. It is thus achieved that one higher tensile force can be applied to the film in the longitudinal direction, whereby the settlement of the winding core can be done faster. In addition, it is possible that due to the higher load capacity in the longitudinal direction of the perforated foil tighter fitting can be used on a product. This is particularly advantageous in the case of temperature loading of the perforated foil during use, since in this case perforated foils stretch, and thus possibly only loosely against the product, or is it advantageous in all those applications where the perforated foil should remain as taut as possible even if it is exposed to higher temperatures (higher than 20 ° C). In addition, it is generally their resilience in the longitudinal direction can be improved.

It can further be provided that at least partially thickenings are formed around the openings. It can thus be increased the degree of stretching, since there is less risk of tearing of the film in the region of the openings during stretching. However, it can also be used to increase the drawing speed, as a result of which the mechanical properties of the perforated film can be influenced.

According to another embodiment of the method, it is provided that the transverse stretching of the film body is carried out after the longitudinal stretching. Thus, the speed of the longitudinal stretching can be increased, whereby improved mechanical properties of the perforated foil can be achieved.

To improve the stretchability of the perforated film can also be provided that the film body is heated during the hiding. By tempering the formability of the plastic is improved so that it can be stretched faster and / or to a higher degree.

It is also possible that the film body is relaxed or relaxed after hiding. It is thus achieved a stabilization of the structure produced and a controlled adjustment of the elongation of the perforated film. In addition, a reduction of the shrinkage of the film body is achieved, whereby the shrinkage stress occurring at the winding core, on which the perforated film is wound up after processing, can be reduced. It is thus possible to make the winding cores thin-walled, since the pressure acting on them is lower in comparison to known stretched hole foils. It is thus a reduction of Wall thickness of the winding core and thus a corresponding cost and weight savings and a reduction of the waste feasible. In addition, the unwinding of the perforated film from the winding core is simplified and the number of running meters per winding core can be increased (in comparison to known from the prior art products). Due to the adjustability of the elongation, application-specific product properties can also be set in a targeted manner.

It is also possible for the longitudinal side edges of the film body to be produced with an edge reinforcement, in particular a thickening, in order thereby to increase the elongation of the perforated film, i. the strain in the direction orthogonal to the longitudinal extent

(= Production direction) of the perforated film to reduce. This is particularly advantageous in view of the automatic processing of the perforated film by the user since it causes fewer disturbances during this processing, because the fully automatic feeding of the perforated foil can be effected more uniformly by increasing the stability.

For the same reasons, it is also possible that the perforated foil may alternatively or in addition to the edge reinforcement have a center reinforcement, wherein center reinforcement means a reinforcement in the region between the two longitudinal side edges. The center reinforcement can be done by the thickening and / or broadening of at least one, formed between the two longitudinal side edges longitudinal bar, wherein more than one

Longitudinal bar, e.g. two, three, four, etc. can be strengthened. With more than one reinforced longitudinal bar, at least one non-reinforced longitudinal bar can be arranged between the reinforced longitudinal bars. The arrangement of the or the reinforced longitudinal bar or longitudinal bars can be effected symmetrically or asymmetrically with respect to the longitudinal center axis of the perforated foil.

Reinforcement in one or more areas of the perforated foil can also be done by increasing the number of longitudinal bars in that area (s). That is, the distance between the longitudinal bars to each other is reduced, whereby it comes in this / this area (s) to a material accumulation, associated with a concomitant increase in strength. According to a further embodiment variant of the method, it is provided that at least one of the surfaces of the film body is surface-treated, in particular roughened. It can thus be influenced the sliding behavior of the perforated film. This is particularly advantageous in applications of the perforated film in which it is automatically withdrawn from the winding core into a processing device, since this prevents the perforated film from being pushed in the feed, so that the feed can be improved in the application. In addition, it can also be used to improve the static friction of the perforated film on a product. Depending on the application, the lubricity of the perforated foil can be reduced or even increased. In general, roughening can be used to achieve a functional surface preparation.

According to another embodiment of the perforated film, it is possible for the transverse bars to be arranged centrally on the longitudinal bars with respect to a film thickness. This is particularly advantageous if the film is used in connection with flexible or yielding goods or products, as this can better press the longitudinal bars in the goods or products and thus a closer concern of the perforated film can be reached, among other things in view of the above-mentioned temperature load is advantageous. By this construction, a three-dimensional shaping of the perforated foil is made possible in the loaded state.

But it is also possible that the cross bars are arranged off-center - with respect to a film thickness - on the longitudinal bars, whereby a flat contact surface or compared to the central arrangement a slight curl of the perforated film is achieved in their use. In particular, this is advantageous if the perforated film is used in connection with rigid goods. In addition, it can also be achieved with respect to the power flow in the transverse direction an improvement.

The perforated film may have thick areas between the openings. It is thus a targeted adjustment of the power flow in the hole film in their use achievable, whereby the perforated film can be applied under higher voltage and thus holds the products surrounded by the perforated film tighter. It is also advantageous if a widened edge without breakthroughs is formed as a welded edge on the perforated film along the longitudinal side edges, since it is thus possible to provide very large width of the perforated foil without significantly greater effort in the production and the machine equipment.

To improve the tear strength of the perforated film, the longitudinal bars bordering on the longitudinal side edges of the film body can have a larger cross section than the longitudinal bars arranged centrally in the film body. It is thus also the stretching can be improved by the film can be stretched within a shorter time, as thus an improved clamping or holding the side edges during hiding can be achieved.

Due to the diverse adaptability of the production process, it is possible to provide perforated films in which the number of apertures in the film body is selected from a range with a lower limit of 100 breakthroughs / m ² and an upper limit of 10,000 breakthroughs / m ² and / or in which the openings have a size - viewed in plan view - which is selected from a range with a lower limit of 10 mm ² and an upper limit of 1000 cm ² . The perforated film can therefore be used in a wide variety of applications.

For a better understanding of the invention, this will be explained in more detail with reference to the following figures.

Each shows in a schematically simplified representation:

1 shows a detail of a first embodiment of a perforated film in plan view.

2 shows a detail of a second embodiment of a perforated foil in plan view;

3 shows a detail of a third embodiment of a perforated foil in plan view; 4 shows various patterns for producing a perforated foil in plan view; 5 shows a variant of a perforated foil in cross section;

Fig. 6 shows a first embodiment of the material distribution of the plastic melt for

Production of the perforated film;

FIG. 7 shows an embodiment variant of a breakthrough of the perforated foil in plan view; FIG.

8 shows a device for producing the perforated film;

9 shows a stretching section for widthwise stretching of the perforated foil in plan view;

10 shows a variant of the perforated foil with different material distribution in cross section;

11 shows the central connection of the transverse rods with the longitudinal bars;

FIG. 12 shows an off-center connection of the transverse rods with the longitudinal rods; FIG.

Fig. 13 is a schematic representation of a section of a perforated foil for explaining the determination of the proportions in the longitudinal and the transverse rods.

By way of introduction, it should be noted that in the differently described embodiments, the same parts are provided with the same reference numerals or the same component names, wherein the disclosures contained in the entire description can be mutatis mutandis to the same parts with the same reference numerals or component names. Also, the position information selected in the description, such as top, bottom, side, etc. related to the immediately described and illustrated figure and are to be transferred to a new position analogous to the new situation. 1 to 3 show different sections of perforated films 1 in plan view. It should be noted that the illustrated embodiments are not limitative of the scope of protection as set forth in the claims. The perforated foil 1 has a foil body 2 made of a plastic, ie a polymer.

This film body 2 may have a film thickness selected from a range of 0.01 mm to 5 mm, in particular from a range of 0.01 mm to 3 mm, wherein, as will be explained below, the film body 2 over its entire surface does not have to have an at least approximately constant film thickness.

The film body 2 is formed of longitudinal bars 3 and 4 of transverse bars, wherein the transverse bars 4 connect the longitudinal bars 3 together.

The cross bars 4 extend in these embodiments, at least approximately orthogonal to the longitudinal bars 3. However, it is also possible embodiments in which the

Transverse rods 4 extend at a different angle of 90 ⁰ to the longitudinal rods. 3 This angle may in particular be selected from a range of 25 ⁰ to 85 °, preferably from a range of 30 ⁰ to 75 °. For example, this angle may be at least approximately or at least approximately 45 ⁰ 60 ^0th

The plastic or the polymer is a thermoplastically processable material, in particular a thermoplastic or a thermoplastic elastomer, and may for example be selected from a group comprising PE (HDPE, UMHDPE, LDPE, LLDPE, MDPE), PP (isotactic, atactic), PS , PET, PA and mixtures and compounds thereof, such as PE / PP. In general, however, other extendible polymers can be used. Also

Biopolymers, ie non-petroleum-based, synthetic polymers, ie polymers derived from natural raw materials, such as from corn or starch, can be used, provided that they are stretchable. Recyclates (of the polymers) can also be used. Of course, the material for producing the perforated film 1, the usual additives to achieve certain properties, for example, the UV resistance, or auxiliary materials for processing. Reference is made to the relevant prior art. Between the longitudinal bars 3 and the transverse bars 4 breakthroughs 5, so the holes of the perforated foil 1, formed, that is, the openings are surrounded in the plane of the film body 2 by the longitudinal bars 3 and the transverse bars 4.

The openings 5 may, for example, have an oval or elliptical (FIG. 1), a diamond-shaped or diamond-shaped (FIG. 2) or a square (FIG. 3) cross-section - viewed in plan view. However, other cross-sectional shapes are possible, such as e.g. triangular, rectangular, round, trapezoidal, or generally in the form of rotationally symmetric quadrilaterals, hexagonal, etc. have.

It must be pointed out in this connection that the explanations concerning the cross-sectional shapes of the apertures 5 represent the idealized state, since these apertures 5 result from the stretching of the film body 2, as will be explained below, and therefore these idealized cross-sectional shapes in reality are formed predominantly more or less deformed, due to the stretching conditions, such as the stretching speed.

Preferably, the apertures 5 are arranged in rows in the longitudinal direction of the perforated sheet 1. There is the possibility that the rows are untransposed or offset from one another, as can be seen, for example, from FIGS. 1 and 2 or FIG. 3. For example, the rows of openings 5 may be offset by half the distance between the centers of the openings 5. However, there is also the possibility of another geometry. For example, every third or every fourth row can be offset in the longitudinal direction of the perforated foil 1 with respect to the other rows. Likewise, each row of apertures 5 may be staggered. The size of the offset may also differ from the example value of 50%. For example, the value of the offset may be selected from a range of 20% to 80%, based on the respective neighbor row. In addition, the value of the offset of the rows in the perforated film may also vary, so that, for example, rows of 50% and rows of 30% offset may be present in a perforated sheet 1. The perforated foil 1 can have between 100 breakthroughs / m ² and 10,000 breakthroughs / m ² , wherein the number depends on the use of the perforated foil 1. For example, the perforated foil 1 can have between 100 breakthroughs / m ² and 500 breakthroughs / m ² or between 600 breakthroughs / m ² and 2500 breakthroughs / m ² or between 3,000 breakthroughs / m ² and 7,500 breakthroughs / m ² or between 8,000 breakthroughs / m ² and 10,000 breakthroughs / m ² .

Further, the apertures 5 may have a size - viewed in plan view - which is selected from a range with a lower limit of 10 mm ² and an upper limit of 1000 cm ² . Also with respect to the size of the openings 5, this depends on the use of the perforated sheet 1. For example, the size of the apertures 5 between 10 mm ² and 199 mm ² or between 200 mm ² and 2000 mm ² or between 2001 mm ² and 100000 mm ² be. The number or size of the openings 5 depends on the required properties, such as the permeability or the mechanical properties. Possible fields of application of the perforated film 1 are, for example, the holding together or retention of piece goods or goods in general, in which case apertures 5 with a smaller cross-sectional area can be used for small piece goods and apertures 5 with a larger cross-sectional area for coarse general cargo, in palletizing of goods, as a protective film, eg in orchards against birds, as a windscreen, as a hail protection film (even in these last-mentioned application of the perforated film 1, the cross-sectional area of the apertures is chosen smaller, but the number of apertures 5 per m ² perforated film 1 can be higher) , as (ski) piste barrier, as a barrier of construction sites, as a rockfall protection film, as sound insulation film, as a film for applying turf, as a reinforcing film, as a sub-base in geotextiles, etc. Generally, the perforated film 1 for industrial applications or in the production of food and Feed presented be seen.

To produce the apertures 5, these are not punched out of the film body 2 in the final geometry or the apertures 5 are not cut out of the film body 2 in the finished geometry. Instead, the film is slit, ie provided with slots 6, or partially provided with thin areas and then stretched. The final or finished geometry designates the geometry that the breakthroughs 5 in the finished However, a punching tool can also be used for the insertion of the slots 6 or of the thin bodies.

FIG. 4 shows, by way of example, some patterns for slots 6 or thin spots or weakenings in the film body 2. The slots 6 may be straight, arcuate or cross-shaped or made as combinations of these patterns. You can fishbone-like, zigzag-shaped, in the direction of the longitudinal extent or transversely to the longitudinal extent of the film body 2, etc. are arranged. It is also possible that the course of the slots 6, which are arranged in rows, for example, of arcuate slots 6, in every second row or generally every x-th row is reversed, as can be seen from Fig. 4.

The cutting patterns shown in FIG. 4 are not restrictive but rather the cutting patterns are based on the desired geometry of the apertures 5. For example, by means of slots extending in the longitudinal direction of the film body 2 (shown at the top in FIG. 1 openings shown when stretching the film body 2, wherein the ovality depends on the degrees of stretching in the longitudinal and in the transverse direction. At least some or all of the slots 6 and thin spots can be rotated, for example, formed in the film body 2 to the illustration in Fig. 4 through 90 ⁰ to a different angle or.

The introduction of the slots 6 can be done for example with a cutting roller, but preferably the slots 6 are cut with a laser. The slots 6 can be produced continuously through the film body 2, but on the other hand it is also possible for the slots 6 to be designed only as depressions, which subsequently act as a predetermined breaking point during stretching.

Instead of slitting the polymer melt in or through a mold, for example, in a roller mill with at least one embossing roll, are performed in which at the locations of the openings material tapers are generated, which stretch as a predetermined breaking point when Ver tear to form the openings 5. It is envisaged that the proportion of material of the plastic or of the polymer on the film body 2 is unevenly divided in the longitudinal direction and in the transverse direction of the perforated film 1, ie unevenly on the longitudinal bars 3 and the transverse bars 4, based on the total material content of the perforated film 1. Dabei it is possible to provide the cross bars 4 with a higher proportion of material. Preferably, however, the longitudinal bars 3 have a higher proportion of material on the plastic than the transverse bars 4. The material in nodes 7 formed by the longitudinal bars 3 and the transverse bars 4 (indicated as a dashed circle in FIG. 1, their shape being based on the perforation pattern of FIG Perforated film 1) is divided on the longitudinal bars 3 and the cross bars 4 as explained below.

For the purposes of the invention, the proportion of material in the longitudinal direction is understood as meaning that proportion of the total proportion of the polymer or the plastic present in the longitudinal bars 3. Accordingly, the proportion of material in the transverse direction denotes that proportion of the total proportion of the polymer or the plastic which is present in the transverse rods 4.

To determine the weight distribution in the longitudinal and transverse directions, reference is made to the comments below. Illustratively, it should be noted that the longitudinal direction refers to the direction in which the perforated foil 1 has the greatest extent. Usually, this is also the production direction of the perforated film 1. For the special case that the perforated film is square, so the longitudinal is indistinguishable from the orthogonal transverse direction means the different material distribution on the longitudinal bars 3 and the cross bars 4, that proportion the material is larger in one of the two directions than in the other.

Due to the uneven distribution of the plastic in the longitudinal direction and the transverse direction, the longitudinal strength and the transverse strength of the perforated sheet 1 can be influenced. The division of the material in the two directions, in particular in the ratio longitudinal bars 3: transverse bars 4, can in particular be selected from a range of 40% by weight: 60% by weight to 60% by weight: 40% by weight, excluding the ratio 50% by weight: 50% by weight. For example, the proportion may be 80% by weight: 20% by weight. However, the distribution can also be selected in a ratio of from 70% by weight: 30% by weight to 90% by weight: 10% by weight. It can thus hole films 1 are produced, which have a fineness of the longitudinal bars 3 and the cross bars 4 of up to 7 g / in the longitudinal and or transverse direction. The tenacity is calculated as follows:

1 denier [den] = g / m * 9,000

1 Newton [N] = 101.97 grams-fource [gf]

or 0.981 N = 100 grams-force [gf]

that is, F / den = g / den

Example:

Linear tensile strength: 2800 N

2800 N * 101.97 = 285,516 gf

Product weight / m: 9.52 g / m

9.52 g / m * 9,000 = 85714 den

Tenacity = 285.516gf / 85.714den = 3.33g / den

The elongation at break can be up to 30%, based on the initial length.

5 and 6 show along transverse bars 4 extending cross sections in the direction of the longitudinal extent by embodiments of the perforated sheet 1 (the longitudinal extent of the perforated sheet 1 extends in the direction perpendicular to the paper plane) with different material distribution, the proportion of material in the longitudinal bars 3 is higher In this case, each longitudinal bar 3 has a higher proportion of material than the individual transverse bars. In principle, however, it is possible that only the sum of the material portions of the longitudinal bars 3 is higher than the sum of the material proportions of the transverse bars 4. Thus, embodiments are possible in which individual longitudinal bars 3, in particular the longitudinal bars 3 formed centrally in the foil body 2, have no higher proportion of material as the individual cross bars, as long as the described condition for the sum proportion is fulfilled. With the Fig. 5 and 6 is to be clarified that the geometric arrangement or design of the longitudinal bars 3 is variably adaptable to the particular application. In the case of the variant according to FIG. 5, the longitudinal bars 3 all have the same cross-section both in terms of shape and in terms of size of the area. In addition, they are distributed at equal intervals 8 to each other over a width 9 of the perforated sheet 1.

In the Au sführungs variant of Fig. 6, however, distances 10, 11 and 12 are formed between the longitudinal bars 3, each having a different value. In particular, adjacent to the longitudinal side edges of the perforated foil 1 extending in each case three longitudinal bars 3 (it may also be a different number of longitudinal bars 3 are arranged in the edge region, for example, two, four, five, six, etc.) in the smaller distance 11 (with respect formed on the further distances 10, 12). Thereafter follows the longitudinal bar 3 with the largest distance 10. In the middle of the longitudinal bars 3 are again with the smaller distance 12, which is greater than the distance 11, arranged to each other. It is thus a gain of the edge area achieved by the higher relative number of longitudinal bars, which can be achieved on the one hand advantages in terms of stretching but also with regard to the subsequent use of the perforated sheet 1.

It is therefore possible within the scope of the invention, for example, a plurality of "fine" longitudinal bars 3 or in comparison to provide a few but thicker longitudinal bars 3.

However, it should be expressly pointed out that the representation in FIG. 6 has only exemplary character. Other variants with different distances 10 to 12 and / or different sizes of the cross-sectional areas of the longitudinal bars 3 are also possible.

Although in FIGS. 5 and 6 the profiling is shown only on one side, ie on the upper side of the film body 2, it is also possible within the scope of the invention to provide this profiling on two sides, ie also on the underside of the film body 2. In general, the uneven distribution of the proportion of material in the polymer on the longitudinal bars 3 and the cross bars 4 can be achieved by the cross-sectional areas of the bars are different from each other, for example, the longitudinal bars 3 have a larger cross-sectional area than the cross bars. In this case, the respective rods, that is, for example, the longitudinal bars 3, have a greater height and / or width than the transverse bars. In addition, the uneven distribution can also be achieved in that the number of longitudinal bars 3 is higher than the number of transverse bars 4, based on one square meter area of the perforated foil 1. The cross-sectional shape of the longitudinal bars 3 and / or the transverse bars 4 may preferably be round, oval , triangular, square, rectangular, trapezoidal, diamond-shaped, or generally be in the form of a rotationally symmetrical quadrilateral. But there are also other cross-sectional shapes, such as hexagonal, octagonal, etc. possible. Fig. 7 shows another embodiment of a breakthrough 5 in the perforated foil 1. Der

Breakthrough 5 has in principle a square (or quadrangular) outer shape but in the middle of the opening 5 a part of the film body 2 was left, which is connected via the transverse webs 4 with the film body 2 surrounding the opening 5. The opening 5 is thus partially "covered", so that the cross-sectional area of the opening 5 is reduced. <br/> <br/> It is advantageous with such an embodiment of the perforated foil 1 that the direction of force flow can be better distributed to the longitudinal bars 3 in the case of mechanical stress on the perforated foil 1. Since the apertures 5 occupy a relatively large area, however, the openings 5 through the remaining part of the film body 2 in the middle of the opening can also be used for relatively small piece goods, thus also achieving better moisture protection in various applications.

For completeness, it is noted that the aperture 5 can also be considered differently in FIG. 7, namely that it is composed of four apertures with trapezoidal cross section, are offset in the manner of a rectangle at 90 ⁰ to each other arranged (in the circumferential direction of the opening) are.

FIG. 8 shows a simplified embodiment of a device 13 for producing the perforated foil 1. This comprises an extruder 14 with a metering device 15 for However, it should be noted that instead of the extruder 14, another device for melting the raw material can be used, as is known from the prior art.

On the extruder 14, a slot die 16 is arranged, from which the molten polymer is already led out like a film, as is known per se. The slot die 16 may have a correspondingly profiled cross-section in order to allow the above-described described different material distribution by the longitudinal bars 3 broader and / or higher (thicker) are formed.

In the direction of production behind the slot die 16, a rolling mill 17 (calender) is arranged, which comprises a plurality of rollers 18. In the rolling mill, the polymer melt is cooled, as is also known from the prior art for film production. For this purpose, the film body 2 is passed between in each case 2 rolls 18 arranged at a small distance from each other. At least one of the rollers can be designed as a cutting roller with which the slots 6 (FIG. 4) are introduced into the film body 2. Alternatively or additionally, at least one of the rollers 18 may be a molding tool (two cooperating rollers 18 may be correspondingly profiled, so that the processing of the film body 2 from above and from below, ie from two sides) with the in the film body. 2 , or the melt, material tapers are introduced, which preferably already have the cross-sectional shape of the apertures 5 formed therefrom by the drawing. Thus, in this embodiment, the profiling of the roller (s) 18 results in displacement (squeezing) of the melt or solidified plastic film and thus targeted material distribution depending on the application of the perforated foil 1, so that the longitudinal bars 3 and / or the cross bars 4 are formed. The material may be present as a semi-finished product in the process for further processing according to weight percent distributions described above. Alternatively or additionally, a cutting device 19 may be arranged between the slot die 16 and the rolling mill 17 or after the rolling mill 17, in particular a laser cutting device, with which the slots 6 can likewise be introduced into the film body 2. It can take place in the rolling mill 17 already the longitudinal stretching of the film body by a corresponding tensile force is applied in the longitudinal direction to the film body 2. Preferably, however, is stretched after the shaping of the perforated sheet 1.

In the direction of production behind the rolling mill 17, a stretching table 20 or a stretching device is arranged, in which the width of the film body 2 is stretched, on which the apertures 5 essentially receive their final shape. After the stretching table 20 or the stretching device can still be arranged a relaxation device 21, in which the perforated film can be relaxed. This can for example be designed as a multi-zone temperature control.

At the end of the production line, the winding of the perforated foil onto a winding core 22 takes place in a winding device 23 as well as the packaging of the perforated foil 1.

9 shows an embodiment variant of the stretching table 20. This comprises two lateral guides 24, 25, for example obliquely placed rails, in which the film body 2, which has already been stretched longitudinally, is guided. Alternatively, the lateral guides 24, 25 may comprise gripping elements or clamping elements with which the film body 2 is grasped during the width stretching or between which it is clamped. To adjust the degree of width stretching, the side guides 24, 25 may be pivotable, whereby an angle 26 can be adjusted, in which the side guides 24, 25 are oriented to the film body 2.

In this stretching table 20, the film body 2 essentially has its final width 9.

Alternatively, the stretching table 20 can also comprise at least one heating device 27, for example IR emitters, which can or can be arranged above and / or below the film body 2 in the region between the side guides 24, 25. In this variant of the production method, the longitudinal stretching is carried out before the width is stretched. In principle, however, the longitudinal stretching can also take place after or simultaneously with the width stretching. The degree of longitudinal stretching of the film body 2 may be selected from a range of 1: 1.5 to 1: 12.

The width extensor, e.g. the stretching table 20, allows a variable stretching ratio in the range of 1: 1 to 1: 12. The film body 2 can be stretched to a stretching ratio selected from this range.

As an alternative to this embodiment for the production of the perforated film 1, the film can also be driven smoothly or structured from an extrusion die or a blow head into a calender, a water bath, via air cooling or onto a chill roll. From there, the film body can in a second step by mechanical embossing by heated or unheated rollers 18 or similar. Tools are brought into shape.

As an alternative, the film body 2 can be extruded and mechanical geometries introduced into it. This can be done by punching, pressing, cutting, embossing or weakening. By punching but not the finished trained breakthroughs 5 are generated.

As already mentioned, it is also possible to produce a film tube by means of bubble extrusion, which can run through the described procedures. Before winding up, however, the tube is cut open to produce the perforated foil 1 therefrom.

It is also possible that the plastic melt from the extruder for profiling, i. for material distribution according to the above explanations, on a relief roller with from grazing he poured.

The stretching of the, in particular embossed, film web can - held on width - linear in the longitudinal direction. Alternatively, the film body 2 can be stretched in the longitudinal direction conventionally stretching units and stretched in the transverse direction via a rolling device.

According to a variant embodiment of the perforated foil 1, it can be provided that at least individual, in particular all, apertures 5 are provided on one or both sides at least partially, in particular entirely, with an edge bead 28, ie a thickening, as indicated by dashed lines in FIG is indicated.

According to another embodiment of the perforated film 1, the longitudinal side edges of the film body 2 can be produced with a rim reinforcement 29, in particular a thickening or an edge bead, as shown in FIG. The embodiment with the uneven distribution of the longitudinal bars 3 is also apparent from this figure. This edge reinforcement 29 may optionally be formed in addition to or as an alternative to the edge reinforcement described above with reference to FIG. 6. In particular, the arrangement of the edge reinforcement 29 also has advantages with regard to the guidance of the perforated film 1 in the stretching table 20 or the stretching device.

It is also possible that the transverse rods 4 are arranged centrally in relation to a film thickness on the longitudinal bars 3 and connected to these, as shown in Fig. 11, or off-center, as shown in Fig. 12. This can be achieved for example by the above-described two-sided or one-sided profiling or shaping of the plastic melt.

Further, at least one, preferably at both, longitudinal side edges of the film body 2, a widened, preferably planar, welding edge 30 may be formed, as shown in Fig. 1 by dashed lines. The marginal longitudinal bars 3 can thus be arranged at a distance from the longitudinal side edges of the film body 2.

For further refinement of the perforated film 1, it can be surface-treated on at least one surface, for example matted or coated with a wax.

In addition, at least one of the surfaces of the perforated foil 1 can be roughened, for example with a microstructured (embossing) roller. If appropriate, this can be carried out as part of a matting of the perforated foil 1. The roughening can be done in addition to see procedure also be carried out thermally or chemically. Combinations of at least two of these methods can also be used with each other. Likewise, however, the surface can also be leveled or smoothed. It is also possible for an (adhesion) adhesive to be applied to at least one of the surfaces of the perforated foil 1, for example in the form of a microvasculature.

It is also possible that 5 thick points 31 are formed between the apertures, as indicated by dashed lines in Fig. 3, so as to influence the direction of force flow, as has already been mentioned above.

A thick point 31 is understood to be a discrete region in the film body 2, which has a greater thickness than the transverse rods 4 and possibly a greater thickness than the longitudinal rods 3, so that in the latter case they protrude beyond the longitudinal rods 3.

However, the thick point 31 may also be formed in the form of a corrugated longitudinal profile 32, which extends approximately in the direction of the length of the film, as is also shown in Fig. 3 by dashed lines. It is also possible that this longitudinal profile at least partially encloses at least individual openings 5.

It is also possible that in relation to the longitudinal side edges of the film body 2 edge longitudinal bars 3 have a larger cross-section than the centrally arranged in the film body 2 longitudinal rods 3. It can be incorporated with the invention constructively and deliberately thick points and flats with one of Application adapted distribution. These thick and flat areas can be realized in the longitudinal direction and / or transverse direction of the perforated sheet 1. So it can be created in longitudinal and transverse changing material structures, profiles and film thicknesses. Fine structures for area protection and large holes for rough applications can be created.

It is also the formation of multi-layered hole foils 1 possible, wherein the plurality of layers can be processed simultaneously and with each other. In this case exists also the possibility that at least individual layers are made of a different polymer in order to give the perforated film a property mix of different materials. It is also possible for fibers, for example short fibers up to a length of 30 mm, to be incorporated into the plastic melt.

In addition, the polymer can be crosslinked during the production of the perforated sheet 1. The perforated film 1 is in particular formed in one piece and not fibrillating or fibrillated. This prevents fiber residues from remaining in the respective product after removal of the perforated foil 1.

The perforated foil 1 also has a better cutting behavior and the elongation can be adjusted via the material distribution.

The distribution of the proportion of the plastic on the longitudinal bars 3 and the cross bars 4 is determined by the following method.

1. Definition of the hole area

Hole edges 33 are marked with a horizontal straight line 34 and a vertical straight line 35, as shown in FIG. The arrow to the right of the perforated foil 1 marks its longitudinal direction. The horizontal and the vertical lines 34, 35 are at the hole edges 33, so represent tangents of the hole edges. This results in a clearly defined geometric shape (an orthogonal grid), which is subsequently removed in the processing of the sample and processed accordingly or analyzed. The measurement of the distribution is gravimetric.

The method of defining the edge surfaces is applicable regardless of the geometric distribution of the holes on the finished film. Thus, offset holes can be determined exactly without restriction. In order to be able to define the directions "horizontal" and "vertical" exactly, the sample is prepared according to item 4 below.

2. Allocation of the interfaces

Edge surfaces 36 of the removed form (in the corners of the grid, shown hatched in Fig. 13 top left for a breakthrough 5) are attributed to the longitudinal bars 3 and the transverse bars 4 proportionally to 50 percent by weight.

3. Assembly and size of the test piece From the finished product, i. the finished stretched hole film 1, a sample over the entire width of the finished product or, if the perforated film has a Lochfolienbreite 37 of more than one meter, taken from an outermost edge of the hole to an opposite outermost Längsstegrand, as in Fig. 13 based on a sample width 38 is shown by way of example.

Generally it is important to take at least as many longitudinal webs as complete holes into the sample. By way of example, FIG. 13 shows that the sample width 38 is selected such that it has two rows of holes 39 and two complete longitudinal bars 3. The longitudinal bars 3 are therefore not divided during the sampling.

The sample size must be min. 1000x1000 mm and be taken from the preloaded finished product.

If the finished product has a perforated foil width 37 which is smaller than 1000 mm, then by juxtaposition, stack by row, edge to edge, several juxtaposed foil foil strips of width 1000 mm are to be produced.

As a test series at least 50 pieces of test specimens are to be evaluated. 4. Preparation of the test First a force in the longitudinal direction (vertical) of 5% of the breaking force and in the transverse direction (horizontal) a force of 5% of the breaking force is applied to the removed sample. If the sample straightens due to the applied force, gradually reduce the applied force until the test specimen lies flat. In the stretched state, the entire test piece is placed over the entire surface on a smooth, flat plate or a table biased.

To ensure the testability and regularity of the test, the surface of the plate or the table is covered with a double-sided adhesive film over the entire surface. This ensures that the test specimen is prepared in a well-prepared position and the further test steps can be carried out. Regardless of the stretched length of the test sample, the measuring surface is 1000x1000 mm.

5. Carrying out the test

The fixed present and flat glued test piece is now in the methodology as described under point 1) by means of a thin marking pen (line width maximum 0.5 mm) provided with the dashed line in Fig. 13 drawn cut. Along the grid is cut with a scalpel or a standard, sharp utility knife.

The pieces are taken out as explained in point 1 below.

If, due to the geometry, the extracted surface does not contain edge surfaces 36, for example because the hole geometry is geometrically right-angled and quadrangular, there are thus no edge surfaces 36 (in the case that the hole geometry 4 has right angles) and Consequently, an allocation of the areas is not possible and given the clear attribution of the material in the transverse and longitudinal direction. If the geometry is such that it can be perfectly defined which parts can be attributed to the transverse and longitudinal direction, the step of dividing in the 50:50 percentage ratio is also eliminated.

6. Measurement methods:

If steps 3. to 5. have been performed as described, the edge surfaces are separate from the rest of the film.

Subsequently, in the vertical test direction, the cross-connections along the cutting edge from point 5 are likewise separated again with an exact cut. It is now possible to divide the material into four groups and to determine their weight:

Length of material

Cross-material ratio

- edge areas (in each case to 50% by weight of the transverse and longitudinal direction)

Accounts point material

The node material in the nodes 7 (Fig. 1) is corresponding to the ratio of a longitudinal bar width 40 of the cut longitudinal bars 3 to a transverse bar width 41 of the cut-out transverse bars 4 (each viewed in plan view of the perforated sheet 1, Fig. 13) on the longitudinal and transverse bars 3, 4 split.

If the case occurs that a row of holes 39 is cut through the definition of the measuring surface of 1000 mm x 1000 mm, whereby the associated longitudinal bar 3 is also wegge- cut, the this hole series 39 assignable cross bars 4, which are the openings 5 of this row of holes 39 separate, seperate. In this case, the resulting smaller measuring area is extrapolated to the measuring area of 1000 mm x 1000 mm after the measurement and the resulting additional material proportion is calculated according to the ratio of the measured material content of the longitudinal bars 3 to the measured material content of the transverse bars 4 on the longitudinal and the transverse bars 3, 4 divided.

The embodiments show possible embodiments of the perforated foil 1, wherein it should be noted at this point that various combinations of the individual variants are possible with each other and this possibility of variation due to the teaching of technical action by objective invention in the skill of those working in this technical field. For the sake of order, it should finally be pointed out that, for a better understanding of the structure of the perforated foil 1, these or their constituents have been shown partly unevenly and / or enlarged and / or reduced in size.

REFERENCE NUMBERS

Perforated foil 31 thick spot

Film body 32 longitudinal profile

Longitudinal bar 33 hole edge

Cross bar 34 line

Breakthrough 35 line

Slot 36 edge surface

Node 37 perforated film width

Distance 38 sample width

Width 39 hole row

Distance 40 Bar width Distance 41 Bar width Distance

contraption

extruder

Metering device slot die

roll mill

roller

cutter

Recktisch Relaxiereinrichtung

winding core

winding device

cornering

Side guide angle

heater

bead

edge reinforcement

welding edge

Claims

Patent claims

1. A process for the production of a perforated film (1) from a plastic melt, a film body (2) is produced, in the slots (6) and / or thin bodies are introduced or made at least approximately lattice-shaped or provided with a lattice-shaped structure is and then the film body (2) to a structure with longitudinal bars (3), which are interconnected by transverse bars (4) is stretched to form apertures (5), in particular biaxially in a longitudinal direction and in a transverse direction, characterized the proportion of the material of the plastic is divided unevenly over the longitudinal direction and the transverse direction of the film body (2).

2. The method according to claim 1, characterized in that the plastic melt for splitting the plastic on the longitudinal bars (3) and the transverse rods (4) is processed with a profiled molding tool before the stretching is performed.

3. The method according to claim 1 or 2, characterized in that the plastic melt is distributed such that in a longitudinal direction of the film body (2) a higher proportion of the plastic melt is present than in a transverse direction of the Folienkör- pers (2).

4. The method according to any one of claims 1 to 3, characterized in that at least partially thickenings are formed around the openings (5).

5. The method according to any one of claims 1 to 4, characterized in that the

Querverstreckung of the film body (2) after the longitudinal stretching is performed.

6. The method according to any one of claims 1 to 5, characterized in that the film body (2) is tempered during the hiding.

7. The method according to any one of claims 1 to 6, characterized in that the film body (2) is relaxed or relaxed after stretching.

8. The method according to any one of claims 1 to 7, characterized in that the longitudinal side edges of the film body (2) with a rim reinforcement (29), in particular a thickening, are produced.

9. The method according to any one of claims 1 to 8, characterized in that at least one of the surfaces of the film body (2) surface-treated, in particular roughened, is.

10. perforated film (1) with a film body (2) made of a plastic of longitudinal bars (3) and transverse bars (4), wherein by the transverse rods (4) the longitudinal bars (3) are interconnected, wherein the longitudinal bars (3 ) and the transverse rods (4) openings (5) surrounded, characterized in that the material content of the plastic on the film body (2) is unevenly divided on the longitudinal bars (3) and the transverse rods (4).

11. perforated film (1) according to claim 10, characterized in that the longitudinal bars (3) have a higher proportion of material to the plastic, as the transverse rods (4).

12. perforated film (1) according to claim 10 or 11, characterized in that the transverse rods (4) are arranged centrally - in relation to a film thickness - on the longitudinal bars (3).

13. perforated foil (1) according to claim 10 or 11, characterized in that the transverse rods (4) off-center - in relation to a film thickness - on the longitudinal bars (3) are arranged.

14. perforated film (1) according to any one of claims 10 to 13, characterized in that between the apertures (5) thick spots are formed.

15. perforated film (1) according to one of claims 10 to 14, characterized in that along the longitudinal side edges a widened edge without openings (5) is formed as a welding edge (30).

16. perforated film (1) according to one of claims 10 to 15, characterized in that with respect to the longitudinal side edges of the film body (2) peripheral longitudinal bars (3) have a larger cross-section than in the middle in the film body (2) arranged longitudinal rods (3 ).

17. perforated film (1) according to any one of claims 10 to 16, characterized in that the number of openings (5) in the film body (2) is selected from a range having a lower limit of 100 openings / m ² and an upper limit of 10,000 breakthroughs / m ² .

18. perforated film (1) according to one of claims 10 to 17, characterized in that the openings (5) have a size - viewed in plan view - which is selected from a range with a lower limit of 10 mm ² and an upper limit of 1000 cm ² .