Method for shaping a material of reticular structure, installation for implementing the method and reticular material resulting from the method

[0001] The present invention relates to a method of shaping a material with a mesh structure or mesh structure, which also includes an installation for carrying out this method and a mesh material obtained by this method.

[0002] This method is used to process a material of synthetic material with a mesh structure, in particular having the shape of a tubular sleeve, which is one of the types of known constitution and obtained by means of an extrusion process.

[0003] The mesh material resulting from this method is used in particular in principle in the packaging industry, and it is worth mentioning how important it is to use in packaging food products, and more particularly fruit and vegetable products.

Background Art [0004] It has been known for many years to use mesh containers, either of the braided type, such as mesh bags / sacks, or the type of ordinary knitting, such as sacks of loosely woven fabrics, such as hemp canvas, sacks, mats , linen weave, etc., for transporting onions, potatoes, etc., at commercial level, or the type obtained by extrusion of synthetic plastic material, such as used for the production of bags and sacks for the packaging of various products used at home level, such as oranges, potatoes, onions, nuts, chestnuts, lemons, etc.

[0005] Spanish Utility Model No. 158,340 is known which describes an extruded mesh which is oriented one or biaxially, without reaching places

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EP 2 006 077 Bl an intersection that has low tensile strength, good dimensional stability and reduced coverage.

[0006] The present Applicant is the owner of Spanish utility models Nos. 290.122, 290.123, 290.124, 290.125 and 290.126, which refer to different varieties of sleeved flattened extruded mesh systems made of two or three non-molecularly oriented fibers having properties such as low strength tension / tension, good dimensional stability and high coverage.

[0007] Also known is patent EP 0 788 974, which relates to packaging made of non-oriented extruded mesh, which is assembled with a plastic film and connected to 2.014.712, by which it describes sealing, and Patent ES, packaging sacks / bags made of woven plastic fiber mesh, which is composed of a plastic film connected to a woven mesh by welding.

[0008] Finally, patent ES 2.023.601 is known, which describes a method for obtaining a flexible load-bearing net as well as a net obtained in this way.

[0009] Furthermore, the field of application of the material which is the subject of the invention, whose use may be restricted, on the one hand, for packaging of food products in general, and in particular fruit and vegetables, on the other, for storage of palletised loads, should also be taken into account .

[0010] Regarding the case of the first use, it is worth emphasizing, due to their wide applications and good functional usability, packaging made of net (mesh) and auxiliary printed elements, such as printed foil bands, paper labels, plastic labels e.t.c.

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EP 2 006 077 Bl [0011] In these packages, comprising a mesh and plastic tapes (bands), the mesh may be of a fabric of the extruded oriented or extruded oriented types. Each of these types of mesh has, due to its main function as an element for placing the product inside the packaging, some advantages and disadvantages, namely:

[0012] Woven mesh has a good strength-to-weight ratio, which allows optimization of packaging costs. It also has the advantage that, due to its low weight and volume, large amounts of meters of material can be placed on the reels at once, which increases the autonomy of automatic packaging machines. The disadvantage of woven mesh is that it has very low dimensional stability, so packaging made of this type of mesh is easily deformable, which has a negative effect on the vertical structure and the ability to display information or printed designs on the packaging.

[0013] Packages obtained from oriented extruded meshes have the same advantages and disadvantages as those made from woven meshes, with such an additional element that, in general, oriented extruded meshes have a low product coverage ratio, since the oriented threads have a small cross section, ] From non-oriented extruded meshes, packaging is obtained that maintains its vertical structure and provides a clear view of the pattern printed on bands or foil tapes. However, these nets have a very low strength-to-weight ratio, so heavy nets must be used, which has a negative impact on the cost of the packaging. On the other hand, because their threads are not oriented and have a large cross-section, these nets have a high product coverage ratio, but at the same time

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The reels can only fit a few meters at a time, which causes frequent stoppages of automatic packaging machines to replace empty reels.

[0015] As far as the second application is concerned, mesh structures or flat (mesh) meshes are used when air circulation inside the pallet loads is important, so that there is no water vapor as in the case of pallets containing boxes with fruit, vegetables or fresh vegetables; or when placing hot products that are to cool in the atmosphere, such as bricks and ceramics, as soon as they have been fired.

[0016] In this case, perforated films, woven meshes or biaxially oriented extruded meshes may be used.

[0017] The perforated films have good elasticity and are not too thick, so a large number of meters can be placed on one spool, and they do not produce loose threads or a large amount of waste when unpacking the pallets. As far as the disadvantages are concerned, it is worth noting that they have limited tensile strength and that, due to their consistency, the perforated surface cannot be very large, and thus the ventilation effect inside the palletized load is very strongly limited.

[0018] The extruded meshes provide good tensile strength, but they have the disadvantage that, due to their thickness and rigidity, the spool only fits a few meters and that the mesh takes up a lot of space when the pallets are demoulded and must be placed in waste containers.

[0019] Woven meshes do not provide as good shear strength as oriented extruded meshes, especially in the case where the palletized load has edges with edges, but their main disadvantage is that during

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EP 2 006 077 BI to cut the mesh to form the pallets, the threads that accumulate in the wheels and axles of the rear parts of the pallets and forklifts fall off, and that this may cause malfunctions or that this means at least the need to increase the frequency of cleaning and maintenance of these machines.

[0020] Document US 4,190,692 describes the production of a plastic mesh formed by extrusion technique of a plurality of spaced plastic bands to obtain a mesh structure. US 3.3177.951 describes a device for stretching a pipe (sleeve), which is intended for both longitudinal and lateral stretching of a synthetic material pipe. FR 1.566.717 describes a process for producing extruded plastic netting, especially for packaging fruit and vegetables.

Description of the invention [0021] In the light of the cited prior art, the detailed disadvantages of the sleeve nets used up to now, and the properties required for the mesh made of synthetic material of the plastic type obtained in the extrusion process, and depending on the use of the bag, a solution has been adopted, as a result of which the mesh has the highest tensile strength, high coverage, ribbed or slightly stiff structure, so that, when filled, kept its dimensional shape at rest, avoiding the typical flaccidity of traditional sacks, while being very light.

[0022] In order to achieve the above ideal conditions for a plastic mesh intended for use in the abovementioned applications, a solution was adopted which resulted in a synthetic plastic mesh

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The extruded synthetic material obtained has been given maximum tensile strength, while reducing, as far as possible, the thickness of said mesh.

[0023] According to the previous solution, a method according to the invention was developed, whereby a synthetic plastic material with a tubular mesh structure obtained by extrusion technique is subjected to hot two-dimensional molecular orientation operations by stretching, both in longitudinal and transverse direction, followed by the operation of leveling the thickness of the synthetic plastic material by laminating it with a calender.

[0024] A characteristic of the method according to the invention is that the sleeve-shaped synthetic plastic material with a mesh structure is subjected, like a rope, to the molecular orientation operation of said material by longitudinal stretching of said material, and then the material is given a flattened shape sleeve by expanding it to complete molecular orientation by transverse stretching.

[0025] Another characteristic of the method of the invention is that the synthetic plastic material with a tubular mesh structure and obtained by extrusion is subjected to hot molecular orientation operations by longitudinal stretching, transverse stretching operations by expanding the mesh structure of the sleeve and the operations of leveling the thickness of synthetic plastic material by laminating it by passing it through a calender, while maintaining the flattened and expanded said sleeve structure

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EP 2 006 077 Bl made of said material of synthetic plastic.

[0026] Other characteristics of the method according to the invention are that the lamination of the mesh structure can be carried out after longitudinal stretching and before transverse stretching, or after transverse stretching takes place.

[0027] The invention includes an installation for implementing the above method, which, in principle, comprises a device for extruding a tubular mesh structure made of thermoplastic, after which a device for two-dimensional hot stretching of said rope-like structure and a device for expanding said structure now having a shape flattened sleeve, followed by direct laminating with a calender.

the synthetic material is sequentially located. [0028] A characteristic feature of the installation according to the invention is that the longitudinal stretching device, which is made hot, is essentially composed of two sets of pairs of ironing rolls, the output pair being in second place according to the forward direction of the sleeve mesh structure rotates at a higher speed than the input pair, which is in the first place in the forward direction of said structure.

[0029] Another characteristic of the installation according to the invention is that the longitudinal stretching device is composed of a pair of rollers or rollers for a sleeved rope-like net structure, said rollers or rollers being arranged on a holding drum, the lower of which said rope for a large part of the perimeter of the retaining drum from which it is

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EP 2 006 077 B1 separated by means of a roller or guide roller that leads it in a vertical direction to a drive roller immersed in a thermal bath through which the mesh structure passes until it reaches another drive roller which sends it to the guide roller which he feeds it onto the stretching drum, from which it passes to the driving drum, and then to the pair of rollers / pull rollers.

[0030] Another characteristic of the installation according to the invention is that the transverse stretching device is made up of a dilator from the group consisting of pin (needle) and clamp chain extenders.

[0031] Another characteristic of the installation according to the invention is that the laminating device is composed of a calender with two cylinders, which has an adjustable range and is heated, said device having at its entrance an expansion tool for expanding the mesh structure of a flattened sleeve shape .

The invention comprises a material with a mesh structure produced by the above method which has the property of consisting of a synthetic plastic shaped according to a thread-like mesh structure in which, having the shape of a flattened sleeve, fibers forming the sides of the mesh of said structure and the intersection points of said fibers to shape this mesh have the same common thickness.

[0033] Another characteristic of the material according to the invention is that the thickness of the mesh intersection points is equal to the thickness of the fibers forming the sides of the mesh that are not subjected to laminating calender and, in some cases, the thickness of

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EP 2 006 077 B1 of the mesh intersection and the thickness of its sides is smaller than the thickness of the sides of the mesh before being subjected to a lamination process using a calender.

[0034] Finally, a feature of the invention is also that the mesh structure of the mesh is monolithic and obtained by extrusion of a synthetic material of plastic having elastomeric properties.

Brief description of the drawings [0035] In order to facilitate the understanding of the above concepts, the method of shaping the mesh material, installations for carrying out the said method and the material obtained by the said method is described below, all according to the invention and with reference to the accompanying drawings, in which:

Figure 1 is an expected schematic elevational view of the expected course of the shaping steps of the mesh material made by the method of the invention.

Figure 2 is an expected schematic plan view of the shaping steps of the mesh material made by the method of the invention.

Figure 3 is a geometrical, flat schematic view of a piece of material with an ideal mesh structure, on which the sides of the eyelets are regularly rectilinear, and the places of their intersection are represented by widened projections.

Figure 4 is a cross section along line IV-IV in Figure 3.

Fig. 5 is a geometric, schematic perspective view of the intersection on the sides of the four meshes in Figure 3, after laminating a material with a mesh structure depending on the thickness of its sides.

Figure 6 is a cross section along the line VI-VI of Figure 5.

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Figure 7 is a plan view of a fragment of a conventional extruded grid with square meshes that have only one molecular orientation.

Figure 8 is a perspective view of a portion of the mesh portion with square meshes in the previous figure, showing the intersection of the mesh sides.

Figure 9 is a perspective view of a portion of the mesh with square meshes in the previous figure after subjecting the mesh crossing locations to lamination.

Figure 10, similar to Figure 7, is a plan view of a portion of an extruded mesh with diamond-shaped (parallelogram) eyelets that can have only one molecular orientation.

Figure 11 is a perspective view of a portion of the mesh portion with the parallelogram-shaped eyelets in the previous figure, showing the highlighted intersection of the sides of the mesh.

Figure 12, similar to Figure 9, is a perspective view of a portion of the grid in the previous figure after laminating operations at the intersection.

Figure 13 is a schematic view of a tubular mesh extrusion plant to which an extruded mesh drying and longitudinal molecular orientation plant is connected, behind which there is a transverse laminating calender, and a laminated net winding device.

Figure 14 is a schematic view of an installation for obtaining an extruded tubular mesh, followed by longitudinal stretching for its molecular orientation and lamination in the calender, which ends with winding the mesh.

Fig. 15 is a schematic view of the installation

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EP 2 006 077 B1 intended for transverse orientation of an extruded tubular mesh which may or may not be oriented in the longitudinal direction.

Figure 16 is a schematic view from above of a calendering head for expanding the flattened sleeve mesh and laminating it immediately.

Figure 17 is a schematic cross-sectional view along the line XVII - XVII of Figure 16, in a side view, a distinctive device for expanding or pressing the flattened tubular mesh placed at the entrance to the laminating calender.

Figure 18 is a schematic cross-sectional view along the line XVIII-XVIII in Figure 16.

Figure 19 is a comparative graph of strength and elongation of two sleeve meshes, one of the standard type and the other laminated according to the invention.

Figure 20 is a comparative graph of strength relative to the unit of mass of two tubular meshes, one of the standard type and the other laminated according to the invention.

Description of Some Preferred Embodiments of the Invention [0036] Figures 1 and 2 graphically depict in a graph the method that is the subject of the present invention, which consists essentially of subjecting a synthetic plastic material with a tubular mesh structure to hot, two-dimensional molecular orientation operations , in longitudinal and transverse direction, by stretching, followed by an operation to even out the thickness of a synthetic plastic material by laminating it in a calender.

[0037] Figure 1 shows what, by default, is a side view of the course of the material forming steps

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EP 2 006 077 Bl a thermoplastic with a sleeve mesh structure 1, obtained in this sleeve shape from an extrusion nozzle 2, from which an extrusion nozzle 2 is collected in the form of a rope 3 between two rotary input rollers 4 that feed it to two other rotary rollers pulling 5, which have a higher angular velocity than the former, resulting in longitudinal stretching, which determines the molecular orientation of the material with a mesh structure 1, which determines its higher tensile strength.

[0038] Then, after exiting the rotatable stretching rollers 5, the rope-like material 3 with the sleeve mesh structure 1 is introduced into the expansion device 6 in which said rope 3 opens and is placed as a flattened sleeve structure 7 and is immediately fed between two rotary press rollers 8 which laminate between themselves material with a mesh structure 1, to transform it into a material of a mesh laminated material having a reduced, constant thickness, which has also been subjected to molecular orientation in the transverse direction.

[0039] Figure 2 also shows a default top view of the steps of shaping a thermoplastic material with a tubular mesh structure 1, showing the same components as in the previous figure, indicating their function which is not obvious in said previous figure.

[0040] Figure 3 is a geometrically schematic view of a fragment of a material with a sleeve mesh structure 1 which has been determined not to be laminated, in which the mesh, which is square, is composed of regularly rectilinear sides 10 which intersect regularly to form spots junctions 11 that are thicker than 10 sides

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EP 2 006 077 B1 and are shown as clearly lenticular extended projections.

Figure 4 is a side view of said widened projections according to a section along the line IV IV in Figure 3.

[0041] Figure 5 is a schematic perspective view of the mesh structure material 1A in Figure 3 after being subjected to a lamination operation by calendering to flatten the extended projections of the intersection sites 11, reducing them to the disc intersection sites 12 having a thickness equal to the diameter of the sides of the 10 square mesh. Figure 6 is a view of said disk intersection points 12 according to a section along the line VI-VI in Figure 5.

[0042] Figure 7 shows a fragment of the material with a mesh structure and actual shape and which is defined as a conventional extruded mesh 13 with square meshes, which has a two-dimensional molecular orientation assumed, and has a mesh formed by perpendicular intersections of the fibers that form its sides 14 and fix appropriate crossing points 15, which are suitable for said fibers due to the increased thickness resulting from the sum of their thickness at the intersection of said fibers of the sides of the mesh 14, with their projections visible in a perspective view of a part of said embossed mesh 13 forming Figure 8. Figure 9 shows part of the extruded mesh 13A in Figure 8, after being subjected to a lamination operation, in which it can be seen that the thickness of the respective junction locations 15 in the mesh, indicated in said Figure 8, is reduced with respect to the thickness of the sides 14 of its mesh forming flat crossing points 16.

[0043] Figure 10, similar to Figure 7, will show a fragment of the material with a mesh structure and a real one

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EP 2 006 077 B1 a shape which is defined as a conventional extruded mesh 17 with parallelogram mesh, which has a two-dimensional molecular orientation, and has a parallelogram mesh formed by the intersection of the fibers forming its sides 18 and that it determines the appropriate intersection points 19, constructed as such for the same reasons as those given above in Figure 8, with their projection (convexity) visible in a perspective view of a part of said embossed mesh 17, forming Figure 11. Figure 12 shows a portion of the extruded mesh 17A in Figure 10, after it has been subjected to the lamination operations, in which it can be seen that the thickness of the respective mesh crossing points 19, indicated in said Figure 11, is reduced with respect to the thickness of the sides 18 thereof meshes forming flat intersection points 20.

[0044] Figure 13 shows an installation for carrying out the method according to the invention, which comprises, in principle, an extruder 21 which, by means of a rotary nozzle head or nozzle 22, produces a material having a mesh structure in the shape of a conventionally shaped extruded sleeve mesh 23, which is extruded the sleeve mesh 23 is cooled in a ladle containing water and led to the installation 24, which shakes it, and from which it goes to the installation 25 for molecular orientation, comprising a pair of driven input rollers 26, an air-heated tunnel 27 and a pair of driven output rollers 28 that rotate faster than the previous pair, from which the extruded tubular oriented mesh 23A is passed to an expansion device 29 and to a laminating head consisting of a pair of driven rollers 30 calenders, at the exit of which an embossed, flattened oriented and laminated net 23B is collected on a winding device 31.

[0045] Figure 14 corresponds to another installation to be implemented

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EP 2 006 077 B1 of the method according to the invention, which, like the installation described in Figure 13, comprises an extruder 21 and a rotary nozzle head or nozzle 22 from which a mesh structure material emerges in the shape of a conventional type of extruded tubular mesh 23, which is guided to a longitudinal stretching device which is composed of a pair of pull rollers 32 to said sleeved, rope-like net 23, where, of said rollers lying on the holding drum 33, the lower roller applies said rope to a large part of the circumference of said holding drum 33, from which it is separated by means of a guide roller 34, which leads it in a vertical direction to the drive roller 35, immersed in a bath in ladle 36, in which the netting 23 with a sleeve structure circulates until it reaches the next drive roller 35, which sends it to the guide roller 37, which is placed on the stretching drum 38, from which it passes to a drive drum 39 and, then, to a pair of pull rollers 40, which deliver oriented material to the driven rollers 30 in a calendering machine, which material is then collected on the winding device 41.

[0046] Figure 15 corresponds to an installation intended for transverse orientation of a material with a mesh structure, which consists of a conventional device in the textile industry for processing fabrics along the width, which are known under the name of dilators 43 and which includes a tunnel equipped with heating means through which There are two chains that have pins that move parallel to each other.

[0047] Figures 16, 17 and 18 show a schematic view of an embodiment of the means for expanding and laminating a tubular mesh structure that includes an expansion device 29 consisting of a triangular curvilinear plate 44 that is mounted in a floating state, but

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In a retained, within the mesh net structure 23A (see Figure 13), between two passive rollers 45 that rotate on said tubular mesh structure 23A allowing it to move towards the driven rollers of the calendering device while maintaining said expansion device 29 thanks to its two rollers 46, which prevent the triangular curvilinear plate 44 from passing between the passive rollers 45.

[0048] The upper driven roll 30 is mounted in a rotatable frame 47 which allows, with the help of micrometer screws, to change the spacing between two driven rollers in order to set and adjust the spacing between them to the thickness desired for laminating the 23A mesh material.

[0049] Both driven rollers 30 are equipped with thermal adjustment means 48, gears 49 (gears) and drive motor 50.

oriented both materials [0050] An example of the behavior of a standard material with a tubular mesh structure and non-oriented parallelogram meshes, and a laminated material with a mesh mesh structure and parallelogrammatic meshes, consisting of mesh with two threads, the weight of the first material per square meter is 54 g, and the weight of the second material, per square meter, is 37 g, with properties in terms of absolute strength depending on elongation, which are shown in Figure 21, while their strength per unit weight is shown in Figure 22. In both cases, the graphs in said figures were developed based on tests carried out using an Instron 4301 measuring device, in which sensors have a width of 250 mm, distance between

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EP 2 006 077 Bl with jaws is 50 mm and the draft speed is 500 mm / min.

[0051] In the views of Figures 19 and 20, it should be noted that the material with a tubular mesh structure that has been subjected to two-dimensional molecular orientation and lamination is more durable than the standard material, despite having a lower weight, and consideration should be given to that the normal operating conditions do not exceed the elongation value above 5%, otherwise the meshes could deform, as fully detailed in the table below:

<td>Strength (kp / sample) elongation</td><td> 5%</td><td> 10%</td><td> 15%</td><td> 20%</td><td> 25%</td>

<td>- standard mesh</td><td> 8.8</td><td> 13.2</td><td> 15</td><td> 16.2</td><td> 17.2</td>

<td>- laminated mesh</td><td> 18.4</td><td> 29.5</td><td> 37</td><td> 42.4</td><td> 47</td>

<td>Strength (kp / unit weight) elongation</td><td> 5%</td><td> 10%</td><td> 15%</td><td> 20%</td><td> 25%</td>

<td>- standard mesh</td><td> 16.3</td><td> 24.4</td><td> 27.8</td><td> 30.0</td><td> 31.9</td>

<td>- laminated mesh</td><td> 49.7</td><td> 79.7</td><td> 100.0</td><td> 114.0</td><td> 127.0</td>

[0052] Practical improvements have been achieved with the sleeve laminated mesh described in the present invention that overcome the disadvantages detailed at the beginning of this description that other types of mesh and film exhibit, and with the help of the mesh structure or mesh which is the subject of the present invention, it is possible a combination of the advantages of the grid described in the previous paragraphs, while overcoming the disadvantages.

[0053] Since the mesh originates from an extruded sleeve mesh, and is oriented in the longitudinal and transverse direction (biaxially oriented), it has a high degree of resistance to all types of loads. Because the threads and knots are flattened, the mesh loses serious

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EP 2 006 077 B1 part of its stiffness and therefore takes up less space when it is removed, and, in addition, because of its consistency, a large number of meters can be wound on a single spool. Since it is not a woven mesh, there is no waste in the form of loose threads when said mesh is cut to form pallets and, as a consequence, the problem of dirt in the rear of the pallets and forklift trucks is avoided. Another important advantage is that, depending on the materials used and the stretching ratio used, the mesh may have greater flexibility, which greatly facilitates its application.

[0054] The tubular, two-dimensional oriented and laminated mesh which is described in the invention has a good strength-to-weight ratio because it comes from extruded oriented mesh, whereby cheap packaging can be obtained. It has good dimensional stability, so the packaging obtained from this mesh maintains its vertical shape and provides clear visibility of the information printed on the foil band / tape. Because the threads and knots formed by the intersections between them are flattened, this mesh provides a better coverage of the product and, for the same reason, the possibility of winding a greater number of meters on a spool than in the case of an extruded, non-oriented mesh.

Intermas Nets, SA

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POLSfc'RVICE

Kancelaria Rzeczników Patentowych sp.z o.o.

uh Biuszczańaka 73

00-712 WARSAW

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EP 2 006 077 Bl