Method for producing plastics strapping bands

Abstract

The invention relates to a method for producing plastics strapping bands. The method comprises the following method steps: providing at least a first plastics material, subsequently melting the first plastics material, subsequently forming a film strand, subsequently splitting the film strand, in a material-transport direction, into first band strands having first band-strand widths and first band-strand thicknesses by means of splitting devices, and subsequently stretching the first band strands in the material-transport direction by means of a stretching device to form second band strands having second band-strand widths and second band-strand thicknesses.

Description

[0001] METHOD FOR THE MANUFACTURE OF PLASTIC STRAPPING BANDS

[0002] The invention relates to a method for producing plastic strapping bands.

[0003] Plastic strapping is primarily used to secure goods or to securely hold goods. The goods to be secured are wrapped around the strapping, tensioned, and the strap ends are usually joined together, for example, by welding. Plastic strapping offers numerous advantages over strapping made of other materials, such as steel. For example, plastic strapping is simpler and cheaper to produce, easier to handle, corrosion-free, and also has a low carbon footprint. Such strapping, their intended use, and their properties are generally specified, for example, in EN 13394 or in national standards corresponding to this European standard, such as ÖNORM EN 13394.

[0004] Thermoplastics or plastic materials are used to manufacture plastic strapping. The high tensile strength required for the intended application is achieved by monoaxial stretching using so-called stretching machines. This type of stretching induces an orientation of the macromolecule chains in the stretching direction or longitudinal direction, thereby achieving the high tensile strength of the plastic materials in this direction. Especially with semi-crystalline, thermoplastic materials, this can achieve tensile strengths similar to those of steel.

[0005] The usual manufacturing methods for plastic strapping involve melting the thermoplastic materials, usually during extrusion, shaping, cooling, and stretching. This can involve, for example, producing individual strap strands and then stretching them, although it is also possible to extrude, shape, and stretch multiple strap strands in parallel.

[0006] Alternatively, a manufacturing method is used in which a very wide strand is extruded in the form of a film, formed, and then monoaxially stretched. The resulting stretched film is then cut lengthwise into individual strapping strands and further processed. Typically, the resulting strapping strands are wound onto spools as so-called continuous strands and cut at the point of use into ready-to-use strapping bands of the appropriate or required length.

[0007] The method of producing films, stretching them, and subsequently cutting them into individual strands has been known for a long time. This manufacturing method is summarized and described at the beginning of DE 4007 560 A1, for example. In principle, such cutting or dividing of monoaxially stretched films in the longitudinal or stretching direction can be accomplished without excessive force, since the films to be cut usually do not have high tensile or tear strength in this direction. Cutting monoaxially stretched films also allows for good control of the desired strip widths.

[0008] However, this well-known process step of cutting or dividing a stretched film can also be problematic. Due to their solid consistency, cutting stretched films inherently involves high levels of abrasion, and the cutting tools used can therefore be subject to significant wear. Furthermore, cutting or dividing stretched films can lead to damage to the divided strip strands themselves. In particular, due to the low tensile strength along the stretching direction, the dividing process can lead to a so-called splitting of the monoaxially stretched plastic strands and / or the formation of notches at the strip strand edges. This can result in an increased level of rejects.Furthermore, in this previously known process, the plastic materials used must have a high degree of purity, as foreign material other than the thermoplastic polymers can impair the cutting process of the stretched films. Furthermore, the stretching process preceding the cutting process can also be problematic due to the large width of the film strand, particularly leading to inconsistent strand thickness along the width of the film strand.

[0009] The object of the present invention was to overcome the remaining disadvantages of the prior art and to provide a method by means of which plastic strapping bands can be produced with a high degree of process reliability, as independently as possible of the plastic material used and without high wear of cutting devices and without high levels of waste.

[0010] This object is achieved by a method according to the claims. The method for producing plastic strapping comprises the following process steps in the specified sequence:

[0011] - Providing a first plastic material consisting of 70 wt.% to 100 wt.% thermoplastic, first polymer and 0 wt.% to 30 wt.% of one or more further components,

[0012] - subsequently melting the first plastic material by means of an extrusion device to form a first plastic melt,

[0013] - subsequently forming a film strand by feeding at least the first plastic melt in a material transport direction to a forming device, and cooling the first plastic material,

[0014] - subsequently dividing or cutting the film strand along the material transport direction into first strip strands with first strip strand widths and first strip strand thicknesses by means of dividing devices,

[0015] - subsequently stretching in the material transport direction of the first strip strands by means of a stretching device to form second strip strands with second strip strand widths and second strip strand thicknesses.

[0016] The specified sequence of process steps and the term "subsequent" are to be understood to mean that each "subsequent" process step must be carried out after the previously specified process step. However, this does not require that a "subsequent" process step must be carried out immediately after the preceding process step. Rather, the execution of intermediate steps, including intermediate steps not explicitly described here, between the individual specified process steps is possible and not excluded. The material transport direction mentioned can also be referred to as machine direction (MD), as is well known, or is synonymous with this.

[0017] The process in question can be used in particular for the production of plastic strapping as specified in (ÖNORM) EN 13394 or in accordance with (ÖNORM) EN 13394. The process can therefore be used for the production of plastic strapping with a tensile strength of at least 300 N / mm 2 be provided.

[0018] As the first plastic material, in particular, a plastic material consisting of 80 wt.% to 98 wt.% thermoplastic first polymer and 2 wt.% to 20 wt.% of one or more further components can be provided. Regardless of the amount of the further component(s) of the first plastic material, this / these further component(s) can be formed, for example, by fillers, additives, plasticizers, or even by one or more polymer(s) other than the first polymer.

[0019] The targeted cooling of the film strand to a desired target temperature for the subsequent cutting step can be achieved exclusively by means of the forming device itself. For this purpose, the first plastic melt can be cooled, for example, by means of at least one temperature-controlled roller or roller with a temperature-controlled roller surface of the forming device. For example, at least one roller of the forming device can be subjected to a coolant. In addition, however, a separate cooling of the plastic melt before forming the film strand and / or an additional, separate cooling of the film strand after forming the film strand can also be carried out by means of an additional cooling device, such as a water bath.A film strand thickness can be specifically adjusted, for example, as is known per se, by passing the first plastic melt through a gap between adjacent rollers, wherein at least one of the adjacent rollers can be arranged to be adjustable to vary the film strand thickness. The forming device can be formed, as is known per se, by a rolling mill, also referred to as a calender or smoothing mill.

[0020] The cutting of the film strand can be carried out, for example, by means of knife blades, non-rotatable or round blades that can be rotated along or against the material transport direction, or by means of cutting devices designed as lasers or water jets.

[0021] By cutting the film strand before stretching, the cutting or cutting process can be carried out very gently and with very little wear and tear. This is because the film strand is still at a high temperature and relatively soft at this point in the process. This relatively high temperature is also necessary for the subsequent stretching step.

[0022] The thickness of the film strand after forming, or the first strapping strand thickness after cutting, can be adjusted, for example, to between 0.6 mm and 3.8 mm, preferably between 0.8 mm and 2.8 mm. By stretching, the second strapping strand thicknesses can be adjusted to between 0.15 mm and 1.8 mm, preferably between 0.2 mm and 1.4 mm. By cutting and subsequent stretching, the second strapping strand widths can be adjusted to between 3 mm and 40 mm, in particular between 4 mm and 36 mm, with the second strapping strand widths being selected primarily according to the intended use of the plastic strapping.

[0023] Surprisingly, it has been demonstrated that, despite the film strand's still soft consistency, it can be very precisely divided into the individual, first strip strands using conventional cutting or slicing devices, with hardly any deviations in the respective first strip strand widths. Equally surprising, it has been shown that, using this process, second, stretched strip strands with very uniform strip strand widths and thicknesses can be produced after stretching. This is despite the considerable deformation inherent in the stretching of the first strip strands following the cutting.To achieve the required tensile strength of the plastic strapping, stretch ratios of 1:4 to 1:20 are typically necessary, which, as mentioned, causes considerable deformation of the plastic materials during stretching.

[0024] Furthermore, it has also been shown that dividing a film or film strand before stretching is more tolerant with regard to the plastic materials that can be used than dividing it after stretching, as is the case with the prior art. In particular, dividing the film or film strand before stretching is less problematic with regard to the uniformity and quality of the plastic material(s) used, as will be explained in more detail below.

[0025] Following the stretching process step, further process steps can optionally be performed. For example, a stretched strap strand can be embossed, waxed, or treated in some other way. Finally, the strap strands can, of course, be finished. Typically, the resulting strap strands are wound onto spools as so-called endless strands for finishing and only cut at the point of use into ready-to-use strapping bands of the appropriate or required strap length. In a further development of the process, it can be provided that the film strand is cooled to a temperature of 75°C to 135°C for the cutting process step.

[0026] Below the specified temperature range, some plastic materials may experience increased wear on the cutting devices, particularly those in the form of cutting tools. Above the specified temperature range, increased material flow of the plastic material may, for example, lead to re-sticking of the first strip strands, as well as the formation of first strip strands with inhomogeneous widths and thicknesses, especially in the edge areas of the strip strands. In particular, the film strand can be cooled to a temperature of 80 °C to 130 °C for the cutting process step.

[0027] Furthermore, the method can provide for the film strand to be formed by means of a forming device comprising rotatably mounted rollers.

[0028] In particular, the shaping device can be formed by a so-called rolling mill, also referred to as a calender or smoothing mill. As already mentioned, the film strand can be shaped using such rollers, wherein the film strand thickness can be specifically adjusted, for example, by passing the first plastic melt through a gap between adjacent rollers. In this case, at least one of the adjacent rollers can be arranged so as to be adjustable in order to change the film strand thickness. Shaping devices comprising rollers have proven particularly well suited in the present process for shaping film strands with a very uniform and even structure and very evenly designed surfaces on the top and bottom sides.

[0029] In this context, it may also be expedient if, during the process step of forming the film strand, at least one surface of the film strand is structured by means of at least one structured roller surface.

[0030] Such a surface structure on at least one surface can be particularly helpful when using plastic strapping to form a strap. For example, such a surface structure can support or simplify the welding process that is usually carried out. In particular, such a surface structure can make a so-called friction welding process considerably easier or more efficient. For example, at least one surface of the film strand can be provided with a microstructure, in particular with a microstructure that is not visible to the naked eye, in the sense of a matting. Alternatively, it can also be advantageous for certain applications if the surfaces of the film strand are designed to be very smooth, i.e. smoothed using at least one roller surface.

[0031] In a preferred embodiment of the method, it can be provided that at least some of the cutting devices for adjusting the first strip strand widths are adjusted along the direction running parallel to the strip strand widths.

[0032] Such a process allows for simple but efficient adjustment of the desired first strip width of the undrawn strips, and in conjunction with the subsequent stretching, therefore also for targeted adjustment of the desired second strip widths of the second strips or the ultimately resulting plastic strapping bands. In particular, all existing cutting devices for adjusting the first strip widths can be adjusted along the direction running parallel to the strip widths. Furthermore, in conjunction with the adjustment along the strip widths, it can also be provided that at least some of the cutting devices are adjusted away from the film strand or the first strip strands.

[0033] Furthermore, in connection with the adjustment of the cutting devices, it may also be useful that, following the stretching, actual values ​​of the second strip strand widths are recorded by means of at least one sensor device and, based on these determined actual values, the cutting devices are adjusted with regard to the respective desired target values ​​for the second strip strand widths along the direction running parallel to the strip strand widths in order to set the first strip strand widths.

[0034] This measure allows for simple and variable adjustment of the desired strip widths of the first and second strip strands, thus providing particularly flexible process control. The at least one sensor device can be formed, in particular, by an optical sensor, in particular a camera.

[0035] In order to automate the adjustment of the cutting devices along the direction of the strip strand widths, it may be expedient if the detected actual values ​​of the second strip strand widths are transmitted from the sensor device to a control device and the cutting devices are adjusted in an automated manner along the direction running parallel to the strip strand widths by the control device for setting the first strip strand widths.

[0036] This makes it possible to achieve a high degree of automation of the process.

[0037] Irrespective of this, however, a method variant may also be advantageous in which, following the stretching, actual values ​​of the second strip strand thicknesses are detected by means of at least one sensor device and in that a film strand thickness of the film strand is adjusted with respect to respectively desired target values ​​for the second strip strand thicknesses by means of the shaping device.

[0038] This measure specifically allows for simple and variable adjustment of the desired strip thicknesses of the first and second strip strands. The at least one sensor device can in turn be formed by an optical sensor, in particular a camera. In this case, the same sensor device can be used that is also used to determine the second strip strand widths, or, of course, a separate sensor device.

[0039] Also in connection with the determination of the second strip strand thicknesses, it can again be provided that the detected actual values ​​of the second strip strand thicknesses are transmitted from the sensor device to a control device and the film strand thickness is adjusted in an automated manner by controlling the forming device by means of the control device.

[0040] This measure also allows for a highly automated procedure.

[0041] In a further preferred embodiment of the method, it can be provided that a second plastic material consisting of 90 wt.% to 100 wt.% of semi-crystalline, thermoplastic, second polymer and 0 wt.% to 10 wt.% of a further component or several further components is also provided, which second plastic material is melted by means of a further extrusion device to form a second plastic melt, which second plastic melt is brought together with an upper side and / or a lower side of the first plastic melt before forming the film strand so that the second plastic melt completely covers the upper side and / or the lower side of the first plastic melt,and that the film strand is formed by means of the forming device by jointly forming the first plastic material and the second plastic material so that a multi-layer film strand is formed with a base strand layer made of the first plastic material and at least one surface strand layer made of the second plastic material connected to a top or bottom side of this base strand layer, wherein this multi-layer film strand is formed such that it consists of 50 wt.% to 95 wt.% of the first plastic material and 5 wt.% to 50 wt.% of the second plastic material.

[0042] Using this process, multi-layer plastic strapping bands can also be produced, whereby the properties of the first plastic material in the base strand layer and the properties of the second plastic material in the surface strand layer can complement each other synergistically. In particular, the multi-layer film strand can be formed in such a way that it consists of 55% to 90% by weight of the first plastic material and 10% to 45% by weight of the second plastic material. The cutting according to the process before the stretching step is particularly advantageous when forming multi-layer film or band strands, since, in contrast to cutting after stretching, delamination tendencies can be prevented. As has been proven, when forming a multi-layer film strand orIn the case of multilayered first and second tape strands, inferior first plastic material can also be used or provided as the first plastic material for the base strand layer. In particular, the at least one surface layer made of the second plastic material bonded to the base strand layer appears to provide sufficient stability to the first tape strands after cutting, particularly during the mechanically very stressful and thus process-critical stretching step.

[0043] When forming a multi-layer film strand, it can be provided, for example, that the first plastic material is provided with a proportion of 50 wt.% to 100 wt.% exclusively mechanically recycled plastic material. With such a process, the plastic strapping bands can be produced more sustainably and also more cost-effectively. In addition to the exclusively mechanically recycled plastic material, the first plastic material can also comprise up to 50 wt.% non-recycled or chemically recycled plastic material. Preferably, the first plastic material can be provided with a proportion of 80 wt.% to 100 wt.% exclusively mechanically recycled plastic material and additionally up to 20 wt.% non-recycled or chemically recycled plastic material. Regardless of the type of production or processing orthe type of provision of the components for the first plastic material, the first plastic material as specified in the claims consists of 70 wt.% to 100 wt.% of the thermoplastic, first polymer and 0 wt.% to 30 wt.% of the further component or components.

[0044] If the second plastic material is also employed or provided and used, a plastic material consisting of 70 wt.% to 98 wt.% thermoplastic, first polymer and 2 wt.% to 30 wt.% of a further component or several further components can certainly be provided as the first plastic material. For example, a plastic material with a proportion of foreign polymer, i.e. a different polymer than the first thermoplastic polymer, can then be provided as the first plastic material. For example, the proportion of foreign polymer can be from 2 wt.% to 30 wt.%. The foreign polymer can also comprise a layer-forming gas or liquid barrier plastic and / or a copolymer. However, a plastic material with a proportion of inorganic fillers can also be provided as the first plastic material, for example a proportion of inorganic fillers of 2 wt.% to 30 wt.%, in particular 5 wt.% to 30 wt.% can be provided. The inorganic filler can be formed, for example, by chalk, talc or a mixture thereof. Independently of this or additionally, a plastic material can be provided which comprises solid particles with a particle size of up to 500 pm, in particular 150 pm to 500 pm. Accordingly, the first plastic material can be filtered or have been filtered by means of a filter device with a mesh size of 500 pm during the melting process or during a melting process preceding the present method. A plastic material comprising dyes, such as printing inks, for example in a proportion of 2 wt.% to 30 wt.% can also be provided as the first plastic material. A post-consumer recycling (PCR) plastic material can preferably be provided as the first plastic material.As the first plastic material, a plastic material can also be provided which comprises components which do not melt at a melting or processing temperature during the melting of the first plastic material.

[0045] The thermoplastic first polymer can be formed, for example, from polyethylene terephthalate, polypropylene, polyethylene, polyamide, or polystyrene. In particular, the first plastic material can be a plastic material that consists entirely of mechanically recycled plastic material. The second plastic material can be a non-recycled or chemically recycled plastic material, or a high-quality, mechanically recycled plastic material, in particular a mechanically recycled post-industrial recycled plastic material.The same applies to the second plastic material: regardless of the amount of the further component or components of the second plastic material, this or these further component(s) can be formed, for example, by fillers, additives, plasticizers or by one or more other polymer(s) than the second, semi-crystalline polymer.

[0046] Unlike the first plastic material, the second plastic material can be a plastic material that does not contain any printing inks, any layer-forming gas or liquid barrier plastic, or any components that do not melt at a melting or processing temperature during the melting of the second plastic material, such as metals, wood fillers, glass (fibers), or polymers that melt at temperatures higher than the melting or processing temperature. Furthermore, the second plastic material can be a plastic material that contains a maximum proportion of 10% by weight, preferably a maximum of 5% by weight, of inorganic filler, such as chalk or talc, or also, for example, dyes for coloring plastic materials, such as masterbatch dyes.The second plastic material can be a plastic material comprising solid particles with a particle size of up to 150 μm. Accordingly, the second plastic material can be filtered or have been filtered during melting, or during a melting process preceding the present method, using a filter device with a mesh size of 150 μm. An exclusively mechanically recycled plastic material is understood to mean a plastic material that has already been used or employed at least once and in which no chemical recycling, in particular no targeted chemical reaction, was carried out during recycling. As is known, chemical recycling can occur through chain scission or depolymerization of polymers down to monomers, followed by repolymerization.In particular, the first plastic material can be post-consumer and / or post-industrial goods or plastic material.

[0047] A chemically recycled plastic material is understood to be a plastic material in which such chemical reactions have been deliberately induced during the recycling process, in particular depolymerization and subsequent repolymerization. A non-recycled plastic material is understood to be a freshly polymerized or manufactured plastic material that has not yet been used, i.e., a new plastic material or a new product.

[0048] Furthermore, when forming a multilayer film strand, it can be provided that the first plastic material is a plastic material with a melt mass flow rate (MFR) according to ISO 1133 of 2 g / 10 min to 35 g / 10 min, and that the second plastic material is a plastic material with a melt mass flow rate (MFR) according to ISO 1133 that is the same or higher than the first plastic material. This process allows, in particular, a process-stable forming of the multilayer film strand with a homogeneous and regular or uniform formation of the layers. In particular, irregularities in the layer formation can be prevented.

[0049] In principle, the first, thermoplastic polymer and the second, semi-crystalline, thermoplastic polymer can each be formed by any polymers.

[0050] Preferably, however, in the case of forming a multi-layer film strand, it can be provided that similar plastic materials are provided as the first plastic material and as the second plastic material. This measure makes it possible to produce, in particular, a film strand with a stable and permanently uniform layer structure, as well as improved adhesion of the base strand layer and the surface strand layer(s) to one another. Similar plastic materials are understood to mean plastic materials that comprise the same type of thermoplastic polymer. Thus, in this embodiment, both the first and the second plastic materials can comprise, as thermoplastic polymers, for example, a polyolefin, a polyester, or a polyamide as the first and second polymers, respectively.

[0051] Specifically, when forming a multilayer film strand, it can be provided that plastic materials are provided as the first plastic material and as the second plastic material in which a chemical formula of the thermoplastic, first polymer corresponds to a chemical formula of the semi-crystalline thermoplastic, second polymer. This process can further improve, in particular, the adhesion of the surface strand layer(s) to the base strand layer during the formation of the multilayer film strand, as well as in the first and second band strands or during the subsequent process steps of cutting and stretching, but also subsequently during the use of the multilayer plastic strapping bands.

[0052] When forming a multilayer film strand, it can be particularly useful to provide plastic materials as the first plastic material and as the second plastic material in which both the thermoplastic first polymer and the semi-crystalline thermoplastic second polymer are formed from polypropylene. Plastic materials based on polypropylene have proven particularly suitable for forming multilayer plastic strapping.

[0053] When forming a multi-layer film strand, it can also be provided that during the process step of combining the first plastic melt and the second plastic melt are combined in such a way that the second plastic melt completely covers an upper side and a lower side of the first plastic melt. This measure allows the multi-layer film strand and the first and second strap strands to be even better stabilized during processing, as well as the multi-layer plastic strapping bands during use. This is presumably because the inferior, exclusively mechanically recycled plastic material, which makes up at least 50% by weight of the first plastic material, is protected or stabilized on both the upper side and the lower side by a surface (strand) layer made of the second plastic material.In the case of forming a multilayer film strand, the first plastic material used can, for example, be a plastic material with a filler content of 2% to 30% by weight. This can, in particular, reduce the manufacturing costs of the multilayer plastic strapping, since a plastic material with a high filler content is generally more cost-effective to produce.

[0054] Specifically, when forming a multilayer film strand, the first plastic material can be a plastic material containing 2% to 30% by weight of coloring filler(s). Such fillers can be present in the first plastic material as particularly cost-effective materials. Nevertheless, for example, the second film strands, in particular, can be printed on a surface strand layer or layers after stretching, since a surface strand layer can act as a cover layer over a base strand layer connected to it, thus providing good coverage for coloring of the base layer.

[0055] For a better understanding of the invention, it is explained in more detail using the following figures.

[0056] They show in a highly simplified, schematic representation:

[0057] Fig. 1 shows an embodiment of process steps melting plastic materials, combining plastic melts and forming a film strand, in side view;

[0058] Fig. 2 shows an embodiment of a method step for cutting a film strand, in side view and in plan view from above;

[0059] Fig. 3 shows an embodiment of a method step for stretching strip strands in a side view and in a plan view from above;

[0060] Fig. 4 shows an embodiment of further process steps after stretching strip strands, in side view.

[0061] By way of introduction, it should be noted that in the variously described embodiments, identical parts are provided with identical reference symbols or component designations. The disclosures contained throughout the description can be applied analogously to identical parts with identical reference symbols or component designations. Furthermore, the positional information chosen in the description, such as top, bottom, side, etc., refers to the directly described and illustrated figure, and these positional information must be applied analogously to the new position in the event of a change in position.

[0062] The present process for the production of plastic strapping can be used in particular for the production of strapping as specified in (ÖNORM) EN 13394. The process can therefore be used for the production of plastic strapping with a tensile strength of at least 300 N / mm 2 be provided.

[0063] The method initially comprises providing at least one first plastic material 1. This at least one first plastic material 1 consists of 70 wt.% to 100 wt.% thermoplastic, first polymer and 0 wt.% to 30 wt.% of one or more further constituents, and can in particular consist of 80 wt.% to 98 wt.% thermoplastic, first polymer and 2 wt.% to 20 wt.% of one or more further constituents. Regardless of the amount of the further constituent(s) of the first plastic material 1, the same can be formed, for example, by fillers, additives, plasticizers, or by one or more other polymer(s) than the first polymer.

[0064] As schematically shown in Fig. 1, the at least one first plastic material 1 is melted by means of an extrusion device 2 to form a first plastic melt 3. In the exemplary embodiment shown in Fig. 1, a second plastic material 4 can also be provided, which second plastic material 4 can be melted by means of a further extrusion device 5 to form a second plastic melt 6. As the second plastic material 4, for example, a plastic material consisting of 90 wt.% to 100 wt.% of a semi-crystalline, thermoplastic, second polymer and 0 wt.% to 10 wt.% of one or more further components can be provided. Regardless of the amount of the further component or components of the second plastic material 4,These can be formed, for example, by fillers, additives, plasticizers, or even by one or more other polymers than the semi-crystalline, second polymer. However, contrary to the exemplary embodiments shown in Fig. 1 and the following Figs. 2 to 4, the method can of course also be carried out using only the first plastic material 1 alone. The second plastic material 4 can be processed together with the first plastic material 1 to form a multi-layer plastic strapping band, as will be described in more detail below. If only the first plastic material 1 is provided and processed, a plastic strapping band with only one layer will of course result or be produced using the method.

[0065] If a second plastic material 4 is also provided and processed by the method, as will be described below with reference to the exemplary embodiments according to Figs. 1 to 4, the first plastic material 1 can, for example, be provided with a proportion of 50 wt.% to 100 wt.% of exclusively mechanically recycled plastic material. In addition to the exclusively mechanically recycled plastic material, the first plastic material 1 can also comprise up to 50 wt.% of non-recycled or chemically recycled plastic material. Preferably, the first plastic material 1 can be provided with a proportion of 80 wt.% to 100 wt.% of exclusively mechanically recycled plastic material and additionally up to 20 wt.% of non-recycled or chemically recycled plastic material.The thermoplastic first polymer can be formed, for example, from polyethylene terephthalate, polypropylene, polyethylene, polyamide, or polystyrene. In particular, the first plastic material 1 can be a plastic material that consists entirely of mechanically recycled plastic material.

[0066] If the second plastic material 4 is also employed or provided and used, a plastic material consisting of 70 wt.% to 98 wt.% thermoplastic, first polymer and 2 wt.% to 30 wt.% of a further component or several further components can certainly be provided as the first plastic material 1. For example, a plastic material with a proportion of foreign polymer, i.e. a different polymer than the first thermoplastic polymer, can be provided as the first plastic material 1. For example, the proportion of foreign polymer can be from 2 wt.% to 30 wt.%. The foreign polymer can also comprise a layer-forming gas or liquid barrier plastic and / or a copolymer. However, a plastic material with a proportion of inorganic fillers can also be provided as the first plastic material 1, for example a proportion of inorganic fillers of 2 wt.% to 30 wt.%, in particular 5 wt.% to 30 wt.% can be provided. The inorganic filler can be formed, for example, by chalk, talc or a mixture thereof. Independently of this or additionally, a plastic material can be provided which comprises solid particles with a particle size of up to 500 pm, in particular 150 pm to 500 pm. Accordingly, the first plastic material 1 can be or have been filtered by means of a filter device with a mesh size of 500 pm during the melting process or during a melting process preceding the present method. A plastic material comprising dyes, such as printing inks, in a proportion of, for example, 2 wt.% to 30 wt.% can also be provided as the first plastic material 1. A post-consumer recycling (PCR) plastic material can preferably be provided as the first plastic material 1.As the first plastic material 1, a plastic material can also be provided which comprises components which do not melt at a melting or processing temperature during the melting of the first plastic material.

[0067] As the second plastic material 4, a non-recycled or chemically recycled plastic material, or also a high-quality, mechanically recycled plastic material, in particular a mechanically recycled post-industrial-recycling plastic material, can be provided.

[0068] Unlike the first plastic material 1, the second plastic material 4 can be a plastic material that does not contain any printing inks, any layer-forming gas or liquid barrier plastic, or any components that do not melt at a melting or processing temperature during the melting of the second plastic material, such as metals, wood fillers, glass (fibers), or polymers that melt at temperatures higher than the melting or processing temperature. Furthermore, the second plastic material 4 can be a plastic material that contains a maximum proportion of 10% by weight, preferably a maximum of 5% by weight, of inorganic filler, such as chalk or talc, or also, for example, dyes for coloring plastic materials, such as master batch dyes.As the second plastic material 4, a plastic material can be provided which comprises solid particles with a particle size of up to 150 pm. Accordingly, the second plastic material 4 can be filtered or have been filtered during the melting process, or during a melting process preceding the present method, using a filter device with a mesh size of 150 pm. If a second plastic material 4 is used, a plastic material with a melt mass flow rate (MFR) according to ISO 1133 of 2 g / 10 min to 35 g / 10 min can be provided as the first plastic material 1, and then a plastic material with a melt mass flow rate (MFR) according to ISO 1133 that is the same as or higher than the first plastic material can be provided as the second plastic material 4.

[0069] Preferably, in the case of processing a second plastic material 4, it can be provided that plastic materials of the same type are provided as the first plastic material 1 and as the second plastic material 4. In particular, in the case of an intended additional processing of the second plastic material 4, plastic materials can be provided as the first plastic material 1 and as the second plastic material 4 in which a chemical molecular formula of the thermoplastic, first polymer corresponds to a chemical molecular formula of the semi-crystalline, thermoplastic, second polymer. In particular, plastic materials can then be provided as the first plastic material 1 and as the second plastic material 4 in which both the thermoplastic, first polymer and the semi-crystalline, thermoplastic, second polymer are formed from polypropylene.

[0070] In the case of additional processing of the second plastic material 4, a plastic material with a filler content of 2 wt.% to 30 wt.% can be provided as the first plastic material 1. In this case, a plastic material with a color-imparting filler content of 2 wt.% to 30 wt.% can also be provided as the first plastic material 1.

[0071] Regardless of whether only the first plastic material 1 or also the second plastic material 4 is processed by means of the method, a film strand 7 is subsequently formed, as can be seen from Fig. 1. This takes place by feeding at least the first plastic melt 3 in a material transport direction 8 to a forming device 9. If only the first plastic material 1 is processed, this first plastic material 1 is formed into the film strand 7 by means of the forming device 9. According to the embodiment shown in Fig. 1, the second plastic material 4 shown here can also be fed to the forming device 9 together with the first plastic material 1, so that the film strand 7 is formed from both plastic materials 1, 4.In this case, the procedure can be such that the second plastic melt 6 is brought together with an upper side 10 and / or a lower side 11 of the first plastic melt 3 before the film strand 7 is formed, such that the second plastic melt 6 completely covers the upper side 10 and / or the lower side 11 of the first plastic melt 3. In particular, it can also be provided that during the process step of bringing together the first plastic melt 3 and the second plastic melt 6 are brought together in such a way that the second plastic melt 6 completely covers the upper side 10 and the lower side 11 of the first plastic melt 3, as is also shown in the exemplary embodiment according to Fig. 1.

[0072] If the first plastic material 1 and the second plastic material 4 are to be formed into a multi-layer film strand 7, the first plastic melt 3 and the second plastic melt 6 can be combined using several methods known per se. For example, the two plastic melts 3, 6 can be combined using a so-called coextrusion box 12, also referred to as a feed block, as roughly schematically illustrated in Fig. 1, and after being combined, they can be output via a film extrusion tool 13 with a slot die and fed to the shaping device 9. As an alternative to the embodiment outlined in Fig. 1, other known methods for combining the plastic melts 3, 6 are of course also conceivable, such as using a so-called coextrusion tool or multi-layer dies, the use of several extrusion tools, each with a nozzle, and so on.

[0073] Subsequently, according to the embodiment shown in Fig. 1, the film strand 7 can be formed by means of the forming device 9 by jointly forming the first plastic material 1 and the second plastic material 4.

[0074] As a result, as shown in Fig. 1, a multi-layer film strand 7 can be formed with a base strand layer 14 made of the first plastic material 1 and at least one surface strand layer 15 made of the second plastic material 4 connected to a top side 15 or bottom side 16 of this base strand layer 14. In the exemplary embodiment shown in Fig. 1, it can be provided, as shown, that a three-layer film strand 7 is formed with a base strand layer 14 made of the first plastic material 1 and surface strand layers 17 made of the second plastic material 4 connected to a top side 15 and bottom side 16 of this base strand layer 14. Such a multi-layer film strand 7 can, for example, be formed such that it consists of 50 wt.% to 95 wt.% of the first plastic material 1 and 5 wt.% to 50 wt.% of the second plastic material 4, in particular of 55 wt.% to 90 wt.% of the first plastic material 1 and 10 wt.% to 45 wt.% of the second plastic material 4.

[0075] As further illustrated in Fig. 1, the forming of the film strand 7 can be carried out by means of the forming device 9, which comprises rotatably mounted rollers 18, 19, 20, 21. The forming device 9 can therefore be formed, as is known per se, by a rolling mill, also referred to as a calender or smoothing mill, as is also shown in the exemplary embodiment illustrated in Fig. 1. In this case, a film strand thickness 22 of the film strand 7 can be specifically adjusted, for example, as is known per se by passing the first plastic melt 3 and optionally also the second plastic melt 6, as shown in the exemplary embodiment, through a gap 23 between adjacent rollers 19, 20. For this purpose, at least one of the adjacent rollers 19, 20 can be adjustable to change the film strand thickness 22. A thickness of the film strand 7 after forming or the thickness shown in Fig.The film strand thickness 22 illustrated in Figure 1 can be set, for example, to 0.6 mm to 3.8 mm, preferably 0.8 mm to 2.8 mm.

[0076] In addition, at least the first plastic material 1 is cooled, and in the embodiment shown in Fig. 1, the second plastic material 4 is also cooled, for the subsequent process step of dividing the film strand 7, shown in Fig. 2. The cooling of the film strand 7 to a desired target temperature for the subsequent dividing step can take place exclusively by means of the shaping device 9 itself. For this purpose, the first plastic melt 3 and optionally also the second plastic melt 6 can be cooled, for example, by means of at least one temperature-controlled roller 18, 21 or roller with a temperature-controlled roller surface of the shaping device 9. For example, at least one roller 18, 21 of the shaping device can be subjected to a coolant.Additionally and / or alternatively, a separate cooling of the plastic melt(s) 3, 6 can also be carried out before forming the film strand 7 and / or an additional, separate cooling of the film strand 7 after forming the film strand 7 can be carried out by means of an additional cooling device, such as a water bath, not shown in Fig. 1. Preferably, the film strand 7 can be cooled to a temperature of 75°C to 135°C, in particular 80°C to 130°C, for the subsequent process step of cutting.

[0077] Furthermore, during the process step of forming the film strand 7, at least one surface 24 of the film strand 7 can be structured by means of at least one structured roller surface 25. For example, the at least one surface 24 of the film strand 7 can be provided with a microstructure, in particular with a microstructure not visible to the naked eye in the sense of a matting. Alternatively, for certain applications, it can also be advantageous if the surfaces 24 of the film strand 7 are designed to be very smooth, i.e., even smoothed by means of at least one roller surface.

[0078] Fig. 2 illustrates the subsequent method step of dividing the film strand 7, wherein in Fig. 2, the same reference numerals are used for the same parts / elements as in the preceding Fig. 1. To avoid unnecessary repetition, reference is made to the detailed description in the preceding Fig. 1.

[0079] As can be seen from Fig. 2, the film strand 7 is divided or cut along the material transport direction 8 into first strip strands 26 with first strip strand widths 27 and first strip strand thicknesses 28 by means of cutting devices 29. The film strand 7 can be divided, for example, by means of round blades that are designed as knife blades, non-rotatable or rotatable along or against the material transport direction, or also by means of cutting devices 29 designed as lasers or water jets. The number of cutting devices 29 or strip strands 26 in the embodiment according to Fig. 2 is of course only an example, and the respective number of cutting devices 29 or strip strands 26 can of course be varied. In addition to the cutting devices 29 shown in Fig. 2, if necessary or desired, further cutting or cutting devices can also be provided in the edge regions of the film strand 7 or the outer strip strands 26Cutting devices are provided to trim the edges of the outer band strands 26 or to make them as flat as possible.

[0080] The method can further provide for at least some of the cutting devices 29 to be adjusted along a direction 30 running parallel to the strip strand widths 27 for setting the first strip strand widths 27, as is illustrated in Fig. 2 by the corresponding double arrows. With this measure, in particular the first strip strand widths 27 can be varied or adjusted as required or desired. For this purpose, the cutting devices 29 can, for example, be adjustably mounted or held on a holding strip 31 aligned parallel to the direction 30 of the strip strand widths 27, as shown schematically in Fig. 2. In particular, all existing cutting devices 29 can be adjusted along the direction 30 running parallel to the strip strand widths 27 for setting the first strip strand widths 27.In addition, in connection with the adjustment along the direction 30 of the strip strand widths 27, it can also be provided that at least some of the cutting devices 29 are adjusted away from the film strand 7 or the first strip strands 26.

[0081] Following the cutting process step, as illustrated in Fig. 3, the first strip strands 26 are stretched in the material transport direction 8 by means of a stretching device 32 to form second strip strands 33 with second strip strand widths 34 and second strip strand thicknesses 35. In Fig. 3, the same reference numerals or component designations are used for the same parts as in the preceding Figs. 1 and 2. To avoid unnecessary repetition, reference is made to the detailed description in the preceding Figs. 1 and 2.

[0082] As is known per se, the stretching or drawing device 32 can be formed by a so-called stretching unit, in which the first ribbon strands 26 are pulled or stretched into the catches of the second ribbon strands 33 by means of successively faster rotating stretching or drawing devices 36, 37 in the transport direction 8. This achieves the desired preferential orientation of the macromolecule chains of the plastic material 1, or in the case of multi-layer ribbon strands 26, 33 of the plastic materials 1, 4. Depending on the plastic material(s) 1, 4 used, the ribbon strands 26, 33 can be stretched with stretching ratios of 1:4 to 1:20. Upstream of the stretching device 32 or, if appropriate, between drawing devices 36, 37 of the stretching device 32 orAs is known per se, at least one temperature control device can also be arranged in the stretching unit in order to allow targeted temperature control of the plastic material 1 or the plastic materials 1, 4 for the stretching process. Such temperature control devices, such as water baths, cooling or heating air, or infrared radiators, are generally known from the prior art and are not shown in detail in Fig. 3. The stretching or elongation of the first strip strands 26 to form the second strip strands 33 is naturally accompanied by a deformation, in particular by a cross-sectional reduction, so that the second strip strand widths 34 and thicknesses 35 are smaller than the first strip strand widths 27 and thicknesses 28, as can also be seen from Fig. 3. By stretching, the second strip strand thicknesses 35 can be set, for example, to a value of 0.15 mm to 1.8 mm, preferably from 0.2 mm to 1.4 mm.The second band strand widths 34 can be adjusted to a value of 3 mm to 40 mm, in particular 4 mm to 36 mm, by cutting and subsequent stretching, wherein the second band strand widths 34 can be selected primarily according to the respective intended use for the plastic strapping bands.

[0083] As best seen by looking at Fig. 2 and Fig. 3 together, the method can be provided that, following the stretching, actual values ​​of the second strip strand widths 34 are recorded by means of at least one sensor device 38 and, based on these determined actual values, the cutting devices 29 are adjusted with respect to the respective desired target values ​​for the second strip strand widths 34 along the direction 30 running parallel to the strip strand widths 34 for setting the first strip strand widths 27. The sensor device 38 can be formed by an optical sensor device, in particular by a camera.

[0084] As can also best be seen by looking at Fig. 2 and Fig. 3 together, it can also be provided that the recorded actual values ​​of the second strip strand widths 34 are transmitted from the sensor device 38 to a control device 39 and the cutting devices 29 are adjusted in an automated manner along the direction 30 running parallel to the strip strand widths 27, 34 by the control device 39 to set the first strip strand widths 27. A signaling connection between the sensor device 38, Fig. 3, and the cutting devices 29, Fig. 2, with the control device 39 is indicated in Figs. 2 and 3 by the dashed lines.

[0085] As can best be seen by looking at Fig. 1 together with Fig. 3, in the method, following stretching, actual values ​​of the second strip strand thicknesses 35 can be recorded by means of at least one sensor device 40, and by means of the shaping device 9, one or the film strand thickness 22 of the film strand 7, and thus also the first strip strand widths 27 of the first strip strands 26 before stretching, can be adjusted with regard to respective desired target values ​​for the second strip strand thicknesses 35. The at least one sensor device 40 for determining the actual values ​​of the second strip strand thicknesses 35 can in turn be formed by an optical sensor, in particular a camera. In this case, essentially the same sensor device 38 can be used which is also used to determine the second strip strand widths 34, or of course also a separate sensor device 40, as illustrated in Fig. 3.

[0086] Also, in connection with the detection of the actual values ​​of the second strip strand thicknesses 35, it can be provided that these detected actual values ​​of the second strip strand thicknesses 35 are transmitted from the sensor device 40 to a control device 39, and the film strand thickness 22 is adjusted in an automated manner by controlling the shaping device 9 by means of the control device 39. The signal connections required for this purpose between the sensor device 40 and the shaping device 9 and the control device 39 are indicated by dashed lines in Fig. 1 and Fig. 3.

[0087] Fig. 4 illustrates further possible steps of the process following stretching. In Fig. 4, the same reference numerals or component designations are used for identical parts as in the preceding Figs. 1 to 3. To avoid unnecessary repetition, reference is made to the detailed description in the preceding Figs. 1 to 3.

[0088] For example, it can be provided that the second strip strands 33 or one or both of their surfaces are subjected to a surface treatment by means of one or more surface treatment devices 41. Such a surface treatment can, for example, comprise coating the surface(s), such as with a wax or other coating agent. However, a surface treatment can also comprise, for example, irradiation or plasma treatment of the surface(s) of the second strip strands 33.

[0089] Furthermore, one or both surfaces of the second strip strands 33 can be embossed, for example, by means of an embossing device 42. This may be done in addition to the previously mentioned structuring by means of the shaping device 9. Finally, the second strip strands 33 can be finished, as also illustrated in Fig. 4, for example, wound onto the winding device 43 shown in Fig. 4, often also referred to as a spooler, and thus prepared for transport.

[0090] Finally, for the sake of completeness, it should be mentioned again that the method shown in Figs. 1 to 4, contrary to the embodiment shown here with multi-layer, in particular three-layer film strand 7, first tape strands 26 and second tape strands 33, can of course also be carried out with only single-layer film strand 7, and accordingly also single-layer first and second tape strands 26, 33, which each consist only of the first plastic material 1.

[0091] The embodiments show possible embodiments, whereby it should be noted at this point that the invention is not limited to the specifically illustrated embodiments thereof, but rather various combinations of the individual embodiments with each other are also possible and this possibility of variation lies within the skill of the person skilled in the art in this technical field due to the teaching of technical action by means of the objective invention.

[0092] The scope of protection is determined by the claims. However, the description and drawings must be used to interpret the claims. Individual features or combinations of features from the various embodiments shown and described may represent independent inventive solutions. The problem underlying these independent inventive solutions can be derived from the description.

[0093] All information on value ranges in this description is to be understood as including any and all sub-ranges thereof, e.g. the information 1 to 10 is to be understood as including all sub-ranges starting from the lower limit of 1 and the upper limit of 10, ie all sub-ranges begin with a lower limit of 1 or greater and end with an upper limit of 10 or less, e.g. 1 to 1.7, or 3.2 to 8.1, or 5.5 to 10.

[0094] For the sake of clarity, it should be noted that some elements have been shown not to scale and / or enlarged and / or reduced in size to improve understanding of the structure.

[0095] Plastic material 32 stretching device

[0096] Extrusion device 33 Strip strand plastic melt 34 Strip strand width

[0097] Plastic material 35 strip thickness

[0098] Extrusion device 36 Pulling device plastic melt 37 Pulling device

[0099] Film strand 38 sensor device

[0100] Material transport direction 39 control device

[0101] Shaping device 40 Sensor device top side 41 Surface treatment device

[0102] Bottom tung

[0103] Coextrusion box 42 embossing device

[0104] Film extrusion tool 43 winding device

[0105] Base strand layer

[0106] Top

[0107] bottom

[0108] Surface strand layer

[0109] roller

[0110] roller

[0111] roller

[0112] roller

[0113] Film strand thickness

[0114] gap

[0115] surface

[0116] Roller surface

[0117] Band strand

[0118] Band width

[0119] Strip thickness

[0120] Cutting device

[0121] Direction

[0122] retaining strips

Claims

Patent claims 1. A process for producing plastic strapping, comprising the following process steps, - Providing at least one first plastic material (1) consisting of 70 wt.% to 100 wt.% thermoplastic, first polymer and 0 wt.% to 30 wt.% of one or more further components, - subsequently melting the first plastic material (1) by means of an extrusion device (2) to form a first plastic melt (3), - subsequently forming a film strand (7) by feeding at least the first plastic melt (3) in a material transport direction (8) to a forming device (9), and cooling the first plastic material (1), - subsequently cutting the film strand (7) along the material transport direction (8) into first strip strands (26) with first strip strand widths (27) and first strip strand thicknesses (28) by means of cutting devices (29), - subsequently stretching in the material transport direction (8) of the first strip strands (26) by means of a stretching device (32) to form second strip strands (33) with second strip strand widths (34) and second strip strand thicknesses (35).

2. Method according to claim 1, characterized in that the film strand (7) is cooled to a temperature of 75 °C to 135 °C for the cutting step.

3. Method according to claim 1 or 2, characterized in that the forming of the film strand (7) is carried out by means of the forming device (9), which comprises rotatably mounted rollers (18, 19, 20, 21).

4. Method according to claim 3, characterized in that in the course of the method step of forming the film strand (7), at least one surface (24) of the film strand (7) is structured by means of at least one structured roller surface (25).

5. Method according to one of the preceding claims, characterized in that at least some of the cutting devices (29) for adjusting the first Strip widths (27) are adjusted along a direction (30) running parallel to the strip widths (27, 34).

6. Method according to claim 5, characterized in that following the stretching, actual values ​​of the second strip strand widths (34) are detected by means of at least one sensor device (38) and, based on these determined actual values, the cutting devices (29) are adjusted with respect to respectively desired target values ​​for the second strip strand widths (34) along the direction (30) running parallel to the strip strand widths (27, 34) for setting the first strip strand widths (27).

7. Method according to claim 6, characterized in that the detected actual values ​​of the second strip strand widths (34) are transmitted from the sensor device (38) to a control device (39) and the cutting devices (29) are adjusted in an automated manner along the direction (30) running parallel to the strip strand widths (27, 34) by the control device (39) for setting the first strip strand widths (27).

8. Method according to one of the preceding claims, characterized in that following the stretching, actual values ​​of the second strip strand thicknesses (35) are detected by means of at least one sensor device (40), and in that a film strand thickness (22) of the film strand (7) is adjusted with respect to respectively desired target values ​​for the second strip strand thicknesses (35) by means of the shaping device (9).

9. Method according to claim 8, characterized in that the detected actual values ​​of the second strip strand thicknesses (35) are transmitted from the sensor device (40) to a control device (39) and the film strand thickness (22) is adjusted in an automated manner by controlling the shaping device (9) by means of the control device (39).

10. Method according to one of the preceding claims, characterized in that a second plastic material (4) consisting of 90 wt.% to 100 wt.% of semi-crystalline, thermoplastic, second polymer and 0 wt.% to 10 wt.% of a further component or several further components is also provided, which second Plastic material (4) is melted by means of a further extrusion device (5) to form a second plastic melt (6), which second plastic melt (6) is brought together with an upper side (10) and / or a lower side (11) of the first plastic melt (3) before forming the film strand (7) so that the second plastic melt (6) completely covers the upper side (10) and / or the lower side (11) of the first plastic melt (3), and that the film strand (7) is formed by means of the forming device (9) by jointly forming the first plastic material (1) and the second plastic material (4), so that a multi-layer film strand (7) is formed with a base strand layer (12) made of the first plastic material (1) and at least one surface strand layer (15) made of the second plastic material (4) connected to an upper side (13) or lower side (14) of this base strand layer (12),wherein said multi-layer film strand (7) is formed such that it consists of 50 wt.% to 95 wt.% of the first plastic material (1) and 5 wt.% to 50 wt.% of the second plastic material (4).

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