PLASTIC STRAP AND PROCESS FOR MANUFACTURING PLASTIC STRAPS

Abstract

A plastic strap includes a semi-crystalline thermoplastic material which is monoaxially or predominantly monoaxially stretched during a process for manufacturing the plastic strap. At least one surface of the plastic strap is provided with a microstructure, in particular a microstructure that cannot be optically resolved by the human eye.

Claims

1-21. (canceled)

22. A method for production of plastic straps (2), comprising: making available a semi-crystalline, thermoplastic plastic material (3), melting the plastic material (3), and extrusion of the melted plastic material (3) to form at least one plastic strand (7), by means of an extrusion apparatus (5), cooling of the extruded plastic strand (7), monoaxial or predominantly monoaxial stretching of the cooled plastic strand (7) to form a stretched strand (15), by means of at least one elongation unit (14), which stretched strand (15) has two surfaces (22), which are spaced apart from one another by a thickness (21) of the stretched strand (15), wherein at least one surface (22) of the stretched strand (15) is provided with a microstructure (24), by means of a surface treatment apparatus (23), in particular with a microstructure (24) that cannot be optically resolved by the naked human eye, and wherein an embossing apparatus (25) comprising at least one embossing roll (26) is used as the surface treatment apparatus (23), wherein the at least one surface (22) of the stretched strand (15) is provided with the microstructure (24) by means of at least one embossing roll (26), having a surface profile (27) with an average roughness R.sub.a between 2 m and 15 m.

23. The method according to claim 22, wherein the at least one surface (22) of the stretched strand (15) is provided with the microstructure (24) by means of at least one embossing roll (26), having a surface profile (27) with an averaged roughness depth R.sub.z between 10 m and 100 m.

24. The method according to claim 22, wherein the at least one surface (22) of the stretched strand (15) is provided with the microstructure (24) by means of at least one embossing roll (26), having a surface profile (27) with an average groove width RS.sub.m between 50 m and 400 m.

25. The method according to claim 22, wherein the at least one surface (22) of the stretched strand (15) is continuously provided with the microstructure (24).

26. The method according to claim 22, wherein both surfaces (22) of the stretched strand (15) are each provided with a microstructure (24).

27. The method according to claim 26, wherein the stretched strand (15) is passed through between at least two embossing rolls (26) that lie opposite one another and rotate in opposite directions, each having microstructured embossing surfaces (28), and wherein both surfaces (22) of the stretched strand (15) are each provided with a microstructure (24) by means of the two embossing rolls (26).

28. The method according to claim 22, wherein the at least one surface (22) of the stretched strand (15) is provided with a microstructure (24) at a temperature of the stretched strand (15) between 60 C. and 120 C.

29. The method according to claim 28, wherein the stretched strand (15) is tempered by means of at least one embossing roll (26) and/or by means of a tempering apparatus (29) that precedes the at least one embossing roll (26).

30. A plastic strap (2) having a longitudinal expanse (35) and, normal to it, a width expanse (36) and a strip thickness (37), which longitudinal expanse (35) and width expanse (36) form two strip surfaces (38) that are spaced apart from one another by the strip thickness (37), wherein the plastic strap (2) comprises a semi-crystalline thermoplastic plastic material (3), which plastic material (3) is stretched monoaxially or predominantly monoaxially in the direction of the longitudinal expanse (35), and wherein at least one of the strip surfaces (38) of the plastic strap (2) is provided with a microstructure (24), in particular with a microstructure (24) that cannot be resolved optically by the human eye, and wherein the microstructure (24) is formed by an embossed microstructure, wherein the at least one strip surface (38) of the plastic strap (2) has an average roughness R.sub.a between 0.1 m and 2.6 m in the region of the microstructure (24).

31. The plastic strap according to claim 30, wherein the microstructure (24) is formed by a random structure.

32. The plastic strap according to claim 30, wherein the at least one strip surface (38) of the plastic strap (2) has an averaged roughness depth R.sub.z between 1 m and 15 m in the region of the microstructure (24).

33. The plastic strap according to claim 30, wherein the at least one strip surface (38) of the plastic strap (2) has an average groove width RS.sub.m between 50 m and 400 m in the region of the microstructure (24).

34. The plastic strap according to claim 30, wherein the at least one strip surface (38) of the plastic strap (2) is continuously provided with the microstructure (24).

35. The plastic strap according to claim 30, wherein both strip surfaces (38) of the plastic strap (2) are each provided with a microstructure (24).

36. The plastic strap according to claim 30, wherein a stretching ratio of the plastic material (3) amounts to between 2 and 20.

37. The plastic strap according to claim 30, wherein it has a tensile strength between 200 N/mm.sup.2 and 600 N/mm.sup.2.

Description

[0071] For a better understanding of the invention, it will be explained in greater detail using the following figures.

[0072] These show, each in a greatly simplified, schematic representation:

[0073] FIG. 1 A schematic representation of a system for production of a plastic strap, which illustrates the method for production;

[0074] FIG. 2 As a detail, a plastic strap in a top view of a strip surface provided with a microstructure.

[0075] As an introduction, it should be stated that in the different embodiments described, the same parts are provided with the same reference symbols or the same component designations, wherein disclosures contained in the description as a whole can be applied analogously to the same parts having the same reference symbols or component designations. Also, the position information selected in the description, such as at the top, at the bottom, at the side, etc., for example, relates only to the figure being directly described and shown, and this position information must be applied analogously to a new position in the case of a change in position.

[0076] To avoid repetition, individual embodiments are not listed more explicitly or illustrated graphically in the following description. In this regard, reference is made, in each instance, to the preceding description. In the description as a whole, the term stretching is used synonymously with the term elongation.

[0077] In FIG. 1, an apparatus 1 for production and a method for production of plastic straps 2 are illustrated schematically. At the beginning of the method, a semi-crystalline thermoplastic plastic material 3 is made available.

[0078] In this regard, in principle any semi-crystalline thermoplastic plastic material 3 can be made available, which can be thermoplastically rough-formed, stretched, and surface-treated. For example, it can be provided that a plastic material 3 from the group of polyolefins, polyesters, polyamides or from mixtures or blends of these polymer materials is made available. The polymer materials last mentioned are suitable, to a particular degree, for production of straps, since they are very well suited for an extrusion process, for one thing, and furthermore can also be processed, by means of stretching, to produce plastic straps 2 that have a high tensile strength.

[0079] Specifically, it can be provided that a polyester, in particular polyethylene terephthalate, is made available as the plastic material 3. Polyesters are particularly well suited for production of straps having excellent mechanical properties, such as high tensile strengths and great rigidity, for example. This in turn has a positive effect on carrying out strapping, in particular on strapping or encircling carried out by machine, and tensioning during a strapping procedure.

[0080] As is shown schematically in FIG. 1, the semi-crystalline thermoplastic plastic material can be fed or metered to an extrusion apparatus 5 by way of a feed apparatus or metering apparatus 4. In this regard, fillers and additives, in particular pigments, anti-oxidants and/or other processing aids can also be mixed into the plastic material 3. In the extrusion apparatus 5, for example a screw extruder, the thermoplastic plastic material 3 is then melted, and extruded by way of an extrusion tool 6 disposed on or attached to the extrusion apparatus 5.

[0081] For this purpose, it can be provided, for example, that the extrusion tool 6 has one or more die(s), in particular dies having a slot-shaped cross-section, through which slotted die(s) the melted plastic material is pressed or extruded to form a strip-shaped plastic strand 7 or to form multiple strip-shaped plastic strands 7. If multiple strip-shaped or band-shaped plastic strands 7 are extruded, these can run through the subsequent method steps jointly. Alternatively, it can also provided that the extrusion tool 6 comprises a die or slotted die having an expanded cross-section width, in other words what is called a broad-slot die, so that a film-shaped plastic strand 7 having a great width expanse is extruded. After carrying out further method steps, such a film-shaped plastic strand 7 can be separated into band-shaped or strip-shaped strands or strips in a finishing step, along the longitudinal orientation of the plastic strand 7, in each instance, so as to produce straps having suitable dimensions or width expanses. In any case, at least one extruded plastic strand 7 is produced by extrusion by means of the extrusion apparatus 5, the rough shape or rough cross-sectional geometry of which can be established in terms of essential features by way of the die(s) on the extrusion tool 6.

[0082] As is furthermore shown in FIG. 1, cooling of the extruded plastic strand 7 can be carried out after extrusion. In this way, in particular, the rough shape or cross-sectional geometry of the extruded plastic strand 7 can be preserved. In principle, passive cooling of the extruded plastic strand 7 by means of ambient air can be carried out for this purpose. If necessary, an air stream can also be used for cooling. Preferably, the extruded plastic strand 7 is passed through a cooling apparatus 9 in the guidance or transport direction 8 for efficient cooling, as shown in FIG. 1. The cooling apparatus 9 shown can be formed by a water bath 10, for example. The cooling apparatus 9 can contain water at a specific temperature, for example, through which the extruded plastic strand 7 is passed. A temperature of the plastic strand 7 after cooling can be influenced or controlled by a specific length 11 of the cooling apparatus 9, for example at a given temperature of the cooling liquid or of the water of the cooling apparatus 9.

[0083] A pull-off apparatus 12 can be disposed behind the cooling apparatus 9, for pulling off or guiding the plastic strand 7 in the transport direction 8. As shown in FIG. 1, such a pull-off apparatus 12 can comprise multiple roller elements 13 that rotate at a specific angular velocity, and form a godet trio, for example. In principle, it can also be provided, in this regard, that one or more roller element(s) are structured so that they can be tempered, so that the plastic strand 7 can be heated or cooled for the subsequent further processing, in particular the elongation procedure. For this purpose, the roller element 13 can be tempered by means of tempering liquids, for example, or electrically. Alternatively, other means for tempering a plastic strand 7, such as sprinkler apparatuses, immersion baths or infrared radiators, for example, can also be provided for heating or cooling the plastic strand 7.

[0084] The elongation procedure or stretching of the plastic strand 7 to form a stretched strand 15 is carried out by means of an elongation unit 14, as shown in FIG. 1. For this purpose, a further transport or pull-off apparatus 17 having roller elements 13 can be disposed along an elongation segment 16 of the elongation unit 14. All of the roller elements 13 shown in FIG. 1 can rotate at different angular velocities, in each instance, when carrying out the method, to respectively establish a pull-off speed or displacement speed for the plastic strand 7. With regard to the angular velocity during rotation, of course, a respective circumference of the individual roller elements 13 must also be taken into consideration in this regard. For a better illustration, all the roller elements 13 in FIG. 1 have the same circumference. This can hold true or also not hold true in the case of apparatuses 1 for production of plastic straps 2.

[0085] In the exemplary embodiment shown in FIG. 1, it can be provided that the roller elements 13 of the pull-off apparatus 17 rotate at a higher angular velocity than the roller elements 13 of the preceding pull-off apparatus 12. In this way, a pull-off speed or transport speed of the further pull-off apparatus 17 is selected to be greater than the pull-off speed for the plastic strand 7 of the preceding pull-off apparatus 12, and the plastic strand 7 is stretched along a main stretching direction 18, i.e. pulled to become longer.

[0086] Furthermore, an additional transport or pull-off apparatus 19 can be provided at the end of the elongation unit 14 or of the elongation segment 16. In the case of this additional pull-off apparatus 19, an even greater pull-off speed for the plastic strand 7 than the pull-off speed of the pull-off apparatus 17, which is disposed ahead of it with reference to the transport direction 8, can be provided during operation of the apparatus 1. In this way, the plastic strand 7 can be pulled to become longer or stretched once again between the further pull-off apparatus 17 and the additional pull-off apparatus 19. In total, the plastic strand 7 is elongated monoaxially or at least predominantly monoaxially in the elongation unit 14 or along the elongation segment 16, along the main stretching direction 18, to produce a stretched strand 15.

[0087] An elongation ratio for the plastic material 3 can be selected from a range between 2 and 20 in the case of the stretched strand 15. This with reference to the extruded plastic strand 7 before the stretching procedure. During the course of the stretching procedure, a thickness of the plastic strand 7 is therefore also reduced by means of the stretching. Preferably, a stretching ratio for the plastic material 3 is selected from a range between 3 and 15, in particular between 4 and 12. As is evident from FIG. 1, stretching can be carried out predominantly along the main stretching direction 18. However, slight stretching or elongation transverse to the main stretching direction 18 cannot be completely excluded, in this regard, and for this reason a stretched strand 15 can be stretched predominantly monoaxially.

[0088] The exemplary embodiment of an elongation unit 14 shown in FIG. 1 only serves as a schematic illustration, and of course such elongation units 14 can also have further elements and apparatus for carrying out or influencing and controlling the stretching procedure. For example, it can be provided, to better carry out an elongation or a stretching procedure, that or multiple heating apparatuses 20 are provided along the elongation segment 16. A plastic strand 7 can be brought to a processing temperature that is advantageous for the stretching procedure, in each instance, by means of such heating apparatuses 20, wherein an advantageous processing temperature depends, among other things, on the plastic material 3 used or made available, in each instance.

[0089] After stretching, a stretched strand 15 is present, which has an increased risk for what is called splitting, in other words separation or fraying along the main stretching direction 18, due to the preferential orientation of the macromolecules in the main stretching direction 18 that has now been introduced into the plastic material. The stretched strand 15 has two surfaces 22, which are spaced apart from one another by a thickness 21 of the stretched strand 15.

[0090] At least one of these surfaces 22 of the stretched strand 15 is subsequently provided with a microstructure 24 subsequent to stretching, by means of a surface treatment apparatus 23, as is also evident from FIG. 1. In particular, it can be provided that the microstructure 24 cannot be optically resolved with the naked human eye, in other words that the individual structural elements of the microstructure as such are not clearly recognizable as such with the naked human eye.

[0091] A surface treatment apparatus 23 can be formed, for example, by means of a laser treatment apparatus, by means of which the microstructure 24 or the micro-pattern can be introduced into the at least one surface 22 of the stretched strand 15. This can take place, for example, by means of partial ablation, i.e. in certain sections, in the micrometer range, or also by melting, in certain sections, of the at least one surface 22, in the micrometer range. Alternatively, however, a surface treatment apparatus 23 in the manner of a sand-blasting apparatus, for processing of the at least one surface 22 of the stretched strand 15 with solid particles, is also conceivable for providing the at least one surface 22 of the stretched strand 15 with a microstructure 24. In this regard, the solid particles used can have a particle size in the single-digit and/or two-digit micrometer range for application or introduction of the microstructure 24. Likewise, chemical methods for providing the at least one surface 22 with a microstructure 24 are conceivable, for example etching surface(s) 22 of the stretched plastic strand 15.

[0092] Preferably, a surface treatment apparatus 23 structured as an embossing apparatus 25 is used for providing the at least one surface 22 with the microstructure 24. Such an embossing apparatus 25 can comprise at least one embossing roll 26, which embossing roll 26 is brought into contact with the stretched strand 15, as shown in FIG. 1. In this manner, a microstructured surface profile 27 can be transferred from an embossing surface 28 of the embossing roll 26 onto the at least one surface 22 of the stretched strand 15. In this regard, the microstructure 24 is introduced into the at least one surface 22 of the stretched strand 15 as a negative structure of the microstructured surface profile 27 of the embossing surface 28. It is understood that slight deviations of the microstructure 24 essentially formed as a negative of the surface profile 27 from the actual surface profile 27 of the embossing surface 28 of the embossing roll 26 are possible. It is advantageous if only a slight press-down pressure of the embossing roll 26 onto the at least one surface 22 of the stretched strand 15 is required for providing it with the microstructure 24.

[0093] The microstructured embossing surface 28 of the embossing roll 26, i.e. the surface profile 27 can be produced, for example, by means of a laser ablation apparatus. If necessary, other physical methods, or also mechanical methods, for example grinding processes and the like, or also chemical methods such as chemical removal of layers close to the surface, are also possible for production of the surface profile 27 on the embossing surface 28 of an embossing roll 26.

[0094] Fundamentally, it can be provided that an embossing roll 26 having an embossing surface 28 with a structurally well-defined or orderly surface profile 27, in other words with a surface profile 27 having recurring structural elements, is used. Laser ablation apparatuses having a corresponding track controller of one or more laser beam(s), suitable for production of the structurally ordered surface profile 27, for example, are suitable for production of such surface profiles 27.

[0095] However, it can also be practical if the at least one surface 22 of the stretched strand 15 is provided with the microstructure 24 by means of at least one embossing roll 26 having a surface profile 27 with a random structure. Measures for ordered structuring with recurring or repeating structure units can be eliminated for production of such surface profiles 27. For example, a random structure can be produced by means of a laser apparatus, in particular a laser ablation apparatus, the laser beam(s) of which are guided over the surface of the corresponding embossing roll 26 in a restrictedly random-generated track pattern. If necessary, other physical methods or mechanical methods, for example bombardment with particles in the sense of sand-blasting or grinding, or also chemical methods such as chemical removal of layers close to the surface, for production of a random microstructure or for production of the embossing surface 28 of an embossing roll 26, the surface having a randomly structured surface profile 27, are possible.

[0096] In FIG. 1, the at least one surface 22 of the stretched strand 15 after the surface treatment, as well as the embossing surface 28 of the embossing roll 26 were shown with a graphic filling to illustrate the microstructure 24 and the microstructured surface profile 27 of the embossing roll 26. In this regard, the filling selected was shown merely as an illustration, and this filling should not be interpreted as an image of an actual microstructure 24 or of an actual surface profile 27, for example. Embodiments of actual microstructures 24 or surface profiles 27 can be found in the description text.

[0097] Fundamentally, it can be provided that the at least one surface 22 of the stretched strand 15 is provided with the microstructure 24 by means of at least one embossing roll 26, having a surface profile 27 or an embossing surface 28 having an average roughness R.sub.a between 2 m and 15 m. The average roughness R.sub.a is frequently also referred to as an arithmetical medium roughness value. Preferably, an embossing roll 26 is used that has a surface profile 27 or embossing surface 28 with an average roughness R.sub.a between 4 m and 12 m.

[0098] Furthermore, it can be advantageous if the at least one surface 22 of the stretched strand 15 is provided with the microstructure 24 by means of at least one embossing roll 26 having a surface profile 27 or an embossing surface 28 with an averaged roughness depth R.sub.z between 10 m and 100 m. Preferably, an embossing roll 26 is used that has a surface profile 27 or embossing surface 28 with an averaged roughness depth R.sub.z between 20 m and 80 m.

[0099] Furthermore, it can be practical if the at least one surface 22 of the stretched strand 15 is provided with the microstructure 24 by means of at least one embossing roll 26 having a surface profile 27 or an embossing surface 28 with an average groove width RS.sub.m between 50 m and 400 m. Preferably, an embossing roll 26 is used that has a surface profile 27 or embossing surface 28 with an average groove width RS.sub.m between 100 m and 300 m.

[0100] By means of the indicated ranges for profile parameters at least for sections of the embossing surface 28 of the embossing roll 26, stretched strands 15 can be provided with a correspondingly structured embossing structure or microstructure 24. During the course of the embossing procedure, the micro-surface profile 27 of the embossing surface 28, having the indicated ranges of the profile parameters, is transferred accordingly to the at least one surface 22 of the stretched strip 15 as a negative structure, at least to a great extent, as illustrated in FIG. 1. In this regard, of course, a resulting roughness and a resulting averaged roughness depth depend on a respective penetration depth of the embossing surface 28 of the embossing roll 26 into the stretched strip 15 during the embossing procedure, i.e. they can be varied by means of a respective penetration depth.

[0101] The profile parameters for profiles as indicated, as well as methods for determination of these profile parameters, are defined in EN ISO 4287. More recent definitions and area-related or area-capturing measurement methods for profiled surfaces are defined in the standards series EN ISO 25178, wherein the measurement values can in turn be transferred or converted to profile parameters or 2D parameters according to EN ISO 4287.

[0102] In principle, it can be provided that the embossing surface 28 of the embossing roll 26 has a microstructured surface profile 27 in certain sections, and thereby in the method, only partial sections of the at least one surface of the stretched strand 15 are provided with the microstructure 24.

[0103] Preferably, the at least one surface 22 of the stretched strand 15 is provided with the microstructure 24 continuously, as is also shown in FIG. 1. In this way, it can be guaranteed, among other things, that at least one strip surface of a plastic strap 2 is provided, in each instance, with the or with a microstructure 24, in each instance, in the region of the two longitudinal ends. In this way, plastic straps 2 can be produced, in which a microstructure 24 is made available, in each instance, on at least one strip surface in the region, for improved welding, independent of a respective longitudinal expanse required for strapping or encircling of goods.

[0104] In cases in which only one surface 22 of the stretched strand 15 is provided with the microstructure 24, the stretched strand 15 can be passed through between the embossing roll 26 and a further guide roll having a smooth or non-profiled surface, for example with direct contact, in each instance. Alternatively, a guide track having a smooth surface can also be provided opposite the embossing roll, for example.

[0105] However, it can also be advantageous if both surfaces 22 of the stretched strand 15 are provided, in each instance, with the or with a microstructure 24, in each instance.

[0106] As shown in FIG. 1, the stretched strand 15 can is passed through between at least two embossing rolls 26 that lie opposite one another and rotate in opposite directions for this purpose, and both surfaces 22 of the stretched strand 15 can be provided with the microstructure 24, in each instance, by means of the two embossing rolls 26.

[0107] In this manner, plastic straps 2 can be produced that can be guided and welded particularly well in automated manner during the course of strapping or of a strapping procedure by machine. Alternatively to processing of a stretched strand 15 on both sides, with an embossing roll 26, in each instance, of course the two surfaces 22 of a stretched strand 15 can also be treated with other surface treatment apparatuses 23, for example by bombardment with particles, etc. Preferably, an embossing apparatus 25 with embossing rolls 26 is used for providing the surfaces 22 of a stretched band 15 with the microstructure 24.

[0108] In this regard, it can also be provided that at least one of the embossing rolls 26 shown in the exemplary embodiment in FIG. 1 is structured so that it can be tempered. For this purpose, the at least one embossing roll 26 can have channels for passing a tempered liquid medium through them. Of course, both of the embossing rolls 26 shown in FIG. 1 can also be structured so that they can be tempered. Also, electrical heating of at least one of the embossing rolls 26 shown is possible, for example. In this way, the stretched strand 15 or the stretched strands 15 can be tempered by means of at least one embossing roll 26.

[0109] Alternatively and/or in addition, a stretched or elongated strand 15 can also be tempered by means of a tempering apparatus 29 that precedes the at least one embossing roll 26. In principle, any apparatus suitable for heating or cooling a stretched strand 15 can be used as a preceding tempering apparatus 29. For example, the use of a further water bath is conceivable. In this regard, such a water bath can either be provided for cooling a stretched strand 15, or such a water bath can be heated, so as to heat a stretched strand 15. Alternatively or in addition, heating of a stretched strand 15 by means of infrared radiation is also conceivable. In FIG. 1, a sprinkling apparatus 30 is shown as an example of a preceding tempering apparatus 29, by means of which a stretched strand 15 can be sprinkled with a liquid having a preset or adjustable temperature.

[0110] The procedure for providing the at least one surface 22 with the microstructure 24 can be significantly influenced by tempering of the stretched strand 15 or of the stretched strands 15, since the temperature during micro-embossing influences the plastic formability of a stretched strand 15. Furthermore, the risk of damage to a plastic strap 2 during production or during use can be further prevented by means of suitable tempering for the surface treatment. A respective temperature of a stretched strand 15, suitable for the surface treatment for providing at least one surface 22 with the microstructure 24, is also dependent on the plastic material 3 made available, in each instance.

[0111] Fundamentally, it can be provided that the at least one surface 22 of the stretched strand 15 is provided with the microstructure 24 at a temperature of the stretched strand 15 between 60 C. and 120 C. This temperature range for a stretched strand 15 has proven to be particularly practical for providing at least one surface 22 with the microstructure 24.

[0112] At the end of the method, further process steps for final production of the stretched strand 15 or of the stretched strands 15 can also be provided for production of plastic straps 2. For example, a division apparatus 31 can be provided so as to divide a stretched and surface-treated strand 15 into multiple partial strands. This is particularly practical so as to obtain plastic straps 2 from a film-shaped strand 15 having a relatively great width expanse transverse to the transport direction 8. In this regard, it can be provided that such a stretched strand 15 is divided when viewed over its width. The division apparatus 31 can have cutting blades or cutting rolls, for example.

[0113] Furthermore, a splitting-up apparatus 32 can also be provided for final production. Such a splitting-up apparatus 32 can be configured for cutting a strand 15 of multiple strands 15, if applicable obtained by division with the division apparatus 31, into pieces 33 suitable for storage or for transport. For storage or for transport, these pieces 33 can be wound onto spools 34, for example, as illustrated in FIG. 1. Such spools 34 can be used, in particular, for portioning of large amounts, wherein plastic straps 2 for final use or sale can be cut off from such a spool 34 in suitable lengths, in each instance. Alternatively, of course, direct splitting-up into lengths of plastic straps 2 ready for use is also possible.

[0114] In FIG. 2, a detail of a plastic strap 2 ready for use is shown in perspective. The plastic strap 2 can be produced, in particular, by means of the method described.

[0115] The plastic strap 2 shown has a longitudinal expanse 35 and, normal to it, a width expanse 36 and a strip thickness 37. The longitudinal expanse 35 and width expanse 36 form two strip surfaces 38 that are spaced apart from one another by the strip thickness 37. The plastic strap 2 comprises a semi-crystalline thermoplastic plastic material 3, which plastic material 3 is stretched monoaxially or predominantly monoaxially in the direction of the longitudinal expanse 35. The plastic material 3 can specifically be a polyester; in particular, the plastic material can be formed by polyethylene terephthalate.

[0116] It is essential that one of the strip surfaces 38 of the plastic strap 2 is provided with a microstructure 24, in particular with a microstructure 24 that cannot be optically resolved by the human eye, as illustrated in FIG. 2. Such a plastic strap 2 is excellently suited for partly automated or fully automated strapping procedures performed by machine, due to the microstructure 24. In the case of a plastic strap 2 in which only one strip surface 38 is provided with a microstructure 24, the strip surface 38 having the microstructure 24 can be welded to the opposite, non-structured or smooth strip surface 38, during welding of the two longitudinal ends in each instance.

[0117] In FIG. 2, once again for illustration of the microstructure 24, the at least one strip surface 22 of the plastic strap 2 was shown with a graphic filling. In this regard, the selected filling is shown only for the sake of illustration, and this filling should not be interpreted as an image of an actual microstructure 24, for example. Embodiments of actual microstructures 24 can be found in the description text.

[0118] Preferably, both strip surfaces 38 of the plastic strap 2 are provided, in each instance, with the or with a microstructure 24, in each instance. In particular, in this way, the efficiency of a weld, in particular in the case of friction welding, during the course of a strapping procedure, can be further improved once again with regard to the expenditure of time and energy, since in this case, two strip surfaces 38 of a plastic strap 2, each having a microstructure 24, are welded to one another.

[0119] In principle, it is furthermore possible that only partial sections of the at least one surface 38 of the plastic 2 strap are provided with the microstructure 24 or with a microstructure 24, in each instance. Preferably, the at least one strip surface 38 is continuously provided with the microstructure 24, as is also illustrated in FIG. 2. This brings with it the advantage, among other things, that independent of the length of the plastic strap 2 required for a specific strapping for encircling, in each instance, at least one strip surface 38, in each instance, has a microstructure 24 in the region of the longitudinal ends to be welded together.

[0120] A stretching ratio of the plastic material 3 of the plastic strap 2 can amount to between 2 and 20. This with reference to the plastic material 3 before the stretching procedure. Preferably, the stretching ratio amounts to between 3 and 15, particularly between 4 and 12.

[0121] Subsequently, it can be provided that the plastic strap 2 has a tensile strength between 200 N/mm.sup.2 and 600 N/mm.sup.2. By means of the ranges indicated for tensile strength, a plastic strap that has sufficient tensile strength, in each instance, for a respective purpose of use or respective strapping can be made available. Preferably, the plastic strap can have a tensile strength between 250 N/mm.sup.2 and 550 N/mm.sup.2, in particular between 300 N/mm.sup.2 and 500 N/mm.sup.2.

[0122] A strip thickness 37 of the plastic strap 2 can amount to between 0.2 mm and 1.6 mm, for example. Preferably, a strip thickness 37 amounts to between 0.25 mm and 1.4 mm, in particular between 0.3 mm and 1.3 mm. It is obvious to a person skilled in the art that the strip thickness 37 of the plastic strap 2 can vary at least slightly, for example in the single-digit or two-digit micrometer range, in particular due to the microstructure 24, in certain sections or certain regions along the plastic strap 2.

[0123] The microstructure 24 can comprise individual structural elements such as elevations and depressions, the expanse or dimension of which lies in the single-digit to two-digit micrometer range. In particular, a microstructure 24 on the at least one strip surface 38 of the plastic strap 2 cannot be clearly optically resolved by the naked human eye, for example from a distance of 1 meter. This means that the microstructure 24 cannot be recognized as a structure by the human eye from an observation distance of 1 meter. This does not mean that the at least one microstructured strip surface 38 of a plastic strap 2 according to the invention could not be differentiated from a surface of a smooth strap without a microstructure 24. As a result of the microstructure 24, the at least one strip surface 38 can appear, in particular, to be more matte, in other words frosted in comparison with a smooth surface of the same plastic material without a microstructure 24.

[0124] In particular, the microstructure 24 can be formed by an embossed microstructure, in other words the at least one strip surface 38 was provided with the microstructure 24 by means of an embossing apparatus 25 comprising at least one embossing roll 26.

[0125] The microstructure 24 can fundamentally be formed by a structurally well-defined or ordered structure in the micrometer range. This means that the microstructure 24 can have recurring structural elements. In particular, however, it can also be provided that the microstructure 24 is formed by a random structure. Such a microstructure 24, formed by a random pattern, can be introduced into the at least one strip surface 38 of the plastic strap 2 or applied to the at least one strip surface 38 with relatively little effort.

[0126] In the case of the plastic strap 2 shown in FIG. 2, it can be provided that the at least one strip surface 38 has an average roughness R.sub.a between 0.1 m and 2.6 m in the region of the microstructure 24 or brought about by the microstructure 24. In particular, the at least one strip surface 38 can have an average roughness R.sub.a between 0.15 m and 1.6 m in the region of the microstructure 24 or brought about by the microstructure 24.

[0127] Furthermore, it can be advantageous if the at least one strip surface 38 of the plastic strap 2 has an averaged roughness depth R.sub.z between 1 m and 15 m in the region of the microstructure 24 or brought about by the microstructure 24. In particular, the at least one strip surface 38 can have an averaged roughness depth R.sub.z between 1.5 m and 12 m in the region of the microstructure 24 or brought about by the microstructure 24.

[0128] Finally, it can be practical if the at least one strip surface 38 of the plastic strap 2 has an average groove width RS.sub.m between 50 m and 400 m in the region of the microstructure 24 or brought about by the microstructure 24. In particular, the at least one strip surface 38 can have an average groove width RS.sub.m between 100 m and 300 m in the region of the microstructure 24 or brought about by the microstructure 24.

[0129] By means of the indicated ranges for profile parameters, a plastic strap 2 can be made available, in which excellent mechanical properties, in particular high tensile strengths are implemented simultaneously with good processing properties, in particular with regard to guidance and welding by machine.

[0130] The profile parameters for profiles as indicated, as well as methods for determination of these profile parameters, are defined in EN ISO 4287. More recent definitions and area-related or area-capturing measurement methods for profiled surfaces are defined in the standards series EN ISO 25178, wherein the measurement values can in turn be transferred or converted to profile parameters or 2D parameters according to EN ISO 4287. In the case of stretched plastic straps 2, the profile parameters are supposed to be determined using measurement segments oriented along the main stretching direction 18 or the longitudinal expanse 35, so as to be able to exclude possible measurement errors caused by superimposition of longitudinal structures, which can occur on the basis of the stretching procedure.

[0131] The ranges indicated for values of the roughness and groove width are average values determined according to EN ISO 4287 from a plurality of measurement segments. In this regard, a microstructure 24 can have individual structural elements, such as depressions and elevations, for example, the dimensions of which deviate greatly from one another, in each instance. Thus, a microstructure 24 can have individual structural elements, the individual dimensions of which lie in the single-digit or two-digit micrometer range, in each instance, or, in borderline cases, also in the low three-digit micrometer range. The dimensions of individual structural elements of the microstructure 24 can therefore certainly vary by more than a power of ten or even slightly above that. This in particular if the microstructure is formed by a random structure.

[0132] The exemplary embodiments show possible embodiment variants, wherein it should be noted at this point that the invention is not restricted to the embodiment variants that are specifically represented, but rather, instead, various combinations of the individual embodiment variants with one another are possible, and this variation possibility lies within the ability of a person skilled in the art and working in this technical field, on the basis of the teaching concerning technical action provided by the present invention.

[0133] The scope of protection is determined by the claims. However, the description and the drawings must be used to interpret the claims. Individual characteristics or combinations of characteristics from the different exemplary embodiments shown and described can represent independent inventive solutions on their own. The task on which the independent inventive solutions are based can be derived from the description.

[0134] All information regarding value ranges in the present description should be understood to mean that these include any and all partial ranges of them; for example, the information 1 to 10 should be understood to mean that all partial ranges, proceeding from the lower limit 1 and also including the upper limit 10 are also included; i.e. all partial ranges start with a lower limit of 1 or more and end at an upper limit of 10 or less, for example 1 to 1.7, or 3.2 to 8.1, or 5.5 to 10.

[0135] For the sake of good order, it should be pointed out, in conclusion, that for a better understanding of the structure, some elements have been shown not to scale and/or larger and/or smaller.

REFERENCE SYMBOL LISTING

[0136] 1 apparatus

[0137] 2 plastic strap

[0138] 3 plastic material

[0139] 4 metering apparatus

[0140] 5 extrusion apparatus

[0141] 6 extrusion tool

[0142] 7 plastic strand

[0143] 8 transport direction

[0144] 9 cooling apparatus

[0145] 10 water bath

[0146] 11 length

[0147] 12 pull-off apparatus

[0148] 13 roller element

[0149] 14 elongation unit

[0150] 15 strand

[0151] 16 elongation segment

[0152] 17 pull-off apparatus

[0153] 18 main stretching direction

[0154] 19 pull-off apparatus

[0155] 20 heating apparatus

[0156] 21 thickness

[0157] 22 surface

[0158] 23 surface treatment apparatus

[0159] 24 microstructure

[0160] 25 embossing apparatus

[0161] 26 embossing roll

[0162] 27 surface profile

[0163] 28 embossing surface

[0164] 29 tempering apparatus

[0165] 30 sprinkling apparatus

[0166] 31 division apparatus

[0167] 32 splitting-up apparatus

[0168] 33 piece

[0169] 34 spool

[0170] 35 longitudinal expanse

[0171] 36 width expanse

[0172] 37 strip thickness

[0173] 38 strip surface