Abstract:
The present invention relates to apparatus for fibrillating ribbons or foils, wherein two or more strips each having a plurality of projecting fibrillating elements are disposed on the circumference of a fibrillating roll in a uniform distribution. To ensure gentle guidance of the ribbons and foils during fibrillation, the regions on the fibrillating roll between the circumferential strips each exhibit a friction-reducing surface contact.

Description:
[0001]    This application is a continuation-in-part of and claims the benefit of priority from PCT application PCT/EP2011/056929 filed May 2, 2011; German Patent Application DE 10 2010 019 144.2 filed May 3, 2010; and German Patent Application DE 10 2010 033 546.0 filed Aug. 5, 2010, the disclosure of each is hereby incorporated by reference in its entirety. 
     
    
       [0002]    The invention relates to an apparatus for fibrillating ribbons or foils according to the preamble of claim  1 . 
       BACKGROUND 
       [0003]    Such devices for fibrillation of synthetic ribbons or synthetic foils, which have previously been extruded from a thermoplastic material, are generally known and are used to structure ribbons or foils. This allows, in particular, the form a structure extending in the longitudinal direction on otherwise smooth surfaces of strips or foils. 
         [0004]    Fibrillation is typically conducted by a fibrillating roll as it is known for example from DE 1907 007 A1. On the periphery of the fibrillating roll are arranged a plurality of fibrillation elements, for example, in the form of projecting pins or needles so that during the guidance of the ribbons on the fibrillating roll, the pins pierce the ribbons and, depending on the wrapping of the ribbons around the fibrillating role, produce elongated tears in the ribbons. Thus, by the number and offset of such pins or needles on the periphery of the fibrillating roll, fibrillation structures can be so formed within a band. 
         [0005]    In the known apparatus, the fibrillation elements are fastened to strips, which in a plurality are uniformly distributed on the periphery of the fibrillating roll. In this manner, surface areas are created on the periphery of the fibrillating roll between the strips, on which areas ribbons or foils can be conducted. It has now been found that, on the one hand, with increasing thickness of the ribbons, there occurs an undesired increase of the tensile forces in order to allow the penetration and tear of the ribbons. On the other hand, such preferred relative speeds between the fibrillating roll and the ribbons or the foil are set that one obtains a certain fibrillation pattern. Increasingly, particularly in the production of synthetic fiberglass ribbons made of several material components are formed that are sensitive to surface friction and are prone to damage. 
       SUMMARY 
       [0006]    It is therefore the technical task of the invention to provide a further developed device for fibrillating of the generic type so that the ribbons or the foil for fibrillation can be conducted around the fibrillating roll in larger wraps. 
         [0007]    Another technical task of the invention is to provide a device for fibrillation of ribbons or a foil, by means of which fibrillation structures can be generated with even higher relative speeds. 
         [0008]    This technical task is resolved by a device of the invention in that the fibrillating roll comprises a friction-reducing contact surface between the strips on the circumference. 
         [0009]    Advantageous developments of the invention are defined by the features and combinations of features of the dependent claims. 
         [0010]    The invention has the particular advantage that the fibrillating roll can be used with high flexibility to produce structures in ribbons and foils. Here, the ribbons and the foils can be particularly gently conducted on the contact surfaces of the fibrillating roll. In the manufacture of special fiberglass it has been found that very sticky and elastic materials are used that are very sensitive. In order to counteract the friction arising from the relative speed between the fibrillating roll and the ribbons, the ribbons can be advantageously conducted on the friction-reducing contact surfaces at the periphery of the fibrillating roll. 
         [0011]    In order to ensure low friction values, on the one hand, and, on the other hand, to prevent premature wear of the fibrillating roll, the further development of the invention is particularly suitable, because the contact surfaces carry a multiple coating with a plurality of coating materials, which are formed from a plurality of sandwich-type single coatings. 
         [0012]    To maintain the characteristics of the coating materials over very long periods, the further development of the invention is preferably specifically designed. Here, the individual coatings of the multi-layer coating each have a minimum thickness of &gt;20 μm. 
         [0013]    It is particularly advantageous if a single inner coating has a thickness greater by a factor of 5 than an outer single coating. This allows making coarser surface structures of the main body more uniform with a first single coating and thus protects them. 
         [0014]    The preferred coating material of the outer coating is a low-friction material to reduce friction, and the coating material of the inner coating is formed by a single protective material to reduce wear. 
         [0015]    Plastic materials, in particular PTFE, are preferably used as the low-friction material, and a ceramic material is preferably used as a protective material. This allows very high operation durability and provides a particularly gentle guiding on the fibrillating roll. 
         [0016]    In the inventive device, the fibrillation elements are typically formed by needles in order to produce a fibrillation structure. However, in order to also fibrillate tear-sensitive and thicker ribbons or foils, cutting tips are advantageously used as fibrillation elements, whose blades are arranged as protruding elements. 
         [0017]    For the production of reticulated fibrillation structures in ribbons, such development of the invention is particularly advantageous in which the adjacent blade rows on the circumference of the fibrillating roll are held on the respective strips offset to each other with their blades. The distribution of the partial incisions in the ribbons can be influenced both by the spacing of the blade strips on the circumference of the fibrillating roll and by the distance between the blade tips to each other. 
         [0018]    According to another embodiment of the invention, the fibrillation roll comprises a controlled drive, which is connected to a machine control unit for setting a predetermined peripheral speed on the fibrillating roll. In the manufacture of such fibrillation structures, this allows directly using the predetermined process parameters, such as the draw ratio of the ribbons or foil, to set up a respective peripheral speed of the material roll specifically predetermined for the particular process and the particular material. 
         [0019]    The device according to the invention is particularly suitable to fibrillate ribbons or foils of a relatively greater thickness and a relatively high material elongation after stretching them. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    The device according to the invention will hereinafter be explained in detail by way of an embodiment example with reference to the accompanying figures. The content of the individual figures: 
           [0021]      FIG. 1  shows a schematic diagram of a view of an embodiment of the inventive device in an extrusion process. 
           [0022]      FIG. 2  shows a schematic cross-section of the embodiment of  FIG. 1 . 
           [0023]      FIG. 3  shows a schematic plan view of the embodiment of  FIG. 1 . 
           [0024]      FIG. 4  shows a schematic view of the fibrillating a roll. 
           [0025]      FIG. 5  schematically shows a cross-sectional view of a contact surface of the fibrillating roll of  FIG. 4 . 
           [0026]      FIG. 6  shows a schematic view of a pin of the fibrillating roll of  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION 
       [0027]      FIGS. 1 to 3  schematically illustrate an embodiment of the invention apparatus for fibrillating ribbons in an extrusion process.  FIG. 1  shows the exemplary embodiment in an overall view of the extrusion process,  FIG. 2  shows a side view and  FIG. 3  shows schematically a plan view. The following description applies to all the figures, unless an explicit reference is made to one of the figures. 
         [0028]      FIG. 1  shows the embodiment of the inventive apparatus in an overall view of an extrusion process. The exemplary embodiment has an extrusion device  1  for producing a foil from a thermoplastic material. In this example, the extrusion device  1  comprises an extruder  2 . The extruder  2  is connected to an extrusion head  3 , which extrudes a flat foil  22 , made of thermoplastic material that has previously been molten by the extruder  2 . 
         [0029]    At this point it should be noted that the extrusion device  1  could also comprises to extrude, for example, a two-colored flat foil or a flat foil with different polymer materials. 
         [0030]    The extrusion head  3  is associated with a cooling bath  4 . On the outlet side of the cooling bath  4  is provided a re-direction mechanism  5  to remove from the foil  22  any residual liquid sticking to it by deflection and suction. For this purpose, the re-direction mechanism  5  is usually combined with a suction device, which drains off the adhering cooling liquid of the cooling bath  4 . 
         [0031]    A cutting device  6  is arranged downstream of the re-direction  5  to cut the foil  22  that has been produced in the extrusion device  1  into number of ribbons  24 . In the cutting device  6 , the foil  22  is cut into a plurality of individual ribbons  23  of a predetermined width. 
         [0032]    For withdrawing the foil  22  or the ribbons  24  and stretching the ribbons, several godet feeding mechanisms  7 . 1  and  7 . 2  with driven godets are arranged after each other. The ribbons  23  are led with a simple wrap around the circumference of the driven godets of the godet feeding mechanisms  7 . 1  and  7 . 2  in parallel run side by side. 
         [0033]    A heater  8  is arranged between the godet feeding mechanisms  7 . 1  and  7 . 2 . The heating device  8  could be formed, for example, by a forced-air oven, in which the strips are heated up to a stretching temperature. In order to stretch the ribbons, the godets of the godet feeding mechanisms  7 . 1  and  7 . 2  are driven with a speed difference. 
         [0034]    The fibrillation device designed according to the invention is arranged between the heater  8  and the second godet feeding mechanism  7 . 2  and is identified with reference numeral  9 . The fibrillation device  9  has a fibrillating roll  10 , on the periphery of which the ribbons are led with a partial wrap to be fibrillated. The fibrillating roll  10  is driven by an electric motor  25 , which is controlled by the control unit  26 . The control unit  26  is coupled to a machine control  27  so that it is possible to set a particular peripheral speed of the roll  10 , depending on the production speed of the ribbons defined by the godet drives. Thus it is possible to drive the roll drive  10  with a circumferential speed that is preferably greater than the production speed of the ribbons  23 . 
         [0035]    To further explain the fibrillation device  9 , additional reference is made to  FIGS. 2 and 3 .  FIG. 2  shows a side view of the fibrillation device  9  and  FIG. 3  shows a plan view of the fibrillation device  9 . 
         [0036]    The fibrillating roll  10  carries a plurality of strips  28  that are circumferentially equally spaced from each other, each having a plurality of protruding fibrillation elements  29 . In this case, the fibrillation elements are formed by blade tips  30 . Each blade tip  30  comprises a cutting edge  31 , which is aligned in the direction of rotation of the fibrillating roll  10 . This structure will be described in more detail below. 
         [0037]    At this point, it should be explicitly noted that the fibrillating elements  29  on the fibrillation roll  10  can alternatively be formed by protruding needles, which are held on the strips  28 . 
         [0038]    On the inlet side of the ribbons  24 , the fibrillating roll  10  is associated with an adjusting device  14 . The adjusting device  14  comprises a plurality of essentially vertically aligned guide pins  15 , which are held on a carrier  16 . The guide pins  15 , which could alternatively be formed by freely rotatable guide rollers on vertical axes, each extend between two adjacent ribbons  23  of the group of ribbons  24 . The guide pins  15  are dimensioned in their outer diameter such that the ribbons  23  are guided essentially without clearance between two adjacent pins  15 . The carrier  16  that carries the guide pins  15  is held in a guide rail  17  and can be shifted within the guide rail  17  transversely to the running direction of the ribbons  23 . By shifting the carrier  16 , the ribbons  23  of the group of  24  can be adjusted relative to the position of the blade tips  30  on the periphery  30  of the fibrillating roll  10 . In particular, this therefore allows symmetrical cuts to be made by the blade tips  30  in the ribbons  23 . In particular, this allows minimum distances at the edge areas in the ribbons to be achieved. 
         [0039]    In order to obtain a defined wrap of the group of ribbons around the periphery of the fibrillating roll  10 , two guide rollers  20 . 1  and  20 . 2  are provided, which lead the inlet and the outlet of the group of ribbons  24 . 
         [0040]    After fibrillation and stretching, the ribbons  23  are fed to a crimping device  12  and a wind-up device  18 . The crimping device  12  and the wind-up device  18  comprise several texturizer means  13  and wind-up stations  19  to texture and wind up the ribbons individually or in groups. For this purpose, using a guide device  11  the ribbons  24  can be isolated or led together in groups. 
         [0041]    In the extrusion process shown in the example in  FIG. 1 , a grass yarn is produced, which in a finishing process could already be processed directly into an artificial turf. The fibrillation device  9  used there can in principle be also used in other extrusion processes, in which for example a foil must be fibrillated. 
         [0042]    To allow as gentle as possible a guidance of the ribbons on the periphery of the fibrillating roll  10 , friction-reducing contact surfaces  32  are formed on the periphery between the strips  28 . For clarification,  FIG. 4  shows the fibrillating roll  10  of the aforementioned exemplary embodiment in a perspective view. The fibrillating roll  10  comprises several strips  28 , which are uniformly arranged on the periphery of the fibrillating roll  10 . Between the strips  28  on the circumference of the fibrillating roll  10  are arranged several friction-reducing contact surfaces  32 . The contact surfaces  32  of the fibrillating roll  10  that extend between the strips  28  have a multi-layer coating  33 . In order to enable an optimum low-friction and stable guidance of the ribbons on the contact surfaces  32 , the multi-layer coating  33  is preferably formed from a plurality of individual layers, which are arranged one above the other like a sandwich. 
         [0043]      FIG. 5  shows a schematically cross-sectional view of a typical multiple-layer coating  33 . The multi-layer coating  33  in this embodiment is formed by an inner single coating  34 . 1  and an outer single coating  34 . 2 , which are superposed like a sandwich. Here, the inner individual coating  34 . 1  is applied directly on the coating surface  36  of the shell  35  of the fibrillating roll  10 . The inner single coating  34 . 1  is applied with a layer thickness S 1 . Above the inner single coating  34 . 1  is applied an outer single coating  34 . 2  with a thickness S 2 . The outer single coating  34 . 2  has a low-friction material as a coating material so that contact surface  32  directly facing the ribbons is determined by the material properties of the low-friction material. In contrast, the coating material of the inner single coating  34 . 1  is formed by a protective material, which represents a wear-resistant layer over the shell  35  of the fibrillating roll  10 . A ceramic material is preferably used as a protective material, which is applied directly onto the coating surface  36  of the shell  35 . Such ceramic materials can be applied, for example, as a plasma coating. In this embodiment, the interfacial surface of the inner individual coating  34 . 1  to the outer single coating  34 . 2  is roughly structured so that in the operating state after the low-friction coating in the outer coating  34 . 2  wears off, there is a mixed surface, which is formed by surface portions of the low-friction material and surface portions of the protective material. Such a guide surface has the particular advantage that the ribbons or the foil can be led with low friction and in a wear-resistant fashion. The low-friction material is commonly formed from plastics, where in particular PTFE materials (Teflon) turned out to be particularly advantageous for the guidance of ribbons. 
         [0044]    In one embodiment of the fibrillation roll  35 , the shell may initially be applied with a plasma coating with a ceramic material in a layer thickness S 1  of about 0.3 mm. Then a PTFE coating of a layer thickness S 2  of about 0.04 mm may be applied in a sandwich-like manner over the ceramic layer. There has been found that a particularly advantageous ratio of the layer thicknesses in the combination of an outer low-friction coating and an inner protective material is when the thickness of the inner individual coating  34 . 1  is greater by factor of 5 than the outer single coating  34 . 2  (S 1 &gt;5×S 2 ). 
         [0045]    As further shown in the illustration in  FIG. 4 , the strips  28  carry has a plurality of blade tips  30  that are held as a set of blades protruding from the bar  28  with a certain distance from each other. Each of the blade tips  30  comprises a cutting edge  31 , which is aligned in the circumferential direction of the running fibrillating roll  10 . As an example,  FIG. 6  shows a view of the blade tip  30 . The blade tips  30  are held on the blade strip  28 , wherein the strip  28  is arranged in a groove of the fibrillating roll  10 . The blade tip  30  is of a triangular design with a protruding peak. On one side of the blade tip  30 , the cutting edge  31  is ground, which extends up to the tip. The blade  31  is oriented in the direction of circulation of the fibrillating roll  10  so that during the rotation of the fibrillating roll a finite partial incision is produced depending on the wrapping of the ribbon. 
         [0046]    The arrangement of the blade tips  30  and the strips  28  can be selected such that different fibrillation patterns arise. Thus, for example, parallel arrangements of blade tips and offset arrangement of blade tips are both possible. 
         [0047]    For the fibrillation, the fibrillating roll  10  is preferably operated at a peripheral speed, which is 20% to 60% faster than a withdrawal speed of the ribbons. Due to the low cutting resistance of the blade tips  30  during the fibrillation, relatively small differences in speed between the ribbons and the fibrillating role can be maintained. The small incision resistance during the fibrillation is also particularly suitable for providing very elastic ribbons and very thick ribbons with a uniform fibrillation structure. 
         [0048]    Thus, the inventive device is useful, in particular, in the production of grass yarns. Due to the very good low-friction properties of the contact surfaces  32  on the circumference of the fibrillating roll  10 , even elastic and sticky materials could be fibrillated with relative speeds. Ribbons, which are preferably produced by co-extrusion and have a thicknesses ranging from 150 to 500 μm, can be advantageously fibrillated. The expansions of the ribbons can have values of above 50%. Thus, elastic ribbons with an elongation of up to 75% can be securely fibrillated. 
         [0049]    The device according to the invention is basically suitable to fibrillate all conventional ribbons and foils made of thermoplastic materials. There is also the possibility that in the embodiment shown in  FIG. 1 , the extrusion head  3  is replaced by a monofilament extrusion tool so that directly during the extrusion a plurality of individual ribbons can be produced. In this case, the cutting device shown in  FIG. 1  is omitted. In that regard, the apparatus according to the invention is also particularly suited after stretching to fibrillate singly generated ribbons. Here, in particular high densities of partial cuts in the individual ribbons are possible. By proper adjusting, even small minimum distances on the edge of the ribbons can be set up and safely maintained. The PP, LLDPE, HDPE, or PA types of polymer have proven to be most suitable for this purpose. 
       REFERENCE NUMBERS LIST 
       [0000]    
       
           1  Extrusion device 
           2  Extruder 
           3  Extrusion head 
           4  Cooling bath 
           5  Re-direction mechanism 
           6  Cutting device 
           7  Godet mechanism 
           8  Heater 
           9  Fibrillation device 
           10  Fibrillating roll 
           11  Guide device 
           12  Crimping device 
           13  Texturizer 
           14  Adjusting device 
           15  Guide pin 
           16  Carrier 
           17  Guide rail 
           18  Wind-up device 
           19  Wind-up station 
           20  Guide roller 
           21  Guide groove 
           22  Foil 
           23  Single ribbon 
           24  Group of ribbons 
           25  Electric motor 
           26  Control unit 
           27  Machine control 
           28  Cutting blade 
           29  Fibrillation element 
           30  Blade tip 
           31  Cutting edge 
           32  Contact surface 
           33  Multiple coatings 
           34 . 1 ,  34 . 2  Single coating 
           35  Shell 
           36  Coating surface