Abstract:
In the device ( 1 ) for connecting two-dimensional materials ( 51, 52 ), a first material web ( 51 ) is coated with a hot-melt mass in a hot-melt mass deposition station. The first material web ( 51 ) is subsequently contacted with a second material web ( 52 ). The contact between the two material webs ( 52 ) is fixed in a belt press ( 30 ). Thus the processing of combinations of materials and adhesives which until now were not or hardly considered at all become possible. The material webs ( 51, 52 ) are treated in a gentle manner. An improved connection quality at a higher processing speed is achieved. A greater field of application becomes accessible in that the processing window is extended with regard to the parameters of pressure time and temperatures is extended.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to a method and to a device for connecting two-dimensional materials, in particular material webs of preferably textile materials, according to the preambles of the independent patent claims.  
         [0002]     It is known to coat a two-dimensional material with a hot-melt mass—also called hotmelt. A bonding to a second material web may occur directly subsequent to this, wherein the two material webs are joined together in a roller laminating mill. Thus e.g. two textile material webs may be joined together with a hot-melt adhesive. This method however is unsuitable for thick materials and materials which are elastic in thickness, such as foams and bulk nonwovens, since these are pressed together in a roller laminating mill, and the connection is damaged due to shearing and tearing. Moreover, with many highly viscous adhesives, the residence time or the press time in the roller laminating mill is too short for the hot-melt adhesive to be able anchor in the material webs.  
         [0003]     Furthermore, belt presses are known, by way of which two sheet formations are to be connected or laminated amid the application of heat and pressure. A bonding mass is used for bonding, which usually itself has the shape of a sheet formation.  
       SUMMARY OF THE INVENTION  
       [0004]     It is the object of the invention to specify a method and a device for connecting two-dimensional materials which permit new applications and a greater freedom with regard to the applied adhesive. A good connection quality is to be achieved at a high processing speed. A gentle treatment of the materials to be connected is to be ensured. The device should have a compact construction and should also be suitable for retrofitting existing installations.  
         [0005]     These and other objects are achieved by the method according to the invention and the device according to the invention, as are defined in the independent patent claims. Advantageous embodiments of the method and of the device are specified in the dependent patent claims.  
         [0006]     The invention is based on the idea of combining a holt-melt mass deposition station with a belt press station, or combining the methods implemented in these.  
         [0007]     Accordingly, in the method according to the invention for connecting two-dimensional materials, a surface of a first, two-dimensional material is coated with a hot-melt mass and is brought into contact with a surface of a second, two-dimensional material. The contact between the two two-dimensional materials is fixed in a belt press.  
         [0008]     The device according to the invention for connecting two-dimensional materials contains coating means for coating a surface of a first two-dimensional material with a hot-melt mass, and contacting means for contacting the coated surface of the first, two-dimensional material with a surface of a second, two-dimensional material. Furthermore, the device contains a belt press for fixing the contact between the two two-dimensional materials.  
         [0009]     The coating means may comprise a rotation deposition body, e.g., a gravure roller or a rotation screen printing stencil. In a preferred embodiment of the invention, the relative speed of the gravure roller to the material web is variable. This characteristic permits the same gravure roller to be used in a multitude of applications without having to exchange the gravure roller. A great flexibility is achieved by way of this. The conversion times are significantly reduced, since an exchange of the gravure roller is done away with, which in turn has a cost-reducing effect. One may also retain one and the same gravure roller during a conversion to another application in the coating module at a high temperature, by which means a curing of the hot-melt mass on the gravure roller is avoided. The deposition weight (in this document this is to be understood as the deposited mass per area; also called coating thickness) in this embodiment is determined by the relative speed between the gravure roller and the material web which runs past. The relative speed may be positive or negative. The change of the relative speed may e.g. be achieved by a change in the rotational speed of the gravure roller. In a preferred embodiment, not only the rotational speed but also the rotational direction of the gravure roller may be changed. By way of this, one may change the relative speed and so too the deposition weight by a factor of  100  without any problem. The change and [closed-loop] control of the rotational speed is less demanding with regard to technology than the change and the [closed-loop] control of a distance of hot rollers. This advantage particularly makes a difference when dealing with hot-melt mass, where the temperature conditions render an accurate control of the distances considerably more difficult. Furthermore, the dosing of the hot-melt mass is effected with a very simple doctor system which ensures a very uniform preparation of the hot-melt mass in the longitudinal and transverse direction.  
         [0010]     Until now, gravure rollers have been used in the application of hot-melt mass coating/laminating with an approximately slip-free synchronous running with the material web, for a 1:1 transfer of the gravure pattern onto the material web. The preferred embodiment of the present invention upsets this basic principle, in that it permits an asynchronous running and thus a rubbing of the gravure pattern on the material web. This rubbing effect in the context of gravure rollers was completely undesirable with the holt-melt method until now, since a deposition true to gravure was to be achieved. The present invention opens completely new possibilities also in this aspect in that, as previously the case, it permits a transfer of the gravure pattern (with the same speed of the gravure roller and the material web), but also permits its rubbing up to a homogeneous coating of the material web (at greatly different speeds). With this, the relative speed between the gravure roller surface and the material web determines the intensity of the rubbing or transfer.  
         [0011]     The invention permits access to a wider field of application in that it widens the processing window with regard to the parameters of pressure, time and temperature.  
         [0012]     Thanks to the invention, the processing of combinations of materials and adhesives which until now were not considered or hardly considered becomes possible. The two-dimensional materials are treated in a gentle manner, since various variable heating and/or cooling zones may be provided along a longer path in the belt press station, so that the two-dimensional materials may be heated or cooled with a lower intensity and do not suffer any temperature shocks. An improved connection quality is achieved at a higher processing speed.  
         [0013]     The device according to the invention is preferably designed in a modular construction manner. This means that at least one autonomous hot-melt module and one autonomous belt press module are present, which in each case comprise a well-defined interface for the transfer of a coated, two-dimensional material. In this context, “autonomous” means that the modules in each case are capable of being applied on their own, independently of one another. The modular construction manner offers the additional advantage that the two modules may also be operated individually or together with further modules. A multi-functional solution with a large field of application is provided by way of this. This covers the requirement of a greater flexibility in the material selection and the functions of the manufactured textile laminates and coated substrates, and entails a reduction of costs. This feature is particularly attractive for contract manufacturers or piecework manufacturers, who are required to convert their production installation to the requirements of different customers within the shortest time. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     One preferred embodiment of the invention is explained in a detailed manner by way of the accompanying drawings. There are schematically shown in:  
         [0015]      FIG. 1  the device according to the invention, in an opened lateral view and  
         [0016]      FIG. 2  the device according to the invention, in a perspective view. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0017]     The preferred embodiment of the device  1  according to the invention shown in the drawings contains two modules: an autonomous hot-melt module  2  and an autonomous belt-press module  3 . A delimitation between the two modules is indicated in  FIG. 1  with a dashed line  4 . Each module  2 ,  3  comprises a well-defined interface for the transfer of a coated, two-dimensional material  51 .  
         [0018]     The hot-melt module  2  serves for coating a first, two-dimensional material or substrate  51  with a hot-melt mass. The first, two-dimensional material  51  in the represented embodiment is a flexible material web which is unwound from a first contact unwinder  61  and is led to a hot-melt mass deposition station  20  via various rollers. A dancer for compensating the tension and/or a cord stretching means for spreading the material web  51  may be present, as is known from the state of the art. The first contact unwinder  61  may be arranged outside the hot-melt module  2  (cf.  FIG. 1 ) or within the hot-melt module  2  (alternative; cf.  FIG. 2 ).  
         [0019]     In the shown embodiments, the hot-melt mass deposition station  20  is equipped with a gravure roller  21  whose surface—peripheral surface to be more accurate—is provided with recesses for receiving hot-melt mass. The recesses are preferably arranged in a regular pattern and are designed for example as truncated pyramids, diagonal grooves, grooves arranged a net-like manner or a hatching. The surface density of the hot-melt mass accommodated by the gravure roller  21  may for example be 5-100 g/m 2  and preferably 10-40 g/m 2 . The surface of the gravure roller  21  is heatable and is preferably [closed-loop] controlled with regard to temperature, so that the hot-melt mass located in the recesses of the gravure roller  21  may be kept exactly at the required temperature. With thermoplastic adhesives, this temperature is typically 220-240° C. The surface of the gravure roller  21  is preferably metallic, for example of chromium, but may also be non-metallic.  
         [0020]     In one preferred embodiment of the invention, the relative speed of the gravure roller  21  to the material web  51  is variable in the hot-melt mass deposition station  20 . This relative speed may be positive or negative. The change of the relative speed may e.g. be achieved by a change of the rotational speed of the gravure roller  21 . Preferably not only may the rotational speed be changed, but also the rotational direction of the gravure roller  21 .  
         [0021]     The hot-melt mass is introduced into the recesses in the surface of the gravure roller  21  for example via a heated doctor beam  22  by way of a doctor blade  23 . In order to take both possible rotational directions of the gravure roller  21  into account, the doctor blade  23  may be adjustable according to the rotational direction, or a second doctor blade for the other rotational direction may be provided (not drawn in).  
         [0022]     A counter roller  24  is attached in the direct vicinity of the gravure roller  21 , and the material web  51  bears on this counter roller  24  in a slip-free manner and party wraps around this. The counter-roller  24  is preferably formed of a siliconized rubber roller, but may e.g. also consist of steel and be coated with chromium or Teflon. The axes of the gravure roller  21  and the counter roller  24  run parallel to one another, and the surfaces of the gravure roller  21  and the counter roller  24  have a well-defined distance to one another. The distance is preferably mechanically and/or electrically adjustable, for example by way of an electric motor. It is preferably between −0.5 mm and +10 mm depending on the thickness and the nature of the material web  5 , wherein a negative distance means that the surface of the counter roller  24  is reversibly deformed, i.e. pressed in, due to the less flexible gravure roller  21 . The distance determines the bearing pressure of the material web  51  on the gravure roller  21 . The counter roller  24  may be equipped with its own drive. Otherwise, another drive roller may accomplish the transport of the material web  51 .  
         [0023]     The gravure roller  21  has a drive means (not drawn), for example its own electro-motor drive which is independent of that of the counter roller  24 , and in particular a servo motor or direct current motor, by way of which it may be set into rotation with a settable rotational speed. The rotational speed is kept constant during a coating procedure, but this is not absolutely necessary. The desired deposition speed is determined by way of the relative speed V G -V T  between the surface of the gravure roller  21  and the material web  51 , which for example is between 2 g/m 2  and 200 g/m 2  and preferably between 10 g/m 2  and 100 g/m 2 . In order to be able to achieve a large scope of deposition speeds with one and the same device, the rotational speed of the gravure roller  21  should be able to be changed in an as large as possible range. The ratio V G /V T  of the speed V G  Of the surface of the gravure roller  21  to the transport speed V T  of the material web  51  should preferably be able to be selected between 0.1 and 10. In a preferred embodiment, a rotation of the gravure roller  21  in both directions is possible, by which means even high relative speeds V G -V T  may be obtained. With a counter-running, the ratio V G /V T  of the speed V G  of the surface of the gravure roller  21  to the transport speed V T  of the material web  51  should preferably be able to be selected between −0.2 and −5.  
         [0024]     A post-heating element  24  which is arranged downstream of the hot-melt mass deposition station  20  ensures that the deposited hot-melt mass does not cool to below a lower limit temperature of for example 160°, or heats it to a temperature which is even higher than the deposition temperature, in order to create optimal conditions for the connecting. The post-heating element  25  may for example be designed as an infrared radiator.  
         [0025]     In the present embodiment example a calendar  26  with preferably two calendar rollers is provided at the exit of the hot-melt module  2 . The two material webs  51 ,  52  are deflected in this calendar  26  and are brought into contact with one another for the first time. Additionally, the two material webs  51 ,  52  are fixed onto one another in the calendar  26  and thus are prepared for the subsequent treatment in the belt press module  3 . Such a calendar  26  arranged downstream is however purely facultative. The material webs  51 ,  52  could also be brought into contact only until in a belt press station  30 .  
         [0026]     The gravure roller  21  is only one of several possible embodiment examples for the design of the hot-melt mass deposition stations  20 . Further embodiment forms of the device  1  according to the invention, alternatively to the gravure roller  21  may be the following hot-melt mass deposition systems which are known to the man skilled in the art: 
    (i) Slot die. With this, a complete-surfaced homogeneous coating of the material web  51  may be achieved. The deposition weight may be influenced via the exit speed of the hot-melt mass and/or via the transport speed of the material web  51 .     (ii) Multi-roll coating. The hot-melt mass is deposited onto the smooth surface of an unstructured deposition roller by way of a heated roller dosing mill and is transferred by this deposition roller onto the material web. A complete-surfaced coating of the material web  51  is achieved. The parameters for influencing the deposition weight are the distance between the deposition roller and the material web  51  (or a counter roller on which the material web bears) as well as the relative speed between the deposition roller and the material web  51 .     (iii) Rotation screening printing     (iv) Melt-blow method    
 
         [0031]     In the belt press module  3 , the first, two-dimensional material or substrate  51  which is coated with the hot-melt mass is connected to a second, two-dimensional material or substrate  52  into a laminate  53 . The second, two-dimensional material  52  may e.g. be a flexible material web which is led from a second contact unwinder  62  to the first, two-dimensional material  51 . It is advantageous to preheat the second, two-dimensional material  52  to a suitable temperature, for example in the region of the fixation temperature which for thermoplasts for example is approx. 160° C., before the joining-together. A preheat element  36 , for example an infrared radiator may be provided for this purpose.  
         [0032]     The belt press module  3  contains two transport belts or conveyor belts  31 ,  32  which are arranged essentially above one another. In a belt press station  30 , two belt faces  33 ,  34  of the transport belts  31 ,  32  are directed facing one another and run essentially parallel to one another. Between these belt faces  33 ,  34 , the two two-dimensional material  51 ,  52  amid the application of heat and pressure are connected or fixed to one another by way of the hot-melt mass already deposited on the first, two-dimensional material  51 .  
         [0033]     The heat may be supplied by way of at least one press heating element  35 . Such a press heat element  35  may e.g. consist of several elongate heating profiles which are arranged next to one another in the transport direction at a small distance. With regard to their direction of longitudinal extension, the elongate heating profiles are aligned transversely to the transport direction. In  FIG. 1 , for the sake of simplicity, a press heating element  35  is allocated to only one belt face  33 , but analogously a press heating element may also be allocated to an upper belt face  34 . Likewise, cooling elements (not shown) may be provided in the region of the belt press station  30 . With a suitable sequence of press heating elements and/or cooling elements, one may influence or control the temperature of the laminate  53  along its length and/or width in a targeted manner. The laminate  53  may thus run through a temperature profile which is well defined with regard to time. In  FIG. 1 , only a single press heating element  35  within the belt press station  30  is drawn in for representation. However, further elements influencing the temperature are possible within the belt press module  3 . With this, it may be the case of heating and/or cooling elements which may be attached within or outside the actual belt press station  30 . The laminate is treated in a gentle manner by way of the provision of several heating and/or cooling zones distributed over an as large as possible length, in that it may be treated with lower heating intensities and the transitions between the various temperatures may last longer.  
         [0034]     The belt faces  33 ,  34  of the belt press station  30  may have a straight course, a simple curved course (e.g. circular-arc-shaped, as shown in  FIG. 1 ), a multiple-curved course (e.g. S-shaped) or a combination of these. A curved course may have the advantage that with flexible substrates  51 ,  52 , an undesirable formation of creases may be prevented without the application of excessive pressure. The distance of the belt faces  33 ,  34  needs to be adapted to the respective application in dependence on the substrate thickness, on the pressure to be applied, etc., with means which are known per se.  
         [0035]     The heating elements and/or cooling elements may be immovably fixed in the belt press module  3 . Alternatively, they may be movable in a direction perpendicular to the plane of the laminate in order to process different laminate thicknesses or in order to execute a thickness compensation. In the latter variant, a travel of the heating elements and/or cooling elements may be adjustable. The heating elements and/or cooling elements may also be elastically mounted, and the directional quantity (spring rate) may be adjustable. The heating elements and/or cooling elements may be movable separately or in groups of several mechanically connected heating elements and/or cooling elements. It is also possible to provide movable heating elements and/or cooling elements which are lockable in a certain position. Corresponding means for movably mounting the heating elements and/or cooling elements may be mechanical, pneumatic, hydraulic and/or electromagnetic.  
         [0036]     The pressure for connecting and fixing the two two-dimensional materials  51 ,  52  may be reduced on processing particularly pressure-sensitive materials  51 ,  52  in that the upper belt face  34  is held up without contact. This may be effected e.g. magnetically or pneumatically (by suctioning). The sagging of the upper belt face  34  is alleviated by way of this, and an undesired high compression loading of the materials  51 ,  52  to be connected is avoided.  
         [0037]     In the case that the belt press station  30  is not to be applied, bypass paths  71 ,  72  for the two materials webs  51 ,  52  are provided. These in the present embodiment example run below the belt press station  30  and are shown in  FIG. 1  as phantom lines. The possibility of bypassing the belt press station  30  increases the flexibility of the field of application of the device  1  according to the invention.  
         [0038]     Although the embodiment example represented in the drawings relates to flexible sheet formations  51 ,  52  such as textile material webs, the invention is also suitable for connecting rigid or stiff substrates such as steel, aluminum plate veneering, plastics or nonwovens. Thus a rigid plate as a second, two-dimensional material  52  may be introduced into the calendar  26  which is arranged in entry region of the belt press module  3 . In the case that the rigid, two-dimensional material  52  is plane, the belt faces  33 ,  34  of the belt press station  30  need to have a straight course.  
         [0039]     The hot-melt module  2  and the belt press module  3  may be expanded by further modules (not drawn in). These further modules may be arranged in front of, between and/or after the modules  2 ,  3  discussed above. Such further modules may e.g. be an intermediate storage means, a cutting station, a transport table, a winding station and/or an unwinding station.  
         [0040]     One may provide a platform  81  and an operating unit  82  for operating persons  80 .  
       LIST OF REFERENCE NUMERALS  
       [0000]    
       
           1  device  
           2  hot-melt module  
           20  hot-melt mass deposition station  
           21  gravure roller  
           22  doctor beam  
           23  doctor blade  
           24  counter roller  
           25  post-heating element  
           26  calendar  
           3  belt press module  
           30  belt press station  
           31 ,  32  transport belts  
           33 ,  34  belt faces  
           35  press heating element  
           36  preheat element  
           4  module delimitation  
           51 ,  52  first and second, two-dimensional material  
           53  laminate  
           61 ,  62  unwinding stations  
           71 ,  72  bypass paths  
           80  operating person  
           81  platform  
           82  operating unit