Abstract:
Provided is a method for bonding continuous traveling webs, which allows for significant increase in web processing speeds. A method according to the present invention includes providing a web including a bonding agent that may require activation prior to adhesion. Bonding agent activation may be, for example, by heat transfer or wetting. The primary activation of the bonding agent occurs separately from any applied force required for proper adhesion. Adhesion force may be applied by a noncatalytic pressure means including a crimp roller. The method may further include the insertion of a product between web layers to be brought into adhesive engagement with one another. A further web process step may include the cutting of bonded webs.

Description:
RELATED APPLICATION  
       [0001]     This application claims the benefit of co-pending U.S. Provisional Patent Application No. 60/840,584, filed 28 Aug. 2006. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     Generally, the present invention relates to bonding multiple webs. More specifically, the present invention is directed to a method for bonding traveling continuous webs by activating an applied bonding agent prior to applying pressure with a crimp roller that is noncatalytic with respect to the bonding agent.  
         [0003]     Prior art methods exist for bonding traveling webs. However, these methods are limiting, especially with respect to the speed of the traveling web. Often, webs to be joined contain a bonding agent that requires activation for bonding, such as thermoplastic resin materials which may be joined and sealed under the application of heat. In such an instance the heat acts as a bonding agent catalyst, thereby changing the bonding agent phase generally from a solid to a liquid. Some bonding agents, and especially heat seal synthetics, have been limiting. Most often, prior art methods supply the required catalyst simultaneously with a required bonding pressure, as through the use of a heated crimp roller. A heated crimp roller, as understood in the art, is a roller that has a heated surface, which applies desired pressure at the nip of the heated roller and an opposing surface. The opposing surface may also be a roller. Therefore, the heat, or bonding agent catalyst, is applied at the same time as the pressure.  
         [0004]     While seemingly efficient, the process of applying heat and pressure simultaneously is not advantageous for webs traveling at very high speeds. That is, bonding agents requiring activation also generally require some finite activation duration. Therefore, the speed at which a web having a deactivated bonding agent can travel through an activating roller is constrained by the activation duration. As an example, if a bonding agent requires an activating duration of J seconds at a predetermined temperature, then the maximum cycles at which a combined process can run is 1/J cycles per second. Currently, the processes employed in the art run at a maximum speed of around 85-120 cycles per second, thus indicating an activating duration of about 8-12 milliseconds.  
       SUMMARY OF THE INVENTION  
       [0005]     Surprisingly, the separation of the processes of bonding agent activation and bonding pressure application allows exponential increase in the speed of the traveling web. Conversely, an exponential increase in the speed of a traveling web allows the separation of adhesive activation and bonding pressure application. That is, although workable at a variety of speeds, a high rate of speed makes possible the activation of the bonding agent prior to applying pressure because the activated bonding agent does not have enough time to deactivate prior to the pressure application.  
         [0006]     The present invention provides a method for bonding continuous traveling webs using a pressure means that is noncatalytic with respect to a web bonding agent. The device and method allow the speed of the traveling web to increase beyond the previously limiting bonding agent activation dwell time. By ensuring that the applied bonding agent is active at the time the webs reach the pressure means, there is no need to include the bonding agent activation within the same device.  
         [0007]     By employing an embodiment of the method of the present invention, the output of a sealing process has increased dramatically. Rather than running at a limited 85-120 cycles per minute, speeds can be substantially increased by approximately five hundred percent or more.  
         [0008]     Provided is a method for bonding traveling webs. The method involves a provided web or plurality of webs, at least one of which has a bonding agent applied thereto. The bonding agent is activated, thereby creating an activated web portion. The activated web portion is conveyed some distance and then the web or plurality of webs is compressed, thereby forming a bonded web by an adhesive engagement between at least two of the plurality of webs or between two surfaces of the same web having been arranged in a general C-shaped cross-section. The arrangement of a single web into a general C-shaped cross-section relative to its direction of travel may occur prior to the providing of the web material. In other words, a prefolded web may be provided. In addition, the arrangement may occur before or after the activating step. In one embodiment, the activating step may include heating said bonding agent by conductive heat transfer by way of heated rollers, for example. In another embodiment, heating may include radiant heat transfer, such as induction heating. As different bonding agents may require different activation, an alternate embodiment may include an activating step comprising wetting the bonding agent.  
         [0009]     The compression of web surfaces may be achieved by a pressure means to which the webs are conveyed after the bonding agent having been activated. In one embodiment the pressure means comprises a crimp roller and an opposing roller. The crimp roller may include at least one indentation protruding radially inward from an outer surface of the roller. The pressure means is noncatalytic with respect to said bonding agent. That is, although a portion of the bonding agent activation may occur at the pressure means, the primary bonding agent activation occurs separately from the pressure means. The bonding agent may be applied to one or more webs in a uniform pattern.  
         [0010]     The compression of the webs creates an adhesive engagement between two web surfaces. The adhesive engagement may be a closed shape, such as a generally rectangular, generally elliptical, or generally triangular. Alternatively, the adhesive engagement may be an open shape, such as a general C-shape, general V-shape or general W-shape.  
         [0011]     A method according to the present invention may include further processing steps. For instance an embodiment of the present invention further includes a step of cutting the bonded web. Another additional processing step may be the insertion of a consumable product between at least two bonded web layers, where the product is contained at least partially by the adhesive engagement holding the web layers together. Examples of such consumable product are a preparation pad moistened with isopropyl alcohol or even a food product. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is a diagrammatic representation showing two traveling webs being joined by a method according to the present invention.  
         [0013]      FIG. 2  is a diagrammatic representation of an embodiment of the present invention.  
         [0014]      FIG. 3  is a diagrammatic representation of a second embodiment of the present invention.  
         [0015]      FIG. 4  is a top perspective view of noncatalytic crimp rolls as employed in the present invention.  
         [0016]      FIG. 5  is a top plan view of a single bonded compartment made by a method according to the present invention.  
         [0017]      FIG. 6  is a cut away view of the compartment of  FIG. 5  taken along line  6 - 6 . 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0018]     Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention which may be embodied in other specific structures. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims.  
         [0019]     Definition: The adjective NONCATALYTIC, as used in this specification, is meant to convey that the noun which it modifies is not the primary source of bonding agent activation. That is, if the bonding agent is heat activated, a noncatalytic roller is a roller that is not the primary source of heat which activates the bonding agent.  
         [0020]     If there exists any discrepancy between the ordinary understanding of the term NONCATALYTIC and the above stated definition, then both definitions shall apply.  
         [0021]     Referring to  FIG. 1 , a diagrammatic representation of two traveling webs  11 , 12  being joined by a method according to the present invention is shown. Generally, the method includes the steps of providing a plurality of webs  11 , 12  having an applied bonding agent  112  at a first location  20 , activating  100  the bonding agent  112 , thereby producing a pair of separated webs having activated bonding agent  112  at a second location  21 , causing the webs  11 , 12  to travel some distance and applying pressure to the webs  11 , 12  at a third location  200 , thereby forming a bonded web  17 . This operation can especially be seen in  FIG. 4 . The applied bonding agent  112  may be applied across the entire surface of the traveling webs  11 , 12  or in a predetermined pattern. Additionally, the bonded web  17  may further be cut at a fourth location  300 , or simultaneously with the application of pressure at the second location  200 . The cutting of the bonded web  17  is preferably carried out by first longitudinally slicing the bonded web  17  by a rotary cutter and anvil  19  followed by a cutter roll  15  acting on an anvil roll  16 . The cutter roll  15  has a plurality of projections  151  that act in a cooperative fashion with the surface  161  of the anvil roll  16  at the nip  156 . The result of cutting may be a plurality of single bonded compartments  18 . Alternatively, rather than provide a plurality of webs  11 , 12 , a single web turned on itself in a C configuration could also be employed. The method is then be utilized to bond the opposing surfaces of the single web.  
         [0022]     The activation  100  is generally dependent upon the type of bonding agent  112  that is used. An example of a bonding agent  112  requiring activation, as mentioned above, is a thermoplastic resin material, which is activated by heat. A representative thermoplastic resin material is Surlyn®, an ionomer resin that has a good affinity for many coating materials. Furthermore, the bonding agent  112  could be a material that is activated by a catalyst, such as an aqueous solution, electric fields, electromagnetic radiation/induction heating, among others.  
         [0023]     Referring now to  FIG. 2 , an embodiment of the method according to the present invention is shown. Generally, the method has an activation stage  100  and a pressure application stage  200 . This embodiment also includes a cutting stage  300 . The bonding agent  112  activation  100  is carried out by heated rollers  101 , 102 . The bonding agent  112 , through the webs  11 , 12  in this embodiment, is sufficiently heated to bring the bonding agent  112  to a temperature that sufficiently activates, but does not destroy, the agent  112 . The temperature at which the bonding agent  112  activates is dependent upon the bonding agent  112  and additional heat may be required, depending upon the distance between a point at which the webs  11 , 12  leave the heated rollers  101 , 102  and a nip point  134  of crimp rollers  13  and  14 .  
         [0024]     Specifically, a first web  11  having a bonding agent  112  applied thereto is fed around a first deflection roller  103  and subsequently around a first heated roller  101 . The first deflection roller  103  may or may not be required, depending upon how the first web  11  is presented to the process. Prior to contact with the first heated roller  101 , the first web  11  can be said to be in a first position  20 . A second web  12  having a bonding agent  112  applied thereto is fed around a second heated roller  102 . While it may be desirable to provide a bonding agent  112  on the second web  12  as well, it may not be necessary, depending upon the particular application. If a bonding agent  112  is not provided on the second web  12 , the second web roller  12  is preferably not heated. After the webs  11 , 12  leave their respective rollers  101 , 102 , the webs  11 , 12  can be said to be in a second position  21 . At the second position  21 , any bonding agent  112  that was applied to either web  11  or  12  is activated. Furthermore, if desired, product  30  to be sandwiched or packaged between the two webs  11 , 12  can be placed while the webs are in the second position  21 . Examples of such product  30  include without limitation a cut or folded, moistened preparation pad saturated with isopropyl alcohol or even a food product.  
         [0025]     Upon reaching the nip  134  of the noncatalytic crimp rollers  13  and  14 , the bonding agent  112  applied to the webs  11 , 12  is still in its active state. The noncatalytic crimp roller  13  preferably has a plurality of indentations  131  in the circumferential surface  132  thereof. If simply mating a first relatively flat web  11  to a second relatively flat web  12 , the indentations may not be desirable. However, where product  30  is placed between the first traveling web  11  and the second traveling web  12 , the indentations  131  may be required to provide adequate sealing pressure between the noncatalytic crimp roller  13  and the opposing roller  14 . After pressure is applied  200 , a bonded web  17  has been formed, which comprises the first web  11  bonded to the second web  12 , perhaps containing a product  30  sandwiched therebetween.  
         [0026]     The resultant seal created by the pressure of the noncatalytic crimp roller  13  may be of any desirable shape. For example, the seal could be a closed shape such as a square, triangle, or circle; the seal could be an open shape like a C shape V shape or W shape; the seal could be linear, longitudinal, transverse or any angle therebetween; or the seal could be continuous, thereby completely laminating a plurality of webs together. The bonded web  17  may contain a plurality of individually sealed products wherein the seal forms the periphery of a product  30  compartment. Alternatively, where a single web may be turned on itself in a C shape, the seal created by the process may itself be C-shaped. That is, the open side of the seal is maintained by a fold in the web. The webs  11 , 12  provided to the process could be single layer webs having a bonding agent provided thereon, or alternatively could be webs having multiple layers of similar or different materials.  
         [0027]     The bonded web  17  may be the final desired product. Alternatively, the bonded web  17  may be subject to further processing, such as cutting. In this embodiment, the bonded web  17  is first longitudinally sliced by a rotary cutter and anvil  19  and then laterally divided by a cutter roll  15  in cooperation with an anvil roll  16 .  
         [0028]     Referring to  FIG. 3 , an alternate embodiment of the method according to the present invention is shown. Like the first embodiment, the method has an activation stage  100 , a bonding stage  200 , and a cutting stage  300 . Rather than use only a first heated roller  101  to heat the first web  11 , and a second heated roller  102  to heat the second web  12 , this embodiment also uses a third heated roller  104  to provide heating to the first web  11  and a fourth heated roller to provide heating to the second web  12 . This arrangement may prove useful where the webs  11 , 12  enter the process at an undesirable angle such that adequate heating could not be provided by only the first heated roller  101 . Additionally, use of multiple heated rollers on the same web allows for more gradual heating of the web. Such an arrangement proves beneficial where the web  11  must be heated to an elevated degree so that the bonding agent  112  can remain activated over an extended distance until pressure is applied  200 . Furthermore, gradual heating is desirable while the webs are traveling at slower speeds or while a machine incorporating the process is idle. Use of a more rapid heating single roller can leave to scorching the webs. More gradual heating could also be achieved by using a larger heated first roller  101  and second roller  102 . An arrangement of that type may require more physical space, however, and such requirement may not be desirable. Also, it may prove difficult to maintain an approximately equal, evenly distributed temperature across the entire surface of a larger roller.  
         [0029]     Other alternatives exist for the activating stage  100  of the bonding method. Although the disclosed method utilizes conductive heat transfer, other means exist for heating a heat activated bonding agent. For instance induction heating, radiant heat emitted by heating coils or lamps may prove desirable. Alternatively, although not desired for the handling of more fragile web material, hot air convection could prove useful in some situations.  
         [0030]     Referring now to  FIGS. 5 and 6 , a single bonded compartment  18  made by a method according to the present invention is shown. The bonded compartment  18  was created by the noncatalytic crimp roller  13  and opposing roll  14  of  FIG. 4 . Generally a desired product  30  was placed between the webs  11 , 12  prior to the application of pressure by the roller  13 . Alternatively, in the case of sandwiching two relatively flat webs to create a multiple layer web, a product  30  is not placed and the bonding agent  112  may be bonded across the entire surface of the webs  11 , 12 .  
         [0031]     The foregoing is considered as illustrative only of the principles of the invention. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims.