Patent Number: 047913037
Section: description

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS The present invention is directed to both apparatus and methods for the utilization of cold plasma techniques in laminating at least two polymeric sheets, without the use of any substantial heat which might cause a degradation of the structure of such polymeric sheets and thus result in a diminution of the physical properties and desirable characteristics thereof, and also without the use of any separate adhesive material. The cold plasma reactor methods and apparatus of the present invention are specifically directed to activating the surface of a first sheet of polymeric film material to form free radicals thereon for effecting adhesion with a second sheet of polymeric sheet material. The cold plasma reactor apparatus of the present invention in a broad embodiment thereof comprises cold plasma generating cathode and anode respectively disposed is spaced proximity with the first sheet of polymeric material. Means are providing for flowing a stream of a cold plasma generateable gaseous medium past the cold plasma generating cathode. In addition thereto, sheet transporting means for effectuating relative movement between the cathode and the treated surface of the first sheet of polymeric film material for exposing a substantial portion of the surface of such first sheet to such cold plasma is further provided. Such cold plasma reactor includes cathode means which are disposed and spaced at a selected distance from one side of the first sheet of polymeric material. In such embodiments, the accompanying anode is disposed also in selected spaced array from the opposite side of such first sheet, and in certain preferred embodiments in contact with such opposite side thereof. In these preferred embodiments, the cathode comprises a pair of conductive cathode bodies projecting towards the adjacent surface of the first sheet. Such conductive cathode bodies may preferably comprise a pair of elongated elements which extend in a longitudinal direction. Such elongated pair of cathode bodies are preferably disposed substantially parallel to each other along the longitudinal extent thereof. The conductive cathode bodies as described hereinabove have a substantially sharp terminal edge facing the surface of the first sheet of polymeric material to be treated with the cold plasma. Each of such pair of upwardly projecting cathode bodies is also preferably substantially thin, and in preferred embodiments such conductive cathode bodies may comprise a plurality of razor blade bodies disposed end-to-ed and with the sharpened edge portion thereof disposed upwardly and toward such surface of such first sheet. The means for flowing a stream of the cold plasma generatable gaseous medium is disposed in preferred embodiments to provide flow of such gas in a stream between the pair of conductive cathode bodies. The above means for effectuating relative movement between the cathode and the treatment surface of the first sheet preferably comprises at least one conductive roller disposed opposite the cathode. The conductive roller extends in a longitudinal direction, and in such preferred embodiments the conductive roller also comprises the anode. Also included in preferred embodiments of the cold plasma reactor apparatus of the present invention is a cathode housing means for defining a cold plasma containing chamber. Such cold plasma containing chamber has the cathode disposed therein. Such cathode housing defines the cold plasma containing treatment chamber, and which treatment chamber extends longitudinally, and essentially parallel with the longitudinal dimension of the conductive anodic roller. Thus, the cold plasma containing, or treatment, chamber is defined by such cathode housing walls and is formed of an insulator material, and has a mouth at one end thereof for disposition of the first sheet of polymeric material thereacross to form a substantial relative seal of the chamber by means of the first sheet of polymeric material. Although such relative seal in preferred embodiments is sufficient to permit some pressurization of such chamber, other alternative embodiments do not require a seal, but rather comprehend such polymeric material as constituting a not substantially sealing cover means for the end of such chamber. In such preferred embodiments, the first sheet of polymeric material is transported across the mouth of the cold plasma containing chamber while simultaneously substantially maintaining the relative seal on such chamber to prevent substantial loss of cold plasma from the cold plasma containing chamber, and wherein the treatment surface of the first sheet of polymeric film material faces the cathode within the chamber and is accordingly exposed to such gaseous cold plasma. At least one, and preferably two, non-conductive roller(s) are disposed in spaced array from the conductive roller to assist in effectuating such relative movement between the cathode and the treatment surface of the first sheet of polymeric material in preferred embodiments by functioning as a transporting roller for such first sheet. Such non-conductive rollers are each disposed in spaced array generally on opposite sides of the conductive roller to assist in such relative movement, and in particular to form an ingress roller and an egress roller for transporting such polymeric sheet into such cold plasma reactor, across the cold plasma containing chamber, and out of such cold plasma reactor. In such preferred embodiments, each of the non-conductive rollers is disposed for contact with one surface of the first sheet of polymeric material, and preferably the treatment surface, and the conductive roller is disposed for contact with the opposite surface thereof. In the above preferred embodiments, the cathode bodies are carried by a cathode frame. Means for flowing a stream of the cold plasma generatable gaseous medium between the pair of elongated conductive cathode bodies comprises a plurality of substantially evenly spaced gaseous medium inlets disposed in longitudinal array in the cathode frame. Such evenly spaced gaseous inlets open within a longitudinally extending trough formed in the cathode frame and between the longitudinally extending, elongated, and evenly spaced cathodes. Thereby, such cathodes in conjunction with the associated trough spaced therebetween function together to maintain the pressure of the gaseous medium at a substantially equal level over the longitudinal dimension of the elongated cold plasma containing chamber. Also, in preferred embodiments of the cold plasma reactor apparatus of the present invention, pressurization means for pressurizing the cold plasma containing chamber are provided. Such pressurization means may preferably comprise means for substantially providing continuous gas flow to the cold plasma containing chamber. Means for substantially continuously removing gas from the cold plasma containing chamber to provide a constant flow thereof are also provided. Such means further function substantially to diminish leakage of the gas from the chamber, and may further function to reclaim such gaseous medium for reuse. The above cathode frame further includes at least one internal channel extending longitudinally along the length thereof for supplying gas to the plurality of gaseous inlets which are substantially evenly spaced along the length of the cathode frame. Such cathode frame is dimensioned to fit snugly and removably within the cathode housing along the respective longitudinal dimensions thereof. In such preferred embodiments, such cathode housing defines the cold plasma containing chamber and includes a longitudinally extending slot in the wall thereof opposite the first sheet, into which slot the longitudinally extending pairs of cathodes are disposed to project into the cold plasma containing chamber, and to provide the gaseous medium to such cold plasma containing chamber from the trough disposed between the pair of elongated cathode bodies. As set forth in the description hereof, the above cold plasma reactor apparatus provides examples of apparatus suitable for carrying out the cold plasma techniques and methods of the present invention for laminating at least two polymeric sheets into a composite having improved and/or hybrid properties. Such methods comprise in certain broad embodiments thereof the steps of first providing a first sheet of polymeric material; next, exposing the surface of the first sheet of polymeric material to cold plasma to activate the surface thereof; and finally, disposing such activated surface of the first sheet into intimate proximity with the second sheet of polymeric material and pressing such first sheet and second sheets together to effect adhesion therebetween, to form a laminated composite in the absence of any substantial heating of either of such sheets and without application to either of such sheets of a separate adhesive. In the inventive cold plasma methods of the present invention, such first and second and/or further polymeric sheets may be composed of different polymeric materials. At least one of such first sheet and such second sheet may be maintained in rolled form prior to such laminating to form such composite. After such laminating, such laminating composite is preferably also wound into rolled form for convenience of transportation and storage. The cold plasma utilized in the methods of the present invention preferably comprises cold argon plasma. Such cold argon plasma is generated in preferred embodiments by application to a gaseous mixture of approximately at least one percent to two percent argon, or other inert gas, in air of an electromagnetic energy discharge of at least approximately 180,000-500,000 volts, such gaseous mixture preferably comprising a stream of such gaseous material and which preferably comprises argon. The cold plasma utilized in the methods of the present invention is generated by application of electromagnetic energy of a frequency in the radio wave length to the inert gas. Such radio frequency discharge is carried out at approximately the frequency of 12.56 megaHertz. The cold plasma is also preferably maintained at a selected pressure of approximately at least 1.1 Torr during such treatment by such cold plasma of such first sheet. In some preferred embodiments of the method of the present invention, the pressure of the cold plasma and the voltage applied thereto may be individually controlled and maintained in proportional relationship to each other. In such methods, there may be preferably an inverse proportional relationship between the pressure of the cold plasma and the voltage applied thereto. Such inverse proportional relationship may be controlled automatically, such as for example by means of an adiabatic pressure valve, examples of which are known to those skilled in the pressure valve arts. In certain preferred embodiments, the first sheet of polymeric material in such improved methods of the present invention is exposed to the cold plasma for a period of approximately less than approximately 5.0 milliseconds. Such first sheet is run through such cold plasma treatment chamber at a rate of approximately 500 feet per second. In the improved methods of the present invention, the cold plasma is generated by means of application of energy of a selected frequency to a gas wherein such gas has a flow rate of approximately at least 10 milliliters per second per linear meter onto the surface of such first sheet. Referring now to the drawing and to FIGS. 1 and 2 in particular, wherein illustrative embodiments of the cold plasma apparatus generally 10 are shown, left side end plate 12 includes therein the three axes of rotation 14, 16, 18 for the respective journals for rollers 20,22,24, as shown in FIG. 2. In particular, conductive roller 20 comprising the anode is disposed between the two non-conductive rollers 22,24. FIG. 1 further depicts the cover plate 26 for the electrical terminal 28, and which is secured by means nylon cap screws 30, and stainless steel cap screws 32. Such cover plate 26 is disposed generally between such non-conductive roller axes 14,18. FIG. 1 further shows the reactor covers 34,36 which are hemispherically shaped in cross-section with ingress and egress openings 38,40 respectively located at the bottom and top respectively thereof, and with such reactor covers 34,36 maintained and secured thereon by means of thumb screws 42. Tapped screw holes 43 are provided for securing reactor apparatus 10 to externally associated frame and support means (not shown) for positioning in proper relationship with the various rolls of sheet material stock and the roller(s) for the composite laminate in its various stages of formation. FIG. 2 shows left side and right side end plates 12,44, which hold means thereon for journaling for rotation the pair of non-conductive rollers 22,24 disposed on either side of the conductive anodic roller 20. The respective end portions 46,48 of anodic roller 20 include spring-loaded electrical clips 50,51 for contacting commutator rings 52,54 to provide electrical contact between the power source (not shown) and the commutator rings 52,54 disposed at each respective end 46,48 and around the conductive, anodic roller 20. Such electrical clips 50,51 are secured by means of thumb screws 56,58 to a removable electrical clip support bar 53 which extends longitudinally across the length of reactor apparatus 10, as shown in FIG. 2 and in cross section as shown in FIG. 6. FIG. 2 further illustrates spring-loaded grips 60,62 for holding such clip support bar 53, the structure and functioning of which are shown in greater detail in FIG. 7, as described, infra. FIG. 3 shows electrical terminal 28 connected to electrical contact 64 and to spring 66 for insuring contact with cathode contact 70 which is connected to the cathode generally 80 by means of cathode connector plates 82. Cathode 80 is supported by a longitudinally extending cathode frame 84 having supported thereon the longitudinally extending conductive cathode bodies 86,87 comprising a plurality of end-to-end positioned, upwardly directed razor blade bodies, the sharp edges of which are disposed in proximity to such conductive roller 20 and forming a treatment chamber 88 therebetween, as depicted more particularly in FIG. 6. In the jogged right hand portion of FIG. 3 generally 90, securement means in the form of cathode bolts 92 for securing such razor blade cathodes 86 to such cathode frame 84 are shown. Cover bar 83 and shim 85 in FIGS. 3,4,5 and 6 are secured to and under cathode frame 84 by bolts 85, and to cathode holder 100 by bolts 87, as shown in FIG. 5, to hold cathode bodies 86 in functional position. In FIG. 4 gas inlet 94 for supplying the gaseous medium from an external source (not shown to) longitudinally disposed gaseous supply conduit 96 is shown for in turn providing the gaseous plasma medium to gaseous inlets 98 in cathode holder 84 which also carries such cathode bodies 86. Such gaseous inlets serve to uniformly distribute such gaseous medium upwardly into the cold plasma chamber 88, as shown by the path of Arrows B,B in FIGS. 3 and 4. FIGS. 5 and 6 depict cathode holder 100 of the cold plasma reactor apparatus 10 which contains means for continuously removing the gaseous cold plasma from reactor appaaratus 10 in the path as shown at Arrows C,C in FIGS. 5 and 6 through vacuum outlet 102. In particular, cathode holder 100 includes downwardly directed gaseous medium exhaust channels 101,101, which in turn feed into horizontally directed gas exit passages 103,103 eventually to exit reactor 10 through vacuum outlet 102. Exit passages 103,103 lead into and communicate with a single exhaust collection chamber 93 defined by an end cap 95 covering an aperture cut into right side end plate 44, which end cap 75 is secure to end plate 44 by bolts 97. Such cathode holder 100 is secured to each end plate 12,44 by means of screws 104, as shown in FIG. 5. As shown particularly in FIG. 6, cathode housing 100 includes upwardly extending walls 108 for defining cold plasma containing chamber 88. Such cold plasma containing chamber 88 has the cathode bodies 86 disposed therein. Such cathode housing 100 thus defines the cold plasma containing treatment chamber 88, and which treatment chamber 88 extends longitudinally, and essentially parallel with the longitudinal dimension of conductive roller 20 as shown in FIGS. 3-5. Cold plasma containing, or treatment, chamber 88 comprising housing walls 108 formed of an insulator material has a mouth at one side thereof, which is the tope side as shown in the embodiment of FIG. 6, for disposition of the first sheet 106 of polymeric material thereacross to form a substantial relative sealing of chamber 88 by means of the first sheet 106 of polymeric material covering and disposed across such mouth of chamber 88. In such preferred embodiments, the first sheet 106 of polymeric material is transported across the mouth of cold plasma containing chamber 88 in the direction of Arrows A,A while simultaneously substantially maintaining the seal on such chamber 88 to prevent substantial loss of cold plasma from the cold plasma containing chamber 88, and wherein the treatment surface 105 of the first sheet 106 of polymeric film material faces cathode bodies 86 within chamber 88 and is exposed to such gaseous cold plasma. As shown in FIG. 6, each of non-conductive rollers 22,24 is disposed is spaced array from conductive roller 20 to assist in effectuating such relative movement between cathode bodies 86 and the treatment surface 105 of the first sheet 106 of polymeric material in preferred embodiments by functioning as a transporting roller for such first sheet 106. Such non-conductive rollers 22,24 are each disposed in spaced array generally on opposite sides of conductive roller 20 to assist in such relative movement and in particular to form an ingress roller 24, and an egress roller 22 for transporting such polymeric sheet 106 into such cold plasma reactor 10 at ingress 38 across the cold plasma containing chamber 88, and out of such cold plasma reactor 10 at egress 40. As shown in FIG. 6, in such preferred embodiments each of non-conductive rollers 22,24 is disposed for contact with treatment surface 105 of the first sheet 106 of polymeric material, and conductive roller 20 is disposed for contact with the opposite surface 107 thereof. In the above preferred embodiments as shown in FIG. 3, cathode bodies 86 are attached to, and carried and supported by cathode frame 84. Means for flowing a stream of the cold plasma generatable gaseous medium between the pair of elongated conductive cathode bodies 86,86 as shown best in FIG. 6 comprises a plurality of substantially evenly spaced gaseous medium inlets 98,98 as shown in FIGS. 3-4, and which are disposed in upwardly directed longitudinal array in cathode frame 84. Such evenly spaced gaseous inles 98 open within a longitudinally extending trough 112 formed in cathode frame 84 and between the longitudinally extending, elongated, and evenly spaced cathode bodies 86. Thereby, because off such uniform dimensions and spacing, such cathode bodies 86 in conjunction with associated trough 112 spaced therebetween function together to maintain a uniform volume for such gaseous medium and thereby to maintain the pressure of the gaseous medium at a substantially equal level over the longitudinal dimension of the elongated cold plasma containing chamber 88. Also, in preferred embodiments of the cold plasma reactor apparatus 10 of the present invention, pressurization means for pressurizing the cold plasma containing chamber are provided. Such pressurization means may preferably comprise means for substantially providing continuous gas flow to the cold plasma containing chamber 88 as shown in FIG. 4 by means of gaseous medium inlet 94. Means for substantially continuously removing gas from cold plasma containing chamber 88 to provide a constant flow thereof are also provided as shown in FIGS. 5-6. Such means further function substantially to diminish leakage of the gas from the chamber, and may further function to reclaim such gaseous medium for reuse. Cathode frame 84 further includes at least one internal channel comprising gaseous supply conduit 96 extending longitudinally along the length thereof for supplying such gaseous plasma medium to the plurality of gaseous inlets 98 which are substantially evenly spaced along the length of cathode frame 84. Such cathode frame 84 is dimensioned to fit snugly and removably within the cathode housing 100 as shown in FIG. 6 along the respective longitudinal dimensions thereof. In such preferred embodiments, such cathode housing 100 defines the cold plasma containing chamber 88 and includes a longitudinally extending slot 114 in the wall thereof opposite first sheet 106 into which slot the longitudinally extending pairs of cathode bodies 86,86 are disposed to project into the cold plasma containing chamber 88, and to provide the gaseous medium to such cold plasma containing chamber 88 from trough 112 disposed between the pair of elongated cathode bodies 86,86. Referring now to FIG. 7, the anti-rotational mechanism for preventing rotation of the journal for non-conductive roller 22 is depicted, and comprises a non-rotational pin 116 which interconnects rotational journal holder 118 with left side end plate 12. As depicted, roller bearings 120 are disposed on non-conductive roller 22 for rotation thereof about shaft 122. FIG. 8 depicts the grip and locking mechanism for the contact springs 50 and includes a slideable grip 60 which is slideable within slot 61 and is connected by screws 63,63 to a locking bar 65 as disposed within right side end plate 44 and as urged by coil spring 67. Thus, the functioning of grip 60 is to permit removal of bar 53 which functions to hold contact springs 50,51. The above methods and apparatus may be utilized in several variations and alternative embodiments. Specifically, the above laminate may comprise two layers, one of which comprises a sealant layer, and the other which comprises a barrier layer. Such sealant layer may comprise a polyolefin, such as for example polyethylene. The barrier layer may comprise polyvinyledine chloride, polyvinyl alcohol, polyacrylonitrile, etc. In other embodiments, the barrier layer may be sandwiched between two such sealant polymer layers. Also in yet other embodiments of the invention hereof, such laminate may form a primary web, which may then be further joined to a secondary and non-laminated web. In yet other embodiments, the above laminate may be joined on both sides thereof by separate secondary non-laminated webs. In the above embodiments, the secondary web may comprise a heavier gauge plastic sheet, such as high density polyethylene, polyvinyl chloride, polyacrylonitrile, polyethylene teraphthalate, nylon, polyurethanes, polystyrenes, polyvinylidene chloride, acrylonitrile, and/or other suitable polymers. Other gases useful for generating such cold plasma may comprise nitrogen, helium, xenon, krypton, neon, and/or other inert gases. Various different materials may be utilized as and for the elements of the cold plasma reactor apparatus of the present invention. The conductive roller may preferably comprise stainless steel. The contact springs and the commutator rings may comprise phosphor bronze. The various thumb screws may be formed from brass or nylon. The plate cover may also preferably comprise stainless steel, as does the compression spring. The connector screws may comprise stainless steel, brass, etc. The cathode bodies may preferably comprise one half of double-edged stainless steel razor blades, and preferably with platinum coating, as produced, for example, under the Schick.RTM. trademark by Warner Lambert Company of Morris Plains, New Jersey. Most of the non-conductive structural materials, such as the right and left side end plates, the non-conductive rollers, the cathode frame, the cathode housing, etc. may be formed from a high density polymeric material sold under the trademark Delrin.RTM. produced by E. I. Dupont Company of Wilmington, Del. The ball bearings contained within the journal for the non-conductive rollers preferably comprise a nonmetallic material, such as nylon orfoss. The male connector for the gas input is preferably formed from black polyethylene, as is the male connector for the vacuum suction. Cap screws and other screws which are not subjected to large amounts of force may be formed of nylon. The basic and novel characteristics of the improved methods and apparatus of the present invention will be readily understood from the foregoing disclosure by those skilled in the art. It will become readily apparent that various changes and modifications may be made in the form, construction and arrangement of the improved apparatus of the present invention, and in the steps of the inventive methods hereof, which various respective inventions are as set forth hereinabove without departing from the spirit and scope of such inventions. Accordingly, the preferred and alternative embodiments of the present invention set forth hereinabove are not intended to limit such spirit and scope in any way.