Abstract:
A fastening system for releasably securing a diaper provides both mechanical and adhesive or cohesive securement. Tab members comprise a facestock layer, a contact layer of adhesive or cohesive overlying at least a portion of the facestock layer, and mechanical fastening elements projecting from at least a portion of the contact layer. The facestock layer includes extensible and substantially nonextensible polymeric portions. A landing member includes complementary mechanical fastening elements and a contact surface or cohesive for engagement with the tab adhesive or cohesive. A method is also disclosed for making the fastening system.

Description:
This application claims the priority of U.S. Provisional Application No. 60/010,042, filed Jan. 16, 1996. 
    
    
     BACKGROUND OF THE INVENTION AND RELATED ART 
     The present invention relates to closures and methods of making closures for fastening adjacent portions or edges of materials or components together. The closures are useful as fastening system closures for disposable diapers. 
     Diapers of this general type are widely used. A typical diaper construction comprises an absorbent pad or batt or the like enclosed in an outer plastic shell or a non-woven backsheet that is non-woven fabric laminated with a water impermeable layer such as a polyethylene film. A water permeable inner shell or liner is also provided to promote separation of fluid from the user. 
     The fastener tape system generally includes adhesive tabs fastened to one end of the diaper assembly construction at each lateral side of the diaper in a permanent “factory joint” by the diaper manufacturer using adhesives or other techniques. The tabs have a face coated with pressure-sensitive adhesive. The tabs are releasably attachable to the other end of the diaper at each lateral side in a “user joint”. The attachment is releasable both to allow permanent removal of the diaper and to allow unfastening to inspect the diaper followed by refastening if indicated. 
     The user joint may be formed by direct connection of the tab to the diaper outer surface whether the latter is formed of a plastic film or a non-woven backsheet. In the case of plastic film shells, it is typical to provide a “landing zone” formed of reinforcing tape or the like for receiving the end of the tab to form the user joint. The landing zone may provide a plastic surface or a non-woven surface and may comprise a knit type fabric landing pad. 
     The fastener tape system may rely solely upon pressure-sensitive adhesive in the formation of the user joint as shown in U.S. Pat. Nos. 4,795,456, 4,710,190, 4,020,842 and 3,833,456. The use of combined adhesive and mechanical fastener systems is shown in U.S. Pat. Nos. 5,019,065, 5,053,028 and 4,869,724. The teachings of all of these patents being incorporated herein by reference. 
     The use of extensible or stretchable tabs to promote user comfort through better fit and more secure mounting is also known in the art. The tabs operate as extensible diaper side waistbands. Examples of such diaper fastening systems are disclosed in U.S. Pat. Nos. 4,795,456, 4,066,081, 4,051,853 and 3,800,796. 
     Related art includes U.S. Pat. Nos. 3,464,094, 4,239,829, 5,250,253 and European Publication No. 0 191 355. 
     SUMMARY OF THE INVENTION 
     The present invention provides an extensible tab fastener system having a user joint that enables combined mechanical and adhesive attachment. The mechanical and adhesive attachments each contribute to the total integrity or strength of the diaper closure or user joint, and neither has to be fully effective to provide the required total closure strength. The tab fastener system may be produced by high speed manufacturing processes including coextrusion. 
     In the illustrated embodiments, the fastening system tab members comprise a facestock layer, a contact securement portion comprising a layer of adhesive or cohesive overlying at least a portion of the facestock layer, and mechanical fastening elements projecting from at least a portion of the contact layer. The tab contact securement portion extends over at least a portion of the extensible and substantially nonextensible polymeric portions of the facestock layer. A landing member includes complementary mechanical fastening elements and contact securement portion comprising a contact surface or cohesive for engagement with the tab adhesive or cohesive. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a tab fastener of a tab fastener system in accordance with the invention; 
     FIG. 2 is a fragmentary perspective view on a reduced scale showing the tab fastener system of FIG. 1 applied to a diaper with the tab in the deployed position ready for closure; 
     FIG. 3 is a fragmentary schematic plan view showing the process for making a tab fastener in accordance with the invention; and 
     FIG. 4 is a perspective view similar to FIG. 1 showing a tab fastener in accordance with another embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIGS. 1 and 2, a diaper tab  10  for use in closure of a diaper  12  is shown. The diaper tab  10  includes a facestock film  14 , an adhesive layer  16  and mechanical engagement or fastening elements  18 . 
     The facestock film  14  includes an extensible central polymeric portion  14   a  and nonextensible terminal or polymeric portions  14   b . The extensible portion  14   a  may be formed of elastomers such as the thermoplastic elastomers sold by the Shell Chemical Company under the designations Kraton. These elastomers may be SBS, SIS, SI, S(IS) x  and SEBS block copolymers and mixtures thereof. The nonextensible portions  14   b  of the film  14  may be formed of polypropylene, polyethylene and combinations of such polymers having suitable film forming characteristics. 
     The adhesive layer  16  may be formed of known adhesive materials such as a pressure-sensitive adhesives including acrylic resin and natural or synthetic based rubber adhesives. Preferred adhesives include hot melt pressure-sensitive adhesives of the A-B-A block copolymer type comprising an elastomeric B-block derived from isoprene and thermoplastic A-blocks derived from styrene as disclosed in U.S. Pat. No. 3,932,328. Illustrative rubber based adhesives include styrene-isoprene-styrene and styrene-butadiene-styrene which may optionally contain diblock components such as styrene isoprene and styrene butadiene. The layer  16  may comprise a cohesive as taught in U.S. Pat. No. 5,085,655 to Mann, which patent is also owned by the assignee herein. The adhesives or cohesives may be applied using hot-melt, solvent or emulsion techniques. The adhesive or cohesive layer  16  may extend along a portion of or substantially all of the adjacent surface of the layer  14 . 
     The elements  18  are integrally formed with the facestock film  14  in the illustrated embodiment. However, the elements  18  may be separately formed and attached to the surface of the facestock. The elements  18  extend generally perpendicular from the facestock film  14  and project through the adhesive layer  16 . The protuberances provided by the projecting or exposed ends of the elements  18  should be of sufficient length to provide mechanical engagement with a locking or engaging array of elements, or with a fibrous material such as a non-woven landing tape or member  20  having fibers  20   a  as shown in FIG. 2 or a non-woven backsheet of a diaper. Further, the polymer forming the nonextensible portions  14   b  and the elements  18  should be of sufficient stiffness to provide the required shear strength engagement. It is preferred to dispose the elements  18  along only the nonextensible portions  14   b  since is believed to enhance the shear resistance by limiting tendency of the elements  18  to be laterally displaced. 
     The pressure-sensitive adhesive is relatively more extensible or stretchable than other adjacent layers, and the tab  10  has overall extensibility characteristics substantially corresponding with the facestock film  14 . That is, the tab  10  includes a central elastic portion  10   a  corresponding with the location of the portion  14   a  and nonextensible terminal portions  10   b  corresponding with the locations of portions  14   b . As shown, each of the portions  14   a  and  14   b  extend across the width of the tab  10  at spaced locations along the length of the tab extending between the end portions of the diaper to be joined. 
     Referring to FIG. 2, one of the terminal portions  10   b  of the tab  10  is secured to the diaper  12  at a factory joint at one of the lateral sides at one end of the diaper  12 . The other terminal portion  10   b  is deployable to form a user joint with the landing tape  20  to close the diaper about a wearer such as an infant. It should be appreciated that the tab  10  may be provided with nonextensible facestock portions adjacent each end thereof to facilitate the provision of the factory joint with the diaper at one end and the manipulation of the tab to form the user joint at the other end. 
     The tab  10  and the landing member  20  provide a fastener system having both mechanical and adhesive engagement. During use, the elements  18  particularly provide shear strength and the pressure-sensitive adhesive layer particularly provides tack strength. This may be achieved with the adhesive bond between the pressure-sensitive adhesive layer  16  and the fibrous surface of the landing member  20 . If the layer  16  is a cohesive, then the landing member  20  must also include the cohesive as a coating having the fibers  20   a  extending therethrough, discrete cohesive particles carried by the fibers  20   a  or as a separate cohesive area. 
     Referring to FIG. 3, a coextrusion die  22  extrudes the facestock film  14  as a side-by-side coextrusion including adjacent portions  14   a  and  14   b . For convenience, the film  14  is shown to include a limited number of adjacent extensible and nonextensible portions, however, a much larger number of such portions may be provided along the width or cross direction of the film  14 . 
     The film  14  upon exiting the die  22  engages a molding-casting roll  24  for purposes of further shaping the film. In this instance, the roll  24  cooperates with the die to form mechanical engagement elements  18  at least along the nonextensible portions  14   b . The elements  18  may have a variety shapes such as hooks or mushrooms as are well known in the art. Fibrous hook and loop engagement elements are preferred. 
     The coextrusion processing requires a matching or near matching of the melt flow characteristics of the plastic materials forming the portions  14   a  and  14   b . Such matching and processing techniques are known in the art and illustrated, for example, in U.S. Pat. No. 3,800,796. 
     The adhesive layer  16  is applied to the facestock film  14  along the surface having the elements  18  extending therefrom. As indicated above, the thickness of the adhesive layer  16  assures a sufficient projection of the elements  18  to effect mechanical engagement. The adhesive may be applied at the time of the manufacture of the film  14  or at a later time and, in either case, known techniques may be used with regulation of thickness to assure projection of elements  18 . An adhesive coating roll  26  is shown in FIG. 3 applying the adhesive layer  16  to the film  14 . 
     As shown by the dotted outline in FIG. 3, the film  14  having the adhesive layer  16  applied thereto is subsequently cut in the cross direction, as by a diaper manufacturer, to provide tabs  10 . Each of tabs  10  has a central extensible portion  10   a  and nonextensible terminal portions  10   b  as described above. For convenience of illustration, the film  14  is shown to correspond in width with three tabs  10 . In practice, the film  14  may have a width corresponding with a much larger number of tabs. 
     Referring to FIG. 4, a tab  30  includes a facestock layer  32 , an adhesive layer  34  and mechanical engagement elements  36 . In the tab  30 , a plurality of extensible portions  32   a  are provided along the length of the tab. As compared with the tab  10 , the tab  30  is similarly extensible, but it does not have a single central extensible portion. Further, the elements  36  in the tab  30  are located along the entire surface of the adhesive layer  34 . However, the elements  36  may be positioned along only the nonextensible portions  32   b  in a similar manner as in the above described embodiment. 
     While the invention has been shown and described with respect to particular embodiments thereof, this is for the purpose of illustration rather than limitation, and other variations and modifications of the specific embodiments herein shown and described will be apparent to those skilled in the art all within the intended spirit and scope of the invention. Accordingly, the patent is not to be limited in scope and effect to the specific embodiments herein shown and described nor in any other way that is inconsistent with the extent to which the progress in the art has been advanced by the invention.