DIAPERS HAVING PRECOMBINED MECHANICAL CLOSURES This application is a continuation-in-part of application Serial No. 673 , 309 , filed June 28 , 1996 , which in turn is a continuation-in-part of application Serial No . 598 , 922 , filed February 9 , 1996.
BACKGROUND OF THE INVENTION AND RELATED ART The present invention relates to fastener* tab or tape assemblies for use in closure of disposable diapers or securement of other garments. The tab includes a fastening element that is deployable to effect garment closure with a mechanical joint. For convenience, the invention is described hereinafter with respect to diaper applications. Diapers of the type of interest herein are widely used. A typical diaper construction comprises an absorbent pad or batt core enclosed in an outer liquid impermeable shell or backsheet and an inner liquid permeable shell or top sheet. The backsheet may comprise a plastic film such as a polyethylene film or a non-woven fabric laminated with such a film. The fastener tab assemblies are typically fastened to one end of the diaper at each lateral side or longitudinal edge of the diaper in a permanent "factory joint" by the diaper manufacturer using adhesives or other techniques. The tabs are releasably attachable to the other end of the diaper 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 connection of the tab to a "landing member" on the diaper backsheet or directly to a fibrous backsheet in the case of a non-woven backsheet laminate construction. In the case of plastic film shells, the landing member is often provided as a
reinforcing tape including exposed mechanical fastening elements or a knit type fabric landing pad. The fastener tab assembly includes multiple layers that are secured together along their lengths with varying degrees of bonding including substantially permanent bond portions and separable bond portions. The bond portions maintain the assembly of the tab layers and proper alignment thereof during application of the tab to the diaper and while the tab is in the storage position. The separable bond portions are "opened" to separate lengthwise segments of the tab layers during deployment of the tab to form the user joint. The provision of a mechanically fastening user joint is advantageous since it eliminates the occurrence of insufficient adhesion for effective diaper closure due to contamination of adhesive surfaces by baby powder or oil, or some other type of contaminant. The elimination of the user adhesive bond portion is advantageous during the manufacture of such tabs, and may be more convenient also during diaper usage since no adhesion layer is available for inadvertent attachment, e.g. to a non-woven backsheet or to other accidental targets. However, such a mechanically fastening user joint does not contribute to the stability of the tab in the storage position if it is disposed against the plastic film backsheet. It important that proper separation occurs during deployment, that is, separation occurs at proper interfaces with appropriate portions of layers being maintained with associated layers. Accordingly, there is a need to provide secure bonding for maintaining the assembly prior to deployment while simultaneously assuring reliable separation of layers. These objectives present somewhat contrary construction requirements. It is desirable to achieve both objectives in a construction
that is sufficiently reliable to assure a commercially acceptable product without excessive costs. Additional adhesive layers or portions have been used in combination with mechanical fastening to provide closure with an arbitrary location on a plastic film backsheet upon rolling the soiled diaper for disposal and also to dontribute to the tab stability during storage. Such combined mechanical and adhesive fasteners are disclosed in U.S. Patents 4,869,724, 5,019,065 and 5,053,028. The additional adhesive layers in such tab systems may serve to impede deployment of the tab for diaper closure. A tab delamination introducing zone is disclosed in US Patent 3,833,456, owned by the assignee of the present application, and also in US Patent 5,549,591 wherein a portion of the adhesive layer is deleted or rendered ineffective by masking at the beginning of the intended separation location.
SUMMARY OF THE INVENTION The present invention provides a multilayer tab or tape assembly arranged to form the user joint with a mechanical securement portion and to provide at least one adhering or adhesive securement portion for maintaining tab stability as the tab is assembled with the diaper and during tab storage on the diaper prior to tab deployment. The mechanical securement portion includes a mechanical fastening user joint and the adhering securement portion includes a separation interface or separable bond portion that is separable to provide non- adhesive surfaces upon tab deployment to the fastening position. In the storage position, the separable bond portion is adhered together along the length of the tab to facilitate handling and assembly of the tab to a diaper. The deployment or opening movement of the tab to
the diaper fastening position causes separation of the separable bond portion. In a first arrangement, the separable bond portion is provided by a transferable release system that enables the separation of an adhesive layer from an adjacent layer. Upon tab deployment to the diaper fastening position,! the transferable release system includes a release coat that remains attached to the adhesive layer and masks the adhesive properties thereof. In this manner, the release coat covers the now exposed surface of the adhesive layer and effectively masks the adhesive properties thereof to cooperate in the provision of the non-adhesive exposed surfaces upon tab deployment. In a second arrangement, the separable bond portion is provided by a non-pressure sensitive adhesive or cohesive. In this second arrangement, the non-pressure sensitive adhesive or cohesive is not tacky upon separation and it may remain with either the fastening element or the release element, or it may fracture or split between the two elements. Once again, non-adhesive surfaces are exposed upon tab deployment. In a third arrangement, the separable bond portion is provided by separable or peelable films or film layers that releasably secure the adhering tab portions together along inner adjacent faces that form the separation interface. The separation interface may be opened to expose the two inner faces which provide non-adhesive separation surfaces. Additional film layers may be present, but the peelable films provide a divisible core formed by a pair of films of unlike polymers of different compositions. The core films are separably joined at the separation interface with sufficient strength to enable conventional processing of the diaper tab during tape manufacture, assembly of the tab to the diaper and during tab storage. Upon deployment of the tab for diaper
closure, the separation surfaces are "dry" and cleanly separate without either being tacky. In each of the foregoing arrangements and embodiments, it should be appreciated that the separation interface or separable bond portion is formed by permanently combining or more strongly attaching adjacent layers td surfaces of the diaper. That is, the separation interface or separable bond requires supporting layers to be more strongly adhered or attached to support layers or substrates. In the first and second arrangements, a central fingerlift, as defined more fully below, may be provided to facilitate proper layer separation and deployment of the tab during use. The central fingerlift is constructed to interact with the movement of the tab during deployment to assure proper separation of layers. The separation movement of the tab layers initially encounters the fingerlift prior to any required separation of adhesive or adhering interfaces of the tab. The central fingerlift is not a fingerlift that is intended to be grasped to manipulate the tab, but rather, it comprises a combination of relative bond strengths between adjacent surfaces, and/or layer configurations and a separation or shear joint that enhances, if not assures, desired layer separation. The fingetlift is located between the mechanical and adhesive securement portions, and the separation or shear joint extends across the width of the adhesive securement portion. As the fastening element is separated for deployment, the proper separation of the adhesive securement portion is promoted by the fingerlift. The adhesion between the fastening element and the release element is typically less than the adhesion between the release element and the diaper. However, if adhesive joints between these elements are presented in a single plane across the
direction of separation movement of the fastening element, as would be the case in the absence of the fingerlift in accordance with the invention, the fastening element may remain bonded to the release element, and the latter may be stripped from the diaper during an improper release separation. With respect to the direction of separation movement, the joint between the fastening element and the release element is recessed from the joint between the release element and the diaper by the fingerlift. Separation movement may be considered to freely travel to the joint between the fastening element and the release element, and to thereby bias the proper separation in the manner a "peel crack" or "crack back" facilitates separation of an adhesive label from a liner as compared with separation of the label at the liner edge. Also, the bond between the fastening element and securement portion may be stronger than the bond between the release element and the securement portion adjacent the separation joint. In all of the illustrated embodiments and arrangements, the tab comprises a fastening element or tape secured to a release element or tape at least in part by the adhering or adhesive securement portion. As used herein, the adhesive or adhering securement portion may be formed of adhesives including pressure-sensitive adhesives, non-pressure sensitive adhesives including cohesives and separable polymeric films.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a disposable diaper having a tab fastener in accordance with the invention; FIG. 2 is a schematic sectional view on an enlarged scale of the tab fastener arranged in a flat condition, the plane of the section being perpendicular to the width
of the tab fastener and extending along the length thereof; FIG. 3 is a fragmentary sectional view on an enlarged scale approximately along the line 3-3 of FIG. 1; FIG. 4 is a fragmentary sectional view on an enlarged Iscale approximately along the line 4-4 of FIG. 1; FIG. 5 is a schematic sectional view similar to Fig. 2 showing a modified tab fastener that does not include a central fingerlift; FIG. 6 is a fragmentary sectional view similar to FIG. 2 showing a tab fastener in accordance with a second embodiment of the invention, the tab being in a folded condition for winding in roll form; FIG. 7 is a fragmentary sectional view showing the tab fastener of FIG. 6 in a storage position on a diaper; FIG. 8 is a schematic sectional view showing the tab fastener of FIG. 6 in a deployed condition for diaper fastening; FIG. 9 is a schematic view similar to FIG. 2 of another arrangement and a third embodiment of a tab fastener in accordance with the invention; FIG. 9a is a fragmentary sectional view on an enlarged scale taken along the line 9a-9a in FIG. 9; FIG. 9b is a sectional view similar to FIG. 9a showing a modification of the embodiment of FIG. 9; FIG. 10 is a fragmentary sectional view similar to FIG. 3 showing the tab fastener of FIG. 9 in a stored condition on the diaper; FIG. 11 is a fragmentary sectional view similar to FIG. 4 showing the tab fastener of FIG. 10 in a deployed condition for diaper fastening; FIG. 12 is a fragmentary sectional view similar to FIG. 2 showing a tab fastener in accordance with another
arrangement and fourth embodiment of the invention, the tab being in a folded condition for winding in roll form; FIG. 13 is a fragmentary sectional view showing the tab fastener of FIG. 12 in a storage position on a diaper; and FIG. 14 is a schematic sectional view showing the tab faste'ner of FIG. 12 in a deployed condition for diaper fastening.
DETAILED DESCRIPTION OF THE DRAWINGS Referring to FIG. 1, there is shown a disposable diaper 10 in accordance with the invention. The diaper 10 comprises a laminate or layered assembly 12 having an inside surface 14 and an outside surface 16. The diaper 10 is of generally rectangular configuration having a first end 18 and a second end 20 connected by longitudinally extending edges 22 and 24. The layered assembly 12 includes a liquid absorbent pad or batt core 26 enclosed within a liquid permeable inner shell or top sheet 28 and a liquid impermeable outer shell or backsheet 30. The core 26 may be of slightly smaller dimensions than the shells 26 and 28 so as to form a perimeter or border about the core 26. Referring to FIGS. 1 and 2, the diaper 10 includes tab or tape fastener assemblies 32 secured to the first end 18 of the diaper adjacent associated longitudinal edges 22 and 24. The tabs 32 are arranged to provide side closure of the diaper 10 about an infant upon engagement with landing member or zone 34. As described in further detail below, the tabs 32 and landing member 34 provide mechanical closure of the diaper 10 through the use of complimentary engaging mechanical elements. The tab 32 has a multilayer construction including a fastening element or tape 36 having an outer face 38 and an opposed inner face 40. The fastening element 36 is
secured to a release element or tape 42 having an outer face 44 and an opposed inner face 46. The elements 36 and 42 are secured together in lengthwise alignment and adjacency along their inner faces, and have substantially similar widths typical in diaper applications, e.g. 20 to 40mm (0.8 to 1.6" ). The fastening element 36 is 62mm (2.44") ctnd the release element 42 is 42mm (1.65") long in the illustrated tab 32. The elongate dimensions of the elements 36 and 42 are referred to as their length dimensions or directions herein, even though such dimensions or directions generally correspond with the width or cross machine direction of the films from which the elements are cut. Further, locations adjacent the diaper 10 are referred to as "proximal" and remote locations are designated "distal". Accordingly, element 36 has a proximal end 36a adjacent the diaper 10 and a distal end 36b remote of the diaper 10. The fastening element 36 includes a fastening substrate or carrier 48 adjacent its outer face 38. The substrate 48 has an outer surface 48a and an opposed inner surface 48b. The substrate 48 may comprise a polymeric film of conventional diaper tab polymers such as polyethylene, polypropylene, blends and copolymers of polyethylene and polypropylene, and polyester, the latter enabling thinner gauge film to be used. Also, the fastening substrate 48 may be formed of a non-woven and polymer film laminate, the latter being of similar polymer materials as mentioned immediately above. Further, the fastening substrate 48 may be formed of paper based compositions such as K 080, sold by Kimberly- Clark Corporation of Neenah, Wisconsin. The use of extensible or stretchable tabs to promote wearer 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 US Patents 4,795,456, 4,066,081, 4,051,853 and 3,800,796. To that end, the fastening element 36 may be formed of extensible materials as taught in US Patent 5,057,097 or a side-by- side coextrusion of extensible and non-extensible polymerid materials as disclosed in US Patent 3,800,796. The fastening substrate 48 may be provided with a conventional release finish or coating to assure reliable self-winding of the stock to be used in making the tab. To that end, a silicone or carbamate release coating 49 may be applied to the outer face 48a of the substrate 48. The thickness of the fastening substrate 48 is not critical. Typical diaper tab substrate film thicknesses such as 4 mils (0.1mm) may be used. For convenience, a fold line "F" shown in FIG. 2 corresponds with the location or plane of folding of the tab 32 about an associated longitudinal edge 22 or 24 of the diaper 10. The plane of folding extends along the width of the tab 32 at substantially a right angle to the tab length. The fastening element 36 includes first, second and third securement portions 50, 52 and 54 at its inner face 40. The portion 50 is about 19mm (0.75") long, the portion 52 is about 15mm (0.47") long and the portion 54 is about 12mm (0.47") long, the latter being spaced from the adjacent edge of the portion 52 by a distance of 8 to 12mm (0.31 to 0.47") . In this embodiment, the securement portion 52 is a pressure-sensitive adhesive. Accordingly, the securement portions 50 and 52 comprise adhesive layers secured to the inner surface 48b of the substrate 48 for adhesive attachment to the inner face 46 of the release element 42 as discussed more fully below.
The securement portion 54 comprises a mechanical fastening member including a mechanical engaging element such as a multiplicity of hooks 54b mounted on a base substrate 54c as diagrammatically shown in the drawings for engaging a complimentary mechanical engaging element such as loops 34a provided by the landing member 34. An example df a suitable mechanical engaging element is Ultramate 811 which is a high density polyethylene hook construction including a base sold by Velcro USA. Of course, other mechanical engaging systems may be used. Further, the securement portion 54 (and possibly the landing member 34) may provide both mechanical and adhesive attachment, the latter occurring intermediate the mechanical engaging elements as taught in US Patent 4,946,527. The securement portion 54 may be mounted to the surface 48b by any convenient means such as adhesives, welding, ultrasonic sealing or cold glue. Herein, the use of a pressure-sensitive adhesive is contemplated. In such case, the mechanical engaging member should have a length slightly less than that of the mounting pressure- sensitive adhesive and, if any overhang occurs, it should be at the downstream side of the direction of movement of the fastening element 36 during separation movement or to the left as shown in FIG. 2. The mounting pressure-sensitive adhesive for the securement of the portion 54 may be applied to the substrate 48 by a tape supplier or film converter and the mechanical engaging member may be mounted to the adhesive by the diaper manufacturer or an intermediate third party. The subsequent assembly of the mechanical engaging member facilitates the provision of the tab in roll stock form since it may be more easily self-wound. The additional thickness of the engaging member, e.g. 16- 40 mil (0.4-1 mm), tends to limit the roll length. It is
estimated that the added thickness reduces the manageable roll length from about 750m (820 yards) to about e.g. 300m (328 yards) . The release element 42 includes a release* substrate 56 having a mounting surface 58 at its inner face 46 and an attachment portion 59 at its outer face 44. The substrate' 56 should be substantially non-extensible and may comprise a polymeric film of conventional diaper tab polymers such as polyethylene, polypropylene, and blends and copolymers of polyethylene and polypropylene as well as polyester which allows thinner gauge film to be used. Also, the release substrate 56 may be formed of paper based compositions such as Bg 40, sold by Denayere, of Willebroek, Belgium. The mounting surface 58 includes first and second mounting surface portions 60 and 62 for receiving securement portions 50 and 52, respectively, in adhesive contact. The mounting surface 58 also includes a third surface portion 64 remote of the portions 60 and 62. The securement portion 50 and corresponding mounting surface portion 60 extend from the proximal end 36a of the element 36 and adjacent end of the element 42 to the location of the fold line "F" as shown in FIG. 2. Securement portion 52 and corresponding mounting surface portion 62 extend from the fold line "F" toward the distal end 36b of the element 36, but terminate together short of the end of the element 42. The third surface portion 64 corresponds in length with the space between the termination of the portion 52 and the end of the element 42. This spacing may be as small as 2mm (0.08") . As discussed above, the third surface portion 64 is provided by the termination of the securement portion 52 to form a fingerlift 66 in this region including a separation joint 68. In addition to the separation joint 68, the fingerlift 66 contemplates the relatively lower
peel strength of the adhesive bond between second portion 52 and surface portion 62 as compared with the peel strength of the bond between the portion 52 and the adjacent surface 48b of the fastening element 36. In addition to the selected relative peel strengths adjacent the portions 52 and 62, it is also desirable to provide non-adhesive, non-tacky exposed surfaces upon separation. To that end, the tab 32 includes a transferable release coat 70 that provides separation of the fastening tape 36 from the release tape 42 along a separation interface 72. The release coat 70 is applied at least along the mounting surface portion 62 of the release tape 42 to an extent necessary to transfer to the securement portion 52 and mask the adhesion characteristics thereof. For convenience of manufacture, the release coat 70 may also be applied along some or all of the mounting surface portion 64. In the illustrated embodiment, the release coat 70 extends across the full width of the release tape 42 and along the length thereof extending from the fold line F to the distal end of the release tape 42. As shown in Fig. 4, upon movement of the <tab 32 for diaper closure, the release coat 70 breaks at the separation joint 68 with a first portion 70a remaining on the mounting surface portion 64 of the release tape 42 and a second portion 70b separating with and remaining on the surface of the securement portion 52 of the fastening tape 36. In addition to the above described deployment advantages, the fingerlift 66 also promotes the breaking of the release coat 70 at the separation joint 68 and proper separation between the mounting surface portion 62 and the adjacent surface of the release coat 70. The fingerlift 66 cooperates with the release coat 70 to provide the proper layer separation of the securement portion 52 from the release element 42 by the
provision of the separation joint 68 of relatively lower peel strength as the fastening element 36 is peeled from the release element 42. It should be appreciated further that the fingerlift 66 also provides a material savings due to the elimination of adhesive along the surface 64. The fingerlift 66 extends across the entire width of the tab 3l2 and may have a length as short as 2mm (0.08"). That is, it is only necessary that the fingerlift 66 be spaced at least about 2mm (0.08") from the edg*e .of the element 42 and/or any adhesive forming the adjacent portion of the securement portion 54. The maximum length of the fingerlift 66 is determined by the required minimum length of the securement portion 52 to reliably maintain the elements 36 and 42 in alignment during tab processing and assembly to the diaper. Typically, the securement portion 52 length may be about 15ram (0.6") to reliably provide both of these functions. The portions 50 and 52 may be conventional or known diaper tab adhesives such as acrylic or rubber based pressure-sensitive adhesives. Preferred adhesives include hot melt adhesives such as the adhesives taught in US Patent 3,932,328. The latter adhesives comprise an elastomeric component based on an elastomeric and thermoplastic A-B-A block copolymer wherein the A blocks are derived from styrene and the B blocks are derived from isoprene. The elastomeric component is blended with a combination of solid and liquid tackifiers. The securement portions 50 and 52 may comprise the same adhesive or different adhesives. It is desirable that a strong permanent-type bond be formed between the fastening element 36 and the release element 42 at the proximal end of the tab 32 that is secured to the diaper 10. To that end, an aggressive adhesive is favored for the securement portion 50, and, for example, a hot melt rubber based adhesive, a polyurethane adhesive or a two
component adhesive may be used to achieve a sufficiently strong bond. If a separate adhesive is used for the securement portion 52, a less aggressive adhesive can be used. For example, a less aggressive acrylic based adhesive or hot melt adhesive may be used. As noted above, the release coat 70 is transferrable with the ^adhesive of the securement portion 52 and masks the adhesive properties thereof upon tab deployment. Typically, it has been found to be more efficient and economical to coat two pressure-sensitive adhesives, whether the same or different, to form the portions 50, 52, and to mask the adhesive properties of the portion 52 upon tab deployment using the trarsferrable release coat 70. A variety of resin or polymer compositions may be used to form the release coat 70 with solvent free formulations being preferred for environmental reasons. Particularly good results have been obtained with resins designed for a relatively high degree of volume shrinkage upon radiation cure. Highly acrylated resins having a relatively short backbone displaying limited flexibility have been found to result in stiff polymers displaying a degree of shrinkage that can not be absorbed by polymer tension forces. Such shrinkage is effective to weaken or destroy adhesion bonds at the interface between the resin and substrate and to thereby give rise to the transferable and breakable characteristics. With these teachings in mind, suitable formulations may be derived for various adhesive and adjacent surface separation interfaces. Essentially, the release coat comprises a polymeric composition curable to form a release film having opposed surfaces. A first surface of the release coat or film is adhered to a non-adhesive layer (mounting surface portion 62) of the tab by wet bonding, e.g. bonding resulting from application of the
polymeric composition in a liquid state to the non- adhesive layer followed by curing of the polymeric composition. A second surface of the release film is adhered to an adhesive layer (e.g. securement portion 52) of the tab subsequent to the curing of the polymeric composition. The separation interface 72 is provided by the release film and non-adhesive layer and, upon tab deployment, the exposed non-adhesive surfaces are provided by the first surface of the release film and the adjacent surface of the non-adhesive layer. Routine experimentation will readily enable desired wet bonding strengths lower than those of the adhesive layer. Examples of suitable resins for making the release coat 70 include acrylated polyurethane and/or polyester compositions. Suitable resin compositions are available from UCB Chemicals of Drogenbos, Belgium. For example, Ebecryl 220 is a mixture of 70% hexafunctional aromatic urethane acrylate and 30% pentaerythritol having tri- and tetra- acrylate functionality. The viscosity of Ebecryl 220 may be reduced for coating purposes by combination with Ebecryl 160 which is a trimethylolpropane ethoxy triacrylate. Generally, the polyurethane and polyester components are blended in a weight ratio of 30:60 to 60:30 to achieve a suitable processing viscosity. If the release element 42, or more particularly the surface portion 62, has a high energy surface, or is provided with the same as by corona treatment, the resin compositions may be used with formulation to a suitable viscosity. If the release tape has relatively lower energy surface, an acrylated silicone component may be combined with the resin or resins to improve wetting of the tape surface. A suitable silicone based surface tension modifier is sold by Th. Goldschmidt of Essen, Germany under the designation RC 704. This is a highly
acrylated polydimethylsilioxane polymer, and it may be used in an amount ranging up to about 20% by weight. The curing of the release coat 70 may be by electron beam ("EB") or ultra violet ("UV") radiation. In the case of the latter, an initiator may be included in the release coat. Irgacure 500 by Ciba Geigy may be used as a suitable photo-initiator comprising a 1:1 mixture of benzofenon and l-hydroxycyclohexyl-phenyl-ketone. A typical amount of initiator is about 5% by weight. In the case of a release tape 42 having a substrate 56 formed of cast polypropylene, white color and corona treated up to 40 dynes/cm, e.g. PP-SK GLAT WEISS/cor 68 micron sold by Rhenolit of Germany, a suitable, r.elease coating 70 is provided by a 60:40 blend of Ebecryl 220 and Ebecryl 160 applied at a coating weight of from 1.0 to 5.0 g/m2. In the case of a non-corona treated cast polypropylene, up to 15% by weight of the RC 704 may be added to the blend and similar coating weights may be used. A biaxially oriented polypropylene film, white color and corona treated, 40-60 microns, may be suitably processed as described above at coating weights of from 3.5 to 7.0 g/m2. The resin blend forming the release coat 70 may be applied to the substrate 56 by known roll coating techniques such as a "5 roller" set-up using conventional equipment. If UV curing is to be used, inertiza ion of the UV unit (nitrogen knife) is important. In the above examples, inertization of less than 50 ppm oxygen was maintained. The application of the liquid resin composition forming the release coat 70 will provide sufficient adhesion to the mounting surface portion 62 and 64 of the substrate 56. The resulting release coat 70 may be used in combination with conventional adhesives such as diaper
suitable pressure-sensitive adhesives for forming the securement portion 52. The pressure-sensitive adhesive may be acrylic or rubber based; preferred adhesives including hot melt adhesives as taught in US Patent 3,932,328 as noted above. The foregoing release coating and adhesive have been found to Iprovide the desired separation between the surface of the substrate 56 of the release tape 42 and the release coat 70. That is, the release coat 70 separates with the fastening tape 36 and covers the securement portion 52 which would otherwise be exposed for adhesive contact upon movement of the tab 100 to the diaper closure position. The transferable release coat 70 simplifies the construction of the tab 32. As compared with a separate release liner such as a film or release liner insert, the release coat 70 provides the desired layer separation without a separate liner piece to be inserted during diaper manufacture and to be disposed of during diaper use. The release coat 70 may be applied to the release tape 42 along the surface portion 62 and 64 using conventional coating, spraying or other techniques well known in the art. Thus, the release coat 70 also simplifies manufacture as compared with the use of a non- pressure sensitive adhesive or a cohesive. This is true since the tab 32 may be prepared using conventional web coating processes and techniques wherein pressure- sensitive adhesives are applied to the fastening tape 36 and the release coat 70 is applied to the release tape 42. In contrast, the use of non-adhesive or cohesives may involve compositions sufficiently different from typical pressure-sensitive adhesive compositions to prevent the use of conventional web processing equipment and techniques.
Referring to FIG. 3, the tab 32 is shown in the storage position folded along fold line "F" about the longitudinal edge 22 of the diaper 10. The attachment portion 59 adhesively secures the release element 42 to both the inside and outside surfaces 14, 16 of the diaper 10, about equal lengths of the attachment portion 59 being sedured to each surface. The fastening element 36 is secured to the release element 42 by securement portions 50 and 52. The adhesive bond between the securement portion 50 and the surface portion 60 is quite strong, effectively constituting a permanent bond in this environment. The adhesive bond between the securement portion 52 and the surface portion 62, or more particularly, the release coat 70, is adequate to maintain lengthwise alignment and control of the fastening element 36 including its distal end 36b during the diaper manufacture process and while the tab 32 is in the storage position. Thus, the present invention provides a material savings by reducing the length (and expanse) of the securement portion 52 without loss of lengthwise alignment and control thereof while also improving the reliability of the layer separation during deployment of the tab 32. Also, the adhesive properties of the portion 52 upon tab deployment- are masked by the transferred release coat portion 70b. Referring to FIG. 4, the tab 32 is shown in the deployed position ready for engagement with the landing member 34. A conventional fingerlift 74 may be provided in a known manner at the distal end 36b of the fastening element 36 to facilitate such deployment. As shown, the tab 32 forms a Y-bond type attachment with the diaper 10 and the distal end 36b of the fastening element 36 is extended for attachment of the securement portion 54 to the landing member 34.
As illustrated in FIG. 4, the fastening element 36 has been pulled from the storage position, "back-on- itself", in a lengthwise or separation direction. Such movement is essentially unopposed along the length of the surface portion 64 and fingerlift 66 until separation of the securement portion 52 from the surface portion 62 is required.! At that point, the separation forces are imposed on the separation joint 68 which presents the least strong peel strength or adhesive bond resisting layer separation, and continued movement causes separation of the securement portion 52 together, with release coat 70 from the surface portion 62. At the end of the deployment separation movement, the securement portion 52 is substantially fully separated from the portion 62 at about the plane of the fold line "F" which also corresponds with the end of the release coat 70. The securement portion 52 is now covered by the transferred release coat portion 70b and no adhesive properties thereof are exposed. The tab fastener of the present invention may be provided and used without the central fingerlift 66 as in the tab or tape assembly 32a as shown in FIG. 5. In this embodiment, similar components are identified with corresponding reference numerals. In the tab 32a, securement portion 52a extends to the distal end of the release tape 42 so as to eliminate the fingerlift 66. Proper separation upon tab deployment is provided by the relative bond strengths between the adjacent surfaces of the portion 52a, the release coat 70 and the mounting surface portion 62. Separation is achieved along the separation interface 72 and the entire expanse of the release coat 70 is transferred to the surface of the portion 52a. The tab fastener of the present invention may be supplied to the diaper manufacturer in a number of
different configurations or stages of assembly. In all cases, conventional laminating, slitting and roll handling equipment may be used. Several supply configurations are discussed below. The tab 32 is shown as a combined fastener system wherein the fastening element 36 and release element 42 have been' combined by a tape supplier or film converter. The tape supplier may also provide the securement portion 54 in whole or in part. For example, the tape supplier may apply a suitable mounting adhesive at the location of the securement 54 and the diaper manufacturer or an intermediate third party may combine the particular mechanical fastening element as by adhering a first complimentary portion of a commercially available fastener Ultramate sold by Velcro USA. Of course the other complimentary portion of the fastener would be secured to the diaper backsheet or landing member. It is also possible to supply the tab 32 as a two tape system consisting of the fastening element 36, with or without securement portion 54, and release element 42. Once again, the diaper manufacture or an intermediate third party may complete the mechanical fastener as described above. The elements 36 and 42 may be sold as separate but complete constructions, and the two tapes may be applied to the diaper by the diaper manufacturer using only conventional laminating and slitting roll processing equipment. Referring to FIGS. 6, 7 and 8, a tab fastener 80 in accordance with a second embodiment is shown. For convenience of illustration, corresponding elements are similarly numbered with the addition of a prime designation. It should be understood that the assembly and proportions of the corresponding elements may vary slightly in each of the embodiments, but the essential functions of the elements are similar and the tab
fasteners similarly enjoy the improvements of the invention. The tab fastener 80 is of conventional Y-bond construction providing separate tape attachments to the inside and outside of the diaper to form the factory bond. Referring to FIG. 6, the tab 80 is shown in its roll stodk configuration, that is, the position of the elements forming the tab when wound in roll form as a precombined tab or tape system sold by a tape supplier or film converter. As shown, elements 36' and 42' are secured together. The tab 80 is applied to the longitudinal edge of the diaper 10 as shown in Fig. 7. To that end, the tab 80 includes a fastening element or tape 36' for engaging the outside surface 16 of the diaper 10 and a release tape 42' for engaging the inside surface 14 of the diaper 10. More particularly, the fastening element 36' includes a first securement portion 50' adapted to engage the backsheet 30 of the diaper 10 and the release element 42' includes an attachment portion 59' adapted to engage the top sheet 28 of the diaper 10. A small extent of the attachment portion 59' and the securement portion 50' engage with each other to secure the two elements together in the Y-bond configuration at the longitudinal edge 24 of the diaper 10. The fastening element 36' also includes a second securement portion 52' for engaging the release tape mounting surface portion 62'. The fastening element 36' further includes a third securement portion 54' comprising a mechanical engaging element such as a multiplicity of hooks 54b' mounted on a base substrate 54'c similar to the first tab embodiment described above. The releasable engagement between the portion 52' and the mounting surface portion 62', or more specifically, the release coat 70', assures the stability
of the distal end 36b' of the substrate 36' during tab storage on the diaper 10. The release coat 70' assures that the bond strength between the securement portion 52' and the mounting surface 62' is less than that between the attachment portion 59' and the top sheet 28 of the diaper 10. More particularly, the release coat 70' provides la separation interface 72' between the portion 62' and the release coat 70' so that the latter remains fixed to the portion 52' upon tab deployment. The portion 52' extends towards the distal end 36b' of the element 36' and ends short of the securement portion 54'. As most clearly shown in FIG. 7, the securement portion 52' in the storage position extends along the mounting surface portion 62' and terminates at the mounting surface portion 64' to form a fingerlift 66' and a separation joint 68'. Accordingly, the securement portion 52' extends along the mounting surface portion of the element 42' and terminates at the adjacent surface portion 64' so that the latter is free of adhesive and attachment to the fastening element 36'. The fingerlift 66' is similar in construction and operation to the fingerlift 66. Upon tab deployment as shown in Fig. 8, the release coat 70' breaks at separation joint 68' leaving release coat portion 70a' on the porti'on 64' of the release coat 42' and release coat portion 70b' on the securement portion 52' of the fastening tape 36'. The fingerlift 66' also provides a material savings in respect to decreased amount of adhesive surface. In addition, the fingerlift 66' enables the length of the release element 42' to be decreased as compared to the length required in a similar tab construction not including a central fingerlift in accordance with the invention. As in the first embodiment, the tab fastener 80 may be provided without a fingerlift 66' by extension of the
length of the increasing the length of the portion 52' or otherwise terminating the distal ends of the portion 52' and 62' in a common plane. The tab 80 may also be supplied to a diaper manufacturer as a two tape system comprising the completed elements 36' and 42'. The precombined or two tape systems may be supplied with or without the mechanical fasteners. In the latter case, the mechanical fasteners such as hooks may be secured to the tab by a diaper manufacturer or an intermediate third party. Referring to FIGS. 9 and 9a, a tab fastener 90 in accordance with a third embodiment of the invention is shown. For convenience of illustration, corresponding elements are similarly numbered with the addition of a double prime ('') designation. The tab fastener 90 has a Y-bond construction similar to that of tab fastener 32 of the first embodiment. However, it should be understood that separate tape attachments to the inside and outside of the diaper to form the factory bond may be used as shown in the tab fastener 80. The tab 90 includes a fastening element or tape 36'' having an outer face 38'' and an inner face 40''. The element 36'' is secured to a release tape 42'' having an outer face 44'' and an inner face 46''. The elements 36'' and 42'' are secured together in lengthwise alignment and adjacency along their inner faces, and have similar widths as described above in connection with the first embodiment. The fastening element 36'' includes a fastening substrate or carrier 48'' adjacent its outer face 38''. The substrate 48'' has an outer surface 48a'' and an opposed inner surface 48b''. The substrate 48'' may be provided with a release finish or coating 49'' to assure
reliable self-winding of the stock to be used in making the tab. For convenience, a fold line "F" shown in FIG. 9 corresponds with the location or plane of folding of the tab 90 about an associated longitudinal edge 22 or 24 of the diaper 10. The plane of folding extends along the width of the tab 90 at substantially a right angle to the tab length. The fastening element 36' ' includes first, second and third securement portions 50'', 52'' and 54'' at its inner face 40, . The portions 50'' and 54'' are similar to the portions 50 and 54, respectively, as described in connection with the tab 32 of the first embodiment. The portion 52'' is similar to the portion 52 in that it also maintains the alignment of the elements of the tab 90 during diaper assembly and while the tab is in the storage condition. The release element 42'' includes a release substrate 56' ' having a mounting surface 58'' at its inner face 46'' and an attachment portion 59'' at its outer face 44''. The attachment portion 59'' mounts the tab 90 to the diaper 10 in the storage position as shown in FIG. 10. The release element 42'' generally corresponds with the element 42 described above. However, the release coat 70 is not required and such has been omitted herein since the securement portion 52 ' ' is not a pressure-sensitive adhesive. The mounting surface 58'' includes first and second mounting surface portions 60'' and 62'' for receiving securement portions 50'' and 52'', respectively, in adhesive contact. The mounting surface 58'' also includes a third surface portion 64'' remote of the portions 60'' and 62''. The securement portion 50'' and associated mounting surface portion 60'' are similar to the corresponding
elements in the tab 32. In the tab fastener 90, the securement portion 52'' comprises one or more stripes or drops of adhesive located adjacent the distal side of the fold line "F". The corresponding mounting surf ce portion 62" may extend from the fold line "F" toward the distal end 36b'' of the element 36' ' and at least corresponds in length with the major length dimension or extent of the stripe or drop shaped securement portion 52". The portion 52'' comprises a single stripe of adhesive having a thickness about equal to the thickness of the portion 50''. As determined by the preferences of the diaper manufacturer, the width of the portion 52" may be equal to from about lmm (0.04") to about the width of the fastening element 36". The length of £h£ portion 52" may be equal to from about lmm (0.04") to the length of the release element 42" on the distal side of the fold line F less about 2mm (0.08") to allow for the surface portion 64". The same dimensional considerations also apply to the overall size of the portion 52" when it is formed of two or more stripes or drops of adhesive. As in the first embodiment, the securement portion 52" is spaced from or terminates short of the end of the element 42". The third surface portion 64'' corresponds in length with the space between the termination of the portion 52" and the end of the element 42''. This spacing may be as small as 2mm (0.08"). The cross-section of the stripe configuration of the securement portion 52" is shown in FIG. 9a. As noted above, the securement portion 52" may be provided in a drop or dollop configuration as shown in FIG. 9b. As discussed above, the third surface portion 64" is provided by the termination of the securement portion 52" to form a fingerlift 66" in this region including a separation joint 68". In addition to the separation
joint 68", the fingerlift 66" contemplates the relatively lower peel strength of the adhesive' bond between second portion 52" and surface portion 62" as compared with the peel strength of the bond between the portion 52" and the adjacent surface 48b" of the fastening element 36''. Accordingly, a release coating or an adhesive detackifier or deadening agent can be used between the adjacent faces of the portion 52" and the adjacent surface 62". The fingerlifts 66" and 66 operate in similar manners. The securement portion 52' ' may be a non-pressure sensitive adhesive or a cohesive suitable for use in a diaper tab. The adhesive or cohesive should be easily applied and result in a bond sufficient to maintain the elements 36'' and 42'' aligned in their adhered position during diaper manufacture and during tab storage on the diaper prior to deployment for diaper closure. It is also necessary that the adhesive or cohesive be separable from at least one of the adjacent surfaces (e.g. 62") or fracture by the deployment movement within the requirements of the fingerlift 66''. Herein, a separation interface 72" is provided between the surface portion 62" and the portion 52". The non-pressure sensitive adhesive or cohesive of the portion 52" may be applied to the tab 90 using conventional solvent or hot techniques, e.g., by use of a hot melt nozzle, a hot melt die or a roll coater. Useful non-pressure sensitive adhesives include hot melt adhesives based on polyolefin resins and cold seal adhesives applied from a solvent. A commercially available suitable hot melt adhesive is sold with the designation Crodamelt by the Croda company in Kapellen, Belgium. Suitable cohesives are disclosed in U.S. Patent 5,085,655. Since the cohesive is applied hot or in solvent form, it bonds with the mounting surfaces 62" of
the release element 42" and the inner surface 48b'' of the fastening element 36". After the bond is broken during tab deployment, the cohesive coheres to itself, but does not adhere to other materials. Following deployment of the tab fastener 90 to the diaper closure position as shown in FIG. ll, the separated or exposed surface of the portion 52" is a non-pressure sensitive, not tacky, and does not provide adhesive closure with the diaper. As noted above, the portion 52" is formed of a non-pressure-sensitive adhesive and, after its adhesive bond with the surface 62" is broken during tab deployment, the exposed surface of the portion 52' ' does not provide a further adhesive bond as in the case of the portion 52. As shown in FIG. 11, the mounting surface portion 62" of the release element 42" may include a conventional or non-transferrable release coat (e.g. a silicone or carbamate coat extending along its surface, not shown) and the securement portion 52" remains on the fastening element 36" upon tab deployment. However, it is not necessary to use such a release coat on the mounting surface portion 62" and, upon tab deployment, the non-pressure sensitive adhesive or the cohesive portion 52" may remain with either of the elements 36" and 42" depending upon the surfaces of the elements or fracture with parts of the portion 52" remaining on each of the elements. Referring to Figs. 12, 13 and 14, a tab or tape fastener 100 in accordance with a fourth embodiment of the invention is shown. The construction of the tab 100 is similar to that of the tab 80 shown in Figs. 6-8 and includes a corresponding fastening element or tape 36' . For convenience, like reference numerals are used in connection with like parts in the two embodiments.
The tab 100 includes a release element or tape 102 having an outer face 104 and an inner face 106. The elements 36' and 102 are secured together in lengthwise alignment and adjacency along their inner faces. Further, the elements 36' and 102 have substantially similar widths typical in diaper applications, e.g. 20 to 40mm (0.81 to 1.6" ). The fastening element 36' is 62mm (2.44") and the release element 102 is 42mm (1.65") long in the illustrated tab 100. The release element 102 includes a pair o*£ ■ releasably joined film layers comprising a release substrate 108 releasably secured to a separable film 110 along a separation interface 112. The substrate 108 and film 110 cooperate to form a divisible core that may be separated along interface 112. As described in detail below, the separable film 110 operates to mask or deaden the adhesive the adhesive surface of the securement portion 52' of the fastening tape 36' in the same manner as the release coat 70' in the tab 80. The tab fastener 100 is of conventional Y-bond construction providing separate tape attachments to the inside and outside of the diaper to form the factory bond. To that end, the fastening tape 36' is arranged to engage the outside surface 16 of the diaper 10 and the release element 102 is arranged to engage the inside surface 14 of the diaper 10. More particularly, the fastening element 36' includes a first securement portion 50' adapted to engage the backsheet 30 of the diaper 10 and the release element 102' includes an attachment portion 114 adapted to engage the top sheet 28 of the diaper 10. A small extent of the attachment portion 114 and the securement portion 50' engage with each other to secure the two elements together in the Y-bond configuration at the longitudinal edge 22 or 24 of the diaper 10.
The fastening element 36' also includes a second securement portion 52' for engaging the release tape mounting surface portion 116. In this embodiment, the release element 102 ends at the distal extremity of the securement portion 52'. A separation joint 118 is provided by the exposed or distal edge of the separation interface' 112, and the distal ends or extremities of the release element 102 including the release substrate 108 and the separable film 110 together with the distal end of the securement portion 52' are in a common plane with the separation joint 118. The release substrate 108 and separable film 110 may be extruded together with the formation of separation interface 112 therebetween as taught in US Patent 4,925,714, also owned by the assignee herein. Upon separation along the interface 112, the exposed surfaces are "dry" and cleanly separate without either being tacky. Suitable polymer extrudates for the substrate 108 and film 110 include polyethylene and polypropylene. The interfacial peel strength at the interface 112 is a function of several parameters, including, among others, the identities of the two dissimilar thermoplastic layers, the presence or absence of pigments in one or both films, the pressure exerted by, and the temperature of, the nip rollers, and thermal aging of the coextruded layers. While several factors can play a role in providing a desired peel strength, that desired peel
« strength can be achieved through routine experimentation. Peel strengths of less than about 50 newtons/meter are possible using this technique, and preferred peel strengths are in the range of from about 30 to 200 newtons/meter. The adhesive compositions to which the substrate 108 and the film 110 are secured should have peel strengths
exceeding those of the interfacial peel strength along the separation interface 112. Suitable adhesives including those mentioned above and/or described in US Patent 4,925,714 may exhibit an adhesive force of about 15 to about 50 ounces per inch (about 170 to about 560 g/cm) of adhesive width in the 180° peel adhesive test of the P.S.T C. test #1, with a 20 minute dwell time. More preferably, the peel strength is about 20 to about 45 ounces per inch (about 220 to about 450 g/cm) . As particularly shown in Fig. 14, deployment of the tab 100 to the diaper closure position causes separation along the separation interface 112 with exposure of surface 110a of the separable film 110 and surface 108a of the substrate 108. The surfaces 110a and 108a are dry and do not display tackiness. In the preparation of the tabs or tapes of the present invention, the adhesive layers such as the securement and attachment portions may be applied to suitable substrate materials using extrusion coating, die coating and/or roll coating techniques as well as the hot melt nozzle technique noted above for the portion 52''. The adhesive layers may be of conventional diaper tab thickness, such as about 30 microns (0.1 mil) thick, and extend across the full width of the substrate of the tab or tape and may be in the form of one or more stripes or drops as used in the portion 52". The tabs may be formed of adhesive coated film or stock materials using known laminating and slitting techniques. The separable or peelable film constructions shown in connection with the tab 100 may be made using coextrusion techniques and multi-manifold dies as described in US Patents 4,197,069 and 4,152,387. The invention is not restricted to the slavish imitation of each and every detail set forth above. Obviously, devices may be provided which change,
eliminate, or add certain specific details without departing from the invention.