WO1997025954A1 - Diaper closure having selectively combined mechanical engagement elements - Google Patents

Abstract

A fastening system for a disposable diaper (12) includes tab members (10) adapted to mechanically and adhesively engage and disengage for diaper (12) closure and opening. The tab member (10) comprises a face stock layer (14) including a pressure-sensitive adhesive layer (16) and mechanical fastener comprising a plurality of randomly oriented fastener elements (18). Each of the fastener elements (18) has at least three rod shape arms (18a) extending in at least two different planes so that at least one arm (18a) extends from the adhesive layer (16) when the fastener element (18) is partially embedded in the pressure-sensitive adhesive layer (16).

Description

DIAPER CLOSURE HAVING SELECTIVELY COMBINED MECHANICAL ENGAGEMENT ELEMENTS

This application is a continuation-in-part and claims the priority of US Provisional Application No. 60/010,018, filed January 16, 1996.

BACKGROUND OF THE INVENTION AND RELATED ART The present invention relates to closures for fastening adjacent portions or edges of materials together and to methods of making the closures. 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 releasabie 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 iε 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 US Patents 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 US Patents 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 US Patents 4,795,456, 4,066,081, 4,051,853 and 3,800,796. Related art includes US Patents 3,991,534 and 4,198,734.

SUMMARY OF THE INVENTION The present invention provides a 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 mechanical engagement elements may be separately manufactured and selectively combined with a support substrate or with tab fastener facestock. The tab fastener system may be provided as an extensible system. The tab fastener system may be produced by high speed manufacturing processes. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view showing a diaper tab in accordance with the present invention; Fig. 2 is fragmentary perspective view on a reduced scale the diaper tab of Fig. 1 applied to a diaper and in a deployed condition ready for diaper closure; Fig. 3 is a schematic view showing a production line for making a tape product which may be converted to provide a diaper tab in accordance with the present invention; and Fig. 4 is a perspective view on an enlarged scale showing a diaper tab converted from the tape of Fig. 3.

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 closure elements 18. The size of the elements 18 in the drawing is greatly exaggerated for clarity of illustration and a minimal number of elements are shown. The facestock film 14 includes an extensible central portion 14a and nonextensible terminal portions 14b. The extensible portion 14a 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)_χ and SEBS block copolymers and mixtures thereof. The nonextensible portions 14b 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 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 US Patent 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 adhesives may be applied using hot-melt, solvent or emulsion techniques. The adhesive layer 16 extends along the entire adjacent surface of the layer 14 or it may be have a narrower width as described below. The mechanical elements 18 are separately formed and may be attached to the facestock film 14 in the any convenient manner. In the illustrated embodiment, the elements 18 are randomly dispersed with pressure into the adhesive layer 16 after the later has been applied to the facestock film 14. However, the elements 18 may be separately formed and attached to the surface of the facestock film 14 prior to coating with adhesive layer 16. The elements 18 may be directly adhered to the surface of the film 14 as the latter is extruded or they may be later adhered to the surface of film 14 by an intermediate adhesive. Also, the elements 18 may be applied to the surface of the film 14 following the wet coating thereof. The heat welding or sonic welding of the elements 18 to the surface of the film 14 is also contemplated. The elements 18 may be formed of any suitably rigid material that provides adequate shear strength for the contemplated diaper application. Illustrative plastic materials include nylon, polycarbonate, polyester, polystyrene and polyproylene. It is not necessary that the elements 18 be of identical or even regular shape, and they may range from 10 to 500 microns in overall height or diameter. The element 18 has a six point configuration similar to a child's jack. It is important that the elements 18 include a plurality of angularly offset arms 18a which cooperate to achieve self-orientation wherein the element 18 may be randomly disposed on a surface, or embedded into a supporting layer, and supported by one or more arms 18a and have at least one arm 18a that projects away from the surface or layer for engagement with an accommodating closure material such as complimentary arms or a fibrous material such as non-woven fabric. The projecting or exposed ends of the elements 18a should be of sufficient length to provide mechanical engagement with a locking or engaging array of similar or different mechanical elements, or with a fibrous material such as a non-woven landing tape or member 20 as shown in Fig. 2 or a non-woven backsheet of a diaper. The arms 18a are sufficiently slender or rod-shape to provide interfitting and interengagement, and are joined at a common joint 18b. In all cases, the pressure-sensitive adhesive provides a contact or tact bond with adjacent surfaces, such as the fibrous surface of a non-woven fabric. The pressure-sensitive adhesive is extensible or stretchable, 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 10a corresponding with the location of the film portion 14a and nonextensible terminal portions 10b corresponding with the locations of film portions 14b. Referring to Fig. 2, one of the terminal portions 10b 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 10b is deployable to form a user joint with the landing tape 20 to close the diaper about a wearer such as an ^infant with both mechanical and adhesive engagement. During use, the mechanical elements 18 particularly provide shear strength and the pressure-sensitive adhesive layer particularly provides immediate tack strength. Referring to Fig. 3, a coextrusion die 22 extrudes the facestock film 14 as a side-by-side coextrusion including adjacent portions of extensible polymer film 14a and nonextensible polymer film 14b. For convenience, the film 14 is shown to include a limited number of adjacent extensible and nonextensible film portions, however, a much larger number of such portions may be provided along the width or cross direction of the film 14. The coextrusion processing requires a matching or near matching of the melt flow characteristics of the plastic materials forming the portions 14a and 14b. Such matching and processing techniques are known in the art and illustrated, for example, in US Patent 3,800,796. The film 14 upon exiting the die 10 engages a conventional casting roll 24 for purposes of handling and further shaping the film. The adhesive layer 16 is applied to the facestock film 14 along the upper surface at an adhesive coating roll station 26 as shown in Fig. 3. Thereafter, the elements 18 are randomly disposed onto the exposed surface of the adhesive layer 16, and the arms 18a are wholly or partially embedded into the adhesive with pressure at an element embedding station 28. Typically, the pressure applied to the elements 18 is sufficient to cause them to fully penetrate the adhesive layer thickness with one or more arms 18a in contact with the adjacent surface of the facestock film 14. As indicated above, the thickness of the adhesive layer 16 assures a sufficient projection of the elements 18 to effect the desired 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. The thickness of the adhesive layer 16 may vary from about one-fiftieth to about one-half the height of the element 18. As shown by the dotted outline in Fig. 3, the film 14 having the adhesive layer 16 applied thereto and the embedded elements 18 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 10a and nonextensible terminal portions 10b as described above. For convenience of illustration, the film 14 is shown to correspond in width with two 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 32a 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 32b in a similar manner as in the above described embodiment. It should be understood that the facestock film 14 does not have to comprise a coextrusion with extensible and nonextensible portions. The film 14 may comprise a nonextensible extrusion of polypropylene or polypropylene copolymer. It should be evident that this disclosure is by way of example and that various changes may be made by adding, modifying or eliminating details without departing from the fair scope of the teaching contained in this disclosure. The invention is therefore not limited to particular details of this disclosure except to the extent that the following claims are necessarily so limited.

Claims

WHAT IS CLAIMED IS: 1. A method of making a fastener for releasably securing a first component to a second component comprising the steps of: providing a plurality of fastener elements, each of said fastener elements having at least three rod-shape arms extending in at least two different planes; and providing a facestock layer; applying a layer of adhesive to said facestock layer; dispersing said fastener elements with a random orientation onto said adhesive; partially embedding said fastener elements in said layer of adhesive so that at least one arm of each of said fastener elements extends from said facestock layer when said fastener element iε partially embedded in said pressure-sensitive adhesive layer.

2. A method as in claim 1, wherein the step of providing said facestock layer includes extruding a polymer charge to form said facestock layer.

3. A method as in claim 2, the step of extruding said facestock layer includes coextruding said facestock layer as a side-by-side coextrusion including adjacent portions of extensible and nonextensible polymer.

4. A method as in claim 2, wherein the step of partially embedding said fastener elements includes applying pressure to the fastener elements to force at least one or more fastener arms of each fastener element into said adhesive.

5. A method as in claim 4, wherein each of said fastener elements includes a common joint connecting a plurality of arms.

6. A method as in claim 3, wherein the step of dispersing said fastener elements onto said adhesive includes dispersing said fastener elements onto said adhesive along only said adhesive layer disposed adjacent said nonextensible polymer portions.

7. A method as in claim 6, wherein the step of partially embedding said fastener elements includes applying pressure to the fastener elements to force at least one or more fastener arms of each fastener element into said adhesive.

8. A method as in claim 7, wherein each of said fastener elements includes a common joint connecting a plurality of arms.

9. A disposable diaper having opposed first and second ends and a fastening system for releasably securing said diaper ends together about a user, said fastening system including tab members secured to said first end of said diaper and a landing member secured to said second end of said diaper, said tab members and landing member being adapted to mechanically and adhesively engage and disengage for diaper closure and opening, said tab member comprising a facestock layer including a pressure-sensitive adhesive layer and mechanical fastener means, said mechanical fastener means comprising a plurality of randomly oriented fastener elements, each of said fastener elements having at least three rod-shape arms extending in at least two different planes so that at least one arm extends from said adhesive layer when said fastener element is partially embedded in said preεεure-sensitive adhesive layer.

10. A diaper as in claim 9, wherein said fastener element includes a common joint connecting each of said arms.

11. A diaper as in claim 10, wherein said fastener element includes six arms.

12. A diaper as in claim 11, wherein said six arms of said fastener element are arranged in three colinear pairs extending through said common joint, one member of each pair being on an opposite side of said common joint, one of said pairs being disposed in a first plane and the remaining pairs being disposed in a second plane perpendicular to said first plane.

13. A diaper as in claim 9, wherein each of said arms of said fastener element includes a distal end portion having interlocking means.

14. A diaper as in claim 13, wherein said interlocking means comprise an angulated arm end.

15. A diaper as in claim 14, wherein said fastener element is heat or sonic welded to said facestpck layer.

16. A diaper as in claim 14, wherein said fastener element is secured to said facestock layer by said pressure-sensitive adhesive layer.

17. A diaper as in claim 9, wherein said tab member is extensible.

18. A fastening system for releasably securing first and second components together, said fastening system including a first member secured to said first component and a second member secured to said second component, said first and second members being adapted to mechanically and adhesively engage and disengage for securement and release of said components, said first member including a facestock layer including a pressure- sensitive adhesive layer and mechanical fastener means, said mechanical fastener means comprising a plurality of fastener elements, each of said fastener elements having at least three rod-shape arms extending in at least two different planes so that at least one arm extends from said adhesive layer when said fastener element is partially embedded in said pressure-sensitive adhesive layer.

19. A system as in claim 18, wherein said first and second members are flexible.

20. A system as in claim 19, wherein said fastener element includes a common joint connecting each of said arms.

21. A system as in claim 20, wherein said fastener element includes six arms.

22. A system as in claim 21, wherein said six arms are arranged in three colinear pairs extending through said common joint, one member of each pair being on an opposite side of said common joint, one of said pairs being disposed in a first plane and the remaining pairs being disposed in a second plane perpendicular to said first plane.

23. A system as in claim 22, wherein each of said arms of said fastener element includes an angulated arm end.