Absorbent article

The present invention pertains to to diapers.

Diapers generally comprise a liquid-impermeable barrier sheet, a liquid-permeable bodyside liner, and an absorbent medium therebetween. They may generally include some type of attaching system for fitting the diaper to the wearer.

Mechanical attachments, such as hook-and-loop systems, have been used on garments in the past. However, various limitations have prevented the widespread commercialization of these systems on disposable garments or other disposable articles. The most apparent limitations to the commercialization include the cost of the system and the functionality of that system. Typically, the cost and functionality of the system is a tradeoff. In other words, greater functionality and performance can be achieved by using more expensive materials.

For example EP-A-0 374 730 refers to a fastener system for a disposable diaper. The diaper has a first mechanical fastener to close the waistband and a second fastener to enable rolling and folding the garment after use and thereby securing it in a net bundle for disposal. The fasteners disclosed do not present any particular feature of improved performance in order to avoid failures in the hook-and-loop systems.

EP 0278866 A discloses a diaper having hook and loop panels for fastening the diaper around a wearer.

Generally, hook-and-loop systems fail in the "peel" mode. For example, a peel mode exists when one component is held stationary, while the second component is pulled off the first component sequentially. When two attaching components, such as a plurality of hooks and a plurality of loops, are disengaged in the peel mode, the hooks and loops are progressively separated. That is, each row or line of hooks is disengaged a little at a time until all of the hooks are disengaged from their respective loops. The peel performance of hook-and-loop systems is very sensitive to the cost/performance ratio. Generally, to obtain higher peel, a higher basis weight loop must be used which ultimately translates to more loops, thicker fabric, and greater overall cost.

A "shear" mode failure, in comparison, exists when the two components are being pulled apart by oppositely directed forces lying in the same plane. The shear mode action is a sliding, linear action, in contrast to the peel mode which is a curvilinear type of motion or action.

A "latching" mode failure exists when the two components are being pulled apart by oppositely directed forces acting generally perpendicular to the plane of the components.

The present invention suggests various features and techniques to improve the performance of hook-and-loop systems and provides a diaper according to independent claim 1. Further advantageous features, aspects and details of the article are evident from the dependent claims, the description and the drawings.

More specifically, the invention provides a disposable diaper, in which attachment, especially tensioning attachment, is accomplished with an improved mechanical fastening system.

The present invention may thus provide a diaper comprising a composite including a substrate, an absorbent, and front and back end portions. A first releasably engageable member is on the back end portion and a second releasably engageable member is with the front end portion. The first releasably engageable member comprises a plurality of hook members and the second releasably engageable member comprises a plurality of loop members. A buckling mechanism joins the second releasably engageable member to the front end portion.

A tensioning mechanism applies tension to the first and second releasably engageable members.

The present invention may provide diaper, comprising a composite comprising a substrate and an absorbent on said substrate, said composite further comprising oppositely disposed front and back end portions, a first releasably engageable member, comprising a plurality of hook members on said back end portion of said composite, a second releasably engageable member comprising a plurality of loop members on said front end portion of said composite, said first and said second releasably engageable members being releasably engageable together, and a tensioning means for applying a predetermined tension to said first and said second releasably engageable members when engaged.

According to a further aspect, the present invention may provide a diaper comprising buckling means joining the second releasably engageable member to the front end portion for assisting engagement between said first and second releasable members whereby the second releasable member tends to buckle or distort during engagement.

According to a still further aspect, the present invention may provide a diaper, comprising a composite comprising a substrate and an absorbent on said substrate, said composite further comprising oppositely disposed front and back end portions, a first releasably engageable member comprising a plurality of hook members on said back end portion of said composite, a second releasably engageable member comprising a plurality of loop members associated with said front end portion of said composite, said first and said second releasably engageable members being releasably engageable together, and a buckling means joining said second releasably engageable member to said front end portion for assisting engagement between said first and said second releasably engageable members, whereby said front end portion tends to buckle or distort during engagement.

Preferably the diaper includes buckling means comprising a plurality of spaced-apart coupling means for intermittently coupling the loop panel to said front end portion.

Preferably, said coupling means has a width from about 1 millimeter, to about 15 millimeters.

Preferably, said coupling means are spaced apart from about 1 millimeter to about 30 millimeters.

Preferably said coupling means comprises spaced apart lines of joinder.

Preferably, said joinder lines are lines of adhesive or lines of sonic bonding or lines of heat sealing.

The plurality of hooks may be oriented in a single direction or may be multiply oriented.

In preferred embodiments of the present invention the first and said second releasably engageable members are elastically disposed with said composite to provide tension thereto.

Preferably a tension between 50 grams per inch* to 500 grams per inch is applied between said first (40) and second (22) releasabiy engageable members when engaged. *1 inch = 2.54 cm

Preferably the plurality of hooks have a hook density in the range from about 30 hooks per square centimeter to about 160 hooks per square centimeter and/or said plurality of hooks are generally arranged in rows and have a row density in the range from about 3 rows per lineal centimeter to about 30 rows per lineal centimeter.

The present invention may also provide an article wherein one of said engageable means comprises a stationary base panel and a freely moveable flap panel, and said other engageable member is releasably engageable between said stationary base panel and said freely moveable flap panel.

According to yet another aspect, the present invention may provide an absorbent article comprising a composite comprising a substrate and an absorbent on said substrate, said composite further comprising oppositely disposed front and back end portions, an attaching member comprising a plurality of hook members on said back end portion of said composite and a foldable trapping panel comprising a plurality of loop members on said front end portion of said composite, and comprising a base panel stationary on said front end portion and a flap panel freely foldable relative to said base panel said attaching member being releasably engageable between said base- panel and said flap panel.

In this aspect the article comprises a buckling means joining said base panel to said front end portion, said buckling means comprising a plurality of spaced-apart coupling means for intermittently coupling said base panel to said front end portion.

The hook members may be oriented in one direction or in multiple directions.

Preferably the attaching member is stretchable.

The above-mentioned and other features and aspects of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of the embodiments of the invention taken in conjunction with the accompanying drawings, wherein: <ul id="ul0001" list-style="none"><li>Fig. 1 is a perspective view of the back of a diaper incorporating some principles of the present invention;</li><li>Fig. 2 is a perspective front view of the diaper in Fig. 1 partially broken away;</li><li>Fig. 3 is a cross-sectional view of Fig. 2 taken along line 3-3 and viewed in the direction of the arrows;</li><li>Fig. 4 is a cross-sectional view of Fig. 2 taken along line 4-4 and viewed in the direction of the arrows;</li><li>Fig. 5 is a schematic of an apparatus for applying adhesive beads in a spaced-apart fashion upon a material sheet;</li><li>Fig. 6 is a plan view of the applied adhesive beads on the material sheet;</li><li>Fig. 7 is a graph comparing the closure force of a conventional hook-and-loop system and a hook-and-loop system of the present invention;</li><li>Fig. 8 is an enlarged side elevational view illustrating the attachment of a loop material on a substrate in accordance with the present invention;</li><li>Fig. 9 is an enlarged side elevational view of the loop material in Fig. 8 in a buckled, tensioned state;</li><li>Fig. 10 is a perspective view of the back of a diaper not in accordance with the present invention; but which has been retained for the purposes of facilitating understanding of certain features of the present invention;</li><li>Fig. 11 is an enlarged side elevational view illustrating the closed position of the attaching system illustrated in Fig. 10; and</li><li>Fig. 12 is a graph comparing the closure force of a hook-and-loop system without a trap feature and a hook-and-loop system incorporating a trap feature of the present invention.</li><li>Fig. 13A is an enlarged side elevational view illustrating a hook-and-loop system in a conventional untensioned state;</li><li>Fig. 13B is an enlarged side elevational view illustrating a hook-and-loop system of the present invention in a tensioned state;</li><li>Fig. 14 is a graph illustrating increases in latching forces as tension is increased on the system;</li><li>Fig. 15 is a graph comparing improved mechanical fastening for different hook types under varying tensions; and</li><li>Fig. 16 is an illustration of equipment used with the described latching test procedure.</li></ul>

Referring to Figs. 1-4, diaper 2 generally comprises backsheet 4, topsheet 6, and absorbent medium 8 therebetween. Leg elastics 10 are joined to side margins 12 of diaper 2 in order to gather or shirr at least intermediate portion 14 of diaper 2. Diaper 2 further comprises a front waist portion 16, rear waist portion 17, and ear portions 18 that are generally integral with rear waist portion 17. As can be seen in Figs. 1 and 2, intermediate portion 14 has a more narrow width that front and rear waist portions 16, 17, thereby giving diaper 2 a generally hour-glass shape. In Fig. 1, the arrow designated L represents the length dimension of diaper 2 and the machine direction in the manufacture of diaper 2, and the arrow perpendicular thereto designated as T indicates the width of diaper 2, as well the cross direction of the diaper during the manufacturing process.

Front waist portion 16 includes ear sections 20 which have disposed therebetween loop panel 22, which comprises the loop component of the hook-and-loop system. Loop panel 22 can be a fabric material manufactured to have a raised loop construction in which the fabric is stabilized, i.e., the individual loops are erect from the fabric's base, through a napping treatment. Panel 22 can also be any suitable material having non-woven loops thereon. Loop panel 22 is attached to front waist portion 16 of backsheet 4 such that the loops extend outwardly therefrom. The geometric shape of loop panel 22 can be any desired shape, such as rectangular, irregular, diamond, triangular, circular, oval, chevron, or the like. As illustrated, loop panel 22 is generally rectangular in shape.

Referring to Figs. 1-6, loop panel 22 is bonded or attached to backsheet 4 in a manner that is unique and results in enhanced mechanical attaching, specifically increasing the peel, shear, and latching strengths of the attaching system. Rather than bonding the entire undersurface of loop panel 22 to the surface of backsheet 4, only discrete or predetermined sections of panel 22 are attached or bonded to backsheet 4, thereby leaving portions of loop panel 22 unattached and free to move relative to backsheet 4. By thus controlling the bonding or attaching pattern of loop panel 22, the peel, shear, and latching properties of the hook-and-loop system are significantly enhanced, as graphically illustrated in Fig. 7.

Referring specifically to Figs. 5 and 6, a roll of loop material 24 is unwound from reel 26 and passed below hot melt die 28 that is in fluid communication with hopper 30, which contains a hot melt adhesive. The hot melt adhesive is applied by running loop material 24 under die 28 which applies spaced-apart beads 32 of adhesive onto loop material 24 in the machine direction, as illustrated by the arrow in Fig. 5. Since beads 32 are spaced apart, they naturally form spaces 34 therebetween.

The apparatus in Fig. 5 further includes a cutting device 36 including blade 38, which is reciprocated downwardly to cut a plurality of loop panels 22 from loop material 24.

The adhesive beads 32 range in their width from about 1 millimeter to about 15 millimeters, and the width of each space 34 is generally in the range from about 1 millimeter to about 30 millimeters. In one preferred embodiment, beads 32 are 3 millimeters in width, and are spaced about 3 millimeters apart, i.e., spaces 34 have a width of about 3 millimeters. Loop panel 22 is then attached to backsheet 4 between ear sections 20, as illustrated in Fig. 1.

As illustrated in Figs. 5 and 6, adhesive beads 32 are applied in a parallel, linear fashion, but the present invention contemplates application of adhesive beads 32 in any desired pattern as long as the resulting application produces spaced-apart areas of adhesive, such as beads 32.

Referring to Figs. 1-4, 8, 9, each ear portion 18 includes a hook tab 40 extending outwardly thereon and including a plurality of hook members 42 for engaging a plurality of loop members 44. As illustrated in Fig. 3 and Fig. 9, each individual hook member 42 can face a single direction. However, the present invention contemplates that the hook members 22 can be oriented in two or more directions. For example, a first predetermined set of rows of hook members 42 could face inwardly, as illustrated in Fig. 3, while other predetermined remaining rows can have their hook members 42 facing in an opposite direction. Alternatively, individual ones of hook members 42 can be oriented in any different number of directions as required.

Hook members 42 can have any desired geometry or shape, and can be made of any suitable material. Hook members 42 can be made of a nylon material, or of materials represented in Fig. 15 as unidirectional HTH 706, HTH 707, or HTH 708 that can be purchased from Velcro Industries B.V., Amsterdam, Netherlands or affiliates thereof. Shapes of members 42 can be hook-, mushroom-shaped, or any other desired shape. Hook member density on a respective hook tab 40 is generally within the range of about 30 to about 160 hooks per square centimeter, and preferably about 115 hooks per square centimeter. Each hook tab 40 also may have a row density within the range of about 3 to about 30 rows per lineal centimeter of width, and preferably a row density of about 15 rows per lineal centimeter. Naturally, these ranges of hook density and row density can vary and be dependent upon the peel and shear characteristics of the type and geometry of material used.

The present invention contemplates interchanging the position or placement of the hook members and loop members on their particular garment or article.

Referring now to Fig. 8, there is illustrated an enlarged side elevational view of backsheet 4 having attached thereto loop panel 22 and its loop members 44 by the spaced-apart adhesive beads 32. Between beads 32 are spaces 34 in which loop panel 22 is unattached to backsheet 4. Upon engaging a respective hook tab 40 to loop panel 22 such that hook members 42 engage loop members 44, and upon application of a tension as illustrated by the arrow in Fig. 9, loop panel 22 will distort or flex with a plurality of buckles 46. This generally results in an increase in the peel, shear, and/or latching strengths between hook tabs 40 and loop panel 22. As graphically illustrated in Fig. 7, graph line C illustrates the closure force of a conventional hook-and-loop system in which the loop panel is totally adhered to its substrate. In contrast, graph line I illustrates the increase in closure force provided by the present invention in which loop panel 22 is intermittently or discretely attached to its backsheet 4. Without being bound to any specific theory or mechanism, it has been found that the increase in peel, shear, and latching strengths results from intermittent attachment of loop panel 22 to backsheet 4, thereby forming a plurality of buckles 46 when hook tabs 40 are engaged under tension to loop panel 22. A preferred tension range is between about 19.69 g per cm (about 50 grams per inch to about 196.9 g per cm (500 grams per inch).

Referring now to Fig. 10, diaper 48 illustrates another diaper not in accordance with the present invention as the diaper does not include a loop panel which tends to buckle or distort into a plurality of buckles when engaged with a hook panel. Diaper 48 is identical to diaper 2 except in the following description. Each ear portion 18 has joined thereto hook tab 50 having a plurality of hook members 42 disposed on both inner surface 52 and outer surface 54 of a respective hook tab 50. Generally, hook tab 50 can be made of a stretchable or elastomeric material, or hook tab 50 can be joined to a respective ear portion 18 by an intermediate strip of stretchable or elastic material that joins hook tab 50 to ear portion 18.

Front waist portion 16 of backsheet 4 has disposed thereon two separate loop panels 56, 58. Since loop panels 56, 58 are identical, a description of only loop panel 56 will be made. Loop panel 56 includes loop panel base 60 joined to backsheet 4 and loop panel flap 62 which is hingedly connected to loop panel base 60, as illustrated in Fig. 10. This permits loop panel flap 62 to be folded back and forth between a generally unfolded position, in which it is substantially coplanar with loop panel base 60, and a folded position, in which it is folded over and on top of loop panel base 60 such that their respective loop members 44 are in mutually tacing relationship.

Referring to Figs. 10 and 11, upon placing diaper 48 about the wearer, each ear portion 18 is drawn around the waist section of the wearer and a respective hook tab 50 is stretched, i.e., placed under tension, as necessary for a proper fit, and placed against loop panel base 60 to engage hook members 42 on inner surface 52 with loop members 44 of loop panel base 60. Loop panel flap 62 is then folded over and engaged with hook tab 50 such that loop members 44 of loop panel flaps 62 engage hook members 52 on outer surface 54 of hook tab 40. Although Fig. 11 illustrates hook members 52 as having their open or mouth ends oriented in the same direction, hook members 52 may be multiply directed as required to provide the desired attachment.

Referring to Fig. 12, graph line A represents the closure force of a conventional hook-and-loop system without a loop panel flap, and graph line P illustrates the present invention in which loop panel flap 62 and loop panel base 60 trap hook members 52 of hook tab 50.

Referring to Fig. 13A, a conventional hook-and-loop system in an untensioned state is illustrated. Because of the untensioned state, there is a certain amount of looseness or play between individual hooks and loops that can result in a less than desirable fastening system. In contrast, Fig. 13B illustrates the hook-and-loop system of the present invention in a tensioned state that causes the hooks to be engaged firmly without play with their respective loops. This increases the stability and performance of the fastening system.

For example, Figs. 14 and 15 illustrate the increase in latching forces for hooks made of different materials as tension is increased. Thus, regardless of the hook material or article with which the fastening system of the present invention may be used, tension enhances the performance of all systems to some degree.

Test Procedures

PEEL TEST PROCEDURE

Peel is determined according to ASTM Designation D1876-72, "Standard Test Methods for Peel Resistance of Adhesives (T-Peel Test)", subject to the following modification: No test panels are used; hook-and-loop materials are directly engaged and are not mounted on any other substrate unless specified. Test direction of the materials should be noted. No panels are used. The engaged test materials are rolled five cycles; where one cycle equals once in each direction. The hook material is clamped into the upper jaw and the loop material is clamped into the lower jaw.

SHEAR TEST PROCEDURE

Shear is determined according to ASTM Designation D3654-82, "Standard Test Method for Holding Power of Pressure-Sensitive Tapes", and which is subject to the following modification: In relation to the test, the closure is placed under an increasing load. The system being tested is a hook-and-loop closure system. The apparatus should include an "INSTRON" or equivalent tensile tester. In carrying out the procedure, test direction of the materials should be noted. The test materials are rolled five cycles (6.45 cm² (one square inch)), where one cycle equals once in each direction. The hook material is clamped into the lower jaw of the INSTRON tensile tester. The engaged system (hook-and-loop) is pulled until failure. In doing calculations, the peak load is determined and recorded in grams.

LATCHING TEST PROCEDURE

Latching.force is measured by applying a hook material to a loop material, applying a lateral force to the interface between the hook and loop materials, and then separating them with a vertical force. The value of the vertical force necessary to separate the two materials is the peak force or load in grams. This test method indicates the effect of tension, such as that applied by an elastic member, on a hook and loop closure system. In this test the phrase "latching force" means the force required to disengage a hook material from a loop material resulting from a pull perpendicular to the plane of attachment of the materials to which a fixed lateral force is applied. The phrase "lateral force" means the force applied in parallel to the interface of the hook and loop materials, and the phrase "vertical force" means the force applied perpendicular to the interface of the hook and loop materials.

Referring to figure 16, there is illustrated a suitable tensile testing machine 70 including a suspension line 72 connected to machine 70 and hanging dpwnwardly therefrom. Latching force test fixture 74 is horizontally mounted and is selectively moveable in the horizontal by means of threaded rod 76. Fixture 74 includes a spring 78. Base support 80, which may be a part of tensile testing machine 70, is used to fix a stainless steel test panel 82 in a stationary position. Hook mounting block 84 includes a vertically oriented eye screw 86 connected to suspension line 72 and a horizontally disposed eye screw 88 connected to spring 78.

A hook and loop closure system is tested by mounting the hook material on the undersurface of hook mounting block 84 and mounting a loop material on the top surface of test panel 82, and then utilizing a lateral force applied by fixture 74 and a vertical force applied by machine 70. This test method is used to analyze the effect of tension on a hook and loop closure system particularly when the hooks are oriented in the direction of the applied tension force.

Tensile testing machine 70 can be any suitable machine that can supply a constant rate of extension having a rate of traverse of about 305 millimeters per minute. Test panel 82 preferably has the dimensions of 51 millimeters x 152 millimeters. Hook mounting block 84 should be made of aluminum having a mounting surface with a dimension of about 25 millimeters x 13 millimeters.

The test procedure occurs in generally two stages, one being the preparing of the specimens and the other being the determination of latching force. The preparations of specimens includes cutting a 25 millimeter square specimen of the hook material and attaching it to the hook mounting block 84 with a two-sided adhesive tape that has an adhesive strength greater than the hook and loop closure system being tested. The hook material should be mounted in a manner that will enable any directionality of the hooks to be utilized in the most efficient manner with regard to the tensioning force. The loop material is cut to have the dimensions of about 30 millimeters x 90 millimeters, and then'attached to the stainless steel test panel 82 so that there is approximately six millimeters distance between the edge of the loop specimen and the edge of the test panel 82. Again, a two-sided adhesive tape is used to attach the loop material with the tape having a greater adhesive strength than the hook and loop closure system.

The determination of the latching force is accomplished by first inserting an empty test panel 82 in base support 80. An empty hook mounting block 84 is centered in tensile testing machine 70 by means of suspension line 72. Hook mounting block 84 is then positioned to slightly rest on test panel 82 with minimal slack in suspension line 72. The empty test panel is then replaced with a test panel 82 having the loop material attached thereto. Hook mounting block 84, which has the material attached to its undersurface, is then placed on top of the loop material without applying any pressure. A lateral force is then selectively applied by means of latching force test fixture 74. Thereafter, tensile testing machine 70 is activated to apply a vertical force until the hook and loop materials are separated. The applied force at which the hook and loop materials separate is the peak load for the applied lateral force.