Absorbent composite web

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ABSORBENT COMPOSITE WEB

FIELD OF THE INVENTION

The present invention provides an absorbent composite web comprising a fluid distributing, apertured primary material and an absorbent secondary material. The apertures of the primary material are substantially filled-in by the secondary material which may also cover the bottom surface of the primary material thereby producing a multi-layered, absorbent composite web.

BACKGROUND OF THE INVENTION

It has long been known in the disposable absorbent article art that it is extremely desirable to construct absorptive devices such as disposable diapers, catamenial pads, sanitary napkins, incontinence briefs, incontinence pads, and the like, which present a dry surface feel to the user for improving wearer comfort and to minimize the development of undesirable skin conditions due to prolonged exposure to moisture absorbed within the absorbent article. Accordingly, it is generally desirable to promote fluid transfer in a direction away from the wearer and into an absorbent element, while resisting fluid transfer in the reverse direction.

Conventional absorbent articles typically include an absorbent element (sometimes referred to as an absorbent core) interposed between a fluid pervious body-contacting element (sometimes referred to as a topsheet or an overwrap) and a fluid impervious protective barrier (sometimes referred to as a backsheet). The absorbent element is. of course, intended to receive and contain body fluids such as menses and urine. The body-contacting element is intended to provide more or less comfortable and dry-feeling contact with body surfaces while allowing free passage of fluids therethrough and into the absorbent element. The protective barrier is intended to prevent body fluids, which are expelled or which escape from the absorbent element, from soiling the user's garments.

The comfort of the user is enhanced if the absorbent article, in addition to its properties of high fluid transmisivity and fluid retention, exhibits the characteristic of unidirectional fluid transmisivity. This will improve what is known as the rewet characteristic of the absorbent product. Fluid should quickly and easily transmit through the topsheet and into the absorbent core. As the absorbent core becomes saturated, fluid will tend to pass back through the absorbent article, or rewet. causing user discomfort. As the absorbent core becomes increasingly saturated during use or is subjected to a pressure, there will be a tendency of the fluid to transmit back through the cover, or rewet the cover's surface and hence the body of the user. This discomfort caused by rewetting can cause the user to discard the absorbent product before its useful life has terminated. Therefore, it is desirable to inhibit such rewetting and thereby reduce user discomfort.

SUMMARY OF THE INVENTION

Accordingly, the invention provides an absorbent composite web comprising a primary material having a top surface, a bottom surface, and a plurality of apertures extending therethrough from the top surface to the bottom surface. Furthermore, a secondary material is preferably positioned adjacent to the primary material bottom surface whereby the secondary material extends into the plurality of apertures within the primary material.

In one application of the embodiment herein, the secondary material of the web may comprise from about 10 wt. %

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to about 90 wt. % of cellulosic material. In a further embodiment herein, the secondary material may comprise from about 10 wt. % to about 90 wt. % of synthetic material. A web herein preferably comprises a secondary material 5 having both cellulosic material and synthetic material.

Preferably, the web herein comprises a primary material that may comprise bi-component fibers, monocomponent fibers, tri-component fibers or a combination of all three.

In a particularly preferred embodiment herein, the pri10 mary material may further comprise a wetting agent, e.g.. a surfactant, to more efficiently draw fluid away from a user and/or the top surface of the primary material. Also preferably, the secondary material may comprise an element selected from the group consisting of absorbent gelling 15 material, superabsorbent polymers, silica, perfume, cyclodextrins. zeolite, charcoal, silica, cyclodexrrins and combinations thereof

In an alternative embodiment herein, the web may further comprise a tertiary material having a top surface placed 20 immediately adjacent to the bottom of the secondary material.

In one embodiment of the invention herein, a disposable diaper comprises a chassis having an upper surface and a

25 bottom surface, a front portion, a back portion positioned opposite to the front portion, a crotch portion positioned between the front portion and the back portion, a longitudinal axis, a transverse axis, a pair of end edges being parallel to the transverse axis and a pair of longitudinal

30 edges being parallel to the longitudinal axis. The chassis further comprises a topsheet and a backsheet joined to the topsheet. The backsheet has an inner surface and an outer surface. A fluid handling member is positioned between the topsheet and the backsheet. The fluid handling member

35 comprises a primary material having a top surface, a bottom surface, and a plurality of apertures extending from the top surface of the primary material to its bottom surface. Furthermore, a secondary material is positioned adjacent to the primary material bottom surface. The secondary material

w extends into the plurality of apertures in the primary material.

The fluid handling member may comprise at least a portion of the topsheet and/or the absorbent core. Also, if there is a separate topsheet and/or absorbent core, the fluid 45 handling member is preferably positioned between and placed adjacent to the topsheet and the absorbent core, respectively.

BRIEF DESCRIPTION OF THE DRAWINGS

so While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which is regarded as forming the present invention, it is believed that the invention will be better understood from the following descriptions which are taken in conjunction with the

55 accompanying drawings in which like designations are used to designate substantially identical elements, and in which: FIG. 1 is a perspective view of the absorbent composite web of the present invention; FIG. 2 is a perspective view of a portion of a patterned

go screen used in a process for the forming of a primary material;

FIG. 3A is a perspective view of an alternative embodiment of a raised portion;

FIG. 3B is a perspective view of an alternative embodi65 ment of a raised portion;

FIG. 3C is a perspective view of an alternative embodiment of a raised portion;

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all approximately equal. In such a case, there is little or no discernible density gradient established across the primary material IS, the secondary material 20 or the material within apertures 25.

Preferably, the secondary material 20 will have a greater basis weight than the primary material 15. This corresponds to the secondary material 20 also preferably having the greater density than the primary material 15 and helps to ensure that a density gradient from the primary material 15 to the secondary material 20 is established.

The calipers for both the primary material 15 and the secondary material 20 are in the ranges of 0.5 to 10 mm. preferably 1 to 5 mm and more preferably 1.5 to 2.0 mm. The basis weights for the primary material 15 and the secondary material 20 are in the ranges of 20-3000 g/m2, preferably 40-1000 g/m2 and more preferably 50-300 g/m2.

In an alternative embodiment herein, density gradients are created within either the primary material 15, the secondary material 20 or both. When a density gradient is established within the primary material 15. it relates also to the varying pore sizes established throughout the primary material 15 and is thus also referred to as the pore size gradient. The density within the primary material 15 may be made to be less dense towards its top surface 16 and more dense towards the upper surface 21 of the secondary material 20. i.e., the bottom surface of the primary material 15. This inner densification may be performed by compacting the fibers within the primary material 15 and/or through forming the primary material 15 from like or similar fibers of varying denier, i.e., the coarseness or fineness of a fiber.

In like fashion, the secondary material 20 may be inner denisified whereby the portion of the material 20 closest to the upper surface 21 is less dense than the portion nearest to the lower surface 23 of the secondary material 20. Again, this inner densification may be performed through compaction of the fibers within the secondary material 20 and/or through forming the secondary material 20 from like or similar fibers of varying denier, i.e., the coarseness or fineness of a fiber.

The varying denier of the fibers within a material establishes the density or pore size gradient within the materials. Preferably, higher denier fibers, which correspond to coarser fibers, will reside closest to the top and upper surfaces of the primary and secondary materials. Lower denier fibers will then therefore preferably reside closest to the lower or bottom surfaces of the primary and secondary materials. Such preferred construction creates primary and secondary materials that are less dense at their upper surfaces and more dense at their lower surfaces. Specifically, the coarser upper fibers (i.e., those having higher deniers) are more resilient and less structurally compressive and thus allow for the creation of greater void volumes in the upper surfaces of a material. Finer upper fibers (i.e., those having lower deniers) are less resilient and more structurally compressive and thus allow for the creation of greater compaction and fewer void volumes in the lower surfaces of a material. It is preferred herein that the lower or bottom portion of a material be more dense and that their upper portions be less dense to receive fluids quickly, thereby pulling them away from the top surfaces and holding them within the lower surfaces of a material away from its upper surfaces.

FIG. 7 shows a cross-sectional view of a web 10 having primary material 15 and a secondary material 20 that have been inner densified with fibers 17 and fibers 22, respectively. As has been mentioned above, this inner densification may have occurred either through compaction of the fibers

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and/or through the inclusion of fibers of varying deniers. It should be noted herein that though the primary material 15. for example, may comprise fibers 17 of varying deniers. the basis weights of the fibers are all approximately equal. That

5 is, the basis weights of the fibers do not vary as the denier of the fibers within a material varies. It is further noted that the inner densification of fibers may occur by the use of varying fiber types having different weights, thicknesses, bulk densities and other attributes that may affect density within the materials 15 and 20.

The primary material 15 may also be formed from a nonwoven web which may be a spunbonded web. a meltblown web. a bonded carded web, or a thermally bonded airlaid web. The nonwoven web may be made of fiber forming polymers such as. for example, polyesters.

15 polyamines. and polyolefins. Exemplary polyolefins include one or more of polypropylene, polyethylene, ethylene copolymers, propylene copolymers, and butene copolymers.

In another preferred embodiment, the nonwoven web may comprise bicomponent fibers. The bicomponent fiber used

20 herein is preferably a thermobondable bicomponent fiber having an inner core component and outer sheath component where the inner core component has a higher melting point than the outer sheath component The fiber is typically hydrophobic, but can be made hydrophilic by incorporating

25 a surfactant into the sheath of the bicomponent fiber and/or by treating the external surface of the sheath with a surfactant. Exemplary bicomponent fibers and processes for producing the same are described in U.S. Pat. No. 5.456,982 entitled "Bicomponent Synthesis Fibre And Process For

30 Producing Same", issued to Hansen et al. on Oct. 10, 1995 and U.S. Pat. No. 5,603.707 entitled "Absorbent Article Having A Rewet Barrier", issued to Trombetta et al. on Feb. 18, 1997. each of which patents are incorporated herein by reference. Whatever bicomponent fiber is used herein, it

35 must be substantially moisture insensitive so as not to absorb an amount of fluid mat would either hinder rewet of the primary material 15 or cause the structural integrity of the primary material 15 to collapse or be otherwise compromised.

40 The primary material 15 should have an operable level of density and basis weight to rapidly acquire and then drain liquid surges into the underlying secondary material 20, thus remaining substantially empty to receive subsequent liquid surges, i.e., insults. The primary material 15 should have

45 sufficient void volume capacity to temporarily retain the amount of liquid that is typically discharged by a wearer during a single insult or surge of liquid into the web 10. Insufficient void volume capacity may result in excessive pooling of liquid against the wearer's skin or excessive

50 run-off of liquid. It should be noted herein that the primary material 15 preferably comprises substantially no cellulosic material or any type of absorbent fiber that would retain and not substantially transfer all of the fluid received by the primary material 15 to the secondary material 20 and/or the

55 fibers 22 within an aperture 25.

The secondary material 20 preferably comprises from about 10 wt. % to about 90 wt. % of cellulosic material and from about 10 wt. % to about 90 wt. % of synthetic material. More preferably, the secondary material 20 comprises from

60 about 10 wt. % of a synthetic fiber like polyolefin to about 90 wt % of a cellulosic fiber like wood pulp or rayon. The purpose for the secondary material 20 is to create an absorbent, fluid-retaining structure for the fluid transported to the secondary material 20 by the primary material 15. This

65 is especially true where the web 10 is the only or primary fluid absorbing and retaining structure in an absorbent article.