AU2001292937A1

AU2001292937A1 - Absorbent having good absorbency and wicking properties

Info

Publication number: AU2001292937A1
Application number: AU2001292937A
Authority: AU
Inventors: Michael Tod Morman; Jian Qin; Hannong Rhim
Original assignee: Kimberly Clark Worldwide Inc; Kimberly Clark Corp
Current assignee: Kimberly Clark Worldwide Inc
Priority date: 2000-09-22
Filing date: 2001-09-21
Publication date: 2002-04-02
Also published as: KR20030034200A; AR030767A1; RU2279267C2; PL363084A1; BR0113639A; ZA200301135B; JP2004510472A; EP1318780A2; CN1464783A; MXPA03002086A; WO2002024132A3; WO2002024132A2

Description

ABSORBENT HAVING GOOD ABSORBENCY AND WICK1NG PROPERTIES

BACKGROUND OF THE INVENTION

The present invention concerns retention materials mainly for personal care products like diapers, training pants, swim wear, absorbent underpants, adult incontinence products and feminine hygiene products. This material may also be used in other applications such as, for example, in bandages and wound dressings, nursing pads and veterinary applications. Personal care articles usually have absorbent material of some sort to absorb liquids from the body. This absorbent material or absorbent core is generally made from multiple layers or materials and may include natural fibers, synthetic fibers and superabsorbent particles in varying proportions. When liquid such as urine is deposited into a personal care product like a diaper, it goes through the uppermost layers, typically a liner against the body and a "surge" layer designed to provide temporary liquid hold-up. After going through these upper layers, the urine enters the absorbent core portion of the product. The absorbent core permanently retains the liquid. In the case of an absorbent core having superabsorbent particles, the liquid is absorbed to the limit of the particular absorbent. ^* Absorbency of superabsorbents may be limited by physical constraints imposed upon the system. If the superabsorbent is confined and unable to swell upon contact with liquid, the volume of liquid absorbed will be limited. If the superabsorbent swells and is unable to expand freely, the pores between the superabsorbent particles will be compressed and reduced in size. Extreme reduction in pore size results in a phenomenon known as "gel blocking" in which further entry of liquid is prohibited by the expansion of superabsorbent in the region of liquid entry, and wicking of fluid within the superabsorbent layer ceases. This may occur even if other areas of the absorbent core have not been wetted with fluid and is obviously wasteful of superabsorbent and inefficient. On the other hand, if superabsorbent is allowed to swell without limit, the pore size becomes too large to wick fluid to a certain height and it will eventually block entry of fluid. It is desirable, therefore, to allow superabsorbent to swell in a controlled manner and to a controlled degree so that pore integrity is maintained and wicking continued and so that contact between any wicking materials and the superabsorbent and between superabsorbent particles, is maintained.

There remains a need, therefore, for an absorbent core system that will have good liquid intake and distribution properties yet allow the continuation of sufficient wicking within the superabsorbent layer and so utilize more of the absorbent core. Such a system should maintain pore integrity to a large degree and a suitable pore size distribution so that liquid may continue to be absorbed despite the wetting of upper portions of the absorbent core.

SUMMARY OF THE INVENTION

In response to the discussed difficulties and problems encountered in the prior art, a new absorbent core system for personal care products has been discovered, where the superabsorbent-containing layer is located between two layers. The first layer is an extendible outer cover and the second layer is on a side opposite the first layer. At least one of the layers is liquid permeable. The layers may be bonded together in a pattern. Both facing layers may be extendible and/or elastic and, depending on the material used for the layer(s) the direction of stretch may be controlled. A separate wicking layer may also be present. DEFINITIONS

"Disposable" includes being disposed of after a single use and not intended to be washed and reused. "Liquid communication" means that liquid is able to travel from one layer to another layer, or one location to another within a layer.

"Hydrophilic" describes fibers or the surfaces of fibers that are wetted by the aqueous liquids in contact with the fibers. The degree of wetting of the materials can, in turn, be described in terms of the contact angles and the surface tensions of the liquids and materials involved. Equipment and techniques suitable for measuring the wettability of particular fiber materials can be provided by a Cahn SFA-222 Surface Force Analyzer System, or a substantially equivalent system. When measured with this system, fibers having contact angles less than 90° are designated "wettable" or hydrophilic, while fibers having contact angles equal to or greater than to 90° are designated "nonwettable" or hydrophobic.

As used herein the term "nonwoven fabric or web" means a web having a structure of individual fibers or threads which are interlaid, but not in an identifiable manner as in a knitted fabric. Nonwoven fabrics or webs have been formed from many processes such as for example, meltblowing processes, spunbonding processes, and bonded carded web processes. The basis weight of nonwoven fabrics is usually expressed in ounces of material per square yard (osy) or grams per square meter (gsm) and the fiber diameters useful are usually expressed in microns. (Note that to convert from osy to gsm, multiply osy by 33.91).

"Spunbonded fibers" refers to small diameter fibers that are formed by extruding molten thermoplastic material as filaments from a plurality of fine capillaries of a spinneret. Such a process is disclosed in, for example, US Patent 4,340,563 to Appel et al. and US Patent 3,802,817 to Matsuki et al. The fibers may also have shapes such as those described, for example, in US Patents 5,277,976 to Hogle et al. which describes fibers with unconventional shapes.

"Bonded carded web" refers to webs that are made from staple fibers which are sent through a combing or carding unit, which separates or breaks apart and aligns the staple fibers in the machine direction to form a generally machine direction-oriented fibrous nonwoven web. This material may be bonded together by methods that include point bonding, through air bonding, ultrasonic bonding, adhesive bonding, etc.

"Airlaying"is a well-known process by which a fibrous nonwoven layer can be formed. In the airlaying process, bundles of small fibers having typical lengths ranging from about 3 to about 52 millimeters (mm) are separated and entrained in an air supply and then deposited onto a forming screen, usually with the assistance of a vacuum supply. The randomly deposited fibers then are bonded to one another using, for example, hot air or a spray adhesive. Airlaying is taught in, for example, US Patent 4,640,810 to Laursen et al.

Various processes are known for the bonding of nonwoven webs. These include through air bonding, stitchbonding, ultrasonic bonding, point bonding, and pattern (or point) unbonding. Examples of these bonding processes may be seen in US Patents 4,891 ,957 to Strack et al., 4,374,888 to Bornslaeger, 3,855,046 to Hansen and Pennings, and 5,858,515 to Stokes et al.

As used herein the term "composite elastic material" refers to an elastic material which may be a multicomponent material or a multilayer material in which at least one layer is elastic. These materials may be, for example, "neck bonded" laminates, "stretch bonded" laminates, "neck-stretch bonded" laminates and "zero strain stretch" laminates. "Neck bonding" refers to the process wherein an elastic member is bonded to a non-elastic member while only the non-elastic member is extended or necked so as to reduce its dimension in the direction perpendicular to the extension. "Neck bonded laminate" refers to a composite elastic material made according to the neck bonding process, i.e.: the layers are joined together when only the non-elastic layer is in an extended condition. Such laminates usually have cross directional stretch properties. Examples of neck-bonded laminates are such as those described in US Patents 5,226,992, 4,981 ,747, 4,965,122 and 5,336,545 to Morman and US Patent 5,514,470 to Haffner et al. Conventionally, "stretch bonding" refers to a process wherein an elastic member is bonded to another member while only the elastic member is extended at least about 25 percent of its relaxed length. "Stretch bonded laminate" refers to a composite elastic material made according to the stretch bonding process, i.e.: the layers are joined together when only the elastic layer is in an extended condition so that upon relaxing the layers, the non-elastic layer is gathered. Such laminates usually have machine directional stretch properties and may be stretched to the extent that the non-elastic material gathered between the bond locations allows the elastic material to elongate. One type of stretch bonded laminate is disclosed, for example, by US Patent 4,720,415 to Vander Wielen et al., in which multiple layers of the same polymer produced from multiple banks of extruders are used. Other composite elastic materials are disclosed in US Patent 4,789,699 to Kieffer et al. , US Patent 4,781,966 to Taylor and US Patents 4,657,802 and 4,652,487 to Morman and 4,655,760 to Morman et al.

US Patent 4,657,802, for example, discloses a process for producing a composite nonwoven elastic web including a nonwoven elastic web joined to a fibrous nonwoven gathered web. The process includes the steps of providing a nonwoven elastic web having a relaxed unbiased length and a stretched, biased length, stretching the nonwoven elastic web to its stretched, biased length, forming a fibrous nonwoven gatherable web directly upon a surface of the nonwoven elastic web at its stretched, biased length, forming a composite nonwoven elastic web by joining the fibrous nonwoven gather able web to the nonwoven elastic web while continuing to maintain the nonwoven elastic web at its stretched length, and relaxing the nonwoven elastic web to its relaxed length to gather the fibrous nonwoven gatherable web. The joining of the fibrous nonwoven gatherable web to the nonwoven elastic web occurs simultaneously with formation of the gatherable web on the surface of the elastic web.

"Neck-stretch bonding" generally refers to a process wherein an elastic member is bonded to another member while the elastic member is extended at least about 25 percent of its relaxed length and the other layer is a necked, non-elastic layer. "Neck- stretch bonded laminate" refers to a composite elastic material made according to the neck-stretch bonding process, i.e.: the layers are joined together when both layers are in an extended condition and then allowed to relax. Such laminates usually have omni- directional stretch properties.

"Zero strain" stretch bonding generally refers to a process wherein at least two layers are bonded to one another while in an untensioned (hence zero strain) condition and wherein one of the layers is stretchable and elastomeric and the second is stretchable but not necessarily elastomeric. Such a laminate is stretched incrementally through the use of one or more pairs of meshing corrugated rolls which reduce the strain rate experienced by the web. "Zero strain stretch laminate" refers to a composite elastic material made according to the the zero strain stretch bonding process, i.e., the elastic and non-elastic layers are joined together when both layers are in an unextended condition and stretched though meshing corrugated rolls. The second layer, upon stretching of the laminate, will be at least to a degree permanently elongated so that the laminate will not return to its original undistorted condition upon release of the stretching force. This results in z-direction bulking of the laminate and subsequent elastic extensibility in the direction of initial stretching at least up to the point of initial stretching. Examples of such laminates and their production processes may be found in US Patents 5,143,679 to Weber et al., 5,151 ,092 to Buell et al., 5,167,897 to Weber et al., and 5,196,000 to Clear et al. "Personal care product" means products for the absorption of body exudates, such as diapers, training pants, swim wear, absorbent underpants, adult incontinence products, bandages, veterinary and mortuary products, and feminine hygiene products.

"Target area" refers to the area or position on a personal care product where an insult is normally delivered by a wearer.

TEST METHODS AND MATERIALS

Basis Weight: The basis weight may be determined by cutting circular sample of 7.6 cm (3 inches) diameter and weighing using a balance. Weight is recorded in grams. The weight is divided by the sample area.

Material caliper (thickness): The caliper of a material is a measure of thickness and is measured at 0.05 psi (3.5 g/cm²) with a STARRET®-type bulk tester, in units of millimeters. Density: The density of the materials is calculated by dividing the weight per unit area of a sample in grams per square meter (gsm) by the material caliper in millimeters (mm). The caliper should be measured at 0.05 psi (3.5 g/cm²) as mentioned above. The result is multiplied by 0.001 to convert the value to grams per cubic centimeter (g/cc).

DETAILED DESCRIPTION OF THE INVENTION

This invention relates to an absorbent system used in a personal care product to provide good wicking and absorbency.

In one embodiment, the invention includes an absorbent surrounded by an elastic web. The absorbent may include superabsorbent material in varying forms; particles, fibers, foams, and the like, and may include natural fibers, binders and synthetic fibers. The elastic material in this embodiment must be a liquid permeable layer. Liquid permeable materials include apertured, filled and fibrillated films, woven and nonwoven webs, open celled foams, netting and any other layer that will allow liquid water to pass through it. The elastic material may also be any suitable liquid permeable elastic bonded with tissue using elastic latex. This absorbent system may be made by placing the absorbent material onto an elastic material and rolling the elastic material to enclose the absorbent, producing a round absorbent system.

In still another embodiment, the absorbent may be made from two elastic layers, between which is placed absorbent material. The layers in this embodiment are also preferably bonded together in some manner to contain the absorbent and only one layer must be liquid permeable. If both layers are elastic, they may be elastic in the same, different or all directions. If they are both elastic in the same direction, the laminate will be elastic in that direction in a wet or dry condition. Suitable elastic materials which are elastic in one direction include stretch bonded laminates and neck bonded laminates, discussed above. Omni-directional materials include neck-stretch bonded laminates, also discussed above. The elastic material may be any suitable material such as an elastic apertured film, woven or nonwoven web, or netting. The elastic material may also be any of the suitable liquid permeable elastics bonded with other materials using elastic latex. The elastic layer may also be liquid permeable.

In another embodiment, the absorbent may be made from two extendible layers, between which is placed absorbent material. The layers are preferably bonded together in a pattern in order to keep the absorbent material in approximately the same place when the absorbent system is moved. In this embodiment, only one of the outer layers must be liquid permeable.

In another embodiment, the absorbent may be made from an elastic layer and an extendible layer, between which is placed absorbent material. The layers are preferably bonded together in a pattern in order to keep the absorbent material in approximately the same place when the absorbent system is moved. In this embodiment, only one of the outer layers must be liquid permeable.

In another embodiment, the absorbent may be made from a non-extendible layer and an extendible layer, between which is placed absorbent material. The layers are preferably bonded together in a pattern in order to keep the absorbent material in approximately the same place when the absorbent system is moved. In this embodiment, only one of the outer layers must be liquid permeable.

The extendible layer in these embodiments may be, for example, a reversibly necked spunbond fabric as taught in US Patent 4,965,122. This material is capable of stretching at least about 75 percent and recovering at least about 50 percent when stretched about 75 percent, typically in a direction generally parallel to the direction of necking. This material is made by applying a tensioning force to at least one material to neck the material, heating the necked material, and cooling the necked material such that the reversibly necked material possesses a greater heat of fusion and/or a lower onset of melting than the materials before heating while stretched.

In another embodiment, the absorbent system may be made from a flat, non- elastic layer and an elastic layer, with absorbent materials placed between the two layers. The layers are preferably bonded together in a pattern in order to keep the absorbent material in approximately the same place when the absorbent system is moved. In this embodiment, only one of the outer layers must be liquid permeable.

Many other embodiments are possible because of the myriad of composite elastic materials available. The outer layers of the absorbent system may have multiple layers and may be, for example, neck bonded laminates, stretch bonded laminates, neck stretch bonded laminate and zero stretch-strain laminates. In any of the embodiments, additional layers may be place within the structure. A layer of bonded-carded web, airlaid fabric or spunbond fabric, for example, may be placed inside the system in order to provide more wicking ability than that of only the outer layers or absorbent material. The cross-section of such a structure may include the wicking layer in the center with absorbent on either or both sides, and then the outer layers.

It should be noted that if it is desired to have a laminate that is elastic or extendable in one or more directions, inelastic materials should not be used in the laminate in such a manner as to restrict stretching. Superabsorbents or other materials present in the inner layer should, therefore, be in particulate or short fiber form, i.e., be discrete to allow movement or be elastic if in indiscrete form such as a long fibers, foam, film or nonwoven fabric.

Suitable system materials for the outer layers may be nonwoven webs made from elastomeric and non-elastomeric polymers according to various processes known in the art including meltblowing, spunbonding, bonding and carding, and airlaying. The webs may be bonded according to known processes as well, including through air bonding, stitchbonding, ultrasonic bonding, point bonding, and pattern (or point) unbonding. Liquid permeable elastomeric and non-elastomeric films may also be used in the practice of this invention and include apertured, fibrillated and filled films.

The extendible layer allows the superabsorbent to swell to a controlled degree upon being wetted so that pore integrity and suitable pore size and distribution are maintained and sufficient wicking of fluid through the superabsorbent is continued. The pore size and distribution control may be accomplished via suitable tensioning of the extendible layer material according to the curvature of the underlying body, and thus controlling the pressure onto the superabsorbent-containing layer. The pressure may be designed to vary according to the height through suitable tension distribution of the extendible material. In addition to conventionally known superabsorbent, any liquid swellable material should perform in a similar manner. Elastomeric polymers useful in the practice of this invention may be those made from block copolymers such as polyurethanes, copolyether esters, polyamide polyether block copolymers, ethylene vinyl acetates (EVA), block copolymers having the general formula A-B-A' or A-B like copoly(styrene/ethylene-butylene), styrene-po!y(ethylene- propylene)-styrene, styrene-poly(ethylene-butylene)-styrene, (polystyrene/poly(ethylene- butylene)/polystyrene, poly(styrene/ethylene-butylene/styrene) and the like. The elastomeric copolymers and formation of elastomeric nonwoven webs from those elastomeric copolymers are disclosed in, for example, U.S. Patent 4,803,117. The elastomeric nonwoven web may be formed from, for example, elastomeric (polystyrene/poly(ethylene- butylene)/ polystyrene) block copolymers. Commercial examples of such elastomeric copolymers are, for example, those known as KRATON® materials which are available from Shell Chemical Company of Houston, Texas. KRATON® block copolymers are available in several different formulations, a number of which are identified in U.S. Patents 4,663,220, 4,323,534, 4,834,738, 5,093,422 and 5,304,599.

Polymers composed of an elastomeric A-B-A-B tetrablock copolymer may also be used in the practice of this invention. Such polymers are discussed in U.S. Patent 5,332,613 to Taylor et al. In such polymers, A is a thermoplastic polymer block and B is an isoprene monomer unit hydrogenated to a substantially a poly(ethylene-propylene) monomer unit. An example of such a tetrablock copolymer is a styrene-poly(ethylene- propylene)-styrene-poly(ethylene-propylene) or SEPSEP elastomeric block copolymer available from the Shell Chemical Company of Houston, Texas under the trade designation KRATON®. Other exemplary elastomeric materials which may be used include polyurethane elastomeric materials such as, for example, those available under the trademark ESTANE® from B. F. Goodrich & Co. or MORTHANE® from Morton Thiokol Corp., polyester elastomeric materials such as, for example, those available under the trade designation HYTREL® from E. I. DuPont De Nemours & Company, and those known as ARNITEL®, formerly available from Akzo Plastics of Arnhem, Holland and now available from DSM of Sittard, Holland.

Another suitable material is a polyester block amide copolymer having the formula: O O

II II

HO-[~C-PA-C~O-PE~0-]_n~H

Such materials are available in various grades under the trade designation PEBAX® from ELF Atochem Inc. of Glen Rock, New Jersey. Examples of the use of such polymers may be found in U.S. Patents 4,724,184, 4,820,572 and 4,923,742, to Killian et al. and assigned to the same assignee as this invention.

The thermoplastic copolyester elastomers include copolyetheresters having the general formula:

O O O O

II II II II

H-([O-G-O-C-C₆H₄-C]_b-[O-(CH₂)_a-O-C- C₆H₄-C]_rn)_n-O-(CH₂)_a-OH

where "G" is selected from the group consisting of poly(oxyethylene)-alpha,omega-diol, poly(oxypropylene)-alpha,omega-diol, poly(oxytetramethylene)-alpha,omega-diol and "a" and "b" are positive integers including 2, 4 and 6, "m" and "n" are positive integers including 1-20. Such materials generally have an elongation at break of from about 600 percent to 750 percent when measured in accordance with ASTM D-638 and a melt point of from about 350°F to about 400°F (176 to 205°C) when measured in accordance with ASTM D-2117. Commercial examples of such copolyester materials are, for example, those known as ARNITEL®, formerly available from Akzo Plastics of Arnhem, Holland and now available from DSM of Sittard, Holland, or those known as HYTREL® which are available from E.I. duPont de Nemours of Wilmington, Delaware. Formation of an elastomeric nonwoven web from polyester elastomeric materials is disclosed in, for example, U.S. Patent 4,741,949 to Morman et al. and US Patent 4,707,398 to Boggs. Elastic polyolefin polymers are also useful in the practice of this invention. Such polymers are referred to as "metallocene" polymers and are available from Exxon Chemical Company of Baytown, Texas under the trade name ACHIEVE® for polypropylene based polymers and EXACT® and EXCEED® for polyethylene based polymers. Dow Chemical Company of Midland, Michigan has polymers commercially available under the name ENGAGE®. These materials are believed to be produced using non-stereo selective metallocene catalysts. Exxon generally refers to their metallocene catalyst technology as "single site" catalysts while Dow refers to theirs as "constrained geometry" catalysts under the name INSIGHT® to distinguish them from traditional Ziegler-Natta catalysts which have multiple reaction sites. In the practice of the instant invention, elastic polyolefins like polypropylene and polyethylene are preferred, most especially elastic polypropylene.

Natural fibers include wool, cotton, flax, hemp and wood pulp. Wood pulps include standard softwood fluffing grade such as CR-1654 (US Alliance Pulp Mills, Coosa, Alabama). Pulp may be modified in order to enhance the inherent characteristics of the fibers and their processability. Curl may be imparted to the fibers by methods including chemical treatment or mechanical twisting. Curl is typically imparted before crosslinking or stiffening. Pulps may be stiffened by the use of crosslinking agents such as formaldehyde or its derivatives, glutaraldehyde, epichlorohydrin, methylolated compounds such as urea or urea derivatives, dialdehydes such as maleic anhydride, non-methylolated urea derivatives, citric acid or other polycarboxylic acids. Some of these agents are less preferable than others due to environmental and health concerns. Pulp may also be stiffened by the use of heat or caustic treatments such as mercerization. Examples of these types of fibers include NHB416 which is a chemically crosslinked southern softwood pulp fibers which enhances wet modulus, available from the Weyerhaeuser Corporation of Tacoma, WA. Other useful pulps are debonded pulp (NF405) and non-debonded pulp (NB416) also from Weyerhaeuser. HPZ3 from Buckeye Technologies, Inc of Memphis, TN, has a chemical treatment that sets in a curl and twist, in addition to imparting added dry and wet stiffness and resilience to the fiber. Another suitable pulp is Buckeye HPF2 pulp and still another is IP SUPERSOFT® from International Paper Corporation. Suitable rayon fibers are 1.5 denier merge 18453 fibers from Tencel Incorporated of Axis, Alabama. Superabsorbents that are useful in the present inventions can be chosen from classes based on chemical structure as well as physical form. These include superabsorbents with low gel strength, high gel strength, surface cross-linked superabsorbents, uniformly cross-linked superabsorbents, or superabsorbents with varied cross-link density throughout the structure. Superabsorbents may be based on chemistries that include poly(acrylic acid), poly(iso-butylene-co-maleic anhydride), poly(ethylene oxide), carboxy-methyl cellulose, poly(-vinyl pyrrollidone), and poly(-vinyl alcohol). The superabsorbents may range in swelling rate from slow to fast. The superabsorbents may be in the form of foams, macroporous or microporous particles or fibers, particles or fibers with fibrous or particulate coatings or morphology. The superabsorbents may be in the shape of ribbons, particles, fibers, sheets or films. Superabsorbents may be in various length and diameter sizes and distributions. The superabsorbents may be in various degrees of neutralization. Counter-ions are typically Li, Na, K, Ca.

Materials of this invention may include superabsorbents of the types mentioned above. Exemplary superabsorbents may be obtained from The Dow Chemical Company. An Example of these types of superabsorbents may be obtained from Stockhausen, Inc and is designated FAVOR® SXM 880. An example of fibrous superabsorbents may be obtained from Camelot Technologies, Ltd., of High River, Alberta, Canada and is designated FIBERDRI® 1241. Another Example included in these types of superabsorbents is obtained from Chemtall Inc. of Riceboro, GA, and is designated FLOSORB 60 LADY®, also known as LADYSORB 60®. Examples of superabsorbents with fibrous or particulate coatings are microcrystalline cellulose coated on FAVOR® 880 and cellulose fiber coated FAVOR® 880. These are described in US Provisional Patent Application 60/129,774. Additional types of superabsorbents not listed here which are commonly available and known to those skilled in the art can also be useful in the present inventions. Binders typically used in these structures help provide mechanical integrity and stabilization. Binders include fiber, liquid or other binder means which may thermally activated. Preferred fibers for inclusion are those having a relative melting point such as polyolefin fibers. Lower melting point polymers provide the ability to bond the fabric together at fiber crossover points upon the application of heat. In addition, fibers having a lower melting polymer, like conjugate and biconstituent fibers are suitable for practice of this invention. Fibers having a lower melting polymer are generally referred to as "fusible fibers". By "lower melting polymers" what is meant are those having a glass transition temperature less than about 175° C. It should be noted that the texture of the absorbent web could be modified from soft to stiff through selection of the glass transition temperature of the polymer. Exemplary binder fibers include conjugate fibers of polyolefins, polyamides and polyesters. Three suitable binder fibers are sheath core conjugate fibers available from KoSa Inc. (Charlotte, North Carolina) under the designation T-255 polyethylene/polyethyleneterephathalate and T-256 or Copolyester designation, though many suitable binder fibers are known to those skilled in the art, and are available by many manufacturers such as Chisso and Fibervisions LLC of Wilmington, DE. KoSa has developed a suitable co-polyester binder fiber as a sheath core application and is known by designation T-254 (low melt CoPET). A suitable liquid binder is KYMENE® 557LX available from Hercules Inc. of Wilmington, DE. Other suitable liquid binders include ethylene vinyl acetate emulsion polymers sold by National Starch and Chemical Company (Bridgewater, New Jersey) under the tradename DUR-O-SET® ELITE® series (including ELITE® 33 and ELITE® 22). Air Products Polymers and Chemicals sells other suitable binder fibers under the name AIRFLEX®. The fibers used to produce the materials useful in this invention may be monocomponent, conjugate (bicomponent), multicomponent or biconstituent fibers. If conjugate, they may have side-by-side, sheath/core or islands-in-the-sea configurations. The fibers may be crimped or crimpable according to, for example, US Patent 5,382,400 to Pike.

Examples of suitable absorbent systems according to the invention follow:

Example 1

A laminate was made using stretch bonded laminate (SBL) outer layers, both layers having stretch in the same direction made according to US Patent 4,657,802 to Morman. The SBL was made by stretching an elastic meltblown layer and bonding it to a non-elastic layer on either side. The elastic layer was a 71 gsm (2.1 osy) meltblown layer made from KRATON® G-2740 polymer. The non-elastic layers were 30.9 gsm (0.91 osy) spunbond layers made from polypropylene from ESCORENE® polymer from Exxon Chemical Corp. The basis weight of the SBL was 132.6 gsm (3.9 osy). One facing was removed from the SBL material and the first SBL layer was placed on a flat surface, meltblown side up. Superabsorbent particles, in this case FAVOR® 880 superabsorbent, were distributed onto the SBL layer at an addition rate of 88.8 gsm (2.62 osy). A second layer of the same SBL, meltblown side down, was placed on the superabsorbent and the layers were laminated in a press with about a 12 mm (half inch) square grid pattern at 6000 psi ram pressure. The press was made by PHI in the City of Industry, California, and was model no. 0230 C-X1-4B-7, serial no. 92-10-012. The laminate had a basis weight of 293 gsm (8.64 osy).

The dry laminate was very thin, stretchy and conformable. A sample was cut in the following dimensions: 6 cm (2.375 inches) in the stretch direction and 8.26 cm (3.25 inches) in the non-stretch direction, 2.5 mm (0.099 inches) thick. This sample weighed 1.46 grams and stretched to about 11.4 cm (4.5 inches) using normal tension applied by hand.

The sample was placed in water with a minor amount of surfactant for about a half an hour. Afterwards, the sample was 5.7 cm (2.25 inches) long, 7.6 cm (3 inches) wide and varied in thickness from 8.1 to 13.3 mm (0.319 to 0.525 inches). The sample weighed 26.9 grams and stretched to 10.2 cm (4.25 inches) under approximately the same tension applied by hand by the same person as above.

As can be seen from the above, the wet thickness of the sample was more than about 3 times the dry thickness, yet the wet and dry extendibility were about the same. The weight and thickness changed because of the absorption of water but other properties remained the same.

Example 2

Two airlaid layers were used to make a wicking laminate sample and a control and each was 5.1 cm by 15.24 cm (2 inches by 6 inches). The airlaid wicking layer was made using 90 weight percent Weyerhaueser NB416 pulp and 10 weight percent T-255 Merge 34821 A, 6 mm, 2.8 denier binder fibers. The airlaid wicking layer had a basis weight of 150 gsm, a density of 0.15 g/cc and a thickness of 1 mm. The airlaid layers weighed 1.05 and 1.08 grams.

Control The 1.08 g piece of airlaid fabric was placed vertically with about 2.54 cm (1 inch) of the airlaid layer in water. After 1.5 hours, the sample was raised from the water, allowed to drip for 10 seconds, and weighed. The airlaid sample weight 12.45 gm, meaning it had absorbed 11.37 gms of water or 10.5 gms water/gram airlaid fabric.

Wicking example The other piece of airlaid fabric, the lighter one in this case, was sprayed with an adhesive and sprinkled with FAVOR® 880 superabsorbent particles. The add-on rate on this piece was 0.67 grams. This procedure was repeated with the other side of the same airlaid piece. The add-on rate on the second side was 1.57 g.

The airlaid fabric/superabsorbent material was placed on a piece of single-faced

SBL (same as Example 1). The SBL was 15.24 cm (6 inches) in the non-stretch direction and 10.12 cm (4 inches) in the stretch direction where the non-stretch direction is the length direction of the airlaid layer. The SBL was folded over the end of the airlaid layer and the three edges sealed together, leaving the excess airlaid material protruding from the SBL by about 5.1 cm (2 inches). The adhesive width was about 2.5 cm (1 inch). The wicking sample was further sealed using a Carver Press at 1000 psi for 5 seconds and slightly trimmed to about 7.6 cm by 6.3 cm (3 inches by 2.5 inches). The wicking sample weighed 5.45 gm.

The wicking sample was placed vertically with about 2.54 cm (1 inch) of the airlaid fabric in water. At 5 minutes the wicking sample weighed 21.6 gm, i.e., had gained 16.2 gm of water. After 1 minute the sample was placed in its original position and, after 5 more minutes, weighed 33.23 gm and had gained 27.8 gm water. After another 1 minute wait, the sample was re-immersed in the same manner for 5 minutes and weighed 55 gm, and had gained 49.6 gm water. The bottom seal of the laminate was beginning to fail so the test was discontinued.

Assuming the wicking sample airlaid layer had the same amount of water as the control, the wicking sample contained 17 gm water/gram superabsorbent. The original

SBL bag was about 0.2 cm (0.08 inches) thick and after testing was about 2.3 cm (0.92 inches).

As the superabsorbent swelled, the SBL outer layers expanded, allowing wicking to continue in the airlaid layer since it was not crushed by the expanding superabsorbent. It is believed to be important in this embodiment that good contact be maintained between the superabsorbent and the wicking medium so that the superabsorbent does not lose liquid communication with the wicking medium. Binders or adhesives may be used to adhere the superabsorbent to the wicking medium.

In yet another embodiment of this invention; the airlaid layer of this Example 2 may be gathered in some manner prior to lamination, e.g., by creping, thus allowing the laminate to stretch.

As will be appreciated by those skilled in the art, changes and variations to the invention are considered to be within the ability of those skilled in the art. Examples of such changes are contained in the patents identified above, each of which is incorporated herein by reference in its entirety to the extent it is consistent with this specification. Such changes and variations are intended by the inventors to be within the scope of the invention.

Claims

What is claimed is:

I) An absorbent system for personal care products comprising a first extendible outer layer and a second outer layer on a side opposite said extendible outer layer, said layers having therebetween an absorbent material. 2) The absorbent system of claim 1 wherein said layers are bonded together with a pattern bond.

3) The absorbent system of claim 1 wherein said absorbent layer comprises superabsorbent and pulp.

4) The absorbent system of claim 1 wherein said absorbent layer comprises superabsorbent and synthetic fibers.

5) The absorbent system of claim 1 wherein said second layer is extendible.

6) The absorbent system of claim 5 wherein said first layer is elastic.

7) The absorbent system of claim 6 wherein said elastic layer is made from a polymer selected from the group consisting of polyurethanes, polyester block amide copolymers, polyesters, polyamides, copolyetheresters, and polyolefins.

8) The absorbent system of claim 6 wherein said second layer is elastic.

9) The absorbent system of claim 1 wherein said first layer is elastic and said second layer is non-extendible.

10) The absorbent system of claim 6 wherein said elastic layer is chosen from a group consisting of apertured film, woven fabrics, nonwoven fabrics, and netting.

I I) The absorbent system of claim 10 further comprising another elastic layer laminated to said first elastic layer with an elastic latex adhesive.

12) The absorbent system of claim 6 wherein said elastic layer is a laminate selected from the group consisting of neck-bonded laminates, stretch-bonded laminates, neck-stretch- bonded laminates and zero stretch-strain laminates.

13) The absorbent system of claim 1 further comprising a wicking layer between said outer layers. 14) The absorbent system of claim 13 wherein said wicking layer is made according to a process selected from the group consisting of spunbonding, bonding and carding, and airlaying.

15) The absorbent system of claim 2 wherein said second outer layer comprises fibers made from polyolefin.

16) An absorbent system for personal care products comprising a wicking layer having superabsorbent on at least one side, and at least one extendible outer layer and at least one liquid permeable outer layer.

17) The absorbent system of claim 16 wherein said extendible outer layer is liquid permeable.

18) The absorbent system of claim 16 wherein said wicking layer is made according to a process selected from the group consisting of spunbonding, bonding and carding, and airlaying.

19) The absorbent system of claim 16 wherein said elastic layer is a laminate selected from the group consisting of neck-bonded laminates, stretch-bonded laminates, neck-stretch- bonded laminates and zero stretch-strain laminates.

20) An absorbent system for personal care products comprising an airlaid wicking layer having a basis weight between 17 and 170 gsm (0.5 and 5 osy), said wicking layer having superabsorbent particles on at least one side, and at least one liquid permeable, neck-bonded laminate outer layer having a basis weight between 17 and

170 gsm, (0.5 and 5 osy).

21) A diaper comprising the system of claim 1.

22) 16) A training pant comprising the system of claim 1.

23) An incontinence product comprising the system of claim 1. 24) A bandage comprising the system of claim 1.

25) A sanitary napkin comprising the system of claim 1. 26) An absorbent system for personal care products comprising absorbent material within a liquid permeable elastic outer layer.

27) An absorbent system for personal care products comprising a first extendible outer layer and a second outer layer on a side opposite said extendible outer layer, said layers having therebetween an absorbent material, wherein said system has a dry thickness and a wet thickness and a dry extendibility and a wet extendibility, wherein said wet thickness at least about 3 times said dry thickness and said wet and dry extendibility are approximately equal.

28) The absorbent system of claim 21 wherein said first and second outer layers are elastic.