MXPA00008310A - Absorbent article having reinforced elastic absorbent core - Google Patents

Abstract

An absorbent elastic nonwoven composite material having stretch properties in a machine direction includes an elastic filament matrix and, contained with the matrix, absorbent fibers and superabsorbent material. A plurality of bond lines oriented in a direction transverse to the machine direction provides reinforcement of the elastic filament matrix so that, when the composite material is stretched, there is less tearing and separation of the elastic filaments. The reinforcement by the bonding lines reduces the separation and shake-out of the absorbent and superabsorbent materials from the matrix during stretching and recovery of the composite material, and improves the recovery. The absorbent elastic nonwoven composite material is useful in a wide variety of personal care absorbent articles and medical absorbent articles.

Description

ABSORBENT ARTICLE WITH REINFORCED ELASTIC ABSORBENT NUCLEUS FIELD OF THE INVENTION This invention is directed to an absorbent article having an elastic absorbent core. The absorbent core is reinforced and strong using high density tie lines which extend transversely to the direction of stretching.

BACKGROUND OF THE INVENTION There is a current in the industry of absorbent garments to make absorbent articles, such as diapers, more stretchable. In the past, these absorbent articles have been made primarily from inelastic materials. Limited stretchability was limited by incorporating the elastic bands in the leg and / or waist regions of the garments. More recently, there have been attempts to make these elastic items. The absorbent articles contain multiple layers.

Disposable layers, for example, typically contain a liquid-permeable body-side liner, an outer shell impervious to liquid essentially impervious to liquid, an absorbent core layer between the side-to-body liner and the outer shell, and often a emergence management layer on either side of the liner to the body that properly channels the discharge of the liquid to the absorbent core. To make a fully elastic absorbent article, it is required that all layers be stretchable or stretchable, or that at least one of the layers be elastically recoverable. If even one of the layers can not be stretched then the article can not be stretched.

Various technologies are known for making the lining elastic and stretchable on the body and the cover. However, the manufacture of the elastic or stretchable absorbent core poses a great challenge. Absorbent core layers often contain a high percent by weight of one or more absorbent means such as wood pulp fibers, fluff, superabsorbent particles or fibers or the like, entangled and dispersed at a lower percent by weight of an absorbent material. fibrous matrix. Stretching the absorbent core can • cause tearing of the relatively weak fibrous matrix and / or release the absorbent and superabsorbent materials. There is a need to desire a stretchable compound which is capable of withstanding stretch and retraction with minimal tearing and minimal agitation.

SYNTHESIS OF THE INVENTION The present invention is directed to a highly absorbent and comfortable and conformable elastic nonwoven composite which relates to the above occupations. The absorbent nonwoven composite includes a blend of non-woven elastomeric polymer fibers, absorbent fibers and superabsorbent particles or fibers. The elastomeric polymer fibers can be essentially continuous or basic in length and are preferably essentially continuous. In one embodiment, the elastic nonwoven polymer fibers constitute less than 20% by weight of the absorbent nonwoven composite, and at least about 3% by weight of the absorbent nonwoven composite. The absorbent fibers and superabsorbent particles or fibers each constitute about 20-77% by weight of the absorbent nonwoven composite. Compounds of this nature in general are described in U.S. Patent Application No. 09 / 197,268 filed November 20, 1998 in the name of McDowall et al., Which is incorporated herein by reference.

In another embodiment, which has a higher integrity but somewhat less absorbency, the non-woven elastomeric polymer fibers constitute about 20-80% by weight of the absorbent nonwoven composite. The absorbent fibers and the superabsorbent particles and the fibers each constitute about 10-70% by weight of the absorbent nonwoven composite. Compounds of this nature in general are described in U.S. Patent No. 5,645,542 issued to Anjur et al., Which is incorporated herein by reference.

The absorbent nonwoven composites are elastic in at least one machine direction. The "machine direction" is the primary orientation direction of the elastomeric polymer fibers that form the matrix to contain the absorbent and superabsorbent materials. The direction of the machine corresponds to the direction of movement of a conveyor belt or similar apparatus used during the extrusion of the elastomeric polymer fibers and combination of the elastomeric polymer fibers with the superabsorbent and absorbent ingredients. When the elastomeric polymer fibers are essentially continuous, one way to determine the direction of the machine in an absorbent nonwoven composite is to pull a square of 5 centimeters by 5 square centimeters onto a sample of the composite. Most filaments of elastic polymer will pass through two of the four sides of the square, thus defining the direction of the machine.

According to the invention, the absorbent compound is reinforced by forming a plurality of connecting lines transverse to the machine direction. The bond lines can be formed using one or more techniques of ultrasonic bonding, thermal bonding, pressure bonding and adhesive bonding. Preferably, the bond creates densified regions along the bond lines.

The bond lines provide the absorbent composite with improved recovery strength during stretching, and somewhat less extensibility. The increased strength results from the stabilization of the elastic polymer fibers, which are anchored or fixed in place in the bonded or densified regions. This anchoring and periodic intervals relieves the tearing of the elastic polymer matrix fibers during stretching. Reduced tearing also results in improved elastic recovery of the absorbent composite. In addition, the stabilization of the elastic polymer matrix fibers at periodic intervals restricts the lateral separation of the fibers, thereby reducing the shaking of the absorbent and the superabsorbent material. With the foregoing in mind, it is a feature and advantage of the present invention to provide a reinforced elastic absorbent composite having improved strength and recovery, for use in absorbent articles.

It is also a feature and advantage of the present invention to provide an absorbent article for personal care with elastic properties using the elastic absorbent composite of the invention.

It is also a feature and an advantage of the invention to provide a medical absorbent article having elastic properties using the elastic absorbent composite of the invention.

These and other features and advantages will also become apparent from the following detailed description of the currently preferred embodiments, read with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an exploded perspective view of an absorbent article according to the present invention, in this case a diaper.

Figure 2 is a plan view of an elastic absorbent nonwoven fabric composite useful in the absorbent article of the invention.

DEFINITIONS The term "nonwoven fabric or fabric" means a fabric having a structure of individual filaments or fibers which are interlocked but not in an identifiable manner as a woven fabric. The terms "fibers" and "filaments" are used interchangeably here.The non-woven fabrics or fabrics have been formed by many processes such as, for example, meltblowing processes, spinning processes and laying processes by The term also includes films that have been punctured or otherwise treated to allow air to pass through them.The basis weight of non-woven fabrics is usually expressed in ounces of material per square yard (osy) or grams per square meter (gsm) and fiber diameters are usually expressed in microns (note that to convert from ounces per square yard to grams per square meter, you must multiply ounces per square yard by 33.91).

The term "microfibers" means small diameter fibers having an average diameter of no more than about 75 microns, for example, having a small diameter of from about one to about 50 microns or more particularly having an average diameter from around a miera to around 30 micras.

The term "spunbonded fibers" refers to fibers of small diameter, which are formed by extruding the molten thermoplastic material as filaments from a plurality of fine capillary vessels of a spinner having a circular or other configuration, with the diameter of the extruded filaments then being rapidly reduced by the blow of air as explained, for example, in U.S. Patents Nos. 4,340,563 granted to Appel et al., 3,692,618 granted to Dorschner et al., 3,802,817 granted to Matsuki. and others, 3,338,992 and 3,341,394 granted to Kinney, 3,502,763 granted to Hartman, 3,502,538 granted to Peterson and 3,542,615 granted to Dobo and others. Spunbonded fibers are cooled and generally are not tacky on the surface when they enter the pulling unit, or when they are deposited on a collecting surface. Spunbonded fibers are generally continuous and may have average diameters larger than 7 microns, often between about 10 and 30 microns.

The term "meltblown fibers" means fibers formed by extruding a molten thermoplastic material through a plurality of thin, usually circular, capillaries, such as filaments or fused filaments into heated (high) gas streams. speed and converging, which attenuate the filaments of molten thermoplastic material to reduce its diameter, which can be to a microfiber diameter. Then, the meltblown fibers are carried by the high velocity gas stream and are deposited on a collecting surface to form a meltblown and randomly dispersed fiber fabric. Such a process is described, for example, in United States of America Patent No. 3,849,241 issued to Butin et al. Melt blown fibers are microfibers, which may be continuous or discontinuous generally smaller than 10 microns in diameter, and are generally self-supporting when deposited on a collecting surface. The melt blown fibers used in the invention are preferably and essentially continuous.

The term "essentially continuous fibers or filaments" refers to fibers or filaments prepared by extrusion from a spinning organ, including without limitation fibers bonded with spinning and meltblowing, which are not cut from their original length before being formed in a nonwoven fabric or fabric. The essentially continuous fibers or filaments can have lengths ranging from about more than 15 centimeters, or more than one meter; and up to the length of the fabric or the non-woven fabric being formed. The definition of "essentially nonwoven fibers or filaments" includes those which are not cut before being formed into a nonwoven fabric or fabric, but which are subsequently cut when the nonwoven fabric is cut.

The term "short fibers or filaments" means filaments or fibers which are natural or which are cut from a filament manufactured prior to forming into a fabric, and which have a length varying from about 0.1-15 centimeters, more commonly around 0.2 - 7 centimeters.

The term "fiber" or "fibrous" is intended to refer to a particulate material wherein the ratio of the diameter length of such particulate material is greater than about 10. Inverse form, to a "non-fiber" material or "non-fibrous" is meant to refer to a particulate material wherein the diameter length ratio of such particulate material is about 10 or less.

The terms "elastic and" elastomeric "are used interchangeably to mean a material that is generally capable of recovering its shape after deformation when the deformation is removed.Specifically, as used herein, the elastic or the elastomeric is intended to be that ownership of any material which, with the application of a pressing force, allows the material to be stretched to a stretched and drawn length which is at least about 25 percent greater than its unstressed and relaxed length, and which will cause the material to recover at least 40 percent of its elongation with the release of the stretching elongation force.A hypothetical example which will satisfy this definition of an elastomeric material would be one of a one-inch sample of a material which at be lengthened to at least 1.25 inches and released will recover to a length of no more than 1.15 inches. Elastic wastelands can be stretched for much more than 25 percent of their relaxed length, and many of these will recover to essentially their original relaxed length with the release of the stretching and stretching force. This last class of materials is generally beneficial for the purposes of the present invention.

The term "recover" or "retract" refers to a concentration of material stretched upon the termination of a pressing force after stretching of the material by application of the pressing force.

The term "superabsorbent material" refers to an organic or inorganic material insoluble in water or swellable in water, capable under the most favorable conditions of absorbing at least about 20 times its weight, preferably at least about 30 times its weight in an aqueous solution containing 0.9% by weight of sodium chloride. The term "absorbent material" refers to a material which absorbs from about 1 to less than 20 times its weight in an aqueous solution containing 0.9% by weight of sodium chloride. The standard test method INDA IST 10.1 (95), entitled "Standard Test Method for Absorbency Time, Absorbency Capacity and Transmission Time" published by INDA, Association of the Non-Woven Fabrics Industry, of Cary, North Carolina , provides the basis for a suitable test method to measure absorbency. The "Absorbent Capacity Test" (for small samples) can be used to determine the absorbency of a material for the purpose of the present invention with the following two modifications: (i) IST 10.1 (95) specifies that water will be used; to replace a 0.9% aqueous sodium chloride solution; (ii) IST 10.1 (95) specifies that a 5 gram sample is used. If necessary, a smaller sample obtained from the absorbent product may be used instead.

The term "pulp fibers" refers to fibers from natural sources, such as woody and non-woody plants. Woody plants include, for example, * deciduous and coniferous trees. Non-woody plants include, for example, cotton, flax, esparto, grass, bencetocigo, straw, jute and bagasse.

The term "absorbent article" includes without limitation diapers, training briefs, swimwear, absorbent underwear, adult incontinence products, women's hygiene products and medical absorbent products (eg, absorbent medical garments, undergarments, bandages, bandages and medical cleansing cloths).

The term "machine direction" refers to a direction of the primary orientation of the fibers in a thermoplastic nonwoven fabric. After extrusion of the filaments of the non-woven fabric, such as filaments spunbond or meltblown, the filaments are typically cooled and carried on a conveyor device or the like. The direction of the machine is the direction of the primary orientation assumed by the filaments in a non-woven fabric that results from being pulled and carried.

The term "transverse direction" refers to both the directions perpendicular to the machine direction and the directions within plus or minus 45 degrees of the perpendicular to the machine direction.

DETAILED DESCRIPTION OF CURRENTLY PREFERRED INCORPORATIONS The present invention is directed to an absorbent non-woven fabric elastic composite, and to an absorbent article which it utilizes. A preferred absorbent article is a disposable diaper. Figure 1 illustrates an exploded perspective view of a disposable diaper to the preferred embodiment of the invention. The disposable diaper 10 includes an outer cover 12, a side-to-body liner 14, and an absorbent compound 44 located between the outer cover 12 and the side-to-body liner 14.

Subject to the outer cover 12 are the waist elastics 26, the fastening tapes 28 and the leg elastics 30. The leg elastics 30 comprise a carrier sheet 32 and the individual elastic threads 34.

The body side liner 14 includes the containment fins 36 having the proximal edges 38 and the distant edges 40. An emergence management layer 42 is located between the proximal edges 38 of the containment fins 36.

A possible construction method and materials of a diaper similar to those illustrated in Figure 1 are set forth in greater detail in commonly assigned United States of America Patent No. 5,509,915 issued April 25, 1996 in the name of Hanson and others and incorporated here by reference. Possible modifications to the diaper illustrated in Figure 1 are set forth in the commonly assigned United States of America patent 5,509,915 mentioned above and in commonly assigned United States of America patent No. 5,364,382 issued on November 19, 1994 on behalf of from Matthews and others. Possible modifications include the placement of the emergence management layer 42 between the side-to-body liner 14 and the absorbent compound 44 and reducing the length of the emergence management layer to extend the length of the absorbent or piling compound (reduce the length and increasing the basis weight) of the emergence management layer in the diaper area where the liquid waste initially accumulates (target zone).

In one embodiment, an absorbent elastic nonwoven fabric composite having a high load of an absorbent material and an excellent conformation is provided as compound 44. In this embodiment, the absorbent elastic nonwoven fabric composite includes about 3 to less 20 percent by weight of an elastic filament matrix including a plurality of thermoplastic elastomeric nonwoven filaments, about 20-77% by weight absorbent fibers, and about 20-77% by weight of a superabsorbent material. The absorbent fibers and the superabsorbent material are contained in the matrix. Preferably, the absorbent elastic nonwoven fabric composite includes about 5-18% by weight of the elastic filament matrix about 25-70% by weight of absorbent fibers, and about 25-70% by weight of superabsorbent material. More preferably, the absorbent elastic nonwoven fabric composite includes about 5-15% by weight of the elastic filament matrix, about 30-62% by weight of absorbent fibers and about 40-65% by weight of the superabsorbent material. .

In another embodiment, an absorbent elastic nonwoven fabric composite having a somewhat higher strength and somewhat higher elastic recovery, but in some form less absorbency, is provided as compound 44. In this second embodiment, the nonwoven fabric composite elastic absorbent includes about 20-80% by weight of the elastic filament matrix including thermoplastic elastomeric nonwoven filaments, about 10-70% by weight absorbent fibers, and about 10-70% by weight superabsorbent material. Again, the absorbent fibers and the superabsorbent material are contained in the matrix. Preferably, the composite absorbent elastic nonwoven fabric includes about 25-60% by weight of the elastic filament matrix about 15-60% by weight of the absorbent fibers, and about 15-60% by weight of the superabsorbent material.

Suitable materials to be used to prepare the thermoplastic elastomeric fibers herein include diblock, triblock or multiblock copolymers, such as olefinic copolymers, including styrene-isoprene-styrene, styrene-butadiene-styrene, styrene-ethylene / butylene-styrene, or styrene-ethylene / propylene-styrene, which can be obtained from Shell Chemical Company, under the trade designation elastomeric resin KRATON®; polyurethanes, including those available from E.l. DuPont de Nemours Company, under the trade name LYCRA®, polyurethanes; polyamides, including polyether block amides available from Ato Chemical Company, under the trade name PEBAX® amide block of polyether polyesters, such as those available from E.l. DuPont de Nemours Company under the trade name HYTREL® polyester and single-site or metallocene-catalyzed polyolefins having a density less than about 0.89 grams / cubic centimeter, available from Dow Chemical Company under the trade name AFFINITY® and from Exxon Chemical Company under the trade name EXACT®.

A number of block copolymers can be used to prepare the thermoplastic elastomeric fibers of this invention. Such block copolymers generally comprise an elastomeric middle block portion B and a thermoplastic end block part A. The block copolymers used in this invention generally have a three dimensional physical cross-linked structure below the glass transition temperature of the end block part and they are elastomeric. Block copolymers are also thermoplastic in the sense that they can be melted, formed and resolidified several times with little or no change in physical properties (assuming a minimum of oxidative degradation).

The block end A generally comprises a poly (vinyl arene) such as polystyrene having an average molecular weight between 1000 and 60,000. The middle block part B generally comprises an essentially amorphous polyolefin such as polyisoprene, ethylene / propylene polymers, ethylene / butylene polymers, polybutadiene, and the like or mixtures thereof, having an average molecular weight of between about 5000 and around 450,000. The total molecular weight of the block copolymer is suitably from about 10,000 to about 500,000 and more suitably from about 200,000 to about 300,000. Some suitable copolymers used in this invention comprise with at least two parts of polystyrene end blocks essentially and at least one middle block part of essentially ethylene / butylene. As an example, ethylene / butylene typically can comprise the largest amount of the repeating units in such a block copolymer and can constitute, for example, 70 percent by weight or more of block copolymer. The block copolymer can have three or more arms, and can obtain good results with, for example, four, five and six arms. The middle block parts can be hydrogenated if desired.

Linear block copolymers such as A-B-A, A-B-A-B-A or the like are suitably selected from the base of the end block content, the large end blocks being preferred. For polystyrene-ethylene / butylene-polystyrene block copolymers, a styrene content in excess of about 10 percent by weight is suitable, such as between about 12 to about 30 percent by weight. With the higher styrene content, the polystyrene end block parts generally have a relatively high molecular weight. A commercially available example of such styrene-ethylene / butylene-styrene block copolymer block copolymer, which contains about 13% by weight of styrene units and essentially the balance is ethylene / butylene units, commercially available from Shell Chemical Company, under the trade designation Elastomeric resin KRATON® G1657. Typical properties of the KRATON® G1657 elastomeric resin are reported to include a tensile strength of 3,400 pounds per square inch (2.3 x 107 pass), a 300 percent modulus of 350 pounds per square inch (2.4 x 106 pass) , an elongation of 750 percent at break, a Shore A hardness of 65 and a Brookfield viscosity, when a concentration of 25 percent by weight in a toluene solution of about 4200 centipoise at room temperature. Another suitable elastomer, KRATON® G2740, is a block copolymer of styrene butadiene mixed with a binder and a low density polyethylene.

Other suitable elastomeric polymers can also be used to make the thermoplastic elastic fibers. These include without limitation, elastomeric polypropylene (metallocene or single site catalyzed) polyethylene and other alpha-olefin homopolymers and copolymers, having a density of less than about 0.89 grams / cubic centimeter; ethylene vinyl acetate copolymers; and essentially amorphous copolymers and terpolymers of ethylene-propylene, butene-propylene and ethylene-propylene-butene.

The elastomeric copolymers catalyzed by metallocene are relatively new and are currently preferred.

The metallocene process for making the polyolefins uses a metallocene catalyst which is activated (eg, ionized) by a co-catalyst.

The polymers produced using metallocene catalysts have a narrow molecular weight distribution. The "narrow molecular weight distribution polymer" refers to a polymer that exhibits a molecular weight distribution of less than 3.5. As is known in the art, the molecular weight distribution of a polymer is the average molecular weight distribution of the polymer of the average molecular weight of a polymer. Methods for determining molecular weight distribution are described in the Encyclopedia of Polymer Science and Engineering, volume 3, pages 299-300 (1985). Examples of the narrow molecular weight distribution polyolefins include the metallocene catalyzed polyolefins, the single-site catalyzed polyolefins, and the constrained geometry-catalyzed polyolefins described above. As is known in the art, metallocene-catalyzed polyolefins and constricted geometry-catalyzed polyolefins are sometimes referred to as single-site catalyzed polymer types. Polydispersities (Mw / Mn) below 3.5 and even below 2 are possible for polymers produced with metallocene. These polymers also have a narrow short chain branching distribution when compared to the otherwise similar Ziegler-Natta produced polymers.

The elastomeric fibers can be essentially continuous or short in length, but are preferably and essentially continuous. The essentially continuous filaments exhibit better containment of cellulose fibers and superabsorbent material, have a better elastic recovery and provide a distribution of liquids than short length fibers. The elastomeric fibers can be produced using a spinning process, a meltblowing process or other suitable process. The elastomeric fibers may have an average diameter of about 1-75 microns, preferably about 1-40 microns, more preferably about 1-30 microns.

The absorbent fibers used in compound 44 may be any natural or synthetic liquid absorbent fiber which are capable, under the most favorable conditions of absorbing about 1 to less than 20 times their weight in an aqueous solution containing 0.9% by weight of sodium chloride. Absorbent fibers include, without limitation, basic rayon fibers, cotton fibers, natural cellulose fibers such as wood pulp fibers and cotton lint, other pulp fibers, and fiberized feathers (e.g. fibrized, such as the fibrillated chicken fibers).

The pulp fibers are especially useful as the absorbent fibers in the elastomeric nonwoven composite. Preferred pulp fibers include pulps of cellulose fibers and the like. Other types of absorbent pulp can also be used.

The pulp fibers can be unrefined or can be struck at various degrees of refinement. The cross-linking agents and / or the moisturizing agents can also be added to the pulp mixture. The debinding agents can be added to reduce the degree of hydrogen bonding if a loose or very open nonwoven pulp fabric is desired. An example binder agent is available from Quaker Oats Chemical Company, from Conshohocken Pennsylvania, under the trade designation Quaker 2008. The addition of certain binder agents in the amount of for example, 1-4% by weight of the compound can reduce the measured dynamic and static coefficients of friction and improve the resistance to abrasion of continuous thermoplastic polymer filaments. The debinding agents act as lubricants or friction reducers. The debonding pulp fibers are commercially available from Weyerhaeuser Corporation, under the designation NB-405.

The superabsorbent material used in compound 44 may be in the form of fibers or particles or combinations thereof. As explained above, the term "superabsorbent" or "superabsorbent material" refers to an organic or inorganic material insoluble in water and swellable in water capable, under the most favorable conditions of absorbing at least about 20 times its weight and more desirably at least about 30 times its weight in an aqueous solution containing 0.9% by weight of sodium chloride.

The superabsorbent materials can be natural, synthetic and modified natural materials and polymers. In addition, the superabsorbent materials may be inorganic materials, such as silica gels, or organic compounds, such as crosslinked polymers. The term "cross-linked" refers to any means for effectively making the materials normally water-soluble essentially insoluble, but swellable in water. Such media may include, for example, physical entanglement, crystalline domains, covalent bonds, complexes and ionic associations, hydrophilic associations, such as hydrogen bonding, and hydrophobic associations or Van Der Waals forces.

Examples of the polymers of synthetic superabsorbent material include the ammonium and alkali metal salts of poly (acrylic acid) and poly (methacrylic acid), poly (acrylamide), poly (vinyl ethers), copolymers of maleic anhydride with ethers of vinyl and alpha olefins, poly (vinyl pyrrolidone), poly (vinyl morpholinone), poly (vinyl alcohol), and mixtures and copolymers thereof. Additional superabsorbent materials include modified natural and natural polymers, such as hydrolyzed acrylonitrile grafted starch, acrylic acid grafted starch, methyl cellulose, chitosan, carboxymethyl cellulose, hydroxypropyl cellulose, natural gums, such as alginates , xanthan gum, locust bean gum and the like. Mixtures of natural or fully or partially synthetic superabsorbent polymers may be useful in the present invention. Other suitable absorbent gelation materials are described by Assarsson et al. In U.S. Patent No. 3,901,236 issued August 26, 1975. Processes for preparing absorbent gelation polymers are described in U.S. Pat. of America No. 4,076,663 granted on February 28, 1978 to Masuda et al. and in United States of America No. 4,286,082 issued August 25, 1981 to Tsubakimoto et al.

The superabsorbent materials can be xero gels, which form hydrogels when wetted. The term "hydrogel", however, has been commonly used to also refer to both wet and unmoistened forms of the superabsorbent polymer material. The superabsorbent materials can be in many forms, such as flakes, powders, particles, fibers, continuous fibers, nets, wovens and spun filaments of solution. The particles may be of any desired shape, for example, spiral or semi-spiral, cubic, rod-like, polyhedral, etc. Needles, flakes, fibers and combinations can also be used.

The superabsorbents are generally available in particle size ranging from about 20 to about 1000 microns. Examples of commercially available and suitable particulate superabsorbents include SANWET® IM 3900 and SANWET® IM-5000P, available from Hoescht Celanese located in Portsmouth, Virginia, DRYTECH® 2035LD available from Dow Chemical Company, located in Midland, Michigan and FAVOR® SXM 880, available from Stockhausen, located in Greensboro, North Carolina. An example of a fibrous superabsorbent is OASIS® 101, available from Technical Absorbents, located in Grimsby, United Kingdom.

Thermoplastic elastomeric nonwoven filaments can be combined with absorbent and superabsorbent materials using processes well known in the art. For example, a coform process may be employed, in which at least one meltblown die head is arranged near a conduit through which other materials are aggregated while the tissue is being formed. The Coform processes are described in U.S. Patents Nos. 4,818,464 to Lau and 4,100,324 to Anderson et al., Whose descriptions are incorporated by reference. The thermoplastic elastomeric filaments and the absorbent and superabsorbent material can also be combined using a hydraulic entanglement and a mechanical entanglement. A hydraulic entangling process is described in U.S. Patent No. 3,485,706 issued to Evans, the disclosure of which is incorporated herein by reference. After combining the ingredients, the absorbent elastic nonwoven composite can be a fabric bonded together using the thermal bonding or air bonding techniques described above to provide a high integrity and coherent structure.

Alternatively, the absorbent structures can be formed as layered structures using two die tips to extrude the elastomeric filaments, and inject the absorbent and superabsorbent materials as a middle layer between two layers of elastomeric filament. The various degrees of mixing of the elastomeric filaments and the absorbent / superabsorbent materials can be achieved to facilitate regions of greater or lesser concentration of the elastomeric filaments. This layered structure is an alternative of absorbent structures produced by a coform process, in which the absorbent ingredients are essentially evenly distributed between the individual filaments of an elastomeric nonwoven fabric.

Referring now to FIGS. 1 and 2, the absorbent composite 44 includes a plurality of relatively undensified and relatively open regions 45, separated by the bond lines representing the densified regions 46. The absorbent composite 44 may include a central portion 48, the which is stretchable in a first (longitudinal) direction 1, and two end portions 47 and 49, which are stretchable in a second direction 2 (lateral). These preferred stretching directions are ideal for diaper garments or panty type absorbers, which are preferably stretched lengthwise in the crotch region and laterally the two waist regions. Parts 47, 48 and 49 can be provided using three pieces of an elastic absorbent nonwoven fabric composite, for example, a coform compound, as described above. The central part 48 can be oriented so that its machine direction corresponds to the longitudinal direction 1. The end portions 47 and 49 can be oriented so that their machine direction corresponds to the lateral direction 2. The parts 47 , 48 and 49 can be joined at their respective edges using thermal bonding, ultrasonic bonding, adhesive bonding, mechanical seaming bonding, or the like.

The connecting lines 46 in the central part 48 are oriented in the lateral direction 2, which is transverse to the direction of stretching in the central region. The connecting lines 46 may reduce somewhat in the longitudinal stretching of the central part 48, but may substantially eliminate any stretching in the lateral direction. Additionally, the tie lines 46 improve the strength of the composite 44 during stretching, and improve its elastic recovery, by reducing the tearing of the elastic matrix filaments. Also, the tie lines 46 reduce the lateral spacing of the matrix filaments, thereby reducing the agitation of the absorbent and the superabsorbent during stretching and retraction.

The connecting lines 46 at the end portions 47 and 49 are oriented in the longitudinal direction 1, which is transverse to the direction of stretching at the end portions 47 and 49. The connecting lines 46 may somewhat reduce the lateral stretch of the end portions 47 and 49, but can essentially eliminate any stretching in the longitudinal direction. Again, the bond lines improve the strength and elastic recovery of the composite that reduce the shaking of the absorbent and superabsorbent materials.

The bond lines 46 can be formed using heat bonding (e.g., thermal calender bonding process), ultrasonic bonding, adhesive bonding, mechanical compression or the like. Preferably, the tie lines 46 cause compaction and densification of the absorbent composite in the bonded regions, such as to anchor the elastic matrix filaments in these regions. Desirably, the density of the absorbent composite in the bonded regions 46 may be about 1.5-3 times the density of the unbonded regions. The tie lines 46 must each have a thickness, or width in the direction of stretching (in the machine direction) of about 0.5 millimeters to about 25 millimeters, suitably from about 1 millimeter to about 15 millimeters , ideally from around 2 millimeters to around 10 millimeters. The connecting lines 46 should have a length, transverse to the direction of stretching, which is at least about 5 times the width, suitably at least about 10 times its width, desirably at least about 15 times its width. The connecting lines 46 can be essentially continuous in length, or they can be divided into closely spaced segments.

The tie lines should be sufficiently thick or wide enough to cover a minor but significant part of the length of a machine direction (stretch direction) of the absorbent composite. Referring to Figure 2, for example, the ratio of the thicknesses of the tie lines 46 to the shortest distance between the consecutive tie lines 46 should be at least about 1:20, suitably at least around 1:15, desirably at least 1:10. At the same time, the tie lines 46 should not be so thick as to substantially prevent the elasticity of the absorbent compound in the direction of stretching. For this purpose, the ratio of the thicknesses of the tie lines 46 to the shortest distance between the adjacent tie lines should not be more than about 1: 1, suitably no more than about 1: 3, desirably of no more than about 1: 5.

The tie lines 46 are preferably perpendicular to the desired stretch direction, which is typically the machine direction. However, to have the desired effect, the connecting lines 46 can form angles of any of between about 45-135 degrees relative to the direction of stretching. Suitably, the connecting lines 46 form angles of between about 60-120 degrees, desirably between about 75-105 degrees, relative to the direction of stretching of the machine.

In order for the diaper 10 to have an elasticity similar to the absorbent compound 44 the other layers must be at least as stretchable, and may not be independently recoverable. Both, the emergence layer 42 and the side-to-body liner 14 are constructed of materials highly permeable to liquid. These layers function to transfer the liquid from the user to the absorbent compound 44. Suitable materials include porous woven materials, porous nonwoven materials and perforated films. Examples include, without limitation, any porous, stretchable sheets of polymeric fibers, carded and bonded fabrics of natural or synthetic fibers or combinations thereof. Any layer can be a stretchable and perforated plastic film.

The outer cover 12 may include a single stretchable layer or may include multiple stretchable layers or followed together by means of adhesive bonding, thermal bonding, ultrasonic bonding or the like. The outer cover 12 can be made from a wide variety of woven or non-woven materials, from films or from a non-woven material coated with film, including, for example, blown or blown films. The outer cover 12 may also be a composite of a material bonded or bonded or bonded with spinning or meltblowing, for example, a spin-melt-bonding composite with melt of thermoplastic material or a thermoplastic material bonded with spin-blow with melt-bonded with spinning, wherein the spin-linked layer can provide a cloth-like texture and the melt-blown layer can provide liquid impermeability. The outer cover 12 preferably has a high capacity to breathe with respect to water vapor.

Examples Compound samples of absorbent compound were prepared using a process similar to that described in U.S. Patent No. 4,100,324 issued to Anderson et al. The samples had a basis weight of about 350-400 grams per square meter (gsm) and a density of about 0.1 grams per cubic centimeter. Each absorbent composite coform contained about 10% by weight of essentially continuous meltblown fibers made of KRATON® elastomer.

G2740 from Shell Chemical Company, about 40% by weight of particulate superabsorbent FAVOR®880 from Stockhausen and about 50% by weight of cellulose fluff.

The rectangular test samples were cut by measuring 30.5 centimeters in the machine direction, and 5.1 centimeters in the cross machine direction. Some of the test samples were joined at intervals using a Bransonic ultrasonic bonding device with a rectangular anvil oriented perpendicular to the machine so that the joined regions were of a preselected width in the machine direction, and 5.1 centimeters long in the direction transverse to the machine. The rectangular anvil was designed to impart about 10 point junctions closely spaced per square centimeter, arranged in a pattern that corresponds to the rectangle.

For example 1, a control, no lines were attached to the samples. For example 2, the ultrasonic bond lines having two millimeters wide, and separated by 17 millimeters of unbound region were imparted to the samples. For example 3, the ultrasonic bond lines that had a width of 5 millimeters were separated by 40 millimeters of unbound region, were imparted to the samples. The union approximately doubled the density of samples in the joined regions.

The test strips (about 5 for example were then elongated using an Instron test apparatus, model 5277, and the lengthening procedure of manufacturer EMT029) For the example the test strips were elongated to 200% of their initial length (bent in length) resulting in a significant separation and delamination of the elastomeric filament matrix of the cellulose fluff and the super absorbent.When allowed to retract, the test strips increased in thickness due to wrinkling of the separated cellulose fluff and of the superabsorbent , and they did not recover completely to their initial length.

For examples 2 and 3, the test strips were elongated to 200% of their initial length without any noticeable separation of the ingredients. In essence, the densified joined regions prevented the global separation of the ingredients. The loads required to stretch these samples were somewhat higher than for those of Example 1, due to the densified bound regions. However, when they were allowed to retract, the test strips essentially recovered their initial length.

Although the embodiments of the invention described herein are currently considered to be preferred, various modifications and improvements can be made without departing from the spirit and scope of the invention. The scope of the invention is indicated by the appended claims, and it is intended that all changes that fall within the meaning and range of equivalences be covered here.

Claims (28)

R E I V I N D I C A C I O N S

1. An elastomeric and absorbent nonwoven composite material comprising: an elastic filament matrix including a plurality of elastomeric nonwoven filaments; Y contained within the matrix, absorbent fibers and a superabsorbent material; the composite material has a machine direction corresponding to a primary direction of orientation of the elastomeric nonwoven filaments, and a plurality of spaced and spaced apart lines oriented in a direction transverse to the machine direction.

2. The composite material as claimed in clause 1 characterized in that it comprises about 3 to less than 20% of the elastic filament matrix, about 20-77% of the absorbent fibers, and about 20-77% by weight of the superabsorbent material.

3. The composite material as claimed in clause 1 comprising about 5-18% by weight of the elastic filament matrix, about 25-70% by weight of the absorbent fibers and about 25-70% by weight of the superabsorbent material.

4. The composite material as claimed in clause 1 characterized in that it comprises about 5-15% by weight of elastic filament matrix, about 30-62% by weight of absorbent fibers, and about 40-65% by weight. weight of the superabsorbent material.

5. The composite material as claimed in clause 1 characterized in that it comprises about 20-80 by weight of the elastic filament matrix, about 10-70% by weight of the absorbent fibers, and about 10-70% by weight. weight of the superabsorbent material.

6. The composite material as claimed in clause 1, characterized in that it comprises about 25-60% by weight of the elastic filament matrix, about 15-60% by weight of the absorbent fibers and about 15-60% by weight of the superabsorbent material.

7. The composite material as claimed in clause 1 characterized in that the joint lines, each have a width of about 0.5-25 millimeters.

8. The composite material as claimed in clause 1 characterized in that the connecting lines each have a width of about 1-15 millimeters.

9. The composite material as claimed in clause 1 characterized in that the joining lines each have a width of about 2-10 millimeters.

10. The composite material as claimed in clause 7 characterized in that the connecting lines each have a length which is at least about 5 times its width.

11. The composite material as claimed in clause 7 characterized in that the lines of attachment each have a length which is at least about 10 times its width.

12. An absorbent article comprising the composite material as claimed in clause 1.

13. The absorbent article as claimed in clause 12, characterized in that it comprises a diaper.

14. The absorbent article as claimed in clause 12, characterized in that it comprises training underpants.

15. The absorbent article as claimed in clause 12, characterized in that it comprises swimwear.

16. The absorbent article as claimed in clause 12, characterized in that it comprises underpants.

17. The absorbent article as claimed in clause 12, characterized in that it comprises a product for adult incontinence.

18. The absorbent article as claimed in clause 12, characterized in that it comprises a product for the hygiene of women.

19. The absorbent article as claimed in clause 12, characterized in that it comprises a medical absorbent product.

20. An absorbent nonwoven composite material, comprising: an elastic filament matrix including a plurality of thermoplastic elastomeric nonwoven filaments; contained within the matrix the absorbent fibers and a superabsorbent material; the composite material has a central part and two end parts; each end and central part has a machine direction corresponding to a primary direction of orientation of the thermoplastic elastomeric nonwoven filaments, and a plurality of spaced and spaced apart lines with regions therebetween, the joined lines are oriented in a direction transverse to the direction of the machine; ! wherein the direction of the machine in the central region is essentially perpendicular to the machine direction in the two end regions.

21. A diaper comprising the use of a composite material as claimed in clause 20.

22. The training underpants comprising the composite material as claimed in clause 20.

23. Swimwear comprising the composite material as claimed in clause 20.

24. Underwear characterized in that it comprises the composite material as claimed in clause 20.

25. A product for adult incontinence that comprises the composite material as claimed in clause 20.

26. A product for the hygiene of women that comprises the composite material as claimed in clause 20.

27. A product for the hygiene of women that comprises the composite material as claimed in clause 20.

28. An absorbent article comprising: a liquid-permeable body side liner; an outer cover essentially impermeable to liquid; Y an absorbent elastic nonwoven composite material between the side-to-body liner and the outer shell; the composite material comprises an elastic filament matrix including a plurality of thermoplastic elastomeric nonwoven filaments of absorbent fibers and a superabsorbent material; The composite material contains a machine direction corresponding to a primary direction of orientation of the thermoplastic elastomeric nonwoven filaments, and a plurality of spaced and spaced apart lines oriented in a direction transverse to the machine direction. E S U M E N An absorbent thermoplastic nonwoven composite having stretch properties in a machine direction that includes a matrix of elastic filaments and contained within the matrix, absorbent fibers and a superabsorbent material. A plurality of tie lines oriented in a direction transverse to the machine direction provides reinforcement of the elastic filament matrix so that, when the composite material is stretched, there is less tearing and separation of the elastic filaments. The reinforcement of the bond lines reduces the separation and shaking of the absorbent and of the matrix absorbing materials during the stretching of the operation of the composite, and improves the recovery. The absorbent elastic non-woven composite material is useful in a wide variety of absorbent articles for personal care and medical absorbent articles.