HIGHLY CONFORMABLE PERSONAL CARE PRODUCTS

Abstract: There is provided a personal care product having a mixture made from an absorbent and a water soluble polymer, which, when wetted and subjected to a minimal force, will become a gel. Such a personal care product is more conformable, and thus more comfortable than typical personal care products. Such a product also allows fluid flow to other parts of the product and so uses less material in its construction, further reducing feelings of discomfort.

Description: Highly Conformable Personal Care Products FIELD OF THE INVENTION The invention is related to absorbent personal care products. More particularly, it concerns absorbent disposable articles such as feminine care napkins, diapers and training pants, wound care dressings and bandages, and adult incontinence products, that are highly conformable to the body of the wearer. BACKGROUND OF THE INVENTION Personal care products typically are made with a top sheet material (also referred to as a cover sheet or liner) an absorbent core and a liquid impervious back sheet. Some may also have a surge layer or other specialized layers between the top sheet and absorbent core. Such materials, particularly for feminine hygiene product usage, can be somewhat stiff and uncomfortable. The layers of these products are usually made from polymer fibers and films, and the absorbent core layer is usually made from wood pulp and superabsorbent particles that swell when wetted. In addition to the issue of comfort, such structures often do not allow fluid movement throughout, thus filling or overfilling the portion of the product in the area where an insult is typically delivered. Attempts have been made to address the movement of fluid in personal care products, again with the use of polymer fibers and the like. There remains a need for a personal care product that is more conformable, and thus more comfortable than current products and which allows for fluid movement through the structure. It is an object of the invention to provide a personal care product that conforms to the body for increased comfort. It is a further object of the invention to provide a personal care product in which the product permits the movement of fluid through the structure. SUMMARY OF THE INVENTION The objects of the invention are achieved by a personal care product which is comprised of an absorbent, preferably superabsorbent, and more preferably superabsorbent fibers, and water-soluble polymer. When wetted and subjected to minimal force, such a structure will become a gel that can move in such a way as to conform to the body for greater comfort. Such a wetted structure will also allow the gel to flow and so move liquid throughout its structure. DEFINITIONS 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. 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. "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. As used herein, the term "coform" means a process in which at least one meltblown diehead is arranged near a chute through which other materials are added to the web while it is forming. Such other materials may be pulp, superabsorbent particles, natural polymers (for example, rayon or cotton fibers) and/or synthetic polymers (for example, polypropylene or polyester) fibers, for example, where the fibers may be of staple length. Coform processes are shown in commonly assigned US Patents 4,818,464 to Lau and 4,100,324 to Anderson et al. Webs produced by the coform process are generally referred to as coform materials. "Bonded carded web" refers webs are made from staple fibers which are sent through a combing or carding unit, which breaks apart and aligns the staple fibers in the machine direction to form a generally machine direction-oriented fibrous nonwoven web. Such fibers are are usually purchased in bales which are placed in a picker which separates the fibers prior to the carding unit. Once the web is formed, it then is bonded by one or more of several known bonding methods. One such bonding method is powder bonding, wherein a powdered adhesive is distributed through the web and then activated, usually by heating the web and adhesive with hot air. Another suitable bonding method is pattern bonding, wherein heated calender rolls or ultrasonic bonding equipment are used to bond the fibers together, usually in a localized bond pattern, though the web can be bonded across its entire surface if so desired. Another suitable and well-known bonding method, particularly when using bicomponent staple fibers, is through-air bonding. The term "gel" means a fluid in which dispersed and continuous phases have mixed to a sufficient degree to produce a viscous or visco-elastic, jelly-like product. As used herein, the term "personal care product" means bandages and wound care items, diapers, training pants, swimwear, absorbent underpants, adult incontinence products, and feminine hygiene products. TEST MATERIALS Preparation of menses simulant: The artificial menses fluid used in the testing was made according to US Patent 5,883,231 from blood and egg white by separating the blood into plasma and red cells and separating the white into thick and thin portions, where "thick" means it has a viscosity after homogenization above about 20 centipoise at 150 sec "1 , combining the thick egg white with the plasma and thoroughly mixing, and finally adding the red cells and again thoroughly mixing. A more detailed procedure follows: Blood, in this Example defibrinated swine blood, is separated by centrifuging at 3000 rpm for 30 minutes, though other methods or speeds and times may be used if effective. The plasma is separated and stored separately, the buffy coat removed and discarded and the packed red blood cells stored separately as well. It should be noted that the blood must be treated in some manner so that it may be processed without coagulating. Various methods are known to those skilled in the art, such as defibrinating the blood to remove the clotting fibrous materials, the addition or anti-coagulant chemicals and others. The blood must be non-coagulating in order to be useful and any method that accomplishes this without damaging the plasma and red cells is acceptable. Jumbo chicken eggs are separated, the yolk and chalazae discarded and the egg white retained. The egg white is separated into thick and thin portions by straining the white through a 1000-micron nylon mesh for about 3 minutes, and the thinner portion discarded. The thick portion of egg white, which is retained on the mesh, is collected and drawn into a 60 cc syringe, which is then placed on a programmable syringe pump and homogenized by expelling and refilling the contents five times. The amount of homogenization is controlled by the syringe pump rate of about 100 ml/min, and the tubing inside diameter of about 0.12 inches. After homogenizing the thick egg white has a viscosity of about 20 centipoise at 150 sec "1 and is then placed in the centrifuge and spun to remove debris and air bubbles at about 3000 rpm for about 10 minutes After centrifuging, the thick, homogenized egg white, which contains ovamucin, is added to a 300 cc FENWAL® Transfer pack container using a syringe. Then 60 cc of the swine plasma is added to the FENWAL® Transfer pack container. The FENWAL® Transfer pack container is clamped, all air bubbles removed, and placed in a Stomacher lab blender where it is blended at normal (or medium) speed for about 2 minutes. The FENWAL® transfer pack container is then removed from the blender, 60 cc of swine red blood cells are added, and the contents mixed by hand kneading for about 2 minutes or until the contents appeared homogenous. A hematocrit of the final mixture should show a red blood cell content of about 30 weight percent and generally should be at least within a range of 28-32 weight percent for artificial menses made according to this Example. The amount of egg white is about 40 weight percent. The ingredients and equipment used in the preparation of artificial menses are readily available. Below is a listing of sources for the items used, though of course other sources may be used providing they are approximately equivalent. Blood (swine): Cocalico Biologicals, Inc., 449 Stevens Rd., Reamstown, PA 17567, (717) 336-1990. FENWAL® Transfer pack container, 300 ml, with coupler, code 4R2014: Baxter HealthCare Corporation, Fenwal Division, Deerfield, IL 60015. Harvard Apparatus Programmable Syringe Pump model no. 55-4143: Harvard Apparatus, South Natick, MA 01760. Stomacher 400 laboratory blender models no. BA 7021, serial no. 31968: Seward Medical, London, England, UK. 1000 micron mesh, item no. CMN-1000-B: Small Parts, Inc., PO Box 4650, Miami Lakes, FL 33014-0650, 1-800-220-4242. Hemata Stat-ll device to measure hemocrits, serial no. 1194Z03127: Separation Technology, Inc., 1096 Rainer Drive, Altamont Springs, FL 32714. DETAILED DESCRIPTION Typical personal care product structures include a top sheet, absorbent core and impervious backsheet and, optionally, a surge layer between the top sheet and absorbent core. The top sheet material is the layer against the wearer's skin and so the first layer in contact with liquid or other exudate from the wearer. The top sheet further serves to isolate the wearer's skin from the liquids held in an absorbent structure and should be compliant, soft feeling and non-irritating. Various materials can be used in forming the bodyside top sheet of the present invention, including apertured plastic films, woven fabrics, nonwoven webs, foams and the like. An optional surge layer may be interposed between and in intimate, liquid communicating contact with the top sheet and another layer. Various foams and woven and nonwoven webs are used to construct a surge layer, and there may be a number of surge layers of different fiber size, basis weight, etc. Exemplary surge materials may be found in US Patent numbers 5,879,343 and 5,820,973 to Dodge et al. The retention or absorbent core layer is usually made from wood pulp and/or superabsorbent particles. Pulps include standard soft-wood fluffing grade such as CR- 1654 from US Alliance Pulp Mills, Coosa, Alabama, and high bulk additive formaldehyde free pulp (HBAFF) available from the Weyerhaeuser Corporation of Tacoma, WA. Another useful pulp is a chemically cross-linked pulp fiber such as Weyerhaeuser NHB- 416. Useful particulate superabsorbents are available from the Dow Chemical Company of Midland Ml, and the Stockhausen Company of Greensboro, NC 27406 (e.g., FAVOR® 870 superabsorbent) as well as others. The backsheet is sometimes referred to as the outer cover and is the farthest layer from the wearer. The outer cover is typically formed of a thin thermoplastic film, such as polyethylene film, which is substantially impermeable to liquid. The outer cover functions to prevent body exudates contained in an absorbent structure from wetting or soiling the wearer's clothing, bedding, or other materials contacting the diaper. The outer cover may be, for example, a polyethylene film having an initial thickness of from about 0.5 mil (0.012 millimeter) to about 5.0 mil (0.12 millimeter). The polymer film outer cover may be embossed and/or matte finished to provide a more aesthetically pleasing appearance. The outer cover may optionally be composed of a vapor or gas permeable, microporous "breathable" material, that is permeable to vapors or gas yet substantially impermeable to liquid. The typical personal care product configuration described above functions well for most purposes. In some product applications, however, particularly feminine hygiene product applications, the combined bulk of these layers can result in the product being uncomfortable for the wearer. The swelling of the superabsorbent in the absorbent core layer upon wetting exacerbates this effect. The inventor has found that a personal care product having a novel blend of materials can alleviate or eliminate this uncomfortable feeling. This construction also allows fluid movement through the product and so utilizes more of the available absorbent capacity of the product and may obviate the need for a surge layer in many products. This more efficient utilization of the absorbent capacity allows for smaller and thinner product structures, which further alleviates the uncomfortable feeling when compared with typical products. It should be noted that, though the invention is intended to have only a single layer comprised of the novel materials, the mere addition of layers to a personal care product of the invention should not be construed as being beyond the scope of the claims. The personal care product of the invention includes water-soluble materials and absorbent materials. When wetted and after the application of minimal force, this material becomes gelatinous and can conform to the shape of the wearer by flowing under load. This flowing can also serve to distribute the absorbed fluid throughout the structure. A certain amount of force is required to produce gelling even when sufficient liquid is present. The inventor believes that the reason for this is to break bonds in the material or to induce more thorough mixing of the liquid and the materials. The force required to produce gelling of the material in a personal care product of this invention is not excessive. The amount of pressure exerted by a wearer by merely walking is believed to be sufficient for feminine hygiene products, for example. In the case of a diaper, the amount of force exerted by a wearer by sitting down or walking is believed to be sufficient. The absorbent materials may include wood pulp fibers and superabsorbent and blends thereof. 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 HP2 pulp and still another is IP Supersoft from International Paper Corporation. Suitable rayon fibers are 1.5 denier Merge 18453 fibers from Acordis Cellulose Fibers 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 but are not limited to acrylic acid, iso-butylene/maleic anhydride, polyethylene oxide, carboxy-methyl cellulose, poly vinyl pyrrollidone, and poly vinyl alcohol. The superabsorbents may range in rate from slow to fast. The superabsorbents may be in the form of foams, macroporous or microporous particles or fibers, may have fuzzy or fibrous 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. Neutralization occurs through use of counter ions such as Li, Na, K, Ca. An Example of these superabsorbents may be obtained from the Stockhausen Company (of Greensboro, NC) and is designated as FAVOR® 880. Fibrous superabsorbents include superabsorbents obtained from Camelot Superabsorbents Inc., (of Charlotte, NC) are designated as FIBERDRI® 1241 and FIBERDRI® 1161. Examples of superabsorbents obtained from Technical Absorbents, Ltd. (of Grimsby, UK) are designated as OASIS® 101 and OASIS® 111. Fibrous superabsorbents also include FIBERSORB®, which is a 100 percent fibrous superabsorbent (formerly available from the Arco Chemical Company of Newtown Square, PA). Single or common fibers produced from a mixture of superabsorbent and water soluble polymers are available as ABSORVATE® superabsorbent (from BFF Nonwovens of Somerset, UK). An example of a water-soluble polymer includes a water-soluble poly(vinyl alcohol) copolymer named Ecomaty AX10000 and manufactured by Nippon-Gohsei of Osaka, Japan. The meltflow rate of this AX10000 copolymer was 100 grams per 10 minutes at a temperature of 190 C under 2.16 kilograms load using ASTM Test Method D-1238. This polymer may be made into fibers in known fiber producing processes such as meltblowing. Another water-soluble polymer is a polyamide polymer with the code number NP 2068 and available from the H.B. Fuller Company of St. Paul, Minnesota. The viscosity of the NP 2068 polymer was 95 Pascal-seconds at a temperature of 204°C. Another such polyamide polymer is available under the code number NP 2074 from H.B. Fuller. These polymers may also be made into fibers in known fiber producing processes such as meltblowing. Additional water-soluble polymers suitable for incorporation into the invention may be found in US patent 5,916,678 and US patent applications 08/798,751 and 08/774,417, for which the issue fees have been paid. These documents are directed toward personal care products and materials for use therein, which will degrade upon exposure to water for the purpose of biodegradability or environmental protection. These "flushable" materials may be disposed of in typical sanitary systems and be unrecognizable upon arrival at a waste treatment facility. Additional polymers available for fiber production include polylactic acid (PLA) and a blend of BIONOLLE®, adipic acid and UNITHOX® (BAU). PLA is not a blend but a pure polymer like polypropylene. BAU represents a blend of BIONOLLE®, adipic acid, and UNITHOX® at different percentages. Typically, the blend for staple fiber is 44.1 percent BIONOLLE® 1020, 44.1 percent BIONOLLE® 3020, 9.8 percent adipic acid and 2 percent UNITHOX® 480, though spunbond BAU fibers typically use about 15 percent adipic acid. BIONOLLE® 1020 is polybutylene succinate, BIONOLLE® 3020 is polybutylene succinate adipate copolymer, and UNITHOX® 480 is an ethoxylated alcohol. BIONOLLE® is a trademark of Showa Highpolymer Co. of Japan. UNITHOX® is a trademark of Baker Petrolite which is a subsidiary of Baker Hughes International. The web of water-soluble polymer and superabsorbent for use in the instant invention may be made by a number of different processes, limited only by the idiosyncratic constraints imposed by a particular polymer. Polyvinyl alcohol (PVOH), for example, may be successfully fiberized according to the meltblowing process and pulp or superabsorbent particles or fibers may be admixed with it according to the coform process. Superabsorbent/water-soluble polymer mixtures such as ABSORVATE® material, for example, may be processed by meltblowing and solution spinning as well. Alternatively, superabsorbent and water-soluble polymers may be meltblown in separate banks of a typical meltblowing operation to produce a mixed fiber fabric in one processing step. Alternatively, the polymers may be separately fiberized and subsequently mixed in a desired ratio by various known processes such as bonding and carding, airlaying, etc. In yet another alternative method, the superabsorbent fibers may be made into a web and a liquid, water soluble polymer introduced to the web as an adhesive to give structural integrity to the web. The adhesive polymers include polyvinyl alcohol, polyethylene oxide and polyvinyl pyrollidone and they may be added to the web by spraying, dipping and any other suitable method known in the art. The gel properties of the blend of water-soluble and superabsorbent fibers may be controlled by controlling the ratio of the fibers, the molecular weight and other properties of the polymers chosen, as well as the fabric properties such as basis weight, bonding pattern if any, fabric density and the like. A successful blend will flow as a gel after being wetted and after the application of minimal force, but will not be so liquid as to escape from the personal care product. Careful product design and a reasonable amount of experimentation will allow one skilled in the art to develop the proper blend for his application. The inventor believes that the most efficacious blends will be found within the range of between 20 and 80 weight percent water-soluble polymer and 80 and 20 weight percent superabsorbent fiber to produce a gel after wetting. More particularly a range of from 70 percent water soluble polymer to 70 percent superabsorbent fiber and still more particularly from 60 percent water soluble polymer to 60 percent superabsorbent fiber, with the balance being the other component, are believed to be desirable. Additional components, such as surfactants, skin wellness additives, odor control additives, colorants and the like may also be present in a minor amount. Example A thermally point bonded carded web designated NCF200, commercially available from BFF Nonwovens (Somerset, England, UK) was saturated with an artificial menses solution prepared according to the method above. This web was made from fibers composed of superabsorbent and water-soluble polyvinyl alcohol in a common (i.e., the same) fiber and had a basis weight of about 200 gsm. The web was allowed to absorb the solution and then rolled with a glass mixing rod. Upon the application of the force from the rolled rod, the web became a gel. 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. Such changes and variations are intended by the inventor to be within the scope of the invention.

Claims: What is claimed is: 1. A personal care product comprising an absorbent and water-soluble polymers which becomes a gel upon contact with liquid and with an application of a minimal force. 2. The personal care product of claim 1 wherein said absorbent is a superabsorbent. 3. The personal care product of claim 2 wherein said superabsorbent is a fiber and is present in an amount between 20 and 80 weight percent. 4. The personal care product of claim 3 wherein said superabsorbent fibers are present in an amount between 30 and 70 weight percent. 5. The personal care product of claim 1 wherein said absorbent is a wood pulp. 6. The personal care product of claim 1 wherein said absorbent and water soluble polymer are present in a common fiber. 7. The personal care product of claim 1 wherein said absorbent and water-soluble polymer are combined using a method selected from the group consisting of meltblowing, coforming, bonding and carding, solution spinning and airlaying. 8. The personal care product of claim 2 wherein said superabsorbent is made into a web of fibers and said water soluble added to said web as an adhesive. 9. The personal care product of claim 1 further comprising apertures in said layer. 10. A feminine hygiene pad comprising the fabric of claim 1. 11. A diaper comprising the fabric of claim 1. 12. An adult incontinence product comprising the fabric of claim 1.

Inventors: DALEY MICHAEL ALLEN, LATIMER MARGARET GWYN, DALEY, MICHAEL, ALLEN, LATIMER, MARGARET, GWYN
Applicants: KIMBERLY CLARK CO, KIMBERLY-CLARK WORLDWIDE, INC.
Application year: 2001
Main classification: A61L15
IPC codes: A61F5, A61F13, A61L15