A METHOD FOR SEALING AN ABSORBENT MEMBER

Abstract: A web (110) including a fibrous material and superabsorbent material is fed to a knife (120). The web (110) has a first surface, a second surface, a first side edge and a second side edge. The knife (120) cuts the web (110) into individual absorbent members having a pair of opposing cut ends. The individual absorbent members have a first surface, a second surface, a first side edge, the second side edge, a first end edge and a second end edge, with the first and second end edges corresponding to the cut ends. A superabsorbent material movement obstruction agent (122) is applied to the first and second end edges.

Description: A METHOD FOR SEALING AN ABSORBENT MEMBER FIELD OF THE INVENTION This invention relates to a method for sealing an absorbent member, and more particularly to a method for sealing an absorbent member which is suitable for use as an absorbent core in a disposable absorbent article. BACKGROUND OF THE INVENTION Absorbent webs which comprise masses of fibers, i.e., fibrous web, are well known in the art. Such webs can imbibe liquids, such as discharged body fluids, both by an absorption mechanism wherein fluid is taken up by the fiber material itself and by a wicking mechanism wherein fluid is acquired by, distributed through and stored in the capillary interstices between fibers. One means for improving the absorbency characteristics of such fibrous web structures is to incorporate therein superabsorbent material, such as polymeric gelling material (also referred to as hydrogel-forming material superabsorbent polymers, etc.) which imbibe fluid. The superabsorbent material serves to retain fluid such as discharge body liquids. An absorbent structure of this type wherein hydrogel-forming materials in paniculate form are incorporated into fibrous webs is disclosed in Weisman and Goldman, U.S. Patent 4,610,678, issued September 9, 1986. The improvement in absorbency provided by incorporation of absorbent gelling materials has permitted the realization of absorbent articles, such as disposable diapers, which employ relatively thin absorbent cores and which are, therefore, relatively thin products. Notwithstanding the existence of absorbent cores as described above, there remains a need to provide absorbent cores which reduce and preferably eliminate the phenomena referred to as gel-on-skin. Gel-on-skin is the situation where absorbent gelling materials escape from the absorbent core and travel through the bodyside liner or topsheet of the absorbent article where they come into contact the wearer's skin. In prior art continuous lay down operations, fibers and superabsorbent materials are mixed together in a continuous web. The continuous web is then cut into individual absorbent members or cores. The individual absorbent members are then placed between a liquid pervious topsheet and a liquid impervious backsheet to form an absorbent article. Unfortunately, this configuration provided an unsatisfactory product as absorbent gelling material easily penetrated through the topsheet creating unacceptable amounts of gel-on- skin. One solution to the above continuous lay down operation, was to place another web, such as a tissue or nonwoven web on top of the continuous web and then cut both the tissue and continuous web into individual members comprising the core and the tissue. The individual members were then placed in the product with the tissue positioned between the topsheet and the absorbent core substantially preventing absorbent gelling material from escaping from the uppermost surface of the absorbent core and thus reducing the amount of gel-on-skin. Unfortunately, when for example, the tissue and the continuous web are cut into individual members, the ends of the absorbent core are left open, i.e., the ends of the absorbent core are not covered by the tissue, allowing absorbent gelling material to escape through the ends of the absorbent core. It is an object of this invention to provide a method of sealing an absorbent core via a continuous lay down operation which circumvents the problems of gel-on-skin. BRIEF SUMMARY OF THE INVENTION The invention is a method for sealing an absorbent member. To form the absorbent member, a web comprising a fibrous material and superabsorbent material is fed to a knife. The web has a first surface, a second surface, a first side edge and a second side edge. The knife cuts the web into individual absorbent members having a pair of opposing cut ends. The individual absorbent members have a first surface, a second surface, a first side edge, the second side edge, a first end edge and a second end edge, with the first and second end edges corresponding to the cut ends. A superabsorbent material movement obstruction agent is applied to the first and second end edges. The superabsorbent material movement obstruction agent preferably extends from the first side edge to the second side edge, and from the first surface to the second surface of the individual absorbent members. The individual absorbent members preferably form an absorbent core in a disposable absorbent article and are positioned between a liquid pervious topsheet and a liquid impervious backsheet. As used herein the term "superabsorbent material movement obstruction agent" refers an external agent applied to a web comprising fibrous material and superabsorbent material which obstructs the movement of the superabsorbent material through a cut end of the web. BRIEF DESCRIPTION OF THE DRAWINGS While the specification concludes with claims pointing out and distinctly claiming the present invention, it is believed the same will be better understood by the following drawings taken in conjunction with the accompanying specification wherein like components are given the same reference number. Figure 1 is a plan view of an absorbent article comprising an absorbent core manufactured in accordance with the method of the present invention. Figure 2 is a simplified schematic illustration of a continuous lay down method for sealing absorbent cores of the present invention. Figure 3 is an enlarged cross-sectional illustration of the application of superabsorbent material movement obstruction agent to the individual absorbent members. Figure 4 is a plan view of an individual absorbent member after the application of superabsorbent material movement obstruction agent. DETAILED DESCRIPTION OF THE INVENTION The method of the present invention is particularly suitable for manufacturing absorbent cores for use in disposable absorbent articles. As used herein, the term "absorbent article" refers to devices which absorb and contain body exudates, and, more specifically, refers to devices which are placed against or in proximity to the body of the wearer to absorb and contain the various exudates discharged from the body. The term "disposable" is used herein to describe absorbent articles which are not intended to be laundered or otherwise restored or reused as an absorbent article (i.e., they are intended to be discarded after a single use and, preferably, to be recycled, composted or otherwise disposed of in an environmentally compatible manner). A "unitary" absorbent article refers to absorbent articles which are formed of separate parts united together to form a coordinated entity so that they do not require separate manipulative parts like a separate holder and liner. A preferred embodiment of a unitary absorbent article comprising an absorbent core manufactured by the method of the present invention is the unitary disposable absorbent article, diaper 20, shown in Figure 1. As used herein, the term "diaper" refers to an absorbent article generally worn by infants and adult incontinent persons and is worn about the lower torso of the wearer. It should be understood, however, that the present invention is also applicable to other absorbent articles such as incontinence briefs, incontinence undergarments, absorbent inserts, diapers holders and liners, feminine hygiene garments, and the like. With reference to Figure 1, an absorbent article, such as a diaper 20, generally comprises a liquid pervious topsheet 22, a liquid impervious backsheet 24 joined with the topsheet 22; and an absorbent core 26 intermediate the topsheet 22 and the backsheet 24. The diaper 20 preferably further comprises a front waist region 36, a rear waist region 38, a crotch region 37 positioned between the front waist region 36 and the rear waist region 38, elasticized leg cuffs 28, ear flaps 30, an elastic waist feature 32 and a fastening system 34 comprising at least one tape tab 40. An example of a suitable absorbent article to which the absorbent core of the present invention may be inserted is more fully and completely described in U.S. Patent No. 5 151 092 issued to Buell et al. on September 29, 1992. The absorbent core 26 of the present invention may be produced on the apparatus 100, as shown in Figure 2. In a preferred embodiment, the apparatus 100 is integrated into a disposable absorbent article manufacturing line such that the absorbent core 26 of the present invention may be manufactured "on-line". (As used herein, the term "integrated" means interconnected process modules that operate concurrently to produce finished products from source materials. The term "on-line" is used to refer to the process of manufacturing the absorbent cores of the present invention on an apparatus that is integrated with the manufacturing line that produces the disposable absorbent articles to which the tape tabs will be joined.) Examining apparatus 100 in greater detail, a web 110 is provided. Web 110 comprises fibrous material and superabsorbent material. The fibrous material may comprise cellulose fibers, in the form of fluff; modified cellulose fibers such as stiffened cellulose fibers; synthetic fibers such as those made of cellulose acetate, polyvinyl fluoride, polyvinylidene chloride, acrylics, polyvinyl acetate, non-soluble polyvinyl alcohol, polyethylene, polypropylene, polyamides (such as nylon), polyesters, bi- component fibers, tri-component fibers, mixtures thereof and the like. Preferred synthetic fibers have a denier of from about 3 denier per filament to about 25 denier per filament, more preferably from about 5 denier per filament to about 15 denier per filament. Also preferably, the fiber surfaces are hydrophilic or are treated to be hydrophilic. Suitable superabsorbent materials include but are not limited to discrete particles of absorbent gelling material and superabsorbent fibrous material such as acrylate grafted fibers and superabsorbent modified fibers. The superabsorbent material can be in any form which can be incorporated into a flexible web or sheet to form the web 110. The superabsorbent material, upon contact with fluids such as water or body fluids, absorb such fluids. The superabsorbent material is typically in the form of discrete particles of absorbent gelling material. Continuous web 110 is fed to knife 120 in the direction indicated by the arrows shown in Figure 2. Web 110 has a first or uppermost surface 146, an opposing second or lowermost surface 148, a first side edge 140 (not shown in Figure 2), and an opposing second side edge 142. Knife 120 cuts the web into individual absorbent members 26 having a pair of opposing cut ends. The individual absorbent members 26 are then fed to applicator 130 which applies a superabsorbent material movement obstruction agent 122 to the individual absorbent members 26. Of course other webs may be fed with continuous web 110 to knife 120. For example, a tissue or nonwoven web may be positioned adjacent the first surface 146 and/or the second surface 148 and the composite is then fed to knife 120. However, for simplicity, only a single web 110 is shown in Figure 2. As an alternative to the cutting operation with knife 120, any process can be used that provides individual absorbent members to the applicator 130. For example, a discrete absorbent member formation process can be used. Referring now to Figures 3 and 4, the individual absorbent members 26 have first and second end edges 163 and 165 corresponding to the cut ends of the web 110, a first side edge 160, a second side edge 162, a first or uppermost surface 246, and a second or lowermost surface 248. Superabsorbent material movement obstruction agent 122 is applied only to the ends of the individual absorbent members 26. Preferably, the superabsorbent material movement obstruction agent 122 is applied directly to the end edges 163 and 165. However, the superabsorbent material movement obstruction agent 122 may be applied to the first or uppermost surface 246 directly over the end edges 163 and 165 and then allowed to migrate through the member 26 from the first surface 246 to the second surface 248. Alternatively, the superabsorbent material movement obstruction agent 122 may be applied to both the end edges 163 and 165 and the uppermost surface 246. Preferably, a sufficient amount of superabsorbent material movement obstruction agent 122 is applied to the ends of the individual absorbent members 26 to completely seal the ends thus preventing the absorbent gelling material from escaping through the ends of the absorbent members 26. By application of the superabsorbent material movement obstruction agent 122 to only the end edges 163 and 165, each individual absorbent member 26 has a pair of discrete, spaced apart sealing zones 243 and 245. Zone 243 is located adjacent first end edge 163 and zone 245 is located adjacent end edge 165. Preferably, a thin film of the superabsorbent material movement obstruction agent 122 is applied to the web such that each zone 243 and 245 is relatively thin. However, the superabsorbent material movement obstruction agent 122 may migrate inwardly from the end edges 163 and 165. Preferably, the amount of migration of superabsorbent material movement obstruction agent 122 is minimal such that zones 243 and 245 have a width dimension 270 of less that about 10 cm, more preferably, less than about 5 cm, and most preferably less than about 1 cm. As can be seen in Figure 3 the superabsorbent material movement obstruction agent extends along the end edges 163 and 165 through the entire absorbent member 26 from the first surface 246 to the second surface 248. Zones 243 and 245 preferably occupy less than 30 % of the volume of absorbent member 26, more preferably less than 20 % of the volume of absorbent member 26, and most preferably less than 10 % of the volume of absorbent member 26. Suitable agents for the superabsorbent material movement obstruction agent include, but are not limited, to polymeric solutions or emulsions, both natural (e.g. natural rubber latex) and synthetic, in which the liquid is water or any other suitable liquid or mixture of liquids. Waterborne emulsions are preferred and more preferred are waterborne emulsions of acrylic or vinylic adhesive polymers. Other suitable agents for the superabsorbent material movement obstruction agent also include thermoplastic polymers or polymeric compositions having a softening point, as determined by the ASTM Method E 28 "Ring and Ball", in the range between 50 °C and 300 °C. Preferably such thermoplastic polymer or polymeric composition is a wax or a composition containing at least 50 % by weight of a wax, such wax or composition preferably having a softening point less than about 180 °C. More preferably such thermoplastic agent (being it a polymer, a wax or a composition derived therefrom) is or contains at least 50 % by weight of a copolymer having, at least as one of its co- monomers, Acrylic Acid, Acrylamide, Acrylic Esters and/or derivatives therefrom. The superabsorbent material movement obstruction agent is preferably not applied to the entire web, but only in discrete, spaced apart zones. While the superabsorbent material movement obstruction agent does provide the benefit of obstructing the movement of the superabsorbent material through the cut end of a web, it may have some negative effects if applied to the entire web. For example, the agent may increase the stiffness of the web such that it becomes uncomfortable for the wearer if applied to the entire web. The agent may inhibit some of the absorbent properties of the web and thus would negatively impact the absorbent article which employed a web having the agent applied to the entire web. Thus, in order to achieve the desired effect of obstructing the movement of the superabsorbent material through the cut end of a web without negatively impacting the performance, comfort or other properties and characteristics of the web and an absorbent article which employs such a web, the superabsorbent material movement obstruction agent is applied to the web in only discrete, spaced apart zones. When incorporated into an absorbent article, such as diaper 20 shown in Figure 1, zones 243 and 245 of absorbent member 26 are preferably positioned within the front waist region 36 and the rear waist region 38, respectively. While, zones 243 and 245 may be of such dimension that they extend into crotch region 37, this is not preferred. While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.

Claims: What is claimed is: 1. A method for sealing an absorbent member (26), said method comprising the steps of: a) feeding a web (110) comprising a fibrous material and superabsorbent material, said web having a first side edge (140) and a second side edge (142); b) cutting said web into individual absorbent members (26) having a pair of opposing cut ends; and c) applying a superabsorbent material movement obstruction agent (122) to each of said cut ends of said individual absorbent members. 2. The method of claim 1 wherein said individual members have a first surface (246), a second surface (248), a first side edge (160), a second side edge (162), a first end edge (163) and a second end edge (165), said first and second end edges corresponding to said cut ends, and discrete, spaced apart sealing zones (243, 245). 3. The method of claim 1 or claim 2 wherein zones extend from said first side edge to said second side edge and from said first surface to said second surface. 4. The method of either claim 2 or claim 3 wherein said zones of superabsorbent material movement obstruction agent have a width of less than about 10 cm. 5. The method of either claim 2 or claim 3 wherein said zones of superabsorbent material movement obstruction agent have a width of less than about 5 cm. 6. The method of either claim 2 or claim 3 wherein said zones of superabsorbent material movement obstruction agent have a width of less than about 1 cm. 7. The method of any one of the preceding claims wherein said superabsorbent material movement obstruction agent is a material selected from the group of polymeric solutions or emulsions. 8. The method of any of claim 1 through claim 6 wherein said superabsorbent material movement obstruction agent is a thermoplastic polymer or polymeric composition having a softening point in the range between 50° Celsius and 300° Celsius. . The method of claim 8 wherein said thermoplastic polymer or polymeric composition is a wax or a composition containing at least 50% by weight of a wax. 10. The method of claim 7 wherein said polymeric solutions or emulsions are either natural or synthetic.

Inventors: CORZANI ITALO, LINDNER TORSTEN, SCHMITT JOHN CHRISTIAN, CORZANI, ITALO, LINDNER, TORSTEN, SCHMITT, JOHN, CHRISTIAN
Applicants: CORZANI ITALO, LINDNER TORSTEN, PROCTER & GAMBLE, SCHMITT JOHN CHRISTIAN, CORZANI, ITALO, LINDNER, TORSTEN, SCHMITT, JOHN, CHRISTIAN, THE PROCTER & GAMBLE COMPANY
Application year: 1999
Main classification: A61F13
IPC codes: A61F5, A61F13