|Publication number||US3729005 A|
|Publication date||Apr 24, 1973|
|Filing date||Feb 1, 1971|
|Priority date||Feb 1, 1971|
|Publication number||US 3729005 A, US 3729005A, US-A-3729005, US3729005 A, US3729005A|
|Inventors||C Lee, F Sorrells|
|Original Assignee||Int Paper Co|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (9), Referenced by (9), Classifications (9)|
|External Links: USPTO, USPTO Assignment, Espacenet|
United States Patent Lee et al. [4 1 Apr. 24, 1973 1 DISPOSABLE DIAPER  Inventors: Charles A. Lee; Frank D. Sorrells,  ABSTRACT both of KnXvi1le,Tenn- A disposable diaper of generally rectangular outline  Assigneez International Paper Company, New having longitudinal and transverse directions including York NY. a pad of absorbent matter encompassed by a cover sheet comprising a laminated nonwoven fibrous fabric  Filed: Feb. 1, 1971  US. Cl ..128/287  Int. Cl ..A6lf 13/16  Field of Search ..128/284, 287, 290
 References Cited UNITED STATES PATENTS 2,295,439 9/1942 Voigtman 128/290 W 3,036,573 5/1962 Voigtman et al. ..128/287 3,063,454 11/1962 Coates et al. ..128/290 W 3,085,309 4/1963 Olson 128/284 X 3,180,335 4/1965 Duncan et al. ..128/287 3,402,715 9/1968 Liloia et al. 128/287 3,430,629 3/1969 Murphy ..128/284 3,544,420 12/1970 Murphy et al. 128/284 3,543,756 12/1970 Murphy et al. 128/284 Primary ExaminerCharles F. Rosenbaum AltorneyFitch, Even, Tabin & Luedeka including fibrous web plies having respective longitudinal directions, the web plies being reinforced in their respective longitudinal directions and bonded in superposed relation with their respective longitudinal directions at angle to each other and at angle to the longitudinal direction of the diaper thereby reinforcing the diaper at angles to its longitudinal and transverse directions. The diaper includes wing folds extending longitudinally along the side edges of the diaper to provide a seal around the legs of the child and prevent body exudate from passing outwardly of the diaper in the vicinity of the legs. In one aspect of the inveniton, fibers of the web plies are bonded to the reinforcing medium in a manner such that the fibers are retained in the fabric cover sheet and do not become dislodged to deposit upon the child or other surface even though the diaper becomes wet and is subected to abrasion in the course of normal movements of the child. The desirable absorptivity of the fibrous webs is retained in the product.
15 Claims, 9 Drawing Figures Patented April 24, 1973 3 Sheets-Sheet 1 INVENTQRS. Charles A. Lee- I BY Frank D. Sorrel/s #M ATTORNEYS.
. Patented Ap;il24,1973 3,729,005
3 Sheets-Sheet 2 INVENTORS. Charles AQLee By Frank D. Sorrel/s "ATTORNEYS.
Patented April 24, 1973 '3 Sheets-Sheet 5 INVENTORS. Charles A. Lee
DISPOSABLE DIAPER This invention relates to disposable diapers.
Disposable diapers, in general, serve as throwaway replacements for the common cloth diaper. For a disposable diaper to be attractive to the consumer, it should exhibit the physical properties of a cloth diaper and be available at a low cost approximating the cost per use of the conventional cloth diaper which may be washed and reused many times.
Whereas low cost materials such as loosely felted cellulosic fluff possessing acceptable absorbency characteristics have been available and used in the manufacture of disposable diapers, such materials possess minimal tensile strength and tend to disintegrate when wet and hence must be supported in position within the diaper. Creped tissue which is desirable as a cover sheet has a low wet rub resistance and when the diaper becomes wet and the child is active, the cellulosic tissue may fragment and deposit objectionable cellulosic matter on a childs body.
In another aspect of diapers, the usual procedure for securing a diaper on a child is to fold opposite ends of a diaper about the childs waist and pin opposite corners of the diaper to each other as is well understood. Particularly in the pinning area, it is desirable to have high strength so that the diaper may be pulled and held snugly against the child's body.
Accordingly, it is a general object of the present invention to provide an improved disposable diaper. It is also an object to provide an improved cover sheet for a disposable diaper. It is a still further object to provide a cellulosic disposable diaper wherein the cellulosic fibrous matter thereof resists abrasion and fragmentation, especially when wet.
Other objects and advantages of the invention will be apparent from the following description with the ac companying drawings in which:
FIG. 1 is a representation of a diaper depicting various features of the invention;
FIG. 2 is a representation showing one manner of folding the cover sheet of the disclosed diaper;
FIG. 3 is a sectional view taken along line 3-3 of the diaper shown in FIG. 1.
FIG. 4 is a representation of one type of laminated reinforced nonwoven fabric employed to make the diaper cover sheets disclosed herein;
FIG. 5 is a fragmentary sectional view taken along line 5-5 of the fabric shown in FIG. 4;
FIG. 6 is a fragmentary representation, partly cutaway, showing the web and filament plies of the laminated fabric of FIG. 4;
FIG. 7 is a fragmentary representation showing the bonding of web fibers to the reinforcing filaments of the fabric of FIG. 4;
FIG. 8 is a sectional view of the disclosed diaper wherein the absorbent pad is provided with additional material in its central portion and showing a diaper having no pad material in the wing folds and including a water repellent in a portion of the cover sheet in the wing fold areas; and
FIG. 9 is a sectional view of the disclosed diaper having a moisture barrier included therein.
Broadly stated, the diaper disclosed herein is of the disposable type and fabricated of low-cost materials. The diaper is of rectangular outline and includes a pad of absorbent matter encompassed by a cover sheet comprising a laminated fabric including a plurality of creped cellulosic tissue web piles reinforced in their respective longitudinal directions by means of one or more plies of reinforcing matter and bonded in superposed relation with their respective reinforced directions at an angle to each other and to the longitudinal direction of the laminated fabric. As a cover sheet, this reinforced laminated fabric, referred to herein at times as reinforced bias laid fabric or cover sheet, is disposed with its longitudinal direction aligned with the longitudinal direction of the diaper thereby placing the reinforced directions of the plies at angle to the longitudinal direction of the diaper and reinforcing the diaper at angles to its longitudinal direction. As illustrated in accompanying drawings, the diaper is folded along its longitudinal side margins with wing folds which gather the diaper in its central section to cause it to conform to the crotch of the child and which expands in its end portions to provide areas suitable for encompassing the waist of the child and providing overlapping portions for pinning to secure the diaper in position on the child.
The preferred reinforcing provided each of the web plies of the laminated fabric comprising the cover sheet serves also as anchor points for the fibers of the web plies thereby increasing the wet rub resistance of the diaper and substantially eliminating the prior art problem of cover sheet fragmentation and resultant adhesion of tissue to the body of a child.
Bonding of the several plies of tissue one to another and anchoring of the fibers to the reinforcing matter is achieved without deleterious loss of absorptivity of the diaper materials thereby creating a diaper capable of satisfactorily receiving and retaining exudates. I
With reference to FIGS. l and 3, one embodiment of the diaper l0 disclosed herein is of rectangular outline having a longitudinal central portion l2 flanked by longitudinal wing folds 14, 16 extending parallel to the central portion 12 on opposite sides thereof and coextensive in length with the longitudinal dimension of the diaper.
As depicted in FIG. 2, the illustrated diaper is assembled by depositing a pad 22 of absorbent loosely felted cellulosic matter in the approximate center of a cover sheet 24 and subsequently folding the side edges 26, 28 of the cover sheet inwardly of the diaper and overlying the pad 22 thereby causing the coversheet to envelop the pad. These side edges 26, 28 are preferably folded along fold lines A, B which are spaced inwardly toward the centerline of the cover sheet 24 to provide sufficiently wide side edge portions as will cause the folded cover sheet to fully overlie the pad and overlap sufficiently to assure complete encirclement of the pad and prevent the cellulosic matter comprising the pad from escaping even though the overlapped edges are not held in position by an adhesive or similar sealing means. Alternatively the side edge portions of the cover sheet overlap only a small amount and are secured in position by a seam formed of an adhesive or as by the application of sufficient heat and/or pressure to glassine, and thereby seal, the overlapping edges of the cover sheet. This latter alternative is useful in reducing the quantity of cellulosic matter employed in the cover sheet and thereby reducing the overall cost of the diaper, consideration being given to the cost involved in making the seal along the overlapped edges of the cover sheet.
In a continuous diaper manufacturing process, it is advantageous to utilize a cellulosic carrier sheet 30 of slightly greater width than the pad for receiving the pad. This carrier sheet 30 is disposed between the pad and the cover sheet 24 with the pad 22 being deposited on the carrier sheet 30 as illustrated. The ends of the enveloped assemblage are sealed as by embossments 32, 33 (FIG. 1) to prevent the loss of cellulosic pad matter from the ends. The assemblage is folded with the wing folds 14, 16 which extend longitudinally along the side edges of the diaper to bring the side margins of the diaper toward the longitudinal center of the diaper and thereby accumulate the diaper into a relatively narrow configuration in the central part thereof. This folded central part of the diaper is comfortably received in a childs crotch and the folded end portions of the diaper are expandable to develop portions of the diaper which encircle the waist of the child and receive the pins that hold the diaper in position on the childs body. Additionally, the wing folds in the central portion of the diaper provide good contact with the childs legs and develop a seal around the legs of the child to prevent body exudate from passing outwardly of the diaper in the vicinity of the legs. In this instance, the wing folds are formed by bringing longitudinal side edge portions of the diaper inwardly toward the center of the diaper. Each such folded side edge portion extends inwardly of the diaper a distance less than about one-third the width of the diaper to form a first longitudinal fold along each side of the diaper. As thus folded, each longitudinal side edge of the diaper overlies the longitudinal central portion of the diaper and extends the length of the diaper. Each of these first folds is next folded back upon itself to form a second fold extending along the length of the diaper and overlying the first fold, thereby providing two folds 34, 35 and 36, 37 (FIG. 3) in each wing fold 14, 16, respectively, overlying the marginal edges of a central portion 12 of the diaper. Herein, the first folds 3S and 37 are secured to the underlying center portion to cause the folded diaper to retain its folded form at least while the diaper is being secured to the childs body thereby insuring that the accumulated configuration of the central portion of the diaper comfortably and snugly resides within the childs crotch and in position to efficiently receive body exudate. These first folds 35 and 37 preferably are held in their folded position by points of bonding 38, 39 (FIG. 1) located generally centrally of the fold, i.e. medially of both the longitudinal and transverse dimensions of each fold. Spot embossures made with sufficient pressure to glassine the cellulose have been found effective to hold the folds 35 and 37 in place. Spots of adhesive have also been found suitable for this purpose but may be less desirable in a manufacturing operation.
In the folded diaper illustrated in FIG. 3 in cross section, it is shown how that, by appropriate selection of the width of the cellulosic pad 22 and by folding the diaper in wing folds as noted above, the diaper may be provided with the desired absorptive matter thereof disposed in the central portion of the diaper and in the first folds 35, 37 of the wing folds l4 and 16, respectively. When the illustrated folded diaper is pinned in position on a child's body the upper folds 34 and 36 of the wing folds 14 and 16, respectively, encircle the childs legs and secure the diaper against leakage of exudate in this region. These upper folds, being unattached to the lower folds 35, 37 permit the absorptive central portion of the diaper to fall somewhat free of the childs body thereby forming a type of receptacle whose walls comprise the absorptive matter of the cellulosic pad 22. This type of cellulosic receptacle receives the body exudate and efficiently absorbs the exudate to draw it away from the childs body and maintain it therein and away from the childs body to reduce the possibility of irritation due to prolonged contact between the childs body and a soiled diaper. Both of the folds 34, 35 and 36, 37 of each wing fold 14 and 16, respectively, are spot bonded to the underlying central portion 12 of the diaper when it is desired to maintain the wing folds more completely in their folded state.
A cover sheet 24 for the illustrated diaper comprises a soft, strong, reinforced, nonwoven fabric as depicted in FIGS. 4-6, which encompasses the relatively weak absorbent pad 22 and imparts strength, integrity and shape to the diaper. In accordance with one aspect of the invention, this fabric 32 includes a plurality of reinforcing filamentary plies 41, 42 interposed between outer web plies 44, 46, the several plies being bonded to at least adjacent plies to develop a coherent fabric whose reinforced plies are oriented at an angle of between about 60 and about 90 to each other and at an angle of between about 25 and about 45 to the transverse direction of the fabric, i.e. perpendicular to the machine direction of the fabric, which is also the longitudinal direction thereof in the accompanying drawings. One method for manufacturing the fabric includes bonding a plurality of strong reinforcing filaments to a tissue web with the filaments generally aligned with the machine direction of the web, simultaneously spirally winding two such filament-bearing webs 48 and 50 (FIG. 4) into a tubular configuration with the webs overlapping along their side margins 52, 54, respectively, and collapsing the tube to form a flat sheet comprising inner plies 41, 42 of crossing filaments interposed between outer web plies 44, 46 whose machine directions are disposed at an angle, e.g. obliquely, with respect to the longitudinal direction (i.e. machine direction) of the fabric 40. The cross filaments and/or the overlaid webs are bonded one to another to impart integrity and strength to the fabric. When spirally wound, the superposed web plies preferably are disposed with their reinforced longitudinal directions at an angle of about to each other thereby positioning the reinforced directions at an angle of about 40 to the longitudinal direction and at an angle of about 50 to the transverse direction of the resultant fabric. Smaller angles of crossing of the filaments are acceptable but result in increased usage of raw material (more reinforced web per linear foot of fabric product). Angles of filament crossing greater than about degrees are generally undesirable from a manufacturing standpoint and normally no strength advantage is obtained through the use of such larger angles of filament crossing.
Creped cellulosic tissue is preferred as the material for the web plies 38, 40 of the cover sheet 24. One acceptable web is creped cellulosic tissue having a crepe ratio of between about 1.2 and 1.5 and a basic weight between about 5 and pounds per ream of 2,880 sq. ft. Other weights of cellulosic tissue webs are suitable, however, as the weight is increased the softness and hand of the product decrease. Crepe ratios of the individual cellulosic tissue webs greater than about 1.5 are acceptable but are not necesary to produce a diaper having the improved qualities referred to herein. Typically, the fibers in the creped tissue have a length between about one thirty-second and one-eighth inch, but other fiber lengths are acceptable for use in the web plies of the present diaper covers.
As noted hereinbefore, the creped tissue webs generally possess low resistance to rupture, at least in the cross direction, but are soft, pliable, relatively inexpensive and possess desirable absorptivity characteristics. Each web presents a relatively even surface irrespective of the creping of the respective web fibers and when serving as an outermost layer of the fabric imparts good hand to the fabric.
Each of the web plies 44, 46 of the cover sheet illustrated in FIGS. 4-6 is reinforced with discrete filaments 52 aligned generally parallel to the longitudinal direction of the web prior to its incorporation into the fabric 40 so as to impart strength to the web ply. Synthetic filaments, particularly those which possess thermoplastic properties such as the polyester and polyamide resins in filament form, have been found suitable as reinforcements. Mineral filament, such as glass filaments, provide strength when employed as reinforcements but lack the degree of stretchability displayed by the resin filaments. Each filament 52 of a given ply is preferably spaced apart from adjacent filaments within the same ply without interfilament contact, but a filamentary mat having entanglement or Contact between the individual filaments thereof, such as an expanded tow web, is likewise suitable for reinforcing the web ply. In any event, the reinforcing filaments 50 of a web ply are bonded to the respective web ply to insure the desired enhancement of the web strength. This bonding is accomplished by means of an adhesive 54 disposed between the web and filaments, or in some instances, the filaments are heat-bendable to the web so as to require only the application of heat to effect the desired bonding.
In one method for bonding the individual filaments 52 to a base web, the individual filaments are passed over a smooth-surfaced printing roll which is provided with a film of adhesive on its outer surface so as to transfer a quantity of adhesive from the roll to each filament. Preferably, the thickness of the film on the printing roll is maintained sufficiently great so that a filament passingover the roll in contact therewith will be completely covered with adhesive and pick up a uniform coat of adhesive. The adhesive-bearing filaments are laid down, preferably in a continuous fashion, upon a base web and subsequently directed to a heating station maintained at a temperature at least as high as the film-forming temperature of the adhesive to insure that the adhesive thoroughly coats each filament and also to cause the adhesive to migrate from each filament into the web. As the web and adhesive-bearing filaments pass through the heating station, the adhesive is at least partly dried and filaments adhered to the web.
Adhesive migration laterally from each filament and contact between the adhesive and individual fibers of the web is depicted in FIG. 7. Preferably, the adhesive is of a type which will not penetrate the fibers to destroy their absorptivity but will remain as a film on the portion of the outer fiber surface. Moreover, control over the quantity and viscosity of the adhesive deposited on each filament is maintained so as to limit the lateral migration of the adhesive and prevent substantial blocking of the interstices between fibers with resultant stiffness in the fabric and destruction of its softness and absorptivity. A film of adhesive over the entire surface of each filament assures that presence of adhesive at each filament-to-filament intersection when the reinforced web is bias-laid, and hence insures a bond at each such intersection. One suitable adhesive is an acrylic latex adhesive sold by B. F. Goodrich Company under the trade name of Geon Latex.
The individual reinforcing filaments 52 preferably are generally aligned in a single direction and are bonded to their respective web ply with their alignment direction substantially parallel to the machine direction of the creped tissue web ply. The filaments thus are disposed generally perpendicular to the lines of creping 56, 58 of their respective web ply. The reinforcing filaments thus reinforce the creped tissue and strengthen it in its machine direction. When the reinforced creped tissue subsequently is overlaid upon itself or upon another reinforced web with the respective directions of increased strength disposed obliquely to each other, and obliquely to the longitudinal direction of the fabric product, the resultant multi-ply fabric exhibits generally omnidirectional improvement in strength. The fabric 40 (see FIG. 4) is divided transversely thereof as at lines D, E, F and G into cover sheets 24 for individual diapers.
The omnidirectionally improved strength of the fabric is transferred to a diaper when the fabric is used as the cover sheet of the diaper in the manner disclosed herein. When the cover sheet 24 is folded about the pad 22 to envelop the pad and form a diaper of rectangular outline, the strong reinforced longitudinal directions of the web plies of the cover sheet are aligned at angle to the longitudinal and transverse directions of the resultant diaper, thereby developing a diaper which is of generally omnidirectionally improved strength. Specifically, the cover sheet of the resultant diaper is divided into many relatively small interconnected squares or diamond-shaped regions 60 (FIG. 6) whose peripheries are defined by the cross linear reinforcements 52. The reinforcements are bonded to one another at their crossings and to at least their adjacent web ply. Substantial area of fibrous web ridges each such square or diamond-shaped region 60, the individual fibers of such web region being bonded to a reinforcement as by an end of a fiber being joined to a reinforcement, leaving substantial portions of the fibers free to work as the diaper is stressed first in one direction then in another direction as a child moves. The fibers are held against separating when stressed beyond their ability to remain interlocked within the web by reason of .the strong interconnected reinforcements to which the fibers are bonded. Because individual ones of the reinforcements extend at angle to both the longitudinal and transverse direction of the diaper, the diaper itself exhibits improved resistance to rupture when stressed at an angle to its longitudinal or transverse direction. When the diaper is stressed in a direction generally parallel to its longitudinal or transverse direction, the interconnected reinforcements articulate about their bonded crossings and combine in function to reinforce the diaper in these latter directions, thereby providing a diaper which strongly resists rupture irrespective of the directionality of the applied stress. When a diaper is pinned in position on a childs body and the child subsequently engages in normal body movement and activities, the diaper is subjected to stresses in many and varied directions. These stresses, of course, also vary in magnitude over a wide range. In the present diaper, the reinforcements extend into all areas of the diaper to provide strength in each area of the diaper. Accordingly, the present diaper resists splitting in the crotch area by reason of the reinforcements which extend at angles to the longitudinal and transverse directions of the diaper. These reinforcements and their generally omnidirectional strengthening effect extend also into all other areas of the diaper such as in the pinning areas where the diaper v is strengthened against tears and resultant falling away of the diaper from the child. The present diaper, therefore, is strong in all areas thereof with its strength being exhibited in many directions to withstand the many and varied stresses to which it is subjected during normal use.
Preferably, the reinforcing filaments 52 are sufficiently small in diameter as will permit their being disposed between two outer web plies 44, 46 without producing undesirable ridges or impressions on the outer surfaces of the fabric. Larger diameter filaments may be used with an accompanying degradation in surface characteristics. Nylon filaments each of about 40 denier have been found satisfactory as reinforcing filaments for creped tissue webs of the kind referred to hereinbefore. Such nylon filaments normally exhibit an extensibility of about 8 percent thereby imparting a degree of elasticity to the strengthened diaper and causing it to more nearly exhibit the desirable extensibility found in the woven diapers and which contributes to the soft hand of the diaper. Less elasticity is obtainable through the use of mineral fibers or certain of the organic synthetic fibers but the resultant diaper posseses a less desirable hand. A diaper having a cover sheet fabricated from creped tissue webs reinforced with nylon filaments as disclosed herein exhibits extensibility and strength characteristics which indicate that the creped webs initially absorb applied stress by extending toward their uncreped lengths. The stronger nylon filaments initially stretch with the creped webs but before the webs reach their rupture stress, the nylon filaments assume the stress and prevent failure of the diaper.
As illustrated in FIG. 7 and described hereinbefore, many of the individual fibers 62, 64 of the respective web plies are adhered to the respective reinforcing filaments 52 which are bonded to the respective web plies. As indicated above, preferably the aligned reinforcing filaments are spaced apart from one another on a respective web ply. The filaments, however, are sufficiently close to one another to permit many of the fibers of the respective web ply to be bonded to the filaments. In one embodiment, the interfilament spacing is not greater than of the order of the typical fiber length of the fibrous web ply plus about twice the average distance which the adhesive extends laterally of each filament into the web ply. Thus substantial numbers of individual fibers of a web ply will be adjacent at least one of its reinforcing filaments and be bonded thereto, creating a desirably coherent fabric. Creped tissue webs provided with between about 5 and 10 40-denier nylon filaments per inch of web width are sufficiently reinforced for producing a diaper having the strength referred to herein and provide sufficiently closely spaced filaments for anchoring many of the fibers of the web. As a result of the preferred fiber to filament bonding pattern, the fibers remain secured to a filament even when the fiber to fiber interlocking bond is broken due to overstressing of the diaper beyond the tensile strength of an individual web ply. Consequently, when the diaper becomes wet and is stressed locally by the childs movements, fibers which are caused to separate from other fibers in their respective web do not become dislodged from the diaper but instead are retained, attached to a filament. The surface of the diaper thus does not fragment with the deposition of fibers on the child or upon floors, bedding or the like. Since many of the individual fibers of a tissue web ply are bonded to at least one of a plurality of the reinforcing filaments, the individual fibers remain adhered to such filaments upon the fabric 40 being subjected to rupture or abrasive forces. As noted above, the individual fibers of each tissue web ply tend to remain attached to the reinforcing filaments even when the diaper is wet.
It is preferred to space the reinforcing filaments 52 as set forth above, but fabrics having fewer reinforcing filaments per unit of web width are acceptable in certain instances. Such fabrics are weaker, however, and exhibit increased tendency to deposit lint, etc. Moreover, it is acceptable to overlay two reinforced web plies, one web ply having closely spaced reinforcing filaments (e.g. about one fiber length apart) and the other web ply having more widely spaced filaments.
In accordance with a further aspect of the invention, the outer web plies of the cover sheet fabric are each reinforced in their respective longitudinal directions by means of a plurality of lines of thermoplastic matter. These lines of thermoplastic are similar to the individual filaments 52 described hereinbefore in that preferably they are disposed on each of the web plies and the reinforced web plies are superposed with the thermoplastic lines facing each other and crossing one another at an angle, the several plies being bonded to at least adjacent plies to develop a coherent fabric whose reinforced plies are oriented at an angle to each other and at angle to the longitudinal and transverse directions of the fabric as is shown in FIGS. 4-7 in connection with filamentary reinforcements.
One method for manufacturing a fabric reinforced with lines of a thermoplastic includes printing a plurality of continuous lines of thermoplastic such as a polyvinyl chloride onto a creped tissue web of the kind described hereinbefore as the web is fed forwardly between the nip between a smooth roll and a printing roll having a plurality of thermoplastic-bearing circumferential projections on its exterior surface so as to transfer the thermoplastic to the tissue web in the form of a plurality of generally parallel lines of thermoplastic extending along the longitudinal direction of the web. The preferred lines of thermoplastic are of the order of 0.050 inch in width. Preferably, about grams of the thermoplastic are picked up on each 100 grams of web when printing five lines of thermoplastic per each inch of web width. Whereas five lines of thermoplastic per inch of web width is preferred, other lateral spacings are suitable, as are other rates of thermoplastic pickup, consistent with maintaining the desired tactile properties in the product, particularly its hand, strength and absorptivity.
The thermoplastic, when applied to the web in its liquid state, is solidified as by curing or drying as appropriate for the chosen thermoplastic. Because the thermoplastic is heat-bondable, the biased superposed web plies having their respective plies of thermoplastic facing inwardly of the multi-ply product, are bonded in their mutually angular orientation by passing the superposed plies through a heated nip to enhance the adhesion of the fibers of the webs to the lines of thermoplastic. The reinforced web may be overlaid on itself or another reinforced web as described hereinbefore. The lines of thermoplastic on the overlaid webs are bonded to each other at their crossings as by passing the overlaid webs through a set of heated nip rolls. The bonded reinforced webs provide a coherent fabric useful as a diaper cover sheet as noted before. The strength of this latter described fabric when incorporated into a diaper as a cover sheet, is normally less than the strength of diapers having cover sheets whose web plies are reinforced with filaments; however, the thermoplastic reinforcing matter is less expensive and is useful in producing diapers which exhibit many of the desirable properties referred to hereinin connection with filament-reinforced diapers.
in the illustrated fabrics, the reinforcing matter of the respective reinforcing plies are bonded to their respective web plies and the reinforcing matter of one ply is bonded to the reinforcing matter of the other ply at the points where the reinforcements cross. This bonding at the cross-overs securely interconnects the reinforcements, and consequently their respective web plies, at spaced points throughout the respective fabric to develop a network of crisscrossing strengthening elements within the fabric which makes the fabric much stronger with less bulk than if an equal number of web plies were laminated. Being bonded to one another at only their crossings, the strengthening reinforcements articulate about their crossover bonds to give the laminated fabric flexibility which carries over into the diaper causing it to display many of the tactile properties of a cloth diaper. Contrary to certain prior art diaper constructions wherein the components con-.
tributed significantly toward increasing the weight and bulk of the fabric and the resultant diaper, the multi-ply fabrics disclosed herein comprise a combination of tissue webs, each having a substantially continuous surface for reasons of hand, integrity and pleasing appearance, and a plurality of reinforcing plies preferably disposed between the web plies and strengthening the web plies without undesirably adding to the weight, stiffness, and bulk of the diaper. As disclosed, the spaced-apart reinforcements of each reinforcing ply reinforce the web plies while leaving significant areas of tissue between reinforcements free of reinforcing matter. Accordingly, the illustrated reinforced fabric strengthens the diaper in its several directions as has long been desired, but does not adversely affect the drape and hand characteristics thereof. In addition, the expanses of tissue web between the reinforcements are substantially free of adhesive and the fibers of the web in such regions readily accept liquid exudate and rapidly transmit the liquid matter to the absorbent pad of the diaper where it is retained. The illustrated reinforced cover sheet provides the desired improvement in strength and tactile properties while employing a minimum number of web plies thereby reducing any tendency toward blocking the transfer of liquid exudate to the internal absorptive pad by the more dense web plies, particularly when such web plies are multi-plies excessively. Economically, the present diaper is stronger and has good absorptivity while utilizing less raw material in its manufacture.
The absorptive pad 22 of the diaper 10 illustrated in FIG. 3 is of constant cross section throughout its longitudinal length. To enhance an efficient reception and retention of body fluids, the pad 22 in the exemplary embodiments of FIGS. 8 and 9 each are provided with a non-uniform cross-sectional configuration having the longitudinally extending portion 66 of greater thickness than flanking side portions 68, 70. For example, the central portion 66 is approximately one-quarter inch in thickness while the outer portions 68, 70 are approximately one-eighth inch in thickness. Thus, the central portion has an increased fluid retaining capacity as compared to the central portion of a pad of uniform cross-sectional configuration and, generally speaking, fluid will flow to the side edges of the diaper only when this capacity is exceeded.
In the preferred diaper 10, the childs skin is protected against lint emanating from the wood pulp pad 22 by the bias laid cover sheet 24. Also, the cover sheet protects against the loss of fluid and absorbent pad material which tends to disintegrate when wetted. As large quantities of fluids are received over a short period of time, they rapidly penetrate the upper central portion 12 of the cover sheet and are absorbed and spread by the pad 22. The wing folds 14 and 16 form effective seals about the childs legs and thereby prevent the escape of fluid from about the childs legs. The lower portion of the bias laid cover sheet also assists in preventing the fluids from striking through the diaper. Because of the increased strength provided by the bias laid cover sheet the diaper is protected against failures which reduce the effective absorptive capacity of the diaper. Thus by assuring against failures, the amount of absorbency can be closely approximated and it is possible to eliminate excessive fibers or plies of material heretofore added to increase the diaper strength.
Whereas suitable diapers have been made using pads of loosely felted wood fibers, enhanced lateral distribution of body fluids has been accomplished by embossing a plurality of intersecting channels '72 in the pad 22, preferably prior to enveloping the pad with the lll cover sheets as shown in FIG. 2. Alternatively, the diaper is embossed with such intersecting channels after the side edges of the cover sheet have been folded inwardly to overlie the pad and prior to folding of the wing folds 14, 16. Body fluids received in the diaper flow along the channels 72 in bulk quantities thereby rapidly distributing the fluids to the absorptive pad and causing the fluids to be quickly taken up by the pad.
A still further feature of the diaper disclosed herein includes selective disposition of the absorbent cellulosic matter within the diaper for controlling the flow of exudate within the diaper. In accordance with this additional feature, the highly absorptive pad 22, e.g. cellulosic fluff, is restricted to those areas of the diaper which are adjacent to the point of exudate discharge, that is, the fluff is eliminated from the margins of the diaper, thereby restricting the dispersion of the exudate to the central area of the diaper. A diaper having this kind of pad is shown in FIG. 8. Sufficient absorptive fluff is provided in such central area 66 for receiving and retaining the anticipated exudate. The reduction of absorptive capacity brought about by removing fluff from the diaper margins is compensated by increasing the quantity of fluff in the central region of the diaper as desirable. In the margin areas of the diaper from which fluff is eliminated there is no vehicle other than the cover sheet 24 for the transport of liquid exudate into the margin areas and they remain relatively free of liquid and retain their relatively greater dry strength, resulting in a stronger diaper. Also in these areas of little or no fluff or other highly absorptive matter, there is a reduction in the quantity of exudate which is transferred to these areas and resultant less leakage or strike-through of liquid matter in these areas. When the usual fluff pad is eliminated in at least the top fold of each of the longitudinal wing folds of the diaper, thus limiting the flow of liquid exudate into these areas, there is an accompanying reduction in the tendency of the diaper to leak in the leg areas and less likelihood that a wet margin of the diaper will contact and transfer moisture to items of outer clothing or bed clothes.
Alternatively or in addition, the absorbent fluff is eliminated from the ends of the diaper, that is, in the region often referred to as the belley band of the diaper. Here again, the absence of fluff reduces wicking, hence wetness, in the belly band and limits the leakage of exudate in this area. The degree of wetness of the diaper in the belly band is particularly important when the diaper is worn by a child who is in a reclined position where soilage of bed covering or the childs clothing could occur upon leakage of exudate. The reduction of wetness in the belly band area also permits retention of the relatively greater dry pinning strength of the cover sheet in this area. With reference to the diaper pinning strength, because of the increased strength provided by the bias laid cover sheet, employed in the present diaper, particularly at an angle of about 45 to the transverse direction of the diaper, the ends of the diaper may be fastened relatively tightly and securely about the babys waist by conventional fasteners such as safety pins and, even when wet, the bias laid cover sheet protects against failures occasioned by inordinate stressing of the diaper in the pinning areas. Accordingly, in the illustrated diaper there is less of the annoyance and frustration which heretofore accompanied many of the prior art disposable diapers due to their failure because of low pinning strength.
The diaper disclosed herein, having a reinforced bias laid cover sheet, is made more resistant to the strikethrough of liquid exudate to the outer surface of the diaper by providing an internal moisture barrier 74 within the diaper as illustrated in FIG. 9. A preferred barrier 74 is a thin sheet of a plastic such as polyethylene, the impervious plastic precluding leaking or moisture transmission from the fluff pad through the cover sheet. Accordingly, this barrier sheet is preferably dimensionally coextensive with the fluff pad and disposed between the pad 22 and cover sheet 24. In those diapers where a carrier sheet is used, the barrier preferably is disposed between the carrier sheet and the cover sheet.
Contrary to the harsh plastic outer liners heretofore used in disposable diapers, the present plastic sheet moisture barrier is disposed fully within the enveloping fibrous cover sheet. Accordingly, the childs body is not exposed to the irritating effects of the plastic and the diaper is more pleasing to both the child and mother. The fabric cover sheet of the present diaper provides a soft surface for contacting the child but exudate discharged into the diaper is held within the diaper by the absorptive matter and the impervious sheet. The inner plastic liner is notably useful in preventing strikethrough of exudate to the outer surface of the diaper. When a child sits, lays, or falls to a sitting position, etc., its body presses the diaper against the supporting surface. If the diaper is wet, under such circumstances there is a significant hydrostatic pressure developed which forces liquid through the diaper such as would not occur by the usual wicking and absorption mechanisms. The liquid impervious sheet disposed between the fluff pad and cover sheet of the present diaper blocks this movement of liquid toward the outer surface of the diaper as a consequence of hydrostatic pressure.
Another useful barrier sheet material is a tissue web having a water-repellent included therein. In this diaper assemblage there is a controlled transfer of moisture to the outside of the diaper which becomes damp rather than wet after a relatively extended period of use. This damp condition signals that the diaper has not utilized its full capacity and is more than adequate to the job. But more importantly, the damp diaper as distinguished from a wet diaper, eliminates the unpleasantness of handling a diaper that is soaking wet on the outside. In addition, this assemblage offers the convenience of putting a soiled diaper down without worrying about contaminating the bed, furniture, floor covering or any other surface where a diaper must temporarily be placed during the process of replacing a soiled diaper. Still further, a soiled diaper which is merely damp on the outside, as opposed to being soaking wet, provides greater pleasantness and/or peace of mind which comes from removing a diaper which does not feel wet on the outside.
While the present description has included specific examples and embodiments, it will be understood that there is no intent to limit the invention by such disclosure, but, rather, it is intended to cover all modifications and alternate constructions falling within the spirit and scope of the invention as defined in the appended claims. What is claimed is:
1. A disposable diaper of rectangular outline having longitudinal and transverse dimensions comprising a pad of absorbent matter, a cover sheet encompassing said pad to form an encompassed assemblage, the opposite side margins of said encompassed assemblage being folded along longitudinal fold lines inwardly toward the longitudinal centerline of said assemblage and further folded along longitudinal fold lines back upon themselves to define wing folds extending along the opposite side edges of said diaper, said cover sheet comprising laminated nonwoven fabric having longitudinal and transverse directions including a first web ply, a first ply of discrete linear reinforcements aligned generally in the longitudinal direction of said first web ply and bonded thereto to reinforce it in its longitudinal direction, a second web ply, a second ply of discrete linear reinforcements aligned generally in the longitudinal direction of said second web ply and bonded to said second web ply to reinforce it in its longitudinal direction, each of said web plies comprising creped tissue having a basis weight between about and about l0 pounds per 2,880 square feet and a crepe ratio between about 1.2 and about 1.5, said first and second web plies being bonded together and disposed with their longitudinal directions crossing each other and directed obliquely with respect to the longitudinal and transverse directions of said fabric, said reinforced directions of the respective plies of said fabric being disposed at angle to the longitudinal direction of said diaper, said reinforcements being spaced apart on a respective web ply by a distance about twice the usual fiber length of the fibers of said webs and extending into substantially all areas of said diaper and being bonded one to another at their crossings to develop a system of interconnected reinforcements defining regions between adjacent interconnected filaments encompassing fibers therein which are bonded to not more than one reinforcing filament leaving substantial portions of such fibers free to work as the diaper is stressed.
2. The disposable diaper of claim 1 wherein said pad of absorptive matter terminates inwardly from the side edges of said cover sheet by an amount such that when said encompassed assemblage is folded into wing folds from the side edges of said cover sheet said pad is included in the first fold of each wing fold and the upper fold of each of said wing folds is free of said pad thereby reducing the transport of fluid exudate into said upper fold.
3. The disposable diaper of claim 1 wherein said linear reinforcements are extensible and when said diaper is stressed, said creped webs extend to absorb the initial stress and said linear reinforcements assume the stress as the webs approach their rupture stress,
tive web. I
5. The disposable diaper of claim 1 wherein said quantity of absorptive matter terminates inwardly from opposite ends of said diaper to leave said encapsulating cover sheet free of such absorptive matter in the regions thereof which encircle the waist when said diaper is worn.
6. The disposable diaper of claim 1 and including a moisture barrier substantially coextensive in length and breadth as said absorptive matter and interposed between said absorptive matter and said cover sheet on that side of said absorptive matter opposite the side thereof which receives liquid exudate.
7. The disposable diaper of claim 6 wherein said moisture barrier is impervious to fluid body exudates.
8. The disposable diaper of claim 7 wherein said moisture barrier comprises a plastic sheet.
9. The disposable diaper of claim 6 wherein said moisutre barrier is pervious to air to permit significant transfer of air therethrough and limitedly pervious to liquid body exudates thereby restricting the transfer of such exudates whereby said cover sheet receives a limited amount of wetting during the interval between a period of discharge of body exudate into the diaper and its subsequent removal from the body of the wearer and does not become wet to the touch.
10. The disposable diaper of claim 9 wherein said moisture barrier comprises a cellulosic sheet including a water repellent.
11. The disposable diaper of claim l and including an adhesive bonding said plies one to another in superposed relation.
12. The disposable diaper of claim 1 wherein said filaments are thermoplastic and said plies are bonded one to another by heating said filaments while said plies are in superposed relation.
13. The disposable diaper of claim ll wherein said filaments comprise nylon of about 40 denier per filament.
14. The disposable diaper of claim 1 wherein said plies of linear reinforcements each comprise a plurality of spaced apart lines of a thermoplastic which are aligned generally parallel to the longitudinal direction of the respective web ply.
15. The disposable diaper of claim 14 wherein said lines of thermoplastic are spaced apart of the order of five lines per inch of web width.
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|U.S. Classification||604/366, 604/371, 604/378, 604/375|
|Cooperative Classification||A61F13/49406, A61F13/53418|
|European Classification||A61F13/534B2, A61F13/494A|