US3757785A - Airfelt diaper with short fiber material in the pinning area - Google Patents

Abstract

A diaper wherein the absorbent body is of low tensile strength, e.g., airfelt, and the absorbent body extends throughout the pinning area, wherein the airfelt material in the pinning area has an average fiber length of from about 0.5 mm. to about 0.9 mm. so that those fibers do not accumulate on a pin as the pin tip moves through the absorbent body during pinning of the diaper.

Description

United States Patent 11 1 1111 3,757,785 Wosaba, II Sept. 11, 1973 [54] AIRFELT DIAPER WITH SHORT FIBER 3,426,756 2/1969 Romanek 128/287 MATERAL IN THE PINNING AREA 3,444,859 5/1969 Kalwaites..... 128/284 3,523,536 8/1970 Ruffo 128/287 lnvemorl Charles Wosaba, ll, p gfi 3,682,761 8/1972 Lee et al 128/284 Township, Hamilton County, Ohio [73] Assignee: The Procter & Gamble Compan Primary ExaminerCharles F. Rosenbaum Cincinnati, Ohio Attorney-Richard C. Witte et al.

[22] Filed: Dec. 9, 1971 211 App]. No.: 208,043 [571 ABSTRACT A diaper wherein the absorbent body is of low tensile 52 us. (:1. 128/287 Strength aide, absmbem extends 51 1m. (:1. A6lf 13/16 throughout the Pimmg area wherein the aide" male- [58] Field of Search 128/284 286 287 rial the Pinning area has an average fiber length of 2 6 from about 0.5 mm. to about 0.9 mm. so that those fibers do not accumulate on a pin as the pin tip moves [56] References Cited through the absorbent body during pinning of the dia- UNITED STATES PATENTS 3,180,335 14/1965 Duncan et a1. 128/287 3 Claims, 4 Drawing Figures PATENTEU SEN I 1975 INVENTOR. Charles L. Wosubo,11 BY W6, (92A ATTORNEY AIRFELT DIAPER WITH SHORT FIBER MATERIAL IN THE PlNNllNG AREA FIELD OF THE INVENTION This invention relates to diapers and diapering systems for infants, and more specifically, to diapers having absorbent bodies wherein there are substantially no bonds between the fibers of the absorbent body.

BACKGROUND OF THE lNVENTlON Disposable diapers are now well known and the absorbent body within such diapers is generally of two types, i.e., paper wadding or airfelt (fluff made typically from coniferous bleached Kraft wood pulp, hereinafter referred to as wood pulp).

The wadding used in disposable diapers is generally a creped cellulose wadding as described in detail in U.S. Pat. No. Re. 26,151, Duncan et al. reissued Jan. 31, 1967. This wadding is made on typical paper making machines whereby the individual fibers comprising the wadding are bonded together by what is generally referred to as hydrogen bonding. The bonding between juxtaposed fibers in wadding gives tensile strength to the wadding, albeit the tensile strength is not the same in all directions. This bonding between adjacent fibers also gives removal resistance to each individual fiber within the wadding in that a fiber is attached in one or more locations along its length and any force exerted upon the fiber is resisted by the tensile strength of the fiber and the strength of those bonds holding the fiber. Therefore, although a pointed probe, such as a diaper pin, encountersresistance while piercing the wadding, the individual fibers encountered by the pin do not accumulate on the tip of the pin because of two phenomena attributable to the tensile properties of bonded individual fibers, i.e., individual fibers slip off or out of the path of the tip of the pin and individual fibers impaled on the tip of the pin are severed by the force exerted on the pin. Thus, the fibers encountered by the tip of the pin are disposed of as the pin progresses through the wadding.

The airfelt used as the absorbent medium in disposable diapers has advantages in that airfelt is a good fluid absorbent, bulky, resilient and economically advantageous by nature, but certain real problems have been and are encountered in incorporating the advantageous aspects of such airfelts in disposable articles. These problems result from the inherent flimsy nature of a fibered airfelt in that these airfelts have little or no inherent tensile strength. its lack of tensile strength arises from the fact that no bonding exists between adjacent fibers comprising the airfelt. Airfelt is typically formed by comminuting wood pulp fibers and delivering these comminuted wood pulp fibers by a stream of air to a porous receiving medium whereon the airfelt pad is built-up. The process of making airfelt does not foster bonds between adjacent fibers in the airfelt pad.

The tip of a diaper pin encounters individual fibers as it passes through an airfelt pad just asit does in passing through wadding. But, unrestrained wood pulp fibers which are normally encountered in an airfelt pad (1.5-5 mm. long) accumulate on the tip of the pin due to the lack of bonding between these fibers in airfelt and their ability to drape over the pin tip. The accumulation of fibers continues at an ever increasing rate as the pin progresses through the airfelt pad because the tip passing through the diaper becomes broader and broader with the buildup of accumulated fibers, resulting in a ball of fibers accumulated on the tip of the pin. Therefore, when the pin tip exits the side opposite its entrance, it rips out a large section of the airfelt pad. Fibers in an airfelt pad are not automatically stripped from the pin tip as it is pushed through the pad because unbonded fibers do not have sufficient tensile properties to either slip off or out of the path of the pin tip, or induce tension within a fiber impaled on the pin tip in order that the force behind the pin can sever that iiber. Thus, we see there is an inherent problem associated with pinning through an airfelt absorbent pad.

One approach in solving the inherent problem of pinning through an airfelt pad is exemplified by U.S. Pat. No. 3,295,526, issued to Sabee Jan. 3, 1967 wherein the airfelt pad stops short of the longitudinal ends of the diaper which are defined by the extension of the top and back sheet attached thereat to form a waist band which is adapted to be joined by pins and in which the top and back sheets are attached without having any absorbent material between them to reduce the bulk and resistance to pinning of the waist band. This reference teaches using airfelt as the absorbent material in a disposable diaper and eliminating all absorbent material from the pinning areas of the diaper in orderto escape the problem of pinning through an airfelt pad.

The approach taught by the Sabee reference does indeed eliminate the balling problem associated with pinning a diaper wherein the absorbent material is airfelt, but there are disadvantages associated with solving the problem in this manner. One of these disadvantages is that the pinning areas of the diaper appear and feel less substantial than the remainder of the diaper. If these pinning areas are large, they could be floppy, making them somewhat less easy to manipulate while pinning the diaper. Another disadvantage associated with the absence of absorbent material in the pinning areas occurs because a reduction of absorbent material in any area either reduces the absorbent capacity of the diaper or necessitates thickening the absorbent pad in other areas, which results in a bulkier, harder-to-handle diaper. A third disadvantage is the negative consumer impression created upon noting the lack of absorbent material throughout the diaper when he expects absorbent material throughout the diaper. He immediately jumps to the conclusion he is receiving less value because he did not get as much absorbent material.

OBJECTS OF THE INVENTlON Accordingly, it is an object of this invention to provide a disposable diaper which is easy to pin having an absorbent body without tensile properties and the absorbent body extending throughout the pinning areas.

Another object of this invention is to provide a disposable diaper, which can be pinned without creating a visual deficiency in the diaper, having an absorbent 7 does not push a ball of the absorbent material from the absorbent body out the side opposite the pin's entrance.

With more particularity, it is an object of this invention to provide a disposable diaper having an absorbent body of airfelt extending to the perimetric limits of the diaper and a thin waterproof backing sheet wherein said back sheet is not ripped by pinning the diaper in its pinning areas.

It is a further related object of this invention to provide a disposable diaper as above-mentioned which feels relatively uniform throughout and does not have an area wherein the absorbent material is reduced to a level disagreeable to consumers.

SUMMARY OF THE INVENTION In accordance with the present invention there is provided a diaper comprising an absorbent body of nonbonded fibers contained between a superposed top sheet and one other web which have substantial strength when wet, said diaper being adapted to be pinned through the absorbent body to retain it in its operative position, the absorbent body being formed from fibers having an average length of from about 0.5 mm. to about 0.9 mm. in the pinning areas through which diaper pins are pierced during the pinning process.

BRIEF DESCRIPTION OF THE DRAWINGS While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which is regarded as forming the present invention, it is believed that the invention will be better understood from the following description taken in connection with the accompanying drawings in which the thickness of some of the materials is exaggerated for clarity and in which:

FIG. 1 is a perspective view of a diaper of the present invention, partially unfolded and partially broken away to show details of construction;

FIG. 2 is a section view taken along line 22 of FIG.

FIG. 3 is a fragmentary perspective view of the diaper of FIGS. 1 and 2 with all elements folded in their proper place and partially broken away;

FIG. 4 is a perspective view showing the form which the diaper of FIGS. 1 through 3 assumes in use.

While the invention will be described in connection with a preferred embodiment, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION Referring to the drawings, FIG. 1 illustrates a diaper 11 embodying the subject of thisinvention. The diaper 11 comprises a pad 12 comprising a body 13 of absorbent material having essentially no tensile properties and an overlying layer or top sheet 14. The diaper 11 has a length and width adapted to enclose the lower portion of the torso of an infant and has end areas 15 and 16 adapted to embrace the waist of the infant. An optional waterproof back sheet 17 is shown which can be made of a thin, flexible, plastic film of polyethylene, polypropylene, polyvinylchloride, or other suitable flexible material. The waterproof back sheet normally acts as a web having substantial strength when wet to support the absorbent body. The waterproof back sheet 17 is not necessarry to the practice of this invention in that the absorbent pad 12 can be used in conjunction with a separate pair of waterproof pants which would provide a barrier for accumulated fluids to prevent them from soiling either the infants clothes or anything else coming in contact with the infant. Should the diaper 11 be made without the back sheet 17, the receiving media 18 for the absorbent body 13 must be strong enough to contain the absorbent body in use. However, it is desirable to incorporate a back sheet 17 into a diaper 11 of this type because the diapering chore is then easier and quicker.

The back sheet 17 has a length and width preferably greater than the corresponding dimensions of the pad 12. The pad 12 and the back sheet 17 are united by fastening means, e.g., hot melt adhesive, along four areas. These areas of attachment, which need not be continuous, are on the top surface of the top sheet parallel to and near the edges of the pad 12 such as represented by the lines of adhesive 19 and 20 of FIG. 3 and on the back side of the pad 12 parallel to and near the ends of the pad as represented by the lines of adhesive 21 and 22 in FIGS. 1 and 2. The ends of the diaper 11 and its component parts are the termini of its longitudinal dimension whereas the edges of the diaper and its component parts are the termini of its lateral dimension. Pad 12, as shown in its preferred form in FIG. 1, comprises an absorbent body 13 of airfelt enclosed on one face and two edges by a porous, hydrophobic, nonwoven fabric top sheet 14 which has tensile properties in both its longitudinal and lateral directions. The top sheet 14 is preferably greater in its longitudinal dimension than the longitudinal dimension of the absorbent body 14 in order that the top sheet 14 can be wrapped around and folded under the end areas of the absorbent body 14. When the extra length is sufficient to overlap the pinning area, the advantages are detailed in the copending application of Kenneth B. Buell, Ser. No. 143,514 filed May 14, 1971 entitled AIRFELT DIA- PER WITH A FIBER STRIPPER MATERIAL IN THE PINNING AREA. Any fibers which adhere to the tip of the pin will be stripped off. However, in general, there is no need to overlap the pinning area with the diaper of this invention.

The absorbent body 13 used in the diaper of this invention is an airfelt material. Airfelt as used in this application is intended to refer to sheets which are formed from wood pulp fibers or similar cellulosic fibers by dispersing the fibers in an air or gaseous stream which deposits them on a moving, porous, receiving media such as tissue paper 18, shown in FIG. 1, to form minimally cohesive sheets or pads which have little or no inherent tensile strength. Airfelt lacks tensile strength because the individual fibers within the airfelt are not bonded to one another, therefore they are free to slide back and forth on one another. A force applied to one fiber is not transmitted to other fibers. The airfelt merely pulls apart rather than offering any tensile resistance to a force. Processes for the formation of airfelt pads are well known in the art as exemplified by the processes and apparatus of US. Pat. No. 2,618,8l6 issued to C. G. Joa on Nov. 25, 1962 and US. Pat. No. 2,689,985 issued to W. H. Burger et al. on Sept. 28, I954.

the glue. As can be seen from FIG. 3, the side panel extensions 25 and 26 must be folded over to the top side of the pad 12 in order that the bond along areas 19 and 20 is between side panel extensions 25 and 26 and top sheet 14. But bonding areas 19 and 20 are located close to the edges of the top sheet 14 to permit flapping movement of the side panel extensions 25 and 26.

The top sheet 14 may be any compliant, soft feeling, porous paper or non-woven fabric web which has a minimal tensile strength of about 500 grams per inch, preferably 800 grams per inch in both its longitudinal and lateral directions. An example of a non-woven fabric sheet which has been found-to function well on diapers of this invention is one which comprises 1.5 to 3 denier rayon and contains approximately 20-35 percent thermoplastic binder (as, for example, a copolymer of esters of acrylic acid such as is sold by the Rohm and Haas Company and identified as 3-1 and having a weight of about 15-19 grams per square yard. The tensile strength of such a non-woven fabric sheet incorporated in the preferred diaper is about 750 grams per inch in its longitudinal dimension (fabric cross machine direction) and about 2,400 grams per inch in its lateral dimension (fabric machine direction). Preferably, the wet tensile strength is at least 30 percent of the dry tensile strength in either direction. With absorbent body 13 dimensioned as set forth above, i.e., 12% inches wide by 16 inches long, an economically and functionally sized top sheet 14 may measure approximately 12% inches wide by about 24 inches long, preferably 18 inches long.

Thus, it is apparent that there has been provided, in

accordance with the invention, a disposable diaper having an airfelt absorbent body that fully satisfies the objects, aims, and advantages set forth above. While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alter natives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims.

What is claimed is:

1. A diaper comprising an absorbent body of nonbonded fibers contained between a superposed top sheet and one other web which have substantial strength when wet, said diaper being adapted to be pinned through the absorbent body to retain it in its operative position, the absorbent body being formed from fibers having an average length of from about 0.5 mm. to about 0.9 mm. in the pinning areas through which diaper pins are pierced during the pinning process, the basis weight of said absorbent body in the pinning areas being at least approximately 0.08 grams per square inch and less than approximately 0.25 grams per square inch.

2. The diaper of claim I backed by a thin flexible back sheet of waterproof material.

3. The diaper of claim 2 in which said absorbent body is comprised of air laid wood pulp fibers and said top sheet is a porous, non-woven material.

Claims (3)

1. A diaper comprising an absorbent body of non-bonded fibers contained between a superposed top sheet and one other web which have substantial strength when wet, said diaper being adapted to be pinned through the absorbent body to retain it in its operative position, the absorbent body being formed from fibers having an average length of from about 0.5 mm. to about 0.9 mm. in the pinning areas through which diaper pins are pierced during the pinning process, the basis weight of said absorbent body in the pinning areas being at least approximately 0.08 grams per square inch and less than approximately 0.25 grams per square inch.

2. The diaper of claim 1 backed by a thin flexible back sheet of waterproof material.

3. The diaper of claim 2 in which said absorbent body is comprised of air laid wood pulp fibers and said top sheet is a porous, non-woven material.

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