US3065751A - Disposable diaper - Google Patents

Description

E. GoBBo, sn., ETAL DISPOSABLE DIAPER Filed May 27, 1959 Nov. 27, 1962 United States Patent Ohice 3,065,751 DISPSAELE DIAPER Edward Gobbo, Sr., East Brunswick, Nicholas D. Lincoln, @ld Bridge, and Joseph J. Sepkoslri, Plainfield, NJ., assignors to Chicopee Manufacturing Corporation, a corporation of Massachusetts Filed May 27, 1959, Ser. No. 816,286 Claims. (Cl. 12S-287) The present invention relates to flat sheet-like disposable diapers which nor-mally are flat and rectangular in shape and are adapted to be disposed of after each use, more particularly to such diapers which comprise an absorbent layer of intermingled woodpulp fibers.

Disposable diapers comprising an absorbent layer of woodpulp `fibers have been made by depositing the fibers in the form of a sliver on a facing or collecting web and then cutting the web and the sliver at spaced intervals to provide diaper pads of a predetermined length. Normally, the woodpulp fibers in the pad are stabilized in some way to prevent them from becoming dislocated in the pad in use and in handling. Such diapers have been relatively bulky with the woodpulp layer more or less retaining the thickness of the original sliver. The libers in the sliver are relatively loosely assembled as would result from deposition of the fibers from an air stream.

Diapers of this type normally are designed to have a capacity of between about 15 and 20 iiuid ounces for a larger size diaper about 171/2 inches long and 13 inches wide and between about l0 and 15 ounces for a smaller size diaper about 14 inches long and 10 inches wide. Prior art woodpulp diapers having the desired capacity for a given area have been relatively bulky and less conformable to the shape of the wearer than competitive cloth diapers, for instance.

According to this invention, there is provided a woodpulp-filled disposable diaper having considerably less bulk, i.e., as little as one half the bulk of comparable prior art diapers, which surprisingly possesses increased flexibility and a high degree of conformability not possessed by prior art pads. ln addition, diapers according to this invention have greatly increased absorption efficiency, i.e., ability to distribute fluid in the plane of the diaper and thus assure that the total absorptive capacity of the diaper is used before undue concentrations of fluid occur. All of this is accomplished without seriously detracting from the total absorptive capacity of the diaper and with the same weight of woodpulp fibers.

We have found that if a diaper pad, comprising a layer of relatively loosely assembled woodpulp fibers contained between thin covering sheets having a negligible effect on the properties of the layer, is compressed in the direction of its thickness in such a way as to increase the bulk density of the pad at least about 50 percent, preferably 85 to 100 percent, or even more under certain conditions, so that the layer of woodpulp libers becomes compressed or densilied in a direction normal to the plane of the layer and the bulk density of the resulting woodpulp layer pad reaches between about 25 and 50 grains per cubic inch, the absorption efficiency and the flexibility of the layer is increased markedly without seriously detracting from the total absorptive capacity of the pad. This means that a diaper pad about 171/2 inches long and 13 inches wide will have a fluid capacity of between 15 and 20 fluid ounces after compression. We have found that best results are obtained when the woodpulp layer pad is between about 25 and 100 mils thick after compression. Thinner layers may not have the desired absorptive capacity, while thicker layers may tend to lose a greater proportion of their absorptive capacity upon being compressed.

henta/'si Patented Nov. Z7, 1962 It is preferred that the bulk density of the resulting compressed diaper pad be between about 30 to 4() grains per cubic inch in order to provide minimum bulk and loss of absorptive capacity with maximum flexibility and absorption efficiency. In the same way, to provide a maximum of the unexpected increased flexibility, it is preferred that the woodpulp pad be between about 40 and 60 mils in thickness. In these preferred ranges, the increase in the flexibility of the resulting compressed diaper pad may be about 55 to 70 percent of the flexibility of the original uncompressed woodpulp pad.

We have discovered that this surprising increase in flexibility of the pad does not continue indefinitely as compression is increased, but that after a certain bulk density of the pad is reached flexibility begins to decrease and eventually the pad begins to become somewhat stiff and board-like.

'Ihis invention will be better understood by reference to the following description and claims taken together with the drawings wherein:

FIG. l is a sche-matic partially cut-away plan view of a diaper according to one embodiment of this invention.

FIG. 2 is an enlarged schematic fragmentary sectional view taken along the line 2`2 of FIG. l.

FIG. 3 is an even more greatly enlarged schematic fragmentary sectional view showing one edge portion of a diaper according to a slightly different embodiment of this invention.

Referring to FIGS. 1 and 2 of the drawings, there is shown a flat sheet-like disposable diaper which comprises a flexible absorbent layer 11 of woodpulp fibers compressed in a direction normal to the plane of the layer. The woodpulp fibers used in the layer 11 are those which result from bleached soft wood kraft pulps and the like and typically are used for absorbent media. A thin permeable facing sheet 12 covers one side of the layer and a backing sheet 13 of the same material covers the other side of the layer and is adhered to the facing sheet along the edges of the pad. Opposite edges 14 of the sheet l2 are turned around corresponding edges of the layer 1li and glued or embossed to the adjacent edges of the backing sheet 13. A plastic backing 15 of a material such as polyethylene or vinyl film may be glued or otherwise adhered to the edges of the pad to provide a disposable diaper having a moistureproof backing.

The pad is embossed along spaced lines 17 through the covering sheets, i.e., the facing sheet l2 and the backing sheet 13, and through the woodpulp layer 11 to stabilize the woodpulp layer. The woodpulp layer 11 is adhered to at least one of the covering sheets 12 or 13 along the lines of embossing to provide the desired stabilization. If the facing sheet and/ or the backing sheet is of an intermittently bonded nonwoven fabric, the embossing may be in accordance with the teachings of Morin Patent No. 2,788,003. However, the facing and backing sheets 12 and 13 may be of tissue paper, such as 13-pound tissue. This means that a ream of the tissue, consisting of 480 24 x 36 inch sheets, weighs 13 pounds. If tissue alone is used to cover the woodpulp layer, it may be desirable to face the inside of the diaper with a thin but strong top sheet 16 of a nonwoven material such as described in Goldman Patent 2,039,312. Such an arrangement is shown in FIG. 3 wherein a nonwoven top sheet 16 is turned around opposite edges of the absorbent tissue covered woodpulp layer 11 and glued to the inside of the waterproof plastic backing film 15 adjacent the edges of the lilm.

The woodpulp layer has been compressed by applying pressure in the direction of its thickness so that its thickness is reduced while its length and width remain roughly the same. This results in a corresponding increase in the bulk density of the pad. The woodpulp fibers are densified in a direction normal to the plane of the layer While approximately retaining their relative positions in the plane of the layer.

The diaper pad of this invention may be used as a complete diapering unit, in which case it is preferred that a moisture-impermeable backing 15, such as that shown in the drawings, be employed; or it may be used as only one part of a diapering unit consisting of disposable pad and a waterproof panty and holder, for instance. In the latter case, a moisture-impermeable backing is not necessary.

Some properties of one embodiment of a diaper according to this invention will be illustrated in the following example.

Example I A disposable diaper pad is made from a layer of bleached soft wood kraft pulp by first enclosing the layer of woodpulp fibers between two sheets of 13-pound tissue and embossing the tissue in a pattern of spaced lines, as shown in the drawing, to stabilize the pulp. Compression of the pad occurring during embossing is negligible except along the lines of embossing. The pad at this point is about 171/2 inches long and 13 inches wide and between about 90 and 100 mils thick and has a bulk density of about 18.6 grains per cubic inch. Its flexibility is measured by a standard Gurley stiffness tester using the standard test procedure recommended by W. and L. E. Gurley, Troy, New York, the manufacturers, and is found to be 23 milligrams per grain of weight. This figure is obtained by applying standard Gurley conversion factors to the results obtained in measuring the stiffness of a sample of the pad l inch wide and 3 inches long. A cut end of the pad is 'immersed in a solution of brilliant blue acetate dye and water for a period of five minutes. Upon drying, the stained area is calculated and found to be approximately 61/2 square inches.

The pad then is placed in a Carver press and compressed in the direction of its thickness until its permanent bulk density is increased to about 34.2 grains per cubic inch, representing about an 85 percent compression. The pad is removed from the press, and its new thickness and density is retained. The Gurley stiffness of the compressed pad is 14.7 milligrams per grain of weight, when measured in the same way, indicating a reduction in stiffness of about 36 percent or an increase in flexibility of about 55 percent. Further compression to a bulk density of about 85.7 grains per cubic inch causes the stiffness of the woodpulp layer to rise and give a Gurley reading of about 16 milligrams per grain of weight, indicating that the fiexibility of the pad has begun to decrease at this density.

A cut end of the pad, compressed to a bulk density of 34.2 grains per cubic inch, is tested in the solution of blue dye as described above for the uncompressed sample; and the stained area is calculated to be about 141/2 square inches, indicating an increase of an absorption efiiciency over the uncompressed sample of about 120 percent.

The total absorptive capacity of the diaper pad, compressed to a density of 34.2 grains per cubic inch, is decreased only about 9 percent from 18 fluid ounces to about 16.4 fluid ounces, still well within the desired range of l to 2() fluid ounces for a large size diaper about 171/2 inches long and 14 inches wide.

Having now described the invention in specific detail and exemplified the manner in which it may be carried into practice, it will be readily apparent to those skilled in the art that innumerable variations, modifications, applications, and extensions of the basic principles involved may be made without departing from its spirit and scope.

The invention claimed is:

1. A fiat sheet-like disposable diaper pad possessing a high degree of conformability, which comprises a stabilized fiexible absorbent layer of woodpulp fibers compressed in a direction normal to the plane of the layer, a thin permeable facing sheet covering one side of said layer and a thin backing sheet covering the other side of said layer, said pad being between about 25 and 100 mils in thickness and having a bulk density of between about 25 and 5() grains per cubic inch and a Gurley stiffness of less than about 20 milligram per grain of weight.

2. A fiat sheet-like disposable diaper pad possessing a high degree of conformability, which comprises a flexible absorbent layer of woodpulp fibers compressed in a direction normal to the plane of the layer, a thin permeable facing sheet covering one side of said layer and a thin backing sheet covering the other side of said layer, said pad being between about 25 and 100 mils in thickness and having a bulk density of between about 25 and 50 grains per cubic inch and a Gurley stiffness of less than about 2O milligrams per grain of weight, said absorbent layer being stabilized by spaced lines of embossing adhering at least one of said covering sheets to said layer along said lines.

3. A fiat sheet-like disposable diaper pad possessing a high degree of conformability, which comprises a fiexible absorbent layer of woodpulp fibers compressed in a direction normal to the plane of the layer, a thin permeable facing sheet covering one side of said layer and a thin backing sheet covering the other side of said layer, said pad being between about 25 and l0() mils in thickness and having a bulk density of between about 30 and 40 grains per cubic inch and a Gurley stiffness of less than about 20 milligrams per grain of weight.

4. A fiat sheet-like disposable diaper pad possessing a high degree of conformability, which comprises a fiexible absorbent layer of woodpulp fibers compressed in a direction normal to the plane of the layer, a thin permeable facing sheet covering one side of said layer and a thin backing sheet covering the other side of said layer, said pad being between about 25 and 100 mils in thickness and having a bulk density of between about 30 and 40 grains per cubic inch and a Gurley stiffness of less than about 16 milligrams per grain of weight.

5. A fiat sheet-like disposable diaper pad about 171/2 inches long and 13 inches wide and possessing a high degree of conformability, which comprises a fiexible absorbent layer of woodpulp fibers compressed in a direction normal to the plane of the layer, a thin permeable facing sheet covering one side of said layer and a thin backing sheet covering the other side of said layer, said pad being between about 25 and 100 mils in thickness and having a bulk density of between about 30 and 40 grains per cubic inch, a Gurley stiffness of less than about 20 milligrams per grain of weight, and a fiuid capacity of between about 15 and 2O fluid ounces.

References Sited in the file of this patent UNITED STATES PATENTS UNITE@ Smm@ www @WEGE CERTIHGZWE @iF @@RRUMN Patent No., 3O6575l November 27n 1962 Edward Gebbe@ et al@ It s hereby certified that error' appears in the above numbered patent requiring correction and that the seid Lettere Patent should read as corrected below.

Column 3 line 66I fer N140 m- 13 ma Signed and sealed this 2ML May 1963 EAL) :est:

.NEST w. SWIDER DAVID L. LADD '.esting Ufficer Commissioner of Patents

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