Patent US3967623 - Disposable absorbent pad

United States Patent im

Butterworth et al.

[in 3,967,623 [45] July 6, 1976

[54] DISPOSABLE ABSORBENT PAD

[75] Inventors: George A. M. Butterworth, Western Springs; Robert T. Elias, Downers Grove, both of 111.

[73] Assignee: Johnson & Johnson, New Brunswick, N.J.

[22] Filed: June 30, 1975

[21] Appl. No.: 591,747

[52] U.S. CI 128/287; 128/156;

128/284

[51] Int. CI.2 A41B 13/02; A6IF 13/16

[58] Field of Search 128/156, 284, 287;

264/56, 72, 88

[56] References Cited

UNITED STATES PATENTS

3,292,619 12/1966 Egler 128/156

3,344,789 10/1967 Arnold et al 128/287

3,399,672 9/1968 Crowe, Jr. et al 128/256

3,814,101 6/1974 Kozak 128/287

3,886,941 6/1975 Duane 128/287

3,916,447 11/1975 Thompson 128/287

Primary Examiner—Aldrich F. Medbery

[57] ABSTRACT

A disposable absorbent pad such as a diaper, sanitary napkin, underpad, surgical dressing or wipe, and the like, is made from a flexible, body fluid-impermeable backing sheet, a layer of absorbent material on the backing sheet, and a soft, body fluid-permeable facing sheet which overlies the absorbent material. The facing sheet is a perforate, substantially hydrophobic thermoplastic web having an integral fibrous or sueded outer surface. In addition to being useful as a separate entity the absorbent pad of this invention can also be incorporated into a disposable or limited use garment as an integral part thereof.

12 Claims, 4 Drawing Figures

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1 . 2

separate entities or as an integral part of a disposable or DISPOSABLE ABSORBENT PAD a limited use garment.

BACKGROUND OF THE INVENTION BRIEF DESCRIPTION OF THE DRAWING

This invention relates to disposable absorbent pads 5 In the drawing,

such as diapers, sanitary napkins, underpads, surgical FIG. 1 is a plan view showing a disposable diaper

dressings and wipes, and the like. embodying the present invention;

Non-woven, bonded, textile/pulp fabrics, hydrauli- FIG. 2 is a sectional elevation on an enlarged scale

cally-entangled and mechanically-bonded textile fiber taken along plane 2—2 in FIG. 1;

fabrics, and relatively thin, spun-bonded fabrics are the 10 FIG. 3 is a fragmentary sectional elevation on an

usual facing fabrics for disposable sanitary and conve- enlarged scale illustrating a further embodiment of this

nience products. Such fabrics should be relatively soft invention; and

and conformable, capable of extended contact with FIG. 4 is a fragmentary sectional elevation on an

external and internal body surfaces without causing enlarged scale illustrating yet another embodiment of

chafing or allergenic reactions, and also capable of 15 the present invention.

transmitting body fluids to a central absorbent core or DESCRIPTION OF PREFERRED EMBODIMENTS layer while maintaining skin dryness. However, such

facing fabrics are relatively expensive inasmuch as As illustrated in FIGS. 1 and 2, an absorbent pad of

synthetic polymeric materials must be first converted this invention such as disposable diaper 10 comprises

to textile filaments or fibers, and the synthetic or natu- 20 flexible backing sheet 11, absorbent panel 12 which is

ral textile length fibers must be further converted into a layer of fluffy absorbent material positioned on back

a web structure and mechanically, hydraulically, Or mg sheet 11, and facing sheet 13 which is a thermoplas

adhesively bonded to produce a facing fabric which tic web havin« fibrous outer surface 14> Durin8 use'

meets the aforementioned requirements. „ c surface 14 is in contact with the user of the abs°rbent

In order to minimize the cost of disposable sanitary 25 Pad" DiaPer 10 is also equipped with fastening tabs 15

and convenience products it is desirable to develop and 16 whlch c°mPrlse a pressure-sensitive adhesive

disposable absorbent pads which do not utilize a fabric- ayer on a ^Xlble back,n8 or The adhesive

type facing sheet yet which retain the above comfort layer on each tab is protected prior to use by removable

and conformably characteristics. ,n coverstnps 17 and 18 which are segments of paper or

U.S. Pat. No. 3,431,911 to Meisel discloses an absor- 30 similar web-like material bearing a suitable release

bent pad having a facing layer made of open-cell poly- comPound on the Sld?thereof ,n contact wlth the adhe

meric foam which is disposed over an underlying layer SWS a^er'j u i ■ u.n u

~e r\..-.A u u . * • i u c J * ■ Facing sheet 13 and backing sheet 11 usually are

of fluid abso bent material. However, foamed facing sub8tanjja„ coextensive and Je joined together about

layers are relatively bulky and tend to increase he 35 the peripheJy of pad 10 by thermal fusion, adhesive, or

overalld.mens.onsoftheabsorbentpad.Moreover.the ^ £hJcJwenient manner. If desired, absorbent

open-cell structure of the foam layer may cause unde- la e/0 anel 12 can be anchored to backing sheet 11

sirable reverse pumping action when an absorbent pad fe ' Qne £ more ,ue ,jnes ,„ A suitab]e backi sheet

of such type is compressed while being used In addi- materjal can fae ^ poiyethylene web imperme

tion foam surfaces do not have the desired surface 40 able to body fluids and about 0.001 inch thick. Another

aesthetics. „ .. , .. suitable sheet material for this purpose is a polyethy

U.S Pat. No. 3,665,921 to Stumpf discloses a dispos- lene terephthalate web having a thickness of about

able diaper having a liner made of a discontinuous Q Qqqj jncjj

sheet material bearing a plurality of individually- Absorbent panel 12 can be a fluffy batt cut from a

looped, textile length hydrophobic fibers embedded in 45 relatively loose web of non-woven fibers having a rela

the sheet material. However, such liners are relatively tively high absorptive capacity. Panel 12 usually is of a

expensive to manufacture and are not commercially rectangular configuration and somewhat smaller than

attractive as components of disposable items. backing sheet 11. Particularly suitable absorbent layers

SUMMARY OF THE INVENTION °J Panel£can be rnade^in accordance with the teachings

50 of U.S. Pat. No- 3,612,055 to Mesek et al.

The present invention contemplates an absorbent Absorbent panel 12 can also be a fibrous batt having

pad which does not utilize a facing fabric yet which an integral densified layer positioned on the backing

retains the desirable characteristics of a fabric facing sheet of the pad so that the densified layer adjoins the

material but at a reduced cost. The absorbent pad com- backing sheet. The densified layer has relatively higher

prises a flexible backing sheet impermeable to body 55 wettability and liquid retentivity than the rest of the

fluids, a layer, of absorbent material on the backing aforesaid batt and usually is formed by slightly moisten

sheet, and a soft, body-fluid permeable facing sheet ing one surface of the batt and thereafter compressing

which overlies the absorbent material. The facing sheet the moistened surface. The nature of the batt having an

is a perforate, substantially thermoplastic web having integral densified layer as well as the method of pro

an integral fibrous or sueded outer surface made up of 60 ducing same are described in detail in U.S. Pat. No.

elementary fibers, i.e., fibers having a mean length-to- 3,017,304 to Burgeni.

diameter ratio of less than 1000. A surface active Facing sheet 13 is a substantially hydrophobic theragent, such as the sodium salt of dioctyl sulfosuccinate, moplastic web provided with random or evenly-spaced can be deposited on or incorporated into the thermo- perforations or pores 20 sufficient in number to permit plastic web to control surface wettability and to pro- 65 a ready transport of excreted body fluids or exudates to mote liquid transport through the facing sheet. The absorbent layer 12. Additionally, facing sheet 13 is absorbent pads of this invention are useful for absorb- provided with soft, fibrous outer surface 14 which coming body fluids. The absorbent pads can be used as prises elementary fibers or tufts integral with and car3,967,623 ^

ried by the thermoplastic web. These fibers are much shorter than textile-length fibers and have a mean length-to-diameter ratio of less than 1000; usually the length of these elementary fibers is about % inch, or less. In this manner, a comfortable outer covering of 5 high liquid throughput capability and having a good, warm feel or hand is provided in contact with the wearer. At the same time fibrous outer surface 14 provides an effective barrier which prevents the protrusion of undesirable fiber ends from the underlying abosrb- 10 ent panel 12 through perforations 20 and obviates a potential source of discomfort to the wearer. Also, fibrous outer surface 14 permits air circulation adjacent to the wearer's skin and minimizes the possibility of skin degradation due to excessive moisture. 15

Hydrophobicity is desirable for facing sheet 13 in order to enhance comfort of the wearer by having a substantially dry contact surface between the wearer and the absorbent pad, yet from the standpoint of liq- 2Q uid transport through facing sheet 13, preferably at least portions thereof initially should be hydrophilic in character so as to initiate liquid flow to absorbent layer 12, especially when perforations or pores 20 in facing sheet 13 are relatively small. To this end facing sheet 25 13 can be treated with a surface active agent or mixtures thereof, for example, with the sodium salt of dioctyl sulfosuccinate (commercially available under the designation Aerosol OT), nonionic polyoxyethylene sorbitan monolaurate (commercially available under 30 the designation Tween 20), or the like, by spraying an aqueous solution of the desired surface active agent onto fibrous outer surface 14 and subsequent drying. The surface active agent can also be deposited on facing sheet 13 by means of a roller wet with an aqueous 35 solution of the surface active agent which is passed over inner surface 21 of facing sheet 13 so as to deposit the surface active agent in perforations 20 and on inner surface 21 while fibrous outer surface 14 retains its substantially hydrophobic character. In the alternative, 40 internal surfactants or wetting agents can be incorporated into the thermoplastic web during manufacture. Suitable wetting agents for this purpose Can be nonionic surfactants based on ethylene oxide, fatty alcohol ethers, ethoxylated adducts of propylene oxide with 45 propylene glycol, fatty esters or sorbitol and glycerol, and the like.

Thermoplastic facing sheets having a fibrous outer surface can be produced by applying a thickness of a molten thermoplastic polymer to a carrier web by a 50 doctor blade arrangement and thereafter passing the carrier web bearing the layer of molten or softened polymeric mass under a heated roller which fibrillates the exposed surface of the molten polymer layer by pulling or ripping polymeric filaments therefrom. An 55 air jet or a similar cooling gas stream is then impinged onto the resulting fibrillated surface to cool the polymeric mass below its softening temperature so as to produce an integral pile surface. The carrier web can be absorbent paper tissue which can be advantageously 60 utilized for liquid transport into the absorbent pad as will be discussed in greater detail hereinbelow.

Thereafter the produced thermoplastic web with a fibrous surface is slit, punctured, buffed, stretch-fractured, or otherwise mechanically worked to produce a 65 perforate web. Porosity of the thermoplastic web can also be produced by incorporating into the polymeric mass prior to web formation soluble particulate materi

als which are subsequently leached out, or by striking a plurality of random electric arcs therethrough.

Suitable thermoplastic polymers that can be utilized to produce perforate webs having at least one fibrous surface are polyethylene, polypropylene, polyvinyl chloride, polycaprolactam, polyamide, polyurethane, polyethylene terephthalate, mixtures of polyvinyl chloride and butadiene-acrylonitrile elastomers, and the like. The webs produced for use as facing sheets in accordance with the present invention usually are about 2 to about 20 mils thick.

Several other methods can also be utilized to produce a web having an integral fibrous or fiber-like surface. For instance, a precast thermoplastic film can also be passed over a smooth roller maintained at a temperature sufficiently high to melt the surface layer of the film in contact therewith which molten surface layer is subsequently ripped from the roller so as to fibrillate the surface layer as described hereinabove.

The foregoing methods of producing a thermoplastic web with a fibrous surface are disclosed in U.S. Pat. No. 3,708,565 and British Pat. No. 1,139,165. Moreover, a scrim or the like can be coated with a molten polymer to provide a self-supporting web which is subsequently fibrillated as described above on one or both sides of the web to provide a fibrous surface and then perforated. Fibrous surfaces on one or both sides of the facing sheet permit the use of relatively large slits in the facing layer while providing an effective retaining screen even for relatively short fibers or linters present in the absorbent layer, thereby preventing dusting. Such a retaining screen is particularly desirable when particulate superabsorbent materials such as the socalled hydrocolloids or hydrogels are also present distributed within the absorbent layer. Additionally, a fibrous inner surface of the facing layer provides a convenient means for increasing the total surface treated with a surface active agent within the pad while maintaining the outer facing sheet surface relatively hydrophobic.

Still other methods that can be used to prepare a thermoplastic web having an integral fibrous surface include pressure molding or embossing of a desired surface texture onto the thermoplastic surface, treating or brushing the surface of a relatively smooth thermoplastic web to roughen the web surface and to produce a soft, cushiony appearance and feel, coating the surface of a smooth thermoplastic web with fibrous polymeric particles of elementary fiber size while the surface of the thermoplastic web is in a molten or tacky state. Spray, melt blowing, electrical or tack spinning, candy floss techniques, and the like can be utilized for this purpose. Such methods are known in the art and are described, for example, in U.S. Pat. No. 3,098,262; U.S. Pat. No. 3,141,051; U.S. Pat. No. 3,316,592; U.S. Pat. No. 3,655,497; U.S. Pat. No. 3,696,183; and U.S. Pat. No. 3,701,621.

Another embodiment of this invention is illustrated in FIG. 3. Polyethylene facing sheet 22 having integral fibrous outer surface 23 overlies absorbent layer 25 and is provided with a plurality of valvular indentations 24 in which excreted body fluid collects prior to being absorbed within absorbent layer 25 of the produced pad. Each valvular indentation is provided with at least one slit 26 which communicates with underlying absorbent layer 25. A thin web of absorbent tissue such as web 35 integral with facing sheet 22, and initially serving as a carrier web for the molten polymeric mass

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Disposable absorbent pad