US 3888255 A
A sanitary napkin is provided to be worn in the crotch portion of an undergarment and comprises a garment contacting surface, a body contacting surface and an absorbent element therebetween. A garment contacting surface is provided with a layer of material thereon having a high co-efficient of friction. Applied to a portion of this layer is a second layer comprising a pressure sensitive adhesive.
Claims available in
Description (OCR text may contain errors)
[ June 10, 1975 United States Patent 1191 Shah et al.
 SANITARY NAPKIN HAVING IMPROVED 3.611686 10/1971 DeWoskin l28/288 ATTACHMENT SYSTEM 3-665923 l28/290 W 5/1972 Champaigne. Jr...
3,724.466 4/]973 Hendricks...t.v...........:..... 128/290 R  Inventors: Praful H. Shah, Kendall Park;
Suhramania Srinivasan, East Brunswick, both of NJ.
Primary Examiner-Aldrich F. Medbery Attorney. Agent, or Firm-Jason Lipow  Assignee: Personal Products Company,
ABSTRACT 22 Filed: on. 4, 1974 APPL 511,979 A sanitary napkin is provided to be worn in the crotch portion of an undergarment and comprises a garment contacting surface, a body contacting surface and an 128/290 128/290 H; absorbent element therebetween. A garment contactl28/290 W A6 13/16 ing surface is provided with a layer of material thereon ] Int. Cl.
having a high co-efficient of friction. Applied to a portion of this layer is a second layer comprising a pressure sensitive adhesive.
This system provides great resistance to repositioning when the napkin is worn.
 References Cited UNITED STATES PATENTS l 799,l47 4/l93l Brisache 128/290 H 9 Claims, 4 Drawing Figures SANITARY NAPKIN HAVING IMPROVED ATTACHMENT SYSTEM BACKGROUND OF THE INVENTION This invention concerns an attachment system for sanitary napkins and is specifically directed toward such a system for the so called beltless sanitary napkins which are worn without the use of belts, pins, or the like.
The art has recognized the great inconvenience associated with conventional napkins which are generally provided with longitudally extending tabs for attaching to a sanitary belt or for pinning to an undergarment to hold the napkin in place. Substitutes have been sought and so napkins are now on the market having pressure sensitive adhesive means for attaching the napkin to the crotch portion of an undergarment. It has also been suggested that a napkin may be held in place in the crotch of an undergarment by the frictional restraining forces between the material of the garment and the bottom of the napkin and to this end, napkins have been provided with layers of polymeric cellular foam on their garment-contacting surface to enhance this frictional resistance.
While both the adhesively attached systems and the frictional systems have been accepted by the consumer to a degree, they have failed to supplant the use of the conventional napkin in many instances in that they do not provide satisfactory assurance to the wearer that they will remain in place and so improvements have been sought.
Naturally, with respect to an adhesive system, sufficient quantities of adhesive having a sufficiently substantial tackiness can be applied to a napkin to insure its maintenance in the proper position when worn. Such a system, however, has great disadvantages in that the adhesive will then cling too tenaceously to the undergarment and therefor be deposited thereon or the adhesive may create so strong a bond as to cause the napkin or the undergarment to tear when the napkin is being discarded, after use.
The frictional securement systems, on the other hand, does not suffer from any of these drawbacks. It should be understood however that, as is implicit in a frictional mechanism, the system is only effective when forces are exerted in a direction normal to the direction in which motion is to be restrained. While such forces are, in fact, exerted on a napkin being worn in the crotch of an undergarment. these forces are sporadic and vary with the positions of the wearer and with her movements. Frequently, at some point in time, no forces sufficient to create any frictional resistance to movement are exerted and accordingly, the napkin is free to, and does, move out of position.
Because of these drawbacks no attachment designed to provide securement for sanitary napkins without the use of belts has been completely satisfactory.
SUMMARY OF THE INVENTION It has been discovered that these drawbacks found in prior beltless attachment systems can be obviated and a superior system provided which does not depend on an aggressively tenacious adhesive, yet does not completely eliminate the ability of an attachment system to be independent of externally applied pressure, as is the case with a frictional system.
In accordance with this invention, there is provided a sanitary napkin to be worn in the crotch portion of an undergarment. The napkin comprises a garment contacting surface, a body contacting surface and an absorbent element therebetween. The garment contacting surface has a layer of material thereon having a high co-efflcient of friction such as, for example, a layer of cellular foam. Applied onto at least a portion of this layer, is a second layer comprising a pressure sensitive adhesive.
It has been discovered that this combination. for reasons not yet clearly understood, has the completely unexpected effect of rendering the napkin, to a surprisingly high degree, resistant to repositioning once it is emplaced in the crotch of an undergarment. It would be expected that, upon the application of a repositioning force, to such an applied napkin, either the adhesive mechanism or the frictional mechanism would be controlling, depending upon such factors as the tenacity of the adhesive layer or the magnitude of forces normal to the repositioning forces. It would, therefore, be expected that the resistance to repositioning for the attachment system of this invention would assume a value equal to either the value for a frictional system alone or for an adhesive system alone.
Even if one were to suspect that the frictional and the adhesive layers in some way were each contributing to the resistance to repositioning, the maximum total resistance to reposition that could possibly be expected would be the sum of the resistance of each of the systems operating alone.
Not withstanding these possible expectations, it has been discovered that an attachment system provided in accordance with the teachings of this invention, exhibits a resistance far greater than the combined sum of a frictional system and an adhesive system each taken alone. In fact, by applying to a frictional substrate substantially less adhesive than has been heretofore used in adhesive attachment systems, a resistance to displacement results which exceeds the sum of the measured resistances for the frictional system and the prior adhesive attachment system when each is operating alone.
BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:
FIG. 1 is a perspective view of a full sized sanitary napkin embodying the teachings of this invention and illustrated with its protective cover partially peeled off;
FIG. 2 is a cross sectional view of the napkin illustrated in FIG. I and taken through line 2-2 of FIG. 1;
FIG. 3 is a perspective view of a minipad also embodying the teachings of this invention; and
FIG. 4 is a cross sectional view of the minipad of FIG. 3 taken through line 44.
DETAILED DESCRIPTION OF THE INVENTION Referring now to FIGS. I and 2 of the drawings, illustrated therein in perspective and cross sectional views, respectively, is a full size sanitary napkin l0 embodying the teachings of this invention and shown with the surface normally worn away from the body facing upwardly. The napkin consists of an absorbent element 12 which is shown in the form of a generally rectangular pad and may consist of loosely associated absorbent material such as; cellulosic fibers, for example, wood pulp, regenerated cellulose or cotton fibers; other chemically or physically modified cellulose fibers; other polymeric absorbent materials, both natural and synthetic, such as hydrophilic foams (e.g. hydrophilic polyurethane foam); or may be such commonly used absorbent material as wadded tissue paper or the like. Alternatively, the absorbent element 12 may be a shaped form such as molded hydrophilic polymer (eg. a molded hydrophilic polyurethane foam or a molded cellulosic form), or any combination of these absorbent materials. The absorbent element 12 is wrapped in a fluid pervious sheet material 14 which overlies the garment contacting surface of the napkin (i.e. that surface normally worn away from the body) and the body contacting surface of the napkin (ie that surface normally worn against the body) as well as the sides of the napkin. The sheet material may be of rectangular shape and somewhat wider and longer than the absorbent element so that it can be sealed by overlapping the longitudinal edges 16 and 18 of the sheet on the garment contacting surface and sealing them together in the area of overlap with a suitable adhesive 20. The ends 22, 24 of the sheet may also be sealed or crimped together thereby fully enclosing the absorbent element. The sheet material may be any woven or nonwoven ma terial pervious to fluid striking its surface, such sheets being well known in the art in connection with sanitary napkins.
In accordance with the teachings of this invention, a frictional layer 26 of material having a high co-efficient of friction is provided on the garment contacting surface of the napkin and as shown in FIGS. 1 and 2, overlies a portion of the sheet material 14. Preferably, the frictional layer overlies the major portion of the sheet on the garment contacting surface. The frictional layer may be secured to the garment contacting layer by any of the methods known in the art, such as with a suitable adhesive, with heat sealing, or may be extruded thereon.
Further, in accordance with the invention, at least a portion of the frictional layer is overlaid with a pressure sensitive adhesive layer 28 which may be arranged in a wide variety of patterns onto the frictional layer 26. As shown in this specific embodiment, the pressure sensitive adhesive layer is in the form of an elongated rectangular strip longitudinally extending on the friction layer 26. To protect this pressure sensitive layer 28, a peelable protective cover 30 is provided which may be removed just prior to use, and is shown partially peeled from the napkin.
In use, the protective cover 30 is peeled from the napkin exposing the pressure sensitive adhesive. The napkin is then pressed into position in the crotch of an undergarment and, because of the unique combination of frictional and adhesive layers taught herein, the napkin will resist repositioning to a remarkable and totally unexpected extent. Notwithstanding the strong tendency to remain in place when worn, the napkin easily peels from the crotch portion of the undergarment when the user is disposing of the same. In fact, because of the greater resistance to repositioning, far less adhe' sive may be used in the napkin of this invention, as contrasted with that used in the prior adhesively supported napkins, and accordingly, the napkin of the invention peels with no more effort than these prior napkins and with less tendency to leave undesirable adhesive residue deposited on the undergarment and less tendency to tear the napkin upon separation from the garment.
Referring to FIGS. 3 and 4 of the drawin s illustrated there in perspective and cross-sectional views, respectively, is a minipad 32 embodying the teachings of this invention, the minipad being shown with thle garment contacting surface facing upwardly. The minipad 32, a smaller, thinner version of the full size sanitary napkin, consists of a relatively thin, flat, generally rectangular, absorbent element 34 which may be comprised pf the same kind of absorbent materials as described abpve in connection with the full size napkin of FIGS. 1 a d 2. A fluid pervious sheet 36 envelopes the body con acting surface, the sides and a portion of both longitu 'nal margins of the garment contacting surface of the ab rbent element. Again this sheet may be of the same ty H e as that used in connection with the above described ftill size napkin. Overlying the garment contacting surface of the element 34 and marginal portion of the sheet 36, is a fluid impervious layer 38 provided to preclude fluid from passing onto an undergarment and which may be any thin flexible impervious layer, for example a polymeric film such as polyethylene or polypropylene film, cellophane, or a generally fluid pervious material that has been treated to be impervious such as impregnated, fluid repellent paper.
Adhesive may be applied to the surface of the imper vious layer 38 which faces the absorbent element 34 and will permeate through the portions of the pervious layer 36 on the garment contacting surface of the element 34, securing both the pervious and impervious layers to the element 34. Likewise, the ends of the minipad may be secured by adhering the pervious and impervious layers together where they extend beyond the ends of the absorbent element 34.
In accordance with the teachings of this invention, a frictional layer 40 is provided overlying the major por tion of the fluid impervious layer on the garment contacting surface of the minipad, this frictional layer 40 having a high coefficient of friction and adhered to the minipad by the means described above, e.g., with heat sealing adhesives, or extrusion. Overlying a portion of the frictional layer 40 are, in this specific embodiment, two generally square-shaped pressure sensitive adhesive layers 42 protected by peelable protective covers 44.
Again, as was the case for the full sized napkin above described, the protective covers 44 may be peeled off to expose the adhesive layer 42. The minipad may be pressed into the crotch of an undergarment where it will remain firmly in place yet be easily peeled off after use and discarded without the tearing of the napkin or the undergarment and without the deposition of adhesive residue.
It will be appreciated by one skilled in the art that many variations are possible in the two above described embodiments, both with respect to the securement systems and with respect to the general structure of the napkin and minipad. For example, the full size napkin may be provided with a fluid impervious sheet, either as an outer cover as is shown for the minipad, or as a barrier sheet disposed between the absorbent element and the pervious layer or even within the absorbent element. Similarly, many variations in the configuration of the frictional layer is possible and in fact, the fricational layer may be discontinuous, e.g., a plurality of patches, spots, or the like distributed on the garment contacting surface of the napkin all without sacrificing any of the advantages taught herein. Likewise, the pressure sensitive adhesive may be disposed in various configurations on the frictional layer. For example, the longitudinally extending strip of pressure sensitive adhesive shown in FIGS. 1 and 2 are to an extent interchangeable with the square patches of adhesive shown in FIGS. 3 and 4.
The frictional layer of this invention may be one or a combination of several available materials which meet the requirements necessary for their use herein in that they are flexible, readily available in the form of sheets and exhibit a high co-efficient of friction which should be greater than 2.0 and preferably greater than about 2.5. As used herein, the co-efficient of friction is defined by the lnstron Frictional Test as will be described in greater detail below but may be generally stated as the force necessary to slidably displace, on a standard surface, the surface being tested divided by a force applied normal to the direction of displacement. Examples of such usable frictional layer materials are those woven and nonwoven fabrics, films and sheets which meet the co-efficient of friction requirements set forth above and are not incompatible with the desired use. The surface of otherwise unsuitable materials may be treated to increase their co-efficient of friction by mechanical means such as by embossing, micropleting or creping or coating or impregnating with binders, adhesives, or chemicals such as vinyl polymers e.g., ethyl vinyl acetate polymer, polystyrene; rubbers e.g., butadiene rubber, nitrile rubber, latex rubber or the like.
Of particular interest for use as the frictional layer are a wide variety of flexible compressible polymeric foams. Examples are the polyurethane foams (both ester and ether type), cellulosic foams, polyethylene foams, both natural and synthetic latex foams, silicone foams, and various polyvinyl foams such as polyvinylchloride, polyvinylchloride-vinyl acetate copolymer and copolymers of vinyl chloride and vinylidene chloride although the latter two are not yet commercially available.
The foams may be used either alone or bonded or otherwise attached to substrates such as films or nonwoven fabrics to add to the foam strength during handling. Such attachment methods as flame lamination, wet adhesive lamination, needling, fusion bonding with hot melt, extrusion coating or transfer coating may be employed.
The pressure sensitive adhesive element may comprise any ofa large number of pressure sensitive adhesives available on the market including, for example, both the so-called cold pressure sensitive adhesives, generally applied in the form of a liquid dispersion and then dried to a tacky mass or alternatively, the rapid setting thermoplastic (hot melt) adhesives, generally applied by heating to a temperature above their melting point and extruding the heated mass onto the substrate. Cold pressure sensitive adhesives are generally based on an elastomer selected from natural or synthetic rubbers, e.g., pale crepe rubber, smoked sheets, reclaimed rubber, Buna-S and Buna-N type rubbers, polyisoprene, polyisobutylene, and synthetic elastomers such as polyvinyl ethers, polyacrylates or the like. The adhesive may be especially compounded or interpolymerized to provide the desired characteristics of pressure sensitive adhesives. Any of the conventional tackifiers such as rosin, polyterpenes, coumaroneindene resins, polyalkyl styrene and the like, may be used in proportions well known in the art. Other ingredients such as fillers, antioxidants and pigments may also be included.
The hot melt adhesives generally comprise such block copolymers such as styrene and butadiene styrene copolymers and are also known in the art.
While the specific dry weight of adhesive disposed on a napkin may vary depending on such factors as the specific adhesive used and the specific geometric arrangement of the adhesive in general, less adhesive is required to obtain a satisfactory resistance to frictional forces when following the teachings of this invention than has heretofor been found necessary. A quantity as low as 0.05 grams of adhesive per napkin has been found to be satisfactory although it is preferred that at least 0.1 gram be used, e.g., 0.15 grams produces a superior product.
The invention, and the surprising advantages which accrue therefrom may be better understood by consideration of the following examples. In each of these examples and wherever else referred to herein, quantitative valves for resistance to friction are obtained by using the Instron Frictional Tester (Model Number TM-S). The surface to be tested is places surface down, onto a standard substrate which has been mounted on the movable carriage of the Tester. One end of the sample being tested is held by a clip which in turn is attached by means of a nylon monofilament thread to the measuring and recording instrument of the Tester which measures and records the force, in ounces, applied to the thread. The movable carriage is moved in a direction away from the attached thread at a fixed constant rate and the resistance to such movement is measured and recorded by the instrument. For the tests used herein, the standard substrate is a sheet of X 80 count, bleached, cotton print cloth obtained from Testfabrics Incorporated of Middlesex, New J ersey and designated by them as Style 400. This substrate is affixed to the cleaned, stainless steel surface of the carriage by using double faced adhesive tape. The surface of the sample to be tested is pressed down upon the standard substrate and a four pound weight is rolled over the sample. When testing a sample for frictional resistance under the influence of a force acting normal to the frictional force, a weight, equal to the desired normal force is placed upon the sample. In all cases, the carriage is moved at a constant speed of l2 inches per minute. The frictional force referred to herein is the maximum force recorded by the instrument during the test and represents the force required to dislodge the sample from the substrate. As repeated herein, the coefficient of friction is defined as the recorded value in grams for the frictional resistance of the sample under normal load of I00 grams divided by 100. When testing samples as described herein, in all cases the sample is tested, is attached to a sanitary napkin and generally the napkin is cut transversely in half to accommodate the size restrictions of the testing equipment.
EXAMPLE 1 A full size sanitary napkin is prepared having the general construction of that illustrated in FIGS. 1 and 2. The napkin has the overall dimensions of 9.72 inches long and 2.68 inches wide and comprises a pad of comminuted wood pulp weighing 13.1 grams and having the dimension of 7.66 inches long, 2.68 inches wide and 0.7 inch thick. The napkin is identical in all respects to the product now being sold by the Personal Products Company of Milltown, New Jersey as their Stayfree, (Registered trademark). Maxipad feminine napkins with the exception that a frictional layer having the planar dimensions of 9.72 inches long and 2 inches wide is adhesively attached to the bottom of the napkin (the face worn against the garment) and an elongated pressure sensitive adhesive strip is applied centrally onto the surface of the frictional layer.
The frictional layer is comprised of a cellular polyurethane foam of the ether type and is obtained from the Tenneco Chemicals Corporation, Plastic and Foam Division of East Rutherford. NJ. and designated by them as code number 3845.
This foam has an average density of 1.38 lbs/cu. it, a tensile strength of at least 11 lbs/sq. in., an elongation at break of about 150%, a tear strength of about 0.1 lb./in., and an open cellular area of 90%. The foam has a thickness of about 0.06 inches. A sample of this foam as attached to a napkin but without adhesive, is tested on the lnstron Frictional Tester and exhibits a co-efficient of friction of 3.9.
The pressure sensitive adhesive layer applied to the surface of the foam is in the form of a rectangular strip having the dimensions of 7.66 inches long by inch wide and is centrally located on the friction layer. The adhesive is one of the rapid-setting, thermoplastic hot melt adhesives and is obtained from the Essex Chemi cal Corporation, BFC Division of Sayreville, New .lersey and designated by them as 52.l. A total weight of 0.15 grams of adhesive is used on the napkin. The adhesive has a viscosity of 6,800 i 700 cps when measured at 350F, a specific gravity of 0.98 at 78F, a melting range of 168 i 8F. The adhesive is heated to a temperature of 325F and then extruded onto the frictional layer through a nozzle.
The napkin, when pressed into the crotch portion of an undergarment and worn, exhibits a great resistance to repositioning and when being discarded after use, easily peels from the undergarment.
EXAMPLE 2 A full size napkin is prepared identical to that of Example l with the exception of the frictional layer and the pressure sensitive adhesive. In this case, the frictional layer is a polyurethane foam of the ester type obtained from the same Tenneco Chemical Corporation and designated by them as F-4100. This foam has an average density of 1.75 lbs/sq. in., a tensile strength of 35 lbs/sq. in., an elongation at break of 300%, a tear of 4 lbs/in. and an average open cellular area of 45%. The foam layer is 0.035 inch thick and when a sample as attached to a napkin, but without adhesive, is tested on the lnstron Frictional Tester, it exhibits a co efficient of friction of 3.4.
Centrally applied to the surface of this frictional layer is a rectangular layer of pressure sensitive adhesive measuring 7.66 inches by inch and comprising 0.2 grams of a pressure sensitive adhesive obtained from the Bostik Division of U.S.M. Corporation of Middleton, Mass. and designated by them with the code num' ber 8760. The adhesive is a 48% solids, water-based emulsion of acrylic polymer having a viscosity range of 2,100 -2,400 cps at 76F and a specific gravity of 1.13. This emulsion is extruded onto the surface of the frictonal layer and allowed to dry into a tacky pressure sensitive layer.
The napkin, when pressed into the crotch portion of an undergarment and worn, again exhibits a great resistance to repositioning although somewhat less than that of the prior example. Again, upon being discarded, the napkin easily peels from the undergarment.
EXAMPLE 3 A series of napkins having the identical configuration and dimensions of the napkins of Example 2 are prepared, with the exception that the quantity of Bostik adhesive is varied, as is shown in Table 1 below. A second series of napkins are also prepared identical to that of Example 2 with the exception that various quantities of the Essex hot melt adhesive described in Example 1 are applied to the ester polyurethane frictional layer as the pressure sensitive element.
These napkins are tested on the lnstron Frictional Tester under condition of essentially zero normal force, by cutting each of the napkins transversely in haalf to accomodate the size restrictions of the testing equipment. As a control, a sample of the product currently being sold by Personal Products Company as Stayfree, Maxi Pad feminine napkins is also cut in half and identically tested. This control sample is identical in all respects to the other samples being tested with the exception that the frictional layer is omitted and instead, the rectangular, pressure sensitive adhesive, comprised of the aforementioned Bostik adhesive, is applied directly to the nonwoven cover on the bottom of the napkin. The control sample has 0.225 grams of this adhesive applied thereon. The results of these tests are reported in Table 1.
TABLE 1 Frictional Force at Zero Nunnal Force As Table 1 indicates, the frictional forces required to dislodge the samples which, in accordance with the teachings of this invention. include a frictional layer between the nonwoven cover and the pressure sensitive adhesive are far greater than the forces required to dislodge the conventional napkin sample. This is totally unexpected in view of the fact that these tests are run under conditions of zero normal force, i.e., when the frictional layer should be contributing nothing to the resistance to dislodgement. It should be noted that an advantageous enhancement in the resistance to dislodgement is evidenced even when a quantity of adhesive substantially less than that applied to the conventional napkin is used.
EXAMPLE 4 A first series of napkins are prepared identical to that of Example 1 in all respects (including the ether type polyurethane frictional layer and the 0.15 gram of Essex hot melt adhesive as the pressure sensitive element.) A second series of napkins are prepared, identical with the first series with the exception that the polyurethane foam of the ester type as described in Exarnple 2 is used as the frictional layer. For comparative purposes, a third series of samples are prepared identical in all respects with the the first series with the exception that the pressure sensitive adhesive is eliminated. Also, for comparative purposes, a fourth series of samples are prepared identical to the conventional Stayfree, Maxi Pad feminine Napkin, described above. Each of the series of napkins are tested on the lnstron Frictional Tester, again by cutting the napkin transversely in half, under conditions of varying normal loads as shown in Table 2 below. The results of these tests are reported in that Table.
TABLE 2 configurations, such is not to be considered limitative of the invention but merely illustrative thereof.
What is claimed is:
l. A sanitary napkin to be adhered to the crotch portion of a garment comprising a garment contacting surface, a body contacting surface and an absorbent ele ment therebetween, said garment contacting surface having a first layer of material therein having a high coefficient of friction, said first layer having over at least a portion thereof a second layer comprising a pressure sensitive adhesive.
2. The sanitary napkin of claim 1 wherein said first layer has a co-efficient of friction greater than about 2.0.
3. The sanitary napkin of claim 1 wherein said first layer has a co-efficient of friction greater than about 2.5.
4. The sanitary napkin of claim 1 wherein said first layer is a flexible, compressible, polymeric foam.
5. A sanitary napkin to be adhered to the crotch portion of a garment comprising an absorbent body enveloped in a fluid pervious sheet, said enveloped body having a garment contacting surface and a body contacting surface, said garment contacting surface having SAMPLE FRICI'IONAL FORCE (02s.)
Normal Force (Gm) No Load 100 gm 200 gm 500 gm 1000 gm 1. Product with ether type Polyurethane Foam and 0.15
gm. hot melt adhesive 144.0 160.0 163.2 174.4 208.0
2. Product with ester type Polyurethane Foam and 0.15
gm. hot melt adhesive 103.4 122.7 143.7 165.4 197.4
3. Product with ether type Polyurethane Foam and no adhesive 27 14.8 22.7 45.9 88.8
4. Conventional Product 74.6 81.3 86.6 97.0 1 10.9
Total of 3. and 4. 77.3 96.1 109.3 142.9 199.7
As can be noted from an examination of Table 2, the products of this invention, as embodied in the first and second series of samples tested, far exceed both the conventional adhesive attachment system and one utilizing only a frictional layer in their abilities to resist dislodgement. Not surprisingly. the system using only the frictional layer does not exhibit any significant resistance to dislodgement until a substantial normal force is applied. In view of this, it is completely surprising that the products embodying this invention show such a marked improvement at zero normal force conditions.
Still more surprisingly, is the fact that the sum of the resistances of the frictional layer and that of the adhesive layer when taken alone, are still less than the combination of these two operating together, as in accordance with this invention.
Although the present invention has been described with reference to several examples and embodiments showing specific products in specific arrangements and a first layer of material thereon having a high coefficient of friction, said first layer having a second layer thereon of an area smaller than said first layer comprising a pressure sensitive adhesive.
6. The sanitary napkin of claim 5 wherein said first layer has a co-efficient of friction greater than about 2.0.
7. The sanitary napkin of claim 6 wherein said first layer has a co-efficient of friction greater than about 2.5.
8. The sanitary napkin of claim 1 wherein said first layer is a flexible, compressible, polymeric foam.
9. A sanitary napkin comprising an absorbent body sandwiched between a fluid impervious sheet and a fluid pervious layer, said fluid impervious sheet having a first layer of material thereon having a high coefficient of friction, said first layer having over at least a portion thereof a second layer comprising a pressure sensitive adhesive.