Note: Descriptions are shown in the official language in which they were submitted.
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~L~57~;3
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Back~round of the In~ention
Thi~ inventlon concernA an attac~ment 3ystem for
sanitaxy napkins and i8 ~pecificatly directed toward such a
system for the 80 called "beltle~s" sanitary nap~lns which
~re worn without the use of belts, pins, or ~he like.
The art ha~ recognized the great incon~enience
a~sociatQd with eon~entional napkins which are generally
provided w~th long~tudally extending tab~ for attaching
to a sanitary belt or for pinning to an underganment to
hold the napkin in pl~ce. Substitutes h~ve been eought and
0 80 n~pkins are now on the market having pr~ssure sensitive ~ ~ :
a & e31ve means for ~tt-ching the napkin to the~crotch~
portion of ~n undergarmen~.~ It has also be~n suggested that
a napkin may be~held in place in tbe croteh of àn under~
garment by the frictional restraining forces between the .~
mzterial of the garment and the bottom of the napkin and to ~ :
this end, napkins have been provided with layer of polymeric
cellular fo~m on their garment-contacting~surface to enhance
.
this frict~onal resistance
. While both the adhe~ively attached sy~tem~ and
the frictional 8y8tem8 have been accepted by the consumer
~o a degree, they have f8~1ed to bupplant the use of the
conventional napkin ~n many ins~ance~ in that they do~not
provide aatis~sctory ~ssurance to the wearer that they will
re~aln in place and 80 improvement3 have been 80ught.
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Naturally, with re~ect to an adhe~ive system,
sufficient quantitie~ of adhesive having a sufflc~ently
substantial tackines~ can be applied to a napkin to
in~ure its maintenance in the proper poeltlon when worn.
S Such a 8y3t~m, how~ver, has great disadvantages in that the :.
adhesive will then cling too tenaceously ~o the untergarment
and therefor be deposi~ed thereon or ~he adhesive may
create ~o strong a bond as tQ cau~e the napkin or the under~
ganment to tear when the napkin is being discarded, after ~ . ~
10 uee. .~ :
The frictional securement 9y~tem8, on the other
hand, does not suffer from any of these drawbacka. It
should be understood howevèr that, as is i~plicit in a
.... .
frictional ~echani~m, the system i8 only effective when
forces~are exer~ed in a direction normal to the dlrectlon
in which ~ion i8 to be restrained. While such~force~
are, in factj exerted on a napkin being worn in the crotch
~ . - .
of an undergarment, these forces are sporadic nd~vary with
the pooition~ of the wearer and with her m~vements. Frequently, . ~:at some point in timej no orces ~ufficlent to cre~te any
friction~l re~lstance to movement are e~erted.and accordin~ly,
the napkin is free to, a~d does, move out of posltlon
~Becau0e of these dr~wbacks.no attachment desig~ed
; to provide secur~ment for sanitary napkins.wlthout the use
of belt~ has been completely satiB~actory.
S~ C~ o!~L~ entlon
..
It ha~ been discovered that thes2 drawbacks found
in prior beltless attach~ent system~ can be obviated and a
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superior system provided which does no~ depend on an aggres-
slvely tenacious adhesive, yet does no~ co~pletely elimin~te
, : .
the abiLity of an attachment system to be independent of
externally applled pressure, as i~ the ca~e with a frlctional
~ystem.
; In accordance with; this invention, ~here is provided
a ~anitary n~p~$n to be:wo~n in:the crotch po~-tion of an
. undergarment. The n~pkin'ccmprises ~ gàr~ent ~on~acting
surface, a body contacting ~ ~è and an abso.rbent el~ment
therebetween.. The g~rment contac~ing sur~acb has a layer o~
terial thereon~having.a:high co-e~fi¢ient of ~riction such
as~ or exa~ple, a layer o.,c.ell.ular ~oam. Applied onto at
least a portio~ of this laye~i,. ls a ~econd Layer compri~ing
a.pressure ~ensitive adhesive. - . .
I~ has been d~scovered that this comb~nation, ~or
rea~ons not yet clear ~ understood, has the c~mpletely ~ :
unexpected effec,t'o~rëndering the napkin, to a ~urprislngly ~: ;
high degree ~ ~fes.lstant to repositioning once it i8 emplaced :~
.j~ in the crot~h of:an undsrgarment. It would be expected that, : ~.
- .: ~
20~ upon the app~lication of a repo3itioning force, to such ~n .
~pplied napkin, e~ther the adhesive mechanis~ or the fric~ional
~echanlsm would be controlling, dependlng upon such factor~ a3 ~:
.. . ~ . ~
:` the tenaci~y of the adhesive layer or the magnitude of force~
..
., normal to the repositioning forces. It wou:ld, thercfore, be
expected that~the res~stance to reposltioning for ~he attacb~
ment system of th~s invention would asR~me a value ~qual to
either the value for a frictional ~y~tem alone or for an
., adheaive syste~ alone.
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Even if one were to 9u8pect that the ~rictional
and the adhesive layers in some way were sach contributing
to the re~istance to repositioning, the m~ximu~ total
re~istance to reposition that could possibly be expected
would be the ~um of the resistance of each of the sy~tem~
operating alone.
Not with~anding these possible expectation3, it ~;
has been discovered that an attachment syst~m provided in : -
accordance with the teachings of this invention, exhib1ts ;~ .
a re~istance far greater than the combined sum of a frlc~ion~
syatem ~nd an a &esive system each taken alone. In faot,: -
:
by applying to a fr~ctional substrate substantially les~
adhesive than ha3 been heretofore used in adhe~i~e attach-
~en~ ~y8~em8, a resistance to di~placement results which .
~i 15 exceed~.the su~ of the measured re~i8tance.s orthe frictional `
8yat~m and the prior adhesive attachment 8y8tem when eachis
operating alone. :.
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, ; Brief lh~ Ecio~ of the Draw__~
. - . ...
In t~rae drawings:
! . . : ~ ~
Fig. l is a perapective view of a full 3ized .-: -
san1tary napkin embodying the teachings of this invention
~- .
and illustrated with it8 protective covcr partially peeled
off;
Fig. 2 13 a crnss ~ectional view of the napkin ;.
illustrated in Fig. 1 and taken through line 2-2 of Fig. 1.
Fig. 3 18 a perspective view of a min~pad al~o . ~:
embodying the teachings of this invention; and .
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574~3
Fig. 4 18 a cross ~ec~ional view of the mlnlpad
of Fig. 3 taken through l~ne 4-4.
D~tailed ~es
Referrlng now to Fig~. 1 and ~ of the drawings, :
illustra~ed th~rel~ in per~pect~ve ~nd cros9 8ectional views~
respecti~ely, is ~ f~ iz~ ~anitsry napkin 10 embodyin~ the
teschin~ of thi~ invention and shown with the surface nor-
mally worn away ~rom the body faclng upwardly. The napkin
consists of an absorbent element 12 whlch i8 shown in he
~orm o~ a generally rectangular p~d and may consist of loo~ely
associ~ted absor~ent materi~l such as;`cellulosic fib~rs, ~or ~-`
- ,
; ex~mple, wQod pulp, rege~erated celiulose or cott3n fibers; ;
other chemically or physlcally modified cellulose ~bers; o~her :~ :
polyi~eric 6bsorbent materials, both natural and ~yn~hetic,~such ~-
as hydrophilic foams~(e.g. hydrophilic~polyurethane foa~); or
;15 may be such commonly used absorbent material as wadded tis~ue ~ `
paper or ~he like. Al~ernatively, the absorbent el~me~t 12
may be a shaped ~orm 3uch~a~s molded hydrophllic polym-r (~.g. ~ ~
molded hydrophilic polyurethane foAm or a m~ldet celluloslc ~ :- foam), or any comblnation of ~h0se ~bsorbent materials. The
absorbent element~12 is wrapped in a fluld p2rvlou~ sheet
material 14 ~hich overlies the garment contactlng surface of the `~
n~pkin (i.e. that surface normally~worn aw~y fr~m the ~ody) and
the body contacting surface o~ the napkin (~.e. ~ha:t 3urface nor-
mally worn ~gainet the body) aæ well as the ~ides of the napkin.
i25 The shee~ material may be of rectangular shape and somewhat
wider and longer than the ~bsorbent element 80 that i~ can be -
.. ., .:
sealed by overlappin~ ~he longi~udinal edges 16 ànd 18 o~ the ~h~et
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1057463
on the garment contacting surface and ~ealing th~m together in
the area of overlap with a suitable adhesive 20. The ends
22, 24 of the sheet may al~o be sealed cr crimped together
thereby fully enclosing the absorbent element. The sheet
mQterial may be any woven or nonwoven material perviou~ to :
fluid striking lt~ ~urf~ce, such sheets being well known in
the art ln connection with ~ani~ary napkins.
In accordance with the teaching~ of thi8 inventionj
a frictional layer 26 of material having a high co-efficient
of friction i~ provlded on the garment contacting surf-ce of :~
the napkin:and ~8 ~hown in Fig~. 1 and 2, overlies a portion . ~
of the sheet material 14. Preferably, the frictlonal layer - :
overlie~ the ma~or portion of the sheet on the garment con~
tacting surface. The frictional layer may be secured to the g~arment `~
contacting layer by any of the methods known in the art, such as
with a suitable adhesi~e, wi~h heat sealing, or may be extruded
thereon.
Further, in accordance with the lnvention, at least a -;
portion of the frictional layer is overlaid with a pressure sen~
sitive adhesive layer 28 which may be arranged in 8 wide variety -
of patterns onto the frictional layer:26. As shown in th~s
~peci~ic embodiment, the pressure sensit~ve adhesive layer i8
in the form of an elongated rectangular strip longitudinally
~xtending on the friction layer 26. To protect this preQaure ~ . -
~i 25 sensitive layer 28, a peel~le protectiYe cover 30 is provided which .
may be removed ~u~t prior to use, and i8 shown partially
peeled~frcm the napkin.
In use, the protective cover 30 i~ peeled from the napkin expo~-
l ing the pre~sure sensitive adhesive. The napkin is then pressed
; 30 into position in the crotch of an undergarment and, because
; of the unique combination of frictional and adhesive layer~
.taught herein, the napkin will resist repositioni~g to a remarkable
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lOS7~L63
and totally'unexpected extent. Notwithst~nding the strong
tendency ~Q`~re~in in place when worn, the napkin easily
peels.from th'e crotch portion of the und~rgarment when the
u~er'is disposing of the same. In fact, because of the greater
r~sii~tance to repositioning , far les~ adhesive may be used
'in the napkin of this invent~on, as contrasted with that u~ed
''' in the prlor adhesively supported napki7ns, and accordin~ly, the
' napkin of the invention peels with no~mo~e.effort than the3e
prior napkins and with less tendency to'leave undesirable
10 a'dheslve 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 drawings illustrated
.. '.there in'pe sp.e ~ and cross-sect~na1 views, respective1y, ' ;'
8 a.'minipad~!32.' ~ ying the!.teachings of this inven~ion, the
~inip~b'~nig shown wlth thë'garmënt.~contacei~g'surface facing
: '' upwardly.~.''The minlpad 32, a smai'i'le'~thinner.version of the full
~size~sanltary napkin, con~ist:s'of a relatively thin, flat, ~.
e~era1iy rectangu1ar, absor~e.nt ëlement 34 which may be com~
pr~sed,'of ~ ~me.;k~nd of:absorbënt'~materiaL~ as described above
.20"' ~":conffe~ion;~ th the.~ull~size napkln of Fig~. l and 2. A
~'' fluld'pervious sheet 36 envelope~ the body contacting surface, ~ .
~he sides and a portion bf both longitudinal margin~ of the ~.
garment eontacting surface of the absorbent element. Again this ~ '
: ' sheet may be of the ~ a~ ~t used in c ~ tionwi~h ~ ~n~
~ ~ bed full size napkin. Overlying the garmene contacting ~ur-
face of the element 34 and marginal p~rtiQn of the sheet 36, 18 a fluid
imperv~ou~ layer 38 providè~.to preclude fluid from pa88ing
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~l~S7463
onto an undergarment and whlch may be any thln flexlble
impervious layer, for example a polymeric film ~uch a~
polyethylene or polypropylene film, cellophane, or a generally
fluid pervious material that has been treated ~ be impervious
such aR ~mpregnated, fluid repellent paper.
Adhesive may be applied-to the surface of the
imperviou~ layer 38 whlch faces the absorbent el~ment 34
and will permeatethrough the portions of the pervious layer
: 36 on the garment contacting surface of the element 34, `;
securing both the pervious and impervious layer~ to the elemen~
34. Likewi~e, ~he end~ of the minipad may be secured by ~-
adhering the pervlous and impervious layers together w~ere
they extend beyond the ends of the ab80rbent elæ~ent 34.
In acco~dance with the teach~ngs of this invention,
a frictional layer 40 i9 provlded overlying the ma~or portion .`~
of the fluid lmp~ous layer on the gan~ent contacting ~urface
of the minipad, this frictional layer 40 having a high co~
efficient of friction and adhered to the minipad by the means
-'. de~cr~bed above, e.g., with heat sealin~ adhèsives, or extru-
. - . .... . . ... .
~ion. Overlying a portion of the frictlonal layér 40 are, in ~:
this specific embodiment, two generally squRre-shaped pressure ~ ~ :
~ensitlve adhesive layers 42 protected by peelable protective
covers 44. ~ ~ ;
Again, as was the case for ~he full sized napkin
above described, the protective covers 44 ~ay be peeled off
to expose the adhesive layer 42. The minlpad may be preosed
: . . .
into the crotch of an undergarment where it will r~main ~ ;
firmly in place yet be easily peeled off after use snd dis- .
~arded w~thout the te~rnæ of ~he n~dn or the unienF~rynt and withDut
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the depositlon of adhe~ive re~due.
It will be appreciated hy one ~killed in the art
that many variations are po3~ible in the two above described
embod~ments, both with respect to the securement systems and
with respect to the general structure of the napkin and minip~d.
For example, the full size napkin may be provided ~ith a :~
fluid impervious sheet, either as an outer cover as i8 shown
for ~he minipad, or as a barrier sheet disposed between the
absorbent element and the pervious layer or even within the
ab~orbent element. Similarly, many ~ariation~ in the con-
figuration of the frictlonal layer i~ possible and in fact, the
frictional layer may be discontinuous, e.g., a plurality
of patches, spots, or the like distributet on the garment
contacting surface of the napki~ all without sacriflcing
any of the advantages taught herein. Likewise, ths pres3ure ~ :
sensitive adhes~ve may be disposed in VNioU~ configurations
- - . . -
on the frictional layer, For example, the longitudinally
extending ~trip of pressure sensit~ve adhesive shown in Figs.
l and 2 are to an extent interchangeable with the square patche~
of adhe~ive shown:in Figs. 3 and 4. .
. ~ . ...................................................... . .
The frictional layer of thi~ invention may b~e one
or a combination of several sv8ilable materials which ~eet
the requirements necessary for their use herein in that they
zre ~lex~ble! readil~ available in the form of sheet~ and
~: 25 exhibit a high co-efficient of friction which should be gre~ter
~n 2.~ and prefer~bly greQ~ than about 2.5. A~ u~ed herein, :
the co-efficient of frictio~ 1~ defined by the In3tron ~rictional ~ :~
, ., . - .
Test as will be described in greater detail below but m~y be
. ..
generally stated as ~he force necessary to ~lidably displace,
~;
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:
on a ~tandard surface, the surf~ce being tested divided by
force applied nor~al to the direction of displacement. Example~
of such usable frictional layer materials are tho3e woven and
nonwoven fabrlcs, films and sheets which meet the co-efficient
of friction requirements set forth above and are not lncom-
patlble with the desired use. The surface of otherwise unsuit-
able materials may be treated to increase their co-efficient ~:
of fri~tion by mechanical means such as by ~mbossing, miero-
: pleting or creping or coating or impregnating w~th binder~
adhe~ives, or chemicals such a3 vinyl polymer~ e.g., ethyl vinyl
scetate polymer, polystyrene; rubbers e . g ., butadiene rubber , -: :
nitrile rubber, latex rubber or the like.
~ :.
~ Of particul~ar intere~t for use as the frictional layer
.~1 are a wide variety of flexible compressible polymeric foams. : - .
~15 Examples are the polyurethane foams (both e~ter and ether type), .
cellulosic foamq, polyethylene foams, both natural and synthetic :
latqx foams, silicone foams, and various polyvinyl foams such ~ ~
., " ~
~; as polyvinylchloride, polyvinylchloride-vinyl acetate copolymer
and copolymers of vinyl chloride and vinylidene chlorLde although l ;
20 the latter two are not yet commercially available. I
;` ~ The~foams may be used either alone or bonded or o~her~
wi~e attached to sub trstes such as films or nonwoven fabrics
to add to the foam strength during handling. Such attachment ~;
~1 methods as flame læmination, wet adhesive lamination, needling,
.25 fusion bonding with hot melt, extrusion coating or transfèr
I coating may be employed. ~ ~ ~
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10~79~S3
The pressure sensitive adhesive element may comprise any
of a large nL~ber of pre~ure sensitlve adhe8ive~ aYailable on the ~rket
; including, for ex~mple, both the so-called cold pres~ure sensitive adhesives,
generally applied in the fonm of a liquld di8per3ion and th~n dried to a
tacky mass or alternatively, the r~pid etting thermoplastic ~hot melt) ad-
he3ives, generally applied by heating to a temperature above their melting ~ :
point and ext ~ the heated mass onto the sub~trate. Cbld pr2sRure ~en-
sitive adhesive~ are generally based on an elastomer selected ~rom natur~
or synthetic r~bber8, e.g., pale crepe rubber, smokæd 8 ~ ets, re~lai~ed
rubber, Buna-S and Buna-N type rubbers, polyisoprene, polyisobutylene, and
sy~hetic elas ~ ~ ~uch as polyv~nyl eth2rs, polyacrylatee or the l~ke. The
adh~sive may be especlally corpourded or inte~olymerized to proYide ~he
.
de~ired characteristlcs of pressure sensitive adhesives. Any of the conven-
tional tackifiers ~ as rDxin, polyterpenes, coum~on~uLIlde~e res~ns, polyElky
styrene and the l~ke, may be used in propor~ion~ well known in the art. O~her .
. ' . . . .
ingredlent3 such a9 fillers, antioKidants and p~t8 m~y also be includ~d.
The hDt melt a & esives generally ccmpri~e such block copDlymErs ~uch as stJrcne ~ -
and butadiene styrene oopDlymers ~nd are al90 knuwn in the art. ~`
~ le the spçcific dry weight of adhe~ive dlsposed on a t~qkLa n~y
vary depend~ng un such factGrs as ~he specific adhesive u~ed and the specific ~:
geometric ~rrangement of the adhe3ive in gen~ral, leas ~dhÆsive i8 r2quired
to obtain a sati~facbory re~istaQce to frictianal fonce~ when following ~he :
teachlngs of this inventiGn ~han ha8 heretofor be~n found nece3~ary. A quan
; tity a~ low as 0.05 gr~ms of adhe~ive per nap ~ has baen found to be 8ati8-
~25 factDry al ~ it i~ preferred that at l~ast 0.1 gram be used, e.g., 0.15
gr~ms p~oduce3 a ~uperior product.
:, m e inNention, ~nd the surpri~ing adv~ntages which ~ccru~ there~ro~
may be better urder~t~xxd by consideration of the follcwi~g eK~?les. In esch -
o~ these ex~mples and wh~rever else referred to herein, qu~nti~ative ValVe9
for resistance to frictl~n ~re obtained by u8ing the Instr~n ~ ctional Tester
el Number IM~S). The ~urface to be tested i8 places ~rface dbwn, ont~ a
'~
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~(~57463 . :~
~ta~rd s~bstrate ~nich has been ~ted on the ~le carrlage of *~
Tester. Orle end of tb~ s&~le b~ng te~ted is held by a cl~p ~ich in turn
i8 attached by means of a nyl~ nDiEil~ent t~read to ~he ~s~si~ ~nd re~
c~rding instr~t oIe the Tester ~ich measures arld recards the f~ce, in
5 a ~ es, applied to ~he tl~e~ he D~vable carrlage is ved in a dlrection :
aM~y from the attached thread at a fixed const~nt rate and the re~istance . ~:to ~uch mrvement i8 n~a~ured and recorded by the in3t~ument. FDr the tests
used herein, the st3ndard substrate is a ~heet of 80 x 80 ccunt, bleached, . .
cotton print cloth obta~ned ~rom Te~tfabrics Incorporated of M~dd1e~eK, New ::
10 Jersey snd de~ignated by them a~ Style 4~0. This 3ubstrate i8 affixed to the
clasned, stainless steel sur~ase of tbe carrlage by using doible ~aced ~ive
tape. me ~urface of ~he s{~mple to be te.~ted i8 pressed do~a ~ t~he st~n3ard ~ ~ :
~ibstrate and a fa~r pound wei~ht is rolled ov~ t~ ~Dple. ~en testing
. ' a s~nple fo~ fric~cicnal resist~ncè under the ~e~ of a force acti~g r~l
~15 to ~he frictianal ~orce, a w~ht, eq~l t~ t~e desired no~al force i~ p~ed~
upon the e~mple. ~n all Ca9e8, *le carriag2 is mDved at a constan~ speed
.. 1. of 12 incl~s per ~ute. ~e fricti~nal force referTed to herein i8 ~he
force recorded by ~e iDstnment d~ing the test and represents ~he force `~
. . , ~ .
re~uired to dislodge the san~le ~rcm the s~bstrate. As r~ted herein, *~
. 20 oo-eficient o friction i~ defir~d 88 ~e r~orded ualue in jgr~ for the ;:
~rictional reslst~ce of tbe sa~le ~der a nGrmal load of 100 gr~na div~d
by 100. Wh~ testi~g sanple~ as d~crlbed herein, in all cases tha s~rQle
. ' i3 te8ted, i8 at~ched ~to a s~riit~y napkin and g~lly the r~i ~ i~ cut ~ ;~
Owv~8ely i.ll hEllf b~ acca~da :e the 8ize restrictior~ of the testing equi~t.
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`'' ~C~574~3
.
,
EXAMPLE L,~
. ' ' . : '
A full size sanitary napkln. is preipared having the
.
general construetion of that illustrated.in Fig~. 1 and 2.
The napkin ha~ the overall dimensions o~ 9 . 72 inches long
and 2.68 inches wide. and compriees a pad of comminuted wood
pulp weighing 13.1 grams and having .ti~imen~lon of 7.66
inche~ long, 2.68 inches wide ~.. 0~ 7 ~.ch thick. The napkin ~ -
is identical in ~11 respect~ to.~.~hë pr~tl~t no~ being sold by
'che Personal Prod~its ~ompany of Milltown, New Jersey a~ their
Stayfree* . ~pad feminine napkins with ~he ~xception that a
,0 friction~ layer 1~ the planar dim~insions of 9 . 72 inches
long and 2 inches ,widëi ~8 adhesively attaehed to the bo~ctom of
;-~ the napkin (the~.~ worn again~t the garment) and an elongated : .
. j ... .~ , ~ ,, . ~ . .
pre~sure sen~itive adhe~ive 8trip i8 appli~id centrally onto the
.~ ~urface of the friction~l làyer.
T}ie fri¢t~ layer i8 comp~iïsed of a. cellular poly^ -
urethane foam :of. t:hei ~t~ier type affd :is ob'tia:ine~ fr~m the .:~
Tenneco Chemi~,s~poration~ ~pI,asbi~ç`and Fo~r~i Division of l~ast
~utherford, N:J. ;and designated by them as code number 3845.
T}liB foam has an average density of 1.38 lbs./cu. ft.,
a tensile strength of at len~t ll lbQ./sq. in,, an elongation at
. .. . .~., ~
break of a~out 150%, &:'tear strength o~ about O.l lb./in., and
., an open cëlIular srea:o'~ 90%. Th~ foam has a thickne~s of
about 0.06 inches. A s~mple of thLs oam ag attached to a naplcin
- but without adhe~, 1~ tested on the Ins~cron Frictional Tes~er
-25 and exhibit3 ~.~ffLcLent of fricti~n. of 3.9.
.. ~ . . .. . . . .
* Re8istered Trad~3~ark ` ` ~ ~
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The presqure Bensi~ive adhe~ive layer applied to
; the surface of the foam i8 in the form of a rectangular strip
having the dimensions of 7.66 inche~ long by 3/8 inch wide
and i~ centrally located on the friction layer. The adhesive i8
S on~ of the rapid-setting, thermoplastic hot melt adhe~ives
and i8 obtained from the E~sex Chemical Corporation, BFC
Division of Sayreville, New Jersey and de~ignated by th~m
as 5~-J. A total weight of 0.15 grams of adhe3ive i~ used on
the napkin. The adhesive has a visco~ity of ~800 +- 700 cps
when measured at 350F, a specific gravity of 0.98 at ~ ;
: 78F, a melting range of 168 + 8F. The adhesive i8
1 heated to a temperature of 325F and then extruded onto the
`1` frictional layer through a nozzle.
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The napkin, when pressed into the crotch portion of
~`~ 15 an undergarment ~nd worn, exhibits a great resistance to
repositioning and when bein~ discarded after u~e, easlly peels
from the undergarment.
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I EXAMPLE 2 ; ~ ~
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A full size napkin is prepared identicaI to t~at of
~xample 1 with the exception of the frictional layer and ;~
the pressure sens~tive adhesive. In this case, the frictiona1
- layer iR a polyurethane foam of the ester type obtàined from
' the same Tenneco Chemical Corpora~ion and designated by ~hem a~
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F-4100. Thi~ fo~m has an average den~ity of 1.75 lb~/Rq. in.,
a tensile strength of 35 lbs./sq. in., an elongation at break
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of 300%, a tear of 4 lbs./in. ant ~n average open cellular
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area of 45%. The fo~m layer i8 .035 inch thick and when a .
sample a8 attached tD a napkin, bu~ without adhesive, i8 tested
on the Instron Frictional Te~ter, it exhibits a co-efficient of ~;
friction of 3.4.
Centrally applied to the surface of this frictional
layer i8 a rectangular layer of pres~ure sen~itive athesive
measuring 7.66 inches by 3l8 inch and compri~ing 0.2 gram~ of
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a pressure sensi~ive adhesive obtained ~rom th~ Bo~tik DiviBion `.:
of U.S.M. Corpora~ion of Middletohl Mas8. and designated by ;~-
them with the code number 8~60. The adhesive ~B a 48% solids, : : ~
~ water-based ~mulsion of acrylic polymer having a viscosity ~ :
`, r~n8e of 2100-2400 Cp8 at 76F and a specific gravity of 1.13.
' Thi8 emulsion i~ extruded onto the surface of the fr~ctonal
.`l layer and allowed to dry into a tacky pre~ure sensitive layer. .
The napkin, when pressed into the crotch portion of an
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` undergarment and wor~.again exhibit~ a great rei~istance to
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~ repos;ltioning although ~omewhat le~s than that of the prior
:- exampla. Again, upon being discarded, the napkin easily peels
~; from the.undergarment.
: EXAMPLE 3
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A ~erie~ of napkins having the identical configuratlon
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and dimension~of the napkins of Example 2 are prepared, with ~
~, the exception ~hat the quant~ty of Bost~k adhe~ive i8 varied, i :
-.~i as is shown in Table 1 below. A second~series of napkins are .-,
~ also prepared identical to that of Example 2 wlththe exception ~ ~ :
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that various quantitie~ o~ the Rs3ex ho~ melt adhesive des~
cribed in Example l are applied to the e~ter polyurethane
.. ~ frictional layer a9 the pressure sen~itive element.
: The~e n~pkin~ a~e tested on the Instron ~rictional Tester ~`
under condition of essentially zero normsl force, by cutting
:, each of the napkins transversely in half to accomodate the
~ize re~trictions o~ the testing equipment. As a con~rol, a
s~mple of the product currently being sold by Personal Products
, Company as Stayfree* Maxi Pad feminine napkins i8 al~o cut
; 10 in half and id ntically te3ted. Thi8 eontrol 3Emple i8 iden- :~
tical in~all respects to the other 8ample3 being tested with
the excep~ion that~the frictional layer is omitted ant in~tesd,
.,, the rectangular, preseure eensitive adhesive, comprised of the
~ aforement~oned Bostik adheslve, is applied directly ~o the -.
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:.~l5 nonwoven cover on the bottom of the napkin. The control ~ample ~ ; : has 0.225 gram~ of this adhe~lve applied thereon. The results
of these te~ts are reported in Table l.
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TABLE 1 __
Fric~cional ~orce at
Zero Normal Force
Sample Tes ted ~'Ozs .
5 1. Control ~ampleswithout foam and
with Bostlk cold adhesive
Wei~h~ of Adhe3ive
~ 70.9
. ~ .
2. Sample~with Polyurethane ester and
Bostik ~old adhesive
Wei~ht of Adhe~lve
0. 08 10~ . 6
` 0. 10 110 . 0
0. 15 136 9
- 0.-18 ~23 3 :~
. 0. 25 ~9 . 6
3. Samples with Polyuret~ane ester and `~ ~ `
;; 20 E~8ex Hot Melt
Wel~ht of Adhesive 83.2 -
15 99 . 3
~ i . 25 - : ~ ~ 106 . 4 ~ ~ .
. 35 135 . 8
.. - 4~ 125.4
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A~ Table lindicates, the frictlonal ~orce~ required to
d~slodge the sa~ple~;:which, in ~ccordance with the ~eachings
of this inven~iion, include i rictional l~ver be~ween the :~
nonwo~en cover and the pressure sensitive adhesive are far
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greater than the for~es requlred to dialod~e the conventional
n~pkin sample. This i8 totally unexpected in view of the
~act that the~e te~ts are run under condlti~ns o~ zero normal
force? i.e., when the frictional iayer.3~0uld bë contributlng
no~hing to~the se~ietance to tislodg~ment. It should be
noted that an advantageous enhancement in the re~i~tance to ~:
dislo~dgement isi evideneed even when a quantity of adhesive
', ~, 8ubRtantlally l'e88 ~.' than that applied to the conveational
napkin i8 used. ,''!''
i EXAMPLE 4.: ., . ~ .
A flrsti ~i,eries of napkins a~e prepared ~jdentical to
thst of Ex ~ :1 in all rèspects~ncludlng ~he~ ether type
. ~:polyurethane frictional layer and the 0.15 gram of Essex hot
- melt adhesive as the preBsure ~ensieive element.) A second~
;
Be~ies of napkin~ are prepared, identical with the first - ::
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~ ' series with the excep~ion that the polyurethane foam of ~ .
. . .
the ester t~pe as tescribed in Rxa~ple 2 i3 used as ~he
frie~ional layer. For ca~parative purposes, a third eerie~ ~-
of ~amples are prepared identic~l in all respect~ with the
the fir3~ serie~ with the exception that ~he pressure sensi- :
tive adhesive i8 elimina~ed. Also, for ~omparative purposes, ;~
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a fourth ~eries of ~mple~ are prepared ldentical ~o the
conventional St~yfree* M~xl Pad feminine Napkin, described
above. Each of the series of napkins are t~ted on the
Instro~ Frictional Te~ter,again by cutting the napkin trans-
versely in half~ under conditions of varying normal loadsas shown in Table 2 below. The results of these tests are
reportet in ~hat Table.
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TABLE 2
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SA~LE _ _ FRICTIOP~9L ~ORC (~- 2
1. Product ~h ether egpe
Polyurethne P~ and 0.15
gm. ~t~mElt s~si~¢ 144.0 16~.0 163.2 174.4 - 208.0 `.
2. Pr~ct wl~ t~r ~pe
- Pol~e E~ and 0.15 .
glD. I~t~laelt adhe8ive~103.4 122.7 lb3.7 165.4 197.4 "
3.~ iuct wl~h e~ type
adh~ive 2.7 14.8~ 22.7 45.9 88.8
4. a~w~l *~ot ~ ~74.6 81.3 86.6 97.0 ~110.9
Tool o~ 3. and 4. 77.3 96.1 109.3 142.9~ 199.7
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A3 csn be n0ted ~ an ~ nation of T~ble 2, the pnxh~ts
of thl~ lnvention, a~ embodied in the first and ~econd
series of semples tested, far exceed both the conventional
sdhesive attachment sya~e~ and one utilizing only a friction~l
layer in their abilitles to reslst diAlodge~ent. Not sur-
prisingly, the 8y8t~m using only the frictional layer does
not exhibit ang significant re~istanee to dislodg~men~
until a ~ubstantial normal force i8 applied. In view of thi~,
it i8 co~pletely surpri~n~ that the product~ embodying thia
invent~on ~how such a marked improvemen~ a~ zero normal
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force condit~ons. -~
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StlIl more s~rprisingly, i~ the fact ~hat the ~um of
the r~sistances of the frictional layer and tha~ of the
~dheaive layer whe~ taken alone, are still le88 ~h~n the
combinstion of these two operating together, a~ ~n accordance
. . . . .
with thi8 in~ention.
Althou~h the pre~ent invention has been de~cribed wi~h
reference to seYeral example~ and embodimen~s ~howing ~pe~ifi~ ~ :
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products in ~peci~lc arrangements and ~onfiguration3, such 18
no~ to be consldered limitative of the invention but mer~ly
illu~trative thereof.
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