Note: Descriptions are shown in the official language in which they were submitted.
BACKGROUND OF THE INVENTION
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FIELD 0~ INVENTION
This invention relates to disposable products,
such as diapers, sanitary napkins and underpads, and more
particularly to the top sheet construction thereof.
DESCRIPTION OF THE PRIOR ART
In the past, disposable products and particularly
diapers, sanitary napkins and ~mderpads, have been constructed
with top sheets of hydrophobic material. This material has
rather low fluid retention and fluid wetback characteristics
and improvements in fluid penetration are desirable especially
to prevent leaking when there are rapid gushes of fluid material,
such as urine, menstral fluid and the like. The hydrophobic
sheets have in the past been made of non-woven polyamide,
polypropylene, polyester fibers or mixtures of these and these
hydrophobic top sheets have needed improvement in fluid penetra-
tion. To this end, United States Patent No. 3,81~,101 shows
the use of a hydrophobic top she~t which is provided with a
series of slits therein which slits serve as valves. This
- 20 hydrophobic top sheet is of a film-like material.
Hydrophobic non-woven materials have been used
in diaper construction, such as shown in United States Patent
No. 3,987,786 which employs the use of a surfactant in partic-
~lar areas on treated materials.
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According to the invention, a disposable product includes an air
permeable hydrophobic top sheet, wherein said top sheet of hydrophobic ma-
terial contains a major amount of non-woven hydrophobic fibe-rs and from 0.1
to 0.6% by weight of a surfactant applied to the top surface of said top
sheet to facilitate fluid passage therethrough but minimize wetback, said
topsheet having a maximum wetback factor of 10, and a penetration factor of
at least about 80.
Preferably the disposable product construction includes a top sheet
of hydrophobic non-woven material, based on polyamide, polypropylene or poly-
ester material, which overlies the absor~ent pad which in turn is underlined
by a water impervious film material. The top sheet is suitably treated with
a surfactant preferably non-ionic to provide for more rapid fluid penetration
while retaining optimum wetback and fluid retention characteristics. To this
end, preferably only spaced areas of the top sheet are coated such as by
spraying the central area or line printing, spot printing in discrete areas
of the top sheet.
In the drawings,
Figure 1 is a perspective view of a diaper constructed in accordance
with the concepts of the present invention with parts thereof broken away
illustrating details of construction;
Figure 2 is a vertical sectional detail view looking along the
plane of line 2-2 in Figure l;
Figure 3 is a schematic elevational view of a diaper;
Figure 4a is a partial plan view illustrating a disposable diaper
having line printed surfactant on the top sheet thereof;
Figure ~b is a partial plan view of a diaper which has surfactant
printed in discrete spaced areas thereon; and,
Figure 5 is a plan view of a preferred embodiment of the invention
wherein the central portion of the top sheet is line printed in spaced dis-
crete areas with surfactant.
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DETAILED DESCRIPTION OF T~E INVENTION
IVith continuing re~erence to the accompanying
drawing, wherein like reference numerals designate similar parts
throughout the various views, reference numeral 10 generally
designates a diaper which includes a bottom sheet 12 of water
impervious plastic film material (which may be embossed or matte
finished) having mounted thereon a pad 14 formed of an absorbent
core J which may have one or more layers of wadding. The top
sheet 16 is made of non-woven hydrophobic material, such as
polypropylene, polyamide or polyes-ter fibers. The elements of
the diaper 10 are assembled in conventional manner. The topsheet
per se is conventional and may be spun-bonded, dry or wet-laid
and may be chemically or thermaIly bonded.
In accordance with the concepts of the present
invention, the top sheet is treated as at 1~ with 0.1 to 0.6%
by weight of a surfactan-t capable of altering the hydrophobic
properties of the material on the top surface thereof. The
surfactant is preferably a non-ionic and more preferably an
ethoxylate of (1) an C12 to C20 alcohol ~e.g. 5-20 moles of E.O.)*,
~2) a C6 to C10 alkyl phenol (e.g. 5-30 moles of E.O.). A prefer-
red nonionic is "Triton X-100" ~a 10 E.O. condensate with octyl
phenol), of the top sheet 16 and, as shown in Figure 3, may be
sprayed or surface printed as at 20 in only the central areas
of the top sheet 16. Conventional dip and roller coating may
be used as well.
As shown in Figure 4a, the surfactant may be line
printed as at 22. Alternatively, the surfactant may be spot
printed as at 24 in Figure 4b in discrete areas at spaced intervals.
* E.O. is ethylene oxide
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In a preferred embodiment, as shown in Figure 5, the surfactant is line
printed at 26 in spaced intervals on each line with the areas being printed
in each line being staggered. Only the central portion of the top sheet is
shown provided with the printed coating or surfactant. If desired, the en-
tire surface may be so treated.
A particularly preferred line treatment is one wherein the lines
2Z, instead of ~eing parallel to the sides of the diaper, are arranged diag-
onally (e.g. at an angle of from 30 to 60 with diaper edge). In a further
desirable embodiment the lines shown in Figure 4A are rotated 90.
In operation, fluid penetration is enhanced by the surfactant
treated areas of the non-woven hydrophobic material to permit more rapid
fluid penetration. However, little change of the desirable fluid wetback
and fluid retention characteristics are evident. In the preferred top-sur-
face treatment, the surfactant does not penetrate fully through the material,
but only serves to initially guide the fluid material to penetrate the non-
woven hydrophobic material, and this further limits wetback.
The treated topsheets of the present invention have a penetration
factor of at least 80 and a wetback factor no greater than 10. These factors
represent the percent of fluid which passes through the sheet in the test pe-
riod time and the percent which "wetsback" in the prescribed test. In thetest procedures 30 c.c. of fluid are used. If all passes through the sheet
with no "roll of~' the penetration factor is 100. If half rolls off then the
factor is 50. Similarly if 15 c.c. of fluid are wet back in the described
procedure the factor is 50. Obviously, the higher the penetration factor and
the lower the wetback factor the more desirable is the product: -
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