U.S. patent number 3,814,101 [Application Number 05/312,131] was granted by the patent office on 1974-06-04 for disposable absorbent articles.
This patent grant is currently assigned to Union Carbide Corporation. Invention is credited to Theodore Fredrick Kozak.
United States Patent |
3,814,101 |
Kozak |
June 4, 1974 |
**Please see images for:
( Certificate of Correction ) ** |
DISPOSABLE ABSORBENT ARTICLES
Abstract
Disposable absorbent articles are disclosed which include a
topsheet of non-fibrous hydrophobic film having a plurality of
valvular openings therein and a system of depressed areas disposed
across the surface of the topsheet. The openings readily permit
flow of liquid in the direction of the absorbent but substantially
reduce the possibility of flow in the opposite direction.
Inventors: |
Kozak; Theodore Fredrick
(Peekskill, NY) |
Assignee: |
Union Carbide Corporation (New
York, NY)
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Family
ID: |
26754212 |
Appl.
No.: |
05/312,131 |
Filed: |
December 4, 1972 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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73185 |
Sep 17, 1970 |
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Current U.S.
Class: |
604/370; 428/136;
604/366; 604/372; 604/375; 604/380 |
Current CPC
Class: |
C08L
23/06 (20130101); A61F 13/5126 (20130101); A61L
15/24 (20130101); A61F 13/51121 (20130101); A61F
13/51305 (20130101); A61F 13/15203 (20130101); A61L
15/24 (20130101); A61F 2013/5395 (20130101); A61F
2013/5127 (20130101); Y10T 428/24314 (20150115); A61F
2013/53445 (20130101); A61F 2013/53721 (20130101); A61F
2013/51372 (20130101); A61F 2013/53782 (20130101); A61F
13/53704 (20130101); A61F 2013/53908 (20130101); A61F
2013/51409 (20130101); A61F 2013/15373 (20130101); A61F
2013/51078 (20130101); A61F 13/534 (20130101); A61F
13/537 (20130101); A61F 13/539 (20130101) |
Current International
Class: |
A61F
13/15 (20060101); A61L 15/16 (20060101); A61L
15/24 (20060101); A41b 013/02 () |
Field of
Search: |
;128/156,284,286,287,29W,296 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Rosenbaum; Charles F.
Attorney, Agent or Firm: Vicari; Clement J.
Parent Case Text
This application is a continuation-in-part of co-pending
application, Ser. No. 73,185 filed Sept. 17, 1970 and now
abandoned.
Claims
What is claimed is:
1. A disposable absorbent article comprising a hydrophobic topsheet
for placement adjacent to the body and having a plurality of
valvular valvular openings therein, a substantially liquid
impermeable backing sheet, an absorbent pad disposed between said
topsheet and backing sheet and being characterized by its ability
to absorb liquid passed through said valvular openings, said
valvular openings being substantially closable to prevent contact
of said absorbent material with the body and to retard backflow of
liquid absorbed by said absorbent pad, and a system of dimples
disposed on said topsheet, said dimples having a frequency of at
least 1 per square inch of absorbent pad area.
2. An absorbent article in accordance with claim 1 wherein said
plurality of valvular openings are substantially straight slits
arranged in parallel rows, each slit being disposed parallel to the
longitudinal axis of said rows.
3. An absorbent article in accordance with claim 2 wherein each
slit is from 0.07 to 0.2 inch in length and wherein said slits are
present in said topsheet in an amount of about 30 to 150 per square
inch of topsheet.
4. An absorbent article according to claim 1 wherein said dimples
are disposed on said topsheet in an amount of about 1 to about 100
dimples per square inch of absorbent pad area.
5. An absorbent article according to claim 1 wherein said dimples
are disposed on said topsheet in an amount of about 3 to about 25
dimples per square inch of absorbent pad area.
6. An absorbent article according to claim 1 wherein said dimples
are disposed on said topsheet in an amount of about 6 to about 15
dimples per square inch of absorbent pad area.
7. An absorbent article in accordance with claim 1 wherein the
total area of said dimples does not exceed more than 20 percent of
the area of said absorbent pad.
8. An absorbent article in accordance with claim 1 wherein the
total area of said dimples is from 4 to 12 percent of the area of
said absorbent pad.
9. An absorbent article in accordance with claim 1 wherein said
dimples have a circular configuration with a diameter of from about
0.025 to about 0.250 inch.
10. An absorbent article in accordance with claim 1 wherein said
dimples have a circular configuration with a diameter of from about
0.075 to about 0.150 inch.
11. An absorbent article in accordance with claim 1 wherein said
plurality of valvular openings are substantially parallel straight
slits disposed in longitudinal rows, each slit being angularly
disposed with respect to the longitudinal axis of said row and
being arranged in a manner such that the end points of each slit
lie in a line substantially between the end points of corresponding
slits in adjacent rows.
12. An absorbent article in accordance with claim 11 wherein said
slits are from about 0.030 to about 0.250 inch in length.
13. An absorbent article in accordance with claim 11 wherein said
slits are from about 0.07 to about 0.2 inch in length.
14. An absorbent article in accordance with claim 11 wherein said
slits are present in said topsheet in an amount of 30 to 150 per
square inch.
15. An absorbent article according to claim 11 wherein said dimples
are disposed on said topsheet in an amount of about 1 to about 100
dimples per square inch of absorbent pad area.
16. An absorbent article according to claim 11 wherein said dimples
are disposed on said topsheet in an amount of about 3 to about 25
dimples per square inch of absorbent pad area.
17. An absorbent article according to claim 11 wherein said dimples
are disposed on said topsheet in an amount of about 6 to about 15
dimples per square inch of absorbent pad area.
18. An absorbent article in accordance with claim 11 wherein the
total area of said dimples does not exceed more than 20 percent of
the area of said absorbent pad.
19. An absorbent article in accordance with claim 11 wherein the
total area of said dimples is from 4 to 12 percent of the area of
said absorbent pad.
20. An absorbent article in accordance with claim 11 wherein said
dimples have a circular configuration with a diameter of from about
0.025 to about 0.250 inch.
21. An absorbent article in accordance with claim 11 wherein said
dimples have a circular configuration with a diameter of from about
0.075 to about 0.150 inch.
22. A disposable baby diaper comprising in combination, the
hydrophobic topsheet, the substantially liquid impermeable backing
sheet, the absorbent pad and the dimples as defined in claim 1
wherein the topsheet and backing sheet are each 0.5 to 2.0 mil
thick and of substantially the same dimensions and being at least
partially adhered to each other around their periphery to form an
integrated diaper structure having the absorbent pad substantially
enclosed and sandwiched between the topsheet and the backing sheet,
and wherein the valvular openings are substantially straight slits
arranged in parallel rows, each slit being disposed parallel to the
longitudinal axis of said rows.
23. A disposable baby diaper in accordance with claim 22 wherein
each slit is from about 0.030 to about 0.250 inch in length and
wherein said slits are present in said topsheet in an amount of
about 30 to 150 per square inch of topsheet.
24. A disposable baby diaper in accordance with claim 23 wherein
the hydrophobic topsheet is an ethylene-ethyl acrylate film and
wherein the absorbent pad is a stack of layers of absorbent
wadding.
25. A disposable baby diaper in accordance with claim 22 wherein
said dimples are disposed on said hydrophobic topsheet in an amount
of about 1 to about 100 dimples per square inch of absorbent pad
area.
26. A disposable baby diaper in accordance with claim 22 wherein
said dimples are disposed on said topsheet in an amount of from
about 3 to about 25 dimples per square inch of absorbent pad
area.
27. A disposable baby diaper in accordance with claim 22 wherein
said dimples are disposed on said topsheet in an amount of from
about 6 to about 15 dimples per square inch of absorbent pad
area.
28. A disposable baby diaper in accordance with claim 22 wherein
the total area of said dimples does not exceed more than 20 percent
of the area of said absorbent pad.
29. A disposable baby diaper in accordance with claim 22 wherein
the total area of said dimples is from 4 to 12 percent of the area
of said absorbent pad.
30. A disposable baby diaper in accordance with claim 22 wherein
said dimples have a circular configuration with a diameter of from
about 0.025 to about 0.250 inch.
31. A disposable baby diaper in accordance with claim 22 wherein
said dimples have a circular configuration with a diameter of from
about 0.075 to about 0.150 inch.
32. A disposable baby diaper according to claim 22 wherein said
topsheet and backing sheet are heat sealed to each around their
periphery.
33. A disposable baby diaper which comprises in combination:
a hydrophobic topsheet, for placement adjacent to the body, having
a plurality of valvular openings therein, said openings being
substantially parallel straight slits disposed in longitudinal
rows, each slit being angularly disposed with respect to the
longitudinal axis of each row;
at least one absorbent pad adjacent to said topsheet characterized
by its ability to absorb and retain liquid passed through said
openings;
a substantially liquid impermeable backing sheet adjacent to the
absorbent layer on the side opposite the topsheet, the openings in
said topsheet being substantially closable to prevent contact of
said absorbent pad with the body and to retard backflow of liquid
from said absorbent pad, and said topsheet and said backing sheet
being of substantially the same dimensions and being at least
partially adhered to each other around their periphery to form an
integral diaper structure having the absorbent pad substantially
enclosed and sandwiched between the topsheet and backing sheet;
and
a system of dimples disposed on said topsheet, said dimples having
a frequency of at least 1 per square inch of absorbent pad
area.
34. A disposable baby diaper in accordance with claim 33 wherein
said slits are further characterized in that they are arranged in a
manner such that the end points of each slit lie in a line
substantially between the end points of corresponding slits in
adjacent rows and are from about 0.030 to about 0.250 inch in
length.
35. A disposable baby diaper in accordance with claim 33 wherein
said dimples have a frequency of about 1 to about 100 dimples per
square inch of absorbent pad area, and wherein said topsheet and
bottom sheet are adhered by heat sealing said topsheet to said
backing sheet.
36. A disposable baby diaper which comprises in combination:
a hydrophobic topsheet, for placement adjacent to the body, having
a plurality of valvular openings therein, said openings being
substantially parallel straight slits disposed in longitudinal
rows, each slit being angularly disposed with respect to the
longitudinal axis of each row and being arranged in a manner such
that the end points of each slit lie in a line substantially
between the end points of corresponding slits in adjacent rows and
are from about 0.030 to about 0.250 inch in length;
at least one absorbent pad adjacent to said topsheet characterized
by its ability to absorb and retain liquid passed through said
openings;
a substantially liquid impermeable backing sheet adjacent to the
absorbent layer on the side opposite the topsheet, the openings in
said topsheet being substantially closable to prevent contact of
said absorbent pad with the body and to retard backflow of liquid
from said absorbent pad, and said topsheet and said backing sheet
being of substantially the same dimensions and being at least
partially heat sealed to each other around their periphery to form
an integral diaper structure having the absorbent pad substantially
enclosed and sandwiched between the topsheet and backing sheet;
and
a system of dimples disposed on said topsheet, said dimples having
a frequency of about 1 to about 100 dimples per square inch of
absorbent pad area.
37. A disposable baby diaper in accordance with claim 36 wherein
said dimples are disposed on said topsheet in an amount of about 3
to about 25 dimples per square inch of absorbent pad area.
38. A disposable baby diaper in accordance with claim 36 wherein
said slits are from about 0.07 to about 0.2 inch in length.
39. A disposable baby diaper in accordance with claim 36 wherein
the slits closest to said dimples are opened to a greater extent
than slits situated further from said dimples.
40. A disposable baby diaper which comprises in combination:
a hydrophobic topsheet, for placement adjacent to the body, having
a plurality of valvular openings therein, said openings being
substantially parallel straight slits disposed in longitudinal
rows, each slit being angularly disposed with respect to the
longitudinal axis of each row and being arranged in a manner such
that the end points of each slit lie in a line substantially
between the end points of corresponding slits in adjacent rows and
are from about 0.07 to about 0.2 inch in length;
at least one absorbent pad adjacent to said topsheet characterized
by its ability to absorb and retain liquid passed through said
openings;
a system of dimples disposed on said topsheet, said dimples having
a frequency of about 3 to about 25 dimples per square inch of
absorbent pad area; and
a substantially liquid impermeable backing sheet adjacent to the
absorbent layer on the side opposite the topsheet, the slits in
said topsheet closest to said dimples being opened to a greater
extent than slits situated further from said dimples, said slits
being substantially closable to prevent contact of said absorbent
pad with the body and to retard backflow of liquid from said
absorbent pad and said topsheet and said backing sheet being of
substantially the same dimensions and being at least partially heat
sealed to each other around their periphery to form an integral
diaper structure having the absorbent pad substantially enclosed
and sandwiched between the topsheet and backing sheet.
41. A disposable baby diaper according to claim 40 wherein said
dimples have a frequency of about 6 to about 15 per square inch of
absorbent pad area.
42. A disposable baby diaper according to claim 36 wherein the
total area of said dimples does not exceed more than 20 percent of
the area of said absorbent pad.
43. A disposable baby diaper according to claim 36 wherein the
total area of said dimples is from 4 to 12 percent of the area of
said absorbent pad.
44. A disposable baby diaper according to claim 36 wherein said
dimples have a circular configuration and are from about 0.025 to
about 0.250 inch diameter.
45. A disposable baby diaper according to claim 36 wherein said
dimples have a circular configuration and are from about 0.075 to
about 0.150 inch diameter.
46. A disposable baby diaper according to claim 36 wherein said
slits are disposed in said topsheet in an amount of about 30 to
about 150 per square inch.
47. A disposable baby diaper which comprises in combination:
a non-fibrous hydrophobic topsheet, for placement adjacent to the
body, having a plurality of valvular openings therein, said
openings being substantially parallel straight slits disposed in
longitudinal rows, each slit being angularly disposed with respect
to the longitudinal axis of each row and being arranged in a manner
such that the end points of each slit lie in a line substantially
between the end points of corresponding slits in adjacent rows and
are from about 0.07 to about 0.2 inch in length and having a
frequency of about 30 to 150 per square inch of topsheet;
at least one absorbent pad adjacent to said topsheet characterized
by its ability to absorb and retain liquid passed through said
openings; and
a system of dimples disposed on said topsheet, said dimples having
a circular configuration and being about from 0.25 to about 0.250
inch diameter, and wherein the total area of said dimples does not
exceed more than 20 percent of the area of said absorbent pad.
48. A disposable baby diaper according to claim 47 wherein the
total area of said dimples is from 4 to 12 percent of the area of
said absorbent pad.
49. A disposable baby diaper according to claim 47 wherein said
non-fibrous hydrophobic topsheet is a film of ethylene-ethyl
acrylate and wherein said absorbent pad is a stack of layers of
absorbent wadding.
50. A disposable baby diaper according to claim 49 wherein said
ethylene-ethyl acrylate film is from 0.5 to 2.0 mil thick.
51. A disposable baby diaper according to claim 47 wherein the slit
size is 0.1 inch and wherein there is present about 81 slits per
square inch of topsheet.
52. A disposable baby diaper according to claim 47 wherein the
slits closest to said dimples are opened to a greater degree than
slits situated further from said dimples.
53. A disposable baby diaper according to claim 47 wherein said
dimples are from about 0.075 to about 0.150 inch diameter.
54. A disposable baby diaper which comprises in combination:
an ethylene-ethyl acrylate film of 0.5 to 2.0 mil thickness as
topsheet, for placement adjacent to the body, having a plurality of
valvular openings therein, said openings being substantially
parallel straight slits disposed in longitudinal rows, each slit
being angularly disposed with respect to the longitudinal axis of
each row and being arranged in a manner such that the end points of
each slit lie in a line substantially between the end points of
corresponding slits in adjacent rows and are about 0.1 inch in
length and of a frequency of about 81 per square inch of
topsheet;
at least one absorbent pad comprising a stack of layers of
absorbent wadding adjacent to said topsheet characterized by its
ability to absorb and retain liquid passed through said openings;
and
a system of dimples disposed on said topsheet, said dimples having
a circular configuration and being about from 0.25 to about 0.250
inch diameter, and wherein the total area of said dimples does not
exceed more than 20 percent of the area of said absorbent pad, said
diaper being further characterized in that the slits closest to
said dimples are opened to a greater degree than slits situated
further from said dimples.
55. A disposable baby diaper according to claim 54 wherein the
dimples have a frequency of about 1 to about 100 per square inch of
absorbent pad area.
56. A disposable baby diaper according to claim 54 wherein the
dimples have a frequency of about 3 to about 25 per square inch of
absorbent pad area.
57. A disposable baby diaper according to claim 54 wherein the
dimples have a frequency of about 6 to about 15 per square inch of
absorbent pad area.
58. A disposable baby diaper which comprises in combination:
a hydrophobic topsheet, for placement adjacent to the body, having
a plurality of valvular openings therein, said openings being
substantially parallel straight slits disposed in longitudinal
rows;
at least one absorbent pad adjacent to said topsheet characterized
by its ability to absorb and retain liquid passed through said
openings;
a substantially liquid impermeable backing sheet adjacent to the
absorbent layer on the side opposite the topsheet, the openings in
said topsheet being substantially closable to prevent contact of
said absorbent pad with the body and to retard backflow of liquid
from said absorbent pad, and said topsheet and said backing sheet
being of substantially the same dimensions and being at least
partially adhered to each other around their periphery to form an
integral diaper structure having the absorbent pad substantially
enclosed and sandwiched between the topsheet and backing sheet;
and
a system of depressed areas disposed on said topsheet the lower
portion of said depressed areas extending below the plane of said
topsheet and being substantially liquid impermeable and in
nonadhering relation with said absorbent pad, said depressed areas
having a frequency of at least 1 per square inch of absorbent pad
area.
59. A disposable baby diaper according to claim 58 further
characterized in that the slits are angularly disposed with respect
to the longitudinal axis of each row and are arranged in a manner
such that the end points of each slit lie in a line substantially
between the end points of corresponding slits in adjacent rows.
Description
This invention relates to disposable articles and more particularly
relates to disposable absorbent articles such as diapers,
incontinency pads and the like.
The use of disposable absorbent articles of the kind mentioned
above has greatly increased in recent years due to their ease of
use, low cost and the obvious sanitary value of having a clean,
fresh, disposable absorbent article for use without the
inconvenience of having to wash and reuse a previously used
nondisposable article. The advantages of using disposable absorbent
articles are particularly apparent in the widespread acceptance of
disposable diapers as a replacement for the cloth diapers which
have traditionally been used.
In addition to the advantages set forth above for disposable
absorbent articles many of these articles include, as an integral
part of their structure, a liquid impermeable backing sheet which
offers other advantages in use. For example, disposable diapers
which include such a backing sheet obviate the necessity of using
rubber pants on the baby to prevent leakage through the diaper and
consequently wetting of the baby's clothing.
The present invention will be described in detail with reference to
a disposable diaper, but it will be obvious to those skilled in the
art that the teachings are applicable to other disposable absorbent
articles such as incontinency pads and the like.
In its most fundamental construction a disposable diaper merely
comprises a layer of disposable absorbent material lining a backing
sheet of liquid impermeable material which may be disposable or
reusable. The thickness of the layer of absorbent material can be
varied depending upon the desired use. For example, if the diaper
were to be used overnight for an older baby it would be required to
have a greater absorptive capacity than one used for a short time
during the day or for an infant and consequently the absorbent
layer would be thicker. The length and width of the diaper can also
be varied for different size babies. Generally, the absorbent pad
will be about one-eighth to one-half inch thick and the diaper will
have a length of about 12 to 18 inches and a width of about 8 to 16
inches.
While a baby diaper constructed in this manner supplies the
essential ingredients of a disposable diaper, namely an absorbent
layer and a liquid impermeable backing sheet, modifications have
previously been proposed to overcome one or more of the defects
inherent in the basic construction. It was found, for example, that
when the absorbent layer became soaked with urine it tended to wad
together or lost most of its integral strength and began to
shred.
In order to overcome these disadvantages it has been common to
place a layer of non-woven, gauze, or other material which will
maintain its integrity after wetting on top of the absorbent layer
of the diaper thereby sandwiching the absorbent layer between a
topsheet of self-supporting but liquid permeable material and a
backing sheet of liquid impermeable material. Such a construction
overcame the disadvantages of shredding but tended to make the baby
uncomfortable after wetting since the urine would partially be
absorbed by the topsheet which was against the skin of the baby.
This contact of the baby's skin with urine on the surface of the
diaper is one of the principal causes of diaper-derived skin rash.
Additionally, upon removal of a wet diaper, it was found that the
baby's skin was wet and drying was necessary before a clean diaper
could be applied.
In an attempt to overcome this deficiency it has been suggested
that the topsheet be made hydrophobic or water-shedding to maintain
the layer which is in contact with the baby's skin as dry as
possible. This has been accomplished by forming the topsheet of the
diaper in part or completely of hydrophobic fibers or by coating or
impregnating an otherwise hydrophilic topsheet with a hydrophobic
resin.
This procedure has not been completely satisfactory since the
topsheet of the diaper, whether it be a woven or nonwoven material,
will contain spaces between its fibers which are continually open
to the passage of liquid in both directions. The spaces are
necessary to allow urine to pass from the baby to the absorbent
layer of the diaper. When the diaper has reached its maximum
capacity or when pressure is applied to the absorbent layer, for
example by the baby sitting in the wet diaper, the absorbent layer
acts much like a sponge which has been fully saturated or
compressed and exudes urine to its surface where it can pass
through the openings in the topsheet and contact the skin of the
baby.
It is an object of this invention to provide a disposable absorbent
article, such as a disposable diaper, having a topsheet which will
readily permit flow of liquid in the direction of the absorbent
layer but which substantially reduces the possibility of flow in
the opposite direction. This and other objects will readily become
apparent to those skilled in the art in light of the teachings
herein set forth.
In its broad aspect, the disposable absorbent articles of this
invention are comprised of, in combination, at least one absorbent
pad and a topsheet adjacent to said pad and having a plurality of
valvular openings therein. The topsheet is preferably formed from a
non-fibrous hydrophobic film such as thermoplastic film having a
plurality of valvular apertures therein.
The invention will be described in detail with reference to the
accompanying drawings in which:
FIG. 1 is a plan view, partially cut away, of a disposable diaper
according to one embodiment of the invention;
FIG. 2 is a plan view, partially cut away of a disposable diaper
according to another and preferred embodiment of the invention;
FIG. 3 is a section taken along the line 3--3 of FIG. 2.
FIG. 4 is an enlarged fragmentary cross-section of FIG. 3 showing a
section of the absorbent article during unsaturation.
FIG. 5 is a view similar to FIG. 4 except that the absorbent
article is saturated with liquid.
FIG. 6 is a plan view, partially cut away of a disposable diaper
according to a further, but less preferred embodiment of the
present invention.
Referring in detail to FIG. 1 there is shown a disposable diaper,
generally designated 10, comprising a rectangular absorbent pad 12
substantially centrally located and sandwiched between a thin,
flexible backing sheet 14 of liquid impermeable material, such as
polyethylene film, and a thin flexible topsheet 16 also of a
normally liquid impermeable material. Topsheet 16 has a plurality
of slits 18 therein which slits will be described in greater detail
hereinafter.
Backing sheet 14 and topsheet 16 are of approximately equal size
and are of a length and width slightly greater than the
corresponding dimensions of absorbent pad 12. The edges of backing
sheet 14 and topsheet 16 are sealed to each other around the entire
periphery of the diaper and just outside the outermost edges of
absorbent pad 12. The sealing can be accomplished by any convenient
means, such as the use of an adhesive, but heat sealing is
preferred and is indicated by heat seal 20 around the periphery of
the diaper.
The absorbent pad 12 is a plurality of layers of absorbent tissue
paper or wadding stacked to the desired thickness. The wadding
layers need not be adhered to each other but, since it has been
common practice to adhesively, mechanically, or otherwise secure
the layers to each other to maintain the relative position of the
layers and the shape of the absorbent pad, such can also be done in
the diaper of the present invention. The wadding can be stacked to
form a pad of any desired thickness and hence absorbency can be
controlled for any particular use. For example, in conventional
disposable diaper constructions designed for use during the day it
has been common to stack the absorbent wadding to a thickness of
about one-eighth inch using generally from about 5 to 10 layers of
wadding. For special uses, for example, as an overnight diaper, it
may be desired to have a thicker and more absorbent pad, and a
thickness of about one-fourth inch, using about 10 to 20 layers of
wadding, would usually be sufficient.
Absorbent materials other than tissue and wadding will of course be
useful in the diaper construction of the present invention. For
example, absorbent non-woven pads can be fabricated to any desired
thickness and substituted for the absorbent pads described above.
One such absorbent pad which has been used extensively in
disposable diapers is a wood pulp product commonly known as wood
fluff and is prepared in the same manner as a non-woven fabric.
The only criteria for utility in the present invention are that the
material be absorbent, be capable of being fabricated in the form
of a pad, be compatible with the waste products with which it will
come in contact and be non-irritating to the skin.
Various natural and synthetic polymeric materials are themselves
absorbent or can be made absorbent and will therefore be useful as,
or in combination with, the absorbent pad of the present invention.
One group of polymers which are particularly preferred are
insoluble hydrophilic homopolymers and copolymers which form a gel
upon absorption of water. These materials offer the obvious
advantage of holding tenaciously to liquid and preventing the
release of liquid from the absorbent article and leaking or wetting
skin or clothing with which the absorbent article is in
contact.
In practice, the materials which have been found particularly
useful are insoluble hydrophilic polymers prepared from the
following starting materials: poly(alkylene oxides), e.g.
poly(ethylene oxide), polyvinyl alcohol, polyvinylmethyl ether,
copolymers of maleic anhydride and ethylene, copolymers of maleic
anhydride and vinylmethyl ether, polyelectrolytes, etc.
Insoluble hydrophilic polymers, sometimes referred to as
"hydrogels," are especially useful in the present invention because
they possess the ability to consume very large amounts of water in
the order of 25 to 100 times their dry weight.
The term "insoluble" or "insolubilization" as employed in relation
to these polymers is intended to define the formation of a gel
which does not flow and does not expel water under the pressures
encountered in the use of products described above.
The insolubilization can be effected by a wide variety of methods
and includes, but is not limited to, ionizing and nonionizing
radiation and chemical cross-linking through covalent and ionic
bonding.
A particularly preferred hydrogel for use in the articles of this
invention is comprised of at least one hydrophilic polymer of the
formula ##SPC1##
which has been cross-linked and wherein R.sub.1 and R.sub.2 are
selected from the group consisting of hydrogen, alkyl radicals and
alkyl substituted aryl radicals, and wherein R.sub.3 --R.sub.6 are
selected from the group consisting of hydrogen, methyl, phenyl and
vinyl radicals, and n is greater than one.
The hydrogels are polymeric compounds containing at least one of
the structural units shown below: ##SPC2##
wherein R.sub.1 --R.sub.4 are selected from the group consisting of
hydrogen, methyl, phenyl and vinyl radicals.
These hydrophilic polymers may include carbon-to-carbon
cross-linking between straight chain carbon atoms and the carbon
atoms of branch chain methyl groups and in addition a very minor
and insignificant number of bonds may include two oxygen atoms
linking the carbon atoms.
The polymeric gel compounds may contain cross-linking bonds present
as inter-molecular bonds (e.g. between two different molecules) and
intramolecular bonds (e.g. between carbon atoms of the same
molecule), and combinations of intra and intermolecular
cross-linking bonds.
The hydrogels can be used in the diaper constructions of the
present invention either in the form of thin transparent sheets
disposed between or in place of wadding layers of the absorbent pad
or can be embedded in the fibers of the absorbent pad as a powder
or in shredded form. The manner in which the materials are
incorporated into the pad is not critical since it is merely
necessary to have the polymers come in contact with the liquid
which penetrates the topsheet of the absorbent article.
The materials used in the fabrication of the topsheet and backing
sheet of the absorbent articles of the present invention are also
not limited to any particular chemical composition since it is
their physical properties rather than their chemical properties
which are important in the articles of the invention. These
materials should, of course, be thin, flexible, self-supporting,
and substantially water impermeable films. Preferably they are
thermoplastic materials which are capable of being heat sealed to
each other.
The backing sheet is preferably an olefinic or vinyl film.
Polyethylene of a thickness of from about 0.4 to about 1.5 mils is
most preferred. This type of film has previously been used
extensively for this purpose and commonly has had an embossed
design in its surface to simulate the appearance and hand of cloth.
These manufacturing techniques will also find use in the absorbent
articles of the present invention.
Any film which is useful as a backing sheet will also be useful as
a topsheet for the disposable absorbent articles of the invention.
It is preferable, however, to use a film for the topsheet which
resembles cloth more closely in feel and appearance since it is
this portion of the article which will come in contact with the
skin of the user. One film which has been found particularly useful
is ethylene-ethyl acrylate film. This copolymer is cloth-like,
softer and stronger after slitting than polyethylene film. The film
should have a thickness of from about 0.4 to about 2.0 mils with
about 1.0 to 1.5 mils being preferred.
As described above, the topsheet is made from a substantially
liquid impermeable film and must be provided with valvular openings
to be effective in the absorbent articles of the present
invention.
The term "valvular" as used throughout the specification and in the
claims is intended to refer to apertures in the topsheet which are
capable of opening to permit passage of liquid under certain
circumstances and reclosing to retard passage of liquid under
certain other circumstances. When open, the valvular openings
should have the ability to pass at least 20 milliliters of liquid
within 10 seconds when an area of about 20 square inches is wetted.
These openings may be of two basic types, substantially straight
slits and punctures.
The slits useful in the present invention must be substantially
straight since, if they are curved, V-shaped or of any other
configuration, they will form flaps in the surface of the film
which are too easily opened and tend to remain open. Such slits,
while permitting sufficient passage of liquid in the direction of
the absorbent pad, do not act to substantially reduce backflow of
liquid, which is the primary object of the present invention. This
advantage is also present if holes are formed in the film by
removing pieces of film material as opposed to puncturing the film
without removal of film material. The film is thereby left open to
the uncontrolled passage of liquid in both directions.
It has previously been suggested (see U.S. Pat. No. 2,877,765 and
U.S. Pat. No. 3,399,672) to incorporate curved slits in the layer
of a surgical dressing or bandage which is applied adjacent to the
skin to permit easy removal of the dressing from the skin. It was
found, however, for that particular use, that straight-sided slits
were inoperative. Conversely, it has been found that, while
straight-sided slits perform excellently and unexpectedly in
topsheets for disposable diapers, curved slits are unsuitable for
such use. This disparity in the performance of straight versus
curved slits can probably best be explained by the different
functions to be performed by the slits in each application.
In surgical dressings, for example, the topsheet must be permeable
to liquid draining from a wound usually slowly over a long period
of time. Backflow from the dressing is not a problem since the
absorbent layer has ample time to distribute the liquid by wicking
and no pool of liquid is formed at the interface between the
absorbent layer and the topsheet.
In a disposable diaper a quite different method of operation is
encountered. Rather than a slow steady flow, before bladder control
is obtained, babies urinate from 5 to as many as 30 or 40 times a
day and average about 10 times a day with about 40 grams of urine
per urination. There are, therefore, intermittent floods of liquid
contacting the topsheet of the diaper. The topsheet must quickly
pass this liquid through to the absorbent layer and prevent
backflow to a degree sufficient to permit the liquid to be
absorbed. This task becomes increasingly more difficult after the
second and subsequent urinations since the absorptive capacity of
the absorbent layers is substantially reduced. In addition, as a
baby sits in a wet diaper it releases liquid to the surface of the
absorbent pad where it will pass through the topsheet and contact
the baby's skin unless the openings in the topsheet act to prevent
this backflow.
As will be demonstrated hereinafter, curved slits permit adequate
drainage of liquid in the direction of the absorbent layer but do
not prevent backflow to a degree sufficient to allow their use in
an improved construction.
The appended drawing shows a preferred topsheet construction
wherein the topsheet 16 contains a plurality of straight slits 18
arranged in staggered parallel rows along the surface of the
topsheet. This construction is preferred since it yields a topsheet
which is strong and yet permits maximum passage of liquid.
To be efficient, the topsheet should contain from about 10 to 1,000
valvular openings per square inch of film. When slits are used,
they should each be from about 0.030 to about 0.5 inch in length.
Preferably there are from about 30 to about 150 slits per square
inch, each of such slits being from about 0.07 to about 0.2 inch in
length. The most preferred film contains about 50 slits per square
inch, each about 0.1 inch in length.
The slits enable the topsheet of the absorbent article to act as a
kind of one-way valve to the flow of liquid. For example, in the
case of a disposable diaper, the motion of the baby within the
diaper, such as by walking or sitting, will cause the slits to open
and close continually. When the baby wets, the urine will contact
the topsheet of the diaper and any motion on the part of the baby
will cause numerous slits to open and allow the urine to drain
through to the absorbent pad below. Even without motion on the part
of the baby a number of slits will be open to the passage of liquid
due to the contour of the diaper around the baby's bottom. Only
minimum contact of liquid with absorbent is necessary. Once contact
has been made and drainage has begun, a kind of siphon action is
initiated which will cause substantially all of the urine to drain
through the topsheet and into the absorbent pad. After the urine
has drained through the slits, the outer surface of the topsheet
will be almost dry due to its hydrophobic nature.
Passage of the urine back through the slits from the absorbent pad
will be retarded since there will not be a pool of liquid in
contact with the underside of the topsheet to flow back through the
slits as they are opened and closed by motion of the baby. An
effective barrier preventing the return of the urine to contact
with the skin of the baby is thereby established and the outermost
portion of the topsheet which contacts the baby's skin is kept
relatively dry.
The valvular openings can be formed in the topsheet in a number of
ways. The easiest involves the use of a roller having a number of
razor edges protruding therefrom across the width of the roller and
around its circumference. The cutting edges can be spaced as
desired on the roller and, if the portion protruding from the
roller is triangular in shape, the length of the slit made in the
film can be controlled by limiting the depth to which the blade
pierces the film. A resilient backup roller can be provided to
assist the piercing of the film which is fed between the slitting
roller and the backup roller. If desired, portions of the topsheet
may be retained in their unpierced condition. This might be
accomplished, for example, along a strip about one inch around the
periphery of the topsheet. Such a strip would act as an additional
safeguard against leakage at the edges of the diaper which might
come into direct contact with the baby's clothing.
After the topsheet is slit, the assembly of the diaper follows,
more or less, conventional methods of fabrication. The topsheet and
backing sheet are cut to approximately the same dimensions which
are equal to the desired size of the final diaper. The size can be
varied according to the desired use, for example, in an infant's
diaper a size of 10 .times. 14 inches might be sufficient whereas
in a diaper for a large child a size of 12 .times. 16 inches would
be better and a size of 14 .times. 18 inches might be preferred for
a diaper which could accommodate a toddler.
The topsheet and backing sheet are juxtaposed one on the other with
the absorbent pad sandwiched therebetween in approximately the
center of the sheets. The absorbent pad should be of a length and
width slightly smaller than the topsheet and backing sheet to
permit sealing of the topsheet to the backing sheet around their
periphery. An overhang of about one-half inch on each side should
be sufficient. Sealing can conveniently be accomplished by heat
sealing the edges. The heat sealing might also be used to
simultaneously accomplish a cutting of the edges to trim excess
sheet material from the diaper and yield a diaper structure which
is neat in its appearance.
If desired, the absorbent pad may be of the same length as the
topsheet and backing sheet and the top and bottom edges of the
diaper may be left unsealed. Such a construction readily lends
itself to mass production techniques since the diapers can be
fabricated in a continuous line and cut to the desired length
without the necessity of further finishing.
It has been found that the diaper can be assembled in the manner
described above before the topsheet is slit and a rotary slitter
can be used to cut the valvular openings in the topsheet of the
finished diaper without damage to the backing sheet or loss of its
liquid impermeability.
It will be obvious to those skilled in the art that applicant has
disclosed a basic diaper construction which is adaptable to the
inclusion of other materials for specific purposes. For example, it
might be desired to add a perfume or deodorizer to the absorbent
pad, to include baby powder or a soothing lotion on the outer
surface of the topsheet, or to incorporate a germicidal agent
somewhere in the diaper construction.
Moreover, it will be obvious to those skilled in the art that the
above teaching, which is set forth in detail with respect to
disposable baby diapers, will be equally applicable to similar
disposable absorbent articles such as incontinency pads and the
like. In each of these uses the construction of the absorbent
article will be basically the same as that set forth for a diaper
construction except that size, shape, and absorbency will be varied
for the particular use. In addition, tabs, adhesives, or some other
attachment means might suitably be included for the convenience of
the wearer.
The following examples are merely illustrative of the present
invention and are not intended to be limitative thereof.
EXAMPLE 1
An absorbent pad consisting of eight layers of absorbent wadding
and measuring approximately 12 inches .times. 16 inches .times.3/16
inch was positioned in the center of a sheet of polyethylene film
measuring about 121/4 inches .times. 161/4 inches .times. 1.25 mil
having a taffeta design embossed therein.
A 1.25 mil thick sheet of ethylene-ethyl acrylate film was
perforated by feeding it through the nip of a roller having a
plurality of small blades spaced around its circumference in
staggered parallel rows and a resilient backup roller. The
perforating roller had a blade density of about 125 blades per
square inch and the resulting perforated film had about 125
parallel slits per square inch each measuring about 0.1 inch in
length.
The perforated film was cut to approximately 121/4 inches .times.
161/4 inches and placed on top of the absorbent wadding pad thereby
sandwiching the pad between the perforated film and the
polyethylene film. The edges of the two films were then heat sealed
to each other with a bar sealer to complete the assembly procedure
and the resulting disposable diaper functioned satisfactorily.
EXAMPLE 2
A disposable diaper was fabricated from a backing sheet of
translucent polyethylene film measuring about 121/4 inches
.times.161/4 inches .times. 1.25 mil and a top sheet of translucent
ethylene-ethyl acrylate film measuring about 121/4 inches
.times.161/4 inches .times.1.25 mil. The absorbent pad was eight
layers of absorbent wadding and measured about 12 inches .times. 16
inches .times. 3/16 inch. The three layers of the diaper were
assembled and heat sealed in the manner set forth in Example 1 and
the completed diaper was run, topsheet side up under a rotary
slitter. The blades of the slitter were set to pierce the topsheet
and protrude partially into the absorbent pad but not to penetrate
through the absorbent pad to contact the backing sheet. The slits
formed were of the size and placement of those of Example 1 and the
diaper performed as well as the diaper of Example 1.
EXAMPLE 3
A diaper was fabricated in the manner described in Example 2 except
that the absorbent pad used was formed with about 2 grams of
cross-linked powdered poly(ethylene oxide) sprinkled on 4 layers of
wadding and covered with another 2 layers of wadding. The entire
assembly was then used in the fabrication of the diaper.
The resulting diaper was thinner than the diaper of Example 2 yet
had a greater absorptive capacity.
The following experiments were conducted to compare the performance
of curved versus straight slits in the topsheet of a simulated
diaper construction.
EXPERIMENT 1
A 53/8 inch diameter circle of test film supported on a screen and
covered by a 53/8 inch diameter circle of absorbent was clamped
between a 53/8 inch diameter glass cylinder and a 5 inch diameter
funnel leading to a graduate. A No. 13 rubber stopper was placed on
top of the test film and 200 milliliters of water was quickly added
to the glass cylinder. Times were recorded when the first drop of
water was collected and when 100 milliliters had been
collected.
Test films having about 45-48 slits per square inch and an average
slit length of 0.10 inch were tested. When straight slits were
tested, the first drop of water was collected in 2 seconds and 100
milliliters was collected in 14 seconds. When curved slits were
tested the first drop was collected in 1 second and 100 milliliters
was collected in 3 seconds.
The results of this comparison indicates that both straight and
curved slits performed satisfactorily in passing liquid through an
absorbent.
EXPERIMENT 2
The same glassware as in Experiment 1 was employed but the test
procedure was modified to determine the backflow obtained with
samples of test film identical to those of Experiment 1.
The film was placed across the top opening of the funnel such that
it did not sag nor stretch open. A circle of wadding was placed
over the film and the glass cylinder was clamped in place. One
hundred milliliters of water was added to the cylinder and the
times were recorded for collection of the first drop and 10
milliliters of water in the graduate.
The first drop through both straight slits and curved slits was
collected in 1 second but curved slits collected 10 milliliters in
10 seconds whereas straight slits took 95 seconds to collect the
same volume. Backflow for curved slits is therefore considerably
faster than for straight slits and unsatisfactory for an improved
diaper construction.
EXPERIMENT 3
Backflow was also measured for films having curved and straight
slits of the same size and quantity as the films of Experiments 1
and 2 by wetting a 5 inch diameter absorbent pad with 30
milliliters of water covering the pad with the test film and
covering the film with another dry absorbent pad of known weight
and a 12 pound weight. After 2 seconds the dry pad was weighed to
determine water pick-up.
The average backflow for curved slits was 5.1 grams while straight
slits averaged only 3.0 grams, again indicating that straight slits
would be more suitable for use in diaper constructions than curved
slits.
As a control the experiment was also run with no film between the
wet and dry pads and with a nonwoven having 50 per cent open spaces
between the pads. Without any film between the pads 8.9 grams of
water was picked-up while with the nonwoven 7.1 grams was
absorbed.
As will be evident from the foregoing, the absorbent article
described in connection with FIG. 1 solved many of the problems
incident to prior art absorbent articles, particularly those
problems associated with diapers, incontinency pads and the
like.
Unfortunately, however, although the major problems of the
conventional products were eliminated, nevertheless, the advantages
of the novel absorbent articles were off-set, to a limited degree,
by the creation of minor disadvantages which, although not as
serious as the conventional problems, nevertheless served as a
"stumbling-block" to the attainment of an absorbent article,
particularly a baby diaper, which would have optimum
characteristics of functional utility, dimensional (or relative)
stability (including wet integrity), and consumer acceptance.
It should be remembered that the qualities or characteristics which
render an absorbent article, e.g., a baby diaper, superior to any
heretofore known are those characteristics which, among others:
a. permit (where a hydrophobic topsheet is employed) the necessary
passage of urine through the openings of the hydrophobic sheet to
the absorbent layer during a period of time such that the residence
time, i.e., the time between urination and absorption, is below
that which would cause discomfort, skin rashes, external leakage
and the like,
b. substantially reduce the amount of urine exuding back through
the openings of the hydrophobic sheet when the absorbent layer is
wetted and compressed,
c. have dimensional or relative stability, and
d. have an aesthetic appearance, i.e., pleasing to the eye and
touch.
The term "dimensional or relative stability" as it is employed in
item (c) is intended to define the fixed relationship of the
various constituents of the absorbent article. For example, where a
baby diaper contains a topsheet and a backing sheet which
sandwiches an absorbent material, it is advantageous that the
absorbent material be fixed with respect to the topsheet or backing
sheet so as to prevent "migration" of the absorbent material. An
unfixed relationship would ultimately result in "bunching-up" or
wadding of the absorbent particularly when a baby is sitting and
moving in a wet diaper.
It is also intended that the term be used in connection with the
wet integrity of the diaper, i.e., the ability of the constituents
of the diaper to maintain their strength and resist shredding when
wet.
Thus, although the absorbent article depicted in FIG. 1 is an
improvement over the conventional absorbent articles, with respect
to one or more of the above qualities, nevertheless, as mentioned
previously, certain draw-backs are encountered. For example, with
respect to item (a), although the valvular openings in the topsheet
have the ability to pass at least 20 milliliters of liquid within
10 seconds when an area of 20 square inches is wetted, the initial
wicking time, i.e., the commencement of absorption of the liquid
into the absorbent material is still not of optimum standards.
Stated another way, the residence time of the liquid (urine in the
case of diapers) prior to initiation of wicking is of a duration
such that discomfort could result.
With respect to item (c) above, it has been found that the
absorbent article depicted in FIG. 1, does not have the dimensional
or relative stability which would be characterized as significantly
superior to conventional articles. This is probably atrributable to
the fact that the absorbent material is sandwiched between the
topsheet and the backing sheet in non-adhering relation thereto,
and consequently, there is a tendency for the absorbent material to
"migrate" or shift with respect to its relation to the edges of the
top and backing sheets. In addition, the vertically aligned
valvular openings (slits) although providing the proper valvular
action as heretofore described, nevertheless are subject to
"zippering," i.e., the tendency to tear from one vertically
disposed slit to the other corresponding upper or lower disposed
vertical slit.
With respect to item (d), I have found that aesthetic qualities of
the absorbent article are not entirely satisfactory from a
commercial standpoint since the topsheet upon visual observation,
lacks a warm appearance.
Various techniques were tried in an effort to minimize or eliminate
one or more of the disadvantages incident to the absorbent product
depicted in FIG. 1. Initially, in order to preserve the relative
stability of the topsheet with respect to the absorbent material, I
tried adhering the topsheet to the absorbent layer with an
adhesive, but found however that improved dimensional stability is
achieved at the sacrifice of absorption qualities and loss of a
soft hand to the article. In order to eliminate the disadvantage of
"zippering," the vertically aligned slits were eliminated and
curved and V-shaped slits were substituted.
However, these design variations, substantiated previous
observations that curved or V-shaped slits formed flaps in the
surface of the topsheet which were too easily opened and which
tended to remain open thereby permitting the liquid to exude back
through them in contact with the skin.
Various other techniques were considered including, for example,
needle punching the absorbent article to firmly fix the absorbent
material with respect to its relation to the topsheet, but I found,
however, that the additional cost of processing in addition to the
contemplated loss of absorption and strength qualities created
additional disadvantages that far outweighed the problems sought to
be solved.
During the course of development, I tried a procedure whereby the
topsheet was adhered to the absorbent layer at various points along
the lower surface of the topsheet. The adhesion was accomplished by
contacting the absorbent article with a roller containing a system
of probes, and with the aid of heat and pressure, I was able to
depress and soften the topsheet (which is thermoplastic) at the
points of contact with the probes so that the fibers of the
absorbent layer immediately below the probes intermingled with the
softened depressed thermoplastic topsheet. Upon cooling of the
thermoplastic material, the intermingled fibers became permanently
embedded in the topsheet thereby reducing migration of the
absorbent material.
As mentioned previously however, the absorption of liquid takes
place through the valvular slits which must permit the passage of
the liquid to the absorgent layer. It would appear obvious,
therefore, that if the probes are to depress and soften the
thermoplastic material sufficient to "embed" the absorbent fibers
thereto, that any slits in contact with the probes would fuse
thereby decreasing the openings through which the liquid can pass
resulting in poor initial wicking and total absorption of the
liquid. In other words it would appear again that the solution of
one problem (dimensional stability) would be accomplished at the
sacrifice of another quality (good absorption characteristics).
When the resultant absorbent material was analyzed with respect to
absorption qualities, however, it was found surprisingly and
contrary to normal expectations that the absorption and more
significantly the wicking action was improved dramatically. It was
indeed surprising to find that this technique would provide an
absorbent article having outstanding absorption and wicking
qualities since, as mentioned previously, it appears logical and
obvious that if the thermoplastic material is to be selectively
treated with a hot probe, in the manner described, that there would
be a loss of absorption by fusion of those slits in contact with
the hot probe. I am of course aware of the disclosure in U.S. Pat.
No. 3,221,738 issued to G. E. Ekberg et al. on Dec. 7, 1965. The
diaper according to the patent disclosure consists of a core of
moisture-absorbing material, which is completely enclosed by a
liquid-insulating, thin plastic foil, and its main feature is that
the plastic foil on one of the core sides inside its confining
edges is heat-treated in such a way that the liquid insulating
property of the foil is completely or partially neutralized, so
that liquid reaching the heat-treated foil surface is automatically
sucked in through the foil and absorbed by the core. The method is
further characterized in that the foil layer is heated by means of
a number of heated metal bodies placed at a short distance from
each other, so that the foil layer forms a net-like pattern of
liquid-insulating foil.
According to the disclosure, therefore, liquid transfer is provided
through the throughgoing pores formed by heating the foil layer in
the manner described in the patent.
This teaching is diametrically opposed to what is desired by the
instant invention. According to the instant invention the bulk of
absorption of the liquid must be accomplished through the valvular
slits as contrasted to absorption through the thermoplastic
topsheet in the depressed areas. In this way, the valvular action
(as previously explained and as will be more fully explained) will
regulate the desired ingress of liquid. Thus, the depressed areas
in the instant invention (hereinafter referred to as "dimples"),
are for the purposes of providing dimensional stability, improving
the aesthetic appearance of the material and as an aid in
absorption in the manner as will be described with reference to the
drawings.
Referring to FIG. 2 of the drawings where like parts are designated
by like reference numerals (compared to FIG. 1), the improved
disposable diaper 10, includes the rectangular absorbent pad 12,
the flexible backing sheet 14 of liquid impermeable material and
the flexible topsheet 16 also of a normally liquid impermeable
material. The techniques of fabrication, the properties, and the
choice of the materials and characteristics of the improved diaper
depicted in FIG. 2 are identical to the diaper depicted in FIG. 1
except for differences specifically provided for hereinafter.
Situated across the surface of topsheet 16 is a system of valvular
openings (slits), identified by reference numeral 18a and a system
of depressed areas 22 (dimples). The slits 18a are arranged in
longitudinal rows in a manner such that each row constitutes a
longitudinal array of substantially parallel straight slits each
angularly disposed with respect to the longitudinal axis of the
row. Adjacent rows are similarly disposed except that the slits are
arranged in a manner such that the end points of each slit lie in a
line substantially between the end points of corresponding slits in
the adjacent alternate rows. The slits useful in the present
invention must be substantially straight since, if they are curved,
V-shaped or of any other configuration, they will form flaps in the
surface of the film which are too easily opened and tend to remain
opened. Moreover, the angular placement of the slits as described
previously, prevents "zippering" thereby eliminating one of the
major disadvantages of the absorbent articles depicted in FIG. 1.
The slits should each be from about 0.030 to about 0.25 inch in
length. Preferably there are from about 30 to about 150 slits per
square inch, each of such slits being from about 0.07 to about 0.2
inch in length. The most preferred film contains about 81 slits per
square inch, each about 0.1 inch in length.
The slits can be formed according to the methods employed in
connection with the absorbent diaper depicted in FIG. 1. However,
the preferred method for forming the slits in the topsheet
according to the present invention is described in the co-pending
application, Ser. No. 190,908 filed Oct. 20, 1971 and entitled
"Method and Apparatus for Piercing Thin Sheet Material." Briefly,
there is disclosed therein a method and apparatus for piercing thin
sheet material, such as plastic film, wherein the sheet material is
passed between a piercing member having a plurality of
independently resilient protrusions extending therefrom and a
backing member having a retiform exterior surface. The piercing
member or backup member is moved relative to the other member,
thereby causing the resilient protrusions to follow the retiform
surface and selectively pierce the film. The piercing member can be
a metal comb, a wire brush or a metal strip having a plurality of
substantially parallel slits extending from the edge thereof in the
direction of the opposite edge defining the resilient protrusions.
The backing member can be a wire screen, a perforated metal sheet,
an engraved metal roll or an endless belt which is driven
longitudinally with respect to the piercing member.
The depressed areas 22 (dimples) are distributed across the surface
of the topsheet in the manner shown in FIGS. 2-5. Thus, it will be
seen that the topsheet 16 contains a plurality of dimples arranged
in staggered parallel rows along the surface of the topsheet (FIG.
2) and which extend below the plane of the topsheet (FIGS. 3 and
4). The configuration of these dimples can be circular, eliptical,
rectangular, diamond shaped, and the like, the important criteria
being that they be formed in a manner such that there is
substantially no breaking or cutting of the topsheet during or
after fabrication.
I have found that the full advantages of the present invention are
not achieved if, during fabrication of the dimples, the topsheet is
broken, cut, or melted to an extent which would hinder the
controlled passage of liquid to the absorbent pad (which as
explained previously, is the function of the valvular openings). It
will be evident that if cutting or breaking of the topsheet occurs
during fabrication of the dimples, that the liquid will pass
through these cuts or breaks when the absorbent pad is unsaturated
and once the absorbent pad is saturated or even partially
saturated, that these entry points will also serve as points or
sites through which the liquid exudes back through the topsheet in
contact with, for example, a baby's skin.
For these reasons and furthermore in view of the ease and
simplicity of fabrication, I have found that the preferred form of
the dimple is circular as shown in FIGS. 2-4.
The dimples can be formed in the topsheet in a variety of ways. The
easiest and therefore the most preferred method involves the use of
a roller equipped with heating means and having a number of spikes
or probes extending therefrom across the width of the roller and
around its circumference. The spikes, pins, or probes, which have
smooth, rounded end points, can be spaced as desired on the roller
in order to provide the desired number of dimples to the absorbent
article. The dimples are provided on the absorbent article
preferably after the valvular openings, but prior to complete
fabrication of the absorbent article, and this operation can be
effected by passing the absorbent article containing the valvular
openings in contact with the heated roller. In this technique, the
absorbent pad is supported on a resilient back-up member, such as
an endless conveyor belt, or a resilient back-up roller. The depth
of the dimple can be controlled by limiting the depth to which the
probes depress the film. If desired, portions of the topsheet may
be retained in their untreated (without the dimples) condition.
This can be accomplished, for example, along a strip about one inch
wide near the periphery of the topsheet. Since the topsheet is
thermoplastic, the amount of heat and pressure applied to the areas
to be treated should be strictly controlled in order to avoid
substantially puncturing the topsheet. As a general rule, the
amount of heat required should be enough to soften the film, and
the amount of pressure should be sufficient to plastically distort
the film to the general contour of the probe. It will, of course,
be understood that the current heat and pressure conditions will
depend (among other variables) upon the residence time of the
treated absorbent pad, i.e., the length of time the topsheet is in
contact with the roller; the thickness of the absorbent pad, etc.
The correct conditions, however, can be easily ascertained by one
skilled in the art and hence no further detailed description of the
conditions appears necessary.
Referring specifically to FIGS. 3 and 4, it will be seen that the
dimples 22 extend below the plane of the topsheet 16 a short
distance, and that the absorbent material 12a, immediately below
the dimples, is in a compressed state. At the site where a dimple
is formed over a portion of the slit 18a, it will be seen that the
slit is opened to a much greater degree than corresponding slits
situated remote from the dimples 22. However, because of the
placement of the dimples, the slits disposed between corresponding
dimples are opened to a greater extent than would be the case if no
dimples were present. This is attributed to the fact that the
pressure exerted on the surface of the topsheet by the dimples
causes the slits to open slightly under the influence of the
stretching of the topsheet. Portions of the compressed absorbent
pad are associated with these opened slits, and because of this
association, wicking is achieved at a degree never heretofore
achieved. As a matter of fact, in most cases, wicking is
instantaneous. As the liquid is transferred to the absorbent pad
12, the absorbent pad absorbs the liquid throughout its entire area
until either partial or full saturation. As will be seen in FIG. 5,
(which depicts a saturated absorbent pad), the compressed material
12a has expanded and urges the dimple 22 upward, closer to the
plane of the topsheet 16. This action serves to close the
previously opened slits, thereby trapping the bulk of the liquid in
the absorbent pad.
Thus, advantageously, according to the present invention, maximum
wicking and absorption is achieved during the critical period when
flooding, (such as by urination and the like) is experienced,
whereas transfer of the liquid from the absorbent pad back through
the same slit opening is substantially reduced by virtue of the
combination of the valvular action of the slit and the dimple.
The dimples can be arranged on the absorbent article in a variety
of patterns. Thus, the overall design effect can be diamond shaped,
curvilinear, herringbone and the like. The preferred design
configuration is a system of substantially straight staggered,
parallel rows along the surface of the topsheet. The number of
dimples per square inch of absorbent pad area can be varied over a
relatively wide range. Improvements have been noted utilizing as
little as one dimple (having a diameter of 0.05 inch) per square
inch of absorbent pad. I have further observed that good results
are obtained when as many as 100 dimples (0.05 inch diameter) per
square inch of absorbent pad area are utilized. It will of course
be understood that the number of dimples per square inch of
absorbent pad area depends on the dimple size. As a general rule,
the total area occupied by dimples should not exceed more than 20
per cent of the area of the absorbent material. Excellent results
are achieved when the total dimple area is from 4 to 12 per cent of
the area of the absorbent material. Preferably there are from about
3 to about 25 dimples (0.10 inch diameter) per square inch of
absorbent material area, and most preferably from about 6 to about
15 per square inch of absorbent pad area.
As a general rule, dimple size can be in the range of about 0.025
to about 0.250 inch diameter. From the standpoint of functional and
aesthetic qualities, it is preferred that the dimple size range
from about 0.075 to about 0.150 inch diameter.
In still another, but less preferred embodiment, the dimples are
associated with the absorbent pad depicted in FIG. 1, as shown in
FIG. 6.
Thus, referring to FIG. 6, the slits 18 are substantially straight
and arranged in staggered parallel rows, and are shown as being
associated with dimples 22. Although, according to this embodiment
of the invention, improved wicking, dimensional stability and
absorbency is obtained over conventional prior art material, the
problem of "zippering," although improved substantially, is
nevertheless not entirely eliminated.
In the following examples, a different test procedure than
described with reference to Examples 1-3 was employed. According to
the procedure employed in the following examples, a four inch
inside diameter open cylinder is placed over a section of the
absorbent article. 30 CC's of a liquid such as water, or a saline
solution is poured into the cylinder and the time required for the
30 CC's of liquid (maintained at a temperature of
95.degree.-100.degree.F.) to be absorbed through the hydrophobic
film is recorded.
EXAMPLE 4
An absorbent pad consisting of eight layers of absorbent wadding
and measuring approximately 12 inches .times. 16 inches .times.
3/16 inch was positioned in the center of a sheet of polyethylene
film measuring about 121/4 inches .times. 161/4 inches .times. 1.25
mil having a taffeta design embossed therein.
A 1.25 mil thick sheet of ethylene-ethyl acrylate film was
perforated by feeding it through the nip of a roller having a
plurality of small blades spaced around its circumference in
staggered parallel rows and a resilient backup roller. The
perforating roller has a blade density of about 125 blades per
square inch and the resulting perforated film had about 125
parallel slits per square inch each measuring about 0.1 inch in
length.
The perforated film was cut to approximately 121/4 inches .times.
161/4 inches and placed on top of the absorbent wadding pad thereby
sandwiching the pad between the perforated film and the
polyethylene film. The edges of the sandwiched material were then
heat sealed.
The assembly was then placed under the cylinder and tested for
wicking characteristics. 30 cc's of liquid i.e., a saline solution
comprising 0.3N-sodium chloride at body temperature (simulated
urine) was poured into the cylinder. The liquid was fully absorbed
through the top sheet and into the absorbent material in 74
seconds.
The topsheet was thereafter carefully removed and superimposed on
an identical absorbent material and the edges were sealed.
The absorbent article was then passed in contact with a roller
equipped with heating means and having about 10 pins per square
inch extending across the width of the roller and around its
circumference. The diameter of the pin was 7/64 inch and the
endpoint of the pin had a spherical configuration of about 0.0547
inch radius. The absorbent article was supported by a resilient
back-up roller. The pins were heated to a temperature of about
300.degree.F. by a circulating hot oil system wherein the
temperature of the oil was maintained at 350.degree.F. The
resultant absorbent product had about 10 dimples per square inch
disposed along the topsheet of the absorbent article. The absorbent
article was then tested for initial wicking and absorbency
according to the procedure explained previously. The following
results were obtained: The liquid was fully absorbed through the
topsheet and into the absorbent material in 14 seconds.
EXAMPLE 5
This example demonstrates that without valvular openings little or
no liquid passes through the dimples in the topsheet.
An absorbent article substantially identical to the one described
in Example 4 was fabricated except that the slitting procedure was
omitted. Thus, the absorbent article was identical to the article
of Example 4 except that the topsheet did not contain the valvular
openings (slits). The absorbent article was tested for water
absorption according to the procedure of Example 4. After a period
of 3 minutes, no discernible absorption of the liquid had been
observed in the absorbent material. The liquid remained as a pool
on the surface of the topsheet. Thus, substantially no liquid
passed through the dimples of the topsheet.
EXAMPLE 6
An absorbent pad consisting of eight layers of absorbent wadding
and measuring approximately 12 inches .times. 16 inches .times.
3/16 inch was positioned in the center of a sheet of polyethylene
film measuring about 121/4 inches .times. 161/4 inches .times. 1.25
mil having a taffeta design embossed therein.
A 1.25 mil thick sheet of ethylene-ethyl acrylate film was
perforated by feeding it in contact with a reciprocating bar having
a plurality of small blades spaced to an inch across the surface of
the reciprocating bar. The resulting perforated film had about 72
parallel slits per square inch each measuring about 0.08 inch in
length.
The perforated film was cut to approximately 121/4 inches .times.
161/4 inches and placed on top of the absorbent wadding pad thereby
sandwiching the pad between the perforated film and the
polyethylene film. The edges of the sandwiched material were then
heat sealed.
The assembly was then placed under the 4 inch diameter cylinder and
tested for absorption characteristics 30 cc's of liquid (simulated
urine). The liquid was fully absorbed through the topsheet and into
the absorbent pad in 57 seconds.
The topsheet was thereafter carefully removed and superimposed on
an identical absorbent material and the edges were sealed.
The absorbent article was then passed in contact with a roller
equipped with heating means and having about 10 pins per square
inch extending across the width of the roller and around its
circumference. The diameter of the pin was 7/64 inch and the
endpoint of the pin had a spherical configuration of about 0.0547
inch radius. The absorbent article was supported by a resilient
back-up roller. The pins were heated to a temperature of about
300.degree. F. by a circulating hot oil system wherein the
temperature of the oil was maintained at 350.degree.F. The
resultant absorbent product had about 10 dimples per square inch
disposed along the topsheet of the absorbent article. The absorbent
article was then tested for absorbency according to the procedure
explained previously and the liquid was fully absorbed through the
topsheet and into the absorbent material in 4 seconds.
EXAMPLE 7
An absorbent pad consisting of eight layers of absorbent wadding
and measuring approximately 12 inches .times. 16 inches .times.
3/16 inch was positioned in the center of a sheet of polyethylene
film measuring about 121/4 inches .times. 161/4 inches .times. 1.25
mil having a taffeta design embossed therein.
A 1.25 mil thick sheet of ethylene-ethyl acrylate film was
perforated by feeding it in contact with a reciprocating bar having
a plurality of small blades spaced 8 to an inch across the surface
of the reciprocating bar. The resulting perforated film had about
65 parallel slits per square inch each measuring about 0.1 inch in
length.
The perforated film was cut to approximately 121/4 inches .times.
161/4 inches and placed on top of the absorbent wadding pad thereby
sandwiching the pad between the perforated film and the
polyethylene film. The edges of the sandwiched material were then
heat sealed.
The assembly was then placed under the 4 inch diameter cylinder and
tested for wicking characteristics. The liquid was fully absorbed
through the topsheet and into the absorbent material in 36
seconds.
The topsheet was thereafter carefully removed and superimposed on
an identical absorbent material and the edges were sealed.
The absorbent article was then passed in contact with a roller
equipped with heating means and having about 10 pins per square
inch extending across the width of the roller and around its
circumference. The diameter of the pin was 7/64 inch, and the
endpoint of the pin had a spherical configuration of about 0.0547
inch radius. The absorbent article was supported by a resilient
back-up roller. The pins were heated to a temperature of about
300.degree.F. by a circulating hot oil system wherein the
temperature of the oil was maintained at 350.degree.F. The
resultant absorbent product had about 10 dimples per square inch
disposed along the topsheet of the absorbent article. The absorbent
article was then tested for absorbency according to the procedure
explained previously and the liquid (simulated urine) was fully
absorbed through the topsheet and into the absorbent material in 3
seconds.
EXAMPLE 8
An absorbent pad consisting of eight layers of absorbent wadding
and measuring approximately 12 inches .times. 16 inches .times.
3/16 inch was positioned in the center of a sheet of polyethylene
film measuring about 121/4 inches .times. 161/4 inches .times. 1.25
mil having a taffeta design embossed therein.
A 1.25 mil thick sheet of ethylene-ethyl acrylate film was
perforated by feeding it in contact with a reciprocating bar having
a plurality of small blades spaced 9 to an inch across the surface
of the reciprocating bar. The resulting perforated film had about
78 parallel slits per square inch each measuring about 0.07 inch in
length.
The perforated film was cut to approximately 121/4 inches .times.
161/4 inches and placed on top of the absorbent wadding pad thereby
sandwiching the pad between the perforated film and the
polyethylene film. The edges of the sandwiched material were then
heat sealed.
The assembly was then placed under the 4 inch diameter cylinder and
tested for wicking characteristics. The liquid (simulated urine)
was fully absorbed through the topsheet and into the absorbent
material in 87 seconds.
The topsheet was thereafter carefully removed and superimposed on
an identical absorbent material and the edges were sealed.
The absorbent article was then passed in contact with a roller
equipped with heating means and having about 10 pins per square
inch extending across the width of the roller and around its
circumference. The diameter of the pin was 7/64 inch and the
endpoint of the pin had a spherical configuration of about 0.0547
inch radius. The absorbent article was supported by a resilient
back-up roller. The pins were heated to a temperature of about
300.degree.F. by a circulating hot oil system wherein the
temperature of the oil was maintained at 350.degree.F. The
resultant absorbent product had about 10 dimples per square inch
disposed along the topsheet of the absorbent article. The absorbent
article was then tested for absorbency according to the procedure
explained previously and the liquid (simulated urine) was fully
absorbed through the topsheet and into the absorbent material in 5
seconds.
EXAMPLE 9
An absorbent pad consisting of eight layers of absorbent wadding
and measuring approximately 12 inches .times. 16 inches .times.3/16
inch was positioned in the center of a sheet of polyethylene film
measuring about 121/4 inches .times. 161/4 inches .times. 1.25 mil
having a taffeta design embossed therein.
A 1.25 mil thick sheet of ethylene-ethyl acrylate film was
perforated by passing the film through the apparatus disclosed in
co-pending application, Ser. No. 190,908 filed Oct. 20, 1971. The
backing member was a 9 mesh wire screen and the piercing member was
a metal comb. The resulting perforated film had the appearance as
shown in FIG. 2 and contained 81 slits per square inch each
measuring about 0.1 inch in length.
The perforated film was cut to approximately 121/4 inches .times.
161/4 inches and placed on top of the absorbent wadding pad thereby
sandwiching the pad between the perforated film and the
polyethylene film. The edges of the sandwiched material were then
heat sealed.
The assembly was then placed under the cylinder and tested for
absorbing characteristics. The liquid was fully absorbed through
the topsheet and into the absorbent material in 4 seconds.
The topsheet was thereafter carefully removed and superimposed on
an identical absorbent material and backsheet and the edges were
sealed.
The absorbent article was then passed in contact with a roller
equipped with heating means and having about 10 pins per square
inch extending across the width of the roller and around its
circumference. The diameter of the pin was 7/64 inch and the
endpoint of the pin had a spherical configuration of about 0.0547
inch radius. The absorbent article was supported by a resilient
back-up roller. The pins were heated to a temperature of about
300.degree.F. by a circulating hot oil system. The resultant
absorbent product had about 10 dimples per square inch disposed
along the topsheet of the absorbent article. The absorbent article
was then tested for absorbency according to the procedure explained
previously. The following results were obtained: The liquid was
fully absorbed through the topsheet and into the absorbent material
in 3.2 seconds.
EXAMPLE 10
The procedure of Example 9 was repeated except that the size of the
slits measured about 0.07 inch in length. All the other conditions
remained the same. The results are as follows:
Time for Absorption
Before dimpling After dimpling 80 seconds 3 seconds
The following examples 11-15 will demonstrate that the amount of
absorbency in the baby diapers of the present invention is affected
by the number of dimples per square inch of topsheet surface. In
previous test procedures, the liquid was poured onto the fabricated
diapers while the portion of the diaper treated with the liquid was
in a horizontal position. In order to more closely simulate actual
wicking characteristics while the diaper is worn by a baby, the
following test procedure was devised:
The diapers to be tested were each placed and clamped to a 45
degree angled board. A separatory funnel with a delivery rate of 40
ml./30 seconds was placed above the board so that the tip of the
funnel was one inch above the topsheet of the diaper. The funnel
was adjusted so that liquid leaving the tip of the funnel would
fall on the topsheet of the diaper and would travel an eleven inch
linear path across the width of the diaper. The liquid was a water
solution (0.3N NaCl) which was maintained at room temperature. The
forty milliliters were emptied from the funnel over a 30 second
period, and the amount of liquid run-off, i.e., the amount not
absorbed by the diaper, was measured.
The diapers to be tested were fabricated from the same roll of
wadding and the same roll of topsheet material (ethylene-ethyl
acrylate). They were fabricated according to the technique
described in Example 6 except that the number of dimples per square
inch varied as indicated below:
Three runs under each example were conducted (using separate
diapers), and the average of the results are indicated in Table
I.
TABLE I
Water Delivery Speed Test
Amount of water run-off Example Dimples per square inch
(milliliters) 11 0 31 12 2.5 6 13 4.9 2 14 7.2 0 15 9.8 0
The procedure of Examples 16-20 is identical to the procedure of
Examples 11-15 except that the angle of the board was adjusted to
60 degrees. The results are indicated in Table II below:
TABLE II
Water Delivery Speed Test
Amount of water run-off Example Dimples per square inch
(milliliters) 16 0 33 17 2.5 10.8 18 4.9 4.3 19 7.2 0 20 9.8 0
The following Example 21 demonstrates the increase of wet integrity
strength of a diaper which has been dimpled according to the
present invention. A wood pulp fluff was used as the absorbent pad
since the fluff is more drastically effected by loss of wet
integrity strength than wadding.
The test procedure was as follows:
A test apparatus was employed wherein a 4 by 4 inch sample of the
composite pad, as prepared for test by wetting with 2 times its dry
weight with water and allowing it to sit or equilibrate for 1
minute, was restrained in compression between two annular, flat
metal rings of aluminum with an internal opening diameter of 3.5
inches. The bottom center of the 3.5 inch diameter sample thus
restrained rested on a 1.5 inch diameter first plate covered with
one-sixteenth inch polyurethane foam. A second 1 inch diameter
plate covered with one-sixteenth polyurethane foam was centered and
pressed down on the top of the sample, disposed on the first or
bottom plate, with a pressure of 12.7 lb. per sq. in. and the test
sample was additionally wetted with 2 times its dry weight of water
and allowed to equilibrate for 1 minute. The first plate, pressing
on the bottom surface of the sample under test, was free to rotate
in the plane of the sample while the second plate pressing against
the top surface was articulated so that it could be rotated within
an arc of 45.degree. at a frequency of 55 times per minute. The
rotary movement of the first and second plates tended to tear out
the restrained test sample in a circle around the articulated 1
inch diameter central pressure plate. A test period in this
simulated test with the described rotary articulation was 4
minutes, and the test results were recorded as tear grades from 0
to 3 by inspection, with tear grades greater than 1 equated to
unsatisfactory performance in actual use. The tear grades assigned
to the individual test samples had the following meanings:
Tear grade 1 -- tearing in less than a total of 10.degree. around
the compressed area
Tear grade 2 -- tearing in a total of 10.degree. to 90.degree.
around the compressed area
Tear grade 3 -- tearing greater than a total of 90.degree. around
the compressed area
EXAMPLE 21
An absorbent pad consisting of 30 grams of cellulose of which 22
grams were wood pulp fluff and measuring approximately 12 inches
.times. 16 inches .times. 3/16 inch was positioned in the center of
a sheet of polyethylene film measuring about 121/4 inches .times.
161/4 inches .times. 1.25 mil having a taffeta design embossed
therein.
A 1.25 mil thick sheet of ethylene-ethyl acrylate film was
perforated by passing the film through the apparatus disclosed in
co-pending application, Ser. No. 190,908 filed Oct. 20, 1971. The
backing member was a 9 mesh wire screen and the piercing member was
a metal comb. The resulting perforated film had the appearance as
shown in FIG. 2 and contained 81 slits per square inch each
measuring about 0.1 inch in length.
The perforated film was cut to approximately 121/4 inches .times.
161/4 inches and placed on top of the absorbent wadding pad thereby
sandwiching the pad between the perforated film and the
polyethylene film. The edges of the sandwiched material were then
heat sealed. The resulting diaper was thereafter tested for wet
integrity according to the procedure described previously and the
result was a tear grade reading of 2.
Another diaper was fabricated identical to that described above.
The diaper was then passed in contact with a roller equipped with
heating means and having about 10 pins per square inch extending
across the width of the roller and arounds its circumference. The
diameter of the pin was 7/64 inch and the endpoint of the pin had a
spherical configuration of about 0.0547 inch radius. The absorbent
article was supported by a resilient back-up roller. The pins were
heated to a temperature of about 300.degree. F. by a circulating
hot oil system. The resultant absorbent product had about 10
dimples per square inch disposed along the topsheet of the
absorbent article. The absorbent article was then tested for wet
integrity and resulted in a tear grade reading of 1.
EXAMPLE 22
A diaper was constructed using the materials and procedure of
Example 9 except the slits measured 0.07 inch in length and the
dimple size was 0.094 inch radius. The diaper was tested for
absorbency according to the procedure of Example 9, with the
following results:
Before dimpling After dimpling 80 seconds 4 seconds
As will be evident from the foregoing examples and description of
the invention, the absorbent product of the instant invention has
outstanding qualities with respect to the characteristics
enumerated (a) through (d). Variations of the invention are
possible particularly the elimination of features which although
not providing an optimum product as explained previously, would
nevertheless provide an improved product with respect to
conventional products. Thus for example, the fibers in the
absorbent pad need not be adhered to the lowest portions of the
depressed areas. There would be some sacrifice of the dimensional
stability, however the other advantages would not be materially
affected. Thus, rather than passing the absorbent product through
the dimpling process, the topsheet can be pre-treated so as to
provide the depressed areas and thereafter the topsheet joined to
form the final product.
In the claims which follow, the term "dimples" are employed to
characterize the depressed areas. As used in the claims therefore,
the term "dimples" shall mean the depressed areas across the
surface of the topsheet which extend below the plane of the
topsheet and which are fabricated in a manner such that there is
substantially no breaking, melting or cutting of the topsheet
during or after fabrication in a manner which would hinder the
controlled passage of liquid to the absorbent pad. Thus the dimples
are also substantially liquid impermeable.
It will be obvious that while the present invention has been set
forth in some detail and described with particularity, it is
susceptible to changes, modifications and alterations without
departing from the scope and spirit of the invention as defined in
the appended claims.
* * * * *