U.S. patent number 3,860,002 [Application Number 05/360,124] was granted by the patent office on 1975-01-14 for absorbent articles.
This patent grant is currently assigned to Scott Paper Company. Invention is credited to Charles G. Kolbach.
United States Patent |
3,860,002 |
Kolbach |
January 14, 1975 |
ABSORBENT ARTICLES
Abstract
An absorbent article includes an air-laid fibrous web having a
medial portion of a greater basis weight than flanking end and side
portions. The fibers forming one surface of the web are adhesively
bonded together to provide an abrasion resistant, non-pilling,
facing layer, and also to aid in maintaining the structural
integrity of the web. The fibers forming the other surface of the
web are either adhesively bonded together, or a separate backing
sheet, preferably in the form of a water-proof plastic sheet, is
adhered directly to the other surface of the web to form a
stabilized backing layer. The above constructions are adapted for
use as disposable diapers. Apparatus of this invention includes a
vacuum box having an open end underlying a discrete section of a
foraminous forming surface so that regions of the forming surface
extend beyond the open end of the vacuum box. Vacuum connection
means permit the establishment of a different pressure drop across
the discrete section of the foraminous forming surface overlying
the open end of the vacuum box than through regions of the
foraminous forming surface extending beyond the vacuum box. Drive
means move the foraminous forming surface and vacuum box in
registration with each other through a web forming area for
maintaining the same discrete section of the foraminous forming
surface in overlying relationship with the open end of the vacuum
box as the foraminous forming surface and the vacuum box are moved
through the web forming area. The method of this invention employs
the above-described apparatus in which the foraminous forming
surface extends beyond, and completely circumscribes the open end
of the vacuum box. A greater pressure drop is established through
the discrete section of the foraminous forming surface overlying
the vacuum box than through the regions extending beyond the vacuum
box to form a fibrous web having a medial portion with a greater
basis weight of fibers therein than in flanking end and side
portions of the web.
Inventors: |
Kolbach; Charles G. (Media,
PA) |
Assignee: |
Scott Paper Company (Delaware
County, PA)
|
Family
ID: |
23416692 |
Appl.
No.: |
05/360,124 |
Filed: |
May 14, 1973 |
Current U.S.
Class: |
604/365; 428/171;
428/360; 604/375; 428/172; 604/373; 604/380 |
Current CPC
Class: |
A61F
13/53436 (20130101); A61F 13/15658 (20130101); A61F
13/532 (20130101); Y10T 428/24612 (20150115); Y10T
428/24802 (20150115); Y10T 442/671 (20150401); Y10T
428/24603 (20150115); Y10T 442/2484 (20150401); Y10T
442/674 (20150401); A61F 2013/5326 (20130101); Y10T
428/2905 (20150115) |
Current International
Class: |
A61F
13/15 (20060101); A61f 013/16 () |
Field of
Search: |
;128/284,287
;161/116,124,166 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Gaudet; Richard A.
Assistant Examiner: Cohen; Lee S.
Attorney, Agent or Firm: Faigus; Martin L. Foley; William
J.
Claims
Having described my invention, I claim:
1. An absorbent article suitable for use as a disposable diaper and
the like; said absorbent article comprising a unitary assemblage of
randomly arranged fibers in the form of a web, said web having a
transverse dimension defined between spaced, elongate side edges
and an elongate dimension defined between spaced end edges; a
medial portion of said web having a greater basis weight and
greater average thickness than flanking end and side portions
thereof for establishing a step configuration in a upper surface of
said web in both the elongate and transverse directions; adhesive
means on said upper surface of said web for bonding together
exposed surface fibers in said upper surface to provide an abrasion
resistant, non-pilling, facing layer, and to aid in maintaining the
structural integrity of said web and stabilizing means for
stabilizing a lower surface of said web; said upper surface being
adapted to be positioned in contact with a wearer with the medial
portion of the web in the perineal region, the flanking side
portions about the thigh regions, and the flanking end portions
about the front and back regions.
2. The absorbent article according to claim 1, wherein said
flanking end and side portions have substantially the same basis
weight and thickness.
3. The absorbent article according to claim 2, wherein said
stabilizing means is adhesive on said lower surface for bonding
together exposed surface fibers in said lower surface.
4. The absorbent article according to claim 2, wherein said
stabilizing means includes a moisture-impervious sheet secured to
said lower surface.
5. The absorbent article according to claim 2, wherein said
randomly arranged fibers include a major proportion by weight of
short cellulosic fibers of a papermaking length less than 1/4 inch,
and a minor proportion by weight of reinforcing fibers having an
average length over 1/4 inch interspersed and randomly intermingled
with said short cellulosic fibers to enhance the strength of said
web.
6. The absorbent article according to claim 2, wherein said medial
portion includes sections of different basis weights, the greatest
basis weight being a section where it is most needed to absorb body
fluids.
7. The absorbent article according to claim 2, wherein said
adhesive means only partially penetrates through the thickness of
said web in the medial portion thereof to leave interior fibers of
said medial portion unbonded by adhesive.
8. The absorbent article according to claim 7, including compressed
regions in the upper surface of the medial portion of the web to
enhance wicking of fluids along said medial region.
9. The absorbent article according to claim 8, further including
compressed regions in said flanking side and end portions disposed
in a predetermined pattern and separated by substantially
uncompressed high loft regions.
10. The absorbent article according to claim 9, wherein said
adhesive means defines bonded networks completely through the web
in only the compressed regions of the flanking end and flanking
side portions thereof.
11. The absorbent article according to claim 2, wherein said medial
portion joins said flanking side portions along side boundaries and
joins said end portions along end boundaries, at least a portion of
said side boundaries being recessed to define a narrow center
crotch section adapted to be positioned in the perineal region of a
wearer, said medial portion further including a forward section and
rearward section disposed, respectively, on opposite sides of the
crotch section, said forward and rearward sections having a greater
transverse dimension than said crotch section.
12. The absorbent article according to claim 11, wherein said
medial portion includes sections of different basis weights, the
greatest basis weight being in a section where it is most needed to
absorb body fluids.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to air-laid fibrous webs, and to method and
apparatus for manufacturing same.
2. Description of the Prior Art
Absorbent fibrous members having a thick center region therein have
been utilized in sanitary products, such as disposable diapers, as
exemplified in U.S. Pat. No. 2,890,700, issued to LonbergHolm; U.S.
Pat. No. 3,430,629, issued to Murphy; U.S. Pat. No. 3,509,604,
issued to Furbeck; U.S. Pat. No. 3,598,680, issued to Lee; and U.S.
Pat. No. 3,682,761, issued to Lee et al. The absorbent members
described in all of the above patents are internal components of a
sanitary product. Such absorbent members normally are not
sufficiently self-sustaining to be utilized alone, or in
conjunction with only a backing layer, to form a complete sanitary
product, such as a disposable diaper. Stating this another way,
separate facing and backing sheets normally are required to provide
structural support for such absorbent members. Therefore, the
sanitary product connstructions disclosed in the above patents must
be fabricated by utilizing fairly complicated converting equipment
in which the absorbent member is sandwiched between opposed facing
and backing sheets, and in which the facing and backing sheets are
adhered together. In addition, one or both of the facing and
backing sheets is usually an adhesively bonded web to begin with.
Therefore, adhesive is not only utilized to form a self-sustaining
facing and/or backing web, but additional adhesive is required to
adhere the facing and backing webs to each other. It is highly
desirable to decrease the amount of adhesive necessary to fabricate
sanitary products to thereby reduce their cost of manufacture.
Reduced cost is an important consideration in products such as
disposable diapers which are intended for disposal after a single
use.
The absorbent internal members disclosed in the patents to Murphy
(U.S. Pat. No. 3,430,629), Furbeck (U.S. Pat. No. 3,509,604), Lee
(U.S. Pat. No. 3,598,680), and Lee et al (U.S. Pat. No. 3,682,761),
all have a thick central region which extends the full length of
the absorbent member, and thinner flanking side portions. This
construction provides a conformable, snug fit in the thigh region
of a wearer while providing a thicker, more absorbent section in
the perineal region where it is needed to retain body fluids.
However, the forward and rearward regions of the absorbent members
include a portion of the thick central region as well as a portion
of the thinner flanking side portions. Diapers having a forward and
rearward region with thickness variations along the transverse
extent thereof do not provide as conformable a waste band region as
a diaper in which the forward and rearward regions have a
substantially uniform thickness extending for the full transverse
extent thereof.
The absorbent member employed in the diaper disclosed in
Lonberg-Holm includes a heavier basis weight medial portion than
flanking endand side portions thereof. This absorbent member is
formed from a plurality of plies of crepe paper wadding which must
be properly positioned relative to each other on suitable
converting equipment. Lonberg-Holm discloses that the layers or
plies could include a mass of fibrous material which is uniform in
character and of a varying thickness such that there are no
physically distinct layers. However, this discussion implies the
separate formation of fibrous members which are married together to
achieve sufficient interlocking between fibers to render the layers
physically indistinct. Such a method of forming an absorbent member
still requires suitable equipment for precisely aligning various
fibrous webs together in order to achieve the varying thickness
construction. In addition, as stated above, Lonberg-Holm is not
directed to an absorbent member which can be utilized either by
itself as a sanitary product, or in conjunction with only a backing
layer. Lonberg-Holm requires an absorbent member which is
structurally held in place by being disposed between separate
facing and backing layers in the conventional manner employed today
in disposable diapers.
Prior art apparatus and method for forming air-laid, profiled
fibrous webs have included means for establishing a non-uniform
basis weight distribution in the cross-machine direction of web
formation. However, such apparatus do not include means for
affecting a non-uniform basis weight distribution in the machine
direction of web formation by initially depositing different
weights of fibers in different areas. For example, the Lee et al.
apparatus (U.S. Pat. No. 3,682,761) includes a plurality of
stationary vacuum chambers disposed behind a moving foraminous
surface upon which an air-lay fibrous web is formed. Therefore, any
transverse section of the forming surface passes over the same bank
of vacuum boxes, and accordingly, the machine direction basis
weight of the fibrous web formed in any transverse region of the
forming surface will be sustantially the same. However, by properly
adjusting the vacuum levels in the various banks of vacuum boxes, a
crossmachine direction basis weight variation can be achieved.
In the Lee and Furbeck apparatus separate continuous airlaid webs
are formed, and are deposited in partial overlapping relationship
with each other to provide a centrally disposed region having a
greater basis weight than flanking side portions. This arrangement
for forming a profiled fibrous web also results in the formation of
a thickened region extending for the full length of the absorbent
air-laid web.
SUMMARY OF THE INVENTION
Absorbent articles of this invention include a fibrous web in the
form of a unitary assemblage of randomly arranged fibers. The webs
include a medial portion integrally joined through said randomly
arranged fibers to flanking side portions and flanking end
portions; said medial portion having a greater basis weight and
thickness than said flanking side and end portions. Preferably, the
flanking side and end portions in each fibrous web have
substantially the same average thickness and basis weight. All
embodiments include an abrasion resistant, non-pilling, facing
layer provided by an adhesive distribution which bonds together the
fibers forming one surface of the fibrous webs. The adhesive
distribution also functions to establish structural integrity of
the webs. If such webs are intended for use by themselves (i.e.,
without the use of a separate plastic, or other backing sheet) as a
disposable diaper, such fibrous webs are provided with a stabilized
backing layer by an adhesive distribution which bonds together the
fibers forming the back surfaces of the webs. A stabilized backing
layer is provided in all embodiments, either by adhesive or a
separate sheet.
The adhesive distribution within the fibrous webs can be varied;
however, in all embodiments the adhesive distribution must form an
abrasion resistant, non-pilling, facing layer. Also, the adhesive
distribution must provide a structurally stable backing layer when
the fibrous webs are to be utilized by themselves (i.e., with no
separate backing sheet) as a unitary sanitary product. The specific
thickness and basis weight of the various portions of the fibrous
webs is dictated by the specific use to which the absorbent
articles are to be put. For example, when an absorbent article is
intended for use as a disposable diaper, the thickness and basis
weight of the various portions of the fibrous web will be dictated
by the specific use to which the diaper is to be put, i.e.,
daytime, nighttime, toddler, infant, etc.
The fibrous webs utilized in this invention can be provided with an
embossed pattern in the thick medial portion and/or the flanking
side and end portions. Alternatively, the webs can be completely
free of any embossed pattern; however, embossed patterns are
desired for some applications to aid in wicking body fluids which
are impinged on the fibrous webs to provide effective utilization
of the absorptive material.
The higher basis weight medial portion of the fibrous webs can be
of a substantially uniform basis weight, or can be profiled to
provide the greatest basis weight in certain sections thereof. For
example, when a fibrous web is intended for use as a disposable
diaper for a girl, the center section of the medial portion can be
provided with a greater basis weight of fibers therein than
flanking end sections thereof. Alternatively, when a fibrous web is
intended for use as a disposable diaper for a boy, a forward
section of the medial portion can be provided with a greater basis
weight of fibers therein than a rearward section thereof.
The specific shape of the high basis weight medial portion of the
fibrous web can be varied within wide limits. For example, the
thick medial portion can be substantially rectangular, or
alternatively, can be contoured to include a reduced width crotch
region which provides a more comformable structure in the perineal
region of a wearer.
In a preferred use, the absorbent articles of this invention are
employed as disposable diapers. The disposable diapers are placed
on a wearer with the abrasion resistant, non-pilling, facing layer
of the fibrous web in contacting relationship with the wearer. The
high basis weight medial portion of the web is disposed in the
perineal region of the wearer to provide a highly absorptive area
for retaining body fluids. Although the medial portion is fairly
thick, the construction is comfortable and conformable because the
medial portion does not extend for the full length or width of the
web. In the most preferred embodiment of this invention the fibrous
web includes a contoured medial portion having a reduced width
crotch region to enhance conformability of the diaper. The low
basis weight flanking side portions provide an extremely
conformable region which snugly engages the thigh region of the
wearer to prevent leakage of body fluids from the diaper. The low
basis weight flanking end portions of the diaper provides a
conformable waist band region for closely and uniformly engaging
the front and back regions of a wearer. The most desirable fit is
achieved in the preferred construction in which the flanking end
and side portions are of substantially the same average thickness
and basis weight.
Both the apparatus and method of this invention for forming fibrous
webs employ a foraminous forming surface and at least one vacuum
box underlying a discrete section of the forming surface. Vacuum
connection means are provided for permitting the establishment of a
pressure drop across the discrete section of the foraminous forming
surface overlying the vacuum box that is different from a pressure
drop which can be established through the regions of the foraminous
forming surface extending beyond peripheral walls of the vacuum
box. The foraminous forming surface and the vacuum box are moved in
registration with each other through a web forming area so that the
same region of the foraminous forming surface is always in
overlying relationship with the vacuum box. Therefore, the
apparatus of this invention permits the weight of fibers deposited
in the region of the foraminous forming surface overlying the
vacuum box to be controlled independently of the weight of fibers
deposited in the regions of the foraminous forming surface which
extend beyond peripheral walls of said vacuum box.
In the preferred method of this invention in which the medial
portion of the fibrous web is provided with a greater basis weight
of fibers therein than flanking end and side portions thereof, the
foraminous forming surface extends beyond all peripheral walls of
the vacuum box. A greater pressure drop is established through the
vacuum box, and accordingly, through the discrete section of the
foraminous forming surface overlying the vacuum box, than through
regions of the foraminous forming surface extending beyond
peripheral walls of the vacuum box.
In the most preferred method and apparatus of this invention the
foraminous forming surface overlying the vacuum box is a bottom
wall of a three-dimensional compartment in which the thickened
medial region is formed. The specific shape of the thickened medial
region is dictated by the shape of the three-dimensional
compartment. The peripheral walls of the vacuum box define an
opening which has substantially the same shape as the
three-dimensional compartment.
To the best of applicant's knowledge, no prior art air-lay
apparatus employs a foraminous forming surface and at least one
vacuum box which are moved in registration with each other through
a web forming area as described above. Accordingly, applicant's
method and apparatus permits precise separate control of the basis
weight of fibers deposited in discrete sections of the fibrous web
to achieve formation of the fibrous webs employed in this
invention.
Other objects and advantages of this invention will be better
understood by referring to the detailed description which follows,
taken in conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic isometric view showing the sequential steps
in forming unitary fibrous webs according to a preferred method of
this invention;
FIG. 2 is a cross-machine-direction sectional view through the
condenser roll assembly of this invention taken along line 2--2 of
FIG. 3;
FIG. 3 is a sectional view along line 3--3 of FIG. 2;
FIG. 4 is an isometric view of embossing rolls utilized according
to one preferred method of this invention;
FIG. 5 is a plan view of an absorbent article according to this
invention,
FIG. 6 is a sectional view along line 6--6 of FIG. 5;
FIG. 7 is a sectional view similar to FIG. 6, but showing an
alternative embodiment of this invention;
FIGS. 8 and 9 are plan views showing two other alternative
embodiments of this invention;
FIG. 10 is a sectional view along line 10--10 of FIG. 9;
FIGS. 11 and 12 are plan views of two further embodiments according
to this invention;
FIGS. 13 and 14 are enlarged sectional views along lines 13--13 and
14--14 of FIGS. 11 and 12, respectively;
FIGS. 15 and 16 are enlarged sectional views similar to FIGS. 13
and 14, respectively, but showing further embodiments of this
invention;
FIG. 17 is a schematic sectional view, similar to FIG. 3, but
showing an alternative condenser roll assembly according to this
invention;
FIG. 18 is a sectional view along line 18--18 of FIG. 17; and
FIG. 19 is a plan view along line 19--19 of FIG. 17.
DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THIS INVENTION
Referring to FIG. 1, a preferred process of this invention will be
described for forming absorbent articles 10. A fibrous feed mat 12
is directed into an air-lay web forming device 14 for forming a
continuous fibrous web 16. The web forming device 14 includes a
fiberizing roll 18 which is rotatably driven in the direction
indicated by arrow 21 to separate fibers from the mat 12, and to
entrain the fibers in air to form an air suspension of fibers
within a formation duct 20. The air suspension of fibers is
directed toward a foraminous forming surface 22 of a condenser roll
assembly 24. The air of the suspension is directed through the
foraminous forming surface 22, and the fibers in the suspension are
condensed on the forming surface in the form of a continuous
fibrous web 16. The foraminous forming surface 22 includes
cirumferentially spaced, three-dimensional compartments 26. A
greater weight of fibers is directed into the three-dimensional
compartments 26 then onto surrounding regions of the foraminous
forming surface 22 to form the continuous fibrous web 16 with
spaced regions 30 having a greater weight of fibers per unit area
(i.e., basis weight) than circumscribing regions of said web. The
construction of the condenser roll assembly 24 and its mode of
operation for forming a fibrous web with thickened regions 30 forms
an important aspect of the present invention, and will be described
in detail latter in this application.
The fibrous feed mat 12 can include a major proportion by weight of
short cellulosic fibers of a papermaking length less than 1/4 inch,
and a minor proportion by weight of reinforcing fibers over 1/4
inch in length. Preferably the short cellulosic fibers are wood
pulp fibers since they are highly absorbent, readily available and
inexpensive. Other short cellulosic fibers, such as cotton linters,
can also be utilized. The reinforcing fibers preferably are of a
staple length between about 1/2 inch and 3 inches in length, and
these fibers are well known in the prior art. In a preferred
embodiment of this invention the fibrous feed mat 12 includes from
between about 75 percent to about 90 percent by weight wood pulp
fibers, and from about 10 percent to about 25 percent by weight
rayon fibers, 11/2 length, 3 denier. It is also within the scope of
this invention to employ a fibrous feed mat 12 of 100 percent short
cellulosic fibers of a papermaking length less than 1/4 inch;
however, the inclusion of longer fibers is preferred to reinforce
the structure.
The continuous fibrous web 16 is directed past an upper water spray
unit 32 and lower water spray unit 34 for adjusting the moisture
level in the web so that it will receive and retain an embossed
pattern impressed therein. Preferably, the moisture level in the
web is adjusted to from between about 6 percent and about 35
percent by weight, based on the bone dry weight of the fibrous web
16.
Referring to FIGS. 1 and 4, after the fibrous web 16 has passed the
water spray units, it is directed through a nip defined between an
upper embossing roll 36 and a lower embossing roll 38 which are
positively driven in the direction indicated by arrows 40 and 42,
respectively, by any suitable drive means (not shown). The upper
embossing roll 36 has a plurality of circumferentially spaced
recesses 44 therein, and is driven in synchronism with the feed of
the fibrous web 16 so that the recesses 40 align with the thickened
regions 30 of said fibrous web. The upper and lower embossing rolls
have raised projections 46 disposed in a wavy line pattern in their
outermost surfaces. The bottom wall of each of the recesses 40
includes raised surfaces 48 disposed in a different pattern than
the raised surfaces 46. Specifically, the raised surfaces 48 shown
in FIGS. 1 and 4 include a plurality of axial extending raised
projections crossing a plurality of circumferentially directed
raised projections to form a waffle-like pattern.
The specific pattern of raised projections in the embossing rolls
36 and 38, as described in the preceeding paragraph, is
illustrative of particular embossing patterns which can be
utilized; however, the specific pattern of projections is not
critical in the present invention. The purpose of including
embossed regions in the fibrous web 16 is to aid in directing fluid
impinged on the web along substantially the entire extent of said
web to provide effective utilization of its absorbing capacity. Any
embossed pattern can be utilized which achieves this objective, and
in some applications, one or both of the embossed patterns can be
omitted. For example, this invention also relates to absorbent
articles employing fibrous webs which are completely unembossed, as
well as to absorbent articles employing fibrous webs in which only
the spaced, thickened regions 30 are embossed. The embossing rolls
36 and 38 will be appropriately modified to establish the desired
embossed pattern in the fibrous web 16.
Referring to FIG. 1, after the fibrous web 16 has passed through
the nip of the embossing rolls 36 and 38, it is directed through an
adhesive station, which is illustrated in FIG. 1 as including an
upper adhesive spray unit 50 and a lower adhesive spray unit 52.
The adhesive is applied to bond substantially all of the surface
fibers together to provide a self-sustaining web with abrasion
resistant, non-pilling surfaces Any suitable adhesive normally
employed in the manufacture of air-laid absorbent products can be
utilized. The preferred binders are of the self-curing acrylic
latex family, the urethane family, or other binders which can be
utilized in low viscosity solutions or suspensions. If desired, the
adhesive applied to the lower surface of the fibrous web 16 can
include a water repellent agent therein to provide a fluid
impervious backing layer, and the adhesive applied to the upper
surface can include a wetting agent to enhance fluid absorbency
into the interior regions of said web.
The method of applying adhesive to the fibrous web can be varied.
For example, the adhesive can be flowed onto the fibrous web 16
from a weir box in excessive quantities, and a major proportion of
the adhesive can be withdrawn by the application of suction from
below the fabric, according to the method set forth in U.S. Pat.
No. 3,663,348, issued to Liloia et al, and assigned to Johnson
& Johnson.
When the absorbent article includes a fluid impervious backing
sheet, the application of adhesive to the lower surface of the
fibrous web 16 web can be omitted entirely, and the adhesive can be
applied to the separate backing sheet prior to adhering the backing
sheet to the fibrous web. Alternatively, the backing sheet can be
adhered to the fibrous web by directly extruding the backing sheet
onto the lower surface of said fibrous web in the manner suggested
in U.S. Pat. No. 3,402,715, issued to Liloia et al, and assigned to
Johnson & Johnson.
After adhesive has been applied to the fibrous web 16, said web is
directed through an oven 54 to dry the fibrous web and cure or set
the adhesive. After the adhesive has been set the fibrous web 16 is
directed to a cutting station which includes a lower anvil roll 56
and an upper cutter roll 58. The continuous fibrous web 16 is
separated into discrete, absorbent, air-laid absorbent articles 10
at the cutting station, and these discrete articles 10 can be
spaced from each other by a take-off conveyor 60 which is moving at
a faster speed than upstream conveyors (only one of which is shown
at 61) which direct the continuous fibrous web 16 through the
process. The spaced articles 10 can be directed to further
processing stations (not shown), e.g. turning, folding and
packaging stations.
Referring to FIGS. 9 and 10, details of the absorbent article 10
are shown. This absorbent article 10 is intended for use as a
disposable diaper and has a transverse dimension defined between
spaced, elongate side edges 62, and an elongate dimension defined
between spaced end edges 64. The absorbent article 10 includes a
medial portion 66 integrally joined through randomly arranged
fibers to flanking side portions 68 and flanking end portions 70;
said medial portion having a greater basis weight and thickness
than said flanking side and end portions. Preferably, the flanking
side portions 68 and flanking end portions 70 are of substantially
the same, uniform, thickness and basis weight.
The flanking side portions 68 and end portions 70 include an
embossed pattern therein in the form of continuous, compressed
channels 72 having a wavy-line configuration. These compressed
channels are spaced from each other by relatively uncompressed high
loft regions 74. The medial portion 66 includes an embossed pattern
in the form of transversely spaced, longitudinally extending
channels 76 and longitudinally spaced, tranversely extending
channels 78 to define a waffle-like pattern. High loft,
substantially uncompressed regions 80 are disposed between the
longitudinal channels 76 and the transverse channels 78.
Referring specifically to FIG. 10, an upper adhesive layer bonds
substantially all of the surface fibers together to provide an
abrasion resistant, non-pilling, facing surface 82 which can be
positioned in contact with a wearer without fiber pilling or
dusting. The upper adhesive layer penetrates only partially through
the thickness of the web in the thick medial portion 66 thereof,
and in the high loft regions 74 of the flanking side portions 68
and flanking end portions 70. A lower adhesive layer bonds
substantially all of the lower surface fibers together to provide
an abrasion-resistant, non-pilling back surface 84. This lower
adhesive layer penetrates only partially through the thickness of
the web in the medial portion thereof and in the high loft regions
74 of the flanking side portions 68 and the flanking end portions
70. The upper adhesive layer and lower adhesive layer cooperate to
define adhesive networks 86 extending completely through the web in
the compressed channel regions 72 of the flanking side portions 68
and end portions 70. An interior region 87 disposed between the
upper and lower adhesive layers in the medial portion 66 is
substantially free of adhesive, and therefore provides an excellent
moisture absorbent area for retaining body fluids directed onto the
medial portion 66 of the absorbent article 10. The bonded networks
86 which penetrate completely through the web in the flanking side
and end portions thereof enhance the tensile strength of the web
and provide a substantially non-pealing construction. The interior
portions of the web in the high loft regions 74 of the flanking
side and end portions are substantially free of adhesive to provide
regions of good fluid containing capacity.
In use, the diaper 10 is placed on a wearer with the thick, medial
portion 66 disposed in the perineal region. Urine is initially
directed onto the medial portion 66 and is wicked both
longitudinally and transversely by virture of the high capillary
forces in the longitudinal channels 76 and transverse channels 78.
Any body fluids which are directed into the flanking side and end
portions of the diaper will be wicked substantially in the
longitudinal direction of the web 10 by the compressed channels 72.
The greatest tendancy for leakage occurs at the longitudinal side
edges 62, and the longitudinally extending channels 72 function to
wick the body fluids longitudinally to thereby impede transverse
flow toward said side edges.
The flanking side portions 68 and end portions 70 have
substantially the same basis weight. The specific basis weight
utilized is dictated by the particular use of the diaper, i.e.,
infant, toddler, overnight, daytime, etc. However, in the most
preferred embodiment of this invention the basis weight of the
flanking side portions 68 and end portions 70 is in the range of
from about 1.5 ounces per square yard to about 6 ounces per square
yard. Preferably, the density of the flanking side portions 68 and
end portions 70 is in the range of from about 0.05 grams per cubic
centimeter to about 0.15 grams per cubic centimeter. (Determined in
accordance with ASTM Method D-1777, set forth in the manual of the
American Society for Testing Materials).
The medial portion 66 may be slightly compressed; having a slightly
higher density than the flanking side portions 68 and end portions
70. Preferably, the density of the medial portion 66 will be in the
range of from about 0.1 gram per cubic centimeter to about 0.2
grams per cubic centimeter. The basis weight of the medial portion
66 can be varied depending upon the required absorptive capacity,
and the required absorptive capacity will vary depending upon the
particular use of the diaper, i.e., infant, toddler, overnight,
daytime, etc. Generally, the basis weight of the medial portion 66
will be in the range of from between about 8 ounces per square yard
to about 50 ounces per square yard. Also the specific dimensions of
the diaper, including the dimensions of the memdial portion 66, can
be varied depending upon the intended use of the diaper.
As explained earlier in this application the specific adhesive
distribution in the absorbent article 10 can be varied within wide
limits. However, it is critical to this invention that the adhesive
bond the fibers together in the upper surface thereof to provide an
abrasion resistant, non-pilling facing surface 82 which can be
positioned in contact with a wearer without pilling, or dusting
during use. Moreover, if the absorbent article 10 is intended for
use by itself as a diaper (i.e., without the use of a separate
plastic, or other backing sheet), the adhesive must bond the fibers
together in the lower surface of the web to provide a structurally
stable back surface 84. Though preferred, it is not required to
provide bonded networks 86 completely through the web. Therefore,
it is within the scope of this invention to maintain the entire
interior portion of the fibrous web free of adhesive. Also, it is
within the scope of this invention to flow an excessive amount of
adhesive onto the upper surface of the fibrous web from a weir box,
and remove excess adhesive by pulling it through the web by the
application of a vacuum from the underside of the web. In this
manner the fibrous web, at least in the flanking end and side
portions, will be completely bonded by adhesive through the
thickness thereof. In view of the high basis weight in the medial
portion 66 of the diaper, it is doubtful whether complete adhesive
penetration through said medial portion will be achieved.
Referring to FIGS. 5 and 6, a second embodiment of a unitary,
absorbent article 10a, in the form of a disposable diaper, includes
flanking side portions 68a, flanking end portions 70a and a medial
portion 66a. These portions are the same as the corresponding
portions of the diaper described above in connection with FIGS. 9
and 10, with the exception that no embossed pattern is impressed
into the web. Referring to FIG. 6, an upper adhesive layer and a
lower adhesive layer bond substantially all of the surface fibers
together and extend only partially through the thickness of the web
to provide an abrasion resistant facing surface 82a and a
structurally stable back surface 84a. The interior fibers
throughout substantially the entire web are substantially free of
adhesive to provide an excellent moisture containing interior
region. The diaper disclosed in FIGS. 5 and 6 can be made according
to the process of FIG. 1 by replacing the embossing rolls 36 and 38
with plain-surfaced compaction rolls. The use of compaction rolls
is desired to slightly compress the web to impart sufficient
structural integrity to said web so that it can be conveyed through
the subsequent treatment operations.
Referring to FIG. 7 a third embodiment of a disposable diaper 106
is shown. This diaper includes a fluid impervious plastic sheet 88
adhered to the lower surface of the fibrous web. The fibrous web
has an upper adhesive layer bonding substantially all of the upper
surface fibers together to provide an abrasion resistant,
non-pilling facing layer 82b. In this embodiment, a lower adhesive
layer can be omitted, and the plastic sheet 88 can be extruded in a
plastic state directly onto the fibrous web. Alternatively, a lower
layer of adhesive can be applied to the web, and while in a tacky
state, it can be utilized to adhere the plastic sheet 88 to the
web. The adhesive can be applied continuously over the lower
surface of the web, or along spaced lines, dots, or any other
desired pattern which will adhere the plastic sheet 88 to the web.
Alternatively, the adhesive can be applied either continuously or
discontinously directly to the plastic sheet 88.
Referring to FIG. 8, a further embodiment of a unitary, absorbent
article 10c, in the form of a disposable diaper, is identical to
the absorbent aritcle 10a shown in FIG. 5, except that an embossed
pattern is impressed only into a medial portion 66c thereof. This
embossed pattern is identical to the embossed pattern impressed
into the medial portion 66 of the article 10 shown in FIG. 9, and
includes transversely spaced longitudinal channels 76c and
longitudinally spaced transverse channels 78c.
FIGS. 11 and 13 disclose an additional embodiment of an absorbent
article 10d according to this invention. The absorbent article 10d
is identical to the absorbent article 10a shown in FIG. 5 except
that a medial portion 66d thereof has a substantially
hourglass-shaped configuration providing a reduced width central
crotch reguion to provide a construction which conforms confortably
to the perineal region of a wearer.
Referring to FIGS. 12 and 14, an additional embodiment of an
absorbent article 10e according to this invention is identical to
the absorbent article 10a (FIG. 5) and 10d (FIG. 11), except that a
medial portion 66e has a different shape. The medial portion 66e
has a reduced width central crotch region to provide a construction
which conforms comfortably to the perineal region of a wearer.
The above-described absorbent articles all include a medial portion
having a substantially uniform basis weight throughout its entire
extent. However, for some applications, it is desired to provide a
profiled medial portion, i.e., a medial portion having different
basis weights in different predetermined sections thereof. For
example, referring to FIG. 15, when an absorbent article is
intended for use as a disposable diaper for a girl, it is desirable
to provide a center section 88 of a medial portion 66f with a
greater basis weight of fibers therein than adjoining end sections
90 of said medial portion. This construction is preferred because
girl babies tend to directly impinge urine into the medial regions
of the diaper. Alternatively, referring to FIG. 16, when an
absorbent article is intended for use as a disposable diaper for a
boy baby, it is desirable to provide a forward section 92 of a
medial portion 66g with a greater basis weight of fibers therein
than a rearward section 94 of said medial portion. This is
preferred because boy babies tend to directly impinge urine onto
the forward one-half of the medial portion of the diaper.
Preferably the greatest basis weight section in the fibrous webs
shown in FIGS. 15 and 16 is between about 17 oz/yd.sup.2 and about
50 oz/yd.sup.2 ; and the sections of lesser basis weight are
between about 8 oz/yd.sup.2 and 22 oz/yd.sup.2.
The embodiments shown in FIGS. 7, 11, 12, 15 nd 16, can all be
provided with embossed patterns in the same manner as described
above in connection with the fibrous webs 10 (FIG. 9) and 10c (FIG.
8). The specific patterns which are embossed into the fibrous webs
can be varied, and are not intended to be limiting on the present
invention. In addition, all of the fibrous webs can be employed by
themselves as a unitary cloth-like diaper, or in conjunction with a
fluid-impervious plastic sheet, such as is shown in FIG. 7.
It is critical to all embodiments of this invention that the
absorbent articles include a high basis weight medial portion and
lower basis weight flanking side portions and end portions. The
high basis weight medial portion provides a high fluid absorbing
area which is positioned in the perineal region of a wearer. In
addition, this medial portion provides a relatively conformable
construction since it does not extend the full transverse extend of
the fibrous web. The most conformable construction results from
providing a reduced width crotch region in the manner shown in
FIGS. 11 and 13. The low basis weight flanking side portions
provide an extremely conformable construction for snugly engaging
the thigh regions of a wearer. The low basis weight flanking end
portions provide a conformable waist band region for closely
encircling the front and back regions of a wearer.
Referring to FIGS. 2 and 3, a unique condenser roll assembly 24 of
this invention which is employed in the web forming device 14 for
forming the continuous fibrous web 16 with spaced, uniform basis
weight thickened regions 30 therein will now be described. The
condenser roll assembly 24 includes an air-previous condenser roll
100 including a perforated, cylindrical metal shell 102, and a
porous screen 104 secured about the outer periphery of said shell.
The spaced, three-dimensional compartments 26 are established by
providing circumferentially spaced, discrete cut out regions in the
porous screen and cylindrical metal shell, and securing a
foraminous member 106 to the lower surface of the metal shell 102
to bridge each cut out region and form the bottom wall of the
three-dimensional compartments 26. The porous screen 104 and the
foraminous member 106 provide the forming surface 22 (FIG. 1) of
the condenser roll 100.
The condenser roll 100 is attached to a driven axle 108 through a
connecting plate 110. The connecting plate 110 is connected to the
cylindrical metal shell 102 of the condenser roll 100 by any
suitable fastening means, such as screws 112 (only one of which is
shown in FIG. 2). The connecting plate 110 includes a central,
hollow hub 114 which is keyed to the driven axle 108 through a
connecting pin 116. A pulley 118 is fixedly secured to the axle
108, and a belt 120 is in driving engagement with said pulley for
rotating said axle, to thereby rotate the condenser roll 100. The
belt 120 is driven by any suitable power source, such as an
electric motor (not shown).
A vacuum box assembly 122 is mounted within the condenser roll 100,
and is secured to driven axle 108 to be rotated at the same angular
velocity as said condenser roll. The vacuum box assembly 122
includes a plurality of vacuum boxes 124 attached to a hollow,
cylindrical hub 126 through spoke-like support arms 128. The driven
axle 108 extends through the cylindrical hub 126 and is keyed to
said hub through a connecting pin 130. Each vacuum box 124 includes
a bottom wall 132 and peripheral side walls 134. The outer edges of
the peripheral side walls 134 define an opening into each vacuum
box 124 having substantially the same shape as the
three-dimensional compartments 26, and each vacuum box 124 is
aligned with a respective three-dimensional compartment. Since the
condenser roll 100 and vacuum box assembly 122 are rotated at the
same angular velocity, each vacuum box 124 will underlie its
respective compartment 26 throughout the entire path of travel of
the condenser roll assembly 24. A vacuum connection conduit 136 is
in communication with each vacuum box 124 through a peripheral side
wall 134 thereof, and each of said vacuum connection conduits 136
is mounted in communication with a corresponding opening 138 in the
connecting plate 110.
Referring to FIG. 2, an end plate 140 is positioned in sliding
engagement with the outer surface of the connecting plate 110 and
is mounted to fixed structural framework schematically shown at
142. The end plate 140 includes an outer annular recess 144 and an
inner annular recess 146 in the inner surface thereof, and these
recesses ae concentric to the hub 114 of the connecting plate 110.
Suitable elastomeric seals 148 are provided about each of the
annular recesses 144 and 146. Suitable sources of vacuum, such as
fans (not shown) are connected through vacuum lines 150 and 152
which are in communication with the annular recesses 144 and 146,
respectively. In this manner, the vacuum source which is in
communication with the outer annular recess 144 will be effective
to establish a pressure drop across the bottom foraminous wall 106
of the three-dimensional compartments 26 through the underlying
vacuum boxes 124. The other vacuum source, which is in
communication with the inner annular recess 146, will be effective
to establish a pressure drop across the remaining regions of the
foraminous forming surface 22 (FIG. 1).
In order to permit easy removal of the formed web 16 from the
condenser roll 100, it is desirable to terminate the partial vacuum
through the foraminous forming surface 22 at the point of removal.
To achieve this result a masking member 154 is positioned between
the condenser roll 100 and the vacuum box assembly 122. The masking
member 154 includes a perforated cylindrical shell 156 constructed
of any suitable bearing material, said shell having an unperforated
lower region 158. Accordingly, as a region of the condenser roll
100 passes over the unperforated region 158 of the cylinder 156,
the partial vacuum which is established through vacuum lines 150
and 152 (FIG. 2) will not be effective to establish a partial
vacuum through the forming surface 22 to retain allegiance of the
formed continuous fibrous web 16 for the condenser roll 100.
Therefore, the formed web 16 can be easily transferred to a
conveyor (not shown) positioned adjacent the lower side of the
condenser roll 100 by applying a partial vacuum through said
conveyor. The cylinder 156 is nonrotatably mounted within the
condenser roll 100 by being secured to an end support 160 which in
turn is attached to fixed structural framework schematically
indicated at 162 (FIG. 2).
In practicing the method of this invention a greater partial vacuum
is established through the vacuum line 150, which is in
communication with the vacuum boxes 124, than is established
through the vacuum line 152 which is in communication with the
remaining interior portion of the condenser roll 100. Since the
entire forming surface 22 of the condenser roll 100 is exposed to
vacuum for the same period of time, a greater effective or total
volumetric air flow will be established through the bottom walls of
the three-dimensional compartments 26, then is established through
the surfaces flanking said three-dimensional compartments. This
greater effective volumetric air flow results in the deposition of
a greater weight of fibers in each of the three-dimensional
compartments 26 than on the foraminous surface regions flanking
said three-dimensional compartments to thereby establish formation
of the continuous fibrous web 16 with spaced, thickened regions 30.
The thickened regions 30 of the continuous fibrous web 16 can be
formed with any desired shape by providing the three-dimensional
compartments 26 and the outer periphery of the vacuum boxes with
such desired shape.
The above-described method is effective for forming a thickened
medial region which has a substantially uniform basis weight
throughout substantially its entire extent. However, in some
instances, it is desired to provide a thickened medial region
having different basis weights in different predetermined sections
thereof, as described above in connection with FIGS. 15 and 16.
Referring to FIGS. 17 through 19, a condenser roll assembly 24a is
shown which is utilized for forming profiled, thickened medial
regions having different basis weights in different predetermined
sections thereof. Specifically, the description which follows will
be directed to a condenser roll assembly 24a employed in forming
hourglass-shaped, thickened medial regions, as shown in FIG. 11,
having a greater basis weight in the center crotch section thereof
than in flanking end sections thereof, as shown in FIG. 15.
Referring to FIG. 17, the condenser roll assembly 24a includes a
condenser roll 100a, a vacuum box assembly 122a, and a masking
member 154a which are assembled in the identical manner described
earlier in connection with FIGS. 2 and 3. The condenser roll
assembly 24a differs from the condenser roll assembly 24 shown in
FIG. 2 in the specific construction of the masking member 154a and
the specific construction of the end plate (not shown in detail)
which are employed.
Referring to FIGS. 17 and 18, the masking member 154a has a lower
circumferential extent thereof 158a which is unperforated, and
therefore air-impervious, to permit removal of a formed fibrous web
from the condenser roll 100a in the same manner described above in
connection with the condenser roll assembly 24. In addition, the
masking member 154a has axially spaced, circumferentially
extending, air-impervious regions 200 which are axially aligned
with end sections of three-dimensional compartments 26a as said
three-dimensional compartments pass thereover; and a centrally
disposed, circumferentially extending, air-impervious region 202
which is axially aligned with the center section of the
three-dimensional compartments 26a as said compartments pass
thereover (FIG. 18). The circumferential extent of the end
air-impervious regions 200 is greater than the circumferential
extent of the central air-impervious region 202 for a reason to be
described later in this application. The specific orientation of
the masking member 154a relative to the condenser roll 100a will
depend upon the specific location of the web forming area;
therefore, the orientation of the masking member 154a shown in FIG.
17 should not be considered as representing the specific
relationship required during use of the condenser roll assembly
24a.
The end plate (not shown in detail) is mounted in engagement with a
connecting plate (not shown), which is identical to connecting
plate 110, in the same manner as described earlier for connecting
the end plate 140 to the connecting plate 110 (FIG. 2). The end
plate includes an outer annular recess 144a (FIG. 17) for
establishing a vacuum communication between a vacuum source (not
shown) and the vacuum boxes 124a. This annular recess extends for
substantially the same circumferential extent, and in
circumferential alignment with, the end and central air-impervious
regions 200 and 202 of the masking member 154a. In this manner, a
vacuum will be established through the vacuum boxes 124a only when
the three-dimensional compartments 26a, and the corresponding
vacuum boxes 124a, are moving within the circumferential region
which includes the end mask regions 200 and the central mask region
202 of the masking member 154a to thereby provide substantially
complete formation of the hourglass-shaped medial portion 66f (FIG.
15) of the fibrous web in this circumferential region. To further
explain, after each three-dimensional compartment 26a completely
passes the central mask region 202, the vacuum conduit assocaited
with its corresponding vacuum box will be out of alignment with the
outer recess 144a, and therefore, the vacuum established through
the vacuum conduit will not be effective to establish a partial
vacuum through said vacuum box.
The inner annular recess 146a in the end plate is identical to the
inner annular recess 146 described above in connection with FIGS. 2
and 3. This inner annular recess 146a is in communication with the
interior of the condenser roll 100a in the regions surrounding the
vacuum box assembly 122a. Therefore, the sections of the fibrous
web which circumscribe the thick, hourglass-shaped medial portion
66f thereof can be formed throughout the entire circumferential
path of travel of the condenser roll assembly 24a through the
forming area of the web forming device, and this circumferential
extent is greater than the circumferential extent which is
circumscribed by the end mask regions 200 and central mask region
202. The vacuum level established through the inner annular recess
146a is set to achieve only sufficient air flow to deposit the
desired basis weight of fibers in the portions of the fibrous web
circumscribing the hourglass-shaped thickened medial portion
66f.
Since the end masking regions 200 have a greater circumferential
extent than the central mask region 202, the center section of the
hourglass-shaped compartments of the condenser roll will be exposed
to the same vacuum, level as the end sections of said compartments,
but for a greater length of time. Accordingly, a greater volumetric
air flow is established through the center section of the
three-dimensional compartments 26a than through the end sections to
achieve formation of the hourglass-shaped thickened medial region
66f having the profile shown in FIG. 15.
A fibrous web having a thickened medial portion as indicated at 66g
in FIG. 16 can be formed by employing a condenser roll assembly
similar to that shown in FIG. 17. However, the shape of the
three-dimensional compartments will be suitable modified to
correspond to the shape of the thickened medial portion 66g. In
addition, the air-impervious regions of the mask will be positioned
to expose one-half of the three-dimensional compartments to vacuum
for a greater length of time than the other half to thereby
establish the formation of a profiled thickened medial region
having a greater basis weight in one-half thereof than in the other
half thereof as is shown in FIG. 16.
Other profiles can be established by suitably modifying the masking
member. In addition, fibrous webs having different shaped thickened
medial regions can be formed by changing the shape of the
three-dimensional compartments and the shape of the vacuum boxes.
Furthermore, it is within the scope of this invention to provide a
fluid impervious coating directly on the forming surface of the
condenser roll in the form of a transverse stripe disposed
intermediate adjacent three-dimensional compartments to achieve
direct formation of discrete fibrous webs on the forming
surface.
* * * * *