U.S. patent application number 10/036731 was filed with the patent office on 2002-12-05 for process for making textured airlaid materials.
This patent application is currently assigned to Kimberly-Clark Worldwide, Inc.. Invention is credited to Abba, Rodney L., Bednarz, Julie Marie, Chen, Fung-Jou, Colman, Charles W., Lindsay, Jeffrey Dean, Makolin, Robert J., Nickel, David J..
Application Number | 20020180092 10/036731 |
Document ID | / |
Family ID | 46278611 |
Filed Date | 2002-12-05 |
United States Patent
Application |
20020180092 |
Kind Code |
A1 |
Abba, Rodney L. ; et
al. |
December 5, 2002 |
Process for making textured airlaid materials
Abstract
A textured airlaid web is disclosed. The textured web is formed
on a three-dimensional fabric under sufficient force to cause the
web to conform to the surface of the fabric. The textured web
includes, on a minute scale, peak areas and valley areas. The peak
areas and valley areas can improved the liquid handling properties
of the web. For instance, webs can be produced having improved
absorbency characteristics and/or wicking characteristics.
Inventors: |
Abba, Rodney L.; (Oshkosh,
WI) ; Makolin, Robert J.; (Neenah, WI) ;
Nickel, David J.; (Neenah, WI) ; Colman, Charles
W.; (Marietta, GA) ; Lindsay, Jeffrey Dean;
(Appleton, WI) ; Chen, Fung-Jou; (Appleton,
WI) ; Bednarz, Julie Marie; (Neenah, WI) |
Correspondence
Address: |
TIMOTHY A. CASSIDY
Dority & Manning
Attorneys at Law, P.A.
P.O. Box 1449
Greenville
SC
29602
US
|
Assignee: |
Kimberly-Clark Worldwide,
Inc.
|
Family ID: |
46278611 |
Appl. No.: |
10/036731 |
Filed: |
December 21, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10036731 |
Dec 21, 2001 |
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09684039 |
Oct 6, 2000 |
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10036731 |
Dec 21, 2001 |
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09680719 |
Oct 6, 2000 |
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60159629 |
Oct 14, 1999 |
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Current U.S.
Class: |
264/112 ;
264/113; 264/119; 264/121 |
Current CPC
Class: |
D04H 1/732 20130101;
A61F 13/533 20130101; A61F 2013/4958 20130101; D04H 1/76 20130101;
A61F 13/5376 20130101; A61F 2013/53778 20130101; A61F 2013/15943
20130101; D21G 9/00 20130101; A61F 2013/1543 20130101; A61F
13/53717 20130101; D04H 1/558 20130101; A61F 13/15626 20130101;
D04H 1/54 20130101; D04H 1/542 20130101; D21F 11/006 20130101 |
Class at
Publication: |
264/112 ;
264/119; 264/121; 264/113 |
International
Class: |
D04H 001/00 |
Claims
What is claimed:
1. A process for forming a textured airlaid fibrous web comprising
the steps of: combining discrete fibers with a gas; directing the
gas and fiber mixture onto a moving conveyer, the fibers thereby
forming a non-woven web; contacting the web with a fabric having a
three-dimensional surface under sufficient force to cause the web
to conform to the surface of the fabric thereby forming a textured
surface on the airlaid web, the textured surface including a
repeating pattern of peak areas and valley areas; and bonding the
airlaid and textured web together, the formed airlaid web having a
height that is at least 25% greater than the average caliper of the
formed web.
2. A process as defined in claim 1, wherein the fabric having the
three-dimensional surface comprises a forming fabric.
3. A process as defined in claim 1, wherein the fabric having the
three-dimensional surface comprises a transfer fabric.
4. A process as defined in claim 1, wherein the fabric having the
three-dimensional surface comprises a bonding fabric.
5. As process as defined in claim 1, further comprising the step of
calendaring the airlaid web having the textured surface in order to
increase the density of the peak areas in comparison to the density
of the valley areas.
6. A process as defined in claim 1, wherein the airlaid and
textured web is thermally bonded together.
7. A process as defined in claim 1, wherein the textured and
airlaid web is bonded together by applying an adhesive to the
surfaces of the web.
8. A process as defined in claim 1, wherein the web includes at
least 2 peaks per inch in one direction of the web.
9. A process as defined in claim 1, wherein the airlaid web
includes at least 9 peaks per square inch over the textured
surface.
10. A process as defined in claim 1, wherein the textured surface
of the airlaid web has a surface area that is at least 25% greater
than the surface area of a planar web made from the same fibers and
at the same basis weight.
11. A process as defined in claim 8, wherein the web includes at
least 5 peaks per inch in one direction of the web.
12. A process as defined in claim 8, wherein the web includes at
least 10 peaks per inch in one direction of the web.
13. A process as defined in claim 1, wherein the airlaid web
includes at least two peaks per square inch over the textured
surface.
14. A process as defined in claim 1, wherein the textured surface
of the airlaid web has a surface area that is at least 50% greater
than the surface area of a planar web made from the same fibers and
at the same basis weight.
15. A process as defined in claim 1, wherein the textured surface
of the airlaid web has a surface area that is at least 100% greater
than the surface area of a planar web made from the same fibers and
at the same basis weight.
16. A process as defined in claim 1, wherein the web is formed to
include a substantially planar surface opposite the textured
surface.
17. A process as defined in claim 1, further comprising the step of
contacting the web with a second fabric having a three dimensional
surface under sufficient force to cause the web to conform to the
surface of the fabric thereby forming a second textured surface
opposite the first textured surface.
18. A process as defined in claim 1, further comprising the step of
directing further fiber and gas mixtures onto the non-woven web in
order to form a multi-layered web.
19. A process as defined in claim 5, wherein the density of the
peak areas is at least 25% greater than the density of the valley
areas.
20. A process as defined in claim 5, wherein the density of the
peak areas is at least 50% greater than the density of the valley
areas.
21. A process as defined in claim 1, wherein the airlaid web
consists essentially of synthetic fibers.
22. A process as defined in claim 1, wherein the airlaid web
comprises pulp fibers.
23. A process as defined in claim 1, wherein the formed airlaid web
has a height that is at least 50% greater than the average caliper
of the formed web.
24. A process as defined in claim 1, wherein the formed airlaid web
has a height that is at least 100% greater than the average caliper
of the formed web.
25. A process as defined in claim 1, wherein the airlaid web is
bonded together by thermally bonding the web and by supplying an
adhesive to the web.
26. A process for forming a textured airlaid fibrous web comprising
the steps of: combining fibers with a gas, the fibers comprising
synthetic fibers, natural fibers or mixtures thereof; directing the
gas and fiber mixture onto a moving forming fabric, the forming
fabric having a three-dimensional surface, the fibers contacting
the three-dimensional surface of the forming fabric under
sufficient force to cause the fibers to conform to the surface of
the fabric and form an airlaid web, the airlaid web including a
textured surface facing the forming fabric, the textured surface
including a repeating pattern of peak areas and valley areas, the
textured surface including at least three peaks per inch in one
direction of the web; and bonding the airlaid web together, the
formed airlaid web having a height that is at least 25% greater
than the average caliper of the formed web.
27. A process as defined in claim 26, wherein the airlaid web has a
height that is at least 50% greater than the average caliper of the
formed web.
28. A process as defined in claim 26, wherein the textured surface
includes at least 10 peak areas per inch in one direction of the
web.
29. A process as defined in claim 26, wherein the textured surface
includes at least 9 peak areas per square inch.
30. A process as defined in claim 26, wherein the airlaid web
comprises synthetic fibers.
31. A process as defined in claim 26, wherein the airlaid web
includes pulp fibers.
32. A process as defined in claim 26, wherein the airlaid web
includes binder fibers, the web being bonded together by heating
the web containing the binder fibers.
33. A process as defined in claim 26, further comprising the step
of calendaring the airlaid web having the textured surface in order
to increase the density of the peak areas in comparison to the
density of the valley areas.
34. A process as defined in claim 26, further comprising the step
of contacting the web with the three-dimensional forming fabric
under a compression roll.
35. A process as defined in claim 26, wherein the textured surface
has a surface area that is at least 50% greater than the surface
area of a planar web made from the same fibers and at the same
basis weight.
36. A process for forming an airlaid fibrous web comprising the
steps of: combining discreet fibers with a gas; directing the gas
and fiber mixture onto a moving conveyor, the fibers thereby
forming a non-woven web; contacting the web with a fabric having a
three-dimensional surface under sufficient force to cause the web
to conform to the surface of the fabric thereby forming a textured
surface on the airlaid web including peak areas and valley areas;
calendaring the airlaid web having the textured surface in order to
increase the density of the peak areas in comparison to the density
of the valley areas; and bonding the airlaid web together.
37. A process as defined in claim 36, wherein the web is calandared
an amount sufficient to create a substantially planar web.
38. A process as defined in claim 36, wherein the calendared peak
areas have a density that is at least 25% greater than the density
of the valley areas.
39. A process as defined in claim 36, wherein the calendared peak
areas have a density that is at least 50% greater than the density
of the valley areas.
40. A process as defined in claim 36, wherein the textured surface
includes at least 9 peak areas per square inch.
Description
BACKGROUND OF THE INVENTION
[0001] Absorbent articles and structures, such as absorbent pads,
absorbent cores, and absorbent webs, have been formed by employing
various techniques. The absorbent articles are typically
incorporated into various absorbent products, such as diapers,
feminine napkins and incontinence garments. In many applications,
the absorbent articles are formed in an airlaying process.
[0002] Conventional airlaying processes typically include one or
more forming chambers that are placed over a moving foraminous
forming surface, such as a forming screen. Fibrous materials and/or
particulate materials are introduced into the forming chamber and a
vacuum source is employed to draw an airstream through the forming
surface. The airstream deposits the fibers and/or particulate
material onto the moving forming surface.
[0003] Once deposited onto the forming surface, a non-woven web is
formed. Subsequently, the non-woven web can be bonded together. For
example, the web can be bonded together using an adhesive and/or
can be thermally bonded together.
[0004] In the past, flat non-woven sheets have been produced
generally according to the above-described process. In other
embodiments, the non-woven article has been shaped into a contoured
batt or pad which locates more absorbent material or fibers in
those areas which are subjected to higher levels of fluid
loading.
[0005] In general depending upon their use, the airlaid articles
should have good absorbency properties and/or wicking properties.
For example, when used as an absorbent layer in a product, the
airlaid web should quickly absorb fluids and, once absorbed, retain
the fluids within the structure. In this regard, many attempts have
been made to improve the absorbency characteristics of airlaid
webs.
SUMMARY OF THE INVENTION
[0006] The present invention is generally directed to further
improvements to airlaid webs. More particularly, the present
invention is directed to the formation of textured airlaid webs
that can have improved absorbent properties and wicking properties.
For example, textured airlaid webs made according to the present
invention have a substantial increase in surface area in comparison
to planar webs and therefore have more surface area for contact
with liquids. Further, textured webs made according to the present
invention can be made having localized density gradients, i.e.
containing high density and low density areas. The high density
areas can improve the absorption and liquid retaining
characteristics of the web, while the low density areas can
facilitate wicking of fluids off the surface of the web.
[0007] In one embodiment, the textured airlaid fibrous web is made
from natural fibers, synthetic fibers, or mixtures thereof. The
airlaid web is formed on a three-dimensional fabric under
sufficient force to cause the web to conform to the surface of the
fabric. The resulting textured surface that is formed into the web
includes a repeating pattern of peak areas and valley areas. The
height of the web, which refers to the distance between the lowest
point on the web and the highest point on the web, can be at least
25% greater than the average caliper or thickness of the web,
particularly at least 50% greater than the caliper of the web, and
more particularly at least 100% greater than the caliper of the
web.
[0008] According to the present invention, the airlaid textured web
is bonded together after formation of the textured surface. By
bonding the web together, the web becomes resistant to compression
and fluid collapse. The web can be thermally bonded together by
incorporating binder fibers into the web. Alternatively, the web
can be bonded together by applying an adhesive to the surfaces of
the web or can be bonded using both an adhesive and binder
fibers.
[0009] As described above, the textured airlaid web includes a
repeating pattern of peak areas and valley areas. In general, the
web can include at least one peak per inch in one direction of the
web, such as in the machine direction or the cross-machine
direction. Particularly, the web can include at least 3 peaks per
inch in one direction, more particularly at least 5 peaks per inch
in one direction, and more particularly at least 10 peaks per inch
in one direction. When the peak areas extend in more than one
direction on the web, the peak areas can be present in an amount of
at least 2 peaks per square inch, particularly at least 9 peaks per
square inch, and more particularly at least 15 peaks per square
inch.
[0010] The basis weight of webs made according to the present
invention can be from about 40 gsm to about 1500 gsm or greater.
The density of the webs can be from about 0.01 grams per cubic
centimeter to about 0.3 grams per cubic centimeter. Due to the
textured surface, the web includes a substantial amount of surface
area. For instance, the web can have a surface area that is at
least 25% greater than the surface area of a planar web at the same
basis weight, and particularly 100% greater than the surface area
of a planar web at the same basis weight.
[0011] In one embodiment, the textured airlaid web can be
constructed such that the peak areas have a higher density than the
valley areas. For example, the density of the peak areas can be at
least 25% greater than the density of the valley areas.
[0012] If desired, the textured airlaid web can be contoured or
otherwise molded to have a particular shape. The textured web can
be incorporated into various absorbent articles and products, such
as diapers, feminine hygiene products, adult incontinent products,
wiping products and the like.
[0013] In order to form textured airlaid webs in accordance with
the present invention, the process includes the steps of combining
fibrous materials with a gas and/or a mixture of gases. The gas and
fiber mixture is directed onto a moving conveyer to form a
non-woven web. The web is contacted with a fabric having a
three-dimensional surface under sufficient force to cause the web
to conform to the three-dimensional surface and thereby form a
textured surface on the web. The textured surface includes a
repeating pattern of peak areas and valley areas that correspond to
the three-dimensional pattern present on the fabric. After the
textured surface is formed, the airlaid web is bonded together by
thermal bonding and/or through the use of an adhesive.
[0014] In general, the textured surface can be produced on the
non-woven airlaid web at various different locations in the
fabrication process. For instance, the textured web can be formed
on the forming fabric, on a transfer fabric, on a bonding fabric or
on a combination thereof.
[0015] In one embodiment, the web can be subjected to compression
after being textured. For example, the web can be fed through a nip
formed by a pair of calendaring rolls. The calendaring rolls can
partially compress the peak areas formed into the web. Through this
process, the density of the peak areas increases in relation to the
density of the surrounding valley areas.
[0016] According to the present invention, various additives can be
incorporated into the airlaid fibrous web. Such additives include
super-absorbent materials, odor control materials, scented
materials, and the like. The additives can be incorporated
homogeneously throughout the web or can be applied at selected
locations. For example, in one embodiment, the additives can be
located in the valley areas of the webs. In a multi-layered
product, the additives can also be positioned between the separate
layers.
[0017] Other features and aspects of the present invention are
discussed in greater detail below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] A full and enabling disclosure of the present invention,
including the best mode thereof to one of ordinary skill in the
art, is set forth more particularly in the remainder specification,
including reference to the accompanying figures in which:
[0019] FIG. 1 is a simplified cross-sectional view of one
embodiment of an airlaying apparatus that can be used in the
process of the present invention;
[0020] FIG. 2 is a simplified side view of a system for forming
airlaid non-woven webs in accordance with the present
invention;
[0021] FIG. 3 is a perspective view with cutaway portions of one
embodiment of an airlaid web made in accordance with the present
invention; and
[0022] FIG. 4 is a perspective view with cutaway portions of
another embodiment of an airlaid web made in accordance with the
present invention.
[0023] Repeated use of reference characters in the present
specification and drawings is intended to represent the same or
analogous features or elements of the present invention.
DETAILED DESCRIPTION
[0024] It is to be understood by one of ordinary skill in the art
that the present discussion is a description of exemplary
embodiments only, and is not intended in limiting the broader
aspects of the present invention, which broader aspects are
embodied in the exemplary construction.
[0025] In general, the present invention is directed to highly
textured airlaid webs and to various processes for producing the
webs. The airlaid webs are formed on a fabric having a
three-dimensional topography. During formation of the airlaid web,
a sufficient amount of force is placed on the fibers to cause the
web to conform to the three-dimensional surface of the fabric, thus
producing a web having a highly textured surface. Once formed, the
textured web is bonded together making the structure resilient to
compression and fluid collapse.
[0026] Textured webs produced according to the present invention
can have improved absorption and wicking properties. For instance,
the texturized webs of the present invention can be formed with
density gradients and varying pore sizes within the fiber structure
that enhances the ability of the material to absorb and wick away
fluids. Further, since the webs are textured, the webs have an
increased surface area for contact with fluids.
[0027] Referring to FIG. 3, for exemplary purposes only, an airlaid
fibrous web generally 10 made in accordance with the present
invention is shown. As illustrated, the airlaid web 10 includes
peak areas 12 separated by valley areas 14. In this embodiment, the
peaks and valleys form parallel rows that run in either the machine
direction or the cross-machine direction of the web 10. It should
be understood, however that the embodiment illustrated in FIG. 3 is
merely for explanation purposes only and that any desired textured
surface can be made in accordance with the present invention as
will be described in more detail below.
[0028] In general, airlaid textured webs made according to the
present invention will have a repeating pattern of peak areas and
valley areas. The peak areas can extend in a single direction as
shown in FIG. 3 or can extend in multiple directions over the
surface of the web.
[0029] For most applications, the textured web of the present
invention will contain at least one peak area per inch in one
direction of the web, such as in the machine direction or in the
cross-machine direction. For example, in some embodiments, the
repeating pattern of peak areas and valley areas can include at
least 3 peaks areas per inch in one direction, particularly at
least 5 peak areas per inch in one direction, more particularly at
least 7 peak areas per inch in one direction and in one embodiment,
at least 10 peak areas per inch. The amount of peaks present will
depend upon the particular application. For instance, the peak
areas can be made on a very minute scale such that there are up to
20 peak areas per inch, particularly up to about 32 peak areas per
inch, and in one embodiment, up to about 40 peak areas per
inch.
[0030] When the peak areas extend in multiple directions, the
textured webs can include at least 2 peak areas per square inch,
particularly at least 9 peak areas per square inch and in some
embodiments, at least 15 peak areas per square inch. When extending
in multiple directions, it is believed that textured webs can be
made having a peak area density of up to about 40 peak areas per
square inch or greater.
[0031] As shown in FIG. 3, the textured web 10 includes a thickness
T or caliper. For most applications, the caliper T will vary
throughout the web due to the manner in which the web is formed. In
addition to the thickness or caliper, as shown in FIG. 3, the
textured web also includes a height H. As used herein, height
refers to the distance between the lowest point of the web and the
highest point of the web. For example, a web having two textured
surfaces will have a height that is equal to the distance from a
peak on one surface to a peak on an opposing surface.
[0032] For conventionally made flat or planar webs, the height is
generally the same distance as the caliper. Texturized webs made
according to the present invention, however, have a height H that
is much greater than the caliper T of the web. For example, the
height of textured webs made according to the present invention can
be at least 25% greater than the average caliper of the web. For
most applications, the height of the web will be at least 50%
greater than the caliper of the web, particularly at least 100%
greater than the caliper of the web, and, in one embodiment, 200%
greater than the caliper of the web. For patterns where there is a
relatively large amount of space between the peak areas, it is also
believed that textured webs can be made according to the present
invention that have a height that is up to 400% greater than the
average caliper of the web.
[0033] Because the textured webs of the present invention include a
repeating pattern of peak areas and valley areas, the webs have
increased surface area in comparison to flat or planar webs and
contoured webs. For instance, textured webs made according to the
present invention will have a surface area that is at least 25%
greater than the surface area of a planar web at the same caliper,
particularly greater than 50% of a planar web at the same caliper,
more particularly greater than 100% of a planar web at the same
caliper, and more particularly greater than 500% of a planar web at
the same caliper. In some embodiments, it is believed that a
textured web made according to the present invention can have a
surface area that is 800% greater than the surface area of a planar
web at the same caliper.
[0034] Referring to FIG. 4, another embodiment of an airlaid
textured web made in accordance with the present invention is
illustrated. As shown, the textured web 20 includes peak areas 22
separated by valley areas 24. In this embodiment, the peak areas
extend in two directions on the surface of the web. The peak areas
also comprise discrete shapes or "islands" that are completely
surrounded by the valley areas 24.
[0035] The peak areas 22, shown in FIG. 4 appear as small hills.
Depending upon the construction of the three-dimensional fabric on
which the airlaid web is formed, however, various shapes and
designs can be created into the textured surface. For instance,
three-dimensional fabrics can be designed that will create airlaid
webs having peak areas in particular shapes. The peak areas can be
in the shapes of squares, circles, triangles, other aesthetic
designs and the like.
[0036] In an alternative embodiment, it is also possible to create
peak areas 22 that are connected in a reticulated pattern. For
example, a three-dimensional forming fabric can be manufactured
that will create peak areas that appear in a checkered pattern or
in any other desired connected pattern.
[0037] One embodiment of a process for forming textured airlaid
webs in accordance with the present invention will now be described
in detail with particular reference to FIGS. 1 and 2. Referring to
FIG. 1, an airlaying forming station 30 is shown which produces a
non-woven web 32 on a forming fabric or screen 34. The forming
fabric 34 can be in the form of an endless belt mounted on support
rollers 36 and 38. A suitable driving device, such as an electric
motor 40 rotates at least one of the support rollers 38 in a
direction indicated by the arrows at a selected speed. As a result,
the forming fabric 34 moves in a machine direction indicated by the
arrow 42.
[0038] The forming fabric 34 can be provided in other forms as
desired. For example, the forming fabric can be in the form of a
circular drum which can be rotated using a motor as disclosed in
U.S. Pat. No. 4,666,647, U.S. Pat. No. 4,761,258, or U.S. Pat. No.
6,202,259. The forming fabric 32 can be made of various materials,
such as plastic or metal.
[0039] As shown, the airlaying forming station 34 includes a
forming chamber 44 having end walls and side walls. Within the
forming chamber 44 are a pair of material distributors 46 and 48
which distribute fibers and/or other particles inside the forming
chamber 44 across the width of the chamber. The material
distributors 46 and 48 can be, for instance, rotating cylindrical
distributing screens.
[0040] In the embodiment shown in FIG. 1, a single forming chamber
44 is illustrated in association with the forming fabric 34. It
should be understood, however, that more than one forming chamber
can be included in the system. By including multiple forming
chambers, layered webs can be formed in which each layer is made
from the same or different materials.
[0041] Airlaying forming stations as shown in FIG. 1 are available
commercially through Dan-Webforming Int. LTD. of Aarhus, Denmark.
Other suitable airlaying forming systems are also available from M
& J Fibretech of Horsens, Denmark. In general, any suitable
airlaying forming system can be used in accordance with the present
invention.
[0042] As shown in FIG. 1, below the airlaying forming station 30
is a vacuum source 50, such as a conventional blower, for creating
a selected pressure differential through the forming chamber 44 to
draw the fibrous material against the forming fabric 34. If
desired, a blower can also be incorporated into the forming chamber
44 for assisting in blowing the fibers down on to the forming
fabric 34.
[0043] In one embodiment, the vacuum source 50 is a blower
connected to a vacuum box 52 which is located below the forming
chamber 44 and the forming fabric 34. The vacuum source 50 creates
an airflow indicated by the arrows positioned within the forming
chamber 44. Various seals can be used to increase the positive air
pressure between the chamber and the forming fabric surface.
[0044] During operation, typically a fiber stock is fed to one or
more defibrators (not shown) and fed to the material distributors
46 and 48. The material distributors distribute the fibers evenly
throughout the forming chamber 44 as shown. Positive airflow
created by the vacuum source 50 and possibly an additional blower
force the fibers onto the forming fabric 34 thereby forming an
airlaid non-woven web 32.
[0045] The material that is deposited onto the forming fabric 34
will depend upon the particular application. The fiber material
that can be used to form the airlaid web 32, for instance, can
include natural fibers, synthetic fibers, and combinations thereof.
Examples of natural fibers include wood pulp fibers, cotton fibers,
wool fibers, silk fibers and the like, as well as combinations
thereof. Wood pulp fibers can include softwood fibers and hardwood
fibers. Synthetic fibers can include rayon fibers, polyolefin
fibers, polyester fibers and the like, as well as combinations
thereof. Polyolefin fibers include polypropylene fibers and
polyethylene fibers. The fibers can have various lengths, such as
up to about 6 to about 8 millimeters or greater.
[0046] In one embodiment, binder fibers can also be incorporated
into the airlaid web 32. Once incorporated into the web, the binder
fibers can be later heated and at least partially melted and fused
together in order to bond the web together. The binder fibers can
be, for instance, polyethylene fibers, polypropylene fibers, and
polyester fibers. In one embodiment, the binder fibers can be
bicomponent fibers that include, for instance, a sheath polymer and
a core polymer. During bonding, the sheath polymer melts and bonds
to other materials, while the core polymer does not. Suitable
bicomponent fibers include polyester/polyethylene fibers,
polypropylene/polyethylene fibers, and the like. The bicomponent
fibers can be present in the non-woven web in an amount up to 100%
by weight, and particularly from about 2% to about 50% by weight
depending upon the particular application. In multi-layered
products, the amount of bicomponent fibers contained within each
layer can also vary. For example, one layer can be made exclusively
of bicomponent fibers, while another layer can contain bicomponent
fibers in combination with other fibers, such as pulp fibers.
[0047] Besides fibers, the airlaid web 32 can include various other
additives. For instance, additives such as odor absorbents,
antimicrobial agents, super-absorbent materials, scented materials,
and the like can be incorporated into the web.
[0048] When forming the airlaid web 32 from different materials and
fibers, the forming chamber 44 can include multiple inlets for
feeding the materials to the chamber. Once in the chamber, the
materials can be mixed together if desired. Alternatively, the
different materials can be separated into different layers in
forming the web. For example, the system can include multiple
forming chambers for forming multiple layers of different
materials. In one embodiment, a first layer can be made from fibers
while a second layer can be made from any of the above-described
additives alone or in combination with fibers.
[0049] In accordance with the present invention, the airlaid web 32
is formed on a three-dimensional fabric under a sufficient amount
of force to cause the web to conform to the surface of the fabric.
In this manner, textured webs are produced having peak areas and
valley areas as shown in FIGS. 3 and 4. In one embodiment of the
present invention, the three dimensional fabric is the forming
fabric 34 as shown in FIG. 1. The force that is needed to create
the textured web on the three-dimensional forming fabric 34 is
created by the vacuum source 50 located under the forming chamber
44 and/or by some other compressive force, e.g. a compaction roll.
In general, it is believed that any three-dimensional forming
fabric that can impart a repeating pattern of peak areas and valley
areas into the web 32 can be used in the process of the present
invention. The forming fabric 34, however, must have a permeability
that will collect the fibrous material on the surface of the fabric
but will allow sufficient air to pass through the fabric in order
to generate the force necessary to create a textured surface on the
web.
[0050] During the above process, a textured web is produced that,
on a minute scale, includes peak areas and valley areas that
dramatically increase the visible and usable surface area of the
web. The resulting structure can be controlled so as to form
airlaid webs having improved absorption and wicking properties. In
one embodiment, it is believed that the textured webs can also be
formed with different density gradients contained within the
structure. In particular, it is believed that higher density
regions will form in the web at higher localized airflow regions on
the forming fabric. For some applications, these higher density
areas will be created where the peak areas are formed although the
higher density areas can be created in other sections of the web
depending on the construction of the forming fabric. In this
manner, a textured web is formed having higher density areas
capable of absorbing and retaining large amounts of fluids.
[0051] In an alternative embodiment, higher density areas can be
formed by calendaring the web or otherwise compressing the web
after the textured web is formed. If some compression of the web is
done after the textured surface is formed, the compression will
cause the peak areas to densify and have a higher density than the
adjacent valley areas. In one embodiment, the web can be compressed
an amount sufficient to form a planar web having high density areas
and low density areas.
[0052] The difference in density between the peak areas and valley
areas will depend upon the manner in which the peaks and valleys
are formed. In general, the peak areas can have a density that is
at least 25% greater than the density of the valley areas,
particularly 50% greater and more particularly 100% greater than
the density of the valley areas depending on the desired
result.
[0053] Referring to FIG. 2, one embodiment of an entire web forming
system incorporating the airlaying station 30 of FIG. 1 is shown.
In this embodiment, the web 32 is formed under the airlaying
forming station 30 and fed between a pair of calendaring rolls 54
and 56. The calendaring rolls 54 and 56 are optional and provided
for exemplary purposes only. The calendaring rolls 54 and 56 can be
used to increase the density of the peak areas as described
above.
[0054] From the calendaring rolls 54 and 56, the airlaid web 32 is
supported on a transfer fabric 58. A second transfer fabric 60 also
appears in this embodiment for facilitating movement of the web
from the transfer fabric 58 to a bonding fabric 62. As shown in
phantom, the bonding fabric 62 is placed in association with a
bonding station 64. The bonding station 64 can be an oven if the
airlaid fabric contains binder fibers or can be an adhesive
application station.
[0055] From the bonding fabric 62, in this embodiment, a further
pair of calendaring rolls 66 and 68 are shown which form a nip
through which the airlaid web is fed. From the calendaring rolls 66
and 68, the airlaid web 32 is wound onto a reel 70. Similar to
calendaring rolls 54 and 56, calendaring rolls 66 and 68 are
optional, but can be provided in the system in order to alter the
properties and characteristics of the textured web.
[0056] As described above, the textured webs of the present
invention are formed on a three-dimensional fabric that imparts a
textured surface to the airlaid web. In one embodiment as described
above, the three-dimensional fabric can be the forming fabric 34 as
shown in FIG. 1. It should be understood, however, that the
three-dimensional fabric used to form the textured surface can be
contained in any other portion of the web-forming system. For
example, in an alternative embodiment, the three-dimensional fabric
can be the transfer fabric 58 shown in FIG. 2. As shown, when it is
desired to impart a textured surface into an airlaid web, the
transfer fabric 58 can be placed in association with a vacuum box
72. Vacuum box 72 provides the force sufficient to draw the airlaid
web 32 onto the three-dimensional fabric 58 and form the textured
surface. In other embodiments, a compression roller can also be
used alone or in combination with the vacuum box.
[0057] In still another alternative embodiment, the
three-dimensional fabric can be the bonding fabric 62. As shown,
the bonding fabric 62 can be placed in association with a vacuum
box 74 (and/or another compression device) for creating the
textured impressions in the web.
[0058] During the above-described process, webs can be produced
having a textured surface. Depending upon the process conditions
and the materials that are used to make the web, the web can be
formed having a textured surface only on one side or can be formed
having two textured surfaces. For example, in some embodiments, the
textured surface that is formed on one side of the airlaid web will
carry through to the opposite side of the web, depending upon the
amount of force applied to the web during formation of the textured
surface and the basis weight of the web.
[0059] In an alternative embodiment, the process of the present
invention can produce a web having a textured surface on one side
and a relatively flat and planar surface on the opposite surface.
Further, multi-layered webs can be formed with a single textured
surface. In this embodiment, a first layer can be formed with a
textured surface. After the textured surface is created, further
layers can be deposited on one side of the web to form a composite
structure having a textured side and a planar side.
[0060] In still another alternative embodiment of the present
invention, the web can be formed with a textured surface as
described above. The textured surface can be formed on the forming
fabric, a transfer fabric or a bonding fabric. Once one side of the
web has been pressed against a three dimensional fabric to form the
textured surface, the opposite side of the web can then be pressed
against a three dimensional fabric for forming a textured surface
on the opposite side of the web. The textured pattern formed into
the first side of the web and the opposite side of the web can be
the same or different depending upon the three dimensional fabrics
used to produce the web. In this embodiment, the web can have a
single layer or a multi-layer construction.
[0061] After or during formation of the textured surface, the
airlaid web 32 is bonded together. By bonding the structure
together, the structure becomes resilient to compression and fluid
collapse. As described above, the web 32 can be bonded thermally by
using an oven 64. During thermal bonding, a binder material, such
as binder fibers, contained in the non-woven web is melted. Upon
solidification, the binder material contained in the web bonds the
material together.
[0062] Alternatively, however, the bonding station 64 can be an
adhesive application station. The adhesive application station can
be used alone or in combination with thermal bonding. In this
embodiment, an adhesive is applied to the surfaces of the web for
bonding the web together. The adhesive can be applied to the web
through spraying, printing such as rotogravure printing or
flexographic printing, or by any other suitable process. The
adhesive can be, for instance, an ethylene vinyl acetate copolymer
adhesive, a starch adhesive, an acrylic adhesive, a polyvinyl
alcohol adhesive or any other suitable adhesive.
[0063] In one embodiment, the formed airlaid web 32 besides being
textured, can be contoured for a particular application. The web
can be contoured by being placed in a mold under pressure or,
alternatively, by using a scarfing apparatus as disclosed in U.S.
Pat. No. 4,626,184 which is incorporated herein by reference.
[0064] The web can include a contour for various reasons. For
example a contour can be built into the web for making the web
better suited for use with absorbent articles, such as feminine
hygiene products. In addition, making the web contoured can
facilitate absorption of fluids. For example, in one embodiment,
the web can be molded such that the outer edges of the web are
raised in comparison to the middle of the web. In this manner, a
cup-like shape is formed that better traps fluids, especially high
viscous fluids.
[0065] The basis weight of webs made according to the present
invention can vary dramatically depending upon the particular
application. For many applications, the textured airlaid web will
have a basis weight of at least 40 gsm, and particularly from 50
gsm to about 1500 gsm or higher. In one embodiment, the basis
weight of the web can be from about 50 gsm to about 700 gsm.
[0066] The overall density of the web can also vary depending upon
the materials used to form the web, the process used to form the
web, and the desired result. In general the density of the web can
be from about 0.01 grams per cubic centimeter to about 0.3 grams
per cubic centimeter.
[0067] Textured webs made according to the present invention can be
used in a limitless variety of different absorbent articles and
products. For instance, the airlaid textured webs can be
incorporated into feminine hygiene products, wipers, adult
incontinent products, diapers, and the like. Once incorporated into
an absorbent product, the textured web can serve as the outer
lining, as a surge layer, or as an absorbent layer.
[0068] These and other modifications and variations to the present
invention may be understood and realized by those of ordinary skill
in the art, without departing from the spirit and scope of the
present invention, which is more particularly set forth in the
appended claims. In addition, it should be understood that aspects
of the various embodiments may be interchanged both in whole or in
part. Furthermore, those of ordinary skill in the art will
appreciate that the foregoing description is by way of example
only, and is not intended to limit the invention so further
described in such appended claims.
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