U.S. patent application number 13/894516 was filed with the patent office on 2013-11-21 for fibrous nonwoven web with uniform, directionally-oriented projections and a process and apparatus for making the same.
This patent application is currently assigned to Kimberly-Clark Worldwide, Inc.. The applicant listed for this patent is Kimberly-Clark Worldwide, Inc.. Invention is credited to Kenneth B. Close, Michael A. Schmidt, Jillian A. Walter.
Application Number | 20130309439 13/894516 |
Document ID | / |
Family ID | 49581522 |
Filed Date | 2013-11-21 |
United States Patent
Application |
20130309439 |
Kind Code |
A1 |
Close; Kenneth B. ; et
al. |
November 21, 2013 |
Fibrous Nonwoven Web with Uniform, Directionally-Oriented
Projections and a Process and Apparatus for Making the Same
Abstract
A process and apparatus is used for making a fibrous nonwoven
web with uniform, directionally-oriented projections by depositing
fibrous material onto a first forming surface with holes positioned
above a second forming surface with both forming surfaces traveling
at different speeds to one another. As the fibers are deposited
onto the first forming surface, a portion of the fibers are drawn
down into the holes of the first forming surface forming the
projections which contact the second forming surface. Due to the
speed differential between the two forming surfaces the projections
are uniformly skewed in the same direction. The resultant material
is particularly suited for use as a wiping material which can be
more abrasive in one direction but which is softer to the touch
when wiped in the opposite direction thus making it a dual purpose
material.
Inventors: |
Close; Kenneth B.; (New
London, WI) ; Schmidt; Michael A.; (Alpharetta,
GA) ; Walter; Jillian A.; (Atlanta, GA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kimberly-Clark Worldwide, Inc. |
Neenah |
WI |
US |
|
|
Assignee: |
Kimberly-Clark Worldwide,
Inc.
Neenah
WI
|
Family ID: |
49581522 |
Appl. No.: |
13/894516 |
Filed: |
May 15, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61649742 |
May 21, 2012 |
|
|
|
Current U.S.
Class: |
428/91 ; 264/103;
425/505 |
Current CPC
Class: |
A61F 13/535 20130101;
D04H 1/74 20130101; A61F 2013/530233 20130101; D04H 1/565 20130101;
B29L 2031/726 20130101; D04H 1/56 20130101; A61F 2013/530437
20130101; Y10T 428/2395 20150401; D04H 11/08 20130101 |
Class at
Publication: |
428/91 ; 264/103;
425/505 |
International
Class: |
D04H 1/74 20060101
D04H001/74; D04H 11/08 20060101 D04H011/08 |
Claims
1. A process for forming a fibrous nonwoven web with uniform,
directionally-oriented projections comprising: providing a first
forming surface defining a plurality of openings therein; providing
a second forming surface which is pervious to air; overlaying said
first forming surface atop said second forming surface; causing
said first forming surface to travel in a first direction at a
first speed; causing said second forming surface to travel in said
first direction at a second speed to cause a speed differential
between said first forming surface and said second forming surface;
depositing a plurality of fibers onto said first forming surface to
form a fibrous nonwoven web; causing a portion of said plurality of
fibers to extend through said openings in said first forming
surface and contact said second forming surface to form a plurality
of fibrous projections in said fibrous nonwoven web; said speed
differential causing said projections to have a uniform,
directional orientation relative to said first direction of travel
of said first forming surface; and removing said fibrous nonwoven
web with said uniform, directionally-oriented projections from said
first forming surface.
2. The process of claim 1 which further includes providing a vacuum
source beneath said second forming surface on a side of said second
forming surface opposite said first forming surface to aid in a
movement of said fibers through said openings in said first forming
surface and contact said second forming surface.
3. The process of claim 1 which further includes causing said first
and second forming surfaces to travel at a distance differential
"y" as defined herein of between about 51 millimeters (2 inches)
and about 152 millimeters (6 inches).
4. The process of claim 2 which further includes driving one of
said first and second forming surfaces by frictional engagement
with the other of said first and second forming surfaces.
5. The process of claim 2 which further includes driving said first
forming surface in said first direction independently of said
second forming surface.
6. An apparatus for forming a fibrous nonwoven web with uniform,
directionally-oriented projections comprising: a first forming
surface defining a plurality of openings therein, said first
forming surface being capable of moving in a first direction at a
first speed; a second forming surface which is pervious to air
capable of moving in a first direction at a second speed, said
second forming surface being positioned below said first forming
surface, said second speed being different than said first speed; a
fiber deposition apparatus positioned above and distanced from a
surface of said first forming surface opposite said second forming
surface; and a vacuum assist apparatus positioned below said second
forming surface on a side of said second forming surface opposite
said first forming surface.
7. The apparatus of claim 6 wherein said fiber deposition apparatus
is a coform apparatus.
8. The apparatus of claim 6 wherein said first forming surface and
said second forming surface are frictionally engaged with one
another and one of said first and second forming surfaces is driven
by the other of said first and second forming surfaces due to said
frictional engagement between said first and second forming
surfaces.
9. The apparatus of claim 6 wherein said first and second forming
surfaces are driven in said first direction separately from one
another.
10. The apparatus of claim 6 wherein said first forming surface
comprises a flexible belt defining a plurality of holes therein and
extending there through which are spaced apart by a land area in
said belt, said land area being impervious to air emanating from
said fiber deposition apparatus.
11. A fibrous nonwoven web having a top surface, an opposed bottom
surface, a length, a width and a thickness, a plurality of uniform,
directionally-oriented projections emanating from said top surface
of said web.
12. The fibrous nonwoven web of claim 11 wherein said web has a
knap on said top surface due to said projections such that it is
smoother to the touch when engaged in one direction as opposed to
the opposite direction.
13. The fibrous nonwoven web of claim 11 wherein said projections
each have a base portion with a vertical axis generally
perpendicular to a plane formed by said top surface of said web and
a head portion connected to said base portion, said vertical axis
being located at a position in said base portion such that said
base portion has a lateral dimension that is equally spaced on
either side of said vertical axis, said head portion of said
projection being asymmetrically located relative to said base
portion and said vertical axis such that said head portion has a
lateral dimension which is skewed with respect to said vertical
axis so that more of said head portion is located on one side of
said vertical axis than said base portion when viewing said head
portion and said base portion from the same position.
14. The fibrous nonwoven web of claim 13 wherein said head portion
forms an overhang area with respect to said base portion.
15. A wipe comprising the fibrous nonwoven web of claim 11.
16. A personal care absorbent article comprising the fibrous
nonwoven web of claim 11.
17. A personal care absorbent article comprising a body side liner
and a garment-facing sheet with an absorbent core disposed between
said body side liner and said garment facing sheet wherein said
body side liner comprises the fibrous nonwoven web of claim 11.
18. The personal care absorbent article of claim 17 wherein said
article is selected from the group consisting of a diaper, a
sanitary napkin, a child training pant and an adult incontinence
device.
Description
[0001] This application claims the benefit of priority from U.S.
Provisional Application No. 61/649,742 filed on May 21, 2012.
BACKGROUND OF THE INVENTION
[0002] The present invention is directed to fibrous nonwoven webs
with uniform, directionally-oriented projections located on at
least one surface of the formed material as well as the process and
apparatus for making such a material.
[0003] Disposable products are an ever increasing portion of the
consumer market, especially in the context of personal products
such as cleaning products for the face and body. The same is true
for products used for household cleaning and other cleaning
applications. A commonly desired attribute for all such products is
the cleaning ability of the product and its ability to absorb and
retain fluids. Today there are many wiping products that are
available in either a dry or wet state. A large number of such
products are relatively flat, two-dimensional products with little
variability in the topography of the material. Other materials are
textured due to embossing of the wiping material. Still other
materials are tufted. See, for example, U.S. Patent Application No.
2003/0211802 to Keck et al. assigned to Kimberly-Clark Worldwide,
Inc. which discloses three-dimensional coform nonwoven coform webs
which have projections which increase the bulk of the nonwoven web
and aid in the scrubbing and cleaning ability of the coform web.
See also U.S. Pat. No. 5,180,620 to Mende assigned to Mitsui
Petrochemical Industries, Ltd. which discloses a nonwoven fabric
comprised of meltblown fibers with projections extending from the
fabric base. Still a further example is U.S. Patent Application No.
2007/0130713 to Chen et al. and assigned to Kimberly-Clark
Worldwide, Inc. which discloses a cleaning wipe with a textured
surface which may be used as a stand-alone product or can be
incorporated into a cleaning tool. The wipe includes a base
material having an application face and a plurality of projections
extending generally transversely from the application face. The
projections may have various shapes, including a mushroom shape. A
high friction element can be applied to at least a portion of the
projections to provide enhanced abrasive scrubbing functionality.
With the mushroom-shaped embodiment the projections have a
cross-sectional shape such that the head portion extends laterally
beyond and overhangs the base portion. The voids or spaces between
the projections are said to be particularly well suited for
trapping hair and other difficult to retain materials from the
surface being cleaned. The tapered voids (tapered from the head
portion of the projections towards the land areas) allow for hair
and other relatively larger particulate matter to become
essentially "wedged" into the void spaces, with the tapered profile
of the projections serving to "lock" the particulate matter within
the voids. Yet another example of a material with a
three-dimensional shape is disclosed in U.S. Patent Application No.
2002/0132544 to Takagaki assigned to Toyoda Boshoku Corporation
which spins semi-molten fibers onto a mold. U.S. Pat. No. 6,610,173
to Lindsay et al. assigned to Kimberly-Clark Worldwide, Inc.
discloses a method for imprinting a paper web during a wet pressing
event with asymmetrical protrusions corresponding to the deflection
conduits of a deflection member. In certain embodiments, if
substantial shear is applied to the deflection members by way of
differential velocity transfer, a snowplow effect can be produced
in which the moist fibers are sheared and piled up toward one side
of the protrusion.
[0004] Despite the foregoing examples of products and processes for
creating such textured materials, there is still a need for
materials that are textured and easy to produce. The present
invention is directed to a material which has protrusions which are
directionally-oriented in one direction in a uniform manner. In so
doing, the projections can act to provide more friction when wiped
across a surface in one direction than in another. As a result, the
material will have a somewhat rougher feel when wiped in one
direction and a smoother feel in the opposite direction. Also
disclosed is a process and apparatus for making such a
material.
DEFINITIONS
[0005] As used herein, the term "meltblown fibers" means fibers
formed by extruding a molten thermoplastic material through a
plurality of fine, usually circular, die capillaries as molten
threads or filaments into converging high velocity, usually hot,
gas (e.g. air) streams which attenuate the filaments of molten
thermoplastic material to reduce their diameter, which may be to
microfiber diameter. Thereafter, the meltblown fibers are carried
by the high velocity gas stream and are deposited on a collecting
surface to form a web of randomly dispersed meltblown fibers. Such
a process is disclosed, for example, in U.S. Pat. No. 3,849,241 to
Butin, which is hereby incorporated by reference in its entirety.
Meltblown fibers are microfibers, which may be continuous or
discontinuous, and are generally smaller than 10 microns in average
diameter. The term "meltblown" is also intended to cover other
processes in which a high velocity gas (generally air) is used to
aid in the formation of the filaments, such as melt spraying or
centrifugal spinning.
[0006] As used herein, the term "coform nonwoven web" or "coform
material" means composite materials comprising a mixture or
stabilized matrix of thermoplastic filaments and at least one
additional material, usually called the "second material" or the
"secondary material". As an example, coform materials may be made
by a process in which at least one meltblown die head is arranged
near a chute through which the second material is added to the web
while it is forming. The second material may be, for example, an
absorbent material such as fibrous organic materials such as woody
and non-wood pulp such as cotton, rayon, recycled paper, pulp
fluff; superabsorbent materials such as superabsorbent particles
and fibers; inorganic absorbent materials and treated polymeric
staple fibers and the like; or a non-absorbent material, such as
non-absorbent staple fibers or non-absorbent particles. Exemplary
coform materials are disclosed in commonly assigned U.S. Pat. No.
5,350,624 to Georger et al.; U.S. Pat. No. 4,100,324 to Anderson et
al.; and U.S. Pat. No. 4,818,464 to Lau et al.; the entire contents
of each is hereby incorporated by reference in their entirety for
all purposes.
[0007] As used herein the term "spunbond fibers" refers to small
diameter fibers of molecularly oriented polymeric material.
Spunbond fibers may be formed by extruding molten thermoplastic
material as filaments from a plurality of fine, usually circular
capillaries of a spinneret with the diameter of the extruded
filaments then being rapidly reduced as in, for example, U.S. Pat.
No. 4,340,563 to Appel et al., and U.S. Pat. No. 3,692,618 to
Dorschner et al., U.S. Pat. No. 3,802,817 to Matsuki et al., U.S.
Pat. Nos. 3,338,992 and 3,341,394 to Kinney, U.S. Pat. No.
3,502,763 to Hartman, U.S. Pat. No. 3,542,615 to Dobo et al, and
U.S. Pat. No. 5,382,400 to Pike et al. which are incorporated by
reference in their entirety for all purposes. Spunbond fibers are
generally not tacky when they are deposited onto a collecting
surface and are generally continuous. Spunbond fibers are often
about 10 microns or greater in diameter. However, fine fiber
spunbond webs (having and average fiber diameter less than about 10
microns) may be achieved by various methods including, but not
limited to, those described in commonly assigned U.S. Pat. No.
6,200,669 to Mormon et al. and U.S. Pat. No. 5,759,926 to Pike et
al.
SUMMARY OF THE INVENTION
[0008] The present invention is directed to a process for forming a
fibrous nonwoven web with uniform, directionally-oriented
projections. The process involves providing a first forming surface
defining a plurality of openings therein and providing a second
forming surface which is pervious to air. The first forming surface
is overlaid atop the second forming surface and the first forming
surface is caused to travel in a first direction at a first speed
and the second forming surface is caused to travel in the first
direction at a second speed to cause a speed differential between
the first forming surface and the second forming surface. A
plurality of fibers are deposited onto the first forming surface to
form a fibrous nonwoven web while causing a portion of the
plurality of fibers to extend through the openings in the first
forming surface and then contact the second forming surface to form
a plurality of fibrous projections in the fibrous nonwoven web. The
speed differential between the first and second forming surfaces
causes the projections to have a uniform, directional orientation
relative to the first direction of travel of the first forming
surface and once the projections are formed and oriented the
fibrous nonwoven web with the uniform, directionally-oriented
projections is removed from the first forming surface. If desired,
the process can be modified by providing a vacuum source beneath
the second forming surface on a side of the second forming surface
opposite the first forming surface to aid in a movement of the
fibers through the openings in the first forming surface and
contact the second forming surface.
[0009] As a result of the speed differential between the first and
second forming surfaces, one of the first and second forming
surfaces can be caused to travel a differential distance "y" as
defined herein which is between about two and about six inches
(about 5.1 and about 15.2 centimeters) further than the other of
the first and second forming surfaces travels over the same amount
of time in a prescribed distance "D1" from when the material
forming the fibrous nonwoven web is laid down onto the first
forming surface at a first location and a second location when the
heads of the formed projections are no longer in contact with the
second forming surface. It is this difference in distance traveled
due to the speed differential of the first and second forming
surfaces between the first and second locations that causes the
uniform, directional orientation of the projections of the
so-formed fibrous nonwoven web.
[0010] To create the speed differential between the two forming
surfaces, the process can involve driving one of the first and
second forming surfaces by frictional engagement with the other of
the first and second forming surfaces. Alternatively, the process
can involve driving the first forming surface in the first
direction independently of the second forming surface by having
each of the forming surfaces driven by their own separate drive
devices.
[0011] An apparatus for forming a fibrous nonwoven web with
uniform, directionally-oriented projections can include a first
forming surface defining a plurality of openings therein with the
first forming surface being capable of moving in a first direction
at a first speed along with a second forming surface which is
pervious to air and capable of moving in a first direction at a
second speed with the second forming surface being positioned below
the first forming surface and the second speed being different than
the first speed. The apparatus includes a fiber deposition
apparatus positioned above and distanced from a surface of the
first forming surface opposite the second forming surface and a
vacuum assist apparatus positioned below the second forming surface
on a side of the second forming surface opposite the first forming
surface. In certain applications, a coform apparatus can be used as
the fiber deposition apparatus.
[0012] In one embodiment of the apparatus the first forming surface
and the second forming surface can be frictionally engaged with one
another with one of the first and second forming surfaces being
driven by the other of the first and second forming surfaces due to
the frictional engagement between the first and second forming
surfaces. In an alternate embodiment of the apparatus, the first
and second forming surfaces can be driven in the first direction
separately from one another by separate drive devices.
[0013] The first forming surface if desired can comprise a flexible
belt defining a plurality of holes therein and extending there
through which are spaced apart by a land area in the belt with it
being preferable that the land area is impervious to air emanating
from the fiber deposition apparatus.
[0014] Also disclosed herein is a fibrous nonwoven web having a top
surface, an opposed bottom surface, a length, a width and a
thickness with a plurality of uniform, directionally-oriented
projections emanating from the top surface of the web. The fibrous
nonwoven web, because of the uniform directional orientation of the
projections, has a knap on the top surface of the web which is
smoother to the touch when engaged in one direction as opposed to
the opposite direction. The projections each have a base portion
with a vertical axis generally perpendicular to a plane formed by
the top surface of the web and a head portion connected to the base
portion. This vertical axis is located at a position in the base
portion such that at least a portion of the base portion has a
lateral dimension that is equally spaced on either side of the
vertical axis. The head portion of the projection is asymmetrically
located relative to the base portion and the vertical axis such
that the head portion has a lateral dimension which is skewed with
respect to the vertical axis so that more of the head portion is
located on one side of said vertical axis than the base portion
when viewing the head portion and the base portion from the same
position. In addition, the head portion can form an overhang area
with respect to said base portion.
[0015] The fibrous nonwoven web disclosed herein can be used in a
wide variety of products including a wipe and other cleaning
products. It can also be used as a personal care absorbent article
wherein as least a portion of the article comprises the disclosed
fibrous nonwoven web. Such personal care absorbent articles
typically comprise a body side liner and a garment-facing sheet
with an absorbent core disposed between the body side liner and the
garment facing sheet. In such products it is desirable that the
body side liner comprise the fibrous nonwoven web disclosed herein.
Such personal care absorbent articles can be selected from the
group consisting of a diaper, a sanitary napkin, a child training
pant and an adult incontinence device.
BRIEF DESCRIPTION OF THE FIGURES
[0016] A full and enabling disclosure of the present invention,
including the best mode thereof to one skilled in the art, is set
forth more particularly in the remainder of the specification,
which includes reference to the accompanying figures, in which:
[0017] FIG. 1 is a perspective view of one embodiment of a fibrous
nonwoven web with uniform, directionally-oriented projections
according to the present invention.
[0018] FIG. 2 is a cross-section of the material shown in FIG. 1
taken along line 2-2 of FIG. 1 showing a single oriented projection
according to the present invention.
[0019] FIG. 3 is a schematic side view of a process and apparatus
according to the present invention for forming a fibrous nonwoven
web with uniform, directionally-oriented projections according to
the present invention.
[0020] FIG. 4 is a perspective view of a representative portion of
a first forming surface of an apparatus according to the present
invention.
[0021] FIG. 5 is a photo of a cross-sectional view of the material
according to the present invention described in Example 1.
[0022] FIG. 6 is a photo of a cross-sectional view of the material
according to the present invention described in Example 2.
[0023] FIG. 7 is a photo of a cross-sectional view of the material
described in Comparative Example 1.
[0024] FIG. 8 is a cutaway top plan view of a personal care
absorbent article, in this case a diaper, which can employ the
fibrous nonwoven web with uniform, directionally-oriented
projections according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Product Description
[0025] Reference now will be made to the embodiments of the
invention, one or more examples of which are set forth below. Each
example is provided by way of an explanation of the invention, not
as a limitation of the invention. In fact, it will be apparent to
those skilled in the art that various modifications and variations
can be made in the invention without departing from the scope or
spirit of the invention. For instance, features illustrated or
described as one embodiment can be used on another embodiment to
yield still a further embodiment. Thus, it is intended that the
present invention cover such modifications and variations as come
within the scope of the appended claims and their equivalents. When
ranges for parameters are given, it is intended that each of the
endpoints of the range are also included within the given range. 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 as limiting the broader aspects of the present
invention, which broader aspects are embodied exemplary
constructions.
[0026] Turning to FIGS. 1 and 2 there is shown a fibrous nonwoven
web 10 with uniform, directionally-oriented projections according
to the present invention. The web 10 has a top surface 12 an
opposed bottom surface 14, a length 16, a width 18 and a thickness
20.
[0027] Emanating from the top surface 12 is a plurality of
projections 30 which are uniformly oriented in the same direction
and separated by land area 31. The projections 30 have a base
portion 36 which defines a vertical axis 38 which is generally
perpendicular to a plane 40 defined by the top surface 12 of the
web 10. The projections 30 have a head portion 50 connected to the
based portion 36. The projections 30 have an overall height 35 as
measured from the top surface 12 of the web 10 to the top of the
head portion 50 of the projection 30. This distance 35 can be
divided by a line 37 which is generally parallel to the top surface
12 and the plane 40. The portion of the projection 30 above this
line 37 is considered the head portion 50 and the portion of the
projection 30 below this line 37 is considered the base portion 36.
Generally, this line 37 will be drawn at a point that is below the
main overhanging portion of the head portion 50 and thus below the
point where the line 62 contacts the head 50. See FIG. 2.
[0028] The vertical axis 38 is located at a position in the base
portion 36 such that the base portion 36 has a lateral dimension 52
that is equally spaced on either side of the vertical axis 38 when
the projection is viewed from a side such as is shown in FIG. 2. By
"equally spaced" it is meant that the vertical axis 38 can be
positioned such that the lateral dimension 52 (which is determined
below the line 37) can be divided into a left portion 52a and a
right portion 52b and the dimensions of these two portions (52a and
52b) are within plus or minus 10 percent of one another.
[0029] In contrast, the head portion 50 of the projection 30 has a
lateral dimension 54 which is located above the line 37 and which
has a left portion 54a and a right portion 54b relative to the
vertical axis 38. As can be seen from FIG. 2, the head portion 50
is asymmetrically located with respect to the vertical axis 38 and
the base portion 36 such that the head portion 50 is skewed with
respect to the vertical axis 38 with more of the lateral dimension
54 being located on one side (in this case 54a) of the vertical
axis 38 than the other side (in this case 54b) when viewing the
lateral dimensions 52 and 54 from the same position.
[0030] As a result of this vertical skewing of the projections 36,
there is created an overhang area 60 such as is shown in FIG. 2.
This overhang area 60 can be seen when viewing the projections 36
from the side. In FIG. 2, the overhang area 60 is defined by
drawing a vertical line 62 which is tangent to a portion of the
head portion 50 (the overhanging edge 64), which does not intersect
a portion of the head portion 50, and which is also generally
parallel to the vertical axis 38. The overhand area 60 is bounded
by the line 62, the side 63 of the projection 30 and if need be the
top surface 12 of the web 10.
[0031] Due to the nature of the equipment and process by which the
web 10 is made, the overhang areas 60 will be created in a
direction which is generally parallel to the machine direction (MD)
in which the web 10 is made in the process and apparatus such as is
shown in FIG. 3 of the drawings. As explained in more detail below,
depending on the relative speed of the two forming surfaces used to
form the projections 30, the overhang areas 60 and the skewing of
the head portions 50 will be parallel to the machine direction
movement 148 and formation of the web 10. If the first forming
surface 140 of the apparatus 130 is moving faster that the second
forming surface 150, the overhanging edge 64 will point in the
opposite direction of the machine direction 148 of the apparatus
130 in FIG. 3. Conversely, if the first forming surface 140 of the
apparatus 130 is moving slower that the second forming surface 150,
the overhanging edge 64 will point in the same direction as the
machine direction 148 of the apparatus 130 in FIG. 3. Thus, when it
is said that the direction of the orientation of the projections 30
is "uniform" it is meant that in a measured area of the top surface
12 of the web 10, at least 70 percent of the projections 30 are
slanted to the same side of the vertical axis 38.
[0032] The web 10 can be made from a variety of materials including
meltblown materials, coform materials, air-laid materials,
bonded-carded web materials, hydroentangled materials, spunbond
materials and the like, and can comprise synthetic or natural
fibers. A preferred material is a coform web.
[0033] The fibrous nonwoven web 10 may be used as a wet wipe, and
in particular baby wipes. Different physical characteristics of the
fibrous nonwoven web may be varied to provide the best quality wet
wipe. For example, formation, diameter of meltblown fibers, the
amount of lint, opacity and other physical characteristics of the
fibrous nonwoven web may be altered to provide a useful wet wipe
for consumers.
[0034] Typically, the fibrous nonwoven web 10 is a combination of
meltblown fibrous materials and secondary fibrous materials. The
relative percentages of the meltblown fibrous materials and
secondary fibrous materials in the web can vary over a wide range
depending on the desired characteristics of the fibrous nonwoven
web. For example, fibrous nonwoven webs can have from about 20 to
about 60 weight percent (wt. %) of meltblown fibrous materials and
from about 40 to 80 wt. % of secondary fibers. Desirably, the
weight ratio of meltblown fibrous materials to secondary fibers can
be from about 20/80 to about 60/40. More desirably, the weight
ratio of meltblown fibrous materials fibers to secondary fibers can
be from about 25/75 to about 40/60.
[0035] Generally speaking, the overall basis weight of the fibrous
nonwoven web 10 is from about 10 grams per square meter (gsm) to
about 500 gsm, and more particularly from about 17 gsm to about 200
gsm, and still more particularly from about 25 gsm to about 150
gsm. The basis weight of the fibrous nonwoven web may also vary
depending upon the desired end use. For example, a suitable fibrous
nonwoven web for wiping the skin may define a basis weight of from
about 30 to about 80 gsm and desirably about 45 to about 75 gsm.
The basis weight (in grams per square meter, g/m2 or gsm) is
calculated by dividing the dry weight (in grams) by the area (in
square meters).
[0036] One approach in making the fibrous nonwoven web 10 is to mix
meltblown fibrous materials with one or more types of secondary
fibrous materials and/or particulates. The mixture is collected in
the form of fibrous nonwoven web which may be bonded or treated to
provide a coherent nonwoven material that can take advantage of at
least some of the properties of each component. These mixtures are
referred to as "coform" materials because they are formed by
combining two or more materials in the forming step into a single
structure.
[0037] Meltblown fibrous materials suitable for use in the fibrous
nonwoven web include polyolefins, for example, polyethylene,
polypropylene, polybutylene and the like, polyamides, olefin
copolymers and polyesters. In accordance with a particularly
desirable embodiment, the meltblown fibrous materials used in the
formation of the fibrous nonwoven web are polypropylene. See for
example WO 2011/034523 for additional information on suitable
polymers for the meltblown fibers which is incorporated herein for
all purposes in its entirety.
[0038] The fibrous nonwoven web also includes one or more types of
secondary fibrous materials to form the nonwoven web. Any secondary
fibrous material may generally be employed in the coform nonwoven
structure, such as absorbent fibers, particles, etc. In one
embodiment, the secondary fibrous material includes fibers formed
by a variety of pulping processes, such as kraft pulp, sulfite
pulp, thermomechanical pulp, etc. The pulp fibers may include
softwood fibers having an average fiber length of greater than 1
millimeter (mm) and particularly from about 2 to about 5 mm based
on a length-weighted average. Such softwood fibers can include, but
are not limited to, northern softwood, southern softwood, redwood,
red cedar, hemlock, pine (e.g., southern pines), spruce (e.g.,
black spruce), combinations thereof, and so forth. Exemplary
commercially available pulp fibers suitable include those available
from Weyerhaeuser Co. of Federal Way, Wash. under the designation
"Weyco CF-405." Hardwood fibers, such as eucalyptus, maple, birch,
aspen, and so forth, can also be used. In certain instances,
eucalyptus fibers may be particularly desired to increase the
softness of the web. Eucalyptus fibers can also enhance the
brightness, increase the opacity, and change the pore structure of
the web to increase its wicking ability. Moreover, if desired,
secondary fibers obtained from recycled materials may be used, such
as fiber pulp from sources such as, for example, newsprint,
reclaimed paperboard, and office waste. Further, other natural
fibers can also be used, such as abaca, sabai grass, milkweed
floss, pineapple leaf, and so forth. In addition, in some
instances, synthetic fibers can also be utilized. Wood pulp fibers
are particularly preferred as a secondary fibrous material because
of low cost, high absorbency and retention of satisfactory tactile
properties.
[0039] Besides or in conjunction with pulp fibers, the secondary
fibrous material may also include a superabsorbent that is in the
form of fibers, particles, gels, etc. Generally speaking,
superabsorbents are water-swellable materials capable of absorbing
at least about 20 times its weight and, in some cases, at least
about 30 times its weight in an aqueous solution containing 0.9 wt.
% sodium chloride. The superabsorbent may be formed from natural,
synthetic and modified natural polymers and materials. Examples of
synthetic superabsorbent polymers include the alkali metal and
ammonium salts of poly(acrylic acid) and poly(methacrylic acid),
poly(acrylamides), poly(vinyl ethers), maleic anhydride copolymers
with vinyl ethers and alpha-olefins, poly(vinyl pyrrolidone),
poly(vinylmorpholinone), poly(vinyl alcohol), and mixtures and
copolymers thereof. Further, superabsorbents include natural and
modified natural polymers, such as hydrolyzed acrylonitrile-grafted
starch, acrylic acid grafted starch, methyl cellulose, chitosan,
carboxymethyl cellulose, hydroxypropyl cellulose, and the natural
gums, such as alginates, xanthan gum, locust bean gum and so forth.
Mixtures of natural and wholly or partially synthetic
superabsorbent polymers may also be useful. Particularly suitable
superabsorbent polymers are HYSORB 8800AD (BASF of Charlotte, N.C.
and FAVOR SXM 9300 (available from Evonik Stockhausen of
Greensboro, N.C.).
[0040] The secondary fibrous materials are interconnected by and
held captive within the microfibers by mechanical entanglement of
the microfibers with the secondary fibrous materials, the
mechanical entanglement and interconnection of the microfibers and
secondary fibrous materials forming a coherent integrated fiber
structure. The coherent integrated fiber structure may be formed by
the microfibers and secondary fibrous materials without any
adhesive, molecular or hydrogen bonds between the two different
types of fibers. The material is formed by initially forming a
primary air stream containing the meltblown microfibers, forming a
secondary air stream containing the secondary fibrous materials,
merging the primary and secondary streams under turbulent
conditions to form an integrated air stream containing a thorough
mixture of the microfibers and secondary fibrous materials, and
then directing the integrated air stream onto a forming surface to
air form the fabric-like material. The microfibers are in a soft
nascent condition at an elevated temperature when they are
turbulently mixed with the pulp fibers in air.
[0041] In certain embodiments the web 10 may be used as a "wet" or
"premoistened" wipe in that it contains a liquid solution for
cleaning, disinfecting, sanitizing, etc. The particular liquid
solutions are not critical and are described in more detail in U.S.
Pat. Nos. 6,440,437 to Krzysik et al.; 6,028,018 to Amundson et
al.; 5,888,524 to Cole; 5,667,635 to Win et al.; and 5,540,332 to
Kopacz et al., which are incorporated herein in their entirety by
reference thereto for all purposes. The amount of the liquid
solution employed may depend upon the type of wipe material
utilized, the type of container used to store the wipes, the nature
of the cleaning formulation, and the desired end use of the wipes.
Generally, each wipe contains from about 150 to about 600 wt. % and
desirably from about 300 to about 500 wt. % of a liquid solution
based on the dry weight of the nonwoven structure.
Process and Apparatus Description
[0042] Turning to FIG. 3 of the drawings there is shown a process
and apparatus 130 for forming a fibrous nonwoven web 10 with
directionally oriented projections 30 according to the present
invention. The apparatus 130 includes a first forming surface 140
and a second forming surface 150. The first forming surface 140 is
positioned above or atop the second forming surface 150 in the area
where web formation takes place. In FIG. 3, the first forming
surface 140 is a flexible mat or belt with a plurality of apertures
or holes 142 defined therein as also shown in the partial view of
the first forming surface 140 shown in FIG. 4. While the land areas
144 of the surface 140 can be air permeable or impermeable, it is
desirable that the land areas 144 not be permeable to air to
increase the suction effect through the holes 142 caused by the
vacuum assist 160 positioned below the first and second forming
surfaces (140 and 150).
[0043] Rubberized mats or endless belts have been found to work
particularly well as the first forming surface 140. Such mats are
available from F.N. Sheppard and Company of Erlanger, Ky. They are
vulcanized endless belts treated with release coatings. The belt
material must be chosen to be heat resistant and compatible with
the polymers being used. For polyolefin fibers, urethane coatings
work well. Belt thicknesses typically range between about 1.6 and
about 5.9 millimeters (mm). The holes in the belt used for the
below examples had a staggered pattern of circular holes having a
0.25 inch (6.35 mm) diameter with a center-to-center spacing
between holes in each row of 0.38 inches (9.65 mm). Staggered
length between rows was 0.19 inches (4.83 mm) as measured from
edge-to-edge. To facilitate processing, the belt had an
unperforated border on its side edges of approximately 2.63 inches
(66.8 mm). While the holes used for the below examples were
circular, other shapes can also be used. It should be appreciated
that the foregoing description is of one particular embodiment of a
forming surface 140. Other materials and dimensions can be used
depending upon the particular parameters desired in the web
material 10 and projections 30. For example, if projections 30 with
greater overall heights 35 are desired, thicker belt materials may
be used. In addition, the spacing of the holes 142 and the shape of
the holes 142 may be varied depending on the end needs of the web
10.
[0044] The first forming surface 140 is driven by a conventional
drive assembly which for sake of simplicity is shown by one or more
drive rolls 146 in FIG. 3. The drive rolls 146 cause the first
forming surface 140 to travel in a first direction 148 shown by
arrow 148 in FIG. 3 at a first speed. Such drive systems are well
known to those of ordinary skill in the art.
[0045] The second forming surface 150 is positioned below the first
forming surface 140 and is air permeable so as to enable the vacuum
assist apparatus 160 to draw the fibers of the fibrous nonwoven web
10 down into the holes 142 and at least partially contact the top
surface 152 of the second forming surface 150. It is desirable that
the second forming surface 150 be driven by its own drive assembly
which for sake of simplicity is shown by one or more drive rolls
156. The drive roll or rolls 156 causes the second forming surface
to travel in the same first direction 148 but at a second speed
which causes a speed differential to be created between the first
forming surface 140 and the second forming surface 150. Again, such
drive systems are well known to those of ordinary skill in the
art.
[0046] Typically the second forming surface 150 is a woven wire
mesh structure such as is available from Albany International
Company of Rochester, N.H. The spacing of the wires in the wire
mesh can be varied but the wire mesh must be sufficiently open so
as to allow a sufficient vacuum to be pulled by the vacuum assist
apparatus 160. Exemplary of these wire weave geometry forming
surfaces is the forming wire FORMTECH.TM. 6 manufactured by Albany
International Co. of Rochester, N.H. Such a wire has a "mesh count"
of about six strands by six strands per square inch (about 2.4 by
2.4 strands per square centimeter) resulting in about 36 foramina
or "holes" per square inch (about 5.6 per square centimeter). The
FORMTECH.TM. 6 wire is made from polyester and has a warp diameter
of about 1 millimeter, a shute diameter of about 1.07 millimeters,
a nominal air permeability of approximately 41.8 m3/min (1475
ft3/min), a nominal caliper of about 0.2 centimeters (0.08 inch)
and an open area of approximately 51%. Another exemplary forming
surface available from the Albany International Co. is the forming
wire FORMTECH.TM. 10, which has a mesh count of about 10 strands by
10 strands per square inch (about 4 by 4 strands per square
centimeter) resulting in about 100 foramina or "holes" per square
inch (about 15.5 per square centimeter). Still another suitable
forming wire is FORMTECH.TM. 8, which has an open area of 47% and
is also available from Albany International Co. Of course, other
forming wires and surfaces (e.g., drums, plates, etc.) may be
employed. Also, surface variations may include, but are not limited
to, alternate weave patterns, alternate strand dimensions, release
coatings (e.g., silicones, fluorochemicals, etc.), static
dissipation treatments, and the like. Still other suitable
foraminous surfaces that may be employed are described in U.S.
Patent Application Publication No. 2007/0049153 to Dunbar et al.
which is incorporated herein by reference thereto for all
purposes.
[0047] As stated previously, the fibrous nonwoven web 10 can be
formed from any number of fibrous structures such as coform
materials, carded staple fibers, meltblown webs, spunbond webs and
other fibrous web forming processes. The key aspect is that the
fibers on the top surface 147 of the first forming surface 140 are
capable of being drawn down into the holes 142 such that they come
in contact with the top surface 152 of the second forming surface
150 so that the speed differential between the two forming surfaces
can cause the projections 30 to skew and take on a uniform
directional orientation relative to the first direction of movement
148 of the first forming surface 140.
[0048] In FIG. 3, the fibrous nonwoven web 10 is formed from a
coform material which is a mixture of meltblown fibers and wood
pulp fibers. The forming apparatus 170, which in this case is a
coform apparatus 170, includes a central source 172 of pulp fibers
and two meltblown dies 174 which together create meltblown fibers
which mix with the pulp fibers to form a coform mix 176 which is
deposited down onto the top surface 147 of the first forming
surface 140. As the first forming surface 140 moves in the first
direction 148 at its first speed, the coform mix 176 encounters the
vacuum 160 which, along with the force of deposition, causes a
portion of the coform fiber mix 176 to be drawn down into the
apertures 142 in the first forming surface 140 to form the
projections 30. Due to the fact that the first forming surface 140
is positioned atop of the second forming surface 150, the fibers of
the projections 30 coming through the apertures 142 in the first
forming surface 140 contact the top surface 152 of the second
forming surface 150 but are prevented from being drawn down into
the vacuum 160. It should be noted that other configurations of
meltblown and secondary fiber feeds also may be used as well as
multiple banks of coform or other fibrous structures, especially
when higher line speeds or higher basis weights are being used.
Some examples of such coform techniques are disclosed in U.S. Pat.
Nos. 4,100,324 to Anderson et al.; 5,350,624 to Georger et al.; and
5,508,102 to Georger et al., as well as U.S. Patent Application
Publication Nos. 2003/0200991 to Keck et al. and 2007/0049153 to
Dunbar et al., all of which are incorporated herein in their
entirety by reference thereto for all purposes.
[0049] As a result of the speed differential between the two
forming surfaces (140 and 150) and the frictional engagement of the
fibers of the projections 30 in contact with the second forming
surface 150, the symmetrically-formed projections 30 begin to
uniformly skew in the same direction. In the embodiment of FIG. 3,
the first speed of the first forming surface 140 is slower than the
second speed of the second forming surface 150. Consequently, the
head portions 50 of the projections 30 are skewed forward to form
leading hooks 33 as are shown schematically on the left side of the
process in FIG. 3 as the resultant fibrous nonwoven web 10 is wound
up on take-up roll 180. Alternatively, if the speed differential is
such that the second speed of the second forming surface 150 is
slower than that of the first speed of the first forming surface
140, the projections 30 in the fibrous web 10 will skew in the
opposite direction (that is, opposite of the direction of arrow 148
in FIG. 3) as the web 10 is wound up on take-up roll 180. In either
speed configuration, the degree of directional bending of the
projections 30 can be controlled in part by way of the speed
differential between the two forming surfaces (140 and 150).
[0050] In the embodiment of the process and apparatus shown in FIG.
3 of the drawings, the first forming surface 140 and the second
forming surface 150 are each driven independently of one another so
the separate drive systems can be separately controlled to vary the
speed differential and thus the amount of skewing or orienting of
the projections 30 in the web 10. An alternate embodiment, not
shown, is to drive one of the two forming surfaces and not the
other (140 or 150) and allow the two forming surfaces to contact
one another such that the frictional engagement of the two forming
surfaces drives the other surface. It has been found that there is
enough friction between the two surfaces to drive the non-driven
one but there is also enough slip to cause the non-driven surface
to travel at a different speed than the driven surface thereby
creating the same effect needed to skew or orient the projections
30 in the web 10. In this regard, it was generally found that
driving the second forming surface 150 and not driving the first
forming surface 140 worked best. In addition, by adjusting the
rollers 146 and 156, the amount of gap, if any, and thus the
frictional engagement of the two surfaces (140 and 150) can be
adjusted to control the amount of engagement and drag between the
two surfaces.
[0051] The line speeds of the two forming surfaces (140 and 150)
will vary depending upon the materials being used to form the
fibrous web 10, the basis weight needed, the amount of vacuum being
used and other parameters commonly associated with forming such
webs including coform webs. For the basis weights described herein,
generally the line speeds will range between about 30 meters per
minute (100 feet per minute) and about 600 meters per minute (2,000
feet per minute), desirably between about 90 meters per minute (300
feet per minute) and about 378 meters per minute (1240 feet per
minute) and more desirably between about 198 meters per minute (650
feet per minute) and about 304 meters per minute (1000 feet per
minute).
[0052] The meltblown fibers used in the coform process assist in
maintaining the orientation of the projections 30 once the web 10
is formed. It is believed that because the meltblown fibers
crystallize at a relatively slow rate, they are soft upon
deposition onto the first and second forming surfaces (140 and
150). Thus the speed differential between the first and second
forming surfaces creates a drag on the head portion 50 of the
projections 30 which, by the time the web 10 is removed from the
forming surfaces, has set in the oriented formation. After the
fibers crystallize, they are then able to hold the shape and
maintain the orientation.
[0053] The degree of orientation can be varied by varying the
amount of the speed differential between the first and second
forming surfaces (140 and 150) and thus the amount of distance that
one forming surface covers versus the other in the prescribed
amount of time it takes the first forming surface 140 to travel the
distance between the first location 141 and the second location 145
denoted as "D1" in FIG. 3. In the context of distance traveled, to
form the projections 30, it is desirable to cause one of the first
140 and second 150 forming surfaces to travel a distance "y" as
defined herein which is between about 2 inches (51 mm) and about
six inches (152 mm) further than the other of the first and second
forming surfaces, more preferably between about 3 inches (76 mm)
and about 5 inches (127 mm) and more preferably about 4 inches (102
mm) and about 5 inches (127 mm). It should be appreciated, however,
that speed and distance differentials outside this range can also
be used depending on the particular end use and the variance of
other parameters such as, for example, the polymers and fibers
being used, the deposition rate, the size of the holes in the first
forming surface, the dwell time of the web on the forming surfaces,
the gap, if any, between the forming surfaces and the amount of
vacuum being used to draw the fibers down onto the forming
surfaces.
[0054] For the uses described herein, the projections will
typically have overall heights 35 in the range of about 0.25
millimeters (0.01 inches) to at least about 9 millimeters (0.35
inches), and in some embodiments, from about 0.5 millimeters (0.02
inches) to about 3 millimeters (0.12 inches). Generally speaking,
the projections 30 are filled with fibers and thus have desirable
resiliency useful for wiping and scrubbing.
Product Applications
[0055] One of the advantages of the web 10 according to the present
invention is that it has two different aesthetic feels depending on
the direction in which the material is contacted or engaged.
Because of the uniform orientation of the projections 30, a knap is
created on the top surface 12 of the web which is perceptible to
human touch and feel. If the material is rubbed or engaged in one
direction, it has a rougher feel that if rubbed or engaged in the
opposite direction. This is the case when the overhanging edge 64
is the leading edge during the engagement process. Conversely, when
the overhanging edge 64 is the trailing edge during the engagement
process, the web 10 has a smoother feel.
[0056] The fibrous nonwoven web 10 may be used in a wide variety of
articles and uses. For example, the web may be incorporated into an
"absorbent article" that is capable of absorbing water or other
fluids. Examples of some absorbent articles include, but are not
limited to, personal care absorbent articles, such as diapers,
training pants, absorbent underpants, incontinence articles,
feminine hygiene products (e.g., sanitary napkins), swim wear, baby
wipes, mitt wipes, and so forth; medical absorbent articles, such
as garments, fenestration materials, underpads, bedpads, bandages,
absorbent drapes, and medical wipes; food service wipers; clothing
articles; pouches, and so forth. Other applications include facial
and cosmetic wipes, both wet and dry, as well as household cleaning
wipes both as individual sheets and as disposable attachments for
cleaning tools such as mops and other handheld cleaning devices.
Materials and processes suitable for forming such articles are well
known to those skilled in the art.
[0057] Personal care absorbent articles typically have certain key
components which may employ the web 10 of the present invention.
Turning to FIG. 8 there is shown a basic diaper design 200.
Typically such products 200 will include a body side liner or
skin-contacting material 202, a garment-facing material or sheet
also referred to as a backsheet 204 and an absorbent core 206
disposed between the body side liner 202 and the garment facing
sheet 204. In addition, it is also common for the product to have
an optional layer 208 which is commonly referred to as a surge or
transfer layer disposed between the body side liner 202 and the
absorbent core 206.
[0058] The web 10 according to the present invention may be used as
all or a portion of any one or all of these aforementioned
components of such personal care products 200 including one of the
external surfaces (202 or 204). For example, the web 10 may be used
as the body side liner 202 in which case it is more desirable for
the projections 30 to be facing outwardly so as to be in a body
contacting position in the product 200. The laminate 10 may also be
used as the surge or transfer layer 208 or as the absorbent core
206 or a portion of the absorbent core 206. Finally, the web 10 may
be used as the outermost side of the garment facing sheet 204 in
which case it may be desirable to attach a liquid impervious film
or other material (not shown) to the bottom surface 14 of the web
10.
EXAMPLES
[0059] In the following examples, Examples 1 and 2 provide specific
information regarding two embodiments of the process and fibrous
nonwoven web 10 of the invention while Comparative Example 1
describes a similar process and resulting fibrous nonwoven web, but
without the directional orientation of the projections. In all
three examples, the polymer composition used in the production of
the meltblown fibers is the same and is as follows: [0060] 85% by
weight Metocene MF650X, a propylene homopolymer having a density of
0.91 g/cm.sup.3 and melt flow rate of 1200 g/10 minute (230.degree.
C., 2.16 kg), which is available from Basell Polyolefins. [0061]
15% by weight Vistamaxx 2330, a propylene/ethylene copolymer having
a density of 0.868 g/cm.sup.3, meltflow rate of 290 g/10 minutes
(230.degree. C., 2.16 kg) which is available from ExxonMobil
Corp.
[0062] Also, in all 3 examples, the pulp fibers were fully treated
southern softwood pulp obtained from the Weyerhaeuser Co. of
Federal Way, Wash. under the designation "CF-405."
[0063] To calculate the differential in distance traveled between
the first forming surface 140 and the second forming surface 150
and thus the degree of directional orientation of the projections
30 in the web 10, the difference in travel of the two forming
surfaces (140 and 150) must be measured over a prescribed distance.
The distance used to make this measurement in the below examples
was the distance between a first lay down point 141 on the first
forming surface 140 and a second take-up point 145 on the first
forming surface 140. See FIG. 3. The location of the first lay down
point (first location 141) should be below the central-most set of
die tips or other deposition device 172 of the apparatus 170. The
location of the take up point (second location (145) is generally
the point at which the heads 50 of the projections 30 of the
fibrous nonwoven web 10 are no longer in contact with the top
surface 152 of the second forming surface 150. As shown in FIG. 3,
the distance between first location 141 and second location 145 is
referred to as distance "D1". In the time it takes the first
forming surface 140 to travel the distance D1, the second forming
surface 150 will have traveled a different distance "D2" which may
be longer or shorter than D1 depending on the speed of each forming
surface. As this is a variable distance depending on the speed
differential of the two forming surfaces, D2 is not shown in FIG.
3.
[0064] Referring again to FIG. 3 of the drawings, a pair of
markers, first marker 141a and second marker 141b, are made on the
respective upper forming surface 140 and the lower forming surface
150 at a first location 141 directly below the point of fiber
deposition from the apparatus 170. If more than one forming bank is
being used, it is desirable to make the point 141 coincide with the
forming bank which is furthest from the take-up roll 180. The
markers 141a and 141b should be in vertical alignment with one
another and the first location 141 marker. The marker for first
location 141 should be placed at a stationary location relative to
the overall apparatus 130 as should the second location 145 marker
as these are the two stationary reference points for the
calculations set forth below and the constant distance D1.
[0065] Any number of materials may be used to form the markers 141,
141a, 141b and 145 including inks, paints, tapes, mechanical and
electronic markers. Depending on the speeds of the forming surfaces
(140 and 150), the markers may be visible with the naked eye and
changes in the relative position of the markers may be measured
with a ruler or similar device. Alternatively, the markers may
contain components (such as reflective surfaces or
digital/electronic senders or sensors) which can be tracked with
electronic, photographic and/or other imaging and sensing
devices.
[0066] For purposes of demonstrating how to calculate the
difference in distance traveled by the two forming surfaces (140
and 150) between first location 141 and second location 145, assume
that the first forming surface 140 is moving faster than the second
forming surface 150. (The calculation is also valid for the reverse
scenario.) As mentioned previously, the distance D1 between first
location 141 and second location 145 is a known and set distance.
Distance D2 is the distance that the second forming surface 150
will have moved (as tracked by the second marker 141b) in the time
"t" that the first forming surface 140 moves distance D1 (that is
the time that first marker 141a takes to travel between first
location 141 and second location 145). The differential distance
"y" that the first forming surface 140 and thus first marker 141a
travels as compared to the distance the second forming surface 150
has traveled in the same amount of time "t" is equal to the
equation y=D1-D2. Additionally, "S1" is the speed of the first
forming surface 140 and "S2" is the speed of the second forming
surface 150. Also, t=D1/S1 and t=D2/S2. Therefore, substituting for
like values in the foregoing equations:
t=(D2/S2)=(D1-y)/S2) and so:
(D1/S1)=[(D1-y)/S2] and solving for y yields:
y=D1.times.[1-(S2/S1)].
[0067] As a result, the difference in distance that one forming
surface travels versus the other in the process is dependent on
both the distance D1 and the ratio of the speeds (S1 and S2) at
which the two forming surfaces are traveling. In this regard, "y"
will be a positive number when S1 is greater than S2 (that is,
first forming surface 140 is traveling faster than second forming
surface 150), and "y" will be a negative number when S1 is less
than S2 (that is, first forming surface 140 is traveling slower
than second forming surface 150). Consequently, the absolute value
of "y" should be used.
[0068] In view of the above and in view of the examples below, the
distance differential "y" as defined herein will typically be
between about 2 inches (51 mm) and about six inches (152 mm),
alternately between about 3 inches (76 mm) and about 5 inches (127
mm) and still further between about 4 inches (102 mm) and about 5
inches (127 mm).
Example 1
[0069] A coform web was formed via a two-bank process in which each
bank consisted of two heated streams of meltblown fibers and a
single stream of fiberized pulp fibers as described above and shown
in FIGS. 3 and 4. Note that in FIG. 3 only a single bank apparatus
170 is shown but for the below examples, two banks were used.
[0070] In the first bank (that is, the bank that deposits fibers
directly onto the top surface 147 of the first forming surface
140), the polypropylene of each stream was supplied to respective
meltblown dies at a rate of 2.73 kg to 2.95 kg of polymer per 2.54
cm of die tip width per hour (5.0 to 5.5 pounds of polymer per inch
of die tip width per hour). The meltblown dies were positioned such
that the tips were 25.4 cm (10 inches) horizontally from the pulp
nozzle centerline and 25.4 cm (10 inches) above the first forming
surface 140. They were tilted inwardly towards the pulp nozzle at
an angle of 80.degree. from the horizontal. The pulp nozzle was
15.24 cm (6 inches) above the first forming surface. The pulp was
delivered at a rate of 6.4 kg per 2.54 cm of pulp nozzle width per
hour (14 pounds per inch of pulp nozzle width per hour).
[0071] In the second bank (that is, the bank that deposits fibers
on top of the web formed by the first bank), the polypropylene of
each stream was supplied to respective meltblown dies at a rate of
2.27 kg of polymer per 2.54 cm of die tip width per hour (5.0
pounds of polymer per inch of die tip width per hour). The
meltblown dies were positioned such that the tips were 17.8 cm (7
inches) horizontally from the pulp nozzle centerline and 17.8 cm (7
inches) above the first forming surface 140. They were tilted
inwardly towards the pulp nozzle at an angle of 50.degree. from the
horizontal. The pulp nozzle was 24.1 cm (9.5 inches) above the
first forming surface 140. The pulp was delivered at a rate of 2.3
kg per 2.54 cm of pulp nozzle width per hour (5 pounds per inch of
pulp nozzle width per hour).
[0072] In total, the resulting fibrous web had a meltblown fiber
content of about 52% and a pulp fiber content of about 48% on a
weight percent basis. The second forming surface 150 was an
ELECTRATECH.TM. 56 (Albany International Co.) forming wire. To
create the projections 30, the first forming surface 140 was a
rubber mat having a thickness of approximately 2.65 millimeters
(0.10 inch) and containing 6.35 mm (0.25 inch) diameter circular
holes 142 arranged in a pattern similar to that shown in FIG. 4 of
the drawings. The spacing of the holes 142 was 9.53 mm (0.375
inches) from center to center in both the machine and cross
directions. A vacuum box 160 was positioned below the second
forming surface 150 to aid in deposition of the fibers and the
formation of the web and was set to a vacuum level sufficient to
draw the fibrous mixture from the first bank into the holes 142 in
the first forming surface 140. The vacuum level was also sufficient
to draw a portion of the fibers that entered the holes 142 of the
first forming surface 140 into contact with the second forming
surface 150. The second forming surface 150 was driven by a drive
roll (one of the four rolls 156). The first forming surface 140 was
driven by contact with the second forming surface 150 and was not
driven independently of the second forming surface 150. To create
the directional orientation of the projections 30, the first
forming surface 140 was run at a first speed of 195 meters per
minute (640 feet per minute) and the second forming surface 150 was
run at a second speed of approximately 194 meters per minute (637
feet per minute). The speed mismatch between the first and second
forming surfaces resulted in the first forming surface 140
traveling 5.1 cm (2 inches) farther than the second forming surface
150 over the distance "D1" of 12.2 m (40 feet). Thus the distance
differential value "y" was equal to 51 millimeter. The resultant
coform web 10 had a configuration similar to that shown in FIG. 1.
A photographic, cross-sectional side view of the web is shown in
FIG. 5.
Example 2
[0073] A coform web was formed via a two-bank process in which each
bank consisted of two heated streams of meltblown fibers and a
single stream of fiberized pulp fibers as described above with
respect to Example 1.
[0074] In the first bank (that is, the bank that deposits fibers
directly onto the top surface 147 of the first forming surface
140), the polypropylene of each stream was supplied to respective
meltblown dies at a rate of 2.73 kg to 2.95 kg of polymer per 2.54
cm of die tip width per hour (6.0 to 6.5 pounds of polymer per inch
of die tip width per hour). The meltblown dies were positioned such
that the tips were 25.4 cm (10 inches) horizontally from the pulp
nozzle centerline and 25.4 cm (10 inches) above the first forming
surface 140. They were tilted inwardly towards the pulp nozzle at
an angle of 80.degree. from the horizontal. The pulp nozzle was
15.2 cm (6 inches) above the first forming surface 140. The pulp
was delivered at a rate of 13.6 kg per 2.54 cm of pulp nozzle width
per hour (30 pounds per inch of pulp nozzle width per hour).
[0075] In the second bank (that is, the bank that deposits fibers
on top of the web formed by the first bank), the polypropylene of
each stream was supplied to respective meltblown dies at a rate of
2.3 kg of polymer per 2.54 cm of die tip width per hour (5.0 pounds
of polymer per inch of die tip width per hour). The meltblown dies
were positioned such that the tips were 17.8 cm (7 inches)
horizontally from the pulp nozzle centerline and 17.8 cm (7 inches)
above the first forming surface 140. They were tilted inwardly
towards the pulp nozzle at an angle of 50.degree. from the
horizontal. The pulp nozzle was 24.1 cm (9.5 inches) above the
first forming surface 140. The pulp was delivered at a rate of 2.3
kg per 2.54 cm of pulp nozzle width per hours (5 pounds per inch of
pulp nozzle width per hour).
[0076] In total, the resulting fibrous web had a meltblown fiber
content of about 39% and a pulp fiber content of about 61% on a
weight percent basis. To create the directional orientation of the
projections 30, the first forming surface 140 was run at a first
speed of 285 meters per minute (935 feet per minute) and the second
forming surface 150 was run at a second speed of approximately 281
meters per minute (923 feet per minute). The speed mismatch between
the first and second forming surfaces resulted in the first forming
surface 140 traveling 15.2 cm (6''-inches) farther than the second
forming surface 150 over the distance "D1" of 12.2 m (40 feet).
Thus the distance differential value "y" was equal to 152
millimeter. The resultant coform web 10 had a configuration similar
to that shown in FIG. 1. A photographic, cross-sectional side view
of the web is shown in FIG. 6.
Comparative Example 1
[0077] Comparative example 1 was run with no speed differential
between the first forming surface 140 and the second forming
surface 150. The first and second forming surfaces were driven
independently, but at the same speed of approximately 195 meters
per minute (640 feet per minute). As a result, no directional
orientation of the projections was achieved and no overhang area
was created. Further, the distance differential value "y" was equal
to 0 millimeter due to their being no speed differential between
the two forming surfaces.
[0078] A coform web was formed via a two-bank process in which each
bank consisted of two heated streams of meltblown fibers and a
single stream of fiberized pulp fibers as described above and shown
in FIGS. 3 and 4. The forming conditions and delivery rates for the
meltblown fibers and pulp were the same as in Example 1 resulting
in a fibrous web with a meltblown fiber content of about 52% and a
pulp fiber content of about 48% on a weight percent basis. A
photographic, cross-sectional side view of the web is shown in FIG.
7.
[0079] As can be seen from FIGS. 5, 6 and 7, due to the speed
differential and thus the difference in the distance traveled by
the first forming surface 140 versus the second forming surface
150, a series of uniform, directionally-oriented projections 30
could be formed in the fibrous nonwoven web 10. See FIGS. 5 an 6.
Without the speed differential and/or insufficient contact between
the head portions 50 of the projections 30 with the top surface 152
of the second forming surface 150, no directional orientation
occurs. Also it can be seen in comparing the materials of FIGS. 5
and 6 that with increased speed differential and travel distance
differential of the two forming surfaces between fiber laydown and
web take-up (Example 2 as compared to Example 1), greater
directional orientation and overhang can be achieved with respect
to the projections 30.
[0080] While the invention has been described in detail with
respect to the specific embodiments thereof, it will be appreciated
that those skilled in the art, upon attaining an understanding of
the foregoing, may readily conceive of alterations to, variations
of, and equivalents to these embodiments. Accordingly, the scope of
the present invention should be assessed as that of the appended
claims and any equivalents thereto.
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