Title of Invention

A POLYMERIC WEB COMPRISING A PRECURSOR WEB, AND A DISPOSABLE ABSORBENT ARTICLE THEREOF

Abstract A polymeric web exhibiting a soft and silky tactile impression on at least one side thereof is disclosed. The silky feeling side of the web exhibits a pattern of discrete hair-like fibrils, each of the hair-like fibrils being a protruded extension of the web surface and having a side wall defining an open proximal portion and a closed distal portion. The hair-like fibrils exhibit a maximum lateral cross-sectional diameter of between 2 and 5 mils, and an aspect ratio from 1 to 3. Methods and apparatus for making the polymeric web utilize a three-dimensional forming structure having a plurality of protrusions being generally columnar forms having an average aspect ratio of at least about 1.
Full Text FIELD OF THE INVENTION
The present invention relates to a forming structure for making a polymeric web
exhibiting a soft and silky tactile impression on at least one surface. More particularly, the
present invention relates forming structure for making a three-dimensional polymeric web
exhibiting a soft and silky tactile impression that can be used as a body-facing topsheet in
disposable absorbent
BACKGROUND OF THE INVENTION
It is extremely desirable to construct disposable articles, such as absorptive devices,
including sanitary napkins, pantyliners, interlabial devices, diapers, training pants, incontinent
devices, wound dressings and the like, with a soft cloth-like surface feel to the user's skin at any
anticipated points of contact. Likewise, it has long been known in the disposable articles art to
construct absorptive devices that present a dry surface feel to the user, especially during use. By
having a soft, cloth-like body-facing surface that retains a dry surface feel during use, an
absorptive device gives improved wearing comfort, and minimizes the development of
undesirable skin conditions due to prolonged exposure to moisture absorbed within the absorptive
device.
While woven and non-woven fibrous webs are often employed as body-facing topsheets
for absorptive devices because of their pleasant surface feel, macroscopically expanded, three
dimensional, apertured polymeric webs such as the commercially successful DRI-WEAVE™
topsheet marketed by Procter & Gamble Company have also been utilized. One viable polymeric
web of this type is disclosed in U.S. Pat. No. 4,342,314 issued to Radel et al. on Aug. 3,1982.
Such webs have been shown to exhibit desirable fluid transport and fluid retaining characteristics.
Desirable fluid transport characteristics allow the topsheet to acquire fluids, such as urine or
menses, and pass to fluid into the absorptive article. Once absorbed into the absorptive article, the
fluid retaining feature of the topsheet preferably prevents rewet, i.e., the movement of fluid back
through the topsheet. Rewet can be a result of at least two causes: (1) squeezing out of the
absorbed fluid due to pressure on the absorptive article; and/or (2) wetness entrapped within or on
the topsheet Preferably, both properties, fluid acquisition and fluid retention, are maximized.
Said differently, preferably a topsheet will exhibit high rates of fluid acquisition, and low levels of
rewet
Other macroscopically expanded, three dimensional, apertured polymeric webs are
known. For example, U.S. Patent No. 4,463,045 issued to Ahr et al. on July 31,1984 discloses a
macroscopically expanded three-dimensional polymeric web that exhibits a substantially non-
glossy visible surface and cloth-like tactile impression. Ahr et al. teaches the criteria which must
be met with respect to the regularly spaced pattern of surface aberrations in order to diffusely
reflect incident light and thereby eliminate gloss. Ahr, et al teaches that the surface aberrations in
the web should exhibit an average amplitude of at least about 0.2 mils (i.e.,0.0002 inches), and
most preferably at least about 0.3 mils (i.e., 0.0003 inches) for a more clothlike or fiberlike tactile
impression in the resultant web. Despite its advancements in eliminating gloss, the structure of
the surface aberrations of the web in Ahr, et al. can lack desired softness. As recognized in the
art, for example is U.S. Pat. No. 4,629,643, issued to Curro etl al. (discussed below), the lack of
desired softness is believed to be due to the structure of each Aberration, which can be described
as having the properties of an "arch" that behaves as a discrete structural unit, resisting deflection.
This lack of sufficient deflection detracts from the softness impression experienced by the user's
skin.
One proposed solution to improve the softness impression to the web of Ahr et al., was
disclosed in the aforementioned U.S. Pat No. 4,629,643 ( Curro, et al. '643) Curro, et al. '643
discloses a microapertured polymeric web exhibiting a fine scale pattern of discrete surface
aberrations. Each of these surface aberrations have a maximum amplitude and, unlike the web
structure disclosed in Ahr, et al. at least one microaperature is provided that is substantially
coincidental with the maximum amplitude of each surface aberration. The forming of
microapertures at the maximum amplitude of each surface aberration provides a volcano-like cusp
with petal shaped edges. It is believed that the resultant web Surface that is in contact with the
human skin is of smaller total area and is less resistant to compressive and shear forces than the
unapertured "arch-like" structures taught by Ahr et al.
Although the microapertured film of Curro, et al. '643 imparts superior tactile impression
to the skin of the user, it has some drawbacks related to certain fluid handling properties when
used as a topsheet in absorbent articles. For example, it has been found mat a web as disclosed in
Curro, et al. '643, when used as a topsheet on a sanitary pad can permit an unacceptably high
amount of rewet, i.e., fluid that returns back to the skin-facing surface of the topsheet after
initially having passed through the topsheet to be absorbed by the sanitary napkin. In particular, it
appears mat a web according to Curro '643 can be more susceptible to rewet tinder pressure. This
is because when such a product is used as a topsheet in a catamenial product, for example,
absorbed fluid can be urged back out of the product through the many microapertures of the
topsheet It appears mat each of the microapertures in the structure of Curro, et al. '643 can
provide a pathway for fluid to escape from an underlying absorbent core in an absorbent article
under the pressure of normal wearing conditions. These pathways in the web structures therefore
cause decreased fluid retention and increased rewet in the absorbent structures.
Attempts at alleviating the shortcoming of Curro '643, i.e., attempts to both maximize
softness and reduce rewet, can be found, for example, in U.S.i Pat. No. 6,228,462 issued to Lee, et
al., on May 8,2001. Lee discloses a compression resistant web comprising rigid polymers. The
compression resistance of the rigid polymers helps reduce rewet, but the rigid polymers utilized'
tend to decrease the softness of the web.
Furthermore, the hydroforming processes disclosed in Curro, et al. '643 and Lee "462 for
making macroscopically expanded, three dimensional, apertured polymeric webs results in a
formed film that must be dried after hydroforming. Due to the many interstices of the
microapertures that can retain water, drying commercial quantities of these webs consumes
significant amounts of energy, and can require significant capital investments in drying
equipment One example of an approach to effectively dry such webs is disclosed in U.S. Patent
No. 4,465,422 issued September 22,1987 to Curro, et al.
One further drawback associated with the webs disclosed in Curro '643 and Lee '462
when used as topsheets on sanitary napkins is the tendency of the microapertures to entrap fluid,
such as menses. The entrapment can be in the microapertures themselves and/or between adjacent
microapertures. Fluid so entrapped remains at or near the surface of the web, and can, therefore
be in contact with the wearer's skin for prolonged periods of time. This contact negatively affects
the skin health of the wearer and causes the topsheet to not have a clean appearance post-use.
Another attempt at making a soft, three-dimensional, macroscopically-expanded web
having an improved functional surface is U.S. Pat No. 5,670,110, issued to Dirk, et al. on
September 23,1997. The web of Dirk et al. utilizes fibrils achieved via a screen printing roll.
However, screen printing is a relatively slow process for making commercial webs for consumer
articles.
Accordingly, it would be beneficial to have an improved formed film web that has
superior tactile impression and superior fluid handling properties.
Additionally, it would be beneficial to have a formed film web that has superior tactile
impression and provides for superior fluid retention and rewet characteristics.
Additionally, it would be beneficial to have a formed film web that has superior tactile
impression and provides for superior cleanliness for hygiene articles.
Additionally, it would be beneficial to have an improved process for making a formed
film web that has superior tactile impression and provides for superior fluid retention and rewet
characteristics.
Finally, it would be beneficial to have an improved apparatus and method of making a
forming structure for forming a formed film web that has superior tactile impression and provides
for superior fluid retention and rewet characteristics.
SUMMARY OF THE INVENTION
A method for making a forming structure having columnar protrusions extending therefrom, the
method comprising the steps of:
a) providing a forming unit;
b) providing a backing film;
c) providing a foraminous element;
d) juxtaposing the foraminous element and the backing film with respect to the forming
unit so that the backing film is interposed between the foraminous element and the
forming unit;
e) providing a liquid photosensitive resin;
f) applying a coating of the liquid photosensitive resin to the foraminous element;
g) juxtaposing in contacting relationship with the coating of photosensitive resin a first
transparent mask;
h) controlling a first thickness between the backing film and the first mask of the coating
to a preselected value;
i) exposing the liquid photosensitive resin to light having an activating wavelength
through the first mask thereby inducing partial curing of the photosensitive resin to
form a monolithic slab of partially-cured photosensitive resin;
j) removing the first mask;
k) repeating steps (a) - (j) one time with a different, second mask replacing the first
mask in steps (g)-(h) and a second thickness in step (h), the second thickness being
defined between the backing film and the second mask and being greater than the first
thickness, and, in step (i) inducing partial curing of a plurality of protrusions on the
monolithic slab such that they are joined to and integral with the monolithic slab, and
removing the second mask in step (j);
1) immersing the foraminous element and partially cured resin thereon in an oxygen-free
environment;
m) exposing the foraminous element and partially cured resin thereon to light having an
activating wavelength to fully cure the partially cured resin, resulting in the forming
structure having columnar protrusions extending therefrom.
The method can further comprise the step of laser etching a plurality of apertures through the
forming structure to form an apertured forming structure.
BRIEF DESCRIPTION OF THE DRAWING
While the specification concludes with claims particularly pointing out and distinctly
claiming the subject matter of the present invention, it is believed that the invention will be better
understood from the following description taken in conjunction with the accompanying Figures,
in which:
FIG 1 is an enlarged, partially segmented, perspective illustration of a prior art polymeric
web of the type generally disclosed in commonly assigned U.S. Patent No. 4,342,314.
FIG. 2 is an enlarged, partially segmented, perspective illustration of a prior art polymeric
web of the type generally disclosed in commonly assigned U.S. Patent No. 4,629,643.
FIG. 3 is an enlarged, partially segmented, perspective illustration of a polymeric web
made on a forming structure of the present invention.
FIG. 4 is a former enlarged, partial view of a portion of the web shown in FIG. 3
illustrating in greater detail certain features of the polymeric web of the present invention.
FIG. 5 is a cross-sectional depiction of a cross section taken along Section 5-5 of FIG. 4.
FIG. 6 is a plan view of representative aperture shapes projected in the plane of the first
surface of a polymeric web of the present invention.
FIG. 7 is a top plan view of a sanitary napkin with portions cut away to more clearly show
the construction of a catamenial device of the present invention.
FIG. 8 is a cross-sectional view of the sanitary napkin taken along Section 8-8 of FIG. 7.
FIG. 9 is a simplified schematic illustration of a single phase forming process of the
present invention.
FIG. 10 is an enlarged, partially segmented, perspective illustration of a forming structure
of the present invention.
FIG. 11 is a further enlarged, partial view of a portion of the forming structure shown in
FIG. 10.
FIG. 12 is a further enlarged partial view of a portion of the forming structure shown in
FIG. 11.
FIG. 13 is a photomicrograph of one embodiment of a forming structure of the present
invention.
FIG. 14 is an enlarged view of a portion of the forming structure of FIG. 13.
FIG. 15 is a photomicrograph of another embodiment of a forming structure of the present
invention.
FIG. 16 is an enlarged view of a portion of a forming structure similar to that shown in
FIG. 15.
FIG. 17 is a photomicrograph of a portion of a web made on a forming structure of the
present invention.
FIG. 18 is an enlarged view of a portion of the web shown in FIG. 17.
FIG. 19 is a photomicrograph of a portion of a web made on a forming structure of the
present invention.
FIG. 20 is an enlarged view of a portion of a web made on a forming structure of the
present invention. FIG. 21 is a plan view of a forming structure of the present invention.
FIG. 22 is a cross-sectional view of the forming structure shown in FIG. 21.
FIG. 23 is a schematic representation of a method from making a forming structure of the
present invention.
FIG. 24 is a photomicrograph showing an enlarged portion of a forming structure of the
present invention.
FIG. 25 is a photomicrograph showing a further enlarged portion of the forming structure
shown in FIG. 24.
FIG. 26 is a photomicrograph showing in cross section an enlarged portion of the forming
structure shown in FIG. 24.
FIG. 27 is a representation of a first mask used in a process for making a forming
structure of the present invention.
FIG. 28 is a representation of a second mask used in a process for making a forming
structure of the present invention.
FIG. 29 is a simplified schematic illustration of a process for making a web using a belted
forming structure of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is an enlarged, partially segmented perspective illustration of a prior art
macroscopically-expanded, three-dimensional, fluid pervious polymeric web 40 formed generally
in accordance with the aforementioned U.S. Patent 4,342,314; Webs of mis type have been found
to be highly suitable for use as a topsheet in absorbent articles such as sanitary napkins,
pantyliners, interlabial devices, and the like. The fluid pervious web 40 exhibits a plurality of
macroscopic surface aberrations that can be apertures, such as primary apertures 41. Primary
apertures 41 are formed by a multiplicity of interconnecting members, such as fiber like elements,
e.g., 42,43,44,45 and 46, that are interconnected to one another to define a continuous first
surface 50 of the web 40. Each fiber like element has a base portion, e.g., base portion 51, located
in plane 52 of first surface 50. Each base portion has a sidewall portion, e.g., sidewall portion 53,
attached to each longitudinal edge thereof. The sidewall portions extend generally in the direction
of a discontinuous second surface 55 of web 40. The intersecting sidewall portions are
interconnected to one another intermediate the first and second surfaces of the web, and terminate
substantially concurrently with one another in the plane 56 of the second surface 55. In some
embodiments, the base portion 51 may have surface aberrations 58 in accordance with the
aforementioned Ahr '045 patent
As used herein, the term "macroscopically expanded" refers to the structure of a web
formed from a precursor web or film, e.g., a planar web, that has been caused to conform to the
surface of a three-dimensional forming structure so that bom sides, or surfaces, of the precursor
web are permanently altered due to at least partial conformance of the precursor web to the three-
dimensional pattern of the forming structure. Such macroscopically-expanded webs are typically
caused to conform to the surface of the forming structure by embossing (i.e., when the forming
structure exhibits a pattern comprised primarily of male projections), by debossing (i.e., when the
forming structure exhibits a pattern comprised primarily of female depressions, or apertures), or
by a combination of both.
As used herein, the term "macroscopic" refers to structural features or elements that are
readily visible and distinctly discernable to a human having 20/20 vision when the perpendicular
distance between the viewer's eye and the web is about 12 inches. Conversely, the term
"microscopic" is utilized to refer to structural features or elements that are not readily visible and
distinctly discernable to a human having 20/20 vision when the perpendicular distance between
the viewer's eye and the plane of the web is about 12 inches. In general, as used herein, the
primary apertures of a web disclosed herein are macroscopic, and surface aberrations, such as
hair-like fibrils as disclosed more fully below are considered microscopic.
The term "planar" as used herein to refers to the overall condition of a precursor web or
film when viewed by the naked eye on a macroscopic scale, prior to permanently deforming the
web into a three-dimensional formed film. In this context, extruded films prior to post-extrusion
processing and films that do not exhibit significant degree of permanent macroscopic three-
dimensionality, e.g., deformation out of the plane of the film, would generally be described as
planar.
As utilized herein, the term "interconnecting members" refers to some or all of the
elements of a web, e.g., web 40 in FIG. 1, portions of which serve to define the primary
apertures by a continuous network. As can be appreciated from the description of FIG. 1 and the
present invention herein, the interconnecting members, e.g., fiber like elements 42,43,44,45,
and 46, are inherently continuous, with contiguous interconnecting elements blending into one
another in mutually adjoining transition portions. Individual interconnecting members can be
best described with reference to FIG. 1 as those portions of the web disposed between any two
adjacent primary apertures, originating in the first surface and extending into the second surface.
On the first surface of the web the interconnecting members collectively form a continuous
network, or pattern, the continuous network of interconnecting members defining the primary
apertures, and on the second surface of the web interconnecting sidewalk of the interconnecting
members collectively form a discontinuous pattern of secondary apertures. Interconnecting
members are described more generally below with reference to FIG. 6.
In a three-dimensional, macroscopicaUy-expanded web, the interconnecting members
may be described as channel-like. Their two dimensional cross-section may also be described as
"U-shaped", as in the aforementioned Radel '314 patent, or "upwardly concave-shaped", as
disclosed in U.S. Patent No. 5,514,105, issued on May 7,1996 to Goodman, Jr., et al.
"Upwardly-concave-shaped" as used herein, and as represented in FIG. 1, describes the
orientation of the channel-like shape of the interconnecting members with relation to the
surfaces of the web, with a base portion 51 generally in the first surface 50, and the legs, e.g.,
sidewall portions 53, of the channel extending from the base portion 51 in the direction of the
second surface 55, with the channel opening being substantially in the second surface 55. In
general, for a plane cutting through the web, e.g., web 40, orthogonal to the plane, e.g., plane 52,
of the first surface 50 and intersecting any two adjacent primary apertures, e.g., apertures 41, the
resulting cross-section of an interconnecting member disposed therein will exhibit a generally
upwardly concave shape that may be substantially U-shaped.
The term "continuous" when used herein to describe the first surface of a
macroscopicaUy-expanded, three-dimensional formed film web, refers to the uninterrupted
character of the first surface generally in the plane of the first surface. Thus, any point on the first
surface can be reached from any other point on the first surface without substantially leaving the
first surface. Conversely, as utilized herein, the term "discontinuous" when used to describe the
second surface of a three-dimensionally formed film web refers to the interrupted character of the
second surface generally in the plane of the second surface. Thus, any point on the second surface
cannot necessarily be reached from any other point on the second surface without substantially
leaving the second surface in the plane of the second surface.
FIG. 2 shows an enlarged, partially segmented, perspective illustration of a portion of
another prior art polymeric microapertured web 110 formed generally in accordance with the
aforementioned Curro '643 patent. The microapertured surface aberrations 120 can be formed by
a hydroforming process in which a high-pressure liquid jet is utilized to force the web to conform
to a three-dimensional support member. As shown, ruptures which coincide substantially with the
maximum amplitude of each micropertured surface aberration 120 result in the formation of a
volcano-shaped aperture 125 having relatively thin, irregularly shaped petals 126 about its
periphery. The relatively thin, petal-shaped edges of the aperture of such a web provide for
increased softness impression on the skin of a user when compared, for example, to the web of
Ahr '045. It is believed that this softness impression is due to the relative lack of resistance to
compression and shear afforded by the surface aberrations having volcano-shaped apertures.
As mentioned above, although the microapertured film of Curro '643 imparts a superior
tactile impression of softness, it can also permit undesirable rewet when used as a topsheet on a
disposable absorbent article. The web of the present invention solves this problem by providing
for softness via surface aberrations that exhibit low resistance to compression and shear,
comparable to the web of Curro '643, and yet do not permit fluid flow via microapertures.
Therefore, one benefit of the web of the present invention is superior softness together with
minimal rewet when used as a topsheet on a disposable absorbent article, such as a sanitary
napkin.
FIG. 3 is an enlarged, partially segmented perspective illustration of a fluid pervious,
macroscopically-expanded, three-dimensional polymeric web 80 of the present invention. The
geometric configuration of the macroscopic surface aberrations, e.g., primary apertures 71, of the
polymeric web can be generally similar to that of the prior art web 40 illustrated in FIG. 1.
Primary apertures 71 may be referred to as "apertures" or "macroapertures" herein, and refer to
openings in the web that permit fluid communication between a first surface 90 of web 80 and a
second surface 85 of web 80. The primary apertures 71 of the web shown in FIG. 3 are defined in
the plane 102 of first surface 90 by a continuous network of interconnecting members, e.g.,
members 91,92,93,94, and 95 interconnected to one another; The shape of primary apertures 71
as projected in the plane of the first surface 90 may be in the shape of polygons, e.g., squares,
hexagons, etc., in an ordered or random pattern. In a preferred embodiment primary apertures 71
are in the shape of modified ovals, and in one embodiment primary apertures 71 are in the general
shape of a tear drop. Polymer web 80 exhibits a plurality of surface aberrations 220 in the form of
hair-like fibrils 225, described more fully below.
In a three-dimensional, microaperturcd polymeric web 80 of the present invention, each
interconnecting member comprises a base portion, e.g., base portion 81, located generally in plane
102, and each base portion has sidewall portions, e.g., sidewall portions 83 extending from each
longitudinal edge thereof. Sidewall portions 83 extend generally in the direction of the second
surface 85 of the web 80 and join to sidewalls of adjoining interconnecting members intermediate
the first and second surfaces, 90 and 85, respectively, and terminate substantially concurrently
with one another to define secondary apertures, e.g., secondary apertures 72 in the plane 106 of
second surface 85.
FIG. 6 is a plan view of representative primary aperture shapes projected in the plane of
the first surface of an alternative embodiment of a three-dimensional, macroapertured polymer
web of the present invention. While a repeating partem of uniform shapes, for example a
tessellating pattern, is preferred, the shape of primary apertures, e.g., apertures 71, may be
generally circular, polygonal, or mixed, and may be arrayed in an ordered pattern or in a random
pattern.
As shown in FIG. 6 the interconnecting members, e.g., interconnecting members 97 and
98, are each inherently continuous, with contiguous interconnecting elements blending into one
another in mutually adjoining transition zones or portions, e.g., portions 87. In general transition
portions are defined by the largest circle that can be inscribed tangent to any three adjacent
apertures. It is understood that for certain patterns of apertures the inscribed circle of the
transition portions may be tangent to more than three adjacent; apertures. For illustrative
purposes, interconnecting members may be thought of as beginning or ending substantially at the
centers of the transition portions, such as interconnecting members 97 and 98. Interconnecting
members need not be linear, but may be curvilinear. The sidewalls of the interconnecting
members can be described as interconnecting to the sidewalls of adjacent, contiguous
interconnecting members. Exclusive of portions of the transition zones and portions including
hair-like fibrils, as disclosed below, cross-sections of interconnecting members transverse to the
longitudinal centerline between the beginning and end of the interconnecting member may be
generally described as U-shape. However, the transverse cross-section need not be uniform or U-
shaped along the entire length of the interconnecting member, and for certain primary aperture
configurations it may not be uniform along most of its length. In particular, in transition zones or
portions interconnecting members blend into contiguous interconnecting members and transverse
cross-sections in the transition zones or portions may exhibit substantially non-uniform U-shapes,
or no discernible U-shape.
FIG. 4 is a further enlarged, partial view of the three-dimensional polymeric web 80
shown in FIG. 3. The three-dimensional polymeric web 80 comprises a polymer film 120, i.e.,
the precursor film, which can be a single layer of extruded polymer or a multilayer coextruded or
laminate film. As shown in FIG. 4, film 120 is a two layer laminate comprising a first layer 101
and a second layer 103. Laminate materials may be coextruded, as is known in the art for making
laminate films, including films comprising slrin layers. While it is presently preferred that, as
shown in FIG. 4, the polymeric layers, e.g., layers 101 and 103, terminate substantially
concurrently in the plane of the second surface 106 it is not presently believed to be essential that
they do so. One or more layers may extend further toward the second surface than the other(s).
FIG. 4 shows a plurality of surface aberrations 220 in the form of hair-like fibrils 225.
The hair-like fibrils are formed as protruded extensions of the polymeric web 80, generally on the
first surface 90 thereof. The number, size, and distribution of hair-like fibrils 225 on polymeric
web 80 can be predetermined based on desired skin feel. For applications as a topsheet in
disposable absorbent articles, it is preferred that hair-like fibrils 225 protrude only from the base
portion 81 in first surface 90 of polymeric web 80, as shown in FIGS. 3 and 4. Therefore, when
web 80 is used as a topsheet in a disposable absorbent article, the web can be oriented such that
the hair-like fibrils 225 are skin contacting for superior softness impression, and yet, the hair-like
fibrils 225 do not obstruct fluid flow through macroapertures |71. Moreover, having hair-like
fibrils 225 with closed distal portions 226 results in reduced rewet, i.e., reduced amounts of fluid
being re-introduced to the surface of the topsheet after having been first passed through the
topsheet to underlying absorbent layers.
As shown in cross-section FIG. 5, hair-like fibrils 225 can be described as protruding
from first surface 90 of web 80. As such, hair-like fibrils 225 can be described as being integral
with film 120, and formed by permanent local plastic deformation of film 120. Hair-like fibrils
can be described as having a side wall 227 defining an open proximal portion 229 and a closed
distal portion 226. Hair-like fibrils 225 have a height h measured from a minimum amplitude
Amin between adjacent fibrils to a maximum amplitude Amu at the closed distal portion 226.
Hair-like fibrils have a diameter d, which for a generally cylindrical structure is the outside
diameter at a lateral cross-section. By "lateral" is meant generally parallel to the plane of the first
surface 102. For non-uniform lateral cross-sections, and/or nbn-cylindrical structures of hair-like
fibrils, diameter d is measured as the average lateral cross-sectional dimension at Yz the height h
of the fibril, as shown in FIG. 5. Thus, for each hair-like fibril 225, an aspect ratio, defined as
h/d, can be determined. Hair-like fibrils 225 can have an aspect ratio h/d of at least 0.5. The
aspect ratio can be 1, or 1.5 and is preferably at least about 2.
In general, because the actual height h of any individual hair-like fibril 225 can be
difficult to determine, and because the actual height may vary, an average height havg of a
plurality of hair-like fibrils can be determined by determining an average minimum amplitude
Amta and an average maximum amplitude A„m over a predetermined area of web 80. Likewise,
for varying cross-sectional dimensions, an average dimension davg can be determined for a
plurality of hair-like fibrils 225. Such amplitude and other dimensional measurements can be
made by any method known in the art, such as by computer aided scanning microscopy and data
processing. Therefore, an average aspect ratio ARavg of the hair-like fibrils 225 for a
predetermined portion of the web can be expressed as bavg/dtvg.
The dimensions h and d for hair-like fibrils 225 can be indirectly determined based on the
known dimensions of a forming structure, as disclosed more fully below. For example, for a
forming structure made according to predetermined dimensions of male protrusions, e.g.,
protrusions 2250 shown in FIG. 11 below, on which hair-like fibrils 225 are to be formed can
have known dimensions. If precursor film 120 is fully and permanently deformed over protrusions
2250, then h and d can be calculated from these known dimensions, taking into account the
thickness of the precursor film 120, including predicted and/or observed web thinning. If the
precursor film 120 is not fully formed over protrusions 2250, then the height h of hair-like pillars
will be less than the corresponding height of the protrusions 2250/
In one embodiment the diameter of hair-like fibrils 225 is constant or decreases with
increasing amplitude (amplitude increases to a maximum at closed distal end 226). As shown in
FIG, 5, for example, the diameter, or average lateral cross-sectional dimension, of hair-like fibrils
225 can be a maximum at proximal portion 229 and the lateral cross-sectional dimension steadily
decreases to distal end 226. This structure is believed to be necessary to ensure the polymeric
web 80 can be readily removed from the forming structure 350, as more fully described below
with respect to FIG. 10.
As shown in FIG. 5, some thinning of precursor web 120 can occur due to the relatively
deep drawing required to form high aspect ratio hair-like fibrils 225. For example, thinning can
be observed at or near closed distal ends 226. By "observed" is meant that the thinning is distinct
when viewed in magnified cross-section. Such thinning can be beneficial as the thinned portions
offer little resistance to compression or shear when touched by a person's skin. For example,
when a person touches the polymeric web 80 on the side exhibiting hair-like fibrils 225, the finger
tips first contact closed distal ends 226 of hair-like fibrils 225. Due to the high aspect ratio of
hair-like fibrils 225, and, it is believed, to the wall thinning of the film at or near the distal ends
226, the hair-like fibrils offer little resistance to the compression or shear imposed on the web by
the person's fingers. This lack of resistance is registered as a feeling of softness, much like the
feeling of a velour fabric. In fact, it has been found that polymeric webs of the present invention
can provide for a feeling of softness equal to or greater than tbat of prior art polymeric webs, such
as the web disclosed in Curro '643.
It should be noted that a fluid impermeable web having only the hair-like fibrils as
disclosed herein, and not having macroscopic apertures, can offer softness for any application in
which fluid permeability is not required. Thus, in one embodiment of the present invention, the
invention can be described as a polymeric web 80 exhibiting a soft and silky tactile impression on
at least one surface thereof, the silky feeling surface of the web 80 exhibiting a pattern of discrete
hair-like fibrils 225, each of the hair-like fibrils 225 being a protruded extension of the web
surface and having a side wall 227 defining an open proximal! portion 229 and a closed distal
portion 226, the hair-like fibrils maximum lateral cross-sectional dimension at or near said open
proximal portion, exhibiting a cross-sectional diameter d of between about 50 microns (about
0.002 inch) to about 76 microns (about 0.003 inch), and can be at least 100 microns (0.004
inches) 130 microns (0.005 inches). The hair-like fibrils can have an aspect ratio from 0.5 to 3.
For disposable absorbent articles, where a topsheet having a fluid permeable, three-
dimensional structure is desired, the invention can be described as a polymeric web 80 exhibiting
a soft and silky tactile impression on at least one surface 90 thereof, the silky feeling surface 90 of
the web exhibiting a pattern of discrete hair-like fibrils 225, each of the hair-like fibrils 225 being
a protruded extension of the web surface 90 and having a side wall 227 defining an open proximal
portion 229 and a closed distal portion 226, the hair-like fibrils exhibiting an average cross-
sectional diameter d of between 50 microns (0.002 inches) 130 microns (0.005 inches), and an
aspect ratio from at least 0.5,1,1.5,2, or 3 and wherein the web 80 further exhibits a
macroscopically expanded, three-dimensional pattern of macroscopic surface aberrations, e.g.,
primary apertures 71 superposed thereon, the macroscopic surface aberrations 71 being oppositely
oriented from the hair-like fibrils 225, that is, the primary apertures extend from a first surface 90
to a second surface 85 of polymeric web 80.
The "area density" of the hair-like fibrils 225, which is the number of hair-like fibrils 225
per unit area of first surface 90, can be optimized for use in absorbent articles. In general, the
center-to-center spacing can be optimized for adequate tactile impression, while at the same time
minimizing fiber-to-fiber entrapment of fluid. Currently, it is believed that a center-to-center
spacing of about 100 microns to 250 microns (about 0.004 inch to about 0.010 inch) is optimal for
use in sanitary napkins. Minimizing entrapment of menses between fibers improves the surface
cleanliness of the sanitary napkin, which, in turn improves the cleanliness and skin health of the
wearer.
In one embodiment, "superposed thereon" means that the polymeric web appears
generally as shown in FIQ. 3, wherein the pattern of discrete hair-like fibrils 225 is disposed on
the land areas 81 of the interconnecting members only, i.e., only on the first surface 90 of web 80.
However, conceptually, it is contemplated that "superposed thereon" could also cover an
embodiment (not shown) in which the pattern of discrete hair-like fibrils 225 extends into
macroapertures 71, for example on side walls 83 of the interconnecting members. In other
embodiments, hair-like fibrils 225 are disposed only in certain predetermined regions of web 80.
For example, a topsheet for a sanitary napkin can have a central region having hair-like fibrils
225, and the remainder of the topsheet being free from hair-like fibrils 225.
Precursor web 120 can be any polymeric film having sufficient material properties to be
formed into the web of the present invention by the hydroforrning process described herein. That
is, precursor web 120 must have sufficient yield properties such that the precursor web 120 can be
strained without rupture to an extent to produce hair-like fibrils 225 and, in the case of a three-
dimensional, macroscopically-apertured, formed film, rupture to form macroapertures 71. As
disclosed more fully below, process conditions such as temperature can be varied for a given
polymer to permit it to stretch with or without rupture to form the web of the present invention.
In general, therefore, it has been found that preferred starting [materials to be used as the precursor
web 120 for producing the web 80 of the present invention exhibit a low yield and high-
elongation characteristics. In addition, the starting films preferably strain harden. Examples of
films suitable for use as the precursor web 120 in the present invention include films of low
density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and blends of linear
low-density polyethylene and low density polyethylene (LDPE/LLDPE).
Precursor web 120 must also be sufficiently deformable and have sufficient ductility for
use as a polymeric web of the present invention. The term "deformable" as used herein describes
a material which, when stretched beyond its elastic limit, will! substantially retain its newly
formed conformation.
One material found suitable for use as a precursor web 120 of the present invention is
DOWLEX 2045A polyethylene resin, available from The Dow Chemical Company, Midland, MI,
USA. A film of mis material having a thickness of 20 microns can have a tensile yield of at least
12 MPa; an ultimate tensile of at least 53 MPa; an ultimate elongation of at least 635%; and a
tensile modulus (2% Secant) of at least 210 MPa (each of the above measures determined
according to ASTM D 882).
Precursor web 120 can be a laminate of two or more webs, and can be a co-extruded
laminate. For example, precursor web 120 can comprise two layers as shown in FIG. 4, and
precursor web 120 can comprise three layers, wherein the inner most layer is referred to as a core
layer, and the two outermost layers are referred to as skin layers. In one embodiment precursor
web 120 comprises a three layer coextruded laminate having an overall thickness of about 25
microns (0.001 in.), with the core layer having a thickness of about 18 microns (0.0007 in.); and
each skin layer having a thickness of about 3.5 microns (0.00015 in.). In general, for use as a
topsheet in sanitary napkins, precursor web 120 should have an overall thickness (sometimes
referred to as caliper) of at least about 10 microns and less than about 100 microns. The thickness
of precursor web 120 can be about 15 microns, 20 microns, 25 microns, 30 microns, 35 microns,
40 microns, 45 microns, or 60 microns. In general, the ability to form high area density (or low
average center-to-center spacing C) hair-like fibrils 225 on web 80 is limited by the thickness of
precursorweb 120. For example, it is believed that the center-to-center spacing C of two adjacent
hair-like fibrils 225 should be greater than twice the thickness of precursor web 120 to permit
adequate and complete three-dimensional web formation between adjacent protrusions 2250 of
forming structure 350 as disclosed more fully below.
The precursor web 120 preferably comprises a surfactant. In a three layer laminate, the
core layer can comprise a surfactant while the outer layers are initially devoid of surfactants.
Preferred surfactants include those from non-ionic families such as: alcohol ethoxylates,
alkylphenol ethoxylates, carboxylic acid esters, glycerol esters, polyoxyethylene esters of fatty
acids, polyoxyethylene esters of aliphatic carboxylic acids related to abietic acid, anhydrosorbitol
esters, etyhoxylated anhydrosorbitol esters, ethoxylated natural fats, oils, and waxes, glycol esters
of fatty acids, carboxylic amides, diethanolamine condensates, and polyalkyleneoxide block
copolymers. Molecular weights of surfactants selected for the present invention may range from
about 200 grams per mole to about 10,000 grams per mole. Preferred surfactants have a
molecular weight from about 300 to about 1,000 grams per mole.
The surfactant level initially blended into precursor web 120 (or optionally the core layer
in a three layer laminate) can be as much as 10 percent by weight of the total multilayer structure.
Surfactants in the preferred molecular weight range (300-1,000 grams/mole) can be added at
lower levels, generally at or below about 5 weight percent of the total multilayer structure.
The precursor web 120 can also comprise titanium dioxide in the polymer blend.
Titanium dioxide can provide for greater opacity of the finished web 80. Titanium dioxide can be
added at up to about 10 percent by weight to low density polyethylene for blending into the
precursor web 120 material.
Other additives, such as particulate material, e.g., calcium carbonate (CaC03), particulate
skin treatments or protectants, or odor-absorbing actives, e.g., zeolites, can be added in one or
more layers of precursor web 120. In some embodiments, webs 80 comprising particulate matter,
when used in skin-contacting applications, can permit actives to contact the skin in a very direct
and efficient manner. Specifically, in some embodiments, formation of hair-like fibrils 225 can
expose particulate matter at or near the distal ends thereof. Therefore, actives such as skin care
agents can be localized at or near distal ends 226 to permit direct skin contact with such skin care
agents when the web 80 is used in skin contacting applications.
The precursor web 120 can be processed using conventional procedures for producing
multilayer films on conventional coextruded film-making equipment Where layers comprising
blends are required, pellets of the above described components can be first dry blended and then
melt mixed in the extruder feeding that layer. Alternatively, if insufficient mixing occurs in the
extruder, the pellets can be first dry blended and then melt mixed in a pre-compounding extruder
followed by repelletization prior to film extrusion. Suitable methods for making precursor web
120 are disclosed in U.S. Pat. No. 5,520,875, issued to Wnuk et al. on May 28,1996 and U.S.
Pat No. 6,228,462, issued to Lee et al. on May 8,2001; both patents the disclosure of which is
incorporated herein by reference.
A fluid pervious polymeric web of the present invention can be utilized as a topsheet on a
catamenial device, such as a sanitary napkin. For example, a polymeric web 80 of the present
invention exhibiting a macroscopically expanded, three-dimensional pattern of macroscopic
surface aberrations in the form of primary apertures 71 combines softness properties with
excellent fluid rewet properties (i.e., reduced fluid rewet compared to previous webs, such as the
web of Curro'643).
FIG. 7 is a top plan view of a sanitary napkin 20 with portions cut away to more clearly
show the construction of the napkin 20, including topsheet 22, which can comprise a polymeric
web 80 of the present invention. It should be understood that the polymeric web 80 of the present
invention can also be utilized in other absorbent articles such as pantyliners, interlabial devices,
diapers, training pants, incontinent devices, wound dressings and the like. It also should be
understood, that the present invention is not limited to the particular type or configuration of the
sanitary napkin 20 shown in FIG 7, which is simply a representative non-limiting example.
As shown in FIG. 8, the sanitary napkin 20 has two surfaces, a body-facing surface 20a
and an opposed garment-facing surface 20b. The body-facing surface 20a is intended to be worn
adjacent to the body of the wearer. The garment-facing surface 20b is intended to be placed
adjacent to the wearer's undergarments when the sanitary napkin 20 is worn.
The sanitary napkin 20 has two centerlines, a longitudinal centerline "1" and a transverse
centerline "t". The term "longitudinal", as used herein, refers to a line, axis or direction in the
plane of the sanitary napkin 20 that is generally aligned with (e.g., approximately parallel to) a
vertical plane which bisects a standing wearer into left and right body halves when the sanitary
napkin 20 is worn. The terms "transverse" or "lateral" as usedherein, are interchangeable, and
refer to a line, axis or direction which lies within the plane of the sanitary napkin 20 that is
generally perpendicular to the longitudinal direction.
As shown in FIG. 7, the sanitary napkin 20 comprises a liquid pervious topsheet 22,
which can comprise web 80 of the present invention, a liquid impervious backsheet 23 joined with
the liquid pervious topsheet 22, and an absorbent core 24 positioned between the liquid pervious
topsheet 22 and the liquid impervious backsheet 23. FIG. 7 also shows that the sanitary napkin 20
has a periphery 30 which is defined by the outer edges of the sanitary napkin 20 in which the
longitudinal edges (or "side edges") are designated 31 and the end edges (or "ends") are
designated 32.
Sanitary napkin 20 preferably includes optional sidefkps or "wings" 34 that can be folded
around the crotch portion of the wearer's panties. The side flaps 34 can serve a number of
purposes, including, but not limited to protecting the wearer's panties from soiling and keeping the
sanitary napkin secured to the wearer's panties.
FIG. 8 is a cross-sectional view of the sanitary napkin taken along section line 8—8 of
FIG. 7. As can be seen in FIG. 8, the sanitary napkin 20 preferably includes adhesive fastening
means 36 for attaching the sanitary napkin 20 to the undergarment of the wearer. Removable
release liners 37 cover the adhesive fastening means 36 to keep the adhesive from sticking to a
surface other than the crotch portion of the undergarment prio^ to use. In addition to having a
longitudinal direction and a transverse direction, the sanitary napkin 20 also has a "z"direction or
axis, which is the direction proceeding down through the liquid pervious topsheet 22 and into
whatever fluid storage core 24 that may be provided. A continuous path between the liquid
pervious topsheet 22 and underlying layer or layers of the articles herein permits fluid to be drawn
in the "z" direction and away from the topsheet of the article into its ultimate storage layer. In
some embodiments, the continuous path will have a gradient Of increasing capillary attraction,
which facilitates fluid flow down into the storage medium.
In FIG. 9 there is shown single-phase web process for debossing and drying (if necessary)
a continuous polymeric web 80 of the present invention. By single-phase is meant that the
process uses only one three-dimensional forming structure. By continuous is meant to distinguish
the described process from a batch process in which individual, discrete samples of web are made,
often referred to as hand sheets. "While it is recognized that webs of the present invention can be
batch-processed using the structures described for the continuous process, a continuous process is
the preferred method for commercially making a polymeric web of the present invention. Further,
while the process described with respect to FIG. 9 is primarily designed to form macroscopically-
expanded webs having hair-like fibrils 225 and primary apertures, e.g., apertures 71 of web 80, it
is believed that a hydroforming process can be utilized to form a web having only hair-like fibrils
by suitably modifying the forming structure to have only protrusions 2250.
Polymeric web 80 of the present invention can be formed by a hydroforming process on a
single three-dimensional forming structure 350 and can also be annealed and/or dried on the
forming structure 350 prior to rewinding the web into roll stock for further processing. The three-
dimensional structures of a polymeric web, e.g., polymeric web 80 shown in FIG. 4, are formed
by forcing the web to conform to the forming structure 350, which rotates about stationary
forming drum 518. Forming structure 350 is described more fully below, but, in general, it is a
three-dimensional form to which the precursor web 120 is forced to conform.
Precursor web 120 can be extruded and chilled immediately prior to being fed directly
onto the surface of forming structure 350, or it can be fed froni a supply roll, as shown by supply
roll 501 in FIG. 9. In some embodiments it is preferred that the temperature of the precursor web
120 be elevated sufficiently to soften it and make it more conformable to the forming structure
350. The temperature of precursor web 120 can be elevated by applying hot air or steam to the
web or by passing the web through heated nip rolls, prior to subjecting it to the forming process.
In the process described in FIG. 9, precursor web 120 is fed in a substantially planar
condition in the machine direction (MD) from a supply roll 501 onto the surface of forming
structure 350. Forming structure 350 rotates at a speed such that the tangential surface velocity of
the forming structure 350 substantially matches that of the linear velocity of precursor web 120 in
the machine direction, so that during the hydroforming process the web is substantially stationary
relative to forming structure 350.
Once precursor web 120 is adjacent to and being "carried on", so to speak, the forming
structure 350, precursor web 120 is directed over stationary vacuum chamber 520 which is
interior to forming drum 518. Although the hydroforming process described herein can be
accomplished to some degree without vacuum chambers, in general, vacuum chambers aid in
better three-dimensional web formation as well as liquid removal. As precursor web 120 passes
over vacuum chamber 520, the outwardly-exposed surface of precursor web 120 is impinged upon
by a liquid jet 540 discharged from high pressure liquid jet nozzle 535 between a pair of
stationary liquid baffles 525 and 530 which served to help localize splashing liquid. The effect of
the liquid jet 540 is to cause the precursor web to conform to forming structure 350. As precursor
web conforms to forming structure 350, both the hair-like fibrils 225 and the primary apertures 71
can be formed. As primary apertures 71 form, vacuum from vacuum chamber 520 aids in
removing excess liquid from the web, and, in some cases aids in forming precursor web 120 to
forming structure 350. As precursor web 120 is passed under the influence of high pressure liquid
jet 540, it is permanently deformed to conform to the forming structure 350, thereby being formed
into three-dimensional, macroscopically-expanded polymeric web 80 of the present invention.
In the process described with reference to FIG. 9, a single liquid jet 540 is described as
forming both the hair-like fibrils 225 and the primary apertures 71. In another embodiment,
additional liquid (or fluid) jets can be used to form the three-dimensional web structures in
multiple stages. For example, a first fluid, such as water, can impinge precursor web 120 to form
macroapertures 71 in a first stage, and following the first stage, a second fluid, such as hot water
or air (optionally in combination with a vacuum chamber) can impinge the partially-formed web
to further form the hair-like fibrils 225 in a second stage.
In the process described in FIG. 9, liquid jets 540 and/or drying means 590 can be
replaced by re-heat means. Re-heat means refers to means for directing streams of heated gases,
such as air, such that the heated air, alone or in combination with vacuum from vacuum chambers
520 or 555, is sufficient to cause precursor web 120 to conform to forming structure 350. Re-heat
means are known in the art, for example as disclosed in US Pat. No. 4,806,303 issued to Bianco et
al. In general, a re-heat means comprises an air blower and a heater as well as a nozzle to direct
forced, heated air onto the surface of a web. In one embodiment the air exiting the nozzle can be
between 220 and 305 degrees centigrade and the precursor web 120 can be moved under or across
the heated air stream at about 25 meters per minute. In one embodiment vacuum can be
maintained at about 365 mm Hg. In embodiments where re-heat means replaces liquid jets 540,
drying means S90 are not necessary, but can be utilized if desired, for example as annealing
means or further forming means.
Without being bound by theory, it is believed that by adjusting the precursor web
properties, the vacuum dwell time, i.e., the time precursor web is adjacent vacuum chambers 520
and/or 555, and/or the level of vacuum, i.e., partial pressure, it is possible to form web 80 on the
apparatus shown in FIG. 9 in a cast process without using any liquid jets 540. That is, by suitably
adjusting the precursor web properties, e.g., thickness, material, temperature, vacuum alone is
sufficient to form a web 80 that conforms to forming structure 350. In a cast process precursor
web 120 is extruded directly onto the surface of forming structure 350 such that web 80 formation
can occur prior to cooling of precursor web 120.
In general, therefore, one fluid (e.g., water or air) or more than one fluid (e.g., water, air)
can be directed to impinge on, and do energetic work on, precursor web 120 in one or more
stages. It is believed that, for thermoplastic precursor webs 120, as the temperature of the
precursor web approaches its melting point, it more easily stretches without rupture to form over
protrusions 2250 of forming structure 350. However, for forming macroapertures it is more
desirable to have relatively high strain rates and relatively rapid rupture, and for forming hair-like
fibrils it is more desirable to have relatively low strain rates and no rupture. Accordingly, in a
two-stage forming process, the temperature of the impinging fluid at first and/or second stages
can be adjusted independently, depending on the dwell time over which each impingement acts
and the temperature of the precursor web 120 to form both macroapertures 71 and high aspect
ratio hair-like fibrils 225 independently.
For making webs suitable for use as a topsheet in a disposable absorbent article, precursor
web 120 can be a polyolefinic film from about 10 microns to about 100 microns in total thickness.
For such precursor webs 120, high pressure liquid jet 540 is typically water at a temperature from
about 15-95 degrees C, operated at a pressure in the range of about 200 psig to about 1200 psig
and a water flow rate in the range of about 18 liters (4 gallons) per minute to about 62 liters (14
gallons) per minute per 25.4 cross-machine direction (CD) mm (1 inch) of width of the precursor
web 120.
After passing beyond the high pressure liquid jet 540, (or jets, as discussed above),
polymeric web 80 of the present invention can be dried while still on forming structure 350. For
example, as shown in FIG. 9, polymeric web 80 can be directed, while still on forming structure
350, under the influence of drying means 590. Drying means 590 can be any of means for
removing, or driving off liquids from polymeric webs, such as radiant heat drying, convective
drying, ultrasonic drying, high velocity air knife drying, and the like. In general, a drying
medium 600 can be utilized, such as heated air, ultrasonic waves, and the like. A stationary
vacuum chamber 555 can be utilized to aid in drying by means of a partial pressure inside
forming drum 518. Drying means 590 can be designed to drive liquid off of polymeric web 80
and into vacuum chamber 555. Baffles 570 and 580 can be utilized to locally contain any liquid
that gets removed and does not enter vacuum chamber 555. Baffles 570 and 580 can also serve to
localize and direct heat or heated air used for drying.
Using a heated drying medium 600 has an additional benefit for making webs 80 of the
present invention. Prior art macroscopically-expanded, three-dimensional polymeric webs, such
as the webs disclosed in the aforementioned Curro '643, are dried in a separate process after being
removed form their respective forming structures. These webs are typically wound onto a roll for
storage until needed for web processing of disposable articles, for example. One problem
associated with prior art webs is the compression setting that occurs during winding and storage.
Without being bound by theory, it is believed that three-dimensional polyethylene webs can
experience a secondary crystallization over time which "locks in" the collapsed, wound state of
the web. It has been found that by first annealing three-dimensional polymeric webs by
subjecting them to elevated temperatures for a sufficient time, this observed compression set is
reduced or prevented altogether. In general, however, it is difficult to subject prior art webs to
the requisite temperatures due to the relatively fragile structure. That is, if a prior art web is
subjected to annealing temperatures, the web tends to lose me three-dimensional structure formed
on the forming structure. For this reason, therefore, drying the web while still on the forming
structure provides a significant processing benefit by permitting processing with sufficiently high
annealing temperatures to anneal the web, while at the same time drying it The annealing
temperature will vary depending on the time of drying, the polymer used and the thickness of the
web, but, in general, for polyolefinic webs, a drying/annealing temperature of between about 50-
250 degrees C is sufficient.
After polymeric web 80 passes the drying (or drying/annealing) stage of the process it can
be removed from the forming structure 350 about roller 610 and is thereafter rewound or fed
directly to subsequent converting operations.
A forming structure of the present invention, such as forming structure 350 referred to
with respect to FIG. 9, is necessary for making a web of the present invention. The forming
structure is sometimes referred to as a forming screen. FIG. 10 shows a portion of a forming
structure of the present invention 350 in partial perspective view. The forming structure 350
exhibits a plurality of forming structure apertures 710 defined by forming structure
interconnecting members 910. Forming structure apertures 710 permit fluid ccinrnunication
between opposing surfaces, mat is, between forming structure first surface 900 in the plane of the
first surface 1020 and forming structure second surface 850 in the plane of the second surface
1060. Forming structure sidewall portions 830 extend generally between the forming structure
first surface 900 and forming structure second surface 850. Protrusions 2200 extend from
forming structure first surface 900 to form generally columnar, pillar-like forms.
A comparison of FIG. 10 with FIG. 3 shows the general correspondence of forming
structure 350 with polymeric web 80 of the present invention. That is, the three-dimensional
protrusions 2250 and depressions (e.g., apertures 710) of forming structure 350 have a one-to-one
correspondence to the hair-like fibrils 225 and primary apertures 71, respectively, of polymeric
web 80. The one-to-one correspondence is necessary to the extent that the forming structure 350
determines the overall dimensions of the polymeric web 80 of the present invention. However,
the distance between plane of the first surface 102 and plane of the second surface 106 of the
polymeric web 80 need not be the same as the distance between the plane of the first surface 1020
and the plane of the second surface 1060 of forming structure 350. This is because the distance
"T" for polymeric web 80, as shown in FIG. 5, is not dependent upon the actual thickness of
forming structure 350, the thickness being the perpendicular distance between the plane of the
first surface 1020 and the plane of the second surface 1060 of forming structure 350.
FIG. 11 is a further enlarged, partial perspective view of the forming structure 350 shown
in FIG. 10, and compares with the similar view of polymeric web 80 in FIG. 4. Protrusions 2250
can be made by methods described below to extend from first surface 900 to a distal end 2260.
As shown in the further enlarged view of FIG. 12, protrusions 2250 can have a height hp
measured from a minimum amplitude measured from first surface 900 between adjacent
protrusions to distal end 2260. Protrusion height hp can be at least about 50 microns (about 0.002
inch) and can be at least about 76 microns (about 0.003 inch), and can be at least about 152
microns (about 0.006 inch), and can be at least about 250 microns (about 0.010 inch), and can be
at least about 381 microns (about 0.015 inch). Protrusions 2250 have a diameter dp, which for a
generally cylindrical structure is the outside diameter. For non-uniform cross-sections, and/or
non-cylindrical structures of protrusions 2250, diameter dp is measured as the average cross-
sectional dimension of protrusions at Vz the height hp of the protrusions 2250, as shown in FIG.
12. Protrusion diameter dp can be about 50 microns (about 0.002 inch), and can be at least about
66 microns, and can be about 76 microns (about 0.003 inch), and can be at least about 127
microns (about 0.005 inch). Thus, for each protrusion 2250, a protrusion aspect ratio, defined as
hp/dp, can be determined. Protrusions 2250 can have an aspect ratio hp/dp of at least 1, and as
high as 3 or more. The aspect ratio can be at least about 5 and can be about 6. In one
embodiment, protrusions had a substantially uniform diameter of about 66 microns over a height
of about 105 microns, for an aspect ratio of about 1.6. The protrusions 2250 can have a center-to-
center spacing Cp between two adjacent protrusions 2250 of between about 100 microns (about
0.004 inch) to about 250 microns (about 0.010 inch). In one embodiment the center-to-center
spacing was 179 microns. In general, it is believed that the actual distance between two adjacent
protrusions 2250 (i.e., a "side-to-side" dimension) should be greater than twice the thickness t of
precursor web 120 to ensure adequate deformation of precursor web 120 between adjacent
protrusions 2250.
In general, because the actual height hp of each individual protrusion 2250 may vary, an
average height hpaTg of a plurality of protrusions 2250 can be determined by determining a
protrusion average minimum amplitude Ap,*, and a protrusion average maximum amplitude
Apmax over a predetermined area of forming structure 350. Likewise, for varying cross-sectional
dimensions, an average protrusion diameter dp^vg can be determined for a plurality of protrusions
2250. Such amplitude and other dimensional measurements can be made by any method known
in the art, such as by computer aided scanning microscopy and related data processing.
Therefore, an average aspect ratio of the protrusions 2250, ARpaVg for a predetermined portion of
the forming structure 350 can be expressed as hpavg/dpavg The dimensions hp and dp for
protrusions 2250 can be indirectly determined based on the known specifications for making
forming structure 350, as disclosed more fully below.
In one embodiment the diameter of protrusions 2250 is constant or decreases with
increasing amplitude. As shown in FIG. 12, for example, the diameter, or largest lateral cross-
sectional dimension, of protrusions 2250 is a maximum near first surface 900 and steadily
decreases to distal end 2260. This structure is believed to be necessary to ensure that the
polymeric web 80 can be readily removed from the forming structure 350.
Forming structure 350 can be made of any material that can be formed to have protrusions
2250 having the necessary dimensions to make a web of the present invention, is dimensionally
stable over process temperature ranges experienced by forming structure 350, has a tensile
modulus of at least about 5 MPa, more preferably at least about 10M Pa, more preferably at least
about 30 MPa more preferably at least about 100-200 MPa, and more preferably at least about
400 MPa, a yield strength of at least about 2 MPa, more preferably at least about 5 MPa more
preferably at least about 10 MPa, more preferably at least about IS MPa, and a strain at break of
at least about 1%, preferably at least about 5%, more preferably at least about 10%. It has been
found mat relatively tall, high aspect ratio protrusions form better webs as the modulus of the
material of the forming structure increases, as long as it has sufficient strain at break (i.e., not too
brittle) so as not to break. For modulus and yield strength data, values can be determined by
testing according to known methods, and can be tested at standard TAPPI conditions at a strain
rate of 100%/minute.
Dimensional stability with respect to thermal expansion is necessary only for commercial
processes as described with respect to FIG. 9, because for some process conditions the forming
structure 350/forming drum 518 interface can be compromised if the forming structure 350
expands or contracts more than the forming drum 518. For batch processing of polymeric webs
of the present invention dimensional stability is not a requirement. However, for all commercial
processes it is necessary that the forming structure be made of a material suitable for the
processing temperature ranges. Process temperature ranges are affected by process conditions
including the temperature of the fluid jet, e.g., liquid jet 540, and the temperature of forming
structure 350, which can be heated, for example. In general, for polyolefinic webs, including
laminated, co-extruded films for use in webs for disposable absorbent articles (i.e., films having a
thickness, t, of about 10-100 microns), a water temperature of between IS degrees C and 95
degrees C can be used. The drying/annealing air temperature can be 2S0 degrees C or less. In
general, process temperatures can be varied throughout a wide range and still make the polymeric
web 80 of the present invention. However, the temperature ranges can be varied to make
polymeric web 80 at optimal rates depending on film thickness, film type, and line speed.
In a preferred embodiment, protrusions 2250 are made integrally with forming structure
350. That is, the forming structure is made as an integrated structure, either by removing material
or by building up material. For example, forming structure 350 having the required relatively
small scale protrusions 2250 can be made by local selective removal of material, such as by
chemical etching, mechanical etching, or by ablating by use of high-energy sources such as
electrical-discharge machines (EDM) or lasers.
Acid etching of steel structures as disclosed in the aforementioned Ahr '045 patent, is
believed to be only capable of making protrusions having an aspect ratio of 1 or less. Without
being bound by theory it is believed that acid etching steel in small, incremental steps may be
result in the high aspect ratios preferred in a forming structure of the present invention, but it is
expected that the resulting protrusion(s) would be severly undercut to have "mushroom" shaped
profiles. It is not currently known by the inventors of the present invention how one might acid
etch steel as taught in Ahr '045 to form the generally cylindrical protrusions 2250 of the present
invention having the requisite aspect ratio. Likewise, forming protrusions on steel by
electroplating is believed to result in "mushroom" shaped protrusions. In bom instances, i.e., acid
etching and electroplating, the mushroom shape is expected due to the nature of the material
removal/deposition. Material would not be removed/deposited only in a general aligned, e.g.,
vertical manner. Therefore, it is currently known to make metal forming structures 350 only by
use of electrical-discharge machines (EDM) or lasers.
A portion of a prototype forming structure 350 made of steel and having protrusions 2250
made by a conventional EDM process is shown in FIGS. 13 and 14. FIG 13 is a photomicrograph
of a forming structure 350 and FIG. 14 is a further enlarged view the forming structure of FIG.
13. As shown in FIG. 13, a steel forming structure has been subjected to an EDM process to form
integral protrusions 2250 having distal ends 2260. The forming structure 350 shown in FIGS. 13
and 14 has depressions 710 generally similarly shaped to those shown in FIG. 3. However, as can
be seen in FIGS. 13 and 14, the structure is less than ideal for making topsheets for absorbent
articles because of the geometrical constraints of both the forming structure 350 prior to the EDM
process, and the EDM process itself. Specifically, as can be seen, first surface 900 of forming
structure interconnecting members 910 is only one protrusion "wide". Also, as can be seen in
FIG. 13, due to the geometrical constraints of the process of EDM, gaps between protrusions 2250
can result. For example, gap 901 in FIG. 13 resulted from the EDM wire being oriented slightly
off parallel from the respective forming structure interconnecting members 910 shown.
Therefore, for commercially successful production of webs suitable for topsheets in disposable
absorbent articles, the forming structure shown in FIG. 13 may not be acceptable. However, it is
clear that suitably shaped protrusions 2250 having the required aspect ratios can be formed. The
protrusions 2250 of the forming structure shown in FIG. 13 have an average height hp,avg of about
275 microns (0.011 inch), and an average diameter of about dpavgof about 100 microns (0.004
inch), defining an average aspect ratio of ARpavg of about 2.7. (Note that the forming screen
shown in FIGS. 13 and 14 is a prototype, and has been processed by EDM on both sides. In
practice, it is only necessary to form protrusions on one side.)
In another method of making forming structure 350, a base material susceptible to laser
modification is laser "etched" to selectively remove material to form protrusions 2250 and
forming structure apertures 710. By "susceptible to laser modification" means that the material
can be selectively removed by laser light in a controlled manner, recognizing that the wavelength
of light used in the laser process, as well as the power level, may need to be matched to the
material (or vice-versa) for optimum results. Currently known materials susceptible to laser
modification include thermoplastics such as polypropylene, acetal resins such as DELRIN® from
DuPont, Wilmington DE, USA, thermosets such as crosslinked polyesters, or epoxies, or even
metals such as aluminum or stainless steel.
In one embodiment a forming structure can be laser machined in a continuous process.
For example, a polymeric material such as DELRIN® can be provided in a cylindrical form as a
base material having a central longitudinal axis, an outer surface, and an inner surface, the outer
surface and inner surface defining a thickness of the base material. A moveable laser source can
be directed generally orthogonal to the outer surface. The moveable laser source can be moveable
in a direction parallel to the central longitudinal axis of the base material. The cylindrical base
material can be rotated about the central longitudinal axis while the laser source machines, or
etches, the outer surface of the base material to remove selected portions of the base material in a
pattern that defines a plurality of protrusions. Each protrusion can be the generally columnar and
pillar-like protrusions 22S0, as disclosed herein. By moving the laser source parallel to the
longitudinal axis of the cylindrical base material as the cylindrical base material rotates, the
relative movements, i.e., rotation and laser movement, can be synchronized such that upon each
complete rotation of cylindrical base material a predetermined pattern of protrusions can be
formed in a continuous process similar to "threads" of a screw.
FIG. 15 is a photomicrograph of laser-etched embodiment of a forming structure 350 of
the present invention. FIG. 16 is an enlarged view of another, but similar, forming structure 350
of the present invention. The forming structures 350 shown in FIGS. 15 and 16 are made by first
forming a polymer layer having formed therein depressions 710, which as shown are generally
"teardrop" shaped and would make generally teardrop shaped primary apertures 71 in web 80 of
the present invention. The depressions 710 can be formed, for example, by laser etching the
depressions first The polymer layer having depressions 710 therein can also be formed by
radiating a liquid photosensitive resin such as a UV-light-curable polymer, through an appropriate
masking layer on an underlying support layer (not shown) such as a foraminous woven backing.
Suitable polymer layers, support layers, masking layers and UV-curing processes are well known
in the art of making paper-making belts and are disclosed in U.S. Pat. No. 5,334,289 issued to
Trokhan et al., on August 2,1994; and U.S. Pat No. 4,529,480 issued to Trokhan on July 16,
1985; and U.S. Pat. No. 6,010,598 issued to Boutilier et al. on Jan. 4,2000, each of these patents,
being hereby incorporated herein by reference for the teaching of structures, resins and curing
techniques. As disclosed in the Boutilier '598 patent, for example, one suitable liquid
photosensitive resin composition is comprised of four components: a prepolymer; monomers;
photoinitiator and antioxidants. A preferred liquid photosensitive resin is Merigraph L-055
available from MacDermid Imaging Technology, Inc. of Wilmington, Del.
After the polymer layer is cured to have depressions 710 the polymer layer is laser etched
to form protrusions 2250 having distal ends 2260. Laser etching can be achieved by known laser
techniques, selecting wavelength, power, and time parameters as necessary to produce the desired
protrusion dimensions. In the forming structure of FIG. 16, protrusions have an average height
hp of 250 microns and an average diameter dp of 85 microns (at Vz height hp) and an aspect ratio
arp of about 2.9.
Therefore, as disclosed above, in one embodiment, depressions 710 can be made in one
manner, and the protrusions in another, by a separate process. For example, depressions 710 can
be preformed in a forming structure "blank" that is subsequently laser machined, i.e., etched, to
have protrusions formed on the land areas between depressions 710. In one embodiment, forming
structure 350 formed as a cured polymer on a support layer can be used as is, with the support
layer being a part of forming structure 350. However, in another embodiment, the cured polymer
can be removed from the support layer and used alone. In this case, it may be desirable to only
partially cure the polymer, remove the support layer 903 and finish fully curing the polymer
material.
A web 80 made on the forming structure shown in FIG. 15 is shown in the
photomicrographs of FIGS. 17 and 18. FIG. 17 is a photomicrograph of a portion of web 80
showing hair-like fibrils 225 and aperture 71. FIG. 18 is a further enlarged view of web 80
showing in more detail hair-like fibrils 225 having closed distal ends 226. The precursor web 120
for the web 80 shown in FIGS. 17 and 18 was made from a 25 micron (0.001 inch) thick Dowlex
2045A precursor film 120.
FIGS. 19 and 20 show greatly enlarged portions of webs 80 made in batch processes on
the forming structure shown in FIGS. 13 and 14 to more closely show details of hair-like fibrils
225. The polymer webs 80 shown in FIGS. 19 and 20 have primary apertures 71 (not shown)
generally in a pentahexagon shape, each having a projected area in the first surface 90 of about
1.4 square millimeters. The spacing between primary apertures 71 is such that the open area
primary apertures 71 as projected in the first surface 90 is up to 65% of total surface area. The
web 80 exhibits about 4,650 hair-like fibrils 225 per square centimeter of first surface 90 area
(about 30,000 hair-like fibrils 225 per square inch). This concentration of hair-like fibrils 225 is
referred to as the "density" or "area density" of hair-like fibrils 225, and represents the number of
hair-like fibrils per unit area of first surface 90, as opposed to total area of polymer web 80. Thus,
the regions of polymer web 80 corresponding to primary apertures 71 do not contribute to the area
when calculating density. In general, the density is determined by the average center-to-center
spacing of the protrusions 2250 on forming structure 350, which is about ISO microns (0.006
inch) for the forming structure shown in FIGS. 13 and 14.
It is believed that a polymer web 80 of the present invention suitable for use as a topsheet
on a disposable absorbent article (e.g., a sanitary napkin) should have a density of hair-like fibrils
225 of at least about 1550 per square centimeter (about 10,000 per square inch). The density of
hair-like fibrils 225 can be about 2325 per square centimeter (about 15,000 per square inch), and
can be about 3100 per square centimeter (about 20,000 per square inch) and can be about 3875
per square centimeter (about 25,000 per square inch). Since for some webs it may be difficult to
determine exactly where first surface 90 begins and ends, density can be approximated by taking
total area of a predetermined portion of polymer web 80 and subtracting out the area of primary
apertures 71 as projected in the first surface 90 of that predetermined portion. The area of
primary apertures 71 can be based on the projected area of the depressions 710 of forming
structure 350. By "projected area" is meant the area of a surface if it were projected onto a plane
parallel to that surface, and can be imagined by analogy, for example, as an "ink stamp" of the
surface.
FIG. 19 is a photomicrograph of a web 80 made from a 25 micron (0.001 inch)
DOWLEX® 2045 A precursor film 120: As shown, the web 80 of FIG. 19 comprises discrete
hair-like fibrils 225, each of the hair-like fibrils 225 being a protruded extension of first surface
90. Each of the hair-like fibrils 225 has a side wall 227 defining an open portion 229 (as shown in
FIG. 5) and a closed distal portion 226. The hair-like fibrils 225 shown have a height of about
211 microns, and a diameter at Vi their height of about 142 microns, resulting in an aspect ratio of
about 1.5.
The web 80 of FIG. 20 comprises discrete hair-like fibrils 225, each of the hair-like fibrils
225 being a protruded extension of first surface 90. Each of the hair-like fibrils 225 has a side
wall 227 defining an open portion 229 (as shown in FIG. 5) and a closed distal portion 226. The
hair-like fibrils 225 shown in FIG. 20 have an aspect ratio AR of at least 1.
The difference between the webs 80 shown in FIGS. 19 and 20 is that the precursor film
120 used to make the polymeric web 80 shown in FIG. 20 was a coextruded four layer
polyethylene film comprising calcium carbonate in one of the outermost layers. Specifically, the
calcium carbonate was added into the polymer melt for the polymer that forms the first surface of
web 80 after formation of hair-like fibrils 225. The four layers comprised polyethylene in the
follow order (1) ExxonMobil NTX-137 at about 42 volume percent; (2) ExxonMobil Exact 4151
at about 16 volume percent; (3) ExxonMobil Exact 4049 at about 32 volume percent; and (4) a
mixture of 57 weight percent Ampacet 10847 with calcium carbonate blended in as a master batch
and 43 weight percent ExxonMobil LD 129, this mixture at a volume percent of about 10 percent
The precursor film 120 had a starting thickness of about 25 microns (0.001 inch).
One interesting and unexpected result of using a CaCG3/PE blend for a skin layer of
precursor film 120 is the formation of regions of roughened outer surfaces 228 at or near the distal
end 226 of hair-like fibrils 225 as can be seen on the web shown in FIG. 20. These regions of
relatively greater surface roughness 228, which have less surface smoothness than the
surrounding surfaces, such as first surface 90, provide for a more cloth-like appearance due to its
inherent low gloss, and an even greater soft and silky tactile impression. Without being bound by
theory, it is believed mat the relatively roughened surface texture of the distal ends of hair-like
fibrils 225 gives greater texture that is experienced as softness to the skin of a person touching the
surface. Without being bound by theory, it is believed that the formation of roughened outer
surfaces at or near the distal end 226 of hair-like fibrils 225 is a result of deep drawing precursor
web having therein particulate matter. It appears that possibly the particulate matter, in this case
CaC03, causes stress concentrations in the film blend that give rise to surface discontinuities. At
the points of maximum strain, i.e., at the point of maximum draw of hair-like fibrils 225, the
surface of the film (i.e., precursor film 120) breaks up, exposing particulate matter on the surface
of the hair-like fibrils 225.
Therefore, in one embodiment polymer web 80 can be described as having hair-like
fibrils 225 in which at least a portion near the distal end 226 thereof exhibits regions of relatively
greater surface roughness 228 than the remaining portions. By using different additive particulate
matter, the regions of relatively greater surface roughness 228 can provide for other benefits. For
example, particulate skin treatments or protectants or odor-absorbing actives can be used.
Importantly, webs 80 comprising particulate matter permit actives to be delivered to the skin of a
wearer of an article using web 80 in a very direct and efficient manner.
In general, it is believed that any non-diffusing ingredient (particulate and non-
particulate) blended into the melt of a polymer of precursor web 120 can be exposed upon strain
of the polymer near the distal end of hair-like fibrils 225. Specifically, actives such as skin care
agents can be localized substantially at or near distal ends 226 which can be the primary skin
contact surfaces for web 80. Other known methods of imparting localized strain to polymeric
films can also serve to expose non-diffusing ingredients in layers. For example, embossing, ring
rolling, thermovacuum forming, and other known processes can provide for localized rupture and
exposure of active ingredients of polymer films.
Other methods of making forming structure 350 include building up the structure by way
of localized electroplating, 3-D deposition processes, or photoresist techniques. One 3-D
deposition process is a sintering process. Sintering is similar to stereo lithography in which layers
of powdered metal are built up to produce a final work piece. However, it is believed that
sintering processes may be limited in resolution. Photoresist techniques include forming a three
dimensional structure by use of an appropriate mask over a liquid photosensitive resin, such as
the UV-curable polymer disclosed above. UV curing is effective at curing only the portions of a
liquid resin exposed to UV light from a UV light source. The remaining (uncured) portions of the
liquid resin can then be washed off, leaving behind only the cured portions. The liquid resin UV-
curable polymer can be placed on a tray, for example, to a desired depth or thickness and
appropriately masked and UV light-cured to selectively cure the portions to be protrusions 2250
and to not cure the portions that will be the apertures 710.
In another embodiment, a flexible polymeric forming structure 350 as shown in FIGS. 21
and 22 can be formed from the polymerization of a UV-curable polymer on an air-permeable
backing screen 430. First surface 900 defines apertures 710 which, in the illustrated embodiment
are hexagons in a bilaterally staggered array. It is to be understood that, as before, a variety of
shapes and orientations of apertures 710 can be used. FIG. 22 illustrates a cross sectional view of
that portion of forming structure 350 shown in FIG. 28 as taken along line 22-22. Machine
direction reinforcing strands 420 and cross direction reinforcing strands 410 are shown in both
FIGS. 21 and 22. Together machine direction reinforcing strands 420 and cross direction
reinforcing strands 410 combine to form a foraminous woven element 430. One purpose of the
reinforcing strands is to strengthen the flexible polymeric forming structure 350. As shown,
reinforcing strands 410 and 420 can be round and can be provided as a square weave fabric
around which the UV-curable resin has cured. Any convenient filament size in any convenient
weave can be used, although, in general, (he more open the weave the better. A more open weave
generally results in better air flow through the apertures 710. Better air flow results in better, i.e.,
more economical, hydroforming when forming structure 350 is used to form a polymeric web,
such as polymeric web 80. In one embodiment forming structure 350 430 is a metal screen, such
as is commonly used on household doors and windows. In one embodiment the metal screen is an
18X16 mesh bright aluminum screening having a filament diameter for both machine direction
filaments 420 and cross direction filaments 410 of 0.24 mm, available as Hanover Wire Cloth
from Star Brand Screening, Hanover, PA, USA, having.
As shown in FIGS. 21 and 22, protrusions 2250 extend from first surface 900 and have
distal ends 2260 that are generally rounded in shape. In another embodiment, as shown in the
photomicrograph of FIG. 26, the distal ends can be generally flattened into a plateau. The
forming structure shown in FIG. 26 is a flexible polymeric forming structure formed by a two-
stage process of polymerizing a UV-curable resin.
One two-stage method for making flexible polymeric forming structure 350, such as the
forming structure shown in FIGS. 24-26, is described with reference to FIG. 23. The method
described herein makes forming structures 350 having a combination of relatively large openings,
i.e., depressions 710, and relatively fine protrusions, i.e., protrusions 2250. In the preferred
embodiment illustrated in FIG. 23, the method described herein makes continuous belted forming
structures 351. In broad outline, the method involves using a photosensitive resin to construct in
and about a foraminous element a solid, polymeric framework which delineates the preselected
patterns of the relatively large depressions 710 and relatively fine protrusions 2250 of forming
structure 350 (or belted forming structure 351). More particularly, the method comprises a two
stage resin casting process including the steps of:
a. Applying a backing film to the working surface of a forming unit;
b. Juxtaposing a foraminous element to the backing film so that the backing film is
interposed between the foraminous element and the forming unit;
c. Applying a coating of liquid photosensitive resin to the surfaces of the foraminous
element;
d. Controlling the thickness of the coating to a preselected value;
e. Juxtaposing in contacting relationship with the coating of photosensitive resin a mask
comprising both opaque and transparent regions where the opaque regions define a
preselected pattern corresponding to depressions 710;
f. Exposing the liquid photosensitive resin to light having an activating wavelength
through the mask thereby inducing at least partial curing of the photosensitive resin in
those regions which are in register with the transparent regions of the mask; and
g. Removing from the composite foraminous element/partially cured resin substantially
all the uncured liquid photosensitive resin;
h. Repeating one time steps a-g with a different controlled thickness (e.g., a greater
thickness, such as a thickness corresponding to h£2 in FIG. 22) in step (d) and a
different mask in step (e), the mask in step (e) comprising both opaque and
transparent regions where the transparent regions define a preselected pattern
corresponding to protrusions 2250;
L Immersing the foraminous element/cured resin in qn oxygen-free environment such as
a water bath or other aqueous solution;
j. Exposing the foraminous element/partially cured resin to light having an activating
wavelength through the mask thereby inducing full curing of the photosensitive resin,
resulting in the finished belted forming structure.
The exact apparatus (or equipment) used in the practice of the present invention is
immaterial so long as it can, in fact, be used to practice the present invention. After reading the
whole of the following description, one of ordinary skill of the art will be able to select
appropriate apparatus to perform the steps indicated above. A preferred embodiment of an
apparatus which can be used in the practice of this invention to construct a forming structure in
the form of an endless belt is shown in schematic outline in FIG. 23. For convenience, the
invention will be described in terms of that apparatus.
The first step of the process is applying a backing film to the working surface of a
forming unit. In FIG. 23, forming unit 613 has working surface 612 and is indicated as being a
circular element; it is preferably a rotatable drum. The diameter of the forming unit 613 and its
length are selected for convenience. Its diameter should be great enough so that the backing film
and the foraminous element are not unduly curved during the process. It must also be large
enough in diameter that there is sufficient distance of travel about its surface so that the necessary
steps can be accomplished as the forming unit 613 is rotating. The length of the forming unit 613
is selected according to the width of the forming structure 350 being constructed. Forming unit
613 is rotated by a drive means not illustrated. Optionally, and preferably, working surface 612
absorbs light of the activating wavelength. Preferably, forming unit 613 is provided with means
for insuring that backing film 653 is maintained in close contact with working surface 612.
Backing film 653 can be, for example, adhesively secured to working surface 612 or forming unit
613 can be provided with means for securing backing film 653 to working surface 612 through
the influence of a vacuum applied through a plurality of closely spaced, small orifices across
working surface 612 of forming unit 613. Preferably, backing film 653 is held against working
surface 612 by tensioning means not shown in FIG. 23.
Backing film 653 can be introduced into the system from backing film supply roll 631 by
unwinding it therefrom and causing it to travel in the direction indicated by directional arrow D3.
Backing film 653 contacts working surface 612 of forming unit 613, is temporarily constrained
against working surface 612 by the means discussed hereinbefore, travels with forming unit 613
as the latter rotates, is eventually separated from working surface 612, and travels to backing film
take-up roll 632 where it is rewound.
In the embodiment illustrated in FIG. 23, backing film 653 is designed for a single use
after which it is discarded. In an alternate arrangement, backing film 653 can take the form of an
endless belt traveling about a series of return rolls where it is cleaned as appropriate and reused.
Necessary drive means, guide rolls, and the like are not illustrated in FIG. 23. The function of
the backing film 653 is to protect the working surface 612 of the forming unit 613 and to facilitate
removal of the partially cured forming structure 350 from the forming unit The film can be any
flexible, smooth, planar material such as polyethylene or polyester sheeting. Preferably, the
backing film 653 is made from polypropylene and is from about 0.01 to about 0.1 millimeter
(mm) thick.
The second step of the process is the juxtaposing of a foraminous element 601 to the
backing film in such a way that the backing film is interposed between the foraminous element
601 and the forming unit 613. The foraminous element 601 is the material about which the
curable resin is constructed. One suitable foraminous element is a metal wire screen 430 as
illustrated in FIGS. 21 and 22. Screens having polyester filaments are suitable. Screens having
mesh sizes from of about 6 to about 30 filaments per centimeter are suitable. Square weave
screens are suitable as are screens of other, more complex weaves. Filaments having either round
or oval cross sections are preferred. Although advantageous, it is not necessary that the filaments
be transparent to light of the activating wave-length. In addition to screens, foraminous elements
can be provided by woven and nonwoven fabrics, papermaking fabrics, thermoplastic netting, and
the like. The precise nature of the foraminous element selected and its dimensions will be dictated
by the use in which the forming structure 350 will be placed after it is constructed. Since the
forming structure 350 constructed by the apparatus illustrated in FIG. 23 is in the form of an
endless belt, foraminous element 601 is also an endless belt, formed, for example, by seaming
together the ends of a length of screening.
As illustrated in FIG. 23, foraminous element 601 travels in the direction indicated by
directional arrow Dl about return roll 611 up, over, and about forming unit 613 and about return
rolls 614 and 615. Other guide rolls, return rolls, drive means, support rolls and the like can be
utilized as necessary, and some are shown in FIG. 23. Foraminous element 601 is juxtaposed
backing film 653 so that backing film 653 is interposed between foraminous element 601 and
forming unit 613. The specific design desired for the forming structure 350 will dictate the exact
method of juxtaposition. In the preferred embodiment, foraminous element 601 is placed in direct
contacting relation with backing film 653.
When the liquid photosensitive resin 652 is applied to foraminous element 601 from
source 620, the resin 652 will be disposed principally to one side of foraminous element 601 and
foraminous element 601 will, in effect, be located at one surface of the forming structure 350.
Foraminous element 601 can be spaced some finite distance from backing film 653 by any
convenient means, but such arrangement is not usually preferred. Resin source 620 can be a
nozzle, or any of known means for depositing liquid photosensitive resin, including extrusion, slot
coating, and the like.
The third step in the process of this invention is the application of a first layer of coating
of liquid photosensitive resin 652 to the foraminous element 601. The first layer of coating is the
layer that will ultimately comprise the portion of forming structure 350 between the planes of the
first and second surfaces, 1020 and 1060, respectively (shown as bil in FIG. 22). Any technique
by which the liquid material can be applied to the foraminous element 601 is suitable. For
example, nozzle 620 can be used to supply viscous liquid resin. It is necessary that liquid
photosensitive resin 652 be evenly applied across the width of foraminous element 601 prior to
curing and that the requisite quantity of material be applied so as to enter the openings of the
foraminous member 601 as the design of the forming structure 350 requires. For woven
foraminous elements the knuckles, i.e., the raised cross-over points of a woven screen structure,
are preferably in contact with the backing film, so that it will likely not be possible to completely
encase the whole of each filament with photosensitive resin; but as much of each filament as
possible should be encased.
Suitable photosensitive resins can be readily selected from the many available
commercially. They are materials, usually polymers, which cure or cross-link under the influence
of radiation, usually ultraviolet (UV) light) References containing more information about liquid
photo-sensitive resins include Green et al, "Photocross-linkable Resin Systems", J. Macro-Sci.
Revs. Macro Chem., C21 (2),187-273 (1981-82); Bayer, "A Review of Ultraviolet Curing
Technology", Tappi Paper Synthetics Conf. Proa, Sept. 25-27,1978, pp. 167-172; and Schmidle,
"Ultraviolet Curable Flexible Coatings", J. of Coated Fabrics, 8,10-20 (July, 1978). All Ihe
preceding three references are incorporated herein by reference. Especially preferred liquid
photosensitive resins are included in the Merigraph L-055 series of resins made by MacDcrmid
Imaging Technology Inc., Wilmmgtion, DE, USA USA.
The next step in the process of this invention is controlling the thickness of the coating to
a preselected value. The preselected value corresponds to the thickness desired for the forming
structure 350 between first and second surfaces 1020 and 1060, respectively. That is, the
thickness hfi as shown in FIG. 22. When the forming structure 350 is to be used to make the web
80 suitable for use as a topsheet in a disposable absorbent article, it is preferred that hfl be from
about 1 mm to about 2 mm thick. Other applications, of course, can require thicker forming
structures 350 which can be 3 mm thick or thicker.
Any suitable means for controlling the thickness can be used. Illustrated in FIG. 23 is the
use of nip roll 641. The clearance between nip roll 641 and forming unit 613 can be controlled
mechanically by means not shown. The nip, in conjunction with mask 654 and mask guide roll
641, tends to smooth the surface of liquid photosensitive resin 652 and to control its thickness.
The fifth step in the process of the invention comprises juxtaposing a first mask 654 in
contacting relation with the liquid photosensitive resin 652. The purpose of the mask is to shield
certain areas of the liquid photosensitive resin from exposure to light. First mask 654 is
transparent to activating wavelengths of light, e.g., UV light, except for a pattern of opaque
regions corresponding to the pattern of apertures 71 desired in the forming structure 350. A
portion of a suitable first mask 654 showing one pattern of opaque, i.e., shaded, portions 657 and
light-transparent portions 658 is shown in FIG. 27. Note that FIG. 27 shows a measuring scale
superimposed thereunder. The smallest increment of the scale shown is 0.1 mm.
The light-transparent portions 658 of first mask 654, i.e., the areas that are not shielded
from the activating light source correspond to those areas of liquid photosensitive resin that will
be cured to form the connecting members 910 of forming structure 350. Likewise, the opaque
portions 657 of first mask 654 correspond to pattern of the depressions 710 of forming structure
350. First mask 654, can, therefore, have opaque portions 657 corresponding to the partem of
hexagon-shaped depressions of forming structure 350 shown in FIG. 21, or the pentagonal-shaped
depressions 710 shown in FIG. 13, or the teardrop-shaped depressions 710 shown in FIG. 15. In
general, for a forming structure 350 used to form a web 80 for use as a topsheet in a disposable
absorbent article, the opaque portions 657 of first mask 654 should be of a suitable size, shape,
and spacing to provide the necessary structure of apertures 71 for web 80 such that it exhibits
desirable fluid flow properties.
First mask 654 can be any suitable material which can be provided with opaque and
transparent regions. A material in the nature of a flexible film is suitable. The flexible film can be
polyester, polyethylene, or cellulosic or any other suitable material. The opaque regions can be
formed by any convenient means such as photographic or gravure processes, flexographic
processes, and inkjet or rotary screen printing processes. First mask 654 can be an endless loop or
belt (the details of which are not shown) or it can be supplied from one supply roll and transverse
the system to a takeup roll, neither of which is shown in the illustration. First mask 654 travels in
the direction indicated by directional arrow D4, turns under nip roll 641 where it is brought into
contact with the surface of liquid photosensitive resin 652, travels to mask guide roll 642 in the
vicinity of which it is removed from contact with the resin. In this particular embodiment, the
control of the thickness of the resin and the juxtaposition of the mask occur simultaneously.
The sixth step of the process of this invention comprises exposing the liquid
photosensitive resin 652 to light of an activating wavelength through the first mask 654 thereby
inducing at least partial curing of the resin in those regions which are in register with the
transparent regions 658 of first mask 654. The resin need not be fully cured in this step, but at
least partial curing is achieved when exposed resin retains its desired shape during post-light-
exposure steps, such as washing away non-cured resin, as described below. In the embodiment
illustrated in FIG. 23, backing film 653, foraminous element 601, liquid photosensitive resin 652,
and mask 654 all form a unit traveling together from nip roll 641 to the vicinity of mask guide roll
642. Intermediate nip roll 641 and mask guide roll 642 and positioned at a location where backing
film 653 and foraminous element 601 are still juxtaposed forming unit 613, liquid photosensitive
resin 652 is exposed to light of an activating wavelength as supplied by exposure lamp 655.
Exposure lamp 655 is selected to provide ulumination primarily within the wavelength which
causes curing of the liquid photosensitive resin. That wavelength is a characteristic of the liquid
photosensitive resin. In a preferred embodiment the resin is UV-light curable and exposure lamp
655 is a UV light source. Any suitable source of illumination, such as mercury arc, pulsed xenon,
electrodeless, and fluorescent lamps, can be used.
As described above, when the liquid photosensitive resin is exposed to light of the
appropriate wavelength, curing is induced in the exposed portions of the resin. Curing is generally
manifested by a solidification of the resin in the exposed areas. Conversely, the unexposed
regions remain fluid. The intensity of the illumination and its duration depend upon the degree of
curing required in the exposed areas. The absolute values of the exposure intensity and time
depend upon the chemical nature of the resin, its photo characteristics, the thickness of the resin
coating, and the pattern selected. Further, the intensity of the exposure and the angle of incidence
of the light can have an important effect on the presence or absence of taper in the walls of
connecting members 910 through the thickness hfl of forming structure 350. Accordingly, the
light can be collimated to achieve the desired degree of taper.
The seventh step in the process is removing from the cured or partially-cured composite
of foraminous element/partly cured resin 621 substantially all of the uncured liquid photosensitive
resin. That is to say, the resin which has been shielded from exposure to light is removed from the
system. In the embodiment shown in FIG. 23, at a point in the vicinity of mask guide roll 642,
first mask 654 and backing film 653 are physically separated from the composite comprising
foraminous element 601 and the now partly cured resin 621. The composite of foraminous
element 601 and partly cured resin 621 travels to the vicinity of first resin removal shoe 623. A
vacuum is applied to one surface of the composite at first resin removal shoe 623 so that a
substantial quantity of the liquid (uncured) photosensitive resin is removed from the composite.
As the composite travels farther, it is brought into the vicinity of resin wash shower 624 and resin
wash station drain 625 at which point the composite is thoroughly washed with water or other
suitable liquid to remove more of the remaining liquid (uncured) photosensitive resin, which is
discharged from the system through resin wash station drain 625. The wash shower is preferably
primarily water or an aqueous solution at a temperature above about 115 degrees F.
A second resin removal shoe 626 (or a third, etc., as necessary) can be used for further
removal of residual un-cured resin at this stage of the process. (A second curing station in the
form of a second light source 660 and an air-displacing medium, such as water bath 630, is shown
in FIG. 23 but is not used in the first stage of the process.)
At this stage of the process for making forming structure 350, which is the end of the first
stage, the composite now comprises essentially foraminous element 601 and the partially-cured
resin 621 that represents the portion of forming structure 350 comprising connecting elements
910, first surface 900 and second surface 850 and depressions 710.
The next step is to form protrusions 2250 on the partially-formed forming structure 350.
To form protrusions 2250, the process is essentially repeated in a second stage, and with a second
mask 656 replacing first mask 654.
Therefore, step eight starts with partially formed forming structure, denoted as 603 in
FIG. 23 advancing in the direction indicated by directional arrow Dl about return roll 611 up,
over, and about forming unit 613 and about return rolls 614 and 615. As before, other guide rolls,
return rolls, drive means, support rolls and the like can be utilized as necessary, and some are
shown in FIG. 23. Partially formed forming structure 603 is juxtaposed backing film 653 so that
backing film 653 is interposed between partially formed forming structure 603 and forming unit
613. The specific design desired for the forming structure 350 will dictate the exact method of
juxtaposition. In the preferred embodiment, partially formed forming structure 603 is placed in
direct contacting relation with backing film 653. Backing film 653 can be the same backing film
referred to previously for the first stage of the process.
In the ninth step of the process a second coating of liquid photosensitive resin 652 is
again applied as discussed above to partially formed forming structure 603 from source 620, the
resin 652 being applied to fill the depressions, i.e., depressions 710, of partially formed forming
structure 603 and, in addition, apply a coating above the level of partially cured resin of partially
formed forming structure 603. As before, partially formed forming structure 603 can be spaced
some finite distance from backing film 653 by any convenient means, but such arrangement is not
usually preferred.
The second layer of coating is the layer will ultimately be cured to form the protrusions
2250 of forming structure 350. If uniform heights of protrusions 2250 are desired, it is necessary
that the second layer of liquid photosensitive resin 652 be evenly applied across the width of
partially formed forming structure 603. A requisite quantity of photosensitive resin to form
protrusions 2250 is enough so as to fill the openings of the partially formed forming structure 603
and to over fill to a preselected thickness corresponding to the desired protrusion height, such as a
thickness corresponding to distance hf2 of FIG. 22. When the forming structure 350 is to be used
to make the web 80 suitable for use as a topsheet in a disposable absorbent article, it is preferred
that h£2 be from about 1.1 mm to about 2.1 mm thick. As before, any suitable means for
controlling the thickness can be used, including the use of nip roll 641.
The tenth step in the process illustrated in FIG. 23 comprises juxtaposing a second mask
656 in contacting relation with the second layer of liquid photosensitive resin 652. As before, the
purpose of the mask is to shield certain areas of the liquid photosensitive resin from exposure to
light A portion of a suitable first mask 654 showing one pattern of opaque, i.e., shaded, portions
657 and light-transparent portions 658 is shown in FIG. 28. Note that, although difficult to see,
FIG. 28 shows a measuring scale superimposed thereunder. The smallest increment of the scale
shown is 0.1 mm.
As shown in FIG. 28, second mask 656 is opaque to activating wavelengths of light, e.g.,
UV light, except for a pattern of transparent regions 658 corresponding to the pattern of
protrusions 2250 desired in the forming structure 350. the light-transparent portions of second
mask 656, i.e., the areas that are not shielded from the activating light source correspond to those
areas of liquid photosensitive resin that will be cured. Therefore, the transparent regions of
second mask 656 correspond to the preselected pattern of the protrusions 2250 of forming
structure 350. Second mask 656, can, therefore, have a pattern of transparent regions being
closely-spaced spots or dots, which spots or dots have a one-to-one correspondence to the closely-
spaced, round (in cross-section) protrusions, such as those shown in FIGS. 24 and 25. The
pattern of transparent regions of mask 656 can, of course, be other shapes and patterns, depending
on the particular end use of forming structure 350. In general, for a forming structure 350 used to
form a web 80 for use as a topsheet in a disposable absorbent article, the transparent regions 658
of second mask 656 should be of a suitable size, shape, and spacing to provide the necessary
structure of protrusions 2250 for web 80 such that it exhibits desirable tactile properties, such as
perceived softness. In one embodiment, transparent regions 658 of second mask 656 are each
circular with a diameter of about 65 microns, spaced apart on a center-to-center distance of about
188 microns, in a uniform spacing of about 3875 transparent regions 658 per square centimeter
(about 25,000 per square inch).
Second mask 656 can be the same material as first mask 654 such as a flexible film in
which the opaque regions can be applied by any convenient means such as photographic or
gravure processes, flexographic processes, and inkjet or rotary screen printing processes. Second
mask 656 can be an endless loop (the details of which are not shown) or it can be supplied from
one supply roll and transverse the system to a takeup roll, neither of which is shown in the
illustration. Second mask 656 travels in the direction indicated by directional arrow D4, turns
under nip roll 641 where it is brought into contact with the surface of liquid photosensitive resin
652, travels to mask guide roll 642 in the vicinity of which it is removed from contact with the
resin. In this particular embodiment, the control of the thickness of the resin and the juxtaposition
of the mask occur simultaneously.
The eleventh step of the process comprises again exposing the liquid photosensitive resin
652 to light of an activating wavelength through the second mask 656 thereby inducing curing of
the resin in those regions which are in register with the transparent regions of second mask 656,
that is, protrusions 2250. In the embodiment illustrated in FIG. 23, backing film 653, partially
formed forming structure 603, liquid photosensitive resin 652, and second mask 656 all form a
unit traveling together from nip roll 641 to the vicinity of mask guide roll 642. Intermediate nip
roll 641 and mask guide roll 642 and positioned at a location Where backing film 653 and partially
formed forming structure 603 are still juxtaposed forming unit 613, liquid photosensitive resin
652 is exposed to light of an activating wavelength as supplied by exposure lamp 655. As before,
exposure lamp 655, in general, is selected to provide illumination primarily within the wavelength
which causes curing of the liquid photosensitive resin. That wavelength is a characteristic of the
liquid photosensitive resin. As before, n a preferred embodiment the resin is UV-light curable
and exposure lamp 655 is a UV light source (in fact, is the same light source used in the first stage
of the process, described above).
As described above, when the liquid photosensitive resin is exposed to light of the
appropriate wavelength, curing is induced in the exposed portions of the resin. Curing is
manifested by a solidification of the resin in the exposed areas. Conversely, the unexposed
regions remain fluid (or partially-cured in the case of the previously-cured portions of partially
formed forming structure 603). The intensity of the illumination and its duration depend upon
the degree of curing required in the exposed areas. The absolute values of the exposure intensity
and time depend upon the chemical nature of the resin, its photo characteristics, the thickness of
the resin coating, and the pattern selected. Further, the intensity of the exposure and the angle of
incidence of the light can have an important effect on the presence or absence of taper in the walls
of the protrusions 2250. As mentioned before, a light collimator can be utilized to reduce
tapering of the walls.
The twelfth step in the process is again removing from the partially-cured forming
structure 350 substantially all of the uncured liquid photosensitive resin. That is to say, the resin
which has been shielded from exposure to light in the second curing step is removed from the
system. In the embodiment shown in FIG. 23, at a point in the vicinity of mask guide roll 642,
second mask 656 and backing film 653 are physically separated from the now partly cured resin
621 which now includes partially- or substantially fully-cured resin of the completed forming
structure 350, i.e., having both depressions 710 and protrusions 2250. The partly cured resin 621
travels to the vicinity of first resin removal shoe 623. A vacuum is applied to one surface of the
composite at first resin removal shoe 623 so that a substantial quantity of the liquid (uncured)
photosensitive resin, as well as cured "protrusions" adjacent depressions 710, is removed from the
composite. Note that in the second curing step, second mask 656 does not limit curing of resin
only on portions corresponding to first surface 900 of forming structure 350. The second curing
step actually cures "protrusions" uniformly across the entire area of partially cured composite
603. However, only portions of cured resin over connecting members 910 join to connecting
members 910 at first surface 900 and become essentially integral with the previously-cured resin
portions. Thus, in the vacuum and water washing steps, the portions of cured resin corresponding
to "protrusions" that are in the adjacent depressions 710 are simply removed to prior to a final
light-exposure for final curing, as described more fully below.
As the composite travels farther, it is brought into me vicinity of resin wash shower 624
and resin wash station drain 625 at which point the composite is thoroughly washed with water or
other suitable liquid to remove substantially all of the remaining liquid (uncured) photosensitive
resin, as well as any cured resin not forming part of the finished forming structure 350, all of
which is discharged from the system through resin wash station drain 625 for recycling or
disposal. For example, cured resin formed in the second stage light activation in the regions of
the depressions are washed away. Such cured resin is preferably non-adhered to the underlying
foraminous member, and, if adhered, the level of adhesion is preferably insufficient to prevent the
unwanted cured material to wash away.
After substantially all of the uncured resin is removed and the remaining resin is in the
final form for forming structure 350, the remaining resin is fully cured by a second light source
660, preferably in an oxygen free medium, such as water bath 630. The oxygen free medium
ensures that oxygen does not interfere with the final UV-light curing of the remaining uncured
resin. Oxygen can slow down or stop chain growth in free radical polymerization.
As shown in FIG. 23 a series of guide roll 616 can be used as required to guide the
partially-formed forming structure 350 into a water bath 630. However, in practice, any process
configuration can be used, including simply letting the partially-formed forming structure 350 be
immersed in shallow, e.g., 25.4 mm deep, water tray by its own weight. The final exposure of the
resin to activating light 660 ensures complete curing of the resin to its fully hardened and durable
condition.
The above-described twelve-step, two-stage process continues until such time as the
entire length of foraminous element 601 has been treated and converted into the forming structure
350. The finished forming structure, denoted as belted forming structure 351, can then be used in
a web forming process, such as the process described with reference to FIG. 29, for example.
Therefore, in general, curing can be done in stages, so that first a negative mask having
UV blocking portions corresponding to forming structure apertures 710 (having UV blocking
portions in a pattern of teardrops, for example), can be used to first partially cure the polymer by
directing a UV light source orthogonal to the mask for a sufficient amount of time. Once the
polymer is partially cured in the unmasked areas, a second mask comprising a plurality of closely
spaced UV-transparent spots or dots can be placed between the light source and the partially cured
polymer. The polymer is again cured by UV-light to fully cure the portions of the polymer that
will be the protrusions 2250. Once the protrusions are fully cured, the remaining uncured
polymer (and partially cured polymer) can be removed to leave a forming structure having similar
characteristics as those shown in FIGS 22 -26. The procedure described can be used for
prototyping hand sheets of material, for example.
Example of Formation of BeltedForming Structure:
The forming structure 350 shown in FIGS 24-26 was made according to the process
described above with respect to FIG. 23. m partifcular, foraminbus element 601 was an 18X16
mesh bright aluminum screening available from Hanover Wire Cloth Star Brand Screening,
Hanover, PA. The screening was approximately 0.5 mm (0.021 inches) thick, 61 cm (24 inches)
wide and comprised a woven mesh of filaments, each filament having filament diameter of about
0.24 mm. The screening was about 15 meters (50 feet) long and was formed into an endless belt
by a sewn seam.
The backing film was a 0.1 mm (.004 inch) thick biaxially dear polyester film, available
as Item No. R04DC30600 from Graphix, 19499 Miles Road, Cleveland, OH, USA. The
photosensitive resin was XPG2003-1 purchased from MacDermid Imaging Technology Inc.,
Wilmingtion, DE, USA USA which was used at room temperature as received from the
manufacturer.
The first mask was a 0.1 mm (.004 inch) Color Clear Film, 787N, available from Azon of
Chicago EL, USA and was printed with teardrop pattern as shown in FIG. 27. The first mask was
created by inkjet printing the pattern directly onto the Azon Color Clear Film.
The forming unit comprised a drum about 108 cm (42.5 inches) in diameter and about 71
cm (28 inches) wide. It rotated with a surface velocity of about 41 cm (16 inches) per minute.
For the first cast, the photosensitive resin was applied through a nozzle to a controlled
overall thickness of about 1.7 mm (0.067 inches), with the thickness being controlled by the
spacing of the forming unit and nip roll as described above.
The exposure lamp, i.e., lamp 655 discussed above, was a UV light system VPS/1600
system, Model No. VPS-6, purchased from Fusion UV Systems, 910 Clopper Road, Gaithersburg,
MD, USA. The exposure lamp was placed about 35 cm (14 inches) from the first mask and the
exposure was controlled by a quartz aperture (optional, a quartz aperture helps create a uniform
light density across the exposed area of the mask) which was positioned about 6.4 mm (2.5
inches) from the surface of the mask, and which extended the width of the forming unit and about
10 cm (4 inches) in the direction of travel (i.e., about the periphery of forming drum 613). The
light was coUimated (collimator is optional but helps collimate the light for better curing
resolution) through a 12.5 mm (0.5 inch) hexagonal honeycomb collimator that was 38 mm (1.5
inches) tall (i.e., 38 mm long tubes having a honeycomb structure).
After the first resin layer was exposed to UV light, the first mask was separated from the
composite of partially-cured resin and the uncured resin was washed from the composite by an
aqueous solution of water (100 gallons/per minute), Mr. Clean® (0.065 gaUons/minute) and
Merigraph System W6200 defoamer (0.089 gaUons/minute) at a temperature of about 115 degrees
F through 4 sets of showers, each comprising a 28 inch wide manifold of 17 nozzles. Three
showers sprayed from the top of the composite and one from the bottom.
After the first stage the composite was partially cured, which means that the first cast of
resin was not fully cured by second UV source, e.g., lamp 660 described above. The partially
cured composite comprising the first cast of resin now comprised the teardrop shaped depressions
710 of forming structure 350. The first cast of resin exhibited a thickness above the foraminous
element of about 1.3 mm (0.050 inch). The partially cured composite was run back over the
forming unit a second time in the second stage of the process. The same photosensitive resin was
applied to an overall thickness of about 2 mm (0.077 inches), which was about 0.24 mm (0.010
inches) thicker than the first application of resin. A second mask was used, the second mask
having a pattern of small transparent circles 0.08 mm (0.003 inches) in diameter and spaced 0.18
mm (0.007 inches) center-to-center in an equilateral triangle array as illustrated in FIG. 28.
The composite was cured again by light source 655 as described above and subjected to
the showers 624, as described above. After the showers removed substantially all of the uncured
resin, the composite was post cured by directing a post-cure UV light at the composite, e.g., from
source 660, while the composite was submerged in 2.5 cm (1 inch) of water containing 36 grams
of sodium sulfite/gallon of water. The sodium sulfite is optional, but is a good oxygen scavenger.
The post-cure UV light source was placed about 20 cm (8 inches) from the composite.
The resulting belted forming structure 351 exhibited columnar-shaped pillars (i.e.,
protrusions 2250) having a substantially uniform circular cross-section extending from the first
surface. The protrusions each had a height about 105 microns, a diameter of about 66 microns,
and a center-to-center spacing of about 188 microns. The belted forming structure 351
additionally exhibited uniform teardrop-shaped depressions 710. Photomicrographs of
representative portions of the belted forming structure made by the process described above are
shown in FIGS. 24-26. Note that protrusions are seamless, integral extensions of the first surface
of the forming structure. This is believed to be due to the polymer being only partially cured in
the first stage of the process, and finally cured after formation of the protrusions.
Variations on the method of forming a forming structure of the present invention utilizing
the photosensitive resin-curing process described above can be made without departing from the
scope of the present invention. For example, in one embodiment, the above described twelve-step
process can be modified by eliminating the first mask 654, or by simply having mask 654 being
completely transparent. In this embodiment, all the resin deposited in first layer, or coating, 652
of UV-curable resin is partially cured to form a monolithic "slab" of partially cured resin. The
remaining steps of the process are carried out as described above, including the formation of
protrusions 2250 by use of second mask 656. In this manner, a forming structure is formed
having protrusions 2250 but having no depressions 710. Depressions 710 can thereafter be
formed by a separate process, such as by laser etching.
Other methods of making forming structures are contemplated. For example, resins, such
as thermally-cured (e.g., vulcanizable resins) or UV-curable resins can be partially cured (i.e.,
partially polymerized) into "slabs" of material, the partial curing being sufficient to handle the
slabs in a process of wrapping the slabs onto cylindrical sleeves. Once wrapped, either by spiral
wrapping, or by piecing discrete slabs into a complete cylindrical form, the partially-cured resin
can be fully cured, thereby forming a unitary, fully cured, cylindrical sleeve of polymerized
material that can thereafter by laser etched, for example, to form depressions 710 and/or
protrusions 2250. The benefit of such a process is that the cylindrical form of the forming
structure can be achieved without the need to make a seam. Thus, unlike a typical belt-making
process that involves a seaming step, a forming structure so made is inherently seamless.
Additionally, individual layers of curable resin can be laid up in a predetermined manner such that
layers having differing material properties can be arranged to form a forming structure having
varying material properties throughout its thickness, for example. As an additional processing
step, it may be beneficial to apply layers of uncured curable resin between layers of partially-
cured resin in the layering process described above.
Further, as another optional variation on the method of making a forming structure by use
of partially-cured "slabs" of material on a cylindrical form, the partially-cured slabs can be
layered, with the outer-most layer being a layer having formed thereon protrusions 2250. Thus,
upon fully curing, the fully cured resin need only have depressions 710 formed, e.g., via laser
etching, to produce the final cylindrical foraiing structure.
One advantage of making a forming structure by use of partially-cured "slabs" of material
placed on a cylindrical form is that the cylindrical form utilized can be part of an overall support
structure for the forming structure. For example, the partially-cured slabs can be layered over a
foraminous member, such as a metal or polymer screen member. Once fully cured, the partially-
cured slabs can become adhered to the foraminous member, which is then a unitary part of the
forming structure and can provide for strength and durability for the forming structure. Further,
the partially-cured slabs can be laid up onto a relatively rigid but air-permeable membrane, such
as a honeycomb membrane that can provide support and rigidity to the forming structure. Metal
honeycomb structures, for example, can be provided in tubular forms, such that upon fully curing
the partially-cured slabs of material, the final structure is a relatively rigid, cylindrical, air-
permeable forming structure.
Other methods of making forming structures are contemplated, including creation via a
molding technique, in which the forming structure 350 is cast in a negative impression mold,
cured, and removed. In one embodiment, a substrate, such as a polymeric substrate can be laser
machined to form the negative of forming structure 350, i.e., a mold having the internal shape of
forming structure 350. Once laser machined, a polymer could be directly cast into the mold (with
appropriately-applied release agents, and the like, as is known in the art). The resulting forming
structure 350 would have the positive shape of the mold. Alternatively, the laser-machined mold
could have built up therein by electroplating, for example, a metallic forming structure 350. Also,
forming structures could be formed by way of electroplating techniques, in which successive
layers of material are built up into a suitable form.
One of the advantages to making forming structure 350 from a flexible polymeric
material, such as the material described with respect to FIGS, 15 and 24-26 is that the forming
structure is flexible enough to be utilized as a continuous belt, much like a papermaking belt is
used in the above-mentioned Trokhan '289 patent Such a continuous belt is referred to herein as
a flexible "belted" forming structure 351. By "belted" is meant that the forming structure is in the
form of a continuous, flexible band of material, much like a conveyor belt or papermaking belt, as
opposed to a relatively rigid tubular drum-shaped structure, m fact, the forming structure of the
present invention can be utilized as a papermaking belt in papermaking processes for making
textured paper, such as tissue paper.
FIG. 29 shows in simplified schematic representation one embodiment of a process for
making a polymeric web 80 of the invention using a flexible belted forming structure 351. As
shown, belted forming structure 351 can be a continuous belted member guided and held
tensioned by various rollers, e.g., rollers 610. Belted forming structure 351 is guided over
forming drum 518. While on forming drum 518 belted forming structure is supported by forming
drum 518 and precursor film 120 is supported on forming structure 351. The formation of web 80
on forming structure 351 proceeds the same way as described above with respect to FIG. 9 and
forming drum 350. Therefore, precursor web 120 can be subjected to liquid jet 540, (or jets) as
well as drying means 590 (or drying/annealing means). However, in the process described
schematically in FIG. 29, drying means 590 on forming drum 518 is optional, because drying
(and/or annealing) is provided for elsewhere in the process, as described more fully below.
Therefore, in the embodiment described with respect to FIG. 29, drying means 590 can be
replaced by re-heat means to further form precursor web 120.
In one embodiment, liquid jets 540 are not used, and the process is essentially a liquid-
free process. In such a process liquid jets 540 and or drying means 590 are replaced by re-heat
means as described above. Precursor film 120 is heated by reheat means that, together with
vacuum if necessary, conform precursor web 120 to forming structure 351. Because no liquid is
used in this process, no drying is necessary, and the drying steps disclosed herein can be
eliminated.
As can be seen in FIG. 29, belted forming structure 351 does not simply rotate on forming
drum 518 but is guided onto and off of forming drum 518. As belted forming structure 351 is
guided onto forming drum 518 it is preferably dry. After belted forming structure 351 is
supported by forming drum 518, or concurrently therewith, precursor web 120 is guided over
belted forming structure 351 and hydroformed as described above. After passing drying means
590 the belted forming structure 351 and a three-dimensional, apertured, formed film web 80 of
the present invention are guided off of forming drum 518 together. That is, polymer web 80 is
intimately in contact with and supported by belted forming structure 351. This permits further
processing, such as drying or annealing, if necessary, to take place while the polymer web 80 is
still supported by the belted forming structure 351. In this manner, polymer web 80 can endure
much greater work without collapsing, tearing, or otherwise deforming in a negative manner.
Belted forming structure 351 and polymer web 80 are guided in the direction indicated in
FIG. 29, i.e., the machine direction, to a through-air drying means 800. Through air drying means
can be in the form of a rotating drum as shown in FIG. 29, but can be in any of other known
configurations. Drying means 800 preferably utilizes air which is forced through polymer web 80
and belted forming structure 351 to effect drying of the web. However, other drying means are
contemplated, such as the use of capillary drying or limited orifice drying techniques common in
the papermaking industry for drying paper webs.
Drying means shown in FIG. 29 comprises rotating porous drying drum 802. As belted
forming structure 351 and polymeric web 80 are supported by drying drum 802 a drying fluid,
such as air, is forced through belted forming structure 351 and polymeric web 80. Fluid, such as
air, can be forced from the outside to the inside of drying drum 802, as shown in FIG. 29, or it can
be forced from the inside to the outside. In either configuration, the point is that the fluid effects
drying of polymeric web 80 while web 80 remains fully supported on belted forming structure
351. Drying drum dimensions, fluid flow rates, fluid moisture content, drying drum rotation
velocity can all be adjusted as necessary to ensure adequate drying of polymeric web 80 prior to
being guided off of drying drum 802.
Drying drum 802 can have a vacuum chamber 808 to aid in fluid flow through polymeric
web 80 and belted forming structure 351. Additionally, fluid removal means can be utilized to
remove liquid removed from polymeric web 80. Fluid removal means can include a simple drain
in forming drum 802, but can also include active removal via pumps as is known in the art to
recycle water back to the hydroforming apparatus. Drying drum 802 can have a positive pressure
chamber 810 which aids in removing excess moisture from the surface of forming drum 802 prior
to repeating the process of supporting belted forming structure 351. Liquid removed can be
simply captured in container 804 and removed appropriately, such as by draining into a water
recycle system.
Once polymeric web 80 and belted forming structure 351 are guided off of drying drum
802, polymeric web 80 is separated from belted forming structure 351 at separation point 830.
From this point polymeric web 80 may be, if necessary, subjected to additional drying, such as by
radiant heat drying means 840, and likewise, belted forming structure may be subjected to
additional drying means, such as forced air drying means 850. In all cases, other drying means as
suitable under the processing conditions can be utilized as necessary to ensure that polymeric web
80 is sufficiently dry prior to final processing into roll stock and belted forming structure 351 is
sufficiently dry to avoid introducing moisture into the interior of hair like fibrils 225 of polymeric
web 80. Sufficiently dry means dry enough such that post-manufacture moisture related problems
such as mold or mildew in the polymeric web are minimized or eliminated.

WE CLAIM:
1. A polymeric web (80) exhibiting a soft and silky tactile impression on at least one side thereof, said polymeric web comprising a precursor web having a first thickness and a pattern of discrete hair-like fibrils (225), each of said hair-like fibrils being a protruded extension of said precursor web and having a side wall (227) defining an open proximal portion (229) and a closed distal portion (226), wherein said precursor web is thinned at or near said closed distal portions of said hair-like fibrils, wherein said hair-like fibrils have an aspect ratio of at least 0.5.
2. The web of Claim 1, wherein said hair-like fibrils (225) have a largest lateral cross-sectional dimension at said proximal portion, wherein said lateral cross-sectional dimensions steadily decrease to said distal portion,
3. The web as claimed in any of the preceding claims, wherein said sidewall (227) of said hair-like fibrils (225) decrease in thickness with increasing amplitude of hair-like fibrils.
4. The web as claimed in any of the preceding claims, wherein said precursor web comprises a multilayer web.
5. The web as claimed in any of the preceding claims, wherein said web further
comprises a macroscopicaliy expanded, three-dimensional pattern of interconnecting members defining macroscopic surface aberrations, said macroscopic surface aberrations defining a first surface in a first plane of said web, and a second surface in a second plane of said web wherein said macroscopic surface aberrations are primary apertures, said primary apertures placing said first surface and said second surface in fluid communication.
6. The web as claimed in any of the preceding claims, wherein said hair-like fibrils exhibit an average diameter of between 50 microns (0.002 inch) and 130 microns (0.005 inch).

7. The web as claimed in any of the preceding claims, wherein said silky feeling side of said web exhibits at least about 1500 of said hair-like fibrils per square centimeter.
8. The web as claimed in any of the preceding claims, wherein said hair-tike fibrils (225) have an average center-to-center spacing of from about 100 microns to 250 microns (0.004 inch to 0.010 inch).
9. A disposable absorbent article comprising a fluid pervious polymeric web (80) as claimed in any of the preceding claims.
10. The disposable absorbent article as claimed in Claim 9, wherein said absorbent article is a sanitary napkin, wherein said sanitary napkin comprises a topsheet, wherein said topsheet comprises said polymeric web.

Documents:

http://ipindiaonline.gov.in/patentsearch/GrantedSearch/viewdoc.aspx?id=xf6mMDLSjFReECpm8sFedg==&loc=+mN2fYxnTC4l0fUd8W4CAA==


Patent Number 270087
Indian Patent Application Number 4079/DELNP/2008
PG Journal Number 49/2015
Publication Date 04-Dec-2015
Grant Date 27-Nov-2015
Date of Filing 13-May-2008
Name of Patentee THE PROCTER & GAMBLE COMPANY
Applicant Address ONE PROCTER AND GAMBLE PLAZA, CINCINNATI, OHIO 45202, U.S.A.
Inventors:
# Inventor's Name Inventor's Address
1 STONE, KEITH, JOSEPH 1923 AUGUSTA BLVD., FAIRFIELD, OH 45014, U.S.A.
2 GRAY, BRIAN, FRANCIS 565 WOODBROOK LANE, CINCINNATI, OH 45215, U.S.A.
3 BROYLES, NORMAN, SCOTT 4781 OURAY COURT, HAMILTON, OH 45011, U.S.A.
4 COLLINS, DIMITRIS, IOANNIS 4683 CEDAR VILLAGE DRIVE, MASON, OH 45040, U.S.A.
5 LEE, YANN-PER 2347 NORTH SARAZEN DRIVE, VERNON HILLS, IL 60061, U.S.A.
PCT International Classification Number B26F 1/26
PCT International Application Number PCT/US2003/041009
PCT International Filing date 2003-12-19
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 10/324,181 2002-12-20 U.S.A.