U.S. patent number 3,769,659 [Application Number 05/225,327] was granted by the patent office on 1973-11-06 for method and apparatus (continuous imperforate portions on backing means of open sandwich).
This patent grant is currently assigned to Johnson & Johnson. Invention is credited to Frank Kalwaites.
United States Patent |
3,769,659 |
Kalwaites |
November 6, 1973 |
**Please see images for:
( Certificate of Correction ) ** |
METHOD AND APPARATUS (CONTINUOUS IMPERFORATE PORTIONS ON BACKING
MEANS OF OPEN SANDWICH)
Abstract
A method and apparatus for producing, from a layer of fibrous
material such as a fibrous web, nonwoven fabrics that contain
apertures or holes, or other areas of low fiber density, and have a
plurality of patterns of groups of fiber segments that alternate
and extend throughout the fabric. One form of the method includes
the steps of supporting the starting web upon a backing means that
is imperforate except for a discontinuous pattern of foraminous
portions that have protuberances and troughs alternating across
them, then directing fluid rearranging forces substantially
uniformly and continuously across the surface of the web, causing
some of the fluid streams to strike the imperforate portions of the
backing means, and others to strike the protuberances on the
foraminous portions of the backing means, to deflect the same, all
of the fluid streams ultimately passing through the foraminous
portions of the backing means. Each discontinuous foraminous
portion extends along the surface of the backing means in each
direction a distance that includes at least one protuberance and a
trough on each side thereof. The imperforate portions of the
backing means may rise above the foraminous portions. The resulting
fabric consists of fibers that have been rearranged to provide a
first pattern of yarn-like bundles of fiber segments in
discontinuous portions of the fabric, which bundles define areas of
low fiber density arranged in accordance with the pattern of
arrangement of the protuberances on the foraminous portions of the
backing means, and a second pattern of groups substantially aligned
fiber segments extending between and interconnecting adjacent pairs
of the discontinuous portions of the fabric in the first
pattern.
Inventors: |
Kalwaites; Frank (Gladstone,
NJ) |
Assignee: |
Johnson & Johnson (New
Brunswick, NJ)
|
Family
ID: |
26695788 |
Appl.
No.: |
05/225,327 |
Filed: |
February 10, 1972 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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22314 |
Mar 24, 1970 |
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Current U.S.
Class: |
28/104 |
Current CPC
Class: |
D04H
1/74 (20130101); D04H 1/736 (20130101) |
Current International
Class: |
D04H
1/70 (20060101); D04h 011/00 () |
Field of
Search: |
;19/161P ;28/72NW
;161/169,109 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Newton; Dorsey
Parent Case Text
This is a continuation application of my co-pending application
Ser. No. 22,314, filed Mar. 24, 1970 now abandoned.
Claims
I claim:
1. A method of producing a patterned nonwoven fabric having a
plurality of patterns of groups of fiber segments that alternate
and extend throughout said fabric, from a layer of fibrous starting
material whose individual fibers are in mechanical engagement with
one another but are capable of movement under applied liquid
forces, which comprises: supporting said layer of fibrous starting
material in a fiber rearranging zone in which fiber movement in
directions parallel to the plane of said fibrous material is
permitted in response to applied liquid forces, said rearranging
zone having an entry side and an exit side and being subdivided
into deflecting regions arranged in a discontinuous pattern and
barrier regions that are continuous and lie between and
interconnect said deflecting regions; projecting streams of liquid
into the fibrous layer substantially uniformly and continuously
across the surface thereof in a direction perpendicular to said
layer at the entry side of said rearranging zone; passing first
portions of said streams of liquid through the initial part of each
of said deflecting regions, as the fibrous layer lies in said
region, toward a plurality of dispersal points in said deflecting
region adjacent the exit side of the rearranging zone, said
dispersal points being surrounded by fiber accumulating zones; at
each such dispersal point, deflecting said first portions of liquid
diagonally and downwardly away from said perpendicular direction
into the area immediately surrounding said dispersal point, to move
fiber segments lying adjacent said dispersal point into said area
surrounding the dispersal point; positioning fiber segments thus
moved in said fiber accumulating zones located in peripheral
portions of said deflecting region, to form in those locations
yarn-like bundles of closely associated and substantially parallel
fiber segments; simultaneously passing second portions of said
liquid through the parts of said layer of fibrous starting material
that lie in said barrier regions of the rearranging zone to effect
movement of at least some segments of the fibers therein transverse
to the direction of travel of the projected streams; at the exit
side of the rearranging zone, blocking the passage of said second
portions of liquid out of said parts of the fibrous layer that lie
in the barrier regions and deflecting the same sidewise into said
deflecting regions, at least some of said sidewise deflection and
some of said diagonal and downward deflection occuring in the same
plane to move some of the fiber segments that lie in said barrier
regions into said deflecting regions to position them there in the
aforementioned yarn-like bundles of closely associated and
substantially parallel fiber segments and to move others of the
fiber segments that lie is said barrier regions into substantial
alignment with each other in bridging positions extending between
said discontinuous deflecting regions; actively mingling said first
and second portions of liquid after they have been thus deflected;
passing said intermingled first and second portions of liquid out
of said fiber rearranging zone through spaced exits in the
deflecting regions at the exit side of the rearranging zone; at the
same time and intermingled therewith passing out of said exits
third portions of liquid that upon being projected into said
fibrous layer were moved to said exits without passing through a
dispersal point or a barrier region; and applying a vacuum at the
exit side of said fiber rearranging zone to assist in moving all
said liquid through the fibrous starting material and in
rearranging said fiber segments, thereby forming a nonwoven fabric
having a first pattern of yarnlike bundles of fiber segments in
discontinuous portions of said fabric, which yarn-like bundles
define areas of low fiber density arranged in accordance with the
pattern of arrangement of said dispersal points, and a second
pattern of groups of substantially aligned fiber segments extending
between and interconnecting pairs of said discontinuous portions of
the fabric immediately adjacent each other.
2. Apparatus for producing a patterned nonwoven fabric having a
plurality of patterns of groups of fiber segments that alternate
and extend throughout said fabric, from a layer of fibrous starting
material whose individual fibers are in mechanical engagement with
one another but are capable of movement under applied fluid forces,
which comprises: backing means for said layer of fibrous starting
material, said means having portions that are foraminous and
portions that are imperforate, said foraminous portions comprising
at least 20 percent of the total area of the backing means the
remaining area being imperforate, said foraminous portions being
arranged in a discontinuous pattern and said imperforate portions
being continuous and lying between and interconnecting the
discontinuous foraminous portions, the continuous imperforate
portions rising above the plane of the tops of said discontinuous
foraminous portions with the edges of said imperforate portions
lying in substantially the same plane as said foraminous portions
and the central portion of said imperforate portions rising higher
than the edge portions, the maximum distance between adjacent
foraminous portions being less than about 0.5 inch, said
discontinuous foraminous portions having a plurality of
protuberances with troughs surrounding each protuberance
alternating across the surface thereof in both the longitudinal and
transverse direction, the top of each of said protuberances rising
above the bottom of the troughs immediately adjacent to it by at
least 0.005 inch, and the top of each protuberance being spaced
from the tops of adjacent protuberances by a horizontal distance of
at least 0.025 inch; means for moving said backing means, with a
layer of fibrous starting material positioned thereon, through a
rearranging zone; means for projecting streams of rearranging fluid
against said fibrous layer substantially uniformly and continuously
across the surface thereof to pass therethrough, some of said fluid
streams striking said imperforate portions of the backing means,
and others of said fluid streams striking said protuberances on the
backing means, all to be deflected thereby in sidewise directions,
and all of said fluid streams, together with other streams of fluid
that do not strike said backing means, passing through and beyond
said foraminous portions of the backing means; and means to apply
vacuum on the side of said backing means opposite to said fibrous
layer to assist in moving all said rearranging fluid through the
fibrous layer and in rearranging the fibers of said layer.
Description
This invention relates to a method and apparatus for the production
of nonwoven fabrics, and more particularly to a method and
apparatus for the production of nonwoven fabrics from a layer of
fibrous material such as a fibrous web in which the individual
fiber elements are capable of movement under the influence of
applied fluid forces, to form a fabric that contains apertures or
holes, or other areas of low fiber density, and has a plurality of
patterns of groups of fiber segments that alternate and extend
throughout the fabric.
BACKGROUND OF THE INVENTION
Various methods and apparatus for manufacturing apertured nonwoven
fabrics involving the rearrangement of fibers in a starting layer
of fibrous material have been known for a number of years. Some of
the methods and apparatus for the manufacture of such fabrics are
shown and described in U.S. Pat. No. 2,862,251, which discloses the
basic method and apparatus of which the present invention is a
specific form, and in U.S. Pat. Nos. 3,081,500, 3,025,585 and
3,033,721.
The nonwoven fabrics made by the methods and apparatus disclosed in
those patents contain apertures or holes, or other areas of low
fiber density, often outlined by interconnected yarn-like bundles
of closely associated and substantially parallel fiber segments.
(The term "areas of low fiber density" is used in this
specification and claims to include both (1) areas in which
relatively few fibers are found in comparison to the rest of the
fabric, and (2) apertures (holes) that are substantially or
entirely free of fibers.)
One of the specific known methods for producing rearranged nonwoven
fabrics is to support a loose fibrous web or layer upon a
formaminous backing member that has protuberances spaced across its
surface, with troughs or low areas between the protuberances.
Streams of rearranging fluid are applied substantially uniformly
and continuously over the entire surface of the loose fibrous web
or layer, and after the streams pass through the fibrous material
some of them strike the protuberances on the backing means and are
diverted in sidewise directions to cause fiber segments to move
from the area adjacent the high point of each protuberance into the
immediately adjacent troughs. All the streams then pass through the
openings in the foraminous backing means and leave the rearranging
zone.
The effect of these fluid rearranging forces is to pack groups of
fiber segments into interconnected yarnlike bundles of closely
associated and substantially parallel fiber segments and to
position them in the troughs on the backing means so as to define a
pattern of areas of low fiber density throughout the resulting
nonwoven fabric.
In this prior art method, the backing member is uniformly permeable
throughout its area in order to provide an unimpeded route by which
the streams of rearranging fluid can be quickly carried away after
they have moved fiber segments from the protuberances into the
troughs of the backing means. Care is always taken in any fluid
rearrangement to avoid loss of web identity through "flooding"
(U.S. Pat. No. 2,862,251, col. 2, line 60 to col. 3, line 12), and
with the specific prior art method under discussion it is said to
be essential that the backing member be "permeable to the passage
of fluid from the applied streams, so that the fluid may pass
freely through the backing member and away from the layer of fibers
rather than having some or all of the fluid reflected back in the
same general direction from which it is applied" (U.S. Pat. No.
3,025,585, col. 2, lines 38-48).
Another known method for producing rearranged nonwoven fabrics is
to support a loose fibrous web or layer upon solid backing means
with spaced apertures distributed throughout the area thereof, and
direct streams of rearranging fluid against the fibrous starting
layer so that the fluid passes through that layer and then out
through the spaced apertures in the backing means. The result of
this method is to form a nub of interentangled, tightly packed,
helter-skelter fiber segments in each aperture of the backing
means, and to position other fiber segments in flat, ribbon-like
groups of substantially aligned fiber segments between pairs of
immediately adjacent nubs to interconnect the same.
A significant feature of this second method is that streams of
rearranging fluid initially dispersed uniformly across the fibrous
starting layer are consolidated into spaced streams confined by the
walls of the apertures in the apertured backing means as they pass
out of and away from the fiber rearranging zone. It is this
consolidation of the streams of fluid that creates the turbulence
that in turn packs the nubs in the nonwoven fabric of this prior
art method into tightly compacted fiber accumulations, with the
individual fibers thereof having entirely random orientation.
Another significant feature of this second method is that the
apertures in the otherwise solid backing means, if they are single
openings, cannot be too large or fibers will be washed through the
apertures and the fabric will be destroyed.
SUMMARY OF THE INVENTION
I have now discovered that, unexpectedly, one can combine these two
different prior art methods of producing rearranged nonwoven
fabrics, and achieve very satisfactorily two quite different types
of rearrangement of the fibers of the fibrous starting material so
as to produce a fabric having a plurality of patterns of groups of
fiber segments that alternate and extend throughout the entire
fabric.
Thus, I have discovered that one can block off continuous portions
of substantial size of the otherwise permeable backing or support
member in the first prior art method described, to interrupt and
impede the flow of rearranging fluid through the backing member,
and still not impede satisfactory fiber rearrangement brought about
by the impact of the rearranging fluid against the protuberances on
the backing means, to be deflected sidewise and thereby move fibers
of the fibrous starting material into a rearranged nonwoven fabric
having well defined areas of low fiber density. And one can at the
same time mix the controlled rearranging forces of that first
method with the turbulent forces that are characteristic of the
second prior art method, and still maintain the integrity of both
types of fiber rearrangement in the very same nonwoven fabric.
Moreover, the size of the apertures defined by the continuous solid
portions of the backing member in the combined method is no longer
limited by the danger of washing fibers through the backing means,
and those apertures can be made just as large as is required for
any desired pattern of this particular type in the resulting
nonwoven fabric.
In the practice of this invention, the starting material is a layer
of fibrous material whose individual fibers are in mechanical
engagement with one another but are capable of movement under
applied fluid forces. The layer of fibrous starting material is
supported in a fiber rearranging zone that has an entry side and an
exit side and in which fiber movement in directions parallel to the
plane of the fibrous material is permitted in response to applied
fluid forces. The fiber rearranging zone is subdivided into
deflecting regions that are arranged in a discontinuous pattern,
and barrier regions that are continuous and lie between and
interconnect the deflecting regions.
Streams of rearranging fluid, preferably water, are projected into
the fibrous starting material substantially uniformly and
continuously across its surface, in a direction perpendicular to
the fibrous layer at the entry side of the rearranging zone. The
streams of rearranging fluid are comprised of three categories --
first portions that pass through the deflecting regions of the
rearranging zone, second portions that pass through the barrier
regions, and third portions that pass through the deflecting
regions but in a different manner from the first portions.
The first portions of the rearranging fluid are passed through the
initial part of each deflecting region as the layer of fibrous
starting material lies in said region, toward at least one
dispersal point in the deflecting region adjacent the exit side of
the rearranging zone. Each of these dispersal points is surrounded
by fiber accumulating zones.
At each dispersal point, the first portions of rearranging fluid
are deflected diagonally and downwardly away from the perpendicular
direction of their entry into the rearranging zone, and are moved
into the area immediately surrounding the dispersal point. This
movement of the rearranging fluid moves fiber segments lying
adjacent the dispersal point into the area around that point, and
positions them there in yarn-like bundles of closely associated and
substantially parallel fiber segments. At least some of these
yarnlike bundles lie in fiber accumulating zones that are located
in peripheral portions of the deflecting regions, and when there is
a plurality of dispersal points in a single deflecting region, some
of the yarn-like bundles lie in accumulating zones that are located
between immediately adjacent dispersal points.
The second portions of rearranging fluid are passed through the
parts of the layer of fibrous starting material that lie in the
continuous barrier regions of the fiber rearranging zone, and cause
movement of at least some segments of the fibers in those regions
transverse to the direction of travel of the projected streams. At
the exit side of the rearranging zone, the passage of these second
portions of rearranging fluid out of the parts of the fibrous layer
that lie in the barrier regions is blocked, and the fluid is
deflected sidewise into the discontinuous deflecting regions of the
rearranging zone. This movement of the rearranging fluid moves some
of the fiber segments that lie in the barrier regions into at least
some of the yarn-like bundles of closely associated and
substantially parallel fiber segments mentioned above. At the same
time, it moves other fiber segments lying in the barrier regions
into substantial alignment with each other in bridging positions
extending between adjacent discontinuous deflecting regions.
The first and second portions of the rearranging fluid that have
been deflected as described are then actively mingled, and the
intermingled fluid is passed out of the fiber rearranging zone
through spaced exits in the deflecting regions at the exit side of
the rearranging zone. At the same time, third portions of fluid are
intermingled with the first and second portions, to be passed out
of the same exits. The third portions of fluid are projected into
the fibrous starting material and are moved to the exits referred
to without passing through a dispersal point or a barrier
region.
To assist in moving all the rearranging fluid through the layer of
fibrous starting material and in rearranging the fiber segments of
that layer, a vacuum is applied at the exit side of the fiber
rearranging zone.
The result of application of the fluid rearranging forces just
described is to form a nonwoven fabric having a first pattern of
yarn-like bundles of fiber segments in discontinuous portions of
the fabric, which bundles define areas of low fiber density
arranged in accordance with the pattern of arrangement of the
dispersal points in the deflecting regions of the fiber rearranging
zone, and a second pattern of flat, ribbon-like groups of
substantially aligned fiber segments extending between the
interconnecting pairs of immediately adjacent discontinuous
portions of the fabric in the first pattern.
In one form of the method and apparatus of this invention, the
fibrous starting layer is supported on backing means having
foraminous portions arranged in a discontinuous pattern, with
continuous imperforate portions lying between and interconnecting
the foraminous portions. The discontinuous foraminous portions of
the backing means include protuberances tne troughs alternating
across the surface of such portions in both the longitudinal and
the transverse directions. Each of the foraminous portions extends
along the surface of the backing means a distance that includes at
least one of the protuberances and a trough on each side of the
protuberance. There is no maximum limit on the size of the
discontinuous foraminous portions except what is required to
achieve the desired pattern in the resulting nonwoven product.
Each imperforate portion of the backing means may, if desired, rise
above the top surface of the foraminous portions of the backing
means. However, they may if desired be flush with that surface,
depending upon the type of rearranged fabric that is to be
produced. If the imperforate members are higher than the foraminous
portions of the backing means, the central portions of the
imperforate members are preferably higher than the edge portions
thereof.
In the practice of this invention, streams of rearranging fluid,
preferably water, are applied substantially uniformly and
continuously across the surface of the layer of fibrous starting
material as it is supported on the backing means just described.
The streams pass through the fibrous layer and strike the backing
or support means, some striking the imperforate portions of the
backing means and others striking the protuberances on the
foraminous portions of the backing means. In either case, the
streams are deflected in sidewise directions and join other streams
of rearranging fluid that pass through the openings of the
discontinuous foraminous portions of the backing means without
striking the backing means. A vacuum is applied on the opposite
side of the backing means from the layer of fibrous starting
material, to assist in moving the rearranging fluid through that
layer and in rearranging the fibers of the layer.
As the various streams of rearranging fluid follow their courses
described, they cause fiber segments that overlie each protuberance
on the foraminous portions of the backing means to move into the
troughs surrounding the protuberance, and to be positioned there in
yarnlike bundles of closely associated and substantially parallel
fiber segments. At the same time, the streams of rearranging fluid
cause some of the fiber segments that overlie the continuous
imperforate portions of the backing means to be moved into the
adjacent areas of the fibrous layer that overlie the discontinuous
foraminous portions of the backing means, and to be positioned
there, under the influence of the protuberances on the foraminous
portions, in the yarn-like bundles of closely associated and
substantially parallel fiber segments that, as just mentioned, are
formed in the troughs surrounding the protuberances. Meanwhile, the
streams of rearranging fluid move other fiber segments that overlie
the continuous imperforate portions of the backing means into
substantial alignment in positions bridging those imperforate
portions.
The result of these actions of the rearranging fluid is to produce
a nonwoven fabric having two patterns of fiber segments that
alternate and extend throughout the fabric. The first pattern is a
pattern of yarnlike bundles of fiber segments in discontinuous
portions of the fabric, which yarn-like bundles define areas of low
fiber density arranged in accordance with the pattern of
arrangement of the protuberances on the discontinuous foraminous
portions of the backing means. The second is a pattern of flat,
ribbon-like groups of substantially aligned fiber segments
interconnecting the portions of the fabric in the first pattern;
this pattern corresponds to the configuration of the continuous
imperforate portions of the backing means.
FURTHER DESCRIPTION OF INVENTION
The basic method and apparatus of this invention are shown and
described fully in my U.S. Pat. No. 2,862,251, issued Dec. 2, 1958.
Full particulars of the basic invention as disclosed in that patent
are incorporated in this application by reference, although some of
those particulars are repeated here. In addition, the specific
feature peculiar to the method and apparatus of the present
invention -- which is the provision of deflecting regions arranged
in a discontinuous pattern, each such region including dispersal
points surrounded by fiber accumulating zones (for example,
discontinuous foraminous portions of a backing means which have
alternating protuberances and troughs) in a fiber rearranging zone
the remainder of which is comprised of continuous barrier regions
to block and deflect portions of the streams of rearranging fluid
at the exit side of the rearranging zone (defined, for example, by
continuous imperforate portions lying between and interconnecting
the discontinuous foraminous portions of a backing means) -- is
described in detail in this application.
Starting material. The starting material used with the method or
apparatus of this invention may be any of the standard fibrous webs
such as oriented card webs, isowebs, air-laid webs, or webs formed
by liquid deposition. The webs may be formed in a single layer, or
by laminating a plurality of the webs together. The fibers in the
web may be arranged in a random manner or may be more or less
oriented as in a card web. The individual fibers may be relatively
straight or slightly bent. The fibers intersect at various angles
to one another such that, generally speaking, the adjacent fibers
come into contact only at the points where they cross. The fibers
are capable of movement under forces applied by fluids such as
water, air, etc.
To produce a fabric having the characteristic hand and drape of a
textile fabric, the layer of starting material used with the method
or apparatus of this invention may comprise natural fibers such as
cotton, flax, etc.; mineral fibers such as glass; artificial fibers
such as viscose rayon, cellulose acetate, etc.; or synthetic fibers
such as the polyamides, the polyesters, the acrylics, the
polyolefins, etc., alone or in combination with one another. The
fibers used are those commonly considered textile fibers; that is,
generally fibers having a length from about one-fourth inch to
about 2 to 21/2 inches.
Satisfactory products may be produced in accordance with this
invention from starting webs weighing between 80 grains per square
yard to 2,000 grains per square yard or higher. With heavier web
weights, as discussed below, the difference in elevation between
the dispersal points and the fiber accumulating zones in the
deflecting region of a fiber rearranging zone (for example, the
protuberances and troughs, respectively, on the foraminous portions
of a backing means) must be more pronounced in order to achieve the
bundling that is a necessary part of this invention.
Discontinuous foraminous portions of backing means. As already
indicated, in one form of this invention a backing means is
employed that has discontinuous portions that are foraminous and
continuous imperforate portions lying therebetween to provide
barrier regions in the fiber rearranging zone. The discontinuous
foraminous portions of the backing means are provided with a
plurality of protuberances and troughs that alternate throughout
their surfaces, and thus comprise deflecting regions containing
dispersal points each of which is surrounded by fiber accumulating
zones.
As illustrated in the drawings below, for improved results the tops
of the protuberances rise above the bottoms of the immediately
adjacent troughs by a distance equal to at least about three times
the average diameter of the fibers in the layer of fibrous starting
material or at least 0.005 inch. Preferably, the distance is equal
to about ten times the average diameter of those fibers, especially
when the web weight of the fibrous starting material is of the
order of 800 grains per square yard or higher. It also becomes more
important to have prominent protuberances on the foraminous
portions of the backing means the greater is the width of the
imperforate portions of the backing means, since a wide imperforate
portion increases the number of loose fiber ends that will be
washed off those imperforate portions to be added to the fibrous
web already lying above the foraminous portions of the backing
means.
The fibrous starting material used with the method and apparatus of
this invention is comprised of closely intertwined and
interentangled fibers arranged (depending upon the degree of fiber
orientation in the layer) in a more or less helter-skelter fashion.
Some of the fibers of the starting material will by random chance
lie generally parallel to the troughs on the foraminous portions of
the backing means over which they lie, but the great majority of
the fibers will lie at an angle to the longitudinal axes of the
troughs, and a substantial number of these will lie at angles of
45.degree. or more to such an axis.
In the practice of this invention, the movement of fiber segments
into closer association and substantial parallelism with each other
in yarn-like bundles in the troughs of the backing means is more
likely to occur with those fiber segments in the starting material
that already lie only a relatively few degrees away from a position
parallel to the longitudinal axis of a trough. To put it the other
way, this type of movement is more difficult the greater the angle
between a given fiber segment and the axis of the trough, and when
fiber segments lie at too great an angle to the longitudinal axis
of a trough, they simply continue to lie at that angle, matted down
against the backing means by the force of the rearranging fluid.
For the greater the angle between the fiber segment and the trough
axis, the shorter is the portion of the fiber that bridges the
trough, and the more difficult it is for the rearranging fluid
forces to get a "purchase" on the fiber segment to turn it around
into a position parallel with the trough axis.
Likewise, the narrower the troughs are on the backing means, the
more difficult it is for the rearranging fluid forces to get a
"purchase" on the short portion of the fiber segment that bridges
the trough, to swing that segment around into a position parallel
to the axis of the trough to be consolidated there to form a
yarn-like bundle with other similarly positioned fiber segments.
The force of the vacuum assist employed with this invention is of
course added to the force of the other rearranging fluid. With the
use of a vacuum assist, the distance between immediately adjacent
protuberances on the backing means, which determines the width of a
trough from the top of one side to the other, is ordinarily equal
to at least about 15 times the average diameter of the fibers of
the fibrous starting material or at least 0.025 inch.
The minimum spacing of protuberances just mentioned, which affects
the width of the troughs lying between immediately adjacent
protuberances, also assists in providing good visual resolution
between various yarnlike bundles of fiber segments in the fabric
resulting from the practice of this invention. For if the
protuberances are too closely spaced and the troughs between them
are too narrow, yarnlike bundles of fiber segments may be
accumulated in the troughs but will not be discernible one from the
ohter, because each one merges into the next adjacent similar
bundle of fiber segments. If the web weight of the fibrous starting
material is high, the distance between immediately adjacent
protuberances on the backing means should be increased, or
otherwise the yarn-like bundles of fiber segments will be masked
out by the same merging phenomenon just mentioned.
The discontinuous foraminous portions of the backing means are of
sufficiently large area that, with the appropriate web weight in
the starting material, good formation of yarnlike bundles of fiber
segments can be effected above those foraminous portions. Thus,
each discontinuous foraminous portion extends in each direction
along the surface of the backing means a distance that includes at
least one protuberance and a trough on each side of the
protuberance. This minimum size for the discontinuous foraminous
portions of the backing means produces a minimum of one well
defined hole or other area of low fiber density corresponding to
the protuberance on the backing means, with yarnlike bundles of
fiber segments positioned in the troughs surrounding the
protuberance.
There is no maximum limit on the area of the foraminous portions of
the backing means. That area is determined only by the pattern
desired in the nonwoven fabric to be produced. Thus, the width of a
discontinuous foraminous portion may be as much as five or 10 times
the horizontal distance between adjacent troughs, or even more.
The foraminous portions of the backing means used in this invention
are closely enough spaced to each other that they occupy together
at least about 20 percent, and preferably about 30 percent or even
more, of the total area of the backing means.
Continuous imperforate portions of backing means. The continuous
imperforate portions of the backing means may have any shape
desired, i.e., they may be formed of lines that are diagonal,
perpendicular, curved, free form, etc. Their shape is
complementary, of course, to the shapes of the discontinuous
foraminous portions which they lie between and interconnect.
The continuous imperforate portions of the backing means may be
flush with the top surface of the foraminous portions of the
backing means, or at a different elevation. If a three-dimensional
effect is desired for the fiber grouping accumulated at each
foraminous portion of the backing means, the continuous imperforate
portions of the backing means may be raised above the top surface
of the foraminous portion of the backing means by about one
thirty-second inch or one-sixteenth inch or even more, depending
upon the web weight and how much three-dimensional effect is
desired. The higher the imperforate portions rise above the
foraminous portions of the backing means, the more marked the
three-dimensional character of the resulting fabric will be.
In addition, with a foraminous portion at a lower elevation,
generally a medium sized area for the foraminous portion of the
backing means produces a more pronounced three-dimensional effect
in the resulting fabric than an area for such portion that is too
small or too large. The three-dimensional effect also increases
with increased flexibility in the fibers being rearranged, since
the more flexible a fiber is, the more easily it can conform to the
lower elevation of the foraminous portions of the backing
means.
In the practice of this invention, fiber segements are aligned in
bridging positions between discontinuous portions of the nonwoven
fabric containing yarn-like bundles of fiber segments by pulling
them taut between adjacent groups in which they are anchored. This
anchoring and pulling taut of fiber segments, with their resulting
alignment in flat, ribbon-like groups of fiber segments, is
achieved by limiting the maximum spacing between adjacent
foraminous portions of the backing means. To establish two reliable
anchor points for each individual fiber segment, the foraminous
portions of the backing means are spaced from other such portions
immediately adjacent thereto by no more than about one-third the
average length of the fibers being rearranged, and preferably no
more than about one-fifth or one-sixth the length of the fibers. In
general, this means that with 11/2 staple length fibers, each pair
of foraminous portions of the backing means are spaced, at their
closest points, no more than about one-half inch apart, and
preferably no more than about one-fourth inch.
Rearranging fluid. The rearranging fluid for use with this
invention is preferably water or similar liquid. It may also be
other fluids such as a gas, as described in my U.S. Pat. No.
2,862,251.
Application of vacuum. The vacuum applied to the opposite side of
the backing means simultaneously with the application of fluid
rearranging forces to the fibrous starting layer is of the order of
about 1 inch to about 4 inches of mercury, preferably 2 inches of
mercury.
Additional vacuum may be used to advantage after the rearranged
fabric has moved out of the rearranging zone, in order to help
remove excess liquid from the fabric before the fabric is removed
from the backing means.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be more fully described in connection with the
accompanying drawings, in which:
FIG. 1 is a diagrammatic showing in elevation of one type of
apparatus that may be employed in the present invention.
FIG. 2 is an enlarged diagrammatic plan view of a portion of a
backing means that can be used in the apparatus of FIG. 1.
FIG. 3 is a cross sectional view taken along the line 3--3 of FIG.
2.
FIG. 4 is an enlarged fragmentary diagrammatic plan view of one of
the foraminous portions of the backing means of FIG. 2.
FIG. 5 is a cross sectional view taken along line 5--5 of FIG.
4.
FIG. 6 is a cross sectional view taken along line 6--6 of FIGS. 4
and 5.
FIG. 7 is a schematic perspective representation of the paths
followed by various streams of rearranging fluid as they pass
through the foraminous member shown in FIGS. 4 through 6.
FIG. 8 is a schematic plan representation of the paths followed by
the streams of rearranging fluid shown in perspective in FIG.
7.
FIG. 9 is an enlarged diagrammatic plan view of a portion of a
backing means that can be used in the apparatus of FIG. 1.
FIG. 10 is a cross sectional view taken along the line 10--10 of
FIG. 9.
FIG. 10a is a cross-sectional view of a preferred embodiment of a
backing member useful in the practice of the present invention.
FIG. 11 is a photograph of a nonwoven fabric made in accordance
with the present invention, shown in the original drawing at actual
size.
FIG. 12 is a photomicrograph of the nonwoven fabric of FIG. 9,
shown at an original enlargement of five times.
DETAILED DESCRIPTION OF SPECIFIC FORM OF THE INVENTION
FIG. 1 shows one form of apparatus that may be used in accordance
with the present invention.
In this apparatus, horizontal frame members 2 are supported by legs
3 and 4. At the feed end of the machine (on the left hand side of
FIG. 1), a pair of vertical frame members 5 extend upwardly above
horizontal frame members 2, with a pair of wet-out rolls 6 and 7
rotatably mounted between them. Wet-out roll 6 is partially
immersed in a water pan 8, and its shaft 9 is journalled in
bearings (not shown) fixed to vertical frame members 5. Bearings
10, in which shaft 11 of wet-out roll 7 is journalled, are slidably
mounted on vertical frame members 5.
The vertical position of wet-out roll 7 is adjustable, and is
regulated by hydraulic positioning cylinders 13 mounted on the top
of each vertical frame member 5. In this way, the pair of wet-out
rolls 6 and 7 cooperate to control the moisutre content of a web or
layer of fibrous material, of a type such as mentioned above as
being a suitable starting material, that is fed through the nip
between the wet-out rolls. Preferably the moisture content of the
layer of fibers it is moved from the wet-out rolls is in the
neighborhood of from 150 to 200 percent. (The term "percent
moisture," when used in this specification, refers to percentage of
moisture by weight of the dry web.)
The layer of fibers moves from the nip of the wet-out rolls to the
fiber rearranging zone of the apparatus to effect the rearrangement
of the fibers in the starting web or layer 15, to produce a
rearranged fibrous web or layer 15' having a plurality of patterns
of groups of fiber segments and areas of low fiber density as
described above. Thus the starting layer of fibers moves from the
wet-out rolls to be supported on a backing means in the form of
endless belt 16 (described in detail below), which extends around a
pair of parallel rolls 17, 18 rotatably mounted adjacent opposite
ends of the frame. Each of the rolls 17, 18 is mounted on a shaft
19, the ends of which are journalled in bearings 20 carried on
horizontal frame members 2. Conventional driving means (not shown)
are connected to either one of shafts 19.
A water pipe 21, mounted in any suitable manner, supports a pair of
headers 22 above the upper reach of endless belt 16. Each header
extends transversely of belt 16, and has a row of jet nozzles 23 to
provide water sprays across the width of that belt.
A pair of suction boxes 24 are mounted on and extend transversely
across frame members 2 between the rolls 17 and 18 which carry
endless belt 16, with one of the boxes located directly beneath
each row of jet nozzles 23. Each suction box is closed on all sides
except for an opening 25 to which a vacuum line 26 is connected,
and a slot or group of perforations 27 which extend across top wall
28 of the suction box. The top wall of each suction box is
positioned adjacent the underside of the upper reach of endless
belt 16.
Nonwoven fabric 15', after rearrangement but before reaching the
position where endless belt 16 starts to track around roll 18, is
lifted off the belt by causing it to pass upwardly and over a
horizontal cylindrical doffing member 29a that extends transversely
of the machine and is supported at its ends in the side frame. The
fabric then passes downwardly and around through the nip between
guide rolls 29b and 29c on its way to a suitable drying area (not
shown). Guide rolls 29b and 29c are parallel to doffing member 29a,
and like it are supported at their ends in the side frame members
of the machine.
Backing means. Endless belt or backing means 16, as shown in FIG.
2, has foraminous portions 30 arranged in a discontinuous pattern,
and continuous imperforate portions 31 lying between and
interconnecting the discontinuous foraminous portions. In FIG. 2,
the foraminous portions are round and arranged such that four of
them lie in a square pattern over the surface of the backing means,
the remainder of the member being imperforate. As already indicated
above, the foraminous portions of the backing member may have any
shape desired. They may also be arranged in any discontinuous
pattern over the backing means, i.e., they may be aligned
longitudinally and/or transversely, staggered, etc.
FIG. 3 shows a cross section of the backing means of FIG. 2. As
seen, each continuous imperforate portion 31 of backing means 16
has a curved top surface that rises slightly above the top surface
of foraminous portions 30 of the backing means. Because of the
curved top surface, central portion 32 rises above edge portions 33
of each imperforate portion 31 of the backing means. Extreme edge
portions 34 of each imperforate portion 31 are slightly
rounded.
In FIG. 10a there is shown a cross-sectional view of a preferred
embodiment of a backing means 16a in accordance with the present
invention. In this embodiment the permeable portion of the backing
means 30a has superimposed on it impermeable portions 52a. The
outer edges of the impermeable portions terminate in substantially
the same place as the permeable portions whereas the central
portion of the impermeable portions rise above the high points or
protuberances of the permeable portions.
Discontinuous foraminous portions 30, as shown in FIGS. 4 through
6, are formed of a coarse woven screen, preferably metal. In the
embodiment shown, wires 40 running vertically in FIG. 4 are
straight, while wires 41 running horizontally in that figure weave
alternately over and under wires 40. Protuberances 42 are present
throughout foraminous portion 30 as the topmost part of each "knee"
of a given strand 41 of the screen that is formed as the strand
weaves over and under the strands 40 that lie perpendicular to
it.
As a given strand 41 slants downward to pass under a strand 40
perpendicular to it, it crosses two other strands 41 disposed on
either side of it, as those strands slant upward to pass over the
same perpendicular strand that the given strand will pass under.
Each series of such "crossing points" 43 form a trough, such as
trough 44 in FIGS. 4 and 5, that lies between adjacent
protuberances 42. The effective cross sectional shape of troughs
44, as can be best seen in FIG. 5 (which shows a cross section of
element 30 of which a plan view is given in FIG. 4), is
substantially an inverted triangle.
A series of slightly deeper troughs 45 is formed between adjacent
protuberances 42 extending at right angles to troughs 44. As best
seen in FIG. 6, the bottom of each trough 45 is formed by portions
of straight strands 40, with successive protuberances 42 on each
side of the trough forming the tops of the trough. As seen in FIG.
6, the effective cross sectional shape of troughs 45 may be
characterized as a shallow U-shape.
As shown in FIG. 4, troughs 44 and protuberances 42 alternate in
one direction across the surface of each foraminous portion 30 of
backing means 16. FIG. 4 also shows that troughs 45 and
protuberances 42 alternate in a direction perpendicular to troughs
44. Hence troughs and protuberances alternate in both the
longitudinal and transverse directions across the surface of each
discontinuous foraminous portion 30 of backing means 16.
To produce good rearrangement of fibers into yarnlike bundles of
closely associated and substantially parallel fiber segments
positioned in troughs 44 and 45, the vertical distance between the
tops of protuberances 42 and the bottoms of the immediately
adjacent troughs should be at least about three times, and
preferably about ten times, the average diameter of the fibers in
the layer of fibrous starting material. For troughs 44, this
distance is the vertical distance indicated in FIG. 5 by the pair
of dashed lines that pass, respectively, through the tops of
protuberances 42 and the crossing points 43 that define the
troughs. The vertical distance from the bottom of each trough 45 to
the tops of protuberances 42, on the other hand, is somewhat
larger, being shown by FIGS. 5 and 6 to be equal to the diameter of
a strand 41.
In the embodiment shown, each protuberance 42 has a directional
effect in one direction because of its proximity to other similar
protuberances on foraminous portions 30 of the backing means, and
in the other direction for the same reason and in addition because
of the cross sectional shape of the protuberance. Thus, each
protuberance 42 is effective in both the longitudinal and
transverse directions. As an example, the protuberance 42 to which
the designator line runs in the upper left hand corner of FIG. 4,
through cooperation with the protuberance 42 to which the
designator line runs in the left central part of the bottom of that
same figure, is effective as a protuberance that defines one wall
of trough 44 running vertically down the middle of the figure. At
the same time, the first named protuberance 42, through cooperation
with protuberance 42 to which the designator line runs in the upper
right hand part of FIG. 4, is effective as a protuberance that
defines one wall of trough 45 running horizontally across the
middle of the figure. In addition, the cross sectional shape of
each protuberance 42 (as best seen in FIGS. 4 ad 6) exerts a
directional effect on the fibers of the fibrous starting material
by its sharp definition of the side walls of each trough extending
horizontally across FIG. 4, i.e., on the side walls of each trough
45.
Each discontinuous deflecting region or foraminous portion 30 is
wide enough to include at least one dispersal point or protuberance
42 and a fiber accumulating zone or trough 44 or 45 on each side
thereof. In the embodiment of FIGS. 2 and 3, each foraminous
portion 30 includes in each direction about five protuberances 42
and their associated troughs or fiber accumulating zones.
Three portions of rearranging fluid. The directions the projected
streams of rearranging fluid take as they move into and through the
fibrous web determine the types of forces applied to the fibers
and, in turn, the extent of rearrangement of the fibers. Since the
directions the streams of rearranging fluid take as they move
through the fibrous layer are determined in part by the pattern of
the solid wires that make up discontinuous foraminous portions 30
of backing means 16, and in particular the pattern of protuberances
and troughs distributed across the surface of foraminous portions
30, it follows that the pattern of these areas helps determine the
patterns of holes or other areas of low fiber density in the
resultant fabric.
As is seen from FIG. 4, first portions of the streams of
rearranging fluid that have been projected into the fibrous web
strike the wires of woven screen 30, at protuberances 42 or at
other portions of the wire, and are deflected sidewise before they
pass out of the rearranging zone through openings 46. The streams
of rearranging fluid that strike protuberance 42 in the upper left
hand part of FIG. 4, for example, leave the fiber rearranging zone
through openings 46a, 46b, 46c and 46d in the respective sectors or
quadrants of the area surrounding that protuberance.
FIGS. 2 and 3 show that second portions of the rearranging fluid
projected into the layer of starting material strike continuous
imperforate portions 31 of backing means 16, and are deflected
sidewise into the areas above discontinuous foraminous portions 30,
where they are mingled with the first portions of rearranging fluid
and are passed out of the rearranging zone through openings 46.
Third portions of the rearranging fluid projected into the fibrous
web pass directly through openings 46 in foraminous backing
portions 30, without being deflected either by protuberances 42 or
imperforate portions 31.
Flow of first portions of rearranging fluid through deflecting
regions. The dotted lines in FIGS. 5 and 6 give a schematic showing
of the path followed by a stream of rearranging fluid 47 that is
directed into the layer of fibrous starting material, in a
direction perpendicular to that layer, to strike protuberance 42 in
the upper left hand corner of FIG. 4. As is seen, the stream of
fluid is deflected downwardly and outwardly away from its
perpendicular direction of entry into the fiber rearranging zone,
and then moves out of the rearranging zone through the openings
between wires 40 and 41.
The flow of streams of rearranging fluid after being deflected
sidewise upon striking protuberances 42 of foraminous portions 30
of backing means 16 produces sets of counteracting components of
force that act in the plane of the web until the fluid passes out
through the foramina in portions 30. The counteracting fluid forces
in each of these sets work in conjunction with one another to
rearrange fiber segments into yarn-like bundles positioned in
troughs 44 and 45 of portion 30 of backing means 16. Some of these
yarnlike bundles of fiber segments lie in fiber accumulating zones
in peripheral portions of foraminous portions 30 adjacent
discontinuous imperforate portions 31 of backing means 16, while
some lie in troughs or fiber accumulating zones between one
protuberance 42 and another protuberance that is immediately
adjacent to it.
When the layer of fibrous starting material is first positioned in
that part of the fiber rearranging zone located above foraminous
portion 30 of backing means 16, and before a rearranging fluid has
been directed into the layer, the fibrous web of course lies upon
the tops of protuberances 42. After fiber rearrangement has
proceeded under the impact of the streams of rearranging fluid, the
fibers are moved down the sloping sides of protuberances 42 into
troughs 44 and 45. At this juncture, the layer of rearranged fibers
that comprises the nonwoven fabric ordinarily lies largely, if not
altogether, below the tops of protuberances 42.
FIGS. 7 and 8 provide schematic representations of the flow of
streams of rearranging fluid 47 that has been described in
connection with FIGS. 4 through 6. As explained above, in the
practice of this invention the layer of fibrous starting material
is supported in a fiber rearranging zone in which fiber movement in
directions parallel to the plane of the fibrous material is
permitted in response to applied fluid forces. The fiber
rearranging zone has an entry side and an exit side, and is
subdivided into deflecting regions 30 arranged in a discontinuous
pattern and barrier regions 31 that are continuous and lie between
and interconnect the discontinuous deflecting regions. FIGS. 7 and
8 depict a part of a deflecting region 30.
In FIGS. 7 and 8, the fiber rearranging zone is indicated as being
defined by a foraminous portion 30 of backing means 16. Streams of
rearranging fluid are projected into the fibrous layer as thus
supported, in a direction perpendicular to said layer,
substantially uniformly and continuously across the surface of the
layer. In FIGS. 7 and 8, streams 47 represent first portions of
those rearranging streams that take a particular path through the
fiber rearranging zone.
First portions 47 of the rearranging fluid are passed through
initial part 48 of the rearranging zone, as the fibrous layer lies
in the zone. The streams of fluid 47 are passed toward dispersal
points 42 lying adjacent the exit side of the rearranging zone, two
of which dispersal points are shown for illustrative purposes in
FIGS. 7 and 8.
At each dispersal point 42, streams of rearranging fluid 47 are
deflected diagonally and downwardly away from the perpendicular
direction of entry of streams 47 into the fibrous starting
material, into the area immediately surrounding the dispersal
point. In FIGS. 7 and 8, fluid stream 47 that is directed toward
dispersal point 42 in the upper left hand portion of FIG. 8 is
directed upon deflection into sectors or quadrants 46a, 46b, 46c
and 46d of the area surrounding that dispersal point.
A few of the fiber segments of the fibrous starting material that
lie in deflecting region 30 of the rearranging zone remain, after
treatment with streams of rearranging fluid, in substantially the
positions they occupied by random chance in the starting layer.
Most of the fiber segments lying in the deflecting region, however,
are moved by the deflection of rearranging fluid just desribed into
the area surrounding the dispersal point 42 at which each fluid
stream 47 was deflected.
The fiber segments moved by deflected streams of rearranging fluid
47 are positioned in yarn-like bundles of closely associated and
substantially parallel fiber segments in fiber accumulating zones
44 and 45 in the area surrounding each dispersal point 42. As an
example, fiber segments that are moved so that they extend between
areas 46a and 46b of FIG. 8 are positioned there in fiber
accumulating zone 44 which extends vertically in that figure
between the two dispersal points 42, lying adjacent each other,
that are shown in FIG. 8. Likewise, fiber segments that are moved
so that they extend between areas 46b and 46c are positioned in
fiber accumulating zone 45 which extends horizontally in FIG. 8,
and so on. Fiber accumulating zones 44 and 45 correspond to troughs
44 and 45 shown in FIGS. 4 through 6. The yarnlike bundles of fiber
segments positioned in the fiber accumulating zones form a pattern
of yarnlike bundles corresponding to the pattern of the fiber
accumulating zones, which in turn is determined, among other
things, by the position of the various dispersal points 42
throughout the fiber rearranging zone.
The deflected portions of rearranging fluid 47 are then passed out
of the fiber rearranging zone through spaced exits such as 46a
through 46d, and similar exit areas, in FIGS. 7 and 8.
At the same time, other portions of rearranging fluid that are
projected into the layer of fibrous starting material, for example
those portions entering the entry zone in direct registry with exit
46b, are moved to and through the exits on the exit side of the
rearranging zone without passing through a dispersal point 42 to be
deflected from the perpendicular direction at which they enter the
fibrous starting layer.
In the embodiment shown diagrammatically in FIGS. 4 through 6 and
in the schematic representations of FIGS. 7 and 8, the spaced exits
on the exit side of the rearranging zone are located in the fiber
accumulating zones.
Flow of second portions of rearranging fluid through barrier
regions. The directions taken by the second portions of the streams
of rearranging fluid, which are projected into the fibrous starting
material lying in the continuous barrier regions of the fiber
rearranging zone, are of course also important. The directions
those portions of the rearranging fluid take as they move into and
through the fibrous web determine the types of forces applied to
the fibers and, in turn, help determine the extent of rearrangement
of the fibers throughout the barrier regions, and thus help
determine the pattern of holes or other areas of low fiber density
in the resultant fabric.
The second portions of the rearranging fluid which are projected
into each barrier region -- for example, each part of the fiber
rearranging zone overlying an area 31 where backing measn 16 is
imperforate -- are deflected sidewise out of the barrier region
into adjacent deflecting regions. Thus, such streams strike
continuous imperforate portions 31 in FIG. 2, to be deflected
sidewise and effect movement of fiber segments transverse to the
direction of travel of the projected streams.
This fluid flow causes some of the fiber segments that overlie the
continuous imperforate portions 31 of backing means 16 to be moved
into the adjacent areas of the fibrous layer that overlie the
discontinuous foraminous portions 30 of the backing means, and to
be positioned there in the above mentioned yarnlike bundles of
fiber segments in areas adjacent the periphery of those imperforate
portions, and elsewhere in the deflecting regions overlying
foraminous portions 30 of the backing means. At the same time, the
fluid flow described moves other fiber segments that overlie the
continuous imperforate portions 31 of the backing means into flat,
ribbonlike groups of substantially aligned fiber segments that
bridge those imperforate portions.
Flow of third portions of rearranging fluid through deflecting
regions. As indicated above, the passage of rearranging fluid
through the fiber rearranging zone and the layer of fibrous
starting material supported therein is completed by the flow of
third portions of the fluid through the deflecting regions of the
rearranging zone.
As is seen from FIG. 4, third portions of rearranging fluid that
are projected into the fibrous web in a direction perpendicular to
the plane of the web (i.e., perpendicular to the plane of the
drawing in that figure) pass through the fibrous layer and, after
being intermingled with the first and second portions of fluid
discussed above, pass directly out of the fiber rearranging zone
through spaced exits such as openings 46a, 46b, 46c and 46d. These
third portions of fluid do not strike protuberances 42 to be
deflected sidewise, and thus do not pass through any dispersal
points in the deflecting region. Likewise, since they do not enter
the barrier regions of the fiber rearranging zone, they do not
strike imperforate portions 31 of backing means 16.
The rearranged web or fabric produced by the practice of this
invention may be treated with an adhesive, dye or other
impregnating, printing, or coating material in a conventional
manner. For example, to strengthen the rearranged web, any suitable
adhesive bonding materials or binders may be included in an aqueous
or non-aqueous medium employed as the rearranging fluid. Or an
adhesive binder may, if desired, be printed on the rearranged web
to provide the necessary fabric strength. Thermoplastic binders
may, if desired, be applied to the rearranged web in powder form
before, during or after rearrangement, and then fused to bond the
fibers.
The optimum binder content for a given fabric according to this
invention depends upon a number of factors, including the nature of
the binder material, the size and shape of the binder members and
their arrangement in the fabric, the nature and length of the
fibers, total fiber weight, and the like. In some instances,
because of the strength of the fibers used or the tightness of
their interentanglement in the rearranged web or fabric, or both
factors, no binder at all need by employed to provide a usable
fabric.
The following is an illustrative example of the use of the method
and apparatus of this invention to produce a patterned nonwoven
fabric:
EXAMPLE
In apparatus as illustrated in FIG. 1, a web 15 of loosely
assembled fibers, such as may be obtained by carding, is fed
between wet-out rolls 6 and 7, and from there onto endless backing
means 16. The web weight is about 400 grains per square yard, and
its fiber orientation ratio approximately 7 to 1 in the direction
of travel. The web contains viscose rayon fibers approximately
1-9/16 inches long, of 11/2 denier.
Discontinuous foraminous portions 30 of backing means 16 used in
this example are comprised of a woven nylon screen of approximately
28 .times. 34 mesh or substantially 952 openings per square inch.
The top of each protuberance 42 on the backing means rises above
the bottoms of troughs 44 immediately adjacent to it by
approximately 0.007, inch or almost five times the 0.0015 inch
average diameter of the 11/2 denier fibers of the starting
material. They rise approximately 0.010 inch above the bottoms of
troughs 45, or about seven times the average fiber diameter.
Each foraminous portion 30 is oval in shape, measuring
approximately one-eighth inch in one direction and approximately
one-fourth inch in the other, and is spaced diagonally about
one-sixteenth inch from the immediately adjacent foraminous
portions. Foraminous portions 30 are distributed in a diamond
pattern, approximately 16 to the square inch, over backing means
16.
Continuous imperforate portions 31 of backing means 16 comprise a
nylon knitted mesh known as Raschel knit fabric, of the form shown
in plan view in FIG. 9 and in cross-section in FIG. 10. The width
50 of each imperforate portion 31 at its narrowest part is
approximately one-sixteenth inch or about 0.063 inch. Together the
grid of imperforate portions defines foraminous portions 30. The
height 51 of each imperforate portion 31 is approximately one
thirty-second inch at its rounded top portion 52.
The distance measured across foraminous portions 30 of backing
means 16 between the center of one fiber accumulating zone or
trough and the center of the zone or trough immediately adjacent
and parallel to it is about 0.029 inch in one direction, and in the
other direction about 0.034 inch. Hence the 0.063 inch width of
each imperforate portion 31 at its narrowest part is about two
times the distance between trough centers.
In the practice of this invention, water is projected from nozzles
23 against fibrous web 15 in a direction perpendicular to the plane
of the web, to pass through the fibrous layer and through backing
means 16. After given portions of backing means 16 and fibrous web
15 pass through the rearranging zone in which streams of water are
directed against them in this invention, the movement of the upper
reach of endless belt 16 (towards the right as seen in FIG. 1)
brings the rearranged fabric to doffer roll 29a and guide rolls 29b
and 29c, from whence it leaves the apparatus.
With the conditions indicated, good fiber rearrangement and
bundling are obtained, and an excellent nonwoven fabric such as
shown in the photograph of FIG. 11, which has a pluralty of
interesting patterns of groups of fiber segments that alternate and
extend throughout the fabric, is produced.
Nonwoven fabric 60 of FIG. 11 is shown with an original enlargement
of five times in the photomicrograph of FIG. 12. As seen in the
latter figure, fabric 60 contains a first pattern of yarn-like
bundles of closely associated and substantially parallel fiber
segments in discontinuous portions 61 of the fabric corresponding
to foraminous portions 30 of backing means 16. Some of the
yarn-like bundles 62 lie in fiber accumulating zones located in the
peripheral portions of the deflecting regions of the fiber
rearranging zones, as for example in the peripheral portions of
each foraminous portion 30 where it abuts the perimeter of
continuous imperforate portions 31 of the backing means. Other
yarnlike bundles 63 lie in fiber accumulating zones located between
immediately adjacent dispersal points in the deflecting regions, as
for example between immediately adjacent protuberances 42 on
foraminous portions 30.
Yarn-like bundles 62 and 63 together define areas of low fiber
density 64. Most of these areas of low fiber density 64 contain
some fiber segments that bridge across the area.
In addition, nonwoven frabric 60 contains a second pattern of flat,
ribbon-like groups of substantially aligned fiber segments 65 that
extend diagonally between and interconnect pairs of immediately
adjacent discontinuous portions 61 of the fabric. Groups of fiber
segments 65 correspond to the pattern of arrangement of imperforate
portions 31 of backing means 16.
In the embodiment of FIGS. 10 and 11, there is also a third pattern
of groups of substantially aligned fiber segments 66 that extend in
the machine direction between longitudinally adjacent pairs of
discontinuous portions 61 of the fabric. Groups of aligned fiber
segments 66 are of lighter weight than are groups 65. In the fabric
shown, areas of low fiber density 67, each containing a few stray
fibers 68, are defined by fabric portions 61 and groups of aligned
fiber segments 65 and 66.
Each discontinuous fabric portion 61 appears from FIG. 12 to be
approximately 100 times the size of each area of low fiber density
64. This is consistent with the relative size of discontinuous
foraminous portions 30 and protuberances 42 on those foraminous
portions in the apparatus with which the fabric of FIGS. 11 and 12
is made.
Each discontinuous fabric portion 61 includes a plurality --
specifically, about 20 to 25 -- of areas of low fiber density 64.
This follows from the fact that each foraminous portion 30 of the
backing means employed in the production of the fabric of this
example contains approximately 20 to 25 protuberances 42.
The above detailed description has been given for clearness of
understanding only. No unnecessary limitations should be understood
therefrom, as modifications will be obvious to those skilled in the
art.
* * * * *