U.S. patent number 3,800,364 [Application Number 05/225,333] was granted by the patent office on 1974-04-02 for apparatus (discontinuous imperforate portions on backing means of closed sandwich).
This patent grant is currently assigned to Johnson & Johnson. Invention is credited to Frank Kalwaites.
United States Patent |
3,800,364 |
Kalwaites |
April 2, 1974 |
**Please see images for:
( Certificate of Correction ) ** |
APPARATUS (DISCONTINUOUS IMPERFORATE PORTIONS ON BACKING MEANS OF
CLOSED SANDWICH)
Abstract
An 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 that alternate and extend throughout the fabric. One form
of the method includes the steps of positioning the starting web
between apertured forming means and a backing means that is
foraminous except for a discontinuous pattern of imperforate
portions, then directing fluid rearranging forces through the
apertures of the forming means against the fibers of the starting
web, causing some of the fluid streams to strike the imperforate
portions of the backing means and all of the fluid streams
ultimately to pass through the foraminous portions of the backing
means. The discontinuous imperforate portions of the backing means
underlie the entire area of some but not all the apertures of the
apertured forming means. Each of the discontinuous imperforate
portions preferably has an area at least about four times the area
of an aperture of the forming means. 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 holes or other areas of low fiber
density corresponding to the imperforate portions of the backing
means and a second pattern corresponding to the apertures of the
apertured forming means that overlie the foraminous portions of the
backing means. When a plurality of protuberances and troughs
alternate across the surface of the foraminous portions of the
backing means, the fluid rearranging forces of this method and
apparatus rearrange the fibers of the fibrous starting material to
produce a third pattern of holes or other areas of low fiber
density within the second pattern already described.
Inventors: |
Kalwaites; Frank (Gladstone,
NJ) |
Assignee: |
Johnson & Johnson (New
Brunswick, NJ)
|
Family
ID: |
26695766 |
Appl.
No.: |
05/225,333 |
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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22299 |
Mar 24, 1970 |
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Current U.S.
Class: |
28/105 |
Current CPC
Class: |
D04H
1/736 (20130101) |
Current International
Class: |
D04H
1/70 (20060101); D04h 011/00 () |
Field of
Search: |
;19/161P ;161/109,169
;28/72NW |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Newton; Dorsey
Parent Case Text
This is a continuation-in-part application of my copending
application Ser. No. 22,299, filed Mar. 24, 1970 now abandoned.
Claims
I claim:
1. Apparatus for producing a patterned nonwoven fabric having a
plurality of patterns of areas of low fiber density 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 imperforate and
portions that are foraminous, said imperforate portions being
arranged in a discontinuous pattern and the remainder of said
backing means being foraminous and lying between and
interconnecting the imperforate portions; apertured forming means
spaced from said backing means during use of the apparatus to
provide a zone in which said layer of fibrous starting material may
be positioned and in which fiber movement in directions parallel to
said backing means is permitted in response to applied fluid
forces, the apertures in said forming means being longitudinally
and transversely spaced with land areas therebetween, said forming
apertures being larger than the foramina in said foraminous
portions of the backing means, each of said imperforate portions of
the backing means underlying the entire area of at least four of
the apertures in said apertured forming means, each of said
imperforate portions being shaped to provide a compact area with
the maximum dimension of the area of each imperforate portion being
no more than about four times the minimum dimension of said area,
the width of each of said interconnecting foraminous portions
between immediately adjacent imperforate portions of the backing
means being equal to at least about two times the distance between
the center of a pair of immediately adjacent apertures of the
apertured forming means; means for moving said backing means and
said apertured forming means, with a layer of fibrous starting
material positioned therebetween, through a rearranging zone
without any translatory motion between said two means and the
fibrous layer; and means for projecting streams of rearranging
fluid through said apertures in the apertured forming means, and
then against said fibrous layer to pass therethrough, some of said
fluid streams thereafter striking said imperforate portions of the
backing means and being deflected thereby in sidewise directions,
and all of said fluid streams passing through and beyond said
foraminous portions of the backing means.
2. The apparatus of claim 1 in which said imperforate portions of
the backing means rise above the plane of the top of said
foraminous portions of the backing means at least 1/64 inch, with
the central portions of each of said imperforate members rising
higher than the edge portions thereof.
3. The apparatus of claim 1 in which each of said imperforate
portions of the backing means underlies the entire area of from
about 10 to 100 of the apertures in the apertured forming
means.
4. The apparatus of claim 1 in which each of said foraminous
portions of the backing means has a plurality of protuberances and
troughs alternating across the surface thereof in both the
longitudinal and transverse directions, the tops of said
protuberances on the backing means rising above the bottoms of the
immediately adjacent troughs by a vertical distance of at least
0.005 inch, the horizontal distance between the top of one of said
protuberances and the top of the protuberance immediately adjacent
it on the backing means is at least about 0.045 inch and each of
the apertures in the apertured forming means is at least as wide as
said horizontal distance.
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 rearranged
fibers defining a plurality of patterns of apertures or holes, or
other areas of low fiber density, that alternate and extend
throughout the fabric. Some of the rearranged fibers in the fabric
lie in yarn-like bundles of closely associated and substantially
parallel fiber segments, and these bundles help to define the areas
of low fiber density in 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
these 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 and 3,025,585.
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 methods for producing rearranged nonwoven
fabrics that is disclosed in U.S. Pat. No. 2,862,251 is to support
a loose fibrous web or layer between an apertured forming member
and a foraminous backing member, and then direct streams of
rearranging fluid through the apertures of the former member in
order to apply spaced sets of opposing fluid forces to the fibers
of the layer. The spaced streams of fluid pass through the fibrous
layer and over and through the backing member, to pack groups of
fiber segments into closer proximity and substantial parallelism in
interconnected yarn-like bundles of fiber segments that define
holes or other areas of low fiber density corresponding to the
pattern of the apertures in the apertured forming means.
The fluid forces in the specific method described are usually
applied over the entire surface of the loose fibrous web or layer
and the permeable backing member on which it is supported, to
produce fiber bundles uniformly distributed over the entire
resulting fabric. In some instances, however, patterns can be made
in the fabric by not applying fluid forces to predetermined areas
of the fibrous layer, thereby preventing any fiber rearrangement
from taking place in those areas.
In any event, in any area in which rearrangement is to be produced
by the specific method referred to, the backing or support member
is uniformly permeable throughout that area in order to provide a
direct and unimpeded route by which the streams of rearranging
fluid can be quickly carried away from the fiber rearranging zone
between the backing member and apertured forming member. Every
effort is made to avoid "flooding" of the fibrous starting layer by
accumulation of excess fluid in the area where rearrangement is
taking place, and one of the means of avoiding such flooding is to
provide a direct, rapid, and effective escape route for the streams
of rearranging fluid after they have passed through the fibrous
layer.
SUMMARY OF INVENTION
I have now discovered that, unexpectedly, one can block off
substantial portions of the otherwise permeable backing or support
member in the specific method just described, to interrupt and
impede the direct flow of rearranging fluid through the backing
member, and still not impede satisfactory rearrangement of the
fibers of the fibrous starting material into a rearranged nonwoven
fabric having well defined apertures or other areas of low fiber
density.
In the method 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 in which fiber movement in
directions parallel to the plane of the fibrous material is
permitted in response to applied fluid forces, and streams of
rearranging fluid, preferably water, are projected into the fibrous
layer at entry zones spaced from each other adjacent one surface of
said layer, at the entry side of the rearranging zone. These
streams of rearranging fluid are passed through the layer of
fibrous starting material as it lies in the rearranging zone, to
effect movement of at least some segments of the fiber transverse
to the direction of travel of the projected streams.
In the next step of the method, the passage of first portions of
the rearranging fluid out of the fibrous layer is blocked at
barrier zones spaced from each other and lying directly opposite
the entire area of some but not all of the above mentioned entry
zones, adjacent the opposite surface of the fibrous layer, at the
exit side of the rearranging zone. At the same time, those portions
of fluid are deflected sidewise towards the other portions of the
rearranging fluid and are actively mingled with the latter. All the
portions of intermingled rearranging fluid are then passed out of
the rearranging zone through exits lying between the barrier zones
on the exit side of the rearranging zone.
In one form of the method and apparatus of this invention, the
fibrous starting layer is supported on backing means having
imperforate portions arranged in a discontinuous pattern, an
apertured forming means is positioned above the fibrous layer, and
streams of rearranging fluid are projected through the apertures of
the apertured forming means and against the fibrous starting
material. The remainder of the backing means other than the
discontinuous imperforate portions is foraminous and readily
permeable to the fluid streams used in fluid rearrangement, and
these continuous foraminous portions of the backing means lie
between and interconnect the discontinuous imperforate portions.
The apertures of the apertured forming means are substantially
larger than the foramina in the foraminous portions of the backing
means.
The discontinuous imperforate portions of the backing means used in
this form of the invention underlie the entire area of some but not
all of the apertures of the apertured forming means. Each such
imperforate portion has an area that is preferably at least about
four times as large as the area of an aperture of the apertured
forming means, and blocks the flow of rearranging fluid through
that area of the backing means as the fluid seeks to exit from the
layer of fibrous starting material. Nevertheless, good fiber
rearrangement into yarn-like bundles is still achieved.
The fibrous starting material used with the method and apparatus of
this invention is comprised of closely intertwined and
interentangled fibers arranged (depending on the degree of fiber
orientation in the layer) in a more or less helter-skelter fashion.
When streams of rearranging fluid are projected through the
apertures of the apertured forming means against such a fibrous
material where it lies above the imperforate portions of the
backing means, one would expect that the streams would simply mat
the interentangled fibers down against the imperforate portions of
the backing means, with no fiber rearrangement produced in those
areas at all. Or one might expect that the streams of fluid would
subject the fibers to such turbulence -- as those streams struck
the imperforate portions of the backing means -- that the fibers
located there would simply swirl around and become still more
closely intertwined in a helter-skelter arrangement, throughout the
area lying above those imperforate portions, than they had been in
the fibrous starting material.
Either of these two effects would be expected to be even more
pronounced when, as is the case with some forms of the present
invention, the discontinuous imperforate portions of the backing
means have dimensions such that each portion underlies the entire
area of each of a plurality of the apertures in the apertured
forming means, for in that situation the streams of rearranging
fluid would strike an even greater obstacle to passage away from
the rearranging zone between the backing means and apertured
forming means. In addition, in a case such as just described, in
which a given discontinuous imperforate portion of the backing
means spans a plurality of apertures in the forming means lying
above it, one might expect that fiber segments would tend to be
trapped -- by a set of opposed rearranging forces applied by fluid
streams passing through immediately adjacent apertures and
deflected, in part at least, towards each other as they strike the
imperforate portion of the backing means -- in those areas of the
backing means lying beneath the land areas of the apertured forming
means and over imperforate portions of the backing means, and would
thus be held there against further lateral movement.
Still another factor that would be expected to interfere with the
orderly and controlled fiber rearrangement necessary to produce a
nonwoven fabric having a plurality of predetermined patterns of
holes, or other areas of low fiber density, is the marked imbalance
in the magnitude of the fluid rearranging forces that produce such
areas when, as in a preferred form of the present invention, one of
the areas is four times as large as the other. Since satisfactory
rearrangement of fibers into yarn-like bundles of closely
associated and substantially parallel fiber segments requires the
balanced application of opposing fluid forces, such a great
imbalance of rearranging forces would be expected to have a
disruptive effect and make it impossible to achieve good fiber
rearrangement.
The specific minimum size ratio of 4 to 1 between the areas of low
fiber density in different patterns contained in fabrics produced
by the preferred method or apparatus of this invention just
mentioned would also be expected to present a serious difficulty in
connection with removal of rearranging fluid from the fiber
rearranging zone, for this size differential multiplies by four
times the quantity of fluid that must be disposed of from the area
overlying a single discontinuous imperforate area of the backing
means as compared to the area of an aperture of the apertured
forming means, while ordinarily it provides an increase of only
about two times in the comparative perimeters of the two areas.
Surprisingly, it has been found that obstructing the flow of fluid
rearranging streams away from the rearranging zone in the method
and appartus of this invention by providing discontinuous
imperforate portions of considerable size in the backing means does
not have any of the undesirable results described. On the contrary,
the blocking of the path of the fluid rearranging streams actually
improves the bundling effect in some of the rearranged nonwoven
fabrics produced by the method and apparatus of this invention.
Specifically, when a discontinuous imperforate portion is provided
in the backing means beneath the entire area of an aperture of the
apertured forming means, it has been found that the fiber segments
moved into yarn-like bundles in surrounding areas are packed even
more tightly than without such an obstruction to the passage of
fluid. In addition, the practice of this invention unexpectedly
produces nonwoven fabrics having a plurality of predetermined
patterns of areas of low fiber density alternating and extending
throughout the fiber and defined by yarn-like bundles of closely
associated and substantially parallel fiber segments.
The first pattern of holes or other areas of low fiber density
occurs in those areas of the fabric that overlie the discontinuous
imperforate portions of the backing means. This first pattern is
produced by moving fiber segments that are in registry with the
imperforate portions of the backing means into surrounding areas of
the fibrous layer, to position them there in yarn-like bundles of
closely associated and substantially parallel fiber segments that
define the holes or other areas of low fiber density of this
pattern.
At the same time, the fluid rearranging forces bring about bundling
in the usual manner of fiber segments that are in registry with
apertures of the apertured forming means and also overlie
foraminous portions of the backing means. This produces yarn-like
bundles of fiber segments under the adjacent land areas of the
apertured forming means, to define in the resulting nonwoven fabric
a second pattern of holes or other areas of low fiber density
arranged in accordance with the pattern of the apertures in the
apertured forming means below which the backing means is
foraminous.
An interesting result is achieved when each discontinuous
imperforate portion of the backing means underlies the entire area
of each of a plurality of apertures in the apertured forming means,
and the width of the interconnecting foraminous portion lying
between immediately adjacent imperforate portions of the backing
means is equal to at least about two times the distance between the
centers of a pair of immediately adjacent apertures of the
apertured forming means. As a result, there is in the apertured
forming means a continuous band of apertures at least one aperture
in width that has no imperforate portion of the backing means lying
beneath it. This produces a fabric in which there is at least one
band of smaller areas of low fiber density of the second pattern
that runs between each pair of the larger areas of low fiber
density that comprise the first pattern.
Still another interesting result is obtained when each of the
foraminous portions of the backing means has a plurality of
protuberances and troughs alternating across its surface in both
the longitudinal and transverse directions. The resulting fabric
displays three patterns extending throughout the fabric. The first
of these is a pattern of holes or other areas of low fiber density
corresponding to the pattern of the discontinuous imperforate
portions of the backing means. The second pattern is a pattern of
holes or other areas of low fiber density corresponding to the
pattern of apertures of the apertured forming means that overlie
foraminous portions of the backing means. The third pattern of
holes or other areas of low fiber density is disposed within the
second pattern, being defined by yarn-like bundles of fiber
segments that have been positioned by use of this invention in the
troughs on the surface of the foraminous portions of the backing
means.
In every case, the streams of rearranging fluid applied in the use
of the method and apparatus of this invention pass through the
layer of fibrous starting material after they are directed through
the apertures of the forming means, and some of the streams strike
the imperforate portions of the backing means, or any protuberances
present on the backing means, and are deflected in sidewise
directions. From there, these streams of fluid, and all other
streams of rearranging fluid that have not been deflected, are
consolidated into streams of fluid that pass through and beyond the
foraminous portions of the backing means, and thus away from the
fiber rearranging zone.
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 barrier zones to block and
deflect portions of the streams of rearranging fluid, as by
blocking portions of considerable size of the backing means on
which the layer of fibrous starting material is supported, 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 s
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 1/4 inch to about 2 to
2 1/2 inches. Satisfactory products may be produced in accordance
with this invention from starting webs weighing between 80 grains
per square yard to 2000 grains per square yard or higher.
Apertured Forming Means
In one form of the method of this invention, and in the apparatus
of this invention, the fluid entry zones into the fiber rearranging
zone are defined by an apertured forming means.
The apertured forming means used with this invention is solid
throughout its area except for the forming apertures disposed
longitudinally and transversely across the member. The forming
apertures may have any desired shape, i.e., round, square, diamond,
oblong, free form, etc.
The forming apertures are substantially larger in area than the
foramina in the foraminous portions of the backing means. The width
of each forming aperture at its narrowest part is -- for improved
visual resolution of the pattern of areas of low fiber density --
equal to at least about ten times, and preferably twenty times, the
average diameter of the fibers of the fibrous starting
material.
The land areas of the apertured forming means that lie between and
interconnect the forming apertures may be either narrow or broad in
comparison to the forming apertures, as desired. Generally
speaking, the narrower the width of the land areas, the more
tightly compacted will be the yarn-like bundles of closely
associated and substantially parallel fiber segments that are
formed throughout the nonwoven fabric of this invention.
Backing Means
As already indicated, in one form of this invention the fibrous
starting layer is supported on backing means having imperforate
portions arranged in a discontinuous pattern to provide barrier
zones against the passage of fluid out of the fiber rearranging
zone, and continuous foraminous portions that lie between and
interconnect the discontinuous imperforate portions.
With a fibrous starting material having fiber lengths in common
use, good results may be obtained with the method and apparatus of
this invention with openings in the foraminous portions of the
backing means from about 900 openings per square inch to about
50,000 openings per square inch or more, preferably from about
10,000 openings to 40,000 openings per square inch. With a starting
material including fibers of longer staple lengths, the number of
openings in the foraminous members in question may be as low as 150
per square inch or even lower.
For improved results, each discontinuous portion of the backing
means should have an area of at least about four times and
preferably from about 10 times to about 100 times, as large as the
area of an aperture of the apertured forming means so that each
imperforate portion will underlie at least 4 and preferably 10 to
100 of the apertures. The area of each discontinuous portion may if
desired be as much as a few thousand times, and even up to 10,000
times, as great as the area of an aperture of the forming means.
When heavier webs are employed as the starting material for this
invention, the area of each discontinuous imperforate portion of
the backing means should not be more than about 500 to 1,000 times
the area of an aperture of the forming means, in order to avoid
matting of a large number of fibers around the periphery of the
hole in the resulting fabric that corresponds to the discontinuous
portion of the backing means, with consequent obliteration of the
smaller holes in the fabric that correspond to the apertures of the
apertured forming means.
Improved results are obtained if each discontinuous imperforate
portion of the backing means, whatever its precise shape may be, is
a fairly compact area having a maximum dimension not much greater
than its smallest dimension. Thus, improved results are produced if
the maximum dimension of each discontinuous imperforate portion is
no greater than about four times its minimum dimension, and still
further improvement is produced if the maximum dimension is no more
than about one-and-a-half times the minimum dimension of each such
portion.
The maximum dimension of each discontinuous imperforate portion of
the backing means should be substantially less than the staple
length of the fibers in the fibrous starting material, for example,
not more than one inch maximum dimension, and preferably not more
than 1/8 to 1/2 inch maximum dimension, when fibers having an
inch-and-a-half staple length are employed. If one dimension of a
discontinuous portion of the backing means is made smaller, the
other may be increased.
The larger the dimensions of the discontinuous imperforate portions
of the backing means, the more likely it is that some fiber
segments will not be moved off those imperforate portions during
fiber rearrangement but will remain there to lie in areas of low
fiber density in the resulting fabric that correspond to the
discontinuous imperforate portions of the backing means. If the
imperforate portion is longer than it is wide, and the longer
dimension extends in the direction of fiber orientation in the
layer of fibrous starting material, more fiber segments will be
moved off the imperforate portion. On the other hand, if the larger
dimension of such an imperforate portion of the backing means
extends perpendicular to the direction of fiber orientation, more
bridging of fibers across the imperforate portion of the backing
means will result. In any event and regardless of all other
factors, all loose ends of fibers in the layer of fibrous starting
material that are positioned above the imperforate portions of the
backing means will be washed off those imperforate portions by the
fluid rearranging forces applied to the fibrous material.
The discontinuous imperforate portions of the backing means may be
flush with the plane of the top surfaces of the foraminous portions
of the backing means, but for improved results they rise at least
by about 1/64 inch above the plane of that surface, and preferably
by about 1/32 to 1/16 inch. The height of the discontinuous
imperforate portions should generally be no more than about 1/4
inch, but for heavier webs may be somewhat higher.
When relatively heavy starting webs of fibrous material are
employed, a greater height for the discontinuous imperforate
portions of the backing means produces clearer formation of areas
of low fiber density in the resulting fabric. In other words,
increased height for the discontinuous imperforate portions
produces more pronounced formation of yarn-like bundles of fiber
segments at the periphery of the areas of low fiber density which
are formed in the resulting fabric above the imperforate portions
of the backing means. However, if the imperforate portions are
raised too high in relation to the fiber density of the fibrous
starting material, "flooding" is produced, and there is a resulting
lack of controlled formation of yarn-like bundles of fiber segments
in the fabric produced.
In plan view, the discontinuous portions of the backing means may
have any shape desired, i.e., circular, oval, diamond, square,
crescent, half-moon, lace-like, free form, etc.
The discontinuous imperforate portions of the backing means have
walls that are vertical or taper out in a downward direction. The
edges are preferably slightly rounded, but not excessively so. In
any case, the top of the discontinuous portions should be smooth,
in order not to interfere with fiber rearrangement. To improve
fiber rearrangement, the central portion of the top of each
discontinuous imperforate portion may rise higher than the edge
portions.
If an additional pattern of holes or other areas of low fiber
density is desired in the fabric produced by use of the backing
means already described in the method or apparatus of this
invention, the continuous foraminous portions of the backing means
are provided with a plurality of protuberances and troughs
alternating across their surface in both the longitudinal and
transverse directions. For improved results, the tops of the
protuberances rise above the bottoms of the immediately adjacent
troughs by a vertical distance equal to at least about three times
or 0.005 inch, generally no more than about 15 to 20 times, and
preferably about five to about ten times, the average diameter of
the fibers in the layer of fibrous starting material. The
protuberances should not rise so far above their immediately
adjacent troughs as to disrupt formation of the pattern of areas of
low fiber density corresponding to the apertures of the apertured
forming means.
For good resolution of the resulting fiber bundles, the distance
between the tops of the protuberances are preferably at least about
30 times the average diameter of the fibers of the starting
material or 0.045 inch. Each of the forming apertures with which
the backing means described is used should be at least about as
wide as the horizontal distance between the tops of immediately
adjacent protuberances.
During use of the apparatus of this invention, the apertured
forming means and the backing means are spaced from each other to
provide a fiber rearranging zone in which fiber movement may take
place in response to applied fluid forces. The spacing may also be
present while the apparatus of this invention is not in use, or it
may be present only in use, produced for example by a "bellying
out" effect in the backing means under the impact of the
rearranging fluid directed against it, as described in my U.S. Pat.
No. 2,862,251.
Rearranging Fluid
The rearranging fluid for use with this invention is preferably
water or a similar liquid, but it may be other fluids such as a
gas, as described in my U.S. Pat. No. 2,862,251.
The higher the pressure employed, the larger the quantity of water
that is delivered, and as a result any heavier yarn-like bundles of
fiber segments that may extend through the resulting fabric are not
so likely to lie immediately adjacent the larger areas of low fiber
density in the portions of the fabric that overlie the
discontinuous portions of 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 can 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 a further enlarged diagrammatic plan view of the element
shown in FIG. 2, with the apertures of the apertured forming means
used in conjunction therewith shown in dashed lines.
FIG. 5 is an enlarged fragmentary diagrammatic plan view of the
foraminous portion of another backing means that can be used with
the apparatus of FIG. 1, an aperture of the apertured forming means
being shown in dashed lines.
FIG. 6 is a cross sectional view taken along the line 6--6 of FIG.
5.
FIG. 7 is a cross sectional view taken along lines 7--7 of FIGS. 5
and 6.
FIG. 8 is a photomicrograph of nonwoven fabric made in accordance
with the present invention, shown at an original enlargement of
five times.
FIG. 9 is a schematic drawing of another embodiment of a nonwoven
fabric made in accordance with the present invention.
FIG. 10 is a photomicrograph of another fabric made in accordance
with the present invention, shown at an an original enlargement of
five times.
FIG. 11 is a photomicrograph of a cross sectional view taken along
a line similar to that shown as line 11--11 in FIG. 10, shown at an
original enlargement of ten times.
FIG. 12 is a schematic drawing of another embodiment of a nonwoven
fabric made in accordance with the present invention.
DETAILED DESCRIPTION OF SPECIFIC FORMS OF THE INVENTION
FIG. 1 shows one form of apparatus that may be used in accordance
with the present invention. Full particulars of the basic apparatus
of which this apparatus is a specific form, including methods of
mounting, rotation, etc., are more fully described in U.S. Pat. No.
2,862,251 issued Dec. 2, 1958, and are incorporated in the present
application by reference and thus need not be described in complete
detail here. In view of this reference, the apparatus of FIG. 1
will be described in general terms insofar as its essential
elements are the same as in the patent just mentioned, and the
novel feature used to manufacture nonwoven fabrics in accordance
with the present invention, i.e., the backing means and its
relationship to the apertured forming means, will be described in
more detail.
The apparatus of FIG. 1 includes a rotatable apertured drum 15
suitably mounted on flanged guide wheels 17 and 18. The drum has
apertures 19 uniformly spaced over its entire surface, with the
remaining portions of the drum constituting land areas 20. The
guide wheels are mounted for rotation on shafts 25 and 26.
Inside the drum, a stationary manifold 27 to which a fluid is
supplied through conduit 28 extends along the full width of the
drum. On one side of the manifold is a series of nozzles 29 for
directing the fluid against the inside surface of the drum.
About the greater portion of the periphery of the drum there is
positioned a novel backing or support member 30. (The terms backing
member and support member are used interchangeably throughout this
description.) Support member 30, as shown in FIG. 2, has a
continuous pattern of foraminous portions 50 and a discontinuous
pattern of imperforate portions 51. In FIG. 2, the imperforate
portions are round and arranged such that four of them lie in a
square pattern over the surface of the support member, the
remainder of the member being foraminous. As already indicated
above, the imperforate portions of the backing member may have any
shape desired. They may also be arranged in any discontinuous
pattern over the support member; 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 discontinuous imperforate portion 51 of backing means 30
has a curved top surface that rises slightly above the top surface
of foraminous portions 50 of the backing means. Because of the
curved top surface, central portion 52 rises above edge portions 53
of discontinuous imperforate portion 51 of the backing means.
Extreme edge portions 54 are slightly rounded.
Support member 30 passes about drum 15 and separates from the drum
at guide roll 31 which rotates on shaft 32. The support member
passes downwardly around guide roll 33, rotating on shaft 34, then
rearwardly over a vertically adjustable tensioning and tracking
guide roll 35 rotating on shaft 36, and then around guide roll 37
on shaft 38. The member passes upwardly and around guide roll 39
rotating on shaft 40, to be returned about the periphery of the
drum.
Apertured forming drum 15 and backing belt 30 provide a rearranging
zone between them through which a fibrous starting material may
move, to be rearranged under the influence of applied fluid forces
into a nonwoven fabric having a plurality of patterns of holes or
other areas of low fiber density alternating and extending
throughout its area.
Tension on the support member is controlled and adjusted by the
tensioning and tracking guide roll. The guide rolls are positioned
in slideable brackets which are adjustable to assist in the
maintenance of the proper tension of the support member. The
tension required will depend upon the weight of the fibrous web
being treated and the amount of rearrangement and patterning
desired in the final product.
Apertured drum 15 rotates in the direction of the arrow shown, and
support member 30 moves in the same direction at the same
peripheral linear speed and within the indicated guide channels, so
that both longitudinal and lateral translatory motion of the
backing means, the apertured forming means, and the fibrous layer
with respect to each other are avoided. The fibrous material 41 to
be treated is fed between the drum and support member at point "A,"
passes through a fiber rearranging zone where fluid rearranging
forces are applied to it, and is removed in its new, rearranged
form as nonwoven fabric 42 between the support member and apertured
drum at point "B."
A fibrous material 41 passes through the fiber rearranging zone, a
liquid such as water is directed against the inner surfaces of
rotatable apertured drum 15 by nozzles 29 mounted inside the drum,
the liquid passes through apertures 19 into the fibrous web to
produce rearrangement of the fibers of the web, and the water
thence passes out through the backing means. Suction box 43 helps
to remove this water before rearranged fabric 42 reaches takeoff
point "B."
The directions the streams of rearranging fluid projected through
apertures 19 of apertured forming means 15 take as they move into
and through the fibrous web determine the type 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 after
they pass through apertures 19 are determined by foraminous
portions 50 and imperforate portions 51 of support member or
backing means 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.
The portions of the rearranging fluid in the areas where support
member 30 is foraminous pass directly through both the web and the
support member. This type of flow through adjacent apertures 19 of
apertured forming means 15 and then through foraminous portions 50
of backing means 30 produces counteracting components of force
which act in the plane of the web until the fluid is able to pass
out through the support member. These fluid forces work in
conjunction with one another to rearrange fiber segments into
interconnected bundles of fiber segments, packing the fiber
segments into yarn-like bundles that lie beneath land areas 20 of
apertured forming means 15 and above foraminous portions 50 of
backing means 30.
The portions of the rearranging fluid in each area where backing
means 30 is imperforate pass over the support member, and push
fiber segments off the imperforate portions 51 to align the fiber
segments substantially adjacent the periphery of these imperforate
portions. In some instances, the fluid may push all fiber segments
off the imperforate portions of the backing means, while in other
instances some fiber segments are left to span those portions.
FIG. 4 gives a still further enlarged diagrammatic view of a
portion of backing means 30 used in the apparatus of FIG. 1.
Discontinuous imperforate portions 51 are arranged such that four
of the portions lie in a square pattern over the surface of the
backing member. The remainder of the backing member is comprised of
continuous foraminous portions 50. Forming apertures 19 of the
apertured forming means 15 are shown in dashed lines in this FIG.
4. As seen, apertures 19 are arranged such that four of them lie in
a square pattern on means 15.
As is seen, each of the discontinuous imperforate portions 51
underlies the entire area of a plurality of apertures 19, and in
some cases a portion of the area of other such apertures. There are
some apertures 19 under which imperforate portions 51 do not lie at
all.
In the zone of closest spacing of each pair of immediately adjacent
discontinuous imperforate portions 51 of backing means 30, the
width of continuous interconnecting foraminous portions 50 is equal
to at least about two times the distance between the centers of a
pair of immediately adjacent apertures 19 of apertured forming
means 15. This means that when a forming aperture 19 is centered
above an interconnecting foraminous portion 50 between two
imperforate portions 51, a hole or other area of low fiber density
corresponding to that aperture will be produced, defined on both
sides by yarn-like bundles of closely associated and substantially
parallel fiber segments.
When backing means 30 and apertured forming means 15 are employed
in the method or apparatus of this invention as shown in FIG. 4,
fiber segments that are in registry with discontinuous imperforate
portions 51 of backing means 30 are moved by streams of rearranging
fluid into surrounding areas of the fibrous layer and are there
positioned in yarn-like bundles of closely associated and
substantially parallel fiber segments to define a first pattern of
holes or other areas of low fiber density arranged in accordance
with the pattern of arrangement of imperforate portions 51. At the
same time, fiber segments that are in registry both with forming
apertures 19 and with foraminous portions 50 of backing means 30
are moved into surrounding areas of the fibrous layer to form
similar yarn-like bundles of fiber segments defining a second
pattern of holes or other areas of low fiber density in accordance
with the pattern of arrangement of those apertures 19 that overlie
foraminous portions 50.
As is seen from FIG. 4, the holes or other areas of low fiber
density in the first pattern are larger than the holes or other
areas of low fiber density in the second pattern. In the embodiment
shown, the area of each of the discontinuous imperforate portions
51 is approximately thirty times the area of each forming aperture
19, and thus the respective areas of low fiber density that
correspond to these elements in the final fabric produced by use of
this invention have approximately the same relative areas.
In the apparatus of FIG. 1, the relative positioning of backing
means 30 and apertured forming means 15 with respect to the fibrous
layer 41 being rearranged is maintained through the rearranging
zone by guarding against either longitudinal or lateral translatory
movement. This maintains the integrity of the rearranged fabric as
it is subjected to fluid forces from the rearranging liquid.
FIG. 5 gives an enlarged fragmentary diagrammatic plan view of the
foraminous portion 80 of another backing means that can be used
with the apparatus of FIG. 1. Foraminous portion 80 of the backing
means for use in this invention is formed of coarse woven screen,
preferably metal. In the embodiment shown, wires 84 running
vertically in FIG. 5 are straight, while wires 85 running
horizontally in that figure weave alternately over and under wires
84. Protuberances 81 are present throughout foraminous portion 80
as the topmost part of each "knee" of a given strand 85 of the
screen that is formed as the strand weaves over and under the
strands 84 that lie perpendicular to it.
As a given strand 85 slants downward to pass under a strand 84
perpendicular to it, it crosses two other strands 85 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" 86 forms a trough, such as
trough 87 formed by crossing points 86 in FIGS. 5 and 6, that lies
between adjacent protuberances 81. The effective shape of troughs
87, as can be best seen in FIG. 6 (which shows a cross section of
element 80 of which a plan view is given in FIG. 5), is
substantially an inverted triangle.
A series of slightly deeper troughs 88 is formed between adjacent
protuberances 81 but extending at right angles to troughs 87. As
best seen in FIG. 7, the bottom of each trough 88 is formed by
portions of straight strands 84, with successive protuberances 81
on each side of the trough forming the tops of the trough. As seen
in FIG. 7, the effective shape of troughs 88 may be characterized
as a shallow U-shape.
As shown in FIG. 5, a plurality of troughs 87 and a plurality of
protuberances 81 alternate in one direction across the surface of
foraminous portion 80 of the backing means. FIG. 5 also shows that
a plurality of troughs 88 and a plurality of protuberances 81
alternate in a direction perpendicular to troughs 87. Hence a
plurality of troughs and a plurality of protuberances alternate in
both the longitudinal and transverse directions across the surface
of foraminous portion 80 of the backing means.
Use in the method or apparatus of this invention of a backing means
having foraminous portions such as element 80 shown in FIGS. 5
through 7 produces the third pattern of areas of low fiber density
described above. This pattern is disposed within the second pattern
of areas of low fiber density corresponding to apertures 19 of
forming means 15. The third pattern of areas of low fiber density
is defined by yarn-like bundles of fiber segments that have been
positioned in troughs 87 and 88 on the surface of foraminous
portions 80 of the backing means.
To produce improved rearrangement of fibers into yarn-like bundles
of closely associated and substantially parallel fiber segments
positioned in troughs 87 and 88, the vertical distance between the
tops of protuberances 81 and the bottoms of the immediately
adjacent troughs should be at least about three times, generally no
more than about 15 to 20 times, and preferably about five to about
ten times, the average diameter of the fibers in the layer of
fibrous starting material. For troughs 87, this distance is the
vertical distance indicated in FIG. 6 by the pair of dashed lines
that pass, respectively, through the tops of protuberances 81 and
the crossing points 86 that define troughs 87, The vertical
distance from the bottom of each trough 88 to the tops of
protuberances 81, on the other hand, is somewhat larger, being
shown by FIGS. 6 and 7 to be equal to the diameter of a strand
85.
The relative postion of a forming aperture 19 and protuberances 81
of foraminous portion 80 of the backing means in one form of this
invention is shown in dashed lines in FIG. 5. As is seen, aperture
19, in both the longitudinal and transverse directions, has a width
somewhat larger than two times the horizontal distance between the
tops of immediately adjacent protuberances 81.
FIG. 5 also shows that aperture 19 spans two protuberances 81
measured across foraminous portion 80 in both the longitudinal and
transverse directions. In the embodiment shown, each of the two
protuberances 81 in registry with aperture 19 -- having a
directional effect in one direction because of its proximity to
other similar protuberances on backing means 30, and in the other
direction for the same reason and in addition because of the
cross-sectional shape of the protuberance -- is effective in both
the longitudinal and transverse directions.
Protuberance 81 opposite the upper left hand corner of aperture 19
in FIG. 5, through cooperation with protuberance 81 lying just
below the lower left hand corner of aperture 19 in that same
figure, is effective as a protuberance that defines one wall of
trough 87 running vertically down the middle of aperture 19. At the
same time, the first named protuberance 81, through cooperation
with protuberance 81 lying just outside the upper right hand corner
of aperture 19 in FIG. 5, is effective as a protuberance that
defines one wall of trough 88 running horizontally across the
middle of aperture 19. In addition, the cross-sectional shape of
each protuberance 81 (as best seen in FIGS. 5 and 7) exerts a
directional effect on the fibers of the fibrous starting material
by its sharper definition of the side walls of each trough
extending horizontally across FIG. 5, i.e., on the side walls of
each trough 88.
During use of this invention, apertured forming means 15 and the
backing means of which element 80 is a part are spaced to provide a
fiber rearranging zone.
Portions of the streams of rearranging fluid that pass through
forming apertures 19 and the fibrous web pass directly through
openings 89 between adjacent wires of woven screen 80. Other
portions of the streams of rearranging fluid that have passed
through apertures 19 strike the wires of woven screen 80, at
protuberances 81 or at other portions of the wire, and are
deflected sidewise before they pass out of the rearranging zone
through openings 89.
The streams of rearranging fluid just described move some of the
fiber segments that are in registry with apertures 19 and overlie
foraminous portions 80 of the backing means into surrounding areas
of the fibrous layer, positioning the fiber segments there in
yarn-like bundles of closely associated and substantially parallel
fiber segments, to define holes or other areas of low fiber density
in a pattern corresponding to the pattern of apertures 19. This is
referred to above as the second pattern of the nonwoven fabric made
in accordance with this invention, since it is in addition to the
pattern of larger holes or other areas of low fiber density that
correspond to discontinuous imperforate portions 51 of backing
means 30.
At the same time, the fluid rearranging forces move other fiber
segments that are in registry with forming apertures 19 and overlie
foraminous portions 80 into troughs 87 and 88, positioning those
fiber segments there in yarn-like bundles of closely associated and
substantially parallel fiber segments, to define a third pattern of
holes or other areas of low fiber density disposed within the
second pattern just described.
The following are illustrative examples of use of the method and
apparatus of this invention to produce patterned nonwoven
fabrics:
EXAMPLE 1
In apparatus as illustrated in FIG. 1, a web 41 of loosely
assembled fibers, such as may be obtained by carding, is fed
between apertured forming means 15 and backing means 30. The web
weight is about 450 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 1 1/2 denier.
Apertured forming means 15 has about 165 substantially round holes
per square inch, each approximately 0.045 inch in diameter,
arranged in a diamond pattern over the forming means. Each aperture
19 is spaced approximately 0.018 inch in the diagonal direction
from the immediately adjacent aperture on the drum.
The foraminous portions of backing means 30 are comprised of a
woven nylon screen of approximately 28 .times. 34 mesh or
substantially 952 openings per square inch.
Imperforate portions 51 of backing means 30 are smooth round metal
members of a diameter of approximately 1/4 inch and having a cross
sectional shape similar to that shown in FIG. 3. They are
distributed over the area of backing means 30 in a diamond pattern,
with a space of approximately 1/8 inch from each portion 51 to the
nearest other portion 51 in a diagonal direction. Central portions
52 of elements 51 rise 0.012 inch above the plane of the top
surface of continuous foraminous portions 50 of the backing means,
and edge portions 53 rise about 0.010 inch above that plane.
Except for the diamond patterns of imperforate portions 51 and
apertures 19, apertured forming means 15 and support means 30 are
disposed generally as shown in FIG. 4.
Water is projected from nozzles 29 through apertures 19 in
apertured forming means 15, and thence through fibrous web 41 and
backing means 30.
After a given portion of fibrous web 41 passes through the
rearranging zone, in which streams of water are directed against it
as just described, the rotation (in the counterclockwise direction
as seen in FIG. 1) of the sandwich comprised of apertured drum 15,
the rearranged nonwoven fabric 42, and backing means 30 brings the
rearranged fabric over vacuum drying means 43, which helps to
remove the water remaining in the fabric. Fabric 42 is then carried
forward to takeoff zone "B," where 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 photomicrograph of FIG. 8, which has a plurality of
patterns alternating and extending throughout the fabric, is
produced.
Nonwoven fabric 90 of FIG. 8 contains a first pattern of holes 91,
each of which holes overlie a discontinuous imperforate portion 51
of backing means 30, and is defined by yarn-like bundles 92 of
closely associated and substantially parallel fiber segments.
In addition, nonwoven fabric 90 contains a second pattern of areas
of low fiber density 93, arranged in accordance with the pattern of
arrangement of apertures 19 in apertured forming means 15 that
overlie foraminous portions 50 of backing means 30. Each of these
areas 93 is defined by yarn-like bundles 94 of closely associated
and substantially parallel fiber segments.
Each hole 91 appears from FIG. 8 to be approximately 25 times the
size of each area of low fiber density 93, or a little bit larger.
This is consistent with the relative size of discontinuous
imperforate portions 51 of backing means 30 and apertures 19 of
apertured forming means 15 that are included in the apparatus, with
which the fabric of FIG. 8 was made. The round apertures have a
diameter of about 0.045 inch, which gives each of them an area of
about 0.0064 square inches. The imperforate portions of the backing
means have a diameter of about 1/4 inch, which gives each of them
an area of about 0.197 square inches, or in other words about 30
times the area of each aperture of the apertured forming means.
It is evident from FIG. 8 that during the production of the fabric
there illustrated, imperforate portions 51 of backing means 30
underlie some, but not all, of the apertures in the apertured
forming means. Each pair of immediately adjacent large holes or
areas of low fiber density 91 is separated by at least one of the
smaller holes or areas of low fiber density, such as those
designated 93' in FIG. 8. To produce this result, the width of the
interconnecting foraminous portions 50 of backing means 30 (or, in
other words, the closest diagonal spacing between imperforate
portions 51 of the backing means, which is about 1/8 inch or 0.125
inches) is equal to about two times the distance between the
centers of a pair of immediately adjacent apertures 19 of forming
means 15 (or, in other words, two times 0.063 inch).
EXAMPLE 2
FIG. 9 is a schematic drawing of another nonwoven fabric made in
accordance with the present invention, from starting material
similar to that used in Example 1 and by use of apparatus similar
to that described in that example. The fabric of FIG. 9 is
generally similar to the fabric of Example 1, with the exception
that the larger holes are arranged in a square pattern instead of a
diamond pattern throughout the fabric.
Nonwoven fabric 100 has a first pattern of larger holes 101 that
corresponds to the pattern of discontinuous imperforate portions 51
of backing means 30. Each larger hole 101 is defined by a plurality
of yarn-like bundles 102 of closely associated and substantially
parallel fiber segments.
The fabric of FIG. 9 also contains a second pattern of smaller
areas of low fiber density 103 in locations where apertures 19 of
apertured forming means 15 coincide with continuous foraminous
portions 50 of backing means 30. Holes 103 are likewise defined by
yarn-like bundles 104 of closely associated and substantially
parallel fiber segments.
In nonwoven fabric 100, heavier yarn-like bundles 105 of closely
associated and substantially parallel fiber segments extend
generally in the machine direction of the starting fibrous
material. These heavier yarn-like bundles 105 assist in defining
areas of low fiber density 101 (as at 106), as well as areas of low
fiber density 103 (as at 107).
The weight of the starting fibrous web being processed and the
configuration, size and spacing of the imperforate portions of the
backing means will determine whether or not heavier yarn-like
bundles are formed in the fabric produced by use of the method or
apparatus of this invention. These same factors, along with the
topography of the foraminous portions 50 of backing means 30, the
fiber orientation in the starting fibrous web, and the magnitude of
the fluid rearranging forces applied to the starting web, will
determine the disposition of any heavier yarn-like bundles that are
formed.
The nonwoven fabric of this example has excellent properties.
However yarn-like bundles 107 are visible under careful visual
examination of the fabric, and add to the esthetic appearance of
the product.
EXAMPLE 3
In apparatus as illustrated in FIG. 1, a web 41 of loosely
assembled fibers of the type commonly called an isotropic web is
fed between apertured forming means 15 and backing means 30. The
web weight is about 350 grains per square yard, and web strength is
measured at substantially the same magnitude in every direction
throughout the web. The web contains viscose rayon fibers
approximately 1 9/16 inches long of 1 1/2 denier.
The apertured forming means 15 used in this example is the same as
that employed in Example 1.
Backing means 30 is the same as the backing means employed in
Example 1, except that discontinuous imperforate portions 51 are
arranged in a square pattern over the surface of backing means 30,
with a space of approximately 150 inch between each portion 51 and
the nearest other such portion in both the longitudinal and
transverse directions.
Using the same general mode of operation as in Example 1, an
excellent nonwoven fabric such as is shown in the photomicrograph
of FIG. 10 is obtained.
Nonwoven fabric 110 of FIG. 10 contains a first pattern of holes
111, each of which is defined by yarn-like bundles 112 of closely
associated and substantially parallel fiber segments. Each of those
holes is formed in a portion of the fibrous starting material that
overlies a discontinuous imperforate portion 51 of backing means
30.
In addition, nonwoven fabric 110 contains a second pattern of areas
of low fiber density 113, arranged in accordance with the pattern
of arrangement of those apertures 19 in apertured forming means 15
that overlie foraminous portions 50 of backing means 30. Each of
these areas 113 is defined by yarn-like bundles 114 of closely
associated and substantially parallel fiber segments.
Each area 111 appears from FIG. 10 to be approximately 25 times the
size of each area of low fiber density 113, or a little bit larger.
This is consistent with the relative size of imperforate portions
51 and apertures 19 in the apparatus used to make the nonwoven
fabric of FIG. 10, since the former have an area about 30 times as
large as the area of the latter.
It is evident from FIG. 10 that during the production of the fabric
there illustrated, imperforate portions 51 of backing means 30
underlie some, but not all, of the apertures in the apertured
forming means. Each pair of immediately adjacent large areas of low
fiber density 111 spans at least one of the smaller areas of low
fiber density such as those designated at 113' in FIG. 10. To
produce this result, the width of the interconnecting foraminous
portions 50 of backing means 30 at their narrowest portion is equal
to about two times the distance between the centers of a pair of
immediately adjacent apertures 19 of forming means 15, just as was
true in Example 1 above.
A cross sectional view of the fabric of FIG. 10 is given in FIG.
11, taken along a line similar to that shown as line 11--11 in FIG.
10, and with an enlargement twice the enlargement in that figure.
Yarn-like bundles of fiber segments 112 define the larger areas of
low fiber density 111. Smaller areas of low fiber density 113 are
seen in cross section, defined by yarn-like bundles of fiber
segments 114.
EXAMPLE 4
Apparatus, starting material and operating conditions as described
in Example 2 are used in this example, except that the foraminous
portions of the backing means 30 are similar to element 80 of FIGS.
5 through 7. These foraminous portions comprise a woven nylon
screen of approximately 14 .times. 18 mesh or substantially 252
holes per square inch. The tops of protuberances 81 are about 0.005
inch above the bottoms of the immediately adjacent troughs 87, or
in other words a vertical distance a little more than three times
the 0.0015 inch diameter of fibers of 1 1/2 denier of the starting
material used here. Troughs 88 are slightly deeper than troughs 87,
being about 0.007 inch below the tops of protuberances 81.
The horizontal distance between the tops of immediately adjacent
protuberances 81 is about 0.055 inch in one direction and about
0.070 inch in the other, or in other words about 37 and about 47
times, respectively, the 0.0015 inch diameter of the fibers of the
starting material. Each aperture 19 of apertured forming means 15
is about 0.045 inch in diameter, or the same general magnitude as
the horizontal distance between the tops of immediately adjacent
protuberances 81.
FIG. 12 gives a schematic drawing of a portion of the resulting
nonwoven fabric.
Nonwoven fabric 120 has a first pattern of holes 121 that
corresponds to the pattern of discontinuous imperforate portions 51
of backing means 30. Each larger area 121 is defined by a plurality
of yarn-like bundles 122 of closely associated and substantially
parallel fiber segments.
The fabric also contains a second pattern of smaller holes or areas
of low fiber density 123 in locations where apertures 19 of
apertured forming means 15 coincide with continuous foraminous
portions 50 of backing means 30. Areas 123 are likewise defined by
yarn-like bundles 124 of closely associated and substantially
parallel fiber segments.
In nonwoven fabric 120, heavier yarn-like bundles 125 of closely
associated and substantially parallel fiber segments extend
generally in the machine direction of the starting fibrous
material. These heavier yarn-like bundles 125 assist in defining
areas of low fiber density 121 (as at 126), as well as areas of low
fiber density 123 (as at 127).
Still a third pattern of holes or other areas of low fiber density
128 lies within the pattern of smaller areas of low fiber density
123. The third pattern is defined by yarn-like bundles 129 of
closely associated and substantially parallel fiber segments
positioned in troughs 87 and 88 of foraminous portions 80 of the
backing means shown in FIGS. 5 through 7.
The nonwoven fabric of this example has excellent properties, and
the three patterns of areas of low fiber density contribute
substantially to the esthetic appearance of the product.
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 includes 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 be employed to provide a usable
fabric.
To assist in moving rearranging fluid through the layer of fibrous
starting material during use of this invention, and to help bring
about the necessary movement of fiber segments to produce a
rearranged nonwoven fabric, a vacuum may be applied to the opposite
side of the backing means simultaneously with the application of
fluid rearranging forces to the fibrous starting layer. The vacuum
employed is of the order of about 1 to about 4 inches of mercury,
preferably about 2 inches of mercury. In general, the larger the
foraminous areas of the backing means are, the lower the vacuum
used may be. The vacuum may be applied, for example, by vacuum box
44, the side of box 44 adjacent the outer surface of rotating drum
15 being provided with narrow slots 45.
If the apertured forming means used in the apparatus of this
invention is sufficiently flexible, the application of vacuum as
just described causes the land areas of the forming means to clamp
the fibrous starting material so tightly against the backing means
that the fluid rearranging forces are not capable of effecting
fiber rearrangement in those particular areas. These areas in which
fiber rearrangement is prevented add still another pattern of fiber
segments that extends throughout the fabric, to add to the
aesthetic appeal of the fabric.
The above detailed description has been given for clearness of
understanding only. No unnecessary limitations are to be understood
therefrom, as modificiations will be obvious to those skilled in
the art.
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