Note: Descriptions are shown in the official language in which they were submitted.
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OPEN MESH BELT BONDED FABRIC
The present inven-tion provides a nonwoven fabric having
a high bulk and low density, and a method of making same.
Method and apparatus for drying and heat setting fibrous
webs are known. One such method and apparatus is set
forth in U.S. 3,442,740. The apparatus described com-
prises t~e rotating heated roll and flexible endless
restraining belt which travels around the roll. A web is
inserted between the belt and the roll In the modifica-
tion described in this patent, the web travels around the
roll under the restraining belt. The web is doffed from
the heatirlg roll onto the belt which transports it to a
cooling roll. The web travels around the cooling roll
while under tlle restraining belt and is then doffed from
the roll and the belt.
In the commercially available Honeycomb Dryer, a fibrous
web is passed around a foraminous roll while being
subjected to forced air heat directed toward the outside
surface of the roll. This apparatus, although originally
used for drying fibrous webs, has been suggested for use
in fusing fibrous webs comprising thermoplastic materials.
One modification of the apparatus and method comprises the
use of a restraining belt extending about the roll, which
belt is laid down atop the fibrous web to restrain the web
against the surface of the roll during the bonding or
drying process. The foraminous surface of the roll
creates a smooth fabric face. In the method and apparatus
of the present invention, an open mesh network is disposed
about the surface of the roll or substituted for the
surface of the roll. The open mesh network surface
molds the fabric creating a puffed surface.
We know of the use of an open mesh belt as a restrainin~
belt in the Honeycom~ dryer and the use
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of an open mesh belt adjacent a web and between two carrier
bel-ts. The fabrics formed have a pat-terned surface formed
by the -tension of the open mesh belt against the web during
bonding of -the fabric. The fabrics have good strength and
high loft.
Summary of the Inverltion
The present invention comprises a method and fabric formed
thereby for thermal bonding a web comprising at least 10
percent conjugate fibers. In the method of the present
invention, a ~ibrous web comprising conjugate fibers com-
prising a low melting point thermoplastic co~ponent is fed
to and superimposed over the open mesh network rotating on
the rotating drum. Forced heated air impinging on the web
molds the web and puffs the fibers out of the plane of the
fabric into the open areas of the open mesh network and
fuses tlle low melting point component of the conjugate
fibers in the web. The fabric formed thereby is a very
high loft fabric having patterned puffed regions on one
surface tllereof. The method of the present invention ma
also be practiced using a restraining belt causing regions
of densification between the puffed regions. The use of a
conventional smooth surfaced restraining belt compresses
the web against the open mesh structure creating regions
of densification between the puffed regions of the fabric
and a smooth surface on the opposite side of the fabric.
If the restraining belt is ~ormed o~ another open mesh
networ~, it will create densified regions as above, and
will create a pattern of embossed type densified regions
on the surface of the fabric opposite the puffed surface.
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According to a broad aspect of the present
invention there is provided a method of making a
non-woven fabric having high bulk and low deilsity~
A web comprising at least ten percent conjugate
fibers comprising a low melting point component
is superimposed on a moving open mesh network surface
having open areas therein~ Forced heated air is
applied to the exposed surface of the web to bend
the fibers ad~acent the open areas into the open
areas and to fuse the low melting point component
of the conjugate fibers in the web, thereby forming
a fabric with a patterned surface comprising a
pa-ttern of puffed regions of low density adjacent
to the open mesh network.
According to a still further broad aspect of
the present invention there is provided a high loft,
low density thermal bonded nonwoven fabric comprising
at least 10 percent conjugate fibers. The fabric
has a patterned surface comprising a pattern of puffed
regions wherein the fibers are bent out of the plane
of the fabric.
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BrieE Descrip-tion of the Drawings
Figure 1 is a schematic side view of an appara-tus for
carrying out the method of the present invention;
Figure 2 is a perspective view of a portion of an open
mesh network for use in the apparatus and method according
to the present invention;
Figure 3 is a perspective view of one embodiment of a
fabric formed according to the method of the present
invention;
Figure 3A is a fragmentary section of the fabric of Figure
3 illustrating schematically how the fabric is formed;
Figure 4 is a perspective view of another embodiment of a
fabric formed according to the present invention;
Figure 4A is a fragmentary section of the fabric of Figure
4 illustrating schematically how the fabric is formed;
Figure 5 is a perspective view of another embodiment of
the fabric formed according to the method of the present
invention; and
Figure 5A is a fragmentary section of the fabric of Figure
5 illustrating schematically how the fabric is formed.
Detailed Description Of the Drawings
Figure 1 illustrates schematically and in cross-section an
apparatus for carrying out the method of the present inven-
tion. ~n the preferred embodiment shown, the apparatus
comprises a framework shown generally at 10 with a movable
surface comprising in -this embodiment a rotatable drum 12. The
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apparatus llas lleating means (not shown) within the frame
at 14. The heating means directs forced heated air onto
the outside of the movable surface. Though it is not
necessary that the path of the movable surface comprise a
curve when as in this embodiment, when it does, it is
preferred to exhaust the confluence of forced air by
drawing a vacuum from a point within the curve. Most
preferably tlle force of the impinging air and the vacuum
are balanced, which balance is dependent on the web being
processed.
Tll the improved apparatus to carry out the method of the
present invention, an open mesh network 16 is superimposed
on the movable surface. The open mesh network may comprise
an endless belt as shown/ which extends away Erom -the roll
12 and is transported back -to the roll by means 18, 20, and
22 for moving an endless bel-t open mesh structue to and from
l-he movab:le surface. In an alternate embodiment, the open
mesh network may be wouncl tightly about just the drum. In
still anotl-ler alternative, the open mesh network may be
used to for~n the surface of the drum or movable surface.
In tl)e preferred embodiment shown, the endless belt open
mesh network has two advantages. The endless belt open
mesh network may be used to transport the web to a cooling
station as will be described later; and may be easily
replaced by another open mesh network of different
confiyuration.
A portion of an open mesh structure for use in the appara-
tus and method according to the present invention is shown
at 40 in Figure 2. The open mesh structure has open areas
42 and also has a depth 44. In the method according to
the present invention, a web 24 comprising at least 10
percent conjugate fibers is disposed across a moving open
mesh structure surface and the exposed side of the fabric
is thell subjected to forced heated air. The fibers
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disposed across the open areas 22 are bent out of the
plane of the web and into the open regions by the forced
heated air thereby creating a fabric having a pattern of
puffed regions of lesser density than the overall fabric
created by the fibers bent out of the flame o the abric.
The forced heated air also heats and fuses the low melting
point co~ponent of the conjugate fibers of the web to
fibers in the web. The apparatus of ~he present invention
may also comprise a cooling station (not shown) at 26
which in its preferred embodiment comprises forced cooled
air. In a still preerred embodiment, the means for
carrying the endless belt open mesh away from the drum may
comprise means for carrying the open mesh network into the
cooling station.
Figure 3 depicts a fabric formed according to the presen.
invention. The fabric shown generally at 50 has a very
high loft and low density. One face 52 of the fabric
comprises a pattern of puffed regions 54 wherein the
fibers are bent out o the plane 65 of the fabric. As
shown in Figure 3A, these puffs are formed in the open
areas 42 of the open mesh structure by the forced heated
air. These puffed regions have lower density than the
overall fabric. The other surface 56 of the fabric may
have a pattern of recesses 58 corresponding to the puffed
regions 54. At lower air velocities, the fabric formed
has a substantially uniform density throughout, with
puffed regions and recesses being matched to give a molded
fabric wherein the entire fabric is moved into the open
areas, 42, of the open mesh structure.
In a preferred construction, the nonwoven fabrics of the
present invention are made from polyester/polyethylene
conjugate fibers wherein at least about 50 percent of the
surface of the individual fibers is polyethylene. It is
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preferred to employ sheath/core fibers with the polyethy~
lene as the sheath and the polyester as the core. Either
eccentric or concentric sheath/core fibers can be
employed. The fibers will usually have a denier within
the range of from about 1 to about 6, and are in excess of
about l/4-inch in length, up to about 3 or 4 inches long.
Preferably, the conjugate fibers employ high density poly-
ethylene, that is, linear polyethylene that has a density
of at least about 0.~4, and a Melt Index ("M.I.") by ASTM
D-1238(E) (190C., 2160 g~s.) of greater than 1, preferab-
ly greater than about 10, and more preferably from about
20 to about 50. Usually the fibers will be composed of
about ~0 to 60 weight percent, and preferably 45 to 55
weight percent, polyester, the remainder being
polyethylene.
A minor proportion of other fibers, preferably nonabsor-
bent staple fibers such as polyester fibers, can be used
along with the polyester/polyethylene conjugate fibers.
The fabrics of the invention are produced by first forming
a fibrous web comprising a loose array of the conjugate
fibers, as by carding, air laying, or the like. The exact
weight of the fibrous web has not been found to be narrow-
ly critical, although useful weights have been found with-
in the range from about 0.2 to about 4.2 ounces per square
yard.
The web comprising a loose array of polyester/
polyethylene conjugate fibers is laid on an open mesh
network surface and passed under forced air heating means.
The forced heated air pushes the fibers in open areas of
the mesh out of the plane of the fabric and fuses the
polyethylene component of the conjugate fibers and form
bonds at points of fiber-to-fiber contact. Forced heated
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air at a face velocity of at least 100 ft./min. is applied
to a circular drum with a vacuum drawn at three-tenths
inches of water within the drum. The exact temperatures
employed will vary, depending upon the weight and bulk
density of the web, and upon the dwell time employed in
the heated zone. For instance, bonding temperatures
within the range from about 130 to about 180C., have
been found satisfactory. Dwell times in the heated zone
will usually vary from about 2 seconds to about 1 minute,
and more normally will be from about 3 to about 10
seconds.
In an alternative embodiment of a method of
the present invention, an air permeable restraining belt
28 may be provided and carried along means 30 for causing
said restraining belt to travel along with the open mesh
network surface. The restraining belt compresses the web
against the open mesh network creating a fabric as shown
at 60 in Figure 4. The fabric has one surface 63 compris-
ing puffed regions 64 wherein the fibers are bent out ofthe plane 65 of the fabric. The puffed regions have very
low density. As shown especially in Figure 4A, the fabric
also comprises densified regions 66 which extend between
and around the puffed regions. The densification is
caused by the compression of the web against the open mesh
structure by the belt 28. The other surface of the fabric
68 formed next to the belt 28 is smooth.
In yet another alternative of the method of
according to the present invention, the restraining belt
may comprise an endless belt open mesh network. A fabric
formed thereby is shown in Figure 5. The fabric shown
generally at 70 comprises one face 72 which comprises
puffed regions 74 wherein the fibers are puffed out of the
plane 75 of the fabric, and densified regions 76 therebe-
tween formed by the compression of the web against the
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open mesh network restraining belt. The fabric also com-
prises embossed type densification at least at surface 78
introduced by the open mesh network restraining belt. The
emboss-type densification gives an embossed type pattern
to the other surface 78. As shown in Figure 5A, the open
mesh networks 16 and 28' had the same configuration and
were in registry; however, the present invention contem-
plates different open mesh networks used as the moving
surface and as the restraining belt and also contemplates
the belts being used when they are not in registry creat-
ing a fabric wherein the other surface 78 has embossed
type densified regions which do not coincide with the
densified regions created by compressing the web against
the open web structure moving surface.
The foregoing description and drawings are illustrative
but are not to be taken as limiting. Other variations and
modifications are possible without departing from the
spirit and scope of the present invention.
