U.S. patent application number 09/982436 was filed with the patent office on 2002-02-28 for hydroentangled, low basis weight nonwoven fabric and process.
This patent application is currently assigned to Polymer Group, Inc.. Invention is credited to Ferencz, Richard, Putnam, Michael, Storzer, Marlene, Weng, Jian.
Application Number | 20020025753 09/982436 |
Document ID | / |
Family ID | 26680400 |
Filed Date | 2002-02-28 |
United States Patent
Application |
20020025753 |
Kind Code |
A1 |
Putnam, Michael ; et
al. |
February 28, 2002 |
Hydroentangled, low basis weight nonwoven fabric and process
Abstract
A process is disclosed for hydroentangling polymeric filament
webs for production of low basis weight nonwoven fabrics. A
hydroentangling device having a foraminous forming surface is
employed for hydroentangling a precursor web to form a fabric.
High-speed production of relatively low basis weight fabrics can be
achieved, with the fabrics exhibiting desired softness, uniformity,
and strength characteristics.
Inventors: |
Putnam, Michael; (Fuquay
Varina, NC) ; Ferencz, Richard; (Isle of Palms,
SC) ; Storzer, Marlene; (Cornelius, NC) ;
Weng, Jian; (Charlotte, NC) |
Correspondence
Address: |
ROCKEY, MILNAMOW & KATZ, LTD.
TWO PRUDENTIAL PLAZA, STE. 4700
180 NORTH STETSON AVENUE
CHICAGO
IL
60601
US
|
Assignee: |
Polymer Group, Inc.
|
Family ID: |
26680400 |
Appl. No.: |
09/982436 |
Filed: |
October 18, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09982436 |
Oct 18, 2001 |
|
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|
09476313 |
Dec 30, 1999 |
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Current U.S.
Class: |
442/340 ;
442/408 |
Current CPC
Class: |
D04H 3/11 20130101; Y10T
442/614 20150401; D04H 1/492 20130101; Y10T 442/689 20150401 |
Class at
Publication: |
442/340 ;
442/408 |
International
Class: |
D04H 001/00; D04H
003/00 |
Claims
What is claimed is:
1. A process for making a nonwoven fabric having a low basis
weight, comprising the steps of: providing a hydroentangling device
having a foraminous fabric-forming surface; positioning a precursor
web having a length on said device, wherein said precursor web
comprises continuous polymeric filaments, said precursor web having
a basis weight from about 10 to about 30 grams per square meter;
and hydroentangling said precursor web to form said low basis
weight fabric by application of high pressure liquid streams
thereto so that the filaments of said web are rearranged on the
fabric-forming surface of said device, said precursor web being
hydroentangled at a rate of at least 80 feet/minute in a direction
along the length of said web, without substantially altering the
basis weight of said precursor web; and removing the low basis
weight fabric from said fabric-forming surface.
2. A process for making a low basis weight nonwoven fabric in
accordance with claim 1, wherein said hydroentangling device
comprises a 23-mesh forming screen.
3. A process for making a low basis weight nonwoven fabric in
accordance with claim 1, wherein: said precursor web comprises
bonded, continuous polymeric filaments.
4. A process for making a low basis weight fabric in accordance
with claim 3, wherein said precursor web is bonded no more than
minimum tensile strength which permits winding and unwinding of
said precursor web.
5. A process for making a low basis weight fabric in accordance
with claim 4, wherein: during said hydroentangling step, bonds in
said precursor web are broken to unbond said continuous polymeric
filaments while minimizing breakage of said filaments.
6. A process of making a nonwoven fabric having a low basis weight,
comprising the steps of: providing a precursor web having a length,
said precursor web comprising spunbonded continuous polymeric
filaments, and having a basis weight from about 10 to about 30
grams per square meter; providing a hydroentangling device having a
foraminous forming surface; positioning said precursor web on said
hydroentangling device; hydroentangling said precursor web to form
a low basis weight fabric by application of high pressure liquid
streams thereto so that bonds between said filaments are broken,
and the filaments rearranged on the foraminous forming surface, and
removing said fabric from said hydroentangling device.
7. A process of making a nonwoven fabric having a low basis weight
in accordance with claim 6, wherein: said low basis weight fabric
has a machine direction tensile strength of at least about 1,472
grams per centimeter.
8. A process of making a nonwoven fabric having a low basis weight
in accordance with claim 7, wherein: said hydroentangling device
comprises a wire mesh forming surface.
9. A low basis weight nonwoven fabric, comprising: a web of
hydroentangled 0.2 to 3.0 denier polymeric filaments, said
filaments being arranged in a substantially uniform array on a
hydroentangling device, having a foraminous forming surface; said
fabric having a basis weight from about 10 to about 30 grams per
square meter, and a cross-direction tensile strength of at least
about 827 grams per centimeter.
10. A low basis weight nonwoven fabric in accordance with claim 9,
wherein: said polymeric filaments comprise substantially continuous
filaments.
11. A low basis weight nonwoven fabric in accordance with claim 9,
wherein: said filaments comprise spunbond polyester filaments
having about 1.5 denier.
12. A low basis weight nonwoven fabric in accordance with claim 10,
wherein: said web of hydroentangled polymeric filament is formed
from a spunbond precursor web which is bonded no more than a
minimum tensile strength which permits winding and unwinding of
said precursor webs.
Description
TECHNICAL FIELD
[0001] The present invention relates generally to nonwoven fabrics,
and a method for producing such fabrics, and more particularly to a
hydroentangled, low basis weight nonwoven fabric exhibiting
desirable softness and strength characteristics , with manufacture
from a lightly bonded precursor web facilitating efficient and
high-speed production.
BACKGROUND OF THE INVENTION
[0002] Nonwoven fabrics are used in a wide variety of applications
where the engineered qualities of the fabric can be advantageously
employed. These types of fabrics differ from traditional woven or
knitted fabrics in that the fibers or filaments of the fabric are
integrated into a coherent web without traditional textile
processes. Entanglement of the fibrous elements of the fabric
provides the fabric with the desired integrity, with the selected
entanglement process permitting fabrics to be patterned to achieve
desired aesthetics.
[0003] Various prior art patents disclose techniques for
manufacturing nonwoven fabrics by hydroentangling processes. U.S.
Pat. No. 3,485,706, to Evans, hereby incorporated by reference,
discloses a hydroentanglement process for manufacture of nonwoven
fabrics. Hydroentanglement entails the application of high-pressure
water jets to webs of fibers or filaments, whereby the fibers or
filaments are rearranged under the influence of water impingement.
The web is typically positioned on a foraminous forming surface as
it is subjected to impingement by the water jets, whereby the
fibers or filaments of the web become entangled, thus creating a
fabric with coherency and integrity, while the specific features of
the forming surface act to create the desired pattern in the
nonwoven fabric. However, there is no teaching or suggestion in
Evans '706 to form a fabric upon a three-dimensional forming
surface.
[0004] Heretofore, typical hydroentanglement of relatively low
basis weight fabrics with the Evans-type technology has been
problematic. At low basis weights (on the order of less than 30
grams per square meter), there are a relatively low number of
fibers or filaments present for entangling, thus making
entanglement relatively inefficient. Entanglement of these light
basis weight webs on traditional forming surfaces taught by Evans
and its progeny tends to "wash" the low fiber content webs,
rearranging the fibers in a fashion which undesirably results in a
non-uniform product. Entanglement of these low basis weight webs at
relatively high processing speeds compounds the problem of
maintaining uniformity, because the impinging water jet flows
and/or pressures must be relatively increased, which increases the
undesirable tendency to distort the web. Further, the high energy
jets required by high speed entangling processes tend to drive the
fibers into the drain hole openings of the foraminous surface, or
into the interstitial spaces of a woven forming wire. This creates
serious difficulties with web transfer.
[0005] U.S. Pat. No. 5,369,858, to Gilmore et al., discloses a
process for forming apertured nonwoven fabric from melt-blown
microfibers using the Evans-type technology. These types of fibers
are attenuated during known melt-blowing formation techniques,
whereby the fibers have relatively small diameters. This patent
discloses the use of a belt or drum forming surface having a
perforated or foraminated forming surface. Plural hydroentangling
manifolds act against fibers positioned on the forming surface to
displace the fibers from "knuckles" of the forming surface, and
into openings or lower parts of the forming surface topography, as
in Evans. This patent contemplates use of a polymeric net or scrim
for fabric formation, and the formation of fabric having apertures
therein of two different sizes, including formation of fabric from
a first layer of textile fibers or polymeric filaments, and a
second layer of melt-blown microfibers.
[0006] U.S. Pat. No. 5,516,572, to Roe, discloses a disposable
absorbent article including a liquid pervious topsheet, wherein the
topsheet comprises a nonwoven fabric prepared from a homogeneous
admixture of melt-blown fibers and staple length synthetic fibers.
The patent contemplates that fabrics formed in accordance with its
teachings comprise a blend including up to 50% by weight of
melt-blown fibers.
[0007] U.S. Pat. No. 4,805,275, to Suzuki et al., also discloses a
method for forming nonwoven fabrics by hydroentanglement. This
patent contemplates that hydroentanglement of a fibrous web be
effected on a non-three-dimensional smooth-surfaced
water-impermeable endless belt, but notes that at fabric weights
below 15 grams per square meter that irregularities in the fibrous
web occur, and fabrics with substantial uniformity cannot be
obtained.
[0008] In contrast to the above-referenced patents, the present
invention contemplates a process employing a hydroentangling device
having a foraminous forming surface for forming relatively low
basis weight nonwoven fabrics, which can be efficiently practiced
for manufacture of fabrics having a high degree of uniformity. Such
uniformity facilitates use of such fabrics in a wide variety of
applications, with efficient formation facilitating economical
use.
SUMMARY OF THE INVENTION
[0009] A process of making a nonwoven fabric having a low basis
weight in accordance with the principles of the present invention
contemplates hydroentangling on a device having a foraminous
forming surface of a precursor web comprising spunbonded continuous
polymeric filaments. As is known in the art, spunbonding entails
extrusion or "spinning" of thermoplastic polymeric material with
the resultant filaments cooled and drawn or attenuated as they are
collected. The continuous, or essentially endless, filaments may be
bonded, with the process of the subject invention contemplating
that such spunbonded material be employed as the precursor web.
[0010] To form relatively low basis weight fabrics, a precursor web
having a basis weight from about 10 to about 30 grams per square
meter is employed. The present invention further contemplates that
an image transfer device be provided, with the transfer device
having a fabric-forming surface.
[0011] With the precursor web positioned on the hydroentangling
device, hydroentanglement is effected by application of high
pressure liquid streams to the web. Filaments of the web are
rearranged on the fabric-forming surface of the device. The forming
surface of the device, thus acts in concert with the high pressure
liquid streams, to rearrange the filaments of the precursor
web.
[0012] A low basis weight web formed in accordance with the present
invention comprises a web of hydroentangled polymeric filaments
having a denier from 0.2 to 3.0. The filaments are arranged in a
substantially uniform matrix.
[0013] Notably, the characteristics of the spunbonded precursor
web, in particular the strength of its bonds, has a direct
influence on the strength characteristics of the resultant low
basis weight fabric. Development has shown that if the spunbound
precursor web is only relatively lightly bonded, hydroentanglement
acts to break or disrupt the bonds without substantially breaking
the continuous filaments from which the spunbond precursor web is
formed. As a consequence, a low basis weight fabric formed in
accordance with the present invention may be formed to include
substantially continuous filaments (from a relatively lightly
bonded spunbond precursor web), with the resulting fabric having a
machine direction tensile strength of at least about 1,472 grams
per centimeter at 47% machine-direction elongation. The degree of
bonding of the precursor web is specifically selected to facilitate
handling of the web, with the contemplation that higher strength
fabrics can be achieved if the filaments of the precursor web are
maintained in a substantially continuous form. In accordance with
the present invention, it is contemplated that the spunbond
precursor web is subjected to bonding which provides no more than a
minimum tensile strength which permits winding and unwinding of the
precursor web. Thus, the minimal tensile strength of the precursor
web is selected to facilitate efficient handling during
manufacturing of the present low basis weight nonwoven fabric.
[0014] Other features and advantages of the present invention will
become readily apparent from the following detailed description,
the accompanying drawings, and the appended claims.
BRIEF DESCRIPTION OF THE DRAWING
[0015] FIG. 1 is a diagrammatic view of a hydroentangling apparatus
for practicing the process of the present invention, whereby low
basis weight nonwoven fabrics embodying the principles of the
present invention can be formed.
DETAILED DESCRIPTION
[0016] While the present invention is susceptible of embodiment in
various forms, there is shown in the drawings and will hereinafter
be described a presently preferred embodiments, with the
understanding that the present disclosure is to be considered as an
exemplification of the invention, and is not intended to limit the
invention to the specific embodiment illustrated.
[0017] With reference to FIG. 1, therein is illustrated a
hydroentangling apparatus, generally designated 10, which can be
employed for practicing the process of the present invention for
manufacture of a relatively low basis weight nonwoven fabric. The
apparatus is configured generally in accordance with the teachings
of U.S. Pat. No. 5,098,764, to Drelich et al., hereby incorporated
by reference. The apparatus 10 includes an entangling drum 12 which
comprises a hydroentangling device having a foraminous forming
surface upon which hydroentangling of a precursor web is effected
for formation of the present nonwoven fabric.
[0018] In the presently preferred practice of the present
invention, a standard 23-mesh bronze wire screen is employed for
the forming surface of entangling drum 12.
[0019] In the apparatus illustrated in FIG. 1, a plurality of
hydroentangling manifolds, designated 14, 16, and 18, act
sequentially upon a precursor web P trained about entangling drum
12. The precursor web P may be formed in-line with the entanglement
apparatus, as generally illustrated in phantom line, or may be
provided in the form of rolls of material fed into the entangling
apparatus for processing.
[0020] While it is within the purview of the present invention to
employ various types of precursor webs, including fibrous and
continuous filament webs, it is presently preferred to employ
spunbonded continuous filament webs comprising polymeric filaments,
preferably polyester (polyethylene terephthalate). Filament denier
is preferably 0.2 to 3.0, with 1.5 denier filaments being
particularly preferred. The precursor web preferably has a basis
weight from about 10 to 30 grams per square meter, more preferably
from about 15 to 20 grams per square meter. Use of continuous
filament precursor webs is presently preferred because the
filaments are essentially endless, and thus facilitate use of
relatively high energy input during entanglement without
undesirably driving filaments into the image transfer device, as
can occur with staple length fibers or the like. The preferred use
of filamentary precursor webs permits the filament to be subjected
to elevated hydraulic energy levels without undesirable fouling of
the forming surface. Thus, fabrics are formed without substantially
altering the basis weight of the precursor webs.
[0021] A particular benefit of finished fabrics formed in
accordance with the present invention is uniformity of patterning.
Fiber movement from the water jets from the hydroentangling
manifolds is controlled by the shape and depth of the forming
surface and drainage design. The use of higher pressures and flows
is desirably achieved, thus permitting processing of webs at high
speeds and low basis weights. Finished products in the 10 to 30
grams per square meter range are produced at operating speeds up to
hundreds of feet per minute.
[0022] The following is an example of a low basis weight nonwoven
fabric formed in accordance with the present invention. Reference
to manifold pressures is in connection with water pressure, in
pounds per square inch (psi), in the successive hydroentangling
manifolds 14, 16, and 18, illustrated in FIG. 1. Each of these
manifolds included orifice strips having 33.3 holes or orifices per
inch, each having a diameter of 0.0059 inches. The example was made
using a single pass beneath the hydroentangling manifolds, with
each manifold acting against the same side of the precursor web to
form the resultant fabric. Testing of fabrics was conducted in
accordance with ASTON testing protocols.
[0023] A lightly bonded precursor web, as referenced below, may be
produced on a commercial spunbond production line using standard
processing conditions, except thermal point bonding calender
temperatures are reduced, and may be at ambient temperature
(sometimes referred to as cold calendering). For example, during
production of standard polyester spunbond, the thermal point
bonding calender is set at a temperature of 200 to 210 degrees C.
to produce the bonded finished product. In contrast, to prepare a
similar precursor web for subsequent entangling and imaging, the
calender temperature is reduced to 160 degrees C. Similarly, during
production of standard polypropylene spunbond products, the common
thermal point calender conditions are 300 degrees F., and 320
pounds per linear inch (PLI) nip pressure. For a lightly bonded
polypropylene precursor web to be entangled and imaged, these
conditions are reduced to 100 degrees F. and 100 PLI.
EXAMPLE 1
[0024] A relatively lightly bonded spunbond polyester precursor web
was employed having a basis weight of 28 grams per square meter,
with 1.8 denier filaments. The precursor was lightly bonded as
described above. The precursor web was entangled at 80 feet per
minute, with successive manifold pressures of 700, 4,000, and 4,000
psi. A standard 23-mesh bronze wire forming surface was employed.
Energy input was 3.2 horsepower-hour per pound. The resultant
fabric exhibited a basis weight of 32.4 grams per square meter, a
bulk of 0.470 millimeter, a cross-direction strip tensile strength
of 327 grams per centimeter, at a cross-direction elongation of
72%, and a machine direction strip tensile strength of 1,472 grams
per centimeter at a machine direction elongation of 47%.
[0025] It will be noted from the above that Example 1 exhibited
relatively high tensile strength characteristics. It has been
observed that this is a result of the degree of bonding of the
precursor web for the various examples. In Example 1, a relatively
lightly bonded precursor web was employed and it is believed that
when this type of web is subjected to hydroentanglement, there is a
breakage or disruption of the bonds without significant breakage of
the polymeric filaments of the precursor web. In contrast,
precursor webs which were used during development which were
relatively well-bonded, exhibited less strength. It is believed
that during hydroentanglement, disruption and breakage of the
filament bonds resulted in a relatively higher degree of filament
breakage.
[0026] Fabrics formed in accordance with the present invention are
desirably lightweight, exhibiting desirable softness and bulk
characteristics. Fabrics produced in accordance with the present
invention are useful for nonwoven disposable products such as
diaper facing layers, with the present fabrics exhibiting improved
softness compared to typical spunbonded materials. The present
fabrics are preferable to thermally bonded lightweight webs, which
tend to be undesirably stiff. It is believed that fabrics in
accordance with the present invention can be readily employed in
place of traditional point bonded and latex bonded nonwoven
fabrics, dependent upon basis weight and performance
requirements.
[0027] The precursor web used in the above Example which was
characterized as lightly bonded were formed as specified, whereby
the precursor web was bonded to exhibit no more than a minimal
tensile strength which permits winding and unwinding of the web. If
hydroentanglement is effected in-line with production of a spunbond
precursor web, the precursor web may be lightly bonded a sufficient
degree as to permit efficient movement of the precursor web into
the hydroentangling apparatus.
[0028] As illustrated in FIG. 1, subsequent to hydroentanglement,
the fabric being formed may be subjected to dewatering, as
generally illustrated at 20, with chemical application (if any) and
typical drying of the fabric thereafter effected.
[0029] From the foregoing, it will be observed that numerous
modifications and variations can be effected without departing from
the true spirit and scope of the novel concept of the present
invention. It is to be understood that no limitation with respect
to the specific embodiment illustrated herein is intended or should
be inferred. The disclosure is intended to cover, by the appended
claims, all such modifications as fall within the scope of the
claims.
* * * * *