U.S. patent application number 13/821843 was filed with the patent office on 2019-06-27 for method for strengthening a nonwoven fabric.
This patent application is currently assigned to KELHEIM FIBRES GMBH. The applicant listed for this patent is Ingo Bernt, Walter Roggenstein, Anemone Tautenhahn. Invention is credited to Ingo Bernt, Walter Roggenstein, Anemone Tautenhahn.
Application Number | 20190194846 13/821843 |
Document ID | / |
Family ID | 43587658 |
Filed Date | 2019-06-27 |
United States Patent
Application |
20190194846 |
Kind Code |
A1 |
Bernt; Ingo ; et
al. |
June 27, 2019 |
METHOD FOR STRENGTHENING A NONWOVEN FABRIC
Abstract
The invention relates to a method for strengthening a nonwoven
fabric by means of a water jet treatment. The method according to
the invention is characterized in that the nonwoven fabric contains
flat fibers in the form of collapsed hollow viscose fibers with a
ratio of width B to thickness D of B:D.gtoreq.10:1.
Inventors: |
Bernt; Ingo; (Regensburg,
DE) ; Roggenstein; Walter; (Bad Abbach, DE) ;
Tautenhahn; Anemone; (Kelheim, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Bernt; Ingo
Roggenstein; Walter
Tautenhahn; Anemone |
Regensburg
Bad Abbach
Kelheim |
|
DE
DE
DE |
|
|
Assignee: |
KELHEIM FIBRES GMBH
Kelheim
DE
|
Family ID: |
43587658 |
Appl. No.: |
13/821843 |
Filed: |
September 9, 2011 |
PCT Filed: |
September 9, 2011 |
PCT NO: |
PCT/EP2011/065621 |
371 Date: |
May 22, 2013 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
D04H 1/4258 20130101;
D04H 1/492 20130101; D06C 29/005 20130101; D04H 1/4391 20130101;
D04H 1/425 20130101 |
International
Class: |
D04H 1/492 20060101
D04H001/492; D04H 1/4258 20060101 D04H001/4258; D04H 1/4391
20060101 D04H001/4391 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 14, 2010 |
EP |
EP10009534.8 |
Claims
1. A method for strengthening a nonwoven fabric by means of a water
jet treatment, characterized in that the nonwoven fabric comprises
flat fibers in the form of collapsed hollow viscose fibers with a
ratio of width B to thickness D of B:D.gtoreq.10:1.
2. A method according to claim 1, characterized in that the flat
fibers have a ratio B:D ranging from 10:1 to 30:1, preferably of
20:1.
3. A method according to claim 1 or 2, characterized in that the
flat fibers have a titer ranging from 0.9 to 5 dtex, preferably
from 1.3 to 1.9 dtex.
4. A method according to any of the preceding claims, characterized
in that the amount of flat fibers in the nonwoven material is 5% to
100%, preferably 20% or more, particularly preferably 50% or
more.
5. A hydroentangled nonwoven fabric, comprising flat fibers in the
form of collapsed hollow viscose fibers with a ratio of width B to
thickness D of B:D.gtoreq.10:1.
6. A nonwoven fabric according to claim 5, characterized in that
the flat fibers have a ratio B:D ranging from 10:1 to 30:1,
preferably of 20:1.
7. A nonwoven fabric according to claim 5 or 6, characterized in
that the flat fibers have a titer ranging from 0.9 to 5 dtex,
preferably from 1.3 to 1.9 dtex.
8. A nonwoven fabric according to any of claims 5 to 7,
characterized in that the amount of flat fibers in the nonwoven
fabric is 5% to 100%, preferably 20% or more, particularly
preferably 50% or more.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
[0001] The present invention relates to a method for strengthening
a nonwoven fabric by means of a water jet treatment.
[0002] The strengthening of nonwoven fabrics by means of water
jets, which is also referred to as "hydroentanglement" or
"spunlacing", is well known to a person skilled in the art.
[0003] In the production of nonwoven fabrics according to the water
jet process, the strengthening of the presented carded fleece is
achieved by enlacing and swirling the fibers. The presented fibers
are encompassed by the water jets, set in motion and interlaced
with each other three-dimensionally by a swirling motion.
[0004] Cotton is generally regarded as a particularly suitable
fiber material for hydroentanglement, see, for example, the article
"Aquajet Spunlace Verfahren--Technik fur Baumwollfasern" by Alfred
Watzl, Messrs. Fleissner. The low wet modulus of the cotton fibers
as well as the fact that the fiber does not exhibit a round and
smooth fiber cross-section are thereby regarded as beneficial.
[0005] Fibers having a high elastic modulus (hereinafter referred
to as "e-modulus") are suitable for obtaining high web strengths.
These are essentially non-cellulosic fibers.
[0006] In order to achieve sufficient web strengths, high pressures
are required in the course of hydroentanglement, as a result of
which the method is energy-intensive.
SUMMARY OF THE INVENTION
[0007] It is the object of the present invention to provide a
method for the hydroentanglement of nonwoven fabrics which is
feasible with little energy input.
[0008] This object is achieved by a method for strengthening a
nonwoven fabric by means of a water jet treatment which is
characterized in that the nonwoven fabric contains flat fibers in
the form of collapsed hollow viscose fibers with a ratio of width B
to thickness D of B:D.gtoreq.10:1.
[0009] Furthermore, the present invention relates to a
hydroentangled nonwoven fabric containing flat fibers in the form
of collapsed hollow viscose fibers with a ratio of width B to
thickness D of B:D.gtoreq.10:1.
[0010] Preferred embodiments are set forth in the subclaims.
DETAILED DESCRIPTION OF THE INVENTION
[0011] Surprisingly, it has been shown that the use of collapsed
hollow viscose fibers in a nonwoven fabric to be strengthened by
water jets has the effect that, during the hydroentanglement with
equal energy input (i.e., application of equally high treatment
pressures), higher web strengths result than with a similar
nonwoven material which does not contain any flat fibers. Likewise,
a desired web strength can be achieved with an energy input which
is smaller than in case of a nonwoven material which does not
contain any cellulosic flat fibers.
[0012] In this manner, energy can be saved, and process costs can
thus be reduced. In addition, the expenditure with regard to the
equipment can be kept smaller due to the lower pressures. In
addition, it is possible to perform a more gentle strengthening,
i.e., at lower pressures. This is advantageous, for example, in
case of mixtures with cellulose, wherein high pressures cause
cellulose to be washed out, or also in case of mixtures with
delicate fibers. In addition, the use of synthetic fibers (for
achieving particularly high strengths) can be avoided or at least
reduced, respectively.
[0013] In the method according to the invention, the flat fibers
contained in the nonwoven fabric preferably have a ratio B:D
ranging from 10:1 to 30:1, particularly preferably of 20:1.
[0014] Preferably, the flat fibers may have a titer ranging from
0.9 to 5 dtex, particularly preferably from 1.3 to 1.9 dtex.
[0015] Flat fibers and their manufacture are known. In contrast to
the cross-section of fibers which commonly is essentially round,
flat fibers have an essentially flat or, respectively, oblong
cross-section.
[0016] On the one hand, cellulosic flat fibers can be produced by
spinning a spinning dope containing cellulose or a cellulose
derivative through slot-shaped spinnerets. In case of viscose
fibers, flat fibers can alternatively be produced in the form of
collapsed hollow fibers. In doing so, a gas, e.g. nitrogen, or a
blowing agent, e.g., sodium carbonate, is admixed to the spinning
viscose. During the spinning of the fibers through dies, which are
per se conventional, hollow fibers are formed whose walls, however,
are so thin when appropriate process conditions are chosen that the
fibers will collapse and will then be provided in the form of flat
fibers.
[0017] The manufacture of cellulosic flat fibers is known, for
example, from GB 945,306 A, U.S. Pat. Nos. 3,156,605 A, 3,318,990,
GB 1,063,217 A. Such fibers have been recommended especially for
use in paper production, as is described in part in the
above-mentioned documents.
[0018] The article by C. R. Woodings, A. J. Bartholomew; "The
manufacture properties and uses of inflated viscose rayon fibers";
TAPPI Nonwovens Symposium; 1985; pp. 155-165. Source:
http://www.nonwoven.co.uk/publications_cat4.php, describes
different types of hollow fibers and their use.
[0019] WO 2006/134132 describes the use of viscose flat fibers in a
fiber composite for the purpose of improving the dissolubility of
the fiber composite in water. According to WO 2006/134132, the flat
fibers used preferably have a crenelated (pinnacle-type) surface
and, in contrast to collapsed hollow fibers, are thus produced by
being spun through a slot die. The ribbed surface of such flat
fibers reduces the fiber-fiber adhesion and hence the strength. On
the other hand, with conventional flat fibers, the achievable
thickness is limited by the geometry of the die. Final spinnings
with dies having openings with heights of 25 .mu.m generally lead
to a fiber thickness of approx. 4-6 .mu.m. In order to consistently
produce a fiber thickness of approx. 2-3 .mu.m such as with
collapsed hollow fibers, a die opening with a height of approx.
12.5 .mu.m would be required, which is economically feasible
neither in the manufacture of dies, nor in the production of
viscose fibers using conventional methods.
[0020] In contrast, the viscose flat fibers used according to the
invention are collapsed hollow fibers which, as has been mentioned
above, are producible by introducing gas or a blowing agent (in
particular sodium carbonate) into the spinning viscose. The fiber
may be completely collapsed or still slightly opened. However, the
water retention of the fiber should preferably be 200% or less
(measured according to DIN 53814). The fiber cross-section of the
fibers should be predominantly flat and preferably not
branched.
[0021] The amount of flat fibers in the nonwoven fabric is
preferably 5% to 100%, in particular 20% or more, particularly
preferably 50% or more. Hence, the nonwoven material can be made up
entirely of the flat fibers or may also contain a mixture of the
flat fibers with other fibers. All cellulosic and non-cellulosic
fiber materials which are suitable for hydroentanglement are
possible mixing partners. It is obvious to a person skilled in the
art that the effect according to the invention (i.e., the increase
in strength of the nonwoven material and the saving of energy,
respectively) is the more pronounced, the higher the content of
flat fibers in the nonwoven material.
[0022] The invention also relates to a hydroentangled nonwoven
fabric containing flat fibers in the form of collapsed hollow
viscose fibers with a ratio of width B to thickness D of
B:D.gtoreq.10:1. Regarding details as to the flat fibers as well as
their proportion in the nonwoven fabric, see the subclaims and the
above explanations, respectively.
Examples
[0023] For the production of hydroentangled nonwoven fabrics, the
following fibers, each having a titer of 1.7 dtex, were used:
[0024] a) standard viscose fiber (Type Danufil.RTM.) [0025] b)
viscose flat fiber from a hollow fiber process; fiber thickness
approx. 2-3 .mu.m; ratio width:thickness=approx. 20:1
[0026] The fibers were presented as a carded nonwoven and
strengthened on both sides in two passages.
[0027] Nonwoven fabrics with two weights per unit area and, in each
case, two strengthening levels (less-higher strengthening) were
produced from each fiber.
[0028] Weights per unit area: 50 g/m.sup.2 and 80 g/m.sup.2,
respectively
[0029] Strengthening levels: (strengthening pressure in each case
indicated as sum of all pressures of all die bars in both
passages)
Weight per unit area 50 g/m.sup.2-minor strengthening: 65 bar
Weight per unit area 50 g/m.sup.2-higher strengthening: 95 bar
Weight per unit area 80 g/m.sup.2-minor strengthening: 95 bar
Weight per unit area 80 g/m.sup.2-higher strengthening: 145 bar
[0030] The higher strengthening pressure is thus, in each case,
approx. 50% above the low strengthening pressure.
Examination:
[0031] With standard test specimens of 5.times.25 cm, the following
parameters were determined for all nonwoven fabrics: [0032] maximum
tensile strength [N/5 cm] in the production direction (MD) and
transversely to the production direction (CD), in each case wet and
dry [0033] maximum tensile strength elongation
[0034] and, respectively, the ratio MD/CD as well as the sum MD+CD,
which have been derived therefrom
[0035] The results are summarized in the following tables:
TABLE-US-00001 TABLE 1a nonwoven fabric from a viscose flat fiber
(according to the invention) dry maximum tensile weight strength
elongation per unit strengthening [N/5 cm] [%] area level MD CD MD
CD MD/CD 50 g/m.sup.2 minor 40.1 34.0 17.0 31.4 1.18 50 g/m.sup.2
high 38.9 33.3 16.2 29.1 1.17 80 g/m.sup.2 minor 62.0 60.9 18.3
34.5 1.02 80 g/m.sup.2 high 59.8 59.8 14.7 30.6 1.00
TABLE-US-00002 TABLE 1b nonwoven fabric from a viscose flat fiber
(according to the invention) wet maximum tensile weight strength
elongation per unit strengthening [N/5 cm] [%] area level MD CD MD
CD MD/CD 50 g/m.sup.2 minor 27.4 22.6 27.8 34.1 1.21 50 g/m.sup.2
high 29.9 24.6 27.9 31.0 1.22 80 g/m.sup.2 minor 44.3 40.3 28.6
35.8 1.10 80 g/m.sup.2 high 45.0 37.8 28.5 31.7 1.19
TABLE-US-00003 TABLE 2a nonwoven fabric from a standard viscose
fiber (comparison) dry maximum tensile weight strength elongation
per unit strengthening [N/5 cm] [%] area level MD CD MD CD MD/CD 50
g/m.sup.2 minor 21.0 33.5 26.1 41.6 0.62 50 g/m.sup.2 high 38.8
42.5 30.6 37.8 0.91 80 g/m.sup.2 minor 10.8 51.3 13.6 42.4 0.21 80
g/m.sup.2 high 29.7 69.2 19.5 36.1 0.43
TABLE-US-00004 TABLE 2b nonwoven fabric from a standard viscose
fiber (comparison) wet maximum tensile weight strength elongation
per unit strengthening [N/5 cm] [%] area level MD CD MD CD MD/CD 50
g/m.sup.2 minor 18.0 19.8 16.8 29.9 0.91 50 g/m.sup.2 high 21.3
24.7 25.1 30.5 0.86 80 g/m.sup.2 minor 5.9 21.5 16.8 29.9 0.27 80
g/m.sup.2 high 18.5 41.2 25.1 30.5 0.45
[0036] From the above-indicated data, the following conclusions can
be drawn:
Elongation:
[0037] In the dry nonwoven fabric, the maximum tensile strength
elongation (with equal weight per unit area and equal
strengthening) is clearly lower in the nonwoven fabrics produced
from flat fibers, as opposed to a nonwoven fabric produced from
standard viscose fibers. Presumably, this is due to the higher
amount of fiber-fiber bonds.
MD/CD Ratio:
[0038] Under equal experimental settings, nonwoven fabrics
comprising flat fibers exhibit a substantially higher MD/CD ratio
than nonwoven fabrics made of standard viscose fibers.
[0039] Starting from a low MD/CD ratio with minor strengthenings,
the MD/CD ratio increases as a result of a reorientation of the
fibers in the strengthening process. The MD/CD ratio of the
nonwoven fabrics made of flat fibers, which, under equal pressures,
is substantially higher than that of nonwoven fabrics made of
standard viscose fibers, indicates the considerably higher
flexibility of the flat fiber, which significantly facilitates the
strengthening process.
Strength:
TABLE-US-00005 [0040] TABLE 3 nonwoven fabric from a viscose flat
fiber (according to the invention) dry wet maximum maximum weight
tensile strength tensile strength per unit strengthening [N/5 cm]
[N/5 cm] area level MD + CD MD + CD 50 g/m.sup.2 minor 74.1 50.1 50
g/m.sup.2 high 72.3 54.5 80 g/m.sup.2 minor 122.9 84.7 80 g/m.sup.2
high 119.6 82.8
TABLE-US-00006 TABLE 4 nonwoven fabric from a standard viscose
fiber (comparison) dry wet maximum maximum weight tensile strength
tensile strength per unit strengthening [N/5 cm] [N/5 cm] area
level MD + CD MD + CD 50 g/m.sup.2 minor 54.5 37.8 50 g/m.sup.2
high 81.3 46.0 80 g/m.sup.2 minor 62.1 27.4 80 g/m.sup.2 high 98.8
59.8
[0041] For the sake of ease of examining, the sum of the tearing
forces MD+CD is to be used in each case for assessing the
strength:
[0042] As to the nonwoven fabrics according to the invention made
of flat fibers, it is apparent that a higher strength is not
achieved by increasing the strengthening pressure from "minor" to
"high". This means that, obviously, the nonwoven material was
already strengthened to the maximum extent always at the low
strengthening level.
[0043] With equal strengthening, the strength of a nonwoven fabric
normally correlates with the weight per unit area.
[0044] In this case, the ratio of the weights per unit area is 80
g/m.sup.2 to 50 g/m.sup.2=1.6.
[0045] Based, for example, on a measured strength of approx. 72 N/5
cm of the highly strengthened nonwoven fabric having a weight per
unit area of 50 g/m.sup.2, a strength of 72*1.6=115 N/5 cm might
thus be expected for the nonwoven fabric with a weight per unit
area of 80 g/m.sup.2 which has been strengthened equally high,
which complies well with the actually measured value of approx.
120.
[0046] This means that, in all four configurations, the nonwoven
material has already been strengthened to a maximum extent.
[0047] With the nonwoven fabrics made of standard viscose fibers, a
different picture emerges:
[0048] In a haptic assessment, the two nonwoven materials of the
minor strengthening level have been strengthened only
insufficiently.
[0049] Upon an increase of the strengthening pressure from "minor"
to "high" (always by approx. 50%), a clear increase in web strength
can, in each case, be determined. Thus, a further pressure increase
might in this case obviously result in still a further
strengthening, which means that, for maximum strengthening, an even
higher pressure would be required.
[0050] At the higher strengthening level of the 50 g/m.sup.2
nonwoven fabric, the strength of the dry nonwoven fabric is even
slightly above the strength of the nonwoven fabric made of flat
fibers. This is probably caused by the higher single-fiber strength
of the fibers used in the experiment (standard viscose fiber: 22
cN/tex; viscose flat fiber: 16 cN/tex). However, it may be assumed
that the nonwoven material has thereby been strengthened to a large
extent.
[0051] Thus, according to the above calculation, a strength of at
least 81.3.times.1.6=130 N/5 cm might be expected for a completely
strengthened nonwoven material with a weight per unit area of 80
g/m.sup.2. However, only about 99 N/5 cm were measured. Thus, even
with the application of a higher strengthening pressure, the 80
g/m.sup.2 nonwoven fabric is still far from completely
strengthened.
[0052] At said strengthening level, the nonwoven material has
achieved only about 75% of its strengthening potential.
Comparison:
[0053] The example of the 80 g/m.sup.2 nonwoven fabrics clearly
shows the advantages of the use according to the invention of flat
fibers in hydroentanglement.
[0054] Nonwoven fabric from a viscose flat fiber--at a
strengthening pressure of 95 bar:
Strength dry (MD+CD)=120N/5 cm;
Strength wet (MD+CD)=83N/5 cm
[0055] Nonwoven fabric from a standard viscose fiber--at a
strengthening pressure of 145 bar:
Strength dry (MD+CD)=99N/5 cm;
Strength wet (MD+CD)=60N/5 cm
[0056] Hence, by using viscose flat fibers in the nonwoven
material, strengths which are higher by 20% (dry) and,
respectively, higher by 40% (wet) than with standard viscose fibers
can be achieved at 50% lower pressures.
* * * * *
References