U.S. patent application number 10/976850 was filed with the patent office on 2005-05-05 for method of producing a nonwoven material.
This patent application is currently assigned to SCA HYGIENE PRODUCTS AB. Invention is credited to Billgren, Tomas, Lindstedt, Hein, Soderberg, Mats, Versteeg, Mees.
Application Number | 20050091811 10/976850 |
Document ID | / |
Family ID | 34556024 |
Filed Date | 2005-05-05 |
United States Patent
Application |
20050091811 |
Kind Code |
A1 |
Billgren, Tomas ; et
al. |
May 5, 2005 |
Method of producing a nonwoven material
Abstract
Method of producing a nonwoven material, wherein a fibrous web
containing continuous filaments and natural fibers and/or staple
fibers is formed on a forming member (12) and subsequently
hydroentangled to form the nonwoven material. The fibrous web is
transferred to an entangling member (16) while subjecting the
fibrous web to foreshortening and subsequently hydroentangling the
foreshortened fibrous web, thus forming a composite material (19)
wherein the continuous filaments are well integrated with the rest
of the fibers.
Inventors: |
Billgren, Tomas; (Kullavik,
SE) ; Soderberg, Mats; (Sundsvall, SE) ;
Versteeg, Mees; (Suamer, NL) ; Lindstedt, Hein;
(Burgum, NL) |
Correspondence
Address: |
YOUNG & THOMPSON
745 SOUTH 23RD STREET
2ND FLOOR
ARLINGTON
VA
22202
US
|
Assignee: |
SCA HYGIENE PRODUCTS AB
GOTEBORG
SE
|
Family ID: |
34556024 |
Appl. No.: |
10/976850 |
Filed: |
November 1, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60515640 |
Oct 31, 2003 |
|
|
|
Current U.S.
Class: |
28/104 |
Current CPC
Class: |
D04H 5/03 20130101; D04H
1/49 20130101; D04H 1/732 20130101; D04H 5/02 20130101 |
Class at
Publication: |
028/104 |
International
Class: |
D04H 001/46 |
Claims
1. In a method of producing a nonwoven material, which comprises:
forming a fibrous web containing continuous filaments and natural
fibers and/or staple fibers on a forming member and subsequently
hydroentangling to form said nonwoven material; the improvement
which comprises transferring the fibrous web to an entangling
member while subjecting said fibrous web to foreshortening and
subsequently hydroentangling the foreshortened fibrous web, thus
forming a composite material wherein the continuous filaments are
well integrated with the rest of the fibers.
2. The method as claimed in claim 1, wherein the fibrous web is
exerted to a pre-hydroentangling step before being
foreshortened.
3. The method as claimed in claim 1, further comprising driving the
forming member at a higher speed than the entangling member thus
providing a foreshortening effect of the fibrous web when
transferring the web between said members.
4. The method as claimed in claim 3, wherein the fibrous web is
transferred to the entangling member via a transfer member, the
entangling member is driven at a lower speed than the forming
member, and the transfer member is driven at a speed intermediate
that of the forming and entangling members.
5. The method as claimed in claim 1, wherein the fibrous web is
wet-formed or foam-formed.
6. The method as claimed in claim 1, wherein the fibrous web
comprises between 20 and 85% by weight natural fibers.
7. The method as claimed in claim 1, wherein the natural fibers are
pulp fibers.
8. The method as claimed in claim 1, wherein the fibrous web
contains between 5 and 50% by weight synthetic or regenerated
staple fibers.
9. The method as claimed in claim 8, wherein at least a major part
of the synthetic staple fibers have a fiber length between 3 and 7
mm.
10. The method as claimed in claim 1, wherein the fibrous web
contains between 0.5 and 50% by weight continuous filaments.
11. The method as claimed in claim 10, wherein the continuous
filaments are in the form of spunlaid or meltblown filaments.
12. The method as claimed in claim 1, wherein the fibrous web
comprises between 40 and 75% by weight natural fibers.
13. The method as claimed in claim 1, wherein the fibrous web
contains between 5 and 20% by weight synthetic or regenerated
staple fibers.
14. The method as claimed in claim 1, wherein the fibrous web
contains between 15 and 30% by weight continuous filaments.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims the 35 U.S.C. 119(e) benefit of
prior provisional application Ser. No. 60/515,640 filed on Oct. 31,
2003.
FIELD OF THE INVENTION
[0002] The present invention refers to a method of producing a
nonwoven material, wherein a fibrous web containing continuous
filaments and natural fibers and/or synthetic staple fibers is
formed on a forming member and subsequently hydroentangled to form
said nonwoven material.
BACKGROUND OF THE INVENTION
[0003] Hydroentangling or spunlacing is a technique introduced
during the 1970's, see e.g. CA patent no. 841 938. The method
involves forming a fiber web which is either drylaid or wetlaid,
after which the fibers are entangled by means of very fine water
jets under high pressure. The water jets twist the fibers around
each other giving the web strength. Several rows of water jets are
directed against the fiber web which is supported by a movable
wire. The entangled fiber web is then dried. The fibers that are
used in the material can be synthetic or regenerated staple fibers,
e.g. polyester, polyamide, polypropylene, rayon or the like, pulp
fibers or mixtures of pulp fibers and staple fibers. Spunlace
materials can be produced in high quality at a reasonable cost and
have a high absorption capacity. They can e.g. be used as wiping
material for household or industrial use, as disposable materials
in medical care and for hygiene purposes etc. Through e.g. EP-A-0
333 211 and EP-A-0 333 228 it is known to hydroentangle a fiber
mixture in which one of the fiber components is meltblown fibers.
The base material, i.e. the fibrous material which is exerted to
hydroentangling, either consists of at least two preformed fibrous
layers where one layer is composed of meltblown fibers or of a
"coform material" where an essentially homogeneous mixture of
meltblown fibers and other fibers is airlaid on a wire and after
that is exerted to hydroentangling.
[0004] Through EP-A-0 308 320 it is known to bring together a web
of continuous filaments with a wetlaid fibrous material containing
pulp fibers and staple fibers and hydroentangle together the
separately formed fibrous webs to a laminate. In such a material
the fibers of the different fibrous webs will not be integrated
with each other since the fibers already before the hydroentangling
are bonded to each other and only have a very limited mobility.
[0005] EP-A-0 938 601 discloses a method of producing a nonwoven
material by hydroentangling a fiber mixture containing continuous
filaments, e.g. meltblown and/or spunbond fibers, and other fibers
The method is characterized by foamforming a fibrous web of natural
fibers and/or synthetic staple fibers and hydroentangling together
the foamed fiber dispersion with the continuous filaments for
forming a composite material, in which the continuous filaments are
well integrated with the rest of the fibers.
OBJECT AND SUMMARY OF THE INVENTION
[0006] The object of the present invention is to provide a method
for producing a hydroentangled nonwoven material of a fibrous
mixture of continuous filaments, for example in the form of
meltblown and/or spunbond fibers and natural fibers and/or
synthetic or regenerated staple fibers, in which there is given a
high freedom in the choice of fibers and fiber lengths and where
the continuous filaments are well integrated with the rest of the
fibers. This has according to the invention been obtained by
transferring the fibrous web to an entangling member while
subjecting said fibrous web to foreshortening and subsequently
hydroentangling the foreshortened fibrous web, thus forming a
composite material wherein the continuous filaments are well
integrated with the rest of the fibers.
[0007] Other features of the invention are disclosed in the
dependent claims and in the description below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The invention will below be closer described with reference
to an embodiment shown in the accompanying drawings.
[0009] FIG. 1 shows schematically an embodiment of a process for
producing a hydroentangled nonwoven material according to the
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0010] The hydroentangled composite material according to the
invention comprises a mixture of continuous filaments and natural
fibers and/or synthetic staple fibers. These different types of
fibers are defined as follows.
[0011] Continuous Filaments
[0012] The continuous filaments are fibers that in proportion to
their diameter are very long, in principle endless. They can be
produced by extruding a molten thermoplastic polymer through fine
nozzles, whereafter the polymer will be cooled and drawn,
preferably by the action of an air flow blown at and along the
polymer streams, and solidified into strands that can be treated by
drawing, stretching or crimping. Chemicals for additional functions
can be added to the surface.
[0013] Filaments can also be regenerated fibers produced by
chemical reaction of a solution of fiber-forming reactants entering
a reagent medium, for example by spinning of regenerated cellulose
fibers from a cellulose xanthate solution into sulphuric acid.
Examples of regenerated cellulose fibers are rayon, viscose or
lyocell fibers.
[0014] Continuous filaments may be in the form of spunlaid
filaments or meltblown filaments. Spunlaid filaments are produced
by extruding a molten polymer, cool and stretch to an appropriate
diameter. The fiber diameter is usually above 10 .mu.m, e.g.
between 10 and 100 .mu.m. Production of spunlaid filaments is e.g.
described in U.S. Pat. Nos. 4,813,864 and 5,545,371.
[0015] Meltblown filaments are formed by means of a meltblown
equipment 10, for example of the kind shown in the U.S. Pat. Nos.
3,849,241 or 4,048,364. The method shortly involves that a molten
polymer is extruded through a nozzle in very fine streams and
converging hot air streams are directed towards the polymer streams
so that they are drawn out into continuous filaments with a very
small diameter. The filaments can be microfibers or macrofibers
depending on their dimension. Microfibers have a diameter of up to
20 .mu.m, but usually are in the interval between 2 and 12 .mu.m in
diameter. Macrofibers have a diameter of over 20 .mu.m, e.g.
between 20 and 100 .mu.m.
[0016] All thermoplastic polymers can in principle be used for
producing spunlaid and meltblown filaments. Examples of useful
polymers are polyolefins, such as polyethylene and polypropylene,
polyamides, polyesters and polylactides. Copolymers of these
polymers may of course also be used.
[0017] Tow is another type of filaments, which normally are the
starting material in the production of staple fibers, but which
also is sold and used as a product of its own. In the same way as
in the production of spunlaid fibers, tow is produced from fine
polymer streams that are drawn out and stretched, but instead of
being laid down on a moving surface to form a web, they are kept in
a bundle to finalize drawing and stretching. When staple fibers are
produced, this bundle of filaments is then treated with spin finish
chemicals, are often crimped and then fed into a cutting stage
where a wheel with knives will cut the filaments into distinct
fiber lengths that are packed into bales to be shipped and used as
staple fibers. When tow is produced, the filament bundles are
packed, with or without spin finish chemicals, into bales or
boxes.
[0018] The continuous filaments will in the following be described
as spunlaid fibers, but it is understood that also other types of
continuous filaments, e.g. meltblown fibers, can be used.
[0019] Natural Fibers
[0020] The natural fibers are usually cellulose fibers, such as
pulp fibers or fibers from grass or straw. Pulp fibers are the most
commonly used natural fibers and are used in the material for their
tendency to absorb water and for their tendency to create a
coherent sheet. Both softwood fibers and hardwood fibers are
suitable, and also recycled fibers can be used. The fiber lengths
will vary from around 2-3 mm for softwood fibers and around 1-1.5
mm for hardwood fibers, and even shorter for recycled fibers as
well as blends of these. Other natural fibers that are commonly
used in nonwoven materials are cotton and hemp.
[0021] Staple Fibers
[0022] The staple fibers used can be produced from the same
substances and by the same processes as the filaments discussed
above. They may either be synthetic fibers or regenerated cellulose
fibers, such as rayon, viscose or lyocell. The cutting of the fiber
bundles is normally done to result in a single cut length, which
can be altered by varying the distances between the knives of the
cutting wheel. The fiber lengths of conventional wetlaid
hydroentangled nonwovens are usually in the interval 12-18 mm.
However according to the present invention also shorter fiber
lengths, from about 2-3 mm, can be used.
[0023] The Process
[0024] According to the embodiment shown in FIG. 1 continuous
filaments 11 in the form of spunlaid fibers are produced by
extruding a molten polymer, cool and stretch to an appropriate
diameter. The fiber diameter is usually above 10 .mu.m, e.g.
between 10 and 100 .mu.m. The spunlaid filaments are laid down
directly on a forming wire 12 where they are allowed to form a
relatively loose, open web structure in which the fibers are
relatively free from each other. This is achieved either by making
the distance between the spunlaying nozzle and the wire relatively
large, so that the filaments are allowed to cool down before they
land on the wire 12, at which their stickiness is reduced. The
basis weight of the formed spunlaid layer should be between 2 and
50 g/m.sup.2 and the bulk between 5 and 15 cm.sup.3/g.
[0025] In an alternative embodiment meltblown fibers are formed by
means of a meltblown equipment. The meltblown technique shortly
involves that a molten polymer is extruded through a nozzle in very
fine streams and converging air streams are directed towards the
polymer streams so that they are drawn out into continuous
filaments with a very small diameter. The fibers can be microfibers
or macrofibers depending on their dimension. Microfibers have a
diameter of up to 20 .mu.m, but usually are in the interval between
2 and 12 .mu.m in diameter. Macrofibers have a diameter of over 20
.mu.m, e.g. between 20 and 100 .mu.m.
[0026] An aqueous or a foamed fibrous dispersion 13 from a headbox
14 is laid on top of the spunlaid filaments. In wet laying
technique the fibers are dispersed in water, with optional
additives, and the fiber dispersion is dewatered on a forming
fabric to form a wet laid fibrous web. In foam forming technique a
fibrous web is formed from a dispersion of fibers in a foamed
liquid containing water and a tenside. The foamforming technique is
described in for example GB 1,329,409, U.S. Pat. No. 4,443,297, WO
96/02701 and EP-A-0 938 601. A foam-formed fibrous web has a very
uniform fiber formation. For a more detailed description of the
foamforming technique reference is made to the above mentioned
documents.
[0027] Prior to the headbox 14 the spunlaid filaments are according
to one embodiment wetted in a spraybar 23 or gentle shower. The
wettening of the filaments takes place at a very low pressure so
that no substantial bonding of sideways displacement of the fibers
take place. The surface tension of the water will adhere the
filaments to the wire so the formation will not distort while
entering the headbox. In some cases, when hydrophobic polymers are
used for forming the spunlaid filaments, a tenside may be added in
the spraybar 23 to wet the fibers.
[0028] Fibers of many different kinds and in different mixing
proportions can be used for making the wet laid or foam formed
fibrous web. Thus there can be used pulp fibers or mixtures of pulp
fibers and synthetic staple fibers, e.g. polyester, polyethylene,
polypropylene, polyamide, polylactide, rayon, viscose, lyocell etc.
Other natural fibers than pulp fibers may further be used, such as
seed hair fibers, e.g. cotton, kapok and milkweed; leaf fibers e.g.
sisal, abaca, pineapple, New Zealand hamp, or bast fibers, e.g.
flax, hemp, ramie, jute, kenaf. Varying fiber lengths can be used.
However, according to the invention, it is of advantage to use
relatively short staple fibers, below 10 mm, preferably in the
interval 2 to 8 mm and more preferably 3 to 7 mm. This is because
short fibers will more easily mix and integrate with the spunlaid
filaments than longer fibers. There will also be more fiber ends
sticking out form the material, which increases softness and
textile feeling of the material. For short staple fibers both wet
laying and foam forming techniques may be used.
[0029] In foam forming technique longer fibers can be used than
what is possible with wetlaying technique. Long fibers, around
18-30 mm, may be an advantage in hydroentangling, since they
increase the strength of the material in dry as well as in wet
condition.
[0030] It is preferred that the fibrous web contains between 5 and
50% by weight, preferably between 5 and 20% by weight staple
fibers. As stated above, for many applications it is advantageous
to use short staple fibers, between 3 and 7 mm. In one embodiment a
major part have a length in the interval 3 to 7 mm, wherein a major
part refers to at least 50, preferably at least 70, more preferably
at least 90 and most preferably at least 100% by weight of the
staple fibers present in the material have a length in said
interval.
[0031] As a substitute for pulp fibers other natural fibers with a
short fiber length may be used, e.g. esparto grass, phalaris
arundinacea and straw from crop seed.
[0032] It is preferred that the fibrous web comprises between 20
and 85% by weight, preferably between 40 and 75% by weight natural
fibers, such as pulp fibers or substitutes therefore. It is further
preferred that the fibrous web contains between 0.5 and 50% by
weight, preferably between 15 and 30% by weight, continuous
filaments, especially in the form of spunlaid or meltblown
filaments.
[0033] The fiber dispersion laid on top of the spunlaid filaments
is dewatered by suction boxes arranged under the wire 12. This
provides the possibility to control the moisture content of the web
before entering the subsequent foreshortening step. A higher
moisture content increases the mobility of the fibers and their
ability to rearrange and vice versa.
[0034] A spray station 15 may according to one embodiment be a
pre-entangling station including one or several rows of nozzles
from which very fine water jets under high pressure are directed
against the fibrous web to provide a pre-entangling of the fibrous
web. This pre-entangling binds the fibrous web to a certain degree,
which should however not be higher than to allow a certain
rearrangement of the structure in the subsequent foreshortening
step. The pre-entangling step may in an alternative embodiment be
eliminated.
[0035] The fibrous web is then transferred to an entangling wire 16
via a transfer wire 17. The entangling wire 16 is driven at a lower
speed than the forming wire 12, and the transfer wire 17 is
preferably driven at a speed intermediate that of the forming and
entangling wires. Suction boxes 21 and 22 are arranged at the
points of transfer between the wires.
[0036] Due to the speed difference, which normally is below 20%,
the fibrous web is braked at the transfer between the wires,
resulting in a foreshortening or compacting effect. This technique,
sometimes called rush transfer, of transferring a fibrous web
between wires driven with different speed, in order to provide a
foreshortening effect of the fibrous web, is known from the
papermaking field, especially tissue paper making. It is for
example referred to U.S. Pat. No. 5,607,551.
[0037] At this so called rush transfer the fibrous web will in some
sense be stuffed into the second wire. Because of the suction box
21 the fibrous web will be drained from water at the same time as
it is stuffed in the surface of the transfer wire 17. Free from
water the short fibers will to a certain degree rearrange to a more
three-dimensional structure and the spunlaid filaments will catch
some curls, bights and loops. The formation of curls will be eased
if a three-dimensional structure is created already by the forming
wire 12. These curls will ease the formation of loops in the
entangling process and increase the penetration of the pulp into
the spunlaid web. The increased mobility of the fibers will
facilitate the intertwining of the fibers and will result in a
structure where the pulp fibers are more firmly caught in the
material.
[0038] The transfer fabric 17 may be replaced by a transfer
roll.
[0039] The angles between the wires in the points of transfer
should preferably be adjustable.
[0040] The type of foreshortening the fibrous web is exerted to by
transferring it between wires driven at different speeds as
described above, may be replaced by any other appropriate type of
foreshortening a fibrous web, such as creping or micro creping,
which e.g. is disclosed in U.S. Pat. No. 3,260,778 and U.S. Pat.
No. 4,432,927, or through the so called "Clupak"-method, according
to which a wet paper web is compacted by being placed on a rubber
belt and be exerted to a varying tensile stress as is disclosed in
U.S. Pat. No. 2,264,245.
[0041] After having been transferred to the entangling wire 16 the
fibrous web is hydroentangled in an entangling station 18 including
several rows of nozzles from which very fine water jets under high
pressure are directed against the fibrous web to provide an
entangling of the web. For a further description of the
hydroentangling technique or, as it is also called, the spunlace
technique, reference is made to e.g. CA patent 841,938. The
entangling wire may optionally be patterned in order to form a
patterned nonwoven material.
[0042] The foreshortening of the fibrous web creates a structure
that more easily will mix and entangle in the subsequent
hydroentangling step, which results in a composite nonwoven having
a good integration between the spunlaid filaments, pulp and staple
fibers. During the foreshortening when the web is compacted a part
of the short pulp fibers and staple fibers will take a position
oriented more in the z-direction of the web than would otherwise be
obtained. This will result in improved absorption characteristics
of the material. It will also improve the textile feeling of the
material due to an increased amount of fiber ends sticking out.
[0043] The forming wire 12 and/or the entangling wire 16 may of
course be substituted for another appropriate forming and
entangling member respectively, such as an apertured belt, an
apertured drum etc.
[0044] After the hydroentangling the material 19 is dried and wound
up. The material is then converted in a known manner to a suitable
format and is packed.
* * * * *