U.S. patent application number 11/018535 was filed with the patent office on 2005-07-21 for method for adding a softening and/or debonding agent to a hydroentangled nonwoven material.
This patent application is currently assigned to SCA HYGIENE PRODUCTS. Invention is credited to Rucinska, Ewa, Stralin, Anders, Strandqvist, Mikael.
Application Number | 20050155199 11/018535 |
Document ID | / |
Family ID | 34752401 |
Filed Date | 2005-07-21 |
United States Patent
Application |
20050155199 |
Kind Code |
A1 |
Stralin, Anders ; et
al. |
July 21, 2005 |
Method for adding a softening and/or debonding agent to a
hydroentangled nonwoven material
Abstract
Method of adding a softening and/or debonding agent to a fiber
web of a hydroentangled nonwoven material comprising cellulose pulp
fibers. The softening and/or debonding agent is added in an inline
manufacturing process of the hydroentangled nonwoven material,
subsequent to the hydroentanglement of the nonwoven material. The
softening and/or debonding agent is added via a size press or a
foulard comprising a soaking step to soak the hydroentangled
nonwoven material with the added softening and/or debonding agent,
and a pressing step, which causes the added softening and/or
debonding agent to penetrate and impregnate the hydroentangled
nonwoven material.
Inventors: |
Stralin, Anders; (Torslanda,
SE) ; Rucinska, Ewa; (Goteborg, SE) ;
Strandqvist, Mikael; (Lindome, SE) |
Correspondence
Address: |
YOUNG & THOMPSON
745 SOUTH 23RD STREET
2ND FLOOR
ARLINGTON
VA
22202
US
|
Assignee: |
SCA HYGIENE PRODUCTS
GOTEBORG
SE
|
Family ID: |
34752401 |
Appl. No.: |
11/018535 |
Filed: |
December 22, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60530887 |
Dec 22, 2003 |
|
|
|
Current U.S.
Class: |
28/103 ;
264/211.12; 28/104; 28/165 |
Current CPC
Class: |
D04H 1/492 20130101 |
Class at
Publication: |
028/103 ;
264/211.12; 028/104; 028/165 |
International
Class: |
D04H 001/46 |
Claims
1. Method of adding a softening and/or debonding agent to a fiber
web of a hydroentangled nonwoven material comprising cellulose pulp
fibers, which comprises adding the softening and/or debonding agent
in an inline manufacturing process of the hydroentangled nonwoven
material, subsequent to the hydroentanglement of the nonwoven
material, whereby the softening and/or debonding agent is added via
a size press or a foulard comprising a soaking step to soak the
hydroentangled nonwoven material with the added softening and/or
debonding agent, and a pressing step, which causes the added
softening and/or debonding agent to penetrate and impregnate the
hydroentangled nonwoven material.
2. The method according to claim 1, further comprising a dewatering
step between the hydroentanglement step and the subsequent step
where the softening and/or debonding agent is added.
3. The method according to claim 1, wherein the hydroentangled
nonwoven material has a dry content when adding the softening
and/or debonding agent of at least about 25% but not more than
about 50%.
4. The method according to claim 1, wherein the fiber web of the
hydroentangled nonwoven material comprises at least about 20% dry
weight of cellulose pulp fibers.
5. The method according to claim 1, wherein the softening and/or
debonding agent is added in the soaking step via a size press at
the pressing step.
6. The method according to claim 1, wherein the pressing step is
subsequent to the soaking step where the softening and/or debonding
agent is added via a foulard.
7. The method according to claim 1, wherein the hydroentangled
nonwoven material comprises at least one of synthetic fibers,
staple fibers, and continuous filaments.
8. The method according to claim 7, wherein the manufacturing
process of the hydroentangled nonwoven material comprises a step
where the synthetic fibers and/or filaments are extruded or laid
down into a web in one step, and the cellulose pulp fibers are
wetlaid or foamformed onto this thus formed web in a step preceding
the hydroentanglement step.
9. The method according to claim 7, wherein the manufacturing
process of the hydroentangled nonwoven material comprises a step
where the cellulose pulp fibers are wetlaid or foamformed, and the
synthetic fibers and/or filaments are laid down onto this thus
formed web in a step preceding the hydroentanglement step.
10. The method according to claim 8, wherein the cellulose pulp
fibers comprises synthetic fibers in the form of staple fibers when
being wetlaid or foamformed.
11. The method according to claim 9, wherein the cellulose pulp
fibers comprises synthetic fibers in the form of staple fibers when
being wetlaid or foamformed.
12. The method according to claim 1, wherein the hydroentangled
nonwoven material has a dry content when adding the softening
and/or debonding agent of at least about 30% but not more than
about 40%.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the 35 USC 119(e) benefit of prior
U.S. Provisional application 60/530,887 filed on Dec. 22, 2003.
FIELD OF THE INVENTION
[0002] The invention relates to a method of adding a softening
and/or debonding agent to a fiber web of a hydroentangled nonwoven
material comprising cellulose pulp fibers.
BACKGROUND OF THE INVENTION
[0003] Typical properties of hydroentangled nonwoven include the
ready ability to absorb tensile stress energy, their drapability,
and good textile-like flexibility, properties that are frequently
referred to as bulk softness, a high surface softness, and a high
specific volume with a perceptible thickness. Further desirable
properties are as high a liquid absorbency as possible and,
depending on the application, a suitable wet and dry strength as
well as an attractive visual appearance of the outer product
surface. These properties, among others, allow hydroentangled
nonwoven to be used for example as cleaning wipes: paper or
nonwoven wipe, windscreen cleaning wipe, kitchen paper, etc,
sanitary products: e.g. toilet paper, paper or nonwoven
handkerchiefs, household towels, towels, cosmetic wipes: facials
and as serviettes or napkins just to mention some of the products
that can be used.
[0004] The components and added chemicals included in nonwoven
material are chosen in accordance with the intended field of use.
The softening and/or debonding agents decrease the hydrogen bonding
between the cellulose pulp fibers, resulting in higher bulk
softness.
[0005] Added chemical agents or additives are in the conventional
prior art often applied in the wet end of the process. U.S. Pat.
No. 3,736,097 describes a method of producing a nonwoven material
with a softening or swelling agent added to the fibers in the wet
end. In a first step, the fibers are pretreated with the softening
or swelling agent. Subsequently, the fibers are formed into a web
in a forming step. Such a web could have a hydroentanglement
process step succeeding the forming step.
[0006] Hydroentangling or spuilacing is a technique introduced
during the 1970'ies, 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. Several rows of water jets are directed
against the fiber web, which is supported by a movable fabric or
drum. The fibers are thereby subjected to a mechanically entangling
and intertwining action of the fibers to form the nonwoven web. The
entangled fiber web is then dried. The fibers that are used in the
nonwoven web can be synthetic or regenerated cellulose staple
fibers, e.g. polyester, polyamide, polypropylene, rayon or the
like, pulp fibers or mixtures of pulp fibers and staple fibers.
Hydroentangled materials of high quality can be produced to a
reasonable cost and have a high absorption capacity. They can be
used as wiping materials for household or industrial use, for
hygiene purposes or as disposable materials in medical care or
hygiene products, etc.
[0007] Many of the hydroentangled nonwoven materials are also
pressed in order to dewater the material before drying. This
process step makes the material stiffer.
[0008] One of the disadvantages of adding chemicals in the wet end
of the process is that the retention of different chemicals added
in the wet end onto the fibers is generally relatively poor. Also,
to be able to add chemicals in the wet end, the attraction between
the fibers and the chemicals has to be strong enough to withstand
the subsequent hydroentanglement steps. However, the low strength
of the bond between the added chemical and the fiber does not
withstand the hydroentanglement process step. If chemicals, such as
softening or debonding agents are added in the wet end, which is
the case according to the conventional technique, these added
chemicals will thus be flushed away in the hydroentanglement due to
the low strength of the attraction and consequently therefore also
enriched in the water cleaning circulation as well as in the wet
end. There might also be charge problems in the wet end circulation
and/or in the water filtration.
[0009] The enriched chemicals in the water systems will cause a
number of problems, and further it may cause stops in the
production process. As the chemicals are cationically charged they
will disturb the water cleaning process, especially the
flocculation in the flotation filtration, in which most of the dry
substance in the entanglement water is separated. For example
filters could be clogged. There are also and perhaps mostly
problems with formation of foam. The formation of foam is mainly
due to surfactants or tensides or that the added agent has a higher
charge density. There is also a risk that the flocks in the
flocculation are broken, etc. In addition to all this, the chemical
cost may be very expensive. Further, the yield and efficiency of
the chemical additive is very low. The water cleaning process may
be disturbed as well as the different water recirculation
systems.
[0010] It is also common that softening agents are applied onto
paper by spraying onto the surface of the material. In this case
the surface is lubricated and friction between fibers at the
surface and friction between the surface of the material and the
hand of the user is reduced. Through U.S. Pat. No. 5,484,453 it is
known to spray water based treatment liquors onto textile
materials, where the used liquors contain deaeration components,
which are foam-free in order to thoroughly wet the textile material
almost immediately. A coating process is known from EP-B1-594, 983
which comprises a brush spray application method, in which the
material to be treated is passed through a path of fluid spray
emitted from the brush spray applicator.
[0011] When chemicals are added after the hydroentanglement, e.g.
by spraying, the smoothness of the surface will be improved, but
only limited improvement of the softness as to e.g. drapability
stiffness and bulk softness will be obtained. Also, only the fibers
at the surface of the material will be affected.
SUMMARY OF THE INVENTION
[0012] A purpose of the invention is to reduce or remove any of the
above-mentioned problems and negative effects. The invention
relates thus to a method of adding a softening and/or debonding
agent to a fiber web of a hydroentangled nonwoven material
comprising cellulose pulp fibers without encountering the
above-mentioned problems. The present invention relates thus to a
method of adding the softening and/or debonding agent in an inline
manufacturing process of the hydroentangled nonwoven material,
subsequent to the. hydroentanglement of the nonwoven material,
whereby the softening and/or debonding agent is added by means of a
size press or a foulard comprising a soaking step to soak the
hydroentangled nonwoven material with the added softening and/or
debonding agent, and a pressing step, which causes the added
softening and/or debonding agent to penetrate and impregnate the
hydroentangled nonwoven material. Other objects and advantages of
the present invention will become apparent to those skilled in the
art from the following description and practice of the
invention.
[0013] The added softening and/or debonding agent is preferably a
dilute solution, which comprises water and a softening and/or
debonding agent or resin. The provided method enables the softening
and/or debonding agent to penetrate throughout the whole material
and will not only treat the surface of the material. The inline
operation will avoid the drawbacks connected to additions of
softening and/or debonding agents when they are added in a separate
post treatment.
[0014] The manufacturing process is thus an inline operation. This
provides many advantages; among others that there is no need to dry
the material several times, since all is done in the same process.
Offline processes or operations can according to conventional
technique be used in order to achieve the desired bulk and surface
softness in the nonwoven material, and the cost will, due to this,
increase substantially. Also, any offline treatment will negatively
affect the nonwoven material, as it is subjected to two drying
operations. When the material is dried, the available hydrogen
bonding functional groups at the cellulose molecules will bond
within or to other cellulose molecules. Moisture may disrupt or
participate in the disruption of hydrogen bonding, but for each
time the cellulose molecules are subjected to a drying operation,
some covalent bonds to the hydroxyl groups on the cellulose
molecules will stay bonded and will not be disrupted and this will
lead to a less soft material. Consequently it will also be more
difficult to achieve the desired soft feel in the nonwoven material
at an offline softness treatment. An inline process on the other
hand, according to the claimed method, will manufacture a
hydroentangled nonwoven material with improved bulk softness as
well as with improved surface softness in one subsequence of
following process steps without any disrupting, cost demanding or
detonating step where the nonwoven material is substantially dried
as it would be in an offline process.
[0015] Pressing is sometimes optional for a hydroentangled nonwoven
material comprising cellulose pulp fibers in order to get a
smoother web, but it will also lead to a more stiff material.
However, when a softening and/or debonding agent is added according
to an embodiment of the claimed method in combination with the
pressing action a less stiff material is obtained compared to what
it would be if it would have been pressed without adding a
softening and/or debonding agent. As the hydroentangled nonwoven
material is pressed without any addition of a softening and/or
debonding agent, the pressing will result in more hydrogen bondings
and this in turn will result in a stiffer material. Also, as the
material is pressed together with the addition of the softening
and/or debonding agent, a very good surface smoothness can be
obtained. It is according to an embodiment of the claimed method
possible to press and thereby dewater the soaked hydroentangled
nonwoven material without that the hydroentangled nonwoven material
will be stiffer, on the contrary, it can be softer. Also, by being
able to press the hydroentangled nonwoven material, the thickness
of the hydroentangled nonwoven material can be determined without
the conventional drawbacks such as a more stiff material. There may
also be a reduction in linting due to the pressing effect.
[0016] Since a pressing action is possible in the pressing step
where the softening and/or debonding agent are added to the
hydroentangled nonwoven material according to an embodiment of the
claimed method, this will altogether render a softer feel of the
hydroentangled nonwoven material and therefore no further pressing
is needed. When there is no further pressing step, the natural bulk
in the material is kept, which in turn has several positive effects
as to absorbency, softness through bulk, drapability stiffness, the
elasticity in the web, etc.
[0017] The impregnation of webs with liquid chemicals by means of a
size press is known by conventional technique, such as U.S. Pat.
Nos. 6,497,787, 4,109,035 and EP-B1-0 678 614. None of these
documents mentions any hydroentangled nonwoven or hydroentanglement
processes.
[0018] While wishing not to be bound by any theory, it is believed
that the following reasoning is part of the understanding of the
inventive technique and method. It is believed that it is important
for the method claimed that the nonwoven material in question is a
hydroentangled nonwoven material that has just been subjected to
the hydroentanglement at the point of adding the softening and/or
debonding agent. The recently hydroentangled nonwoven material will
probably permit the softening and/or debonding agent to penetrate
into the fiber to fiber intersections in the hydroentangled
nonwoven while the hydroentangled nonwoven still is wet and
affected from the recent hydroentanglement. The high-pressure water
jets at the hydroentanglement in the preceding hydroentanglement
process step will move the fibers in the material and create the
integration of the fibers and/or filaments as well as available
sites on the cellulose molecules that may create bondings of the
fibers and/or filaments to each other. According to an embodiment
of the invention the thereafter added softening and/or debonding
agents may also occupy sites on the cellulose molecule that would
otherwise form hydrogen bonds within or between the cellulose
molecules. It is an advantage that the material is kept wet since
the available sites on the cellulose molecules well as the newly
formed bondings still has many water molecules surrounding the
hydrogen bonding functional groups at the cellulose molecules as
the hydroentangled nonwoven material is kept in its wet state.
Also, the surrounding water molecules may disrupt or participate in
the disrupture of the already formed hydrogen bonding. There are
thus many available sites on the cellulose molecule as the recently
hydroentangled nonwoven is still wet from the hydroentanglement
step and consequently these sites are more available to the
softening and/or debonding agent than it would be if the hydrogen
bondings within and between the cellulose molecules already would
have been formed and firmly established once as the nonwoven
material would have been dried. For each time the material is dried
the number of available sites will decrease. This makes the
hydroentangled nonwoven material sensitive and susceptible to
drying actions.
[0019] The claimed method would make it possible to get the added
softening and/or debonding agent into the fiber-to-fiber
intersections of the nonwoven material. The preceding
hydroentanglement has thus opened up a way and a possibility to
force the added softening and/or debonding agent into these fiber
to fiber intersections by the soaking of the size press or foulard
and the penetrative and impregnation effect of the pressing step.
The added softening and/or debonding agent will penetrate into and
throughout the whole material, get into the bulk and not only treat
the surface. The desired soft feel in the hydroentangled nonwoven
material is achieved by means of a treatment according to an
embodiment of the invention subsequent to the hydroentanglement
step.
[0020] During the soaking step and the pressing step causing the
penetration and impregnation of the hydroentangled nonwoven
material performed during a preferred method, the softening and/or
debonding agent added to the wet fiber web is to some extent
replaced with the preferred dilute solution of the softening and/or
debonding agent. In one embodiment of the invention the softening
and/or debonding agent is applied in an amount such that an
exchange and saturation of the dilute solution comprising the
softening and/or debonding agent can take place in the fiber web.
It is most probably the capillary water in pores and capillary that
can be replaced. A preferred method according to the invention
results in a good retention of the chemical softening and/or
debonding agent. As liquid is replaced, one of the more important
driving forces is the affinity between the cationically charged
agent and the anionically charged cellulose pulp fibers. There will
thus be a good affinity between the cationically charged agent and
the anionically charged cellulose pulp fibers. The high retention
of the softening and/or debonding agent added in the material has
naturally a high influence of the softening effect of the
hydroentangled nonwoven material comprising cellulose pulp
fibers.
[0021] A penetration is especially desirable since the bulk
properties are enhanced as the hydrogen bonds at the fiber-to-fiber
intersections are broken in the material or at least softened or
loosened up by the softening and/or debonding agent. Decreasing or
reducing the interfiber bonding within the web when the nonwoven
web comprises cellulose pulp fibers to a certain degree can thus
increase the softness and bulk. But also the stiffness of the
material will be lower as the softeners and/or debonders will
influence the fibers throughout the material. The effect of the
additive will be greater since substantially most of the fibers and
fiber intersections are treated and not only the surface of the
nonwoven material.
[0022] According to an embodiment of the invention the softening
and/or debonding agent is either used as a separate agent or in
combination with other softening and/or debonding resins or agents.
The softening and/or debonding agent can be a chemical or chemicals
and of course also be a group of chemicals.
[0023] The method according to embodiments of the present invention
gives the hydroentangled nonwoven material a number of other
desirable features as well as the desired bulk and softening
effect. The product manufactured according to an embodiment of the
claimed method is rather homogenous. Also, the softness experience
of the two sides of the nonwoven material can be pretty much the
same on both sides due to the soaking and penetrative impregnation
of the softening and/or debonding agent adjacent and subsequent to
the hydroentanglement step. Further features of the present
invention are disclosed in the description below and also in the
claims.
[0024] It is to be understood that the invention is not limited in
its application to the details of construction and the arrangements
of components set forth in the following description.
DETAILED DESCRIPTION OF THE INVENTION
[0025] In a preferred embodiment there is a dewatering step between
the hydroentanglement step and the subsequent step where the
softening and/or debonding agent is added. According to one
embodiment of the invention the dry content of the material when
adding the softening and/or debonding agent is at least about 25%
but not more than about 50%, preferably at least about 30% but not
more than about 40%. According to different embodiments the
softening and/or debonding.agent is either added in the soaking
step by means of a size press at the pressing step or the pressing
step is subsequent to the soaking step where the softening and/or
debonding agent is added by means of a foulard. The invention could
be embodied in various ways.
[0026] In an embodiment of the invention the hydroentangled
nonwoven material comprises synthetic fibers, such as staple
fibers, and/or continuous filaments. Also, the manufacturing
process of the hydroentangled nonwoven material may comprises a
step where the synthetic fibers and/or filaments are extruded or
laid down into a web in one step, and that the cellulose pulp
fibers are wetlaid or foamformed onto this thus formed web in a
step preceding the hydroentanglement step. In a further embodiment
the manufacturing process of the hydroentangled nonwoven material
comprises a step where the cellulose pulp fibers are wetlaid or
foamformed, and that the synthetic fibers and/or filaments are laid
down onto this thus formed web in a step preceding the
hydroentanglement step. In a preferred embodiment the cellulose
pulp fibers comprises synthetic fibers in the form of staple fibers
when being wetlaid or foamformed.
[0027] There are many options for manufacturing a fiber web of
nonwoven material to which a softening and/or debonding agent could
be added according to the claimed method. The synthetic component,
i.e. fibers and/or filaments, can preferably be synthetic staple
fibers and/or continuous filaments. Continuous filaments can
preferably be laid down directly or extruded on a forming wire
where they form into a web in one step. The cellulose pulp fibers
alone or together with synthetic fibers are either drylaid or
wetlaid. When the synthetic component comprises continuous
filaments, the cellulose pulp fibers, with or without synthetic
fibers, are drylaid or wetlaid in a preceding step or onto the web
of continuous filaments in a subsequent step. The wetlaying step
can be a conventional step or a foam-forming step. Subsequent to
the forming of the fiber web of the nonwoven material comprising
cellulose pulp fibers there could preferably be at least one
hydroentanglement step. The formed fibrous web is hydroentangled
while it is still supported by the wire. The entangling wire may
optionally be patterned in order to form a patterned nonwoven
material.
[0028] The filaments can be manufactured in different ways.
Extruding a molten polymer through a spinneret to form discrete
filaments produces spunlaid fibers. Subsequently, the filaments are
cooled and stretched out to an appropriate diameter in a mechanic
or pneumatic way so that they form a fiber web of continuous
filaments. The fiber diameter is usually above 10 .mu.m, e.g.
between 10 and 100 .mu.m. Meltblown fibers are formed by means of
meltblown equipment, 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
polymer melt is extruded through a nozzle in very fine streams.
When the polymer melt discharges from the nozzle, it is stretched
out into thin, continuous filaments by means of converging air
streams in a high-pressure fluid, such as hot air or vapor, which
are directed towards the polymer streams. The fibers can be
microfibers or macrofibers depending on their dimension.
Microfibers have a diameter of up to 20 .mu.m. The extrusion method
can thus be carried out, for example, by means of a meltblowing or
spunbonding technique.
[0029] According to one embodiment of the invention the cellulose
pulp fiber fraction is laid on top of the continuous filaments as
an aqueous or a foamed fibrous dispersion from a head box. In
wetlaying technique the fibers are dispersed in water and the fiber
dispersion is dewatered on a forming fabric to form a wetlaid
fibrous web. Foam forming is an alternative to the wetforming of
the fiber web. In foam forming, a foam forming surfactant is added
to the fiber dispersion, hereafter the fiber dispersion is
dewatered on a wire in corresponding way as in wetforming. A
foamformed fibrous web has a very uniform fiber formation; the foam
forming technique is described in for example WO 96/02701, GB
1,329,409, U.S. Pat. No. 4,443,297 and EP-A-0938 601. The
hydroentangled nonwoven material can use different fibers in
various mixing proportions. The synthetic fibers and/or filaments
used in the nonwoven material can be fibers such as e.g. polyester,
polypropylene, polyamide, polyethylene, and polylactides.
Copolymers of these polymers may of course also be used, as well as
natural polymers with thermoplastic properties. Further the
nonwoven material can be formed of rayon, lyocell etc, but also of
natural fibers, such as cellulose or cotton fibers, or a mix of
different fibers. The synthetic component may be continuous
filaments in the form of meltblown and/or spunbond fibers, or
prefabricated fibers of a finite length, as synthetic fibers
produced in situ or in the form of staple fibers. As an alternative
to synthetic fibers, natural fibers with a long fiber length can be
used, e.g. above 12 mm, 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.
[0030] Cellulose pulp fibers that can be used in accordance with
the invention may be of any kind available. Some of the
conventional available chemical pulps may be sulphite, sulphate or
organosolve pulp. Mechanical cellulose pulp can be grinded,
refined, thermo-mechanical, high thermo-mechanical,
chemi-mechanical and so on. The pulp may be of any kind:
coniferous, deciduous or any other alternative source of cellulose
fibers or the like. Another important pulp source is recycled
fibers, both from internal rejects and brokes as well as from
external recycled fibers.
[0031] The fiber web of nonwoven material to which a chemical
additive is added according to the invention may thus use any
synthetic fibers. Further, fibers of many different kinds and in
different mixing proportions of varying fiber lengths can be used
for making the wetlaid, drylaid or foam formed fibrous web.
Cellulose pulp fibers, synthetic fibers or mixtures thereof can be
used. Many hydroentangled materials today consist of both synthetic
fibers or filaments and pulp. The hydroentangled nonwoven material
may comprise cellulose pulp fibers and synthetic fibers and/or
filaments. The cellulose pulp makes the material cheaper to produce
since synthetic fibers are expensive. Further, the pulp may be
necessary in order to be able to reach the right material
properties depending on the manufacturing process. In one preferred
embodiment the fiber web of hydroentangled nonwoven material
comprises at least about 20% dry weight of cellulose pulp fibers.
There is a visible and clear change in the nonwoven product when
the cellulose pulp reaches and exceeds the amount of about 20% by
dry weight. The cellulose pulp contributes with absorbent
properties to the material, but it also makes the material stiffer
mainly due to the strong hydrogen bonding. The fibers in the
cellulose pulp fills up the holes in the network and thereby
contributes to the strength and the integrity and opacity of a much
more solid material.
[0032] The softeners and/or debonders used according to an
embodiment of the invention could be any of the commercially
available softeners and/or debonders. Examples of often used
softeners and/or debonders are chemicals containing one or more
substances such as cationic and/or nonionic surfactants, quaternary
ammonium compounds, polyhydroxy compounds and imidazolinium
quaternary compounds, polysiloxanes, or mixtures thereof.
[0033] The strength of tissue paper consisting mainly of cellulose
fibers depends very much on the fiber-to-fiber bond. Therefore,
when a material with cellulose pulp fibers is treated with
softeners or debonders, the hydrogen fiber to fiber hydrogen
bonding of the cellulose pulp fibers is reduced and higher bulk
softness is obtained, however at the same time the material tends
to lose some or even much of its original strength which may
adversely affect the strength of the product. However, the strength
in hydroentangled nonwoven materials depend more on the
hydroentanglement of the pulp and the synthetic staple fibers
and/or the continuous filaments. The strength is of course also
highly dependent of any continuous filaments in the hydroentangled
nonwoven material, which have a reinforcement effect of the
material. The effect on strength reduction by debonder or softening
chemicals is thus less in a hydroentangled nonwoven material
compared with tissue paper manufactured in a conventional paper
machine. Therefore, the chemical treatments to improve softness and
bulk have a great potential in hydroentangled nonwoven
materials.
[0034] In conventional techniques there are generally several
hydroentanglement steps as well as each hydroentanglement step
include several hydroentanglement manifolds. Further, there is at
least one vacuum-collecting box under the wire carrying the fiber
web from the hydroentanglement to the following adjacent step
comprising the addition of the softening and/or debonding agent. In
one embodiment, there is a dewatering step between the
hydroentanglement step and the subsequent step where the softening
and/or debonding agent is added. The dry content of the material
when adding the softening and/or debonding agent is preferably
about 30-40% by weight.
[0035] There are many ways to characterize softness. There is for
example a relation between the softness and the measured values of
the bulk, the drapability stiffness and also the tensile stiffness.
To measure the parameters of the bulk, the drapability stiffness
and the tensile stiffness have therefore been considered important
when the softness is to be characterized. The effect of the
softness when measured as drapability stiffness has been evaluated
in the following Example.
EXAMPLES
[0036] Pilot trials were conducted in order to simulate a process
for adding a softening and/or debonding agent subsequent to the
hydroentanglement according to the invention.
[0037] In these trials, a commercially available hydroentangled
nonwoven material intended for use in industrial wipes (E-TORK
Strong.RTM., manufactured by SCA Hygiene Products AB) was subjected
to the different additions. E-TORK Strong.RTM. is produced by means
of hydroentangling a precursor web consisting of a mixture of
bleached softwood sulphate pulp fibers, polyester staple fibers,
and polypropylene staple fibers.
[0038] A sample treated without any chemical additives of the
hydroentangled nonwoven material was extracted as a control for
subsequent testing. In the trials prewetted hydroentangled nonwoven
web materials to about 40-45% dry weight were treated with
different softening and/or debonding agents in a lab size press at
3 bar. The solutions had a dilute concentration of 0.5% and 1.0% of
the softening and/or debonding agent.
[0039] The addition of the softening and/or debonding agent for
soaking the hydroentangled nonwoven fiber web is applied in an
amount such that an exchange and saturation of the softening and/or
debonding agent will take place in the fiber web.
[0040] Three different softening and/ or debonding chemicals were
evaluated, Berocell 589 and XP 7026 supplied by Eka Chemicals, and
TQ1003 supplied by Hercules AB. The debonder Berocell 589 is an
additive in the manufacture of fluff pulp and is a mixture of
cationic and nonionic surfactants and comprises
alkyl-benzyl-dimethyl ammonium chloride and fatty alcohol
ethoxylate. XP 7026 is a softener for tissue and also a mixture of
cationic and nonionic surfactants and comprises
benxyl-dimethylammonium chloride. TQ1003 is a fatty acid amine.
[0041] As the materials were treated with a debonding agent, the
experience of a much softer material in the hand was obtained.
Softness in relation to the Drapability stiffness can be seen in
Table 1 below.
[0042] The material testing was performed with methods, which
should be well known to the skilled person. Therefore, the test
methods will be described only briefly in the following
description.
[0043] The method for determining the Drapability stiffness is
based on Edana, 50.2-80. A rectangular shaped test specimen is cut
from the nonwoven material and will be bent under its own weight to
a specific angle. The test specimen is brought over the edge of a
measuring instrument and the length of the material will be
determined as the intersecting point of the test specimen and an
imagined sloped plane of a specific angle is reached.
[0044] Table 1 below shows results from drapability stiffness Sqr
root (MDCD) [cm] measurements on the different samples by
impregnation of wet sheets with a size press with the three
different softening and/or debonding agents added.
1 Chem. liquid Conc. Drapability stiffness Sqr Sample [%] root
(MDCD) [cm] Reference None 8.4 TQ1003 0.5 6.5 TQ1003 1.0 6.6
Berocell 589 0.5 7.0 Berocell 589 1.0 6.6 XP 7026 0.5 6.4 XP 7026
1.0 6.5
[0045] When studying the samples it is clear and obvious that the
softening effects obtained effectively show distinctly lower values
of drapability stiffness. The result of the decreased values of the
drapability stiffness (cm) relates to the experienced felt softness
in hand which is correspondingly greater. It could also be worth
knowing that even small changes in drapability stiffness have large
effects on the experienced soft feel in hand.
[0046] The invention also comprises any evidently suitable method
or methods that will involve the claimed method. The invention is
also capable of other embodiments and of being carried out in
various ways.
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