U.S. patent application number 14/070442 was filed with the patent office on 2014-02-27 for method for manufacturing soft, resistant and bulky nonwoven and nonwoven thus obtained.
This patent application is currently assigned to AHLSTROM CORPORATION. The applicant listed for this patent is AHLSTROM CORPORATION. Invention is credited to Roberto PEDOJA.
Application Number | 20140057093 14/070442 |
Document ID | / |
Family ID | 38818486 |
Filed Date | 2014-02-27 |
United States Patent
Application |
20140057093 |
Kind Code |
A1 |
PEDOJA; Roberto |
February 27, 2014 |
METHOD FOR MANUFACTURING SOFT, RESISTANT AND BULKY NONWOVEN AND
NONWOVEN THUS OBTAINED
Abstract
Methods for manufacturing nonwovens and nonwovens obtained by
such methods are provided. Particularly, nonwovens are provided
with improved tactile and absorbent characteristics, which make
them suitable for use in the field of surface cleaning, personal
hygiene, or formation of garments. The methods are based on the use
of lobed spunbonded filaments which have been treated by a
thickening apparatus.
Inventors: |
PEDOJA; Roberto; (Cuasso al
Monte (Varese), IT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
AHLSTROM CORPORATION |
Helsinki |
|
FI |
|
|
Assignee: |
AHLSTROM CORPORATION
Helsinki
FI
|
Family ID: |
38818486 |
Appl. No.: |
14/070442 |
Filed: |
November 1, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12513051 |
Jan 8, 2010 |
8597555 |
|
|
PCT/EP2007/008360 |
Sep 26, 2007 |
|
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14070442 |
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Current U.S.
Class: |
428/220 ; 28/134;
442/335 |
Current CPC
Class: |
D04H 1/492 20130101;
D04H 1/4382 20130101; D04H 3/11 20130101; Y10T 428/2395 20150401;
Y10T 442/609 20150401; D04H 3/011 20130101; D04H 1/724 20130101;
D04H 1/498 20130101; D04H 1/4391 20130101; D04H 3/14 20130101; D04H
3/007 20130101; D04H 1/74 20130101; B32B 5/022 20130101; D04H 3/16
20130101; D04H 3/013 20130101 |
Class at
Publication: |
428/220 ; 28/134;
442/335 |
International
Class: |
D04H 1/724 20060101
D04H001/724; B32B 5/02 20060101 B32B005/02 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 30, 2006 |
EP |
PCT/EP2006/010422 |
Claims
1. A mono- or multi-layer nonwoven obtained by a method comprising
the following sequential steps; a) extruding continuous thread
filaments or microfilaments through spinnerets to produce
spunbonded continuous filaments or microfilaments having a lobed
cross-section, b) laying at least one layer (T.sub.1) of spunbonded
lobed filaments or microfilaments on a suitable three dimensional
support having a surface with ribs in contact with said filaments
or microfilaments, and c) effecting a pre-consolidation of said
layer T.sub.1 by passing the layer T.sub.1, supported by said three
dimensional support, between two rollers, one of the rollers facing
the layer T.sub.1, wherein the ribs of said surface of said support
have a height between 0.3 and 5 mm, said ribs being distributed to
cover less than 14% of said surface, and wherein said roller facing
the layer T.sub.1 is provided with a metal outer surface and is
subject to heating.
2. The nonwoven according to claim 1, further comprising a step of
laying at least one layer (T.sub.3) of absorbent material fibres on
the nonwoven layer (T.sub.1) subsequent to said step c).
3. The nonwoven according to claim 2, further comprising a step of
laying at least one further layer (T.sub.2) of spunbonded lobed
filaments or microfilaments or carded staple fibres on the at least
one layer (T.sub.3) of fibres of absorbent material.
4. The nonwoven according to claim 3, further comprising,
subsequent to the step of laying said at least one layer (T.sub.1),
a step of treating said at least one further layer (T.sub.2) to
obtain an increase in the thickness thereof, said step being
performed by thickening means which comprises the two rollers and a
support (S) having the surface with ribs in contact with said
filaments.
5. The nonwoven according to claim 3, wherein at least one of the
layers (T.sub.1) and (T.sub.2) has a thickness ranging from 0.54 mm
to 0.9 mm, a cotton wool-like appearance and is soft and smooth to
the touch.
6. The nonwoven according to claim 3, wherein said at least one of
the layers (T.sub.1) and (T.sub.2) is a lobed spunbonded layer.
7. The nonwoven according to claim 3, further comprising a step of
consolidating the layer (T.sub.2) after step c) of treatment to
obtain an increase in the thickness thereof.
8. A method for manufacturing single-layer or bi-layer of lobed
spunbonded nonwoven comprising the steps of: i) providing at least
one layer of lobed spunbonded nonwoven which has been subjected to
swelling treatment by passing a layer T.sub.1 through means of
thickening which comprises two rollers and at least one surface
provided with ribs having an height comprised between 0.3 and 5 mm,
a free head with a contact surface for the fibres or microfibres
having an extension of less than 0.80 mm.sup.2, said ribs being
distributed so that to cover less than 14% of said at least one
surface; and ii) consolidating said layer through
hydro-entanglement.
9. The method according to claim 8, wherein said step i) comprises
providing at least one layer of fibres (T.sub.3) of absorbent
material.
10. The method according to claim 9, wherein said step i) further
comprises providing at least one second layer (T.sub.2) of lobed
spunbonded or staple fibres carded nonwoven, which has been
subjected to swelling treatment.
11. The method according to claim 8, wherein the contact surface is
about 0.50 mm.sup.2, and the distribution of said ribs covering
from 7-9% of the contact surface.
Description
CROSS-REFERENCE
[0001] This application is a divisional of commonly owned copending
U.S. application Ser. No. 12/513,051, filed Jan. 8, 2010 (U.S. Pat.
No. ______), which is the national phase application under 35 USC
.sctn.371 of PCT/EP2007/008360, filed Sep. 26, 2007, which
designated the US and claims priority to European Application No.
PCT/EP2006/010422, filed Oct. 30, 2006, the entire contents of
which are hereby incorporated by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a method for manufacturing
a nonwoven of the spunbonded type in-line and off-line and a
nonwoven obtainable by said method. Particularly, the invention
relates to a nonwoven provided with such improved tactile,
resistant and bulky characteristics that make it suitable for use
in the field of surface cleaning, personal hygiene, and formation
of garments.
BACKGROUND OF THE ART
[0003] A nonwoven is widely used as a replacement for traditional
textile products in numerous sectors, for example in the field of
surface cleaning and protection, or in the production of garments.
Compared to conventional fabrics, the nonwovens have the advantage
of lower production costs, outstanding mechanical properties and a
high biocompatibility with skin.
[0004] Among the nonwovens, those of the spunbonded type are formed
either by synthetic (polymer) or natural material fibres which are
laid on a mat in the form of a layer after being solidified when
just coming out from the spinneret and subsequently attenuated at a
prefixed distance from the spinneret by the application of forced
air substantially at ambient temperature. The material forming said
fibres is conventionally subjected to a stretching or elongation
force causing the formation of continuous filaments.
[0005] The thus obtained structure can be consolidated by dynamic
treatments such as bonding by stitches or by weft (calendering), or
by jets of water (hydro-entanglement). Other bonding methods known
in the field are mechanical needling, thermobonding, chemical
bonding.
[0006] Generally, the spunbonding methods provide the extrusion of
thermoplastic polymers through spinnerets such as to form a
plurality of continuous filaments. These filaments, which are first
solidified and then elongated, typically by means of a high-speed
fluid, are random laid on a collecting surface such as a conveyor
belt and form a non-consolidated ply. Subsequently, the filaments
are bonded to provide the final ply having cohesion and strength
characteristics.
[0007] The bonding step can be obtained by directly applying heat
and pressure to the non-consolidated ply by means of heated
calenders.
[0008] Particularly, after the non-consolidated ply has been laid
down, it is carried on said conveyor belt to the calenders where it
leaves the belt and is taken by two calender rolls to be heated and
crushed. Thereby, the polymer ply is only carried until reaching
the calenders and both rollers of the same calenders also act as
the supports/conveyors as well as consolidators for the ply.
[0009] The product resulting from said method is normally in the
form of a very thin ply, in the range of 0,18-0,3 mm weighing 15-17
g/m.sup.2, compact, of threadlike appearance, and provided by
slightly embossed patterns defined by the gaps between the cohesion
points of the calender design.
[0010] Such a product, though showing good cohesion properties, is
not very suitable for use in the hygiene sector, and however in
those sectors requiring particular performance in terms of softness
and thickness.
[0011] In addition, the cohesion is not sufficient when the product
is used for instance in the cleaning field or as garments so that
the product easily tends to wear out and, further, tends to cause
an undesirable "pilling" effect particularly when the cohesion is
carried out by hydroentangled technology, i.e. formation of fine
loops onto the surface of the final product which engage with the
roughness of for instance hands during using.
SUMMARY OF THE INVENTION
[0012] Therefore, the object of the present invention is to provide
a nonwoven which is provided with improved softness and bulky
properties compared to known products though still retaining
optimum cohesion properties and avoiding the pilling effect.
[0013] This object is achieved by a method for manufacturing a
nonwoven and a nonwoven thus obtained, such as claimed in the
independent claims annexed below.
[0014] A first object of the present invention is to provide a
method for manufacturing a nonwoven of the spunbonded type.
[0015] A second object is to provide a nonwoven obtained by said
method, wherein the end product is particularly advantageous in
terms of softness, bulky, and cohesion.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Further characteristics and the advantages of this invention
will be better understood from the following detailed description
of some embodiments thereof, which are provided by way of
non-limiting examples wherein:
[0017] FIG. 1 is a schematic view of a cross-section of a filament
in accordance with a first embodiment of the invention;
[0018] FIG. 2 is a schematic view of a cross-section of a filament
in accordance with a second embodiment of the invention;
[0019] FIG. 3 is a schematic view of a cross-section of a filament
in accordance with a third variant embodiment of the invention;
[0020] FIG. 4 is a schematic view of a cross-section of a filament
in accordance with a four embodiment of the invention;
[0021] FIG. 5 is a schematic view of a cross-section of a filament
in accordance with a fifth embodiment of the invention;
[0022] FIG. 6 is a perspective view of a cross-section of a
filament in accordance with a sixth embodiment of the
invention;
[0023] FIG. 7 is a schematic view of a cross-section of a filament
in accordance with a seventh embodiment of the invention;
[0024] FIG. 8 is a schematic view of a cross-section of a filament
in accordance with an eighth embodiment of the invention;
[0025] FIG. 9 is a schematic view of a cross-section of a filament
in accordance with a ninth embodiment of the invention;
[0026] FIG. 10 is a schematic view of a cross-section of a filament
in accordance with a tenth embodiment of the invention;
[0027] FIG. 11 is a schematic view of a cross-section of a filament
in accordance with an eleventh embodiment of the invention;
[0028] FIG. 12 is a schematic view of a manufacturing process
according to the invention;
[0029] FIG. 13 is a schematic view of a manufacturing process in
accordance with a first variant embodiment of the invention;
[0030] FIG. 14a is a schematic view of a manufacturing process in
accordance with a second variant embodiment of the invention;
[0031] FIG. 14b is a schematic view of a manufacturing process in
accordance with a third variant embodiment;
[0032] FIG. 15a is a schematic view of a manufacturing process in
accordance with a fourth variant embodiment of the invention;
[0033] FIG. 15b is a schematic view of a manufacturing process in
accordance with a fifth variant embodiment;
[0034] FIG. 16a is a perspective view of the support for the
nonwoven filaments of the invention;
[0035] FIG. 16b is a perspective view of a variant of the support
for the nonwoven filaments of the invention;
[0036] FIG. 17 is a schematic view of a manufacturing process in
accordance with a sixth variant embodiment of the invention;
[0037] FIG. 18 is a schematic view of a manufacturing process in
accordance with a seventh variant embodiment of the invention;
[0038] FIG. 19 is a schematic view of a manufacturing process in
accordance with an eighth variant embodiment of the invention;
[0039] FIG. 20 is a schematic view of a manufacturing process in
accordance with a ninth variant embodiment of the invention;
[0040] FIG. 21 is an enlarged perspective view of a particular of a
roll of the calender according to the invention;
[0041] FIG. 22 is an enlarged sectional side view along the line
XXI-XXI of FIG. 21.
DETAILED DESCRIPTION OF THE INVENTION
[0042] As stated above, the scope of the present invention is to
provide a particular kind of nonwoven designed in order to improve
the bulky and softness characteristics while, at the same time, to
improve the its cohesion.
[0043] The idea upon which the invention is based is therefore to
modify the structure of nonwoven in order to achieve the desired
results. With this aim in mind, it has been proposed to modify the
structure of the basic elements composing the nonwoven structure,
i.e. the spunbonded filaments.
[0044] Several experiments have been carried out to verify if
changing in the shape of the single filaments could bring to any
advantages. In particular, the typical rounded cross-section of the
filaments has been modified.
[0045] Surprisingly, it has been found that filaments having a
lobed cross-section produced by suitable spunbonded spinnerets and
entangled in order to form a mono or multi layered nonwoven can
provide all the desired effects of improving softness, bulkiness
and resistance.
[0046] In particular, spunbond filaments according to the present
invention can be provided by means of conventional spunbond
technologies and apparatuses wherein the corresponding spinnerets
are modified in order to have orifices with holes presenting lobed
shapes.
[0047] It is to be noticed that with the term "lobed filaments" it
is intended a cross-section of a spunbond filaments whose external
perimeter is not constant in its direction but changes. In other
words, the external perimeter of the cross-section is provided with
grooves alternated by protrusions or lobes.
[0048] For instance, as represented in the drawings, protrusions or
lobes can have a rounded shape (FIGS. 1 and 3) or angular shape
(FIG. 2). Moreover, they can be symmetric or asymmetric.
[0049] In addition, they can reproduce substantially the shape of
letters, such as "T", "Y", "I", "Z", "E", "S", "C", numbers like
"3", signs like ">" or symbols like stars (FIGS. 2, 4-11).
[0050] The main feature all the particular cross-sections of the
spunbond filaments should have is to allow the definition of spaces
and, at the same time, to allow a sort of connection between
filaments when they are entangled to form a web of nonwoven. In
fact, from one side the protrusions of a filament can randomly
engage the grooves of another filament to create a connection and
from the other side protrusion can randomly create spaces between
cores of the filaments.
[0051] Accordingly, when the filaments are entangled, the nonwoven
web of mono or multi layers shows an improved cohesion due to the
above engagements and, at the same time, an improved volume due to
the above spaces which consequently corresponds to an improved
softness.
[0052] It is also to be noticed that the spaces so created can be
advantageously filled up with for instance lotions, detergents,
creams depending on the particular use the operator intends to do.
Alternatively, said spaces can act as absorbent spaces when the
nonwoven is used to absorb liquids in an improved manner with
respect to the known nonwovens.
[0053] Furthermore, it has also surprisingly been observed that if
the above lobed spunbond filaments are used in a method for
manufacturing a spunbonded nonwoven as described later, the
softness, bulkiness and cohesion can be further implemented.
[0054] In view of the above, with reference to FIG. 12, the first
object of the present invention is a method for manufacturing
spunbonded nonwoven comprising the step of:
[0055] a) laying at least one layer (T.sub.1) of lobed spunbonded
continuous on a suitable support S:
[0056] b) treating said layer T.sub.1 such as to obtain an increase
in the thickness thereof by passing the layer T.sub.1 through means
of thickening which comprises two rollers 2, 3 and at least one
surface provided with ribs having an height comprised between 0.3
and 5 mm, a free head with a contact surface for said filaments
having an extension of less than 0,80 mm.sup.2, said ribs being
distributed so that to cover less than 14% of said at least one
surface.
[0057] Preferably, step b) takes place by means of said thickening
means which comprises two rollers 2, 3, for instance of a
conventional compactor or embosser, and a support S having said
particular surface, in contact with said filaments, provided with
the above described ribs.
[0058] Moreover, the height of the ribs can preferably be from 0.5
to 3, more preferably from 0.8 to 1 mm, the contact surface of the
free heads of the ribs can preferably be from 0.70 to 0.20
mm.sup.2, more preferably about 0.50 mm.sup.2 and the distribution
of the ribs can preferably be so that to cover 10-5%, more
preferably 9-7% on said surface.
[0059] By the term "continuous thread filaments" is meant herein
continuous filaments substantially endless consisting of one or
more polymer components, either synthetic or natural, optionally
splittable into two continuous individual microfilaments. Polymer
filaments splittable into microfilaments are splittable
bi-component lobed polymer filaments.
[0060] Step b) of treatment to obtain an increased thickness of the
nonwoven layer may be called, in other words, "thickening", thereby
meaning an operating step allowing to turn the filaments of a
spunbonded nonwoven laid on a support in the form of a thin,
threadlike, and non-consolidated ply into a non-consolidated or
poorly consolidated ply (pre-consolidation) of a cotton wool-like,
thick, and soft appearance.
[0061] As stated above, it has been surprisingly found that if the
thickening step is carried out on a rib-operated, i.e. embossed,
and however not smooth surface, using lobed spunbonded filaments
the resulting ply gains unexpected properties of softness,
thickness and cohesion or resistance which are considerably
increased compared to any other nonwoven ply of the spunbonded or
carded type produced without said combination of method and
filaments.
[0062] On the basis of this result, different variant embodiments
of a nonwoven of the spunbonded type, both single-layer and
multi-layer, have been provided.
[0063] For the production of a single layer (FIG. 12), the
manufacturing steps generally comprise feeding the nonwoven layer
T.sub.1 in the form of filaments by means of a spinneret 1
(extruder) coupled to a conventional suction fan A, a
hydro-entangling station 5, a drying station 6 and a rewinding
station 4 of the hydro-entangled layer on a roller.
[0064] Particularly, step a) of laying a single layer comprises,
such as schematically represented in FIG. 12, extruding the
nonwoven layer T.sub.1 in the form of continuous lobed filaments by
means of a spinneret 1 (extruder) having suitable orifices to
produce the above described lobed cross-sections and laying said
filaments on a suitable support S by means of a conventional
suction fan A.
[0065] Step b) of thickening is preferably carried out by passing
the layer T.sub.1, supported by support S, between two rollers 2
and 3 of a conventional compactor or embosser C.
[0066] It should be noted that by the term compactor or embosser is
meant herein a device known per se, such as described below, which
has only the function of changing the surface of a nonwoven ply to
obtain a slight consolidation (pre-consolidation) and in addition,
in the case of embosser, such as to form patterns, writings or
drawings in relief. In other words, the compactor would have a
pre-consolidation function, actually weak, whereas the embosser
would have a pre-consolidation and ornamental function, thereby
increasing the thickness of the ply. On the contrary, the
conventional calender, though being provided with a similar general
structure, has the basic function to consolidate, and bond the
fibres or filaments composing the nonwoven while minimizing or at
most maintaining the ply thickness being laid down.
[0067] Preferably, roller 2 of the compactor generally has a
thermoplastic smooth rubber surface for the layer T.sub.1 to be
pressed thereon, which layer is supported by support S, by means of
roller 3. Roller 3 is normally made of smooth metal materials.
Moreover, roller 3 is heated to the polymer filaments melting
temperature. Accordingly, due to the use of lobed spunbonded
filaments, mechanical action of both rollers, the heating of the
filaments and the three-dimensional support S (mat interposed
between both cylinders) the thickening of the nonwoven layer
T.sub.1 or, in other words, a "volumizing effect", a "flimsy
effect" is thus obtained. In the case where an ornamental
appearance is also desired, the embosser may be used, where the
support S has deeper, more marked ribs and respective grooves, i.e.
the ornamental matrix, such as to obtain the desired ornamental
effect.
[0068] On the other hand, roller 3 in a conventional calender is
engraved, i.e. it has ribs in the form of dots or dashes evenly
alternating with grooves. In particular, the ribs have a height
comprised between 0.4 and 0.6 mm, a free head with a contact
surface for the filaments of 0.88 mm.sup.2 and a distribution so
that to cover 19-23% of the surface of the roller. It is to be
noticed that said combination of features is just responsible of a
firm consolidation of the nonwoven ply.
[0069] As already explained above, these ribs in the calender act
by forming melting points. Moreover, in the calender, the nonwoven
ply is not supported by any support. On the contrary, either in the
compactor device or in the embosser, ribs on rollers are not
provided or provided so that to create the above described effects
typical of conventional embossers or compactors. On the other hand,
there is provided a support S having a three-dimensional surface
which gives considerable thickness, softness, and the above
mentioned cotton wool-like appearance. These effects are further
improved by means of the use of the above described lobed
spunbonded filaments.
[0070] In addition, as already stated, the use of the lobed
filaments improves considerably the cohesion between filaments so
that the whole nonwoven results much more resistant to wearing and
is free from the peeling effect.
[0071] Support S can be a single continuous support stretching
beneath all the nonwoven working stations and is advantageously
provided with a surface in contact with the filaments, which is
provided by ribs alternating with grooves. Non-limiting examples of
said support S can be those represented in FIGS. 16a and 16b where
the contact surface with said filaments has a section with crimps
or steps according to what has been described in the international
patent application PCT/IT2004/000220 in the name of the same
applicant. Alternatively, the ribs can be either dots or dashes.
Furthermore, said ribs can be of any other known conventional type
such as truncated pyramid with substantially squared base or
truncated cone with oval or circular base, the last one being the
preferred shape.
[0072] Accordingly, as described above, when the spunbonded
filaments are passed between two rollers 2 and 3 while being
supported by a support S such as that described above, the
resulting ply acquires softness, smoothness and thickness similar
to cotton wool.
[0073] Moreover, the effect described above can be created by
employing lobed continuous spunbonded filaments on a support
surface having ribs of substantially any shape, which filaments can
be passed between the rollers of a compactor or embosser according
to conventional procedures together with for instance carded
fibres. In any case, the support S should be sufficiently solid to
withstand the operating pressure of rollers 2 and 3 and withstand
the fibre melting temperature.
[0074] Therefore, the support S described above can be a conveyor
belt or tape made of any type of plastic material which is normally
used in the field. Preferably, the support S is a metal sheet or a
hard heat-resistant plastic sheet. Preferably, support S can
further consist of a punched sheet through which the air can be
sucked in order to maintain the filaments adherent to said sheet
while they are being worked.
[0075] This support S can alternatively be a closed conveyor belt
(not shown) limited to the level of rollers 2 and 3 of compactor or
embosser C. Thereby, the filaments can be laid on a conventional
support which carries said filaments to said conveyor belt such as
to deliver the filaments thereto and allow the thickening treatment
to be carried out in the advantageous conditions described
above.
[0076] Following the passage of ply T.sub.1 of lobed continuous
spunbonded nonwoven supported by support S through the compactor C,
the ply T.sub.1 passes underneath the hydro-entangling machine 5 to
be consolidated (step c)) in accordance with widely established
methods. Subsequently, the ply T.sub.1 is conventionally dried in
dryer 6 (FIG. 12).
[0077] In addition, such as shown in FIG. 12, the fabric ply
T.sub.1 can be wound around a winding roller 4, also of the
conventional type.
[0078] Particularly, the single- or multi-layer nonwoven can be of
the hydro-entangled type based on splittable bi-component
continuous filaments. The nonwoven filaments generally consist of
only one component; however, for personal care products they may
also be manufactured in the bi-component form, through the joint
extrusion of different polymers according to known technologies. It
is to be noticed that in any case the bi-component filaments have
to be produced in order to maintain a lobed profile even when
split.
[0079] In addition, the multi-layer composite nonwovens can contain
one or more nonwoven layers, associated to a layer of cellulose
fibres: in such cases, the final composite advantageously combines
the mechanical properties of the nonwoven with the absorbent
properties of the cellulose fibres.
[0080] The above bi-component filament technology is described in
the patent application PCT/IT2004/000220 in the name of the same
applicant and fully incorporated herein by reference.
[0081] Production of Splittable Synthetic Polymer Filaments
[0082] For the production of a single layer, reference is made to
what is illustrated in FIG. 12, where the difference from the
method described above is that the spinneret 1 employed is herein a
device, known per se, which is capable of manufacturing polymer
filaments splittable into lobed microfilaments.
[0083] For the details of each step, reference should be made to
the description below, with reference to FIGS. 13, 14 and 15 in
which the steps with similar names are identical to those outlined
above.
[0084] The method for manufacturing a nonwoven, according to this
first variant embodiment of the invention, comprises the
manufacturing steps a) to b) such as described above, in which the
filaments laid in step a) comprise splittable bi-component lobed
polymer filaments which split into mono-component lobed
microfilaments by entangling to one other during the consolidation
step by hydro-entanglement.
[0085] According to a variant embodiment of the invention, such as
illustrated in FIG. 13, the method provides a further step of
laying at least one layer of absorbent material fibres T.sub.3 on
said at least one layer T.sub.1 subsequent to the thickening step
b), therefore the hydro-entangling step takes place such as to
obtain a nonwoven in which the bi-component polymer filaments split
into mono-component micro-filaments entangle with one another and
with the fibres of the absorbent material.
[0086] Generally, said method provides feeding the nonwoven first
layer T.sub.1 through a suitable spinneret 7, one or more stations
8 for laying the cellulose pulp 80, hydro-entanglement 10, drying
11 and rewinding on a roller 12.
[0087] On the other hand, the manufacture of a three-layer
composite in accordance with the invention (FIG. 14a where the same
reference numbers as those from FIG. designate similar operating
equipment or stations) generally provides feeding the first
nonwoven layer T.sub.1 through a suitable spinneret 7 according to
the above description, one or more stations 8 for laying the
cellulose pulp 80, laying a second nonwoven layer T.sub.2 similar
to the nonwoven layer T.sub.1 through a suitable spinneret 9,
hydro-entanglement 10, drying 11 and rewinding on a roller 12.
[0088] Referring to a multi-layer product, it is widely known that
splittable bi-component lobed filaments may be produced through
extrusion by spinnerets of polymer materials so as to form
continuous filaments. These filaments, on output from the
spinnerets, are hit by a jet of compressed air that causes the
elongation and the electrostatic charging thereof such to cause a
mutual repulsion causing them to fall randomly onto a conveyor
belt.
[0089] With reference to FIG. 14a, a method for the production of
multi-layer nonwoven fabric comprising outer layers made with
splittable filaments according to the abovementioned technology
will be now described. In any case, the subject method comprises
the following steps:
a) laying at least one layer T.sub.1 of said continuous splittable
bi-component lobed polymer filaments on a suitable support S; b)
treating said layer T.sub.1 such as to obtain an increase in the
thickness thereof as disclosed above; c) laying on said at least
one first layer T.sub.1 at least one layer T.sub.3 of absorbent
material fibres 80; d) laying at least one second layer T.sub.2 of
splittable bi-component lobed polymer filaments on said at least
one layer of absorbent material fibres T.sub.3; e) treating said
layer T.sub.2 such as to obtain an increase in the thickness
thereof as disclosed above; f) consolidate said layers T.sub.1,
T.sub.2 and T.sub.3 by hydro-entanglement.
[0090] Preferably, step b) and step e) take place by said layer
T.sub.1 and said layers T.sub.1, T.sub.2 and T.sub.3, passing
between two rollers, respectively, onto a support having a contact
surface to said filaments being provided with ribs alternating with
grooves as specified above.
[0091] As stated above, the hydro-entanglement of the laid
filaments layers takes place such as to obtain a multi-layer
nonwoven wherein the bi-component lobed polymer filaments are split
into single mono-component micro-filaments entangling with one
another and with the fibres of the absorbent material.
[0092] Particularly, splittable bi-component synthetic lobed
filaments can be formed by separately extruding individual polymers
in a molten state in the form of threads 70, 90 exiting from
orifices, of capillary dimensions, of a spinneret 7, 9 and linking
them beneath the spinneret. The polymers at the molten state are
linked in a single fibre combined by extrusion of the individual
polymer threads in such directions to cause the contact thereof and
the adhesion thereof, such as described in U.S. Pat. No. 6,627,025
herein incorporated by reference. A suction fan A positioned
underneath the spinneret has the function of sucking and conveying
the individual threads of extruded polymer in order to favour the
bonding thereof into a single filament.
[0093] The synthetic filament is composed of two threads of a
single polymer (bi-component), be they homopolymers, copolymers or
blends thereof. The polymers may be selected from polyesters,
polyamides, polyolefins, polyurethane, polyester modified with
additives, polypropylene, polyethylene, polypropylene
terephthalate, polybutylene terephthalate.
[0094] Preferably, such polymers may be selected such that in the
fibres adjacent polymers cannot blend or in any case have poor
affinity in order to favour the subsequent separation thereof.
Alternatively, the polymers may be additized with lubricants that
prevent the adhesion thereof. In addition, as the longitudinal,
axial portion of the fibre usually has a greater force of cohesion
than the peripheral portion, it may be advantageous to spin
bi-component filaments so as to leave an axial hole or in any case
a weakened axial portion.
[0095] As shown in FIG. 14a, once a layer of splittable
bi-component lobed polymer filaments has been laid through the
special spinneret 7 onto a conveyor belt S such as to create a
first layer of spun-bonded nonwoven T.sub.1, one layer of absorbent
material T.sub.3 such as cellulose pulp is laid on said layer of
nonwoven.
[0096] Subsequently, a second layer T.sub.2 of nonwoven
substantially identical to that prepared previously is laid on the
layer of cellulose pulp T.sub.3, such as illustrated in FIG. 14a at
the station identified with reference number 9.
[0097] At this point, the fibres are subject to hydro-entangling at
the hydro-entangling station 10. This treatment, widely known per
se, advantageously enables to split the polymer filaments that
compose the nonwoven outer layers nonwoven in micro-filaments and
to entangle them with one another and with the cellulose pulp
fibres.
[0098] Preferably, the hydro-entangling is made not only on side
S.sub.1 of the support S on which the filaments are laid but also
on side S.sub.2, opposite side S.sub.1, through special through
holes (not shown in the figures) and suitable equipment positioned
on said side S.sub.2 (not shown).
[0099] FIGS. 12 to 14 also schematically represent a conventional
filtering device 20 for the water originating from the
hydro-entangling machines positioned after the cellulose pulp
laying step. Said device has the function of recovering the water
of the hydro-entangling machine and filtering it of any cellulose
pulp fibres besides filtering the chemical components that are
contained in the fibres and may be released in the course of
hydro-entanglement.
[0100] In accordance with a further variant embodiment of the
invention, FIG. 14b illustrates a support S', identical to that
described above, on which the second layer T.sub.2 of nonwoven
filaments is laid. As will be seen, said S' is at a different level
from support S on which the first layer T.sub.1 is laid. Thereby,
the second layer T.sub.2 can be separately subjected to thickening
(embossing). Thickening only layer T.sub.2 is advantageous in that
two substantially even layers can be obtained.
[0101] Subsequently to the thickening treatment, the layer T.sub.2
is carried and laid on the layer of absorbent material fibres
T.sub.3, by support S' or by a conventional conveyor belt, such as
described above, and the three layers are subjected together to
hydro-entanglement.
[0102] The drying step in the dryer 11 and the final winding on
roller 12 take place as described above.
[0103] A further advantage also in relation to the technology that
employs splittable polymer filaments lies in the fact that a
greater density of individual micro-filaments per each filament is
obtained. In other words the filament divides into a number of
components at equal initial dimension, i.e. the micro-filaments
that are obtained are at least 10 times finer, preferably up to 100
times finer.
[0104] Regardless of the type of traditional spunbonded or
splittable filament used in the case one wishes to pre-entangle the
nonwoven before bonding it into the form of a multi-layer composite
(FIGS. 15a and 15b), the steps are as follows: laying the first
layer T.sub.1 by means of the spinneret 13 or a carding machine,
pre-hydro-entangling through equipment 14, drying through equipment
15, laying cellulose pulp T.sub.3 through equipment 16, laying the
second layer T.sub.2 through spinneret 17 or carding machine,
hydro-entangling with hydro-entangling machine 18, drying through
equipment 19 and rewinding onto a roller 21.
[0105] The manufacturing method and plant may as well provide a
dewatering step or station 22 associated to the drying step or
station. The advantage of a pre-hydro-entangling step is that it
allows to create a first layer of spunbonded lobed polymer
bi-component filaments thanks to the greater density of the
entangling of the micro-filaments of said filaments, favours the
laying of filaments of absorbent material and prevents the partial
loss thereof through spaces too wide, which are left by prior art
technologies.
[0106] As mentioned previously, the step of laying fibres of
absorbent material is preferably made with cellulose pulp fibres
having a length that may vary from 0, i.e. cellulose powder, to 2.5
mm, preferably from 1 to 2 mm.
[0107] In addition, the process according to the invention may
provide a drying step after the hydro-entangling step and,
preferably also after the pre-hydro-entangling step.
[0108] A further step may consist in the elimination of the water
contained in the fibres by means of a dewatering step.
Particularly, said step consists in arranging a condenser 22 below
support S and for example at dryer 15 to which an entirely
conventional suction fan (not shown) is usually coupled up. The air
sucked through the holes made on said support is conveyed into said
condenser where it releases the water contained therein. Equipment
of this type is described for example in patent application
PCT/IT2004/000127 of the same applicant.
[0109] The method may also comprise an embossing step to make
products with patterns of the multi-layer nonwoven. Particularly,
the embossing may consist in a calendering treatment made by making
the nonwoven being heated and pass under pressure between a pair of
engraved rollers, in accordance with conventional techniques, or
through a further step in a hydro-entangling machine. It should be
noted that the term "embossing step" is not referred to a
consolidation of the nonwoven as occurs according to the prior art
mentioned previously but is simply enabling to make captions and/or
three dimensional drawings in order to tailor or decorate the
nonwoven through a "thermo-embossing"or "hydro-embossing" calender,
in this case in the hydro-entangling process.
[0110] Preferably, the process comprises sucking the air at room
temperature through the abovementioned through holes (not shown in
the drawings) made in the support S for the fibres. In this way,
the splittable lobed polymer filaments, laid at the molten state,
are cooled and cured.
[0111] Still more preferably, said method may comprise one or more
of the following final steps, known per se, in order to increase or
add additional characteristics to the end product: colouring or
finishing of a chemical nature as the anti-pilling treatment and
the hydrophilic treatment, antistatic treatment, improvement of
flame proof properties, substantially mechanical treatments such as
napping, sanforizing, emerizing.
[0112] In addition, the nonwoven may be subject to a further
process of multicolor printing using the equipment described in
patent application PCT/IT2004/000127 in the name of the same
applicant. In this case, a nonwoven sheet at the end of the process
described above may be printed directly in-line following the steps
of:
[0113] providing equipment for nonwoven printing comprising a
moving support for the transport of said nonwoven and at least one
moving print organ;
[0114] feeding said nonwoven sheet to said equipment;
[0115] performing the printing on said nonwoven under the command
and control of a command and control unit, in which said command
and control unit is operatively connected with said support and at
least one printing organ in order to detect electrical signals
originating from said support and at least one print organ,
transforming said signals into numerical values representative of
the state of their angular speed and torsional moment, comparing
said numerical values with ratios of preset numerical values of
said angular speeds and torsional moments and sending signals to
said support and at least one print organ in order to correct any
variation of said values that fall outside said ratios.
[0116] Finally, the process in accordance with the present
invention may comprise a step of winding the nonwoven onto a roller
21.
[0117] The method of the present invention enables to obtain
various types of product:
[0118] A. single-layer fabric with basic weight of between 8 and 50
g/m.sup.2. The manufacturing method is such as illustrated in FIG.
12. The filament used may be either a synthetic bi-component lobed
filament, splittable with a hydro-entangling machine or a normal
lobed spunbonded fibre.
[0119] B. multi-layer fabric with single-layer hydro-entangling or
three-layer hydro-entangling with or without
pre-hydro-entanglement. For example, the product may be a
three-layer, one of which is a central cellulose pulp layer and the
outer layers with different combinations of the technologies
illustrated above (20 to 200 g/m.sup.2).
[0120] In any case, regardless of the type of single-layer or
multi-layer nonwoven, the tactile and visual characteristics of the
individual ply which forms it and differentiate it from any other
ply comprise, weights being equal, a 3-5 times greater thickness,
softness and smoothness similar to cotton and a cotton wool-like
appearance, i.e. similar to a mellow and delicate flock, as well a
degree of resistance to the wearing which is from 1,5 to 2 fold
greater.
[0121] Particularly, and by way of non-limiting examples, exemplary
fibres obtainable in accordance with the inventive method are
described below.
Splittable Bi-Component Spunbonded Polymer Synthetic Filaments
[0122] Preferably, the splittable bi-component lobed polymer
filaments are composed of micro-filaments of polymer such as those
described above with reference to the manufacturing method. The
micro-filaments may have a diameter of between 0.5 dTex and 0.9
dTex and the corresponding filaments may vary according to the
number of micro-filaments that compose it but generally are of
dimensions of between 1.7 dTex and 2.2 dTex.
[0123] As to a three-layer nonwoven having an inner layer of
cellulose pulp fibres and two outer layers of polymer filaments
consisting of two different splittable lobed polymer components
such as polypropylene/polyethylene wherein 50% is fluff pulp and
50% is spunbonded, analytical tests have shown the following
physical characteristics: [0124] weight in grams per square meter
ranging between 20 and 200, preferably between 30 and 50; [0125]
tensile strength in the machine direction expressed in Newton per 5
cm (N/5 cm) between 70 and 150, preferably between 80 and 120,
whereas in the cross-direction between 30 and 75, it is preferably
between 35 and 65 for a 45-50 g/m.sup.2 product; 50% fluff and 50%
2 continuous filament layers [0126] elongation, calculated as a
percentage of the length in a relaxed state, ranged between 35% and
85% in machine direction (MD), preferably between 45% and 75%,
whereas it ranged between 70% and 130% in the cross-direction (CD),
preferably between 80% and 110%; [0127] final content of the
cellulose pulp fibre ranged between 30% and 75% of the total weight
of the nonwoven; [0128] power of absorption calculated as a
percentage of total weight in relation to the weight of the dry
nonwoven was between 600% and 800% (according to the percentage of
pulp in the end product).
[0129] A non-limiting example of one embodiment of the process
according to the present invention is described below.
EXAMPLE
[0130] Isotactic polypropylene polymer material has been employed
to carry out this example, having a melt flow rate of 40 g/10 min,
such as established by ASTM D-1238, in the form of "chips". The
polymer has been loaded in an extruder connected to a spinneret
having an operating pressure of about 9646 kPa. The spinneret
consists of capillaries having a diameter of 0,038 cm and a slot
length of 0,152 cm. The molten isotactic polypropylene passes
through the spinnerets at a speed of 0.6 g/min/hole and is extruded
at a temperature of 227.degree. C. The polymer is random laid on a
perforated support having a fibre-collecting surface provided with
truncated cone-shaped ribs of 0.9 mm height and alternating with
specular grooves, a 0.5 mm.sup.2 head pressure surface and a total
pressure surface onto the nonwoven of 9-7%. Subsequently, the
support is moved forward until reaching two rollers of an embosser
where it is pinched between said rollers together with the
non-consolidated polymer fibre ply carried thereonto. The pressure
applied by the embosser, which normally ranges between 10 and
100N/mm, is about 45N/mm whereas the operating temperature, which
normally ranges between 80 and 200.degree. C., is 140.degree. C.
the rotation and dragging speed of the ply, which varies between 20
and 600 m/min, is 300 m/min. At the calender outlet, the
consolidated ply has a cotton wool-like appearance, is soft, has a
weight in grams ranging between 8 and 20 g/m.sup.2 and is up to
five times thicker than a spunbonded nonwoven of the same weight in
grams, which is usually no more than 0,18 mm thick, and has a
cohesion of 1.5 fold greater. Now, the continuous ply is winded on
a roll to be then carried to a subsequent manufacturing line or, in
the case of in-line operation, to the hydro-entangling station to
be subjected to the normal treating conditions. It should be noted,
however, that the end product does not exhibit substantial
modifications of the tactile, thickness and functional
characteristics such as described above.
[0131] It should be appreciated by what has been stated above that
the present patent application provides a method for manufacturing
a particularly soft, smooth, thick and resistant nonwoven, as well
as a nonwoven obtainable by said method.
[0132] Furthermore, those of ordinary skill in the art may carry
out a number of modifications both to the method and the nonwoven,
all being within the scope of protection of the claims appended
herein.
[0133] Referring to FIG. 17 wherein the same reference numbers as
the reference numbers in FIG. 14a designate the same working
stations, there is schematically represented a manufacturing line
or a method for manufacturing a three-layer carded fibres/cellulose
pulp/lobed spunbonded mixed nonwoven.
[0134] Compared to the method described in FIG. 14a, this method is
different in that the first spinneret 7 for laying the first
nonwoven layer T.sub.1 is replaced with a conventional carding
machine 23.
[0135] It should be noted that, also in this case, all the variants
discussed above are valid, i.e. the nonwoven layers can be
previously hydro-entangled, the second nonwoven layer T.sub.2 can
be laid and passed through the compactor or embosser on a different
level from any previous laying of fibres and the above-mentioned
supplementary machining operations such as moulding and decoration
(thermo-embossing) may be provided.
[0136] Furthermore, in the mixed multi-layer nonwoven, either the
first laid layer, such as illustrated in FIG. 17, or the second
layer can be the carded layer.
[0137] In addition, in FIG. 18 there is illustrated a manufacturing
method in which a roller 24 of spunbonded lobed filaments, treated
only by a compactor or embosser such as discussed above, is
subjected to machining in a different line, in accordance with what
has been already discussed above. Particularly, the nonwoven ply T
is unwound from roller 24 and subjected for example to
hydro-entangling by equipment 5, similarly to what has been
described above, then it is dried and finally wound again on a
roller 4'.
[0138] Similarly to what has been illustrated in FIGS. 13 and 14a,
FIGS. 19 and 20 represent identical methods, wherein, again, a
roller 24 of spunbonded lobed filaments replaces the spinnerets and
the carding machines for laying said fibres, respectively; the
other machining operation remaining unchanged. In both latter
cases, the variant embodiments described above may be also adopted,
such as employing two rollers carrying the same fabric of the type
spunbonded/spunbonded, spunbonded/staple fibres treated by
compactor or embosser.
[0139] With reference to FIG. 21, a further embodiment of the
invention consists in performing the method disclosed above
wherein, in particular, said at least one surface is the surface of
one of the rollers of the compactor or embosser. The provision of
the surface with ribs on one of said rollers allows to avoid the
support S disclosed above without altering the result to be
obtained, i.e. increasing the thickness and softness of the
nonwoven layer so that to look like a cotton wool-like.
[0140] In detail, the compactor C comprises two rollers (only one
is represented in FIG. 21) similar to the rollers of a conventional
compactor or embosser, wherein the surface 200 of one roller 201 is
provided with ribs 202 having an height comprised between 0.3 and 5
mm, a free head with a contact surface for the fibres or
microfibres having an extension of less than 0,80 mm.sup.2, said
ribs being distributed so that to cover less than 14% of said at
least one surface. The ribs can be of the same type as disclosed
above with reference to the ribs of the support S and the same
preferred range are to be considered herein included, too.
[0141] In particular, said ribs 202 can have a preferred shape
substantially in the form of a frustum of cone with a grater
circular base attached to the surface 201, as can be better seen in
FIG. 22.
* * * * *