U.S. patent application number 12/206828 was filed with the patent office on 2009-03-12 for elastic spunbonded nonwoven and elastic nonwoven fabric comprising the same.
This patent application is currently assigned to ALBIS Spa. Invention is credited to Galliano Boscolo, Antonino Maltese.
Application Number | 20090068912 12/206828 |
Document ID | / |
Family ID | 38969558 |
Filed Date | 2009-03-12 |
United States Patent
Application |
20090068912 |
Kind Code |
A1 |
Boscolo; Galliano ; et
al. |
March 12, 2009 |
ELASTIC SPUNBONDED NONWOVEN AND ELASTIC NONWOVEN FABRIC COMPRISING
THE SAME
Abstract
The elastic spunbonded nonwoven has high elastic recovery
properties and includes a plurality of multicomponent filaments.
Each multicomponent filament, preferably of the sheath/core type,
includes a first polymeric component extending along the length of
the filament in at least a first section of the filament, and a
second polymeric component extending along the length of the
filament in at least a second section of the filament that is
distinct from the first section. The first polymeric component
comprises an elastic propylene-based olefin copolymer, and the
second polymeric component comprises an elastic propylene-based
olefin and has a melt flow rate that is higher than the melt flow
rate of the first polymeric component. The elastic propylene-based
olefin copolymer for the first polymeric component and for the
second polymeric component includes propylene and from 10 to 25
weight % of one or more C2 and/or C4 to C10 alpha-olefin
co-monomers.
Inventors: |
Boscolo; Galliano; (Vigliano
Biellese, IT) ; Maltese; Antonino; (Gorle,
IT) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 828
BLOOMFIELD HILLS
MI
48303
US
|
Assignee: |
ALBIS Spa
Milano
IT
|
Family ID: |
38969558 |
Appl. No.: |
12/206828 |
Filed: |
September 9, 2008 |
Current U.S.
Class: |
442/329 |
Current CPC
Class: |
Y10T 442/602 20150401;
D01D 5/0985 20130101; D01F 8/06 20130101; D04H 3/147 20130101; D04H
3/02 20130101; D04H 13/00 20130101 |
Class at
Publication: |
442/329 |
International
Class: |
D04H 13/00 20060101
D04H013/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 10, 2007 |
EP |
EP 07 017 656.5 |
Claims
1. An elastic spunbonded nonwoven comprising a plurality of
multi-component filaments, wherein each multi-component filament
comprises a first polymeric component extending along the length of
the filament in at least a first section of the filament, and a
second polymeric component extending along the length of the
filament in at least a second section of the filament that is
distinct from the first section, wherein the first polymeric
component comprises an elastic propylene-based olefin copolymer,
and the second polymeric component comprises an elastic
propylene-based olefin and has a melt flow rate MFR2 that is higher
than the melt flow rate MFR1 of the first polymeric component, and
wherein the elastic propylene-based olefin copolymer for the first
polymeric component and for the second polymeric component
comprises propylene and from 10 to 25 weight % of one or more C2
and/or C4 to C10 alpha-olefin co-monomers.
2. An elastic spunbonded nonwoven according to claim 1, wherein
each multi-component filament comprises a core and an outer sheath,
and wherein the core comprises the first polymeric component, and
the sheath comprises the second polymeric component.
3. An elastic spunbonded nonwoven according to claim 1, wherein the
ratio MFR2/MFR1 is higher than 1.5.
4. An elastic spunbonded nonwoven according to claim 1, wherein the
first polymeric component comprises a blend of at least two elastic
propylene-based olefin copolymers of different melt flow rate.
5. An elastic spunbonded nonwoven according to claim 1, wherein the
elastic propylene-based olefin copolymer for the first polymeric
component and for the second polymeric component is an ethylene
propylene copolymer.
6. An elastic spunbonded nonwoven according to claim 1, wherein the
elastic propylene-based olefin copolymer for the first polymeric
component and for the second polymeric component has a melt flow
rate of 0.1 to 2000 g/10 min, most preferably greater than 2 g/10
min and less than 100 g/10 min, as measured by ASTM D-1238 at
230.degree. C. and 2.16 kg.
7. An elastic spunbonded nonwoven according to claim 1, wherein the
elastic propylene-based olefin copolymer for the first polymeric
component and for the second polymeric component has a molecular
weight distribution of less than 5, preferably between 1 and 4.
8. An elastic spunbonded nonwoven according to claim 1, wherein the
elastic propylene-based olefin copolymer for the first polymeric
component and for the second polymeric component comprises at least
80 wt % of propylene units.
9. An elastic spunbonded nonwoven according to claim 1, wherein the
elastic propylene-based olefin copolymer for the first polymeric
component and for the second polymeric component is a
metallocene-catalysed polymer.
10. An elastic spunbonded nonwoven according to claim 1, wherein at
least 50% of the whole surface of each filament is constituted by
the second polymeric component.
11. An elastic spunbonded nonwoven according to claim 10, wherein
100% of the whole surface of each filament is constituted by the
second polymeric component.
12. An elastic spunbonded nonwoven according to claim 1, having a
root mean square (RMS) average recovery of at least 85%, said RMS
average recovery being calculated from the formula: RMS average
recovery=[1/2(R.sub.CD.sup.2+R.sub.MD.sup.2)].sup.1/2, wherein
R.sub.MD and R.sub.CD are recovery values (R) measured on a
nonwoven specimen respectively in machine direction and cross
direction, after 50% elongation and one pull, and calculated from
the formula: R=[(Ls-Lr)/(Ls-Lo)]%, wherein Ls represents the
stretched length of the specimen; Lr represents the recovered
length of the specimen, Lo represents the original length of the
specimen.
13. An elastic spunbonded nonwoven according to claim 12, and
having a RMS recovery, after two successive 50% pulls, of at least
80%.
14. An elastic spunbonded nonwoven according to claim 1, wherein
the amount of the first polymeric component is at least 50 wt % of
the total weight of the filament, and the amount of the second
polymeric component is less than 50 wt % of the total weight of the
filament.
15. A spunbonded nonwoven according to claim 14, wherein the amount
of the second polymeric component is less than 40 wt % of the total
weight of the filament, and preferably equal or less than 30 wt %
of the total weight the filament.
16. An elastic nonwoven fabric comprising at least one first
elastic spunbonded nonwoven layer according to claim 1 and at least
one additional nonwoven layer.
17. An elastic nonwoven fabric according to claim 16, wherein the
said at least one additional nonwoven layer is selected from the
group: a carded nonwoven layer, a meltblown layer, a spunbonded
layer, a polyolefin-based nonwoven layer, a polypropylene-based
nonwoven layer.
18. An elastic nonwoven fabric according to claim 16, comprising at
least two additional carded nonwoven layers and wherein the elastic
spunbonded nonwoven layer is sandwiched between the two carded
layers.
19. An elastic nonwoven fabric according to claim 18, and
comprising an additional meltblown layer interposed between the
elastic spunbonded nonwoven layer and one carded nonwoven
layer.
20. An elastic nonwoven fabric according to claim 16, wherein the
layers are bonded together by one of the following bonding
technologies: thermal bonding, water needling, mechanical needling,
ultrasonic bonding, air trough bonding and chemical bonding.
21. An elastic nonwoven fabric according to claim 16, wherein the
layers are perforated.
22. An elastic nonwoven fabric according to claim 16, and having a
CD permanent set after two cycles at 150% elongation less than 50%,
and preferably less than 40%.
23. An elastic nonwoven fabric according to claim 16, and having a
CD elongation@Peak of at least 150%, and preferably of at least
200%.
24. An elastic nonwoven fabric according to claim 16 wherein the
layers have been hydroentangled.
25. A hydroentangled elastic nonwoven fabric according to claim 24,
wherein the layers are perforated, notably by means of hydro jets.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a novel elastic spunbonded
nonwoven made from multi-component filaments, and having a
remarkable elastic recovery, and to an elastic nonwoven fabric
comprising at least two superposed layers, one of which being
constituted by the said novel elastic spunbonded nonwoven.
PRIOR ART
[0002] Elastic nonwoven fabrics advantageously offer the ability to
conform to irregular shapes, and thus enable to increase fit and to
allow more freedom and comfort, for example to body movements, than
other textile fabrics with more limited extensibility. Elastic
nonwoven fabrics are thus widely used in many industrial
applications. Elastic nonwoven fabrics are used in the hygienic and
personal care industry for making, for example, disposable diapers,
child swim pants, child training pants, adult incontinent garments,
sanitary napkins, wipes and other personal care products. Elastic
nonwoven fabrics are also used in the manufacture of medical
products, such as, for example, gowns, linens, bandages, masks,
heads wraps and drapes. Others additional applications of elastic
nonwoven fabrics include consumer products, like seat covers and
car covers.
[0003] The demand for innovative and low cost elastic nonwoven
products has increased in the last years. Several techniques can be
used to produce nonwoven fabrics, but recently, due to the
increasing of a higher cost efficiency requested by the market,
methods based on melt spinning continuous filaments of
thermoplastic materials have increased their importance. Such
nonwoven fabrics, called "spunbonded" nonwovens can advantageously
give the required combinations of physical properties, like
softness, strength and durability.
[0004] One solution used in the prior art for making elastic
spunbonded nonwoven webs consists in melt spinning filaments made
of elastomeric polymer, such as, for example, thermoplastic
polyurethane (TPU).
[0005] Significant problems have been however encountered with this
solution.
[0006] One of these problems is linked to the "sticky" nature of
the elastomeric polymer, typically employed in producing elastic
nonwoven materials. In fact during the spunbonding process, the
large air flow used for drawing the filament can make the filaments
stick together and therefore the resulting web uniformity will be
negatively affected. Furthermore this bigger filament bundling can
give trouble due to the blocking effect when the fabric is wound
into rolls.
[0007] Another problem encountered when elastomeric polymers are
used for making spunbonded nonwovens is the breakage of the
filaments during extrusion and/or drawing for attenuating the
filaments. When filaments break they can obstruct the flow of
filaments and/or mesh with other filaments, resulting in the
formation of a defect in the nonwoven web.
[0008] A further drawback of the use of elastomeric polymers such
as TPU for making spunbonded nonwoven is their poor bonding
ability, especially thermal-bonding ability, with the most used
polyolefin materials.
[0009] In order to overcome these problems, it has been proposed in
U.S. Pat. No. 6,225,243 and in PCT application WO 00/08243 to
produce spunbonded nonwoven webs made of multi-component filaments
including at least two components: a first elastic polymeric
component, and a second, extensible polymeric component, the first
elastic polymeric component having an elasticity that is greater
than the elasticity of the second polymeric component. The first
elastic polymeric component preferably comprises at least one
elastomer that includes an elastic polypropylene; the second
polymeric component preferably comprises at least one polyolefin
that is a linear low density polyethylene (LLDPE) having a density
greater than 0.90 g/cc.
[0010] This solution disclosed in U.S. Pat. No. 6,225,243 and in
PCT application WO 00/08243 is however not satisfying in terms of
elastic properties, especially in terms of elastic recovery.
[0011] In PCT application WO2005/090659, elastic nonwovens made of
extensible conjugate fiber are disclosed. The extensible conjugate
fiber has a total heat of melting of less than 80 Joules per gram,
and comprises: [0012] a. from 0.001% to about 20% by weight of the
total fiber of a first component A which comprises at least a
portion of the fiber surface, said first component A comprising a
polypropylene homopolymer or a polypropylene copolymer, [0013] b.
and a second component B which comprises an elastic propylene-based
olefin polymer.
[0014] Japanese patent application JP 11 323716 discloses an
extensible spunbonded nonwoven fabric made of filaments of the
eccentric sheath-core type. This spunbonded nonwoven fabric is
extensible, but does not exhibit very high elastic properties, in
particular high recovery.
OBJECTIVE OF THE INVENTION
[0015] The present invention proposes a novel elastic spunbonded
nonwoven that overcomes the aforesaid problems inherent to the use
of elastomeric polymers such as TPU, and that enables to achieve
very high elastic properties.
SUMMARY OF THE INVENTION
[0016] The above-mentioned objective is achieved by the elastic
spunbonded nonwoven of claim 1. This spunbonded nonwoven comprises
a plurality of multi-component filaments; each multi-component
filament comprises a first polymeric component (P) extending along
the length of the filament in at least a first section of the
filament, and a second polymeric component (P') extending along the
length of the filament in at least a second section of the filament
that is distinct from the first section. The said first polymeric
component (P) comprises an elastic propylene-based olefin
copolymer, and the said second polymeric component (P') comprises
an elastic propylene-based olefin and has a melt flow rate MFR2
that is higher than the melt flow rate MFR1 of the first polymeric
component. The elastic propylene-based olefin copolymer for the
first polymeric component and for the second polymeric component
comprises propylene and from 10 to 25 weight % of one or more C2
and/or C4 to C10 alpha-olefin co-monomers.
[0017] As used therein, the wording "multi-component filament"
means a filament that is formed by combining multiple extrudates in
the filament resulting in a heterogeneous filament cross section
wherein at least two sections are occupied by separate polymeric
components along the entire length of the filament. The cross
section of the multi-component filament may take different
configurations such as side-by-side, sheath-core, eccentric
sheath-core, and islands-in-the sea. "Multi-component filaments"
are also commonly referred as "conjugate filaments".
[0018] The first polymeric component (P) can advantageously exhibit
very high elastic properties, and in particular one can use an
elastic polymeric component with a low melt flow rate that would be
practically not spinnable alone.
[0019] For measuring the melt flow rates (MFR1, MFR2) of the first
and second polymeric components, standard method ASTM D-1238 can be
used.
[0020] The wording "elastic propylene-based olefin copolymer", as
used therein, means polypropylene polymers, selected from the group
of thermoplastic olefin-based elastomers, that incorporate a low
level of a co-monomer, such as ethylene or a higher alpha-olefin in
the backbone to form an elastomeric copolymer. The term
"copolymers" means any polymer comprising two or more monomers,
where the monomer present in the polymer is the polymerized form of
the monomer. Likewise when catalyst components are described as
comprising neutral stable forms of the components, it is well
understood that the active form of the component is the form that
reacts with the monomers to produce polymers.
[0021] As used herein, the term "polypropylene", "propylene
polymer," or "PP" refers to homopolymers, copolymers, terpolymers,
and interpolymers, comprising from 50 to 100 weight % of
propylene.
[0022] More particularly, "elastic propylene-based olefin
copolymer" can be a single semi-amorphous copolymer or a blend of
several semi-amorphous polymers, each semi-amorphous polymer
comprising propylene and from 10 to 25 weight % of one or more C2
and/or C4 to C10 alpha-olefin co-monomers, preferably ethylene,
wherein the copolymer comprises isotactically crystallizable
alpha-olefin sequences. The term "crystallizable" describes those
polymers or sequences which are mainly amorphous in the undeformed
state, but upon stretching or annealing, crystallization
occurs.
[0023] Most preferably, the copolymer is an ethylene propylene
copolymer, e.g., ethylene propylene thermoplastic elastomer. The
copolymer has a substantially uniform composition distribution
preferably as a result of polymerization with a metallocene
catalyst. Composition distribution is a property of copolymers
indicating a statistically significant intermolecular or
intramolecular difference in the composition of the polymer.
[0024] Preferably, each semi-amorphous polymers has: a) heat of
fusion of 4 to 70 J/g, as determined by Differential Scanning
Calorimetry (DSC); b) a Melt Flow Rate of 0.1 to 2000 dg/min, most
preferably greater than 2 dg/min and less than 100 dg/min, as
measured by ASTM D-1238 at 230.degree. C., and 2.16 kg.
[0025] A semi-amorphous copolymer may be produced in a continuous
solution process using a metallocene catalyst.
[0026] Preferably, copolymers having a narrow molecular weight
distribution are used. To produce a copolymer having a narrow
molecular weight distribution, a single sited metallocene catalyst
is advantageously used, which allows only a single statistical mode
of addition of the first and second monomer sequences, and the
copolymer is advantageously well-mixed in a continuous flow stirred
tank polymerization reactor, which allows only a single
polymerization environment for substantially all of the polymer
chains of the copolymer.
[0027] Preferred semi-amorphous polymers useful in this invention
preferably have a molecular weight distribution (Mw/Mn) of less
than 5, preferably between 1 and 4.
[0028] As used herein, molecular weight (Mn and Mw) and molecular
weight distribution (MWD or Mw/Mn) are determined by gel permeation
chromatography using polystyrene standards.
[0029] As used herein, "metallocene" means one or more compounds
represented by the formula Cp1nMRnXq, wherein Cp is a
cyclopentadienyl ring which may be substituted, or derivative
thereof (such as indene or fluorene) which may be substituted; M is
a transition metal, for example titanium, zirconium, hafnium,
vanadium, niobium, tantalum, chromium, molybdenum and tungsten; R
is a substituted or unsubstituted hydrocarbyl group or hydrocarboxy
group having from one to 20 carbon atoms; X may be a halide, a
hydride, an alkyl group, an alkenyl group or an arylalkyl group;
and typically, m=I-3; n=0-3; q=0-3.
[0030] A slip agent selected for example from the group consisting
of: erucamide, oleylamide, oleamide, and stearamide and used in a
concentration from 50 ppm to 10 weight % can be successful added.
During the processing of thermoplastic polymers it is often
required to modify the rheology or surface properties of polymers
by addition of selected slip agents, in order to reduce the
friction and polymer tackiness, and facilitate the whole
spunbonding process.
[0031] Preferred elastic propylene-based olefin copolymers suitable
for the invention include thermoplastic elastic propylene-ethylene
copolymers formed by using metallocene polymerization catalysis.
Such polymers include those commercially available from ExxonMobil
Chemical Co, Huston, Tex. under the trademark of VISTAMAXX.RTM.),
e.g. Vistamaxx 2120 or Vistamaxx 2125 for second polymeric
component in the sheath and a blend of Vistamaxx 2125 and Vistamaxx
6100 (or Vistamaxx 6102) for first polymeric component in the
core.
[0032] Preferably, but not necessarily, each multi-component
filament comprises a core and an outer sheath; the core comprises
the first polymeric component and the sheath comprises the second
polymeric component.
[0033] Preferably, but not necessarily, the ratio MFR2/MFR1 between
the melt flow rates of the second and first polymeric components is
higher than 1.5.
[0034] In one variant, the first polymeric component comprises a
blend of at least two elastic propylene-based olefin copolymers of
different melt flow rate (MFR1a and MFR1b).
[0035] Optionally, the elastic spunbonded nonwoven of the invention
is further characterized by the following optional features that
can be combined or taken alone: [0036] the elastic propylene-based
olefin copolymer for the first polymeric component and for the
second polymeric component is an ethylene propylene copolymer;
[0037] the elastic propylene-based olefin copolymer for the first
polymeric component and for the second polymeric component has a
melt flow rate of 0.1 to 2000 g/10 min, most preferably greater
than 2 g/10 min and less than 100 g/10 min, as measured by ASTM
D-1238 at 230.degree. C. and 2.16 kg; [0038] the elastic
propylene-based olefin copolymer for the first polymeric component
and for the second polymeric component has a molecular weight
distribution (Mw/Mn) of less than 5, preferably between 1 and 4;
[0039] the elastic propylene-based olefin copolymer for the first
polymeric component and for the second polymeric component
comprises at least 80 wt % of propylene units; [0040] the elastic
propylene-based olefin copolymer for the first polymeric component
and for the second polymeric component is a metallocene-catalysed
polymer; [0041] the spunbonded nowoven has a root mean square (RMS)
average recovery of at least 85%, said RMS average recovery being
calculated from the formula:
[0041] RMS average=[1/2(R.sub.CD.sup.2+R.sub.MD.sup.2)].sup.1/2,
[0042] wherein R.sub.MD and R.sub.CD are recovery values (R)
measured on a nonwoven specimen respectively in machine direction
and cross direction, after 50% elongation and one pull, and
calculated from the formula:
[0042] R=[(Ls-Lr)/(Ls-Lo)]%, [0043] wherein Ls represents the
stretched length of the specimen; Lr represents the recovered
length of the specimen, Lo represents the original length of the
specimen; [0044] the spunbonded nonwoven has a RMS recovery, after
two successive 50% pulls, of at least 80%; [0045] the amount of the
first polymeric component is at least 50 wt % of the total weight
of the filament, and the amount of the second polymeric component
is less than 50 wt % of the total weight of the filament; [0046]
the amount of the second polymeric component is less than 40 wt %
of the total weight of the filament, and preferably equal or less
than 30 wt % of the total weight the filament.
[0047] Another object of the invention is to propose an elastic
nonwoven fabric comprising at least one first elastic spunbonded
nonwoven layer as defined above, and at least one additional
nonwoven layer.
[0048] More particularly, and optionally, the composite nonwoven is
characterized by the following optional features that can be taken
alone or combined together: [0049] the additional nonwoven layer is
selected from the group: carded nonwoven; spunbonded nonwoven,
meltblown nonwoven; [0050] the additional nonwoven layer can be
constituted by a polyolefin-based nonwoven; [0051] In one variant,
the elastic nonwoven fabric comprises at least two additional
carded nonwoven layers (C) and an elastic spunbonded nonwoven layer
(W) of the invention, and sandwiched between the two carded layers;
More particularly, the elastic nonwoven fabric can further comprise
an additional meltblown layer (M) interposed between the elastic
spunbonded nonwoven layer (W) and one carded nonwoven layer (C).
[0052] the layers can be bonded together by one of the following
bonding technologies: thermal bonding, water needling, mechanical
needling, ultrasonic bonding, air trough bonding and chemical
bonding; [0053] in one variant, the layers are perforated. [0054]
the elastic nonwoven fabric has a CD permanent set after two cycles
at 150% elongation less 50%, and preferably less than 40%. [0055]
the elastic nonwoven fabric has a CD elongation@Peak of at least
150%, and preferably of at least 200%.
[0056] The wording "polyolefin-based nonwoven layer", as used
therein, means any nonwoven layer that is essentially made from a
polymer or copolymer that is exclusively or predominantly made up
of polyolefin units.
[0057] Preferably, at least one polyolefin-based nonwoven layer is
a polypropylene-based nonwoven layer.
[0058] The wording "polypropylene-based nonwoven layer", as used
therein, means any nonwoven layer that is essentially made from a
polymer or copolymer that is exclusively or predominantly made up
of polypropylene units.
[0059] A further object of the invention is a hydroentangled
elastic nonwoven fabric comprising at least one first elastic
spunbonded nonwoven layer (W) and at least one second nonwoven
layer, and wherein the said first elastic spunbonded nonwoven layer
(W) comprises a plurality of multi-component filaments, each
multi-component filament comprising a first polymeric component (P)
and a second polymeric component (P'), and wherein the first
polymeric component (P) comprises an elastic propylene-based olefin
copolymer, and the second polymeric component (P') comprises an
elastic propylene-based olefin and has a melt flow rate MFR2 that
is higher than the melt flow rate MFR1 of the first polymeric
component.
[0060] More particularly, in one variant, the layers of the
hydroentangled elastic nonwoven fabric are perforated, more
especially by means of hydro jets.
BRIEF DESCRIPTION OF DRAWINGS
[0061] Other characteristics and advantages of the invention will
appear more clearly on reading the following detailed description
which is made by way of non-exhaustive and non-limiting examples,
and with reference to the accompanying drawings on which:
[0062] FIGS. 1A to 1F are different examples of spun filaments
cross-sections that are suitable for practising the invention,
[0063] FIG. 2 is a schematic drawing of a first example of
production line that is used for making a thermo-bonded elastic
nonwoven fabric of the invention;
[0064] FIG. 3 is a schematic drawing of a second example of
production line that is used for making a hydroentangled elastic
nonwoven fabric of the invention,
[0065] FIG. 4 is a schematic drawing of a third example of
production line that is used for making a hydroentangled elastic
nonwoven fabric of the invention,
[0066] FIG. 5 is a schematic drawing of a fourth example of
production line that is used for making a hydroentangled elastic
nonwoven fabric of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0067] The elastic nonwoven of the invention is obtained by a
spunbonding process and is made of multi-component filaments F
comprising at least two different polymeric components P, P' that
are specific of the invention. First polymeric component (P)
extends along the entire length of each filament in at least a
first section of the filament, and a second polymeric component
(P') extends along the entire length of each filament in at least a
second section of the filament that is distinct from the first
section.
[0068] According to the invention, both the first (P) and the
second (P') polymeric components comprise an elastic
propylene-based olefin copolymer, but have two different melt flow
rates (MFR1; MFR2), the melt flow rate MFR2 of the second polymeric
component being higher than the melt flow rate MFR1 of the first
polymeric component.
[0069] The elastic propylene-based olefin copolymers that are
suitable for the first and second polymeric components are
copolymers comprising propylene and from 10 to 25 weight % of one
or more C2 and/or C4 to C10 alpha-olefin co-monomers, like for
example the ones commercially available from ExxonMobil Chemical
Co, Huston, Tex. under the trademark of VISTAMAXX.RTM..
[0070] More particularly, the elastic propylene-based olefin
copolymers that are suitable for the first polymeric components are
for example a blend of at least two different propylene-ethylene
copolymers commercially available from ExxonMobil Chemical Co,
Huston, Tex. under the trademark of VISTAMAXX.RTM. and having two
different melt flow rate (MFR1a and MFR1b).
[0071] The first and second polymeric components can also include
others materials, like pigments or colorants, or opacizers (like
TiO.sub.2) antioxidants, stabilizers, fillers, surfactants, waxes,
flow promoters or special additives to enhance processability of
the composition, like for example slip agents. It is particularly
recommended to add slip agents in the second polymeric
component.
[0072] Various shapes in cross section for the filaments F can be
envisaged (round shape, oval shape, bilobal shape, trilobal shape,
etc. . . . ).
[0073] Preferably, the multi-component filaments are bi-component
filaments. Some non-limiting examples of different cross sections
for bicomponent filaments that are suitable for the invention are
illustrated on FIGS. 1A, 1B, 1C, 1D, 1E, 1F.
[0074] Preferably, as depicted on the particular examples of FIG.
1A to 1F, at least 50% of the whole surface of the filament F is
constituted by the second polymeric component P', and even more
preferably 100% of the whole surface of the filament F is
constituted by the second polymeric component P' (FIGS. 1B, 1C, 1D,
1E).
[0075] Bicomponent filament of the sheath/core type, like the ones
illustrated in FIGS. 1A, 1B, 1C, 1D, and wherein the core is made
of the first polymeric component P and the sheath is made of the
second polymeric component P are preferably used for a better
thermal-bondability of the elastic spunbonded web with other
polyolefin layers, as described hereafter. Although the sheath/core
configuration is preferred, the invention is however not limited to
that particular configuration.
[0076] In other variant of the invention, the filaments can however
comprise more than two polymeric components.
[0077] The method applied to produce the elastic nonwoven web
according to the present invention is the spunbonding process.
Various types of spunbonding processes are described in U.S. Pat.
No. 3,338,992 to Kenney, U.S. Pat. No. 3,692,613 to Dorschner, U.S.
Pat. No. 3,802,817 to Matsuki, U.S. Pat. No. 4,405,297 to Appel,
U.S. Pat. No. 4,812,112 to Balk and U.S. Pat. No. 5,665,300 to
Brignola et al.
FIG. 2--Thermo-Bonded Elastic Nonwoven Fabric (L1/W/L2)
[0078] One example of a suitable process line for producing an
elastic nonwoven fabric of the invention is illustrated in FIG. 2.
In this example, the process line comprises: [0079] a spunbonding
unit (SU) for producing an elastic spunbonded nonwoven W made of
bi-components filaments, preferably of the sheath/core type; [0080]
a first delivering mean 11, in the form of a roll, for delivering a
first additional nonwoven layer L1, upstream the area where the
spunbonded nonwoven W is being formed; [0081] a second delivering
mean 15, in the form of a roll, for delivering a second additional
nonwoven layer L2, downstream the area where the spunbonded
nonwoven W is being formed.
Spunbonding Unit (SU)
[0082] The spunbonding unit (SU) comprises two hoppers 1 and 2,
containing respectively the first polymeric component (P) and the
second (P') polymeric components. These two hoppers 1 and 2 feed in
parallel two extruders 3 and 4, for separately melting the two
polymeric components. The outputs of the two extruders 3 and 4 are
connected to two melt polymer pumps 5, 6 respectively. Said pumps
5, 6 feed a dosed amount of polymers to the bi-component spinning
pack 7.
[0083] The bi-component spinning pack 7 usually contains a certain
number of plates stacked one on top of the other to distribute the
polymers to the lower plate which is the spinnerets plate, having
one or more rows of capillary holes and where the bi-component
filaments are extruded. Typical spinnerets die systems well known
designed for polypropylene can be used, for example with a die hole
density of 2000-6000 holes per meter, and a die capillary hole
diameter of 0.3 to 0.8 mm. The barrel temperatures of the two
extruders are, for example, ranging from a minimum of 170.degree.
C. to a maximum 260.degree. C., depending on screws speed and
design.
[0084] When the two polymers P, P' are extruded through the
spinnerets holes a curtain of filaments F' is formed downward and
it encounters the quench air which flow is rectified inside the
quench boxes 8, by means of a suitable system, like honey-comb
structure, well known to those of ordinary skilled in the art.
[0085] During the filaments solidification this system avoids air
turbulences which can bring to stick together the filaments in
formation. It is recommended to apply the quench air from both
sides of the filaments curtain in order to improve the cooling
efficiency, as elastic polymers usually show a tendency to
stickiness, as well as to keep down the air flow temperature to the
minimum reachable. Temperatures below 20.degree. C. are considered
suitable for the scope, but lower temperatures, in the range of
10.degree. C. to 15.degree. C., are recommended when more elastic
and soft materials are applied in the sheath arrangement. To this
purpose two quench boxes 8 are shown in the FIG. 1. Each quench box
8 is connected to a blower which delivers the right low pressure
air flow necessary for the filaments cooling.
[0086] After having been cooled the filament curtain enters in a
draw unit 9, which in the most preferred case is constituted by a
slot through which the filaments are drawn by means of air flow
entering from the sides of the slot and flowing downward through
the passage. The filaments are laid onto a foraminous transport
belt (for example a wire belt) forming a transport surface T. A
vacuum box 12 is positioned below the transport surface T, and
delimitates a web forming area on the transport surface T.
[0087] The spunbonding unit (SU) further comprises a compression
roller 10 which stabilizes, by means of a low compression, the web
W just after it is formed and a pair of thermal point calander
rolls 13 (one heated engraved roll and one heated smooth roll),
that can be used to bond the layers (L1, W and L2) together.
Delivering Means 11, 15
[0088] The first delivering mean 11 is used for laying directly
onto the transport surface T, and upstream the web formation area
of the spunbonding unit (SU), a bottom pre-consolidated nonwoven
layer L1 (for example a spun layer, a meltblown layer or a carder
layer). In this configuration, the elastic spunbonded layer W of
the invention is formed on top of this bottom layer L1.
[0089] The second delivering mean 15 is used for laying directly
onto the spunbonded web W a top pre-consolidated nonwoven layer L2
(for example a spun layer, a meltblown layer or a carder layer).
The nonwoven layer W is thus sandwiched between the two outer
nonwoven layers L1 and L2.
[0090] In another variant, the elastic spunbonded layer W of the
invention can be manufactured off line and wound up in the form of
a roll, and the final elastic nonwoven fabric (L1/W/L2) can be
manufactured from a roll of said elastic nonwoven W.
[0091] Referring to FIG. 2, the three layers (L1, W and L2) can be
thermo-bonded together by means of calander rolls 13, and the
elastic nonwoven fabric (L1/W/L2) is wound up in the form of rolls
on a winding machine 14. This winding machine 14 has to be suitable
for elastic material, and preferably enables a strict control of
tension variations during winding, said tension variations being
caused by the elastic properties of the final composite
nonwoven.
[0092] The invention is not limited to an elastic composite
nonwoven fabric that is consolidated by thermal bonding, but within
the scope of the invention the elastic fabric can be consolidated
by using any bonding technology known in the field of nonwoven, and
including notably: water needling (also called hydroentanglement)
by means of hydro jets (on one side or on both sides of the
composite nonwoven), mechanical needling, ultrasonic bonding, air
trough bonding and chemical bonding.
[0093] The elastic composite nonwoven fabric of the invention can
be also perforated by using any perforation technology that is
known in the field of nonwoven, including notably mechanical
perforation and perforation by means of hydro jets.
FIG. 3--Hydroentangled Elastic Nonwoven Fabric (C/W/S)
[0094] One example of a suitable process line for producing a
hydroentangled elastic nonwoven fabric of the invention is
illustrated in FIG. 3.
[0095] In this example, the process line comprises a carding unit
18, a first spunbonding unit SU, second spunbonding unit 19, a
hydraulic needling unit 20, a dewatering unit 21, a drying unit 22,
and a winding unit 23.
[0096] The carding unit 18, which is mounted upstream the
spunbonding unit SU, is used for producing in line a bottom carded
nonwoven layer C.
[0097] Preferably, between this first carding unit 18 and the
spunbonding unit SU, the carded nonwoven layer C is compressed by
compaction rolls (not shown on FIG. 3) and/or by means of calander
rolls like the calander rolls 13 previously described in reference
to FIG. 2. This compression and/or the calandering is performed in
order to pre-consolidate the layer C, before the spunbonded layer W
is formed. The same considerations apply for the production lines
of FIGS. 4 and 5.
[0098] The spunbonding unit SU is similar to the one of FIG. 2 and
is used for producing in line the elastic spunbonded nonwoven layer
W of the fabric.
[0099] The spunbonding unit 19 is similar to spunbonding unit (SU),
but in contrast with spunbonding unit SU, spunbonding unit 19 does
not comprise any calender rolls. This spunbonding unit 19 is used
for laying a top spunbonded layer S onto the elastic spunbonded
layer W.
[0100] The composite nonwoven (C/W/S) is transported, downstream
the spunbonding unit 19, by means of a conveyor belt 200 through
the hydraulic needling unit 20. This hydraulic needling unit 20 is
used for bonding together the layers of the nonwoven composite
(C/W/S), by means of high pressure water jets (hydroentanglement
process) that are directed at least towards the surface of the top
layer S, and that penetrate through the structure of the composite
and are partially reflected back to the structure.
[0101] In the particular example of FIG. 3, the water needling
process is performed on both sides of the composite nonwoven
(C/W/S).
[0102] More particularly, in the example of FIG. 3, the hydraulic
needling unit 20 comprises four successive perforated drums. First
perforated drum 201 is associated with two successive hydro-jet
beams 201a and 201b. Second perforated drum 202 is associated with
two successive hydro-jet beams 202a and 202b. Third perforated drum
203 is associated with two successive hydro-jet beams 203a and
203b. Fourth perforated drum 204 is associated with two successive
hydro-jet beams 204a and 204b. The water pressure of the upstream
hydro-jet beam 201a is lower than the water pressure of all the
other downstream hydro-jet beams 201b, 202a, 202b, 203a, 203b,
204a, 204b, in order to obtain a pre-hydroentanglement of the
layers.
[0103] At the exit of hydraulic needling unit 20, a hydroentangled
elastic composite C/W/S is obtained.
[0104] The fourth drum 204 can be equipped with a perforation
screen, in order to create apertures in the multilayer elastic
fabric C/W/S. This perforation step can be also performed by
replacing the fourth drum 204 by a suitable drum for perforation,
having the surface constituted by one net or several nets
superposed one on the other.
[0105] The hydroentangled elastic composite C/W/S is transported
downstream the hydraulic needling unit 20 by the conveyor belt 210
of a dewatering unit 21, and over a vacuum box 211, that enables to
remove by suction from the fabric most of the water that has been
absorbed during the water needling process (conventional dewatering
process).
[0106] The hydroentanglement unit 20 and the dewatering unit 21 can
be integrated in the same industrial equipment.
[0107] The dewatered hydroentangled elastic fabric (C/W/S) issued
from the dewatering unit 21 is continuously fed through the oven of
the drying unit 22, wherein heat is applied to the fabric (for
example by means of hot air), in order to remove the remaining
water still contained within the fabric.
[0108] Then the dried fabric (C/W/S) is wound in the form of a
roll, by means of the winding unit 23.
FIG. 4--Hydroentangled Elastic Nonwoven Fabric (C/W/C)
[0109] Another example of a suitable process line for producing a
hydroentangled elastic nonwoven fabric of the invention is
illustrated in FIG. 4.
[0110] The process line of FIG. 4 differs from the process line of
FIG. 3 by the use of a second carding unit 18' (similar to first
carding unit 18), that is substituted to the spunbonding unit
19.
FIG. 5--Hydroentangled Elastic Nonwoven Fabric (C/W/M/C)
[0111] Another example of a suitable process line for producing a
hydroentangled elastic nonwoven fabric of the invention is
illustrated in FIG. 5.
[0112] The process line of FIG. 5 differs from the process line of
FIG. 4 by the use of an additional meltblown unit 24, that is
positioned between the first spunbonding unit SU and the second
carding unit 18'. This meltblown unit 24 is used for producing a
meltblown layer M, sandwiched between the elastic spunbonded layer
W issued from the first spunbonding unit SU and the carded layer C
issued from the second carding unit 18'.
[0113] The term "meltblown layer", as used therein, means any layer
essentially made of "meltblown fibers".
[0114] "Meltblown fibers" are well known in the prior art and a
meltblown process for making meltblown fibers is disclosed, for
example, in U.S. Pat. No. 3,849,241 to Butin. "Meltblown fibers"
are generally formed by extruding a molten thermoplastic material
through a plurality of fine, usually circular, die capillaries. The
molten threads or filaments issued from the die capillaries are fed
into converging high velocity air streams which attenuate the
filaments of molten thermoplastic material and reduce their
diameter. Said diameter is generally reduced in order to obtain
microfibers. Meltblown fibers are thus microfibers that may be
continuous or discontinuous, and are generally smaller than 10
microns in diameter. Thereafter, the meltblown fibers are carried
by the high velocity air stream and are deposited onto a collecting
surface (i.e. the elastic spunbonded nonwoven of the invention) to
form a layer of randomly distributed meltblown fibers.
[0115] For example, an additional meltblown layer M is
advantageously used when opacity for the elastic nonwoven fabric is
required. In particular, in hygienic applications, wherein nonwoven
fabrics of higher opacity are required (e.g. for making elastic
back ear for diapers or elastic side panel for training pants), a
meltblown layer is preferably laid on top of the elastic spunbonded
layer W of the invention; for example, the weight of the meltblown
layer M is at least 5 gsm, preferably 8 gsm and more preferably 10
gsm. This meltblown layer gives a more uniform white colour to the
elastic nonwoven fabric, and thus improves the aesthetic
thereof.
EXAMPLES
Elastic Spunbonded Nonwoven (W)
[0116] Different samples of fabric (L1/W/L2) have been produced on
a pilot plant, like the one of FIG. 2, but without using the
calander rolls 13, in order to produce a fabric (L1/W/L2) wherein
the layers L1, W and L2 were not thermo-bonded. Then the layers L1
and L2 were removed in order to keep only the elastic spunbonded
layer W.
[0117] In all samples, the spunbonded nonwoven (W) was made from
bi-component filaments having a sheath/core arrangement and having
the round cross section of FIG. 1D.
[0118] The polymeric materials that have been used for producing
these spunbonded nonwovens (W) were the following.
First Polymeric Component (P)
[0119] A dry blend of VM2125 (polymer P.sub.a) and VM6100 (polymer
P.sub.b) was used as first polymeric component (P).
VM 2125
[0120] VM 2125 is a specialty polyolefin elastomer commercially
available from ExxonMobil Chemical Co, Huston, Tex. under the
trademark of VISTAMAXX.RTM.. This specialty polyolefin elastomer is
a semi-crystalline elastic propylene-based olefin copolymer
comprising at least 85 wt % of propylene units and made in the
presence of a metallocene catalyst during the polymerization
process. This copolymer has a melt flow rate (MFR1a) of 80 g/10 min
(measured at 230.degree. C. and 2.16 Kg-ASTM D-1238), a broad
melting temperature range and a highest melting peak of 160.degree.
C. This copolymer has a slower crystallization rate than
polypropylene homopolymers.
VM6100 (VMX6102)
[0121] VM 6100 is a specialty polyolefin elastomer commercially
available from ExxonMobil Chemical Co, Huston, Tex. under the
trademark of VISTAMAXX.RTM.. This specialty polyolefin elastomer is
a semi-crystalline elastic propylene-based olefin copolymer
comprising at least 80 wt % of propylene units and made in the
presence of a metallocene catalyst during the polymerization
process. This copolymer has a low melt flow rate (MFR1b) of 3 g/10
min (measured at 230.degree. C. and 2.16 Kg-ASTM D-1238), a broad
melting temperature range and a highest melting peak of 160.degree.
C. This copolymer has a slower crystallization rate than
polypropylene homopolymers. VMX 6100 can be replaced by the
equivalent grade VM 6102, having same chemical properties as VM
6100 and giving the same elastic properties to the nonwovens
produced.
[0122] The melt low rate (MFR1) of the first polymeric component
(P) was calculated by means of the following equation:
ln(MFR1)=Wa.times.ln(MFR1a)+Wb.times.ln(MFR1b) (1)
Wherein:
[0123] MFR1a is the melt flow rate of polymer P.sub.a (MFR1a=80
g/10 min for VM2125) [0124] MFR1b is the melt flow rate of polymer
P.sub.b (MFR1b=3 g/10 min for VM6100 or VM6102) [0125] Wa and Wb
are the weight ratios of polymers P.sub.a and P.sub.b in the blend
(Wa+Wb=1).
[0126] In the following examples, the weight ratio (Wa) of VM2125
was 0.8 and the weight ratio (Wb) of VM6100 (or VM6102) was 0.2.
The melt flow rate MFR1 of the blend (first polymeric component P)
calculated by means of above formula (1) was thus around 41 g/10
min.
Second Polymeric Component (P')
[0127] The second polymeric component was made of aforesaid elastic
propylene-based olefin copolymer VM2115
[0128] Other technical characteristics of materials VM6100 (VM6102)
and VM 2125 are given in table 1.
TABLE-US-00001 TABLE 1 VM 6100-VM 6102-VM 2125-VM 2320 MAIN
CHARACTERISTICS VM 6100 VM6102 VM 2125 VM 2320 VM 2120 CHEMICAL
FAMILY POLYOLEFIN POLYOLEFIN POLYOLEFIN POLYOLEFIN POLYOLEFIN
METHOD MFR_g/10 min (1) 3 3 80 200 80 ASTM D-1238 DENSITY_g/cm3
0.855 0.863 0.865 0.866 0.868 / Ethylene Content (wt %) / 16 13 14
13 ASTM D-3900 HARDNESS 55 59 63 62 64 ASTM (SHORE A) D-2240
FLEXURAL / 8.5 29.8 18.6 21.1 ASTM MODULUS_Mpa D-790 TENSILE @ /
>8.3 8.1 6.7 8.6 ASTM BREAK_Mpa D-412 ULTIMATE / >2000 860
853 1007 ASTM ELONGATION D-412 TENSILE STRESS @ / 1.6 3.5 2.8 3.2
ASTM 100% ELONG._Mpa D-412 TENSILE STRESS @ / 2.0 4.6 3.6 4 ASTM
300% ELONG. Mpa D-412
[0129] The compositions of the filaments of the different samples
of spunbonded nonwoven W are summarized in table 2.
TABLE-US-00002 TABLE 2 Filaments composition (P') Weight (Additive)
Core Core Sheath % in Additive Weight % Core_wt % Sheath_wt %
material/ Material/ Material the in the in the Sample (P) (P')
P.sub.a Wa P.sub.b Wb (P') Sheath Sheath Sheath E-7-6 85 15 VM2125
0.8 VM6100 0.2 VM2125 97% (a) 3% E-7-8 85 15 VM2125 0.8 VM6100 0.2
VM2125 97% (a) 3% E-7-10 85 15 VM2125 0.8 VM6100 0.2 VM2125 97% (a)
3% (a) the additive in the sheath is a slip agent masterbatch
containing lubricant and used for facilitating spinning.
[0130] The main spunbonding process parameters are summarized in
the following table 3 for each sample of spunbonded nonwoven W.
TABLE-US-00003 TABLE 3 Spunbonding production data - web forming
(I) (III) (IV) (V) Basis (II) T.degree. of T.degree. of T.degree.
of (VI) (VII) (VIII) weight Filament extruder extruder Spinning
Through- Through- Line of W count (3) (4) Beam put put speed Sample
(gsm) (dpf) (.degree. C.) (.degree. C.) (.degree. C.) (kg/h*m)
(ghm) (m/min) E-7-6 60 4-6 270 265 240 150 0.50 54 E-7-8 30 4-6 270
265 240 150 0.50 113 E-7-10 80 4-6 270 265 240 150 0.50 40.5
[0131] The elastic properties of the resulting spunbonded nonwoven
W of the invention were measured at 23.degree. C..+-.2, using an
Instron Testing apparatus set at 5 inch gauge length and a
stretching rate of 5 inches per minute. At the designated 50%
elongation value, the sample is held in the stretched state for 30
seconds and then allowed to fully relax at zero force. The percent
recovery can then be measured. At the end the recovery (R) was
measured in both CD and MD directions, according to the formula:
R=[(Ls-Lr)/(Ls-Lo)]%, wherein Ls represents the stretched length of
the specimen; Lr represents the recovered length of the specimen,
Lo represents the original length of the specimen.
Recovery 1st Pull--50%:
[0132] Web samples of a predetermined length Lo in the relaxed
state were cut in each web W. The web samples were elongated at 50%
elongation, held in the stretched state for 30 seconds and then
relaxed to zero tensile force.
Recovery 2nd Pull--50%:
[0133] The web samples were elongated a second time at 50%
elongation, held in the stretched state for 30 seconds and then
relaxed to zero tensile force. At the end the recovery (R) was
measured.
[0134] The resulting nonwoven of the invention has a root mean
square (RMS) average recovery of at least 85%, said RMS average
recovery being based on machine direction (R.sub.MD) and cross
direction (R.sub.CD) recovery values after 50% elongation and one
pull. RMS average recovery are calculated from the formula:
RMS average
recovery=[1/2(R.sub.CD.sup.2+R.sub.MD.sup.2)].sup.1/2
wherein R.sub.CD is the recovery measured in the cross direction
and R.sub.MD is the recovery measured in the machine direction.
Preferably, the fabrics have at least about a RMS recovery of 80%
after two successive 50% pulls.
[0135] The recovery results issued from these experiments are
summarized in Table 4 (elastic spunbonded nonwoven W of the
invention).
[0136] Table 5 relates to recovery results obtained with
comparative spunbonded webs W not covered by the invention. The
main characteristics of the TPU materials used in the comparative
examples of table 5 are also summarized in table 6.
TABLE-US-00004 TABLE 4 Elastic spunbonded nonwoven (W) of the
invention Total Spunbonded Web Root Mean Square Filament Spunbonded
(W) - Recovery Recovery Example bi- Filament weight 1st pull 2nd
pull N.sup.o Arrangement component composition gsm 50% 50% E-7-6
core 85 wt % VM2125(80 wt %) + 60 92.3 90.2 VM6100 (20 wt %) sheath
15 wt % VM 2125 (97 wt %) + slip agent (3 wt %) E-7-8 core 85 wt %
VM2125(80 wt %) + 30 89.5 87.3 VM6100 (20 wt %) sheath 15 wt % VM
2125 (97 wt %) + slip agent (3 wt %) E-7-10 core 85 wt % VM2125(80
wt %) + 80 94.1 92.6 VM6100 (20 wt %) sheath 15 wt % VM 2125 (97 wt
%) + slip agent (3 wt %)
TABLE-US-00005 TABLE 5 Elastic spunbonded nonwoven web -
Comparative examples Root Mean Square Web (W) - Recovery Recovery
Example Filament bi- Filament weight 1st pull 2nd pull N.sup.o
component composition gsm 50% 50% 19 core 70 wt % TPU 1185 AM 49
97.1 96.1 sheath 30 wt % TPU 1185 AM 20 core 70 wt % TPU 1180 A 50
97.3 96.7 sheath 30 wt % TPU 1180 A 21 core 70 wt % TPU 2180 A 49
96.0 94.3 sheath 30 wt % TPU 2180 A 22 core 70 wt % VM 2125 50 88.1
86.4 sheath 30 wt % VM 2125 23 core 70 wt % VM 2120 51 86.3 83.6
sheath 30 wt % VM 2120
TABLE-US-00006 TABLE 6 Elastollan grades Grade 2180 A Grade Grade
TPU 1180A 1185 AM Basis MAIN TPU TPU polyol: CHARACTERISTICS Basis
polyol: Basis polyol: Polyester- CHEMICAL FAMILY Polyether
Polyether ether METHOD DENSITY_g/cm3 1.14 1.11 1.13 DIN 53479
HARDNESS (SHORE A) (1) 80 88 77 DIN 53505 TENSILE STRENGTH_Mpa 45
45 45 DIN 53504 ELONGATION @ BREAK_% 650 600 450 DIN 53504 TENSILE
STRESS @ 100% 4.5 7 4.5 DIN 53504 ELONG._Mpa TENSILE STRESS @ 300%
8 12 10 DIN 53504 ELONG. Mpa (1) Measurements were performed on
compression molded specimens
[0137] The spunbonded layer (W) of the invention (samples E-7-6;
E-7-8; E-7-10) exhibits very high recovery values. These recovery
values are higher than recovery values that are obtained for
example with spunbonded web made of Sheath/Core bi-component
filaments (LLDPE/TPU) as the ones described in examples No 10 of
U.S. Pat. No. 6,225,243.
[0138] The comparative examples no 19, 20 and 21 were based on pure
TPU, same in core and in sheath arrangement. Even though elasticity
was good, the elastic TPU layer exhibits a high stickiness.
Furthermore, the elastic TPU layer was not thermo-bondable to other
polypropylene-based layers. In addition, because of the degradation
of the TPU during melting, TPU materials can not be processed in
standard polypropylene extruders.
[0139] Compared to examples 19 to 21 (TPU/TPU), the elastic
spunbonded layer of the invention (samples E-7-6; E-7-8; E-7-10) is
advantageously less sticky, and thus easier to be wound and
unwound. Furthermore, the chemical composition of the sheath is
similar to polyolefin materials that are mostly used in the field
of nonwoven. The polymeric materials used for practicing the
invention can thus be advantageously processed in standard
polypropylene extruders. Furthermore, thermal bondability of the
spunbonded layers (W) of the invention with other polyolefin-based
nonwoven layers (L1, L2) is improved.
[0140] The comparative examples No 22 and No 23 were based on pure
VM2125 or VM 2120. Compared to examples No 22 and No 23 (VM/VM),
the spunbonded layers (W) of the invention (E-7-6; E-7-8; E-7-10)
have advantageously a higher elasticity and elastic recovery.
[0141] Additionally, it has to be outlined that advantageously, and
in contrast with other solutions of the prior art as the ones
described, for example, in US patent application No 2005/0215964,
the spunbonded nonwoven layer W of the invention does not
necessarily require any activation step for obtaining its elastic
properties.
EXAMPLES
Perforated Hydroentangled Elastic Nonwoven Fabrics
[0142] Different perforated composite nonwoven fabric (C/W, C/W/S
and C/W/C) have been produced according to the manufacturing
processes of FIGS. 3 and 4 (examples E-150-FP, E-151-FP, E-152-FP,
E-153-FP, E-155-FP).
The compositions of these composite nonwoven fabrics are summarized
in Table 7.
TABLE-US-00007 TABLE 7 Perforated hydroentangled elastic nonwoven
of the invention Elastic total Bottom spunbonded B.W. Layer, Layer
W Top Layer, Examples structure (gsm) type gsm (see table 4) gsm
type gsm E-150- C/W 60 on line 30 E-7-8 30 NONE 0 FP carded PP
E-151- C/W/S 58 on line 20 E-7-8 30 Spunbonbded 8 FP carded PP PP
E-152- C/W/S 110 on line 20 E-7-10 80 Spunbonbded 10 FP carded PP
PP E-153- C/W/S 90 on line 20 E-7-6 60 Spunbonbded 10 FP carded PP
PP E-155- C/W/C 94 on line 20 E-7-6 60 Carded PP 14 FP carded PP C:
carded layer W: Elastic spunbonded layer of the invention S:
Spunbonded layer PP: Polypropylene
[0143] The outer carded layers (C) with low basis weight give
textile appearance and soft touch to the final nonwoven fabric.
This property is particularly useful in all applications wherein
the composite nonwoven has to come into contact with the skin, for
example in diapers, feminine/adult care or the like. The outer
polypropylene carded layers (C) also give advantageously a
dimensional stabilization to the nonwoven fabric in the machine
direction.
[0144] The main process parameters for the final hydroentanglement
and perforation steps by means of hydro-jets are summarized in the
following table 8.
TABLE-US-00008 TABLE 8 Production data - Hydroentanglement and
perforation HET Pressures (bar) beam beam beam beam beam beam beam
beam speed, Examples Pattern 201a 201b 202a 202b 203a 203b 204a
204b m/min E-150-FP perfo, 50 60 NA NA NA NA 150 150 16 screen, 4th
drum (i) E-151-FP perfo, 50 70 NA 70 NA NA 180 180 16 screen, 4th
drum (i) E-152-FP perfo, 50 70 NA 70 NA NA 200 200 16 screen, 4th
drum (i) E-153-FP perfo, 50 70 NA 70 NA NA 200 200 16 screen, 4th
drum (i) E-155-FP perfo, 30 40 NA 70 NA NA 180 180 16 screen, 4th
drum (i) NA: Not active jet beam (i) In all these examples, the
screen used for performing the perforation on the fourth drum 204
was the same, namely a screen manufactured by ALBANY under
reference BZ FW 9.5. The specifications of this screen provided by
the manufacturer were the following: Mesh count: 9.5 .times. 8.5/cm
Warp diameter: 0.63 .times. 0.33 mm BZ Shute diameter: 0.51 mm BZ
Caliper: 0.93 mm Nominal air permeability: 3.77 m/s-850 CFM.
EXAMPLE
Non-Perforated Hydroentangled Elastic Nonwoven Fabrics
[0145] A non perforated composite nonwoven fabric (C/W/M/C) of
basis weight 92 gsm has been also produced in a pilot plant
according to the manufacturing process of FIG. 5 (example referred
"E-105/HET").
[0146] In this example the two external layers were carded layers
(C) made of PP (polypropylene fibers). The basis weight of each
carded layer (at the output of the carded unit) was 14 gsm.
[0147] The elastic spunbonded layer W was made of bicomponent
sheath/core filaments having the round cross-section of FIG. 1D.
The core of the filaments was made (first polymeric component P) of
a blend VM2125 (70 wt %) and VM6100 (30 wt %). The melt flow rate
MFR1 of this blend (first polymeric component P) calculated by
means of formula (I) was thus around 29.87 g/10 min.
[0148] The outer sheath of the filaments was made of VM 2125
(second polymeric component P'). The weight of the core was 90% of
the total basis weight, and the weight of the sheath was 10% of the
total basis weight. The basis weight of the elastic spunbonded
layer (W) was 54 gsm.
[0149] In this example the material used for the elastic meltblown
layer (M) was VM 2320. The basis weight of the meltblown layer (M)
was 10 gsm.
VM 2320
[0150] VM 2320 is a specialty polyolefin elastomer suitable for
melt blown process commercially available from ExxonMobil Chemical
Co, Huston, Tex. under the trademark of VISTAMAXX.RTM.. This
specialty polyolefin elastomer is a semi-crystalline elastic
propylene-based olefin copolymer comprising at least 80 wt % of
propylene units and made in the presence of a metallocene catalyst
during the polymerization process. This copolymer has a MFR (Melt
Flow Rate) of 200 (measured at 230.degree. C. and 2.16 Kg-ASTM
D-1238), a broad melting temperature range and a highest melting
peak of 160.degree. C. This copolymer has a slower crystallization
rate than polypropylene homopolymers.
[0151] Other technical characteristics of materials VM 2320 are
given in table 1.
[0152] More generally, the thermoplastic materials used for making
the meltblown fibers will be knowingly selected by one skilled in
the art, in respect of the properties required for the elastic
nonwoven fabric. Specialty elastomeric polyolefin VM2320 is given
only by way of example. This specialty elastomeric polyolefin can
be replaced by any other known thermoplastic material, in
particular by any thermoplastic material that are used in the field
of hygienic product (diapers, training pants, . . . ) for making
meltblown layers.
[0153] Elastic properties of these elastic nonwoven fabrics of the
invention were measured at 23.degree. C..+-.2, using an Instron
Testing apparatus equipped with Grips type line contact or similar.
The grip defines the gauge for the specimen, therefore those
skilled in the art know that the grip must hold the specimen to
avoid slipping or damage. The above mentioned apparatus has to be
set at 1 inch gauge length and a stretching rate of 10 inches per
minute. The specimens will have the following dimensions: width 1
inch and length 3 inches. The forces were measured in Newton/inch.
Tensile tests, load at peak and elongation at peak and hysteresis
cycles have been performed on the above mentioned specimens
specifically in cross direction (CD). The Instron Testing apparatus
is equipped with a software which plots the load-elongation curve
and the data are stored in the buffer memory.
CD Load@peak: The specimen has been pulled at a stretching rate of
10 inches per minute until the maximum load has been reached. The
corresponding value of the CD Load@peak expressed in N/inch is
reported in table 9. CD Elongation@peak:
[0154] From the load-elongation curve of the same specimen used
during the previous test measurement we obtain the corresponding
value of the CD Elongation@peak expressed in %.
CD Load@150% Elongation:
[0155] From the load-elongation curve of the same specimen used
during the first test measurement we obtain the corresponding value
of the CD Load@150% Elongation, expressed in N/inch. CD Permanent
Set after 2 Cycles@150% Elongation: A new specimen has been pulled
(1.sup.st cycle) at a stretching rate of 10 inches per minute till
the designated 150% elongation value: the sample is then held in
the stretched state for 30 seconds and allowed to fully relax at
zero force for 60 seconds. A second pull is applied (2.sup.nd
cycle) at a stretching rate of 10 inches per minute till the
designated 150% elongation value, held in the stretched state for
30 seconds and then allowed to fully relax at zero force. The
percent permanent set can then be measured in CD direction and
expressed in %, according to the formula:
CD Permanent Set after 2 Cycles 150%
Elongation=[(Lr-Lo)/(Ls-Lo)]%,
wherein Ls represents the stretched length of the specimen, Lr
represents the recovered length of the specimen after the 2.sup.nd
cycle, Lo represents the original length of the specimen.
[0156] The results issued from these tests are summarized in Table
9.
TABLE-US-00009 TABLE 9 CD PERMANENT SET CD CD CD AFTER 2 ELONGATION
LOAD@150% LOAD @ CYCLES@150% @ PEAK Elongation PEAK ELASTIC
Examples Elongation (%) (%) (N/inch) (N/inch) layer % E-150-FP 48
207 4.9 11.3 50 E-151-FP 44 238 10.2 13.5 52 E-152-FP 36 239 13.2
16.5 73 E-153-FP 39 210 15.6 19.2 67 E-155-FP 34 265 8 15.2 64
E-105/HET 28 245 8 10.7 70
The data in the last column of Table 9 ("ELASTIC layer %) represent
the weight percentage of the elastic material [i.e. elastic
spunbonded layer (W) and elastic meltblown layer for example
E-105/HET and elastic spunbonded layer (W) for examples E-150-FP,
E-151-FP, E-152-FP, E-153-FP, E-155-FP] on the total weight of the
elastic nonwoven fabric.
EXAMPLE
Elastic Spunbonded Nonwoven (W/M)
[0157] Samples of multilayer nonwoven (C/W/M/C) have been produced
on a pilot plant, without bonding the layers together. Then the two
outer carded layers were removed in order to keep only the elastic
spunbonded (W) and meltblown (M) layers.
[0158] The elastic spunbonded layer W was made of bicomponent
sheath/core filaments having the round cross-section of FIG. 1D.
The core of the filaments was made (first polymeric component P) of
a blend VM2125 (70 wt %) and VM6100 (30 wt %). The outer sheath of
the filaments was made of VM 2125 (second polymeric component P').
The weight of the core was 90% of the total basis weight, and the
weight of the sheath was 10% of the total basis weight. The basis
weight of the elastic spunbonded layer (W) was 54 gsm.
[0159] In this example the material used for the elastic meltblown
layer (M) was VM 2320. The basis weight of the meltblown layer (M)
was 10 gsm. The elastic properties of the elastic spunbonded
nonwoven (W/M) were measured and are given in table 10.
TABLE-US-00010 TABLE 10 CD PERMANENT SET AFTER 2 CD CYCLES CD LOAD
CD @ 150% ELONGATION @ 150% LOAD @ Elongation @ PEAK Elongation
PEAK Examples (%) (%) (N/inch) (N/inch) E-105 21 398 1.4 3.5
[0160] The elastic nonwoven fabric of the invention is not limited
to the particular multilayered structures of the examples
previously described. The invention actually encompasses any
elastic nonwoven fabric wherein at least one of the layer is an
elastic spunbonded nonwoven W as the one defined in the claims.
* * * * *