Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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ELASTIC SPUNBONDED NONWOVEN AND ELASTIC NONWOVEN
FABRIC COMPRISING THE SAME
FIELD OF THE INVENTION
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
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.
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
CONFIRMATION COPY
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importance. Such nonwoven fabrics, called "spunbonded" nonwovens can
advantageously give the required combinations of physical properties, like
softness, strength and durability.
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).
Significant problems have been however encountered with this
solution.
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.
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.
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.
In order to overcome these problems, it has been proposed in US
patent 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
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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.
This solution disclosed in US patent 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.
In PCT application W02005/090659, 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:
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,
b. and a second component B which comprises an elastic propylene- based
olefin polymer.
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
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
The above-mentioned objective is achieved by the elastic spunbonded
nonwoven which 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
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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.
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".
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.
For measuring the melt flow rates (MFR1, MFR2) of the first and
second polymeric components, standard method ASTM D-1238 can be
used.
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
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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.
As used herein, the term "polypropylene", "propylene polymer," or
5 "PP" refers to homopolymers, copolymers, terpolymers, and
interpolymers,
comprising from 50 to 100 weight % of propylene.
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.
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.
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 C, and 2.16 kg.
A semi-amorphous copolymer may be produced in a continuous
solution process using a metallocene catalyst.
Preferably, copolymers having a narrow molecular weight
distribution are used. To produce a copolymer having a narrow molecular
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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.
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.
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.
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=l-3; n=0-3; q=0-3.
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.
Preferred elastic propylene-based olefin copolymers suitable for
the invention include thermoplastic elastic propylene-ethylene copolymers
formed by using metallocene polymerization catalysis. Such polymers
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include those commercially available from DownMobil Chemical Co,
Huston, TX under the trademark of VISTAMNOM, e.g. Vistama)oc 2120 or
Vistamm( 2125 for second polymeric component in the sheath and a
blend of Vistamaxx 2125 and Vistama)a 6100 (or Vistama)oc 6102) for
first polymeric component in the core.
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.
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.
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).
Optionally, the elastic spunbonded nonwoven of the invention is
further characterized by the following optional features that can be
combined or taken alone:
- the elastic propylene-based olefin copolymer for the first polymeric
component and for the second polymeric component is an ethylene
propylene copolymer;
- 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/10min, most preferably greater than 2
g/10min and less than 100 g/10min, as measured by ASTM D-1238
at 230 C and 2.16 kg ;
- 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;
- the elastic propylene-based olefin copolymer for the first polymeric
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component and for the second polymeric component comprises at
least 80wt% of propylene units;
- the elastic propylene-based olefin copolymer for the first polymeric
component and for the second polymeric component is a
metallocene-catalysed polymer;
- the spunbonded nowoven has 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(RcD2 + RMD 2)] Y2,
wherein RmD and RDD 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 ;
- the spunbonded nonwoven has a RMS recovery, after two
successive 50% pulls, of at least 80%;
- the amount of the first polymeric component is at least 50wt%
of the total weight of the filament, and the amount of the
second polymeric component is less than 50wt% of the total
weight of the filament;
- the amount of the second polymeric component is less than
40wt% of the total weight of the filament, and preferably equal
or less than 30wt% of the total weight the filament.
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.
More particularly, and optionally, the composite nonwoven is
characterized by the following optional features that can be taken alone or
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combined together:
- the additional nonwoven layer is selected from the group: carded
nonwoven ; spunbonded nonwoven, meltblown nonwoven;
- the additional nonwoven layer can be constituted by a polyolefin-
based nonwoven;
- 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).
- 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;
- in one variant, the layers are perforated.
- the elastic nonwoven fabric has a CD permanent set after two
cycles at 150% elongation less 50%, and preferably less than 40%.
2 0 - the elastic nonwoven fabric has a CD elongation@Peak of at least
150 %, and preferably of at least 200 %.
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.
Preferably, at least one polyolefin¨based nonwoven layer is a
polypropylene¨based nonwoven layer.
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.
A further object of the invention is a hydroentangled elastic
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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 (VV) comprises a
plurality of multi-component filaments, each multi-component filament
5 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
10 polymeric component.
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
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:
- Figures 1A to 1F are different examples of spun filaments cross-
sections that are suitable for practising the invention,
- Figure 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 ;
- Figure 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,
- Figure 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,
- Figure 5 is a schematic drawing of a fourth example of production line
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that is used for making a hydroentangled elastic nonwoven fabric of
the invention.
DETAILED DESCRIPTION OF THE INVENTION
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.
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.
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 BoconMobil Chemical Co, Huston, TX under the trademark of
VI STAMA)0(e.
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 DoconMobil Chemical Co, Huston, TX under the trademark of
VISTAMPOOM and having two different melt flow rate (MFR1a and MFR1b).
The first and second polymeric components can also include others
materials, like pigments or colorants, or opacizers (like Ti02) 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
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component.
Various shapes in cross section for the filaments F can be
envisaged (round shape, oval shape, bilobal shape, trilobal shape, etc...).
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
figures 1A, 1B, 1C, 1D, 1E, 1F.
Preferably, as depicted on the particular examples of figure 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' ( figures 1B, 1C, 1D, 1E).
Bicomponent filament of the sheath/core type, like the ones
illustrated in figures 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.
In other variant of the invention, the filaments can however comprise
more than two polymeric components.
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 US patent 3,338,992 to Kenney,
US patent 3,692,613 to Dorschner, US patent 3,802, 817 to Matsuki, US
patent 4,405,297 to Appel, US patent 4,812,112 to Balk and US patent
5,665,300 to Brignola et al.
Figure 2- Thermo-bonded elastic nonwoven fabric (L1/VV/L2)
One example of a suitable process line for producing an elastic
nonwoven fabric of the invention is illustrated in Figure 2. In this example,
the process line comprises:
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- a spunbonding unit (SU) for producing an elastic spunbonded
nonwoven W made of bi-components filaments, preferably of the
sheath/core type;
- 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;
- 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)
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.
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 C to a maximum
260 C, depending on screws speed and design.
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.
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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 C are
considered suitable for the scope, but lower temperatures, in the range of
C to 15 C, are recommended when more elastic and soft materials are
applied in the sheath arrangement. To this purpose two quench boxes 8 are
10 shown in
the Figure 1. Each quench box 8 is connected to a blower which
delivers the right low pressure air flow necessary for the filaments cooling.
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.
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
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.
The second delivering mean 15 is used for laying directly onto the
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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.
In another variant, the elastic spunbonded layer W of the invention
5 can be manufactured off line and wound up in the form of a roll, and
the final
elastic nonwoven fabric (L1/VV/L2) can be manufactured from a roll of said
elastic nonwoven W.
Referring to figure 2, the three layers (L1, W and L2) can be thermo-
bonded together by means of calander rolls 13, and the elastic nonwoven
10 fabric (L1/VV/12) 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.
15 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.
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.
Figure 3- Hydroentangled elastic nonwoven fabric (C/VV/S)
One example of a suitable process line for producing a
hydroentangled elastic nonwoven fabric of the invention is illustrated in
Figure 3.
In this example, the process line comprises a carding unit 18, a first
spunbonding unit SU, second spunbonding unit 19, a hydraulic needling unit
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20, a dewatering unit 21, a drying unit 22, and a winding unit 23.
The carding unit 18, which is mounted upstream the spunbonding
unit SU, is used for producing in line a bottom carded nonwoven layer C.
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 figure 3) and/or by means of calander rolls like the calander
rolls 13 previously described in reference to figure 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 figures 4 and 5.
The spunbonding unit SU is similar to the one of figure 2 and is used
for producing in line the elastic spunbonded nonwoven layer W of the fabric.
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.
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/VV/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.
In the particular example of figure 3, the water needling process is
performed on both sides of the composite nonwoven (C/VV/S).
More particularly, in the example of figure 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
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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.
At the exit of hydraulic needling unit 20, a hydroentangled elastic
composite CNV/S is obtained.
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.
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).
The hydroentanglement unit 20 and the dewatering unit 21 can be
integrated in the same industrial equipment.
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.
Then the dried fabric (C/W/S) is wound in the form of a roll, by
means of the winding unit 23.
Figure 4- Hvdroentangled elastic nonwoven fabric (CNV/C)
Another example of a suitable process line for producing a
hydroentangled elastic nonwoven fabric of the invention is illustrated in
Figure 4.
The process line of figure 4 differs from the process line of figure 3
by the use of a second carding unit 18' (similar to first carding unit 18),
that is
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substituted to the spunbonding unit 19.
Figure 5- Hydroentangled elastic nonwoven fabric (C/VV/M/C)
Another example of a suitable process line for producing a
hydroentangled elastic nonwoven fabric of the invention is illustrated in
Figure 5.
The process line of figure 5 differs from the process line of figure 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'.
The term "meltblown layer ", as used therein, means any layer
essentially made of "meltblown fibers".
"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.
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
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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
gsm. This meftblown layer gives a more uniform white colour to the
elastic nonwoven fabric, and thus improves the aesthetic thereof.
5 Examples-elastic spunbonded nonwoven (W)
Different samples of fabric (L1/VV/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/VV/L2) wherein the layers L1, W and L2 were not
thermo-bonded. Then the layers L1 and L2 were removed in order to keep
10 only the elastic spunbonded layer W.
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 figure 1D,.
The polymeric materials that have been used for producing these
spunbonded nonwovens (W) were the following.
First polymeric component (P)
A dry blend of VM2125 (polymer Pa) and VM6100 (polymer Pb) was
used as first polymeric component (P).
VM 2125
VM 2125 is a specialty polyolefin elastomer commercially available from
ExxonMobil Chemical Co, Huston, TX under the trademark of
VISTAMAXX . This specialty polyolefin elastomer is a semi-crystalline
elastic propylene-based olefin copolymer comprising at least 85wt% 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/10min (measured at 230 C and 2.16Kg - ASTM D-1238), a broad
melting temperature range and a highest melting peak of 160 C. This
copolymer has a slower crystallization rate than polypropylene
homopolymers.
VM6100 (VMX6102)
VM 6100 is a specialty polyolefin elastomer commercially available from
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ExxonMobil Chemical Co, Huston, TX under the trademark of
VISTAMAXX . This specialty polyolefin elastomer is a semi-crystalline
elastic propylene-based olefin copolymer comprising at least 80wt% of
propylene units and made in the presence of a metallocene catalyst during
5 the polymerization process. This copolymer has a low melt flow rate
(MFR1b) of 3 g/10min (measured at 230 C and 2.16Kg - ASTM D-1238), a
broad melting temperature range and a highest melting peak of 160 C.
This copolymer has a slower crystallization rate than polypropylene
homopolymers. VMX 6100 can be replaced by the equivalent grade VM
10 6102, having same chemical properties as VM 6100 and giving the same
elastic properties to the nonwovens produced.
The melt low rate (MFR1) of the first polymeric component (P) was
calculated by means of the following equation:
(1) ln(MFR1) = Wa xln(MFR1a) + Wb x ln(MFR1b)
Wherein:
- MFR1a is the melt flow rate of polymer Pa ( MFR1a = 80 g/10min for
VM2125 )
- MFR1b is the melt flow rate of polymer Pb ( MFR1b = 3 g/10min for
VM6100 or VM6102)
- Wa and Wb are the weight ratios of polymers Pa and Pb in the blend
(VVa+VVb=1).
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/10min.
Second polymeric component(P')
The second polymeric component was made of aforesaid elastic
propylene-based olefin copolymer VM2115
Other technical characteristics of materials VM6100 (VM6102) and
VM 2125 are given in table 1.
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TABLE 1 : VM 6100-VM 6102-VM 2125 -VM 2320
MAIN VM 6100 VM6102 VM 2125 VM 2320 VM 2120 a
CHARACTERISTICS 0
I
1-==
CHEMICAL FAMILY POLYOLEFIN POLYOLEFIN POLYOLEFIN POLYOLEFIN POLYOLEFIN
Ili
ASTM
3 3 80 200 80
MFR_g/10min (1) D-1238
DENSITY_g/cm3 0.855 0.863 0.865 0.866 0.868 /
Ethylene Content ASTM
/ 16 13 14 13
(wt%) 0-3900
HARDNESS ASTM
55 59 63 62 64
(SHORE A) D-2240
FLEXURAL ASTM
/ 8.5 29.8 18.6 21.1
MODULUS Mpa D-790
TENSILE @ ASTM
/ >8.3 8.1 6.7 8.6
BREAK_Mpa 0-412
ULTIMATE ASTM
/ >2000 860 853 1007
ELONGATION D-412
TENSILE STRESS @ASTM
/ 1.6 3.5 2.8 3.2
100% ELONG._Mpa D-412
TENSILE STRESS @ASTM
/ 2.0 4.6 3.6 4
300% ELONG. Mpa D-412
The compositions of the filaments of the different samples of
spunbonded nonwoven W are summarized in table 2.
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TABLE 2: Filaments composition
(P') .. (Additive)
Core Core Weight Additive
Core wt% Sheath wt% Weight %
Sample ¨
(F'¨) material Wa Material Wb Sheath
% in in the in the
(P) Maten'al
/F. /Pothe Sheath
(13') 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.
The main spunbonding process parameters are summarized in the
following table 3 for each sample of spunbonded nonwoven W..
TABLE 3: Spunbonding production data ¨ web forming
co (11) (111) (IV) on (vi) (vio (vim
0) r of r of r of
0- Basis extruder extruder Spinning
Through- Through- Line
E
co weight Filament (3) (4) Beam put put speed
co of W count
(gsm) (dpf) ( C) ( C) ( 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
The elastic properties of the resulting spunbonded nonwoven W of
the invention were measured at 23 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
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specimen; Lr represents the recovered length of the specimen, Lo
represents the original length of the specimen.
Recovery 1st pull - 50%:
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%:
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.
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 (RmD) and cross direction (RD()) recovery
values after 50% elongation and one pull. RMS average recovery are
calculated from the formula:
RMS average recovery =[1/2(Rc02 + RmD 2)] 1/2
wherein RCD is the recovery measured in the cross direction and RmD 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.
The recovery results issued from these experiments are
summarized in Table 4 (elastic spunbonded nonwoven W of the invention).
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.
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TABLE 4 : Elastic spunbonded nonwoven (W) of the invention
Root Mean Square
Example Arrangement Spunbonded Spunbonded Total Recovery
Recovery
N Filament Filament Web
bi- composition ON) -
component weight
gsm 1st pull 2nd pull
50% 50%
VM2125(80wt%)
core 85wt%
E-7-6 +VM6100 (20wt%)
60 92.3 90.2
VM 2125 (97wt%) +
sheath 15wt%
slip agent(3wt%)
VM2125(80wt%)
core 85wt%
+VM6100 (20wt%)
E-7-8 30 89.5 87.3
VM 2125 (97wt%) +
sheath 15wt%
slip agent (3wt%)
VM2125(80wt%)
core 85wt%
+VM6100 (20wt%)
E-7-10 80 94.1 92.6
VM 2125 (97wt%) +
sheath 15wt%
slip agent (3wt%)
TABLE 5: Elastic spunbonded nonwoven web - Comparative examples
Root Mean
Square
Web
Recovery Recovery
Example Filament bi- Filament (W) -
1st pull 2nd pull
N component composition weight
50% 50%
gsm
core 70wt% TPU 1185 AM
19 49 97.1 96.1
sheath 30wt% TPU 1185 AM
core 70wt% TPU 1180 A
20 50 97.3 96.7
sheath 30wrio TPU 1180 A
core 70wt% TPU 2180 A
21 49 96.0 94.3
sheath 30wt% TPU 2180 A
core 70wt% VM 2125
22 50 88.1 86.4
sheath 30wt% VM 2125
core 70wt% VM 2120
23 51 86.3 83.6
sheath 30wt% VM 2120
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TABLE 6: Elastollan grades
MAIN Grade Grade Grade
CHARACTERISTICS 1180A 1185AM 2180A
' TPU TPU TPU
Basis METHOD
Basis polyol: Basis polyol: polyol:
CHEMICAL FAMILY Polyether Polyether Polyester-
ether
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%
ELONG._Mpa 4.5 7 4.5 DIN 53504
TENSILE STRESS @ 300%
ELONG. Mpa 8 12 10 DIN 53504
(1) Measurements were performed on compression molded specimens
The spunbonded layer (VV) of the invention (samples E-7-6; E-7-8;
5 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 /MU) as the ones
described in examples No 10 of US patent 6,225,243.
The comparative examples n 19, 20 and 21 were based on pure
10 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.
15 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
20 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.
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The comparative examples N 22 and N 23 were based on pure
VM2125 or VM 2120. Compared to examples N 22 and N 23 (VMNM), the
spunbonded layers (W) of the invention (E-7-6; E-7-8; E-7-10) have
advantageously a higher elasticity and elastic recovery.
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
Different perforated composite nonwoven fabric (C/VV, CNV/S and
C/W/C) have been produced according to the manufacturing processes of
figures 3 and 4 (examples E-150-FP, E-151-FP, E-152-FP, E-153-FP, E-
1 55-FP).
The compositions of these composite nonwoven fabrics are summarized in
Table 7.
TABLE 7: Perforated hydroentangled elastic nonwoven of the invention
Elastic
total Bottom
spunbonded Top Layer,
Examples structure B.W. Layer, gsmgsm
Layer W gsm type
(gsm) type
(see table 4)
E 150 on line
FP -
-
C/W 60 carded 30 E-7-8 30 NONE 0
PP
on line -
E-151- Spunbonbded
C/W/S 58 carded 20 E-7-8 30 8
FP PP
PP
on line
E-152- CAWSSpunbonbded
110 carded 20 E-7-10 80 10
FP PP
PP
on line
E-153- Spunbonbded
C/W/S 90 carded 20 E-7-6 60 10
FP PP
PP
E-155-
on line
FP
C/W/C 94 carded 20 E-7-6 60 Carded PP
14
PP
C: carded layer W: Elastic spunbonded layer of the invention S: Spunbonded
layer
PP : Polypropylene
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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.
The main process parameters for the final hydroentanglement and
perforation steps by means of hydro-jets are summarized in the following
table 8.
TABLE 8: Production data ¨ Hydroentanglement and perforation
HET Pressures (bar)
Examples Paftembeam beam beam beam beam beam beam beam speed,
201a 201b 202a 202b 203a 203b 204a 204b m/min
perfo,
E-150-FP screen , 4th 50 60 NA NA NA NA 150 150 16
drum (i)
perfo,
E-151-FP screen , 4th 50 70 NA 70 NA NA 180 180 16
drum (i)
perfo,
E-152-FP screen , 4th 50 70 NA 70 NA NA 200 200 16
drum (i)
perfo,
E-153-FP screen , 4th 50 70 NA 70 NA NA 200 200 16
drum (i)
perfo,
E-155-FP screen , 4th 30 40 NA 70 NA NA 180 180 16
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
FVV 9,5.
The specifications of this screen provided by the manufacturer were the
following:
Mesh count: 9.5 x 8.5 /cm
Warp diameter: 0.63x0.33 mm BZ
Shute diameter: 0.51 mm BZ
Caliper: 0.93mm
2 0 Nominal air permeability: 3.77 m/s - 850 CFM.
Example ¨ Non-perforated hydroentangled elastic nonwoven fabrics
A non perforated composite nonwoven fabric (CNV/M/C) of basis
weight 92gsm has been also produced in a pilot plant according to the
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manufacturing process of figure 5 (example referred "E-105/HET").
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 14gsm.
The elastic spunbonded layer W was made of bicomponent
sheath/core filaments having the round cross-section of figure 1D. The core
of the filaments was made (first polymeric component P) of a blend VM2125
(70wt% ) and VM6100 (30wt%). The melt flow rate MFR1 of this blend (first
polymeric component P) calculated by means of formula (1) was thus
around 29.87g/10min.
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 54gsm.
In this example the material used for the elastic meltblown layer (M)
was VM 2320. The basis weight of the meltblown layer (M) was lOgsm.
VM 2320
VM 2320 is a specialty polyolefin elastomer suitable for melt blown
process commercially available from DoconMobil Chemical Co, Huston,
TX under the trademark of VISTAMAXX . This specialty polyolefin
elastomer is a semi-crystalline elastic propylene-based olefin copolymer
comprising at least 80wt% 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 C and 2.16Kg -
ASTM D-1238), a broad melting temperature range and a highest melting
peak of 160 C. This copolymer has a slower crystallization rate than
polypropylene homopolymers.
Other technical characteristics of materials VM 2320 are given in
table 1.
More generally, the thermoplastic materials used for making the
meltblown fibers will be knowingly selected by one skilled in the art, in
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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.
Elastic properties of these elastic nonwoven fabrics of the
invention were measured at 23 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 lnstron 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 Elonqation@peak :
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 Load150%Elongation :
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 NAnch.
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CD Permanent Set after 2 Cycles(150% Elongation:
A new specimen has been pulled (1st 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
5 for 60 seconds. A second pull is applied (2nd 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:
10 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 2nd cycle, Lo represents the
original length of the specimen.
The results issued from these tests are summarized in Table 9.
15 TABLE 9
CD PERMANENT SET CD CD CD
Exam ples AFTER 2 ELONGAllON LOAD@150% LOAD @ ELASTIC
CYCLES@150%Elongation @ PEAK Elongation PEAK layer %
(%) (%) (Winch) (Niinch)
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
20 layer (VV) 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.
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Example-elastic spunbonded nonwoven (W/M)
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.
The elastic spunbonded layer W was made of bicomponent
sheath/core filaments having the round cross-section of figure 1D. The core
of the filaments was made (first polymeric component P) of a blend VM2125
(70wt% ) and VM6100 (30wt%). 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 (VV) was
54gsm.
In this example the material used for the elastic meltblown layer (M)
was VM 2320. The basis weight of the meltblown layer (M) was lOgsm.
The elastic properties of the elastic spunbonded nonwoven (W/M) were
measured and are given in table 10.
TABLE 10:
CD PERMANENT SET CD CD CD
Exam ples AFTER 2 ELONGATION LOAD@150% LOAD @
CYCLES@150%Elongation @ PEAK Elongation PEAK
(%) (%) (N/inch) (Winch)
E-105 21 398 1.4 3.5
2 0 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.
