Note: Descriptions are shown in the official language in which they were submitted.
GATHERED NONWOVEN ELASTIC WEB
FIELD OF THE INVENTION
The field of the present invention encompasses a
5 composite nonwoven elastic web which includes a nonwoven
elastic web which is joined to a nonwoven gathered web and
processes for forming such composite nonwoven elastic webs.
The field of the present invention also encompasses
processes for forming a gathered nonwoven web exhibiting
10 elastic properties by separating the gathered web from the
nonwoven elastic web after gathering has been effected by
retraction of the elastic web.
BACKGROUND OF THE INVENTION
There has been a desire in the area of diaper
fabrication to provide an outer cover for a diaper which is
(1) totally elastic over its entire surface --to provide a
tight yet comfortable fit; ~2) water repellent --to retain
fluid materials within the confines of the diaper; (3)
20 breathable --to allow an exchange of vapors through the
diaper material; (4) soft --for improved comfort and (5)
inexpensive to manufacture --so that that diaper may be
economically marketed to the consumer.
Unfortunately, the known composite nonwoven materials
25 which have, to date, been marketed have been lacking in one
or more of these characteristics. Furthermore, these
composite elastic nonwoven materials have not been formed
by utilization of the novel and economical processes of the
present invention.
For example, U.S. patent 2,957,512 to Wade discloses a
method for producing an elastic composite sheet material in
which a creped or corrugated flexible sheet material is
bonded to, for example, an elastic meltblown material. At
column 5, lines 39-48, it is stated that a fibrous web of
elastomeric material may be stretched and bonded to the
3~-
r~
corrugated web at spaced points or areas and, upon allowing
the fibrous elastomeric web to relax, the composite will
assume the structure illustrated in Figure 7.
Yet another method for forming a composite elastic
fabric is disclosed in U.S. patent 3,316,136 to Pufahl.
The preferred method of fabrication of this fabric involves
the utilization of an adhesive which is first applied in a
predetermined pattern to an elastic backing material and
the elastic backing material is then stretched to an
10 elongated state. While the elastic material is in the
stretched, elongated state an overlying fabric is placed in
contact therewith and held in pressurized engagement with
the elastic material for a time period sufficient to insure
adhesion of the two layers. Thereafter, upon drying of the
15 applied adhesive, the tension on the elastic backing
material is released causing the overlying fabric to gather
in the areas outlined by the adhesive.
U.S. Patent 3,485,706 to Evans at example 56 discloses
the fabrication of an elongatable nonwoven, multilevel
20 patterned structure having elasticity in one direction from
an initially layered material. The structure is composed
of two webs of polyester staple fibers which have a web of
spandex yarn located therebetween. The webs are joined to
each other by application of hydraulic jets of water which
entangle the fibers of one web with the fibers of an
adjacent web. During the entanglement step the spandex
yarn is stretched 200 percent.
U.S. patent 3,673,026 to Brown discloses a method for
manufacturing a laminated fabric and specifically discloses
a method for manufacturing a nonwoven laminated fabric of
controlled bulk. In this method separate webs of nonwoven
material, e.g. creped tissue or bonded synthetic fiber, are
elastically stretched to different degrees of elongation
and laminated by bonding to one another while in their
differentially stretched states. The bonded webs are
1 3 ~
thereafter relaxed so as to produce different degrees O r
contraction in each web with resultant separation of the
webs in the unbonded regions and controlled bulk in the
laminate. It is stated that the differential stretching
includes the situation where only one web is actually
stretched and the other web is maintained slack or nearly
so .
U.S. patent 3,687,797 to Wideman discloses a method
for producing a resilent cellulosic wadding product
obtained by laminating a lower cellulosic wadding web to a
prestretched polyurethane foam web. The process involves
applying adhesive in a desired pattern to either of the
webs with the wadding web then being laminated to the
prestretched polyurethane foam web. During lamination of
the wadding web to the polyurethane foam web the foam web
is maintained in a stretched condition. After lamination
of the two webs, the tension on the prestretched
polyurethane foam web is released to cause a contraction of
the foam web. The adhesive retains the wadding product and
foam together while permitting bulking in areas between the
adhesive zones. The stresses still remaining in the
product after contraction may be further relieved by
wetting.
U.S. patent 3,842,832 to Wideman is directed to a
disposable stretch product such as a bandage and a method
for production of the product. The product is manufactured
by passing a longitudinally oriented nonwoven material over
a roller so as to apply an adhesive to one surface of the
nonwoven material. At the same time a polyurethane web is
heated and longitudinally stretched and adhered to the
nonwoven material. Thereafter, a second nonwoven material
is adhexed to the other surface of the polyurethane web to
form a laminate consisting of a stretched inner
polyurethane core and outer unstretched nonwoven fabric
layers adhered to the core by the adhesive. Next, the
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laminate is passed through a moistening device which
results in a relaxing of the engagement between the
nonwoven fabric outer layer~ and the adhesive connecting
the outer layers to the stretched polyurethane core layer.
5 This allows the stretched polyurethane layer to return to
substantially its original length which results in the
outer nonwoven layers being buckled or undulated to form
wrinkles.
U.S. patent 4,104,170 to Nedza discloses a liquid
filter having an improved extended polypropylene element.
Fabrication of the polypropylene element is accomplished by
forming a spunbonded underlayer of a continuous
polypropylene fiber which adheres to itself as it is laid
down in a random pattern. Thereafter, an overlayer of
short polypropylene fibers is deposited onto the underlayer
by, for example, meltblowing the overlayer onto an extended
sheet of the underlayer.
A method for producing an elastic cloth structure
which includes fibers of a synthetic, organic, relatively
elastomeric polymer and fibers of a synthetic, organic,
elongatable, but relatively nonelastic polymer is disclosed
in U.S. patent 4,209,563 to Sisson. The method includes
the steps of forwarding the relatively elastic fibers and
elongatable but relatively non-elastic fibers for a well
25 dispersed random lay-down on a porous forming surface of an
unbonded web having random fiber crossings. Thereafter, at
least some of the fiber crossings are bonded to form a
coherent bonded cloth web which is stretched to elongate
some of the fibers in at least one direction and then
released so that retraction of the web by the relatively
elastomeric fibers provides for looping and bunching of the
elongatable relatively nonelastic fibers. Forwarding of
the fibers to the porous forming surface is positively
controlled, and this positive control is contrasted at
column 7, lines 19-33 of the patent to the use of air
- 5 -
streams to convey the fibers. It is also stated at column
9, line 4~ et. seq. of the patent that bonding of the
Eilaments to form the coherent cloth may utilize embossing
patterns or smooth heated roll nips.
U. .S. Patent 4,296,]63 to Emi et al. discloses a
fibrous composite having a coalcesed assembly of (A) a
sheet-like mesh structure composed of fibers of a synthetic
elastomeric polymer, the individual Eibers o which are
interconnected at random in irregular relationship to orm
a number oE meshes o different sizes and shape with the
mesh structure having a recovery ratio after 10% stretch of
at least 70% in two arbitrarily selected, mutua1ly perpen-
dicular directions on the plane of the mesh structure, and
(B) a matt-, web- or sheet-like fiber structure composed of
short or long fibers, with the fiber structure having a
recovery ratio after 10% stretch of less than 50% in at
least one arbitrarily selected direction. It is stated
that the elastic composite is suitable as various apparel
based materials and industrial materials such as filter
cloths, absorbents, and heat insulating materials. Methods
for forming the composite are described at column 6, line
64 et seq. and these methods include spun bonding, see
column 9, lines 15-41.
U. S. patent ~,323,53~ to DesMarais discloses an
extrusion process for a thermoplastic resin composition for
fabric fibers with exceptional strength and good elas-
ticity. ~t column 8 under the subtitle "Fiber-Forming"
meltblowing of a compounded resin comprising 79.13% *RR~TON
g-1652, 19.78% stearic acid, 0.98% titanium dioxide and
0.1% *Irqanox 1010 antioxidant is disclosed. It is stated
that individual fibers were extruded from the meltblowing
die.
U. S. patent 4,355,~25 to Jones discloses a panty with
a built-in elastic system to minimize gathering and to
provide a comfortable, conforming fit and a method for
* - trade-marks
_ 6 -
assembling the panty. It is stated that a material made of
meltblown KRATON rubber is well suited for the panty fabric
material. It is also stated that a process for making
meltblown XRATON fabrics is disclosed and shown
5 schematically in figure 8 of the patent. The process which
appears to utilize KRATON G-1652 is discussed starting at
column 4, line 67 of the patent.
U.S. patent 4,379,192 to Wahlquist discloses a method
for forming an impervious absorbent barrier fabric
10 embodying film and fibrous webs where one or more
meltblowing dies meltblow discontinuous fibers of small
diameter as a mat directly on a prebonded web of continuous
filaments. At column 3, lines 35-40 of the patent it is
stated that by forming the microfiber mat directly onto the
15 prebonded continuous filament web, primary bonds are
created between the microfibers and the continuous
filaments which attach the microfiber mat to the continuous
filament web.
U.S. patent 4,426,420 to Likhyani discIoses
20 hydraulically entangled spunlaced fabrics composed of at
least two types of staple fibers and processes for their
formation which include heat treating elastomeric fibers,
which behave as ordinary staple fibers until they are heat
treated, to impart improved stretch and resilience
25 properties to the fabric. The method includes the steps of
drawing a potentially elastomeric fiber and allowing it to
relax between the drawing and wind-up steps.
U.S. patent 4,446,189 to Romanek discloses a nonwoven
textile fabric laminate which includes at least one layer
of nonwoven textile fabric which is secured by needle
punching to an elastic layer so that the nonwoven layer of
textile fabric will be permanently stretched when the
elastic layer is drafted within its elastic limits. When
the elastic layer is allowed to relax and return to
substantially its condition prior to being drafted the
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-- 7 --
nonwoven fabric layer is stated to exhibit increased
bulk as a result of its concurrent relaxation. It is
also stated that the nonwoven textile fabric laminate
may be utilized to form wearing apparel which has
enhanced freedom of movement.
The abstract of Japanese patent document number
47-43150, July 17, 1969, of Toyo Spinning Co. Ltd.,
discloses a method for producing a nonwoven fabric
having high tenacity with the method being carried out
lo by (a) monoaxially stretching a sheet or film made of a
mixture of imcompatible polymers, (b) laminating this
sheet or material with a layer of foamed polymer, (c)
stretching the laminate at right angles to the direction
of orientation of the substrate and then (d) stretching
in the direction orientation of the substrate.
Preferred polymers are stated to include polyamides,
linear polyesters, and polyolefins. Preferably, the
upper layer is a polypropylene foam.
A Shell Chemical Company brochure entitled "KRATON
Thermoplastic Rubber" generally discusses thermoplastic
KRATON materials. This brochure is code designated by
"SC: 198-83 printed in U.S.A. 7/83 SM".
While the above-discussed documents may disclose
products and processes which exhibit some of the
characteristics or method steps of the present invention
none of them discloses or implies the presently claimed
processes or the products resulting from these processes.
DEFINITIONS
The terms "elastic" and "elastomeric" are used
interchangeably herein to means any material which, upon
application of a biasing force, is stretchable to a
stretched, biased length which is at least about 125
percent, that is about one and one quarter, of its
relaxed, unbiased length, and which will recover at
least about 40 percent of its elongation upon release of
the stretching, elongating force. A hypothetical
example which would
_ 8 - ~ 3 ~
satisfy this definition of an elastomeric material would be
a one (l) inch sample of a material which is elongatable to
at least 1.25 inches and which, upon being elongated to
1.25 inches and released will recover to a length of not
5 more than 1.15 inches. Many elastic materials may be
stretched by much more than 25 percent of their relaxed
length and many of these will recover to substantially
their original relaxed length upon release of the
stretching, elongating force and this latter class of
10 materials is generally preferred for purposes of the
present invention.
As used herein the term "recover" refers to a
contraction of a stretched material upon termination of a
biasing force following stretching of the material by
15 application of the biasing force. For example, if a
material having a relaxed, unbiased length of one (1) inch
was elongated 50 percent by stretching to a length of one
and one half (1.5) inches the material would have a
stretched length that is 150 percent of its relaxed length.
If this exemplary stretched material contracted, that is
recovered, to a length of one and one tenth (i.1) inches,
after release of the biasing and stretching force, the
material would have recovered 80 percent (0.4 inch) of its
elongation.
As used herein the terms n nonelastic" or
"nonelastomeric" refer to and include any material which is
not encompassed by the terms "elastic" or "elastomeric."
As used herein the term "meltblown microfibers" refers
to small diameter fibers having an average diameter not
greater than about 100 microns, preferably having a
diameter of from about 0.5 microns to about 50 microns,
more preferably having an average diameter of from about 4
microns to about 40 microns and which are made by extruding
a molten thermoplastic material through a plurality of
fine, usually circular, die capillaries as molten threads
9 1 3 ~
or filaments into a high velocity gas (e.g. air) stream
which attenuates the filaments of molten thermoplastic
material to reduce their diameter to the range stated
above. Thereafter, the meltblown microfibers are carried
by high velocity gas stream and are deposited on a collect-
ing surface to form a web of randomly disbursed meltblown
microfibers. Such a process is disclosed , for example, in
U.S. patent 3,849,241 to Butin.
As used herein the term "spunbonded microfibers"
refers to small diameter fibers having a diameter not
greater than about 100 microns, preferably having a
diameter of from about 10 microns to about 50 microns, more
preferably having a diameter of from about 12 microns to
about 30 microns and which are made by extruding a molten
thermoplastic material as filaments through a plurality of
fine, usually circular, capillaries of a spinnerette with
the diameter of the extruded filaments then being rapidly
reduced as by, for example, eductive drawing or other well
known spunbonding mechanisms. The production of spunbonded
nonwoven webs is illustrated in U.S. patent 4,340,563 to
Appel.
As used herein the term "nonwoven web" includes any
web of material which has been formed without use of
textile weaving processes which produce a structure of
individual fibers which are interwoven in an identifiable
repeating manner. Specific examples of nonwoven webs would
include, without limitation, a meltblown nonwoven web, a
spunbonded nonwoven web, an apertured film, a microporous
web or a carded web of staple fibers. These nonwoven webs
have an average basis weight of not more than about 300
grams per square meter. Preferably, the nonwoven webs have
an average basis weight of from about 5 grams per square
-- 10 --
1~6~ ~
meter to about 100 grams per square meter. More
preferably, the nonwoven webs have an average basis weight
of from about 10 grams per square meter to about 75 grams
per square meter.
As used herein the term "consisting essentially of"
does not exclude the presence of additional materials which
do not significantly affect the elastomeric properties and
characteristics of a given composition. Exemplary
materials of this sort would include, pigments,
10 anti-oxidants, stabilizers, surfactants, waxes, flow
promoters, solid solvents, particulates and materials added
to enhance processability of the composition.
As used herein the term n styrenic moiety" means a
monomeric unit represented by the formula:
CH~ --Cl-~
C ~
CH CH
C~ C~
~ ~/
CH
Unless specifically set forth and defined or otherwise
limited, the terms "polymer" or "polymer resin" as used
herein generally include, but are not limited to,
homopolyers, copolymers, such as, for example, block,
25 graft, random and alternating copolymers, terpolymers, etc.
and blends and modifications thereof. Furthermore, unless
otherwise specifically limited, the terms "polymer" or
"polymer resin" shall include all possible geometrical
configurations of the material. These configurations
30 include, but are not limited to, isotactic, syndiotactic
and random symmetries.
OBJE~TS OF THE INVENTION
~ ccordingly, it is a general object of the present
invention to provide a new process for forming a composite
35 nonwoven elastic web which is composed of a nonwoven
1 3 ~
elastic web having a fibrous nonwoven gathered web joined
thereto.
Another general object of the present invention is to
provide a new process for forming a composite nonwoven
elastic web which includes a nonwoven elastic web joined to
a fibrous nonwoven gathered web where the fibrous nonwoven
gathered web has been gathered as a result of the fibrous
nonwoven gathered web having been directly formed, in a
gatherable condition, on a surface of the nonwoven elastic
10 web while the nonwoven elastic web is maintained in a
stretched, biased condition and, thereafter, relaxing the
nonwoven elastic web from its stretched, biased condition
or length to a relaxed, unbiased condition or length.
Yet another object of the present invention is to
15 provide a composite nonwoven elastic web which includes a
nonwoven elastic web joined to a fibrous nonwoven gathered
web where the fibrous nonwoven gathered web is formed, in a
gatherable condition, on a surface of the nonwoven elastic
web and simultaneously joined thereto.
A further object of the present invention is to
provide the composite nonwoven elastic webs formed by the
processes of the present invention.
One other object of the present invention is to
provide a new process for forming a gathered nonwoven web
possessing elastic characteristics solely from nonelastic
materials.
Another object of the present invention is to provide
a new process for forming a gathered nonwoven elastic web
which process inc~udes forming a nonwoven gatherable web
directly on a surface of a nonwoven elastic web while the
nonwoven elastic web is being maintained in a stretched,
biased condition so as to separably join the gatherable web
to the nonwoven elastic web and thereafter relaxing the
nor.woven elastic web from its stretched, biased condition
or length to a relaxed, unbiased condition or length so
- 12 -
that the gatherable web is gathered and separating the
gathered web from the elastic web to form a gathered web
having elastic properties.
Yet another object of the present invention is to
5 provide a new process for forming a gathered nonwoven
elastic web which process includes forming a gatherable web
directly on the surface of an extendable and retractable
porous forming surface while the forming surface is being
maintained in the extended condition so as to separably
join the gatherable web to the extendable and retractable
forming surface, retracting the forming surface to gather
the gatherable web and thereafter separating the gathered
web from the forming surface to form a gathered web having
elastic properties.
A further object of the present invention is to
provide the gathered nonwoven webs possessing elastic
characteristics formed by the processes of the present
invention.
Still further objects and the broad scope of
applicability of the present invention will become apparent
to those of skill in the art from the details given
hereinafter. However, it should be understood that the
detailed description of the presently preferred embodiments
of the present invention is given only by way of
illustration because various changes and modifications well
within the spirit and scope of the invention will become
apparent to those of skill in the art in view of this
detailed description.
SUMMARY OF THE INVENTION
The present invention is directed to a process for
producing a composite nonwoven elastic web which is
composed of a nonwoven elastic web that is joined to a
fibrous nonwoven gathered web. In particular, the process
of the present invention produces a composite nonwoven
elastic web which, in its relaxed, nonstretched state, is
- 13 - ~ 3~
composed of a gathered nonwoven fibrous web that is joined
to a nonwoven elastic web with the nonwoven elastic web
having been relaxed from a stretched, biased length to a
relaxed, unbiased, nonstretched length so as to gather the
5 fibrous nonwoven gathered web. An important feature of the
process of the present invention is that the fibrous
nonwoven gatherable web is formed directly onto a surface
of the nonwoven elastic web while the nonwoven elastic web
is maintained in a stretched, biased and elongated
10 condition-
The nonwoven elastic web may be formed by, forexample, a meltblowing process or any other process for
forming a nonwoven elastic web. For example, the nonwoven
elastic web could be an apertured web of an elastic film as
15 opposed to a meltblown fibrous nonwoven elastic web. The
formed nonwoven elastic web has a normal relaxed,
nonstretched, nonbiased length. Thereafter, the nonwoven
elastic web is elongated by being stretched to a stretched,
biased length.
In a subsequent step of the process a fibrous nonwoven
gatherable web may be formed, for example, by either a
meltblowing or spunbonding process or any other process for
forming a fibrous nonwoven gatherable web, directly upon a
surface of the nonwoven elastic web while the nonwoven
25 elastic web is maintained at its elongated, stretched and
biased length. During formation of the fibrous nonwoven
gatherable web the nonwoven elastic web is maintained at a
stretched length which is at least about 125 percent, that
is at least about one and one quarter of the relaxed,
30 unbiased length of the nonwoven elastic web. For example,
the stretched, biased length of the nonwoven elastic web
may be maintained in the range of from at least about 125
percent of the relaxed, unbiased length of the nonwoven
elastic web to about 700 or more percent of the relaxed,
35 unbiased length of the nonwoven elastic web.
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Y~
The fibrous nonwoven gatherable web is joined to the
nonwoven elastic web while the nonwoven elastic web is
maintained at its elongated stretched, biased length. This
results in the formation of a composite nonwoven elastic
5 web which includes the nonwoven elastic web which is joined
to the fibrous nonwoven gatherable web. Because the
fibrous nonwoven gatherable web is formed directly onto the
surface of the nonwoven elastic web while the nonwoven
elastic web is being maintained at its stretched, biased
10 length, the nonwoven elastic web is, at this stage in the
process, elongated, stretched and biased and the fibrous
nonwoven gatherable web is in an ungathered but gatherable
condition.
In one embodiment of the present invention, joining of
15 the fibrous nonwoven gatherable web to the nonwoven elastic
web is achieved by heat-bonding to fuse the two webs to
each other. The heat-bonding may be carried out within the
temperature range of from about 50 degrees centigrade below
the melt temperature of at least one of the materials
20 utilized to form at least one of the two webs to about the
melt temperature of at least one of the materials utilized
to form at least one of the two webs. At high through-put
rates the heat-bonding can be carried out above the melt
temperature of one or more of the materials utilized to
25 form the webs. The heat-bonding may also be carried out
under appropriate conventional pressurized conditions. If
desired, conventional sonic bonding techniques may be
substituted for the heat-bonding steps.
In another embodiment of the present invention joining
30 of the fibrous nonwoven gatherable web to the stretched
nonwoven elastic web is achieved solely by the entanglement
of the individual fibers of the fibrous nonwoven gatherable
web with the nonwoven elastic web during formation of the
fibrous gatherable web on the surface of the elastic web.
35 If the nonwoven elastic web is a fibrous nonwoven elastic
-- 15 --
web formed by, for example, meltblowing, entanglement of
the individual fibers of the fibrous nonwoven gatherable
web with the fibrous nonwoven elastic web is achieved by
entanglement of the individual fibers of the fibrous
5 gatherable web with the individual fibers of the fibrous
elastic web. If the nonwoven elastic web is an apertured
film, joining of the fibrous nonwoven web with-the film is
achieved by entanglement of the individual fibers of the
fibrous gatherable web within the apertures of the film.
In yet another embodiment, discussed below, the
joining of the two webs to each other is achieved by also
forming the nonwoven elastic web out of a tacky elastic
material.
In any of the embodiments of the presently inventive
15 process joining of the two webs to each other may be
further enhanced by applying pressure to the two webs after
the gatherable web has been formed on the surface of the
elastic web. Also, in any embodiment, joining of the two
webs may be further improved by applying an adhesive
20 material to the upper surface of the nonwoven elastic web
prior to formation of the fibrous nonwoven gatherable web
thereon.
After joining of the two webs to each other has been
achieved to form a composite elastic web, the biasing force
is removed from the composite nonwoven elastic web and the
composite elastic web is allowed to relax to its normal
relaxed, unbiased length. ~ecause the fibrous nonwoven
gatherable web is joined to the nonwoven elastic web while
the nonwoven elastic web is stretched, relaxation of the
composite nonwoven elastic web results in the gatherable
web being carried with the contracting nonwoven elastic web
and thus being gathered.
After gathering of the fibrous nonwoven gatherable web
has occurred by reducing the biasing force on the composite
nonwoven elastic web, the composite nonwoven elastic web
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~ 3 ~
may be rolled up in rolls for storage and shipment. The
composite elastic web may thereafter be utilized to form a
wide range of products, such as, for example, an outer
cover for a diaper.
Alternatively the gathered nonwoven web mav be
separated from the nonwoven elastic web subsequent to its
being gathered by the retractive forces of the nonwoven
elastic web. In this embodiment the gathered nonwoven web
can be utilized alone or in conjunction with a variety of
10 other webs or film materials to form numerous different
products. Interestingly, the separated gathered nonwoven
web retains a substantial degree of its gathered
configuration and also exhibits elastic properties. The
gathered nonwoven web may be formed, as discussed above, in
15 a gatherable condition directly onto the surface of the
elastic nonwoven web with the elastic nonwoven web being in
an extended state.
Upon its formation on the surface of the nonwoven
elastic web, the fibrous nonwoven gatherable web is
separably joined to the nonwoven elastic web while the
nonwoven elastic web is maintained at its extended
stretched, biased length. This results in the formation of
a composite nonwoven elastic web which includes the
nonwoven elastic web and the fibrous nonwoven gatherable
25 web with the fibrous nonwoven gatherable web being
separably joined to the nonwoven elastic web. Because the
fibrous nonwoven gatherable web is formed directly onto the
surface of the nonwoven elastic web while the nonwoven
elastic web is being maintained at its extended stretched,
biased length, the nonwoven elastic web is, at this stage
in the process, extended, stretched and biased and the
fibrous nonwoven gatherable web is in an ungathered but
gatherable condition.
The separable joining of the fibrous nonwoven
gatherable web to the extended, stretched nonwoven elastic
- 17 -
web is achieved by the entanglement of the individual
fibers of the fibrous nonwoven gatherable web with the
nonwoven elastic web during formation of the fibrous
nonwoven gatherable web on the surface of the nonwoven
5 elastic web. If the nonwoven elastic web is a fibrous
nonwoven elastic web formed by, for example, meltblowing,
the separable joining of the fibrous nonwoven gatherable
web to the fibrous nonwoven elastic web is achieved by
entanglement of the individual fibers of the fibrous
10 gatherable web with the individual fibers of the fibrous
nonwoven elastic web. If the nonwoven elastic web is an
apertured film, the separable joining of the fibrous
nonwoven web with the nonwoven elastic web is achieved by
entanglement of the individual fibers of the fibrous
15 gatherable web within the apertures of the apertured film.
After the separable joining of the two webs to each
other has been achieved to form the composite elastic web,
the biasing force is removed from the composite nonwoven
elastic web and the composite elastic web is allowed to
20 contract, due to contraction of the stretched nonwoven
elastic web, to its normal contracted, unbiased length.
Because the fibrous nonwoven gatherable web is separably
joined to the nonwoven elastic web while the nonwoven
elastic web is extended and stretched, contraction of the
25 composite nonwoven elastic web results in the gatherable
web being carried with the contracting nonwoven elastic web
and thus being gathered on the surface of the nonwoven
elastic web.
After gathering of the fibrous nonwoven gatherable web
30 has occurred by reducing the biasing force on the composite
nonwoven elastic web the gathered fibrous nonwoven web is
separated from the nonwoven elastic web and the gathered
web may, for example, be rolled up for storage. After
separation of the fibrous nonwoven gathered web from the
- 18 - ~ 3 ~
nonwoven elastic web, the nonwoven elastic web may be
reused as a forming surface.
Upon its separation from the nonwoven elastic web, the
'ibrous nonwoven gathered web retains a gathered
5 configuration and, upon application of a stretching and
biasing force in the direction in which the fibrous
nonwoven gatherable web was gathered, the gathered web
extends to the extent that the gathers allow. Importantly,
upon release of the stretching and biasing force the
10 extended, fibrous nonwoven gathered web contracts
substantially to the gathered configuration and length
which it possessed after its separation from the nonwoven
elastic web. That is, the fibrous nonwoven gathered web
exhibits elastic characteristics and properties. The fact
15 that the gathered web, upon its separation from the
nonwoven elastic web, retains a gathered configuration is
surprising. However, it is even more surprising that the
separated fibrous nonwoven gathered web, upon being
stretched to an extended length, exhibits elastic
20 properties such as recovering at least about 40 percent of
its elongation. That is, the separated fibrous nonwoven
web exhibits elastic or elastomeric properties as defined
herein. In fact, it has been found that the fibrous
nonwoven gathered web exhibits these elastic properties
25 even when the fibrous nonwoven gathered web was formed from
a nonelastic material such as polypropylene.
Preferably, the fibrous nonwoven gatherable web
includes at least one meltblown fibrous nonwoven web.
Alternative methods which may be utilized in forming the
fibrous nonwoven gatherable web include spunbonding or any
other process for forming a fibrous nonwoven gatherable
web. The gathered fibrous nonwoven web may be formed
entirely from one nonelastic material or from a blend of
one or more nonelastic materials. However, the gathered
fibrous nonwoven may be formed from blends o. one or more
-- 19 --
nonelastic materials with one or more elastic materials or
from one or more elastic materials. Nonelastic materials
for forming the fibrous nonwoven gatherable web include
nonelastic polyester materials, nonelastic polyolefin
5 materials ~r blends of one or more nonelastic polyester
materials with one or more nonelastic polyolefin materials.
An exemplary nonelastic polyester material is polyethylene
terephthalate. An exemplary nonelastic polyolefin is a
nonelastic polypropylene which may be obtained under the
trade designation PF 301.
Alternatively, the necessity for the elastic nonwoven
web can be eliminated by forming the gathered nonwoven web
in a gatherable condition directly onto an extensible and
contractable surface, such as, for example, an extendable
and retractable mesh screen.
In one particular embodiment of the process of the
present invention a tacky fibrous nonwoven elastic web is
formed by, for example, meltblowing microfibers of a tacky
elastic material such as, for example, an A-B-A' block
copolymer or blends of such A-B-A' block copolymers with
poly (alpha-methylstyrene) where A and A' are each
thermoplastic polystyrene or polystyrene homologue end
blocks and B is an elastic polyisoprene midblock. In some
embodiments A may be the same thermoplastic polystyrene or
polystyrene homologue endblock as A'. The tacky fibrous
nonwoven elastic web is then elongated by being stretched
to an elongated, stretched length and a fibrous nonwoven
gatherable web is formed, for example, by meltblowing or
spunbonding the fibrous nonwoven gatherable web, directly
upon a surface of the tacky fibrous nonwoven elastic web
while maintaining the fibrous nonwovén elastic web at its
stretched length. As a result of the fact that the fibrous
nonwoven elastic web is tacky, the fibrous nonwoven
gatherable web is simultaneously formed upon and adhesively
joined to the surface of the tacky fibrous nonwoven elastic
- 20 -
web. This embodiment results in the formation of
composite nonwoven elastic web having an ungathered fibrous
gatherable web adhesively joined to the tacky fibrous
nonwoven elastic web with the joining of the two webs to
5 each other being achieved by the adhesive joining which
occurs during formation of the fibrous nonwoven gatherable
web on the surface of the fibrous nonwoven elastic web.
The adhesive joining of the two webs to each other may be
increased upon application pressure to the composite
10 nonwoven elastic web by passing the composite nonwoven
elastic web through the nip between rollers, which may be
unheated, after the composite web has been formed but
before the fibrous tacky nonwoven elastic web is allowed to
relax. The adhesive joining may be further enhanced by
lS application of an adhesive material to the surface of the
tacky fibrous nonwoven elastic web prior to formation of
the gatherable web thereon.
The composite nonwoven elastic web is then allowed to
relax to its normal relaxed, unbiased length. Because the
fibrous nonwoven gatherable web was joined to the tacky
fibrous nonwoven elastic web while the tacky fibrous
nonwoven elastic web was in a stretched condition,
relaxation of the composite nonwoven elastic web and thus
the tacky fibrous nonwoven elastic web results in the
gatherable web being carried with the contracting fibrous
nonwoven elastic web and thus being gathered.
After gathering of the fibrous nonwoven gatherable web
has occurred the composite nonwoven elastic web may be
rolled up in rolls for storage and shipment. In order to
avoid adhesion of the exposed side of the tacky fibrous
nonwoven elastic web upon rolling-up of the composite
nonwoven elastic web it is preferred for a second fibrous
nonwoven gatherable web to be applied to the exposed
surface of the fibrous nonwoven elastic web prior to the
gathering step. Alternatively, butcher paper may be
- 21 -
applied~ either before or after gathering of the gatherable
web, to the exposed tacky surface of the tacky fibrous
nonwoven elastic web and later removed prior to utilization
of the composite nonwoven elastic web. The composite
5 elastic web may thereafter be utilized to form a wide
variety of products.
The invention is also directed to a composite nonwoven
elastic web composed of a nonwoven elastic web that is
joined to a gatherable fibrous nonwoven web which has been
10 gathered and with the composite web having been formed by
any of the embodiments of the inventive process. In
particular, the composite nonwoven elastic web, in its
relaxed, nonstretched state, is composed of a nonwoven
elastic web that is joined to a fibrous nonwoven gathered
15 web which has been gathered as a result of the nonwoven
elastic web having been relaxed from an elongated
stretched, biased length to a relaxed, unbiased
nonstretched length. Exemplary elastomeric materials for
use in formation of the fibrous nonwoven elastic web
include polyester elastomeric materials, polyurethane
elastomeric materials, and polyamide elastomeric materials.
Other elastomeric materials for use in formation of the
fibrous nonwoven elastic web include (a) A-B-A' block
copolymers, where A and A' are each a thermoplastic polymer
25 endblock which includes a styrenic moiety and where A may
be the same thermoplastic polymer endblock as A', such as a
poly (vinyl arene), and where B is an elastomeric polymer
midblock such as a conjugated diene or a lower alkene or
(b) blends of one or more polyolefins or poly (alpha-methyl
styrene) with A-B-A' block copolymers, where A and A' are
each a thermoplastic polymer endblock which includes a
styrenic moiety, where A may be the same thermoplastic
polymer endblock as A', such as a poly (vinyl arene) and
where B is an elastomeric polymer midblock such as a
conjugated diene or a lower alkene. The A and A' endblocks
- 22 ~ &~
may be selected from the group including polystyrene and
polystyrene homologs and the B midblock may be selected
from the group including polyisoprene, polybutadiene or
poly (ethylene-butylene). If A and A' are selected from
the group including polystyrene or polystyrene homologs and
B is poly (ethylene-butylene), materials which may be
blended with these block copolymers are polymers, including
copolymers o ethylene, propylene, butene, other lower
alkenes or one or more of these materiàls. If A and A' are
selected from the group including polystyrene or
polystyrene homologs and B is a polyisoprene midblock, a
material for blending with this type of ~lock copolymer is
poly (alpha-methylstyrene).
Preferably, the gatherable web includes at least one
fibrous nonwoven web that includes nonelastic fibers which
may be formed by meltblowing, spunbonding or any other
process for forming a fibrous nonwoven gatherable web.
Preferred materials for forming the gatherable web include
polyester materials, polyolefin materials or blends of one
or more polyester materials with one or more polyolefin
materials. An exemplary polyester material is polyethylene
terephthalate. An exemplary polyolefin material is
polypropylene.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic view illustrating one mode for
carrying out the method of one of the embodiments of the
present invention.
Figure 2 is a schematic view illustrating a mode for
carrying out the method of another of the embodiments of
the present invention.
Figure 3 is a schematic view illustrating one mode for
carrying out the method of an embodiment of the present
invention where the gathered web is separated from the
elastic web.
,. ., ~
- 23 -
Figure 4 is a schematic view illustrating another mode
for carrying out the method of another embodiment of the
present invention where the gathered web is separated from
the elastic web.
Figure 5 is a top plan view of an unbiased and
retracted extendable and retractable forming screen which
may be utilized as a forming screen in the process
illustrated in Figure 4.
Figure 6 is a top plan view of the extendable and
retractable forming screen of Figure 5 in the biased,
extended configuration.
Figure 7 is a schematic view of yet another mode for
carrying out the method of yet another embodiment of the
present invention where the two gathered webs are separated
from the elastic web.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Turning now to the figures wherein like reference
numerals represent like structure and, in particular, to
figure 1, it can be seen that meltblown microfibers 10
which are formed by a conventional meltblowing die 12 are
collected on a porous collecting screen 14 which is moving,
as indicated by the arrows 16 in figure 1, about the
rollers 18 and 20. The material which is utilized to form
the meltblown microfibers 10 is, for reasons which will
hereinafter become clear, an elastomeric material. The
porous collecting screen 14 is driven by the rotating
rollers 18 and 20 which, in turn, are driven by a
conventional drive arrangement ~not shown). Also not shown
for purposes of clarity is a conventional vacuum box
located between the _ollers 18 and 20 and beneath the lower
surface of the upper portion o~ the screen 14. The vacuum
box assists in the retention of the microfibers 10 on the
upper surface of the screen 14. As the meltblown
microfibers 10 are deposited upon the moving collecting
screen 14 they entangle and cohere to form a cohesive
- 24 ~
fibrous nonwoven elastic web 22. The entangled cohesive
fibrous nonwoven elastic web 22 is carried by the porous
collecting screen 14 to the nip or gap 24 between the
rotating roller 20 and a rotating nip roller 26. The nip
5 or gap 24 between the two rollers 20 and 26 is adjusted so
that the rollers 20 and 26 firmly engage the fibrous
nonwoven elastic web 22 without adversely affecting the web
22. The rate of rotation of the rollers 20 and 26 is
adjusted so that the peripheral surface speed of the
10 rollers 20 and 26 is substantially the same as the speed of
the moving porous collecting screen 14. If, upon lay-down
on the surface of the porous screen 14, the meltblown
microfibers 10 are insufficiently cohered to each other to
form a cohesive web 22 capable of performing the
15 hereinafter discussed stretching and relaxing steps without
being adversely affected (e.g. the web separates, loses it
integrity, upon application of a stretching force), the
cohesion of the microfibers 10 to each other may be
improved by, for example, heat-bonding the microfibers 10
to each other by maintaining the roller 26 at an
appropriate elevated temperature which will vary depending
upon the degree of cohesion desired and the cohesive
characteristics of the material utilized to form the
microfibers 10. Typical heat-bonding temperatures range
from about 50 degrees centigrade below the melting
temperature of at least one of the materials utilized to
form the web 22 to about the melting temperature of at
least one of the materials utilized to form the web 22.
However, at high throughput rates temperatures exceeding
the melting temperature of the material may be employed.
After passing through the nip 24 the fibrous nonwoven
elastic web 22 is forwarded by the action of the rollers 20
and 26 into and passe~ through a second nip or gap 28 which
is formed between a rotating roller 30 and a second
rotating nip roller 32. Rotation of the rollers 30 and 32
- 25 -
1 3 ~
is adjusted so that the peripheral surface speed of the
rollers 30 and 32 is greater than the peripheral surface
speed of the rollers 20 and 26. The nip 28 between the two
rollers 30 and 32 is adjusted so that the rollers 30 and 32
firmly engage the fibrous nonwoven elastlc web 22 without
adversely affecting the web 22. As a result of the
increase in the peripheral surface speed of the rollers 30
and 32 with respect to the peripheral surface speed of the
rollers 20 and 26 a longitudinal or machine direction (MD)
10 biasing force is placed on the fibrous nonwoven elastic web
22 and the web 22 is stretched to an extended, stretched,
biased length in the longitudinal or machine direction
(MD). The degree of stretching of the fibrous nonwoven
elastic web 22 which occurs in the area 34 between the
15 rollers 20 and 26 and the rollers 30 and 32 may be varied,
for example, by varying the peripheral surface speed of the
rollers 30 and 32 with respect to the peripheral surface
speed of the rollers 20 and 26. For example, if the
peripheral surface speed of the rollers 30 and 32 is twice
that of the rollers 20 and 26, the fibrous nonwoven elastic
web 22 will be stretched to a stretched length of
substantially about twice, that is, about 200 percent, of
its original relaxed unstretched, unbiased length. It is
preferred that the fibrous nonwoven web 22 be stretched to
a stretched length of at least about 125 percent of its
original, relaxed, unbiased length. In particular, it is
preferred for the fibrous nonwoven web 22 to be stretched
to a stretched length of from at least about lS0 percent of
the relaxed, unbiased length of the fibrous nonwoven web 22
to about 700 or ~ore percent of the relaxed, unbiased
length of the fibrous nonwoven web 22.
After the fibrous nonwoven elastic web 22 has been
stretched, by the combined actions of rollers 20 and 26 and
and 32, the web 22 is passed onto a second porous
collecting screen 36 which is moving as is indicated by the
- 26 -
~ 3 ~
arrows 38 in figure 1. The second porous collecting screen
36 moves about and is driven by the rotating roller 30 in
conjunction with a rotating roller 40. The rotating
rollers 30 and 40 are, in turn, driven by a conventional
5 driving arrangement (not shown) which may be the same
arrangement that is driving the rotating rollers 18 and 20.
Also not shown for purposes of clarity is a conventional
vacuum box located between the rollers 30 and 40 and
beneath the lower surface of the upper portion of the
screen 36. The vacuum box assists in the retention of the
web 22 on the upper surface of the screen 36. The
stretched fibrous nonwoven elastic web 22 is carried by the
second porous collecting screen 36 to a nip or gap 42 which
is formed between the rotating roller 40 and a third
15 rotating nip roller 44. Rotation of the rotating roller 40
and the nip roller 44 is adjusted so that the peripheral
surface speed of the two rollers 40 and 44 is substantially
the same as the peripheral surface speed of the rollers 30
and 32. Because the peripheral surface speed of the
rollers 40 and 44 is maintained at substantially the same
peripheral surface speed as that of the rollers 30 and 32
and because the nip 42 is adjusted so that the rollers 40
and 44 firmly retain the fibrous nonwoven elastic web 22,
without adversely affecting the web 22, the stretched
condition of the fibrous nonwoven elastic web 22 is
maintained while the fibrous nonwoven elastic web 22 is
being carried by the second porous collecting screen 36.
While the stretched fibrous nonwoven elastic web 22 is
being carried by the second porous collecting screen 36
meltblown microfibers 46, formed by a conventional
meltblowing die 48, are meltblown directly onto the upper
surface of the stretched nonwoven elastic web 22 to form a
cohesive fibrous nonwoven gatherable web 50 which is
located on the upper surface of the stretched fibrous
nonwoven elastic web 22. Care should be taken to adjust
- 27 ~
the distance between the die tip of the meltblowing die 48
and the elastic web 22 and the speed at which the elastic
web 22 passes under the die tip of the meltblowing die 48,
as it has been found that the hot air exiting the die tip
5 will melt the elastic web 22 if these adjustments, which
will vary with the material or blend of materials from
which the elastic web 22 is formed, are not properly made.
As the meltblown microfibers 46 are collected on the upper
surface of the fibrous nonwoven elastic web 22, they
entangle and cohere with each other to form the cohesive
fibrous nonwoven gatherable web 50. Depending upon the
distance between the die tip of the meltblowing die 48 and
the upper surface of the stretched fibrous nonwoven elastic
web 22 the meltblown microfibers 46 may also mechanically
entangle with the fibers of the elastic web 22. Generally
speaking, as the distance between the die tip of the
meltblowing die 48 and the upper surface of the stretched
fibrous nonwoven elastic web 22 is increased the mechanical
entanglement of the fibers of the web 50 with the fibers of
the web 22 decreases. To assure mechanical entanglement of
the fibers of the web 50 with the fibers of the web 22 the
distance between the die tip of the meltblowing die 48 and
the upper surace of the web 22 should be no greater than
about 25 inches. Preferably, the distance between the die
tip of the meltblowing die 48 and the upper surface of the
web 22 should range from about 6 inches to about 16 inches.
Depending on the materials utilized to form the webs 22 and
50 and the distance between the die tip of the meltblowing
die 48 and the upper surface of the web 22 some adhesion of
the fibers of the gatherable web 50 to the fibers of the
elastic web 22 may also occur. The materials which are
appropriate for utilization in forming the fibrous nonwoven
elastic web 22 are preferably selected after selection of
the material or materials which will be utilized in
formation of the fibrous nonwoven gatherable web 50 has
- 28 -
occurred. In particular, the material selected to form the
fibrous nonwoven gatherable web 50 must be a material which
forms a web 50 that is gatherable by the contracting force
of the fibrous nonwoven elastic web 22. Because the
5 contracting force of the web 22 will vary with the material
selected for formation of the web 22, the material selected
for formation of the web 22 will have to be selected so
that the contracting force of the web 22 is capable of
gathering the web 50. Exemplary, materials for utilization
10 in forming the webs 22 and 50 are disclosed hereinafter.
Depending upon the characteristics which are desired
for the final product, the materials which are utilized to
form the fibers which compose the two webs 22 and 50 and
the process steps/conditions utilized, the two cohesive
15 webs 22 and 50 may be joined to each other in a variety of
ways. For example, if a relatively weak joining of the two
- webs 22 and 50 to each other is desired, the two webs 22
and 50 can be joined to each other solely by the
entanglement of the individual meltblown fibers of the
fibrous nonwoven gatherable web 50 with the individual
meltblown fibers of the fibrous nonwoven elastic web 22
which occurs during formation of the web 50 on the
stretched surface of the web 22. In this embodiment, the
two webs 22 and 50 are separable from each other upon
25 application of a relatively small amount of force such as,
for example, a light picking or rubbing force applied by an
individual's fingers. In the event that a stronger joining
of the two cohesive webs 22 and 50 to each other is
desired, joining of the fibrous nonwoven gatherable web 50
to the fibrous nonwoven elastic web 22 can be achieved,
while continuing to maintain the fibrous nonwoven elastic
web 22 at its stretched length, by heat-bonding the two
webs 22 and 50 to each other. The heat-bonding can be
achieved by, for example, passing the two webs 22 and 50
between the rollers 40 and 44 with the rollers 40 and 44
- 2~
being arranged to apply appropriate heat-bonding
temperatures and pressures to the two webs 22 and 50. For
example, joining of the fibrous nonwoven gatherable web 50
to the fibrous nonwoven elastic web 22 may be achieved by
5 heat-bonding of the two webs 22 and 50 to each other with
the rollers 40 and 44 being maintained within the
temperature range of from about 50 degrees centigrade below
the melting point of at least one of the materials used to
form the web 22 and 50 to about the melt temperature of at
least one of the materials utilized to form the webs 22 and
50. However, at high through-put rates the heat-bonding
can be carried out above the melt temperature of one or
more of the materials utilized to form the two webs 22 and
50 since the webs 22 and 50 will be exposed to the high
15 temperature for a short time. Pressurized heat-bonding of
the two webs 22 and 50 to each other may be carried out at
conventional, appropriate bonding pressures by adjusting
the nip 42. Other conventional alternatives to
heat-bonding the two webs 22 and 50 to each other may be
substituted for the heat-bonding steps. For example, a
conventional sonic bonding arrangement (not shown) could be
substituted for the heat-bonding arrangement 40 and 44. It
should be noted that the joining of the two webs 22 and 50
to each other is usually improved somewhat just by passage
25 of the webs 22 and 50 through the nip 42 since such passage
results in application of pressure to the two webs 22 and
50 and thus increased entanglement of the individual fibers
of the two webs 22 and 50.
After the fibrous nonwoven elastic web 22 has been
joined (separably or nonseparably, depending upon the final
product which is desired) to the fibrous nonwoven
gatherable web 50 to form a composite nonwoven elastic web
52 the biasing force on the fibrous nonwoven elastic web 22
is relaxed by, for example, passing the composite nonwoven
elastic web 52, which includes both the fibrous nonwoven
- 30 - 1 3 ~
elastic web 22 and the fibrous nonwoven gatherable web 50,
through the nip or gap 54 formed by a pair of rotatins nip
rollers 56 and 58. The nip 54 is adjusted so that the
rollers 56 and 58 firmly engage the composite web 52
5 without adversely affecting the composite web 52. The
rotation of the pair of nip rollers 56 and 58 is adjusted
so that the peripheral surface speed of the nip rollers 56
and 58 allows the composite nonwoven elastic web 52 to
relax and, as a result of its elastic properties, to
10 contract to its relaxed, unbiased length. The relaxing and
contracting of the composite nonwoven elastic web 52 to its
relaxed, unbiased length results in the fibrous nonwoven
gatherable web 50, which is joined to the fibrous nonwoven
elastic web 22, being carried along with, that is
15 contracted, and thus gathered upon the upper surface of the
contracting fibrous nonwoven elastic web 22.
After relaxing and contracting of the composite
nonwoven elastic web 52, the composite web 52 may be rolled
up on a supply roller 60 for storage and shipment. The
20 composite nonwoven elastic web 52 may thereafter be
utilized in the manufacture of wide variety of items such
as, for example, an outer cover material for a diaper or
other garment.
Alternatively, if the gathered nonwoven web 50 is to
;~ 25 be separated from the elastic nonwoven web 22, separation
of the two webs 22 and 50 from each other is effected in
this embodiment by passing the fibrous nonwoven gathered
web S0 through the nip 62 between two rotating nip rollers
64 and 66 and passing the nonwoven elastic web 22 through
the nip 68 between two rotating nip rollers 70 and 72. The
nips 62 and 68 are adjusted so that the rollers 64 and 66
engage the web 50 without adversely affecting the web 50
and the rollers 70 and 72 engage the web 22 without
adversely affecting the web 22. After separation of the
two webs 22 and 50, the two webs 22 and 50 are wound up on
~` - 31 ~
storage rolls 74 and 76, respectively. Care should be
taken in winding up the fibrous nonwoven gathered web 50 so
that the web 50 is not stored under high tension or biasing
in an ungathered condition because, if the web 50 is stored
S in a rolled-up tensioned, ungathered condition it is
believed that the web 50 will lose its ability to retain
its gathers. Loss of the gathers in the web 50 will result
in a loss of the elastic characteristics of the web 5d.
Accordingly, in order to retain the gathered condition of
10 the web 50 while the web 50 is stored the rotation of the
storage roll 76 should be adjusted so that the peripheral
surface speed of the roll 76 is generally equal to or just
slightly greater than the peripheral surface speed of the
rollers 64 and 66.
Upon its separation from the nonwoven elastic web 22
the gathered fibrous nonwoven web 50 exhibits a creped or
gathered appearance. Accordingly, upon application of an
extending force in the machine direction (i.e. is a
direction substantially perpendicular to the lines of
20 gathering) the web 50 is extended to the extent that the
gathers allow, e.g. until the web 50 has assumed a
generally planar configuration as opposed to a gathered
configuration and, surprisingly, upon release of the
extending force on the gathers, the gathered web 50
25 exhibits elastic characteristics as defined herein. The
gathered web 50 exhibits elastic characteristics even when
the web 50 was 'ormed from a nonelastic material such as a
polypropylene obtained from the Himont Corporation under
the trade designation PF 301.
The fibrous nonwoven elastic web 22 portion of the
composite nonwoven elastic web 52 may be formed from any
elastomeric material which may be formed into a _ibrous
nonwoven elastic web 22. Exemplary elastomeric materials
for use in formation of the fibrous nonwoven elastic web 22
35 include polyester elastomeric materials such as, for
- 32 - ~3~ 6~5 ~
example, polyester elastomeric materials available under
the trade-mark Hytrel from E. I. ~uPont DeNemours & Co.,
plolyurethane elastomeric materials such as, for example,
polyurethane elastomeric materials avai]able under the
trade-mark Estane from B.F. Goodrich & Co. and polyamide
elastomeric materials such as, for example, polyamide
elastomeric materials available under the trade-mark Pebax
from the Rilsan Company. Other elastomeric materials for
use in forming the fibrous nonwoven elastic web 22 include
(a) elastomeric A-B-A' block copolymers, where A and A' are
each a thermoplastic polymer endblock which includes a
styrenic moiety and where ~ may be the same thermoplastic
polymer endblock as A', for example, a poly tvinyl arene),
and where B is an elastomeric polymer midblock such as
conjugated diene or a lower alkene and ~b) blends of one or
more polyolefins or poly (alpha-methylstyrene) with
elastomeric A-B-A' block copolymer materials, where A and
A' are each polymer thermoplastic endblocks containing a
styrenic moiety and where A may be the same thermoplastic
polymer endblock as A', such as a poly (vinyl arene) and
where B is an elastomeric polymer midblock, such as a
conjugated diene or a lower alkene. The ~ and A' materials
may be selected from the group of materials including
polystyrene or polystyrene homologs and the B material may
be selected from the group of materials including polyisop-
rene, polybutadiene and poly (ethylene-butylene). Mater-
ials of this genera] type are disclosed in U.S. patents4,323,534 to DesMarais and 4,355,425 to Jones and in the
aforementioned Shell brochure. Commercially available
elastomeric A-B-~' block copolymers having a saturated or
essentially saturated poly (ethylene-butylene) midblock "B~
represented by the formula:
~ - 33 -
1 3 ~ ~ ~ e~ .
;r ~
, where x, y and n are positive integers, and polystyrene
endblocks A and A' represented by the formula:
H2 -- CH
C
~,H Ch
CH CH
i/
CH
, where n is a positive integer which may be the same or
different for A and A', are sometimes referred to as S-EB-S
block copolymers and are available under the trade
designation KRATON G, for example, KRATON G 1650, KRATON G
201652 and KRATON GX 1657, from the Shell Chemical Company.
Other elastomeric resins which may be utilized are A-B-A'
block copolymers where A and A' are polystyrene endblocks,
as defined above, and "B" is a polybutadiene midblock
represented by the following formula:
~ CH2--CH = CH--Ch2 ~
. .
....
~ 34 ~ 13166~
, where n is a positive integer. This material is
sometimes referred to as an S-B-S block copolymer and is
available under the trade-mark KRATON D, for example,
KRATON D 1101, KRATON D 1102 and KRATON D 1116, from the
Shell Chemical Company. Another S-B-S block copolymer
material may be obtained under the trade-mark Solprene 418
from the Phillips Petroleum Company. Yet other elastomeric
resins which may be utilized are A-B-A' block copolymers
where A and A' are polystyrene endblocks, as defined above,
and B is a polyisoprene midblock where the midblock is
represented by the formula:
CH7--CH = C--CH2
CH,
, where n is a positive integer. These block copolymers
are sometimes referred to as S-I-S block copolymers and are
available under the trade-mark KRATON D, for example,
KRATON D 1107, KRATON D 1111, KRATON D 1112 and KR~TON D
1117, from the Shell Chemical Company.
A summary of the typical properties of the above-
identified KRATON D and KRATON G resins at 74 Fahrenheit
is presented below in Tables I and II.
- 35 -
TABLE I
KRATON D
PROPERTY D-1101 D-1102 D-1107 D-llll D-1112 D-1116 D-1117
Tensile
5 Strength, 2 2 2 2 5 2
psil 4,6002 4,600 3,100 2,900 1,500 4,600 1,200
300%
ModTlUs,
psi 400 400 100 200 70 350 60
E~ongation,
10 % 880 880 1,300 1,200 1,400 900 1,300
Set at
Break, %10 10 10 10 20 10 15
Hardness,
Shore A71 71 37 52 34 65 32
Specific
Gravity0.940.94 0.92 0.93 0.92 0.94 0.92
Brookfield
Viscosity,
(~oluene
Solution)
20 cps at 4,0003 1,200 1,600 1,300 900 9,000 500
Melt Viscosity
Melt }ndex,
Condition G,
gms/10 min. 1 6 9
Plasticizer
Oil Content,
~w O O O O O O O
Styrene/6
Rubber
Ratio31/6928/7214/8621/7914/8621/7917/83
Physical
Form Porous Porous Pellet Porous Pellet Porous Pellet
Pellet Pellet Pellet Pellet
:
~: 35
~ - 36 - ~3~
TABLE II
KRATON G
PROPERTYG-1650 G-1652 GX-1657
Ten~ile Strength, 2 2
5 psi 5,oo02 4,500 3,400
300~ Modulus, psi 800 ~00 350
Elongation, %500 500 750
10 Set at Break, ~_ _ _
Hardness, Shore A ?5 75 65
Specific Gravity 0.91 0.91 0.90
Brookfield Viscosity,
15 (Toluene Solution) 4 4 4
cps at 77F 1,500 550 1,200
Melt Viscosity,
Melt Index,
Condition G,
gms/10 min. - - -
Plasticizer Oil
Content, ~w 0 0 0
Sytrene/Rubber
Ratio 28/72 29/71 14/86
Physical FormCrumb Crumb Pellet
ASTM method D412-tensile test jaw separation speed 10
in./min.
2 Typical properties determined on film cast from a
toluene
3 solution.
4 Neat polymer concentration, 25%w.
Neat polymer concentration, 20%w.
Property determined by extrapolation to zero oil content
of results measured on oil extended films cast from
toluene solution.
The ratio of the sum of the molecular weights of the
end-
1 3 1 ~
blocks (A + A' ) to the molecular weight of the B
midblock.
For example, with respect to KRATON G - 1650 the
molecular weight of the endblocks (A + A' ) is 28
percent of the molecular weight of the A-B-A'
block copolymer.
Meltblowing of the S-EB-S KRATON G block copolymers in
pure, i.e. neat, form has proven to be difficult except at
elevated temperatures and low through-puts such as from at
least about 550 degrees Fahrenheit to about 625 de~rees
Fahrenheit or more and below at least about 0.14 grams per
die capillary per minute. In order to avoid these elevated
temperature and low through-put conditions, blending of
certain materials with several of the different types of
15 KRATON G materials has proven to provide a satisfactory
meltblown material. For example, blends of certain
polyolefin materials with the S-EB-S block copolymer has
resulted in a meltblownable material. In particular, if a
polyolefin is to be blended with the KRATON G S-E~-S block
copolymers, the polyolefin is preferably a polymer,
including copolymers, of ethylene, propylene, butene, other
lower alkenes or blends of one or more of these materials.
A particularly preferred polyolefin for blending with the
KRATON G S-~B-S block copolymers is polyethylene and a
preferred polyethylene may be obtained from U.S. I.
Chemicals Company under the trade-mark Petrothene Na601.
(Also referred to herein as PE Na601 or Na601.)
Information obtained from U.S.I. Chemical Company
states that the Na601 is a low molecular weight, low
density polyethylene for application in the areas of hot
melt adhesives and coatings. ~.S.I. has also stated that
the NA601 has the following nominal values: (1) a Brook-
field Viscosity, cP at 150 degrees Centigrade of 8500 and
at 190 degrees Centigrade of 3300 when measured in accor-
dance with ASTM D 3236; (2) a density of 0.903 grams percubic centimeter when measured in accordance with ASTM
1505 (3) an equivalent Melt index of 2000 grams per ten
- 38 -
~ 9
minutes when measured in accordance with ASTM D 1238; (4) a
ring and ball softening point of 102 degrees Centigrade
when measured in accordance with ASTM E 28; (5) a tensile
of 850 pounds per square inch when measured in accordance
5 with ASTM D 638; (6) an elongation of 90 percent when
measured in accordance with ASTM D 638; (7) a modulus of
Rigidity, TF (45,000) of -34 degrees Centigrade and (8) a
penetration Hardness, (tenths of mm) at 77 degrees
Fahrenheit of 3.6.
The Na601 is believed to have a number average
molecular weight (Mn) of about 4,600; a weight average
molecular weight (Mw) of about 22,400 and a Z average
molecular weight (Mz) of about 83,300. The polydisperisity
of the Na601 (Mw/Mn) is about 4.87.
where Mn is calculated by the formula:
Mn = Sum [(n) ~MW)]
Sum (n)
and Mw is calculated by the formula:
Mw = Sum [(n) (MW) ]
Sum [(n) (MW)]
and MZ is calculated by the formula:
Mz = Sum [(n) (MW)3]
Sum ~(n) (MW) ]
where:
MW = The various molecular weights of the
individual molecules in a sample, and5
~ ~ 39 ~ 13~
n = The number of molecules in the given sample
which have a given molecular weight of MW.
Blending polyolefins with the S-I-S and S-B-~ block
copolymers followed by meltblowing of the blend has, to
date, proved to be unsatisfactory in that the blends appear
to be incompatible. However, a good material for blending
with the S-I-S block copolymers is poly
(alpha-methylstyrene) and a preferred poly
(alpha-methylstyrene) may be obtained from Amoco under the
trade designation 18-210.
Preferably, the fibrous nonwoven gatherable web 50
portion of the composite nonwoven elastic web 52 formed by
the process of the present invention may be formed from any
15 gatherable material which may be formed into a fibrous
nonwoven gatherable web 50. For example, the fibrous
nonwoven gatherable web 50 could be formed from a blend of
a nonelastic material with an elastic material, one or more
nonelastic materials or a blend of one or more elastic
20 materials with two or more nonelastic materials.
Preferably, the fibrous nonwoven gatherable web 50 is
formed from a fiber-forming meltblowable or spunbondable
nonelastic gatherable material. Exemplary fiber-forming
materials for use in forming the fibrous nonwoven
gatherable web are polyester materials, polyolefin
materials or blends of one or more polyester materials with
one or more polyolefin materials. An exemplary polyester
fiber-forming material is polyethylene terephthalate. An
exemplary fiber-forming polyolefin material is
polypropylene. Preferred polypropylene materials may be
obtained under the trade designation PC 973 and PF 301 from
the Himont Company.
Typical characteristics of the Himont PC-973
polypropylene stated by Himont are a density of about 0.900
grams per cubic centimeter, measured in accordance with
- 40 -
ASTM D 792; a meltflow rate obtained in accordance with
ASTM D 1238, condition L, of 35 grams per ten (10) minutes;
tensile of about 4,300 pounds per square inch (psi)
measured in accordance with ASTM D 638; flex modulus of
5 about 182,000 psi measured in accordance with ASTM D 790, B
and a Rockwell hardness, R scale, of 93 measured in
accordance with ASTM D 785 A. The PC-973 is believed to
have a number average molecular weight (Mn) of about
40,100; a weight average molecular weight (Mw) of about
10 172,000 and a Z average molecular weight of about 674,000.
The polydispersity (Mw/Mn) of the PC-973 is about 4.29.
If the gatherable web 50 is to be separated from the
elastic web 22 after it has been gathered, it is preferred
that the gathered web 50 be capable of substantially
15 returning to its gathered condition upon its separation
from the elastic web 22. It is presently believed that, in
most embodiments, the gathered condition (e.g.,
configuration) which the fibrous nonwoven gatherable web 50
exhibits upon its separation from the web 22 will be
20 somewhat longer in the direction of gathering (i.e. machine
direction) as compared to the length of the same amount of
web 50 when the web 50 is separably joined to the elastic
web 22. In other words, the web 50 will extend somewhat in
the direction of gathering after its separation from the
Z5 web 22. Accordingly, the gathered, relaxed, unbiased
length of the separated web 50 will be somewhat greater
than or equal to the gathered, relaxed, unbiased length of
the same amount of the web 50 while it is joined to the
elastic web 22.
In one particular embodiment of the present invention
: the composite nonwoven elastic web 52 is composed of a
fibrous nonwoven elastic web 22 which is joined to a
gatherable fibrous nonwoven web 50. The composite nonwoven
elastic web 52 of this embodiment differs from the
composite nonwoven elastic web 52 of the above-described
-
- 41 -
~ ~ P ~
embodiments in that the joining of the two webs 22 and 50
of the composite nonwoven elastic web 52 is achieved
without appl_cation of heat and/or pressure during the
bonding step yet is stronger than the joining achieved by
5 entanglement of the fibers of the nonwoven gatherable web
50 with the fibers of the nonwoven elastic web 22 during
formation of the web 50 on the web 22. In this particular
embodiment the fibrous nonwoven elastic web 22 is formed
from a tacky elastomeric material so that, upon its
formation, the fibrous nonwoven elastic web 22 is tacky.
The tacky fibrous nonwoven elastic web 22 is formed by
meltblowing the web 22 onto the porous collecting screen
14. Alternatively, a tacky nonwoven elastic apertured film
(not shown) could be substituted for the tacky fibrous
15 nonwoven elastic web 22. Thereafter, the tacky fibrous
nonwoven elastic web 22 is stretched to a stretched length
of at least about one and one quarter, that is at least
about 150 percent of its relaxed, unbiased length by the
combined action of the rollers 20 and 26 and 30 and 32. In
20 particular, it is preferred for the tacky fibrous nonwoven
elastic web 22 to be stretched to a length of from about
lS0 percent of the relaxed, unbiased length o. the tacky
fibrous nonwoven elastic web to about 700 or more percent
of the relaxed, unbiased length of the tacky fibrous
25 nonwoven web 22.
After the tacky fibrous nonwoven elastic web 22 has
been stretched it is carried by the second porous
collecting screen 36 to the nip or gap 42 between the
rotating roller 40 and the rotating nip roller 44. While
the web 22 is being carried by the second porous collecting
screen 36, the fibrous nonwoven gatherable web 50 is formed
directly on the upper surface of the tacky web 22 by either
a conventional meltblowing or spunbonding process or by any
other conventional method which may be utilized to form a
fibrous nonwoven gatherable web 50, such as, for example,
- 42 - ~3~6~cJ.~
conventional carding apparatus for forming a carded web.
As was the case with the prior discussed embodiments,
during formation of the fibrous nonwoven gatherable web 50
on the surface of the web 22 the tacky fibrous nonwoven
5 elastic web 22 is maintained at its stretched, biased
length by appropriately adjusting the peripheral surface
speed of the rollers 40 and 44 with respect to the
peripheral speed of the rollers 30 and 32. As a result of
the fact that the fibrous nonwoven elastic web 22 is, upon
10 its formation, tacky, an improved joining (as compared to
~oining of the two webs solely by entanglement) of the
tacky fibrous nonwoven elastic web 22 to the ribrous
nonwoven gatherable web 50 is achieved by adhesion of the
two webs 20 and 50 to each other during formation of the
fibrous nonwoven gatherable web 50 upon the top surface of
the fibrous nonwoven elastic web 22. This results in the
simultaneous formation and joining of the fibrous nonwoven
gatherable web 50 to the fibrous nonwoven elastic web 22.
While any tacky elastomeric material may be utilized in
forming the tacky fibrous nonwoven elastic web 22 of this
embodiment a preferred tacky elastomeric material is an
elastomeric A-B-A' block copolymer, where A and A' are each
thermoplastic polystyrene endblocks and where B is a
polyisoprene midblock. Tri-block copolymer materials of
this type are sometimes called S-I-S block copolymers and
may be obtained under the trade designation KRATON D, for
example, KRATON D 1107, KRATON D 1111, KRATON D 1112 and
KRATON D 1117, from the Shell Chemical Company.
Alternatively, a blend of a S-I-S block copolymer and poly
(alpha-methylstyrene) may be utilized.
The materials which may be utilized to form the
fibrous nonwoven gatherable web 50 of this embodiment may
include any of the materials which were stated above with
regard to the fibrous nonwoven gatherable web 50. That is,
the fibrous nonwoven gatherable web may be formed from any
.
_ 43 ~
gatherable material which may be formed into a fibrous
nonwoven gatherable web S0. For example, the fibrous
nonwoven gatherable web 50 could be formed from a blend of
a nonelastic material with an elastic material, one or more
5 nonelastic materials or a blend of one or more elastic
materials with two or more nonelastic materials.
Preferably, the fibrous nonwoven gatherable web S0 is
formed from a fiber-forming meltblowable or spunbondable
nonelastic gatherable material. However, the fibrous
10 nonwoven gatherable web 50 may be formed by depositing a
carded web on the surface of the fibrous nonwoven elastic
web 22 or by any other method which may be utilized to form
a fibrous nonwoven gatherable web 50 on the surface of the
web 22. Exemplary fiber-forming materials for use in
15 forming the fibrous nonwoven gatherable web S0 are
polyester materials, polyolefin materials or blends of one
or more polyester materials with one or more polyolefin
materials. An exemplary polyester fiber-forming material
is polyethylene terephthalate. An exemplary fiber-forming
20 polyolefin material is polypropylene. Preferred
polypropylene materials may be obtained from the Himont
Company under the trade designations PC 973 and PF 301.
In some situations it may be desirable to incorporate
discrete particles of one or more solid materials into one
25 or both of the webs 22 and 50 during formation of the webs
22 and 50. For example, it may be desirable to incorporate
one or more fibers such as cotton fibers, wood pulp fibers,
polyester fibers or other particulates into one or both of
the webs 22 and 50 during their formation. This mav be
accomplished by utilization of conventional coforming
apparatus in conjunction with the meltblowing or
spunbonding apparatus 12 and/or 48. Such coforming
apparatus is well known to those in the art and is
generally illustrated by the apparatus disclosed in U. S.
patent 4,100,432 to Anderson.
- 44 -
i 3 ~
After the fibrous nonwoven gatherable web 50 has been
formed upon and simultaneously joined to the upper surface
of the fibrous nonwoven tacky elastic web 22 the composite
nonwoven elastic web 52 is passed through the rollers 40
5 and 44 which, for the reasons stated above, need not be
heated or need not apply any excessive pressure to the
composite elastic web 52. Thereafter, the stretching and
biasing force on the tacky nonwoven elastic web 2Z is
released so as to relax and contract the composite nonwoven
10 elastic web 52. Because the fibrous nonwoven gatherable
web 50 is joined to the surface of the tacky fibrous
nonwoven elastic 22 while the tacky fibrous nonwoven
elastic web 22 is stretched, relaxing and contraction of
the composite nonwoven tacky web 52 results in the fibrous
15 nonwoven gatherable web 50 being carried with, contracted
and thereby gathered into a soft batted or matted web 50
which is joined to the surface of the elastic web 22.
EXAMPLE I
A fibrous nonwoven elastic web which had previously
20 been formed by meltblowing a blend of 60 percent, by
weight, of an A-B-A' block copolymer having polystyrene A
and A' end blocks and a poly (ethylene-butylene) "B"
midblock ~obtained from the Shell Chemical Company under
the trade designation KRATON GX 1657) and 40 percent, by
25 weight, of a polyethylene (obtained from U.S.I. Chemical
Company under the trade designation PE Na601) was provided
in rolled-up form.
The prior meltblowing of the fibrous nonwoven elastic
web was accomplished bv extruding the blend of materials
30 through a meltblowing die having thirty extrusion
capillaries per lineal inch of die tip. The capillaries
each had a diameter of about 0.0145 inches and a length of
about 0.113 inches. The blend was extruded through the
capillaries at a rate of about 0.52 grams per capillary per
35 minute at a temperature of about 595 degrees Fahrenheit.
i
- 45 - ~ 3~
The extrusion pressure exerted upon the blend was measured
as 73 pounds per square inch, gage in the capillaries. The
die tip configuration was adjusted so that it was recessed
about 0.090 inches inwardly from the plane of the external
5 surface of the air plates which form the forming air gaps
on either side of the capillaries. The air plates were
adjusted so that the two forming air gaps, one on each side
of the extrusion capillaries, formed air gaps of about
0.067 inches. Forming air for meltblowing the blend was
10 supplied to the air gaps at a temperature of about 600
degrees Fahrenheit and at a pressure of about 4 pounds per
square inch, gage. The meltblown fibers thus formed were
blown onto a forming screen which was approximately 15
inches from the die tip.
Later, the thus formed fibrous nonwoven elastic web
was unrolled and stretched by applying a tensioning, i.e.
biasing, force in the machine direction (MD) and a fibrous
nonwoven gatherable web was formed on the surface of the
elastic web by meltblowing polypropylene (obtained from the
20 Himont Company under the trade designation PC 973~ as
microfibers onto the upper surface of the fibrous nonwoven
elastic web while the fibrous nonwoven elastic web was
maintained at its stretched length.
Meltblowing of the fibrous nonwoven gatherable
25 polypropylene web was accomplished by extruding the
polypropylene through a meltblowing die having thirty
extrusion capillaries per lineal inch of die tip. The
capillaries each had a diameter of about 0.0145 inches and
a length of about 0.113 inches. The polypropylene was
30 extruded through the capillaries at a rate of about 0.38
grams per capillary per minute and at a temperature of
about 590 degrees Fahrenheit. The extrusion pressure
exerted upon the polypropylene was measured as 29 pounds
per square inch, gage in the capillaries. The die tip
configuration was adjusted so that it was about coplanar
--46 ~ & ~
with the plane of the external surface of the air plates
which form the forming air gaps on either side of the
capillaries. The air plates were adjusted so that the two
forming air gaps, one on each side of the extrusion
capillaries, formed air gaps of about 0.015 inches.
Forming air for meltblowing the polypropylene was supplied
to the air gaps at a temperature of about 600 degrees
Fahrenheit and at a pressure of about 4 pounds per square
inch, gage. The meltblown polypropylene microfibers thus
formed were meltblown directly onto the upper surface of
the fibrous nonwoven elastic web which was located
approximately sixteen inches from the die tip. Because of
these processing conditions the viscosity of the
polypropylene was about 20 poise and very fine diameter
polypropylene microfibers were formed on the surface of the
fibrous nonwoven elastic web.
Next, the tensioning, biasing force was reduced so as
to allow the fibrous nonwoven elastic web to retract and
for the meltblown polypropylene web to be gathered in the
machine direction. The composite nonwoven elastic web
which was formed had inter-layer integrity which,
apparently, resulted from the entanglement of the
individual fibers of the two webs with each other since the
webs were not otherwise joined by adhesives or
heat-bonding.
Samples of the fibrous nonwoven elastic web, itself,
and samples of the composite nonwoven elastic web were then
stretched by an Instron tensile tester model 1122 which
elongated each sample 100 percent, that is twice its
unstretched length, and then allowed the sample to return
to an unstretched condition. This procedure was then
repeated three (3) times and then each sample was elongated
to break. Each sample was two (2) inches wide by five (5)
inches long and the initial jaw separation on the tester
was set at one (1) inch. The samples were placed
_ 47 - 13~
lengthwise in the tester and elongated at a rate of five
(5) inches per minute. The machine direction data was
obtained from samples having a machine direction length of
five (5) inches and a transverse direction width of two (2)
5 inches. The transverse or cross machine direction
measurements were obtained from samples having a length of
five (5) inches in the transverse machine direction and a
width of two (2) inches in the machine direction. The data
which was obtained for the fibrous nonwoven elastic web is
10 tabulated in Table III below and the data which was
obtained for the composite elastic web is tabulated in
Table IV below.
TABLE III - FIBROUS NONWOVEN ELASTIC WE_
15 Machine Direction Measurement
Peak
Stretch Peak TEA* Peak Load Elongation
Stretched Number ~Inch-Pounds) (Pounds) (Inches)
100~ #1 Avg** 1,94 .9144.9968
Std Dev*** .40 .197 .0009
100% #2 Avg 1.38 .9303.9870
: 25 Std Dev.29 .188.0006
100% #3 Avg 1.30 .9074.9873
Std Dev.28 .181.0008
100~ #4 Avg 1.24 .8903.9873
Std Dev.25 .178.0005
To break #5 Avg 10.08 1.44883.1394
Std Dev3.14 .2982.5181
_ 48
Transverse Direction Measurements
Peak
Stretch Peak TEA* PeakLoad
Elongation
Stretched Number (Inch-Pounds) ~Pounds) (Inches)
100% #1 Avg** 1.50 .7811 .9974
Std Dev*** .12 .0593 .0017
10 100% #2 Avg 1.08 .7459 .9866
Std Dev.08 .0568 .0009
100~ #3 Avg 1.01 .7261 .9870
Std Dev.07 .0542 .0007
100% #4 Avg .96 .7107 .9863
Std Dev.07 .0533 .0008
To break #5 Av~ 10.41 1.295 3.644
Std Dev1.24 .095 .268
_ 49 -
TABLE IV - COMPOSITE NONWOVEN ELASTIC WEB
Machine Direction Measurement
Peak
Stretch Peak TEA* Peak Load
Elongation
Stretched Number (Inch-Pounds) (Pounds) (Inches)
100% #1 Avg**2.04 1.2606 .9976
Std Dev*** .17 .0793 .0009
100% #2 Avg 1.37 1.2056 .9866
Std Dev.12 .0810 .0012
100% #3 Avg 1.29 1.1798 .9874
Std Dev.11 .0773 .0011
100~ #4 Avg 1.24 1.161 .9876
Std Dev.11 .0792 .0012
20 To break #5 Avg 9.65 2.5134 2.281
Std Dev1.87 .1659 .2243
t
~ ~ ~ ~ 3
Transverse Direction Measurements
Peak
Stretch Peak TEA* Peak Load
Elongation
Stretched Number ~Inch-Pounds) (Pounds) (Inches)
100~#1 Avg** 2.28 1.277.9009
Std Dev*** .48 .1593.0900
10 100%#2 Avg .70 1.077.~853
Std Dev .09 .2206.0002
100~#3 Avg .58 1.022.9874
Std Dev .08 .2139.0013
100%#4 Avg .53 .9846.9873
Std Dev .08 .2148.0012
To break#5 Avg*~** .88 1.1591.0865
Std Dev .21 .2220.0120
Tables III and IV disclose the total energy absorbed,
in inch-pounds, the peak (maximum) load, in pounds,
encountered during each repetition and the amount of each
peak (maximum) elongation, in inches in stretching the
samples in each repetition of the 100 percent elongation
procedure and in elongating the sample to break. It can be
seen that the total energy required to stretch the sample
100 percent in the machine direction at the peak load
encountered in such stretching is about the same for the
fibrous nonwoven elastic web and the composite nonwoven
elastic web. This is to be expected since the meltblown
polypropylene web is gathered in the machine direction and
generally requires little energy to be elongated in the
machine direction. Upon elongation to break, the peak load
for the composite nonwoven elastic web increased over 70
percent indicating that the meltblown polypropylene web was
contributing strength to the strength of the composite
5 nonwoven elastic web.
In the transverse machine direction tTD), where the
meltblown polypropylene is not gathered, the peak load for
the initial stretch of the composite nonwoven elastic web
is over 60 percent greater than the peak load for the
10 fibrous nonwoven elastic web. This indicates that the
meltblown polypropylene web contributes to the strength of
the composite nonwoven elastic web even at low elongations.
Additionally, the peak total energy absorbed for the
composite nonwoven elastic web represents a 50 percent
lS increase over that of the fibrous nonwoven elastic web for
the first stretch and then actually decreases on subsequent
stretchings. This indicates that the meltblown
polypropylene web was substantially ruptured (torn) during
the first stretch and is no longer contributing to total
20 energy of the composite web.
It was observed that the "breathability" of the
composite nonwoven elastic web was still good as compared
to the "breathability" of the fibrous nonwoven elastic web.
Additionally, because of the thin web of meltblown
25 polypropylene microfibers which have been applied to the
surface of the fibrous nonwoven elastic web the composite
web was more water repellent due to the water repellent
characteristics of polypropylene. Moreover, application of
the thin web of meltblown microfibers to the surface of the
30 meltblown nonwoven elastic web changed the rubbery feel of
the fibrous nonwoven elastic web to a soft, desirable
feeling.
, ~ .
-- - 52 -
EXAMPLE II
A fibrous nonwoven web which had previously been
formed by meltblowing a blend of sixty percent (60%), bv
weight, of an A-B-A' block copolymer having polystyrene "A"
5 and "A'" endblocks and a poly (ethylene-butylene) "B"
midblock (obtained from the Shell Chemical Company under
the trade designation KRATON GX 1657) and forty percent
(40%) by weight, of a polyethylene (obtained from U~S.I.
under the trade designation PE Na 601) was provided in
10 rolled-up form.
The prior meltblowing of the fibrous nonwoven elastic
web was accomplished by extruding the blend of materials
through a meltblowing die having thirty extrusion
capillaries per lineal inch of die tip. The capillaries
15 had a diameter of about 0.0145 inches and a length of about
0.113 inches. The blend was extruded through the
capillaries at a rate of about 0.50 grams per capillary per
minute at a temperature of about 570 degrees Fahrenheit.
The extrusion pressure exerted upon the blend was measured
as 144 pounds per square inch, gage in the capillaries.
However, it is presently believed that this measurement was
inaccurate due to a faulty pressure probe. The die tip
configuration was adjusted so that it was recessed about
0.110 inches inwardly from the plane o. the external
surface of the air plates which form the forming air gaps
on either side of the capillaries. The air plates were
adjusted so that the two forming air gaps, one on each side
of the extrusion capillaries, formed gaps of about 0.110
inches. Forming air for meltblowing the blend was supplied
to the air gaps at a temperature of about 614 degrees
Fahrenheit and at a pressure of about 4 pounds per square
inch, gage. The meltblown microfibers were formed onto a
forming screen which is believed to have been about 16
inches from the die tip. ~owever, measurement of this
distance was not actually taken.
- 53 -
Later, the thus formed fibrous nonwoven elastic web
was unrolled and stretched by applying a tensioning, i.e.
biasing, force in the machine direction (MD) and a fibrous
nonwoven gatherable web was formed on the surface of the
5 elastic web by meltblowing polypropylene (obtained from the
Himot Company under the trade designation PF 301) as
microfibers on to the upper surface of the fibrous nonwoven
elastic web while the fibrous nonwoven elastic web was
maintained at its stretched length.
Meltblowing of the fibrous nonwoven polypropylene
gatherable web was accomplished by extruding the
polypropylene through a meltblowing die having thirty
extrusion capillaries per lineal inch of die tip. The
capillaries each had a diameter of about 0.0145 inches and
a length of about 0.113 inches. The polypropylene was
extruded through the capillaries at a rate of about 0.75
grams per capillary per minute at a temperature of about
590 degree~ Fahrenheit. The extrusion pressure exerted
upon the polypropylene was measured as about 186 pounds per
square inch, gage in the capillaries. The die tip
configuration was adjusted so that it extended about 0.010
inches beyond the plane of the external surface of the a r
plates which form the forming air gaps on either side of
the capillaries. The air plates were adjusted so that the
two forming air gaps, one on each side of the extrusion
capillaries, formed air gaps of about 0.018 inches.
Forming air for meltblowing the polypropylene was supplied
to the air gaps at a temperature of about 600 degrees
Fahrenheit and at a pressure of about 2 pounds per square
inch, gage. The distance between the die tip and the
surface of the fibrous nonwoven elastic web upon which the
gatherable polypropylene web was formed was about 10
inches. Because of these processing conditions, the
viscosity of the polypropylene was about 124 poise and
larger diameter meltblown polypropylene microfibers were
formed on the surface of the stretched fibrous nonwoven
elastic web.
Next, the tensioning, biasing force was reduced so as
to allow the fibrous nonwoven elastic web to contract and
for the meltblown polypropylene web to be gathered in the
machine direction. The composite nonwoven elastic web
which was formed had inter-layer integrity which,
apparently, resulted from the entanglement of the
individual fibers of the two webs with each other since the
webs were not otherwise joined by adhesives or
heat-bonding.
Samples of this fibrous nonwoven elastic web, itsel_,
and samples of the composite nonwoven elastic web were then
stretched by an Instron tensile tester model 1122 which
elongated each sample 100 percent, that is to twice its
unstretched length, and then allowed the sample to return
to an unstretched condition. This procedure was then
repeated three (3~ times and then each sample was elongated
to break. Each sample was two (2) inches wide by five (5)
inches long and the initial jaw separation on the tester
was set at one (1) inch. The samples were placed
lengthwise in the tester and elongated at a rate of five
(5) inches per minute. ~he machine direction data was
obtained from samples having a machine direction length of
five (5) inches and a transverse direction width of two (2)
inches. The transverse or cross machine direction
measurements were obtained from samples having a length of
five (5) inches in the transverse direction and a width of
two (2) inches in the machine direction. The data which
was obtained for the composite nonwoven elastic web formed
by example 2 is tabulated in Table V below.
Table V, below, illustrates that the, 100 percent,
elongations required little energy or load in the machine
direction while the total energy absorbed increased about
seven (7) times and the peak load increased about three (3)
- 55 ~
times when the composite was stretched to break in the
machine direction. In the transverse direction, where the
meltblown was not gathered, the initial, 100 percent
elongation absorbed about three and one half (3.5) times as
much total energy as the total energy absorbed to break and
about four (4) to five (5) times as much energy as any of
the subsequent, 100 percent stretchings. Further, the peak
load for the first stretching in the transverse direction
was about 40 percent higher than the peak load for an~
subsequent stretching in the transverse direction,
including stretching to break.
TABLE V - COMPOSITE NONWOVEN ELASTIC WEB
Machine Direction Measurement
Peak
Stretch Peak TEA* Peak Load
Elongation
Stretched Number (Inch-Pounds) (Pounds) (Inches)
100% #1 Avg** .95 .7708 .9978
Std Dev*** .28 .1742 .0016
100% #2 Avg .75 .7388 .9870
Std Dev .23 .1675 .0015
100% #3 Avg .71 .7204 .9864
Std Dev .22 .1636 .0010
100% #4 Avg .68 .7083 .9860
Std Dev .22 .1631 .0011
At break #5 Avg 5.75 1.974 2.023
Std Dev1.36 .2437 .2037
- 56 ~
Transverse Direction Measurements
Peak
StretchPeak TEA* Peak Load
Elongation
Stretched Number (Inch-Pounds) (Pounds) (Inches)
100% #1 Avg**3.08 2.042 .7529
Std Dev*** .77 .2333 .0913
10 100~ #2 Avg .83 1.422 .9876
Std Dev.08 .3076 .0010
100% #3 Avg .72 1.3403 .9870
Std Dev.08 .2905 .0009
100~ #4 Avg .65 1.281 .9878
Std Dev.07 .2740 .0012
At break #5 Avg .85 1.322 1.052
Std Dev.07 .2500 .0446
- 57 -
NOTES FOR TABLES III, IV AND V
~ = Total Energy Absorbed
** = Average
*** = Standard Deviation
**** = Average of two measurements. The third measurement
obtained values of 2.376 for Peak TEA, 1.232 for
Peak
Load and 5.609 Peak Elongation. These values are
believed to be incorrect since they are so abberant5
from the other values obtained by the other two
measurements.
Unless otherwise specifically noted the data reported
in tables III, IV and V (above) represent an average value
which was obtained by taking five (5) individual
measurements for each machine direction measurement and
three (3) individual measurements for each transverse
direction measurement.
The basis weight of the mel.blown fibrous nonwoven
elastic web utilized for example I was 67.3 grams per
square meter and the basis weight of the meltblown
gatherabie polypropylene web which was formed on the
surface of the fibrous nonwoven elastic web of example I
was measured as being 12.2 grams per square meter. The
degree of relaxation or contractlon of the composite
nonwoven elastic web of example I was about 54 percent.
~ - 58 -
~ 3 ~
This degree of relaxation of the composite was determined
by taking a sample of the composite having a relaxed length
of about 4.0 inches in the machine direction and elongating
the sample, in the machine direction, until resistance to
the elongation by the gathered polypropylene web was
encountered. That is, just until the gathers in the
polypropylene web were removed. At this point the 4.0 inch
sample had been stretched to about 8.75 inches in the
machine direction.
The basis weight of the fibrous nonwoven elastic web
utilized in example II was about 66.2 grams per square
meter and the basis weight of the fibrous nonwoven
gatherable polypropylene web meltblown onto the surface of
1 the elastic web in example II was measured at about 21.4
grams per square meter. The degree of relaxation or
contracting of the composite nonwoven elastic web of
example II was determined to be about 42 percent. This
degree of relaxation was determined by tak-ng a sample of
the composite having a relaxed length of about 12 inches in
the machine direction and elongating the sample, in the
machine direction, until resistance to the elongation bv
the gathered polypropylene web was encountered. That is,
just until the gathers in the polypropylene web were
removed. At this point the 12 inch sample had been
stretched to about 20.7 inches.
- Upon observation of the relaxed, contracted composite
nonwoven elastic web it was seen that the meltblown
polypropylene web presented a creped, gathered, appearance
with the lines of creping or gathering being generally
transverse to the direction in which the fibrous nonwoven
elastic web was stretched during formation of the meltblown
. . .
~ 59 - 13~
polypropylene web on the surface of the fibrous nonwoven
elastic web (i.e. transverse to the machine direction).
Interestingly, it was also observed that the fibrous
nonwoven elastic web of the contracted and relaxed
composite nonwoven elastic web exhibited lines of creping
or gathering which were generally parallel to the direction
of stretching of the fibrous nonwoven elastic web during
formation of the meltblown polypropylene included on the
surface thereof (i.e. the lines of creping or gathering of
the fibrous nonwoven elastic web were generally parallel to
the machine direction). Accordingly, the two webbed
composite included webs having transposed lines of
gathering or creping which generally crossed each other
generally at right angles. Formation of the lines of
gathering or creping in the fibrous nonwoven gatherable
polypropylene web would be expected in view of the
gathering of that web in the machine direction. However,
formation of lines of gathering or creping in the fibrous
nonwoven elastic web and, in particular, formation of lines
of gathering or creping in the fibrous nonwoven elastic
which are generally at right angles with the lines
gathering or creping of the fibrous nonwoven gatherable
polypropylene webs was unexpected.
A portion of the composite nonwoven elastic web having
an approximate machine direction (MD) length of about S and
7/8 inches and an approximate transverse direction (TD)
dimension of about 4-1/2 inches was cut off of the
composite nonwoven elastic web and the gathered fibrous
nonwoven meltblown polypropylene web was separated from the
fibrous nonwoven elastic web. After the gathered fibrous
nonwoven meltblown polypropylene web had been separated
- 60 -
1 3 ~
from the fibrous nonwoven elastic web it was observed that
the gathered fibrous nonwoven meltblown polypropylene web
assumed a relaxed machine direction dimension of about 7
inches and retained its cross-direction dimension of about
4-1/2 inches. Importantly, the fibrous nonwoven gathered
web substantially retained its creped or gathered
configuration in the machine direction. Moreover, the
separated gathered polypropylene web could be elongated in
the machine direction upon application of a tensioning and
biasing force in the machine direction and would, upon
removal of the tensioning and biasing force, return, that
is, contract, substantially to its relaxed and unbiased and
untensioned gathered dimension (7 inches by 4-1/2 inches).
For example, upon elongation of the 7 inch by 4-1/2 inch
sample of gathered fibrous nonwoven polypropylene web in
the machine direction (MD) to an extent where the gathers
had been substantially straightened out, the sample was
measured and found to have a machine direction (MD) length
- of about 9-1/2 inches and a transverse direction (TD)
dimension of about 4-1/2 inches. When the elongating,
biasing force was removed from the sample it returned to a
machine direction (MD) dimension of just over seven inches
and a transverse direction (TD) dimension of about 4-1/2
inches within one minute. Upon repetition of the
elongation procedure, the sample assumed a machine
direction (MD) dimension of about 9-1/2 inches and a
transverse direction (TD) dimension of about 4-1/2 inches.
Upon termination of the second elongating and stretching
force, the polypropylene web assumed a machine direction
(MD) dimension of about 7-1/16 inches and a transverse
direction (TD) dimension of about 4-1/2 inches within one
._
minute. This result was unexpected since the PF 301
polypropylene was not believed to possess elastic
properties.
Other variations of the present inventive process and
the product formed by the process are possible. For
example, two or more fibrous nonwoven gatherable webs 50
could be bonded one on top of another in stacked
configuration to give the fibrous nonwoven gatherable web
50 additional thickness. Additionally, a fibrous nonwoven
gatherable web 50 could be joined, either separably or
otherwise as discussed herein, to both surfaces of the
fibrous nonwoven elastic web 22 to form a composite
nonwoven elastic web having the following three web
sequence: fibrous nonwoven gatherable web/fibrous nonwoven
elastic web/fibrous nonwoven gatherable web.
The three web sequence where the fibrous nonwoven
elastic web is sandwiched between two fibrous nonwoven
gatherable webs is especially preferred where the fibrous
nonwoven elastic web 22 is formed from a tacky elastomeric
material as described above bPcause sandwiching of the
tacky elastic web 22 between the two webs prevents the
tacky web 22 from adhering to other portions of the web 52
upon rolling-up of the web 52 for storage. The three web
material could be formed by the process which is
illustrated schematically in figure 3. This process is
identical to the process schematically illustrated in
figure 1 until the two layered composite nonwoven elastic
web 52 exits rol'ers 40 and 42. Thereafter, instead of
proceding to the nip or gap 54 between the roller 56 and
58, the composite web 52 passes through the nip or gap 78
between a rotating roller 80 and a rotating nip roller 82.
62 -
The composite web 52 is then carried by a third porous
collecting screen 84 to the nip or gap 86 between a
rotating nip roller 88 and a rotating roller 74. The
porous collecting screen 68 moves about and is driven by
S the rollers 80 and 84 in the direction indicated by the
arrows 92 in figure 3. ~otation of the rollers 80, 82, 88
and 90 is adjusted so that the peripheral surface speed of
the rollers 80, 82, 88 and 90 is the same as the peripheral
surface speed of the rollers 40 and 44. Accordingly, the
fibrous nonwoven elastic web 22 is maintained at its
stretched, biased length as it is carried by the porous
collecting screen 84.
While the composite nonwoven elastic web S2 is being
carried by the porous collecting screen 84, a conventional
meltblowing die 94 (if desired, a conventional spunbonding
die or carding apparatus can be utilized) forms a second
nonwoven gatherable web 96 on the other surface of the
stretched fibrous nonwoven elastic web 22 by meltblowing
microfibers 98 directly onto the stretched upper surface of
the nonwoven elastic web 22. The materials which may be
utilized to form the second gatherable web 96 may include
any of the materials which were stated above as being
utilizable to form the first fibrous nonwoven gatherable
web 50. Particulate materials may also be incorporated
within the web 96 as was stated abcve with regard to the
webs 22 and 50. Thereafter, the second fibrous nonwoven
gatherable web 96 may be heat-bonded to the fibrous
nonwoven elastic web 22 by the action of rollers 88 and 90
which are essentially equivalent to rollers 40, 44. The
heat-bonding of the second fibrous nonwoven gatherable web
96 to the fibrous nonwoven elastic web 22 can be carried
- 63 ~
out within ~he same temperature ranges and within the same
pressure ranges as were stated above with regard to the
heat-bonding of the first fibrous nonwoven gatherable web
50 to the fibrous nonwoven elastic web 22. If desired,
conventional sonic bonding techniques (not shown) may be
substituted for the heat-bonding step. Alternatively, if
the fibrous nonwoven elastic web 22 is tac~y, as described
above, heat bonding of the fibrous nonwoven gatherable web
96 to the fibrous nonwoven elastic web will not be required
since the second fibrous nonwoven gatherable web 96 will be
simultaneously formed upon and joined to the surface of the
fibrous nonwoven elastic web 22.
In another embodiment, if separation of the gatherable
web 96 from the elastic web 22 will be effected at a later
step, the second fibrous nonwoven gatherable web 96 may be
separably joined to the surface of the fibrous nonwoven
elastic web 22 by entanglement of the individual fibers of
the web 96 with the individual fibers of the web 22 during
formation of the web 96 on the surface of the web 22. In
this embodiment the fibrous nonwoven gatherable web 96 is
simultaneously formed upon and joined to the fibrous
nonwoven elastic web 22.
In any of these embodiments improved joining of the
webs S0 and 96 to the web 22 can be effected by application
of a coating of an adhesive material to the surface of the
elastic web 22 prior to formation of the webs S0 and 96
upon the stretched surface of the web 22. Application of
such an adhesive coating to the surface of web 22 may be
conventionally readily effected by the nip rollers 32 and
82. For example, the adhesive material could be
conventionally applied to the surface of the rollers 32 and
- - 64 -
13~ ~$~
82 so that the rollers 32 and 82 would transfer the
adhesive onto the surface of the web 22 as the web 22
passes through the nips 28 and 78. Alternatively, the
adhesive may be applied onto the surface of the web 22 in a
configuration of spots.
After joining of the gatherable web 96 to the elastic
web 22 has been achieved, the biasing force on the web 22
is relaxed by passing the three webbed composite 100
through the nip or gap 102 between two rotating nip rollers
104 and 106. Rotation of the rollers 104 and 106 is
adiusted so that the peripheral surface speed of the
rollers 104 and 106 allows the composite web 100 to relax
and, as a result of its elastic properties, to contract to
its relaxed, unbiased length. The relaxing and contracting
of the web 100 to its relaxed, unbiased length results in
both of the fibrous nonwoven gatherable webs 50 and 96
being gathered by the relaxing and contracting of the
fibrous nonwoven elastic web 22. Lastly, the composite web
100 can be rolled up and stored as is illustrated at 108.
Since the tacky elastic web 22 is sandwiched between the
webs 50 and 96 it will not adhere to other portions of the
composite web 100 during storage. This material may be
utilized to form a variety of products, such as, for
example, diaper products.
It should be recognized that the three webbed
composite 100 discussed above with respect to a tacky
nonwoven elastic web 22 could be formed without using a
tacky material to form the web 22. In this case, the other
methods of joining, for example, fibrous entanglement,
heat-bonding or sonic bonding, the web 96 to the web 22
would have to be utilized.
- 65 -
~ 3 ~
Another variation of the present invention would
involve gathering of one or more of the gatherable webs 50
and 96 in the transverse machine direction (TD) as opposed
to the machine direction (MD) as illustrated in the
figures. If gathering of the gatherable webs 50 and/or 96
in the transverse machine direction (TD) is desired,
additional arrangements for stretching and allowing
contraction of the elastic web 22 in the transverse
direction would be utilized. For example, Figure 4
illustrates another embodiment of the present invention
which avoids the requirement of forming the gathered
nonwoven elastic web 50 of the embodiment of Figure l on
the stretched, extended surface of the nonwoven elastic web
22. In the embodiment of Figure 4 the gathered nonwoven
elastic web 50 is formed directly on the surface of a
porous forming screen 110 which, itself, is extendable and
retractable in the machine direction of movement as is
indicated by the arrow 112. For example, the extendable
and retractable porous collecting screen 110 could be
formed from a continuous web of the nonwoven elastic web
22. Alternatively, the extendable and retractable porous
collecting screen 110 could be formed from a wire mesh
screen 114 which is generally illustrated in Figure 5. The
wire mesh screen 114 could be formed from a plurality of
substantially parallel springs 116 coiled and extending in
the machine direction (MD) with the springs 116 being
connected to each other in the transverse machine direction
(TD) by a plurality of fine, generally parallel wires 118
: extending in the transverse machine direction (TD). The
transverse direction wires 118 may be arranged very closely
to each other so that, when the wire mesh screen 114 is in
- 66 -
1 3 ~
an unbiased, retracted or contracted configuration, the
transverse direction wires 118 contact each other. UF~n
application of a tensioning or biasing force in the machine
direction, the coiled springs 116 will extend, that is,
stretch, in the machine direction and the fine transverse
direction wires 118 will separate from each other to form
the porous collecting surface 110. This biased, stretched,
extended configuration is generally illustrated in
Figure 6.
Alternatively, the wire mesh screen 114 could be
formed by a plurality of substantially parallel springs
coiled and extending in the transverse machine direction
(TD) with the springs being connected to each other in the
machine direction (MD) by a plurality of fine, generally
parallel wires extending in the machine direction (MD).
This config~ration would be illustrated upon rotating
Figures 5 and 6 90 and results in a configuration by which
the gatherable web 96 could be gathered in the transverse
machine direction (TD) as opposed to the machine direction
(MD) as is illustrated in the figures. If gathering of the
gatherable web 96 in the transverse direction is desired
additional conventional arrangements ~not shown) for
extending and contracting the screen 114 in the transverse
direction would replace the arrangement illustrated in the
figures for extending and contracting the screen 114 in the
machine direction (MD~.
Returning to Figure 4 it can be seen that movement of
the extendable and retractable porous collecting screen 110
in the machine direction 112 is accomplished by the screen
110 being driven by rollers 120 and 122 which are, in turn,
driven by conventional drive mechanism (not shown). Also
1 3 ~
not shown for purposes of clarity is a conventional vacuum
box located between the rollers 120 and 122 and beneath the
lower surface of the upper portion of the screen 110. The
vacuum box assists in the retention of the web 22 on the
upper surface of the screen 110. The extendable and
contractable porous collecting screen 110 passes through
the nip 124 between a pair of rotating nip rollers 126 and
128. The nip 124 is adjusted so that the rollers 126 and
128 firmly engage the extendable and retractable or
contractable porous collecting screen 110 without adversely
affecting the screen 110. Rotation of the rollers 126 and
128 is adjusted so that the peripheral surface speed of the
rollers 126 and 128 is substantially the same as the
peripheral surface speed of the rollers 120 and 122. The
extendable and retractable or contractable porous
collecting screen 110 also passes through the nip 130
between another pair of rotating nip rollers 132 and 134
with the nip 130 being adjusted so that the rollers 132 and
134 firmly engage the porous collecting screen 110 without
adversely affecting the porous collecting screen 110. The
rotation of the rollers 132 and 134 is adjusted so that the
peripheral surface speed of the rollers 132 and 134 is
greater than the peripheral surface speed of the rollers
120 and 122. As a result of the increase in the peripheral
surface speed of the rollers 132 and 134 with respect to
the peripheral surface speed of the rollers 120 and 122 a
longitudinal or machine direction (MD) biasing and
extending force is placed on the extendable and
contractable porous collecting screen 110 and the screen
110 is extended to an extended, biased length in the
longitudinal direction in the area 136. The degree of
- 68 -
extension of the porous collecting screen 110 which occurs
in the area 136 between the rollers 126 and 128 and the
rollers 132 and 134 may be varied, for example, by varying
the peripheral surface speed of the rollers 132 and 134
5 with respect to the peripheral surface speed of the rollers
126 and 128. For example, if the peripheral surface speed
of the rollers 132 and 134 is about twice that of the
rollers 126 and 128, the extendable and retractable porous
10 collecting screen 110 will be extended to an extended,
biased length of substantially about twice, that is, about
200 percent, of its retracted, unbiased length. It is
preferred for the extendible and retractable porous
collecting screen 110 to be extended, in the area 136, to a
length which is at least about 125 percent of its
contracted, unbiased and unextended length. In particular,
it is preferred for the screen 110 to be extended to an
extended length, in the area 136, of from at least about
150 percent of its retracted, unbiased and unextended
length. More particularly, it is preferred for the porous
collecting surface 110 to be extended to an extended length
of from at least about 150 percent of the retracted,
unbiased and unextended length of the porous collecting
surface 110 to about 700 or more percent of the retracted,
unbiased and unextended length of the porous collecting
surface 110.
~ hile the extendable and retractable porous collecting
screen 110 is in the extended configuration in the area
136, meltblown microfibers 138, which are formed by a
conventional meltblowing die 140 are meltblown onto the
extended surface of the porous collecting screen 110. As
the meltblown microfibers 138 are deposited upon the
... ~ . .. .... . . . . .
~ - 69 -
~ 3 ~
extended porous collecting screen 110 they entangle and
cohere to form a cohesive fibrous nonwoven gatherable web
96. The entangled cohesive fibrous nonwoven gatherable web
96 is carried by the porous collecting screen 110 through
the nip 130 and on to a nip 142 formed between the rotating
roller 120 and a rotating nip roller 144. The peripheral
surface speed of the rotating nip roller 144 is adjusted so
that it is substantially the same as the peripheral surface
speed of the rotating roller 120 and the rollers 122 and
126 and 128. Because the peripheral surface speed of the
rollers 144 and 120 is substantially the same as the
peripheral surface speed of the rollers 122 and 126 and 128
the extending force is removed from the extended porous
collecting screen 110 and the screen 110 is retracted, that
is allowed to contract, as a result of its contractable
properties, to its contracted, unbiased length. The
relaxing and contracting of the porous collecting screen
110 to its contracted, unbiased length results in the
fibrous nonwoven gatherable web 96, which was formed on the
surface of the screen 110 while the screen 110 was being
maintained in its extended configuration, being carried
along with, and retracted and thus gathered upon the upper
surface of the retracting porous collecting screen 110.
The gathering of the fibrous nonwoven gatherable web 96,
accordingly, occurs in the area 146 between the pairs of
rollers 132 and 134 and 120 and 144.
After retracting and contracting Oc the porous
collecting screen 110, the fibrous nonwoven gatherable web
96 may be rolled up on a supply roller 148 for storage and
shipment. For the reasons stated earlier the rate of
rotation of the supply roller 148 should be controlled so
... ~..... .. .
- 70 -
that the gathered fibrous nonwoven 96 i5 stored in
substantially an untensioned state. This may be
accomplished by adjusting the rate of rotation of the
roller 148 so that the peripheral surface speed of the
roller 148 is substantially equal to or just slightly
greater than the peripheral surface speed of the rollers
120 and 144.
In the event that a three layer composite web is
formed, as illustrated in Figure 3, it may be desirable to
separate the two outer gathered nonwoven webs from the
elastic nonwoven web. If this is the case the fibrous
nonwoven gathered webs 50 and 96 are separated from the
fibrous nonwoven elastic web 22 by passing the web 50
through the nip 150 between two rotating nip rollers 152
and 154 and passing the web 96 through the nip 156 between
two rotating nip rollers 158 and 160. The webs 50 and 96
are then wound-up for storage and later used on their
respective storage rolls 162 and 164. For the reasons
stated earlier, care should be exercised in winding-up the
gathered nonwoven webs S0 and 96 to assure that the webs 50
and 96 are stored in an untensioned or substantially
untensioned fashion on the rolls 162 and 164. This can be
effected by rotating the rolls 162 and 164 so that the
p2ripheral surface speed of the roller 162 is equal to or
just slightly greater than the peripheral surface speed of
the rolls 152 and 154 and that the peripheral surface speed
of the roller 164 is equal to or just slightly greater than
the peripheral surface speed of the rollers 158 ard 160.
After separation of the webs 50 and 96 the fibrous nonwoven
elastic web 22 passes through the nip 166 between the two
- 71 -
~ 3 ~
rotating nip rollers 168 and 170 and is wound up on a
storage roller 172.
While the specific examples discussed herein have
usually stated that the fibrous nonwoven gatherable webs 50
5 and 96 were formed by utilization of a conventional
meltblowing die and meltblowing processes, conventional
spunbonding dies and spunbonding processes may be
substituted for the meltblowing dies and processes and the
lO scope of the present invention is intended to include
materials formed by the substitution of spunbonding dies
and processes or any other apparatus and process for
forming a nonwoven gatherable web for the meltblowing dies
and processes 48 and 94. In the event that spunbonding
15 dies and processes were substituted for either or both of
the meltblowing dies or processes 48 and 94 joining of the
gatherable web(s) 50 and, if applicable 96, to the fibrous
nonwoven elastic web 22 should be effected, as stated
20 above, by inter-web adhesion (if a tacky elastomeric
material is utilized to form the web 22), by heat-bonding
or sonic bonding and/or by application of an adhesive to
the surface(s) of the web 22 prior to formation of the
web(s) 50 and 96 thereon. These methods of joining should
25 be utilized with spunbonded gatherable web since the fibers
of spunbonded gatherable webs do not readily entangle with
the fibers of the web 22. If the joining of one or more of
the webs 50 and 96 to the web 22 is to be effected by
30 heat-bonding (whether the webs 50 and 96 are spun bonded,
meltblown or formed by other processes) care should be
taken to allow the web 22 to relax and contract to
substantially an untensioned, unbiased condition or
configuration as soon as is practical after the
heat-bonding step has occurred because it is believed that
the nonwoven elastic web 22 will lose its elasticity if it
is maintained above its softening for any significant
period of time. This loss of elasticity may result from
the cooling elastic web 22 "setting" while in the stretched
configuration if it is maintained in the stretched
configuration for a significant period of time after
heat-bonding.
It is to be understood that variations and
modifications of the present invention may be made without
departing from the scope of the invention. It is also to
be understood that the scope of the present invention is
not to be interpreted as limited to the specific
embodiments disclosed herein, but only in accordance with
the appended claims when read in light of the foregoing
disclosure.
