Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1 334376
The present invention relates to an
elastomeric composite material, and more particularly to
a material which includes at least one nonwoven sheet of
pressure-sensitive adhesive elastomer and at least one
gatherable material bonded to the nonwoven sheet.
The present application is a division of
co-pending Canadian Patent Application Serial No.
549,224, filed October 14, 1987.
For some time those in the art have been
attempting to form elastomeric resins into fibrous
nonwoven elastomeric webs. For example, attempts have
been made to form fibrous nonwoven elastomeric webs
utilizing KRATON~G elastomeric resins. KRATON~ is a
trademark of Shell Chemical Company of Houston, Texas,
for various polystyrene/poly(ethylene-butylene)/
polystyrene elastomeric block copolymers. In U.S.
Patent No. 4,323,534, it is disclosed that the KRATON~G
rubber resins are too viscous to be extruded alone
without substantial melt fracture of the product; and
that various of the KRATON~G resins should be blended
with a fatty chemical such as stearic acid prior to
extrusion and, e.g., meltblown, so as to overcome the
viscosity problem. However, physical properties of the
product obtained by this process, for example, a
nonwoven mat of meltblown fibers, were apparently
unsatisfactory because, after formation of the nonwoven
web, substantially all the fatty chemical is leached out
of the nonwoven web of extruded microfibers by
1 334376
soaking the web in alcohols having a good ability to solubil-
ize the fatty chemical utilized.
In order to overcome, e.g., the above-stated viscosity
problems, it has been proposed to form elastomeric block
copolymer materials into nonwoven elastomeric products by
providing extrudable elastomeric compositions which are
blends of (1) an A-B-A' block copolymer, where "A" and "A"'
are the same or different and are each a thermoplastic
polymer endblock which includes a styrenic moiety such as a
poly (vinyl arene) and where "B" is an elastomeric poly
(ethylene-butylene) midblock, with (2) a polyolefin which,
when blended with the ~-B-A' block copolymer and
subjected to appropriate elevated pressure and elevated
temperature conditions, is extrudable in blended form, with
the A-B-A' block copolymer. The presence of the polyolefin
in the blend serves to reduce the viscosity of the compo-
sition as compared to the viscosity of the pure A-B-A' block
copolymer and thus enhances the extrudability of the composi-
tion. Such blend must be a composition which, after ex-
trusion, solidifies to form elastomeric products.
Thus, utilizing a blend of the block copolymer and thepolyolefin, the composition can be extruded at conventional
temperatures and pressures, and, in particular, can be
extruded at temperatures lower than temperatures at which the
block copolymers degrade or burn. The extrudable composition
may be formed into a variety of products such as, for
example, fibrous nonwoven elastomeric webs preferably having
microfibers with an average diameter not greater than about
100 microns, and preferably having an average basis weight
of not more than about 300 grams per square meter, for
example, an average basis weight of from about 5 grams per
square meter to about 100 grams or more per square meter. In
connection with this extrudable composition, note Canadian
Patent Application Serial No. 514,960, filed July 30, 1986,
of Tony J. Wisneski and Michael T. Morman, for "Polyolefin-
Containing Extrudable Compositions and Methods for Their
3 1 334376
Formation Into Elastomeric Products".
Moreover, uses for nonwoven elastomeric webs, either by
themselves or as part of a cornposite laminate, are being
investigated. Thus, composite fabrics comprising at least
one layer of nonwoven textile fabric mechanically secured to
an elastomeric layer are known. For example, U.S. Patent No.
4,446,189 discloses textile laminate materials comprising an
inner layer of elastic material, such as a polyurethane foam
of a thickness of about 0.025 inches, needle punched at a
plurality of locations to a nonwoven textile fabric layer.
The needle punched superposed layers are then stretched
within the elastic limits of the elastic layer to permanently
stretch the nonwoven fabric layer material needle punched
thereto. When the elastic layer is allowed to relax and
return to substantially its condition prior to being
stretched, the nonwoven fabric layer is stated to exhibit
increased bulk by virtue of the relaxation of its permanently
stretched fibers.
Moreover, U.S. Patent No. 4,209,563 discloses a method
of making an elastic material which includes continuously
forwarding relatively elastomeric fibers and elongatable but
relatively non-elastic fibers onto a forming surface and
bonding at least some of the fiber crossings to form a
coherent cloth which is subsequently mechanically worked, as
by stretching, following which is it allowed to relax. As
described by the patentee at column 8, line 19 et seq, the
elastic modulus of the cloth is substantially reduced after
the stretching, resulting in the permanently stretched non-
elastic filaments relaxing and looping to increase the bulk
and improve the feel of the fabric. This patent discloses
that the bonding of the filaments to form the coherent cloth
may utilize embossing patterns or smooth, heated roll nips.
U.S. Patent No. 2,957,512 concerns a ~ethod of pro-
ducing elastic composite sheet materials and discloses that a
reticulated, fibrous web formed of an elasto~eric material
.
1 334376
such as rubber, including butadiene-styrene copoly~ers, may
be utilized as the elastic ply of a composite material. The
patent discloses that a relaxed sheet material ply may have
a fibrous web of elastomeriC material of smaller area than
the sheet material stretched so as to conform it in area to
the area of the sheet material and the plies are bonded
together at spaced points or areas. Upon allowing the
fibrous elastomeric ply to relax, the composite body is
stated to assume a structure of a fibrous web of elastomeric
material bonded at spaced areas or lines to a ply of a
creped or corrugated flexible sheet material.
Furthermore, it has been proposed to provide a composite
elastic material comprising at least one gatherable web
bonded to at least one elastic web, wherein the elastic web
(which may comprise a fibrous web such as a nonwoven web of
elastomeric fibers, e.g., meltblown elastomeric fibers) is
tensioned to elongate it; the elongated elastic web is
bonded to at least one gatherable web under conditions which
soften at least portions of the elastic web to form a bonded
composite web; and (c) the composite web is relaxed imme-
diately after the bonding step whereby the gatherable web is
gathered to form the composite elastic material. Such
proposed method includes bonding the elongated elastic web
to the gatherable web by overlaying-the elastic and
gatherable webs and applying heat and pressure to the
overlaid webs, for example, by heating bonding sites on the
elastic web to a temperature from at least about 65C to
about 120C, preferably fro~. at least about 70C to about
90C. In such proposed method, the elastomeric fibers may
be formed from (l) A-B-A' block copolymers, wherein A and A'
may be the same or different endblocks and each is a thermo-
plastic polymer endblock or segment which contains a
styrenic moiety such as polystyrene or polystyrene homologs,
and B is an elastomeric polymer midblock or segment, e.g.,
a midblock selected from the group including
poly(ethylene-butylene), polyisoprene and polybutadiene, or
(2) blends of one or more polyolefins with the A-B-A' block
1 ~34376
copolymers, the polyolefin being selected from one or more of
polyethylene, polypropylene, polybutene, ethylene copolymers,
propylene copolymers and butene copolymers. The gatherable
web can be a nonwoven, non-elastic material, preferably one
composed of fibers formed from materials selected from the
group including polyester fibers, e.g., poly(ethylene-
terephthalate) fibers, polyolefin fibers, polyimide fibers,
e.g., nylon fibers, cellulosic fibers, e.g., cotton fibers
and mixtures thereof. In connection with this proposed
composite elastomeric material and method, note Canadian
Patent No. 1,261,723, granted September 26, 1989, of Jack D.
Taylor and Michael J. Vander Wielen, for "Composite Elas-
tomeric Material and Process for Making the Same".
In this proposed metllod for making composite elastomeric
materials, bonding between the layers of the laminate are
provided by means of, for example, thermal bonding or ultra-
sonic welding, which will soften at least portions of at
least one of the webs, so as to effectuate bonding by heat
application and pressure. Due to the bonding of the films
with heating, and since the elastomeric film is bonded in its
stretched state, the difficulty arises that such bonding
while applying heat renders the elastomeric web susceptible
to losing its ability to contract if it is allowed to cool,
even briefly, in the stretched condition. A proposed
technique for overcoming this difficulty is to allow the
composite web to immediately contract after bonding.
However, such requirement to immediately relax the composite
after bonding imposes an additional condition on the
procedure. Moreover, additional problems arise due to use of
heating during bonding. Thus, the number of breaks of the
web are disadvantageously high, and burn-through (aperturing
of the elastomeric web at the bonding points) and undesirable
re-setting of the elastomeric meltblown occur due to the
relatively high bonding temperatures.
1 ~34376
~ Furthermore, utilizing, e.g., KRATON~/polyethylene
blends for forming the elastomeric web, it is very difficult
to bond such elastomeric web to various desirable materials,
such as spunbond polypropylene, as, e.g., the gatherable web
of the composite material.
Various pressure-sensitive adhesive compositions are
known. For example, U.S. Patent No. 4,294,936 discloses
pressure-sensitive adhesive compositions comprising (1) a
synthetic rubbery thermoplastic block copolymer, e.g., an
A-B-A or A-B block copolymer, where the A blocks are
thermoplastic blocks and the B blocks are rubbery blocks and
may be linear, branched or radial, or a mixture thereof: (2)
a non-rubbery polymer which is preferably a copolyester,
e.g., one of at least two different ester units; and a
tackifier resin. As examples of the block copolymers are
described KRATON~1102 (a styrene-butadiene-styrene block
copolymer) and KRATON~1107 (a styrene-isoprene-styrene
block copolymer). As the non-rubbery component is disclosed
a copolyester, although polyethylene and polypropylene may
be used. As the tackifier resin is disclosed rosin and
dehydrogenated rosin, and oil soluble phenol-formaldehyde
resins, among others. This patent further discloses that
the adhesive composition can be applied by blending and
melting the materials in an extruder and directly coating
onto a suitable backing; and that the adhesives may be
applied to, inter alia, non-woven fabrics.
U.S. Patent No. 3,783,072 discloses processes for
producing normally tacky and pressure-sensitive adhesive
sheets and tapes, by extrusion, wherein a blend of A-B-A
block copolymer (wherein A is a thermoplastic polymer block
derived from styrene and B is an elastomeric polymer block
derived from isoprene) and a solid tackifier is extruded
onto a backing sheet. As the tackifier agent is disclosed
conventional compatible solid tackifier agents including
hydrocarbon resins or the like. KRATON~1107 thermoplastic
elastomer block copolymer is disclosed as a material which
can be utilized in the described adhesive formulation.
1 ~34376
U.S. Patent No. 4,543,099 discloses pressure-sensitive
adhesives for imparting elastic characteristics to materials
which are relatively inelastic, by extruding hot melt
pressure-sensitive adhesive into contact with a substrate,
the hot melt pressure-sensitive adhesive comprising (1) a
rubbery block copolymer which includes a rubbery midblock
portion terminated with crystalline vinyl arene blocks; (2)
a tackifying resin generally compatible with and generally
associated with the midblock portion of the block copoly-
mer; and (3) an aromatic, essentially hydrocarbon resinhaving a glass transition temperature and a softening point
above those of the tackifying resin and the endblocks of
the block copolymer. This patent discloses that the block
copolymers which can be used include KRATON~, and the
tackifying resins can include natural and synthetic essen-
tially hydrocarbon resins.
U.S. Patent No. 4,539,364 discloses hot melt sizes for
glass fibers, applied as a hot melt to the glass fibers as
they are formed so as to provide a coating on the glass
fibers. The described hot melt size consists of a thermo-
plastic, block copolymer rubber, such as KRAToN3; a low
molecular weight polyethylene wax; and any low molecular
weight resin compatible with the end styrenic block of the
rubber block copolymer, the resin preferably being a
hydrogenated styrene/methyl styrene copolymer having a
weight average molecular weight of about 1000, a melt
viscosity of 1 poise at 209C, and a glass transition
temperature of about 65C, one particularly suitable
hydrocarbon low molecular weight resin being REGALREZ~ resin
1126 available from Hercules Incorporated.
Despite the foregoing, a void exists with respect to
elastomeric composite materials (e.g., elastomeric composite
laminates) that can be easily manufactured and that have
desirable properties. Moreover, a void exists with respect
to extrudable compositions for forming elastomeric sheet
materials, e.g., for such composite materials, that can be
used to easily form the elastomeric sheet materials (e.g.,
1 334376
-- 8
-
fibrous nonwoven webs such as meltblown webs).
Furthermore, a void exists with respect to such
elastomeric sheet materials which can be used to impart
elastomeric properties to a composite laminate, with
bonding between the elastomeric sheet material and
another sheet (e.g., web) of such composite laminate
being accomplished without the necessity of high
temperatures.
The invention resides in elastomeric composite
material including at least one nonwoven sheet of
pressure sensitive adhesive elastomer and at least one
gatherable material bonded to the nonwoven sheet of
pressure sensitive adhesive elastomer which is
extensible and contractible with the sheet of elastomer
upon stretching and relaxing the composite material.
The nonwoven sheet of pressure sensitive adhesive
elastomer is bonded to the gatherable material without
heating of the sheet of elastomer and gatherable
material so as to soften the sheet of elastomer and
gatherable material, the bonding of the sheet of
elastomer and gatherable material being accomplished due
to the adhesivity of the nonwoven sheet of pressure
sensitive adhesive elastomer.
The invention also resides in method of
producing a composite elastomeric material having at
least one gatherable web bonded to at least one nonwoven
sheet of pressure sensitive adhesive elastomer. The
steps of the method include tensioning a nonwoven sheet
of pressure sensitive adhesive elastomer to elongate it,
and bonding the elongated pressure sensitive adhesive
elastomer to at least one gatherable material by
applying pressure to the tension pressure sensitive
adhesive elastomer sheet and gatherable material,
without heating the pressure sensitive adhesive
elastomer sheet and gatherable material so as to soften
the elastomer sheet and gatherable material, the bonding
being accomplished due to the adhesivity of the nonwoven
sheet of pressure sensitive adhesive elastomer.
- 9 1 334376
More specifically, it is desirable that the
fibrous elastomeric nonwoven web is one which can be
bonded to layers of various other materials, including
spunbond polypropylene, without application of high
temperatures. In another aspect of the present
invention, the elastomeric nonwoven sheet may be an
elastomeric nonwoven web, for example, a fibrous
elastomeric nonwoven web formed by meltblowing, which
forms at least one layer of a stretch bonded laminate.
Other layers of the stretch bonded laminate (i.e., other
than the elastomeric web) may be made of a gatherable
material.
The nonwoven sheet of pressure sensitive
adhesive may be an extrudable composition (i.e.,
elastomeric polymer and tackifying resin) and may also
contain a polyolefin. The polyolefin may be added for
the purpose of reducing the viscosity of the extrudable
composition, so that the composition can be extruded
(e.g., meltblown) at a sufficiently low temperature such
that the elastomeric polymer is not degraded and/or
burned. Substances other than a polyolefin can be used
for the viscosity-reducing function, whereby the
polyolefin is unnecessary, and in a specific embodiment
the tackifying resin itself (e.g., a low molecular
weight hydrocarbon resin) can be used as the
viscosity-reducer, in addition to providing a tackifying
function, where such resin can sufficiently reduce the
viscosity of the composition to permit extrusion at
sufficiently low temperatures so the elastomeric polymer
is not degraded and/or burned.
In connection with including polyolefins in the
composition, as indicated in the above-discussed Canadian
1 334376
Patent Application Serial No. 514,960, filed July 30, 1986, of
Tony J. Wisneski and Michael T. Morman for "Polyolefin-
Containing Extrudable Compositions and Methods for Their
Formation Into Elastomeric Products" various polyolefins can
be utilized, in amounts such that the entire composition has
a sufficiently low viscosity to be extruded at sufficiently low
temperatures to avoid degradation and/or burning of the block
copolymer.
By use of the composition including at least the
elastomeric polymer and tackifying resin, and a composition
also including the polyolefin, an elastomeric nonwoven
material, e.g., a web of fibrous elastomeric nonwoven material,
such as a meltblown elastomeric web! can be formed and such
elastomeric nonwoven material can be utilized as a pressure
sensitive adhesive for bonding to a gatherable material, such
as spunbond polypropylene, at relatively low temperatures.
More particularlyj such nonwoven elastomeric web can be
stretched and, while stretched, bonded (for example, at a
temperature in the range of 60- to 180F, preferably lower
temperatures, in the range of 100 to 140F, e.g., at ambient
temperature, without substantial heating of the web for bonding
purposes) to a web of gatherable material, whereupon after
relaxation of the stretching of the elastomeric web a composite
material having elasticity is formed.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a schematic illustration of a continuous
manufacturing in-line process for stretch bond laminating
gatherable webs to each of the two opposite sides of an
elastomeric web.
1 334376
-- DETAILED DESCRIPTION OF THE INVENTION
While the invention will be described in connection with
specific and preferred embodiments, it will be understood
that it is not intended to limit the invention to those
embodiments. on the contrary, it is intended to cover all
alterations, modifications and equivalents as may be
included within the spirit and scope of the invention as
defined by the appended claims. Prior to more specifically
describing the invention, various terms used throughout will
be defined. Thus, the term "compatible" is used to refer to
the relationship of one polymeric material to another with
respect to the extrusion process and extrudates. To be
compatible, two different polymeric materials must have
similar rheological behavior, they must form a homogeneous
melt, and after being blown into fibers and solidifying,
must form a homogeneous solid product.
The terms "elastic" and "elastomeric" are used inter-
changeably to mean that property of any material that, upon
application of a biasing force, permits that material to be-
stretchable to a stretched, biased length which is at least
about 125%, that is about 1-lt4 times, its relaxed, unbiased
length, and that will cause the material to recover at least
40% of its elongation upon release of the stretching,
elongating force. A hypothetical example which would
satisfy this definition of an elastomeric material would be
a one (1) 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 more
than 1.15 inches. Many elastic materials may be stretched
by much more than 25% of their relaxed length and many of
these will recover to substantially their original relaxed
length upon release of the stretching, elongating force.
This latter class of materials is generally preferred for
- purposes of the present invention.
The term "recover" relates to a contraction of a
stretched material upon termination of a biasing force
~2- 1 334376
following stretching of the material by application of the
biasing force. For example, if a material having a relaxed,
unbiased length of one (1) inch were elongated 50% by
stretching to a length of 1-1/2 (1.5) inches, the material
would have been elongated 50~ and would have a stretched
length that is 150~ of its relaxed length. If this exemplary
stretched material contracted, that is, recovered to a length
of 1-1/10 (1.1) inches after release of the biasing and
stretching force, the material would have recovered 80% (0.4
inch) of its elongation.
The~term "microfibers" refers to small diameter fibers
having an average diameter not greater than about 200
microns, preferably having diameters in the range from about
O.S micron to about 50 microns, more preferably having an
average diameter of from about 4 microns to about 40 microns.
Microfibers may be meltblown by extruding a molten ther-
moplastic material through a plurality of small diameter,
usually circular die capillaries as molten threads and
attenuating the molten threads by application of a high
velocity gas, usually air, stream to reduce their diameters
to be within the range stated above.
The term "spunbond" material refers to a material made
by extruding a molten thermoplastic material as filaments
through a plurality of capillaries of a spinnerett, with the
diameter of the extruded filaments then being reduced by, for
example, eductive drawing or other well-known spunbonding
mechanisms. The product of spunbonded nonwoven webs, as well
as methods for making such spunbonded nonwoven webs, is
illustrated in U.S. Patent No. 4,340,563 to Appel.
The term "fibrous nonwoven web" means a web of material
which has been formed without the use of a weaving process.
A fibrous nonwoven web has a structure of individual fibers
or threads which are interlaid, but not in an identifiable,
repeating manner. Fibrous nonwoven webs in the past have
3S been formed by a variety of processes such as, for example,
_ 13 1334376 - ~
meltblowing processes, spunbonding processes, film aperturing
processes and staple fiber carding processes. These fibrous
nonwoven webs generally have an average basis weight of not
more than about 300 grams per square meter, and preferably
have an average basis weight from about 15 grams per square
meter to about 100 grams per square meter.
As indicated previously, the extrudable composition
includes an elastomeric polymer, for example, an
elastomeric block copolymer. Exemplary block copolymers
include the A-B-A~ or A-B block copolymer, with A
being a thermoplastic polymer block, e.g., containing a
styrenic moiety such as a poly(vinyl arene), and where B is
an elastomeric polymer block, such as a conjugated diene or a
lower alkene polymer. Such block copolymer of the A-B-A'
type can have different or the same thermoplastic block
polymers for the A and A' blocks, and the present block
copolymers are intended to embrace linear, branched and
radial block copolymers. In this regard, the radial block
copolymers may be designated (A-B)m X, wherein X is a
polyfunctional atom or molecule and in which each (A-B)
radiates ~rom X in a way that A is an endblock. In the
radial block copolymer, X may be an organic or inorganic-
polyfunctional atom or molecule and m is an integer having
the same value as the functional group originally present in
X. It is usually at least 3, and is frequently 4 or 5, but
is not limited thereto. Thus, in the present invention, the
expression "block copolymer", and particularly "A-B-A"' and
A-B block copolymer, is intended without qualification to
embrace all block copolymers having such rubbery blocks and
thermoplastic blocks as discussed above, which can be
extruded (e.g., by meltblowing), and without limitation as to
the number of blocks. As for various block copolymers,
attention is directed to U.S. Patent No. 4,301,255.
of these block copolymers, the preferred are those of
the A-B-A' type, wherein A and ~' can be the same or dif-
ferent and are thermoplastic endblocks, and B is a
1 334376
~- rubbery midblock. Block copolymers within the scope of
A-B-A' block copolymers include the KRATON~G block
copolymers. In particular, two specific KRAToN3 polymers
useful in the..present invention are KRATON~G-1652 and
5 KRATON~GX-1657. Such rubbery block copolymers are
polystyrene/poly(ethylene-butylene)/polystyrene block
copolymers, with the 1652 designation having a weight ratio
of polystyrene A endblocks to poly(ethylene-butylene) B
midblocks of 29:71, and the 1657 designation having such
weight ratio of 14:86. Various properties of these two
designations of KRATON~G are set forth in the following
table.
1 334376
.
TABLE 1
KRATON~G
PROPERTY G-1652 GX-1657
Tensile Strength
psi 4,5002 3,4002
300% Modulus, psil 700 350
Elongation, %1 500 750
Set at Break, ~ - -
Hardness, Shore A 75 65
Specific Gravity 0.91 0.90
Brookfield Viscosity,
(Toluene Solution)
cps at 77F 5503 1,1003
Melt Viscosity,
Melt Index,
Condition G,
gms/10 min.
Plasticizer Oil
Content, %w 0 0
Styrene/Rubber4
- Ratio 29/71 14/86
Physical Form Crumb Pellet
1 ASTM method D 412-tensile test jaw separation speed
10 in./min.
2 Typical properties determined on film cast from a
toluene solution
3 Neat polymer concentration, 20%w
4 The ratio of the sum of the molecular weights of the
endblocks (A+A') to the molecular weight of the B
midblock. For example, with respect to KRATON~G-1652,
the sum of the molecular weights of the two endblocks
(A+A') is 29 percent of the molecular weight of the
A-B-A' block copolymer.
_ 16 1 334376
Of course, the present invention is not limited to use
of such KRATON ~ G rubbery block copolymers as the elas-
tomeric polymer of the present invention, and attention is
directed to, e.g., the various thermoplastic rubbers which
are block copolymers and characterized by having a styrenic
moiety such as a poly(vinyl arene) and elastomeric polymer
midblocks such as conjugated dienes or alkene polymers as set
forth in U.S. Patent No. 4,301,255 to Korpman. Reference is
also made to the various elastomeric materials used in
forming the fibrous elastic webs in Canadian Patent No.
1,261,723, granted September 26, 1989, of Jack D. Taylor and
Michael J. Vander Wielen for "Composite Elastomeric Material
and Process for Making the Same"-, and Canadian Patent
Application Serial No. 514,960, filed July 30, 1986, of Tony
J. Wisneski and Michael T. Morman for "Polyolefin-Containinq
Extrudable Compositions and Methods for Their Formation Into
Elastomeric Products". Thus, generally, any elastomeric
polymer which is capable of being extruded (e.g., thermoplas-
tic) into a solid elastomeric material as part of the
composition of the present invention (including, e.g., a
tackifying resin) is within the contemplation of the present
invention.
The polyolefin which is utilized in the extrudable
composition must be one which, when blended with the A-B-A'
block copolymer and subjected to an appropriate combination
of elevated pressure and elevated temperature conditions, is
extrudable, in blended form, with the A-B-A' block copolymer.
In particular, preferred polyolefin materials include
polyethylene, polypropylene and polybutene, including
ethylene copolymers, propylene copolymers and butene
copolymers. Blends of two or more of the polyolefins may be
utilized.
A particularly preferred polyethylene may be obtained
from U.S.I. Chemical Company under the trade designation
17
1 334376
-
Petrothene Na601 (also referred to herein as PE 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. U.S.I. has also stated that the
Na601 has the following nominal values: (1) a Brookfield
viscosity, cP at lS0 degrees Centigrade of 8,500 and at
190 degrees Centigrade of 3,300 when measured in accordance
with ASTM D 3236; (2) a density of 0.903 grams per cubic
centimeter when measured in accordance with ASTM D 1505; (3)
an equivalent Melt index of 2,000 grams per 10 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 strength of 850
pounds per s~uare inch when measured in accordance with ASTM
D 638; (6) an elongation of 90% 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 has 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 of about 83,300.
The polydispersity (Mw/Mn) of the Na601 is about 4.87.
Mn, Mw and Mz as indicated previously, are calculated by the
following formulae:
Mn is calculated by the formula:
Mn = Sum~(n) (MW~
Sum (n)
Mw is calculated by the formula:
Mw = Sum ~(n) (MU)2]
Sum t(n) (MW)]
Mz is calculated by the formula:
Mz = Sum ~(n) (MW)3~
Sum [(n) (MW)2]
1 334376
18
where:
MW = The various molecular weights of the
individual molecules in a sample, and
n = The number of molecules in the given
sample which have a given molecular weight of
MW.
Of course, the present invention is not limited to use
or such specific polyolefin described herein. In this
regard, note the polyolefins as described in Canadian Patent
Application Serial No. 514,960, filed July 30, 1986, of Tony
J. Wisneski and Michael T. Morman for "Polyolefin-Containing
Extrudable Compositions and Method for Their Formation Into
Elastomeric Products". More generally, and noting the
specific purpose of the polyolefin, as described in the
Canadian Patent application of Tony J. Wisneski and Michael
T. Morman, various polyolefins which can be utilized in the
present invention can easily be determined.
Various tackifying resins which can be used in the
present invention will now be set forth. In particular, the
purpose of the tackifying resin is to provide an elastomeric
web that can act as a pressure sensitive adhesive, e.g., to
bond the elastomeric sheet to a gatherable web. Of course,
various tackifying resins are known, and are discussed,- e.g.,
in the previously mentioned U.S. Patent Nos. 4,294,936 and
3,783,072. Any tackifier resin can be used which is com-
patible with the elastomeric polymer and the polyolefin, and
can withstand the high processing (e.g., extrusion) ternpera-
tures. Generally, hydrogenated hydrocarbon resins are
preferred tackifying resins, because of their better tempera-
ture stability. In the following paragraphs are disclosedinformation on three specific tackifying resins, two of which
(REGALREZ ~ and ARRON ~ P series tackifiers) are examples
1 334376
~ of hydrogenated hydrocarbon resins, and the ZONATAC~501 lite
being a .terpene hydrocarbon. of course, while the three
tackifying resins are specifically discussed, the present
invention is not limited to use of such three tackifying
s resins, and other tackifying resins which are compatible
with the other components of the composition and can
withstand the high processing temperatures, and can achieve
the objectives of the present invention, can also be used.
REGALREZ~ hydrocarbon resins, a product of Hercules,
Incorporated, are fully hydrogenated st.yrene-type low
molecular weight hydrocarbon resins, produced by polymeri-
zation and hydrogenation of pure monomer hydrocarbon feed
stocks. Grades 1094, 3102, 6108 and 1126 are highly stable,-
light-colored low molecular~ weight, nonpolar resins
suggested for use in plastics modification, adhesives,
coatings, sealants and caulks. The resins are compatible
with a wide variety of oils, waxes, alkyds, plastics and
elastomers and are soluble in co~mon organic solvents.
Product specifications of the above-mentioned four grades of
REGALREZ~ hydrocarbon resins, and compatibility information
for such four grades, are set forth below respectively in
Tables 2 and 3.
- ~
1 334376
TABLE 2
REGALREZ~ Resins
10943102 6108 1126
Softening point,
R&B, C 90-9898-106 104-112 122-130
Color crystal-clear
Typical Properties
Softening point,
R~B, C 94102 108 126
Color ` crystal-clear
Acid number <1
Saponification
number <1
Specific gravity
at 21C 0.99 1.04 1.01 0.97
Flashpoint, COC,
C (F) 235(455)293(560)243(470)243(470)
Melt viscosity, C
1 poise 190 196 200 209
10 poises 151 164 168 182
100 poises 126 149 143 159
Glass transition
(Tg), C 33 51 52 65
TABLE 3
Compatibility Information
REGALREZ~ Resins
Compatibility With 1094 3102 6108 1126
Natural rubber G G G G
SBR 1011 P G G P
KRATON 1107 (MB) G G E G
KRATON 1101 (MB) P F G P
Styrene end block copolymersP G F P
KRATON "G" (MB) G F G G
E/VA copolymers
(low vinyl acetate content)E F G E
(high ~inyl acetate content) P E F P
Paraffin wax E G E E
Microcrystalline wax E G E E
XEY: E = Excellent; G = Good; F = Fair; P = Poor
~ 3 3~
Moreover, REGALREz~ll26 has the following molecular
weight, as determined by refractive index indicator: (1)
weight average molecular weight (Mw) = 1385; (2) number
average molecular weight (Mn) = 919; (3) Mw/Mn = 1.51.
ARKON~P series resins, a product of Arakawa Chemical
(U.S.A), Inc., is a synthetic tackifying resin for
pressure-sensitive adhesives which is based on petroleum
hydrocarbon resins, such tackifying resins being colorless
and odorless, with resistance to weather and heat, and
having the general properties as set forth in the following
Table 4:
TABLE 4
ARKONARKON ARKON ARKON ARKON
P-70 P-90 P-100 P-115 P-125
Color number
(Hansen) 50 50 50 50 50
Softening point 70OC 90C 100C 115C 125C
Acid number 0 0 0 0 o
Specific gravity
(20C) - 0.973 0.982 0.985 0.989
Refractive index
(20C) - 1.515 1.519 1.523 1.530
Molecular Weight - 650 700 850 1000
Ash (%) - 0.05 0.0s 0.05 0.05
Dielectric constant
50 MC - 2.3 2.3 2.3 2.3
1000 MC - 2.3 2.3 2.3 2.3
Loss tangent
S0 MC -0.0001 max0.0001 max0.0001 max0.0001 max
1000 MC -0.0001 max0.0001 max0.0001 max0.0001 max
ZONATEC~501 lite resin, a product of Arizona Chemical
Co., has a softening point of 105C, a Gardner color 1963
(50~ in heptane~ of 1- and a Gardner color neat (pure) of
2+; a color (approximate Gardner color equal to 1- (50% in
heptane); APHA color = 70) of water white, a specific
gravity (25/25C) of 1.02 and a flash point (closed cup,
F) of 480E.
22 1 334376
The components of the composition can be utilized
over broad ranges of the amounts of each component, such
amounts being easily determinable by one of ordinary skill
in the art. As a guide, when utilizing an A-B-A block
copolymer, a polyolefin, and REGALREZ~ as the three
components of the extrudable composition, the following
broad and preferred ranges, as shown in Table 5, are
exemplary. It is emphasized that these ranges are merely
illustrative, serving as a guide for amounts of the
various components in the composition.
TABLE ~
Pol~mer Broad Ranqe Preferred Range
A-B-A block
Copolymer40-80% 60-70%
15Polyolefin5-40% 15-2S%
REGALREZ5-30% 10-20%
As stated previously, while the composite has
been discussed in terms of a three-component extrudable
composition of (1) elastomeric polymer; (2) polyolefin; and
(3) tackifying resin, the polyolefin, whose function is a
viscosity-reducer for the total composition (as compared
with the viscosity of the elastomeric polymer per se), can
be substituted by other compatible viscosity reducers, or
can be eliminated altogether where the tackifying resin can
also act as the viscosity reducer. For example, low
molecular weight hydrocarbon resins such as REGALREZ~ can
also act as the viscosity reducer, whereby the extrudable
composition can be comprised of the elastomeric polymer and
tackifying resin (e.g., REGALREZ~).
While the principal components of the extrudable
composition have been described in the foregoing, such
extrudable composition is not limited
_ 1 ~34376
thereto, and can include other components not adversely
effecting the composition attaining the stated objectives.
Exemplary materials which could be used as additional
components would include, without limitation, pigments,
antioxidants, stabilizers, surfactants, waxes, flow pro-
moters, solid solvents, particulates and materials added to
enhance processability of the composition.
As indicated previously, the extrudable composition can
be formed into a nonwoven web (e.g., a film, porous film or
fibrous nonwoven web) by known extrusion techniques. A
preferred extrusion technique is to form a fibrous nonwoven
elastomeric web by meltblowing techniques. Meltblowing
processes generally involve extruding a thermoplastic
polymer resin through a plurality of small diameter capil-
laries of a meltblowing die as molten threads into a heated
gas stream (the primary air stream) which is flowing
generally in the same direction as that of the extruded
threads so that the extruded threads are attenuated, i.e.,
drawn or extended, to reduce their diameter to fiber or
preferably microfiber size. The thus formed microfibers are
then borne away from the vicinity of the die by the gas
stream. The gas stream is directed onto a foraminous
member, such as a screen belt or a screen drum which is
moving over a vacuum box, so that the gas-borne fibers
impinge upon and are collected on the surface of the
foraminous member and form a cohesive fibrous nonwoven web.
Meltblowing die arrangements usually extend across the
foraminous collecting member in a direction which is
substantially transverse to the direction of movement of the
collecting surface. The die arrangements include a
plurality of small diameter capillaries arranged linearly
along the transverse extent of the die with the transverse
extent of the die being approximately as long as the desired
width of the fibrous nonwoven web which is to be produced.
3S That is, the transverse dimension of the die is the dimen-
sion which is defined by the linear array of die capil-
laries. Typically, the diameter of the capillaries will be
-- 1 334376
24
on the order of from about 0.01 inches to about 0.02 inches,
for example, from about 0.0145 to about 0.018 inches. From
about 5 to about 50 such capillaries will be provided per
linear inch of die face. Typically, the length of the
capillaries will be from about 0.05 inches to about 0.20
inches, for example, about 0.113 inches to about 0.14 inches
long. ~ meltblowing die can extend for from about 30 inches
to about 60 or more inches in length in the transverse direc-
tion.
Such meltblowing techniques, and apparatus therefor, are
known in the art, and are discussed fully in Canadian Patent
Application Serial No. 514,960, filed July 30, 1986, of
Tony J. Wisneski and Michael T. Morman for "Polyolefin-
Containing Extrudable Compositions and Methods for Their
Formation Into Elastomeric Products". For example, utilizing
a composition containing, by weight, 67% KRATON ~ G-1657, 22%
PE Na601 and 11% REGALREZ ~ 1126, such composition was
meltblown with the composition at a temperature of 520F.
Generally, and intended to be illustrative and not limitin~,
the following described parameters can be used for meltblow-
ing of the extrudable compositions of the present invention.
Thus, the extrudable composition can be meltblown while at a
temperature of 500 to 600F, preferably 525 to 575F,
during the meltblowing. The primary air temperature, during
the meltblowing, can be 500 to 6S0F, preferably 550 to
600F; and the primary air pressure can be 2-8 pounds per
square inch (psi), gage, preferably 4-5 psi, gage.
The above-described extrudable composition and the
method of producing it are also described and are claimed
in above-identified Canadian Application No. 549,224.
1 334376
- 24a -
With respect to forming the laminate, various gatherable
materials can be utilized; in connection therewith, attention
is directed to Canadian Patent No. 1,261,723, granted
September 26, 1989, of Jack D. Taylor and Michael J. Vander
Wielen for "Composite Elastomeric Material and Process for
Making the Same". The gatherable web materials can include,
but are not limited
1 334376
.
to, non-elastic webs such as bonded carded non-elastic
polyester or non-elastic polypropylene fiber web, spunbonded
non-elastic polyester or polypropylene non-elastic fiber
web, non-elastic cellulosic fiber webs, e.g., cotton fiber
webs, polyamide fiber webs, e.g., nylon 6-6 webs sold under
the trademark CEREX by Monsanto, and blends of two or more
of the foregoing. Of particular desirability is utilizing
the gatherable web as outer cover layers (e.g., as a
sandwich wherein the elastomeric web is the intermediate
layer with cover layers of the gatherable web). The basis
weight of the gatherable web(s) depends on various factors
including the retraction force of the elastic web and the
desired retraction by the elastic web. Exemplary, and not
`limiting, values for the basis weight of the gatherable
web(s) are 5-100 grams per square meter (gsm), preferably
10-30 gsm.
A preferred material for the gatherable web is spunbond
p o ly p rop y l ene. I n th is rega r d, p rev ious
XRATON~/polyethylene blends could not be acceptably bonded
to webs of spunbond polypropylene as the gatherable web. By
the present invention, utilizing the tackifying resin as
part of the composition with the elastomeric polymer and
polyethylene extruded to form an elastomeric web having
adhesive properties, the capability of bonding the elasto-
meric webs to webs of other polymers, including spunbond
polypropylene, is achieved.
~eference is made to Figure 1 of the drawings, in
connection with the discussion of the stretch- bonded
laminating procedure. This Figure 1 shows schematically a
continuous manufacturing in-line process for stretch-bond
laminating gatherable webs, which may be non-elastic webs,
to each of the two opposite sides of a stretchable elastic
web. Thus, the elastic web 3 of the present invention was
formed by conventional meltblown equipment 1 on a forming
wire 2, and travels in the direction indicated by the arrows
associated with the rolls for the forming wire 2. The web 3
then passes through the bonder (rolls 6 and 7). The bonder
1 334376
roll arrangement can be compri6ed of a patterned calender
roller 6 and a ~mooth anvil roller 7. Various bonder roll
~rrangements, known in the art, can be used. The first
gatherable substrate web 4 is unwound from a supply roll, as
i~ the second gatherable substrate web 5. Fir~t web 4 and
6econd web 5 travel in the direction indicated by the arrows
associated with webs 4 and 5, respectively. Elastic web 3
is stretched to a desired percent elongation between wire 2
And bonder 6 and 7, by having the bonding rolls rotating at
a faster speed than the forming wire 2. The pressure
between the rollers 6 and 7 bonds the webs (4 and 5) to
elastic web 3 to form a compasite elastic material 8. As
can be seen in Fig. 1, the elastic material relaxes upon
relaxation of the stretching provided by the bonding rolls,
whereby the gatherable webs are gathered in the composite
elastic material 8. The web 8 is then wound up on a winder
9.
As can be appreciated, the bonding between the
gatherable webs and the elastic-web is a point bonding.
Various bonding patterns can be used, depending upon the
desired tactile properties of the final composite laminate
material. Such bonding can be performed at temperatures as
low as 60F, for example. A range of temperatures for the
calender roll6 during bonding is 60 to 180F, preferably
100 to 140F. In this regard, the bonding can be performed
without heating the calender rolls; however, without heating
the calender rolls there would be 6ub6tantially no control
of the temperature of the webs during bonding. Accordingly,
it is preferred to heat the bonder (the calender rolls) to a
temperature in the range o~ 100 to 140F to control the
temperature of the webs during bonding. As can be appre-
ciated, in such temperature range (100 to 140F) bonding is
provided by the tackiness of the elastic web (that is, the
temperature is not so high as to cause softening of the
- 35 elastic web and bonding primarily due to such ~oftening).
An advantage of the present invention is that due to the
relatively low temperatures which can be used in the bonding
1 334376
27
step of the present invention, smaller distances between the
bonding points can be used in the present invention, as
compared with the distances used in conventional laminating
techniques. Generally, the bonder rolls press against the
laminate of webs such that the pressure between the rolls 6
and 7 is, for example, 100-S00 pounds per linear inch (pli),
preferably 250-350 pli. These pressures are about the same
as utilized in conventional techniques to form composite
elastic materials.
As specific conditions of the stretch bond laminating,
and referring to Example II below, the forming wire 2 speed
was 50 feet per minute (fpm); the bonder rollers 6 and 7 were
going 153 fpm; and the winder was going 73 fp~.
The following specific examples of the present invention
exemplify formation of a fibrous meltblown nonwoven elasto-
meric web and use of such web to form a stretch bonded
laminate, as indicated previously. Of course, the present
invention is not limited to such examples, the examples
merely being exemplary of the present invention.
In the following examples, on-line apparatus as shown
in, e.g., Fiq. 1 was used. As for the meltblowing die
structure, reference is made to the Canadian Patent Applica-
tion Serial No. 514,960, filed July 30, 1986, of Tony J.
Wisneski and Michael T. Morman, for "Polyolefin-Containing
Extrudable Compositions and Methods for Their Formation into
Elastomeric Products", particularly Fig. 3 thereof. The
meltblowing die had apertures of 0.0145 inch, with 30
apertures per inch. The air gap (between the die tip and air
plate) of the meltblowing die was 0.063 inch, and the
distance the tip of the die extended beyond the air plate was
0.008 inch. Moreover, in the examples spunbond
polypropylene, having a basis weight of 0.40 oz/yd2, was used
for the gatherable webs, with gatherable webs being applied
to both sides of the elastic web.
28
1 334376
Example I
A blend of, by weight, 62.5% KRATON~G-1657; 25% poly-
ethylene Na601; and 12.5% REGALREZ~1126 was meltblown
under the conditions of a melt temperature of 531F; a
primary (forming) air temperature of 595F and a primary
(forming) air pressure of 4 pounds per square inch, gauge.
The forming distance between the dies for the meltblowing
and the forming wire was 10 inches. After formation of the
meltblown web, the web was then passed directly to the
stretch bond laminating. In this regard, attention is
directed to Fig. 1. For such stretch bond laminating, the
forming wire traveled at a speed of 53 fpm; the bonder
traveled at a speed of 158 fpm and the winder traveled at a
speed of 73 fpm. The bonder was at a temperature of 120F,
with a bonding pressure of 150 pli.
ExamPle II
A blend of, by weight, 63~ KRATON~G-1657, 20% poly-
ethylene Na601 and 17~ REGALREZ~1126 was meltblown under
the conditions of a melt temperature of 530F and a primary
air temperature of 600F. The primary air pressure was 4
pounds per square inch, gauge, with a forming distance from
- the dies to the forming wire of 10 inches. The formed
meltblown web was then passed directly to the stretch bond
laminating, with the forming wire traveling at a speed of 50
fpm, the bonder traveling at a speed of 153 fpm and the
winder traveling at a speed of 73 fpm. The bonder was at a
temperature of 140F, with the pressure of the bonder being
280 pli.
Comparative Exam~le I
A composition of, by weight, 60% KRATON~G-1657 and 40%
polyethylene Na601, with no tackifier, was meltblown under
the conditions of a melt temperature of 535F, a primary air
temperature of 603F, a primary air pressure of 4 pounds per
square inch, gauge, and a forming distance between the dies
and forming wire of 14 inches. The formed meltblown web was
29 ' 1'334376
-
then passed directly to the stretch bond laminating, the
forming wire traveling at a speed of 50 fpm, the bonder
traveling at a speed of 150 fpm and the winder traveling at
a speed of 75 fpm. The bonder was at a temperature of
180F, with the bonder having a pressure of 150 pli.
The characteristics of the meltblown web and stretch
bonded laminate, formed in the above-three Examples, are set
forth below in Table 6.
The physical characteristics (machine direction physical
characteristics) of the fibrous nonwoven (meltblown) webs
and stretch bonded laminates formed by the processes
detailed in Examples I and II, and Comparative Example I, as
shown in Table 6, were determined by the utilization of an
Instron tensile tester model 1130. Each sample was 3 inches
wide (transverse machine direction) by 7 inches long
(machine direction). Each sample was placed lengthwise in
the Instron's jaws with an initial jaw separation setting of
4 inches. The following tests were then carried out, with
the results shown in Table 6.
(1) The sample was then stretched at a rate of
20 inches per minute, to determine the load,
in grams, required to elongate such sample
- 100 percent in the machine direction. That
is, the load in grams required to elongate
each sample to a machine direction length
of twice its unstretched machine direction
length was determined, for purposes of
finding the load at 100% elongation.
(2) Load at 500% elongation was determined by
finding the load, in grams, required to
elongate each sample to a machine direction
length of five times its unstretched
machine direction length.
(3) Percent elongation at 1000 grams is the
percent the sample stretches when a 1000
gram force is applied in the machine
direction.
30
1 334376
(4) Load at 50% elongation was determined by
finding the load, in grams, required to
elongate each sample to a machine direction
length 50~ over its unstretched machine
direction length.
(5) The internal cohesion test consisted of
measuring the peak load obtained while
pulling a stretch bonded laminate apart
between two pressure plates covered with
d~uble coated pressure sensitive tape.
The test indicates the force required to
delaminate the stretch bonded laminate.
TABLE 6
Comparative
Meltblown Attributes Example I Example II ExamPle I
Basis Weight 76 GSM 72 GSM 7~ GSM
Load@100% Elongation 448 Gms/3" 392 Gms/3" 983 Gms/3"
Load@500~ Elongation 875 Gms/3" 828 Gms/3" 449 Gms/3"
SBL Attributes
Basis Weight 162 GSM 130 GSM 130 GSM
%Elong.@lOOOGms 123 % 117 % 102 %
Load@50% Elongation 452 Gms/3" 556 Gms/3" 507 Gms/3"
Internal Cohesion 3.9 Kilograms 6.1 Kilograms 2.3 Kilograms
GSM = grams per square meter
As can be seen in the foregoing Table, incorporation of,
or increase in the amount of, the tackifying resin clearly
increases the cohesion of the stretch bonded laminate.
Moreover, use of such tackifier resin enables the bonder to
be operated at a lower temperature.
Accordingly, the present invention provides the
following advantageous effects:
(1) Due to the lower bonding temperature, there
are less web breaks during the bonding;
~ 31
1 334376
(2) Capability of bonding to many different
types of outer layers, including, specifically,
spunbonded polypropylene, is achieved;
(3) A higher elongation is attainable in the
stretch bonded laminate because of lower
permanent set due to lower bonding
temperatures; and
(4) The resulting fabric has machine direction
stretch as well as good internal cohesion.
While the present invention has been described in terms
of various embodiments thereof, the present invention is not
to be limited thereto, but is capable of various embodiments
within the skill of the ordinary worker in the art. For
example, the formulations are not limited to the specific
embodiments, but could include other ratios and polymers to
achieve the same`end. Thus, ethylene vinyl acetate or other
hydrogenated styrene-type polymers could be used in the
composition.
While we have shown and described several embodiments in
accordance with the present invention, it is understood that
the same is not limited thereto but is susceptible of
numerous changes and modifications as known to one having
ordinary skill in the art and we therefore do not wish to be
limited to the details shown and described herein, but
intend to cover all such modifications as are encompassed by
the scope of the appended claims.
