U.S. patent application number 14/443403 was filed with the patent office on 2015-10-29 for extrusion coated textile laminate with improved peel strength.
The applicant listed for this patent is DOW GLOBAL TECHNOLOGIES LLC, DOW QUIMICA MEXICANA S.A.DE C.V.. Invention is credited to Fabricio Arteaga Larios, Barbara Bonaboglia, Gert J. Claasen, Elena E. Cordublas, Jacquelyn A. Degroot, Carlos E. Ruiz.
Application Number | 20150308039 14/443403 |
Document ID | / |
Family ID | 47519959 |
Filed Date | 2015-10-29 |
United States Patent
Application |
20150308039 |
Kind Code |
A1 |
Bonaboglia; Barbara ; et
al. |
October 29, 2015 |
EXTRUSION COATED TEXTILE LAMINATE WITH IMPROVED PEEL STRENGTH
Abstract
The present invention relates to nonbreathable extrusion coated
nonwoven structures. The structures comprise a nonwoven web
comprised of monocomponent or bicomponent fibers having a coating
comprising LDPE optionally blended with LLDPE and/or an elastomer.
The monocomponent or bicomponent fibers comprise an ethylene based
polymer, preferably at the surface of the fiber.
Inventors: |
Bonaboglia; Barbara;
(Horgen, CH) ; Cordublas; Elena E.; (Tarragona,
ES) ; Claasen; Gert J.; (Richterswil, CH) ;
Degroot; Jacquelyn A.; (Freeport, TX) ; Arteaga
Larios; Fabricio; (Mexico City, MX) ; Ruiz; Carlos
E.; (Katy, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DOW GLOBAL TECHNOLOGIES LLC
DOW QUIMICA MEXICANA S.A.DE C.V. |
Midland
Colonia Lomas De Chapultepec |
MI |
US
MX |
|
|
Family ID: |
47519959 |
Appl. No.: |
14/443403 |
Filed: |
November 14, 2013 |
PCT Filed: |
November 14, 2013 |
PCT NO: |
PCT/US2013/069981 |
371 Date: |
May 18, 2015 |
Current U.S.
Class: |
428/219 ;
442/62 |
Current CPC
Class: |
B32B 2307/50 20130101;
B32B 2307/584 20130101; B32B 27/32 20130101; D06M 15/21 20130101;
B32B 27/12 20130101; B32B 2307/7246 20130101; B32B 2262/0253
20130101; B32B 27/20 20130101; D06M 2101/18 20130101; B32B 5/022
20130101; B32B 2274/00 20130101; D06M 2200/00 20130101; B32B
2270/00 20130101 |
International
Class: |
D06M 15/21 20060101
D06M015/21 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 15, 2012 |
EP |
12382451.8 |
Claims
1. A non-breathable extrusion coated nonwoven structure comprising
a. a nonwoven web comprised of monocomponent or bicomponent fibers,
wherein the monocomponent or bicomponent fibers comprise an
ethylene based polymer; b. a non-breathable extrusion coating
layer, wherein the coating layer is comprised of an ethylene based
polymer.
2. The structure of claim 1 wherein the coating layer has a basis
weight of less than 20 gsm
3. The structure of claim 1 wherein the nonwoven web has a basis
weight of less than 20 gsm.
4. The structure of claim 1 wherein the structure has an abrasion
resistance of lower than 0.5 mg/cm.sup.3.
5. The structure of claim 1 wherein the structure has an elongation
at break in CD of greater than 50%
6. The structure of claim 1 wherein the structure has softness
lower than 45 as measured by handle-o-meter
7. The structure of claim 1 wherein the structure has a peel
strength exceeding the test method capabilities.
8. The structure of claim 1 wherein the coating layer comprises a.
5 to 100 percent by weight of LDPE; and b. from 0 to 95 percent by
weight of LLDPE.
9. The structure of claim 8 wherein the LLDPE has a Comonomer
Distribution Constant in the range of greater than 45 to 400 and a
zero shear viscosity range of 2 to 20.
10. The structure of claim 1 wherein the coating layer further
comprises an adhesion promoter.
11. The structure of claim 10 wherein the adhesion promoter is
blended with the ethylene based polymer.
12. The structure of claim 10 wherein the adhesion promoter is a
tie layer located between the coating layer and the nonwoven
web.
13. The structure of claim 11 wherein the adhesion promoter is
selected from the group consisting of PBPEs, olefin block
copolymers and linear polyethylenes having a density of less than
0.905 g/cm.sup.3.
14. The structure of claim 1 wherein the structure has a basis
weight of from 9 to 40 gsm.
15. The structure of claim 1 wherein the structure has a basis
weight of from 12 to 25 gsm.
16. The structure of claim 1 wherein the nonwoven web is a spunbond
web, a carded web, airlaid web, spunlaced web, meltblown web, or
combinations thereof in a multilayer structure.
17. The structure of claim 1 wherein the structure is used in a
medical application and has a basis weight in the range of 10-50
gsm
18. The structure of claim 1 wherein the structure is used in
hygiene application and has a basis weight in the range of 6-30
gsm
19. The structure of claim 1 wherein the structure is used in
industrial application and has a basis weight in the range of 10-50
gsm.
20. The structure of claim 1 wherein the coating layer contains
less than 25% filler by weight of the coating layer.
Description
FIELD OF INVENTION
[0001] The present invention relates to non-breathable extrusion
coated nonwoven structures comprising a nonwoven web of ethylene
based fibers onto which has been extrusion coated a non-breathable
ethylene-based film.
BACKGROUND AND BRIEF SUMMARY OF THE INVENTION
[0002] Nonwoven webs or fabrics are desirable for use in a variety
of products such as bandaging materials, garments, disposable
diapers, and other personal hygiene products, including
pre-moistened wipes. Nonwoven webs having high levels of strength,
softness, and abrasion resistance are desirable for disposable
absorbent garments, such as diapers, incontinence briefs, training
pants, feminine hygiene garments, and the like. For example, in a
disposable diaper, it is highly desirable to have soft, strong,
nonwoven components, such as top sheets or backsheets (also known
as outer covers). For use in applications such as diapers it is
desired that the fabric be non-breathable. Typically, this is
achieved by lamination of the nonwoven to a film.
[0003] As used herein, the term "nonwoven web", refers to a web
that has a structure of individual fibers or threads which are
interlaid, but not in any regular, repeating manner. Nonwoven webs
have been, in the past, formed by a variety of processes, such as,
for example, air laying processes, meltblowing processes,
spunbonding processes and carding processes, including bonded
carded web processes. These various processes each have their own
strengths and weaknesses. For example, spunbonded webs tend to have
higher tensile strength than meltblown webs whereas the meltblown
process tends to produce webs having increased liquid barrier
properties as compared to spunbond nonwovens.
[0004] Propylene-based polymers, particularly homo-polypropylene
(hPP) are well known in the art, and have long been used in the
manufacture of fibers. Fabrics made from hPP, particularly nonwoven
fabrics, exhibit high modulus but poor elasticity and softness.
Nevertheless, these fabrics are commonly incorporated into
multicomponent articles, e.g., diapers, wound dressings, feminine
hygiene products and the like.
[0005] In comparison, polyethylene-based elastomers, and the fibers
and fabrics made from these polymers, tend to exhibit low modulus
and good elasticity, but they also tend to have low tenacity,
stickiness and exhibit a hand feel which is generally considered as
unacceptable for many applications.
[0006] Tensile strength of nonwovens and tenacity of fibers is
important because the manufacture of multicomponent articles
typically involves multiple steps (e.g., rolling/unrolling,
cutting, adhesion, etc.), and webs lacking tensile strength may not
survive one or more of these steps. Fibers with a high tensile
strength (also known as tenacity) are also advantaged over fibers
with a low tensile strength because the former will experience
fewer line breaks, and thus greater productivity will be obtained
from the manufacturing line. Moreover, the end-use of many products
also typically requires a level of tensile strength specific to the
function of the component. Tensile strength must be balanced
against the cost of the process used to achieve the higher tensile
strength or to achieve higher tenacity. Optimized fabrics will have
the minimum material consumption (basis weight) to achieve the
minimum required tensile strength for the manufacture and end-use
of the fiber, component (e.g., nonwoven fabric) and article.
[0007] Hand feel is another important aspect for many nonwoven
structures, particularly those structures intended for use in the
hygiene and medical field. Low modulus is one aspect of hand feel.
Fabrics made from fibers with a low modulus will feel "softer", all
else being equal, than fabrics made from fibers with a high
modulus. A fabric comprised of lower modulus fibers will also
exhibit lower flexural rigidity which translates to better
drapability and better fit. In contrast, a fabric made from a
higher modulus fiber, e.g., hPP, will feel harsher (stiffer) and
will drape less well resulting in a poorer fit. Fabrics made from
polyethylene-based elastomers also tend to lack adequate hand feel
as they tend to have an undesirable feel to the skin commonly
characterized by descriptors such as tacky, sticky, clammy,
rubbery, or wet.
[0008] Fiber extensibility/elasticity is another important
criterion for nonwoven structures, particularly those used in
hygiene and medical applications, because the characteristic
translates to a better comfort and fit as the article made from the
fiber will be able to be more body conforming in all situations.
Diapers with elastic components will have less sagging in general
as body size and shape and movement vary. With improved fit, the
general well being of the user is improved through improved
comfort, reduced leakage, and a closer resemblance of the article
to cotton underwear.
[0009] Used in combination with other materials such as another
nonwoven, film, apertured film, fibers, woven fabric or others,
nonwoven structures with synergistic properties may be achieved.
One such structure involves the combination of nonwoven webs with
non-breathable polyolefin films. The lamination of these two
components is currently frequently done using hot melt adhesive s
(HMA). Typical speed for such lamination process is in the order of
200-300 m/min. The nonwoven currently used for such applications is
typically a spunbond or spunbond-meltblown-spunbond web made with
polypropylene. The typical nonwoven basis weight is 6-80 grams per
square meter (GSM). The non-breathable film is typically a
polyethylene rich film. The typical basis weight for the films is
10-30 GSM.
[0010] In the current HMA lamination step, the film and the
nonwoven are fed separately to the lamination line. Therefore both
the film and the nonwoven need to have a certain level of tensile
strength in order to be able to survive the process Moreover, given
the very low basis weight of the film, sometime the application of
the HMA burns the film. This obviously limits further downgauging
of the film.
[0011] To further downgauge a textile backsheet, the extrusion
coating process can be used. Via extrusion coating, the film layer
is deposited in melt form directly on top of a nonwoven layer. In
this way, the basis weight of the film layer can be less than 10
GSM. Moreover, the typical production speeds of extrusion coating
are above 300 m/min, further increasing the economical advantages
of this process. However, when the standard polypropylene nonwovens
are used in this process, the extrusion coated textile backsheet is
perceived as significantly less soft than the
hot-melt-adhesive-laminated textile backsheet. The elongation at
break of such extrusion coated backsheets was also observed to be
lower than what can be achieved via HMA lamination.
[0012] Accordingly, structures having extrusion coated films onto
nonwovens are desired, where the structure is perceived as soft
with relatively higher elongation to break.
[0013] Some of these advantages are obtained when using the present
invention which, in a first aspect, is a coating of a LDPE
optionally blended with LLDPE or an elastomer onto non-wovens made
from bico or mono fibers having polyethylene on the surface. It has
been discovered that when such nonwovens are used, the textile
backsheet obtained via extrusion coating offers significantly
better softness and higher elongation at break than if a
polypropylene nonwoven is used. It also offers improved abrasion
resistance than if polypropylene NW is used. Moreover, the
extrusion coated textile backsheets with bico or mono PE nonwovens
have similar softness and elongation at break than HMA laminated
textile backsheet nonwoven structures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a bargraph showing the handle-o-meter results of
the indicated examples.
[0015] FIGS. 2-4 show the stress strain curves in the cross
direction for the various coating formulations on each of the
nonwoven substrates.
[0016] FIGS. 5-7 show the stress strain curves in the machine
direction for the various coating formulations on each of the
nonwoven substrates.
[0017] FIGS. 8-13 show the stress strain curves in the cross
direction (FIGS. 8-10), and machine direction (FIGS. 11-13) for the
various coating on the various nonwoven substrates.
[0018] FIG. 14 shows the abrasion resistance of the various
coatings on the various nonwoven substrates.
DETAILED DESCRIPTION OF THE INVENTION
[0019] As used herein, the term "nonwoven web" or "nonwoven fabric"
or "nonwoven", refers to a web that has a structure of individual
fibers or threads which are interlaid, but not in any regular,
repeating manner. Nonwoven webs have been formed by a variety of
processes, such as, for example, air laying processes, meltblowing
processes, spunbonding processes and carding processes, including
bonded carded web processes.
[0020] As used herein, the term "meltblown", refers to the process
of extruding a molten thermoplastic material through a plurality of
fine, usually circular, die capillaries as molten threads or
filaments into a high velocity gas (e.g., air) stream which
attenuates the filaments of molten thermoplastic material to reduce
their diameter, which may be to a microfiber diameter. Thereafter,
the meltblown fibers are carried by the high velocity gas stream
and are deposited on a collecting surface to form a web of randomly
dispersed meltblown fibers.
[0021] As used herein, the term "spunbonded", refers to the process
of extruding a molten thermoplastic material as filaments from a
plurality of fine, usually circular, capillaries of a spinneret
with the diameter of the extruded filaments then being rapidly
reduced by drawing the fibers and collecting the fibers on a
substrate.
[0022] As used herein, the term "microfibers", refers to small
diameter fibers having an average diameter not greater than about
100 microns. Fibers, and in particular, spunbond and meltblown
fibers used in the present invention can be microfibers. More
specifically, the spunbond fibers can advantageously be fibers
having an average diameter of about 14-28 microns, and having a
denier from about 1.2-5.0, whereas the meltblown fibers can
advantageously be fibers having an average diameter of less than
about 15 microns, or more advantageously be fibers having an
average diameter of less than about 12 microns, or even more
advantageously be fibers having an average diameter of less than
about 10 microns. It also contemplated that the meltblown fibers
may have even smaller average diameters, such as less than 5
microns.
[0023] As used herein, the term "polymer" generally includes, but
is not limited to, homopolymers, copolymers, such as, for example,
block, graft, random and alternating copolymers, terpolymers, etc.,
and blends and modifications thereof. Furthermore, unless otherwise
specifically limited, the term "polymer" shall include all possible
geometrical configurations of the material. These configurations
include, but are not limited to, isotactic, syndiotactic and random
symmetries.
[0024] "Polyethylene" shall mean polymers comprising greater than
50% by weight of units which have been derived from ethylene
monomer. This includes polyethylene homopolymers or copolymers
(meaning units derived from two or more comonomers). Common forms
of polyethylene known in the art include Low Density Polyethylene
(LDPE); Linear Low Density Polyethylene (LLDPE); Medium Density
Polyethylene (MDPE); and High Density Polyethylene (HDPE). These
polyethylene materials are generally known in the art; however the
following descriptions may be helpful in understanding the
differences between some of these different polyethylene resins
[0025] The term "LDPE" may also be referred to as "high pressure
ethylene polymer" or "highly branched polyethylene" and is defined
to mean that the polymer is partly or entirely homopolymerized or
copolymerized in autoclave or tubular reactors at pressures above
14,500 psi (100 MPa) with the use of free-radical initiators, such
as peroxides (see for example U.S. Pat. No. 4,599,392, herein
incorporated by reference). LDPE resins typically have a density in
the range of 0.916 to 0.940 g/cm.sup.3.
[0026] "LLDPE" refers to linear ethylene alpha olefin copolymers
having a density in the range of from about 0.855 about 0.912
g/cm.sup.3 to about 0.925 g/cm.sup.3). "LLDPE" may be made using
chromium, Ziegler-Natta, metallocene, constrained geometry, or
single site catalysts. The term "LLDPE" includes znLLDPE, uLLDPE,
and mLLDPE. "znLLDPE" refers to linear polyethylene made using
Ziegler-Natta or chromium catalysts and typically has a density of
from about 0.912 to about 0.925 and a molecular weight distribution
greater than about 2.5, "uLLDPE" or "ultra linear low density
polyethylene" refers to linear polyethylene having a density of
less than 0.912 g/cm.sup.3), but which is made using chromium or
Ziegler-Natta catalysts and thus typically have a molecular weight
distribution ("MWD") greater than 2.5. "mLLDPE" refers to LLDPE
made using metallocene, constrained geometry, or single site
catalysts. These polymers typically have a molecular weight
distribution ("MWD") in the range of from 1.5 to 8.0. These resins
will typically have a density in the range of from about 0.855 to
0.925 g/cm.sup.3. Preferred copolymers include 1-hexene and
1-octene.
[0027] "MDPE" refers to linear polyethylene having a density in the
range of from greater than 0.925 g/cm.sup.3 to about 0.940
g/cm.sup.3). "MDPE" is typically made using chromium or
Ziegler-Natta catalysts or using metallocene, constrained geometry,
or single cite catalysts. and typically have a molecular weight
distribution ("MWD") greater than 2.5.
[0028] "HDPE" refers to linear polyethylene having a density in the
range greater than or equal to 0.940 g/cm.sup.3). "HDPE" is
typically made using chromium or Ziegler-Natta catalysts or using
metallocene, constrained geometry, or single cite catalysts and
typically have a molecular weight distribution ("MWD") greater than
2.5.
[0029] "Polypropylene" shall mean polymers comprising greater than
50% by weight of units which have been derived from propylene
monomer. This includes homopolymer polypropylene, random copolymer
polypropylene, impact copolymer polypropylene, and propylene based
plastomers and elastomers. These polypropylene materials are
generally known in the art.
[0030] As used herein, the term "polypropylene based plastomers
(PBP) or elastomers (PBE)" (collectively, these may be referred to
as "PBPE") includes reactor grade copolymers of propylene having
heat of fusion less than about 100 Joules/gm and MWD<3.5. The
PBPs generally have a heat of fusion less than about 100
Joules/gram while the PBEs generally have a heat of fusion less
than about 40 Joules/gram. The PBPs typically have a weight percent
ethylene in the range of about 3 to about 10 wt % ethylene, with
the elastomeric PBEs having an ethylene content of from about 10 to
15 wt % ethylene.
[0031] As used herein, the term "extensible" refers to any nonwoven
material which, upon application of a biasing force, is able to
undergo elongation to at least about 50 percent strain and more
preferably at least about 70 percent strain without experiencing
catastrophic failure.
[0032] As used herein, the term "tensile strength" describes the
peak force for a given basis weight when pulled in either the
machine direction (MD) or cross direction (CD) of a nonwoven when
pulled to break. The peak force may or may not correspond to the
force at break or strain at break. "Elongation" unless otherwise
specified, refers to the strain corresponding to the tensile
strength.
[0033] The following analytical methods are used in the present
invention:
[0034] Density is determined in accordance with ASTM D792.
[0035] "Melt index" also referred to as "MI" or "I.sub.2" is
determined according to ASTM D1238 (190.degree. C., 2.16 kg). "Melt
flow rate" or "MFR" is determined according to ASTM D1238
(230.degree. C., 2.16 kg). Melt index is generally associated with
polyethylene polymers, while melt flow rate is associated with
propylene based polymers
[0036] "Abrasion Resistance" was measured according to the method
described below:
[0037] A nonwoven fabric or laminate is abraded using a Sutherland
2000 Rub Tester to determine the fuzz level. A lower fuzz level is
desired which means the fabric has a higher abrasion resistance. An
11.0 cm.times.4.0 cm piece of nonwoven fabric is abraded with
sandpaper according to ISO POR 01 106 (a cloth sandpaper aluminum
oxide 320-grit is affixed to a 2 lb. weight, and rubbed for 20
cycles at a rate of 42 cycles per minute) so that loose fibers are
accumulated on the top of the fabric. The loose fibers were
collected using tape and measured gravimetrically. The fuzz level
is then determined as the total weight of loose fiber in grams
divided by the fabric specimen surface area (44.0 cm.sup.2).
[0038] "Elongation at Break" is determined according to ISO method
527-3 Ed. 1995, for both the cross direction and the machine
direction.
[0039] "Softness" is determined using the Handle-o-meter
(manufactured by Edana, part number WSP 90.3 (05)). The method uses
10.times.10 cm, min 3 samples, a slit width of 5 mm, and an arm
weight of 100 grams. Measurements are done in machine direction
(MD) and cross-direction stiffness (CD), and reported as
combination or for specific direction.
[0040] "Peel strength is measured according to this method:
[0041] The delamination is initiated manually and then the laminate
sample is cut into specimens of 35 mm length and 15 mm width. The
two delaminated layers of the specimen are then clamped in an
Instron instrument with load cell of 50 N. The test speed used is
125 mm/min and the average force to peel is detected. If the
delamination was unable to be started manually, or if the sample
did not delaminate at the maximum force of the instrument, or if
the delamination force exceeds that of the film or nonwoven's
maximum tensile strength, the results were reported in the Examples
as "no delamination possible",
[0042] Water Vapor Transmission Rate (or WVTR) is the absolute
transmission rate, which can be reported, for example, in units of
g/m.sup.2 day. The ranges of WVTR covered in claims are determined
according to ASTM E 398 using a Lissy L80-5000 measurement device,
at 38.degree. C., with relative humidity of 90% on side and 0% on
the other. The sample size used for measurements was 5 cm.sup.2.
WVTR data may be normalized with respect to sample thickness to a
permeability coefficient, for example, in units of (g mm)/(m.sup.2
day) as used herein.
[0043] Nonwoven Structure
[0044] The non-breathable extrusion coated nonwoven structures of
the present invention comprise a nonwoven web onto which a
non-breathable film layer has been extrusion coated, wherein the
film layer is comprised of an ethylene based polymer.
[0045] Nonwoven
[0046] The nonwoven web is comprised of monocomponent or
bicomponent fibers wherein the monocomponent or bicomponent fibers
comprise an ethylene based polymer. The non-breathable film is
comprised of an ethylene based polymer.
[0047] The nonwoven web may comprise a single web, such as a
spunbond web, a carded web, an airlaid web, a spunlaced web, or a
meltblown web. However, because of the relative strengths and
weaknesses associated with the different processes and materials
used to make nonwoven fabrics, composite structures of more than
one layer are often used in order to achieve a better balance of
properties. Such structures are often identified by letters
designating the various lays such as SM for a two layer structure
consisting of a spunbond layer and a meltblown layer, SMS for a
three layer structure, or more generically SX.sub.nS structures,
where X can be independently a spunbond layer, a carded layer, an
airlaid layer, a spunlaced layer, or a meltblown layer and n can be
any number, although for practical purposes is generally less than
5. In order to maintain structural integrity of such composite
structures, the layers must be bonded together. Common methods of
bonding include point bonding, adhesive lamination, and other
methods known to those skilled in the art. All of these structures
may be used in the present invention.
[0048] The fibers which make up the nonwoven web may be
monocomponent or bicomponent fibers. In either case, it is
preferred that the surface of the fiber comprise a polyethylene
resin other than LDPE. The polyethylene resin can advantageously be
a single site catalyzed resin (mLLDPE), or a post metallocene
catalyzed LLDPE, or a Ziegler-Natta catalyzed LLDPE, or HDPE, or
MDPE. If monocomponent fibers are used it is preferred that the
resin used in the fiber comprise 100% linear (including
"substantially linear") polyethylene.
[0049] If bicomponent fibers are used, it is preferred that the
fibers be in a sheath-core form, with the sheath comprising a
polyethylene other than LDPE as described for the monocomponent
fiber. The core of such fibers may comprise homopolymer
polypropylene (hPP), polyester or an elastomeric polymer. It is
preferred that the sheath comprise from 10 to 50 percent by weight
of the fiber.
[0050] It is also contemplated that the nonwoven web for use in the
structure of the present invention may comprise bicomponent staple
fibers thermally bonded to a nonwoven web. The bicomponent staple
fibers can be in a sheath-core form, with the sheath comprising an
LLDPE as described for the monocomponent fiber. The core of such
fibers may comprise homopolymer polypropylene (hPP), polyester or
an elastomeric polymer. It is preferred that the sheath comprise
from 20 to 50 percent by weight of the fiber.
[0051] Coating Layer
[0052] The coating layer for the structures of the present
invention comprises from 0% to 100% by weight LDPE, 0% to 100% by
weight linear polyethylene, and 0% to 15% by weight elastomer. It
should be understood that all individual values and subranges are
considered to be within the scope of this invention, and are
disclosed herein. In some examples, the LDPE may be present in the
coating layer in amounts of 5% to 100%, 5% to 95%, 5% to 90%, 5% to
80%, 10% to 90%, 10% to 80%, or 20% to 80%, by weight, of the
coating layer. In other examples, the LDPE is present in the
coating layer in amounts of 50-100%, 50-95%, 50-90%, 65-100%,
65-95%, 65-90%, or 75-95%, by weight, of the coating layer. In
further examples, the LDPE may be present in the coating layer in
amounts of 3-35%, 5-35%, 5-25%, 5-20%, or 5-15%, by weight, of the
coating layer. In some examples, the linear polyethylene may be
present in the coating layer in amounts of 0% to 95%, 0% to 90%, 0%
to 85%, 0% to 80%, 20% to 95%, or 20% to 80%, by weight of the
coating layer. In other examples, the coating layer may comprise at
least 50 wt. % LLDPE. In some examples, the elastomer may be
present in the coating layer in amounts of 0 to 15%, 0% to 10% or
0% to 7.5% of an elastomer. It should be understood that there may
also be fillers or other additives in the coating layer.
[0053] The preferred LDPE for use in the coating layer will have a
density between 0.915 and 0.925 g/cm3, preferably in the range of
from 0.915 and 0.920 g/cm3. The preferred LDPE will also have a
melt index between 0.5 and 10 g/10 min, preferably between 1 and 8
g/10 min.
[0054] The linear polyethylene, if present in the coating layer,
will preferably have a melt index between 5 and 35 g/10 min, more
preferably from 15 to 25 g/10 min. The preferred linear
polyethylene for the coating layer will also have a density of from
0.902 to 0.955 g/cm.sup.3. Multimodal polyethylene is also
contemplated for use in the linear polyethylene component.
[0055] One type of linear polyethylene which may be preferred for
some embodiments of the present invention are those described in
WO/2011/002868 or U.S. provisional application 61/543,425 (filed on
Oct. 5, 2011), hereby incorporated by reference in their entirety.
Such ethylene/.alpha.-olefin interpolymer compositions (linear low
density polyethylene (LLDPE)) comprise (a) less than or equal to
100 percent, for example, at least 70 percent, or at least 80
percent, or at least 90 percent, by weight of the units derived
from ethylene; and (b) less than 30 percent, for example, less than
25 percent, or less than 20 percent, or less than 10 percent, by
weight of units derived from one or more .alpha.-olefin comonomers.
The term "ethylene/.alpha.-olefin interpolymer composition" refers
to a polymer that contains more than 50 mole percent polymerized
ethylene monomer (based on the total amount of polymerizable
monomers) and, optionally, may contain at least one comonomer.
[0056] The .alpha.-olefin comonomers of this preferred embodiment
typically have no more than 20 carbon atoms. For example, the
.alpha.-olefin comonomers may preferably have 3 to 10 carbon atoms,
and more preferably 3 to 8 carbon atoms. Exemplary .alpha.-olefin
comonomers include, but are not limited to, propylene, 1-butene,
1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, and
4-methyl-1-pentene. The one or more .alpha.-olefin comonomers may,
for example, be selected from the group consisting of propylene,
1-butene, 1-hexene, and 1-octene; or in the alternative, from the
group consisting of 1-hexene and 1-octene.
[0057] The ethylene/.alpha.-olefin interpolymer composition of this
preferred embodiment is characterized by having a Comonomer
Distribution Constant in the range of from greater than from 45 to
400, for example from 100 to 400, or from 75 to 300, or from 75 to
200, or from 85 to 150, or from 85 to 125.
[0058] The ethylene-based polymer composition of this preferred
embodiment is characterized by having a zero shear viscosity ratio
(ZSVR) in the range of from 1 to 20, for example, from 2 to 10, or
from 2 to 6, or from 2.5 to 4. In some embodiments it is preferred
that the ZSVR is in the range of from 1 to less than 2.
[0059] The ethylene/.alpha.-olefin interpolymer composition of this
preferred embodiment has a density in the range of 0.903 to 0.965
g/cm.sup.3. For example, the density can be from a lower limit of
0.903, 0.910, 0.915 0.920, 0.925 or 0.930 g/cm.sup.3 to an upper
limit of 0.945, 0.950, 0.955, 0.960, or 0.965 g/cm.sup.3.
[0060] The ethylene/.alpha.-olefin interpolymer composition of this
preferred embodiment has a molecular weight distribution
(M.sub.w/M.sub.n) in the range of from 1.8 to 3.5. For example, the
molecular weight distribution (M.sub.w/M.sub.n) can be from a lower
limit of 1.8, 2, 2.1, or 2.2 to an upper limit of 2.5, 2.7, 2.9,
3.2, or 3.5.
[0061] The ethylene/.alpha.-olefin interpolymer composition of this
preferred embodiment has a molecular weight (M.sub.w) in the range
of 50,000 to 250,000 Daltons. For example, the molecular weight
(M.sub.w) can be from a lower limit of 50,000, 60,000, or 70,000
Daltons to an upper limit of 150,000, 180,000, 200,000 or 250,000
Daltons.
[0062] The ethylene/.alpha.-olefin interpolymer composition of this
preferred embodiment has a molecular weight distribution
(M.sub.z/M.sub.w) in the range of less than 4, for example, less
than 3, less than 2.
[0063] The ethylene/.alpha.-olefin interpolymer composition of this
preferred embodiment has a vinyl unsaturation of less than 0.15
vinyls, preferably less than 0.1 vinyls per one thousand carbon
atoms present in the backbone of the ethylene-based polymer
composition.
[0064] The ethylene/.alpha.-olefin interpolymer composition of this
preferred embodiment has a long chain branching frequency in the
range of from 0.02 to 3 long chain branches (LCB) per 1000 C
[0065] In one embodiment, the ethylene/.alpha.-olefin interpolymer
composition of this preferred embodiment comprises less than or
equal to 100 parts, for example, less than 10 parts, less than 8
parts, less than 5 parts, less than 4 parts, less than 1 parts,
less than 0.5 parts, or less than 0.1 parts, by weight of metal
complex residues remaining from a catalyst system comprising a
metal complex of a polyvalent aryloxyether per one million parts of
the ethylene-based polymer composition. The metal complex residues
remaining from the catalyst system comprising a metal complex of a
polyvalent aryloxyether in the ethylene-based polymer composition
may be measured by x-ray fluorescence (XRF), which is calibrated to
reference standards. The polymer resin granules can be compression
molded at elevated temperature into plaques having a thickness of
about 3/8 of an inch for the x-ray measurement in a preferred
method. At very low concentrations of metal complex, such as below
0.1 ppm, ICP-AES would be a suitable method to determine metal
complex residues present in the ethylene-based polymer
composition.
[0066] In one embodiment, ethylene/.alpha.-olefin interpolymer
composition has a comonomer distribution profile comprising a
monomodal distribution or a bimodal distribution in the temperature
range of from 35.degree. C. to 120.degree. C., excluding purge.
[0067] Any conventional ethylene (co)polymerization reaction
processes may be employed to produce the ethylene-based polymer
composition. Such conventional ethylene (co)polymerization reaction
processes include, but are not limited to, gas phase polymerization
process, slurry phase polymerization process, solution phase
polymerization process, and combinations thereof using one or more
conventional reactors, e.g. fluidized bed gas phase reactors, loop
reactors, stirred tank reactors, batch reactors in parallel,
series, and/or any combinations thereof.
[0068] Elastomers which can optionally be blended with the LDPE
and/or LLDPE for use in the coating layer of the present invention
include propylene based plastomers or elastomers (PBPEs), olefin
block copolymers ("OBCs") and linear polyethylene having a density
less than 0.905 g/cm.sup.3. Preferred PBPEs are those comprising
from 5 and 18% of units derived from ethylene, preferably from 7 to
10%, and a melt flow rate (MFR, 2.16 kg @ 230.degree. C.) of from 5
to 30 g/10 min, and a density in the range of from 0.86 to 0.905
g/cm.sup.3. PBPEs are a relatively new class of
propylene/alpha-olefin copolymers which are further described in
details in the U.S. Pat. Nos. 6,960,635 and 6,525,157, incorporated
herein by reference. Such propylene/alpha-olefin copolymers are
commercially available from The Dow Chemical Company, under the
tradename VERSIFY.TM., or from ExxonMobil Chemical Company, under
the tradename VISTAMAXX.TM.. Olefin block copolymers, are a
relatively new class of material which are more fully described in
WO 2005/090427, US2006/0199931, US2006/0199930, US2006/0199914,
US2006/0199912, US2006/0199911, US2006/0199910, US2006/0199908,
US2006/0199907, US2006/0199906, US2006/0199905, US2006/0199897,
US2006/0199896, US2006/0199887, US2006/0199884, US2006/0199872,
US2006/0199744, US2006/0199030, US2006/0199006 and US2006/0199983;
each publication being fully incorporated herein by reference. OBCs
are commercially available from The Dow Chemical Company under the
INFUSE.TM. trademark
[0069] Preferred elastomeric LLDPEs are ethylene-octene copolymers
having a density between 0.86 and 0.905 g/cm.sup.3 and a melt index
(MI, 2.16 kg @ 190.degree. C.) between 2 to 25 g/10 min, preferably
between 5 and 15 g/10 min.
[0070] The coating layer may optionally contain one or more
additives as is generally known in the art. Such additives include,
but are not limited to, antistatic agents, color enhancers, dyes,
lubricants, fillers such as TiO.sub.2 or CaCO.sub.3, opacifiers,
nucleators, processing aids, pigments, primary antioxidants,
secondary antioxidants, processing aids, UV stabilizers,
anti-blocks, slip agents, tackifiers, fire retardants,
anti-microbial agents, odor reducer agents, anti fungal agents, and
combinations thereof. In some applications it is preferred that the
coating layer comprise TiO.sub.2 and/or CaCO.sub.3. The coating
layer should be non-breathable meaning that it preferably has a
WVTR less than or equal to 150 (g*mm)/(m.sup.2*day), preferably
less than or equal to 130 (g*mm)/(m.sup.2*day) Considering the goal
of providing a non-breathable layer, it is generally preferred that
the coating layer comprise less than 25% by weight filler, more
preferably less than 20% by weight, or even less than 10% by
weight.
[0071] In one embodiment, a tie layer may be located between the
nonwoven web and the coating layer
[0072] The nonwoven material of the present invention will
preferably have a basis weight (weight per unit area) from about 5
grams per square meter (GSM) to about to about 20 gsm. The basis
weight for the coating layer can advantageously be from 4 to 20
GSM, more preferably from about 8 to 12 GSM.
[0073] The coating layer is applied to the nonwoven wed using an
extrusion coating process. Preferably the coating process is run at
a line speed of from 200 to 700 m/min, preferably from 300 to 500
m/min.
[0074] The coated nonwoven structures of the present invention can
be characterized by their unique combination of properties.
Preferably the coated nonwoven structure has an abrasion resistance
as determined by the method described above of maximum 0.5
mg/cm.sup.3, more preferably maximum 0.3 mg/cm.sup.3. Abrasion
resistance can be optimized for some compositions by going beyond
the peak bonding temperature to slightly over-bond the
material.
[0075] Preferably the coated nonwoven structure has an elongation
at break in CD as determined by ISO method 527-3 Ed. 1995 of at
least 50%, more preferably at least 60%, and an elongation at break
in MD as determined by ISO method 527-3 Ed. 1995 of at least 40%,
more preferably at least 50%. Preferably the coated nonwoven
structure when normalized to a basis weight of 28 gsm, has a
softness as determined by handle-o-meter of maximum 45, more
preferably maximum 35. Preferably the coated nonwoven structure has
a peel strength which exceeds the testing limits of the described
method due to the inability to start the delamination or that the
delamination force exceeds that of the film or nonwoven's maximum
tensile strength.
[0076] The coated nonwoven structures of the present invention may
be used in a wide variety of applications. For example, they may be
well suited for use in medical applications, particularly when the
structure has a basis weight of in the range of 10-50 gsm. They may
also be used in hygiene applications, particularly with a basis
weight in the range of 6-30 gsm. It is also envisaged that they may
be used in industrial applications, particularly with a basis
weight in the range of 10-50 gsm.
EXAMPLES
[0077] The following resins are used in the following Examples:
[0078] Resin A is an LDPE prepared in an autoclave reactor having a
density of 0.918 g/cc and a melt index (190.degree. C./2.16 kg) of
7.5 g/10 min;
[0079] Resin B is a PBPE produced in solution process via
metallocene catalysis having an ethylene content of 9% and an MFR
(230.degree. C./2.16 kg) of 25 g/10 min and a density of 0.876
g/cc
[0080] Resin C is a linear polyethylene resin having a melt index
(190.degree. C./2.16 kg) of 21.5 g/10 min and a density of 0.907
g/cc.
[0081] Resin D is an LDPE prepared in an autoclave reactor having a
density of 0.918 g/cc and a melt index (190.degree. C./2.16 kg) of
2.3 g/10 min
[0082] Resin E is a blend of 70% Resin C and 30% Resin D. The blend
has a density of 0.911 g/cc and a MI (190.degree. C./2.16 kg) of 12
g/10 min.
[0083] The nonwovens used for the examples are all spunbond
nonwovens having a basis weight of 20 g/m.sup.2. The fibers used to
make the nonwoven are 1.8 denier fibers which were either
polypropylene, polyethylene or a bico fiber having a polypropylene
core and a polyethylene sheath (50-50), as indicated in the
tables.
Extrusion Coating Process Data
TABLE-US-00001 [0084] Bicomponent NW Example 1 Example 2 Example 3
Coating Formulation 85% Resin A + 15% 85% Resin E + 100%
(monolayer) Resin B 15% Resin B Resin E Neck-in 133 mm 146 mm 138
mm @ 300 m/min and 8 GSM coating layer
TABLE-US-00002 PP NW Comp. Comp. Comp. Example 4 Example 5 Example
6 Coating Formulation 85% Resin A + 85% Resin E + 100% Resin E
(monolayer) 15% Resin B 15% Resin B Neck-in 133 mm 146 mm 138 mm @
300 m/min and 8 GSM coating layer
TABLE-US-00003 PE NW Example 7 Example 8 Example 9 Coating
Formulation 85% Resin A + 85% Resin E + 100% Resin E (monolayer)
15% Resin B 15% Resin B Neck-in 133 mm 146 mm 138 mm @ 300 m/min
and 8 GSM coating layer
[0085] Reference Sample: A commercial HMA laminated textile
backsheet containing hPP homopolymer nonwoven and polyethylene film
laminated thereto via Hot Melt Adhesive was use as a comparative
Example, as this type of structure is currently considered to be
the industry standard for softness. Total GSM is reported in the
charts.
[0086] As can be seen in FIG. 1 below, with same coating
formulation, mono PE and bico NW give softer textile backsheets
than hPP NW on the handle-o-meter testing apparatus.
[0087] With the formulation based on blends of Resins B and Resin E
and bico NW, the softness is similar to the one of the commercial
baseline (which is HMA laminated).
[0088] With the formulations based on only polyethylene NW, each of
the coating formulations give softer samples than the commercial
baseline.
[0089] FIGS. 2-4 show the stress strain curves in the cross
direction for the various coating formulations on each of the
nonwoven substrates. As can be seen, for each coating formulation,
a bico NW and a mono PE NW give much higher elongation at break in
cross-direction than the PP NW.
[0090] FIGS. 5-7 show the stress strain curves in the machine
direction for the various coating formulations on each of the
nonwoven substrates. As can be seen, for each coating formulation,
a bico NW and a mono PE NW give much higher elongation at break in
machine-direction than the PP NW.
[0091] FIGS. 8-13 show the stress strain curves in the cross
direction (FIGS. 8-10), and machine direction (FIGS. 11-13) for the
various coating on the various nonwoven substrates. As seen in
these figures, in both the Cross-direction and Machine Direction,
only using a bico NW or a mono PE NW allows one to use extrusion
coating and still reach the same level of elongation at break as
with HMA lamination.
[0092] FIG. 14 shows the abrasion resistance of the various
coatings on the various nonwoven substrates. As can be seen, using
the same coating formulation, the samples with the current hPP NW
give worse results than the samples with bico PP:PE and mono PE NW,
which is not the case with uncoated samples. For the uncoated
nonwovens, the hPP shows similar values to bico NW and
significantly better than mono PE.
Peel Strength
[0093] The table below reports the peel strength results. As can be
seen, when an elastomer such as a PBPE is used in sufficient
amount, it is not possible to delaminate the samples irrespective
of the non-woven used. Hence the peel force values cannot be
determined because the delamination cannot be initiated. If no
elastomer is used, then only samples having bico PP:PE or mono PE
non-wovens show perfect adhesion and no delamination can be
initiated. Contrarily, a mono PP non-woven can be delaminated from
the non-breathable coating layer if an elastomer is not used
TABLE-US-00004 85% Resin A + 85% Resin E + 15% Resin B 100% Resin E
15% Resin B Homo PP No 0.46N No NW delamination delamination
possible possible Bico PP:PE No No No 50:50 NW delamination
delamination delamination possible possible possible PE NW No No No
delamination delamination delamination possible possible
possible
* * * * *