Nonwoven fabric laminate with good conformability

There is provided a laminate having at least one layer of meltblown elastic fibers bonded on either side with a layer of soft non-elastic fibers of greater than 7 microns in average diameter. The laminate has a drape stiffness less than half of a similar fabric having a layer of meltblown non-elastic fibers in place of the layer of meltblown elastic fibers.

BACKGROUND OF THE INVENTION 
This invention relates to nonwoven fabrics for use in garments, personal 
care products and infection control products. 
In the case of items to be worn like, for example, gowns, the softness, 
drape and conformability are important considerations. Softness, at least 
for the side against the wearer, is an important consideration to avoid 
skin irritaton. Softness becomes more of an issue for longer term usage 
such as in the case of a surgical gown which may be worn for a period of 
hours. Conformability is the degree to which a fabric will adapt itself to 
the shape of an object it is covering. A highly conformable fabric, for 
example will adapt itself well to a wearer's body and as a result will not 
feel stiff. A stiff fabric is, of course, to be avoided when designing a 
comfortable garment. One measure of the conformability of a fabric is the 
drape stiffness. 
A fabric for these application must also have the ability to stretch and 
recover from such stretching or deformation and must also be breathable so 
as not to inhibit skin comfort. 
It is an object of this invention to provide a nonwoven fabric which may be 
used in garments and infection control products and which is breathable 
while having good softness, drape and conformability. 
SUMMARY OF THE INVENTION 
The objects of the invention are satisfied by a laminate of having at least 
one layer of meltblown elastic fibers bonded on either side with a layer 
of soft non-elastic fibers of greater than 7 microns in average diameter. 
The fabric so produced has a drape stiffness less than half of a similar 
fabric having a layer of meltblown non-elastic fibers in place of the 
layer of meltblown elastic fibers. The soft fibers may be made from 
polyethylene and polypropylene and may be conjugate side-by-side, sheath 
core, islands in the sea or other configurations. 
DEFINITIONS 
As used herein the term "nonwoven fabric or web" means a web having a 
structure of individual fibers or threads which are interlaid, but not in 
an identifiable manner as in a knitted fabric. Nonwoven fabrics or webs 
have been formed from many processes such as for example, meltblowing 
processes, spunbonding processes, and bonded carded web processes. The 
basis weight of nonwoven fabrics is usually expressed in ounces of 
material per square yard (osy) or grams per square meter (gsm) and the 
fiber diameters useful are usually expressed in microns. (Note that to 
convert from osy to gsm, multiply osy by 33.91). 
As used herein the term "microfibers" means small diameter fibers having an 
average diameter not greater than about 75 microns, for example, having an 
average diameter of from about 0.5 microns to about 50 microns, or more 
particularly, microfibers may have an average diameter of from about 2 
microns to about 40 microns. Another frequently used expression of fiber 
diameter is denier, which is defined as grams per 9000 meters of a fiber 
and may be calculated as fiber diameter in microns squared, multiplied by 
the density in grams/cc, multiplied by 0.00707. A lower denier indicates a 
finer fiber and a higher denier indicates a thicker or heavier fiber. For 
example, the diameter of a polypropylene fiber given as 15 microns may be 
converted to denier by squaring, multiplying the result by 0.89 g/cc and 
multiplying by 0.00707. Thus, a 15 micron polypropylene fiber has a denier 
of about 1.42 (15.sup.2 .times.0.89.times.0.00707=1.415). Outside the 
United States the unit of measurement is more commonly the "tex", which is 
defined as the grams per kilometer of fiber. Tex may be calculated as 
denier/9. 
As used herein, the term "elastic" when referring to a fiber or fabric mean 
a material which upon application of a biasing force, is stretchable to a 
stretched, biased length which is at least about 150 percent, or one and a 
half times, its relaxed, unstretched length, and which will recover at 
least 50 percent of its elongation upon release of the stretching, biasing 
force. Elastic materials are also referred to as "elastomeric" and 
sometimes as "plastomeric". Non-elastic materials are those which do not 
meet the definition of "elastic". 
As used herein the term "recover" refers to a contraction of a stretched 
material upon termination of a biasing force following stretching of the 
material by application of the biasing force. For example, if a material 
having a relaxed, unbiased length of one (1) inch was elongated 50 percent 
by stretching to a length of one and one half (1.5) inches the material 
would have a stretched length that is 150 percent of its relaxed length. 
If this exemplary stretched material contracted or recovered to a length 
of one and one tenth (1.1) inches after release of the biasing and 
stretching force, the material would have recovered 80 percent (0.4 inch) 
of its elongation. 
Conventionally, "stretch bonded" refers to an elastic member being bonded 
to another member while the elastic member is extended. "Stretch bonded 
laminate" or SBL conventionally refers to a composite material having at 
least two layers in which one layer is a gatherable layer and the other 
layer is an elastic layer. The layers are joined together when the elastic 
layer is in an extended condition so that upon relaxing the layers, the 
gatherable layer is gathered. Such a multilayer composite elastic material 
may be stretched to the extent that the nonelastic material gathered 
between the bond locations allows the elastic material to elongate. One 
type of multilayer composite elastic material is disclosed, for example, 
by U.S. Pat. No. 4,720,415 to Vander Wielen et al., which is hereby 
incorporated by reference in its entirety, and in which multiple layers of 
the same polymer produced from multiple banks of extruders are used. Other 
composite elastic materials are disclosed in U.S. Pat. No. 4,789,699 to 
Kieffer et al., U.S. Pat. No. 4,781,966 to Taylor and U.S. Pat. Nos. 
4,657,802 and 4,652,487 to Morman and U.S. Pat. Nos. 4,655,760 and 
4,692,371 to Morman et al. 
Conventionally, "neck bonded" refers to an elastic member being bonded to a 
non-elastic member while the non-elastic member is extended or necked. 
"Neck bonded laminate" or NBL conventionally refers to a composite 
material having at least two layers in which one layer is a necked, 
non-elastic layer and the other layer is an elastic layer. The layers are 
joined together when the non-elastic layer is in an extended condition. 
Examples of neck-bonded laminates are such as those described in U.S. Pat. 
Nos. 5,226,992, 4,981,747, 4,965,122 and 5,336,545 to Morman. 
As used herein the term "spunbonded fibers" refers to small diameter fibers 
which are formed by extruding 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 as by, 
for example, in U.S. Pat. No. 4,340,563 to Appel et al., and U.S. Pat. No. 
3,692,618 to Dorschner et al., U.S. Pat. No. 3,802,817 to Matsuki et al., 
U.S. Pat. Nos. 3,338,992 and 3,341,394 to Kinney, U.S. Pat. No. 3,502,763 
to Hartman, U.S. Pat. No. 3,502,538 to Levy, and U.S. Pat. No. 3,542,615 
to Dobo et al. Spunbond fibers are generally not tacky when they are 
deposited onto a collecting surface. Spunbond fibers are microfibers which 
are generally continuous and have average diameters (from a sample size of 
at least 10) larger than 7 microns, more particularly, between about 10 
and 30 microns. 
As used herein the term "meltblown fibers" means fibers formed by extruding 
a molten thermoplastic material through a plurality of fine, usually 
circular, die capillaries as molten threads or filaments into converging 
high velocity gas (e.g. air) streams which attenuate the filaments of 
molten thermoplastic material to reduce their diameter, which may be to 
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 disbursed meltblown fibers. Such a process is disclosed, 
for example, in U.S. Pat. No. 3,849,241 to Buntin. Meltblown fibers are 
microfibers which may be continuous or discontinuous, are usually smaller 
than 10 microns in average diameter, and are generally tacky when 
deposited onto a collecting surface. 
Spunbond and meltblown fabrics may be combined into "SMS laminates" wherein 
some of the layers are spunbond and some meltblown such as a 
spunbond/meltblown/spunbond (SMS) laminate as disclosed in U.S. Pat. No. 
4,041,203 to Brock et al., U.S. Pat. No. 5,169,706 to Collier, et al, and 
U.S. Pat. No. 4,374,888 to Bomslaeger. Such a laminate may be made by 
sequentially depositing onto a moving forming belt first a spunbond fabric 
layer, then a meltblown fabric layer and last another spunbond layer and 
then bonding the laminate in a manner described below. Alternatively, the 
fabric layers may be made individually, collected in rolls, and combined 
in a separate bonding step. Such fabrics usually have a basis weight of 
from about 0.1 to 12 osy (6 to 400 gsm), or more particularly from about 
0.75 to about 3 osy. 
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 configuration of the 
material. These configurations include, but are not limited to isotactic, 
syndiotactic and random symmetries. 
As used herein the term "conjugate fibers" refers to fibers which have been 
formed from at least two polymers extruded from separate extruders but 
spun together to form one fiber. Conjugate fibers are also sometimes 
referred to as multicomponent or bicomponent fibers. The polymers are 
usually different from each other though conjugate fibers may be 
monocomponent fibers. The polymers are arranged in substantially 
constantly positioned distinct zones across the cross-section of the 
conjugate fibers and extend continuously along the length of the conjugate 
fibers. The configuration of such a conjugate fiber may be, for example, a 
sheath/core arrangement wherein one polymer is surrounded by another or 
may be a side by side arrangement, a pie arrangement or an 
"islands-in-the-sea" arrangement. Conjugate fibers are taught in U.S. Pat. 
No. 5,108,820 to Kaneko et al., U.S. Pat. No. 5,336,552 to Strack et al., 
and U.S. Pat. No. 5,382,400 to Pike et al. For two component fibers, the 
polymers may be present in ratios of 75/25, 50/50, 25/75 or any other 
desired ratios. 
As used herein "thermal point bonding" involves passing a fabric or web of 
fibers to be bonded between a heated calender roll and an anvil roll. The 
calender roll is usually, though not always, patterned in some way so that 
the entire fabric is not bonded across its entire surface. As a result, 
various patterns for calender rolls have been developed for functional as 
well as aesthetic reasons. One example of a pattern has points and is the 
Hansen Pennings or "H&P" pattern with about a 30% bond area with about 200 
bonds/square inch as taught in U.S. Pat. No. 3,855,046 to Hansen and 
Pennings. The H&P pattern has square point or pin bonding areas wherein 
each pin has a side dimension of 0.038 inches (0.965 mm), a spacing of 
0.070 inches (1.778 mm) between pins, and a depth of bonding of 0.023 
inches (0.584 mm). The resulting pattern has a bonded area of about 29.5%. 
Another typical point bonding pattern is the expanded Hansen and Pennings 
or "EHP" bond pattern which produces a 15% bond area with a square pin 
having a side dimension of 0.037 inches (0.94 mm), a pin spacing of 0.097 
inches (2.464 mm) and a depth of 0.039 inches (0.991 mm). Another typical 
point bonding pattern designated "714" has square pin bonding areas 
wherein each pin has a side dimension of 0.023 inches, a spacing of 0.062 
inches (1.575 mm) between pins, and a depth of bonding of 0.033 inches 
(0.838 mm). The resulting pattern has a bonded area of about 15%. Yet 
another common pattern is the C-Star pattern which has a bond area of 
about 16.9%. The C-Star pattern has a cross-directional bar or "corduroy" 
design interrupted by shooting stars. Other common patterns include a 
diamond pattern with repeating and slightly offset diamonds and a wire 
weave pattern looking as the name suggests, e.g. like a window screen. 
Typically, the percent bonding area varies from around 10% to around 30% 
of the area of the fabric laminate web. As is well known in the art, the 
spot bonding holds the laminate layers together as well as imparts 
integrity to each individual layer by bonding filaments and/or fibers 
within each layer. 
As used herein, through-air bonding or "TAB" means a process of bonding a 
nonwoven bicomponent fiber web in which air which is sufficiently hot to 
melt one of the polymers of which the fibers of the web are made is forced 
through the web. The air velocity is between 100 and 500 feet per minute 
and the dwell time may be as long as 6 seconds. The melting and 
resolidification of the polymer provides the bonding. Through air bonding 
has relatively restricted variability and since through-air bonding TAB 
requires the melting of at least one component to accomplish bonding, it 
is restricted to webs with two components like conjugate fibers or those 
which include an adhesive. In the through-air bonder, air having a 
temperature above the melting temperature of one component and below the 
melting temperature of another component is directed from a surrounding 
hood, through the web, and into a perforated roller supporting the web. 
Alternatively, the through-air bonder may be a flat arrangement wherein 
the air is directed vertically downward onto the web. The operating 
conditions of the two configurations are similar, the primary difference 
being the geometry of the web during bonding. The hot air melts the lower 
melting polymer component and thereby forms bonds between the filaments to 
integrate the web. 
As used herein, the term "personal care product" means diapers, training 
pants, absorbent underpants, adult incontinence products, and feminine 
hygiene products. Such products generally include outer cover layers and 
inner absorbent layers. 
As used herein, the term "garment" means any type of non-medically oriented 
apparel which may be worn. This includes industrial work wear and 
coveralls, undergarments, pants, shirts, jackets, gloves, socks, and the 
like. 
As used herein, the term "infection control product" means medically 
oriented items such as surgical gowns and drapes, face masks, head 
coverings like bouffant caps, surgical caps and hoods, footwear like shoe 
coverings, boot covers and slippers, wound dressings, bandages, 
sterilization wraps, wipers, garments like lab coats, coveralls, aprons 
and jackets, patient bedding, stretcher and bassinet sheets, and the like. 
TEST METHODS 
Hydrohead: A measure of the liquid barrier properties of a fabric is the 
hydrohead test. The hydrohead test determines the pressure of water (in 
mbar) which the fabric will support before a predetermined amount of 
liquid passes through. A fabric with a higher hydrohead reading indicates 
it has a greater barrier to liquid penetration than a fabric with a lower 
hydrohead. The hydrohead test is performed according to Federal Test 
Standard No. 191A, Method 5514. 
Drape: The drape stiffness test, also sometimes called the cantilever 
bending test, determines the bending length of a fabric using the 
principle of cantilever bending of the fabric under its own weight. The 
bending length is a measure of the interaction between fabric weight and 
fabric stiffness. A 1 inch (2.54 cm) by 8 inch (20.3 cm) fabric strip is 
slid, at 4.75 inches per minute (12 cm/min) in a direction parallel to its 
long dimension so that its leading edge projects from the edge of a 
horizontal surface. The length of the overhang is measured when the tip of 
the specimen is depressed under its own weight to the point where the line 
joining the tip of the fabric to the edge of the platform makes a 41.5 
degree angle with the horizontal. The longer the overhang the slower the 
specimen was to bend, indicating a stiffer fabric. The drape stiffness is 
calculated as 0.5 x bending length. A total of 5 samples of each fabric 
should be taken. This procedure conforms to ASTM standard test D-1388 
except for the fabric length which is different (longer). The test 
equipment used is a Cantilever Bending tester model 79-10 available from 
Testing Machines Inc., 400 Bayview Ave., Amityville, N.Y. 11701. As in 
most testing, the sample should be conditioned to ASTM conditions of 
65.+-.2 percent relative humidity and 72.+-.2.degree. F. (22.+-.1.degree. 
C.), or TAPPI conditions of 50.+-.2 percent relative humidity and 
72.+-.1.8.degree. F. prior to testing. 
Mullen Burst: This test measures the resistance of textile fabrics to 
bursting when subjected to hydraulic pressure. The bursting strength is 
defined as the hydrostatic pressure required to rupture a fabric by 
distending it with a force, applied through a rubber diaphragm, at right 
angles to the plane of the fabric. This method measures the bursting 
strength of products up to 0.6 mm thick, having a bursting strength up to 
about 200 pounds per square inch. The pressure is generated by forcing a 
liquid (glycerin) into a chamber at the rate of 95.+-.5 ml/min. The 
specimen, held between annular claims, is subjected to increasing pressure 
at a controlled rate until the specimen ruptures. The bursting strength is 
expressed in pounds. This procedure conforms to TAPPI official standard 
T-403 os-76, except that specimen size is 5 inches (12.6 cm) square and 
ten specimens are tested. The test equipment used is a motor driven Mullen 
bursting strength tester from B.G. Perkins & Son Inc., G.P.O. 366, 
Chicopee, Mass. 01021 or from Testing Machines Inc., 400 Bayview Ave., 
Amityville, N.Y. 11701. The sample should be conditioned to ASTM 
conditions of 65.+-.2 percent relative humidity and 72.+-.2.degree. F. 
(22.+-.1.degree. C.), or TAPPI conditions of 50.+-.2 percent relative 
humidity and 72.+-.1.8.degree. F. prior to testing. 
Cup Crush: The softness of a nonwoven fabric may be measured according to 
the "cup crush" test. The cup crush test evaluates fabric stiffness by 
measuring the peak load (also called the "cup crush load" or just "cup 
crush") required for a 4.5 cm diameter hemispherically shaped foot to 
crush a 23 cm by 23 cm piece of fabric shaped into an approximately 6.5 cm 
diameter by 6.5 cm tall inverted cup while the cup shaped fabric is 
surrounded by an approximately 6.5 cm diameter cylinder to maintain a 
uniform deformation of the cup shaped fabric. An average of 10 readings is 
used. The foot and the cup are aligned to avoid contact between the cup 
walls and the foot which could affect the readings. The peak load is 
measured while the foot is descending at a rate of about 0.25 inches per 
second (380 mm per minute) and is measured in grams. The cup crush test 
also yields a value for the total energy required to crush a sample (the 
"cup crush energy") which is the energy from the start of the test to the 
peak load point, i.e. the area under the curve formed by the load in grams 
on one axis and the distance the foot travels in millimeters on the other. 
Cup crush energy is therefore reported in gm-mm. Lower cup crush values 
indicate a softer laminate. A suitable device for measuring cup crush is a 
model FTD-G-500 load cell (500 gram range) available from the Schaevitz 
Company, Pennsauken, N.J. 
DETAILED DESCRIPTION OF THE INVENTION 
Thermoplastic polymers are useful in the production of films, fibers and 
webs for use in a variety of products such as personal care products, 
infection control products, garments and protective covers. 
Materials for gowns must have good strength, durability and puncture 
resistance. It is also usually desired that such materials be thin in 
order to retain minimal heat and preferably to conform to an object easily 
for increased comfort. Increased softness, conformability and comfort have 
been pursued in the past by topical treatments and/or mechanical means, 
such as that discussed in U.S. Pat. No. 5,413,811 to Fitting et al. which 
uses chemical and mechanical means to increase softness. Also discussed in 
Fitting is the wash softening process and other softening processes. 
The inventors have found that a laminate of spunbond and meltblown fabrics 
having lower drape stiffness values, and therefore greater conformability 
and comfort, surprisingly may be produced by using elastic meltblown 
fabric in the interior. While one would expect the substitution of an 
elastic interior meltblown layer for an inelastic interior meltblown layer 
to have little effect on external fabric sensory characteristics, such is 
not the case. Even though the overall fabric is not elastic, the interior 
elastic meltblown layer produces a dramatic decrease in drape stiffness. 
This appears to be irrespective of the type of elastic meltblown employed. 
The barrier properties of a fabric may be measured using the hydrohead 
test. This test determines the height of water (in millibars) which the 
fabric will support before a predetermined amount of liquid passes 
through. A fabric with a higher hydrohead reading indicates it has a 
greater barrier to liquid penetration than a fabric with a lower 
hydrohead. The hydrohead value of a material will be influenced by such 
factors as the size of the fibers, finer fibers producing smaller pores 
for liquid to pass through, and the hydrophobicity of the fibers. The 
inventors believe that a material having a hydrohead value of at least 10 
millibars is necessary in infection control applications. 
The strength of a fabric may be measured by the Mullen Burst strength test. 
The conformability of a fabric may be measured by the Drape Stiffness test, 
or simply Drape test. This test measures how far a fabric may be extended 
off the edge of a table before bending. The lower the reading the more 
conformable, and presumably comfortable, a fabric will be on the wearer. 
Elastomeric thermoplastic polymers useful in the practice of this invention 
may be those made from block copolymers such as polyurethanes, 
copolyesters, polyamide polyether block copolymers, ethylene vinyl 
acetates (EVA), block copolymers having the general formula A-B-A' or A-B 
like copoly(styrenelethylene-butylene), 
styrene-poly(ethylene-propylene)-styrene, 
styrene-poly(ethylene-butylene)-styrene, 
(polystyrene/poly(ethylene-butylene)/polystyrene, 
poly(styrene/ethylene-butylene/styrene) and the like. 
Useful elastomeric resins include block copolymers having the general 
formula A-B-A' or A-B, where A and A' are each a thermoplastic polymer 
endblock which contains a styrenic moiety such as a poly (vinyl arene) and 
where B is an elastomeric polymer midblock such as a conjugated diene or a 
lower alkene polymer. Block copolymers 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).sub.m -X, wherein X is a polyfunctional 
atom or molecule and in which each (A-B).sub.m - radiates from 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 not limited thereto. 
Thus, in the present invention, the expression "block copolymer", and 
particularly "A-B-A'" and "A-B" block copolymer, is intended 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. The elastomeric nonwoven 
web may be formed from, for example, elastomeric 
(polystyrene/poly(ethylene-butylene)/polystyrene) block copolymers. 
Commercial examples of such elastomeric copolymers are, for example, those 
sold as part of the polymer family known as KRATON.RTM. materials which 
are available from Shell Chemical Company of Houston, Tex. KRATON.RTM. 
block copolymers are available in several different formulations, a number 
of which are identified in U.S. Pat. Nos. 4,663,220 and 5,304,599, hereby 
incorporated by reference. 
Polymers composed of an elastomeric A-B-A-B tetrablock copolymer may also 
be used in the practice of this invention. Such polymers are discussed in 
U.S. Pat. No. 5,332,613 to Taylor et al. In such polymers, A is a 
thermoplastic polymer block and B is an isoprene monomer unit hydrogenated 
to substantially a poly(ethylene-propylene) monomer unit. An example of 
such a tetrablock copolymer is a 
styrene-poly(ethylene-propylene)-styrene-poly(ethylene-propylene) or 
SEPSEP elastomeric block copolymer available from the Shell Chemical 
Company of Houston, Tex. as part of the KRATON.RTM. polymer family. 
Other exemplary elastomeric materials which may be used include 
polyurethane elastomeric materials such as, for example, those available 
under the trademark ESTANE.RTM. from B. F. Goodrich & Co. or MORTHANE.RTM. 
from Morton Thiokol Corp., polyester elastomeric materials such as, for 
example, those available under the trade designation HYTREL.RTM. from E. 
I. DuPont De Nemours & Company, and those known as ARNITEL.RTM., formerly 
available from Akzo Plastics of Arnhem, Holland and now available from DSM 
of Sittard, Holland. 
Another suitable material is a polyester block amide copolymer having the 
formula: 
##STR1## 
where n is a positive integer, PA represents a polyamide polymer segment 
and PE represents a polyether polymer segment. In particular, the 
polyether block amide copolymer has a melting point of from about 
150.degree. C. to about 170.degree. C., as measured in accordance with 
ASTM D789; a melt index of from about 6 grams per 10 minutes to about 25 
grams per 10 minutes, as measured in accordance with ASTM D-1238, 
condition Q (235 C/1 Kg load); a modulus of elasticity in flexure of from 
about 20 Mpa to about 200 Mpa, as measured in accordance with ASTM D-790; 
a tensile strength at break of from about 29 Mpa to about 33 Mpa as 
measured in accordance with ASTM D-638 and an ultimate elongation at break 
of from about 500 percent to about 700 percent as measured by ASTM D-638. 
A particular embodiment of the polyether block amide copolymer has a 
melting point of about 152.degree. C. as measured in accordance with ASTM 
D-789; a melt index of about 7 grams per 10 minutes, as measured in 
accordance with ASTM D-1238, condition Q (235 C/1 Kg load); a modulus of 
elasticity in flexure of about 29.50 Mpa, as measured in accordance with 
ASTM D-790; a tensile strength at break of about 29 Mpa, a measured in 
accordance with ASTM D-639; and an elongation at break of about 650 
percent as measured in accordance with ASTM D-638. Such materials are 
available in various grades under the trade designation PEBAX.RTM. from 
Atochem Inc. Polymers Division (RILSAN.RTM.), of Glen Rock, N.J. Examples 
of the use of such polymers may be found in U.S. Pat. Nos. 4,724,184, 
4,820,572 and 4,923,742 hereby incorporated by reference, to Killian et 
al. and assigned to the same assignee as this invention. 
Elastomeric polymers also include copolymers of ethylene and at least one 
vinyl monomer such as, for example, vinyl acetates, unsaturated aliphatic 
monocarboxylic acids, and esters of such monocarboxylic acids. The 
elastomeric copolymers and formation of elastomeric nonwoven webs from 
those elastomeric copolymers are disclosed in, for example, U.S. Pat. No. 
4,803,117. 
The thermoplastic copolyester elastomers include copolyetheresters having 
the general formula: 
##STR2## 
where "G" is selected from the group consisting of 
poly(oxyethylene)-alpha,omega-diol, poly(oxypropylene)-alpha,omega-diol, 
poly(oxytetramethylene)-alpha,omega-diol and "a" and "b" are positive 
integers including 2, 4 and 6, "m" and "n" are positive integers including 
1-20. Such materials generally have an elongation at break of from about 
600 percent to 750 percent when measured in accordance with ASTM D-638 and 
a melt point of from about 350.degree. F. to about 400.degree. F. (176 to 
205.degree. C.) when measured in accordance with ASTM D-2117. 
Commercial examples of such copolyester materials are, for example, those 
known as ARNITEL.RTM., formerly available from Akzo Plastics of Amhem, 
Holland and now available from DSM of Sittard, Holland, or those known as 
HYTREL.RTM. which are available from E.I. duPont de Nemours of Wilmington, 
Del. Formation of an elastomeric nonwoven web from polyester elastomeric 
materials is disclosed in, for example, U.S. Pat. No. 4,741,949 to Morman 
et al. and U.S. Pat. No. 4,707,398 to Boggs, hereby incorporated by 
reference. 
The above mentioned polymers are generally limited to meltblowing 
applications though the inventors have had some success in spunbonding 
some of them. The inventors contemplate, therefore, that these materials 
may be used for either spunbonding or meltblowing. 
These materials have recently been joined by a new class of polymers which, 
when made into fabric, has excellent barrier, breathability, elasticity 
and a pleasing hand. The new class of polymers is referred to as 
"metallocene" polymers or as produced according to the metallocene 
process. Metallocene polymers have been developed which may be processed 
by meltblowing or spunbonding. 
The metallocene process generally uses a metallocene catalyst which is 
activated, i.e. ionized, by a co-catalyst. Metallocene catalysts include 
bis(n-butylcyclopentadienyl)titanium dichloride, 
bis(n-butylcyclopentadienyl)zirconium dichloride, 
bis(cyclopentadienyl)scandium chloride, bis(indenyl)zirconium dichloride, 
bis(methylcyclopentadienyl)titanium dichloride, 
bis(methylcyclopentadienyl)zirconium dichloride, cobaltocene, 
cyclopentadienyltitanium trichloride, ferrocene, hafnocene dichloride, 
isopropyl(cyclopentadienyl,-1-flourenyl)zirconium dichloride, molybdocene 
dichloride, nickelocene, niobocene dichloride, ruthenocene, titanocene 
dichloride, zirconocene chloride hydride, zirconocene dichloride, among 
others. A more exhaustive list of such compounds is included in U.S. Pat. 
No. 5,374,696 to Rosen et al. and assigned to the Dow Chemical Company. 
Such compounds are also discussed in U.S. Pat. No. 5,064,802 to Stevens et 
al. and also assigned to Dow. 
The metallocene process, and particularly the catalysts and catalyst 
support systems are the subject of a number of patents. U.S. Pat. No. 
4,542,199 to Kaminsky et al. describes a procedure wherein 
methylaluminoxane (MAO) is added to toluene, the metallocene catalyst of 
the general formula (cyclopentadienyl)2MeRHal wherein Me is a transition 
metal, Hal is a halogen and R is cyclopentadienyl or a C1 to C6 alkyl 
radical or a halogen, is added, and ethylene is then added to form 
polyethylene. U.S. Pat. No. 5,189,192 to LaPointe et al. and assigned to 
Dow Chemical describes a process for preparing addition polymerization 
catalysts via metal center oxidation. U.S. Pat. No. 5,352,749 to Exxon 
Chemical Patents, Inc. describes a method for polymerizing monomers in 
fluidized beds. U.S. Pat. No. 5,349,100 describes chiral metallocene 
compounds and preparation thereof by creation of a chiral center by 
enantioselective hydride transfer. 
Co-catalysts are materials such as methylaluminoxane (MAO) which is the 
most common, other alkylaluminums and boron containing compounds like 
tris(pentafluorophenyl)boron, lithium tetrakis(pentafluorophenyl)boron, 
and dimethylanilinium tetrakis(pentafluorophenyl)boron. Research is 
continuing on other co-catalyst systems or the possibility of minimizing 
or even eliminating the alkylaluminums because of handling and product 
contamination issues. The important point is that the metallocene catalyst 
be activated or ionized to a cationic form for reaction with the 
monomer(s) to be polymerized. 
Polymers produced using metallocene catalysts have the unique advantage of 
having a very narrow molecular weight range. Polydispersity numbers 
(Mw/Mn) of below 4 and as even below 2 are possible for metallocene 
produced polymers. These polymers also have a narrow short chain branching 
distribution when compared to otherwise similar Ziegler-Natta produced 
type polymers. 
It is also possible using a metallocene catalyst system to control the 
isotacticity of the polymer quite closely when stereo selective 
metallocene catalysts are employed. In fact, polymers have been produced 
having an isotacticity of in excess of 99 percent. It is also possible to 
produce highly syndiotactic polypropylene using this system. 
Controlling the tacticity of a polymer can also result in the production of 
a polymer which contains blocks of isotactic and blocks of atactic 
material alternating over the length of the polymer chain. This 
construction results in an elastic polymer by virtue of the atactic 
portion. Such polymer synthesis is discussed in the journal Science, vol. 
267, (Jan. 13, 1995) at p. 191 in an article by K. B. Wagner. Wagner, in 
discussing the work of Coates and Waymouth, explains that the catalyst 
oscillates between the stereochemical forms resulting in a polymer chain 
having running lengths of isotactic sterocenters connected to running 
lengths of atactic centers. Isotactic dominance is reduced producing 
elasticity. Geoffrey W. Coates and Robert M. Waymouth, in an article 
entitled "Oscillating Stereocontrol: A Strategy for the Synthesis of 
Thermoplastic Elastomeric Polypropylene" at page 217 in the same issue, 
discuss their work in which they used metallocene 
bis(2-phenylindenyl)-zirconium dichloride in the presence of 
methylaluminoxane (MAO), and, by varying the pressure and temperature in 
the reactor, oscillate the polymer form between isotactic and atactic. 
Commercial production of metallocene polymers is somewhat limited but 
growing. Such polymers are available from Exxon Chemical Company of 
Baytown, Tex. under the trade name ACHIEVE.RTM. for polypropylene based 
polymers and EXACT.RTM. for polyethylene based polymers. A joint venture 
of the Dow Chemical Company of Midland, Mich. and E.I Dupont called Dupont 
Dow Elastomers L.L.C. has polymers commercially available under the name 
ENGAGE.RTM.. These materials are believed to be produced using non-stereo 
selective metallocene catalysts. Exxon generally refers to their 
metallocene catalyst technology as "single site" catalysts while Dow 
refers to theirs as "constrained geometry" catalysts under the name 
INSITE.RTM. to distinguish them from traditional Ziegler-Natta catalysts 
which have multiple reaction sites. Other manufacturers such as Fina Oil, 
BASF, Amoco, Hoechst and Mobil are active in this area and it is believed 
that the availability of polymers produced according to this technology 
will grow substantially in the next decade. In the practice of the instant 
invention, elastic polyolefins like polypropylene and polyethylene are 
preferred, most especially elastic polypropylene. 
Regarding metallocene based elastomeric polymers, U.S. Pat. No. 5,204,429 
to Kaminsky et al. describes a process which may produce elastic 
copolymers from cycloolefins and linear olefins using a catalyst which is 
a sterorigid chiral metallocene transition metal compound and an 
aluminoxane. The polymerization is carried out in an inert solvent such as 
an aliphatic or cycloaliphatic hydrocarbon such as toluene. The reaction 
may also occur in the gas phase using the monomers to be polymerized as 
the solvent. U.S. Pat. Nos. 5,278,272 and 5,272,236, both to Lai et al., 
assigned to Dow Chemical and entitled "Elastic Substantially Linear-Olefin 
Polymers" describe polymers having particular elastic properties. 
Suitable polymers for the elastic layer are available commercially under 
the trade designation "Catalloy" from the Himont Chemical Company of 
Wilmington, Del., and polypropylene. Specific commercial examples are 
Catalloy KS-084P and Catalloy KS-057P. These types of polymers are 
disclosed in European Patent Application EP 0444671 A3 (based on 
Application number 91103014.6), European Patent Application EP 0472946 A2 
(based on Application number 91112955.9), European Patent Application EP 
0400333 A2 (based on Application number 90108051.5), U.S. Pat. No. 
5,302,454 and U.S. Pat. No. 5,368,927. 
European Patent Application EP 0444671 A3 teaches a composition comprising 
first, 10-60 weight percent of a homopolymer polypropylene having an 
isotactic index greater than 90 or or a crystalline copolymer of propylene 
with ethylene and/or other alpha-olefins containing more than 85 weight 
percent of propylene and having an isotactic index greater than 85; 
second, 10-40 weight percent of a copolymer containing prevailingly 
ethylene, which is insoluble in xylene at room temperature; and third, 
30-60 weight percent of an amorphous ethylene-propylene copolymer, which 
is soluble in xylene at room temperature and contains 40-70 weight percent 
of ethylene, wherein the propylene polymer composition has a ratio between 
the intrinsic viscosities, in tetrahydronaphthalene at 135.degree. C., of 
the portion soluble in xylene and of the portion insoluble in xylene at 
room temperature of from 0.8 to 1.2. 
European Patent Application EP 0472946 A2 teaches a composition comprising 
first, 10-50 weight percent of a homopolymer polypropylene having an 
isotactic index greater than 80 or or a crystalline copolymer of propylene 
with ethylene, a CH.sub.2 .dbd.CHR alpha-olefin where R is a 2-8 carbon 
alkyl radical or combinations thereof, which copolymer contains more than 
85 weight percent of propylene; second, 5-20 weight percent of a copolymer 
containing ethylene, which is insoluble in xylene at room temperature; and 
third, 40-80 weight percent of a copolymer fraction of ethylene and 
propylene or another CH.sub.2 .dbd.CHR alpha-olefin, where R is a 2-8 
carbon alkyl radical, or combinations thereof, and, optionally, minor 
portions of a diene, the fraction containing less than 40 weight percent 
of ethylene and being soluble in xylene at ambient temperature and having 
an intrinsic viscosity from 1.5 to 4 dl/g; where the percent by weight of 
the sum of the second and third fractions with respect to the total 
polyolefin composition is from 50 to 90 percent and the second to third 
fraction weight ratio being lower than 0.4. 
European Patent Application EP 0400333 A2 teaches a composition comprising 
first, 10-60 weight percent of a homopolymer polypropylene having an 
isotactic index greater than 90 or or a crystalline propylene copolymer 
with ethylene and/or a CH.sub.2 .dbd.CHR olefin where R is a 2-8 carbon 
alkyl radical containing more than 85 weight percent of propylene and 
having an isotactic index greater than 85; second, 10-40 weight percent of 
a crystalline polymer fraction containing ethylene, which is insoluble in 
xylene at room temperature; and third, 30-60 weight percent of an 
amorphous ethylene-propylene copolymer containing optionally small 
proportions of a diene, which is soluble in xylene at room temperature and 
contains 40-70 weight percent of ethylene; where the composition has a 
flex modulus smaller than 700 MPa, tension set at 75 percent, less than 60 
percent, tensile stress greater than 6 MPa and notched IZOD resilience at 
-20.COPYRGT. and -40.degree. greater than 600 J/m. 
U.S. Pat. No. 5,302,454 teaches a composition comprising first, 10-60 
weight percent of a homopolymer polypropylene having an isotactic index 
greater than 90 or of a crystalline propylene copolymer with ethylene with 
CH.sub.2 .dbd.CHR olefin where R is a 2-6 carbon alkyl radical, or 
combinations thereof, containing more than 85 weight percent of propylene 
and having an isotactic index greater than 85; second, 10-40 weight 
percent of a crystalline polymer fraction containing ethylene and 
propylene, having an ethylene content of from 52.4 percent to about 74.6 
percent and which is insoluble in xylene at room temperature; and third, 
30-60 weight percent of an amorphous ethylene-propylene copolymer 
containing optionally small proportions of a diene, soluble in xylene at 
room temperature and contains 40-70 weight percent of ethylene; where the 
composition has a flex modulus smaller than 700 MPa, tension set at 75 
percent, less than 60 percent, tensile stress greater than 6 MPa and 
notched IZOD resilience at -20.COPYRGT. and -40.degree. greater than 600 
J/m. 
U.S. Pat. No. 5,368,927 teaches a composition comprising first, 10-60 
weight percent of a homopolymer polypropylene having an isotactic index 
greater than 80 or of a crystalline propylene copolymer with ethylene 
and/or an alpha-olefin having 4-10 carbon atoms, containing more than 85 
weight percent of propylene and having an isotactic index greater than 80; 
second, 3-25 weight percent of an ethylene-propylene copolymer insoluble 
in xylene at room temperature; and third, 15-87 weight percent of a 
copolymer of ethylene with propylene and/or an alpha-olefin having 4-10 
carbon atoms, and optionally a diene, containing 20-60 percent of 
ethylene, and completely soluble in xylene at ambient temperature. 
Another elastic polymer suitable for the practice of this invention is 
known as "flexible polyolefin" or FPO from Rexene of Odessa and Dallas, 
Tex. which has a controlled isotacticitiy. Other olefin polymer with an 
appropriate atactic portion and meeting the definition of "elastic" would 
be suitable as well. 
It is important in the practice of the invention that the outer layer be 
made from soft fibers. By "soft fiber" what is meant is a fiber which may 
be made into a web where the web has a cup crush energy of less than 1200 
gm-mm and cup crush load of less than 70 grams for, for example, a 1 osy 
(34 gsm) web. Since a soft fabric laminate is desired, the inventors have 
chosen the side-by-side polyethylene-polypropylene conjugate fiber 
spunbond fabric as the preferred outer layer. Polyethylene is known in the 
art as having a soft hand when used in nonwoven fabrics while 
polypropylene has greater strength. A conjugate fiber of the two polymers 
produces a strong yet soft layer which is non-elastic. A suitable soft 
monocomponent or homofilament fiber may be made from a Shell Chemical 
polypropylene copolymer designated WRD60277. Any other soft non-elastic 
outer layer may be substituted for the preferred soft layer provided it 
may be successfully bonded to the interior elastic layer(s). Other soft 
fiber layers include, for example, conjugate or monocomponent fibers of 
various types of nylon, polyester, polyolefins like polyethylene, 
polypropylene and polybutylene and polyolefin copolymers and blends of 
copolymers and/or polyolefins. 
In the practice of this invention, laminates may be made by sequentially 
depositing onto a moving forming belt first a spunbond fabric layer, then 
a meltblown fabric layer and last another spunbond layer and then bonding 
the laminate. It is preferred that the basis weight of the meltblown layer 
be between 0.1 and 2 osy (3.4 and 68 gsm) and the spunbond layers between 
0.2 and 2 osy (6.8 and 68 gsm) each. 
The layers may be bonded together by any method known in the art to be 
effective. Such methods include thermal point bonding, through-air bonding 
and adhesive bonding. 
A number of samples of material were tested in order to determine their 
barrier, breathability and elastic properties. The materials are described 
below and the results given in Table 1. The numbers reported in Table 1 
are averages of 5 readings except where noted. All samples used 0.4 osy 
(14 gsm) side-by-side polypropylene polyethylene conjugate spunbond fiber 
webs produced according to U.S. Pat. No. 5,382,400 to Pike et al. as 
facing materials. The polymers used to produce the facings were 
ESCORENE.RTM. PD-3445 polypropylene and ASPUN.RTM. 6811A polyethylene from 
Exxon Chemical Co. of Baytown, Tex. and Dow Chemical Co. of Midland, Mich. 
respectively. The facings were produced at a melt temperature of 
430.degree. F. (221.degree. C.) and 0.7 grams per hole per minute (ghm) 
and bonded at 252 to 255.degree. F. (122-124.degree. C.).

The Mullen Burst, Drape Stiffness and hydrohead tests described above under 
"Test Methods" were performed and the results are given in Table 1. Note 
that only the Examples are considered by the inventors to be within the 
practice of their invention. 
CONTROL 1 
This material is an SMS fabric comprised of the two facing spunbond layers 
mentioned above and a 1 osy (34 gsm) meltblown layer made from a polymer 
available commercially as PF-015 from Montell Chemical of Wilmington, Del. 
The layers were produced separately and bonded at a bonding temperature of 
280.degree. F. (138.degree. C.) with a nip pressure of 22 psig (1140 mm 
Hg) at a speed of 60 feet per minute (18.3 meters/minute). None of the 
layers of this material is elastic. 
EXAMPLE 1 
This material is an SMS fabric using the two 0.4 osy conjugate spunbond 
facings with a 1 osy (34 gsm) elastic meltblown layer produced from a 
polymer available from the Dow Chemical Co. of Midland, Mich. under the 
trade name ENGAGE.RTM. XU58200.02 elastic polymer. This material is a 
polyethylene copolymer having a density of 0.87 g/cc and a melt flow index 
of 30 grams/10 minutes at 190.degree. C. and 2160 grams according to ASTM 
test 1238-90b. The layers were produced separately and bonded at a bonding 
temperature of 150.degree. F. (65.degree. C.) with a nip pressure of 30 
psig (1550 mm Hg) at a speed of 38 feet per minute (11.6 meters/minute). 
EXAMPLE 2 
This material is an SMS fabric using the two 0.4 osy conjugate spunbond 
facings with a 1 osy (34 gsm) elastic meltblown layer produced from a 
polyethylene polymer designated EXACT.RTM. 4014 by the Exxon Chemical 
Company of Houston, Tex. The layers were produced separately and bonded at 
a bonding temperature of 150.degree. F. (65.degree. C.) with a nip 
pressure of 30 psig (1550 mm Hg) at a speed of 38 feet per minute (11.6 
meters/minute). 
EXAMPLE 3 
This material is an SMS fabric using the two 0.4 osy conjugate spunbond 
facings with a 2 osy (68 gsm) elastic meltblown layer produced from a 
blend of 95 weight percent of a polymer available from the Dow Chemical 
Co. of Midland, Mich. under the trade name ENGAGE.RTM. XU58200.02 elastic 
polymer and 5 weight percent of a polymer available from the Shell 
Chemical Co. under the trade name Kraton.RTM. G-2755. Kraton.RTM. G-2755 
is a styrene/ethylene/butadiene/styrene polymer (SEBS). The layers were 
produced separately and bonded at a bonding temperature of 150.degree. F. 
(65.degree. C.) with a nip pressure of 30 psig (1550 mm Hg) at a speed of 
38 feet per minute (11.6 meters/minute). 
TABLE 1 
______________________________________ 
Basis Drape Drape Hydro- Mullen 
Weight CD MD head Burst 
Sample (gsm) (cm) (cm) (mbar) (psi) 
______________________________________ 
Control 1.83 3.1 5.17 21.3 26.6 
Example 1 
1.7 na 2.08* 14 22.25 
Example 2 
1.82 2.27 2.5 14.3 22.3 
Example 3 
2.73 2.42 2.07 14.3 22.3 
______________________________________ 
*2 samples 
The results in Table 1 show that the material of this invention has good 
barrier properties and burst strength while providing improved drape 
stiffness. In particular it should be noted that the laminates of this 
invention have a drape stiffness (in the MD) less than half of a similar 
fabric having a layer of meltblown non-elastic fibers in place of the 
layer of meltblown elastic fibers. Surprisingly, even the heavier basis 
weight Example 3 has an MD drape of less than half of the Control and all 
the Examples have an MD drape of at most 2.5 cm. In regard to the burst 
strength, it should be noted that the fabric of this invention did not 
"burst" in the traditional sense of a catastrophic hole being created in 
the fabric as was the case with the control. Instead, the fabric of this 
invention gave way in a more controlled, slow manner, due presumably to 
the elastic center layer. 
The inventors believe that the highly conforming, breathable barrier 
material of this invention provides a mix of attributes which is different 
from and superior to that of current competitive materials. One would not 
have expected a soft laminate where the layer producing the softness and 
conformability of the laminate was sandwiched in the interior and 
surrounded by non-elastic layers. Previous attempts at producing soft 
laminates have taught away from this approach by focusing on the exterior 
layers of the laminate. 
Although only a few exemplary embodiments of this invention have been 
described in detail above, those skilled in the art will readily 
appreciate that many modifications are possible in the exemplary 
embodiments without materially departing from the novel teachings and 
advantages of this invention. Accordingly, all such modifications are 
intended to be included within the scope of this invention as defined in 
the following claims. In the claims, means plus function claims are 
intended to cover the structures described herein as performing the 
recited function and not only structural equivalents but also equivalent 
structures. Thus although a nail and a screw may not be structural 
equivalents in that a nail employs a cylindrical surface to secure wooden 
parts together, whereas a screw employs a helical surface, in the 
environment of fastening wooden parts, a nail and a screw may be 
equivalent structures.