Note: Descriptions are shown in the official language in which they were submitted.
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PATTERNED ~MR088BD NONWOVEN FABRIC, CLOTH-LIRE LIQUID R~P~T~
MATERIAL AND METHOD FOR MARING 8AME
TECHNICAL FIELD
This invention relates to patterned embossed nonwoven
fabrics, and more particularly relates to liquid barrier
materials such as the outer cover of personal care absorbent
articles which include a layer of patterned embossed nonwoven
fabric.
BACRGROUND OF THE lNV~h ~ lON
Nonwoven fabrics are useful for a wide variety of
applications, including absorbent personal care products,
garments, medical applications, and cleaning applications.
Nonwoven personal care products include infant care items such
as diapers, child care items such as training pants, feminine
care items such as sanitary napkins, and adult care items such
as incontinence products. Nonwoven garments include protective
workwear and medical apparel such as surgical gowns. Other
nonwoven medical applications include nonwoven wound dressings
and surgical dressings. Cleaning applications for nonwovens
include towels and wipes. Still other uses of nonwoven fabrics
are well known. The foregoing list is not considered
exhaustive.
Various properties of nonwoven fabrics determine the
suitability of nonwoven fabrics for different applications.
Nonwoven fabrics can be engineered to have different
combinations of properties to suit different needs. Variable
properties of nonwoven fabrics include liquid handling
properties such as wettability, distribution, and absorbency,
strength properties such as tensile strength and tear strength,
softness properties, durability properties such as abrasion
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resistance, and aesthetic properties.
The manufacture of nonwoven fabrics is a highly developed
art. Generally, nonwoven webs and their manufacture involve
forming filaments or fibers and depositing the filaments or
fibers in such a manner so as to cause the filaments or fibers
to overlap or entangle. Depending on the degree of web
integrity desired, the filaments or fibers of the web may then
be bonded by means such as an adhesive, the application of heat
or pressure, or both, sonic bonding techniques, or
hydroentangling, or the like. There are several methods within
this general description; however, one commonly used process is
known as spunbonding and resulting nonwoven fabric is known as
spunbond fabric.
Generally described, the process for making spunbond
nonwoven fabric includes extruding thermoplastic material
through a spinneret and drawing the extruded material into
filaments with a stream of high velocity air to form a random
web on a collecting surface. Such a method is referred to as
meltspinning. Spunbond processes are generally defined in
numerous patents including, for example, U.S. Patent 4,692,618
to Dorschner, et al.; U.S. Patent 4,340,563 Appel, et al.; U.S.
Patent 3,338,992 to Kinney; U.S. Patent 3,341,394 to Kinney;
U.S. Patent 3,502,538 to Levy; U.S. Patent 3,502,763 to
Hartmann; U.S. Patent 3,909,009 to Hartmann; U.S. Patent
3,542,615 to Dobo et al.; and Canadian Patent 803,714 to
Harmon.
Other methods of making nonwoven fabrics involve the
formation of fibrous webs with staple fibers. As used herein,
polymeric fibers and filaments are referred to generically as
polymeric strands. Filaments means continuous strands of
material and fibers means cut or discontinuous strands having
a definite length. Staple fibers may be formed into entangled
webs by conventional processes such as carding, airlaying, or
the like.
Although nonwoven fabric properties such as liquid handling
properties, strength properties, softness properties and
durability properties, are normally of primary importance in
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designing nonwoven fabrics, the appearance and feel of nonwoven
fabrics are often critical to the success of a nonwoven fabric
product. The appearance and feel of nonwoven fabrics is
particularly important for nonwoven fabrics which form exposed
portions of products. For example, it is often desirable that
the outer covers of nonwoven fabric products have a cloth-like
feel and a pleasing decorative design.
Outer covers of personal care products typically function
as a liquid barrier and normally include a solid film of
thermoplastic material such as polyethylene film rather than
a nonwoven fabric. As a result, such materials often have a
firm, smooth outer surface whereas it is more desirable that
such materials have a more cloth-like feel.
One method of applying a decorative design to nonwoven
products is by printing a decorative design on the outer cover
with ink. However, printing does not alter the feel of the
material. Embossing is one method to alter the feel of
nonwoven fabrics and add a decorative design. Different
methods for embossing nonwoven fabrics and films are known.
Some bonding methods are designed primarily to affect the
strength properties of the fabric and are not capable of
imparting a particularly decorative design to the fabric. One
such example is a method disclosed in U.S. Patent 4,592,943 to
Cancian et al. In that method, a nonwoven web is heated as the
web passes between two grids so that the grids impart a pattern
of rectangular densified areas to the web. Although this
method is effective to alter the strength properties of the
fabric, its use in applying a decorative pattern to fabric is
limited because the possible designs of the grids are limited.
A more versatile method of embossing nonwoven fabrics and films
is pattern roll embossing. For example, U.S. Patent 4,774,124
to Shimalla et al. discloses a method wherein a pair of pattern
embossing rollers are used to emboss nonwoven fabric.
Despite the advances in the art described above, there is
still a need for improved patterned nonwoven webs and methods
of their manufacture. In particular, there is a need for
liquid barrier outer cover materials with improved appearance
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and feel and improved methods for making such materials.
SUMMARY OF THE lNv~ lON
Accordingly, an aspect of the present invention is to
provide an improved patterned nonwoven fabric.
Another aspect of the present invention is to provide a
more efficient and economical method for making patterned
nonwoven fabric.
Another aspect of the present invention is to provide
nonwoven fabric embossed with relatively detailed patterns and
methods for making the same.
Still another aspect of the present invention is to provide
improved liquid barrier outer cover materials for nonwoven
fabrics.
A further aspect of the present invention is to provide an
efficient and economical process for making patterned liquid
barrier outer cover materials.
A still further aspect of the present invention is to
provide liquid barrier outer cover materials with relatively
detailed embossed patterns and methods for making the same.
Yet another aspect of the present invention is to provide
liquid barrier outer cover materials with a cloth-like feel and
improved aesthetic properties.
Therefore, there is provided a patterned nonwoven fabric
comprising polymeric strands which include a primary polymeric
component and are bonded together with a heat-activated
adhesive polymeric component which adheres the respective
primary components together without compression. The fabric
has an embossed pattern of densified areas separated by high
loft areas. Preferably, the nonwoven fabric is laminated to a
liquid barrier film to form an outer cover material for
products such as personal care absorbent articles and the like.
According to one aspect of the present invention, the nonwoven
fabric includes continuous polymeric filaments. According to
another aspect of the present invention, the nonwoven fabric
includes crimped polymeric strands. Methods for making these
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materials are also encompassed by the present invention.
The nonwoven fabric of the present invention has a
cloth-like feel even when laminated to a barrier film. In
addition, because the fabric has relatively high loft, when
embossed, it has a relatively distinct pattern because of the
depth of the pattern which is formed between the high loft
areas. Furthermore, because the nonwoven fabric is bonded with
adhesive and without compression before embossing, the high
loft areas are more durable and less likely to fray than if the
material was simply embossed. When the nonwoven fabric is made
with crimped fibers or filaments, the loft of the unembossed
areas is even higher and the pattern is even more distinct.
According to one embodiment, the nonwoven fabric of the
present invention comprises continuous polymeric filaments
extending continuously along the length of the fabric. Each
filament has a primary polymeric component extending
continuously along the length of the filament. The filaments
are bonded together without the use of compression, but instead
are bonded with a heat-activated adhesive polymeric component
which adheres the respective primary components together. The
fabric is then embossed with a pattern of densified areas
separated by high loft areas.
The present invention also encompasses a process for making
a nonwoven fabric such as the above disclosed nonwoven fabric
with continuous polymeric filaments. This process includes the
steps of: melt-spinning continuous spunbond polymeric
filaments; drawing the continuous filaments; quenching the
filaments; thereafter, collecting the drawn filaments on a
moving forming surface to form a nonwoven fabric web of
continuous filaments; bonding together the filaments of the web
with a heat activated polymeric adhesive to integrate the web
without the application of pressure; and embossing the web with
a pattern of densified areas separated by high loft areas.
This continuous process provides for production of the nonwoven
fabric of the present invention in a single process line.
According to another embodiment, the nonwoven fabric of the
present invention comprises polymeric strands (fibers or
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filaments, or both) which are crimped. Preferably, the strands
have natural helical crimp which adds bulk to the fabric.
Preferably, the strands have from about 5 to about 15 crimps
per extended inch of strand, counting 1 crimp per cycle of the
helical strands according to method described in ASTM-3937.
The present invention also encompasses a process for making
the above-described nonwoven fabric comprising crimped
polymeric strands. This process includes the steps of: forming
a web of crimped polymeric strands having a primary polymeric
component; bonding together the filaments of the web with a
heat activated polymeric adhesive to integrate the web without
the application of pressure; and embossing the web with a
pattern of densified areas separated by high loft areas.
The nonwoven fabric of the present invention is bonded by
heating the web. The fabric may be heated by forcing heated
air through the web. There are several suitable methods for
applying the heat-activated adhesive polymer to the web.
According to one method, the heat-activated adhesive polymer is
added as a polymeric powder and the web is heated to activate
the adhesive powder and bond the fibers or filaments together.
Another suitable method for adding the heat-activated adhesive
polymer to the fabric is to add strands of the heat-activated
adhesive polymer to the web and then heat the web to activate
the adhesive strands. Still another method of adding the
heat-activated adhesive polymer to the fabric is to include
multicomponent strands in the fabric. The multicomponent
strands include the primary polymeric component and the
heat-activated adhesive component. The primary and adhesive
components are arranged in substantially distinct zones across
the cross-section of the multicomponent strands and extend
continuously along the length of the multicomponent strands.
The adhesive component constitutes at least a portion of the
peripheral surface of the multicomponent strands continuously
along the length of the strands. The multicomponent strands
3S are bonded by heating the web to a temperature which is
sufficient to activate the adhesive component of the strands
and is less than the melting temperature of the primary
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polymeric component of the strands. As a result, the
multicomponent strands become fused at their points of contact.
Another advantage to using multicomponent strands is that
multicomponent strands can be made with a high level of natural
helical crimp when the respective components are properly
arranged. It is particularly advantageous when making the
fabric of the present invention with continuous multicomponent
filaments in a continuous spunbond process to activate the
latent helical crimp of the filaments before the filaments are
collected on the forming surface. This results in a lofty
fabric web and is a relatively low cost process.
Preferably, the fabric of the present invention is embossed
by passing the fabric web through the nip between a pair of
embossing rolls, at least one of the rolls being heated. The
total embossed area of the fabric is preferably from about 5 to
about 30% of the surface area of the fabric.
According to yet another aspect of the present invention,
a composite material is provided comprising a layer of nonwoven
fabric laminated to a polymeric film. The layer of nonwoven
fabric comprises polymeric strands which include a primary
polymeric component. The strands are bonded together, as
described above, with a heat-activated adhesive polymeric
component which adheres the respective primary components of
the strands together without compression. The fabric has an
embossed pattern of densified areas separated by high-loft
regions, also as described above. Preferably, the polymeric
film is a liquid barrier film when the composite material of
the present invention is used to make the outer cover of
products such as personal care absorbent products. The layer
of fabric in the polymeric film can be laminated with an
adhesive or can be laminated during the embossing step by
simultaneously passing the polymeric film and the nonwoven
fabric together through the nip between a pair of embossing
rolls with at least one of the rolls being heated.
The nonwoven fabric of the present invention can be used to
make a variety of products including personal care articles
such as infant diapers, adult incontinence products, feminine
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care absorbent products, and training pants. The nonwoven
fabric of the present invention is also useful to make
garments, medical products and cleaning products. The
composite material of the present invention is particularly
s useful as an outer cover liquid barrier material for personal
care articles such as infant diapers. The composite material
of the present invention provides an outer cover material with
a cloth-like feel and an aesthetic design.
Still further aspects and the broad scope of the
applicability of the present invention will become apparent to
those of skill in the art from the details given hereinafter.
However, it should be understood that the detailed description
of the preferred embodiments of the present invention is given
only by way of illustration because various changes and
modifications well within the spirit and scope of the invention
should become apparent to those of skill in the art in view of
the following detailed description.
BRIEF DE8CRIPTION OF THE DRAWING8
Figure 1 is a schematic drawing of a process line for
making a preferred embodiment of the present invention.
Figure 2A is a schematic drawing illustrating the cross
section of a filament made according to a preferred embodiment
of the present invention with the polymer components A and B
in a side-by-side arrangement.
Figure 2B is a schematic drawing illustrating the cross
section of a filament made according to a preferred embodiment
of the present invention with the polymer components A and B
in an eccentric sheath/core arrangement.
Figure 2C is a schematic drawing illustrating the cross
section of a filament made according to a preferred embodiment
of the present invention with the polymer components A and B
in an concentric sheath/core arrangement.
Figure 3 is a perspective view of embossing rolls being
used to make a preferred embodiment of the present invention.
Figure 4 is a plan view of an infant diaper made in
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accordance with a preferred embodiment of the present
invention.
D~T~TT~n DE8CRIPTION OF THE INVENTION
As discussed above, the present invention provides a
patterned nonwoven fabric having a cloth-like feel and an
aesthetic decorative design. The fabric comprises polymeric
strands which include a primary polymeric component and are
bonded with a heat-activated polymeric adhesive component which
adheres the respective primary components together without the
use of compression. The decorative design is provided by an
embossed pattern of densified areas separated by high-loft
areas. The present invention also comprehends a composite
material comprising a layer of the above described fabric
laminated to a polymeric film and methods for making the
nonwoven fabric and the composite material.
The fabric and composite material of the present invention
are particularly useful for making personal care articles,
garment materials, medical products, and cleaning products.
Personal care articles include infant care items such as infant
diapers, child care items such as training pants, and adult
care items such as incontinence products, and feminine care
- items. Suitable garments include medical-apparel, workwear,
and the like.
The fabric of the present invention preferably includes
continuous multicomponent polymeric filaments and a process for
making such an embodiment is shown in Figure 1 and is described
in detail below. Preferably, the fabric of the present
invention includes bicomponent polymeric filaments wherein the
two polymeric components are the primary polymeric component
and the adhesive polymeric component. However, it should be
understood that the fabric of the present invention can also be
made with staple bicomponent fibers which are formed into a web
by conventional carding, or air laying techniques, or the like.
A wide variety of staple bicomponent fibers can be used to make
the fabric of the present invention. Suitable commercially
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available staple fibers include low density
polyethylene/polypropylene ES (eccentric sheath/core)
bicomponent fibers available from Danaklon A/S of Varde,
Denmark and high density polyethylene/polyethylene
terephthalate eccentric sheath/core bicomponent fibers
available from BASF Corporation, Fiber Division, of Greensboro,
North Carolina.
The fibers or filaments used to make the fabric of the
present invention are preferably crimped for higher loft. The
type of crimp is preferably natural helical crimp. Bicomponent
fibers and filaments with a side-by-side or eccentric sheath
core configuration can be helically crimped as described below.
Preferably the fibers or filaments have from about 5 to about
15 crimps per inch of extended length, counting 1 crimp per
repeat cycle of the helical fibers or filaments. When the
crimp is less than about 5 crimps per extended inch and the
fabric has a low basis weight, the bulk of the fabric tends to
be too low to form a distinct embossed pattern in the fabric,
and when the crimp is greater than about 15 crimps per extended
inch, the fabric tends to have a nonuniform density. Filaments
and fibers having a medium crimp (5 to 15 crimps per extended
inch) result in a fiber with sufficient bulk and uniformity.
After formation of the fabric web, either by continuous
spunbond techniques or staple fiber techniques, the filaments
of the web are bonded together with the heat-activated
polymeric adhesive to integrate the web without the application
of pressure. The preferred method of bonding the filaments or
fibers is by through-air bonding wherein heated air is passed
through the web. Through-air bonding is described in more
detail below. The filaments can also be bonded by other means
of applying heat such as infrared heating, oven heating, or
the like. By bonding the web with heat activated adhesive
instead of some type of compression bonding, the web retains
its loft and has integrity through the remainder of processing
and does not disintegrate during embossing or transfer or
subsequent processing steps.
After the fibers or filaments are bonded tGgether, the web
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is embossed with a pattern of densified areas. Preferably the
embossing is carried out with embossing rolls, at least one of
which is heated. When embossing rolls are used, the fabric can
be embossed with very intricate patterns which are clearly
visible in the fabric. The temperature of the embossing rolls
can vary depending on the polymers used, the polymer components
of the fibers or filaments, the basis weight of the fabric, the
line speed, and other factors, but it must be sufficient to
cause cold fusion bonding between the fibers or filaments. The
densified area which results from the embossing is preferably
from about 5 to about 30% of the fabric area. When the
densified area is less than about 5%, the abrasion resistance
of the fabric is too low. When the densified area of the
fabric is greater than about 30~, the fabric tends to be too
stiff.
The fabric web is preferably laminated to a polymeric film,
such as a liquid barrier film, to make liquid impermeable
outercover materials for garments, personal care absorbent
articles, and the like. The fabric web can be simultaneously
embossed and laminated to the polymeric film by passing the
fabric web and polymeric film simultaneously through the
embossing rolls. The temperature of the embossing rolls
becomes particularly important when the embossing and
lamination steps are bonded simultaneously. Again, the
appropriate temperature of the embossing rolls depends on the
particular polymers used and other factors, but if the
temperature of the embossing rolls is too low, then there is
insufficient lamination between the fabric web and the
polymeric film, and if the temperature of the embossing rolls
is too high, pinholes develop in the polymeric film which can
allow leakage.
The polymeric film can also be laminated to the fabric by
other means such as adhesive bonding. Suitable adhesives
include hot-melt, water-based, and solvent-based adhesives.
After the fiber web is embossed, the web can be adhered to the
polymeric film with the adhesive by spraying the adhesive on
the fabric or the film and then passing the fabric and film
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between the nip of two compression rolls.
Suitable polymeric films for the composite material of the
present invention include XBPP-4.0 soft, blown polypropylene or
polyethylene film available from Consolidated Thermoplastics
Company of Schaumburg, Illinois.
Although the fabric of the present invention is preferably
made with continuous bicomponent filaments or staple
bicomponent fibers, the fabric of the present invention can
also be made with single component fibers or filaments.
Instead of the primary polymeric component and the adhesive
polymeric component being contained in single fiber such as
with bicomponent fibers, the primary polymeric component and
the adhesive polymeric component can be separate fibers or
filaments integrated into a single web. According to another
method, the polymeric adhesive can be added to a web of fibers
or filaments in the form of a polymeric adhesive powder. In
either case, the fabric web is bonded in the same manner as
when the fabric web includes multicomponent fibers or
filaments.
The fabric of the present invention preferably has a basis
weight of at least 0.4 ounces per square yard (osy) and a
thickness, in the high loft areas, of at least 20 mils. When
the thickness of the high loft areas is less than about 20
mils, the embossed pattern becomes less visible. Also
preferably, the polymeric components of the fibers or filaments
and the degree of embossing are such that the densified areas
of the embossed fabric have a luster which contrasts with the
flat appearance of the high loft areas so that the embossed
pattern of the fabric is clearly visible.
As discussed above, a preferred embodiment of the present
invention is a polymeric fabric including continuous
bicomponent filaments. The bicomponent filaments comprise a
primary polymeric component A and an adhesive polymeric
component B and have a cross-section, a length, and a
peripheral surface. The primary and adhesive components A and
B are arranged in substantially distinct zones across the
cross-section of the bicomponent filaments and extend
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continuously along the length of the bicomponent filaments.
The adhesive component B constitutes at least a portion of the
peripheral surface of the bicomponent filaments continuously
along the length of the bicomponent filaments.
The components A and B are arranged in either a
side-by-side arrangement as shown in Fig. 2A or an eccentric
sheath/core arrangement as shown in Fig. 2B when filaments
having a natural helical crimp are desired. When uncrimped
filaments are desired the components A and B may be arranged in
a concentric sheath/core pattern as shown in Fig. 2C. Primary
polymer component A is the core of the filament and adhesive
polymer component B is the sheath in the sheath/core
arrangement. Methods for extruding multicomponent polymeric
filaments into such arrangements are well-known to those of
ordinary skill in the art.
A wide variety of polymers are suitable to practice the
present invention including polyolefins (such as polyethylene
and polypropylene), polyesters, polyamides, polyurethanes, and
the like. Primary polymer component A and adhesive polymer
component B must be selected so that the resulting bicomponent
filament is capable of developing a natural helical crimp.
Preferably, the adhesive polymer component B has a melting
temperature which is less than the melting temperature of the
primary polymer component A.
Preferably, primary polymer component A comprises
polypropylene or random copolymer of propylene and ethylene.
Adhesive polymer component B preferably comprises polyethylene
or random copolymer of propylene and ethylene. Preferred
polyethylenes include linear low density polyethylene and high
density polyethylene. In addition, adhesive polymer component
B may comprise additives for enhancing the natural helical
crimp of the filaments, lowering the bonding temperature of
the filaments, and enhancing the abrasion resistance, strength
and softness of the resulting fabric.
When polypropylene is the primary component A and
polyethylene is the adhesive component B, the bicomponent
filaments may comprise from about 20 to about 80% by weight
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polypropylene and from about 20 to about 80% polyethylene.
More preferably, the filaments comprise from about 40 to about
60% by weight polypropylene and from about 40 to about 60% by
weight polyethylene.
Turning to Figure 1, a process line 10 for preparing a
preferred embodiment of the present invention is disclosed.
The process line 10 is arranged to produce bicomponent
continuous filaments, but it should be understood that the
present invention comprehends nonwoven fabrics made with
multicomponent filaments having more than two components. For
example, the fabric of the present invention can be made with
filaments having three or four components.
The process line 10 includes a pair of extruders 12a and
12b for separately extruding the primary polymer component A
and the adhesive polymer component B. Polymer component A is
fed into the respective extruder 12a from a first hopper 14a
and polymer component B is fed into the respective extruder
12b from a second hopper 14b. Polymer components A and B are
fed from the extruders 12a and 12b through respective polymer
conduits 16a and 16b to a spinneret 18. Spinnerets for
extruding bicomponent filaments are well-known to those of
ordinary skill in the art and thus are not described here in
detail. Generally described, the spinneret 18 includes a
housing containing a spin pack which includes a plurality of
plates stacked one on top of the other with a pattern of
openings arranged to create flow paths for directing polymer
components A and B separately through the spinneret. The
spinneret 18 has openings arranged in one or more rows. The
spinneret openings form a downwardly extending curtain of
filaments when the polymers are extruded through the spinneret.
For the purposes of the present invention, spinneret 18 may be
arranged to form side-by-side, eccentric sheath/core, or
concentric sheath/core bicomponent filaments illustrated in
Figures 2A, 2B, and 2C.
The process line 10 also includes a quench blower 20
positioned adjacent the curtain of filaments extending from the
spinneret 18. Air from the quench air blower 20 quenches the
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filaments extending from the spinneret 18. The quench air can
be directed from one side of the filament curtain as shown in
Fig. 1, or both sides of the filament curtain.
A fiber draw unit or aspirator 22 is positioned below the
spinneret 18 and receives the quenched filaments. Fiber draw
units or aspirators for use in melt spinning polymers are
well-known as discussed above. Suitable fiber draw units for
use in the process of the present invention include, for
example, a linear fiber aspirator of the type shown in U.S.
Patent No. 3,802,817 and eductive guns of the type shown in
U.S. Patent Nos. 3,692,618 and 3,423,266, the disclosures of
which are incorporated herein by reference. It should be
understood, however, that other types of fiber draw units can
be used to practice the present invention, such as the fiber
draw unit disclosed in U.S. Patent No. 4,340,563, the
disclosure of which is also incorporated herein by reference.
Generally described, the fiber draw unit 22 includes an
elongate vertical passage through which the filaments are drawn
by aspirating air entering from the sides of the passage and
flowing downwardly through the passage. A heater 24 supplies
hot aspirating air to the fiber draw unit 22. The hot
aspirating air draws the filaments and ambient air through the
fiber draw unit.
An endless foraminous forming surface 26 is positioned
below the fiber draw unit 22 and receives the continuous
filaments from the outlet opening of the fiber draw unit. The
filaments form a nonwoven web 27 on top of the forming surface
26. The forming surface 26 travels around guide rollers 28.
A vacuum 30 positioned below the forming surface 26 where the
filaments are deposited draws the filaments against the forming
surface.
The process line 10 further includes a compression roller
32 which, along with the forwardmost of the guide rollers 28,
receive the web as the web is drawn off of the forming surface
26. In addition, the process line includes a noncompressive
bonding apparatus such as a through-air bonder 36. Through-air
bonders are well-known to those skilled in the art and are not
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disclosed here in detail. Generally described, the through-air
bonder 36 includes a perforated roller 38, which receives the
web, and a hood 40 surrounding the perforated roller.
A pair of embossing rolls which include a pattern roll 42
and an anvil roll 44 simultaneously emboss the nonwoven fabric
web 27 and laminate the web to a polymeric film 46 to form a
composite material 48. Rolls 41 and 43 guide the nonwoven
fabric 27 and film 46 to the nip between the embossing rolls 42
and 44. Lastly, the process line 10 includes a winding roll 50
for taking up the finished composite material 48.
The embossing rolls 42 and 44 are best shown in Fig. 3.
The pattern roll 42 has a detailed raised pattern 52 which
imparts corresponding densified areas 56 in the nonwoven web
27. The densified areas 56 are separated by high-loft areas 58
which are not embossed.
To operate the process line 10, the hoppers 14a and 14b are
filled with the respective polymer components A and B. Polymer
components A and B are melted and extruded by the respective
extruders 12a and 12b through polymer conduits 16a and 16b and
the spinneret 18. Although the temperatures of the molten
polymers vary depending on the polymers used, when
polypropylene and polyethylene are used as components A and B
respectively, the preferred temperatures of the polymers range
from about 370 to about 530F and preferably range from 400 to
about 450F.
As the extruded filaments extend below the spinneret 18, a
stream of air from the quench blower 20 at least partially
quenches the filaments to develop a latent helical crimp in
the filaments. The quench air preferably flows in a direction
substantially perpendicular to the length of the filaments at
a temperature of about 45 to about 90F and a velocity from
about 100 to about 400 feet per minute.
After quenching, the filaments are drawn into the vertical
passage of the fiber draw unit 22 by a flow of hot air from the
heater 24 through the fiber draw unit. The fiber draw unit is
preferably positioned 30 to 60 inches below the bottom of the
spinneret 18. The temperature of the air supplied from the
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heater 24 is sufficient that, after some cooling due to mixing
with cooler ambient air aspirated with the filaments, the air
heats the filaments to a temperature required to activate the
latent crimp. The temperature required to activate the latent
crimp of the filaments ranges from about 110F to a maximum
temperature less than the melting point of the lower melting
component which for through-air bonded materials is the second
component B. The temperature of the air from the heater 24 and
thus the temperature to which the filaments are heated can be
varied to achieve different levels of crimp. Generally, a
higher air temperature produces a higher number of crimps.
The crimped filaments are deposited through the outlet
opening of the fiber draw unit 22 onto the traveling forming
surface 26. The vacuum 20 draws the filaments against the
forming surface 26 to form an unbonded, nonwoven web 27 of
continuous filaments. The web 27 is then lightly compressed by
the compression roller 32 and then through-air bonded in the
through-air bonder 36. In the through-air bonder 36, air
having a temperature above the melting temperature of component
B and below the melting temperature of component A is directed
from the hood 40, through the web 27, and into the perforated
roller 38. The hot air melts the lower melting adhesive
polymer component B and thereby forms bonds between the
bicomponent filaments to integrate the web 27. When
polypropylene and polyethylene are used as polymer components
A and B respectively, the air flowing through the through-air
bonder preferably has a temperature ranging from about 230 to
about 280F and a velocity from about 100 to about 500 feet per
minute. The dwell time of the web in the through-air bonder is
preferably less than about 6 seconds. It should be understood,
however, that the parameters of the through-air bonder depend
on factors such as the type of polymers used and thickness of
the web.
After being through-air bonded, the web 27 is directed by
guide roll 41 to the nip between the embossing rolls 42 and 44
along with the polymeric barrier film 46 which is directed by
guide roll 43. Lastly, the finished web is wound onto the
21~5:01
_
winding roller 50 and is ready for further treatment or use.
Although the preferred method of carrying out the present
invention includes contacting the multicomponent filaments with
heated aspirating air, the present invention encompasses other
methods of activating the latent helical crimp of the
continuous filaments before the filaments are formed into a
web. For example, the multicomponent filaments may be
contacted with heated air after quenching but upstream of the
aspirator. In addition, the multicomponent filaments may be
contacted with heated air between the aspirator and the web
forming surface. Furthermore, the filaments may be heated by
methods other than heated air such as exposing the filaments to
electromagnetic energy such as microwaves or infrared
radiation.
The following Examples 1-3 are designed to illustrate
particular embodiments of the present invention and to teach
one of ordinary skill in the art the manner of carrying out the
present invention.
BxamDle 1
A 0.7 osy basis weight bonded carded web comprising 2
denier, crimped low density polyethylene/polypropylene ES
bicomponent staple fibers available from Danaklon A/S of Varde,
Denmark was made using a Cardmaster 19724 carding machine,
available from John Hollingsworth On Wheels, Inc. of
Greenville, South Carolina. The fibers had an average length
~of 1.5 inches and a 50:50 eccentric sheath/core configuration.
The fibers had a natural helical crimp ranging from about 10 to
about 15 crimps per extended inch, counting 1 crimp per repeat
cycle of the helical fibers in accordance with ASTM D-3937.
The line speed of the carding machine was 100 feet per minute.
The carded web was through-air bonded and the temperature of
the air in the through-air bonder was 263F. The through-air
bonded carded web was then embossed by a pair of embossing
rollers. The patterned roll had a temperature of 285F and the
anvil roll had a temperature of 250F. Th~ rolls applied
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- 21 695~1
pressure of 35 psi to the fabric and the line speed of the
embossing step was 30 feet per minute. The fabric was
simultaneously embossed and thermally laminated to XBPP-4.0,
soft, blown polypropylene film available from Consolidated
Thermoplastics Company, of Schaumburg, Illinois. The
polypropylene film had a thickness of 0.6 mils. The fabric was
embossed with the detailed decorative pattern shown in Figure
3. The pattern had a bond area of 13%.
Example 2
A 0.8 osy basis weight bonded carded web comprising 1.8
denier polyethylene/polyethylene terephthalate bicomponent
staple fibers available from BASF Corporation, Fiber Division,
Greensboro, North Carolina was made. The fibers had a length
of 1.5 inches and a 50:50 eccentric sheath/core configuration.
The fibers had a natural helical crimp of about 12 crimps per
extended inch, counting 1 crimp per repeat cycle of the helical
fibers according to ASTM D-3937. The web was carded on a
Cardmaster 19724 carding machine available from John
Hollingsworth On Wheels, Inc of Greenville, South Carolina.
The carded web was through-air bonded at 273F at a line speed
of 120 feet per minute. The bonded carded web was then
embossed with a detailed pattern similar to that shown in
Figure 3. The temperature of the pattern roll was 238F and
the temperature of the anvil roll was 210F. The line speed of
the embossing step was 18 feet per minute and the pressure
between the nip of the embossing rolls was 32 psi. After
embossing, the fabric was laminated to 1.0 mil, XBPP-4.0 soft,
blown polyethylene film available from Consolidated
Thermoplastics Company, of Schaumburg, Illinois. The fabric
was laminated to the film with H2096 hot melt adhesive,
available from Findley Company, of Wauwatosa, Wisconsin, by
spraying the hot melt adhesive on the polyethylene film at the
rate of 2 grams per square meter and then passing the fabric in
film between a pair of compression rolls.
-- 19 --
21 6~501
-
Example 3
A 0.8 osy basis weight nonwoven fabric web comprising
continuous bicomponent filaments was made with the process
illustrated in Fig. 1 and described above. The configuration
of the filaments was side-by-side, the weight ratio of one side
to the other side being 1:1. The spinhole geometry was 0.6mm
D with an L/D ratio of 4:1 and the spinneret had 525 openings
arranged with 50 openings per inch in the machine direction.
The composition of component A was 100% by weight PD-3445
polypropylene from Exxon of Houston, Texas, and the composition
of component B was 95% by weight ASPUN 6811A polyethylene from
Dow Chemical Company of Midland, Michigan. The melt
temperature in the spin pack was 450F and the spinhole
throughput was 0.5 to 0.6 GHM. The quench air flow rate was
29.5 scfm and the quench air temperature was ambient, about
65F. The aspirator feed temperature was 250F and the
manifold pressure was 3 to 4 psi. The forming height was 10
inches. The filaments had a natural helical crimp ranging from
about 3 to about 15 crimps per extended inch, counting 1 crimp
per repeat cycle of the helical filaments according to ASTM
D-3937. The resulting web was through-air bonded at a
temperature of 257F and a line speed of 200fpm. The web was
embossed with a detailed pattern similar to that shown in Fig.
3 at pattern/anvil bond temperatures of 260/200F, a pressure
of 20 psi, and a line speed of 25 fpm. The bond pattern had a
total bond area of 13%. The embossed web was then laminated
with a hot-melt adhesive to a 1.0 mil XBPP-4.0 blown
polyethylene film available from Consolidated Thermoplastics of
Schaumburg, Illinois. The hot-melt adhesive was the same as
that used in Example 2 and was applied in the same manner.
The strength and the liquid barrier integrity of the
composite materials from Examples 1-3 were measured. The
strength of the lamination was measured by measuring the
adhesion force between the two layers of the composite
material. For each Example, the adhesion force of a 2" x 4"
sample was measured using a force transducer AccuForce Cadet
- 20 -
2 1 6950 1
Gage Model #544 supplied by Ametek, Inc., U.S. Gauge Division,
of Sellersville, Pennsylvania. The minimum force required to
separate the two plies was given in kilograms. The integrity
of the liquid barrier film was measured by measuring the
hydrostatic head which is a fabric's resistance to the
penetration of water under static pressure. Under controlled
conditions, a sample is subjected to water pressure that
increases at a constant rate until leakage appears on the
material's lower surface. Water pressure is measured as the
hydrostatic head height reached at the first sign of leakage.
Values are recorded in centimeters of water. A higher number
indicates higher resistance to water penetration. The adhesion
forces of the samples from Examples 1-3 were 2.4Kg, 4.OKg, and
4.3Kg respectively, and the hydrostatic head of the samples
from Examples 1-3 were llOcm, >llOcm, and >llOcm, respectively.
Turning to Figure 4, a disposable diaper-type article 100
made according to a preferred embodiment of the present
invention is shown. The diaper 100 includes a front waistband
panel section 112, a rear waistband panel section 114, and an
intermediate section 116 which interconnects the front and rear
waistband sections. The diaper comprises a substantially
liquid impermeable outer cover layer 120 made according to a
preferred embodiment of the present invention as described
above, a liquid permeable liner layer 130, and an absorbent
body 140 located between the outer cover layer and the liner
layer. Fastening means, such as adhesive tapes 136 are
employed to secure the diaper 100 on a wearer. The liner 130
and outer cover 120 are bonded to each other and to absorbent
body 140 with lines and patterns of adhesive, such as a
hot-melt, pressure-sensitive adhesive. Elastic members 160,
162, and 164 can be configured about the edges of the diaper
for a close fit about the wearer.
It is desirable that both the liner layer 130 and the
absorbent body 140 be hydrophilic to absorb and retain aqueous
liquids such as urine. Although not shown in Figure 4, the
disposable diaper 100 may include additional liquid handling
layers such as a surge layer, a transfe~r layer or a
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21 69501
distribution layer. These layers may be separate layers or may
be integral with the liner layer 120 or the absorbent pad 140.
Although the absorbent article 100 shown in Figure 4 is a
disposable diaper, it should be understood that the nonwoven
fabric and composite material of the present invention may be
used to make a variety of absorbent articles, and other
products such as those identified above.
While the invention has been described in detail with
respect to specific embodiments thereof, it will be appreciated
that those skilled in the art, upon attaining an understanding
of the foregoing, may readily conceive of alterations to,
variations of and equivalents to these embodiments.
Accordingly, the scope of the present invention should be
assessed as that of the appended claims and any equivalents
thereto.
