Note: Descriptions are shown in the official language in which they were submitted.
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BASE SHEET WITH SURFACE FIBER STRUCTURE
BACKGROUND
Conventional absorbent articles, including wiping products have been made from
woven and
knitted fabrics. Such wipers have been used in all different types of
industries, such as for industrial
applications, food service applications, health and medical applications, and
for general consumer use.
Conventional rags and washcloths can be reusable if laundered properly.
Disposable wipers,
however, continue to gain in popularity and are readily displacing many
conventional woven or knitted
products. Disposable wipers, for instance, can offer many advantages. For
example, disposable
wipers are generally more sterile, as they are generally free of debris and
contaminants, and can also
be pre-loaded with a cleaning solvent. Laundered rags and washcloths, for
instance, can still contain
residual debris from past use and can also pick up debris during the
laundering process. In addition,
laundering woven or knitted wipers can not only create a great expense, but
also requires the use of
copious amounts of water and detergents that must be properly disposed of.
Further, laundered rags
and dishcloths require separate solvents or surfactants to be kept on hand, as
they cannot be pre-
loaded unlike disposable wipers.
However, disposable wipers are often limited by conflicting interests. For
instance, industrial
wipers, food service wiping products, household cleaning wipers, medical
wiping products, and the like
generally need greater amounts of strength and should be capable of absorbing
not only water-based
solutions but also oily substances. Historically, however, problems have been
encountered in
producing such wipers that have both good water absorbency properties and good
oil absorbency
properties. For example, increasing the oil affinity of a wiping product may
result in a more
hydrophobic sheet that is less water absorbent. Similarly, increasing the
water affinity of a wiping
product may result in a hydrophilic sheet that has decreased oil absorbency.
Additionally, providing a
wiping product with good abrasiveness, for example, can limit the softness and
overall absorbance of
the wiper. Similarly, barrier fabrics, such as those used in masks and
performance fabrics suffer from
conflicting interests. For instance, treating the barrier fabric to have
improved barrier properties can
also increase the abrasiveness of the fabric, providing discomfort when the
fabric contacted the skin of
a user.
Further, altering the characteristics of these articles requires altering the
composition used to
form the base of the article, such as, by changing the fibers or other
components used during
formation of the underlying nonwoven web. This can cause further problems, as
any change to the
base composition can cause tradeoffs as discussed above, cause delays and
difficulties during
manufacturing, as well as be limited by the underlying properties of the
material.
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Therefore, in one aspect, it would be beneficial to provide a base sheet that
has overall
improved performance. For instance, in one aspect, it would be beneficial to
provide a base sheet that
exhibits improved performance in one or more of softness, absorption,
abrasion, and barrier
properties. Furthermore, it would be beneficial to provide an article formed
from a base sheet that
exhibits improved properties on opposed sides of the article.
SUMMARY
In one aspect, the present disclosure is generally directed to a base sheet
having a
microstructured topography. The base sheet includes a nonwoven web having a
first surface and an
opposed second surface, and extends in a first plane. The base sheet further
includes an adhesive,
and a plurality of staple fibers that extend in one or more second planes that
are not parallel to the first
plane, that are affixed to the first surface of the nonwoven web by the
adhesive. Furthermore, at least
a portion of the staple fibers have a length of about 5000 micrometers or
less, a denier of about 5 or
less, or a combination thereof.
In a further aspect, the base sheet is a wiping product or an absorbent
article. Furthermore, in
an aspect, at least a portion of the staple fibers have a length of about 1500
micrometers or less and a
denier of about 3 or less, or a length of about 1500 micrometers to about 5000
micrometers, and a
denier of about 3 to about 5.
Moreover, in an aspect, the nonwoven web includes elastomeric fibers, three-
dimensional
fibers, debonded cellulosic fibers, pulp fibers, or mixtures thereof.
Additionally or alternatively, the
nonwoven web includes polyethylene fibers, polyethylene fibers, pulp fibers,
or a combination thereof.
In a further aspect, the nonwoven web is a spunbond nonwoven web. Furthermore,
in one aspect, the
nonwoven web is embossed
In yet another aspect, the plurality of staple fibers include polyethylene
fibers, polypropylene
fibers, rayon fibers, nylon fibers, or a combination thereof. Furthermore, in
an aspect, the adhesive
includes an anionic component, the plurality of staple fibers contain a
cation, or a combination thereof.
In one aspect, the anionic component and adhesive are coated on at least a
portion of the nonwoven
web. Additionally or alternatively, 50% or more of the nonwoven web is coated
with the anionic
component and adhesive. In one aspect, the anionic component and adhesive are
applied on the
nonwoven web in a pattern that includes circles, squares, lines, or a
combination thereof. Moreover, in
an aspect, the base sheet includes a second plurality of staple fibers adhered
to the second surface of
the nonwoven web by an adhesive. In an aspect, the second plurality of staple
fibers have a different
length, denier, or fiber composition than the first plurality of staple
fibers, or a combination thereof.
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Furthermore, in one aspect, the nonwoven web exhibits: a water capacity of
about 200% to
about 800%, a cup crush load of less than about 100 grams, when measured using
a 34 gsm
nonwoven web, a bacterial filtration efficiency of about 80% or greater, or a
combination thereof. In an
aspect, the base sheet exhibits a 10% or greater improvement in one or more of
water capacity, cup
crush load, or bacterial filtration, as compared to the same nonwoven web that
does not include the
plurality of staple fibers
The present disclosure is also generally directed to a method of forming a
base sheet. The
method includes forming a nonwoven web that extends in a first plane, applying
an adhesive to a first
surface of the nonwoven web, and adhering a plurality of staple fibers to the
nonwoven web. In such
an aspect, at least a portion of the plurality of staple fibers extend in one
or more second planes that
are not parallel to the first plane, and have a length of 5000 micrometers or
less, a denier of 501 less,
or a combination thereof.
In another aspect, the adhesive includes an anionic component, where the
anionic component
and the adhesive are printed on the nonwoven web. In yet a further aspect, the
anionic component and
the adhesive are flexographically printed onto the nonwoven web and the
plurality of staple fibers are
electrostatically adhered to the nonwoven web. Additionally or alternatively,
the base sheet is
calendared.
Other features and aspects of the present disclosure are discussed in greater
detail below.
BRIEF DESCRIPTION OF THE DRAWINGS
A full and enabling disclosure of the present disclosure is set forth more
particularly in the
remainder of the specification, including reference to the accompanying
figures, in which:
Fig. 1 illustrates a cross-sectional view of an aspect of a base sheet
according to the present
disclosure;
Fig. 2 illustrates a cross-sectional view of an aspect of a base sheet
according to the present
discosure; and
Fig. 3 illustrates a method of forming a base sheet according to the present
disclosure.
Repeat use of reference characters in the present specification and drawings
is intended to
represent the same or analogous features or elements of the present invention.
DEFINITIONS
The terms "about," "approximately," or "generally,", when used herein to
modify a value,
indicates that the value can be raised or lowered by 10%, such as 7.5%, such
as 5%, such as 4%,
such as 3%, such as 2%, or such as 1%, and remain within the disclosed aspect.
The term "fiber" as used herein refers to an elongate particulate having an
apparent length
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greatly exceeding its apparent width, i.e. a length to diameter ratio of at
least about 10. More
specifically, as used herein, fiber refers to papermaking fibers. The present
invention contemplates the
use of a variety of papermaking fibers, such as, for example, natural fibers
or synthetic fibers, or any
other suitable fibers, and any combination thereof. Papermaking fibers useful
in the present invention
include cellulosic fibers commonly and more particularly wood pulp fibers.
The term "nonwoven web" generally refers to a web having a structure of
individual fibers or
threads which are interlaid, but not in an identifiable manner as in a knitted
fabric. Examples of
suitable nonwoven fabrics or webs include, but are not limited to, meltblown
webs, spunbond webs,
bonded carded webs, airlaid webs, coform webs, hydraulically entangled webs,
and so forth.
The term "meltblown web" generally refers to a nonwoven web that is formed by
a process in
which a molten thermoplastic material is extruded through a plurality of fine,
usually circular, die
capillaries as molten fibers into converging high velocity gas (e.g., air)
streams that attenuate the fibers
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 dispersed meltblown fibers. Such
a process is disclosed,
for example, in U.S. Patent No. 3,849,241 to Butin, et al., which is
incorporated herein in its entirety by
reference thereto for all purposes. Generally speaking, meltblown fibers may
be microfibers that are
substantially continuous or discontinuous, generally smaller than 10 microns
in diameter, and generally
tacky when deposited onto a collecting surface.
The term "spunbond web" generally refers to a web containing small diameter
substantially
continuous fibers. The fibers are formed by extruding a molten thermoplastic
material from a plurality
of fine, usually circular, capillaries of a spinnerette with the diameter of
the extruded fibers then being
rapidly reduced as by, for example, eductive drawing and/or other well-known
spunbonding
mechanisms. The production of spunbond webs is described and illustrated, for
example, in U.S.
Patent Nos. 4,340,563 to Appel, et al., 3,692,618 to Dorschner, et al.,
3,802,817 to Matsuki, et al.,
3,338,992 to Kinney, 3,341,394 to Kinney, 3,502,763 to Hartman, 3,502,538 to
Levy, 3,542,615 to
Dobo, et al., and 5,382,400 to Pike, et al., which are incorporated herein in
their entirety by reference
thereto for all purposes. Spunbond fibers are generally not tacky when they
are deposited onto a
collecting surface. Spunbond fibers may sometimes have diameters less than
about 40 microns, and
are often between about 5 to about 20 microns.
The term "coform" generally refers to composite materials comprising a mixture
or stabilized
matrix of thermoplastic fibers and a second non-thermoplastic material. As an
example, coform
materials may be made by a process in which at least one meltblown die head is
arranged near a
chute through which other materials are added to the web while it is forming.
Such other materials
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may include, but are not limited to, fibrous organic materials such as woody
or non-woody pulp such
as cotton, rayon, recycled paper, pulp fluff and also superabsorbent
particles, inorganic and/or organic
absorbent materials, treated polymeric staple fibers and so forth. Some
examples of such coform
materials are disclosed in U.S. Patent Nos. 4,100,324 to Anderson, et al.,
5,284,703 to Everhart, et al.,
and 5,350,624 to Georger, et al., each of which are incorporated herein in
their entirety by reference
thereto for all purposes.
The term "bonded carded web" refers to webs made from staple fibers which are
sent through
a combing or carding unit, which breaks apart and aligns the staple fibers in
the machine direction to
form a generally machine direction-oriented fibrous nonwoven web. Such fibers
are usually purchased
in bales which are placed in a picker or fiberizer which separates the fibers
prior to the carding unit.
Once the web is formed, it is then bonded by one or more of several known
bonding methods.
The term "elastomeric" and "elastic" and refers to a material that, upon
application of a
stretching force, is stretchable in at least one direction (such as the CD
direction), and which upon
release of the stretching force, contracts/returns to approximately its
original dimension. For example,
a stretched material may have a stretched length that is at least 50% greater
than its relaxed
unstretched length, and which will recover to within at least 50% of its
stretched length upon release of
the stretching force. A hypothetical example would be a one (1) inch sample of
a material that is
stretchable to at least 1.50 inches and which, upon release of the stretching
force, will recover to a
length of not more than 1.25 inches. Desirably, the material contracts or
recovers at least 50%, and
even more desirably, at least 80% of the stretched length.
The term "thermal point bonding" generally refers to a process performed, for
example, by
passing a material between a patterned roll (e.g., calender roll) and another
roll (e.g., anvil roll), which
may or may not be patterned. One or both of the rolls are typically heated.
The term "ultrasonic bonding" generally refers to a process performed, for
example, by
passing a material between a sonic horn and a patterned roll (e.g., anvil
roll). For instance, ultrasonic
bonding through the use of a stationary horn and a rotating patterned anvil
roll is described in U.S.
Patent Nos. 3,939,033 to Grgach, et al., 3,844,869 to Rust Jr., and 4,259,399
to Hill, which are
incorporated herein in their entirety by reference thereto for all purposes.
Moreover, ultrasonic
bonding through the use of a rotary horn with a rotating patterned anvil roll
is described in U.S. Patent
Nos. 5,096,532 to Neuwirth, et al., 5,110,403 to Ehlert, and 5,817,199 to
Brennecke, et al., which are
incorporated herein in their entirety by reference thereto for all purposes.
Of course, any other
ultrasonic bonding technique may also be used in the present invention.
The term "slurry" as used herein refers to a mixture comprising fibers and
water.
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The term "absorbent article" or "article" when used herein refers to products
made from fibrous
webs which includes, but is not limited to, personal care absorbent articles,
such as baby wipes, mitt
wipes, diapers, pant diapers, open diapers, training pants, absorbent
underpants, incontinence
articles, feminine hygiene products (e.g., sanitary napkins), swim wear and so
forth; medical absorbent
articles, such as garments, fenestration materials, underpads, bedpads,
bandages, absorbent drapes,
and medical wipes; food service wipers; clothing articles; pouches, and so
forth. Materials and
processes suitable for forming such articles are well known to those skilled
in the art. An absorbent
article, for example, can include a liner, an outer cover, and an absorbent
material or pad formed from
a fibrous web positioned therebetween.
The term "wiping product" as used herein refers to products made from fibrous
webs and
includes paper towels, industrial wipers, foodservice wipers, napkins, medical
pads, and other similar
products. It should be understood that, in one aspect, a wiping product may be
included when referring
to an absorbent article or absorbent web according to the present disclosure.
As used herein, the term "basis weight" generally refers to the dry weight per
unit area of a
fibrous product and is generally expressed as grams per square meter (gsm).
Basis weight is
measured using TAPPI test method T-220.
The term "machine direction" as used herein refers to the direction of travel
of the forming
surface onto which fibers are deposited during formation of a nonwoven web.
The term "cross-machine direction" as used herein refers to the direction
which is
perpendicular to the machine direction defined above and in the plane of the
forming surface.
The term "pulp" as used herein refers to fibers from natural sources such as
woody and non-
woody plants. Woody plants include, for example, deciduous and coniferous
trees. Non-woody plants
include, for example, cotton, flax, esparto grass, milkweed, straw, jute,
hemp, and bagasse. Pulp fibers
can include hardwood fibers, softwood fibers, and mixtures thereof.
The term "average fiber length" as used herein refers to an average length of
fibers, fiber
bundles and/or fiber-like materials determined by measurement utilizing
microscopic techniques. A
sample of at least 20 randomly selected fibers is separated from a liquid
suspension of fibers. The
fibers are set up on a microscope slide prepared to suspend the fibers in
water. A tinting dye is added
to the suspended fibers to color cellulose-containing fibers so they may be
distinguished or separated
from synthetic fibers. The slide is placed under a Fisher Stereomaster II
Microscope--S19642/S19643
Series. Measurements of 20 fibers in the sample are made at 20X linear
magnification utilizing a 0-20
mils scale and an average length, minimum and maximum length, and a deviation
or coefficient of
variation are calculated. In some cases, the average fiber length will be
calculated as a weighted
average length of fibers (e.g., fibers, fiber bundles, fiber-like materials)
determined by equipment such
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as, for example, a Kajaani fiber analyzer Model No. FS-200, available from
Kajaani Oy Electronics,
Kajaani, Finland. According to a standard test procedure, a sample is treated
with a macerating liquid
to ensure that no fiber bundles or shives are present. Each sample is
disintegrated into hot water and
diluted to an approximately 0.001% suspension. Individual test samples are
drawn in approximately 50
to 100 ml portions from the dilute suspension when tested using the standard
Kajaani fiber analysis
test procedure. The weighted average fiber length may be an arithmetic
average, a length weighted
average or a weight weighted average and may be expressed by the following
equation:
(Xi * ) n=
x = =
where
k=maximum fiber length
xFfiber length
ni=number of fibers having length xi
n=total number of fibers measured.
One characteristic of the average fiber length data measured by the Kajaani
fiber analyzer is
that it does not discriminate between different types of fibers. Thus, the
average length represents an
average based on lengths of all different types, if any, of fibers in the
sample.
The term "staple fibers" means discontinuous fibers made from synthetic
polymers such as
polypropylene, polyester, post consumer recycle (PCR) fibers, polyester,
nylon, and the like, and those
not hydrophilic may be treated to be hydrophilic. Staple fibers may be cut
fibers or the like. Staple
fibers can have cross-sections that are round, bicomponent, multicomponent,
shaped, hollow, or the
like.
As used herein, the term "abrasive" is intended to represent a surface texture
which enables
the nonwoven web to scour a surface being wiped or cleaned with the nonwoven
web and remove dirt
and the like. The abrasiveness can vary depending on the polymer used to
prepare the abrasive fibers
and the degree of texture of the nonwoven web.
DETAILED DESCRIPTION
It is to be understood by one of ordinary skill in the art that the present
discussion is a
description of exemplary aspects only, and is not intended as limiting the
broader aspects of the
present disclosure.
Generally speaking, the present disclosure is directed to a base sheet having
a
microstructured topography that is formed from a nonwoven web and at least a
first plurality of staple
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fibers adhered to a first side of the nonwoven web. Particularly, the present
disclosure has found that
by carefully selecting staple fibers and adhering the staple fibers to the
nonwoven web such that the
staple fibers extend in a direction generally non-planar with the nonwoven
web, one or more properties
of the base sheet can be improved without impacting the properties of the
nonwoven web, and without
the need for altering the composition of the nonwoven web. Furthermore, in one
aspect, the present
disclosure has found that a second plurality of staple fibers can be adhered
to a second side of the
nonwoven web. In such an aspect, the second plurality of staple fibers can be
different in size, shape,
or properties (such as water absorbency, oil absorbency, etc) than the first
plurality of fibers, providing
the base sheet with different properties on each of its surfaces, without
requiring change in
composition or treatment of the nonwoven web.
For instance, in one aspect, the first and/or second plurality of staple
fibers may be selected to
improve one or more properties of the nonwoven web, such as water absorbency,
oil absorbency,
softness, abrasiveness, durability, barrier properties or the like. For
instance, a staple fiber may be
selected based upon the material's ability to improve these properties, and
can be formed from one or
more synthetic fibers. In one aspect, the staple fiber(s) can be formed from
polypropylene, polyester,
post consumer recycle (PCR) fibers, pre-consumer (e.g. post industrial)
recycle fibers, rayon,
polyester, nylon, and the like. In one aspect, the fibers can be formed from
polypropylene, polyester,
rayon, nylon, or a combination thereof. While a fiber inherently have one or
more of the above
properties may be selected, it should be understood that, in one aspect, the
fiber(s) selected may be
treated to impart, or increase their hydrophobicity, absorbency, or others as
known in the art.
However, in one aspect, the staple fibers can also include cellulosic fibers,
such as cotton, including
fibers from waste and recycling, including agro-industrial and textile waste.
Nonetheless, in one aspect, one or more of the above materials may be used to
form the
staple fibers, and the length and/or denier of the fiber may be altered to
impart further advantages. For
instance, shorter and/or thinner (e.g. lower denier) fibers can provide a
softer surface whereas longer
and/or thicker (e.g. higher denier) fibers can improve abrasiveness or
durability. Thus, in one aspect,
the first and/or second plurality of staple fibers can have a denier of about
20 or less, such as about
17.5 or less, such as about 15 or less, such as about 12.5 or less, such as
about 10 or less, such as
about 8 or less, such as about 6 or less, such as about 5 or less, such as
about 4 or less, such as
about 3 or less, such as about 2 or less, or any ranges or values
therebetween.
Furthermore, additionally or alternatively, the fibers may have a length,
which is the staple
fiber's longest dimension, of about 10 micrometers to about 5000 micrometers,
such as about 50
micrometers to about 4000 micrometers, such as about 100 micrometers to about
3000 micrometers,
such as about 150 micrometers to about 2000 micrometers, such as about 200
micrometers to about
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1000 micrometers, such as about 250 micrometers toa bout 750 micrometers, or
any ranges or values
therebetween.
Furthermore, in one aspect, a staple fiber providing softness may have a
denier of about 4 or
less, such as about 3.5 or less, such as about 3 or less, such as about 2.5 or
less, such as about 2 or
less, such as about 1.5 or less, such as about 1 or less, such as about 0.9 or
less, such as about 0.8
or less, or any ranges or values therebetween, and/or a length of about 2000
micrometers or less,
such as about 1750 micrometers or less, such as about 1500 micrometers or
less, such as about 1000
micrometers or less, such as about 500 micrometers or less. For instance, in
one aspect, soft fibers
have a denier of about 2.5 to about 3.5 and a length of about 1000 micrometers
to about 1700
micrometers, a denier of about 1 to about 2 and a length of about 500
micrometers to about 1500
micrometers, a denier of about 0.5 to about 1, and a length of about 250
micrometers to about 1000
micrometers, or any ranges or values therebetween.
Similarly, a fiber having good abrasiveness or wear properties may have a
denier of about 4 or
greater, such as about 5 or greater, such as about 7.5 or greater, such as
about 10 or greater, such as
about 15 or greater, such as about 20 or greater, such as about 25 or greater,
such as about 30 or
greater, such as about 35 or greater, such as about 45 or less, such as about
40 or less, such as
about 35 or less, such as about 30 or less, such as about 25 or less, or any
ranges or values
therebetween, and/or a length of about 10 millimeters or less, such as about 9
millimeters or less,
such as about 8 millimeters or less, such as about 7 millimeters or less, such
as about 6000
micrometers or less, such as about 5000 micrometers or less, such as about
4000 micrometers or
less, such as about 3000 micrometers or less, such as about 2000 micrometers
or less, such as about
1200 micrometers or greater, such as about 1300 micrometers or greater, such
as about 1400
micrometers or greater, such as about 1500 micrometers or greater, or any
values or ranges
therebetween. For instance, in one aspect, an abrasive fiber has a denier of
about 5 to about 7 and a
length of about 1250 micrometers to about 4000 micrometers, a denier of about
9.5 to about 12 and a
length of about 2500 micrometers to about 5500 micrometers, a denier of about
19 to about 21 and a
length of about 4500 micrometers to about 7500 micrometers, a denier of about
38 to about 41 and a
length of about 6500 micrometers to about 10,000 micrometers, or any ranges or
values
therebetween.
Regardless of the type and size of fibers selected, the fibers are treated
with a cation. In one
aspect, the cation is incorporated during formation of the staple fibers,
however, it should be
understood that the cation can be incorporated into the staple fibers after
formation, such as by
treating the staple fibers. In one aspect, the cation is a metal cation, such
as an alkali metal cation,
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and, in one aspect, may be selected from potassium, sodium, lithium, or a
combination thereof. In one
aspect, a suitable cationically charged fibers can be obtained as treated
staple fibers from Agatex.
Particularly, in one aspect, as discussed above, the plurality of fibers are
attached to the
nonwoven web via an adhesive after being exposed to a magnetic field. As will
be discussed in greater
detail below, the adhesive can be applied to the nonwoven web using a variety
of techniques,
including printing, spraying, dipping, and the like. Nonetheless, in one
aspect, the adhesive may be
any adhesive known in the art, but may be treated with an anion. Thus, as will
be discussed in greater
detail below, the plurality of fibers may be plated or deposited on the
nonwoven web due to the
attraction between the cation incorporated into or onto the fibers, and the
anionic component
incorporated into the adhesive. While any anion known in the art may be used,
in one aspect, the
anion is an anion with suitable attraction to a metal cation, such as an
alkali metal cation. Thus, in one
aspect, the anion can include a mineral anion, such as chlorine, bromine,
iodine, or a fluorinated salt
anion, such as PF6 , SON-, 0104 , 0F3803 , (FS02)2N , (CF3S02)2N , (02F6502)2N
, and
(CF3S02)30-, or a combination thereof. In one aspect, a suitable anionically
treated adhesive can be
obtained from Agatex.
Notwithstanding the adhesive selected, in one aspect, the fibers are adhered
to one or more
surfaces of the nonwoven web via the adhesive. For instance, referring to Fig.
1, a nonwoven web 102
can have an adhesive 104 applied thereon, and a first plurality of staple
fibers 106 affixed to the
nonwoven web via the adhesive to form a base web 100 having a microstructured
topography.
Moreover, referring to Fig. 2, and as discussed above, in one aspect, the
first plurality of staple fibers
are affixed to a first side 108 of the nonwoven web, and a second plurality of
staple fibers 114 are
affixed to a second side 110 of the nonwoven web 102 via adhesive 112. In one
aspect, the first
plurality of staple fibers 106 may be the same or different than the second
plurality of staple fibers 114
as discussed above. Similarly, in one aspect, the adhesive 112 may be the same
or different than
adhesive 104. For instance, in one aspect, the adhesive itself may be
generally the same or similar,
but adhesive 104 may be treated with a different anion that adhesive 112.
However, in one aspect,
adhesive 104 is the same, or generally the same, as adhesive 112.
Further, while the adhesive 104 and/or 112 is shown in Figs. 1 and 2 as
covering the entire
nonwoven web 102, it should be understood that, in some aspects, that the
adhesive may be applied
to about 50% or more of the nonwoven web, such as about 60% or more, such as
about 70% or more,
such as about 75% or more such as about 80% or more, such as about 85% or
more, such as about
90% or more, such as about 95% or more, such as about 100% or less, such as
about 99% or less,
such as about 95% or less, such as about 90% or less, such as about 85% or
less, such as ab out
80% or less of the first and/or second surface of the nonwoven web, or any
ranges or values
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therebetween. Thus, in one aspect, the adhesive may be applied in a pattern,
such as dots, squares,
lines, and the like.
Nonetheless, as shown in Figs. 1 and 2, the first and/or second plurality of
staple fibers
106/114 extend along their length (e.g. largest dimension from the surface of
the nonwoven web to a
distal end of the staple fiber) in one or more planes which are not planar
with or parallel to nonwoven
web 102. Particularly, as shown, in one aspect, and for example only, nonwoven
web 102 extends in a
generally horizontal direction along the x-axis, whereas staple fibers 106/116
extend in a variety of
second planes that are not planar with, or parallel to the x-axis, forming a
microstructured topography
on the first and/or second surface of the nonwoven web. It should be
understood that, due to the
1 0 process of attaching the fibers, which will be discussed in greater
detail below, some staple fibers
106/114 may become attached such that the length extends generally parallel to
nonwoven web 102,
however, at least a portion, such as about 50% or more, such as about 60% or
more, such as about
70% or more, such as about 75% or more, such as about 80% or more, of the
fibers may extend in
one or more second planes that are not planar with or parallel to the first
plane in which nonwoven
web 102 extends. Thus, the first or second plurality of staple fibers are
further distinguished from an
outer layer in a laminate or layered nonwoven configuration.
Furthermore, the present disclosure has surprisingly found that the plurality
of staple fibers do
not diminish the underlying properties of the base web, and can, in fact,
increase one or more of
absorbency, abrasiveness, softness, barrier properties or the like.
For instance, in one aspect, the nonwoven web may be capable of absorbing
between 3.5 and
6.0 grams of water per gram of nonwoven web. In certain exemplary aspects, the
water capacity of the
nonwoven web, determined by measuring the increase in the weight of a material
sample resulting
from the absorption of a liquid, may be between about 200% to about 800%, such
as about 250% to
about 750%, such as about 300% to about 700%, such as about 350% to about
600%, or any ranges
or values therebetween. Further, the nonwoven web may be capable of absorbing
between 3.7 and
4.3 grams of water in an amount of time between about 1 second and about 2
seconds, such as about
1.1 seconds to about 1.9 seconds, such as about 1.2 seconds to about 1.8
seconds, such as about
1.25 to about 1.6 second, or any ranges or values therebetween. Moreover, as
discussed above, it
was unexpectedly found that by forming the base sheet according to the present
disclosure, the
properties of the nonwoven web may be maintained at the above levels, or even
increased if a fiber
improving absorbency is selected.
In one aspect, the nonwoven web may also exhibit good barrier properties, and
may filter at
least about 70% or more of airborne particles having a size of about 0.65
microns or greater according
to EN 13274-7 (utilizing a Sodium Chloride aerosol have a particle size of
0.65 microns and a velocity
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of 95 liters/minute over an area of 100 cm), such as about 75% or more, such
as about 80% or more,
such as about 85% or more, such as about 90% or more of particles having a
size of about 0.65
microns or greater. Similarly, these barrier properties may be exhibited while
maintaining good air
permeability through the nonwoven web. For instance, the nonwoven web can
exhibit an air
permeability measured according to ASTM D737 (2020, measured using a 38 cm2
sample and a
pressure of 125 Pa) of about 20 cfm or greater, such as about 25 cfm or
greater, such as about 30 cfm
or greater, such as about 32.5 cfm or greater, such as about 35 cfm or
greater, such as about 40 cfm
or greater, or any ranges or values therebetween. Additionally or
alternatively, the nonwoven web may
exhibit a bacterial filtration efficiency (BCE), the test for which is defined
below, of about 80% or
greater, such as about 85% or greater, such as about 90% or greater, such as
about 95% or greater.
The nonwoven web may also have softness measured as cup crush energy, of less
than
about 1500 gm-mm, such as about 1400 gm-mm or less, such as about 1300 gm-mm
or less, such as
about 1200 gm-mm or less, and cup crush load of less than about 100 grams,
such as about 95
grams, such as about 90 grams, such as about 85 grams, such as about 80 grams,
such as about 75
grams, such as about 70 grams, when testing a 34 gsm web according to the cup
crush test set forth
below.
Furthermore, the present disclosure has found that these properties can be
maintained or
even improved by incorporating staple fibers according to the present
disclosure. For instance, one or
more of the above properties may be improved by about 10% of the above values
or more, such as
about 20%, such as about 30%, such as about 40%, such as about 50% or more
based upon the fiber,
denier, and length selected. Furthermore, in one aspect, a property that is
not inherent to the
nonwoven web may be imparted to the nonwoven web/base sheet by incorporating a
fiber having one
or more of the above properties without impacting (e.g. decreasing or
reducing) the above discussed
properties of the nonwoven web. For instance, a nonwoven web having barrier
properties according to
the above may be combined with fibers having high softness, improving the
softness of the barrier
fabric without impacting the barrier properties. In such an aspect, the base
sheet may have a softness
that is 10% or greater than the same nonwoven web having barrier properties
that has not been
treated with a plurality of staple fibers, such as about 15% or greater, such
as about 20% or greater,
such as about 25% or greater. Similarly, in one aspect, an absorbent nonwoven
web may be treated
with abrasive fibers which increase the abrasiveness by about 10% or more than
the same absorbent
nonwoven web that has not been treated with a plurality of staple fibers, such
as about 15% or
greater, such as about 20% or greater, such as about 25% or greater. Moreover,
in one aspect, a
nonwoven web having water or oil absorbency may contain a plurality of fibers
to improve the other of
water or oil absorbency, such that a first side of the nonwoven web may be oil
absorbent and the
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opposite be water absorbent. For instance, the absorbent nonwoven web may be
treated with oil or
water absorbent fibers which increase the respective absorbency by about 10%
or more than the
same absorbent nonwoven web that has not been treated with a plurality of
staple fibers, such as
about 15% or greater, such as about 20% or greater, such as about 25% or
greater. Of course, as
noted above, it should be understood that a first plurality of fibers may be
adhered to a first side of the
nonwoven wed, and a second plurality may be adhered to a second side of the
nonwoven web, such
that two or more of the above properties may be improved while maintaining, if
not improving, the
properties of the nonwoven web.
The nonwoven web may be formed from one or more of a variety of polymers that
can be
used in forming the nonwoven web material can include olefins (e.g.,
polyethylenes and
polypropylenes), polyesters (e.g., polybutylene terephthalate, polybutylene
naphthalate), polyamides
(e.g., nylons), polycarbonates, polyphenylene sulfides, polystyrenes,
polyurethanes (e.g.,
thermoplastic polyurethanes), etc. In one particular embodiment, the fibers of
the nonwoven web
material can include an olefin homopolymer. One suitable olefin homopolymer is
a propylene
homopolymer having a density of 0.91 grams per cubic centimeter (g/cm3), a
melt flow rate of 1200
g/10 minute (230 C, 2.16 kg), a crystallization temperature of 113 C, and a
melting temperature of
156 C, and is available as METOCENE MF650X polymer from LyondellBasell
Industries in Rotterdam,
The Netherlands. Another suitable propylene homopolymer that can be used has a
density of 0.905
9/cm3, a melt flow rate of 1300 g/10 minute (230 C, 2.16 kg), and a melting
temperature of 165 C, and
is available as Polypropylene 3962 from Total Petrochemicals in Houston,
Texas. Another suitable
polypropylene is available as EXXTRALim 3155, available from DomnMobil
Chemical Company of
Houston, Texas.
Further, a variety of thermoplastic elastomeric and plastomeric polymers may
generally be
employed in the nonwoven web material of the present invention, such as
elastomeric polyesters,
elastomeric polyurethanes, elastomeric polyamides, elastomeric copolymers,
elastomeric polyolefins,
and so forth. In one particular embodiment, elastomeric semi-crystalline
polyolefins are employed due
to their unique combination of mechanical and elastomeric properties. Semi-
crystalline polyolefins
have or are capable of exhibiting a substantially regular structure. For
example, semi-crystalline
polyolefins may be substantially amorphous in their undeformed state, but form
crystalline domains
upon stretching. The degree of crystallinity of the olefin polymer may be from
about 3% to about 60%,
in some embodiments from about 5% to about 45%, in some embodiments from about
5% to about
30%, and in some embodiments, from about 5% and about 15%. Likewise, the semi-
crystalline
polyolefin may have a latent heat of fusion (AFIr), which is another indicator
of the degree of
crystallinity, of from about 15 to about 210 Joules per gram ("Jig"), in some
embodiments from about
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20 to about 100 J/g, in some embodiments from about 20 to about 65 J/g, and in
some embodiments,
from 25 to about 50 J/g. The semi-crystalline polyolefin may also have a Vicat
softening temperature
of from about 10 C to about 100 C, in some embodiments from about 20 C to
about 80 C, and in
some embodiments, from about 30 C to about 60 C. The semi-crystalline
polyolefin may have a
melting temperature of from about 20 C to about 120 C, in some embodiments
from about 35 C to
about 90 C, and in some embodiments, from about 40 C to about 80 C. The latent
heat of fusion
(AK) and melting temperature may be determined using differential scanning
calorimetry ("DSC") in
accordance with ASTM D-3417 as is well known to those skilled in the art. The
Vicat softening
temperature may be determined in accordance with ASTM D-1525.
Exemplary semi-crystalline polyolefins include polyethylene, polypropylene, as
well as their
blends and copolymers thereof. In one particular embodiment, a polyethylene is
employed that is a
copolymer of ethylene and an a-olefin, such as a C3-C2o a-olefin or 03-012 a-
olefin. Suitable a-
olefins may be linear or branched (e.g., one or more C1-C3 alkyl branches, or
an aryl group). Specific
examples include 1-butene; 3-methyl-1-butene; 3,3-dimethy1-1-butene; 1-
pentene; 1-pentene with one
or more methyl, ethyl or propyl substituents; 1-hexene with one or more
methyl, ethyl or propyl
substituents; 1-heptene with one or more methyl, ethyl or propyl substituents;
1-octene with one or
more methyl, ethyl or propyl substituents; 1-nonene with one or more methyl,
ethyl or propyl
substituents; ethyl, methyl or dimethyl-substituted 1-decene; 1-dodecene; and
styrene. Particularly
desired a-olefin comonomers are 1-butene, 1-hexene, and 1-octene. The ethylene
content of such
copolymers may be from about 60 mole% to about 99 mole%, in some embodiments
from about 80
mole% to about 98.5 mole%, and in some embodiments, from about 87 mole% to
about 97.5 mole%.
The a-olefin content may likewise range from about 1 mole% to about 40 mole%,
in some
embodiments from about 1.5 mole% to about 15 mole%, and in some embodiments,
from about 2.5
mole% to about 13 mole%.
The density of the polyethylene may vary depending on the type of polymer
employed, but
generally ranges from about 0.85 g/cm3 to about 0.96 g/cm3. Polyethylene
"plastomers", for instance,
may have a density in the range of from 0.85 g/cm3 to 0.91 g/cm3. Likewise,
"linear low density
polyethylene" ("LLDPE") may have a density in the range of from about 0.91
g/cm3 to about 0.94
g/cm3; "low density polyethylene" ("LDPE") may have a density in the range of
from about 0.91 g/cm3
to about 0.94 g/cm3; and "high density polyethylene" ("HDPE") may have density
in the range of from
0.94 g/cm3 to 0.96 g/cm3. Densities may be measured in accordance with ASTM
1505.
Particularly suitable polyethylene copolymers are those that are "linear" or
"substantially
linear." The term "substantially linear" means that, in addition to the short
chain branches attributable
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to comonomer incorporation, the ethylene polymer also contains long chain
branches in the polymer
backbone. "Long chain branching" refers to a chain length of at least 6
carbons. Each long chain
branch may have the same comonomer distribution as the polymer backbone and be
as long as the
polymer backbone to which it is attached. Preferred substantially linear
polymers are substituted with
from 0.01 long chain branch per 1000 carbons to 1 long chain branch per 1000
carbons, and in some
embodiments, from 0.05 long chain branch per 1000 carbons to 1 long chain
branch per 1000
carbons. In contrast to the term "substantially linear", the term "linear"
means that the polymer lacks
measurable or demonstrable long chain branches. That is, the polymer is
substituted with an average
of less than 0.01 long chain branch per 1000 carbons.
The density of a linear ethylene/a-olefin copolymer is a function of both the
length and amount
of the a-olefin. That is, the greater the length of the a-olefin and the
greater the amount of a-olefin
present, the lower the density of the copolymer. Although not necessarily
required, linear polyethylene
"plastomers" are particularly desirable in that the content of a-olefin short
chain branching content is
such that the ethylene copolymer exhibits both plastic and elastomeric
characteristics ¨ i.e., a
"plastomer." Because polymerization with a-olefin comonomers decreases
crystallinity and density,
the resulting plastomer normally has a density lower than that of polyethylene
thermoplastic polymers
(e.g., LLDPE), but approaching and/or overlapping that of an elastomer. For
example, the density of
the polyethylene plastomer may be 0.91 g/cm3 or less, in some embodiments,
from about 0.85 g/cm3
to about 0.88 g/cm3, and in some embodiments, from about 0.85 g/cm3 to about
0.87 g/cm3. Despite
having a density similar to elastomers, plastomers generally exhibit a higher
degree of crystallinity and
may be formed into pellets that are non-adhesive and relatively free flowing.
The distribution of the a-olefin comonomer within a polyethylene plastomer is
typically random
and uniform among the differing molecular weight fractions forming the
ethylene copolymer. This
uniformity of comonomer distribution within the plastomer may be expressed as
a comonomer
distribution breadth index value ("ODBI") of 60 or more, in some embodiments
80 or more, and in
some embodiments, 90 or more. Further, the polyethylene plastomer may be
characterized by a DSC
melting point curve that exhibits the occurrence of a single melting point
peak occurring in the region
of 50 to 110 C (second melt rundown).
Preferred plastomers for use in the present invention are ethylene-based
copolymer
plastomers available under the designation EXACTIm from ExxonMobil Chemical
Company of
Houston, Texas. Other suitable polyethylene-based plastomers are available
under the designation
ENGAGETM and AFFINITYTm from Dow Chemical Company of Midland, Michigan. An
additional
suitable polyethylene-based plastomer is an olefin block copolymer available
from Dow Chemical
Company of Midland, Michigan under the trade designation INFUSErm, such as
INFUSETM 9807. A
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polyethylene that can be used in the fibers of the present invention is DOWTM
61800.41. Still other
suitable ethylene polymers are available from The Dow Chemical Company under
the designations
DOWLEXTM (LLDPE), ASPUNTM (LLDPE), and ATTANETm (ULDPE). Other suitable
ethylene
polymers are described in U.S. Patent Nos. 4,937,299 to Ewen et al.; 5,218,071
to Tsutsui et al.;
5,272,236 to Lai et al.; and 5,278,272 to Lai et al., which are incorporated
herein in their entirety by
reference thereto for all purposes.
Of course, the present invention is by no means limited to the use of ethylene
polymers. For
instance, propylene polymers may also be suitable for use as a semi-
crystalline polyolefin. Suitable
plastomeric propylene polymers may include, for instance, copolymers or
terpolymers of propylene
include copolymers of propylene with an a-olefin (e.g., C3-C20), such as
ethylene, 1-butene, 2-butene,
the various pentene isomers, 1-hexene, 1-octene, 1-nonene, 1-decene, 1-
unidecene, 1-dodecene, 4-
methyl-1-pentene, 4-methyl-1-hexene, 5-methyl-1-hexene, vinylcyclohexene,
styrene, etc. The
comononner content of the propylene polymer may be about 35 wt.% or less, in
some embodiments
from about 1 wt.% to about 20 wt.%, and in some embodiments, from about 2 wt.%
to about 10 wt.%.
Preferably, the density of the polypropylene (e.g., propylene/a-olefin
copolymer) may be 0.91 grams
per cubic centimeter (g/cm3) or less, in some embodiments, from 0.85 to 0.88
g/0m3, and in some
embodiments, from 0.85 g/cm3 to 0.87 g/cm3. Suitable propylene-based copolymer
plastomers are
commercially available under the designations VISTAMAXXTm (e.g., 2330, 6202,
and 6102), a
propylene-ethylene copolymer-based plastomer from Exxon Mobil Chemical Co. of
Houston, Texas;
FINATM (e.g., 8573) from Atofina Chemicals of Feluy, Belgium; TAFMERTm
available from Mitsui
Petrochemical Industries; and VERSIFYTM available from Dow Chemical Co. of
Midland, Michigan.
Other examples of suitable propylene polymers are described in U.S. Patent No.
6,500,563 to Datta
et al.; 5,539,056 to Yang, et al.; and 5,596,052 to Resconi, et al., which are
incorporated herein in their
entirety by reference thereto for all purposes.
Any of a variety of known techniques may generally be employed to form the
semi-crystalline
polyolefins. For instance, olefin polymers may be formed using a free radical
or a coordination
catalyst (e.g., Ziegler-Natta). Preferably, the olefin polymer is formed from
a single-site coordination
catalyst, such as a metallocene catalyst. Such a catalyst system produces
ethylene copolymers in
which the comonomer is randomly distributed within a molecular chain and
uniformly distributed
across the different molecular weight fractions. Metallocene-catalyzed
polyolefins are described, for
instance, in U.S. Patent. Nos. 5,571,619 to McAlpin et al.; 5,322,728 to Davis
et al.; 5,472,775 to
Obiieski et al.; 5,272,236 to Lai et al.; and 6,090,325 to Wheat, et al.,
which are incorporated herein in
their entirety by reference thereto for all purposes. Examples of metallocene
catalysts include bis(n-
butylcyclopentadienyl)titanium dichloride, bis(n-
butylcyclopentadienyl)zirconium dichloride,
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bis(cyclopentadienyl)scandium chloride, bis(indenyl)zirconium dichloride,
bis(methylcyclopentadienyl)titanium dichloride,
bis(methylcyclopentadienyl)zirconiurn dichloride,
cobaltocene, cyclopentadienyltitanium trichloride, ferrocene, hafnocene
dichloride,
isopropyl(cyclopentadieny1,-1-flourenyl)zirconium dichloride, molybdocene
dichloride, nickelocene,
niobocene dichloride, ruthenocene, titanocene dichloride, zirconocene chloride
hydride, zirconocene
dichloride, and so forth. Polymers made using metallocene catalysts typically
have a narrow
molecular weight range. For instance, nnetallocene-catalyzed polymers may have
polydispersity
numbers (Mw/Mn) of below 4, controlled short chain branching distribution, and
controlled isotacticity.
The melt flow index (M1) of the semi-crystalline polyolefins may generally
vary, but is typically
in the range of about 0.1 grams per 10 minutes to about 100 grams per 10
minutes, in some
embodiments from about 0.5 grams per 10 minutes to about 30 grams per 10
minutes, and in some
embodiments, about 1 to about 10 grams per 10 minutes, determined at 190 C.
The melt flow index is
the weight of the polymer (in grams) that may be forced through an extrusion
rheometer orifice
(0.0825-inch diameter) when subjected to a force of 5000 grams in 10 minutes
at 190 C, and may be
determined in accordance with ASTM Test Method D1238-E.
Of course, other thermoplastic polymers may also be used to form nonwoven web
material.
For instance, a substantially amorphous block copolymer may be employed that
has at least two
blocks of a monoalkenyl arene polymer separated by at least one block of a
saturated conjugated
diene polymer. The monoalkenyl arene blocks may include styrene and its
analogues and
homologues, such as o-methyl styrene; p-methyl styrene; p-tert-butyl styrene;
1,3 dimethyl styrene p-
methyl styrene; etc., as well as other monoalkenyl polycyclic aromatic
compounds, such as vinyl
naphthalene; vinyl anthrycene; and so forth. Preferred monoalkenyl arenes are
styrene and p-methyl
styrene. The conjugated diene blocks may include homopolymers of conjugated
diene monomers,
copolymers of two or more conjugated dienes, and copolymers of one or more of
the dienes with
another monomer in which the blocks are predominantly conjugated diene units.
Preferably, the
conjugated dienes contain from 4 to 8 carbon atoms, such as 1,3 butadiene
(butadiene); 2-methyl-1,3
butadiene; isoprene; 2,3 dimethyl-1,3 butadiene; 1,3 pentadiene (piperylene);
1,3 hexadiene; and so
forth.
The amount of monoalkenyl arene (e.g., polystyrene) blocks may vary, but
typically constitute
from about 8 wt.% to about 55 wt.%, in some embodiments from about 10 wt.% to
about 35 wt.%, and
in some embodiments, from about 25 wt.% to about 35 wt.% of the copolymer.
Suitable block
copolymers may contain monoalkenyl arene endblocks having a number average
molecular weight
from about 5,000 to about 35,000 and saturated conjugated diene midblocks
having a number
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average molecular weight from about 20,000 to about 170,000. The total number
average molecular
weight of the block polymer may be from about 30,000 to about 250,000.
Particularly suitable thermoplastic elastomeric block copolymers are available
from Kraton
Polymers LLC of Houston, Texas under the trade name KRATON TM KRATON TM
polymers include
styrene-diene block copolymers, such as styrene-butadiene, styrene-isoprene,
styrene-butadiene-
styrene, and styrene-isoprene-styrene. KRATON TM polymers also include styrene-
olefin block
copolymers formed by selective hydrogenation of styrene-diene block
copolymers. Examples of such
styrene-olefin block copolymers include styrene-(ethylene-butylene), styrene-
(ethylene-propylene),
styrene-(ethylene-butylene)-styrene, styrene-(ethylene-propylene)-styrene,
styrene-(ethylene-
butylene)-styrene-(ethylene-butylene), styrene-(ethylene-propylene)-styrene-
(ethylene-propylene), and
styrene-ethylene-(ethylene-propylene)-styrene. These block copolymers may have
a linear, radial or
star-shaped molecular configuration. Specific KRATON TM block copolymers
include those sold under
the brand names G 1652, G 1657, G 1730, MD6673, MD6703, MD6716, and MD6973.
Various
suitable styrenic block copolymers are described in U.S. Patent Nos.
4,663,220, 4,323,534, 4,834,738,
5,093,422 and 5,304,599, which are hereby incorporated in their entirety by
reference thereto for all
purposes. Other commercially available block copolymers include the S-EP-S and
S-E-E-P-S
elastomeric copolymers available from Kuraray Company, Ltd. of Okayama, Japan,
under the trade
designation SEFTON TM . Still other suitable copolymers include the S-I-S and
S-B-S elastomeric
copolymers available from Dexco Polymers of Houston, Texas under the trade
designation
VECTOR-rm. Also suitable are polymers composed of an A-B-A-B tetrablock
copolymer, such as
discussed in U.S. Patent No. 5,332,613 to Taylor, et al., which is
incorporated herein in its entirety by
reference thereto for all purposes. An example of such a tetrablock copolymer
is a styrene-
poly(ethylene-propylene)-styrene-poly(ethylene-propylene) ("S-EP-S-EP") block
copolymer.
A single polymer as discussed above can be used to form the fibers from which
the nonwoven
web material is comprised, and when utilized, can be utilized in amount up to
100 wt.% based on the
total weight of the nonwoven web material, such as from about 75 wt.% to about
99 wt.%, such as
from about 80 wt.% to about 98 wt.%, such as from about 85 wt.% to about 95
wt.%. However, in
other embodiments, the nonwoven web material can include two or more polymers
from the polymers
discussed above. For instance, monocomponent fibers from which the nonwoven
web material can
include fibers formed from an olefin homopolymer in an amount ranging from
about 5 wt.% to about 80
wt.%, such as from about 10 wt.% to about 75 wt.%, such as from about 15 wt.%
to about 70 wt.%,
based on the total weight of the nonwoven web material. Meanwhile, the fibers
can also include a
derivative of an olefin polymer. For instance, the nonwoven web material can
include an elastomeric
semi-crystalline polyolefin or "plastomer" (e.g., an ethylene/a-olefin
copolymer, a propylene/a-olefin
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copolymer, or a combination thereof); a thermoplastic elastomeric block
copolymer; or a combination
thereof in an amount ranging from about 20 wt.% to about 95 wt.%, such as from
about 25 wt.% to
about 90 wt.%, such as from about 30 wt.% to about 85 wt.% based on the total
weight of the
nonwoven web material.
In additional embodiments, the fibers from which the nonwoven web material is
formed can be
multicomponent and can have a sheath-core arrangement or side-by-side
arrangement. For instance,
in a sheath-core multicomponent fiber arrangement, the sheath can include a
blend of a polypropylene
and a polypropylene-based plastomer, (e.g., VISTAMAXX-9, while the core can
include a blend of a
polyethylene and a polyethylene-based plastomer (e.g., INFUSETm). On the other
hand, the sheath
can include a blend of a polyethylene and a polyethylene-based plastomer
(e.g., INFUSE-9, while the
core can include a blend of a polypropylene and a polypropylene-based
plastomer, (e.g.,
VISTAMAXXTm). Further, in still other embodiments, the core can include 100%
of a polyethylene or a
polypropylene homopolymer.
For instance, in some embodiments, the fibers from which the nonwoven web
material is
formed can have a sheath-core arrangement where the sheath can include from
about 20 wt.% to
about 90 wt.%, such as from about 25 wt.% to about 80 wt.%, such as from about
30 wt.% to about 70
wt.% of an olefin homopolymer (e.g., polypropylene or polyethylene) based on
the total weight of the
sheath component of the multicomponent fiber. Meanwhile, the sheath can also
include from about 10
wt.% to about 80 wt.%, such as from about 20 wt.% to about 75 wt.%, such as
from about 30 wt.% to
about 70 wt.% of an olefin-based plastomer (e.g., a polypropylene-based
plastomer or an ethylene-
based plastomer) based on the total weight of the sheath component of the
multicomponent fiber.
In addition, the core can include from about 30 wt.% to about 100 wt.%, such
as from about 40
wt.% to about 95 wt.%, such as from about 50 wt.% to about 90 wt.% of an
olefin homopolymer (e.g.,
polypropylene or polyethylene) based on the total weight of the core component
of the multicomponent
fiber. Further, the core can include from about 0 wt.% to about 70 wt.%, such
as from about 5 wt.% to
about 60 wt.%, such as from about 10 wt.% to about 50 wt.% of an olefin-based
plastomer (e.g., a
polypropylene-based plastomer or an ethylene-based plastomer) based on the
total weight of the core
component of the fiber.
Further, the weight percentage of the sheath can range from about 10 wt.% to
about 70 wt.%,
such as from about 15 wt.% to about 65 wt.%, such as from about 20 wt.% to
about 60 wt.%, based on
the total weight of the fiber. Meanwhile, the weight percentage of the core
can range from about 30
wt.% to about 90 wt.%, such as from about 35 wt.% to about 85 wt.%, such as
from about 40 wt.% to
about 80 wt.% based on the total weight of the fiber.
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In addition, the fibers from which the nonwoven web material is formed can
have a side-by-
side arrangement where two fibers are coextruded adjacent each other. In such
an embodiment, the
first side can include a polyethylene and a polyethylene-based plastomer,
while the second side can
include a polypropylene and a polypropylene-based plastomer. The polyethylene
can be present in
the first side in an amount ranging from about 30 wt.% to about 90 wt.%, such
as from about 35 wt.%
to about 80 wt.%, such as from about 40 wt.% to about 70 wt.% based on the
total weight of the first
side. Meanwhile, the polyethylene-based plastomer can be present in the first
side in an amount
ranging from about 20 wt.% to about 80 wt.%, such as from about 25 wt.% to
about 70 wt.%, such as
from about 30 wt.% to about 60 wt.% based on the total weight of the first
side. In addition, the
polypropylene can be present in the second side in an amount ranging from
about 30 wt.% to about 90
wt.%, such as from about 35 wt.% to about 80 wt.%, such as from about 40 wt.%
to about 70 wt.%
based on the total weight of the second side. Meanwhile, the polypropylene-
based plastomer can be
present in the second side in an amount ranging from about 20 wt.% to about 80
wt.%, such as from
about 25 wt.% to about 70 wt.%, such as from about 30 wt.% to about 60 wt.%
based on the total
weight of the second side.
With such fiber configurations as those discussed above, in some embodiments,
a propylene-
ethylene copolymer can be utilized in either the sheath and/or the core or the
first side and/or the
second side to act as a compatibilizer and enhance bonding between the sheath
and core. For
instance, the propylene-ethylene copolymer can be present in the sheath in an
amount ranging from
about 0.5 wt.% to about 20 wt.%, such as from about 1 wt.% to about 15 wt.%,
such as from about 2
wt.% to about 10 wt.% based on the total weight of the sheath. Alternatively,
the propylene-ethylene
copolymer can be present in the core in an amount ranging from about 0.5 wt.%
to about 20 wt.%,
such as from about 1 wt.% to about 15 wt.%, such as from about 2 wt.% to about
10 wt.% based on
the total weight of the core.
Other additives may also be incorporated into the nonwoven web material, such
as melt
stabilizers, processing stabilizers, heat stabilizers, light stabilizers,
antioxidants, heat aging stabilizers,
whitening agents, antiblocking agents, viscosity modifiers, etc. Viscosity
modifiers may also be
employed, such as polyethylene wax (e.g., EPOLENETM C-10 from Eastman
Chemical). Phosphite
stabilizers (e.g., IRGAFOS available from Ciba Specialty Chemicals of
Tarrytown, N.Y. and
DOVERPHOS available from Dover Chemical Corp. of Dover, Ohio) are exemplary
melt stabilizers. In
addition, hindered amine stabilizers (e.g., CH IMASSORB available from Ciba
Specialty Chemicals) are
exemplary heat and light stabilizers. Further, hindered phenols are commonly
used as an antioxidant
in the production of films. Some suitable hindered phenols include those
available from Ciba Specialty
Chemicals of under the trade name IRAGANOXTM, such as IRGANOXTm 1076, 1010, or
E 201. When
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employed, such additives (e.g., antioxidant, stabilizer, etc.) may each be
present in an amount from
about 0.001 wt.% to about 25 wt.%, in some embodiments, from about 0.005 wt.%
to about 20 wt.%,
and in some embodiments, from 0.01 wt.% to about 15 wt.% of the nonwoven web
material.
The polymer(s) discussed above, as well as the other optional additive
components discussed
above, can be formed into monocomponent or multicomponent fibers and extruded
or spun to form the
nonwoven web material of the present invention, which can then be used in
various products such a
wipe, an absorbent article, a wearable article, or the like, and discussed in
more detail below.
Monoconnponent fibers can be formed from a polymer or a blend of polymers as
well as an optional
tackifier, which are compounded and then extruded from a single extruder.
Meanwhile,
multicomponent fibers can be formed from two or more polymers (e.g.,
bicomponent fibers) extruded
from separate extruders, where one or more of the polymers can be compounded
with a tackifier,
although this is not required when one of the polymers exhibits inherent
tackiness, such as
VISTAMAXXim polymers and INFUSEim polymers. The polymers may be arranged in
substantially
constantly positioned distinct zones across the cross-section of the fibers.
The components may be
arranged in any desired configuration, such as sheath-core, side-by-side, pie,
island-in-the-sea, three
island, bull's eye, or various other arrangements known in the art, and so
forth. Various methods for
forming multicomponent fibers are described in U.S. Patent Nos. 4,789,592 to
Taniguchi et al.
5,336,552 to Strack et al., 5,108,820 to Kaneko, et al., 4,795,668 to Krueqe,
et al., 5,382,400 to Pike
et al., 5,336,552 to Strack et al., and 6,200,669 to Marmon, et al., which are
incorporated herein in
their entirety by reference thereto for all purposes. Multicomponent fibers
having various irregular
shapes may also be formed, such as described in U.S. Patent Nos. 5,277,976 to
Hogle, et al.,
5,162,074 to Hills, 5,466,410 to Hills, 5,069,970 to Largman, et al., and
5,057,368 to Largman, et al.,
which are incorporated herein in their entirety by reference thereto for all
purposes. In addition, hollow
fibers are also contemplated by the present invention, and such fibers can
reduce the amount of
polymer required, as well as the basis weight of the resulting nonwoven web
material.
In any event, whether the nonwoven web material is formed by meltblowing,
spunbonding, or
any other nonwoven web material technique, when a tackifier and/or any
optional additives are
compounded with one or more polymers However, it is also to be understood
that, in some
embodiments, the core can be a blend of two or more polymers such as
polypropylene and a
VISTAMAXXTm plastomer, while the sheath can also be a blend of two or polymers
such as
polyethylene and an INFUSETM plastomer. Generally, the composition of the core
can be chosen such
that the resulting overall material is cloth-like, drapable, and soft, while
the composition of the sheath
can be chosen such that the sheath provides the level of tackiness needed for
efficient dirt removal
without the user experiencing stick and slip motion, while at the same time
leaving no residue.
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Various embodiments of forming the fibers and nonwoven web material of the
present
invention will now be described in greater detail. Of course, it should be
understood that the
description provided below is merely exemplary, and that other methods of
forming nonwoven web
materials are contemplated by the present Disclosure. Particularly, the
nonwoven web material can be
formed from meltblown fibers or by other methods than meltblowing, such as
spunbonding. One
advantage of forming the nonwoven web material by spunbonding is that higher
molecular weight
polymers can be utilized as compared to the polymers used to form a meltblown
nonwoven web
material because the size of the capillary dies used in spunbonding equipment
is larger than in
meltblowing equipment. However, it is also to be understood that in the case
of forming a meltblown
nonwoven web material, the size of the capillary of the melt blown die can be
increased to
accommodate high viscosity (e.g., high molecular weight. Generally, however,
the melt flow rate of
the polymers of the present invention can range from about 3 grams per 10
minutes to about 50 grams
per 10 minutes when subjected to a load of 2160 grams at a temperature of 190
C according to ASTM
Test Method D1238-E. As such, in forming spunbond nonwoven web materials,
polymers having
higher viscosity and crystallinity can be used. For instance, polypropylene
having a melt flow rate of
from about 15 grams per 10 minutes to about 50 grams per 10 minutes, such as
from about 20 grams
per 10 minutes to about 35 grams per 10 minutes; olefinic block copolymer
plastomers having a melt
flow rate of from about 3 grams per 10 minutes to about 20 grams per 10
minutes, such as from about
10 grams per 10 minutes to about 15 grams per 10 minutes; and polyethylenes
having a melt flow rate
of from about 5 grams per 10 minutes to about 30 grams per 10 minutes, such as
from about 10
grams per 10 minutes to about 25 grams per 10 minutes can be utilized.
If desired, the nonwoven web material may have a multi-layer structure.
Suitable multi-
layered materials may include, for instance, spunbond/meltblown/spunbond (SMS)
laminates and
spunbond/meltblown (SM) laminates, where the spunbond and meltblown layers are
formed generally
as discussed above. However, in one aspect, the present disclosure includes
nonwoven webs and/or
base sheets that are free of SMS laminates. Particularly, as discussed above,
nonwoven webs
according to the present disclosure may instead have properties introduced to
the nonwoven web via
the adhered staple fibers, and may therefore not require any of the
traditional benefits associated with
SMS laminates.
Another example of a nonwoven web material that is contemplated by the present
invention is
a spunbond web produced on a multiple spin bank machine in which a spin bank
deposits fibers over
a layer of fibers deposited from a previous spin bank. Such an individual
spunbond nonwoven web
may also be thought of as a multi-layered structure. In this situation, the
various layers of deposited
fibers in the nonwoven web may be the same, or they may be different in basis
weight and/or in terms
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of the composition, type, size, level of crimp, and/or shape of the fibers
produced. As another
example, a single nonwoven web may be provided as two or more individually
produced layers of a
spun bond web, a carded web, etc., which have been bonded together to form the
nonwoven web.
These individually produced layers may differ in terms of production method,
basis weight,
composition, and fibers.
A nonwoven web material as contemplated by the present invention may also
contain an
additional fibrous component such that it is considered a composite. For
example, a nonwoven web
may be entangled with another fibrous component using any of a variety of
entanglement techniques
known in the art (e.g., hydraulic, air, mechanical, etc.). In one embodiment,
a nonwoven web formed
from one polymer can be integrally entangled with fibers containing another
polymer using hydraulic
entanglement. A typical hydraulic entangling process utilizes high pressure
jet streams of water to
entangle fibers to form a highly entangled consolidated fibrous structure,
e.g., a nonwoven web.
Hydraulically entangled nonwoven webs are disclosed, for example, in U.S.
Patent Nos. 3,494,821 to
Evans and 4,144,370 to Boulton, which are incorporated herein in their
entirety by reference thereto
for all purposes. The fibrous component of the composite may contain any
desired amount of the
resulting composite. For instance, the fibrous component may contain greater
than about 50% by
weight of the composite, and in some embodiments, from about 60% to about 90%
by weight of the
composite. Likewise, the nonwoven web may contain less than about 50% by
weight of the
composite, and in some embodiments, from about 10% to about 40% by weight of
the composite. In
some embodiments, the nonwoven web can include a spunbond polyolefin-based web
(e.g.,
polypropylene or polyethylene), while the fibrous component can include fibers
containing a blend of
polypropylene and VISTAMAXXTm or any other propylene-based plastomer, or a
blend of polyethylene
and INFUSETM or any other suitable ethylene-based plastomer.
The nonwoven web material can also be hydroentangled. Hydroentangled nonwoven
webs
are disclosed, for example, in U.S. Patent No. 7,779,521 to Topolkaraev, et
al. With hydroentangling,
layer of fibers is deposited on a foraminous support. The foraminous support
is commonly a
continuous wire screen, sometimes called a forming fabric. Forming fabrics are
commonly used in the
nonwovens industry and particular types are recognized by those skilled in the
art as being
advantageous for hydroentangling purposes. Alternatively, the foraminous
support may be the surface
of a cylinder, and generally may be any surface that supports the fibers and
transports them under the
water jets or water curtain that impart the energy to entangle the fibers.
lnnovent Inc. of Peabody,
Mass., USA, the aforementioned Rieter Perfojetand, and Fleissner sell screens
and cylinders suitable
for this purpose.
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Typically the foraminous support has holes to allow water drainage, but
alternatively or
additionally the foraminous support may have elevations or grooves, to allow
drainage and impart
topographic features on the finished fabric. In this context "water" indicates
a fluid that is
predominantly water, but may contain intentional or unintentional additives,
including minerals,
surfactants, defoamers, and various processing aides.
When the fibers are deposited on the support they may be completely unbonded,
alternatively the
fibers may be lightly bonded in the form of a nonwoven when they are deposited
on the foraminous
support. In other aspects of this invention, unbonded fibers may be deposited
on the support and prior
to hydroentangling the fibers may be lightly bonded using heat or other means.
It is generally
desirable that the fibers passing under the water jets have sufficient
motility to efficiently
hydroentangle.
The general conditions of hydroentangling, i.e., water pressure, nozzle-type,
design of the
foraminous support, are well known to those skilled in the art.
"Hydroentangle" and its derivatives
refer to a process for forming a fabric by mechanically wrapping and knotting
fibers into a web through
the use of a high-velocity jets or curtains of water. The resulting
hydroentangled fabric is sometimes
called "spunlaced" or "hydroknit" in the literature.
Generally, a high pressure water system delivers water to nozzles or orifices
from which high
velocity water is expelled. The layer of fibers is transported on the
foraminous support member
through at least one high velocity water jet or curtain. Alternatively, more
than one water jet or curtain
may be used. The direct impact of the water on the fibers causes the fibers to
wind and twist and
entangle around nearby fibers. Additionally, some of the water may rebound off
the foraminous
support member, this rebounding water also contributes to entanglement. The
water used for
hydroentangling is then drained into a manifold, typically from beneath the
support member, and
generally recirculated. As a result of the hydroentangling process, the fibers
are converted into a
coherent fabric.
Regardless of the type of nonwoven web material formed, the basis weight of
the nonwoven
web material may generally vary, such as from about 10 grams per square meter
("gsm") to about 150
gsm, in some embodiments from about 20 gsm to about 125 gsm, and in some
embodiments, from
about 25 gsm to about 100 gsm. When multiple nonwoven web materials are used,
such materials
may have the same or different basis weights.
Furthermore, the present disclosure also generally includes a method of
forming a base sheet
according to the present disclosure. For instance, referring to Fig. 3, a
nonwoven web 202, formed
according to any method known in the art using the above discussed materials
or the like may be
unwound from a first roll 204. The nonwoven web 202 can undergo various
processes as known in the
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art, including embossing (not shown) and has an adhesive 206 applied thereto.
As shown in Fig. 3, the
present disclosure has found that the adhesive may be applied in-line using a
flexographic printer 208.
However, it should be understood that, in some aspects, other application
methods may be used.
Nonetheless, the nonwoven web 202 having the adhesive 206 applied thereto,
enters an electroplating
apparatus 210 containing staple fibers treated with a cation. As known in the
art, the electroplating
module 210 contains an electrode, and an electrolyte, causing the plurality of
staple fibers to be plated
or deposited onto the anion containing adhesive 206. Finally, in one aspect,
the nonwoven web 202
containing the electroplated fibers 210 may be calandered 212 to further
improve fiber adhesion
before being wound on roll 214 as a base sheet according to the present
disclosure.
Once the meltblown nonwoven web material, the spunbond nonwoven web material,
or any
other nonwoven web material is formed, and either prior to or after undergoing
electroplating and/or
calandering, the nonwoven web material can be further processed to reduce lint
left behind when the
nonwoven web material is used, to minimize the amount of residue or streaks
present on a surface
after the surface is contacted with the nonwoven web material, and to enhance
the dust holding
capacity of the nonwoven web material.
For instance, as discussed above, the nonwoven web material can be apertured,
post-
bonded, or both. Aperturing can enhance the dust holding capacity of the
nonwoven web material by
creating pockets in the nonwoven web material in which particulates, dust,
pathogens, etc. can be
trapped. Aperturing can occur by any suitable method known to one having
ordinary skill in the art,
such as laser aperturing, slit aperturing, pin aperturing, or thermal
aperturing using a patterned roll.
Meanwhile post-bonding can reduce the amount of lint produced by the nonwoven
web material and
can also enhance the dust holding capacity of the nonwoven web material by
creating indentations in
the nonwoven web material in which particulates, dust, pathogens, etc. can be
trapped. Although not
required, the processes to form apertures and bonds in the nonwoven web
material can occur
concurrently. However, it should be understood that other methods of forming
the apertures and
bonds that are not concurrent can also be utilized, as is known to those
having ordinary skill in the art.
To concurrently form apertures and textured elements on the nonwoven web
material, a patterned
bonding technique (e.g., thermal point bonding, ultrasonic bonding, etc.) is
generally used in which the
nonwoven web material is supplied to a nip defined by at least one patterned
roll. Thermal point
bonding, for instance, typically employs a nip formed between two rolls, at
least one of which is
patterned. Ultrasonic bonding, on the other hand, typically employs a nip
formed between a sonic
horn and a patterned roll. Regardless of the technique chosen, the patterned
roll contains a plurality
of raised bonding elements to concurrently bond the nonwoven web material and
form apertures in the
nonwoven web material.
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The size of the bonding elements may be specifically tailored to facilitate
the formation of
apertures in the nonwoven web material and enhance bonding between the fibers
contained in the
nonwoven web material. For example, the length dimension of the bonding
elements may be from
about 300 to about 5000 micrometers, in some embodiments from about 500 to
about 4000
micrometers, and in some embodiments, from about 1000 to about 2000
micrometers. The width
dimension of the bonding elements may likewise range from about 20 to about
500 micrometers, in
some embodiments from about 40 to about 200 micrometers, and in some
embodiments, from about
50 to about 150 micrometers. In addition, the "element aspect ratio" (the
ratio of the length of an
element to its width) may range from about 2 to about 100, in some embodiments
from about 4 to
about 50, and in some embodiments, from about 5 to about 20.
Besides the size of the bonding elements, the overall bonding pattern may also
be selectively
controlled to achieve the desired aperture formation. In one embodiment, for
example, a bonding
pattern is selected in which the longitudinal axis (longest dimension along a
center line of the element)
of one or more of the bonding elements is skewed relative to the machine
direction ("MD") of the
nonwoven web material. For example, one or more of the bonding elements may be
oriented from
about 30 to about 150 , in some embodiments from about 45 to about 135 , and
in some
embodiments, from about 60 to about 120 relative to the machine direction of
the nonwoven web
material. In this manner, the bonding elements will present a relatively large
surface to the nonwoven
web material in a direction substantially perpendicular to that which the
nonwoven web material
moves. This increases the area over which shear stress is imparted to the
nonwoven web material
and, in turn, facilitates aperture formation.
The pattern of the bonding elements is generally selected so that the nonwoven
web material
has a total bond area of less than about 50% (as determined by conventional
optical microscopic
methods), in some embodiments, less than about 40%, and in some embodiments,
less than about
25%. The bond density is also typically greater than about 50 bonds per square
inch, and in some
embodiments, from about 75 to about 500 pin bonds per square inch. One
suitable bonding pattern
for use in the present invention is known as an "S-weave" pattern and is
described in U.S. Patent No.
5,964,742 to McCormack, et al., which is incorporated herein in its entirety
by reference thereto for all
purposes. S-weave patterns typically have a bonding element density of from
about 50 to about 500
bonding elements per square inch, and in some embodiments, from about 75 to
about 150 bonding
elements per square inch. An example of a suitable "S-weave" pattern in shown
in Fig. 9, which
illustrates S-shaped bonding elements 88 having a length dimension "L" and a
width dimension "W."
Another suitable bonding pattern is known as the "rib-knit" pattern and is
described in U.S. Patent No.
5,620,779 to Levy, et al., which is incorporated herein in its entirety by
reference thereto for all
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purposes. Rib-knit patterns typically have a bonding element density of from
about 150 to about 400
bonding elements per square inch, and in some embodiments, from about 200 to
about 300 bonding
elements per square inch. An example of a suitable "rib-knit" pattern in shown
in Fig. 10, which
illustrates bonding elements 89 and bonding elements 91, which are oriented in
a different direction.
Yet another suitable pattern is the "wire weave" pattern, which has a bonding
element density of from
about 200 to about 500 bonding elements per square inch, and in some
embodiments, from about 250
to about 350 bonding elements per square inch. An example of a suitable "wire-
weave" pattern in
shown in Fig. 11, which illustrates bonding elements 93 and bonding elements
95, which are oriented
in a different direction. Other bond patterns that may be used in the present
invention are described in
U.S. Patent Nos. 3,855,046 to Hansen et al.; 5,962,112 to Haynes et al.;
6,093,665 to Sayovitz et al.;
D375,844 to Edwards, et al.; D428,267 to Romano et al.; and D390,708 to Brown,
which are
incorporated herein in their entirety by reference thereto for all purposes.
The selection of an appropriate bonding temperature (e.g., the temperature of
a heated roll) will help
melt and/soften nonwoven web material at regions adjacent to the bonding
elements. The softened
nonwoven web material may then flow and become displaced during bonding, such
as by pressure
exerted by the bonding elements.
To achieve such concurrent aperture and bond formation without substantially
softening the
polymer(s) of the nonwoven web material, the bonding temperature and pressure
may be selectively
controlled. For example, one or more rolls may be heated to a surface
temperature of from about
50 C to about 160 C, in some embodiments from about 60 C to about 140 C, and
in some
embodiments, from about 70 C to about 120 C. Likewise, the pressure exerted by
rolls ("nip
pressure") during thermal bonding may range from about 75 to about 600 pounds
per linear inch
(about 1339 to about 10,715 kilograms per meter), in some embodiments from
about 100 to about 400
pounds per linear inch (about 1786 to about 7143 kilograms per meter), and in
some embodiments,
from about 120 to about 200 pounds per linear inch (about 2143 to about 3572
kilograms per meter).
Of course, the residence time of the materials may influence the particular
bonding parameters
employed.
Another factor that influences concurrent aperture and bond formation is the
degree of tension
in the nonwoven web material. An increase in nonwoven web material tension
when it is passed over
the bonding elements, for example, typically correlates to an increase in
aperture size. Of course, a
tension that is too high may adversely affect the integrity of the nonwoven
web material, which could
negatively impact the ability to form a cloth with sufficient tackiness and
minimal lint production. Thus,
in most embodiments of the present invention, a stretch ratio of about 1.5 or
more, in some
embodiments from about 2.5 to about 7.0, and in some embodiments, from about
3.0 to about 5.5, is
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employed to achieve the desired degree of tension in the film during
lamination. The stretch ratio may
be determined by dividing the final length of the film by its original length.
Generally, the size and/or pattern of the resulting apertures in the nonwoven
web material
correspond to the size and/or pattern of the bonding elements discussed above.
That is, the apertures
may have a length, width, aspect ratio, and orientation as described above.
For example, the length
dimension of the apertures may be from about 200 to about 5000 micrometers, in
some embodiments
from about 350 to about 4000 micrometers, and in some embodiments, from about
500 to about 2500
micrometers. The width dimension of the apertures may likewise range from
about 20 to about 500
micrometers, in some embodiments from about 40 to about 200 micrometers, and
in some
embodiments, from about 50 to about 150 micrometers. In addition, the "aspect
ratio" (the ratio of the
length of an aperture to its width) may range from about 2 to about 100, in
some embodiments from
about 4 to about 50, and in some embodiments, from about 5 to about 20.
Similarly, the longitudinal
axis of one or more of the apertures (longest dimension along a center line of
the aperture) may be
skewed relative to the machine direction of the nonwoven web material, such as
from about 30 to
about 150 , in some embodiments from about 45 to about 135 , and in some
embodiments, from
about 60 to about 120 relative to the machine direction of the nonwoven web
material.
Furthermore, certain aspects of the present disclosure may be better
understood according to
the following examples, which are intended to be non-limiting and exemplary in
nature.
Examples:
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.
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PCT/US2020/066378
Example 1
A spunbond/spunbond nonwoven web having a basis weight of about 23 gsm and
barrier
properties was formed. A water-based adhesive treated with an anionic agent
supplied by Agatex was
applied by flexographic printing to the nonwoven web at a thickness of 100
micrometers. Polyethylene
staple fibers having a denier of about 1.5 and having a length of 500
micrometers treated with a cation
supplied by Agatex were adhered to the nonwoven web using an electroplating
apparatus described
above, forming a base sheet. The base sheet exhibited improved softness while
maintaining good
barrier properties. For instance, after attachment of the staple fibers, the
base sheet exhibited a
bacterial filtration efficiency of 98.2% as measured according to UNE-EN
14683:2019 annex B, a
breathability of 14.1 Pa/cm2 as measured according to UNE-EN 14683:2019 annex
C, and a splash
resistance of less than 10.6 kPa as measured according to ISO 22609:2004 ASTM
F1862.
Example 2
A polypropylene nonwoven web coformed with pulp fibers was prepared having a
basis weight
of about 82 gsm. A water-based adhesive treated with an anionic agent supplied
by Agatex was
applied to the nonwoven web via flexographic printing at a thickness of 100
micrometers. Polyethylene
staple fibers having a denier of about 1.5 and having a length of 500
micrometers were treated with a
cation supplied by Agatex, and adhered to the nonwoven web using an
electroplating apparatus
described above, forming a 150 gsm base sheet with 15% improvement in abrasion
as compared to
the same nonwoven web without the plurality of staple fibers.
These and other modifications and variations to the present invention may be
practiced by
those of ordinary skill in the art, without departing from the spirit and
scope of the present invention,
which is more particularly set forth in the appended claims. In addition, it
should be understood that
aspects of the various aspects may be interchanged both in whole or in part.
Furthermore, those of
ordinary skill in the art will appreciate that the foregoing description is by
way of example only, and is
not intended to limit the invention so further described in such appended
claims.
29
CA 03202783 2023- 6- 19
