Note: Descriptions are shown in the official language in which they were submitted.
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FIBROUS STRUCTURES COMPRISING POLYSACCHARIDE FILAMENTS AND METHODS
FOR MAKING SAME
FIELD OF THE INVENTION
The present invention relates to fibrous structures, more particularly to
fibrous structures
comprising a plurality of solid additives and a plurality of filaments, and
even more particularly to
fibrous structures comprising a plurality of solid additives and a plurality
of starch filaments, and
methods for making such fibrous structures.
BACKGROUND OF THE INVENTION
Fibrous structures comprising solid additives, such as pulp fibers, and
filaments, such as
starch filaments, are known in the art. Such fibrous structures have been made
using filament
sources, such as meltblow dies. Conventionally, the meltblow dies have been
oriented the same as
one another with respect to the machine direction of the fibrous structure
being made by filaments
provided by such meltblow dies. For example, the meltblow dies have been
oriented at 900 angles to
the machine direction. The problem with making fibrous structures with the
filament sources, such
as meltblow dies, oriented the same, for example at 90 angles to the machine
direction, is that each
layer of filaments within the fibrous structure provided by each filament
source exhibit the same
orientation as each other layer of filaments each other filament source as
shown in Fig. 1. Fig. 1
shows a fibrous structure 10 comprising three layers 12 of filaments 14 where
each layer 12 is
produced by a filament source that is oriented at a 90 angle to the machine
direction, which results
in each layer 12 of filaments 14 exhibiting a machine direction orientation.
As a result, the fibrous
structure 10, which contains solid additives 16 (for example pulp fibers) and
three layers 12 of
filaments 14 that exhibit the same orientation, exhibits an average Tensile
Ratio of greater than 2 as
measured according to the Dry Tensile Strength Test Method described herein.
The impact of the
layers of filaments exhibiting the same orientation can be exasperated by the
fibrous structure being
made at speeds of greater than 200 ft/min and/or by the fibrous structure
being greater than 20 inches
wide.
In addition to the above, it is known in the art to make fibrous structures,
void of solid
additives, for example void of pulp fibers, from thermoplastic polymer
filaments provided by
spunbond dies and/or meltblow dies that are oriented at different angles with
respect to the machine
direction of the fibrous structure.
Accordingly, there is a need for a fibrous structure that comprises a
plurality of solid
additives, for example pulp fibers, and a plurality of filaments, for example
starch filaments,
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wherein the filaments are present in the fibrous structure in two or more
different layers based on
their orientation in each layer and methods for making such fibrous
structures.
SUMMARY OF THE INVENTION
The present invention fulfills the needs described above by providing novel
fibrous
structures comprising a plurality of solid additives, for example pulp fibers,
and a plurality of
filaments, for example starch filaments.
In one example of the present invention, a fibrous structure comprising a
plurality of solid
additives and a plurality of filaments wherein the filaments are present in
the fibrous structure in
two or more different layers of filaments based on their orientation in each
layer, is provided.
In another example of the present invention, a fibrous structure comprising a
plurality of
filaments comprising one or more polysaccharides, wherein the fibrous
structure exhibits a
Tensile Ratio of 2 or less as measured according to the Dry Tensile Strength
Test Method
described herein, is provided.
In another example of the present invention, a single- or multi-ply sanitary
tissue product
comprising a fibrous structure according to the present invention, is
provided.
In still another example of the present invention, a method for making a
fibrous structure,
the method comprising the steps of:
a. providing a plurality of filaments from a filament source; and
b. collecting the filaments on a collection device to form a fibrous structure
such that the
fibrous structure exhibits a Tensile Ratio of 2 or less as measured according
to the Tensile Ratio
Test Method described herein, is provided.
In even another example of the present invention, a method for making a
fibrous
structure, the method comprising the steps of:
a. providing first filaments from a first source of filaments;
b. providing second filaments from a second source of filaments;
c. optionally, providing additional filaments from additional sources of
filaments;
d. providing solid additives from a source of solid additives; and
e. collecting the first and second filaments (and any additional filaments)
and the solid
additives to form a fibrous structure, wherein the first source of filaments
is oriented at a first
angle to the machine direction of the fibrous structure and the second source
of filaments is
oriented at a second angle to the machine direction different from the first
angle, is provided.
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Accordingly, the present invention provides fibrous structures and methods for
making
fibrous structures that fulfill the needs described above.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a schematic representation of a prior art fibrous structure;
Fig. 2 is a schematic representation of an example of a fibrous structure in
accordance
with the present invention;
Fig. 3 is a photograph of a layer of filaments of a fibrous structure produced
by a source
of filaments oriented at a 900 angle to the machine direction of the fibrous
structure;
Fig. 4 is a photograph of a layer of filaments of a fibrous structure produced
by a source
of filaments oriented at about a 40 angle to the machine direction of the
fibrous structure;
Fig. 5 is a schematic representation of one example of a fibrous structure in
accordance
with the present invention;
Fig. 6 is a cross-sectional view of the fibrous structure of Fig. 5 taken
along line 6-6;
Fig. 7 is a schematic representation of one example of a method for making a
fibrous
structure according to the present invention;
Fig. 8 is a schematic representation of one example of a portion of fibrous
structure
making process according to the present invention;
Fig. 9 is a schematic representation of an example of a meltblow die in
accordance with
the present invention;
Fig. 10A is a schematic representation of an example of a barrel of a twin
screw extruder
in accordance with the present invention; and
Fig. 10B is a schematic representation of a screw and mixing element
configuration for
the twin screw extruder of Fig. 10A.
DETAILED DESCRIPTION OF THE INVENTION
Definitions
"Fibrous structure" as used herein means a structure that comprises one or
more
filaments, for example a plurality of filaments, and one or more solid
additives, such as a
plurality of pulp fibers. In one example, a fibrous structure according to the
present invention is
an association of filaments and solid additives that together form a structure
capable of
performing a function.
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Non-limiting examples of processes for making fibrous structures according to
the
present invention include known wet, solution, and dry filament spinning
processes that are
typically referred to as nonwoven processes. In one example, the filament
spinning process is a
meltblowing process where filaments are provided from a meltblow die (a
filament source).
Further processing of the fibrous structure may be carried out such that a
finished fibrous
structure is formed. For example, the finished fibrous structure is a fibrous
structure that is
wound on a reel at the end of a fibrous structure making process. The finished
fibrous structure
may subsequently be converted into a finished product, e.g. a sanitary tissue
product.
"Filament" as used herein means an elongate particulate having a length
greatly
exceeding its average diameter, i.e. a length to average diameter ratio of at
least about 10. In one
example, the filament is a single filament rather than a yarn, which is a
strand of filaments
twisted together along their lengths. In one example, a filament exhibits a
length of greater than
or equal to 5.08 cm and/or greater than or equal to 7.62 cm and/or greater
than or equal to 10.16
cm and/or greater than or equal to 15.24 cm.
Filaments are typically considered continuous or substantially continuous in
nature
especially with respect to the fibrous structure in which they are present.
Filaments are relatively
longer than fibers. Non-limiting examples of filaments include meltblown
and/or spunbond
filaments. Non-limiting examples of polymers that can be spun into filaments
include natural
polymers, such as starch, starch derivatives, cellulose, such as rayon and/or
lyocell, and cellulose
derivatives, hemicellulose, hemicellulose derivatives, and synthetic polymers
including, but not
limited to thermoplastic polymer filaments, such as polyesters, nylons,
polyolefins such as
polypropylene filaments, polyethylene filaments, and biodegradable
thermoplastic fibers such as
polylactic acid filaments, polyhydroxyalkanoate filaments, polyesteramide
filaments and
polycaprolactone filaments.
The filaments of the present invention may be monocomponent and/or
multicomponent.
For example, the filaments may comprise bicomponent filaments. The bicomponent
filaments
may be in any form, such as side-by-side, core and sheath, islands-in-the-sea
and the like.
"Solid additive" as used herein means a solid particulate such as a powder,
granule,
and/or fiber.
"Fiber" as used herein means an elongate particulate as described above that
exhibits a
length of less than 5.08 cm and/or less than 3.81 cm and/or less than 2.54 cm.
Fibers are typically considered discontinuous in nature especially with
respect to the
fibrous structure. Non-limiting examples of fibers include pulp fibers, such
as wood pulp fibers,
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and synthetic staple fibers such as polypropylene, polyethylene, polyester,
copolymers thereof,
rayon, glass fibers and polyvinyl alcohol fibers.
Staple fibers may be produced by spinning a filament tow and then cutting the
tow into
segments of less than 5.08 cm thus producing staple fibers.
5 In
one example of the present invention, a fiber may be a naturally occurring
fiber, which
means it is obtained from a naturally occurring source, such as a vegetative
source, for example a
tree and/or plant. Such fibers are typically used in papermaking and are
oftentimes referred to as
papermaking fibers. Papermaking fibers useful in the present invention include
cellulosic fibers
commonly known as wood pulp fibers. Applicable wood pulps include chemical
pulps, such as
Kraft, sulfite, and sulfate pulps, as well as mechanical pulps including, for
example,
groundwood, thermomechanical pulp and chemically modified thermomechanical
pulp.
Chemical pulps, however, may be preferred since they impart a superior tactile
sense of softness
to tissue sheets made therefrom. Pulps derived from both deciduous trees
(hereinafter, also
referred to as "hardwood") and coniferous trees (hereinafter, also referred to
as "softwood") may
be utilized. The hardwood and softwood fibers can be blended, or
alternatively, can be deposited
in layers to provide a stratified web. Also applicable to the present
invention are fibers derived
from recycled paper, which may contain any or all of the above categories of
fibers as well as
other non-fibrous polymers such as fillers, softening agents, wet and dry
strength agents, and
adhesives used to facilitate the original papermaking.
In addition to the various wood pulp fibers, other cellulosic fibers such as
cotton linters,
rayon, lyocell and bagasse fibers can be used in the fibrous structures of the
present invention.
In another example, the fibrous structure may comprise solid additives that
comprise
trichomes and/or seed hairs.
"Layer of filaments" as used herein means a plurality of filaments that form
at least a part
of a fibrous structure wherein the filaments of the layer extend along a
common primary
direction. In other words, the filaments of the layer exhibit the common
primary direction
orientation. For example, the filaments of a layer may exhibit a machine
direction orientation.
In another example, the filaments of a layer may exhibit an orientation that
is different from the
machine direction, for example an orientation along an angle between the
machine direction and
the cross machine direction. In one example, one or more layers of filaments
may be combined,
such as deposited on one another, to form a fibrous structure according to the
present invention.
In addition, the fibrous structure may comprise two or more different layers
of filaments. For
example, as shown in Fig. 2, a fibrous structure 10 may comprise a first layer
18 of filaments 14
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that exhibits a machine direction orientation and a second layer 20 of
filaments 14 that exhibits
an orientation different from the machine direction orientation exhibited by
the first layer 18.
"Orientation" as used herein with respect to orientation of filaments within a
layer of
filaments means that the filaments within a layer extend along a common
primary direction.
Obviously, there may be some filaments that extend in a secondary direction
within a layer, but
the vast majority of the filaments in a layer extend in a common primary
direction and that
common primary direction establishes the orientation of the filaments within a
layer. As shown
in Fig. 3, a layer of filaments exhibits a machine direction orientation. In
Fig. 4, a layer of
filaments exhibits an angled orientation with respect to the machine direction
of the layer. In
another example, the angle of a source of filaments (with respect to the
machine direction of a
fibrous structure being made), such as a meltblow die, provides the filaments
of the layer of
filaments produced from the source of filaments with an defined orientation.
Therefore, if two or
more layers of filaments are produced by two or more sources of filaments (for
example
meltblow dies) that are oriented at different angles (for example within the
range of 0 to 90
positive or negative from the MD) with respect to the machine direction, then
the filaments
within the two or more layers will exhibit different orientations by default.
For purposes of measuring the angle of orientation of a source of filaments,
such as a
meltblow die, the smaller angle with respect to the machine direction is
measured and considered
as the angle of orientation of the source of filaments. If the angles of
orientation of a source of
filaments are the same with respect to the machine direction, then the angle
of orientation is 90 .
"Nonwoven substrate" as used herein means a web comprising one or more layers
of
filaments of the present invention.
"Sanitary tissue product" as used herein means a fibrous structure useful as a
wiping
implement for post-urinary and post-bowel movement cleaning (toilet tissue),
for
otorhinolaryngological discharges (facial tissue), and multi-functional
absorbent and cleaning
uses (absorbent towels). The sanitary tissue product may be convolutedly wound
upon itself
about a core or without a core to form a sanitary tissue product roll.
In one example, the sanitary tissue product of the present invention comprises
one or
more fibrous structures according to the present invention.
The sanitary tissue products of the present invention may exhibit a basis
weight between
about 10 g/m2 to about 120 g/m2 and/or from about 15 g/m2 to about 110 g/m2
and/or from about
20 g/m2 to about 100 g/m2 and/or from about 30 to 90 g/m2. In addition, the
sanitary tissue
product of the present invention may exhibit a basis weight between about 40
g/m2 to about 120
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g/m2 and/or from about 50 g/m2 to about 110 g/m2 and/or from about 55 g/m2 to
about 105 g/m2
and/or from about 60 to 100 g/m2.
The sanitary tissue products of the present invention may exhibit a density of
less than
about 0.60 g/cm3 and/or less than about 0.30 g/cm3 and/or less than about 0.20
g/cm3 and/or less
than about 0.10 g/cm3 and/or less than about 0.07 g/cm3 and/or less than about
0.05 g/cm3 and/or
from about 0.01 g/cm3 to about 0.20 g/cm3 and/or from about 0.02 g/cm3 to
about 0.10 g/cm3.
The sanitary tissue products of the present invention may be in the form of
sanitary tissue
product rolls. Such sanitary tissue product rolls may comprise a plurality of
connected, but
perforated sheets of fibrous structure, that are separably dispensable from
adjacent sheets.
The sanitary tissue products of the present invention may comprise additives
such as
softening agents, temporary wet strength agents, permanent wet strength
agents, bulk softening
agents, lotions, silicones, wetting agents, latexes, patterned latexes and
other types of additives
suitable for inclusion in and/or on sanitary tissue products.
"Scrim" as used herein means a web material, such as a web comprising
filaments, that is
used to overlay solid additives within the fibrous structures of the present
invention such that the
solid additives are positioned between the web material and another layer of
filaments within the
fibrous structures. In one example, the scrim comprises a web material that
exhibits a basis
weight of less than 10 g/m2 and/or less than 7 g/m2 and/or less than 5 g/m2
and/or less than 3
g/m2 and the remaining layer(s) of filaments of the fibrous structure of the
present invention
exhibit a basis weight of greater than 10 g/m2 and/or greater than 15 g/m2
and/or greater than 20
g/m2 and/or to about 120 g/m2.
"Hydroxyl polymer" as used herein includes any hydroxyl-containing polymer
from
which filaments of the present invention may be made. In one example, the
hydroxyl polymer of
the present invention includes greater than 10% and/or greater than 20% and/or
greater than 25%
by weight hydroxyl moieties. In another example, the hydroxyl within the
hydroxyl-containing
polymer is not part of a larger functional group such as a carboxylic acid
group.
"Non-thermoplastic" as used herein means, with respect to a filament as a
whole and/or a
polymer within a filament, that the filament and/or polymer exhibits no
melting point and/or
softening point, which allows it to flow under pressure, in the absence of a
plasticizer, such as
water, glycerin, sorbitol, urea and the like.
"Thermoplastic" as used herein means, with respect to a filament as a whole
and/or a
polymer within a filament, that the filament and/or polymer exhibits a melting
point and/or
softening point at a certain temperature, which allows it to flow under
pressure.
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"Non-cellulose-containing" as used herein means that less than 5% and/or less
than 3%
and/or less than 1% and/or less than 0.1% and/or 0% by weight of cellulose
polymer, cellulose
derivative polymer and/or cellulose copolymer is present in fibrous element.
In one example,
"non-cellulose-containing" means that less than 5% and/or less than 3% and/or
less than 1%
and/or less than 0.1% and/or 0% by weight of cellulose polymer is present in
fibrous element.
"Associate," "Associated," "Association," and/or "Associating" as used herein
with
respect to filaments means combining, either in direct contact or in indirect
contact, filaments
such that a fibrous structure is formed. In one example, the associated
filaments may be bonded
together for example by adhesives and/or thermal bonds. In another example,
the filaments may
be associated with one another by being deposited onto the same fibrous
structure making belt.
"Weight average molecular weight" as used herein means the weight average
molecular
weight as determined using gel permeation chromatography according to the
protocol found in
Colloids and Surfaces A. Physico Chemical & Engineering Aspects, Vol. 162,
2000, pg. 107-
121.
"Basis Weight" as used herein is the weight per unit area of a sample reported
in g/m2.
"Machine Direction" or "MD" as used herein means the direction parallel to the
flow of
the fibrous structure through a fibrous structure making machine, such as a
papermaking machine
and/or product manufacturing equipment.
"Cross Machine Direction" or "CD" as used herein means the direction
perpendicular to
the machine direction in the same plane of the fibrous structure and/or
sanitary tissue product
comprising the fibrous structure.
"Ply" or "Plies" as used herein means an individual fibrous structure
optionally to be
disposed in a substantially contiguous, face-to-face relationship with other
plies, forming a
multiple ply fibrous structure. It is also contemplated that a single fibrous
structure can
effectively form two "plies" or multiple "plies", for example, by being folded
on itself.
"Spinnerette" as used herein means a plate that comprises one or more filament
forming
nozzles from which filaments of a melt composition can flow. In one example,
the spinnerette
comprises a plurality of filament forming nozzles arranged in one or more rows
and/or columns.
Such a spinnerette is referred to as a multi-row spinnerette.
"Abut one another" as used herein with reference to two or more spinnerettes
that abut
one another means that a surface of one spinnerette is in contact with a
surface of another
spinnerette.
"Seam" as used herein means the line of contact between two abutting
spinnerettes.
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"Seam filament forming nozzle opening" as used herein means one or more
filament
forming nozzle openings that are closest in distance to the seam formed by two
abutting
spinnerettes.
As used herein, the articles "a" and "an" when used herein, for example, "an
anionic
surfactant" or "a fiber" is understood to mean one or more of the material
that is claimed or
described.
All percentages and ratios are calculated by weight unless otherwise
indicated. All
percentages and ratios are calculated based on the total composition unless
otherwise indicated.
Unless otherwise noted, all component or composition levels are in reference
to the active
level of that component or composition, and are exclusive of impurities, for
example, residual
solvents or by-products, which may be present in commercially available
sources.
Filaments
In one example, the fibrous structure of the present invention comprises
filaments
comprising a hydroxyl polymer. In another example, the fibrous structure may
comprise starch
and/or starch derivative filaments. The starch filaments may further comprise
polyvinyl alcohol
and/or other polymers.
The filaments of the present invention may be produced from a polymer melt
composition
comprising a hydroxyl polymer, such as an uncrosslinked starch, a crosslinking
system
comprising a crosslinking agent, such as an imidazolidinone, and water. The
polymer melt
composition may also comprise a surfactant, such as a sulfosuccinate
surfactant. A non-limiting
example of a suitable sulfosuccinate surfactant comprises Aerosol AOT (a
sodium dioctyl
sulfosuccinate) and/or Aerosol MA-80 (a sodium dihexyl sulfosuccinate), which
is
commercially available from Cytec Industries, Woodland Park, NJ.
In one example, the filaments of the present invention comprise greater than
25% and/or
greater than 40% and/or greater than 50% and/or greater than 60% and/or
greater than 70% to
about 95% and/or to about 90% and/or to about 80% by weight of the filament of
a hydroxyl
polymer, such as starch, which may be in a crosslinked state. In one example,
the filament
comprises an ethoxylated starch and an acid thinned starch, which may be in
their crosslinked
states.
In addition to the hydroxyl polymer, the filament may comprise polyvinyl
alcohol at a
level of from 0% and/or from 0.5% and/or from 1% and/or from 3% to about 15%
and/or to
about 12% and/or to about 10% and/or to about 7% by weight of the filament.
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The filaments may comprise a surfactant, such as a sulfosuccinate surfactant,
at a level of
from 0% and/or from about 0.1% and/or from about 0.3% to about 2% and/or to
about 1.5%
and/or to about 1.1% and/or to about 0.7% by weight of the filament.
The filaments may also comprise a polymer selected from the group consisting
of:
5 polyacrylamide and its derivatives; polyacrylic acid, polymethacrylic
acid, and their esters;
polyethyleneimine; copolymers made from mixtures of monomers of the
aforementioned
polymers; and mixtures thereof at a level of from 0% and/or from about 0.01%
and/or from
about 0.05% and/or to about 0.5% and/or to about 0.3% and/or to about 0.2% by
weight of the
filament. Such polymers may exhibits a weight average molecular weight of
greater than
10 500,000 g/mol. In one example, the filament comprises polyacrylamide.
The filaments may also comprise a crosslinking agent, such as an
imidazolidinone, which
may be in its crosslinked state (crosslinking the hydroxyl polymers present in
the filaments) at a
level of from about 0.5% and/or from about 1% and/or from about 2% and/or from
about 3%
and/or to about 10% and/or to about 7% and/or to about 5.5% and/or to about
4.5% by weight of
the filament. In addition to the crosslinking agent, the filament may comprise
a crosslinking
facilitator that aids the crosslinking agent at a level of from 0% and/or from
about 0.3% and/or
from about 0.5% and/or to about 2% and/or to about 1.7% and/or to about 1.5%
by weight of the
filament.
The filament may also comprise various other ingredients such as propylene
glycol,
sorbitol, glycerine, and mixtures thereof.
Polymers
The filaments of the present invention that associate to form the fibrous
structures of the
present invention may contain various types of polymers such as hydroxyl
polymers, non-
thermoplastic polymers, thermoplastic polymers and mixtures thereof.
Non-limiting examples of hydroxyl polymers in accordance with the present
invention
include polyols, such as polyvinyl alcohol, polyvinyl alcohol derivatives,
polyvinyl alcohol
copolymers, starch, starch derivatives, starch copolymers, chitosan, chitosan
derivatives, chitosan
copolymers, cellulose, cellulose derivatives such as cellulose ether and ester
derivatives,
cellulose copolymers, hemicellulose, hemicellulose derivatives, hemicellulose
copolymers, gums,
arabinans, galactans, proteins and various other polysaccharides and mixtures
thereof.
In one example, a hydroxyl polymer of the present invention is a
polysaccharide.
In another example, a hydroxyl polymer of the present invention is a non-
thermoplastic
polymer.
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The hydroxyl polymer may have a weight average molecular weight of from about
10,000
g/mol to about 40,000,000 g/mol and/or greater than about 100,000 g/mol and/or
greater than
about 1,000,000 g/mol and/or greater than about 3,000,000 g/mol and/or greater
than about
3,000,000 g/mol to about 40,000,000 g/mol. Higher and lower molecular weight
hydroxyl
polymers may be used in combination with hydroxyl polymers having a certain
desired weight
average molecular weight.
Well known modifications of hydroxyl polymers, such as natural starches,
include
chemical modifications and/or enzymatic modifications. For example, natural
starch can be acid-
thinned, hydroxy-ethylated, hydroxy-propylated, and/or oxidized. In addition,
the hydroxyl
polymer may comprise dent corn starch hydroxyl polymer.
Polyvinyl alcohols herein can be grafted with other monomers to modify its
properties. A
wide range of monomers has been successfully grafted to polyvinyl alcohol. Non-
limiting
examples of such monomers include vinyl acetate, styrene, acrylamide, acrylic
acid, 2-
hydroxyethyl methacrylate, acrylonitrile, 1,3-butadiene, methyl methacrylate,
methacrylic acid,
vinylidene chloride, vinyl chloride, vinyl amine and a variety of acrylate
esters. Polyvinyl
alcohols comprise the various hydrolysis products formed from polyvinyl
acetate. In one
example the level of hydrolysis of the polyvinyl alcohols is greater than 70%
and/or greater than
88% and/or greater than 95% and/or about 99%.
"Polysaccharides" as used herein means natural polysaccharides and
polysaccharide
derivatives and/or modified polysaccharides. Suitable polysaccharides include,
but are not
limited to, starches, starch derivatives, chitosan, chitosan derivatives,
cellulose, cellulose
derivatives, hemicellulose, hemicellulose derivatives, gums, arabinans,
galactans and mixtures
thereof. The polysaccharide may exhibit a weight average molecular weight of
from about
10,000 to about 40,000,000 g/mol and/or greater than about 100,000 and/or
greater than about
1,000,000 and/or greater than about 3,000,000 and/or greater than about
3,000,000 to about
40,000,000.
Non-cellulose and/or non-cellulose derivative and/or non-cellulose copolymer
hydroxyl
polymers, such as non-cellulose polysaccharides may be selected from the group
consisting of:
starches, starch derivatives, chitosan, chitosan derivatives, hemicellulose,
hemicellulose
derivatives, gums, arabinans, galactans and mixtures thereof.
In one example, the filaments of the present invention are void of
thermoplastic, water-
insoluble polymers.
Solid Additives
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Solid additives of the present invention can be applied to a surface of a
layer of filaments
in a solid form. In other words, the solid additives of the present invention
can be delivered
directly to a surface of a layer of filaments without a liquid phase being
present, i.e. without
melting the solid additive and without suspending the solid additive in a
liquid vehicle or carrier.
As such, the solid additive of the present invention does not require a liquid
state or a liquid
vehicle or carrier in order to be delivered to a surface of a layer of
filaments. The solid additive
of the present invention may be delivered via a gas or combinations of gases.
In one example, in
simplistic terms, a solid additive is an additive that when placed within a
container, does not take
the shape of the container.
In one example, one or more solid additives may be present on a surface of a
fibrous
structure of the present invention.
The solid additives of the present invention may have different geometries
and/or cross-
sectional areas that include round, elliptical, star-shaped, rectangular,
trilobal and other various
eccentricities.
In one example, the solid additive may exhibit a particle size of less than 6
mm and/or
less than 5.5 mm and/or less than 5 mm and/or less than 4.5 mm and/or less
than 4 mm and/or
less than 2 mm in its maximum dimension.
The solid additive of the present invention may exhibit an aspect ratio of
less than about
25/1 and/or less than about 15/1 and/or less than about 10/1 and/or less than
5/1 to about 1/1. A
particle is not a fiber as defined herein.
The solid additives may be present in the fibrous structures of the present
invention at a
level of greater than about 1 and/or greater than about 2 and/or greater than
about 4 and/or to
about 20 and/or to about 15 and/or to about 10 g/m2. In one example, a fibrous
structure of the
present invention comprises from about 2 to about 10 and/or from about 5 to
about 10 g/m2 of
solid additives.
In one example, the solid additives are present in the fibrous structures of
the present
invention at a level of greater than 5% and/or greater than 10% and/or greater
than 20% to about
50% and/or to about 40% and/or to about 30% by weight.
In one example, the solid additives 14 comprise fibers, for example wood pulp
fibers.
The wood pulp fibers may be softwood pulp fibers and/or hardwood pulp fibers.
In one example,
the wood pulp fibers comprise eucalyptus pulp fibers. In another example, the
wood pulp fibers
comprise Southern Softwood Kraft (SSK) pulp fibers
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The solid additives may be chemically treated, for example chemically treated
pulp fiber.
In one example, the solid additives comprise softening agents and/or are
surface treated with
softening agents. Non-limiting examples of suitable softening agents include
silicones and/or
quaternary ammonium compounds, such as PROSOFT available from Hercules
Incorporated.
In one example, the solid additives comprise a wood pulp treated with a
quaternary ammonium
compound softening agent, an example of which is available from Georgia-
Pacific Corporation.
One advantage of applying a softening agent only to the solid additives versus
applying it to the
entire fibrous structure and/or nonwoven substrate and/or bonding material,
ensures that the
softening agent softens those components of the entire fibrous structure that
need softening
compared to the other components of the entire fibrous structure.
Nonwoven Substrate
The nonwoven substrate of the present invention comprises one or more layers
of
filaments. Two or more layers of filaments making up the nonwoven substrate
may have the
same or different orientations. In one example, the nonwoven substrate
comprises two or more
layers of filaments that exhibit different orientations.
In one example, the nonwoven substrate comprises a plurality of filaments
comprising a
hydroxyl polymer. The hydroxyl polymer may be selected from the group
consisting of
polysaccharides, derivatives thereof, polyvinyl alcohol, derivatives thereof
and mixtures thereof.
In one example, the hydroxyl polymer comprises a starch and/or starch
derivative. The
nonwoven substrate 12 may exhibit a basis weight of greater than about 10 g/m2
and/or greater
than about 14 g/m2 and/or greater than about 20 g/m2 and/or greater than about
25 g/m2 and/or
greater than about 30 g/m2 and/or greater than about 35 g/m2 and/or greater
than about 40 g/m2
and/or less than about 100 g/m2 and/or less than about 90 g/m2 and/or less
than about 80 g/m2.
Fibrous Structures
In one example, as shown in Figs. 5 and 6, the fibrous structure 10 of the
present
invention comprises a nonwoven substrate 26 comprising one or more layers of
filaments, a
plurality of solid additives 16, such as pulp fibers that are positioned
between the nonwoven
substrate 26 and a scrim 28 which is bonded to the nonwoven substrate 26 at
one or more bond
sites 30. The bond site 30 is where at least a portion of the scrim 28 and a
portion of the
nonwoven substrate 26 are connected to one another, such as via a thermal
bond, or a bond
created by applying high pressure to both the scrim 28 and the nonwoven
substrate 26 such that a
glassining effect occurs ("a pressure bond").
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In one example, the solid additives 16 may be uniformly distributed on a
surface 32 of
the nonwoven substrate 26.
In one example, the scrim 28 comprises one or more layers of filaments of the
present
invention. In one example, the scrim 28 consists of a single layer of
filaments of the present
invention. The scrim 28 and nonwoven substrate 26 may comprise filaments
having the same
composition, for example hydroxyl polymer-containing filaments, such as starch
filaments. The
scrim 28 may be present in the fibrous structure of the present invention at a
basis weight of
greater than 0.1 and/or greater than 0.3 and/or greater than 0.5 and/or
greater than 1 and/or
greater than 2 g/m2 and/or less than 10 and/or less than 7 and/or less than 5
and/or less than 4
g/m2. In one example, the scrim 28 may be present in the fibrous structure of
the present
invention at a basis weight of from about 0.1 to about 4 g/m2.
One purpose of the scrim 28 is to reduce the lint produced by the fibrous
structure 10 by
inhibiting the solid additives 16 from becoming disassociated from the fibrous
structure 10. The
scrim 28 may also provide additional strength properties to the fibrous
structure 10.
As shown in Figs. 5 and 6 the bond sites 30 may comprise a plurality of
discrete bond
sites. The discrete bond sites may be present in the form of a non-random
repeating pattern. One
or more bond sites 30 may comprise a thermal bond and/or a pressure bond.
In one example, the fibrous structures of the present invention comprise a
plurality of
filaments, such as hydroxyl polymer-containing filaments, wherein the
filaments are present in
the fibrous structure in two or more different layers of filaments based on
their orientation in
each layer.
The fibrous structures of the present invention unexpectedly exhibit an
average Tensile
Ratio (MD Tensile/CD Tensile) of 2 or less and/or less than 1.7 and/or less
than 1.5 and/or less
than 1.3 and/or less than 1.1 and/or greater than 0.7 and/or greater than 0.9
as measured
according to the Dry Tensile Strength Test Method described herein. In one
example, the fibrous
structures of the present invention exhibit an average Tensile Ratio of from
about 0.9 to about 1.1
as measured according to the Dry Tensile Strength Test Method described
herein.
Table 1 below shows examples of Tensile Ratios for fibrous structures of the
present
invention and comparative fibrous structures.
Sample Filaments Solid Layers of Tensile Ratio
(Y/N) Additives Filaments of (Average)
(Y/N) Different
Orientation
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Invention Y ¨ starch Y Y 1.66
Sample 1
Invention Y ¨ starch Y Y 1.51
Sample 2
Invention Y- starch Y y 1.45
Sample 3
Invention Y- starch Y y 2
Sample 4
Invention Y- starch Y y 1.69
Sample 5
Invention Y ¨ starch Y Y 1.34
Sample 6
Invention Y - starch Y Y 1.21
Sample 7
Invention Y-starch Y Y 1.61
Sample 8
Invention Y-starch Y Y 1.77
Sample 9
Prior Art 1 Y ¨ starch Y N 3
Prior Art 2 Y ¨ starch Y N 3.01
Prior Art 3 Y - starch Y N 2.4
Prior Art 4 Y ¨ starch Y N 2.6
Prior Art 5 Y ¨ starch Y N 2.52
Prior Art 6 Y ¨ starch Y N 3.09
Prior Art 7 Y ¨ starch Y N 2.73
Chamiin N Y N 1.08
Ultra Soft
Chamiin N Y N 0.96
Ultra Soft
Table 1
The fibrous structure of the present invention may comprise a surface
softening agent.
The surface softening agent may be applied to a surface of the fibrous
structure. The softening
agent may comprise a silicone and/or a quaternary ammonium compound.
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The fibrous structure of the present invention may comprise embossments such
that the
fibrous structure is embossed.
In one example, the fibrous structure comprises a nonwoven substrate, which
has a
plurality of solid additives present on both of the nonwoven substrate's
opposite surfaces that are
positioned between the nonwoven substrate surfaces and one or more scrims that
are bonded to
each of the nonwoven substrate surfaces. The solid additives may be different
or the same and
may be present at different levels or at same levels and may be uniformly
distributed on the
opposite surfaces of the nonwoven substrate. The scrim may be different or the
same and may be
present at different levels or at same levels and be bonded to opposite
surfaces of the nonwoven
substrate at one or more bond sites.
In another example, the fibrous structure of the present invention may
comprise one ply
within a multi-ply sanitary tissue product.
In another example, a multi-ply sanitary tissue product comprising two or more
plies of
the fibrous structure according to the present invention is provided. In one
example, two or more
plies of the fibrous structure according to the present invention are combined
to form a multi-ply
sanitary tissue product. The two or more plies may be combined such that the
solid additives are
adjacent to at least one outer surface and/or each of the outer surfaces of
the multi-ply sanitary
tissue product.
Methods for Making Fibrous Structure
Figs. 7 and 8 illustrate one example of a method for making a fibrous
structure of the
present invention. As shown in Figs. 7 and 8, the method 34 comprises the
steps of:
a. providing first filaments 36 from a first source 38 of filaments, which
form a first
layer 40 of filaments;
b. providing second filaments 42 from a second source 44 of filaments, which
form a
second layer 46 of filaments;
c. providing third filaments 48 from a third source 50 of filaments, which
form a third
layer 52 of filaments;
d. providing solid additives 16 from a source 54 of solid additives;
e. providing fourth filaments 56 from a fourth source 58 of filaments, which
form a
fourth layer 60 of filaments; and
f. collecting the first, second, third, and fourth filaments 36, 42, 48, 56
and the solid
additives 16 to form a fibrous structure 10, wherein the first source 38 of
filaments is oriented at
a first angle a to the machine direction of the fibrous structure 10, the
second source 44 of
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filaments is oriented at a second angle p to the machine direction different
from the first angle a, the
third source 50 is oriented at a third angle 6 to the machine direction
different from the first angle a
and the second angle p, and wherein the fourth source 58 is oriented at a
fourth angle E to the
machine direction different from the second angle p and third angle 6.
The first, second, and third layers 40, 46, 52 of filaments are collected on a
collection device
62, which may be a belt or fabric. The collection device 62 may be a patterned
belt that imparts a
pattern, such as a non-random, repeating pattern to the fibrous structure 10
during the fibrous
structure making process. The first, second, and third layers 40, 46, 52 of
filaments are collected (for
example one on top of the other) on the collection device 62 to form a multi-
layer nonwoven
substrate 26 upon which the solid additives 16 are deposited. The fourth layer
60 of filaments may
then be deposited onto the solid additives 16 to form a scrim 28.
The first angle a and the fourth angle may be the same angle, for example 90
to the
machine direction.
The second angle p and the third angle 6 may be the same angle, just positive
and negative of
one another. For example the second angle p may be -40 to the machine
direction and the third
angle 6 may be +40 to the machine direction.
In one example, at least one of the first, second, and third angles a, p, 5 is
less than 90 to the
machine direction. In another example, the first angle a and/or fourth angle E
is about 90 to the
machine direction. In still another example, the second angle p and/or third
angle 6 is from about
10 to about 80 and/or from about 30 to about 60 to the machine
direction and/or about 40
to the machine direction.
In one example, the first, second, and third layers 40, 46, 52 of filaments
may be formed into
a nonwoven substrate 26 prior to being utilized in the process for making a
fibrous structure
described above. In this case, the nonwoven substrate 26 would likely be in a
parent roll that could
be unwound into the fibrous structure making process and the solid additives
16 could be deposited
directly onto a surface 32 of the nonwoven substrate 26.
In one example, the step of providing a plurality of solid additives 16 onto
the nonwoven
substrate 26 may comprise airlaying the solid additives 16 using an airlaying
former. A non-limiting
example of a suitable airlaying former is available from Dan-Web of Aarhus,
Denmark.
In one example, the step of providing fourth filaments 56 such that the
filaments contact the
solid additives 16 comprises the step of depositing the fourth filaments 56
such that at least a portion
(in one example all or substantially all) of the solid additives 16 are
contacted by the fourth filaments
56 thus positioning the solid additives 16 between the fourth layer 60 of
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filaments and the nonwoven substrate 26. Once the fourth layer 60 of filaments
is in place, the
fibrous structure 10 may be subjected to a bonding step that bonds the fourth
layer 60 of
filaments (in this case, the scrim 28) to the nonwoven substrate 26. This step
of bonding may
comprise a thermal bonding operation. The thermal bonding operation may
comprise passing the
fibrous structure 10 through a nip formed by thermal bonding rolls 64, 66. At
least one of the
thermal bonding rolls 64, 66 may comprise a pattern that is translated into
the bond sites 30
formed in the fibrous structure 10.
In addition to being subjected to a bonding operation, the fibrous structure
may also be
subjected to other post-processing operations such as embossing, tuft-
generating, gear rolling,
which includes passing the fibrous structure through a nip formed between two
engaged gear
rolls, moisture-imparting operations, free-fiber end generating, and surface
treating to form a
finished fibrous structure. In one example, the fibrous structure is subjected
to gear rolling by
passing the fibrous structure through a nip formed by at least a pair of gear
rolls. In one example,
the fibrous structure is subjected to gear rolling such that free-fiber ends
are created in the fibrous
structure. The gear rolling may occur before or after two or more fibrous
structures are
combined to form a multi-ply sanitary tissue product. If it occurs after, then
the multi-ply
sanitary tissue product is passed through the nip formed by at least a pair of
gear rolls.
The method for making a fibrous structure of the present invention may be
close coupled
(where the fibrous structure is convolutedly wound into a roll prior to
proceeding to a converting
operation) or directly coupled (where the fibrous structure is not
convolutedly wound into a roll
prior to proceeding to a converting operation) with a converting operation to
emboss, print,
deform, surface treat, or other post-forming operation known to those in the
art. For purposes of
the present invention, direct coupling means that the fibrous structure can
proceed directly into a
converting operation rather than, for example, being convolutedly wound into a
roll and then
unwound to proceed through a converting operation.
In one example, one or more plies of the fibrous structure according to the
present
invention may be combined with another ply of fibrous structure, which may
also be a fibrous
structure according to the present invention, to form a multi-ply sanitary
tissue product that
exhibits a Tensile Ratio of 2 or less and/or less than 1.7 and/or less than
1.5 and/or less than 1.3
and/or less than 1.1 and/or greater than 0.7 and/or greater than 0.9 as
measured according to the
Dry Tensile Strength Test Method described herein. In one example, the multi-
ply sanitary tissue
product may be formed by combining two or more plies of fibrous structure
according to the
present invention. In another example, two or more plies of fibrous structure
according to the
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present invention may be combined to form a multi-ply sanitary tissue product
such that the solid
additives present in the fibrous structure plies are adjacent to each of the
outer surfaces of the
multi-ply sanitary tissue product.
The process of the present invention may include preparing individual rolls of
fibrous
structure and/or sanitary tissue product comprising such fibrous structure(s)
that are suitable for
consumer use.
In one example, the sources of filaments comprise meltblow dies that produce
filaments
from a polymer melt composition according to the present invention. In one
example, as shown
in Fig. 9 the meltblow die 68 may comprise at least one filament-forming hole
70, and/or 2 or
more and/or 3 or more rows of filament-forming holes 70 from which filaments
are spun. At
least one row of the filament-forming holes 70 contains 2 or more and/or 3 or
more and/or 10 or
more filament-forming holes 70. In addition to the filament-forming holes 70,
the meltblow die
68 comprises fluid-releasing holes 72, such as gas-releasing holes, in one
example air-releasing
holes, that provide attenuation to the filaments formed from the filament-
forming holes 70. One
or more fluid-releasing holes 72 may be associated with a filament-forming
hole 70 such that the
fluid exiting the fluid-releasing hole 72 is parallel or substantially
parallel (rather than angled like
a knife-edge die) to an exterior surface of a filament exiting the filament-
forming hole 70. In one
example, the fluid exiting the fluid-releasing hole 72 contacts the exterior
surface of a filament
formed from a filament-forming hole 70 at an angle of less than 30 and/or
less than 20 and/or
less than 10 and/or less than 5 and/or about 0 . One or more fluid releasing
holes 72 may be
arranged around a filament-forming hole 70. In one example, one or more fluid-
releasing holes
72 are associated with a single filament-forming hole 70 such that the fluid
exiting the one or
more fluid releasing holes 72 contacts the exterior surface of a single
filament formed from the
single filament-forming hole 70. In one example, the fluid-releasing hole 72
permits a fluid, such
as a gas, for example air, to contact the exterior surface of a filament
formed from a filament-
forming hole 70 rather than contacting an inner surface of a filament, such as
what happens when
a hollow filament is formed.
Synthesis of Polymer Melt Composition
A polymer melt composition of the present invention may be prepared using a
screw
extruder, such as a vented twin screw extruder.
A ban-el 74 of an APV Baker (Peterborough, England) 40:1, 48 mm twin screw
extruder
is schematically illustrated in Fig. 10A. The barrel 74 is separated into
eight zones, identified as
zones 1-8. The ban-el 74 encloses the extrusion screw and mixing elements,
schematically shown
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in Fig. 10B, and serves as a containment vessel during the extrusion process.
A solid feed port
76 is disposed in zone 1 and a liquid feed port 78 is disposed in zone 1. A
vent 80 is included in
zone 7 for cooling and decreasing the liquid, such as water, content of the
mixture prior to exiting
the extruder. An optional vent stuffer, commercially available from APV Baker,
can be
5 employed to prevent the polymer melt composition from exiting through the
vent 80. The flow
of the polymer melt composition through the ban-el 74 is from zone 1 exiting
the ban-el 74 at
zone 8.
A screw and mixing element configuration for the twin screw extruder is
schematically
illustrated in Fig 10B. The twin screw extruder comprises a plurality of twin
lead screws
10 (TLS) (designated A and B) and paddles (designated C) and reverse twin
lead screws
(RTLS) (designated D) installed in series as illustrated in Table 2 below.
Total Element
Length Length Type
Zone Ratio Element Pitch Ratio
1 1.5 TLS 1 1.5 A
1 3.0 TLS 1 1.5 A
1 4.5 TLS 1 1.5 A
2 6.0 TLS 1 1.5 A
2 7.5 TLS 1 1.5 A
2 9.0 TLS 1 1.5 A
3 10.5 TLS 1 1.5 A
3 12.0 TLS 1 1.5 A
3 13.0 TLS 1 1 A
3 14.0 TLS 1 1 A
4 15.0 TLS 1 1 A
4 16.0 TLS 1 1 A
4 16.3 PADDLE 0 0.25 C
4 16.5 PADDLE 0 0.25 C
4 18.0 TLS 1 1.5 A
4 19.5 TLS 1 1.5 A
5 21.0 TLS 1 1.5 A
5 22.5 TLS 1 1.5 A
5 24.0 TLS 1 1.5 A
5 25.0 TLS 1 1 A
6 25.3 TLS 1 0.25 A
6 26.3 TLS 1 1 A
6 27.3 TLS 1 1 A
6 28.3 TLS 0.5 1 B
6 29.3 TLS 0.5 1 B
6 29.8 RTLS 0.5 0.5 D
7 30.3 RTLS 0.5 0.5 D
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7 30.8 RTLS 0.5 0.5 D
7 32.3 TLS 1 1.5 A
7 33.8 TLS 1 1.5 A
7 34.8 TLS 1 1 A
8 35.8 TLS 1 1 A
8 36.8 TLS 0.5 1 B
8 37.8 TLS 0.5 1 B
8 38.8 TLS 0.5 1 B
8 40.3 TLS 0.5 1.5 B
Table 2
Screw elements (A ¨ B) are characterized by the number of continuous leads and
the
pitch of these leads. A lead is a flight (at a given helix angle) that wraps
the core of the screw
element. The number of leads indicates the number of flights wrapping the core
at any given
location along the length of the screw. Increasing the number of leads reduces
the volumetric
capacity of the screw and increases the pressure generating capability of the
screw.
The pitch of the screw is the distance needed for a flight to complete one
revolution of the
core. It is expressed as the number of screw element diameters per one
complete revolution of a
flight. Decreasing the pitch of the screw increases the pressure generated by
the screw and
decreases the volumetric capacity of the screw.
The length of a screw element is reported as the ratio of length of the
element divided by
the diameter of the element.
This example uses TLS and RTLS. Screw element type A is a TLS with a 1.0 pitch
and varying length ratios. Screw element type B is a TLS with a 0.5 pitch and
varying
length ratios.
Bilobal paddles, C, serving as mixing elements, are also included in series
with the
TLS and RTLS screw elements in order to enhance mixing. Paddle C has a length
ratio of
1/4. Various configurations of bilobal paddles and reversing screw elements D,
single and
twin lead screws threaded in the opposite directions, are used in order to
control flow and
corresponding mixing time. Screw element D is a RTLS with a 0.5 pitch and a
0.5 length
ratio.
In zone 1, the hydroxyl polymer is fed into the solid feed port at a rate of
230
grams/minute using a K-Tron (Pitman,NJ) loss-in-weight feeder. This hydroxyl
polymer is
combined inside the extruder (zone 1) with water, an external plasticizer,
added at the liquid feed
at a rate of 146 grams/minute using a Milton Roy (Ivyland, PA) diaphragm pump
(1.9 gallon per
hour pump head) to form a hydroxyl polymer/water slurry. This slurry is then
conveyed down
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the barrel of the extruder and cooked. Table 3 below describes the
temperature, pressure, and
corresponding function of each zone of the extruder.
Zone Temp .( F) Pressure Description of Screw Purpose
1 70 Low Feeding/Conveying Feeding and Mixing
2 70 Low Conveying Mixing and Conveying
3 70 Low Conveying Mixing and Conveying
4 130 Low Pressure/ Decreased Conveying and Heating
Conveying
300 Medium Pressure Generating Cooking at Pressure and
Temperature
6 250 High Reversing Cooking at Pressure and
Temperature
7 210 Low Conveying Cooling and Conveying
(with
venting)
8 210 Low Pressure Generating Conveying
Table 3
5 After the slurry exits the extruder, part of the melt processed hydroxyl
polymer is dumped and
another part (100g) is fed into a Zenith , type PEP II (Sanford NC) and pumped
into a SMX style static
mixer (Koch-Glitsch, Woodridge. Illinois). The static mixer is used to combine
additives such as
crosslinking agent, crosslinking facilitator, external plasticizer, such as
water, with the melt processed
hydroxyl polymer. The additives are pumped into the static mixer via PREP 100
HPLC pumps (Chrom
Tech, Apple Valley MN). These pumps provide high pressure, low volume addition
capability. The
polymer melt composition of the present invention is ready to be processed by
a polymer processing
operation.
Synthesis of Filaments
A non-limiting example of a process for producing filaments by polymer
processing a
polymer melt composition of the present invention. "Polymer processing" as
used herein means
any operation and/or process by which a filament comprising a processed
hydroxyl polymer is
formed from a polymer melt composition. Nonlimiting examples of polymer
processing
operations include extrusion, molding and/or fiber spinning. Extrusion and
molding (either
casting or blown), typically produce films, sheets and various profile
extrusions. Molding may
include injection molding, blown molding and/or compression molding. Fiber
spinning may
include spun bonding, melt blowing, rotary spinning, continuous filament
producing and/or tow
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fiber producing. A "processed hydroxyl polymer" as used herein means any
hydroxyl polymer
that has undergone a melt processing operation and a subsequent polymer
processing operation.
One example of a process for making a filament of the present invention from a
polymer
melt composition of the present invention follows.
A polymer melt composition is prepared according to the Synthesis of a Polymer
Melt
Composition described above. The polymer melt composition present in the twin
screw extruder
is pumped to a meltblow die using a suitable pump, such as a Zenith , type PEP
II, having a
capacity of 10 cubic centimeters per revolution (cc/rev), manufactured by
Parker Hannifin
Corporation, Zenith Pumps division, of Sanford, NC, USA. The hydroxyl
polymer's, such as
starch, flow to the meltblow die is controlled by adjusting the number of
revolutions per minute
(rpm) of the pump. Pipes connecting the extruder, the pump, the meltblow die,
and optionally a
mixer are electrically heated and thermostatically controlled to 65 C.
The meltblow die has several rows of circular extrusion nozzles spaced from
one another
at a pitch P of about 2.489 mm. The nozzles are arranged in a staggered grid
with a spacing
of about 2.489 mm within rows and a spacing of 2.159 mm between rows. The
nozzles 200
have individual inner diameters of about 0.254 mm and individual outside
diameters of about
0.813 mm. Each individual nozzle is encircled by an annular orifice formed in
an orifice plate
having a thickness of about 1.9 mm. A pattern of a plurality of the orifices
in the orifice plate
correspond to a pattern of extrusion nozzles in the meltblow die. Once the
orifice plate is
combined with the meltblow dies, the resulting area for airflow is about 36
percent. The
plate is fixed so that the filaments being extruded through the extrusion
nozzles are surrounded
and attenuated by generally cylindrical, humidified air streams supplied
through the orifices of
the orifice plate. The extrusion nozzles can extend to a distance from about
1.5 mm to about 4
mm, and more specifically from about 2 mm to about 3 mm, beyond the exterior
surface of the
orifice plate. A plurality of boundary-layer air orifices is formed by
plugging extrusion nozzles
of two outside rows on each side of the plurality of extrusion nozzles, as
viewed in plane, so that
each of the boundary-layer air orifices comprise an annular orifice described
herein above.
Additionally, every other row and every other column of the remaining
extrusion nozzles are
blocked, increasing the spacing between active extrusion nozzles
Attenuation air for attenuating the filaments being produced through the
extrusion nozzles
can be provided by heating compressed air by an electrical-resistance heater,
for example, a
heater manufactured by Chromalox, Division of Emerson Electric, of Pittsburgh,
PA, USA. An
appropriate quantity of steam at an absolute pressure of from about 240 to
about 420 kiloPascals
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(kPa), controlled by a globe valve, is added to saturate or nearly saturate
the heated air at the
conditions in the electrically heated, thermostatically controlled delivery
pipe. Condensate is
removed in an electrically heated, thermostatically controlled, separator. The
attenuating air has
an absolute pressure from about 130 kPa to about 310 kPa, measured in the
controlled delivery
pipe. The filaments being extruded from the extrusion nozzles have a moisture
content of from
about 20% and/or from about 25% to about 50% and/or to about 55% by weight.
The filaments
are dried by a drying air stream having a temperature from about 149 C to
about 315 C by an
electrical resistance heater supplied through drying nozzles and discharged at
an angle generally
perpendicular relative to the general orientation of the filaments being
extruded. The filaments
are dried from about 45% moisture content to about 15% moisture content (i.e.,
from a
consistency of about 55% to a consistency of about 85%) and are collected on a
collection
device, for example a moving foraminous belt.
The process parameters for making the filaments of the present invention are
set forth
below in Table 4.
Sam = le Units Value
Attenuation Air Flow Rate G/min 9000
Attenuation Air Temperature C 65
Attenuation Steam Flow Rate G/min 1800
Attenuation Steam Gage Pressure kPa 213
Attenuation Gage Pressure in Delivery kPa 14
Pipe
Attenuation Exit Temperature C 65
Solution Pump Speed Revs/min 12
Solution Flow G/min/hole 0.18
Drying Air Flow Rate g/min 17000
Air Duct Type Slots
Air Duct Dimensions mm 356 x 127
Velocity via Pitot-Static Tube M/s 65
Drying Air Temperature at Heater C 260
Dry Duct Position from Die mm 80
Drying Duct Angle Relative to Fibers degrees 0
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Sam = le Units Value
Drying Duct to Drying Duct Spacing mm 205
Die to Forming Box distance Mm 610
Forming Box Machine direction Length Mm 635
Forming Box Cross Direction Width Mm 380
Forming Box Flowrate g/min 41000
Table 4
A crosslinking system via a crosslinking agent, such as an imidazolidinone,
may crosslink
the hydroxyl polymers together to provide the filament with wet strength, with
or without being
subjected to a curing step. The crosslinking occurs such that the polymer melt
composition is
5 capable of being delivered through the extrusion nozzles and producing
filaments. In other
words, the crosslinking system does not prematurely crosslink the hydroxyl
polymers in the
polymer melt composition so that the extrusion nozzles are clogged and thus no
filaments can be
produced.
The filaments of the present invention do not include coatings and/or other
surface
10 treatments that are applied to a pre-existing form, such as a coating on
a fiber, film or foam.
However, in one embodiment of the present invention, a filament in accordance
with the present
invention may be coated and/or surface treated with the crosslinking system of
the present
invention.
In one example, the filaments produced via a polymer processing operation may
be cured
15 at a curing temperature of from about 110 C to about 215 C and/or from
about 110 C to about
200 C and/or from about 120 C to about 195 C and/or from about 130 C to about
185 C for a
time period of from about 0.01 and/or 1 and/or 5 and/or 15 seconds to about 60
minutes and/or
from about 20 seconds to about 45 minutes and/or from about 30 seconds to
about 30 minutes.
Alternative curing methods may include radiation methods such as UV, e-beam,
IR and other
20 temperature-raising methods.
Further, the filaments may also be cured at room temperature for days, either
after curing
at above room temperature or instead of curing at above room temperature.
The filaments of the present invention may include melt spun filaments and/or
spunbond
filaments, hollow filaments, shaped filaments, such as multi-lobal filaments
and multicomponent
25
filaments, especially bicomponent filaments. The multicomponent filaments,
especially
bicomponent filaments, may be in a side-by-side, sheath-core, segmented pie,
ribbon, islands-in-
the-sea configuration, or any combination thereof. The sheath may be
continuous or non-
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continuous around the core. The ratio of the weight of the sheath to the core
can be from about
5:95 to about 95:5. The filaments of the present invention may have different
geometries that
include round, elliptical, star shaped, rectangular, and other various
eccentricities.
Non-limiting Example of a Fibrous Structure
Example 1 - Fibrous Structure comprising Starch Filaments/Wood Pulp Fibers
A polymer melt composition comprising 7.5% Mowiol 10-98 commercially available
from Kuraray Co. (polyvinyl alcohol), 19% Ethylex 2035 commercially available
from Tate &
Lyle (ethoxylated starch), 19% CPI 050820-156 commercially available from Corn
Products
International (acid-thinned starch), 0.5% sulfosuccinate surfactant, such as
Aerosol AOT,
commercially available from Cytec Industries, 0.25% Hyperfloc NF221
commercially available
from Hychem, Inc. (polyacrylamide), 3.25% imidazolidinone crosslinking agent
(DHEU), and
0.5% ammonium chloride available from Aldrich (crosslinking facilitator) is
prepared. The melt
composition is cooked and extruded from a co-rotating twin screw extruder at
approx 50% solids
(50% H20) as described hereinabove.
The polymer melt composition is then pumped to a series of meltblow
spinnerettes that
are oriented at different angles to the machine direction to provide a
plurality of filaments from
each spinneret. The filaments from each spinnerette are attenuated with
saturated air stream to
form a layer of filaments that are collected one on top of the other to form a
nonwoven substrate.
The filaments of two or more of the layers of filaments exhibit different
orientations with respect
to the machine direction. The nonwoven substrate formed exhibits a basis
weight of from about
10 g/m2 to about 120 g/m2 as described hereinabove The filaments are dried by
convection
drying before being deposited on a belt to form the nonwoven substrate. These
meltblown
filaments are essentially continuous filaments.
If two or more spinnerettes are used to make a source of filaments, such as by
abutting
two or more spinnerettes together, then the spinnerette assembly may be made
by abutting a first
spinnerette with a second spinnerette such that the maximum distance between a
seam filament
forming nozzle opening in the first spinnerette and a seam filament forming
nozzle opening in
the second spinnerette is less than 9 mm and/or less than 7 mm and/or less
than 5 mm. In
addition to the abutting spinnerettes, an air plate is used in the spinnerette
assembly to cover the
seam formed by the abutting spinnerettes. The air plates' purpose to result in
air flow that avoids
causing the filaments produced by the spinnerette assemblies to collide with
neighboring
filaments which can result in roping of filaments and/or spitters from the
spinnerette assemblies.
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Wood pulp fibers, Southern Softwood Kraft (SS K) commercially available from
Georgia
Pacific available as roll comminution pulp, is disintegrated by a hammermill
and conveyed to an
airlaid former commercially available from Dan-Web via a blower. The wood pulp
fibers are
deposited onto a surface of the nonwoven substrate as solid additives.
Additional polymer melt composition is pumped to an additional meltblow
spinnerette
that is oriented at an angle to the machine direction of about 900 to produce
an additional layer of
filaments (which is a scrim), which is deposited on top of the wood pulp
fibers to position the
wood pulp fibers between the nonwoven substrate and the scrim to form a
fibrous structure. The
scrim typically exhibits a basis weight of from about 0.1 g/m2 to about 10
g/m2.
The fibrous structure is then subjected to a bonding process wherein bond
sites are
formed between the nonwoven substrate and the scrim such that the wood pulp
fibers are
positioned between the nonwoven substrate and the scrim to form a finished
fibrous structure.
The bonding process can be used to impart a pattern to the finished fibrous
structure and/or the
finished fibrous structure may be embossed. The fibrous structure can be
subjected to
humidification during the fibrous structure making process, for example prior
to being bonded
and/or embossed.
The finished fibrous structure is then convolutely wound about a core to
produce a
sanitary tissue product.
The fibrous structure, finished fibrous structure, and/or sanitary tissue
product
incorporating the finished fibrous structure exhibits a Tensile Ratio of 2 or
less.
Test Methods
Unless otherwise specified, all tests described herein including those
described under the
Definitions section and the following test methods are conducted on samples
that have been
conditioned in a conditioned room at a temperature of 23 C 1.0 C and a
relative humidity of
50% 2% for a minimum of 2 hours prior to the test. The samples tested are
"usable units."
"Usable units" as used herein means sheets, flats from roll stock, pre-
converted flats, and/or
single or multi-ply products. All tests are conducted under the same
environmental conditions
and in such conditioned room. Do not test samples that have defects such as
wrinkles, tears,
holes, and like. Samples conditioned as described herein are considered dry
samples (such as
"dry filaments") for testing purposes. All instruments are calibrated
according to manufacturer's
specifications.
Basis Weight Test Method
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Basis weight of a fibrous structure is measured on stacks of twelve usable
units using a
top loading analytical balance with a resolution of 0.001 g. The balance is
protected from air
drafts and other disturbances using a draft shield. A precision cutting die,
measuring 3.500 in
0.0035 in by 3.500 in 0.0035 in is used to prepare all samples.
With a precision cutting die, cut the samples into squares. Combine the cut
squares to
form a stack twelve samples thick. Measure the mass of the sample stack and
record the result
to the nearest 0.001 g.
The Basis Weight is calculated in lbs/3000 ft2 or g/m2 as follows:
Basis Weight = (Mass of stack) / [(Area of 1 square in stack) x (No.of squares
in stack)]
For example,
Basis Weight (lbs/3000 ft2) = [[Mass of stack (g) / 453.6 (g/lbs)] / 1112.25
(in2 ) / 144 (in2 /ft2 ) x
1211x 3000
or,
Basis Weight (g/m2) = Mass of stack (g) / 1179.032 (cm2) / 10,000 (cm2/m2) x
121
Report result to the nearest 0.1 lbs/3000 ft2 or 0.1 g/m2. Sample dimensions
can be changed or
varied using a similar precision cutter as mentioned above, so as at least 100
square inches of
sample area in stack.
Dry Tensile Strength Test Method
Tensile Strength is measured on a constant rate of extension tensile tester
with computer
interface (a suitable instrument is the EJA Vantage from the Thwing-Albert
Instrument Co. Wet
Berlin, NJ) using a load cell for which the forces measured are within 10% to
90% of the limit of
the load cell. Both the movable (upper) and stationary (lower) pneumatic jaws
are fitted with
smooth stainless steel faced grips, with a design suitable for testing 1 inch
wide sheet material
(Thwing-Albert item #733GC). An air pressure of about 60 psi is supplied to
the jaws.
Eight usable units of fibrous structures are divided into two stacks of four
usable units
each. The usable units in each stack are consistently oriented with respect to
machine direction
(MD) and cross direction (CD). One of the stacks is designated for testing in
the MD and the
other for CD. Using a one inch precision cutter (Thwing-Albert JDC-1-10, or
similar) take a CD
stack and cut one, 1.00 in 0.01 in wide by 3 - 4 in long stack of strips
(long dimension in CD).
In like fashion cut the remaining stack in the MD (strip's long dimension in
MD), to give a total
of 8 specimens, four CD and four MD strips. Each strip to be tested is one
usable unit thick, and
will be treated as a unitary specimen for testing.
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29
Program the tensile tester to perform an extension test, collecting force and
extension data
at an acquisition rate of 20 Hz as the crosshead raises at a rate of 2.00
in/min (5.08 can/min) until
the specimen breaks. The break sensitivity is set to 80%, i.e., the test is
terminated when the
measured force drops to 20% of the maximum peak force, after which the
crosshead is returned
to its original position.
Set the gage length to 1.00 inch. Zero the crosshead and load cell. Insert the
specimen
into the upper and lower open grips such that at least 0.5 inches of specimen
length is contained
each grip. Align specimen vertically within the upper and lower jaws, then
close the upper grip.
Verify specimen is aligned, then close lower grip. The specimen should be
fairly straight between
grips, with no more than 5.0 g of force on the load cell. Start the tensile
tester and data collection.
Repeat testing in like fashion for all four CD and four MD specimens.
Program the software to calculate the following from the constructed force (g)
verses
extension (in) curve:
Tensile Strength is the maximum peak force (g) divided by the specimen width
(1 in), and
reported as Win to the nearest 1 g/in.
The Tensile Strength (Win) is calculated for the four CD unitary specimens and
the four
MD unitary specimens. Calculate an average for each parameter separately for
the CD and MD
specimens.
Calculations:
Tensile Ratio = MD Tensile Strength (gun)! CD Tensile Strength (Win)
The dimensions and values disclosed herein are not to be understood as being
strictly
limited to the exact numerical values recited. Instead, unless otherwise
specified, each such
dimension is intended to mean both the recited value and a functionally
equivalent range
surrounding that value. For example, a dimension disclosed as "40 mm" is
intended to mean
"about 40 mm."
The citation of any document, including any cross referenced or related patent
or
application is not an admission that it is prior art with respect to any
invention disclosed or
claimed herein or that it alone, or in any combination with any other
reference or references,
teaches, suggests or discloses any such invention. Further, to the extent that
any meaning or
definition of a term in this document conflicts with any meaning or definition
of the same term in
a document cited herein, the meaning or definition assigned to that term in
this document shall
govern.
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While particular embodiments of the present invention have been illustrated
and
described, it would be obvious to those skilled in the art that various other
changes and
modifications can be made without departing from the invention described
herein.
