Note: Descriptions are shown in the official language in which they were submitted.
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HYDROXYL POLYMER FIBER STRUCTURES COMPRISING
AMMONIUM ALKYLSULFONATE SALTS AND METHODS FOR
MAKING SAME
FIELD OF THE INVENTION
The present invention relates to hydroxyl polymer polymeric structures, for
example
fibrous elements, such as filaments and/or fibers, and more particularly to
hydroxyl polymer
filaments that comprise an ammonium alkylsulfonate salt, fibrous structures
made therefrom, and
methods for making same.
BACKGROUND OF THE INVENTION
Hydroxyl polymer polymeric structures, such as fibrous elements, produced from
crosslinked hydroxyl polymers are known in the art. It is generally known to
crosslink hydroxyl
polymers together via a crosslinking agent, such as dihydroxyethyleneurea
(DHEU), to produce a
hydroxyl polymer polymeric structure. This crosslinking is facilitated by a
crosslinking
facilitator that prevents unacceptable crosslinking of the hydroxyl polymers
by the crosslinking
agent to occur. The challenge of managing the crosslinking of the hydroxyl
polymers is
especially problematic when spinning fibrous elements from a hydroxyl polymer
melt
composition, for example an aqueous hydroxyl polymer melt composition.
Ammonium salts, such as ammonium chloride, ammonium sulfate, and ammonium
citrate, are known to act as crosslinking facilitators. Such ammonium salts
are inactive
crosslinking catalysts in the hydroxyl polymer melt composition, but become
active acid
catalysts during heating of an embryonic polymeric structure produced from a
hydroxyl polymer
melt composition during a curing step. However, introduction of a kosmotropic
salt, such as
ammonium sulfate, and/or ammonium citrate, in the hydroxyl polymer melt
composition at the
level necessary for complete curing of the polymeric structure during the
curing step, can induce
salting out of the hydroxyl polymer, which results in weaker polymeric
structures formed
therefrom during the polymer processing step.
In addition to the negatives discussed above, the presence of ammonium sulfate
in the
hydroxyl polymer melt composition lowers the Critical Micelle Concentration of
any fast wetting
surfactants present in the hydroxyl polymer melt composition, which in turn
decreases the fast
wetting surfactants' wetting ability and thus their ability to increase drying
of the polymeric
structures. This ultimately results, for example, in increased diameters of
fibrous elements
formed from the hydroxyl polymer melt composition.
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Carboxylic ammonium salts, such as ammonium citrate, undesirably buffers the
embryonic polymeric structure's pH to above pH 5, which prevents complete
crosslinking of the
hydroxyl polymers to occur during the curing step.
Finally other salts, such as ammonium chloride, tend to also impart an
undesirable yellow
color to the polymeric structure during the high temperature of the curing
step. Additionally,
ammonium chloride causes corrosion of the processing equipment used to make
the polymeric
structure.
In light of the above, one problem associated with the known crosslinking
facilitators is
that they do not facilitate sufficient crosslinking of the hydroxyl polymers
during the production
of the hydroxyl polymer polymeric structures to provide the polymeric
structures with improved
physical properties, such as strength, and color properties compared to known
hydroxyl polymer
polymeric structures comprising known cros slinking facilitators.
Accordingly, there is a need for a crosslinking facilitator, especially a
crosslinking
facilitator for the crosslinking agent, dihydroxyethyleneurea (DHEU), for
crosslinking hydroxyl
polymers, especially melt processed hydroxyl polymers, and processes for
crosslinking such
hydroxyl polymers to form polymeric structures, wherein the processes overcome
the problems
described above; namely, the problem of crosslinking hydroxyl polymers within
a polymeric
structure during a curing operation without associated negatives discussed
above.
SUMMARY OF THE INVENTION
The present invention fulfills the need described above by providing a
polymeric
structure, for example a fibrous element, comprising an ammonium
alkylsulfonate salt, a fibrous
structure formed therefrom, and a method for making such a fibrous element
and/or fibrous
structure.
A solution to the problem identified above is to incorporate an ammonium
alkylsulfonate
salt into the aqueous polymer melt composition and perform the curing step
after the polymeric
structure, for example fibrous element, is formed such that salting out of the
hydroxyl polymers
does not occur in the polymer melt composition, that the hydroxyl polymer is
not crosslinked
prior to the polymer processing step, that the polymeric structure is
effectively crosslinked during
the curing step to provide the polymeric structure with acceptable physical
properties, such as
strength, both dry and wet, and that the cured polymeric structure has an
acceptable color (for
example not yellow).
In one example of the present invention, a fibrous element comprising a blend
comprising
a fibrous element-forming polymer, such as a crosslinked hydroxyl polymer, and
an ammonium
alkylsulfonate salt and/or acid, is provided.
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In another example of the present invention, a fibrous structure comprising a
plurality of
fibrous elements of the present invention, is provided.
In still another example of the present invention, an aqueous polymer melt
composition
comprising a fibrous element-forming polymer, such as a hydroxyl polymer, and
a crosslinking
system comprising a crosslinking agent and an ammonium alkylsulfonate salt, is
provided.
In yet another example of the present invention, a polymeric structure, such
as a fibrous
element, derived from an aqueous polymer melt composition of the present
invention, is
provided.
In still yet another example of the present invention, a method for making a
fibrous
element of the present invention comprising the steps of:
a. providing an aqueous polymer melt composition comprising a fibrous element-
forming polymer, such as a hydroxyl polymer, and a crosslinking system
comprising a
crosslinking agent and an ammonium alkylsulfonate salt; and
b. polymer processing the aqueous polymer melt composition such that one or
more
fibrous elements are formed, is provided.
In even still yet another example of the present invention, a method for
making a
polymeric structure, for example a fibrous element, of the present invention
comprising the steps
of:
a. providing an aqueous polymer melt composition comprising a fibrous element-
forming polymer, such as a hydroxyl polymer, and a crosslinking system
comprising a
cros slinking agent and an ammonium alkylsulfonate salt; and
b. polymer processing the aqueous polymer melt composition such that one or
more
polymeric structures, for example fibrous elements, are formed, is provided.
In even yet another example of the present invention, a method for making a
fibrous
structure of the present invention comprising the steps of:
a. providing an aqueous polymer melt composition comprising a fibrous element-
forming polymer, such as a hydroxyl polymer, and a crosslinking system
comprising a
crosslinking agent and an ammonium alkylsulfonate salt; and
b. polymer processing the aqueous polymer melt composition such that a
plurality of
fibrous elements are formed;
c. collecting the fibrous elements on a collection device such that a fibrous
structure is
formed, is provided.
In even still another example of the present invention, a single- or multi-ply
sanitary
tissue product comprising a fibrous structure of the present invention, is
provided.
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Accordingly, the present invention relates to polymeric structures, such as
fibrous
elements, comprising ammonium alkylsulfonate salts and/or acids, fibrous
structures made from
such fibrous elements, and processes for making same.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a schematic representation of one example of a method for making a
fibrous
structure according to the present invention;
Fig. 2 is a schematic representation of one example of a portion of fibrous
structure
making process according to the present invention;
Fig. 3 is a schematic representation of an example of a meltblow die in
accordance with
the present invention;
Fig. 4A is a schematic representation of an example of a barrel of a twin
screw extruder in
accordance with the present invention;
Fig. 4B is a schematic representation of an example of a screw and mixing
element
configuration for the twin screw extruder of Fig. 4A;
Fig. 5A is a schematic representation of an example of a barrel of a twin
screw extruder
suitable for use in the present invention;
Fig. 5B is a schematic representation of an example of a screw and mixing
element
configuration suitable for use in the barrel of Fig. 5A;
Fig. 6 is a schematic representation of an example of a process for
synthesizing a fibrous
element in accordance with the present invention;
Fig. 7 is a schematic representation of a partial side view of the process
shown in Fig. 6
showing an example of an attenuation zone;
Fig. 8 is a schematic plan view taken along lines 8-8 of Fig. 7 and showing
one possible
arrangement of a plurality of extrusion nozzles arranged to provide fibrous
elements of the
present invention; and
Fig. 9 is a view similar to that of Fig. 8 and showing one possible
arrangement of
orifices for providing a boundary air around the attenuation zone shown in
Fig. 7.
DETAILED DESCRIPTION OF THE INVENTION
Definitions
"Polymeric structure" as used herein means any physical structure formed as a
result of
processing a polymer melt composition in accordance with the present
invention. Non-limiting
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examples of polymeric structures in accordance with the present invention
include fibrous
elements, such as filaments and/or fibers, films and/or foams.
The fibrous structures of the present invention may be homogeneous or may be
layered.
If layered, the fibrous structures may comprise at least two and/or at least
three and/or at least
5 four and/or at least five and/or at least six and/or at least seven
and/or at least 8 and/or at least 9
and/or at least 10 to about 25 and/or to about 20 and/or to about 18 and/or to
about 16 layers.
In one example, the fibrous structures of the present invention are
disposable. For
example, the fibrous structures of the present invention are non-textile
fibrous structures. In
another example, the fibrous structures of the present invention are
flushable, such as toilet
tissue.
"Fibrous element" 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. A
fibrous element may be a filament or a fiber. In one example, the fibrous
element is a single
fibrous element rather than a yarn comprising a plurality of fibrous elements.
The fibrous elements of the present invention may be spun from polymer melt
compositions, for example aqueous polymer melt compositions, via suitable
spinning operations,
such as meltblowing and/or spunbonding and/or they may be obtained from
natural sources such
as vegetative sources, for example trees.
The fibrous elements of the present invention may be monocomponent and/or
multicomponent. For example, the fibrous elements may comprise bicomponent
fibers and/or
filaments. The bicomponent fibers and/or filaments may be in any form, such as
side-by-side,
core and sheath, islands-in-the-sea and the like.
"Filament" as used herein means an elongate particulate as described above
that exhibits
a length of greater than or equal to 5.08 cm (2 in.) and/or greater than or
equal to 7.62 cm (3 in.)
and/or greater than or equal to 10.16 cm (4 in.) and/or greater than or equal
to 15.24 cm (6 in.).
Filaments are typically considered continuous or substantially continuous in
nature.
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 polyvinyl alcohol, thermoplastic
polymer, 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.
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"Fiber" as used herein means an elongate particulate as described above that
exhibits a
length of less than 5.08 cm (2 in.) and/or less than 3.81 cm (1.5 in.) and/or
less than 2.54 cm (1
in.).
Fibers are typically considered discontinuous in nature. Non-limiting examples
of fibers
include pulp fibers, such as wood pulp fibers, 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 (2 in.) thus producing fibers.
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 as trichomes. 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 fibrous structures 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.
"Fibrous structure" as used herein means a structure that comprises one or
more fibrous
elements. In one example, a fibrous structure according to the present
invention means an
association of fibrous elements that together form a structure capable of
performing a function.
In another example of the present invention, a fibrous structure comprises a
plurality of inter-
entangled fibrous elements, for example filaments.
"Sanitary tissue product" as used herein means a soft, relatively low density
fibrous
structure useful as a wiping implement for post-urinary and post-bowel
movement cleaning
(toilet tissue), for otorhinolaryngological discharges (facial tissue), multi-
functional absorbent
and cleaning uses (absorbent towels) and wipes, such as wet and dry wipes. The
sanitary tissue
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product may be convolutedly wound upon itself about a core or without a core
to form a sanitary
tissue product roll or may be in the form of discrete sheets.
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 and/or fibrous structures of the present
invention may exhibit
a basis weight between about 1 g/m2 to about 5000 g/m2 and/or from about 10
g/m2 to about 500
g/m2 and/or from about 10 g/m2 to about 300 g/m2 and/or from 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 as determined by the Basis Weight Test Method
described herein. In
addition, the sanitary tissue product of the present invention may exhibit a
basis weight between
about 40 g/m2 to about 120 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 g/m2 to 100 g/m2 as determined
by the Basis
Weight Test Method described herein.
The sanitary tissue products of the present invention may exhibit a total dry
tensile strength
of greater than about 59 g/cm and/or from about 78 g/cm to about 394 g/cm
and/or from about 98
g/cm to about 335 g/cm. In addition, the sanitary tissue product of the
present invention may
exhibit a total dry tensile strength of greater than about 196 g/cm and/or
from about 196 g/cm to
about 394 g/cm and/or from about 216 g/cm to about 335 g/cm and/or from about
236 g/cm to
about 315 g/cm. In one example, the sanitary tissue product exhibits a total
dry tensile strength
of less than about 394 g/cm and/or less than about 335 g/cm as measured
according to the Dry
Tensile Strength Test Method described herein.
The sanitary tissue products of the present invention may exhibit an initial
total wet tensile
strength of less than about 78 g/cm and/or less than about 59 g/cm and/or less
than about 39 g/cm
and/or less than about 29 g/cm and/or less than about 23 g/cm as measured
according to the
Initial Total Wet Tensile Test Method described herein.
The sanitary tissue products of the present invention may exhibit a density of
less than
0.60 g/cm3 and/or less than 0.30 g/cm3 and/or less than 0.20 g/cm3 and/or less
than 0.15 g/cm3
and/or less than 0.10 g/cm3 and/or less than 0.07 g/cm3 and/or less than 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
0.15 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
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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 material that is used to overlay solid
additives within the
fibrous structures of the present invention such that the solid additives are
positioned between the
scrim and a layer of the fibrous structure. In one example, the scrim covers
the solid additives
such that they are positioned between the scrim and a surface of a nonwoven
substrate of the
fibrous structure. In another example, the scrim is a minor component (for
example less than
25% of the basis weight) relative to the nonwoven substrate of the basis
weight of the fibrous
structure.
"Hydroxyl polymer" as used herein includes any hydroxyl-containing polymer
that can be
incorporated into a polymeric structure such as a fibrous element of the
present invention. 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 material, such as
a fibrous
element as a whole and/or a polymer, such as a crosslinked polymer, within a
fibrous element,
that the fibrous element 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 material, such as a
fibrous
element as a whole and/or a polymer within a fibrous element, that the fibrous
element and/or
polymer exhibits a melting point and/or softening point at a certain
temperature, which allows it
to flow under pressure.
"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.
"Fast wetting surfactant" as used herein means a surfactant that exhibits a
Critical Micelle
Concentration of greater 0.15% by weight and/or at least 0.25% and/or at least
0.50% and/or at
least 0.75% and/or at least 1.0% and/or at least 1.25% and/or at least 1.4%
and/or less than 10.0%
and/or less than 7.0% and/or less than 4.0% and/or less than 3.0% and/or less
than 2.0% by
weight.
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"Aqueous polymer melt composition" as used herein means a composition
comprising
water and a melt processed polymer, such as a melt processed fibrous element-
forming polymer,
for example a melt processed hydroxyl polymer.
"Melt processed fibrous element-forming polymer" as used herein means any
polymer,
which by influence of elevated temperatures, pressure and/or external
plasticizers may be
softened to such a degree that it can be brought into a flowable state, and in
this condition may be
shaped as desired.
"Melt processed hydroxyl polymer" as used herein means any polymer that
contains
greater than 10% and/or greater than 20% and/or greater than 25% by weight
hydroxyl groups
and that has been melt processed, with or without the aid of an external
plasticizer. More
generally, melt processed hydroxyl polymers include polymers, which by the
influence of
elevated temperatures, pressure and/or external plasticizers may be softened
to such a degree that
they can be brought into a flowable state, and in this condition may be shaped
as desired.
"Blend" as used herein means that two or more materials, such as a fibrous
element-
forming polymer, for example a hydroxyl polymer, and an ammonium
alkylsulfonate salt and/or
acid are in contact with each other, such as mixed together homogeneously or
non-
homogeneously, within a polymeric structure, such as a fibrous element. In
other words, a
polymeric structure, such as a fibrous element, formed from one material, but
having an exterior
coating of another material is not a blend of materials for purposes of the
present invention.
However, a fibrous element formed from two different materials is a blend of
materials for
purposes of the present invention even if the fibrous element further
comprises an exterior
coating of a material.
"Associate," "Associated," "Association," and/or "Associating" as used herein
with
respect to fibrous elements means combining, either in direct contact or in
indirect contact,
fibrous elements such that a fibrous structure is formed. In one example, the
associated fibrous
elements may be bonded together for example by adhesives and/or thermal bonds.
In another
example, the fibrous elements 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 as generally
described in Colloids
and Surfaces A. Physico Chemical & Engineering Aspects, Vol. 162, 2000, pg.
107-121 and
detailed in the Weight Average Molecular Weight Test Method described herein.
"Average Diameter" as used herein, with respect to a fibrous element, is
measured
according to the Average Diameter Test Method described herein. In one
example, a fibrous
element of the present invention exhibits an average diameter of less than 25
um and/or less than
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20 um and/or less than 15 um and/or less than 10 um and/or less than 6 um
and/or greater than 1
um and/or greater than 3 um.
"Basis Weight" as used herein is the weight per unit area of a sample reported
in lbs/3000
ft2 or g/m2 as determined by the Basis Weight Test Method described herein.
5 "Machine Direction" or "MD" as used herein means the direction parallel
to the flow of
the fibrous structure through a fibrous structure making machine and/or
sanitary tissue product
manufacturing equipment. Typically, the MD is substantially perpendicular to
any perforations
present in the fibrous structure
"Cross Machine Direction" or "CD" as used herein means the direction
perpendicular to
10 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.
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.
Fibrous Elements
The fibrous elements of the present invention comprise a fibrous element-
forming
polymer, such as a hydroxyl polymer, for example a crosslinked hydroxyl
polymer, and an
ammonium alkylsulfonate salt and/or acid. In one example, the fibrous elements
may comprise
two or more fibrous element-forming polymers, such as two or more hydroxyl
polymers. In
another example, the fibrous elements may comprise two or more ammonium
alkylsulfonate salts
and/or acids. In another example, the fibrous elements may comprise two or
more ammonium
salts at least one of which is an ammonium alkylsulfonate salt, such as
ammonium
methanesulfonate, and one of which is not ammonium alkylsulfonate salt, such
as ammonium
toluenesulfonate. In another example, the fibrous element may comprise two or
more fibrous
element-forming polymers, such as two or more hydroxyl polymers, at least one
of which is
starch and/or a starch derivative and one of which is a non-starch and/or non-
starch derivative,
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such as polyvinyl alcohol. In still another example, the fibrous elements of
the present invention
may comprise two or more fibrous element-forming polymers at least one of
which is a hydroxyl
polymer and at least one of which is a non-hydroxyl polymer.
In yet another example, the fibrous elements of the present invention may
comprise two
or more non-hydroxyl polymers. In one example, at least one of the non-
hydroxyl polymers
exhibits a weight average molecular weight of greater than 1,400,000 g/mol
and/or is present in
the fibrous elements at a concentration greater than its entanglement
concentration (Ce) and/or
exhibits a polydispersity of greater than 1.32.
In one example, the fibrous element comprises a filament. In another example,
the
fibrous element comprises a fiber, such as a filament that has been cut into
fibers.
Cros slinking System
A crosslinking system comprising a crosslinking agent capable of crosslinking
a fibrous
element-forming polymer, for example a hydroxyl polymer, and a crosslinking
facilitator are
present in the aqueous polymer melt composition of the present invention. The
crosslinking
results in a crosslinked polysaccharide.
The crosslinking agent and/or crosslinking facilitator may be added to the
aqueous
polymer melt composition, for example before polymer processing of the aqueous
polymer melt
composition. The crosslinking agent and/or crosslinking facilitator are
present in the fibrous
elements produced from the aqueous polymer melt compositions of the present
invention.
Upon crosslinking the hydroxyl polymer during the curing step, the
crosslinking agent
becomes an integral part of the filament as a result of crosslinking the
hydroxyl polymer as
shown in the following schematic representation:
Hydroxyl polymer ¨ Crosslinking agent ¨ Hydroxyl polymer
"Crosslinking facilitator" as used herein means any material that is capable
of activating a
crosslinking agent thereby transforming the crosslinking agent from its
unactivated state to its
activated state. In other words, when a crosslinking agent is in its
unactivated state, the hydroxyl
polymer present in the aqueous polymer melt composition does not undergo
unacceptable
crosslinking. Unacceptable crosslinking causes the shear viscosity and n value
to fall outside the
ranges specified which are determined according to the Shear Viscosity of a
Polymer Melt
Composition Measurement Test Method. In the case of imidazolidinone
crosslinkers, the pH and
the temperature of the aqueous polymer melt composition should be in the
desired ranges, from
pH of from about 2 to about 11 and/or from about 2.5 to about 9 and/or from
about 3 to about 8.5 and/or
from about 3.2 to about 8 and/or from about 3.2 to about 7.5 as measured by
the Polymer Melt
Composition pH Test Method described herein; unacceptable crosslinking occurs
outside these
ranges.
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The crosslinking facilitator of the present invention comprises one or more
ammonium
alkylsulfonate salts and/or acids and/or derivatives of the alkylsulfonate
salts and/or acids that
may exist after the transformation/activation of the crosslinking agent. For
example, a
crosslinking facilitator salt being chemically changed to its acid form and
vice versa.
Non-limiting examples of suitable ammonium alkylsulfonate salt crosslinking
facilitators
of the present invention include ammonium salts of methanesulfonic acid,
ethanesulfonic acid,
propanesulfonic acid, isopropylsulfonic acid, butanesulfonic acid,
isobutylsulfonic acid, sec-
butylsulfonic acids.
In one example, the polymeric structures, for example fibrous elements,
comprise one or
more crosslinking facilitators, at least one of which is an ammonium
alkylsulfonate salt and/or
acid and/or a derivative thereof. In one example, the crosslinking facilitator
may comprises an
ammonium salt of trifluoromethanesulfonic acid.
The ammonium alkylsulfonate salt of the present invention may have the
following
formula (I):
RS03- NH4+
I
where R is a Ci-C18 alkyl and/or a C1-C12 alkyl and/or a C1-C8 alkyl group.
Non-limiting examples of suitable alkyl groups are selected from the group
consisting of:
methyl, ethyl, propyl, butyl, octyl, decyl, and dodecyl.
The ammonium alkylsulfonate may be present in the polymeric structure at a
level of
from about 0.1 to about 5% and/or from about 0.3 to about 4% and/or from about
0.5 to about 3%
by weight of the polymeric structure, for example by weight of the hydroxyl
polymer filament.
In addition, metal salts, such as magnesium and zinc salts, can be used in
combination
with the ammonium alkylsulfonate salts and/or acids thereof, as additional
crosslinking
facilitators.
The crosslinking facilitator may include derivatives of the material that may
exist after
the transformation/activation of the crosslinking agent. For example, a
crosslinking facilitator
salt being chemically changed to its acid form and vice versa.
Non-limiting examples of additional crosslinking facilitators include acids
having a pKa
of between 2 and 6 or salts thereof. The crosslinking facilitators may be
Bronsted Acids and/or
salts thereof, such as ammonium salts thereof.
In addition, metal salts, such as magnesium and zinc salts, can be used alone
or in
combination with Bronsted Acids and/or salts thereof, as crosslinking
facilitators.
Non-limiting examples of suitable crosslinking facilitators include benzoic
acid, citric
acid, formic acid, glycolic acid, lactic acid, maleic acid, phthalic acid,
phosphoric acid,
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hypophosphoric acid, succinic acid, and mixtures thereof and/or their salts,
such as their
ammonium salts, such as ammonium glycolate, ammonium citrate, ammonium
chloride,
ammonium sulfate
Additional non-limiting examples of suitable crosslinking facilitators include
glyoxal
bisulfite salts, primary amine salts, such as hydroxyethyl ammonium salts,
hydroxypropyl
ammonium salt, secondary amine salts, ammonium toluene sulfonate, ammonium
benzene
sulfonate, ammonium xylene sulfonate, magnesium chloride, and zinc chloride.
The crosslinking facilitator may be present from about 0.1% to 5% by weight of
the
polymer melt composition
In one example, the crosslinking facilitators, polymeric structures, and
aqueous polymer
melt compositions are void or essentially void (less than 0.025% by weight)
of kosmotropic salts, such as ammonium sulfate and ammonium citrate. The
inclusion 0.025%
and greater of a kosmotropic salt, such as ammonium sulfate, even when an
ammonium
alkysulfonate salt and/or acid is present, may negatively impact the
properties, such as strength
(for example TEA), of the polymeric structures. However, the inclusion of an
amount of an
ammonium salt, such as ammonium chloride, for example an amount that does not
produce
negative corrosive effects in the processing and spinning equipment, in
combination with an
ammonium alkylsulfonate salt may be desired.
Fibrous Element-Forming Polymers
The aqueous polymer melt compositions of the present invention and/or polymer
structures, for example fibrous elements, such as filaments and/or fibers, of
the present invention
that associate to form fibrous structures of the present invention contain at
least one fibrous
element-forming polymer, such as a hydroxyl polymer, and may contain other
types of polymers
such as non-hydroxyl polymers that exhibit weight average molecular weights of
greater than
500,000 g/mol, and mixtures thereof as determined by the Weight Average
Molecular Weight
Test Method described herein.
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 comprises a
polysaccharide.
In another example, a hydroxyl polymer of the present invention comprises 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 100,000 g/mol and/or
greater than 1,000,000
g/mol and/or greater than 3,000,000 g/mol and/or greater than 3,000,000 g/mol
to about
40,000,000 g/mol as determined by the Weight Average Molecular Weight Test
Method
described herein. Higher and lower molecular weight hydroxyl polymers may be
used in
combination with hydroxyl polymers having a certain desired weight average
molecular weight.
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, starch copolymers, chitosan,
chitosan derivatives, chitosan
copolymers, cellulose, cellulose derivatives, cellulose copolymers,
hemicellulose, hemicellulose
derivatives, hemicelluloses copolymers, 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 as
determined by the Weight Average Molecular Weight Test Method described
herein.
The polysaccharides of the present invention may comprise non-cellulose and/or
non-
cellulose derivative and/or non-cellulose copolymer hydroxyl polymers. Non-
limiting example
of such non-cellulose polysaccharides may be selected from the group
consisting of: starches,
starch derivatives, starch copolymers, chitosan, chitosan derivatives,
chitosan copolymers,
hemicellulose, hemicellulose derivatives, hemicelluloses copolymers, and
mixtures thereof.
In one example, the hydroxyl polymer comprises starch, a starch derivative
and/or a
starch copolymer. In another example, the hydroxyl polymer comprises starch
and/or a starch
derivative. In yet another example, the hydroxyl polymer comprises starch. In
one example, the
hydroxyl polymer comprises ethoxylated starch. In another example, the
hydroxyl polymer
comprises acid-thinned starch. In still another example, the hydroxyl polymer
comprises Dent
corn starch.
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As is known, a natural starch can be modified chemically or enzymatically, as
well
known in the art. For example, the natural starch can be acid-thinned, hydroxy-
ethylated,
hydroxy-propylated, ethersuccinylated or oxidized. In one example, the starch
comprises a high
amylopectin natural starch (a starch that contains greater than 75% and/or
greater than 90%
5 and/or greater than 98% and/or about 99% amylopectin). Such high
amylopectin natural starches
may be derived from agricultural sources, which offer the advantages of being
abundant in
supply, easily replenishable and relatively inexpensive. Chemical
modifications of starch
typically include acid or alkaline-catalyzed hydrolysis and chain scission
(oxidative and/or
enzymatic) to reduce molecular weight and molecular weight distribution.
Suitable compounds
10 for chemical modification of starch include organic acids such as citric
acid, acetic acid, glycolic
acid, and adipic acid; inorganic acids such as hydrochloric acid, sulfuric
acid, nitric acid,
phosphoric acid, boric acid, and partial salts of polybasic acids, e.g.,
KH2PO4, NaHSO4; group Ia
or Ha metal hydroxides such as sodium hydroxide, and potassium hydroxide;
ammonia;
oxidizing agents such as hydrogen peroxide, benzoyl peroxide, ammonium
persulfate, potassium
15 permanganate, hypochloric salts, and the like; and mixtures thereof.
"Modified starch" is a starch that has been modified chemically or
enzymatically. The
modified starch is contrasted with a native starch, which is a starch that has
not been modified,
chemically or otherwise, in any way.
Chemical modifications may also include derivatization of starch by reaction
of its
hydroxyl groups with alkylene oxides, and other ether-, ester-, urethane-,
carbamate-, or
isocyanate- forming substances. Hydroxyalkyl, ethersuccinylated, acetyl, or
carbamate starches
or mixtures thereof can be used as chemically modified starches. The degree of
substitution of
the chemically modified starch is from 0.001 to 3.0, and more specifically
from 0.003 to 0.2.
Biological modifications of starch may include bacterial digestion of the
carbohydrate bonds, or
enzymatic hydrolysis using enzymes such as amylase, amylopectase, and the
like.
Generally, all kinds of natural starches can be used in the present invention.
Suitable
naturally occurring starches can include, but are not limited to: corn starch,
potato starch, sweet
potato starch, wheat starch, sago palm starch, tapioca starch, rice starch,
soybean starch, arrow
root starch, amioca starch, bracken starch, lotus starch, waxy maize starch,
and high amylose
corn starch. Naturally occurring starches, particularly corn starch and wheat
starch, can be
particularly beneficial due to their low cost and availability.
In one example, to generate rheological properties suitable for high-speed
fibrous element
spinning processes, the molecular weight of the natural, unmodified starch may
be reduced. The
optimum molecular weight is dependent on the type of starch used. For example,
a starch with a
low level of amylose component, such as a waxy maize starch, disperses rather
easily in an
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aqueous solution with the application of heat and does not retrograde or
recrystallize
significantly. With these properties, a waxy maize starch can be used at a
weight average
molecular weight, for example in the range of 500,000 g/mol to 40,000,000
g/mol as determined
by the Weight Average Molecular Weight Test Method described herein. Modified
starches such
as hydroxy-ethylated Dent corn starch, which contains about 25% amylose, or
oxidized Dent
corn starch tend to retrograde more than waxy maize starch but less than acid
thinned starch.
This retrogradation, or recrystallization, acts as a physical cross-linking to
effectively raise the
weight average molecular weight of the starch in aqueous solution. Therefore,
an appropriate
weight average molecular weight for a typical commercially available
hydroxyethylated Dent
corn starch with 2 wt. % hydroxyethylation or oxidized Dent corn starch is
from about 200,000
g/mol to about 10,000,000 g/mol. For ethoxylated starches with higher degrees
of ethoxylation,
for example a hydroxyethylated Dent corn starch with 5 wt% hydroxyethylation,
weight average
molecular weights of up to 40,000,000 g/mol as determined by the Weight
Average Molecular
Weight Test Method described herein may be suitable for the present invention.
For acid thinned
Dent corn starch, which tends to retrograde more than oxidized Dent corn
starch, the appropriate
weight average molecular weight is from about 100,000 g/mol to about
15,000,000 g/mol as
determined by the Weight Average Molecular Weight Test Method described
herein.
The weight average molecular weight of starch may also be reduced to a
desirable range
for the present invention by physical/mechanical degradation (e.g., via the
thermomechanical
energy input of the processing equipment).
The natural starch can be hydrolyzed in the presence of an acid catalyst to
reduce the
molecular weight and molecular weight distribution of the composition. The
acid catalyst can be
selected from the group consisting of hydrochloric acid, sulfuric acid,
phosphoric acid, citric
acid, ammonium chloride and any combination thereof. Also, a chain scission
agent may be
incorporated into a spinnable starch composition such that the chain scission
reaction takes place
substantially concurrently with the blending of the starch with other
components. Non-limiting
examples of oxidative chain scission agents suitable for use herein include
ammonium persulfate,
hydrogen peroxide, hypochlorite salts, potassium permanganate, and mixtures
thereof.
Typically, the chain scission agent is added in an amount effective to reduce
the weight average
molecular weight of the starch to the desirable range. It is found that
compositions having
modified starches in the suitable weight average molecular weight ranges have
suitable shear
viscosities, and thus improve processability of the composition. The improved
processability is
evident in less interruptions of the process (e.g., reduced breakage, shots,
defects, hang-ups) and
better surface appearance and strength properties of the final product, such
as fibers of the
present invention.
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In one example, the fibrous element of the present invention is void of
thermoplastic,
water-insoluble polymers.
Other Polymers
The aqueous polymer melt compositions of the present invention and/or
polymeric
structures such as fibrous elements of the present invention may comprise, in
addition to the
fibrous element-forming polymer, other polymers, such as non-hydroxyl
polymers.
Non-limiting examples of suitable non-hydroxyl polymers that may be included
in the
fibrous elements of the present invention include non-hydroxyl polymers that
exhibit a weight
average molecular weight of greater than 500,000 g/mol and/or greater than
750,000 g/mol
and/or greater than 1,000,000 g/mol and/or greater than 1,250,000 g/mol and/or
at greater than
1,400,000 g/mol and/or at least 1,450,000 g/mol and/or at least 1,500,000
g/mol and/or less than
10,000,000 g/mol and/or less than 5,000,000 g/mol and/or less than 2,500,00
g/mol and/or less
than 2,000,000 g/mol and/or less than 1,750,000 g/mol as determined by the
Weight Average
Molecular Weight Test Method described herein.
In one example, the non-hydroxyl polymer exhibits a polydispersity of greater
than 1.10
and/or at least 1.20 and/or at least 1.30 and/or at least 1.32 and/or at least
1.40 and/or at least
1.45.
In another example, the non-hydroxyl polymer exhibits a concentration greater
than its
entanglement concentration (Ce) and/or a concentration greater than 1.2 times
its entanglement
concentration (Ce) and/or a concentration greater than 1.5 times its
entanglement concentration
(Ce) and/or a concentration greater than twice its entanglement concentration
(Ce) and/or a
concentration greater than 3 times its entanglement concentration (Ce).
Non-limiting examples of suitable non-hydroxyl polymers include polyacrylamide
and
derivatives such as carboxyl modified polyacrylamide polymers and copolymers
including
polyacrylic, poly(hydroxyethyl acrylic), polymethacrylic acid and their
partial esters; vinyl
polymers including polyvinylalcohol, polyvinylpyrrolidone, and the like;
polyamides;
polyalkylene oxides such as polyethylene oxide and mixtures thereof.
Copolymers or graft
copolymers made from mixtures of monomers selected from the aforementioned
polymers are
also suitable herein. Non-limiting examples of commercially available
polyacrylamides include
nonionic polyacrylamides such as N300 from Kemira or Hyperfioc NF221, NF301,
and NF241
from Hychem, Inc.
Typically, the non-hydroxyl polymers are present in an amount of from about
0.01% to
about 10% and/or from about 0.05% to about 5% and/or from about 0.075% to
about 2.5%
and/or from about 0.1% to about 1%, by weight of the aqueous polymer melt
composition,
polymeric structure, fibrous element and/or fibrous structure.
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In yet another example, the non-hydroxyl polymer comprises a linear polymer.
In
another example, the non-hydroxyl polymer comprises a long chain branched
polymer. In still
another example, the non-hydroxyl polymer is compatible with the hydroxyl
polymer at a
concentration greater than the non-hydroxyl polymer's entanglement
concentration Ce.
Non-limiting examples of suitable non-hydroxyl polymers are selected from the
group
consisting of: polyacrylamide and its derivatives; polyacrylic acid,
polymethacrylic acid and
their esters; polyethyleneimine; copolymers made from mixtures of the
aforementioned
polymers; and mixtures thereof. In one example, the non-hyrdoxyl polymer
comprises
polyacrylamide. In one example, the fibrous elements comprises two or more non-
hydroxyl
polymers, such as two or more polyacrylamides, such at two or more different
weight average
molecular weight polyacrylamides.
Fast Wetting Surfactants
Any suitable fast wetting surfactant may be present in the aqueous hydroxyl
polymer melt
composition and/or polymeric structure of the present invention. Non-limiting
examples of
suitable fast wetting surfactants include surfactants that exhibit a twin-
tailed general structure, for
example a surfactant that exhibits a structure IIA or JIB as follows.
SO3M OSO3M
RR
R R
Structure HA or Structure JIB
wherein R is independently selected from substituted or unsubstituted, linear
or branched
aliphatic groups and mixtures thereof. In one example, R is independently
selected from
substituted or unsubstituted, linear or branched C4-C7 aliphatic chains and
mixtures thereof. In
another example, R is independently selected from substituted or
unsubstituted, linear or
branched C4-C7 alkyls and mixtures thereof. In another example, R is
independently selected
from substituted or unsubstituted, linear or branched C5-C6 alkyls and
mixtures thereof. In still
another example, R is independently selected from substituted or
unsubstituted, linear or
branched C6 alkyls and mixtures thereof. In even another example, R is an
unsubsituted,
branched C6 alkyl having the following structure III.
CH3 CH3
I
.CH
H3C
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Structure III
In another example, R is independently selected from substituted or
unsubstituted, linear
or branched C5 alkyls and mixtures thereof. In yet another example, R is
independently selected
from unsubstituted, linear C5 alkyls and mixtures thereof. The C5 alkyl may
comprise a mixture
of unsubstituted linear C5 alkyls, for example C5 n-pentyl, and/or 1-methyl
branched C5 alkyls as
shown in the following structure IV.
CH3
H3C
Structure IV
In even another example, R comprises a mixture of C4-C7 alkyls and/or a
mixture of C5-C6
alkyls.
The fast wetting surfactants may be present in the polymer melt compositions,
fibrous
elements, and/or fibrous structures of the present invention, alone or in
combination with other
non-fast wetting surfactants.
In one example, the fast wetting surfactants of the present invention may be
used
individually or in mixtures with each other or in a mixture with one or more
non-fast wetting
surfactants, for example a C8 sulfosuccinate surfactant where R is the
following structure V
CH3
H3C
C
H2
Structure V
In one example a fast wetting surfactant comprises a sulfosuccinate surfactant
having the
following structure VI.
MO3S
0
_______________________________________________ 0
OR RO
Structure VI
wherein R is independently selected from substituted or unsubstituted, linear
or branched
aliphatic groups and mixtures thereof. In one example, R is independently
selected from
substituted or unsubstituted, linear or branched C4-C7 aliphatic chains and
mixtures thereof. In
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another example, R is independently selected from substituted or
unsubstituted, linear or
branched C4-C7 alkyls and mixtures thereof. In another example, R is
independently selected
from substituted or unsubstituted, linear or branched C5-C6 alkyls and
mixtures thereof. In still
another example, R is independently selected from substituted or
unsubstituted, linear or
5
branched C6 alkyls and mixtures thereof. In even another example, R is an
unsubsituted,
branched C6 alkyl having the following structure III.
CH3 C H3
I
CH
H3C
Structure III
10 Non-
limiting examples of fast wetting surfactants according to the present
invention
include sulfosuccinate surfactants, for example a sulfosuccinate surfactant
that has structure III as
its R groups (Aerosol MA-80), a sulfosuccinate surfactant that has C4
isobutyl as its R groups
(Aerosol IB), and a sulfosuccinate surfactant that has a mixture of C5 n-
pentyl and structure IV
as its R groups (Aerosol AY), all commercially available from Cytec.
15
Additional non-limiting examples of fast wetting surfactants according to the
present
invention include alcohol sulfates derived from branched alcohols such as
Isalchem and Lial
alcohols (from Sasol) ie. Dacpon 27 23 AS and Guerbet alcohols from Lucky
Chemical. Still
another example of a fast wetting surfactant includes paraffin sulfonates such
as Hostapur 5A530
from Clariant.
20
Typically, the fast wetting surfactants are present in an amount of from about
0.01% to
about 5% and/or from about 0.5% to about 2.5% and/or from about 1% to about 2%
and/or from
about 1% to about 1.5%, by weight of the aqueous polymer melt composition,
polymeric
structure, fibrous element and/or fibrous structure.
In one example, the fast wetting surfactants of the present invention exhibit
a Minimum
Surface Tension in Distilled Water of less than 34.0 and/or less than 33.0
and/or less than 32.0
and/or less than 31.0 and/or less than 30.0 and/or less than 29.0 and/or less
than 28.0 and/or less
than 27.0 and/or less than 26.75 and/or less than 26.5 and/or less than 26.2
and/or less than 25.0
mN/m and/or to greater than 0 and/or greater than 1.0 mN/m.
In still another example, the fast wetting surfactants of the present
invention exhibit a
CMC of greater than 0.15% and/or at least 0.25% and/or at least 0.50% and/or
at least 0.75%
and/or at least 1.0% and/or at least 1.25% and/or at least 1.4% and/or less
than 10.0% and/or less
than 7.0% and/or less than 4.0% and/or less than 3.0% and/or less than 2.0% by
weight and a
Minimum Surface Tension in Distilled Water of less than 34.0 and/or less than
33.0 and/or less
CA 02909453 2015-10-13
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than 32.0 and/or less than 31.0 and/or less than 30.0 and/or less than 29.0
and/or less than 28.0
and/or less than 27.0 and/or less than 26.75 and/or less than 26.5 and/or less
than 26.2 and/or less
than 25.0 mN/m and/or to greater than 0 and/or greater than 1.0 mN/m. In even
another example,
the fast wetting surfactants of the present invention exhibit a CMC of at
least 1.0% and/or at least
1.25% and/or at least 1.4% and/or less than 4.0% and/or less than 3.0% and/or
less than 2.0% by
weight and a Minimum Surface Tension in Distilled Water of less than 34.0
and/or less than 33.0
and/or less than 32.0 and/or less than 31.0 and/or less than 30.0 and/or less
than 29.0 and/or less
than 28.0 and/or less than 27.0 and/or less than 26.75 and/or less than 26.5
and/or less than 26.2
and/or less than 25.0 mN/m and/or to greater than 0 and/or greater than 1.0
mN/m. CMC and
Minimum Surface Tension in Distilled Water values of surfactants can be
measured by any
suitable methods known in the art, for example those methods described in
Principles of Colloid
and Surface Chemistry, p370-375.
It is also possible to use ammonium salts of the fast wetting surfactants with
structure IIA
above where M = NH4, ethanolammonium, hydroxypropy lammon ium, N,N"-
dimethylethanolammonium, 2-ammonium-2-methylpropanol, Mg24, Ca2', Zn24, or
Al3+ as the
crosslinking facilitator of the present invention. Similarly, the ammonium
salts of structures IIA
and JIB where M = the aforementioned ammonium species are also acceptable as
crosslinking
facilitators of the present invention. The aforementioned ammonium salts of
structure V where R
= methyl, ethyl, and propyl are also acceptable as crosslinking facilitators
of the present
invention. The aforementioned ammonium salts of alpha-olefin sulfonates and
paraffin
sulfonates produced via sulfochlorination or sulfoxidation are also acceptable
as crosslinking
facilitators of the present invention.
Additional non-limiting examples of ammonium salts of fast wetting surfactants
according to the present invention include ammonium salts of alcohol sulfates
derived from
branched alcohols such as Isalchem and Lial alcohols (from Sasol) ie. Dacpon
27 23 AS and
Guerbet alcohols from Lucky Chemical. Still another example of a fast wetting
surfactant
includes ammonium salts of paraffin sulfonates such as Hostapur SAS30 from
Clariant.
Hueing Agents
The aqueous hydroxyl polymer melt compositions and/or polymeric structures,
for
example fibrous elements, of the present invention may comprise one or more
hueing agents. In
one example, the total level of one or more hueing agents present within one
or more, for
example a plurality, of the fibrous elements of a fibrous structure of the
present invention is less
than 1% and/or less than 0.5% and/or less than 0.05% and/or less than 0.005%
and/or greater
than 0.00001% and/or greater than 0.0001% and/or greater than 0.001% by weight
of the dry
fibrous element and/or dry fibrous structure formed by fibrous elements
containing the hueing
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agents. In one example, the total level of one or more hueing agents present
within one or more,
for example a plurality, of the fibrous elements of a fibrous structure of the
present invention is
from about 0.0001% to about 0.5% and/or from about 0.0005% to about 0.05%
and/or from
about 0.001% to about 0.05% and/or from about 0.001% to about 0.005% by weight
of the dry
fibrous element and/or dry fibrous structure formed by fibrous elements
containing the hueing
agents.
Hueing agents can be used either alone or in combination. Hueing agents may be
selected
from any known chemical class of dye, including but not limited to acridine,
anthraquinone
(including polycyclic quinones), azine, azo (e.g., monoazo, disazo, trisazo,
tetrakisazo, polyazo),
including premetallized azo, benzodifurane and benzodifuranone, carotenoid,
coumarin, cyanine,
diazahemicyanine, diphenylmethane, formazan, hemicyanine, indigoids, methane,
naphthalimides, naphthoquinone, nitro and nitroso, oxazine, phthalocyanine,
pyrazoles, stilbene,
styryl, triarylmethane, triphenylmethane, xanthenes and mixtures thereof.
Non-limiting examples of hueing agents include dyes, dye-clay conjugates, and
organic
and inorganic pigments and mixtures thereof. Suitable dyes include small
molecule dyes and
polymeric dyes. Suitable small molecule dyes include small molecule dyes
selected from the
group consisting of dyes falling into the Colour Index (C.I.) classifications
of Direct, Basic,
Reactive or hydrolysed Reactive, Solvent or Disperse dyes for example that are
classified as
Blue, Violet, Red, Green or Black, and mixtures thereof. In another aspect,
suitable small
molecule dyes include small molecule dyes selected from the group consisting
of Colour Index
(Society of Dyers and Colourists, Bradford, UK) numbers Direct Violet dyes
such as 9, 35, 48,
51, 66, and 99, Direct Blue dyes such as 1, 71, 80 and 279, Acid Red dyes such
as 17, 73, 52, 88
and 150, Acid Violet dyes such as 15, 17, 24, 43, 49 and 50, Acid Blue dyes
such as 15, 17, 25,
29, 40, 45, 75, 80, 83, 90 and 113, Acid Black dyes such as 1, Basic Violet
dyes such as 1, 3, 4,
10 and 35, Basic Blue dyes such as 3, 16, 22, 47, 66, 75 and 159, Disperse or
Solvent dyes such
as those described in US 2008/034511 Al or US 8,268,016 B2, or dyes as
disclosed in US
7,208,459 B2, and mixtures thereof. In another aspect, suitable small molecule
dyes include
small molecule dyes selected from the group consisting of C.I. Acid Violet 17,
Direct Blue 71,
Direct Violet 51, Direct Blue 1, Acid Red 88, Acid Red 150, Acid Blue 29, Acid
Blue 113 or
mixtures thereof.
Suitable polymeric dyes include polymeric dyes selected from the group
consisting of
polymers containing covalently bound (sometimes referred to as conjugated)
chromogens, (dye-
polymer conjugates), for example polymers with chromogens co-polymerized into
the backbone
of the polymer and mixtures thereof. Polymeric dyes include those described in
W02011/98355,
US 2012/225803 Al, US 2012/090102 Al, US 7,686,892 B2, and W02010/142503.
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23
In another aspect, suitable polymeric dyes include polymeric dyes selected
from the
group consisting of hueing agents commercially available under the trade name
of Liquitint
(Milliken, Spartanburg, South Carolina, USA), dye-polymer conjugates formed
from at least one
reactive dye and a polymer selected from the group consisting of polymers
comprising a moiety
selected from the group consisting of a hydroxyl moiety, a primary amine
moiety, a secondary
amine moiety, a thiol moiety and mixtures thereof. In still another aspect,
suitable polymeric
dyes include polymeric dyes selected from the group consisting of Liquitint
Violet CT,
carboxymethyl cellulose (CMC) covalently bound to a reactive blue, reactive
violet or reactive
red dye such as CMC conjugated with C.I. Reactive Blue 19, sold by Megazyme,
Wicklow,
Ireland under the product name AZO-CM-CELLULOSE, product code S-ACMC,
alkoxylated
triphenyl-methane polymeric colourants, alkoxylated thiophene polymeric
colourants, and
mixtures thereof.
Non-limiting examples of suitable hueing agents include the whitening agents
found in
WO 08/87497 Al, W02011/011799 and US 2012129752 Al. In addition, other non-
limiting
examples of suitable hueing agents include dyes disclosed in these references,
including those
selected from Examples 1-42 in Table 5 of W02011/011799. Other dyes disclosed
in US
8,138,222 and US 7,090,890 B2 are also suitable hueing agents. Further
examples of suitable
whitening agents include whitening agents described in U52008034511 Al
(Unilever), for
example "Violet 13."
Suitable dye clay conjugates include dye clay conjugates selected from the
group
comprising at least one cationic/basic dye and a smectite clay, and mixtures
thereof. In another
aspect, suitable dye clay conjugates include dye clay conjugates selected from
the group
consisting of one cationic/basic dye selected from the group consisting of
C.I. Basic Yellow 1
through 108, C.I. Basic Orange 1 through 69, C.I. Basic Red 1 through 118,
C.I. Basic Violet 1
through 51, C.I. Basic Blue 1 through 164, C.I. Basic Green 1 through 14, C.I.
Basic Brown 1
through 23, CI Basic Black 1 through 11, and a clay selected from the group
consisting of
Montmorillonite clay, Hectorite clay, Saponite clay and mixtures thereof. In
still another aspect,
suitable dye clay conjugates include dye clay conjugates selected from the
group consisting of:
Montmorillonite Basic Blue B7 C.I. 42595 conjugate, Montmorillonite Basic Blue
B9 C.I. 52015
conjugate, Montmorillonite Basic Violet V3 C.I. 42555 conjugate,
Montmorillonite Basic Green
G1 C.I. 42040 conjugate, Montmorillonite Basic Red R1 C.I. 45160 conjugate,
Montmorillonite
C.I. Basic Black 2 conjugate, Hectorite Basic Blue B7 C.I. 42595 conjugate,
Hectorite Basic
Blue B9 C.I. 52015 conjugate, Hectorite Basic Violet V3 C.I. 42555 conjugate,
Hectorite Basic
Green G1 C.I. 42040 conjugate, Hectorite Basic Red R1 C.I. 45160 conjugate,
Hectorite C.I.
Basic Black 2 conjugate, Saponite Basic Blue B7 C.I. 42595 conjugate, Saponite
Basic Blue B9
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C.I. 52015 conjugate, Saponite Basic Violet V3 C.I. 42555 conjugate, Saponite
Basic Green G1
C.I. 42040 conjugate, Saponite Basic Red R1 C.I. 45160 conjugate, Saponite
C.I. Basic Black 2
conjugate and mixtures thereof.
Suitable pigments include pigments selected from the group consisting of
flavanthrone,
indanthrone, chlorinated indanthrone containing from 1 to 4 chlorine atoms,
pyranthrone,
dichloropyranthrone, monobromodichloropyranthrone,
dibromodichloropyranthrone,
tetrabromopyranthrone, perylene-3,4,9,10-tetracarboxylic acid diimide, wherein
the imide groups
may be unsubstituted or substituted by C1-C3 -alkyl or a phenyl or
heterocyclic radical, and
wherein the phenyl and heterocyclic radicals may additionally carry
substituents which do not
confer solubility in water, anthrapyrimidinecarboxylic acid amides, viol
anthrone,
isoviolanthrone, dioxazine pigments, copper phthalocyanine which may contain
up to 2 chlorine
atoms per molecule, polychloro-copper phthalocyanine or polybromochloro-copper
phthalocyanine containing up to 14 bromine atoms per molecule and mixtures
thereof.
In another example, suitable pigments include pigments selected from the group
consisting of Ultramarine Blue (C.I. Pigment Blue 29), Ultramarine Violet
(C.I. Pigment Violet
15) and mixtures thereof.
Solid Additives
The polymeric structures, for example fibrous structures and/or sanitary
tissue products of
the present invention may further comprise one or more solid additives. "Solid
additive" as used
herein means an additive that is capable of being applied to a surface of a
fibrous structure or
nonwoven substrate component of the fibrous structure in a solid form. In
other words, the solid
additive of the present invention can be delivered directly to a surface of a
nonwoven substrate
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 nonwoven substrate. 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, a solid additive comprises a naturally occurring
fiber, such as a pulp
fiber.
Non-limiting examples of suitable solid additives include hydrophilic
inorganic particles,
hydrophilic organic particles, hydrophobic inorganic particles, hydrophobic
organic particles,
naturally occurring fibers, non-naturally occurring particles and non-
naturally occurring fibers.
In one example, the naturally occurring fibers may comprise wood pulp fibers,
trichomes,
seed hairs, protein fibers, such as silk and/or wool, and/or cotton linters.
In one example the
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solid additive comprises chemically treated pulp fibers. Non-limiting examples
of chemically
treated pulp fibers are commercially available from Georgia-Pacific
Corporation
In another example, the non-naturally occurring fibers may comprise polyolefin
fibers,
such as polypropylene fibers, and/or polyamide fibers.
5 In
another example, the hydrophilic inorganic particles are selected from the
group
consisting of: clay, calcium carbonate, titanium dioxide, talc, aluminum
silicate, calcium silicate,
alumina trihydrate, activated carbon, calcium sulfate, glass microspheres,
diatomaceous earth and
mixtures thereof.
In one example, hydrophilic organic particles of the present invention may
include
10
hydrophobic particles the surfaces of which have been treated by a hydrophilic
material. Non-
limiting examples of such hydrophilic organic particles include polyesters,
such as polyethylene
terephthalate particles that have been surface treated with a soil release
polymer and/or
surfactant. Another example is a polyolefin particle that has been surface
treated with a
surfactant.
15 In
another example, the hydrophilic organic particles may comprise superabsorbent
particles and/or superabsorbent materials such as hydrogels, hydrocolloidal
materials and
mixtures thereof. In one example, the hydrophilic organic particle comprises
polyacrylate. Other
Non-limiting examples of suitable hydrophilic organic particles are known in
the art.
In another example, the hydrophilic organic particles may comprise high
molecular
20
weight starch particles (high amylose-containing starch particles), such as
Hylon 7 available from
National Starch and Chemical Company.
In another example, the hydrophilic organic particles may comprise cellulose
particles.
In another example, the hydrophilic organic particles may comprise compressed
cellulose
sponge particles.
25 In
one example of a solid additive in accordance with the present invention, the
solid
additive exhibits a surface tension of greater then about 30 and/or greater
than about 35 and/or
greater than about 40 and/or greater than about 50 and/or greater than about
60 dynes/cm as
determined by ASTM D2578.
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.
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"Particle" as used herein means an object having 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 additive.
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%.
Scrim Material
The fibrous structure and/or sanitary tissue product may further comprise a
scrim
material. The scrim material may comprise any suitable material capable of
bonding to the
nonwoven substrate of the present invention. In one example, the scrim
material comprises a
material that can be thermally bonded to the nonwoven substrate of the present
invention. Non-
limiting examples of suitable scrim materials include filaments of the present
invention. In one
example, the scrim material comprises filaments that comprise hydroxyl
polymers. In another
example, the scrim material comprises starch filaments. In yet another
example, the scrim
material comprises filaments comprising a thermoplastic polymer. In still
another example, the
scrim material comprises a fibrous structure according to the present
invention wherein the
fibrous structure comprises filaments comprising hydroxyl polymers, such as
starch filaments,
and/or thermoplastic polymers. In another example, the scrim material may
comprise a film. In
another example, the scrim material may comprise a nonwoven substrate
according to the present
invention. In even another example, the scrim material may comprise a latex.
In one example, the scrim material may be the same composition as the nonwoven
substrate.
The scrim material may be present in the fibrous structures 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 as determined by the Basis Weight Test Method described herein.
METHODS OF THE PRESENT INVENTION
The methods of the present invention relate to producing filaments from
aqueous polymer
melt compositions comprising a fibrous element-forming polymer, such as a
hydroxyl polymer, a
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crosslinking agent, such as dihydroxyethyleneurea (DHEU), and a crosslinking
facilitator, such
as an ammonium alkylsulfonate salt.
Methods for Making Fibrous Structure
Figs. 1 and 2 illustrate one example of a method for making a fibrous
structure of the
present invention. As shown in Figs. 1 and 2, the method 10 comprises the
steps of:
a. providing first filaments 12 from a first source 14 of filaments, which
form a first
layer 16 of filaments;
b. providing second filaments 18 from a second source 20 of filaments, which
form a
second layer 22 of filaments;
c. providing third filaments 24 from a third source 26 of filaments, which
form a third
layer 28 of filaments;
d. providing solid additives 30 from a source 32 of solid additives;
e. providing fourth filaments 34 from a fourth source 36 of filaments, which
form a
fourth layer 38 of filaments; and
f. collecting the first, second, third, and fourth filaments 12, 18, 24, 34
and the solid
additives 30 to form a fibrous structure 40, wherein the first source 14 of
filaments is oriented at
a first angle a to the machine direction of the fibrous structure 40, the
second source 20 of
filaments is oriented at a second angle 13 to the machine direction different
from the first angle a,
the third source 26 is oriented at a third angle 8 to the machine direction
different from the first
angle a and the second angle 13, and wherein the fourth source 36 is oriented
at a fourth angle e to
the machine direction different from the second angle 13 and third angle 8.
The first, second, and third layers 16, 22, 28 of filaments are collected on a
collection
device 42, which may be a belt or fabric. The collection device 42 may be a
patterned belt that
imparts a pattern, such as a non-random, repeating pattern to the fibrous
structure 40 during the
fibrous structure making process. The first, second, and third layers 16, 22,
28 of filaments are
collected (for example one on top of the other) on the collection device 42 to
form a multi-layer
nonwoven substrate 44 upon which the solid additives 30 are deposited. The
fourth layer 38 of
filaments may then be deposited onto the solid additives 30 to form a scrim
46.
The first angle a and the fourth angle c may be the same angle, for example 90
to the
machine direction.
The second angle 13 and the third angle 8 may be the same angle, just positive
and
negative of one another. For example the second angle 13 may be -40 to the
machine direction
and the third angle 8 may be +40 to the machine direction.
In one example, at least one of the first, second, and third angles a, 13, 8
is less than 90 to
the machine direction. In another example, the first angle a and/or fourth
angle c is about 90 to
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the machine direction. In still another example, the second angle 13 and/or
third angle 8 is from
about 100 to about 80 and/or from about 30 to about 60 to the machine
direction and/or
about 400 to the machine direction.
In one example, the first, second, and third layers 16, 22, 28 of filaments
may be formed
into a nonwoven substrate 44 prior to being utilized in the process for making
a fibrous structure
described above. In this case, the nonwoven substrate 44 would likely be in a
parent roll that
could be unwound into the fibrous structure making process and the solid
additives 30 could be
deposited directly onto a surface of the nonwoven substrate 44.
In one example, the step of providing a plurality of solid additives 30 onto
the nonwoven
substrate 44 may comprise airlaying the solid additives 30 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 34 such that the
filaments contact
the solid additives 30 comprises the step of depositing the fourth filaments
34 such that at least a
portion (in one example all or substantially all) of the solid additives 30
are contacted by the
fourth filaments 34 thus positioning the solid additives 30 between the fourth
layer 38 of
filaments and the nonwoven substrate 44. Once the fourth layer 38 of filaments
is in place, the
fibrous structure 40 may be subjected to a bonding step that bonds the fourth
layer 38 of
filaments (in this case, the scrim 46) to the nonwoven substrate 44. This step
of bonding may
comprise a thermal bonding operation. The thermal bonding operation may
comprise passing the
fibrous structure 40 through a nip formed by thermal bonding rolls 48, 50. At
least one of the
thermal bonding rolls 48, 50 may comprise a pattern that is translated into
the bond sites 52
formed in the fibrous structure 40.
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
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29
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, for example with glue, 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 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 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 an aqueous polymer melt composition according to the present invention.
In one example,
as shown in Fig. 3 the meltblow die 54 may comprise at least one filament-
forming hole 56,
and/or 2 or more and/or 3 or more rows of filament-forming holes 56 from which
filaments are
spun. At least one row of the filament-forming holes 56 contains 2 or more
and/or 3 or more
and/or 10 or more filament-forming holes 56. In addition to the filament-
forming holes 56, the
meltblow die 54 comprises fluid-releasing holes 58, such as gas-releasing
holes, in one example
air-releasing holes, that provide attenuation to the filaments formed from the
filament-forming
holes 56. One or more fluid-releasing holes 58 may be associated with a
filament-forming hole
56 such that the fluid exiting the fluid-releasing hole 58 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 56. In one example, the fluid exiting the fluid-releasing hole 58
contacts the
exterior surface of a filament formed from a filament-forming hole 56 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 58 may be arranged around a filament-forming hole 56. In one
example, one or
more fluid-releasing holes 58 are associated with a single filament-forming
hole 56 such that the
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fluid exiting the one or more fluid releasing holes 58 contacts the exterior
surface of a single
filament formed from the single filament-forming hole 56. In one example, the
fluid-releasing
hole 58 permits a fluid, such as a gas, for example air, to contact the
exterior surface of a filament
formed from a filament-forming hole 56 rather than contacting an inner surface
of a filament,
5 such as what happens when a hollow filament is formed.
Aqueous Polymer Melt Composition
The aqueous polymer melt composition of the present invention from which the
polysaccharide filaments are produced comprises a melt processed fibrous
element-forming
polymer, such as a melt processed hydroxyl polymer, for example a melt
processed
10 polysaccharide, and a crosslinking system comprising a crosslinking
agent and a crosslinking
facilitator, such as an ammonium alkylsulfonate salt and/or acid thereof,
according to the present
invention.
The aqueous polymer melt compositions may already be formed or a melt
processing step
may need to be performed to convert a raw material fibrous element-forming
polymer, such as a
15 polysaccharide, into a melt processed fibrous element-forming polymer,
such as a melt processed
polysaccharide, thus producing the aqueous polymer melt composition. A peak
processing
temperature to bring the aqueous polymer melt composition to between 170 to
175 C should be
applied to the aqueous polymer melt composition. This can be accomplished by
heating through
the barrel heating of a twin screw extruder or using a shell in tube heat
exchanger. The aqueous
20 polymer melt composition should be held at 170 to 175 C for 1 to 2
minutes. If the aqueous
polymer melt composition is at a peak temperature between 170 and 175 C for
residence times
longer than 2 minutes unwanted side reactions may occur. Thus it is important
to very quickly
cool the aqueous polymer melt composition using a rapid quenching method, such
as flash
vaporization of the water phase. The crosslinking agent is added to the
aqueous polymer melt
25 composition after the cooling step. A suitable melt processing step
known in the art may be used
to convert the raw material fibrous element-forming polymer, for example the
polysaccharide,
into the melt processed fibrous element-forming polysaccharide. "Melt
processing" as used
herein means any operation and/or process by which a polymer is softened to
such a degree that
it can be brought into a flowable state.
30 The aqueous polymer melt compositions of the present invention may have
a shear
viscosity, as measured according to the Shear Viscosity of a Polymer Melt
Composition
Measurement Test Method described herein, of from about 0.5 Pascal=Seconds to
about 25
Pascal=Seconds and/or from about 2 Pascal=Seconds to about 20 Pascal=Seconds
and/or from
about 3 Pascal=Seconds to about 10 Pascal=Seconds, as measured at a shear rate
of 3,000 sec-1 and
at the processing temperature (50 C to 100 C). The aqueous polymer melt
compositions may
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have a thinning index n value as measured according to the Shear Viscosity of
a Polymer Melt
Composition Measurement Test Method described herein of from about 0.4 to
about 1.0 and/or
from about 0.5 to about 0.8.
The aqueous polymer melt compositions may have a temperature of from about 50
C to
about 100 C and/or from about 65 C to about 95 C and/or from about 70 C to
about 90 C when
spinning filaments from the aqueous polymer melt compositions.
In one example, the aqueous polymer melt composition of the present invention
may
comprise from about 30% and/or from about 40% and/or from about 45% and/or
from about 50%
to about 75% and/or to about 80% and/or to about 85% and/or to about 90%
and/or to about 95%
and/or to about 99.5% by weight of the aqueous polymer melt composition of a
fibrous element-
forming polymer, such as a polysaccharide. The fibrous element-forming
polymer, such as a
polysaccharide, may have a weight average molecular weight greater than
100,000 g/mol as
determined by the Weight Average Molecular Weight Test Method described herein
prior to any
cro s slinking .
A fast wetting surfactant may be present in the aqueous polymer melt
compositions and/or
may be added to the aqueous polymer melt composition before polymer processing
of the
aqueous polymer melt composition.
A non-hydroxyl polymer, such as polyacrylamide, may be present in the aqueous
polymer
melt composition and/or may be added to the aqueous polymer melt composition
before polymer
processing of the aqueous polymer melt composition.
A hueing agent may be present in the aqueous polymer melt compositions and/or
may be
added to the aqueous polymer melt composition before polymer processing the
aqueous polymer
melt composition. In one example, the fibrous structure comprises
polysaccharide filaments
comprising a hueing agent such that the fibrous structure exhibits a Whiteness
Index of greater
than 72 and/or greater than 75 and/or greater than 77 and/or greater than 80
as measured
according to the Whiteness Index Test Method described herein.
Non-limiting Example - Synthesis of an Aqueous Polymer Melt Composition
An aqueous polymer melt composition of the present invention may be prepared
using
screw extruders, such as a vented twin screw extruder.
A ban-el 60 of an APV Baker (Peterborough, England) 40:1, 58 mm diameter twin
screw
extruder is schematically illustrated in Fig. 4A. The barrel 60 is separated
into eight zones,
identified as zones 1-8. The barrel 60 encloses the extrusion screw and mixing
elements,
schematically shown in Fig. 4B, and serves as a containment vessel during the
extrusion process.
A solid feed port 62 is disposed in zone 1, a first liquid feed port 64 is
disposed in zone 2, a
second liquid feed port 66 is disposed in zone 3, a third liquid feed port 68
is disposed in zone 4,
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and a fourth liquid feed port 70 is disposed in zone 5. A vent 72 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 employed
to prevent the
polymer melt composition from exiting through the vent 72. The flow of the
aqueous polymer
melt composition through the barrel 60 is from zone 1 exiting the barrel 60
at zone 8.
A screw and mixing element configuration for the twin screw extruder is
schematically
illustrated in Fig 4B. The twin screw extruder comprises a plurality of twin
lead screws
(TLS) (designated A and B) and paddles (designated C) and reverse twin lead
screws
(RTLS) (designated D) installed in series as illustrated in Table 1 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
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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
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 1
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
SLS and TLS screw elements in order to enhance mixing. Paddle C has a length
ratio of 1/4.
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Various configurations of bilobal paddles and reversing elements D, single and
twin lead
screws threaded in the opposite direction, 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, one or more fibrous element-forming polymers, such as one or more
hydroxyl
polymers, are fed into the solid feed port 62 at a rate of 330 grams/minute
using a K-Tron
(Pitman, NJ) loss-in-weight feeder. These hydroxyl polymers are combined
inside the extruder
(zone 2) with a fast wetting surfactant (Aerosol MA-80) added at liquid feed
port 64 (zone 2) at
a rate of 12 grams/minute. Water, an external plasticizer, is added at the
liquid feed port 64
(zone 2) at a rate of 25 grams/minute using a Milton Roy (Ivyland, PA)
diaphragm pump (1.9
gallon per hour pump head) to form a hydroxyl polymer/fast wetting
surfactant/water slurry. A
crosslinking facilitator, such as ammonium methanesulfonate, may be added to
the water at
liquid feed port 64 (zone 2) also. Another fibrous element-forming polymer,
such as a hydroxyl
polymer, for example polyvinyl alcohol, may be added to the slurry at liquid
feed port 68 (zone
3). A non-hydroxyl polymer, such as polyacrylamide may be added to the slurry
at liquid feed
port 64 (zone 2). Additional additives such as other surfactants, other non-
hydroxyl polymers,
other salts and/or acids may be added at various feed ports along the length
of the barrel 60. This
slurry is then conveyed down the ban-el 60 of the extruder and cooked to
produce an aqueous
polymer melt composition comprising a melt processed hydroxyl polymer and a
fast wetting
surfactant. Table 2 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
5 355 Medium Pressure Generating Cooking at Pressure and
Temperature
6 355 High Reversing Cooking at Pressure and
Temperature
7 355 Low Conveying Cooling and Conveying
(with venting)
8 355 Low Pressure Generating Conveying
Table 2
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After the aqueous polymer melt composition exits the first extruder, part of
the aqueous
polymer melt composition is dumped and another part (450g) is fed into a Mahr
(Charlotte, NC)
gear pump and pumped to a second extruder. The second extruder provides a
means to cool the
5 polymer melt composition by venting the polymer melt composition to
atmospheric pressure and
provides additional points to incorporate additives. A ban-el 74 of an APV
Baker (Peterborough,
England) 13:1, 70 mm diameter twin screw extruder is schematically illustrated
in Fig. 5A as the
second extruder. The barrel 74 is separated into five zones, identified as
zones 1-5. The barrel
74 encloses the extrusion screw and mixing elements, schematically shown in
Fig. 5B, and serves
10 as containment vessel during the extrusion process. A first liquid feed
port 76 is disposed in
zone 2, a second liquid feed port 78 is disposed in zone 3, and a third liquid
feed port 80 is
disposed in zone 4. A vent 82 is included in zone 1 for cooling and decreasing
the liquid, such as
water, content of the mixture prior to exiting the second extruder. An
optional vent stuffer,
commercially available from APV Baker, can be employed to prevent the aqueous
polymer melt
15 composition from exiting through the vent 82. The flow of the aqueous
polymer melt
composition through the barrel 74 is from zone 2 exiting the barrel 74 at zone
5.
A screw and mixing element configuration for the second extruder consists of
twin lead
screws (TLS) (designated A, E, F), paddles (designated C), and single lead
screws (SLS)
(designated G) installed in series as illustrated in Table 3 below.
Total Element Purpose
Length Length Type
Zone Ratio Element Pitch Ratio
1 0.25 Paddle 0 0.25 C Mixing
1 1.75 TLS 2 1.5 E Vent Location
2 3.25 TLS 2 1.5 E Conveying
2 4.75 TLS 3 1.5 F Feed Inlet Location
3 6.25 TLS 3 1.5 F Conveying
3 7.75 TLS 3 1.5 F Conveying
4 9.25 TLS 2 1.5 E Conveying
4 10.25 TLS 1 1 A Conveying
4 11.25 TLS 1 1 A Conveying
4 11.38 Paddle 0 0.125 C Mixing
4 11.50 Paddle 0 0.125 C Mixing
5 11.63 Paddle 0 0.125 C Mixing
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11.75 Paddle 0 0.125 C Mixing
5 12.75 SLS 0.5 1 G Conveying
5 13.75 SLS 0.5 1 G Conveying
Table 3
The aqueous polymer melt composition comprising the melt processed hydroxyl
polymer
and fast wetting surfactant coming from the first extruder is fed into the
second extruder at a
point about 5 L/D down the barrel, liquid feed port 76 (zone 2). A vent 82
open to atmospheric
5 pressure is situated at about 1.5 L/D down the barrel 74 (zone 1). Some
water vapor escapes
from the aqueous polymer melt composition and exits through the vent 82.
Water, an external
plasticizer, and a crosslinking facilitator, such as ammonium
methanesulfonate, may be added at
the liquid feed port 78 (zone 3). A non-hydroxyl polymer, such as
polyacrylamide, may be
added at liquid feed port 80 (zone 4). Additional additives such as other
surfactants, other non-
hydroxyl polymers, other salts and/or acids may be added at various feed ports
along the length
of the barrel 74. The aqueous polymer melt composition is then conveyed
through the extruder to
the end of the barrel 74 (zone 5).
At least a portion of the aqueous polymer melt composition is then dumped and
another
part (400g) is fed into a Mahr (Charlotte, NC) gear pump and pumped into a SMX
style static
mixer (Koch-Glitsch, Woodridge, Illinois). The static mixer is used to combine
additional
additives such as cros slinking agents, for example an imidazolidinone, cros
slinking facilitators,
such as ammonium methanesulfonate, external plasticizers, such as water, with
the aqueous
polymer melt composition comprising the melt processed hydroxyl polymer and
fast wetting
surfactant. 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 aqueous polymer melt composition of the present invention is now ready to
be processed by
a polymer processing operation.
b. Polymer Processing
"Polymer processing" as used herein means any operation and/or process by
which a
polymeric structure comprising a processed hydroxyl polymer is formed from an
aqueous
polymer melt composition comprising a melt processed hydroxyl polymer. Non-
limiting
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 fiber producing.
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A "processed hydroxyl polymer" as used herein means any hydroxyl polymer that
has
undergone a melt processing operation and a subsequent polymer processing
operation.
c. Polymeric Structure
The aqueous polymer melt composition can be subjected to one or more polymer
processing operations such that the polymer melt composition is processed into
a polymeric
structure comprising the hydroxyl polymer and a crosslinking system according
to the present
invention.
"Polymeric structure" as used herein means any physical structure formed as a
result of
processing an aqueous polymer melt composition in accordance with the present
invention. Non-
limiting examples of polymeric structures in accordance with the present
invention include
fibrous elements (such as filaments and/or fibers) and/or fibrous structures
comprising such
fibrous elements.
A crosslinking system via a crosslinking agent and ammonium alkylsulfonate
salt, a
crosslinking facilitator, may be able to crosslink the processed hydroxyl
polymers together to
produce the polymeric structure of the present invention, with or without
being subjected to a
curing step. In other words, the crosslinking system in accordance with the
present invention
acceptably crosslinks the processed hydroxyl polymers of a processed polymer
melt composition
together via the crosslinking agent to form an integral polymeric structure,
such as a fibrous
element. The crosslinking agent can function as a "building block" for the
polymeric structure.
In one example, without the crosslinking agent, no polymeric structure in
accordance with the
present invention could be formed.
Polymeric structures of the present invention do not include coatings and/or
other surface
treatments that are applied to a pre-existing form, such as a coating on a
fibrous element, film or
foam. However, in one example of the present invention, a polymeric structure,
such as a fibrous
element, in accordance with the present invention may be coated and/or surface
treated with a
crosslinking system of the present invention.
In one example, the polymeric structure produced via a polymer processing
operation
may be cured 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 temperature-raising methods.
Further, the polymeric structure may also be cured at room temperature for
days, either
after curing at above room temperature or instead of curing at above room
temperature.
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The polymeric structure may exhibit an initial total wet tensile, as measured
by the Initial
Total Wet Tensile Test Method described herein, of at least about 1.18 g/cm (3
g/M) and/or at
least about 1.57 g/cm (4 g/in) and/or at least about 1.97 g/cm (5 g/in) to
about 23.62 g/cm (60
g/in) and/or to about 21.65 g/cm (55 g/in) and/or to about 19.69 g/cm (50
g/in).
The polymeric structures of the present invention may include melt spun fibers
and/or
spunbond fibers, staple fibers, hollow fibers, shaped fibers, such as multi-
lobal fibers and
multicomponent fibers, especially bicomponent fibers. The multicomponent
fibers, especially
bicomponent fibers, 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-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 fibers of the present invention may have different geometries that
include round,
elliptical, star shaped, rectangular, and other various eccentricities.
One or more polymeric structures of the present invention may be incorporated
into a
multi-polymeric structure product, such as a fibrous structure and/or web, if
the polymeric
structures are in the form of fibers. Such a multi-polymeric structure product
may ultimately be
incorporated into a commercial product, such as a single- or multi-ply
sanitary tissue product,
such as facial tissue, bath tissue, paper towels and/or wipes, feminine care
products, diapers,
writing papers, cores, such as tissue cores, and other types of paper
products.
Non-limiting examples of processes for preparing polymeric structures in
accordance
with the present invention follow.
i) Fibrous Element Formation
An aqueous polymer melt composition comprising a melt processed hydroxyl
polymer
and a fast wetting surfactant is prepared according to the Synthesis of an
Aqueous Polymer Melt
Composition described above. As shown in Fig. 6, the aqueous polymer melt
composition may
be processed into a fibrous element. The aqueous polymer melt composition
present in an
extruder 102 is pumped to a die 104 using pump 103, 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 aqueous polymer
melt
composition's flow to die 104 is controlled by adjusting the number of
revolutions per minute
(rpm) of the pump 103. Pipes connecting the extruder 102, the pump 103, the
die 104, and
optionally a mixer 116 are electrically heated and thermostatically controlled
to 65 C.
The die 104 has several rows of circular extrusion nozzles 200 spaced from one
another at
a pitch P (Fig. 7) of about 2.489 millimeters (about 0.098 inches). The
nozzles are arranged in
a staggered grid with a spacing of 2.489 millimeters (about 0.098 inches)
within rows and a
spacing of 2.159 millimeters (about 0.085 inches) between rows. The nozzles
200 have
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individual inner diameters D2 of about 0.254 millimeters (about 0.010 inches)
and individual
outside diameters (D1) of about 0.813 millimeters (about 0.032 inches). Each
individual nozzle
200 is encircled by an annular orifice 250 formed in a plate 260 (Figs. 7 and
8) having a
thickness of about 1.9 millimeters (about 0.075 inches). A pattern of a
plurality of the orifices
250 in the plate 260 correspond to a pattern of extrusion nozzles 200. Once
the orifice plate is
combined with the dies, the resulting area for airflow is about 36 percent.
The plate 260 is
fixed so that the embryonic filaments 110 being extruded through the nozzles
200 are surrounded
and attenuated by generally cylindrical, humidified air streams supplied
through the orifices 250.
The 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 a surface 261 of the plate 260 (Fig. 7).
As shown in
Fig. 9, a plurality of boundary-air orifices 300, is formed by plugging
nozzles of two outside
rows on each side of the plurality of nozzles, as viewed in plane, so that
each of the boundary-
layer orifice comprised a annular aperture 250 described herein above.
Additionally, every other
row and every other column of the remaining capillary nozzles are blocked,
increasing the
spacing between active capillary nozzles
As shown in Fig. 6, attenuation air can be provided by heating compressed air
from a
source 106 by an electrical-resistance heater 108, for example, a heater
manufactured by
Chromalox, Division of Emerson Electric, of Pittsburgh, PA, USA. An
appropriate quantity of
steam 105 at an absolute pressure of from about 240 to about 420 kiloPascals
(kPa), controlled
by a globe valve (not shown), is added to saturate or nearly saturate the
heated air at the
conditions in the electrically heated, thermostatically controlled delivery
pipe 115. Condensate is
removed in an electrically heated, thermostatically controlled, separator 107.
The attenuating air
has an absolute pressure from about 130 kPa to about 310 kPa, measured in the
pipe 115. The
filaments 110 being extruded 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 110 are dried by a
drying air stream
109 having a temperature from about 149 C (about 300 F) to about 315 C
(about 600 F) by an
electrical resistance heater (not shown) supplied through drying nozzles 112
and discharged at an
angle generally perpendicular relative to the general orientation of the
embryonic fibers being
extruded. The filaments 110 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 111, such as, for example, a movable foraminous belt.
The process parameters are as follows in Table 4.
Sample Units
Attenuation Air Flow Rate G/min 9000
Attenuation Air Temperature C 65
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Sample Units
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
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
ii) Foam Formation
The aqueous polymer melt composition for foam formation may be prepared
similarly as
for fibrous element formation except that the added water content may be less,
typically from
5 about 10-21% of the hydroxyl polymer weight. With less water to
plasticize the hydroxyl
polymer, higher temperatures are needed in extruder zones 5-8 (Fig. 4A),
typically from about
150-250 C. Also with less water available, it may be necessary to add the
crosslinking system,
especially the cros slinking agent, with the water in zone 1. In order to
avoid premature
crosslinking in the extruder, the aqueous polymer melt composition pH should
be between 7 and
10 8, achievable by using a crosslinking facilitator e.g., ammonium salt,
as measured according to
the Polymer Melt Composition pH Test Method described herein. A die is placed
at the location
where the extruded material emerges and is typically held at about 160-210 C.
Modified high
amylose starches (for example greater than 50% and/or greater than 75% and/or
greater than 90%
by weight of the starch of amylose) granulated to particle sizes ranging from
about 400-1500
15 microns may be used in the present invention. It may also be
advantageous to add a nucleating
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agent such as microtalc or alkali metal or alkaline earth metal salt such as
sodium sulfate or
sodium chloride in an amount of about 1-8% of the starch weight. The foam may
be shaped into
various forms.
iii) Film Formation
The aqueous polymer melt composition for film formation may be prepared
similarly as
for foam formation except that the added water content may be less, typically
3-15% of the
hydroxyl polymer weight and a polyol external plasticizer such as glycerol is
included at about
10-30% of the hydroxyl polymer weight. As with foam formation, zones 5-7 (Fig.
4A) are held
at about 160-210 C, however, the slit die temperature is lower between 60-120
C. As with foam
formation, the crosslinking system, especially the crosslinking agent, may be
added along with
the water in zone 1 and the aqueous polymer melt composition pH may be between
about 7-8
achievable by using a crosslinking facilitator e.g., ammonium salt, as
measured according to the
Polymer Melt Composition pH Test Method described herein.
Non-limiting Example of Fibrous Structure of Present Invention
With reference to Fig. 4A, an aqueous polymer melt composition comprising 50%
CPI
058020 acid thinned dent corn starch (hydroxyl polymer) from Corn Products
International and
0.55% Hyperfloc NF301 polyacrylamide (non-hydroxyl polymer), 0.65% Aerosol MA-
80 (fast
wetting surfactant) and 47% water (external plasticizer), is prepared
according to Synthesis of
Aqueous Polymer Melt Composition of the present invention. Polyacrylamide is
added as a
2.2% aqueous solution at liquid feed port 70, and fast wetting surfactant is
added as a 80%
aqueous propylene glycol/water solution at liquid feed port 64. To this
aqueous polymer melt
composition is added a crosslinking agent (DHEU) (20% aqueous solution), a
crosslinking
facilitator (see table) (25% aqueous solution), and water at a static mixer to
produce an aqueous
polymer melt composition comprising about 48% CPI 058020 acid thinned dent
corn starch,
0.55% Hyperfloc NF301 polyacrylamide, 0.36% ammonium methanesulfonate (AMS),
2.70%
DHEU, 0.93% sulfosuccinate surfactant, and 47.5% water.
Fibrous elements are formed from the aqueous polymer melt composition in
accordance
with the present invention. Fibrous elements are formed at a drying air flows
(21620g / mm) and
are collected on a moving foraminous belt. A vacuum is used to remove air
while leaving the
fibers to form as a fibrous structure on the belt. The belt transports the
fibrous structure to
subsequent equipment, all of which operate at about 0.20 meters/second (40
feet/minute). The
fibrous structure feeds through a thermal bonding nip consisting of two heated
metal rolls. The
rolls are 0.133 meters in diameter and are heated to about 199 C (390 F). One
roll is smooth, the
other has square knobs representing 12.8% of the surface area; the knobs are
0.508 mm wide on a
1.499 mm grid. The rolls are loaded with about 18900 Newtons per linear meter
of roll (about
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108 pounds per linear inch). The fibrous structure continues to a heating oven
to cure the fibrous
structure. The fibrous structure is supported on a separate foraminous belt
and feeds through a
1.054 meter long oven operating at 199 C (390 F) or 215 C (420 F) circulating
about 13600
grams per minute of heated air. Heat transfer to the polymeric structure and
thus polymeric
structure temperature is a function of the air flow and air temperature. The
polymeric structure's
temperature may be measured according to the Polymeric Structure Temperature
Measurement
Test Method described herein. Accordingly, the cure temperature of the
polymeric structure may
be achieved by adjusting air flow and air temperature. The fibrous structure
continues to another
foraminous belt where the fibrous structure is humidified to about 7 percent
moisture by the
addition of steam. Steam is supplied by an Armstrong International series 9000
conditioned-
steam humidifier. Finally the fibrous structure is wound onto a paper core.
The cured fibrous structures are characterized by basis weight, initial total
wet tensile, dry
peak TEA and dry fail stretch (both measured according to the Dry Tensile
Strength Test Method
described herein) and fiber diameter according to their respective Test
Methods described herein.
The resulting data is shown in Table 5 for the examples set forth therein.
Example Crosslinker Curing
Normalized Dry Fail Normalized L
Facilitator (% Temp Dry Peak Stretch ITWT a
in melt) ( F) TEA (%) (g / in) b
(g / in)
1 Ammonium 93.2
Alkylsulfonate -1.6
Salt ("AMS") 6.0
(0.25%)
Invention 350 62.1 26.7 96.9
2 Ammonium 94.9
Alkylsulfonate -1.8
Salt (0.25%)/ 6.3
Ammonium
Sulfate
(0.025%)
Invention 350 12.1 18.2 58.3
3 Ammonium 94
Chloride (1%) -1.9
Prior Art 330 45.4 25.5 92.5 7.9
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4 Ammonium 93.0
Citrate (1%) -1.9
Prior Art 350 21.3 11.3 67.3 6.5
Table 5
TEST METHODS OF THE PRESENT INVENTION
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 12 hours prior to the test. All plastic and paper
board packaging
articles of manufacture, if any, must be carefully removed from the samples
prior to testing. 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. Except where
noted all tests are
conducted in such conditioned room, all tests are conducted under the same
environmental
conditions and in such conditioned room. Discard any damaged product. Do not
test samples
that have defects such as wrinkles, tears, holes, and like. All instruments
are calibrated according
to manufacturer's specifications.
Shear Viscosity of a Polymer Melt Composition Measurement Test Method
The shear viscosity of a polymer melt composition comprising a crosslinking
system is
measured using a capillary rheometer, Goettfert Rheograph 6000, manufactured
by Goettfert
USA of Rock Hill SC, USA. The measurements are conducted using a capillary die
having a
diameter D of 1.0 mm and a length L of 30 mm (i.e., L/D = 30). The die is
attached to the lower
end of the rheometer's 20 mm barrel, which is held at a die test temperature
of 75 C. A
preheated to die test temperature, 60 g sample of the polymer melt composition
is loaded into the
barrel section of the rheometer. Rid the sample of any entrapped air. Push the
sample from the
barrel through the capillary die at a set of chosen rates 1,000-10,000 seconds-
1. An apparent
shear viscosity can be calculated with the rheometer's software from the
pressure drop the
sample experiences as it goes from the barrel through the capillary die and
the flow rate of the
sample through the capillary die. The log (apparent shear viscosity) can be
plotted against log
(shear rate) and the plot can be fitted by the power law, according to the
formula
i = K711-1, wherein K is the material's viscosity constant, n is the
material's thinning index and 7
is the shear rate. The reported apparent shear viscosity of the composition
herein is calculated
from an interpolation to a shear rate of 3,000 sec-lusing the power law
relation.
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 8.890 cm
0.00889 cm by 8.890 cm 0.00889 cm 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 g/m2 as follows:
Basis Weight = (Mass of stack) / [(Area of 1 square in stack) x (No.of squares
in stack)]
Basis Weight (g/m2) = Mass of stack (g) / 1179.032 (em2) / 10,000 (cm2/1112) x
121
Report result to the nearest 0.1 g/m2. Sample dimensions can be changed or
varied using a
similar precision cutter as mentioned above, so as at least 645 square
centimeters of sample area
is in the stack.
Initial Total Wet Tensile Test Method
Cut tensile strips precisely in the direction indicated; four to the machine
direction (MD)
and four to the cross direction (CD). Cut the sample strips 4 in. (101.6 mm)
long and exactly 1
in. (25.4 mm) wide using an Alpha Precision Sample Cutter Model 240-7A
(pneumatic):
Thwing-Albert Instrument Co and an appropriate die.
An electronic tensile tester (Thwing-Albert EJA Vantage Tester, Thwing-Albert
Instrument Co., 10960 Dutton Rd., Philadelphia, Pa., 19154) is used and
operated at a crosshead
speed of 4.0 inch (about 10.16 cm) per minute, using a strip of a fibrous
structure of 1 inch wide
and a length of about 4 inches long. The gauge length is set to 1 inch. The
strip is inserted into the
jaws with the 1 inch wide section in the clamps, verifying that the sample is
hanging straight into the
bottom jaw. The sample is then pre-loaded with 20-50 Win of pre-load force.
This tension is applied to
the web to define the adjusted gauge length, and, by definition is the zero
strain point. The sample is then
wet thoroughly with water using a syringe to gently apply the water on the
uppermost portion of the web
sample inside the jaws. Crosshead movement is then initiated within 3-8
seconds after initial water
contact. The initial result of the test is an array of data in the form load
(grams force) versus
crosshead displacement (centimeters from starting point).
The sample is tested in two orientations, referred to here as MD (machine
direction, i.e.,
in the same direction as the continuously wound reel and forming fabric) and
CD (cross-machine
direction, i.e., 90 from MD). The MD and CD wet tensile strengths are
determined using the
above equipment and calculations in the following manner:
Initial Total Wet Tensile = ITWT (gf/inch) = Peak Loadmp (gf) / 2 (inchwidth)
+
/ 2 (inchwidth)
Peak Loadco (gd
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The Initial Total Wet Tensile value is then normalized for the basis weight of
the strip
from which it was tested. The normalized basis weight used is 24 g/m2, and is
calculated as
follows:
Normalized IITWT = IITWT * 24 (g/m2) / Basis Weight of Strip (g/m2)
5 In one example, the initial total wet tensile of a polymeric structure,
such as a fibrous
structure, of the present invention is at least 1.18 g/cm (3 g/M) and/or at
least 1.57 g/cm (4 g/in)
and/or at least 1.97 g/cm (5 g/in) then the crosslinking system is acceptable.
The initial total wet
tensile may be less than or equal to about 23.62 g/cm (60 g/in) and/or less
than or equal to about
21.65 g/cm (55 g/in) and/or less than or equal to about 19.69 g/cm (50 g/in).
10 Dry Tensile Strength Test Method
Elongation (Stretch), Tensile Strength, TEA and Tangent Modulus are 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)
15 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
20 (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
25 will be treated as a unitary specimen for testing.
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 cm/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
30 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
in 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
35 between grips, with no more than 5.0 g of force on the load cell. Add a
pre-tension force of 3g
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This tension is applied to the specimen to define the adjusted gauge length,
and, by definition is
the zero strain point. 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.
Eight samples are run on the Tensile Tester (four to the MD and four to the
CD) and
average of the respective dry total tensile, dry peak TEA and dry Fail Stretch
is reported as the
Dry Total Tensile, Dry peak TEA and Dry Fail Stretch. Peak TEA is defined as
tensile energy
absorbed (area under the load vs. strain tensile curve) from zero strain to
peak force point, with
units of g/in. Dry Fail Stretch is defined as the percentage strain measured
after the web is
strained past its peak load point, where the force drops to exactly 50% of its
peak load force.
The dry peak TEA is then normalized for the basis weight of the strip from
which it was
tested. The normalized basis weight used is 24 g/m2, and is calculated as
follows:
Normalized {dry peak TEA} = {dry peak TEA} * 24 (g/m2) / Basis Weight of Strip
(g/m2)
The MD and CD dry tensile strengths are determined using the above equipment
and
calculations in the following manner.
Tensile Strength in general is the maximum peak force (g) divided by the
specimen width (1
in), and reported as g/M to the nearest 1 g/M.
Average Tensile Strength=sum of tensile loads measures (MD)/(Number of tensile
stripes
tested (MD)* Number of useable units or plys per tensile stripe)
This calculation is repeated for cross direction testing.
Dry Total Tensile = Average MD tensile strength + Average CD tensile strength
The Dry Tensile value is then normalized for the basis weight of the strip
from which it
was tested. The normalized basis weight used is 24 g/m2, and is calculated as
follows:
Normalized IDTT1 = IDTT1 * 24 (g/m2) / Basis Weight of Strip (g/m2)
The various values are calculated for the four CD specimens and the four MD
specimens.
Calculate an average for each parameter separately for the CD and MD
specimens.
Polymer Melt Composition pH Test Method
A polymer melt composition pH is determined by adding 25 mL of the polymer
melt
composition to 100 mL of deionized water, stiffing with a spatula for 1 min
and measuring the
pH.
Weight Average Molecular Weight Test Method
The weight average molecular weight (Mw) of a material, such as a hydroxyl
polymer is
determined by Gel Permeation Chromatography (GPC) using a mixed bed column. A
high
performance liquid chromatograph (HPLC) having the following components:
Millenium ,
Model 600E pump, system controller and controller software Version 3.2, Model
717 Plus
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autosampler and Ci4M-009246 column heater, all manufactured by Waters
Corporation of
Milford, MA, USA, is utilized. The column is a PL gel 20 pm Mixed A column
(gel molecular
weight ranges from 1,000 g/mol to 40,000,000 g/mol) having a length of 600 mm
and an internal
diameter of 7.5 mm and the guard column is a PL gel 20 um, 50 mm length, 7.5
mm ID. The
column temperature is 55 C and the injection volume is 200 L. The detector is
a DAWN
Enhanced Optical System (EOS) including Astra software, Version 4.73.04
detector software,
manufactured by Wyatt Technology of Santa Barbara, CA, USA, laser-light
scattering detector
with K5 cell and 690 nm laser. Gain on odd numbered detectors set at 101. Gain
on even
numbered detectors set to 20.9. Wyatt Technology's Optilab differential
refractometer set at
50 C. Gain set at 10. The mobile phase is HPLC grade dimethylsulfoxide with
0.1% w/v LiBr
and the mobile phase flow rate is 1 mL/min, isocratic. The run time is 30
minutes.
A sample is prepared by dissolving the material in the mobile phase at
nominally 3 mg of
material /1 mL of mobile phase. The sample is capped and then stirred for
about 5 minutes using
a magnetic stirrer. The sample is then placed in an 85 C convection oven for
60 minutes. The
sample is then allowed to cool undisturbed to room temperature. The sample is
then filtered
through a 5um Nylon membrane, type Spartan-25, manufactured by Schleicher &
Schuell, of
Keene, NH, USA, into a 5 milliliter (mL) autosampler vial using a 5 mL
syringe.
For each series of samples measured (3 or more samples of a material), a blank
sample of
solvent is injected onto the column. Then a check sample is prepared in a
manner similar to that
related to the samples described above. The check sample comprises 2 mg/mL of
pullulan
(Polymer Laboratories) having a weight average molecular weight of 47,300
g/mol. The check
sample is analyzed prior to analyzing each set of samples. Tests on the blank
sample, check
sample, and material test samples are run in duplicate. The final run is a run
of the blank sample.
The light scattering detector and differential refractometer is run in
accordance with the "Dawn
EOS Light Scattering Instrument Hardware Manual" and "Optilab DSP
Interferometrie
Refractometer Hardware Manual," both manufactured by Wyatt Technology Corp.,
of Santa
Barbara, CA, USA.
The weight average molecular weight of the sample is calculated using the
detector
software. A dn/dc (differential change of refractive index with concentration)
value of 0.066 is
used. The baselines for laser light detectors and the refractive index
detector are corrected to
remove the contributions from the detector dark current and solvent
scattering. If a laser light
detector signal is saturated or shows excessive noise, it is not used in the
calculation of the
molecular mass. The regions for the molecular weight characterization are
selected such that
both the signals for the 90 detector for the laser-light scattering and
refractive index are greater
than 3 times their respective baseline noise levels. Typically the high
molecular weight side of
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the chromatogram is limited by the refractive index signal and the low
molecular weight side is
limited by the laser light signal.
The weight average molecular weight can be calculated using a "first order
Zimm plot" as
defined in the detector software. If the weight average molecular weight of
the sample is greater
than 1,000,000 g/mol, both the first and second order Zimm plots are
calculated, and the result
with the least error from a regression fit is used to calculate the molecular
mass. The reported
weight average molecular weight is the average of the two runs of the material
test sample.
Average Diameter Test Method
A fibrous structure comprising fibrous elements of appropriate basis weight
(approximately 5 to 20 grams/square meter) is cut into a rectangular shape,
approximately 20 mm
by 35 mm. The sample is then coated using a SEM sputter coater (EMS Inc, PA,
USA) with gold
so as to make the fibers relatively opaque. Typical coating thickness is
between 50 and 250 nm.
The sample is then mounted between two standard microscope slides and
compressed together
using small binder clips. The sample is imaged using a 10X objective on an
Olympus BHS
microscope with the microscope light-collimating lens moved as far from the
objective lens as
possible. Images are captured using a Nikon D1 digital camera. A Glass
microscope micrometer
is used to calibrate the spatial distances of the images. The approximate
resolution of the images
is 1 pm/pixel. Images will typically show a distinct bimodal distribution in
the intensity
histogram corresponding to the fibers and the background. Camera adjustments
or different basis
weights are used to achieve an acceptable bimodal distribution. Typically 10
images per sample
are taken and the image analysis results averaged.
The images are analyzed in a similar manner to that described by B.
Pourdeyhimi, R. and
R. Dent in "Measuring fiber diameter distribution in nonwovens" (Textile Res.
J. 69(4) 233-236,
1999). Digital images are analyzed by computer using the MATLAB (Version. 6.1)
and the
MATLAB Image Processing Tool Box (Version 3.)The image is first converted into
a grayscale.
The image is then binarized into black and white pixels using a threshold
value that minimizes
the intraclass variance of the thresholded black and white pixels. Once the
image has been
binarized, the image is skeltonized to locate the center of each fiber in the
image. The distance
transform of the binarized image is also computed. The scalar product of the
skeltonized image
and the distance map provides an image whose pixel intensity is either zero or
the radius of the
fiber at that location. Pixels within one radius of the junction between two
overlapping fibers are
not counted if the distance they represent is smaller than the radius of the
junction. The
remaining pixels are then used to compute a length-weighted histogram of fiber
diameters
contained in the image.
Polymeric Structure Temperature Measurement Test Method
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The temperature of the polymeric structure after curing is measured using a
Fluke 566 IR
Thermometer or equivalent. Measurements are conducted using the thermometer's
"average"
function, where real-time temperature measurements are reported as an average
over the entire
measurement time. The thermometer is activated by depressing a trigger and
focused using a
laser reference dot.
Since temperature can vary with position in both the CD and MD direction, an
average
temperature profile of the polymeric structure is generated. Care must be
taken to measure at a
consistent distance from any heat sources (curing oven, etc.), but before
appreciable cooling has
occurred.
With the thermometer held perpendicular to the polymeric structure, the
trigger is
depressed. Using the laser guide as a reference, the thermometer is scanned
back-and-forth
across the material in the CD direction, maintaining a distance from the edges
of 2 inches and a
distance from the curing heat source of approximately 3 inches. Measurement is
continued for
10 seconds, and the resulting average temperature recorded.
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."
All documents cited in the Detailed Description of the Invention are not to be
construed
as an admission that they are prior art with respect to the present invention.
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.
