U.S. patent application number 14/088492 was filed with the patent office on 2014-03-20 for polymeric structures and method for making same.
This patent application is currently assigned to The Procter & Gamble Company. The applicant listed for this patent is The Procter & Gamble Company. Invention is credited to David William CABELL, Fred J. KECK, David Warren LOEBKER, Larry Neil MACKEY, Mark Ryah RICHARDS.
Application Number | 20140079914 14/088492 |
Document ID | / |
Family ID | 35187439 |
Filed Date | 2014-03-20 |
United States Patent
Application |
20140079914 |
Kind Code |
A1 |
CABELL; David William ; et
al. |
March 20, 2014 |
POLYMERIC STRUCTURES AND METHOD FOR MAKING SAME
Abstract
Polymeric structures, methods for making same, fibrous
structures comprising same and fibrous product incorporating same
are provided.
Inventors: |
CABELL; David William;
(Cincinnati, OH) ; LOEBKER; David Warren;
(Cincinnati, OH) ; MACKEY; Larry Neil; (Liberty
Township, OH) ; RICHARDS; Mark Ryah; (Wayne Township,
OH) ; KECK; Fred J.; (Cincinnati, OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
The Procter & Gamble Company |
Cincinnati |
OH |
US |
|
|
Assignee: |
The Procter & Gamble
Company
Cincinnati
OH
|
Family ID: |
35187439 |
Appl. No.: |
14/088492 |
Filed: |
November 25, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12784817 |
May 21, 2010 |
8623246 |
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14088492 |
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11167356 |
Jun 27, 2005 |
7754119 |
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12784817 |
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10834540 |
Apr 29, 2004 |
6977116 |
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11167356 |
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Current U.S.
Class: |
428/156 ;
524/52 |
Current CPC
Class: |
C08L 3/00 20130101; Y10T
428/29 20150115; D04H 1/56 20130101; Y10T 428/24479 20150115; Y10T
428/2929 20150115; D04H 3/03 20130101; D04H 3/16 20130101; Y10T
428/2913 20150115; D01F 6/14 20130101; Y10T 428/2927 20150115 |
Class at
Publication: |
428/156 ;
524/52 |
International
Class: |
C08L 3/00 20060101
C08L003/00 |
Claims
1. A fibrous structure comprising a fiber comprising a PVOH and a
hydroxyl polymer starch, wherein the fibrous structure exhibits a
dry lint score of less than about 50.
2. The fibrous structure according to claim 1 wherein the fibrous
structure comprises two or more fibers that are associated with one
another.
3. The fibrous structure according to claim 1 wherein the fibrous
structure comprises two or more regions that exhibit different
values of a common intensive property relative to each other.
4. The fibrous structure according to claim 3 wherein the common
intensive property is selected from the group consisting of:
density, basis weight, caliper, substrate thickness, elevation,
opacity, crepe frequency and mixtures thereof.
5. A fibrous product comprising one or more fibrous structures
according to claim 1.
6. The fibrous structure according to claim 1 wherein the fibrous
structure exhibits a wet pill area of less than about 4%.
7. The fibrous structure according to claim 1 wherein the fiber
further comprises a crosslinking system comprising a crosslinking
agent, wherein the hydroxyl polymer starch is crosslinked by the
crosslinking agent such that the fiber as a whole does not exhibit
a melting point.
8. The fibrous structure according to claim 1 wherein the fiber
exhibits a fiber diameter of less than about 50 .mu.m.
9. The fibrous structure according to claim 1, wherein the fibrous
structure comprises two or more fibers at least one of which
comprises a fiber comprising PVOH and a hydroxyl polymer starch,
wherein the fibrous structure comprises a first region comprising
associated fibers and a second region comprising non-associated
fibers.
10. The fibrous structure according to claim 9 wherein the fibrous
structure comprises two or more regions that exhibit different
values of a common intensive property relative to each other.
11. The fibrous structure according to claim 10 wherein the common
intensive property is selected from the group consisting of:
density, basis weight, caliper, substrate thickness, elevation,
opacity, crepe frequency and mixtures thereof.
12. A fibrous product comprising one or more fibrous structures
according to claim 9.
13. The fibrous product according to claim 12 wherein the fibrous
product exhibits a stretch at peak load of at least about 5%.
14. The fibrous product according to claim 12 wherein the fibrous
product exhibits a stretch at failure load of at least about 10%.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to polymeric structures
comprising a PVOH processed hydroxyl polymer composition comprising
a hydroxyl polymer comprising at least a polyvinyl alcohol (PVOH)
hydroxyl polymer, fibrous structures comprising such polymeric
structures and methods for making same.
BACKGROUND OF THE INVENTION
[0002] In recent years, formulators of fibrous structures have
attempted to move away from wood-based cellulosic fibers to
polymeric fibers. Polymeric fiber-containing fibrous structures are
known in the art. See for example, EP 1 217 106 A1.
[0003] However, such prior art attempts to make polymeric
fiber-containing fibrous structures have failed to achieve the
intensive properties of their wood-based cellulosic
fiber-containing fibrous structure cousins.
[0004] Accordingly, there is a need for a polymeric structure
and/or a fibrous structure comprising a polymeric structure in
fiber form that exhibits intensive properties substantially similar
to or better than wood-based cellulosic fiber-containing fibrous
structures.
SUMMARY OF THE INVENTION
[0005] The present invention fulfills the need described above by
providing a polymeric structure and/or a fibrous structure
comprising a polymeric structure in fiber form that exhibits
substantially similar or better intensive properties as compared to
wood-based cellulosic fiber-containing fibrous structures.
[0006] In one aspect of the present invention, a polymeric
structure comprising a PVOH processed hydroxyl polymer composition
comprising a hydroxyl polymer comprising at least a PVOH hydroxyl
polymer, wherein the polymeric structure exhibits a stretch at peak
load of at least about 5% and/or at least about 8% and/or at least
about 10% and/or a stretch at failure load of at least about 10%
and/or at least about 13% and/or at least about 20%, is
provided.
[0007] In another aspect of the present invention, a fibrous
structure comprising a polymeric structure in the form of a fiber
in accordance with the present invention, wherein the fibrous
structure exhibits a stretch at peak load of at least about 5%
and/or at least about 8% and/or at least about 10% and/or a stretch
at failure load of at least about 10% and/or at least about 13%
and/or at least about 20%, is provided.
[0008] In even another aspect of the present invention, a fibrous
product comprising one or more fibrous structures in accordance
with the present invention is provided.
[0009] In still another aspect of the present invention, a method
for making a polymeric structure, the method comprising the steps
of: [0010] a. providing a PVOH polymer melt composition comprising
a hydroxyl polymer comprising at least a PVOH hydroxyl polymer; and
[0011] b. polymer processing the PVOH polymer melt composition to
form a polymeric structure; [0012] wherein the polymeric structure
exhibits a stretch at peak load of at least about 5% and/or at
least about 8% and/or at least about 10% and/or a stretch at
failure load of at least about 10% and/or at least about 13% and/or
at least about 20%, is provided.
[0013] In yet another aspect of the present invention, a polymeric
structure in fiber form produced in accordance with a method of the
present invention, is provided.
[0014] In even still another aspect of the present invention, a
method for making a fibrous structure, the method comprising the
steps of: [0015] a. providing a PVOH polymer melt composition
comprising a hydroxyl polymer comprising at least a PVOH hydroxyl
polymer; [0016] b. polymer processing the PVOH polymer melt
composition to form a polymeric structure in fiber form; and [0017]
c. incorporating the polymeric structure in fiber form into a
fibrous structure; [0018] wherein the fibrous structure exhibits a
stretch at peak load of at least about 5% and/or at least about 8%
and/or at least about 10% and/or a stretch at failure load of at
least about 10% and/or at least about 13% and/or at least about
20%, is provided.
[0019] In even yet another aspect of the present invention, a
fibrous structure comprising two or more fibers at least one of
which comprises a polymeric structure in fiber form, wherein the
fibrous structure comprises a first region comprising associated
fibers and a second region comprising non-associated fibers, is
provided.
[0020] In still yet another aspect of the present invention, a
fibrous product comprising one or more fibrous structures
comprising a first region comprising associated fibers and a second
region comprising non-associated fibers, is provided.
[0021] In even still yet another aspect of the present invention, a
method for making a fibrous structure, the method comprising the
steps of: [0022] a. providing a fibrous structure comprising two or
more fibers at least one of which comprises a polymeric structure
in fiber form; and [0023] b. associating the two or more fibers
with each other such that a fibrous structure comprising a first
region comprising associated fibers and a second region comprising
non-associated fibers is formed, is provided.
[0024] Accordingly, the present invention provides a polymeric
structure, a fibrous structure comprising such a polymeric
structure in fiber form, a fibrous product comprising one or more
such fibrous structures, method for making such a polymeric
structure, method for making such a fibrous structure comprising a
polymeric structure in fiber form and a polymeric structure in
fiber form produced by such a method.
BRIEF DESCRIPTION OF DRAWINGS
[0025] FIG. 1 is a schematic illustration of a method for making a
polymeric structure in accordance with the present invention.
[0026] FIG. 2 is a schematic illustration of a camera set-up
suitable for use in the Lint/Pilling Test Method described
herein.
DETAILED DESCRIPTION OF THE INVENTION
Definitions
[0027] "Polymeric structure" as used herein means any physical
structure produced by polymer processing the PVOH polymer melt
composition of the present invention. Nonlimiting examples of such
polymeric structures include fibers, films and foams. Such
polymeric structures, especially when in fiber form, may be used,
optionally along with other physical structures such as cellulosic
fibers and thermoplastic water-insoluble polymer fibers, to form
fibrous structures. Preferably the polymeric structure of the
present invention as a whole has no melting point or in other words
the polymeric structure is a non-thermoplastic polymeric structure.
It is also desirable that the polymeric structure of the present
invention be substantially homogeneous.
[0028] "Fail Stretch" as used herein is defined by the following
formula:
Length of Polymeric Structure FL - Length of Polymeric Structure I
Length of Polymeric Structure I .times. 100 % ##EQU00001##
wherein: Length of Polymeric Structure.sub.FL is the length of the
polymeric structure at failure load; Length of Polymeric
Structure.sub.I is the initial length of the polymeric structure
prior to stretching.
[0029] "Peak Stretch" as used herein is defined by the following
formula:
Length of Polymeric Structure PL - Length of Polymeric Structure I
Length of Polymeric Structure I .times. 100 % ##EQU00002##
wherein: Length of Polymeric Structure.sub.PL is the length of the
polymeric structure at peak load; Length of Polymeric
Structure.sub.I is the initial length of the polymeric structure
prior to stretching.
[0030] The Strength of the Polymeric Structure is determined by
measuring a polymeric structure's Total Dry Tensile Strength (both
MD and CD) or "TDT". TDT or Stretch is measured by providing one
(1) inch by five (5) inch (2.5 cm.times.12.7 cm) strips of
polymeric structure and/or fibrous product comprising such
polymeric structure in need of testing. Each strip is placed on an
electronic tensile tester Model 1122 commercially available from
Instron Corp., Canton, Mass. The crosshead speed of the tensile
tester is 2.0 inches per minute (about 5.1 cm/minute) and the gauge
length is 1.0 inch (about 2.54 cm). The tensile tester calculates
the stretch at Peak Load and the stretch at Failure Load.
Basically, the tensile tester calculates the stretches via the
formulae described above. The Stretch at Peak Load, as used herein,
is the average of the Stretch at Peak Load for MD and CD. The
Stretch at Failure Load, as used herein, is the average of the
Stretch at Failure Load for MD and CD.
[0031] "Machine direction" (or MD) is the direction parallel to the
flow of the polymeric structure being made through the
manufacturing equipment.
[0032] "Cross machine direction" (or CD) is the direction
perpendicular to the machine direction and parallel to the general
plane of the polymeric structure.
[0033] "Fiber" as used herein means a slender, thin, and highly
flexible object having a major axis which is very long, compared to
the fiber's two mutually-orthogonal axes that are perpendicular to
the major axis. Preferably, an aspect ratio of the major's axis
length to an equivalent diameter of the fiber's cross-section
perpendicular to the major axis is greater than 100/1, more
specifically greater than 500/1, and still more specifically
greater than 1000/1, and even more specifically, greater than
5000/1.
[0034] The fibers of the present invention may be continuous or
substantially continuous. A fiber is continuous if it extends 100%
of the MD length of the fibrous structure and/or fibrous product
made therefrom. In one embodiment, a fiber is substantially
continuous if it extends greater than about 30% and/or greater than
about 50% and/or greater than about 70% of the MD length of the
fibrous structure and/or fibrous product made therefrom.
[0035] The fiber can have a fiber diameter as determined by the
Fiber Diameter Test Method described herein of less than about 50
microns and/or less than about 20 microns and/or less than about 10
microns and/or less than about 8 microns and/or less than about 6
microns.
[0036] The polymeric structures of the present invention,
especially fibers of the present invention, may be produced by
crosslinking hydroxyl polymers together. In one embodiment, the
polymeric structure, especially in fiber form, formed as a result
of the crosslinking, as a whole, exhibits no melting point. In
other words, it degrades before melting. Nonlimiting examples of a
suitable crosslinking system for achieving crosslinking comprises a
crosslinking agent and optionally a crosslinking facilitator,
wherein the hydroxyl polymer is crosslinked by the crosslinking
agent.
[0037] The fibers comprising a hydroxyl polymer may include melt
spun fibers, dry 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.
[0038] In another embodiment, the fibers comprising a hydroxyl
polymer may include a multiconstituent fiber, such as a
multicomponent fiber, comprising a hydroxyl polymer of the present
invention along with a thermoplastic, water-insoluble polymer. A
multicomponent fiber, as used herein, means a fiber having more
than one separate part in spatial relationship to one another.
Multicomponent fibers include bicomponent fibers, which are defined
as fibers having two separate parts in a spatial relationship to
one another. The different components of multicomponent fibers can
be arranged in substantially distinct regions across the
cross-section of the fiber and extend continuously along the length
of the fiber.
[0039] A nonlimiting example of such a multicomponent fiber,
specifically a bicomponent fiber, is a bicomponent fiber in which
the hydroxyl polymer represents the core of the fiber and the
thermoplastic, water-insoluble polymer represents the sheath, which
surrounds or substantially surrounds the core of the fiber. The
polymer melt composition from which such a fiber is derived
preferably includes the hydroxyl polymer and the thermoplastic,
water-insoluble polymer.
[0040] In another multicomponent, especially bicomponent, fiber
embodiment, the sheath may comprise a hydroxyl polymer and a
crosslinking system having a crosslinking agent, and the core may
comprise a hydroxyl polymer and a crosslinking system having a
crosslinking agent. With respect to the sheath and core, the
hydroxyl polymer may be the same or different and the crosslinking
agent may be the same or different. Further, the level of hydroxyl
polymer may be the same or different and the level of crosslinking
agent may be the same or different.
[0041] One or more substantially continuous or continuous fibers of
the present invention may be incorporated into a fibrous structure,
such as a web. Such a fibrous structure may ultimately be
incorporated into a commercial product, such as a single- or
multi-ply fibrous 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.
[0042] "Ply" or "Plies" as used herein means a single fibrous
structure optionally to be disposed in a substantially contiguous,
face-to-face relationship with other plies, forming a multi-ply
fibrous product. It is also contemplated that a single fibrous
structure can effectively form two "plies" or multiple "plies", for
example, by being folded on itself. Ply or plies can also exist as
films or other polymeric structures.
[0043] "Basis Weight" as used herein is the weight per unit area of
a sample reported in lbs/3000 ft.sup.2 or g/m.sup.2.
[0044] Basis weight is measured by preparing one or more samples of
a certain area (m.sup.2) and weighing the sample(s) of a fibrous
structure and/or film according to the present invention on a top
loading balance with a minimum resolution of 0.01 g. The balance is
protected from air drafts and other disturbances using a draft
shield. Weights are recorded when the readings on the balance
become constant. The average weight (g) is calculated and the
average area of the samples (m.sup.2). The basis weight (g/m.sup.2)
is calculated by dividing the average weight (g) by the average
area of the samples (m.sup.2).
[0045] "Caliper" as used herein means the macroscopic thickness of
a fibrous structure, fibrous product or film. Caliper of a fibrous
structure, fibrous product or film according to the present
invention is determined by cutting a sample of the fibrous
structure, fibrous product or film such that it is larger in size
than a load foot loading surface where the load foot loading
surface has a circular surface area of about 3.14 in.sup.2. The
sample is confined between a horizontal flat surface and the load
foot loading surface. The load foot loading surface applies a
confining pressure to the sample of 15.5 g/cm.sup.2 (about 0.21
psi). The caliper is the resulting gap between the flat surface and
the load foot loading surface. Such measurements can be obtained on
a VIR Electronic Thickness Tester Model II available from
Thwing-Albert Instrument Company, Philadelphia, Pa. The caliper
measurement is repeated and recorded at least five (5) times so
that an average caliper can be calculated. The result is reported
in millimeters. In one embodiment of the present invention, the
fibrous structure exhibits an average caliper that is less than its
bulk caliper
[0046] "Apparent Density" or "Density" as used herein means the
basis weight of a sample divided by the caliper with appropriate
conversions incorporated therein. Apparent density used herein has
the units g/cm.sup.3.
[0047] "Weight average molecular weight" as used herein means the
weight average molecular weight as determined using gel permeation
chromatography according to the protocol found in Colloids and
Surfaces A. Physico Chemical & Engineering Aspects, Vol. 162,
2000, pg. 107-121.
[0048] "Plasticity" as used herein means at least that a polymeric
structure and/or fibrous structure exhibits a capability of being
shaped, molded and/or formed.
[0049] "Fibrous product" as used includes but is not limited to a
wiping implement for post-urinary and post-bowel movement cleaning
(toilet tissue), for otorhinolaryngological discharges (facial
tissue), and multi-functional absorbent and cleaning uses
(absorbent towels).
[0050] "Lint" and/or "Pills" as used herein means discrete pieces
of a polymeric structure, especially a fibrous structure and/or
fibrous product that become separated from the original polymeric
structure and/or fibrous structure and/or fibrous product typically
during use.
[0051] Traditional toilet tissue and toweling are comprised
essentially of short cellulose fibers. During the wiping
process--both wet and dry, these short fibers can detach from the
structure and become evident as lint or pills. The present
invention employs essentially continuous fibers vs. traditional
discrete, short cellulose fibers. Generally speaking, fibrous
structures of the present invention resist linting vs. their
cellulose cousins due to the continuous nature of the fibers.
Furthermore, fibrous structures of the present invention will
resist pilling vs. their cellulose cousins provided the bonding and
fiber strength and stretch are sufficient enough to prevent free
fiber breakage and entanglement with adjacent fibers during the
wiping process.
[0052] "Intensive Properties" and/or "Values of Common Intensive
Properties" as used herein means density, basis weight, caliper,
substrate thickness, elevation, opacity, crepe frequency, and any
combination thereof. The fibrous structures of the present
invention may comprise two or more regions that exhibit different
values of common intensive properties relative to each other. In
other words, a fibrous structure of the present invention may
comprise one region having a first opacity value and a second
region having a second opacity value different from the first
opacity value. Such regions may be continuous, substantially
continuous and/or discontinuous.
[0053] "Dry spinning" and/or "Solvent spinning" as used herein
means that polymeric structures are not spun into a coagulating
bath, unlike wet spinning.
[0054] "Associated" as used herein with respect to fibers means
that two or more discrete fibers are in close proximity to one
another at one or more positions along the fiber lengths, but less
than their entire lengths such that one fiber influences the
actions of the other fiber. Nonlimiting examples of means for
associating fibers include bonding together (adhesively and/or
chemically and/or electrostatically) and/or fusing together such
that at the point of association one fiber unit is formed.
[0055] "Non-associated" as used herein with respect to fibers means
that the fibers are not associated as defined herein.
METHODS OF THE PRESENT INVENTION
[0056] The methods of the present invention relate to producing
polymeric structures such as fibers, films or foam from a PVOH
polymer melt composition comprising a hydroxyl polymer comprising
at least a PVOH hydroxyl polymer and/or to producing fibrous
structures comprising a polymeric structure in fiber form.
[0057] In one nonlimiting embodiment of a method in accordance with
the present invention, as described below, a PVOH polymer melt
composition is polymer processed to form a fiber. The fiber can
then be incorporated into a fibrous structure.
[0058] Any suitable process known to those skilled in the art can
be used to produce the polymer melt composition and/or to polymer
process the polymer melt composition and/or to produce the
polymeric structure of the present invention. Nonlimiting examples
of such processes are described in published applications: EP 1 035
239, EP 1 132 427, EP 1 217 106, EP 1 217 107, WO 03/066942 and
U.S. Pat. No. 5,342,225.
A. PVOH Polymer Melt Composition
[0059] "PVOH polymer melt composition" as used herein means a
composition that comprises a melt processed hydroxyl polymer
comprising at least a melt processed PVOH hydroxyl polymer. "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
and/or with or without the presence of a pH adjusting agent. 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 (all melt processing
operations/processes), and in this condition may be shaped as
desired.
[0060] The PVOH polymer melt composition may be a composite
containing a blend of different polymers, wherein at least one is a
melt processed hydroxyl polymer according to the present invention,
and/or fillers both inorganic and organic, and/or fibers and/or
foaming agents. In one embodiment, the PVOH polymer melt
composition comprises two or more different melt processed hydroxyl
polymers according to the present invention. As used herein,
"different melt processed hydroxyl polymers" includes without
limitation, melt processed hydroxyl polymers that contain at least
one different moiety relative to another melt processed hydroxyl
polymer and/or melt processed hydroxyl polymers that are members of
different chemical classes (e.g., PVOH versus starch versus
chitosan).
[0061] The PVOH polymer melt composition may already be formed or a
melt processing step may need to be performed to convert a raw
material hydroxyl polymer into a melt processed hydroxyl polymer,
thus producing the PVOH polymer melt composition. Any suitable melt
processing step known in the art may be used to convert the raw
material hydroxyl polymer into the melt processed hydroxyl
polymer.
[0062] The PVOH polymer melt composition may comprise a) from about
30% and/or 40% and/or 45% and/or 50% to about 75% and/or 80% and/or
85% and/or 90% and/or 99.5% by weight of the PVOH polymer melt
composition of a hydroxyl polymer comprising at least a PVOH
hydroxyl polymer; b) a crosslinking system comprising from about
0.1% to about 10% by weight of the PVOH polymer melt composition of
a crosslinking agent; and c) from about 0% and/or 10% and/or 15%
and/or 20% to about 50% and/or 55% and/or 60% and/or 70% by weight
of the PVOH polymer melt composition of an external plasticizer
(e.g., water).
B. Polymer Processing
[0063] "Polymer processing" as used herein means any operation
and/or process by which a polymeric structure comprising a
processed hydroxyl polymer is formed from a PVOH polymer melt
composition. Nonlimiting examples of polymer processing operations
include extrusion, molding and/or fiber spinning. Extrusion and
molding (either casting or blown), typically produce films, sheets
and various profile extrusions. Molding may include injection
molding, blown molding and/or compression molding. Fiber spinning
may include spun bonding, melt blowing, continuous fiber producing
and/or tow fiber producing.
[0064] 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
[0065] The PVOH polymer melt composition can be subjected to one or
more polymer processing operations such that the PVOH polymer melt
composition is processed into a polymeric structure such as a
fiber, film or foam comprising the hydroxyl polymer and a
crosslinking system according to the present invention.
Post Treatment of Polymeric Structures
[0066] Once the PVOH polymer melt composition has been processed
into a polymeric structure, such as a fiber, a film, a foam, or a
plurality of fibers that together form a fibrous structure, the
structure may be subjected to post-treatment curing and/or
differential densification.
[0067] Curing of the structure may occur before and/or after
densifying a region of the structure. Preferably curing occurs
before densifying a region of the structure.
[0068] In one embodiment, the structure produced via a polymer
processing operation may be cured at a curing temperature of from
about 110.degree. C. to about 200.degree. C. and/or from about
120.degree. C. to about 195.degree. C. and/or from about
130.degree. C. to about 185.degree. 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 prior to densifying a region of the
structure. Alternative curing methods may include radiation methods
such as UV, e-beam, IR and other temperature-raising methods.
[0069] Further, the 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.
[0070] The structure prior to being densified may comprise
non-associated substantially continuous or continuous fibers
comprising a hydroxyl polymer. Further, the substantially
continuous or continuous fibers may comprise crosslinked hydroxyl
polymers. Even further yet, the structure may comprise from about
10% and/or from about 15% and/or from about 20% to about 60% and/or
to about 50% and/or to about 40% by weight of the structure of
moisture.
[0071] Before differential densification, the structure may be in
the form of a non-associated structure, especially if the structure
comprises one or more fibers. The structure in such
non-differential densified form is inferior in intensive
properties, especially tensile (stretch), than its wood-based
cellulosic fibrous structure cousins.
[0072] Accordingly, the structure of the present invention may be
subjected to differential densification via a differentially
densifying operation. Such differential densification can occur
on-line in a continuous process that includes forming the structure
and then differentially densifying the structure. Alternatively,
the differential densification can occur off-line in a
non-continuous process.
[0073] Any differentially densifying process known to those of
ordinary skill in the art may be used to differentially densify the
structures of the present invention.
[0074] As a result of differential densification, the structure
comprises two or more regions that exhibit different densities as
compared to the other.
[0075] In one embodiment, the differentially densifying process
comprises the step of imparting plasticity into a structure in need
of differential densification such that regions of different
density can be created in the structure. In other words, the
differentially densifying process comprises the step of imparting
plasticity into a structure in need of differential densification
such that a pattern can be created in the structure. The pattern is
designed to impart regions of different densities in the structure.
Exposing the structure in need of differential densification to a
humid environment, such as from about 20% to about 95% and/or from
about 40% to about 90% and/or from about 50% to about 85% and/or
from about 65% to about 80% relative humidity for a sufficient
time, such as at least 1 second and/or at least 3 seconds and/or at
least 5 seconds, can impart sufficient plasticity to the structure
to permit differential densification to be created in the
structure.
[0076] In one embodiment, the differentially densifying process
comprises subjecting the structure to a patterned roller such that
the pattern on the roller is imparted to the structure, thus
causing the structure to become differentially densified.
[0077] In another embodiment, the differentially densifying process
comprises contacting the structure, which is in contact with a
patterned belt/fabric with pressure from a smooth roller thus
imparting the pattern of the belt/fabric to the structure causing
the structure to become differentially densified.
[0078] The differentially densifying of a structure in accordance
with the present invention preferably occurs after the structure
has been formed, not concurrent with the formation of the
structure.
[0079] The structure of the present invention may be differentially
densified more than once. For example, a structure may be
differentially densified, then cured, and then differentially
densified again according to the present invention.
[0080] In another embodiment, the structure may comprise two or
more "plies" of structure which can then be differentially
densified as a multi-ply structure.
[0081] The structure may be differentially densified, then
differential densified again and then cured.
[0082] Alternatively, the structure of the present invention may be
cured, then differentially densified according to the present
invention
[0083] Curing of the structure, in accordance with the present
invention, may occur at any point in time relative to any
differentially densifying process. It may occur before (preferably
immediately before), after (preferably immediately after), before
and after (preferably immediately before and immediately after), or
not at all.
[0084] The differentially densifying process may occur once or a
plurality of times.
[0085] Ultrasonics may also be used to aid in differential
densification of the structure, especially in conjunction with a
patterned roller. The ultrasonics may be generated by any suitable
ultrasonic device. For example, a horn or ultrasonic wave generator
that is capable of imparting energy to the structure such that the
structure deforms according to the pattern on the patterned roller
can be used.
[0086] In still another embodiment, the step of differentially
densifying comprises contacting the fibrous structure with a
structure-imparting element comprising a pattern in the presence of
humidity and applying a force to the fibrous structure and/or
structure-imparting element such that the fibrous structure takes
the shape of the pattern on the structure-imparting element to form
a differential densified polymeric structure.
[0087] In yet still another embodiment, step of differentially
densifying the fibrous structure comprises sandwiching the fibrous
structure between two belts in the presence of humidity, wherein at
least one of the belts is a structured belt comprising a pattern
and applying a force to at least one of the belts such that the
fibrous structure takes the shape of the pattern on the structured
belt to form a differential densified polymeric structure.
[0088] A nonlimiting example of a differential densification
process for differentially densifying a structure in accordance
with the present invention is provided below.
Differential Densification Example
[0089] A PVOH polymer melt composition containing approximately 40%
water is extruded from a twin screw extruder. Crosslinker and other
additives are introduced into the PVOH polymer melt composition and
mixed via in-line static mixers. The PVOH polymer melt composition
with additives is then pumped to a meltblown style spinnerette
where fibers are extruded and attenuated into fine fibers.
Crosslinkers and additives used are urea glyoxal adduct ("UGA"),
ammonium sulfate, and acrylic latex. Total additives are typically
10% or less on a wt % basis of dry hydroxyl polymer. The attenuated
fibers are dried with entrained hot air and deposited on a
collector belt. The collector belt is typically set at 22-25'' from
the end of the spinnerette and the structure, a fibrous structure,
formed on the collector belts is a non-associated fibrous
structure.
[0090] FIG. 1 schematically illustrates one embodiment of a
differential densification operation 10. After forming, the
non-associated fibrous structure 12 is subjected to an
environmentally controlled humid environment, such as in a humidity
chamber 14. Typical relative humidity range is 70-78%. As the
fibrous structure 12 is conveyed through the chamber 14, the fine
starch fibers are plasticized, allowing differential densification
to be possible. Upon exiting the chamber 14, the plasticized
fibrous structure 12' is passed through a patterned nip 16 to
associate regions of the fibrous structure, thus producing an
associated fibrous structure 12''. The associated fibrous structure
regions 18 correspond to the pattern utilized on either the carrier
belt (not shown) or the roller itself 20. One patterned belt
employed has been a square weave open mesh belt, available from
Albany International Inc and known as style "Filtratech 10". Nip
pressure varies depending on the pattern employed, but is typically
in the 200-300 pli range. The fibers present in the fibrous
structure are now associated and the fibrous structure exhibits
excellent handling properties. After a curing period for the
crosslinking system and additives to react, the associated fibrous
structure exhibits dry and wet properties acceptable for disposable
fibrous products and can be used as a variety of disposable
implements, especially toilet tissue or toweling.
Hydroxyl Polymers
[0091] Hydroxyl polymers in accordance with the present invention
include any hydroxyl-containing polymer that can be incorporated
into a polymeric structure of the present invention, preferably in
the form of a fiber.
[0092] In one embodiment, 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.
[0093] Nonlimiting examples of hydroxyl polymers in accordance with
the present invention include polyols, such as polyvinyl alcohol,
polyvinyl alcohol derivatives, starch, starch derivatives,
chitosan, chitosan derivatives, cellulose derivatives such as
cellulose ether and ester derivatives, gums, arabinans, galactans,
proteins and various other polysaccharides and mixtures
thereof.
[0094] The hydroxyl polymer preferably has a weight average
molecular weight of from about 10,000 to about 40,000,000 g/mol.
Higher and lower molecular weight hydroxyl polymers may be used in
combination with hydroxyl polymers having the preferred weight
average molecular weight.
[0095] Well known modifications of natural starches include
chemical modifications and/or enzymatic modifications. For example,
the natural starch can be acid-thinned, hydroxy-ethylated or
hydroxy-propylated or oxidized.
[0096] "Polysaccharides" herein means natural polysaccharides and
polysaccharide derivatives or modified polysaccharides. Suitable
polysaccharides include, but are not limited to, gums, arabinans,
galactans and mixtures thereof.
Crosslinking System
[0097] The crosslinking system of the present invention may further
comprise, in addition to the crosslinking agent, a crosslinking
facilitator.
[0098] "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 PVOH
polymer melt composition does not undergo premature crosslinking
("unacceptable" crosslinking) as determined according to the Shear
Viscosity Change Test Method described herein.
[0099] When a crosslinking agent in accordance with the present
invention is in its activated state, the hydroxyl polymer present
in the polymeric structure may, and preferably does, undergo
acceptable crosslinking via the crosslinking agent as determined
according to the Initial Total Wet Tensile Test Method described
herein.
[0100] 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.
[0101] A crosslinking system may be present in the PVOH polymer
melt composition and/or may be added to the PVOH polymer melt
composition before polymer processing of the PVOH polymer melt
composition.
[0102] Nonlimiting examples of suitable crosslinking facilitators
include acids having a pKa of between about 0 and about 6 and/or
between about 1.5 and about 6 and/or between about 2 and about 6 or
salts thereof. The crosslinking facilitators may be Bronsted Acids
and/or salts thereof, preferably ammonium salts thereof.
[0103] 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.
[0104] Nonlimiting examples of suitable crosslinking facilitators
include acetic acid, benzoic acid, citric acid, formic acid,
glycolic acid, lactic acid, maleic acid, phthalic acid, phosphoric
acid, sulfuric acid, succinic acid and mixtures thereof and/or
their salts, preferably their ammonium salts, such as ammonium
glycolate, ammonium citrate and ammonium sulfate.
[0105] Nonlimiting examples of suitable crosslinking agents include
polycarboxylic acids, imidazolidinones and other compounds
resulting from alkyl substituted or unsubstituted cyclic adducts of
glyoxal with ureas, thioureas, guanidines, methylene diamides, and
methylene dicarbamates and derivatives thereof and mixtures
thereof.
Test Methods
[0106] 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 73.degree. F..+-.4.degree. F. (about
23.degree. C..+-.2.2.degree. C.) and a relative humidity of
50%.+-.10% for 24 hours prior to the test. Further, all tests are
conducted in such conditioned room. Tested samples and felts should
be subjected to 73.degree. F..+-.4.degree. F. (about 23.degree.
C..+-.2.2.degree. C.) and a relative humidity of 50%.+-.10% for 24
hours prior to capturing images.
A. Lint/Pilling Test Method
[0107] i. Sample Preparation
[0108] Prior to the testing, fibrous product samples,
4.5''.times.16'' strips of fibrous product, are conditioned
according to Tappi Method #T4020M-88.
[0109] Each fibrous product sample (6 samples if testing both
sides, 3 samples if testing a single side) is first prepared by
removing and discarding any pieces of the sample which might have
been abraded in handling. For fibrous products formed from multiple
plies of fibrous structure, this test can be used to make a lint
measurement on the multi-ply fibrous product, or, if the plies can
be separated without damaging the fibrous product, a measurement
can be taken on the individual plies making up the fibrous product.
If a given sample differs from surface to surface, it is necessary
to test both surfaces and average the scores in order to arrive at
a composite lint score. In some cases, fibrous products are made
from multiple-plies of fibrous structures such that the facing-out
surfaces are identical, in which case it is only necessary to test
one surface.
[0110] Each sample is folded upon itself to make a 4.5''
CD.times.4'' MD sample. For two-surface testing, make up 3 (4.5''
CD.times.4'' MD) samples with a first surface "out" and 3 (4.5''
CD.times.4'' MD) samples with the second surface "out". Keep track
of which samples are first surface "out" and which are second
surface "out".
[0111] Obtain a 30''.times.40'' piece of Crescent #300 cardboard
from Cordage Inc. (800 E. Ross Road, Cincinnati, Ohio, 45217).
Using a paper cutter, cut out six pieces of cardboard of dimensions
of 2.5''.times.6''. Puncture two holes into each of the six pieces
of cardboard by forcing the cardboard onto the hold down pins of
the Sutherland Rub tester.
[0112] Center and carefully place each of the cardboard pieces on
top of the six (two surface testing) or three (single surface
testing) previously folded samples. Make sure the 6'' dimension of
the cardboard is running parallel to the machine direction (MD) of
each of the samples.
[0113] Fold one edge of the exposed portion of the sample onto the
back of the cardboard. Secure this edge to the cardboard with
adhesive tape obtained from 3M Inc. (3/4'' wide Scotch Brand, St.
Paul, Minn.). Carefully grasp the other over-hanging tissue edge
and snugly fold it over onto the back of the cardboard. While
maintaining a snug fit of the sample onto the cardboard, tape this
second edge to the back of the cardboard. Repeat this procedure for
each sample.
[0114] Turn over each sample and tape the cross direction edges of
the sample to the cardboard for the dry lint/pilling test. One half
of the adhesive tape should contact the sample while the other half
is adhering to the cardboard. Repeat this procedure for each of the
samples. If the sample breaks, tears, or becomes frayed at any time
during the course of this sample preparation procedure, discard and
make up a new sample with a sample strip.
[0115] For the wet lint/pilling test, tape the leading cross
direction edge of the sample to the cardboard and a table top upon
which the sample is placed. Position the sample on the cardboard
such that the trailing edge of the sample is approximately 1/4''
from the cardboard edge. The leading edge of the sample is taped to
the cardboard and table top such that the opposite (trailing) edge
of the cardboard is positioned at the edge of the table top.
[0116] There will now be 3 first surface "out" samples on cardboard
and (optionally) 3 second surface "out" samples on cardboard.
ii. Felt Preparation
[0117] Obtain a 30''.times.40'' piece of Crescent #300 cardboard
from Cordage Inc. (800 E. Ross Road, Cincinnati, Ohio, 45217).
Using a paper cutter, cut out six pieces of cardboard of dimensions
of 2.25''.times.7.25''. Draw two lines parallel to the short
dimension and down 1.125'' from the top and bottom most edges on
the white side of the cardboard. Carefully score the length of the
line with a razor blade using a straight edge as a guide. Score it
to a depth about half way through the thickness of the sheet. This
scoring allows the felt/cardboard combination to fit tightly around
the weight of the Sutherland Rub tester. Draw an arrow running
parallel to the long dimension of the cardboard on this scored side
of the cardboard.
[0118] Cut six pieces of a black felt (F-55 or equivalent from New
England Gasket, 550 Broad Street, Bristol, Conn. 06010) to the
dimensions of 2.25''.times.8.5''.times.0.0625''. Place the felt on
top of the unscored, green side of the cardboard such that the long
edges of both the felt and cardboard are parallel and in alignment.
Also allow about 0.5'' of the black felt to overhang the top and
bottom most edges of the cardboard. Snugly fold over both
overhanging felt edges onto the backside of the cardboard with
Scotch brand tape, alternatively, the felt can be snugly fit to the
cardboard when attaching the felt/cardboard combination to the
weight, discussed below. Prepare a total of six of these
felt/cardboard combinations.
[0119] For the wet lint/pilling test, the felt/cardboard
combination includes a 9'' strip of Scotch brand tape (0.75'' wide)
that is placed along each edge of the felt (parallel to the long
side of the felt) on the felt side that will be contacting the
sample. The untapped felt between the two tape strips has a width
between 18-21 mm. Three marks are placed on one of the strips of
tape at 0, 4 and 8 centimeters from the trailing back edge of the
felt.
[0120] All samples must be run with the same lot of felt.
iii. Felt/Cardboard/Weight Component
[0121] The felt/cardboard combination is associated with a weight.
The weight may include a clamping device to attach the
felt/cardboard combination to the weight. The weight and any
clamping device totals five (5) pounds. The weight is available
from Danilee Company, San Antonio, Tex. The weight has an effective
contact area of 25.81 cm.sup.2 (4 in.sup.2) and provides a contact
pressure of about 1.25 psi.
iv. Conducting Dry Lint/Pills Test
[0122] The amount of dry lint and/or dry pills generated from a
fibrous product according to the present invention is determined
with a Sutherland Rub Tester (available from Danilee Company, San
Antonio, Tex.). This tester uses a motor to rub a
felt/cardboard/weight component 5 times (back and forth) over the
fibrous product, while the fibrous product is restrained in a
stationary position. The gray value of the felt is measured before
and after the rub test. The difference between these two gray
values is then used to calculate a dry lint score and/or a dry pill
score.
[0123] The Sutherland Rub Tester must first be calibrated prior to
use. First, turn on the Sutherland Rub Tester pressing the "reset"
button. Set the tester to run 5 strokes at the lower of the two
speeds. One stroke is a single and complete forward and reverse
motion of the weight. The end of the rubbing block should be in the
position closest to the operator at the beginning and at the end of
each test.
[0124] Prepare a calibration sample on cardboard as described
above. In addition, prepare a calibration felt on cardboard as
described above. Both of these calibration articles will be used
for calibration of the instrument and will not be used in the
acquisition of data for the actual samples.
[0125] Place the calibration sample/cardboard combination on the
base plate of the tester by slipping the holes in the board over
the hold-down pins. The hold-down pins prevent the sample from
moving during the test. Clip the calibration felt/cardboard
combination onto the weight component described above with the
cardboard side contacting the pads of the weight. Make sure the
calibration felt/cardboard combination is resting flat against the
weight. Hook this weight onto the tester arm of the Sutherland Rub
Tester gently placing it on top of the calibration sample/cardboard
combination. The calibration felt must rest level on the
calibration sample and must be in 100% contact with the calibration
sample surface. Activate the Sutherland Rub Tester by pressing the
"start" button.
[0126] Keep a count of the number of strokes and observe and make a
mental note of the starting and stopping position of the
calibration felt covered weight in relationship to the calibration
sample. If the total number of strokes is five and if the position
of the calibration felt covered weight is the same at the end as it
was in the beginning of the test, the tester is calibrated and
ready to use. If the total number of strokes is not five or if the
start and end positions of the calibration felt covered weight are
different, then instrument may require servicing and/or
recalibration. During the actual testing of samples, monitor and
observe the stroke count and the starting and ending points of the
felt covered weight.
v. Conducting Wet Lint/Pills Test
[0127] Wet lint/pills are determined by pulling, during one pass, a
wetted felt/cardboard/weight component over a sample.
[0128] To wet the felt, pipet 0.6 ml of deionized water onto the
felt, distributing the water as evenly as possible between the 4
and 8 cm marks as represented on the tape attached to the felt.
Wait 10 seconds and then place the felt/cardboard/weight component
on the center of the sample. After 1 second, pull the
felt/cardboard/weight component by the leading edge horizontally
until the felt/cardboard/weight component is completely off the
table. Pull the weight in a manner to avoid placing any additional
force on the felt/cardboard/weight component other than the
horizontal pull force. The process of pulling the
felt/cardboard/weight component takes about 0.5 to 1.5 seconds. The
pulling process should occur as a substantially continuous or
continuous motion.
[0129] Carefully remove the felt/cardboard combination from the
felt/cardboard/weight component and allow to dry before capturing
the image. Then complete image analysis operations and calculations
on the felt and/or sample as described below.
vi. Image Capture
[0130] The images of the felt (untested), sample (untested) and
felt (tested) are captured using a Nikon Digital Camera (DIX) with
a Nikon Nikkor 24-85 mm f2.8-f4 D 1F AF lens (set to 85 mm maximum
zoom) and Nikon Capture software installed on an appropriate
computer. As schematically illustrated in FIG. 2, the camera 22
attached to a Kodak camera stand/lighting set-up (not shown) having
four incandescent lamps 24 (Polaroid MP-4 Land Camera model 44-22,
120 volt 150 watts each) that are directed at the felt 26
positioned 31 cm (12.2 inches) under the lens of the mounted
camera. The individual incandescent lamps 24 are positioned 27.94
cm (11 inches) apart. Each pair of incandescent lamps 24 are
positioned 88.9 cm (35 inches) apart. The incandescent lamps 24 are
positioned 56.83 cm (223/8 inches) above the felt 26. The camera is
connected via an appropriate cable to the computer. The camera
should be turned on in PC mode. Turn the button to macro on the
camera lens and flip the switch to the orange mark on the lens
base. Adjust zoom to its maximum level of 85 mm. Turn the auto
focus feature off. The Nikon Capture software needs to be in
operating order to capture images. The settings for the Nikon
Capture software are as follows: Exposure 1--manual exposure mode,
1/30 second shutter speed, f/6.3 aperture and 0EV exposure
compensation; Exposure 2--center weighted meter mode, ISO 125
sensitivity and incandescent white balance; Storage Settings--raw
(12 bit) data format, no compression, color image type and large
(3008.times.1960) image size; Mechanical--single shooting mode,
single area AF area mode, manual focus mode. A calibration
felt/cardboard combination is placed under the camera such that the
felt is centered under the lens of the camera. Manually focus the
camera on the felt. Take an image. The exposure difference needs to
be in the range of +2.5 to +2.75. Save the image as a TIFF file
(RGB) 8-bit. This image is used to perform the lint and pilling
calculations in the Image Analysis Software (Optimas 6.5).
Additional images of the sample/cardboard combination (untested)
and the felt/cardboard combination (tested) need to be captured in
the same manner. Also, an image of a known length standard (e.g., a
ruler) is taken (exposure difference does not matter for this
image).
vii. Image Analysis
[0131] The images captured are analyzed using Optimas 6.5 Image
Analysis software commercially available from Media Cybernetics,
L.P. Imaging set-up parameters, as listed herein, must be strictly
adhered to in order to have meaningfully comparative lint score and
pill score results.
[0132] First, an image with a known length standard (e.g., a ruler)
is brought up in Optimas, and used to calibrate length units
(millimeters in this case).
[0133] For dry testing, the tested felt image has a region of
interest (ROI area) of approximately 4510 mm.sup.2 (82 mm by 55
mm). The exact ROI area is measured and recorded (variable name:
ROI area).
[0134] For wet lint/pills testing, the tested felt image has 2
regions of interest (ROI areas):
1) the "wetted" region (between the 4-8 cm marks on the tape) and
2) the "dragged" region (between the 0-4 cm marks on the tape).
Each ROI area is approximately 608 mm.sup.2 (38 mm.times.16 mm).
The exact ROI area is measured and recorded (variable name: ROI
area).
[0135] An image of an untested black felt is opened, and the
average gray value (using the same ROI of the untested felt as the
tested felt) is measured and recorded (variable name: untested felt
Gray Value avg).
[0136] The tested sample luminance is saturated white (gray
value=255) and constant for samples of interest. If believed to be
different, measure the tested sample in a similar fashion as was
done for the untested felt, and record (variable name: untested
sample Gray Value avg).
[0137] The luminance threshold is calculated as the numerical
average of the untested felt Gray Value avg and untested sample
Gray Value avg.
[0138] The tested felt image is opened, and the ROI is created and
properly positioned such that the ROI surrounds the region of the
tested felt image to be analyzed. The average luminance for the ROI
is recorded (variable name: ROI Gray Value avg).
[0139] Pills are determined as follows: Optimas creates boundary
lines in the image where pixel luminance values cross through the
threshold value (e.g., if the threshold a Gray Value of 155,
boundary lines are created where pixels of higher and lower value
exist on either side. The criteria for determining a pill is that
it must have an average luminance greater than the threshold value,
and have a perimeter length greater than 2 mm for dry pills, and
0.5 mm for wet pills. The pill areas present in the ROI are summed
(variable name: Total Pilled Area).
viii. Calculations
[0140] The data obtained from the image analysis is used in the
following calculations:
Pilled Area %=Total Pilled Area/ROI area
Avg. Pill Size(Area Weighted Avg.,mm.sup.2)=.SIGMA.(Pilled
Areas).sup.2/Total Pilled Area
Lint Score=unpilled felt Gray Value avg-untested felt Gray Value
avg [0141] where: [0142] unpilled felt Gray Value avg=[(ROI Gray
Value avg*ROI area)-(pilled Gray Value avg*pilled area)]/Total
Unpilled Area [0143] Total Area Lint & Pill Score=ROI Gray
Value avg-untested felt Gray Value avg
[0144] By taking the average of the lint score on the first-side
surface and the second-side surface, the lint is obtained which is
applicable to that particular web or product. In other words, to
calculate lint score, the following formula is used:
Dry Lint Score = Dry Lint Score , 1 st side + Dry Lint Score , 2 nd
side 2 ##EQU00003## Dry Pill Area % = Dry Pill Area % , 1 st side +
Dry Pill Area % , 2 nd side 2 ##EQU00003.2## Wet Lint Score = [ (
Wetted Area Lint Score + Dragged Area Lint Score ) 1 st side + (
Wetted Area Lint Score + Dragged Area Lint Score ) 2 nd side ] 2
##EQU00003.3## Wet Pill Area % = [ ( Wetted Area Pill Area % +
Dragged Area Pill Are a % ) 1 st side + ( Wetted Area Pill Area % +
Dragged Area Pill Area % ) 2 nd side ] 2 ##EQU00003.4##
[0145] The fibrous structure and/or fibrous product of the present
invention may exhibit a wet lint score of less than about 25 and/or
a wet pill area of less than about 4% and/or a dry lint score of
less than about 50 and/or a dry lint pill area of less than about
5%.
B. Shear Viscosity of a Polymer Melt Composition Measurement Test
Method
[0146] The shear viscosity of a polymer melt composition of the
present invention is measured using a capillary rheometer,
Goettfert Rheograph 6000, manufactured by Goettfert USA of Rock
Hill S.C., 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.degree. 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.sup.-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
.eta.=K.gamma..sup.n-1,
wherein K is the material's viscosity constant, n is the material's
thinning index and .gamma. 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.sup.-1 using the power
law relation.
C. Shear Viscosity Change Test Method
[0147] Viscosities of three samples of a single polymer melt
composition of the present invention comprising a crosslinking
system to be tested are measured by filling three separate 60 cc
syringes; the shear viscosity of one sample is measured immediately
(initial shear viscosity) (it takes about 10 minutes from the time
the sample is placed in the rheometer to get the first reading)
according to the Shear Viscosity of a Polymer Melt Composition
Measurement Test Method. If the initial shear viscosity of the
first sample is not within the range of 5-8 PascalSeconds as
measured at a shear rate of 3,000 sec.sup.-1, then the single
polymer melt composition has to be adjusted such that the single
polymer melt composition's initial shear viscosity is within the
range of 5-8 PascalSeconds as measured at a shear rate of 3,000
sec.sup.-1 and this Shear Viscosity Change Test Method is then
repeated. Once the initial shear viscosity of the polymer melt
composition is within the range of 5-8 PascalSeconds as measured at
a shear rate of 3,000 sec.sup.-1, then the other two samples are
measured by the same test method after being stored in a convection
oven at 80.degree. C. for 70 and 130 minutes, respectively. The
shear viscosity at 3000 sec.sup.-1 for the 70 and 130 minute
samples is divided by the initial shear viscosity to obtain a
normalized shear viscosity change for the 70 and 130 minute
samples. If the normalized shear viscosity change is 1.3 times or
greater after 70 minutes and/or is 2 times or greater after 130
minutes, then the crosslinking system within the polymer melt
composition is unacceptable, and thus is not within the scope of
the present invention. However, if the normalized shear viscosity
change is less than 1.3 times after 70 minutes and/or (preferably
and) is less than 2 times after 130 minutes, then the crosslinking
system is not unacceptable, and thus it is within the scope of the
present invention with respect to polymer melt compositions
comprising the crosslinking system. Preferably, the crosslinking
system is acceptable with respect to polymeric structures derived
from polymer melt compositions comprising the crosslinking system
as determined by the Initial Total Wet Tensile Test Method.
[0148] Preferably, the normalized shear viscosity changes will be
less than 1.2 times after 70 minutes and/or less than 1.7 times
after 130 minutes; more preferably less than 1.1 times after 70
minutes and/or less than 1.4 times after 130 minutes.
D. Initial Total Wet Tensile Test Method
[0149] An electronic tensile tester (Thwing-Albert EJA Materials
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 and a gauge length of 1.0
inch (about 2.54 cm), using a strip of a polymeric structure of 1
inch wide and a length greater than 3 inches long. The two ends of
the strip are placed in the upper jaws of the machine, and the
center of the strip is placed around a stainless steel peg (0.5 cm
in diameter). After verifying that the strip is bent evenly around
the steel peg, the strip is soaked in distilled water at about
20.degree. C. for a soak time of 5 seconds before initiating
cross-head movement. The initial result of the test is an array of
data in the form load (grams force) versus crosshead displacement
(centimeters from starting point).
[0150] 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.degree. 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(g.sub.f/inch)=Peak
Load.sub.MD(g.sub.f)/2(inch.sub.width)+Peak
Load.sub.CD(g.sub.f)/2(inch.sub.width)
[0151] 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 36 g/m.sup.2, and is calculated as
follows:
Normalized{ITWT}={ITWT}*36(g/m.sup.2)/Basis Weight of
Strip(g/m.sup.2)
[0152] If the initial total wet tensile of a polymeric structure,
especially a fibrous structure and/or fibrous product comprising a
polymeric structure comprising a crosslinking system of the present
invention is at least 3 g/2.54 cm (3 g/in) and/or at least 4 g/2.54
cm (4 g/in) and/or at least 5 g/2.54 cm (5 g/in), then the
crosslinking system is acceptable and is, along with its
corresponding polymeric structure and/or fibrous structure and/or
fibrous product, within the scope of the present invention.
E. Fiber Diameter Test Method
[0153] A polymeric structure comprising fibers 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 10.times. 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 .mu.m/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.
[0154] 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. 6.3) 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
skeletonized 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.
[0155] All documents cited in the Detailed Description of the
Invention are, in relevant part, incorporated herein by reference;
the citation of any document is not to be considered as an
admission that it is prior art with respect to the present
invention.
[0156] 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 spirit and scope of the
invention. It is therefore intended to cover in the appended claims
all such changes and modifications that are within the scope of
this invention.
* * * * *