U.S. patent application number 13/916195 was filed with the patent office on 2013-10-17 for tampon including crosslinked cellulose fibers and improved synthesis processes for producing same.
The applicant listed for this patent is PLAYTEX PRODUCTS, LLC. Invention is credited to Eugene P. Dougherty, JR., Andrew Wilkes.
Application Number | 20130269890 13/916195 |
Document ID | / |
Family ID | 40637889 |
Filed Date | 2013-10-17 |
United States Patent
Application |
20130269890 |
Kind Code |
A1 |
Dougherty, JR.; Eugene P. ;
et al. |
October 17, 2013 |
TAMPON INCLUDING CROSSLINKED CELLULOSE FIBERS AND IMPROVED
SYNTHESIS PROCESSES FOR PRODUCING SAME
Abstract
A tampon pledget includes crosslinked cellulose fibers having
microstructures treated to provide improved absorbency and higher
wet strength. The fibers are treated with a crosslinking agent to
provide at least one of a molecular weight between crosslinks of
from about 10 to 200 and a degree of crystallinity of from about
25% to 75%. The crosslinking agent includes citric acid in 1% by
weight. The crosslinking agent may further include sodium
hypophosphite in 1% by weight. In another embodiment, the
crosslinking agent may be a difunctional agent including a glyoxal
or a glyoxal-derived resin. In still another embodiment, the
crosslinking agent is a multifunctional agent including a cyclic
urea, glyoxal, polyol condensate. The crosslinking agent is added
in an amount from about 0.001% to 20% by weight based on a total
weight of cellulose fibers to be treated and, preferably, in an
amount of about 5% by weight.
Inventors: |
Dougherty, JR.; Eugene P.;
(Camden-Wyoming, DE) ; Wilkes; Andrew; (Solihull,
GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
PLAYTEX PRODUCTS, LLC |
Shelton |
CT |
US |
|
|
Family ID: |
40637889 |
Appl. No.: |
13/916195 |
Filed: |
June 12, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12370687 |
Feb 13, 2009 |
|
|
|
13916195 |
|
|
|
|
61029073 |
Feb 15, 2008 |
|
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Current U.S.
Class: |
162/9 |
Current CPC
Class: |
D06M 13/432 20130101;
A61L 15/42 20130101; C08B 15/10 20130101; D06M 11/70 20130101; D01F
2/08 20130101; A61F 13/2082 20130101; A61F 13/2051 20130101; D06M
13/192 20130101; A61L 15/28 20130101; A61L 15/28 20130101; D06M
13/123 20130101; D06M 2101/06 20130101; D21C 9/005 20130101; C08L
1/02 20130101 |
Class at
Publication: |
162/9 |
International
Class: |
D21C 9/00 20060101
D21C009/00 |
Claims
1. A method for forming crosslinked cellulose fibers, comprising
selecting a cellulose raw material; steeping the raw material in a
sodium hydroxide immersion to provide alkali cellulose; pressing
the alkali cellulose; shredding the pressed cellulose; aging the
shredded cellulose; reacting the aged cellulose with carbon
disulphide to form cellulose xanthate; dissolving the cellulose
xanthate to form viscose; ripening the viscose; filtering the
ripened viscose to remove undissolved materials; degassing the
filtered viscose; spinning the degassed viscose through a spinneret
to form cellulose filaments; drawing the filaments to lengthen the
cellulose chains; purifying the drawn filaments; cutting the
purified filaments to form cellulose fibers; and post-crosslinking
by at least one of chemical or hydrothermal treatment; wherein for
a dry crosslinking formation, the method includes adding a
crosslinking agent to the pressing step, and for a wet crosslinking
formation, the method includes adding the crosslinking agent to at
least one of the dissolving and ripening steps.
2. The method for forming of claim 1, wherein the crosslinking
agent includes at least citric acid in one percent (1%) by weight
based on the total weight of cellulose fibers.
3. The method of forming of claim 2, wherein the crosslinking agent
further includes at least sodium hypophosphite in one percent (1%)
by weight based on the total weight of cellulose fibers.
4. The method of forming of claim 1, wherein the crosslinking agent
is comprised of a difunctional crosslinking agent.
5. The method of forming of claim 4, wherein the difunctional
crosslinking agent is comprised of at least one of glyoxal and a
glyoxal-derived resin.
6. The method of forming of claim 1, wherein the crosslinking agent
is comprised of a multifunctional crosslinking agent.
7. The method of forming of claim 6, wherein the multifunctional
crosslinking agent is comprised of a cyclic urea, glyoxal, polyol
condensate.
8. The method of forming of claim 1, wherein the crosslinking agent
is added in an amount from about a hundredth of one percent
(0.001%) to about twenty percent (20%) by weight based on a total
weight of cellulose fibers to be treated.
9. The method of forming of claim 1, wherein the crosslinking agent
is added in an amount of about five percent (5%) by weight based on
the total weight of cellulose fibers.
10. The method for forming of claim 1, further including expanding
a duration of the drawing step to further lengthen cellulose chains
and improve interchain hydrogen bonds to provide greater areas of
crystallinity.
11. The method for forming of claim 1, wherein said
post-crosslinking is by hydrothermal treatment.
12. The method for forming of claim 11, wherein said hydrothermal
treatment is carried out at a temperature of about 90 to about 150
degrees Celsius.
13. The method for forming of claim 11, wherein said hydrothermal
treatment is carried out at a temperature of about 100 to about 125
degrees Celsius.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This patent application is a divisional application of and
claims priority benefit to co-pending U.S. patent application Ser.
No. 12/370,687, filed Feb. 13, 2009, which claims priority benefit
under 35 U.S.C. .sctn.119(e) of U.S. Provisional Patent Application
Ser. No. 61/029,073, filed Feb. 15, 2008, the disclosure of both
applications are incorporated by reference herein in their
entireties.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates generally to absorbent articles such
as catamenial tampons and methods for making such tampons and, more
particularly, to tampon pledgets comprised of crosslinked cellulose
fibers formed using improved synthetic approaches.
[0004] 2. Description of the Related Art
[0005] A wide variety of configurations of absorbent catamenial
tampons are known in the art. Typically, commercially available
tampons are made from a tampon pledget that is compressed into a
generally cylindrical form having an insertion end and a withdrawal
end. A string is generally coupled to the withdrawal end to assist
in removing the tampon from the vaginal cavity after use. Before
compression, the tampon pledget is typically rolled, spirally
wound, folded or otherwise assembled as a rectangular pad of
absorbent material.
[0006] Many commercially available tampon pledgets are made of
cellulose fibers such as rayon. Rayon has many advantages for
tampon applications including, for example: it is absorbent;
generally recognized as safe and hygienic for use in the human
body; raw materials are reasonably low cost; it can be derived from
sustainable, natural sources (e.g., eucalyptus trees); and
manufacturing processes are well established and commercially
viable. Moreover, rayon can be easily blended with other fibers
such as, for example, cotton, to tailor properties toward
particular applications. However, problems still exist with the use
of rayon for tampons. For example, rayon was initially developed as
an "artificial silk" and used in apparel, home furnishing and in
the manufacture of tires. Rayon was also adapted for use in the
feminine care. The inventors have realized, however, that this
adaptation did not involve an in-depth effort to modify the
attributes of rayon to the special needs of feminine care. For
example, it appears that polymeric synthetic routes have not been
determined to optimize a cellulosic synthetic fiber to satisfy the
unique balance of properties required for feminine care. Rather,
improvements of commercial tampons to date have instead focused on
design changes and physical process changes seeking to, for
example, increase how much or how fast a tampon expands.
[0007] One conventional method for forming catamenial tampons
includes the use of bulking, crimping and texturing of a continuous
filament rayon yarn, wet cross-linking the yarn and twisting or
stretching yarn to produce a tampon. Such a forming method is said
to provide tampons exhibiting an increase in the volume of water
taken up per gram of fiber as well as an increase in wet diameter.
Perceived problems in this formation method include the use of
formaldehyde as a cross-linking agent; the use of rayon yarn rather
than nonwoven materials; and the fact that few, if any, analytical
measures, such as molecular weight and extent of crosslinking and
crystallinity, were employed to evaluate effectiveness and safety
of the formed tampons.
[0008] It is also known that more liquid could be held in an
absorbent if the stiffness of the fibers is increased by either
chemical or physical (e.g., compression) means. Increased stiffness
and, in particular, higher wet strength, decreases the tendency of
the fiber to draw together and thus maintain greater inter-fiber
capillary volumes in which the absorbed fluid could reside. In the
case of compressed absorbent materials, the dry modulus and dry
resilience must be taken into account. Maximum fluid holding
ability in compressed assemblies requires fibers with high wet
modulus, coupled with a low modulus and resilience in the dry
state. By this method, the desired dry compaction can be achieved
under the lowest possible forces of compression, without the
excessive forces that lead to permanent setting and fiber damage.
On contact with liquid, the fiber transitions from low to high
modulus rates. It is generally known that wet crosslinked rayon, a
fiber that has the requisite combination of dry and wet state
properties, provides a sixty-two percent (62%) increase by measure
of volume capacity at compressed bulk densities.
[0009] It is also known that crosslinked cellulosic fibers produce
absorbent products that wick and redistribute fluid better than
non-crosslinked cellulosic fibers due to enhanced wet bulk
properties. An inability of wetted cellulosic fibers in absorbent
products to further acquire and to distribute liquid to sites
remote from liquid intake may be attributed to the loss of fiber
bulk associated with liquid absorption. Further, crosslinked
cellulosic fibers generally have enhanced wet bulk compared to
non-crosslinked fibers. The enhanced bulk is a consequence of the
stiffness, twist, and curl imparted to the fiber as a result of the
crosslinking. As such, it is generally acknowledged that
crosslinked fibers should be incorporated into absorbent products
to enhance their bulk as well as speed up the liquid acquisition
rates.
[0010] It is recognized that synthetic schemes could leverage the
above-mentioned findings to provide better and safer synthesis
processes for balancing properties of rayon to improve conventional
tampon pledgets.
[0011] Accordingly, the inventors have discovered that there is a
need for an improved tampon pledget formed from crosslinked
cellulose fibers and, in particular, for a tampon pledget that is
formed from crosslinked rayon that exhibits a desired molecular
weight between crosslinks and a balance of order (e.g.,
crystallinity) and disorder (e.g., amorphous regions) to improve
tampon absorbency. The present invention meets this need.
SUMMARY OF THE INVENTION
[0012] The present invention is directed to a tampon pledget
including crosslinked cellulose fibers having microstructures
treated to provide improved absorbency. The fibers are treated with
a crosslinking agent to provide at least one of a molecular weight
between crosslinks of from about ten (10) to about two hundred
(200) and a degree of crystallinity of from about twenty-five
percent (25%) to about seventy-five percent (75%). In one
embodiment, the crosslinking agent is comprised of a difunctional
crosslinking agent. The difunctional crosslinking agent may include
a glyoxal or a glyoxal-derived resin. In one embodiment, the
crosslinking agent is comprised of a multifunctional crosslinking
agent. The multifunctional crosslinking agent may include a cyclic
urea, glyoxal, polyol condensate.
[0013] In one embodiment, the crosslinking agent is added in an
amount from about one thousandth of one percent (0.001%) to about
twenty percent (20%) by weight based on a total weight of cellulose
fibers to be treated. In still another embodiment, the crosslinking
agent is added in an amount of about five percent (5%) by weight
based on the total weight of cellulose fibers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The features and advantages of the present invention will be
better understood when the Detailed Description of the Preferred
Embodiments given below is considered in conjunction with the
figures provided.
[0015] FIG. 1 depicts a conventional process for forming viscous
rayon fibers.
[0016] FIG. 2 depicts a process for forming crosslinked cellulose
fibers, in accordance with one embodiment of the present
invention.
[0017] FIG. 3 illustrates basic cellulose chemistry, as is known in
the art.
[0018] FIG. 4 depicts a three-dimensional view of a stereochemistry
of atoms in cellulose molecule, with an example hydroxyl (-OH)
group highlighted as a site for crosslinking and/or hydrogen
bonding.
[0019] FIG. 5 illustrates molecular weight distributions for
various grades of pulp used in rayon manufacture.
[0020] FIG. 6 illustrates wet tenacities for various grades of
rayon, where the wet tenacity at 5% elongation is typically used to
evaluate wet strength in conventional rayon and where the wet
tenacity value is higher for rayon made in accordance with the
present invention.
[0021] FIG. 7 illustrates a method for preparing bags for bagged
tampons in accordance with one embodiment of the present
invention.
[0022] FIG. 8 illustrates a machine set-up for forming tampons in
accordance with the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] In accordance with the present invention, a tampon pledget
is formed from crosslinked cellulose fibers such as, for example,
rayon. In one aspect of the invention, an overall molecular weight
of the crosslinked rayon is adjusted, as is the percent
crosslinking and the molecular weight between crosslinks in order
to increase the absorbency of the crosslinked rayon and to achieve
a balance in dry modulus and wet modulus that leads to better
performing tampons.
[0024] Tampon performance considerations are addressed by tampon
pledgets formed in accordance with the present invention to provide
an ability to: (a) absorb viscoelastic fluids like menses more than
conventional tampons; (b) absorb menses faster than conventional
tampons; (c) conform to the shape and contours of the vagina better
to enhance wearing comfort; (d) prevent early bypass failure by
expanding rapidly during use to occlude all routes by which fluids
could escape the vaginal cavity; (e) exhibit high gram per gram
syngyna absorbencies required by agencies such as the Food and Drug
Administration (FDA) that regulates tampons; (f) require only a
small amount of force to remove the tampon from an applicator; and
(g) maintain stability of these aforementioned properties under
high temperature and humidity.
[0025] As described herein, the present invention has combined
and/or adjusted a number of synthetic properties to provide an
improved tampon pledget. In one aspect of the present invention,
basic cellulosic raw materials used in rayon synthesis, as well as
the most common and recognized process for forming rayon, namely
the viscous process, were examined. As is generally known, rayon
can be produced from almost any cellulosic source. Conventional
sources include, for example, pulp from hardwoods, pulp from
softwoods, bacterial cellulose, switchgrass, jute, hemp, flax,
ramie, and the like. Some of these sources include large
percentages of non-cellulosic components, for example, lignin and
hemicelluloses, that have few advantages for use as rayon based
tampons. Moreover, these raw material sources exhibit significant
orientation and crystallinity that detracts from rayon's absorbency
properties. Accordingly, it has been discovered that pulp from, for
example, eucalyptus trees, contains high proportions of cellulose
(e.g., about ninety-eight percent (98%)), are easy to grow in large
plantations (e.g., it is thin and fast growing) and thus, are a
good source of raw material for providing rayon in accordance with
aspects of the present invention.
[0026] With a raw material source selected, focus was on synthetic
routes, as applied to the viscose rayon forming process. As
illustrated in FIG. 1, a conventional process 100 of manufacturing
viscose rayon includes steps of: selecting, steeping, pressing,
shredding, aging, xanthation, dissolving, ripening, filtering,
degassing, spinning, drawing, washing, and cutting to provide
staple rayon fibers. As noted above, at Block 110, a cellulose raw
material is selected. At Block 120, the steeping step includes
immersing the cellulose raw material in an aqueous solution of, for
example, about seventeen to twenty percent (17-20%) sodium
hydroxide (NaOH) at a temperature in the range of about eighteen to
twenty-five degrees Celsius (18 to 25.degree. C.) to swell the
cellulose fibers and convert the cellulose to alkali cellulose. The
alkali cellulose is passed to Block 130 where, in the pressing
step, the swollen alkali cellulose is pressed to a wet weight of
about two and a half to three (2.5 to 3.0) times its original raw
material weight. The pressing is typically performed to provide a
preferred ratio of alkali to cellulose. At Block 140, the pressed
alkali cellulose is shredded to finely divided particles or
"crumbs." As can be appreciated, shredding the pressed alkali
cellulose increases the surface area of the alkali cellulose thus
increasing its ability to react in later steps of the viscose
forming process. At Block 150, the shredded alkali cellulose is
aged under controlled time and temperature conditions to break down
the cellulose polymers (e.g., depolymerize the cellulose) to a
desired level of polymerization. Typically, the shredded alkali
cellulose is aged for about two or three days (about 48 to 72
hours) at temperatures between about eighteen to thirty degrees
Celsius (18 to 30.degree. C.). The aging step generally reduces the
average molecular weight of the original cellulose raw material by
a factor of two to three. Aging and the resulting reduction of the
cellulose's molecular weight are performed to provide a viscose
solution of desired viscosity and cellulose concentration. The aged
alkali cellulose is passed to Block 160 where a xanthation step is
performed. At Block 160, the aged alkali cellulose crumbs are added
to vats and a liquid carbon disulphide is introduced. The alkali
cellulose crumbs react with carbon disulphide under controlled
temperatures from about twenty to thirty degrees Celsius (20 to
30.degree. C.) to form cellulose xanthate. At Block 170, the
cellulose xanthate is dissolved in a diluted solution of caustic
soda (e.g., sodium hydroxide (NaOH)) at temperatures of about
fifteen to twenty degrees Celsius (15 to 20.degree. C.) under
high-shear mixing conditions to form a viscous solution generally
referred to as viscose.
[0027] The viscous solution is passed from Block 170 to Block 180,
where the viscose is allowed to stand for a period of time to
"ripen." During ripening, two reactions occur, namely,
redistribution and loss of xanthate groups. The reversible
xanthation reaction allows some of the xanthate groups to revert to
cellulosic hydroxyls. Also, carbon disulphide (CS2) is freed. The
freed CS2 escapes or reacts with other hydroxyl on other portions
of the cellulose chain. In this way, the ordered or crystalline
regions are gradually broken down and a more complete solution is
achieved. As is generally known, the CS2 that is lost reduces the
solubility of the cellulose and facilitates regeneration of the
cellulose after it is formed into a filament. At Block 190, the
viscose is filtered to remove any undissolved materials. After
filtering, the viscose is passed to Block 200 where a degassing
step (e.g., vacuum treatment) removes bubbles of air entrapped in
the viscose to avoid voids or weak spots that may form in the rayon
filaments.
[0028] From Block 200, the degassed viscose is passed to Block 210
where an extrusion or spinning step forms viscose rayon filament.
At Block 210 the viscose solution is metered through a spinneret
into a spin bath containing, for example, sulphuric acid, sodium
sulphate, and zinc sulphate. The sulphuric acid acidifies (e.g.,
decomposes) the sodium cellulose xanthate, the sodium sulphate
imparts a high salt content to the bath which is useful in rapid
coagulation of viscose, and the zinc sulphate exchanges with the
sodium xanthate to form zinc xanthate to cross-link the cellulose
molecules. Once the cellulose xanthate (viscose solution) is
neutralized and acidified, rapid coagulation of the rayon filaments
occurs. At Block 220, in a drawing step, the rayon filaments are
stretched while the cellulose chains are relatively mobile.
Stretching causes the cellulose chains to lengthen and orient along
the fiber axis. As the cellulose chains become more parallel,
interchain hydrogen bonds form and give the rayon filaments
properties necessary for use as textile fibers (e.g., luster,
strength, softness and affinity for dyes). For example, the
simultaneous stretching and decomposition of cellulose xanthate
slowly regenerates cellulose at a desired tenacity and leads to
greater areas of crystallinity within the fiber.
[0029] At Block 230, the regenerated rayon is purified by washing
to remove salts and other water-soluble impurities. Several
conventional washing techniques may be used such as, for example,
an initial thoroughly washing, treating with a dilute solution of
sodium sulfide to remove sulfur impurities, bleaching to remove
discoloration (e.g., an inherit yellowness of the cellulose fibers)
and impart an even color, and a final washing. At Block 240, the
purified rayon filaments (typically referred to as "tow") are cut
to desired lengths of fiber (typically referred to as "staple"
fiber) by, for example, a rotary cutter and the like. The staple
rayon fiber is then ready for use in a desired application.
[0030] As is generally known, the steps of the above-described
viscous rayon forming process 100 can be modified to impart varying
characteristics to the rayon fibers. For example, high modulus and
high tenacity rayon is made using an Asahi steam explosion process
(Asahi Chemical Industry Co. Ltd, Osaka, Japan). In another
modified process, the cellulose raw material is complexed with a
mixture consisting of cupric oxide and ammonia to provide a
cuprammonium rayon. In another modified process, the cellulose raw
material produces high tenacity rayon by using N-methyl morpholine
N-oxide (NMMO) as a polar solvent or suspension agent (e.g., Tencel
or Lyocell rayons). In yet another modified process, the cellulose
raw material produces high tenacity rayon by using ionic liquids,
for example, 1-butyl-3-methylimidazolium chloride or other solvents
such as ammonia or ammonium thiocyanate, as dissolving or
suspending agents. In still another modified process, a blowing
agent or air is added to produce "hollow" rayon fibers. As
described above, a number of conventional synthetic routes are
available to produce rayon fibers.
[0031] Even in the standard, viscose process for making regular
rayon, process changes and/or additives can be introduced to
synthesize rayon having properties that would be preferred for
tampon performance. For example, certain nitrogen and oxygen based
modifiers are added to modify an amount of orienting stretch
imparted to the fiber. Additionally, dimethylamine (DMA) can be
introduced to form dimethyldithiocacarbamate, an effective agent in
modifying viscose. In one embodiment, DMA is added to the salt-acid
spin bath (at Step 210 of FIG. 1) to produce an appropriate level
of zinc crosslinking.
[0032] The inventors have recognized that of these synthetic
routes, the viscose rayon forming process, described above with
reference to FIG. 1, provides preferred results due, in part, to
practical economic and manufacturing considerations. However, the
inventors also recognize that the use of NMMO and ionic liquids as
solvents provide preferred environmental results, since the
synthetic routes typically employ solvent recycling. Moreover,
synthetic routes using NMMO and ionic liquids are becoming
increasingly more economical and provide means for crosslinking and
tailoring rayon microstructures (e.g., molecular weight and degree
of crystallinity) that viscose synthetic routes do not easily
permit. Accordingly, the inventors have recognized that differing
synthetic routes may be employed to achieve needs of differing
tampon applications.
[0033] The inventors have also discovered that varying specific
synthetic details (e.g., time, temperature, humidity, pressure
settings, and the like) within the above-described synthetic routes
improves product performance and particularly when, as the
inventors have discovered, eucalyptus pulp is employed as the
cellulose raw material. For example, the inventors have discovered
that the amount of time cellulosic raw material pulp sheets are
steeped in caustic soda, dried, shredded, and pre-aged, as well as
the temperature and humidity settings, affects the amount of
oxidative degradation and thus, affects overall rayon average
molecular weight. Moreover, the inventors have discovered that
methods used to extrude, stretch and crimp filaments, and the size
and shape of spinnerets affect the morphology, orientation and
degree of crystallinity of the rayon being produced. The inventors
have also discovered that producing rayon using viscose processes
and employing Y-shaped spinnerets provides high absorbency.
[0034] FIGS. 3-6 illustrate certain aspects of cellulosic chemistry
as well as typical properties of rayon made by conventional means
that are evaluated and refined by, for example, modifying the
process steps illustrated in FIG. 1, to provide a superior grade of
rayon adapted to requirements of tampon products. FIGS. 3 and 4
illustrate the known chemistry of cellulose. As shown in FIGS. 3
and 4, cellulose 260 is comprised of repeating units of D-glucose,
which are six-membered rings known as "pyranoses." The pyranose
rings are joined by single oxygen atoms (acetal linkages) between
one of the carbons of one of the pyranose rings and a different
carbon on an adjacent pyranose ring. Since a molecule of water is
lost when an alcohol and a hemiacetal react to form an acetal, the
glucose units in the cellulose molecule are referred to as
"anhydroglucose" units. As shown in FIG. 3, the internal
anhydroglucose units each have three (3) alcoholic groups (e.g.,
--OH groups), while end anhydroglucose units of the long chain
molecule have four (4) alcoholic groups.
[0035] One aspect of the acetal linkage that is important is the
spatial arrangement. When glucose forms a first pyranose ring, the
hydroxyl group on one carbon of the first ring can approach the
carbonyl on a second ring from either side and thus, result in
different stereochemistries. For example, in one stereochemistry
with functional groups in equatorial positions, the molecular chain
of cellulose extends in a straight line making it a good
fiber-forming polymer. In a slightly alternative chemistry with the
linkage in an axial position, starch molecules are formed which
tend to coil rather than extend.
[0036] With so many --OH groups in a molecule, one would expect
that cellulose is water-soluble. But it is not. Because of the
equatorial positions of these hydroxyls on the cellulose chain,
they protrude laterally along the extended molecule as shown
generally at 270 of FIG. 4. This positioning makes them readily
available for hydrogen bonding. These strong hydrogen bonds
produced several key properties of cellulose, namely: 1) the bonds
prevent penetration of the solid cellulose by aqueous solvents,
resulting in a lack of solubility not only in water, but in almost
all other solvents; 2) the bonds cause the chains to group together
in highly ordered structures (e.g., crystal like structures); 3)
the bonds provide high strength; and 4) the hydrogen bonds also
prevent cellulose from melting, like most thermoplastics ordinarily
do.
[0037] But cellulose is not entirely crystalline. Typically, the
cellulose chains are usually longer than the crystalline regions.
Thus, there are regions of both order (i.e. crystalline regions)
and disorder (i.e. amorphous regions). In less ordered regions, the
chains are further apart and more available for hydrogen bonding to
other molecules, such as water. Most cellulosic structures, rayon
included, can absorb large amounts of water. Thus, rayon does not
dissolve in water, but it does swell in it readily.
[0038] In view thereof, the inventors have recognized that a key to
synthesizing a good grade of rayon for tampon performance requires
a proper "balancing" of the cellulose structure. For example, the
rayon must have enough disorder to get good absorbency and wicking
of aqueous-based fluids such as menses, while retaining enough
crystalline structure to maintain good strength especially once the
rayon has been wetted and to allow the fibers to be formed stably
in a viable, economic, manufacturing process. The inventors have
recognized that a number of synthesis guidelines can be followed to
achieve the aforementioned balancing.
[0039] As described above, in order for fibers to be formed the
molecular weight of standard cellulose is first lowered from that
of pulp (FIG. 5) to a level such that extrusion through relatively
small spinerettes is technically possible and economically
feasible. As FIG. 5 illustrates, typical pulp degrees of
polymerization (DP) range from about 30 to over 3000. By
comparison, the degree of polymerization of rayon is only about
260. As noted above with respect to the conventional process 100 of
manufacturing viscose rayon (FIG. 1) and as described below with
respect to an improved manufacturing process 300 of FIG. 2, several
steps accomplish this lowering of molecular weight. First, a
suitable choice of a raw material is made (at Blocks 110, 310).
Second, as the pulp is "steeped (at Blocks 120, 320) in caustic and
then pressed (at Blocks 130, 330), there is some oxidative
degradation and alkaline hydrolysis to reduce the molecular weight
to an acceptable level for processing.
[0040] The degree of crystallinity can be controlled in several
steps in the manufacture of rayon. There are three (3) hydroxyl
groups available on each internal anhydroglucose ring but, given
the discussion above, the inventors have recognized that it is
difficult to react all (3n+2) of these groups, where n is the
degree of cellulosic polymerization. For example, the hydrogen
bonding is so strong that reactions to disrupt that bonding tend to
be sterically limited. Thus, in the xanthation step (Block 160,
360), the degree of substitution (DS) is typically only about seven
tenths (0.7), for example, about seventy percent (70%) of the
hydroxyls are typically reacted. Many of the hydroxyls that are
relatively easy to react are in the less ordered regions. Higher
degrees of xanthate substitution can disrupt the crystalline
regions. The inventors have noted that this can interfere with the
inter-chain hydrogen bonds and, in a subsequent step, lower the
fiber wet tenacity and strength.
[0041] The inventors have discovered that one way to change
cellulosic microstructure is to, for example, add a relatively
small amount of crosslinking agent (about one tenth of one percent
(0.1%) or less) just after the xanthation reaction (Blocks 160,
360), in order to provide some intermolecular and intramolecular
crosslinks involving unsubstituted --OH groups. Crosslinking levels
should be low at this stage so as to allow subsequent steps of
dissolving (at Blocks 170, 370), ripening (at Blocks 180, 380) and
filtration (at Blocks 190, 390) to occur.
[0042] The inventors have recognized that another step where
crosslinking agents may be added is a spinning step (e.g., Blocks
210, 410). For example, one conventional process developed by
Courtaulds North America, Inc. (Mobile, Ala., USA) ("Courtaulds")
used small amounts of formaldehyde in the spin bath to develop a
fiber called W-63 that had unusually high tenacity and modulus
(e.g., about 7-10 g/den). Based on this technology Courtaulds
produced a yarn called "Tenex." However, there are perceived
deficiencies with the Tenex yarn. For example, the fiber was too
brittle and there were problems associated with recovery of the
fiber from the spin bath. Thus, the inventors have recognized that
to achieve the balance act of crystallinity, water absorption, wet
strength and fiber formability, special spinning conditions and
spin modifiers such as those outlined above could be added to the
manufacturing process (at Blocks 210, 410) to affect the degree of
crystallinity. Also, during the drawing step (at Blocks 220, 420),
the rate of drawing can be changed in order to change the
crystallinity of the filaments. The degree of stretch imparts some
orientation, hence influences the degree of crystallinity, to the
fibers made at this stage.
[0043] Additionally, post crosslinking agents could be added to
fibers, for example, after the fibers have been drawn (at Blocks
220, 420) or before a final washing step (at Blocks 230, 430). The
inventor notes that crosslinking at these later stages (e.g., at
Blocks 420 or 430) can help produce a stronger, tougher fiber and
hence a stronger, tougher web used in tampon manufacture.
[0044] The inventors have also discovered that the choice of
crosslinking agents is a significant factor in the formation of
improved rayon materials. For example, conventional processes
typically employ formaldehyde as a crosslinking agent preferring
cost and efficiency considerations. Moreover, the inventor notes
that there is a perceived disadvantage from a safety prospective
with the use of formaldehyde in a product that will be used in a
human body. Accordingly, the inventors favor use of citric acids as
cellulosic crosslinking agents. The inventors have found that to
crosslink cellulose effectively, at least two hydroxyl groups
should be combined in a cellulose molecule (e.g., intramolecular
crosslinking) or in adjacent cellulose molecules (e.g.,
intermolecular crosslinking). Effective crosslinking typically
requires that the crosslinking agent be difunctional (e.g.,
1,3-Dichloro-2-propanol) with respect to cellulose for reaction
with the two hydroxyl groups. As an alternative to a single
difunctional crosslinking agent, a mix of two or more different
molecules can be employed to provide an effective difunctional and
multifunctional crosslinking. For example, in one embodiment, a
crosslinking agent may include glyoxal as well as a glyoxal-derived
resin. In one embodiment, a cyclic urea/glyoxal/polyol condensate
(e.g., sold under the designation SUNREZ 700M by Sequa Chemicals,
Inc., Chester, S.C. USA) provides a multifunctional crosslinking
agent.
[0045] Other examples of crosslinking agents are familiar to those
skilled in the art. Since zinc salts are typically used in the spin
bath (at Blocks 210, 410), ionic crosslinkers involving zinc
sulfates and similar divalent cations and appropriate anions may be
used. Other crosslinking agents would include, but are not be
limited to, butanetetracarboxylic acid, cyclobutane tetracarboxylic
acid, tetramethylenebisethylene urea, tetramethylenedidisocyanate
urea, polymeric polyacids such as polymethacrylic acid, methylated
derivatives of urea or melanine such as
dimethyloldihydroxyethyleneurea, glutaraldehyde, ethylene glycol
bis-(anhydrotrimellitate) resin compositions, and hydrated ethylene
glycol bis-(anhydrotrimellitate) resin compositions.
[0046] The inventors have recognized that the choice of a
particular crosslinking agent for tampon applications depends on a
variety of factors. Besides achieving the crystallinity/wet
strength/absorbency/fiber formability "balance" discussed herein,
the choice of chemistry used depends upon such other factors as,
for example: product health and safety, regulatory approvals,
product quality; sufficiently high reaction rates at temperatures
of interest, the propensity of undesirable side reactions,
manufacturing issues, raw material cost of particular crosslinking
agent, and the like.
[0047] The inventors have recognized that crosslinking is likely to
take place, to a greater extent, in crystalline fractions of the
cellulose rather than in the non-crystalline fractions. This result
is apparently seen because polymer segments are closer together in
crystallites since the chain packing density is greater. Thus,
interaction of crystallinity and crosslinking is expected. The
inventors have recognized that such an interaction influences key
polymer properties, such as tampon performance.
[0048] The inventors have also discovered that in addition to the
choice of a crosslinking agent, the amount of crosslinking agent
used is relevant. For example, the inventors have discovered that
the amount of a crosslinking agent that is used may be dependent
upon the degree of crosslinking desired, the efficiency of the
crosslinking reaction and the desired molecular weight between
crosslinks that would produce enhanced wet bulk and enhanced tampon
properties that would accrue from the reaction. The inventors have
found that a level of crosslinking agent used ranges from a value
of about one thousandth of one percent (0.001%) to a value of about
twenty percent (20%), based on a total amount of cellulose present
to be treated. In one embodiment, a crosslinking agent would be
present in an amount of about five percent (5%) by weight based on
the total weight of cellulose fibers. With respect to the
efficiency of the cross linking reaction, the inventors have
determined that, like most chemical reactions, there is a
temperature that is most optimal for the particular chemical
reaction of interest. In many cases the crosslinking reaction
proceeds reasonably rapidly at the same temperature at which rayon
is normally processed in the steps outlined with reference to the
convention process 100 of FIG. 1. In other cases, it is desirable
to add a catalyst to promote the reaction either by free-radical
means or by an oxidation-reduction catalytic reaction. General
examples of catalysts include, for example, peroxides,
perchlorates, persulfates, and/or hypophosphites.
[0049] In another aspect of the present invention, the inventor
selectively introduces the crosslinking reaction to the rayon
synthesis process. An improved viscous rayon forming process 300 is
illustrated in FIG. 2, and is similar to the aforementioned viscous
rayon forming process 100 of FIG. 1, where like steps of the
improved forming process 300 having reference numerals prefixed by
"3" and "4" correspond to steps prefixed "1" and "2", respectively,
of the conventional rayon forming process 100 of FIG. 1. As shown
in FIG. 2, the crosslinking reaction may be introduced early in,
for example, the viscose "ripening" reaction (e.g., at Block 380 of
FIG. 2) or during the introduction of a solvent or slurry agent
(e.g., NMMO) to the shredded pulp pieces (e.g., at Block 340 of
FIG. 2). Alternatively, crosslinking can be carried out later in
the viscous reaction such as, for example, after the degraded rayon
cellulose has been largely formed (e.g., at Block 410 of FIG. 2).
Crosslinking reactions can also be employed on the developing,
coagulating fiber filaments, the finished fiber tow, cut rayon
fibers or on carded webs produced from the finished rayon
fibers.
[0050] Additionally, it is within the scope of the present
invention to employ wet and dry crosslinking reactions. Dry
crosslinking may be performed when the cellulose is in a collapsed
state where it is substantially free of water and moisture (e.g.,
within the pressing step at Block 330 of FIG. 2). Wet crosslinking
may be performed with the cellulose in a swollen or wet state. In
one embodiment, the crosslinking process is performed on finished
but swollen staple fibers (e.g., after cutting at Block 440 of FIG.
2), prior to web formation. In this manner unused crosslinking
agents could be dispersed in a suitable solvent, treated at high
temperature in an oven or like vessel at, for example, about one
hundred degrees Celsius (100.degree. C.) for about one (1) hour, to
complete the crosslinking reaction and optimally increase the wet
bulk properties. The crosslinking agents, crosslinking catalysts
(if any), and polar solvents are washed out with water and
thoroughly dried prior to web formation and tampon forming.
[0051] It is also within the scope of the present invention to vary
the amount and type of crosslinking catalysts used to speed up the
crosslinking reactions. In addition to those listed above, the
inventors have discovered that preferred cellulose crosslinking
catalysts include, for example: magnesium chloride or magnesium
nitrate; zinc chloride, zinc nitrate, or zinc fluroborate; lactic
acid, tartaric acid or hydrochloric acid; ammonium sulfate or
ammonium phosphate; or amine hydrochlorides. In one embodiment,
crosslinking catalyst levels range from about a thousandth of one
percent (0.001%) to about ten percent (10%) by weight based on a
total weight of cellulose fibers to be treated. It should be
appreciated, however, that it is not a necessary step in the
crosslinking reaction to introduce a crosslinking catalyst.
Accordingly, it is within the scope of the present invention to
conduct crosslinking reactions without the use of a crosslinking
catalyst.
[0052] The inventors have discovered that one or more of the
ingredients used above as part of the crosslinking reaction impart
secondary advantages when employed within tampons products. For
example, ingredients such as glycerol monolaurate, sorbitan
monolaurate (Tween 20), sodium lauryl sulfate, sodium dioctyl
sulfosuccinate, potassium oleate, and other surfactants, provide an
anti-bacterial action. These ingredients may also be beneficial in
assisting fiber finishing as the ingredients have surface-active
properties that affect fiber surface properties, interaction and
thus absorption of menses. Moreover, surfactants such as these
ingredients could be used to improve the wettability of cellulose
and thus promote the substitution and crosslinking reactions as
well. Finally, these same ingredients promote as fiber-fiber
friction and cohesion force that, in turn, contribute to effective
processing of fibers into webs.
[0053] As shown in FIG. 2, at Block 450, it is within the scope of
the present invention to employ post-crosslinking by chemical or
hydrothermal treatment to further improve the strength of the
fiber. Post-crosslinking is described further below.
[0054] It should be appreciated that the above described
improvements to the rayon synthesis process provide a number of
factors or "levers" that can be tuned and adjusted by product
developers to achieve a desired "balance" of rayon properties for
particular tampon applications. As noted above, to maximize
performance different types of tampons require different rayon
properties. For example, tampons rated "light" and/or "regular"
absorbency include rayon having less absorbency, less crosslink
density, and greater crystallinity. Accordingly, the inventors have
found that by expanding the duration of the drawing step conducted
at Block 420 of FIG. 2, cellulose chains are lengthened and
interchain hydrogen bonds are formed to provide greater areas of
crystallinity within the rayon fiber and thus provide rayon
tailored more toward light and regular absorbency applications.
Tampons rated "super" and/or "super plus" absorbency include rayon
having a relatively higher gram per gram syngyna absorbency,
relatively higher crosslink density and a greater amorphous polymer
fraction.
[0055] As illustrated above, in one aspect of the invention the
inventors have discovered that by adjusting the various factors
described above, interactions within the rayon synthesis process
may be controlled and optimized to provide improved synthesis
processes and, as a result, improved rayon for use in tampon
pledgets. The inventors have determined that the optimized
synthesis processes result in rayon having a number of desirable
properties. For example, the inventors have discovered that by
adjusting one or more of the aforementioned factors the synthesis
process may be tailored to improve tampon absorbency capacity and
wicking rate, improve fiber physical properties (e.g., polymeric
microstructure including the degree of crystallinity, molecular
weight distributions, and reduce levels of unreacted impurities and
byproducts), and fiber surface properties.
[0056] In one embodiment, conventional test analyses and methods
may be employed in a novel manner to determine, as described
herein, key attributes of the inventive process 300 of making
modified rayon. For example, to determine the crystallinity of the
treated samples at different conditions, a sample is placed into a
chamber of an analytical x-ray diffractometer and scanned using an
appropriate level of x-ray energy and intensity for a sufficient
length of time to get a signal. X-ray diffraction photographs of
cellulose show both a regular pattern, characteristic of the
crystalline portion, and a diffuse halo, characteristic of the
amorphous material. Besides the x-ray methods, density methods,
NMR, infrared absorption and other methods can be used to infer the
degree of crystallinity.
[0057] Similarly, absorbency can be determined in accordance with
prior art methods. There are standard methods for determining
absorbency, for example, INDA Test Method IST 10.1 (5), "Standard
Test Method for Absorbency Time, Absorbency Capacity, and Wicking
Rate," Association of the Nonwoven Fabrics Industry, Cary, N.C.,
1995. For tampons, there is also the FDA-mandated Syngyna test
method (Federal Register, Volume 54, Number 206, pp.
43773-43774).
[0058] Moreover, for fiber tenacity (dry or wet strength), there
are a variety of test methods. For example, ASTM D 2256-95a,
"Standard Test Method for Tensile Properties of Yarns by the Single
Strand Method," is one such standard test methodology. This and
similar test methods could be performed using instruments available
at, for example, Instron (825 University Ave, Norwood, Mass.,
U.S.A.; www.instron.com). FIG. 6 shows results as a plot of
tenacity versus percent elongation for various rayon grades. Fibers
of the present invention exhibit wet strengths that are typically
higher than regular rayon but not as high as the some other grades,
for example, wet tenacity at five percent (5%) elongation would be
about five tenths of one gram (0.5) per denier for rayon of the
present invention, as illustrated generally at 500 of FIG. 6.
[0059] Dynamic mechanical analysis methods are useful to evaluating
mechanical properties of crosslinked polymers that may exhibit both
elastic (solid-like) and inelastic (liquid-like) properties. Such
viscoelastic methods are typically used to evaluate the extent to
which a polymer has been crosslinked.
[0060] Further, gel permeation chromatography (GPC), solution
viscosity, high pressure liquid chromatography (HPLC), and other
standard analytical methods such as gas chromatography, simple
titrations and solubility determinations) can be used to analyze
the molecular characteristics of the present invention. The first
two analytical methods are useful for determining the cellulose
molecular weight; whereas the latter methods are used to determine
the concentration of unreacted small molecular species that may
present themselves during the various crosslinking reactions
described herein.
[0061] The inventors analyzed a number of exemplary fibers to
illustrate various features of the present invention. In the
examples provided below treatments were applied to a viscose rayon
fiber such as, for example, a Kelheim Multilobal fiber sold under
the brand name GALAXY by Kelheim Fibres, Ltd., Kelheim, Germany.
Chemical and/or hydrothermal treatments were applied to the viscose
rayon fiber.
[0062] High Temperature Wet Treatment of Viscose Rayon Fibers
[0063] Procedures for High Temperature Wet Treatment (Hydrothermal
Treatment)
[0064] Pre-treatment--The viscose rayon fiber is first washed three
(3) times with distilled water at a room temperature of about
twenty-three degrees Celsius (23.degree. C.) to remove any
lubricating agents (fiber finish). The fiber is then dried by
compressing and placing in a vacuum oven at about sixty degrees
Celsius (60.degree. C.) overnight.
[0065] High temperature wet treatment (HTWT)--In an embodiment, a
temperature range of about ninety to about one hundred fifty
degrees Celsius (90 to 150.degree. C.) is used. In another
embodiment, a temperature range of about one hundred to about one
hundred twenty-four degrees Celsius (100 to 124.degree. C.) is used
for the high temperature wet treatment. Each includes the following
steps.
[0066] 1. In an autoclave, an about one thousand milliliter (1000
ml) water bath was preheated to a temperature of about one hundred
degrees Celsius (100.degree. C.).
[0067] 2. Twenty grams (20 g) of the viscose rayon fiber was
immersed in the water bath. The autoclave was then immediately
sealed. The water bath temperature was monitored. When the
temperature reached a target temperature, a stopwatch was
started.
[0068] 3. The fiber sample is keep at a setting temperature level
for a desired time period.
[0069] 4. Then, the pressure of autoclave is released, and the
fiber sample was removed and then soaked in a one thousand
milliliter (1000 ml) distilled water bath at about twenty-three
degrees Celsius (23.degree. C.) for about five (5) minutes.
[0070] 5. After that, the fiber sample is dried by compressing and
placing the sample in a vacuum oven at a temperature of about sixty
degrees Celsius (60.degree. C.) overnight.
[0071] Note: Some time was taken to heat up to the desired target
temperature. The time value ranged from about fifteen to about
forty (15-40) minutes to heat up to the target temperatures, which
ranged in the examples provided below from about one hundred and
eight degrees Celsius to about one hundred twenty-four degrees
Celsius (108.degree. C-124.degree. C.).
[0072] The above described procedures were repeated until a desired
amount of fiber sample was prepared for evaluation. In one
embodiment, the desired amount of fiber sample was about one
hundred (100) grams.
[0073] Procedures for Chemically Crosslinking Treatment (CCT)
[0074] Pre-Treatment
[0075] Rayon viscose fiber was first washed three times with
distilled water at a room temperature of about twenty-three degrees
Celsius (23.degree. C.) to remove the fiber finish, i.e.
lubricating agent. It was then dried by compressing and placing in
a vacuum oven at a temperature of about sixty degrees Celsius
(60.degree. C.) overnight. The pre-treated rayon fiber was used for
a sample preparation.
[0076] Chemically Crosslinking Treatments
[0077] Six different crosslinking chemical agent systems were
investigated for the chemically crosslinking treatment (CCT) of
viscose rayon fibers. The CCT procedures using each crosslinking
agent system, are described below.
[0078] Polycarboxylic Acids
[0079] Polycarboxylic acids such as, for example,
1,2,3,4-Butanetetracarboxylic acid and citric acid are used as
crosslinkers through esterification reactions with the hydroxyl
groups of cellulose in the presence of catalysts.
[0080] A. 1,2,3,4-Butanetetracarboxylic Acid
[0081] Crosslinking system
[0082] Crosslinking agent: 1,2,3,4-butanetetracarboxylic acid
(BTCA),
[0083] Catalyst: sodium hypophosphite monohydrate NaH2PO2. H2O
[0084] B. Citric Acid
[0085] Crosslinking system
[0086] Crosslinking agent: citric acid (CA)
[0087] Catalyst: sodium hypophosphite monohydrate NaH2PO2.H2O
[0088] Procedures for small trials
[0089] 1. At room temperature, eleven grams (11 g) of rayon fiber
was immersed in an about two hundred twenty milliliters (220 ml) of
an aqueous solution containing 1,2,3,4-Butanetetracarboxylic acid
or citric acid (about one to five percent by weight (1 to 5 wt %)
based on the weight of rayon fiber) and about one to five percent
by weight (1 to 5 wt %) of sodium hypophosphite for about ten
minutes (10 min.).
[0090] 2. After about ten minutes (10 min.), the fiber was pressed
to remove most of liquid and then dried at about fifty to sixty
degrees Celsius (50-60.degree. C.) in a vacuum oven, to a level
containing a desired amount of liquid, e.g., about twenty-five
percent by weight (25 wt %) or about fifty percent by weight (50 wt
%) based on the dry fiber basis.
[0091] 3. Then the fiber was cured at about one hundred sixty-five
to about one hundred seventy degrees Celsius (165 to 170.degree.
C.) for about two minutes (2 min.).
[0092] 4. The cured fiber was washed three (3) times with distilled
water to remove the unreacted acid and catalyst. At each wash, the
cured fiber was washed for about five minutes (5 min) in about two
hundred twenty milliliters (220 ml) of distilled water. Once
washed, the fiber is then fully dried in a vacuum oven at a
temperature of about sixty degrees Celsius (60.degree. C.).
[0093] Dimethyldihydroxyethylene Urea
[0094] Crosslinking system
[0095] Crosslinking agent: modified formaldehyde-free agent
dimethyldihydroxyethylene urea (DMDHEU).
[0096] Catalyst: MgCl2
[0097] Procedures for small trials
[0098] 1. At room temperature, eleven grams (11 g) of rayon fiber
was immersed in an about two hundred twenty milliliters (220 ml)
aqueous solution containing DMDHEU (one or five percent by weight
(1 or 5 wt %) based on the weight of rayon fiber) and one to five
percent by weight (1-5 wt %) of MgCl2 for about ten minutes (10
min.).
[0099] 2. After about ten minutes (10 min.), the fiber was pressed
to remove most of liquid and then dried in a vacuum oven at a
temperature of between about fifty to sixty degrees Celsius
(50-60.degree. C.), to a level containing a desired amount of
liquid, e.g., about twenty-five or fifty percent by weight (25 or
50 wt %) based on the dry fiber basis.
[0100] 3. Then the fiber was cured at about one hundred sixty-five
to about one hundred seventy degrees Celsius (165 to 170.degree.
C.) for about two minutes (2 min).
[0101] 4. The cured fiber was washed three (3) times with distilled
water to remove the unreacted crosslinking agent and catalyst. At
each wash, the cured fiber was washed for about five minutes (5
min) in about two hundred twenty milliliters (220 ml) of distilled
water. Once washed, the fiber is then fully dried in a vacuum oven
at a temperature of about sixty degrees Celsius (60.degree.
C.).
[0102] 2,4-dichloro-6-hydroxy-1,3,5-triazine
[0103] Crosslinking system
[0104] Crosslinking agent: 2,4-dichloro-6-hydroxy-1,3,5-triazine
(DCH-Triazine)
[0105] Catalyst: NaHCO3 (for pH adjustment)
[0106] As an initial step, a water-soluble DCH-Triazine sodium salt
was prepared by reacting cyanuric chloride with NaOH at a low
temperature.
[0107] Procedures for Small Trials
[0108] At room temperature, about eleven grams (11 g) of rayon
fiber was immersed in an about two hundred twenty milliliters (220
ml) aqueous solution containing DCH-Triazine sodium salt (one to
five percent by weight (1 to 5 wt %) based on the weight of rayon
fiber) and one to five percent by weight (1 to 5 wt %) of NaHCO3
for about ten minutes (10 min).
[0109] After about ten minutes (10 min), the fiber was pressed to
remove most of liquid and then dried in a vacuum oven at a
temperature of between about fifty to sixty degrees Celsius
(50-60.degree. C.), to a level containing desired amount of liquid,
e.g., about twenty-five or fifty percent by weight (25 or 50 wt %)
based on the dry fiber basis.
[0110] Then the fiber was cured at about one hundred sixty-five to
about one hundred fifty to about one hundred sixty degrees Celsius
(150 to 160.degree. C.) for about two minutes (2 min).
[0111] The cured fiber was neutralized with about two hundred
twenty milliliters (220 ml) of two percent by weight (2 wt %) of
acetic acid.
[0112] The cured fiber was washed three (3) times with distilled
water to remove the unreacted crosslinking agent and catalyst. At
each wash, the cured fiber was washed for about five minutes (5
min) in about two hundred twenty milliliters (220 ml) of distilled
water. Once washed, the fiber is then fully dried in a vacuum oven
at a temperature of about sixty degrees Celsius (60.degree.
C.).
[0113] Glyoxal/Glyoxal Derivative Resin
[0114] Crosslinking system
[0115] Crosslinking agent: glyoxal and glyoxal derivative resin
[0116] Catalyst: MgCl2
[0117] Glyoxal Resin Preparation
[0118] A cyclic urea/glyoxal/polyol condensate (Glyoxal resin) is
prepared by reacting glyoxal, cyclic urea and polyol. The detailed
procedure is as the following.
[0119] To an about one liter flask sixty (60) parts (1.0 mole)
urea, seventy-five (75) parts of water, seventy-five (75) parts of
1,4-dioxane, sixty (60) parts (1.0 mole) of aqueous formaldehyde,
and seventy-two (72) parts (1.0 mole) of isobutyraldehyde were
added. The reaction mixture was stirred and heated at about fifty
degrees Celsius (50.degree. C.) for about two (2) hours.
[0120] Following the addition of a catalytic amount of acid, the
reaction mixture is heated at its reflux temperature for about six
(6) hours. The product is a clear solution that contained
4-hydroxy-5,5-dimethyltetrahydropyrimidin-2-one. The inventors
confirmed this by IR spectroscopy, identifying peaks at 3300 cm-1
as NH or OH moeties, 1660 cm-1 as C.dbd.O, and 1075 cm-1 as
C--O.
[0121] The above product was heated with one hundred fifty (150)
parts (1.08 moles) of forty percent (40%) glyoxal and thirty-two
(32) parts (0.4 mole) of propylene glycol at a temperature of about
seventy degrees Celsius (70.degree. C.) for about four (4) hours to
form the cyclic urea/glyoxal/polyol condensate (Glyoxal resin).
[0122] Procedures for Small Trials
[0123] 1. At room temperature, about eleven grams (11 g) of rayon
fiber was immersed in an about two hundred twenty milliliters (220
ml) of an aqueous solution containing glyoxal (one to five percent
by weight (1 to 5 wt %) based on the weight of rayon fiber),
glyoxal resin (one to five percent by weight (1 to 5 wt %) based on
the weight of rayon fiber), and one to five percent by weight (1 to
5 wt %) of MgCl2, for about ten minutes (10 min).
[0124] 2. After about ten minutes (10 min), the fiber was pressed
to remove most of liquid and then dried in a vacuum oven at a
temperature of between about fifty to sixty degrees Celsius
(50-60.degree. C.), to a level containing desired amount of liquid,
e.g., about twenty-five or fifty percent by weight (25 or 50 wt %)
based on the dry fiber basis.
[0125] 3. Then the fiber was cured at about one hundred sixty
degrees Celsius (160.degree. C.) for about two minutes (2 min).
[0126] 4. The cured fiber was washed three (3) times with distilled
water to remove the unreacted crosslinking agent and catalyst. At
each wash, the cured fiber was washed for about five minutes (5
min) in about two hundred twenty milliliters (220 ml) of distilled
water. Once washed, the fiber is then fully dried in a vacuum oven
at a temperature of about sixty degrees Celsius (60.degree.
C.).
[0127] Ethylene glycol-diglycidylether (EDGE)
[0128] Crosslinking system
[0129] Crosslinking agent: ethylene glycol-diglycidylether
(EDGE)
[0130] Catalyst: NaOH
[0131] Procedures for Small Trials
[0132] 1. About eleven grams (11 g) of rayon fiber was immersed in
an about two hundred twenty milliliters (220 ml) of an aqueous
solution containing EDGE (one to seven percent by weight (1 to 7 wt
%) based on the weight of rayon fiber), and one to two percent by
weight (1 to 2 wt %) of NaOH, for about four to six hours (4-6 hrs)
at about forty degrees Celsius (40.degree. C.).
[0133] 2. The treated fiber is washed three (3) times with
distilled water to remove the unreacted crosslinking agent and
catalyst. At each wash, the cured fiber was washed for about five
minutes (5 min) in about two hundred twenty milliliters (220 ml) of
distilled water. Once washed, the fiber is then fully dried in a
vacuum oven at a temperature of about sixty degrees Celsius
(60.degree. C.).
[0134] In all the CCT preparations described above, procedures were
repeated in order to obtain enough treated fiber for evaluations,
usually this was about one hundred (100) grams.
[0135] Procedures for Evaluation of Crosslinked Rayon Fibers
[0136] Multilobal fibers (Kelheim fibers) that have been chemically
or hydrothermally crosslinked by a variety of treatments were
usually checked versus appropriate controls (usually untreated
Kelheim Galaxy fiber). The inventors evaluated the fibers using the
"bagged pledget" test method, using special nonwoven bags.
Procedures for making up these nonwoven bags are described
below.
[0137] For each example, typically about twenty-five (25) bagged
tampons were made by the methods described below for each "cell",
for example, each aliquot of hydrothermally or chemically
crosslinked rayon or a control sample of fiber.
[0138] Procedures for Making Bagged Tampons
[0139] 1. Obtain a sufficient number of bags to enclose the loose
rayon fiber.
[0140] 2. Obtain a sufficient number of commercial tampon such as,
for example, GENTLE GLIDE super white applicators (barrels and
plungers) as well as a sufficient supply of standard string (gentle
glide is a registered trademark of Playtex Products, Inc., Shelton,
Conn., USA). Also, collect together the fiber samples to be
tested.
[0141] 3. Collect a supply of standard multilobal rayon as control
samples.
[0142] 4. From the bags and fibers above, typically several "cells"
would be run at a time, each with about twenty-five plus (25+)
tampons. Operators were instructed to handle the fiber using rubber
gloves.
[0143] For each of the cells:
[0144] 5. At least twenty-five plus (25+) aliquots of 2.7+/-0.1
grams of the selected (absorbent) fiber variant were weighed out
into containers such as, for example, aluminum muffin tins. In one
series, for example, there were twenty-five plus (25+) aliquots
("fluffballs") weighed out for eight (8) different cells to provide
about two hundred (200) weigh-ups in all.
[0145] 6. For each of these aliquots a Hauni HP simulator was set
up for forming super tampons. Standard operations for forming using
this simulator from nonwoven webs are provided below. These
instructions provide one example of machine settings and the
general sequence of operation. Steps 7-19 below are used
specifically for forming bagged tampons from fibers.
[0146] 7. Using the preweighed out fluffballs, form the fluffball
by pushing small amounts of the fluffball into the transfer throat
of the HP Simulator until the entire fluffball is in the transfer
throat, which is about 0.527 inch in diameter.
[0147] 8. The fluffball was then transferred into a hot oven tube,
preheated at about two hundred sixty degrees Fahrenheit
(260.degree. F., 127.degree. C.). The oven tube diameter was about
0.495 inch.
[0148] 9. The hot oven tube was compressed on a Domer, as is
generally known in the art. Then the pledget was re-positioned. The
heated "Dome" fixture was turned around so that the flat shaft-like
back end of the fixture actually presses against the pledget in the
oven tube. The flat pusher end of the air cylinder has two spacers
on it: one is about one half inch (0.5 in.) and the other is about
three sixteenth inch (0.187 in).
[0149] 10. The warmed pledget in the oven tube is then placed into
a conveying oven at about five hundred twenty-five degrees
Fahrenheit (525.degree. F., 274.degree. C.), with a speed of about
thirty-six and one half (36.5) inches per minute. The conveying
oven is generally known in the art.
[0150] 11. The hot oven tube is then taken back to the Hauni HP
Simulator.
[0151] 12. Put the right nonwoven bag having a length of about two
to about two and one quarter inches (2-2.25 in.) long, inside out,
over the end of an "upside down" cold oven tube (0.531'' in
diameter). This second, cold oven tube is "cold" because it has not
been preheated. The cold oven tube is placed onto a transfer
station on the HP Simulator.
[0152] 13. Remove the pledget from the hot oven tube and put the
oven tube back into the warm oven, which is maintained at a
temperature of about two hundred sixty degrees Fahrenheit
(260.degree. F., 127.degree. C.).
[0153] 14. The hot formed pledget is then placed into the transfer
throat. It is then transferred into the cold oven tube through the
bag. This will push the bag and the pledget into the cold oven
tube.
[0154] 15. Transfer the bagged pledget from the cold oven tube into
the stringer chain with the open end of the bag at the "stringing"
end of the chain link.
[0155] 16. The string is then put through the bottom of the
pledget.
[0156] 17. The excess open portion of the bag is then folded into
the middle.
[0157] 18. The flat bag end is folded down to the end of the
pledget. Then a knot is tied to secure the string to the
pledget.
[0158] 19. The formed, strung pledget is then transferred, using
air cylinder pressure, to a super GENTLE GLIDE white
applicator.
[0159] 20. Steps 5-19 are repeated a sufficient number of times to
make the twenty-five plus (25+) tampons for the cell of interest.
Then the tampons are placed into a large polyethylene bag for each
cell. Each bag is then labeled with the particular cell number,
including a short description of which fiber treatment was used, if
any, for the particular cell.
[0160] Two tests were done to demonstrate aspects of the present
invention, the standard Syngyna testing for absorbency and moisture
testing. The procedure for Syngyna testing is provided below.
Moisture testing, e.g., a loss of weight on drying, was done using
a Mettler-Toledo Halogen Analyzer, Model No. MR-73. Three to five
replicate moisture analyses were typically done for each
example.
[0161] Preparation of Bags Used in the Bagged Pledget Forming Tests
Described Above
[0162] The following descriptions outline exemplary methods for
preparing nonwoven bags used to evaluate small amounts of different
fibers. Four different types of nonwoven material were used to make
bags in experiments described herein. Although, the inventors did
not observe any differences in results obtained that would be
attributed to different types of bags used.
[0163] The nonwoven material used for many of the examples
described herein was a "cover stock" type of nonwoven material
designated in the tables below as "PGI-1," which is a 0.5 oz. per
sq. yd. material sold as BiCo #4139 by PGI (Chicopee, Ark.). A
variant of the PGI nonwoven web, prepared at a slightly lower basis
weight, was used and is labeled in the tables below as "PGI-2,"
which is a 0.4 oz. per square yard material. Also, some nonwoven
bags, labeled as "BDK," were made from material purchased from BDK
Nonwovens (NC, USA) under Style number 1014, R-73763. Finally, some
bags were made using a spunbond polyethylene/polyester
heat-sealable nonwoven blend, labeled "HDK" in the tables below, 16
gsm, available from HDK Industries, Inc. (Rogersville, Tenn.
USA).
[0164] Cutting:
[0165] 1. Coverstock should be cut to the right size. A sample of
an appropriate coverstock nonwoven (one of the three described
above) should be cut, using the automated cutter such as, for
example, a Sur-Size.TM. cutter, Model #SS-6/JS/SP, available from
Azco Corp., NJ. As described herein, in one embodiment, a preferred
size for the cover stock is about five inches by about three and
three quarters inches (5.0''.times.3.75'') nonwoven piece.
[0166] Bag Making:
[0167] 2. A special fixture was set up for sealing the bags. The
sealing fixture was set at a temperature of two hundred ninety-six
degrees Fahrenheit (296.degree. F., 147.degree. C.) with a dwell
time of about 5.1 seconds. Air and vacuum lines should be put into
place, and the targeted temperature reached to +/-two degrees
Fahrenheit (2.degree. F., 1.degree. C.). The cover stock is then
wrapped around the heated horizontal vacuum mandrel as described
below.
[0168] 3. A horizontal vacuum mandrel is manually rotated utilizing
a hub collar until a set of double row vacuum holes are located at
a predetermined location such as, for example, at a "top dead
center" (e.g., a 12 o'clock position).
[0169] 4. Place the pre-cut piece of cover stock 600 on a vacuum
mandrel 610 as illustrated in FIG. 7.
[0170] 5. The cover stock 600 is manually wrap around the vacuum
mandrel 610 until the trailing cut edge overlaps the starting edge
by about one quarter of an inch (0.25 in).
[0171] 6. Grasping a hub collar 620, rotate the vacuum mandrel 610
clockwise toward the sealing bar by about ninety degrees
(90.degree.) until it clicks into place. The overlapped seam will
now be facing towards the sealing bar.
[0172] 7. With hands positioned clear of the mandrel 610, press the
"start" button on the control panel to actuate the sealing bar.
[0173] 8. After about 5.1 seconds, the sealing bar retracts and the
sealed cylindrical cover stock tube is removed, by sliding it off
of the mandrel.
[0174] 9. After removing the cover stock cylindrical tube, the
sealed overlap seam is inspected so that uniform bonding/sealing
has been ensured.
[0175] 10. A sufficient number of such bags are made from the cover
stock pieces cut in step 1, using this special fixture.
[0176] 11. Use the formed bags in the procedure described above for
bagged pledgets.
Standard Procedure for Making Tampons Using the HP Simulator
[0177] 1. Install the following individual sub-component parts
based on the type of pledget outlined in the test request (see
instructions above). Sub-component parts include, for example, a
fluted ram 710 (add shims as required), a solid ram 720 (add shims
as required), a forming throat 730, a forming chain link 740, a
delivery cone 750, an oven tube 760 and a stringer chain 770. FIG.
8 illustrates a detailed set up using these subcomponent parts of
an HP simulator 700. More particularly, FIG. 8 illustrates the
arrangement of tubes used in the formation of a folded tampon by
the procedure outlined above. In the simulator 700, the fluted ram
710 is used to ram the crosspad pledget into the forming chain 740.
Then, the solid ram 720 delivers the folded pledget into the heated
oven tube 760, before it is ejected into the stringer tube 770 for
stringing. It should be appreciated that the appropriate sizes for
the various rams and tubes are selected, in accordance to what size
and what absorbency range is required for the particular tampon. In
one embodiment, a 0.25'' fluted ram 710 (with a 3 mm shim), a
0.374'' solid ram 720 (no shims), a 0.618'' forming throat 730, a
0.621'' forming chain 740, a 0.527'' delivery cone 750, a 0.495''
oven tube 760, and a 0.539'' stringer chain 770 were used to make
the tampons described in this invention.
[0178] 2. First, nonwoven webs are made by using, for example, a
Rando webber (Rando Machines, NY). A needle punching machine is
used to form and bind the appropriate nonwoven webs together.
Slitting and winding is done to form web doffs. The webs are all
made in the webbing machine to target the desired web density, by
adjusting the air-to-fiber ratio in the Rando machine. Typically,
the web density is, for example, about 300 gsm. Then, using the
automated cutting machine, as described in step 1 of the Bag Making
Instructions above, web pieces are cut to the appropriate size. For
example, typically two inch by four inch (2 in.times.4 in) pieces
are cut.
[0179] 3. Once the web pieces have been cut, place the cross-pad
layup (2 web pieces or pads) on the staging platform of the
simulator. The pads should be centered equally to one another to
form a symmetrical cross pattern.
[0180] 4. Center the lay-up under the fluted ram 710 located on the
right side of the simulator 700.
[0181] 5. Ensure that the forming chain 740 is positioned to the
right against the mechanical stop. The forming chain 740 should be
situated directly under the forming throat 730.
[0182] 6. Place one finger from each hand on the left and right
"Pressure Switches" simultaneously. Continue to hold these switches
during the entire cycle. The machine will start, and the ram will
descend as soon as both switches have pressure applied.
[0183] 7. Remove both hands from the pressure switches at the end
of the cycle. This is the point at which the fluted ram 710 has
returned to the full up starting position.
[0184] 8. With the pledget having now been inserted into the
forming chain 740 and the machine stopped, the operator should
swing the forming chain 740 to the left until it is against the
left side mechanical stop. The forming chain 740 must now be
situated directly over the delivery cone 750 and under the solid
ram 720.
[0185] 9. Place the appropriate size "pre-heated" oven tube 760
directly under the throat of the delivery cone 750. Engage the
spring loaded oven tube retainer arm. The heated oven tube 760
should be fully inserted or the machine will jam severely during
the pledget insertion cycle.
[0186] 10. Once again, place one finger from each hand on the left
and right "Pressure Switches" simultaneously and continue to hold
switches during the entire cycle. The machine will start and ram
will descend as soon as both switches have pressure applied.
[0187] 11. Remove both hands from the pressure switches at the end
of the cycle which will be when the solid ram 720 has returned to
the full up starting position.
[0188] 12. Disengage the oven tube retaining arm.
[0189] 13. With a glove, remove the oven tube 760. At this point
the oven tube 760 now has a formed "uncured" pledget inside.
[0190] 14. Optionally, a special tapering/doming tool is used to
shape the pledget and taper it to reduce the diameter at the
pledget insertion end. This is done by air actuating a mandrel with
a specially shaped, molded end.
[0191] 15. Place the oven tube 760 with the pledget inside onto the
curing oven conveyor.
[0192] 16. Pledgets are then ejected out of the oven tube 760 into
an appropriate sized stringer chain tube 770. Using a barbed
needle, a string is attached to the pledget and then tied into a
knot to secure the string to the pledget, with the needle removed.
Then the pledget is removed from the stringer chain tube 770. It is
then added to an appropriate size tampon applicator using an air
actuated ram.
[0193] 17. Finally, the applicator petals are heated to close off
the applicator barrel (top portion of the applicator. This keeps
the pledget from getting contaminated.
[0194] 18. Steps 2 through 17 are repeated for each tampon to be
made.
[0195] Syngyna Test Method (Absorbent Capacity)
[0196] Testing is done, in accordance with Standard FDA Syngyna
capacity as outlined in the Federal Register Part 801, 801.43.
[0197] An un-lubricated condom, with tensile strength between 17-30
MPa, is attached to the large end of a glass chamber with a rubber
band and pushed through the small end using a smooth, finished rod.
The condom is pulled through until all slack is removed. The tip of
the condom is cut off and the remaining end of the condom is
stretched over the end of the tube and secured with a rubber band.
A tampon pre-weighed (to the nearest 0.01 gram) is placed within
the condom membrane so that the center of gravity of the tampon is
at the center of the chamber. An infusion needle (14 gauge) is
inserted through the septum created by the condom tip until it
contacts the end of the tampon. The outer chamber is filled with
water pumped from a temperature controlled water bath to maintain
the average temperature at twenty-seven degrees Celsius (27.degree.
C.) plus or minus one (1) degree Celsius. The water returns to the
water bath.
[0198] A Syngyna fluid (10 grams sodium chloride, 0.5 grams
Certified Reagent Acid Fuchsin, diluted to 1,000 milliliters with
distilled water) is then pumped through the infusion needle at a
rate of about fifty (50) milliliters per hour. The test terminates
when the tampon is saturated and the first drop of fluid exits the
apparatus. The test is aborted if fluid is detected in the folds of
the condom before the tampon is saturated. The water is then
drained and the tampon is removed and immediately weighted to the
nearest 0.01 grams. The absorbent capacity of the tampon is
determined by subtracting its dry weight from the wet final weight.
The condom is replaced after ten (10) tests or at the end of the
day during which the condom is used in testing, whichever comes
first.
[0199] Results
[0200] Table 1 below provides a list of examples conducted to
illustrate aspects of the present invention. The examples include
post-crosslinking of rayon fiber, specifically multilobal rayon
fiber.
[0201] As can seen, several control samples were run with standard,
e.g., untreated, uncrosslinked fiber for comparison purposes. The
control samples were included since various nonwoven bags were
used. Several examples show that hydrothermal treatments were done
on fiber, using various conditions. Finally, a variety of
chemically crosslinked schemes were investigated. A detailed
description is provided for these examples, as well as a shorter
name, for reference in subsequent data tables. The hydrothermal and
chemical crosslinking schemes have been outlined above. The various
treatments listed in the tables correspond to the specific schemes
listed above.
TABLE-US-00001 TABLE 1 Description of Examples. (Those labeled with
C are Comparative Examples). Level of Crosslinking Crosslinker or
Example type (short Hydrothermal Nonwoven ID name) Conditions Bag
Used Full Description C1 Control NA HDK Kelheim ML Control Fiber in
Bag C2 Control NA HDK Kelheim ML Control Fiber in Bag C3 Control NA
BDK Kelheim ML Control Fiber in Bag C4 Control NA HDK Kelheim ML
Control Fiber in Bag C5 Control NA PGI-1 Kelheim ML Control Fiber
in Bag C6 Control NA PGI-2 Kelheim ML Control Fiber in Bag E1 HT
100 deg/60 min BDK Hydrothermal Treatment, 100 deg C., 60 minutes
E2 HT 108 deg/60 min HDK Hydrothermal Treatment, 108 deg C., 60
minutes E3 HT 116 deg/45 min PGI-1 Hydrothermal Treatment, 116 deg
C., 45 minutes E4 HT 116 deg/45 min BDK Hydrothermal Treatment, 116
deg C., 45 minutes E5 HT 116 deg/45 min PGI-1 Hydrothermal
Treatment, 116 deg C., 45 minutes E6 HT 116 deg/45 min PGI-2
Hydrothermal Treatment, 116 deg C., 45 minutes E7 HT 116 deg/45 min
BDK Hydrothermal Treatment, 116 deg C., 45 minutes E8 HT 116 deg/45
min HDK Hydrothermal Treatment, 116 deg C., 45 minutes E9 HT 124
deg/30 min BDK Hydrothermal Treatment, 124 deg C., 30 minutes E10
Cit 1% PGI-2 Rayon treated with Citric acid/NaH2PO2 (1%/1%), 25%
dried before curing E11 Cit 1% PGI-2 Rayon treated with Citric
acid/NaH2PO2 (1%/1%), 50% dried before curing E12 Cit 1% PGI-1
Rayon treated with Citric acid/NaH2PO2 (1%/1%), 25% dried before
curing E13 Cit 1% PGI-1 Rayon treated with Citric acid/NaH2PO2
(1%/1%), 25% dried before curing E14 Gly 1% HDK Rayon treated with
Glyoxal/glyoxal resin/MgCl2(1%/1%/1%), 50% dried before curing E15
Gly 3% HDK Rayon treated with Glyoxal/glyoxal
resin/MgCl2(3%/3%/3%), 50% dried before curing E16 Gly 3% PGI-1
Rayon treated with Glyoxal/glyoxal resin/MgCl2(3%/3%/3%), 50% dried
before curing E17 Gly 3% PGI-1 Rayon treated with Glyoxal/glyoxal
resin/MgCl2(3%/3%/3%), 50% dried before curing E18 BTCA 1% BDK
Rayon treated with BTCA, 25% dried before curing E19 BTCA 1% BDK
Rayon treated with BTCA, 50% dried before curing E20 DMD 1% BDK
Rayon treated with DMDHEU (1%)/MgCl2 E21 DMD 5% BDK Rayon treated
with DMDHEU (5%)/MgCl2 E22 EDGE 3% PGI-2 Rayon treated with
Ethylene Glycol-Diglycidylether (EDGE) (3%) E23 EDGE 5% PGI-2 Rayon
treated with Ethylene Glycol-Diglycidylether (EDGE) (5%) E24 DCHTRI
1% HDK Rayon treated with DCH-Triazine-NaHCO3 (1%/1%), 25% dried
before curing E25 DCHTRI 3% HDK Rayon treated with
DCH-Triazine-NaHCO3 (3%/3%), 50% dried before curing.
[0202] Table 2 provides the results for the Syngyna absorbency
(absolute and gram per gram) as well as the results for the
moisture values for the examples listed in Table 1 above. As shown,
absorbency results are slightly lower than expected for super
tampons. This is as a consequence of the bagged tampon method used
to form these tampons. It should be noted that the differences in
absorbency and moisture for the various treatments are quite a bit
different than would be expected based upon the standard errors for
these measurements. Results for Syngyna absorbency averages, for
example, range from a minimum of 5.61 grams to a maximum of 9.56
grams in Table 2, even though the standard error of estimate is
about 0.16 grams.
TABLE-US-00002 TABLE 2 Key Syngyna and Moisture Results for the
Examples Listed in Table 1 Level of Average Crosslinking
Crosslinker or Moisture Example type (short Hydrothermal Average
avg. g/g level (LOD), ID name) Conditions absorbency absorbency %
C1 Control NA 7.825 2.548 10.360 C2 Control NA 7.628 2.489 10.038
C3 Control NA 7.364 2.433 11.960 C4 Control NA 7.258 2.402 11.917
C5 Control NA 8.036 2.619 9.833 C6 Control NA 8.069 2.634 10.673 E1
HT 100/60 7.455 2.279 6.750 E2 HT 108/60 8.704 2.666 7.063 E3 HT
116/45 9.324 2.960 8.348 E4 HT 116/45 7.870 2.474 8.420 E5 HT
116/45 9.555 2.942 6.503 E6 HT 116/45 8.899 2.769 8.225 E7 HT
116/45 8.799 2.756 8.370 E8 HT 116/45 8.904 2.701 6.523 E9 HT
124/30 8.728 2.668 6.440 E10 Cit 1% 8.375 2.619 6.898 E11 Cit 1%
8.083 2.520 6.370 E12 Cit 1% 8.991 2.797 6.958 E13 Cit 1% 9.590
2.963 5.803 E14 Gly 1% 7.628 2.357 7.173 E15 Gly 3% 7.921 2.405
6.123 E16 Gly 3% 8.795 2.765 7.080 E17 Gly 3% 9.245 2.882 6.848 E18
BTCA 1% 7.579 2.403 8.923 E19 BTCA 1% 7.850 2.429 7.828 E20 DMD 1%
7.614 2.402 8.830 E21 DMD 5% 7.071 2.221 8.355 E22 EDGE 3% 8.049
2.523 6.855 E23 EDGE 5% 8.307 2.587 6.128 E24 DCHTRI 1% 6.170 1.876
5.910 E25 DCHTRI 3% 5.609 1.715 6.233 Average standard error for
measurements 0.156 0.052 0.229 (estimated from replicates)
[0203] Table 3 repeats some of the key data from Table 2 and
provides a statistical analysis of results for some promising
crosslinking treatments.
[0204] In summary, lab tests illustrate that the average absorbency
results for multilobal fiber that has been heat treated in an
autoclave at one hundred sixteen degrees Celsius (116.degree. C.)
for about forty-five (45) minutes (examples E3-E8) is about sixteen
percent (16%) more absorbent overall, ten percent (10%) on a gram
per gram basis, than that of comparable control fiber samples
(C1-C6). Absorbency results may be influenced by large moisture
level differences and slight forming and bagging differences.
However, the inventors have noted that differences in moisture
level from eight to eleven percent (8% to 11%), as reported here,
are not sufficient enough to account for a sixteen percent (16%)
absorbency increase. Example E3 is seen to represent a good
exemplification of the inventive concepts disclosed herein.
[0205] It should be appreciated that Tables 2 and 3 illustrate that
the one percent (1%) citric acid/one percent (1%) sodium
hypophosphite crosslinking treatment results (e.g., examples
E10-E13) also look acceptable relative to control results. These
samples are even drier than those for the hydrothermal treatments,
yet there is evidently a sizable (e.g., fourteen percent (14%))
absorbency increase.
[0206] The three percent (3%) glyoxal/three percent (3%) glyoxal
resin/three percent (3%) magnesium chloride treatment results
(e.g., examples E15-E17) also exhibit high Syngyna absorbency
relative to control results. Results are about thirteen percent
(13%) higher overall for this treatment. All other treatments
exhibited absorbency values which were roughly comparable or
statistically nearly equivalent to that of the control fiber
samples. Of course, the inventors expect that slight adjustment of
crosslinking conditions or levels may influence these results.
TABLE-US-00003 TABLE 3 Key Comparisons from Table 2: Controls vs.
Hydrothermal Treatment Avg Syngyna Avg gram per Avg Absorbency,
gram moisture X-linker X-Linker Example g absorbency value, %
synth. type Level/Trmt Control vs. Hydrothermal Treatment (116 deg
C./45 min.) C1 7.825 2.548 10.360 Control NA C2 7.628 2.489 10.038
Control NA C3 7.364 2.433 11.960 Control NA C4 7.258 2.402 11.917
Control NA C5 8.036 2.619 9.833 Control NA C6 8.069 2.634 10.673
Control NA E3 9.324 2.960 8.348 HT 116/45 E4 7.870 2.474 8.420 HT
116/45 E5 9.555 2.942 6.503 HT 116/45 E6 8.899 2.769 8.225 HT
116/45 E7 8.799 2.756 8.370 HT 116/45 E8 8.904 2.701 6.523 HT
116/45 t tests 0.0024 0.0182 0.0002 (signif if <0.05) Avg. %
difference 15.53% 9.77% -28.39% Control vs. 1% Citrid Acid E10
8.375 2.619 6.898 Cit 1% E11 8.083 2.520 6.370 Cit 1% E12 8.991
2.797 6.958 Cit 1% E13 9.590 2.963 5.803 Cit 1% t tests 0.0423
0.1257 0.0000 (signif if <0.05) Avg. % difference 13.81% 8.09%
-39.73% Control vs. 3% Glyoxal E15 7.921 2.405 6.123 Gly 3% E16
8.795 2.765 7.080 Gly 3% E17 9.245 2.882 6.848 Gly 3% t tests
0.1195 0.3733 0.0001 (signif if <0.05) Avg. % difference 12.43%
6.48% -38.10%
[0207] Although described in the context of preferred embodiments,
it should be realized that a number of modifications to these
teachings may occur to one skilled in the art. Accordingly, it will
be understood by those skilled in the art that changes in form and
details may be made therein without departing from the scope and
spirit of the invention.
* * * * *
References