U.S. patent application number 10/313762 was filed with the patent office on 2003-06-19 for method for regulating agglomeration of elastic material.
Invention is credited to Ng, Wing-Chak, Zhou, Peiguang.
Application Number | 20030114815 10/313762 |
Document ID | / |
Family ID | 27389256 |
Filed Date | 2003-06-19 |
United States Patent
Application |
20030114815 |
Kind Code |
A1 |
Zhou, Peiguang ; et
al. |
June 19, 2003 |
Method for regulating agglomeration of elastic material
Abstract
The present invention is directed to regulating agglomeration of
elastic material (e.g., elastic strand) by regulating exposure of
the material to water or water vapor. In some versions of the
invention, regulating agglomeration in this way decreases,
minimizes, or eliminates strand breaks on a production machine
using the strand as raw material. Representative embodiments
encompass regulating the material's exposure to water or water
vapor by regulating temperature, humidity, or both around the
elastic material, or containers containing the elastic material, so
that the elastic material remains substantially unagglomerated.
Other representative embodiments encompass packaging the elastic
material in a way that regulates the material's exposure to water
or water vapor so that the material remains substantially
unagglomerated.
Inventors: |
Zhou, Peiguang; (Appleton,
WI) ; Ng, Wing-Chak; (Suwanee, GA) |
Correspondence
Address: |
KIMBERLY-CLARK WORLDWIDE, INC.
401 NORTH LAKE STREET
NEENAH
WI
54956
|
Family ID: |
27389256 |
Appl. No.: |
10/313762 |
Filed: |
December 5, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10313762 |
Dec 5, 2002 |
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09715808 |
Nov 16, 2000 |
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60166348 |
Nov 19, 1999 |
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60222812 |
Aug 4, 2000 |
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Current U.S.
Class: |
604/372 ;
264/340; 264/40.1; 428/364; 53/403; 53/432; 53/477 |
Current CPC
Class: |
D02J 13/00 20130101;
Y10T 428/2913 20150115; A61F 13/4902 20130101; D01F 6/70
20130101 |
Class at
Publication: |
604/372 ;
264/40.1; 264/340; 53/403; 53/432; 53/477; 428/364 |
International
Class: |
A61F 013/15; B65B
031/00; B65B 051/10; D02G 003/22; D06M 011/05 |
Claims
What is claimed is:
1. A method of handling substantially unagglomerated elastic strand
so that the strand remains substantially unagglomerated, the method
comprising the steps of: providing substantially unagglomerated,
elastic strand; and regulating exposure of the strand to water or
water vapor so that the strand remains substantially
unagglomerated.
2. The method of claim 1 wherein the strand's exposure to water or
water vapor is regulated such that the specific humidity around the
strand does not exceed about 0.01 pounds-mass of water vapor per
pound-mass of dry air during storage of the strand at the
geographic site where the strand is made, shipping of the strand
between the geographic site where the strand is made and the
geographic site where the strand is to be used as a raw material,
storage of the strand at the geographic site where the strand is to
be used as a raw material, or some combination thereof.
3. The method of claim 2 wherein the strand is used as a raw
material to produce a substrate composite comprising the strand or
an absorbent article comprising the strand.
4. The method of claim 3 wherein the specific humidity around the
strand does not exceed about 0.005 pounds-mass of water vapor per
pound-mass of dry air.
5. The method of claim 3 wherein the strand's exposure to water
vapor is regulated during shipping of the strand between the
geographic site where the strand is made and the geographic site
where the strand is used as a raw material.
6. The method of claim 5 wherein regulating the strand's exposure
to water vapor comprises controlling the temperature around the
strand or around a container that contains the strand.
7. The method of claim 6 wherein the temperature is controlled to a
value not exceeding about 55 degrees Fahrenheit.
8. The method of claim 5 wherein regulating the strand's exposure
to water vapor comprises controlling the humidity around the strand
or around a container that contains the strand.
9. The method of claims 7 or 8 wherein the strand comprises
polyester, polyurethane, polyether, polyamide, polyacrylate,
polyester-b-polyurethan- e block copolymer,
polyether-b-polyurethane block copolymer, or polyether-b-polyamide
block copolymer.
10. The method of claim 8 wherein the strand's exposure to water
vapor is regulated such that the Agglomeration Index Value of the
strand at the time the strand is used as a raw material to produce
a substrate composite comprising the strand, or an absorbent
article comprising the strand, is less than about 20 grams per
strand.
11. The method of claim 8 wherein the strand's exposure to water
vapor is regulated such that the Agglomeration Index Value of the
strand at the time the strand is used as a raw material to produce
a substrate composite comprising the strand, or an absorbent
article comprising the elastic strand, is substantially zero.
12. The method of claim 1 wherein regulating the strand's exposure
to water or water vapor comprises the steps: placing the strand in
a container comprising a barrier material resistant to penetration
by water vapor; and closing the container comprising the barrier
material.
13. The method of claim 12 wherein the container comprising the
barrier material is closed at a time t.sub.1, time t.sub.1 being
after the time when the strand is first produced and before the
time when the strand is shipped from the geographical site where
the strand is made to the geographical site where the strand is
used as a raw material.
14. The method of claim 13 wherein the specific humidity around the
strand does not exceed 0.017 pounds-mass of water vapor per
pound-mass of dry air between time t.sub.1 and time t.sub.2, time
t.sub.2 being the time when the closed container comprising a
barrier material is first opened.
15. The method of claim 13 wherein the specific humidity around the
strand does not exceed 0.01 pounds-mass of water vapor per
pound-mass of dry air between time t.sub.1 and time t.sub.2, time
t.sub.2 being the time when the closed container comprising a
barrier material is first opened.
16. The method of claim 13 wherein the specific humidity around the
strand does not exceed 0.005 pounds-mass of water vapor per
pound-mass of dry air between time t.sub.1 and time t.sub.2, time
t.sub.2 being the time when the closed container comprising a
barrier material is first opened.
17. The method of claim 14 wherein the barrier material is
polyethylene, polypropylene, polyvinyl chloride, polyvinylidene
chloride, polyester, polycarbonate, nylon, cellulose, or some
combination thereof.
18. The method of claim 17 wherein closing the container comprising
a barrier material comprises heat sealing the container, the
barrier material, or both.
19. The method of claim 14 further comprising the step of placing
desiccant material with the strand before closing the container
comprising the barrier material.
20. The method of claim 19 wherein the desiccant material comprises
calcium chloride, calcium sulfate, silica gel, a molecular sieve,
Al.sub.2O.sub.3, or some combination of these.
21. The method of claim 18 or 20 further comprising the steps of
displacing any mixture of air and water vapor from the interior of
the container comprising a barrier material with an inert dry gas
before heat sealing the container, barrier material, or both;
placing a humidity indicator inside the container comprising a
barrier material before heat sealing the container, barrier
material, or both; or both.
22. The method of claims 17 wherein the elastic strand comprises
polyester, polyurethane, polyether, polyamide, polyacrylate,
polyester-b-polyurethane block copolymer, polyether-b-polyurethane
block copolymer, or polyether-b-polyamide block copolymer.
23. The method of claim 14 wherein the strand's exposure to water
vapor is regulated such that the Agglomeration Index Value of the
strand at the time the strand is used as a raw material to produce
a substrate composite comprising the strand, or an absorbent
article comprising the strand, is less than about 20 grams per
strand.
24. The method of claim 14 wherein the strand's exposure to water
vapor is regulated such that the Agglomeration Index Value of the
strand at the time the strand is used as a raw material to produce
a substrate composite comprising the strand, or an absorbent
article comprising the elastic strand, is substantially zero.
25. The method of claim 23 or 24 wherein the tensile strength of
the strand at the time the strand is used as a raw material to
produce a substrate composite comprising the strand, or an
absorbent article comprising the strand, has not decreased by more
than about 20% from the tensile strength of the strand when the
strand was first produced
26. Elastic strand handled by the method of claims 13, 17, 18, 20,
or 23.
27. A substrate composite comprising the elastic strand of claim
26.
28. A disposable absorbent product comprising the substrate
composite of claim 27.
29. Elastic strand handled by the method of claims 8, 10, or
11.
30. A substrate composite comprising the elastic strand of claim
29.
31. An absorbent product comprising the substrate composite of
claim 30.
Description
[0001] This application claims priority from U.S. Provisional
Application No. 60/166,348 filed or Nov. 19, 1999 and No.
60/222,812 filed on Aug. 4, 2000.
BACKGROUND
[0002] People rely on disposable absorbent articles to make their
lives easier.
[0003] Disposable absorbent articles, such as adult incontinence
articles and diapers, are generally manufactured by combining
several components. These components typically include a
liquid-permeable topsheet; a liquid-impermeable backsheet attached
to the topsheet; and an absorbent core located between the topsheet
and the backsheet. When the disposable article is worm, the
liquid-permeable topsheet is positioned next to the body of the
wearer. The topsheet allows passage of bodily fluids into the
absorbent core. The liquid-impermeable backsheet helps prevent
leakage of fluids held in the absorbent core. The absorbent core
generally is designed to have desirable physical properties, e.g. a
high absorbent capacity and high absorption rate, so that bodily
fluids can be transported from the skin of the wearer into the
disposable absorbent article.
[0004] Some disposable absorbent articles are constructed with
various types of elasticized waistbands and elasticized leg bands
or leg cuffs. One method of constructing elasticized regions is to
incorporate elastic strands, ribbon, or other material into the
disposable absorbent product. For example, elastic strands have
been laminated between layers of polymer film and/or layers of
woven or nonwoven fabrics to provide such regions. Folded-over
layers have also been employed to enclose or envelop selected
strands of material. These folded-over layers have been employed to
enclose elastomeric strands within the waistband, leg cuff and
inner barrier cuff components of disposable diapers and other
disposable absorbent articles. The polymeric film or films, layers
of woven or nonwoven fabrics, and/or folded-over layers may be an
integral portion of the topsheet and/or backsheet discussed above,
or may be separate components that are attached to the topsheet
and/or backsheet.
[0005] In order to introduce an elastic material to the product
being made, a spool of the material is generally placed on an
unwind stand. For example, a spool of elastic strand on an unwind
stand is continuously unwound, in the machine direction, with the
strand being attached to a substrate, such as a base layer of
material, to provide a substrate composite. As stated above,
examples of a base material include, but are not limited to,
polymeric films and/or woven or nonwoven fabrics. If a segment of
the elastic strand sticks or adheres to a neighboring segment of
the elastic strand, then the resulting agglomeration of neighboring
segments may be difficult to pull apart when the spool is unwound.
In fact, a strand segment may break, leading to costly downtime on
a production machine.
[0006] What is needed is a method for handling a spool, bobbin,
roll, or other container of elastic material so that the material
remains substantially unagglomerated; spools, bobbins, rolls, or
containers of elastic material in which neighboring segments of the
material remain substantially unagglomerated; and substrate
composites and absorbent products made using elastic material
handled such that the material remains substantially unagglomerated
prior to the material's use as a raw material.
SUMMARY
[0007] We have determined that neighboring segments of elastic
material agglomerate when the material is exposed to water or water
vapor. For example, if elastic strand is made at a location
different from where the strand is used as a raw material, then the
elastic strand must be shipped. During shipping, storage, or other
steps the elastic strand may be exposed to amounts of water or
water vapor sufficient to cause neighboring segments of the strand
to agglomerate. If the strand agglomerates, then it may break more
frequently when used as a raw material in a production process
(e.g., a conventional, high-speed, disposable-absorbent-article
production process running at about 1000 feet per minute or more).
Accordingly, the present invention is directed to regulating
agglomeration of elastic material by regulating the material's
exposure to water or water vapor.
[0008] One method having features of the present invention
comprises the steps of providing substantially unagglomerated
elastic strand; and regulating exposure of the strand to water or
water vapor so that the strand remains substantially
unagglomerated.
[0009] In one representative embodiment, an elastic strand's
exposure to water or water vapor is regulated such that the
specific humidity around the strand does not exceed about 0.017
pounds-mass of water vapor per pound-mass of dry air, specifically
about 0.01 pounds-mass of water vapor per pound-mass of dry air,
and more specifically about 0.005 pounds-mass of water vapor per
pound-mass of dry air during: storage of the strand at the
geographic site where the strand is made, shipping of the strand
between the geographic site where the strand is made and the
geographic site where the strand is to be used as a raw material,
storage of the strand at the geographic site where the strand is to
be used as a raw material, or some combination thereof. In some
versions of the invention, the strand is used as a raw material to
produce a substrate composite comprising the strand or an absorbent
article comprising the strand.
[0010] Another representative embodiment in which an elastic
strand's exposure to water or water vapor is regulated comprises
controlling the temperature around the strand or around a container
that contains the strand so that the strand remains substantially
unagglomerated before the strand's use as a raw material. In one
aspect, the temperature is controlled so that it does not exceed
about 55 degrees Fahrenheit. By regulating temperature, the maximum
humidity that might be attained is regulated (i.e., as air
temperature decreases, the capacity of the air to hold water vapor
decreases).
[0011] In another embodiment, a method in which an elastic strand's
exposure to water or water vapor is regulated comprises controlling
the humidity around the strand or around a container that contains
the strand so that the strand remains substantially unagglomerated
before the strand's use as a raw material. In one aspect, the
specific humidity is controlled so that it does not exceed about
0.017 pounds-mass of water vapor per pound-mass of dry air,
specifically about 0.01 pounds-mass of water vapor per pound-mass
of dry air, and more specifically about 0.005 pounds-mass of water
vapor per pound-mass of dry air.
[0012] In some versions of the invention, the elastic strand to
which exposure to water or water vapor is regulated comprises
polyester, polyurethane, polyether, polyamide, polyacrylate,
polyester-b-polyurethan- e block copolymer,
polyether-b-polyurethane block copolymer, or polyether-b-polyamide
block copolymer.
[0013] Another method having features of the present invention
includes the steps of: providing an elastic strand, the elastic
strand having been made by steps comprising extruding, spinning, or
otherwise making the strand; and regulating the strand's exposure
to water vapor so that the Agglomeration Index Value (defined
below) does not exceed about 10 grams per strand, particularly does
not exceed about 20 grams per strand, more particularly does not
exceed about 25 grams per strand, more specifically does not exceed
about 30 grams per strand, and suitably is substantially zero at
the time it is used as a raw material on a production machine. In
another aspect, the production machine is a machine that
incorporates one or more elastic strands into a substrate composite
or disposable absorbent article.
[0014] In another version of the invention, regulation of an
elastic strand's exposure to water or water vapor comprises the
steps of placing the strand in a container comprising a barrier
material resistant to penetration by water vapor, and closing the
container so that the strand remains substantially
unagglomerated.
[0015] In another method of the present invention, the container
comprising a barrier material is closed at a time t.sub.1, time
t.sub.1 being after the time when the strand is first produced and
before the time when the strand is shipped from the geographical
site where the strand is made to the geographical site where the
strand is used as a raw material. In another aspect, the specific
humidity around the strand does not exceed about 0.017 pounds-mass
of water vapor per pound-mass of dry air, specifically about 0.01
pounds-mass of water vapor per pound-mass of dry air, and more
specifically about 0.005 pounds-mass of water vapor per pound-mass
of dry air between time t.sub.1 and time t.sub.2, time t.sub.2
being the time at which the closed container comprising a barrier
material is first opened.
[0016] In yet another aspect, the barrier material comprises
polyethylene, polypropylene, polyvinyl chloride, polyvinylidene
chloride, polyester, polycarbonate, nylon, cellulose, or a
combination thereof.
[0017] In some versions of the invention, the container comprising
barrier material is closed by heat sealing the container, barrier
material, or both.
[0018] Another method having features of the present invention
comprises placing desiccant material with the strand before the
container comprising a barrier material is closed (e.g., by heat
sealing the barrier material). In another aspect, the desiccant
material comprises calcium chloride, calcium sulfate, silica gel, a
molecular sieve, Al.sub.2O.sub.3, or some combination of
thereof.
[0019] Other representative embodiments comprise the steps of
displacing any mixture of air and water vapor from the interior of
the container comprising a barrier material with an inert dry gas
before the container is closed (e.g., by heat sealing the barrier
material); placing a humidity indicator inside the container
comprising a barrier material before the container is closed (e.g.,
by heat sealing the barrier material); or both.
[0020] Still other representative embodiments of the invention
include elastic strand handled such that the strand remains
substantially unagglomerated by regulating exposure of the strand
to water or water vapor, and substrate composites and disposable
absorbent products made using such elastic strand.
[0021] These and other versions, features, aspects, and advantages
of the present invention will become better understood with regard
to the following description, appended claims, and accompanying
drawings.
DRAWINGS
[0022] FIG. 1 shows a sectional view of one apparatus for making an
elastic strand.
[0023] FIG. 2 shows a sectional view of one apparatus for making an
elastic strand.
[0024] FIG. 3 shows an image of a slit-open spool of strand
(specifically, Glospan 1060, which is available from Globe
Manufacturing Company, a business having offices in Fall River,
Mass.) after the spool had been exposed to a relative humidity of
20% and a temperature of 72.degree. F. for 45 days.
[0025] FIG. 4 shows an image of a slit-open spool of strand
(specifically, Glospan 1060) after the spool had been exposed to a
relative humidity of 80% and a temperature of 100.degree. F. for 3
days.
[0026] FIG. 5 shows an image of a slit-open spool of strand
(specifically, Glospan 1060) after the spool had been exposed to a
relative humidity of 80% and a temperature of 100.degree. F. for 5
days.
[0027] FIG. 6 shows an image of a slit-open spool of strand
(specifically, Glospan 1060) after the spool had been exposed to a
relative humidity of 80% and a temperature of 100.degree. F. for 2
weeks.
[0028] FIG. 7 shows an image of a slit-open spool of strand
(specifically, Glospan 1060) after the spool had been exposed to a
relative humidity of 80% and a temperature of 100.degree. F. for 4
weeks.
[0029] FIG. 8 shows an image of a slit-open spool of strand
(specifically, Glospan 1060) after the spool had been exposed to a
relative humidity of 80% and a temperature of 100.degree. F. for 35
days.
[0030] FIG. 9 shows an image of a slit-open spool of strand
(specifically, Glospan 1060) after the spool, which had been placed
in a bag with 100 g of CaSO.sub.4 and sealed after the air/water
mixture inside the bag had been displaced by substantially dry
nitrogen gas, had been exposed to a relative humidity of 80% and a
temperature of 100.degree. F. for two weeks.
[0031] FIG. 10 shows an image of a slit-open spool of strand
(specifically, Glospan 1060) after the spool, which had been placed
in a bag with 100 g of CaSO.sub.4 and sealed after the air/water
mixture inside the bag had been displaced by substantially dry
nitrogen gas, had been exposed to a relative humidity of 80% and a
temperature of 100.degree. F. for 35 days.
[0032] FIG. 11 shows an image of a slit-open spool of strand
(specifically, Glospan 770, which is available from Globe
Manufacturing Company, a business having offices in Fall River,
Mass.) after the spool had been exposed to a relative humidity of
80% and a temperature of 100.degree. F. for four weeks.
[0033] FIGS. 12.A. and 12.B. show images of a slit-open spool of
strand (specifically, Glospan 1120, which is available from Globe
Manufacturing Company, a business having offices in Fall River,
Mass.) after the spool had been exposed to a relative humidity of
80% and a temperature of 100.degree. F. for 15 days.
[0034] FIGS. 13.A., 13.B., 13.C., and 13.D show images of a
slit-open spool of strand being tested using a tensile-testing
device for purposes of determining the Agglomeration Index Value
(see below).
DESCRIPTION
[0035] The present invention is directed to regulating
agglomeration of elastic material by regulating exposure of the
material to water or water vapor. In some versions of the
invention, regulating agglomeration decreases, minimizes, or
eliminates strand breaks on a production machine using the elastic
material as a raw material. Several representative embodiments of
the present invention are discussed in the following
paragraphs.
[0036] An elastic strand may be made in various ways, including,
but not limited to extrusion and spinning. In an extrusion process,
depicted in FIG. 1, polymer chips, particulates, pellets, or other
solid forms 10 are placed in a hopper 12. The solid polymer is
directed from the hopper to a chamber 14. The polymer is propelled
continuously through the chamber by a rotating screw 16. As the
polymer proceeds through the chamber, the temperature and pressure
are such that the solid polymer melts and is compacted. Some of the
heat is generated by friction, but typically, an external heating
source 18 is also used to heat the polymer. The molten polymer is
then forced through a die 20 to give a strand, continuous fiber,
ribbon, or filament of a desired structural shape. Possible
cross-sectional shapes include, but are not limited to, circular,
tri-lobal, polyhedral, rectangular, ribbon-like, or ellipsoidal
shapes. Furthermore, the strand may have a variety of
cross-sectional dimensions, cross-sectional areas, and/or other
physical measurements (e.g., denier or decitex; see Examples
below). As discussed below, the present invention covers elastic
material that is susceptible to agglomeration due to the action of
water or water vapor. The strand cools and solidifies after exiting
the extruder.
[0037] Rather than use a polymer as a feed material, one or more
monomers or pre-polymeric materials may be added to the extruder in
chip, particulate, pellet or other solid form. The monomers or
pre-polymers may be added with compounds that promote
polymerization. Polymerization occurs within the extruder chamber,
but may or may not be complete before the material exits through
the die. If polymerization is not complete, then some
polymerization could occur after the material is extruded. Also,
some of the monomer may not ultimately react to become a part of a
polymeric chain in the strand.
[0038] A number of materials may be extruded to give an elastic
strand. The present invention is directed to a strand that is
elastic, but is susceptible to attack by water or water vapor
(e.g., by a hydrolysis reaction). Examples of materials that can
give such an elastic strand include, but are not limited to:
polyester, polyurethane; polyether; polyamide; polyacrylate; or
combinations thereof, including random, block, or graft copolymers
such as polyester-b-polyurethane block copolymers,
polyether-b-polyurethane block copolymers, and/or
polyether-b-polyamide block copolymers. As stated above, monomeric
or pre-polymeric precursors may be added to the extruder to give
the polymeric materials of the type just recited.
[0039] Crosslinking agents may also be used when making an elastic
strand. To the extent that polymeric chains are crosslinked, it is
more likely that crosslinking reactions are initiated after the
material is extruded. This may be accomplished, for example, in a
separate processing step after the strand is extruded.
[0040] After the strand exits the extruder, it may be subjected to
additional processing steps. These processing steps may take place
at some location between extrusion of the strand and the strand
being wound up at a bobbin, spindle, or spool for the first time.
Alternatively, one or more of these processing steps may take place
after the strand has been wound up for the first time. After a
bobbin of elastic strand is made, it may later be unwound and
treated in some fashion prior to its being wound up again.
[0041] Additional processing steps include, but are not limited to,
the following. Air might be directed at the strand exiting the die
to increase the cooling rate. A scouring step might be included to
remove impurities from the strand by exposing the strand to soaps
or detergents. A lubricant may be applied to the strand to reduce
friction between strands or between the strand and pieces of
equipment. Possible lubricants include, but are not limited to, a
vegetable or mineral oil, a suitably refined petroleum product, a
silicone-based material, or a surfactant. And a drawing step may be
included to help orient the polymers to produce desirable physical
properties. In one example of a separate drawing step, the strand
is directed over two sets of rolls. The strand passes over a first
set of rolls moving at a first velocity, then passes over a second
set of rolls moving at a second velocity, the second velocity being
greater than the first velocity. The difference in velocity between
the first and second sets of rolls increases tension on the strand,
thereby helping to orient the constituent polymers of the strand,
change physical dimensions of the strand, or effect other
changes.
[0042] After these or other additional processing steps, the strand
is wound up for storage or shipment to another geographic location.
During this or other steps in which a spool, reel, or bobbin of an
elastic strand is unwound and then wound, the strand may be treated
with various additives such as cleaning agents, lubricants, or
dyes.
[0043] In addition to the example of an extrusion process discussed
above, various spinning processes may be used to produce an elastic
strand or fiber. In general, these processes require dissolving the
polymer in solution or melting the polymer.
[0044] In a melt spinning process, as depicted in FIG. 2, polymer
chips, particulates, pellets, or other solid forms 30 are heated by
a heated-metal grid 32 or other heating device. The resulting
molten polymer 34 is pumped under high pressure through a plate
called a spinneret 38. The plate generally defines a plurality of
small holes. The molten polymer emerges from the face of the
spinneret, usually into air, and solidifies. A number of these
strands 40 may be brought together to form a cable- or rope-like
structure comprising a plurality of strands.
[0045] The polymer typically is melted by contacting a hot grid in
the form of steel tubing, which is heated electrically, or by some
other means. A metering pump 36, or a combination of a metering
pump and a booster pump, may be used to conduct the molten polymer
to, and through, the spinneret. Alternatively, an extrusion-type
screw may be used to help melt the polymer, and meter the resulting
molten polymer, to and through the spinneret.
[0046] Generally strands or filaments emerge from the spinneret
face into air and begin to cool. Air jets or blasts directed at the
emerging strands may be used to speed up the cooling process. After
the strands or filaments have traveled far enough to solidify they
are processed further. As stated above, additional process steps
include, but are not limited to, scouring, lubricating, or drawing
the strand or strands. FIG. 2, for example, depicts a lubricating
disk and trough 42 for applying a lubricant to one or more strands.
After processing is complete the strand--in this case a cable- or
rope-like structure--is wound up on a reel, spindle, spool, or
bobbin 44 at a winding station. Before being wound up, the strand
may pass over one or more rolls 46.
[0047] Other spinning processes include wet spinning, in which a
solution of a polymer or polymer derivative emerges from a
spinneret into a liquid that coagulates the polymer or polymer
derivative to form a strand; and dry spinning in which a solution
of polymer emerges from the spinneret into air or an inert gas
atmosphere into which solvent evaporates, thereby forming a
filament or strand.
[0048] Generally, the same polymeric or monomeric materials useful
for extruding an elastic strand are also useful for spinning an
elastic strand. As discussed above, the present invention is
directed to a strand that is elastic but is susceptible to attack
by water or water vapor. Examples of monomeric or polymeric
materials that give such a strand are discussed above. Also,
crosslinking agents may be used. Again crosslinking will likely be
effected after the strand or filament emerges from the
spinneret.
[0049] Other descriptions of processes for making strand are given
in various publications, e.g. U.S. Pat. Nos. 4,340,563 and
3,692,618, which are hereby incorporated by reference in a manner
consistent herewith. It should be understood that the above
discussion and referenced publications recite exemplars of ways in
which strand is made. The present invention is not limited to these
exemplars, but may be used in conjunction with other processes that
make an elastic material susceptible to attack by water or water
vapor such that neighboring segments of the material stick to or
adhere to each other, thus producing agglomeration.
[0050] If an elastic strand is made at a geographic location
different from the location where the strand is used as a raw
material, then the elastic strand must be shipped. Prior to
shipment the strand may be stored for some period of time. And the
strand may be stored for some period of time after delivery but
prior to use as a raw material. Even if the elastic strand is made
at the same place where the strand is used as a raw material, the
strand may be stored for some time. Depending on the time of year;
the location of the site where the strand is made; the location of
the site where the strand is used as a raw material; the method of
shipment; the time that elapses between spinning, extruding, or
otherwise making the strand and utilization of the strand as a raw
material, as well as other factors, the elastic strand may be
exposed to water or water vapor sufficient to produce
agglomeration.
[0051] Before referring to figures demonstrating that water vapor
may cause a segment of elastic material to attach, stick, or adhere
to one or more neighboring segments of elastic material, it is
advantageous to discuss certain terms. As discussed herein, "peak
load" or "peak-load value" refers to either: (a) the load, measured
in grams, placed on a strand segment when the strand segment is
pulled from a spool of elastic strand that has been slit lengthwise
(discussed below in the section entitled Agglomeration Index
Value); or (b) the tensile load, measured in grams, placed on the
strand when the strand breaks or fails (discussed below and in
co-pending U.S. Patent Application No. 60/166,348 [Attorney Docket
No. 15,427], which the present non-provisional application claims
priority from and incorporates by reference in a manner consistent
herewith). It should be understood that other measures may be used
to characterize the effect of water or water vapor on the tendency
of neighboring segments of elastic strand to agglomerate, or the
strength characteristics of a strand. As discussed herein,
"elongation" refers to the change in length per unit length at peak
load. Typically, elongation is recited as a percentage. The term
specific humidity generally refers to the mass of vapor carried by
a unit mass of vapor-free gas. As used herein, "specific humidity"
refers to the mass of water vapor carried by a unit mass of
vapor-free gas, the gas typically being air. The term relative
humidity generally refers to the ratio of the partial pressure of
the vapor to the vapor pressure of the liquid at the gas
temperature. It is usually expressed on a percentage basis, so 100
percent relative humidity means that the gas is saturated with
vapor and 0 percent relative humidity means that the gas is vapor
free. As used herein, "relative humidity" refers to the ratio of
the partial pressure of water vapor to the vapor pressure of water
at the gas temperature, the gas typically being air. For purposes
of this document, "humidity" refers to a measure of the amount of
water vapor in a gas, typically air, and unless stated otherwise,
refers to specific humidity and/or relative humidity. The term dew
point generally refers to the temperature at which a vapor-gas
mixture must be cooled--at constant humidity--to become saturated.
As used herein, "dew point" refers to the temperature at which a
water vapor-gas mixture must be cooled--at constant humidity--to
become saturated, the gas generally being air.
[0052] A comparison of two figures gives a visual example of
agglomeration behavior. FIG. 3 presents an image of a slit-open
spool of GLOSPAN 1060, an elastic material made by Globe
Manufacturing Company, a business having offices in Fall River,
Mass. GLOSPAN 1060 comprises a polyester-b-polyurethane block
copolymer. The strand has cross-sectional dimensions of about 0.2
mm and 1.0 mm, giving a cross-sectional area of about 0.2 mm.sup.2.
The spool itself comprises a hollow cylinder around which the
strand is wound, the cylinder having a radius of 7.5 cm and a
length of 28 cm. The strand was wound around the hollow cylinder in
a spiral or helical fashion, with the outer surface of the wound-up
strand extending radially outwardly from the surface of the hollow
cylinder or core a distance of about 3.5 cm from the surface of the
cylinder or core. Prior to the spool being slit open, the spool, in
its wound-up form, was placed in an environment in which the
temperature was 72.degree. F. and the relative humidity was about
20%. A humidity chart for air at atmospheric pressure shows that
these conditions correspond to a humidity of about 0.004
pounds-mass ("lb.sub.m") of water vapor per lb.sub.m of dry air.
For an example of such a humidity chart, see Warren L. McCabe and
Julian C. Smith, Unit Operations of Chemical Engineering, pg. 748
(3d ed. 1976). After 45 days of exposure to these conditions, the
spool, after being slit open, remained substantially
unagglomerated.
[0053] FIG. 7 also presents an image of a slit-open spool of
GLOSPAN 1060, but in this case the spool was exposed to a relative
humidity of 80%, at a temperature of 100.degree. F., for 35 days.
These conditions correspond to a humidity of about 0.034 lb.sub.m
of water vapor per lb.sub.m of dry air. As can be seen in this
image, segments of the strand have adhered or attached to
neighboring segments of the strand such that slab-like agglomerates
have formed. If such a spool of agglomerated elastic strand was
unwound during production of an article, then a strand segment,
when unwound from the spool, would be more likely to break because
it might be attached to one or more neighboring segments. The
present invention addresses this issue by regulating the amount of
water or water vapor experienced by the strand during one or more
processing and handling steps occurring after the strand has been
extruded, spun, or otherwise made.
[0054] In one version of the present invention, one or more of the
processing and/or handling steps following extrusion, spinning, or
other strand-manufacturing process are conducted in a
controlled-humidity environment. This is generally accomplished by
carrying out one or more of said steps in a room, compartment, or
other enclosure in which a value corresponding to the humidity in
the enclosure is controlled so that it does not exceed a selected
set point. The set point corresponds to a desired specific humidity
or relative humidity. Control generally comprises first sensing or
measuring a value corresponding to the specific humidity or
relative humidity in the enclosure. Typically, the device used to
sense or measure humidity will be in the vicinity of the elastic
strand. The sensed or measured value is transmitted to a
controller, computer, or other device that compares the sensed or
measured value to a set-point value. If the sensed or measured
value is different from the set-point value, then a control action
may be taken such that the specific humidity or relative humidity
in the enclosure is force adjusted to be at or below the desired
specific humidity or relative humidity.
[0055] Typically, the specific humidity or relative humidity is
force adjusted by directing the air/water-vapor mixture across
cooling coils so that the temperature of the mixture is reduced
below the mixture's dew point. As a result of this cooling process,
a portion of the water vapor condenses on the coils and is removed
as liquid, thereby reducing humidity. By directing a sufficient
amount of the air/water-vapor mixture across the cooling coils, and
then conducting the dehumidified air into the enclosure, humidity
is force adjusted to the desired level. After water vapor has been
condensed and removed by this cooling process, the air may be
heated to increase the dry-bulb temperature. As used herein,
"dry-bulb temperature" refers to the temperature of the
air/water-vapor mixture as indicated by a thermometer placed in the
mixture. Accordingly, as used herein, "controlled-humidity" refers
to environments in which specific humidity and/or relative humidity
are controlled, and, if the air is heated to increase the dry-bulb
temperature after the air/water vapor mixture is dehumidified,
environments in which the dry-bulb temperature is also controlled
or regulated.
[0056] The air/water vapor mixture may be taken from inside the
enclosure, dehumidified, and then recirculated back to the
enclosure; or it may be taken from outside the enclosure,
dehumidified, and brought into the enclosure; or both. For example,
if an enclosure is built around a winding station to which an
elastic strand is continuously directed, there will be an opening
in the enclosure to allow the strand to enter and be wound up. If
the manufacturing environment is hot and humid, then a slight
positive pressure will likely be maintained inside the enclosure to
reduce the amount of hot, humid air entering the enclosure through
the opening. In this case, some quantity of the air/water vapor
mixture outside the enclosure will have to be dehumidified and
brought into the enclosure to replace the air/water vapor mixture
inside the enclosure that is escaping through the opening because
of the positive pressure.
[0057] Rather than control humidity so that it is at or below a
set-point value, the air inside the room or enclosure can be
adjusted to a temperature set point such that the maximum specific
humidity cannot exceed a certain level. Humidity charts for air at
atmospheric pressure may be used to select the appropriate
temperature set point. For example, at a temperature of 40.degree.
F., even at a relative humidity of 100%, the specific humidity is
about 0.006 lb.sub.m of water vapor per lb.sub.m of dry air. As
discussed above, a exposure of elastic material to a specific
humidity of about 0.004 lb.sub.m of water vapor per lb.sub.m of dry
air for 45 days did not produce significant agglomeration.
Accordingly, as used herein, "controlled-temperature" refers to
environments in which temperature is controlled to some value in
order to regulate the amount of water vapor experienced by the
elastic strand.
[0058] As stated above, one embodiment of the invention is directed
to controlling the humidity of one or more of the processing and/or
handling steps following extrusion or spinning. Alternatively, the
temperature of the processing and/or handling step(s) may be
controlled to limit the capacity of the air to hold water vapor.
For example, the step in which the elastic strand is first wound up
at a winder may be carried out in a controlled-humidity or
controlled-temperature environment. Processing steps upstream or
downstream of the first winder may also be carried out in a
controlled-humidity or controlled-temperature environment. As used
herein, "first winder" refers to the winder at which the strand is
first wound up after it is extruded, spun, or otherwise made;
"upstream" refers to those processing steps that occur after the
strand is extruded or spun, but before the first winder; and
"downstream" refers to those processing steps that occur after the
first winder. If one or more additional processing steps occur
after the first winding step at a separate unwinding/winding
station (i.e., a station where the elastic strand is unwound,
processed in some way, and rewound), these one or more additional
processing steps may be carried out in a controlled-humidity or
controlled-temperature environment. To the extent that bobbins of
elastic strand are stored prior to use or shipment, the bobbins may
be stored in a controlled-humidity or controlled-temperature
environment. If elastic strand is being shipped to another
location, the step in which the elastic strand is prepared--perhaps
involving another step in which the elastic strand is unwound and
then wound back up again--and packaged for shipment may also be
carried out in a controlled-humidity or controlled-temperature
environment. And the step of shipping or transporting the elastic
strand itself may be carried out in a controlled-humidity or
controlled-temperature environment.
[0059] All of these steps--winding, storing, preparing and
packaging for shipment (if shipping is necessary), shipping, and
perhaps storing again at the location where the strand will be used
as a raw material--can be carried out in a controlled-humidity or
controlled-temperature environment such that the Agglomeration
Index Value does not exceed about 10 grams per strand, particularly
about 20 grams per strand, more particularly about 25 grams per
strand, and specifically about 30 grams per strand at the time it
is used as a raw material on a production machine (e.g., a machine
for making a disposable absorbent article).
[0060] In some embodiments of the invention, however, one or more
of the steps need not be carried out in a controlled-humidity or
controlled-temperature environment. For example, the elastic strand
can be placed in a container comprising a barrier material. As used
herein, "barrier material" refers to a material that is resistant
to penetration by water vapor. The step of placing elastic strand
in a container comprising a barrier material, e.g. packaging the
elastic strand for storage or shipment, may be accomplished in a
number of ways. Bobbins of elastic strand, or pallets of bobbins of
elastic strand, can be wrapped or encased by a barrier material,
e.g. a suitable shrink-wrap. Alternatively, bobbins of elastic
strand, or pallets of bobbins of elastic strand, may be placed in a
flexible plastic bag comprising a barrier material. Or the elastic
strand may be placed in a box or carton comprising a barrier
material, e.g. lined with or holding a flexible plastic bag that is
resistant to penetration by water vapor. It should be understood
that the present invention encompasses other containers comprising
a barrier material.
[0061] If the elastic strand is placed in a container comprising a
barrier material while in a low-humidity environment, then the
microenvironment immediately around the elastic strand inside the
container will correspond to that low-humidity environment. In
another version of the invention, the air/water vapor mixture
inside the container may be displaced by a substantially dry gas to
create a low-humidity microenvironment around the strand inside the
container (see below). Or a desiccant might be added to
adsorb/absorb any water vapor inside the container. After the
container is closed, subsequent processing steps might be carried
out such that the humidity or temperature outside the container is
not regulated. The container would likely not be opened until the
elastic strand was to be used as a raw material in a production
process.
[0062] A number of methods may be used to package the elastic
strand. The elastic strand may be wound up at a first winder in a
controlled-humidity or controlled-temperature environment, and then
taken, conducted, or conveyed to a controlled-humidity or
controlled-temperature environment for packaging. Alternatively,
the elastic strand may be wound up at a first winder and, soon
thereafter, taken, conducted, or conveyed to a controlled-humidity
or controlled-temperature environment for packaging.
[0063] While in a controlled-humidity or controlled-temperature
environment, bobbins of elastic strand, or pallets of bobbins of
elastic strand are placed in a container comprising a barrier
material. Suitable barrier materials that are resistant to
penetration by water vapor include, but are not limited to,
polyethylene, polypropylene, polyvinyl chloride, polyvinylidene
chloride, polyester, polycarbonate, nylon, cellulose, or a
combination thereof. The density, thickness, identity, and/or other
physical characteristics (e.g., the solubility of water in the
selected barrier material) of the barrier material may be selected
so that the mass transport of water vapor through the barrier
material over the anticipated shipping and/or storage time of the
bobbins, spools, or rolls of elastic material will not lead to
agglomeration of the material, or will not exceed a selected value.
The container is then closed in a way that minimizes the amount of
water vapor that might reach the packaged strand during subsequent
storage and/or shipping steps. For example, if the container
comprising a barrier material is a flexible polyethylene bag or
other flexible, water-vapor-resistant plastic bag, then the
container can be heat sealed after bobbins of elastic strand, or
pallets of bobbins of elastic strand, are inserted into the bag.
Alternatively, bobbins of elastic strand, or pallets of bobbins of
elastic strand, can be placed in a carton or box lined with a
barrier material such as a polyethylene bag, the bag being heat
sealed after the bobbins of elastic strand are in place.
[0064] In another aspect, a method of the present invention further
comprises placing a desiccant material near the elastic strand
prior to the container comprising a barrier material being closed,
e.g. heat sealed. To the extent that the container allows water
vapor to penetrate into and around the elastic strand, the
desiccant acts to preferentially adsorb or absorb the water vapor.
Accordingly, the desiccant helps to keep the humidity inside the
container at a level that minimizes strength degradation.
[0065] Examples of useful desiccants include calcium chloride,
calcium sulfate, silica gel, a molecular sieve, Al.sub.2O.sub.3,
and the like. Typically, the desiccant will be put in a receptacle
that allows passage of water vapor into the interior of the
receptacle and in contact with the desiccant, but keeps the
desiccant separate from the elastic strand. An example of a
receptacle is a pouch comprising a fibrous web of naturally
occurring fibers--typically having cellulose as a primary
constituent--or a nonwoven material such as a polyethylene or
polypropylene nonwoven fabric. Various physical characteristics of
a desiccant (e.g., the mass of water removed per unit mass of
desiccant; the residual concentration of water in air after an
air/water vapor mixture has been placed in contact with the
desiccant under specified conditions) may be evaluated in selecting
the type and amount of desiccant to be used. Furthermore, after a
barrier material having a specific thickness and density has been
selected, one can estimate the amount of water vapor that will
diffuse through the barrier material over the anticipated shipping
and/or storage time. The type and amount of desiccant may then be
selected so that the amount of water vapor that is estimated to
penetrate the barrier material will not exceed the capacity of the
desiccant to adsorb/absorb the water vapor.
[0066] In another aspect, the present invention further comprises
the step of displacing the air/water vapor mixture inside the
container comprising a barrier material with a dry, inert gas
before closing the container. For example, after pallets of bobbins
of elastic material have been placed inside a container, dry
nitrogen gas may be directed to the interior of the container using
a flexible conduit. After sufficient time has passed to allow
displacement of the air/water-vapor mixture from inside the
container, the conduit is removed from the container, and the
container is then closed. This displacement step may be used in
conjunction with the step of placing a desiccant material with the
elastic material prior to closing the container. The displacement
step may or may not be conducted in a controlled-temperature or
controlled-humidity environment.
[0067] In another aspect, a humidity detector is placed with the
elastic strand before the container comprising a barrier material
is closed. When the bag or container is opened, most likely after
it has been shipped to a purchaser of the elastic strand, the
humidity detector can be examined to determine if the humidity
inside the container exceeded a certain value. Alternatively, if
the bag or container comprising a barrier material is transparent,
then the detector could be examined without opening the container.
If the humidity did exceed a certain value, then the bag or
container could be rejected and sent back to the supplier.
Alternatively, a sample from the shipment could be tested
immediately. If the strength characteristics of the strand were
deemed acceptable, then the shipment could be accepted for use as a
raw material. One example of a suitable humidity detector is the
humidity indicator corresponding to catalogue number HC-10160-200,
available from Omega Engineering Inc., of Stamford, Conn. The
indicator is capable of detecting relative humidity over the range
10 to 60 percent.
[0068] The step of placing a humidity detector with the elastic
strand may be used in conjunction with: placing a desiccant with
the strand before a container comprising a barrier material is
closed; displacing the air/water-vapor mixture inside the container
comprising a barrier material with a dry, inert gas before closing
the container; or both.
[0069] In some embodiments of the present invention, bobbins of
elastic strand are stored either at the site where the strand is
made, at the site where the strand is used as a raw material, or
both. If the strand is unpackaged during these storage steps, and
the strand is to be stored for more than 10, specifically more than
20, and particularly more than 30 days, then the room, facility, or
area in which the strand is stored may be a controlled-humidity or
controlled-temperature environment. But, as discussed above, all of
the process and handling steps subsequent to the strand being
extruded or spun may be carried out in controlled-humidity or
controlled-temperature environment--regardless of the total time
between extrusion or spinning of the strand and use of the strand
as a raw material--to minimize or eliminate strength degradation.
Or the elastic strand can be packaged so that the
"micro-environment" inside the container comprising a barrier
material has a low water-vapor content (i.e., a low humidity),
thereby allowing subsequent processing steps to be carried out such
that the environment outside the package need not be
controlled.
[0070] Elastic strands processed or handled in accordance with the
present invention may be incorporated into a number of substrate
composites and disposable absorbent articles. Examples of such
substrate composites and/or disposable absorbent articles are
described in U.S. Pat. No. 4,940,464, entitled "Disposable
Incontinence Garment or Training Pant," which is hereby
incorporated by reference in its entirety; U.S. Pat. No. 5,904,675,
entitled "Absorbent Article with Improved Elastic Margins and
Containment System," which is hereby incorporated by reference in
its entirety, with column 7, lines 7 through 34 discussing use of
elastic strands with a containment flap, and column 9, line 29
through column 10, line 36 discussing elastic members; U.S. Pat.
No. 5,904,672, entitled "Absorbent Article having Improved Waist
Region Dryness and Method of Manufacture," which is hereby
incorporated by reference in its entirety, with column 11, line 39
through column 12, line 2 discussing elastic leg members; and U.S.
Pat. No. 5,902,297, entitled "Absorbent Article Having a Collection
Conduit," which is hereby incorporated by reference in its
entirety. It should be understood that the present invention is
applicable to other structures, composites, or products
incorporating one or more elastic strands.
[0071] An example of a method and apparatus for making an
elastomeric laminate web (i.e., for purposes of the present
application, a substrate composite incorporating elastic strand)
which may be used with the present invention is found in U.S. Pat.
No. 5,964,973, entitled "Method and Apparatus for Making an
Elastomeric Laminate Web," which is hereby incorporated by
reference in a manner consistent with the present specification.
Again it should be understood that this patent gives exemplars of
methods and apparatuses for incorporating elastic strands into
substrate composites, and the present invention may be used with
other methods and apparatuses used to make substrate
composites.
Tests
[0072] Agglomeration Index Value
[0073] Agglomeration Index Value is measured in the following
manner. First, a roll of strand, typically comprising strand wound
around a core, is obtained. The core generally is cylindrical with
an axial dimension and a radial dimension. The strand is slit or
cut with a razor, knife, or other cutting instrument such that the
slit or cut is parallel to the axial dimension of the core. The
depth of the slit or cut may equal the distance from the outer
surface of the roll of strand to the outer surface of the core
around which the strand is wound up, or some increment thereof.
FIG. 3 displays an image of a roll in which the roll of elastic
strand, after being cut in the axial dimension, unraveled in the
form of substantially unagglomerated strand segments. FIG. 7
displays an image of a roll in which the roll of elastic strand,
after being cut in the axial dimension, unraveled in the form of
agglomerated strand segments (e.g., slab-like agglomerates in which
one strand segment is attached to one or more neighboring strand
segments).
[0074] If the rolled-up strand, after being slit, unravels in the
form of substantially unagglomerated strand, then the Agglomeration
Index Value is not measured (the measurement would prove difficult
if an individual strand did not adhere to any of its neighbors).
Instead the Agglomeration Index Value is equated to zero. If,
however, the rolled-up strand, after being slit, unravels in the
form of agglomerated strand, then the core and agglomerated strand
are placed on a support proximate to a tensile-testing device. For
our measurements, a Sintech tensile tester having model number
3108-128, available from MTS System Corporation, a business having
offices in Eden Prairie, Minn., was used. The tensile tester was
modified by attaching an alligator clamp to a length of wire. The
wire was then attached to the tensile tester such that tester was
capable of operably measuring the load, in grams, required to pull
1 or 2 strand segments from the strand agglomerate, with the strand
segment(s) secured by the closed alligator clamp (see FIGS. 13.A.,
13.B., 13.C., and 13.D.).
[0075] The slit-open roll of strand is placed on the support such
that the cut(s) or slit(s) in the rolled-up strand is opposite the
clamp used to pull a predetermined number of strand segments away
from the strand agglomerate (for our experiments, 1 or 2 strand
segments; see FIGS. 13.A., 13.B., 13.C., and 13.D.). When
manipulating the clamp so that a predetermined number of segments
are fastened by the clamp prior to starting the test, the clamp is
manipulated so as to minimize initial separation between the strand
segment(s) to be pulled away from neighboring strand segments. The
tester is then activated so that the clamp is drawn away from the
surface of the slit-open strand material. The clamp is drawn away
in a direction that is substantially perpendicular to the surface
of the slit-open strand material, and at a speed of 300 mm/min. As
the alligator clamp is drawn away from the surface of the strand
agglomerate by the action of the tensile tester, the 1 or 2 strands
that are fastened by the closed alligator clamp are pulled away,
and detached, from the strand agglomerate. The tensile tester
measures the load, in grams, required to pull the predetermined
number of strand segments from neighboring strand segments. The
Agglomeration Index Value corresponds to the average of five to ten
replicates of this test, with load measured as the peak load that
occurs during the test (i.e., the maximum load detected during the
course of the test). If two strands are used when conducting the
test, then the peak load (in grams) is divided by two to give
dimensions of grams per strand.
[0076] In some cases, the Agglomeration Index Value was determined
for strand located at a position proximate to: the surface of the
wound-up spool of strand; the surface of the core around which the
strand was wound ("core position"); and/or a region approximately
half way between the surface of the core and the surface of the
spool of strand ("middle position"). The Agglomeration Index Value
of strand at the middle- and core-positions was measured by cutting
or slicing the wound-up spool and peeling off strands, or layers of
strand, until a strand (or strands) at the desired testing position
was exposed for completing the test as outlined above. Also, as
shown in FIG. 13.C., an object may be inserted into the core around
which the elastic strand is wound if the pulling of strand(s) away
from the strand agglomerate would move the core (typically this
doesn't occur.)
[0077] Although the present invention has been described in
considerable detail with reference to certain versions, other
versions are possible. The spirit and scope of the appended claims
should not be limited to the description of specific versions
contained herein.
EXAMPLES
Example 1
[0078] A bobbin or spool of GLOSPAN 1060, an elastic strand
comprising a polyester-b-polyurethane block copolymer, was obtained
from Globe Manufacturing Company. The number "1060" corresponds to
the denier of the strand; i.e. about 1060 denier or about 1060
grams per 9000 meters of strand. The elastic strand had been coated
with a lubricant. As received, the strand was wound up around a
hollow core. The core had a radius of 7.5 cm (radial dimension) and
a length of 28 cm (axial dimension). The strand was wound around
the core to form a tube comprising the helically- or spirally-wound
strand. The outer surface of the tube of strand extended radially
outwardly from the surface of the core at a distance of about 3.8
cm from the surface of the core. The length of the tube of
helically- or spirally-wound strand was about the same as the
length of the core. (Note: the strand might be systematically
accumulated to form shapes other than a tube or cylinder comprising
the individual strand or strands.) The individual strand had a
cross-sectional area of about 0.2 mm.sup.2 (calculated by
multiplying the cross-sectional dimensions of the strand: 1.0 mm
multiplied by 0.2 mm).
[0079] When received from the manufacturer, the spool comprised
substantially unagglomerated strand. Spools of Glospan 1060 were
placed in a controlled environment, with the temperature controlled
to a value of about 100.degree. F. and the relative humidity
controlled to a value of about 80%. The spools were exposed to
these conditions for various times: 3 days, 5 days, 2 weeks, 4
weeks, and 35 days. After each of these conditioning times had
elapsed, a spool was taken to a room having a temperature of about
72-75.degree. F. and a relative humidity of about 50%. The spool
was then systematically slit along its length with a razor blade.
Typically, the spool was slit within 30 minutes after the spool was
removed from the environment having a temperature of about
100.degree. F. and a relative humidity of about 80%. Generally, the
blade was inserted so that the edge of the blade penetrated to a
depth of about 0.5 to 1 cm or so from the surface of the spool. The
razor was then drawn along the axial dimension of the spool from
one end of the spool to the other. This slitting process was
repeated, generally until a position proximate to the core was
reached. Depending on the time of exposure to the temperature of
about 100.degree. F. and the relative humidity of about 80%, the
roll of strand exhibited different degrees of agglomeration. After
3 days of exposure, a majority of the roll remained substantially
unagglomerated, but the edge of the roll appeared to show some
agglomeration (see FIG. 4; agglomeration of the strand at the edge
is denoted as "edge blocking" in the figure). Similar behavior was
seen after 5 days of exposure (see FIG. 5; agglomeration of the
strand at the edge is denoted as "edge blocking" in the figure;
"open to air" indicates that exposure to the prevailing
conditions-a temperature of about 100.degree. F. and the relative
humidity of about 80%-was not regulated; unless otherwise
specified, spools of elastic material were placed in conditioning
environments so that the material was exposed to the prevailing
conditions). After 2 weeks of exposure to a temperature of about
100.degree. F. and a relative humidity of about 80%, a spool of
Glospan 1060 that had been systematically slit down shows that
agglomeration had increased, with slab-like structures resulting
from the slitting process. (see FIG. 6). In other words,
systematically cutting the spool produced a peeled-onion-like
structure comprising layered slabs of agglomerated strand. Spools
of Glospan 1060 exposed to a temperature of about 100.degree. F.
and the relative humidity of about 80% for 4 weeks and 35 days
again showed agglomeration throughout the roll of strand. (see
FIGS. 7 and 8, respectively). The sequence of images depicted in
FIGS. 4, 5, 6, 7, and 8 establish that exposure to certain
conditions causes a roll of elastic material to agglomerate (i.e.,
strand segments begin to adhere to a least some portion of
neighboring strand segments).
Example 2
[0080] A bobbin or spool of GLOSPAN 770, an elastic strand
comprising a polyester-b-polyurethane block copolymer, was obtained
from Globe Manufacturing Company. The number "770" corresponds to
the denier of the strand; i.e. about 770 denier or about 770 grams
per 9000 meters of strand. The elastic strand had been coated with
a lubricant. The strand was wound up around a hollow core. The core
had a radius of 7.5 cm (radial dimension) and a length of 28 cm
(axial dimension). The strand was wound around the core to form a
tube comprising the helically- or spirally-wound strand. The outer
surface of the tube of strand extended radially outwardly from the
surface of the core at a distance of about 3.5 cm from the surface
of the core. The length of the tube of helically- or spirally-wound
strand was about the same as the length of the core. (Note: the
strand might be systematically accumulated to form shapes other
than a tube or cylinder comprising the individual strand or
strands.) The individual strand had a cross-sectional area of about
0.1 mm.sup.2 (calculated by multiplying the cross-sectional
dimensions of the strand: 0.2 mm multiplied by 0.5 mm).
[0081] When received from the manufacturer, the spool comprised
substantially unagglomerated strand. The spool of Glospan 770 was
placed in a controlled environment, with the temperature controlled
to a value of 100.degree. F. and the relative humidity controlled
to a value of 80%. After the spool was exposed to these conditions
for 4 weeks, it was removed from the environment. The spool was
then taken to a room having a temperature of about 72-75.degree. F.
and a relative humidity of about 50%. The spool was then
systematically slit along its length with a razor blade. Typically,
the spool was slit within about 30 minutes after the spool was
removed from the environment having a temperature of about
100.degree. F. and a relative humidity of about 80%. The blade was
inserted so that the edge of the blade penetrated to a depth of
about 0.5 to 1 cm or so from the surface of the spool. The razor
blade was then drawn along the axial dimension of the spool from
one end of the spool to the other. As depicted in FIG. 11, slitting
the spool of strand in this fashion produced a first slab of
agglomerated strand (this first slab is located farthest from the
core). Repeated slits made in a similar fashion produced additional
slabs of agglomerated strand. Systematically cutting the spool in
this way produced a peeled-onion-like structure comprising layered
slabs of agglomerated strand. Thus, a four-week exposure to a
temperature of 100.degree. F. and a relative humidity of 80% caused
the strand to agglomerate.
Example 3
[0082] A bobbin or spool of GLOSPAN 1120, an elastic strand
comprising a polyester-b-polyurethane block copolymer, was obtained
from Globe Manufacturing Company. The number "1120" corresponds to
the denier of the strand; i.e. about 1120 denier or about 1120
grams per 9000 meters of strand. The elastic strand had been coated
with a lubricant. The strand was wound up around a hollow core. The
core had a radius of 8 cm (radial dimension) and a length of 11 cm
(axial dimension). The strand was wound around the core to form a
tube comprising the helically- or spirally-wound strand. The outer
surface of the tube of strand extended radially outwardly from the
surface of the core at a distance of about 6 cm from the surface of
the core. The width of the tube of helically- or spirally-wound
strand was about 7.5 cm. (Note: the strand might be systematically
accumulated to form shapes other than a tube or cylinder comprising
the individual strand or strands.) The individual strand had a
cross-sectional area of about 0.22 mm.sup.2 (calculated by
multiplying the cross-sectional dimensions of the strand: 0.22 mm
multiplied by 1.0 mm).
[0083] When received from the manufacturer, the spool comprised
substantially unagglomerated strand. The spool of Glospan 1120 was
placed in a controlled environment, with the temperature controlled
to a value of 100.degree. F. and the relative humidity controlled
to a value of 80%. After the spool was exposed to these conditions
for 15 days, it was removed from the environment. The spool was
then taken to a room having a temperature of about 72-75.degree. F.
and a relative humidity of about 50%. The spool was then
systematically slit along its length with a razor blade. Typically,
the spool was slit within about 30 minutes after the spool was
removed from the environment having a temperature of about
100.degree. F. and a relative humidity of about 80%. The blade was
inserted so that the edge of the blade penetrated to a depth of
about 0.5 to 1 cm or so from the surface of the spool. The razor
blade was then drawn along the axial dimension of the spool from
one end of the spool to the other. As depicted in FIGS. 12.A. and
12.B., slitting the spool of strand in this fashion produced a
first slab of agglomerated strand (this first slab is located
farthest from the core). Repeated slits made in a similar fashion
produced additional slabs of agglomerated strand. Systematically
cutting the spool in this way produced a peeled-onion-like
structure comprising layered slabs of agglomerated strand. Thus a
fifteen-day exposure to a temperature of 100.degree. F. and a
relative humidity of 80% caused the strand to agglomerate.
Example 4
[0084] The process outlined in Example 1 for systematically
slitting a spool of strand was carried out on another spool of
Glospan 1060. In this case, the spool of Glospan 1060 was placed in
an environment having a temperature of about 72.degree. F. and a
relative humidity of about 20%. The spool of Glospan 1060 was
removed from this environment after 45 days of exposure to these
conditions and slit down as described in Example 1. As shown in
FIG. 3, slitting the spool of Glospan 1060 in this manner unraveled
the spool to produce substantially unagglomerated strand. Thus
exposure to a lesser amount of water or water vapor reduced or
eliminated agglomeration of the strand.
Example 5
[0085] Spools of GLOSPAN 770 and GLOSPAN 1060 were obtained from
the Globe Manufacturing Company. The elastic strand had been coated
with a lubricant for each of these bobbins. The approximate
dimensions of the core, the tube of helically- or spirally-wound
strand surrounding the tube, and the cross-sectional area of an
individual strand are given in the above examples for GLOSPAN 1060
and GLOSPAN 770.
[0086] When received from the manufacturer, each of the spools
comprised substantially unagglomerated strand. One spool of Glospan
770 and two spools of Glospan 1060 were both placed in a controlled
environment, with the temperature controlled to a value of about
100.degree. F. and the relative humidity controlled to a value of
about 80%. After 2 weeks of exposure to these conditions, one spool
of GLOSPAN 1060 was removed from the controlled environment. Using
the Agglomeration-Index-Value test described above, the
Agglomeration Index Value was determined for strand proximate to
two locations: the surface of the spool of strand; and surface of
the core. After 2 months of exposure to these conditions, the
remaining spool of GLOSPAN 1060 and the remaining spool of GLOSPAN
770 were both removed from the controlled environment. Using the
Agglomeration-Index-Value test described above, the Agglomeration
Index Value was determined for strand proximate to two locations
for GLOSPAN 1060: the surface of each spool of strand; and the
surface of each core. The Agglomeration Index Value was determined
at three locations for GLOSPAN 770, as discussed below.
[0087] Table 1 presents results for GLOSPAN 1060.
1TABLE 1 Measurement of blocking force between Glospan 1060 strands
aged @ 80% RH, 100.degree. F. (By Sintech, 300 mm/min, 75.degree.
F.) Strand Blocking/peak Sample Aging time position load (gm) Note
Fresh Glospan 0 Surface 0 Strand falls from roll, no blocking Fresh
Glospan 0 Core 0 No blocking Aged Glospan 2 weeks Surface 30
Blocking 2 weeks Core 76 Blocking Aged Glospan 2 months Surface
43.5 Blocking 2 months Core 133 Blocking
[0088] Glospan 1060 denoted as "fresh" (i.e., examined and tested
as received from the manufacturer without the spools of strand
being placed in a controlled environment having a temperature of
100.degree. F. and a relative humidity of 80%) did not exhibit
agglomeration (i.e., did not exhibit "blocking"). When a spool of
"fresh" GLOSPAN 1060 was systematically slit down as described
above, the strand unraveled in the form of substantially
unagglomerated strands. Accordingly, the Agglomeration Index Value
(i.e., the peak-load value measured using the
Agglomeration-Index-Value test described above) was equated to
0.
[0089] After exposure to a temperature of 100.degree. F. and a
relative humidity of 80% for two weeks, a spool of GLOSPAN 1060
exhibited agglomeration behavior at locations proximate to the
surface of the tube of strand and the surface of the core.
Furthermore, the Agglomeration Index Value at these locations was
determined to be 30 and 76 grams per strand, respectively (with the
Agglomeration Index Value denoted as "Blocking/Peak Load" in Table
1).
[0090] After exposure to a temperature of 100.degree. F. and a
relative humidity of 80% for two months, a spool of GLOSPAN 1060
exhibited agglomeration behavior at locations proximate to the
surface of the tube of strand and the surface of the core.
Furthermore, the Agglomeration Index Value at these locations was
determined to be 43.5 and 133 grams per strand, respectively.
[0091] The spool of GLOSPAN 770 exposed to a temperature of
100.degree. F. and a relative humidity of 80% for two months
exhibited agglomeration behavior at locations proximate to the
surface of the tube of strand, the region half way between the
surface of the tube of strand and the surface of the core, and the
surface of the core. Furthermore, the Agglomeration Index Value at
these locations was determined to be 24.5, 42.5, and 71 grams per
strand, respectively.
[0092] The data show that continued exposure to water or water
vapor causes strands or strand segments to attach or adhere to
neighboring strands or strand segments, thus forming agglomerated
strand that requires additional force to pull apart.
Example 6
[0093] Spools of GLOSPAN 1060 were obtained from the Globe
Manufacturing Company. The elastic strand had been coated with
lubricant for each of these bobbins. The approximate dimensions of
the core, the tube of helically- or spirally-wound strand
surrounding the tube, and the cross-sectional area of an individual
strand are given in the above examples for GLOSPAN 1060.
[0094] When received from the manufacturer, each of the spools
comprised substantially unagglomerated strand. Eight spools of
Glospan 1060 were placed in a controlled environment, with the
temperature controlled to a value of about 100.degree. F. and the
relative humidity controlled to a value of about 80%. Four of the
spools were placed in the controlled environment so that they were
exposed to the prevailing conditions. Four of the spools were first
prepared in accordance with one version of the invention in order
to regulate exposure of the strand to water or water vapor. Before
these four spools were put in the controlled environment, each
spool was placed in a polyethylene bag having dimensions of 60 cm
by 30 cm by 10 cm and a thickness of 4 mils (i.e., 0.0004 inches).
After a spool was placed in the bag, 100 grams of a drying agent,
in this case CaSO.sub.4, was placed in the bag. In this experiment,
the drying agent was first placed in a nonwoven polypropylene
receptacle, and the polypropylene receptacle containing the drying
agent was then placed in the polyethylene bag containing the spool.
A dry nitrogen gas (purity of gas was 99.99% nitrogen) was then
conducted to the interior of the bag. This was done by connecting
one end of a piece of tubing to a cylinder of nitrogen gas,
positioning the other end of the tubing inside the bag, and opening
the valve on the cylinder. After approximately 5 minutes, the
tubing was withdrawn from inside of the bag and the bag was heat
sealed using heat-sealing equipment. The room in which these four
spools were sealed in polyethylene bags containing a drying agent
had a temperature of about 72-75.degree. F. and a relative humidity
of about 50%. After four spools were prepared in accordance with
one version of the invention, they too were placed in the
controlled environment having temperature controlled to a value of
about 100.degree. F. and the relative humidity controlled to a
value of about 80%.
[0095] After about 5 days (114 hours), a spool of Glospan 1060 that
had been open to the conditioned environment and a spool of Glospan
1060 that had been sealed in a polyethylene bag with desiccant were
removed from the controlled environment. Each of these spools was
systematically slit down as described in the above Examples.
Furthermore, the mechanical properties of strand segments were
measured at locations proximate to the surface of the tube of
wound-up strand, the region half way between the surface of the
tube of strand and the surface of the core, and the surface of the
core. Furthermore, observations were made regarding the degree of
agglomeration (described as "blocking" in the table) that had
occurred. This process was repeated at about 234 hours
(approximately 10 days), 14 days, and 35 days. The results of these
measurements are presented in Table 2 (see next page).
2TABLE 2 Effect of aging on mechanical properties of Glospan 1060
Aging @ 80% RH, 100.degree. F. for different times (Rolls of
Glospan 1060 were aged. The samples were taken from surface, middle
and core of the roll then tested.) Strand from surface Strand from
middle Strand from core Sample T.S. gm Elong. % T.S. gm Elong. %
T.S. gm Elong. % Note Aging 114 hr Open to air 535 1043 591 1250
597 1226 Edge blocking *sealed/dry 586 1273 616 1408 605 1380 No
discoloration of CaSO.sub.4 Aging 234 hr Open to air 416 977 444
1116 493 1084 Some blocking *sealed/dry 600 1239 596 1181 604 1260
-20% of CaSO.sub.4 discolored; no blocking Aging 14 days Open to
air 475 998 493 1091 515 1142 Some blocking *sealed/dry 638 1144
616 1232 606 1217 Discoloration of CaSO.sub.4; no blocking Aging 35
days Open to air 420 997 425 972 474 1024 Blocking *sealed bag 574
1114 576 1324 562 1271 Most CaSO.sub.4 discolored after 20 days; no
blocking *SEALED/DRY = Roll of Glospan 1060 was put in polyethylene
bag with 100 gm dry agent and sealed under N.sub.2. T.S. = tensile
strength, peak load gm; Elong. % = elongation @ break %
[0096] Co-pending U.S. Patent Application No. 60/166,348 (Attorney
Docket No. 15,427) is entitled "Method for Regulating Strength
Degradation in an Elastic Strand," and was filed on Nov. 19, 1999.
This co-pending application is hereby incorporated by reference in
a manner consistent herewith. The co-pending application is
generally directed to a method and apparatus for regulating
exposure of an elastic strand to water or water vapor, thereby
regulating degradation of strength characteristics of the strand
due to the action of water vapor or water on the strand. The
results in Table 2 of the present application demonstrate that
strength degrades due to the action of water vapor. For spools of
Glospan 1060 left open to the prevailing conditions in the
controlled environment (i.e., about 80% relative humidity at a
temperature of about 100.degree. F.), tensile strength (as
represented by the peak-load value, in grams, corresponding to the
load at which the strand failed) generally decreases with time of
exposure to the prevailing conditions. For spools of Glospan 1060
that had been sealed in polyethylene bags with a drying agent, any
strength decrease that may have occurred was less than that for the
spools of Glospan 1060 that had been left open to the prevailing
conditions in the controlled environment (as indicated in Table 2,
the drying agent became discolored indicating that the drying agent
may have been close to saturation, thereby decreasing its ability
to adsorb water). Thus the peak-load values (i.e., tensile
strength) of elastic material sealed in polyethylene bags with a
desiccant were significantly higher than for elastic material that
was exposed to the conditions prevailing in the controlled
environment (i.e., about 80% relative humidity at a temperature of
about 100.degree. F.).
[0097] Furthermore, sealing spools of Glospan 1060 in polyethylene
bags with a drying agent significantly decreased agglomeration. As
shown in FIGS. 5, 6, and 8 (these images correspond to the spools
from which individual strand segments were removed for determining
the mechanical properties presented in Table 2), those spools of
Glospan 1060 left open to conditions prevailing in the controlled
environment became agglomerated (or "blocked"). Those spools that
were sealed in polyethylene bags with a drying agent, however,
experienced significantly less agglomeration. For example, the
slit-down spool depicted in FIG. 9 shows a spool of Glospan 1060
that had been sealed in a polyethylene bag with 100 grams of
CaSO.sub.4 before being placed in a controlled environment having a
temperature of about 100.degree. F. and a relative humidity of
about 80% for two weeks. The figure shows that the strand is
substantially unagglomerated. FIG. 6, on the other hand, depicts a
slit-down spool of Glospan 1060 that had been left open to the
conditions prevailing in the controlled environment for two weeks.
Slab-like agglomerates of strand have formed.
[0098] A similar comparison is found at 35 days. Glospan 1060 left
exposed to the conditions prevailing in the controlled environment
experienced significant agglomeration (see FIG. 8). Glospan 1060,
sealed in a polyethylene bag with 100 grams of CaSO.sub.4
experienced little, if any agglomeration (see FIG. 10).
Example 7
[0099] A bobbin or spool of LYCRA 940, an elastic strand comprising
a polyether-b-polyurethane block copolymer, was obtained from
Dupont Corp., a business having offices in Wilmington, Del. The
number "940" corresponds to the decitex of the strand. The strand
was wound up around a hollow core. The core had a radius of 7.5 cm
(radial dimension) and a length of 8.5 cm (axial dimension). The
strand was wound around the core to form a tube comprising the
helically- or spirally-wound strand. The outer surface of the tube
of strand extended radially outwardly from the surface of the core
at a distance of about 9 cm from the surface of the core. The
length of the tube of helically- or spirally-wound strand was about
the same as the length of the core. (Note: the strand might be
systematically accumulated to form shapes other than a tube or
cylinder comprising the individual strand or strands.) The
individual strand had a cross-sectional area of about 0.2 mm.sup.2
(calculated by multiplying the cross-sectional dimensions of the
strand: 0.2 mm multiplied by 1.0 mm).
[0100] As received the spool of LYCRA 940 had some agglomeration. A
slit-down spool had a peeled-onion-like structure of slabs of
agglomerated strand. The Agglomeration Index Values were determined
to be 19.5, 40, and 35 grams per strand at locations proximate to
the surface of the tube of strand, the region half way between the
surface of the tube of strand and the surface of the core, and the
surface of the core.
[0101] A spool was then placed in a controlled environment at a
temperature of about 100.degree. F. and a relative humidity of
about 80%. The spool was left exposed to the conditions prevailing
in the controlled environment. After the spool had been exposed to
these conditions for 1 month, the spool was removed and
Agglomeration Index Values determined. The Agglomeration Index
Values were determined to be 27, 53, and 67 grams per strand at
locations proximate to the surface of the tube of strand, the
region half way between the surface of the tube of strand and the
surface of the core, and the surface of the core. Thus, exposure to
these conditions resulted in an increase in the degree of adherence
between neighboring strand segments in the spool of LYCRA 940.
Furthermore, exposure to these conditions resulted in an decrease
of the average peak-load value from about 740 grams to about 660
grams.
* * * * *