U.S. patent application number 11/537973 was filed with the patent office on 2008-04-03 for methods for the preparation of cellulose fibers having superabsorbent particles adhered thereto.
This patent application is currently assigned to Weyerhaeuser Co.. Invention is credited to Su Bing, S. Ananda Weerawarna.
Application Number | 20080078514 11/537973 |
Document ID | / |
Family ID | 39259986 |
Filed Date | 2008-04-03 |
United States Patent
Application |
20080078514 |
Kind Code |
A1 |
Weerawarna; S. Ananda ; et
al. |
April 3, 2008 |
Methods for the preparation of cellulose fibers having
superabsorbent particles adhered thereto
Abstract
A method for adhering superabsorbent particles to cellulose
fibers, comprising optionally treating cellulose treated with a
hydrophilic polysaccharide polymer with a crosslinking agent in
water to provide a first aqueous mixture; adding a plurality of
superabsorbent particles to the first aqueous suspension to provide
a second aqueous mixture; and mixing the second aqueous mixture
with a water-miscible solvent to provide cellulose fibers having
superabsorbent particles adhered thereto.
Inventors: |
Weerawarna; S. Ananda;
(Seattle, WA) ; Bing; Su; (Federal Way,
WA) |
Correspondence
Address: |
WEYERHAEUSER COMPANY;INTELLECTUAL PROPERTY DEPT., CH 1J27
P.O. BOX 9777
FEDERAL WAY
WA
98063
US
|
Assignee: |
Weyerhaeuser Co.
Federal Way
WA
|
Family ID: |
39259986 |
Appl. No.: |
11/537973 |
Filed: |
October 2, 2006 |
Current U.S.
Class: |
162/9 ;
162/182 |
Current CPC
Class: |
D21C 9/005 20130101 |
Class at
Publication: |
162/9 ;
162/182 |
International
Class: |
D21C 9/00 20060101
D21C009/00; D21H 23/00 20060101 D21H023/00 |
Claims
1. A method for adhering superabsorbent particles to cellulose
fibers, comprising: (a) adding a plurality of superabsorbent
particles to a first aqueous mixture comprising cellulose treated
with a polysaccharide polymer to provide a second aqueous mixture;
and (b) mixing the second aqueous mixture with a water-miscible
solvent to provide cellulose fibers having superabsorbent particles
adhered thereto.
2. The method of claim 1 further comprising drying the cellulose
fibers having particles adhered thereto to provide a
partially-dried composite fibers.
3. The method of claim 2 further comprising fiberizing the
partially-dried composite fibers to provide partially-dried
fiberized composite fibers.
4. The method of claim 3 further comprising drying the
partially-dried fiberized composite fibers to provide dried
fiberized composite fibers.
5. The method of claim 1, wherein the polysaccharide is selected
from the group consisting of galactomannan polymers, glucomannan
polymers, alginic acids, carageenans, carboxymethyl cellulose,
hydroxyethyl cellulose, starch, carboxymethyl starch, and
hydroxyethyl starch.
6. The method of claim 1, wherein the polysaccharide comprises guar
gum.
7. The method of claim 1, wherein the particles are selected from
the group consisting of synthetic polymers, carboxyalkyl cellulose
polymers, carboxyalkyl starch polymers, alginates, chitosans, and
starches.
8. The method of claim 7, wherein the synthetic polymers are
selected from the group consisting of polyacrylic acid polymers,
polyacrylamide polymers, and polyaspartic acid polymers.
9. The method of claim 1 further comprising applying a crosslinking
agent to the cellulose treated with polysaccharide in the first
aqueous mixture prior to adding the particles.
10. The method of claim 9, wherein the crosslinking agent is
selected from the group consisting of aluminum (III) compounds,
titanium (IV) compounds, bismuth (III) compounds, boron (III)
compounds, and zirconium (IV) compounds.
11. The method of claim 9 further comprising drying the cellulose
fibers having particles adhered thereto to provide a
partially-dried composite fibers.
12. The method of claim 11 further comprising fiberizing the
partially-dried cellulose fibers to provide partially-dried
fiberized composite fibers.
13. The method of claim 12 further comprising drying the
partially-dried fiberized cellulose fibers to provide dried
fiberized composite fibers.
14. The method of claim 9, wherein the polysaccharide is selected
from the group consisting of galactomannan polymers, glucomannan
polymers, alginic acids, carageenans, carboxymethyl cellulose,
hydroxyethyl cellulose, starch, carboxymethyl starch, and
hydroxyethyl starch.
15. The method of claim 9, wherein the polysaccharide comprises
guar gum.
16. The method of claim 95 wherein the particles are selected from
the group consisting of synthetic superabsorbent polymers,
carboxyalkyl cellulose polymers, carboxyalkyl starch polymers,
alginates, chitosans, and starches.
17. The method of claim 9, wherein the synthetic superabsorbent
polymers are selected from the group consisting of polyacrylic acid
polymers, polyacrylamide polymers, and polyaspartic acid polymers.
Description
BACKGROUND OF THE INVENTION
[0001] Personal care absorbent products, such as infant diapers,
adult incontinent pads, and feminine care products, typically
contain an absorbent core that includes superabsorbent polymer
particles distributed within a fibrous matrix. Superabsorbents are
water-swellable, generally water-insoluble absorbent materials
having a high absorbent capacity for body fluids. Superabsorbent
polymers (SAPS) in common use are mostly derived from acrylic acid,
which is itself derived from petroleum oil, a non-renewable raw
material. Acrylic acid polymers and SAPs are generally recognized
as not being biodegradable. Despite their wide use, some segments
of the absorbent products market are concerned about the use of
nonrenewable petroleum oil derived materials and their
non-biodegradable nature. Acrylic acid based polymers also comprise
a meaningful portion of the cost structure of diapers and
incontinent pads. Users of SAP are interested in lower cost SAPs.
The high cost derives in part from the cost structure for the
manufacture of acrylic acid which, in turn, depends upon the
fluctuating price of petroleum oil. Also, when diapers are
discarded after use they normally contain considerably less than
their maximum or theoretical content of body fluids. In other
words, in terms of their fluid holding capacity, they are
"over-designed". This "over-design" constitutes an inefficiency in
the use of SAP. The inefficiency results in part from the fact that
SAPs are designed to have high gel strength (as demonstrated by
high absorbency under load or AUL). The high gel strength (upon
swelling) of currently used SAP particles helps them to retain a
lot of void space between particles, which is helpful for rapid
fluid uptake. However, this high "void volume" simultaneously
results in there being a lot of interstitial (between particle)
liquid in the product in the saturated state. When there is a lot
of interstitial liquid the "rewet" value or "wet feeling" of an
absorbent product is compromised.
[0002] In personal care absorbent products, U.S. southern pine
fluff pulp is commonly used in conjunction with the SAP. This fluff
is recognized worldwide as the preferred fiber for absorbent
products. The preference is based on the fluff pulp's advantageous
high fiber length (about 2.8 mm) and its relative ease of
processing from a wetland pulp sheet to an airlaid web. Fluff pulp
is also made from renewable and biodegradable cellulose pulp
fibers. Compared to SAP, these fibers are inexpensive on a per mass
basis, but tend to be more expensive on a per unit of liquid held
basis. These fluff pulp fibers mostly absorb within the interstices
between fibers. For this reason, a fibrous matrix readily releases
acquired liquid on application of pressure. The tendency to release
acquired liquid can result in significant skin wetness during use
of an absorbent product that includes a core formed exclusively
from cellulosic fibers. Such products also tend to leak acquired
liquid because liquid is not effectively retained in such a fibrous
absorbent core.
[0003] Superabsorbent composites in fiber form have a distinct
advantage over particle forms in some applications. Such
superabsorbent composite fibers can be made into a pad form
directly. Liquid acquisition will be more uniform compared to a
fiber pad with shifting superabsorbent particles.
[0004] A need therefore exists for fibrous superabsorbent materials
that have the ability to have superabsorbent particles attached to
the fibers. Biodegradable renewable fibers such as cellulose fiber
is ideally suitable for such a fibrous superabsorbent composite
material, if it can be treated and made to have strong affinity to
superabsorbent particles. In this way, the superabsorbent material
can be used in absorbent product designs that are efficient. These
and other objectives are accomplished by the invention set forth
below.
SUMMARY OF THE INVENTION
[0005] The invention provides a method for adhering superabsorbent
particles to cellulose fibers, comprising adding a plurality of
superabsorbent particles to a first aqueous mixture comprising
cellulose treated with a polysaccharide polymer to provide a second
aqueous mixture; and mixing the second aqueous mixture with a
water-miscible solvent to provide cellulose fibers having
superabsorbent particles adhered thereto. In one embodiment, the
method includes applying a crosslinking agent to the cellulose
treated with the polysaccharide in the first aqueous mixture prior
to adding the particles.
DESCRIPTION OF THE DRAWINGS
[0006] The foregoing aspects and many of the attendant advantages
of this invention will become more readily appreciated as the same
become better understood by reference to the following detailed
description, when taken in conjunction with the accompanying
drawings, wherein:
[0007] FIG. 1 is a scanning electron microscope photograph
(13.times.) of representative fibers with adhered superabsorbent
particles made in accordance with the method of the invention
(Sample 3, Table 1);
[0008] FIG. 2 is a scanning electron microscope photograph
(100.times.) of representative fibers with adhered superabsorbent
particles made in accordance with the method of the invention
(Sample 3, Table 1);
[0009] FIG. 3 is a scanning electron microscope photograph
(13.times.) of representative fibers with adhered superabsorbent
particles made in accordance with the method of the invention
(Sample 4, Table 1); and
[0010] FIG. 4 is a scanning electron microscope photograph
(100.times.) of representative fibers with adhered superabsorbent
particles made in accordance with the method of the invention
(Sample 4, Table 1).
DETAILED DESCRIPTION OF THE INVENTION
[0011] In one aspect, the present invention provides a method for
adhering particles (e.g., superabsorbent particles) to cellulose
fibers. The method includes the steps of adding a plurality of
particles to a first aqueous mixture comprising cellulose treated
with a polysaccharide polymer to provide a second aqueous mixture;
and mixing the second aqueous mixture with a water-miscible solvent
to provide cellulose fibers having particles adhered thereto. In
one embodiment, the method includes applying a crosslinking agent
to the cellulose treated with the polysaccharide in the first
aqueous mixture prior to adding the particles.
[0012] The product fibers are obtained by filtration. In one
embodiment, the method further includes the steps of drying the
cellulose fibers having particles adhered thereto to provide
partially-dried composite fibers (30-50% consistency). The
partially-dried composite fibers can be fiberized to provide
partially-dried fiberized composite fibers. The partially-dried
fiberized composite fibers can be further dried to provide dried
fiberized cellulose fibers having particles adhered thereto.
[0013] In the method, cellulose fibers that have been treated with
a hydrophilic polysaccharide are combined with superabsorbent
particles.
[0014] Although available from other sources, suitable cellulosic
fibers are derived primarily from wood pulp. Suitable wood pulp
fibers for use with the invention can be obtained from well-known
chemical processes such as the kraft and sulfite processes, with or
without subsequent bleaching. Pulp fibers can also be processed by
thermomechanical, chemithermomechanical methods, or combinations
thereof. A high alpha cellulose pulp is also a suitable wood pulp
fiber. The preferred pulp fiber is produced by chemical methods.
Ground wood fibers, recycled or secondary wood pulp fibers, and
bleached and unbleached wood pulp fibers can be used. Softwoods and
hardwoods can be used. Suitable fibers are commercially available
from a number of companies, including Weyerhaeuser Company. For
example, suitable cellulosic fibers produced from southern pine
that are usable with the present invention are available from
Weyerhaeuser Company under the designations CF416, NF405, PL416,
FR516, and NB416. Other suitable fibers include northern softwood
and eucalyptus fibers.
[0015] As used herein, the term "hydrophilic polysaccharide
polymer" refers to any one of a variety of polysaccharide polymers
that are hydrophilic and that have a tendency to associate with
cellulose. Representative hydrophilic polysaccharide polymers
include natural polymers, such as galactomannan polymers,
glucomannan polymers, alginic acids, carageenans, starches and
starch derivatives such as carboxymethyl starch, and hydroxyethyl
starch, and cellulose derivatives such as such as carboxymethyl
cellulose, hydroxyethyl cellulose. In one embodiment, the
hydrophilic polysaccharide polymer is a galactomannan polymer.
Representative galactomannan polymers include guar gum, locust bean
gum, and tara gum. In one embodiment, the hydrophilic
polysaccharide polymer is a glucomannan polymer. Representative
glucomannan polymers include konjac gum. The cellulose treated with
hydrophilic polysaccharide polymer includes from about 1 to about
20 percent by weight hydrophilic polysaccharide polymer based on
the weight of cellulose.
[0016] The preparation of representative cellulose fibers treated
with a hydrophilic polysaccharide polymer (e.g., guar gum treated
cellulose fibers) is described in Example 1. In general,
hydrophilic polysaccharide polymer treated cellulose is prepared by
dissolving a desired amount of the hydrophilic polysaccharide
polymer in water (e.g., 10 g in 1000 mL water) to provide a
solution and then adding cellulose fibers (e.g., 1.00 g) with
mixing to provide a suspension. The treated fibers are obtained by
filtration and drying (e.g., 1.0% by weight hydrophilic
polysaccharide polymer treated cellulose).
[0017] In one embodiment, an aqueous mixture of cellulose fibers
treated with a hydrophilic polysaccharide polymer are treated with
a crosslinking agent prior to the addition of the superabsorbent
particles. The use of a crosslinking agent will depend on the
nature of the particles to be adhered to the fibers. If the
particles are highly crosslinked, added crosslinking agent is not
required. However, if the particles are not adequately crosslinked
to provide sufficient insolubility in water, then the crosslinking
agent is used.
[0018] Suitable crosslinking agents include crosslinking agents
that are reactive toward hydroxyl groups and carboxyl groups.
Representative crosslinking agents include metallic crosslinking
agents, such as aluminum (III) compounds, titanium (IV) compounds,
bismuth (III) compounds, boron (III) compounds, and zirconium (IV)
compounds. The numerals in parentheses in the preceding list of
metallic crosslinking agents refers to the valency of the
metal.
[0019] Representative metallic crosslinking agents include aluminum
sulfate; aluminum hydroxide; dihydroxy aluminum acetate (stabilized
with boric acid); other aluminum salts of carboxylic acids and
inorganic acids; other aluminum complexes, such as Ultrion 8186
from Nalco Company (aluminum chloride hydroxide); boric acid;
sodium metaborate; ammonium zirconium carbonate (AZC); zirconium
compounds containing inorganic ions or organic ions or neutral
ligands; bismuth ammonium citrate (BAC); other bismuth salts of
carboxylic acids and inorganic acids; titanium (IV) compounds, such
as titanium (IV) bis(triethylaminato) bis(isopropoxide)
(commercially available from the Dupont Company under the
designation Tyzor TE); and other titanates with alkoxide or
carboxylate ligands.
[0020] The crosslinking agent is applied in an amount up to about
20 percent by weight based on the total weight of the treated
cellulose fibers. The amount of first crosslinking agent applied to
the treated cellulose will vary depending on the crosslinking
agent. In general, the fibers have an aluminum content up to about
2.0% by weight based on the weight of the composite fibers for
aluminum crosslinked fibers, a titanium content of up to about 4.5%
by weight based on the weight of the composite fibers for titanium
crosslinked fibers, a zirconium content of up to about 6.0% by
weight based on the weight of the composite fibers for zirconium
crosslinked fibers, and a bismuth content up to about 5.0% by
weight based on the weight of the composite fibers for bismuth
crosslinked fibers.
[0021] In the method, a plurality of superabsorbent particles is
added to the first aqueous suspension including the cellulose
treated with a hydrophilic polysaccharide polymer that has been
optionally treated with a crosslinking agent, Suitable particles
include those derived from synthetic hydrophilic polymers (e.g.,
superabsorbent polymers or SAPs), such as polyacrylic acids,
polyacrylamides, and polyaspartic acids; and hydrophilic polymers
(e.g., superabsorbent polymers) derived natural polymers, such as
celluloses (e.g., carboxymethyl cellulose), alginates, chitosans,
and starches (e.g., carboxymethyl starch). The combination of a
carboxyalkyl cellulose and either a glucomannan or galactomannan
polymer is not considered to be a superabsorbent particle in the
context of this invention.
[0022] Superabsorbent particles in the product cellulose fibers are
be present in an amount form about 50 to about 80% by weight of the
product fibers. The polysaccharide treated fiber in the product
cellulose fibers are present in an amount form about 20 to 50%, by
weight of the product fibers.
[0023] The cellulose fibers having superabsorbent particles
attached thereto are obtained by mixing the second aqueous mixture
including the plurality of superabsorbent particles and treated
cellulose with a water-miscible solvent. Suitable water-miscible
solvents include water-miscible alcohols and ketones.
Representative water-miscible solvents include acetone, methanol,
ethanol, isopropanol, and mixtures thereof. In one embodiment, the
water-miscible solvent is ethanol. In another embodiment, the
water-miscible solvent is isopropanol.
[0024] The volume of water-miscible solvent added to the gel ranges
from about 1:1 to about 1:5 water to water-miscible solvent.
[0025] In the method, mixing the gel with the water-miscible
solvent includes stirring to provide fibers with adhered
superabsorbent particles. The mixing step and the use of the
water-miscible solvent controls the rate of dehydration and solvent
exchange and provides fiber with adhering superabsorbent particles.
Mixing can be carried out using a variety of devices including
overhead stirrers, Hobart mixers, British disintegrators, and
blenders.
[0026] Thus, in one embodiment, the invention provides a method for
adhering superabsorbent particles to cellulose fibers, comprising
adding a plurality of particles to a first aqueous mixture
comprising cellulose treated with a polysaccharide polymer to
provide a second aqueous mixture; and mixing the second aqueous
suspension with a water-miscible solvent to provide cellulose
fibers having superabsorbent particles adhered thereto.
[0027] As noted above, in another embodiment, the method further
comprising adding a crosslinking agent to the cellulose treated
with polysaccharide in the first aqueous suspension prior to adding
the particles.
[0028] The methods of the invention provide cellulose fibers having
superabsorbent particles adhered thereto.
[0029] In one embodiment, the cellulose fibers having particles
adhered thereto, include cellulose fibers treated with a
hydrophilic polysaccharide polymer and the adhered superabsorbent
particles include synthetic hydrophilic polymers (e.g.,
superabsorbent polymers or SAPs), such as polyacrylic acids,
polyacrylamides, and polyaspartic acids; and hydrophilic polymers
(e.g., superabsorbent polymers) derived natural polymers, such as
celluloses (e.g., carboxymethyl cellulose), alginates, chitosans,
and starches (e.g., carboxymethyl starch).
[0030] In another embodiment, the cellulose fibers having particles
adhered thereto, include cellulose fibers treated with a
hydrophilic polysaccharide polymer and a crosslinking agent and the
adhered superabsorbent particles include synthetic hydrophilic
polymers (e.g., superabsorbent polymers or SAPs), such as
polyacrylic acids, polyacrylamides, and polyaspartic acids; and
hydrophilic polymers (e.g., superabsorbent polymers) derived
natural polymers, such as celluloses (e.g., carboxymethyl
cellulose), alginates, chitosans, and starches (e.g., carboxymethyl
starch).
[0031] As noted above, suitable hydrophilic polysaccharide polymers
include natural polymers, such as galactomannan polymers,
glucomannan polymers, alginic acids, carageenans, starches and
starch derivatives such as carboxymethyl starch, and hydroxyethyl
starch, and cellulose derivatives such as such as carboxymethyl
cellulose, hydroxyethyl cellulose. In one embodiment, the
polysaccharide is guar gum.
[0032] For hydrophilic polysaccharide treated cellulose fibers also
treated with a crosslinking agent suitable crosslinking agents
include of aluminum (III) compounds, titanium (IV) compounds,
bismuth (III) compounds, boron (III) compounds, and zirconium (IV)
compounds. Representative crosslinking agents are described
above.
[0033] Representative cellulose fibers having superabsorbent
particles adhered thereto are shown in FIGS. 1-4. FIG. 1 is a
scanning electron microscope photograph (13.times.) of
representative cellulose fibers having adhered superabsorbent
particles (Sample 3, Table 1). FIG. 2 is a scanning electron
microscope photograph (100.times.) of representative cellulose
fibers having adhered superabsorbent particles (Sample 3, Table 1).
FIG. 3 is a scanning electron microscope photograph (13.times.) of
representative cellulose fibers having adhered superabsorbent
particles (Sample 4, Table 1). FIG. 4 is a scanning electron
microscope photograph (100.times.) of representative cellulose
fibers having adhered superabsorbent particles (Sample 4, Table
1).
[0034] The fibers are prepared by a process that includes
optionally treating an aqueous mixture of a plurality of
superabsorbent particles and cellulose treated with a hydrophilic
polysaccharide polymer with a metal crosslinking agent to provide a
mixture, and then further mixing the mixture with a water-miscible
solvent. The fibers produced by the method are substantially
insoluble in water while being capable of absorbing water.
[0035] When a crosslinking agent is optionally used before adding
superabsorbent particles to the aqueous solution containing the
cellulose fiber treated with the hydrophilic polysaccharide
polymer, the agent provides additional crosslinking of the polymers
of the superabsorbent particles. This is suitable when the
particles are not sufficiently crosslinked (or under crosslinked by
design). When the particles are highly crosslinked, this additional
crosslinking is not used to prevent loss of absorbent capacity of
the product composite fibers. When a crosslinking agent is
optionally used, the agent can also provide additional crosslinks
between polymer molecules of the superabsorbent particles and the
hydrophilic polymer bound to the cellulose fibers. To take
advantage of this favorable attractions between superabsorbent
particles and the hydrophilic polysaccharide treated cellulose
fibers, the superabsorbent particles used should not be highly
crosslinked. The metal crosslink arises as a consequence of an
associative interaction (e.g., bonding) between functional groups
on the hydrophilic polymers (e.g., carboxy, carboxylate, or
hydroxyl groups) and a multi-valent metal species (see description
of crosslinking agents above). The superabsorbent particles and the
treated cellulose fiber contain hydrophilic polymers that can form
metal crosslinks. Suitable multi-valent metal species include metal
ions having a valency of three or greater and that are capable of
forming an associative interaction with a polymer (e.g., reactive
toward associative interaction with the polymer's carboxy,
carboxylate, or hydroxyl groups). The polymers are intermolecularly
crosslinked when the multi-valent metal species forms an
associative interaction with functional groups on two or more
polymer molecules. A crosslink may be formed within one polymer
molecule or may be formed between two or more polymer
molecules.
[0036] The product fibers are highly absorptive. The fibers have a
Free Swell Capacity of from about 30 to about 60 g/g (0.9% saline
solution), a Centrifuge Retention Capacity (CRC) of from about 15
to about 35 g/g (0.9% saline solution), and an Absorbency Under
Load (AUL) of from about 15 to about 30 g/g (0.9% saline
solution).
[0037] The product fibers are useful as a superabsorbent in
personal care absorbent products (e.g., infant diapers, feminine
care products and adult incontinence products). The fibers have the
ability to absorb water, saline solutions and biological fluids
such as urine and the fibrous form also helps in wicking. The
fibers are useful in a variety of other applications, including,
for example, wound dressings, cable wrap, absorbent sheets or bags,
and packaging materials.
[0038] The preparations of representative fibers are described in
Examples 2 and 3 The composition and liquid absorbent
characteristics of representative fibers are summarized in the
Table 1. In Table 1, for the superabsorbent particle and the
polysaccharide polymer treated cellulose, the values in parentheses
refer to the relative weight of each in the composite
superabsorbent fiber (wgt % total wgt); "Crosslinking agent/4 g"
refers to the amount of crosslinking agent applied per 4 g product;
"SANIWET-4500" refers to a synthetic superabsorbent particle (a
polyacrylic acid particle) commercially available from Hoechst
Celanese; "NKS pulp with 10% GG" refers to northern kraft spruce
(NKS) pulp treated with 10 weight % guar gum; and "with wash"
refers to washing the treated fibers with 100% ethanol or 100%
isopropanol before drying.
Test Methods
Free Swell and Centrifuge Retention Capacities
[0039] The materials, procedure, and calculations to determine tree
swell capacity (g/g) and centrifuge retention capacity (CRC) (g/g)
were as follows.
[0040] Test Materials:
[0041] Japanese pie-made empty tea bags (available from
Drugstore.com, IN PURSUIT OF TEA polyester tea bags 93 mm..times.70
mm with fold-over flap. (http:www.mesh.ne.jp/tokiwa/)).
[0042] Balance (4 decimal place accuracy, 0.0001 g for air-dried
superabsorbent polymer (ADS SAP) and tea bag weights); timer; 1%
saline; drip rack with clips (NLM 211); and lab centrifuge (NLM
211, Spin-X spin extractor, model 776S, 3,300 RPM, 120v).
[0043] Test Procedure:
[0044] 1. Determine solids content of ADS.
[0045] 2. Pre-weigh tea bags to nearest 0.0001 g and record.
[0046] 3. Accurately weigh 0.2025 g.+/-0.0025 g of test material
(SAP), record and place into pre-weighed tea bag (air-dried (AD)
bag weight). (ADS weight+AD bag weight=total dry weight).
[0047] 4. Fold tea bag edge over closing bag.
[0048] 5. Fill a container (at least 3 inches deep) with at least 2
inches with 1% saline.
[0049] 6. Hold tea bag (with test sample) flat and shake to
distribute test material evenly through bag.
[0050] 7. Lay tea bag onto surface of saline and start timer.
[0051] 8. Soak bags for specified time (e.g., 30 minutes).
[0052] 9. Remove tea bags carefully, being careful not to spill any
contents from bags, hang from a clip on drip rack for 3
minutes.
[0053] 10. Carefully remove each bag, weigh, and record (drip
weight).
[0054] 11. Place tea bags onto centrifuge walls, being careful not
to let them touch and careful to balance evenly around wall.
[0055] 12. Lock down lid and start timer. Spin for 75 seconds.
[0056] 13. Unlock lid and remove bags. Weigh each bag and record
weight (centrifuge weight).
[0057] Calculations:
[0058] The tea bag material has an absorbency determined as
follows:
[0059] Free Swell Capacity, factor=5.78
[0060] Centrifuge Capacity, factor 0.50
[0061] Z=Oven dry SAP wt (g)/Air dry SAP wt (g)
[0062] Free Capacity (g/g):
[ ( drip wt ( g ) - dry bag wt ( g ) ) - ( AD SAP wt ( g ) ) ] - (
dry bag wt ( g ) * 5.78 ) ( AD SAP wt ( g ) * Z ) ##EQU00001##
[0063] Centrifuge Retention Capacity (g/g):
[ centrifuge wt ( g ) - dry bag wt ( g ) - ( AD SAP wt ( g ) ) ] -
( dry bag wt ( g ) * 0.50 ) ( AD SAP wt * Z ) ##EQU00002##
Absorbency Under Load (AUL)
[0064] The materials, procedure, and calculations to determine AUL
were as follows.
[0065] Test Materials:
[0066] Mettler Toledo PB 3002 balance and BALANCE-LINK software or
other compatible balance and software, Software set-up: record
weight from balance every 30 sec (this will be a negative number.
Software can place each value into EXCEL spreadsheet.
[0067] Kontes 90 mm ULTRA-WARE filter set up with fritted glass
(coarse) filter plate. clamped to stand; 2 L glass bottle with
outlet tube near bottom of bottle; rubber stopper with glass tube
through the stopper that fits the bottle (air inlet); TYGON tubing;
stainless steel rod/plexiglass plunger assembly (71 mm diameter);
stainless steel weight with hole drill through to place over
plunger (plunger and weight=867 g); VWR 9.0 cm filter papers
(Qualitative 413 catalog number 28310-048) cut down to 80 mm size;
double-stick SCOTCH tape; and 0.9% saline.
[0068] Test Procedure:
[0069] 1. Level filter set-up with small level.
[0070] 2. Adjust filter height or fluid level in bottle so that
fritted glass filter and saline level in bottle are at same
height.
[0071] 3. Make sure that there are no kinks in tubing or air
bubbles in tubing or under fritted glass filter plate.
[0072] 4. Place filter paper into filter and place stainless steel
weight onto filter paper.
[0073] 5, Wait for 5-10 min while filter paper becomes fully wetted
and reaches equilibrium with applied weight.
[0074] 6. Zero balance.
[0075] 7. While waiting for filter paper to reach equilibrium
prepare plunger with double stick tape on bottom.
[0076] 8. Place plunger (with tape) onto separate scale and zero
scale.
[0077] 9. Place plunger into dry test material so that a monolayer
of material is stuck to the bottom by the double stick tape.
[0078] 10. Weigh the plunger and test material on zeroed scale and
record weight of dry test material (dry material weight 0.15
g+/-0.05 g).
[0079] 11. Filter paper should be at equilibrium by now, zero
scale.
[0080] 12. Start balance recording software.
[0081] 13. Remove weight and place plunger and test material into
filter assembly.
[0082] 14. Place weight onto plunger assembly.
[0083] 15. Wait for test to complete (30 or 60 min)
[0084] 16. Stop balance recording software.
[0085] Calculations: [0086] A=balance reading (g)*-1 (weight of
saline absorbed by test material) [0087] B=dry weight of test
material (this can be corrected for moisture by multiplying the AD
weight by solids %). [0088] AUL (g/g)=A/B (g 1% saline/1 g test
material)
[0089] The following examples are provided for the purpose of
illustrating, not limiting, the invention.
EXAMPLES
Example 1
The Preparation of Representative Guar Gum Treated Cellulose
Fibers
[0090] In this example, the preparation of representative guar gum
treated cellulose fibers is described.
[0091] Guar gum (4.0 g) was dissolved in 3200 ml of deionized
water. Northern kraft spruce (NKS) pulp (40.0 g) was dispersed in
the guar gum solution and oven dried at 105.degree. C. This
material was used for binding superabsorbent composite
particles.
Example 2
The Preparation of a Representative Fibrous Superabsorbent
Composite
[0092] In this example, the preparation of a representative fibrous
superabsorbent composite containing cellulose and commercial
superabsorbent particles crosslinked with aluminum sulfate.
[0093] Aluminum sulfate octadecahydrate 0.035 g was dissolved in 50
ml of deionized water at 80.degree. C. Guar gum treated cellulose
fiber (prepared as described as in Example 1) 1.2 g was then
dispersed in the aluminum sulfate solution for 15 minutes.
Commercial superabsorbent particles (SANWET IM-4500 from Hoechst
Celanese) 2.8 g was added to the fiber slurry and mixed for 2
minutes. To the swollen mass of fiber gel was added 150 ml of
isopropanol and mixed for 5 minutes to obtain composite fiber with
attached superabsorbent particles. The composite fiber obtained was
then filtered. The fiber mass was partially dried in the oven at
66.degree. C., The fiber mass was then fiberized and dried in the
oven at 66.degree. C.
[0094] T-bag test gave free swell of 39.75 g/g; centrifuge capacity
of 19.86 g/g; and AUL of 27.36 g/g (at 0.3 psi) for 0.9% saline
solution.
Example 3
The Preparation of a Representative Fibrous Superabsorbent
Composite
[0095] In this example, the preparation of a representative fibrous
superabsorbent composite containing cellulose and commercial
superabsorbent particles without added crosslinking agent.
[0096] Guar gum treated cellulose fiber (prepared as described as
in Example 1) 1.2 g was then dispersed in 50 ml of deionized water
at 80.degree. C. for 15 minutes. Commercial superabsorbent
particles (SANWET IM-4500 from Hoechst Celanese) 2.8 g was added to
the fiber slurry and mixed for 2 minutes. To the swollen mass of
fiber gel was added 150 ml of isopropanol and mixed to obtain
composite fiber with attached superabsorbent particles. The
composite fiber obtained was the filtered. The fiber mass was
partially dried in the oven at 66.degree. C. The fiber mass was
then fiberized and dried in the oven at 66.degree. C.
[0097] T-bag test gave free swell of 40.50 g/g; centrifuge capacity
of 23.54 g/g; and AUL of 28.15 g/g (at 0.3 psi) for 0.9% saline
solution.
TABLE-US-00001 TABLE 1 Composition and Absorbent Properties of
Composite Superabsorbent Fiber from Synthetic Superabsorbent and
Galactomannan Treated Cellulose Polysaccharide polymer treated
Superabsorbent particle cellulose Free Swell CRC AUL Sample (wgt %
total wgt) (wgt % total wgt) Crosslinking agent/4 g (g/g) (g/g)
(g/g) 1 SANWETIM-4500 (50%) NKS pulp with 10% GG (50%) 0.017 g
Al.sub.2(SO.sub.4).sub.3 with wash 35.3 15.62 23.31 2 SANWETIM-4500
(50%) NKS pulp with 10% GG (50%) -- 33.95 16.61 23.8 3
SANWETIM-4500 (70%) NKS pulp with 10% GG (30%) 0.017 g
Al.sub.2(SO.sub.4).sub.3 with wash 39.75 19.86 27.36 4
SANWETIM-4500 (70%) NKS pulp with 10% GG (30%) -- 40.5 23.54
28.15
[0098] White illustrative embodiments have been illustrated and
described, it will be appreciated that various changes can be made
therein without departing from the spirit and scope of the
invention.
* * * * *