U.S. patent application number 10/596578 was filed with the patent office on 2010-02-11 for absorbent hydrophobic boronate galactomannan complexes and process for producing same.
This patent application is currently assigned to Archer-Daniels-Midland Company. Invention is credited to Mohammed Berrada, Anne-Claude Couffin, Andre Laforest, Nicolas Nourry.
Application Number | 20100036337 10/596578 |
Document ID | / |
Family ID | 37396158 |
Filed Date | 2010-02-11 |
United States Patent
Application |
20100036337 |
Kind Code |
A1 |
Couffin; Anne-Claude ; et
al. |
February 11, 2010 |
ABSORBENT HYDROPHOBIC BORONATE GALACTOMANNAN COMPLEXES AND PROCESS
FOR PRODUCING SAME
Abstract
Absorbent boronate-galactomannan complexes comprising a
hydrophobic group are disclosed. The boronate-galactomannan
complexes are solid materials capable of gel forming upon
contacting with liquids. The boronate-galactomannan complexes are
particularly suitable for absorbing liquids.
Inventors: |
Couffin; Anne-Claude;
(Montreal, CA) ; Berrada; Mohammed; (Longueuil,
CA) ; Laforest; Andre; (Longueuil, CA) ;
Nourry; Nicolas; (St-Amable, CA) |
Correspondence
Address: |
FULBRIGHT & JAWORSKI L.L.P.
600 CONGRESS AVE., SUITE 2400
AUSTIN
TX
78701
US
|
Assignee: |
Archer-Daniels-Midland
Company
Decatur
IL
|
Family ID: |
37396158 |
Appl. No.: |
10/596578 |
Filed: |
May 12, 2006 |
PCT Filed: |
May 12, 2006 |
PCT NO: |
PCT/CA2006/000772 |
371 Date: |
February 6, 2009 |
Current U.S.
Class: |
604/367 ;
536/123.1 |
Current CPC
Class: |
A61L 15/18 20130101;
B01J 2220/4825 20130101; A61L 15/60 20130101; B01J 20/262 20130101;
B01J 20/26 20130101; B01J 20/24 20130101; A61L 15/28 20130101 |
Class at
Publication: |
604/367 ;
536/123.1 |
International
Class: |
A61F 13/15 20060101
A61F013/15; C07H 3/00 20060101 C07H003/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 12, 2005 |
CA |
2507121 |
Claims
1. An absorbent material comprising one or more absorbent boronate
galactomannan complexes, the said boronate galactomannan complexes
comprising a hydrophobic group.
2. The absorbent material of claim 1, wherein the hydrophobic group
is selected from the group consisting of aromatic groups, aliphatic
groups and cyclic aliphatic groups.
3. The absorbent material of claim 1, wherein the galactomannan is
selected from the group consisting of guar gum, locust bean gum,
fenugreek gum, tara gum, mesquite gum and mixtures thereof.
4. The absorbent material of claim 3, wherein the galactomannan
comprises a galactose to mannose ratio ranging from about 1:5 to
about 1:1.
5. The absorbent material of claim 1, wherein the boronate
galactomannan complexes are solid materials.
6. The absorbent material of claim 5, wherein the solid materials
comprise a granular material.
7. The absorbent material of claim 6, wherein the granular material
comprises particles having a size ranging from about 80 .mu.m to
about 800 .mu.m.
8. Use of the absorbent material of claim 1, in products selected
from the group consisting of diapers, incontinence articles,
feminine hygiene products, airlaids, absorbent dressings, household
articles, sealing materials, humectants, anti-condensation
coatings, concrete products, litter products, soil conditioning
products, mining fluids, oil drilling fluids, absorbent paper
products, bandages, surgical pads, chemical absorbents, controlled
release polymeric gels, artificial snow, fire-fighting gels, and
food pads.
9. Use of the absorbent material of claim 1 for absorbing liquids
selected from the group consisting of water, aqueous solutions,
physiological solutions and saline solutions.
10. An absorbent composition comprising at least one absorbent
material as defined in claim 1, and at least one co-absorbent
material.
11. The absorbent composition of claim 10, wherein the co-absorbent
material is selected from the group consisting of synthetic
superabsorbent polymers, starch-based absorbents, ionic
polysaccharides, fibers and mixtures thereof.
12. Use of the absorbent composition of claim 10, in products
selected from the group consisting of diapers, incontinence
articles, feminine hygiene products, airlaids, absorbent dressings,
household articles, sealing materials, humectants,
anti-condensation coatings, concrete products, litter products,
soil conditioning products, mining fluids, oil drilling fluids,
absorbent paper products, bandages, surgical pads, chemical
absorbents, controlled release polymeric gels, artificial snow,
fire-fighting gels, and food pads.
13. Use of the absorbent composition of claim 10 for absorbing
liquids selected from the group consisting of water, aqueous
solutions, physiological solutions and saline solutions.
14. A method for absorbing liquids comprising contacting said
liquids with the absorbent material of claim 1.
15. The method of claim 14, wherein the liquids are selected from
the group consisting of water, aqueous solutions, physiological
solutions and saline solutions.
16. A method for absorbing liquids comprising contacting said
liquids with the absorbent composition of claim 10.
17. The method of claim 16, wherein the liquids are selected from
the group consisting of water, aqueous solutions, physiological
solutions and saline solutions.
18. A process for producing a boronate galactomannan complex
comprising a hydrophobic group, said process comprising: a)
dispersing a galactomannan in an aqueous solution producing an
aqueous suspension; b) reacting a hydrophobic group containing
boronate with said suspension, producing said boronate
galactomannan complex; c) recovering said boronate galactomannan
complex.
19. The process of claim 18, wherein the recovering comprises
precipitating the boronate galactomannan complex from an organic
hydrophilic solvent and drying the precipitated complex.
20. The process of claim 19, wherein the dried precipitated complex
is ground.
21. The process of claim 18, wherein the boronate is produced by
dissolving a boronic acid in a suitable solvent followed by
adjusting the pH of the solvent to alkalinity.
22. The absorbent material of claim 1, wherein the boronate
galactomannan complexes are capable of forming a gel upon
contacting with a liquid.
23. The absorbent composition of claim 10, wherein the boronate
galactomannan complexes are capable of forming a gel upon
contacting with a liquid.
Description
[0001] The present application claims the benefit of Canadian
Application No. 2,507,121 filed May 12, 2005, the entire contents
of which are incorporated by reference.
FIELD OF THE INVENTION
[0002] The present teachings relate to absorbent hydrophobic
galactomannan complexes. More specifically, but not exclusively,
the present teachings relates to absorbent hydrophobic boronate
galactomannan complexes and to a process for producing same.
BACKGROUND OF THE INVENTION
[0003] Water absorbent materials, such as superabsorbent polymers,
can be employed in various applications such as in disposable
sanitary products (i.e. diapers, incontinence articles, feminine
hygiene products, airlaids and absorbent dressings), household
articles, sealing materials, humectants in agricultural products
for soil conditioning, in oil-drilling fluids (i.e.
lost-circulation material, fracturing fluids), anti-condensation
coatings, in agricultural, horticultural and forestry applications
for retaining water in the soil and for the release of water to the
roots of plants and trees, in the textile industry, in printing
applications, in absorbent paper products, in bandages and surgical
pads (i.e. wound dressings), in ore treatments, in pet litter, in
water treatment, in food pads (i.e. applications related to the
transportation of fresh food and food packaging), in detergents, in
fire-fighting gels, in sealing materials, as chemical absorbents
for the cleanup of acidic and/or basic aqueous spills including
water soluble chemical spills, as polymeric gels for the slow and
controlled release of cosmetics and pharmaceuticals (also known as
drug delivery systems), as airlaids, and finally in the manufacture
of artificial snow. However, the primary use of superabsorbent
polymers, also referred to a "SAPs", is in disposable personal
hygiene products. Such products include, in increasing order of
volume of superabsorbent materials used, diapers, training pants,
adult incontinence products and feminine hygiene products.
[0004] Increased oil prices have had a negative impact on the
superabsorbent industry such that natural polysaccharide-based
superabsorbents have become an attractive alternative. Such natural
superabsorbent materials can be readily obtained from renewable
sources such as starch. Various absorbent compositions comprising
polysaccharide-based superabsorbents have been proposed by Le Group
Lysac Inc. Huppe et al. (CA 2,308,537) teach the use of
biodegradable, glass-like pregelatinized starch as absorbents for
liquids. Couture et al. (CA 2,362,006) teach the use of oligomeric
polyethylene glycol crosslinked polysaccharides, in particular
polyethylene glycol crosslinked starch as absorbent materials.
Thibodeau et al. (CA 2,462,053) teach the use of crosslinked
amylopectin as absorbent materials. Bergeron et al. (CA 2,426,478)
teach the use of modified starches (i.e. crosslinked amylopectin)
and mannose containing polysaccharides, ionic polysaccharides,
gelling proteins and mixtures thereof in formulating absorbent
materials. Berrada et al. (CA 2,483,049) teach the use of
phylosilicates dispersed in an absorbent polysaccharide matrix, as
having absorbent characteristics. Berrada (CA 2,519,417) teaches
the use of guanidinated polysaccharides as absorbent materials.
[0005] The use of galactomannans, essentially cross-linked with
borate, titanium or zirconium ions, as superabsorbent
polysaccharides, has been disclosed in a number of patents: U.S.
Pat. No. 3,661,154; U.S. Pat. No. 3,903,889; U.S. Pat. No.
4,624,868; U.S. Pat. No. 4,333,461; U.S. Pat. No. 5,532,350; U.S.
Pat. No. 5,801,116; JP 2004-089401; JP 2004-075773; JP 2004-073370;
JP 2004-066203; JP 2003-311150; JP 2003-154262; JP 2002-253961; JP
2002-035037; JP 2001-278998; JP 2002-037924; JP 2002-053859; JP
2001-120992; JP 2002-053859; JP 2001-226525 and JP 2001-122905.
However, these polysaccharides suffer from syneresis and gel
flowing problems. Crosslinking will seriously limit the
manipulation of the absorbent materials, especially when shear
thinning behavior is desired.
[0006] Complexes of aliphatic boronates with galactomannans have
been disclosed by Bavouzet et al. (WO 97/47658). Complexes of
aromatic boronates with galactomannans were disclosed by Bishop et
al. (Dalton Transactions; 17; 2004; 2621-2634). PEG-diboronate
galactomannan complexes have been disclosed by Coveney et al.
(Molecular simulation, 2000, Vol. 25, pp. 265-299). Synthetic
boronate polymer complexes with polysaccharides have also been
disclosed by Miyazaki et al. (EP 0424168); Filipini (EP 0159521);
Pelton et al. (WO 06/010268); and Destarac et al. (FR 2839723).
However, these complexes were not disclosed as being absorbent
materials.
[0007] There thus remains a need for absorbent hydrophobic boronate
galactomannan complexes, as well as a process for producing
same.
[0008] The present teachings seek to meet these and other
needs.
[0009] The present teachings refer to a number of documents, the
content of which is herein incorporated by reference in their
entirety.
SUMMARY OF THE INVENTION
[0010] The present teachings broadly relate to novel absorbent or
superabsorbent materials. More specifically, as broadly claimed,
the present teachings relate to boronate-galactomannan complexes
comprising a hydrophobic group, the boronate-galactomannan
complexes having absorbent properties suitable for use in personal
hygiene products. In an embodiment, the boronate-galactomannan
complexes of the present teachings are dry, solid materials having
good fluid-swelling properties and capable of gel forming upon
contacting with a liquid.
[0011] In a further embodiment, the present teachings relate to the
use of the boronate-galactomannan complexes comprising a
hydrophobic group as absorbents in disposable sanitary products
(i.e. diapers, incontinence articles, feminine hygiene products,
airlaids and absorbent dressings), household articles, sealing
materials, humectants in agricultural products for soil
conditioning, in oil-drilling fluids (i.e. lost-circulation
material, fracturing fluids), anti-condensation coatings, in
agricultural, horticultural and forestry applications for retaining
water in the soil and for the release of water to the roots of
plants and trees, in the textile industry, in printing
applications, in absorbent paper products, in bandages and surgical
pads (i.e. wound dressings), in ore treatments, in pet litter, in
water treatment, in food pads (i.e. applications related to the
transportation of fresh food and food packaging), in detergents, in
fire-fighting gels, in sealing materials, as chemical absorbents
for the cleanup of acidic and/or basic aqueous spills including
water soluble chemical spills, as polymeric gels for the slow and
controlled release of cosmetics and pharmaceuticals (also known as
drug delivery systems), as airlaids, and finally in the manufacture
of artificial snow.
[0012] In a further embodiment, the present teachings relate to the
use of the boronate-galactomannan complexes comprising a
hydrophobic group as absorbents for liquids, non-limitative
examples of which include water, aqueous solutions, physiological
fluids and saline solutions.
[0013] In yet a further embodiment, the present teachings relate to
compositions including at least one boronate-galactomannan complex
comprising a hydrophobic group, and a co-absorbent material.
[0014] Finally, in a further embodiment, the present teachings
relate to processes for preparing boronate-galactomannan complexes,
the boronate-galactomannan complexes comprising a hydrophobic
group.
[0015] The foregoing and other objects, advantages and features of
the present teachings will become more apparent upon reading of the
following non restrictive description of illustrative embodiments
thereof, given by way of example only with reference to the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] In the appended drawings:
[0017] FIG. 1 is a graph illustrating the pH effect on the
performance characteristics of a boronate-galactomannan complex
comprising a hydrophobic group, according to an embodiment of the
present teachings.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0018] In order to provide a clear and consistent understanding of
the terms used in the present specification, a number of
definitions are provided below. Moreover, unless defined otherwise,
all technical and scientific terms as used herein have the same
meaning as commonly understood to one of ordinary skill in the art
to which the present teachings pertain.
[0019] The use of the word "a" or "an" when used in conjunction
with the term "comprising" in the claims and/or the specification
may mean "one", but it is also consistent with the meaning of "one
or more", "at least one", and "one or more than one". Similarly,
the word "another" may mean at least a second or more.
[0020] As used in this specification and claim(s), the words
"comprising" (and any form of comprising, such as "comprise" and
"comprises"), "having" (and any form of having, such as "have" and
"has"), "including" (and any form of including, such as "include"
and "includes") or "containing" (and any form of containing, such
as "contain" and "contains"), are inclusive or open-ended and do
not exclude additional, unrecited elements or process steps.
[0021] As used in this specification and claim(s), the term "about"
is used to indicate that a value includes an inherent variation of
error for the device or the method being employed to determine the
value.
[0022] As used in this specification, the term "percent" or "%"
refers to a percentage by weight (i.e. % (W/W)).
[0023] As used in this specification, the term "discrete particle"
refers to individual particles.
[0024] As used in this specification, the term "Free Swell
Capacity" (FSC), also called "Total Absorption", refers to the
amount (g) of fluid absorbed per gram of the composition. Typical
fluids are saline solutions (0.9% Weight/Weight NaCl solution,
hereinafter called 0.9% NaCl solution or saline).
[0025] As used in this specification, the term "Centrifuge
Retention Capacity" (CRC) also called "Retention", refers to the
amount (g) of fluid retained per gram of the composition, following
exposure of the composition to a centrifugation force of 250 G.
Typical fluids are saline solutions (0.9% Weight/Weight NaCl
solution, hereinafter called 0.9% NaCl solution or saline).
[0026] As used in this specification, the term "Absorption Under
Load" (AUL), at 0.3 PSI, 0.7 PSI or 0.9 PSI, also called
"Absorption Against Pressure" (AAP), refers to the amount (g) of
fluid absorbed per gram of the composition under a given applied
pressure. Typical fluids are saline solutions (0.9% Weight/Weight
NaCl solution, hereinafter called 0.9% NaCl solution or
saline).
[0027] The present description refers to a number of chemical terms
and abbreviations used by those skilled in the art. Nevertheless,
definitions of selected terms are provided for clarity and
consistency.
[0028] As used in this specification, the term "absorbent material"
or "absorbent polymer" refers to materials in a dry, solid state,
having good fluid-swelling properties and capable of gel forming
upon contacting with a fluid. Non limiting examples of such fluids
are water, aqueous solutions, saline, or physiological fluids.
[0029] As used in this specification, the term "superabsorbent",
"superabsorbent polymer" or "SAP" refers to absorbent materials
capable of gel forming upon contacting with a fluid such as water,
aqueous solutions, saline, or physiological fluids. Such materials
are characterized a Centrifuge Retention Capacity (CRC) of at least
15 g/g.
[0030] As used in this specification, the term galactomannan"
refers to naturally occurring polysaccharides comprising a poly
.beta.-(1-4)-mannose backbone having varying degrees of branching
(DB), and to which single D-galactopyranosyl residues are attached
via .alpha.-(1-6) linkages. Non-limiting examples of galactomannans
are guar gum, locust bean gum, tara gum, fenugreek gum, mesquite
gum and mixtures thereof. Endosperms of coffee (US 2004/0199943
A1), alfalfa, red-clover, and some soybeans (US 2004/0143871 A1)
are also known to comprise galactomannans.
[0031] As used in this specification, the term "diol" refers to a
pair of adjacent hydroxyl functions of galactomannans capable of
reacting with complexing agents such as a boronate. Adjacent
hydroxyl functions comprise a pair hydroxyl functions located on
vicinal carbon atoms. As reported by Bishop et al. (Dalton
Transactions; (17); 2004; 2621-2634), the 3,4 cis-diols on
galactopyranosyl residues and the 2,3-cis-diols on the mannose
backbone are diols capable of reacting with complexing agents
(Scheme 1).
##STR00001##
[0032] As used in this specification, the term "boronate" or
"boronates" refers to boron derivatives having the following
general molecular structure:
##STR00002##
wherein R.sub.1 is a hydrophobic group selected from the group
consisting of aromatic groups, aliphatic groups and cyclic
aliphatic groups.
[0033] As used in this specification, the term "complex" refers to
boron-containing materials obtained by adding a boronate to a
solution containing one or more galactomannans. The complexes of
the present teachings are derived from interactions between the 3,4
cis-diols on galactopyranosyl residues and the 2,3-cis-diols on the
mannose backbone with boronates. Complexes between such 3,4
cis-diols or 2,3-cis-diols and boronates are known as diol boronic
ester linkages.
[0034] As used in this specification, the term "hydrophobic",
"hydrophobic moiety" or "hydrophobic group" refers to those
compounds, groups or moieties being immiscible in water.
[0035] As used in this specification, the term "hydrophilic",
"hydrophilic moiety" or "hydrophilic group" refers to those
compounds, groups or moieties being miscible in water.
[0036] As used in this specification, the term "amphiphilic",
"amphiphilic moiety" or "amphiphilic group" refers to those
compounds, groups or moieties having both hydrophilic and
hydrophobic properties.
[0037] As used in this specification, the term "aliphatic" or
"aliphatic group" refers to, and is inclusive of, all non-aromatic
acyclic or cyclic groups. The aliphatic moieties may be saturated
or unsaturated, and may be substituted. Non-limiting examples of
aliphatic groups include alkyl groups, alkenyl groups, alkynyl
groups, cycloalkyl groups, and cycloalkenyl groups.
[0038] As used in this specification, the term "alkyl" refers to
straight, branched or substituted chain radicals having up to
twenty carbon atoms. Non-limiting examples include methyl, ethyl,
propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl,
isopropyl, isobutyl, isopentyl, neopentyl, isohexyl, isodecyl,
3-methylpentyl, 2,3,4-trimethylhexyl, sec-butyl, tert-butyl, or
tert-pentyl.
[0039] As used in this specification, the term "alkenyl" refers to
straight, branched or substituted chain radicals of 2 to 10 carbon
atoms having one or more double bonds.
[0040] As used in this specification, the term "alkynyl" refers to
straight, branched or substituted chain radicals of 2 to 10 carbon
atoms having one or more triple bonds.
[0041] As used in this specification, the term "cycloalkyl" refers
to cyclic chain radicals, optionally branched or substituted,
having up to ten carbon atoms. Non-limiting examples include
cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl.
[0042] As used in this specification, the term "cycloalkenyl"
refers to cyclic chain radicals, optionally branched or
substituted, of 2 to 10 carbon atoms having one or more double
bonds. Non-limiting examples include cyclopentenyl and
cyclohexenyl.
[0043] As used in this specification, the term "aromatic",
"aromatic groups" or "aromatic moiety" refers to unsaturated
conjugated cyclic hydrocarbons containing one or more rings.
Aromatic groups include 5- and 6-membered single-ring groups.
[0044] As used in this specification, the term "granular material",
"granules", "particles", "powders", "grains" or "dusts" refers to
particulate matter in a finely divided state. Granular material can
include highly pulverized material with very small diameters. The
particles need not be of any particular shape, but can be
spherical, roughly spherical, cubic, or non regular in shape.
[0045] As used in this specification, the term "particle size"
refers to the largest dimension of the particle. The particle size
can be directly determined using sieving methods, optical or
scanning electron microscopes as well as by other well-known
methods. The particle size is often considered the diameter of the
particle.
[0046] As used in this specification, the term "alkaline" refers to
any pH greater than 7.0.
[0047] The present teachings broadly relate to absorbent boronate
galactomannan complexes comprising a hydrophobic group. More
specifically, the galactomannan is complexed with a boronate
comprising a hydrophobic moiety. It was surprisingly discovered
that such complexes exhibit absorbent characteristics similar to
borax cross-linked galactomannans.
[0048] Efficient galactomannan-based absorbent materials are
obtained by complexing the galactomannans with a boronate
comprising a hydrophobic moiety. The hydrophobic moiety is selected
from the group consisting of aromatic groups, aliphatic groups or
cyclic aliphatic groups. Efficient absorbent materials are thus
obtained without the need for cross-linking the galactomannans.
[0049] Boronates are well documented in the art to form complexes
with the D-galactopyranosyl residues of galactomannans. Such
D-galactopyranosyl residues are also known to be at the origin of
the swelling characteristics of galactomannans. Hydrophobic pockets
are created when a boronate comprising a hydrophobic moiety is
complexed with the D-galactopyranosyl residues of galactomannans.
Without being bound by any theory, it is believed that the
hydrophobic pockets will become associated by means of weak Van der
Waals interactions. Even though weak, it is believed that such
interactions are sufficient to create a network of galactomannans
having good swelling properties and efficient absorbent
characteristics.
[0050] Gels of boronate-galactomannan complexes can be readily
obtained by dispersing a galactomannan in an aqueous solution
followed by the addition of a boronate comprising a hydrophobic
moiety. The resulting reaction mixture is stirred at alkaline pH
until gel formation. In an embodiment of the present teachings, an
alkaline pH of at least 8.5 was used.
[0051] The boronates of the present teachings are amphiphilic in
nature; the boronate, while bearing a hydrophobic moiety, being
hydrophilic. Because of this amphiphilic character, the boronates
only dissolve with great difficulty in water. However, the
boronates readily dissolve in non-aqueous polar solvents, a
non-limiting example of which includes tetrahydrofuran (THF).
[0052] The boronate-galactomannan complexes of the present
teachings can be prepared in accordance with a process in which a
galactomannan is dispersed in an aqueous solution, followed by the
addition of a boronate comprising a hydrophobic moiety. The
resulting boronate-galactomannan complex is then recovered by
precipitation from one or more hydrophilic organic solvents. The
precipitated boronate-galactomannan complex may then be optionally
ground into a granular material having a particle size ranging from
about 80 to about 800 .mu.m.
[0053] In an embodiment of the present teachings, the boronate
galactomannan complexes are in a dry solid state. Such dry boronate
galactomannan complexes can be easily handled and stocked. In a
further embodiment of the present teachings, the boronate
galactomannan complexes are in a dry, solid granular state. In a
further embodiment of the present teachings, the granular
galactomannan complexes comprise a particle size ranging from about
80 to about 800 .mu.m. In yet a further embodiment of the present
teachings, the granular galactomannan complexes comprise a particle
size ranging from about 150 to about 600 .mu.m.
[0054] Dry boronate galactomannan complexes can be obtained by
precipitating the complexes using hydrophilic organic solvents.
Non-limiting examples of hydrophilic organic liquids as
contemplated by the present teachings include C.sub.1-C.sub.3
alcohols, acetone, and acetonitrile. In an embodiment of the
present teachings, the boronate galactomannan complexes are
precipitated using methanol. Once precipitated, the boronate
galactomannan complexes may further processed such as by
grinding.
[0055] Non-limiting examples of galactomannans as contemplated by
the present teachings include guar gum, locust bean gum, tara gum,
fenugreek gum, mesquite gum and mixture thereof. The galactose to
mannose ratio of galactomannans typically ranges from about 1:5 to
about 1:1.
[0056] Guar gum, a typical galactomannan, is derived from ground
endosperm of the guar plant, which is grown extensively in the
semi-arid regions of Pakistan and India. As shown hereinabove in
Scheme 1, the structure of guar gum comprises a random galactose to
mannose ratio of about 1:1.6. This ratio is subject to fluctuations
from crop to crop or from subspecies to subspecies (Jasinski et al.
J. Polym. Sci., part. B: Polym. Phys. 1996, 34, 1477-1488).
[0057] Non-limiting examples of boronates as contemplated by the
present teachings include phenyl boronate, phenethyl boronate,
2-naphtalen boronate, 3-biphenyl boronate, trans-1-octen-1-yl
boronate and cyclohexyl boronate.
[0058] By virtue of their deficient valence, boronic acids possess
a vacant p-orbital. This characteristic confers them unique
properties as mild organic Lewis acids that can coordinate basic
molecules. As such, boronates can be readily obtained from the
corresponding boronic acids under alkaline conditions as
illustrated in Scheme 2. Typical alkaline conditions comprise a pH
of at least 8.5.
##STR00003##
[0059] Boronic acid, bearing a hydrophobic group, is dissolved in a
suitable solvent such as water, aqueous alkaline solutions or
non-aqueous polar solvents such as tetrahydrofuran (THF). The
solution may be heated to increase the boronic acid solubility. As
reported in the literature (Bishop et al; Dalton Transactions;
(17); 2004; 2621-2634; Pezron, E. et al. Macromolecules, 1988, 21,
1121-1125; Jasinski et al., J. Polym. Sci. Part B: Polym. Phys.,
1996, 34, 1477-1488), the type of boronate species present in
solution is directly dependent on the pH of the solution. It was
observed that an alkaline pH was particularly suitable for
generating boronates capable of complexing with galactomannans.
Typical alkaline conditions comprise a pH of at least 8.5.
[0060] The absorbent boronate galactomannan complexes of the
present teachings may be incorporated into absorbent personal
hygiene products such as, for example, baby diapers, incontinence
products, sanitary napkins and the like. They may be also used in
absorbent members such as absorbent cores, airlaids or foamed
structures.
[0061] The absorbent boronate galactomannan complexes of the
present teachings may also be used in other applications such as in
food pads, in agricultural and forestry applications for the
retention of water in the soil and for the release of water to the
roots of plants and trees; in fire-fighting techniques; in bandages
and surgical pads; for the cleanup of acidic or basic solution
spills, including water soluble chemical spills; as polymeric gels
for the controlled release of cosmetics and pharmaceuticals (also
known as drug delivery systems); and in artificial snow.
[0062] The absorbent boronate galactomannan complexes of the
present teachings may be mixed with other co-absorbent materials to
provide absorbent compositions. In an embodiment, the absorbent
compositions comprise from about 1 to about 99% (w/w) of boronate
galactomannan complex, and from about 99 to about 1% (w/w) of
co-absorbent material. Non-limiting examples of co-absorbent
materials include synthetic absorbent polymers, starch-based
absorbents, ionic polysaccharides, fibers and mixtures thereof. In
an embodiment of the present teachings, absorbent compositions are
obtained by mixing one or more boronate galactomannan complexes
with ionic polysaccharides; either cationic or anionic
polysaccharides or mixtures thereof. In a further embodiment of the
present teachings, absorbent compositions are obtained by mixing
one or more boronate galactomannan complexes with one or more
anionic polysaccharides.
[0063] Non-limiting examples of anionic polysaccharides as
contemplated by the present teachings include carboxyalkyl
polysaccharides, carboxymethyl cellulose, carboxymethyl starch,
oxidized polysaccharides, xanthan, carrageenans, pectin and
mixtures thereof.
[0064] Non-limiting examples of fibers as contemplated by the
present teachings include cellulose, viscose, rayon, cellulose
acetate, polyamides (i.e. Nylon.TM.), polyalkylenes, polyethylene,
polypropylene, bi-component fibers, polyesters, polylactides,
polypropanediols, Lyocell.TM., sphagnum and mixtures thereof.
[0065] Non-limiting examples of starch-based absorbents as
contemplated by the present teachings include glass-like starches
such as disclosed by Huppe et al. (CA 2,308,537); amylopectin
networks such as disclosed by Thibodeau et al. (CA 2,462,053);
starch agglomerates, hydroxyethyl starch, hydroxypropyl starch,
carboxymethyl starch, starch nanocomposites such as disclosed by
Berrada et al. (CA 2,483,049); and mixtures thereof.
[0066] The synthetic absorbent polymers to be used as co-absorbent
materials in the absorbent compositions of the present teachings,
are generally obtained from the polymerization, typically by
radical or radical graft polymerization, of monomers, non-limiting
examples of which include acrylic acid, acrylate salts, acrylic
ester, acrylic anhydride, methacrylic acid, methacrylate salts,
methacrylic esters, methacrylic anhydride, maleic anhydride, maleic
salts, maleate esters, acrylamide, acrylonitrile, vinyl alcohol,
vinyl pyrrolidone, vinyl acetate, vinyl guanidine, aspartic acid,
aspartic salts and mixtures thereof.
[0067] The boronate galactomannan complexes of the present
teachings, or absorbent compositions comprising such complexes, are
used in methods for absorbing liquids. In an embodiment of the
present teachings, one or more of the boronate galactomannan
complexes are contacted with a liquid to be absorbed. Non-limiting
examples liquids as contemplated by the present teachings include
water, aqueous solutions, physiological fluids and saline
solutions. The boronate galactomannan complexes, or absorbent
compositions comprising such complexes, upon contacting with the
liquid(s) to be absorbed, will form a gel trapping the liquid(s)
within.
EXPERIMENTAL
Materials
[0068] Guar gum (Procol.RTM.) was obtained from Polypro
(Minneapolis, USA). Phenethyl boronic acid, phenyl boronic acid,
trans-1-octen-1-yl boronic acid, cyclohexyl boronic acid, research
grade methanol and sodium hydroxide were obtained from
Sigma-Aldrich (St-Louis, USA). Hydrochloric acid was obtained from
Labmat (Quebec city, Canada).
Convection Oven
[0069] Samples were dried using a Lab tray drier TY 2, National
Drying Machinery Company, (Philadelphia, USA).
Grinder
[0070] A Braun.TM. model KSM coffee grinder was used to grind the
samples.
Test Methods
[0071] As discussed in Modern Superabsorbent Polymer Technology
(Buchholz F. L. and Graham A. T. Eds., Wiley-VCH, New York, 1998,
section 4.6.1. Swelling Capacity: Theory and Practice, p. 147),
several methods of measurement are used in order to characterize
the swelling capacity of a polymer. In the field of
superabsorbents, the Gravimetric Swelling Capacity [also called the
Free Swell Capacity (FSC)] and the Centrifuge Capacity [also called
the Centrifuge Retention Capacity (CRC)] are recommended methods.
The FSC and the CRC were used to compare the swelling capacities of
the obtained absorbent products.
Tea Bags for FSC and CRC Measurements
[0072] Tea bags (10.times.10 cm) were made from heat sealable
Ahistrom.TM. filter paper (16.5.+-.0.5) g/m.sup.2.
FSC Measurements
[0073] The Free Swell Capacity (FSC) in a 0.9% NaCl solution was
determined according to the recommended test method 440.2-02 from
EDANA.
CRC Measurements
[0074] The Centrifuge Retention Capacity (CRC) in a 0.9% NaCl
solution was determined according to the recommended test method
441.2-02 from EDANA.
EXAMPLES
Comparative Example 1
Phenylboronate Guar Complexes
[0075] A mixture comprising guar gum (6.00 g) and water (300 ml)
was prepared and left to swell for at least 45 minutes. Phenyl
boronic acid (1.34 g) was dissolved in water (40 ml) by increasing
the pH of the solution to 13.0 by the addition of an aqueous sodium
hydroxide solution (15%). The phenylboronate solution was added to
the guar suspension and the resulting suspension stirred 30
minutes. Half of the resulting gel was blended with methanol (300
ml), triturated, and transferred into a beaker. The pH of the
suspension was adjusted to 7.9 using hydrochloric acid (10%), under
vigorous mechanical stirring. The final suspension was filtered,
washed with methanol (3.times.50 ml), dried overnight in a
convection oven at 60.degree. C., and crushed with a mortar to
provide a white granular material having a FSC of 51.2 g/g and a
CRC of 39.5 g/g.
Comparative Example 2
Phenethylboronate Guar Complexes
[0076] A mixture comprising guar gum (6.00 g) and water (300 ml)
was prepared and left to swell for at least 45 minutes. Phenethyl
boronic acid (1.67 g) was dissolved in water (40 ml) by increasing
the pH of the solution to 13.0 by the addition of an aqueous sodium
hydroxide solution (15%). The phenethylboronate solution was added
to the guar suspension and the resulting suspension stirred 30
minutes. Half of the resulting gel was blended with methanol (300
ml), triturated, and transferred into a beaker. The pH of the
suspension was adjusted to 7.9 using hydrochloric acid (10%), under
vigorous mechanical stirring. The final suspension was filtered,
washed with methanol (3.times.50 ml), dried overnight in a
convection oven at 60.degree. C., and crushed with a mortar to
provide a white granular material having a FSC of 62.8 g/g and a
CRC of 45.4 g/g.
Comparative Example 3
Trans-1-octen-1-ylboronate Guar Complexes
[0077] A mixture comprising guar gum (6.00 g) and water (300 ml)
was prepared and left to swell for at least 45 minutes.
Trans-1-octen-1-ylboronic acid (1.73 g) was dissolved in THF (40
ml). The trans-1-octen-1-ylboronic acid solution was added to the
guar suspension. The pH of the suspension was increased to 10.0 by
the addition of an aqueous sodium hydroxide solution (15%) and the
suspension stirred 30 minutes. Half of the resulting gel was
blended with methanol (300 ml), triturated, and transferred into a
beaker. The pH of the suspension was adjusted to 8.0 using
hydrochloric acid (10%), under vigorous mechanical stirring. The
final suspension was filtered, washed with methanol (3.times.50
ml), dried overnight in a convection oven at 60.degree. C., and
crushed with a mortar to provide a white granular material having a
FSC of 94.8 g/g and a CRC of 68.4 g/g.
Comparative Example 4
Cyclohexylboronate Guar Complexes
[0078] A mixture comprising guar gum (6.00 g) and water (300 ml)
was prepared and left to swell for at least 45 minutes. Cyclohexyl
boronic acid (1.43 g) was dissolved in water (40 ml) by increasing
the pH of the solution to 13.0 by the addition of an aqueous sodium
hydroxide solution (15%). The cyclohexylboronate solution was added
to the guar suspension and the resulting suspension stirred 30
minutes. Half of the resulting gel was blended with methanol (300
ml), triturated, and transferred into a beaker. The pH of the
suspension was adjusted to 7.9 using hydrochloric acid (10%), under
vigorous mechanical stirring. The final suspension was filtered,
washed with methanol (3.times.50 ml), dried overnight in a
convection oven at 60.degree. C., and ground to provide a white
granular material having a FSC of 112.0 g/g and a CRC of 91.0
g/g.
Comparative Example 5
pH Effect on the Performances Characteristics of Phenylboronate
Complexes
[0079] A mixture comprising guar gum (6.00 g) and water (300 ml)
was prepared and left to swell for at least 45 minutes. Phenyl
boronic acid (1.35 g) was dissolved in water (40 ml) by increasing
the pH of the solution to 10.0 by the addition of an aqueous sodium
hydroxide solution (15%). The phenylboronate solution was added to
the guar suspension and the resulting suspension stirred 30
minutes. Half of the resulting gel was blended with methanol (300
ml), triturated, and transferred into a beaker. The pH of the
suspension was adjusted to 6.0, 7.0, 8.0, 9.0, 10.0 and 12.0 using
hydrochloric acid (10%) and/or sodium hydroxide (15%), under
vigorous mechanical stirring. The final suspension was filtered,
washed with methanol (3.times.50 ml), dried overnight in a
convection oven at 60.degree. C., and crushed with a mortar to
provide a white granular material having the FSC and CRC
performance characteristics as illustrated in FIG. 1.
[0080] It is to be understood that the invention is not limited in
its application to the details of construction and parts as
described hereinabove. The invention is capable of other
embodiments and of being practiced in various ways. It is also
understood that the phraseology or terminology used herein is for
the purpose of description and not limitation. Hence, although the
present teachings have been described hereinabove by way of
illustrative embodiments thereof, it can be modified, without
departing from the spirit, scope and nature of the subject
teachings as defined in the appended claims.
* * * * *