U.S. patent application number 17/100523 was filed with the patent office on 2021-03-11 for modified biopolymers and methods of producing and using the sam.
The applicant listed for this patent is Anavo Technologies, LLC. Invention is credited to Ali Ayoub, James Charles Bray, Ryan Nicholas Chan.
Application Number | 20210070888 17/100523 |
Document ID | / |
Family ID | 1000005234871 |
Filed Date | 2021-03-11 |
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United States Patent
Application |
20210070888 |
Kind Code |
A1 |
Ayoub; Ali ; et al. |
March 11, 2021 |
MODIFIED BIOPOLYMERS AND METHODS OF PRODUCING AND USING THE SAM
Abstract
Modified biopolymers, such as, charge-modified biopolymers,
cross-linked biopolymers, and cross-linked, charged modified
biopolymers are provided along with methods of producing and using
the same.
Inventors: |
Ayoub; Ali; (Raleigh,
NC) ; Bray; James Charles; (Raleigh, NC) ;
Chan; Ryan Nicholas; (Cary, NC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Anavo Technologies, LLC |
Raleigh |
NC |
US |
|
|
Family ID: |
1000005234871 |
Appl. No.: |
17/100523 |
Filed: |
November 20, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14728240 |
Jun 2, 2015 |
|
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17100523 |
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62006317 |
Jun 2, 2014 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08B 15/005 20130101;
A61L 2400/04 20130101; C08B 31/04 20130101; C08B 37/0057 20130101;
C08H 1/00 20130101; B27N 3/28 20130101; A61L 15/425 20130101; C08B
31/006 20130101; C08B 37/0045 20130101; A61L 15/28 20130101; A61L
15/60 20130101; B01J 39/19 20170101; C08B 37/003 20130101; B01J
39/22 20130101; C08B 31/003 20130101; A61L 15/32 20130101 |
International
Class: |
C08B 31/00 20060101
C08B031/00; C08B 37/00 20060101 C08B037/00; C08H 1/00 20060101
C08H001/00; C08B 37/08 20060101 C08B037/08; B01J 39/19 20060101
B01J039/19; C08B 31/04 20060101 C08B031/04; A61L 15/28 20060101
A61L015/28; A61L 15/32 20060101 A61L015/32; A61L 15/42 20060101
A61L015/42; A61L 15/60 20060101 A61L015/60; B01J 39/22 20060101
B01J039/22; C08B 15/00 20060101 C08B015/00 |
Claims
1. A method for producing a cross-linked, charge-modified
biopolymer comprising: combining a biopolymer and a plasticizer to
form a homogenous reaction blend, wherein the homogenous reaction
blend comprises a plasticized biopolymer; reacting the plasticized
biopolymer and at least one charge-modifying agent in the
homogenous reaction blend to form a charge-modified biopolymer; and
cross-linking the charge-modified biopolymer to form a
cross-linked, charge-modified biopolymer, wherein the cross-linked,
charge modified starch is free of crystalline domains.
2. The method of claim 1, wherein the combining step further
comprises combining a catalyst with the biopolymer and the
plasticizer to form the homogenous reaction blend.
3. The method of claim 1, wherein the cross-linking step further
comprises reacting the charge-modified biopolymer with at least one
cross-linking agent.
4. The method of claim 1, wherein the biopolymer comprises at least
two different biopolymers.
5. The method of claim 1, wherein the cross-linked, charge-modified
biopolymer has a net positive charge.
6. The method of claim 1, wherein the combining step comprises melt
blending the biopolymer and the plasticizer using a reactive
extrusion process.
7. The method of claim 1, wherein the method is carried out in an
extruder.
8. The method of claim 1, wherein the cross-linked, charge-modified
biopolymer is in the form of a particle have a diameter in a range
of about 10 microns to about 1000 microns.
9. The method of claim 1, wherein the reacting and/or cross-linking
step(s) is/are carried out at a temperature in a range of about
80.degree. C. to about 150.degree. C.
10. The method of claim 1, further comprising heating the
cross-linked, charge-modified biopolymer at a temperature in a
range of about 100.degree. C. to about 150.degree. C. for a period
of time in a range of about 1 minute to about 8 hours.
11. The method of claim 1, wherein the cross-linked,
charge-modified biopolymer has a net negative charge.
12. The method of claim 11, wherein the cross-linked,
charge-modified biopolymer includes at least one negatively charged
moiety selected from the group consisting of a carboxyl, sulfonate,
a sulfate, and phosphate.
13. A cross-linked, charge-modified biopolymer prepared according
to the method of claim 1.
14. The cross-linked, charge-modified biopolymer of claim 13 having
a charge density of at least 3 meq/g as determined by
titration.
15. A cross-linked, charge-modified biopolymer, wherein the
cross-linked, charge- modified biopolymer is cationic, wherein the
cross-linked, charge-modified biopolymer is free of crystalline
domains, and wherein the biopolymer is starch.
16. The cross-linked, charge-modified biopolymer of claim 15,
wherein the cross-linked, charge-modified biopolymer has a degree
of substitution of at least 0.1, as measured by nitrogen
content.
17. The cross-linked, charge-modified biopolymer of claim 15,
wherein the cross-linked, charge-modified biopolymer includes at
least one positively charged moiety selected from the group
consisting of a quaternary ammonium, sulfonium, and/or phosphonium
group.
18. A cross-linked, charge modified biopolymer, wherein the
cross-linked, charge modified biopolymer is anionic and wherein the
cross-linked, charge modified biopolymer is free of crystalline
domains, and wherein the biopolymer is starch.
19. The cross-linked, charge-modified biopolymer of claim 18,
wherein the cross-linked, charge modified biopolymer has a degree
of substitution of at least 0.1, as measured by nitrogen
content.
20. The cross-linked, charge-modified biopolymer of claim 18,
wherein the cross-linked, charge-modified biopolymer includes at
least one negatively charged moiety selected from the group
consisting of a carboxyl, sulfonate, a sulfate, and phosphate.
Description
RELATED APPLICATION DATA
[0001] This application claims the benefit of U.S. Provisional
Patent Application Ser. No. 62/006,317, filed Jun. 2, 2014, the
disclosure of which is incorporated herein by reference in its
entirety.
FIELD
[0002] The present invention relates to modified biopolymers,
including charge-modified biopolymers, cross-linked biopolymers,
and cross-linked, charge-modified biopolymers. Methods of producing
and using a modified biopolymer of the present invention are also
provided.
BACKGROUND
[0003] Biopolymers are of interest due to their many uses. For
example, biopolymers may be useful as absorbents, such as in
diapers, hygiene products, and wound dressings, and may be useful
as adsorbents. In addition, biopolymers may have the advantage of
providing environmentally friendly products.
[0004] However, methods of forming and/or processing biopolymers
into useful products, such as traditional heterogeneous wet
chemistry methods, can often be complex, expensive, and
inefficient.
[0005] The present invention addresses previous shortcomings in the
art by providing modified biopolymers and methods of producing and
using the same.
SUMMARY
[0006] A first aspect of the present invention includes a method
for producing a cross-linked, charge-modified biopolymer
comprising: combining a biopolymer and at least one
charge-modifying agent to form a homogenous reaction blend;
reacting the biopolymer and the at least one charge-modifying agent
in the homogenous reaction blend; and cross-linking the biopolymer
in the homogeneous reaction blend to form a cross-linked,
charge-modified biopolymer.
[0007] The method may include reacting the biopolymer and the at
least one charge-modifying agent to form a charge-modified
biopolymer. In some embodiments, the charge-modified biopolymer may
be cross-linked with a different biopolymer, which may optionally
be charged-modified.
[0008] The method may include forming a homogenous reaction blend
in an extruder, optionally using a reactive extrusion process.
[0009] Another aspect of the present invention includes a method
for producing a cross-linked, charge-modified starch-chitosan
comprising: combining starch, chitosan, at least one
charge-modifying agent, a catalyst, and a plasticizer to form a
homogenous reaction blend; charge-modifying the starch and chitosan
to form a charge-modified starch and a charge-modified chitosan;
and cross-linking the charge-modified starch and charge-modified
chitosan to form a cross-linked, charge-modified
starch-chitosan.
[0010] In a further aspect of the present invention, a method for
producing a cross-linked, charge-modified starch-chitosan
comprises: combining starch, a first charge-modifying agent, and a
catalyst to form a homogeneous reaction blend comprising a
charge-modified starch; adding charge-modified chitosan and a
plasticizer to the homogeneous reaction blend comprising the
charge-modified starch; and cross-linking the charge-modified
starch and charge-modified chitosan to form a cross-linked,
charge-modified starch-chitosan.
[0011] Another aspect of the present invention includes a method
for producing a cross-linked, charge-modified starch-chitosan
comprising: combining starch, a first charge-modifying agent, and a
catalyst, to form a charge-modified starch; forming a homogeneous
reaction blend comprising the charged-modified starch, a
charged-modified chitosan, and a plasticizer; and cross-linking the
charge-modified starch and charged-modified chitosan to form a
cross-linked, charge-modified starch-chitosan.
[0012] A further aspect of the present invention includes a
cross-linked, charge-modified biopolymer prepared according to a
method of the present invention.
[0013] Another aspect of the present invention includes a
cross-linked, charge-modified biopolymer having a charge density of
at least 3 meq/g as determined by titration.
[0014] A further aspect of the present invention includes a
cross-linked, charge-modified biopolymer having an increased charge
density and/or degree of cross-linking compared to a cross-linked,
charge-modified biopolymer prepared using a conventional
method.
[0015] An additional aspect of the present invention includes a
cross-linked, charge-modified biopolymer having an increased
porosity and/or pore size compared to a cross-linked,
charge-modified biopolymer prepared using a conventional
method.
[0016] A further aspect of the present invention includes a method
of absorbing a fluid comprising contacting a cross-linked,
charge-modified biopolymer of the present invention with the fluid,
thereby absorbing the fluid.
[0017] Another aspect of the present invention includes a
cross-linked, charge-modified biopolymer having an increased salt
uptake and/or metal chelation property compared to a cross-linked,
charge-modified biopolymer prepared using a conventional
method.
[0018] Another aspect of the present invention includes a method of
reducing the amount of a salt and/or metal in a solution comprising
contacting the cross-linked, charge-modified biopolymer of the
present invention with a solution comprising a salt and/or metal,
wherein the salt and/or metal binds to the cross-linked,
charge-modified biopolymer, thereby reducing the amount of the salt
and/or metal in the solution.
[0019] The foregoing and other aspects of the present invention
will now be described in more detail with respect to other
embodiments described herein. It should be appreciated that the
invention can be embodied in different forms and should not be
construed as limited to the embodiments set forth herein. Rather,
these embodiments are provided so that this disclosure will be
thorough and complete, and will fully convey the scope of the
invention to those skilled in the art.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1A is a schematic of a heterogeneous phase
reaction.
[0021] FIG. 1B is a schematic of a homogeneous phase reaction.
[0022] FIG. 2 illustrates a parallel twin screw extruder with
multiple injection and reaction zones according to embodiments of
the present invention.
[0023] FIG. 3 illustrates FTIR spectra for unmodified hemicellulose
and charge-modified hemicellulose according to embodiments of the
present invention.
[0024] FIG. 4 illustrates FTIR spectra for unmodified pectin and
charge-modified pectin according to embodiments of the present
invention.
[0025] FIG. 5 illustrates FTIR spectra for unmodified soy protein
and charge-modified soy protein according to embodiments of the
present invention.
[0026] FIG. 6 illustrates exemplary screw configurations according
to embodiments of the present invention.
[0027] FIG. 7A shows a SEM image of a commercially available
cationic starch at 33.times..
[0028] FIG. 7B shows a SEM image of the commercially available
cationic starch at 1000.times..
[0029] FIG. 7C shows a SEM image of an EDS chlorine map of the
commercially available cationic starch.
[0030] FIG. 7D shows a SEM image of a cationic starch prepared
according to methods of the present invention at 33.times..
[0031] FIG. 7E shows a SEM image of the cationic starch prepared
according to methods of the present invention at 1000.times..
[0032] FIG. 7F shows a SEM image of an EDS chlorine map of the
cationic starch prepared according to methods of the present
invention.
DETAILED DESCRIPTION
[0033] The present invention will now be described more fully
hereinafter. This invention may, however, be embodied in different
forms and should not be construed as limited to the embodiments set
forth herein. Rather, these embodiments are provided so that this
disclosure will be thorough and complete, and will fully convey the
scope of the invention to those skilled in the art.
[0034] The terminology used in the description of the invention
herein is for the purpose of describing particular embodiments only
and is not intended to be limiting of the invention. As used in the
description of the invention and the appended claims, the singular
forms "a", "an" and "the" are intended to include the plural forms
as well, unless the context clearly indicates otherwise.
[0035] Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which this
invention belongs. It will be further understood that terms, such
as those defined in commonly used dictionaries, should be
interpreted as having a meaning that is consistent with their
meaning in the context of the present application and relevant art
and should not be interpreted in an idealized or overly formal
sense unless expressly so defined herein. The terminology used in
the description of the invention herein is for the purpose of
describing particular embodiments only and is not intended to be
limiting of the invention. All publications, patent applications,
patents and other references mentioned herein are incorporated by
reference in their entirety. In case of a conflict in terminology,
the present specification is controlling.
[0036] Also as used herein, "and/or" refers to and encompasses any
and all possible combinations of one or more of the associated
listed items, as well as the lack of combinations when interpreted
in the alternative ("or").
[0037] Unless the context indicates otherwise, it is specifically
intended that the various features of the invention described
herein can be used in any combination. Moreover, the present
invention also contemplates that in some embodiments of the
invention, any feature or combination of features set forth herein
can be excluded or omitted. To illustrate, if the specification
states that a complex comprises components A, B and C, it is
specifically intended that any of A, B or C, or a combination
thereof, can be omitted and disclaimed.
[0038] As used herein, the transitional phrase "consisting
essentially of" (and grammatical variants) is to be interpreted as
encompassing the recited materials or steps "and those that do not
materially affect the basic and novel characteristic(s)" of the
claimed invention. See, In re Herz, 537 F.2d 549, 551-52, 190
U.S.P.Q. 461, 463 (CCPA 1976) (emphasis in the original); see also
MPEP .sctn. 2111.03. Thus, the term "consisting essentially of" as
used herein should not be interpreted as equivalent to
"comprising."
[0039] The term "about," as used herein when referring to a
measurable value, such as, for example, an amount or concentration
and the like, is meant to refer to variations of up to .+-.20% of
the specified value, such as, but not limited to, .+-.20%, .+-.15%,
.+-.10%, .+-.5%, .+-.1%, .+-.0.5%, or even .+-.0.1% of the
specified value, as well as the specified value. For example,
"about X" where X is the measurable value, is meant to include X as
well as variations of .+-.20%, .+-.15%, .+-.10%, .+-.5%, .+-.1%,
.+-.0.5%, or even .+-.0.1% of X. A range provided herein for a
measureable value may include any other range and/or individual
value therein.
[0040] According to some embodiments of the present invention,
provided herein are modified biopolymers, such as, charge-modified
biopolymers, cross-linked biopolymers, and/or cross-linked,
charge-modified biopolymers. The cross-linked, charged-modified
biopolymers of the present invention may comprise one biopolymer
that has been charge-modified and cross-linked. In some
embodiments, the cross-linked, charged-modified biopolymers of the
present invention may comprise two or more different biopolymers
that are cross-linked and at least one of the biopolymers has been
charge-modified. The two or more different biopolymers may be
cross-linked with each other. In certain embodiments, a
cross-linked, charge-modified biopolymer may comprise two different
biopolymers that are cross-linked and both of the biopolymers may
be charge-modified.
[0041] A "biopolymer" as used herein refers to a polymer that has
at least one free amine and/or hydroxyl group present on a majority
of the monomeric units of the polymer and is a polymer produced by
a living organism or a derivative thereof. In some embodiments, a
free amine and/or hydroxyl group may be present on each of the
monomeric units of the polymer backbone. Exemplary biopolymers
include, but are not limited to, proteins and/or polysaccharides.
As one of ordinary skill in the art will understand, a biopolymer
may be synthetically obtained (e.g., through laboratory synthesis)
and/or obtained and/or derived from nature (e.g., from a living or
previously living organism). Therefore, the biopolymer may be the
same as a polymer found in nature (i.e., a native biopolymer) or
may be a derivative thereof. For example, a biopolymer of the
present invention may be a derivative of a polymer produced by a
living organism, the derivative caused by the synthetic method used
to obtain or isolate the biopolymer from nature. In some
embodiments, a biopolymer may be a polymer produced by bacteria
and/or microbes.
[0042] Further exemplary biopolymers include, but are not limited
to, starches (including amylose and/or amylopectin), chitosans,
hemicelluloses, lignins, celluloses, chitins, alginates, dextrans,
pullanes, polyhydroxyalkanoates, fibrins, cyclodextrins, proteins
(e.g., soy protein), polysaccharides (e.g., pectin), and/or
polylactic acids.
[0043] A biopolymer used in a method of the present invention may
have a moisture content of about 20% by weight or less. In some
embodiments, the biopolymer may have a moisture content of about
20%, 15%, 10%, 5%, or less by weight. In certain embodiments, the
biopolymer may have a moisture content in a range of about 5% to
about 20% by weight or about 10% to about 15% by weight. In some
embodiments, a method of the present invention utilizes a
biopolymer, such as, for example, starch, having a moisture content
of about 20% by weight or less, and the biopolymer may be in powder
form.
[0044] A biopolymer used in a method of the present invention may
have a molecular weight of about 10,000 Daltons or more. In some
embodiments, the biopolymer may have a molecular weight of about
10,000; 20,000; 30,000; 40,000, 50,000; 60,000; 70,000; 80,000;
90,000; 100,000; 200,000; 300,000; 400,000; 500,000; 600,000;
700,000; 800,000; 900,000; 1,000,000; 2,000,000; 3,000,000,
4,000,000 Daltons or more. In certain embodiments, the biopolymer
may have a molecular weight of about 50,000 Daltons or more. In
some embodiments, the biopolymer may have a molecular weight of
about 100,000 Daltons to about 4,000,000 Daltons, about 500,000
Daltons to about 3,000,000 Daltons, or about 1,000,000 Daltons to
about 2,000,000 Daltons. In some embodiments, when only one
biopolymer is used to prepare a modified biopolymer of the present
invention (e.g., a cross-linked, charge-modified biopolymer), the
biopolymer may have a molecular weight of greater than about 50,000
Daltons. In some embodiments, when two or more different
biopolymers are used to prepare a modified biopolymer of the
present invention (e.g., a cross-linked, charge-modified
biopolymer), at least one of the two or more different biopolymers
may have a molecular weight of about 10,000 Daltons or more, such
as, for example, about 20,000; 30,000; 40,000, 50,000 Daltons or
more. In certain embodiments, a modified biopolymer of the present
invention (e.g., a cross-linked, charge-modified biopolymer) may be
prepared using a biopolymer having a molecular weight of greater
than about 50,000 Daltons optionally with a second different
biopolymer having a molecular weight of greater than about 10,000
Daltons. In some embodiments, the biopolymer may be
polydisperse.
[0045] In some embodiments, the biopolymer used in a method of the
present invention may be a starch. Exemplary starches include, but
are not limited to, potato starch, wheat starch, tapioca starch,
cassava starch, rice starch, corn starch, waxy corn starch, waxy
wheat starch, waxy rice starch, waxy sorghum starch, waxy cassava
starch, waxy barley starch, and/or waxy potato starch. The starch
may have an amylopectin content of about 70% w/w or more and an
amylose content of about 30% w/w or less. In certain embodiments,
the starch may have an amylopectin content of about 70%, 75%, 80%,
85%, 90%, 95% w/w or more and an amylose content of about 30%, 25%,
20%, 15%, 10%, 5% w/w or less. In some embodiments, the starch may
have an amylopectin content of less than 90%, such as, for example,
about 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%,
25%, 20%, 15%, 10%, etc. In some embodiments, starch may have an
amylopectin content in a range of about 10% to about 85%, such as,
for example, about 25% to about 85% or about 50% to about 80%.
[0046] In some embodiments, the starch may be dissolvable in water
(e.g., pre-gelatinized starch). In certain embodiments, the starch
may be steam exploded to form a pre-gelatinized starch. In some
embodiments, a starch used in a method of the present invention may
have a reduced degree of crystallinity compared to a native starch.
In certain embodiments, the biopolymer used in a method of the
present invention may be a chitosan. The chitosan may have a degree
of deacetylation of about 50% to about 100%. In some embodiments,
the chitosan may have a degree of deacetylation of about 50%, 55%,
60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 100%. In certain
embodiments, the chitosan may have a degree of deacetylation in a
range of about 70% to about 100% or greater than about 80%. In some
embodiments, the chitosan may have a molecular weight of greater
than about 80,000 Daltons.
[0047] A biopolymer used in a method of the present invention may
be charge-modified according to a method described herein (e.g., by
reacting the biopolymer with a charge-modifying agent in a
homogeneous reaction blend). However, as one of skill in the art
will recognize, a biopolymer may naturally carry a charge (i.e.,
the biopolymer may natively be charged in that the charge is
present on the biopolymer not through a method of the present
invention). Thus, a method of the present invention may change the
charge present on a biopolymer (e.g., type and/or amount of
charge). In some embodiments, a charge-modified biopolymer may be
soluble (e.g., partially or fully soluble) in a polar solvent, such
as, for example, water and/or a polar organic solvent at room
temperature and/or a nonpolar solvent at room temperature. In some
embodiments, a charge-modified biopolymer of the present invention
may be at least 70% soluble in a polar and/or nonpolar solvent at
room temperature. Solubility may be used as an indication and/or
characteristic of the degree of charge modification.
[0048] "Charge-modifying agent" as used herein refers to a molecule
or compound comprising one moiety that may react with an amine
and/or hydroxyl group of the biopolymer and a second moiety that
may be positively charged or negatively charged under suitable
conditions, such as, for example, at a certain pH. "Moiety" as used
herein, refers to a portion of a molecule or compound having a
particular functional or structural feature. For example, a moiety
may comprise a functional group or a reactive portion of a
compound. As those of skill in the art recognize, a strong acidic
moiety (e.g., --SO.sub.3H) or a weak acidic moiety (e.g., --COOH)
may form a negatively charged moiety and a strong basic moiety
(e.g., --NH.sub.3OH) or a weak basic moiety (--NH.sub.2) may form a
positively charged moiety.
[0049] The charge-modifying agent may comprise at least one moiety
that may be a positively charged group, such as, but not limited
to, a primary amine, secondary amine, tertiary amine, quaternary
ammonium, sulfonium, and/or phosphonium group. Exemplary
charge-modifying agents that can have a positively charged moiety
include, but are not limited to, ethylene imine, N-(2-hydroxyethyl)
ethylene imine, cyanamide, beta-morpholinoethylchloride,
beta-diethyl aminoethylchloride, S-diethyl amino 1,2-epoxypropane
dimethyl aminoethyl methacrylate, epoxy 3-methyl ammonium,
glycidyltrimethylammonium chloride (e.g., QUAB.RTM. 151),
N-(2,3-epoxypropyl) trimethyl ammonium chloride, (4-chlorobutene-2)
trimethyl ammonium chloride, 2-chloroethyl methyl ethyl sulfonium
iodide, and/or Z-chloroethyl tributylphosphonium chloride. In some
embodiments, the charge-modifying agent comprises a tertiary amino
alkyl group, a hydroxyalkyl group, a quaternary ammonium alkyl
group, or a hydroxyalkyl group.
[0050] In some embodiments, a positively charged moiety may be
introduced into and/or onto a biopolymer by reacting the biopolymer
and charge-modifying agent in a homogeneous reaction blend,
optionally in the presence of a catalyst. This reaction may be a
dry melt process and/or may be an etherification or esterification
reaction.
[0051] The charge-modifying agent may comprise at least one moiety
that may be a negatively charged group, such as, but not limited
to, a carboxyl, sulfonate, sulfate, and/or a phosphate group (e.g.,
sodium tripolyphosphate). Exemplary charge-modifying agents that
can have a negatively charged moiety include, but are not limited
to, acids (e.g., citric acid, glacial acetic acid,
ethylenediaminetetraacetic acid (EDTA), and/or diethylene triamine
pentaacetic acid (DTPA)); mono-halogen substituted fatty acids
(e.g., monochloroacetic acid); acetates (e.g., sodium
monochloroacetate); anhydrides (e.g., succinic anhydride, maleic
anhydride, citraconic anhydride, and/or octenyl succinicanhydride);
alkyl esters of acrylic acid, crotonic acid or itaconic acid (e.g.,
methyl and ethyl esters of acrylic acid, crotonic acid or itaconic
acid); acrylonitrile; sodium periodate; sulfones; and/or sulfonic
acids (e.g., halo alkane sulfonic acids, chlorooxypropane sulfonic
acid, epoxypropane sulfonic acid, chlorooxypropane sulfonic acid,
epoxypropane sulfonic acid, ethene sulfonic acid, and/or salts
thereof).
[0052] In some embodiments, a negatively charged moiety may be
introduced into a biopolymer by reacting the biopolymer and
charge-modifying agent in a homogeneous reaction blend in the
presence an alkaline catalyst. In certain embodiments, the
charge-modifying agent may be acrylonitrile and the reaction of the
biopolymer and acrylonitrile in the presence of an alkaline
catalyst may be followed by hydrolysis of the cyanoethyl groups.
When the charge-modifying agent is sodium periodate, the reaction
with the biopolymer may be followed by a treatment to transform the
carbonyl groups into carboxyl groups, such as, but not limited to,
by treating with sodium chlorite, and/or by a treatment with sodium
bisulfite and/or potassium bisulfite. In certain embodiments, both
carboxyl and sulfonate groups may be introduced into a biopolymer
by reacting the biopolymer with an anhydride of an unsaturated acid
(e.g., maleic acid) and a bisulfite. The bisulfite may be reacted
with the unsaturated bond of the polysaccharide half ester.
[0053] In some embodiments, the charge-modifying agent may react
with an amine and/or hydroxyl group of a biopolymer to provide a
charge-modified biopolymer. The charge-modified biopolymer may be
cationic (i.e., have a net positive charge) or may be anionic
(i.e., have a net negative charge). In some embodiments, the
charge-modified biopolymer may contain both positively and
negatively charged moieties.
[0054] A biopolymer used in a method of the present invention may
be cross-linked by reacting a cross-linking agent with the
biopolymer and optionally with at least one different biopolymer
that may optionally be charge-modified. In some embodiments, a
cross-linking agent may be reacted with at least one
charge-modified biopolymer. "Cross-linking agent" as used herein
refers to a compound that links two or more biopolymer chains
and/or portions of the biopolymer together, the biopolymer
optionally being charge-modified. The linkage may be achieved via a
covalent bond or an ionic bond. In some embodiments, the linkage
may be through a moiety or group of the biopolymer or different
biopolymers.
[0055] Exemplary cross-linking agents include, but are not limited
to, epichlorohydrin, glutaraldehyde, oxalic acid, malonic acid,
succinic acid, glutaric acid, adipic acid, pimelic acid, fumaric
acid, maleic acid, malic acid, tartartic acid, sodium
trimetaphosphate, sodium tripolyphosphate, ionic cross-linkers
(e.g., calcium chloride, calcium hydroxide, etc.), poly(ethylene
glycol) diglycidyl ether (PEGDE), poly(propylene glycol) diglycidyl
ether (PPGDE), and/or an anhydride, such as, for example, succinic
anhydride and maleic anhydride. In some embodiments, the
cross-linking agent is non-toxic.
[0056] Without wishing to be bound to any particular theory, in
some embodiments, a charge-modifying agent, such as, for example,
citric acid, when heated inside an extruder may dehydrate to yield
an anhydride. The free hydroxyl groups from a biopolymer, such as,
for example, starch, present in the reaction mixture may react with
the anhydride to form starch citrate. Further, without wishing to
be bound to any particular theory, in some embodiments, additional
dehydration of the biopolymer and/or charge-modified biopolymer may
allow for cross-linking of the biopolymer and/or charge-modified
biopolymer to occur. In some embodiments, cross-linking of the
biopolymer and/or charge-modified biopolymer may be achieved due to
the heat inside the extruder and/or during a post treatment
process, such as, for example, a thermal post-treatment process. In
some embodiments, a charge-modified biopolymer may be prepared
using a ring-opening polymerization of anhydrous acids.
[0057] A modified biopolymer of the present invention (e.g., a
cross-linked, charge-modified biopolymer) may comprise a plurality
of pores or void spaces formed therein. The pores or void spaces
may have an average diameter of about 0.1 micron to about 500
microns, such as, but not limited to, about 10 microns to about 500
microns, about 50 microns to about 500 microns, about 100 microns
to about 400 microns, or about 250 microns to about 500 microns. In
certain embodiments, the pores or void spaces may have an average
diameter of about 0.1 micron, 1 micron, 10 microns, 25 microns, 50
microns, 100 microns, 150 microns, 200 microns, 250 microns, 300
microns, 350 microns, 400 microns, 450 microns, or 500 microns.
[0058] In some embodiments, a modified biopolymer of the present
invention (e.g., a cross-linked, charge-modified biopolymer) has a
net positive charge (i.e., is cationic) or a net negative charge
(i.e., is anionic). In certain embodiments, the modified biopolymer
(e.g., a cross-linked, charge-modified biopolymer) is a
polyampholyte. In some embodiments, the modified biopolymer may be
a polyelectrolyte, which may be hydrophilic (e.g., due to the
number of ionizable groups present on the modified biopolymer). In
some embodiments, a modified biopolymer of the present invention
(e.g., a cross-linked, charge-modified biopolymer) may be a
superabsorbent. In some embodiments, a superabsorbent of the
present invention, may absorb a fluid in an amount of about 15
times or more (e.g., 20.times., 30.times., 40.times., 50.times.,
100.times., etc.) relative to its weight. A superabsorbent, in some
embodiments, may absorb a 0.9% saline solution in an amount of
about 20 times or more (e.g., 25.times., 30.times., etc.) at room
temperature and/or water in an amount of about 35 times or more
(e.g., 40.times., 45.times., etc.) at room temperature. In some
embodiments, a cross-linked, charge-modified biopolymer of the
present invention is charge-modified and cross-linked in an
extruder. Some embodiments of the present invention may provide a
cross-linked, charge-modified biopolymer in a one step extrusion
process.
[0059] A modified biopolymer of the present invention (e.g., a
cross-linked, charge-modified biopolymer) may be a biosorbent
and/or may be biodegradable. A "biosorbent" as used herein may
refer to an absorbent (e.g., that may be utilized in the removal of
a fluid) and/or an adsorbent (e.g., that may be utilized as an ion
exchange material and/or metal chelating material). In some
embodiments, a biosorbent may be a superabsorbent.
[0060] A modified biopolymer of the present invention (e.g., a
cross-linked, charge-modified biopolymer and/or charge-modified
biopolymer) may have a charge density of about 3 meq/g or more as
determined by titration. For example, in some embodiments, charge
density may be determined by titration as described in Example 1.1.
In some embodiments, the modified biopolymer may have a charge
density of about 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9,
9.5, 10 meq/g or more as determined by titration. In certain
embodiments, the modified biopolymer may have a charge density of
at least about 5 meq/g as determined by titration.
[0061] In some embodiments, a method of the present invention may
provide a modified biopolymer (e.g., a cross-linked,
charge-modified biopolymer and/or charge-modified biopolymer)
having the charge modification substantially uniformly distributed
throughout the bulk of the modified biopolymer. Thus, the modified
biopolymer may have a substantially uniform charge density. In some
embodiments, the uniformity of the charge density of a modified
biopolymer may be determined by evaluating the presence of
insoluble materials after exposure of the modified biopolymer to a
solvent, such as, for example water. Observation of particles (such
as, for example, 1-10 .mu.m particles) may indicate the lack of
charge modification within the particles and/or modified
biopolymer. In some embodiments, charge density distribution on a
modified biopolymer may be determined and/or evaluated using one or
more spectrographic analytical techniques such as, but not limited
to, EDS, EPS, and/or TOF-SIMS of the charged moiety's counter ion.
In some embodiments, an uneven distribution of counter ions and/or
the presence of particles (e.g., 1-10 .mu.m particles) lacking the
counter ion indicates non-uniformity and/or inhomogeneity in regard
to the distribution of the charge on the modified biopolymer.
[0062] In some embodiments, the modified biopolymer may have an
increased charge density and/or degree of cross-linking compared to
a modified biopolymer (e.g., a cross-linked, charge-modified
biopolymer) prepared using a conventional method. "Conventional
method" as used herein in reference to a method for preparing a
modified biopolymer refers to a method for preparing a modified
biopolymer in which the biopolymer is a solid (e.g., a particulate)
and a reaction of the biopolymer with at least one reactant in the
method occurs at a solid interface of the biopolymer. In some
embodiments, a conventional method may be a method that does not
involve forming a homogeneous reaction blend and/or that does not
involve a melt extrusion process, such as a reactive extrusion
process. In some embodiments, a conventional method may be a
semi-dry process, a multi-phase process, a process having a liquid
interface with a solid material, and/or a heterogeneous process. In
certain embodiments, a conventional method may be a heterogeneous
wet chemistry method and/or a multi-phase process.
[0063] The modified biopolymer may have a charge density and/or
degree of cross-linking that is increased by at least about 5% or
more compared to a modified biopolymer prepared using a
conventional method. In some embodiments, the modified biopolymer
may have a charge density and/or degree of cross-linking that is
increased by at least about 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%,
45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, 150%,
200%, or more compared to a modified biopolymer prepared using a
conventional method.
[0064] In some embodiments, the degree or amount of cross-linking
present in a modified biopolymer of the present invention (e.g., a
cross-linked, charge-modified biopolymer and/or cross-linked
biopolymer) may provide mechanical rigidity to the modified
biopolymer and/or correlate with the degree of mechanical rigidity
in the modified biopolymer.
[0065] In some embodiments, a modified biopolymer of the present
invention (e.g., a cross-linked, charge-modified biopolymer) may
have a degree of substitution of about 0.01 or more, such as, for
example, in a range of about 0.01 to about 0.3. For example, in
some embodiments, the modified biopolymer may have a degree of
substitution of about 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07,
0.08, 0.09, 0.1, 0.15, 0.2, 0.25, 0.3, or more. In some
embodiments, a modified biopolymer may have a degree of
substitution in a range of about 0.09 to about 0.3 or about 0.1 to
about 0.25. In some embodiments, the degree of substitution may be
measured by nitrogen content.
[0066] In some embodiments, a modified biopolymer of the present
invention (e.g., a cross-linked, charge-modified biopolymer) may
have a free swell capacity (FSC) of about 5 g/g or more, such as,
for example, in a range of about 5 g/g to about 100 g/g. For
example, in some embodiments, the modified biopolymer may have a
FSC of about 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19,
20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36,
37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53,
54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70,
71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87,
88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, or more.
[0067] In some embodiments, a modified biopolymer of the present
invention (e.g., a cross-linked, charge-modified biopolymer) may
have a Centrifuge Retention Capacity (CRC) of about 1 g/g or more,
such as, for example, in a range of about 1 g/g to about 60 g/g.
For example, in some embodiments, the modified biopolymer may have
a CRC of about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,
16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32,
33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49,
50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, or more.
[0068] A modified biopolymer of the present invention (e.g., a
cross-linked, charge-modified biopolymer) may comprise a plurality
of pores and/or void spaces. The modified biopolymer may have an
increased porosity and/or pore size compared to a modified
biopolymer prepared using a conventional method. The porosity may
be increased by increasing the number of pores or void spaces. The
pores or void spaces may be substantially the same size (e.g.,
varying in size or diameter by less than about 20%) or may be
different sizes. The modified biopolymer may have a porosity and/or
pore size that is increased by at least about 5% or more compared
to a modified biopolymer prepared using a conventional method. In
some embodiments, the modified biopolymer may have a porosity
and/or pore size that is increased by at least about 5%, 10%, 15%,
20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%,
85%, 90%, 95%, 100%, 150%, 200%, or more compared to a modified
biopolymer prepared using a conventional method.
[0069] In some embodiments, the modified biopolymer may have a more
uniform porosity and/or pore size compared to a modified biopolymer
prepared using a conventional method. A more uniform porosity may
include a more uniformly or evenly dispersed number of pores or
void spaces throughout the modified biopolymer. In some
embodiments, a more uniform pore size may include a more uniform
diameter of the pores or void spaces throughout the modified
biopolymer. In certain embodiments, the porosity and/or pore size
of the modified biopolymer may be more uniform compared to the
porosity and/or pore size of a modified biopolymer prepared using a
conventional method, and may vary by less than about 20%, such as,
for example, by about 20%, 15%, 10%, 5% or less, as determined by
comparing two or more defined areas of the modified biopolymer
compared to two or more defined areas of the modified biopolymer
prepared using a conventional method.
[0070] A modified biopolymer of the present invention (e.g., a
cross-linked, charge-modified biopolymer) may sequester, bind,
absorb, chelate, uptake, adsorb, and/or the like a fluid (e.g.,
water, hydrocarbons, oils, alcohols, aqueous solutions, non-aqueous
solutions, ionic solutions such as salt solutions, biological
fluids such as blood and/or urine, gases, waste water, and/or
fracking fluids), a charged species (e.g., ions such as potassium
ions (K.sup.+), calcium ions (Ca.sup.2+), sodium ions (Na.sup.+),
chloride ions (Cl.sup.-), fluoride ions (F.sup.-), phosphite ions
(PO.sub.3.sup.3-), sulfate ions (SO.sub.4.sup.2-), sulfite ions
(SO.sub.3.sup.2-), phosphate ions (PO.sub.4.sup.3-), polyatomic
ions, and/or metal ions; charged peptides, polypeptides, nucleic
acids, and/or oligonucleotides; and the like), and/or a metal
(e.g., lead, mercury, cadmium, arsenic, copper, chromium, thallium,
selenium, zinc, calcium, magnesium, silver, boron, and the like).
In some embodiments, a modified biopolymer of the present invention
(e.g., a cross-linked, charge-modified biopolymer) may physically
adsorb a species present in a fluid, such as, but not limited to an
ionic species and/or a metal. The species may be dissolved in the
fluid. In certain embodiments, a modified biopolymer may bind, such
as, for example, via hydrogen bonding, covalent bonding, van der
waals/adsorptive binding, and/or ionic bonding, a fluid, charged
species, and/or metal.
[0071] In certain embodiments, a modified biopolymer of the present
invention (e.g., a cross-linked, charge-modified biopolymer) may
sequester, bind, absorb, chelate, uptake, adsorb, and/or the like
an ion and/or a metal. The metal may be in an ionized form, such as
in the form of a salt. As those skilled in the art recognize, a
metal may exist in a number of ionized forms, such as, monovalent,
divalent, polyvalent, anionic, and/or cationic forms. Further
exemplary ions and/or metals, in any ionized form, that a modified
biopolymer of the present invention may sequester, bind, absorb,
chelate, uptake, adsorb, and/or the like include, but are not
limited to, sodium, potassium, lithium, ammonium, barium,
strontium, manganese, silver, cesium, zinc, cadmium, selenium,
calcium, magnesium, iron, radium, mercury, copper, lead, nickel,
chromium, arsenic, gold, uranium, chloride, bromide, nitrate,
iodide, carbonate, sulphate, and/or phosphate.
[0072] In some embodiments, a modified biopolymer of the present
invention (e.g., a cross-linked, charge-modified biopolymer) may
sequester, bind, absorb, chelate, uptake, adsorb, and/or the like
an organic. Exemplary organics include, but are not limited to,
toluene, xylenes, benzene, ethylbenzene, trimethylbenzene, acetone,
and/or methanol.
[0073] A modified biopolymer of the present invention (e.g., a
cross-linked, charge-modified biopolymer) may sequester, bind,
absorb, chelate, uptake, adsorb, and/or the like an increased
amount or concentration of a fluid, a charged species, and/or a
metal compared to a modified biopolymer prepared using a
conventional method. The modified biopolymer may sequester, bind,
absorb, chelate, uptake, adsorb, and/or the like an increased
amount or concentration of a fluid, charged species, and/or a metal
by at least about 5% or more compared to a modified biopolymer
prepared using a conventional method. In some embodiments, the
modified biopolymer may sequester, bind, absorb, chelate, uptake,
adsorb, and/or the like an increased amount or concentration of a
fluid, charged species, and/or a metal by at least about 5%, 10%,
15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%,
80%, 85%, 90%, 95%, 100%, 150%, 200%, or more compared to a
modified biopolymer prepared using a conventional method.
[0074] In some embodiments, a modified biopolymer of the present
invention may comprise starch and chitosan. The starch and chitosan
may both be charged-modified and cross-linked with each other to
form a cross-linked, charged-modified starch-chitosan
biopolymer.
[0075] According to some embodiments of the present invention, a
method for producing a charge-modified biopolymer may be provided.
The method may comprise reacting a biopolymer and at least one
charge-modifying agent in a homogeneous reaction blend to form a
charge-modified biopolymer. In some embodiments, the method may
comprise combining the biopolymer and at least one charge-modifying
agent, optionally with a plasticizer and/or catalyst, to form a
homogenous reaction blend. In some embodiments, the method may
comprise reacting two or more different biopolymers with a
charge-modifying agent in a homogeneous reaction blend. Optionally,
at least one of the two or more different biopolymers may be
charge-modified (e.g., according to a method of the present
invention) prior to the reacting step.
[0076] According to some embodiments of the present invention, a
method for producing a cross-linked biopolymer may be provided. The
method may comprise reacting a biopolymer and at least one
cross-linking agent in a homogeneous reaction blend to form a
cross-linked biopolymer. In some embodiments, the method may
comprise combining the biopolymer and at least one cross-linking
agent, optionally with a plasticizer and/or catalyst, to form a
homogenous reaction blend. In some embodiments, the method may
comprise reacting two or more different biopolymers with a
cross-linking agent in a homogeneous reaction blend.
[0077] According to some embodiments of the present invention, a
method for producing a cross-linked, charge-modified biopolymer may
be provided. The method may comprise reacting a biopolymer and at
least one charge-modifying agent in a homogenous reaction blend to
form a charge-modified biopolymer and cross-linking the
charge-modified biopolymer in the homogeneous reaction blend to
form a cross-linked, charge-modified biopolymer. Some embodiments
may include reacting two or more different biopolymers with the at
least one charge-modifying agent in the homogeneous reaction blend
to form at least one charge-modified biopolymer. In some
embodiments, the charge-modified biopolymer may be cross-linked to
one or more different biopolymers in the homogeneous reaction
blend, and the one or more different biopolymers may optionally be
charge-modified, such as, for example, prior to a combining,
reacting, and/or cross-linking step. In some embodiments, a
charge-modified biopolymer prepared according to a method of the
present invention is used to prepare a cross-linked,
charge-modified biopolymer of the present invention. In some
embodiments, the biopolymer and the at least one charge-modifying
agent may be combined to form a homogeneous reaction blend.
[0078] In some embodiments, one or more steps of a method of the
present invention (e.g., a combining, reacting, and/or
cross-linking step) may occur simultaneously and/or sequentially
with another step in the method. For example, in some embodiments,
a reacting step to form a charged-modified biopolymer of the
present invention may occur simultaneously with a cross-linking
step to form a cross-linked, charge-modified biopolymer of the
present invention. A further example includes, in some embodiments,
that a cross-linking step to form a cross-linked, charge-modified
biopolymer of the present invention may occur after a reacting step
to form a charged-modified biopolymer has occurred. In some
embodiments, a reacting and cross-linking step occur in different
reaction zones of an extruder.
[0079] In some embodiments, a method for producing a cross-linked,
charge-modified biopolymer may comprise combining a first
charge-modified biopolymer and a second charge-modified biopolymer
that is different than the first charge-modified biopolymer,
optionally with a plasticizer, cross-linking agent, and/or
catalyst, to form a homogeneous reaction blend, and cross-linking
the first and second charge-modified biopolymers in the homogeneous
reaction blend to form a cross-linked, charge-modified biopolymer.
The first and/or second charge-modified biopolymers may be
charge-modified according to a method of the present invention.
[0080] Some embodiments include a method for producing a
cross-linked, charge-modified biopolymer comprising: combining a
first biopolymer, a second biopolymer that is different than the
first biopolymer, at least one charge-modifying agent, a
plasticizer, and optionally a catalyst to form a homogenous
reaction blend; reacting the first biopolymer and second biopolymer
with the at least one charge-modifying agent to form a
charge-modified first biopolymer and a charge-modified second
biopolymer; and cross-linking the charge-modified first biopolymer
and charge-modified second biopolymer to form a cross-linked,
charge-modified biopolymer.
[0081] In some embodiments, a method for producing a cross-linked,
charge-modified biopolymer comprises: combining a first biopolymer,
a first charge-modifying agent, and optionally a catalyst to form a
homogeneous reaction blend comprising a charge-modified first
biopolymer; adding a charge-modified second biopolymer and a
plasticizer to the homogeneous reaction blend comprising the
charge-modified first biopolymer; and cross-linking the
charge-modified first biopolymer and charge-modified second
biopolymer to form a cross-linked, charge-modified biopolymer. In
some embodiments, the charge-modified second biopolymer is prepared
according to a method of the present invention.
[0082] Some embodiments include a method for producing a
cross-linked, charge-modified biopolymer comprising: combining a
first biopolymer, a first charge-modifying agent, and optionally a
catalyst to form a charge-modified first biopolymer; forming a
homogeneous reaction blend comprising the charged-modified first
biopolymer, a charged-modified second biopolymer, and a
plasticizer; and cross-linking the charge-modified first biopolymer
and charged-modified second biopolymer to form a cross-linked,
charge-modified biopolymer. In some embodiments, the
charge-modified second biopolymer is prepared according to a method
of the present invention.
[0083] In some embodiments, a method for producing a cross-linked,
charge-modified biopolymer comprises: forming a homogenous reaction
blend comprising a first biopolymer, a second biopolymer that is
optionally charged-modified, and at least one charge-modifying
agent; reacting the first biopolymer and the at least one
charge-modifying agent in the homogenous reaction blend to form a
charge-modified biopolymer; and cross-linking the charge-modified
biopolymer and the second biopolymer in the homogeneous reaction
blend to form a cross-linked, charge-modified biopolymer. In some
embodiments, the second biopolymer may be charge-modified according
to a method of the present invention.
[0084] In some embodiments, a method for producing a cross-linked,
charge-modified biopolymer comprises: forming a first homogenous
reaction blend comprising a first biopolymer and at least one
charge-modifying agent; reacting the first biopolymer and the at
least one charge-modifying agent in the first homogenous reaction
blend to form a charge-modified biopolymer; combining the
charge-modified biopolymer with a second biopolymer that is
optionally charge-modified to form a second homogeneous reaction
blend; and cross-linking the charge-modified biopolymer and second
biopolymer in the second homogeneous reaction blend to form a
cross-linked, charge-modified biopolymer. In some embodiments, the
second biopolymer may be charge-modified according to a method of
the present invention.
[0085] In some embodiments, a method for producing a modified
biopolymer of the present invention (e.g., a cross-linked,
charge-modified biopolymer) may occur and/or be carried out in a
continuous process. In some embodiments, the reacting and/or
cross-linking steps may occur and/or be carried out in a continuous
process. A continuous process is one that does not involve
intermediate steps that stop a reaction in process. Exemplary
intermediate steps include, but are not limited to, changing a
buffer or providing a wash step before obtaining the product. The
continuous process may be carried out or performed in an extruder
optionally using a reactive extrusion process. For example, a
continuous process includes a process in which all reactants are
added to an extruder either at the same time or different times and
the process occurs continuously (i.e. without stopping for
intermediate steps) until the modified biopolymer is extruded. A
continuous process may also include a step in a method of the
present invention that is carried out or performed in an extruder,
such as a reacting and/or cross-linking step.
[0086] In some embodiments, a method of the present invention may
comprise a continuous process followed by a non-continuous process,
such as, but not limited to, a post-treatment step. In certain
embodiments, a method of the present invention may comprise a
continuous process, a non-continuous process (e.g., a batch
process), and optionally a subsequent continuous process. In some
embodiments, a method of the present invention may comprise a
continuous process to prepare a charge-modified biopolymer (e.g., a
charge-modified starch), and then the charge-modified biopolymer
may undergo a post-treatment, which may optionally be a batch
process. The method may further comprise another continuous process
in which the charged-modified biopolymer may be reacted with
another biopolymer (e.g., chitosan), which may optionally be
charge-modified.
[0087] A "reactive extrusion process" as used herein refers to a
process in which a biopolymer is both chemically and physically
modified. A reactive extrusion process may provide for a chemical
modification of a biopolymer, such as, but not limited to, grafting
onto the biopolymer, cross-linking of the biopolymer,
functionalization of the biopolymer, and/or charge-modification of
the biopolymer. In some embodiments, a reactive extrusion process
may provide for polymerization and/or branching of a biopolymer.
The polymerization and/or branching may be with a different
biopolymer to provide a co-polymer. An exemplary physical
modification may be changing the form of the biopolymer, such as,
but not limited to, from a powder, particulate, and/or solid form
to a molten or melted form.
[0088] At least one charge-modifying agent may be present in a
homogeneous reaction blend in an amount of about 5% to about 200%
or more by weight of a biopolymer present in the homogeneous
reaction blend. In some embodiments, at least one charge-modifying
agent may be present in a homogeneous reaction blend in an amount
of about 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%,
110%, 120%, 130%, 140%, 150%, 160%, 170%, 180%, 190%, 200%, or more
by weight of a biopolymer present in the homogeneous reaction
blend. In some embodiments, at least one charge-modifying agent may
be present in a homogeneous reaction blend in an amount of at least
about 75% by weight of a biopolymer present in the homogeneous
reaction blend. In some embodiments, a method of the present
invention may include at least one charge-modifying agent present
in a homogeneous reaction blend in an amount of at least about 75%
by weight of the biopolymer and provide a modified biopolymer
having a charge density of at least 1.5 meq/g of the modified
biopolymer.
[0089] A homogeneous reaction blend is a melted blend of all the
components in a single phase. In some embodiments, a homogeneous
reaction blend may be obtained using an extruder. In certain
embodiments, a homogeneous reaction blend may be obtained using a
reactive extrusion process in an extruder. The homogeneous reaction
blend may be in the form of a single liquid phase. A homogeneous
reaction blend may provide a uniform distribution of the components
or reactants as compared to a conventional method. In some
embodiments, a method of the present invention may provide a
chemical reaction that occurs more uniformly and/or completely due
to the formation of a homogeneous reaction blend as compared to a
conventional method. In some embodiments, the biopolymer in the
homogeneous reaction blend may be a melted thermoplastic. A
biopolymer may react thermo-mechanically and/or chemically with one
or more reagents to form a charge-modified biopolymer of the
present invention, which may be thermoplastic and/or a viscoelastic
material. In some embodiments, a method of the present invention
removes hydrogen bonding and/or crystalline domains present in a
biopolymer. This may allow for all or substantially all portions of
the biopolymer to be available for chemical reaction, such as, for
example, charge-modification and/or cross-linking.
[0090] In some embodiments, a homogeneous reaction blend may
contain a plasticized biopolymer, which may allow for greater
access to moieties throughout the biopolymer. In contrast, in a
heterogeneous phase reaction (for example, in which modified
biopolymers are synthesized by a coating process, in a diluted
suspension, or with a concentrated gel solution) there is a limited
amount of moieties (e.g., free hydroxyls) exposed to the reagent as
the surface moieties are exposed to the reagent, but not the
interior moieties are not exposed. The reaction is thus carried out
on the surface of the solid granule as shown in FIG. 1A, such as,
for example, by direct conversion of either the semi-crystalline
granules in aqueous suspension or as a dry process. FIG. 1B shows
an exemplary schematic of a homogeneous phase reaction in which a
biopolymer in the presence of a plasticizer is a plasticized to
obtain thermoplastic behavior. Under the action of
thermo-mechanical energy, the starch granule will melt. The
plasticizer may be adsorbed to the starch by heating the mixture
and destruction of the granule structure of the biopolymer may
occur with the introduction of mechanical and heat energy. In the
presence of a plasticizer, biopolymer granules may be transferred
to a continuous phase and moieties (e.g., hydroxyl free groups) may
be available to react with the reagent. In some embodiments, a
homogeneous reaction blend may aid in distributing a modification
(e.g. a charge-modification) along a biopolymer chain and/or more
uniformly throughout a biopolymer in contrast to a conventional
method, such as, for example, one in which the modification is only
achieved at the surface (e.g. at the surface of a solid biopolymer
granule).
[0091] In some embodiments, a method of the present invention may
provide a modified biopolymer (e.g., a charge-modified biopolymer
and/or a cross-linked, charge-modified biopolymer) that lacks a
granular structure and/or morphology. In some embodiments, a method
of the present invention may destroy or remove the crystalline
structure and/or domains of a biopolymer and/or modified
biopolymer.
[0092] In certain embodiments, a method of the present invention
may provide a reaction with faster kinetics than the kinetics of
the same reaction in a conventional method. The speed of at least
one reaction in a method of the present invention may be increased
compared to the speed of the same reaction in a conventional
method. In some embodiments, a method of the present invention
provides an overall greater speed of reaction to produce a modified
biopolymer of the present invention compared to a conventional
method. In some embodiments, a plasticizer may be present in the
homogeneous reaction blend with a biopolymer and a charge-modifying
agent. In some embodiments, a plasticizer may be combined with the
biopolymer and the at least one charge-modifying agent to form a
homogenous reaction blend. A plasticizer may be present in a
homogeneous reaction blend in an amount of about 10% to about 400%
or more by weight of a biopolymer present in the homogeneous
reaction blend. In some embodiments, a plasticizer may be present
in a homogeneous reaction blend in an amount of about 10%, 20%,
30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 110%, 120%, 130%, 140%,
150%, 160%, 170%, 180%, 190%, 200%, 210%, 220%, 230%, 240%, 250%,
260%, 270%, 280%, 290%, 300%, 310%, 320%, 330%, 340%, 350%, 360%,
370%, 380%, 390%, 400%, or more by weight of a biopolymer present
in the homogeneous reaction blend. In some embodiments, a
plasticizer may be present in a homogeneous reaction blend in an
amount of at least about 30% or more by weight of a biopolymer
(e.g., starch) present in the homogeneous reaction blend. In some
embodiments, a plasticizer may be present in a homogeneous reaction
blend in an amount of at least about 100% or more by weight of a
biopolymer (e.g., chitosan, hemicellulose, pectin, and/or soy
protein) present in the homogeneous reaction blend.
[0093] In some embodiments, where a reactive plasticizer is used
(i.e., a plasticizer that serves as both a plasticizer and a
reagent), such as, for example, citric acid, the plasticizer may be
present in an amount of about 100%, 125%, 150%, 175%, 200% or more
by weight of a biopolymer (e.g., starch) present in the homogeneous
reaction blend. In some embodiments, a reactive plasticizer may be
present in an amount of about 70% to about 175% by weight of a
biopolymer (e.g., starch) present in the homogeneous reaction
blend, such as, for example, about 75% to about 100% or about 90%
to about 150%. In some embodiments, where a non-reactive
plasticizer is used (i.e., a plasticizer that only functions to
allow the material to extrude and does not serve as a reagent),
such as, for example, water and, at some pHs, glycerol, the
plasticizer may be present in amount of about 100% or less, such
as, for example, less than 75%, 50%, or 25%. In some embodiments, a
non-reactive plasticizer may be present in an amount of about 20%
to about 200% by weight of a biopolymer present in the homogeneous
reaction blend, such as, for example, about 20% to about 50%, about
75% to about 100%, or about 90% to about 150%.
[0094] The plasticizer may reduce the glass transition temperature
(T.sub.g). In some embodiments, the plasticizer may improve the
flexibility, workability, distensibility, and/or processability of
a biopolymer and may do so by lowering the glass transition
temperature (T.sub.g). In certain embodiments, a biopolymer to be
extruded by a method of the present invention may not be
thermoplastic. Thus, to extrude a biopolymer that is not
thermoplastic, the glass transition temperature (T.sub.g) must be
lowered by addition of a plasticizer.
[0095] A plasticizer may reduce the tension of deformation,
hardness, density, viscosity and/or electrostatic charge of a
biopolymer and at the same time may increase the biopolymer chain
flexibility, resistance to fracture and/or dielectric constant.
Other properties of the biopolymer may also be affected by the
inclusion of a plasticizer, such as, but not limited to, the degree
of crystallinity, optical clarity, electric conductivity, fire
behavior and/or resistance to biological degradation. In some
embodiments, a plasticizer may disrupt hydrogen bonds present in a
crystalline structure of the biopolymer and this may lead to the
breaking of the crystalline domains that prevent thermal
processing.
[0096] In some embodiments, the plasticizer may allow for the
biopolymer to melt and/or become thermoplastic to provide a single
phase. In some embodiments, a plasticizer may lower the T.sub.g by
solvating the inherent crystallinity of the biopolymer and
disrupting hydrogen bonding. This may allow for the melt
processability of biopolymers that are not traditionally melt
processable.
[0097] A plasticizer may be a low molecular weight non-volatile
compound. Additional exemplary plasticizers include, but are not
limited to, citric acid, triphenyl phosphate, camphor oil,
amylacetate, allyurea, citrate esters, phthalic acid esters,
dioctyl phthalate, fatty acid esters, benzoates, tartrates,
chlorinated hydrocarbons, esters of adipic acid, polyols (e.g.,
glycerol, ethylene glycol (EG), diethylene glycol (DEG),
triethylene glycol (TEG), tetraethylene glycol, polyethylene
glycol, propylene glycol (PG), sorbitol, mannitol, xylitol, fatty
acids, and/or vegetable oils), lecithin, waxes, amino acids,
surfactants, and/or water.
[0098] In some embodiments, citric acid is present in a homogeneous
reaction blend and it may function as both a charge-modifying agent
and a plasticizer.
[0099] A catalyst may optionally be present in a homogeneous
reaction blend. In some embodiments, a catalyst and/or a
plasticizer may be combined with a biopolymer and at least one
charge-modifying agent to form a homogenous reaction blend. A
catalyst may be present in a homogeneous reaction blend in an
amount of about 1% to about 100% or more by weight of a biopolymer
present in the homogeneous reaction blend. In some embodiments, a
catalyst may be present in a homogeneous reaction blend in an
amount of about 1%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%,
90%, 100%, or more by weight of a biopolymer present in the
homogeneous reaction blend.
[0100] A catalyst may accelerate the charge-modification and/or
cross-linking reaction. In some embodiments, a catalyst may adjust
the pH to enhance the opening of chemical bonds. Exemplary
catalysts include, but are not limited to, sodium hypophosphite,
sodium bisulfate, sodium bisulfite, and/or caustics (e.g., sodium
hydroxide, calcium hydroxide, etc.). In some embodiments, a method
of the present invention may be carried out at a pH of about 2, 3,
4, 5, 6, 7, 8, 9, 10, 11, or 12. In some embodiments, a method of
the present invention may be carried out at a pH in a range of
about 9 to about 12, about 10 to about 12, about 2 to about 7, or
about 2 to about 5.
[0101] In some embodiments, the catalyst may be an initiator. In
some embodiments, the cross-linking step may comprise reacting the
biopolymer with at least one cross-linking agent, optionally in the
presence of an initiator. The biopolymer may be a charge-modified
biopolymer. Exemplary initiators include, but are not limited to,
peroxides such as acyl peroxides (e.g., benzoyl peroxide) and
dialkyl or aralkyl peroxides (e.g., di-t-butyl peroxide, dicumyl
peroxide, cumyl butyl peroxide,
1,1-di-t-butylperoxy-3,5,5-trimethylcyclohexane,
2,5-dimethyl-2,5-di-t-butylperoxy hexane, and
bis(t-butylperoxyisopropyl)benzene); ketone peroxides (e.g.,
cyclohexanone peroxide and methylethylketone peroxide); sodium
methoxide, potassium persulfate, ceric ammonium, sodium hydroxide,
and/or azo compounds (e.g., azobisisobutyronitrile).
[0102] An initiator may be present in a homogeneous reaction blend
in an amount of about 1% to about 100% or more by weight of a
biopolymer present in the homogeneous reaction blend. In some
embodiments, an initiator may be present in a homogeneous reaction
blend in an amount of about 1%, 5%, 10%, 20%, 30%, 40%, 50%, 60%,
70%, 80%, 90%, 100%, or more by weight of a biopolymer present in
the homogeneous reaction blend.
[0103] Optional additives may be used in a method of preparing a
modified biopolymer. Exemplary optional additives include, but are
not limited to, dyes, pigments, organic fillers, inorganic fillers,
softening agents (e.g., mineral oils and synthetic oils), flame
retardants, crystallization accelerators, stabilizers (e.g., heat
and light stabilizers), tie-agents, nucleating agents, other
polymers (e.g., non-biopolymers), and/or the like.
[0104] Forming a homogenous reaction blend may comprise melt
blending at least one biopolymer and at least one charge-modifying
agent, optionally with at least one plasticizer, a catalyst (e.g.,
an initiator), and/or optional additives. In some embodiments, at
least one biopolymer, at least one charge-modifying agent, at least
one plasticizer, and optionally a catalyst may be combined to form
a homogeneous reaction blend. In some embodiments, a homogeneous
reaction blend may be formed and/or prepared using a reactive
extrusion process. The reactive extrusion process may be carried
out in an extruder.
[0105] In certain embodiments, a homogeneous reaction blend may be
formed comprising at least two different biopolymers. In some
embodiments, a homogeneous reaction blend may be formed comprising
a charge-modified biopolymer and at least one different biopolymer,
which may optionally be charge-modified. When two biopolymers are
present in a homogeneous reaction blend, a first biopolymer may be
present in the homogeneous reaction blend in an amount of about 10%
to about 200% or more by weight of a second biopolymer present in
the homogeneous reaction blend. In some embodiments, a first
biopolymer may be present in a homogeneous reaction blend in an
amount of about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%,
110%, 120%, 130%, 140%, 150%, 160%, 170%, 180%, 190%, 200%, or more
by weight of a second biopolymer present in the homogeneous
reaction blend.
[0106] In some embodiments, a first biopolymer and a second
biopolymer may be present in a homogeneous reaction blend in a
ratio in a range of 0.1:1 to 4:1 (first biopolymer:second
biopolymer), such as, for example, in a ratio in a range of 0.5:1
to 2:1 or 1:1 to 3:1. In certain embodiments, a first biopolymer
and a second biopolymer may be present in a homogeneous reaction
blend in a ratio of about 0.5:1, 1:1, or 1:0.5.
[0107] In some embodiments, the reacting and/or cross-linking
step(s) may be carried out and/or performed in a homogeneous
reaction blend. The reacting and/or cross-linking step(s) may be
carried out and/or performed using a reactive extrusion process. In
some embodiments, the reacting and/or cross-linking step(s) may be
carried out at a temperature in a range of about 80.degree. C. to
about 200.degree. C., such as, for example, at a temperature in a
range of about 80.degree. C. to about 120.degree. C., about
80.degree. C. to about 150.degree. C., about 90.degree. C. to about
120.degree. C., about 100.degree. C. to about 120.degree. C., about
100.degree. C. to about 200.degree. C., about 150.degree. C. to
about 180.degree. C., or about 110.degree. C. to about 130.degree.
C. In certain embodiments, the reacting and/or cross-linking
step(s) may be carried out at a temperature of about 90, 91, 92,
93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107,
108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120,
121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133,
134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146,
147, 148, 149, or 150.degree. C. In some embodiments, the reacting
and/or cross-linking step(s) may be carried out at a temperature of
about 140.degree. C. or less.
[0108] In some embodiments, the reacting and/or cross-linking
step(s) may be carried out at a temperature that avoids degradation
of a biopolymer and/or modified biopolymer. In some embodiments,
increasing the temperature of the reacting and/or cross-linking
steps may provide for an increased amount of charge-modification on
the biopolymer if the temperature remains below the degradation
temperature for the biopolymer. In some embodiments, the reacting
step may be carried out and/or performed at a temperature in a
range of about 100.degree. C. to about 175.degree. C., such as, for
example, about 120.degree. C. to about 140.degree. C. or about
100.degree. C. to 150.degree. C. In some embodiments, the
cross-linking steps may be carried out and/or performed at a
temperature in a range of about 120.degree. C. or more, such as,
for example, about 120.degree. C. to about 175.degree. C. or about
120.degree. C. to about 140.degree. C.
[0109] One or more process conditions for a method of the present
invention may be modified to provide a particular modified
biopolymer, such as, for example, a super absorbent, ion exchange
resin, etc., and/or a particular property of a modified biopolymer,
such as, for example, the degree of charge modification,
cross-linking, etc. Example processing conditions for a method of
the present invention include, but are not limited to, the type of
extruder (e.g., single screw vs. twin screw); screw diameter (D);
screw length (L) (L/D may be used to describe an extruder
configuration); screw configuration (i.e., specific types of shear
inducing sections within an extruder which may range from gentle
conveying elements to more shear intensive elements that may be
designed to enhance uniform mixing within the extruder and/or
accelerate a chemical reaction); temperature (overall and profile
along various extruder zones); screw RPM; number of separate
extruder zones where both temperature can be changed independent of
other zones and different ingredients of the formulation can be
added; and feed rate of different formulation elements into
different zones. In some embodiments, the combination of one or
more independently controlled process variables may influence
dependent variables of residence time, mechanical energy input
(SME) and/or shear. Changes in screw RPM may induce changes in
shear, heating and/or residence time in the extruder.
[0110] In some embodiments, the reacting and/or cross-linking
step(s) may be carried out in an extruder. The reacting and/or
cross-linking step(s) may carried out in an extruder with a
residence time in a range of about 0.1 minutes to about 30 minutes,
such as, for example, in a range of about 0.1 minutes to about 10
minutes, about 0.5 minutes to about 5 minutes, about 1 minute to
about 10 minutes, about 1 minute to about 5 minutes, or about 1
minute to about 3 minutes. In certain embodiments, the reacting
and/or cross-linking step(s) may be carried out in an extruder with
a residence time of about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8,
0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,
19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30 minutes. In some
embodiments, the reacting and/or cross-linking step(s) may be
carried out in an extruder with a residence time of about 5
minutes. In some embodiments, increasing the residence time of the
reacting and/or cross-linking steps may provide for an increased
amount of charge-modification on the biopolymer.
[0111] The reacting and/or cross-linking step(s) may carried out in
an extruder having a screw RPM in a range of about 10 to about 500
rpm, such as, but not limited to, about 10 to about 200, about 50
to about 200, about 100 to about 200, about 125 to 250, about 100
to about 500, or about 90 to about 130. In certain embodiments, the
reacting and/or cross-linking step(s) may be carried out in an
extruder having a screw RPM in a range of about 40, 50, 60, 70, 80,
90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210,
220, 230, 240, 250, 260, 270, 280, 290, 300, 310, 320, 330, 340,
350, 360, 370, 380, 390, 400, 410, 420, 430, 440, 450, 460, 470,
480, 490, or 500 rpm. In some embodiments, the reacting and/or
cross-linking step(s) may be carried out in an extruder having a
screw RPM of about 120 rpm.
[0112] In some embodiments, the reacting and/or cross-linking
step(s) may be carried out in an extruder with a Specific
Mechanical Energy (SME) value of at least about 20 kJ/kg. In
certain embodiments, the reacting and/or cross-linking step(s) may
be carried out in an extruder with a SME value in a range of about
20 kJ/kg to about 500 kJ/kg or about 25 kJ/kg to about 250 kJ/kg.
The SME value may be measured using methods known to those of skill
in the art.
[0113] The step of reacting a biopolymer with a charge-modifying
agent and the step of cross-linking the biopolymer may occur
simultaneously. Alternatively or in addition, in some embodiments,
the step of reacting the biopolymer with the charge-modifying agent
and the step of cross-linking the biopolymer may be done
sequentially. Thus, in some embodiments, the step of reacting the
biopolymer with the charge-modifying agent may be carried out first
to form a charge-modified biopolymer and then cross-linking step
may be carried out with the charge-modified biopolymer.
[0114] Exemplary devices for carrying out a method of the present
invention include, but are not limited to, co-rotational and
counter rotational twin screws, thermal kinetic compounders, high
shear mixers, paddle mixers, static mixers blenders, open-type
mixing roll, closed Banbury mixer, kneader, single-screw extruder,
vented screw extruder, and/or twin-screw extruder (e.g., a parallel
or conical twin-screw extruder). In some embodiments, an extruder
is used to carry out a method of the present invention. Exemplary
screw configurations include those illustrated in FIG. 6. A low
shear screw configuration may include a low number or no shear
inducing elements or zones along the screw profile where shear
inducing elements or zones may include mixing, kneading, and/or
reversing elements or zones which increase the torque or load on
the extrusion motor for a given mass flow rate. A medium and/or
high shear screw configuration may include an increased number of
shear inducing elements or zones compared to a low shear screw
configuration.
[0115] In some embodiments, the components or reactants for one or
more steps in a method of the present invention may be dry mixed
together prior addition to an extruder. Alternately or in addition,
two or more feeders (e.g., loss-in-weight feeders) may be used that
supply the components or reactants to be blended to an extruder. In
certain embodiments, multiple extruders may be used to feed melts
of the blend components, such as in co-extrusion. In some
embodiments, one or more components or reactants may be added to an
extruder in powder form. The components and/or mixture blends may
be sized by conventional means such as pelletization, granulation,
and/or grinding.
[0116] A method of the present invention may be performed and/or
carried out as a single-stage direct extrusion process or a
multi-stage extrusion process. In some embodiments, the method
comprises in-line compounding. In some embodiments, the method is
carried out in an extruder comprising at least two reaction zones
and the at least two reaction zones are used for one or more steps
in the method for preparing a modified biopolymer of the present
invention (e.g., a cross-linked, charge-modified biopolymer). For
example, a method of the present invention may comprise reacting a
biopolymer and at least one charge-modifying agent at a first
reaction zone to form a charge-modified biopolymer and
cross-linking the charge-modified biopolymer at a second reaction
zone to form a cross-linked, charge-modified biopolymer.
[0117] In some embodiments, one or more reagents may be in powder
form when added to an extruder and may not be in the form of a
liquid or paste. In some embodiments, the one or more reagents in
powder form may have a moisture content of about 20% by weight or
less. Some embodiments include adding a biopolymer and/or
charged-biopolymer to an extruder in powder form and/or adding one
or more additional reagents (e.g., a charge-modifier, plasticizer,
cross-linker, etc.) to the extruder in powder form. The one or more
additional reagents may be added in the same or a different
reaction zone than the biopolymer and/or charged-biopolymer.
[0118] In some embodiments, an extruder is used as one complete
reaction vessel, which may allow for the reaction to occur along
the entire length of the extruder. When two or more reaction zones
are provided, the one or more process conditions (e.g.,
temperature, shear, etc.) in one or more reaction zones may be
independently provided and/or changed. Some embodiments may include
providing a different temperature and/or screw element in at least
one reaction zone compared to another reaction zone. For example,
in some embodiments, a mixture of a biopolymer (e.g., starch),
plasticizer, charge-modifying agent, and catalyst may be introduced
into a feed zone in an extruder and in the extruder the mixture may
form a homogenous reaction blend. The reaction taking place in the
extruder may be modified (e.g., accelerated and/or slowed) by
varying the temperature in one or more reaction zones in the
extruder. In some embodiments, the reaction may be accelerated by
increasing the temperature in one or more reaction zones in the
extruder. Some embodiments may include introducing shear in one
more reaction zones, such as, e.g., zone 3 and/or zone 5 of an
extruder, by having intense mixing elements in the screw to
facilitate mixing and/or shear induced reaction. In some
embodiments, the length of different reaction zones and/or the
length of the extruder itself (e.g., by moving the injection zone
closer to the end of the extruder) may be varied or adjusted, such
variations or adjustments may modify the degree of reaction. The
length of the extruder is generally defined as the length over
diameter ratio or L/D.
[0119] In some embodiments, an extruder may be used as a sequential
reactor. For example, in some embodiments, a mixture of a
biopolymer (e.g., starch), plasticizer, and charge-modifying agent
may be introduced into a feed zone of an extruder. The mixture may
be heated as it is transported through one or more reaction zones
(e.g., one or more initial reaction zones, such as, e.g., zones 1
and 2) using conveying elements on the screw, and the
charge-modifying agent may react with the biopolymer to form a
charge-modified biopolymer. Then, a cross-linking agent may be
added in either solid or liquid form into one or more reaction
zones (e.g., zone 3) to form the cross-linked, charge-modified
biopolymer. In some embodiments, following the reaction zone(s) in
which the charge-modifying agent was added, an intense mixing screw
element may be placed on the screw in one or more reaction zones
(e.g., in zone 4 and/or 5) to mix the cross-linking agent with the
charge-modified biopolymer. The cross-linking reaction may be
facilitated by different temperatures and/or different screw
elements in one or more reaction zones (e.g., zone 4 and/or 5). In
some embodiments, a foaming agent (e.g., water) may be injected
into an extruder (e.g., in a reaction zone near the end of the
extruder, such as, e.g., at zone 6), which may cause the
cross-linked, charge-modified biopolymer to expand as it exits the
die. Some embodiments include that the biopolymer introduced into a
feed zone of an extruder is in powder form.
[0120] In some embodiments, a method of the present invention may
comprise foaming a modified biopolymer of the present invention
(e.g., a cross-linked, charge-modified biopolymer). Foaming may be
done to induce porosity and/or void size of the modified
biopolymer, such as by opening and/or increasing cell porosity.
Foaming may aid in increasing fluid, charged species, and/or metal
sequestration, binding, absorption, chelation, uptake and/or the
like. In some embodiments, the modified biopolymer may have open,
connected pores, which may facilitate mass transfer within the
modified biopolymer and access of ions in a fluid to the ionic
binding sites of the modified biopolymer. Foaming the modified
biopolymer may modify (e.g., increase or decrease) the viscoelastic
properties of the modified biopolymer. In some embodiments, the
amount or degree of the modification may vary with the amount of a
fluid (e.g., water, carbon dioxide, nitrogen, etc.) absorbed in the
modified biopolymer at the time of foaming.
[0121] A foaming agent may be a chemical agent or physical agent.
Exemplary foaming agents, include, but not are limited to,
supercritical nitrogen (N.sub.2) calcium carbonate (CaCO.sub.3),
water (e.g., steam), and/or supercritical carbon dioxide
(CO.sub.2).
[0122] In some embodiments, a method of the present invention may
comprise treating a modified biopolymer of the present invention
(i.e., a post-treatment), such as, for example, thermally treating
a charge-modified biopolymer and/or cross-linked, charge-modified
biopolymer post extrusion. A post-treatment of the prevent
invention may increase the degree of cross-linking present in a
modified biopolymer of the present invention and/or may increase
and/or improve charge density and/or charge modification of a
modified biopolymer. In some embodiments, a post-treatment of the
present invention may decrease the soluble gel fraction in a
modified biopolymer. The modified biopolymer in solid form may be
undergo a post-treatment. In some embodiments, a post-treatment of
the present invention may fine tune and/or modify the properties of
a modified biopolymer of the present invention.
[0123] A post-treatment may comprise heating the modified
biopolymer. In some embodiments, a method of the present invention
may comprise heating the modified biopolymer at a temperature in a
range of about 80.degree. C. to about 180.degree. C., such as, for
example, about 100.degree. C. to about 150.degree. C. or about
120.degree. C. to about 140.degree. C., for a period of time in a
range of about 0.5 minutes to about 24 hours, such as, for example,
about 5 minutes to about 180 minutes, or about 30 minutes to about
90 minutes. In some embodiments, a post-treatment may comprise
heating the modified biopolymer at a temperature of about
110.degree. C. to about 130.degree. C. for a period of time in a
range of about 60 minutes to about 120 minutes. In some
embodiments, a post-treatment may comprise heating the modified
biopolymer at a temperature of about 130.degree. C. to about
150.degree. C. for a period of time in a range of about 10 minutes
to about 50 minutes.
[0124] In some embodiments, a method of the present invention may
comprise removing unreacted reagents, soluble and/or low molecular
weight species, and/or degradation products from a modified
biopolymer of the present invention, such as, for example, by
rinsing, dialyzing, and/or the like the modified biopolymer. Some
embodiments include removing unreacted reagants from the modified
biopolymer after a post-treatment. Some embodiments of the present
invention may include drying the modified biopolymer (e.g., drying
at a temperature of about 40.degree. C.). In some embodiments, a
method of the present invention may comprise sizing the modified
biopolymer by conventional means, such as, for example,
pelletization, granulation, milling, and/or grinding.
[0125] According to some embodiments of the present invention, a
method of the present invention may comprise forming a homogeneous
reaction blend comprising a starch, at least one charge-modifying
agent, optionally at least one plasticizer, and optionally a
catalyst, and reacting the starch and the at least one
charge-modifying agent to form a charged-modified starch. In some
embodiments, the at least one charge-modifying agent may be an acid
such as, for example, citric acid, the optional at least one
plasticizer may be water and/or glycerol, and/or the optional
catalyst may be sodium hypophosphite. The reacting step may
comprises reacting starch and the charge-modifying agent (e.g.,
citric acid) in a ratio in a range of 0.1:1 to 4:1
(charge-modifying agent:starch), such as, for example, in a ratio
in a range of 0.5:1 to 2:1 or 1:1 to 3:1.
[0126] The charge-modified starch may be cross-linked with another
biopolymer, such as, for example chitosan to form a cross-linked,
charge-modified starch-chitosan. In some embodiments, the chitosan
is charged modified, such as, but not limited, protonated. In
certain embodiments, the method may comprise combining
charged-modified starch with chitosan, at least one plasticizer,
and optionally a charge-modifying agent, and cross-linking the
charged-modified starch and chitosan. In some embodiments, a
charge-modifying agent may be an acid (e.g., acetic acid, such as
glacial or concentrated acetic acid) and may react with the
chitosan to form charge-modified chitosan that may be cross-linked
with the charge-modified starch. In some embodiments,
charge-modified chitosan may be prepared by reacting chitosan and
acetic acid in an amount of about 1% to about 40%, such as, for
example, about 2.5% to about 13% or about 20% to about 40% by
weight of the chitosan, wherein acetic acid is added directly to
the chitosan without the presence of water.
[0127] A method of preparing a cross-linked, charge-modified
starch-chitosan may comprise providing in an extruder starch in an
amount in a range of about 5 wt % to about 50 wt % and chitosan in
an amount in a range of about 5 wt % to about 50 wt % to form a
homogeneous reaction blend. In some embodiments, the chitosan may
be charge-modified chitosan. The homogeneous reaction blend may
further comprise a charge-modifying agent (e.g., citric acid) in an
amount in a range of about 5 wt % to about 40 wt %, a catalyst in
an amount in a range of about 0.1 wt % to about 5 wt %, and a
plasticizer in an amount in a range of about 20 wt % to about 40 wt
%.
[0128] According to some embodiments, a method of the present
invention may comprise combining starch, chitosan, at least one
charge-modifying agent, a catalyst, and a plasticizer to form a
homogenous reaction blend; charge-modifying the starch and chitosan
to form a charge-modified starch and a charge-modified chitosan;
and cross-linking the charge-modified starch and charge-modified
chitosan to form a cross-linked, charge-modified starch-chitosan.
In some embodiments, the combining step may be carried out by
providing, adding, feeding, injecting and/or the like all
components into the extruder at substantially the same time. This
may allow for the charge-modifying and cross-linking reactions to
occur simultaneously.
[0129] In some embodiments, a method of the present invention may
comprise combining starch, a first charge-modifying agent, and a
catalyst to form a homogeneous reaction blend comprising a
charge-modified starch; adding chitosan, a plasticizer, and
optionally a second charge-modifying agent to the homogeneous
composition comprising the charge-modified starch; and
cross-linking the charge-modified starch and chitosan to form a
cross-linked, charge-modified starch-chitosan. The chitosan, in
some embodiments, may be charged-modified and/or added to an
extruder in the presence of a charge-modifying agent, such as, for
example, glacial acetic acid. In some embodiments, the method may
use multiple inlets of an extruder. For example, starch, the first
charge-modifying agent, and the catalyst may be added at a first
inlet and/or reaction zone in an extruder, and chitosan, the
plasticizer, and optionally the second charge-modifying agent may
be added at a second inlet and/or reaction zone in an extruder.
This may allow for the charge-modifying and cross-linking reactions
to occur simultaneously and/or sequentially.
[0130] In certain embodiments, a method of the present invention
may comprise combining starch, a first charge-modifying agent, and
a catalyst to form a charge-modified starch; forming a homogeneous
reaction blend comprising the charged-modified starch, chitosan, a
plasticizer, and optionally a second charge-modifying agent; and
cross-linking the charge-modified starch and chitosan to form a
cross-linked, charge-modified starch-chitosan. This may allow for
the charge-modifying and cross-linking reactions to occur
sequentially. The chitosan, in some embodiments, may be
charged-modified and/or added to an extruder in the presence of a
charge-modifying agent, such as, for example, glacial acetic
acid.
[0131] In some embodiments, the charge-modified starch is prepared
and/or formed by forming a homogeneous reaction blend in an
extruder. The charge-modified starch may be extruded and the
extrudate may optionally be ground into a powder and/or pelletized.
The extrudate may then be combined with chitosan, a plasticizer,
and optionally a second charge-modifying agent to form a
homogeneous reaction blend.
[0132] A method of the present invention may provide a formed
modified biopolymer (e.g., a cross-linked, charge-modified
biopolymer). In some embodiments, the method may comprise grinding,
milling, pelletizing, drawing, compressing, shaping, and/or the
like to provide a formed modified biopolymer of the present
invention. The formed product may be of any shape and/or size. In
some embodiments, a method of the present invention provides a
plurality of formed products of substantially uniform size and/or
shape (e.g., varying in size and/or shape by less than about 20%).
In some embodiments, a method of the present invention provides a
variety of particle sizes and/or shapes. In some embodiments, a
method of the present invention may provide a modified biopolymer
(e.g., a cross-linked, charge-modified biopolymer) that is in the
form of a bead, column, sheet, powder, particle (e.g.,
nanoparticles, microparticles, etc.), ribbon, fiber, film, pellet,
and/or the like. In some embodiments, a method of the present
invention may provide a modified biopolymer in the form of a
particle having a diameter in a range of about 1 micron to 2,000
microns, such as, but not limited to, in a range of about 10
microns to about 1000 microns, about 100 microns to about 1000
microns or about 300 to about 800 microns. In some embodiments, a
modified biopolymer of the present invention (e.g., a cross-linked,
charge-modified biopolymer) having a particle size in a range of
about 300 to about 800 microns or less than about 500 microns may
be suitable for use as an absorbent. In some embodiments, a
modified biopolymer of the present invention (e.g., a cross-linked,
charge-modified biopolymer) having a particle size in a range of
about 10 to about 150 microns or less than about 100 microns may be
suitable for use as an ion exchange material.
[0133] In some embodiments, a modified biopolymer of the present
invention (e.g., a cross-linked, charge-modified biopolymer) may be
used as and/or to prepare a consumer product, such as, but not
limited to, a diaper, hygiene product, and/or wound dressing. In
some embodiments, a modified biopolymer of the present invention
(e.g., a cross-linked, charge-modified biopolymer) may be used as
and/or to prepare an ion exchange resin and/or absorbent. Thus, in
some embodiments, a modified biopolymer of the present invention
may be an ion exchange resin, ion removal resin, metal chelating
and/or adsorbing resin, and/or an absorbent including high
performing absorbents, such as, for example, super absorbents. In
some embodiments, a modified biopolymer of the present invention
(e.g., a cross-linked, charge-modified biopolymer) may remove
contaminants from a fluid and/or absorb a fluid.
[0134] Further exemplary industries and/or uses for a modified
biopolymer of the present invention include, but are not limited
to, water treatment such as, for example, single-use ion exchange
for water deionization (e.g., for laboratories and/or electronics),
potable water desalination, potable water contaminant and heavy
metals adsorbents, and an alternative to activated carbon for
dechlorination; hygienic super absorbent applications (SAP) such
as, for example, baby diaper absorbents, adult incontinence
absorbents, feminine hygiene absorbents; non-hygenic SAP
applications such as, for example, sub-sea cable wraps, re-usable
gel/ice packs, liquid waste solidification, pet pads, meat pads,
concrete additives, remove water from oil and/or hydrocarbons,
liquid/solid separation, waste lagoon remediation, paint
solidification, agricultural and horticultural soil amendments,
mortuary absorbents, whole blood or blood mixture absorbents,
medical waste solidification and spill control, drug delivery
systems, and wound dressings; energy such as, for example,
hydraulic fracturing flowback water treatment or reuse, guar
alternative hydraulic fracturing viscosifying agent, hydraulic
fracturing friction reducer additive, lost circulation drilling
fluid additive, oil refinery water treatment, cooling tower water
softening, boiler feed water deionization, coal ash and flu vent
remediation, and nuclear isotope removal; mining such as, for
example, metals mining water treatment, metal removal from mining
solutions, and coal mining water treatment; environmental such as,
for example, pump and treat water remediation, in situ reactive
barrier remediation, and sludge absorption and dewatering;
packaging such as, for example, biobased packaging films and
biobased structural packaging; paper such as, for example, pulp and
paper strength additives and/or coatings for paper; textiles such
as, for example, textile adhesives, starch ester alternative for
textile manufacture, and textile non-woven thickening agents;
and/or construction such as, for example, construction adhesive in
wallboard. In some embodiments, a modified biopolymer of the
present invention may be useful in the paper industry, cosmetics,
tissue engineering, hydrogels, drug delivery applications,
photonics applications, and/or as a flocculant and/or
coagulant.
[0135] The present invention is explained in greater detail in the
following non-limiting Examples.
EXAMPLES
Example 1.1--Extruded Charge Modified Biopolymer (Example of Citric
Acid Grafted on to Starch at .about.2mm Scale)
[0136] A twin screw conical extruder manufactured by DSM, a
parallel twin screw extruder manufactured by Leistritz, and a
parallel twin screw extruder manufactured by Wegner were used to
prepare charge-modified starch. The extruder properties are
provided in Table 1. Various extruders listed here allow for
demonstration of scalability from lab scale to production-relevant
scale. Furthermore, multiple extruders allow for transposition of
process parameters across a range of extruder configurations and
size.
[0137] Additionally, the parallel twin screw extruders manufactured
by Lestritz and Wegner supported multiple reactions zones, allowing
for increased capabilities, including: temperature, screw, and
injection profiles. Examples of temperature and injection profiles
may be found in Examples 1.2, 5.1, and 7, below.
TABLE-US-00001 TABLE 1 Extruder properties for a range of extruder
configurations and sizes Extruder Manufacturer DSM Thermo Fisher
Leistritz Wegner Extruder Model Xplore Process 11 N/A TX-52
Residence Time 0.25-10 mins 0.25-5 mins ~3 mins ~3 mins Screw Size
(Screw Diameter) 3 cm 11 mm 18 mm 52 mm L/D 5 40 40 27 Die Size 1-2
mm 0.5-11 mm 1 mm & 4.5 mm 2-4 mm Rotation Corotating
Co-rotating Corotating Corotating Screws Screws Screws Screws
Throughput 0.05-0.2 Kg/hr 0.1-5 Kg/hr 0.5-8 Kg/hr 3-30 Kg/hr Type
of heating Electric Electric Electric Electric Number of heating
zones 1 8 8 1 Type of Die Single Single single holes 1 or 2 holes
hole/circular hole/circular Additive zones One 8 3 feed ports 2
feed ports, 1 extra for foaming agent Type of cooling Water Water
Air Water
[0138] In preparing the charge-modified starch, the following
parameters were varied: temperature, screw RPM, and amount of
citric acid using each extruder. Table 2 sets forth the ranges for
the temperature, screw RPM, and amount of citric acid tested using
each extruder.
TABLE-US-00002 TABLE 2 Parameter ranges for charge-modified starch
for each extruder. Range Range Range Parameter (DSM) (Leistritz)
(Wegner) Temperature Ranges (.degree. C.) 90-150 100-120 100-125
RPM Ranges (RPM) 60-200 120-200 120-200 Citric Acid Ranges (rel
50-100 50-100 50-100 % to starch)
[0139] Starch (Native Corn Starch, Item 18321, Batory Foods, Des
Plaines Ill.), citric acid (Item 756707, Univar, Downers Grove,
Ill.) as a charge modifier and plasticizer, and sodium
hypophosphate (SHP) (Item S1320, Spectrum Chemical, New Brunswick,
N.J.) as a catalyst were combined and hand mixed in powder form.
Powder mixtures were loaded into custom powder injectors and input
into the extruder feed port. Various amounts of citric acid were
added to the mixture as provided in Table 2. The resulting mixture
was added to the extruder as a powder at varying extrusion
conditions as provided in Table 2. The powder mixture was
melt-blended in the extruder to form a homogeneous blend reaction
in which the citric acid was grafted onto the starch to form a
charge-modified starch, termed starch citrate. In some runs, this
charge-modified starch was utilized as a precursor polymer to
subsequently cross-link to another biopolymer as described in
Example 5. Select samples underwent a thermal post treatment
following extrusion by way of vacuum oven at 120.degree. C. for 90
mins.
[0140] Table 3 provides specific parameters tested on the DSM
extruder with responses described in Table 4 and described below.
Each sample was titrated to determine its charge density, and
analyzed via FTIR (at wavelengths of 1720 cm.sup.-1) to determine
each sample's relative carboxyl content via methods described
below. Additionally, parameters such as DI uptake, and %
extractables were measured as qualitative gauges of material
performance.
TABLE-US-00003 TABLE 3 Process parameters for preparing
charged-modified starch on a DSM extruder Sample # Sample 1.1A
Sample 1.1B Sample 1.1C Sample 1.1D Sample 1.1E Temperature
(.degree. C.) 140 140 100 140 125 RPM 120 120 120 120 120 Post
Treatment Yes No Yes Yes Yes Citric Acid (wt % 150 150 50 50 75
relative to Starch) SHP (wt % relative 20 20 20 20 20 to Citric
Acid)
[0141] Fourier Transform Infrared Spectroscopy (FTIR) is a measure
of a samples' absorbance/transmittance of wavelengths in the IR
spectrum. The intensity of absorbed IR radiation at a given
wavelength can be correlated to particular covalent bonds. When
data is normalized to the primary alcohol peak (.about.1000
cm.sup.-1), relative peak intensities may be used to estimate the
amount characteristic groups on the polymer, where decreasing
transmittance or, inversely, increasing absorbance indicates an
increased degree of reagent grafting. Bonds of interest for
biopolymers modified with citric acid, such as, for example, starch
citrate, include the carboxyl (R--CO2H) bond at .about.1713
cm.sup.-1,where decreasing transmittance or, inversely, increasing
absorbance indicates an increased degree of charge density.
[0142] Back titration is a measure of charge density in anionic,
charge-modified biopolymer samples. The results of this measurement
technique scales with the FTIR data. As described here in Example
1.1, along with Examples 1.2, 1.3, 2.1. 3.1, 3.2, and 3.3, 0.2-0.3
g of sample was exposed to 50 ml of 0.05 M NaOH solution for 1 hr.
One drop of phenolphthalein (Item 3241N80, Thomas Scientific,
Swedesboro, N.J.) was added and mixed into solution to act as a
visual indication, approximating neutrality of the solution. A pH
probe was used to monitor acid/alkaline nature of the solution
during mixing and titration. The solution was then titrated with
0.05M HCl at, .about.0.05 ml/second. The volume of HCl required to
reach pH neutrality was recorded and assumed to be equivalent to
the number of mols needed to neutralize excess NaOH in solution.
The difference between the recorded mols and initial mols was then
normalized to the original sample weight to yield a mol/g or mol/g
charge density unit.
[0143] DI uptake is a measure of a sample's degree of swelling
(i.e., its absorbency by weight under given conditions). DI uptake
was measured by inserting .about.0.25 g sample/cm in 33 mm
diameter, of 12-14 kD dialysis tubing (Item 684219, Carolina
Biological, Burlington, N.C.). The ends of tubing were sealed and
labeled, then exposed to 20 ml DI water per gram of sample for 72
hours. DI water was replaced every 2-3 hours over the course of a
72 hr period. Samples were then removed from the dialysis tubing
and weighed. Changes in weight between the initial and final (wet)
measurements were normalized to initial mass to grams of DI water
absorbed per gram of sample (g/g).
[0144] Samples were then dried using a forced air oven and/or
freeze dryer. Weight loss between dried sample and initial sample
weight (pre dialysis) was used to calculate extractables as a % of
initial sample (inverse of yield). These extractables reflect a
measure of the amount of sample that elutes upon initial contact
with water. This parameter qualitatively measures the mass fraction
of unreacted moieties, plasticizer, and/or degraded polymeric
products in a given sample.
TABLE-US-00004 TABLE 4 Properties of the charged-modified starch.
FTIR Titration DI Uptake Extractables Sample # (% Trans.) (meq/g)
(g/g) (%) 1.1A 36 5.9 3.4 89 1.1B 96 1.9 2.8 87 1.1C 59 2.8 2.7 37
1.1D 48 4.2 3.1 30 1.1E 49 3.8 5.4 49
[0145] As can be seen from Tables 3 and 4, charge-modified starch
was produced in the process example of reactive extrusion described
here. % Transmittance as measured via FTIR is shown to decrease
significantly below that of starch (94.5%) while titration values
are shown to increase significantly over that of starch (0
meq/g).
[0146] Temperature and citric acid (charge modifying agent)
concentration are the parameters where increasing inputs show
increased charge density. Furthermore, inclusion of a thermal post
treatment after extrusion was also studied and addition of a post
treatment also shows increasing charge density. Relative similarity
and relatively low values of DI uptake parameters across indicate a
lack of crosslinking. Extractable values are indicative of excess
reagent and generally trend with charge modifier concentration.
FTIR transmittance values achieved ranged from approximately 35-98%
while charge density values achieved ranged from approximately 1 to
6.5 meq/g.
Example 1.2--Extruded Charge Modified Biopolymer (Example of Citric
Acid Grafted on to Starch at 18 mm Scale)
[0147] A parallel twin screw extruder with multiple injection and
reaction zones manufactured by Leistritz was also used to prepare
charge-modified starch citrate. These experiments were performed to
determine scalability and behavior of materials through varied
reaction zones. The extruder properties are provided in Table 1
above. FIG. 2 illustrates the 8-zone extruder with injection ports
in this configuration located prior to zone 1 and at zone 3.
[0148] Raw materials were prepared in a similar manner to extrusion
as described above in Example 1.1. However, samples were mixed in 1
kg units and fed using gravimetric powder feeders manufactured by
Brabender (Duisburg, Germany) to account for scale. Studies below
utilized multiple injection and reaction zones to simulate
full-scale extrusion processes. Screw profile utilized is described
in FIG. 6 (medium shear screw). Powder samples of each of the
following components: starch, citric acid, and SHP were fed into
the primary injection zone (prior to zone 1) where the mixture was
allowed to react at 120.degree. C. Without wishing to be bound to
any particular theory, at this temperature the citric acid
dehydrates to yield an anhydride that reacts faster with the free
hydroxyl groups. Temperature profiles for each zone are detailed in
Table 5 below. Extrusion and composition parameters for starch
citrate were varied as described in Table 6 below. In some runs,
extruded samples in solid form were post-treated by placing the
charge-modified starch in an oven at 120.degree. C. for 90 minutes.
Specific examples of process parameters and resulting responses are
shown in Tables 7 & 8 below, respectively.
TABLE-US-00005 TABLE 5 Temperature and injection parameters for
charge-modified starch via parallel twin- screw extruder. Zone 1 2
3 4 5 6 7 8 Temperature (.degree. C.) 100 105 115 120 120 120 120
115 Injection Starch + N/A N/A N/A N/A N/A N/A N/A N/A Reagents
TABLE-US-00006 TABLE 6 Parameter ranges for charge-modified starch
via 18 mm, parallel twin-screw extruder. Temperature Ranges
(.degree. C.) 100-120 (see Table 5) RPM Ranges (RPM) 120-200 Citric
Acid Ranges (rel % to starch) 50-100
TABLE-US-00007 TABLE 7 Process parameters for preparing
charged-modified starch via 18 mm, parallel twin-screw extruder.
Sample # Sample 1.2A Sample 1.2B Sample 1.2C Sample 1.2D
Temperature (.degree. C.) 100-120 100-120 100-120 100-120 (multiple
zones) (multiple zones) (multiple zones) (multiple zones) RPM 100
160 100 170 Post Treatment Yes Yes Yes Yes Citric Acid (wt %
relative to Starch) 100 50 75 75 SHP (wt % relative to starch) 20
20 20 20
TABLE-US-00008 TABLE 8 Properties of the charged-modified starch.
FTIR Titration DI Uptake Extractables Sample # (% Trans.) (meq/g)
(g/g) (%) 1.2A 35 6.55 1.7 32 1.2B 53 2.10 1.1 10.5 1.2C 54 2.0 1.8
45 1.2D 43 5.8 1.3 10
[0149] As can be seen from Tables 7 and 8, this work demonstrated
the feasibility of producing charge-modified starch via a reactive
extrusion process. % Transmittance as measured via FTIR is shown to
decrease significantly below that of starch (94.5%) while titration
values are shown to increase significantly over that of starch (0
meq/g). Furthermore, it should be noted that titration and FTIR
values have a positive correlation. While not wishing to be bound
to any particular theory, it appears that increased RPM in this
method can improve the degree of charge modification as a response
to increased shear.
Example 1.3--Extruded Charge Modified Biopolymer (Example of Citric
Acid Grafted on to Starch at 52 mm Scale)
[0150] A parallel twin screw extruder manufactured by Wegner was
used to prepare charged-modified starch and to further demonstrate
scaling. The extruder properties are provided in Table 1.1 above.
Screw profile utilized largely conforms to a purely conveying screw
as described in FIG. 6 (low shear screw).
[0151] Raw materials for charge-modified starch were prepared in a
similar manner to the extrusion processes described above. However,
samples were mixed and injected in .about.2 kg units to account for
the larger scale and continuous nature of this extruder. Extrusion
and composition parameters for starch citrate were varied as
described in Table 9 below. Specific examples of process parameters
and resulting responses are shown respectively in Tables 10 and 11
below, respectively. In some runs, extruded samples in solid form
were post-treated by placing the charge-modified starch in an oven
at 120.degree. C. for 90 minutes.
TABLE-US-00009 TABLE 9 Parameter ranges for charge-modified starch
via 52 mm, parallel twin-screw extruder. Temperature Ranges
(.degree. C.) 100-125 RPM Ranges (RPM) 120-200 Citric Acid Ranges
(wt % relative 50-100 to starch)
TABLE-US-00010 TABLE 10 Process parameters for preparing
charged-modified starch via 52 mm, parallel twin screw extruder.
Sample # Sample 1.3A Sample 1.3B Temperature (.degree. C.) 110 120
RPM 120 100 Post Treatment Yes Yes Citric Acid (wt % relative to 66
66 Starch) SHP (wt % relative to Citric Acid) 20 20
TABLE-US-00011 TABLE 11 Properties of the charged-modified starch.
FTIR Titration DI Uptake Extractables Sample# (% Trans.) (meq/g)
(g/g) (%) 1.3A 65 2.9 N/A 64 1.3B 69 2.4 N/A 68
[0152] This work demonstrated the feasibility of producing
charge-modified starch via a reactive extrusion process. %
Transmittance as measured via FTIR is shown to decrease
significantly below that of starch (94.5%) while titration values
are shown to increase significantly over that of starch (0 meq/g).
Examples 1.1E, 1.2C and 1.3 are used to compare samples at similar
processing conditions. It is concluded from the similar responses
that parameters listed in these examples are transposable across a
significant range of extruder sizes (representing from laboratory
benchtop to commonly-used industrial sizes).
Example 2.1--Extruded Charge Modified Biopolymer (Examples of
Additional Anionic Charge Modifiers Grafted on to Starch)
[0153] In addition to citric acid, additional anionic charge
modifiers are demonstrated in the example below. Starch was charged
modified using maleic anhydride (Item 63200-500G-F, Sigma-Aldrich,
Mo., St. Louis) a catalyst (NaOH, Reagent ACS, Item 630, GFS
Chemicals, Powell Ohio), and plasticizer to form an anionic starch.
Table 12 sets forth the ranges for the temperature, screw rpm, and
amount of reagent tested using a Process 11, 11 mm parallel twin
screw extruder as described in Example 1.1, above. Screw profile
utilized is described in FIG. 6 (medium shear screw). Specific
examples of process parameters and resulting responses are shown in
Tables 13 and 14 below, respectively. In some runs, extruded
samples in solid form were post-treated by placing the
charge-modified starch in an oven at 120.degree. C. for 90
minutes.
[0154] In addition to charge density (measured via titration),
solubility of each sample was also studied. Here, purified samples
(as described in the dialysis process above) are used. 0.25 g of
sample is mixed into in a beaker with 25 ml of DI water at 60C.
Beaker with mixture is set stirring on hotplate and held at 60 C
for 15 mins. Mixture is then centrifuged at 250 g (1800 RPM & 7
cm radius) for 20 mins to separate solid fraction from the liquid
fraction, including dissolved solids. A pipette is then used to
decant the liquid layer and discarded. Aluminum weigh pans stored
in a desiccator and with predetermined weights are used to collect
remaining solids. Weigh pans and solids are then dried in a forced
air oven for 48 hrs at 40.degree. C. Weigh pans and samples are
removed from the forced air oven and immediately weighed. Sample
weights as a fraction of initial weights are recorded as a %
Solubility.
TABLE-US-00012 TABLE 12 Parameter ranges of the anionic-modified
starch on an 11 mm, parallel twin screw extruder. Temperature
Ranges (.degree. C.) 85-140 RPM Ranges (RPM) 10-500 Maleic
Anhydride Ranges (wt % 5-120 relative to starch) Catalyst (NaOH)
Ranges (wt % 2-60 relative to starch Plasticizer Ranges (wt %
relative Water, Glycerol, & to starch) Water/Glycerol mixes at
40%
TABLE-US-00013 TABLE 13 Process parameters for preparing
anionic-modified starch via 11 mm, parallel twin screw extruder.
Example 2.1A Example 2.1B Temperature (.degree. C.) 110 110 RPM
(RPM) 50 50 Post Treatment No No Maleic Anhydride Ranges (wt 30 60
% relative to starch) Catalyst (NaOH) Ranges (wt % 12 24 relative
to starch Plasticizer (wt % relative to Water (40%) Water (40%)
starch)
TABLE-US-00014 TABLE 14 Properties of the Anionic Modified Starch
FTIR Titration Solubility Sample# (% Trans) (meq/g) (%) 2.1A 83
3.26 76 2.1B 73 5.11 84
[0155] Data indicated that a charge-modified starch was produced
via a reactive extrusion process. % Transmittance as measured via
FTIR is shown to decrease significantly below that of starch
(94.5%) while titration and solubility values are shown to increase
significantly over that of starch (0 meq/g and 7%, respectively).
Ranges of charge density varied from 1.3-6.3 meq/g, and solubility
varied from 27-86%. The level of charge modification of the starch
increased with increasing reagent concentration. Data are further
confirmed via increasing solubility with increasing charge
density.
Example 2.2--Extruded Charge Modified Biopolymer (Examples of
Cationic Charge Modifiers Grafted on to Starch)
[0156] In addition to anionc charges, starch was charge-modified to
form a cationic starch. The cationic charge-modified starch was
prepared by varying the following parameters: temperature, screw
rpm, amount of charge modifying reagent (glycidyltrimethylammonium
chloride [Sigma Aldrich Item 50053-1L]), catalyst (Sodium
Hydroxide) and plasticizer content. Table 15 sets forth the ranges
for the studied parameters in the Leistritz, 11 mm extruder.
TABLE-US-00015 TABLE 15 Parameter ranges of the anionic-modified
starch on an 11 mm, parallel twin screw extruder. Temperature
Ranges (.degree. C.) 85-140 RPM Ranges (RPM) 10-500
glycidyltrimethylammonium chloride 5-150 Ranges (wt % relative to
starch) Catalyst (NaOH) Ranges (wt % 2-60 relative to starch
Plasticizer Ranges (wt % relative Water, Glycerol, & to starch)
Water/Glycerol mixes at 40%
[0157] Starch powder was mixed with a catalyst (NaOH) in powder
form. Plasticizer was then added to the mixture containing the
starch and catalyst and mixed well by hand. The mixture was then
input into the extruder.
[0158] Table 16 provides specific parameters tested with test
responses described in Table 17. Note, temperature settings were
set to apply a uniform temperature for all heating zones. Although
temperature profiles were utilized in other experiments, they are
not detailed here. Screw profile utilized is described in FIG. 6
(medium shear screw). Each sample was tested to determine its
charge density (degree of substitution) via elemental analysis
(measuring nitrogen).
[0159] Elemental analysis may be used to measure charge density for
cationic charge-modified biopolymer samples, whereas titration may
be used to measure charge density for anionic charge-modified
biopolymer samples. Elemental analysis was carried out by means of
Perkin Elmer 2400 CHNS Analyzer: The Perkin Elmer 2400 was used to
determine total elemental carbon, nitrogen, hydrogen, or sulfur by
total combustion. The Degree of Substitution (DS) was determined by
nitrogen and calculated according to Equation (1) below:
DS=162.15.times.% N/1401-151.64.times.% N (1),
where DS is the degree of substitution and % N is the measured
nitrogen content. Furthermore, % N is nearly 0% but a non-zero
number (e.g. 0.002). It is subtracted from all measurements for
precision.
TABLE-US-00016 TABLE 16 Process and formulation parameters for
preparing cationic charge-modified starch. Sample # Sample 2.2A
Sample 2.2B Sample 2.2C Sample 2.2D Temperature (.degree. C.) 90
120 90 90 Plasticizer (wt % relative to starch) Water (40%) Water
(40%) Water (40%) Water (40%) RPM 100 120 50 50 Post Treatment No
No No Yes glycidyltrimethylammonium 4 85 30 30 chloride (wt %
relative to Starch) NaOH (wt % relative to Starch) 1.2 24 12 12
TABLE-US-00017 TABLE 17 Properties of the cationic charged-modified
starch. Sample # Degree of Substitution* Solubility (%) 2.2A 0.035
28 2.2B 0.12 68 2.2C 0.19 76 2.2D 0.21 13 *Degree of substitution
as measured by nitrogen content
[0160] Once again, a charge-modified starch was produced in this
reactive extrusion process. Degree of substitution and solubility
values were significantly greater than that of starch (0 DS, and
0.4% solubility, respectively) and demonstrate charge modification
of a cationic starch via reactive extrusion. A range of DS values
are produced. The DS values achieved here are significantly higher
than previously reported values of DS for cationic starch produced
via reactive extrusion.
[0161] In example 2.2D, inclusion of post treatment shows increased
degree of substitution with simultaneous reduction in solubility
indicating presence of cross linking as discussed in later
examples.
Example 3.1--Extruded Charge Modified Biopolymer (Demonstration of
Charge Grafting onto Hemicellulose)
[0162] In addition to starch, additional biopolymers were utilized
to demonstrate charge modification. Hemicellulose (Xylan from
Beechwood>=90%, Item X4252, Sigma Aldrich, St. Louis Mo.) was
charge modified with citric acid to form an anionic hemicellulose
using the DSM extruder described in Example 1.1. In preparing the
charge-modified hemicellulose, the following parameters were
varied: temperature, screw rpm, and amount of citric acid. Table 18
sets forth the ranges for the temperature, screw rpm, and amount of
citric acid tested using the twin screw conical extruder.
TABLE-US-00018 TABLE 18 Parameter ranges for charge-modified
hemicellulose via twin screw conical extruder. Temperature Ranges
(.degree. C.) 90-150 RPM Ranges (RPM) 50-200 Citric Acid Ranges (wt
% relative 40-150 to hemicellulose)
[0163] Reagents in powder form were hand mixed in 50 g batches,
loaded into the extruder using custom powder injectors, and fed
into the extruder at feed rates determined to be relatively and
qualitatively consistent. Table 19 provides specific parameters
tested with test responses described in Table 20. The FTIR spectra
for the charge-modified hemicellulose and for unmodified
hemicellulose is provided in FIG. 3. Charge density values are
reported according to the titration method described in Example
1.1. It should be noted that in this example, charge density values
of the raw materials are measured and then subtracted from measured
values to show a degree of change in charge density above that of
the raw biopolymer.
TABLE-US-00019 TABLE 19 Process and formulation parameters for
preparing charge-modified hemicellulose. Sample # Sample 3.1A
Sample 3.1B Temperature (.degree. C.) 140 140 RPM 120 120 Post
Treatment No Yes Citric Acid (wt % relative to 150 150
Hemicellulose) SHP (wt % relative to Citric Acid) 20 20
TABLE-US-00020 TABLE 20 Properties of the charged-modified
hemicellulose. Sample # FTIR (% Trans.) Titration (meq/g) 3.1A
81.4% 1.66 3.1B 53.4% 4.68
[0164] A charge-modified hemicellulose was produced via reactive
extrusion. FTIR analysis shows % Transmission values significantly
lower than that of unmodified hemicellulose (91%) and titration
values significantly greater than that of unmodified hemicellulose
(0 meq/g), indicating charge modification of the hemicellulose.
Example 3.2--Extruded Charge Modified Biopolymer (Demonstration of
Charge Grafting onto Pectin)
[0165] Pectin (Item 76282, Sigma Aldrich, St. Louis, Mo.) was
charge modified to increase the anionic property of pectin by
grafting additional carboxylic acid groups onto pectin using the
DSM extruder described in Example 1.1. Experimental methods
followed those in Example 3.1. Table 21 sets forth the ranges for
the temperature, screw rpm, and amount of citric acid tested using
the twin screw conical extruder.
TABLE-US-00021 TABLE 21 Parameter ranges for charge-modified pectin
via twin screw conical extruder. Temperature Ranges (.degree. C.)
90-150 RPM Ranges (RPM) 50-200 Citric Acid Ranges (wt % relative
40-150 to pectin)
[0166] Table 22 provides specific parameters tested with test
responses described in Table 23. If the sample underwent a post
treatment, then the sample was placed in a vacuum oven at
120.degree. C. for 90 mins. Each sample was tested to determine its
charge density (meq/g), and absorbance/transmittance via Fourier
Transform Infrared Spectroscopy (FTIR) at 1720cm.sup.-1. The FTIR
spectra for the charge-modified pectin and for unmodified pectin is
provided in FIG. 4. Charge density values are reported according to
the titration method described in Example 1.1. It should be noted
that in this example, charge density values of the raw materials
are measured and then subtracted from measured values to show a
degree of change in charge density above that of the raw
biopolymer.
TABLE-US-00022 TABLE 22 Process and formulation parameters for
preparing charge-modified pectin. Sample # Sample 3.2A Sample 3.2B
Temperature (.degree. C.) 140 140 RPM 120 120 Post Treatment No Yes
Citric Acid (% relative to pectin) 150 150 SHP (% relative to
Citric Acid) 20 20
TABLE-US-00023 TABLE 23 Properties of the charged-modified pectin.
Sample # FTIR (% Trans.) Titration (meq/g) 3.2A 59.1 4.96 3.2B 26.6
5.72
[0167] A charge-modified pectin was produced via reactive
extrusion. FTIR analysis shows % Transmission values significantly
lower than that of unmodified pectin (63%) and titration values
significantly greater than that of unmodified pectin (0 meq/g),
indicating charge modification of the pectin.
Example 3.3--Extruded Charge Modified Biopolymer (Demonstration of
Charge Grafting onto Soy Protein)
[0168] Soy protein was charge modified to form an anionic soy
protein using the DSM extruder described in Example 1.1. In
preparing the charge-modified soy protein, Experimental methods
followed those in Example 3.1. Table 24 sets forth the ranges for
the temperature, screw rpm, and amount of citric acid tested using
the twin screw conical extruder.
TABLE-US-00024 TABLE 24 Parameter ranges for charge-modified soy
protein via twin screw conical extruder. Temperature Ranges
(.degree. C.) 90-150 RPM Ranges (RPM) 50-200 Citric Acid Ranges (wt
% relative 40-150 to soy protein)
[0169] Table 25 provides specific parameters tested with test
responses described in Table 26. If the sample underwent a post
treatment, then the sample was placed in a vacuum oven at
120.degree. C. for 90 mins. Each sample was tested to determine its
charge density (meq/g), and absorbance/transmittance via Fourier
Transform Infrared Spectroscopy (FTIR) at 1720cm.sup.-1. The FTIR
spectra for the charge-modified soy protein and for unmodified soy
protein is provided in FIG. 5. Charge density values are reported
according to the titration method described in Example 1.1. It
should be noted that in this example, charge density values of the
raw materials are measured and then subtracted from measured values
to show a degree of change in charge density above that of the raw
biopolymer.
TABLE-US-00025 TABLE 25 Process and formulation parameters for
preparing charge-modified soy protein. Sample # Sample 3.3A Sample
3.3B Temperature (.degree. C.) 140 140 RPM 120 120 Post Treatment
No Yes Citric Acid (wt % relative to 150 150 Hemicellulose) SHP (wt
% relative to soy protein) 20 20
TABLE-US-00026 TABLE 26 Properties of the charged-modified soy
protein. Sample # FTIR (% Trans.) Titration (meq/g) 3.3A 68.4 1.66
3.3B 42.8 4.68
[0170] A charge-modified soy protein was produced via reactive
extrusion. FTIR analysis shows % Transmission values significantly
lower than that of unmodified soy protein (93%) and titration
values significantly greater than that of unmodified pectin (0
meq/g), indicating charge modification of the soy protein. Charge
modification was enhanced by thermal post treatment.
Example 4.1--Extruded Cross Linked Biopolymer (Demonstration of
Starch Modified With a Range of Cross Linkers)
[0171] In addition to charge modifiers, cross-linkers were utilized
to form a cross-linked starch using the DSM extruder described in
Example 1.1. In preparing the cross-linked starch, experimental
methods followed those in Example 1.1. The following parameters are
varied: temperature, screw rpm, and the amount of cross linker. In
this example, water was used as the plasticizer at the level of 40
wt % relative to starch. Cross linkers included: Epichlorohydrin
(EPI, >=99% (GC), Item 45340, Sigma-Aldrich, St. Louis, Mo.),
Poly(ethylene glycol) diglycidyl ether (PEDGE, Avg. MN 500, Item
475696, Sigma-Aldrich, St. Louis, Mo.), and Poly(propylene glycol)
diglycidyl ether (PPDGE, Avg. CA. 640, Item 406740, Sigma-Aldrich,
Mo., St. Louis) with sodium hydroxide as catalyst. Table 27 sets
forth the ranges for the temperature, screw rpm, and amount of
cross-linker tested using the twin screw conical extruder. Table 28
provides specific parameters tested with test responses described
in Table 29.
TABLE-US-00027 TABLE 27 Process and formulation ranges for
preparing cross-linked starch. Temperature (.degree. C.) 80-110 RPM
50-120 Crosslinker Epichlorohydrin, PEDGE, and PPDGE Crosslinker
(wt % relative to starch) 0.01-0.1 NaOH (wt % relative to Starch)
0.005-0.2
TABLE-US-00028 TABLE 28 Process and formulation parameters for
preparing cross-linked starch. Sample 4.1A Sample 4.1B Sample 4.1C
Temperature (.degree. C.) 90 90 90 RPM 120 120 120 Post-treatment
No No No Crosslinker EPI PEDGE PPDGE Crosslinker (wt % 0.1 0.1 0.1
relative to starch) NaOH (wt % 0.2 0.2 0.2 relative to Starch)
Plasticizer (40% Water Water Water relative to starch)
TABLE-US-00029 TABLE 29 Properties of cross-linked starch.
Solubility (%) Swelling (g/g) Sample 4.1A 1.6 0.35 Sample 4.1B 2.53
2.67 Sample 4.1C 4.07 3.15
[0172] Here, cross-linked biopolymers were produced via a reactive
extrusion process. Reactive extrusion of starch with cross linkers
show: as cross linker chain length (molecular weight) is increased
(EPI<PEDGE<PPDGE), swelling values improve beyond that of
uncross-linked starch (0.4g/g) and solubility values approach that
of uncross-linked starch (7%).
Example 4.2--Extruded, Cross Linked, Charge Modified Biopolymer
(Demonstration of Cationic Starch Modified With Various Cross
Linkers)
[0173] In addition to starch, charge-modified starch were utilized
to form a cross-linked, charge-modified starch using the DSM
extruder described in Example 1.1. In preparing the cross-linked,
charge-modified starch, experimental methods followed those in
Example 4.1. Aquaflocc 330 AW, manufactured by Aquasol Corp (Rock
Hill, S.C.) was used as the cationic starch in this example.
Additional commercially-available cationic starches, as well as
cationic starches as described in Example 2.2 were also utilized.
The following parameters are varied: temperature, screw rpm, amount
of cross linker, and plasticizer. Cross linkers included:
Epichlorohydrin, Poly(ethylene glycol) diglycidyl ether, and
Poly(propylene glycol) diglycidyl ether with sodium hydroxide as
catalyst. Table 30 sets forth the ranges for the temperature, screw
rpm, and amount of cross-linker tested using the twin screw conical
extruder. Table 31 provides specific parameters tested with test
responses described in Table 32.
TABLE-US-00030 TABLE 30 Process and formulation ranges for
preparing cross-linked, cationic starch. Temperature (.degree. C.)
80-160 RPM 10-300 Crosslinker (wt % relative to starch) 0.0001 to
10 NaOH (wt % relative to Starch) 0.001 to 20 Plasticizer (%)
Water, Glycerol (20-50%)
TABLE-US-00031 TABLE 31 Process and formulation parameters for
preparing cross-linked, cationic starch. Sample 4.2A Sample 4.2B
Sample 4.2C Temperature (.degree. C.) 90 90 90 RPM 120 120 120
Post-treatment No No No Crosslinker EPI PEDGE PPDGE Crosslinker (wt
% 0.1 0.1 0.1 relative to starch) NaOH (wt % 0.2 0.2 0.2 relative
to Starch) Plasticizer (% Water Water Water relative to starch)
(40%) (40%) (40%)
TABLE-US-00032 TABLE 32 Properties of cross-linked cationic starch.
Solubility (%) Swelling (g/g) Sample 4.2A 12.6 1.9 Sample 4.2B 39.9
11.2 Sample 4.2C 40.3 14.7
[0174] Here, cross linked, charge modified biopolymers were created
via reactive extrusion. Solubility results show values
significantly lower than that of the raw material (84%). Here,
decreasing solubility indicates increased degree of cross-linking.
Swelling results may be higher or lower than that of the raw
material (4.4 g/g) depending on degree of cross-linking.
Example 5.1--Extruded Cross Linked, Charge Modified Biopolymer
(Demonstration of Cross Linking Multiple Biopolymers Using 2-Step,
in Line Method)
[0175] To demonstrate crosslinking two charge modified biopolymers,
cross-linked, charged-modified starch citrate chitosan was prepared
using a 2-step inline process using the Leistritz, 18 mm extruder
as described in Example 1.1. Grafting citric acid onto starch
provides an anionic charge, which changes the degree of charge as
can be measured using back titration (meq/g). Acetic acid may be
used to protonate chitosan upon mixing, thereby providing a
cationic charge on the chitosan. The charge-modified chitosan may
be assumed to be partially (i.e., 50% or more) or fully (100%)
protonated due to its solubility in water.
[0176] Furthermore, the extruder having multiple zones as shown in
FIG. 2, allows for implementation of temperature and injection
profiles. Extrusion and composition parameters for preparing
cross-linked, charge-modified starch citrate chitosan were varied
as described in Table 33. Here, powder samples of starch, citric
acid, and SHP were fed into the initial injection zone (Step 1),
while chitosan (Trading Resources, Cocoa Beach, Fla.), acetic acid
(Sigma Aldrich, Item # A6283, St. Louis, Mo.), and plasticizers
were simultaneously added in at injection zone 3 (Step 2) as shown
in Table 34 below. Reactions zones 1-2 were used for charge
modification, while reaction zones 3-8 were used for crosslinking
the charge modified-starch to charge-modified chitosan. Temperature
profiles for each zone are provided in Table 34 below. Screw
profile utilized largely conforms to the medium shear screw as
described in FIG. 6 (medium shear screw). After the graft reaction
of citric acid onto starch, the temperature was decreased to
100.degree. C. to allow for the injection of protonated chitosan
inside the extruder in zone 3 before raising the temperature to
105.degree. C. and 110.degree. C. in zones 4 and 5, respectively,
to initiate the crosslinking reaction between the starch
carboxylate and the free amine groups on the backbone of chitosan.
In some runs, extruded samples in solid form were post-treated by
placing the charge-modified, cross-linked polymer in an oven at
120.degree. C. for 90 minutes. The simultaneous injection of two
mixtures demonstrated below is defined as a 2-step, inline
reaction.
TABLE-US-00033 TABLE 33 Parameter ranges for cross-linked starch
citrate chitosan via parallel twin screw extruder. Temperature
Ranges (.degree. C.) 100-120 (see Table 34) RPM Ranges (RPM)
140-170 Chitosan Ranges (wt % relative to Starch) 100 Acetic Acid
Ranges (wt % relative to Chitosan) 33 Starch Citrate Ranges (wt %
relative to Chitosan) 100 Plasticizer Types Citric Acid Plasticizer
Ranges (wt % relative to Chitosan) 90-140
TABLE-US-00034 TABLE 34 Example of temperature and injection
profile for charge-modified starch cross- linked to another
biopolymer via parallel twin-screw extruder. Zone 1 2 3 4 5 6 7 8
Temperature (.degree. C.) 120 120 100 105 110 110 110 105 Injection
Starch + N/A N/A Chitosan + N/A N/A N/A N/A N/A Reagents
Reagents
[0177] Specific examples of process parameters and resulting
responses are shown in Tables 35 and 36 below, respectively. The
methods for determining the measured responses (e.g. solubility, DI
uptake, and extractables) are described in Example 1. For FTIR
analysis, bonds of interest for charged-modified starch, cross
linked to chitosan system include the Amide-Carbonyl
(R--CO--CNH--R) stretch at .about.1650 cm.sup.-1.
TABLE-US-00035 TABLE 35 Process parameters for preparing
cross-linked, charge-modified starch citrate chitosan. Sample #
Sample 5.1A Sample 5.1B Sample 5.1C Temperature (.degree. C.)
100-120 100-120 100-120 (multiple (multiple (multiple zones) zones)
zones) RPM 140 140 170 Post Treatment Yes No Yes Reaction Type
2-step inline 2-step inline 2-step inline Plasticizer Type Citric
Acid Citric Acid Citric Acid Plasticizer (wt % 75 75 75 relative to
Chitosan) Starch Citrate (wt % 100 100 100 relative to Chitosan)
Acetic Acid (wt % 33 33 33 relative to Chitosan)
TABLE-US-00036 TABLE 36 Properties of the cross-linked, charge-
modified starch citrate chitosan. Solubility FTIR DI Uptake
Extractables Sample # (%) (% Trans) (g/g) (%) 5.1A 4.1 67.5 2.6 19
5.1B 2.4 65.4 9.5 69 5.1C 4.1 68.2 1.9 19
[0178] As described in Example 2, charge modified polymers without
cross-linking show increasing solubility with increasing charge
density (>5% and up to 100%). Due to the presence of charge
modified starch and charge modified chitosan, solubility values
<5% indicate presence of crosslinking. FTIR analysis confirms
presence of the amide-carbonyl stretch where a modified and
unmodified chitosan shows transmission values of 26% and modified
and unmodified starch shows values of 5%. % Transmission values
above 26% indicate presence of charge modified starch cross linked
to charge modified chitosan, confirming the ability to form a
charge modified biopolymer cross linked to another biopolymer in a
2-step, in-line method.
Example 5.2--Extruded Cross Linked, Charge Modified Biopolymer
(Demonstration of Cross Linking Multiple Biopolymers Using 2-step,
2-Pass Method)
[0179] To demonstrate a method where charged-modified biopolymers
may be produced and subsequently cross linked to another
biopolymer, charged-modified starches as prepared in Example 1.1
were cross-linked with chitosan by mixing powdered starch citrate
(i.e., the citric acid-modified starch) with acetic acid, chitosan,
and plasticizer so that the mixture was in powdered form. To obtain
the powdered charge-modified starch, the charge-modified starch was
ground using a blender to sugar/starch consistency where there were
no visible chunks/inconsistencies in the powder mixtures. At least
one plasticizer selected from: glycerol [Item #0854, Amresco,
Solon, Ohio], citric acid, and polyethylene glycol [molecular
weights of 400, 800, 20,000, Sigma Aldrich, St. Louis, Mo.] was
added to the mixture comprising of starch citrate, acetic acid,
chitosan, and plasticizer to induce melt blending during the
extrusion process. The resulting powder mixture was added to the
extruder described in Example 1.1 in a method resembling the
process for preparing charge-modified starch as described in
Example 1.1. Extrusion parameters and compositions were modified
according to Table 37 below.
TABLE-US-00037 TABLE 37 Parameter ranges for cross-linked,
charge-modified starch citrate chitosan via twin screw conical
extruder. Temperature Ranges (.degree. C.) 90-130 RPM Ranges (RPM)
60-200 Chitosan Ranges (rel % to Starch) 50-150 Acetic Acid Ranges
(rel % to Chitosan) 5-100 Starch Citrate Ranges (rel % to Chitosan)
150-250 Plasticizer Types Glycerol Citric Acid, Water Plasticizer
Ranges (rel % to Chitosan) 120-275
[0180] Completion of the reaction in two steps is defined here as a
"2-step, 2-pass" reaction. Examples of process parameters for
cross-linked, charge-modified starch citrate chitosan and measured
responses are shown in Tables 38 and 39, respectively below. The
charge-modified starch used to prepare the cross-linked,
charge-modified starch citrate chitosan had previously been
prepared as described in Example 1 according to parameters
described in sample 1.1A.
[0181] Each sample was analyzed via FTIR to characterize chemical
identity, determine its deionized water (DI) uptake, and to measure
extractables (inverse of yield) following the methods described in
Example 1.
TABLE-US-00038 TABLE 38 Process parameters for preparing
cross-linked, charge-modified starch citrate chitosan. Sample #
Sample 5.2A Sample 5.2B Extruder DSM DSM Temperature (.degree. C.)
100 110 RPM 120 120 Post Treatment No No Reaction Type 2-step,
2-pass 2-step, 2-pass Plasticizer Type Citric acid Citric Acid
Plasticizer (wt % 175 175 relative to Chitosan) Starch Citrate (wt
% 100 250 relative to Chitosan) Acetic Acid (wt % 33 33 relative to
Chitosan)
TABLE-US-00039 TABLE 39 Properties of the cross-linked starch
citrate chitosan. FTIR DI Uptake Extractables Sample # (% Trans)
(g/g) (%) 5.2A 59.4 2.7 73 5.2B 62.6 1.5 61
[0182] As described in Example 5.1, a citric acid modified starch
cross-linked to chitosan may show the amide-carbonyl
(R--CO--CNH--R) stretch at .about.1650 cm.sup.-1 when subjected to
FTIR analysis. FTIR analysis confirms presence of the
amide-carbonyl stretch where a modified and unmodified chitosan
shows transmission values of 26% and modified and unmodified starch
shows values of 5%. Here, % Transmission values of 59 and 62%
(>26%) indicate presence of charge modified starch cross linked
to charge modified chitosan and confirming the ability to form a
charge modified biopolymer cross linked to another biopolymer in a
2-step, 2-pass method.
Example 5.3--Extruded Cross Linked, Charge Modified Biopolymer
(Demonstration of Cross Linking Multiple Biopolymers Using
All-In-One Method)
[0183] To demonstrate simultaneous charge modification and
cross-linking via reactive extrusion, all raw materials (i.e.,
starch, citric acid, SHP, chitosan, acetic acid, and plasticizer as
described in Examples 5.1 and 5.2) were injected simultaneously in
powder form to induce charge modification and cross-linking
reactions in one injection through multiple extruders (defined here
as an "all-in-one" reaction). Here, the mixture of all raw
materials was added to the extruder described in Example 1.1 and
1.3 in a method resembling the process for preparing
charge-modified starch as described in Example 1.1 and 1.3.
Extrusion parameters and compositions were modified according to
Table 40 below. Examples of process parameters for preparing
cross-linked, charge-modified starch citrate chitosan are shown in
Table 41 below with measured responses provided in Table 42. The
methods for determining the measured responses are provided in
Examples 1 and 2.
TABLE-US-00040 TABLE 40 Parameter ranges for cross-linked,
charge-modified starch citrate chitosan via twin screw conical
extruder and 52 mm. parallel twin screw extruder. Extruder DSM
Wegner TX-52 Temperature Ranges (.degree. C.) 90-130 105-130 RPM
Ranges (RPM) 60-200 120-250 Chitosan Ranges (wt % 50-150 50-75
relative to Starch) Acetic Acid Ranges (wt % 5-100 N/A relative to
Chitosan) Starch Ranges (wt % 150-250 100 relative to Chitosan)
Plasticizer Types Glycerol Citric Citric Acid, Acid, Poly Ethylene
Water Glycol, Water Plasticizer Ranges (wt % 120-275 100-130
relative to Chitosan)
TABLE-US-00041 TABLE 41 Process parameters for preparing
cross-linked, charge-modified starch citrate chitosan. Sample #
Sample 5.3A Sample 5.3B Sample 5.3C Sample 5.3D Extruder DSM DSM
Wegner Wegner TX-52 TX-52 Temperature 100 133 120 110 (.degree. C.)
RPM 120 120 120 200 Post Treatment No No No No Reaction Type All-
All- All- All- in-one in-one in-one in-one Plasticizer Citric
Glycerol Citric Citric Type Acid Acid Acid Plasticizer (% 175 175
100 100 rel to Chitosan) Starch (% rel 150 100 150 150 to Chitosan)
Citric Acid (% 66 66 N/A N/A rel to Starch) SHP (% rel to 20 20 20
20 Starch) Acetic Acid (% 33 33 N/A N.A rel to Chitosan)
TABLE-US-00042 TABLE 42 Properties of the cross-linked, charge-
modified starch citrate chitosan. FTIR DI Uptake Extractables
Sample # (% Trans) (g/g) (%) 5.3A 58.8 4.3 58 5.3B 66.9 4.9 54 5.3C
67.2 N/A 67 5.3D 65.3 N/A 65
[0184] As described in Example 5.1 and 5.2, a citric acid modified
starch cross-linked to chitosan may show the Amide-Carbonyl
(R--CO--CNH--R) stretch at .about.1650 cm.sup.-1 when subjected to
FTIR analysis. The presence of carbonyl groups indicate citric acid
charge modification on starch, and the presence of the
Amide-carbonyl group indicates cross-linking. FTIR analysis
confirms presence of the Amide-carbonyl stretch where a modified
and unmodified chitosan shows transmission values of 26% and
modified and unmodified starch shows values of 5%. Here, %
Transmission values of >26% indicate simultaneous charge
modification and cross linking of charge modified starch cross
linked to chitosan to form a charge modified biopolymer cross
linked to another biopolymer in an all-in-one method.
Example 6--Example of Modified Biopolymer for IEX Application
(Demonstration of Salt/Heavy Metal Uptake)
[0185] To demonstrate ion removal capabilities of a charge
modified, cross linked biopolymer, citric acid-modified starch
cross-linked to chitosan were prepared according to Examples 5.1,
5.2, and 5.3. Samples were tested for their salt uptake capacity
measured by conductivity and ash content post exposure to a saline
solution.
[0186] Ash content testing is a measure of residual inorganic
material in a sample upon exposure to high temperatures. 0.3 g of
samples was exposed to a 10% saline (NaCl) solution for 5 minutes,
then squeezed by hand to remove absorbed liquids. Samples were then
transferred to clean, dry, glass vials whose weights were
previously recorded. Samples were then exposed to high temperatures
in a muffle furnace (Vulcan, Model 3-550), for 4 hours at
575.degree. C. following TAPPI Standard: T211 om-02--"Ash in wood,
pulp, paper and paperboard, combustion at 525.degree. C.". To
determine the ash content, the vial weight was subtracted from the
final recorded weight comprising of vial and ash. Final ash weight
was assumed to be residual captured salts where the final ash
weight is divided by the initial sample weight to normalize data to
a g NaCl/g sample (g/g) format.
[0187] Conductivity is a measure of ionic mobility in a given
solution. Reductions in conductivity may be attributed to captured
ions, changes in system energy (i.e., temperature, pressure, etc.),
and/or potential of dissolved ions (i.e., pH changes in presence of
acids/bases). Samples (0.3 g) were exposed to 25 ml of 10% NaCl
solution where initial conductivity (Metler-Toledo conductivity
instrument [model #51302530]) was measured to be 142 mS/cm with a
standard deviation of 3.7. Final conductivity measurements were
assumed to be attributed to ion capture and was therefore used to
calculate a percent difference in conductivity (captured salt). The
uptake of salt was correlated to the resulting decrease in
conductivity by the following formula:
Uptake=(volume in mL*salinity* % .DELTA.)/sample weight,
where % .DELTA. is the % change in conductivity. The % change in
conductivity is attributed to a reduction in mass of NaCl in
solution and is normalized to samples weight. The resulting
measurement parameter yields salt uptake as g NaCl/g sample.
TABLE-US-00043 TABLE 43 Salt removal properties of a charge
modified and cross linked biopolymer system. Salt Uptake - Salt
Uptake - Sample # Conductivity (g/g) Ash Content (g/g) 5.1A 0.24
0.98 5.1B 0.22 1.1 5.1C 0.16 0.69 5.2A 0.13 N/A 5.2B 0.13 N/A 5.3A
N/A 0.1 5.3B 0.25 0.74 5.3C 0.2 N/A 5.3D 0.24 N/A
[0188] Here, salt uptake results of a cross linked biopolymer
(cross-linked cationic starch as prepared via the method found in
Example 4.2) as measured by conductivity show values of 0 g/g.
While not wishing to be bound to any particular theory, the
presence of amphoteric charge (including both cationic and anionic
charge simultaneously) is expected to improve the polymer's
interaction with free ions in solution and is shown in Table 43.
Data demonstrated the ability of charge modified and cross linked
biopolymers to remove ions from solution at a greater rate than a
cross-linked biopolymer. Salt uptake is further demonstrated
through ash content measurements as shown in Table 43 above.
Example 7--Example of Modified Biopolymer for SAP Application
(Demonstration of Charge Modified Starch (Cationic) Crosslinked to
Form Superabsorbent
[0189] A superabsorbent polymer was prepared using a commercially
available charged cationic starch (AquaFlocc 330AW) and a catalyst
on the P11 extruder described in Example 1.1. The extruder having
multiple zones similar to that shown in FIG. 2, allows for
implementation of temperature and injection profiles. Screw profile
utilized is described in FIG. 6 (medium shear screw). Extrusion and
composition parameters for preparing a material for super absorbent
material were varied as described in Table 44. In preparing the
super absorbent polymer, powder cationic starch (Aquafloc 330AW)
and sodium hydroxide were fed into the initial injection zone via
volumetric powder feeder (olumetric MiniTwin Process 11, Typ
567-7660, Thermo Electron/Thermo Fisher Scientific, Germany), while
plasticizer (glycerol) was simultaneously added in at injection
zone 2 via liquid injector and peristaltic pump (Masterflex P/S
Peristaltic Pump, Model No 1300-3600-0004, Thermo Fisher
Scientific, USA) with corresponding peristaltic pump head
(Masterflex P/S Easy Load II, Model No 955-0000, Thermo Fisher
Scientific, USA). In some runs, extruded samples in solid form were
post-treated by placing the modified cationic polymer in an oven at
120.degree. C. for 90 minutes. The simultaneous injection of two
mixtures demonstrated below is defined as a 2-step, inline
reaction.
[0190] In preparing the absorbent polymers, the following
parameters were varied: temperature, screw rpm, plasticizer,
plasticizer concentration, and amount of catalyst. Table 44 sets
forth the ranges for the temperature, screw rpm, and amount of
catalyst tested using the 11 mm, parallel twin screw extruder.
[0191] Samples were tested as absorbents using the EDANA/INDA
method WSP 240.2.R3: free swell capacity in saline by gravimetric
determination in order to measure the fluid uptake of samples. For
the gravimetric method, 0.2 g of sample was sealed in a
2''.times.2'' teabag. The teabag/sample packet was submerged in a
solution for 1 hr, then hanged to dry for 10 mins. Solutions were
prepared according to an industrially relevant application (0.9%
NaCl). Weight measurements were recorded pre- and-post submerging
and normalized for a teabag control sample undergoing the same
conditions. The calculation was as follows:
W w - W b - W i W i ##EQU00001##
where W.sub.w is the wet weight of the teabag/sample, W.sub.b is
the wet weight of the teabag alone, and W.sub.i is the initial
weight of the teabag/sample.
TABLE-US-00044 TABLE 44 Parameter ranges absorbent polymers via
twin screw conical extruder. Temperature Ranges (.degree. C.)
80-160 RPM Ranges (RPM) 50-200 Plasticizer Water, Glycerol, PEG
Plasticizer (wt % relative to cat. Starch) 20-60% NaOH (wt %
relative to cat. starch) .sup. 0-30%
[0192] Table 45 provides specific parameters tested with specific
temperature profiles shown in Table 46 and test responses described
in Table 47. Each sample was tested to determine its swelling
capacity according to the method described above, and solubility
according to the method in example 2.
TABLE-US-00045 TABLE 45 Process and formulation parameters for
absorbent polymers. Sample # Sample 7A Sample 7B Temperature
(.degree. C.) Temp Profile 7 Temp Profile 7 RPM 150 80 Post
Treatment Yes Yes Plasticizer (wt % Glycerol (25%) Glycerol (25%)
relative to cat. starch) NaOH (wt % relative 7.5% 7.5% to cat.
starch)
TABLE-US-00046 TABLE 46 Temperature and injection profiles for
examples 7A and 7 B: charge-modified starch via 11 mm, parallel
twin-screw extruder. Sample # Zone 1 2 3 4 5 6 7 8 Die Temp Profile
7 Unheated 70 75 80 95 110 100 100 100 (.degree. C.) Injection Cat.
Starch + Glycerol N/A N/A N/A N/A N/A N/A N/A NaOH 7A Feed Rate 50
5.9 N/A N/A N/A N/A N/A N/A N/A (RPM) 7B Feed Rate 25 2.4 N/A N/A
N/A N/A N/A N/A N/A (RPM)
TABLE-US-00047 TABLE 47 Properties of the absorbent polymers.
Sample # Free Swell Capacity (g/g) Solubility (g/g) 7A 31.6 4.5 7B
28.8 2.0
[0193] As shown by results in Table 47, reactive extrusion is used
to make a biopolymer material that is useful for absorbing liquids
in industrially relevant applications.
Example 8--Example of modified biopolymer for biosorbent
application
[0194] Additionally, samples as described in Example 7 were tested
as absorbents for other fluids using a modified the EDANA/INDA
method WSP 240.2.R3: free swell capacity in saline by gravimetric
determination in order to measure the fluid uptake of samples.
Here, alternative solutions are used as shown in Table 48, in place
of the specified 0.9% NaCl (saline). Instant Ocean Seal Salt was
used as a sea water simulant. Canola oil, conventional motor oil,
and synthetic motor oil, were used as oil references. Gasoline and
diesel fuel were used as fuel references, and whole bovine blood
was used as a blood reference. The results demonstrated an improved
performance for cross-linked, charge-modified biopolymers of the
present invention relative to conventional superabsorbent
materials: Sodium Polyacrylate (NaPoly, Item 432784, Sigma-Aldrich,
St. Louis, Mo.) in Table 48 below.
TABLE-US-00048 TABLE 48 Biosorbent properties of a cross-linked,
charge-modified biopolymer of the present invention ("Modified
Biopolymer") relative to commercially available superabsorbent
polymers (NaPoly). Solution Sample Uptake (g/g) Instant Ocean (Sea
Water) Modified Biopolymer 29 Na Poly 19 Canola Oil Modified
Biopolymer 18 Na Poly 2.2 Motor Oil (Conventional) Modified
Biopolymer 5.3 Na Poly 1.7 Motor Oil (Synthetic) Modified
Biopolymer 9.2 Na Poly 2.3 Gasoline Modified Biopolymer 3.9 Na Poly
0.8 Diesel Modified Biopolymer 4.7 Na Poly 3.4 Blood Modified
Biopolymer 16.6 Na Poly 1.48
[0195] As shown by results in Table 48, reactive extrusion is used
to make a biopolymer material that is useful for absorbing liquids
in a range of industrially relevant applications.
Example 9--Example of Modified Biopolymer Showing Comparative
Homogeneity (Homogeneity Analysis)
[0196] A JEOL JSM-6010LA scanning electron microscopy (SEM) with a
solid state EDS detector was used to characterize and compare
samples. Samples were adhered to a mount using double sided carbon
tape and analyzed at 20 kV. Micrographs were collected along with
corresponding EDS scans of the target area.
[0197] Indications of homogeneity were derived from the comparison
of commercially available cationic starch to an extruded cationic
starch of the present invention (Example 2.2C). AquaFlocc 330AW
manufactured by Aquasol Corp (Rock Hill, S.C.) represented the
commercially available starch. It is believed that the commercially
available cationic starch is modified in a dry process, which
maintains starch in granular form and allows only for surface
modification of the starch. In contrast, while not wishing to be
bound to any particular theory, the extrusion process is believed
to completely destroy the granular structure of the biopolymer
(e.g., starch).
[0198] As can be seen in FIGS. 7A and 7B, which are SEM images of
commercially available starch, the commercially available starch
retains the starch's characteristic granular structure. In
contrast, as can be seen in FIGS. 7D and 7E, which are SEM images
of extruded cationic starch prepared according to methods of the
present invention, starches extruded according to embodiments of
the present invention exhibit complete destruction of the granular
structure and morphology arises only from topology in sample
preparation. This can be seen by comparing FIGS. 7A and 7B with
FIGS. 7D and 7E.
[0199] Furthermore, when exposed to water and dried, the
commercially available starches showed the presence of insoluble
materials. These insoluble materials indicate uncharged or lowly
charged regions, which are a product of inhomogeneous processing.
These results were confirmed via Energy-Dispersive X-ray
Spectroscopy (EDS of EDXS), which was used to map the elemental
composition of the SEM image for the commercially available starch
(FIG. 7C) and the extruded cationic starch prepared according to
methods of the present invention (FIG. 7F). As can be seen in FIG.
7C, a clear/defined dark region is present where the discrete
particles are imaged. This indicates that these particles are
different in composition (lacking chlorine) compared to the
surrounding region. In contrast, as can be seen in FIG. 7F, EDS
scans of the extruded starch show a gradual change in contrast
towards the bottom right of the image. This change correlates to a
sloping region on the SEM image towards the bottom right. However,
the top left of the image in FIG. 7F also shows a sloping region in
the SEM image, with little change in the EDS map. Thus, it can be
concluded that any contrast here is from a shadowing effect, rather
than a compositional effect and the sample is therefore
homogeneous.
[0200] The foregoing is illustrative of the present invention, and
is not to be construed as limiting thereof. The invention is
defined by the following claims, with equivalents of the claims to
be included therein. All publications, patent applications,
patents, patent publications, and other references cited herein are
incorporated by reference in their entireties for the teachings
relevant to the sentence and/or paragraph in which the reference is
presented.
* * * * *