Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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CROSSLINKED POLYSACCHARIDE, OBTAINED BY CROSSLINKING WITH
SUBSTITUTED POLYETHYLENE GLYCOL, AS SUPERABSORBENT
The present invention relates to a cross-linked polysaccharide(s) which is
(are) useful as
an absorbent(s) or superabsorbent(s); such cross-linked polysaccharide(s) may
be exploited either
alone or in a mixture with one or more other absorbent components, e.g. with
absorbents of the
same or different type as well s other desired or necessary components. The
present invention
also relates to cross-linked polysaccharides which are biodegradable. The
present invention
further relates to a process(es) for preparing such cross-linked
polysaccharide(s); such process
may for example exploit one or more relatively inexpensive cross-linking
agents.
BACKGROUND OF THE INVENTION
The polysaccharides are a group of carbohydrates composed of long chains of
simple
sugars, such as for example, starch, cellulose, dextrins, polygalactomannan,
chitin/chitosan,
alginate compositions, gums, xantan gum, carageenan gum, gum karaya, gum
Arabic, pectin and
glass-like polysaccharides as well as other derivatives thereof such as ionic
and/or non-ionic
derivatives. Examples of starches are: corn, wheat, rice, potato, tapioca,
waxy maize, sorghum,
waxy sarghum, sago and modified starches such as dextrinated, hydrolysed,
oxidized, crosslinked,
alkylated, hydroxyalkylated, acetylated, fractionated (e.g.amylose and
amylopectin), and
physically modified starches.
Polysaccharides have been exploited as absorbent or superabsobents with
respect to the
uptake of aqueous substances (e.g. water, etc.).
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Superabsorbent polysaccharide-based polymers may be obtained through grafting
of an
unsaturated monomer (acrylonitrile, acrylic acid, acrylamide) onto starch or,
less frequently,
cellulose. These polymers also called "Super Slurper" showed water absorption
from 700 to
5,300 g/g for deionised water and up to 140 g/g in saline solution (Riccardo
PO, Water-Absorbent
Polymers: A Patent Survey. J. Macromol.Sci., Rev. Macromol. Chem. Phys., 1994,
607-662
(p.634) and cited references). Despite their very high water absorption, these
grafted
polysaccharides, prepared by radical polymerization are not known to be
biodegradable.
Carboxymethylcellulose (CMC) having the following formula
OCO2Na
O
RO O~
OR m
R = H, carboxymethyl
m is an integer of from 100 to 12,000
is a known polysaccharide-based superabsorbent which is commercially available
from numerous
vendors ( Modern Superabsorbent Polymer Technology, Buchholz F. L. and Graham
A. T. ed.,
Wiley-VCH, Toronto, 1998, pages-239-241 and cited references).
Carboxymethylstarch (CMS) having the following formula
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OC02Na
O
RO
OR
O~
m
R = H, carboxymethyl
m is an integer of from 1000 to 3
million for (natural) starches
is another known polysaccharide-based superabsorbent which is also
commercially available
from numerous vendors are among known polysaccharide-based superabsorbents
(Gross and
Greuel, US 5,079,354, Jan.07, 1992, 536/111) .
Anbergen and Oppermann have studied the elasticity and the swelling behaviour
of
sodium carboxymethylcellulose and hydroxyethylcellulose, chemically
crosslinked with
divinylsulfone (Andergen U. and Oppermann W., Elasticity and swelling
behaviour of chemically
crosslinked cellulose ethers in aqueous systems. Polymer, 1990, 31, 1854-
1858).
Kabra and Gehrke (WO 95/31500, Nov.23, 1995, C08J 9/28) have reported the
sorption
capacity of hydroxypropylcellulose, crosslinked with different concentration
of divinylsulfone
(from 0.28 to 2.98 weight %). The best results showed a water sorption
capacity of 44 g/g with
a crosslink of 0.91 weight %. The authors also mention that other
hydrophobically modified
carbohydrate polymers can be chosen, such as hydroxypropylstarch.
More recently, SCA Hygiene Products AB (Annergren and Lundstrom. WO 00/21581,
Apr.20, 2000, A61L 15/28, 15/60) extended the study with divinylsulfone to low-
cost, readily
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available, renewable starting materials such as carboxymethylcellulose,
carboxymethylstarch,
and others.
According to the authors, results may be obtained with a mixture of
carboxymethylcellulose: hydroxyethylcellulose (3 : 1) which absorbs close to
95 g of synthetic
urine per g of polymer after free swelling for 120 min. In this patent,
however, the quantity of
divinylsulfone used is not reported. Divinylsulfone has been applied with
respect to other
polysaccharides containing acidic groups (Thornton et al. WO 00/35504, June
22, 2000, A61L
15/60, 15/28.). It appears that the best result was obtained with
carboxymethylcellulose
crosslinked with 14 mol% of divinylsulfone. This results in a centrifuge
retention capacity (CRC)
of 111 g/g with synthetic urine. On page 6 of WO 00/35504 it has been
mentioned that the
superabsorbent polysaccharides combine high absorption capacity with control
of bacterial
growth and control of odour, as well as with biodegradability. There is
however no evidence that
such compounds would be biodegradable.
Starch ethers have been crosslinked with numerous other bifunctional groups
such as
acrylamido, chloroazomethine, allyloxy-azomethine groups to give absorbent
materials (Holst
et al., US 4,117,222, Sep.26, 1978, 536/50).
There is still a continuing need for environmentally safe and economical
producible
polysaccharide-based absorbents and superabsorbents and in particular
polysaccharide-based
absorbents and superabsorbents with at least a significant biodegradability.
Accordingly it would be advantageous to be able to make a cross-linked
polysaccharide
(and in particular a cross-linked starch) by exploiting a cross-linking
agent(s) giving rise to a
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cross-linked product having desirable water absorption properties. It would in
particular be
advantageous to be able to make a cross-linked polysaccharide (and in
particular a cross-linked
starch) by exploiting a relatively cheap cross-linking agent(s). It would
further be advantageous
to be able to to be able to make a cross-linked polysaccharide (and in
particular a cross-linked
starch) by exploiting a cross-linking agent(s) giving rise to a cross-linked
product having
desirable biodegradability properties.
STATEMENT OF INVENTION
The present invention in one aspect relates to a cross-linked
polysaccharide(s) (e.g. a
cross-linked starch), said cross-linked polysaccharide(s) (e.g. a cross-linked
starch), being a
polysaccharide (e.g. starch) cross-linked by an ether linkage consisting of a
backbone chain of
atoms, said backbone chain of atoms consisting of two terminal ether oxygen
atoms, one or more
intermediate oxygen link atoms and two or more -CH2- link groups, each oxygen
link atom
being an ether oxygen atom. The backbone chain of atoms may thus be considered
to have the
formula 1
O Linker O 1
wherein said Linker consists of one or more intermediate ether oxygen link
atoms and two or
more -CH2- link groups (e.g. the Linker may be -CHZ-O-CHz ); as may be seen
the backbone
chain of atoms of formula 1, (in addition to the Linker), includes two
terminal oxygen atoms
spaced apart by the Linker, these terminal oxygen atoms are the terminal ether
oxygen atoms
referred to above. Please see for example the compound of formula 9 below
which illustrates the
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incorporation of a backbone chain of atoms into a cross-linked starch half
ester; as may be seen
from formula 9 the terminal oxygens are connected to the starch residues as
ether oxygens.
The present invention in particular relates to a cross-linked
polysaccharide(s) (e.g. a
starch) wherein the cross-linkage is an above described ether linkage, said
backbone chain of
atoms comprising at least one -0-Alkylene- group, wherein Alkylene comprises
one or more -
CHZ groups; Alkylene may more particularly comprise from 1 to 5-CH2- groups
(e.g. Alkylene
may be methylene (i. e. -CH2-) , ethylene (i.e. -CH2CH2-), n-propylene (i.e. -
CH2CH2CH2-), etc... . ).
More particularly the backbone chain of atoms may have the formula 2
2
O Alkylen O Alkylen 0
n
wherein each Alkylene is as defined above (e.g.. consists of one or more -CH2-
groups), wherein
the two terminal oxygen atoms are ether oxygen atoms, and n is an integer of
from 1 to 1000 (e.g.
n may be an integer of from 1 to 100, for example n may be 1, 2 or 3).
A backbone chain of atoms is to be unsubstituted as indicated above. However,
a
backbone chain of atoms may if so desired be substituted by one or more -CH3
and/or -CH2CH3
groups; e.g. an Alkylene group may if so desired be substituted by one or more
-CH3 and/or -
CHzCH3 groups; if desired other higher alky groups may be used as
substituents.
The present invention more particularly relates to a cross-linked
polysaccharide (e.g. a
cross-linked starch), wherein the cross-linkage is an above described ether
linkage, said backbone
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chain of atoms comprising at least one -O-CHZ-CHz- group; for example, a
polysaccharide (e.g.
starch) cross-linked by an above described ether linkage may comprise two,
three or four -0-
CH2-CH2- groups in the backbone chain of atoms.
In accordance with the present invention the degree of cross-linking is to be
chosen
keeping in mind the purpose thereof, namely to achieve an absorbent material.
The degree of
cross-linking may be chosen on the basis of suitable experimentation. It may
for example be
sufficient to get a high CRC (as discussed herein) with high gel strength
values. For example
a quantity as low as 0.02 g of triglycol dichloride may be used to obtain a
hard gel superabsorbent
with a CRC of 39 g/g. The degree of cross-linking may be determined using NNIR
techniques.
The present invention in accordance with an other aspect provides a process
for the
preparation of a cross-linked polysaccharide (e.g. cross-linked starch), said
cross-linked
polysaccharide being a polysaccharide (e.g. a starch) cross-linked by an ether
linkage consisting
of a backbone chain of atoms, said backbone chain of atoms consisting of two
terminal ether
oxygen atoms, one or more intermediate oxygen link atoms and two or more -CH2-
link groups,
each oxygen link atom being an ether oxygen atom (i.e. a backbone chain of
atoms of formula 1
above), said process comprising the step of contacting a polysaccharide (e. g.
a starch) with at least
one cross-linking agent selected in the group consisting of activated
polyalkylene glycols of
formula 1 a
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X Linker X la
so as to obtain said cross-linked polysaccharide (e.g. cross-linked starch),
wherein said Linker is as defined above (i.e. consists of one or more
intermediate ether oxygen
link atoms and two or more -CH2- link groups (e.g. the Linker may be -CHZ O-
CHz-)), and
each X group is a group able to react with an alcohol hydroxyl group of said
polysaccharide (e.g.
starch)
so as to provide an ether oxygen atom link.
The present invention in particular a process for the preparation of a cross-
linked
polysaccharide (e.g. cross-linked starch), said cross-linked polysaccharide
being a polysaccharide
(e.g. a starch) cross-linked by an ether linkage consisting of a backbone
chain of atoms, said
backbone chain of atoms consisting of two terminal ether oxygen atoms, one or
more intermediate
oxygen link atoms and two or more -CH2- link groups, each oxygen link atom
being an ether
oxygen atom (i.e. a backbone chain of atoms of formula 2 above) , said process
comprising the
step of contacting a polysaccharide (e.g. a starch) with at least one cross-
linking agent selected
in the group consisting of activated polyalkylene glycols of formula 2a
X Alkylen O Alkylen X 2a
n
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so as to obtain said cross-linked polysaccharide (e.g. cross-linked starch),
wherein each Alkylene is as defined above (i.e. each Alkylene comprises or
consists of one or
more -CHz- groups (for example each Alkylene may consist of from 1 to 5-CH2-
groups (e.g.
Alkylene may as mentioned above be methylene (i.e.-CHZ ), ethylene (i.e. -
CH2CH2-), n-
propylene (-CH2CH2CH2-), etc....))
each X group is as defined above (i.e. each X group is a group able to react
with an alcohol
hydroxyl group of said polysaccharide (e.g. starch))
so as to provide an ether oxygen atom link and
n is as defined above (i.e. n is an integer of from 1 to 1000, e.g. 1 to 100).
A mixture of two or more different cross-linking agents as described herein
may of course
be used instead of just one linking agent.
For the above formulae 1 a and 2a, as well as for other activated glycols as
described
herein, each X may, for example, be the same; similarly each Alkylene may, for
example, be the
same. Each X may for example be selected from the group consisting of halogen
(e.g. Cl, Br,
I), -O-Ms, -O-Ts, and -O-Tf, wherein Ms is CH3SO2-, Ts isp-CH3C6H4SO2- and Tf
is CF3SO2-.
The reference to an "alcohol hydroxyl group" of a polysaccharide (e.g. starch)
is to be
understood herein as being a reference to an hydroxyl group linked to a
methylene type group
(i.e. a primary alcohol -CHz OH, or a secondary alcohol=CH-OH, the alcohol
hydroxyl group
being underlined) as distinct, for example, from an "acid hydroxyl group"
linked to a carbonyl
group (i.e. -CO-OH, the acid hydroxyl group being underlined).
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The reference to a "starch" is to be understood herein as being a reference to
starch (i.e.
to a starch per se such as for example wheat starch) as well as to modified
starch such as for
example carboxyalkyl starch, starch maleate half-ester (as described herein)
and the like.
The activated polyalkylene (e.g. polyethylene) glycols may for example be any
polyfunctional glycol having any suitable (known) types of reactive functional
groups able to
provide cross-linkage between polysaccharide (e.g. starch) components, e.g.
such as, for example,
terminal halogen substituted glycols as described herein. The activated
polyalkylene (e.g.
polyethylene) glycol compounds of formula 1 a may, for example, have an
average molecular
weight up to 10,000, for example up to 300 (such as from about 100 to about
300).
A process of the present invention is of course to be carried out under
conditions which
favour cross-linkage; for example, the process is to be carried out under
basic conditions
sufficient to facilitate the cross linkage but avoid the hydrolysis of any
hydrolysis susceptible
functional groups which may be attached to the polysaccharide (e.g. starch).
A cross-linked polysaccharide (e.g. cross-linked starch) as described herein
may for
example be obtained by reacting a polysaccharide such as for example a starch
(preferably
containing one or more carboxylates groups) with at least one cross-linking
agent selected in the
group constituted by halogenated (e.g. Cl, Br, I), mesylated, tosylated, or
triflated polyethylene
glycol, for example a compound of formula 1 a above wherein each Alkylene is -
CH2-CH2- and
each X is selected from the group consisting of halogen (e.g. Cl, Br, I), -O-
Ms, -O-Ts, and -O-Tf,
wherein Ms is CH3SO2-, Ts isp-CH3C6H4SO2- and Tf is CF3SO2-.
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The cross-linked polysaccharides (e.g. starches) according to the invention
may be
characterized by 0-alkylation on the primary hydroxyl groups of the polymeric
unit, then on the
secondary hydroxyl groups at C2 or C3 carbon atoms of the polysaccharide (e.g.
starch).
In accordance with the present invention a cross-linked polysaccharides may be
prepared
by a process exploiting one or more relatively inexpensive cross-linking
agent(s) (e.g. 1,5-
dichloro-3-oxopentane (i.e. a dichloropolyethylene oxide)). Preferred cross-
linking agents are
1, 5 -dichloro-3 -oxopentane, 1, 8-dichloro-3, 6-dioxooctane, 1, 11 -dichoro-
3,6, 9-trioxoundecane as
well as homologous dichloro polyethylene glycol compounds with an average
molecular weight
up to 10,000.
The polysaccharide(s) (e.g. starch) may have a non-ionic or ionic
characteristic, e.g. the
polysaccharide (e.g. starch) may have an anionic or cationic characteristic.
The polysaccharide(s)
may if desired or necessary contain any suitable or desired carboxyalkyl
groups keeping in mind
the cross-linking aspect as well as absorbent characteristic; in particular,
for example,
carboxyalkyl groups wherein the alkyl moiety thereof comprises from 1 to 18
carbon atoms e.g
1 to 3 carbon atoms.
Preferred polysaccharides are anionic and contain carboxyalkyl groups
(preferably
carboxymethyl groups) or half-ester prepared with maleic, succinic,
sulfosuccinic, citraconic,
glutaric or phthalic anhydride, where maleic anhydride is preferred. Anionic
polysaccharides also
include dicarboxylates such as iminodiacetate groups and tricarboxylates such
as citrate groups.
Examples of polysaccharides as starting materials are: starch, cellulose,
dextrins,
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polygalactomannans and more ionic and/or non-ionic derivatized,
chitin/chitosan and derivatives
thereof, alginate compositions, gums, xantan gum, carageenan gum, gum karaya,
gum Arabic,
pectin and glass-like polysaccharides. Examples of starches are starches from:
corn, wheat, rice,
potato, tapioca, waxy maize, sorghum, waxy sarghum, sago and modified starches
such as
dextrinated, hydrolysed, oxidized, alkylated, hydroxyalkylated, acetylated,
fractionated
(e.g.amylose and amylopectin), and physically modified starches.
The present invention further relates to the use of a polysaccharide cross-
linked as
described herein as a biodegradable absorbent or superabsorbent and or/and as
a hypoallergenic
absorbent or superabsorbent; a superabsorbent being for example an absorbent
having an
absorption capacity with respect to of saline solution of higher than 15 g
water / g cross-linked
polymer.
The present invention additionally relates to absorbent mixtures comprising at
least one
cross-linked polysaccharide (e.g. cross-linked starch) as described herein
and, if so desired one
or more othere known absorbents /superabsorbents such as CMC, polyacrylates,
etc..
A cross-linked polysaccharide or mixture thereof in accordance with the
present invention
may be used as an absorbent and in particular as a superabsorbent ; such a
cross-linked
polysaccharide or mixture thereof may, for example, be incorporated into (i.e.
contained in)
absorbent personal hygiene products such as, for example, baby diapers,
incontinence products,
sanitary napkins, tampons and the like.
A cross-linked polysaccharide or mixture thereof in accordance with the
present invention
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may be used in several other applications such as for example: food pad;
telecommunication cable
wrappings (for non-biodegradable polymer); in agricultural and forestry
applications to retain
water in soil and to release water to the roots of plants; in fire-fighting
techniques; bandages and
surgical pads; for cleanup of acidic or basic aqueous solutions spills,
including water soluble
chemicals spills and; as polymeric gels for cosmetics and pharmaceuticals also
known as drug
delivery systems and slow release substances and; for artificial snow.
In the following specific reference will be made to polyethylene glycol as
well as to
derivatives thereof, in particular activated derivatives thereof; however, it
is to be understood of
course that other polyalkylene glycols as well as other ether type cross-
linking agents are
contemplated in the context of the present invention keeping in mind that the
linking agent is to
be chosen so as to provide an unsubstituted backbone chain of atoms or if so
desired a backbone
chain of atoms substituted by one or more -CH3 and/or -CH2CH3 groups.
Cross-linkers (i.e. cross-linking agents) used to prepare cross-linked
starches of the
invention may for example be chosen from among activated polyethylene glycols
with average
molecular weight varying from 100 to 10,000 and preferably from 100 to 300.
Polyethylene glycol may have the structure as set forth in general formula 2b
below
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HO--~40 OH
n 2b
n= 1 to 1,000 and
Mõ = up to 10,000 (e.g. 100 to
3 00-10,000)
Mn = average molecular weight
Polyethylene glycols are known to be biodegradable aerobically and
anaerobically (Kawai
F. The Biochemistry of Degradation ofPolyethers. Crit. Rev. Biotech., 1987, 6,
273-307) and the
microbial oxidation of diethylene glycol and polyethylene glycol with the
average molecular
weights of 200, 400, 600, 1000 and 2000 have been reported (Matsumura S. et
al. Microbial
transformation of poly(ethylene glycol)s into mono- and dicarboxylic
derivatives by specific
oxidation of the hydroxymethyl groups. Makromol. Chem. Rapid Commun., 1989,
10, 63-67
The crosslinked polysaccharides according to the present invention may be
obtained by
reacting polysaccharides such as for example starch (preferably containing
carboxylates groups)
with at least one activated polyethylene glycol wherein the terminal hydroxyl
groups are replaced
by Cl, Br, I, mesylates, tosylates or triflates.
A preferred embodiment of the invention is constituted by crosslinking
starches with at
least one activated polyethylene glycol of formula 3 below
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X~0--~+X 3
n
X = Cl, Br, I, OMs, OTs, OTf
n is an integer of from 1 to 1,000 and Mn = 100 to 10,000
Mn = average molecular weight
Ms = mesylate (CH3SO2-)
Ts = tosylate (p-toluenesulfonate, p-CH3C6H4SO2-)
Tf = triflate (CF3SO2-)
As a matter of exemplification, starches crosslinked with polyglycol
dichloride (such as
for example diglycol dichloride of formula 3 wherein each X is Cl and n is
1(herein after referred
to as diglycol dichloride 3a), triglycol dichloride of formula 3 wherein each
X is Cl and n is 2
(hereinafter referred to as triglycol dichloride 3b), tetraglycol dichloride
of formula 3 wherein
each X is Cl and n is 3 (hereinafter referred to as tetraglycol dichloride
3c)), are preferred; i.e.
since starch is a renewable and inexpensive starting material and some
polyglycol dichlorides are
commercially available or easily prepared from polyethylene glycol of formula
2b above by
reaction at reflux with thionyl chloride in benzene or dichloromethane in the
presence of pyridine.
In accordance with the present invention a starch half ester may be cross-
linked by an
activated polyethylene glycol; an example of such a starch half ester cross-
linked with a
polyethylene glycol as set forth in formula 9 below
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O
O)~ R'
O 9
O
OR
O
\ m
n STARCH HALF ESTER
R H, half ester, crosslink
n is an integer of from 1 to 1,000
m is an integer of from 1000 to 3 million for (natural) starches
R' may for example be selected from the group
comprising -CH=CHCO2Na, -CH2CH2CO2Na,
-CH=C(CH3)CO2Na, -C(CH3)=CHCO2Na,
-(CH2)3CO2Na, -(o-CO2Na)C6H4,
-CH(SO3Na)CH2CO2Na, or
-CH2CH(SO3Na)CO2Na, etc.
. A starch half ester of formula 9, wherein R' =-CH=CHCO2Na and n = 2, may be
referred
to as a cross-linked starch maleate half ester (herein sometimes referred to
simply as compound
9a or as maleate 9a); a starch half ester of formula 9, wherein R' =-
CH2CHZCO2Na and n = 2,
may be referred to as a cross-linked starch succinate half ester (herein
sometimes referred to
simply as compound 9b or as succinate 9b); a starch half ester of formula 9,
wherein R' =
-CH=C(CH3)CO2Na or -C(CH3)=CHCOZNa and n = 2, may be referred to as a cross-
linked
starch citraconate half ester (herein sometimes referred to simply as compound
9c or as
citraconate 9c); a starch half ester of formula 9, wherein R' =-(CHz)3CO2Na
and n = 2, may be
referred to as a cross-linked starch glutarate half ester (herein sometimes
referred to simply as
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compound 9d or as glutarate 9d); a starch half ester of formula 9, wherein R'
=-(o-CO2Na)C6H4
and n = 2, may be referred to as a cross-linked starch phthalate half ester
(herein sometimes
referred to simply as compound 9e or as phthalate 9e); and a starch half ester
of formula 9,
wherein R' =
-CH(SO3Na)CHZCO2Na, or -CH2CH(SO3Na)CO2Na, and n= 2, may be referred to as a
cross-linked starch sulfonate succinate half ester (herein sometimes referred
to simply as
compound 9f or as sulfosuccinate 9f).
Tests were conducted to compare cross-linkage of polysaccharide by activated
polyethylene
glycol relative to cross-linkage by divinylsulfone (DVS) of formula 10
O\\ 0 10
Comparisons were conducted on the one hand with respect to cross-linked starch
compounds of formula lla (CMS cross-linked with DVS), and llb (starch
citraconate cross-
linked with DVS) and on the other hand of cross-linked starch compounds of
formula 12 (CMS
cross-linked with polyethylene oxide) below:
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R Ooe R.
O
O -~' 0
O OR lla O OR llb
0 O/'
S~~ m SO m
\
0 O CMA ~O STARCH CITRACONATE
R H, half ester, crosslink R = H, half ester, crosslink
R' = carboxymethyl R' = -COCH=C(CH3)CO2Na or
-COC(CH3)=CHCO2Na
m is as defined above m is as defined above
R'
O~
O
12
O
OR
O
Om ~ _
n \STARCH or CMS 12a n _ - 1, R--CH2CO2Na (CMS)
12b n = 2, R' = -CH2CO2Na (CMS)
R H, carboxymethyl, crosslink 12c n 3, R =-CH2CO2Na (CMS)
12d n= 3, R' = H (STARCH)
m is as defined above
A compound of formula 12 wherein n is 1 and R' =-CHzCO2Na is sometimes
referred to
herein simply as compound 12a; a compound of formula 12 wherein n is 2 and R'
=-CH2CO2Na
is sometimes referred to herein simply as compound 12b; a compound of formula
12 wherein
n is 3 and R' =-CHzCO2Na is sometimes referred to herein simply as compound
12c; and a
compound of formula 12 wherein n is 3 and R' = H is sometimes referred to
herein simply as
compound 12d.
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According to the Zahn-Wellens/EMPA test (US Environmental Protection Agency
(EPA),
Fate, Transport and Transformation Test Guidelines, OPPTS 832.3200, Zahn-
Wellens / EMPA
test, EPA712-C-98-084, January 1998), starch A maleate half-ester, crosslinked
with triglycol
dichloride 3b (herein compound 9a) having a centrifuge retention capacity
(CRC) of 30 g/g in
saline solution, showed 77.3 %, 92.3 % and 96.1 % biodegradability after
respectively 14, 28 and
46 days (see example 21 below).
A study of the crosslinker length was performed by preparing diglycol
dichloride 3a,
triglycol dichloride 3b, and tetraglycol dichloride 3c (SOC12, pyridine,
dichloromethane or
benzene, reflux). Experimental results thereby obtained show that
carboxymethylstarch cross-
linked with 0.62 % of divinylsulfone 10 (namely compound of formula l la),
gives a CRC of 23
g/g in 0.9% saline solution, compared to 30 g/g when crosslinked with 9.85 %
of triglycol
dichloride 3b (namely, compound 12b). The starch-citraconic half ester
crosslinked with 0.6%
of divinylsulfone 10 (namely, compound of formula l lb) were found to exhibit
a good CRC (25
g/g), suggesting that carboxymethyl groups and other carboxyalkyl groups could
be replaced by
half esters. The effect of divinylsulfone and triglycol dichloride
concentrations on the water
retention of resulting compound of formula lla, and compound 12b in 0.9 %
saline solution,
are shown on figure 1. Even if 15 times more quantity of triglycol dichloride
is required to reach
the maximum water retention, the choice of the former is still advantageous
since divinylsulfone
is very expensive.
Crosslinked carboxyalkylstarches and preferably carboxymethylstarches with
activated
polyethylene glycols (for example the compounds 12a-12c) can be prepared in
two steps. First,
starch can be alkylated with halogenocarboxylates, preferably with sodium
chloroacetate or other
CA 02362006 2001-11-09
salts (Li, Ca, K, Mg) followed by crosslinking with activated polyethylene
glycols. In reverse
order, it is possible to perform the crosslinking before the alkylation step
without negative effect
on the water retention. Furthermore, these crosslinked carboxymethylstarches
can also be
prepared in one pot, without affecting the water retention. For alkylation and
crosslinking, basic
conditions are required and sodium hydroxide, potassium hydroxide, litium
hydroxide, calcium
hydroxide, magnesium hydroxide, magnesium oxide, sodium or potassium
carbonates, and
sodium or potassium bicarbonates can be used. Sodium hydroxide is preferred.
Two example reaction schemes or process flow sheets are set forth below:
PROCESS A
OH OC02Na
CI 11--\C02Na O
HO
OH CI 0 O OR
O~
Starch m CI 0
"' O m
NaOH 30%, 700C, 6 hrs /CMS
CMS = carboxymethylstarch
R = H or carboxymethyl
or crosslink
m is as defined above
21
CA 02362006 2001-11-09
PROCESS B
cl o
OH
CI O
O O O
NaOH 30 /a, 700C, 6 hrs 0 O
HO OR
OH 2. O O O~
~ C02N m O\
Starch m SMA
pH 8.5-9.0
room temperature SMA = starch maleate half ester
R = H or nialeate half ester
or crosslink
m is as defined above
Camelot Superabsorbents Limited has reported non polysaccharide-based
copolymers
having two or more pendant carboxylic acid groups arranged in mutual proximity
to absorb water
containing multivalent, particularly divalent ions (Dan and Zhong, WO
97/15367, May 01, 1997,
BO1D 15/00). In more specific examples, monomers having two carboxylic acid
groups attached
to adjacent carbon atoms are particularly preferred. In this current
invention, we report the use
of iminodiacetic acid disodium salt and citric acid trisodium salt as
dicarboxylates and
tricarboxylates pendant anionic groups to chelate divalent ions such as
calcium. As a matter of
fact, iminodiacetic acid disodium salt have been attached to starch to produce
effective materials
for heavy metal removal such as copper and cadmium (Rayford W. E. and Wing R.
E.,
Crosslinked Cationic and Anionic Starches: Preparation and Use in Heavy Metal
Removal.
Starch/Starke, 1979, 31, 361-365; Rayford and Wing, US 4,237,271, Dec.02,
1980, 536/47). On
the other hand, citric acid also has been attached to starch through its
carboxylic acid groups for
22
CA 02362006 2001-11-09
applications as ion exchanger or to enhance the dietary fibre content in foods
(Wing R. E., Starch
Citrate: Preparation and Ion Exchange Properties. Starch/Starke, 1996, 48, 275-
279; Wepner et
al. Citrate Starch-Application as Resistant Starch in Different Food Systems.
Starch/Starke, 1999,
51, 354-361). In our invention, we have attached sodium citrate to starch
through the secondary
hydroxy group with epichlorohydrin as linker arm, leaving the tricarboxylates
groups free, for
calcium chelation and water absorption.
Carboxyalkyl groups attach to starch can be replaced by maleate 9a, succinate
9b,
citraconate 9c, glutarate 9d, phthalate 9e, sulfosuccinate 9f as well. Starch
half esters alone,
without crosslinking have been reported to be biodegradable detergent builders
(Finley, US
4,029,590, June 14, 1977, 252/89R; Finley, US 3,941,771, Mar. 02, 1976,
260/233.5) and
biodegradable non-aging superabsorbers (Wolf et al., US 6,063,914, May 16,
2000, 536/45;
Buchholz et al., US 5,789,570, Aug.04, 1998, 53 6/107.). Moreover, already in
1945, Caldwell
has reported an amazing increase in water absorptive powers when starch are
esterified with
maleic, glutaric or citraconic anhydrides (Caldwell, US 2,461,139, Febr.08,
1949, Cl. 260-234,
application January 08, 1945.).
For the preparation of starch half esters of this current invention, the
crosslinking with
activated polyethylene glycol is realized first at 70 C, followed by reaction
with cyclic anhydrides
at room temperature.
23
CA 02362006 2001-11-09
Examples of starches useful as starting materials are: corn, wheat, rice,
potato, tapioca,
waxy maize, sorghum, waxy sorghum, sago, and modified starches such as
dextrinated,
hydrolysed, oxidized, alkylated, hydroxyalkylated (in both case alkyl being
for example as
defined herein), acetylated, fractionated (e.g., amylose and amylopectin), and
physically modified
starches. Ungelatinised starches and procedure to make carboxymethylstarches
without
gelatinisation in organic solvents could be used. (Beenackers A. A. C. M. et
al., An Experimental
Study on the Carboxymethylation of Granular Potato Starch in Non-Aqueous Media
Carbohydr.
Polymers, 2001, 45, 219-226). Other polysaccharides can also be used such as:
cellulose,
dextrins, polygalactomannans and more ionic and/or non-ionic derivatized,
chitin/chitosan and
derivatives thereof, alginate compositions, gums, xanthan gum, carageenan gum,
gum karaya,
gum arabic, pectin and glass-like polysaccharides (Huppe et al., WO 00/67809,
Nov.16, 2000,
A61L 15/28, 15/30; Lane et al., US 5,360,903, Nov.01, 1994, 536/124). In
general, natural
polysaccharides, polysaccharides from genetically modified organisms (GMO) and
synthetic
polysaccharides can be used. In all cases, anionic and cationic
functionalizations of the selected
polysaccharide could eventually be introduced before, during or after the
crosslinking.
Any other known activated polyethylene glycols may be used as cross-linkers
provided
that they provide a cross-linked product having the desired ether linkage as
described herein.
Moreover, carboxyalkyl groups attach to starch can be replaced by maleate 9a,
succinate 9b,
citraconic 9e, glutaric 9d, phthalates half esters 9e, and sulfosuccinate 9f
as well. Starch half
esters alone, without crosslinking have been reported to be biodegradable
detergent builders
(Finley, US 4,029,590, June 14,1977, 252/89R; Finley, US 3,941,771, Mar.
02,1976, 260/233.5)
and biodegradable non-aging superabsorbers (Wolf et al., US 6,063,914, May 16,
2000, 536/45;
Buchholz et al., US 5,789,570, Aug.04, 1998, 536/107). Moreover, already in
1945, Caldwell
24
CA 02362006 2001-11-09
has reported an amazing increase in water absorptive powers when starch are
esterified with
maleic, glutaric or citraconic anhydrides (Caldwell, US 2,461,139, Febr.08,
1949, Cl. 260-234,
application January 08, 1945).
For the preparation of starch half esters of this current invention, the
crosslinking with
activated polyethylene glycol is realised first at 70 C, followed by reaction
with cyclic anhydrides
at room temperature.
In accordance with the present invention the presence of ionic groups (i.e.
anionic or
cationic groups) may enhance the absorption characteristic of a cross-linked
polysaccharide.
Thus for example, the attachment of iminodicarboxylic acid disodium salt of
formula 13
/-CO2Na
HN 13
~CO2Na
and citric acid trisodium salt of formula 14
CO2Na
HO CO2Na 14
CO2Na
CA 02362006 2001-11-09
to starch, it is possible for example to use, as a linker arm, epichlorohydrin
of formula 15
0 15
CI
This linker arm showed application to attach primary, secondary and tertiary
amines (Rayford
W. E. and Wing R. E., Crosslinked Cationic and Anionic Starches: Preparation
and Use in Heavy
Metal Removal. Starch/Starke, 1979, 31, 361-365; Rayford and Wing, US
4,237,271, Dec.02,
1980, 53 6/47) and we have adapted the procedure for the attachment of the
secondary alcohol of
sodium citrate. In practice, epichlorohydrin can be attach first to starch
with acid catalyst,
followed by amination with iminodiactic acid disodium salt (Rayford W. E. and
Wing R. E.,
Crosslinked Cationic and Anionic Starches: Preparation and Use in Heavy Metal
Removal.
Starch/Starke, 1979, 31, 361-365; Rayford and Wing, US 4,237,271, Dec.02,
1980, 536/47) or
0-alkylation of sodium citrate in basic conditions. However, it has been
reported that starch and
epichlorohydrin appeared to form unstable adducts when hydrochloric acid
catalysis was used
(Trimnell D. et al. Preparation of Starch 2-Hydroxyl-3-Mercaptopropyl Ethers
and Their Use in
Graft Polymerizations, J. Appl. Polymer Sc., 1978, 22, 3579-3586). Since
perchloric acid is a
better catalyst than hydrochloric acid to give higher incorporation rate of
epichlorohydrin on
starch, (Trimnell D. et al. Preparation of Starch 2-Hydroxyl-3-Mercaptopropyl
Ethers and Their
Use in Graft Polymerizations. J. Appl. Polymer Sc., 1978, 22, 3579-3586) and
since perchloric
acid is an explosive substance, we choose an alternative approach. Since
epichlorohydrin-tertiary
amines adducts can be prepared first in basic condition, followed by
attachment to starch in basic
condition (Zhu Z. and Zhuo R., Crosslinked Quaternary Ammonium Cornstarch
Matrix for Slow
Release of Carboxylic Groups-containing Herbicides. Starch/Starke, 2000, 52,
58-63; EDANA,
26
CA 02362006 2001-11-09
Recommended Test Method: Centrifuge Retention Capacity in Saline by
Gravimetric
Determination 441.1-99, Febr., 1999), we have selected this alternative
procedure for the
attachment of iminodiacetic acid disodium salt and citric acid trisodium salt
on starch.
It is to be understood herein, that if a "range" or "group of substances",
"group of
substituents or functional groups" or the like is mentioned or if ranges of
other types of a
particular characteristic (e.g. temperature, pressure, chemical structure,
concentration, molecular
weight, time, etc.) is mentioned, the present invention relates to and
explicitly incorporates herein
each and every specific member and combination of sub-ranges or sub-groups
therein whatsoever.
Thus, any specified range or group is to be understood as a shorthand way of
referring to each and
every member of a range or group individually as well as each and every
possible sub-ranges or
sub-groups encompassed therein; and similarly with respect to any sub-ranges
or sub-groups
therein. Thus, for example,
with respect to a time range, temperature range, a pressure range, a pH range
etc., this is
to be understood as specifically incorporating herein each and every
individual time,
temperature, presure, and pH state etc., as well as sub-ranges thereof; i.e. a
temperature
above 100 C, is to be understood as specifically referring to 101 C, 105 C
and up, 110
C and up, 115 C and up, 110 to 135 C, 115 c to 135 C, 102 C to 150 C, up
to 210
C, etc.;
and
with respect to a class or group of substituents or functional groups, this is
to be
understood as specifically incorporating herein each and every individual
member of the
27
CA 02362006 2001-11-09
class or group as well as sub-classes or sub-groups thereof; i.e. a reference
to alkyl of 1
to 5 carbon atoms is to be understood as specifically referring to each and
every
individual alkyl group (e.g. methyl, propyl, butyl, etc.) as well as to
subgroups such as
2 to 5 carbon atoms, 1 to 3 carbon atoms, 2 to 4 carbon atoms etc.
and similarly with respect to other parameters such as, concentrations,
molecular weights, etc.
In the drawings which illustrate example embodiments of the present invention:
Figure 1: Effect of triglycol dichloride (T3G-diCl) and divinyl sulfone (DVS)
concentrations on crosslinked carboxymethylstarch' CRC;
Figure 2: Effect of sodium chloroacetate (SCA) and diglycol dichloride (DG-
diCl)
concentrations on starch derivatives' CRC;
Figure 3: Effect of sodium chloroacetate (SCA) and triglycol dichloride (T3G-
diCl)
concentrations on starch derivatives' CRC;
Figure 4: Effect of sodium chloroacetate (SCA) and tetraglycol dichloride (T4G-
diCl)
concentrations on starch derivatives' CRC;
Figure 5: Effect of maleic anhydride (MA) and triglycol dichloride (T3G-diCl)
concentrations on starch derivatives' CRC - Optimization study; and
Figure 6: Effect of maleic anhydride (MA) and triglycol dichloride (T3G-diCl)
concentrations on starch derivatives' CRC - Optimization study.
28
CA 02362006 2001-11-09
Centrifuge Retention Capacity (CRC)
The centrifuge retention capacity (CRC) has been measured by the following
procedure
which represents a modified procedure from the EDANA test method (EDANA,
Recommended
Test Method: Centrifuge Retention Capacity in Saline by Gravimetric
Determination 441.1-99,
Febr., 1999) and a modified procedure described by Annergren and Lundstrom
(Annergren and
Lundstrom. WO 00/21581, Apr.20, 2000, A61L 15/28, 15/60.).
Two empty 15 ml test tubes (duplicata) are weighted (Te). Samples around 0.3 g
0.005
g (S) are introduced into both tubes. Saline solution (0.9 %, 10 ml) is added
and the gel is
vortexed for 1 minute then allowed to stand for 15 minutes. Tubes are
centrifuged at 2000RPM
for 5 minutes and the upper aqueous layer is decanted at 30 angle for 5
seconds and tubes are
weighted again (T). In case there is no aqueous layer, the procedure is
repeated with 0.2 g
0.005 g samples. CRC is calculated according to the equation (1) and is
expressed in g of saline
solution per g of absorbent.
CRC = Ts-Te-S (1)
S
Those skilled in the art will gain further and better understanding of this
invention and the
new and important advantages, which is offered from the following
illustrative, but not limiting,
examples of this invention as it has been carried out.
29
CA 02362006 2001-11-09
Gel Strength
The gel strength is arbitrary measured on a 0 to 5 scale, where 0 = no gel,
(liquid), 1=
viscous liquid, 2 = soft gel, 3 = medium gel, 4 = hard gel and 5 = very hard
gel
Biodegradability
According to the United States Environmental Protection Agency (EPA), the Zahn-
Wellens test is useful to test the biodegradability of a substance soluble in
water to at least 50 mg
of dissolved organic carbon (DOC) per litre (US Environmental Protection
Agency (EPA), Fate,
Transport and Transformation Test Guidelines, OPPTS 832.3200, Zahn-Wellens /
EMPA test,
EPA712-C-98-084, January 1998). For substances which are not completely
soluble it offers
only a qualitative indication of whether these substances are basically
susceptible to biological
degradation or not (Buchholz et al., US 5,789,570, Aug.04, 1998, 536/107).
We used activated sludge to evaluate the biodegradability of compound 9a
(example 21).
Technicon carbon analyser has been used to measure DOC and the percentage of
biodegradability
has been calculated according to DOC obtained and reported in the equation
given in reference
36. Compound 9a showed no toxicity for microorganisms and no toxic product
have been
detected to destroy the aquatic flora, particularly the micro crustacean:
Daphnia magna. The
blank used was the mineral medium alone and the positive control was ethylene
glycol, which
showed 100% biodegradability after 14 days.
CA 02362006 2001-11-09
Preparation of crosslinkers
EXANIl'LE 1
Preparation of the 1,5-dichloro-3-oxapentane (diglycol dichloride 3a)
10.0 g (94 mmol) of diethylene glycol were dissolved in 100 ml benzene. To
this solution, 30.8
ml (4 eq.) of pyridine were added, followed by a dropwise addition of 27.5 ml
(4 eq.) of
thionylchloride. The reaction mixture was heated at reflux for 24 hours. At
room temperature,
the organic layer was decanted from the pyridinium hydrochloride salt, washed
with 150 ml of
water, dried on anhydrous sodium sulfate, filtered and evaporated to dryness
to give 8.4g ( 65%
yield) of the dichloride as a light yellow liquid, used without further
purification. Infrared
spectroscopy showed the absence of hydroxyl band.
IR (neat): 2964, 2865, 1450, 1125, 747, 669 cm"1
.
EXAMPLE 2
Preparation of 1,8-dichloro-3,6-dioxaoctane (triglycol dichloride 3b).
10.0 g (67 mmol) of triethylene glycol were treated as example 1 with 22 ml (4
eq.) of pyridine
and 19 ml (4 eq.) of thionylchloride to give 8.8 g (62 % yield) of the
dichloride as a yellow oil,
used without further purification. Infrared spectroscopy showed the absence of
hydroxyl band.
IR (neat): 2962, 2870, 1452, 1123, 747, 666 cm'.
31
CA 02362006 2001-11-09
EXAMPLE 3
Preparation of 1, 11 -dichloro-3,6,9-trioxaundecane (tetraglycol dichloride
3c).
10.0 g (52 mmol) of tetraethylene glycol were treated as example 1 with 17 ml
(4 eq. ) of pyridine and 15 ml (4 eq.) of thionylchloride to give 7.2g (61 %
yield) of the dichloride
as a yellow oil, used without further purification. Infrared spectroscopy
showed the absence of
hydroxyl band.
IR (neat): 2951, 2870, 1459, 1118, 746, 665 cm"1.
Comparaison of Divinylsulfone and triglycol dichloride as crosslinkers to
obtain starch-
based superabsorbents (fi"gures 1,2)
EXAMPLE 4
Preparation of a carboxymethylstarch, crosslinked with 0.62 % w/w
divinylsulfone:
compound lla.
2.0 g (12.3 mmol) of wheat starch A ( Supercell 1201-C, ADM/Ogilvie) was
suspended in 40 ml
of deionized water. Under stirring, 3.5 m130% NaOH (26.3 mmol, 2.1 eq.) was
added dropwise
and the solution stirred at room temperature for 1 hour. Chloroacetic acid
(1.16 g, 12.3 mmol,
1 eq), dissolved in 10 ml of deionized water and neutralized with 1.6 ml 30%
NaOH (12.3 mmol,
1 eq.) was added dropwise and the reaction mixture was heated at 70 C for 24
hours. At room
temperature, 12mg (0.62 weight %) of divinylsulfone dissolved in lOml acetone,
was added
32
CA 02362006 2001-11-09
dropwise and the solution was stirred for 2 hours. The polymer was
precipitated with 100 ml of
methanol, triturated in a blender, washed with 3 portions of 60 ml methanol,
filtered and dry at
60 C for 16 hours to give 1.97g of a white solid. The solid was grinded with a
coffee grinder to
get compound lla as a fine powder.
.
IR (KBr): 3428, 2928, 1611, 1430, 1159, 1083, 1020, 762, 711, 577 cm"1
CRC = 23 g/g
EXAMPLE 5
Preparation of a carboxymethylstarch, crosslinked with 39.38% w/w
divinylsulfone:
compound lla.
2.0 g of wheat starch A was treated as in example 4 with 0.784 g (39.38 weight
%) of
divinylsulfone dissolved in 10 ml acetone to give 2.35 g of compound l la as a
fine white powder.
IR (KBr): , 3427, 2927, 1603, 1415, 1321, 1154, 1083, 1025, 712, 578 cm'.
CRC = 5.7 g/g
The CRC results for the materials of examples 4 and 5, as well as for starting
concentrations are
shown in table I and figure 1, below, table I appearing after the examples
below.
33
CA 02362006 2001-11-09
EXAMPLE 6
Preparation of carboxymethylstarch, crosslinked with 9.85 % w/w triglycol
dichloride:
compound 12b.
2.0 g (12.3 mmol) of wheat starch A ( Supercell 1201-C, AD1VI/Ogilvie) was
suspended in 40 ml
of deionized water. Under stirring, 3.5 m130 % NaOH (26.3 mmol, 2.1 eq.) was
added dropwise
and the solution stirred at room temperature for 1 hour. Chloroacetic acid
(1.16 g, 12.3 mmol,
1.0 eq), dissolved in 10 ml of deionized water and neutralized with 1.6 ml 30
% NaOH (12.3
mmol, 1.0 eq.) was added dropwise and the reaction mixture was heated at 70"C
for 24 hours.
At room temperature, 0. 197g (9.85 weight %) of triglycol dichloride dissolved
in l Oml acetone,
was added dropwise and the solution was heated at 70 C for 24 hours. The
polymer was
precipitated with 100 ml of methanol, triturated in a blender, washed with 3
portions of 60 ml
methanol, filtered and dry at 60 C for 16 hours to give 1.95g of a white
solid. The solid was
grinded with a coffee grinder to get compound 12b as fine powder.
IR (KBr): 3408, 2929, 1607, 1423, 1327, 1158, 1083, 1021, 937, 849, 762, 710,
581, 530cm'.
CRC = 0 g/g
34
CA 02362006 2001-11-09
EXAMPLE 7
Preparation of carboxymethylstarch, crosslinked with 40% w/w triglycol
dichloride:
compound 12b.
2.0 g of wheat starch A was treated as in example 6 with 0.80 g (40 weight %)
of triglycol
dichloride dissolved in l Oml acetone to give 2.06g of compound 12b as a fine
white powder.
IR (KBr): 3404, 2928, 1607, 1424, 1327, 1155, 1084, 1020, 934, 849, 762, 710,
580, 530cm'.
CRC = 21 g/g
The CRC results for the materials of examples 6 and 7 , as well as for other
starting
concentrations are shown in table II and figure 1, below, table II appearing
after the examples
below.
Referring to Figure 1, this figure illustrates the " Effect of triglycol
dichloride (T3G-diCl)
and divinyl sulfone (DVS) concentrations on crosslinked carboxymethylstarch'
CRC". The
figure 1 shows that for the crosslinking of carboxymethylstarch (1.0 eq sodium
chloroacetate
used), the optimum concentration of divinylsulfone is reached at lower
concentration than
triglycol dichloride. A concentration of 0.62 % of divinylsulfone gives a CRC
of 23 g/g and a
concentration of 9.85 % of triglycol dichloride gives a CRC of 30 g/g.
Therefore, triglycol
dichloride is superior to divinylsulfone as crosslinker for
carboxymethylstarch to obtain high
CRC. The figure also shows that at low concentration of triglycol dichloride
(0 to 5 % weight),
CA 02362006 2001-11-09
no gel is obtained and a concentration as low as 0.31 % weight of
divinylsulfone is sufficient to
obtain a gel.
Effect of sodium chloroacetate concentration, crosslinker length and
crosslinker
Concentration on CRC (figures 2-4)
EXAMPLE 8
Preparation of carboxymethylstarch, with 0.25 eq sodium chloroacetate and
without
crosslinkage.
2.0 g (12.3 mmol) of wheat starch A ( Supercell 1201-C, ADM/Ogilvie) was
suspended in 40 ml
of deionized water. Under stirring at 2000 rpm, 5.0 ml 30% NaOH (37 mmol, 3.0
eq.) was added
dropwise and the solution stirred at room temperature for 1 hour. Sodium
chloroacetate (1. 13 ml,
2.74 M, 3.10 mmol, 0.25 eq) was added dropwise and the reaction mixture was
heated at 70 C
for 16 hours. The polymer was precipitated with 75 ml of methanol, and the
mother liquor is
discarded. The polymer is triturated in a blender with 150m1 methanol,
filtered, washed with 3
portions of 50 ml methanol, and dry at 60 C for 16 hours to give
carboxymethylstarch as a fine
white powder after grinding.
CRC = 1 g/g
Gel Strength (GS) = 0
36
CA 02362006 2001-11-09
EXAMPLE 9
Preparation of carboxymethylstarch with 2.0 eq. sodium chloroacetate and
crosslinked
with 0.05 eq. diglycol dichloride: compound 12a.
2.Og (12.3 mmol) of wheat starch A ( Supercell 1201-C, ADM/Ogilvie) was
suspended in 40 ml
of deionized water. Under stirring at 2000 rpm, 5.0 m130% NaOH (37 mmol, 3.0
eq.) was added
dropwise and the solution stirred at room temperature for 1 hour. Sodium
chloroacetate (9.0 ml,
2.74 M, 24.7 mmol, 2.0 eq) was added dropwise followed by diglycol dichloride
(88 mg, 6.17
mmol, 0.05 eq.), weighted in 1.0 ml seringue, and the reaction mixture was
heated at 70 C for 16
hours. The polymer was treated as in example 9 to give compound 12a as a fine
powder.
CRC = 52 g/g
Gel strength(GS) = 2
EXAMPLE 10
Preparation of carboxymethylstarch with 0. 5 eq. sodium chloroacetate and
crosslinked with
0.20eq. diglycol dichloride: compound 12a.
2.0 g (12.3 mmol) of wheat starch Awas treated as in example 9 with sodium
chloroacetate (2.26
ml, 2.74 M, 6.17 mmol, 0.5 eq) and diglycol dichloride (353 mg, 2.47 mmol,
0.20 eq.) to give
compound 12a as a fine powder.
CRC = 11 g/g
37
--- - --------- -
CA 02362006 2001-11-09
Gel strength (GS) = 4
EXAMPLE 11
Preparation of carboxymethylstarch with 2.0 eq. sodium chloroacetate and
crosslinked
with 0.20 eq. diglycol dichloride: compound 12a.
2.0 g (12.3 mmol) of wheat starch A was treated as in example 9 with sodium
chloroacetate (9.0
ml, 2.74 M, 24.7 mmol, 2.0 eq.) and diglycol dichloride (353 mg, 2.47 mmol,
0.20 eq.) to give
compound 12a as a fine powder.
CRC = 33 g/g
Gel strength (GS) = 4
The CRC and gel strength results for the materials of examples 8 to 11 , as
well as for
other starting concentrations are shown in table III and figure 2, below,
table III appearing after
the examples below.
Referring to figure 2, this figure illustrates the effect of sodium
chloroacetate (SCA) and
diglycol dichloride (DG-diCl) concentrations on starch derivatives' CRC. The
figure 2 (and
table III) show that no gel are obtained when no crosslinker (diglycol
dichloride) is used. When
only the crosslinker is attached to starch in the absence of sodium
chloroacetate, a viscous liquid
absorbent (CRC of 9 g/g and GS of 1 from table III) can be obtained (0.15 eq
diglycol dichloride,
no sodium chloroacetate). The figure also shows the concentration region when
it is possible to
obtain superabsorbency (CRC greater than 15 g/g in saline solution) with a CRC
maximum of
38
CA 02362006 2001-11-09
52 g/g, when 0.05 eq of diglycol dichloride and 2.00 eq of sodium
chloroacetate are used. For
this experiment, only a soft gel is obtained (GS of 2 from table III).
According to table III, hard
gels are especially obtained when 0.20 eq of diglycol dichloride,
independently of the sodium
chloroacetate concentration used. The best result obtained with diglycol
dichoride in term of
CRC and GS has been found to be respectively 36 g/g and 5, when 0.25 eq of
diglycol dichloride
and 2.0 eq of sodium chloroacetate are used.
EXAMPLE 12
Preparation of carboxymethylstarch with 0.5 eq. sodium chloroacetate and
crosslinked
with 0.05 eq. triglycol dichloride: compound 12b.
2.0 g (12.3 mmol) of wheat starch A was treated as in example 9 with sodium
chloroacetate (2.3
ml, 2.74 M, 6.17 mmol, 0.5 eq.) and triglycolglycol dichloride (115 mg, 0.62
mmol, 0.05 eq.) to
give compound 12b as a fine powder.
CRC = 11 g/g
Gel strength (GS) = 2
EXAMPLE 13
Preparation of carboxymethylstarch with 2.0 eq. sodium chloroacetate and
crosslinked
with 0.10 eq. triglycol dichloride: compound 12b.
39
CA 02362006 2001-11-09
2.0 g (12.3 mmol) of wheat starch A was treated as in example 9 with sodium
chloroacetate (9.0
ml, 2.74 M, 24.7 mmol, 2.0 eq.) and triglycolglycol dichloride (115 mg, 0.062
mmol, 0.05 eq.)
to give compound 12b as a fine powder.
CRC = 49 g/g
Gel strength (GS) = 3
EXAMPLE 14
Preparation of carboxymethylstarch with 1.5 eq. sodium chloroacetate and
crosslinked
with 0.15eq. triglycol dichloride; compound 12b.
2.0 g (12.3 mmol) of wheat starch A was treated as in example 9 with sodium
chloroacetate (6.8
ml, 2.74 M, 18.5 mmol, 1.5 eq.) and triglycolglycol dichloride (346 mg, 1.85
mmol, 0.15 eq.) to
give compound 12b as a fine powder.
CRC = 27 g/g
Gel strength (GS) = 5
EXAMPLE 15
Preparation of carboxymethylstarch with 0.25 eq. sodium chloroacetate and
crosslinked
with 0.20 eq. triglycol dichloride; compound 12b.
CA 02362006 2001-11-09
2.0 g(12.3 mmol) of wheat starch A was treated as in example 9 with sodium
chloroacetate (1.1
ml, 2.74 M, 3.09 mmol, 0.25 eq.) and triglycolglycol dichloride (462mg, 2.47
mmol, 0.20 eq.)
to give compound 12b as a fine powder.
CRC = 15 g/g
Gel strength (GS) = 2
The effect of sodium chloroacetate (SCA) and triglycol dichloride (T3G-diCl)
concentrations on starch derivatives' CRC for the materials of examples 12 to
15 , as well as for
other starting concentrations are shown in table IV and figure 3, below, table
IV appearing after
the examples below.
Referring to figure 3, this figure illustrates the dffect of sodium
chloroacetate (SCA) and
triglycol dichloride (T3G-diCl) concentrations on starch derivatives' CRC. The
figure 3 (and
table IV) shows that a medium gel or hard gel absorbent are obtained when the
crosslinker
(triglycol dichloride) is used, without sodium chloroacetate. More
specifically, 0.15 eq of
triglycol dichloride gives a hard gel absorbent with a CRC of 10 g/g. The
figure also shows the
concentration region for superabsorbency (CRC higher than 15 g/g in saline
solution) with a
CRC maximum of 49 g/g, when 0.10 eq of diglycol dichloride and 2.00 eq of
sodium
chloroacetate are used. For this experiment, a medium gel is obtained (GS of 3
from table IV).
According to table IV, very hard gels are obtained when 0.15 eq of triglycol
dichloride are used,
with sodium chloroacetate concentration varying from 1.0 eq to 1.5 eq and with
0.20 eq. of
triglycol dichloride with 2.0 eq. of sodium chloroacetate. For very hard gels,
the optimum is
reached at a CRC of 27 g/g (0.20 eq. triglycol dichloride and 2.0 eq sodium
chloroacetate).
41
CA 02362006 2001-11-09
EXAMPLE 16
Preparation of carboxymethylstarch with 0.50 eq. sodium chloroacetate and
crosslinked
with 0.05 eq. tetraglycol dichloride: compound 12c.
2.0 g (12.3 mmol) of wheat starch A was treated as in example 9 with sodium
chloroacetate (2.3
ml, 2.74 M, 6.17 mmol, 0.50 eq.) and tetraglycolglycol dichloride (143 mg,
0.617 mmol, 0.05 eq.)
to give compound 12c as a fine powder.
CRC = 17 g/g
Gel strength (GS) = 5
EXAMPLE 17
Preparation of carboxymethylstarch with 2.0 eq. sodium chloroacetate and
crosslinked
with 0.05 eq. tetraglycol dichloride: compound 12c.
2.0 g(12.3 mmol) of wheat starch A was treated as in example 9 with sodium
chloroacetate (9.0
ml, 2.74 M, 24.7 mmol, 2.0 eq.) and tetraglycolglycol dichloride (143 mg,
0.617 mmol, 0.05 eq.)
to give compound 12c as a fine powder.
CRC=33 g/g
Gel strength (GS) = 5
42
CA 02362006 2001-11-09
EXAMPLE 18
Preparation of carboxymethylstarch with 1.0 eq. sodium chloroacetate and
crosslinked
with 0.15 eq. tetraglycol dichloride: compound 12c.
2.0 g (12.3 mmol) of wheat starch A was treated as in example 9 with sodium
chloroacetate (4.5
ml, 2.74 M, 12.3 mmol, 1.0 eq.) and tetraglycolglycol dichloride (428 mg, 1.85
mmol, 0.15 eq.)
to give compound 12c as a fine powder.
CRC = 25 g/g
Gel strength (GS) = 3
EXAMPLE 19
Preparation of starch crosslinked with 0.25 eq. tetraglycol dichloride:
compound 12d
2.0 g (12.3 mmol) of wheat starch A was treated as in example 9 except that
sodium chloroacetate
was omitted and tetraglycol dichloride (713 mg, 3.09 mmol, 0.25 eq.) was used
to give compound
12d as a fine powder.
CRC = 17 g/g
Gel strength (GS) = 3
The effect of sodium chloroacetate (SCA) and triglycol dichloride (T3G-diCl)
concentrations on starch derivatives' CRC for the materials of examples 16 to
19 , as well as for
43
CA 02362006 2001-11-09
other starting concentrations are shown in table IV and figure 3, below, table
IV appearing after
the examples below.
Referring to figure 4, this figure illustrates the effect of sodium
chloroacetate (SCA) and
tetraglycol dichloride (T4G-diCl) concentrations on starch derivatives' CRC.
The figure 4 (and
table V) shows that a medium gel superabsorbents is obtained when the
crosslinker (tetraglycol
dichloride) is used, without sodium chloroacetate. More specifically, 0.25 eq
of tetraglycol
dichloride gives a medium gel superabsorbent with a CRC of 17 g/g. The figure
also shows the
concentration region where superabsorbency (CRC higher than 15 g/g) is
obtained with a CRC
maximum of 33 g/g, when 0.05 eq of tetraglycol dichloride and 2.0 eq of sodium
chloroacetate
are used. For this experiment, a very hard gel is obtained (GS of 5 from table
V). According to
table V, very hard gels are frequently obtained with tetraglycol dichloride by
comparison to other
crosslinkers (tables III and IV). For very hard gels, the optimum is reached
at a CRC of 27 g/g
(0.15 eq. Triglycol dichloride and 1.5 eq sodium chloroacetate).
Other carboxylate groups
EXAMPLE 20
Preparation of starch citraconate half ester, crosslinked with 0.62% w/w
divinylsulfone:
compound llb.
2.0 g (12.3 mmol) of wheat starch A( Supercell 1201-C, ADM/Ogilvie) was
suspended in 40 ml
of deionized water. Under stirring, 5.0 ml 30% NaOH (37.5 mmol, 3 eq.) was
added dropwise
44
CA 02362006 2001-11-09
and the solution stirred at room temperature for 1 hour. Citraconic anhydride
(1.73 g, 13.3 mmol,
1.1 eq.), dissolved in 10 ml acetone was added dropwise and the reaction
mixture was stirred at
room temperature for 2 hours. 12 mg (0.62%) of divinylsulfone, dissolved in
10m1 acetone, was
added dropwise and the solution was stirred for 2 hours. The polymer was
treated as in example
4 to give 1.92 g of compound 11b as a fine white powder.
IR (KBr): 3399, 2929, 1715, 1644, 1571, 1446, 1407, 1276, 1153, 1081, 1026,
930, 853, 762,
710, 579, 530 cm 1.
CRC = 25 g/g
Gel strength (GS) = 5
EXAMPLE 21
Preparation of starch maleate half ester, crosslinked with 0.08 eq. triglycol
dichloride:
compound 9a.
6.0 g (37.1 mmol) of wheat starch A ( Supercell 1201-C, ADM/Ogilvie) was
suspended in 120
ml of deionized water. Under stirring, 2.5 ml 30% NaOH (18.6 mmol, 0.5 eq.)
was added
dropwise and the solution stirred at room temperature for 1 hour. Triglycol
dichloride (0.5 ml,
2.97 mmol, 0.08eq.) was added and the solution was heated at 70 C for 16
hours. After cooling
at room temperature, maleic anhydride (18 ml, 1.64M in ethyl acetate, 29.6
mmol, 0.8eq.) was
added and the two phases mixture was vigorously stirred at room temperature
for 1 hour. The
polymer was precipitated with 225 ml of methanol, and the mother liquor is
discarded. The
polymer is triturated in a blender with 450 ml methanol, filtered, washed with
3 portions of 150
CA 02362006 2001-11-09
ml methanol, and dry at 60 C for 16 hours to give after grinding, 6.58 g of
compound 9a as a fine
white powder.
IR (KBr): 3398, 2931, 1720, 1632, 1583, 1423, 1351, 1304, 1228, 1155, 1081,
1024, 934, 850,
.
762, 709, 610, 578, 530 cm1
CRC = 33 g/g
Gel strength (GS) = 5
Biodegradability: 77.3, 92.3 and 96.1% after 14, 28 and 46 days, respectively.
EXAMPLE 22
Preparation of disodium iminodicarboxylate epichlorohydrin adduct 16
/-CO2Na
N
~-C02Na
O
16
Iminodiactic acid (3.28 g, 24.6 mmol) was dissolved in 6.6 ml 30% NaOH (2.0
eq.) and
epichlorohydrin (1.92 ml, 24.6 mmol) was added. The heterogeneous reaction
mixture was
stirred at room temperature for 2 hours to give an homogeneous solution which
was completed
to 20 ml with deionized water. Samples of this stock solution were used
without further
purification. Since the reaction has been done with a strong base (NaOH), we
expect the presence
of the epoxide group instead of the N-(3-chloro-2-hydroxypropyl) group, as
reported by Zhu and
Zhuo (Zhu Z. and Zhuo R., Crosslinked Quaternary Ammonium Cornstarch Matrix
for Slow
46
CA 02362006 2001-11-09
Release of Carboxylic Groups-containing Herbicides. Starch/Starke, 2000, 52,
58-63.) for a
reaction between epichlorohydrin and trimethylamine at pH 9.1.
EXAMPLE 23
Preparation of trisodium citrate epichlorohydrin adduct 17
CO2Na
O COZNa
O
CO2Na
17
Trisodium citrate (7.23 g, 24.6 mmol) was dissolved in 3.3 ml 30% NaOH (1.0
eq.) and
epichlorohydrin (1.92 ml, 24.6 mmol) was added. The heterogeneous reaction
mixture was
stirred at room temperature for 16 hours to give an homogeneous solution which
was completed
to 20 ml with deionized water. Samples of this stock solution were used
without further
purification. For the same reason discussed in example 22, we expect the
presence of the epoxide
group in the adduct.
47
CA 02362006 2001-11-09
EXAMPLE 24
Preparation of starch dicarboxylates of formula 18a
HO
N COzNa
0 CO2Na
O iga R = H, dicarboxylate, crosslink
n=2
0
OR m is as defined above
O`
O T
O \ m
n STARCH DICARBOXYLATE
2.0 g (12.3 mmol) of wheat starch A was suspended in 40 ml of deionized water.
Under stirring,
3.3 ml 30% NaOH (24.3 mmol, 2.Oeq.) was added dropwise and the solution
stirred at room
temperature for 1 hour. The disodium iminidiacetate epichlorohydrin adduct
solution (15.0 ml
18.45 mmol, 1.5 eq), was added dropwise, followed by triglycol dichloride
(0.30 ml, 1.85 mmol,
0.15 eq.) and the reaction mixture was heated at 70 C for 24 hours. The
polymer was treated as
in example 9 to give compound 18a as a fine powder.
IR (KBr): 3408, 2929, 1607, 1423, 1327, 1158, 1083, 1021, 937, 849, 762, 710,
581, 530cm'.
CRC = 24 g/g
Gel strength (GS) = 4
48
CA 02362006 2001-11-09
EXAMPLE 25
Preparation of starch tricarboxylates of formula 19a.
CO2Na
COzNa
HO O CO2Na
O
O 19a R = H, tricarboxylate, crosslink
n2
0
OR m is as defined above
O O~
O vJ m
n STARCH TRICARBOXYLATE
2.0 g (12.3 mmol) of wheat starch A was suspended in 40 ml of deionized water.
Under stirring,
3.3 ml 30 % NaOH (24.3 mmol, 2.0 eq.) was added dropwise and the solution
stirred at room
temperature for 1 hour. The trisodium citrate epichlorohydrin adduct solution
(15.0 ml 18.45
mmol, 1.5 eq), was added dropwise, followed by triglycol dichloride (0.30 ml,
1.85 mmol, 0.15
eq.) and the reaction mixture was heated at 70 C for 24 hours. The polymer was
treated as in
example 9 to give compound 19a as a fine powder.
.
IR (KBr): 3408, 2929, 1607, 1423, 1327, 1158, 1083, 1021, 937, 849, 762, 710,
581, 530cm1
CRC = 23 g/g
Gel strength (GS) = 4
49
CA 02362006 2001-11-09
Centrifugal retention capacity and gel strength Optimization for starch
maleate half ester,
crosslinked with triglycol dichloride, compound 9a, (figures 5 and 6)
EXAMPLE 26
Preparation of starch crosslinked with 0.03 eq. triglycol dichloride, compound
12d.
2.0 g(12.3 mmol) of wheat starch A( Supercell 1201-C, ADMIOgilvie) was
suspended in 40 ml
of deionized water. Under stirring, 0.82 ml 30% NaOH (6.17 mmol, 0.50 eq.) was
added
dropwise and the solution stirred at room temperature for 1 hour. Triglycol
dichloride (0.5 ml,
2.97 mmol, 0.08 eq.) was added and the solution was heated at 70 C for 16
hours. After cooling
at room temperature, the pH was adjusted between 8.5 and 9.0 and the polymer
was precipitated
with 150 ml of methanol, and the mother liquor is discarded. The polymer is
triturated in a
blender with 150 nil methanol, filtered, washed with 2 portions of 50 ml
methanol, and dry at
60 C for 16 hours to give after grinding, compound 12d as a fine white powder.
IR (KBr): 3387, 2927, 2891, 1641, 1464, 1432, 1370, 1156, 1081, 1023, 930,
850, 762, 711 and
680 cni'.
CRC = 17 g/g
Gel strength (GS) = 4
EXANIl'LE 27
Preparation of starch maleate half ester with 1,05 eq. maleic anhydride, and
crosslinked
CA 02362006 2001-11-09
with 0.03 eq. triglycol dichloride, compound 9a.
2.0 g (12.3 mmol) of wheat starch A ( Supercell 1201-C, ADM/Ogilvie) was
suspended in 40 ml
of deionized water. Under stirring, 0.82 ml 30 % NaOH (6.17 mmol, 0.50 eq.)
was added
dropwise and the solution stirred at room temperature for 1 hour. Triglycol
dichloride (69 mg,
0.37 mmol, 0.03 eq.) was added and the solution was heated at 70 C for 16
hours. After cooling
at room temperature, the pH was adjusted between 8.5 to 9.0 and maleic
anhydride (8.9 ml, 1.45
M in ethyl acetate, 13.0 mmol, 1.05 eq.) was slowly added and the aquous
mixture containing
ethyl acetate droplets was vigorously stirred at 300 RPM at room temperature.
During the
addition, the pH was carefully maintained between 8.5 and 9.0 with 10% HCl
solution. At the
end ofthe addition, when the pH remained constant between 8.5 and 9.0, the
reaction mixture was
allowed to stand for 30 min. under stirring at 300 RPM. The polymer was then
precipitated with
150 ml of methanol, and the mother liquor was discarded. The polymer was
triturated in a
blender with 150 ml methanol, filtered, washed with 2 portions of 50 ml
methanol, and dry at
60 C for 16 hours to give after grinding, compound 9a as a fine white powder.
IR(KBr): 3424, 2942, 2162, 2061, 1728, 1641, 1590, 1469, 1430, 1352, 1287,
1220, 1178, 1156,
1080, 1019, 852, 817, 763 and 711 cm'.
CRC = 40 g/g
Gel strength (GS) = 4
EXAMPLE 28
Preparation of starch maleate half ester with 0.52 eq. maleic anhydride, and
crosslinked
with 0.18 eq. triglycol dichloride, compound 9a.
51
CA 02362006 2001-11-09
2.0 g (12.3 mmol) of wheat starch A was treated as in example 27 with
triglycol dichloride (416
mg, 2.22 mmol, 0.18 eq.) and maleic anhydride (4.5 ml, 1.45 M in ethyl
acetate, 6.47 mmol, 0.52
eq.) to give compound 9a as a fine white powder.
IR(KBr): 3417, 2928, 2152, 2066, 1724, 1638, 1584, 1462, 1429, 1381, 1353,
1295, 1217, 1156,
1108, 1081, 1022, 931, 900, 852, 814, 763 and 711 cm'.
CRC = 34 g/g
Gel strength (GS) = 4
EXAMPLE 29
Preparation of starch maleate half ester with 0.50 eq. maleic anhydride,
without
crosslinking.
3.0 g (18.52 mmol) of wheat starch A ( Supercell 1201-C, ADM/Ogilvie) was
suspended in 60
ml of deionized water. Under stirring, 1.23 ml 30 % NaOH (9.26 mmol, 0.50 eq.)
was added
dropwise and the solution stirred at room temperature for 1 hour. The pH was
adjusted between
8.5 and 9.0 and maleic anhydride (8.9 ml, 1.45 M in ethyl acetate, 13.0 mmol,
1.05 eq.) was
slowly added followed by the same treatment reported in example 30 with 225 ml
of methanol
for the precipitation and 2 portions of 75 ml of methanol for washing, to give
starch maleate half
ester as a fine powder.
IR(KBr): 3408, 2927, 2152, 2051, 1712, 1647, 1576, 1459, 1432, 1373, 1302,
1237, 1206, 1158,
.
1105, 1082, 1021, 994, 928, 852, 762 and 711 cm"1
CRC = 15 g/g
52
CA 02362006 2001-11-09
Gel strength (GS) = 5
EXAMPLE 30
Preparation of starch maleate half ester with 1.50 eq. maleic anhydride, and
crosslinked
with 0.02 eq. triglycol dichloride, compound 9a.
3.0 g (18.52 mmol) of wheat starch A ( Supercell 1201-C, ADM/Ogilvie) was
suspended in 60
ml of deionized water. Under stirring, 1.23 ml 30 % NaOH (9.26 mmol, 0.50 eq.)
was added
dropwise and the solution stirred at room temperature for 1 hour. Triglycol
dichloride (69 mg,
0.37 mmol, 0.02 eq.) was added and the solution was heated at 70 C for 16
hours. After cooling
to room temperature, the pH was adjusted between 8.5 and 9.0 and maleic
anhydride (19.0 ml,
1.45 M in ethyl acetate, 27.8 mmol, 1.50 eq.) was slowly added followed by the
same treatment
reported in example 27 with 225 rnl of methanol for the precipitation and 2
portions of 75 ml of
methanol for washing, to give compound 9a, as a fine powder.
IR(KBr): 3409, 2937, 2157, 2076, 1724, 1638, 1583, 1428, 1351, 1279, 1219,
1177, 1158, 1077,
1020, 936, 852, 817, 764, and 713 cm'.
CRC = 28 g/g
Gel strength (GS) = 5
EXAMPLE 31
Preparation of starch maleate half ester with 1.10 eq. maleic anhydride, and
crosslinked
with 0.10 eq. triglycol dichloride, compound 9a.
53
CA 02362006 2001-11-09
3.0 g (18.52 mmol) of wheat starch A as example 30 with triglycol dichloride
(346 mg, 1.85
mmol, 0.10 eq.) and maleic anhydride (14.0 ml, 1.45 M in ethyl acetate, 20.4
mmol, 1.10 eq.),
to give to give compound 9a, as a fine powder.
IR(KBr): 3408, 2939, 1721, 1636, 1583, 1469, 1428, 1352, 1217, 1176, 1156,
1080, 1023, 936,
853, 818, 763 and 712 cm'.
CRC = 51 g/g
Gel strength (GS) = 4
Referring to figure 5 (as well as table VI) illustrate the effect of maleic
anhydride (MA)
and triglycol dichloride (T3G-diCl) concentrations on starch derivatives'
CRC.(Optimization
study). The figure 5 (and table VI) show that pratically all experiments gives
products with
superabsorbency (CRC higher than 15 g/g) with a maximum of CRC of 40 g/g, when
0.05 eq
of triglycol dichloride and 1.05 of maleic anhydride are used. For this
experiment, an hard gel
is obtained (GS of 4 from table VI). Hard gel and very hard gel
superabsorbents can be obtained
by crosslinking unsubstituted starch with triglycol dichloride, when the
polymer is precipitated
at a pH between 8.5 and 9Ø For instance, an hard gel can be obtained (CRC =
19 g/g and GS
= 4) with 0.12 eq of triglycol dichloride and a very hard gel (CRC = 17 and GS
= 5) can be
obtained with 0.06 eq of triglycol dichloride. According to table VI, very
hard gels
superabsorbents are also obtained independently of the concentration of
triclycol dichloride and
maleic anhydride. For very hard gels, the optimum CRC of 35 g/g can be reached
in two
experiments, one in the upper concentrations of reactants (0.18 eq triglycol
dichloride and 1.25
eq maleic anhydride), and one in the lower concentrations of reactants (0.09
eq triglycol
54
CA 02362006 2001-11-09
dichloride and 0.75 eq maleic anhydride).
Referring to figure 6 (as well as table VII) also illustrate the effect of
maleic anhydride
(MA) and triglycol dichloride (T3G-diCl) concentrations on starch derivatives'
CRC.(Optimization study). The figure 6 (and table VII) show results for the
optimization of
CRC and GS at low concentration of reactants. All experiments give hard gels
or very hard gels
superabsorbents. Maleate starch without crosslinking can give very hard gel
superabsorbent
(CRC = 20 g/g and GS = 5). The highest CRC obtained is 51 g/g for a hard gel
superabsorbent
prepared with 0.10 eq. triglycol dichloride and 1.10 eq maleic anhydride. The
optimum for a
very hard gel reached a CRC of 40 g/g when 0.02 eq of triglycol dichloride and
1.30 eq of maleic
anhydride are used.
CA 02362006 2001-11-09
Table I
Effect of Divinyl Sulfone (DVS) Concentration on
Crosslinked Carboxymethylstarch' CRC.
DVS 0.00 0.31 0.62 1.58 3.11 7.88 19.69 39.38 78.76 118.15 157.53
% w/w
CRC 0.30 18.00 23.00 22.40 21.00 13.00 8.90 5.70 7.40 6.60 1.70
(g/g)
Table II
Effect of Triglycol Dichloride (T3G-diCl) Concentration on
Crosslinked Carboxymethylstarch' CRC.
T3GdiCI 0.00 0.49 0.98 2.46 5.00 9.85 20.00 24.62 30.00 40.00 150.0
%o w/w
CRC 0.00 0.00 0.00 0.00 0.00 30.00 30.00 26.00 24.00 21.00 15.00
(g/g)
56
CA 02362006 2001-11-09
Table III
Effect of Sodium Chloroacetate (SCA) and Diglycol Dichloride (DG-diCl)
Concentrations on Starch Derivatives' CRC and Gel Strenght (GS).
SCA DG-diCl CRC GS SCA DG-diCl CRC GS
(eq) (eq) (g/g) (0-5) (eq) (eq) (g/g) (0-5)
0.00 0.00 0 0 0.00 0.15 9 1
0.25 0.00 1 0 0.25 0.15 7 2
0.50 0.00 0 0 0.50 0.15 18 5
0.75 0.00 0 0 0.75 0.15 16 4
1.00 0.00 0 0 1.00 0.15 18 3
1.25 0.00 0 0 1.25 0.15 21 3
1.50 0.00 0 0 1.50 0.15 26 3
2.00 0.00 1 0 2.00 0.15 27 3
0.00 0.05 2 0 0.00 0.20 3 4
0.25 0.05 2 0 0.25 0.20 7 4
0.50 0.05 2 0 0.50 0,20 11 4
0.75 0.05 3 0 0.75 0.20 14 4
1.00 0.05 1 0 1.00 0.20 12 4
1.25 0.05 15 2 1.25 0.20 26 4
1.50 0.05 25 2 1.50 0.20 28 4
2.00 0.05 52 2 2.00 0.20 33 4
0.00 0.10 2 1 0.00 0.25 2 3
0.25 0.10 4 1 0.25 0.25 2 3
0.50 0.10 12 4 0.50 0.25 3 3
0.75 0.10 11 4 0.75 0.25 3 3
1.00 0.10 9 4 1.00 0.25 19 3
1.25 0.10 26 3 1.25 0.25 26 4
1.50 0.10 30 3 1.50 0.25 28 5
2.00 0.10 31 3 2.00 0.25 36 5
57
CA 02362006 2001-11-09
Table IV
Effect of Sodium Chloroacetate (SCA) and Triglycol Dichloride (T3G-diCl)
Concentrations on Starch Derivatives' CRC and Gel Strenght (GS).
SCA T3GdiCl CRC GS SCA T3GdiCl CRC GS
(eq) (eq) (g/g) (0-5) (eq) (eq) (g/ls) (0-5)
0.00 0.00 0 0 0.00 0.15 10 4
0.25 0.00 1 0 0.25 0.15 10 2
0.50 0.00 0 0 0.50 0.15 13 3
0.75 0.00 0 0 0.75 0.15 16 4
1.00 0.00 0 0 1.00 0.15 22 5
1.25 0.00 0 0 1.25 0.15 22 5
1.50 0.00 0 0 1.50 0.15 27 5
2.00 0.00 1 0 2.00 0.15 33 4
0.00 0.05 0 0 0.00 0.20 13 2
0.25 0.05 9 2 0.25 0.20 15 2
0.50 0.05 11 2 0.50 0.20 15 4
0.75 0.05 10 2 0.75 0.20 18 4
1.00 0.05 10 2 1.00 0.20 21 4
1.25 0.05 24 3 1.25 0.20 23 4
1.50 0.05 20 4 1.50 0.20 26 4
2.00 0.05 19 3 2.00 0.20 26 5
0.00 0.10 0 0 0.00 0.25 9 3
0.25 0.10 5 1 0.25 0.25 9 3
0.50 0.10 10 4 0.50 0.25 11 3
0.75 0.10 12 4 0.75 0.25 12 4
1.00 0.10 18 4 1.00 0.25 15 4
1.25 0.10 26 4 1.25 0.25 17 4
1.50 0.10 29 4 1.50 0.25 20 4
2.00 0.10 49 3 2.00 0.25 32 3
58
CA 02362006 2001-11-09
Table V
Effect of Sodium Chloroacetate (SCA) and Tetraglycol Dichloride (T4G-diCl)
Concentrations on Starch Derivatives' CRC and Gel Strenght (GS).
SCA T4GdiCl CRC GS SCA T4GdiCl CRC GS
(eq) (eq) (g/g) (0-5) (eq) (eq) (9/g) (0-5)
0.00 0.00 0 0 0.00 0.15 11 2
0.25 0.00 1 0 0.25 0.15 15 2
0.50 0.00 0 0 0.50 0.15 17 3
0.75 0.00 0 0 0.75 0.15 19 3
1.00 0.00 0 0 1.00 0.15 25 3
1.25 0.00 0 0 1.25 0.15 21 5
1.50 0.00 0 0 1.50 0.15 22 5
2.00 0.00 1 0 2.00 0.15 28 4
0.00 0.05 9 2 0.00 0.20 12 2
0.25 0.05 12 5 0.25 0.20 14 2
0.50 0.05 17 5 0.50 0.20 16 2
0.75 0.05 21 5 0.75 0.20 17 3
1.00 0.05 25 5 1.00 0.20 24 3
1.25 0.05 28 5 1.25 0.20 27 4
1.50 0.05 27 5 1.50 0.20 28 4
2.00 0.05 33 5 2.00 0.20 32 4
0.00 0.10 13 2 0.00 0.25 17 3
0.25 0.10 15 2 0.25 0.25 14 5
0.50 0.10 21 2 0.50 0.25 16 2
0.75 0.10 20 5 0.75 0.25 16 4
1.00 0.10 22 5 1.00 0.25 21 4
1.25 0.10 26 5 1.25 0.25 21 4
1.50 0.10 27 5 1.50 0.25 26 5
2.00 0.10 27 5 2.00 0.25 30 5
59
CA 02362006 2001-11-09
Table VI
Effect of Maleic Anhydride (MA) and Triglycol Dichloride (T3G-diCl)
Concentrations on Starch Derivatives' CRC and Gel Strenght (GS).
Optimization study
MA T3GdiCl CRC GS MA T3GdiC1 CRC GS
(eq) (eq) (g/g) (0-5) (eq) (eq) (g/g) (0-5) 0.00 0.03 17 4 2.10 0.12 33 5
0.52 0.03 29 5 2.62 0.12 33 4
0.75 0.03 30 4 3.14 0.12 33 4
1.05 0.03 40 4 4.19 0,12 30 4
1.25 0.03 33 4 0.00 0.15 13 4
1.57 0.03 31 4 0.52 0.15 27 4
2.10 0.03 26 4 0.75 0.15 33 5
2.62 0.03 34 4 1.05 0.15 32 5
3.14 0.03 34 5 1.25 0.15 24 4
4.19 0.03 34 4 1.57 0.15 30 4
0.00 0.06 17 5 2.10 0.15 31 5
0.52 0.06 25 4 2.62 0.15 15 4
0.75 0.06 29 5 3.14 0.15 16 4
1.05 0.06 32 4 4.19 0.15 12 4
1.25 0.06 20 4 0.00 0.18 17 5
1.57 0.06 33 4 0.52 0.18 34 4
2.10 0.06 28 3 0.75 0.18 34 3
2.62 0.06 28 3 1.05 0.18 33 5
3.14 0.06 32 4 1.25 0.18 35 5
4.19 0.06 31 4 1.57 0.18 32 4
0.00 0.09 18 4 2.10 0.18 28 5
0.52 0.09 30 4 2.62 0.18 26 4
0.75 0.09 35 5 3.14 0.18 12 4
1.05 0.09 10 4 4.19 0.18 15 4
1.25 0.09 21 4 0.00 0.21 17 5
1.57 0.09 34 5 0.52 0.21 34 4
2.10 0.09 23 4 0.75 0.21 29 4
2.62 0.09 32 4 1.05 0.21 36 4
3.14 0.09 32 4 1.25 0.21 31 4
4.19 0.09 30 4 1.57 0.21 35 4
0.00 0.12 19 4 2.10 0.21 32 4
0.52 0.12 26 4 2.62 0.21 35 4
0.75 0.12 34 4 3.14 0.21 32 4
1.05 0.12 32 4 4.19 0.21 30 4
1.25 0.12 24 4
1.57 0.12 30 5
CA 02362006 2001-11-09
Table VII
Effect of Maleic Anhydride (MA) and Triglycol Dichloride (T3G-diCl)
Concentrations on Starch Derivatives' CRC and Gel Strength (GS).
Optimization Study
MA T3GdiCl CRC GS MA T3GdiCl CRC GS
(eq) (eq) (g/g) (0-5) (eq) (eq) (g/g) (0-5)
0.50 0.00 15 5 0.50 0.06 30 4
0.70 0.00 20 5 0.70 0.06 18 4
0.90 0.00 18 5 0.90 0.06 35 5
1.10 0.00 20 4 1.10 0.06 41 4
1.30 0.00 20 4 1.30 0.06 35 5
1.50 0.00 21 4 1.50 0.06 37 5
0.50 0.02 29 4 0.50 0.08 18 4
0.70 0.02 31 4 0.70 0.08 21 4
0.90 0.02 36 4 0.90 0.08 24 4
1.10 0.02 38 5 1.10 0.08 25 4
1.30 0.02 40 5 1.30 0.08 18 4
1.50 0.02 28 5 1.50 0.08 20 4
0.50 0.04 18 4 0.50 0.10 26 4
0.70 0.04 19 4 0.70 0.10 34 4
0.90 0.04 19 4 0.90 0.10 39 4
1.10 0.04 21 4 1.10 0.10 51 4
1.30 0.04 25 4 1.30 0.10 36 5
1.50 0.04 18 4 1.50 0.10 37 5
61
