Note: Descriptions are shown in the official language in which they were submitted.
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9183P/5582A
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TITLE OF THE INVENTION
GELLAN GUM FIBERS
BACKGROUND OF THIS INVENTION
Alginate fibers have been known for use in
surgical dressings for some time. UK 653,341 is an
example of an early disclosure of the use of calcium
alginate materials in surgical dressings. The
earliest such materials were calcium alginate fibers,
but they suffered from the disadvantage of belng
quite insoluble in water or wound exudate matter.
Later a portion of the calcium ions in calcium
alginate was exchanged with other cations, whose
alginate salts are soluble. UK 653,341 therefore
proposed that some of the calcium ions be replaced
with sodium ions, to form a mixed salt algina~e.
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Other uses for alginate fibers have been
proposed which involve shaping the fiber~ as by
weaving or knitting into sheets or pads. -These
materials are useful because they absorb water and
swell but retain their shape and structural integrity.
Other polysaccharides have been proposed for
fiber formation. For example, Burrow et al. (EP
232,121) have described cross-linked polysaccharides
~starch, gellan, curdlan, pullulan, and glycogen)
fibers. These cross-linked fibers are produced by
extruding a dissolved carboxylate ester of the
polysaccharide while simultaneously hydrolyzing the
ester groups and cross-linking the resultant hydro2yl
groups.
SUMMARY OF THIS INVENTION
It has now been found that gellan gum fibers
may be produced by extrusion~of a gum soIution into a
gelling bath. The process, advantageously, does not
require esterification and subsequent hydrolysis.
The process also produces hybrid fibers comprising
gellan and one or more additional gums.
DETAILED DESCRIPTION
By the t~rm "gellan gum", as used herein, is
meant the extracellularly produced gum made by the
heteropolysaccharide-producing bacterium Pseudomonas
elode~, ATCC 31461, by the whole culture fermentation
under a variety of conditions of a medium
comprising: a fermentable carbohydrate, a nitrogen
source, and other appropriate nutrients. Included is
the nativet deacylated, partially deacylated, and
clarified form~ therefore. Gellan gum is also known
as S-60.
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Processes for producing gellan gum are
well-known in the art, e.g., U.S. Patents 4,326,052,
4,326,053, 4,377,636, 4,385,126, and 4,503,084.
Particularly preferred is deacylated gellan
gum, described in U.S.P. 4,326,05Z.
In general, gellan ~um solutions containing
2-6% gum (percentages herein are on a wt./wt. basis
unless stated otherwise) are extruded through fine
orifices into coagulating baths containing various
lo cations to produce filamentous fibers which can be
used in wound dressings, catamenial devlces, etc.
Gellan gum may be used by itself or in combination
with other polysaccharides æuch as alginates, xanthan
gum, and locust bean gum. Solutions may be extruded
cold (room temperature-50C) ox hot (50-80C); if
hot, the addition of another gum is usually
necessary. Gellan gum is especially useful for
producing fibers containing magnesium for controlled
release of that cation. The fibers may also contain
known wound hea~ing agents.
When the gellan gum is co-extruded with
other polysaccharides, this produces fibers with
hybrid properties.
The bath of gelling salts is an aqueous
solution of 0.5-5% of a soluble salt, the cation of
which may be mono-, di-, or tri-valent and selected
from those of Groups I, II, and III of the Perodic
Table, especially Na+, K+9 Ca~+, Mg~, and
Al+++. Ca~+ and Mg+~ are especially
preferred. The anion may be chloride sulfate,
lactate, phosphate, carbonate, gluconate, or
tartrate. Residence time is the bath is 5 seconds -
5 minutes.
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When a second polysaccharide is used it is
one which exhibits a high viscosity when hot; 1n
particular, algin, xanthan gum, and locust bean gum
or combinations of these. The second gum can replace
up to 33 1/3% of the gellan gum; i.e., up to 2a/~ of a
6% gum solution may be comprised of one or more of a
second polysaccharide.
In the final product, therefore, the ratio
of gellan gum to said second gum is at least 2:1.
lo By algin is meant the soluble derivatives of
alginic acid, which may be chemically extracted from
all species of Phaeophvceae, brown algae. The term
is intended to include the soluble salts of alginic
acid (e.g., sodium, potassium, or ammonium alginate)
and the salts of its ethers (e.g., propylene glycol
alginate).
By xanthan gum is meant the biosynthetic
polysaccharide produced by the organism Xanthomonas
campestris by the whole culture fermentation of a
medium comprising a fermentable carbohydrate, a
nitrogen source and appropriate other nutrients.
Xanthan gum preparation is described in
numerous publications and patents, e.g., ~.S. Pat.
Nos. 3,671,398; 3,594,280; 3,591,578; 3,481,889;
2s 3,433,708; 3,427,226; 3,391,061; 3,391,060;
3,271,267; 3,251,749; and 3j020,206.
Locust bean gum (lbg) is an extract of the
locust bean or carob, Cera~onia sili~ua. It is
commercially available and used as a stabilizer in
foods such as ice cream, sausages, and cheese.
Gellan gum is normally gelled by heating an
aqueous solution to dissolve the gum then simply
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9183P/5582A -5- K-2099
cooling to produce a gel, provided cations are
present. It is also known that solutions may be
prepared cold in distilled or deionized water by the
addition of a small amount of sequestrant. The
sequestrants which can be used in this invention
include trisodium orthophosphate (TSP), ethylenedi-
aminetetraacetic acid (EDTA), sodium citrate, tetraso-
dium pyrophosphate (TSPP), sodium hexametaphospha~e
(Calgon) and the like. Gellan gum fibers can
therefore be prepared by forcing a solution of ~.0%
deacylated, clarified gellan gum containing 0.25%
sodium citrate in deionized water through a nozzle
having a diameter of eleven thousandth of an inch
into a 2% calcium chloride bath where fiber formation
immediately occurs.
Gellan gum is particularly useful for
forming fibers containing magnesium ions as it also
gels in the presence of magnesium salts. The 2%
gellan gum solution above was also forced into a bath
containing 2% magnesium sulfate wherein fiber
formation also immediately occurred. Fibers
containing a source of magnesium are valuable
additives to catamenial devices such as tampons where
magnesium ions are said to prevent toxic shock
syndrome. Magnesium alginate is soluble in water;
therefore it cannot be formed by useful methods but
must be formed by ion exchange ~rom insoluble calcium
alginate fibers already produced by the usual
methods. A small amount can be formed simultaneously
with gellan gum fibers however, by incorporating
sodium alginate into gellan gum solutions before
extrusion into the gelling bath. Up to about 25%
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9183P/5582A -6- K-2099
sodium alginate based on the weight of the gellan gum
is possible without destroying the fiber integrity.
Thus, 2.0% gellan gum plus 0.5% alginate having a
viscosity of 95,000 cP as measured on a Brook~ield
LVT viscometer, spindle 4, 6 rpm, 25~C was extruded
into a bath containing 2~/o magnesium sulfate wherein
gelation and fiber formation immediately occurred.
Since the alginate tends to swell slightly the bath
may also contain up to 50% of a lower alcohol such as
isopropanol to minimize swelling. The same solution
above was extruded into a 2% calcium chloride bath
wherein fiber formation immediately occurred.
Fiber formation from hot solutions i9 more
complicated. Gellan gum solutions have high
viscosity when cold but low viscosity w~en heated,
which makes it possible to prepare more concentrated
solutions which gel more rapidly with higher gel
strength. Fiber production by extrusion from~hot gum
solutions into a bath were not successful, however,
because the low viscosity solution dispersed into~
flocs without forming a continuous fiber. It has
been found that the addition of another
polysaccharide which produces more viscosity at
temperatures of 50-80C make fiber formation
possible. Thus, a hot 4% gellan gum solution ~orced
through a nozzle into a 2% calcium chloride bath
instantly dispersed while a 4% gellan gum solution
containing 1% sodium alginate having a viscosity of
4,400 cP as measured on a Brookfield LVT viscometer,
spindle 4, 60 rpm, 70~C formed fibers under the same
conditions. The high viscosity thickeners xanthan
gum and locust bean gum or a combination of the two
also produced ~ibers when combined with the gellan
gum at levels of 0.5-1.0%.
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9183P/5582A -7- K-2099
The fibers of this invention can be used in
various forms. If a non-woven fabric is to be
prepared, and this is the fabric of choice, a cotton
card may be used to form a web, which may then be
cross-lapped and then needle punched in conventional
equipment.
If a woven fabric is to be prepared, the
fibers may be carded and then spun into a yarn, which
can be woven in a conventional loom. Alternatively,
lo the fibers may be collected in a spinning box,
according to the method of Tallis (UK S68,177) and
woven. If a knitted fabric is to be prepared, the
fibers can be prepared as a continuous filament yarn
(again according to UK 568,177) which is then knitted
on a conventional knitting machine.
The fiber end product (e.g., a pad) may
include one or more antimicrobial (for example,
antibacterial or antifungal) agents and/or one or
more local anesthetics (for example, procaine) and
additionally or alternatively one or more
pharmaceutical agents.
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