Note: Descriptions are shown in the official language in which they were submitted.
~z~7~S~8
VAC-82-3/I
SODIUM HYDROSULFITE SLURRIES
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates -to aqueous slurries and
particularly relates to non-settling and flowable aqueous
slurries of sodium dithionite that remain in pumpable form
without significant expansion, settling, or gellation.
Review of the Prior Art
Sodium dithionite, commonly termed sodium hydrosulfite
and, less correctly, sodium hyposulfite, is a powerful reducing
agent that has long been used for bleaching, particularly for
bleaching textiles and wood pulps such as ground wood and semi-
chemical pulps.
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Sodium dithioni.te has usually been manufactured by
significantly different processes that are alternatively based
Il on zinc dust, sodium formate, sodium borohydride, or sodium
¦ bisulfite (electrolytic). Such processes are disclosed, for
example, in United States Patent Numbers 2,938,771: 3,004,825;
I 3,259,457; 3,411,875; 3,718,732; 3,872,221; 3,887,695;
! !
3,897,544; 3,927,190; and 4,127,642.
The products of these processes are herein
I respectively identified as zinc-derived, formate-derived,
~ borohydride-derived, and electr-olyticall.y-derived sodium
dithionite. Because the zinc process produces zinc dithionite,
which is no longer ecologically acceptable, zinc dithionite is
¦ converted to sodium dithionite by adding sodium hydroxide or
¦ sodium ca.rbonate, whereby zinc hydroxide or zinc carbonate is
precip~tated and removed by filtering.
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¦l When anhydrous sodium dithionite crystals are
dissolved under either aerobic or anaerobic conditions to make
a large quantity of aqueous solution, the resulting solution
cannot be stored for use over a long period of time. Due to
hydrolytic decomposition at the natural pH of the sodium
dithionite solution, decomposition will proceed rapidly from
that point by self-propagation because the decomposition
products create an acidic condition which accelerates the
¦ll decomposition.
ll Aqueous solutions of the dithionite will decompose at
11 a commercially tolerable rate, however, if stabilized by
¦l additives such as are disclosed in United States Patent Nos.
il 3,819,807 and 3,985,674. These additives include chelating
¦ agents, sodium carbonate, sodium tripolyphosphate, sodium
hydroxide, and amines.
¦l Although such stabilized solutions can be protected
jl from decomposition for long enough periods Eor shipment and
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routine commercial use under suitable conditions, it has been a
j more common practice to store the anhydrous dithionite crystals
¦ under a dry, inert gas in a sealed container. Even though the
crystals are thereby chemically stable for long periods, they
begin to decompose as soon as exposed to the air and moisture
when the container is opened for use thereof.
Furthermore, commercially available solutions of
I sodium dithionite are expensive to transport because they are
!! typically at concentrations of 12-13 5~, when combined with
ll suitable additives, and, additionally, generally require
refrigeration during shipment and storage. Thus, the transport
oE about seven times as much water as product tends to cause
il the sale oE the commodity to become distance-dependent. In
consequence, slurries have seemed to offer an inviting means to
avoid or at least to minimize the cost of storage and
difficulties associated with solution forms of sodium
,l dithionite, without decreasing the convenience that the
I purchaser derlves from solutions.
I¦ However, the economical preparation, stabilization,
1! handlingr and shipping of such slurries is not simple.
j Adequate suspension without agitation, so that pumping can be
j done from a tank truck after shipment, is also not easy. In
~ fact, after considering the variety of processes that are
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- available for manufacturing sodium dithionite, including t~e
indigenous by-products, crystal structures, and the like, the
complexities of the concept are readily appreciated. Moreover
slurries have not been as widely investigated nor as
Il commercially utilized as other forms of sodium dithionite.
: I United States Patent 3,536,445 describes a process for
i~ making sodium dithionite from sodium-zinc alloy by initially
producing zinc dithionite and then converting it to sodium
Il dithionite by adding caustic soda. After removal of the zinc
ll hydroxide by filtration, the dihydrate of sodium dithionite is
¦l "salted out" of the mother liquor with sodium chloride and
alcohol to form a slurry.
United States Patent 3,804,944 gives some stability
storage data for 30% slurries (18.5% formate-derived and 11.5
i¦ zinc-derived sodium dithionite) containing 1-8% caustic soda
¦ (dithionite basis). Tests showed that these slurries required
! frequent agitation to prevent caking and handling
difficulties.
I¦ United States Patent 3,83~,217 shows that by reducing
20 1I the particle size of the sodium dithionite crystals and/or
,j introducing a suspending or thickening agent into a liquid
1~ containing the crystals, such as alcohollc brine, it is
! possible to form a fluent, homogeneous, pourable dispersion of
,
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'I the solid dithionite particles which is chemically and
1 physically stable for long periods of time, provided that a
1, .
material, such as the salt in the brine and/or an alcohol, be
present which suppresses the dissolution of the dithionite so
that the dispersion can be stored at about 20C. The majority
of the particles should be about 0.6-0.8 micron in size.
Methylcellulose, hydroxyethyl cellulose, polyvinyl alcohol,
guar gum, and other common thickening, dispersing, or
suspending agents can be used. The thickened dispersion
lll exemplarily has a Brookfield viscosity of 9,000 cps and
contains up to 34% Na2S2O4.
United States Patent 3,839,218 provides a method Eor
maintaining a dispersion of crystalline zinc or alkali metal
dithionite by continuous or periodic mechanical agitation so
that the crystals can be stored for long periods without
decomposition, the dispersing medium being aqueous or
non-aqueous and containing a material which suppresses
dissolution of the dithionite solids. The pH of the liquid
must be at least 6.5, the viscosity of the dispersion must be
below about 50,000 centipoises, and the suppressing material
may be a water-soluble organic compound or a saturated brine or
mixtures thereof. A thickening and suspending agent can be
used. suitable agents i~clude polysaccharides, water-soluble
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ii
polymers, and proteins of moderate molecular weight. Exemplary
agents include guar gum, gum tragacanth, gelatin, and starchO
United States Patent 4,283,3Q3 discloses a method for
making substantially stable slurries containing 30 35% by
¦ weight of sodium dithionite by evaporating sodium dithionite
solutions while maintaining the heating medium at 220-250F and
the solution and slurry at 110-155F under a vacuum of at least
, 25 inches Hg and by promptly cooling the resultant slurry while
Il agitating it. The vacuum is preferably 26.5-27.5 inches Hg.
~~ Zinc-derived sodiation liquor is the preEerred sodium
dithionite solution to which 4-5~ by weight of the sodium
dithionite, NaOH, and a chelator, as a stabiliæing agent, are
added.
! Although these evaporated slurries have excellent
stabilization qualities, they have developed problerns with
settling which has occurred over a period of 2-~ days and
especially under the vibrations produced by tank car shipment.
Such settling, and subsequent hardening, has resulted in
j shipments which could not be unloaded by pumping as would
I normally be done.
Slurries in general are utilized as foods, coatings,
paints, dyes, explosives, oilwell fluids, and the like, and
often include natural or synthetic gums to form a liquid
colloidal
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system in which the solid particles are dispersed. Such a gum-
i containing fluid system, without the solid particles, is
identified as a sol and is more accurately termed a hydrosol
¦1 when based on water.
Il The gums typically impart viscosity to sols in which
they are incorporated and thereby function as thickeners. When
shear forces are created by agitating a sol and there is no
change in viscosity, the behavior of a thickener is said to be
~ Newtonian. ~1hen the viscosity of the sol in a quiescent state
~l is greater than when a shear force is applied through
agitation, wherl the viscosity decreases as the applied shear
I force increases and when the viscosity recovers immediately
I' when the magnitude of the shear force is decreased, the
- l¦ behavior of a thickener is said to be plastic. When the rate
il of Elow increases faster than normal in relation to the applied
shearing stress, the sol is described as pseudoplastic.
I Generally, when the sol is at rest, the molecules of a plastic
¦ thickener arrange themselves into a more or less stable form.
Il In order to break this stable molecular arrangement and cause
!I the sol to yield, the application of a shear force is
necessary. The shear force that is required to cause the sol
to yield and flow is termed the yield point or the gel
strength. Once the gel strength of a plastic sol is overcome,
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the viscosity of the sol proportionately decreases as greater
shear force is applied.
Numerous natural and synthetic gums are widely used
for manufacturing hydrosols. Favored gums for many hydrosols
are galactomannan gums such as guar gum, which is derived from
the endosperm of the guar plant, Cyamopsis tetragonolobus.
Other water-soluble gums which are increasingly utilized are
the xanthonomas hydrophilic colloids, commonly termed xanthan
gums, which may be produced by the action of various bacterial
species of the genus Xanthomonas on carbohydrates ~and like
materials). The fermentation product of the reaction of the
bacteria Xanthomonas _mpestris, a preferred species, on
carbohydrates is commerically available as "ICelzan " made by
Kelco Corporation of San Diego, California.
In a typical process for clarification of a
xanthomonas fermentation broth and/or recovery of the
xanthomonas hydrocolloid component, the broth is diluted with
water to reduce its viscosity and, optionally the diluted broth
is centrifuged or filtered to remove suspended insoluble solids.
A salt such as potassium chloride and a nonsolvent such as
methanol or isopropanol are added to the broth to flocculate
the gum in the potassium form, whlch gum is then recovered by
centrifugation or other solid/liquid separation
*Trade Mark
_g_
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techniques. Further dissolving, reprecipitating, and washing
steps are usually employed. The heteropolysaccharides thus
prepared by bacteria of the genus xanthomonas on carbohydrates
are normally obtained as thick viscous solutions having a dull
¦ yellow c~lor.
Xanthan gum is an excellent and widely used suspending
and viscosity building agent. Some oE its particular uses are
in oil well fluids, paint, sprays, and cleaning fluids.
I Xanthan gum, however, has a few disadvantages. It is very
1I difficult to disperse and wet i-n water or brine so that
hydration can take place. h high degree of she~r is usually
j necessary in order to wet each gurn particle. Once dispersal
and wetting are accomplished, the hydration of the gum, as
evidenced by the development of viscosity, is quite rapid.
Xanthan gum and guar exhibit very different rheological
characteristics, having different molecular configurations, and
are obtained from entirely different sources.
There is clearly a need Eor a stable dithionite
I hydrosol composition having such pseudoplastic properties that
1 it is readily storable, even though subject to vibrations
during tank car or tank truck shipment to a textile mill or to
a pulp mill, for exarnple, and readily pumpable when thereaEter
delivered to a storage tank for dilution to a desired solids
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. 1 content and short-term storage until needed, such as for
~I bleaching textiles or woodpulp. However, our attempts to use
both guar gum and xanthan gum as suspending agents for sodium
dithionite crystals have demonstrated that they have
1~ surprisingly unpredictable tendencies from each other to form
1 either gels or settled slurries, even during quiescent
storage.
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SUMMARY OF THE INVENTION
It is accordingly an object of this invention to
provide a process for producing stable dithionite slurries,
comprising hydrosols in which dithionite crystals can be
suspended for an extended period during storage and shipment
and which are readily pumpable when needed.
It is also an object to provide storable and pumpable
dithionite slurries as new compositions which utilize xanthan
gums as the suspending component thereof.
Thus, an aspect of the invention provides a storable
and pumpable aqueous slurry of sodium dithionate, which comprises
solid sodium dithionate crystals, a xanthan gum, a chelate,
an alkali and water, wherein the xanthan gum is in such an
amount that the solid sodium dithionate crystals are stably
suspended in the water and at least 0.13~ by weight.
Another aspect of the invention provides a method
for making the storable and pumpable aqueous sodium dithionite
slurry , which comprises:
(A) preparing a dilute hydrosol containing the xanthan
gum in an amount sufficient to stably suspend sodium dithionite
crystals in the final product;
(B) sequentially adding aqueous solutions of the
chelate and the alkali ot the dilute hydrosol, while stirring
-the said dilute hydrosol, to form an alkaline hydrosol;
(C) cooling the said alkaline hydrosol to less than
about 7C in an ice bath to form a cold alkaline hydrosol;
(D) adding anhydrous sodium dithionite to the said
cold alkaline hydrosol at such a rate as to maintain its
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temperature below 7C and in sufficient amount to provide
the said slurry.
The fermentation of carbohydrates to produce bio-
synthtic water-soluble xanthan gums by the action of
~anthomonas bacteria is well known. The earliest work in
this field was conducted by the United States Department of
Agriculture and is described in United States Patent 3,000,790.
Particularly well known is the action of Xanthomonas campestris
NRLL B-1459 on a glucose subs-trate.
Xanthomonas hydrophilic colloid (i.e., xanthan gum)
is produced by transferring Xanthomonas campestris bacteria
to a suitable medium and conditioning i-t to growth through
two steps before allowing it to grow ina Einal medium contain-
ing 3% glucose. ~fter 96 hours at 30C with suitable aeration
and stirring, Xanthomonas hydrophilic colloid is produced
in approximately 1% concentration.
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~ hile Xanthomonas compestris is the bacteria of choice
for the purpose of producing the biosynthetic Xanthomonas
hydrophilic colloid, other Xanthomonas species may be employed
such as X. begoniae, X. malvacearum, X. carotenase, X. incanae,
X. phaseoli, X. vesicatoria, X. papaveriocola, X. translucens,
X. vasculorum, and X. hedrae.
There are numerous patents and publications describing
the preparation of Xanthan gum including United States Patents
Nos. 3,391,060; 3,391,061; 3,427,226; 3,455l786; 3,565,763;
3,966,618; 4,094,739, 3,773,752; 4,051,317; 4,135,979,
4,296,203; 3,919,189; 3,119,812; 3,316,241; ~,282,321;
4,299,825; and EncYclopedia of Chemical TechnoloqY, 3rd Ed.
(1980 John Wiley & Sons, pages 62-64).
Various proprietary xanthan gums, having slightly
different molecular structures and rheological properties made
from X. Campestris or mutants thereof are available from several
manufacturers including the Kelco Company under the trade
marks "Kelzan" or "Keltrol"; from Pfizer Chemical Division
under the trade mark "FLOCON"; from Rhone-Poulenc under the
trade mark "RHODOPOL 23"; from Meer Corporation under the
trade marks "MEREZON 8" and "MERETEC 30" as well as from other
manufacturers.
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For example, a widely available polysaccharide,
produced in a culture fermentation by the microorganism
Xanthomonas Campestris and sold by Kelco, a division of Merck
!
and Company, ~nc., under the trademar~ Kelzan as an
industrial-grade xantham gum, is a dry, cream-colored powder
having a moisture content of 12~, an ash content of 10~, a
specific gravity of 1.6, a bulk density of 52.4 pounds per
cubic foot, a nitrogen content of 1.2%, and a mesh size of 40.
As a 1% solution in distilled water, its pH is 7.0, its surface
tension is 75 dynes/crn, its viscosity is 850 cps as measured
with a Brookfield LVF viscosimeter at 60 rpm, and its freezing
point is 0.0C.
Another solid xanthan gum which is produced by Kelco
i under the trademark K9C57 has rheological propeeties of high
viscosity at low concentration, pseudoplastic flow over a wide
shear rate range, and a significant yield point. Such
properties indicate that the xanthan gum molecules have a rigid
molecular structure. At a very low shear rate ~below one
I reciprocal second), this mutant xanthan gum exhibits more
Newtonian flow than the Kelzan gum. Sold as a dry powder, its
solids content is 85 92~. As a 1% solution in distilled water,
its pH range is 6-8 and its viscosity is 630-1000 cp.
A whole xanthan broth, having a viscosity in the range
of 3500-4500 cps, which is readily pumped or poured and has an
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observable yield point at biopolymer concentrations above 0.1%,
is available as FLOCON Biopolymer 4800 from the Pfizer Chemical
Company at biopolymer concentrations of 13.8% or 3.7%. This
material is described in United States Patent 4,11g,546. ;'
The aqueous broth is believed to be made from a mutant strain of
Xanthomonas Campestris. It is preserved with formaldehyde and
-
never exceeds 1.5% concentration of unreacted sugar. It is a
tan gelatinous fluid in appearance. It has an apparent content
of active purified carbohydrate that is higher than commercial
solid xanthan.
Solutions of FLOCON 4800 are highly pseudoplastic in
nature so that the viscosity, which decreases upon exposure to
high shear, is fully restored when solutions return to low-
shear conditions. Solution viscosities of this biopolymer are
not affected by pH in the range of 5-12.
It is to be understood that any and all forms of
xanthan gum are operable in the instant invention providing the
slurry does not contain an alkaline tripolyphosphate such as
sodium tripolyphosphate. It is only when said tripolyphosphate
is present that certain modifications must be followed as will
be later explained.
*Trade Mark
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In general, a suspendable, pourable, and purnpable
dithionite slurry free of tripolyphosphates can be prepared
with as little as 0.25 pound of xanthan gum per 100 pounds of
' slurry (0.25~ xanthan content) gum. This amount is equivalent
Il to about 146 pounds of commercial hydrosulfite per pound of
xanthan. The slurry is non-settling and completely pourable at
any desired solids content within the utility limits imposed by
slurry viscosities. Such slurries, for example, are readily
~ poured and pumped at viscosities of up to 8,000 cps.
~ However, by tolerating a slight settling, a soft and
di.spersible settled .slurry containiny as little as 0.20%
xanthan gum is obtained. Such a partially suspended but
dispersible slurry is useful for many purposes, such as for
shipping over relatively short distances. This quantity is
equivalent to about 182 pounds of hydrosulfite per pound of the
xanthan gum, exemplified by a slurry comprising 36.4
hydrosulfite and 0.20% xanthan gum.
Preferably, the slurries comprise at least about 20%
of hydrosulEite, a chelate, and an alkali, so that the slurries
I have a pH of at least about 10. The alkali is suitably sodium
hydroxide. Other bases can be used such as potassium hydroxide
or soda ash. Howeve~, sodium hydroxide is preferred
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particularly over soda ash since less is needed on an
equivalent weight basis to achieve the desi:red pH.
The method of making the storable and pumpable
dithionite slurry from sodium hydrosulfite comprises,
(A) preparing a dilute hydrosol (from for example
a l~ aqueous solution) of xanthan gum in an amount sufficient
to stably suspend sodi.um dithionite crystals in the final
product, such as a solution containing about 0.13 - 0.25%
by weight of xanthan gum;
(B) sequentially adding aqueous solutions of the
chelate and the alkali (which is for example 50~ NaOH solution),
while stirring the above solution to form an alkaline hydrosol;
(C) cooling the resulting alkaline solution to a
temperature below 45F (7C) preferably slightly above 32F
(0C) in an ice bath, to form a cold alkaline hydrosol; and
(D) adding the anhydrous sodium dithionite to the
cold solution at such a rate as to maintain its temperature
below 45F (7C) and in sufficient amount to provide the slurry,
which preferably contains 28-36% of sodium dithionite (commer-
cial grade) and has a pH oE at least 10.
When the slurries are to be utilized for textilebleaching, they preferably comprise, on a weight basis, at
least about 36~ of commercial sodium dithionite, at least
about
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3% of sodium hydroxide as the alkali, at least about 0.25% of
mixed chelates, and at least about 0.25% of xanthan gum such as
Xelzan grade. The viscosity is within the range of 6000-8000
cps~ Quite obviously, lesser amounts of dithionite can be used,
e.g., 20% on a pure basis but the above ranges are preferred.
When the slurries are to be utilized for woodpulp
bleaching, they additionally comprise at least about 3% by
weight of sodium carbonate and approximately 2% by weight of
sodium tripolyphosphate; see United States Patent 3,985,674.
For example, the chelate is the tetrasodium salt of ethylenedia-
mine tetraacetic acid and is at least about 0.08% by weight of
the slurry.
It is precisely when sodium tripolyphosphate is
present that difficulties arise for reasons which are not fully
understood. As has heretofore been stated, all forms of
xanthan gum are operable to produce the tripolyphosphate-free
slurries. However, when tripolyphosphate is present, all forms
of xanthan are operable at any one data point and two forms of
xanthan are operable at all data points. The two forms of
xanthan which are broadly applicable are "K9C57 " and "FLOCON
*
4800 " previously described. In fact, when these two forms of
xanthan gum are used, they can be present in concentrations as
low as 0.13 weight percent.
*Trade Mark
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19 - 65284-58
The one data point whereln all forms of xanthan
are operable ls 28% by weight of commercial sodlum
dithionite, 0.17% by welght of xanthan gum, 1.92% of Na5P3O10,
3.28 - 3.29% by weight o:E Na~CO3, 0~78% by weight of sodium
hyclroxi.de, 0.08% o~ a chel~te, and water.
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EXAMPLES
Experimental work to produce a storable and then
pumpable dithionite slurry utilized a formate-derived sodium
¦ dithionite (F/hydrosulfite), having an average content of 88%
to 89% of pure Na2S2O4. In many experiments, the
F/hydrosulEite was used as a component of two types of
commercially distributed bleaching preparations: (1) a textile
bleaching system and l2) a wood pulp bleaching system, both
being proprietary blends. These slurries are stable for at
least three weeks during storage at 32-40F. The physical
properties of the slurries are as follows:
I'extile SlurryWoodpulp Slurry
Density 1.4 g/ml 1.4 g/ml
pH 13 10-11
; Appearance White White
Viscosity* 6000-8000 cps3000-4000 cps
Freezing Point 17-18F 16-17F
*Saybolt Viscosimeter
I The lab stirrer used in these experiments was a Model
HS of the Jiffy Mixer Company Inc., Irvine, California.
20 -
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. Examples l - 13
Attempts to prepare dithionite slurries which would
neither settle or gel, thereby creating unpumpable shipments,
1 began by addiny eight materials having either thickeniny or
charge repulsion characteristics to the dithionite slurries
containing 35% F/hydrosulfite. All of these slurries were
determined by observation to be unsatisfactory, as noted in
Table I.
- 21 -
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~1 ~1 ~ tl) tU tU tU tU a) Q) tI U ~ Or~l
L~l I O U~ Y ,Y Y X X X ~ t~ X X X X t7) tU l ~ ~ h
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FI~ rl O O .rl I ~ n~ .n L~ h ~I h ~I rd 1-- ~, I
r~ ) C L~ ra ~a r-l r~ nJ rd nd I ) ~J ~ r-l ~ I L~
rJ rd rJ O O tU ru nJ r~ d 11~ tU O r~ r~ r-~
Fl~ tn tn tn tn t~ t~ t~ Ln tn ~n Z Z Z ~n O tU
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nd r. tn
nd U r-l rd
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r~ r~ r~ r I
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Examples 14 - 23
Experiments were then conducted with guar gum as a
suspending agent for two types of E/hydrosulfite slurries that
are marketed as bleaching systems. Examples 14 - 19 utilized
the textile bleaching type and are given in Table II. Examples
20 - 23 utilized the woodpulp bleaching type and are given in
Table III. In both tables, "~ F/hydro" indicates the weight
percentage of formate-derived sodium hydrosulfi.te that was used
in the slurry. As noted in these two tables, none of the
1.0 guar-thickened slurries was satisfactory, as was readily
determinable by observat.ion.
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- 23 -
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-25--
Examples 24 - 36
A 1% solu-tion of Kelzan xanthan gum in water was first
prepared for Examples 24 - 26 and 29 - 35. An appropriate
weighed amount o~ this solution was added to predetermined
amounts of water, then an alkali and a chelate were added. The
alkali was in the form of 50% NaOH. The che:Late was either the
sodium salt of ethylenediamine tetraacetic acid (EDTA) or
Hampene OH , a liquid mixture of chelating agents sold by the
Organic Chemicals Division of W.R. Grace and Company, Nashua,
New Hampshire.
The solution was cooled to 32F, and the solid
F/hydrosulfite was added at such a rate as to maintain the
temperature at 40-45F. The slurry was then returned to the
cooling bath and checked in three days for its pourability, etc.
The use of xanthan gum is shown at various levels in a
textile bleaching slurry in Table IV. The parts bv weight of
the l~ xanthan solution are given as parts by weight of xanthan
gum for each example. Although the complete flowing of Example
24 is preferred, the slight settling and flowing of Examples 25
and 26 is suitable for some usages, particularly for shipment
situations involving relatively mild vibrations or short times
of transit~
*Trade Mark
-26-
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27
7~8
!l
Examples 27 and 28 were prepared by dissolving the
xanthan gum (Kelzan grade) in 21~ of the total amount of water
that was used to form a hydrosol. The NaOH solution and the
chelate were then added to the remainder of the water and the
admixed solution was chilled to about 35C. The crystalline
F/hydrosulfite (88% Na2S2O4) was then added to the costic
solution with cooling to maintain a temperature of 45C. To
this aqueous slurry, the hydrosol was added to produce a stable
j slurry that did not settle within three days. After two days
lll of storage at about 35C, the slurry of Example 27 had a
i viscosity of 7,120 cps; the slurry of Example 28 had a
viscosity o~ 7,9~0 cps.
1~ Examples 29 - 36, taken with Examples 24 - 28,
il demonstrate that all forms of xanthan gum are operable.
, Example 29 utilized Kelzan-~i7, Examples 30 - 32 utilized
Kelzan-S, Example 35 utilized K9C57 - all products oE Kelco.
, Examples 33 and 35 utilized FLOCON (3.7%) and Examples 34 and
l 36 utilized FLOCON (13.84~) - both products of Pfizer.
20 1,
.
- 28 -
'.j
,
7~
Examples 37 - 48
The following examples will illustrate that various
concentrations oE commercial sodium hydrosulfite (i.e., 88-89
pure) can be used to form pumpable slurries with xanthan gum
1~ whereas guar is totally inoperable. The results are shown in
Table V.
10 1 `
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- 29 -
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~30--
~2~7~8
Compositions Containiny Tripolyphosphate
As indicated earlier, compositions containing
polyphosphates show a scatter of results with the exception of
FLOCO~ of Pfizer or K9CS7 of Kelco except at one data point
where all forms of Kelzan gum are operable. The following
Examples will illustrate this.
l - 31 -
~ . ,
~2~
Examples 49 - 65
Experiments to produce a storable but pumpable slurry,
using the woodpulp bleaching system, comE~rised first making a
¦ 1% aqueous solution of Kelzan gum and then adding an
appropriate amount of this solution to water for Examples 48 -
63. The next additions to the water were solutions of sodium
carbonate, sodium tripolyphosphate, chelate, and then 50% NaOH
solution. The entiee solution was then cooled to 32F in an
~l ice bath. The required amount of solid (crystalline
' F/hydrosulfite) was added at such a rate so as to maintain the
temperature below 45F. The slurry was then again cooled in
the ice bath for three days and observed for separation,
settling, and pourability.
¦I Examples 64 and 65 were prepared similarly to Examples
27 and 28 by dissolving the xanthan gum in 12~ of the total
water to form a hydrosol and then adding the Na2CO3, the
Na5P3O10, the NaOH solution, and the chelate. Then the
solution was cllilled to about 35C. The solid, crystalline
~ F/hydrosulfite, was added with cooling to rnaintain a
I temperature of 45C. To this aqueous slurry, the xanthan
! hydrosol was added to produce stable slurries which had not
settled after three days of storage. The slurry of Example 64
had a density of 1.37 g/ml and a viscosity of 3,900 cps. The
slurry of ExaMple 65 had a viscosi:y of 4,040 cps.
- 32 -
I .
,1 "
~2~7~
! I '
,
The following examples in Table VI illustrate the
criticality of the xanthan concentration, all observations
being made after three days in a wet ice bath and all
I percentages being given on a weight basis, without correcting
'I for the impurity in the F/hydrosulfite. Correcting for the
;; impurity in the F/hydrosulfite by multiplying by 0.885 as an
average value, the amount of pure Na2S2O4 in the
F/hydrosulfite of the examples is as follows:
Pure
F/hydro, % ~a2_2_4
27 23.9
` 2~3 2~.3
26.6
3.l 27.9
36.4 32.2
As can be seen, only Examples 49, 63 and 64 gave acceptable
~ results.
-- 33 --
I,
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~2~7~
-34- 65284-58
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-34a- 65284-58
* Ratio = Mols 100% Na2S2o4
Mols Na5P3Olo + Mols Na2~ 3
**Examples 29-34, 44, 45 - EDTA-Na4
**Examples 38-43 - Hampene OH-l
~1
~Z~7~
xamples 66 - 70
The following two examples in Tables VII illustrate
the use of Pfizer's FLOCON Biopolymer 4800 as a 13.8% FLOCON
broth in Example 66 and a 3~7% FLOCON broth in Example 67 at
0.19% Xanthan with a woodpulp slurry, both having been made
with F/hydrosulfite.
Experiments with K9C57 xanthan gum are given as
Examples 68 - 70 in Table VIII to illustrate the use of this
,I xanthan in woodpulp slurries that would ordinarily set up or be
ll in some way unstahle with Kelzan gum. The ratio in the
next-to-last column i.s obtained by dividing the total mols of
sodium tripolyphosphate (expressed as Na5P3O10) plus mols
Na2CO3 into the mols of 100~ Na2S2O4. Ideally, this
ratio should be around 4.0 plus/minus 0.2 for the use of
Kelzan. Excursions above and below this ratio require the use
of K9C57 or the FLOCON Biopolymer.
On a weight basis, lt appears that biopolymer broth is
approximately equivalent to the solid xanthan which is sold
under the trademark K~C57 in its ability to produce a
l hydrosulfite slurry of acceptable storage and pumping
, capability.
'
I j .
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', - 35 -
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-36- 65284-5~
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--37-- .
