Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1~774SZ
The present invention relates to the use of
particular ethylenically unsaturated polymers and in~
organic salt dispersant materials to achieve a reduction -
in the water demand of finely-divided solids in water.
It relates particularly to this use as an improvement in
wet process production of portland cement.
More particularly, the present invention relates
to the use of particular polyelectrolytes of low mole-
cular weight or styrene-maleic anhydride copolymers and -
inorganic salt dispersant materials to achieve a reduc-
tion in the water demand of finely-divided solids in
water.
It is known that polyelectrolytes such as
polyacrylic acid salts, copolymers of acrylic acid and
acrylamide, hydrolyzed polyacrylonitrile and the like
which are flocculants at higher molecular weights
show different properties and act as dispersants at
lower molecular weights show different properties and
act as dispersants at lower molecular weights. Such
polymers having molecular weights from a few thousand
up to about 50,000, for example, have been recommended
for use in various dispersant applications. See, for
example, U.S. Patent Nos. 3,534,911 and 3,604,634,
relating to the grinding of calcium carbonate.
Combinations of polyacrylates and certain in-
organic compounds have also been used in forming foundry
sand compositions and in clay benefication and drilling
fluids and muds. For example, polyacrylic acids and
alkali metal salts, e.g., sodium carbonate, sodium
silicate and the like are disclosed in U.S. Patent No.
--, '.
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2,702,788 as resulting in increased drilling and Vi8-
cosity and, hence, an increased yield of mud is obtained.
Typically, the polyacrylates are used in amounts of
about 0.1 percent or more and the sodium carbonate in
amounts of from about 3 percent, or more. See also U.S.
Patent Nos. 3,583,911, 2,552,775 and 3,220,946, which
generally disclose similar applications. -
It is also known that copolymers of maleic
anhydride and divinyl ether, ethylene, propylene butylene
and isobutylene or mixtures of olefins and hexadiene-1,5
function as water-loss preventives in drilling fluids.
See U.S. Patent No. 3,157,599.
The above copolymers have also been employed
with alkali metal compounds in preparing beneficated
clay compositions for use in drilling fluids. U.S.
Patent No. 3,216,934 teaches the use of such copolymers
with from 1 to 7 percent by weight of an alkali metal salt
such as, for example, alkali metal carbonates, hypo-
phosphites, oxalates, phosphates, silicates, sulfites
and tartrates, to increase yields of clay. Similarly,
U.S. Patent No. 3,220,946 discloses the use of such
maleic anhydride copolymers and certain alkali metal
salts in clay benefication of sodium bentonites only.
Salts selected from the group consisting of sodium for-
mate, calcium formate, calcium acetate, sodium thiocyanate,
sodium sulfate, magnesium sulfate, calcium sulfate,
lithium sulfate and potassium sulfate are employed to
provide a postulated synergistic response with the
copolymer in changing the rheological properties of
clay. Salts such as sodium chloride, sodium bicarbonate,
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calcium carbonate and calcium chloride, however, are
taught as being ineffective for ~uch uses.
It is also known that styrene-maleic anhydride
copolymers are useful as water-demand reducing agents
in the wet process for producing portland cement. Such
copolymers are employed in amounts from 0.01 to 0.1
weight percent. See U.S. Patent No. 3,923,717.
A two-part study by the Portland Cement
Association, Chicago Illinois, entitled "Slurry Thinners"
(Part I, Clausen et al., May 1953, Part II by Dersnah,
March 1955) discloses the evaluation of various in-
organic salt dispersants and mixtures thereof with other
surface active agents in reducing the water content of -
cement slurries in wet process applications.
Of the above prior art references only the
'717 patent and the Portland Cement Association Study
relate to a wet grinding process for making portland
cement, wherein limestone and clay and, optionally, a
small amount of iron oxide are ground in the presence
of water to obtain a slurry of very fine particles.
Such slurry is then fed into a high temperature kiln
where it is dried and calcined to form the clinker which
is then ground to make portland cement. The water
demand of the finely ground limestone-clay slurry is
fairly high and usually requires a relatively large
proportion of water, for example, from 30 to 50 percent
by weight, usually from 25 to 35 percent, to obtain a -
fluid, pumpable slurry. This limits the rate at which
the slurry can be processed and fed to the kiln and it
also requires a large fuel input to dry and calcine a
given quantity of solids to the clinker stage.
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Many substanceæ with dispersant activity are
available and have been tried in order to decrease the
water demand of æuspended inorganic æolids in various
high solids water suspensions or slurries for various
applications. Most of theæe, particularly in the wet
process for making portland cement, have proven rela-
tively ineffectlve or undeæirable for one reason or
another. Complex phoæphateæ are undesirable because
they tend to hydrolyze at the warm temperatures developed
during grinding and in storage of the slurry and because
of the adverse effect of residual phosphate on the -~-
properties of the final portland cement product. Ligno-
sulfonates, alone and in combina~ion with inorganic salt
dispersants have been tried for this use, but these
require high addition levelæ for only marginal improve-
ment. They alæo lose their activity rapidly during
storage of the slurry. Many materials are alæo too
expensive to be economically utilized in such operations.
It has now been discovered that the water
demand of suspended inorganic solids necessary to make
a pumpable slurry in the wet grinding process for making
cement can be significantly reduced by use of a combination
of water-demand reducing agents as described below.
Specifically, it has been discovered that
mixtures of low molecular weight polyacrylic acid salts
or mixtures of water-soluble salts of styrene-maleic
anhydride copolymers and an inorganic compound such as
alkali metal salts of carbonates, bicarbonates, silicates,
oxalates, aluminates and borates and ammonium salts of
carbonates, bicarbonates, oxalates and borates which
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form insoluble salts with calcium, are unexpectedly
effective for reducing the water demand of solids sus-
pended in water while maintaining desired pumpability
levels of high solids-content aqueous suspensions, par-
ticularly those encountered in the wet process for making
portland cement. The action of the polyacrylic acid
salt or the copolymers of styrene-maleic anhydride
(hereinafter "SMA") in combination with the selected
inorganic compound (hereinafter collectively referred
to from time to time as "water-demand reducing system
or agent(s)") represents true synergism, said combinations
effectively reducing the water demand of suspended solids
at concentrations where neither additive alone is as
effective.
These water-demand reducing agents are extremely
effective for reducing water demand while maintaining
desired vi~cosity levels for pumping purposes in various
kinds of high solids suspensions in water of finely
divided minerals, particularly in raw cement slurries
consisting largely of limestone and clay, usually with
a small amount of iron oxide. In this latter application
especially, the above-described water-demand reducing
system has a unique combination of efficiency, stability
and compatability in the wet grinding process slurried
together with a lack of any adverse effects in the cal-
cining process. A reduction in water content can be
achieved so that, with the same volume feed to the cement
kiln, increases in production can be obtained with lower
fuel costs. Increasing the feed rate to the kiln while
operating at normal fuel input results in even further
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increases in clinker production. Retardation of set
times are al~o obtained by use of the water-demand re-
ducing system when recycle kiln dust (high in calcium
oxide) is added to fresh cement kiln feed.
The invention resides in a wet process for the
production of cement solids wherein limestone and clay
are ground in the presence of water to form a pumpable
kiln feed slurry, comprising the step of adding to said
slurry an amount of a water-demand reducing system
sufficient to synergistically reduce the water demand
of said slurry, said system comprising (1) a water-soluble
salt of an ethylenically unsaturated polymer having a
molecular weight of from 1000 to 50,000 and (2) an in-
organic compound selected from alkali metal salts of
carbonates, bicarbonates, oxalates, silicates, aluminates
or borates or ammonium salts of carbonates, bicarbonates,
oxalates or borates, (1) and (2) being employed in a
ratio of from 1:1 to 1:80.
The polyacrylic acid salt which can be employed
in thi~ invention can be any such polymer salt having an
average polymer ~olecular weight in the range of from
2000 to 50,000 and preferably in the range of from 2000
to 20,000. An especially preferred molecular weight is
in the range of from 5000 to 10,000. The preferred polymer
molecules are further characterized in that one-eighth
one-half of them have terminal sulfonate groups. In
another embodiment, polymers having a viscosity of from
75 to 150, preferably from 75 to 110, cps at 30 percent
by weight solids and a molecular weight range from 5000
to 10,000 are preferred. The salt of the acid may be that of
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alkali metal or ammonium salts, such as sodium or potas- -
sium. However, the sodium and ammonium salts are preferred
over other alkali metal salts. -
Polymers of acrylic acid which are useful in
S this invention are readily prepared from the monomer by
the action of heat, light, and/or catalysts. Catalysts -
which are particularly effective for this polymerization
are the organic peroxides. The properties and nature -~of the polymer can be varied over a considerable range
by the proper choice of catalysts and/or reaction condi-
tions. The polymer can be further modified by the
addition of small amounts of copolymerization agents,
such as acrylamides, acrylonitrile, methyl acrylate, ethyl
acrylate, 2-methyl propenoic acid and the like. These
copolymers of acrylic acid containing up to about 10
percent by weight of the copolymerization agent are
useful and operable in the application of this invention.
Certain preferred polyacrylates of the present
invention are most advantageously prepared by polymerizing
acrylic acid in aqueous solution from 50 to 170C in
the presence of a redox polymerization catalyst system.
The acrylic acid and a peroxy catalyst are separately
and continuously dispersed into the aqueous medium at
rates such that an effective and substantially constant
concentration of the catalyst system is maintained in
contact with the acrylic acid throughout the polymer-
ization. A sulfite reducing agent, the preferred other
component of the redox catalyst system, can be combined
with the acrylic acid and the two added as a single
aqueous solution, but preferably, the reducing agent
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is added separately and continuously as a third stream.
Suitable sulfite reducing agents include sodium metabi-
sulfite, sodium sulfite or bisulfite, sodium formaldehyde-
sulfoxylate, sodium formaldehyde hydrosulfite.
Other reducing agents can be used to obtain
polymers of essentially the same molecular weight and
molecular weight distribution, but which differ in not
having terminal sulfonate groups and which may be
slightly less advantageous in some solids suspensions.
A hypophosphite such as sodium or ammonium hypophosphite
can be used as the reducing component of the redox catalyst
system to obtain polymers having the same proportion of
terminal phosphonate groups in place of the sulfonate
groups derived from a sulfite. Other reducing agents
provide the low molecular weight distribution effects
although these do not supply tlle terminal sulfonate or
phosphonate groups which are of added advantage, par-
ticularly in reducing foaming tendencies. These reducing
agents include urea, potassium thiosulfate, and oxidizable
salts such as ferrous sulfate.
The peroxy catalyst component can be any peroxide
useful as a polymerization catalyst. Suitable peroxides,
which preferably are water soluble, include hydrogen
peroxide, tert-butyl hydroperoxide, and salts of per acids
such as sodium persulfate, potassium percarbonate, ammonium
peracetate, sodium perbenzoate, sodium perborate, diiso-
propyldipercarbonate and the like.
The concentration of peroxygen-containing catalyst
can vary widely within limits from 0.1 to 10 percent
based on the entire polymerization mixture and referring
to active catalyst present in the system at any one time
.
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during the process. Preferably, the amount of aqueous -
medium and the rates of addition of catalyst and acrylic
acid are adjusted so that a relatively high peroxy catalyst
concentration is maintained. Total peroxy catalyst used
based on the acrylic acid is preferably from 0.5 to 5
mole percent. The reducing agent is employed in at
least a molar equivalent amount based on the peroxy
component and preferably is used in a quantity from 20
to 100 percent excess. Both components of the redox
catalyst system are preferably added as aqueous solutions
of relatively high concentration. - -
The aqueous polymerization medium is preferably ~-water but it may include up to about 30 percent by volume
of a water-miscible organic solvent such as acetone, a
lower alkanol, or dimethyl sulfoxide. Efficient stirring i
of the polymerization mixture or agitation by other
effective means is required so that the streams of peroxy ~-
catalyst, reducing agent, and acrylic acid are quickly
and thoroughly dispersed and intimately mixed in the
polymerization medium. Superatmospheric pressure may be
advantageous.
Other modes of polymerization may also be
employed. These are well known in the art and the par-
ticular process of preparing the polymers is not critical
to this invention.
The polymer product is used in the form of a
water-soluble salt, usually the sodium salt. Other such
salts will serve as well, for example, the potassium and
ammonium salts. Surprisingly, these low molecular weight
polyacrylate salts in combination with an inorganic salt
17,899A-F -9-
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are substantially more effective in maintaining fluidity
of aqueous suspensions, particularly high solids mineral
suspensions, than analogous polymers of similar molecular
weight. Thus, corresponding polymers such as polyacryl-
amide, acrylamide-acrylic acld copolymers are inferior in
this activity to the polyacrylates described herein even
though these related polymers do havè dispersant properties.
Examples of other suitable water-soluble anionic
polymers include trademarked products such as, for example,
Dispex N-40, which is manufactured by Allied Colloids
Manufacturing Company Ltd., Daxad (available from the
W. R. Grace Co.) and Tamol 850 (Rohm and Haas). Other
suitable materials available in acid form would include
Goodrich K732 (Goodrich Tire and Rubber Co.) and Uniroyal
ND2 (avaiable from Uniroyal Corp.).
The styrene-maleic anhydride copolymers which
are useful in the present invention can be made by known
processes such as are disclosed, for example, in U.S.
Patent No. 2,606,891; No. 2,640,891 or No. 3,085,994.
It is to be understood, however, that the process of
making the styrene-maleic anhydride copolymer is not
critical to this invention. Any styrene-maleic anhydride
copolymer, within the molecular weight range and the
mole ratio specified herein can be used, without regard
to its method of preparation. The water content of the
finished slurry can be as low as 25 percent and as high
as 35 percent, by weight.
The styrene-maleic anhydride copolymer product
is used in the form of a water-soluble salt, usually the
sodium salt. Other such salts, for example, the potassium -;
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~077452
and ammonium salts will also serve, but not as well as
the sodium salt. Surprisingly, these copolymeric salts
are very effective in maintaining fluidity of the aqueous
high solids mineral suspensions.
The water-soluble inorganic salts of copolymers
of styrene and maleic anhydride which can be used in the
present invention are those having a molecular weight of
from 1000 to 5000. These copolymers are further charac-
terized by a ratio of from 50 to 67 mole percent of
styrene and from 50 to 33 mole percent of maleic anhydride.
The preferred copolymer molecules have a molecular weight
of from 1200 to 3000 with a mole ratio of styrene to
maleic anhydride of 1:1. These are particularly effec-
tive as a component of the water-demand reducing system
for limestone-clay suspensions used in wet grinding
process for making cement.
The inorganic compound employed in the water-
-demand reducing system is a water-soluble salt of ammonium
or an alkali metal radical which will form an insoluble
salt with calcium and acts synergistically with the poly-
acrylic acid salt or the SMA copolymer. The water-soluble
inorganic salts which may be employed in the present
invention are those which form insoluble salts with cal-
cium and are selected from alkali metal salts, i.e.,
sodium or potassium salts, of aluminates, borates, oxalates,
carbonates, bicarbonates and silicates or ammonium salts
of borates, oxalates, carbonates and bicarbonates. Alkali
metal silicate salts, especially orthosilicates, are -
preferred as they exhibit the least tendency for the
visco ity improvement to show some tendency to diminish
17,899A-F -11-
1~77452
upon standing for periods of 18 hours or more although
such viscosity reversion tendency is a significant factor
to consider where slurries are temporarily stored prior
to processing. Especially preferred are the alkali
metal carbonate, bicarbonate and silicate and ammonium
carbonate and bicarbonate salts. Where more alkaline
slurries are employed, or where kiln dust having a high
calcium oxide content is recycled to the slurry, the
metal silicate and waterglass silicate salt forms are
preferred whereas the orthosilicate form is desirably
employed in less alkaline slurries. Similar consider-
ations as to slurry alkalimity apply where less basic
ammonium salts are utilized.
The water-demand reducing agents of the present
invention can be added to the cement slurry sequentially
or as a premixed solution. When added sequentially, it
is desirable that the inorganic salt be added first,
followed by the polyacrylic acid salt or by the SMA co-
polymer. Preferably, the agents are added sequentially
to the slurry, although the premix will be advantageous
in certain situations.
In general any combinations of the polyacrylate
or the SMA copolymer and of the inorganic salt which act
synergistically to reduce the water demand of high
solids-content aqueous suspensions are considered to be
within the scope of the present invention. Generally,
ratios of the polyacrylate salt to inorganic salt range
from 1:1 to as high as 1:80, although ratios of from 1:1
to 1:10 are preferred. An especially preferred ratio
range is from 1:1 to 1:~. A ratio of 1:4 consitutes a
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preferred embodiment. Ratios of the SNA copolymer salt
to inorganic salt range from about 1:1 to as high as about
1:10 although ratios of from 1:1 to about 1:6 are preferred. --
An especially preferred ratio range is from 1:1 to about
1:4. A ratio of 1:3 constitutes a preferred embodiment.
The ratio employed will, as those skilled in the art will -~-
recognize, vary depending upon the concentration of the ;
water-demand reducing system employed, the viscosity
required for a particular operation, the grinding time,
the type and composition of cement slurry being treated,
and the like. Generally, in treating portland cement
slurries, it has been found that concentrations of from
0.005 to 0.06 weight percent (based on slurry solids) of
the polyacrylic acid salt used in comblnation with from
0.05 to 0.4 weight percent inorganic salt produce syner-
gistic reduction of slurry water demand. In a preferred
embodiment, concentrations of from 0.01 to 0.05 weight
percent polyacrylic acid salt and from 0.05 to 0.2 weight
~- percent inorganic salt are employed. In another embodiment,
polyarcylic acid concentrations of from 0.01 to 0.05
~~ weight percent and inorganic salt concentrations of from
0.1 to 0.2 weight percent are preferred. Concentrations
of from 0.0025 to 0.0125 weight percent (based on slurry
solids) of the SMA copolymer salt used in combination
with from 0.008 to 0.04 weight percent inorganic salt
produce synergistic reduction of slurry water demand. In
a preferred embodiment, concentrations of from 0.003 to
0.009 weight percent SMA copolymer salt and from 0.009 to ;
0.02 weight percent inorganic salt are employed. In
another embodiment, SMA copolymer salt concentrations of
- ~ .
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1077452
from 0.003 to 0.006 weight percent and inorganic salt
concentrations of from 0.009 to 0.02 weight percent are
preferred.
Those skilled in the art will recognize that
it is difficult to establish any one preferred concen-
tration range for the polyacrylates or SMA copolymer and
inorganic salts as this will depend upon the viscosity
required for a particular operation as well as the parti-
cular type of high solids suspension being treated. There
are, for example, many different types of known and
commercially available cement slurries of varying com-
positions which can be treated according to the present
invention. The desired synergistic concentrations can
- readily~be determined by those skilled in the art according
to known procedures and by those illustrated in the exam-
ples set forth below.
In the wet process for making portland cement,
the raw materials, including ingredients such as limestone,
dolomite, oyster shells, blast furnace slag or other well
~20 known high calcium-containing products, are mixed with ~ -
silicious materials, including slag, clay, shale or any
other silica containing ingredient in amounts such that ~ -
the calcium and silica materials constitute about 85 percent
by weight of the clinker formed after heating in a kiln.
The remaining ingredients include aluminum-containing and
iron-containing ingredients. The mixture of raw ingredients,
using well-known process steps, is ground with addition of
water to prepare an aqueous kiln feed slurry, which is
then screened and pumped into storage tanks preparatory
~30 to further blending with other slurries or feeding into
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a clinker kiln. Usually, the portion which passes a 200
mesh screen is used for preparing the clinker. Such
slurries usually contain from 30 to 50 percent by weight
water.
On an emperical basis, the cements made by
grinding the resulting clinker will contain
SiO2 19-23%
A123 4-8%
Fe2O3 1.5-6%
CaO 62-67%
MgO .6-5%
Pumpable aqueous kiln feed slurry compositions
containing from 0.005 to 0.06 weight percent (based on
slurry solids) polyacrylate and from 0.05 to 0.4 weight
percent inorganic salt constitute another preferred em-
bodiment in the wet process for making portland cement.
Preferably, such slurry compositions contain from 0.01
to 0.05 weight percent polyacrylic acid salt and from
0.05 to 0.02 weight percent inorganic salt.
Compositions containing SMA copolymer to inor-
ganic salt ratios of from 1:1 to 1:10, preferably from
1:1 to 1:4, constitute preferred embodiments in the wet
process for making portland cement. Preferably, such
slurry compositions contain from 0.0025 to 0.0125 weight
percent SMA copolymer salt and from .008 to .04 weight -
percent inorganic salt. Premix concentrate compositions
containing SMA copolymer to inorganic salt ratios of from
1:1 to 1:10, preferably from 1:1 to 1:4, and most prefer-
ably about 1:3, constitute additional embodiments of the
present invention.
,
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The following examples are presented to
illustrate the invention, but are not to be construed
as limiting it in any manner whatsoever. The weight
percent of water-demand reducing agents, unless other-
wise specified is based on the solids present in the slurry
being treated.
Example 1
The following illustrates the preparation of a
polyacrylic acid which may be utilized in the present in-
vention.
A reaction flask having multiple inlets and
equipped with an efficient stirrer was charged with 1600
ml. of water and the water was heated to boiling. At
this point, separate streams of 25 percent aqueous sodium
persulfate and 25 percent aqueous sodium metabisulfite -
were started into the boiling water. After 1-2 minutes,
a third stream of acrylic acid was started into the boiling
and agitated solution. All three streams were continued at
essentially constant rates under the above conditions so
that in about 90 minutes there had been added 1250 gm. of
acrylic acid (17.3 gm. moles), 400 gm. of 25 percent aqueous
metabisulfite solution (0.526 gm. mole), and 300 gm. of 25
percent aqueous persulfate solution (0.315 gm. mole). Rates
were calculated so that addition of acrylic acid was
completed 1 to 2 minutes before all of the persulfate and
bisulfite had been added.
The reaction product was a clear, slightly
viscous solution. To it was added about the theoretical
quantity of 50 percent aqueous NaOH to convert the poly-
acrylic acid product to its sodium salt, having final
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pH about 10. Vapor phase osmometric and membrane osmometric
analysis of the product after dialysis to remove inorganic
salts indicated respectively that the polymer (sodium form)
was polyacrylic acid from 5000 to 10,000 molecular weight
S and a viscosity of from 75 to 110 cps at 30 percent solids.
Elemental analysis indicated that about one-fourth of the
- polymer molecules were terminated by a sulfonate group.
Example 2
- Various commercial samples of portland cement
slurries were treated with polyacrylic acid salts and
inorganic salt dispersants, both alone and in combination
and the degree of reduction in water-demand of the
dispersed solids was determined. In typical operations,
a sample quantity of a ground, undried cement slurry is
filtered to concentrate the same and raise the slurry
solids content. About 100 ml. of such concentrated slurry
is then stirred vigorously and the viscosity is deter-
mined with a Brookfield Helipath ~iscometer. The slurry
sample i8 diluted with a measured volume of filtrate,
usually O.S ml. to S.0 ml., mixed and the viscosity re-
determined. This process is repeated until a viscosity
of less than about 4000 cps is obtained. Approximately
10 gms. of each slurry sample is weighed, evaporated to
dryness at about 120C and reweighed. From the percent
solids 80 obtained, a control logarithmic plot of vis-
cosity versus percent solids is prepared and the percent
solids at 4000 cps, (a viscosity value which is in the
range preferred for pumpability in the wet process pro-
duction of portland cement) is determined.
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7745Z
Inorganic salt test reagents are added to the
cement slurry as received and the slurry concentrated as
above and the viscosity versus solids plot determined.
The polyacrylate test materials or polyacrylates in
combination with the inorganic salt are added to the
cement slurry after the same has been concentrated as
filtration of the cement slurries containing these addi-
tives are well dispersed and are difficult or impossible
to filter. Viscosity and solids determinations are -
similarly plotted. ~
Comparisons of the solids density determinations -
at 4000 cps for the untreated control slurries with
slurries treated with each dispersant above and in com-
bination can then be made to determine the degree of
reduction in the water-demand of suspended solids.
In operations employing the above procedures, ~
samples of portland cement slurry (obtained from the ;
Oregan Portland Cement Co.) were treated with: -
(1) 0.05 percent of the polyacrylate of Example -`
1 above;
(2) 0.2 percent of sodium carbonate (added
before the slurry is concentrated);
(3) 0.2 percent sodium carbonate (added before
the slurry is concentrated) and 0.05 percent ~
of the polyacrylate of Example 1 above; -
(4) a premixed combination of the same ingred-
ients and amounts thereof used in (3).
The untreated cement slurry was found to have a
solids density of about 63.25 percent at a viscosity of
4000 cps whereas the slurry treated with the polyacrylate
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alone (1) was determined to have slightly increased solids
density of 65.8 pexcent at 4000 cps. The slurry (2) treated
with sodium carbonate alone was determined to have a solids
- desnity of about 66.6 percent. However, ~he slurry treated
with sodium carbonate followed by the polyacrylate (mixture -
3) unexpectedly exhibited a dramatic increase in solids
density to 78.8 percent at 4000 cps. The same agents added
as a premix (mixture 4) also caused a great increase in
solids density to 76.5 percent at 4000 cps.
By comparison with the untreated control sample
and the samples (mixtures 1 and 2) treated with only one . :.
of the water-demand reducing agents, the synergistic effect
of the sodium carbonate - sodium polyacrylate combination
in reducing water demand of the suspended solids and ~-:
increasing solids density at comparative viscosities
is evident.
The slurry solids density for mixture (3) was
increased (absolute values) by about 15 weight percent
over the untreated control and from 12 to 13 weight percent
over the slight improvements seen with mixtures (1) and
(2). Relative gains of about 24.5 percent, 19.7 percent
and 18.3 percent, respectively, over the control and
mixtures 1 and 2 were thus obtained by mixture 3. The
solids density for mixture (4) similarly increased about
13.2 weight percent (absolute) over the untreated slurry
and about 10.7 and 9.9 weight percent over mixtures (1)
and (2), respectively, thus amounting to relative gains
of about 20 percent, 16.2 percent and 14.8 percent,
respectively, over the untreated control and control
samples 1 and 2.
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Example 3
In operations employing the procedures described
in Example 2, samples of the same portland cement slurry
were treated with sodium ortho silicate and sodium poly-
acrylate water-demand reducing agents. The untreated
control slurry had a solids density of 64.1 weight percent
at 4000 cps while a slurry sample treated with 0.2 percent
sodium ortho silicate had a solids density of about 64 - -
weight percent at 4000 cps (thus having no affect on the
slurry). A slurry sample treated with 0.05 weight percent
sodium polyacrylate had a solids density of about 65.8
weight percent at 4000 cps. The slurry sample treated with
0.2 weight percent sodium ortho silicate was concentrated
and 0.05 weight percent sodium polyacrylate added thereto,
with the resulting slurry having a solids density of about
76.3 weight percent at 4000 cps, or a total gain over the
untreated control and silicate treated control of about
19 percent and a gain of about 16 percent over the poly-
acrylate-treated control. In an additional run, the
silicate and polyacrylate were premixed and then added
to the slurry. The resulting slurry had a solids density
of about 75 weight percent.
Example 4
Samples of the portland cement slurry in
Example 2 were treated as in Example 2, the untreated
control sample having a solids density of 65.2 weight
percent at 4000 cps and control~sample treated with
0.05 percent sodium polyacrylate having a solids density
of 66.7 percent at 4000 cps. A control sample treated
with 0.2 weight percent sodium oxalate was found to
; , ' `'.
17,899A-F -20-
- : -. -,-- '' . ', -' ' ' . - '
. , ., - ~.............. - ~... , .. , ~ ,
~07745Z
have solids density of 68.0 at 4000 cps. Concentration
of the latter sample and addition of 0.05 weight percent
sodium polyacrylate resulted in a slurry having a solids
density of about 76 weight percent at 4000 cps. A
slight reversion in the slurry viscosity was noted after -
a period of about 18 hours.
Example 5
A portland cement slurry (obtained from the
Calaveras Cement Co.) having about 80 parts limestone,
about 8 parts silica, about 10 parts clay and about 2
parts iron oxide was treated according to the procedure
set forth in Example 2. The untreated control slurry
was found to have a solids density of about 65.2 weight
percent at 4000 cps. Addition of 0.05 weight percent
sodium polyacrylate raised the solids density at 4000
cps to 68.6 weight percent while addition of 0.2 weight
percent Na2CO3 to another sample raised the solids density
to 70.4 weight percent at 4000 cps. Concentration of
the latter sodium carbonate treated sample and addition . .
thereto of 0.05 weight percent sodium polyacrylate gave
a slurry having a solids density of about 80.3 percent
at 4000 cps, an increase in solids density over the other
control samples varying from 10 to 15 weight percent, or
total gains in density of from 14 to 23 percent.
: 25 Example 6
Additional evaluations utilizing portland cement
slurries from the Calaveras Cement Co. were carried out as
in Example 2 and the results are set forth in the following
. Table I.
.
17,899A-F -21-
1077~5Z
TABLE I
% SOLIDS DENSITY AT 4000 CPS -
% % Sodium Polyacrylate
ControlNa2CO3 0% .005~ .01 .02 .04 .08 ~ -
. _ .
67.8 0 67.8 68.5 69.4 69.7 70.5 75.1
68.3 0.05 72.1 74.3 74.5 75.3 79.6 80.3
68.1 0.1 74.9 77.0 77.8 80.0 80.6 80.9
67.7 0.2 75.7 76.7 77.9 80.4 80.6 80.4
% . ~ -
4 3 `~ ~
: . ,
67.3 0 67.3 68.5 68.7 69.6 71.3 76.9
67.9 0.1 71.7 77.5 78.5 79.8 -- --
66.0 0.2 70.1 -- -- 78.0 79.0 79.6
67.7 0.4 73.8 75.1 76.2 77.2 -- --
- .. ~
The foregoing experiments demonstrate the syner- -
gistic action of polyacrylates with inorganic salts as
herein designated in discussing the water-demand of high
solids density cement slurries. The reduction in water
content provides cement slurries which have a higher
solids loading per given volume of slurry and which can
readily be pumped to the clinker kiln. Thus, equal
volume feed rates of cement slurries treated according
to the present invention provide for an increase in clinker
production without increasing fuel costs for the calcination
operation. The synergistic combinations of the present
invention possess additional economic advantages in that
relatively expensive polyacrylates can be used at rates
which do not render their use prohibitively expensive.
17,899A-F -22-
~07745Z
Example 8
A wet portland cement slurry obtained from a
commercial source contained about 34 percent by weight
water. The viscosity was determined by a Brookfield LTV :
viscometer employing a number S spindle at 20 RPM after : :
60 seconds of stirring. As received, this slurry was
determined to have a viscosity of about 16,800 cps. A
30 weight percent aqueous solution comprising one part of
the disodium salt of a 1:1 mole ratio of styrene-maleic
anhydride copolymer having a molecular weight of about
1600 and three parts by weight Na2SiO2 was added in
varying small amounts to samples of the slurry and the
viscosity determined as above. The following results
(weight percent being b~ ed on slurry solids) were
recorded:
.' ' ':
~ '
17,899A-F -23-
~ . ~
10774S2
TABLE II
Weight % Weight ~Viscosity :
Run No. SMA Copolymer 2 3 cps
1 * 0 0 16,800
2 .0028 .0085 9,200
3 .0057 ` .0170 3,000
4 .0068 .0205 2,000
.0079 .0239 1,000
6 .0091 .0273 500
7 .0102 .0306 ~340
8 .0113 .0341 ~200
.: .
9 .0114 0 9,800 --
.0227 0 4,500 : -
11 .0273 0 3,400
12 .0318 0 2,400 :
13 .0364 0 1,800 ::- :
14 .0409 0 1,200
.0455 0 800 :
-
* = control
Comparing runs 2 to 8 with runs 9 through 15,
it is seen that the total concentration of the SMA-Na2SiO3 ~ : -
system i8 the same as.the concentration of the SMA copolymer
utilized alone. The synergistic effect of the SMA-Na2SiO3
system is evident from these data, the SMA-Na2SiO3 system
requiring only about one-~ourth (or about a 75 percent
decrease) the concentration of the expensive SMA copolymer
to obtain slurries having (a) substantially the same
or better viscosities than obtained with the SMA copolymer
''
. ..
17,899A-F -24-
-` ~077452
alone in larger quantities, and (b) the same water con-
tent as the high viscosity control sample but which instead
have viscosities whiçh render the slurries readily pumpable.
The above experiments again demonstrate the syner-
gistic action of the water-demand reducing system of the
present invention in lowering the high viscosity (without
addition of water) of the higher solids density slurries
to manageable ranges, thus providing for the use of slurries -
having higher solids densities and attendant benefits as -
discussed herein.
In commercial operations, the water-demand
reducing system is usually added once the slurry or slurries
are formed in the grinding operations. Preferably, the
system is added to the slurry formed after grinding.
Similar results can be obtained with SMA copoly-
mers and inorganic salts specified herein. Having disclosed
our invention, it is apparent to those skilled in the art
that modifications may be made which do not depart from
the spirit of the invention. The specific experiments
presented in this disclosure are illustrative of the
invention and are not intended to be limitations upon
the true scope of the invention.
17,899A-F -25-
