Note: Descriptions are shown in the official language in which they were submitted.
~ckground of the Invention
1. Field of the Invention
This invention relates to a calcium carbonate-con-
taining granular matrix wherein the ultrafine calcium carbonate
particles maintain a high effective surface area and exhibit
low agglomeration. Calcium carbonate-containing granules formed
in the present invention may be used in U.S. Patent No. ~,040,988
issued August 9, 1977 or in the detergent composition disclosed
in Belgian Patent No. 798,856 to Jacobsen et al.
2. Description of the Prior Art Practices
This invention relates to a calcium carbonate-
containing granule wherein the calcium carbonate particles
within the granule retain a substantially discrete form and
have a high effective surface area.
It is known that finely-divided or microcrystalline
calcium carbonate particles may be used as a crystallization
seed in combination with a precipitating buil`der to accelerate
the removal of soluble calcium ions from wash water. The term
; "soluble calcium ions" includes not only divalent calcium
-~ 20 ions but also calcium salts which have associated but have not
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?recipitated, for instance, singular calcium carbonate mole-
cules. The associated forms of soluble calcium such as the
monomolecular calcium carbonate exist in rapid equilibrium
with calcium ions and carbonate ions such that depletion of
both the free calcium ions and the other soluble associated
- calcium species is necessary.
Crystallization seeds such as those employed in the
present invention are believed to function by providing growth
sites for the precipitating free calcium ions and other
soluble calcium species. The number of crystallization seeds
- present per unit weight and the surface area of each
particle determines the total surface area present per unit
weight. The number of growth sites upon which soluble calcium
may precipitate appears to be directly proportional to the
~; total surface area of the crystallization seeds. The problem
not previously solved is to economically incorporate the
ultrafine or microcrystalline calcium carbonate particles
into a granular detergent composition such that the particles
? are maintained in their discrete or nonagglomerated high
effective surface area form thereby requiring a minimal amount
of calcium carbonate. The term "effective surface area"
indicates a measurement of the surface area available for
crystal growth which is area available to precipitate soluble
calcium onto a given weight of calcium carbonate crystalliza-
tion seeds. The term "nominal surface area" indicates the
total surface area of a given weight of calcium carbonate
crystallization seed without regard to the effectiveness in
soluble calcium depletion. To provide favorable kinetics for
- soluble calcium removal from a wash water solution, it is
desirable that the calcium carbonate crystallization seeds
have a high effective surface area per unit weight and a
large number of particles.
-- 2
,
Several methods are known in the art for the prep-
aration of calcium carbonate particles which in slurry form
exhibit high surface areas and particle diameters within the
range desirable for incorporation into laundry detergent
compositions. The known methods for maintaining large numbers
of discrete calcium carbonate particles of a high nominal
surface area in a slurry include the addition to the aqueous
slurry of a material such as sodium tripolyphosphate, sodium
pyrophosphate, soluble silicates, and various anionic sur-
factants. The problem with using the aforementioned materialsto maintain a high nominal surface area and a large number of
calcium carbonate particles is that the effective surface
area is substantially reduced by the adsorption of the afore-
mentioned salts and detergents onto the crystal surfaces.
The apparent effect of, for example, polyphosphate ions is
to bind to the lattice of the calcium carbonate crystallization
seed to form a stable layer onto which the precipitation of
the soluble calcium will not occur. The rendering of a
crystallization seed ineffective with respect to the growth
or nucleation sites such as by adsorption is known as
~- poisoning.
The calcium carbonate crystallization seeds within
an aqueous slurry when dried agglomerate resulting in a sub-
; stantial loss of the number of discrete particles present as
well as a reduction in the effective surface area of the
calcium carbonate particles. However, the drying of a slurry
of calcium carbonate particles while substantially reducing
the effective surface area may in many instances reduce the
nominal surface area only slightly. The phosphate salts,
silicates, and anionic detergents, which were previouslymentioned as having the ability to maintain a large number
of particles in a slurry do not in any case at the levels
.. .
.. . . :
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disclosed prevent the agglomeration of the calcium carbonate
crystallization seed particles upon drying.
It is intended throughout the specification and
claims that the term "agglomeration" or "agglomerate" is to
embrace aggregate or composite which are more fully defined
in U.S. Patent No. 2,964,382 entitled PRODUCTION OF PRECIPITA-
TED CALCIUM CARBONATE and issued to G.E. Hall on December 13,
1960 .
For the purposes of this invention, the effective
surface area and the nominal surface area are equivalent for
a given slurry of nonpoisoned, non-agglomerated calcium
carbonate particles. It is intended throughout the specifica-
tion and claims that the terms free calcium ions, soluble
- calcium, and soluble calcium species, may be used inter-
changeably.
It has now been discovered that an aqueous slurry of
discrete submicron high surface area calcium carbonate
particles can be dried to give a calcium carbonate-containing
granule wherein the calcium carbonate particle retains its
high effective surface area and has a lessened tendency
towards agglomeration or aggregation by including in the
slurry an alkali metal carbonate, bicarbonate, or sesqui-
carbonate.
As a result of practicing this invention, it is
possible to dry a calcium carbonate-containing slurry to
give a calcium-carbonate-containing granule which will
rapidly dissolve upon addition to a wash water solution and
present a calcium carbonate crystallization seed of high
effective surface area onto which soluble calcium ions in
the wash solution may precipitate.
As was mentioned above, it is desirable that the
calcium carbonate particles present in a wash solution exhibit
4 _
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a high effective surface area substantially e~uivalent to
the nominal surface area of the calcium carbonate particlés
present in the slurry prior to drying. It will also be
observed that by practicing the present invention that the
tendency of the calcium carbonate particles to agglomerate
during drying is substantially lessened as evidenced again by
the calcium depletion rates of the non-dried slurry of calcium
carbonate particles and the similar measurements made when
the dried calcium carbonate-containing granule is dissolved
in a wash solution. Rapid soluble calcium depletion is
necessary to prevent the soluble calcium from interfering with
the detergent or depositing upon the fabric as calcium carbonate.
It has also been observed that previous attempts to
use finely-divided or microcrystalline calcium carbonate
particles in detergent compositions is objectionable because
of the dust problems which can occur in handling calcium
sarbonate as a substantially dry material.
Another deficiency resulting from the incorporation
of calcium carbonate crystallization seeds into detergent
products is that the calcium carbonate particles during
handling and shipping tend to segregate from the material with
which they are admixed. It is further noted that when calcium
~ carbonate crystallization seed particles are admixed directly
: into the granular detergent product that these particles when
stored under conditions of high temperature and humidity have
- a tendency to cluster together to give a caked product.
It is an object of the present invention to prepare
a calcium carbonate-containing granule from a calcium
carbonate-containing aqueous slurry such that the discrete
nature and the high effective surface area of the calcium
carbonate particles in the slurry are substantially retained
by the calcium carbonate particles within the dried granule.
.
.
-' ' , '' ; :
. . ~ ,
: ~ . . :
It is a further object of the present invention to
prepare a calcium carbonate crystallization seed-containing
granule which will rapidly dissolve when added to a wash
solution such that the high surface area discrete calcium
carbonate crystallization seed particles are rapidly available
to induce the removal of soluble calcium ions from the wash
solution.
; The benefits of the present invention are further
; described in U.S. Patent 3,992,314, issued November 16, 1976.
SUMMARY OF THE INVENTION
A non-phosphate, calcium carbonate-containing spray-
dried granule, substantially free of water-soluble salts of
silicates and consisting essentially of:
(a) submicron calcium carbonate particles having a
; high effective surface area and a low degree of agglomeration;
and,
(b) a member selected from the group consisting of
alkali metal carbonates, bicarbonates, and sesquicarbonates
and mixtures thereof;
wherein the weight ratio of the alkali metal salt to
the calcium carbonate is from about 1:2 to about 75:1.
Percentages and ratios throughout the specification
and claims are by weight unless otherwise stated. Temperatures
are in degrees Farenheit unless otherwise indicated.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The granules of the present invention are produced
by forming an aqueous slurry comprising submicron calcium
carbonate particles and a water-soluble salt selected from
the group consisting of alk-ali metal carbonates, bicarbonates,
and sesquicarbonates. The second step in carrying out the
present invention is drying the aqueous slurry comprising the
,' - :
,
aforementioned water-soluble salt, and the calcium carbonate
crystallization seeds to form the calcium carbonate-containing
granule.
To be effective as a crystallization seed the calcium
carbonate particle as was noted earlier, must be of a high
effective surface area and further be present in a sufficient
number of particles to ensure rapid depletion of the free
calcium ions from a wash solution. The manner of determining
the effectiveness of the crystallization seed will be discussed
later.
Generally it is sufficient to statR that to be ef-
fective as acrystallization seed that the calcium carbonate
particle should have a mean diameter less than one micron,
preferably from about 0.01 to about 0.50 micron, more pre-
ferably from about 0.01 to about 0.25 micron, and most pre-
ferably the discrete calcium carbonate crystallization seed
particle is from about 0.01 to about 0.10 micron in diameter.
The number of crystallization seed particles present
per weight unit is affected by the agglomeration of the
crystallization seed particles employed. The calcium carbonate
particles may pack together tightly to form a composite such
that fewer particles are present with a correspondingly smaller
effective surface area to induce precipitation of the free
calcium ions. This is to say that effective surface area of
the calcium carbonate crystallization seed is partially deter-
mined by the extent of the agglomeration which has occurred
between the calcium carbonate crystallization particles.
The crystallization 3eeds of the present invention
vary in mean particle diameter from about 0.01 micron up to
1 micron. The mean diameter of the particle is the maximum
~,
dimension of a straight line passing through the center of
-:
~-
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. . .
~ne particle. Calcium carbonate crystallization seed parti-
cles ranging from about 0.2 micron and larger may be obtained
commercially in dry form and slurried with water to an
appropriate concentration before proceeding with the present
invention. One commercially available form of calcium car-
bonate is marketed under the trade mark PURECAL O which has
mean individual calcium carbonate particles of approximately
0.25 micron in diameter. Preferably, however, the calcium
carbonate particles used in the present invention are in the
lower particle size ranges to ensure rapid free calcium
depletion from the wash solution. Such fine particles can be
manufactured by the process given in U.S. Patent 2,981,596
entitled PREPARATION OF ALKALINE EARTH CARBONATES to
Raymond R. McClure patented April 25, 1961. The McClure
process of the preparation of ealcium carbonate utilizes cal-
eium chloride and sodium earbonate whieh results in the form-
ation of not only ealcium carbonate but also sodium ehloride.
While some diluent salts sueh as sodium ehloride or sodium
sulfate may be present in the final, dried granule of the
present invention,
. .
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- 8
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,
-he benefits of using these salts is outweighed by the loss
of formula room. Thus in the McClure process it is desirable
to fllter the solution after the calcium carbonate particles
have been made such that the calcium carbonate is washed free
of undesirable salts such as sodium chloride. Any convenient
filtration apparatus may be used to concentrate the crystalli-
zation seeds.
The preferred calcium carbonate crystallization seed
particle is calcite as opposed to the aragonite and vaterite
crystal forms. Calcite is the preferred crystallization seed
as it is the most stable form of calcium carbonate crystal.
As calcium carbonate in the desired particle size
is usually prepared in an aqueous slurry it is preferred but
not necessary that the calcium carbonate be dispersed in the -
slurry before the addition of the water-soluble salt.
The next step in the preparation of the calcium
carbonate-containing grahule is the addition to the slurry
containing the calcium carbonate crystallization seeds of a
water-soluble salt selected from the group consisting of
2Q alkali metal carbonates, bicarbonates, and sesquicarbonates.
Examples of such water-soluble salts are the alkali metals
most notably sodium, potassium, and lithium.
The effectiveness of the calcium carbonate crystal-
lization seeds depends not only on the choice of the
precipitating builder employed, but also upon the respective
. concentrations in the wash solution. Thus, for instance,
- while sodium carbonate is perhaps the most desirable builder
to be used in the present invention, larger amounts of
sesquicarbonates may be used and thus build more effectively
than a lesser amount of sodium carbonate.
Generally the weight ratio of the water-soluble salt
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to the submicron calcium carbonate particles in the calcium
carbonate-containing granule is from about 1 : 2 to about
75 : 1, preferably from about 1 : 1 to about 50 : 1, more
preferably from about 3 : 2 to about 20 : 1, and most prefer-
ably from about 2 : 1 to about 10 : 1. The water-soluble salt
may be added to the calcium carbonate slurry èither dry or
in solution preferably the former to minimize the amount of
water which must be removed in the drying operation. Within
the ratios of the water-soluble salt to the calcium carbonate
of the present invention, the amount of water present in the
combined slurry ranges from about 20% to about 95%, preferably
from about 30~ to about 90%, and most preferably from about
40~ to about 80% by weight.
The calcium carbonate-containing granule formed
in the present invention can be supplemented to provide more
precipitating builder`by admixing therewith additional amounts
of alkali metal carbonates, bicarbonates, and sesquicarbonates
or mixtures thereof, in a weight ratio to the calcium carbonate-
containing granule of from 100:1 to 1:100.
The formation of the calcium carbonate-containing
granule is preferably carried out using conventional detergent
spray-drying apparatus, although vacuum or freeze-drying may
be employed. Basically, a spray-drying operation involves
the carrying of the slurry of the material to be dried to a
drying tower wherein the slurry is introduced under pressure
through a stream of drying gases. The drying gases employed
for example include air or nitrogen.
The temperature of the combined slurry containing
the water-soluble salt and the calcium carbonate to be spray
dried is in the range of from about 50F to about 250F,
preferably from about 80F to about 190F, and most preferably
from about 90F to about 120F. It will be recognized that the
slurry temperature may
-- 10 --
.
.:
ae adjusted for such factors as the solubility of the
water-soluble salt, and the ease of carrying out the spray- ,
drying operation from a heated slurry.
The introduction of the slurry to the spray-drying
, tower takes place through a series of atomizing nozzles at
which point the material to be dried forms droplets. The
droplets are then dried by the drying gas to form granules
which are preferably hollow or puffed to provide rapid
dissolution in the wash water. Without limitation to the
present invention it is desirable but not necessary that the
spray-dried calcium carbonate-containing granules are from
about 0.1 to about 2 millimeters in diameter.
Preferably the slurry in the present invention con- -
tains only inorganic materials which allows the spray-
drying operation to proceed within a temperature range, the
low side of which is effectively determined only by the de-
sired rate of drying with the high temperature being deter-
' mined by the temperature at which the salts prese~t begin
to decompose. If organic matter is to be present in the
slurry, temperature adjustments may be necessary to avoid
charring. Thus the spray-drying operation may be carried
out at temperatures o from about 200F. to about 1500F.,
''' preferably from about,250F. to about 1200F., and more
preferably from about 300F. to about 800F. The slurry
may be spray dried in either a countercurrent or concurrent
spray-drying tower. In a countercurrent spray-drying
operation such as that described in U.S. Patent 3,629,951,
entitled MULTILEVEL SPRAY-DRYING METHOD issued to Robert
P. Davis et al, December 28, 1971, the slurry of material to
be spray-dried is fed into the spray tower such that the
flow of droplets is opposite to that of the drying gases.
While the Davis et al patent discloses a multilevel
-- 11 --
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.
operation, a single-level arrangement of the atomizing nozzles
is well within the scope of the present invention. Convenient-
ly, however, the apparatus employecl for spray drying may allow
for the introduction of the slurry of the calcium carbonate
particles and the water-soluble salt wherein the atomizing
nozzles are placed closely to the source of the drying gas
and the slurry is sprayed concurrently or in the same direction
as the flow of the drying gas. The object of forming the
calcium carbonate-containing granule such that it will be
rapidly dissolved in a wash solution is best met by a granule
which is concurrently spray dried to ensure that the granule
is well puffed leaving the outer surface of the granule
porous.
The Davis et al spray-drying method may be effect-
ively utilized to incorporate the calcium carbonate-containing
granule into a detergent product without the necessity of
admixing a separate detergent base granule with the calcium
carbonate-containing granule. The Davis et al method may be
modified such that the slurry containing the water-soluble
salt and the calcium carbonate particles is introduced through
nozzles placed near the source ofithe drying gas while the
remainder of the detergent formulation is then fed through
other atomizing nozzles positioned above the nozzles through
which the calcium carbonate is introduced. In such a fashion
` it is possible to spray dry the calcium carbonate-containing
granule as well as the detergent base granule in the same spray
tower to form a substantially homogenized product of two
distinct granule forms. The operation referred to above
eliminates the necessity of storing large quantities of the
base detergent granule or the calcium carbonate-containing
granule. Organic detergents, for example, linear alkyl
benzene sulfonates may be slurried with sodium sulfate or
- - 12 -
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, .~ . . . .
- , . . .. . .
ldditional sodium carbonate in a weight ratio to the detergent
of 10:1 to 1:10 to form the previously-mentioned detergent
granule.
The determination of the nominal surface area of
the calcium carbonate crystallization seed particle utilized
in the present invention may be made by three techniques,
namely, the Brunauer, Emmet, Teller (BET), dye adsorption,
and the calcium depletion rate. In the BET method a dry
sample of the material of which the surface area is to be
determined is placed in a vial and exposed to nitrogen gas
at liquifying temperatures. The surface area by BET is
measured by the pressure differential caused by gas adsorbing
- onto the sample and calculated by assuming that the gas has
formed at monolayers on the sample.
- The dye adsorption technique for measuring surface
areas is essentially similar to the sET method to the extent
that the dyes employed adsorb in a simple monolayer onto the
surface of the sample to be tested. The advantage of the dye
adsorption method over the BET method is that the dye adsorp-
tion may be used in a slurry containing the material to be
measured. Dye adsorption by measuring the surface area in a
slurry avoids the loss of a substantial amount of surface area
due to agglomeration during drying. The dye adsorption method
provides a reliable manner of determining the nominal surface
area of calcium carbonate particles in an aqueous slurry. The
dye employed in determining the calcium carbonate surface area
in solution is known as Alizerin Red and may be effectively
- used at concentrations of the dye at about 2-5 x 10 4M. The
slurry may contain as much as 12% solids by weight. The sample
slurry is mixed with a volume of dye and the amount of dye
adsorbed is determined centrifuging the sample and measuring
the absorbence of the supernatant. The amount of dye adsorbed
- 13 -
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lO~
is compared to dry samples run by BET with results reproduc~
ible at +5%.
The method of determining the effective surface area
of the calcium carbonate crystallization seed particles is
that of measuring the soluble calcium depletion rate more
simply known as calcium depletion rate, from a wash solution.
The effective surface area of the calcium carbonate crystal-
lization seeds in a slurry is equal to the nominal surface
area if the crystallization seeds are nonpoisoned.
The calcium depletion rate is determined by filling
a vessel with distilled water and then carefully adding water
hardness which may be either calcium or calcium and magnesium
preferably in a ratio of calcium to magnesium of 2:1 to
approximate the water hardness in most areas of the Unitèd
States. The overall hardness is added generally at 4, 7, or
11 grains per gallon as CaCO3. The artificially hardened water
may be maintained at any temperature, preferably at 80F to
120F to approximate washing conditions. The calcium carbonate
crystallization seeds and the water-soluble builder salt are
added at approximately 0.01 to 0.12% by weight to the wash
water. The calcium carbonate-containing granule may be
`~ augmented by adding additional water-soluble builder salt to
the wash water.
To determine the ealcium depletion rate, samples of
the wash solution are withdrawn at speeified intervals after
the erystallization seed and builder salt have been added and
the sample is filtered through a suitable Millipore filter. -
The filtrate is then measured by atomie adsorption spectro-
photometry to determine the amount of soluble calcium ion
remaining in the system. It will be observed that the calcium
carbonate in the calcium carbonate-containing granules has
substantially the same effective surface area as the calcium
- 14 -
. ' - : ', , ' "'~ ... .
21
arbonate in the slurry.
It has been observed that the spray-dried calcium
carbonate-containing granule of the present invention may
serve as an excellent carrier granule for materials which do
not lessen the effective crystallization seed surface area
as previously defined. Materials such as soil suspension
agents, namely polyethylene glycols, may be sprayed onto or
incorporated in the calcium carbonate-containing granule to
avoid processing the soil suspension agent with the remainder
of the detergent composition.
The rate of soluble calcium depletilon is subject to
such conditions as the effective surface area of the calcium
carbonate crystallization seeds, the number of particles
present, the temperature of the wash solution and the pH
thereof, and the concentration and type of the precipitating
builder employed.
Generally the rate of depletion of free calcium ions
increases as the temperature of a wash solution increases in
a system using calcium carbonate crystallization seed particles.
The most effective pH range with which the calcium carbonate
crystallization seed particles may be employed with any given
builder is generally from about 8 to about 12. It will be
- recognized at this point that the particular materials which
- were chosen as the water-soluble salt to be dried with the
calcium carbonate particles are also known as-detergency
builders. The most effective of the materials chosen are
the carbonate salts which when dissolved in water with the
crystallization seed present will function as an effective
builder without adjustment to the pH of the wash solution.
The other salts dried with the calcium carbonate crystallization
. seed which are the soluble sesquicarbonates and soluble bi-
- 15 -
,
- . , , : . .
~arbonates are also effective detergency builders, however,
the use of large quantities of those builder salts may lower
the pH of the wash solution to a point where the precipitation
of calcium from the solution is somewhat inhibited. When using
soluble sesquicarbonates or bicarbonates in the present inven-
tion, the pH can be adjusted by adding caustic or the calcium
carbonate-containing granule can be admixed with a detergent
product which is formulated to the proper pH. The inclusion
of sodium silicate in most detergent compositions is sufficient
because of its high alkalinity to raise the pH to the point at
which sodium sesquicarbonate and sodium bicarbonate are
effective detergent builders.
- It was previously noted that several materials most
notably anionic surfactants and water-soluble salts of
silicates and polyphosphates have the ability to substantially
poison the surface area of a calcium carbonate crystallization
seed. Therefore, to retain the highest effective surface area
of the calcium carbonate crystallization seed, it is necessary
that the aforementioned materials not come into contact with
the aqueous calcium carbonate-containing slurry.
The following examples illustrate the present
invention. Variations and modifications can be made in the
~- examples without deviating from the practices taught and
contemplated by the present invention.
- 16 -
EXAMPLE I
Calcium carbonate-containing granules are prepared
by forming a slurry of calcium carbonate calcite particles
having a mean diameter of about 0.02 mieron and thoroughly
mixing therewith sodium carbonate in a weight ratio of sodium
carbonate to the calcium carbonate of 5 : 1. The combined
slurry which is about 66~ by weight water at 120F is then
pumped to a standard spray-drying unit and contaeted with the
drying gas which is introdueed at about 550F.
10The calcium carbonate particle within the granule
so formed retains substantially the same effective surfaee
area and mean partiele diameter as the ealeium earbonate
partieles in the slurry. The granule itself is highly puffed
or porous allowing for rapid dissolution in the wash water.
The puffed granule reduees plant dust probIems signifieantly
while segregation and eaking are markedly retarded when eompared
to admixing dry ealeium earbonate particles.
- Substantially similar results as those obtained
- above are enjoyed when vaterite or aragonite erystallization
seed erystals are employed.
.
EXAMPLE II
- Caleium earbonate-eontaining granules are prepared
by forming a slurry of ealcium earbonate calcite partieles
having a mean diameter of about 0.02 micron and thoroughly
admixing therewith sodium earbonate in a wieght ratio of
~,sodium earbonate to the ealeium earbonate of 3 : 1. The
eombined slurry whieh is about 64% by weight water at 100F
- 17 -
. --
,
. . .
is then pumped to a standard spray-drying unit and contacted
with the drying gas which is introduced at about 550F.
The calcium carbonate particle within the granule
so formed retains substantially the same effective surface
area and mean particle diameter as the calcium carbonate par-
ticles in the slurry. The granule itself is highly puffed or
porous allowing for rapid dissolution in the wash water.
The puffed granule reduces plant dust problems significantly
while segregation and caking are markedly retarded when
compared to admixing dry calcium carbonate particles.
Substantially similar results are obtained when
the aqueous slurry is 78~ by weight water and the slurry
temperature is 120F. Similar granules are formed by freeze-
drying and by vacuum-drying the slurry formed by this example.
EXAMPLE III
Calcium carbonate-containing g~anules are prepared
by forming a slurry of calcium carbonate calcite particles
having a mean diameter of about 0.25 micron and thoroughly
mixing therewith sodium bicarbonate in a weight ratio of
sodium bicarbonate to the calcium carbonate of 4 : 1. The
combined slurry which is about 30% by weight water at 150F
is then pumped to a standard spray-drying unit and contacted
with the drying gas which is introduced at about 400F.
The calcium carbonate particle within the granulé
so formed retains substantially the same effective surface
area and mean particle diameter as the calcium carbonate
particles in the slurry. The granule itself is highly puffed
or porous allowing for rapid dissolution in the wash water.
.
-
~ - 18 -
~he puffed granule reduces plant dust problems significantly
while segregation and caking are markedly retarded when
- compared to admixing dry calcium carbonate particles.
Substantially similar results are obtained when
the drying gas is introduced at 450F, 500F, and 600F.
EXAMPLE IV
Calcium carbonate-containing granules are prepared
by forming a slurry of calcium carbonate caleite partieles
having a mean diameter of about 0.01 mieron and thoroughly
mixing therewith sodium earbonate in a weight ratio of sodium
carbonate to the calcium earbonate of 3 : 1. The combined
slurry whieh is about 60% by weight water at 120F is then
pumped to a standard spray-drying unit and eontaeted with
the drying gas which is introduced at about 600F.
- The calcium carbonate particle within the granule
so formed retains substantially the same effective surfaee
area and mean partiele diameter as the ealeium carbonate
partieles in the slurry. The granule itself is highly puffed
. or porous allowing for rapid dissolution in the wash water.
The puffed granule reduees plant dust problems signifieantly
while segregation and caking are markedly retarded when
eompared to admixing dry ealeium earbonate particles.
Substantially similar results are obtained where
the water-soluble salt is potassium earbonate in a weight
~- ratio to the ealeium earbonate of 2 : 1, or potassium
~; bicarbonate in a weight ratio to the ealeium carbonate of
3 : 1.
, .
.,
-- 19 --
'
.'~ .
.
.
EXAMPLE V
Calcium carbonate-containing granules are prepared
by forming a slurry of calcium carbonate calcite particles
having a mean diameter of about 0.025 micron and thoroughly
mixing therewith sodium carbonate in a weight ratio of sodium
carbonate to the calcium carbonate of 5 : 1. The combined
slurry which is about 78~ by weight water at 100F is then
pumped to a standard spray-drying unit and contacted with
the drying gas which is introduced at about 700F.
The aalcium carbonate particle within the granule
so formed retains substantially the same effective surface
area and mean particle diameter as the calcium carbonate
particles in the slurry. The granule itself is highly
puffed or porous allowing for rapid dissolution in the
wash water. The puffed granule reduces plant dust problems
significantly while segregation and caking are markedly
retarded when compared to admix7ng dry calcium carbonate
particles.
To demonstrate the benefits of spray drying the
crystallization seeds in the presence of a water-soluble
builder salt, the calcium depletion rates for the granule
- (A) formed in accordance with the above example are compared
to crystallization seeds spray dried in the absence of the
water-soluble builder. ~7hen the crystallization seeds are
spray dried separately (B~, the builder is dry mixed with
- the seeds. The dry samples in the test are preslurried to
minimize the effect of dispersion of the granule. For
purposes of cross-comparison, the test includes the slurry
- 20 - -
',, ...... . '
~f calcium carbonate with the water-soluble builder present
added directly to the water without being spray-dried (C).
All tests are run at 0.006% by weight calcium
carbonate crystallization seeds and 0.03% by weight sodium
: carbonate.
. The results are compared in Table 1.
'.
- 21 -
;'
a lOti"Z~
H
~Y
~ a - -
H~
P P~
cq cn
r~ a~ D ~ N ~ _~
a
Zt`
r~
.
.
,
'~
_ Z
o~ ~
WX . . ..
H
,~ a a
C ~ u~
o ~ .~:
~ U~ ~
: ~ ~ o~ .. . . ..
~' ~ ~ C~ s: ~ .
~ O ~
",
~ .
- .,,
- U o~
. ~ ~ ' ~
_/~ Z H ~ ~ l O
', ' O ~¢ ~Z . ~ . . . . ~ ' .
U~ I H r--'1 ~1 _~ ~ ~1 ~ .
~Z
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.
. ' . ~
. ':
- u~
o ~ o ~ ~ ~ ~
. . O ~ ~1 c~ N ') It') OD ~1
-- 22 --
, ~ . ,
.
The initial water hardness in the wash soiution is
about 12 grains/gallon of calcium and magnesium ions in a 2:1
ratio. The temperature throughout the test is maintained at
100F. The soluble calcium levels are determined by atomic
absorption spectrophotometry as is previously described. The
results show that the calcium carbonate-containing granules
prepared by the present invention have an effective calcium
; carbonate surface area substantially equivalent to the non-
dried calcium carbonate particles in the slurry.
10EXAMPLE VI
Calcium carbonate-containing granules are prepared by
forming a slurry of calcium carbonate calcite particles
h~ving a mean diameter of about 0.025 micron and thoroughly
mixing therewith sodium carbonate in a weight ratio of sodium
carbonate to the calcium carbonate of 1:1. The combined slurry
which is about 7~/O by weight water at 100F is then pumped
to a standard spray-drying unit and contacted ~Jith the
drying gas which is introduced at about 700F.
The calcium carbonate particle within the granule so
formed retains substantially the same effective surface area
and mean particle diameter as the calcium carbonatè particles
in the slurry. The granule itself is highly puffed or
porous allowing for rapid dissolution in the wash water.
The puffed granule reduces plant dust problems significantly
while segregation and caking are markedly retarded when
compared to admixing dry calcium carbonate particles.
- 23 -
- ' . . .
To demonstrate the benefits of spray drying the
crystallization seeds in the presence of a water-soluble builder
salt the calcium depletion rates for tile granule (A) formed in
accordance with the above example are compared to crystalli-
zation seeds spray dried in the absence of the water-soluble
builder. When the crystallization seeds are spray dried
separately (B), the builder is dry mixed with the seeds.
The dry samples in the test are preslurried to minimize the effect
; of dispersion of the granule. For purposes of cross-
examination, the test includes the slurry of calcium carbonate
with the water-soluble builder present added directly to
the wash water without being spray dried (C).
All tests are run with the calcium carbonate crystalli-
zation seeds in water at 0.006% by weight while the sodium
carbonate is present at 0.03YO by weight. In test A, the
granule is supplemented with additional sodium carbonate up
to the 0.03% level.
The res~lts are conp ed in Table 2.
I
I
- 24 -
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, . . . . . . .
10~
a
0~
C :
~ I
C~
H
~ tn
~ a
r~
o ~ .
D
~ ,.
! .
_ æ
~ o .-
o
V
0 a~
t) ~ . x .,
H H
0 C~l
' O P:~ ~ ....
Id u~ ~
.~ ~ ~ 0~
." W CJ C~ 5:
,~ ~ E~
. ~ (d H
~ ~ . . ~. .
' ~a . ..
. S~ .
. . _ .
.
~ r'W
,~ 0
., ~ U~
~ Z . .
5~ n . .. ~
~_1 H Z G~~~')Ul~i~ In ~ .--1
O .¢ P:; H .
a I~
Z
0
., .. ..'
.', .
.'
U~
O ~ O ~ ~ ~ ' ~ :~
æ O e O ~ O
- 25 -
. .
The initial water hardness in the wash solution is
about 12 grains/gallon of calcium and magnesium ions in a
ratio of 2 : l. The temperature throughout the test is
maintained at 100F. The calcium depletion rates are deter-
mined by atomic absorption spectrophotometry as is previously
described.
EXAMPLE VII
Calcium carbonate-containing granules are prepared
by forming a slurry of calcium carbonate calcite particles
having a mean diameter of about 0.025 micron and thoroughly
mixing therewith sodium carbonate in a weight ratio of
sodium carbonate to the calcium carbonate of 3 : 1. The
combined slurry which is about 78% by weight water at 100F
is then pumped to a standard spray-drying unit and contacted
with the drying gas which is introduced at about 700F.
The calcium carbonate particle within the granule
so formed retains substantially the same effective surface
area and mean particle diameter as the calcium carbonate
particles in the slurry. The granule itself is highly
puffed or porous allowing for rapid dissolution in the wash
water. The puffed granule reduces plant dust problems
significantly while segregation and caking are markedly
retarded when compared to admixing dry calcium carbonate -
particles.
o demonstrate the benefits of spray drying the
crystallization seeds in the presence of a water-soluble
builder salt, the calcium depletion rates for the granule
(A) formed in accordance with the above example are compared
. ' ~
. - :
- 26 - ~
.
' .
,
~Vt~
.o crystallization seeds spray dried in the absence of the
water-soluble builder. When the crystallization seeds are
spray dried separately (B), the builder is dry mixed with
the seeds. The dry samples in the test are preslurried to
minimize the effect of dispersion of the granule. For
purposes of cross-comparison, the test includes the slurry
of calcium carbonate with the water-soluble builder present
added directly to the wash water without being spray-dried
(C) .
The aalcium carbonate crystallization seeds are
present in the wash water at 0.006~ by weight, while the
sodium carbonate is present at 0.03% by weight. In test
A, the granule is supplemented with additional sodium
carbonate up to the 0.03% level.
The results are compared in Table 3.
.
~` .
~ - 27 -
,. ,; .
- ~ o
a lOt~
W . ' I .
C~;
c: a
~3 1 . - !
C~ ~
~ 5
~ ~4
D P.
~ u~
U. Q E~
O r~
0~
V D
~ ~ ,.
IY
<~t O
U ~Q
Q X
H H
a ~ Q
:, I ~
:: o tt~ ~:
_I ~ O
., ~ ~ ~
''. ~ ~' CO~ ' .:
~ H
h . U 3
_t ,
- .
,, ~ .
,1 ; ,
t) ~W
.~ 0~
Id C~ 3
U Z
;
,R a ~
~ ~ .. . ..
,~ H Z ~ ~ I~
O ~: ~; H
u, ~a ZH
.
h
0
U~o . ' ' ~
,
. .,
. ' -.
, U~
~ ~ ~ a) 0
O ~ O ~ ~ ~ ~ ~s
æ 0 ~ O ~ O
-- 28 --
.
.
. .
The initial water hardness in the wash solution
ls 12 grains/gallon of calcium and magnesium ions in a 2 : l
ratio. The temperature throughout the test is maintained at
100F. The calcium depletion rates are determined by atomic
absorption spectrophotometry as is previously ~described.
EXAMPLE VIII
Calcium carbonate~containing granules are prepared
by forming a slurry of calcium carbonate calcite particles
having a mean diameter of about 0.95 micron and thoroughly
mixing therewith sodium bicarbonate in a weight ratio of
sodium bicarbonate to the calcium carbonate of 1 : 2. The
combined slurry which is about 80% by weight water at 115F
is then pumped to a standard spray-drying unit and contacted
with the drying gas which is introduced at about 500F.
The calcium carbonate particle within the granule
so formed retains substantially the same effective surface
area and mean particle diameter as the calcium carbonate
particles in the slurry. The granule itself is highly
puffed or porous allowing for rapid dissolution in the
wash water. The puffed granule reduces plant dust problems
significantly while segregating and caking are markedly
retarded when compared to admixing dry calcium carbonate
particles.
Similar results to those obtained above are enjoyed
when the mean diameter of the calcium carbonate particles in
the slurry are 0.50 micron, 0.25 micron, and 0.10 micron.
ij .
- 29 -
,
.
lV~
`EXAMPLE IX
Calcium carbonate-containing granules are prepared
by forming a slurry of calcium carbonate calcite particles
having a mean diameter of about 0.01 micron and thoroughly
mixing therewith sodium carbonate in a weight ratio of sodium
carbonate to the calcium carbonate of 50 :1. The combined
slurry which is about 90~ by weight water at 100F. is then
pumped to a standard spray-drying unit and contacted with
the drying gas which is introduced at about 800F.
~- 10 The calcium carbonate particle within the granule
so formed retains substantially the same effective surface
area and mean particle diameter as the calcium carbonate
particles in the slurry. The granule it~elf is highly
puffed or porous allowing for rapid dissolution in the wash
water. The puffed granule reduces plant dust problems
significantly while segregation and caking are markedly
retarded when compared to admixing dry calcium carbonate
particles.
Substantially similar results as those above are
obtained when sodium bicarbonate in a weight ratio to the
calcium carbonate of 75:1 is substituted for the sodium
, carbonate.
- In this example the calcium carbonate containing
granule is spray dried contemporaneously with a detergent
base granule in the apparatus déscribed in U.S. Patent
3,629,951, issued to Davis et al. In this variation of the
Davis process the calcium carbonate-containing slurry is
sprayed through the atomizing nozzle labeled 20 in Fig. 1
; of the Da~is et al patent, while the detergent base
granule is introduced through the atomizing nozzles 16 and
18. The detergent slurry introduced in this process, when
- 30 -
.~, .. . .
~~ .
.. . . . .: . :, .: , ,
dried, comprises 20 parts of sodium dodecylalkylbenzene sul-
fonate, 20 parts sodium sulfate, and 10 parts sodium silicate.
Any other detergen~ may be employed at from 5-40~ by weight
for example sodium alkyl ether sulfate salts or sodium
alkyl sulfate salts, as well as other detergent components
such as those disclosed in U.S. Patent 3,664,961, issued
May 23, 1972 to Norris.
Example X
Calcium carbonate-containing granules are prepared
by forming a slurry of calcium carbonate calcite particles
having a mean diameter of about 0.03 micron and thoroughly
mi~xing therewith sodium sesquicarbonate in a weight ratio of
sodium sesquicarbonate in a weight ratio of sodium sesqui-
carbonate to the calcium carbonate of 10:1. The combined
slurry which is about 95% by weight water at 150F. is then
` pumped to a standard spray-drying unit and contacted with
the drying gas which is introduced at about 575F.
The calcium carbonate particle within the granule
so formed retains substantially the same effective surface
area and mean particle diameter as the calcium carbonate
particles in the slurry. The granule itself is highly puffed
or porous allowing for rapid dissolution in the wash water.
The puffed granule reduces plant dust problems significantly
while segregation and lumping are markedly retarded when
compared to admixing dry calcium carbonate particles.
Equivalent results to those obtained above are
enjoyed when the water-soluble salt is sodium carbonate in a
weight ratio to the calcium carbonate of 8:1. This example
may be varied by admixing dry sodium carbonate with the
calcium carbonate-containing granule in a respective weight
ratio of (a) 100:1 and (b) 1:100.
- 31 -
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,, ' ' ' , , ''. ' ' ' ' , '' ' ' .
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