Note: Descriptions are shown in the official language in which they were submitted.
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FREE FLOWING AGGLOMERATED NONIONIC SURFACTANT
DETERGENT COMPOSITION AND PROCESS FOR MAKING SAME
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a free-flowing agglomerated powder
detergent containing ~ high levels of nonionic surfactant and a process for
making the same.
Discussion of related art
There is an on-going effort to provide powdered laundry detergents
having an increased amount of detergent surfactants. The benefits of highly
concentrated detergents include a savings in packaging use and cost.
Unfortunately, there are limits to the amount of detergent surfactant that can
be
included in a powdered detergent while still providing the consumer desired
characteristics of flowability, solubility, cleaning and whitening
performance.
Most granular detergents are produced by spray drying. This process
involves mixing detergent components such as surfactants and builders with
water to form a slurry which is then sprayed into a high temperature air
stream
to evaporate excess water and to form bead-type hollow particles. While spray
drying the detergent slurry produces a hollow granular detergent having an
excellent solubility, extremely large amounts of heat energy are needed to
remove the large amounts of water present in the slurry. Another disadvantage
of the spray drying process is that because large scale production equipment
is
required, a large initial investment is necessary. Further, because the
granules
obtained by spray drying have a low bulk density, the granule packaging
volume is large which increases costs and paper waste. Also, the flowability
and appearance of the granules obtained by spray drying may be poor because
of the presence of Large irregularities on the surface of the granules.
In addition to these characteristic processing and product problems
associated with the spray drying process, volatile materials, such as nonionic
surfactants, are emitted into the air when processed by this method. This
volatilization problem, manifested by the discharge of dense "blue" smoke from
the spray tower, is referred to as "pluming." Air pollution standards limit
the
opacity of the plume. Consequently, it is necessary to limit the capacity of
the
spray tower or, in extreme instances, discontinue operation.
In an attempt to avoid the problems caused by spray drying,
considerable developmental effort has focused on post-dosing the product with
nonionic surfactants after the spray drying operation. Unfortunately, post-
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dosing of the spray dried base with surfactant in amounts sufficient to
provide
satisfactory wash performance generally results in a product that has poor
dissolution characteristics. Accordingly, the amount of surfactant that may be
employed in the detergent formulation is severely limited. Because heavy-duty
laundry detergents need large amounts of nonionic surfactant present,
inorganic silicates have been added to these detergent formulations to absorb
the nonionic liquids.
For example, U.S. Pat. No. 3,769,222 to Yurko et al. discloses mixing
liquid nonionic surfactants with sodium carbonate until partial solidification
occurs followed by the addition of large amounts of silica (silicon dioxide)
to
produce a dry free-flowing detergent composition. A disadvantage to this
technique, however, is that because the silica has no significant cleaning
activity, its inclusion in a detergent formulation in large amounts merely
serves
to increase the cost of the product. Further, the use of silica in detergents
adds
to the total suspended solids (TSS) content of laundry waste water contrary to
the dictates of many local and state water pollution standards. Therefore,
there
is an incentive to keep low the amount of silica added to the detergent
composition.
U.S. Pat. No. 4,473,485 to Greene reports that a free-flowing granular
detergent can be prepared by mixing a polycarboxylic structuring agent
solution
with a micronized carbonate followed by the addition to the mixture of a
nonionic surfactant and water, followed by removal of the excess water. The
preferred micronized carbonate is calcium or sodium carbonate. A
disadvantage of this process, however, is that the micronized carbonate used
by Greene to enhance the flowability of the detergent product is quite
expensive as compared to standard sodium carbonate. Without the use of the
micronized carbonate, Greene's product would not have such good flowability.
In addition, where the micronized carbonate is calcium carbonate, the building
capability of the detergent is reduced.
Therefore, a need exists for a process and its resulting composition that
substantially overcomes the problem of free-flowability in highly loaded
nonionic
detergents.
SUMMARY OF THE INVENTION
The present invention relates to a free-flowing agglomerated detergent
powder that contains a high level of nonionic detergent surfactant and a
process for making it. More broadly, the present invention relates to a free
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flowing agglomerated detergent powder that contains high levels of detergent
surfactants and a process for making the free flowing detergent powder. The
present invention also relates to a process for making a free-flowing
agglomerated detergent powder, particularly one that contains a high level of
nonionic detergent surfactant. The method includes the steps of loading an
alkali metal carbonate with a surfactant selected from the group consisting of
anionics, nonionics, ampholytics, cationics, zwitterionics, and mixtures
thereof
to form a homogeneous coated alkali metal carbonate premix; admixing a
carboxylic acid into the premix; introducing water onto the mixture; and
agitating
the mixture to accomplish agglomeration. Preferably, the mixture is fed to a
rotating agglomerator where a minor amount of water is sprayed into the
mixture as the agglomerator rotates. The agglomerate is preferably dried to
remove the excess water, i.e., water not bound as the hydrate, to form the
free-
flowing detergent composition of the present invention.
Optionally, minor amounts of other known detergent ingredients may be
present in the premix. For example, minor amounts of silicas and
carboxymethylcellulose can be mixed with the alkali metal carbonate prior to
being loaded with the surfactant.
Preferably, the process includes loading sodium carbonate with a
surfactant to form a homogeneous surfactant coated alkali metal carbonate
premix. The surfactant is selected from the group consisting of avionics,
nonionics, zwitterionics, ampholytics, cationics, and mixtures thereof.
Preferably, the surfactant is a nonionic surfactant. A carboxylic acid that is
selected from the group of carboxylic acids that, below a first temperature,
have
a greater water solubility than the water solubility of its corresponding
alkali-
metal salt is admixed with the premix to form a mixture. As will be discussed
below, the first temperature is from about 15°C to about 40°C.
Preferably, the
carboxylic acid is selected from the group consisting of citric acid, malic
acid,
and mixtures thereof. The mixture is agitated while a minor amount of water,
less than about 7%, is incorporated into the mixture causing the carboxylic
acid
to solubilize and neutralize forming the sodium salt of the carboxylic acid
and
causing the mixture to agglomerate. The agglomerated mixture is dried to
remove at least about 50% of the added water to form a free-flowing powder
detergent composition.
The resulting agglomerated detergent comprises an alkali metal
carbonate present in about 5% to about 80% weight of the final product; a
detergent surfactant, preferably, a nonionic detergent surfactant present in
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about 5% to about 50% by weight of the final product; and up to about 25% of
an alkali metal salt of ,a carboxylic acid, wherein the carboxylic acid is
selected
from those carboxylic acids that, below a first temperature, have a greater
water
solubility than the water solubility of its corresponding alkali-metal salt.
As will
be discussed below, the first temperature is from about 15°C to about
40°C.
Preferably, the agglomerated detergent powder of the present invention
comprises from about 5% to about 80% sodium carbonate, from about 5% to
about 50% of a nonionic detergent surfactant, wherein the nonionic surfactant
is the sole detergent surfactant present, and from about 4% to about 18% of
the sodium citrate, sodium malate, and mixtures thereof.
More preferably, the agglomerated detergent powder of the present
invention comprises from about 20% to about 70% of sodium carbonate, from
about 20% to about 40% of a nonionic detergent surfactant wherein the
nonionic surfactant is the sole detergent surfactant present; and from about
5%
to about 13% of a substantially completely neutralized carboxylic acid
selected
from the group consisting of sodium citrate, sodium malate, and mixtures
thereof, wherein the sodium citrate or sodium malate is formed by the
reaction,
upon the addition of water, between a premix comprising (a) the nonionic
surfactant and sodium carbonate and (b) admixed citric acid, malic acid, or
mixtures thereof.
The term "coated" is used in the specification and claims to mean that
the surfactant is present on the surface of the carbonate (and other
particles)
as well as within the carbonate (and other particles), e.g. by absorption.
Preferably, the process includes mixing sodium carbonate (and,
optionally, other detergent ingredients) and a nonionic surfactant to form a
homogeneous nonionic surfactant coated sodium carbonate premix, wherein
the nonionic surfactant is the sole surfactant present in the premix. a
carboxylic
acid selected from the group consisting of citric acid, malic acid, and
mixtures
thereof is admixed with the premix to form a mixture. The mixture is agitated
while water is incorporated into the mixture causing the carboxylic acid to
soiubilize and neutralize to form the sodium salt of the carboxylic acid and
to
cause the mixture to agglomerate. The agglomerated mixture is dried to form a
free-flowing powder detergent composition.
The term "free water" is used in the following specification and claims to
indicate water that is not firmly bound as water of hydration or
crystallization to
inorganic materials.
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Unless specifically noted, all percentages used in the following
specification and claims are by weight of the final product.
DETAILED DESCRIPTION OF THE INVENTION
AND PREFERRED EMBODIMENTS
The present invention provides a free-flowing agglomerated detergent
powder that contains a high level of surfactant, particularly a nonionic
surfactant.
The present invention also provides for a process for making a free-
flowing agglomerated detergent powder that contains a high level of surfactant
particularly a nonionic surfactant. The method includes loading an alkali
metal
carbonate (and, optionally, other detergent ingredients) with a surfactant to
form a premix comprising a homogeneous mixture of surfactant coated
carbonate. A carboxylic acid is admixed with the premix to form a mixture. The
carboxylic acid is preferably selected from those carboxylic acids that, below
a
first temperature, have a water solubility that is greater than the water
solubility
of its corresponding alkali-metal salt. The mixture is introduced into a
mixer,
preferably a rotating drum agglomerator, where water is introduced to the
mixture causing the carboxylic acid to solubilize and react with the alkali
metal
carbonate to form the alkali metal salt of the carboxylic acid at a
temperature
lower than the first temperature and to cause the mixture to agglomerate into
particles. The particles are dried and sized.
The detergent composition comprises three essential ingredients: an
alkali metal carbonate, a nonionic surfactant and a substantially completely
neutralized carboxylic acid.
The alkali metal carbonate is preferably sodium carbonate for reasons of
cost and efficiency. Among the preferred sodium carbonates used in the
following examples are light density (LT) soda ash (Solvay process), mixtures
of light density (LT) and medium density soda ash (Sesquicarbonate process),
a special high porosity "medium-light" ash (Sesquicarbonate process) and
mixtures of light density and "medium-light" ash. These particles of sodium
carbonate have an average density of from about 0.5 to about 0.7 and an
average mesh size ranging from about 20 to about 200, U.S. Standard Sieve
number. Carbonates such as these are commercially available from FMC
Corp. and General Chemical and are relatively inexpensive as compared to
more processed carbonates because they do not require further processing
such as grinding.
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The sodium carbonate can be present in the free-flowing detergent
composition in the amount of about 5% to about 80% by weight of the final ,
product. The amount of sodium carbonate added to the final product is
balanced against the amount of nonionic surfactant which lnrill be loaded into
the sodium carbonate as well as the amount which will be neutralized by the
admixed carboxylic acid. The preferred range for the sodium carbonate is from
about 20% to about 70%, more preferably from about 30% to about 65% by
weight of the final product. It should be mentioned that within the preferred
range the higher levels tend to be required under conditions of use at low
product concentrations, as is commonly the practice in North America, and the
converse applies under conditions of use at higher product concentrations, as
tends to occur in Europe.
!f desired, the alkali metal carbonate can be mixed with other minor
amounts, not to exceed about 10% of the final product, of detergent
ingredients
before the nonionic surfactant is added to it. Alternatively, the nonionic
surfactant can be, added to other minor amounts of detergent ingredients, not
to
exceed about 10% of the final product, after which they can be mixed with the
nonionic surfactant coated alkali metal carbonate. In one embodiment, the
carbonate, optional detergent ingredients, and surfactant are mixed in the
manner fully disclosed in U.S. Pat. No. 5,458,769 or 5,496,486.
In another embodiment, a minor amount, up to about 5%, of a silica such
as a silicon dioxide hydrate is mixed with the alkali metal carbonate prior to
loading with the nonionic surfactant. A variety of siliceous substances are
acceptable for addition to the detergent composition, although highly
absorbent
silica of the precipitated or fumed variety is preferred. The preferred
siliceous
compounds have oil absorption numbers of 150 to about 350 or greater,
preferably about 250 or greater. As examples of operable silicas, the
following
siliceous material are representative: Sipernat 50, Syloid 266, Cabosil M-5,
Hisil 7-600. Preferably, from about 0.5% to about 4% by weight of the final
product, of silica is mixed with the alkali metal carbonate prior to loading
by the
nonionic surfactant. More preferably, from about 3% to about 4% of silica by
weight of the final product is mixed with the alkali metal carbonate.
Low levels of carboxymethylcellulose, for example from about 0.1 % up
to about 5%, to aid in the prevention of soil suspended in the wash liquor
from
depositing onto cellulosic fabrics such as cotton, may also be mixed with the
alkali metal carbonate prior to loading with the nonionic surfactant.
Preferably,
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from about 1 % to about 3%, more preferably from about 2°,'° to
about 3% of
' carboxymethylcellulose is mixed with the alkali metal carbonate prior to
loading ,
with the nonionic surtactant. !n a preferred embodiment, both the silica and
the
carboxymethylcellulose are mixed with the sodium carbonate prior to being
loaded with the nonionic surfactant.
The second essential ingredient is a detergent surfactant and is selected
from the group consisting of anionics, nonionics, zwitterionics, ampholytics,
cationics, and mixtures thereof. The detergent surfactant used in the present
invention may be any of the conventional materials of this type which are very
well known and fully described in the literature, for example in "Surtace
Active
Agents and Detergents" Volumes I and II by Schwartz, Perry & Berch, in
"Nonionic Surfactants" by M. J. Schick, and in McCutcheon's "Emuls~ers &
Detergents,. "
The surfactant is present at a level of from about 1 °~o to about
90%. .
Desirably, the surfactant is present at a level of from about 10% to about
50%,
and preferably, the surfactant is included in an amount from about 20% to
about 40%.
Useful anionic surfactants include the water soluble salts of the higher
fatty acids, i.e., soaps. This includes alkali metal soaps such as the sodium,
potassium, ammonium, and alkyl ammonium salts of higher fatty acids
containing from about 8 to about 24 carbon atoms. Soaps can be made by
direct saponification of fats and oils or by the neutralization of free fatty
acids.
Particularly useful are the sodium and pofiassium salts of the mixtures of
fatty
acids derived from coconut oil and tallow, i.e., sodium or potassium tallow
and
coconut soap.
Useful anionic surfactants also include the water-soluble salts, preferably
the alkali metal, ammonium and alkyloiammonium salts, of organic sulfuric
reaction products having in their molecular structure an alkyl group
containing
from about 8 to about 20 carbon atoms and a sulfonic acid or sulfuric acid
ester
group. Included in the term "alkyl" is the alkyl portion of acyl groups.
Examples
of this group of synthetic surfactants are the sodium and potassium alkyl
sulfates, especially those obtained by sulfating the higher primary or
secondary
alcohols (Ce C,e carbon atoms} such as those produced by reducing the
glycerides of tallow or coconut oil; and the sodium and potassium alkylbenzene
sulfonates in which the alkyl group contains from about 10 to about ; 6 carbon
atoms, in straight chain or branched chain conficJuration, e.g., see U.S. Pat.
Nos. 2,220,099 and alkylbenzene sulfonates in which the average i;umber of
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carbon atoms in the alkyl group is from about 11 to 14, abbreviated as C".,4
LAS. -
The anionic surfactants useful in the present invention may also include
the potassium, sodium, calcium, magnesium, ammonium or lower
alkanolammonium, such as triethanolammonium, monoethanolammonium, or
diisopropanolammonium paraffin or olefin sulfonates in which the alkyl group
contains from about 10 to about 20 carbon atoms. The lower alkanol of such
alkanolammonium will normally be of 2 to 4 carbon atoms and is preferably
ethanol. The alkyl group can be straight or branched and, in addition, the
sulfonate is preferably joined to any secondary carbon atom, i.e., the
sulfonate
is not terminally joined.
The anionic surfactants useful in the present invention may also include
the potassium, sodium, calcium, magnesium, ammonium or lower
alkanolammonium, such as triethanolammonium, monoethanolammonium, or
diisopropanolammonium paraffin or olefin sulfonates in which the alkyl group
contains from about 10 to about 20 carbon atoms. The lower alkanol of such
alkanolammonium will normally be of 2 to 4 carbon atoms and is preferably
ethanol. The alkyl group can be straight or branched and, in addition, the
sulfonate is preferably joined to any secondary carbon atom, i.e., the
sulfonate
is not terminally joined.
Other anionic surfactants that may be useful in the present invention
include the secondary alkyl sulfates having the general formula
R2
R,-CH-O-S03 M+
wherein M is potassium, sodium, calcium, or magnesium, R, represents an
alkyl group having from about 3 to about 18 carbon atoms and R2 represents an
alkyl group having from about 1 to about 6 carbon atoms. Preferably, M is
sodium, R, is an alkyl group having from about 10 to about 16 carbon atoms,
and R2 is an alkyl group having from about 1 to about 2 carbon atoms.
Other anionic surfactants useful herein are the sodium alkyl glycerol
ether sulfonates, especially those ethers of higher alcohols derived from
tallow
and coconut oil; sodium coconut oil fatty acid monoglyceride sulfonates and
sulfates; sodium or potassium salts of alkyl phenol ethylene oxide ether
sulfates
containing from about 1 to about 10 units of ethylene oxide per molecule and
wherein the alkyl group contains from about 10 to about 20 carbon atoms.
The ether sulfates useful in the present invention are those having the
formula RO(C2H,0)XS03M wherein R is alkyl or alkenyl having from about 10 to
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about 20 carbon atoms, x is 1 to 30, and M is a water soluble ration
preferably
sodium. Preferably, R has 10 to 16 carbon atoms. The alcohois can be ,
derived from natural fats, e.g., coconut oil or tallow, or can be synthetic.
Such
alcohols are reacted with 1 to 30, and especially 1 to 12, molar proportions
of
ethylene oxide and the resulting mixture of molecular species is sulfated and
neutralized.
Other useful anionic surfactants herein include the water-soluble salts of
esters of alpha-sulfonated fatty acids containing from about 6 to 20 carbon
atoms in the fatty acid group and from about 1 to 10 carbon atoms in the ester
group; water-soluble salts of 2-acyloxyalkane-1-sulionic acids containing from
about 2 to 9 carbon atoms in the aryl group and from about 9 to about 23
carbon atoms in the alkane moiety; water-soluble salts of olefin and paraffin
sulfonates containing from about 12 to 20 carbon atoms; and beta-alkyloxy
alkane sulfonates containing from about 1 to 3 carbon atoms in the alkyl group
and from about 8 to 20 carbon atoms in the alkane n~~oiety.
Another example of anionic surfactants that may be useful in the present
invention are those compounds that contain two anionic functional groups.
These are referred to as di-anionic surfactants. Suitable di-anionic
surfactants
are the disuifonates, disuifates, or mixtures thereof v~~hich may be
represented
by the following formula:
R(S03)ZMz,R(S04)ZMZ,R(SO3)(S04)MZ
where R is an acyclic aliphatic hydrocarbyl group having 15 to 20 carbon atoms
and M is a water-solubilizing ration, for example, the C,5 to C2o dipotassium-
1,2-
alkyldisulfonates or disulfates, disodium 1,9-hexadecyl disulfates, C,5 to CZo
disodium 1,2-alkyldisulfonates, disodium 1,9-stearyldisulfates and 6,10-
octadecyldisulfates.
The nonionic detergent surfactant may be any of the conventional
materials of this type which are very well known and fully described in the
literature, for example in "Surface Active Agents and Detergents" Volumes I
and II by Schwartz, Perry & Berch, "Nonionic Surfa;iants" by M. J. Schick, and
McCutcheon's "Emulsifiers & Detergents . "
For example, the nonionic materials may include compounds
produced by the condensation of alkylene oxide groups (hydrophilic in nature)
with an organic hydrophobic compound, which nay be aliphatic or alkyl
aromatic in nature. The length of the polyoxr alkylene group which is
condensed with any particular hydrophobic group can be readily adjusted to
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yield a water-soluble compound having the desired degree of balance between
hydrophilic and hydrophobic elements.
Other useful nonionic surfactants include the polyoxyethylene or
polyoxypropylene condensates of aliphatic carboxylic acids, whether linear- or
branched-chain and unsaturated or saturated, containing from about 8 to about
18 carbon atoms in the aliphatic chain and incorporating from 5 to about 50
ethylene oxide or propylene oxide units. Suitable carboxylic acids include
"coconut" fatty acid (derived from coconut oil) which contains an average of
about 12 carbon atoms, "tallow" fatty acids (derived from tallow-class fats)
which contain .an average of about 18 carbon atoms, palmitic acid, myristic
acid, stearic acid and lauric acid.
The nonionic surfactants can also include , polyoxyethylene or
polyoxypropylene condensates of aliphatic alcohols, whether linear or branched
chain and unsaturated or saturated, containing from about 8 to about 24 carbon
atoms and incorporating from about 5 to about 50 ethylene oxide or propylene
oxide units. Suitable alcohols include the coconut fatty alcohol, tallow fatty
alcohol, lauryl alcohol, myristyl alcohol, and oleyl alcohol.
Alkyl saccharides may also find use in the composition. In general, the
alkyl saccharides are those having a hydrophobic group containing from about
8 to about 20 carbon atoms, preferably from about 1 C to about 16 carbon
atoms, and a polysaccharide liydrophillic group containing from about 1 (mono)
to about 10 (poly), saccharide units (e.g., galactoside, glucoside, f.
uctoside,
glucosyl, fructosyl, and/or galactosyl units). Mixtures of saccharide moieties
may be used in the alkyl saccharide surfactants. Preferably, the alkyl
saccharides are the alkyl glucosides having the formula
R'~(C~H2~0)t~Z)x
wherein Z is derived from glucose, R' is a hydrophobic group selected from the
group consisting of alkyl, alkyl-phenyl, hydroxyalkyl, hydroxyalkylphenyl, and
mixtures thereof in which the alkyl groups contain from about 10 to about 18
carbon atoms, n is 2 or 3, t is from 0 to about 10, and x is from 1 to about
8.
Examples of such alkyl saccharides are described in U.S. Pat. No. 4,565,647
(at col. 2, line 25 through col. 3, line 57) and U.S. Pat. No. 4,732,704 (at
col. 2,
lines 15-25) .
Semi-polar nonionic surfactants include water-soluble amine oxides
containing one alkyl moiety of from about 10 to 18 carbon atoms and two
moieties selected from the group of alkyl and hydroxy alkyl moieties of from
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about 1 to about 3 carbon atoms; water-soluble phosphine oxides containing
one alkyl moiety of about 10 to 18 carbon atoms and two moieties selected
from the group consisting of alkyl groups and hydroxy alkyl groups containing
from about 1 to 3 carbon atoms; and water-soluble sulfoxides containing one
alkyl moiety of from about 10 to 18 carbon atoms and a moiety selected from
the group consisting of alkyl and hydroxy alkyl moieties of from about 1 to 3
carbon atoms.
Ampholytic surfactants include derivatives of aliphatic or aliphatic
derivatives of heterocyclic secondary and tertiary amines in which the
aliphatic
moiety can be straight chain or branched and wherein one of the aliphatic
substituents contains from about 8 to 18 carbon atoms and at least one
aliphatic substituent contains an anionic water-solubilizing group.
Zwitterionic surfactants include derivatives of aliphatic, quaternary,
ammonium, phosphonium, and sulfonium compounds in which one of the
aliphatic substituents contains from about 8 'to 18 carbon atoms.
Cationic surfactants can also be included in the present detergent.
Cationic surfactants comprise a wide variety of compounds characterized by
one or more organic hydrophobic groups in the cation and generally by a
quaternary nitrogen associated with an acid radical. Pentavalent nitrogen ring
compounds are also considered quaternary nitrogen compounds. Halides,
methyl sulfate and hydroxide are suitaiale. Tertiary amines can have
characteristics similar to cationic surfactant; at washing solution pH values
less
than about 8.5. A more complete disclosure of these and other cationic
surfactants useful herein can be found in U.S. Pat. No. 4,228,044, Cambre,
issued Oct. 14, 1980 .
The ethoxylated alkyl phenols with C8-C,s alkyl groups, preferably C8 C9
alkyl groups and from about 4-12 EO units per molecule, or ethoxylated fatty
acid amides may be used. Other nonionic detergent compounds which can be
used for the purposes of the present invention will be readily apparent to
those
skilled in the art. It will be appreciated that the nonionic compounds which
are
used to the greatest benefit are liquid corc;pounds which are more difficult
to
incorporate into detergent compositions otherwise, though pas!y or solid
nonionic detergent compounds may also be used. In the fatter case,
adsorption of the nonionic compound ono the calcium carbonate may be
facilitated by the use of elevated temperatures.
Preferably, the nonionic surfactant is a polyoxyethylene or
polyoxypropylene condensate of an aliphatic alcohol, whether linear- or
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branched-chain and unsaturated or saturated, containing from about 8 to about
24 carbon atoms and incorporating from about 5 to about 50 ethylene oxide or
propylene oxide units. The nonionic detergent compounds of most commercial
interest and which are most readily available include the ethoxylated
synthetic
or natural fatty alcohols, preferably linear primary or secondary monohydric
alcohols with C8 C,e, preferably C,°-C,B, alkyl groups and about 3-80,
preferably
5-20, ethylene oxide (EO) units per molecule.
Examples of the preferred nonionic surfactant compounds in this
category are the nonionic surfactants having the formula R'(OCZH4)~OH, where
R' is a C8 C,e alkyl group or a CB C,2 alkyl phenyl group, and n is from 3 to
about 80. Particularly preferred nonionic surfactants are the condensation
products of C8-C,g alcohols with from about 5 to about 20 moles of ethylene
oxide per mole of alcohol, e.g., a C,2-C,e alcohol condensed with about 5 to
about 9 moles of ethylene oxide per mole of alcohol. Nonionic surfactants of
this type include the NEODOLTM products, e.g., Neodol 23-6.5, Neodol 25-7,
and Neodol 25-9 which are respectively, a C,2_,3 linear primary alcohol
ethoxylate having 6.5 moles of ethylene oxide, a C,2_,5 linear primary alcohol
ethoxylate having 7 moles of ethylene oxide, and a C,2_,5 linear primary
alcohol
ethoxylate having 9 moles of ethylene oxide.
The amount of a surtactant particularly a liquid nonionic surfactant that
can be adsorbed on the alkali metal carbonate to give a free flowing product
is
generally up to about 50% by weight of the resultant product. Although higher
levels of nonionic detergent surfactants can be used if desired, this tends to
defeat the object of the present invention because the resultant product is a
paste or a powder with poor flow properties. On the other hand, with very low
levels of less than, say, about 5% of the nonionic detergent compound, there
is
clearly little benefit achieved.
Desirably, the ratio of alkali metal carbonate to nonionic surfactant is
from about 2:1 to about 3.5:1. Within this range of ratios, it is believed
that an
effective cleaning free-flowing powder can be produced. Preferably, the ratio
is
from about 2.2:1 to about 3.3:1, more preferably from about 2.3:1 to about
2.8:1. In the most preferred embodiment the ratio of alkali metal carbonate to
nonionic surfactant is about 2.4:1.
Preferably, the surfactant is a nonionic surfactant which is incorporated
in an amount of about 5% to about 50% by weight of the final product. Of
course, the detergent benefits of high nonionic concentration must be balanced
against cost-performance. Therefore, the preferred range for the nonionic
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surfactants is from about 20% to about 40% by weight of the final product,
more
preferably, from about 20% to about 30%. Most preferably, the nonionic
surfactant is present at a level of about 25%. It should be mentioned that
within
the above ranges the lower levels tend to be required under conditions of use
at higher product concentrations, as is commonly the practice in Europe, and
the converse applies under conditions of use at lower product concentrations,
as tends to occur in North America and Asia.
Loading, adsorption, and absorption of the nonionic surfactant onto the
alkali metal carbonate (and into its porous structure) can be achieved by
simple
admixture with sufficient agitation to distribute the nonionic compound
entirely
on the alkali metal carbonate to form a premix comprising a homogeneous
mixture of nonionic surfactant coated alkali metal carbonate. The loading can
be accomplished in any of the known mixers such as by a ribbon or plow
blender. Preferably, the nonionic surfactant is sprayed onto the alkali metal
carbonate and other optional ingredients, if present, while they are agitated.
In
preparing the premix of the present invention, it is important that the alkali
metal
carbonate is sufficiently coated with the nonionic surfactant so that when
water
is later added, the water does not immediately contact uncoated carbonate and
hydrate the carbonate. It is believed that excessive hydration of the
carbonate
reduces the amount of water available to solubilize the carboxylic acid which
will require additional water to achieve the desired agglomerated particle
size.
At the same time, if an excess amount of nonionic surfactant is present
in the premix, the later admixed carboxylic acid may be coated with the excess
nonionic surfactant. As a result, the amount of carboxylic acid available to
solubilize and neutralize with the alkali metal carbonate will be reduced,
which,
in turn will reduce the agglomeration efficiency and require additional
carboxylic
acid to achieve the desired particle size.
In the preferred embodiment of the present invention, from about 5% to
about 80% sodium carbonate is blended with from about 5% to about 50% of a
nonionic surfactant, wherein the nonionic surfactant is the sole surfactant
present to form a form a premix comprising a homogeneous mixture of nonionic
surfactant coated alkali metal carbonate. More preferably, the premix is
formed
by blending from about 20% to about 70% of sodium carbonate with up to
about 5%, preferably from about 2% to about 4% of silica, and from about 1
to about 3% of minor detergent ingredients including carboxymethylcellulose
and, loading the sodium carbonate, silica, and carboxymethylcellulose with
from about 20% to about 40% of a nonionic surfactant wherein the nonionic
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surfactant is the sole surfactant present in the premix. In a more preferred
embodiment, the premix is formed by mixing from about 30% to about 65% of
sodium carbonate, from about 0.5% to about 4% of a silica, from about 2% to
about 3% of carboxymethylcellulose, and a minor amount of other optional
detergent ingredients; and spraying from about 20% to about 30% of a nonionic
surfactant wherein the nonionic surfactant is the sole detergent surfactant
present, onto the mixed carbonate, silica, carboxymethylcellulose, and
optional
ingredients.
As discussed above, the surfactant, particularly the nonionic surtactant is
added in an amount so that it is within a particular ratio with respect to the
sodium carbonate. Within this ratio range, the surfactant adequately coats the
sodium carbonate yet does not provide a substantial excess of surfactant which
would then undesirably coat the carboxylic acid. Moreover, it is believed that
the order of addition is important to achieving the desired agglomeration. By
loading the alkali metal carbonate with the surfactant prior to the admixture
of
carboxylic acid and introduction of water, the desired particle size is
achieved
while still producing a free-flowing powder.
The third essential ingredient in the free-flowing agglomerated powder
detergent composition of the present invention is the alkali metal salt of a
carboxylic acid wherein the carboxylic acid is selected from those carboxylic
acids that, below a first temperature, have a greater water solubility than
the
water solubility of its corresponding alkali-metal salt. Preferably, the
alkali metal
carboxylate is provided solely by the reaction of the corresponding carboxylic
acid and the alkali metal carbonate. Preferred alkali metal carboxylates are
selected from the group consisting of alkali metal citrate, alkali metal
malate,
and mixtures thereof. Alkali metal citrate is the most preferred because
citric
acid is relatively inexpensive and is readily obtainable. In the preferred
embodiment where the alkali metal carbonate is sodium carbonate, the alkali
metal carboxylate is selected from the group consisting of sodium citrate,
sodium malate, and mixtures thereof.
The alkali metal carboxylate is present in the detergent composition at a
level of up to about 25%, preferably from about 4% to about 18% and is
provided solely by the reaction of the carboxylic acid corresponding to the
alkali
metal carboxylate, and the alkali metal carbonate. It is believed that when
the
amount of alkali metal carboxylate is within this range, the desired
agglomeration of the nonionic surfactant loaded alkali metal carbonate will be
efficiently achieved and will produce the desired particle size. More
preferably,
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the alkali metal carboxylate is present at a level of from about 5% to about
13%
and in the most preferred embodiment is present at a level of about 9% to
about 11 %.
Desirably, as will be further discussed below, the carboxylic acid should
be substantially completely neutralized by reaction with the alkali metal
carbonate to its corresponding alkali metal salt during processing. For
example, malic acid should be substantially completely neutralized to an
alkali
metal malate. Because of reaction and processing limitations, it is believed
that
the carboxylic acid is not completely neutralized. Therefore, it is desirable
to
neutralize at least about 90%, preferably at least about 95% and more
preferably at least about 99% of the carboxylic acid to its alkali metal
carboxylate. Preferably, the substantially completely neutralized carboxylic
acid
will be selected from the group consisting of the alkali metal salts of citric
acid,
malic acid, and mixtures thereof. In the preferred embodiment where the alkali
metal carbonate is sodium carbonate, the substantially completely neutralized
carboxylic acid is selected from the group consisting of sodium citrate,
sodium
malate, and mixtures thereof.
The amount of carboxylic acid to be admixed can be determined from
the amount of substantially completely neutralized carboxylic acid desired in
the
final product as well as the amount of alkali metal carbonate present. It
would
be desirable to use the minimum amount of carboxylic acid necessary to
achieve acceptable agglomeration. This amount, however, must be balanced
against the desire to provide an amount of the alkali metal carboxylate in the
final product sufficient to control hard water filming in those instances
where
hard water is used. Acid levels which are too high can result in lower
alkalinity
by neutralization of the alkali metal carbonate which can detrimentally afFect
detergent performance. Too little acid, on the other hand, reduces the ability
of
the acid salt hydrate to entrap the added moisture and hampers agglomeration.
The carboxylic acid is therefore incorporated in an amount such that the ratio
between the alkali metal carbonate and the carboxylic acid is in the range
from
about 6.5:1 to about 12:1, preferably in the range from about 6.5:1 to about
8:1,
more preferably about 7:1.
The carboxylic acid is admixed with the premix at a level of up to about
18% by weight of the final product. The preferred range of admixed acid is
from about 3% to about 13% by weight of the final product, more preferably
from about 4% to about 10% and most preferably from about 7% to about 9%.
The carboxylic acid is only lightly admixed with the premix prior to the later
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introduction of water to minimize the potential for coating of the carboxylic
acid
by the nonionic surfactant.
After the carboxylic acid is lightly admixed with the premix, a small
amount of water is incorporated to accomplish agglomeration of the particles.
The water may be incorporated as a mist, steam, or in another suitable
fashion.
Desirably, the amount of water used is as small as practical in order to
minimize subsequent drying time, energy and thus cost. The water is therefore
incorporated at a level from about 0.1 % to no more than about 7%, preferably
no more than about 5%. In a more preferred embodiment, the water is
incorporated in a range between about 4% and about 5%.
The water is incorporated into the mixture using any suitable mixing
apparatus to achieve agglomeration of the mixture. Preferably, a drum
agglomerator is used. The agglomerator rotates to distribute the mixture along
the length of the drum as the falling sheets of the mixture are sprayed with
water to produce a well controlled agglomeration of the particles.
Without wishing to be bound by any particular theory, it is believed that
the carboxylic acid is solubilized and neutralized by the alkali metal
carbonate
at the same time the alkali metal carbonate is hydrated. The carboxylic acid
should be substantially completely neutralized to its corresponding alkali
metal
salt which, below a first temperature, is less water soluble than the acid
form.
During the neutralization of the carboxylic acid, the alkali metal carboxylate
binds the surfactant coated alkali metal carbonate particles to agglomerate
them and to produce the desired particle size. As the drum rotates and the
particles are agglomerated, the Larger particles move from the inlet end to
the
outlet end of the agglomerator where they exit and are conveyed to a dryer to
remove the free water from the agglomerated particles. The agglomerator is
preferably inclined from the inlet to the outlet so that as the particles
agglomerate, the larger agglomerated particles move from the inlet end to the
outlet end where they are dried.
In particular, while not wishing to be held to a specific theory, it is
believed that the carboxylic acid is solubilized with the water and reacts
with the
alkali metal carbonate to become substantially completely neutralized. The
salts of the carboxylic acids, for example, citric and malic, have a water
solubility less than their acid form below a first temperature and therefore
the
salts come out of solution to bind and thus agglomerate the particles. As
noted
above, insufficient coating by the surfactant on the surface of the alkali
metal
carbonate will produce excessive hydration of the sodium carbonate. As a
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result, the water required to solubilize the carboxylic acid will not be
available
and additional water and processing time will be required to produce the
desired agglomerated particle size. In addition, hydration of sodium carbonate
is exothermic and excessive hydration of sodium carbonate will generate
undesirable heat and increase the temperature of the mixture above the first
temperature. At the same time, an excess of surfactant present in the premix
may cause coating of the carboxylic acid resulting in a reduction of
agglomeration efficiency. In addition, additional carboxylic acid and water
may
be required to achieve the desired agglomerated particle size. Consequently,
the order of addition as well as the temperature are believed to be important
to
achieving the desired agglomeration and particle size.
It is believed that by adding the carboxylic acid after the premix has
been formed, the desired solubilization of the carboxylic acid is achieved
prior
to a substantial reaction with the alkali metal carbonate. If the citric acid
were
admixed with the alkali metal carbonate prior to adding the surtactant, it is
believed that the resulting product would not achieve the desired free flowing
and dissolution properties.
As noted above, the preferred carboxylic acid has a greater water
solubility than its corresponding alkali metal salt below a first temperature.
An
increase in temperature above the first temperature therefore adversely
affects
the relative solubility of the acid form of the carboxylic acid in comparison
to the
salt form which, in turn, adversely affects the agglomeration efficiency. As a
result, the formation of the alkali metal salt of the carboxylic acid is
controlled so
as to prevent the temperature of the mixture from rising above the first
temperature.
Generally, the first temperature can range from about 15°C to
about
40°C, preferably from about 32°C to about 35°C. A first
temperature higher
than about 42°C appears to adversely affect the product characteristics
and is,
therefore, undesirable.
It will be understood by one skilled in the art that several factors can be
varied to control the residence time (i.e., the weight of the mixture on the
bed
divided by the total feed rate) and agglomerate size, e.g., feed rate to the
drum,
angle of the drum, rotational speed of the drum, the number and location of
the
water spray. The result of manipulating such factors is desired control of the
particle size and density of the agglomerates.
The wetted agglomerated particles are dried to remove any free water.
The drying may be accomplished by any known method such as by a tumbling
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dryer or air drying on a conveyor. As one skilled in the art will appreciate,
the
time, temperature, and air flow may be adjusted to provide for an acceptable
drying rate. Using a high ambient temperature in the dryer can shorten the
residence time in the dryer, while lower temperatures may unduly lengthen the
residence time. Short residence times, however, may increase the risk of
adversely affecting the stability of the agglomerates or of incompletely
drying
the agglomerate.
It is desirable to remove as much water as practicable since the
presence of water, even when bound, may detrimentally react with post-added
moisture sensitive detergent ingredients such as bleaches and enzymes. In
addition, the presence of water may, over time and under typical storage
conditions, cause product caking. Therefore, in a preferred embodiment, a
minor amount of water is added to accomplish agglomeration and furthermore,
at least about 50% of the added water is removed by drying. More preferably,
at least about 60% of the added water is removed by drying. Consequently,
the resulting composition contains less than about 3% of bound water, more
preferably less than about 2% of bound water.
The dried particles have an average particle mesh size of up to about 20
U.S. Standard Sieve number. Preferably, the particles have a particle mesh
size such that about 90% of the particles are in the range from about 20 to
about 100 U.S. Standard Sieve number. The resulting powder has a bulk
density of at least 0.7 g/cc, preferably from about 0.8 to about 0.9 g/cc,
more
preferably from about 0.85 to about 0.9 g/cc.
The mixing steps in the process to prepare the detergent compositions
of this invention can be accomplished with a variety of mixers known in the
art.
For example, simple, paddle or ribbon mixers are quite effective although
other
mixers, such as drum agglomerators, fluidized beds, pan agglomerators and
high shear mixers may be used.
The preferred embodiment of the agglomerated detergent composition
of the present invention includes from about 20% to about 70% of sodium
carbonate, from about 20% to about 40% of a surfactant, particularly a
nonionic
detergent surfactant and from about 3% to about 13% of a sodium carboxylate
selected from the group consisting of sodium citrate, sodium malate, and
mixtures thereof, wherein the sodium carboxylate is provided solely by the
reaction, at a temperature, below a first temperature, or (a) a premix
comprising
a surfactant and sodium carbonate, (b) a carboxylic acid selected from the
group consisting of citric acid, malic acid, and mixtures thereof, and (c)
water.
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Preferably, the agglomerated detergent composition resulting from the
process of ' the present invention includes from about 20% to about 70% of ,
sodium carbonate, from about 20% to about 40% of a nonionic detergent
surfactant, wherein the nonionic surfactant is the sole detergent surfactant
present, and from about 4% to about 18% of a sodium salt of a carboxylic acid
selected from the group consisting of sodium citrate, sodium malate, and
mixtures thereof, wherein the sodium salt of the carboxylic acid is formed by
the
reaction at a temperature below a first temperature of (a) a premix comprising
a
nonionic surfactant loaded sodium carbonate, {b) a carboxylic acid selected
from the group consisting of citric acid, malic acid, and mixtures thereof,
and (c)
water.
tn addition to the essential ingredients mentioned above, it is possible to
include in the detergent composition of the invention other conventional
detergent additives. Examples of such optional additives are lather boosters
such as alkanolamides, particularly the monoethanolamides derived from palm
kernel fatty acids and coconut fatty acids, lather depressants such as alkyl
phosphates and silicone oils, anti-redeposition agents such as sodium
carboxymethyl cellulose, oxygen releasing bleaching agents such as sodium
perborate and sodium percarbonate, peracid bleach precursors, chlorine
releasing bleaching agents such as trichloroisocyanuric acid and alkali metal
salts of dichloroisocyanuric acid, fabric softening agents, inorganic salts
such
as sodium sulfate, anti-tarnish and anticorrosion agents, soil suspending
agents, soil release agents and, usually present in very minor amounts,
fluorescent agents, perfumes, enzymes, enzyme stabilizing agents and
germicides. These optional additives may be added when convenient during or
after, preferably after, the drying of the detergent compositions of the
present
invention. Such ingredients are described in U.S. Pat. No. 3,936,537.
A tow level of silicate, for example up to about 5% by weight, is usually
advantageous in decreasing the corrosion of metal parts in fabric washing
machines. Useful silicates such as an alkali metal silicate, particularly
sodium
neutral, alkaline, meta- or orthosilicate can be used.
Water-soluble, organic builders may also find use in the detergent
composition of the present invenfiion. For example, the salts of
ethylenediaminetetraacetic acid, nitriiotriacetic acid, oxydisuccinic acid,
mellitic
acid, benzene polycarboxylic acid, polyacrylic acid, and polymaleic acid may
be
included.
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Aluminosilicate ion exchange materials may be useful in the detergent
composition of this invention and may include the naturally-occurring
aluminosilicates or synthetically derived. a method for producing
aluminosilicate ion exchange materials is discussed in U.S. Pat. No. 3,985,669
.
Such synthetic crystalline aluminosilicate ion
exchange materials are available under the designations Zeolite A, Zeolite B,
and Zeolite X. In addition, layered or structured silicates such as those sold
under the designation SKS-6 by Hoechst-Celanese may also find use in the
detergent composition.
Bleaching agents and activators that may find use in the present
detergent composition are described in U.S. Pat. No. 4,412,934, and
4,483,781 . Suitable
bleach compounds include sodium perborate, sodium percarbonate, etc, and
the like, and mixtures thereof. The bleach compounds may also be used in
combination with an activator such as, for example, tetra-acetyl-
ethylenediamine (TAED), sodium nonanoyloxybenzene sulfonate (SNOBS),
diperoxydodecanedioc acid (DPDDA) and the like, and mixtures thereof.
Chelating agents are described in U.S. Pat. No. 4,663,071, from column 17,
line 54 through column 18, line 68. Suds
modifiers are also optional ingredients and are described ici U.S. Pat. Nos.
3,933,672, and 4,136,045,
Smectite clays may be suitable for use herein and are uescribed in U.S.
Pat. No. 4,762,645, at column 6, line 3 t~~rough column 7, line; 24 .
Other suitable additional detergency bulders that may be
used herein are enumerated in U.S. Pat. No. 3,936,537, column 13, line 54
through column 16, line 16, and in U.S. Pat. No. 4,663,071 .
In addition, whitening agent particles may be added tL the dried powder
detergent described above. The whitening agent part;,les comprise a
fluorescent whitening agent and an anionic surfactant that suk;stantially
protects
the whitening agent from degradation caused by the pres:.~nce of nonionic
surfactant. The preferred whitening agent particle composition and method of
making it more fully described in U.S. Patent Application Serial No.
08/616,570
and U.S. Patent Application Serial No. 08/616,208, respectiv:~ ely..
The laundry detergent compositions of the present invention can be
formulated to provide a pH (measured at a concentration or 1 % by weight in
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water at 20° C.) of from about 7 to about 11.5. A pH range of from
about 9.5 to
about 11.5 is preferred for best cleaning performance.
The detergent composition may also contain a post-added acidulant for
improved solubility, as more particularly described in U.S. Application Serial
No.
08/617,941.
The following examples are for illustrative purposes only and are not to
be construed as limiting the invention.
EXAMPLE 1
The ingredients listed in Table 1 were agglomerated into an acceptable
free-flowing powder detergent in the following manner. The sodium carbonate,
whitener, silica, and carboxymethylcellulose were mixed for about 1 minute in
a
ribbon mixer to achieve a uniform mixture. Neodol 25-7 (a C,2-C,5 alcohol
ethoxylated with 7 moles of ethylene oxide) was poured info the above mixture
while mixing to uniformly coat the sodium carbonate and other ingredients. The
loaded sodium carbonate (and other ingredients) were transferred to a
laboratory scale agglomerator (O'Brien Industrial Equip. Co., 3 foot diameter,
1
foot long) which was rotated at about 9 rpm for about 2 minutes after which
water was sprayed on the mixture to cause agglomeration of the particles.
Thereafter, the mixture was dried to a moisture content of about 2.15. The
resulting composition had a bulk density of 0.85 and had a Flodex value of 12
as tested in a Model No. 211, Hansen Research Corp. Flodex testing
apparatus.
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TABLE 1
Material Amount (weight
%)
Sodium Carbonate (FMC Grade 55.88
90)
Brightener (Tinopal SWN) 0.02
Silica (Sipernat 50) 3.0
Carboxymethylcellulose 2.0
Neodol 25-7 22.0
Citric Acid 7.5
Water (added) 4.0
Water (after drying) 1.5
Post-added fumaric acid 5.0
Post-added ingredients 3.1
(fragrance, enzyme, whitener)
EXAMPLES 2-4
The following ingredients were agglomerated in the same fashion as
described in Example 1, above, with the results also shown in Table 2.
TABLE 2
Example No. 2 3 4
Material Amount (Formula
Weight)
Sodium Carbonate 55.88 55.88 53.18
Silica 3.0 3.0 3.0
Carboxymethylcellulose 2.0 - 2.0
Brightener 0.02 0.02 0.02
Citric Acid 7.5 7.5 7.5
Water (added for agglomeration) 4.0 4.0 4.0
Water (after drying) 2.2 1.2 1.2
Density 0.85 0.87 0.84
Flodex 12 9 10
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EXAMPLES 5-6
Table 3 lists typical amounts of ingredients useful to make a free-flowing
nonionic surfactant detergent according to the present invention. The sodium
carbonate, silica, and carboxymethylcellulase can be mixed and, while mixing,
the nonionic surfactant can be sprayed onto the mixture to coat the mixture.
The citric acid can then mixed and, while mixing, water can be sprayed onto
the
mixture to cause the particles to agglomerate. The agglomerated particles can
be dried. Thereafter, any post-added optional ingredients like enzymes,
fragrances, and the like can be added as well as an acidulant such as fumaric
acid.
TABLE 3
Example No. 5 6
Materials Amount (Weight %)
Sodium Carbonate 59.6 53.2
Silica 3.0 3.0
Carboxymethylcellulose 2.2 2.0
Pareth 25-7 24.7 22.0
Citric Acid 8.4 7.5
Water (after drying) 2.1 1.5
Optional Minor Ingredients -- 5.8
Post-added fumaric --- 5.p
acid
It should be understood that a wide range of changes and modifications
can be made to the embodiments described above. It is therefore intended that
the foregoing description illustrates rather than limits this invention, and
that it is
the following claims, including all equivalents, which define this invention.
