Note: Descriptions are shown in the official language in which they were submitted.
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GRANULAR DETERGENT COMPOSITIONS HAVING HOMOGENOUS PARTICLES
AND PROCESS FOR PRODUCING SAME
FIELD OF THE INVENTION
The present invention relates to improved granular detergent compositions of
homogeneous particles which have superior solubility, especially in cold
temperature
laundering solutions (i.e., less than about 30°C), and excellent
flowability.
BACKGROUND OF THE INVENTION
Recently, there has been considerable interest within the detergent industry
for
laundry detergents which have the convenience, aesthetics and solubility of
liquid laundry
detergent products, but retain the cleaning performance and cost of granular
detergent
products. The problems, however, associated with past granular detergent
compositions
with regard to aesthetics, solubility and user convenience are formidable.
Such problems
have been exacerbated by the advent of "compact" or low dosage granular
detergent
products which typically do not dissolve in washing solutions as well as their
liquid laundry
detergent counterparts. These low dosage detergents are currently in high
demand as they
conserve resources and can be sold in small packages which are more convenient
for
consumers prior to use, but less convenient upon dispensing into the washing
machine as
compared to liquid laundry detergent which can be simply poured directly from
the bottle
as opposed to "scooped" from the box and then dispensed into the washing
solution.
As mentioned, such low dosage or "compact" detergent products unfortunately
experience dissolution problems, especially in cold temperature laundering
solutions (i.e.,
less than about 30°C). More specifically, poor dissolution results in
the formation of
"clumps" which appear as solid white masses remaining in the washing machine
or on the
laundered clothes after conventional washing cycles. These "clumps" are
especially
prevalent under cold temperature washing conditions and/or when the order of
addition to
the washing machine is laundry detergent first, clothes second and water last
(commonly
known as the "Reverse Order Of Addition" or "ROOA"). Such undesirable "clumps"
are
also formed if the consumer loads the washing machine in the order of clothes,
detergent
and then water. Similarly, this clumping phenomenon can contribute to the
incomplete
dispensing of detergent in washing machines equipped with dispenser drawers or
in other
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dispensing devices, such as a granulette. In this case, the undesired result
is undissolved
detergent residue in the dispensing device.
It has been found that the cause of the aforementioned dissolution problem is
associated with the "bridging" of a "gel-like" substance between surfactant-
containing
particles to form undesirable "clumps." The gel-like substance responsible for
the
undesirable "bridging" of particles into "clumps" originates from the partial
dissolution of
surfactant in the aqueous laundering solutions, wherein such partial
dissolution causes the
formation of a highly viscous surfactant phase or paste which binds or
otherwise "bridges"
other surfactant-containing particles together into "clumps." This undesirable
dissolution
phenomena is commonly referred to as "lump-gel" formation. In addition to the
viscous
surfactant "bridging" effect, inorganic salts have a tendency to hydrate which
can also
cause "bridging" of particles which linked together via hydration. In
particular, inorganic
salts hydrate with one another to form a cage structure which exhibits poor
dissolution and
ultimately ends up as a "clump" after the washing cycle. It would therefore be
desirable to
have a detergent composition which does not experience the dissolution
problems identified
above so as to result in improved cleaning performance.
The prior art is replete with disclosures addressing the dissolution problems
associated with granular detergent compositions. For example, the prior art
suggests
limiting the use and manner of inorganic salts which can cause clumps via the
"bridging" of
hydrated salts during the laundering cycle. Specific ratios of selected
inorganic salts are
contemplated so as to minimize dissolution problems. Such a solution, however,
constricts
the formulation and process flexibility which are necessary for current
commercialization
of large-scale detergent products. Various other mechanisms have been
suggested by the
prior art, all of which involve formulation alteration, and thereby reduce
formulation
flexibility. As a consequence, it would therefore be desirable to have a
detergent
composition having improved dissolution without significantly inhibiting
formulation
flexibility.
Accordingly, despite the disclosures in the prior art discussed previously, it
would
be desirable to have a granular detergent composition which exhibits improved
solubility,
has improved flowability and exhibits improved cleaning performance. Also, it
would be
desirable to have such a detergent composition which exhibits such improved
dissolution
without significantly inhibiting formulation flexibility.
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SUMMARY OF THE INVENTION
The present invention meets the aformentioned needs by providing a detergent
composition which has a controlled scale of heterogeneity between selected
chemical
ingredients which in turn provides the improved solubility or dissolution in
laundering
solutions, especially in solutions kept at cold temperatures (i.e., less than
about 30°C), and
has improved flowability of the as-packaged granules for ease of handling and
scooping by
the consumer.
In accordance with a first aspect of the present invention, a granular
detergent
composition is provided having a homogeneity number of less than about 0.5 or
greater
than about one ( 1 ) where the homogeneity number is defined by the formula:
Xbulk~Xpart
where Xbulk ~S the ratio of the concentration of a selected detergent
ingredient in the
particulate admixture component containing the selected ingredient at the
lowest
concentration of any admixture particulate component to the concentration of
the selected
ingredient in the particulate admixture component with the highest levels
ofthat ingredient
and XP", is the ratio of the concentration of a detergent ingredient in a
discrete volume of a
particle (referred to hereafter as a "domain") with the lowest levels of that
ingredient to the
concentration of the detergent ingredient in a separate discrete volume (i.e.,
a domain) of
the particle with the highest levels of the ingredient, of less than about 0.5
or greater than
about I . Preferably, the selected detergent ingredient upon which the
homogeneity number
is based is surfactant concentration. More preferably, the homogeneity number
is greater
than about I .25 and most preferably greater than 1.5.
In preferred embodiments, the detergent composition comprises at least about
50%
by weight of particles having a geometric mean particle diameter of from about
500
microns to about 1 S00 microns with a geometric standard deviation of from
about 1 to
about 2, wherein at least a portion of the particles contain a detersive
surfactant and a
detergent builder.
In accordance with a second aspect of the present invention, a process for
producing the aformentioned detergent composition is provided. The process
comprises
providing a granular feed stream selected from detergent particles being
selected from at
least two of the group consisting of spray-dried granules, wet agglomerates,
dry
agglomerates, detergent adjunct ingredients and mixtures thereof, passing the
feed stream
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through at least one mixer selected from high speed, moderate speed, low
speed, and low
shear mixers to produce a detergent composition.
Accordingly, it is an advantage of the invention to provide a granular
detergent
composition which exhibits improved solubility, has improved flowability and
exhibits
improved cleaning performance. It is also an advantage to have such a
detergent
composition which exhibits such improved dissolution without significantly
inhibiting
formulation flexibility.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Definitions
As used herein, the word "particles" means the entire size range of a
detergent final
product or component or the entire size range of discrete particles,
agglomerates, or
granules in a final detergent product or component admixture. It specifically
does not refer
to a size fraction (i.e., representing less than 100% of the entire size
range) of any of these
types of particles unless the size fraction represents 100% of a discrete
particle in an
admixture of particles. For each type of particle component in an admixture,
i.e., for each
particulate admixture component, the entire size range of discrete particles
of that type have
the same or substantially similar composition regardless of whether the
particles are in
contact with other particles. For agglomerated components, the agglomerates
themselves
are considered as discrete particles and each discrete particle may be
comprised of a
composite of smaller agglomerates, primary particles and binder compositions.
As used
herein, the phrase "geometric mean particle diameter" means the geometric mass
median
diameter of a set of discrete particles as measured by any standard mass-based
particle size
measurement technique, preferably by dry sieving. As used herein, the phrase
"geometric
standard deviation" or "span" of a particle size distribution means the
geometric breadth of
the best-fitted log-normal function to the above-mentioned particle size data
which can be
accomplished by the ratio of the diameter of the 84.13 percentile divided by
the diameter of
the 50'" percentile of the cumulative distribution (D84.,3/DS°); See
Gotoh et al, Powder
Technology Handbook, pp. 6-1 l, Meral Dekker 1997. .
As used herein, the phrase "builder" means any inorganic material having
"builder"
performance in the detergency context, and specifically, organic or inorganic
material
capable of removing water hardness from washing solutions. As used herein, the
term
"bulk density" refers to the uncompressed, untapped powder bulk density, as
measured by
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pouring an excess of powder sample through a funnel into a smooth metal vessel
(e.g., a
500 ml volume cylinder), scraping off the excess from the heap above the rim
of the vessel,
measuring the remaining mass of powder and dividing the mass by the volume of
the
vessel.
The granular detergent composition of the present invention achieves the
desired
benefits of solubility, and flowability via providing a homogeneous detergent
composition
wherein the homogeneous detergent contributes to the aforementioned benefits.
The homogeneity number describes the distribution of ingredients within
specific
particles and between particles in a composition. In the past, it was believed
that
homogeneous distribution of key ingredients such as surfactant was optimal, as
measured
between particles as well as within a given particulate domain structure.
Thus, detergent
composition would consist of a uniform type of particle made up of a
combination of
detergent ingredients , such as spray-dried detergent ingredients and had
significant
solubility drawbacks. In recent years, detergent compositions have consisted
of differing
particles of dual or multi-particle systems. While these multi-particle
systems, e.g. spray-
dried granules and agglomerates, may differ in form and/or composition between
particle
types, these detergent products also experience solubility drawbacks.
The present invention, on the other hand, is directed toward the surprising
discovery that specific distributions of ingredients, either between
particulate admixture
components or within a defined domain microstructure of a specific particulate
component,
improve many product attributes such as solubility and physical attributes
such as
flowability, etc. Specifically, the present invention is directed toward a
detergent
composition that has a homogeneity number of less than about 0.5 or greater
than about 1.0,
more preferably, either less than 0.25 or greater than 1.25 and most
preferably greater than
about 1.5. The homogeneity number is represented by the formula:
HN = X~,,k/XP,"where Xb"~k measures the degree of compositional homogeneity
between
particulate admixture components within the product composition, while XP~, is
the
measure of the compositional homogeneity within a defined domain structure of
the
individual particles comprising a specific particulate component. Thus, Xb"ik
is the ratio of
the concentration of the selected ingredient in the particle with the lowest
non-zero level of
that ingredient to the concentration of the selected ingredient in the
particle with the highest
level of the selected ingredient and XPe" is the ratio of the concentration in
the discrete
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volume with the lowest amount of the selected ingredient to the concentration
in the
discrete volume of the particle having the highest amounts of the selected
ingredient.
Accordingly, in a detergent composition, X~,,k is the ratio of the
concentration of a
selected detergent ingredient such as surfactant, builder, polymer, etc. in
particulate
component with the lowest non-zero level of the selected ingredient to the
concentration of
the selected ingredient in the particulate component with the highest level of
the selected
ingredient. This provides the homogeneity between particles in the
composition. Thus,
Xb"~k is represent by the formula:
Xbulk - Xmi~~u
where Xmi" is the concentration of the selected ingredient in the particles in
the composition
with the lowest levels of the selected ingredient and Xm,~ concentration of a
selected
detergent ingredient in the particles in the composition with the highest
levels of the
selected ingredient. For example, for a detergent composition in which all the
particles
have the same concentration such as a spray-dried granule with an active
concentration of
25% surfactant, Xb"~k would be equal to one ( 1 ) or 0.25/0.25. However, in a
composition
which comprises a spray dried granule of 20% active surfactant and a detergent
agglomerate of 30% detergent active Xb"~k would be equal to 0.67 or 0.2/0.3.
Xp,~ is the ratio of the concentration of a selected detergent ingredient such
as
surfactant, builder, etc. across domains within the same particle, or in other
words a
measure of the homogeneity of the individual particle. Xpart is the ratio of
the selected
ingredient in discrete domains of the particle. Xp,~ is the ratio of the
concentration in the
domain with the lowest concentration of the ingredient to the concentration of
the selected
ingredient in the domain with the highest concentration within the same
particle. Thus,
Xp,rt is represent by the formula:
Xpart - Xmin/Xmuc
where Xmi" is the concentration of the selected ingredient in the discrete
area in the particle
with the lowest levels of the selected ingredient and Xm,x concentration of a
selected
detergent ingredient in the discrete areas in the particle with the highest
levels of the
selected ingredient. A discrete volume or domain of the present invention is
one in which
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there is a clear morphological difference between the domains; typically a
domain
accounts for more than 1 %, preferably, 5% of the volume of the particle. For
example, a
particle that is homogeneous throughout the particle has only one ( 1 )
domain.. Thus, a
particle which has the same concentration throughout such as a spray-dried
granule with a
active concentration of 25% surfactant, XPe" would be equal to one ( 1 ) or
0.25/0.25 as the
particle contains only one domain.. However, in a particle, which is
agglomerated from
two different starting ingredients such as spray-dried granules having S%
active surfactant
and dry detergent agglomerates having 50% active surfactant to form mixed
agglomerates
as defined herein (i.e., where the compositional differences in the starting
materials remain
clearly evident within the microstructure of the resultant mixed agglomerate),
XPart would
be equal to 0.1 or 0.05/0.5. When a composition contains more than one
particulate
component , XP,rt is taken as the average of Xm;"lX",ex for each component.
The homogeneity number of the present invention is to be calculated on
particles
which comprise the bulk of the detergent composition. Thus, particles which
individually
or collectively account for less than about 10% by weight of the finished
composition
should not be employed in the calculation of homogeneity number. These low
level
ingredients typically include admix ingredients such for example, enzymes,
bleach
ingredients, perfume ingredients, sodium carbonate, sodium sulfate and various
other minor
additions.
While not wishing to be bound by theory, it is believed that by concentrating
certain ingredients and/or selectively separating them, one can prevent the
gelling upon
dissolution due to chemical interactions between the particles.
The present invention provides a detergent composition that has superior
solubility
performance and flowability due to the homogeneity profile of the composition.
Preferably, the geometric mean particle diameter of the particles is from
about 400 microns
to about 1500 microns, more preferably from about 500 microns to about 1200
microns,
and most preferably from about 600 microns to about 1000 microns. The particle
size
distribution is defined by a relative tight geometric standard deviation or
"span" so as not to
have too many particles outside of the target size. Accordingly, the geometric
standard
deviation is preferably is from about 1 to about 2, more preferably is from
about 1.0 to
about 1.7, even more preferably is from about 1.0 to about l .4, and most
preferably is from
about 1.0 to about 1.2. The average bulk density of the particles is
preferably at least about
400 g/I, more preferably at least about 550 g/I, and most preferably at least
about 600 g/l.
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While not intending to be bound by theory, it is believed that solubility is
enhanced
as a result of the particles in the detergent composition having the
aforementioned
homogeneity profile. Specifically, as a result of the particles being more
uniform in size,
the actual "contact points" among the particles in the detergent composition
is reduced
which, in turn, reduces the "bridging effect" commonly associated with the
"lump-gel"
dissolution difficulties of granular detergent compositions. Previous granular
detergent
compositions contained particles of homogeneity number in the range of from
about 0.5 to
about 1 and particle diameter sizes which leads to more contact points among
the particles.
For example, finer particles have more inter-particle contacts per unit volume
than do
coarser particles, and increasing in the contacts per unit volume increases
the per-volume
strength of lump-gel formations, thereby increasing the probability of said
lump-gel
formations persisting through the agitation in the wash cycle and leaving
undesired residues
on fabrics. The homogeneity number, level and uniform size of the particles in
the granular
detergent composition of the present invention avoids such problems.
By "a portion" of the particles, it is meant that at least some particles in
the
detergent composition contain a detersive surfactant and/or a detergent
builder to provide
the fundamental building blocks of a typical detergent composition. The
various
surfactants and builders as well as their respective levels in the composition
are set forth
hereinafter. Typically, the detergent composition will contain from about I%
to about 50%
by weight of a detersive surfactant and from about 1 % to about 75% by weight
of a
detergent builder.
Another important attribute of the granular detergent products of this
invention is
the shape of the individual particles. Shape can be measured in a number of
different ways
known to those of ordinary skill in the art. One such method is using optical
microscopy
with Optimus (V5.0) image analysis software. Important calculated parameters
are:
"Circularity" which is defined as (measured perimeter length of the particle
image)2/(measured area of the particle image). The circularity of a
perfectly smooth sphere (minimum circularity) is 12.57; and
"Aspect Ratio" which is defined as the length/width of the particle image.
Each of these attributes is important and can be averaged over the bulk
granular
detergent composition. Further, the combination of the two parameters as
defined by the
product of the parameters is important as well (i.e. both must be controlled
to get a product
with good appearance).
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Preferably, the granular detergent compositions of this invention have
circularity
less than about 50, preferably less than about 30, more preferably less than
about 23, most
preferably less than about 18. Also preferred are granular detergent
compositions with
aspect ratios less than about 2, preferably less than about 1.5, more
preferably less than
about 1.3 most preferably less than about 1.2.
Additionally, it is preferred to have a uniform distribution of shapes among
the
particles in the composition. Specifically, the granular detergent
compositions of this
invention have a standard deviation of the number distribution of circularity
less than about
20, that is preferably less than about 10, more preferably less than about 7
most preferably
less than about 4. And the standard deviation of the number distribution of
aspect ratios is
preferably less than about l, more preferably less than about 0.5, even more
preferably less
than about 0.3, most preferably less than about 0.2.
In an especially preferred process of the present invention, granular
detergent
compositions are produced wherein the product of circularity and aspect ratio
is less than
about 100, preferably less than about 50, more preferably less than about 30,
and most
preferably less than about 20. Also preferred are granular detergent
compositions with the
standard deviation of the number distribution of the product of circularity
and aspect ratio
of less than about 45, preferably less than about 20, more preferably less
than about 7 most
preferably less than about 2.
The preferred detergent compositions of this invention meet at least one and
most
preferably all, of the attribute measurements and standard deviations as
defined above, that
is for homogeneity number, whiteness, color, uniformity, circularity and
aspect ratio.
The present invention also comprises a process for the production of a
detergent
composition having a superior homogeneity profile. The detergent granules of
the present
invention comprise at least one detergent active material and are preferably
selected from
spray-dried detergent granules, wet detergent agglomerates, dry detergent
agglomerates and
detergent adjunct ingredient or other granules typically incorporated into a
detergent
composition. The granules may be in particle, agglomerate or flake form.
Detergent adjunct ingredients includes but is not limited to, raw materials
such as
carbonates, phosphates, sulfates, zeolites, surfactants, bleaches, enzymes,
perfumes or the
like. Of course, other conventionally known ingredients may be included as
well. Spray-
dried detergent granules include those particles which are manufactured via a
conventional
spray-drying technique wherein a slurry of detergent materials is prepared and
sprayed
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downward into a upwardly flowing stream of gas to dry the particles. A dry
free flowing
material is produced from the process. Wet detergent agglomerates includes
those particles
that are manufactured via an granulation type process wherein detergent
adjunct ingredients
such as described above are admixed with a liquid binder material such as
surfactant or
precursor thereof in a mixer or series of mixer to form granules of detergent
materials.
These particles are known as "wet agglomerates" until dried and as dry
agglomerates upon
exiting a drying stage
Accordingly, the present invention entails the introduction of both raw
materials
such as surfactants and builders or the introduction of previously formed
detergent granules
for continued processing of the granules. In one preferred embodiment of the
present
invention. the granules of the present invention are agglomerates of a mixture
of feed
streams such as spray-dried granules, dry agglomerates and optionally
detergent adjuncts
that are agglomerated in an agglomeration process such as that described
below. The
preferred agglomerates are herein referred to as mixed agglomerates.
Dry or wet agglomerates of the present invention are typically formed by an
agglomeration of a highly viscous surfactant paste or a liquid acid precursor
of a surfactant
and the aforementioned detergent adjunct ingredients or formed granules such
as spray-
dried granules agglomerates or detergent adjuncts are described above may be
substituted.
The agglomeration may be carried out in a high or moderate speed mixer after
which an
optional low or moderate speed mixer may be employed for further
agglomeration, if
necessary. Low speed mixers according to the present invention may include
Alternatively, the agglomeration may be carried out in a single mixer that can
be
low, moderate or high speed. The particular mixer used in the present process
should
include pulverizing or grinding and agglomeration tools so that both
techniques can be
carried forth simultaneously in a single mixer. To that end, it has been found
that the first
processing step can be successfully completed, under the process parameters
described
herein, in a Lodige KMT"" (Ploughshare) moderate speed mixer, Lodige CBT""
high speed
mixer, or mixers made by Fukae, Drais, Schugi or similar brand mixer. The
Lodige KMT"'
(Ploughshare) moderate speed mixer, which is a preferred mixer for use in the
present
invention, comprises a horizontal, hollow static cylinder having a centrally
mounted
rotating shaft around which several plough-shaped blades are attached.
Preferably, the
shaft rotates at a speed of from about 15 rpm to about 140 rpm, more
preferably from about
80 rpm to about 120 rpm. The grinding or pulverizing is accomplished by
cutters,
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generally smaller in size than the rotating shaft, which preferably operate at
about 3600
rpm. Other mixers similar in nature which are suitable for use in the process
include the
Lodige PloughshareT"" mixer and the Drais~ K-T 160 mixer. Generally, in the
process of
the present invention, the shear will be no greater than the shear produced by
a Lodige KM
mixer with a tip speed of the ploughs below 30 m/s or even below 10 m/s or
even lower.
Preferably, the mean residence time of the various detergent ingredients in
the low,
moderate or high speed mixer is preferably in range from about 0.1 seconds to
about 30
minutes, most preferably the residence time is about 0.5 to about 5 minutes.
In this way,
the density of the resulting detergent agglomerates is at the desired level.
This agglomeration is typically followed by a drying step. This drying step
may be
carried out in a wide variety of equipment including, but not limited to a
fluid bed drying
apparatus. Examples of dryer characteristics include fixed or vibrating;
rectangular bed or
round bed; and straight or serpentine dryers. Manufacturers of such dryers
include Niro,
Bepex, Spray Systems and Glatt. By way of example, an apparatus such as a
fluidized bed
can be used for drying while an airlift can be used for cooling should it be
necessary. The
air lift can also be used to force out the "fine" particles so that they can
be recycled to the
particle agglomeration process.
The agglomeration may comprise the step of spraying an additional binder in
the
mixers or fluid bed to facilitate production of the desired detergent
particles. A binder is
added for purposes of enhancing agglomeration by providing a "binding" or
"sticking"
agent for the detergent components. The binder is preferably selected from the
group
consisting of water, anionic surfactants, nonionic surfactants, polyethylene
glycol,
polyvinyl pyrrolidone, acetates, polyacrylates, citric acid and mixtures
thereof. Other
suitable binder materials including those listed herein are described in
Beerse et al, U.S.
Patent No. 5,108,646 (Procter & Gamble Co.), the disclosure of which is
incorporated
herein by reference.
Another optional processing step to form the particles of the present
invention
includes continuously adding a coating agent such as zeolites, recycled
"fines" as described
above and fumed silica to the mixer to improve the particle color, increase
the particle
"whiteness or facilitate free flowability of the resulting detergent particles
and to prevent
over agglomeration. When employing recycled fines as the coating agent, the
fines are
preferably in the approximate size range of 0.01 to 0.5 times the mean
particle size of the
larger particles. The granule coating will also improve the integrity of the
fines layering
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and provide abrasion and attrition resistance during handling. In addition,
the detergent
starting materials can be fed into a pre-mixer, such as a Lodige CB mixer or a
twin-screw
extruder, prior to entering in the mixer. This step, although optional, does
indeed facilitate
agglomeration.
Also particularly preferred in the present invention are spray-dried detergent
granules which comprise tower blown particles. In this process, the granules
are formed by
the preparation of a slurry of surfactant materials, water and detergent
adjunct ingredients
materials. The resultant slurry is then passed to a tower where the slurry is
sprayed into a
stream of air at temperatures typically ranging from about 175°C to
about 375°C to dry the
detergent slurry and formed detergent particles. Typically, resultant
densities of these
particles range from about 200 to about 600 g/l.
The particles of the present invention comprise at least about 50% by weight
of
particles having a geometric mean particle diameter of from about 500 microns
to about
1 S00 microns and preferably have a geometric standard deviation of from about
1 to about
2. Preferably the geometric standard deviation is from about 1.0 to about 1.7,
preferably
from about 1.0 to about 1.4. The granular detergent composition resulting from
the
processes may comprise undersized or fine particles, wherein "fine particles"
are defined as
particles that have a geometric mean particle diameter that is less than about
1.65 standard
deviations below the chosen geometric mean particle diameter of the granular
detergent
composition at a given span or geometric standard deviation. Oversized or
large particles
may also exist wherein "large particles" are defined as particles that have a
geometric mean
particle diameter that is greater than about 1.65 standard deviations above
the chosen
geometric mean particle diameter of the granular detergent composition at a
given span or
geometric standard deviation. The fine particles are preferably separated from
the granular
detergent composition and returned to the process by adding them to at least
one of the
mixers and/or the fluid bed dryer as described in detail below. Likewise, the
large particles
are preferably separated from the granular detergent composition and then fed
to a grinder
where their geometric mean particle diameter is reduced. After the geometric
mean particle
diameter of the large particles is reduced, the large particles are returned
to the process by
adding them to at least one of the mixers and/or the fluid bed dryer.
In preferred processing of the present invention, the granules of the present
invention are produced in a fluidized bed via the combination of spray-dried
granules,
adjunct ingredients and dry agglomerates. A liquid binder material such as
silicates,
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polyethylene glycols, surfactants and precursors thereof and various other
materials may be
added to the fluid bed to enhance agglomeration. Optionally, the feed
materials are passed
through a pre-mixer or series of mixers such as a moderate speed mixer as
described above.
The fluidized bed is preferably operated such that the flux number FN of the
fluid
bed is at least about 2.5 to about 4.5. Flux number (FNm) is a ratio of the
excess velocity
(Ue) of the fluidisation gas and the particle density (pP) relative to the
mass flux (q,;q) of the
liquid sprayed into the bed at a normalized distance (Do) of the spraying
device. The flux
number provides and estimation of the operating parameters of a fluidized bed
to control
granulation within the bed. The flux number may be expressed either as the
mass flux as
determined by the following formula:
FNm = logiol{PPU~}/qsq~
or as the volume flux as determined by the formula:
FN" = logio[{U~}/q~sq~
where q",;b is the volume of spray into the fluid bed. Calculation of the flux
number and a
description of its usefulness is fully described in WO 98/58046 the disclosure
of which is
herein incorporated by reference.
In addition, the fluidized bed is operated at a Stokes number of less than
about I,
more preferably from about 0.1 to about 0.5. The Stokes number is a measure of
particle
coalescence for describing the degree of mixing occurring to particles in a
piece of
equipment such as the fluid bed. The Stokes number is measured by the formula:
Stokes number = 4pvd/9u
wherein p is the apparent apparent particle density, v is the excess velocity,
d is the mean
particle diameter and a is the viscosity of the binder. The Stokes number and
a description
of its usefulness is described in detail in WO 99/03964, the disclosure of
which is herein
incorporated by reference.
The granules of the present invention are passed into a fluid bed dryer having
multiple internal "stages" or "zones". A stage or zone is any discrete area
within the dryer,
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and these terms are used interchangeably herein. The process conditions within
a stage
may be different or similar to the other stages in the dryer. It is understood
that two
adjacent dryers are equivalent to a single dryer having multiple stages. The
various feed
streams of granules and coating material can be added at the different stages,
depending on,
for example, the particle size and moisture level of the feed stream. Feeding
different
streams to different stages can minimize the heat load on the dryer, and
optimize the
particle size and shape as defined herein.
Typically, the fluid bed mixer of the present invention comprises a first
spraying
zone where the binder material is applied. The spraying zone involves the
spraying of the
binder in aqueous or slurry form onto the fluidized particles. The bed is
typically fluidized
with heated air in order to dry or partially dry moisture from the spray as it
is applied. The
spraying is achieved via nozzles capable of delivering a fine or atomized
spray of the
coating mixture to achieve complete coverage of the particles. Typically, the
droplet size
from the atomizer is less than about 2 times the particle size. This
atomization can be
achieved either through a conventional two-fluid nozzle with atomizing air, or
alternatively
by means of a conventional pressure nozzle. To achieve this type of
atomization, the
solution or slurry rheology is typically characterized by a viscosity of less
than about 500
centipoise, preferably less than about 200 centipoise at the point of
atomization. While the
nozzle location in the fluid bed may be in most any location, the preferred
location is a
positioning that allows a vertical down spray of the coating mixture such as a
top spray
configuration. To achieve best results, the nozzle location is placed at or
above the
fluidized height of the particles in the fluid bed. The fluidized height is
typically
determined by a weir or overflow gate height. The coating zone of the fluid
bed is then
typically followed by a drying zone and a cooling zone. Of course, one of
ordinary skill in
the art will recognize that alternative arrangements are also possible to
achieve the resultant
coated particles of the present invention.
Typical conditions within a fluid bed apparatus of the present invention
include (i)
from about 1 to about 20 minutes of mean residence time, (ii) from about 100
to about 600
mm of depth of unfluidized bed, (iii) a droplet size of 2 times the particle
size, preferably
not more than about 100 micron more preferably not more than 50 micron, (iv)
from about
150 to about 1600 mm of spray height from the fluid bed plate or preferably 0-
600 mm
from the top of the fluid bed, (v) from about 0.1 to about 4.0 m/s of
fluidizing velocity,
preferably about 1.0 to 3.0 m/s and (vi) from about 12 to about 200 °C
of bed temperature,
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preferably about 15 to about 100 °C. Once again, one of ordinary skill
in the art will
recognize that the conditions in the fluid bed may vary depending on a number
of factors.
The coated granules exiting the coating mixer may comprise in and of
themselves a
fully formulated detergent composition or in preferred embodiments may be
admixed with
additional ingredients, such as bleaching agents, enzymes, perfumes, non-
coated detergent
particles, and various other ingredients to produce a fully formulated
detergent
composition.
DETERGENT COMPONENTS
The surfactant system of the detergent composition may include anionic,
nonionic,
zwitterionic, ampholytic and cationic classes and compatible mixtures thereof.
Detergent
surfactants are described in U.S. Patent 3,664,961, Norris, issued May 23,
1972, and in U.S.
Patent 3,919,678, Laughlin et al., issued December 30, 1975, both of which are
incorporated herein by reference. Cationic surfactants include those described
in U.S.
Patent 4,222,905, Cockrell, issued September 16, 1980, and in U.S. Patent
4,239,659,
Murphy, issued December 16, 1980, both of which are also incorporated herein
by
reference.
Nonlimiting examples of surfactant systems include the conventional C 11-C18
alkyl benzene sulfonates ("LAS") and primary, branched-chain and random C 10-
C20 alkyl
sulfates ("AS"), the C 10-C 1 g secondary (2,3) alkyl sulfates of the formula
CH3(CH2)x(CHOS03 M+) CH3 and CH3 (CH2)y(CHOS03 M+) CH2CH3 where x and
(y + 1 ) are integers of at least about 7, preferably at least about 9, and M
is a
water-solubilizing cation, especially sodium, unsaturated sulfates such as
oleyl sulfate, the
C 10-C 1 g alkyl alkoxy sulfates ("AEXS"; especially EO 1-7 ethoxy sulfates),
C 10-C 1 g alkyl
alkoxy carboxylates (especially the EO 1-5 ethoxycarboxylates), the C 1 p_ 1 g
glycerol
ethers, the C 10-C 1 g alkyl polyglycosides and their corresponding sulfated
polyglycosides,
and C 12-C 1 g alpha-sulfonated fatty acid esters. If desired, the
conventional nonionic and
amphoteric surfactants such as the C 12-C 1 g alkyl ethoxylates ("AE")
including the so-
called narrow peaked alkyl ethoxylates and C6-C12 alkyl phenol alkoxylates
(especially
ethoxylates and mixed ethoxy/propoxy), C 12-C 1 g betaines and sulfobetaines
("sultaines"),
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C 10-C 1 g amine oxides, and the like, can also be included in the surfactant
system. The
C 10-C I g N-alkyl polyhydroxy fatty acid amides can also be used. Typical
examples
include the C 12-C 1 g N-methylglucamides. See WO 9,206,154. Other sugar-
derived
surfactants include the N-alkoxy polyhydroxy fatty acid am ides, such as C 10-
C 1 g N-(3-
methoxypropyl) glucamide. The N-propyl through N-hexyl C 12-C 1 g glucamides
can be
used for low sudsing. C I 0-C20 conventional soaps may also be used. If high
sudsing is
desired, the branched-chain C 10-C 16 soaps may be used. Mixtures of anionic
and nonionic
surfactants are especially useful. Other conventional useful surfactants are
listed in
standard texts.
The detergent composition can, and preferably does, include a detergent
builder.
Builders are generally selected from the various water-soluble, alkali metal,
ammonium or
substituted ammonium phosphates, polyphosphates, phosphonates,
polyphosphonates,
carbonates, silicates, borates, polyhydroxy sulfonates, polyacetates,
carboxylates, and
polycarboxylates. Preferred are the alkali metal, especially sodium, salts of
the above.
Preferred for use herein are the phosphates, carbonates, silicates, C 10-18
fatty acids,
polycarboxylates, and mixtures thereof. More preferred are sodium
tripolyphosphate,
tetrasodium pyrophosphate, citrate, tartrate mono- and di-succinates, sodium
silicate, and
mixtures thereof (see below).
Specific examples of inorganic phosphate builders are sodium and potassium
tripolyphosphate, pyrophosphate, polymeric metaphosphate having a degree of
polymerization of from about 6 to 21, and orthophosphates. Examples of
polyphosphonate
builders are the sodium and potassium salts of ethylene diphosphonic acid, the
sodium and
potassium salts of ethane 1-hydroxy-1, 1-diphosphonic acid and the sodium and
potassium
salts of ethane, 1,1,2-triphosphonic acid. Other phosphorus builder compounds
are
disclosed in U.S. Patents 3,159,581; 3,213,030; 3,422,021; 3,422,137;
3,400,176 and
3,400,148, all of which are incorporated herein by reference.
Examples of nonphosphorus, inorganic builders are sodium and potassium
carbonate, bicarbonate, sesquicarbonate, tetraborate decahydrate, and
silicates having a
weight ratio of Si02 to alkali metal oxide of from about 0.5 to about 4.0,
preferably from
about 1.0 to about 2.4. Water-soluble, nonphosphorus organic builders useful
herein
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include the various alkali metal, ammonium and substituted ammonium
polyacetates,
carboxylates, polycarboxylates and polyhydroxy sulfonates. Examples of
polyacetate and
polycarboxylate builders are the sodium, potassium, lithium, ammonium and
substituted
ammonium salts of ethylene diamine tetraacetic acid, nitrilotriacetic acid,
oxydisuccinic
acid, mellitic acid, benzene polycarboxylic acids, and citric acid.
Polymeric polycarboxylate builders are set forth in U.S. Patent 3,308,067,
Diehl,
issued March 7, 1967, the disclosure of which is incorporated herein by
reference. Such
materials include the water-soluble salts of homo- and copolymers of aliphatic
carboxylic
acids such as malefic acid, itaconic acid, mesaconic acid, fumaric acid,
aconitic acid,
citraconic acid and methylenemalonic acid. Some of these materials are useful
as the
water-soluble anionic polymer as hereinafter described, but only if in
intimate admixture
with the nonsoap anionic surfactant.
Other suitable polycarboxylates for use herein are the polyacetal carboxylates
described in U.S. Patent 4,144,226, issued March 13, 1979 to Crutchfield et
al., and U.S.
Patent 4,246,495, issued March 27, 1979 to Crutchfield et al., both of which
are
incorporated herein by reference. These polyacetal carboxylates can be
prepared by
bringing together under polymerization conditions an ester of glyoxylic acid
and a
polymerization initiator. The resulting polyacetal carboxylate ester is then
attached to
chemically stable end groups to stabilize the polyacetal carboxylate against
rapid
depolymerization in alkaline solution, converted to the corresponding salt,
and added to a
detergent composition. Particularly preferred polycarboxylate builders are the
ether
carboxylate builder compositions comprising a combination of tartrate
monosuccinate and
tartrate disuccinate described in U.S. Patent 4,663,071, Bush et al., issued
May 5, 1987, the
disclosure of which is incorporated herein by reference.
Water-soluble silicate solids represented by the formula Si02~M20, M being an
alkali metal, and having a Si02:M20 weight ratio of from about 0.5 to about
4.0, are useful
salts in the detergent granules of the invention at levels of from about 2% to
about 15% on
an anhydrous weight basis, preferably from about 3% to about 8%. Anhydrous or
hydrated
particulate silicate can be utilized, as well.
Any number of additional ingredients can also be included as components in the
granular detergent composition. These include other detergency builders,
bleaches. bleach
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activators, suds boosters or suds suppressors, anti-tarnish and anti-corrosion
agents, soil
suspending agents, soil release agents, germicides, pH adjusting agents,
nonbuilder
alkalinity sources, chelating agents, smectite clays, enzymes, enzyme-
stabilizing agents and
perfumes. See U.S. Patent 3,936,537, issued February 3, 1976 to Baskerville,
Jr. et al.,
incorporated herein by reference.
Bleaching agents and activators are described in U.S. Patent 4,412,934, Chung
et
al., issued November 1, 1983, and in U.S. Patent 4,483,781, Hartman, issued
November 20,
1984, both of which are incorporated herein by reference. Chelating agents are
also
described in U.S. Patent 4,663,071, Bush et al., from Column 17, line 54
through Column
18, line 68, incorporated herein by reference. Suds modifiers are also
optional ingredients
and are described in U.S. Patents 3,933,672, issued January 20, 1976 to
Bartoletta et al.,
and 4,136,045, issued January 23, 1979 to Gault et al., both incorporated
herein by
reference.
Suitable smectite clays for use herein are described in U.S. Patent 4,762,645,
Tucker et al., issued August 9, 1988, Column 6, line 3 through Column 7, line
24,
incorporated herein by reference. Suitable additional detergency builders for
use herein are
enumerated in the Baskerville patent, Column 13, line 54 through Column 16,
line 16, and
in U.S. Patent 4,663,071, Bush et al., issued May 5, 1987, both incorporated
herein by
reference.
The following examples are presented for illustrative purposes only and are
not to
be construed as limiting the scope of the appended claims in any way.
Example I
A finished detergent composition is produced dry blending or admixing two feed
streams.
The first is a 20% by weight surfactant active spray-dried granules. The
second is a 30%
surfactant active agglomerated granule. The two particles are mixed at 50
weight % each.
The homogeneity number of the finished detergent is 0.67 as calculated from
Xb~p = 0.2/0.3
= 0.67 and XP,~ _ (0.2/0.2) + (0.3/0.3)/2 = 1
Example II
A detergent composition is produced in a batch process in a fluidized bed
having a depth of
6 inches and a batch weight of 1 SOOg. The inlet temperature of the bed was
130 °C the bed
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temperature was 45 °C and the air velocity was 1 m/s. The feed
comprises 50% dry
agglomerates having a surfactant active concentration of 50% and 50% spray-
dried
granules having a surfactant active concentration of 5%. A total of 250 grams
of a 30 wt%
solution of PEG 4000 was sprayed into the fluidized bed to agglomerate the
feed
ingredients into a mixed agglomerate. The final composition has a median
particle size of
~600um, and a homogeneity number of 10 as calculated from Xb~" = 1 from
Xm;~(.275)/Xm~(.275) = I and XP~, = 0.1 from Xm;~ (0.05)IXm,~(0.5).
Example Ill
A detergent composition is produced by dry blending the feed streams of
Example II
without agglomeration of the two streams. The finished composition has a
homogeneity
number of 0.1 as calculated from Xbulk = 0.05/0.5 = 0.1 and XPa" _ (0.05/0.05
+ 0.5/0.5)/2 =
Having thus described the invention in detail, it will be obvious to those
skilled in
the art that various changes may be made without departing from the scope of
the invention
and the invention is not to be considered limited to what is described in the
specification.
