Note: Descriptions are shown in the official language in which they were submitted.
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PROCESS FOR MAKING GRANULAR DETERGENTS
The present invention relates to a process for preparing a
particulate detergent composition, in particular by spray
drying an aqueous slurry. Particulate detergent
compositions are also disclosed.
Many granular detergents which are sold commercially
comprise sodium aluminosilicate as the sole builder, or as
a component of a builder system. It is known, for example
from JP204098/1983, laid open on November 28th 1983, that
heated aqueous slurries, such as those used in conventional
spray-drying processes, which comprise both sodium
aluminosilicate and water-soluble silicate, cause insoluble
complexes to form. These insoluble complexes are
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undesirable~in laundry detergents because they can result
in residues on washed fabrics. Furthermore, without the
silicate to act as a powder structurant, the particle size "
distribution of the spray-dried powder may be unacceptably
broad.
In the absence of water-soluble silicate in the aqueous
slurry, various other components have been proposed as
powder structurants, useful to achieve a crisp, free-
flowing spray-dried powder. Included amongst the powder
structurants that have been suggested are film-forming
polymer: polycarboxylates (for example, US-A-4 379 080);
polyacrylates (for example, JP204098/1983); sucrose and
derivatives (for example, EP-A-0 215 637) ; sodium
sesquicarbonate (for example, EP-A-0 242 138).
However, unless the powder structurants are required by the
formulator as active ingredients, then they are an
expensive processing aid.
An aqueous slurry which does not comprise either water-
soluble silicate, or one of the alternative powder
structurants is difficult to spray dry. In particular high
water concentrations are generally needed in order to
maintain the viscosity of the slurry low enough to provide
crisp, free-flowing particles of the desired particle size .
when spray-dried. The disadvantage of high water
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concentrations is that the excess water must be removed
during the drying step and a lot of energy is needed to do
this.
W090/04630, published on 3rd May 1990, describes a process
for preparing a carbonate containing detergent slurry
comprising an alkylpolyglycoside and an alkali metal
chloride. Zeolite A is suggested as one possible builder
albeit in the presence of silicate (at 7o by weight in
Table VI).
The object of the present invention is to avoid residue
problems by substantially omitting silicate from an aqueous
slurry which comprises anionic surfactant and
aluminosilicate, and at the same time to provide a low
viscosity slurry suitable for spray-drying to form crisp,
free-flowing powder.
Summary of the Invention
According to the invention this object is achieved by a
process for preparing a particulate detergent composition
which comprises: (a) forming an aqueous slurry comprising
water, an anionic surfactant as the sole surfactant,
chelating agents and at least 0.5%, by weight, of sodium
aluminosilicate and copolymers of acrylic and malefic acid as
the sole builders; (b) adding to the aqueous slurry an
inorganic salt selected from the group consisting of:
(i) alkali metal salts of halides and nitrates; (ii)
alkaline earth metal salts of halides and nitrates; and
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(iii) mixtures thereof; (c) drying the slurry; wherein the
aqueous slurry comprises at least 1% by weight of the
inorganic salt, and whereby the addition of the inorganic
salt increases the ionic conductivity of the aqueous slurry,
and wherein the aqueous slurry contains essentially no
water-soluble silicate and the particulate composition
comprises from 5% to 20% by weight, of the anionic
surfactant.
Preferably the inorganic salt is an alkali metal or alkaline
earth metal salt, or mixtures thereof of halide, nitrate or
citrate, most preferably sodium chloride.
In a more preferred embodiment of the invention the step of
adding the inorganic salt raises the ionic conductivity of
the aqueous slurry by at least 3 milliSiemens, and
preferably by at least 5 milliSiemens.
A further aspect of the invention concerns spray-dried
detergent powder compositions. Preferred compositions
comprise: at least one surfactant, and preferably at least
5% by weight of surfactant; from 2 to 80%, and preferably
from 10% to 50% by weight of aluminosilicate from 1% to 20%
by weight of an inorganic salt selected from the group
consisting of alkali metal, alkaline earth metal salts, or
mixtures thereof; halides, nitrates, citrates or mixtures
thereof, and preferably from 2% to 10% by weight of an
alkali metal, preferably sodium, chloride, and less than 5%,
preferably less than 2% by weight of silicate.
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Detailed Description of the Inverition
Essential components of the compositions of the present
invention are aluminosilicate builders such as those having
the empirical formula:
Mz ( zA102 ) y ] ~ x H20
wherein z and y are integers of at least 6, the molar ratio
of z to y is in the range from 1.0 to about 0.5, and x is
an integer from about 15 to about 264.
Useful aluminosilicate ion exchange materials are
commercially available. These aluminosilicates can be
crystalline or amorphous in structure and can be naturally-
occurring aluminosilicates or synthetically derived. A
method for producing aluminosilicate ion exchange materials
is disclosed in US Patent 3,985,669, Krummel et al, issued
October 12, 1976. Preferred synthetic crystalline
aluminosilicate ion exchange materials useful herein are
available under the designations zeolite A, zeolite P(B),
zeolite MAP, zeolite X and zeolite Y. In an especially
preferred embodiment, the crystalline aluminosilicate ion
exchange material has the formula .
Nal2 [ (A102 ) 12 ~ (Si02 ) 12 ] ' x H20
wherein x is from about 20 to about 30, especially about
27. This material is known as zeolite A. Dehydrated
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zeolites (x=0-10), and "overdried" zeolites (x=10-20) may
also be used herein. The "overdried" zeolites are
particularly useful when a low moisture environment is
required, for example to improve stability of detergent
bleaches such as perborate and percarbonate. Preferably,
the aluminosilicate has a particle size of about 0.1-10
micrometers in diameter. Preferred ion exchange materials
have a particle size diameter of from about 0.2 micrometers
to about 4 micrometers. The term "particle size diameter"
herein represents the average particle size diameter by
weight of a given ion exchange material as determined by
conventional analytical techniques such as, for example,
microscopic determination utilizing a scanning electron
microscope. The crystalline zeolite A materials herein are
usually further characterized by their calcium ion exchange
capacity, which is at least about 200 mg equivalent of
CaC03 water hardness/g of aluminosilicate, calculated on an
anhydrous basis, and which generally is in the range of
from about 300 mg eq./g to about 352 mg eq./g. The zeolite
A materials herein are still further characterized by their
calcium ion exchange rate which is at least about 2 grains
Ca++/gallon/minute/gram/gallon (0.13g
Ca++/litre/minute/gram/litre) of aluminosilicate (anhydrous
basis), and generally lies within the range of from about 2
grains/gallon/minute/gram/gallon(0.13g
Cap'+/litre/minute/gram/litre) to about 6
grains/gallon/minute/gram/gallon (0.39g
Ca++/litre/minute/gram/litre), based on calcium ion
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hardness. Optimum aluminosilicate for builder purposes
exhibit a calcium ion exchange rate of at least about 4
grains/gallon/minute/gram/gallon (0.26g
Ca++/litre/minute/gram/litre).
The granular agglomerates of the present invention also
comprise other detergent ingredients.
Water-soluble salts of the higher fatty acids, i.e.,
"soaps", are useful anionic surfactants in the compositions
herein. This includes alkali metal soaps such as the
sodium, potassium, ammonium, and alkylammonium salts of
higher fatty acids containing from about 8 to about 24
carbon atoms, and preferably from about 12 to about 18
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 potassium
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
alkylolammonium salts, of organic sulfuric reaction
products having in their molecular structure an alkyl group
containing from about 10 to about 20 carbon atoms and a
sulfonic acid or sulfuric acid ester group. (Included in
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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 alcohols (Cg-Clg carbon
atoms) such as those produced by reducing the glycerides of
tallow or coconut oil; and the sodium and potassium alkyl
benzene sulfonates in which the alkyl group contains from
about 9 to about 15 carbon atoms, in straight or branched
chain configuration, e.g., those of the type described in
U.S. Pat. Nos. 2,220,099 and 2,477,383; and methyl ester
sulphonates. Especially valuable are linear straight chain
alkyl benzene sulfonates in which the average number of
carbon atoms in the alkyl group is from about 11 to 13,
abbreviated as C11-C13
Other anionic surfactants herein are the sodium alkyl
glyceryl 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 groups contain from about 8 to about 12 carbon
atoms and sodium or potassium salts of alkyl 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.
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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-acyloxy-alkane-1-sulfonic
acids containing from about 2 to 9 carbon atoms in the acyl
group and from about 9 to about 23 carbon atoms in the
alkane moiety; alkyl ether sulfates containing from about
to 20 carbon atoms in the alkyl group and from about 1
to 30 moles of ethylene oxide; watersoluble salts of olefin
sulfonates containing from about 12 to 24 carbon atoms; and
beta-alkyloxy alkane sulfonates containing from about 1 to
3 carbon atoms in the alkyl group and from about 8 to about
carbon atoms in the alkane moiety.
Water-soluble nonionic surfactants are also useful as
surfactants in the compositions of the invention. Indeed,
preferred processes use anionic/nonionic blends. Such
nonionic materials include compounds produced by the
condensation of alkylene oxide groups (hydrophilic in
nature) with an organic hydrophobic compound, which may be
aliphatic or alkyl aromatic in nature. The length of the
polyoxyalkylene group which is condensed with any
particular hydrophobic group can be readily adjusted to
yield a water-soluble compound having the desired degree of
balance between hydrophilic and hydrophobic elements.
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Suitable nonionic surfactants include the polyethylene
oxide condensates of alkyl phenols, e.g., the condensation
products of alkyl phenols having an alkyl group containing
from about 6 to 16 carbon atoms, in either a straight chain
or branched chain configuration, with from about 9 to 25
moles of ethylene oxide per mole of alkyl phenol.
Preferred nonionics are the water-soluble condensation
products of aliphatic alcohols containing from B to 22
carbon atoms, in either straight chain or branched
configuration, with from 2 to 25 moles of ethylene oxide
per mole of alcohol, especially 2 to 7 moles of ethylene
oxide per mole of alcohol. Particularly preferred are the
condensation products of alcohols having an alkyl group
containing from about 9 to 15 carbon atoms; and
condensation products of propylene glycol with ethylene
oxide.
Other pzeferred nonionics are polyhydroxy fatty acid amides
which may be prepared by reacting a fatty acid ester and an
N-alkyl polyhydroxy amine. The preferred amine for use in
the present invention is N-(R1)-CHz(CH20H)4-CH2-OH and the
preferred ester is a C12-C20 fatty acid methyl ester. Most
preferred is the reaction product of N-methyl glucamine
(which may be derived from.glucose) with C12-C20 fatty acid
methyl ester.
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Methods of manufacturing polyhydroxy fatty acid amides have
been described in WO 9206073, published on 16th April,
1992. This application describes the preparation of
polyhydroxy fatty acid amides in the presence of solvents.
In a highly preferred embodiment of the invention N-methyl
glucamine is reacted with a C12-C2o methyl ester. It also
says that the formulator of granular detergent compositions
may find it convenient to run the amidation reaction in the
presence of solvents which comprise alkoxylated, especially
ethoxylated (E0 3-8) C12_C14 alcohols (page 15, lines 22-
27). This directly yields nonionic surfactant systems which
are suitable for use in the present invention, such as
those comprising N-methyl glucamide and C12-C14 alcohols
with an average of 3 ethoxylate groups per molecule.
Semi-polar nonionic surfactants include water-soluble amine
oxides containing one alkyl moiety of from about 10 to 18
carbon atoms and 2 moieties selected from the group
consisting of alkyl groups and hydroxyalkyl groups
containing from 1 to about 3 carbon atoms; water-soluble
phosphine oxides containing one alkyl moiety of about 10 to
18 carbon atoms and 2 moieties selected from the group
consisting of alkyl groups and hydroxyalkyl 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 hydroxyalkyl moieties of from
about 1 to 3 carbon atoms.
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Ampholytic surfactants include derivatives of aliphatic or
aliphatic derivatives of heterocyclic secondary and
tertiary amines in which the aliphatic moiety can be either
straight or branched chain 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.
Useful cationic surfactants include water-soluble
quaternary ammonium compounds of the form R4RSR6R~N+X-,
wherein R4 is alkyl having from 10 to 20, preferably from
12-18 carbon atoms, and R5, R6 and R~ are each C1 to C~
alkyl preferably methyl; X- is an anion, e.g. chloride.
Examples of such trimethyl ammonium compounds include C12-
14 alkyl trimethyl ammonium chloride and cocalkyl trimethyl
ammonium methosulfate.
The granular detergents of the present invention can
contain neutral or alkaline salts which have a pH in _
solution of seven or greater, and can be either organic or
inorganic in nature. The builder salt assists in providing
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the desired density and bulk to the detergent granules
herein. While some of the salts are inert, many of them
also function as detergency builder materials in the
laundering solution.
Useful water-soluble salts include the compounds commonly
known as detergent builder materials. Builders are
generally selected from the various water-soluble, alkali
metal, ammonium or substituted ammonium phosphates,
polyphosphates, phosphonates, polyphosphonates, carbonates,
silicates, borates, and polyhyroxysulfonates. Preferred
are the alkali metal, especially sodium, salts of the
above.
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 orthophosphate. 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. Pat. Nos. 3,159,581; 3,213,030; 3,422,021: 3,422,137;
3, 400, 176 and 3, 400, 148,
Examples of nonphosphorus, inorganic builders are sodium
and potassium carbonate, bicarbonate, sesquicarbonate,
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tetraborate decahydrate, and silicate having a molar 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.
Polymers
Also useful are various organic polymers, some of which
also may function as builders to improve detergency.
Included among such polymers may be mentioned sodium
carboxy-lower alkyl celluloses, sodium lower alkyl
celluloses and sodium hydroxy-lower alkyl celluloses, such
as sodium carboxymethyl cellulose, sodium methyl cellulose
and sodium hydroxypropyl cellulose, homo & co polymers of
amino acids (particularly homo and co polymers of aspartic
acid glutamic acid), polyvinyl alcohols (which often also
include some polyvinyl acetate), polyacrylamides,
polyacrylates and various copolymers, such as those of
malefic and acrylic acids, in particular
maleic/acrylic/vinyl alcohol terpolymers. Molecular
weights for such polymers vary widely but most are within
the range of 2,000 to 100,000. Other suitable polymers are
polyamine N-oxide polymers, copolymers of N-
vinylpyrrolidone and N-vinylimidazole, polyvinylpyrrolidone
polymers, polyvinyloxazolidones and polyvinylimidazoles or
mixtures thereof.
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Polymeric polycarboxyate builders are set forth in U.S.
Patent 3,308,067, Diehl, issued March 7, 1967. 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, methylenemalonic acid, methyl
acrylic and PEG. In the present invention it is preferred
that polymeric polycarboxylates are substantially omitted
from the aqueous slurry. By substantially omitted, less
than 5$ by weight of the aqueous slurry is preferred, and
less than 2~ by weight is more preferred.
Inorganic salts
Whilst the skilled person has a wide range of inorganic
salts from which to choose, it is an essential feature of
the present invention that the inorganic salt should result
in an increased ionic conductivity of the aqueous slurry.
The ionic conductivity of the aqueous slurry depends not
only on the inorganic salt used, but also on the amount of
inorganic salt used, and also on the composition of the
aqueous slurry. Halides, especially chlorides, nitrates and
citrates have been found to be particularly effective
inorganic salts which when .used at the preferred levels,
have the effect of increasing the ionic conductivity of the
aqueous slurry. Carbonates and sulphates are less
effective, and may well cause a decrease in the ionic
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conductivity of the slurry. Without wishing to be bound by
theory, it is believed that the higher ionic conductivity
of the aqueous slurry suppresses the formation of highly
viscous surfactant phases which are subsequently difficult
to dry. By promoting less viscous surfactant phases the
aqueous slurry is more readily formed into free-flowing,
crisp particles having a good particle size distribution.
Silicone Oils
Particulate suds suppressors may also be incorporated into
the finished composition by dry adding. Preferably the suds
suppressing activity of these particles is based on fatty
acids or silicones.
Optionals
Other ingredients commonly used in detergent compositions
can be included in the compositions of the present
invention. These include flow aids, color speckles,
bleaching agents and bleach activators, suds boosters or
suds suppressors, antitarnish and anticorrosion agents,
soil suspending agents, anionic and nonionic soil release
agents, dyes, clays, flocculating agents, STS, fillers,
optical brighteners, germicides, pH adjusting agents,
nonbuilder alkalinity sources, hydrotropes, enzymes,
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s
enzyme-stabilizing agents, chelating agents, (including
EDDS) and perfumes.
These optional ingredients, especially optical brighteners,
may be incorporated either directly in the agglomerates
herein or may be components of separate particles suitable
for dry adding to the agglomerates of the present
invention.
Processing
The aqueous slurry may be prepared by a batch or continuous
process. Most conveniently a batch mixer, or "crutcher" is
used in which the various detergent components or dissolved
in, or slurried with, water. Typically the aqueous slurry
contains from about 20~ to about 60~ by weight of water, in
particular from about 30$ to about 40$ by weight of water.
This is referred to as the crutcher mix moisture. In the
process of the present invention, the order of addition of
the inorganic salt and the other components of the aqueous
slurry (or "crutcher mix") is not considered to be
critical. It is an essential feature of the present
invention that the ionic conductivity of the aqueous slurry
which comprises the inorganic salt must be greater than the
ionic conductivity of the aqueous slurry in the absence of
the inorganic salt. It is preferred that the addition of
the inorganic salt results in an aqueous slurry having an
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ionic conductivity which is at least 3 milliSiemens higher
than a corresponding aqueous slurry from which the
inorganic salt has been omitted.
The drying of the aqueous slurry may be achieved by any one
of several processes known to the skilled man, but it is
preferably prepared by spray drying. Following the spray
drying route, an aqueous slurry is prepared comprising the
solids. The slurry is then pumped at high pressure through
atomising nozzles into a drying tower where excess water is
driven off, producing a flowable powder. The resulting
powder may then be oversprayed with liquid ingredients,
especially nonionic surfactants for which the powder has a
high adsorption capacity before it loses its good flow
characteristics. Other powdered components of the finished
laundry detergent may be dry mixed with the flowable powder
produced by the above process.
TEST METHOD
Procedure for the Conductivity Test
1. Prepare a l5kg sample of aqueous slurry ready for spray -
drying.
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2. Place the sample in a large bucket 400mm diameter and
SOOmm in height.
3. Let the mix cool to 30°C.
4. Using a Jenwat 4020 Conductivity Meter, measure the
conductivity of the aqueous slurry.
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EXAMPLES
Aqueous Slurry Composition by weight)
(~
Reference Ex. Ex. Ex. 3 Ex.4
1 2
LAS 11.2 11.2 11.7 11.2 11.2
Zeolite A 26.2 26.2 30.0 26.2 26.2
Water 33.0 33.0 34.5 33.0 33.0
Chelant 0.3 0.3 0.3 0.3 0.3
Brightener 0.1 0.1 0.1 0.1 0.1
Magnesium Sulphate 0.3 0.3 0.3 0.3 0.3
Carboxy Methyl 0.3 0.3 0.3 0.3 0.3
Cellulose
HEDP 0.3 0.3 0.3 0.3 0.3
Copolymer of 0.4 0.4 0.4 0.4 0.4
acrylic & malefic
acid
Miscellaneous 2.2 2.2 2.3 2.2 2.2
Sodium Sulphate 25.7 21.4 21.4 24.3 18.5
Sodium Chloride 0 4.3 1.4 7.2 0
Sodium Citrate 0 0 0 0 4.3
Conductivity 10 19 17 21 13
(milliSiemens)
a
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Aqueous Composition by weight)
Slurry (~
Ex. 5 Ex. 6 Ex. 7 Ex. Ex. 9
8
LAS 11.2 11.2 11.7 11.2 11.2
Zeolite A 26.2 26.2 30.0 26.2 26.2
Water 33.0 33.0 34.5 33.0 33.0
Chelant 0.3 0.3 0.3 0.3 0.3
Brightener 0.1 0.1 0.1 0.1 0.1
Magnesium Sulphate 0.3 0.3 0.3 0.3 0.3
Carboxy Methyl 0.3 0.3 0.3 0.3 0.3
Cellulose
HEDP 0.3 0.3 0.3 0.3 0.3
Copolymer of 0.4 0.4 0.4 0.4 0.4
acrylic & malefic
acid
Miscellaneous 2.2 2.2 2.3 2.2 2.2
Sodium Sulphate 21.4 21.4 21.4 21.4 21.4
Potassium Chloride 4.3 0 0 0 0
Potassium Nitrate 0 4.3 0 0 0
Potassium Citrate 0 0 4.3 0 0
Calcium Chloride 0 0 0 4.3 0
Calcium Nitrate 0 0 0 0 4.3
c Conductivity 19 17 13 16 14
(milliSiemens)
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The aqueous slurry is heated to 70°C and is fed through
to a series of pressure pumps. This increases the
pressure of the mix up to 80 bar. Air is then injected "
into the mix at a pressure of 100 bar. The high pressure
mix is then directed to the top of the spray drying tower.
Here it is blown through a set of nozzles, which range in
aperture diameter up to lmm. These atomise the slurry
into droplets. The moisture is driven off these particles
as they fall through the tower with a residence time of up
to 180 seconds by contact with hot air at 275°C. At the
bottom of the tower a blown powder is collected with a
density in the range of 300 - 550g/1. The resulting blown
powder has a moisture in the range of 5 - 15$ with the
majority of the particles having a size in the range of
150 - 1200 micrometers.
