Note: Descriptions are shown in the official language in which they were submitted.
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PROCESS FOR MAKING SOLID AMINE OXIDE
SURFACTANT COMPOSITION
10 FIELD
The present invention relates to a process for preparing solid
compositions containing amine oxide-acid salts. Such compositions are a
source of solid, concentrated amine oxide surfactants for incorporation into
cleaning products, especially solid or granular cleaning products.
BACKGROUND
Amine oxides are commonly used in cleaning compositions to boost and
maintain suds formation. Such compositions include, for example, laundry,
shampoo and dish washing detergent compositions.
Many methods for preparing amine oxide surfactants from the
corresponding tertiary amine are known. Such methods involve the conversion
of a tertiary amine in the presence of a strong oxidizing agent to the
corresponding amine oxide. For example, tertiary amines can be reacted with
hydrogen peroxide to yield a 30-40% aqueous solution of the corresponding
amine oxide. Catalysts are commonly used to facilitate the reaction. Most of
these methods, however, result in liquid formulations containing the amine
oxide.
For shipping economy and for use in solid or granular detergent
compositions, solid amine oxide surfactant formulations are desirable than
typical amine oxide surfactant formulations that are commercially available,
such
as in liquid, gel, or paste form. There have been many attempts at preparing
amine oxide surfactants in solid or granular formulations. U.S. 5,399,296,
granted on March 21, 1995 to Wierenga et al. and U.S. 5,389,306 granted on
February 14, 1995 to Wierenga et al. disclose solid amine oxide compositions
containing amine oxide-malefic acid salts and the process for making such
compositions.
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The foregoing considerations involving amine oxide surfactant
formulations and the processes for preparing them indicate that there is a
continuing need to provide solid formulations containing amine oxide
surfactants. None of the existing art provides all of the advantages and
benefits
of the present invention.
It has now been found that in addition to solid amine oxide compositions
containing amine oxide-malefic acid salts, other solid amine oxide surfactant
compositions can be formed. Such other solid amine oxide surfactant
compositions can be used as a source of amine oxide surfactants in cleaning
compositions.
SUMMARY
The present invention is directed to a process for preparing solid amine
oxide surfactant compositions which are useful in formulating detergent
products, such as laundry detergents, shampoos, personal cleansing
compositions, and cosmetic compositions, especially solid or granular cleaning
products. The process comprises
admixing the complexing acid with an amine oxide surfactant formulation by
admixing 1 mole of complexing acid with X moles) of amine oxide, where X is
from about 1 to about equal to the number of acid groups of the complexing
acid.
The pH of the admixture is from about 1 to about 3, whereby a visible
precipitate
in the admixture is formed. The formed precipitate is separated from the
admixture, preferably by mechanical means, and allowed to dry. The separated
precipitate forms the solid compositions of the present invention, which solid
compositions consist of the amine oxide and complexing acid described above.
These and other features, aspects, and advantages of the present
invention will become evident to those skilled in the art from a reading of
the
present disclosure.
DETAILED DESCRIPTION
While this specification concludes with claims distinctly pointing out and
particularly claiming that which is regarded as the invention, it is believed
that
the invention can be better understood through a careful reading of the
following
detailed description of the invention.
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All percentages, ratios, and proportions are by weight, all temperatures
are expressed in degrees Celsius, molecular weights are in weight average, and
the decimal is represented by the point (.), unless otherwise indicated.
All ratios are weight ratios unless specifically stated othenNise.
As used herein, "comprising" means that other steps and other
ingredients which do not affect the end result can be added. This term
encompasses the terns "consisting of and "consisting essentially of'.
As used herein, the term "solid compositions" mean particulate (e.g.
powders, granules, agglomerates) and non-particulate solids.
As used herein, all pKa and pH values are measured in water at
25°C.
All cited references are incorporated herein by reference in their
entireties. Citation of any reference is not an admission regarding any
determination as to its availability as prior art to the claimed invention.
The process for preparing the solid amine oxide surfactant compositions
of the present invention, including preferred embodiments thereof, are
described
in detail as follows.
Amine Oxide Formulations
Amine oxide formulations for use in the process herein comprise varying
amounts of amine oxide surfactant therein. Such amine oxide formulations, and
the processes for preparing them, are well known in the surfactant art.
The amine oxide formulations for use in the instant process comprise
varying percentages of amine oxide surfactant. Amine oxide surfactants are
commercially available in many physical forms, including liquid, paste, gel
and
solid. The percentage of amine oxide surfactant in the formulation, as well as
the type of such amine oxide surfactant, are not critical to the successful
operation of the instant process. Accordingly, any known or conventional amine
oxide formulation can be used. Such known or conventional formulations
typically contain from about 3°~ to about 80%, more typically from
about 5°r6 to
about 20°~, most preferably from about 5°~6 to about 10°~
by weight of amine
oxide surfactant in a dilute water solution. It is understood, however, that
formulations containing higher and lower concentrations of amine oxide
surfactant can also be used in the instant process.
Amine oxide surfactants for use in the instant process preferably have the
formula RR'R"N0, where R is a substituted or unsubstituted alkyl or alkenyl
group containing from about 6 to about 30, preferably about 8 to 18 carbon
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atoms. Groups R' and R" are each substituted or unsubstituted alkyl or alkenyl
groups containing from about 1 to about 18, preferably from about 1 to about
4,
carbon atoms. More preferably, R' and R" are each methyl groups, examples of
which include dodecyldimethyl amine oxide, tetradecyldimethyl amine oxide,
hexadecyldimethyl amine oxide, octadecyldimethyl amine oxide, and
coconutalkyldimethylamine oxides.
Examples of suitable amine oxide surfactants for use in the instant
process include, but are not limited to, dodecyldimethyl amine oxide,
tridecyfdimethyl amine oxide, tetradecyldi-methyl amine oxide,
. pentadecyldimethyl amine oxide, hexadecyldimethyl amine oxide,
heptadecyidimethyl amine oxide, octadecyldimethyl amine oxide, dodecyldiethyl
amine oxide, tetradecyldimethyl amine oxide, hexadecyldiethyl amine oxide,
octadecyldiethyl amine oxide, dodecyldipropyl amine oxide, tetradecyldipropyl
amine oxide, hexadecyldipropyl amine oxide, octadecyldipropyl amine oxide,
dodecyldibutyl amine oxide, tetradecyldibutyl amine oxide, hexadecyldibutyl
amine oxide, octadecyldibutyl amine oxide, dodecylmethylethyl amine oxide,
tetradecylethylpropyl amine oxide, hexadecylpro-pylbutyl amine oxide, and
octadecylmethyibutyi amine oxide.
Another preferred amine oxide is ADMOXT"", which is a C14 amine oxide
dehydrate. ADMOXT'r' and other amine oxides useful in the present process are
set forth in U.S. Patent No. 5,292,955 (Smith and Sauer, issued March 8,
1994).
Also useful are amine oxide surfactants made by the oxidation of tertiary
amines prepared from mixed alcohols obtainable from coconut oil. Such
coconutalkyl amine oxides are preferred from an economic standpoint inasmuch
as it is not necessary for the present purposes, to separate the mixed alcohol
fractions into their pure components to secure the pure chain length fractions
of
the amine oxides.
Amine oxide formulations for use in the present process can be prepared
by known and conventional methods. Such methods normally involve the
controlled oxidation of tertiary amines to the corresponding amine oxide using
a
strong oxidizing agent. A preferred oxidizing agent is hydrogen peroxide. A
dilute, or preferably concentrated (30°~ by weight of more), hydrogen
peroxide
solution is added in a stoichiometric or greater amount to a liquid solution
containing the tertiary amine for conversion thereof to the amine oxide.
Reaction rates and amine oxide yields can be improved by incorporation of
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catalysts and or chelating agents well known in the surfactant art for this
particular application. Methods for making amine oxide surfactants are
described, for example, in U.S. Patent 3,215,741 (Chadwick, issued November
2, 1965), U.S. Patent 3,223,647 (Drew and Voss, issued December 14, 1965),
5 British Patent 437,566 (issued October 31, 1935), and U.S. Patent 4,565,891
(Correa and Riley, issued July 19, 1984).
Comalexin4 acid
The process for preparing the solid compositions of the present invention
involved admixing a complexing acid with the amine oxide formulation described
herein before. Complexing acid is defined as a saturated carboxylic acid with
at
least 5 carbon atoms, unsaturated carboxylic acid with at least 5 carbon
atoms,
phosphoric acid, and mixtures thereof. Such complexing acids will effectively
precipitate amine oxide surfactants from the amine oxide formulations. As used
herein, the term "carboxylates" means carboxyl-containing compounds
generally.
The complexing acids of the present invention can be in a powdery form,
or in an aqueous solution, although the physical form of the complexing acid
is
not critical to the invention. The complexing acid is soluble in water at less
than
about 35°C.
Examples of saturated and unsaturated carboxylic acids with at least 5
carbon atoms includes citric acid, polyacrylic acid, malonic acid, adipic
acid,
oxalic acid, glutaric acid, pthalic acid, lauric acid, oleic acid, benzoic
acid, and
butyric acid. Examples of phosphoric acids include tetra sodium pyrophosphate
(TSPP), sodium tripolyphosphate (STPP), diethylene triamine yenta methyl
phosphoric acid, hydroxyethane diphosphonic acid, and ethylenediamine tetra
methylene phosphoric acid.
Preferred polyacrylic acids have a molecular weight range of from about
2,500 to 70,000, preferably a molecular weight range of from about 10,000 to
about 50,000.
Water soluble salts of the complexing acid can also be used in the instant
process. Such salts can comprise alkali metals (e.g., sodium, potassium),
alkali
earth metals, ammonium, substituted ammonium, and so forth. Preferred among
such salts are sodium citrate, diammonium citrate, sodium tripolyphosphate and
sodium pyrophosphate. Other water soluble salts can be used in the instant
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process provided that such salts are compatible with the amine oxide
surfactant
selected for use herein.
An essential step in the instant process is adding the complexing acid in
the requisite amounts to the amine oxide formulation to form a solid amine
oxide
surfactant composition. It is preferred that the amine oxide be diluted in a
water
solution, having an active level of from about 3% to about 80%, preferably
from
about 5% to about 20°~, most preferably from about 5% to about
10°~.
pH adjustment of the amine oxide formulation to the requisite level to
about 1 to about 3 is normally needed when the compiexing acid is used in the
instant process. Precipitation of the desired amine oxide salt will not occur
to
any large extent until such admixture pH values are realized.
The complex is formed by admixing 1 mole of complexing acid with X
moles) of amine oxide, where X is from about 1 to about equal to the number of
acid groups of the complexing acid. X should be within about plus or minus
25°~6, preferably about plus or minus 10%, of the number of acid groups
in the
complexing acid. The pH of the admixture is from about 1 to about 3, whereby a
visible precipitate in the admixture is formed. The formed precipitate is
separated from the admixture, preferably by mechanical means, and allowed to
dry.
The process of the present invention is described herein in terms of the
addition of the complexing acid to an amine oxide formulation. It is
understood,
however, that any reference herein to complexing acid implicitly includes
salts of
compiexing acids (described herein before), complexing acids which are acids,
and mixtures thereof.
Process
The process of the present invention comprises admixing the complexing
acid and an amine oxide formulation to form a visible precipitate therein, and
then separating the formed precipitate from the admixture. The process is
described in detail as follows.
In a first step of the process, one mole of a complexing acid and X moles
of an amine oxide formulation described herein (10% active in a dilute
solution
of water) are admixed, wherein X is from about 1 to about equal to the number
of
acid groups of the complexing acid. The pH of the admixture is from about 1 to
about 3, whereby a visible precipitate in the admixture is formed.
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The formed precipitate made in accordance with the instant process is a
salt of the amine oxide surfactant and complexing acid.
In one preferred method, an excess of complexing acid is used to
accelerate the formation of the precipitate. An excess of about 30% complexing
acid above the molar amount described above is preferred.
In a second step of the process herein, the formed precipitate is
separated from the admixture. Preferably, such separation is accomplished by
mechanical means such as screening, filtering, centrifuging and the like. The
separated precipitate can then be washed with cold water (pH adjusted to about
the pKa of the amine oxide) to remove unprecipitated reactants, and then dried
to form a solid formulation. Preferably, significantly all of the impurities
have
been removed from the water before washing. The solid formulation can be
reduced to fine particles, agglomerated, and so forth. Since the precipitate
can
be separated by mechanical means, there is no need to use organic extraction
solvents to perform such separations. It is understood, however, that the use
of
organic extraction solvents can be used in the instant process, but that their
use
is neither preferred or necessary. Water of hydration of the formed complex
will
vary depending on the drying operation utilized, e.g., air drying, forced air
drying, convection hot air drying, organic solvent dryinglwashing, and so
forth.
Examples
ft is understood that the examples and embodiments described herein are
for illustrative purposes only and that various modifications or changes in
fight
thereof will be suggested to one skilled in the art without departing from the
scope of the present invention.
Example 1
About 0.92 grams of citric acid complexing acid is admixed with about 30
grams of amine oxide solution (C14 alkyldimethyl amine oxide, 10°~
active in a
solution of water). The molar ratio of complexing acid to active amine oxide
is
about 1:2. The pH of the admixture of amine oxide solution and citric acid is
from about 1 to about 3. pH is adjusted with the addition of excess citric
acid. A
visible precipitate forms almost immediately. The admixture is allowed to set
for
about 5 minutes. The precipitate is then filtered from the admixture, washed
with
water (pH of 7), in which the water has substantially all the impurities
removed,
and air dried before it is reduced to a fine powder. The citric acid is
preferably in
a powder form.
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Example 2
The process described in Example 1 is repeated, except that 30 grams of
C16 alkyldimethyl amine oxide (7.85°~ solution) is admixed with a
solution of
0.76 grams of citric acid, thereby forming a precipitate. After adding the
initial
citric acid and after the precipitate is formed, an additional 0.40 grams of
citric
acid is added to adjust the viscosity. The molar ratio of complexing acid to
active amine oxide is 1:1.5.
Example 3
The process described in Example 1 is repeated, except that 5.27 grams
of C16 alkyldimethyi amine oxide (6.4°r6 solution) is admixed with a
solution of
0.09 grams of citric acid. The molar ratio of complexing acid to active amine
oxide is 1:3, and the pH of C16 alkyldimethyl amine oxide solution is adjusted
using 1 N HCI to a pH of 0.97, before the addition of the citric acid.
Example 4
The process described in Example 1 is repeated except that 365 grams of
C14 alkyldimethyl amine oxide (10°~ solution) is admixed with 0.34
grams of
STPP complexing acid (98% active). The molar ratio of complexing acid to
active amine oxide is 1:5, and the pH is adjusted using 1 N HCI to a pH of
1.26
before the addition of STPP.
Example 5
The process described in Example 1 is repeated except that 20 grams of
C14 alkyldimethyl amine oxide (10% solution) is admixed with 4.31 grams of
diethylene triamine yenta methyl phosphonic acid (25% active). The molar ratio
of complexing acid to active amine oxide is 1:5, and the pH is adjusted using
1 N
HCI to a pH of 1.0 before the addition of the complexing acid.
Example 6
The process described in Example 1 is repeated except that 47 grams of C14
alkyldimethyl amine oxide (9.8°~ solution) is admixed with 9.35 grams
of
polyacrylic acid (molecular weight 4,500) complexing acid (48% active). The
molar ratio of complexing acid to active amine oxide is 1:24. No pH adjustment
is necessary before the addition of the polyacrylic acid.
