Note: Descriptions are shown in the official language in which they were submitted.
WO 92/07926
2 0 9 5 0 ~ 7 PCT/US91/07758
IMPROVING THE COLOR OF SURFACTANT AGGLOMERATES
BY ADMIXING A SOLID BLEACHING AGENT
The invention relates to a process for producing
surfactant agglomerates with improved color by admixing a
solid bleaching agent.
Backcrround of the Invention
The present invention involves a novel process for
producing surfactant aggloanerates with improved color for
use in detergent compositions by admixing a solid bleaching
agent. In particular, the surfactant agglomerate produced
by the process of the present invention comprises methyl
ester sulfonates (MFS) as one of the components. The
production of alkali metal salts of a-sulfofatty acid alkyl
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esters ("ester sulfonates") by sulfonation of fatty acid
methyl esters with gaseous So3 and subsequent
neutralization of the sulfonic acids formed with aqueous
alkali metal hydroxides, for example with sodium hydroxide,
has been known for some time. The end products of this
process, i.e. the alkali metal salts of the corresponding
a-sulfofatty acid alkyl esters, are predominantly used as
detergents in washing and cleaning preparations.
However, all hitherto known production processes have
remained unsatisfactory either because, although light
colored end products suitable for direct use in the
detergent industry can be obtained, the yields of the
sulfonation step leading to those products are highly
unsatisfactory, or because although high sulfonation yields
can be obtained, the color instability of the fatty acids
or fatty acid esters in the sulfonation step means that
dark-colored to brown-black.crude products unsuitable for
direct use in washing and cleaning preparations are
regularly obtained. Accordingly, a sulfonation step taken
to high yields normally has to be followed by bleaching of
the dark a-sulfofatty acid derivatives fonaed in the
sulfonation step to obtain light-colored products suitable
for use in washing and cleaning systems. Methyl ester
sulfonates in particular have been used in many detergent
compositions as "natural" surfactants - i.e. surfactants
derived from such sources as tallow, coconut and palm.
These products, in particular, have been made only while
encountering numerous problems, including the major problem
that when combining MES with inorganic powders to make MES
agglo~rates, such MES agglomerates are generally dark to
black in color, and therefore contain qualities unsuitable
to the consumer for a detergent product.
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Another difficulty of hitherto known processes for the
production of aqueous ester sulfonates is that, in the
course of the production process, the products accumulate
in the form of water-containing pastes having high
active-substance content. In particular, past attempts to
come up with a acceptably colored detergent product
caaaprising MES yielded high viscosity pastes using other
systems. However, pastes such as these can no longer be
pumped on their own; the. high viscosity behavior of ester
sulfonate pastes such as these always involves the risk of
blockages in apparatus and pipes. Accordingly, there has
long been a need to find production processes for such
alkali metal salts of a-sulfofatty acid alkyl esters in
which the high viscosity of the products obtained is
avoided, or lessened in the process.
A third problem often encountered with ester sulfonates
and particularly MES comprising detergents, is that
addition of hypochlorite or hydrogen peroxide to the acid
mixture to solve the color problem (in addition to causing
a highly viscous paste) have also tended to cause
hydrolysis at the ester in alkaline solution and formation
of a disalt too hydrophilic for general dirt/grease
detergency use.
Japanese published patent application no. 84-16870
describes a process for the production of alpha-sulfofatty
acid ester salts, in which alpha-sulfofatty acid esters
formed during the sulfonation step are bleached with
H2o2 in the presence of a polycarboxylic acid or one of
its salts and subsequently converted by neutralization into
the corresponding alpha-sulfofatty acid esters salt.
Although the salts formed are very suitable for use as
detergents in washing and cleaning preparations, the
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reaction time required for the bleaching step is of the
order of 1 hour which does not include the time required
for the following neutralization reaction.
US-A-4 547 318 describes a process for the production
of color-stable, light-colored aqueous salt pastes of
washing-active alpha-sulfofatty acid esters in which the
dark-colored alpha-sulfofatty acid esters emanating from
the sulfonation step are.first prebleached with alkali
metal hypochlorites in neutral to mildly alkaline aqueous
solution and are then fully bleached with hydrogen peroxide
in the usual way in a mildly acidic aqueous solution. The
bleaching process as a whole takes several hours, involves
a change in the pH value of the reaction medium with all
the ensuing disadvantages, and gives aqueous salt pastes of
which the active substance content is in the range of from
20 to 60% by weight which, as described above, gives rise
to problems affecting the process due to the considerable
increase in viscosity with increasing active substance
content.
US-A-3 142 691 describes the production of
light-colored sulfonated fatty acids and fatty acid
derivatives, more particularly through a process for
bleaching dark-colored sulfonated fatty acids and
sulfonated fatty acid derivatives by treatment with
oxyacids having a strong oxidizing effect, or salts or
anhydrides of these oxyacids.
US-A4 874 552 describes the production of solid,
substantially anhydrous alkali metal salts of
alpha-sulfofatty acid alkyl esters by simultaneously mixing
the esters with an aqueous solution of hydrogen peroxide or
an H202-yielding compound with a solid alkali metal
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carbonate at particular temperature ranges , optionally in
the presence of aqueous alkali metal hydroxide.
The present invention seeks to provide a process for
improving the color of surfactant agglomerates,
particularly MES comprising agglomerates. It further seeks
to provide a process which avoids the prior art two-step
process of bleaching and agglomeration separately, with no
visible detriment to agglomerate color with time. The
present invention further describes a process which avoids
the addition of water or aqueous bleaching agents or
solutions comprising other bleaching agents, thus reducing
the problems associated with high viscous pastes and/or
foaming acid product which is often associated with the
high quantity of water in the processes of the prior art.
In accomplishing this, the present invention seeks to
provide the advantage of a process for producing highly
active particle agglomerates with decreased water content,
which thereby reduces the need for drying of the
agglomerates.
The present irnrention relates to a process for
producing improved color surfactant aggloa~rates comprising
ester sulfonates, especially methyl ester sulfonates
(MES). In currently practiced processes, many surfactant
agglomerates, such as those co~prising MES, retain
undesirable color properties, rendering the surfactants
unsuitable for use in the most widely used detergent
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products. For this reason, most detergents comprising MES
have bleached MES granules after esterification with an
aqueous bleaching agents prior to its neutralization.
It has now surprisingly been found that solid
a-sulfofatty acid alkyl ester salts substantiallywfree from
water, and particularly MES comprising agglomerates, having
outstanding color values and high color stability can be
obtained by carrying out. bleaching with solid bleaching
agents, and preferably, neutralization (especially dry
neutralization) of the dark-colored a-sulfofatty acid alkyl
esters such as MES, resulting from the sulfonation step.
In the process of the present invention, by avoiding
early bleaching or neutralization of the product before
agglomeration of the granules, the high viscous paste
product is avoided, and thus the present invention also
provides the unexpected benefit of ease in formation of the
color-acceptable product. The present invention also
reduces the problem of an overly hydrated paste which
increases the tendency to disalt formation.
By avoiding the addition of hypochlorite or hydrogen
peroxide to the acid mixture, and the subsequent step of
hydrolysis at the ester in alkaline solution and formation
of a disait, the present imrention unexpectedly reduces the
problem of an overly hydrated paste. In the process of the
irnrention, a preferred embodiment allows that any alkali
metal carbonates can be used either individually or in
admixture as the alkali metal carbonate both in the
presence and in the absence of the aqueous alkali metal
hydroxide solution. However, sodium carbonate is
preferably used for the process of the invention by virtue
of its ine~cpensive availability.
WO 92/07926 2 0 9 5 0 3 7 pCT/US91/07758
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In addition, the products formed have a high solids or
active-substance content and are much easier to further
process and use as detergents in washing and cleaning
preparations than state-of-the-art products. Alkali metal
salts of a-sulfofatty acid esters prepared from czude
a-sulfofatty acid esters by neutralization and, optionally,
bleaching always contain a certain proportion of dialkali
metal salts of the free a-sulfofatty acids. These disalts
emanate partly from the alkaline hydrolysis of the mixed
anhydrides of a-sulfofatty acid esters and methyl sulfuric
acid proportionately present in the crude sulfonation
product. Another proportion of disalt emanates from the
unwanted alkaline hydrolysis of the a-sulfofatty acid
methyl ester at elevated temperature and at pH values of 9
and higher. Therefore, extreme care must be exercised
during the execution of these steps to avoid disalt
formation.
It has surprisingly been found that the alkali metal
salts of a-sulfofatty acid esters (MES agglomerates)
prepared by the process of the present invention avoid
substantial disalt problems, without any special
consideration.
Detailed description of the Invention
The present imrention relates to a process for
manufacturing improved color surfactant agglomerates,
particularly comprising methyl ester sulfonates, for use in
detergent compositions, said process comprising sulfonation
of methyl ester, digestion of the sulfonation product,
esterification of said sulfonated product to produce an
acid product and agglomeration of said acid product,
characterized in that said acid product is exposed to a
VO 92/07926 PCT/US91/07758
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solid bleaching agent immediately prior to or during
agglomeration of said acid product. The agglomerates thus
formed and ultimately used in detergent compositions are
generally of adequate particle size for detergent, and
especially powder detergent compositions (preferably from
about 100 um to 1400 um in diameter), and exhibit good free
flowing characteristics.
In such a process, it is preferred that said acid
product is neutralized simultaneous with or subsequent to
its exposure to the solid bleaching agent: it is even more
preferred that said in said process said acid product is
neutralized subsequent to its exposure to the solid
bleaching agent. It is further preferred that subsequent,
concurrent with, or preferably before the formation of the
MES comprising agglomerates, the acid product is
neutralized by dry neutralization.
The terms used herein are those generally known to the
man skilled in the art. Some of the initial steps of the
process of the present invention are also known to the man
skilled in the art. An example of digestion is an
a-sulphofatty acid sulphoester process by which the mixture
of products leaving the falling film sulphonator adjust to
the maximization of the a-sulphofatty acid ester. This can
be done in a holding tank at a given temperature with a
residence time large enough so that the kinetically
preferred a-sulphofatty acid sulphoester slowly rearranges
to the thermodynamically preferred a-sulphofatty acid
ester. Another step known to the man skilled in the art is
esterification, an example being a process by which the
acid mixture after digestion is contacted with methanol for
a given residence time at a certain temperature in order to
maximize the formation of the a-sulphofatty acid ester and
WO 92/07926 PCT/US91/07758
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g
reduce the level of disalt formation. Other steps, such as
addition of perfua~s, coating agents, solubilizing agents,
etc., can also be found in coammon agglomeration processes.
In describing characteristics of deterge__nt agglomerates a
man of skill in the art recognizes that good free flowing
characteristics include such qualities as low caking
tendency, lvw stickiness, low angle of repose, and the
like. Percentages herein are generally by weight, unless
otherwise indicated.
Any of a number of solid bleaching agents may be
utilized in the process of the present invention. Solid
bleaching agents include sodium perborates in any hydration
form (monohydrate, tetrahydrate, etc.), sodium
percarbonate, etc. Non limiting-examples of such solid
bleaching agents include sodium perborates (monohydrate,
tetrahydrate, etc.), sodium percarbonate, urea peroxide,
phosphate peroxyhydrates (such as sodium pyrophosphate
peroxyhydrate), calcium hypochlorite, lithium hypochlorite,
chlorinated trisodium phosphate, sodium chlorite, potassium
permonosulphate, sodium or potassium bisulphites, sodium or
zinc dithionites, and sodium borohydride. Preferred solid
bleaching agents for use in the present invention include
solid bleaching agents selected from the group consisting
of perborates, percarbonates, aixi organic peroxygens
(peracid); more preferred being sodium or potassium
percarbonate. It is also preferred that the solid
bleaching agent of the present invention be in a finely
divided, powder-type form. It is more preferred that the
solid bleaching agent have an average particle size of less
than 800 ~xm, even mare preferred less than 200 Vim.
The solid bleaching agents of the present invention may
be used at various levels and in quantities presently used
to bleach detergent granules and in conventional ratios to
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the acid product before bleaching. Preferably, the solid
bleaching agent is used at a level related to the acid
product wherein the ratio of said solid bleaching agent is
between 1% to 200% of said acid product, preferably between
10% to 100% of said acid product. It has also been found
that the acid product, at the time of exposure to...the solid
bleaching agent, is preferably at a temperature of between
60'C - 90'C.
In a preferred embodiment, the process of the present
invention comprises the steps of
1) Contacting the acid MES with the desired amount of the
solid bleaching agent in a finely divided powder form to
form a mix;
2) contacting the above mix immediately with a dry
neutralizing agent (or alternatively, a dry neutralizing
agent, and other desirable powders), in a suitable
mixer/aggloaaerator:
3) manufacturing MES agglomerates with good free flowing
characteristics in the agglomerating equipment:
where suitable (improved color) finished agglomerates
comprising MES are obtained.
Steps 1 and 2 could alternative be done simultaneously,
thus allowing contact between the acid MES with the bed of
premixed powders in the mixer/agglomerator. In this
manner, adequate product is formed, but there may be a
slight decrease in color improvement ever the above
described method.
The agglomerates made by the process of the present
invention may initially appear of less than desired or
adequate color, but upon storage the color continuously
improves.
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Accordingly, the present invention relates to a process
for the production of methylalkali metal salts of ester
sulfonate comprising agglomerates, and particularly MES
comprising agglaanerates, by bleaching and, preferably
neutralization of methyl ester sulfates in an apparatus
suitable for the processing of products. The I~'.S is mixed
at 20'C to 120'C, preferably 60'C to 120'C, more
particularly at 60'C to 90'C, simultaneously with a solid
bleaching agent or an H2o2-yielding compound and with
solid alkali metal carbonate, optionally in the presence of
the ratio by weight of ester to solid bleaching agent being
from 0.5 to 25: preferably from about 1.5 to 5. The
product formed is a particle (agglomerate) of adequate
characteristics to be dry added to granular detergents and
the solids formed are blended by known methods.
~Y app~~, plants or units suitable for the
processing of MES can be used for carrying out the process
according to the invention. Suitable apparatus includes,
for example, falling film sulphonating reactors, digestion
tanks, esterification reactors, etc. For
mixing/agglomeration any of a number of mixers/
agglomerators can be used. In one preferred embodiment,
the process of the invention is continuously carried out.
Especially preferred are mixers of the Fuka~ FS-G series
manufactured by Fukae Powtech ICogyo Co., Japan: this
apparatus is essentially in the form of a bowl-shaped
vessel accessible via a top port, provided near its base
with a stirrer having a substantially vertical axis, and a
cutter positioned on a side wall. The stirrer and cutter
may be operated independently of one another and at
separately variable speeds. The vessel can be fitted with
a cooling jacket or, if necessary, a cryogenic unit.
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Other similar mixers found to be suitable for use in
the process of the invention include Diosn~ V series ex
Dierks & Sohne, Germany: and the Pharma Matri~ ex T K
Fielder Ltd., England. Other mixers believed to be
suitable for use in the process of the invention are the
Fuj~ VG-C series ex Fuji Sangyo Co., Japan: and the
Rot ex Zanchetta & Co srl, Italy.
Other preferred suitable equipment can include
EiricZi=y, series RV, manufactured by Gustau Eirich
Hardheim, Germany: Lodig~, series FM for batch mixing,
series Baud KM for continuous mixing/agglameration,
manufactured by Lodige Machinenbau GmbH, Paderborn Germany:
Drais~ T160 series, manufactured by Dzais Werke G~bH,
Mannheim Germany: and Winkwort~ RT 25 series,
manufactured by Winkworth Machinery Ltd., Bershire,
England.
The a-sulfofatty acid alkyl esters used as starting
materials for the process emanate from the processes
typically used in the prior art for the sulfonation of
fatty acid alkyl esters. Esters such as these are obtained
from synthetic, semi-synthetic or natural oils and/or fats
which may in turn originate from plants, land animals or
aquatic animals. Their fatty acid residues contain from 8
to 22 carbon ato~s and preferably from 12 to 18 carbon
atoms. More preferred fatty acid residues of the present
invention contain from 16 to 18 carbon atoms. The ester
group of the fatty acid alkyl esters normally contains from
1 to 6 and preferably from 1 to 3 carbon atoms, the
corresponding methyl esters being particularly preferred.
These esters are generally formed by saponification of
synthetic, semi-synthetic or natural oils and/or fats and
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mixtures thereof and reaction of the fatty acids formed
with monohydric alcohols containing from 1 to 6 carbon
atoms or by direct transesterification with the
corresponding alcohols, particularly methanol. The
corresponding fatty acid esters are then~sulfonated in
known manner at elevated temperature with a mixture of
gaseous sulfur trioxide and inert gas in a sulfonation
reactor, resulting in the formation of products having a
degree of sulfonation of.more than 90%, which are more or
less dark in color due to the color instability of the
fatty acid alkyl esters.
In an embodiment of the process of the invention,
neutral to mildly alkaline a-sulfofatty acid alkyl ester
salts (~~ester sulfonates~~) having a water content of less
than 10% and Klett color values below 100 can be prepared
by simultaneous oxidative bleaching and neutralization.
The starting materials used are the crude products of the
sulfonation of fatty acid alkyl esters containing from 8 to
22 carbon atoms and preferably fraan 12 to 18 carbon atoms
in the fatty acid chain, i.e., a-sulfofatty acid alkyl
esters.
Bleaching is carried out with solid bleaching agents as
disclosed herein or a combination of solid bleaching
agents. The neutralization may be carried out with alkali
metal carbonates, particularly sodium carbonate or sodium
bicarbonate or other alkaline solids such as sodium
citrate, sodium silicate, etc. In the course of a
preferred embodiment of the present invention, a preferably
simultaneous bleaching and dry neutralization reaction
occurs, the bleaching effect of the solid bleaching agent
being surprisingly enhanced or not substantially affected
by the dual reactions, without the problems to a
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significant extent which often occur with two-step
bleaching and neutralization treatments known from the
prior art. There is thus no need for a second alkaline
bleaching treatment. Neutral to mildly alkaline solids
which may be pelletized, granulated or flaked by methods
known per se are obtained as the products of the
simultaneous bleaching and neutralization reaction upon
cooling of the reaction mixture to room temperature the
products are not tacky and are readily soluble in water.
The more or less dark-colored a-sulfofatty acid alkyl
esters obtained from the sulfonation of fatty acid alkyl
esters are used in substantially (anhydrous) form in the
process of the imiention. The starting materials may be
solid or molten, depending on the a-sulfofatty acid alkyl
esters used as raw material and the particular reaction
temperature selected. The reaction temperature is normally
in the range of from 20'C to 120'C, preferably from 20'C to
90'C, most preferably in a temperature range of from 60'C
to 90'C, being particularly preferred for carrying out the
bleaching and, preferably, neutralization process according
to the invention. At high temperatures, for example at
temperatures of from 60'C to 90'C, the a-sulfofatty acid
alkyl esters used are preferably present in molten form.
Solid bleaching agent and a solid alkali metal
carbonate or bicarbonate are simultaneously added in the
temperature range indicted to the a-sulfofatty acid alkyl
esters used as starting materials, of which - as described
above - the methyl esters are particularly preferred by
virtue of their ready accessibility from native sources,
such as tallow, coconut oil or palm kernel oil, after
reaction with methanol. Solid bleaching agents having
application in typical detergent formulations such as
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sodium perborates and percarbonates are preferably used in
practice. The safety precautions required for the handling
of concentrated hydrogen peroxide solutions are known to
the man of skill in the art and have to be taken here.
The agglomeration process itself is well known in the
art. Numerous standardly used powders can be of use in
agglomerate formation, including, for example, carborates,
zeolites, silicon, and the like.
In some processes where. a-sulfofatty acid alkyl esters
or ester mixtures are obtained directly from the
sulfonation of native fatty acid alkyl esters, the esters
are mixed as such with the bleach and possibly ~a
neutralizing agent, in a suitable mixer/agglomerator. The
reaction begins spontaneously. The beginning of the
reaction is reflected in the foaming (under the effect of
carbon dioxide released) and gradual lightening of the
mixture. In the present invention, the problem of foaming
is avoided, thus simplifying the obtainment of acceptable
agglomerates.
The following examples illustrate same of the possible
embodiments of the present invention, but are not intended
to limit the scope of the application.
In the following composition examples, the agglomerates
contain the following particulate composition.
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Ingredients Percent by weight
Composition 1
Methyl ester sulphuric acid (acid MFS) -25.0%
Zeolite A 40.0%
Sodium carbonate 25.0%
Bleaching agent (perborate monohydrate) 10.0%
Composition 2
Methyl ester sulphuric acid 25.0%
Zeolite A 40.0%
Bleaching agent (perborate monohydrate) 10.0%
other ingredients Balance to 100%
Composition 3
Methyl ester sulphuric acid 25.0%
Zeolite A 30.0%
Bleaching agent (perborate monohydrate) 20.0%
Other ingredients Balance to l00%
Composition 4
Methyl ester sulphuric acid 25.0%
Zeolite A 0.0%
Sodium carbonate 25.0%
Bleaching agent (perborate monohydrate) 50.0%
Composition 5
Methyl ester sulphuric acid 25.0%
Zeolite A 45.0%
Sodium carbonate 25.0%
Bleaching agent (perborate monohydrate) 5.0%
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Composition 6
Methyl ester sulphuric acid 25.0%
Zeolite A 45.0%
Bleaching agent (perborate monohydrate) 5.0%
Other ingredients Balance to:100%
EXAN~LE I
Acid MES (methyl ester sulphuric acid) is heated up
in a conventional oven until it reaches 60'C. At the same
time, a mixture of powders is prepared containing the solid
bleaching agent (perborate adonohydrate), the dry
neutralizing agent (sodium carbonate) and some flowing
acids (Zeolite A). The mixture of these powders is placed
inside an Eirich mincer model RV02 (from Maschinenfabrik
Gustav Eirich) and the equipanent is started. The acid MES
is then slowly poured on the powder bed until acceptable
agglomerates are formed.
EXAD~LE 2
The methyl ester sulphuric acid is again heated up
to about 60'C in a suitable vessel (for example in a
thermostated bath). The desired amount of the solid
bleaching agent is then added to the acid and the mix is
stirred until good dispersion is observed. This mix is
then poured into the Eirich mixer model RV02 where a
mixture of the rest of the powder ingredients (dry
neutralizing agent, flowing aids, etc.) has been placed.
The mixer is then operated until acceptable agglomerates
are formed.
