Note: Descriptions are shown in the official language in which they were submitted.
WO93/21290 2117 7 4 6 PCT/US93/02943
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,1 Process for Manufacture of
A High Active Detergent Composition Containing Succinic Acid
Backqround
Succinic acid and its salts are known ingredients of
detergent compositions. They are used for their surface
active and hydrotropic properties as well as calcium and
magnesium binding capacity.
They are easily processed directly into a detergent
liquid or slurry by in situ hydrolysis of the corresponding
succinic anhydride, and subsequent neutralisation.
This hydrolysis typically requires a considerable excess
of water and the presence of solvents (eg. lower alcohols),
in an alkaline environment in order to make the hydrolysis
reaction move rapidly to completion.
WO93/21290 ~ ~2 1 17 7 4 6 PCT/US93/02943
There is now a trend to more concentrated detergents
containing very little water. As the water level is
decreased in the hydrolysis step the rate of reaction
decreases and undesirable side reactions between the
anhydride and the solvents forming, for example esters, start
to become significant.
Various prior art has dealt with detergent compositions
containing succinic acid. These applications are in general,
dilute.
GB-A-2 049 723, published December 31, 1980, discloses a
composition containing partly neutralised succinic acid with
one of its salts such that the pH is in the range from 5.5 to
8Ø It describes liquid compositions containing 3%-50% by
weight of the partly neutralised succinic acid.
EP 0 028 850, published May 5, 1981, discloses a liquid
detergent composition containing succinates and a low level
of alkyl benzene sulphonate, for improved storage stability.
The application mentions the neutralisation of the acid or
anhydride in situ, but there is no mention of high active
composltlons .
GB 1 285 582, published August 16, 1972, discloses a
composition substantially containlng 25-90% succinic acid,
which may be derived from the anhydride, and 10-75% nonionic
surfactant. There is no disclosure of a suitable process for
making such compositions.
However, none of the prior art deals with the problem of
making a highly concentrated solution of succinic acid which
is suitable for further processing into a concentrated liquid
detergent. There is a need for a process of hydrolysis of
_ 3
~ succinic anhydrides which can be carried out effectively
in an environment in which very little water is present.
The present invention provides a new process for
hydrolysis of the succinic anhydride to yield a solution
of at least 85~ by weight of partly neutralised succinic
acid. The process can be carried out in situ,
continuously or batch-wise, and offers a flexible process
for making a concentrated liquid detergent.
Summary of the Invention
A process for making a concentrated liquid detergent
composition which comprises
(A) succinic acid R - CH - CH2
COOX COOY
where R is a C1o-C20 alk(en)yl moiety, X,Y are
independently H,Na,K, alkanolamine
and (B) water,
characterised in that succinic anhydride, water and an
alkaline catalyst are:
i) mixed in a ratio of succinic anhydride to water
(B) of not less than 4:1, and wherein the alkaline
catalyst is selected from the group consisting of
sodium hydroxide and potassium hydroxide, the ratio
of hydroxide present to hydroxide needed for
stoichiometric neutralisation being 0.15 or less, in
order to start an exothermic hydrolysis reaction
ii) held in a buffer tank, and
iii) mixed with other detergent ingredients.
Detailed Description of the Invention
The present invention provides a process for the
hydrolysis of succinic anhydride to succinic acid in the
presence of a small excess of water. The process takes
place in the presence of an alkali which catalyses the
reaction and partly neutralises the succinic acid. Firstly
the succinic anhydride, water and alkali are intimately
mixed, either by passing through static mixers, or,
preferably, in a high shear mixer. The mixture is then
stored in a buffer tank (which may be in-line in a
continuous process) until the exothermic hydrolysis
reaction is substantially completed. The resulting high
active partly neutralised succinic acid may then be stored
or transferred directly into a batch tank or continuous
process for further processing to a concentrated liquid
detergent.
THE SUCCINIC ANHYDRIDE
Any succinic anhydride of the general formula:
R - CH - CO- _
CH2 -- CO /
is suitable for use in the present invention. The choice
of R will be made by the detergent formulator. A
particularly preferred chain is when: R is
CH3-(CH2) n - CH=CH-CH2- and n=8-10 or mixtures thereof.
THE ALKALI
Any suitable alkali may be used including sodium
hydroxide, potassium hydroxide, monoethanolamine and
ammonia. Preferred are sodium hydroxide and potassium
hydroxide. The
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WO93/21290 2 1 1 7 7 ~ 6 PCT/US93/02943
ratio of hydroxide present : hydroxide needed for
stoichiometric neutralisation, should be 0.15 or less.
The alkali may be added to the succinic acid in the form
of a solution (typically 50% aqueous solution of either
sodium or potassium hydroxide). Extra water may also be added
in order to ensure complete hydrolysis by the following
reaction:
R - CH - CO ' R - CH - COOH
~ ~ + H20 ~ l
CH2- CO CH2 - COOH
However total water which is present (both added and
with the aqueous alkali) should be limitecl in order to avoid
diluting the final composition, and to avoid an excessively
long reaction time. It has been found that the ratio of
succinic anhydride to water should be not less than 4:1 by
weight.
THE HYDROLYSIS PROCESS
The reactants are brought together and mixed, preferably
in a high shear mixer. Suitable mixers include Pentax (trade
name), supplied by Bran and Luebbe, Germany; Dispax (trade
name), supplied by Janke and Kunkel, and mixers supplied by
Karg and Fryma. This mixture is then pumped into buffer tank
where the hydrolysis reaction will proceed. Preferably the
buffer tank already contains an amount of succinic acid which
itself promotes rapid hydrolysis of the mixture. In a most
preferred embodiment, the buffer tank is in-line in a
continuous process and gives a residence time sufficient for
,,,
hydrolysis to be substantially completed. In this embodiment
of the invention the buffer tank contains at all times a
mixture of succinic acid, water, alkali and partly
neutralised succinic anhydride. The hydrolysis reaction is
PCT/US93/02943
W093/21290
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exothermic, and the temperature rises, preferably to about
9 o c C
The buffer tank should be gently stirred or agitated in order
to keep the reactants mixed. In the case of a continuous
process the buffer tank should be designed to give a
residence time of from 2 to 30 minutes, preferably from 5 to
20 minutes.
The high active succinic acid made according to the
above ratios and process has a pH of less than 5.5,
preferably about pH4.5 when it is diluted to a 0.5% aqueous
solution. Furthermore, after hydrolysis the ratio of partly
neutralised succinic acid to water will not be less than
about 6:l by weight.
START-UP AND SHUT-DOWN PROCEDURE
When a continuous process is in use as described
hereinabove, the process is shut-down by firstly closing the
supply of water and alkali to the mixer. The supply of
succinic anhydride is allowed to continue until all water and
alkali have been flushed through the mixer then this supply
is also shut-down. This procedure ensures that no hydrolysis
continues in the mixer whilst not in use.
Preferably not all of the succinic acid is flushed through
the buffer tank. This means that when the supplies of
succinic anhydride, water and alkali are switched on for
start-up, there is still some acid in the buffer tank to
"seed" the hydrolysis reaction.
During the period that the process is not operating, the
buffer tank should be maintained at an elevated temperature
(typically 60-80~C) in order to prevent solidification of the
succinic acid/anhydride mix.
WO93/21290 2 1 1 7 7 4 6 PCT/US93/02943
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FURTHER PROCESSING
The highly active, partly neutralised succinic acid made
by the present invention may subsequently be added to other
detergent ingredients including surfactants, builders,
chelants, enzymes and softening clays, in order to make a
finished liquid detergent composition. An example of this is
given hereinbelow.
Preferably the high active succinic acid is mixed with
compatible detergent ingredients which allow its temperature
to be reduced below 60~C, before it is mixed with lower
alcohols. Such short chain alcohols may be present in the
final formulation as solvents, examples include ethanol,
propanol, propane diol and glycerol. If the succinic acid and
such solvents are present at temperatures in excess of 60-C,
then undesirable side products such as esters may be formed.
An intermediate composition may be formed which is a stable,
pumpable liquid at temperatures below 60-C. This intermediate
composition preferably consists of at least 40% by weight of
partly neutralised succinic acid.
Example 1
Dodecyl/tetradecyl succinic anhydride 300 kg/hour
Potassium hydroxide (50% aq. soln.)20 kg/hour
Water 40 kg/hour
Succinic anhydride, potassium hydroxide solution and water
are supplied at ambient temperature from metering pumps at
the rates descri~ed above, into a Pentax KMF8 (Trade Mark)
high shear mixer.
This mixture is transferred directly from the outlet
port of this mixer into the bottom of a buffer tank. The
buffer tank has a diameter of about 0.4m and a height of
about 0.8m, giving a residence time of about 17 minutes.
The temperature in the buffer tank rises to 92~C as the
exothermic hydrolysis reaction takes place.
WO93/21290 2 1 1 7 ~ 4 6 PCT/US93/0294~,
The reacted material leaving from the top of the buffer tank
has a composition of:
Dodecyl/tetradecyl succinic acid (partly neutralised) 90%
Water lO%
and, when diluted to give a aqueous solution of 0.5% by
weight, has a pH of 4.5.
In this example, the high active, partly neutralised succinic
acid is mixed with a nonionic surfactant in the ratio of l:l.
The surfactant is supplied at am~ient temperature and the
resulting mix has a temperature of 55~C. The resulting
mixture is a stable, pumpable intermediate composition at
this temperature.
A finished composition is made by mixing the acid/ surfactant
mixture with other detergent ingredients as follows (all
given as % by weight):
Succinic acid/nonionic surfactant 18
Ethanol & l,2 propane diol 12
Sodium hydroxide 9*
Alkyl benzene sulphonic acid 12
Sodium alkyl sulphate 2
Citric acid 7
Enzymes and minors
Miscellaneous (suds suppressor, perfume etc.)l
Water to balance to 100%
*Level of sodium hydroxide may be varied in order to give
finished pH8
