Note: Descriptions are shown in the official language in which they were submitted.
~WO 94/04640 2 1 ~ % 9 1 ~ PCI/US93/07700
CONCENTRATED ~IQUID DETERGENT COMPOSITION COMPRISING AN ALKYL
ETHER SULPHATE AND A PROCESS FOR MAKING THE COMPOSlTlON
Background of the Invention
Recent trends in the detergent industry have been towards
delivering a more concentrated product to the consumer.
This has the benefits of both smaller and lighter bottles,
boxes etc. for the consumer to handle, as well as lowering
the requirement for packaging materials. Decreasing the
packaging materials in turn reduces the load on waste
disposal into the environment.
With this in mind it has been the goal of detergents
manufacturers to produce raw materials which have a higher
concentration of active detergent ingredients. This goal
challenges the manufacturers to formulate, and develop
processes for, compositions which are increasingly
concentrated, but still stable over a period of time.
This invention provides a stable concentrated aqueous or
aqueous/alcohol solution of an alkyl ether sulphate useful
as a component in formulating cleaning products especially
dish washing liquids.
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The solution contains alkaline earth metal ions, which are
known to boost performance of dish washing formulations,
but very few or no chloride or sulphate ions, which have a
detrimental effect on the stability of concentrated
solutions and on finished products made from said
concentrated solutions.
The invention also describes a two-stage neutralising
process for making such compositions.
The composition may be used as a finished product in its
own right, but preferably it will be mixed with other
ingredients to produce a finished product. It is intended
that the sulphating/neutralising processes may be carried
out at locations remote from the sites were the finished
product is blended. This allows for economical and flexible
manufacturing and transportation.
The use of magnesium cations as performance boosters in
dish washing liquids for at least part of the anionic
surfactant has been widely disclosed in the prior art, for
example, British patent numbers 1 524 441 and 1 551 074 and
British published patent application 2 010 893.
US 4133779, published on January 9th, 1979, discloses a
detergent composition comprising anionic and nonionic
semipolar surfactants. It suggests that a concentrated
liquid/paste containing from 45% to 95% active surfactant
(which can be alkyl ether sulphate) can be made.
Neutralisation by magnesium hydroxide is one of a number of
options, but no process details are given, and no incentive
to avoid chloride or sulphate ions is suggested. Indeed
addition of magnesium in the form of magnesium sulphate is f
preferred. These compositions contain at least 1% of a semi
polar nonionic surfactant
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EP 039110, published November 4th, 1981, says that chloride
and sulphate ions should be avoided or minimised because
additional chloride or sulphate ions can increase the chill
point temperature (the temperature at which inorganic salts
precipitate as crystals in the finished product). EP 039110
deals with compositions of alkyl ether sulphate in
combination with other surfactants, especially linear alkyl
benzene sulphonate and alkyl sulphate in finished products.
These finished products are not concentrated, and therefore
the level of alkyl ether sulphate is around 10~.
Neutralisation with mixed sodium/magnesium cations is
disclosed.
EP 181212, published on May 14th, 1986, discloses that
neutralisation of the alkyl ether sulphuric acid and the
alkyl sulphuric acid can be carried out with the
appropriate alkali or with a magnesium oxide or hydroxide
slurry which avoids the addition of chloride or sulphate
ions. This publication also describes detergent
compositions comprising 22% to 65% by weight of a
surfactant system composed of a mixture of anionic,
nonionic, and zwitterionic surfactants in an organic
solubiliser/hydrotrope-water medium. However this
disclosure is limited to less than 24% by weight of alkyl
ether sulphate.
US 4169078, published on September 25th, 1979 and EP
487170, published on May 27th, 1992, both deal with
neutralisation processes for use with light duty liquid
detergents. However, both of these disclosures are directed
towards compositions comprising alkyl benzene sulphonic
acid.
US 4129515, published on December 12th, 1978, describes a
neutralisation process for various detergent sulphates and
sulphonates. Here, the neutralisation is completed with
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alkanolomines, and the resulting compositions are intended
mainly for washing fabrics.
It is the aim of the present invention to provide for a
highly concentrated alkyl ether sulphate solution which is
stable over time and during storage. The composition
contains alkaline earth metal ions which are known
performance boosters in dish washing liquids. However, the
compositions contain a very low level, of chloride or
sulphate ions.
It is a further aim of the invention to provide a process
for making such compositions.
It is a further aim of the invention to provide a process
for making stable compositions which comprise alkyl ether
sulphate and which also comprise nonionic surfactants based
on polyhydroxy groups such as those derived from sugars.
Summary of the Invention
An aqueous solution comprising from 50% to 90% by weight of
alkyl ether sulphate which is associated with counterions
chosen from alkali metal ions, alkaline earth metal ions or
ammonium ions, or mixtures thereof, and which comprises at
least 0.5% by weight of alkaline earth metal, preferably
magnesium, ions and low levels of chloride or sulphate
ions. Specifically the molar ratio of the alkaline earth
metal to (the sum of chloride and inorganic sulphate) is
greater than 1:1, preferably greater than 3:2.
These compositions may be made by a neutralisation process
comprising two stages. In the first stage the acid form of
the alkyl ether sulphate is partly neutralised by a slurry
of alkaline earth metal hydroxide, preferably magnesium
hydroxide or alkaline earth metal, preferably magnesium
oxide. In the second stage further neutralisation is
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W094/04~0 PCT/US93/07700
carried out in the presence of another alkali, such as
sodium hydroxide.
i Optionally, either a short chain alcohol, a hydrotrope, or
other surfactants may be present in either or both stages
of the neutralisation for viscosity control and improved
stability of the product.
Detailed Description of the Invention
Detergent compositions in accordance with the present
invention comprise from 50% to 90% by weight, preferably
60% to 80% by weight of alkyl ether sulphate, together with
at least 0.5% by weight, preferably at least 1% by weight
of an alkaline earth metal, preferably magnesium. The
compositions comprise low levels of chloride or sulphate.
(As referred to herein, "sulphate" means S042-, either as
an ion or as an i n ~ganic salt. The term excludes the
sulphates of ethoxylated alcohols or other organic
surfactants).
Optionally the composition may also comprise from 0% to 20%
of a short chain alcohol, a hydrotrope, other surfactants
or a mixture of these. Preferably the alcohol is chosen
from ethanol or propylene glycol and, preferably, the
hydrotrope is preferably an anionic aromatic hydrotrope
such as cumene sulphonate, xylene sulphonate, or urea,
other surfactant is preferably chosen from nonionic
surfactant, polyethylene glycol or betaine.
The alkyl ether sulphate component comprises a primary
alkyl ether sulphate derived from the condensation product
of a Cl0-C20 alcohol with an average of up to 8 ethylene
oxide groups. The alcohol itself can be obtained from
natural fats or Ziegler olefin build-up or OXO synthesis.
Examples of synthetically derived materials include Dobanol
23 R , sold by Shell Chemicals (UK) Ltd., Ethyl 24 R sold
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by Ethyl Corp., a blend of C13-C15 alcohols in the ratio of
67% C13, 33% C15 sold under the trade name Lutensol by BASF
GmbH and Synprol R from ICI plc, and Lial 125 R sold by
Liquichemica R Italia. Examples of naturally occurring
materials from which the alcohols can be derived are
coconut oil and palm kernel oil and the corresponding fatty
acids.
C12-15 alkyl ether sulphates are preferred, and C12-13
alkyl ether sulphates are most preferred.
Conventional base-catalysed ethoxylation processes result
in a distribution of individual ethoxylates, so that the
desired average can be obtained in a variety of ways.
Blends can be made of material having different degrees of
ethoxylation and/or different ethoxylate distributions
arising from the specific ethoxylation techniques employed
and subsequent processing steps such as distillation.
The average number of ethoxylate groups per molecule of
alkyl ether sulphate should be less than 8, and preferably
less than 4. A average ethoxylation level of about 0.8 is
particularly suitable for use in this invention.
Sulphation of the alcohol ethoxylate can employ any of the
conventional sulphating agents such as sulphur trioxide or
chlorosulphonic acid. The sulphation process may be carried
out in a falling film reactor, or in a batch reactor, or in
any other suitable sulphating equipment. A continuous
process using a falling film reactor is preferred in order
to minimise degradation of the unstable acid surfactant
prior to neutralisation.
It is consistent with the invention to maximise the
completeness of the sulphation reaction in order to
minimise the levels of inorganic sulphate or chloride which
are present in the neutralised composition.
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In order to control the viscosity of the concentrated
surfactant composition and to ease subsequent handling
and/or processing steps, it may be useful to add short
chain alcohols containing from 2 to 5 carbon atoms. For
example, ethanol, propylene glycol, isopropanol and butanol
may be used, preferably ethanol is used.
Alternatively hydrotropes may be used as viscosity
regulators/stabilising agents. For example cumene
sulphonate, xylene sulphonate and urea may be used.
Neutralisation Process
The neutralisation process of the present invention is
carried out in two stages. In the first stage the acid form
of the sulphated ethoxylated alcohol is partly neutralised
by a slurry of alkaline earth metal, preferably magnesium,
hydroxide or alkaline earth metal, preferably magnesium
oxide, preferably with a solids content of at least 30%.
The neutralisation is preferably carried out continuously
using a conventional neutralisation loop comprising a high
shear mixer in which the acid and base are rapidly and
intimately mixed, a pump and a heat exchanger. Some of the
neutralised product is then allowed to pass to the next
process stage, whilst the rest is returned to the high
shear mixer. Normally the fraction of product allowed to
leave the loop and pass to the next processing stage is
from 6% to 25% by weight, preferably from 9% to 17% by
weight, whilst the remainder of the product continues
around the loop.
It is an essential feature of the invention that the
product at the exit of the heat exchanger shall be less
than pH4, preferably about pH3. pH control may be effected
by the addition of another alkaline solution into the first
neutralisation loop, as well as the alkaline earth metal
hydroxide/oxide. Preferably, the additional alkaline
W094/04640 2~9~3 PCT/US93/0770 ~
solution, if present, is sodium, potassium, or ammonium
hydroxide solution.
Viscosity may be controlled, if necessary, by addition of
short chain alcohol, hydrotropes, or other ingredients
commonly used in detergents, such as surfactants, into the
first neutralisation loop.
The concentration of the intermediate product leaving the
neutralisation loop may be adjusted by the addition of
water to the neutralisation loop.
Other detergent ingredients may be added, such as nonionic
surfactants and/or betaine.
The intermediate product leaving the first neutralisation
loop is then passed directly to a second neutralisation
loop where the neutralisation is completed. The second
neutralisation loop also comprises a high shear mixer, a
pump and a heat exchanger. The intermediate product from
the first heat exchanger is mixed with an alkaline solution
in the high shear mixer in order to complete the
neutralisation. The product leaving the neutralisation loop
should be at least pH7, preferably from pH7 to pH9, most
preferably about pH8.
Any suitable alkaline solution may be used in the second
neutralisation loop, preferred alkaline solutions are
sodium, potassium and ammonium hydroxide.
Short chain alcohols, hydrotropes, water or mixtures of
these, may also be added into the second neutralising loop,
although it will generally be more advantageous to add
these components via the first neutralisation loop.
Although not essential, it is preferred that all of the
alkaline earth metal ions are introduced via the first
neutralisation loop.
~WO 94/0464U 2 1 ~ 2 91 3 Pcr/uss3/~77no
Further Processing
It is intended that the detergent composition made by the
present invention may be stored and transported as required
by manufacturing operations. The compositions may then be
mixed with additional detergent ingredients prior to
packing and shipping to consumers. The additional detergent
ingredients used will be chosen by the formulator from a
wide range of active ingredients. For example, additional
surfactants which are anionic, nonionic, or zwitterionic in
nature, suds promoting agents such as alkanolamides,
opacifiers, thickeners, anti-tarnish agents, heavy metal
chelating agents are all useful in a finished dish washing
liquid composition.
In particular, it is preferred that the concentrated alkyl
ether sulphate composition of the invention is blended with
nonionic surfactant(s) in order to give formulations which
are particularly suitable for dish washing liquids.
Nonionic surfactant(s) may be present in compositions of
the invention at levels of from 0% to 50% by weight. The
present invention has been found to be particularly useful
when used to make finished compositions which comprise
nonionic surfactants based on polyhydroxy groups such as
those derived from sugars. Nonionic surfactants of this
type include polyhydroxy fatty acid amides and alkyl
polyglucosides.
The preferred polyhydroxy fatty acid amides include alkyl
N-methyl glucamide in which the alkyl chain may contain
between 8 and 22 carbon atoms, preferably from 12 to 18
carbon atoms, and in particular coconut N-methyl glucamide
containing predominantly alkyl groups of 12 and 14 carbon
atoms. Suitable processes for preparing these polyhydroxy
fatty acid amides are disclosed in WO 92/06984.
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q~
The preferre~ alkyl polyglucosides include those having an
alkyl group containing from about 12 to about 18 carbon
atoms and a polyglucoside hydrophilic group containing, on
average, from about 1.5 to 4 glucoside units. Suitable
alkyl polyglucosides are dodecyl, tetradecyl, hexadecyl,
and octadecyl, di-, tri-, tetra-, penta- and hexa-
glucosides and mixtures thereof. Further descriptions of
alkyl poly glucosides are given in EP 70074.
In preferred finished product compositions, polyhydroxy
fatty acid amide or alkyl poly glucoside, or mixtures
thereof is present at a level of at least 1% by weight,
preferably at least 5% by weight.
Examples
A detergent composition was made according to the present
invention comprising:
AE0.8S (acid form)70~
Mg(OH)2 (33% slurry)8%
NaOH (50% soln.) 13%
Water 4 5%
Ethanol '.5%
The acid form of the alkyl ether sulphate, with an average
number of ethoxylate groups per molecule of alkyl ether
sulphate of 0.8 (AE0.8S), was made by continuous sulphation
of the corresponding ethoxylated alcohol on a falling film
reactor. The alkyl chain was predominantly a mixture of C12
and C13 chain lengths (Dobanol 23 R, supplied by Shell).
The acid was injected into the high shear mixer of the
first neutralisation loop at a rate of 1.5 tonnes/hour.
All of the magnesium hydroxide needed for the final
composition was added into the loop, along with 60% of the
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sodium hydroxide solution. The water and ethanol were also
added into the first loop.
The partly neutralised sulphate leaving the neutralisation
loop, just after the exit of the heat exchanger had a
temperature of 40~C and pH3. This sulphate was then
injected directly into the high shear mixer of the second
neutralisation loop.
The remaining 40% of the sodium hydroxide solution was also
pumped into the second loop, and neutralisation of the
sulphate was completed. The product leaving the second
neutralisation loop, after the heat exchanger had a
temperature of 40~C and pH8.
The product made in this example was analysed and found to
contain 1.1% by weight of magnesium, 0.6% of chloride, and
1.0% of sulphate. Expressed in moles% this is 0.045mol%
magnesium, 0.016mol% chloride and O.Olmol% sulphate. The
molar ratio of maynesium to sulphate and chloride being
(0.045):(0.01 + 0.016) which is 1.7 : 1 (or 1 : 0.6).
It was stable upon storage, showing no phase separation or
viscosity drift even after storage at sooc for one week.
The high active surfactant composition of this example was
further processed to make a finished product by mixing with
an ethoxylated alcohol with an average of 8 ethoxylate
groups per molecule and a carbon chain length of 10 (C10
AE8), with a coconut N-methyl glucamide, and with other
ingredients as defined below (all % are by weight of
finished product):
Surfactant Composition 20%
C10 AE8 8%
N-methyl glucamide 8%
C12/14 betaine 2%
Ethanol 5%
Sodium cumene sulphonate 2%
Dye/perfume 1%
Water to balance
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This flnished product was also stable upon storage.
Comparative Example 2
The concentrated surfactant composition in example 1 was
remade, replacing magnesium hydroxide by magnesium chloride
in order to get the same level of magnesium (1.1%) in the
surfactant composition:
parts
AE0.8S (acid form) 70
NaOH (50% soln.) to pH 8
Water 4.5
Ethanol 4.5
MgCl2 4-3
The product made in this example was analysed and found to
contain 1.1% by weight of magnesium, 3.71% of chloride, and
0.32% of sulphate. Expressed in moles% this is 0.045mol~
magnesium, O.llmol% chloride and 0.003mol% sulphate. The
molar ratio of magnesium to sulphate and chloride being
(0.045):(0.11 + 0.003) which is 1 : 2.5.
Although the concentrated surfactant composition defined in
this example was stable, the finished product made using
this surfactant composition, according to the formulation
of example 1 was found to be unstable.
Comparative Example 3
The same high active surfactant composition as made in
example 2 was repeated with a further 4.3 parts of
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magnesium chloride added. This concentrated surfactant
composition was not stable, and rapidly separated into
~ three separate phases.
r The product made in this example was analysed and found to
contain 2.2% by weight of magnesium, 6.9% of chloride, and
0.32% of sulphate. Expressed in moles% this is 0.092mol%
magnesium, 0.2mol% chloride and 0.003mol% sulphate. The
molar ratio of magnesium to sulphate and chloride being
(0.092):(0.2 + 0.003) which is 1 : 2.2.
This concentrated surfactant composition was not stable and
showed phase separation.
