Note: Descriptions are shown in the official language in which they were submitted.
CA 022~8218 1998-12-16
BENCKISER N.V.
World Trade Center AA
~ Schiphol Boulevard 229
NL-1118 BH Schiphol Airport
Netherlands
MGDA-contAi n; ng ~; 51 ~asher detergents of low alkalinity
The invention relates to dishwasher detergents
of low alkalinity which comprise methylglycinediacetic
acid (MGDA) or a salt thereof, and which preferably
have a reduced content of bleach.
Highly bleach-free alkaline dishwasher
15 detergents having a high content of complexing agents
are known in the prior art. In the past, they were sold
as compositions for household dishwashers and they are
still used today for industrial equipment.
US-A 3 673 098 discloses bleach-free caustic
20 compositions which are based on KOH and
nitrilotriacetic acid (NTA) .
FR-A 1 590 416 likewise discloses bleach-free
caustic compositions which are based on alkali metal
hydroxides, pyrophosphates and NTA.
Such compositions were later formulated without
caustic alkalis, and the loss in performance was
compensated for by adding chlorine bleach, as is
described, for example, in US-A-3 826 748. These
compositions without caustic alkalis still had a high
30 pH of more than 11.
The trend towards safer and environmentally
friendlier compositions initially led to the
replacement of strong complexing agents by builders and
later to a new generation of mildly alkaline
35 dishwashing detergents with a pH of from 9 to 11. 5, the
chlorine bleaches in which were replaced by oxygen
bleaches and enzymes.
Good examples of such compositions can be found
in EP-A-135 226, EP-A-135 227 and EP-A-414 197. In
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these compositions, complexing agents are normally only
present in small amounts, if at all.
EP-A-530 635 discloses acidic to mildly
alkaline compositions (pH 5-9) which do not comprise
complexing agents and are based on builders, enzymes
and, optionally, oxygen bleaches.
DE-A-3 833 047 discloses acidic compositions
(pH 2-6) containing hydrolases and builders or
complexing agents. The examples disclose compositions
with a high NTA or EDTA content (up to 30%). Although
these compositions can readily remove, for example, tea
residues, their effect in the case of milk residues,
measured on a scale from 0 to 10, is always below 5.
The use of other biodegradable complexing
agents, such as ~-alaninediacetic acid (~-ADA) and
isoserinediacetic acid (ISDA) in detergents is
disclosed in DE-A-3 829 847 and DE-A-4 036 995. Where
these publications include application examples of
dishwasher detergents, the dishwasher detergents have,
in about 0.5% strength aqueous solution, a pH of more
than 10.5.
Moreover, these compounds have a significantly
lower complexing action than NTA and are only a poor
replacement for the latter in the finished composition.
DE-A-4 319 935 discloses the use of MGDA in
dishwasher detergents without giving an example. In a
GDCH [Association of German Chemists] lecture on
May 30, 1995, one of the inventors of DE-A-4 319 935
published the use of methylglycinediacetic acid (MGDA)
as a complexing agent for cleaning equipment in the
milk industry on an industrial scale and in dishwashing
detergents having a pH in solution of more than 10.5.
The same information can also be found in the
"Prel;m;n~ry Technical Information, Trilon~ ES 9964n,
April 1995, from BASF AG. The dishwashing detergents
disclosed therein comprise 5-30% of MGDA and 1.12% of
active oxygen, MGDA achieving a comparable result to
NTA in inhibiting encrustation (formation of calcium
carbonate deposits). The effectiveness of the
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dishwashing detergents on milk residues or tea residues
is not mentioned. MGDA should, however, be better able
to dissolve calcium phosphate residues than NTA during
dairy cleaning. During dairy cleaning, the working
range is usually strongly alkaline.
In an article in the SOFW [Soaps, Oils, Fats
and Waxes] Journal 122, 1996, 392, the use of MGDA in
laundry detergents is proposed. Particularly in the
~ case of blood-stained laundry, MGDA is said to have a
better effect than phosphonates, and in the case of
tea-soiled laundry has approximately the same effect as
phosphonates. The same publication discloses that MGDA
in a dishwashing detergent, in a similar manner to NTA,
exhibits very good encrustation inhibition on glass,
metal and porcelain, a dishwashing detergent being
disclosed which, in solution, produces a pH of more
than 10.5. It is also proposed to use MGDA under very
strongly alkaline conditions for dairy cleaning.
The dishwasher detergents proposed to date
which use complexing agents therefore have the
disadvantage that they are either effective at a
relatively high pH or do not have sufficient detergency
for certain food residues, in particular for milk
residues and tea residues.
- 25 An object of the invention is to provide a
dishwasher detergent which is effective not only at a
low pH, but moreover also removes difficult-to-remove
food residues which dishwasher detergents effective at
such a pH are usually unable to remove satisfactorily.
In particular, such a dishwashing detergent should have
excellent detergency in the case of dishes soiled
either with milk or else with tea residues. This object
is achieved by a dishwasher detergent which comprises
methylglycinediacetic acid or salts thereof as
complexing agent and which, in about 0.5% strength
aqueous solution, does not exceed a pH of 10.4.
Milk residues are composed of a mixture of
denatured proteins (casein), fats, sugars and mineral
deposits and consist of about 70% of calcium phosphate
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-- 4
(Ca3(PO4)2). Complexing agents thus have an essential
influence on the removal of milk residues because they
dissolve calcium phosphates by complexing the calcium
ions.
Tea residues, as well, are based inter alia on
Ca deposits, which form when tea is made using hard
water. However, tea residues usually place different
demands on a dishwasher detergent to milk residues,
something which is immediately evident from the fact
10 that the detergent disclosed in DE-A 3 833 047
satisfactorily removes tea residues in the acidic range
(pH 2-6), but is not convincing in the case of milk
residues.
The ability (based on the weight of the
complexing agent) to complex calcium ions at a certain
pH depends on the stability constant of the calcium
complex (pKc), the acidic character of the complexing
agent (pK3) and on its molecular weight.
Although, at a pH of 11, MGDA has a higher
theoretical degree of complexation for calcium
carbonate than NTA (as has been disclosed in the
abovementioned GDCH lecture and which can be calculated
theoretically), at a pH of 7 and 10.4 and for calcium
phosphates, the result is different.
In fact, at a pH of 10.4, the theoretical
degree of complexation for calcium phosphates is
360 mg/g when using NTA and 340 mg/g when using MGDA,
and at a pH of 8, the theoretical values are 510 mg/g
for NTA and 490 mg/g for MGDA.
With reference to these theoretical
considerations, it therefore follows that MGDA has a
poorer complexing action on calcium phosphates in the
case of a dishwashing detergent which, in about 0.5%
strength aqueous solution, produces a pH of less than
10.4, and thus should be less able to remove milk
residues than the conventional NTA.
Also, MGDA was used in the prior art only in
dishwashing detergents which have, in about 0.5%
strength aqueous solution, a pH of more than 10.4.
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- 5 -
At a lower pH, the use of NTA is preferable;
this is said to have a better complexing action than
MGDa on calcium phosphates at such a pH, and in
addition satisfactorily removes tea residues in the
acidic range (pH 2-6) (DE-A 38 33 047).
Surprisingly, it has, however, been found
according to the invention that dishwashing detergents
which comprise MGDA and which produce an approximately
0.5% strength aqueous solution having a pH of up to
10.4 are better able to remove tea residues and also
milk residues and, overall, have better detergency than
dishwashing detergents which comprise another
complexing agent instead of MGDA, such as the
conventional NTA.
Surprisingly, it has also been found that for a
dishwashing detergent according to the invention which
has a sufficient amount of complexing agent MGDA, the
amount of oxygen bleach can be reduced without thereby
impairing the detergency and, in particular, the
ability to remove milk residues and tea residues. This
surprising finding even opens up the possibility of
dispensing completely with the use of oxygen bleach
when a sufficiently large amount of complexing agent is
used.
The dishwashing detergent according to the
invention can be liquid or pulverulent and can likewise
be in the form of a single-layer or multilayer tablet.
Corresponding dosing forms and methods for their
preparation are known to the person skilled in the art.
3 0 The dishwasher detergents according to the
invention preferably comprise one or more enzymes, such
as, for example, amylase, protease, lipase or
cellulase. The best cleaning results are obtained by
the combined use of amylase and protease. For the pH
ranges described here, these enzymes can be used
particularly effectively; thus, for example, the
temperature-stable amylase Termamyl (Novo) achieves the
optimum of its activity spectrum at pH 7-8. The enzymes
are used in granular form or in solutions having
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standard commercial concentrations or activities, it
being possible for the content of enzymes to be 0.5-6%
by weight, preferably 1-4% by weight.
Examples of suitable builders are homopolymers
and copolymers of polycarboxylic acids and their
partially or completely neutralized salts, monomeric
polycarboxylic acids and hydroxycarboxylic acids and
their salts, carbonates, bicarbonates, borates,
phosphates, silicates, aluminosilicates and mixtures of
such substances.
Preferred salts of the abovementioned compounds
are the ammonium and/or alkali metal salts, i.e. the
lithium, sodium, potassium and rubidium salts, and a
particularly preferred salt is the sodium salt.
Suitable polycarboxylic acids are acyclic,
alicyclic, heterocyclic and aromatic carboxylic acids,
in which case they contain at least two carboxyl groups
which are in each case separated from one another by,
preferably, no more than two carbon atoms.
Polycarboxylates which comprise two carboxyl
groups include, for example, water-soluble salts of
succinic acid, malonic acid, (ethylenedioxy)diacetic
acid, maleic acid, diglycolic acid, tartaric acid,
tartronic acid and fumaric acid. Polycarboxylates which
contain three carboxyl groups include, for example,
water-soluble citrate. Correspondingly, a suitable
hydroxycarboxylic acid is, for example, citric acid.
Another specific builder for dishwasher
detergents which can be mentioned is a polymer, derived
from aspartic acid
HOOC-CH(NH2)-CH2-COOH
containing monomer units of the formula
and ~ ~a
02X
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Another suitable polycarboxylic acid is the
homopolymer of acrylic acid.
Borate builders which can be used are, in
addition to borates such as sodium borate, also those
builders which liberate borates under the detergent
storage conditions or washing conditions.
Suitable phosphates are polyphosphates, such as
tripolyphosphate, pyrophosphate, orthophosphate and the
polymeric metaphosphate. Examples which may be
mentioned are alkali metal tripolyphosphates, sodium,
potassium and ammonium pyrophosphate, sodium and
potassium orthophosphate and sodium polymetaphosphate,
the degree of polymerization in which preferably being
from 5 to 21.
Suitable silicates are sodium silicates such as
sodium disilicate, sodium metasilicate and crystalline
phyllosilicates. Sodium aluminosilicates (zeolites) are
also suitable.
Other suitable builders are disclosed in
WO 95101416, to the contents of which express reference
is hereby made.
Particular preference is given to a builder
system of the salt of a hydroxycarboxylic acid or of
the mixture of a hydroxycarboxylic acid and the salt of
a hydroxycarboxylic acid. Both the hydroxycarboxylic
acid and the salt of the hydroxycarboxylic acid can be
replaced completely or partially by tripolyphosphate,
although this is not preferable.
The builder system preferably consists of a
hydroxypolycarboxylic acid containing 2-4 carboxyl
groups (or acidic inorganic salts), which can be mixed
with its salt to adjust the pH. Citric acid or a
mixture of sodium citrate with citric acid is
preferably used. For adjustment of the pH, which is
required according to the invention, mixtures having a
major proportion of citric acid, for example, are
suitable, depending on the other constituents of the
mixture.
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The water content of the liquid dishwashing
detergents can be 40-80% by weight.
The liquid dishwashing detergents also comprise
0.2-5.0% by weight, preferably 0.5-2% by weight, of a
thickener. Suitable thickeners are high molecular
organic polymers having molecular weights of from
5 x 105 to ca. 5 x 106, which are composed of
olefinically unsaturated carboxylic acids. Carboxyvinyl
polymers, as are commercially available, for example,
from B.F. Goodrich under the production name
"Carbopol", have proven to be highly suitable.
Inorganic compounds which have thickening properties
for this product composition can also be used. Examples
thereof are natural or synthetic thickeners based on
different silicate structures. Their use is described
in various patents, for example in US-A-4 933 101 or
EP-A2-0 407 187.
Suitable surfactants are, for example, nonionic
surfactants. These include, for example, water-soluble
ethoxylated C6l6 fatty acid alcohols and C6l6 mixed
ethoxylated, propoxylated fatty acid alcohols and
mixtures thereof and also polyglucosides.
Another class of nonionic surfactants includes
polyhydroxy fatty acid amides.
Other suitable surfactants are disclosed in
WO 95/01416, to the contents of which express reference
is hereby made.
The dishwasher detergent according to the
invention can also comprise one or more foam control
agents. Suitable foam control agents for this purpose
are all those used in this field, such as, for example,
silicones and paraffin oil.
The foam control agents are preferably present
in the dishwasher detergent according to the invention
in amounts of less than 5% by weight of the total
weight of the detergent.
The dishwasher detergents according to the
invention may comprise, as bleach, bleaches which are
preferably chlorine-free and liberate active oxygen,
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such as inorganic perhydrates or organic peracids and
the salts thereof.
Examples of inorganic perhydrates are
perborates, percarbonates and persulfates such as
peroxymonopersulfate. The inorganic perhydrates are
normally alkali metal salts, such as lithium, sodium,
potassium or rubidium salts, in particular sodium salt.
The inorganic perhydrates may be present in the
detergent as crystalline solids without further
protection. For certain perhydrates, it is however
advantageous to use them as granular compositions
provided with a coating which gives the granular
products a longer shelf life.
The preferred perborate is sodium perborate,
which can be in the form of the monohydrate having the
formula NaBO2H2O2 or in the form of the tetrahydrate of
the formula NaBO2H2O2.3H2O.
The preferred percarbonate is sodium
percarbonate of the formula 2Na2CO3.3H2O2- The
percarbonate is preferably used for increasing its
stability in a coated form.
Organic peracids include all organic peracids
traditionally used as bleaches, including, for example,
perbenzoic acid and peroxycarboxylic acids such as
mono- or diperoxyphthalic acid, 2-octyldiperoxysuccinic
acid, diperoxydodecanedicarboxylic acid, diperoxy-
azelaic acid and imidoperoxycarboxylic acid and,
optionally, the salts thereof.
The dishwasher detergent according to the
invention can also comprise one or more bleach
activators. These are preferably used in detergents for
dishwashing cycles at temperatures in the range below
60~C in order to achieve an adequate bleaching action.
Particularly suitable examples are N- and O-acyl
compounds, such as acylated amines, acylated
glycolurils or acylated sugar compounds. Preference is
given to N,N,N',N'-tetraacetylethylenediamine (TAED),
pentaacetylglucose (PAG) and tetraacetylglycoluril
(TAGU). Other suitable bleach activators are, however,
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-- 10 --
catalytically active metal complexes and, preferably,
transition metal complexes. TAED is most preferable.
Other suitable bleach activators are disclosed
in WO 95/01416, to the contents of which express
reference is hereby made.
By using MGDA at a relatively low pH, it is,
however, possible to reduce the use of bleaches, and
the dishwasher detergents according to the invention
preferably comprise an oxygen bleach in an amount of
less than 1% by weight, based on the active oxygen. The
amount of bleach activator used is correspondingly
adjusted.
In one embodiment, the dishwasher detergents
have a large content of MGDA, such as 25% or more,
preferably 30% or more, in each case based on the free
acid, and an oxygen bleach is dispensed with.
The dishwasher detergent according to the
invention can also comprise a silver/copper corrosion
inhibitor. This term encompasses agents which are
intended to prevent or reduce the tarnishing of non-
ferrous metals, in particular of silver and copper.
Preferred silver/copper corrosion inhibitors are
benzotriazole or bis-benzotriazole and substituted
derivatives thereof.
Other suitable agents are organic and/or
inorganic redox-active substances and paraffin oil.
Benzotriazole derivatives are those compounds
in which the available substitution sites on the
aromatic ring are partially or completely substituted.
Suitable substituents are linear or branch-chain Cl20-
alkyl groups and hydroxyl, thio, phenyl or halogen such
as fluorine, chlorine, bromine and iodine. A preferred
substituted benzotriazole is tolyltriazole.
Suitable bis-benzotriazoles are those in which
the benzotriazole groups are each linked in the 6-
position by a group X, where X may be a bond, a
straight-chain alkylene group which is optionally
substituted by one or more Clg-alkyl groups and
preferably has 1-6 carbon atoms, a cycloalkyl radical
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having at least 5 carbon atoms, a carbonyl group, a
sulfuryl group, an oxygen atom or a sulfur atom. The
aromatic rings of the bis-benzotriazoles may be
substituted as defined above for benzotriazole.
Suitable organic redox-active substances are,
for example, ascorbic acid, indole, methionine, an N-
mono-(C1-C4-alkyl)glycine, an N,N-di-(Cl-C4-
alkyl)glycine, 2-phenylglycine or a coupler and/or
developer compound chosen from the group consisting of
diaminopyridines,aminohydroxypyridines,
dihydroxypyridines, heterocyclic hydrazones,
aminohydroxypyrimidines,dihydroxypyrimidines,
tetraaminopyrimidines,triaminohydroxypyrimidines,
diaminodihydroxypyrimidines, dihydroxynaphthalenes,
15 naphthols, pyrazolones, hydroxyquinolines,
aminoquinolines, of primary aromatic amines which, in
the ortho-, meta- or paraposition, have another
hydroxyl or amino group which is free or substituted by
C1-C4-alkyl or C2-C4-hydroxyalkyl groups, and of di- or
20 trihydroxybenzenes.
Suitable inorganic redox-active substances are,
for example, metal salts and/or metal complexes chosen
from the group consisting of manganese, titanium,
zirconium, hafnium, vanadium, cobalt and cerium salts
25 and/or complexes, the metals being in one of the
oxidation states II, III, IV, V or VI.
Particularly suitable metal salts and/or metal
complexes are chosen from the group consisting of
MnSO4, Mn(II) citrate, Mn(II) stearate, Mn(II)
acetylacetonate, Mn(II)[1-hydroxyethane-1,1-
diphosphonate], V2O5, V2O4, VO2, TioSo4, K2TiF6, K2ZrF6,
CoSO4, Co (NO3)2 and Ce(NO3) 3.
Organic and inorganic redox-active substances
which are suitable as silver/copper corrosion
inhibitors are also mentioned in WO 94/26860 and
WO 94/26859, to the contents of which reference is
hereby made.
Suitable paraffin oils are predominantly
branched aliphatic hydrocarbons having a number of
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- - 12 -
carbon atoms in the range from 20 to 50. Preference is
given to the paraffin oil chosen from predominantly
branched-chain C25g5 species having a ratio of cyclic to
noncyclic hydrocarbons of from 1:10 to 2:1, preferably
from 1:5 to 1:1.
If a silver/copper corrosion inhibitor is
present in the dishwasher detergent according to the
invention, it is preferably present in an amount of
from 0.01 to 5% by weight, particularly preferably in
an amount of from 0.1 to 2% by weight, of the total
weight.
In the embodiment of the invention in which the
content of MGDA in the dishwasher detergent is
sufficiently high, such as 25% or more, preferably 30%
or more, in each case based on the free acid, with the
result that bleach can be omitted, it is also possible
to dispense with a silver/copper corrosion inhibitor.
Other customary additives are, for example,
dyes and perfumes and optionally in the case of liquid
products, preservatives, suitable examples of which are
compounds based on isothiazolinone.
The dishwasher detergents according to the
invention are not caustic and therefore do not require
particularly secured packaging. A good detergency can
be achieved using a relatively low use amount of
15-20 g of powder or 20-50 ml of liquid detergent.
According to current knowledge, none of the ingredients
is either toxic or detrimental to health in any other
way. The detergents described here thus also represent
an environment- and consumer-friendly alternative to
conventional detergents containing complexing agents
which are effective in the strongly basic range.
The methylglycinediacetic acid used according
to the invention has the following structural formula:
HO2C ~ _<CH3
HO2C-- CC~2H
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The methylglycinediacetic acid is particularly
preferably used as the free acid or as the sodium or
potassium salt, and is preferably present in the
dishwashing detergent in an amount of from 3% to 90%,
based on the free acid.
In bleach-free dishwasher detergents which are
based on phosphates as the principal constituent of the
builder system, the amount of MGDA is preferably at
least 5%, based on the free acid.
According to the invention, it is essential
that an approximately 0.5% strength aqueous solution of
the detergent has a pH of no more than 10.4. The pH of
an approximately 0.5% strength aqueous solution of the
detergent according to the invention is preferably from
more than 6 to 10.4, particularly preferably from 7 to
10 . O .
The following comparative experiment
demonstrates that the dishwashing detergents proposed
in the article in the SOFW Journal 122, 1996, 392-397,
have in 0.5% strength aqueous solutions, a pH of more
than 10.4. The disclosure of this article is therefore
in agreement with the theoretical expectation that MGDA
is an excellent complexing agent at a pH of more than
10.4, but is inferior to the traditional NTA at a pH of
10.4 or below.
Comparative Experiment
30 In agreement with the disclosure of the article
in the SOFW Journal 122, 1996, 392-397, dishwashing
detergents are prepared from the following
constituents:
Sodium citrate dihydrate
Sodium carbonate
Sodium hydrogen carbonate
Sodium perborate monohydrate
TAED
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- 14 -
C13-C1s-OxO alcohol + 4 mol of PO + 2 mol of EO
MGDA (trisodium salt of methylglycinediacetic acid)
(77% strength solution in water) = TRILON ES 9964
obtainable from BASF AG.
The table below shows the amounts of the
respective constituents in g and %. The constituents
were dissolved in one litre of water having a hardness
of 10~, and the pH of the solution was determined in
each case. The total amount of the constituents (100%)
10 is in each case 4 g, corresponding to a 0. 4% strength
concentration, as is disclosed in Figure 14 of the
article.
MGDA in pure form is not available
commercially, and therefore a 77% strength solution in
water was used. A relatively large amount of the
commercially available product therefore had to be
used, as the Table shows. For MGDA, the Table gives two
values in each case. The first value is the amount in g
of the commercial product, and the second value
20 corresponds to the corresponding amount of pure
substance (100%).
SOFW Journal 122, 1996, 392-397
Example 1 Example 2 Example 3
Amounts in g (%'
Citrate 2 (50%) 1.6 (40%) 1 (25%)
Carbonate 1 (25%) 1 (25%) 1 (25%)
Hydrogen-
carbonate 0.36 (9%) 0.36 (9%) 0.36 (9%)
Perborate 0.28 (7%) 0.28 (7%) 0.28 (7%)
TAED 0.08 (2%) 0.08 (2%) 0.08 (2%)
Nonionic 0. 08 (2%) 0.08 (2%) 0.08 (2%)
surfactant
MGDA 0.26/0.2 (5%) 0.78/0.6 (15%) 1.56/1.2 (30%)
(77% solu-
tion)/(100%)
Total 4.06 4 4.18 4 4.36 4
¦pH ¦10. 64 ¦ 10.79 ¦ 10.82
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-- 15 --
Although the pH of 0.5% strength solutions of
the agents was not determined directly, the pH of 0.4%
strength solutions was determined. At a higher
concentration of the detergent, the solutions of the
detergent will obviously have the same or, more
probably, a higher pH.
The example below shows that when some of the
builder of a dishwasher detergent is replaced by
methylglycinediacetic acid, at a low pH, excellent
detergency can be achieved and, in particular, contrary
to the theoretical expectations, the ability to remove
milk residues and tea residues is greater than in the
case of other traditional complexing agents such as
NTA. The example illustrates the invention.
ExA~nple
Liquid dishwashing detergents having a
composition as given in Table 1 were prepared (both in
accordance with the invention using MGDA and using the
NTA customary in the prior art), and their detergency
was determined using dishes soiled with both milk and
tea residues. In this experiment, the DIN Standard
No. 44990, Part 2 was essentially followed. A Bosch
SMS 5062 dishwasher was used. The water had a hardness
of 19~ German hardness (3.39 mmol of calcium
carbonate), the temperature of the water was 65~C and
20 ml of detergent were used in each case. The
detergency results were evaluated on a scale from 1 to
5 (where 5 is 100% clean dishes) and are also given in
Table 1.
The nonionic surfactant is a customary, low-
foaming ethoxylated and propoxylated fatty alcohol.
Customary proteases and amylases are used.
CA 022~82l8 l998-l2-l6
- 16 -
Table 1
NTA I MGDA I NTA II MGDA NTA MGDA
II III III
Water 1.47 0.00 3.57 0.57 7.67 3.77
Citric acid 8.00 9.47 5.90 8.90 1.80 5.70
MGDA (35.6%) 0.00 87.1 0.00 87.1 0.00 87.1
NTA (35.6%) 87.1 0.00 87.1 0.00 87.1 0.00
Nonionic 1.50 1.50 1.50 1.50 1.50 1.50
surfactants
Protease 0.50 0.50 0.50 0.50 0.50 0.50
Amylase 0.50 0.50 0.50 0.50 0.50 0.50
Preservative 0.03 0.03 0.03 0.03 0.03 0.03
Perfume 0.10 0.10 0.10 0.10 0.10 0.10
Thickener 0.80 0.80 0.80 0.80 0.80 0.80
ioo loo loo loo loo loo
pH (0.5% 8.1 8.0 9.4 9.3 10.4 10.3
strength)
Tea 4.2 4.7 4.4 4.8 4.6 5.0
Milk 3.1 3.3 3.2 3.3 3.0 3.4
The results in Table 1 show that in a pH range
below 10. 4 detergents which comprise MGDA achieve
surprisingly better results both in the removal of milk
residues and in the removal of tea residues than the
corresponding detergents which comprise the customary
NTA instead of MGDA.
