Note: Descriptions are shown in the official language in which they were submitted.
2145~63
WO 94/07981 PCT/EP93/02510
Nildly alkaline dishwashing detergents
Mildly alkaline detergents for dishwashing machines
are known per se. They essentially contain peroxy
compounds as bleaching agents, enzymes as detergency
boosters, penta-alkali metal triphosphates and alkali
metal silicates as builders, nonionic surfactants and
alkali metal carbonates as buffer. Their pH value in use
is below 11, but may even be 7 (cf. FR 1 544 393, US
4,162,289, EP 135 226, EP 135 227). Accordingly, com-
pounds showing a basically alkaline reaction have hither-
to been used as one of the starting materials and the pHvalue of - up to then - usually above 11 has been corre-
spondingly reduced by suitable combinations and addi-
tives.
It has now been found that highly effective deter-
gents for dishwashing machines can also be obtained by
approaching the solution to the problem from the side of
a neutral pH value. In this way, penta-alkali metal
triphosphate can be completely replaced and the content
of hitherto typical phosphate substitutes, such as native
and synthetic polymers (cf. DE 41 02 743, DE 41 12 075,
DE 41 10 510, DE 41 37 470, DE 42 05 071), can also be
greatly reduced or completely eliminated.
The present invention relates to a mildly alkaline
detergent for dishwashing machines which is characterized
in that it contains sodium citrate, sodium hydrogen
carbonate, a bleaching agent, a bleach activator and
enzymes as essential components and, in the form of a 1~
by weight aqueous solution, has a pH value of about 8 to
< 10 and preferably of about 9 to 9.5.
Anhydrous trisodium citrate or, preferably, trisodi-
um citrate dihydrate may be used as the sodium citrate.
Trisodium citrate dihydrate may be used in the form of a
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WO 94/07981 2 PCT/EP93/02510
finely or coarsely crystalline powder.
The content of trisodium citrate dihydrate is around
20 to 60% by weight and preferably of the order of 30 to
50% by weight. All or part of the trisodium citrate
dihydrate, i.e. around 80% by weight and preferably
around 50% by weight, may be replaced by naturally
occurring hydroxycarboxylic acids such as, for example,
monohydroxysuccinic acid, dihydroxysuccinic acid, ~-
hydroxypropionic acid and glucose acid.
The alkali metal hydrogen carbonate is preferably
sodium bicarbonate. The sodium bicarbonate should
preferably be used in a coarse compacted form with a
particle size in the main fraction of around 0.4 to 1.0
mm. Its percentage content in the detergent is of the
order of 5 to 50% by weight and preferably of the order
of 25 to 40% by weight.
As bleaching agents, active oxygen carriers have for
some time been preferred constituents of detergents for
domestic dishwashing machines (DDWM). They include above
all sodium perborate monohydrate and tetrahydrate and
sodium percarbonate. Compacted sodium perborate monohy-
drate is preferred by virtue of the increase in apparent
density. However, the use of sodium percarbonate stabil-
ized, for example, with boron compounds (DE-OS 33 21 082)
also has advantages insofar as this compound has a
particularly favorable effect on the corrosion benavior
of glasses. Since active oxygen only becomes fully
active on its own at elevated temperatures, so-called
bleaching activators are used for activation at around
60C, the approximate temperature of the washing process
in DDWM. Preferred bleach activators are TAED (tetraace-
tyl ethylenediamine), PAG (pentaacetyl glucose), DADHT
(1,5-diacetyl-2,2-dioxohexahydro-1,3,5-triazine) and ISA
(isatoic anhydride). In addition, it can be useful to
add small quantities of known bleach stabilizers such as,
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WO 94/07981 3 PCT/EP93/02510
for example, phosphonates, borates or metaborates and
metasilicates. The percentage content of bleaching agent
in the detergent as a whole is of the order of 2 to 20%
by weight and preferably of the order of 5 to 10% by
weight while the percentage content of bleaching ac-
tivator is around 1 to 8% by weight and preferably around
2 to 6% by weight.
To improve the removal of protein- and starch-
containing food residues, it is possible to use enzymes,
such as proteases, amylases, lipases and cellulases, for
example proteases, such as BLAP~ 140, a product of
Henkel; Optimase$-M-440, Optimase~-M-330, Opticlean~-M-
375, Opticlean~-M-250, products of Solvay Enzymes;
Maxacal~ CX 450.000, Maxapem~, products of Ibis, Savin-
ase~ 4,0 T 6,0 T 8,0 T, products of Novo, or Experase~ T,
a product of Ibis, and amylases, such as Termamyl~ 60 T,
90 T, products of Novo; Amylase-LT~, a product of Solvay
Enzymes, or Maxamyl~ P 5000, CXT 5000 or CXT 2900,
products of Ibis, lipases, such as Lipolase~ 30 T, a
product of Novo, cellulases, such as Celluzym~ 0,7 T, a
product of Novo Nordisk. The enzymes may each be present
in the detergent in quantities of around 0.2 to 4% by
weight and preferably in quantities of around 0.5 to 1.5%
by weight, based on the detergent as a whole.
Alkali metal carbonates may also be added as alkali
carriers to the detergents according to the invention.
However, if the detergents are to remain free from
special labelling, it is important to keep to the EEC
preparation guidelines for detergents. The alkali metal
carbonate may be used in a quantity of around 0 to around
20% by weight and is preferably used in a quantity of
around 7 to 12% by weight. If naturally occurring
Na2CO3 NaHCO3 (Trona, a product of Solvay) is used, the
quantity used may have to be doubled. To protect the
articles to be washed (more particularly aluminium,
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WO 94/07981 4 PCT/EP93/02510
glazed-on decorations and glasses) against corrosion,
sodium disilicate (Na2O:SiO2 = 1:2) may usefully be added.
The quantities need only be small, amounting to between
o and about 10% by weight and preferably to between 0 and
about 4% by weight.
If distinctly higher contents of soda or disilicate,
for example 10 or 5% by weight, are used, the pH value of
a 1% detergent formulation increases beyond the required
mildly alkaline range of around 9.0 to 9.5. In this
case, sodium hydrogen carbonate may be replaced by citric
acid in quantities of 0 to around 15% by weight and
preferably in quantities of around 0 to 8% by weight.
Although there is no need to add native or synthetic
polymers, they may be added to detergents intended for
use in hard-water areas in quantities of at most about
12% by weight and preferably in quantities of around 3 to
8% by weight. The native polymers include, for example,
oxidized starch (for example German patent application P
42 28 786.3) and polyamino acids, such as polyglutamic
acid or polyaspartic acid (for example the products of
Cygnus and SRCHEM).
The synthetic polymer used is preferably the suc-
cessful powder-form poly(meth)acrylate with an active
substance content of around 92 to 95% by weight and/or a
granular alkaline detergent additive based on sodium
salts of homopolymeric or copolymeric (meth)acrylic acids
which is the subject of DE-OS 39 37 469. This additive
consists of:
(a) 35 to 60% by weight of sodium salts of at least one
homopolymeric or copolymeric (meth)acrylic acid,
(b) 25 to 50% by weight of sodium carbonate (anhydrous),
(c) 4 to 20% by weight of sodium sulfate (anhydrous) and
(d) 1 to 7% by weight of water
and preferably of
(a) 40 to 55% by weight and, more particularly, 45 to
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WO 94/07981 5 PCT/EP93/02510
52% by weight,
(b) 30 to 45% by weight and, more particularly, 30 to
40% by weight,
(c) 5 to 15% by weight and, more particularly, 5 to 10%
by weight and
(d) 2 to 6% by weight and, more particularly, 3 to 5% by
weight
of the compounds mentioned above.
The poly(meth)acrylates may be used in powder form
or in the form of a 40% aqueous solution, but preferably
in granular form. Suitable polyacrylates include Alco-
sperse~ types, products of Alco: Alcosperse~ 102, 104,
106, 404, 406; Acrylsol~ types, products of Norsohaas:
Acrylsol~ A lN, LMW 45 N, LMW 10 N, LMW 20 N, SP 02N,
Norasol~ SLl, WL2, WL3, WL4; Degapas~, a product of
Degussa; Goodrite~ K-XP 18, a product of Goodrich.
Copolymers of polyacrylic acid and maleic acid (poly-
(meth)acrylates) may also be used and include, for
example, Sokalan~ types, products of BASF: Sokalan~ CP 5,
CP 7; Acrysol~ types, products of Norsohaas: Acrysol~ QR
1014; Alcosperse~ of Alco: Alcosperse~ 175; the granular
alkaline detergent additive according to DE 39 37 469.
Up to about 5.0% by weight and, more particularly,
around 0.01 to 0.3% by weight of nitrogen-containing
corrosion inhibitors are preferably added to the deter-
gents according to the invention to prevent tarnishing,
above all of silver dishes and cutlery. These nitrogen-
containing compounds may be amino acids, such as histi-
dine or cysteine, or heterocycles containing 2 or 3 N
atoms in the ring. Effective compounds containing 2 N
atoms in the ring include, for example, 4-methyl-2-
pyrazolin-5-one and 3-methyl-3-pyrazolin-5-one. Repre-
sentatives of compounds containing 3 N atoms in the ring
are, for example, benzotriazole, tolyl triazole and N-
alkylated tolyl triazole (Belclene~ 512). However,
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WO 94/07981 6 PCT/EP93/02510
isocyanuric acid and melamine have also proved to beeffective. These compounds may be used either individu-
ally or in the form of mixtures.
Nonionic surfactants may also be added to the
detergents according to the invention to improve the
removal of fat-containing food remains and to act as
wetting agents and as granulation aids. They may be
added in quantities of 0 to around 4% by weight and
preferably in quantities of 1 to 2% by weight. Extremely
low-foaming compounds are normally used, C12l8 alkyl
polyethylene glycol/polypropylene glycol ethers contain-
ing up to 8 moles of ethylene oxide and 8 moles of
propylene oxide units in the molecule being preferred.
However, it is also possible to use nonionic surfactants
other than known low-foaming types, such as for example
C1218 alkyl polyethylene glycol/polybutylene glycol ethers
containing up to 8 moles of ethylene oxide and 8 moles of
butylene oxide units in the molecule, end-capped alkyl
polyalkylene glycol mixed ethers and the foaming, but
ecologically attractive C810 alkyl polyglucosides and/or
C1214 alkyl polyethylene glycols containing 3 to 8 ethy-
lene oxide units in the molecule for a degree of polymer-
ization of around 1 to 4, which are used together with 0
to about 1% by weight and preferably 0 to about 0.5% by
weight, based on the detergent as a whole, of foam
inhibitors, such as for example silicone oils, mixtures
of silicone oil and hydrophobicized silica, paraffin oil/
Guerbet alcohols, bis-stearyl acid diamide, hydrophobi-
cized silica and other known commercially available foam
inhibitors. C810 alkyl polyglucoside with a degree of
polymerization of around 1 to 4 may be used. A bleached
type should be used because otherwise the granules
obtained will be brown in color.
Finally, other typical detergent components, such as
dyes and fragrances for example, may be added to the
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WO 94/07981 7 PCT/EP93/02510
detergents according to the invention.
To produce the detergents according to the inven-
tion, the sodium salts of homopolymeric or copolymeric
(meth)acrylic acids (as polymer) may optionally be
introduced with sodium carbonate and sodium bicarbonate
into a mixer, for example a plowshare mixer, and subse-
quently subjected to agglomerating granulation in the
presence of liquids, such as water, a nonionic surfactant
or liquid poly(meth)acrylate, the resulting granules
optionally adjusted to a uniform size distribution in a
second granulation stage and then dried with agitation in
a stream of warm air, after which fine and coarse partic-
les are removed and the granules are subsequently mixed
with a bleaching agent and, optionally, a bleach acti-
vator, a bleach stabilizer, fragrance, enzymes, nonionicsurfactants, trisodium citrate dihydrate and/or dyes.
The trisodium citrate dihydrate may even be added in
the first granulation stage.
Since the alkali metal carbonate content has a
considerable bearing on the alkalinity of the product,
drying has to be carried out in such a way that the
bicarbonate decomposition of the sodium bicarbonate to
sodium carbonate is minimal (or at least constant). This
is because any sodium carbonate additionally formed by
drying would have to be taken into account in the for-
mulation of the granules. Low drying temperatures not
only counteract the decomposition of sodium bicarbonate,
they also increase the solubility of the granular deter-
gent in use. Accordingly, the drying process is advan-
tageously carried out at a temperature of the inflowingair which, on the one hand, should be as low as possible
to avoid bicarbonate decomposition but which, on the
other hand, should be as high as necessary to obtain a
product with good storage properties. Drying is prefer-
ably carried out at a temperature of the inflowing air of
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W0 94/07981 8 PCT/EP93/02510
around 80C. The granules themselves should not be
heated to temperatures above about 60C. In contrast to
the production process, the decomposition of the sodium
bicarbonate is entirely desirable in the subsequent use
of the detergent in the dishwashing machine because the
alkalinity of the liquor and hence its cleaning perform-
ance are increased in this way. The in situ formation of
sodium carbonate (which irritates the eyes and the skin)
from sodium hydrogen carbonate (non-irritating) reduces
dangers for the consumer, for example in the event of
improper use by children.
The following ranges, for example, are suitable for
starting formulations of virtually all possible constitu-
ents of the granular detergents produced in accordance
with the invention, representing the active substance
content in % by weight and always adding up to 100% by
weight:
20 to 60 and preferably around 30 to 50% by weight of
citrate or salts of hydroxycarboxylic acids,
0 to 15 and preferably around 0 to 8% by weight of
citric acid,
0 to 12 and preferably around 3 to 8% by weight of
polymer (native or synthetic),
0 to 20 and preferably around 7 to 12% by weight of soda
or 0 to 40 and preferably 14 to 24% by weight of
Trona,
0 to 10 and preferably around 0 to 4% by weight of
sodium silicate,
5 to 50 and preferably around 25 to 40% by weight of
sodium hydrogen carbonate,
0 to 15 and preferably around 5 to 10% by weight of
sodium perborate,
0 to 20 and preferably around 5 to 10% by weight of
sodium percarbonate, either perborate or percar-
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WO 94/07981 9 PCT/EP93/02510
bonate having to be present,
1 to 8 and preferably around 2 to 6% by weight of TAED,
0 to 5 and preferably around 0.01 to 0.3% by weight of
corrosion inhibitors,
5 0 to 4 and preferably around 1 to 2% by weight of
nonionic surfactant,
< 4 and preferably around 0.5 to 1.5% by weight of
amylase,
< 4 and preferably around 0.5 to 1.5% by weight of
protease,
< 4 and preferably around 0.5 to 1.5% by weight of
lipase,
< 4 and preferably around 0.5 to 1.5% by weight of
cellulose.
E x a m p 1 e s
The favorable properties of the- mildly alkaline
detergents according to the invention in preventing bloom
were tested in comparison with known detergents contain-
ing pentasodium triphosphate.
The increased calcium binding capacity of citrate at
pH values of 7 to 10 was demonstrated by the Hampshire
test (Tenside, Surf. Deterg. 24 (1987), 213-216) as a
function of temperature and pH value. It was surprising
to find that the calcium binding capacity of pentasodium
triphosphate under these low-alkali conditions is signif-
icantly lower than that of the citrate at the same pH
value. Accordingly, the advantage of pentasodium tri-
phosphate lies above all at relatively high pH values (>
pH 10 for 1% solutions), as prevail in conventional
detergents.
1. Calcium binding capacity of trisodium citrate
dihydrate (expressed in mg of calcium carbonate per
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WO 94/07981 10 PCT/EP93/02510
g of citric acid) and of pentasodium triphosphate
(expressed in mg of calcium carbonate per g of
triphosphoric acid) as a function of the washing
temperature at pH values of 10, 9.5 and 9Ø
Table 1 shows that the calcium binding capacity of
citrate is distinctly dependent both on temperature and
on pH. At the operating temperatures of 50C to 65C and
pH values of 9 to 10, the calcium binding capacity
improves with decreasing pH and with decreasing tempera-
ture. By contrast, pentasodium triphosphate shows hardly
any dependence on pH (Table 2). For the comparison with
pentasodium triphosphate, this means that, at pH 9.5/50C
for example, the calcium binding capacity of citrate is
distinctly higher.
Table 1:
Calcium complexing capacity of sodium citrate
Temperature [C]
pH value 50 55 60 65 70
9.0 480470 390 370 310
9.5 370250 250 240 180
10.0 240180 180 170 150
Calcium binding capacity in mg of CaC03/g
of complexing agent (acid form)
Table 2:
Calcium complexing capacity of pentasodium triphosphate
Temperature [C]
pH value 50 55 60 65 70
9.0 310290 260 260 230
9.5 320290 270 260 230
10.0 320 300 280 230 230
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WO 94/07981 11 PCT/EP93/02510
Calcium binding capacity in mg of CaC03/g
of complexing agent (acid form)
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WO 94/07981 12 PCT/EP93/02510
2. Comparison of bloom formation under hard water
conditions in the dishwashing machine
The detergents according to Example 4 were tested
for bloom formation after 10 wash cycles in a Miele G 590
dishwashing machine (6.2 l of water with a hardness of
16dH, operating temperature 65C) with addition of 50 g
of a pumpable soil. The detergents were used in the
quantities shown. On a scale of 1 (= no bloom) to 10 (=
very heavy bloom), detergents 2 to 6 according to the
invention achieved the scores shown in Table 5 below for
bloom formation in the machine (value A) and bloom
formation on the machine load (china/glass/cutlery; value
B). Comparison of the low-alkali formulations (2 to 6,
pH value approx. 9.5) with the high-alkali phosphate-
containing formulation C showed that the bloom-inhibiting
effect of the detergents according to the invention was
as good as or far better than that of the conventional
detergent.
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214566~
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WO 94/07981 14 PCT/E~93/02510
Table 5:
Scoring of bloom formation in the dishwashing machine
under hard water conditions
Formulation Quantity used [g] Bloom A Bloom B
1 15 8 9.5
2 20 3 6.5
3 20 3.5 6.0
4 20 3.0 2.0
1.5 2.0
6 20 3.0 2.0
1 30 3.0 6.0
2 30 1.5 2.5
C 30 6.5 6.0
3. Table 3 compares the calcium binding capacity of a
few natural carboxylic acids, as determined by the
Hampshire test. The citric acid containing three func-
tional carboxyl groups has the highest calcium binding
capacity. pH dependence is similar for all carboxylic
acids, the highest binding capacity being observed with
decreasing pH. Similarly, the calcium binding capacity
increases analogously with the number of carboxyl groups.
The letters appearing in the Table have the following
meanings:
Hydroxymonocarboxylic acids:
A = lactobionic acid potassium salt (Solvay)
B = L-ascorbic acid sodium salt (Fluka)
C = D-gluconic acid sodium salt (Magazin, Henkel)
Hydroxydicarboxylic acids:
D = D-glucaric acid potassium salt (Aldrich)
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WO 94/07981 15 PCT/EP93/02510
E = tartaric acid disodium salt dihydrate (Merck)
Hydroxytricarboxylic acid:
F = trisodium citrate dihydrate (Magazin, Henkel)
Dicarboxylic acid mixture, HOOC-(CH2)~0COOH, n =
2,3,4:
G = SOKALAN~ DCS (BASF)
Note:In the case of tartaric acid and citrate, the
weighed sample was based on the empirical formula
without water of crystallization!
Table 3:
Comparison of the calcium complexing capacity of various
naturally occurring carboxylic acids at 20C and, for
example F', at 50C
Natural carboxylic acids / types
pH value A B C D E F G F'
9.0 203168 196 589 687 937 223 480
9.5 127118 121 323 343 625 132 370
10.0 1009 95 155 143 478 100 240
Calcium binding capacity in mg of CaCO3/g of
complexing agent (acid form)
