Note: Descriptions are shown in the official language in which they were submitted.
2070~ 8~2/1 ~1
Alkyl polyethYleneqlvcol ethers as foam-suPpressinq additives
for cleaninq aqents
The invention relates to the use of terminally-blocked alkyl
polyethyleneglycol ethers as foam-suppres~ing additives in
low-foaming cleaning agents.
Aqueous cleaning agents intended for use in trade and
industry, particularly those for cleaning surfaces made of
metal, glass, ceramics and plastics, generally contain
substances which can counteract any undesired foam formation.
In most cases, the use of foam-suppressing additives is
required because the contaminants which are removed from the
substrates and accumulate in the cleaning baths act as
foaming agents. The use of anti-foaming agents may also be
necessary because the cleaning agents themselves contain
components which under the given working conditions give rise
to undesired foam formation, for example, anionic surfactants
or nonionic surfactants which foam at working temperature.
DE-OS 33 15 951 describes the use of alkyl
polyethyleneglycol ethers of the general formula (Ia),
R1-0-(CH2CH20)n-R2 (Ia)
in which
R1 represents a straight-chain or branched alkyl radical or
alkenyl radical with 8 to 18 carbon atoms,
R2 represents an alkyl radical with 4 to 8 carbon atoms and
n represents a number from 7 to 12,
as foam-suppressing additives in cleaning agents.
These compounds, however, exhibit no anti-foaming effect
below 20 to 25 C.
DE-OS 37 27 378 describes the use of alkyl polyethyleneglycol
ethers of the same general formula (Ia), with the radicals R1
and R2 having the same meaning, but with n = 2 to 6, as foam-
~uppressing additives in cleaning agents. However, these
compounds exhibit no anti-foaming effect below 15C. The
foam layer (foam-height) in the anti-foaming effect test was
< 1 cm at temperatures of > 15 C. Due to their method of
production, namely the ethoxylation of fatty alcohols in the
presence of alkaline catalysts, even the alkyl
polyethyleneglycols which are not yet terminally blocked
exhibit a wide homologue distribution relative to n. This
207~41 ~
homologue distribution remains unchanged by the 6ubsequent
reaction stage of etherification. An effect on the formation
of foam at still lower temperatures is desired, however.
Additionally, during formulation these additives display a
disadvantage in terms of the quantities which can be admixed,
namely phase separation even in the case of small
proportions.
The object of the present invention was therefore to find
foam-suppressing substances whose industrial application
properties are superior to those of the agents of the prior
art, even at temperatures below 15C and which at the same
time have the required biodegradability. Furthermore, the
additives should be superior to the additives of the prior
art with regard to ease of formulation.
It was surprisingly found that alkyl polyethyleneglycol
ethers, which have a narrow homologue distribution in
relation to the number of (CH2CH20)-units contained in the
molecule, have an even better foam-inhibiting effect down to
temperatures of 5C and a substantially better ease of
formulation, which is reflected in the greater possible
quantities which can be formulated. A narrow homologue
distribution was achieved by using calcined hydrotalcites as
catalysts during the ethoxylation of the fatty alcohols.
The invention therefore relates to the use of terminally-
blocked alkyl polyethyleneglycol ethers of the formula
R1-0-(CH2CH20)n-R2 (I),
in which
R1 represents a straight-chain, branched or cyclic alkyl
radical or alkenyl radical with 6 to 18 carbon atoms,
R2 represents an alkyl radical with 4 to 8 carbon atoms and
n represents a number between 3 and 6,
which are produced from ethylene oxide and a fatty alcohol or
fatty alcohol mixtures, containing Rl, followed by
etherification with an alkyl halide containing R2 by
ethoxylation of the fatty alcohol in the presence of calcined
hydrotalcites as the catalyst, as foam-suppressing additives
for low-foaming cleaning agents.
Hydrotalcite is a natural mineral with the ideal formula
Mg6Al2(oH)l6co3 4H20 ~
207~
the structure of which i6 derived from that of brucite
(Mg(OH)2). Brucite crystallizes in a layered structure with
the metal ions in octahedral holes between two layers of
densely packed hydroxyl ions, with only every second layer of
the octahedral holes being occupied. In hydrotalcite, some
magnesium ions are replaced by aluminium ions, with the
result that the layered stack receives a positive charge.
This is balanced by the anions which are situated in the
interlayers together with zeolitic water of crystallization.
The layered structure i8 clear in the X-ray powder diagram
(ASTM card No. 14-l91), which can be used for
characterization.
Synthetically produced hydrotalcites are also known, these
are described, e.g., in DE-PS 15 92 126, DE-OS 33 46 943,
DE-OS 33 06 8Z2 and EP-A 0 207 811.
In natural and synthetic products the Mg2+:Al3+-ratio can
vary between about 1 and 5. The OH-:CO32- ratio can also
fluctuate. Natural and synthetic hydrotalcites can be
described approximately by the general formula (II)
MgxAl(oH)y(co3)z m H20 (II)
where the conditions 1 ~ x < 5, y > z, (y + 0.5z) = 2 x + 3
and O ~ m < 10 apply. Differences in the composition of the
hydrotalcites, in particular with regard to the water
content, lead to line displacements in the X-ray diffraction
diagram.
Natural or synthetic hydrotalcites continuously yield water
during heating and calcination. Dehydration is complete at
200 C, and it can be proved by X-ray diffraction that the
structure of the hydrotalcite is retained. The further
increase in temperature leads to the degradation of the
structure, with the separation of hydroxyl groups (as water)
and carbon dioxide. Natural hydrotalcites and those produced
synthetically by various processes, e.g. as in the above
publications, show a generally similar behavior during
calcination.
Hitherto, the following among others were, for example, used
as catalysts for the polyalkoxylation: Calcium- and strontium
hydroxide~, -alkoxides and -phenoxides (EP-A 0 092 256),
calcium alkoxides (EP-A 0 091 146), barium hydroxide (EP-B-0
115 083), basic magnesium compounds, e.g. alkoxides (EP-A-0
207~41 ~
082 569), magnesium and calcium fatty acid salts (EP-A-0 085
167). One of the disadvantages of the aforementioned
catalysts is that they are difficult to incorporate into the
reaction system and/or are difficult to produce. Other known
polyalkoxylation catalysts are potassium hydroxide and sodium
methylate.
When these catalysts are used, each of the fatty alcohols
reacts with several molecules of ethylene oxide.
It has been found that using calcined hydrotalcites as
catalysts, fatty alcohols (RlOH) can be polyethoxylated in
short reaction times with high yields and the reaction
products can be obtained with a narrow band-width or
homologue distribution, such that the distribution curve
comes very close to that calculated by Poisson.
For the purposes of the invention, all those catalysts which
can be obtained by calcination from the aforementioned
natural and/or synthetic hydrotalcites are suitable.
Hydrotalcites are preferred which prior to calcination have
the general formula (II), with the above conditions for x, y,
z and m. Values of x from 1.8 to 3 are particularly
preferred.
The calcined hydrotalcites used according to the invention
also have the advantage that they are easily incorporated
into the reaction mixture for the ethoxylation and that due
to their insolubility in the reaction mixture they can be
easily separated off again. They can, however, also remain
in the reaction mixture provided that their presence is not
disruptive during further use of the reaction products.
As the fatty alcohols R1OH, the following are suitable, all
alcohols with a straight-chain, branched or cyclic alkyl
radical or alkenyl radical with 6 to 18 carbon atoms,
particularly n-hexanol, cyclohexanol, n-octanol, n-nonanol,
n-decanol, n-undecanol, n-dodecanol, n-tridecanol, n-
tetradecanol, n-pentadecanol, n-hexadecanol, n-heptadecanol,
n-octadecanol, n-octadec-9-en-1-ol (oleyl alcohol) and also
their isomers branched on the alkyl radical and their isomers
with OH-groups on interior carbon atoms and oxoalcohols of
the given number of carbon atoms, singly or in mixture. Of
the mixtures of R1OH, the C12/C14- and C12/C18-mixtures are
particularly important.
207~41~
According to a further advantageous embodiment of the present
invention, the calcined hydrotalcites are added to the
reaction mixtures in a quantity of 0.1 to 2 % by weight,
relative to the end product of the ethoxylation.
The calcined hydrotalcites to he used can be obtained from
natural or synthetic hydrotalcites by heating for several
hours to temperatures of above 100C. Particularly preferred
are calcination temperatures of 400 to 600 C.
The catalyst thus obtained is added to the reaction mixture
which consists of one of the previously described fatty
alcohols and ethylene oxide. The molar ratio of fatty
alcohol to ethylene oxide here is preferably 1 : 3.S to 1
5, particularly preferably 1 : 4.5.
The etherification of the free hydroxyl groups is preferably
carried out under the known conditions of the Williamson
ether synthesis with straight-chain or branched C4-Cg-alkyl
halides (R2X; X = Cl, Br, I), for example with n-butyl
iodide, sec-butyl bromide, tert.-butyl chloride, amyl
chloride, tert.-amyl bromide, n-hexyl chloride, n-heptyl
bromide and n-octyl chloride. It can be useful here to use
alkyl halide and alkaline compound in stoichiometric excess,
for example from 100 to 200 ~, over the hydroxyl groups that
are to be etherified of the alkyl polyethyleneglycol ethers.
The biodegradability of the terminally-blocked alkyl
polyethyleneglycol ethers of the general formula (I) which
are to be used in accordance with the invention, corresponds
to the statutory determination methods in the regulations in
the [German] Detergents Act.
The alkyl polyethyleneglycol ethers of formula (I) to be used
in accordance with the invention are distinguished by their
alkaline and acid stability. When the compounds of formula
(I) are used according to the invention the foam-suppressing
effect at temperatures of down to 5C in alkaline to weakly
acidic cleansing liquors is clearly superior to the known
foam-inhibitors. The foam-height is relatively low and lies
between 0 and 0.5 cm. The cleaning agents in which the
terminally-blocked alkyl polyethyleneglycol ethers (I) are
used in accordance with the invention, can contain the usual
components of such agents, such as wetting agents, matrix
materials and complexing agents, alkalis or acids, corrosion
inhibitors and optionally also anti-microbial active
2070~1.s
ingredients and/or organic solvents.
The following non-ionogenic surface-active 6ubstances can be
considered as wetting agent6: polyglycol ethers which are
obtained by the addition of ethylene oxide to alcohols, in
particular fatty alcohols, alkyl phenols, fatty amines and
carboxylic acid amides, and anion-active wetting agents, such
as alkaline metal, amine and alkanolamine salts of fatty
acids, alkylsulphuric acids, alkylsulphonic acids and
alkylbenzene sulphonic acids. As matrix substances and
complexing agents, the cleaning agents can contain
particularly alkaline metal orthophosphates, -polyphosphates,
-silicates, -borates, -carbonates, -polyacrylates and
gluconates and also citric acid, nitriloacetic acid,
ethylenediamine tetraacetic acid, l-hydroxylalkane-l,l--
diphosphonic acid, aminotri-(methylene phosphonic acid) and
ethylene diaminetetra-(methylene phosphonic acid), phosphono-
alkane-polycarboxylic acids, e.g. phosphono-butane-
tricarboxylic acid, and alkaline metal salts and/or amine
salts of these acids. Highly alkaline cleaning agents, in
particular those for bottle-cleaning, contain substantial
amounts of caustic potash in the form of sodium and potassium
hydroxide. If particular cleaning effects are desired, the
cleaning agents can contain organic solvents, for example
alcohols, gasoline fractions and chlorinated hydrocarbons,
and free alkanolamines.
In the context of the invention, the term 'cleaning agents"
refers to the aqueous solutions intended for direct
application on the substrates to be cleaned; the term
"cleaning agents" also includes the liquid concentrates and
solid mixtures used for the production of the application
solutions.
The ready-for-use solutions can be weakly acidic to strongly
alkaline.
Due to industrial processing factors (control measurements,
problems with materials), the surfactants according to the
invention can be used in cleaning agents in industrial plants
which are not or cannot be heated (J. Geke, Metalloberflaeche
41 (1987), 227 ff~.
The improved ease of formulation of the surfactants is
reflected in the invention in the greater proportion of the
respective mixed ethers of formula (I), in comparison to
20~15
mixed ethers of the prior art, which can be incorporated in
corresponding industrial cleaner formulations with a good
homogeneity without phase separation of the concentrates.
This effect is e~tremely important for industrial
application, firstly because large amounts of otherwise
foaming substances, such as, e.g., quaternary ammonium
compounds (DE-OS 36 20 011, DE-PS 27 12 900), can be used and
can be foam-inhibited by the now possible, but also
necessarily higher dose of mixed ethers, and secondly because
it is possible to achieve a distinctly more effective foam-
inhibition when foaming substances are incorporated into the
corresponding industrial cleaner baths. This means a greater
effectiveness per se with a simultaneously temporarily longer
inhibition phase. Longer bath standing times are the result;
the volume of effluent is kept to a minimum.
Surfactants are used as described here in particular in
industrial cleaners, either for the formulation of cold-
sprayable industrial cleaners, or for industrial cleaners
which are also generally cold-sprayable, but which, for
example, are formulated with quaternary ammonium compounds or
other additional non-ionic surfactants with higher cloud
points, which would not be sprayable without troublesome foam
if these mixed ethers were not used.
The terminally-blocked alkyl polyethyleneglycol ethers to be
used according to the invention are added to the cleaning
agents preferably in such quantities that their concentration
in the ready-for-use application solutions is 10 to 2,500
ppm, and particularly preferably 50 to 500 ppm.
Figures 1 to 4 show the curves as determined by gas
chromatography of the homologue distribution of various
polyethyleneglycol ethers which have been produced using
calcined hydrotalcites as the catalyst, in comparison with
those which have been produced in the presence of sodium
methanolate as the catalyst.
~he invention is explained in more detail by the following
examples, without however being limited thereto.
2~70415
Example~
I. Ethoxylation of fattY alcohols in the Presence of
calcined hYdrotalcite
Example 1
A commercially available synthetic hydrotalcite was calcined
for 8 hours at 500C.
For the reaction of a commercially available lauryl alcohol
with 6 mole of ethylene oxide, the lauryl alcohol was placed
in a pressure reactor and mixed with 0.5 % by weight,
relative to expected end product, of the previously obtained
calcined hydrotalcite. The reactor was flushed with nitrogen-
and evacuated for 30 minutes at a temperature of 100 C. The
temperature was then increased to 180 C and the desired
quantity of ethylene oxide was pressurized to a pressure of 4
to 5 bar. After completion of the reaction, the mixture was
left to react for 30 minutes. After filtering off suspended
catalyst, the sought reaction mixture was obtained, with the
characteristic data seen in Table 1.
Examples 2 to 5
The fatty alcohols listed in Table 1 were reacted with
ethylene oxide in a similar manner to that described in
Example 1 using calcined synthetic hydrotalcites. The
compounds used, the reacted quantities of ethylene oxide, the
calcination conditions for the hydrotalcites, the catalyst
concentration, the reaction time of the ethoxylation and also
the OH numbers of some of the ethoxylation products obtained
are collected in Table 1 for some compounds. In addition, a
note iB also made for some compounds in Table 1 as to the
Figure which shows the homologue compounds obtained in
comparison to sodium methylate.
In Examples 1 and 3, calcined hydrotalcites were used in
which the atomic ratio of Mg : Ca (corresponding to x in the
above general formula (II)) 2.17 was 2.17. For the calcined
hydrotalcites of Examples 2 and 4, the Mg/Ca atomic ratio was
2.17. Prior to the etherification, in particular the
butylation of the polyethyleneglycol ethers to the alkyl
polyethyleneglycol ethers, the homologue distribution was
determined by gas chromatography. The figures show the
homologue distributions obtained in the examples in
20~1 .'3~
comparison to the homologue distributions which can be
obtained using sodium methylate.
20704~5
-- 10 --
,
o .~ , ~ ~ ~ ~
_I L. I I
o ~ ~ . . . .
O ~ I ~
S 1~ , ~ ~ ~ ~ , _
S U
o r I ~ ~ 0 ~ c~l I
U I ~
. I I
U --I I
~ 0
o ~ ' In ~ u~ O ~ '
~ u I ~ ~ a) ~ r- I
113 C
_I o
o .,,, I U~ o
U ~ I
D~
,.
~i 0 Ul
--11 ~ 0 U
~1 o ~ c ~ I
0; 0 0 3 1 0 0 0 0 0
E- C O t~
O
I I
0
~ ~ C ^ I O O O O O
X ~ ~ C I O O O O O I
C O ~ O I O O O O O I
W 0 C ~ I ~ ~ ~ ~ ~ I
O U ~ ~ 0
--~ CI C .C ~ C r
O
W
X
l _
O I X
C I O
O O O O
I ~ W W W ~C I ~
U I ,C I r
I + + + + O I
I _I 1 11
O I ~`1 ~ C~ U I
N
O
X O
~-1 Z I ~ ~ ~ ~ In I
207041~
II. Test of anti-foamina effect
Surfactants A and 8 (Table 2) are comparison compounds, whose
alkyl polyethyleneglycol ether pre-stages have been produced
according to conventional processes with alkaline catalysts
(DE-OS 37 27 378) and have a wide homologue distribution.
The alkyl polyethyleneglycol ether pre-stages of surfactants
C and D were produced in the presence of calcine
hydrotalcites as the catalyst. n gives the maximum homologue
of the homologue distribution in each case. The anti-foaming
effect test was carried out in a field-trial 10-liter
throughput spray plant at a spray pressure of 3 to 10 bar (30
mm even jet nozzle). The circulating volume here was approx.
10 to 19 liter/min.
In the following examples, at the application temperatures
given in each case, the cleaning solutions which, during
continuous operation with an otherwise rapid foam collapse,
had practically no foam layer (O to < 0.5 cm), were described
as sprayable in industrial applications with a minimal foam
load.
~he individual compounds used can be seen in Table 2 below.
Table 2
Surfactant Composition (I) Ex. Sprayable
R1 R2 n
_____________________________________________________________
A C8_10H17-21 C4Hg 4 Comp. 1,3,4 > 15C
B Cg-1OH17-21 C4Hg 3 Comp. 2 > 15C
C C8H17 C4H9 4 6 - 9 > 5 C
D C8H17 C4Hg 4.5 6 - 9 > 5 C
_____________________________________________________________
Example 6
400 ppm of surfactants C/D:
Iron and steel sheetR were treated with an aqueous solution
of this surfactant at 5C. No troublesome foam formation was
observed, and there was good cleaning effect. The
application solution is sprayable without foam-formation.
2~70~1~
Comparison example 1
400 ppm of surfactant A:
Below 15 C, ~ 1 cm of foam-formation (foam layer) was
observed.
Comparison examPle 2
400 ppm of surfactant B:
Foam-free sprayability only at temperatures > 15C.
Example 7
2,500 ppm of diethanolamine salt of isononanic acid
2,000 ppm of diethanolamine
100 ppm of benzotriazole
400 ppm of surfactant C/D:
Iron and steel sheets were treated with an aqueous solution
of this cleaner (pH 9). At 5C no troublesome foam-formation
was observed, and there was a good cleaning effect.
Comparison example 3
When 400 ppm of surfactant A were added in place of surfactant
CJ~ in the above composition, only up to a temperature of
15C was the absence of troublesome foam-formation combined
with good cleaning effect observed.
Example 8
3,000 ppm of sodium caprylate
1,000 ppm of sodium tetraborate . 10 H20 (Borax)
1,400 ppm of sodium tripolyphosphate
1,000 ppm of triethanolamine
200 ppm of monoethanolamine
600 ppm of surfactant C/D:
Iron and steel sheets were treated at 5C with an aqueous
solution of this cleaner (pH 9). No troublesome foam-
formation occurred, and there was a good cleaning effect.
Comparison example 4
When 600 ppm of surfactant B were used in place of surfactant
C/D in the above formulation, a good cleaning effect was
observed only up to a temperature of 15C.
2070~1~
- 13 -
Example 9
2,500 ppm of sodium dihydrogenphosphate
2,100 ppm of disodium hydrogenphosphate
1,000 ppm of tartaric acid
500 ppm of phosphoric acid, 75
400 ppm of surfactant C/D:
Iron sheets were treated at 5C with an aqueous solution of
this cleaner (pH 3.5). No troublesome foam-formation was
observed, and there was a good cleaning effect.
Comparison example 5
When 400 ppm of surfactant A were used in place of surfactant
C/D in the above composition, the combination of a good-
cleaning effect and an absence of troublesome foam-formation
was observed only up to 15 C.
III. Ease of formulation
The bases 1 and 2 represent examples of cleaning agent
formulations, to which the surfactants C or D were added.
These are compared with formulations which contained the
comparison surfactant A.
Base 1:
58 parts by weight of water
10 parts by weight of monoethanolamine
20 parts by weight of triethanolamine
2 parts by weight of carboxylic acid, 8 carbon atoms
10 parts by weight of branched carboxylic acid
Base 2:
60 parts by weight of water
20 parts by weight of diethanolamine
20 parts by weight of branched carboxylic acid
207~
- 14 -
Table 3
Ba6e Surfactant Quantity able to be
formulated
in wt.% relative to
the base
________________________________________________________
1 A 1.5
1 C 2.5
1 D 3.5
2 A 1.5
2 C 4.0
2 D 7.0
__________________________~_____________________________
