Mixture of at least two alkoxylated alcohols and use thereof as a foam-suppressing surfactant additament in cleaning compositions for mechanized cleaning processes

A mixture suitable for use as a foam-suppressing surfactant additament in cleaning compositions for mechanized cleaning processes comprises at least two mixtures of alkoxylated alcohols I EQU R--O--(C.sub.2 H.sub.4 O).sub.x --(C.sub.3 H.sub.6 O).sub.y --H (I) where x is an average degree of ethoxylation between 1 and 12, y is an average degree of propoxylation between 1 and 15, one alkoxylated alcohol mixture carries straight-chain or branched C.sub.8 -C.sub.18 -alkyl groups as the radical R and one other alkoxylated alcohol mixture carries straight-chain or branched C.sub.10 -C.sub.20 -alkyl groups as the radical R, subject to the proviso that the two radicals R differ by at least 0.5 in the average number of carbon atoms, and the two alkoxylated alcohol mixtures present in a ratio of from 10:90 to 90:10.

This application is a 371 of PCT/EP92/00289, filed Feb. 11, 1992. 
DESCRIPTION 
The present invention relates to process for preparing a mixture of 
alkoxylated alcohols of the general formula I 
EQU R--O--(C.sub.2 H.sub.4 O).sub.x --(C.sub.3 H.sub.6 O).sub.y --H (I) 
where 
x is an average degree of ethoxylation of from 1 to 12, 
y is an average degree of ethoxylation of from 1 to 15, 
In the present invention, one alkoxylated alcohol mixture carries a 
straight-chain or branched C.sub.8 -C.sub.18 -alkyl group as the radical R 
and one other alkoxylated alcohol mixture carries a straight-chain or 
branched C.sub.10 -C.sub.20 -alkyl group as the radical R, subject to the 
proviso that the two radicals R in each of the mixtures differ by at least 
0.5 in the average number of carbon atoms, and the two mixtures of 
alkoxylated alcohols are present in a ratio of from 10:90 to 90:10. 
The present invention also relates to the use of this mixture as a 
foam-suppressing surfactant additament in cleaning compositions for 
mechanized cleaning processes. It further relates to cleaning compositions 
comprising such mixtures of alkoxylated alcohols I. 
It is known from practical experience that in mechanized cleaning 
processes, for example in mechanized dishwashing, it is in general 
necessary to carry out two successive cleaning cycles, usually separated 
by an intermediate rinse cycle with water using different cleaning 
compositions. The actual cleaning liquor comprises alkaline agents for 
detaching and emulsifying, for example, food residues. The after- or 
final-rinse liquor, by contrast, comprises specific final rinse 
compositions for a clear, spot- and streak-free surface, for example on 
dishes. These compositions must have a good wetting effect so that the 
rinse water may run off the surface as a film and not leave visible 
residues, and be readily dispersible in water. Owing to the high degree of 
liquor agitation in the cleaning and rinsing machines used here, final 
rinse compositions also must be sufficiently low-foam. 
Compositions agents of this type are known in large numbers; examples are 
wetting agents such as ethylene and/or propylene oxide adducts with 
alcohols, phenols or amines. 
For instance, EP-A-034 275 (1) relates to the use of nonionic surfactants 
obtained by reacting at least one C.sub.8 -C.sub.20 -alkanol ethoxylate 
(4-14 EO) with 1,2-butylene oxide in a molar ratio of from 1:1.6 to 1:2.4 
in biodegradable and low-foaming cleaning and rinsing compositions. 
EP-A-161 537 (2) concerns the use of methyl-, ethyl- or allyl-tipped 
nonionic surfactants obtainable by stepwise alkoxylation of C.sub.8 
-C.sub.22 -alkanols with at least two different alkylene oxides as 
low-foam, foam-suppressing and biodegradable surfactants in industrial 
cleaning processes. 
EP-B-019 173 (3) concerns the use of C.sub.9 -C.sub.18 -alkanols reacted 
first with propylene oxide and then with ethylene oxide as low-foam and 
biodegradable surfactant additaments in dishwashing compositions for 
dishwashers. 
Surfactants of the type mentioned and also mixtures thereof, however, prove 
to be still in need of improvement when used in cleaning compositions for 
mechanized cleaning processes. Especially the foam suppression 
characteristics and the dispersibility in water are still not optimal. 
It is an object of the present invention to remedy the above-described 
defects of the prior art. 
We have found that this object is achieved by the above-defined process for 
preparing a mixture of alkoxylated alcohols I, which comprises mixing at 
least two mixtures of alcohols of the general formula 
EQU R--O--H 
where one alcohol mixture carries straight-chain or branched C.sub.8 
-C.sub.18 -alkyl groups as the radical R and one other alcohol mixture 
carries straight-chain or branched C.sub.10 -C.sub.20 -alkyl groups as the 
radical R, subject to the proviso that the two radicals R differ by at 
least 0.5 in the average number of carbon atoms, and the two alcohol 
mixtures are present in a weight ratio of from 10:90 to 90:10, with one 
another and reacting this mixture first with the corresponding amount of 
ethylene oxide and then with the corresponding amount of propylene oxide, 
and the use of such a mixture as a foam-suppressing surfactant additamant 
in cleaning compositions for mechanized cleaning processes. 
As straight-chain or branched C.sub.8 -C.sub.18 - and C.sub.10 -C.sub.20 
-alkyl radicals R there may be mentioned for example: n-octyl, 
2-ethylhexyl, n-nonyl, isononyl, n-decyl, isodecyl, n-undecyl, n-dodecyl, 
n-tridecyl, isotridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, 
n-heptadecyl, n-octadecyl and n-eicosyl. The radicals R are preferably 
straight-chain or only slightly branched; that is, they contain not more 
than 3 methyl or ethyl side chains. 
Depending on the origin of the alkanol used in the synthesis of the 
compounds I, R is a radical of a naturally occurring fatty alcohol or 
preferably of a synthetically produced oxo or Ziegler alcohol. Examples of 
readily usable alcohols produced by the oxo process are C.sub.9 /C.sub.11 
-, C.sub.12 /C.sub.14 -, C.sub.13 /C.sub.15 - and C.sub.16 /C.sub.18 
-alkanol mixtures. Examples of readily usable alcohols produced by the 
Ziegler process are C.sub.8 /C.sub.10 -, C.sub.10 /C.sub.12 -, C.sub.12 
/C.sub.14 -, C.sub.12 /C.sub.16 - and C.sub.16 /C.sub.20 -alkanol 
mixtures. 
Since the alkanols used in the synthesis of the compounds I are in general 
random homolog mixtures and even isomer mixtures, it is advisable to speak 
of an average number of carbon atoms. This average value will usually be 
the most frequently occurring value. 
The alkoxylated alcohols I are advantageously prepared in a conventional 
manner by ethoxylation and subsequent propoxylation of the alkanols 
mentioned. These processes are known to the person skilled in the art and 
do not need to be more particularly described herein. 
The degree of ethoxylation x is from 1 to 12, preferably from 2 to 5, in 
particular from 3 to 4; the degree of propoxylation is from 1 to 15, 
preferably from 2 to 6, in particular from 4 to 6. The degrees of 
alkoxylation x and y are in general likewise average values. 
The mixture used comprises at least two, preferably two or three, in 
particular two, mixture of alcohols of the formula R--O--H in which two 
radicals R have to differ by at least 0.5 in the average number of carbon 
atoms, the corresponding two alcohol mixtures being present in a ratio of 
from 10:90 to 90:10, preferably from 25:75 to 75:25. It is of particular 
advantage for the difference in the average number of carbon atoms of the 
two radicals R to be at least 1, in particular from 1 to 2. 
Mechanized cleaning processes are chiefly found in the metal industry, in 
the food industry (for example the beverage, canned food or sugar industry 
or the milk-, meat- and fat-processing industry) in the catering trade and 
even in the home. For instance, metal articles frequently have to be 
cleaned after they have been made or processed to remove impurities and 
residues of, for example, drawing and rolling greases or organic corrosion 
inhibitors. All surfaces of containers and processing machines which come 
into contact with a food in the course of production and further 
processing and in transport have to be cleaned at certain intervals to 
remove food residues and other soiling. A typical example of an industrial 
mechanized cleaning process from the beverage industry is the washing of 
used bottles which contained, for example, beer, milk, refreshments or 
mineral water. 
Of particular importance is the use according to the invention of the 
designated mixture of alkoxylated alcohols I in the mechanized dishwashing 
in the home, in catering businesses and in industry. Here the mixtures 
mentioned are used to outstanding effect, in particular as 
foam-suppressing surfactant additaments in final rinse compositions for 
mechanized dishwashing. 
Further details concerning the technology of mechanized dishwashing and the 
composition of cleaning and final rinse compositions used for that purpose 
are found for example in Tenside Detergents 19 (1982), 123-126, (4), or 
Ullmanns Encyklopadie der technischen Chemie, 4th edition, volume 20 
(1981), pages 149-150, (5). 
According to these references, a customary final rinse composition 
comprises nonionic surfactants, hydrotropes (solubilizers) such as 
isopropanol, ethanol and/or cumene sulfonate, water and optionally organic 
or inorganic acids and assistants, such as dyes and preservatives. 
The present invention also provides a process for preparing cleaning 
compositions for mechanized cleaning processes, in particular final rinse 
compositions for mechanized dishwashing, which comprises incorporating in 
these compositions a foam-suppressing surfactant additament comprising a 
mixture of alkoxylated alcohols I. 
The present invention further provides cleaning compositions for mechanized 
cleaning processes comprising a mixture of alkoxylated alcohols I as a 
foam-suppressing surfactant additament in an amount of from 0.1 to 40% by 
weight, preferably from 0.5 to 20% by weight, based on the total amount of 
the formulation. 
The present invention further provides final rinse compositions for 
mechanized dishwashing comprising a mixture of alkoxylated alcohols I as a 
foam-suppressing surfactant additament in an amount of from 0.5 to 30% by 
weight, preferably from 1 to 15% by weight, based on the total amount of 
the formulation. 
The mixture of alkoxylated alcohols I according to the invention represents 
an optimum of the properties desired for cleaning the hard surfaces 
mentioned, for example metal or crockery, namely good wetting power, 
streak-free runoff from the rinsed stock, foam suppression or absence of 
foam, and good dispersibility in water. It is also an advantage that the 
defined mixture of the compounds I is readily biodegradable.

EXAMPLES 
Example 1 
Preparation of a mixture of alkoxylated oxo alcohols 
An autoclave was charged with 100 g of a C.sub.12 /C.sub.14 -oxo alcohol 
having on average 13 carbon atoms (corresponding to 0.5 mol) and 107 g of 
a C.sub.13 /C.sub.15 -oxo alcohol having on average 14 carbon atoms 
(corresponding to 0.5 mol) together with 0.2 g of potassium hydroxide as 
an alkoxylation catalyst. 154 g of ethylene oxide (corresponding to 3.5 
mol) were injected continuously at from 110.degree. to 120.degree. C. To 
complete the reaction, the contents were subsequently stirred for 1 hour 
at the same temperature. Then 319 g of propylene oxide (corresponding to 
5.5 mol) were added continuously at from 130.degree. to 140.degree. C. The 
contents were subsequently allowed to react at that temperature for 2 
hours. 
The result was 680 g of a mixture of the alkoxylated oxo alcohols having an 
OH number of 83 and a cloud point of 32.degree. C., measured in 
butyldiglycol in accordance with DIN 53 917. 
Application properties 
To measure the application properties, final rinse formulations for 
mechanized dishwashing in the home were prepared. The table below shows 
the compositions of these formulations. 
To characterize the formulations, the cloud points of the formulations, the 
foam suppression behavior in the dishwasher and the dispersibility in hot 
water were determined. 
The cloud point was determined in accordance with DIN 53 917. It is known 
from practical studies that decreasing cloud points, equivalent to an 
increase in the hydrophobicity, result in improvements in the foaming 
characteristics, but also in reductions in dispersibility, which leads to 
nonuniform distribution of the final rinse in the rinse liquor and hence 
to impairment of the runoff characteristics (spotting, smudging and 
streaking). At cloud points &lt;40.degree. C., moreover, instability, ie. 
phase separation, of the final rinse formulation is observed. 
The foam suppression behavior is tested in the dishwasher using the 
so-called "egg test". Magnetic induction measurement is used in a 
commercial domestic dishwashing machine to determine the number of 
revolutions of a spraying arm with the aid of a counter. Foaming, which 
occurs in particular in the presence of proteins (egg white), reduces the 
speed of the arm. Thus, the number of revolutions per minute, because of 
the reduced thrust, represents a measure of the suitability of surfactants 
for use in high-agitation cleaning equipment. The test time is 12 minutes, 
over which the average number of revolutions per minute is calculated from 
the total number of revolutions. The wash is started at room temperature, 
but after about 10 minutes the temperature of the wash liquor is 
60.degree. C. 
To assess the dispersibility, the final rinse formulation is injected by 
means of a membrane pump into a glass tube through which hot tap water at 
90.degree. C. flows. At the end of the glass tube, the dispersion thus 
produced is sprayed through a second nozzle into a glass beaker. In the 
course of about 3.5 min about 30 ml of final rinse formulation are metered 
into a stream of 2 liters of water at 90.degree. C. The dispersion is 
visually assessed and rated in the glass tube and in the glass beaker on 
the basis of the following scheme: 
A rating of 1 indicates: no dispersion, product floats on top (large 
drops&gt;5 mm) 
A rating of 2 indicates: incipient dispersion in the glass tube, smaller 
drops (2-3 mm) in the beaker 
A rating of 3 indicates: moderate dispersion in the glass tube, moderate 
dispersion in the beaker (fine droplets of about 1 mm) 
A rating of 4 indicates: good dispersion in the tube, fine dispersion in 
the beaker (droplets&lt;0.5 mm) 
A rating of 5 indicates: very fine dispersion in the glass tube and in the 
beaker. 
The results of the measurements are reproduced in the following table: 
TABLE 
______________________________________ 
Composition, cloud point, dishwasher 
speed and dispersibility of final rinse formulations 
Composition 
of formulation 
Example No. 
[% by weight] 2 3 4 5 6 7 
______________________________________ 
Surfactant A 10 10 15 10 15 15 
Surfactant B 10 5 
Surfactant C 10 5 
Mixture of Example 1 10 5 
Ethanol 2 2 2 2 2 2 
Cumenesulfonate 
3 3 3 3 3 3 
Water 75 75 75 75 75 75 
Cloud point [.degree.C.] 
45 43.5 50 36 47 44 
Dishwasher speed [rpm] 
112 114 108 118 115 110 
Dispersibility [rating] 
4-5 2 4-5 4-5 4-5 2 
______________________________________ 
Prior art formulation: 
Surfactant A: C.sub.13 /C.sub.15 -oxo alcohol + 11 mol of ethylene oxide 
2 mol of butylene oxide as per (1) 
Surfactant B: C.sub.9 /C.sub.11 -oxo alcohol + 7 mol of ethylene oxide + 
mol of butylene oxide + methyl tipping as per (2) 
Surfactant C: C.sub.13 /C.sub.15 -oxo alcohol + 4 mol of propylene oxide 
2 mol of ethylene oxide as per (3) 
The above Examples reveal that using the surfactant additaments according 
to the invention (Examples 5 and 6) gives final rinse formulations which 
combine excellent foam suppression characteristics with excellent 
dispersibility, notwithstanding an occasionally very low cloud point 
(Example 5). It is true that the lowering of the cloud point due to the 
addition of a hydrophobic surfactant frequently leads to improved foam 
suppression, but at the same time to the loss of the dispersing 
properties. Solubilizers are usually added to push the cloud point back up 
again and improve the dispersibility. Example 5 shows that the addition of 
the defined mixtures of compounds I makes it possible to dispense partly 
or entirely with solubilizers for raising the cloud point. 
Comparative Examples 2, 3, 4 and 7 show how the addition or mixing of known 
agents of the prior art does improve foam suppression somewhat, but it 
also reduces the dispersibility as a result of lowering the cloud point.