Polyglycol ethers as foam-inhibiting additives in low-foam cleaning agents

Polyethylene glycol ethers of the type obtained by the addition of from 4 to 20 parts by weight of ethylene oxide onto 1 part by weight of polyglycerol having a hydroxyl number in the range from 900 to 1200 and subsequent etherification of the free hydroxyl groups with linear or branched alkyl halides containing from 4 to 8 carbon atoms, and their use as foam-inhibiting additives for low-foam cleaning agents.

BACKGROUND OF THE INVENTION 
This invention relates to terminal-group-blocked polyglycerol polyethylene 
glycol ethers and their use as foam-inhibiting additives in low-foam 
cleaning agents. 
Aqueous cleaning agents intended for use in industry and commerce, 
particularly for cleaning metal, glass ceramic and plastic surfaces, 
generally contain substances which are capable of counteracting 
undesirable foaming. The use of foam-inhibiting additives is generally 
necessitated by the fact that the impurities detached from the substrates 
and accumulated in the cleaning baths act as foam formers. In addition, 
the use of antifoam agents may also be necessitated by the fact that the 
cleaning agents themselves contain constituents which give rise to 
undesirable foaming under the particular working conditions, for example 
anionic tensides or nonionic tensides which foam at the particular working 
temperature. 
Adducts of alkylene oxide with organic compounds containing--preferably 
several--reactive hydrogen atoms in the molecule have long been 
successfully used as foam-inhibiting additives. Adducts of propylene oxide 
with aliphatic polyalcohols (see German Pat. Nos. 1,280,455 and 1,621,592, 
corresponding to U.S. Pat. No. 3,491,029 and G.B. Pat. No. 1,172,135, 
respectively) and with aliphatic polyamines (see German Pat. No. 1,289,597 
and No. 1,621,593, corresponding to U.S. Pat. No. 3,463,737 and G.B. Pat. 
No. 1,172,134 respectively) and also adducts of ethylene oxide and 
propylene oxide with aliphatic polyamines, particularly ethylene diamine 
(see German Pat. No. 1,944,569 corresponding to U.S. Pat. No. 3,696,057), 
have proved to be particularly effective in practice. In addition to a 
favorable foam-inhibiting effect, alkylene oxide adducts such as these 
also show the stability to alkalis generally required for use in 
industrial and commercial cleaners. However, compounds of this class are 
not sufficiently biodegradable to satisfy many current legislative 
requirements. 
OBJECTS OF THE INVENTION 
An object of the present invention is to provide foam-inhibiting substances 
of which the performance properties are at least equivalent to those of 
known foam-inhibiting agents and which, in addition, also show improved 
biodegradability. 
Another object of the present invention is the development of a 
polyglycerol polyethylene glycol alkyl ether of 1 part by weight of 
polyglycerol having a hydroxyl number in the range of from 900 to 1200 
adducted with from 4 to 20 parts by weight of ethylene oxide and 
etherified at the free hydroxyl groups with alkyls having from 4 to 8 
carbon atoms. 
A further object of the present invention is an improvement in the process 
of controlling undesirable foam development when subjecting surfaces of 
metal, glass ceramic or plastic to an aqueous washing process by addition 
of a foam-inhibiting substance thereto, the improvement consisting of 
using a foam-inhibiting amount of a polyglycerol polyethylene glycol alkyl 
ether of 1 part by weight of polyglycerol having a hydroxyl number in the 
range of from 900 to 1200 adducted with from 4 to 20 parts by weight of 
ethylene oxide and etherified at the free hydroxyl groups with alkyls 
having from 4 to 8 carbon atoms, as said foam-inhibiting substance. 
These and other objects of the invention will become more apparent as the 
description thereof proceeds. 
DESCRIPTION OF THE INVENTION 
The drawbacks of the prior art have been overcome and the above objects 
have been achieved in the present invention starting out from the 
observation that certain terminal-group-blocked adducts of ethylene oxide 
with polyglycerols, which are defined hereinafter, are capable of 
satisfying current requirements both in regard to performance and in 
regard to improved biodegradability. 
The present invention relates to the use of polyethylene glycol ethers of 
the type obtained by the addition of from 4 to 20 parts by weight of 
ethylene oxide onto 1 part by weight of polyglycerol having a hydroxyl 
number in the range from 900 to 1200 and subsequent etherification of the 
free hydroxyl groups with linear or branched alkyl halides containing from 
4 to 8 carbon atoms, as foam-inhibiting additives for low-foam cleaning 
agents. 
More particularly, the present invention relates to a polyglycerol 
polyethylene glycol alkyl ether of 1 part by weight of polyglycerol having 
a hydroxyl number in the range of from 900 to 1200 adducted with from 4 to 
20 parts by weight of ethylene oxide and etherified at the free hydroxyl 
groups with alkyls having from 4 to 8 carbon atoms as well as an 
improvement in the process of controlling undesirable foam development 
when subjecting surfaces of metal, glass ceramic or plastic to an aqueous 
washing process by addition of a foam-inhibiting substance thereto, the 
improvement consisting of using a foam-inhibiting amount of a polyglycerol 
polyethylene glycol alkyl ether of 1 part by weight of polyglycerol having 
a hydroxyl number in the range of from 900 to 1200 adducted with from 4 to 
20 parts by weight of ethylene oxide and etherified at the free hydroxyl 
groups with alkyls having from 4 to 8 carbon atoms, as said 
foam-inhibiting substance. 
The polyglycerols used as starting material for producing the polyglycol 
ethers used in accordance with the invention accumulate as distillation 
residues in the industrial production of glycerol. The distillation 
residues in question are mixtures of relatively high molecular weight 
condensation products of glycerol, preferably those containing from 2 to 
10 glycerol residues in the molecule. These polyglycerols are 
characterized by their hydroxyl number which is generally in the range 
from 900 to 1200. Corresponding polyglycerols may of course also be 
synthetically obtained, for example by the prolonged heating of glycerol 
to 200.degree. to 240.degree. C. in the presence of caustic alkali, 
preferably in an inert gas atmosphere, and distilling off the water formed 
during the condensation reaction. 
To produce the polyglycerol polyglycol ethers used in accordance with the 
invention, the polyglycerols described above are best reacted with 
ethylene oxide in a ratio by weight of from 1:4 to 1:20, followed by 
etherification of the hydroxyl groups present in the reaction product 
obtained. The reaction with ethylene oxide is carried out under the known 
alkoxylation conditions, preferably in the presence of suitable alkaline 
catalysts. The etherification of the free hydroxyl groups is preferably 
carried out under the known conditions of Williamson's ether synthesis 
using linear or branched C.sub.4 -C.sub.8 -alkyl halides, for example 
n-butyl iodide, sec.-butyl bromide, tert.-butyl chloride, amyl chloride, 
tert.-amyl bromide, n-hexyl chloride, n-heptyl bromide and n-octyl 
chloride. In this connection, it may be advisable to use the alkyl halide 
and alkali, such as an alkali metal hydroxide, in a stoichiometric excess, 
for example of from 100% to 200%, over the hydroxyl groups to be 
etherified. However, the etherification of the free hydroxyl groups may 
also be carried out in accordance with German Pat. No. 868,147 by reaction 
with iso-olefins, for example isobutylene, in the presence of an acid 
catalyst. 
The terminal-group-blocked polyglycol ethers used in accordance with the 
invention are distinguished by their stability to alkalis and acids. Their 
foam-inhibiting effect in alkaline to mildly acidic cleaning solutions is 
at least as good as that of comparable known foam inhibitors. 
The cleaning agents in which the terminal-group-blocked polyglycol ethers 
are used in accordance with the invention may contain the constituents 
normally present in in preparations of this type, such as wetting agents, 
builders and complexing agents, alkalis or acids, corrosion inhibitors 
and, if desired, even antimicrobial agents and/or organic solvents. 
Suitable wetting agents are nonionic surface-active compounds, such as 
polyglycol ethers of the type obtained by the addition of ethylene oxide 
onto alcohols, particularly higher fatty alcohols, alkyl phenols, higher 
fatty amines and carboyxlic acids amides, particularly higher fatty acid 
amides, and anion-active wetting agents, such as alkali metal, amine and 
alkylol amine salts of fatty acids, alkyl sulfuric acids, alkyl sulfonic 
acids and alkyl benzene sulfonic acids. 
The builders and complexing agents which the cleaning agents may contain 
are, above all alkali metal orthophosphates, alkali metal polymer 
phosphates, alkali metal silicates, alkali metal borates, alkali metal 
carbonates, alkali metal polyacrylates and alkali metal gluconates as well 
as citric acid, nitriloacetic acid, ethylene diamine tetra acetic acid, 
1-hydroxyalkane-1,1-diphosphonic acid, amino-(tri-methylene-phosphonic 
acid) and ethylene diamine-(tetra-methylene-phosphonic acid), 
phosphonoalkane polycarboxylic acids such as, for example, phosphonobutane 
tricarboxylic acid and alkali metal salts of these acids. Highly alkaline 
cleaning agents, particularly those for washing bottles, contain 
considerable quantities of caustic alkali in the form of sodium and 
potassium hydroxide. If it is desired to obtain special cleaning effects, 
the cleaning agents may contain organic solvents, for example alcohols, 
petrol fractions and chlorinated hydrocarbons, and free alkylol amines. 
In the context of the invention, cleaning agents are primarily understood 
to be the aqueous solutions intended for direct application to the 
substrates to be cleaned. In addition, the expression "cleaning agents" 
also applies to the concentrates and solid mixtures intended for the 
preparation of the working solutions. 
The concentrates and solid mixtures are especially a cleaning composition 
for use in an aqueous system comprising from 0 to 25% of at least one 
wetting agents, from 0 to 80% of at least one builder and complexing 
agent, from 0 to 80% of an alkali metal hydroxide, and from 1% to 30% of 
at least of a polyglycerol polyethylene glycol alkyl ether of 1 part by 
weight of polyglycerol having a hydroxyl number in the range of from 900 
to 1200 adducted with from 4 to 20 parts by weight of ethylene oxide and 
etherified at the free hydroxyl groups with alkyls having from 4 to 8 
carbon atoms, where the total amount of ingredients is 100% 
The solutions ready for use may be mildly acidic to strongly alkaline. 
The terminal-group-blocked polyglycol ethers used in accordance with the 
invention are added to the cleaning agents in such quantities that their 
concentration in the ready-to-use solutions makes up from 10 to 2500 ppm 
and preferably from 50 to 500 ppm. 
The following examples are illustrative of the practice of the invention 
without being deemed limitative.

EXAMPLES 
Production of the terminal-group-blocked polyglycerol polyethylene glycol 
ethers 
In a lift-type mixer autoclave, 137 g of polyglycerol (hydroxyl number 961) 
were reacted with 1176 g of ethylene oxide (ratio by weight 1:8.6) at 
180.degree. C. and 10 bar in the presence of 3 g of sodium methylate. 1313 
g of polyglycerol ethylene glycol ether, hydroxyl number 113, were 
obtained. 
350 g of the product obtained, 171 g of n-hexyl chloride and 228 g of 75% 
by weight sodium hydroxide solution were stirred for 4 hours at 
120.degree. C. The aqueous phase was separated off from the cooled 
reaction mixture. The organic phase was washed with water at 50.degree. C. 
until the washing liquid showed a neutral reaction. Unreacted hexyl 
chloride and water were removed from the reaction mixture by heating to 
150.degree. C. in a water jet vacuum. 281.5 g of polyglycerol polyethylene 
glycol hexyl ether (1 part by weight of polyglycerol+8.6 parts by weight 
of EO+hexyl) were obtained. The product had a hydroxyl number of 3.5. 
Other terminal-group-blocked polyglycerol polyethylene glycol ethers were 
similarly produced. These substances and the product described above are 
shown in Table I together with their cloud points in water or 1% by weight 
NaOH-solution. 
TABLE I 
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Terminal-group-blocked polyglycerol polyethylene glycol ethers 
Pro- 
duct Composition CpH Cp 
Ex- (PG = polyglycerol; EO = ethylene 
(H.sub.2 O) 
(NaOH)* 
ample oxide; pbw = part by weight) 
.degree.C. 
.degree.C. 
______________________________________ 
A 1 pbw PG + 4.3 pbw EO + n-butyl 
-- 21 
B 1 pbw PG + 5.0 pbw EO + n-butyl 
-- 28 
C 1 pbw PG + 5.7 pbw EO + n-butyl 
-- 40 
D 1 pbw PG + 5.7 pbw EO + n-hexyl 
5 -- 
E 1 pbw PG + 8.6 pbw EO + n-butyl 
-- 45 
F 1 pbw PG + 8.6 pbw EO - n-hexyl 
15 -- 
G 1 pbw PG + 8.6 pbw EO + n-octyl 
-- 5 
H 1 pbw PG + 13.0 pbw EO + n-hexyl 
29-31 -- 
______________________________________ 
*as measured in 1% by weight NaOH--solution 
EXAMPLE 1 
The antifoam effect was tested using test solutions containing 1% by weight 
of sodium hydroxide and 0.03% by weight (300 ppm) of defoaming agent. In 
the course of the tests, triethanolamine tetrapropylene benzene sulfonate 
was added to these solutions as the test foaming agent in quantities 
increasing in stages by amounts of 100 ppm. The defoaming agents tested 
were products A to H and, for comparison, 
(I) ethylene diamine+30EO+60PO (PO=propylene oxide). 
Quantities of 200 ml of the test solutions were tested at 65.degree. C. in 
the foam beating apparatus according to DIN 53902. The foam volume in ml 
was read off at 5-seconds intervals after a series of 100 beats in 100 
seconds. An average value from five individual measurements was determined 
for each concentration of the test foam agent. From the results obtained, 
the foam volume observed at a concentration of the test foaming agent of 
1200 ppm is shown in the second column of Table II below. As a second 
representative measured value, the concentration of test foaming agent at 
which a foam volume of more than 200 ml was measured for the first time is 
shown in the third column of Table II. 
TABLE II 
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ppm of test 
foaming agent 
Defoaming ml of foam at 1200 ppm 
for 200 ml 
agent of test foaming agent 
of foam 
______________________________________ 
A 80 2000 
B 60 1800 
C 100 1800 
D 40 2800 
E 100 1800 
F 65 2800 
G 50 2800 
H 100 2400 
I 40 1800 
(Comparison) 
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EXAMPLE 2 
A storage, solid bottle washing preparation was prepared by mechanically 
mixing the following components: 80 parts by weight of caustic soda, 12 
parts by weight of sodium tripolyphosphate, 5 parts by weight of sodium 
silicate (molar ratio of Na.sub.2 O to SiO.sub.2 1:3.35) and 3 parts by 
weight of product G. 
Using a 1% by weight solution of this preparation, milk bottles were washed 
at 80.degree. C. in a standard bottle washing machine having two solution 
zones and an hourly throughput of 18,000 bottles. The cleaning effect was 
good and no troublesome foaming was observed. 
EXAMPLE 3 
A storable solid mixture was obtained by mechanically mixing the following 
active components: 80 parts by weight of sodium tripolyphosphate and 20 
parts by weight of product B. 
Beer bottles were washed at 85.degree. C. in a bottle washing machine 
having three solution zones and an hourly throughput of 80,000 bottles. 
The beer bottles were labeled with paper labels using casein glue which 
normally causes vigorous foaming in the immersion baths. When 1.5% by 
weight sodium hydroxide solution containing 0.15% by weight of the active 
mixtures described above was used for cleaning, the machine could be 
operated without any troublesome foaming. 
EXAMPLE 4 
A storable mixture was prepared by mechanically mixing the following active 
components: 40 parts by weight of sodium ethylene diamine tetraacetate, 20 
parts by weight of sodium tripolyphosphate, 30 parts by weight of sodium 
gluconate and 10 parts by weight of product H. 
Wine bottles were washed at 65.degree. C. in a standard bottle washing 
machine having two separate solution zones and an hourly throughput of 
24,000 bottles. A 1.5% by weight sodium hydroxide solution to which 0.5% 
by weight of the concentrate described above had been added was used as 
the cleaning solution. Washing was not accompanied by any troublesome 
foaming and the bottles were satisfactorily clean. 
EXAMPLE 5 
A concentrated cleaning agent was prepared by dissolving the following 
components in phosphoric acid: 5 parts by weight of 
amino-(tri-methylene-phosphonic acid), 10 parts by weight of 
1-hydroxyethane-1,1-diphosphonic acid, 5 parts by weight of 
phosphonobutane tricarboxylic acid, 30 parts by weight of product C, 10 
parts by weight of ethanol, 40 parts by weight of phosphoric acid (75% by 
weight). 
Mineral water bottles were washed at 80.degree. C. in a bottle washing 
machine having three solution zones and an hourly throughput of 120,000 
bottles. A 2% by weight sodium hydroxide solution to which 1% by weight of 
the concentrate described above had been added was used as the washing 
solution. Washing was not accompanied by any troublesome foaming and the 
bottles was satisfactorily clean. 
EXAMPLE 6 
An immersion-type degreasing agent for metals was prepared by mechanically 
mixing the following components: 40 parts by weight of sodium metasilicate 
pentahydrate, 35 parts by weight of sodium carbonate, 20 parts by weight 
of sodium tripolyphosphate, 2.5 parts by weight of sodium alkyl benzene 
sulfonate, 2.5 parts by weight of nonylphenol+14EO and 5 parts by weight 
of product G. 
The foam formation and foam collapse of a 4% by weight solution of this 
degreasing agent was tested at 60.degree. C. in accordance with DIN 53902 
by comparison with an agent which did not contain product G, but which had 
otherwise the same composition. The results are set out in Table III 
below. 
TABLE III 
______________________________________ 
ml of foam after minutes 
Cleaning agent 
0 1 2 10 
______________________________________ 
Comparison 950 900 810 650 
According to the 
70 30 30 10 
invention 
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EXAMPLE 7 
An immersion-type degreasing agent for metals was prepared by mechanically 
mixing the following components: 40 parts by weight of sodium metasilicate 
penta hydrate, 35 parts by weight of sodium carbonate, 20 parts by weight 
of sodium tripolyphosphate, 2.5 parts by weight of sodium alkyl benzene 
sulfonate, 2.5 parts by weight of nonyl phenol+14EO and 5 parts by weight 
of product A. 
Greasy steel moldings were cleaned at 60.degree. C. by immersion in a 4% by 
weight solution of this cleaning agent. The degreasing effect was very 
good and no troublesome foaming was observed. 
EXAMPLE 8 
A storable concentrate for cleaning metal surfaces was prepared by 
dissolving the following components in water: 30 parts by weight of sodium 
caprylate, 10 parts by weight of borax, 14 parts by weight of sodium 
tripolyphosphate, 10 parts by weight of triethanolamine, 2 parts by weight 
of monethanolamine, 6 parts by weight of product F and 78 parts by weight 
of water. 
Steel surfaces were sprayed at 20.degree. C. to 40.degree. C. with a 1.5% 
by weight solution of this cleaning agent (pH value 8.5). The cleaning 
effect was good and no troublesome foaming was observed. 
EXAMPLE 9 
A storable concentrate for cleaning metal surfaces was prepared by 
dissolving the following components in water: 25 parts by weight of the 
diethanolamine salt of isononanoic acid, 20 parts by weight of 
diethanolamine, 1 part by weight of benztriazole, 2 parts by weight of 
product D and 52 parts by weight of water. 
Grey iron castings were sprayed at 50.degree. C. to 55.degree. C. with a 1% 
by weight solution of this cleaning agent. The cleaning effect was good 
and no troublesome foaming was observed. 
The preceding specific embodiments are illustrative of the practice of the 
invention. It is to be understood however, that other expedients known to 
those skilled in the art or disclosed herein may be employed without 
departing from the spirit of the invention or the scope of the appended 
claims.