CA2070415A1

CA2070415A1 - Alkyl polyethyleneglycol ethers as foam-suppressing additives in cleaning agents

Info

Publication number: CA2070415A1
Application number: CA002070415A
Authority: CA
Inventors: Juergen Geke; Gilbert Schenker; Hans-Christian Raths; Raina Hirthe
Original assignee: Individual
Current assignee: Henkel AG and Co KGaA
Priority date: 1989-10-24
Filing date: 1990-10-15
Publication date: 1991-04-25
Also published as: ATE109503T1; WO1991006620A1; ES2057591T3; DK0497790T3; EP0497790B1; TR25066A; JPH05501272A; DE59006725D1; BR9007774A; EP0497790A1; ZA908485B; DE3935374A1

Abstract

Abstract Alkyl Polyethyleneglycol ethers as foam-suppressing additives for cleaning agents The invention relates to the use of terminally blocked alkyl polyethyleneglycol ethers of the formula R1-O-(CH2CH2O)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 R1 followed by etherification with an alkyl halide containing R2 by ethoxylation of the fatty alcohol in the presence of calcined hydrotalcites as catalyst, as foam-suppressing additives for low-foaming cleaning agents.

Description

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.

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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~

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~

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 __________________________~_____________________________

Claims

1. Use of terminally blocked alkyl polyethyleneglycol ethers of the formula R1-O-(CH2CH2O)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 R1 followed by etherification with an alkyl halide containing R2 by-ethoxylation of the fatty alcohol in the presence of calcined hydrotalcites as catalyst, as foam-suppressing additives for low-foaming cleaning agents.

2. Use according to claim 1, characterized in that the hydrotalcites, prior to calcination, have a composition of the formula (II) MgxAl(OH)y(CO3)z ? mH2O (II) in which the conditions 1 < x < 5, y > z, (y + 0.5 z) = 2x + 3 and 0 < m < 10 apply.

3. Use according to claims 1 and 2, characterized in that for the hydrotalcites of the general formula (II), x is a number from 1.8 to 3 and y, z and m are defined as above.

4. Use according to claims 1 to 3, characterized in that the hydrotalcites were calcined at temperatures between 400 and 600 °C.

5. Use according to claims 1 to 4, characterized in that the calcined hydrotalcites are used in a quantity of 0.1 to 2 % by weight, relative to the end product of the ethoxylation.

6. Use according to claims 1 to 5, characterized in that in the formula (I), n is 3.5 to 5, preferably 4.5.

7. Use according to claims 1 to 6, characterized in that in the formula (I), R2 = n-butyl and R1 = octyl, decyl or dodecyl.

8. Use according to claims 1 to 7, characterized in that the terminally-blocked alkyl polyethyleneglycol ethers are used in such quantities that their concentration in the ready-for-use solutions is from 10 to 2,500 ppm, preferably 50 to 500 ppm.