EP0326795A2 - Use of polyglycol ethers as anti-foaming agents in detergents - Google Patents

Abstract

Polyethylene glycol ethers of the general formula (I> R1O-(CH2CH2O)n-R2 (I> in which R1 is a straight-chain or branched alkyl or alkenyl radical with 20 to 28 C atoms, R2 is an alkyl radical with 4 to 8 C atoms and n is a number from 6 to 20, are employed as foam-suppressant additives for low-foam cleaning agents.

Description

The invention relates to the use of selected end group-sealed polyethylene glycol ethers as foam-suppressing additives in low-foam cleaning agents. The invention aims to provide tools of the type mentioned which combine high effectiveness with physiological harmlessness and biodegradability. The new auxiliaries of the invention should in particular also be suitable for effectively suppressing undesired foam formation in the case of strongly foam-generating cleaning processes, for example spray cleaning, in the range of low temperatures, in particular in the range of room temperature or only slightly elevated temperatures.

Aqueous cleaning agents intended for use in trade and industry, in particular those for cleaning metal, glass and ceramic surfaces, generally contain substances which are able to counteract undesirable foam development. In most cases, the use of foam-suppressing additives is due to the fact that the contaminants detached from the substrates and accumulating in the cleaning baths act as foaming agents. In addition, the use of anti-foaming agents may also be necessary due to the fact that the cleaning agents themselves Contain components that give rise to undesirable foaming under the specified working conditions. An example of this are the anionic surfactants widely used in cleaning agents.

Addition products of alkylene oxides with organic compounds with reactive hydrogen atoms in the molecule have long been used as foam-suppressing additives. Here, in particular, addition products of propylene oxide to aliphatic polyalcohols - see, for example, DE-PS 1 280 455 and DE-PS 1 621 592 - and to aliphatic polyamines - compare, for example, DE-PS 1 289 597 and DE-PS 1 621 593 - and addition products of ethylene oxide and propylene oxide to aliphatic polyamines, especially ethylenediamine - compare DE-PS 1 944 569 - proven in practice. In addition to a good foam-suppressing effect, these alkylene oxide addition products also have the alkali stability which is usually required for use in commercial and industrial cleaning agents. However, the compounds in this class are not sufficiently biodegradable to meet the applicable legal requirements.

A class of highly effective and at the same time biodegradable defoaming agents is described in DE-OS 33 15 951. There is described the use of end-capped polyethylene glycol ethers of the formula (I) R₁O- (CH₂CH₂O) _n -R₂, in which formula R₁ is a straight-chain or branched alkyl radical or alkenyl radical with 8 to 18 carbon atoms, R₂ is an alkyl radical with 4 to 8 carbon atoms and n is a number from 7 to 12. In practice, a product of this type has proven particularly useful, in which the radical R₁ is a fatty alcohol radical having 12 to 18 carbon atoms and R₂ is the n-butyl radical, where n is the number 10.

The teaching of the present invention is based on the surprising finding that even more effective auxiliaries of the type concerned here can be obtained by slightly varying the structure of the fatty alcohol polyethylene glycol ethers which have been end-capped. In the sense of the action according to the invention, it is not only possible to set a general increase in activity while maintaining the physiological harmlessness and biodegradability of these foam-suppressing additives, with the now described varied ethylene glycol ethers, in particular, improved working in the lower temperature range, for example in the area of the room temperature, is revealed or only slightly elevated temperatures.

This is a very important extension compared to the known foam-suppressing additives. It is known that in industrial cleaning processes, rinsing processes are often to be carried out at low temperatures, for example in order to carry out an energy-saving pre-cleaning. Conventional, foam-suppressing additives are often characterized by the fact that they are very effective in combating foam in the temperature range of approximately 50 ° C. and above, but their use at temperatures of approximately 20 ° C. leads to comparatively weaker foam damping. Surprisingly, it has been found that the additives according to the invention described below develop particular effectiveness precisely at lower temperatures and also exhibit this property when they are blended with structurally similar, known components.

The invention accordingly relates to the use of polyethylene glycol ethers of the general formula (I)
R₁O- (CH₂CH₂O) _n -R₂ (I)
in the
R₁ is a straight-chain or branched alkyl or alkenyl radical having 20 to 28 carbon atoms,
R₂ is an alkyl radical with 4 to 8 carbon atoms and
n is a number from 6 to 20,
as foam-suppressing additives for low-foam cleaning agents.

The preferred compounds of general formula (I) contain a radical R₁ of the type specified with 20 to 24 carbon atoms. Branched residues of this type are of particular importance, as will be indicated below. The preferred radical R₂ in the compounds according to the invention is the butyl radical, in particular the n-butyl radical. The preferred values for n in the general formula (I) are 6 to 12.

The decisive modification of the polyethylene glycol ether of the general formula (I) according to the invention compared to the structure-like compounds of the aforementioned DE-OS 33 15 951 lies in the variation of the radical R 1. According to the invention, the carbon number of this radical is increased compared to the radicals described above, and is at least 20 carbon atoms. Fatty alcohols of natural origin of this type can be obtained in a manner known per se by hydrogenating the top sections of natural fatty acid mixtures or the methyl esters obtained therefrom. In particular, however, the class of Guerbet alcohols is affected by the invention. As is known, alcohols of this type are formed by the condensation of fatty alcohols with a lower carbon number in the presence of alkali, for example potassium hydroxide or potassium alcoholate. The reaction takes place, for example, at temperatures of 200 to 300 ° C and leads to branched Guerbet alcohols, which branch in 2 parts have to hydroxyl group. Selected fatty alcohols or also mixtures of different fatty alcohols can be used for the synthesis; the resulting alcohol mixture with a higher carbon number is then of a correspondingly complex composition.

For example, 2-hexyldecanol-1, 2-octyldodecanol-1 and 2-decyl-tetradecanol-1 as well as hexadecanol and octadecanol or their mixtures can be used as starting material for the preparation of the polyglycol ethers of the formula (I).

The end group-capped fatty alcohol polyglycol ethers of the formula (I) are prepared in accordance with the specifications of DE-OS 33 15 951. The fatty alcohols of higher carbon number described above are advantageously reacted with ethylene oxide in a molar ratio of 1: 6 to 1:20 and then etherified the hydroxyl groups present in the reaction product obtained. The reaction with ethylene oxide takes place 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 straight-chain or branched C₄ to C₈ alkyl halides. The n-butyl radical for the radical R₂ from the general formula (I) is of particular importance in the course of the inventive action. Examples of such a final etherification are accordingly n-butyl halides, such as n-butyl iodide. However, the invention is not restricted to this; further examples are sec-butyl bromide, tert-butyl chloride, amyl chloride, tert-amyl bromide, n-hexyl chloride, n-heptyl bromide and n-octyl chloride.

It may be expedient to use a stoichiometric excess of alkyl halide and alkali, for example from 10 to 50%, about the hydroxyl groups to be etherified.

In a preferred embodiment of the invention, polyglycol ethers of the formula (I) are used in which n denotes a number from 6 to 12.

The end group-capped polyglycol ethers of the formula (I) to be used according to the invention are used in an important embodiment in a mixture with structurally identical polyethylene glycol ethers, in which, however, the radical R 1 is a straight-chain or branched alkyl or alkenyl radical with 8 to 18 C atoms and n is one Number is from 7 to 12, and preferably from 8 to 10. In this embodiment, the invention thus provides to blend the newly described here, longer R₁ long-chain polyglycol ethers with the foam-suppressing additives from DE-OS 33 15 951. Mixing ratios of the two types in the range from 10 to 90 to 90 to 10% by weight, in particular in weight ratios from 60 to 40 to 40 to 60% by weight, are suitable for this embodiment.

The end group-capped polyglycol ethers of the formula (I) which are now to be used according to the invention are also notable for high alkali and acid stability. Their foam-preventing effect in alkaline and neutral cleaning liquors is strengthened in the specified sense, moreover they also meet the legal requirements for biodegradability.

The cleaning agents in which the end-capped polyglycol ethers of the invention are used can contain the constituents customary in such agents, such as wetting agents, builders and complexing agents, alkalis or acids, Cor corrosion inhibitors and optionally also contain organic solvents. Suitable wetting agents are nonionic surface-active compounds such as polyglycol ethers, which are obtained by adding ethylene oxide to alcohols, in particular fatty alcohols, alkylphenols, fatty amines and carboxamides, and anionic wetting agents such as alkali metal, amine and alkylolamine salts of fatty acids, alkylsulfuric acids, alkylsulfonic acids and alkylbenzenesulfonic acids. On builders and complexing agents, the cleaning agents can, in particular, alkali metal orthophosphates, polymer phosphates, silicates, borates, carbonates, polyacrylates and gluconates, as well as citric acid, nitrilotriacetic acid, ethylenediaminetetraacetic acid, 1-hydroxyalkane-1,1-diphosphonic acid and ethylenediphosphonic acid and ethylenediphosphonic acid, Contain phosphonoalkane polycarboxylic acids such as phosphonobutane tricarboxylic acid and alkali metal salts of these acids. Highly alkaline cleaning agents, especially those for bottle cleaning, contain considerable amounts of caustic alkali in the form of sodium and / or potassium hydroxide. If special cleaning effects are desired, the cleaning agents can contain organic solvents, for example alcohols, gasoline fractions and chlorinated hydrocarbons as well as free alkylolamines.

In connection with the invention, cleaning agents are once understood to mean the aqueous solutions intended for direct application to the substrates to be cleaned, but the term cleaning agents also includes the concentrates and solid mixtures intended for the preparation of the application solutions.

The ready-to-use solutions can be acidic to strongly alkaline; they are generally used at temperatures of around 20 to 90 ° C.

The end group-sealed polyglycol ethers to be used according to the invention give effective effects even in low concentrations. They are preferably added to the cleaning agents in amounts such that their concentration in the ready-to-use solutions is approximately in the range from 50 to 500 ppm.

Examples

In the following examples, the foam attenuation of the additives selected according to the invention - and, in comparison, structurally similar additives, but not within the scope of the invention - is determined using a test method which is described as follows:

300 ml of a 1% aqueous sodium hydroxide solution are heated to 20 or 65 ° C. in a double-walled 2 l measuring cylinder. The selected foam-suppressing additive is then added in the amounts specified below. With the help of a laboratory hose pump, the liquid is pumped at a circulation rate of 4 l per minute. The test solution is sucked in approx. 5 mm above the bottom of the measuring cylinder by means of a 55 cm long glass tube (inner diameter 8.5 mm, outer diameter 11 mm), which is connected to the pump via a silicone hose, and through a second glass tube (length 20 cm) attached to the 2000 ml mark in free fall.

After 30 seconds, 1 ml of a 1% aqueous solution of the triethernolamine salt of tetrapropylene benzene sulfonate (referred to in the tables below as "test foamer") is first metered into the liquor and after a further 30 seconds the volume formed, which is formed by liquid and foam, is determined . At intervals of 1 minute each, further test foamers are then metered in in portions of 1 ml and the volume of liquid and foam formed after 30 seconds is determined. This step-by-step cycle of metering the test foamer and determining the volume after 30 seconds is maintained until the surfactant solution in the measuring cylinder has foamed to 2000 ml.

example 1

Two foam-suppressing additives A and B selected according to the invention are used in each case at 20 ° C. and 65 ° C. and their foam-suppressing action is compared with an additive of the prior art (product C). The foam-suppressing additives A to C are used in the test method specified in amounts of 0.1 ml of the pure substance.

The products A to C used are the following:
Products
according to the invention
A 2-octyldodecanol-8 EO-n-butyl ether
B 2-Hexyldecanol-6 EO-n-butyl ether
for comparison
C coconut alcohol 10 EO n-butyl ether

The values determined in the comparative experiments are summarized in Table 1 below. Table 1 ml test foamer Product A Product B Product C 20 ° C 65 ° C 20 ° C 65 ° C 20 ° C 65 ° C 0 300 300 320 300 400 300 1 300 300 320 300 460 320 2nd 300 300 340 300 580 340 3rd 300 300 380 300 680 360 4th 340 300 440 300 800 400 5 380 300 460 320 1000 420 6 400 320 480 420 1400 440 7 420 400 520 460 1600 460 8th 420 460 540 520 1820 540 9 460 520 600 600 2000 780 10th 480 620 700 660 940 11 500 760 840 760 1240 12 540 860 1100 820 1760 13 580 1000 1280 1100 1880 14 600 1100 1500 1180 1940 15 660 1220 1700 1240 2000 16 720 1480 1880 1320 17th 800 1620 2000 1480 18th 1000 1760 1660 19th 1300 1860 1820 20th 1680 2000 2000 21st 2000

Example 2

According to the test method specified, 2 bottle cleaner formulations with the composition shown in Table 2 below are examined. The first of the two formulations contains only the aforementioned product C of the prior art as a foam-suppressing additive. The second recipe uses a mixture of the foam-suppressing additive A in admixture with the product C according to the prior art in the sense of the inventive action.

Table 2 below summarizes the read values. It also shows a further advantage for the teaching according to the invention:

The bottle cleaner formulation according to the invention is also stable in storage as a liquid phase at temperatures below 0 ° C.

Claims (4)

1. Use of polyethylene glycol ethers of the general formula (I)
R₁O- (CH₂CH₂O) _n -R₂ (I)
in the
R₁ is a straight-chain or branched alkyl or alkenyl radical having 20 to 28 carbon atoms,
R₂ is an alkyl radical with 4 to 8 carbon atoms and
n is a number from 6 to 20,
as foam-suppressing additives for low-foam cleaning agents. 2. Embodiment according to claim 1, characterized in that compounds of the general formula (I) are used in which R₁ has 20 to 24 carbon atoms and in particular is a branched radical of the type specified, R₂ preferably the butyl radical and in particular the n Butyl is, while the preferred value for n is 6 to 12. 3. Embodiment according to claims 1 and 2, characterized in that the compounds of general formula (I) are used in admixture with structurally identical polyethylene glycol ethers, but in which the radical R₁ is a straight-chain or branched alkyl or alkenyl radical having 8 to 18 carbon atoms and n is a number from 7 to 12, preferably 8 to 10. 4. Embodiment according to claims 1 to 3, characterized in that the end group-capped polyethylene glycol ethers are used in such amounts that their concentrations is about 50 to 500 ppm in the ready-to-use solutions.