Polyglycol Ethers as Foam-Inhibiting Additives in Low-Foam Cleaning Agents

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.