EP0108321B1 - Application of low molecular organic compounds as viscosity regulators for highly viscous technical tenside concentrates - Google Patents

Abstract

An aqueous anionic surfactant concentrate containing certain low molecular weight organic compounds as viscosity regulators and a method of regulating the viscosity of highly viscous concentrates, e.g. alpha -sulfo fatty acid ester surfactants in concentrations about 30% by weight. The viscosity regulators are selected from: (a) a C1-C6-alkyl monocarboxylic acid substituted in the alpha -position by a halogen, cyano or sulfo group, a salt thereof, or an ester thereof with a C1-C6-alkanol, (b) a C1-C6-alkylene dicarboxylic acid substituted in the alpha -position by a halogen, cyano or sulfo group, a salt thereof, or an ester thereof with a C1-C6-alkanol, (c) nitrilotriacetic acid and its salts, (d) an ether alcohol containing from 2 to 4 alkylene glycol units and 1 alkoxy group, (e) and mixtures thereof.

Description

In the production of powdery or granular detergents and cleaning agents according to the hot spray process customary on an industrial scale, aqueous slurries (called "slurry") are used which contain a large part of the detergent constituents or also all detergent constituents. From an economic point of view, it is important that the slurry is as rich as possible in detergent components, i.e. is as low in liquid fiber as possible. The lowest possible amount of water is therefore used to prepare the slurries. Concentration is limited by the highest possible viscosity at which the slurry can just be processed.

An essential component of most detergents and cleaning agents are anionic surfactants, which are mostly used as paste-like concentrates in the form of their alkali or ammonium salts in the production of the detergent slurries. In the case of α-sulfotalg fatty acid methyl esters, for example, the surfactant content of technical concentrates is approx. 30% by weight. Pastes with a higher surfactant content can no longer be processed.

A special feature of the rheological behavior of surfactant concentrates is that they do not react to the addition of water with a reduction in viscosity, but first with a thickening to a gel-like state, which poses further problems for the processor. For example, it is often not easy to get gel clumps back into solution, or valves on pumps and containers become blocked.

Various proposals have been made to solve these problems. DE-OS 2251 405, for example, describes the salts of certain carboxylic acids, in particular hydroxycarboxylic acids, as viscosity regulators. According to the teaching of DE-OS 2305554, sulfonated aromatic compounds are suitable for these purposes. DE-OS 2326006 mentions sulfates or sulfonates of aliphatic, optionally substituted hydrocarbons as viscosity regulators. The addition of lower alkanols is also listed as a possibility for reducing the viscosity in the publications mentioned. The addition of the well-known hydrotropes such as cumene sulfonate or acidic phosphoric acid esters (DE-AS 1617160) or of polyhydric alcohols, certain carboxylic acids and / or esters of these compounds is described (EP-OS 8060). From European published application No. 24711 it is known to add sulfates of certain polyalkyl ether glycols to improve the flow behavior of anionic surfactant concentrates.

Some of the additives mentioned in the literature do not work with all surfactant concentrates, others have to be used in high concentrations, and still others, such as lower alkanols, lower the flash point of the concentrates.

The object of the present invention is therefore to provide substances for improving the flow behavior of aqueous technical anionic surfactant concentrates, in particular of a-sulfofatty acid esters, so that they can be processed in higher concentrations than before or have no increase in viscosity when diluted with water.

• a) in a-Stellung durch Halogen-, Cyan- oder Sulfogruppen substituierte C_l- bis C₆-Alkylmono- carbonsäuren, deren Salze oder deren Ester mit C_l- bis C₆-Alkanolen, insbesondere mit Ethanol oder Methanol,
• b) in a-Stellung durch Halogen-, Cyan- oder Sulfogruppen substituierte C_l- bis C_6-Alkylendi- carbonsäuren, deren Salze oder deren Ester mit C_l- bis C₆-Alkanolen,insbesondere mit Ethanol oder Methanol,
• c) Nitrilotriessigsäure und deren Salze,
• d) Etheralkohole mit 2 bis 4 Alkylenglykoleinheiten und einer Alkoxygruppe, insbesondere einer Methoxy- oder Ethoxy-Gruppe

als Viskositätsregler für hochviskose technische Tensid-Konzentrate vom Typ der synthetischen anionischen Tenside, insbesondere von a-Sulfofettsäureestern mit wenigstens 30 Gew.% a-Sulfofettsäureester, wobei man den Viskositätsregler in Mengen von 1-15 Gew.%, bezogen auf die Tensid-Menge, zusetzt, so dass eine Viskositätsverminderung der Konzentrate auf höchstens 10000 mPas bei 70°C eintritt, die gewünschten Effekte erzielen kann. D.h., man kann die Viskosität der Konzentrate bei der jeweiligen Verarbeitungstemperatur, d.h. bei der Temperatur, bei der die Tensidkonzentrate hergestellt, gepumpt, mit anderen Waschmittelbestandteilen vermischt oder versprüht werden, was man im allgemeinen zwischen 60 und 90°C vornimmt, auf eine für eine Verarbeitung geeignete Viskosität von höchstens 10 000 mPas vermindern.It has now been found that by using low molecular weight organic compounds comprising one or more compounds of the following groups:

• a) C ₁ to C ₆ alkyl monocarboxylic acids substituted in the a position by halogen, cyano or sulfo groups, their salts or their esters with C ₁ to C ₆ alkanols, in particular with ethanol or methanol,
• b) C ₁ to C ₆ alkylene dicarboxylic acids substituted in the a position by halogen, cyano or sulfo groups, their salts or their esters with C ₁ to C ₆ alkanols, in particular with ethanol or methanol,
• c) nitrilotriacetic acid and its salts,
• d) ether alcohols with 2 to 4 alkylene glycol units and an alkoxy group, in particular a methoxy or ethoxy group

as a viscosity regulator for highly viscous technical surfactant concentrates of the synthetic anionic surfactant type, in particular of a-sulfofatty acid esters with at least 30% by weight of a-sulfofatty acid ester, the viscosity regulator being used in amounts of 1-15% by weight, based on the amount of surfactant , is added so that a reduction in the viscosity of the concentrates to a maximum of 10,000 mPas at 70 ° C. occurs, which can achieve the desired effects. That is, the viscosity of the concentrates at the respective processing temperature, ie at the temperature at which the surfactant concentrates are produced, pumped, mixed with other detergent components or sprayed, which is generally done between 60 and 90 ° C, for one Reduce processing viscosity to a maximum of 10,000 mPas.

Another very significant advantage of the use according to the invention is that the surfactant content can be adjusted to approximately 60% by weight in the industrial manufacture of the surfactant concentrates without the viscosity exceeding the upper limit of about 10,000 mPas permissible for processability , whereby surfactant concentrates with lower water ballast are obtained. When these concentrates are diluted, the temporary increase in viscosity which is otherwise observed does not occur, which is also advantageous for processing.

The viscosity regulators are preferably added to the aqueous industrial anionic surfactant concentrates in amounts of approximately 10% by weight, ie in particular 7-12% by weight, based on the surfactant stop, whereby the desired viscosity reduction of the concentrate is determined by the amounts of the viscosity regulator added. The compounds suitable as viscosity regulators are derived, for example, from acetic acid, succinic acid or malonic acid. The sodium salts of the compound mentioned are particularly suitable. Examples of the compounds mentioned are the sodium salts of monochloroacetic acid, a-sulfosuccinic acid, a-sulfomalonic acid, a-sulfoacetic acid, a-sulfoacetic acid methyl ester, cyanoacetic acid and also cyanoacetic acid ethyl ester.

The compounds mentioned can be added individually or in a mixture. The viscosity-reducing effect is particularly pronounced at low pH values, for example at pH values below 7. In some cases, this is a further advantage of the use of the compounds mentioned according to the invention. The addition of other compounds with electron-withdrawing groups also reduces the viscosity of anionic surfactant concentrates; Examples of such compounds are the sodium salts of vinyl sulfonate and nitrilotriacetic acid. Dipropylene glycol monomethyl ether is also suitable as a viscosity regulator. This type d) compound of the aforementioned viscosity regulators is an ether alcohol which contains two propylene glycol units and a methoxy group. Compounds of type d) in which the alkylene group represents ethylene glycol or trimethylene glycol units are just as suitable as compounds whose alkoxy groups are ethoxy, propoxy or butoxy groups. However, ether alcohols with propylene glycol units and methoxy groups are preferred. 10% by weight additions of the sodium salts of nitrilotriacetic acid, methyl a-sulfoacetic acid, chloroacetic acid and ethyl cyanoacetate have proven particularly useful. They are therefore preferred.

Viscosity regulation is a particular problem for concentrates of a-sulfofatty acid esters, since concentrates with a surfactant content of more than about 30% by weight are no longer easy to process. Without the viscosity problem, it would be technically possible to produce surfactant concentrates with up to about 80% by weight of surfactant. The reduction in viscosity of a-sulfofatty acid ester concentrates is therefore a particular object of the present invention.

The a-sulfofatty acid esters, to the concentrates of which the viscosity regulators mentioned are added, are derived from fatty acids with 10 to 20, preferably 12 to 18, carbon atoms and from aliphatic alcohols with 1 to 10, preferably 1 to 4, carbon atoms in the molecule. The sulfo group is introduced either by sulfonation of the fatty acid and subsequent esterification of the carboxyl group with alcohol or by sulfonation of a corresponding fatty acid ester. According to both methods, esters of sulfo fatty acids are obtained which contain the sulfo acid group in the a position. Particularly suitable a-sulfofatty acid esters are the alkali or ammonium salts of the ethyl and especially the methyl ester of tallow fatty acid with a sulfo group in the a-position, the acid component of the fatty acid esters consisting essentially of saturated Cw and C, ₈ fatty acids. The salts are prepared by neutralizing the acidic esters with the appropriate bases.

Examples

• A = a-Sulfoessigsäuremethylester, Natriumsalz
• B = Chloressigsäure, Natriumsalz
• C = Cyanessigsäureethylester

The effectiveness of viscosity regulators on about 50 to about 60% by weight concentrates of the sodium salt of methyl a-sulfo tallow fatty acid is shown below. A corresponding 30% by weight paste (degree of sulfonation 97.4%) was evaporated to dryness. The powder obtained was used to prepare the concentrates at the concentrations given in the table below and checked by Epton titration. The following viscosity regulators were added to the concentrates:

• A = methyl a-sulfoacetate, sodium salt
• B = chloroacetic acid, sodium salt
• C = ethyl cyanoacetate

The concentrates with the viscosity regulators were heated on the steam bath until clear liquids were obtained. After defoaming these liquids in a centrifuge, their viscosities were determined in a Höppler falling ball viscometer at various temperatures. The viscosity reduction achieved is shown in the following table. Comparable results were obtained with a-sulfosuccinic acid ethyl ester, a-sulfoadipic acid methyl ester or a-chlorovaleric acid.

The following results were obtained:

In contrast, an α-sulph tallow fatty acid methyl ester concentrate with approx. 50% by weight of active substance at 65 ° C without the addition of a viscosity regulator had a viscosity of over 50,000 mPas and an approx. 29% by weight concentrate had a viscosity of approx. 25,000 mPas. Replacing the viscosity regulators A, collar C with other of the compounds mentioned gives comparable effects. Concentrates of tallow alcohol sulfates react similarly; Increasing the working temperature also reduces the viscosity; however, this is not appropriate because of the higher energy consumption.

Claims (5)

1. The use of low molecular weight organic compounds comprising one or more compounds from the following groups:

a) C₁-C₆ alkylmonocarboxylic acids substituted in the a-position by halogen, cyano or sulfo groups, salts or esters thereof with C₁-C₆ alkanols, particularly ethanol or methanol,

b) C₁-C₆alkylenedicarboxylic acids substituted in the a-position by halogen, cyano or sulfo groups, salts or esters thereof with C₁-C₆ alkanols, particularly ethanol or methanol,

c) nitrilotriacetic acid and salts thereof,

d) ether alcohols containing from 2 to 4 alkylene glycol units and one alkoxy group, particularly a methoxy or ethoxy group,

as viscosity regulators for highly viscous technical surfactant concentrates of the synthetic anionic surfactant type, more especially α-sulfofatty acid esters containing at least 30% by weight of the Na-salt of a-sulfo fatty acid esters, the viscosity regulator being added in quantities of from 1 to 15% by weight, based on the quantity of surfactant, so that the viscosity of the concentrates is reduced to at most 10000 mPas at 70°C.

2. The use of the compounds claimed in Claim 1 as viscosity regulators in quantities of from 7 to 12% by weight, based on the surfactant content of the concentrates.

3. The use of the sodium salts of a-sulfosuccinic acid, a-sulfomalonic acid, a-sulfoacetic acid, cyanoacetic acid and particularly monochloroacetic acid, a-sulfoacetic acid methyl ester, nitrilotriacetic acid and cyanoacetic acid ethyl ester according to Claims 1 and 2 as viscosity regulators for concentrates and anionic surfactants, particularly a-sulfofatty acid esters.

4. The use of the compounds claimed in Claims 1 to 3 as viscosity regulators in a-sulfofatty acid ester concentrates having pH-values below 7.

5. The use of the compounds claimed in Claims 1 to 4 as viscosity regulators for concentrates of a-sulfo-(hydrogenated tallow)-fatty acid ethlyl and particularly methyl ester in the form of its alkali or ammonium salts.