EP0040346B1 - Process for refining a raw condensation product from aminoalkylalkanol amines and fatty acids, and as soon as required for the subsequent recovery of amphotensides with higher stability - Google Patents

Abstract

1. A process for purifying the crude condensation product of aminoalkyl alkanolamines corresponding to the following general formula H2 N-(CH2 )2 -NH-(CH2 )n -OH in which n is the number 2 or 3, and C6 -C22 fatty acids and, if desired, for subsequently alkylating and, optionally, quaternizing the purified condensation product to form amphoteric surfactants having improved stability in storage, characterized in that the crude condensation product of fatty acids and aminoalkyl alkanolamines is subjected to alkaline hydrolysis at temperatures in the range from 70 to 100 degrees C.

Description

An important process for the production of amphoteric surfactants is based on condensation products of N-monosubstituted alkylenediamines, which are alkylated in a further reaction with alkylating agents, for example sodium chloroacetate. Products based on N-aminoethylethanolamine and fatty acids play a major role as skin-friendly surfactants.

The process for the preparation of such compounds is known in principle from US Pat. Nos. 2,528,378, 2,528,379 and 2,528,380. While it was previously assumed that this reaction would result in alkylation or quaternization products of imidazoline, it has now been shown that they are predominantly alkylation or quaternization products of aminoamides which are formed by hydrolysis of the imidazoline intermediate in an aqueous medium , see for example DE-AS-1 084 414.

The basic procedure for the preparation of these surfactants is that about 1 mole of fatty acid or fatty acid mixture is condensed with one mole of an aminoalkylalkanolamine - in particular aminoethylethanolamine - with a gradual increase in temperature, lastly in vacuo. This condensation product is then converted to the amphoteric surfactant with varying amounts of an alkylating agent, for example sodium chloroacetate, usually in an aqueous alkaline solution. Details of these process stages can be found in the literature cited, see also Dr. K. Lindner "Tenside-Textile Aid Detergent Raw Materials" Wissenschaftliche Verlags GmbH, Stuttgart 1964 pages 1041/1042 and the original literature cited here as well as DE-OS-2 752 116, European patent application 001 006 and US-PS-2 773 068 and 3 408 361.

The quality of the ampotensides obtained and in particular their storage stability is crucially determined by the purity of the imidazoline derivative obtained in the first condensation step. The reaction between fatty acids and aminoalkylalkanolamines not only proceeds in the direction of the formation of the desired imidazoline derivative, multiple side reactions complicate the course of the reaction. The importance of this aspect has only recently been emphasized again, see EG Lomax "New and improved balanced amphoterics", Manufacturing Chemist and Aerosol News, Volume 50 No. 8, August 1979, pages 39 and 41. For example, that the undesirable side reactions in the stage of imidazoline formation can be suppressed by an excess of aminoethylethanolamine, but this excess must be removed at the end of the reaction by distillation. Excess aminoethylethanolamine, in turn, can create new difficulties by cyclization to the piperazine. The purity of the imidazoline obtained in the first reaction stage has a decisive influence on the storage stability of the amphoteric surfactants or their aqueous solutions obtained by subsequent alkylation. Even a small amount of contamination leads to the separation of a solid phase after a shorter or longer storage period, be it in the form of cloudiness or precipitation. Such products are unusable for practical use or at least of limited value.

The invention is based on the object of creating improvements in the production of the class of amphoteric surfactants described here, which are characterized in particular by increased storage stability of the amphoteric surfactants.

The invention aims to eliminate the troublesome by-products present here by switching on a simple cleaning step on the condensate of aminoalkylalkanolamine and fatty acid obtained in the first place. The aim of the invention is to make the previously expensive detours for obtaining the purest possible condensation product of this first process stage superfluous.

The teaching of the invention is based on the surprising finding that the crude condensation product of fatty acids and aminoalkylalkanolamines can be converted by simple alkaline hydrolysis to a refined product which, in the subsequent alkylation and optionally quaternization, provides improved amphoteric surfactants with, in particular, increased storage stability.

in der n die Zahl 2 oder 3 bedeutet, und Fettsäuren mit 6 bis 22 C-Atomen und gewünschtenfalls zur nachfolgenden Alkylierung und gegebenenfalls Quaternierung des gereinigten Kondensationsproduktes zu Amphotensiden mit erhöhter Lagerstabilität, wobei dieses Verfahren dadurch gekennzeichnet ist, daß man das rohe Kondensationsprodukt aus Fettsäuren und Aminoalkylalkanolaminen bei 70 bis 100°C einer alkalischen Hydrolyse unterwirft.The invention accordingly relates to a process for refining the crude condensation product from aminoalkylalkanolamines of the general formula

in which n is the number 2 or 3, and fatty acids having 6 to 22 carbon atoms and, if desired, for subsequent alkylation and, if appropriate, quaternization of the purified condensation product to amphoteric surfactants with increased storage stability, this process being characterized in that the crude condensation product is obtained from fatty acids and subjecting aminoalkylalkanolamines to alkaline hydrolysis at 70 to 100 ° C.

abgestimmt. Dabei wird insbesondere die Alkalimenge in dieser Verfahrensstufe so bemessen, daß sie vorzugsweise in wenigstens etwa equimolarem Betrag zum Diamid im rohen Kondensationsprodukt vorliegt.In the process according to the invention, the amount of alkali used in this alkaline hydrolysis is preferably based on the amount of the diamide of the general amount present in the crude condensate formula

Voted. In this process step, the amount of alkali in particular is such that it is preferably present in the crude condensation product in at least an approximately equimolar amount to the diamide.

The invention is based on the finding that the content of disruptive by-products in the finished surfactant can be drastically reduced if the fatty acid / amine condensation product is subjected to an alkaline pretreatment in an aqueous medium before a further reaction with alkylating agents. As can be shown from experiments, diamide formed in particular in the course of the reaction by aqueous alkali on the tert. Amide group quantitatively split into the monoamide of the primary amino group and fatty acid. In the cleaning treatment according to the invention, the fatty acid forms soap which can remain in the reaction mixture.

It is indeed extremely surprising that the difficulties with respect to the storage stability of the amphoteric surfactants obtained in the last stage, which have hitherto been overcome only with comparatively expensive cleaning steps, are eliminated by the intermediate treatment according to the invention. However, it must be taken into account here that the alkylation and optionally quaternization of the reaction product obtained in the first stage - with, for example, sodium chloroacetate - takes place in an aqueous alkaline medium, process conditions with regard to temperature and alkalinity being selected which are at least comparable to the conditions of the intermediate step according to the invention. It was not to be expected that the separate alkaline hydrolysis of the crude condensation product from the first process stage provided according to the invention could provide better results than a corresponding aqueous alkaline treatment in the course of the alkylation or quaternization of the condensation product.

However, the alkaline pretreatment according to the invention gives products which remain clear even after dilution for longer than 6 months. Costly cleaning steps such as recovery of the excess amine or distillation of the imidazoline are no longer necessary. The alkaline hydrolytic treatment according to the invention is preferably carried out in the temperature range from 80 to 90 ° C. Alkali hydroxides, especially sodium hydroxide, are particularly suitable as alkalis. The amount of alkali is preferably in the range of about 1 to 3 times the equimolar amount of alkali, based on the diamide present in the crude condensation product. In particular, alkali amounts in the range of 1 to 2 equivalents, based on diamide, are used. For the alkaline hydrolysis according to the invention, the crude condensation product is expediently suspended in an amount of water which corresponds to 0.5 to 10 times, in particular 1 to 5 times, the crude condensation product. The aqueous alkaline hydrolysis is carried out until the diamide present as a by-product is virtually completely eliminated. The diamide content of the crude product and its decrease in the treatment according to the invention can in a known manner, for. B. can be determined by working with ion exchangers.

werden solche Verbindungen eingesetzt, in denen n den Wert von 2 oder 3 aufweist; die bevorzugte Bedeutung für n ist 2. Das für die Praxis wichtigste Ausgangsamin der hier betroffenen Art ist Aminoethylethanolamin. Die zur Kondensation mitverwandten Fettsäuren weisen Kohlenstoffzahlen im Bereich von 6 bis 22 auf, wobei besondere Bedeutung der Bereich von 8 bis 18 C-Atomen hat. Die Carbonsäuren können als reine Komponenten oder auch als Mischungen vorliegen. Sie können dabei natürlichen und/oder synthetischen Ursprungs sein.As aminoalkylalkanolamines of the general formula

such compounds are used in which n has the value of 2 or 3; the preferred meaning for n is 2. The most important starting amine in practice of the type concerned here is aminoethylethanolamine. The fatty acids related to the condensation have carbon numbers in the range from 6 to 22, the range from 8 to 18 carbon atoms being particularly important. The carboxylic acids can be present as pure components or as mixtures. They can be of natural and / or synthetic origin.

The condensation product pretreated by the alkaline hydrolysis in the sense of the invention is then converted to the finished amphoteric surfactant in a manner known per se. Here too, the details of the cited extensive prior art apply. The pretreatment according to the invention proves to be valuable not only for the production of the so-called imidazolinium surfactants, but rather it can be used in many different ways. Clear and storage-stable products are also obtained when the alkali-treated amine condensation products are reacted with alkylating agents of the type of chlorohydroxypropane sulfonic acid, propane sultone and in the case of alkylation with vinylogenic compounds such as acrylic acid or acrylic acid ester with subsequent saponification and 2-acrylamido-2-methylpropanesulfonic acid or the corresponding alkali salts.

Depending on the structure and extent of the reaction, the amphoteric surfactants can have alkylated and optionally quaternized nitrogen in the second reaction stage. In a further embodiment, the invention comprises the production of such amphoteric surfactants using a condensation precursor which has been treated according to the alkaline hydrolytic process of the invention described.

In the following examples, the percentages relate to% by weight. The diamide content is determined as follows: The condensation product is sent as an alcoholic solution through a strongly acidic ion exchanger. The eluate is evaporated and the remaining residue is related to the weight. The amount of diamide can be calculated by determining the S.Z. and the total nitrogen.

example 1 Condensation products of fatty acids with aminoethylethanolamine 1.1 molar ratio 1: 1

In a three-necked flask equipped with a stirrer, nitrogen flow, thermometer and distillation attachment, 208 g (1 mol) of C8 / 18 coconut fatty acid were mixed with 104 g (1 mol) of aminoethylethanolamine and slowly heated to 200 ° C .; Duration approx. 6 hours. After distilling off a total of 20 g of water containing amine, about 290 g of a slowly solidifying, yellow mass were obtained, which had the following key figures:

Diamide content (determined via ion exchanger) 16.1% (= 0.04 mol / 100 g). A UV spectroscopic.

Examination at 230 mm showed an imidazoline content of 8.0%.

1.2 molar ratio 1: 1.1

As described under 1.1, 208 g (1 mol) of coconut fatty acid were condensed with 114.5 g (1.1 mol) of aminoethylethanolamine.

Approx. 300 g of a slowly solidifying, yellow mass were obtained with the following key figures:

1.3 molar ratio 1: 1.5

As described under 1.1, 208 g (1 mol) of coconut fatty acid were condensed with 156 g (1.5 mol) of aminoethylethanolamine with slow heating so that the free amine content remained as high as possible during the reaction. Reaction temp. up to 180 ° C, lastly at approx. 14 mbar.

After the excess amine had been distilled off, about 270 g of residue remained with the following key figures:

Example 2 Reactions with sodium chloroacetate 2.1 Without alkaline pretreatment

• 2.1.1. 90 g (0.3 mol, calculated from N _titr ) of product from experiment 1.1 were dispersed with 148 g of water and 203 g (0.7 mol) of a freshly prepared 40% sodium chloroacetate solution were added at 60 ° C. When adding 56 g (0.7 mol) of 50% sodium hydroxide solution the pH rose to 11.52. The mixture was stirred at this temperature for 2 hours and then raised to 80 ° C. for 1 hour; the pH slowly dropped to approx. 10. The approx. 40% product began to cloud over after 2 days at RT.
• 2.1.2. 80 g (0.32 mol, calculated from N _titr. ) Product from experiment 1.2 were dispersed with 134 g of water and 214 g (0.74 mol) of a freshly prepared 40% solution of sodium chloroacetate were added at 60 ° C. 58.8 g (0.74 mol) of 50% sodium hydroxide solution were then run in at 60 ° C., the mixture was kept at 60 ° C. for 2 hours and the temperature was then increased to 80 ° C.; the pH was adjusted to 11.5 upon addition of the sodium hydroxide solution and slowly decreased to 10.1 after heating at 80 ° C. for 1 hour. A clear solution with about 40% solids content was obtained, which, however, began to cloud over after only 2 days at RT.
• 2.1.3 90 g (0.3 mol) of imidazoline from experiment 1.3 were dispersed with 134 g of water, kept at 60 ° C. for 1 hour and then 203 g (0.7 mol) of a freshly prepared 40% sodium chloroacetate solution were added . Then 56 g (0.7 mol) of 50% sodium hydroxide solution were added. The pH rose to 11.6. The mixture was stirred at this temperature for 2 hours and at 80 ° C. for a further hour. After about 10 weeks of storage at R. T., the first signs of turbidity appeared.

2.2 With alkaline pretreatment

• 2.2.1 a) 90 g (0.3 mol, calculated from N _titr. ) Product from experiment 1.1, containing 0.035 mol diamide, were dispersed in 148 g water, 1.2 g 50% NaOH (0.015 mol) were added and Stirred at 80-90 ° C. for 1 hour. The procedure was as in 2.1.1. described. The product is clear as in 2.1.1, but also clouded after 6 days, since not all diamide has been saponified.
  • b) The experiment was repeated with the addition of 4.8 g of 50% NaOH (0.06 mol). As the analysis also showed, the diamide was saponified quantitatively to give the monoacyl product; the product is still clear even after> 6 months.
• 2.2.2 80 g (0.32 mol) of product from experiment 1.2 were dispersed in 60 g of water, mixed with 4.8 g (0.06 mol) of 50% sodium hydroxide solution and stirred at 80 ° C. for 1 hour. After further implementation, as described under 2.1.2, a surfactant was obtained which is still clear even after> 6 months.

• Auch die Verwendung eines sehr reinen Imidazolins als Vorstufe (2.1.3) führt nicht zu der Qualitätsverbesserung, wie sie selbst bei diamidreichen Rohstoffen (1.1 u. 1.2) nach alkalischer Vorbehandlung erreicht wird. Zweckmäßigerweise wird eine Natronlaugemenge eingesetzt, die äquivalent, am besten jedoch etwa doppelt so hoch ist, wie aufgrund des Diamid-Gehalts erforderlich ist.

From experiments 2.1.1-2.1.3 and 2.2.1 and 2.2.2 it can be seen:

• The use of a very pure imidazoline as a preliminary stage (2.1.3) does not lead to the quality improvement that is achieved even with diamide-rich raw materials (1.1 and 1.2) after alkaline pretreatment. An amount of sodium hydroxide solution is expediently used, which is equivalent, but ideally about twice as high as is necessary due to the diamide content.

Example 3 Reactions with 2-acrylamido-2-methylpropanesulfonic acid (AMPS) or Na salt 3.1 Without alkaline pretreatment

75.0 g (0.3 mol, calculated from _nitrite ) _. Product from experiment 1.2 were suspended in 200 g of water, 80.6 g (0.39 mol) of AMPS were added, and then 31.2 g (0.1 39 mol) 50% sodium hydroxide solution. The mixture was stirred at 80 ° C for 4 hours.

The finished product is clear and fluid, but shows deposits after 2 days.

3.2 With alkaline pretreatment

75.0 g (0.3 mol) of product from experiment 1.2 were suspended in 200 g of water and stirred for 1 hour with 4.8 g (0.06 mol) of 50% sodium hydroxide solution at 80-90 ° C. Further implementation as under 3.1. The product is still completely clear after> 6 months.

Example 4 Reactions with chlorhydroxypropanesulfonic acid or Na salt 4.1 Without alkaline pretreatment

75 g (0.3 mol) of product from experiment 1.2 were dispersed in 200 ml of water, 63.6 g (0.3 mol) of chlorohydroxypropanesulfonic acid (Na salt) were added and 24.0 at 80 ° C. in 30 minutes g (0.3 mol) 50% sodium hydroxide solution. 4 hours after-reaction at 50 ° C.

The end product is clear, but becomes cloudy after 3 days.

4.2 With alkaline pretreatment

The reaction was carried out analogously to 3.1, but before adding the chlorohydroxypropanesulfonic acid (sodium salt), stirring was carried out at 80-90 ° C. for 1 hour after the addition of 4.8 g (0.06 mol) of 50% sodium hydroxide solution.

The product is still clear after more than 6 months.

Example 5 Reactions with acrylic acid 5.1 Without alkaline pretreatment

75.0 g (0.3 mol) of product from experiment 1.1 were mixed with 21.6 g (0.3 mol) of acrylic acid and stirred for 4 hours at 80 ° C. and then diluted with 145 g of water. The product becomes cloudy after 2 weeks.

5.2 With alkaline pretreatment

75.0 g (0.3 mol) of product from experiment 1.1 were stirred with 4.8 g (0.06 mol) of 50% sodium hydroxide solution at 80 ° C. for 1 hour and then treated as in 4.1.

The product remains clear for> 6 months.

Claims (4)

1. A process for purifying the crude condensation product of aminoalkyl alkanolamines corresponding to the following general formula

in which n is the number 2 or 3, and C₆―C₂₂ fatty acids and, if desired, for subsequently alkylating and, optionally, quaternizing the purified condensation product to form amphoteric surfactants having improved stability in storage, characterized in that the crude condensation product of fatty acids and aminoalkyl alkanolamines is subjected to alkaline hydrolysis at temperatures in the range from 70 to 100" C.

2. A process as claimed in Claim 1, characterized in that the quantity of alkali used in the alkaline hydrolysis step is coordinated with the quantity of diamide present in the crude condensation product, the alkali preferably being used at least approximately in an equimolar quantity and, more particularly, in no more than 3 times the molar quantity.

3. A process as claimed in Claims 1 and 2, characterized in that the alkaline hydrolysis step is carried out at temperatures in the range from 80 to 90° C.

4. A process as claimed in Claims 1 to 4, characterized in that pure fatty acids or fatty acid mixtures containing the number of carbon atoms indicated above and, more particularly, from 8 to 18 carbon atoms, are used.