DE1160449B - Process for the preparation of fatty acid alkanolamides - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Boarding school Class: C 07 c

German KL: 12 q- 32/01

Number: 1 160 449

File number: J 20093 IVb / 12 q

Filing date: June 16, 1961

Opened on: January 2, 1964

The invention relates to a process for the preparation of fatty acid alkanolamides by converting Esters of higher fatty acids with the corresponding alkanolamines ^

In general, three different routes are used for the preparation of fatty acid alkanolamides. The oldest process (see, for example, US Pat. No. 2,679,504) is used to heat higher fatty acids with mono- or dialkanolamines for a few hours at temperatures of up to 160 ° C to complete elimination of the water of reaction. Under these conditions, however, only very polluted ones become Products received, since at the required temperatures a rearrangement of the formed Alkanolamides to oxazolidines takes place and the formation of amino esters is also relatively large. Of the The content of such by-products can vary particularly with regard to the subsequent intended use of the alkanolamides produced in this way have an unfavorable effect. As emulsifiers for cosmetic preparations z. B. only very pure products can be used. Another procedure leads to essential purer products, namely the conversion of fatty acid halides with alkanolamines in the absence of water (see British Patent 693 086). In this process, however, the technically very important disadvantageous detour via the acid halide must be accepted. The strongest today A common method consists in the conversion of higher fatty acid esters, preferably methyl esters or glycerides, with the corresponding alkanolamines at temperatures between about 125 and 250 ° C. Relatively short reaction times are achieved at temperatures of around 180 to 250 ° C, but the formation of the above-mentioned by-products, oxazolidines and amino esters, is not thereby prevented prevents, but rather favors.

At low reaction temperatures, very long reaction times and only inadequate conversions achieved. Alkali metals are used to shorten the reaction times and improve conversions or their hydroxides or alcoholates (German patent specification 876 815, USA patent specification 863 888) used as catalysts, which are separated off or neutralized after the reaction has ended.

It has now been found that the disadvantages outlined above, ie the formation of by-products, can be prevented in a simple manner. The process according to the invention for producing fatty acid alkanolamides by reacting fatty acid esters with alkanolamines by heating and in the presence of a catalyst is a process for producing them
of fatty acid alkanolamides

Applicant:

INVENTA A.G.

for research and patent exploitation,

Lucerne (Switzerland)

Representative:

Dr.-Ing. Dr. jur. H. Mediger, patent attorney,

Munich 9, Aggensteinstr. 13th

Named as inventor:

Dr.-Ing. Manfred Hoppe,

Dr. Chem. Wilhelm Deiters, Chur (Switzerland)

Claimed priority:

Switzerland of July 30, 1960 (No. 8713)

characterized in that sodium bicarbonate is used as the catalyst. One heats after this Process 1 mole of fatty acid ester, preferably the methyl ester, with 1 to 1.1 moles of mono- or diethanolamine and about 1 to 3 weight percent sodium bicarbonate based on the weight of the one used Esters, with vigorous stirring to temperatures of 120 to 150 ° C, preferably to 130 ° C, and the resulting methanol is continuously distilled off. When it is the boiling point of the ester and the alkanolamine permitted, it is advantageous to work at a pressure of about 50 mm Hg column and so can do that Drive off the methanol still significantly accelerate.

The advantage of the new process over those processes in which no catalysts are used are, consists in the much shorter reaction time and the greater purity of the resulting Alkanolamides and those processes according to which with basic catalysts work is carried out to avoid undesirable side reactions.

The following examples relate to a discontinuous procedure; the simple setup

I 160

However, processing of the reaction mixture readily allows the process to be carried out continuously.

example 1

In a 500 cm ³ three-necked flask, which is equipped with a stirrer, a thermometer and a distillation attachment, 107 g of methyl laurate (corresponding to 1 mol), 57.7 g of diethanolamine (corresponding to 1.1 mol) and 3 g of sodium bicarbonate are stirred up vigorously 130 ° C heated. A vacuum of 50 mm Hg is applied to the apparatus so that the methanol which forms is immediately removed from the reaction mixture. After the start of the reaction, the reaction mixture, which initially has two phases, immediately becomes completely homogeneous. In order to capture all the methanol distilling off, it is advantageous to connect a cold trap between the apparatus and the vacuum pump, which is filled with liquid air or carbon dioxide snow - methanol. After about 40 minutes, 15 g of methanol have distilled off; in general, 90 to 95 ^fl / o of the theoretical amount is obtained. The reaction mixture is then cooled to about 90 to 100 ° C. and 150 cm ^{3 of} hot distilled water are added while stirring vigorously. Now is added as much dilute hydrochloric or sulfuric acid, that the reaction mixture has a _pH value of. 7 After the stirring is stopped, the reaction mixture immediately separates into two layers and the upper amide layer is separated from the lower, aqueous layer. After the aqueous layer has cooled, some amide precipitates out of it. The amide is then dried under vacuum and 152.3 g, corresponding to 98% of theory, of pure amide with a melting point of 37 to 37.5 ° C. are obtained. No free amine could be detected by titration with bromophenol blue.

Example 2

In the apparatus described in Example 1, 107 g of methyl laurate (corresponding to 1 mol), 30.5 g of monoethanolamine (corresponding to 1 mol) and 3 g of sodium bicarbonate are heated to 130 ° C. with vigorous stirring. The production of monoethanolamide is carried out under normal pressure, since the boiling point of the free amine is too low. Understandably, only about 80% of the theoretical amount of methanol can be distilled off under these conditions. After about I ¹ 2 to 2 hours, the reaction mixture is cooled to 90 to 100 ° C, at this temperature with 150 cm ³ of hot distilled water with vigorous stirring. After adjusting the p _H -value to 7 using dilute hydrochloric acid the Amidschicht is separated and dried under vacuum. This gives 117.3 g, corresponding to 97.1% of theory, of pure lauric acid monoethanolamide with a melting point of 78 to 78.5 ° C. No free amine could be detected by titration with bromophenol blue.

Claims (3)

Patent claims: 1. Process for the preparation of fatty acid alkanolamides by reacting fatty acid esters with alkanolamines by heating and in the presence of a catalyst, characterized in that that sodium bicarbonate is used as a catalyst. 2. The method according to claim 1, characterized in that 1 to 3 percent by weight sodium bicarbonate, based on the amount of ester used, can be used as a catalyst. 3. The method according to claim 1 or 2, characterized in that at a reaction ^{temperature of 120 to 150 0} C, the reaction time is 30 to 120 minutes. 309 777/395 12.63 © Bundesdruckerei Berlin