The invention relates to a process for the preparation of a bis(cyclic imino ether).

It is known to prepare a bis(cyclic imino ether) starting from a dicarboxylic acid and an amino alcohol (see, for example. Chemical Reviews, 1971, Vol. 71, No. 5, pp. 384-505). Furthermore, the article entitled "Cyclische

Imidsaure-ester aus Nitrillen und Aminoalkoholen", Liebigs Ann. Chem. 1974, pp. 996-1009, describes the preparation of a bis(cyclic imino ether), for example a bis-2- oxazoline, starting from a dinitrile with three of more carbon atoms between the nitrilβ groups and an amino alcohol.

The preparation of a 1,2-alkylene-alkane- bis(cyclic imino ether), for example 2,2'-ethylene-bis(2- oxazoline), starting from a 1,2-dinitrile and an amino alcohol, has not been described previously. On the contrary, page 1004 of the above-mentioned article states that the conversion of a 1,2-dinitrile with an amino alcohol does not yield a l,2-bis(cyclic imino ether). In particular the conversion of phthalodinitrile with ethanolamine to form l,3-bis-(2-hydroxyethyl imino)isoindolenine is described.

A bis(cyclic imino ether) with carbon atoms in between the functional groups, for example 2,2'-ethylene- bis(2-oxazoline) is known per se from Polymer Letters, 1966, Vol. 4, p. 257. This oxazoline was prepared by means of an isomerization reaction starting from a bis-N,N'- ethylene imide obtained by the Schotten-Bauman reaction starting from a diacid chloride and ethylene imine.

Ethylene i ine is a highly toxic aziridine, and this forms a serious objection to this known process.

The aim of the invention is to provide a process for the preparation of a bis(cyclic imino ether) starting from 1,2-alkylene-dinitrile and an amino alcohol. According to the process of the subject invention this aim is achieved in that an aliphatic 1,2- dinitrile with an amino alcohol is converted into the corresponding l,2-alkylene-bis(cyclic imino ether) while being heated. This ensures that a l,2-alkylene-bis(cyclic imino ether) can be obtained in a simple manner. Preferably, the conversion takes place in the absence of a catalyst. This has the advantage that the reaction product obtained according to the process of the subject invention need not be separated from the catalyst. It is most surprising that it is yet possible to prepare 1,2- alkylene-bis(cyclic imino ether)s in this way.

According to a suitable embodiment of ^' the process according to the subject invention an aliphatic 1,2-dinitrile is dissolved in an amino alcohol and the reaction mixture is heated for some time, whether or not in the presence of a catalyst, while the ammonia that is released escapes. Subsequently, the reaction mixture is heated for some more time after the initial ammonia development has stopped, the amino alcohol released being removed.

Starting from ethanolamine as amino alcohol and succinonitrile as aliphatic 1,2-dinitrile, initially an imino azacyclopentane polyol, for example the l-(2- hydroxyethyl)-2,5-bis-(2-hydroxyethyl imino)- azacyclopentane (the triol) and/or the 2,5-bis(2- hydroxyethyl imino)-azacyclopentane (the diol), is obtained as intermediate product. After ammonia development has stopped and any amino alcohol still present has been removed, for example by distillation under reduced pressure, thus a mixture of the diol and the triol is obtained.

The intermediate product formed is subsequently converted further into the desired l,2-bis(cyclic imino ether), for example, 2,2'-ethylene-bis(2-oxazoline) , while being heated. The amino alcohol released during the continued reaction is removed by, for example, distillation under reduced pressure.

After the conversion of the aliphatic 1,2- dinitrile with the amino alcohol into the imino azocyclopentane polyol, the resulting polyol is preferably separated and upgraded in a manner known per se before allowing it to react further. This renders it possible to prepare a l,2-alkylene-bis(cyclic imino ether) with a high yield and a high purity, starting from an imino azocyclopentane polyol that has already been upgraded and purified.

The ¹ conversion generally takes place at a temperature of 50-190 ^β C, preferably 120-130°C, with the released ammonia escaping. Further reaction of the reaction mixture generally takes place at a temperature of 120-190°C, preferably 140-170°C, the amino alcohol released being discharged, preferably by evaporation under reduced pressure, for example 5-50 mm Hg, and preferably 20-30 mm Hg. Distillation of the reaction product generally takes place at a temperature of 150-180°C and reduced pressure, for example 5-10 mm Hg.

If succinonitrile is used as 1,2-dinitrile, the temperature during conversion is rather critical. A temperature that is too high, for example higher than 190°C, leads to an unacceptable degree of tar formation. If the temperature is too low, conversion will be too slow and incomplete.

The entire reaction may take place in 0.5-15 hours. Preferably, the entire reaction takes place in 1-12 hours.

Dinitriles that are suitable for the process according to the subject invention are aliphatic 1,2- dinitriles, whether or not substituted in the main chain

by one or more alkyl groups with 1-4 carbon atoms, preferably methyl groups or ethyl groups. Examples of suitable dinitriles are succinonitrile, dimethyl succinonitrile, diethyl succinonitrile, methyl succinonitrile, ethyl succinonitrile or methyl ethyl succinonitrile. Preferably, use is made of succinonitrile.

Suitable amino alcohols are alkanol amines chosen from the group formed by ethanolamine, l-amino-2- propanol, 2-amino-l-propanol, 1-amino-3-propanol, 1-amino- 2-butanol, l-amino-3-butanol, l-amino-4-butanol, 2-amino- 1-butanol, 2-amino-3-butanol, 3-amino-l-butanol, 1-amino- 2-methyl-2-propanol, 2-amino-2-methyl-l-propanol. Preferably, an alkanol amine is chosen from the group formed by ethanolamine, l-amino-2-propanol, 2-amino-l- propanol, 1-amino-3-propanol, l-amino-2-methyl-2-propanol, 2-amino-2-methyl-l-propanol.

Mixtures of amino alcohols and/or dinitriles can,, if desired, also be applied according to the process of the subject invention.

Conversion generally takes place without a solvent, but it is also possible to add a suitable inert solvent. Preferably, an inert solvent is added after formation of the imino azacyclopentane polyol, the amino alcohol released during further reaction being subsequently distilled off, azeotropically or otherwise. This ensures that the amino alcohol can be removed more easily.

The invention will be elucidated on the basis of the following examples and the comparative experiment, without being limited thereto.

Example I

With stirring, 160 g of succinonitrile was dissolved in 488 g of ethanol amine (molar ratio 1:8). The reaction mixture was then heated for 6 hours to 120-130°C. The mixture started reacting at about 100°C, as could be deduced from the ammonia development. After no more

ammonia escaped, the ethanolamine excess was removed at 120-130°C and a pressure of 20-30 mm Hg.

Analysis of the resulting reaction product using ^-NMR indicated that it comprised 85% of l-(2- hydroxyethyl)-2,5-bis(2-hydroxyethyl imino)- azacyclopentane (the triol), calculated on the basis of the succinonitrile. In addition, it contained 5% of 2,5- bis(2-hydroxyethyl imino) azacyclopentane (the diol) and 8% of 2,2'-ethylene-bis(2-oxazoline) that had already been formed.

The reaction product thus obtained was subsequently heated at 160-170°C and a pressure of 20-30 mm Hg while nitrogen was being bubbled through it. The ethanolamine released was distilled over. After two hours the 2,2'-ethylene-bis(2-oxazoline) content was 60%, after four hours 85%, and after 6 hours 90%. Subsequently, the product was distilled at a bottom temperature of 160-180°C and a pressure of 5-10 mm Hg. The yield was 90%, calculated on the basis of the imino azacyclopentane polyol. The purity of the product obtained was 98%.

Example II With stirring, 80 g of succinonitrile was dissolved in 300 g of l-amino-2-propanol (molar ratio 1:4). The reaction mixture was then heated for 3 hours to 120-130°C. This reaction proceeded faster, as witness the fact that ammonia development stopped already after 3 hours. The l-amino-2-propanol still present was subsequently removed at a temperature of 120-130°C and a pressure of 20-30 mm Hg.

¹ H-NMR analysis of the reaction product indicated that l-(2-hydroxypropyl)-2,5-bis(2-hydroxypropyl imino)azacyclopentane had been formed. Further heating of this reaction product while nitrogen was bubbled through it at 120-130°C and a pressure of 20-30 mm Hg in two hours led to 2,2'-ethylene-bis(5-methyl-2-oxazolinej .

The yield was 90%, calculated on the basis of the succinonitrile. The purity of the product obtained was 95%.

Example III

With stirring, 80 g of succinonitrile was dissolved in 360 g of 2-amino-2-methyl-l-propanol (molar ratio 1:4). The reaction mixture was then heated for 3 hours to 120-130°C. After ammonia development had stopped, the 2-amino-2-methyl-l-propanol still present was removed at a temperature of 150°C and a pressure of 20-30 mm Hg.

¹ H-NMR analysis of the resulting reaction product indicated that no polyol had been formed but, rather, the desired l,2-bis(cyclic imino ether), viz. 2,2'-ethylene-bis-(4,4'-dimethyl-2-oxazoline) . Distillation of the reaction product at a temperature of 150°C and a pressure of 5 mm Hg yielded the desired 1,2- bis(cyclic imino ether) in a yield of 90%, calculated on the basis of the succinonitrile. The purity of the product obtained was 96%.

Comparative experiment

With stirring, 24.5 g of phthalodinitrile (1,2- dicyano benzene) was dissolved in 49 g of ethanolamine

(molar ratio 1:4). The reaction mixture was then heated for 6 hours to 120-130°C. After no more ammonia escaped, the ethanolamine excess was removed at 120-130°C and a pressure of 20-30 mm g Hg. ¹ H-NMR analysis of the reaction product obtained indicated that a large number of compounds had been formed, including 1,3-bis(2-hydroxyethyl imino)isoindolenine.

The reaction product thus obtained was subsequently heated at 160-170°C and a pressure of 20-30 mm Hg while nitrogen was bubbled through it. After 4 hours' heating a tarry material resulted, which contained no l,2-bis(cyclic imino ether).