Bis(aminopropyl) arylacetonitriles and preparation thereof

This invention relates to new aliphatic diamines containing cyanide groups, a process for their preparation by hydrogenation of the corresponding trinitriles and their use as chain lengthening agents in the isocyanate polyaddition process.

BACKGROUND OF THE INVENTION 
It is known that 2 molecules of acrylonitrile can be added to aryl 
substituted acetonitriles. As described by Bruson and Reiner in 
J.Amer.Chem.Soc. 64. 2850 (1942) and U.S. Pat. No. 2,305,529, the reaction 
proceeds smoothly and in high yields to trinitrile compounds of the 
general formula 
##STR1## 
It is also known from a publication by Badger et al. in J.Chem.Soc. 1949, 
1141-4, that hydrogenation of such trinitrile compounds may lead to 
cyclized products or decomposition products, e.g. 3-phenyl-piperidine, 
ammonia and other, unidentified high melting basic compounds. 
U.S. Pat. No. 3,661,918, however, describes the formation of a bicyclic 
tertiary amine compound of the formula 
##STR2## 
which is obtained from the above phenyl substituted trinitrile compound by 
varying the hydrogenation conditions. 
All the above mentioned hydrogenation products are thus either secondary or 
tertiary amines. 
The amino compounds mentioned above are not suitable for the production of 
high molecular weight synthetic resins by the isocyanate addition process 
which mainly requires difunctional components. 
It has now surprisingly been found that the above mentioned trinitriles can 
be hydrogenated in such a way that new diamines are obtained in high 
yields. These new diamines still contain an unchanged nitrile group. 
Because of the presence of this nitrile group, the new diamines are 
suitable for the production of nitrile-containing polyurethane ureas or 
polyureas by the isocyanate polyaddition process. The nitrile-containing 
polyaddition products obtained using the new diamines as chain lengthening 
agents are distinguished by numerous remarkably advantageous properties, 
in particular their excellent adherence to a variety of substrates and 
their exceptional oil resistance. 
SUMMARY OF THE INVENTION 
The present invention, thus, relates to compounds of the formula 
##STR3## 
in which Ar represents an aromatic hydrocarbon group having from 6 to 14 
carbon atoms and which may carry one or more substituents which are inert 
towards amino groups and 
R represents hydrogen or an aliphatic hydrocarbon group having from 1 to 4 
carbon atoms. 
The present invention also relates to a process for the preparation of 
these new compounds, characterized in that the trinitriles of the formula 
##STR4## 
in which Ar and R have the meaning indicated above, 
are hydrogenated in solvents or solvent mixtures containing at least about 
80% by weight of one or more weakly polar or non-polar organic solvents, 
at temperatures below about 130.degree. C and in the presence of 
hydrogenation catalysts. 
Finally, the invention relates to the use of the new diamines as chain 
lengthening agents in the production of polyurethane ureas or polyureas by 
the isocyanate polyaddition process. 
DETAILED DESCRIPTION OF THE INVENTION 
The trinitriles to be used in the process according to the invention are 
obtainable according to U.S. Pat. No. 2,305,529, incorporated herein by 
reference, from arylacetonitriles of the formula 
EQU Ar -- CH.sub.2 -- C.tbd.N 
and acrylonitriles of the formula 
##STR5## 
in which formula, as well as in the preceding and following formula, Ar 
represents an aromatic hydrocarbon group having from 6 to 14 carbon atoms, 
preferably a phenyl group, which may be substituted by one or more 
substituents which are inert towards amino groups, and 
R represents hydrogen or an aliphatic hydrocarbon group having from 1 to 4 
carbon atoms, preferably hydrogen or a methyl group and most preferably 
hydrogen. 
Possible substituents on the group Ar include in particular halogen, 
preferably chlorine, C.sub.1 to C.sub.4 alkyl, preferably methyl, or 
C.sub.1 to C.sub.4 alkoxy, preferably methoxy groups. 
Examples of suitable arylacetonitriles include phenylacetonitrile, 
naphthylacetonitrile, 4 -chlorophenylacetonitrile and 
4-methoxyphenylacetonitrile. Phenylacetonitrile is preferred. 
Examples of suitable acrylonitriles include acrylonitrile, 
methacrylonitrile, ethyl-acrylonitrile and butylacrylonitrile. 
Acrylonitrile and methacrylonitrile are preferred, particularly 
acrylonitrile. 
The groups Ar and R in the compounds according to the invention are the 
same as the corresponding groups Ar and R in the above mentioned starting 
compounds. 
When carrying out the process according to the invention, the trinitriles 
of the following formula prepared from the aforesaid starting materials: 
##STR6## 
in which Ar and R have the meaning indicated above, 
are dissolved in an organic solvent or a mixture of several organic 
solvents. The concentration of the solution should be between about 15 and 
40% by weight. At least about 80% by weight of the solvent or solvent 
mixture should consist of a weakly polar or non-polar organic solvent, 
that is to say a solvent with a dielectric constant (DIN 53483) below 
about 7. 
The following are examples of such solvents: 
Aromatic hydrocarbons, which may be alkyl substituted, e.g. benzene, 
toluene, ethylbenzene, o-, m- or p-xylene, chlorobenzene or anisole; 
aliphatic and cycloaliphatic hydrocarbons such as octane, nonane, and 
decane and their isomers, cyclohexane, methylcyclohexane, ethylcyclohexane 
and dimethylcyclohexane as well as commercial solvent mixtures having a 
dielectric constant below about 7, such as the usual commercial petroleum 
ethers. Aromatic hydrocarbons are preferred. 
The solvent mixtures used in the process according to the invention may 
contain up to about 20% by weight, preferably about 0 to 10% by weight of 
polar solvents, i.e. solvents with dielectric constants (DIN 53483) above 
about 7. 
Examples of such solvents include methanol, ethanol, propanol and their 
higher homologues as well as araliphatic alcohols, e.g. benzyl alcohol. 
It is preferred to carry out the process without the addition of polar 
solvents. Hydrogenation of the starting compounds is carried out by known 
methods using hydrogen, preferably with the addition of ammonia, in an 
autoclave. According to the invention, the reaction temperature should not 
exceed about 130.degree. C and is preferably maintained between about 
80.degree. and 130.degree. C. The reaction proceeds particularly smoothly 
and in high yields at a temperature of from about 100.degree. to 
120.degree. C. 
The autoclave pressure during hydrogenation is preferably maintained at 
about 120 to 200 bar, in particular 140 to 170 bar. 
Hydrogenation is preferably carried out in the presence of a catalyst. 
Raney cobalt and Raney nickel are suitable hydrogenation catalysts. Other 
catalysts based on platinum or palladium may in principle also be used but 
Raney cobalt is preferred. 
The solutions of diamines according to the invention obtained as described 
above may be freed from hydrogenation catalyst by filtration and then used 
in this form for various purposes; for example they may be worked up into 
solutions of the corresponding isocyanates by known methods. Also, the 
solvents may be removed by distillation, the diamines according to the 
invention then being left behind as pale yellow, low viscosity liquids. It 
is a particular advantage of the process according to the invention that 
the diamines are obtained in a highly pure state very suitable for 
commercial purposes and do not require the usual processes of purification 
by distillation or chromatography. 
The diamines according to the invention are eminently suitable for use as 
chain lengthening agents for the production of lightfast polyurethane 
elastomers or polyurea elastomers. They are also valuable components for 
the formation of polyamides and for hardening polyepoxides. 
When the diamines according to the invention are used as chain lengthening 
agents, they may be used instead of or as mixtures with the chain 
lengthening agents conventionally used in polyurethane chemistry. One 
possible use of the new diamines, and one which is preferred according to 
the present invention, is as chain lengthening agents in the preparation 
of aqueous polyurethane dispersions. For this purpose, prepolymers 
containing free isocyanate groups are reacted with aqueous solutions of 
the diamines according to the invention. Polyurethane polyureas and 
polyureas produced with the aid of the new diamines are distinguished by 
their excellent adherence to any substrates and exceptionally high oil 
resistance. 
The following Examples serve to explain the invention more fully without 
restricting it.

EXAMPLES 
PREATION OF STARTING COMPOUNDS 
EXAMPLE 1 
3-Phenyl-pentane-1,3,5-tricarboxylic acid trinitrile may be prepared either 
as described by Bruson and Riener in J.Amer.Chem.Soc. 65, 23 (1943) or as 
follows: 
450 g (8.5 mol) of acrylonitrile are added dropwise to a mixture of 468 g 
(4 mol) of benzyl cyanide, 14 g of potassium hydroxide (3%), 240 ml of 
dioxane and 160 ml of water at room temperature with stirring and at such 
a rate that the temperature is maintained at 30.degree. to 35.degree. C, 
if necessary with cooling. Stirring is then continued for a further 2 
hours to complete the reaction. The crystalline paste is acidified, 
diluted with methanol/water, suction filtered and dried. 840 g (94% of the 
theory) of colorless crystals melting at 70.degree. C are obtained. 
EXAMPLE 2 
3-(4-Chloro-phenyl)-pentane-1,3,5,-tricarboxylic acid trinitrile 
212 g (4 mol) of acrylonitrile are added dropwise to a mixture of 302 g (2 
mol) of 4-chlorophenylacetonitrile, 10 g of potassium hydroxide, 400 ml of 
dioxane and 20 ml of water at 40.degree. C with stirring at such a rate 
that the temperature is maintained at 40.degree. to 45.degree. C. Stirring 
is continued for 6 hours at room temperature after all the acrylonitrile 
has been added. The crystalline paste which precipitates is acidified with 
dilute hydrochloric acid suction filtered, washed with methanol and dried. 
450 g (87% of the theory) of colorless crystals, m.p. 122.degree. C, are 
obtained. 
PROCESS ACCORDING TO THE INVENTION 
EXAMPLE 3 
4-Amino-1-aminopropyl-1-phenyl-butane carboxylic acid nitrile. 
1800 g of the trinitrile compound prepared according to Example 1 are 
hydrogenated in 4500 ml of toluene to which 500 g of liquid ammonia are 
added, hydrogenation being carried out in a 10 liter autoclave in the 
presence of 200 g of Raney cobalt at 115.degree. C and a pressure of 150 
bar until uptake of hydrogen is completed. After removal of the catalyst 
by filtration and concentration of the hydrogenated solution by 
evaporation under a vacuum of 14 Torr, a pale yellow oil is left behind. 
According to gas chromatographic determination, this oil contains the 
desired diamine in a degree of purity of 96%. The constitution of this 
diamine is confirmed by its IR, NMR and mass spectrum and by GC-MS 
coupling and quantitative analysis: 
C.sub.14 H.sub.21 N.sub.3 (Mw 231) Calculated: C 73.0 H 9.1 W 18.2 Found 
72.7 9.1 18.0 
EXAMPLE 4 
4-Amino-1-aminopropyl-1-phenyl-butane carboxylic acid nitrile (see Example 
3) 
600 g of the trinitrile compound prepared according to Example 1 are 
hydrogenated in a mixture of 1100 ml of cyclohexane, 100 ml of methanol 
and 250 g of ammonia in a 3 liter autoclave in the presence of 70 g of 
Raney cobalt at 110.degree. C and a pressure of 170 bar until uptake of 
hydrogen is completed. The reaction mixture is then worked up as described 
in Example 3. The diamine is obtained as a pale yellow oil which is 98% 
pure. 
EXAMPLE 5 
(Comparison Example) 
4a-Phenyl-1,2,3,4,4a, 5,6,7-tetrahydro-1,8-naphthryridine 
##STR7## 
600 g of the trinitrile compound prepared according to Example 1 are 
hydrogenated in 1100 ml of methanol and 200 g of ammonia in a 3 liter 
autoclave in the presence of 70 g of Raney cobalt at 150.degree. C and a 
pressure of 150 bar until uptake of hydrogen is completed. The products 
obtained after working up the reaction mixture as described in Example 3 
is a solid which recrystallizes from methanol to yield 400 g (70% of the 
theory) of colorless crystals melting at 152.degree. C. 
The constitution of this amine is confirmed by its IR, NMR and mass 
spectrum. 
EXAMPLE 6 
4-Amino-1-aminopropyl-1-(4-chlorophenyl)-butane carboxylic acid nitrile 
500 g of the trinitrile compound prepared according to Example 2 are 
hydrogenated in 1400 ml of toluene and 200 g of ammonia in a 3 liter 
autoclave in the presence of 65 g of Raney cobalt at 115.degree. C and a 
pressure of 150 bar until uptake of hydrogen is completed. After removal 
of the catalyst by filtration and concentration of the hydrogenated 
solution by evaporation under vacuum of 14 Torr at 90.degree. C, a pale 
yellow oil is left behind. 
According to gas chromatographic determination, this oil contains the 
desired diamine in a degree of purity of C.sub.14 H.sub.20 N.sub.3 Cl (Mw 
265). 
Although the invention has been described in detail for the purpose of 
illustration, it is to be understood that such detail is solely for that 
purpose and that variations can be made therein by those skilled in the 
art without departing from the spirit and scope of the invention except as 
it may be limited by the claims.