Polyamines containing urea groups

The present invention relates to novel polyamines containing urea groups and a process for the preparation of these polyamines, represented by the general formula: ##STR1## where n is: 2.ltoreq.n.gtoreq.1; and R denotes an alkylene radical having 2-14 C atoms which may optionally be substituted by 1-3 CH.sub.3 or C.sub.2 H.sub.5 groups, or 1-3 CH.sub.2 groups of the alkylene radical R may be substituted by --O--, --NH-- or --NCH.sub.3 --.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to novel polyamines containing urea groups 
and a process for the preparation of these polyamines. 
2. Discussion of the Background 
The epoxy resins based on bisphenol A and cured with polyamines are 
distinguished in practice by a number of desirable properties, such as, 
for example, good adhesion to all possible substrates, good solvent 
resistance and chemical resistance. These properties of the cured 
polyamine/epoxy mixtures could be further improved if the polyamines 
contained urea groups. The preparation of polyamines containing urea 
groups by condensation of 2 mol of polyamine and 1 mol of urea leads to 
solids or highly viscous products which cannot be processed without 
solvents. 
SUMMARY OF THE INVENTION 
It is thus the object of the present invention to provide a process which 
permits the preparation of polyamines which contain urea groups and are 
processable at room temperature with epoxy resins. 
Surprisingly, this object could be achieved by condensing urea in the 
presence of a large excess of polyamine, of 1:(2-30), preferably 1:(5-20), 
and removing the unconverted polyamine from the reaction product 
comprising the polyamine containing urea groups, by evaporation in a 
thin-film evaporator. 
The present invention thus relates to a polyamine containing a plurality of 
urea groups and having the following general formula: 
##STR2## 
where n is: 2.ltoreq.n.gtoreq.1; R represents an alkylene radical having 
1-14 C atoms which may optionally be substituted by 1 to 3 CH.sub.3 or 
C.sub.2 H.sub.5 groups, or 1 to 3 CH.sub.2 groups of the alkylene radical 
R may be substituted by --O--, --NH-- or --NCH.sub.3 --. 
The compounds according to the invention are characterized by a basic amine 
content of 4-14 mmol NH.sub.2 /g. 
The concentration of urea groups in the polyamines according to the 
invention is 4-13 mmol/g. The viscosity of the compounds according to the 
invention at 25.degree. C. varies from 5,000 to 100,000 mPas. 
The present invention furthermore relates to a process for the preparation 
of polyamines which contain urea groups and are processable at room 
temperature, characterized in that urea is reacted with polyamines having 
the following composition: 
EQU H.sub.2 N--R--NH.sub.2, 
at a molar ratio of urea to polyamine of 1:(2-30), preferably 1:(5-20),in 
such a way that the mixture is first heated to 130.degree.-150.degree. C. 
until about 80% of the calculated amount of NH.sub.3 has been liberated 
and is further heated slowly to 180.degree.-220.degree. C., preferably to 
200.degree. C. until NH.sub.3 has been substantially quantitatively 
eliminated, and, after the reaction is complete, the unconverted polyamine 
is separated from the reaction product by evaporation in a thin-film 
evaporator at a temperature of 100.degree.-180.degree. C. and under a 
reduced pressure of between 0.05 to 0.2 mmHg, preferably of 0.1 mmHg; 
where R denotes an alkylene radical having 2-14 C atoms, which may 
optionally be substituted by 1-3 CH.sub.3 or C.sub.2 H.sub.5 groups, or 
1-3 CH.sub.2 groups of the alkylene radical R may be substituted by --O--, 
--NH-- or --NCH.sub.3 groups, 
The polyamines to be used for the purposes of the present invention are 
open-chain amines, such as, for example, ethylenediamine, 
1,2-propanediamine, 1,3-diaminopropane, 1,4-diaminobutane, 
neopentanediamine, 2-methylpentamethylenediamine, 
5-methylnonamethylenediamine, 4,7-dioxadecane-1,10-diamine, 
4,9-dioxadodecane-1,12-diamine, 4,7,10-trioxatridecane-1,13-diamine, 
2,2,4(2,4,4)-trimethylhexamethylenediamine, diethylenetriamine, 
dipropylenetriamine or N,N'-bis-(3-aminopropyl)-ethylenediamine. 
In the process according to the invention, urea and the stated polyamines 
are reacted with one another in a molar ratio of 1:(5-20) and, after the 
reaction is complete, i.e. after elimination of NH.sub.3, the unconverted 
polyamine is separated off in a second stage by evaporation in a thin-film 
evaporator. 
In the condensation of the urea with the polyamine, the components are 
heated in the stated molar ratio at a temperature of 
130.degree.-150.degree. C. until about 80% of the expected amount of 
NH.sub.3 has been liberated. Thereafter, in order to complete the 
reaction, the mixture is heated slowly to 180.degree.-220.degree. C., 
preferably to 200.degree. C. and is heated further until the elimination 
of NH.sub.3 is quantitative. The reaction mixture is then cooled and, 
after intermediate storage at room temperature, the unconverted polyamine 
is removed at a temperature of 100.degree.-180.degree. C. and a reduced 
pressure of 0.05 to 0.2 mmHg, preferably of 0.1 mmHg by means of 
evaporation in a thin-film evaporator. The temperature at which the 
polyamine is separated off by evaporation in a thin-film evaporator 
depends on the boiling point of the polyamine to be separated off. The 
higher its boiling point, the higher is the temperature at which the 
polyamine is separated off in the thin-film evaporator (under a reduced 
pressure of about 0.05 to 0.2 mmHg). 
The compounds according to the invention are exceptionally suitable for 
curing epoxy resins at room temperature. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
For the purpose of illustration only, the invention will be described in 
connection with certain preferred embodiments. However, it is recognized 
that various modifications, changes, additions and improvements may be 
made in the preferred embodiments without departing from the spirit and 
scope of the invention. 
GENERAL PREATION METHOD FOR THE CONDENSATION OF POLYAMINES WITH UREA 
Area and a polyamine present in a molar ratio of 1:(5-20) are heated at 
about 150.degree. C. with thorough stirring for about 5 hours until about 
80% of the amount of NH.sub.3 has been liberated. Thereafter, in order to 
complete the reaction, the temperature of the mixture is raised to 
200.degree. C. and kept at that temperature for about 1 hour. Most often, 
the reaction is completed under these conditions. 
The ammonia liberated in the reaction is collected in a 2N H.sub.2 SO.sub.4 
solution, the content of which is tested at regular intervals. The 
reaction can be readily monitored in this way.

EXAMPLE 1 
a) Urea was reacted with 2-methylpentamethylenediamine in a molar ratio of 
1:8 under the conditions described in the general preparation method for 
the condensation of polyamines with urea. The reaction mixture had a basic 
amine content of 14.3 mmol NH.sub.2 /g. 
b) The reaction mixture la was evaporated in a thin-film evaporator at 
100.degree. C. under vacuum of 0.1 mbar in order to separate off the 
unconverted 2-methylpentamethylenediamine. The reaction product, which 
remains as the residue after the evaporation in the thin-film evaporator, 
had a viscosity of 12,500 mPas at 25.degree. C.; the basic amine content 
was 6.8 mmol NH.sub.2 /g; the 2-methylpentamethylenediamine content was 
0.7%. 
EXAMPLE 2 
a) Urea was reacted with 2,2,4(2,4,4)-trimethylhexamethylenediamine (TMD) 
in a molar ratio of 1:10, as described in Example 1a. The reaction mixture 
had a basic amine content of 10.8 mmol NH.sub.2 /g. 
b) The reaction mixture from 2a was evaporated in a thin-film evaporator at 
110.degree. C. and 0.1 mbar in order to separate off the unconverted TMD. 
The reaction product, the residue from the evaporation in the thin-film 
evaporator, had a viscosity of 70,000 mPas at 25.degree. C.; the basic 
amine content was 5.1 mmol NH.sub.2 /g; the TMD content was 0.6%. 
EXAMPLE 3 
a) Urea was reacted with diethylenetriamine in a molar ratio of 1:10, as 
described in Example 1a. The reaction mixture had a basic amine content of 
16.8 mmol NH.sub.2 /g. 
b) The reaction mixture from 3a was evaporated in a thin-film evaporator at 
100.degree. C. and 0.1 mbar in order to separate off the unconverted 
diethylenetriamine. The reaction product had a viscosity of 15,200 mPas at 
25.degree. C.; the basic amine content was 11.5 mmol NH.sub.2 /g; the 
diethylenetriamine content was 0.6%. 
EXAMPLE 4 
a) Urea was reacted with 5-methylnonamethylenediamine in a molar ratio of 
1:15, as described in Example 1a. The reaction mixture had a basic amine 
content of 10.5 mmol NH.sub.2 /g. 
b) The reaction mixture from 4a was evaporated in a thin-film evaporator at 
110.degree. C. and under vacuum of 0.1 mbar in order to separate off the 
unconverted 5-methylnonamethylenediamine. The reaction product had a 
viscosity of 51,000 mPas at 25.degree. C.; the basic amine content was 5.1 
mmol NH.sub.2 /g; the 5-methylnonamethylenediamine content was less than 
0.7%.