Chemistry Reference
In-Depth Information
7.3.2 Fatty Polyamides
The fatty polyamides are produced by reacting di- and polyfunctional amines with polybasic acids
that result from condensations of unsaturated vegetable oil acids. The most commonly used amines
are ethylene diamine and diethylene triamine. The dicarboxylic acids are synthesized by heating
mixtures of unsaturated vegetable fatty acids. The starting materials may come from linseed, soybean,
or tung (also called China wood) oil. The fatty acids are heated for several hours at 300
C. If a catalyst
is used, the heating is done at a lower temperature. After condensation, the volatile fractions are
removed by vacuum. The residues, called
dimer acids
, are then condensed with the amines. A
formation of one such dimer acid from linoleic acid can be illustrated as follows:
5
7
COOH
isomerized linoleic acid
COOH
4
7
linoleic acid
5
4
COOH
HOOC
7
7
The polyamide from the above shown dimer acid condensed with a diamine, like ethylene
diamine, can be illustrated as follows:
5
H
O
H
O
4
N
N
N
7
N
7
H
H
Two types of fatty polyamides are available commercially, solid and liquid. The solid polymers
are mostly linear condensation products of diacids and diamines that range in molecular weights from
2,000 to 15,000. The liquid ones are highly branched, low molecular weights materials produced by
condensations of the dimer acids with triamines and even higher polyamines.
7.3.3 Special Reactions for Formation of Polyamides
There are occasional reports in the literature on use of special reactions to form polyamides. One is a
synthesis via enamines. In this case, diisocyanates are condensed with cyclopentanone enamines of
morpholine or of piperidine [
77
]:
