TABLE OF CONTENTS The reaction between dialkanolamines with organic acids or better still with their methyl esters gives the well known dialkanolamides. This reaction is used industrially for the synthesis of diethanolamides of fatty acids, which are well known nonionic surfactants (reaction 19.1) [1-10]:
| (19.1) |  |
With methyl esters of fatty acids, the reaction takes place at a higher yield (around 90-92%) as compared to the free fatty acids (the yield is 60-70%) [2, 7-9]. The catalysts of this amidation reaction are: KOH, NaOH, CH 3ONa, CH 3OK, etc. (the most used catalyst is sodium methylate). The diethanolamides of fatty acids, as presented in Chapter 17, are used sometimes as copolyols in rigid polyurethane (PU) foams, to improve the compatibility of other rigid polyols with pentanes, used as blowing agents [4-8].
By using the principles of this classic reaction, new aromatic polyols were created, based on the reaction between dimethyl phthalate, dimethyl isophthalate and dimethylterephthalate with diethanolamine, using sodium or potassium methylate as catalyst (reactions 19.2, 19.3 and 19.4):
| (19.2) |  |
| (19.3) |  |
| (19.4) |  |
A partial esterification reaction takes places (19.5). This side reaction does not have a negative effect on rigid PU foam fabrication because it gives a very convenient tetrafunctional compound, which participates, together with the amidic polyol, to build the crosslinked structure of polyurethane. These compounds containing ester groups are present in low concentrations, maximum 5-7% [1, 2].
| (19.5) |  |
Except for the diamide derived from phthalic acid (19.2) which is a viscous liquid at room temperature, the diamides...
