Science Record

17

; oe and Co, the initial concentration

of the carboxyl group of dibasic acid in equivalent per kilogram.

where P is the extent of reaction, K =

The experimental procedures of this paper are the same as those in our first report. The results of the polyesterification reactions between equivalent

quantity ratios of succinic acid, glutaric acid, adipic acid, pimelic acid, suberic

acid, azelaic acid and sebacic acid with ethylene glycol, 1,2-propylene glycol, 1,4-butylene glycol, diethylene glycol and 1,6-hexamethylene glycol at 150°C in the absence of foreign acid respectively are shown in Table 1 and Figs. 1, 2, 3, 4 and 5 according to eq. (1). All the results are in conformity with a 2% order reaction. The mechanism of hydrogen ion catalysis in polyesterification reactions suggested by us is further examined here by a large amount of experimental data. The relationships between velocity constants and molecular structures of dibasic acids and glycols are plotted in Figs. 6 and 7. In Fig. 7 the coordinate axes are so selected that in the ordinate axis the original point for succinic acid, glutaric acid, adipic acid, etc., corresponds to zero, 1, 2, - ++ respectively; while in the abscissa axis we regard propylene glycol and hexamethylene glycol as having three and five carbon atoms of glycols respectively.

Table 1

The velocity constants of the polyesterification reactions between dibasic acids and glycols, Kel0? in (kg/equi.)9/2/min.

Dibasic acids Ethylene 1, 2-Propylene| Diethylene 1, 4-Butylene |1, 4-Hexamethy-

glycol glycol glycol glycol lene glycol Succinic acid 0.68 0.37 .80 65 2.24 Glutaric acid 0.64 0,34 B/D) 44 1,96 Adipic acid 0.57 0. 65 E27; 1.48 Pimelic acid 0.48 0.28 64 .07 1.67 Suberic acid 0.57 0.30 .61 a7, 1.49 Azelaic acid 0.61 0.30 .63 a2 1.49 Sebacic acid 0.70 0.36 69 1.39 fear

From Table 1 and Fig. 6 it is clearly shown that the velocity constants of the polyesterification reactions between a same glycol with dissimilar dibasic acids almost have no difference, their average values all varying in the range of +207. This explains that two carboxyl groups at the end of the molecule have the same velocity constant independent of the number of carbon atoms in the midst of the chain for the dibasic acid.

From Table | and Fig. 7 it is also obviously seen that the relationships of the velocity constants of the polyesterification reactions between a same dibasic acid with different glycols are essentially the same independent of the chainlength of the molecules themselves. This explains that the effects between two hydroxyl groups at the end of the molecule with each other may be