Aggregation characterization

The ring-opening polymerization of traditional caprolactam, 12-lactam and other lactam has many different ways, but the ring-opening polymerization of butyrolactam is relatively difficult because of its special five-membered ring structure stability, so the polymerization of Polyamide 4 is mainly conducted by anionic ring-opening polymerization. The classic polymerization process of Polyamide 4 is to react butyrolactam with basic catalyst to prepare butyrolactam anion, and then add activator for polymerization reaction to get Polyamide 4. According to the traditional anionic ring-opening polymerization theory, the polymerization of Polyamide 4 theoretically is a controlled polymerization, and its molecular weight is strictly related to the ratio of activator to butyrolactam. However, in the actual polymerization practice, the process of synthesis of Polyamide 4 by anionic polymerization is completely uncontrollable. It is almost impossible to obtain stable and adjustable Polyamide 4.

FIG. 1 Polymerization process of Polyamide 4

This phenomenon is closely related to the triple transmission in the polymerization process of Polyamide 4. In the polymerization process, the polymerization rate is very fast, and the crystallization of Polyamide 4 is very strong, which makes the polymerization system heterogeneous polymerization. The momentum transfer, heat transfer and mass transfer in the polymerization process are greatly inhibited, so the reaction will randomly occur chain termination reaction, resulting in the overall polymerization is uncontrollable. Therefore, Polyamide 4 prepared by the traditional method is not only low molecular weight, wide molecular weight distribution, low monomer conversion and batch instability, the reaction process and reaction results are not controllable, and it is not practical value.

Bacskai studied the thermal stability of Polyamide 4 oligomers with low polymerization degree, and the results showed that in the melting state, Polyamide 4 oligomers had an obvious trend of conversion to thermodynamically more stable butyrolactam, and proved that the molecular weight distribution of Polyamide 4, catalyst residues and end groups had a great influence on the thermal decomposition temperature of Polyamide 4.

Therefore, the development of the controlled polymerization process of Polyamide 4 is particularly important, which is not only the basis of its large-scale synthesis, but also the key to the processing performance. Shanghai Institute of Cleantech Innovation, has a deep technical accumulation in the development of the controlled polymerization process of Polyamide 4. And the successful development of 20-50L complete sets of polymerization process and equipment and a variety of modified Polyamide 4, is currently developing 100 tons of polymerization process and the corresponding process design, can provide kg samples, welcome to exchange and discuss.