A non‐hydrolytic polymerization of ϵ‐caprolactam. The polymerization initiated by hydrogen chloride

Abstract

Some experiments are described which show that the polymerization of ϵ‐caprolactam (CL) can be accomplished by heating the lactam under anhydrous conditions in the presence of hydrogen chloride or of salts of strong acids and ammonia or amines at temperatures of 220–260°C. To study this type of polymerization more closely, two series of kinetic experiments with the sytem CL–HCl hae been performed (254°C.; initial molar ratios of HCl to CL, 0.025 and 0.0125). The progress of the reaction, characterized by the degree of conversion (determined by extraction of the unconverted lactam with water), is compared with the polymerization of CL initiated by corresponding amounts of water or of ϵ‐aminocaproic acid. The products obtained have been characterized by endgroup titration values and intrinsic viscosity. Some additional data have been obtained by chromatography and IR investigations. The titrations show that the molecules bear an amino group at one end of the chain; the nature of the other endgroup is still obscure. Reaction constants calculated for an uncatalyzed additon of CL to amino groups prove to be of about the same magnitude as those of the water‐initiated polymerization without additional HCl. At the same time some kinetic experiments with the system CLH2OHCl are presented. Both systems have some striking features in common. The catalytic effect of the HCl present in this system can be attributed to the rapid formation of amino groups in the very first moments of the reaction, thus leading to an enhanced rate of polymerization by addition of CL to amino groups.

Cationic Ring Opening polymerization of ε-caprolactam by a Montmorillonite Clay Catalyst

“…Poly (ε-caprolactam) usually known as (nylon 6 or Polyamide 6) are an attractive class of nylons, and have been applied very widely due to their excellent tensile properties, low friction, high melting point, and chemical and wear resistance [3,4,5], it is synthesized by ring opening polymerization of ε-caprolactam. The cationic polymerization of ε-caprolactam and its reaction mechanism has been studied for many years in the presence of cationic initiators [6][7][8][9][10][11]. Various strong protonic acids able to promote the polymerization of ε-caprolactam have been reported [12][13][14][15][16][17][18].…”

Untersuchung der basischen Endgruppen bei der mit Aminsalzen initiierten kationischen Lactampolymerisation

“…Bei einer Initiatorkonzentration iiber 1 M01-7~ wird 1 g, bei 1 Mol-yo oder niedrigeren Initiatorkonzentrationen werden ca. 2…”

Über Probleme der kationischen Polymerisation des Caprolactams. VI. Die Konzentrationsänderung der funktionellen Gruppen bei der durch Salzsäure katalysierten Polymerisation

“…Daraus ergibt sich, dalj im Laufe der Polymerisation die Konzentration der funktionellen Gruppen zu einem konstanten, aber kleineren als der Ausgangskonzentration des Katalysators (Ao) entsprechenden Wert konvergieren muR, obwohl die bisherigen Untersuchungen zu einem abweichenden Ergebnis fiihrten4* 6,9,11,12). Die Konzentration des Caprolactam-hydrochlorids nimmt mit der Zeit bis zum Wert 0 ab, die der salzsauren Salze der basischen Endgruppen (Primaramin-hydrochloride9711712)) dagegen bis zum Erreichen der Ausgangskonzentration der Salzsaure zu.…”