Lactams diisocyanates

In this study a diisocyanate or the product of the reaction between a diisocyanate and the impact modifier was used as accelerator. The polymerization was catalysed with common basic catalysts such as potassium lactamate, sodium lactamate and/or bromomagnesium lac tamate. 

There are five primary methods to polymerize nylon. They are reaction of a diamine with a dicarboxylic acid, condensation of the appropriate amino acid, ring opening of a lactam, reaction of a diamine with a diacid chloride, and reaction of a diisocyanate with a dicarboxyhc acid. ... 

Spectroscopic evidence of the seven-membered rings has been found in the preparation of polyimides from pyromellitic dianhydride and methylenediphenyl-diisocyanate (MDI) [105]. The reaction is conducted in solution of aprotic solvents, with reagents addition at low temperature and a maximum reaction temperature of about 130 °C. On the other hand, polyimides of very high molecular weight have not been reported by this method. The mechanism is different when the reaction is accelerated by the action of catalysts. Catalytic quantities of water or alcohols facilitate imide formation, and intermediate ureas and carbamates seem to be formed, which then react with anhydrides to yield polyimides [106]. Water as catalyst has been used to exemplify the mechanism of reaction of phthalic anhydride and phenyl isocyanates, with the conclusion that the addition of water, until a molecular equivalent, markedly increases the formation of phthalimide [107] (Scheme 13). The first step is actually the hydrolysis of the isocyanates, and it has been claimed that ureas are present in high concentration during the intermediate steps of the reaction [107]. Other conventional catalysts have been widely used to accelerate this reaction. Thus, tertiary amines, alkali metal alcoholates, metal lactames, and even mercury organic salts have been attempted [108]. 

Caprolactam can be polymerized in the melt by use of a base and an activator. Two components, I and II, are used as starting materials. Component I is a catalyst-containing lactam melt and component II is an activator-containing lactam melt. The catalyst can be the sodium salt of caprolactam and the activator can be a derivative of caprolactam such as that prepared by the reaction of caprolactam with acetic anhydride or a diisocyanate [19]. The following example uses the derivative of caprolactam withhexamethylene diisocyanate. 

It is apparent that a jxrssible preparation of the block copolymers of lactams and a lactone (i.e. CL, LL and CLO) must be kineticaUy controlled in order to suppress the transamidation and transacylation reactions a short polymerization time and an intensive stirring must be guaranteed. When a,(D-dihydroxy poly (e-caprolactone), functionaUzed ex situ by diisocyanates (MDI), was used as a starting substance, the gradual charging of this material into the Brabender internal mixer, together with a partially polymerized feed (LL, NaH, AcCL 13) yielded a copolymer in which longer sequences of e-caprolactone units were present [74]. 

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