CAPROLACTAM COMPOSITION, METHOD FOR MAKING A SEALING ELEMENT, AND RESERVOIR

Composition comprises azepan-2-one monomer (I) at 70-90 wt.%, an epsilon-caprolactam activator (II) at 0.1-1 wt.%, an epsilon-caprolactam catalyst (III) at 2-6 wt.%, and oxepan-2-one (IV) at 10-20 wt.%. Composition comprises azepan-2-one monomer (I) at 70-90 wt.%, an epsilon-caprolactam activator at 0.1-1 wt.% of formula (II), an epsilon-caprolactam catalyst at 2-6 wt.% of formula (III), and oxepan-2-one (IV) at 10-20 wt.%. R : C nH 2n+2, OH, OC nH 2n+2 or NHR-a; n : 1-10; R-a : C nH 2n+2 or NH 2; and X : MgBr, MgI, Li or Na. Independent claims are included for: (1) a process of making a sealing cover comprising preparing and introducing the composition in a rotational molding, subjecting anionic polymerization of the composition to form polycaprolactam at a temperature greater than equal to the melting point of the monomer and less than the melting point of polycaprolactam using the rotation mold, where the polycaprolactam is obtained without melting, crystallizing the obtained polycaprolactam, and demolding the obtained caprolactam bag; and (2) a type IV reservoir (1) and a hydraulic accumulator comprising the sealing envelope (2) obtained by the process.