Polymide prepolymer of addition reacted type, prepreg obtained therefrom, and the method of producing laminate from said prepreg

Abstract From the Canadian patent

Superior polyimide prepolymers particularly suitable for fabrication of multi-layer printed boards are produced by reacting unsaturated bisimides with diamines to consist essentially of 41 - 55% of unreacted reactants, 39 - 54% of components having a molecular weight of between 400 and 15000, and 3.0 - 6.8% of components having a molecular weight of more than 15000. The resulting prepolymers enable the preparation of their solution having enough working life for successfully impregnating a given substrate therewith in the preparation of prepregs. The prepregs, prepared from the above prepolymers in such a way as to contain within the resin content thereof 29 - 35% of of unreacted reactants …