Development of highly reactive hardening agents for MP tapes

The reactivity of isocyanate groups was examined using molecular orbital ca lculations and magnetochemical measurements. We found a linear relationship between the logarithm of kinetic constants for the addition reaction of th e phenylisocyanates with 2-ethylhexanol and the atomic charges of the carbo n atoms in the isocyanate group. A linear relationship was also found betwe en the kinetic constants and the C-13 chemical shifts of the same carbon. O n the basis of these relationships. a new hardening agent consisting of Cl- substituted phenyldiisocyanates (CPDI) was synthesized. The degree of cross -linking of the binder film was improved by using the new highly reactive h ardening agent. Furthermore, the loss of signal amplitude of MP tape using the new agent was less than that using the conventional agent in pause mode test. (C) 1999 Elsevier Science B.V. All rights reserved.