New limits on di-nucleons decay into invisible channels

Data of the radiochemical experiment (E. L. Fireman, 1978) with 1.7 t of KC$_2$H$_3$O$_2$, accumulated deep underground during $\simeq$1 yr, were reanalyzed to set limits on di-nucleons ($nn$ and $np$) decays into invisible channels (disappearance, decay into neutrinos, etc.). The obtained lifetime bounds $\tau_{np}>2.1\cdot 10^{25}$ yr and $\tau_{nn}>4.2\cdot 10^{25}$ yr (at 90% C.L.) are better (or competitive) than those established in the recent experiments.