Metering of peroxidic polymerization initiators at elevated pressure

Metering of polymerization initiators, which has to take place at relatively low temperatures to prevent premature decomposition, involves the risk of the initiators crystallizing out at the high pressures involved. For this reason, the solubility of different peroxides, which are highly efficient initiators for radical chain polymerization, was investigated in isododecane and other commonly used solvents. The measurements were carried out at temperatures of −30 to +40°C and pressures up to 3000 bar in ranges of concentration between 50 and 100 wt.‐%. It was found that both tert.‐butyl perpivalate and tert.‐butyl perbenzoate, and to a lesser extent, di‐tert. ‐butyl peroxide, need to be diluted in order to avoid undesirable precipitation of solids. A substantial improvement in the solubility of the peroxides examined could be achieved by replacing the tertiary butyl group with a tertiary amyl group. On the basis of the solubility values determined, recommendations are made on the necessary dilution of the peroxides and the choice of solvent.