The invention discloses a method for preparing a halogenated monoolefine-
conjugated diene copolymer. The method comprises the steps that under the condition of
cationic polymerization, monoolefine shown as the formula I,
conjugated diene shown as the formula III and all components in an initiator
system are in contact in a mixed
solvent of
alkane and
haloalkane,
alkane is used for displacement and
polymerization to obtain
haloalkane in the solution, meanwhile, unreacted monomers are separated out and then are in contact with a
halogen containing compound for a halogenating reaction, the initiator
system contains a compound, lewis acid and an activating agent capable of providing protons, and the activating agent is selected from a compound shown as the formula I-1 and a compound shown as the formula I-2. According to the method, the
polymerization efficiency can be obviously improved, and the higher
polymer yield can be obtained. The
polymer with the high molecular weight can be obtained; meanwhile, the
polymer redissolving process necessary for a
slurry polymerization method is omitted, and the production process is simplified. The formula is shown in the specification.